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-<html><head><title>N1516 Committee Draft -- October 4, 2010 ISO/IEC 9899:201x</title></head><body><pre>
-N1516 Committee Draft -- October 4, 2010 ISO/IEC 9899:201x
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-INTERNATIONAL STANDARD (C)ISO/IEC ISO/IEC 9899:201x
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-Programming languages -- C
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- ABSTRACT
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- (Cover sheet to be provided by ISO Secretariat.)
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-This International Standard specifies the form and establishes the interpretation of
-programs expressed in the programming language C. Its purpose is to promote
-portability, reliability, maintainability, and efficient execution of C language programs on
-a variety of computing systems.
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-Clauses are included that detail the C language itself and the contents of the C language
-execution library. Annexes summarize aspects of both of them, and enumerate factors
-that influence the portability of C programs.
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-Although this International Standard is intended to guide knowledgeable C language
-programmers as well as implementors of C language translation systems, the document
-itself is not designed to serve as a tutorial.
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-Recipients of this draft are invited to submit, with their comments, notification of any
-relevant patent rights of which they are aware and to provide supporting documentation.
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-Changes from the previous draft (N1494) are indicated by ''diff marks'' in the right
-margin: deleted text is marked with ''*'', new or changed text with '' ''.
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-[page i]
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-[page ii]
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-<a name="Contents" href="#Contents">Contents</a>
-<a href="#Foreword">Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii</a>
-<a href="#Introduction">Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii</a>
-<a href="#1">1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1</a>
-<a href="#2">2. Normative references . . . . . . . . . . . . . . . . . . . . . . . 2</a>
-<a href="#3">3. Terms, definitions, and symbols . . . . . . . . . . . . . . . . . . . 3</a>
-<a href="#4">4. Conformance . . . . . . . . . . . . . . . . . . . . . . . . . . 8</a>
-<a href="#5">5. Environment . . . . . . . . . . . . . . . . . . . . . . . . . . 10</a>
-<a href="#5.1"> 5.1 Conceptual models . . . . . . . . . . . . . . . . . . . . . 10</a>
-<a href="#5.1.1"> 5.1.1 Translation environment . . . . . . . . . . . . . . . . 10</a>
-<a href="#5.1.2"> 5.1.2 Execution environments . . . . . . . . . . . . . . . . 12</a>
-<a href="#5.2"> 5.2 Environmental considerations . . . . . . . . . . . . . . . . . 22</a>
-<a href="#5.2.1"> 5.2.1 Character sets . . . . . . . . . . . . . . . . . . . . 22</a>
-<a href="#5.2.2"> 5.2.2 Character display semantics . . . . . . . . . . . . . . 24</a>
-<a href="#5.2.3"> 5.2.3 Signals and interrupts . . . . . . . . . . . . . . . . . 25</a>
-<a href="#5.2.4"> 5.2.4 Environmental limits . . . . . . . . . . . . . . . . . 25</a>
-<a href="#6">6. Language . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35</a>
-<a href="#6.1"> 6.1 Notation . . . . . . . . . . . . . . . . . . . . . . . . . . 35</a>
-<a href="#6.2"> 6.2 Concepts . . . . . . . . . . . . . . . . . . . . . . . . . 35</a>
-<a href="#6.2.1"> 6.2.1 Scopes of identifiers . . . . . . . . . . . . . . . . . 35</a>
-<a href="#6.2.2"> 6.2.2 Linkages of identifiers . . . . . . . . . . . . . . . . . 36</a>
-<a href="#6.2.3"> 6.2.3 Name spaces of identifiers . . . . . . . . . . . . . . . 37</a>
-<a href="#6.2.4"> 6.2.4 Storage durations of objects . . . . . . . . . . . . . . 38</a>
-<a href="#6.2.5"> 6.2.5 Types . . . . . . . . . . . . . . . . . . . . . . . 39</a>
-<a href="#6.2.6"> 6.2.6 Representations of types . . . . . . . . . . . . . . . . 44</a>
-<a href="#6.2.7"> 6.2.7 Compatible type and composite type . . . . . . . . . . . 47</a>
-<a href="#6.2.8"> 6.2.8 Alignment of objects . . . . . . . . . . . . . . . . . 48</a>
-<a href="#6.3"> 6.3 Conversions . . . . . . . . . . . . . . . . . . . . . . . . 50</a>
-<a href="#6.3.1"> 6.3.1 Arithmetic operands . . . . . . . . . . . . . . . . . 50</a>
-<a href="#6.3.2"> 6.3.2 Other operands . . . . . . . . . . . . . . . . . . . 54</a>
-<a href="#6.4"> 6.4 Lexical elements . . . . . . . . . . . . . . . . . . . . . . 57</a>
-<a href="#6.4.1"> 6.4.1 Keywords . . . . . . . . . . . . . . . . . . . . . . 58</a>
-<a href="#6.4.2"> 6.4.2 Identifiers . . . . . . . . . . . . . . . . . . . . . . 59</a>
-<a href="#6.4.3"> 6.4.3 Universal character names . . . . . . . . . . . . . . . 61</a>
-<a href="#6.4.4"> 6.4.4 Constants . . . . . . . . . . . . . . . . . . . . . . 62</a>
-<a href="#6.4.5"> 6.4.5 String literals . . . . . . . . . . . . . . . . . . . . 70</a>
-<a href="#6.4.6"> 6.4.6 Punctuators . . . . . . . . . . . . . . . . . . . . . 72</a>
-<a href="#6.4.7"> 6.4.7 Header names . . . . . . . . . . . . . . . . . . . . 73</a>
-<a href="#6.4.8"> 6.4.8 Preprocessing numbers . . . . . . . . . . . . . . . . 74</a>
-<a href="#6.4.9"> 6.4.9 Comments . . . . . . . . . . . . . . . . . . . . . 75</a>
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-[page iii]
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-<a href="#6.5"> 6.5 Expressions . . . . . . . . . . . . . . . . . . . . . . . . 76</a>
-<a href="#6.5.1"> 6.5.1 Primary expressions . . . . . . . . . . . . . . . . . 78</a>
-<a href="#6.5.2"> 6.5.2 Postfix operators . . . . . . . . . . . . . . . . . . . 79</a>
-<a href="#6.5.3"> 6.5.3 Unary operators . . . . . . . . . . . . . . . . . . . 88</a>
-<a href="#6.5.4"> 6.5.4 Cast operators . . . . . . . . . . . . . . . . . . . . 91</a>
-<a href="#6.5.5"> 6.5.5 Multiplicative operators . . . . . . . . . . . . . . . . 92</a>
-<a href="#6.5.6"> 6.5.6 Additive operators . . . . . . . . . . . . . . . . . . 92</a>
-<a href="#6.5.7"> 6.5.7 Bitwise shift operators . . . . . . . . . . . . . . . . . 94</a>
-<a href="#6.5.8"> 6.5.8 Relational operators . . . . . . . . . . . . . . . . . . 95</a>
-<a href="#6.5.9"> 6.5.9 Equality operators . . . . . . . . . . . . . . . . . . 96</a>
-<a href="#6.5.10"> 6.5.10 Bitwise AND operator . . . . . . . . . . . . . . . . . 97</a>
-<a href="#6.5.11"> 6.5.11 Bitwise exclusive OR operator . . . . . . . . . . . . . 98</a>
-<a href="#6.5.12"> 6.5.12 Bitwise inclusive OR operator . . . . . . . . . . . . . . 98</a>
-<a href="#6.5.13"> 6.5.13 Logical AND operator . . . . . . . . . . . . . . . . . 99</a>
-<a href="#6.5.14"> 6.5.14 Logical OR operator . . . . . . . . . . . . . . . . . 99</a>
-<a href="#6.5.15"> 6.5.15 Conditional operator . . . . . . . . . . . . . . . . . 100</a>
-<a href="#6.5.16"> 6.5.16 Assignment operators . . . . . . . . . . . . . . . . . 101</a>
-<a href="#6.5.17"> 6.5.17 Comma operator . . . . . . . . . . . . . . . . . . . 104</a>
-<a href="#6.6"> 6.6 Constant expressions . . . . . . . . . . . . . . . . . . . . . 105</a>
-<a href="#6.7"> 6.7 Declarations . . . . . . . . . . . . . . . . . . . . . . . . 107</a>
-<a href="#6.7.1"> 6.7.1 Storage-class specifiers . . . . . . . . . . . . . . . . 108</a>
-<a href="#6.7.2"> 6.7.2 Type specifiers . . . . . . . . . . . . . . . . . . . . 109</a>
-<a href="#6.7.3"> 6.7.3 Type qualifiers . . . . . . . . . . . . . . . . . . . . 119</a>
-<a href="#6.7.4"> 6.7.4 Function specifiers . . . . . . . . . . . . . . . . . . 123</a>
-<a href="#6.7.5"> 6.7.5 Alignment specifier . . . . . . . . . . . . . . . . . . 125</a>
-<a href="#6.7.6"> 6.7.6 Declarators . . . . . . . . . . . . . . . . . . . . . 126</a>
-<a href="#6.7.7"> 6.7.7 Type names . . . . . . . . . . . . . . . . . . . . . 134</a>
-<a href="#6.7.8"> 6.7.8 Type definitions . . . . . . . . . . . . . . . . . . . 135</a>
-<a href="#6.7.9"> 6.7.9 Initialization . . . . . . . . . . . . . . . . . . . . 137</a>
-<a href="#6.7.10"> 6.7.10 Static assertions . . . . . . . . . . . . . . . . . . . 143</a>
-<a href="#6.8"> 6.8 Statements and blocks . . . . . . . . . . . . . . . . . . . . 144</a>
-<a href="#6.8.1"> 6.8.1 Labeled statements . . . . . . . . . . . . . . . . . . 144</a>
-<a href="#6.8.2"> 6.8.2 Compound statement . . . . . . . . . . . . . . . . . 145</a>
-<a href="#6.8.3"> 6.8.3 Expression and null statements . . . . . . . . . . . . . 145</a>
-<a href="#6.8.4"> 6.8.4 Selection statements . . . . . . . . . . . . . . . . . 146</a>
-<a href="#6.8.5"> 6.8.5 Iteration statements . . . . . . . . . . . . . . . . . . 148</a>
-<a href="#6.8.6"> 6.8.6 Jump statements . . . . . . . . . . . . . . . . . . . 149</a>
-<a href="#6.9"> 6.9 External definitions . . . . . . . . . . . . . . . . . . . . . 153</a>
-<a href="#6.9.1"> 6.9.1 Function definitions . . . . . . . . . . . . . . . . . . 154</a>
-<a href="#6.9.2"> 6.9.2 External object definitions . . . . . . . . . . . . . . . 156</a>
-<a href="#6.10"> 6.10 Preprocessing directives . . . . . . . . . . . . . . . . . . . 158</a>
-<a href="#6.10.1"> 6.10.1 Conditional inclusion . . . . . . . . . . . . . . . . . 160</a>
-<a href="#6.10.2"> 6.10.2 Source file inclusion . . . . . . . . . . . . . . . . . 162</a>
-<a href="#6.10.3"> 6.10.3 Macro replacement . . . . . . . . . . . . . . . . . . 164</a>
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-<a href="#6.10.4"> 6.10.4 Line control . . . . . . . . . . . . . . . . . . . . . 171</a>
-<a href="#6.10.5"> 6.10.5 Error directive . . . . . . . . . . . . . . . . . . . . 172</a>
-<a href="#6.10.6"> 6.10.6 Pragma directive . . . . . . . . . . . . . . . . . . . 172</a>
-<a href="#6.10.7"> 6.10.7 Null directive . . . . . . . . . . . . . . . . . . . . 173</a>
-<a href="#6.10.8"> 6.10.8 Predefined macro names . . . . . . . . . . . . . . . . 173</a>
-<a href="#6.10.9"> 6.10.9 Pragma operator . . . . . . . . . . . . . . . . . . . 175</a>
-<a href="#6.11"> 6.11 Future language directions . . . . . . . . . . . . . . . . . . 177</a>
-<a href="#6.11.1"> 6.11.1 Floating types . . . . . . . . . . . . . . . . . . . . 177</a>
-<a href="#6.11.2"> 6.11.2 Linkages of identifiers . . . . . . . . . . . . . . . . . 177</a>
-<a href="#6.11.3"> 6.11.3 External names . . . . . . . . . . . . . . . . . . . 177</a>
-<a href="#6.11.4"> 6.11.4 Character escape sequences . . . . . . . . . . . . . . 177</a>
-<a href="#6.11.5"> 6.11.5 Storage-class specifiers . . . . . . . . . . . . . . . . 177</a>
-<a href="#6.11.6"> 6.11.6 Function declarators . . . . . . . . . . . . . . . . . 177</a>
-<a href="#6.11.7"> 6.11.7 Function definitions . . . . . . . . . . . . . . . . . . 177</a>
-<a href="#6.11.8"> 6.11.8 Pragma directives . . . . . . . . . . . . . . . . . . 177</a>
-<a href="#6.11.9"> 6.11.9 Predefined macro names . . . . . . . . . . . . . . . . 177</a>
-<a href="#7">7. Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178</a>
-<a href="#7.1"> 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 178</a>
-<a href="#7.1.1"> 7.1.1 Definitions of terms . . . . . . . . . . . . . . . . . . 178</a>
-<a href="#7.1.2"> 7.1.2 Standard headers . . . . . . . . . . . . . . . . . . . 179</a>
-<a href="#7.1.3"> 7.1.3 Reserved identifiers . . . . . . . . . . . . . . . . . . 180</a>
-<a href="#7.1.4"> 7.1.4 Use of library functions . . . . . . . . . . . . . . . . 181</a>
-<a href="#7.2"> 7.2 Diagnostics <assert.h> . . . . . . . . . . . . . . . . . . 184</a>
-<a href="#7.2.1"> 7.2.1 Program diagnostics . . . . . . . . . . . . . . . . . 184</a>
-<a href="#7.3"> 7.3 Complex arithmetic <complex.h> . . . . . . . . . . . . . . 186</a>
-<a href="#7.3.1"> 7.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . 186</a>
-<a href="#7.3.2"> 7.3.2 Conventions . . . . . . . . . . . . . . . . . . . . . 187</a>
-<a href="#7.3.3"> 7.3.3 Branch cuts . . . . . . . . . . . . . . . . . . . . . 187</a>
-<a href="#7.3.4"> 7.3.4 The CX_LIMITED_RANGE pragma . . . . . . . . . . . 187</a>
-<a href="#7.3.5"> 7.3.5 Trigonometric functions . . . . . . . . . . . . . . . . 188</a>
-<a href="#7.3.6"> 7.3.6 Hyperbolic functions . . . . . . . . . . . . . . . . . 190</a>
-<a href="#7.3.7"> 7.3.7 Exponential and logarithmic functions . . . . . . . . . . 192</a>
-<a href="#7.3.8"> 7.3.8 Power and absolute-value functions . . . . . . . . . . . 193</a>
-<a href="#7.3.9"> 7.3.9 Manipulation functions . . . . . . . . . . . . . . . . 194</a>
-<a href="#7.4"> 7.4 Character handling <ctype.h> . . . . . . . . . . . . . . . . 198</a>
-<a href="#7.4.1"> 7.4.1 Character classification functions . . . . . . . . . . . . 198</a>
-<a href="#7.4.2"> 7.4.2 Character case mapping functions . . . . . . . . . . . . 201</a>
-<a href="#7.5"> 7.5 Errors <errno.h> . . . . . . . . . . . . . . . . . . . . . 203</a>
-<a href="#7.6"> 7.6 Floating-point environment <fenv.h> . . . . . . . . . . . . . 204</a>
-<a href="#7.6.1"> 7.6.1 The FENV_ACCESS pragma . . . . . . . . . . . . . . 206</a>
-<a href="#7.6.2"> 7.6.2 Floating-point exceptions . . . . . . . . . . . . . . . 207</a>
-<a href="#7.6.3"> 7.6.3 Rounding . . . . . . . . . . . . . . . . . . . . . . 210</a>
-<a href="#7.6.4"> 7.6.4 Environment . . . . . . . . . . . . . . . . . . . . 211</a>
-<a href="#7.7"> 7.7 Characteristics of floating types <float.h> . . . . . . . . . . . 214</a>
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-<a href="#7.8"> 7.8 Format conversion of integer types <inttypes.h> . . . . . . . . 215</a>
-<a href="#7.8.1"> 7.8.1 Macros for format specifiers . . . . . . . . . . . . . . 215</a>
-<a href="#7.8.2"> 7.8.2 Functions for greatest-width integer types . . . . . . . . . 216</a>
-<a href="#7.9"> 7.9 Alternative spellings <iso646.h> . . . . . . . . . . . . . . . 219</a>
-<a href="#7.10"> 7.10 Sizes of integer types <limits.h> . . . . . . . . . . . . . . 220</a>
-<a href="#7.11"> 7.11 Localization <locale.h> . . . . . . . . . . . . . . . . . . 221</a>
-<a href="#7.11.1"> 7.11.1 Locale control . . . . . . . . . . . . . . . . . . . . 222</a>
-<a href="#7.11.2"> 7.11.2 Numeric formatting convention inquiry . . . . . . . . . . 223</a>
-<a href="#7.12"> 7.12 Mathematics <math.h> . . . . . . . . . . . . . . . . . . . 229</a>
-<a href="#7.12.1"> 7.12.1 Treatment of error conditions . . . . . . . . . . . . . . 231</a>
-<a href="#7.12.2"> 7.12.2 The FP_CONTRACT pragma . . . . . . . . . . . . . . 233</a>
-<a href="#7.12.3"> 7.12.3 Classification macros . . . . . . . . . . . . . . . . . 233</a>
-<a href="#7.12.4"> 7.12.4 Trigonometric functions . . . . . . . . . . . . . . . . 236</a>
-<a href="#7.12.5"> 7.12.5 Hyperbolic functions . . . . . . . . . . . . . . . . . 238</a>
-<a href="#7.12.6"> 7.12.6 Exponential and logarithmic functions . . . . . . . . . . 240</a>
-<a href="#7.12.7"> 7.12.7 Power and absolute-value functions . . . . . . . . . . . 245</a>
-<a href="#7.12.8"> 7.12.8 Error and gamma functions . . . . . . . . . . . . . . . 247</a>
-<a href="#7.12.9"> 7.12.9 Nearest integer functions . . . . . . . . . . . . . . . . 249</a>
-<a href="#7.12.10"> 7.12.10 Remainder functions . . . . . . . . . . . . . . . . . 252</a>
-<a href="#7.12.11"> 7.12.11 Manipulation functions . . . . . . . . . . . . . . . . 253</a>
-<a href="#7.12.12"> 7.12.12 Maximum, minimum, and positive difference functions . . . 255</a>
-<a href="#7.12.13"> 7.12.13 Floating multiply-add . . . . . . . . . . . . . . . . . 256</a>
-<a href="#7.12.14"> 7.12.14 Comparison macros . . . . . . . . . . . . . . . . . . 257</a>
-<a href="#7.13"> 7.13 Nonlocal jumps <setjmp.h> . . . . . . . . . . . . . . . . 260</a>
-<a href="#7.13.1"> 7.13.1 Save calling environment . . . . . . . . . . . . . . . 260</a>
-<a href="#7.13.2"> 7.13.2 Restore calling environment . . . . . . . . . . . . . . 261</a>
-<a href="#7.14"> 7.14 Signal handling <signal.h> . . . . . . . . . . . . . . . . . 263</a>
-<a href="#7.14.1"> 7.14.1 Specify signal handling . . . . . . . . . . . . . . . . 264</a>
-<a href="#7.14.2"> 7.14.2 Send signal . . . . . . . . . . . . . . . . . . . . . 265</a>
-<a href="#7.15"> 7.15 Alignment <stdalign.h> . . . . . . . . . . . . . . . . . 266</a>
-<a href="#7.16"> 7.16 Variable arguments <stdarg.h> . . . . . . . . . . . . . . . 267</a>
-<a href="#7.16.1"> 7.16.1 Variable argument list access macros . . . . . . . . . . . 267</a>
-<a href="#7.17"> 7.17 Atomics <stdatomic.h> . . . . . . . . . . . . . . . . . . 271</a>
-<a href="#7.17.1"> 7.17.1 Introduction . . . . . . . . . . . . . . . . . . . . . 271</a>
-<a href="#7.17.2"> 7.17.2 Initialization . . . . . . . . . . . . . . . . . . . . 272</a>
-<a href="#7.17.3"> 7.17.3 Order and consistency . . . . . . . . . . . . . . . . . 273</a>
-<a href="#7.17.4"> 7.17.4 Fences . . . . . . . . . . . . . . . . . . . . . . . 276</a>
-<a href="#7.17.5"> 7.17.5 Lock-free property . . . . . . . . . . . . . . . . . . 277</a>
-<a href="#7.17.6"> 7.17.6 Atomic integer and address types . . . . . . . . . . . . 278</a>
-<a href="#7.17.7"> 7.17.7 Operations on atomic types . . . . . . . . . . . . . . . 280</a>
-<a href="#7.17.8"> 7.17.8 Atomic flag type and operations . . . . . . . . . . . . . 283</a>
-<a href="#7.18"> 7.18 Boolean type and values <stdbool.h> . . . . . . . . . . . . 285</a>
-<a href="#7.19"> 7.19 Common definitions <stddef.h> . . . . . . . . . . . . . . . 286</a>
-<a href="#7.20"> 7.20 Integer types <stdint.h> . . . . . . . . . . . . . . . . . . 288</a>
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-<a href="#7.20.1"> 7.20.1 Integer types . . . . . . . . . . . . . . . . . . . . 288</a>
-<a href="#7.20.2"> 7.20.2 Limits of specified-width integer types . . . . . . . . . . 290</a>
-<a href="#7.20.3"> 7.20.3 Limits of other integer types . . . . . . . . . . . . . . 292</a>
-<a href="#7.20.4"> 7.20.4 Macros for integer constants . . . . . . . . . . . . . . 293</a>
-<a href="#7.21"> 7.21 Input/output <stdio.h> . . . . . . . . . . . . . . . . . . 295</a>
-<a href="#7.21.1"> 7.21.1 Introduction . . . . . . . . . . . . . . . . . . . . . 295</a>
-<a href="#7.21.2"> 7.21.2 Streams . . . . . . . . . . . . . . . . . . . . . . 297</a>
-<a href="#7.21.3"> 7.21.3 Files . . . . . . . . . . . . . . . . . . . . . . . . 299</a>
-<a href="#7.21.4"> 7.21.4 Operations on files . . . . . . . . . . . . . . . . . . 301</a>
-<a href="#7.21.5"> 7.21.5 File access functions . . . . . . . . . . . . . . . . . 303</a>
-<a href="#7.21.6"> 7.21.6 Formatted input/output functions . . . . . . . . . . . . 308</a>
-<a href="#7.21.7"> 7.21.7 Character input/output functions . . . . . . . . . . . . . 329</a>
-<a href="#7.21.8"> 7.21.8 Direct input/output functions . . . . . . . . . . . . . . 333</a>
-<a href="#7.21.9"> 7.21.9 File positioning functions . . . . . . . . . . . . . . . 334</a>
-<a href="#7.21.10"> 7.21.10 Error-handling functions . . . . . . . . . . . . . . . . 337</a>
-<a href="#7.22"> 7.22 General utilities <stdlib.h> . . . . . . . . . . . . . . . . 339</a>
-<a href="#7.22.1"> 7.22.1 Numeric conversion functions . . . . . . . . . . . . . . 340</a>
-<a href="#7.22.2"> 7.22.2 Pseudo-random sequence generation functions . . . . . . . 345</a>
-<a href="#7.22.3"> 7.22.3 Memory management functions . . . . . . . . . . . . . 346</a>
-<a href="#7.22.4"> 7.22.4 Communication with the environment . . . . . . . . . . 348</a>
-<a href="#7.22.5"> 7.22.5 Searching and sorting utilities . . . . . . . . . . . . . . 352</a>
-<a href="#7.22.6"> 7.22.6 Integer arithmetic functions . . . . . . . . . . . . . . 354</a>
-<a href="#7.22.7"> 7.22.7 Multibyte/wide character conversion functions . . . . . . . 355</a>
-<a href="#7.22.8"> 7.22.8 Multibyte/wide string conversion functions . . . . . . . . 357</a>
-<a href="#7.23"> 7.23 String handling <string.h> . . . . . . . . . . . . . . . . . 359</a>
-<a href="#7.23.1"> 7.23.1 String function conventions . . . . . . . . . . . . . . . 359</a>
-<a href="#7.23.2"> 7.23.2 Copying functions . . . . . . . . . . . . . . . . . . 359</a>
-<a href="#7.23.3"> 7.23.3 Concatenation functions . . . . . . . . . . . . . . . . 361</a>
-<a href="#7.23.4"> 7.23.4 Comparison functions . . . . . . . . . . . . . . . . . 362</a>
-<a href="#7.23.5"> 7.23.5 Search functions . . . . . . . . . . . . . . . . . . . 364</a>
-<a href="#7.23.6"> 7.23.6 Miscellaneous functions . . . . . . . . . . . . . . . . 367</a>
-<a href="#7.24"> 7.24 Type-generic math <tgmath.h> . . . . . . . . . . . . . . . 369</a>
-<a href="#7.25"> 7.25 Threads <threads.h> . . . . . . . . . . . . . . . . . . . 372</a>
-<a href="#7.25.1"> 7.25.1 Introduction . . . . . . . . . . . . . . . . . . . . . 372</a>
-<a href="#7.25.2"> 7.25.2 Initialization functions . . . . . . . . . . . . . . . . . 374</a>
-<a href="#7.25.3"> 7.25.3 Condition variable functions . . . . . . . . . . . . . . 374</a>
-<a href="#7.25.4"> 7.25.4 Mutex functions . . . . . . . . . . . . . . . . . . . 376</a>
-<a href="#7.25.5"> 7.25.5 Thread functions . . . . . . . . . . . . . . . . . . . 379</a>
-<a href="#7.25.6"> 7.25.6 Thread-specific storage functions . . . . . . . . . . . . 381</a>
-<a href="#7.25.7"> 7.25.7 Time functions . . . . . . . . . . . . . . . . . . . . 383</a>
-<a href="#7.26"> 7.26 Date and time <time.h> . . . . . . . . . . . . . . . . . . 384</a>
-<a href="#7.26.1"> 7.26.1 Components of time . . . . . . . . . . . . . . . . . 384</a>
-<a href="#7.26.2"> 7.26.2 Time manipulation functions . . . . . . . . . . . . . . 385</a>
-<a href="#7.26.3"> 7.26.3 Time conversion functions . . . . . . . . . . . . . . . 387</a>
-
-
-[page vii]
-
-<a href="#7.27"> 7.27 Unicode utilities <uchar.h> . . . . . . . . . . . . . . . . . 394</a>
-<a href="#7.27.1"> 7.27.1 Restartable multibyte/wide character conversion functions . . 394</a>
-<a href="#7.28"> 7.28 Extended multibyte and wide character utilities <wchar.h> . . . . . 398</a>
-<a href="#7.28.1"> 7.28.1 Introduction . . . . . . . . . . . . . . . . . . . . . 398</a>
-<a href="#7.28.2"> 7.28.2 Formatted wide character input/output functions . . . . . . 399</a>
-<a href="#7.28.3"> 7.28.3 Wide character input/output functions . . . . . . . . . . 417</a>
-<a href="#7.28.4"> 7.28.4 General wide string utilities . . . . . . . . . . . . . . 421</a>
-<a href="#7.28.4.1"> 7.28.4.1 Wide string numeric conversion functions . . . . . 422</a>
-<a href="#7.28.4.2"> 7.28.4.2 Wide string copying functions . . . . . . . . . . 426</a>
-<a href="#7.28.4.3"> 7.28.4.3 Wide string concatenation functions . . . . . . . 428</a>
-<a href="#7.28.4.4"> 7.28.4.4 Wide string comparison functions . . . . . . . . 429</a>
-<a href="#7.28.4.5"> 7.28.4.5 Wide string search functions . . . . . . . . . . 431</a>
-<a href="#7.28.4.6"> 7.28.4.6 Miscellaneous functions . . . . . . . . . . . . 435</a>
-<a href="#7.28.5"> 7.28.5 Wide character time conversion functions . . . . . . . . . 435</a>
-<a href="#7.28.6"> 7.28.6 Extended multibyte/wide character conversion utilities . . . . 436</a>
-<a href="#7.28.6.1"> 7.28.6.1 Single-byte/wide character conversion functions . . . 437</a>
-<a href="#7.28.6.2"> 7.28.6.2 Conversion state functions . . . . . . . . . . . 437</a>
-<a href="#7.28.6.3"> 7.28.6.3 Restartable multibyte/wide character conversion
- functions . . . . . . . . . . . . . . . . . . 438</a>
-<a href="#7.28.6.4"> 7.28.6.4 Restartable multibyte/wide string conversion
- functions . . . . . . . . . . . . . . . . . . 440</a>
-<a href="#7.29"> 7.29 Wide character classification and mapping utilities <wctype.h> . . . 443</a>
-<a href="#7.29.1"> 7.29.1 Introduction . . . . . . . . . . . . . . . . . . . . . 443</a>
-<a href="#7.29.2"> 7.29.2 Wide character classification utilities . . . . . . . . . . . 444</a>
-<a href="#7.29.2.1"> 7.29.2.1 Wide character classification functions . . . . . . 444</a>
-<a href="#7.29.2.2"> 7.29.2.2 Extensible wide character classification
- functions . . . . . . . . . . . . . . . . . . 447</a>
-<a href="#7.29.3"> 7.29.3 Wide character case mapping utilities . . . . . . . . . . . 449</a>
-<a href="#7.29.3.1"> 7.29.3.1 Wide character case mapping functions . . . . . . 449</a>
-<a href="#7.29.3.2"> 7.29.3.2 Extensible wide character case mapping
- functions . . . . . . . . . . . . . . . . . . 449</a>
-<a href="#7.30"> 7.30 Future library directions . . . . . . . . . . . . . . . . . . . 451</a>
-<a href="#7.30.1"> 7.30.1 Complex arithmetic <complex.h> . . . . . . . . . . . 451</a>
-<a href="#7.30.2"> 7.30.2 Character handling <ctype.h> . . . . . . . . . . . . 451</a>
-<a href="#7.30.3"> 7.30.3 Errors <errno.h> . . . . . . . . . . . . . . . . . 451</a>
-<a href="#7.30.4"> 7.30.4 Format conversion of integer types <inttypes.h> . . . . 451</a>
-<a href="#7.30.5"> 7.30.5 Localization <locale.h> . . . . . . . . . . . . . . 451</a>
-<a href="#7.30.6"> 7.30.6 Signal handling <signal.h> . . . . . . . . . . . . . 451</a>
-<a href="#7.30.7"> 7.30.7 Boolean type and values <stdbool.h> . . . . . . . . . 451</a>
-<a href="#7.30.8"> 7.30.8 Integer types <stdint.h> . . . . . . . . . . . . . . 451</a>
-<a href="#7.30.9"> 7.30.9 Input/output <stdio.h> . . . . . . . . . . . . . . . 452</a>
-<a href="#7.30.10"> 7.30.10 General utilities <stdlib.h> . . . . . . . . . . . . . 452</a>
-<a href="#7.30.11"> 7.30.11 String handling <string.h> . . . . . . . . . . . . . 452</a>
-
-
-
-[page viii]
-
-<a href="#7.30.12"> 7.30.12 Extended multibyte and wide character utilities
- <wchar.h> . . . . . . . . . . . . . . . . . . . . 452</a>
-<a href="#7.30.13"> 7.30.13 Wide character classification and mapping utilities
- <wctype.h> . . . . . . . . . . . . . . . . . . . . 452</a>
-<a href="#A">Annex A (informative) Language syntax summary . . . . . . . . . . . . 453</a>
-<a href="#A.1"> A.1 Lexical grammar . . . . . . . . . . . . . . . . . . . . . . 453</a>
-<a href="#A.2"> A.2 Phrase structure grammar . . . . . . . . . . . . . . . . . . . 460</a>
-<a href="#A.3"> A.3 Preprocessing directives . . . . . . . . . . . . . . . . . . . 468</a>
-<a href="#B">Annex B (informative) Library summary . . . . . . . . . . . . . . . . 470</a>
-<a href="#B.1"> B.1 Diagnostics <assert.h> . . . . . . . . . . . . . . . . . . 470</a>
-<a href="#B.2"> B.2 Complex <complex.h> . . . . . . . . . . . . . . . . . . . 470</a>
-<a href="#B.3"> B.3 Character handling <ctype.h> . . . . . . . . . . . . . . . . 472</a>
-<a href="#B.4"> B.4 Errors <errno.h> . . . . . . . . . . . . . . . . . . . . . 472</a>
-<a href="#B.5"> B.5 Floating-point environment <fenv.h> . . . . . . . . . . . . . 472</a>
-<a href="#B.6"> B.6 Characteristics of floating types <float.h> . . . . . . . . . . . 473</a>
-<a href="#B.7"> B.7 Format conversion of integer types <inttypes.h> . . . . . . . . 473</a>
-<a href="#B.8"> B.8 Alternative spellings <iso646.h> . . . . . . . . . . . . . . . 474</a>
-<a href="#B.9"> B.9 Sizes of integer types <limits.h> . . . . . . . . . . . . . . 474</a>
-<a href="#B.10"> B.10 Localization <locale.h> . . . . . . . . . . . . . . . . . . 474</a>
-<a href="#B.11"> B.11 Mathematics <math.h> . . . . . . . . . . . . . . . . . . . 474</a>
-<a href="#B.12"> B.12 Nonlocal jumps <setjmp.h> . . . . . . . . . . . . . . . . 479</a>
-<a href="#B.13"> B.13 Signal handling <signal.h> . . . . . . . . . . . . . . . . . 479</a>
-<a href="#B.14"> B.14 Alignment <stdalign.h> . . . . . . . . . . . . . . . . . 480</a>
-<a href="#B.15"> B.15 Variable arguments <stdarg.h> . . . . . . . . . . . . . . . 480</a>
-<a href="#B.16"> B.16 Atomics <stdatomic.h> . . . . . . . . . . . . . . . . . . 480</a>
-<a href="#B.17"> B.17 Boolean type and values <stdbool.h> . . . . . . . . . . . . 482</a>
-<a href="#B.18"> B.18 Common definitions <stddef.h> . . . . . . . . . . . . . . . 482</a>
-<a href="#B.19"> B.19 Integer types <stdint.h> . . . . . . . . . . . . . . . . . . 482</a>
-<a href="#B.20"> B.20 Input/output <stdio.h> . . . . . . . . . . . . . . . . . . 483</a>
-<a href="#B.21"> B.21 General utilities <stdlib.h> . . . . . . . . . . . . . . . . 486</a>
-<a href="#B.22"> B.22 String handling <string.h> . . . . . . . . . . . . . . . . . 488</a>
-<a href="#B.23"> B.23 Type-generic math <tgmath.h> . . . . . . . . . . . . . . . 490</a>
-<a href="#B.24"> B.24 Threads <threads.h> . . . . . . . . . . . . . . . . . . . 490</a>
-<a href="#B.25"> B.25 Date and time <time.h> . . . . . . . . . . . . . . . . . . 491</a>
-<a href="#B.26"> B.26 Unicode utilities <uchar.h> . . . . . . . . . . . . . . . . . 492</a>
-<a href="#B.27"> B.27 Extended multibyte/wide character utilities <wchar.h> . . . . . . 492</a>
-<a href="#B.28"> B.28 Wide character classification and mapping utilities <wctype.h> . . . 497</a>
-<a href="#C">Annex C (informative) Sequence points . . . . . . . . . . . . . . . . . 498</a>
-<a href="#D">Annex D (normative) Universal character names for identifiers . . . . . . . 499</a>
-<a href="#E">Annex E (informative) Implementation limits . . . . . . . . . . . . . . 501</a>
-<a href="#F">Annex F (normative) IEC 60559 floating-point arithmetic . . . . . . . . . . 503</a>
-<a href="#F.1"> F.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 503</a>
-
-[page ix]
-
-<a href="#F.2"> F.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 503</a>
-<a href="#F.3"> F.3 Operators and functions . . . . . . . . . . . . . . . . . . . 504</a>
-<a href="#F.4"> F.4 Floating to integer conversion . . . . . . . . . . . . . . . . . 506</a>
-<a href="#F.5"> F.5 Binary-decimal conversion . . . . . . . . . . . . . . . . . . 506</a>
-<a href="#F.6"> F.6 The return statement . . . . . . . . . . . . . . . . . . . . 507</a>
-<a href="#F.7"> F.7 Contracted expressions . . . . . . . . . . . . . . . . . . . . 507</a>
-<a href="#F.8"> F.8 Floating-point environment . . . . . . . . . . . . . . . . . . 507</a>
-<a href="#F.9"> F.9 Optimization . . . . . . . . . . . . . . . . . . . . . . . . 510</a>
-<a href="#F.10"> F.10 Mathematics <math.h> . . . . . . . . . . . . . . . . . . . 513</a>
-<a href="#F.10.1"> F.10.1 Trigonometric functions . . . . . . . . . . . . . . . . 514</a>
-<a href="#F.10.2"> F.10.2 Hyperbolic functions . . . . . . . . . . . . . . . . . 516</a>
-<a href="#F.10.3"> F.10.3 Exponential and logarithmic functions . . . . . . . . . . 516</a>
-<a href="#F.10.4"> F.10.4 Power and absolute value functions . . . . . . . . . . . 519</a>
-<a href="#F.10.5"> F.10.5 Error and gamma functions . . . . . . . . . . . . . . . 521</a>
-<a href="#F.10.6"> F.10.6 Nearest integer functions . . . . . . . . . . . . . . . . 521</a>
-<a href="#F.10.7"> F.10.7 Remainder functions . . . . . . . . . . . . . . . . . 524</a>
-<a href="#F.10.8"> F.10.8 Manipulation functions . . . . . . . . . . . . . . . . 525</a>
-<a href="#F.10.9"> F.10.9 Maximum, minimum, and positive difference functions . . . 525</a>
-<a href="#F.10.10"> F.10.10 Floating multiply-add . . . . . . . . . . . . . . . . . 526</a>
-<a href="#F.10.11"> F.10.11 Comparison macros . . . . . . . . . . . . . . . . . . 526</a>
-<a href="#G">Annex G (informative) IEC 60559-compatible complex arithmetic . . . . . . 527</a>
-<a href="#G.1"> G.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 527</a>
-<a href="#G.2"> G.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 527</a>
-<a href="#G.3"> G.3 Conventions . . . . . . . . . . . . . . . . . . . . . . . . 527</a>
-<a href="#G.4"> G.4 Conversions . . . . . . . . . . . . . . . . . . . . . . . . 528</a>
-<a href="#G.4.1"> G.4.1 Imaginary types . . . . . . . . . . . . . . . . . . . 528</a>
-<a href="#G.4.2"> G.4.2 Real and imaginary . . . . . . . . . . . . . . . . . . 528</a>
-<a href="#G.4.3"> G.4.3 Imaginary and complex . . . . . . . . . . . . . . . . 528</a>
-<a href="#G.5"> G.5 Binary operators . . . . . . . . . . . . . . . . . . . . . . 528</a>
-<a href="#G.5.1"> G.5.1 Multiplicative operators . . . . . . . . . . . . . . . . 529</a>
-<a href="#G.5.2"> G.5.2 Additive operators . . . . . . . . . . . . . . . . . . 532</a>
-<a href="#G.6"> G.6 Complex arithmetic <complex.h> . . . . . . . . . . . . . . 532</a>
-<a href="#G.6.1"> G.6.1 Trigonometric functions . . . . . . . . . . . . . . . . 534</a>
-<a href="#G.6.2"> G.6.2 Hyperbolic functions . . . . . . . . . . . . . . . . . 534</a>
-<a href="#G.6.3"> G.6.3 Exponential and logarithmic functions . . . . . . . . . . 538</a>
-<a href="#G.6.4"> G.6.4 Power and absolute-value functions . . . . . . . . . . . 539</a>
-<a href="#G.7"> G.7 Type-generic math <tgmath.h> . . . . . . . . . . . . . . . 540</a>
-<a href="#H">Annex H (informative) Language independent arithmetic . . . . . . . . . . 541</a>
-<a href="#H.1"> H.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 541</a>
-<a href="#H.2"> H.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 541</a>
-<a href="#H.3"> H.3 Notification . . . . . . . . . . . . . . . . . . . . . . . . 545</a>
-<a href="#I">Annex I (informative) Common warnings . . . . . . . . . . . . . . . . 547</a>
-
-
-[page x]
-
-<a href="#J">Annex J (informative) Portability issues . . . . . . . . . . . . . . . . . 549</a>
-<a href="#J.1"> J.1 Unspecified behavior . . . . . . . . . . . . . . . . . . . . . 549</a>
-<a href="#J.2"> J.2 Undefined behavior . . . . . . . . . . . . . . . . . . . . . 552</a>
-<a href="#J.3"> J.3 Implementation-defined behavior . . . . . . . . . . . . . . . . 566</a>
-<a href="#J.4"> J.4 Locale-specific behavior . . . . . . . . . . . . . . . . . . . 573</a>
-<a href="#J.5"> J.5 Common extensions . . . . . . . . . . . . . . . . . . . . . 574</a>
-<a href="#K">Annex K (normative) Bounds-checking interfaces . . . . . . . . . . . . . 577</a>
-<a href="#K.1"> K.1 Background . . . . . . . . . . . . . . . . . . . . . . . . 577</a>
-<a href="#K.2"> K.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 578</a>
-<a href="#K.3"> K.3 Library . . . . . . . . . . . . . . . . . . . . . . . . . . 578</a>
-<a href="#K.3.1"> K.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . 578</a>
-<a href="#K.3.1.1"> K.3.1.1 Standard headers . . . . . . . . . . . . . . . 578</a>
-<a href="#K.3.1.2"> K.3.1.2 Reserved identifiers . . . . . . . . . . . . . . 579</a>
-<a href="#K.3.1.3"> K.3.1.3 Use of errno . . . . . . . . . . . . . . . . . 579</a>
-<a href="#K.3.1.4"> K.3.1.4 Runtime-constraint violations . . . . . . . . . . 579</a>
-<a href="#K.3.2"> K.3.2 Errors <errno.h> . . . . . . . . . . . . . . . . . 580</a>
-<a href="#K.3.3"> K.3.3 Common definitions <stddef.h> . . . . . . . . . . . 580</a>
-<a href="#K.3.4"> K.3.4 Integer types <stdint.h> . . . . . . . . . . . . . . 580</a>
-<a href="#K.3.5"> K.3.5 Input/output <stdio.h> . . . . . . . . . . . . . . . 581</a>
-<a href="#K.3.5.1"> K.3.5.1 Operations on files . . . . . . . . . . . . . . 581</a>
-<a href="#K.3.5.2"> K.3.5.2 File access functions . . . . . . . . . . . . . . 583</a>
-<a href="#K.3.5.3"> K.3.5.3 Formatted input/output functions . . . . . . . . . 586</a>
-<a href="#K.3.5.4"> K.3.5.4 Character input/output functions . . . . . . . . . 597</a>
-<a href="#K.3.6"> K.3.6 General utilities <stdlib.h> . . . . . . . . . . . . . 599</a>
-<a href="#K.3.6.1"> K.3.6.1 Runtime-constraint handling . . . . . . . . . . 599</a>
-<a href="#K.3.6.2"> K.3.6.2 Communication with the environment . . . . . . . 601</a>
-<a href="#K.3.6.3"> K.3.6.3 Searching and sorting utilities . . . . . . . . . . 602</a>
-<a href="#K.3.6.4"> K.3.6.4 Multibyte/wide character conversion functions . . . 605</a>
-<a href="#K.3.6.5"> K.3.6.5 Multibyte/wide string conversion functions . . . . . 606</a>
-<a href="#K.3.7"> K.3.7 String handling <string.h> . . . . . . . . . . . . . 609</a>
-<a href="#K.3.7.1"> K.3.7.1 Copying functions . . . . . . . . . . . . . . 609</a>
-<a href="#K.3.7.2"> K.3.7.2 Concatenation functions . . . . . . . . . . . . 612</a>
-<a href="#K.3.7.3"> K.3.7.3 Search functions . . . . . . . . . . . . . . . 615</a>
-<a href="#K.3.7.4"> K.3.7.4 Miscellaneous functions . . . . . . . . . . . . 616</a>
-<a href="#K.3.8"> K.3.8 Date and time <time.h> . . . . . . . . . . . . . . . 619</a>
-<a href="#K.3.8.1"> K.3.8.1 Components of time . . . . . . . . . . . . . . 619</a>
-<a href="#K.3.8.2"> K.3.8.2 Time conversion functions . . . . . . . . . . . 619</a>
-<a href="#K.3.9"> K.3.9 Extended multibyte and wide character utilities
- <wchar.h> . . . . . . . . . . . . . . . . . . . . 622</a>
-<a href="#K.3.9.1"> K.3.9.1 Formatted wide character input/output functions . . . 623</a>
-<a href="#K.3.9.2"> K.3.9.2 General wide string utilities . . . . . . . . . . . 634</a>
-<a href="#K.3.9.3"> K.3.9.3 Extended multibyte/wide character conversion
- utilities . . . . . . . . . . . . . . . . . . . 642</a>
-
-
-[page xi]
-
-<a href="#L">Annex L (normative) Analyzability . . . . . . . . . . . . . . . . . . 647</a>
-<a href="#L.1"> L.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 647</a>
-<a href="#L.2"> L.2 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 647</a>
-<a href="#L.3"> L.3 Requirements . . . . . . . . . . . . . . . . . . . . . . . . 648</a>
-<a href="#Bibliography">Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . 649</a>
-<a href="#Index">Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 653</a>
-
-
-
-
-[<a name="#pxii" href="pxii">page xii</a>] (<a href="#Contents">Contents</a>)
-
-<a name="Foreword" href="#Foreword"><b> Foreword</b></a>
-1 ISO (the International Organization for Standardization) and IEC (the International
- Electrotechnical Commission) form the specialized system for worldwide
- standardization. National bodies that are member of ISO or IEC participate in the
- development of International Standards through technical committees established by the
- respective organization to deal with particular fields of technical activity. ISO and IEC
- technical committees collaborate in fields of mutual interest. Other international
- organizations, governmental and non-governmental, in liaison with ISO and IEC, also
- take part in the work.
-2 International Standards are drafted in accordance with the rules given in the ISO/IEC
- Directives, Part 2. This International Standard was drafted in accordance with the fifth
- edition (2004).
-3 In the field of information technology, ISO and IEC have established a joint technical
- committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
- committee are circulated to national bodies for voting. Publication as an International
- Standard requires approval by at least 75% of the national bodies casting a vote.
-4 Attention is drawn to the possibility that some of the elements of this document may be
- the subject of patent rights. ISO and IEC shall not be held responsible for identifying any
- or all such patent rights.
-5 This International Standard was prepared by Joint Technical Committee ISO/IEC JTC 1,
- Information technology, Subcommittee SC 22, Programming languages, their
- environments and system software interfaces. The Working Group responsible for this
- standard (WG 14) maintains a site on the World Wide Web at http://www.open-
- std.org/JTC1/SC22/WG14/ containing additional information relevant to this
- standard such as a Rationale for many of the decisions made during its preparation and a
- log of Defect Reports and Responses.
-6 This third edition cancels and replaces the second edition, ISO/IEC 9899:1999, as
- corrected by ISO/IEC 9899:1999/Cor 1:2001, ISO/IEC 9899:1999/Cor 2:2004, and
- ISO/IEC 9899:1999/Cor 3:2007. Major changes from the previous edition include:
- -- conditional (optional) features (including some that were previously mandatory)
- -- support for multiple threads of execution including an improved memory sequencing
- model, atomic objects, and thread-local storage (<a href="#7.17"><stdatomic.h></a> and
- <a href="#7.25"><threads.h></a>)
- -- additional floating-point characteristic macros (<a href="#7.7"><float.h></a>)
- -- querying and specifying alignment of objects (<a href="#7.15"><stdalign.h></a>, <a href="#7.22"><stdlib.h></a>)
- -- Unicode characters and strings (<a href="#7.27"><uchar.h></a>) (originally specified in
- ISO/IEC TR 19769:2004)
- -- type-generic expressions
-
-
-[<a name="#pxiii" href="pxiii">page xiii</a>] (<a href="#Contents">Contents</a>)
-
- -- static assertions
- -- anonymous structures and unions
- -- no-return functions
- -- macros to create complex numbers (<a href="#7.3"><complex.h></a>)
- -- support for opening files for exclusive access
- -- removed the gets function (<a href="#7.21"><stdio.h></a>)
- -- added the aligned_alloc, at_quick_exit, and quick_exit functions
- (<a href="#7.22"><stdlib.h></a>)
- -- (conditional) support for bounds-checking interfaces (originally specified in
- ISO/IEC TR 24731-1:2007)
- -- (conditional) support for analyzability
-7 Major changes in the second edition included:
- -- restricted character set support via digraphs and <a href="#7.9"><iso646.h></a> (originally specified
- in AMD1)
- -- wide character library support in <a href="#7.28"><wchar.h></a> and <a href="#7.29"><wctype.h></a> (originally
- specified in AMD1)
- -- more precise aliasing rules via effective type
- -- restricted pointers
- -- variable length arrays
- -- flexible array members
- -- static and type qualifiers in parameter array declarators
- -- complex (and imaginary) support in <a href="#7.3"><complex.h></a>
- -- type-generic math macros in <a href="#7.24"><tgmath.h></a>
- -- the long long int type and library functions
- -- increased minimum translation limits
- -- additional floating-point characteristics in <a href="#7.7"><float.h></a>
- -- remove implicit int
- -- reliable integer division
- -- universal character names (\u and \U)
- -- extended identifiers
- -- hexadecimal floating-point constants and %a and %A printf/scanf conversion
- specifiers
-
-
-
-[<a name="#pxiv" href="pxiv">page xiv</a>] (<a href="#Contents">Contents</a>)
-
--- compound literals
--- designated initializers
--- // comments
--- extended integer types and library functions in <a href="#7.8"><inttypes.h></a> and <a href="#7.20"><stdint.h></a>
--- remove implicit function declaration
--- preprocessor arithmetic done in intmax_t/uintmax_t
--- mixed declarations and code
--- new block scopes for selection and iteration statements
--- integer constant type rules
--- integer promotion rules
--- macros with a variable number of arguments
--- the vscanf family of functions in <a href="#7.21"><stdio.h></a> and <a href="#7.28"><wchar.h></a>
--- additional math library functions in <a href="#7.12"><math.h></a>
--- treatment of error conditions by math library functions (math_errhandling)
--- floating-point environment access in <a href="#7.6"><fenv.h></a>
--- IEC 60559 (also known as IEC 559 or IEEE arithmetic) support
--- trailing comma allowed in enum declaration
--- %lf conversion specifier allowed in printf
--- inline functions
--- the snprintf family of functions in <a href="#7.21"><stdio.h></a>
--- boolean type in <a href="#7.18"><stdbool.h></a>
--- idempotent type qualifiers
--- empty macro arguments
--- new structure type compatibility rules (tag compatibility)
--- additional predefined macro names
--- _Pragma preprocessing operator
--- standard pragmas
--- __func__ predefined identifier
--- va_copy macro
--- additional strftime conversion specifiers
--- LIA compatibility annex
-
-
-[<a name="#pxv" href="pxv">page xv</a>] (<a href="#Contents">Contents</a>)
-
- -- deprecate ungetc at the beginning of a binary file
- -- remove deprecation of aliased array parameters
- -- conversion of array to pointer not limited to lvalues
- -- relaxed constraints on aggregate and union initialization
- -- relaxed restrictions on portable header names
- -- return without expression not permitted in function that returns a value (and vice
- versa)
-8 Annexes D, F, K, and L form a normative part of this standard; annexes A, B, C, E, G, H,
- I, J, the bibliography, and the index are for information only. In accordance with Part 2 of
- the ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples
- are also for information only.
-
-
-
-
-[<a name="#pxvi" href="pxvi">page xvi</a>] (<a href="#Contents">Contents</a>)
-
-<a name="Introduction" href="#Introduction"><b> Introduction</b></a>
-1 With the introduction of new devices and extended character sets, new features may be
- added to this International Standard. Subclauses in the language and library clauses warn
- implementors and programmers of usages which, though valid in themselves, may
- conflict with future additions.
-2 Certain features are obsolescent, which means that they may be considered for
- withdrawal in future revisions of this International Standard. They are retained because
- of their widespread use, but their use in new implementations (for implementation
- features) or new programs (for language [6.11] or library features [7.30]) is discouraged.
-3 This International Standard is divided into four major subdivisions:
- -- preliminary elements (clauses 1-4);
- -- the characteristics of environments that translate and execute C programs (clause 5);
- -- the language syntax, constraints, and semantics (clause 6);
- -- the library facilities (clause 7).
-4 Examples are provided to illustrate possible forms of the constructions described.
- Footnotes are provided to emphasize consequences of the rules described in that
- subclause or elsewhere in this International Standard. References are used to refer to
- other related subclauses. Recommendations are provided to give advice or guidance to
- implementors. Annexes provide additional information and summarize the information
- contained in this International Standard. A bibliography lists documents that were
- referred to during the preparation of the standard.
-5 The language clause (clause 6) is derived from ''The C Reference Manual''.
-6 The library clause (clause 7) is based on the 1984 /usr/group Standard.
-
-
-
-
-[<a name="#pxvii" href="pxvii">page xvii</a>] (<a href="#Contents">Contents</a>)
-
-
-
-[<a name="#pxviii" href="pxviii">page xviii</a>] (<a href="#Contents">Contents</a>)
-
-
-
- Programming languages -- C
-
-
-
-<a name="1" href="#1"><b> 1. Scope</b></a>
-1 This International Standard specifies the form and establishes the interpretation of
- programs written in the C programming language.1) It specifies
- -- the representation of C programs;
- -- the syntax and constraints of the C language;
- -- the semantic rules for interpreting C programs;
- -- the representation of input data to be processed by C programs;
- -- the representation of output data produced by C programs;
- -- the restrictions and limits imposed by a conforming implementation of C.
-2 This International Standard does not specify
- -- the mechanism by which C programs are transformed for use by a data-processing
- system;
- -- the mechanism by which C programs are invoked for use by a data-processing
- system;
- -- the mechanism by which input data are transformed for use by a C program;
- -- the mechanism by which output data are transformed after being produced by a C
- program;
- -- the size or complexity of a program and its data that will exceed the capacity of any
- specific data-processing system or the capacity of a particular processor;
- -- all minimal requirements of a data-processing system that is capable of supporting a
- conforming implementation.
-
-
- 1) This International Standard is designed to promote the portability of C programs among a variety of
- data-processing systems. It is intended for use by implementors and programmers.
-
-[<a name="#p1" href="p1">page 1</a>] (<a href="#Contents">Contents</a>)
-
-
-<a name="2" href="#2"><b> 2. Normative references</b></a>
-1 The following referenced documents are indispensable for the application of this
- document. For dated references, only the edition cited applies. For undated references,
- the latest edition of the referenced document (including any amendments) applies.
-2 ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and symbols for
- use in the physical sciences and technology.
-3 ISO/IEC 646, Information technology -- ISO 7-bit coded character set for information
- interchange.
-4 ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1: Fundamental
- terms.
-5 ISO 4217, Codes for the representation of currencies and funds.
-6 ISO 8601, Data elements and interchange formats -- Information interchange --
- Representation of dates and times.
-7 ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded
- Character Set (UCS).
-8 IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems (previously
- designated IEC 559:1989).
-
-
-
-
-[<a name="#p2" href="p2">page 2</a>] (<a href="#Contents">Contents</a>)
-
-
-<a name="3" href="#3"><b> 3. Terms, definitions, and symbols</b></a>
-1 For the purposes of this International Standard, the following definitions apply. Other
- terms are defined where they appear in italic type or on the left side of a syntax rule.
- Terms explicitly defined in this International Standard are not to be presumed to refer
- implicitly to similar terms defined elsewhere. Terms not defined in this International
- Standard are to be interpreted according to ISO/IEC 2382-1. Mathematical symbols not
- defined in this International Standard are to be interpreted according to ISO 31-11.
-<a name="3.1" href="#3.1"><b> 3.1</b></a>
-1 access
- <execution-time action> to read or modify the value of an object
-2 NOTE 1 Where only one of these two actions is meant, ''read'' or ''modify'' is used.
-
-3 NOTE 2 ''Modify'' includes the case where the new value being stored is the same as the previous value.
-
-4 NOTE 3 Expressions that are not evaluated do not access objects.
-
-<a name="3.2" href="#3.2"><b> 3.2</b></a>
-1 alignment
- requirement that objects of a particular type be located on storage boundaries with
- addresses that are particular multiples of a byte address
-<a name="3.3" href="#3.3"><b> 3.3</b></a>
-1 argument
- actual argument
- actual parameter (deprecated)
- expression in the comma-separated list bounded by the parentheses in a function call
- expression, or a sequence of preprocessing tokens in the comma-separated list bounded
- by the parentheses in a function-like macro invocation
-<a name="3.4" href="#3.4"><b> 3.4</b></a>
-1 behavior
- external appearance or action
-<a name="3.4.1" href="#3.4.1"><b> 3.4.1</b></a>
-1 implementation-defined behavior
- unspecified behavior where each implementation documents how the choice is made
-2 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
- when a signed integer is shifted right.
-
-<a name="3.4.2" href="#3.4.2"><b> 3.4.2</b></a>
-1 locale-specific behavior
- behavior that depends on local conventions of nationality, culture, and language that each
- implementation documents
-
-
-[<a name="#p3" href="p3">page 3</a>] (<a href="#Contents">Contents</a>)
-
-2 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
- characters other than the 26 lowercase Latin letters.
-
-<a name="3.4.3" href="#3.4.3"><b> 3.4.3</b></a>
-1 undefined behavior
- behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
- for which this International Standard imposes no requirements
-2 NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable
- results, to behaving during translation or program execution in a documented manner characteristic of the
- environment (with or without the issuance of a diagnostic message), to terminating a translation or
- execution (with the issuance of a diagnostic message).
-
-3 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
-
-<a name="3.4.4" href="#3.4.4"><b> 3.4.4</b></a>
-1 unspecified behavior
- use of an unspecified value, or other behavior where this International Standard provides
- two or more possibilities and imposes no further requirements on which is chosen in any
- instance
-2 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
- evaluated.
-
-<a name="3.5" href="#3.5"><b> 3.5</b></a>
-1 bit
- unit of data storage in the execution environment large enough to hold an object that may
- have one of two values
-2 NOTE It need not be possible to express the address of each individual bit of an object.
-
-<a name="3.6" href="#3.6"><b> 3.6</b></a>
-1 byte
- addressable unit of data storage large enough to hold any member of the basic character
- set of the execution environment
-2 NOTE 1 It is possible to express the address of each individual byte of an object uniquely.
-
-3 NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
- defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order
- bit.
-
-<a name="3.7" href="#3.7"><b> 3.7</b></a>
-1 character
- <abstract> member of a set of elements used for the organization, control, or
- representation of data
-<a name="3.7.1" href="#3.7.1"><b> 3.7.1</b></a>
-1 character
- single-byte character
- <C> bit representation that fits in a byte
-[<a name="#p4" href="p4">page 4</a>] (<a href="#Contents">Contents</a>)
-
-<a name="3.7.2" href="#3.7.2"><b> 3.7.2</b></a>
-1 multibyte character
- sequence of one or more bytes representing a member of the extended character set of
- either the source or the execution environment
-2 NOTE The extended character set is a superset of the basic character set.
-
-<a name="3.7.3" href="#3.7.3"><b> 3.7.3</b></a>
-1 wide character
- bit representation that fits in an object of type wchar_t, capable of representing any
- character in the current locale
-<a name="3.8" href="#3.8"><b> 3.8</b></a>
-1 constraint
- restriction, either syntactic or semantic, by which the exposition of language elements is
- to be interpreted
-<a name="3.9" href="#3.9"><b> 3.9</b></a>
-1 correctly rounded result
- representation in the result format that is nearest in value, subject to the current rounding
- mode, to what the result would be given unlimited range and precision
-<a name="3.10" href="#3.10"><b> 3.10</b></a>
-1 diagnostic message
- message belonging to an implementation-defined subset of the implementation's message
- output
-<a name="3.11" href="#3.11"><b> 3.11</b></a>
-1 forward reference
- reference to a later subclause of this International Standard that contains additional
- information relevant to this subclause
-<a name="3.12" href="#3.12"><b> 3.12</b></a>
-1 implementation
- particular set of software, running in a particular translation environment under particular
- control options, that performs translation of programs for, and supports execution of
- functions in, a particular execution environment
-<a name="3.13" href="#3.13"><b> 3.13</b></a>
-1 implementation limit
- restriction imposed upon programs by the implementation
-<a name="3.14" href="#3.14"><b> 3.14</b></a>
-1 memory location
- either an object of scalar type, or a maximal sequence of adjacent bit-fields all having
- nonzero width
-
-[<a name="#p5" href="p5">page 5</a>] (<a href="#Contents">Contents</a>)
-
-2 NOTE 1 Two threads of execution can update and access separate memory locations without interfering
- with each other.
-
-3 NOTE 2 A bit-field and an adjacent non-bit-field member are in separate memory locations. The same
- applies to two bit-fields, if one is declared inside a nested structure declaration and the other is not, or if the
- two are separated by a zero-length bit-field declaration, or if they are separated by a non-bit-field member
- declaration. It is not safe to concurrently update two non-atomic bit-fields in the same structure if all
- members declared between them are also (non-zero-length) bit-fields, no matter what the sizes of those
- intervening bit-fields happen to be.
-
-4 EXAMPLE A structure declared as
- struct {
- char a;
- int b:5, c:11, :0, d:8;
- struct { int ee:8; } e;
- }
- contains four separate memory locations: The member a, and bit-fields d and e.ee are each separate
- memory locations, and can be modified concurrently without interfering with each other. The bit-fields b
- and c together constitute the fourth memory location. The bit-fields b and c cannot be concurrently
- modified, but b and a, for example, can be.
-
-<a name="3.15" href="#3.15"><b> 3.15</b></a>
-1 object
- region of data storage in the execution environment, the contents of which can represent
- values
-2 NOTE When referenced, an object may be interpreted as having a particular type; see <a href="#6.3.2.1">6.3.2.1</a>.
-
-<a name="3.16" href="#3.16"><b> 3.16</b></a>
-1 parameter
- formal parameter
- formal argument (deprecated)
- object declared as part of a function declaration or definition that acquires a value on
- entry to the function, or an identifier from the comma-separated list bounded by the
- parentheses immediately following the macro name in a function-like macro definition
-<a name="3.17" href="#3.17"><b> 3.17</b></a>
-1 recommended practice
- specification that is strongly recommended as being in keeping with the intent of the
- standard, but that may be impractical for some implementations
-<a name="3.18" href="#3.18"><b> 3.18</b></a>
-1 runtime-constraint
- requirement on a program when calling a library function
-2 NOTE 1 Despite the similar terms, a runtime-constraint is not a kind of constraint as defined by <a href="#3.8">3.8</a>, and
- need not be diagnosed at translation time.
-
-3 NOTE 2 Implementations that support the extensions in <a href="#K">annex K</a> are required to verify that the runtime-
- constraints for a library function are not violated by the program; see <a href="#K.3.1.4">K.3.1.4</a>.
-
-[<a name="#p6" href="p6">page 6</a>] (<a href="#Contents">Contents</a>)
-
-<a name="3.19" href="#3.19"><b> 3.19</b></a>
-1 value
- precise meaning of the contents of an object when interpreted as having a specific type
-<a name="3.19.1" href="#3.19.1"><b> 3.19.1</b></a>
-1 implementation-defined value
- unspecified value where each implementation documents how the choice is made
-<a name="3.19.2" href="#3.19.2"><b> 3.19.2</b></a>
-1 indeterminate value
- either an unspecified value or a trap representation
-<a name="3.19.3" href="#3.19.3"><b> 3.19.3</b></a>
-1 unspecified value
- valid value of the relevant type where this International Standard imposes no
- requirements on which value is chosen in any instance
-2 NOTE An unspecified value cannot be a trap representation.
-
-<a name="3.19.4" href="#3.19.4"><b> 3.19.4</b></a>
-1 trap representation
- an object representation that need not represent a value of the object type
-<a name="3.19.5" href="#3.19.5"><b> 3.19.5</b></a>
-1 perform a trap
- interrupt execution of the program such that no further operations are performed
-2 NOTE In this International Standard, when the word ''trap'' is not immediately followed by
- ''representation'', this is the intended usage.2)
-
-<a name="3.20" href="#3.20"><b> 3.20</b></a>
-1 [^ x^]
- ceiling of x: the least integer greater than or equal to x
-2 EXAMPLE [^2.4^] is 3, [^-2.4^] is -2.
-
-<a name="3.21" href="#3.21"><b> 3.21</b></a>
-1 [_ x_]
- floor of x: the greatest integer less than or equal to x
-2 EXAMPLE [_2.4_] is 2, [_-2.4_] is -3.
-
-
-
-
- 2) For example, ''Trapping or stopping (if supported) is disabled...'' (<a href="#F.8.2">F.8.2</a>). Note that fetching a trap
- representation might perform a trap but is not required to (see <a href="#6.2.6.1">6.2.6.1</a>).
-
-[<a name="#p7" href="p7">page 7</a>] (<a href="#Contents">Contents</a>)
-
-
-<a name="4" href="#4"><b> 4. Conformance</b></a>
-1 In this International Standard, ''shall'' is to be interpreted as a requirement on an
- implementation or on a program; conversely, ''shall not'' is to be interpreted as a
- prohibition.
-2 If a ''shall'' or ''shall not'' requirement that appears outside of a constraint or runtime-
- constraint is violated, the behavior is undefined. Undefined behavior is otherwise
- indicated in this International Standard by the words ''undefined behavior'' or by the
- omission of any explicit definition of behavior. There is no difference in emphasis among
- these three; they all describe ''behavior that is undefined''.
-3 A program that is correct in all other aspects, operating on correct data, containing
- unspecified behavior shall be a correct program and act in accordance with <a href="#5.1.2.3">5.1.2.3</a>.
-4 The implementation shall not successfully translate a preprocessing translation unit
- containing a #error preprocessing directive unless it is part of a group skipped by
- conditional inclusion.
-5 A strictly conforming program shall use only those features of the language and library
- specified in this International Standard.3) It shall not produce output dependent on any
- unspecified, undefined, or implementation-defined behavior, and shall not exceed any
- minimum implementation limit.
-6 The two forms of conforming implementation are hosted and freestanding. A conforming
- hosted implementation shall accept any strictly conforming program. A conforming
- freestanding implementation shall accept any strictly conforming program that does not
- use complex types and in which the use of the features specified in the library clause
- (clause 7) is confined to the contents of the standard headers <a href="#7.7"><float.h></a>,
- <a href="#7.9"><iso646.h></a>, <a href="#7.10"><limits.h></a>, <a href="#7.15"><stdalign.h></a>, <a href="#7.16"><stdarg.h></a>, <a href="#7.18"><stdbool.h></a>,
- <a href="#7.19"><stddef.h></a>, and <a href="#7.20"><stdint.h></a>. A conforming implementation may have extensions
- (including additional library functions), provided they do not alter the behavior of any
- strictly conforming program.4)
-
-
-
- 3) A strictly conforming program can use conditional features (see <a href="#6.10.8.3">6.10.8.3</a>) provided the use is guarded
- by an appropriate conditional inclusion preprocessing directive using the related macro. For example:
- #ifdef __STDC_IEC_559__ /* FE_UPWARD defined */
- /* ... */
- fesetround(FE_UPWARD);
- /* ... */
- #endif
-
- 4) This implies that a conforming implementation reserves no identifiers other than those explicitly
- reserved in this International Standard.
-
-[<a name="#p8" href="p8">page 8</a>] (<a href="#Contents">Contents</a>)
-
-7 A conforming program is one that is acceptable to a conforming implementation.5)
-8 An implementation shall be accompanied by a document that defines all implementation-
- defined and locale-specific characteristics and all extensions.
- Forward references: conditional inclusion (<a href="#6.10.1">6.10.1</a>), error directive (<a href="#6.10.5">6.10.5</a>),
- characteristics of floating types <a href="#7.7"><float.h></a> (<a href="#7.7">7.7</a>), alternative spellings <a href="#7.9"><iso646.h></a>
- (<a href="#7.9">7.9</a>), sizes of integer types <a href="#7.10"><limits.h></a> (<a href="#7.10">7.10</a>), alignment <a href="#7.15"><stdalign.h></a> (<a href="#7.15">7.15</a>),
- variable arguments <a href="#7.16"><stdarg.h></a> (<a href="#7.16">7.16</a>), boolean type and values <a href="#7.18"><stdbool.h></a>
- (<a href="#7.18">7.18</a>), common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>).
-
-
-
-
- 5) Strictly conforming programs are intended to be maximally portable among conforming
- implementations. Conforming programs may depend upon nonportable features of a conforming
- implementation.
-
-[<a name="#p9" href="p9">page 9</a>] (<a href="#Contents">Contents</a>)
-
-
-<a name="5" href="#5"><b> 5. Environment</b></a>
-1 An implementation translates C source files and executes C programs in two data-
- processing-system environments, which will be called the translation environment and
- the execution environment in this International Standard. Their characteristics define and
- constrain the results of executing conforming C programs constructed according to the
- syntactic and semantic rules for conforming implementations.
- Forward references: In this clause, only a few of many possible forward references
- have been noted.
-<a name="5.1" href="#5.1"><b> 5.1 Conceptual models</b></a>
-<a name="5.1.1" href="#5.1.1"><b> 5.1.1 Translation environment</b></a>
-<a name="5.1.1.1" href="#5.1.1.1"><b> 5.1.1.1 Program structure</b></a>
-1 A C program need not all be translated at the same time. The text of the program is kept
- in units called source files, (or preprocessing files) in this International Standard. A
- source file together with all the headers and source files included via the preprocessing
- directive #include is known as a preprocessing translation unit. After preprocessing, a
- preprocessing translation unit is called a translation unit. Previously translated translation
- units may be preserved individually or in libraries. The separate translation units of a
- program communicate by (for example) calls to functions whose identifiers have external
- linkage, manipulation of objects whose identifiers have external linkage, or manipulation
- of data files. Translation units may be separately translated and then later linked to
- produce an executable program.
- Forward references: linkages of identifiers (<a href="#6.2.2">6.2.2</a>), external definitions (<a href="#6.9">6.9</a>),
- preprocessing directives (<a href="#6.10">6.10</a>).
-<a name="5.1.1.2" href="#5.1.1.2"><b> 5.1.1.2 Translation phases</b></a>
-1 The precedence among the syntax rules of translation is specified by the following
- phases.6)
- 1. Physical source file multibyte characters are mapped, in an implementation-
- defined manner, to the source character set (introducing new-line characters for
- end-of-line indicators) if necessary. Trigraph sequences are replaced by
- corresponding single-character internal representations.
-
-
-
- 6) Implementations shall behave as if these separate phases occur, even though many are typically folded
- together in practice. Source files, translation units, and translated translation units need not
- necessarily be stored as files, nor need there be any one-to-one correspondence between these entities
- and any external representation. The description is conceptual only, and does not specify any
- particular implementation.
-
-[<a name="#p10" href="p10">page 10</a>] (<a href="#Contents">Contents</a>)
-
- 2. Each instance of a backslash character (\) immediately followed by a new-line
- character is deleted, splicing physical source lines to form logical source lines.
- Only the last backslash on any physical source line shall be eligible for being part
- of such a splice. A source file that is not empty shall end in a new-line character,
- which shall not be immediately preceded by a backslash character before any such
- splicing takes place.
- 3. The source file is decomposed into preprocessing tokens7) and sequences of
- white-space characters (including comments). A source file shall not end in a
- partial preprocessing token or in a partial comment. Each comment is replaced by
- one space character. New-line characters are retained. Whether each nonempty
- sequence of white-space characters other than new-line is retained or replaced by
- one space character is implementation-defined.
- 4. Preprocessing directives are executed, macro invocations are expanded, and
- _Pragma unary operator expressions are executed. If a character sequence that
- matches the syntax of a universal character name is produced by token
- concatenation (<a href="#6.10.3.3">6.10.3.3</a>), the behavior is undefined. A #include preprocessing
- directive causes the named header or source file to be processed from phase 1
- through phase 4, recursively. All preprocessing directives are then deleted.
- 5. Each source character set member and escape sequence in character constants and
- string literals is converted to the corresponding member of the execution character
- set; if there is no corresponding member, it is converted to an implementation-
- defined member other than the null (wide) character.8)
- 6. Adjacent string literal tokens are concatenated.
- 7. White-space characters separating tokens are no longer significant. Each
- preprocessing token is converted into a token. The resulting tokens are
- syntactically and semantically analyzed and translated as a translation unit.
- 8. All external object and function references are resolved. Library components are
- linked to satisfy external references to functions and objects not defined in the
- current translation. All such translator output is collected into a program image
- which contains information needed for execution in its execution environment.
-Forward references: universal character names (<a href="#6.4.3">6.4.3</a>), lexical elements (<a href="#6.4">6.4</a>),
-preprocessing directives (<a href="#6.10">6.10</a>), trigraph sequences (<a href="#5.2.1.1">5.2.1.1</a>), external definitions (<a href="#6.9">6.9</a>).
-
-
-
-7) As described in <a href="#6.4">6.4</a>, the process of dividing a source file's characters into preprocessing tokens is
- context-dependent. For example, see the handling of < within a #include preprocessing directive.
-8) An implementation need not convert all non-corresponding source characters to the same execution
- character.
-
-[<a name="#p11" href="p11">page 11</a>] (<a href="#Contents">Contents</a>)
-
-<a name="5.1.1.3" href="#5.1.1.3"><b> 5.1.1.3 Diagnostics</b></a>
-1 A conforming implementation shall produce at least one diagnostic message (identified in
- an implementation-defined manner) if a preprocessing translation unit or translation unit
- contains a violation of any syntax rule or constraint, even if the behavior is also explicitly
- specified as undefined or implementation-defined. Diagnostic messages need not be
- produced in other circumstances.9)
-2 EXAMPLE An implementation shall issue a diagnostic for the translation unit:
- char i;
- int i;
- because in those cases where wording in this International Standard describes the behavior for a construct
- as being both a constraint error and resulting in undefined behavior, the constraint error shall be diagnosed.
-
-<a name="5.1.2" href="#5.1.2"><b> 5.1.2 Execution environments</b></a>
-1 Two execution environments are defined: freestanding and hosted. In both cases,
- program startup occurs when a designated C function is called by the execution
- environment. All objects with static storage duration shall be initialized (set to their
- initial values) before program startup. The manner and timing of such initialization are
- otherwise unspecified. Program termination returns control to the execution
- environment.
- Forward references: storage durations of objects (<a href="#6.2.4">6.2.4</a>), initialization (<a href="#6.7.9">6.7.9</a>).
-<a name="5.1.2.1" href="#5.1.2.1"><b> 5.1.2.1 Freestanding environment</b></a>
-1 In a freestanding environment (in which C program execution may take place without any
- benefit of an operating system), the name and type of the function called at program
- startup are implementation-defined. Any library facilities available to a freestanding
- program, other than the minimal set required by clause 4, are implementation-defined.
-2 The effect of program termination in a freestanding environment is implementation-
- defined.
-<a name="5.1.2.2" href="#5.1.2.2"><b> 5.1.2.2 Hosted environment</b></a>
-1 A hosted environment need not be provided, but shall conform to the following
- specifications if present.
-
-
-
-
- 9) The intent is that an implementation should identify the nature of, and where possible localize, each
- violation. Of course, an implementation is free to produce any number of diagnostics as long as a
- valid program is still correctly translated. It may also successfully translate an invalid program.
-
-[<a name="#p12" href="p12">page 12</a>] (<a href="#Contents">Contents</a>)
-
-<a name="5.1.2.2.1" href="#5.1.2.2.1"><b> 5.1.2.2.1 Program startup</b></a>
-1 The function called at program startup is named main. The implementation declares no
- prototype for this function. It shall be defined with a return type of int and with no
- parameters:
- int main(void) { /* ... */ }
- or with two parameters (referred to here as argc and argv, though any names may be
- used, as they are local to the function in which they are declared):
- int main(int argc, char *argv[]) { /* ... */ }
- or equivalent;10) or in some other implementation-defined manner.
-2 If they are declared, the parameters to the main function shall obey the following
- constraints:
- -- The value of argc shall be nonnegative.
- -- argv[argc] shall be a null pointer.
- -- If the value of argc is greater than zero, the array members argv[0] through
- argv[argc-1] inclusive shall contain pointers to strings, which are given
- implementation-defined values by the host environment prior to program startup. The
- intent is to supply to the program information determined prior to program startup
- from elsewhere in the hosted environment. If the host environment is not capable of
- supplying strings with letters in both uppercase and lowercase, the implementation
- shall ensure that the strings are received in lowercase.
- -- If the value of argc is greater than zero, the string pointed to by argv[0]
- represents the program name; argv[0][0] shall be the null character if the
- program name is not available from the host environment. If the value of argc is
- greater than one, the strings pointed to by argv[1] through argv[argc-1]
- represent the program parameters.
- -- The parameters argc and argv and the strings pointed to by the argv array shall
- be modifiable by the program, and retain their last-stored values between program
- startup and program termination.
-<a name="5.1.2.2.2" href="#5.1.2.2.2"><b> 5.1.2.2.2 Program execution</b></a>
-1 In a hosted environment, a program may use all the functions, macros, type definitions,
- and objects described in the library clause (clause 7).
-
-
-
-
- 10) Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as
- char ** argv, and so on.
-
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-
-<a name="5.1.2.2.3" href="#5.1.2.2.3"><b> 5.1.2.2.3 Program termination</b></a>
-1 If the return type of the main function is a type compatible with int, a return from the
- initial call to the main function is equivalent to calling the exit function with the value
- returned by the main function as its argument;11) reaching the } that terminates the
- main function returns a value of 0. If the return type is not compatible with int, the
- termination status returned to the host environment is unspecified.
- Forward references: definition of terms (<a href="#7.1.1">7.1.1</a>), the exit function (<a href="#7.22.4.4">7.22.4.4</a>).
-<a name="5.1.2.3" href="#5.1.2.3"><b> 5.1.2.3 Program execution</b></a>
-1 The semantic descriptions in this International Standard describe the behavior of an
- abstract machine in which issues of optimization are irrelevant.
-2 Accessing a volatile object, modifying an object, modifying a file, or calling a function
- that does any of those operations are all side effects,12) which are changes in the state of
- the execution environment. Evaluation of an expression in general includes both value
- computations and initiation of side effects. Value computation for an lvalue expression
- includes determining the identity of the designated object.
-3 Sequenced before is an asymmetric, transitive, pair-wise relation between evaluations
- executed by a single thread, which induces a partial order among those evaluations.
- Given any two evaluations A and B, if A is sequenced before B, then the execution of A
- shall precede the execution of B. (Conversely, if A is sequenced before B, then B is
- sequenced after A.) If A is not sequenced before or after B, then A and B are
- unsequenced. Evaluations A and B are indeterminately sequenced when A is sequenced
- either before or after B, but it is unspecified which.13) The presence of a sequence point
- between the evaluation of expressions A and B implies that every value computation and
- side effect associated with A is sequenced before every value computation and side effect
- associated with B. (A summary of the sequence points is given in <a href="#C">annex C</a>.)
-4 In the abstract machine, all expressions are evaluated as specified by the semantics. An
- actual implementation need not evaluate part of an expression if it can deduce that its
- value is not used and that no needed side effects are produced (including any caused by
-
- 11) In accordance with <a href="#6.2.4">6.2.4</a>, the lifetimes of objects with automatic storage duration declared in main
- will have ended in the former case, even where they would not have in the latter.
- 12) The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status
- flags and control modes. Floating-point operations implicitly set the status flags; modes affect result
- values of floating-point operations. Implementations that support such floating-point state are
- required to regard changes to it as side effects -- see <a href="#F">annex F</a> for details. The floating-point
- environment library <a href="#7.6"><fenv.h></a> provides a programming facility for indicating when these side
- effects matter, freeing the implementations in other cases.
- 13) The executions of unsequenced evaluations can interleave. Indeterminately sequenced evaluations
- cannot interleave, but can be executed in any order.
-
-[<a name="#p14" href="p14">page 14</a>] (<a href="#Contents">Contents</a>)
-
- calling a function or accessing a volatile object).
-5 When the processing of the abstract machine is interrupted by receipt of a signal, the
- values of objects that are neither lock-free atomic objects nor of type volatile
- sig_atomic_t are unspecified, and the value of any object that is modified by the
- handler that is neither a lock-free atomic object nor of type volatile
- sig_atomic_t becomes undefined.
-6 The least requirements on a conforming implementation are:
- -- Accesses to volatile objects are evaluated strictly according to the rules of the abstract
- machine.
- -- At program termination, all data written into files shall be identical to the result that
- execution of the program according to the abstract semantics would have produced.
- -- The input and output dynamics of interactive devices shall take place as specified in
-<a name="7.21.3" href="#7.21.3"><b> 7.21.3. The intent of these requirements is that unbuffered or line-buffered output</b></a>
- appear as soon as possible, to ensure that prompting messages actually appear prior to
- a program waiting for input.
- This is the observable behavior of the program.
-7 What constitutes an interactive device is implementation-defined.
-8 More stringent correspondences between abstract and actual semantics may be defined by
- each implementation.
-9 EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual
- semantics: at every sequence point, the values of the actual objects would agree with those specified by the
- abstract semantics. The keyword volatile would then be redundant.
-10 Alternatively, an implementation might perform various optimizations within each translation unit, such
- that the actual semantics would agree with the abstract semantics only when making function calls across
- translation unit boundaries. In such an implementation, at the time of each function entry and function
- return where the calling function and the called function are in different translation units, the values of all
- externally linked objects and of all objects accessible via pointers therein would agree with the abstract
- semantics. Furthermore, at the time of each such function entry the values of the parameters of the called
- function and of all objects accessible via pointers therein would agree with the abstract semantics. In this
- type of implementation, objects referred to by interrupt service routines activated by the signal function
- would require explicit specification of volatile storage, as well as other implementation-defined
- restrictions.
-
-11 EXAMPLE 2 In executing the fragment
- char c1, c2;
- /* ... */
- c1 = c1 + c2;
- the ''integer promotions'' require that the abstract machine promote the value of each variable to int size
- and then add the two ints and truncate the sum. Provided the addition of two chars can be done without
- overflow, or with overflow wrapping silently to produce the correct result, the actual execution need only
- produce the same result, possibly omitting the promotions.
-
-[<a name="#p15" href="p15">page 15</a>] (<a href="#Contents">Contents</a>)
-
-12 EXAMPLE 3 Similarly, in the fragment
- float f1, f2;
- double d;
- /* ... */
- f1 = f2 * d;
- the multiplication may be executed using single-precision arithmetic if the implementation can ascertain
- that the result would be the same as if it were executed using double-precision arithmetic (for example, if d
- were replaced by the constant <a href="#2.0">2.0</a>, which has type double).
-
-13 EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate
- semantics. Values are independent of whether they are represented in a register or in memory. For
- example, an implicit spilling of a register is not permitted to alter the value. Also, an explicit store and load
- is required to round to the precision of the storage type. In particular, casts and assignments are required to
- perform their specified conversion. For the fragment
- double d1, d2;
- float f;
- d1 = f = expression;
- d2 = (float) expression;
- the values assigned to d1 and d2 are required to have been converted to float.
-
-14 EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in
- precision as well as range. The implementation cannot generally apply the mathematical associative rules
- for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of
- overflow and underflow. Likewise, implementations cannot generally replace decimal constants in order to
- rearrange expressions. In the following fragment, rearrangements suggested by mathematical rules for real
- numbers are often not valid (see <a href="#F.9">F.9</a>).
- double x, y, z;
- /* ... */
- x = (x * y) * z; // not equivalent to x *= y * z;
- z = (x - y) + y ; // not equivalent to z = x;
- z = x + x * y; // not equivalent to z = x * (<a href="#1.0">1.0</a> + y);
- y = x / <a href="#5.0">5.0</a>; // not equivalent to y = x * 0.2;
-
-15 EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
- int a, b;
- /* ... */
- a = a + 32760 + b + 5;
- the expression statement behaves exactly the same as
- a = (((a + 32760) + b) + 5);
- due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is
- next added to b, and that result is then added to 5 which results in the value assigned to a. On a machine in
- which overflows produce an explicit trap and in which the range of values representable by an int is
- [-32768, +32767], the implementation cannot rewrite this expression as
- a = ((a + b) + 32765);
- since if the values for a and b were, respectively, -32754 and -15, the sum a + b would produce a trap
- while the original expression would not; nor can the expression be rewritten either as
-
-
-[<a name="#p16" href="p16">page 16</a>] (<a href="#Contents">Contents</a>)
-
- a = ((a + 32765) + b);
- or
- a = (a + (b + 32765));
- since the values for a and b might have been, respectively, 4 and -8 or -17 and 12. However, on a machine
- in which overflow silently generates some value and where positive and negative overflows cancel, the
- above expression statement can be rewritten by the implementation in any of the above ways because the
- same result will occur.
-
-16 EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the
- following fragment
- #include <a href="#7.21"><stdio.h></a>
- int sum;
- char *p;
- /* ... */
- sum = sum * 10 - '0' + (*p++ = getchar());
- the expression statement is grouped as if it were written as
- sum = (((sum * 10) - '0') + ((*(p++)) = (getchar())));
- but the actual increment of p can occur at any time between the previous sequence point and the next
- sequence point (the ;), and the call to getchar can occur at any point prior to the need of its returned
- value.
-
- Forward references: expressions (<a href="#6.5">6.5</a>), type qualifiers (<a href="#6.7.3">6.7.3</a>), statements (<a href="#6.8">6.8</a>), the
- signal function (<a href="#7.14">7.14</a>), files (<a href="#7.21.3">7.21.3</a>).
-<a name="5.1.2.4" href="#5.1.2.4"><b> 5.1.2.4 Multi-threaded executions and data races</b></a>
-1 Under a hosted implementation, a program can have more than one thread of execution
- (or thread) running concurrently. The execution of each thread proceeds as defined by
- the remainder of this standard. The execution of the entire program consists of an
- execution of all of its threads.14) Under a freestanding implementation, it is
- implementation-defined whether a program can have more than one thread of execution.
-2 The value of an object visible to a thread T at a particular point is the initial value of the
- object, a value stored in the object by T , or a value stored in the object by another thread,
- according to the rules below.
-3 NOTE 1 In some cases, there may instead be undefined behavior. Much of this section is motivated by
- the desire to support atomic operations with explicit and detailed visibility constraints. However, it also
- implicitly supports a simpler view for more restricted programs.
-
-4 Two expression evaluations conflict if one of them modifies a memory location and the
- other one accesses or modifies the same memory location.
-
-
-
-
- 14) The execution can usually be viewed as an interleaving of all of the threads. However, some kinds of
- atomic operations, for example, allow executions inconsistent with a simple interleaving as described
- below.
-
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-
-5 The library defines a number of atomic operations (<a href="#7.17">7.17</a>) and operations on mutexes
- (<a href="#7.25.4">7.25.4</a>) that are specially identified as synchronization operations. These operations play
- a special role in making assignments in one thread visible to another. A synchronization
- operation on one or more memory locations is either an acquire operation, a release
- operation, both an acquire and release operation, or a consume operation. A
- synchronization operation without an associated memory location is a fence and can be
- either an acquire fence, a release fence, or both an acquire and release fence. In addition,
- there are relaxed atomic operations, which are not synchronization operations, and
- atomic read-modify-write operations, which have special characteristics.
-6 NOTE 2 For example, a call that acquires a mutex will perform an acquire operation on the locations
- composing the mutex. Correspondingly, a call that releases the same mutex will perform a release
- operation on those same locations. Informally, performing a release operation on A forces prior side effects
- on other memory locations to become visible to other threads that later perform an acquire or consume
- operation on A. We do not include relaxed atomic operations as synchronization operations although, like
- synchronization operations, they cannot contribute to data races.
-
-7 All modifications to a particular atomic object M occur in some particular total order,
- called the modification order of M. If A and B are modifications of an atomic object M,
- and A happens before B, then A shall precede B in the modification order of M, which is
- defined below.
-8 NOTE 3 This states that the modification orders must respect the ''happens before'' relation.
-
-9 NOTE 4 There is a separate order for each atomic object. There is no requirement that these can be
- combined into a single total order for all objects. In general this will be impossible since different threads
- may observe modifications to different variables in inconsistent orders.
-
-10 A release sequence on an atomic object M is a maximal contiguous sub-sequence of side
- effects in the modification order of M, where the first operation is a release and every
- subsequent operation either is performed by the same thread that performed the release or
- is an atomic read-modify-write operation.
-11 Certain library calls synchronize with other library calls performed by another thread. In
- particular, an atomic operation A that performs a release operation on an object M
- synchronizes with an atomic operation B that performs an acquire operation on M and
- reads a value written by any side effect in the release sequence headed by A.
-12 NOTE 5 Except in the specified cases, reading a later value does not necessarily ensure visibility as
- described below. Such a requirement would sometimes interfere with efficient implementation.
-
-13 NOTE 6 The specifications of the synchronization operations define when one reads the value written by
- another. For atomic variables, the definition is clear. All operations on a given mutex occur in a single total
- order. Each mutex acquisition ''reads the value written'' by the last mutex release.
-
-14 An evaluation A carries a dependency 15) to an evaluation B if:
-
-
- 15) The ''carries a dependency'' relation is a subset of the ''sequenced before'' relation, and is similarly
- strictly intra-thread.
-
-[<a name="#p18" href="p18">page 18</a>] (<a href="#Contents">Contents</a>)
-
- -- the value of A is used as an operand of B, unless:
- o B is an invocation of the kill_dependency macro,
-
- o A is the left operand of a && or || operator,
-
- o A is the left operand of a ? : operator, or
-
- o A is the left operand of a , operator;
- or
- -- A writes a scalar object or bit-field M, B reads from M the value written by A, and A
- is sequenced before B, or
- -- for some evaluation X, A carries a dependency to X and X carries a dependency to B.
-15 An evaluation A is dependency-ordered before16) an evaluation B if:
- -- A performs a release operation on an atomic object M, and B performs a consume
- operation on M and reads a value written by any side effect in the release sequence
- headed by A, or
- -- for some evaluation X, A is dependency-ordered before X and X carries a
- dependency to B.
-16 An evaluation A inter-thread happens before an evaluation B if A synchronizes with B, A
- is dependency-ordered before B, or, for some evaluation X:
- -- A synchronizes with X and X is sequenced before B,
- -- A is sequenced before X and X inter-thread happens before B, or
- -- A inter-thread happens before X and X inter-thread happens before B.
-17 NOTE 7 The ''inter-thread happens before'' relation describes arbitrary concatenations of ''sequenced
- before'', ''synchronizes with'', and ''dependency-ordered before'' relationships, with two exceptions. The
- first exception is that a concatenation is not permitted to end with ''dependency-ordered before'' followed
- by ''sequenced before''. The reason for this limitation is that a consume operation participating in a
- ''dependency-ordered before'' relationship provides ordering only with respect to operations to which this
- consume operation actually carries a dependency. The reason that this limitation applies only to the end of
- such a concatenation is that any subsequent release operation will provide the required ordering for a prior
- consume operation. The second exception is that a concatenation is not permitted to consist entirely of
- ''sequenced before''. The reasons for this limitation are (1) to permit ''inter-thread happens before'' to be
- transitively closed and (2) the ''happens before'' relation, defined below, provides for relationships
- consisting entirely of ''sequenced before''.
-
-18 An evaluation A happens before an evaluation B if A is sequenced before B or A inter-
- thread happens before B.
-
-
-
- 16) The ''dependency-ordered before'' relation is analogous to the ''synchronizes with'' relation, but uses
- release/consume in place of release/acquire.
-
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-
-19 A visible side effect A on an object M with respect to a value computation B of M
- satisfies the conditions:
- -- A happens before B, and
- -- there is no other side effect X to M such that A happens before X and X happens
- before B.
- The value of a non-atomic scalar object M, as determined by evaluation B, shall be the
- value stored by the visible side effect A.
-20 NOTE 8 If there is ambiguity about which side effect to a non-atomic object is visible, then there is a data
- race and the behavior is undefined.
-
-21 NOTE 9 This states that operations on ordinary variables are not visibly reordered. This is not actually
- detectable without data races, but it is necessary to ensure that data races, as defined here, and with suitable
- restrictions on the use of atomics, correspond to data races in a simple interleaved (sequentially consistent)
- execution.
-
-22 The visible sequence of side effects on an atomic object M, with respect to a value
- computation B of M, is a maximal contiguous sub-sequence of side effects in the
- modification order of M, where the first side effect is visible with respect to B, and for
- every subsequent side effect, it is not the case that B happens before it. The value of an
- atomic object M, as determined by evaluation B, shall be the value stored by some
- operation in the visible sequence of M with respect to B. Furthermore, if a value
- computation A of an atomic object M happens before a value computation B of M, and
- the value computed by A corresponds to the value stored by side effect X, then the value
- computed by B shall either equal the value computed by A, or be the value stored by side
- effect Y , where Y follows X in the modification order of M.
-23 NOTE 10 This effectively disallows compiler reordering of atomic operations to a single object, even if
- both operations are ''relaxed'' loads. By doing so, we effectively make the ''cache coherence'' guarantee
- provided by most hardware available to C atomic operations.
-
-24 NOTE 11 The visible sequence depends on the ''happens before'' relation, which in turn depends on the
- values observed by loads of atomics, which we are restricting here. The intended reading is that there must
- exist an association of atomic loads with modifications they observe that, together with suitably chosen
- modification orders and the ''happens before'' relation derived as described above, satisfy the resulting
- constraints as imposed here.
-
-25 The execution of a program contains a data race if it contains two conflicting actions in
- different threads, at least one of which is not atomic, and neither happens before the
- other. Any such data race results in undefined behavior.
-26 NOTE 12 It can be shown that programs that correctly use simple mutexes and
- memory_order_seq_cst operations to prevent all data races, and use no other synchronization
- operations, behave as though the operations executed by their constituent threads were simply interleaved,
- with each value computation of an object being the last value stored in that interleaving. This is normally
- referred to as ''sequential consistency''. However, this applies only to data-race-free programs, and data-
- race-free programs cannot observe most program transformations that do not change single-threaded
- program semantics. In fact, most single-threaded program transformations continue to be allowed, since
- any program that behaves differently as a result must contain undefined behavior.
-
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-
-27 NOTE 13 Compiler transformations that introduce assignments to a potentially shared memory location
- that would not be modified by the abstract machine are generally precluded by this standard, since such an
- assignment might overwrite another assignment by a different thread in cases in which an abstract machine
- execution would not have encountered a data race. This includes implementations of data member
- assignment that overwrite adjacent members in separate memory locations. We also generally preclude
- reordering of atomic loads in cases in which the atomics in question may alias, since this may violate the
- "visible sequence" rules.
-
-28 NOTE 14 Transformations that introduce a speculative read of a potentially shared memory location may
- not preserve the semantics of the program as defined in this standard, since they potentially introduce a data
- race. However, they are typically valid in the context of an optimizing compiler that targets a specific
- machine with well-defined semantics for data races. They would be invalid for a hypothetical machine that
- is not tolerant of races or provides hardware race detection.
-
-
-
-
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-
-<a name="5.2" href="#5.2"><b> 5.2 Environmental considerations</b></a>
-<a name="5.2.1" href="#5.2.1"><b> 5.2.1 Character sets</b></a>
-1 Two sets of characters and their associated collating sequences shall be defined: the set in
- which source files are written (the source character set), and the set interpreted in the
- execution environment (the execution character set). Each set is further divided into a
- basic character set, whose contents are given by this subclause, and a set of zero or more
- locale-specific members (which are not members of the basic character set) called
- extended characters. The combined set is also called the extended character set. The
- values of the members of the execution character set are implementation-defined.
-2 In a character constant or string literal, members of the execution character set shall be
- represented by corresponding members of the source character set or by escape
- sequences consisting of the backslash \ followed by one or more characters. A byte with
- all bits set to 0, called the null character, shall exist in the basic execution character set; it
- is used to terminate a character string.
-3 Both the basic source and basic execution character sets shall have the following
- members: the 26 uppercase letters of the Latin alphabet
- A B C D E F G H I J K L M
- N O P Q R S T U V W X Y Z
- the 26 lowercase letters of the Latin alphabet
- a b c d e f g h i j k l m
- n o p q r s t u v w x y z
- the 10 decimal digits
- 0 1 2 3 4 5 6 7 8 9
- the following 29 graphic characters
- ! " # % & ' ( ) * + , - . / :
- ; < = > ? [ \ ] ^ _ { | } ~
- the space character, and control characters representing horizontal tab, vertical tab, and
- form feed. The representation of each member of the source and execution basic
- character sets shall fit in a byte. In both the source and execution basic character sets, the
- value of each character after 0 in the above list of decimal digits shall be one greater than
- the value of the previous. In source files, there shall be some way of indicating the end of
- each line of text; this International Standard treats such an end-of-line indicator as if it
- were a single new-line character. In the basic execution character set, there shall be
- control characters representing alert, backspace, carriage return, and new line. If any
- other characters are encountered in a source file (except in an identifier, a character
- constant, a string literal, a header name, a comment, or a preprocessing token that is never
-
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-
- converted to a token), the behavior is undefined.
-4 A letter is an uppercase letter or a lowercase letter as defined above; in this International
- Standard the term does not include other characters that are letters in other alphabets.
-5 The universal character name construct provides a way to name other characters.
- Forward references: universal character names (<a href="#6.4.3">6.4.3</a>), character constants (<a href="#6.4.4.4">6.4.4.4</a>),
- preprocessing directives (<a href="#6.10">6.10</a>), string literals (<a href="#6.4.5">6.4.5</a>), comments (<a href="#6.4.9">6.4.9</a>), string (<a href="#7.1.1">7.1.1</a>).
-<a name="5.2.1.1" href="#5.2.1.1"><b> 5.2.1.1 Trigraph sequences</b></a>
-1 Before any other processing takes place, each occurrence of one of the following
- sequences of three characters (called trigraph sequences17)) is replaced with the
- corresponding single character.
- ??= # ??) ] ??! |
- ??( [ ??' ^ ??> }
- ??/ \ ??< { ??- ~
- No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
- above is not changed.
-2 EXAMPLE 1
- ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)
- becomes
- #define arraycheck(a, b) a[b] || b[a]
-
-3 EXAMPLE 2 The following source line
- printf("Eh???/n");
- becomes (after replacement of the trigraph sequence ??/)
- printf("Eh?\n");
-
-<a name="5.2.1.2" href="#5.2.1.2"><b> 5.2.1.2 Multibyte characters</b></a>
-1 The source character set may contain multibyte characters, used to represent members of
- the extended character set. The execution character set may also contain multibyte
- characters, which need not have the same encoding as for the source character set. For
- both character sets, the following shall hold:
- -- The basic character set shall be present and each character shall be encoded as a
- single byte.
- -- The presence, meaning, and representation of any additional members is locale-
- specific.
-
- 17) The trigraph sequences enable the input of characters that are not defined in the Invariant Code Set as
- described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
-
-[<a name="#p23" href="p23">page 23</a>] (<a href="#Contents">Contents</a>)
-
- -- A multibyte character set may have a state-dependent encoding, wherein each
- sequence of multibyte characters begins in an initial shift state and enters other
- locale-specific shift states when specific multibyte characters are encountered in the
- sequence. While in the initial shift state, all single-byte characters retain their usual
- interpretation and do not alter the shift state. The interpretation for subsequent bytes
- in the sequence is a function of the current shift state.
- -- A byte with all bits zero shall be interpreted as a null character independent of shift
- state. Such a byte shall not occur as part of any other multibyte character.
-2 For source files, the following shall hold:
- -- An identifier, comment, string literal, character constant, or header name shall begin
- and end in the initial shift state.
- -- An identifier, comment, string literal, character constant, or header name shall consist
- of a sequence of valid multibyte characters.
-<a name="5.2.2" href="#5.2.2"><b> 5.2.2 Character display semantics</b></a>
-1 The active position is that location on a display device where the next character output by
- the fputc function would appear. The intent of writing a printing character (as defined
- by the isprint function) to a display device is to display a graphic representation of
- that character at the active position and then advance the active position to the next
- position on the current line. The direction of writing is locale-specific. If the active
- position is at the final position of a line (if there is one), the behavior of the display device
- is unspecified.
-2 Alphabetic escape sequences representing nongraphic characters in the execution
- character set are intended to produce actions on display devices as follows:
- \a (alert) Produces an audible or visible alert without changing the active position.
- \b (backspace) Moves the active position to the previous position on the current line. If
- the active position is at the initial position of a line, the behavior of the display
- device is unspecified.
- \f ( form feed) Moves the active position to the initial position at the start of the next
- logical page.
- \n (new line) Moves the active position to the initial position of the next line.
- \r (carriage return) Moves the active position to the initial position of the current line.
- \t (horizontal tab) Moves the active position to the next horizontal tabulation position
- on the current line. If the active position is at or past the last defined horizontal
- tabulation position, the behavior of the display device is unspecified.
- \v (vertical tab) Moves the active position to the initial position of the next vertical
- tabulation position. If the active position is at or past the last defined vertical
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-
- tabulation position, the behavior of the display device is unspecified.
-3 Each of these escape sequences shall produce a unique implementation-defined value
- which can be stored in a single char object. The external representations in a text file
- need not be identical to the internal representations, and are outside the scope of this
- International Standard.
- Forward references: the isprint function (<a href="#7.4.1.8">7.4.1.8</a>), the fputc function (<a href="#7.21.7.3">7.21.7.3</a>).
-<a name="5.2.3" href="#5.2.3"><b> 5.2.3 Signals and interrupts</b></a>
-1 Functions shall be implemented such that they may be interrupted at any time by a signal,
- or may be called by a signal handler, or both, with no alteration to earlier, but still active,
- invocations' control flow (after the interruption), function return values, or objects with
- automatic storage duration. All such objects shall be maintained outside the function
- image (the instructions that compose the executable representation of a function) on a
- per-invocation basis.
-<a name="5.2.4" href="#5.2.4"><b> 5.2.4 Environmental limits</b></a>
-1 Both the translation and execution environments constrain the implementation of
- language translators and libraries. The following summarizes the language-related
- environmental limits on a conforming implementation; the library-related limits are
- discussed in clause 7.
-<a name="5.2.4.1" href="#5.2.4.1"><b> 5.2.4.1 Translation limits</b></a>
-1 The implementation shall be able to translate and execute at least one program that
- contains at least one instance of every one of the following limits:18)
- -- 127 nesting levels of blocks
- -- 63 nesting levels of conditional inclusion
- -- 12 pointer, array, and function declarators (in any combinations) modifying an
- arithmetic, structure, union, or void type in a declaration
- -- 63 nesting levels of parenthesized declarators within a full declarator
- -- 63 nesting levels of parenthesized expressions within a full expression
- -- 63 significant initial characters in an internal identifier or a macro name (each
- universal character name or extended source character is considered a single
- character)
- -- 31 significant initial characters in an external identifier (each universal character name
- specifying a short identifier of 0000FFFF or less is considered 6 characters, each
-
-
- 18) Implementations should avoid imposing fixed translation limits whenever possible.
-
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-
- universal character name specifying a short identifier of 00010000 or more is
- considered 10 characters, and each extended source character is considered the same
- number of characters as the corresponding universal character name, if any)19)
- -- 4095 external identifiers in one translation unit
- -- 511 identifiers with block scope declared in one block
- -- 4095 macro identifiers simultaneously defined in one preprocessing translation unit
- -- 127 parameters in one function definition
- -- 127 arguments in one function call
- -- 127 parameters in one macro definition
- -- 127 arguments in one macro invocation
- -- 4095 characters in a logical source line
- -- 4095 characters in a string literal (after concatenation)
- -- 65535 bytes in an object (in a hosted environment only)
- -- 15 nesting levels for #included files
- -- 1023 case labels for a switch statement (excluding those for any nested switch
- statements)
- -- 1023 members in a single structure or union
- -- 1023 enumeration constants in a single enumeration
- -- 63 levels of nested structure or union definitions in a single struct-declaration-list
-<a name="5.2.4.2" href="#5.2.4.2"><b> 5.2.4.2 Numerical limits</b></a>
-1 An implementation is required to document all the limits specified in this subclause,
- which are specified in the headers <a href="#7.10"><limits.h></a> and <a href="#7.7"><float.h></a>. Additional limits are
- specified in <a href="#7.20"><stdint.h></a>.
- Forward references: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>).
-<a name="5.2.4.2.1" href="#5.2.4.2.1"><b> 5.2.4.2.1 Sizes of integer types <limits.h></b></a>
-1 The values given below shall be replaced by constant expressions suitable for use in #if
- preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the
- following shall be replaced by expressions that have the same type as would an
- expression that is an object of the corresponding type converted according to the integer
- promotions. Their implementation-defined values shall be equal or greater in magnitude
-
-
- 19) See ''future language directions'' (<a href="#6.11.3">6.11.3</a>).
-
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-
-(absolute value) to those shown, with the same sign.
--- number of bits for smallest object that is not a bit-field (byte)
- CHAR_BIT 8
--- minimum value for an object of type signed char
- SCHAR_MIN -127 // -(27 - 1)
--- maximum value for an object of type signed char
- SCHAR_MAX +127 // 27 - 1
--- maximum value for an object of type unsigned char
- UCHAR_MAX 255 // 28 - 1
--- minimum value for an object of type char
- CHAR_MIN see below
--- maximum value for an object of type char
- CHAR_MAX see below
--- maximum number of bytes in a multibyte character, for any supported locale
- MB_LEN_MAX 1
--- minimum value for an object of type short int
- SHRT_MIN -32767 // -(215 - 1)
--- maximum value for an object of type short int
- SHRT_MAX +32767 // 215 - 1
--- maximum value for an object of type unsigned short int
- USHRT_MAX 65535 // 216 - 1
--- minimum value for an object of type int
- INT_MIN -32767 // -(215 - 1)
--- maximum value for an object of type int
- INT_MAX +32767 // 215 - 1
--- maximum value for an object of type unsigned int
- UINT_MAX 65535 // 216 - 1
--- minimum value for an object of type long int
- LONG_MIN -2147483647 // -(231 - 1)
--- maximum value for an object of type long int
- LONG_MAX +2147483647 // 231 - 1
--- maximum value for an object of type unsigned long int
- ULONG_MAX 4294967295 // 232 - 1
-
-
-[<a name="#p27" href="p27">page 27</a>] (<a href="#Contents">Contents</a>)
-
- -- minimum value for an object of type long long int
- LLONG_MIN -9223372036854775807 // -(263 - 1)
- -- maximum value for an object of type long long int
- LLONG_MAX +9223372036854775807 // 263 - 1
- -- maximum value for an object of type unsigned long long int
- ULLONG_MAX 18446744073709551615 // 264 - 1
-2 If the value of an object of type char is treated as a signed integer when used in an
- expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the
- value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of
- CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of
- UCHAR_MAX.20) The value UCHAR_MAX shall equal 2CHAR_BIT - 1.
- Forward references: representations of types (<a href="#6.2.6">6.2.6</a>), conditional inclusion (<a href="#6.10.1">6.10.1</a>).
-<a name="5.2.4.2.2" href="#5.2.4.2.2"><b> 5.2.4.2.2 Characteristics of floating types <float.h></b></a>
-1 The characteristics of floating types are defined in terms of a model that describes a
- representation of floating-point numbers and values that provide information about an
- implementation's floating-point arithmetic.21) The following parameters are used to
- define the model for each floating-point type:
- s sign ((+-)1)
- b base or radix of exponent representation (an integer > 1)
- e exponent (an integer between a minimum emin and a maximum emax )
- p precision (the number of base-b digits in the significand)
- fk nonnegative integers less than b (the significand digits)
-2 A floating-point number (x) is defined by the following model:
- p
- x = sb e (Sum) f k b-k ,
- k=1
- emin <= e <= emax
-
-3 In addition to normalized floating-point numbers ( f 1 > 0 if x != 0), floating types may be
- able to contain other kinds of floating-point numbers, such as subnormal floating-point
- numbers (x != 0, e = emin , f 1 = 0) and unnormalized floating-point numbers (x != 0,
- e > emin , f 1 = 0), and values that are not floating-point numbers, such as infinities and
- NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates
- through almost every arithmetic operation without raising a floating-point exception; a
- signaling NaN generally raises a floating-point exception when occurring as an
-
-
- 20) See <a href="#6.2.5">6.2.5</a>.
- 21) The floating-point model is intended to clarify the description of each floating-point characteristic and
- does not require the floating-point arithmetic of the implementation to be identical.
-
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-
- arithmetic operand.22)
-4 An implementation may give zero and non-numeric values (such as infinities and NaNs) a
- sign or may leave them unsigned. Wherever such values are unsigned, any requirement
- in this International Standard to retrieve the sign shall produce an unspecified sign, and
- any requirement to set the sign shall be ignored.
-5 The minimum range of representable values for a floating type is the most negative finite
- floating-point number representable in that type through the most positive finite floating-
- point number representable in that type. In addition, if negative infinity is representable
- in a type, the range of that type is extended to all negative real numbers; likewise, if
- positive infinity is representable in a type, the range of that type is extended to all positive
- real numbers.
-6 The accuracy of the floating-point operations (+, -, *, /) and of the library functions in
- <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results is implementation-
- defined, as is the accuracy of the conversion between floating-point internal
- representations and string representations performed by the library functions in
- <a href="#7.21"><stdio.h></a>, <a href="#7.22"><stdlib.h></a>, and <a href="#7.28"><wchar.h></a>. The implementation may state that the
- accuracy is unknown.
-7 All integer values in the <a href="#7.7"><float.h></a> header, except FLT_ROUNDS, shall be constant
- expressions suitable for use in #if preprocessing directives; all floating values shall be
- constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
- and FLT_ROUNDS have separate names for all three floating-point types. The floating-
- point model representation is provided for all values except FLT_EVAL_METHOD and
- FLT_ROUNDS.
-8 The rounding mode for floating-point addition is characterized by the implementation-
- defined value of FLT_ROUNDS:23)
- -1 indeterminable
- 0 toward zero
- 1 to nearest
- 2 toward positive infinity
- 3 toward negative infinity
- All other values for FLT_ROUNDS characterize implementation-defined rounding
- behavior.
-
-
- 22) IEC 60559:1989 specifies quiet and signaling NaNs. For implementations that do not support
- IEC 60559:1989, the terms quiet NaN and signaling NaN are intended to apply to encodings with
- similar behavior.
- 23) Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
- the function fesetround in <a href="#7.6"><fenv.h></a>.
-
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-
-9 Except for assignment and cast (which remove all extra range and precision), the values
- yielded by operators with floating operands and values subject to the usual arithmetic
- conversions and of floating constants are evaluated to a format whose range and precision
- may be greater than required by the type. The use of evaluation formats is characterized
- by the implementation-defined value of FLT_EVAL_METHOD:24)
- -1 indeterminable;
- 0 evaluate all operations and constants just to the range and precision of the
- type;
- 1 evaluate operations and constants of type float and double to the
- range and precision of the double type, evaluate long double
- operations and constants to the range and precision of the long double
- type;
- 2 evaluate all operations and constants to the range and precision of the
- long double type.
- All other negative values for FLT_EVAL_METHOD characterize implementation-defined
- behavior.
-10 The presence or absence of subnormal numbers is characterized by the implementation-
- defined values of FLT_HAS_SUBNORM, DBL_HAS_SUBNORM, and
- LDBL_HAS_SUBNORM:
- -1 indeterminable25)
- 0 absent26) (type does not support subnormal numbers)
- 1 present (type does support subnormal numbers)
-11 The values given in the following list shall be replaced by constant expressions with
- implementation-defined values that are greater or equal in magnitude (absolute value) to
- those shown, with the same sign:
- -- radix of exponent representation, b
- FLT_RADIX 2
-
-
-
-
- 24) The evaluation method determines evaluation formats of expressions involving all floating types, not
- just real types. For example, if FLT_EVAL_METHOD is 1, then the product of two float
- _Complex operands is represented in the double _Complex format, and its parts are evaluated to
- double.
- 25) Characterization as indeterminable is intended if floating-point operations do not consistently interpret
- subnormal representations as zero, nor as nonzero.
- 26) Characterization as absent is intended if no floating-point operations produce subnormal results from
- non-subnormal inputs, even if the type format includes representations of subnormal numbers.
-
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-
--- number of base-FLT_RADIX digits in the floating-point significand, p
- FLT_MANT_DIG
- DBL_MANT_DIG
- LDBL_MANT_DIG
--- number of decimal digits, n, such that any floating-point number with p radix b digits
- can be rounded to a floating-point number with n decimal digits and back again
- without change to the value,
- { p log10 b if b is a power of 10
- {
- { [^1 + p log10 b^] otherwise
- FLT_DECIMAL_DIG 6
- DBL_DECIMAL_DIG 10
- LDBL_DECIMAL_DIG 10
--- number of decimal digits, n, such that any floating-point number in the widest
- supported floating type with pmax radix b digits can be rounded to a floating-point
- number with n decimal digits and back again without change to the value,
- { pmax log10 b if b is a power of 10
- {
- { [^1 + pmax log10 b^] otherwise
- DECIMAL_DIG 10
--- number of decimal digits, q, such that any floating-point number with q decimal digits
- can be rounded into a floating-point number with p radix b digits and back again
- without change to the q decimal digits,
- { p log10 b if b is a power of 10
- {
- { [_( p - 1) log10 b_] otherwise
- FLT_DIG 6
- DBL_DIG 10
- LDBL_DIG 10
--- minimum negative integer such that FLT_RADIX raised to one less than that power is
- a normalized floating-point number, emin
- FLT_MIN_EXP
- DBL_MIN_EXP
- LDBL_MIN_EXP
-
-
-
-
-[<a name="#p31" href="p31">page 31</a>] (<a href="#Contents">Contents</a>)
-
- -- minimum negative integer such that 10 raised to that power is in the range of
- normalized floating-point numbers, [^log10 b emin -1 ^]
- [ ]
- FLT_MIN_10_EXP -37
- DBL_MIN_10_EXP -37
- LDBL_MIN_10_EXP -37
- -- maximum integer such that FLT_RADIX raised to one less than that power is a
- representable finite floating-point number, emax
- FLT_MAX_EXP
- DBL_MAX_EXP
- LDBL_MAX_EXP
- -- maximum integer such that 10 raised to that power is in the range of representable
- finite floating-point numbers, [_log10 ((1 - b- p )b emax )_]
- FLT_MAX_10_EXP +37
- DBL_MAX_10_EXP +37
- LDBL_MAX_10_EXP +37
-12 The values given in the following list shall be replaced by constant expressions with
- implementation-defined values that are greater than or equal to those shown:
- -- maximum representable finite floating-point number, (1 - b- p )b emax
- FLT_MAX 1E+37
- DBL_MAX 1E+37
- LDBL_MAX 1E+37
-13 The values given in the following list shall be replaced by constant expressions with
- implementation-defined (positive) values that are less than or equal to those shown:
- -- the difference between 1 and the least value greater than 1 that is representable in the
- given floating point type, b1- p
- FLT_EPSILON 1E-5
- DBL_EPSILON 1E-9
- LDBL_EPSILON 1E-9
- -- minimum normalized positive floating-point number, b emin -1
- FLT_MIN 1E-37
- DBL_MIN 1E-37
- LDBL_MIN 1E-37
-
-
-
-
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-
- -- minimum positive floating-point number27)
- FLT_TRUE_MIN 1E-37
- DBL_TRUE_MIN 1E-37
- LDBL_TRUE_MIN 1E-37
- Recommended practice
-14 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
- should be the identity function.
-15 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
- requirements of this International Standard, and the appropriate values in a <a href="#7.7"><float.h></a> header for type
- float:
- 6
- x = s16e (Sum) f k 16-k ,
- k=1
- -31 <= e <= +32
-
- FLT_RADIX 16
- FLT_MANT_DIG 6
- FLT_EPSILON 9.53674316E-07F
- FLT_DECIMAL_DIG 9
- FLT_DIG 6
- FLT_MIN_EXP -31
- FLT_MIN 2.93873588E-39F
- FLT_MIN_10_EXP -38
- FLT_MAX_EXP +32
- FLT_MAX 3.40282347E+38F
- FLT_MAX_10_EXP +38
-
-16 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
- single-precision and double-precision numbers in IEC 60559,28) and the appropriate values in a
- <a href="#7.7"><float.h></a> header for types float and double:
- 24
- x f = s2e (Sum) f k 2-k ,
- k=1
- -125 <= e <= +128
-
- 53
- x d = s2e (Sum) f k 2-k ,
- k=1
- -1021 <= e <= +1024
-
- FLT_RADIX 2
- DECIMAL_DIG 17
- FLT_MANT_DIG 24
- FLT_EPSILON 1.19209290E-07F // decimal constant
- FLT_EPSILON 0X1P-23F // hex constant
- FLT_DECIMAL_DIG 9
-
-
- 27) If the presence or absence of subnormal numbers is indeterminable, then the value is intended to be a
- positive number no greater than the minimum normalized positive number for the type.
- 28) The floating-point model in that standard sums powers of b from zero, so the values of the exponent
- limits are one less than shown here.
-
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-
- FLT_DIG 6
- FLT_MIN_EXP -125
- FLT_MIN 1.17549435E-38F // decimal constant
- FLT_MIN 0X1P-126F // hex constant
- FLT_TRUE_MIN 1.40129846E-45F // decimal constant
- FLT_TRUE_MIN 0X1P-149F // hex constant
- FLT_HAS_SUBNORM 1
- FLT_MIN_10_EXP -37
- FLT_MAX_EXP +128
- FLT_MAX 3.40282347E+38F // decimal constant
- FLT_MAX 0X1.fffffeP127F // hex constant
- FLT_MAX_10_EXP +38
- DBL_MANT_DIG 53
- DBL_EPSILON 2.2204460492503131E-16 // decimal constant
- DBL_EPSILON 0X1P-52 // hex constant
- DBL_DECIMAL_DIG 17
- DBL_DIG 15
- DBL_MIN_EXP -1021
- DBL_MIN 2.2250738585072014E-308 // decimal constant
- DBL_MIN 0X1P-1022 // hex constant
- DBL_TRUE_MIN 4.9406564584124654E-324 // decimal constant
- DBL_TRUE_MIN 0X1P-1074 // hex constant
- DBL_HAS_SUBNORM 1
- DBL_MIN_10_EXP -307
- DBL_MAX_EXP +1024
- DBL_MAX 1.7976931348623157E+308 // decimal constant
- DBL_MAX 0X1.fffffffffffffP1023 // hex constant
- DBL_MAX_10_EXP +308
-If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
-example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
-precision), then DECIMAL_DIG would be 21.
-
-Forward references: conditional inclusion (<a href="#6.10.1">6.10.1</a>), complex arithmetic
-<a href="#7.3"><complex.h></a> (<a href="#7.3">7.3</a>), extended multibyte and wide character utilities <a href="#7.28"><wchar.h></a>
-(<a href="#7.28">7.28</a>), floating-point environment <a href="#7.6"><fenv.h></a> (<a href="#7.6">7.6</a>), general utilities <a href="#7.22"><stdlib.h></a>
-(<a href="#7.22">7.22</a>), input/output <a href="#7.21"><stdio.h></a> (<a href="#7.21">7.21</a>), mathematics <a href="#7.12"><math.h></a> (<a href="#7.12">7.12</a>).
-
-
-
-
-[<a name="#p34" href="p34">page 34</a>] (<a href="#Contents">Contents</a>)
-
-
-<a name="6" href="#6"><b> 6. Language</b></a>
-<a name="6.1" href="#6.1"><b> 6.1 Notation</b></a>
-1 In the syntax notation used in this clause, syntactic categories (nonterminals) are
- indicated by italic type, and literal words and character set members (terminals) by bold
- type. A colon (:) following a nonterminal introduces its definition. Alternative
- definitions are listed on separate lines, except when prefaced by the words ''one of''. An
- optional symbol is indicated by the subscript ''opt'', so that
- { expressionopt }
- indicates an optional expression enclosed in braces.
-2 When syntactic categories are referred to in the main text, they are not italicized and
- words are separated by spaces instead of hyphens.
-3 A summary of the language syntax is given in <a href="#A">annex A</a>.
-<a name="6.2" href="#6.2"><b> 6.2 Concepts</b></a>
-<a name="6.2.1" href="#6.2.1"><b> 6.2.1 Scopes of identifiers</b></a>
-1 An identifier can denote an object; a function; a tag or a member of a structure, union, or
- enumeration; a typedef name; a label name; a macro name; or a macro parameter. The
- same identifier can denote different entities at different points in the program. A member
- of an enumeration is called an enumeration constant. Macro names and macro
- parameters are not considered further here, because prior to the semantic phase of
- program translation any occurrences of macro names in the source file are replaced by the
- preprocessing token sequences that constitute their macro definitions.
-2 For each different entity that an identifier designates, the identifier is visible (i.e., can be
- used) only within a region of program text called its scope. Different entities designated
- by the same identifier either have different scopes, or are in different name spaces. There
- are four kinds of scopes: function, file, block, and function prototype. (A function
- prototype is a declaration of a function that declares the types of its parameters.)
-3 A label name is the only kind of identifier that has function scope. It can be used (in a
- goto statement) anywhere in the function in which it appears, and is declared implicitly
- by its syntactic appearance (followed by a : and a statement).
-4 Every other identifier has scope determined by the placement of its declaration (in a
- declarator or type specifier). If the declarator or type specifier that declares the identifier
- appears outside of any block or list of parameters, the identifier has file scope, which
- terminates at the end of the translation unit. If the declarator or type specifier that
- declares the identifier appears inside a block or within the list of parameter declarations in
- a function definition, the identifier has block scope, which terminates at the end of the
- associated block. If the declarator or type specifier that declares the identifier appears
-
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-
- within the list of parameter declarations in a function prototype (not part of a function
- definition), the identifier has function prototype scope, which terminates at the end of the
- function declarator. If an identifier designates two different entities in the same name
- space, the scopes might overlap. If so, the scope of one entity (the inner scope) will end
- strictly before the scope of the other entity (the outer scope). Within the inner scope, the
- identifier designates the entity declared in the inner scope; the entity declared in the outer
- scope is hidden (and not visible) within the inner scope.
-5 Unless explicitly stated otherwise, where this International Standard uses the term
- ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the
- entity in the relevant name space whose declaration is visible at the point the identifier
- occurs.
-6 Two identifiers have the same scope if and only if their scopes terminate at the same
- point.
-7 Structure, union, and enumeration tags have scope that begins just after the appearance of
- the tag in a type specifier that declares the tag. Each enumeration constant has scope that
- begins just after the appearance of its defining enumerator in an enumerator list. Any
- other identifier has scope that begins just after the completion of its declarator.
-8 As a special case, a type name (which is not a declaration of an identifier) is considered to
- have a scope that begins just after the place within the type name where the omitted
- identifier would appear were it not omitted.
- Forward references: declarations (<a href="#6.7">6.7</a>), function calls (<a href="#6.5.2.2">6.5.2.2</a>), function definitions
- (<a href="#6.9.1">6.9.1</a>), identifiers (<a href="#6.4.2">6.4.2</a>), macro replacement (<a href="#6.10.3">6.10.3</a>), name spaces of identifiers (<a href="#6.2.3">6.2.3</a>),
- source file inclusion (<a href="#6.10.2">6.10.2</a>), statements (<a href="#6.8">6.8</a>).
-<a name="6.2.2" href="#6.2.2"><b> 6.2.2 Linkages of identifiers</b></a>
-1 An identifier declared in different scopes or in the same scope more than once can be
- made to refer to the same object or function by a process called linkage.29) There are
- three kinds of linkage: external, internal, and none.
-2 In the set of translation units and libraries that constitutes an entire program, each
- declaration of a particular identifier with external linkage denotes the same object or
- function. Within one translation unit, each declaration of an identifier with internal
- linkage denotes the same object or function. Each declaration of an identifier with no
- linkage denotes a unique entity.
-3 If the declaration of a file scope identifier for an object or a function contains the storage-
- class specifier static, the identifier has internal linkage.30)
-
-
-
- 29) There is no linkage between different identifiers.
-
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-
-4 For an identifier declared with the storage-class specifier extern in a scope in which a
- prior declaration of that identifier is visible,31) if the prior declaration specifies internal or
- external linkage, the linkage of the identifier at the later declaration is the same as the
- linkage specified at the prior declaration. If no prior declaration is visible, or if the prior
- declaration specifies no linkage, then the identifier has external linkage.
-5 If the declaration of an identifier for a function has no storage-class specifier, its linkage
- is determined exactly as if it were declared with the storage-class specifier extern. If
- the declaration of an identifier for an object has file scope and no storage-class specifier,
- its linkage is external.
-6 The following identifiers have no linkage: an identifier declared to be anything other than
- an object or a function; an identifier declared to be a function parameter; a block scope
- identifier for an object declared without the storage-class specifier extern.
-7 If, within a translation unit, the same identifier appears with both internal and external
- linkage, the behavior is undefined.
- Forward references: declarations (<a href="#6.7">6.7</a>), expressions (<a href="#6.5">6.5</a>), external definitions (<a href="#6.9">6.9</a>),
- statements (<a href="#6.8">6.8</a>).
-<a name="6.2.3" href="#6.2.3"><b> 6.2.3 Name spaces of identifiers</b></a>
-1 If more than one declaration of a particular identifier is visible at any point in a
- translation unit, the syntactic context disambiguates uses that refer to different entities.
- Thus, there are separate name spaces for various categories of identifiers, as follows:
- -- label names (disambiguated by the syntax of the label declaration and use);
- -- the tags of structures, unions, and enumerations (disambiguated by following any32)
- of the keywords struct, union, or enum);
- -- the members of structures or unions; each structure or union has a separate name
- space for its members (disambiguated by the type of the expression used to access the
- member via the . or -> operator);
- -- all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
- enumeration constants).
- Forward references: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), labeled statements (<a href="#6.8.1">6.8.1</a>),
- structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), structure and union members (<a href="#6.5.2.3">6.5.2.3</a>), tags
- (<a href="#6.7.2.3">6.7.2.3</a>), the goto statement (<a href="#6.8.6.1">6.8.6.1</a>).
-
- 30) A function declaration can contain the storage-class specifier static only if it is at file scope; see
-<a name="6.7.1" href="#6.7.1"><b> 6.7.1.</b></a>
- 31) As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
- 32) There is only one name space for tags even though three are possible.
-
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-
-<a name="6.2.4" href="#6.2.4"><b> 6.2.4 Storage durations of objects</b></a>
-1 An object has a storage duration that determines its lifetime. There are four storage
- durations: static, thread, automatic, and allocated. Allocated storage is described in
-<a name="7.22.3" href="#7.22.3"><b> 7.22.3.</b></a>
-2 The lifetime of an object is the portion of program execution during which storage is
- guaranteed to be reserved for it. An object exists, has a constant address,33) and retains
- its last-stored value throughout its lifetime.34) If an object is referred to outside of its
- lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
- the object it points to (or just past) reaches the end of its lifetime.
-3 An object whose identifier is declared without the storage-class specifier
- _Thread_local, and either with external or internal linkage or with the storage-class
- specifier static, has static storage duration. Its lifetime is the entire execution of the
- program and its stored value is initialized only once, prior to program startup.
-4 An object whose identifier is declared with the storage-class specifier _Thread_local
- has thread storage duration. Its lifetime is the entire execution of the thread for which it
- is created, and its stored value is initialized when the thread is started. There is a distinct
- object per thread, and use of the declared name in an expression refers to the object
- associated with the thread evaluating the expression. The result of attempting to
- indirectly access an object with thread storage duration from a thread other than the one
- with which the object is associated is implementation-defined.
-5 An object whose identifier is declared with no linkage and without the storage-class
- specifier static has automatic storage duration, as do some compound literals. The
- result of attempting to indirectly access an object with automatic storage duration from a
- thread other than the one with which the object is associated is implementation-defined.
-6 For such an object that does not have a variable length array type, its lifetime extends
- from entry into the block with which it is associated until execution of that block ends in
- any way. (Entering an enclosed block or calling a function suspends, but does not end,
- execution of the current block.) If the block is entered recursively, a new instance of the
- object is created each time. The initial value of the object is indeterminate. If an
- initialization is specified for the object, it is performed each time the declaration or
- compound literal is reached in the execution of the block; otherwise, the value becomes
- indeterminate each time the declaration is reached.
-
-
-
- 33) The term ''constant address'' means that two pointers to the object constructed at possibly different
- times will compare equal. The address may be different during two different executions of the same
- program.
- 34) In the case of a volatile object, the last store need not be explicit in the program.
-
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-
-7 For such an object that does have a variable length array type, its lifetime extends from
- the declaration of the object until execution of the program leaves the scope of the
- declaration.35) If the scope is entered recursively, a new instance of the object is created
- each time. The initial value of the object is indeterminate.
-8 A non-lvalue expression with structure or union type, where the structure or union
- contains a member with array type (including, recursively, members of all contained
- structures and unions) refers to an object with automatic storage duration and temporary
- lifetime.36) Its lifetime begins when the expression is evaluated and its initial value is the
- value of the expression. Its lifetime ends when the evaluation of the containing full
- expression or full declarator ends. Any attempt to modify an object with temporary
- lifetime results in undefined behavior.
- Forward references: array declarators (<a href="#6.7.6.2">6.7.6.2</a>), compound literals (<a href="#6.5.2.5">6.5.2.5</a>), declarators
- (<a href="#6.7.6">6.7.6</a>), function calls (<a href="#6.5.2.2">6.5.2.2</a>), initialization (<a href="#6.7.9">6.7.9</a>), statements (<a href="#6.8">6.8</a>).
-<a name="6.2.5" href="#6.2.5"><b> 6.2.5 Types</b></a>
-1 The meaning of a value stored in an object or returned by a function is determined by the
- type of the expression used to access it. (An identifier declared to be an object is the
- simplest such expression; the type is specified in the declaration of the identifier.) Types
- are partitioned into object types (types that describe objects) and function types (types
- that describe functions). At various points within a translation unit an object type may be
- incomplete (lacking sufficient information to determine the size of objects of that type) or
- complete (having sufficient information).37)
-2 An object declared as type _Bool is large enough to store the values 0 and 1.
-3 An object declared as type char is large enough to store any member of the basic
- execution character set. If a member of the basic execution character set is stored in a
- char object, its value is guaranteed to be nonnegative. If any other character is stored in
- a char object, the resulting value is implementation-defined but shall be within the range
- of values that can be represented in that type.
-4 There are five standard signed integer types, designated as signed char, short
- int, int, long int, and long long int. (These and other types may be
- designated in several additional ways, as described in <a href="#6.7.2">6.7.2</a>.) There may also be
- implementation-defined extended signed integer types.38) The standard and extended
- signed integer types are collectively called signed integer types.39)
-
- 35) Leaving the innermost block containing the declaration, or jumping to a point in that block or an
- embedded block prior to the declaration, leaves the scope of the declaration.
- 36) The address of such an object is taken implicitly when an array member is accessed.
- 37) A type may be incomplete or complete throughout an entire translation unit, or it may change states at
- different points within a translation unit.
-
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-
-5 An object declared as type signed char occupies the same amount of storage as a
- ''plain'' char object. A ''plain'' int object has the natural size suggested by the
- architecture of the execution environment (large enough to contain any value in the range
- INT_MIN to INT_MAX as defined in the header <a href="#7.10"><limits.h></a>).
-6 For each of the signed integer types, there is a corresponding (but different) unsigned
- integer type (designated with the keyword unsigned) that uses the same amount of
- storage (including sign information) and has the same alignment requirements. The type
- _Bool and the unsigned integer types that correspond to the standard signed integer
- types are the standard unsigned integer types. The unsigned integer types that
- correspond to the extended signed integer types are the extended unsigned integer types.
- The standard and extended unsigned integer types are collectively called unsigned integer
- types.40)
-7 The standard signed integer types and standard unsigned integer types are collectively
- called the standard integer types, the extended signed integer types and extended
- unsigned integer types are collectively called the extended integer types.
-8 For any two integer types with the same signedness and different integer conversion rank
- (see <a href="#6.3.1.1">6.3.1.1</a>), the range of values of the type with smaller integer conversion rank is a
- subrange of the values of the other type.
-9 The range of nonnegative values of a signed integer type is a subrange of the
- corresponding unsigned integer type, and the representation of the same value in each
- type is the same.41) A computation involving unsigned operands can never overflow,
- because a result that cannot be represented by the resulting unsigned integer type is
- reduced modulo the number that is one greater than the largest value that can be
- represented by the resulting type.
-10 There are three real floating types, designated as float, double, and long
- double.42) The set of values of the type float is a subset of the set of values of the
- type double; the set of values of the type double is a subset of the set of values of the
- type long double.
-
-
- 38) Implementation-defined keywords shall have the form of an identifier reserved for any use as
- described in <a href="#7.1.3">7.1.3</a>.
- 39) Therefore, any statement in this Standard about signed integer types also applies to the extended
- signed integer types.
- 40) Therefore, any statement in this Standard about unsigned integer types also applies to the extended
- unsigned integer types.
- 41) The same representation and alignment requirements are meant to imply interchangeability as
- arguments to functions, return values from functions, and members of unions.
- 42) See ''future language directions'' (<a href="#6.11.1">6.11.1</a>).
-
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-
-11 There are three complex types, designated as float _Complex, double
- _Complex, and long double _Complex.43) (Complex types are a conditional
- feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.) The real floating and
- complex types are collectively called the floating types.
-12 For each floating type there is a corresponding real type, which is always a real floating
- type. For real floating types, it is the same type. For complex types, it is the type given
- by deleting the keyword _Complex from the type name.
-13 Each complex type has the same representation and alignment requirements as an array
- type containing exactly two elements of the corresponding real type; the first element is
- equal to the real part, and the second element to the imaginary part, of the complex
- number.
-14 The type char, the signed and unsigned integer types, and the floating types are
- collectively called the basic types. The basic types are complete object types. Even if the
- implementation defines two or more basic types to have the same representation, they are
- nevertheless different types.44)
-15 The three types char, signed char, and unsigned char are collectively called
- the character types. The implementation shall define char to have the same range,
- representation, and behavior as either signed char or unsigned char.45)
-16 An enumeration comprises a set of named integer constant values. Each distinct
- enumeration constitutes a different enumerated type.
-17 The type char, the signed and unsigned integer types, and the enumerated types are
- collectively called integer types. The integer and real floating types are collectively called
- real types.
-18 Integer and floating types are collectively called arithmetic types. Each arithmetic type
- belongs to one type domain: the real type domain comprises the real types, the complex
- type domain comprises the complex types.
-19 The void type comprises an empty set of values; it is an incomplete object type that
- cannot be completed.
-
-
-
- 43) A specification for imaginary types is in informative <a href="#G">annex G</a>.
- 44) An implementation may define new keywords that provide alternative ways to designate a basic (or
- any other) type; this does not violate the requirement that all basic types be different.
- Implementation-defined keywords shall have the form of an identifier reserved for any use as
- described in <a href="#7.1.3">7.1.3</a>.
- 45) CHAR_MIN, defined in <a href="#7.10"><limits.h></a>, will have one of the values 0 or SCHAR_MIN, and this can be
- used to distinguish the two options. Irrespective of the choice made, char is a separate type from the
- other two and is not compatible with either.
-
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-
-20 Any number of derived types can be constructed from the object and function types, as
- follows:
- -- An array type describes a contiguously allocated nonempty set of objects with a
- particular member object type, called the element type. The element type shall be
- complete whenever the array type is specified. Array types are characterized by their
- element type and by the number of elements in the array. An array type is said to be
- derived from its element type, and if its element type is T , the array type is sometimes
- called ''array of T ''. The construction of an array type from an element type is called
- ''array type derivation''.
- -- A structure type describes a sequentially allocated nonempty set of member objects
- (and, in certain circumstances, an incomplete array), each of which has an optionally
- specified name and possibly distinct type.
- -- A union type describes an overlapping nonempty set of member objects, each of
- which has an optionally specified name and possibly distinct type.
- -- A function type describes a function with specified return type. A function type is
- characterized by its return type and the number and types of its parameters. A
- function type is said to be derived from its return type, and if its return type is T , the
- function type is sometimes called ''function returning T ''. The construction of a
- function type from a return type is called ''function type derivation''.
- -- A pointer type may be derived from a function type or an object type, called the
- referenced type. A pointer type describes an object whose value provides a reference
- to an entity of the referenced type. A pointer type derived from the referenced type T
- is sometimes called ''pointer to T ''. The construction of a pointer type from a
- referenced type is called ''pointer type derivation''. A pointer type is a complete
- object type.
- These methods of constructing derived types can be applied recursively.
-21 Arithmetic types and pointer types are collectively called scalar types. Array and
- structure types are collectively called aggregate types.46)
-22 An array type of unknown size is an incomplete type. It is completed, for an identifier of
- that type, by specifying the size in a later declaration (with internal or external linkage).
- A structure or union type of unknown content (as described in <a href="#6.7.2.3">6.7.2.3</a>) is an incomplete
- type. It is completed, for all declarations of that type, by declaring the same structure or
- union tag with its defining content later in the same scope.
-
-
-
-
- 46) Note that aggregate type does not include union type because an object with union type can only
- contain one member at a time.
-
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-
-23 A type has known constant size if the type is not incomplete and is not a variable length
- array type.
-24 Array, function, and pointer types are collectively called derived declarator types. A
- declarator type derivation from a type T is the construction of a derived declarator type
- from T by the application of an array-type, a function-type, or a pointer-type derivation to
- T.
-25 A type is characterized by its type category, which is either the outermost derivation of a
- derived type (as noted above in the construction of derived types), or the type itself if the
- type consists of no derived types.
-26 Any type so far mentioned is an unqualified type. Each unqualified type has several
- qualified versions of its type,47) corresponding to the combinations of one, two, or all
- three of the const, volatile, and restrict qualifiers. The qualified or unqualified
- versions of a type are distinct types that belong to the same type category and have the
- same representation and alignment requirements.48) A derived type is not qualified by the
- qualifiers (if any) of the type from which it is derived.
-27 Further, there is the _Atomic qualifier, which may combine with volatile and
- restrict. The size, representation, and alignment of an _Atomic-qualified type need
- not be the same as those of the corresponding unqualified type. (Atomic types are a
- conditional feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.)
-28 A pointer to void shall have the same representation and alignment requirements as a
- pointer to a character type.48) Similarly, pointers to qualified or unqualified versions of
- compatible types shall have the same representation and alignment requirements. All
- pointers to structure types shall have the same representation and alignment requirements
- as each other. All pointers to union types shall have the same representation and
- alignment requirements as each other. Pointers to other types need not have the same
- representation or alignment requirements.
-29 EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is
- pointer, not a floating type. The const-qualified version of this type is designated as ''float * const''
- whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const-
- qualified float'' and is a pointer to a qualified type.
-
-30 EXAMPLE 2 The type designated as ''struct tag (*[5])(float)'' has type ''array of pointer to
- function returning struct tag''. The array has length five and the function has a single parameter of type
- float. Its type category is array.
-
- Forward references: compatible type and composite type (<a href="#6.2.7">6.2.7</a>), declarations (<a href="#6.7">6.7</a>).
-
-
-
- 47) See <a href="#6.7.3">6.7.3</a> regarding qualified array and function types.
- 48) The same representation and alignment requirements are meant to imply interchangeability as
- arguments to functions, return values from functions, and members of unions.
-
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-
-<a name="6.2.6" href="#6.2.6"><b> 6.2.6 Representations of types</b></a>
-<a name="6.2.6.1" href="#6.2.6.1"><b> 6.2.6.1 General</b></a>
-1 The representations of all types are unspecified except as stated in this subclause.
-2 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes,
- the number, order, and encoding of which are either explicitly specified or
- implementation-defined.
-3 Values stored in unsigned bit-fields and objects of type unsigned char shall be
- represented using a pure binary notation.49)
-4 Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT
- bits, where n is the size of an object of that type, in bytes. The value may be copied into
- an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is
- called the object representation of the value. Values stored in bit-fields consist of m bits,
- where m is the size specified for the bit-field. The object representation is the set of m
- bits the bit-field comprises in the addressable storage unit holding it. Two values (other
- than NaNs) with the same object representation compare equal, but values that compare
- equal may have different object representations.
-5 Certain object representations need not represent a value of the object type. If the stored
- value of an object has such a representation and is read by an lvalue expression that does
- not have character type, the behavior is undefined. If such a representation is produced
- by a side effect that modifies all or any part of the object by an lvalue expression that
- does not have character type, the behavior is undefined.50) Such a representation is called
- a trap representation.
-6 When a value is stored in an object of structure or union type, including in a member
- object, the bytes of the object representation that correspond to any padding bytes take
- unspecified values.51) The value of a structure or union object is never a trap
- representation, even though the value of a member of the structure or union object may be
- a trap representation.
-7 When a value is stored in a member of an object of union type, the bytes of the object
- representation that do not correspond to that member but do correspond to other members
-
- 49) A positional representation for integers that uses the binary digits 0 and 1, in which the values
- represented by successive bits are additive, begin with 1, and are multiplied by successive integral
- powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
- Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
- type unsigned char range from 0 to 2
- CHAR_BIT
- - 1.
- 50) Thus, an automatic variable can be initialized to a trap representation without causing undefined
- behavior, but the value of the variable cannot be used until a proper value is stored in it.
- 51) Thus, for example, structure assignment need not copy any padding bits.
-
-[<a name="#p44" href="p44">page 44</a>] (<a href="#Contents">Contents</a>)
-
- take unspecified values.
-8 Where an operator is applied to a value that has more than one object representation,
- which object representation is used shall not affect the value of the result.52) Where a
- value is stored in an object using a type that has more than one object representation for
- that value, it is unspecified which representation is used, but a trap representation shall
- not be generated.
-9 Loads and stores of objects with _Atomic-qualified types are done with
- memory_order_seq_cst semantics.
- Forward references: declarations (<a href="#6.7">6.7</a>), expressions (<a href="#6.5">6.5</a>), lvalues, arrays, and function
- designators (<a href="#6.3.2.1">6.3.2.1</a>), order and consistency (<a href="#7.17.3">7.17.3</a>).
-<a name="6.2.6.2" href="#6.2.6.2"><b> 6.2.6.2 Integer types</b></a>
-1 For unsigned integer types other than unsigned char, the bits of the object
- representation shall be divided into two groups: value bits and padding bits (there need
- not be any of the latter). If there are N value bits, each bit shall represent a different
- power of 2 between 1 and 2 N -1 , so that objects of that type shall be capable of
- representing values from 0 to 2 N - 1 using a pure binary representation; this shall be
- known as the value representation. The values of any padding bits are unspecified.53)
-2 For signed integer types, the bits of the object representation shall be divided into three
- groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
- signed char shall not have any padding bits. There shall be exactly one sign bit.
- Each bit that is a value bit shall have the same value as the same bit in the object
- representation of the corresponding unsigned type (if there are M value bits in the signed
- type and N in the unsigned type, then M <= N ). If the sign bit is zero, it shall not affect
- the resulting value. If the sign bit is one, the value shall be modified in one of the
- following ways:
- -- the corresponding value with sign bit 0 is negated (sign and magnitude);
- -- the sign bit has the value -(2 M ) (two's complement);
-
-
- 52) It is possible for objects x and y with the same effective type T to have the same value when they are
- accessed as objects of type T, but to have different values in other contexts. In particular, if == is
- defined for type T, then x == y does not imply that memcmp(&x, &y, sizeof (T)) == 0.
- Furthermore, x == y does not necessarily imply that x and y have the same value; other operations
- on values of type T may distinguish between them.
- 53) Some combinations of padding bits might generate trap representations, for example, if one padding
- bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
- representation other than as part of an exceptional condition such as an overflow, and this cannot occur
- with unsigned types. All other combinations of padding bits are alternative object representations of
- the value specified by the value bits.
-
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-
- -- the sign bit has the value -(2 M - 1) (ones' complement).
- Which of these applies is implementation-defined, as is whether the value with sign bit 1
- and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones'
- complement), is a trap representation or a normal value. In the case of sign and
- magnitude and ones' complement, if this representation is a normal value it is called a
- negative zero.
-3 If the implementation supports negative zeros, they shall be generated only by:
- -- the &, |, ^, ~, <<, and >> operators with operands that produce such a value;
- -- the +, -, *, /, and % operators where one operand is a negative zero and the result is
- zero;
- -- compound assignment operators based on the above cases.
- It is unspecified whether these cases actually generate a negative zero or a normal zero,
- and whether a negative zero becomes a normal zero when stored in an object.
-4 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
- and >> operators with operands that would produce such a value is undefined.
-5 The values of any padding bits are unspecified.54) A valid (non-trap) object representation
- of a signed integer type where the sign bit is zero is a valid object representation of the
- corresponding unsigned type, and shall represent the same value. For any integer type,
- the object representation where all the bits are zero shall be a representation of the value
- zero in that type.
-6 The precision of an integer type is the number of bits it uses to represent values,
- excluding any sign and padding bits. The width of an integer type is the same but
- including any sign bit; thus for unsigned integer types the two values are the same, while
- for signed integer types the width is one greater than the precision.
-
-
-
-
- 54) Some combinations of padding bits might generate trap representations, for example, if one padding
- bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
- representation other than as part of an exceptional condition such as an overflow. All other
- combinations of padding bits are alternative object representations of the value specified by the value
- bits.
-
-[<a name="#p46" href="p46">page 46</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.2.7" href="#6.2.7"><b> 6.2.7 Compatible type and composite type</b></a>
-1 Two types have compatible type if their types are the same. Additional rules for
- determining whether two types are compatible are described in <a href="#6.7.2">6.7.2</a> for type specifiers,
- in <a href="#6.7.3">6.7.3</a> for type qualifiers, and in <a href="#6.7.6">6.7.6</a> for declarators.55) Moreover, two structure,
- union, or enumerated types declared in separate translation units are compatible if their
- tags and members satisfy the following requirements: If one is declared with a tag, the
- other shall be declared with the same tag. If both are completed anywhere within their
- respective translation units, then the following additional requirements apply: there shall
- be a one-to-one correspondence between their members such that each pair of
- corresponding members are declared with compatible types, and such that if one member
- of a corresponding pair is declared with a name, the other member is declared with the
- same name. For two structures, corresponding members shall be declared in the same
- order. For two structures or unions, corresponding bit-fields shall have the same widths.
- For two enumerations, corresponding members shall have the same values.
-2 All declarations that refer to the same object or function shall have compatible type;
- otherwise, the behavior is undefined.
-3 A composite type can be constructed from two types that are compatible; it is a type that
- is compatible with both of the two types and satisfies the following conditions:
- -- If both types are array types, the following rules are applied:
- o If one type is an array of known constant size, the composite type is an array of
- that size.
- o Otherwise, if one type is a variable length array whose size is specified by an
- expression that is not evaluated, the behavior is undefined.
- o Otherwise, if one type is a variable length array whose size is specified, the
- composite type is a variable length array of that size.
- o Otherwise, if one type is a variable length array of unspecified size, the composite
- type is a variable length array of unspecified size.
- o Otherwise, both types are arrays of unknown size and the composite type is an
- array of unknown size.
- The element type of the composite type is the composite type of the two element
- types.
- -- If only one type is a function type with a parameter type list (a function prototype),
- the composite type is a function prototype with the parameter type list.
-
-
-
- 55) Two types need not be identical to be compatible.
-
-[<a name="#p47" href="p47">page 47</a>] (<a href="#Contents">Contents</a>)
-
- -- If both types are function types with parameter type lists, the type of each parameter
- in the composite parameter type list is the composite type of the corresponding
- parameters.
- These rules apply recursively to the types from which the two types are derived.
-4 For an identifier with internal or external linkage declared in a scope in which a prior
- declaration of that identifier is visible,56) if the prior declaration specifies internal or
- external linkage, the type of the identifier at the later declaration becomes the composite
- type.
- Forward references: array declarators (<a href="#6.7.6.2">6.7.6.2</a>).
-5 EXAMPLE Given the following two file scope declarations:
- int f(int (*)(), double (*)[3]);
- int f(int (*)(char *), double (*)[]);
- The resulting composite type for the function is:
- int f(int (*)(char *), double (*)[3]);
-
-<a name="6.2.8" href="#6.2.8"><b> 6.2.8 Alignment of objects</b></a>
-1 Complete object types have alignment requirements which place restrictions on the
- addresses at which objects of that type may be allocated. An alignment is an
- implementation-defined integer value representing the number of bytes between
- successive addresses at which a given object can be allocated. An object type imposes an
- alignment requirement on every object of that type: stricter alignment can be requested
- using the _Alignas keyword.
-2 A fundamental alignment is represented by an alignment less than or equal to the greatest
- alignment supported by the implementation in all contexts, which is equal to
- alignof(max_align_t).
-3 An extended alignment is represented by an alignment greater than
- alignof(max_align_t). It is implementation-defined whether any extended
- alignments are supported and the contexts in which they are supported. A type having an
- extended alignment requirement is an over-aligned type.57)
-4 Alignments are represented as values of the type size_t. Valid alignments include only
- those values returned by an alignof expression for fundamental types, plus an
- additional implementation-defined set of values, which may be empty. Every valid
- alignment value shall be an integral power of two.
-
-
- 56) As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
- 57) Every over-aligned type is, or contains, a structure or union type with a member to which an extended
- alignment has been applied.
-
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-
-5 Alignments have an order from weaker to stronger or stricter alignments. Stricter
- alignments have larger alignment values. An address that satisfies an alignment
- requirement also satisfies any weaker valid alignment requirement.
-6 The alignment requirement of a complete type can be queried using an alignof
- expression. The types char, signed char, and unsigned char shall have the
- weakest alignment requirement.
-7 Comparing alignments is meaningful and provides the obvious results:
- -- Two alignments are equal when their numeric values are equal.
- -- Two alignments are different when their numeric values are not equal.
- -- When an alignment is larger than another it represents a stricter alignment.
-
-
-
-
-[<a name="#p49" href="p49">page 49</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.3" href="#6.3"><b> 6.3 Conversions</b></a>
-1 Several operators convert operand values from one type to another automatically. This
- subclause specifies the result required from such an implicit conversion, as well as those
- that result from a cast operation (an explicit conversion). The list in <a href="#6.3.1.8">6.3.1.8</a> summarizes
- the conversions performed by most ordinary operators; it is supplemented as required by
- the discussion of each operator in <a href="#6.5">6.5</a>.
-2 Conversion of an operand value to a compatible type causes no change to the value or the
- representation.
- Forward references: cast operators (<a href="#6.5.4">6.5.4</a>).
-<a name="6.3.1" href="#6.3.1"><b> 6.3.1 Arithmetic operands</b></a>
-<a name="6.3.1.1" href="#6.3.1.1"><b> 6.3.1.1 Boolean, characters, and integers</b></a>
-1 Every integer type has an integer conversion rank defined as follows:
- -- No two signed integer types shall have the same rank, even if they have the same
- representation.
- -- The rank of a signed integer type shall be greater than the rank of any signed integer
- type with less precision.
- -- The rank of long long int shall be greater than the rank of long int, which
- shall be greater than the rank of int, which shall be greater than the rank of short
- int, which shall be greater than the rank of signed char.
- -- The rank of any unsigned integer type shall equal the rank of the corresponding
- signed integer type, if any.
- -- The rank of any standard integer type shall be greater than the rank of any extended
- integer type with the same width.
- -- The rank of char shall equal the rank of signed char and unsigned char.
- -- The rank of _Bool shall be less than the rank of all other standard integer types.
- -- The rank of any enumerated type shall equal the rank of the compatible integer type
- (see <a href="#6.7.2.2">6.7.2.2</a>).
- -- The rank of any extended signed integer type relative to another extended signed
- integer type with the same precision is implementation-defined, but still subject to the
- other rules for determining the integer conversion rank.
- -- For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has
- greater rank than T3, then T1 has greater rank than T3.
-2 The following may be used in an expression wherever an int or unsigned int may
- be used:
-
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-
- -- An object or expression with an integer type (other than int or unsigned int)
- whose integer conversion rank is less than or equal to the rank of int and
- unsigned int.
- -- A bit-field of type _Bool, int, signed int, or unsigned int.
- If an int can represent all values of the original type (as restricted by the width, for a
- bit-field), the value is converted to an int; otherwise, it is converted to an unsigned
- int. These are called the integer promotions.58) All other types are unchanged by the
- integer promotions.
-3 The integer promotions preserve value including sign. As discussed earlier, whether a
- ''plain'' char is treated as signed is implementation-defined.
- Forward references: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
- (<a href="#6.7.2.1">6.7.2.1</a>).
-<a name="6.3.1.2" href="#6.3.1.2"><b> 6.3.1.2 Boolean type</b></a>
-1 When any scalar value is converted to _Bool, the result is 0 if the value compares equal
- to 0; otherwise, the result is 1.59)
-<a name="6.3.1.3" href="#6.3.1.3"><b> 6.3.1.3 Signed and unsigned integers</b></a>
-1 When a value with integer type is converted to another integer type other than _Bool, if
- the value can be represented by the new type, it is unchanged.
-2 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or
- subtracting one more than the maximum value that can be represented in the new type
- until the value is in the range of the new type.60)
-3 Otherwise, the new type is signed and the value cannot be represented in it; either the
- result is implementation-defined or an implementation-defined signal is raised.
-<a name="6.3.1.4" href="#6.3.1.4"><b> 6.3.1.4 Real floating and integer</b></a>
-1 When a finite value of real floating type is converted to an integer type other than _Bool,
- the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
- the integral part cannot be represented by the integer type, the behavior is undefined.61)
-
-
- 58) The integer promotions are applied only: as part of the usual arithmetic conversions, to certain
- argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the
- shift operators, as specified by their respective subclauses.
- 59) NaNs do not compare equal to 0 and thus convert to 1.
- 60) The rules describe arithmetic on the mathematical value, not the value of a given type of expression.
- 61) The remaindering operation performed when a value of integer type is converted to unsigned type
- need not be performed when a value of real floating type is converted to unsigned type. Thus, the
- range of portable real floating values is (-1, Utype_MAX+1).
-
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-
-2 When a value of integer type is converted to a real floating type, if the value being
- converted can be represented exactly in the new type, it is unchanged. If the value being
- converted is in the range of values that can be represented but cannot be represented
- exactly, the result is either the nearest higher or nearest lower representable value, chosen
- in an implementation-defined manner. If the value being converted is outside the range of
- values that can be represented, the behavior is undefined.
-<a name="6.3.1.5" href="#6.3.1.5"><b> 6.3.1.5 Real floating types</b></a>
-1 When a float is promoted to double or long double, or a double is promoted
- to long double, its value is unchanged (if the source value is represented in the
- precision and range of its type).
-2 When a double is demoted to float, a long double is demoted to double or
- float, or a value being represented in greater precision and range than required by its
- semantic type (see <a href="#6.3.1.8">6.3.1.8</a>) is explicitly converted (including to its own type), if the value
- being converted can be represented exactly in the new type, it is unchanged. If the value
- being converted is in the range of values that can be represented but cannot be
- represented exactly, the result is either the nearest higher or nearest lower representable
- value, chosen in an implementation-defined manner. If the value being converted is
- outside the range of values that can be represented, the behavior is undefined.
-<a name="6.3.1.6" href="#6.3.1.6"><b> 6.3.1.6 Complex types</b></a>
-1 When a value of complex type is converted to another complex type, both the real and
- imaginary parts follow the conversion rules for the corresponding real types.
-<a name="6.3.1.7" href="#6.3.1.7"><b> 6.3.1.7 Real and complex</b></a>
-1 When a value of real type is converted to a complex type, the real part of the complex
- result value is determined by the rules of conversion to the corresponding real type and
- the imaginary part of the complex result value is a positive zero or an unsigned zero.
-2 When a value of complex type is converted to a real type, the imaginary part of the
- complex value is discarded and the value of the real part is converted according to the
- conversion rules for the corresponding real type.
-<a name="6.3.1.8" href="#6.3.1.8"><b> 6.3.1.8 Usual arithmetic conversions</b></a>
-1 Many operators that expect operands of arithmetic type cause conversions and yield result
- types in a similar way. The purpose is to determine a common real type for the operands
- and result. For the specified operands, each operand is converted, without change of type
- domain, to a type whose corresponding real type is the common real type. Unless
- explicitly stated otherwise, the common real type is also the corresponding real type of
- the result, whose type domain is the type domain of the operands if they are the same,
- and complex otherwise. This pattern is called the usual arithmetic conversions:
-
-
-[<a name="#p52" href="p52">page 52</a>] (<a href="#Contents">Contents</a>)
-
- First, if the corresponding real type of either operand is long double, the other
- operand is converted, without change of type domain, to a type whose
- corresponding real type is long double.
- Otherwise, if the corresponding real type of either operand is double, the other
- operand is converted, without change of type domain, to a type whose
- corresponding real type is double.
- Otherwise, if the corresponding real type of either operand is float, the other
- operand is converted, without change of type domain, to a type whose
- corresponding real type is float.62)
- Otherwise, the integer promotions are performed on both operands. Then the
- following rules are applied to the promoted operands:
- If both operands have the same type, then no further conversion is needed.
- Otherwise, if both operands have signed integer types or both have unsigned
- integer types, the operand with the type of lesser integer conversion rank is
- converted to the type of the operand with greater rank.
- Otherwise, if the operand that has unsigned integer type has rank greater or
- equal to the rank of the type of the other operand, then the operand with
- signed integer type is converted to the type of the operand with unsigned
- integer type.
- Otherwise, if the type of the operand with signed integer type can represent
- all of the values of the type of the operand with unsigned integer type, then
- the operand with unsigned integer type is converted to the type of the
- operand with signed integer type.
- Otherwise, both operands are converted to the unsigned integer type
- corresponding to the type of the operand with signed integer type.
-2 The values of floating operands and of the results of floating expressions may be
- represented in greater precision and range than that required by the type; the types are not
- changed thereby.63)
-
-
-
-
- 62) For example, addition of a double _Complex and a float entails just the conversion of the
- float operand to double (and yields a double _Complex result).
- 63) The cast and assignment operators are still required to perform their specified conversions as
- described in <a href="#6.3.1.4">6.3.1.4</a> and <a href="#6.3.1.5">6.3.1.5</a>.
-
-[<a name="#p53" href="p53">page 53</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.3.2" href="#6.3.2"><b> 6.3.2 Other operands</b></a>
-<a name="6.3.2.1" href="#6.3.2.1"><b> 6.3.2.1 Lvalues, arrays, and function designators</b></a>
-1 An lvalue is an expression (with an object type other than void) that potentially
- designates an object;64) if an lvalue does not designate an object when it is evaluated, the
- behavior is undefined. When an object is said to have a particular type, the type is
- specified by the lvalue used to designate the object. A modifiable lvalue is an lvalue that
- does not have array type, does not have an incomplete type, does not have a const-
- qualified type, and if it is a structure or union, does not have any member (including,
- recursively, any member or element of all contained aggregates or unions) with a const-
- qualified type.
-2 Except when it is the operand of the sizeof operator, the unary & operator, the ++
- operator, the -- operator, or the left operand of the . operator or an assignment operator,
- an lvalue that does not have array type is converted to the value stored in the designated
- object (and is no longer an lvalue). If the lvalue has qualified type, the value has the
- unqualified version of the type of the lvalue; otherwise, the value has the type of the
- lvalue. If the lvalue has an incomplete type and does not have array type, the behavior is
- undefined. If the lvalue designates an object of automatic storage duration that could
- have been declared with the register storage class (never had its address taken), and
- that object is uninitialized (not declared with an initializer and no assignment to it has
- been performed prior to use), the behavior is undefined.
-3 Except when it is the operand of the sizeof operator or the unary & operator, or is a
- string literal used to initialize an array, an expression that has type ''array of type'' is
- converted to an expression with type ''pointer to type'' that points to the initial element of
- the array object and is not an lvalue. If the array object has register storage class, the
- behavior is undefined.
-4 A function designator is an expression that has function type. Except when it is the
- operand of the sizeof operator65) or the unary & operator, a function designator with
- type ''function returning type'' is converted to an expression that has type ''pointer to
- function returning type''.
- Forward references: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), assignment operators
-
- 64) The name ''lvalue'' comes originally from the assignment expression E1 = E2, in which the left
- operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
- object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described
- as the ''value of an expression''.
- An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
- expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.
- 65) Because this conversion does not occur, the operand of the sizeof operator remains a function
- designator and violates the constraint in <a href="#6.5.3.4">6.5.3.4</a>.
-
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-
- (<a href="#6.5.16">6.5.16</a>), common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), initialization (<a href="#6.7.9">6.7.9</a>), postfix
- increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
- (<a href="#6.5.3.1">6.5.3.1</a>), the sizeof operator (<a href="#6.5.3.4">6.5.3.4</a>), structure and union members (<a href="#6.5.2.3">6.5.2.3</a>).
- <a href="#6.3.2.2">6.3.2.2</a> void
-1 The (nonexistent) value of a void expression (an expression that has type void) shall not
- be used in any way, and implicit or explicit conversions (except to void) shall not be
- applied to such an expression. If an expression of any other type is evaluated as a void
- expression, its value or designator is discarded. (A void expression is evaluated for its
- side effects.)
-<a name="6.3.2.3" href="#6.3.2.3"><b> 6.3.2.3 Pointers</b></a>
-1 A pointer to void may be converted to or from a pointer to any object type. A pointer to
- any object type may be converted to a pointer to void and back again; the result shall
- compare equal to the original pointer.
-2 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to
- the q-qualified version of the type; the values stored in the original and converted pointers
- shall compare equal.
-3 An integer constant expression with the value 0, or such an expression cast to type
- void *, is called a null pointer constant.66) If a null pointer constant is converted to a
- pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal
- to a pointer to any object or function.
-4 Conversion of a null pointer to another pointer type yields a null pointer of that type.
- Any two null pointers shall compare equal.
-5 An integer may be converted to any pointer type. Except as previously specified, the
- result is implementation-defined, might not be correctly aligned, might not point to an
- entity of the referenced type, and might be a trap representation.67)
-6 Any pointer type may be converted to an integer type. Except as previously specified, the
- result is implementation-defined. If the result cannot be represented in the integer type,
- the behavior is undefined. The result need not be in the range of values of any integer
- type.
-7 A pointer to an object type may be converted to a pointer to a different object type. If the
- resulting pointer is not correctly aligned68) for the referenced type, the behavior is
- undefined. Otherwise, when converted back again, the result shall compare equal to the
-
-
- 66) The macro NULL is defined in <a href="#7.19"><stddef.h></a> (and other headers) as a null pointer constant; see <a href="#7.19">7.19</a>.
- 67) The mapping functions for converting a pointer to an integer or an integer to a pointer are intended to
- be consistent with the addressing structure of the execution environment.
-
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-
- original pointer. When a pointer to an object is converted to a pointer to a character type,
- the result points to the lowest addressed byte of the object. Successive increments of the
- result, up to the size of the object, yield pointers to the remaining bytes of the object.
-8 A pointer to a function of one type may be converted to a pointer to a function of another
- type and back again; the result shall compare equal to the original pointer. If a converted
- pointer is used to call a function whose type is not compatible with the referenced type,
- the behavior is undefined.
- Forward references: cast operators (<a href="#6.5.4">6.5.4</a>), equality operators (<a href="#6.5.9">6.5.9</a>), integer types
- capable of holding object pointers (<a href="#7.20.1.4">7.20.1.4</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>).
-
-
-
-
- 68) In general, the concept ''correctly aligned'' is transitive: if a pointer to type A is correctly aligned for a
- pointer to type B, which in turn is correctly aligned for a pointer to type C, then a pointer to type A is
- correctly aligned for a pointer to type C.
-
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-
-<a name="6.4" href="#6.4"><b> 6.4 Lexical elements</b></a>
- Syntax
-1 token:
- keyword
- identifier
- constant
- string-literal
- punctuator
- preprocessing-token:
- header-name
- identifier
- pp-number
- character-constant
- string-literal
- punctuator
- each non-white-space character that cannot be one of the above
- Constraints
-2 Each preprocessing token that is converted to a token shall have the lexical form of a
- keyword, an identifier, a constant, a string literal, or a punctuator.
- Semantics
-3 A token is the minimal lexical element of the language in translation phases 7 and 8. The
- categories of tokens are: keywords, identifiers, constants, string literals, and punctuators.
- A preprocessing token is the minimal lexical element of the language in translation
- phases 3 through 6. The categories of preprocessing tokens are: header names,
- identifiers, preprocessing numbers, character constants, string literals, punctuators, and
- single non-white-space characters that do not lexically match the other preprocessing
- token categories.69) If a ' or a " character matches the last category, the behavior is
- undefined. Preprocessing tokens can be separated by white space; this consists of
- comments (described later), or white-space characters (space, horizontal tab, new-line,
- vertical tab, and form-feed), or both. As described in <a href="#6.10">6.10</a>, in certain circumstances
- during translation phase 4, white space (or the absence thereof) serves as more than
- preprocessing token separation. White space may appear within a preprocessing token
- only as part of a header name or between the quotation characters in a character constant
- or string literal.
-
-
-
- 69) An additional category, placemarkers, is used internally in translation phase 4 (see <a href="#6.10.3.3">6.10.3.3</a>); it cannot
- occur in source files.
-
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-
-4 If the input stream has been parsed into preprocessing tokens up to a given character, the
- next preprocessing token is the longest sequence of characters that could constitute a
- preprocessing token. There is one exception to this rule: header name preprocessing
- tokens are recognized only within #include preprocessing directives and in
- implementation-defined locations within #pragma directives. In such contexts, a
- sequence of characters that could be either a header name or a string literal is recognized
- as the former.
-5 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a
- valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex
- might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program
- fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or
- not E is a macro name.
-
-6 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
- increment operators, even though the parse x ++ + ++ y might yield a correct expression.
-
- Forward references: character constants (<a href="#6.4.4.4">6.4.4.4</a>), comments (<a href="#6.4.9">6.4.9</a>), expressions (<a href="#6.5">6.5</a>),
- floating constants (<a href="#6.4.4.2">6.4.4.2</a>), header names (<a href="#6.4.7">6.4.7</a>), macro replacement (<a href="#6.10.3">6.10.3</a>), postfix
- increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
- (<a href="#6.5.3.1">6.5.3.1</a>), preprocessing directives (<a href="#6.10">6.10</a>), preprocessing numbers (<a href="#6.4.8">6.4.8</a>), string literals
- (<a href="#6.4.5">6.4.5</a>).
-<a name="6.4.1" href="#6.4.1"><b> 6.4.1 Keywords</b></a>
- Syntax
-1 keyword: one of
- alignof goto union
- auto if unsigned
- break inline void
- case int volatile
- char long while
- const register _Alignas
- continue restrict _Atomic
- default return _Bool
- do short _Complex
- double signed _Generic
- else sizeof _Imaginary
- enum static _Noreturn
- extern struct _Static_assert
- float switch _Thread_local
- for typedef
- Semantics
-2 The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as
- keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
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-
- specifying imaginary types.70)
-<a name="6.4.2" href="#6.4.2"><b> 6.4.2 Identifiers</b></a>
-<a name="6.4.2.1" href="#6.4.2.1"><b> 6.4.2.1 General</b></a>
- Syntax
-1 identifier:
- identifier-nondigit
- identifier identifier-nondigit
- identifier digit
- identifier-nondigit:
- nondigit
- universal-character-name
- other implementation-defined characters
- nondigit: one of
- _ a b c d e f g h i j k l m
- n o p q r s t u v w x y z
- A B C D E F G H I J K L M
- N O P Q R S T U V W X Y Z
- digit: one of
- 0 1 2 3 4 5 6 7 8 9
- Semantics
-2 An identifier is a sequence of nondigit characters (including the underscore _, the
- lowercase and uppercase Latin letters, and other characters) and digits, which designates
- one or more entities as described in <a href="#6.2.1">6.2.1</a>. Lowercase and uppercase letters are distinct.
- There is no specific limit on the maximum length of an identifier.
-3 Each universal character name in an identifier shall designate a character whose encoding
- in ISO/IEC 10646 falls into one of the ranges specified in <a href="#D">annex D</a>.71) The initial
- character shall not be a universal character name designating a digit. An implementation
- may allow multibyte characters that are not part of the basic source character set to
- appear in identifiers; which characters and their correspondence to universal character
- names is implementation-defined.
-
-
-
- 70) One possible specification for imaginary types appears in <a href="#G">annex G</a>.
- 71) On systems in which linkers cannot accept extended characters, an encoding of the universal character
- name may be used in forming valid external identifiers. For example, some otherwise unused
- character or sequence of characters may be used to encode the \u in a universal character name.
- Extended characters may produce a long external identifier.
-
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-
-4 When preprocessing tokens are converted to tokens during translation phase 7, if a
- preprocessing token could be converted to either a keyword or an identifier, it is converted
- to a keyword.
- Implementation limits
-5 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of significant initial
- characters in an identifier; the limit for an external name (an identifier that has external
- linkage) may be more restrictive than that for an internal name (a macro name or an
- identifier that does not have external linkage). The number of significant characters in an
- identifier is implementation-defined.
-6 Any identifiers that differ in a significant character are different identifiers. If two
- identifiers differ only in nonsignificant characters, the behavior is undefined.
- Forward references: universal character names (<a href="#6.4.3">6.4.3</a>), macro replacement (<a href="#6.10.3">6.10.3</a>).
-<a name="6.4.2.2" href="#6.4.2.2"><b> 6.4.2.2 Predefined identifiers</b></a>
- Semantics
-1 The identifier __func__ shall be implicitly declared by the translator as if,
- immediately following the opening brace of each function definition, the declaration
- static const char __func__[] = "function-name";
- appeared, where function-name is the name of the lexically-enclosing function.72)
-2 This name is encoded as if the implicit declaration had been written in the source
- character set and then translated into the execution character set as indicated in translation
- phase 5.
-3 EXAMPLE Consider the code fragment:
- #include <a href="#7.21"><stdio.h></a>
- void myfunc(void)
- {
- printf("%s\n", __func__);
- /* ... */
- }
- Each time the function is called, it will print to the standard output stream:
- myfunc
-
- Forward references: function definitions (<a href="#6.9.1">6.9.1</a>).
-
-
-
-
- 72) Since the name __func__ is reserved for any use by the implementation (<a href="#7.1.3">7.1.3</a>), if any other
- identifier is explicitly declared using the name __func__, the behavior is undefined.
-
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-
-<a name="6.4.3" href="#6.4.3"><b> 6.4.3 Universal character names</b></a>
- Syntax
-1 universal-character-name:
- \u hex-quad
- \U hex-quad hex-quad
- hex-quad:
- hexadecimal-digit hexadecimal-digit
- hexadecimal-digit hexadecimal-digit
- Constraints
-2 A universal character name shall not specify a character whose short identifier is less than
- 00A0 other than 0024 ($), 0040 (@), or 0060 ('), nor one in the range D800 through
- DFFF inclusive.73)
- Description
-3 Universal character names may be used in identifiers, character constants, and string
- literals to designate characters that are not in the basic character set.
- Semantics
-4 The universal character name \Unnnnnnnn designates the character whose eight-digit
- short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.74) Similarly, the universal
- character name \unnnn designates the character whose four-digit short identifier is nnnn
- (and whose eight-digit short identifier is 0000nnnn).
-
-
-
-
- 73) The disallowed characters are the characters in the basic character set and the code positions reserved
- by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by
- UTF-16).
-
- 74) Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
-
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-
-<a name="6.4.4" href="#6.4.4"><b> 6.4.4 Constants</b></a>
- Syntax
-1 constant:
- integer-constant
- floating-constant
- enumeration-constant
- character-constant
- Constraints
-2 Each constant shall have a type and the value of a constant shall be in the range of
- representable values for its type.
- Semantics
-3 Each constant has a type, determined by its form and value, as detailed later.
-<a name="6.4.4.1" href="#6.4.4.1"><b> 6.4.4.1 Integer constants</b></a>
- Syntax
-1 integer-constant:
- decimal-constant integer-suffixopt
- octal-constant integer-suffixopt
- hexadecimal-constant integer-suffixopt
- decimal-constant:
- nonzero-digit
- decimal-constant digit
- octal-constant:
- 0
- octal-constant octal-digit
- hexadecimal-constant:
- hexadecimal-prefix hexadecimal-digit
- hexadecimal-constant hexadecimal-digit
- hexadecimal-prefix: one of
- 0x 0X
- nonzero-digit: one of
- 1 2 3 4 5 6 7 8 9
- octal-digit: one of
- 0 1 2 3 4 5 6 7
-
-
-
-
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-
- hexadecimal-digit: one of
- 0 1 2 3 4 5 6 7 8 9
- a b c d e f
- A B C D E F
- integer-suffix:
- unsigned-suffix long-suffixopt
- unsigned-suffix long-long-suffix
- long-suffix unsigned-suffixopt
- long-long-suffix unsigned-suffixopt
- unsigned-suffix: one of
- u U
- long-suffix: one of
- l L
- long-long-suffix: one of
- ll LL
- Description
-2 An integer constant begins with a digit, but has no period or exponent part. It may have a
- prefix that specifies its base and a suffix that specifies its type.
-3 A decimal constant begins with a nonzero digit and consists of a sequence of decimal
- digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
- digits 0 through 7 only. A hexadecimal constant consists of the prefix 0x or 0X followed
- by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
- 10 through 15 respectively.
- Semantics
-4 The value of a decimal constant is computed base 10; that of an octal constant, base 8;
- that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
-5 The type of an integer constant is the first of the corresponding list in which its value can
- be represented.
-
-
-
-
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-
- Octal or Hexadecimal
- Suffix Decimal Constant Constant
-
- none int int
- long int unsigned int
- long long int long int
- unsigned long int
- long long int
- unsigned long long int
-
- u or U unsigned int unsigned int
- unsigned long int unsigned long int
- unsigned long long int unsigned long long int
-
- l or L long int long int
- long long int unsigned long int
- long long int
- unsigned long long int
-
- Both u or U unsigned long int unsigned long int
- and l or L unsigned long long int unsigned long long int
-
- ll or LL long long int long long int
- unsigned long long int
-
- Both u or U unsigned long long int unsigned long long int
- and ll or LL
-6 If an integer constant cannot be represented by any type in its list, it may have an
- extended integer type, if the extended integer type can represent its value. If all of the
- types in the list for the constant are signed, the extended integer type shall be signed. If
- all of the types in the list for the constant are unsigned, the extended integer type shall be
- unsigned. If the list contains both signed and unsigned types, the extended integer type
- may be signed or unsigned. If an integer constant cannot be represented by any type in
- its list and has no extended integer type, then the integer constant has no type.
-
-
-
-
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-
-<a name="6.4.4.2" href="#6.4.4.2"><b> 6.4.4.2 Floating constants</b></a>
- Syntax
-1 floating-constant:
- decimal-floating-constant
- hexadecimal-floating-constant
- decimal-floating-constant:
- fractional-constant exponent-partopt floating-suffixopt
- digit-sequence exponent-part floating-suffixopt
- hexadecimal-floating-constant:
- hexadecimal-prefix hexadecimal-fractional-constant
- binary-exponent-part floating-suffixopt
- hexadecimal-prefix hexadecimal-digit-sequence
- binary-exponent-part floating-suffixopt
- fractional-constant:
- digit-sequenceopt . digit-sequence
- digit-sequence .
- exponent-part:
- e signopt digit-sequence
- E signopt digit-sequence
- sign: one of
- + -
- digit-sequence:
- digit
- digit-sequence digit
- hexadecimal-fractional-constant:
- hexadecimal-digit-sequenceopt .
- hexadecimal-digit-sequence
- hexadecimal-digit-sequence .
- binary-exponent-part:
- p signopt digit-sequence
- P signopt digit-sequence
- hexadecimal-digit-sequence:
- hexadecimal-digit
- hexadecimal-digit-sequence hexadecimal-digit
- floating-suffix: one of
- f l F L
-
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-
- Description
-2 A floating constant has a significand part that may be followed by an exponent part and a
- suffix that specifies its type. The components of the significand part may include a digit
- sequence representing the whole-number part, followed by a period (.), followed by a
- digit sequence representing the fraction part. The components of the exponent part are an
- e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
- Either the whole-number part or the fraction part has to be present; for decimal floating
- constants, either the period or the exponent part has to be present.
- Semantics
-3 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
- digit sequence in the exponent part is interpreted as a decimal integer. For decimal
- floating constants, the exponent indicates the power of 10 by which the significand part is
- to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
- by which the significand part is to be scaled. For decimal floating constants, and also for
- hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
- the nearest representable value, or the larger or smaller representable value immediately
- adjacent to the nearest representable value, chosen in an implementation-defined manner.
- For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
- correctly rounded.
-4 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
- type float. If suffixed by the letter l or L, it has type long double.
-5 Floating constants are converted to internal format as if at translation-time. The
- conversion of a floating constant shall not raise an exceptional condition or a floating-
- point exception at execution time.
- Recommended practice
-6 The implementation should produce a diagnostic message if a hexadecimal constant
- cannot be represented exactly in its evaluation format; the implementation should then
- proceed with the translation of the program.
-7 The translation-time conversion of floating constants should match the execution-time
- conversion of character strings by library functions, such as strtod, given matching
- inputs suitable for both conversions, the same result format, and default execution-time
- rounding.75)
-
-
-
-
- 75) The specification for the library functions recommends more accurate conversion than required for
- floating constants (see <a href="#7.22.1.3">7.22.1.3</a>).
-
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-
-<a name="6.4.4.3" href="#6.4.4.3"><b> 6.4.4.3 Enumeration constants</b></a>
- Syntax
-1 enumeration-constant:
- identifier
- Semantics
-2 An identifier declared as an enumeration constant has type int.
- Forward references: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>).
-<a name="6.4.4.4" href="#6.4.4.4"><b> 6.4.4.4 Character constants</b></a>
- Syntax
-1 character-constant:
- ' c-char-sequence '
- L' c-char-sequence '
- u' c-char-sequence '
- U' c-char-sequence '
- c-char-sequence:
- c-char
- c-char-sequence c-char
- c-char:
- any member of the source character set except
- the single-quote ', backslash \, or new-line character
- escape-sequence
- escape-sequence:
- simple-escape-sequence
- octal-escape-sequence
- hexadecimal-escape-sequence
- universal-character-name
- simple-escape-sequence: one of
- \' \" \? \\
- \a \b \f \n \r \t \v
- octal-escape-sequence:
- \ octal-digit
- \ octal-digit octal-digit
- \ octal-digit octal-digit octal-digit
-
-
-
-
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-
- hexadecimal-escape-sequence:
- \x hexadecimal-digit
- hexadecimal-escape-sequence hexadecimal-digit
- Description
-2 An integer character constant is a sequence of one or more multibyte characters enclosed
- in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
- letter L, u, or U. With a few exceptions detailed later, the elements of the sequence are
- any members of the source character set; they are mapped in an implementation-defined
- manner to members of the execution character set.
-3 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
- arbitrary integer values are representable according to the following table of escape
- sequences:
- single quote ' \'
- double quote " \"
- question mark ? \?
- backslash \ \\
- octal character \octal digits
- hexadecimal character \x hexadecimal digits
-4 The double-quote " and question-mark ? are representable either by themselves or by the
- escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
- shall be represented, respectively, by the escape sequences \' and \\.
-5 The octal digits that follow the backslash in an octal escape sequence are taken to be part
- of the construction of a single character for an integer character constant or of a single
- wide character for a wide character constant. The numerical value of the octal integer so
- formed specifies the value of the desired character or wide character.
-6 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
- sequence are taken to be part of the construction of a single character for an integer
- character constant or of a single wide character for a wide character constant. The
- numerical value of the hexadecimal integer so formed specifies the value of the desired
- character or wide character.
-7 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
- constitute the escape sequence.
-8 In addition, characters not in the basic character set are representable by universal
- character names and certain nongraphic characters are representable by escape sequences
- consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
- and \v.76)
-
-
-
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-
- Constraints
-9 The value of an octal or hexadecimal escape sequence shall be in the range of
- representable values for the corresponding type:
- Prefix Corresponding Type
- none unsigned char
- L the unsigned type corresponding to wchar_t
- u char16_t
- U char32_t
- Semantics
-10 An integer character constant has type int. The value of an integer character constant
- containing a single character that maps to a single-byte execution character is the
- numerical value of the representation of the mapped character interpreted as an integer.
- The value of an integer character constant containing more than one character (e.g.,
- 'ab'), or containing a character or escape sequence that does not map to a single-byte
- execution character, is implementation-defined. If an integer character constant contains
- a single character or escape sequence, its value is the one that results when an object with
- type char whose value is that of the single character or escape sequence is converted to
- type int.
-11 A wide character constant prefixed by the letter L has type wchar_t, an integer type
- defined in the <a href="#7.19"><stddef.h></a> header; a wide character constant prefixed by the letter u or
- U has type char16_t or char32_t, respectively, unsigned integer types defined in the
- <a href="#7.27"><uchar.h></a> header. The value of a wide character constant containing a single
- multibyte character that maps to a single member of the extended execution character set
- is the wide character corresponding to that multibyte character, as defined by the
- mbtowc, mbrtoc16, or mbrtoc32 function as appropriate for its type, with an
- implementation-defined current locale. The value of a wide character constant containing
- more than one multibyte character or a single multibyte character that maps to multiple
- members of the extended execution character set, or containing a multibyte character or
- escape sequence not represented in the extended execution character set, is
- implementation-defined.
-12 EXAMPLE 1 The construction '\0' is commonly used to represent the null character.
-
-13 EXAMPLE 2 Consider implementations that use two's-complement representation for integers and eight
- bits for objects that have type char. In an implementation in which type char has the same range of
- values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
- same range of values as unsigned char, the character constant '\xFF' has the value +255.
-
-
-
-
- 76) The semantics of these characters were discussed in <a href="#5.2.2">5.2.2</a>. If any other character follows a backslash,
- the result is not a token and a diagnostic is required. See ''future language directions'' (<a href="#6.11.4">6.11.4</a>).
-
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-
-14 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
- specifies an integer character constant containing only one character, since a hexadecimal escape sequence
- is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
- two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
- escape sequence is terminated after three octal digits. (The value of this two-character integer character
- constant is implementation-defined.)
-
-15 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
- L'\1234' specifies the implementation-defined value that results from the combination of the values
- 0123 and '4'.
-
- Forward references: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbtowc function
- (<a href="#7.22.7.2">7.22.7.2</a>), Unicode utilities <a href="#7.27"><uchar.h></a> (<a href="#7.27">7.27</a>).
-<a name="6.4.5" href="#6.4.5"><b> 6.4.5 String literals</b></a>
- Syntax
-1 string-literal:
- encoding-prefixopt " s-char-sequenceopt "
- encoding-prefix:
- u8
- u
- U
- L
- s-char-sequence:
- s-char
- s-char-sequence s-char
- s-char:
- any member of the source character set except
- the double-quote ", backslash \, or new-line character
- escape-sequence
- Constraints
-2 A sequence of adjacent string literal tokens shall not include both a wide string literal and
- a UTF-8 string literal.
- Description
-3 A character string literal is a sequence of zero or more multibyte characters enclosed in
- double-quotes, as in "xyz". A UTF-8 string literal is the same, except prefixed by u8.
- A wide string literal is the same, except prefixed by the letter L, u, or U.
-4 The same considerations apply to each element of the sequence in a string literal as if it
- were in an integer character constant (for a character or UTF-8 string literal) or a wide
- character constant (for a wide string literal), except that the single-quote ' is
- representable either by itself or by the escape sequence \', but the double-quote " shall
-[<a name="#p70" href="p70">page 70</a>] (<a href="#Contents">Contents</a>)
-
- be represented by the escape sequence \".
- Semantics
-5 In translation phase 6, the multibyte character sequences specified by any sequence of
- adjacent character and identically-prefixed string literal tokens are concatenated into a
- single multibyte character sequence. If any of the tokens has an encoding prefix, the
- resulting multibyte character sequence is treated as having the same prefix; otherwise, it
- is treated as a character string literal. Whether differently-prefixed wide string literal
- tokens can be concatenated and, if so, the treatment of the resulting multibyte character
- sequence are implementation-defined.
-6 In translation phase 7, a byte or code of value zero is appended to each multibyte
- character sequence that results from a string literal or literals.77) The multibyte character
- sequence is then used to initialize an array of static storage duration and length just
- sufficient to contain the sequence. For character string literals, the array elements have
- type char, and are initialized with the individual bytes of the multibyte character
- sequence. For UTF-8 string literals, the array elements have type char, and are
- initialized with the characters of the multibyte character sequence, as encoded in UTF-8.
- For wide string literals prefixed by the letter L, the array elements have type wchar_t
- and are initialized with the sequence of wide characters corresponding to the multibyte
- character sequence, as defined by the mbstowcs function with an implementation-
- defined current locale. For wide string literals prefixed by the letter u or U, the array
- elements have type char16_t or char32_t, respectively, and are initialized with the
- sequence of wide characters corresponding to the multibyte character sequence, as
- defined by successive calls to the mbrtoc16, or mbrtoc32 function as appropriate for
- its type, with an implementation-defined current locale. The value of a string literal
- containing a multibyte character or escape sequence not represented in the execution
- character set is implementation-defined.
-7 It is unspecified whether these arrays are distinct provided their elements have the
- appropriate values. If the program attempts to modify such an array, the behavior is
- undefined.
-8 EXAMPLE 1 This pair of adjacent character string literals
- "\x12" "3"
- produces a single character string literal containing the two characters whose values are '\x12' and '3',
- because escape sequences are converted into single members of the execution character set just prior to
- adjacent string literal concatenation.
-
-9 EXAMPLE 2 Each of the sequences of adjacent string literal tokens
-
-
-
- 77) A string literal need not be a string (see <a href="#7.1.1">7.1.1</a>), because a null character may be embedded in it by a
- \0 escape sequence.
-
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-
- "a" "b" L"c"
- "a" L"b" "c"
- L"a" "b" L"c"
- L"a" L"b" L"c"
- is equivalent to the string literal
- L"abc"
- Likewise, each of the sequences
- "a" "b" u"c"
- "a" u"b" "c"
- u"a" "b" u"c"
- u"a" u"b" u"c"
- is equivalent to
- u"abc"
-
- Forward references: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbstowcs
- function (<a href="#7.22.8.1">7.22.8.1</a>), Unicode utilities <a href="#7.27"><uchar.h></a> (<a href="#7.27">7.27</a>).
-<a name="6.4.6" href="#6.4.6"><b> 6.4.6 Punctuators</b></a>
- Syntax
-1 punctuator: one of
- [ ] ( ) { } . ->
- ++ -- & * + - ~ !
- / % << >> < > <= >= == != ^ | && ||
- ? : ; ...
- = *= /= %= += -= <<= >>= &= ^= |=
- , # ##
- <: :> <% %> %: %:%:
- Semantics
-2 A punctuator is a symbol that has independent syntactic and semantic significance.
- Depending on context, it may specify an operation to be performed (which in turn may
- yield a value or a function designator, produce a side effect, or some combination thereof)
- in which case it is known as an operator (other forms of operator also exist in some
- contexts). An operand is an entity on which an operator acts.
-
-
-
-
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-
-3 In all aspects of the language, the six tokens78)
- <: :> <% %> %: %:%:
- behave, respectively, the same as the six tokens
- [ ] { } # ##
- except for their spelling.79)
- Forward references: expressions (<a href="#6.5">6.5</a>), declarations (<a href="#6.7">6.7</a>), preprocessing directives
- (<a href="#6.10">6.10</a>), statements (<a href="#6.8">6.8</a>).
-<a name="6.4.7" href="#6.4.7"><b> 6.4.7 Header names</b></a>
- Syntax
-1 header-name:
- < h-char-sequence >
- " q-char-sequence "
- h-char-sequence:
- h-char
- h-char-sequence h-char
- h-char:
- any member of the source character set except
- the new-line character and >
- q-char-sequence:
- q-char
- q-char-sequence q-char
- q-char:
- any member of the source character set except
- the new-line character and "
- Semantics
-2 The sequences in both forms of header names are mapped in an implementation-defined
- manner to headers or external source file names as specified in <a href="#6.10.2">6.10.2</a>.
-3 If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters,
- the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the
-
-
-
-
- 78) These tokens are sometimes called ''digraphs''.
- 79) Thus [ and <: behave differently when ''stringized'' (see <a href="#6.10.3.2">6.10.3.2</a>), but can otherwise be freely
- interchanged.
-
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-
- sequence between the " delimiters, the behavior is undefined.80) Header name
- preprocessing tokens are recognized only within #include preprocessing directives and
- in implementation-defined locations within #pragma directives.81)
-4 EXAMPLE The following sequence of characters:
- 0x3<1/a.h>1e2
- #include <1/a.h>
- #define const.member@$
- forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
- by a { on the left and a } on the right).
- {0x3}{<}{1}{/}{a}{.}{h}{>}{1e2}
- {#}{include} {<1/a.h>}
- {#}{define} {const}{.}{member}{@}{$}
-
- Forward references: source file inclusion (<a href="#6.10.2">6.10.2</a>).
-<a name="6.4.8" href="#6.4.8"><b> 6.4.8 Preprocessing numbers</b></a>
- Syntax
-1 pp-number:
- digit
- . digit
- pp-number digit
- pp-number identifier-nondigit
- pp-number e sign
- pp-number E sign
- pp-number p sign
- pp-number P sign
- pp-number .
- Description
-2 A preprocessing number begins with a digit optionally preceded by a period (.) and may
- be followed by valid identifier characters and the character sequences e+, e-, E+, E-,
- p+, p-, P+, or P-.
-3 Preprocessing number tokens lexically include all floating and integer constant tokens.
- Semantics
-4 A preprocessing number does not have type or a value; it acquires both after a successful
- conversion (as part of translation phase 7) to a floating constant token or an integer
- constant token.
-
-
- 80) Thus, sequences of characters that resemble escape sequences cause undefined behavior.
- 81) For an example of a header name preprocessing token used in a #pragma directive, see <a href="#6.10.9">6.10.9</a>.
-
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-
-<a name="6.4.9" href="#6.4.9"><b> 6.4.9 Comments</b></a>
-1 Except within a character constant, a string literal, or a comment, the characters /*
- introduce a comment. The contents of such a comment are examined only to identify
- multibyte characters and to find the characters */ that terminate it.82)
-2 Except within a character constant, a string literal, or a comment, the characters //
- introduce a comment that includes all multibyte characters up to, but not including, the
- next new-line character. The contents of such a comment are examined only to identify
- multibyte characters and to find the terminating new-line character.
-3 EXAMPLE
- "a//b" // four-character string literal
- #include "//e" // undefined behavior
- // */ // comment, not syntax error
- f = g/**//h; // equivalent to f = g / h;
- //\
- i(); // part of a two-line comment
- /\
- / j(); // part of a two-line comment
- #define glue(x,y) x##y
- glue(/,/) k(); // syntax error, not comment
- /*//*/ l(); // equivalent to l();
- m = n//**/o
- + p; // equivalent to m = n + p;
-
-
-
-
- 82) Thus, /* ... */ comments do not nest.
-
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-
-<a name="6.5" href="#6.5"><b> 6.5 Expressions</b></a>
-1 An expression is a sequence of operators and operands that specifies computation of a
- value, or that designates an object or a function, or that generates side effects, or that
- performs a combination thereof. The value computations of the operands of an operator
- are sequenced before the value computation of the result of the operator.
-2 If a side effect on a scalar object is unsequenced relative to either a different side effect
- on the same scalar object or a value computation using the value of the same scalar
- object, the behavior is undefined. If there are multiple allowable orderings of the
- subexpressions of an expression, the behavior is undefined if such an unsequenced side
- effect occurs in any of the orderings.83)
-3 The grouping of operators and operands is indicated by the syntax.84) Except as specified
- later, side effects and value computations of subexpressions are unsequenced.85)
-4 Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |,
- collectively described as bitwise operators) are required to have operands that have
- integer type. These operators yield values that depend on the internal representations of
- integers, and have implementation-defined and undefined aspects for signed types.
-5 If an exceptional condition occurs during the evaluation of an expression (that is, if the
- result is not mathematically defined or not in the range of representable values for its
- type), the behavior is undefined.
-
-
-
- 83) This paragraph renders undefined statement expressions such as
- i = ++i + 1;
- a[i++] = i;
- while allowing
- i = i + 1;
- a[i] = i;
-
- 84) The syntax specifies the precedence of operators in the evaluation of an expression, which is the same
- as the order of the major subclauses of this subclause, highest precedence first. Thus, for example, the
- expressions allowed as the operands of the binary + operator (<a href="#6.5.6">6.5.6</a>) are those expressions defined in
- <a href="#6.5.1">6.5.1</a> through <a href="#6.5.6">6.5.6</a>. The exceptions are cast expressions (<a href="#6.5.4">6.5.4</a>) as operands of unary operators
- (<a href="#6.5.3">6.5.3</a>), and an operand contained between any of the following pairs of operators: grouping
- parentheses () (<a href="#6.5.1">6.5.1</a>), subscripting brackets [] (<a href="#6.5.2.1">6.5.2.1</a>), function-call parentheses () (<a href="#6.5.2.2">6.5.2.2</a>), and
- the conditional operator ? : (<a href="#6.5.15">6.5.15</a>).
- Within each major subclause, the operators have the same precedence. Left- or right-associativity is
- indicated in each subclause by the syntax for the expressions discussed therein.
- 85) In an expression that is evaluated more than once during the execution of a program, unsequenced and
- indeterminately sequenced evaluations of its subexpressions need not be performed consistently in
- different evaluations.
-
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-
-6 The effective type of an object for an access to its stored value is the declared type of the
- object, if any.86) If a value is stored into an object having no declared type through an
- lvalue having a type that is not a character type, then the type of the lvalue becomes the
- effective type of the object for that access and for subsequent accesses that do not modify
- the stored value. If a value is copied into an object having no declared type using
- memcpy or memmove, or is copied as an array of character type, then the effective type
- of the modified object for that access and for subsequent accesses that do not modify the
- value is the effective type of the object from which the value is copied, if it has one. For
- all other accesses to an object having no declared type, the effective type of the object is
- simply the type of the lvalue used for the access.
-7 An object shall have its stored value accessed only by an lvalue expression that has one of
- the following types:87)
- -- a type compatible with the effective type of the object,
- -- a qualified version of a type compatible with the effective type of the object,
- -- a type that is the signed or unsigned type corresponding to the effective type of the
- object,
- -- a type that is the signed or unsigned type corresponding to a qualified version of the
- effective type of the object,
- -- an aggregate or union type that includes one of the aforementioned types among its
- members (including, recursively, a member of a subaggregate or contained union), or
- -- a character type.
-8 A floating expression may be contracted, that is, evaluated as though it were a single
- operation, thereby omitting rounding errors implied by the source code and the
- expression evaluation method.88) The FP_CONTRACT pragma in <a href="#7.12"><math.h></a> provides a
- way to disallow contracted expressions. Otherwise, whether and how expressions are
- contracted is implementation-defined.89)
- Forward references: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), copying functions (<a href="#7.23.2">7.23.2</a>).
-
-
- 86) Allocated objects have no declared type.
- 87) The intent of this list is to specify those circumstances in which an object may or may not be aliased.
- 88) The intermediate operations in the contracted expression are evaluated as if to infinite precision and
- range, while the final operation is rounded to the format determined by the expression evaluation
- method. A contracted expression might also omit the raising of floating-point exceptions.
- 89) This license is specifically intended to allow implementations to exploit fast machine instructions that
- combine multiple C operators. As contractions potentially undermine predictability, and can even
- decrease accuracy for containing expressions, their use needs to be well-defined and clearly
- documented.
-
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-
-<a name="6.5.1" href="#6.5.1"><b> 6.5.1 Primary expressions</b></a>
- Syntax
-1 primary-expression:
- identifier
- constant
- string-literal
- ( expression )
- generic-selection
- Semantics
-2 An identifier is a primary expression, provided it has been declared as designating an
- object (in which case it is an lvalue) or a function (in which case it is a function
- designator).90)
-3 A constant is a primary expression. Its type depends on its form and value, as detailed in
-<a name="6.4.4" href="#6.4.4"><b> 6.4.4.</b></a>
-4 A string literal is a primary expression. It is an lvalue with type as detailed in <a href="#6.4.5">6.4.5</a>.
-5 A parenthesized expression is a primary expression. Its type and value are identical to
- those of the unparenthesized expression. It is an lvalue, a function designator, or a void
- expression if the unparenthesized expression is, respectively, an lvalue, a function
- designator, or a void expression.
- Forward references: declarations (<a href="#6.7">6.7</a>).
-<a name="6.5.1.1" href="#6.5.1.1"><b> 6.5.1.1 Generic selection</b></a>
- Syntax
-1 generic-selection:
- _Generic ( assignment-expression , generic-assoc-list )
- generic-assoc-list:
- generic-association
- generic-assoc-list , generic-association
- generic-association:
- type-name : assignment-expression
- default : assignment-expression
- Constraints
-2 A generic selection shall have no more than one default generic association. The type
- name in a generic association shall specify a complete object type other than a variably
-
- 90) Thus, an undeclared identifier is a violation of the syntax.
-
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-
- modified type. No two generic associations in the same generic selection shall specify
- compatible types. The controlling expression of a generic selection shall have type
- compatible with at most one of the types named in its generic association list. If a
- generic selection has no default generic association, its controlling expression shall
- have type compatible with exactly one of the types named in its generic association list.
- Semantics
-3 The controlling expression of a generic selection is not evaluated. If a generic selection
- has a generic association with a type name that is compatible with the type of the
- controlling expression, then the result expression of the generic selection is the
- expression in that generic association. Otherwise, the result expression of the generic
- selection is the expression in the default generic association. None of the expressions
- from any other generic association of the generic selection is evaluated.
-4 The type and value of a generic selection are identical to those of its result expression. It
- is an lvalue, a function designator, or a void expression if its result expression is,
- respectively, an lvalue, a function designator, or a void expression.
-5 EXAMPLE The cbrt type-generic macro could be implemented as follows:
- #define cbrt(X) _Generic((X), \
- long double: cbrtl, \
- default: cbrt, \
- float: cbrtf \
- )(X)
-
-<a name="6.5.2" href="#6.5.2"><b> 6.5.2 Postfix operators</b></a>
- Syntax
-1 postfix-expression:
- primary-expression
- postfix-expression [ expression ]
- postfix-expression ( argument-expression-listopt )
- postfix-expression . identifier
- postfix-expression -> identifier
- postfix-expression ++
- postfix-expression --
- ( type-name ) { initializer-list }
- ( type-name ) { initializer-list , }
- argument-expression-list:
- assignment-expression
- argument-expression-list , assignment-expression
-
-
-
-
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-
-<a name="6.5.2.1" href="#6.5.2.1"><b> 6.5.2.1 Array subscripting</b></a>
- Constraints
-1 One of the expressions shall have type ''pointer to complete object type'', the other
- expression shall have integer type, and the result has type ''type''.
- Semantics
-2 A postfix expression followed by an expression in square brackets [] is a subscripted
- designation of an element of an array object. The definition of the subscript operator []
- is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that
- apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the
- initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th
- element of E1 (counting from zero).
-3 Successive subscript operators designate an element of a multidimensional array object.
- If E is an n-dimensional array (n >= 2) with dimensions i x j x . . . x k, then E (used as
- other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with
- dimensions j x . . . x k. If the unary * operator is applied to this pointer explicitly, or
- implicitly as a result of subscripting, the result is the referenced (n - 1)-dimensional
- array, which itself is converted into a pointer if used as other than an lvalue. It follows
- from this that arrays are stored in row-major order (last subscript varies fastest).
-4 EXAMPLE Consider the array object defined by the declaration
- int x[3][5];
- Here x is a 3 x 5 array of ints; more precisely, x is an array of three element objects, each of which is an
- array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
- a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually
- entails multiplying i by the size of the object to which the pointer points, namely an array of five int
- objects. The results are added and indirection is applied to yield an array of five ints. When used in the
- expression x[i][j], that array is in turn converted to a pointer to the first of the ints, so x[i][j]
- yields an int.
-
- Forward references: additive operators (<a href="#6.5.6">6.5.6</a>), address and indirection operators
- (<a href="#6.5.3.2">6.5.3.2</a>), array declarators (<a href="#6.7.6.2">6.7.6.2</a>).
-<a name="6.5.2.2" href="#6.5.2.2"><b> 6.5.2.2 Function calls</b></a>
- Constraints
-1 The expression that denotes the called function91) shall have type pointer to function
- returning void or returning a complete object type other than an array type.
-2 If the expression that denotes the called function has a type that includes a prototype, the
- number of arguments shall agree with the number of parameters. Each argument shall
-
-
- 91) Most often, this is the result of converting an identifier that is a function designator.
-
-[<a name="#p80" href="p80">page 80</a>] (<a href="#Contents">Contents</a>)
-
- have a type such that its value may be assigned to an object with the unqualified version
- of the type of its corresponding parameter.
- Semantics
-3 A postfix expression followed by parentheses () containing a possibly empty, comma-
- separated list of expressions is a function call. The postfix expression denotes the called
- function. The list of expressions specifies the arguments to the function.
-4 An argument may be an expression of any complete object type. In preparing for the call
- to a function, the arguments are evaluated, and each parameter is assigned the value of the
- corresponding argument.92)
-5 If the expression that denotes the called function has type pointer to function returning an
- object type, the function call expression has the same type as that object type, and has the
- value determined as specified in <a href="#6.8.6.4">6.8.6.4</a>. Otherwise, the function call has type void.
-6 If the expression that denotes the called function has a type that does not include a
- prototype, the integer promotions are performed on each argument, and arguments that
- have type float are promoted to double. These are called the default argument
- promotions. If the number of arguments does not equal the number of parameters, the
- behavior is undefined. If the function is defined with a type that includes a prototype, and
- either the prototype ends with an ellipsis (, ...) or the types of the arguments after
- promotion are not compatible with the types of the parameters, the behavior is undefined.
- If the function is defined with a type that does not include a prototype, and the types of
- the arguments after promotion are not compatible with those of the parameters after
- promotion, the behavior is undefined, except for the following cases:
- -- one promoted type is a signed integer type, the other promoted type is the
- corresponding unsigned integer type, and the value is representable in both types;
- -- both types are pointers to qualified or unqualified versions of a character type or
- void.
-7 If the expression that denotes the called function has a type that does include a prototype,
- the arguments are implicitly converted, as if by assignment, to the types of the
- corresponding parameters, taking the type of each parameter to be the unqualified version
- of its declared type. The ellipsis notation in a function prototype declarator causes
- argument type conversion to stop after the last declared parameter. The default argument
- promotions are performed on trailing arguments.
-
-
-
- 92) A function may change the values of its parameters, but these changes cannot affect the values of the
- arguments. On the other hand, it is possible to pass a pointer to an object, and the function may
- change the value of the object pointed to. A parameter declared to have array or function type is
- adjusted to have a pointer type as described in <a href="#6.9.1">6.9.1</a>.
-
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-
-8 No other conversions are performed implicitly; in particular, the number and types of
- arguments are not compared with those of the parameters in a function definition that
- does not include a function prototype declarator.
-9 If the function is defined with a type that is not compatible with the type (of the
- expression) pointed to by the expression that denotes the called function, the behavior is
- undefined.
-10 There is a sequence point after the evaluations of the function designator and the actual
- arguments but before the actual call. Every evaluation in the calling function (including
- other function calls) that is not otherwise specifically sequenced before or after the
- execution of the body of the called function is indeterminately sequenced with respect to
- the execution of the called function.93)
-11 Recursive function calls shall be permitted, both directly and indirectly through any chain
- of other functions.
-12 EXAMPLE In the function call
- (*pf[f1()]) (f2(), f3() + f4())
- the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before
- the function pointed to by pf[f1()] is called.
-
- Forward references: function declarators (including prototypes) (<a href="#6.7.6.3">6.7.6.3</a>), function
- definitions (<a href="#6.9.1">6.9.1</a>), the return statement (<a href="#6.8.6.4">6.8.6.4</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>).
-<a name="6.5.2.3" href="#6.5.2.3"><b> 6.5.2.3 Structure and union members</b></a>
- Constraints
-1 The first operand of the . operator shall have a qualified or unqualified structure or union
- type, and the second operand shall name a member of that type.
-2 The first operand of the -> operator shall have type ''pointer to qualified or unqualified
- structure'' or ''pointer to qualified or unqualified union'', and the second operand shall
- name a member of the type pointed to.
- Semantics
-3 A postfix expression followed by the . operator and an identifier designates a member of
- a structure or union object. The value is that of the named member,94) and is an lvalue if
- the first expression is an lvalue. If the first expression has qualified type, the result has
- the so-qualified version of the type of the designated member.
-
- 93) In other words, function executions do not ''interleave'' with each other.
- 94) If the member used to access the contents of a union object is not the same as the member last used to
- store a value in the object, the appropriate part of the object representation of the value is reinterpreted
- as an object representation in the new type as described in <a href="#6.2.6">6.2.6</a> (a process sometimes called ''type
- punning''). This might be a trap representation.
-
-[<a name="#p82" href="p82">page 82</a>] (<a href="#Contents">Contents</a>)
-
-4 A postfix expression followed by the -> operator and an identifier designates a member
- of a structure or union object. The value is that of the named member of the object to
- which the first expression points, and is an lvalue.95) If the first expression is a pointer to
- a qualified type, the result has the so-qualified version of the type of the designated
- member.
-5 Accessing a member of an _Atomic-qualified structure or union object results in
- undefined behavior.96)
-6 One special guarantee is made in order to simplify the use of unions: if a union contains
- several structures that share a common initial sequence (see below), and if the union
- object currently contains one of these structures, it is permitted to inspect the common
- initial part of any of them anywhere that a declaration of the completed type of the union
- is visible. Two structures share a common initial sequence if corresponding members
- have compatible types (and, for bit-fields, the same widths) for a sequence of one or more
- initial members.
-7 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or
- union, f().x is a valid postfix expression but is not an lvalue.
-
-8 EXAMPLE 2 In:
- struct s { int i; const int ci; };
- struct s s;
- const struct s cs;
- volatile struct s vs;
- the various members have the types:
- s.i int
- s.ci const int
- cs.i const int
- cs.ci const int
- vs.i volatile int
- vs.ci volatile const int
-
-
-
-
- 95) If &E is a valid pointer expression (where & is the ''address-of '' operator, which generates a pointer to
- its operand), the expression (&E)->MOS is the same as E.MOS.
- 96) A data race would occur if access to the entire structure or union in one thread conflicts with access to
- a member from another thread, where at least one access is a modification. Such a data race results in
- undefined behavior.
-
-[<a name="#p83" href="p83">page 83</a>] (<a href="#Contents">Contents</a>)
-
-9 EXAMPLE 3 The following is a valid fragment:
- union {
- struct {
- int alltypes;
- } n;
- struct {
- int type;
- int intnode;
- } ni;
- struct {
- int type;
- double doublenode;
- } nf;
- } u;
- u.nf.type = 1;
- u.nf.doublenode = <a href="#3.14">3.14</a>;
- /* ... */
- if (u.n.alltypes == 1)
- if (sin(u.nf.doublenode) == 0.0)
- /* ... */
- The following is not a valid fragment (because the union type is not visible within function f):
- struct t1 { int m; };
- struct t2 { int m; };
- int f(struct t1 *p1, struct t2 *p2)
- {
- if (p1->m < 0)
- p2->m = -p2->m;
- return p1->m;
- }
- int g()
- {
- union {
- struct t1 s1;
- struct t2 s2;
- } u;
- /* ... */
- return f(&u.s1, &u.s2);
- }
-
- Forward references: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), structure and union
- specifiers (<a href="#6.7.2.1">6.7.2.1</a>).
-
-
-
-
-[<a name="#p84" href="p84">page 84</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.5.2.4" href="#6.5.2.4"><b> 6.5.2.4 Postfix increment and decrement operators</b></a>
- Constraints
-1 The operand of the postfix increment or decrement operator shall have qualified or
- unqualified real or pointer type and shall be a modifiable lvalue.
- Semantics
-2 The result of the postfix ++ operator is the value of the operand. As a side effect, the
- value of the operand object is incremented (that is, the value 1 of the appropriate type is
- added to it). See the discussions of additive operators and compound assignment for
- information on constraints, types, and conversions and the effects of operations on
- pointers. The value computation of the result is sequenced before the side effect of
- updating the stored value of the operand. With respect to an indeterminately-sequenced
- function call, the operation of postfix ++ is a single evaluation. Postfix ++ on an object
- with _Atomic-qualified type is a read-modify-write operation with
- 97)
- memory_order_seq_cst memory order semantics.
-3 The postfix -- operator is analogous to the postfix ++ operator, except that the value of
- the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
- it).
- Forward references: additive operators (<a href="#6.5.6">6.5.6</a>), compound assignment (<a href="#6.5.16.2">6.5.16.2</a>).
-<a name="6.5.2.5" href="#6.5.2.5"><b> 6.5.2.5 Compound literals</b></a>
- Constraints
-1 The type name shall specify a complete object type or an array of unknown size, but not a
- variable length array type.
-2 All the constraints for initializer lists in <a href="#6.7.9">6.7.9</a> also apply to compound literals.
- Semantics
-3 A postfix expression that consists of a parenthesized type name followed by a brace-
- enclosed list of initializers is a compound literal. It provides an unnamed object whose
- value is given by the initializer list.98)
-
-
- 97) Where a pointer to an atomic object can be formed, this is equivalent to the following code sequence
- where T is the type of E:
- T tmp;
- T result = E;
- do {
- tmp = result + 1;
- } while (!atomic_compare_exchange_strong(&E, &result, tmp));
- with result being the result of the operation.
-
-[<a name="#p85" href="p85">page 85</a>] (<a href="#Contents">Contents</a>)
-
-4 If the type name specifies an array of unknown size, the size is determined by the
- initializer list as specified in <a href="#6.7.9">6.7.9</a>, and the type of the compound literal is that of the
- completed array type. Otherwise (when the type name specifies an object type), the type
- of the compound literal is that specified by the type name. In either case, the result is an
- lvalue.
-5 The value of the compound literal is that of an unnamed object initialized by the
- initializer list. If the compound literal occurs outside the body of a function, the object
- has static storage duration; otherwise, it has automatic storage duration associated with
- the enclosing block.
-6 All the semantic rules for initializer lists in <a href="#6.7.9">6.7.9</a> also apply to compound literals.99)
-7 String literals, and compound literals with const-qualified types, need not designate
- distinct objects.100)
-8 EXAMPLE 1 The file scope definition
- int *p = (int []){2, 4};
- initializes p to point to the first element of an array of two ints, the first having the value two and the
- second, four. The expressions in this compound literal are required to be constant. The unnamed object
- has static storage duration.
-
-9 EXAMPLE 2 In contrast, in
- void f(void)
- {
- int *p;
- /*...*/
- p = (int [2]){*p};
- /*...*/
- }
- p is assigned the address of the first element of an array of two ints, the first having the value previously
- pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
- unnamed object has automatic storage duration.
-
-10 EXAMPLE 3 Initializers with designations can be combined with compound literals. Structure objects
- created using compound literals can be passed to functions without depending on member order:
- drawline((struct point){.x=1, .y=1},
- (struct point){.x=3, .y=4});
- Or, if drawline instead expected pointers to struct point:
-
-
-
- 98) Note that this differs from a cast expression. For example, a cast specifies a conversion to scalar types
- or void only, and the result of a cast expression is not an lvalue.
- 99) For example, subobjects without explicit initializers are initialized to zero.
- 100) This allows implementations to share storage for string literals and constant compound literals with
- the same or overlapping representations.
-
-[<a name="#p86" href="p86">page 86</a>] (<a href="#Contents">Contents</a>)
-
- drawline(&(struct point){.x=1, .y=1},
- &(struct point){.x=3, .y=4});
-
-11 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
- (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}
-
-12 EXAMPLE 5 The following three expressions have different meanings:
- "/tmp/fileXXXXXX"
- (char []){"/tmp/fileXXXXXX"}
- (const char []){"/tmp/fileXXXXXX"}
- The first always has static storage duration and has type array of char, but need not be modifiable; the last
- two have automatic storage duration when they occur within the body of a function, and the first of these
- two is modifiable.
-
-13 EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory
- and can even be shared. For example,
- (const char []){"abc"} == "abc"
- might yield 1 if the literals' storage is shared.
-
-14 EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly
- linked object. For example, there is no way to write a self-referential compound literal that could be used
- as the function argument in place of the named object endless_zeros below:
- struct int_list { int car; struct int_list *cdr; };
- struct int_list endless_zeros = {0, &endless_zeros};
- eval(endless_zeros);
-
-15 EXAMPLE 8 Each compound literal creates only a single object in a given scope:
- struct s { int i; };
- int f (void)
- {
- struct s *p = 0, *q;
- int j = 0;
- again:
- q = p, p = &((struct s){ j++ });
- if (j < 2) goto again;
- return p == q && q->i == 1;
- }
- The function f() always returns the value 1.
-16 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
- lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
- have an indeterminate value, which would result in undefined behavior.
-
- Forward references: type names (<a href="#6.7.7">6.7.7</a>), initialization (<a href="#6.7.9">6.7.9</a>).
-
-
-
-
-[<a name="#p87" href="p87">page 87</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.5.3" href="#6.5.3"><b> 6.5.3 Unary operators</b></a>
- Syntax
-1 unary-expression:
- postfix-expression
- ++ unary-expression
- -- unary-expression
- unary-operator cast-expression
- sizeof unary-expression
- sizeof ( type-name )
- alignof ( type-name )
- unary-operator: one of
- & * + - ~ !
-<a name="6.5.3.1" href="#6.5.3.1"><b> 6.5.3.1 Prefix increment and decrement operators</b></a>
- Constraints
-1 The operand of the prefix increment or decrement operator shall have qualified or
- unqualified real or pointer type and shall be a modifiable lvalue.
- Semantics
-2 The value of the operand of the prefix ++ operator is incremented. The result is the new
- value of the operand after incrementation. The expression ++E is equivalent to (E+=1).
- See the discussions of additive operators and compound assignment for information on
- constraints, types, side effects, and conversions and the effects of operations on pointers.
-3 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
- operand is decremented.
- Forward references: additive operators (<a href="#6.5.6">6.5.6</a>), compound assignment (<a href="#6.5.16.2">6.5.16.2</a>).
-<a name="6.5.3.2" href="#6.5.3.2"><b> 6.5.3.2 Address and indirection operators</b></a>
- Constraints
-1 The operand of the unary & operator shall be either a function designator, the result of a
- [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is
- not declared with the register storage-class specifier.
-2 The operand of the unary * operator shall have pointer type.
- Semantics
-3 The unary & operator yields the address of its operand. If the operand has type ''type'',
- the result has type ''pointer to type''. If the operand is the result of a unary * operator,
- neither that operator nor the & operator is evaluated and the result is as if both were
- omitted, except that the constraints on the operators still apply and the result is not an
-
-[<a name="#p88" href="p88">page 88</a>] (<a href="#Contents">Contents</a>)
-
- lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor
- the unary * that is implied by the [] is evaluated and the result is as if the & operator
- were removed and the [] operator were changed to a + operator. Otherwise, the result is
- a pointer to the object or function designated by its operand.
-4 The unary * operator denotes indirection. If the operand points to a function, the result is
- a function designator; if it points to an object, the result is an lvalue designating the
- object. If the operand has type ''pointer to type'', the result has type ''type''. If an
- invalid value has been assigned to the pointer, the behavior of the unary * operator is
- undefined.101)
- Forward references: storage-class specifiers (<a href="#6.7.1">6.7.1</a>), structure and union specifiers
- (<a href="#6.7.2.1">6.7.2.1</a>).
-<a name="6.5.3.3" href="#6.5.3.3"><b> 6.5.3.3 Unary arithmetic operators</b></a>
- Constraints
-1 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
- integer type; of the ! operator, scalar type.
- Semantics
-2 The result of the unary + operator is the value of its (promoted) operand. The integer
- promotions are performed on the operand, and the result has the promoted type.
-3 The result of the unary - operator is the negative of its (promoted) operand. The integer
- promotions are performed on the operand, and the result has the promoted type.
-4 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is,
- each bit in the result is set if and only if the corresponding bit in the converted operand is
- not set). The integer promotions are performed on the operand, and the result has the
- promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent
- to the maximum value representable in that type minus E.
-5 The result of the logical negation operator ! is 0 if the value of its operand compares
- unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int.
- The expression !E is equivalent to (0==E).
-
-
-
- 101) Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). It is
- always true that if E is a function designator or an lvalue that is a valid operand of the unary &
- operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of
- an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points.
- Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an
- address inappropriately aligned for the type of object pointed to, and the address of an object after the
- end of its lifetime.
-
-[<a name="#p89" href="p89">page 89</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.5.3.4" href="#6.5.3.4"><b> 6.5.3.4 The sizeof and alignof operators</b></a>
- Constraints
-1 The sizeof operator shall not be applied to an expression that has function type or an
- incomplete type, to the parenthesized name of such a type, or to an expression that
- designates a bit-field member. The alignof operator shall not be applied to a function
- type or an incomplete type.
- Semantics
-2 The sizeof operator yields the size (in bytes) of its operand, which may be an
- expression or the parenthesized name of a type. The size is determined from the type of
- the operand. The result is an integer. If the type of the operand is a variable length array
- type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an
- integer constant.
-3 The alignof operator yields the alignment requirement of its operand type. The result
- is an integer constant. When applied to an array type, the result is the alignment
- requirement of the element type.
-4 When sizeof is applied to an operand that has type char, unsigned char, or
- signed char, (or a qualified version thereof) the result is 1. When applied to an
- operand that has array type, the result is the total number of bytes in the array.102) When
- applied to an operand that has structure or union type, the result is the total number of
- bytes in such an object, including internal and trailing padding.
-5 The value of the result of both operators is implementation-defined, and its type (an
- unsigned integer type) is size_t, defined in <a href="#7.19"><stddef.h></a> (and other headers).
-6 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage
- allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to
- allocate and return a pointer to void. For example:
- extern void *alloc(size_t);
- double *dp = alloc(sizeof *dp);
- The implementation of the alloc function should ensure that its return value is aligned suitably for
- conversion to a pointer to double.
-
-7 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
- sizeof array / sizeof array[0]
-
-8 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a
- function:
- #include <a href="#7.19"><stddef.h></a>
-
-
-
- 102) When applied to a parameter declared to have array or function type, the sizeof operator yields the
- size of the adjusted (pointer) type (see <a href="#6.9.1">6.9.1</a>).
-
-[<a name="#p90" href="p90">page 90</a>] (<a href="#Contents">Contents</a>)
-
- size_t fsize3(int n)
- {
- char b[n+3]; // variable length array
- return sizeof b; // execution time sizeof
- }
- int main()
- {
- size_t size;
- size = fsize3(10); // fsize3 returns 13
- return 0;
- }
-
- Forward references: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), declarations (<a href="#6.7">6.7</a>),
- structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), type names (<a href="#6.7.7">6.7.7</a>), array declarators (<a href="#6.7.6.2">6.7.6.2</a>).
-<a name="6.5.4" href="#6.5.4"><b> 6.5.4 Cast operators</b></a>
- Syntax
-1 cast-expression:
- unary-expression
- ( type-name ) cast-expression
- Constraints
-2 Unless the type name specifies a void type, the type name shall specify qualified or
- unqualified scalar type and the operand shall have scalar type.
-3 Conversions that involve pointers, other than where permitted by the constraints of
- <a href="#6.5.16.1">6.5.16.1</a>, shall be specified by means of an explicit cast.
-4 A pointer type shall not be converted to any floating type. A floating type shall not be
- converted to any pointer type.
- Semantics
-5 Preceding an expression by a parenthesized type name converts the value of the
- expression to the named type. This construction is called a cast.103) A cast that specifies
- no conversion has no effect on the type or value of an expression.
-6 If the value of the expression is represented with greater precision or range than required
- by the type named by the cast (<a href="#6.3.1.8">6.3.1.8</a>), then the cast specifies a conversion even if the
- type of the expression is the same as the named type.
- Forward references: equality operators (<a href="#6.5.9">6.5.9</a>), function declarators (including
- prototypes) (<a href="#6.7.6.3">6.7.6.3</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>), type names (<a href="#6.7.7">6.7.7</a>).
-
-
-
- 103) A cast does not yield an lvalue. Thus, a cast to a qualified type has the same effect as a cast to the
- unqualified version of the type.
-
-[<a name="#p91" href="p91">page 91</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.5.5" href="#6.5.5"><b> 6.5.5 Multiplicative operators</b></a>
- Syntax
-1 multiplicative-expression:
- cast-expression
- multiplicative-expression * cast-expression
- multiplicative-expression / cast-expression
- multiplicative-expression % cast-expression
- Constraints
-2 Each of the operands shall have arithmetic type. The operands of the % operator shall
- have integer type.
- Semantics
-3 The usual arithmetic conversions are performed on the operands.
-4 The result of the binary * operator is the product of the operands.
-5 The result of the / operator is the quotient from the division of the first operand by the
- second; the result of the % operator is the remainder. In both operations, if the value of
- the second operand is zero, the behavior is undefined.
-6 When integers are divided, the result of the / operator is the algebraic quotient with any
- fractional part discarded.104) If the quotient a/b is representable, the expression
- (a/b)*b + a%b shall equal a; otherwise, the behavior of both a/b and a%b is
- undefined.
-<a name="6.5.6" href="#6.5.6"><b> 6.5.6 Additive operators</b></a>
- Syntax
-1 additive-expression:
- multiplicative-expression
- additive-expression + multiplicative-expression
- additive-expression - multiplicative-expression
- Constraints
-2 For addition, either both operands shall have arithmetic type, or one operand shall be a
- pointer to a complete object type and the other shall have integer type. (Incrementing is
- equivalent to adding 1.)
-3 For subtraction, one of the following shall hold:
-
-
-
-
- 104) This is often called ''truncation toward zero''.
-
-[<a name="#p92" href="p92">page 92</a>] (<a href="#Contents">Contents</a>)
-
- -- both operands have arithmetic type;
- -- both operands are pointers to qualified or unqualified versions of compatible complete
- object types; or
- -- the left operand is a pointer to a complete object type and the right operand has
- integer type.
- (Decrementing is equivalent to subtracting 1.)
- Semantics
-4 If both operands have arithmetic type, the usual arithmetic conversions are performed on
- them.
-5 The result of the binary + operator is the sum of the operands.
-6 The result of the binary - operator is the difference resulting from the subtraction of the
- second operand from the first.
-7 For the purposes of these operators, a pointer to an object that is not an element of an
- array behaves the same as a pointer to the first element of an array of length one with the
- type of the object as its element type.
-8 When an expression that has integer type is added to or subtracted from a pointer, the
- result has the type of the pointer operand. If the pointer operand points to an element of
- an array object, and the array is large enough, the result points to an element offset from
- the original element such that the difference of the subscripts of the resulting and original
- array elements equals the integer expression. In other words, if the expression P points to
- the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
- (P)-N (where N has the value n) point to, respectively, the i+n-th and i-n-th elements of
- the array object, provided they exist. Moreover, if the expression P points to the last
- element of an array object, the expression (P)+1 points one past the last element of the
- array object, and if the expression Q points one past the last element of an array object,
- the expression (Q)-1 points to the last element of the array object. If both the pointer
- operand and the result point to elements of the same array object, or one past the last
- element of the array object, the evaluation shall not produce an overflow; otherwise, the
- behavior is undefined. If the result points one past the last element of the array object, it
- shall not be used as the operand of a unary * operator that is evaluated.
-9 When two pointers are subtracted, both shall point to elements of the same array object,
- or one past the last element of the array object; the result is the difference of the
- subscripts of the two array elements. The size of the result is implementation-defined,
- and its type (a signed integer type) is ptrdiff_t defined in the <a href="#7.19"><stddef.h></a> header.
- If the result is not representable in an object of that type, the behavior is undefined. In
- other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of
- an array object, the expression (P)-(Q) has the value i-j provided the value fits in an
-
-[<a name="#p93" href="p93">page 93</a>] (<a href="#Contents">Contents</a>)
-
- object of type ptrdiff_t. Moreover, if the expression P points either to an element of
- an array object or one past the last element of an array object, and the expression Q points
- to the last element of the same array object, the expression ((Q)+1)-(P) has the same
- value as ((Q)-(P))+1 and as -((P)-((Q)+1)), and has the value zero if the
- expression P points one past the last element of the array object, even though the
- expression (Q)+1 does not point to an element of the array object.105)
-10 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
- {
- int n = 4, m = 3;
- int a[n][m];
- int (*p)[m] = a; // p == &a[0]
- p += 1; // p == &a[1]
- (*p)[2] = 99; // a[1][2] == 99
- n = p - a; // n == 1
- }
-11 If array a in the above example were declared to be an array of known constant size, and pointer p were
- declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
- the same.
-
- Forward references: array declarators (<a href="#6.7.6.2">6.7.6.2</a>), common definitions <a href="#7.19"><stddef.h></a>
- (<a href="#7.19">7.19</a>).
-<a name="6.5.7" href="#6.5.7"><b> 6.5.7 Bitwise shift operators</b></a>
- Syntax
-1 shift-expression:
- additive-expression
- shift-expression << additive-expression
- shift-expression >> additive-expression
- Constraints
-2 Each of the operands shall have integer type.
- Semantics
-3 The integer promotions are performed on each of the operands. The type of the result is
- that of the promoted left operand. If the value of the right operand is negative or is
-
- 105) Another way to approach pointer arithmetic is first to convert the pointer(s) to character pointer(s): In
- this scheme the integer expression added to or subtracted from the converted pointer is first multiplied
- by the size of the object originally pointed to, and the resulting pointer is converted back to the
- original type. For pointer subtraction, the result of the difference between the character pointers is
- similarly divided by the size of the object originally pointed to.
- When viewed in this way, an implementation need only provide one extra byte (which may overlap
- another object in the program) just after the end of the object in order to satisfy the ''one past the last
- element'' requirements.
-
-[<a name="#p94" href="p94">page 94</a>] (<a href="#Contents">Contents</a>)
-
- greater than or equal to the width of the promoted left operand, the behavior is undefined.
-4 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with
- zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo
- one more than the maximum value representable in the result type. If E1 has a signed
- type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is
- the resulting value; otherwise, the behavior is undefined.
-5 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
- or if E1 has a signed type and a nonnegative value, the value of the result is the integral
- part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
- resulting value is implementation-defined.
-<a name="6.5.8" href="#6.5.8"><b> 6.5.8 Relational operators</b></a>
- Syntax
-1 relational-expression:
- shift-expression
- relational-expression < shift-expression
- relational-expression > shift-expression
- relational-expression <= shift-expression
- relational-expression >= shift-expression
- Constraints
-2 One of the following shall hold:
- -- both operands have real type; or
- -- both operands are pointers to qualified or unqualified versions of compatible object
- types.
- Semantics
-3 If both of the operands have arithmetic type, the usual arithmetic conversions are
- performed.
-4 For the purposes of these operators, a pointer to an object that is not an element of an
- array behaves the same as a pointer to the first element of an array of length one with the
- type of the object as its element type.
-5 When two pointers are compared, the result depends on the relative locations in the
- address space of the objects pointed to. If two pointers to object types both point to the
- same object, or both point one past the last element of the same array object, they
- compare equal. If the objects pointed to are members of the same aggregate object,
- pointers to structure members declared later compare greater than pointers to members
- declared earlier in the structure, and pointers to array elements with larger subscript
- values compare greater than pointers to elements of the same array with lower subscript
-
-[<a name="#p95" href="p95">page 95</a>] (<a href="#Contents">Contents</a>)
-
- values. All pointers to members of the same union object compare equal. If the
- expression P points to an element of an array object and the expression Q points to the
- last element of the same array object, the pointer expression Q+1 compares greater than
- P. In all other cases, the behavior is undefined.
-6 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
- (greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is
- false.106) The result has type int.
-<a name="6.5.9" href="#6.5.9"><b> 6.5.9 Equality operators</b></a>
- Syntax
-1 equality-expression:
- relational-expression
- equality-expression == relational-expression
- equality-expression != relational-expression
- Constraints
-2 One of the following shall hold:
- -- both operands have arithmetic type;
- -- both operands are pointers to qualified or unqualified versions of compatible types;
- -- one operand is a pointer to an object type and the other is a pointer to a qualified or
- unqualified version of void; or
- -- one operand is a pointer and the other is a null pointer constant.
- Semantics
-3 The == (equal to) and != (not equal to) operators are analogous to the relational
- operators except for their lower precedence.107) Each of the operators yields 1 if the
- specified relation is true and 0 if it is false. The result has type int. For any pair of
- operands, exactly one of the relations is true.
-4 If both of the operands have arithmetic type, the usual arithmetic conversions are
- performed. Values of complex types are equal if and only if both their real parts are equal
- and also their imaginary parts are equal. Any two values of arithmetic types from
- different type domains are equal if and only if the results of their conversions to the
- (complex) result type determined by the usual arithmetic conversions are equal.
-
-
-
- 106) The expression a<b<c is not interpreted as in ordinary mathematics. As the syntax indicates, it
- means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
- 107) Because of the precedences, a<b == c<d is 1 whenever a<b and c<d have the same truth-value.
-
-[<a name="#p96" href="p96">page 96</a>] (<a href="#Contents">Contents</a>)
-
-5 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a
- null pointer constant, the null pointer constant is converted to the type of the pointer. If
- one operand is a pointer to an object type and the other is a pointer to a qualified or
- unqualified version of void, the former is converted to the type of the latter.
-6 Two pointers compare equal if and only if both are null pointers, both are pointers to the
- same object (including a pointer to an object and a subobject at its beginning) or function,
- both are pointers to one past the last element of the same array object, or one is a pointer
- to one past the end of one array object and the other is a pointer to the start of a different
- array object that happens to immediately follow the first array object in the address
- space.108)
-7 For the purposes of these operators, a pointer to an object that is not an element of an
- array behaves the same as a pointer to the first element of an array of length one with the
- type of the object as its element type.
-<a name="6.5.10" href="#6.5.10"><b> 6.5.10 Bitwise AND operator</b></a>
- Syntax
-1 AND-expression:
- equality-expression
- AND-expression & equality-expression
- Constraints
-2 Each of the operands shall have integer type.
- Semantics
-3 The usual arithmetic conversions are performed on the operands.
-4 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
- the result is set if and only if each of the corresponding bits in the converted operands is
- set).
-
-
-
-
- 108) Two objects may be adjacent in memory because they are adjacent elements of a larger array or
- adjacent members of a structure with no padding between them, or because the implementation chose
- to place them so, even though they are unrelated. If prior invalid pointer operations (such as accesses
- outside array bounds) produced undefined behavior, subsequent comparisons also produce undefined
- behavior.
-
-[<a name="#p97" href="p97">page 97</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.5.11" href="#6.5.11"><b> 6.5.11 Bitwise exclusive OR operator</b></a>
- Syntax
-1 exclusive-OR-expression:
- AND-expression
- exclusive-OR-expression ^ AND-expression
- Constraints
-2 Each of the operands shall have integer type.
- Semantics
-3 The usual arithmetic conversions are performed on the operands.
-4 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
- in the result is set if and only if exactly one of the corresponding bits in the converted
- operands is set).
-<a name="6.5.12" href="#6.5.12"><b> 6.5.12 Bitwise inclusive OR operator</b></a>
- Syntax
-1 inclusive-OR-expression:
- exclusive-OR-expression
- inclusive-OR-expression | exclusive-OR-expression
- Constraints
-2 Each of the operands shall have integer type.
- Semantics
-3 The usual arithmetic conversions are performed on the operands.
-4 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
- the result is set if and only if at least one of the corresponding bits in the converted
- operands is set).
-
-
-
-
-[<a name="#p98" href="p98">page 98</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.5.13" href="#6.5.13"><b> 6.5.13 Logical AND operator</b></a>
- Syntax
-1 logical-AND-expression:
- inclusive-OR-expression
- logical-AND-expression && inclusive-OR-expression
- Constraints
-2 Each of the operands shall have scalar type.
- Semantics
-3 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
- yields 0. The result has type int.
-4 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
- if the second operand is evaluated, there is a sequence point between the evaluations of
- the first and second operands. If the first operand compares equal to 0, the second
- operand is not evaluated.
-<a name="6.5.14" href="#6.5.14"><b> 6.5.14 Logical OR operator</b></a>
- Syntax
-1 logical-OR-expression:
- logical-AND-expression
- logical-OR-expression || logical-AND-expression
- Constraints
-2 Each of the operands shall have scalar type.
- Semantics
-3 The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it
- yields 0. The result has type int.
-4 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; if the
- second operand is evaluated, there is a sequence point between the evaluations of the first
- and second operands. If the first operand compares unequal to 0, the second operand is
- not evaluated.
-
-
-
-
-[<a name="#p99" href="p99">page 99</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.5.15" href="#6.5.15"><b> 6.5.15 Conditional operator</b></a>
- Syntax
-1 conditional-expression:
- logical-OR-expression
- logical-OR-expression ? expression : conditional-expression
- Constraints
-2 The first operand shall have scalar type.
-3 One of the following shall hold for the second and third operands:
- -- both operands have arithmetic type;
- -- both operands have the same structure or union type;
- -- both operands have void type;
- -- both operands are pointers to qualified or unqualified versions of compatible types;
- -- one operand is a pointer and the other is a null pointer constant; or
- -- one operand is a pointer to an object type and the other is a pointer to a qualified or
- unqualified version of void.
- Semantics
-4 The first operand is evaluated; there is a sequence point between its evaluation and the
- evaluation of the second or third operand (whichever is evaluated). The second operand
- is evaluated only if the first compares unequal to 0; the third operand is evaluated only if
- the first compares equal to 0; the result is the value of the second or third operand
- (whichever is evaluated), converted to the type described below.109)
-5 If both the second and third operands have arithmetic type, the result type that would be
- determined by the usual arithmetic conversions, were they applied to those two operands,
- is the type of the result. If both the operands have structure or union type, the result has
- that type. If both operands have void type, the result has void type.
-6 If both the second and third operands are pointers or one is a null pointer constant and the
- other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
- of the types referenced by both operands. Furthermore, if both operands are pointers to
- compatible types or to differently qualified versions of compatible types, the result type is
- a pointer to an appropriately qualified version of the composite type; if one operand is a
- null pointer constant, the result has the type of the other operand; otherwise, one operand
- is a pointer to void or a qualified version of void, in which case the result type is a
- pointer to an appropriately qualified version of void.
-
- 109) A conditional expression does not yield an lvalue.
-
-[<a name="#p100" href="p100">page 100</a>] (<a href="#Contents">Contents</a>)
-
-7 EXAMPLE The common type that results when the second and third operands are pointers is determined
- in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two
- pointers have compatible types.
-8 Given the declarations
- const void *c_vp;
- void *vp;
- const int *c_ip;
- volatile int *v_ip;
- int *ip;
- const char *c_cp;
- the third column in the following table is the common type that is the result of a conditional expression in
- which the first two columns are the second and third operands (in either order):
- c_vp c_ip const void *
- v_ip 0 volatile int *
- c_ip v_ip const volatile int *
- vp c_cp const void *
- ip c_ip const int *
- vp ip void *
-
-<a name="6.5.16" href="#6.5.16"><b> 6.5.16 Assignment operators</b></a>
- Syntax
-1 assignment-expression:
- conditional-expression
- unary-expression assignment-operator assignment-expression
- assignment-operator: one of
- = *= /= %= += -= <<= >>= &= ^= |=
- Constraints
-2 An assignment operator shall have a modifiable lvalue as its left operand.
- Semantics
-3 An assignment operator stores a value in the object designated by the left operand. An
- assignment expression has the value of the left operand after the assignment,110) but is not
- an lvalue. The type of an assignment expression is the type of the left operand unless the
- left operand has qualified type, in which case it is the unqualified version of the type of
- the left operand. The side effect of updating the stored value of the left operand is
- sequenced after the value computations of the left and right operands. The evaluations of
- the operands are unsequenced.
-
-
-
-
- 110) The implementation is permitted to read the object to determine the value but is not required to, even
- when the object has volatile-qualified type.
-
-[<a name="#p101" href="p101">page 101</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.5.16.1" href="#6.5.16.1"><b> 6.5.16.1 Simple assignment</b></a>
- Constraints
-1 One of the following shall hold:111)
- -- the left operand has qualified or unqualified arithmetic type and the right has
- arithmetic type;
- -- the left operand has a qualified or unqualified version of a structure or union type
- compatible with the type of the right;
- -- both operands are pointers to qualified or unqualified versions of compatible types,
- and the type pointed to by the left has all the qualifiers of the type pointed to by the
- right;
- -- one operand is a pointer to an object type and the other is a pointer to a qualified or
- unqualified version of void, and the type pointed to by the left has all the qualifiers
- of the type pointed to by the right;
- -- the left operand is a pointer and the right is a null pointer constant; or
- -- the left operand has type _Bool and the right is a pointer.
- Semantics
-2 In simple assignment (=), the value of the right operand is converted to the type of the
- assignment expression and replaces the value stored in the object designated by the left
- operand.
-3 If the value being stored in an object is read from another object that overlaps in any way
- the storage of the first object, then the overlap shall be exact and the two objects shall
- have qualified or unqualified versions of a compatible type; otherwise, the behavior is
- undefined.
-4 EXAMPLE 1 In the program fragment
- int f(void);
- char c;
- /* ... */
- if ((c = f()) == -1)
- /* ... */
- the int value returned by the function may be truncated when stored in the char, and then converted back
- to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
- values as unsigned char (and char is narrower than int), the result of the conversion cannot be
-
-
-
- 111) The asymmetric appearance of these constraints with respect to type qualifiers is due to the conversion
- (specified in <a href="#6.3.2.1">6.3.2.1</a>) that changes lvalues to ''the value of the expression'' and thus removes any type
- qualifiers that were applied to the type category of the expression (for example, it removes const but
- not volatile from the type int volatile * const).
-
-[<a name="#p102" href="p102">page 102</a>] (<a href="#Contents">Contents</a>)
-
- negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
- variable c should be declared as int.
-
-5 EXAMPLE 2 In the fragment:
- char c;
- int i;
- long l;
- l = (c = i);
- the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
- of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
- that is, long int type.
-
-6 EXAMPLE 3 Consider the fragment:
- const char **cpp;
- char *p;
- const char c = 'A';
- cpp = &p; // constraint violation
- *cpp = &c; // valid
- *p = 0; // valid
- The first assignment is unsafe because it would allow the following valid code to attempt to change the
- value of the const object c.
-
-<a name="6.5.16.2" href="#6.5.16.2"><b> 6.5.16.2 Compound assignment</b></a>
- Constraints
-1 For the operators += and -= only, either the left operand shall be a pointer to a complete
- object type and the right shall have integer type, or the left operand shall have qualified or
- unqualified arithmetic type and the right shall have arithmetic type.
-2 For the other operators, each operand shall have arithmetic type consistent with those
- allowed by the corresponding binary operator.
- Semantics
-3 A compound assignment of the form E1 op = E2 is equivalent to the simple assignment
- expression E1 = E1 op (E2), except that the lvalue E1 is evaluated only once, and with
- respect to an indeterminately-sequenced function call, the operation of a compound
- assignment is a single evaluation. If E1 has an _Atomic-qualified type, compound
- assignment is a read-modify-write operation with memory_order_seq_cst memory
- order semantics.112)
-
-
-
-
-[<a name="#p103" href="p103">page 103</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.5.17" href="#6.5.17"><b> 6.5.17 Comma operator</b></a>
- Syntax
-1 expression:
- assignment-expression
- expression , assignment-expression
- Semantics
-2 The left operand of a comma operator is evaluated as a void expression; there is a
- sequence point between its evaluation and that of the right operand. Then the right
- operand is evaluated; the result has its type and value.113)
-3 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot
- appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists
- of initializers). On the other hand, it can be used within a parenthesized expression or within the second
- expression of a conditional operator in such contexts. In the function call
- f(a, (t=3, t+2), c)
- the function has three arguments, the second of which has the value 5.
-
- Forward references: initialization (<a href="#6.7.9">6.7.9</a>).
-
-
-
-
- 112) Where a pointer to an atomic object can be formed, this is equivalent to the following code sequence
- where T is the type of E1:
- T tmp = E1;
- T result;
- do {
- result = tmp op (E2);
- } while (!atomic_compare_exchange_strong(&E1, &tmp, result));
- with result being the result of the operation.
- 113) A comma operator does not yield an lvalue.
-
-[<a name="#p104" href="p104">page 104</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.6" href="#6.6"><b> 6.6 Constant expressions</b></a>
- Syntax
-1 constant-expression:
- conditional-expression
- Description
-2 A constant expression can be evaluated during translation rather than runtime, and
- accordingly may be used in any place that a constant may be.
- Constraints
-3 Constant expressions shall not contain assignment, increment, decrement, function-call,
- or comma operators, except when they are contained within a subexpression that is not
- evaluated.114)
-4 Each constant expression shall evaluate to a constant that is in the range of representable
- values for its type.
- Semantics
-5 An expression that evaluates to a constant is required in several contexts. If a floating
- expression is evaluated in the translation environment, the arithmetic precision and range
- shall be at least as great as if the expression were being evaluated in the execution
- environment.115)
-6 An integer constant expression116) shall have integer type and shall only have operands
- that are integer constants, enumeration constants, character constants, sizeof
- expressions whose results are integer constants, and floating constants that are the
- immediate operands of casts. Cast operators in an integer constant expression shall only
- convert arithmetic types to integer types, except as part of an operand to the sizeof
- operator.
-7 More latitude is permitted for constant expressions in initializers. Such a constant
- expression shall be, or evaluate to, one of the following:
- -- an arithmetic constant expression,
-
-
-
- 114) The operand of a sizeof operator is usually not evaluated (<a href="#6.5.3.4">6.5.3.4</a>).
- 115) The use of evaluation formats as characterized by FLT_EVAL_METHOD also applies to evaluation in
- the translation environment.
- 116) An integer constant expression is required in a number of contexts such as the size of a bit-field
- member of a structure, the value of an enumeration constant, and the size of a non-variable length
- array. Further constraints that apply to the integer constant expressions used in conditional-inclusion
- preprocessing directives are discussed in <a href="#6.10.1">6.10.1</a>.
-
-[<a name="#p105" href="p105">page 105</a>] (<a href="#Contents">Contents</a>)
-
- -- a null pointer constant,
- -- an address constant, or
- -- an address constant for a complete object type plus or minus an integer constant
- expression.
-8 An arithmetic constant expression shall have arithmetic type and shall only have
- operands that are integer constants, floating constants, enumeration constants, character
- constants, and sizeof expressions. Cast operators in an arithmetic constant expression
- shall only convert arithmetic types to arithmetic types, except as part of an operand to a
- sizeof operator whose result is an integer constant.
-9 An address constant is a null pointer, a pointer to an lvalue designating an object of static
- storage duration, or a pointer to a function designator; it shall be created explicitly using
- the unary & operator or an integer constant cast to pointer type, or implicitly by the use of
- an expression of array or function type. The array-subscript [] and member-access .
- and -> operators, the address & and indirection * unary operators, and pointer casts may
- be used in the creation of an address constant, but the value of an object shall not be
- accessed by use of these operators.
-10 An implementation may accept other forms of constant expressions.
-11 The semantic rules for the evaluation of a constant expression are the same as for
- nonconstant expressions.117)
- Forward references: array declarators (<a href="#6.7.6.2">6.7.6.2</a>), initialization (<a href="#6.7.9">6.7.9</a>).
-
-
-
-
- 117) Thus, in the following initialization,
- static int i = 2 || 1 / 0;
- the expression is a valid integer constant expression with value one.
-
-[<a name="#p106" href="p106">page 106</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.7" href="#6.7"><b> 6.7 Declarations</b></a>
- Syntax
-1 declaration:
- declaration-specifiers init-declarator-listopt ;
- static_assert-declaration *
- declaration-specifiers:
- storage-class-specifier declaration-specifiersopt
- type-specifier declaration-specifiersopt
- type-qualifier declaration-specifiersopt
- function-specifier declaration-specifiersopt
- alignment-specifier declaration-specifiersopt
- init-declarator-list:
- init-declarator
- init-declarator-list , init-declarator
- init-declarator:
- declarator
- declarator = initializer
- Constraints
-2 A declaration other than a static_assert declaration shall declare at least a declarator
- (other than the parameters of a function or the members of a structure or union), a tag, or
- the members of an enumeration.
-3 If an identifier has no linkage, there shall be no more than one declaration of the identifier
- (in a declarator or type specifier) with the same scope and in the same name space, except
- that a typedef name can be redefined to denote the same type as it currently does and tags
- may be redeclared as specified in <a href="#6.7.2.3">6.7.2.3</a>.
-4 All declarations in the same scope that refer to the same object or function shall specify
- compatible types.
- Semantics
-5 A declaration specifies the interpretation and attributes of a set of identifiers. A definition
- of an identifier is a declaration for that identifier that:
- -- for an object, causes storage to be reserved for that object;
- -- for a function, includes the function body;118)
-
-
-
- 118) Function definitions have a different syntax, described in <a href="#6.9.1">6.9.1</a>.
-
-[<a name="#p107" href="p107">page 107</a>] (<a href="#Contents">Contents</a>)
-
- -- for an enumeration constant or typedef name, is the (only) declaration of the
- identifier.
-6 The declaration specifiers consist of a sequence of specifiers that indicate the linkage,
- storage duration, and part of the type of the entities that the declarators denote. The init-
- declarator-list is a comma-separated sequence of declarators, each of which may have
- additional type information, or an initializer, or both. The declarators contain the
- identifiers (if any) being declared.
-7 If an identifier for an object is declared with no linkage, the type for the object shall be *
- complete by the end of its declarator, or by the end of its init-declarator if it has an
- initializer; in the case of function parameters (including in prototypes), it is the adjusted
- type (see <a href="#6.7.6.3">6.7.6.3</a>) that is required to be complete.
- Forward references: declarators (<a href="#6.7.6">6.7.6</a>), enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), initialization
- (<a href="#6.7.9">6.7.9</a>), type names (<a href="#6.7.7">6.7.7</a>), type qualifiers (<a href="#6.7.3">6.7.3</a>).
-<a name="6.7.1" href="#6.7.1"><b> 6.7.1 Storage-class specifiers</b></a>
- Syntax
-1 storage-class-specifier:
- typedef
- extern
- static
- _Thread_local
- auto
- register
- Constraints
-2 At most, one storage-class specifier may be given in the declaration specifiers in a
- declaration, except that _Thread_local may appear with static or extern.119)
-3 In the declaration of an object with block scope, if the declaration specifiers include
- _Thread_local, they shall also include either static or extern. If
- _Thread_local appears in any declaration of an object, it shall be present in every
- declaration of that object.
- Semantics
-4 The typedef specifier is called a ''storage-class specifier'' for syntactic convenience
- only; it is discussed in <a href="#6.7.8">6.7.8</a>. The meanings of the various linkages and storage durations
- were discussed in <a href="#6.2.2">6.2.2</a> and <a href="#6.2.4">6.2.4</a>.
-
-
-
- 119) See ''future language directions'' (<a href="#6.11.5">6.11.5</a>).
-
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-
-5 A declaration of an identifier for an object with storage-class specifier register
- suggests that access to the object be as fast as possible. The extent to which such
- suggestions are effective is implementation-defined.120)
-6 The declaration of an identifier for a function that has block scope shall have no explicit
- storage-class specifier other than extern.
-7 If an aggregate or union object is declared with a storage-class specifier other than
- typedef, the properties resulting from the storage-class specifier, except with respect to
- linkage, also apply to the members of the object, and so on recursively for any aggregate
- or union member objects.
- Forward references: type definitions (<a href="#6.7.8">6.7.8</a>).
-<a name="6.7.2" href="#6.7.2"><b> 6.7.2 Type specifiers</b></a>
- Syntax
-1 type-specifier:
- void
- char
- short
- int
- long
- float
- double
- signed
- unsigned
- _Bool
- _Complex
- _Atomic ( type-name )
- struct-or-union-specifier
- enum-specifier
- typedef-name
- Constraints
-2 At least one type specifier shall be given in the declaration specifiers in each declaration,
- and in the specifier-qualifier list in each struct declaration and type name. Each list of
-
-
- 120) The implementation may treat any register declaration simply as an auto declaration. However,
- whether or not addressable storage is actually used, the address of any part of an object declared with
- storage-class specifier register cannot be computed, either explicitly (by use of the unary &
- operator as discussed in <a href="#6.5.3.2">6.5.3.2</a>) or implicitly (by converting an array name to a pointer as discussed in
- <a href="#6.3.2.1">6.3.2.1</a>). Thus, the only operator that can be applied to an array declared with storage-class specifier
- register is sizeof.
-
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-
- type specifiers shall be one of the following multisets (delimited by commas, when there
- is more than one multiset per item); the type specifiers may occur in any order, possibly
- intermixed with the other declaration specifiers.
- -- void
- -- char
- -- signed char
- -- unsigned char
- -- short, signed short, short int, or signed short int
- -- unsigned short, or unsigned short int
- -- int, signed, or signed int
- -- unsigned, or unsigned int
- -- long, signed long, long int, or signed long int
- -- unsigned long, or unsigned long int
- -- long long, signed long long, long long int, or
- signed long long int
- -- unsigned long long, or unsigned long long int
- -- float
- -- double
- -- long double
- -- _Bool
- -- float _Complex
- -- double _Complex
- -- long double _Complex
- -- _Atomic ( type-name )
- -- struct or union specifier
- -- enum specifier
- -- typedef name
-3 The type specifier _Complex shall not be used if the implementation does not support
- complex types; likewise, _Atomic shall not be used if the implementation does not
- support atomic types (see <a href="#6.10.8.3">6.10.8.3</a>).
-
-
-
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-
- Semantics
-4 The _Atomic form of type specifier designates the _Atomic-qualified version of the
- named type.
-5 Specifiers for structures, unions, and enumerations are discussed in <a href="#6.7.2.1">6.7.2.1</a> through
-<a name="6.7.2.3" href="#6.7.2.3"><b> 6.7.2.3. Declarations of typedef names are discussed in 6.7.8. The characteristics of the</b></a>
- other types are discussed in <a href="#6.2.5">6.2.5</a>.
-6 Each of the comma-separated multisets designates the same type, except that for bit-
- fields, it is implementation-defined whether the specifier int designates the same type as
- signed int or the same type as unsigned int.
- Forward references: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
- (<a href="#6.7.2.1">6.7.2.1</a>), tags (<a href="#6.7.2.3">6.7.2.3</a>), type definitions (<a href="#6.7.8">6.7.8</a>).
-<a name="6.7.2.1" href="#6.7.2.1"><b> 6.7.2.1 Structure and union specifiers</b></a>
- Syntax
-1 struct-or-union-specifier:
- struct-or-union identifieropt { struct-declaration-list }
- struct-or-union identifier
- struct-or-union:
- struct
- union
- struct-declaration-list:
- struct-declaration
- struct-declaration-list struct-declaration
- struct-declaration:
- specifier-qualifier-list struct-declarator-listopt ;
- static_assert-declaration
- specifier-qualifier-list:
- type-specifier specifier-qualifier-listopt
- type-qualifier specifier-qualifier-listopt
- struct-declarator-list:
- struct-declarator
- struct-declarator-list , struct-declarator
- struct-declarator:
- declarator
- declaratoropt : constant-expression
-
-
-
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-
- Constraints
-2 A struct-declaration that does not declare an anonymous structure or anonymous union
- shall contain a struct-declarator-list.
-3 A structure or union shall not contain a member with incomplete or function type (hence,
- a structure shall not contain an instance of itself, but may contain a pointer to an instance
- of itself), except that the last member of a structure with more than one named member
- may have incomplete array type; such a structure (and any union containing, possibly
- recursively, a member that is such a structure) shall not be a member of a structure or an
- element of an array.
-4 The expression that specifies the width of a bit-field shall be an integer constant
- expression with a nonnegative value that does not exceed the width of an object of the
- type that would be specified were the colon and expression omitted.121) If the value is
- zero, the declaration shall have no declarator.
-5 A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed
- int, unsigned int, or some other implementation-defined type.
- Semantics
-6 As discussed in <a href="#6.2.5">6.2.5</a>, a structure is a type consisting of a sequence of members, whose
- storage is allocated in an ordered sequence, and a union is a type consisting of a sequence
- of members whose storage overlap.
-7 Structure and union specifiers have the same form. The keywords struct and union
- indicate that the type being specified is, respectively, a structure type or a union type.
-8 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
- within a translation unit. The struct-declaration-list is a sequence of declarations for the
- members of the structure or union. If the struct-declaration-list contains no named
- members, no anonymous structures, and no anonymous unions, the behavior is undefined.
- The type is incomplete until immediately after the } that terminates the list, and complete
- thereafter.
-9 A member of a structure or union may have any complete object type other than a
- variably modified type.122) In addition, a member may be declared to consist of a
- specified number of bits (including a sign bit, if any). Such a member is called a
- bit-field;123) its width is preceded by a colon.
-
-
-
- 121) While the number of bits in a _Bool object is at least CHAR_BIT, the width (number of sign and
- value bits) of a _Bool may be just 1 bit.
- 122) A structure or union cannot contain a member with a variably modified type because member names
- are not ordinary identifiers as defined in <a href="#6.2.3">6.2.3</a>.
-
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-
-10 A bit-field is interpreted as a signed or unsigned integer type consisting of the specified
- number of bits.124) If the value 0 or 1 is stored into a nonzero-width bit-field of type
- _Bool, the value of the bit-field shall compare equal to the value stored; a _Bool bit-
- field has the semantics of a _Bool.
-11 An implementation may allocate any addressable storage unit large enough to hold a bit-
- field. If enough space remains, a bit-field that immediately follows another bit-field in a
- structure shall be packed into adjacent bits of the same unit. If insufficient space remains,
- whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is
- implementation-defined. The order of allocation of bit-fields within a unit (high-order to
- low-order or low-order to high-order) is implementation-defined. The alignment of the
- addressable storage unit is unspecified.
-12 A bit-field declaration with no declarator, but only a colon and a width, indicates an
- unnamed bit-field.125) As a special case, a bit-field structure member with a width of 0
- indicates that no further bit-field is to be packed into the unit in which the previous bit-
- field, if any, was placed.
-13 An unnamed member of structure type with no tag is called an anonymous structure; an
- unnamed member of union type with no tag is called an anonymous union. The members
- of an anonymous structure or union are considered to be members of the containing
- structure or union. This applies recursively if the containing structure or union is also
- anonymous.
-14 Each non-bit-field member of a structure or union object is aligned in an implementation-
- defined manner appropriate to its type.
-15 Within a structure object, the non-bit-field members and the units in which bit-fields
- reside have addresses that increase in the order in which they are declared. A pointer to a
- structure object, suitably converted, points to its initial member (or if that member is a
- bit-field, then to the unit in which it resides), and vice versa. There may be unnamed
- padding within a structure object, but not at its beginning.
-16 The size of a union is sufficient to contain the largest of its members. The value of at
- most one of the members can be stored in a union object at any time. A pointer to a
- union object, suitably converted, points to each of its members (or if a member is a bit-
- field, then to the unit in which it resides), and vice versa.
-
-
- 123) The unary & (address-of) operator cannot be applied to a bit-field object; thus, there are no pointers to
- or arrays of bit-field objects.
- 124) As specified in <a href="#6.7.2">6.7.2</a> above, if the actual type specifier used is int or a typedef-name defined as int,
- then it is implementation-defined whether the bit-field is signed or unsigned.
- 125) An unnamed bit-field structure member is useful for padding to conform to externally imposed
- layouts.
-
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-
-17 There may be unnamed padding at the end of a structure or union.
-18 As a special case, the last element of a structure with more than one named member may
- have an incomplete array type; this is called a flexible array member. In most situations,
- the flexible array member is ignored. In particular, the size of the structure is as if the
- flexible array member were omitted except that it may have more trailing padding than
- the omission would imply. However, when a . (or ->) operator has a left operand that is
- (a pointer to) a structure with a flexible array member and the right operand names that
- member, it behaves as if that member were replaced with the longest array (with the same
- element type) that would not make the structure larger than the object being accessed; the
- offset of the array shall remain that of the flexible array member, even if this would differ
- from that of the replacement array. If this array would have no elements, it behaves as if
- it had one element but the behavior is undefined if any attempt is made to access that
- element or to generate a pointer one past it.
-19 EXAMPLE 1 The following illustrates anonymous structures and unions:
- struct v {
- union { // anonymous union
- struct { int i, j; }; // anonymous structure
- struct { long k, l; } w;
- };
- int m;
- } v1;
- v1.i = 2; // valid
- v1.k = 3; // invalid: inner structure is not anonymous
- v1.w.k = 5; // valid
-
-20 EXAMPLE 2 After the declaration:
- struct s { int n; double d[]; };
- the structure struct s has a flexible array member d. A typical way to use this is:
- int m = /* some value */;
- struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));
- and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
- p had been declared as:
- struct { int n; double d[m]; } *p;
- (there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
- not be the same).
-21 Following the above declaration:
- struct s t1 = { 0 }; // valid
- struct s t2 = { 1, { <a href="#4.2">4.2</a> }}; // invalid
- t1.n = 4; // valid
- t1.d[0] = <a href="#4.2">4.2</a>; // might be undefined behavior
- The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
- contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
-
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-
- sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)
- in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming
- code.
-22 After the further declaration:
- struct ss { int n; };
- the expressions:
- sizeof (struct s) >= sizeof (struct ss)
- sizeof (struct s) >= offsetof(struct s, d)
- are always equal to 1.
-23 If sizeof (double) is 8, then after the following code is executed:
- struct s *s1;
- struct s *s2;
- s1 = malloc(sizeof (struct s) + 64);
- s2 = malloc(sizeof (struct s) + 46);
- and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
- purposes, as if the identifiers had been declared as:
- struct { int n; double d[8]; } *s1;
- struct { int n; double d[5]; } *s2;
-24 Following the further successful assignments:
- s1 = malloc(sizeof (struct s) + 10);
- s2 = malloc(sizeof (struct s) + 6);
- they then behave as if the declarations were:
- struct { int n; double d[1]; } *s1, *s2;
- and:
- double *dp;
- dp = &(s1->d[0]); // valid
- *dp = 42; // valid
- dp = &(s2->d[0]); // valid
- *dp = 42; // undefined behavior
-25 The assignment:
- *s1 = *s2;
- only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes
- of the structure, they might be copied or simply overwritten with indeterminate values.
-
- Forward references: declarators (<a href="#6.7.6">6.7.6</a>), tags (<a href="#6.7.2.3">6.7.2.3</a>).
-
-
-
-
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-
-<a name="6.7.2.2" href="#6.7.2.2"><b> 6.7.2.2 Enumeration specifiers</b></a>
- Syntax
-1 enum-specifier:
- enum identifieropt { enumerator-list }
- enum identifieropt { enumerator-list , }
- enum identifier
- enumerator-list:
- enumerator
- enumerator-list , enumerator
- enumerator:
- enumeration-constant
- enumeration-constant = constant-expression
- Constraints
-2 The expression that defines the value of an enumeration constant shall be an integer
- constant expression that has a value representable as an int.
- Semantics
-3 The identifiers in an enumerator list are declared as constants that have type int and
- may appear wherever such are permitted.126) An enumerator with = defines its
- enumeration constant as the value of the constant expression. If the first enumerator has
- no =, the value of its enumeration constant is 0. Each subsequent enumerator with no =
- defines its enumeration constant as the value of the constant expression obtained by
- adding 1 to the value of the previous enumeration constant. (The use of enumerators with
- = may produce enumeration constants with values that duplicate other values in the same
- enumeration.) The enumerators of an enumeration are also known as its members.
-4 Each enumerated type shall be compatible with char, a signed integer type, or an
- unsigned integer type. The choice of type is implementation-defined,127) but shall be
- capable of representing the values of all the members of the enumeration. The
- enumerated type is incomplete until immediately after the } that terminates the list of
- enumerator declarations, and complete thereafter.
-
-
-
-
- 126) Thus, the identifiers of enumeration constants declared in the same scope shall all be distinct from
- each other and from other identifiers declared in ordinary declarators.
- 127) An implementation may delay the choice of which integer type until all enumeration constants have
- been seen.
-
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-
-5 EXAMPLE The following fragment:
- enum hue { chartreuse, burgundy, claret=20, winedark };
- enum hue col, *cp;
- col = claret;
- cp = &col;
- if (*cp != burgundy)
- /* ... */
- makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
- pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
-
- Forward references: tags (<a href="#6.7.2.3">6.7.2.3</a>).
-<a name="6.7.2.3" href="#6.7.2.3"><b> 6.7.2.3 Tags</b></a>
- Constraints
-1 A specific type shall have its content defined at most once.
-2 Where two declarations that use the same tag declare the same type, they shall both use
- the same choice of struct, union, or enum.
-3 A type specifier of the form
- enum identifier
- without an enumerator list shall only appear after the type it specifies is complete.
- Semantics
-4 All declarations of structure, union, or enumerated types that have the same scope and
- use the same tag declare the same type. Irrespective of whether there is a tag or what
- other declarations of the type are in the same translation unit, the type is incomplete128)
- until immediately after the closing brace of the list defining the content, and complete
- thereafter.
-5 Two declarations of structure, union, or enumerated types which are in different scopes or
- use different tags declare distinct types. Each declaration of a structure, union, or
- enumerated type which does not include a tag declares a distinct type.
-6 A type specifier of the form
-
-
-
-
- 128) An incomplete type may only by used when the size of an object of that type is not needed. It is not
- needed, for example, when a typedef name is declared to be a specifier for a structure or union, or
- when a pointer to or a function returning a structure or union is being declared. (See incomplete types
- in <a href="#6.2.5">6.2.5</a>.) The specification has to be complete before such a function is called or defined.
-
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-
- struct-or-union identifieropt { struct-declaration-list }
- or
- enum identifieropt { enumerator-list }
- or
- enum identifieropt { enumerator-list , }
- declares a structure, union, or enumerated type. The list defines the structure content,
- union content, or enumeration content. If an identifier is provided,129) the type specifier
- also declares the identifier to be the tag of that type.
-7 A declaration of the form
- struct-or-union identifier ;
- specifies a structure or union type and declares the identifier as a tag of that type.130)
-8 If a type specifier of the form
- struct-or-union identifier
- occurs other than as part of one of the above forms, and no other declaration of the
- identifier as a tag is visible, then it declares an incomplete structure or union type, and
- declares the identifier as the tag of that type.130)
-9 If a type specifier of the form
- struct-or-union identifier
- or
- enum identifier
- occurs other than as part of one of the above forms, and a declaration of the identifier as a
- tag is visible, then it specifies the same type as that other declaration, and does not
- redeclare the tag.
-10 EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
- struct tnode {
- int count;
- struct tnode *left, *right;
- };
- specifies a structure that contains an integer and two pointers to objects of the same type. Once this
- declaration has been given, the declaration
-
-
-
-
- 129) If there is no identifier, the type can, within the translation unit, only be referred to by the declaration
- of which it is a part. Of course, when the declaration is of a typedef name, subsequent declarations
- can make use of that typedef name to declare objects having the specified structure, union, or
- enumerated type.
- 130) A similar construction with enum does not exist.
-
-[<a name="#p118" href="p118">page 118</a>] (<a href="#Contents">Contents</a>)
-
- struct tnode s, *sp;
- declares s to be an object of the given type and sp to be a pointer to an object of the given type. With
- these declarations, the expression sp->left refers to the left struct tnode pointer of the object to
- which sp points; the expression s.right->count designates the count member of the right struct
- tnode pointed to from s.
-11 The following alternative formulation uses the typedef mechanism:
- typedef struct tnode TNODE;
- struct tnode {
- int count;
- TNODE *left, *right;
- };
- TNODE s, *sp;
-
-12 EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential
- structures, the declarations
- struct s1 { struct s2 *s2p; /* ... */ }; // D1
- struct s2 { struct s1 *s1p; /* ... */ }; // D2
- specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
- declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
- D2. To eliminate this context sensitivity, the declaration
- struct s2;
- may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then
- completes the specification of the new type.
-
- Forward references: declarators (<a href="#6.7.6">6.7.6</a>), type definitions (<a href="#6.7.8">6.7.8</a>).
-<a name="6.7.3" href="#6.7.3"><b> 6.7.3 Type qualifiers</b></a>
- Syntax
-1 type-qualifier:
- const
- restrict
- volatile
- _Atomic
- Constraints
-2 Types other than pointer types whose referenced type is an object type shall not be
- restrict-qualified.
- Semantics
-3 The properties associated with qualified types are meaningful only for expressions that
- are lvalues.131)
-4 If the same qualifier appears more than once in the same specifier-qualifier-list, either
- directly or via one or more typedefs, the behavior is the same as if it appeared only
- once.
-[<a name="#p119" href="p119">page 119</a>] (<a href="#Contents">Contents</a>)
-
-5 If an attempt is made to modify an object defined with a const-qualified type through use
- of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is
- made to refer to an object defined with a volatile-qualified type through use of an lvalue
- with non-volatile-qualified type, the behavior is undefined.132) If an attempt is made to
- refer to an object defined with an _Atomic-qualified type through use of an lvalue with
- non-_Atomic-qualified type, the behavior is undefined.
-6 An object that has volatile-qualified type may be modified in ways unknown to the
- implementation or have other unknown side effects. Therefore any expression referring
- to such an object shall be evaluated strictly according to the rules of the abstract machine,
- as described in <a href="#5.1.2.3">5.1.2.3</a>. Furthermore, at every sequence point the value last stored in the
- object shall agree with that prescribed by the abstract machine, except as modified by the
- unknown factors mentioned previously.133) What constitutes an access to an object that
- has volatile-qualified type is implementation-defined.
-7 An object that is accessed through a restrict-qualified pointer has a special association
- with that pointer. This association, defined in <a href="#6.7.3.1">6.7.3.1</a> below, requires that all accesses to
- that object use, directly or indirectly, the value of that particular pointer.134) The intended
- use of the restrict qualifier (like the register storage class) is to promote
- optimization, and deleting all instances of the qualifier from all preprocessing translation
- units composing a conforming program does not change its meaning (i.e., observable
- behavior).
-8 If the specification of an array type includes any type qualifiers, the element type is so-
- qualified, not the array type. If the specification of a function type includes any type
- qualifiers, the behavior is undefined.135)
-9 For two qualified types to be compatible, both shall have the identically qualified version
- of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers
- does not affect the specified type.
-
- 131) The implementation may place a const object that is not volatile in a read-only region of
- storage. Moreover, the implementation need not allocate storage for such an object if its address is
- never used.
- 132) This applies to those objects that behave as if they were defined with qualified types, even if they are
- never actually defined as objects in the program (such as an object at a memory-mapped input/output
- address).
- 133) A volatile declaration may be used to describe an object corresponding to a memory-mapped
- input/output port or an object accessed by an asynchronously interrupting function. Actions on
- objects so declared shall not be ''optimized out'' by an implementation or reordered except as
- permitted by the rules for evaluating expressions.
- 134) For example, a statement that assigns a value returned by malloc to a single pointer establishes this
- association between the allocated object and the pointer.
- 135) Both of these can occur through the use of typedefs.
-
-[<a name="#p120" href="p120">page 120</a>] (<a href="#Contents">Contents</a>)
-
-10 EXAMPLE 1 An object declared
- extern const volatile int real_time_clock;
- may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
-
-11 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers
- modify an aggregate type:
- const struct s { int mem; } cs = { 1 };
- struct s ncs; // the object ncs is modifiable
- typedef int A[2][3];
- const A a = {{4, 5, 6}, {7, 8, 9}}; // array of array of const int
- int *pi;
- const int *pci;
- ncs = cs; // valid
- cs = ncs; // violates modifiable lvalue constraint for =
- pi = &ncs.mem; // valid
- pi = &cs.mem; // violates type constraints for =
- pci = &cs.mem; // valid
- pi = a[0]; // invalid: a[0] has type ''const int *''
-
-<a name="6.7.3.1" href="#6.7.3.1"><b> 6.7.3.1 Formal definition of restrict</b></a>
-1 Let D be a declaration of an ordinary identifier that provides a means of designating an
- object P as a restrict-qualified pointer to type T.
-2 If D appears inside a block and does not have storage class extern, let B denote the
- block. If D appears in the list of parameter declarations of a function definition, let B
- denote the associated block. Otherwise, let B denote the block of main (or the block of
- whatever function is called at program startup in a freestanding environment).
-3 In what follows, a pointer expression E is said to be based on object P if (at some
- sequence point in the execution of B prior to the evaluation of E) modifying P to point to
- a copy of the array object into which it formerly pointed would change the value of E.136)
- Note that ''based'' is defined only for expressions with pointer types.
-4 During each execution of B, let L be any lvalue that has &L based on P. If L is used to
- access the value of the object X that it designates, and X is also modified (by any means),
- then the following requirements apply: T shall not be const-qualified. Every other lvalue
- used to access the value of X shall also have its address based on P. Every access that
- modifies X shall be considered also to modify P, for the purposes of this subclause. If P
- is assigned the value of a pointer expression E that is based on another restricted pointer
- object P2, associated with block B2, then either the execution of B2 shall begin before
-
-
- 136) In other words, E depends on the value of P itself rather than on the value of an object referenced
- indirectly through P. For example, if identifier p has type (int **restrict), then the pointer
- expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer
- expressions *p and p[1] are not.
-
-[<a name="#p121" href="p121">page 121</a>] (<a href="#Contents">Contents</a>)
-
- the execution of B, or the execution of B2 shall end prior to the assignment. If these
- requirements are not met, then the behavior is undefined.
-5 Here an execution of B means that portion of the execution of the program that would
- correspond to the lifetime of an object with scalar type and automatic storage duration
- associated with B.
-6 A translator is free to ignore any or all aliasing implications of uses of restrict.
-7 EXAMPLE 1 The file scope declarations
- int * restrict a;
- int * restrict b;
- extern int c[];
- assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
- program, then it is never accessed using either of the other two.
-
-8 EXAMPLE 2 The function parameter declarations in the following example
- void f(int n, int * restrict p, int * restrict q)
- {
- while (n-- > 0)
- *p++ = *q++;
- }
- assert that, during each execution of the function, if an object is accessed through one of the pointer
- parameters, then it is not also accessed through the other.
-9 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence
- analysis of function f without examining any of the calls of f in the program. The cost is that the
- programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the
- second call of f in g has undefined behavior because each of d[1] through d[49] is accessed through
- both p and q.
- void g(void)
- {
- extern int d[100];
- f(50, d + 50, d); // valid
- f(50, d + 1, d); // undefined behavior
- }
-
-10 EXAMPLE 3 The function parameter declarations
- void h(int n, int * restrict p, int * restrict q, int * restrict r)
- {
- int i;
- for (i = 0; i < n; i++)
- p[i] = q[i] + r[i];
- }
- illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
- are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
- modified within function h.
-
-11 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a
- function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments
-
-[<a name="#p122" href="p122">page 122</a>] (<a href="#Contents">Contents</a>)
-
- between restricted pointers declared in nested blocks have defined behavior.
- {
- int * restrict p1;
- int * restrict q1;
- p1 = q1; // undefined behavior
- {
- int * restrict p2 = p1; // valid
- int * restrict q2 = q1; // valid
- p1 = q2; // undefined behavior
- p2 = q2; // undefined behavior
- }
- }
-12 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more
- precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For
- example, this permits new_vector to return a vector.
- typedef struct { int n; float * restrict v; } vector;
- vector new_vector(int n)
- {
- vector t;
- t.n = n;
- t.v = malloc(n * sizeof (float));
- return t;
- }
-
-<a name="6.7.4" href="#6.7.4"><b> 6.7.4 Function specifiers</b></a>
- Syntax
-1 function-specifier:
- inline
- _Noreturn
- Constraints
-2 Function specifiers shall be used only in the declaration of an identifier for a function.
-3 An inline definition of a function with external linkage shall not contain a definition of a
- modifiable object with static or thread storage duration, and shall not contain a reference
- to an identifier with internal linkage.
-4 In a hosted environment, no function specifier(s) shall appear in a declaration of main.
- Semantics
-5 A function specifier may appear more than once; the behavior is the same as if it
- appeared only once.
-6 A function declared with an inline function specifier is an inline function. Making a
- function an inline function suggests that calls to the function be as fast as possible.137)
- The extent to which such suggestions are effective is implementation-defined.138)
-
-[<a name="#p123" href="p123">page 123</a>] (<a href="#Contents">Contents</a>)
-
-7 Any function with internal linkage can be an inline function. For a function with external
- linkage, the following restrictions apply: If a function is declared with an inline
- function specifier, then it shall also be defined in the same translation unit. If all of the
- file scope declarations for a function in a translation unit include the inline function
- specifier without extern, then the definition in that translation unit is an inline
- definition. An inline definition does not provide an external definition for the function,
- and does not forbid an external definition in another translation unit. An inline definition
- provides an alternative to an external definition, which a translator may use to implement
- any call to the function in the same translation unit. It is unspecified whether a call to the
- function uses the inline definition or the external definition.139)
-8 A function declared with a _Noreturn function specifier shall not return to its caller.
- Recommended practice
-9 The implementation should produce a diagnostic message for a function declared with a
- _Noreturn function specifier that appears to be capable of returning to its caller.
-10 EXAMPLE 1 The declaration of an inline function with external linkage can result in either an external
- definition, or a definition available for use only within the translation unit. A file scope declaration with
- extern creates an external definition. The following example shows an entire translation unit.
- inline double fahr(double t)
- {
- return (<a href="#9.0">9.0</a> * t) / <a href="#5.0">5.0</a> + 32.0;
- }
- inline double cels(double t)
- {
- return (<a href="#5.0">5.0</a> * (t - 32.0)) / <a href="#9.0">9.0</a>;
- }
- extern double fahr(double); // creates an external definition
-
-
-
-
- 137) By using, for example, an alternative to the usual function call mechanism, such as ''inline
- substitution''. Inline substitution is not textual substitution, nor does it create a new function.
- Therefore, for example, the expansion of a macro used within the body of the function uses the
- definition it had at the point the function body appears, and not where the function is called; and
- identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a
- single address, regardless of the number of inline definitions that occur in addition to the external
- definition.
- 138) For example, an implementation might never perform inline substitution, or might only perform inline
- substitutions to calls in the scope of an inline declaration.
- 139) Since an inline definition is distinct from the corresponding external definition and from any other
- corresponding inline definitions in other translation units, all corresponding objects with static storage
- duration are also distinct in each of the definitions.
-
-[<a name="#p124" href="p124">page 124</a>] (<a href="#Contents">Contents</a>)
-
- double convert(int is_fahr, double temp)
- {
- /* A translator may perform inline substitutions */
- return is_fahr ? cels(temp) : fahr(temp);
- }
-11 Note that the definition of fahr is an external definition because fahr is also declared with extern, but
- the definition of cels is an inline definition. Because cels has external linkage and is referenced, an
- external definition has to appear in another translation unit (see <a href="#6.9">6.9</a>); the inline definition and the external
- definition are distinct and either may be used for the call.
-
-12 EXAMPLE 2
- _Noreturn void f () {
- abort(); // ok
- }
- _Noreturn void g (int i) { // causes undefined behavior if i <= 0
- if (i > 0) abort();
- }
-
- Forward references: function definitions (<a href="#6.9.1">6.9.1</a>).
-<a name="6.7.5" href="#6.7.5"><b> 6.7.5 Alignment specifier</b></a>
- Syntax
-1 alignment-specifier:
- _Alignas ( type-name )
- _Alignas ( constant-expression )
- Constraints
-2 An alignment attribute shall not be specified in a declaration of a typedef, or a bit-field, or
- a function, or a parameter, or an object declared with the register storage-class
- specifier.
-3 The constant expression shall be an integer constant expression. It shall evaluate to a
- valid fundamental alignment, or to a valid extended alignment supported by the
- implementation in the context in which it appears, or to zero.
-4 The combined effect of all alignment attributes in a declaration shall not specify an
- alignment that is less strict than the alignment that would otherwise be required for the
- type of the object or field being declared.
- Semantics
-5 The first form is equivalent to _Alignas(alignof(type-name)).
-6 The alignment requirement of the declared object or field is taken to be the specified
- alignment. An alignment specification of zero has no effect.140) When multiple
- alignment specifiers occur in a declaration, the effective alignment requirement is the
- strictest specified alignment.
-
-[<a name="#p125" href="p125">page 125</a>] (<a href="#Contents">Contents</a>)
-
-7 If the definition of an object has an alignment specifier, any other declaration of that
- object shall either specify equivalent alignment or have no alignment specifier. If the
- definition of an object does not have an alignment specifier, any other declaration of that
- object shall also have no alignment specifier. If declarations of an object in different
- translation units have different alignment specifiers, the behavior is undefined.
-<a name="6.7.6" href="#6.7.6"><b> 6.7.6 Declarators</b></a>
- Syntax
-1 declarator:
- pointeropt direct-declarator
- direct-declarator:
- identifier
- ( declarator )
- direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
- direct-declarator [ static type-qualifier-listopt assignment-expression ]
- direct-declarator [ type-qualifier-list static assignment-expression ]
- direct-declarator [ type-qualifier-listopt * ]
- direct-declarator ( parameter-type-list )
- direct-declarator ( identifier-listopt )
- pointer:
- * type-qualifier-listopt
- * type-qualifier-listopt pointer
- type-qualifier-list:
- type-qualifier
- type-qualifier-list type-qualifier
- parameter-type-list:
- parameter-list
- parameter-list , ...
- parameter-list:
- parameter-declaration
- parameter-list , parameter-declaration
- parameter-declaration:
- declaration-specifiers declarator
- declaration-specifiers abstract-declaratoropt
-
-
-
- 140) An alignment specification of zero also does not affect other alignment specifications in the same
- declaration.
-
-[<a name="#p126" href="p126">page 126</a>] (<a href="#Contents">Contents</a>)
-
- identifier-list:
- identifier
- identifier-list , identifier
- Semantics
-2 Each declarator declares one identifier, and asserts that when an operand of the same
- form as the declarator appears in an expression, it designates a function or object with the
- scope, storage duration, and type indicated by the declaration specifiers.
-3 A full declarator is a declarator that is not part of another declarator. The end of a full
- declarator is a sequence point. If, in the nested sequence of declarators in a full
- declarator, there is a declarator specifying a variable length array type, the type specified
- by the full declarator is said to be variably modified. Furthermore, any type derived by
- declarator type derivation from a variably modified type is itself variably modified.
-4 In the following subclauses, consider a declaration
- T D1
- where T contains the declaration specifiers that specify a type T (such as int) and D1 is
- a declarator that contains an identifier ident. The type specified for the identifier ident in
- the various forms of declarator is described inductively using this notation.
-5 If, in the declaration ''T D1'', D1 has the form
- identifier
- then the type specified for ident is T .
-6 If, in the declaration ''T D1'', D1 has the form
- ( D )
- then ident has the type specified by the declaration ''T D''. Thus, a declarator in
- parentheses is identical to the unparenthesized declarator, but the binding of complicated
- declarators may be altered by parentheses.
- Implementation limits
-7 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of pointer, array, and
- function declarators that modify an arithmetic, structure, union, or void type, either
- directly or via one or more typedefs.
- Forward references: array declarators (<a href="#6.7.6.2">6.7.6.2</a>), type definitions (<a href="#6.7.8">6.7.8</a>).
-
-
-
-
-[<a name="#p127" href="p127">page 127</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.7.6.1" href="#6.7.6.1"><b> 6.7.6.1 Pointer declarators</b></a>
- Semantics
-1 If, in the declaration ''T D1'', D1 has the form
- * type-qualifier-listopt D
- and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
- T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list
- pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer.
-2 For two pointer types to be compatible, both shall be identically qualified and both shall
- be pointers to compatible types.
-3 EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer
- to a constant value'' and a ''constant pointer to a variable value''.
- const int *ptr_to_constant;
- int *const constant_ptr;
- The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
- but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
- int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
- same location.
-4 The declaration of the constant pointer constant_ptr may be clarified by including a definition for the
- type ''pointer to int''.
- typedef int *int_ptr;
- const int_ptr constant_ptr;
- declares constant_ptr as an object that has type ''const-qualified pointer to int''.
-
-<a name="6.7.6.2" href="#6.7.6.2"><b> 6.7.6.2 Array declarators</b></a>
- Constraints
-1 In addition to optional type qualifiers and the keyword static, the [ and ] may delimit
- an expression or *. If they delimit an expression (which specifies the size of an array), the
- expression shall have an integer type. If the expression is a constant expression, it shall
- have a value greater than zero. The element type shall not be an incomplete or function
- type. The optional type qualifiers and the keyword static shall appear only in a
- declaration of a function parameter with an array type, and then only in the outermost
- array type derivation.
-2 An ordinary identifier (as defined in <a href="#6.2.3">6.2.3</a>) that has a variably modified type shall have
- either block scope and no linkage or function prototype scope. If an identifier is declared
- to be an object with static or thread storage duration, it shall not have a variable length
- array type.
-
-
-
-
-[<a name="#p128" href="p128">page 128</a>] (<a href="#Contents">Contents</a>)
-
- Semantics
-3 If, in the declaration ''T D1'', D1 has one of the forms:
- D[ type-qualifier-listopt assignment-expressionopt ]
- D[ static type-qualifier-listopt assignment-expression ]
- D[ type-qualifier-list static assignment-expression ]
- D[ type-qualifier-listopt * ]
- and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
- T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.141)
- (See <a href="#6.7.6.3">6.7.6.3</a> for the meaning of the optional type qualifiers and the keyword static.)
-4 If the size is not present, the array type is an incomplete type. If the size is * instead of
- being an expression, the array type is a variable length array type of unspecified size,
- which can only be used in declarations or type names with function prototype scope;142)
- such arrays are nonetheless complete types. If the size is an integer constant expression
- and the element type has a known constant size, the array type is not a variable length
- array type; otherwise, the array type is a variable length array type. (Variable length
- arrays are a conditional feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.)
-5 If the size is an expression that is not an integer constant expression: if it occurs in a
- declaration at function prototype scope, it is treated as if it were replaced by *; otherwise,
- each time it is evaluated it shall have a value greater than zero. The size of each instance
- of a variable length array type does not change during its lifetime. Where a size
- expression is part of the operand of a sizeof operator and changing the value of the
- size expression would not affect the result of the operator, it is unspecified whether or not
- the size expression is evaluated.
-6 For two array types to be compatible, both shall have compatible element types, and if
- both size specifiers are present, and are integer constant expressions, then both size
- specifiers shall have the same constant value. If the two array types are used in a context
- which requires them to be compatible, it is undefined behavior if the two size specifiers
- evaluate to unequal values.
-7 EXAMPLE 1
- float fa[11], *afp[17];
- declares an array of float numbers and an array of pointers to float numbers.
-
-8 EXAMPLE 2 Note the distinction between the declarations
-
-
-
-
- 141) When several ''array of'' specifications are adjacent, a multidimensional array is declared.
- 142) Thus, * can be used only in function declarations that are not definitions (see <a href="#6.7.6.3">6.7.6.3</a>).
-
-[<a name="#p129" href="p129">page 129</a>] (<a href="#Contents">Contents</a>)
-
- extern int *x;
- extern int y[];
- The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
- (an incomplete type), the storage for which is defined elsewhere.
-
-9 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
- extern int n;
- extern int m;
- void fcompat(void)
- {
- int a[n][6][m];
- int (*p)[4][n+1];
- int c[n][n][6][m];
- int (*r)[n][n][n+1];
- p = a; // invalid: not compatible because 4 != 6
- r = c; // compatible, but defined behavior only if
- // n == 6 and m == n+1
- }
-
-10 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or
- function prototype scope. Array objects declared with the _Thread_local, static, or extern
- storage-class specifier cannot have a variable length array (VLA) type. However, an object declared with
- the static storage-class specifier can have a VM type (that is, a pointer to a VLA type). Finally, all
- identifiers declared with a VM type have to be ordinary identifiers and cannot, therefore, be members of
- structures or unions.
- extern int n;
- int A[n]; // invalid: file scope VLA
- extern int (*p2)[n]; // invalid: file scope VM
- int B[100]; // valid: file scope but not VM
- void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
- void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
- {
- typedef int VLA[m][m]; // valid: block scope typedef VLA
- struct tag {
- int (*y)[n]; // invalid: y not ordinary identifier
- int z[n]; // invalid: z not ordinary identifier
- };
- int D[m]; // valid: auto VLA
- static int E[m]; // invalid: static block scope VLA
- extern int F[m]; // invalid: F has linkage and is VLA
- int (*s)[m]; // valid: auto pointer to VLA
- extern int (*r)[m]; // invalid: r has linkage and points to VLA
- static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
- }
-
- Forward references: function declarators (<a href="#6.7.6.3">6.7.6.3</a>), function definitions (<a href="#6.9.1">6.9.1</a>),
- initialization (<a href="#6.7.9">6.7.9</a>).
-
-
-
-[<a name="#p130" href="p130">page 130</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.7.6.3" href="#6.7.6.3"><b> 6.7.6.3 Function declarators (including prototypes)</b></a>
- Constraints
-1 A function declarator shall not specify a return type that is a function type or an array
- type.
-2 The only storage-class specifier that shall occur in a parameter declaration is register.
-3 An identifier list in a function declarator that is not part of a definition of that function
- shall be empty.
-4 After adjustment, the parameters in a parameter type list in a function declarator that is
- part of a definition of that function shall not have incomplete type.
- Semantics
-5 If, in the declaration ''T D1'', D1 has the form
- D( parameter-type-list )
- or
- D( identifier-listopt )
- and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
- T '', then the type specified for ident is ''derived-declarator-type-list function returning
- T ''.
-6 A parameter type list specifies the types of, and may declare identifiers for, the
- parameters of the function.
-7 A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to
- type'', where the type qualifiers (if any) are those specified within the [ and ] of the
- array type derivation. If the keyword static also appears within the [ and ] of the
- array type derivation, then for each call to the function, the value of the corresponding
- actual argument shall provide access to the first element of an array with at least as many
- elements as specified by the size expression.
-8 A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to
- function returning type'', as in <a href="#6.3.2.1">6.3.2.1</a>.
-9 If the list terminates with an ellipsis (, ...), no information about the number or types
- of the parameters after the comma is supplied.143)
-10 The special case of an unnamed parameter of type void as the only item in the list
- specifies that the function has no parameters.
-
-
-
- 143) The macros defined in the <a href="#7.16"><stdarg.h></a> header (<a href="#7.16">7.16</a>) may be used to access arguments that
- correspond to the ellipsis.
-
-[<a name="#p131" href="p131">page 131</a>] (<a href="#Contents">Contents</a>)
-
-11 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a
- parameter name, it shall be taken as a typedef name.
-12 If the function declarator is not part of a definition of that function, parameters may have
- incomplete type and may use the [*] notation in their sequences of declarator specifiers
- to specify variable length array types.
-13 The storage-class specifier in the declaration specifiers for a parameter declaration, if
- present, is ignored unless the declared parameter is one of the members of the parameter
- type list for a function definition.
-14 An identifier list declares only the identifiers of the parameters of the function. An empty
- list in a function declarator that is part of a definition of that function specifies that the
- function has no parameters. The empty list in a function declarator that is not part of a
- definition of that function specifies that no information about the number or types of the
- parameters is supplied.144)
-15 For two function types to be compatible, both shall specify compatible return types.145)
- Moreover, the parameter type lists, if both are present, shall agree in the number of
- parameters and in use of the ellipsis terminator; corresponding parameters shall have
- compatible types. If one type has a parameter type list and the other type is specified by a
- function declarator that is not part of a function definition and that contains an empty
- identifier list, the parameter list shall not have an ellipsis terminator and the type of each
- parameter shall be compatible with the type that results from the application of the
- default argument promotions. If one type has a parameter type list and the other type is
- specified by a function definition that contains a (possibly empty) identifier list, both shall
- agree in the number of parameters, and the type of each prototype parameter shall be
- compatible with the type that results from the application of the default argument
- promotions to the type of the corresponding identifier. (In the determination of type
- compatibility and of a composite type, each parameter declared with function or array
- type is taken as having the adjusted type and each parameter declared with qualified type
- is taken as having the unqualified version of its declared type.)
-16 EXAMPLE 1 The declaration
- int f(void), *fip(), (*pfi)();
- declares a function f with no parameters returning an int, a function fip with no parameter specification
- returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an
- int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the
- declaration suggests, and the same construction in an expression requires, the calling of a function fip,
- and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the
- extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function
-
-
- 144) See ''future language directions'' (<a href="#6.11.6">6.11.6</a>).
- 145) If both function types are ''old style'', parameter types are not compared.
-
-[<a name="#p132" href="p132">page 132</a>] (<a href="#Contents">Contents</a>)
-
- designator, which is then used to call the function; it returns an int.
-17 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the
- declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either
- internal or external linkage (depending on what file scope declarations for these identifiers are visible), and
- the identifier of the pointer pfi has block scope and no linkage.
-
-18 EXAMPLE 2 The declaration
- int (*apfi[3])(int *x, int *y);
- declares an array apfi of three pointers to functions returning int. Each of these functions has two
- parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and
- go out of scope at the end of the declaration of apfi.
-
-19 EXAMPLE 3 The declaration
- int (*fpfi(int (*)(long), int))(int, ...);
- declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two
- parameters: a pointer to a function returning an int (with one parameter of type long int), and an int.
- The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more
- additional arguments of any type.
-
-20 EXAMPLE 4 The following prototype has a variably modified parameter.
- void addscalar(int n, int m,
- double a[n][n*m+300], double x);
- int main()
- {
- double b[4][308];
- addscalar(4, 2, b, <a href="#2.17">2.17</a>);
- return 0;
- }
- void addscalar(int n, int m,
- double a[n][n*m+300], double x)
- {
- for (int i = 0; i < n; i++)
- for (int j = 0, k = n*m+300; j < k; j++)
- // a is a pointer to a VLA with n*m+300 elements
- a[i][j] += x;
- }
-
-21 EXAMPLE 5 The following are all compatible function prototype declarators.
- double maximum(int n, int m, double a[n][m]);
- double maximum(int n, int m, double a[*][*]);
- double maximum(int n, int m, double a[ ][*]);
- double maximum(int n, int m, double a[ ][m]);
- as are:
- void f(double (* restrict a)[5]);
- void f(double a[restrict][5]);
- void f(double a[restrict 3][5]);
- void f(double a[restrict static 3][5]);
-
-
-[<a name="#p133" href="p133">page 133</a>] (<a href="#Contents">Contents</a>)
-
- (Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
- non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
-
- Forward references: function definitions (<a href="#6.9.1">6.9.1</a>), type names (<a href="#6.7.7">6.7.7</a>).
-<a name="6.7.7" href="#6.7.7"><b> 6.7.7 Type names</b></a>
- Syntax
-1 type-name:
- specifier-qualifier-list abstract-declaratoropt
- abstract-declarator:
- pointer
- pointeropt direct-abstract-declarator
- direct-abstract-declarator:
- ( abstract-declarator )
- direct-abstract-declaratoropt [ type-qualifier-listopt
- assignment-expressionopt ]
- direct-abstract-declaratoropt [ static type-qualifier-listopt
- assignment-expression ]
- direct-abstract-declaratoropt [ type-qualifier-list static
- assignment-expression ]
- direct-abstract-declaratoropt [ * ]
- direct-abstract-declaratoropt ( parameter-type-listopt )
- Semantics
-2 In several contexts, it is necessary to specify a type. This is accomplished using a type
- name, which is syntactically a declaration for a function or an object of that type that
- omits the identifier.146)
-3 EXAMPLE The constructions
- (a) int
- (b) int *
- (c) int *[3]
- (d) int (*)[3]
- (e) int (*)[*]
- (f) int *()
- (g) int (*)(void)
- (h) int (*const [])(unsigned int, ...)
- name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
- array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
- with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
-
-
- 146) As indicated by the syntax, empty parentheses in a type name are interpreted as ''function with no
- parameter specification'', rather than redundant parentheses around the omitted identifier.
-
-[<a name="#p134" href="p134">page 134</a>] (<a href="#Contents">Contents</a>)
-
- returning an int, and (h) array of an unspecified number of constant pointers to functions, each with one
- parameter that has type unsigned int and an unspecified number of other parameters, returning an
- int.
-
-<a name="6.7.8" href="#6.7.8"><b> 6.7.8 Type definitions</b></a>
- Syntax
-1 typedef-name:
- identifier
- Constraints
-2 If a typedef name specifies a variably modified type then it shall have block scope.
- Semantics
-3 In a declaration whose storage-class specifier is typedef, each declarator defines an
- identifier to be a typedef name that denotes the type specified for the identifier in the way
- described in <a href="#6.7.6">6.7.6</a>. Any array size expressions associated with variable length array
- declarators are evaluated each time the declaration of the typedef name is reached in the
- order of execution. A typedef declaration does not introduce a new type, only a
- synonym for the type so specified. That is, in the following declarations:
- typedef T type_ident;
- type_ident D;
- type_ident is defined as a typedef name with the type specified by the declaration
- specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
- type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
- typedef name shares the same name space as other identifiers declared in ordinary
- declarators.
-4 EXAMPLE 1 After
- typedef int MILES, KLICKSP();
- typedef struct { double hi, lo; } range;
- the constructions
- MILES distance;
- extern KLICKSP *metricp;
- range x;
- range z, *zp;
- are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
- parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
- such a structure. The object distance has a type compatible with any other int object.
-
-5 EXAMPLE 2 After the declarations
- typedef struct s1 { int x; } t1, *tp1;
- typedef struct s2 { int x; } t2, *tp2;
- type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
-
-[<a name="#p135" href="p135">page 135</a>] (<a href="#Contents">Contents</a>)
-
- s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
-
-6 EXAMPLE 3 The following obscure constructions
- typedef signed int t;
- typedef int plain;
- struct tag {
- unsigned t:4;
- const t:5;
- plain r:5;
- };
- declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
- with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
- qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
- [-16, +15], and one named r that contains values in one of the ranges [0, 31], [-15, +15], or [-16, +15].
- (The choice of range is implementation-defined.) The first two bit-field declarations differ in that
- unsigned is a type specifier (which forces t to be the name of a structure member), while const is a
- type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed
- in an inner scope by
- t f(t (t));
- long t;
- then a function f is declared with type ''function returning signed int with one unnamed parameter
- with type pointer to function returning signed int with one unnamed parameter with type signed
- int'', and an identifier t with type long int.
-
-7 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the
- following declarations of the signal function specify exactly the same type, the first without making use
- of any typedef names.
- typedef void fv(int), (*pfv)(int);
- void (*signal(int, void (*)(int)))(int);
- fv *signal(int, fv *);
- pfv signal(int, pfv);
-
-8 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the
- time the typedef name is defined, not each time it is used:
- void copyt(int n)
- {
- typedef int B[n]; // B is n ints, n evaluated now
- n += 1;
- B a; // a is n ints, n without += 1
- int b[n]; // a and b are different sizes
- for (int i = 1; i < n; i++)
- a[i-1] = b[i];
- }
-
-
-
-
-[<a name="#p136" href="p136">page 136</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.7.9" href="#6.7.9"><b> 6.7.9 Initialization</b></a>
- Syntax
-1 initializer:
- assignment-expression
- { initializer-list }
- { initializer-list , }
- initializer-list:
- designationopt initializer
- initializer-list , designationopt initializer
- designation:
- designator-list =
- designator-list:
- designator
- designator-list designator
- designator:
- [ constant-expression ]
- . identifier
- Constraints
-2 No initializer shall attempt to provide a value for an object not contained within the entity
- being initialized.
-3 The type of the entity to be initialized shall be an array of unknown size or a complete
- object type that is not a variable length array type.
-4 All the expressions in an initializer for an object that has static or thread storage duration
- shall be constant expressions or string literals.
-5 If the declaration of an identifier has block scope, and the identifier has external or
- internal linkage, the declaration shall have no initializer for the identifier.
-6 If a designator has the form
- [ constant-expression ]
- then the current object (defined below) shall have array type and the expression shall be
- an integer constant expression. If the array is of unknown size, any nonnegative value is
- valid.
-7 If a designator has the form
- . identifier
- then the current object (defined below) shall have structure or union type and the
- identifier shall be the name of a member of that type.
-[<a name="#p137" href="p137">page 137</a>] (<a href="#Contents">Contents</a>)
-
- Semantics
-8 An initializer specifies the initial value stored in an object.
-9 Except where explicitly stated otherwise, for the purposes of this subclause unnamed
- members of objects of structure and union type do not participate in initialization.
- Unnamed members of structure objects have indeterminate value even after initialization.
-10 If an object that has automatic storage duration is not initialized explicitly, its value is
- indeterminate. If an object that has static or thread storage duration is not initialized
- explicitly, then:
- -- if it has pointer type, it is initialized to a null pointer;
- -- if it has arithmetic type, it is initialized to (positive or unsigned) zero;
- -- if it is an aggregate, every member is initialized (recursively) according to these rules,
- and any padding is initialized to zero bits;
- -- if it is a union, the first named member is initialized (recursively) according to these
- rules, and any padding is initialized to zero bits;
-11 The initializer for a scalar shall be a single expression, optionally enclosed in braces. The
- initial value of the object is that of the expression (after conversion); the same type
- constraints and conversions as for simple assignment apply, taking the type of the scalar
- to be the unqualified version of its declared type.
-12 The rest of this subclause deals with initializers for objects that have aggregate or union
- type.
-13 The initializer for a structure or union object that has automatic storage duration shall be
- either an initializer list as described below, or a single expression that has compatible
- structure or union type. In the latter case, the initial value of the object, including
- unnamed members, is that of the expression.
-14 An array of character type may be initialized by a character string literal or UTF-8 string
- literal, optionally enclosed in braces. Successive bytes of the string literal (including the
- terminating null character if there is room or if the array is of unknown size) initialize the
- elements of the array.
-15 An array with element type compatible with a qualified or unqualified version of
- wchar_t may be initialized by a wide string literal, optionally enclosed in braces.
- Successive wide characters of the wide string literal (including the terminating null wide
- character if there is room or if the array is of unknown size) initialize the elements of the
- array.
-16 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-
- enclosed list of initializers for the elements or named members.
-
-
-[<a name="#p138" href="p138">page 138</a>] (<a href="#Contents">Contents</a>)
-
-17 Each brace-enclosed initializer list has an associated current object. When no
- designations are present, subobjects of the current object are initialized in order according
- to the type of the current object: array elements in increasing subscript order, structure
- members in declaration order, and the first named member of a union.147) In contrast, a
- designation causes the following initializer to begin initialization of the subobject
- described by the designator. Initialization then continues forward in order, beginning
- with the next subobject after that described by the designator.148)
-18 Each designator list begins its description with the current object associated with the
- closest surrounding brace pair. Each item in the designator list (in order) specifies a
- particular member of its current object and changes the current object for the next
- designator (if any) to be that member.149) The current object that results at the end of the
- designator list is the subobject to be initialized by the following initializer.
-19 The initialization shall occur in initializer list order, each initializer provided for a
- particular subobject overriding any previously listed initializer for the same subobject;150)
- all subobjects that are not initialized explicitly shall be initialized implicitly the same as
- objects that have static storage duration.
-20 If the aggregate or union contains elements or members that are aggregates or unions,
- these rules apply recursively to the subaggregates or contained unions. If the initializer of
- a subaggregate or contained union begins with a left brace, the initializers enclosed by
- that brace and its matching right brace initialize the elements or members of the
- subaggregate or the contained union. Otherwise, only enough initializers from the list are
- taken to account for the elements or members of the subaggregate or the first member of
- the contained union; any remaining initializers are left to initialize the next element or
- member of the aggregate of which the current subaggregate or contained union is a part.
-21 If there are fewer initializers in a brace-enclosed list than there are elements or members
- of an aggregate, or fewer characters in a string literal used to initialize an array of known
- size than there are elements in the array, the remainder of the aggregate shall be
- initialized implicitly the same as objects that have static storage duration.
-
-
-
- 147) If the initializer list for a subaggregate or contained union does not begin with a left brace, its
- subobjects are initialized as usual, but the subaggregate or contained union does not become the
- current object: current objects are associated only with brace-enclosed initializer lists.
- 148) After a union member is initialized, the next object is not the next member of the union; instead, it is
- the next subobject of an object containing the union.
- 149) Thus, a designator can only specify a strict subobject of the aggregate or union that is associated with
- the surrounding brace pair. Note, too, that each separate designator list is independent.
- 150) Any initializer for the subobject which is overridden and so not used to initialize that subobject might
- not be evaluated at all.
-
-[<a name="#p139" href="p139">page 139</a>] (<a href="#Contents">Contents</a>)
-
-22 If an array of unknown size is initialized, its size is determined by the largest indexed
- element with an explicit initializer. The array type is completed at the end of its
- initializer list.
-23 The order in which any side effects occur among the initialization list expressions is
- unspecified.151)
-24 EXAMPLE 1 Provided that <a href="#7.3"><complex.h></a> has been #included, the declarations
- int i = <a href="#3.5">3.5</a>;
- double complex c = 5 + 3 * I;
- define and initialize i with the value 3 and c with the value <a href="#5.0">5.0</a> + i3.0.
-
-25 EXAMPLE 2 The declaration
- int x[] = { 1, 3, 5 };
- defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
- and there are three initializers.
-
-26 EXAMPLE 3 The declaration
- int y[4][3] = {
- { 1, 3, 5 },
- { 2, 4, 6 },
- { 3, 5, 7 },
- };
- is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
- y[0]), namely y[0][0], y[0][1], and y[0][2]. Likewise the next two lines initialize y[1] and
- y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
- been achieved by
- int y[4][3] = {
- 1, 3, 5, 2, 4, 6, 3, 5, 7
- };
- The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
- next three are taken successively for y[1] and y[2].
-
-27 EXAMPLE 4 The declaration
- int z[4][3] = {
- { 1 }, { 2 }, { 3 }, { 4 }
- };
- initializes the first column of z as specified and initializes the rest with zeros.
-
-28 EXAMPLE 5 The declaration
- struct { int a[3], b; } w[] = { { 1 }, 2 };
- is a definition with an inconsistently bracketed initialization. It defines an array with two element
- structures: w[0].a[0] is 1 and w[1].a[0] is 2; all the other elements are zero.
-
-
-
- 151) In particular, the evaluation order need not be the same as the order of subobject initialization.
-
-[<a name="#p140" href="p140">page 140</a>] (<a href="#Contents">Contents</a>)
-
-29 EXAMPLE 6 The declaration
- short q[4][3][2] = {
- { 1 },
- { 2, 3 },
- { 4, 5, 6 }
- };
- contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
- object: q[0][0][0] is 1, q[1][0][0] is 2, q[1][0][1] is 3, and 4, 5, and 6 initialize
- q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
- q[0][0] does not begin with a left brace, so up to six items from the current list may be used. There is
- only one, so the values for the remaining five elements are initialized with zero. Likewise, the initializers
- for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their
- respective two-dimensional subaggregates. If there had been more than six items in any of the lists, a
- diagnostic message would have been issued. The same initialization result could have been achieved by:
- short q[4][3][2] = {
- 1, 0, 0, 0, 0, 0,
- 2, 3, 0, 0, 0, 0,
- 4, 5, 6
- };
- or by:
- short q[4][3][2] = {
- {
- { 1 },
- },
- {
- { 2, 3 },
- },
- {
- { 4, 5 },
- { 6 },
- }
- };
- in a fully bracketed form.
-30 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
- cause confusion.
-
-31 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the
- declaration
- typedef int A[]; // OK - declared with block scope
- the declaration
- A a = { 1, 2 }, b = { 3, 4, 5 };
- is identical to
- int a[] = { 1, 2 }, b[] = { 3, 4, 5 };
- due to the rules for incomplete types.
-
-
-
-[<a name="#p141" href="p141">page 141</a>] (<a href="#Contents">Contents</a>)
-
-32 EXAMPLE 8 The declaration
- char s[] = "abc", t[3] = "abc";
- defines ''plain'' char array objects s and t whose elements are initialized with character string literals.
- This declaration is identical to
- char s[] = { 'a', 'b', 'c', '\0' },
- t[] = { 'a', 'b', 'c' };
- The contents of the arrays are modifiable. On the other hand, the declaration
- char *p = "abc";
- defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char''
- with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to
- modify the contents of the array, the behavior is undefined.
-
-33 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using
- designators:
- enum { member_one, member_two };
- const char *nm[] = {
- [member_two] = "member two",
- [member_one] = "member one",
- };
-
-34 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
- div_t answer = { .quot = 2, .rem = -1 };
-
-35 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
- might be misunderstood:
- struct { int a[3], b; } w[] =
- { [0].a = {1}, [1].a[0] = 2 };
-
-36 EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator:
- int a[MAX] = {
- 1, 3, 5, 7, 9, [MAX-5] = 8, 6, 4, 2, 0
- };
-37 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less
- than ten, some of the values provided by the first five initializers will be overridden by the second five.
-
-38 EXAMPLE 13 Any member of a union can be initialized:
- union { /* ... */ } u = { .any_member = 42 };
-
- Forward references: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>).
-
-
-
-
-[<a name="#p142" href="p142">page 142</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.7.10" href="#6.7.10"><b> 6.7.10 Static assertions</b></a>
- Syntax
-1 static_assert-declaration:
- _Static_assert ( constant-expression , string-literal ) ;
- Constraints
-2 The constant expression shall compare unequal to 0.
- Semantics
-3 The constant expression shall be an integer constant expression. If the value of the
- constant expression compares unequal to 0, the declaration has no effect. Otherwise, the
- constraint is violated and the implementation shall produce a diagnostic message that
- includes the text of the string literal, except that characters not in the basic source
- character set are not required to appear in the message.
- Forward references: diagnostics (<a href="#7.2">7.2</a>).
-
-
-
-
-[<a name="#p143" href="p143">page 143</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.8" href="#6.8"><b> 6.8 Statements and blocks</b></a>
- Syntax
-1 statement:
- labeled-statement
- compound-statement
- expression-statement
- selection-statement
- iteration-statement
- jump-statement
- Semantics
-2 A statement specifies an action to be performed. Except as indicated, statements are
- executed in sequence.
-3 A block allows a set of declarations and statements to be grouped into one syntactic unit.
- The initializers of objects that have automatic storage duration, and the variable length
- array declarators of ordinary identifiers with block scope, are evaluated and the values are
- stored in the objects (including storing an indeterminate value in objects without an
- initializer) each time the declaration is reached in the order of execution, as if it were a
- statement, and within each declaration in the order that declarators appear.
-4 A full expression is an expression that is not part of another expression or of a declarator.
- Each of the following is a full expression: an initializer that is not part of a compound
- literal; the expression in an expression statement; the controlling expression of a selection
- statement (if or switch); the controlling expression of a while or do statement; each
- of the (optional) expressions of a for statement; the (optional) expression in a return
- statement. There is a sequence point between the evaluation of a full expression and the
- evaluation of the next full expression to be evaluated.
- Forward references: expression and null statements (<a href="#6.8.3">6.8.3</a>), selection statements
- (<a href="#6.8.4">6.8.4</a>), iteration statements (<a href="#6.8.5">6.8.5</a>), the return statement (<a href="#6.8.6.4">6.8.6.4</a>).
-<a name="6.8.1" href="#6.8.1"><b> 6.8.1 Labeled statements</b></a>
- Syntax
-1 labeled-statement:
- identifier : statement
- case constant-expression : statement
- default : statement
- Constraints
-2 A case or default label shall appear only in a switch statement. Further
- constraints on such labels are discussed under the switch statement.
-
-[<a name="#p144" href="p144">page 144</a>] (<a href="#Contents">Contents</a>)
-
-3 Label names shall be unique within a function.
- Semantics
-4 Any statement may be preceded by a prefix that declares an identifier as a label name.
- Labels in themselves do not alter the flow of control, which continues unimpeded across
- them.
- Forward references: the goto statement (<a href="#6.8.6.1">6.8.6.1</a>), the switch statement (<a href="#6.8.4.2">6.8.4.2</a>).
-<a name="6.8.2" href="#6.8.2"><b> 6.8.2 Compound statement</b></a>
- Syntax
-1 compound-statement:
- { block-item-listopt }
- block-item-list:
- block-item
- block-item-list block-item
- block-item:
- declaration
- statement
- Semantics
-2 A compound statement is a block.
-<a name="6.8.3" href="#6.8.3"><b> 6.8.3 Expression and null statements</b></a>
- Syntax
-1 expression-statement:
- expressionopt ;
- Semantics
-2 The expression in an expression statement is evaluated as a void expression for its side
- effects.152)
-3 A null statement (consisting of just a semicolon) performs no operations.
-4 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the
- discarding of its value may be made explicit by converting the expression to a void expression by means of
- a cast:
- int p(int);
- /* ... */
- (void)p(0);
-
-
-
- 152) Such as assignments, and function calls which have side effects.
-
-[<a name="#p145" href="p145">page 145</a>] (<a href="#Contents">Contents</a>)
-
-5 EXAMPLE 2 In the program fragment
- char *s;
- /* ... */
- while (*s++ != '\0')
- ;
- a null statement is used to supply an empty loop body to the iteration statement.
-
-6 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
- statement.
- while (loop1) {
- /* ... */
- while (loop2) {
- /* ... */
- if (want_out)
- goto end_loop1;
- /* ... */
- }
- /* ... */
- end_loop1: ;
- }
-
- Forward references: iteration statements (<a href="#6.8.5">6.8.5</a>).
-<a name="6.8.4" href="#6.8.4"><b> 6.8.4 Selection statements</b></a>
- Syntax
-1 selection-statement:
- if ( expression ) statement
- if ( expression ) statement else statement
- switch ( expression ) statement
- Semantics
-2 A selection statement selects among a set of statements depending on the value of a
- controlling expression.
-3 A selection statement is a block whose scope is a strict subset of the scope of its
- enclosing block. Each associated substatement is also a block whose scope is a strict
- subset of the scope of the selection statement.
-<a name="6.8.4.1" href="#6.8.4.1"><b> 6.8.4.1 The if statement</b></a>
- Constraints
-1 The controlling expression of an if statement shall have scalar type.
- Semantics
-2 In both forms, the first substatement is executed if the expression compares unequal to 0.
- In the else form, the second substatement is executed if the expression compares equal
-
-
-[<a name="#p146" href="p146">page 146</a>] (<a href="#Contents">Contents</a>)
-
- to 0. If the first substatement is reached via a label, the second substatement is not
- executed.
-3 An else is associated with the lexically nearest preceding if that is allowed by the
- syntax.
-<a name="6.8.4.2" href="#6.8.4.2"><b> 6.8.4.2 The switch statement</b></a>
- Constraints
-1 The controlling expression of a switch statement shall have integer type.
-2 If a switch statement has an associated case or default label within the scope of an
- identifier with a variably modified type, the entire switch statement shall be within the
- scope of that identifier.153)
-3 The expression of each case label shall be an integer constant expression and no two of
- the case constant expressions in the same switch statement shall have the same value
- after conversion. There may be at most one default label in a switch statement.
- (Any enclosed switch statement may have a default label or case constant
- expressions with values that duplicate case constant expressions in the enclosing
- switch statement.)
- Semantics
-4 A switch statement causes control to jump to, into, or past the statement that is the
- switch body, depending on the value of a controlling expression, and on the presence of a
- default label and the values of any case labels on or in the switch body. A case or
- default label is accessible only within the closest enclosing switch statement.
-5 The integer promotions are performed on the controlling expression. The constant
- expression in each case label is converted to the promoted type of the controlling
- expression. If a converted value matches that of the promoted controlling expression,
- control jumps to the statement following the matched case label. Otherwise, if there is
- a default label, control jumps to the labeled statement. If no converted case constant
- expression matches and there is no default label, no part of the switch body is
- executed.
- Implementation limits
-6 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, the implementation may limit the number of case values in a
- switch statement.
-
-
-
-
- 153) That is, the declaration either precedes the switch statement, or it follows the last case or
- default label associated with the switch that is in the block containing the declaration.
-
-[<a name="#p147" href="p147">page 147</a>] (<a href="#Contents">Contents</a>)
-
-7 EXAMPLE In the artificial program fragment
- switch (expr)
- {
- int i = 4;
- f(i);
- case 0:
- i = 17;
- /* falls through into default code */
- default:
- printf("%d\n", i);
- }
- the object whose identifier is i exists with automatic storage duration (within the block) but is never
- initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
- access an indeterminate value. Similarly, the call to the function f cannot be reached.
-
-<a name="6.8.5" href="#6.8.5"><b> 6.8.5 Iteration statements</b></a>
- Syntax
-1 iteration-statement:
- while ( expression ) statement
- do statement while ( expression ) ;
- for ( expressionopt ; expressionopt ; expressionopt ) statement
- for ( declaration expressionopt ; expressionopt ) statement
- Constraints
-2 The controlling expression of an iteration statement shall have scalar type.
-3 The declaration part of a for statement shall only declare identifiers for objects having
- storage class auto or register.
- Semantics
-4 An iteration statement causes a statement called the loop body to be executed repeatedly
- until the controlling expression compares equal to 0. The repetition occurs regardless of
- whether the loop body is entered from the iteration statement or by a jump.154)
-5 An iteration statement is a block whose scope is a strict subset of the scope of its
- enclosing block. The loop body is also a block whose scope is a strict subset of the scope
- of the iteration statement.
-6 An iteration statement that performs no input/output operations, does not access volatile
- objects, and performs no synchronization or atomic operations in its body, controlling
- expression, or (in the case of a for statement) its expression-3, may be assumed by the
- implementation to terminate.155)
-
- 154) Code jumped over is not executed. In particular, the controlling expression of a for or while
- statement is not evaluated before entering the loop body, nor is clause-1 of a for statement.
-
-[<a name="#p148" href="p148">page 148</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.8.5.1" href="#6.8.5.1"><b> 6.8.5.1 The while statement</b></a>
-1 The evaluation of the controlling expression takes place before each execution of the loop
- body.
-<a name="6.8.5.2" href="#6.8.5.2"><b> 6.8.5.2 The do statement</b></a>
-1 The evaluation of the controlling expression takes place after each execution of the loop
- body.
-<a name="6.8.5.3" href="#6.8.5.3"><b> 6.8.5.3 The for statement</b></a>
-1 The statement
- for ( clause-1 ; expression-2 ; expression-3 ) statement
- behaves as follows: The expression expression-2 is the controlling expression that is
- evaluated before each execution of the loop body. The expression expression-3 is
- evaluated as a void expression after each execution of the loop body. If clause-1 is a
- declaration, the scope of any identifiers it declares is the remainder of the declaration and
- the entire loop, including the other two expressions; it is reached in the order of execution
- before the first evaluation of the controlling expression. If clause-1 is an expression, it is
- evaluated as a void expression before the first evaluation of the controlling expression.156)
-2 Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a
- nonzero constant.
-<a name="6.8.6" href="#6.8.6"><b> 6.8.6 Jump statements</b></a>
- Syntax
-1 jump-statement:
- goto identifier ;
- continue ;
- break ;
- return expressionopt ;
- Semantics
-2 A jump statement causes an unconditional jump to another place.
-
-
-
-
- 155) This is intended to allow compiler transformations such as removal of empty loops even when
- termination cannot be proven.
- 156) Thus, clause-1 specifies initialization for the loop, possibly declaring one or more variables for use in
- the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration,
- such that execution of the loop continues until the expression compares equal to 0; and expression-3
- specifies an operation (such as incrementing) that is performed after each iteration.
-
-[<a name="#p149" href="p149">page 149</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.8.6.1" href="#6.8.6.1"><b> 6.8.6.1 The goto statement</b></a>
- Constraints
-1 The identifier in a goto statement shall name a label located somewhere in the enclosing
- function. A goto statement shall not jump from outside the scope of an identifier having
- a variably modified type to inside the scope of that identifier.
- Semantics
-2 A goto statement causes an unconditional jump to the statement prefixed by the named
- label in the enclosing function.
-3 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The
- following outline presents one possible approach to a problem based on these three assumptions:
- 1. The general initialization code accesses objects only visible to the current function.
- 2. The general initialization code is too large to warrant duplication.
- 3. The code to determine the next operation is at the head of the loop. (To allow it to be reached by
- continue statements, for example.)
- /* ... */
- goto first_time;
- for (;;) {
- // determine next operation
- /* ... */
- if (need to reinitialize) {
- // reinitialize-only code
- /* ... */
- first_time:
- // general initialization code
- /* ... */
- continue;
- }
- // handle other operations
- /* ... */
- }
-
-
-
-
-[<a name="#p150" href="p150">page 150</a>] (<a href="#Contents">Contents</a>)
-
-4 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably
- modified types. A jump within the scope, however, is permitted.
- goto lab3; // invalid: going INTO scope of VLA.
- {
- double a[n];
- a[j] = <a href="#4.4">4.4</a>;
- lab3:
- a[j] = <a href="#3.3">3.3</a>;
- goto lab4; // valid: going WITHIN scope of VLA.
- a[j] = <a href="#5.5">5.5</a>;
- lab4:
- a[j] = <a href="#6.6">6.6</a>;
- }
- goto lab4; // invalid: going INTO scope of VLA.
-
-<a name="6.8.6.2" href="#6.8.6.2"><b> 6.8.6.2 The continue statement</b></a>
- Constraints
-1 A continue statement shall appear only in or as a loop body.
- Semantics
-2 A continue statement causes a jump to the loop-continuation portion of the smallest
- enclosing iteration statement; that is, to the end of the loop body. More precisely, in each
- of the statements
- while (/* ... */) { do { for (/* ... */) {
- /* ... */ /* ... */ /* ... */
- continue; continue; continue;
- /* ... */ /* ... */ /* ... */
- contin: ; contin: ; contin: ;
- } } while (/* ... */); }
- unless the continue statement shown is in an enclosed iteration statement (in which
- case it is interpreted within that statement), it is equivalent to goto contin;.157)
-<a name="6.8.6.3" href="#6.8.6.3"><b> 6.8.6.3 The break statement</b></a>
- Constraints
-1 A break statement shall appear only in or as a switch body or loop body.
- Semantics
-2 A break statement terminates execution of the smallest enclosing switch or iteration
- statement.
-
-
-
- 157) Following the contin: label is a null statement.
-
-[<a name="#p151" href="p151">page 151</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.8.6.4" href="#6.8.6.4"><b> 6.8.6.4 The return statement</b></a>
- Constraints
-1 A return statement with an expression shall not appear in a function whose return type
- is void. A return statement without an expression shall only appear in a function
- whose return type is void.
- Semantics
-2 A return statement terminates execution of the current function and returns control to
- its caller. A function may have any number of return statements.
-3 If a return statement with an expression is executed, the value of the expression is
- returned to the caller as the value of the function call expression. If the expression has a
- type different from the return type of the function in which it appears, the value is
- converted as if by assignment to an object having the return type of the function.158)
-4 EXAMPLE In:
- struct s { double i; } f(void);
- union {
- struct {
- int f1;
- struct s f2;
- } u1;
- struct {
- struct s f3;
- int f4;
- } u2;
- } g;
- struct s f(void)
- {
- return g.u1.f2;
- }
- /* ... */
- g.u2.f3 = f();
- there is no undefined behavior, although there would be if the assignment were done directly (without using
- a function call to fetch the value).
-
-
-
-
- 158) The return statement is not an assignment. The overlap restriction of subclause <a href="#6.5.16.1">6.5.16.1</a> does not
- apply to the case of function return. The representation of floating-point values may have wider range
- or precision than implied by the type; a cast may be used to remove this extra range and precision.
-
-[<a name="#p152" href="p152">page 152</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.9" href="#6.9"><b> 6.9 External definitions</b></a>
- Syntax
-1 translation-unit:
- external-declaration
- translation-unit external-declaration
- external-declaration:
- function-definition
- declaration
- Constraints
-2 The storage-class specifiers auto and register shall not appear in the declaration
- specifiers in an external declaration.
-3 There shall be no more than one external definition for each identifier declared with
- internal linkage in a translation unit. Moreover, if an identifier declared with internal
- linkage is used in an expression (other than as a part of the operand of a sizeof
- operator whose result is an integer constant), there shall be exactly one external definition
- for the identifier in the translation unit.
- Semantics
-4 As discussed in <a href="#5.1.1.1">5.1.1.1</a>, the unit of program text after preprocessing is a translation unit,
- which consists of a sequence of external declarations. These are described as ''external''
- because they appear outside any function (and hence have file scope). As discussed in
- <a href="#6.7">6.7</a>, a declaration that also causes storage to be reserved for an object or a function named
- by the identifier is a definition.
-5 An external definition is an external declaration that is also a definition of a function
- (other than an inline definition) or an object. If an identifier declared with external
- linkage is used in an expression (other than as part of the operand of a sizeof operator
- whose result is an integer constant), somewhere in the entire program there shall be
- exactly one external definition for the identifier; otherwise, there shall be no more than
- one.159)
-
-
-
-
- 159) Thus, if an identifier declared with external linkage is not used in an expression, there need be no
- external definition for it.
-
-[<a name="#p153" href="p153">page 153</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.9.1" href="#6.9.1"><b> 6.9.1 Function definitions</b></a>
- Syntax
-1 function-definition:
- declaration-specifiers declarator declaration-listopt compound-statement
- declaration-list:
- declaration
- declaration-list declaration
- Constraints
-2 The identifier declared in a function definition (which is the name of the function) shall
- have a function type, as specified by the declarator portion of the function definition.160)
-3 The return type of a function shall be void or a complete object type other than array
- type.
-4 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
- static.
-5 If the declarator includes a parameter type list, the declaration of each parameter shall
- include an identifier, except for the special case of a parameter list consisting of a single
- parameter of type void, in which case there shall not be an identifier. No declaration list
- shall follow.
-6 If the declarator includes an identifier list, each declaration in the declaration list shall
- have at least one declarator, those declarators shall declare only identifiers from the
- identifier list, and every identifier in the identifier list shall be declared. An identifier
- declared as a typedef name shall not be redeclared as a parameter. The declarations in the
- declaration list shall contain no storage-class specifier other than register and no
- initializations.
-
-
-
- 160) The intent is that the type category in a function definition cannot be inherited from a typedef:
- typedef int F(void); // type F is ''function with no parameters
- // returning int''
- F f, g; // f and g both have type compatible with F
- F f { /* ... */ } // WRONG: syntax/constraint error
- F g() { /* ... */ } // WRONG: declares that g returns a function
- int f(void) { /* ... */ } // RIGHT: f has type compatible with F
- int g() { /* ... */ } // RIGHT: g has type compatible with F
- F *e(void) { /* ... */ } // e returns a pointer to a function
- F *((e))(void) { /* ... */ } // same: parentheses irrelevant
- int (*fp)(void); // fp points to a function that has type F
- F *Fp; // Fp points to a function that has type F
-
-
-[<a name="#p154" href="p154">page 154</a>] (<a href="#Contents">Contents</a>)
-
- Semantics
-7 The declarator in a function definition specifies the name of the function being defined
- and the identifiers of its parameters. If the declarator includes a parameter type list, the
- list also specifies the types of all the parameters; such a declarator also serves as a
- function prototype for later calls to the same function in the same translation unit. If the
- declarator includes an identifier list,161) the types of the parameters shall be declared in a
- following declaration list. In either case, the type of each parameter is adjusted as
- described in <a href="#6.7.6.3">6.7.6.3</a> for a parameter type list; the resulting type shall be a complete object
- type.
-8 If a function that accepts a variable number of arguments is defined without a parameter
- type list that ends with the ellipsis notation, the behavior is undefined.
-9 Each parameter has automatic storage duration; its identifier is an lvalue.162) The layout
- of the storage for parameters is unspecified.
-10 On entry to the function, the size expressions of each variably modified parameter are
- evaluated and the value of each argument expression is converted to the type of the
- corresponding parameter as if by assignment. (Array expressions and function
- designators as arguments were converted to pointers before the call.)
-11 After all parameters have been assigned, the compound statement that constitutes the
- body of the function definition is executed.
-12 If the } that terminates a function is reached, and the value of the function call is used by
- the caller, the behavior is undefined.
-13 EXAMPLE 1 In the following:
- extern int max(int a, int b)
- {
- return a > b ? a : b;
- }
- extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
- function declarator; and
- { return a > b ? a : b; }
- is the function body. The following similar definition uses the identifier-list form for the parameter
- declarations:
-
-
-
-
- 161) See ''future language directions'' (<a href="#6.11.7">6.11.7</a>).
- 162) A parameter identifier cannot be redeclared in the function body except in an enclosed block.
-
-[<a name="#p155" href="p155">page 155</a>] (<a href="#Contents">Contents</a>)
-
- extern int max(a, b)
- int a, b;
- {
- return a > b ? a : b;
- }
- Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
- that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
- to the function, whereas the second form does not.
-
-14 EXAMPLE 2 To pass one function to another, one might say
- int f(void);
- /* ... */
- g(f);
- Then the definition of g might read
- void g(int (*funcp)(void))
- {
- /* ... */
- (*funcp)(); /* or funcp(); ... */
- }
- or, equivalently,
- void g(int func(void))
- {
- /* ... */
- func(); /* or (*func)(); ... */
- }
-
-<a name="6.9.2" href="#6.9.2"><b> 6.9.2 External object definitions</b></a>
- Semantics
-1 If the declaration of an identifier for an object has file scope and an initializer, the
- declaration is an external definition for the identifier.
-2 A declaration of an identifier for an object that has file scope without an initializer, and
- without a storage-class specifier or with the storage-class specifier static, constitutes a
- tentative definition. If a translation unit contains one or more tentative definitions for an
- identifier, and the translation unit contains no external definition for that identifier, then
- the behavior is exactly as if the translation unit contains a file scope declaration of that
- identifier, with the composite type as of the end of the translation unit, with an initializer
- equal to 0.
-3 If the declaration of an identifier for an object is a tentative definition and has internal
- linkage, the declared type shall not be an incomplete type.
-
-
-
-
-[<a name="#p156" href="p156">page 156</a>] (<a href="#Contents">Contents</a>)
-
-4 EXAMPLE 1
- int i1 = 1; // definition, external linkage
- static int i2 = 2; // definition, internal linkage
- extern int i3 = 3; // definition, external linkage
- int i4; // tentative definition, external linkage
- static int i5; // tentative definition, internal linkage
- int i1; // valid tentative definition, refers to previous
- int i2; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
- int i3; // valid tentative definition, refers to previous
- int i4; // valid tentative definition, refers to previous
- int i5; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
- extern int i1; // refers to previous, whose linkage is external
- extern int i2; // refers to previous, whose linkage is internal
- extern int i3; // refers to previous, whose linkage is external
- extern int i4; // refers to previous, whose linkage is external
- extern int i5; // refers to previous, whose linkage is internal
-
-5 EXAMPLE 2 If at the end of the translation unit containing
- int i[];
- the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to
- zero on program startup.
-
-
-
-
-[<a name="#p157" href="p157">page 157</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.10" href="#6.10"><b> 6.10 Preprocessing directives</b></a>
- Syntax
-1 preprocessing-file:
- groupopt
- group:
- group-part
- group group-part
- group-part:
- if-section
- control-line
- text-line
- # non-directive
- if-section:
- if-group elif-groupsopt else-groupopt endif-line
- if-group:
- # if constant-expression new-line groupopt
- # ifdef identifier new-line groupopt
- # ifndef identifier new-line groupopt
- elif-groups:
- elif-group
- elif-groups elif-group
- elif-group:
- # elif constant-expression new-line groupopt
- else-group:
- # else new-line groupopt
- endif-line:
- # endif new-line
-
-
-
-
-[<a name="#p158" href="p158">page 158</a>] (<a href="#Contents">Contents</a>)
-
- control-line:
- # include pp-tokens new-line
- # define identifier replacement-list new-line
- # define identifier lparen identifier-listopt )
- replacement-list new-line
- # define identifier lparen ... ) replacement-list new-line
- # define identifier lparen identifier-list , ... )
- replacement-list new-line
- # undef identifier new-line
- # line pp-tokens new-line
- # error pp-tokensopt new-line
- # pragma pp-tokensopt new-line
- # new-line
- text-line:
- pp-tokensopt new-line
- non-directive:
- pp-tokens new-line
- lparen:
- a ( character not immediately preceded by white-space
- replacement-list:
- pp-tokensopt
- pp-tokens:
- preprocessing-token
- pp-tokens preprocessing-token
- new-line:
- the new-line character
- Description
-2 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the
- following constraints: The first token in the sequence is a # preprocessing token that (at
- the start of translation phase 4) is either the first character in the source file (optionally
- after white space containing no new-line characters) or that follows white space
- containing at least one new-line character. The last token in the sequence is the first new-
- line character that follows the first token in the sequence.163) A new-line character ends
- the preprocessing directive even if it occurs within what would otherwise be an
-
- 163) Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic
- significance, as all white space is equivalent except in certain situations during preprocessing (see the
- # character string literal creation operator in <a href="#6.10.3.2">6.10.3.2</a>, for example).
-
-[<a name="#p159" href="p159">page 159</a>] (<a href="#Contents">Contents</a>)
-
- invocation of a function-like macro.
-3 A text line shall not begin with a # preprocessing token. A non-directive shall not begin
- with any of the directive names appearing in the syntax.
-4 When in a group that is skipped (<a href="#6.10.1">6.10.1</a>), the directive syntax is relaxed to allow any
- sequence of preprocessing tokens to occur between the directive name and the following
- new-line character.
- Constraints
-5 The only white-space characters that shall appear between preprocessing tokens within a
- preprocessing directive (from just after the introducing # preprocessing token through
- just before the terminating new-line character) are space and horizontal-tab (including
- spaces that have replaced comments or possibly other white-space characters in
- translation phase 3).
- Semantics
-6 The implementation can process and skip sections of source files conditionally, include
- other source files, and replace macros. These capabilities are called preprocessing,
- because conceptually they occur before translation of the resulting translation unit.
-7 The preprocessing tokens within a preprocessing directive are not subject to macro
- expansion unless otherwise stated.
-8 EXAMPLE In:
- #define EMPTY
- EMPTY # include <file.h>
- the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
- begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
- replaced.
-
-<a name="6.10.1" href="#6.10.1"><b> 6.10.1 Conditional inclusion</b></a>
- Constraints
-1 The expression that controls conditional inclusion shall be an integer constant expression
- except that: identifiers (including those lexically identical to keywords) are interpreted as
- described below;164) and it may contain unary operator expressions of the form
- defined identifier
- or
- defined ( identifier )
- which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is
-
-
- 164) Because the controlling constant expression is evaluated during translation phase 4, all identifiers
- either are or are not macro names -- there simply are no keywords, enumeration constants, etc.
-
-[<a name="#p160" href="p160">page 160</a>] (<a href="#Contents">Contents</a>)
-
- predefined or if it has been the subject of a #define preprocessing directive without an
- intervening #undef directive with the same subject identifier), 0 if it is not.
-2 Each preprocessing token that remains (in the list of preprocessing tokens that will
- become the controlling expression) after all macro replacements have occurred shall be in
- the lexical form of a token (<a href="#6.4">6.4</a>).
- Semantics
-3 Preprocessing directives of the forms
- # if constant-expression new-line groupopt
- # elif constant-expression new-line groupopt
- check whether the controlling constant expression evaluates to nonzero.
-4 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
- the controlling constant expression are replaced (except for those macro names modified
- by the defined unary operator), just as in normal text. If the token defined is
- generated as a result of this replacement process or use of the defined unary operator
- does not match one of the two specified forms prior to macro replacement, the behavior is
- undefined. After all replacements due to macro expansion and the defined unary
- operator have been performed, all remaining identifiers (including those lexically
- identical to keywords) are replaced with the pp-number 0, and then each preprocessing
- token is converted into a token. The resulting tokens compose the controlling constant
- expression which is evaluated according to the rules of <a href="#6.6">6.6</a>. For the purposes of this
- token conversion and evaluation, all signed integer types and all unsigned integer types
- act as if they have the same representation as, respectively, the types intmax_t and
- uintmax_t defined in the header <a href="#7.20"><stdint.h></a>.165) This includes interpreting
- character constants, which may involve converting escape sequences into execution
- character set members. Whether the numeric value for these character constants matches
- the value obtained when an identical character constant occurs in an expression (other
- than within a #if or #elif directive) is implementation-defined.166) Also, whether a
- single-character character constant may have a negative value is implementation-defined.
-
-
-
-
- 165) Thus, on an implementation where INT_MAX is 0x7FFF and UINT_MAX is 0xFFFF, the constant
- 0x8000 is signed and positive within a #if expression even though it would be unsigned in
- translation phase 7.
- 166) Thus, the constant expression in the following #if directive and if statement is not guaranteed to
- evaluate to the same value in these two contexts.
- #if 'z' - 'a' == 25
- if ('z' - 'a' == 25)
-
-
-[<a name="#p161" href="p161">page 161</a>] (<a href="#Contents">Contents</a>)
-
-5 Preprocessing directives of the forms
- # ifdef identifier new-line groupopt
- # ifndef identifier new-line groupopt
- check whether the identifier is or is not currently defined as a macro name. Their
- conditions are equivalent to #if defined identifier and #if !defined identifier
- respectively.
-6 Each directive's condition is checked in order. If it evaluates to false (zero), the group
- that it controls is skipped: directives are processed only through the name that determines
- the directive in order to keep track of the level of nested conditionals; the rest of the
- directives' preprocessing tokens are ignored, as are the other preprocessing tokens in the
- group. Only the first group whose control condition evaluates to true (nonzero) is
- processed. If none of the conditions evaluates to true, and there is a #else directive, the
- group controlled by the #else is processed; lacking a #else directive, all the groups
- until the #endif are skipped.167)
- Forward references: macro replacement (<a href="#6.10.3">6.10.3</a>), source file inclusion (<a href="#6.10.2">6.10.2</a>), largest
- integer types (<a href="#7.20.1.5">7.20.1.5</a>).
-<a name="6.10.2" href="#6.10.2"><b> 6.10.2 Source file inclusion</b></a>
- Constraints
-1 A #include directive shall identify a header or source file that can be processed by the
- implementation.
- Semantics
-2 A preprocessing directive of the form
- # include <h-char-sequence> new-line
- searches a sequence of implementation-defined places for a header identified uniquely by
- the specified sequence between the < and > delimiters, and causes the replacement of that
- directive by the entire contents of the header. How the places are specified or the header
- identified is implementation-defined.
-3 A preprocessing directive of the form
- # include "q-char-sequence" new-line
- causes the replacement of that directive by the entire contents of the source file identified
- by the specified sequence between the " delimiters. The named source file is searched
-
-
- 167) As indicated by the syntax, a preprocessing token shall not follow a #else or #endif directive
- before the terminating new-line character. However, comments may appear anywhere in a source file,
- including within a preprocessing directive.
-
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-
- for in an implementation-defined manner. If this search is not supported, or if the search
- fails, the directive is reprocessed as if it read
- # include <h-char-sequence> new-line
- with the identical contained sequence (including > characters, if any) from the original
- directive.
-4 A preprocessing directive of the form
- # include pp-tokens new-line
- (that does not match one of the two previous forms) is permitted. The preprocessing
- tokens after include in the directive are processed just as in normal text. (Each
- identifier currently defined as a macro name is replaced by its replacement list of
- preprocessing tokens.) The directive resulting after all replacements shall match one of
- the two previous forms.168) The method by which a sequence of preprocessing tokens
- between a < and a > preprocessing token pair or a pair of " characters is combined into a
- single header name preprocessing token is implementation-defined.
-5 The implementation shall provide unique mappings for sequences consisting of one or
- more nondigits or digits (<a href="#6.4.2.1">6.4.2.1</a>) followed by a period (.) and a single nondigit. The
- first character shall not be a digit. The implementation may ignore distinctions of
- alphabetical case and restrict the mapping to eight significant characters before the
- period.
-6 A #include preprocessing directive may appear in a source file that has been read
- because of a #include directive in another file, up to an implementation-defined
- nesting limit (see <a href="#5.2.4.1">5.2.4.1</a>).
-7 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
- #include <a href="#7.21"><stdio.h></a>
- #include "myprog.h"
-
-
-
-
- 168) Note that adjacent string literals are not concatenated into a single string literal (see the translation
- phases in <a href="#5.1.1.2">5.1.1.2</a>); thus, an expansion that results in two string literals is an invalid directive.
-
-[<a name="#p163" href="p163">page 163</a>] (<a href="#Contents">Contents</a>)
-
-8 EXAMPLE 2 This illustrates macro-replaced #include directives:
- #if VERSION == 1
- #define INCFILE "vers1.h"
- #elif VERSION == 2
- #define INCFILE "vers2.h" // and so on
- #else
- #define INCFILE "versN.h"
- #endif
- #include INCFILE
-
- Forward references: macro replacement (<a href="#6.10.3">6.10.3</a>).
-<a name="6.10.3" href="#6.10.3"><b> 6.10.3 Macro replacement</b></a>
- Constraints
-1 Two replacement lists are identical if and only if the preprocessing tokens in both have
- the same number, ordering, spelling, and white-space separation, where all white-space
- separations are considered identical.
-2 An identifier currently defined as an object-like macro shall not be redefined by another
- #define preprocessing directive unless the second definition is an object-like macro
- definition and the two replacement lists are identical. Likewise, an identifier currently
- defined as a function-like macro shall not be redefined by another #define
- preprocessing directive unless the second definition is a function-like macro definition
- that has the same number and spelling of parameters, and the two replacement lists are
- identical.
-3 There shall be white-space between the identifier and the replacement list in the definition
- of an object-like macro.
-4 If the identifier-list in the macro definition does not end with an ellipsis, the number of
- arguments (including those arguments consisting of no preprocessing tokens) in an
- invocation of a function-like macro shall equal the number of parameters in the macro
- definition. Otherwise, there shall be more arguments in the invocation than there are
- parameters in the macro definition (excluding the ...). There shall exist a )
- preprocessing token that terminates the invocation.
-5 The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like
- macro that uses the ellipsis notation in the parameters.
-6 A parameter identifier in a function-like macro shall be uniquely declared within its
- scope.
- Semantics
-7 The identifier immediately following the define is called the macro name. There is one
- name space for macro names. Any white-space characters preceding or following the
- replacement list of preprocessing tokens are not considered part of the replacement list
-
-[<a name="#p164" href="p164">page 164</a>] (<a href="#Contents">Contents</a>)
-
- for either form of macro.
-8 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
- a preprocessing directive could begin, the identifier is not subject to macro replacement.
-9 A preprocessing directive of the form
- # define identifier replacement-list new-line
- defines an object-like macro that causes each subsequent instance of the macro name169)
- to be replaced by the replacement list of preprocessing tokens that constitute the
- remainder of the directive. The replacement list is then rescanned for more macro names
- as specified below.
-10 A preprocessing directive of the form
- # define identifier lparen identifier-listopt ) replacement-list new-line
- # define identifier lparen ... ) replacement-list new-line
- # define identifier lparen identifier-list , ... ) replacement-list new-line
- defines a function-like macro with parameters, whose use is similar syntactically to a
- function call. The parameters are specified by the optional list of identifiers, whose scope
- extends from their declaration in the identifier list until the new-line character that
- terminates the #define preprocessing directive. Each subsequent instance of the
- function-like macro name followed by a ( as the next preprocessing token introduces the
- sequence of preprocessing tokens that is replaced by the replacement list in the definition
- (an invocation of the macro). The replaced sequence of preprocessing tokens is
- terminated by the matching ) preprocessing token, skipping intervening matched pairs of
- left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
- tokens making up an invocation of a function-like macro, new-line is considered a normal
- white-space character.
-11 The sequence of preprocessing tokens bounded by the outside-most matching parentheses
- forms the list of arguments for the function-like macro. The individual arguments within
- the list are separated by comma preprocessing tokens, but comma preprocessing tokens
- between matching inner parentheses do not separate arguments. If there are sequences of
- preprocessing tokens within the list of arguments that would otherwise act as
- preprocessing directives,170) the behavior is undefined.
-12 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
- including any separating comma preprocessing tokens, are merged to form a single item:
-
-
- 169) Since, by macro-replacement time, all character constants and string literals are preprocessing tokens,
- not sequences possibly containing identifier-like subsequences (see <a href="#5.1.1.2">5.1.1.2</a>, translation phases), they
- are never scanned for macro names or parameters.
- 170) Despite the name, a non-directive is a preprocessing directive.
-
-[<a name="#p165" href="p165">page 165</a>] (<a href="#Contents">Contents</a>)
-
- the variable arguments. The number of arguments so combined is such that, following
- merger, the number of arguments is one more than the number of parameters in the macro
- definition (excluding the ...).
-<a name="6.10.3.1" href="#6.10.3.1"><b> 6.10.3.1 Argument substitution</b></a>
-1 After the arguments for the invocation of a function-like macro have been identified,
- argument substitution takes place. A parameter in the replacement list, unless preceded
- by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
- replaced by the corresponding argument after all macros contained therein have been
- expanded. Before being substituted, each argument's preprocessing tokens are
- completely macro replaced as if they formed the rest of the preprocessing file; no other
- preprocessing tokens are available.
-2 An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
- were a parameter, and the variable arguments shall form the preprocessing tokens used to
- replace it.
-<a name="6.10.3.2" href="#6.10.3.2"><b> 6.10.3.2 The # operator</b></a>
- Constraints
-1 Each # preprocessing token in the replacement list for a function-like macro shall be
- followed by a parameter as the next preprocessing token in the replacement list.
- Semantics
-2 If, in the replacement list, a parameter is immediately preceded by a # preprocessing
- token, both are replaced by a single character string literal preprocessing token that
- contains the spelling of the preprocessing token sequence for the corresponding
- argument. Each occurrence of white space between the argument's preprocessing tokens
- becomes a single space character in the character string literal. White space before the
- first preprocessing token and after the last preprocessing token composing the argument
- is deleted. Otherwise, the original spelling of each preprocessing token in the argument
- is retained in the character string literal, except for special handling for producing the
- spelling of string literals and character constants: a \ character is inserted before each "
- and \ character of a character constant or string literal (including the delimiting "
- characters), except that it is implementation-defined whether a \ character is inserted
- before the \ character beginning a universal character name. If the replacement that
- results is not a valid character string literal, the behavior is undefined. The character
- string literal corresponding to an empty argument is "". The order of evaluation of # and
- ## operators is unspecified.
-
-
-
-
-[<a name="#p166" href="p166">page 166</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.10.3.3" href="#6.10.3.3"><b> 6.10.3.3 The ## operator</b></a>
- Constraints
-1 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
- list for either form of macro definition.
- Semantics
-2 If, in the replacement list of a function-like macro, a parameter is immediately preceded
- or followed by a ## preprocessing token, the parameter is replaced by the corresponding
- argument's preprocessing token sequence; however, if an argument consists of no
- preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
- instead.171)
-3 For both object-like and function-like macro invocations, before the replacement list is
- reexamined for more macro names to replace, each instance of a ## preprocessing token
- in the replacement list (not from an argument) is deleted and the preceding preprocessing
- token is concatenated with the following preprocessing token. Placemarker
- preprocessing tokens are handled specially: concatenation of two placemarkers results in
- a single placemarker preprocessing token, and concatenation of a placemarker with a
- non-placemarker preprocessing token results in the non-placemarker preprocessing token.
- If the result is not a valid preprocessing token, the behavior is undefined. The resulting
- token is available for further macro replacement. The order of evaluation of ## operators
- is unspecified.
-4 EXAMPLE In the following fragment:
- #define hash_hash # ## #
- #define mkstr(a) # a
- #define in_between(a) mkstr(a)
- #define join(c, d) in_between(c hash_hash d)
- char p[] = join(x, y); // equivalent to
- // char p[] = "x ## y";
- The expansion produces, at various stages:
- join(x, y)
- in_between(x hash_hash y)
- in_between(x ## y)
- mkstr(x ## y)
- "x ## y"
- In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
- this new token is not the ## operator.
-
-
- 171) Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
- exist only within translation phase 4.
-
-[<a name="#p167" href="p167">page 167</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.10.3.4" href="#6.10.3.4"><b> 6.10.3.4 Rescanning and further replacement</b></a>
-1 After all parameters in the replacement list have been substituted and # and ##
- processing has taken place, all placemarker preprocessing tokens are removed. The
- resulting preprocessing token sequence is then rescanned, along with all subsequent
- preprocessing tokens of the source file, for more macro names to replace.
-2 If the name of the macro being replaced is found during this scan of the replacement list
- (not including the rest of the source file's preprocessing tokens), it is not replaced.
- Furthermore, if any nested replacements encounter the name of the macro being replaced,
- it is not replaced. These nonreplaced macro name preprocessing tokens are no longer
- available for further replacement even if they are later (re)examined in contexts in which
- that macro name preprocessing token would otherwise have been replaced.
-3 The resulting completely macro-replaced preprocessing token sequence is not processed
- as a preprocessing directive even if it resembles one, but all pragma unary operator
- expressions within it are then processed as specified in <a href="#6.10.9">6.10.9</a> below.
-<a name="6.10.3.5" href="#6.10.3.5"><b> 6.10.3.5 Scope of macro definitions</b></a>
-1 A macro definition lasts (independent of block structure) until a corresponding #undef
- directive is encountered or (if none is encountered) until the end of the preprocessing
- translation unit. Macro definitions have no significance after translation phase 4.
-2 A preprocessing directive of the form
- # undef identifier new-line
- causes the specified identifier no longer to be defined as a macro name. It is ignored if
- the specified identifier is not currently defined as a macro name.
-3 EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
- #define TABSIZE 100
- int table[TABSIZE];
-
-4 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments.
- It has the advantages of working for any compatible types of the arguments and of generating in-line code
- without the overhead of function calling. It has the disadvantages of evaluating one or the other of its
- arguments a second time (including side effects) and generating more code than a function if invoked
- several times. It also cannot have its address taken, as it has none.
- #define max(a, b) ((a) > (b) ? (a) : (b))
- The parentheses ensure that the arguments and the resulting expression are bound properly.
-
-
-
-
-[<a name="#p168" href="p168">page 168</a>] (<a href="#Contents">Contents</a>)
-
-5 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
- #define x 3
- #define f(a) f(x * (a))
- #undef x
- #define x 2
- #define g f
- #define z z[0]
- #define h g(~
- #define m(a) a(w)
- #define w 0,1
- #define t(a) a
- #define p() int
- #define q(x) x
- #define r(x,y) x ## y
- #define str(x) # x
- f(y+1) + f(f(z)) % t(t(g)(0) + t)(1);
- g(x+(3,4)-w) | h 5) & m
- (f)^m(m);
- p() i[q()] = { q(1), r(2,3), r(4,), r(,5), r(,) };
- char c[2][6] = { str(hello), str() };
- results in
- f(2 * (y+1)) + f(2 * (f(2 * (z[0])))) % f(2 * (0)) + t(1);
- f(2 * (2+(3,4)-0,1)) | f(2 * (~ 5)) & f(2 * (0,1))^m(0,1);
- int i[] = { 1, 23, 4, 5, };
- char c[2][6] = { "hello", "" };
-
-6 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the
- sequence
- #define str(s) # s
- #define xstr(s) str(s)
- #define debug(s, t) printf("x" # s "= %d, x" # t "= %s", \
- x ## s, x ## t)
- #define INCFILE(n) vers ## n
- #define glue(a, b) a ## b
- #define xglue(a, b) glue(a, b)
- #define HIGHLOW "hello"
- #define LOW LOW ", world"
- debug(1, 2);
- fputs(str(strncmp("abc\0d", "abc", '\4') // this goes away
- == 0) str(: @\n), s);
- #include xstr(INCFILE(2).h)
- glue(HIGH, LOW);
- xglue(HIGH, LOW)
- results in
-
-
-
-
-[<a name="#p169" href="p169">page 169</a>] (<a href="#Contents">Contents</a>)
-
- printf("x" "1" "= %d, x" "2" "= %s", x1, x2);
- fputs(
- "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0" ": @\n",
- s);
- #include "vers2.h" (after macro replacement, before file access)
- "hello";
- "hello" ", world"
- or, after concatenation of the character string literals,
- printf("x1= %d, x2= %s", x1, x2);
- fputs(
- "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0: @\n",
- s);
- #include "vers2.h" (after macro replacement, before file access)
- "hello";
- "hello, world"
- Space around the # and ## tokens in the macro definition is optional.
-
-7 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
- #define t(x,y,z) x ## y ## z
- int j[] = { t(1,2,3), t(,4,5), t(6,,7), t(8,9,),
- t(10,,), t(,11,), t(,,12), t(,,) };
- results in
- int j[] = { 123, 45, 67, 89,
- 10, 11, 12, };
-
-8 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
- #define OBJ_LIKE (1-1)
- #define OBJ_LIKE /* white space */ (1-1) /* other */
- #define FUNC_LIKE(a) ( a )
- #define FUNC_LIKE( a )( /* note the white space */ \
- a /* other stuff on this line
- */ )
- But the following redefinitions are invalid:
- #define OBJ_LIKE (0) // different token sequence
- #define OBJ_LIKE (1 - 1) // different white space
- #define FUNC_LIKE(b) ( a ) // different parameter usage
- #define FUNC_LIKE(b) ( b ) // different parameter spelling
-
-9 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
- #define debug(...) fprintf(stderr, __VA_ARGS__)
- #define showlist(...) puts(#__VA_ARGS__)
- #define report(test, ...) ((test)?puts(#test):\
- printf(__VA_ARGS__))
- debug("Flag");
- debug("X = %d\n", x);
- showlist(The first, second, and third items.);
- report(x>y, "x is %d but y is %d", x, y);
-
-
-[<a name="#p170" href="p170">page 170</a>] (<a href="#Contents">Contents</a>)
-
- results in
- fprintf(stderr, "Flag" );
- fprintf(stderr, "X = %d\n", x );
- puts( "The first, second, and third items." );
- ((x>y)?puts("x>y"):
- printf("x is %d but y is %d", x, y));
-
-<a name="6.10.4" href="#6.10.4"><b> 6.10.4 Line control</b></a>
- Constraints
-1 The string literal of a #line directive, if present, shall be a character string literal.
- Semantics
-2 The line number of the current source line is one greater than the number of new-line
- characters read or introduced in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>) while processing the source
- file to the current token.
-3 A preprocessing directive of the form
- # line digit-sequence new-line
- causes the implementation to behave as if the following sequence of source lines begins
- with a source line that has a line number as specified by the digit sequence (interpreted as
- a decimal integer). The digit sequence shall not specify zero, nor a number greater than
- 2147483647.
-4 A preprocessing directive of the form
- # line digit-sequence "s-char-sequenceopt" new-line
- sets the presumed line number similarly and changes the presumed name of the source
- file to be the contents of the character string literal.
-5 A preprocessing directive of the form
- # line pp-tokens new-line
- (that does not match one of the two previous forms) is permitted. The preprocessing
- tokens after line on the directive are processed just as in normal text (each identifier
- currently defined as a macro name is replaced by its replacement list of preprocessing
- tokens). The directive resulting after all replacements shall match one of the two
- previous forms and is then processed as appropriate.
-
-
-
-
-[<a name="#p171" href="p171">page 171</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.10.5" href="#6.10.5"><b> 6.10.5 Error directive</b></a>
- Semantics
-1 A preprocessing directive of the form
- # error pp-tokensopt new-line
- causes the implementation to produce a diagnostic message that includes the specified
- sequence of preprocessing tokens.
-<a name="6.10.6" href="#6.10.6"><b> 6.10.6 Pragma directive</b></a>
- Semantics
-1 A preprocessing directive of the form
- # pragma pp-tokensopt new-line
- where the preprocessing token STDC does not immediately follow pragma in the
- directive (prior to any macro replacement)172) causes the implementation to behave in an
- implementation-defined manner. The behavior might cause translation to fail or cause the
- translator or the resulting program to behave in a non-conforming manner. Any such
- pragma that is not recognized by the implementation is ignored.
-2 If the preprocessing token STDC does immediately follow pragma in the directive (prior
- to any macro replacement), then no macro replacement is performed on the directive, and
- the directive shall have one of the following forms173) whose meanings are described
- elsewhere:
- #pragma STDC FP_CONTRACT on-off-switch
- #pragma STDC FENV_ACCESS on-off-switch
- #pragma STDC CX_LIMITED_RANGE on-off-switch
- on-off-switch: one of
- ON OFF DEFAULT
- Forward references: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), the FENV_ACCESS pragma
- (<a href="#7.6.1">7.6.1</a>), the CX_LIMITED_RANGE pragma (<a href="#7.3.4">7.3.4</a>).
-
-
-
-
- 172) An implementation is not required to perform macro replacement in pragmas, but it is permitted
- except for in standard pragmas (where STDC immediately follows pragma). If the result of macro
- replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still
- implementation-defined; an implementation is permitted to behave as if it were the standard pragma,
- but is not required to.
- 173) See ''future language directions'' (<a href="#6.11.8">6.11.8</a>).
-
-[<a name="#p172" href="p172">page 172</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.10.7" href="#6.10.7"><b> 6.10.7 Null directive</b></a>
- Semantics
-1 A preprocessing directive of the form
- # new-line
- has no effect.
-<a name="6.10.8" href="#6.10.8"><b> 6.10.8 Predefined macro names</b></a>
-1 The values of the predefined macros listed in the following subclauses174) (except for
- __FILE__ and __LINE__) remain constant throughout the translation unit.
-2 None of these macro names, nor the identifier defined, shall be the subject of a
- #define or a #undef preprocessing directive. Any other predefined macro names
- shall begin with a leading underscore followed by an uppercase letter or a second
- underscore.
-3 The implementation shall not predefine the macro __cplusplus, nor shall it define it
- in any standard header.
- Forward references: standard headers (<a href="#7.1.2">7.1.2</a>).
-<a name="6.10.8.1" href="#6.10.8.1"><b> 6.10.8.1 Mandatory macros</b></a>
-1 The following macro names shall be defined by the implementation:
- __DATE__ The date of translation of the preprocessing translation unit: a character
- string literal of the form "Mmm dd yyyy", where the names of the
- months are the same as those generated by the asctime function, and the
- first character of dd is a space character if the value is less than 10. If the
- date of translation is not available, an implementation-defined valid date
- shall be supplied.
- __FILE__ The presumed name of the current source file (a character string literal).175)
- __LINE__ The presumed line number (within the current source file) of the current
- source line (an integer constant).175)
- __STDC__ The integer constant 1, intended to indicate a conforming implementation.
- __STDC_HOSTED__ The integer constant 1 if the implementation is a hosted
- implementation or the integer constant 0 if it is not.
-
-
-
-
- 174) See ''future language directions'' (<a href="#6.11.9">6.11.9</a>).
- 175) The presumed source file name and line number can be changed by the #line directive.
-
-[<a name="#p173" href="p173">page 173</a>] (<a href="#Contents">Contents</a>)
-
- __STDC_VERSION__ The integer constant 201ymmL.176)
- __TIME__ The time of translation of the preprocessing translation unit: a character
- string literal of the form "hh:mm:ss" as in the time generated by the
- asctime function. If the time of translation is not available, an
- implementation-defined valid time shall be supplied.
- Forward references: the asctime function (<a href="#7.26.3.1">7.26.3.1</a>).
-<a name="6.10.8.2" href="#6.10.8.2"><b> 6.10.8.2 Environment macros</b></a>
-1 The following macro names are conditionally defined by the implementation:
- __STDC_ISO_10646__ An integer constant of the form yyyymmL (for example,
- 199712L). If this symbol is defined, then every character in the Unicode
- required set, when stored in an object of type wchar_t, has the same
- value as the short identifier of that character. The Unicode required set
- consists of all the characters that are defined by ISO/IEC 10646, along with
- all amendments and technical corrigenda, as of the specified year and
- month. If some other encoding is used, the macro shall not be defined and
- the actual encoding used is implementation-defined.
- __STDC_MB_MIGHT_NEQ_WC__ The integer constant 1, intended to indicate that, in
- the encoding for wchar_t, a member of the basic character set need not
- have a code value equal to its value when used as the lone character in an
- integer character constant.
- __STDC_UTF_16__ The integer constant 1, intended to indicate that values of type
- char16_t are UTF-16 encoded. If some other encoding is used, the
- macro shall not be defined and the actual encoding used is implementation-
- defined.
- __STDC_UTF_32__ The integer constant 1, intended to indicate that values of type
- char32_t are UTF-32 encoded. If some other encoding is used, the
- macro shall not be defined and the actual encoding used is implementation-
- defined.
- Forward references: common definitions (<a href="#7.19">7.19</a>), unicode utilities (<a href="#7.27">7.27</a>).
-
-
-
-
- 176) This macro was not specified in ISO/IEC 9899:1990 and was specified as 199409L in
- ISO/IEC 9899/AMD1:1995 and as 199901L in ISO/IEC 9899:1999. The intention is that this will
- remain an integer constant of type long int that is increased with each revision of this International
- Standard.
-
-[<a name="#p174" href="p174">page 174</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.10.8.3" href="#6.10.8.3"><b> 6.10.8.3 Conditional feature macros</b></a>
-1 The following macro names are conditionally defined by the implementation:
- __STDC_ANALYZABLE__ The integer constant 1, intended to indicate conformance to
- the specifications in <a href="#L">annex L</a> (Analyzability).
- __STDC_IEC_559__ The integer constant 1, intended to indicate conformance to the
- specifications in <a href="#F">annex F</a> (IEC 60559 floating-point arithmetic).
- __STDC_IEC_559_COMPLEX__ The integer constant 1, intended to indicate
- adherence to the specifications in informative <a href="#G">annex G</a> (IEC 60559
- compatible complex arithmetic).
- __STDC_LIB_EXT1__ The integer constant 201ymmL, intended to indicate support
- for the extensions defined in <a href="#K">annex K</a> (Bounds-checking interfaces).177)
- __STDC_NO_COMPLEX__ The integer constant 1, intended to indicate that the
- implementation does not support complex types or the <a href="#7.3"><complex.h></a>
- header.
- __STDC_NO_THREADS__ The integer constant 1, intended to indicate that the
- implementation does not support atomic types (including the _Atomic
- type qualifier and the <a href="#7.17"><stdatomic.h></a> header) or the <a href="#7.25"><threads.h></a>
- header.
- __STDC_NO_VLA__ The integer constant 1, intended to indicate that the
- implementation does not support variable length arrays or variably
- modified types.
-<a name="6.10.9" href="#6.10.9"><b> 6.10.9 Pragma operator</b></a>
- Semantics
-1 A unary operator expression of the form:
- _Pragma ( string-literal )
- is processed as follows: The string literal is destringized by deleting the L prefix, if
- present, deleting the leading and trailing double-quotes, replacing each escape sequence
- \" by a double-quote, and replacing each escape sequence \\ by a single backslash. The
- resulting sequence of characters is processed through translation phase 3 to produce
- preprocessing tokens that are executed as if they were the pp-tokens in a pragma
- directive. The original four preprocessing tokens in the unary operator expression are
- removed.
-
-
- 177) The intention is that this will remain an integer constant of type long int that is increased with
- each revision of this International Standard.
-
-[<a name="#p175" href="p175">page 175</a>] (<a href="#Contents">Contents</a>)
-
-2 EXAMPLE A directive of the form:
- #pragma listing on "..\listing.dir"
- can also be expressed as:
- _Pragma ( "listing on \"..\\listing.dir\"" )
- The latter form is processed in the same way whether it appears literally as shown, or results from macro
- replacement, as in:
- #define LISTING(x) PRAGMA(listing on #x)
- #define PRAGMA(x) _Pragma(#x)
- LISTING ( ..\listing.dir )
-
-
-
-
-[<a name="#p176" href="p176">page 176</a>] (<a href="#Contents">Contents</a>)
-
-<a name="6.11" href="#6.11"><b> 6.11 Future language directions</b></a>
-<a name="6.11.1" href="#6.11.1"><b> 6.11.1 Floating types</b></a>
-1 Future standardization may include additional floating-point types, including those with
- greater range, precision, or both than long double.
-<a name="6.11.2" href="#6.11.2"><b> 6.11.2 Linkages of identifiers</b></a>
-1 Declaring an identifier with internal linkage at file scope without the static storage-
- class specifier is an obsolescent feature.
-<a name="6.11.3" href="#6.11.3"><b> 6.11.3 External names</b></a>
-1 Restriction of the significance of an external name to fewer than 255 characters
- (considering each universal character name or extended source character as a single
- character) is an obsolescent feature that is a concession to existing implementations.
-<a name="6.11.4" href="#6.11.4"><b> 6.11.4 Character escape sequences</b></a>
-1 Lowercase letters as escape sequences are reserved for future standardization. Other
- characters may be used in extensions.
-<a name="6.11.5" href="#6.11.5"><b> 6.11.5 Storage-class specifiers</b></a>
-1 The placement of a storage-class specifier other than at the beginning of the declaration
- specifiers in a declaration is an obsolescent feature.
-<a name="6.11.6" href="#6.11.6"><b> 6.11.6 Function declarators</b></a>
-1 The use of function declarators with empty parentheses (not prototype-format parameter
- type declarators) is an obsolescent feature.
-<a name="6.11.7" href="#6.11.7"><b> 6.11.7 Function definitions</b></a>
-1 The use of function definitions with separate parameter identifier and declaration lists
- (not prototype-format parameter type and identifier declarators) is an obsolescent feature.
-<a name="6.11.8" href="#6.11.8"><b> 6.11.8 Pragma directives</b></a>
-1 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
-<a name="6.11.9" href="#6.11.9"><b> 6.11.9 Predefined macro names</b></a>
-1 Macro names beginning with __STDC_ are reserved for future standardization.
-
-
-
-
-[<a name="#p177" href="p177">page 177</a>] (<a href="#Contents">Contents</a>)
-
-
-<a name="7" href="#7"><b> 7. Library</b></a>
-<a name="7.1" href="#7.1"><b> 7.1 Introduction</b></a>
-<a name="7.1.1" href="#7.1.1"><b> 7.1.1 Definitions of terms</b></a>
-1 A string is a contiguous sequence of characters terminated by and including the first null
- character. The term multibyte string is sometimes used instead to emphasize special
- processing given to multibyte characters contained in the string or to avoid confusion
- with a wide string. A pointer to a string is a pointer to its initial (lowest addressed)
- character. The length of a string is the number of bytes preceding the null character and
- the value of a string is the sequence of the values of the contained characters, in order.
-2 The decimal-point character is the character used by functions that convert floating-point
- numbers to or from character sequences to denote the beginning of the fractional part of
- such character sequences.178) It is represented in the text and examples by a period, but
- may be changed by the setlocale function.
-3 A null wide character is a wide character with code value zero.
-4 A wide string is a contiguous sequence of wide characters terminated by and including
- the first null wide character. A pointer to a wide string is a pointer to its initial (lowest
- addressed) wide character. The length of a wide string is the number of wide characters
- preceding the null wide character and the value of a wide string is the sequence of code
- values of the contained wide characters, in order.
-5 A shift sequence is a contiguous sequence of bytes within a multibyte string that
- (potentially) causes a change in shift state (see <a href="#5.2.1.2">5.2.1.2</a>). A shift sequence shall not have a
- corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
- character.179)
- Forward references: character handling (<a href="#7.4">7.4</a>), the setlocale function (<a href="#7.11.1.1">7.11.1.1</a>).
-
-
-
-
- 178) The functions that make use of the decimal-point character are the numeric conversion functions
- (<a href="#7.22.1">7.22.1</a>, <a href="#7.28.4.1">7.28.4.1</a>) and the formatted input/output functions (<a href="#7.21.6">7.21.6</a>, <a href="#7.28.2">7.28.2</a>).
- 179) For state-dependent encodings, the values for MB_CUR_MAX and MB_LEN_MAX shall thus be large
- enough to count all the bytes in any complete multibyte character plus at least one adjacent shift
- sequence of maximum length. Whether these counts provide for more than one shift sequence is the
- implementation's choice.
-
-[<a name="#p178" href="p178">page 178</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.1.2" href="#7.1.2"><b> 7.1.2 Standard headers</b></a>
-1 Each library function is declared, with a type that includes a prototype, in a header,180)
- whose contents are made available by the #include preprocessing directive. The
- header declares a set of related functions, plus any necessary types and additional macros
- needed to facilitate their use. Declarations of types described in this clause shall not
- include type qualifiers, unless explicitly stated otherwise.
-2 The standard headers are181)
- <a href="#7.2"><assert.h></a> <a href="#7.9"><iso646.h></a> <a href="#7.16"><stdarg.h></a> <a href="#7.23"><string.h></a>
- <a href="#7.3"><complex.h></a> <a href="#7.10"><limits.h></a> <a href="#7.17"><stdatomic.h></a> <a href="#7.24"><tgmath.h></a>
- <a href="#7.4"><ctype.h></a> <a href="#7.11"><locale.h></a> <a href="#7.18"><stdbool.h></a> <a href="#7.25"><threads.h></a>
- <a href="#7.5"><errno.h></a> <a href="#7.12"><math.h></a> <a href="#7.19"><stddef.h></a> <a href="#7.26"><time.h></a>
- <a href="#7.6"><fenv.h></a> <a href="#7.13"><setjmp.h></a> <a href="#7.20"><stdint.h></a> <a href="#7.27"><uchar.h></a>
- <a href="#7.7"><float.h></a> <a href="#7.14"><signal.h></a> <a href="#7.21"><stdio.h></a> <a href="#7.28"><wchar.h></a>
- <a href="#7.8"><inttypes.h></a> <a href="#7.15"><stdalign.h></a> <a href="#7.22"><stdlib.h></a> <a href="#7.29"><wctype.h></a>
-3 If a file with the same name as one of the above < and > delimited sequences, not
- provided as part of the implementation, is placed in any of the standard places that are
- searched for included source files, the behavior is undefined.
-4 Standard headers may be included in any order; each may be included more than once in
- a given scope, with no effect different from being included only once, except that the
- effect of including <a href="#7.2"><assert.h></a> depends on the definition of NDEBUG (see <a href="#7.2">7.2</a>). If
- used, a header shall be included outside of any external declaration or definition, and it
- shall first be included before the first reference to any of the functions or objects it
- declares, or to any of the types or macros it defines. However, if an identifier is declared
- or defined in more than one header, the second and subsequent associated headers may be
- included after the initial reference to the identifier. The program shall not have any
- macros with names lexically identical to keywords currently defined prior to the
- inclusion.
-5 Any definition of an object-like macro described in this clause shall expand to code that is
- fully protected by parentheses where necessary, so that it groups in an arbitrary
- expression as if it were a single identifier.
-6 Any declaration of a library function shall have external linkage.
-
-
-
-
- 180) A header is not necessarily a source file, nor are the < and > delimited sequences in header names
- necessarily valid source file names.
- 181) The headers <a href="#7.3"><complex.h></a>, <a href="#7.17"><stdatomic.h></a>, and <a href="#7.25"><threads.h></a> are conditional features that
- implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.
-
-[<a name="#p179" href="p179">page 179</a>] (<a href="#Contents">Contents</a>)
-
-7 A summary of the contents of the standard headers is given in <a href="#B">annex B</a>.
- Forward references: diagnostics (<a href="#7.2">7.2</a>).
-<a name="7.1.3" href="#7.1.3"><b> 7.1.3 Reserved identifiers</b></a>
-1 Each header declares or defines all identifiers listed in its associated subclause, and
- optionally declares or defines identifiers listed in its associated future library directions
- subclause and identifiers which are always reserved either for any use or for use as file
- scope identifiers.
- -- All identifiers that begin with an underscore and either an uppercase letter or another
- underscore are always reserved for any use.
- -- All identifiers that begin with an underscore are always reserved for use as identifiers
- with file scope in both the ordinary and tag name spaces.
- -- Each macro name in any of the following subclauses (including the future library
- directions) is reserved for use as specified if any of its associated headers is included;
- unless explicitly stated otherwise (see <a href="#7.1.4">7.1.4</a>).
- -- All identifiers with external linkage in any of the following subclauses (including the
- future library directions) and errno are always reserved for use as identifiers with
- external linkage.182)
- -- Each identifier with file scope listed in any of the following subclauses (including the
- future library directions) is reserved for use as a macro name and as an identifier with
- file scope in the same name space if any of its associated headers is included.
-2 No other identifiers are reserved. If the program declares or defines an identifier in a
- context in which it is reserved (other than as allowed by <a href="#7.1.4">7.1.4</a>), or defines a reserved
- identifier as a macro name, the behavior is undefined.
-3 If the program removes (with #undef) any macro definition of an identifier in the first
- group listed above, the behavior is undefined.
-
-
-
-
- 182) The list of reserved identifiers with external linkage includes math_errhandling, setjmp,
- va_copy, and va_end.
-
-[<a name="#p180" href="p180">page 180</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.1.4" href="#7.1.4"><b> 7.1.4 Use of library functions</b></a>
-1 Each of the following statements applies unless explicitly stated otherwise in the detailed
- descriptions that follow: If an argument to a function has an invalid value (such as a value
- outside the domain of the function, or a pointer outside the address space of the program,
- or a null pointer, or a pointer to non-modifiable storage when the corresponding
- parameter is not const-qualified) or a type (after promotion) not expected by a function
- with variable number of arguments, the behavior is undefined. If a function argument is
- described as being an array, the pointer actually passed to the function shall have a value
- such that all address computations and accesses to objects (that would be valid if the
- pointer did point to the first element of such an array) are in fact valid. Any function
- declared in a header may be additionally implemented as a function-like macro defined in
- the header, so if a library function is declared explicitly when its header is included, one
- of the techniques shown below can be used to ensure the declaration is not affected by
- such a macro. Any macro definition of a function can be suppressed locally by enclosing
- the name of the function in parentheses, because the name is then not followed by the left
- parenthesis that indicates expansion of a macro function name. For the same syntactic
- reason, it is permitted to take the address of a library function even if it is also defined as
- a macro.183) The use of #undef to remove any macro definition will also ensure that an
- actual function is referred to. Any invocation of a library function that is implemented as
- a macro shall expand to code that evaluates each of its arguments exactly once, fully
- protected by parentheses where necessary, so it is generally safe to use arbitrary
- expressions as arguments.184) Likewise, those function-like macros described in the
- following subclauses may be invoked in an expression anywhere a function with a
- compatible return type could be called.185) All object-like macros listed as expanding to
-
-
- 183) This means that an implementation shall provide an actual function for each library function, even if it
- also provides a macro for that function.
- 184) Such macros might not contain the sequence points that the corresponding function calls do.
- 185) Because external identifiers and some macro names beginning with an underscore are reserved,
- implementations may provide special semantics for such names. For example, the identifier
- _BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
- appropriate header could specify
- #define abs(x) _BUILTIN_abs(x)
- for a compiler whose code generator will accept it.
- In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
- function may write
- #undef abs
- whether the implementation's header provides a macro implementation of abs or a built-in
- implementation. The prototype for the function, which precedes and is hidden by any macro
- definition, is thereby revealed also.
-
-[<a name="#p181" href="p181">page 181</a>] (<a href="#Contents">Contents</a>)
-
- integer constant expressions shall additionally be suitable for use in #if preprocessing
- directives.
-2 Provided that a library function can be declared without reference to any type defined in a
- header, it is also permissible to declare the function and use it without including its
- associated header.
-3 There is a sequence point immediately before a library function returns.
-4 The functions in the standard library are not guaranteed to be reentrant and may modify
- objects with static or thread storage duration.186)
-5 Unless explicitly stated otherwise in the detailed descriptions that follow, library
- functions shall prevent data races as follows: A library function shall not directly or
- indirectly access objects accessible by threads other than the current thread unless the
- objects are accessed directly or indirectly via the function's arguments. A library
- function shall not directly or indirectly modify objects accessible by threads other than
- the current thread unless the objects are accessed directly or indirectly via the function's
- non-const arguments.187) Implementations may share their own internal objects between
- threads if the objects are not visible to users and are protected against data races.
-6 Unless otherwise specified, library functions shall perform all operations solely within the
- current thread if those operations have effects that are visible to users.188)
-7 EXAMPLE The function atoi may be used in any of several ways:
- -- by use of its associated header (possibly generating a macro expansion)
- #include <a href="#7.22"><stdlib.h></a>
- const char *str;
- /* ... */
- i = atoi(str);
- -- by use of its associated header (assuredly generating a true function reference)
-
-
-
-
- 186) Thus, a signal handler cannot, in general, call standard library functions.
- 187) This means, for example, that an implementation is not permitted to use a static object for internal
- purposes without synchronization because it could cause a data race even in programs that do not
- explicitly share objects between threads.
- 188) This allows implementations to parallelize operations if there are no visible side effects.
-
-[<a name="#p182" href="p182">page 182</a>] (<a href="#Contents">Contents</a>)
-
- #include <a href="#7.22"><stdlib.h></a>
- #undef atoi
- const char *str;
- /* ... */
- i = atoi(str);
- or
- #include <a href="#7.22"><stdlib.h></a>
- const char *str;
- /* ... */
- i = (atoi)(str);
--- by explicit declaration
- extern int atoi(const char *);
- const char *str;
- /* ... */
- i = atoi(str);
-
-
-
-
-[<a name="#p183" href="p183">page 183</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.2" href="#7.2"><b> 7.2 Diagnostics <assert.h></b></a>
-1 The header <a href="#7.2"><assert.h></a> defines the assert and static_assert macros and
- refers to another macro,
- NDEBUG
- which is not defined by <a href="#7.2"><assert.h></a>. If NDEBUG is defined as a macro name at the
- point in the source file where <a href="#7.2"><assert.h></a> is included, the assert macro is defined
- simply as
- #define assert(ignore) ((void)0)
- The assert macro is redefined according to the current state of NDEBUG each time that
- <a href="#7.2"><assert.h></a> is included.
-2 The assert macro shall be implemented as a macro, not as an actual function. If the
- macro definition is suppressed in order to access an actual function, the behavior is
- undefined.
-3 The macro
- static_assert
- expands to _Static_assert.
-<a name="7.2.1" href="#7.2.1"><b> 7.2.1 Program diagnostics</b></a>
-<a name="7.2.1.1" href="#7.2.1.1"><b> 7.2.1.1 The assert macro</b></a>
- Synopsis
-1 #include <a href="#7.2"><assert.h></a>
- void assert(scalar expression);
- Description
-2 The assert macro puts diagnostic tests into programs; it expands to a void expression.
- When it is executed, if expression (which shall have a scalar type) is false (that is,
- compares equal to 0), the assert macro writes information about the particular call that
- failed (including the text of the argument, the name of the source file, the source line
- number, and the name of the enclosing function -- the latter are respectively the values of
- the preprocessing macros __FILE__ and __LINE__ and of the identifier
- __func__) on the standard error stream in an implementation-defined format.189) It
- then calls the abort function.
-
-
-
- 189) The message written might be of the form:
- Assertion failed: expression, function abc, file xyz, line nnn.
-
-
-[<a name="#p184" href="p184">page 184</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The assert macro returns no value.
- Forward references: the abort function (<a href="#7.22.4.1">7.22.4.1</a>).
-
-
-
-
-[<a name="#p185" href="p185">page 185</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.3" href="#7.3"><b> 7.3 Complex arithmetic <complex.h></b></a>
-<a name="7.3.1" href="#7.3.1"><b> 7.3.1 Introduction</b></a>
-1 The header <a href="#7.3"><complex.h></a> defines macros and declares functions that support complex
- arithmetic.190)
-2 Implementations that define the macro __STDC_NO_COMPLEX__ need not provide
- this header nor support any of its facilities.
-3 Each synopsis specifies a family of functions consisting of a principal function with one
- or more double complex parameters and a double complex or double return
- value; and other functions with the same name but with f and l suffixes which are
- corresponding functions with float and long double parameters and return values.
-4 The macro
- complex
- expands to _Complex; the macro
- _Complex_I
- expands to a constant expression of type const float _Complex, with the value of
- the imaginary unit.191)
-5 The macros
- imaginary
- and
- _Imaginary_I
- are defined if and only if the implementation supports imaginary types;192) if defined,
- they expand to _Imaginary and a constant expression of type const float
- _Imaginary with the value of the imaginary unit.
-6 The macro
- I
- expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
- defined, I shall expand to _Complex_I.
-7 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
- redefine the macros complex, imaginary, and I.
-
- 190) See ''future library directions'' (<a href="#7.30.1">7.30.1</a>).
- 191) The imaginary unit is a number i such that i 2 = -1.
- 192) A specification for imaginary types is in informative <a href="#G">annex G</a>.
-
-[<a name="#p186" href="p186">page 186</a>] (<a href="#Contents">Contents</a>)
-
- Forward references: IEC 60559-compatible complex arithmetic (<a href="#G">annex G</a>).
-<a name="7.3.2" href="#7.3.2"><b> 7.3.2 Conventions</b></a>
-1 Values are interpreted as radians, not degrees. An implementation may set errno but is
- not required to.
-<a name="7.3.3" href="#7.3.3"><b> 7.3.3 Branch cuts</b></a>
-1 Some of the functions below have branch cuts, across which the function is
- discontinuous. For implementations with a signed zero (including all IEC 60559
- implementations) that follow the specifications of <a href="#G">annex G</a>, the sign of zero distinguishes
- one side of a cut from another so the function is continuous (except for format
- limitations) as the cut is approached from either side. For example, for the square root
- function, which has a branch cut along the negative real axis, the top of the cut, with
- imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with
- imaginary part -0, maps to the negative imaginary axis.
-2 Implementations that do not support a signed zero (see <a href="#F">annex F</a>) cannot distinguish the
- sides of branch cuts. These implementations shall map a cut so the function is continuous
- as the cut is approached coming around the finite endpoint of the cut in a counter
- clockwise direction. (Branch cuts for the functions specified here have just one finite
- endpoint.) For example, for the square root function, coming counter clockwise around
- the finite endpoint of the cut along the negative real axis approaches the cut from above,
- so the cut maps to the positive imaginary axis.
-<a name="7.3.4" href="#7.3.4"><b> 7.3.4 The CX_LIMITED_RANGE pragma</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- #pragma STDC CX_LIMITED_RANGE on-off-switch
- Description
-2 The usual mathematical formulas for complex multiply, divide, and absolute value are
- problematic because of their treatment of infinities and because of undue overflow and
- underflow. The CX_LIMITED_RANGE pragma can be used to inform the
- implementation that (where the state is ''on'') the usual mathematical formulas are
- acceptable.193) The pragma can occur either outside external declarations or preceding all
- explicit declarations and statements inside a compound statement. When outside external
- declarations, the pragma takes effect from its occurrence until another
- CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit.
- When inside a compound statement, the pragma takes effect from its occurrence until
- another CX_LIMITED_RANGE pragma is encountered (including within a nested
- compound statement), or until the end of the compound statement; at the end of a
- compound statement the state for the pragma is restored to its condition just before the
-
-[<a name="#p187" href="p187">page 187</a>] (<a href="#Contents">Contents</a>)
-
- compound statement. If this pragma is used in any other context, the behavior is
- undefined. The default state for the pragma is ''off''.
-<a name="7.3.5" href="#7.3.5"><b> 7.3.5 Trigonometric functions</b></a>
-<a name="7.3.5.1" href="#7.3.5.1"><b> 7.3.5.1 The cacos functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex cacos(double complex z);
- float complex cacosf(float complex z);
- long double complex cacosl(long double complex z);
- Description
-2 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
- interval [-1, +1] along the real axis.
- Returns
-3 The cacos functions return the complex arc cosine value, in the range of a strip
- mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
- real axis.
-<a name="7.3.5.2" href="#7.3.5.2"><b> 7.3.5.2 The casin functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex casin(double complex z);
- float complex casinf(float complex z);
- long double complex casinl(long double complex z);
- Description
-2 The casin functions compute the complex arc sine of z, with branch cuts outside the
- interval [-1, +1] along the real axis.
- Returns
-3 The casin functions return the complex arc sine value, in the range of a strip
- mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
-
- 193) The purpose of the pragma is to allow the implementation to use the formulas:
- (x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
- (x + iy) / (u + iv) = [(xu + yv) + i(yu - xv)]/(u2 + v 2 )
- | x + iy | = sqrt: x 2 + y 2
- -----
- where the programmer can determine they are safe.
-
-[<a name="#p188" href="p188">page 188</a>] (<a href="#Contents">Contents</a>)
-
- along the real axis.
-<a name="7.3.5.3" href="#7.3.5.3"><b> 7.3.5.3 The catan functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex catan(double complex z);
- float complex catanf(float complex z);
- long double complex catanl(long double complex z);
- Description
-2 The catan functions compute the complex arc tangent of z, with branch cuts outside the
- interval [-i, +i] along the imaginary axis.
- Returns
-3 The catan functions return the complex arc tangent value, in the range of a strip
- mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
- along the real axis.
-<a name="7.3.5.4" href="#7.3.5.4"><b> 7.3.5.4 The ccos functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex ccos(double complex z);
- float complex ccosf(float complex z);
- long double complex ccosl(long double complex z);
- Description
-2 The ccos functions compute the complex cosine of z.
- Returns
-3 The ccos functions return the complex cosine value.
-<a name="7.3.5.5" href="#7.3.5.5"><b> 7.3.5.5 The csin functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex csin(double complex z);
- float complex csinf(float complex z);
- long double complex csinl(long double complex z);
- Description
-2 The csin functions compute the complex sine of z.
-
-
-
-[<a name="#p189" href="p189">page 189</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The csin functions return the complex sine value.
-<a name="7.3.5.6" href="#7.3.5.6"><b> 7.3.5.6 The ctan functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex ctan(double complex z);
- float complex ctanf(float complex z);
- long double complex ctanl(long double complex z);
- Description
-2 The ctan functions compute the complex tangent of z.
- Returns
-3 The ctan functions return the complex tangent value.
-<a name="7.3.6" href="#7.3.6"><b> 7.3.6 Hyperbolic functions</b></a>
-<a name="7.3.6.1" href="#7.3.6.1"><b> 7.3.6.1 The cacosh functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex cacosh(double complex z);
- float complex cacoshf(float complex z);
- long double complex cacoshl(long double complex z);
- Description
-2 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch
- cut at values less than 1 along the real axis.
- Returns
-3 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
- half-strip of non-negative values along the real axis and in the interval [-ipi , +ipi ] along
- the imaginary axis.
-<a name="7.3.6.2" href="#7.3.6.2"><b> 7.3.6.2 The casinh functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex casinh(double complex z);
- float complex casinhf(float complex z);
- long double complex casinhl(long double complex z);
-
-
-
-[<a name="#p190" href="p190">page 190</a>] (<a href="#Contents">Contents</a>)
-
- Description
-2 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts
- outside the interval [-i, +i] along the imaginary axis.
- Returns
-3 The casinh functions return the complex arc hyperbolic sine value, in the range of a
- strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
- along the imaginary axis.
-<a name="7.3.6.3" href="#7.3.6.3"><b> 7.3.6.3 The catanh functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex catanh(double complex z);
- float complex catanhf(float complex z);
- long double complex catanhl(long double complex z);
- Description
-2 The catanh functions compute the complex arc hyperbolic tangent of z, with branch
- cuts outside the interval [-1, +1] along the real axis.
- Returns
-3 The catanh functions return the complex arc hyperbolic tangent value, in the range of a
- strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
- along the imaginary axis.
-<a name="7.3.6.4" href="#7.3.6.4"><b> 7.3.6.4 The ccosh functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex ccosh(double complex z);
- float complex ccoshf(float complex z);
- long double complex ccoshl(long double complex z);
- Description
-2 The ccosh functions compute the complex hyperbolic cosine of z.
- Returns
-3 The ccosh functions return the complex hyperbolic cosine value.
-
-
-
-
-[<a name="#p191" href="p191">page 191</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.3.6.5" href="#7.3.6.5"><b> 7.3.6.5 The csinh functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex csinh(double complex z);
- float complex csinhf(float complex z);
- long double complex csinhl(long double complex z);
- Description
-2 The csinh functions compute the complex hyperbolic sine of z.
- Returns
-3 The csinh functions return the complex hyperbolic sine value.
-<a name="7.3.6.6" href="#7.3.6.6"><b> 7.3.6.6 The ctanh functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex ctanh(double complex z);
- float complex ctanhf(float complex z);
- long double complex ctanhl(long double complex z);
- Description
-2 The ctanh functions compute the complex hyperbolic tangent of z.
- Returns
-3 The ctanh functions return the complex hyperbolic tangent value.
-<a name="7.3.7" href="#7.3.7"><b> 7.3.7 Exponential and logarithmic functions</b></a>
-<a name="7.3.7.1" href="#7.3.7.1"><b> 7.3.7.1 The cexp functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex cexp(double complex z);
- float complex cexpf(float complex z);
- long double complex cexpl(long double complex z);
- Description
-2 The cexp functions compute the complex base-e exponential of z.
- Returns
-3 The cexp functions return the complex base-e exponential value.
-
-
-
-[<a name="#p192" href="p192">page 192</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.3.7.2" href="#7.3.7.2"><b> 7.3.7.2 The clog functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex clog(double complex z);
- float complex clogf(float complex z);
- long double complex clogl(long double complex z);
- Description
-2 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
- cut along the negative real axis.
- Returns
-3 The clog functions return the complex natural logarithm value, in the range of a strip
- mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
- imaginary axis.
-<a name="7.3.8" href="#7.3.8"><b> 7.3.8 Power and absolute-value functions</b></a>
-<a name="7.3.8.1" href="#7.3.8.1"><b> 7.3.8.1 The cabs functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double cabs(double complex z);
- float cabsf(float complex z);
- long double cabsl(long double complex z);
- Description
-2 The cabs functions compute the complex absolute value (also called norm, modulus, or
- magnitude) of z.
- Returns
-3 The cabs functions return the complex absolute value.
-<a name="7.3.8.2" href="#7.3.8.2"><b> 7.3.8.2 The cpow functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex cpow(double complex x, double complex y);
- float complex cpowf(float complex x, float complex y);
- long double complex cpowl(long double complex x,
- long double complex y);
-
-
-
-
-[<a name="#p193" href="p193">page 193</a>] (<a href="#Contents">Contents</a>)
-
- Description
-2 The cpow functions compute the complex power function xy , with a branch cut for the
- first parameter along the negative real axis.
- Returns
-3 The cpow functions return the complex power function value.
-<a name="7.3.8.3" href="#7.3.8.3"><b> 7.3.8.3 The csqrt functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex csqrt(double complex z);
- float complex csqrtf(float complex z);
- long double complex csqrtl(long double complex z);
- Description
-2 The csqrt functions compute the complex square root of z, with a branch cut along the
- negative real axis.
- Returns
-3 The csqrt functions return the complex square root value, in the range of the right half-
- plane (including the imaginary axis).
-<a name="7.3.9" href="#7.3.9"><b> 7.3.9 Manipulation functions</b></a>
-<a name="7.3.9.1" href="#7.3.9.1"><b> 7.3.9.1 The carg functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double carg(double complex z);
- float cargf(float complex z);
- long double cargl(long double complex z);
- Description
-2 The carg functions compute the argument (also called phase angle) of z, with a branch
- cut along the negative real axis.
- Returns
-3 The carg functions return the value of the argument in the interval [-pi , +pi ].
-
-
-
-
-[<a name="#p194" href="p194">page 194</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.3.9.2" href="#7.3.9.2"><b> 7.3.9.2 The cimag functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double cimag(double complex z);
- float cimagf(float complex z);
- long double cimagl(long double complex z);
- Description
-2 The cimag functions compute the imaginary part of z.194)
- Returns
-3 The cimag functions return the imaginary part value (as a real).
-<a name="7.3.9.3" href="#7.3.9.3"><b> 7.3.9.3 The CMPLX macros</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex CMPLX(double x, double y);
- float complex CMPLXF(float x, float y);
- long double complex CMPLXL(long double x, long double y);
- Description
-2 The CMPLX macros expand to an expression of the specified complex type, with the real
- part having the (converted) value of x and the imaginary part having the (converted)
- value of y.
- Recommended practice
-3 The resulting expression should be suitable for use as an initializer for an object with
- static or thread storage duration, provided both arguments are likewise suitable.
- Returns
-4 The CMPLX macros return the complex value x + i y.
-5 NOTE These macros act as if the implementation supported imaginary types and the definitions were:
- #define CMPLX(x, y) ((double complex)((double)(x) + \
- _Imaginary_I * (double)(y)))
- #define CMPLXF(x, y) ((float complex)((float)(x) + \
- _Imaginary_I * (float)(y)))
- #define CMPLXL(x, y) ((long double complex)((long double)(x) + \
- _Imaginary_I * (long double)(y)))
-
-
-
-
- 194) For a variable z of complex type, z == creal(z) + cimag(z)*I.
-
-[<a name="#p195" href="p195">page 195</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.3.9.4" href="#7.3.9.4"><b> 7.3.9.4 The conj functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex conj(double complex z);
- float complex conjf(float complex z);
- long double complex conjl(long double complex z);
- Description
-2 The conj functions compute the complex conjugate of z, by reversing the sign of its
- imaginary part.
- Returns
-3 The conj functions return the complex conjugate value.
-<a name="7.3.9.5" href="#7.3.9.5"><b> 7.3.9.5 The cproj functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double complex cproj(double complex z);
- float complex cprojf(float complex z);
- long double complex cprojl(long double complex z);
- Description
-2 The cproj functions compute a projection of z onto the Riemann sphere: z projects to
- z except that all complex infinities (even those with one infinite part and one NaN part)
- project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is
- equivalent to
- INFINITY + I * copysign(0.0, cimag(z))
- Returns
-3 The cproj functions return the value of the projection onto the Riemann sphere.
-<a name="7.3.9.6" href="#7.3.9.6"><b> 7.3.9.6 The creal functions</b></a>
- Synopsis
-1 #include <a href="#7.3"><complex.h></a>
- double creal(double complex z);
- float crealf(float complex z);
- long double creall(long double complex z);
- Description
-2 The creal functions compute the real part of z.195)
-
-
-[<a name="#p196" href="p196">page 196</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The creal functions return the real part value.
-
-
-
-
- 195) For a variable z of complex type, z == creal(z) + cimag(z)*I.
-
-[<a name="#p197" href="p197">page 197</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.4" href="#7.4"><b> 7.4 Character handling <ctype.h></b></a>
-1 The header <a href="#7.4"><ctype.h></a> declares several functions useful for classifying and mapping
- characters.196) In all cases the argument is an int, the value of which shall be
- representable as an unsigned char or shall equal the value of the macro EOF. If the
- argument has any other value, the behavior is undefined.
-2 The behavior of these functions is affected by the current locale. Those functions that
- have locale-specific aspects only when not in the "C" locale are noted below.
-3 The term printing character refers to a member of a locale-specific set of characters, each
- of which occupies one printing position on a display device; the term control character
- refers to a member of a locale-specific set of characters that are not printing
- characters.197) All letters and digits are printing characters.
- Forward references: EOF (<a href="#7.21.1">7.21.1</a>), localization (<a href="#7.11">7.11</a>).
-<a name="7.4.1" href="#7.4.1"><b> 7.4.1 Character classification functions</b></a>
-1 The functions in this subclause return nonzero (true) if and only if the value of the
- argument c conforms to that in the description of the function.
-<a name="7.4.1.1" href="#7.4.1.1"><b> 7.4.1.1 The isalnum function</b></a>
- Synopsis
-1 #include <a href="#7.4"><ctype.h></a>
- int isalnum(int c);
- Description
-2 The isalnum function tests for any character for which isalpha or isdigit is true.
-<a name="7.4.1.2" href="#7.4.1.2"><b> 7.4.1.2 The isalpha function</b></a>
- Synopsis
-1 #include <a href="#7.4"><ctype.h></a>
- int isalpha(int c);
- Description
-2 The isalpha function tests for any character for which isupper or islower is true,
- or any character that is one of a locale-specific set of alphabetic characters for which
-
-
-
- 196) See ''future library directions'' (<a href="#7.30.2">7.30.2</a>).
- 197) In an implementation that uses the seven-bit US ASCII character set, the printing characters are those
- whose values lie from 0x20 (space) through 0x7E (tilde); the control characters are those whose
- values lie from 0 (NUL) through 0x1F (US), and the character 0x7F (DEL).
-
-[<a name="#p198" href="p198">page 198</a>] (<a href="#Contents">Contents</a>)
-
- none of iscntrl, isdigit, ispunct, or isspace is true.198) In the "C" locale,
- isalpha returns true only for the characters for which isupper or islower is true.
-<a name="7.4.1.3" href="#7.4.1.3"><b> 7.4.1.3 The isblank function</b></a>
- Synopsis
-1 #include <a href="#7.4"><ctype.h></a>
- int isblank(int c);
- Description
-2 The isblank function tests for any character that is a standard blank character or is one
- of a locale-specific set of characters for which isspace is true and that is used to
- separate words within a line of text. The standard blank characters are the following:
- space (' '), and horizontal tab ('\t'). In the "C" locale, isblank returns true only
- for the standard blank characters.
-<a name="7.4.1.4" href="#7.4.1.4"><b> 7.4.1.4 The iscntrl function</b></a>
- Synopsis
-1 #include <a href="#7.4"><ctype.h></a>
- int iscntrl(int c);
- Description
-2 The iscntrl function tests for any control character.
-<a name="7.4.1.5" href="#7.4.1.5"><b> 7.4.1.5 The isdigit function</b></a>
- Synopsis
-1 #include <a href="#7.4"><ctype.h></a>
- int isdigit(int c);
- Description
-2 The isdigit function tests for any decimal-digit character (as defined in <a href="#5.2.1">5.2.1</a>).
-<a name="7.4.1.6" href="#7.4.1.6"><b> 7.4.1.6 The isgraph function</b></a>
- Synopsis
-1 #include <a href="#7.4"><ctype.h></a>
- int isgraph(int c);
-
-
-
-
- 198) The functions islower and isupper test true or false separately for each of these additional
- characters; all four combinations are possible.
-
-[<a name="#p199" href="p199">page 199</a>] (<a href="#Contents">Contents</a>)
-
- Description
-2 The isgraph function tests for any printing character except space (' ').
-<a name="7.4.1.7" href="#7.4.1.7"><b> 7.4.1.7 The islower function</b></a>
- Synopsis
-1 #include <a href="#7.4"><ctype.h></a>
- int islower(int c);
- Description
-2 The islower function tests for any character that is a lowercase letter or is one of a
- locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
- isspace is true. In the "C" locale, islower returns true only for the lowercase
- letters (as defined in <a href="#5.2.1">5.2.1</a>).
-<a name="7.4.1.8" href="#7.4.1.8"><b> 7.4.1.8 The isprint function</b></a>
- Synopsis
-1 #include <a href="#7.4"><ctype.h></a>
- int isprint(int c);
- Description
-2 The isprint function tests for any printing character including space (' ').
-<a name="7.4.1.9" href="#7.4.1.9"><b> 7.4.1.9 The ispunct function</b></a>
- Synopsis
-1 #include <a href="#7.4"><ctype.h></a>
- int ispunct(int c);
- Description
-2 The ispunct function tests for any printing character that is one of a locale-specific set
- of punctuation characters for which neither isspace nor isalnum is true. In the "C"
- locale, ispunct returns true for every printing character for which neither isspace
- nor isalnum is true.
-<a name="7.4.1.10" href="#7.4.1.10"><b> 7.4.1.10 The isspace function</b></a>
- Synopsis
-1 #include <a href="#7.4"><ctype.h></a>
- int isspace(int c);
- Description
-2 The isspace function tests for any character that is a standard white-space character or
- is one of a locale-specific set of characters for which isalnum is false. The standard
-
-[<a name="#p200" href="p200">page 200</a>] (<a href="#Contents">Contents</a>)
-
- white-space characters are the following: space (' '), form feed ('\f'), new-line
- ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
- "C" locale, isspace returns true only for the standard white-space characters.
-<a name="7.4.1.11" href="#7.4.1.11"><b> 7.4.1.11 The isupper function</b></a>
- Synopsis
-1 #include <a href="#7.4"><ctype.h></a>
- int isupper(int c);
- Description
-2 The isupper function tests for any character that is an uppercase letter or is one of a
- locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
- isspace is true. In the "C" locale, isupper returns true only for the uppercase
- letters (as defined in <a href="#5.2.1">5.2.1</a>).
-<a name="7.4.1.12" href="#7.4.1.12"><b> 7.4.1.12 The isxdigit function</b></a>
- Synopsis
-1 #include <a href="#7.4"><ctype.h></a>
- int isxdigit(int c);
- Description
-2 The isxdigit function tests for any hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
-<a name="7.4.2" href="#7.4.2"><b> 7.4.2 Character case mapping functions</b></a>
-<a name="7.4.2.1" href="#7.4.2.1"><b> 7.4.2.1 The tolower function</b></a>
- Synopsis
-1 #include <a href="#7.4"><ctype.h></a>
- int tolower(int c);
- Description
-2 The tolower function converts an uppercase letter to a corresponding lowercase letter.
- Returns
-3 If the argument is a character for which isupper is true and there are one or more
- corresponding characters, as specified by the current locale, for which islower is true,
- the tolower function returns one of the corresponding characters (always the same one
- for any given locale); otherwise, the argument is returned unchanged.
-
-
-
-
-[<a name="#p201" href="p201">page 201</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.4.2.2" href="#7.4.2.2"><b> 7.4.2.2 The toupper function</b></a>
- Synopsis
-1 #include <a href="#7.4"><ctype.h></a>
- int toupper(int c);
- Description
-2 The toupper function converts a lowercase letter to a corresponding uppercase letter.
- Returns
-3 If the argument is a character for which islower is true and there are one or more
- corresponding characters, as specified by the current locale, for which isupper is true,
- the toupper function returns one of the corresponding characters (always the same one
- for any given locale); otherwise, the argument is returned unchanged.
-
-
-
-
-[<a name="#p202" href="p202">page 202</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.5" href="#7.5"><b> 7.5 Errors <errno.h></b></a>
-1 The header <a href="#7.5"><errno.h></a> defines several macros, all relating to the reporting of error
- conditions.
-2 The macros are
- EDOM
- EILSEQ
- ERANGE
- which expand to integer constant expressions with type int, distinct positive values, and
- which are suitable for use in #if preprocessing directives; and
- errno
- which expands to a modifiable lvalue199) that has type int and thread local storage
- duration, the value of which is set to a positive error number by several library functions.
- If a macro definition is suppressed in order to access an actual object, or a program
- defines an identifier with the name errno, the behavior is undefined.
-3 The value of errno in the initial thread is zero at program startup (the initial value of
- errno in other threads is an indeterminate value), but is never set to zero by any library
- function.200) The value of errno may be set to nonzero by a library function call
- whether or not there is an error, provided the use of errno is not documented in the
- description of the function in this International Standard.
-4 Additional macro definitions, beginning with E and a digit or E and an uppercase
- letter,201) may also be specified by the implementation.
-
-
-
-
- 199) The macro errno need not be the identifier of an object. It might expand to a modifiable lvalue
- resulting from a function call (for example, *errno()).
- 200) Thus, a program that uses errno for error checking should set it to zero before a library function call,
- then inspect it before a subsequent library function call. Of course, a library function can save the
- value of errno on entry and then set it to zero, as long as the original value is restored if errno's
- value is still zero just before the return.
- 201) See ''future library directions'' (<a href="#7.30.3">7.30.3</a>).
-
-[<a name="#p203" href="p203">page 203</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.6" href="#7.6"><b> 7.6 Floating-point environment <fenv.h></b></a>
-1 The header <a href="#7.6"><fenv.h></a> defines several macros, and declares types and functions that
- provide access to the floating-point environment. The floating-point environment refers
- collectively to any floating-point status flags and control modes supported by the
- implementation.202) A floating-point status flag is a system variable whose value is set
- (but never cleared) when a floating-point exception is raised, which occurs as a side effect
- of exceptional floating-point arithmetic to provide auxiliary information.203) A floating-
- point control mode is a system variable whose value may be set by the user to affect the
- subsequent behavior of floating-point arithmetic.
-2 The floating-point environment has thread storage duration. The initial state for a
- thread's floating-point environment is the current state of the floating-point environment
- of the thread that creates it at the time of creation.
-3 Certain programming conventions support the intended model of use for the floating-
- point environment:204)
- -- a function call does not alter its caller's floating-point control modes, clear its caller's
- floating-point status flags, nor depend on the state of its caller's floating-point status
- flags unless the function is so documented;
- -- a function call is assumed to require default floating-point control modes, unless its
- documentation promises otherwise;
- -- a function call is assumed to have the potential for raising floating-point exceptions,
- unless its documentation promises otherwise.
-4 The type
- fenv_t
- represents the entire floating-point environment.
-5 The type
- fexcept_t
- represents the floating-point status flags collectively, including any status the
- implementation associates with the flags.
-
-
- 202) This header is designed to support the floating-point exception status flags and directed-rounding
- control modes required by IEC 60559, and other similar floating-point state information. Also it is
- designed to facilitate code portability among all systems.
- 203) A floating-point status flag is not an object and can be set more than once within an expression.
- 204) With these conventions, a programmer can safely assume default floating-point control modes (or be
- unaware of them). The responsibilities associated with accessing the floating-point environment fall
- on the programmer or program that does so explicitly.
-
-[<a name="#p204" href="p204">page 204</a>] (<a href="#Contents">Contents</a>)
-
-6 Each of the macros
- FE_DIVBYZERO
- FE_INEXACT
- FE_INVALID
- FE_OVERFLOW
- FE_UNDERFLOW
- is defined if and only if the implementation supports the floating-point exception by
- means of the functions in 7.6.2.205) Additional implementation-defined floating-point
- exceptions, with macro definitions beginning with FE_ and an uppercase letter, may also
- be specified by the implementation. The defined macros expand to integer constant
- expressions with values such that bitwise ORs of all combinations of the macros result in
- distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
- zero.206)
-7 The macro
- FE_ALL_EXCEPT
- is simply the bitwise OR of all floating-point exception macros defined by the
- implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
-8 Each of the macros
- FE_DOWNWARD
- FE_TONEAREST
- FE_TOWARDZERO
- FE_UPWARD
- is defined if and only if the implementation supports getting and setting the represented
- rounding direction by means of the fegetround and fesetround functions.
- Additional implementation-defined rounding directions, with macro definitions beginning
- with FE_ and an uppercase letter, may also be specified by the implementation. The
- defined macros expand to integer constant expressions whose values are distinct
- nonnegative values.207)
-9 The macro
-
-
-
- 205) The implementation supports an exception if there are circumstances where a call to at least one of the
- functions in <a href="#7.6.2">7.6.2</a>, using the macro as the appropriate argument, will succeed. It is not necessary for
- all the functions to succeed all the time.
- 206) The macros should be distinct powers of two.
- 207) Even though the rounding direction macros may expand to constants corresponding to the values of
- FLT_ROUNDS, they are not required to do so.
-
-[<a name="#p205" href="p205">page 205</a>] (<a href="#Contents">Contents</a>)
-
- FE_DFL_ENV
- represents the default floating-point environment -- the one installed at program startup
- -- and has type ''pointer to const-qualified fenv_t''. It can be used as an argument to
- <a href="#7.6"><fenv.h></a> functions that manage the floating-point environment.
-10 Additional implementation-defined environments, with macro definitions beginning with
- FE_ and an uppercase letter, and having type ''pointer to const-qualified fenv_t'', may
- also be specified by the implementation.
-<a name="7.6.1" href="#7.6.1"><b> 7.6.1 The FENV_ACCESS pragma</b></a>
- Synopsis
-1 #include <a href="#7.6"><fenv.h></a>
- #pragma STDC FENV_ACCESS on-off-switch
- Description
-2 The FENV_ACCESS pragma provides a means to inform the implementation when a
- program might access the floating-point environment to test floating-point status flags or
- run under non-default floating-point control modes.208) The pragma shall occur either
- outside external declarations or preceding all explicit declarations and statements inside a
- compound statement. When outside external declarations, the pragma takes effect from
- its occurrence until another FENV_ACCESS pragma is encountered, or until the end of
- the translation unit. When inside a compound statement, the pragma takes effect from its
- occurrence until another FENV_ACCESS pragma is encountered (including within a
- nested compound statement), or until the end of the compound statement; at the end of a
- compound statement the state for the pragma is restored to its condition just before the
- compound statement. If this pragma is used in any other context, the behavior is
- undefined. If part of a program tests floating-point status flags, sets floating-point control
- modes, or runs under non-default mode settings, but was translated with the state for the
- FENV_ACCESS pragma ''off'', the behavior is undefined. The default state (''on'' or
- ''off'') for the pragma is implementation-defined. (When execution passes from a part of
- the program translated with FENV_ACCESS ''off'' to a part translated with
- FENV_ACCESS ''on'', the state of the floating-point status flags is unspecified and the
- floating-point control modes have their default settings.)
-
-
-
-
- 208) The purpose of the FENV_ACCESS pragma is to allow certain optimizations that could subvert flag
- tests and mode changes (e.g., global common subexpression elimination, code motion, and constant
- folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default
- modes are in effect and the flags are not tested.
-
-[<a name="#p206" href="p206">page 206</a>] (<a href="#Contents">Contents</a>)
-
-3 EXAMPLE
- #include <a href="#7.6"><fenv.h></a>
- void f(double x)
- {
- #pragma STDC FENV_ACCESS ON
- void g(double);
- void h(double);
- /* ... */
- g(x + 1);
- h(x + 1);
- /* ... */
- }
-4 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
- x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
- contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.209)
-
-<a name="7.6.2" href="#7.6.2"><b> 7.6.2 Floating-point exceptions</b></a>
-1 The following functions provide access to the floating-point status flags.210) The int
- input argument for the functions represents a subset of floating-point exceptions, and can
- be zero or the bitwise OR of one or more floating-point exception macros, for example
- FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
- functions is undefined.
-<a name="7.6.2.1" href="#7.6.2.1"><b> 7.6.2.1 The feclearexcept function</b></a>
- Synopsis
-1 #include <a href="#7.6"><fenv.h></a>
- int feclearexcept(int excepts);
- Description
-2 The feclearexcept function attempts to clear the supported floating-point exceptions
- represented by its argument.
- Returns
-3 The feclearexcept function returns zero if the excepts argument is zero or if all
- the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
-
-
- 209) The side effects impose a temporal ordering that requires two evaluations of x + 1. On the other
- hand, without the #pragma STDC FENV_ACCESS ON pragma, and assuming the default state is
- ''off'', just one evaluation of x + 1 would suffice.
- 210) The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
- abstraction of flags that are either set or clear. An implementation may endow floating-point status
- flags with more information -- for example, the address of the code which first raised the floating-
- point exception; the functions fegetexceptflag and fesetexceptflag deal with the full
- content of flags.
-
-[<a name="#p207" href="p207">page 207</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.6.2.2" href="#7.6.2.2"><b> 7.6.2.2 The fegetexceptflag function</b></a>
- Synopsis
-1 #include <a href="#7.6"><fenv.h></a>
- int fegetexceptflag(fexcept_t *flagp,
- int excepts);
- Description
-2 The fegetexceptflag function attempts to store an implementation-defined
- representation of the states of the floating-point status flags indicated by the argument
- excepts in the object pointed to by the argument flagp.
- Returns
-3 The fegetexceptflag function returns zero if the representation was successfully
- stored. Otherwise, it returns a nonzero value.
-<a name="7.6.2.3" href="#7.6.2.3"><b> 7.6.2.3 The feraiseexcept function</b></a>
- Synopsis
-1 #include <a href="#7.6"><fenv.h></a>
- int feraiseexcept(int excepts);
- Description
-2 The feraiseexcept function attempts to raise the supported floating-point exceptions
- represented by its argument.211) The order in which these floating-point exceptions are
- raised is unspecified, except as stated in <a href="#F.8.6">F.8.6</a>. Whether the feraiseexcept function
- additionally raises the ''inexact'' floating-point exception whenever it raises the
- ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
- Returns
-3 The feraiseexcept function returns zero if the excepts argument is zero or if all
- the specified exceptions were successfully raised. Otherwise, it returns a nonzero value.
-
-
-
-
- 211) The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations.
- Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
- in <a href="#F.8.6">F.8.6</a> is in the same spirit.
-
-[<a name="#p208" href="p208">page 208</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.6.2.4" href="#7.6.2.4"><b> 7.6.2.4 The fesetexceptflag function</b></a>
- Synopsis
-1 #include <a href="#7.6"><fenv.h></a>
- int fesetexceptflag(const fexcept_t *flagp,
- int excepts);
- Description
-2 The fesetexceptflag function attempts to set the floating-point status flags
- indicated by the argument excepts to the states stored in the object pointed to by
- flagp. The value of *flagp shall have been set by a previous call to
- fegetexceptflag whose second argument represented at least those floating-point
- exceptions represented by the argument excepts. This function does not raise floating-
- point exceptions, but only sets the state of the flags.
- Returns
-3 The fesetexceptflag function returns zero if the excepts argument is zero or if
- all the specified flags were successfully set to the appropriate state. Otherwise, it returns
- a nonzero value.
-<a name="7.6.2.5" href="#7.6.2.5"><b> 7.6.2.5 The fetestexcept function</b></a>
- Synopsis
-1 #include <a href="#7.6"><fenv.h></a>
- int fetestexcept(int excepts);
- Description
-2 The fetestexcept function determines which of a specified subset of the floating-
- point exception flags are currently set. The excepts argument specifies the floating-
- point status flags to be queried.212)
- Returns
-3 The fetestexcept function returns the value of the bitwise OR of the floating-point
- exception macros corresponding to the currently set floating-point exceptions included in
- excepts.
-4 EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set:
-
-
-
-
- 212) This mechanism allows testing several floating-point exceptions with just one function call.
-
-[<a name="#p209" href="p209">page 209</a>] (<a href="#Contents">Contents</a>)
-
- #include <a href="#7.6"><fenv.h></a>
- /* ... */
- {
- #pragma STDC FENV_ACCESS ON
- int set_excepts;
- feclearexcept(FE_INVALID | FE_OVERFLOW);
- // maybe raise exceptions
- set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
- if (set_excepts & FE_INVALID) f();
- if (set_excepts & FE_OVERFLOW) g();
- /* ... */
- }
-
-<a name="7.6.3" href="#7.6.3"><b> 7.6.3 Rounding</b></a>
-1 The fegetround and fesetround functions provide control of rounding direction
- modes.
-<a name="7.6.3.1" href="#7.6.3.1"><b> 7.6.3.1 The fegetround function</b></a>
- Synopsis
-1 #include <a href="#7.6"><fenv.h></a>
- int fegetround(void);
- Description
-2 The fegetround function gets the current rounding direction.
- Returns
-3 The fegetround function returns the value of the rounding direction macro
- representing the current rounding direction or a negative value if there is no such
- rounding direction macro or the current rounding direction is not determinable.
-<a name="7.6.3.2" href="#7.6.3.2"><b> 7.6.3.2 The fesetround function</b></a>
- Synopsis
-1 #include <a href="#7.6"><fenv.h></a>
- int fesetround(int round);
- Description
-2 The fesetround function establishes the rounding direction represented by its
- argument round. If the argument is not equal to the value of a rounding direction macro,
- the rounding direction is not changed.
- Returns
-3 The fesetround function returns zero if and only if the requested rounding direction
- was established.
-
-
-[<a name="#p210" href="p210">page 210</a>] (<a href="#Contents">Contents</a>)
-
-4 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the
- rounding direction fails.
- #include <a href="#7.6"><fenv.h></a>
- #include <a href="#7.2"><assert.h></a>
- void f(int round_dir)
- {
- #pragma STDC FENV_ACCESS ON
- int save_round;
- int setround_ok;
- save_round = fegetround();
- setround_ok = fesetround(round_dir);
- assert(setround_ok == 0);
- /* ... */
- fesetround(save_round);
- /* ... */
- }
-
-<a name="7.6.4" href="#7.6.4"><b> 7.6.4 Environment</b></a>
-1 The functions in this section manage the floating-point environment -- status flags and
- control modes -- as one entity.
-<a name="7.6.4.1" href="#7.6.4.1"><b> 7.6.4.1 The fegetenv function</b></a>
- Synopsis
-1 #include <a href="#7.6"><fenv.h></a>
- int fegetenv(fenv_t *envp);
- Description
-2 The fegetenv function attempts to store the current floating-point environment in the
- object pointed to by envp.
- Returns
-3 The fegetenv function returns zero if the environment was successfully stored.
- Otherwise, it returns a nonzero value.
-<a name="7.6.4.2" href="#7.6.4.2"><b> 7.6.4.2 The feholdexcept function</b></a>
- Synopsis
-1 #include <a href="#7.6"><fenv.h></a>
- int feholdexcept(fenv_t *envp);
- Description
-2 The feholdexcept function saves the current floating-point environment in the object
- pointed to by envp, clears the floating-point status flags, and then installs a non-stop
- (continue on floating-point exceptions) mode, if available, for all floating-point
- exceptions.213)
-
-[<a name="#p211" href="p211">page 211</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The feholdexcept function returns zero if and only if non-stop floating-point
- exception handling was successfully installed.
-<a name="7.6.4.3" href="#7.6.4.3"><b> 7.6.4.3 The fesetenv function</b></a>
- Synopsis
-1 #include <a href="#7.6"><fenv.h></a>
- int fesetenv(const fenv_t *envp);
- Description
-2 The fesetenv function attempts to establish the floating-point environment represented
- by the object pointed to by envp. The argument envp shall point to an object set by a
- call to fegetenv or feholdexcept, or equal a floating-point environment macro.
- Note that fesetenv merely installs the state of the floating-point status flags
- represented through its argument, and does not raise these floating-point exceptions.
- Returns
-3 The fesetenv function returns zero if the environment was successfully established.
- Otherwise, it returns a nonzero value.
-<a name="7.6.4.4" href="#7.6.4.4"><b> 7.6.4.4 The feupdateenv function</b></a>
- Synopsis
-1 #include <a href="#7.6"><fenv.h></a>
- int feupdateenv(const fenv_t *envp);
- Description
-2 The feupdateenv function attempts to save the currently raised floating-point
- exceptions in its automatic storage, install the floating-point environment represented by
- the object pointed to by envp, and then raise the saved floating-point exceptions. The
- argument envp shall point to an object set by a call to feholdexcept or fegetenv,
- or equal a floating-point environment macro.
- Returns
-3 The feupdateenv function returns zero if all the actions were successfully carried out.
- Otherwise, it returns a nonzero value.
-
-
-
-
- 213) IEC 60559 systems have a default non-stop mode, and typically at least one other mode for trap
- handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For
- such systems, the feholdexcept function can be used in conjunction with the feupdateenv
- function to write routines that hide spurious floating-point exceptions from their callers.
-
-[<a name="#p212" href="p212">page 212</a>] (<a href="#Contents">Contents</a>)
-
-4 EXAMPLE Hide spurious underflow floating-point exceptions:
- #include <a href="#7.6"><fenv.h></a>
- double f(double x)
- {
- #pragma STDC FENV_ACCESS ON
- double result;
- fenv_t save_env;
- if (feholdexcept(&save_env))
- return /* indication of an environmental problem */;
- // compute result
- if (/* test spurious underflow */)
- if (feclearexcept(FE_UNDERFLOW))
- return /* indication of an environmental problem */;
- if (feupdateenv(&save_env))
- return /* indication of an environmental problem */;
- return result;
- }
-
-
-
-
-[<a name="#p213" href="p213">page 213</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.7" href="#7.7"><b> 7.7 Characteristics of floating types <float.h></b></a>
-1 The header <a href="#7.7"><float.h></a> defines several macros that expand to various limits and
- parameters of the standard floating-point types.
-2 The macros, their meanings, and the constraints (or restrictions) on their values are listed
- in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
-
-
-
-
-[<a name="#p214" href="p214">page 214</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.8" href="#7.8"><b> 7.8 Format conversion of integer types <inttypes.h></b></a>
-1 The header <a href="#7.8"><inttypes.h></a> includes the header <a href="#7.20"><stdint.h></a> and extends it with
- additional facilities provided by hosted implementations.
-2 It declares functions for manipulating greatest-width integers and converting numeric
- character strings to greatest-width integers, and it declares the type
- imaxdiv_t
- which is a structure type that is the type of the value returned by the imaxdiv function.
- For each type declared in <a href="#7.20"><stdint.h></a>, it defines corresponding macros for conversion
- specifiers for use with the formatted input/output functions.214)
- Forward references: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>), formatted input/output
- functions (<a href="#7.21.6">7.21.6</a>), formatted wide character input/output functions (<a href="#7.28.2">7.28.2</a>).
-<a name="7.8.1" href="#7.8.1"><b> 7.8.1 Macros for format specifiers</b></a>
-1 Each of the following object-like macros expands to a character string literal containing a
- conversion specifier, possibly modified by a length modifier, suitable for use within the
- format argument of a formatted input/output function when converting the corresponding
- integer type. These macro names have the general form of PRI (character string literals
- for the fprintf and fwprintf family) or SCN (character string literals for the
- fscanf and fwscanf family),215) followed by the conversion specifier, followed by a
- name corresponding to a similar type name in <a href="#7.20.1">7.20.1</a>. In these names, N represents the
- width of the type as described in <a href="#7.20.1">7.20.1</a>. For example, PRIdFAST32 can be used in a
- format string to print the value of an integer of type int_fast32_t.
-2 The fprintf macros for signed integers are:
- PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
- PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
-3 The fprintf macros for unsigned integers are:
- PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
- PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
- PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
- PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
-4 The fscanf macros for signed integers are:
-
-
-
- 214) See ''future library directions'' (<a href="#7.30.4">7.30.4</a>).
- 215) Separate macros are given for use with fprintf and fscanf functions because, in the general case,
- different format specifiers may be required for fprintf and fscanf, even when the type is the
- same.
-
-[<a name="#p215" href="p215">page 215</a>] (<a href="#Contents">Contents</a>)
-
- SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
- SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
-5 The fscanf macros for unsigned integers are:
- SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
- SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
- SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
-6 For each type that the implementation provides in <a href="#7.20"><stdint.h></a>, the corresponding
- fprintf macros shall be defined and the corresponding fscanf macros shall be
- defined unless the implementation does not have a suitable fscanf length modifier for
- the type.
-7 EXAMPLE
- #include <a href="#7.8"><inttypes.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int main(void)
- {
- uintmax_t i = UINTMAX_MAX; // this type always exists
- wprintf(L"The largest integer value is %020"
- PRIxMAX "\n", i);
- return 0;
- }
-
-<a name="7.8.2" href="#7.8.2"><b> 7.8.2 Functions for greatest-width integer types</b></a>
-<a name="7.8.2.1" href="#7.8.2.1"><b> 7.8.2.1 The imaxabs function</b></a>
- Synopsis
-1 #include <a href="#7.8"><inttypes.h></a>
- intmax_t imaxabs(intmax_t j);
- Description
-2 The imaxabs function computes the absolute value of an integer j. If the result cannot
- be represented, the behavior is undefined.216)
- Returns
-3 The imaxabs function returns the absolute value.
-
-
-
-
- 216) The absolute value of the most negative number cannot be represented in two's complement.
-
-[<a name="#p216" href="p216">page 216</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.8.2.2" href="#7.8.2.2"><b> 7.8.2.2 The imaxdiv function</b></a>
- Synopsis
-1 #include <a href="#7.8"><inttypes.h></a>
- imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
- Description
-2 The imaxdiv function computes numer / denom and numer % denom in a single
- operation.
- Returns
-3 The imaxdiv function returns a structure of type imaxdiv_t comprising both the
- quotient and the remainder. The structure shall contain (in either order) the members
- quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
- either part of the result cannot be represented, the behavior is undefined.
-<a name="7.8.2.3" href="#7.8.2.3"><b> 7.8.2.3 The strtoimax and strtoumax functions</b></a>
- Synopsis
-1 #include <a href="#7.8"><inttypes.h></a>
- intmax_t strtoimax(const char * restrict nptr,
- char ** restrict endptr, int base);
- uintmax_t strtoumax(const char * restrict nptr,
- char ** restrict endptr, int base);
- Description
-2 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll,
- strtoul, and strtoull functions, except that the initial portion of the string is
- converted to intmax_t and uintmax_t representation, respectively.
- Returns
-3 The strtoimax and strtoumax functions return the converted value, if any. If no
- conversion could be performed, zero is returned. If the correct value is outside the range
- of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned
- (according to the return type and sign of the value, if any), and the value of the macro
- ERANGE is stored in errno.
- Forward references: the strtol, strtoll, strtoul, and strtoull functions
- (<a href="#7.22.1.4">7.22.1.4</a>).
-
-
-
-
-[<a name="#p217" href="p217">page 217</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.8.2.4" href="#7.8.2.4"><b> 7.8.2.4 The wcstoimax and wcstoumax functions</b></a>
- Synopsis
-1 #include <a href="#7.19"><stddef.h></a> // for wchar_t
- #include <a href="#7.8"><inttypes.h></a>
- intmax_t wcstoimax(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
- uintmax_t wcstoumax(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
- Description
-2 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll,
- wcstoul, and wcstoull functions except that the initial portion of the wide string is
- converted to intmax_t and uintmax_t representation, respectively.
- Returns
-3 The wcstoimax function returns the converted value, if any. If no conversion could be
- performed, zero is returned. If the correct value is outside the range of representable
- values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the
- return type and sign of the value, if any), and the value of the macro ERANGE is stored in
- errno.
- Forward references: the wcstol, wcstoll, wcstoul, and wcstoull functions
- (<a href="#7.28.4.1.2">7.28.4.1.2</a>).
-
-
-
-
-[<a name="#p218" href="p218">page 218</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.9" href="#7.9"><b> 7.9 Alternative spellings <iso646.h></b></a>
-1 The header <a href="#7.9"><iso646.h></a> defines the following eleven macros (on the left) that expand
- to the corresponding tokens (on the right):
- and &&
- and_eq &=
- bitand &
- bitor |
- compl ~
- not !
- not_eq !=
- or ||
- or_eq |=
- xor ^
- xor_eq ^=
-
-
-
-
-[<a name="#p219" href="p219">page 219</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.10" href="#7.10"><b> 7.10 Sizes of integer types <limits.h></b></a>
-1 The header <a href="#7.10"><limits.h></a> defines several macros that expand to various limits and
- parameters of the standard integer types.
-2 The macros, their meanings, and the constraints (or restrictions) on their values are listed
- in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
-
-
-
-
-[<a name="#p220" href="p220">page 220</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.11" href="#7.11"><b> 7.11 Localization <locale.h></b></a>
-1 The header <a href="#7.11"><locale.h></a> declares two functions, one type, and defines several macros.
-2 The type is
- struct lconv
- which contains members related to the formatting of numeric values. The structure shall
- contain at least the following members, in any order. The semantics of the members and
- their normal ranges are explained in <a href="#7.11.2.1">7.11.2.1</a>. In the "C" locale, the members shall have
- the values specified in the comments.
- char *decimal_point; // "."
- char *thousands_sep; // ""
- char *grouping; // ""
- char *mon_decimal_point; // ""
- char *mon_thousands_sep; // ""
- char *mon_grouping; // ""
- char *positive_sign; // ""
- char *negative_sign; // ""
- char *currency_symbol; // ""
- char frac_digits; // CHAR_MAX
- char p_cs_precedes; // CHAR_MAX
- char n_cs_precedes; // CHAR_MAX
- char p_sep_by_space; // CHAR_MAX
- char n_sep_by_space; // CHAR_MAX
- char p_sign_posn; // CHAR_MAX
- char n_sign_posn; // CHAR_MAX
- char *int_curr_symbol; // ""
- char int_frac_digits; // CHAR_MAX
- char int_p_cs_precedes; // CHAR_MAX
- char int_n_cs_precedes; // CHAR_MAX
- char int_p_sep_by_space; // CHAR_MAX
- char int_n_sep_by_space; // CHAR_MAX
- char int_p_sign_posn; // CHAR_MAX
- char int_n_sign_posn; // CHAR_MAX
-
-
-
-
-[<a name="#p221" href="p221">page 221</a>] (<a href="#Contents">Contents</a>)
-
-3 The macros defined are NULL (described in <a href="#7.19">7.19</a>); and
- LC_ALL
- LC_COLLATE
- LC_CTYPE
- LC_MONETARY
- LC_NUMERIC
- LC_TIME
- which expand to integer constant expressions with distinct values, suitable for use as the
- first argument to the setlocale function.217) Additional macro definitions, beginning
- with the characters LC_ and an uppercase letter,218) may also be specified by the
- implementation.
-<a name="7.11.1" href="#7.11.1"><b> 7.11.1 Locale control</b></a>
-<a name="7.11.1.1" href="#7.11.1.1"><b> 7.11.1.1 The setlocale function</b></a>
- Synopsis
-1 #include <a href="#7.11"><locale.h></a>
- char *setlocale(int category, const char *locale);
- Description
-2 The setlocale function selects the appropriate portion of the program's locale as
- specified by the category and locale arguments. The setlocale function may be
- used to change or query the program's entire current locale or portions thereof. The value
- LC_ALL for category names the program's entire locale; the other values for
- category name only a portion of the program's locale. LC_COLLATE affects the
- behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of
- the character handling functions219) and the multibyte and wide character functions.
- LC_MONETARY affects the monetary formatting information returned by the
- localeconv function. LC_NUMERIC affects the decimal-point character for the
- formatted input/output functions and the string conversion functions, as well as the
- nonmonetary formatting information returned by the localeconv function. LC_TIME
- affects the behavior of the strftime and wcsftime functions.
-3 A value of "C" for locale specifies the minimal environment for C translation; a value
- of "" for locale specifies the locale-specific native environment. Other
- implementation-defined strings may be passed as the second argument to setlocale.
-
- 217) ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.
- 218) See ''future library directions'' (<a href="#7.30.5">7.30.5</a>).
- 219) The only functions in <a href="#7.4">7.4</a> whose behavior is not affected by the current locale are isdigit and
- isxdigit.
-
-[<a name="#p222" href="p222">page 222</a>] (<a href="#Contents">Contents</a>)
-
-4 At program startup, the equivalent of
- setlocale(LC_ALL, "C");
- is executed.
-5 A call to the setlocale function may introduce a data race with other calls to the
- setlocale function or with calls to functions that are affected by the current locale.
- The implementation shall behave as if no library function calls the setlocale function.
- Returns
-6 If a pointer to a string is given for locale and the selection can be honored, the
- setlocale function returns a pointer to the string associated with the specified
- category for the new locale. If the selection cannot be honored, the setlocale
- function returns a null pointer and the program's locale is not changed.
-7 A null pointer for locale causes the setlocale function to return a pointer to the
- string associated with the category for the program's current locale; the program's
- locale is not changed.220)
-8 The pointer to string returned by the setlocale function is such that a subsequent call
- with that string value and its associated category will restore that part of the program's
- locale. The string pointed to shall not be modified by the program, but may be
- overwritten by a subsequent call to the setlocale function.
- Forward references: formatted input/output functions (<a href="#7.21.6">7.21.6</a>), multibyte/wide
- character conversion functions (<a href="#7.22.7">7.22.7</a>), multibyte/wide string conversion functions
- (<a href="#7.22.8">7.22.8</a>), numeric conversion functions (<a href="#7.22.1">7.22.1</a>), the strcoll function (<a href="#7.23.4.3">7.23.4.3</a>), the
- strftime function (<a href="#7.26.3.5">7.26.3.5</a>), the strxfrm function (<a href="#7.23.4.5">7.23.4.5</a>).
-<a name="7.11.2" href="#7.11.2"><b> 7.11.2 Numeric formatting convention inquiry</b></a>
-<a name="7.11.2.1" href="#7.11.2.1"><b> 7.11.2.1 The localeconv function</b></a>
- Synopsis
-1 #include <a href="#7.11"><locale.h></a>
- struct lconv *localeconv(void);
- Description
-2 The localeconv function sets the components of an object with type struct lconv
- with values appropriate for the formatting of numeric quantities (monetary and otherwise)
- according to the rules of the current locale.
-
-
-
- 220) The implementation shall arrange to encode in a string the various categories due to a heterogeneous
- locale when category has the value LC_ALL.
-
-[<a name="#p223" href="p223">page 223</a>] (<a href="#Contents">Contents</a>)
-
-3 The members of the structure with type char * are pointers to strings, any of which
- (except decimal_point) can point to "", to indicate that the value is not available in
- the current locale or is of zero length. Apart from grouping and mon_grouping, the
- strings shall start and end in the initial shift state. The members with type char are
- nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not
- available in the current locale. The members include the following:
- char *decimal_point
- The decimal-point character used to format nonmonetary quantities.
- char *thousands_sep
- The character used to separate groups of digits before the decimal-point
- character in formatted nonmonetary quantities.
- char *grouping
- A string whose elements indicate the size of each group of digits in
- formatted nonmonetary quantities.
- char *mon_decimal_point
- The decimal-point used to format monetary quantities.
- char *mon_thousands_sep
- The separator for groups of digits before the decimal-point in formatted
- monetary quantities.
- char *mon_grouping
- A string whose elements indicate the size of each group of digits in
- formatted monetary quantities.
- char *positive_sign
- The string used to indicate a nonnegative-valued formatted monetary
- quantity.
- char *negative_sign
- The string used to indicate a negative-valued formatted monetary quantity.
- char *currency_symbol
- The local currency symbol applicable to the current locale.
- char frac_digits
- The number of fractional digits (those after the decimal-point) to be
- displayed in a locally formatted monetary quantity.
- char p_cs_precedes
- Set to 1 or 0 if the currency_symbol respectively precedes or
- succeeds the value for a nonnegative locally formatted monetary quantity.
-
-
-
-[<a name="#p224" href="p224">page 224</a>] (<a href="#Contents">Contents</a>)
-
-char n_cs_precedes
- Set to 1 or 0 if the currency_symbol respectively precedes or
- succeeds the value for a negative locally formatted monetary quantity.
-char p_sep_by_space
- Set to a value indicating the separation of the currency_symbol, the
- sign string, and the value for a nonnegative locally formatted monetary
- quantity.
-char n_sep_by_space
- Set to a value indicating the separation of the currency_symbol, the
- sign string, and the value for a negative locally formatted monetary
- quantity.
-char p_sign_posn
- Set to a value indicating the positioning of the positive_sign for a
- nonnegative locally formatted monetary quantity.
-char n_sign_posn
- Set to a value indicating the positioning of the negative_sign for a
- negative locally formatted monetary quantity.
-char *int_curr_symbol
- The international currency symbol applicable to the current locale. The
- first three characters contain the alphabetic international currency symbol
- in accordance with those specified in ISO 4217. The fourth character
- (immediately preceding the null character) is the character used to separate
- the international currency symbol from the monetary quantity.
-char int_frac_digits
- The number of fractional digits (those after the decimal-point) to be
- displayed in an internationally formatted monetary quantity.
-char int_p_cs_precedes
- Set to 1 or 0 if the int_curr_symbol respectively precedes or
- succeeds the value for a nonnegative internationally formatted monetary
- quantity.
-char int_n_cs_precedes
- Set to 1 or 0 if the int_curr_symbol respectively precedes or
- succeeds the value for a negative internationally formatted monetary
- quantity.
-char int_p_sep_by_space
- Set to a value indicating the separation of the int_curr_symbol, the
- sign string, and the value for a nonnegative internationally formatted
- monetary quantity.
-[<a name="#p225" href="p225">page 225</a>] (<a href="#Contents">Contents</a>)
-
- char int_n_sep_by_space
- Set to a value indicating the separation of the int_curr_symbol, the
- sign string, and the value for a negative internationally formatted monetary
- quantity.
- char int_p_sign_posn
- Set to a value indicating the positioning of the positive_sign for a
- nonnegative internationally formatted monetary quantity.
- char int_n_sign_posn
- Set to a value indicating the positioning of the negative_sign for a
- negative internationally formatted monetary quantity.
-4 The elements of grouping and mon_grouping are interpreted according to the
- following:
- CHAR_MAX No further grouping is to be performed.
- 0 The previous element is to be repeatedly used for the remainder of the
- digits.
- other The integer value is the number of digits that compose the current group.
- The next element is examined to determine the size of the next group of
- digits before the current group.
-5 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space,
- and int_n_sep_by_space are interpreted according to the following:
- 0 No space separates the currency symbol and value.
- 1 If the currency symbol and sign string are adjacent, a space separates them from the
- value; otherwise, a space separates the currency symbol from the value.
- 2 If the currency symbol and sign string are adjacent, a space separates them;
- otherwise, a space separates the sign string from the value.
- For int_p_sep_by_space and int_n_sep_by_space, the fourth character of
- int_curr_symbol is used instead of a space.
-6 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and
- int_n_sign_posn are interpreted according to the following:
- 0 Parentheses surround the quantity and currency symbol.
- 1 The sign string precedes the quantity and currency symbol.
- 2 The sign string succeeds the quantity and currency symbol.
- 3 The sign string immediately precedes the currency symbol.
- 4 The sign string immediately succeeds the currency symbol.
-
-
-[<a name="#p226" href="p226">page 226</a>] (<a href="#Contents">Contents</a>)
-
-7 The implementation shall behave as if no library function calls the localeconv
- function.
- Returns
-8 The localeconv function returns a pointer to the filled-in object. The structure
- pointed to by the return value shall not be modified by the program, but may be
- overwritten by a subsequent call to the localeconv function. In addition, calls to the
- setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may
- overwrite the contents of the structure.
-9 EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format
- monetary quantities.
- Local format International format
-
- Country Positive Negative Positive Negative
-
- Country1 1.234,56 mk -1.234,56 mk FIM 1.234,56 FIM -1.234,56
- Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234
- Country3 fl. 1.234,56 fl. -1.234,56 NLG 1.234,56 NLG -1.234,56
- Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C
-10 For these four countries, the respective values for the monetary members of the structure returned by
- localeconv could be:
- Country1 Country2 Country3 Country4
-
- mon_decimal_point "," "" "," "."
- mon_thousands_sep "." "." "." ","
- mon_grouping "\3" "\3" "\3" "\3"
- positive_sign "" "" "" ""
- negative_sign "-" "-" "-" "C"
- currency_symbol "mk" "L." "\u0192" "SFrs."
- frac_digits 2 0 2 2
- p_cs_precedes 0 1 1 1
- n_cs_precedes 0 1 1 1
- p_sep_by_space 1 0 1 0
- n_sep_by_space 1 0 2 0
- p_sign_posn 1 1 1 1
- n_sign_posn 1 1 4 2
- int_curr_symbol "FIM " "ITL " "NLG " "CHF "
- int_frac_digits 2 0 2 2
- int_p_cs_precedes 1 1 1 1
- int_n_cs_precedes 1 1 1 1
- int_p_sep_by_space 1 1 1 1
- int_n_sep_by_space 2 1 2 1
- int_p_sign_posn 1 1 1 1
- int_n_sign_posn 4 1 4 2
-
-
-
-
-[<a name="#p227" href="p227">page 227</a>] (<a href="#Contents">Contents</a>)
-
-11 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
- affect the formatted value.
- p_sep_by_space
-
- p_cs_precedes p_sign_posn 0 1 2
-
- 0 0 (<a href="#1.25">1.25</a>$) (<a href="#1.25">1.25</a> $) (<a href="#1.25">1.25</a>$)
- 1 +1.25$ +1.25 $ + <a href="#1.25">1.25</a>$
- 2 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +
- 3 <a href="#1.25">1.25</a>+$ <a href="#1.25">1.25</a> +$ <a href="#1.25">1.25</a>+ $
- 4 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +
-
- 1 0 ($1.25) ($ <a href="#1.25">1.25</a>) ($1.25)
- 1 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
- 2 $1.25+ $ <a href="#1.25">1.25</a>+ $1.25 +
- 3 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
- 4 $+1.25 $+ <a href="#1.25">1.25</a> $ +1.25
-
-
-
-
-[<a name="#p228" href="p228">page 228</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.12" href="#7.12"><b> 7.12 Mathematics <math.h></b></a>
-1 The header <a href="#7.12"><math.h></a> declares two types and many mathematical functions and defines
- several macros. Most synopses specify a family of functions consisting of a principal
- function with one or more double parameters, a double return value, or both; and
- other functions with the same name but with f and l suffixes, which are corresponding
- functions with float and long double parameters, return values, or both.221)
- Integer arithmetic functions and conversion functions are discussed later.
-2 The types
- float_t
- double_t
- are floating types at least as wide as float and double, respectively, and such that
- double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
- float_t and double_t are float and double, respectively; if
- FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
- 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
- otherwise implementation-defined.222)
-3 The macro
- HUGE_VAL
- expands to a positive double constant expression, not necessarily representable as a
- float. The macros
- HUGE_VALF
- HUGE_VALL
- are respectively float and long double analogs of HUGE_VAL.223)
-4 The macro
- INFINITY
- expands to a constant expression of type float representing positive or unsigned
- infinity, if available; else to a positive constant of type float that overflows at
-
-
-
- 221) Particularly on systems with wide expression evaluation, a <a href="#7.12"><math.h></a> function might pass arguments
- and return values in wider format than the synopsis prototype indicates.
- 222) The types float_t and double_t are intended to be the implementation's most efficient types at
- least as wide as float and double, respectively. For FLT_EVAL_METHOD equal 0, 1, or 2, the
- type float_t is the narrowest type used by the implementation to evaluate floating expressions.
- 223) HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
- supports infinities.
-
-[<a name="#p229" href="p229">page 229</a>] (<a href="#Contents">Contents</a>)
-
- translation time.224)
-5 The macro
- NAN
- is defined if and only if the implementation supports quiet NaNs for the float type. It
- expands to a constant expression of type float representing a quiet NaN.
-6 The number classification macros
- FP_INFINITE
- FP_NAN
- FP_NORMAL
- FP_SUBNORMAL
- FP_ZERO
- represent the mutually exclusive kinds of floating-point values. They expand to integer
- constant expressions with distinct values. Additional implementation-defined floating-
- point classifications, with macro definitions beginning with FP_ and an uppercase letter,
- may also be specified by the implementation.
-7 The macro
- FP_FAST_FMA
- is optionally defined. If defined, it indicates that the fma function generally executes
- about as fast as, or faster than, a multiply and an add of double operands.225) The
- macros
- FP_FAST_FMAF
- FP_FAST_FMAL
- are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
- these macros expand to the integer constant 1.
-8 The macros
- FP_ILOGB0
- FP_ILOGBNAN
- expand to integer constant expressions whose values are returned by ilogb(x) if x is
- zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
- -INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
-
-
- 224) In this case, using INFINITY will violate the constraint in <a href="#6.4.4">6.4.4</a> and thus require a diagnostic.
- 225) Typically, the FP_FAST_FMA macro is defined if and only if the fma function is implemented
- directly with a hardware multiply-add instruction. Software implementations are expected to be
- substantially slower.
-
-[<a name="#p230" href="p230">page 230</a>] (<a href="#Contents">Contents</a>)
-
-9 The macros
- MATH_ERRNO
- MATH_ERREXCEPT
- expand to the integer constants 1 and 2, respectively; the macro
- math_errhandling
- expands to an expression that has type int and the value MATH_ERRNO,
- MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is
- constant for the duration of the program. It is unspecified whether
- math_errhandling is a macro or an identifier with external linkage. If a macro
- definition is suppressed or a program defines an identifier with the name
- math_errhandling, the behavior is undefined. If the expression
- math_errhandling & MATH_ERREXCEPT can be nonzero, the implementation
- shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in
- <a href="#7.6"><fenv.h></a>.
-<a name="7.12.1" href="#7.12.1"><b> 7.12.1 Treatment of error conditions</b></a>
-1 The behavior of each of the functions in <a href="#7.12"><math.h></a> is specified for all representable
- values of its input arguments, except where stated otherwise. Each function shall execute
- as if it were a single operation without raising SIGFPE and without generating any of the
- exceptions ''invalid'', ''divide-by-zero'', or ''overflow'' except to reflect the result of the
- function.
-2 For all functions, a domain error occurs if an input argument is outside the domain over
- which the mathematical function is defined. The description of each function lists any
- required domain errors; an implementation may define additional domain errors, provided
- that such errors are consistent with the mathematical definition of the function.226) On a
- domain error, the function returns an implementation-defined value; if the integer
- expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
- errno acquires the value EDOM; if the integer expression math_errhandling &
- MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised.
-3 Similarly, a pole error (also known as a singularity or infinitary) occurs if the
- mathematical function has an exact infinite result as the finite input argument(s) are
- approached in the limit (for example, log(0.0)). The description of each function lists
- any required pole errors; an implementation may define additional pole errors, provided
- that such errors are consistent with the mathematical definition of the function. On a pole
- error, the function returns an implementation-defined value; if the integer expression
-
-
- 226) In an implementation that supports infinities, this allows an infinity as an argument to be a domain
- error if the mathematical domain of the function does not include the infinity.
-
-[<a name="#p231" href="p231">page 231</a>] (<a href="#Contents">Contents</a>)
-
- math_errhandling & MATH_ERRNO is nonzero, the integer expression errno
- acquires the value ERANGE; if the integer expression math_errhandling &
- MATH_ERREXCEPT is nonzero, the ''divide-by-zero'' floating-point exception is raised.
-4 Likewise, a range error occurs if the mathematical result of the function cannot be
- represented in an object of the specified type, due to extreme magnitude.
-5 A floating result overflows if the magnitude of the mathematical result is finite but so
- large that the mathematical result cannot be represented without extraordinary roundoff
- error in an object of the specified type. If a floating result overflows and default rounding
- is in effect, then the function returns the value of the macro HUGE_VAL, HUGE_VALF, or
- HUGE_VALL according to the return type, with the same sign as the correct value of the
- function; if the integer expression math_errhandling & MATH_ERRNO is nonzero,
- the integer expression errno acquires the value ERANGE; if the integer expression
- math_errhandling & MATH_ERREXCEPT is nonzero, the ''overflow'' floating-
- point exception is raised.
-6 The result underflows if the magnitude of the mathematical result is so small that the
- mathematical result cannot be represented, without extraordinary roundoff error, in an
- object of the specified type.227) If the result underflows, the function returns an
- implementation-defined value whose magnitude is no greater than the smallest
- normalized positive number in the specified type; if the integer expression
- math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the
- value ERANGE is implementation-defined; if the integer expression
- math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow''
- floating-point exception is raised is implementation-defined.
-7 If a domain, pole, or range error occurs and the integer expression
- math_errhandling & MATH_ERRNO is zero,228) then errno shall either be set to
- the value corresponding to the error or left unmodified. If no such error occurs, errno
- shall be left unmodified regardless of the setting of math_errhandling.
-
-
-
-
- 227) The term underflow here is intended to encompass both ''gradual underflow'' as in IEC 60559 and
- also ''flush-to-zero'' underflow.
- 228) Math errors are being indicated by the floating-point exception flags rather than by errno.
-
-[<a name="#p232" href="p232">page 232</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.12.2" href="#7.12.2"><b> 7.12.2 The FP_CONTRACT pragma</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- #pragma STDC FP_CONTRACT on-off-switch
- Description
-2 The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
- state is ''off'') the implementation to contract expressions (<a href="#6.5">6.5</a>). Each pragma can occur
- either outside external declarations or preceding all explicit declarations and statements
- inside a compound statement. When outside external declarations, the pragma takes
- effect from its occurrence until another FP_CONTRACT pragma is encountered, or until
- the end of the translation unit. When inside a compound statement, the pragma takes
- effect from its occurrence until another FP_CONTRACT pragma is encountered
- (including within a nested compound statement), or until the end of the compound
- statement; at the end of a compound statement the state for the pragma is restored to its
- condition just before the compound statement. If this pragma is used in any other
- context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
- implementation-defined.
-<a name="7.12.3" href="#7.12.3"><b> 7.12.3 Classification macros</b></a>
-1 In the synopses in this subclause, real-floating indicates that the argument shall be an
- expression of real floating type.
-<a name="7.12.3.1" href="#7.12.3.1"><b> 7.12.3.1 The fpclassify macro</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- int fpclassify(real-floating x);
- Description
-2 The fpclassify macro classifies its argument value as NaN, infinite, normal,
- subnormal, zero, or into another implementation-defined category. First, an argument
- represented in a format wider than its semantic type is converted to its semantic type.
- Then classification is based on the type of the argument.229)
- Returns
-3 The fpclassify macro returns the value of the number classification macro
- appropriate to the value of its argument.
-
-
- 229) Since an expression can be evaluated with more range and precision than its type has, it is important to
- know the type that classification is based on. For example, a normal long double value might
- become subnormal when converted to double, and zero when converted to float.
-
-[<a name="#p233" href="p233">page 233</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.12.3.2" href="#7.12.3.2"><b> 7.12.3.2 The isfinite macro</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- int isfinite(real-floating x);
- Description
-2 The isfinite macro determines whether its argument has a finite value (zero,
- subnormal, or normal, and not infinite or NaN). First, an argument represented in a
- format wider than its semantic type is converted to its semantic type. Then determination
- is based on the type of the argument.
- Returns
-3 The isfinite macro returns a nonzero value if and only if its argument has a finite
- value.
-<a name="7.12.3.3" href="#7.12.3.3"><b> 7.12.3.3 The isinf macro</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- int isinf(real-floating x);
- Description
-2 The isinf macro determines whether its argument value is an infinity (positive or
- negative). First, an argument represented in a format wider than its semantic type is
- converted to its semantic type. Then determination is based on the type of the argument.
- Returns
-3 The isinf macro returns a nonzero value if and only if its argument has an infinite
- value.
-<a name="7.12.3.4" href="#7.12.3.4"><b> 7.12.3.4 The isnan macro</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- int isnan(real-floating x);
- Description
-2 The isnan macro determines whether its argument value is a NaN. First, an argument
- represented in a format wider than its semantic type is converted to its semantic type.
- Then determination is based on the type of the argument.230)
-
-
- 230) For the isnan macro, the type for determination does not matter unless the implementation supports
- NaNs in the evaluation type but not in the semantic type.
-
-[<a name="#p234" href="p234">page 234</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
-<a name="7.12.3.5" href="#7.12.3.5"><b> 7.12.3.5 The isnormal macro</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- int isnormal(real-floating x);
- Description
-2 The isnormal macro determines whether its argument value is normal (neither zero,
- subnormal, infinite, nor NaN). First, an argument represented in a format wider than its
- semantic type is converted to its semantic type. Then determination is based on the type
- of the argument.
- Returns
-3 The isnormal macro returns a nonzero value if and only if its argument has a normal
- value.
-<a name="7.12.3.6" href="#7.12.3.6"><b> 7.12.3.6 The signbit macro</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- int signbit(real-floating x);
- Description
-2 The signbit macro determines whether the sign of its argument value is negative.231)
- Returns
-3 The signbit macro returns a nonzero value if and only if the sign of its argument value
- is negative.
-
-
-
-
- 231) The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is
- unsigned, it is treated as positive.
-
-[<a name="#p235" href="p235">page 235</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.12.4" href="#7.12.4"><b> 7.12.4 Trigonometric functions</b></a>
-<a name="7.12.4.1" href="#7.12.4.1"><b> 7.12.4.1 The acos functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double acos(double x);
- float acosf(float x);
- long double acosl(long double x);
- Description
-2 The acos functions compute the principal value of the arc cosine of x. A domain error
- occurs for arguments not in the interval [-1, +1].
- Returns
-3 The acos functions return arccos x in the interval [0, pi ] radians.
-<a name="7.12.4.2" href="#7.12.4.2"><b> 7.12.4.2 The asin functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double asin(double x);
- float asinf(float x);
- long double asinl(long double x);
- Description
-2 The asin functions compute the principal value of the arc sine of x. A domain error
- occurs for arguments not in the interval [-1, +1].
- Returns
-3 The asin functions return arcsin x in the interval [-pi /2, +pi /2] radians.
-<a name="7.12.4.3" href="#7.12.4.3"><b> 7.12.4.3 The atan functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double atan(double x);
- float atanf(float x);
- long double atanl(long double x);
- Description
-2 The atan functions compute the principal value of the arc tangent of x.
-
-
-
-
-[<a name="#p236" href="p236">page 236</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The atan functions return arctan x in the interval [-pi /2, +pi /2] radians.
-<a name="7.12.4.4" href="#7.12.4.4"><b> 7.12.4.4 The atan2 functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double atan2(double y, double x);
- float atan2f(float y, float x);
- long double atan2l(long double y, long double x);
- Description
-2 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
- arguments to determine the quadrant of the return value. A domain error may occur if
- both arguments are zero.
- Returns
-3 The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
-<a name="7.12.4.5" href="#7.12.4.5"><b> 7.12.4.5 The cos functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double cos(double x);
- float cosf(float x);
- long double cosl(long double x);
- Description
-2 The cos functions compute the cosine of x (measured in radians).
- Returns
-3 The cos functions return cos x.
-<a name="7.12.4.6" href="#7.12.4.6"><b> 7.12.4.6 The sin functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double sin(double x);
- float sinf(float x);
- long double sinl(long double x);
- Description
-2 The sin functions compute the sine of x (measured in radians).
-
-
-
-[<a name="#p237" href="p237">page 237</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The sin functions return sin x.
-<a name="7.12.4.7" href="#7.12.4.7"><b> 7.12.4.7 The tan functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double tan(double x);
- float tanf(float x);
- long double tanl(long double x);
- Description
-2 The tan functions return the tangent of x (measured in radians).
- Returns
-3 The tan functions return tan x.
-<a name="7.12.5" href="#7.12.5"><b> 7.12.5 Hyperbolic functions</b></a>
-<a name="7.12.5.1" href="#7.12.5.1"><b> 7.12.5.1 The acosh functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double acosh(double x);
- float acoshf(float x);
- long double acoshl(long double x);
- Description
-2 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
- error occurs for arguments less than 1.
- Returns
-3 The acosh functions return arcosh x in the interval [0, +(inf)].
-<a name="7.12.5.2" href="#7.12.5.2"><b> 7.12.5.2 The asinh functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double asinh(double x);
- float asinhf(float x);
- long double asinhl(long double x);
- Description
-2 The asinh functions compute the arc hyperbolic sine of x.
-
-
-[<a name="#p238" href="p238">page 238</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The asinh functions return arsinh x.
-<a name="7.12.5.3" href="#7.12.5.3"><b> 7.12.5.3 The atanh functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double atanh(double x);
- float atanhf(float x);
- long double atanhl(long double x);
- Description
-2 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
- for arguments not in the interval [-1, +1]. A pole error may occur if the argument equals
- -1 or +1.
- Returns
-3 The atanh functions return artanh x.
-<a name="7.12.5.4" href="#7.12.5.4"><b> 7.12.5.4 The cosh functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double cosh(double x);
- float coshf(float x);
- long double coshl(long double x);
- Description
-2 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
- magnitude of x is too large.
- Returns
-3 The cosh functions return cosh x.
-<a name="7.12.5.5" href="#7.12.5.5"><b> 7.12.5.5 The sinh functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double sinh(double x);
- float sinhf(float x);
- long double sinhl(long double x);
- Description
-2 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
- magnitude of x is too large.
-[<a name="#p239" href="p239">page 239</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The sinh functions return sinh x.
-<a name="7.12.5.6" href="#7.12.5.6"><b> 7.12.5.6 The tanh functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double tanh(double x);
- float tanhf(float x);
- long double tanhl(long double x);
- Description
-2 The tanh functions compute the hyperbolic tangent of x.
- Returns
-3 The tanh functions return tanh x.
-<a name="7.12.6" href="#7.12.6"><b> 7.12.6 Exponential and logarithmic functions</b></a>
-<a name="7.12.6.1" href="#7.12.6.1"><b> 7.12.6.1 The exp functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double exp(double x);
- float expf(float x);
- long double expl(long double x);
- Description
-2 The exp functions compute the base-e exponential of x. A range error occurs if the
- magnitude of x is too large.
- Returns
-3 The exp functions return ex .
-<a name="7.12.6.2" href="#7.12.6.2"><b> 7.12.6.2 The exp2 functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double exp2(double x);
- float exp2f(float x);
- long double exp2l(long double x);
- Description
-2 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
- magnitude of x is too large.
-
-[<a name="#p240" href="p240">page 240</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The exp2 functions return 2x .
-<a name="7.12.6.3" href="#7.12.6.3"><b> 7.12.6.3 The expm1 functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double expm1(double x);
- float expm1f(float x);
- long double expm1l(long double x);
- Description
-2 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
- error occurs if x is too large.232)
- Returns
-3 The expm1 functions return ex - 1.
-<a name="7.12.6.4" href="#7.12.6.4"><b> 7.12.6.4 The frexp functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double frexp(double value, int *exp);
- float frexpf(float value, int *exp);
- long double frexpl(long double value, int *exp);
- Description
-2 The frexp functions break a floating-point number into a normalized fraction and an
- integral power of 2. They store the integer in the int object pointed to by exp.
- Returns
-3 If value is not a floating-point number or if the integral power of 2 is outside the range
- of int, the results are unspecified. Otherwise, the frexp functions return the value x,
- such that x has a magnitude in the interval [1/2, 1) or zero, and value equals x x 2*exp .
- If value is zero, both parts of the result are zero.
-
-
-
-
- 232) For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1.
-
-[<a name="#p241" href="p241">page 241</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.12.6.5" href="#7.12.6.5"><b> 7.12.6.5 The ilogb functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- int ilogb(double x);
- int ilogbf(float x);
- int ilogbl(long double x);
- Description
-2 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
- compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
- a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
- the corresponding logb function and casting the returned value to type int. A domain
- error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
- the range of the return type, the numeric result is unspecified.
- Returns
-3 The ilogb functions return the exponent of x as a signed int value.
- Forward references: the logb functions (<a href="#7.12.6.11">7.12.6.11</a>).
-<a name="7.12.6.6" href="#7.12.6.6"><b> 7.12.6.6 The ldexp functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double ldexp(double x, int exp);
- float ldexpf(float x, int exp);
- long double ldexpl(long double x, int exp);
- Description
-2 The ldexp functions multiply a floating-point number by an integral power of 2. A
- range error may occur.
- Returns
-3 The ldexp functions return x x 2exp .
-<a name="7.12.6.7" href="#7.12.6.7"><b> 7.12.6.7 The log functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double log(double x);
- float logf(float x);
- long double logl(long double x);
-
-
-
-[<a name="#p242" href="p242">page 242</a>] (<a href="#Contents">Contents</a>)
-
- Description
-2 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
- the argument is negative. A pole error may occur if the argument is zero.
- Returns
-3 The log functions return loge x.
-<a name="7.12.6.8" href="#7.12.6.8"><b> 7.12.6.8 The log10 functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double log10(double x);
- float log10f(float x);
- long double log10l(long double x);
- Description
-2 The log10 functions compute the base-10 (common) logarithm of x. A domain error
- occurs if the argument is negative. A pole error may occur if the argument is zero.
- Returns
-3 The log10 functions return log10 x.
-<a name="7.12.6.9" href="#7.12.6.9"><b> 7.12.6.9 The log1p functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double log1p(double x);
- float log1pf(float x);
- long double log1pl(long double x);
- Description
-2 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.233)
- A domain error occurs if the argument is less than -1. A pole error may occur if the
- argument equals -1.
- Returns
-3 The log1p functions return loge (1 + x).
-
-
-
-
- 233) For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x).
-
-[<a name="#p243" href="p243">page 243</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.12.6.10" href="#7.12.6.10"><b> 7.12.6.10 The log2 functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double log2(double x);
- float log2f(float x);
- long double log2l(long double x);
- Description
-2 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
- argument is less than zero. A pole error may occur if the argument is zero.
- Returns
-3 The log2 functions return log2 x.
-<a name="7.12.6.11" href="#7.12.6.11"><b> 7.12.6.11 The logb functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double logb(double x);
- float logbf(float x);
- long double logbl(long double x);
- Description
-2 The logb functions extract the exponent of x, as a signed integer value in floating-point
- format. If x is subnormal it is treated as though it were normalized; thus, for positive
- finite x,
- 1 <= x x FLT_RADIX-logb(x) < FLT_RADIX
- A domain error or pole error may occur if the argument is zero.
- Returns
-3 The logb functions return the signed exponent of x.
-<a name="7.12.6.12" href="#7.12.6.12"><b> 7.12.6.12 The modf functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double modf(double value, double *iptr);
- float modff(float value, float *iptr);
- long double modfl(long double value, long double *iptr);
- Description
-2 The modf functions break the argument value into integral and fractional parts, each of
- which has the same type and sign as the argument. They store the integral part (in
-[<a name="#p244" href="p244">page 244</a>] (<a href="#Contents">Contents</a>)
-
- floating-point format) in the object pointed to by iptr.
- Returns
-3 The modf functions return the signed fractional part of value.
-<a name="7.12.6.13" href="#7.12.6.13"><b> 7.12.6.13 The scalbn and scalbln functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double scalbn(double x, int n);
- float scalbnf(float x, int n);
- long double scalbnl(long double x, int n);
- double scalbln(double x, long int n);
- float scalblnf(float x, long int n);
- long double scalblnl(long double x, long int n);
- Description
-2 The scalbn and scalbln functions compute x x FLT_RADIXn efficiently, not
- normally by computing FLT_RADIXn explicitly. A range error may occur.
- Returns
-3 The scalbn and scalbln functions return x x FLT_RADIXn .
-<a name="7.12.7" href="#7.12.7"><b> 7.12.7 Power and absolute-value functions</b></a>
-<a name="7.12.7.1" href="#7.12.7.1"><b> 7.12.7.1 The cbrt functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double cbrt(double x);
- float cbrtf(float x);
- long double cbrtl(long double x);
- Description
-2 The cbrt functions compute the real cube root of x.
- Returns
-3 The cbrt functions return x1/3 .
-
-
-
-
-[<a name="#p245" href="p245">page 245</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.12.7.2" href="#7.12.7.2"><b> 7.12.7.2 The fabs functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double fabs(double x);
- float fabsf(float x);
- long double fabsl(long double x);
- Description
-2 The fabs functions compute the absolute value of a floating-point number x.
- Returns
-3 The fabs functions return | x |.
-<a name="7.12.7.3" href="#7.12.7.3"><b> 7.12.7.3 The hypot functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double hypot(double x, double y);
- float hypotf(float x, float y);
- long double hypotl(long double x, long double y);
- Description
-2 The hypot functions compute the square root of the sum of the squares of x and y,
- without undue overflow or underflow. A range error may occur.
-3 Returns
-4 The hypot functions return sqrt:x2 + y2 .
- -
- -----
-<a name="7.12.7.4" href="#7.12.7.4"><b> 7.12.7.4 The pow functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double pow(double x, double y);
- float powf(float x, float y);
- long double powl(long double x, long double y);
- Description
-2 The pow functions compute x raised to the power y. A domain error occurs if x is finite
- and negative and y is finite and not an integer value. A range error may occur. A domain
- error may occur if x is zero and y is zero. A domain error or pole error may occur if x is
- zero and y is less than zero.
-
-
-
-
-[<a name="#p246" href="p246">page 246</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The pow functions return xy .
-<a name="7.12.7.5" href="#7.12.7.5"><b> 7.12.7.5 The sqrt functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double sqrt(double x);
- float sqrtf(float x);
- long double sqrtl(long double x);
- Description
-2 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
- the argument is less than zero.
- Returns
-3 The sqrt functions return sqrt:x.
- -
- -
-<a name="7.12.8" href="#7.12.8"><b> 7.12.8 Error and gamma functions</b></a>
-<a name="7.12.8.1" href="#7.12.8.1"><b> 7.12.8.1 The erf functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double erf(double x);
- float erff(float x);
- long double erfl(long double x);
- Description
-2 The erf functions compute the error function of x.
- Returns
-3 2 x
- (integral) e-t dt.
- 2
- The erf functions return erf x =
- sqrt:pi
- -
- - 0
-
-<a name="7.12.8.2" href="#7.12.8.2"><b> 7.12.8.2 The erfc functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double erfc(double x);
- float erfcf(float x);
- long double erfcl(long double x);
- Description
-2 The erfc functions compute the complementary error function of x. A range error
- occurs if x is too large.
-[<a name="#p247" href="p247">page 247</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 2 (inf)
- (integral) e-t dt.
- 2
- The erfc functions return erfc x = 1 - erf x =
- sqrt:pi
- -
- - x
-
-<a name="7.12.8.3" href="#7.12.8.3"><b> 7.12.8.3 The lgamma functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double lgamma(double x);
- float lgammaf(float x);
- long double lgammal(long double x);
- Description
-2 The lgamma functions compute the natural logarithm of the absolute value of gamma of
- x. A range error occurs if x is too large. A pole error may occur if x is a negative integer
- or zero.
- Returns
-3 The lgamma functions return loge | (Gamma)(x) |.
-<a name="7.12.8.4" href="#7.12.8.4"><b> 7.12.8.4 The tgamma functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double tgamma(double x);
- float tgammaf(float x);
- long double tgammal(long double x);
- Description
-2 The tgamma functions compute the gamma function of x. A domain error or pole error
- may occur if x is a negative integer or zero. A range error occurs if the magnitude of x is
- too large and may occur if the magnitude of x is too small.
- Returns
-3 The tgamma functions return (Gamma)(x).
-
-
-
-
-[<a name="#p248" href="p248">page 248</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.12.9" href="#7.12.9"><b> 7.12.9 Nearest integer functions</b></a>
-<a name="7.12.9.1" href="#7.12.9.1"><b> 7.12.9.1 The ceil functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double ceil(double x);
- float ceilf(float x);
- long double ceill(long double x);
- Description
-2 The ceil functions compute the smallest integer value not less than x.
- Returns
-3 The ceil functions return [^x^], expressed as a floating-point number.
-<a name="7.12.9.2" href="#7.12.9.2"><b> 7.12.9.2 The floor functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double floor(double x);
- float floorf(float x);
- long double floorl(long double x);
- Description
-2 The floor functions compute the largest integer value not greater than x.
- Returns
-3 The floor functions return [_x_], expressed as a floating-point number.
-<a name="7.12.9.3" href="#7.12.9.3"><b> 7.12.9.3 The nearbyint functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double nearbyint(double x);
- float nearbyintf(float x);
- long double nearbyintl(long double x);
- Description
-2 The nearbyint functions round their argument to an integer value in floating-point
- format, using the current rounding direction and without raising the ''inexact'' floating-
- point exception.
-
-
-
-
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-
- Returns
-3 The nearbyint functions return the rounded integer value.
-<a name="7.12.9.4" href="#7.12.9.4"><b> 7.12.9.4 The rint functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double rint(double x);
- float rintf(float x);
- long double rintl(long double x);
- Description
-2 The rint functions differ from the nearbyint functions (<a href="#7.12.9.3">7.12.9.3</a>) only in that the
- rint functions may raise the ''inexact'' floating-point exception if the result differs in
- value from the argument.
- Returns
-3 The rint functions return the rounded integer value.
-<a name="7.12.9.5" href="#7.12.9.5"><b> 7.12.9.5 The lrint and llrint functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- long int lrint(double x);
- long int lrintf(float x);
- long int lrintl(long double x);
- long long int llrint(double x);
- long long int llrintf(float x);
- long long int llrintl(long double x);
- Description
-2 The lrint and llrint functions round their argument to the nearest integer value,
- rounding according to the current rounding direction. If the rounded value is outside the
- range of the return type, the numeric result is unspecified and a domain error or range
- error may occur.
- Returns
-3 The lrint and llrint functions return the rounded integer value.
-
-
-
-
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-
-<a name="7.12.9.6" href="#7.12.9.6"><b> 7.12.9.6 The round functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double round(double x);
- float roundf(float x);
- long double roundl(long double x);
- Description
-2 The round functions round their argument to the nearest integer value in floating-point
- format, rounding halfway cases away from zero, regardless of the current rounding
- direction.
- Returns
-3 The round functions return the rounded integer value.
-<a name="7.12.9.7" href="#7.12.9.7"><b> 7.12.9.7 The lround and llround functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- long int lround(double x);
- long int lroundf(float x);
- long int lroundl(long double x);
- long long int llround(double x);
- long long int llroundf(float x);
- long long int llroundl(long double x);
- Description
-2 The lround and llround functions round their argument to the nearest integer value,
- rounding halfway cases away from zero, regardless of the current rounding direction. If
- the rounded value is outside the range of the return type, the numeric result is unspecified
- and a domain error or range error may occur.
- Returns
-3 The lround and llround functions return the rounded integer value.
-<a name="7.12.9.8" href="#7.12.9.8"><b> 7.12.9.8 The trunc functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double trunc(double x);
- float truncf(float x);
- long double truncl(long double x);
-
-
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-
- Description
-2 The trunc functions round their argument to the integer value, in floating format,
- nearest to but no larger in magnitude than the argument.
- Returns
-3 The trunc functions return the truncated integer value.
-<a name="7.12.10" href="#7.12.10"><b> 7.12.10 Remainder functions</b></a>
-<a name="7.12.10.1" href="#7.12.10.1"><b> 7.12.10.1 The fmod functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double fmod(double x, double y);
- float fmodf(float x, float y);
- long double fmodl(long double x, long double y);
- Description
-2 The fmod functions compute the floating-point remainder of x/y.
- Returns
-3 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
- the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
- whether a domain error occurs or the fmod functions return zero is implementation-
- defined.
-<a name="7.12.10.2" href="#7.12.10.2"><b> 7.12.10.2 The remainder functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double remainder(double x, double y);
- float remainderf(float x, float y);
- long double remainderl(long double x, long double y);
- Description
-2 The remainder functions compute the remainder x REM y required by IEC 60559.234)
-
-
-
-
- 234) ''When y != 0, the remainder r = x REM y is defined regardless of the rounding mode by the
- mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever
- | n - x/y | = 1/2, then n is even. If r = 0, its sign shall be that of x.'' This definition is applicable for
- all implementations.
-
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-
- Returns
-3 The remainder functions return x REM y. If y is zero, whether a domain error occurs
- or the functions return zero is implementation defined.
-<a name="7.12.10.3" href="#7.12.10.3"><b> 7.12.10.3 The remquo functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double remquo(double x, double y, int *quo);
- float remquof(float x, float y, int *quo);
- long double remquol(long double x, long double y,
- int *quo);
- Description
-2 The remquo functions compute the same remainder as the remainder functions. In
- the object pointed to by quo they store a value whose sign is the sign of x/y and whose
- magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where
- n is an implementation-defined integer greater than or equal to 3.
- Returns
-3 The remquo functions return x REM y. If y is zero, the value stored in the object
- pointed to by quo is unspecified and whether a domain error occurs or the functions
- return zero is implementation defined.
-<a name="7.12.11" href="#7.12.11"><b> 7.12.11 Manipulation functions</b></a>
-<a name="7.12.11.1" href="#7.12.11.1"><b> 7.12.11.1 The copysign functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double copysign(double x, double y);
- float copysignf(float x, float y);
- long double copysignl(long double x, long double y);
- Description
-2 The copysign functions produce a value with the magnitude of x and the sign of y.
- They produce a NaN (with the sign of y) if x is a NaN. On implementations that
- represent a signed zero but do not treat negative zero consistently in arithmetic
- operations, the copysign functions regard the sign of zero as positive.
- Returns
-3 The copysign functions return a value with the magnitude of x and the sign of y.
-
-
-
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-
-<a name="7.12.11.2" href="#7.12.11.2"><b> 7.12.11.2 The nan functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double nan(const char *tagp);
- float nanf(const char *tagp);
- long double nanl(const char *tagp);
- Description
-2 The call nan("n-char-sequence") is equivalent to strtod("NAN(n-char-
- sequence)", (char**) NULL); the call nan("") is equivalent to
- strtod("NAN()", (char**) NULL). If tagp does not point to an n-char
- sequence or an empty string, the call is equivalent to strtod("NAN", (char**)
- NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof
- and strtold.
- Returns
-3 The nan functions return a quiet NaN, if available, with content indicated through tagp.
- If the implementation does not support quiet NaNs, the functions return zero.
- Forward references: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
-<a name="7.12.11.3" href="#7.12.11.3"><b> 7.12.11.3 The nextafter functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double nextafter(double x, double y);
- float nextafterf(float x, float y);
- long double nextafterl(long double x, long double y);
- Description
-2 The nextafter functions determine the next representable value, in the type of the
- function, after x in the direction of y, where x and y are first converted to the type of the
- function.235) The nextafter functions return y if x equals y. A range error may occur
- if the magnitude of x is the largest finite value representable in the type and the result is
- infinite or not representable in the type.
- Returns
-3 The nextafter functions return the next representable value in the specified format
- after x in the direction of y.
-
-
- 235) The argument values are converted to the type of the function, even by a macro implementation of the
- function.
-
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-
-<a name="7.12.11.4" href="#7.12.11.4"><b> 7.12.11.4 The nexttoward functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double nexttoward(double x, long double y);
- float nexttowardf(float x, long double y);
- long double nexttowardl(long double x, long double y);
- Description
-2 The nexttoward functions are equivalent to the nextafter functions except that the
- second parameter has type long double and the functions return y converted to the
- type of the function if x equals y.236)
-<a name="7.12.12" href="#7.12.12"><b> 7.12.12 Maximum, minimum, and positive difference functions</b></a>
-<a name="7.12.12.1" href="#7.12.12.1"><b> 7.12.12.1 The fdim functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double fdim(double x, double y);
- float fdimf(float x, float y);
- long double fdiml(long double x, long double y);
- Description
-2 The fdim functions determine the positive difference between their arguments:
- {x - y if x > y
- {
- {+0 if x <= y
- A range error may occur.
- Returns
-3 The fdim functions return the positive difference value.
-<a name="7.12.12.2" href="#7.12.12.2"><b> 7.12.12.2 The fmax functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double fmax(double x, double y);
- float fmaxf(float x, float y);
- long double fmaxl(long double x, long double y);
-
-
-
- 236) The result of the nexttoward functions is determined in the type of the function, without loss of
- range or precision in a floating second argument.
-
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-
- Description
-2 The fmax functions determine the maximum numeric value of their arguments.237)
- Returns
-3 The fmax functions return the maximum numeric value of their arguments.
-<a name="7.12.12.3" href="#7.12.12.3"><b> 7.12.12.3 The fmin functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double fmin(double x, double y);
- float fminf(float x, float y);
- long double fminl(long double x, long double y);
- Description
-2 The fmin functions determine the minimum numeric value of their arguments.238)
- Returns
-3 The fmin functions return the minimum numeric value of their arguments.
-<a name="7.12.13" href="#7.12.13"><b> 7.12.13 Floating multiply-add</b></a>
-<a name="7.12.13.1" href="#7.12.13.1"><b> 7.12.13.1 The fma functions</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- double fma(double x, double y, double z);
- float fmaf(float x, float y, float z);
- long double fmal(long double x, long double y,
- long double z);
- Description
-2 The fma functions compute (x x y) + z, rounded as one ternary operation: they compute
- the value (as if) to infinite precision and round once to the result format, according to the
- current rounding mode. A range error may occur.
- Returns
-3 The fma functions return (x x y) + z, rounded as one ternary operation.
-
-
-
-
- 237) NaN arguments are treated as missing data: if one argument is a NaN and the other numeric, then the
- fmax functions choose the numeric value. See <a href="#F.10.9.2">F.10.9.2</a>.
- 238) The fmin functions are analogous to the fmax functions in their treatment of NaNs.
-
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-
-<a name="7.12.14" href="#7.12.14"><b> 7.12.14 Comparison macros</b></a>
-1 The relational and equality operators support the usual mathematical relationships
- between numeric values. For any ordered pair of numeric values exactly one of the
- relationships -- less, greater, and equal -- is true. Relational operators may raise the
- ''invalid'' floating-point exception when argument values are NaNs. For a NaN and a
- numeric value, or for two NaNs, just the unordered relationship is true.239) The following
- subclauses provide macros that are quiet (non floating-point exception raising) versions
- of the relational operators, and other comparison macros that facilitate writing efficient
- code that accounts for NaNs without suffering the ''invalid'' floating-point exception. In
- the synopses in this subclause, real-floating indicates that the argument shall be an
- expression of real floating type (both arguments need not have the same type).240)
-<a name="7.12.14.1" href="#7.12.14.1"><b> 7.12.14.1 The isgreater macro</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- int isgreater(real-floating x, real-floating y);
- Description
-2 The isgreater macro determines whether its first argument is greater than its second
- argument. The value of isgreater(x, y) is always equal to (x) > (y); however,
- unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point
- exception when x and y are unordered.
- Returns
-3 The isgreater macro returns the value of (x) > (y).
-<a name="7.12.14.2" href="#7.12.14.2"><b> 7.12.14.2 The isgreaterequal macro</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- int isgreaterequal(real-floating x, real-floating y);
- Description
-2 The isgreaterequal macro determines whether its first argument is greater than or
- equal to its second argument. The value of isgreaterequal(x, y) is always equal
- to (x) >= (y); however, unlike (x) >= (y), isgreaterequal(x, y) does
-
-
- 239) IEC 60559 requires that the built-in relational operators raise the ''invalid'' floating-point exception if
- the operands compare unordered, as an error indicator for programs written without consideration of
- NaNs; the result in these cases is false.
- 240) Whether an argument represented in a format wider than its semantic type is converted to the semantic
- type is unspecified.
-
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-
- not raise the ''invalid'' floating-point exception when x and y are unordered.
- Returns
-3 The isgreaterequal macro returns the value of (x) >= (y).
-<a name="7.12.14.3" href="#7.12.14.3"><b> 7.12.14.3 The isless macro</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- int isless(real-floating x, real-floating y);
- Description
-2 The isless macro determines whether its first argument is less than its second
- argument. The value of isless(x, y) is always equal to (x) < (y); however,
- unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point
- exception when x and y are unordered.
- Returns
-3 The isless macro returns the value of (x) < (y).
-<a name="7.12.14.4" href="#7.12.14.4"><b> 7.12.14.4 The islessequal macro</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- int islessequal(real-floating x, real-floating y);
- Description
-2 The islessequal macro determines whether its first argument is less than or equal to
- its second argument. The value of islessequal(x, y) is always equal to
- (x) <= (y); however, unlike (x) <= (y), islessequal(x, y) does not raise
- the ''invalid'' floating-point exception when x and y are unordered.
- Returns
-3 The islessequal macro returns the value of (x) <= (y).
-<a name="7.12.14.5" href="#7.12.14.5"><b> 7.12.14.5 The islessgreater macro</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- int islessgreater(real-floating x, real-floating y);
- Description
-2 The islessgreater macro determines whether its first argument is less than or
- greater than its second argument. The islessgreater(x, y) macro is similar to
- (x) < (y) || (x) > (y); however, islessgreater(x, y) does not raise
-
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-
- the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x
- and y twice).
- Returns
-3 The islessgreater macro returns the value of (x) < (y) || (x) > (y).
-<a name="7.12.14.6" href="#7.12.14.6"><b> 7.12.14.6 The isunordered macro</b></a>
- Synopsis
-1 #include <a href="#7.12"><math.h></a>
- int isunordered(real-floating x, real-floating y);
- Description
-2 The isunordered macro determines whether its arguments are unordered.
- Returns
-3 The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
-
-
-
-
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-
-<a name="7.13" href="#7.13"><b> 7.13 Nonlocal jumps <setjmp.h></b></a>
-1 The header <a href="#7.13"><setjmp.h></a> defines the macro setjmp, and declares one function and
- one type, for bypassing the normal function call and return discipline.241)
-2 The type declared is
- jmp_buf
- which is an array type suitable for holding the information needed to restore a calling
- environment. The environment of a call to the setjmp macro consists of information
- sufficient for a call to the longjmp function to return execution to the correct block and
- invocation of that block, were it called recursively. It does not include the state of the
- floating-point status flags, of open files, or of any other component of the abstract
- machine.
-3 It is unspecified whether setjmp is a macro or an identifier declared with external
- linkage. If a macro definition is suppressed in order to access an actual function, or a
- program defines an external identifier with the name setjmp, the behavior is undefined.
-<a name="7.13.1" href="#7.13.1"><b> 7.13.1 Save calling environment</b></a>
-<a name="7.13.1.1" href="#7.13.1.1"><b> 7.13.1.1 The setjmp macro</b></a>
- Synopsis
-1 #include <a href="#7.13"><setjmp.h></a>
- int setjmp(jmp_buf env);
- Description
-2 The setjmp macro saves its calling environment in its jmp_buf argument for later use
- by the longjmp function.
- Returns
-3 If the return is from a direct invocation, the setjmp macro returns the value zero. If the
- return is from a call to the longjmp function, the setjmp macro returns a nonzero
- value.
- Environmental limits
-4 An invocation of the setjmp macro shall appear only in one of the following contexts:
- -- the entire controlling expression of a selection or iteration statement;
- -- one operand of a relational or equality operator with the other operand an integer
- constant expression, with the resulting expression being the entire controlling
-
-
- 241) These functions are useful for dealing with unusual conditions encountered in a low-level function of
- a program.
-
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-
- expression of a selection or iteration statement;
- -- the operand of a unary ! operator with the resulting expression being the entire
- controlling expression of a selection or iteration statement; or
- -- the entire expression of an expression statement (possibly cast to void).
-5 If the invocation appears in any other context, the behavior is undefined.
-<a name="7.13.2" href="#7.13.2"><b> 7.13.2 Restore calling environment</b></a>
-<a name="7.13.2.1" href="#7.13.2.1"><b> 7.13.2.1 The longjmp function</b></a>
- Synopsis
-1 #include <a href="#7.13"><setjmp.h></a>
- _Noreturn void longjmp(jmp_buf env, int val);
- Description
-2 The longjmp function restores the environment saved by the most recent invocation of
- the setjmp macro in the same invocation of the program with the corresponding
- jmp_buf argument. If there has been no such invocation, or if the function containing
- the invocation of the setjmp macro has terminated execution242) in the interim, or if the
- invocation of the setjmp macro was within the scope of an identifier with variably
- modified type and execution has left that scope in the interim, the behavior is undefined.
-3 All accessible objects have values, and all other components of the abstract machine243)
- have state, as of the time the longjmp function was called, except that the values of
- objects of automatic storage duration that are local to the function containing the
- invocation of the corresponding setjmp macro that do not have volatile-qualified type
- and have been changed between the setjmp invocation and longjmp call are
- indeterminate.
- Returns
-4 After longjmp is completed, program execution continues as if the corresponding
- invocation of the setjmp macro had just returned the value specified by val. The
- longjmp function cannot cause the setjmp macro to return the value 0; if val is 0,
- the setjmp macro returns the value 1.
-5 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation
- might cause memory associated with a variable length array object to be squandered.
-
-
-
-
- 242) For example, by executing a return statement or because another longjmp call has caused a
- transfer to a setjmp invocation in a function earlier in the set of nested calls.
- 243) This includes, but is not limited to, the floating-point status flags and the state of open files.
-
-[<a name="#p261" href="p261">page 261</a>] (<a href="#Contents">Contents</a>)
-
- #include <a href="#7.13"><setjmp.h></a>
- jmp_buf buf;
- void g(int n);
- void h(int n);
- int n = 6;
- void f(void)
- {
- int x[n]; // valid: f is not terminated
- setjmp(buf);
- g(n);
- }
- void g(int n)
- {
- int a[n]; // a may remain allocated
- h(n);
- }
- void h(int n)
- {
- int b[n]; // b may remain allocated
- longjmp(buf, 2); // might cause memory loss
- }
-
-
-
-
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-
-<a name="7.14" href="#7.14"><b> 7.14 Signal handling <signal.h></b></a>
-1 The header <a href="#7.14"><signal.h></a> declares a type and two functions and defines several macros,
- for handling various signals (conditions that may be reported during program execution).
-2 The type defined is
- sig_atomic_t
- which is the (possibly volatile-qualified) integer type of an object that can be accessed as
- an atomic entity, even in the presence of asynchronous interrupts.
-3 The macros defined are
- SIG_DFL
- SIG_ERR
- SIG_IGN
- which expand to constant expressions with distinct values that have type compatible with
- the second argument to, and the return value of, the signal function, and whose values
- compare unequal to the address of any declarable function; and the following, which
- expand to positive integer constant expressions with type int and distinct values that are
- the signal numbers, each corresponding to the specified condition:
- SIGABRT abnormal termination, such as is initiated by the abort function
- SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
- resulting in overflow
- SIGILL detection of an invalid function image, such as an invalid instruction
- SIGINT receipt of an interactive attention signal
- SIGSEGV an invalid access to storage
- SIGTERM a termination request sent to the program
-4 An implementation need not generate any of these signals, except as a result of explicit
- calls to the raise function. Additional signals and pointers to undeclarable functions,
- with macro definitions beginning, respectively, with the letters SIG and an uppercase
- letter or with SIG_ and an uppercase letter,244) may also be specified by the
- implementation. The complete set of signals, their semantics, and their default handling
- is implementation-defined; all signal numbers shall be positive.
-
-
-
-
- 244) See ''future library directions'' (<a href="#7.30.6">7.30.6</a>). The names of the signal numbers reflect the following terms
- (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
- and termination.
-
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-
-<a name="7.14.1" href="#7.14.1"><b> 7.14.1 Specify signal handling</b></a>
-<a name="7.14.1.1" href="#7.14.1.1"><b> 7.14.1.1 The signal function</b></a>
- Synopsis
-1 #include <a href="#7.14"><signal.h></a>
- void (*signal(int sig, void (*func)(int)))(int);
- Description
-2 The signal function chooses one of three ways in which receipt of the signal number
- sig is to be subsequently handled. If the value of func is SIG_DFL, default handling
- for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored.
- Otherwise, func shall point to a function to be called when that signal occurs. An
- invocation of such a function because of a signal, or (recursively) of any further functions
- called by that invocation (other than functions in the standard library), is called a signal
- handler.
-3 When a signal occurs and func points to a function, it is implementation-defined
- whether the equivalent of signal(sig, SIG_DFL); is executed or the
- implementation prevents some implementation-defined set of signals (at least including
- sig) from occurring until the current signal handling has completed; in the case of
- SIGILL, the implementation may alternatively define that no action is taken. Then the
- equivalent of (*func)(sig); is executed. If and when the function returns, if the
- value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined
- value corresponding to a computational exception, the behavior is undefined; otherwise
- the program will resume execution at the point it was interrupted.
-4 If the signal occurs as the result of calling the abort or raise function, the signal
- handler shall not call the raise function.
-5 If the signal occurs other than as the result of calling the abort or raise function, the
- behavior is undefined if the signal handler refers to any object with static or thread
- storage duration other than by assigning a value to an object declared as volatile
- sig_atomic_t, or the signal handler calls any function in the standard library other
- than the abort function, the _Exit function, the quick_exit function, or the
- signal function with the first argument equal to the signal number corresponding to the
- signal that caused the invocation of the handler. Furthermore, if such a call to the
- signal function results in a SIG_ERR return, the value of errno is indeterminate.245)
-6 At program startup, the equivalent of
- signal(sig, SIG_IGN);
-
-
- 245) If any signal is generated by an asynchronous signal handler, the behavior is undefined.
-
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-
- may be executed for some signals selected in an implementation-defined manner; the
- equivalent of
- signal(sig, SIG_DFL);
- is executed for all other signals defined by the implementation.
-7 The implementation shall behave as if no library function calls the signal function.
- Returns
-8 If the request can be honored, the signal function returns the value of func for the
- most recent successful call to signal for the specified signal sig. Otherwise, a value of
- SIG_ERR is returned and a positive value is stored in errno.
- Forward references: the abort function (<a href="#7.22.4.1">7.22.4.1</a>), the exit function (<a href="#7.22.4.4">7.22.4.4</a>), the
- _Exit function (<a href="#7.22.4.5">7.22.4.5</a>), the quick_exit function (<a href="#7.22.4.7">7.22.4.7</a>).
-<a name="7.14.2" href="#7.14.2"><b> 7.14.2 Send signal</b></a>
-<a name="7.14.2.1" href="#7.14.2.1"><b> 7.14.2.1 The raise function</b></a>
- Synopsis
-1 #include <a href="#7.14"><signal.h></a>
- int raise(int sig);
- Description
-2 The raise function carries out the actions described in <a href="#7.14.1.1">7.14.1.1</a> for the signal sig. If a
- signal handler is called, the raise function shall not return until after the signal handler
- does.
- Returns
-3 The raise function returns zero if successful, nonzero if unsuccessful.
-
-
-
-
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-
-<a name="7.15" href="#7.15"><b> 7.15 Alignment <stdalign.h></b></a>
-1 The header <a href="#7.15"><stdalign.h></a> defines two macros.
-2 The macro
- alignas
- expands to _Alignas.
-3 The remaining macro is suitable for use in #if preprocessing directives. It is
- __alignas_is_defined
- which expands to the integer constant 1.
-
-
-
-
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-
-<a name="7.16" href="#7.16"><b> 7.16 Variable arguments <stdarg.h></b></a>
-1 The header <a href="#7.16"><stdarg.h></a> declares a type and defines four macros, for advancing
- through a list of arguments whose number and types are not known to the called function
- when it is translated.
-2 A function may be called with a variable number of arguments of varying types. As
- described in <a href="#6.9.1">6.9.1</a>, its parameter list contains one or more parameters. The rightmost
- parameter plays a special role in the access mechanism, and will be designated parmN in
- this description.
-3 The type declared is
- va_list
- which is a complete object type suitable for holding information needed by the macros
- va_start, va_arg, va_end, and va_copy. If access to the varying arguments is
- desired, the called function shall declare an object (generally referred to as ap in this
- subclause) having type va_list. The object ap may be passed as an argument to
- another function; if that function invokes the va_arg macro with parameter ap, the
- value of ap in the calling function is indeterminate and shall be passed to the va_end
- macro prior to any further reference to ap.246)
-<a name="7.16.1" href="#7.16.1"><b> 7.16.1 Variable argument list access macros</b></a>
-1 The va_start and va_arg macros described in this subclause shall be implemented
- as macros, not functions. It is unspecified whether va_copy and va_end are macros or
- identifiers declared with external linkage. If a macro definition is suppressed in order to
- access an actual function, or a program defines an external identifier with the same name,
- the behavior is undefined. Each invocation of the va_start and va_copy macros
- shall be matched by a corresponding invocation of the va_end macro in the same
- function.
-<a name="7.16.1.1" href="#7.16.1.1"><b> 7.16.1.1 The va_arg macro</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- type va_arg(va_list ap, type);
- Description
-2 The va_arg macro expands to an expression that has the specified type and the value of
- the next argument in the call. The parameter ap shall have been initialized by the
- va_start or va_copy macro (without an intervening invocation of the va_end
-
- 246) It is permitted to create a pointer to a va_list and pass that pointer to another function, in which
- case the original function may make further use of the original list after the other function returns.
-
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-
- macro for the same ap). Each invocation of the va_arg macro modifies ap so that the
- values of successive arguments are returned in turn. The parameter type shall be a type
- name specified such that the type of a pointer to an object that has the specified type can
- be obtained simply by postfixing a * to type. If there is no actual next argument, or if
- type is not compatible with the type of the actual next argument (as promoted according
- to the default argument promotions), the behavior is undefined, except for the following
- cases:
- -- one type is a signed integer type, the other type is the corresponding unsigned integer
- type, and the value is representable in both types;
- -- one type is pointer to void and the other is a pointer to a character type.
- Returns
-3 The first invocation of the va_arg macro after that of the va_start macro returns the
- value of the argument after that specified by parmN . Successive invocations return the
- values of the remaining arguments in succession.
-<a name="7.16.1.2" href="#7.16.1.2"><b> 7.16.1.2 The va_copy macro</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- void va_copy(va_list dest, va_list src);
- Description
-2 The va_copy macro initializes dest as a copy of src, as if the va_start macro had
- been applied to dest followed by the same sequence of uses of the va_arg macro as
- had previously been used to reach the present state of src. Neither the va_copy nor
- va_start macro shall be invoked to reinitialize dest without an intervening
- invocation of the va_end macro for the same dest.
- Returns
-3 The va_copy macro returns no value.
-<a name="7.16.1.3" href="#7.16.1.3"><b> 7.16.1.3 The va_end macro</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- void va_end(va_list ap);
- Description
-2 The va_end macro facilitates a normal return from the function whose variable
- argument list was referred to by the expansion of the va_start macro, or the function
- containing the expansion of the va_copy macro, that initialized the va_list ap. The
- va_end macro may modify ap so that it is no longer usable (without being reinitialized
-
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-
- by the va_start or va_copy macro). If there is no corresponding invocation of the
- va_start or va_copy macro, or if the va_end macro is not invoked before the
- return, the behavior is undefined.
- Returns
-3 The va_end macro returns no value.
-<a name="7.16.1.4" href="#7.16.1.4"><b> 7.16.1.4 The va_start macro</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- void va_start(va_list ap, parmN);
- Description
-2 The va_start macro shall be invoked before any access to the unnamed arguments.
-3 The va_start macro initializes ap for subsequent use by the va_arg and va_end
- macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap
- without an intervening invocation of the va_end macro for the same ap.
-4 The parameter parmN is the identifier of the rightmost parameter in the variable
- parameter list in the function definition (the one just before the , ...). If the parameter
- parmN is declared with the register storage class, with a function or array type, or
- with a type that is not compatible with the type that results after application of the default
- argument promotions, the behavior is undefined.
- Returns
-5 The va_start macro returns no value.
-6 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not
- more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of
- pointers is specified by the first argument to f1.
- #include <a href="#7.16"><stdarg.h></a>
- #define MAXARGS 31
- void f1(int n_ptrs, ...)
- {
- va_list ap;
- char *array[MAXARGS];
- int ptr_no = 0;
-
-
-
-
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-
- if (n_ptrs > MAXARGS)
- n_ptrs = MAXARGS;
- va_start(ap, n_ptrs);
- while (ptr_no < n_ptrs)
- array[ptr_no++] = va_arg(ap, char *);
- va_end(ap);
- f2(n_ptrs, array);
- }
- Each call to f1 is required to have visible the definition of the function or a declaration such as
- void f1(int, ...);
-
-7 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the
- indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list
- is gathered again and passed to function f4.
- #include <a href="#7.16"><stdarg.h></a>
- #define MAXARGS 31
- void f3(int n_ptrs, int f4_after, ...)
- {
- va_list ap, ap_save;
- char *array[MAXARGS];
- int ptr_no = 0;
- if (n_ptrs > MAXARGS)
- n_ptrs = MAXARGS;
- va_start(ap, f4_after);
- while (ptr_no < n_ptrs) {
- array[ptr_no++] = va_arg(ap, char *);
- if (ptr_no == f4_after)
- va_copy(ap_save, ap);
- }
- va_end(ap);
- f2(n_ptrs, array);
- // Now process the saved copy.
- n_ptrs -= f4_after;
- ptr_no = 0;
- while (ptr_no < n_ptrs)
- array[ptr_no++] = va_arg(ap_save, char *);
- va_end(ap_save);
- f4(n_ptrs, array);
- }
-
-
-
-
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-
-<a name="7.17" href="#7.17"><b> 7.17 Atomics <stdatomic.h></b></a>
-<a name="7.17.1" href="#7.17.1"><b> 7.17.1 Introduction</b></a>
-1 The header <a href="#7.17"><stdatomic.h></a> defines several macros and declares several types and
- functions for performing atomic operations on data shared between threads.
-2 Implementations that define the macro __STDC_NO_THREADS__ need not provide
- this header nor support any of its facilities.
-3 The macros defined are the atomic lock-free macros
- ATOMIC_CHAR_LOCK_FREE
- ATOMIC_CHAR16_T_LOCK_FREE
- ATOMIC_CHAR32_T_LOCK_FREE
- ATOMIC_WCHAR_T_LOCK_FREE
- ATOMIC_SHORT_LOCK_FREE
- ATOMIC_INT_LOCK_FREE
- ATOMIC_LONG_LOCK_FREE
- ATOMIC_LLONG_LOCK_FREE
- ATOMIC_ADDRESS_LOCK_FREE
- which indicate the lock-free property of the corresponding atomic types (both signed and
- unsigned); and
- ATOMIC_FLAG_INIT
- which expands to an initializer for an object of type atomic_flag.
-4 The types include
- memory_order
- which is an enumerated type whose enumerators identify memory ordering constraints;
- atomic_flag
- which is a structure type representing a lock-free, primitive atomic flag;
- atomic_bool
- which is a structure type representing the atomic analog of the type _Bool;
- atomic_address
- which is a structure type representing the atomic analog of a pointer type; and several
- atomic analogs of integer types.
-5 In the following operation definitions:
- -- An A refers to one of the atomic types.
-
-
-[<a name="#p271" href="p271">page 271</a>] (<a href="#Contents">Contents</a>)
-
- -- A C refers to its corresponding non-atomic type. The atomic_address atomic
- type corresponds to the void * non-atomic type.
- -- An M refers to the type of the other argument for arithmetic operations. For atomic
- integer types, M is C. For atomic address types, M is ptrdiff_t.
- -- The functions not ending in _explicit have the same semantics as the
- corresponding _explicit function with memory_order_seq_cst for the
- memory_order argument.
- 6 NOTE Many operations are volatile-qualified. The ''volatile as device register'' semantics have not
- changed in the standard. This qualification means that volatility is preserved when applying these
- operations to volatile objects.
-
-<a name="7.17.2" href="#7.17.2"><b> 7.17.2 Initialization</b></a>
-<a name="7.17.2.1" href="#7.17.2.1"><b> 7.17.2.1 The ATOMIC_VAR_INIT macro</b></a>
- Synopsis
-1 #include <a href="#7.17"><stdatomic.h></a>
- #define ATOMIC_VAR_INIT(C value)
- Description
-2 The ATOMIC_VAR_INIT macro expands to a token sequence suitable for initializing an
- atomic object of a type that is initialization-compatible with value. An atomic object
- with automatic storage duration that is not explicitly initialized using
- ATOMIC_VAR_INIT is initially in an indeterminate state; however, the default (zero)
- initialization for objects with static or thread-local storage duration is guaranteed to
- produce a valid state.
-3 Concurrent access to the variable being initialized, even via an atomic operation,
- constitutes a data race.
-4 EXAMPLE
- atomic_int guide = ATOMIC_VAR_INIT(42);
-
-<a name="7.17.2.2" href="#7.17.2.2"><b> 7.17.2.2 The atomic_init generic function</b></a>
- Synopsis
-1 #include <a href="#7.17"><stdatomic.h></a>
- void atomic_init(volatile A *obj, C value);
- Description
-2 The atomic_init generic function initializes the atomic object pointed to by obj to
- the value value, while also initializing any additional state that the implementation
- might need to carry for the atomic object.
-
-
-
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-
-3 Although this function initializes an atomic object, it does not avoid data races;
- concurrent access to the variable being initialized, even via an atomic operation,
- constitutes a data race.
- Returns
-4 The atomic_init generic function returns no value.
-5 EXAMPLE
- atomic_int guide;
- atomic_init(&guide, 42);
-
-<a name="7.17.3" href="#7.17.3"><b> 7.17.3 Order and consistency</b></a>
-1 The enumerated type memory_order specifies the detailed regular (non-atomic)
- memory synchronization operations as defined in <a href="#5.1.2.4">5.1.2.4</a> and may provide for operation
- ordering. Its enumeration constants are as follows:
- memory_order_relaxed
- memory_order_consume
- memory_order_acquire
- memory_order_release
- memory_order_acq_rel
- memory_order_seq_cst
-2 For memory_order_relaxed, no operation orders memory.
-3 For memory_order_release, memory_order_acq_rel, and
- memory_order_seq_cst, a store operation performs a release operation on the
- affected memory location.
-4 For memory_order_acquire, memory_order_acq_rel, and
- memory_order_seq_cst, a load operation performs an acquire operation on the
- affected memory location.
-5 For memory_order_consume, a load operation performs a consume operation on the
- affected memory location.
-6 For memory_order_seq_cst, there shall be a single total order S on all operations,
- consistent with the ''happens before'' order and modification orders for all affected
- locations, such that each memory_order_seq_cst operation that loads a value
- observes either the last preceding modification according to this order S, or the result of
- an operation that is not memory_order_seq_cst.
-7 NOTE 1 Although it is not explicitly required that S include lock operations, it can always be extended to
- an order that does include lock and unlock operations, since the ordering between those is already included
- in the ''happens before'' ordering.
-
-8 NOTE 2 Atomic operations specifying memory_order_relaxed are relaxed only with respect to
- memory ordering. Implementations must still guarantee that any given atomic access to a particular atomic
-
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-
- object be indivisible with respect to all other atomic accesses to that object.
-
-9 For an atomic operation B that reads the value of an atomic object M, if there is a
- memory_order_seq_cst fence X sequenced before B, then B observes either the
- last memory_order_seq_cst modification of M preceding X in the total order S or
- a later modification of M in its modification order.
-10 For atomic operations A and B on an atomic object M, where A modifies M and B takes
- its value, if there is a memory_order_seq_cst fence X such that A is sequenced
- before X and B follows X in S, then B observes either the effects of A or a later
- modification of M in its modification order.
-11 For atomic operations A and B on an atomic object M, where A modifies M and B takes
- its value, if there are memory_order_seq_cst fences X and Y such that A is
- sequenced before X, Y is sequenced before B, and X precedes Y in S, then B observes
- either the effects of A or a later modification of M in its modification order.
-12 Atomic read-modify-write operations shall always read the last value (in the modification
- order) stored before the write associated with the read-modify-write operation.
-13 An atomic store shall only store a value that has been computed from constants and
- program input values by a finite sequence of program evaluations, such that each
- evaluation observes the values of variables as computed by the last prior assignment in
- the sequence.247) The ordering of evaluations in this sequence shall be such that
- -- If an evaluation B observes a value computed by A in a different thread, then B does
- not happen before A.
- -- If an evaluation A is included in the sequence, then all evaluations that assign to the
- same variable and happen before A are also included.
-14 NOTE 3 The second requirement disallows ''out-of-thin-air'', or ''speculative'' stores of atomics when
- relaxed atomics are used. Since unordered operations are involved, evaluations may appear in this
- sequence out of thread order. For example, with x and y initially zero,
- // Thread 1:
- r1 = atomic_load_explicit(&y, memory_order_relaxed);
- atomic_store_explicit(&x, r1, memory_order_relaxed);
-
- // Thread 2:
- r2 = atomic_load_explicit(&x, memory_order_relaxed);
- atomic_store_explicit(&y, 42, memory_order_relaxed);
- is allowed to produce r1 == 42 && r2 == 42. The sequence of evaluations justifying this consists of:
-
-
-
-
- 247) Among other implications, atomic variables shall not decay.
-
-[<a name="#p274" href="p274">page 274</a>] (<a href="#Contents">Contents</a>)
-
- atomic_store_explicit(&y, 42, memory_order_relaxed);
- r1 = atomic_load_explicit(&y, memory_order_relaxed);
- atomic_store_explicit(&x, r1, memory_order_relaxed);
- r2 = atomic_load_explicit(&x, memory_order_relaxed);
- On the other hand,
- // Thread 1:
- r1 = atomic_load_explicit(&y, memory_order_relaxed);
- atomic_store_explicit(&x, r1, memory_order_relaxed);
-
- // Thread 2:
- r2 = atomic_load_explicit(&x, memory_order_relaxed);
- atomic_store_explicit(&y, r2, memory_order_relaxed);
- is not allowed to produce r1 == 42 && r2 = 42, since there is no sequence of evaluations that results
- in the computation of 42. In the absence of ''relaxed'' operations and read-modify-write operations with
- weaker than memory_order_acq_rel ordering, the second requirement has no impact.
-
- Recommended practice
-15 The requirements do not forbid r1 == 42 && r2 == 42 in the following example,
- with x and y initially zero:
- // Thread 1:
- r1 = atomic_load_explicit(&x, memory_order_relaxed);
- if (r1 == 42)
- atomic_store_explicit(&y, r1, memory_order_relaxed);
-
- // Thread 2:
- r2 = atomic_load_explicit(&y, memory_order_relaxed);
- if (r2 == 42)
- atomic_store_explicit(&x, 42, memory_order_relaxed);
- However, this is not useful behavior, and implementations should not allow it.
-16 Implementations should make atomic stores visible to atomic loads within a reasonable
- amount of time.
-<a name="7.17.3.1" href="#7.17.3.1"><b> 7.17.3.1 The kill_dependency macro</b></a>
- Synopsis
-1 #include <a href="#7.17"><stdatomic.h></a>
- type kill_dependency(type y);
- Description
-2 The kill_dependency macro terminates a dependency chain; the argument does not
- carry a dependency to the return value.
-
-
-
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-
- Returns
-3 The kill_dependency macro returns the value of y.
-<a name="7.17.4" href="#7.17.4"><b> 7.17.4 Fences</b></a>
-1 This subclause introduces synchronization primitives called fences. Fences can have
- acquire semantics, release semantics, or both. A fence with acquire semantics is called
- an acquire fence; a fence with release semantics is called a release fence.
-2 A release fence A synchronizes with an acquire fence B if there exist atomic operations
- X and Y , both operating on some atomic object M, such that A is sequenced before X, X
- modifies M, Y is sequenced before B, and Y reads the value written by X or a value
- written by any side effect in the hypothetical release sequence X would head if it were a
- release operation.
-3 A release fence A synchronizes with an atomic operation B that performs an acquire
- operation on an atomic object M if there exists an atomic operation X such that A is
- sequenced before X, X modifies M, and B reads the value written by X or a value written
- by any side effect in the hypothetical release sequence X would head if it were a release
- operation.
-4 An atomic operation A that is a release operation on an atomic object M synchronizes
- with an acquire fence B if there exists some atomic operation X on M such that X is
- sequenced before B and reads the value written by A or a value written by any side effect
- in the release sequence headed by A.
-<a name="7.17.4.1" href="#7.17.4.1"><b> 7.17.4.1 The atomic_thread_fence function</b></a>
- Synopsis
-1 #include <a href="#7.17"><stdatomic.h></a>
- void atomic_thread_fence(memory_order order);
- Description
-2 Depending on the value of order, this operation:
- -- has no effects, if order == memory_order_relaxed;
- -- is an acquire fence, if order == memory_order_acquire or order ==
- memory_order_consume;
- -- is a release fence, if order == memory_order_release;
- -- is both an acquire fence and a release fence, if order ==
- memory_order_acq_rel;
- -- is a sequentially consistent acquire and release fence, if order ==
- memory_order_seq_cst.
-
-
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-
- Returns
-3 The atomic_thread_fence function returns no value.
-<a name="7.17.4.2" href="#7.17.4.2"><b> 7.17.4.2 The atomic_signal_fence function</b></a>
- Synopsis
-1 #include <a href="#7.17"><stdatomic.h></a>
- void atomic_signal_fence(memory_order order);
- Description
-2 Equivalent to atomic_thread_fence(order), except that ''synchronizes with''
- relationships are established only between a thread and a signal handler executed in the
- same thread.
-3 NOTE 1 The atomic_signal_fence function can be used to specify the order in which actions
- performed by the thread become visible to the signal handler.
-
-4 NOTE 2 Compiler optimizations and reorderings of loads and stores are inhibited in the same way as with
- atomic_thread_fence, but the hardware fence instructions that atomic_thread_fence would
- have inserted are not emitted.
-
- Returns
-5 The atomic_signal_fence function returns no value.
-<a name="7.17.5" href="#7.17.5"><b> 7.17.5 Lock-free property</b></a>
-1 The atomic lock-free macros indicate the lock-free property of integer and address atomic
- types. A value of 0 indicates that the type is never lock-free; a value of 1 indicates that
- the type is sometimes lock-free; a value of 2 indicates that the type is always lock-free.
-2 NOTE Operations that are lock-free should also be address-free. That is, atomic operations on the same
- memory location via two different addresses will communicate atomically. The implementation should not
- depend on any per-process state. This restriction enables communication via memory mapped into a
- process more than once and memory shared between two processes.
-
-<a name="7.17.5.1" href="#7.17.5.1"><b> 7.17.5.1 The atomic_is_lock_free generic function</b></a>
- Synopsis
-1 #include <a href="#7.17"><stdatomic.h></a>
- _Bool atomic_is_lock_free(atomic_type const volatile *obj);
- Description
-2 The atomic_is_lock_free generic function indicates whether or not the object
- pointed to by obj is lock-free. atomic_type can be any atomic type.
- Returns
-3 The atomic_is_lock_free generic function returns nonzero (true) if and only if the
- object's operations are lock-free. The result of a lock-free query on one object cannot be
-
-[<a name="#p277" href="p277">page 277</a>] (<a href="#Contents">Contents</a>)
-
- inferred from the result of a lock-free query on another object.
-<a name="7.17.6" href="#7.17.6"><b> 7.17.6 Atomic integer and address types</b></a>
-1 For each line in the following table, the atomic type name is declared as the
- corresponding direct type.
-
-
-
-
-[<a name="#p278" href="p278">page 278</a>] (<a href="#Contents">Contents</a>)
-
-
-
- Atomic type name Direct type
- atomic_char _Atomic char
- atomic_schar _Atomic signed char
- atomic_uchar _Atomic unsigned char
- atomic_short _Atomic short
- atomic_ushort _Atomic unsigned short
- atomic_int _Atomic int
- atomic_uint _Atomic unsigned int
- atomic_long _Atomic long
- atomic_ulong _Atomic unsigned long
- atomic_llong _Atomic long long
- atomic_ullong _Atomic unsigned long long
- atomic_char16_t _Atomic char16_t
- atomic_char32_t _Atomic char32_t
- atomic_wchar_t _Atomic wchar_t
- atomic_int_least8_t _Atomic int_least8_t
- atomic_uint_least8_t _Atomic uint_least8_t
- atomic_int_least16_t _Atomic int_least16_t
- atomic_uint_least16_t _Atomic uint_least16_t
- atomic_int_least32_t _Atomic int_least32_t
- atomic_uint_least32_t _Atomic uint_least32_t
- atomic_int_least64_t _Atomic int_least64_t
- atomic_uint_least64_t _Atomic uint_least64_t
- atomic_int_fast8_t _Atomic int_fast8_t
- atomic_uint_fast8_t _Atomic uint_fast8_t
- atomic_int_fast16_t _Atomic int_fast16_t
- atomic_uint_fast16_t _Atomic uint_fast16_t
- atomic_int_fast32_t _Atomic int_fast32_t
- atomic_uint_fast32_t _Atomic uint_fast32_t
- atomic_int_fast64_t _Atomic int_fast64_t
- atomic_uint_fast64_t _Atomic uint_fast64_t
- atomic_intptr_t _Atomic intptr_t
- atomic_uintptr_t _Atomic uintptr_t
- atomic_size_t _Atomic size_t
- atomic_ptrdiff_t _Atomic ptrdiff_t
- atomic_intmax_t _Atomic intmax_t
- atomic_uintmax_t _Atomic uintmax_t
-2 The semantics of the operations on these types are defined in <a href="#7.17.7">7.17.7</a>.
-
-
-
-[<a name="#p279" href="p279">page 279</a>] (<a href="#Contents">Contents</a>)
-
-3 The atomic_bool type provides an atomic boolean.
-4 The atomic_address type provides atomic void * operations. The unit of
- addition/subtraction shall be one byte.
-5 NOTE The representation of atomic integer and address types need not have the same size as their
- corresponding regular types. They should have the same size whenever possible, as it eases effort required
- to port existing code.
-
-<a name="7.17.7" href="#7.17.7"><b> 7.17.7 Operations on atomic types</b></a>
-1 There are only a few kinds of operations on atomic types, though there are many
- instances of those kinds. This subclause specifies each general kind.
-<a name="7.17.7.1" href="#7.17.7.1"><b> 7.17.7.1 The atomic_store generic functions</b></a>
- Synopsis
-1 #include <a href="#7.17"><stdatomic.h></a>
- void atomic_store(volatile A *object, C desired);
- void atomic_store_explicit(volatile A *object,
- C desired, memory_order order);
- Description
-2 The order argument shall not be memory_order_acquire,
- memory_order_consume, nor memory_order_acq_rel. Atomically replace the
- value pointed to by object with the value of desired. Memory is affected according
- to the value of order.
- Returns
-3 The atomic_store generic functions return no value.
-<a name="7.17.7.2" href="#7.17.7.2"><b> 7.17.7.2 The atomic_load generic functions</b></a>
- Synopsis
-1 #include <a href="#7.17"><stdatomic.h></a>
- C atomic_load(volatile A *object);
- C atomic_load_explicit(volatile A *object,
- memory_order order);
- Description
-2 The order argument shall not be memory_order_release nor
- memory_order_acq_rel. Memory is affected according to the value of order.
- Returns
- Atomically returns the value pointed to by object.
-
-
-
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-
-<a name="7.17.7.3" href="#7.17.7.3"><b> 7.17.7.3 The atomic_exchange generic functions</b></a>
- Synopsis
-1 #include <a href="#7.17"><stdatomic.h></a>
- C atomic_exchange(volatile A *object, C desired);
- C atomic_exchange_explicit(volatile A *object,
- C desired, memory_order order);
- Description
-2 Atomically replace the value pointed to by object with desired. Memory is affected
- according to the value of order. These operations are read-modify-write operations
- (<a href="#5.1.2.4">5.1.2.4</a>).
- Returns
-3 Atomically returns the value pointed to by object immediately before the effects.
-<a name="7.17.7.4" href="#7.17.7.4"><b> 7.17.7.4 The atomic_compare_exchange generic functions</b></a>
- Synopsis
-1 #include <a href="#7.17"><stdatomic.h></a>
- _Bool atomic_compare_exchange_strong(volatile A *object,
- C *expected, C desired);
- _Bool atomic_compare_exchange_strong_explicit(
- volatile A *object, C *expected, C desired,
- memory_order success, memory_order failure);
- _Bool atomic_compare_exchange_weak(volatile A *object,
- C *expected, C desired);
- _Bool atomic_compare_exchange_weak_explicit(
- volatile A *object, C *expected, C desired,
- memory_order success, memory_order failure);
- Description
-2 The failure argument shall not be memory_order_release nor
- memory_order_acq_rel. The failure argument shall be no stronger than the
- success argument. Atomically, compares the value pointed to by object for equality
- with that in expected, and if true, replaces the value pointed to by object with
- desired, and if false, updates the value in expected with the value pointed to by
- object. Further, if the comparison is true, memory is affected according to the value of
- success, and if the comparison is false, memory is affected according to the value of
- failure. These operations are atomic read-modify-write operations (<a href="#5.1.2.4">5.1.2.4</a>).
-3 NOTE 1 The effect of the compare-and-exchange operations is
-
-
-
-
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-
- if (*object == *expected)
- *object = desired;
- else
- *expected = *object;
-
-4 The weak compare-and-exchange operations may fail spuriously, that is, return zero
- while leaving the value pointed to by expected unchanged.
-5 NOTE 2 This spurious failure enables implementation of compare-and-exchange on a broader class of
- machines, e.g. load-locked store-conditional machines.
-
-6 EXAMPLE A consequence of spurious failure is that nearly all uses of weak compare-and-exchange will
- be in a loop.
- exp = atomic_load(&cur);
- do {
- des = function(exp);
- } while (!atomic_compare_exchange_weak(&cur, &exp, des));
- When a compare-and-exchange is in a loop, the weak version will yield better performance on some
- platforms. When a weak compare-and-exchange would require a loop and a strong one would not, the
- strong one is preferable.
-
- Returns
-7 The result of the comparison.
-<a name="7.17.7.5" href="#7.17.7.5"><b> 7.17.7.5 The atomic_fetch and modify generic functions</b></a>
-1 The following operations perform arithmetic and bitwise computations. All of these
- operations are applicable to an object of any atomic integer type. Only addition and
- subtraction are applicable to atomic_address. None of these operations is applicable
- to atomic_bool. The key, operator, and computation correspondence is:
-
-
- key op computation
- add + addition
- sub - subtraction
- or | bitwise inclusive or
- xor ^ bitwise exclusive or
- and & bitwise and
- Synopsis
-2 #include <a href="#7.17"><stdatomic.h></a>
- C atomic_fetch_key(volatile A *object, M operand);
- C atomic_fetch_key_explicit(volatile A *object,
- M operand, memory_order order);
- Description
-3 Atomically replaces the value pointed to by object with the result of the computation
- applied to the value pointed to by object and the given operand. Memory is affected
-[<a name="#p282" href="p282">page 282</a>] (<a href="#Contents">Contents</a>)
-
- according to the value of order. These operations are atomic read-modify-write
- operations (<a href="#5.1.2.4">5.1.2.4</a>). For signed integer types, arithmetic is defined to use two's-
- complement representation. There are no undefined results. For address types, the result
- may be an undefined address, but the operations otherwise have no undefined behavior.
- Returns
-4 Atomically, the value pointed to by object immediately before the effects.
-5 NOTE The operation of the atomic_fetch and modify generic functions are nearly equivalent to the
- operation of the corresponding op= compound assignment operators. The only differences are that the
- compound assignment operators are not guaranteed to operate atomically, and the value yielded by a
- compound assignment operator is the updated value of the object, whereas the value returned by the
- atomic_fetch and modify generic functions is the previous value of the atomic object.
-
-<a name="7.17.8" href="#7.17.8"><b> 7.17.8 Atomic flag type and operations</b></a>
-1 The atomic_flag type provides the classic test-and-set functionality. It has two
- states, set and clear.
-2 Operations on an object of type atomic_flag shall be lock free.
-3 NOTE Hence the operations should also be address-free. No other type requires lock-free operations, so
- the atomic_flag type is the minimum hardware-implemented type needed to conform to this
- International standard. The remaining types can be emulated with atomic_flag, though with less than
- ideal properties.
-
-4 The macro ATOMIC_FLAG_INIT may be used to initialize an atomic_flag to the
- clear state. An atomic_flag that is not explicitly initialized with
- ATOMIC_FLAG_INIT is initially in an indeterminate state.
-5 EXAMPLE
- atomic_flag guard = ATOMIC_FLAG_INIT;
-
-<a name="7.17.8.1" href="#7.17.8.1"><b> 7.17.8.1 The atomic_flag_test_and_set functions</b></a>
- Synopsis
-1 #include <a href="#7.17"><stdatomic.h></a>
- bool atomic_flag_test_and_set(
- volatile atomic_flag *object);
- bool atomic_flag_test_and_set_explicit(
- volatile atomic_flag *object, memory_order order);
- Description
-2 Atomically sets the value pointed to by object to true. Memory is affected according
- to the value of order. These operations are atomic read-modify-write operations
- (<a href="#5.1.2.4">5.1.2.4</a>).
-
-
-
-
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-
- Returns
-3 Atomically, the value of the object immediately before the effects.
-<a name="7.17.8.2" href="#7.17.8.2"><b> 7.17.8.2 The atomic_flag_clear functions</b></a>
- Synopsis
-1 #include <a href="#7.17"><stdatomic.h></a>
- void atomic_flag_clear(volatile atomic_flag *object);
- void atomic_flag_clear_explicit(
- volatile atomic_flag *object, memory_order order);
- Description
-2 The order argument shall not be memory_order_acquire nor
- memory_order_acq_rel. Atomically sets the value pointed to by object to false.
- Memory is affected according to the value of order.
- Returns
-3 The atomic_flag_clear functions return no value.
-
-
-
-
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-
-<a name="7.18" href="#7.18"><b> 7.18 Boolean type and values <stdbool.h></b></a>
-1 The header <a href="#7.18"><stdbool.h></a> defines four macros.
-2 The macro
- bool
- expands to _Bool.
-3 The remaining three macros are suitable for use in #if preprocessing directives. They
- are
- true
- which expands to the integer constant 1,
- false
- which expands to the integer constant 0, and
- __bool_true_false_are_defined
- which expands to the integer constant 1.
-4 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
- redefine the macros bool, true, and false.248)
-
-
-
-
- 248) See ''future library directions'' (<a href="#7.30.7">7.30.7</a>).
-
-[<a name="#p285" href="p285">page 285</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.19" href="#7.19"><b> 7.19 Common definitions <stddef.h></b></a>
-1 The header <a href="#7.19"><stddef.h></a> defines the following macros and declares the following types.
- Some are also defined in other headers, as noted in their respective subclauses.
-2 The types are
- ptrdiff_t
- which is the signed integer type of the result of subtracting two pointers;
- size_t
- which is the unsigned integer type of the result of the sizeof operator;
- max_align_t
- which is an object type whose alignment is as great as is supported by the implementation
- in all contexts; and
- wchar_t
- which is an integer type whose range of values can represent distinct codes for all
- members of the largest extended character set specified among the supported locales; the
- null character shall have the code value zero. Each member of the basic character set
- shall have a code value equal to its value when used as the lone character in an integer
- character constant if an implementation does not define
- __STDC_MB_MIGHT_NEQ_WC__.
-3 The macros are
- NULL
- which expands to an implementation-defined null pointer constant; and
- offsetof(type, member-designator)
- which expands to an integer constant expression that has type size_t, the value of
- which is the offset in bytes, to the structure member (designated by member-designator),
- from the beginning of its structure (designated by type). The type and member designator
- shall be such that given
- static type t;
- then the expression &(t.member-designator) evaluates to an address constant. (If the
- specified member is a bit-field, the behavior is undefined.)
- Recommended practice
-4 The types used for size_t and ptrdiff_t should not have an integer conversion rank
- greater than that of signed long int unless the implementation supports objects
- large enough to make this necessary.
-
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-
-Forward references: localization (<a href="#7.11">7.11</a>).
-
-
-
-
-[<a name="#p287" href="p287">page 287</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.20" href="#7.20"><b> 7.20 Integer types <stdint.h></b></a>
-1 The header <a href="#7.20"><stdint.h></a> declares sets of integer types having specified widths, and
- defines corresponding sets of macros.249) It also defines macros that specify limits of
- integer types corresponding to types defined in other standard headers.
-2 Types are defined in the following categories:
- -- integer types having certain exact widths;
- -- integer types having at least certain specified widths;
- -- fastest integer types having at least certain specified widths;
- -- integer types wide enough to hold pointers to objects;
- -- integer types having greatest width.
- (Some of these types may denote the same type.)
-3 Corresponding macros specify limits of the declared types and construct suitable
- constants.
-4 For each type described herein that the implementation provides,250) <a href="#7.20"><stdint.h></a> shall
- declare that typedef name and define the associated macros. Conversely, for each type
- described herein that the implementation does not provide, <a href="#7.20"><stdint.h></a> shall not
- declare that typedef name nor shall it define the associated macros. An implementation
- shall provide those types described as ''required'', but need not provide any of the others
- (described as ''optional'').
-<a name="7.20.1" href="#7.20.1"><b> 7.20.1 Integer types</b></a>
-1 When typedef names differing only in the absence or presence of the initial u are defined,
- they shall denote corresponding signed and unsigned types as described in <a href="#6.2.5">6.2.5</a>; an
- implementation providing one of these corresponding types shall also provide the other.
-2 In the following descriptions, the symbol N represents an unsigned decimal integer with
- no leading zeros (e.g., 8 or 24, but not 04 or 048).
-
-
-
-
- 249) See ''future library directions'' (<a href="#7.30.8">7.30.8</a>).
- 250) Some of these types may denote implementation-defined extended integer types.
-
-[<a name="#p288" href="p288">page 288</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.20.1.1" href="#7.20.1.1"><b> 7.20.1.1 Exact-width integer types</b></a>
-1 The typedef name intN_t designates a signed integer type with width N , no padding
- bits, and a two's complement representation. Thus, int8_t denotes such a signed
- integer type with a width of exactly 8 bits.
-2 The typedef name uintN_t designates an unsigned integer type with width N and no
- padding bits. Thus, uint24_t denotes such an unsigned integer type with a width of
- exactly 24 bits.
-3 These types are optional. However, if an implementation provides integer types with
- widths of 8, 16, 32, or 64 bits, no padding bits, and (for the signed types) that have a
- two's complement representation, it shall define the corresponding typedef names.
-<a name="7.20.1.2" href="#7.20.1.2"><b> 7.20.1.2 Minimum-width integer types</b></a>
-1 The typedef name int_leastN_t designates a signed integer type with a width of at
- least N , such that no signed integer type with lesser size has at least the specified width.
- Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits.
-2 The typedef name uint_leastN_t designates an unsigned integer type with a width
- of at least N , such that no unsigned integer type with lesser size has at least the specified
- width. Thus, uint_least16_t denotes an unsigned integer type with a width of at
- least 16 bits.
-3 The following types are required:
- int_least8_t uint_least8_t
- int_least16_t uint_least16_t
- int_least32_t uint_least32_t
- int_least64_t uint_least64_t
- All other types of this form are optional.
-<a name="7.20.1.3" href="#7.20.1.3"><b> 7.20.1.3 Fastest minimum-width integer types</b></a>
-1 Each of the following types designates an integer type that is usually fastest251) to operate
- with among all integer types that have at least the specified width.
-2 The typedef name int_fastN_t designates the fastest signed integer type with a width
- of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer
- type with a width of at least N .
-
-
-
-
- 251) The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear
- grounds for choosing one type over another, it will simply pick some integer type satisfying the
- signedness and width requirements.
-
-[<a name="#p289" href="p289">page 289</a>] (<a href="#Contents">Contents</a>)
-
-3 The following types are required:
- int_fast8_t uint_fast8_t
- int_fast16_t uint_fast16_t
- int_fast32_t uint_fast32_t
- int_fast64_t uint_fast64_t
- All other types of this form are optional.
-<a name="7.20.1.4" href="#7.20.1.4"><b> 7.20.1.4 Integer types capable of holding object pointers</b></a>
-1 The following type designates a signed integer type with the property that any valid
- pointer to void can be converted to this type, then converted back to pointer to void,
- and the result will compare equal to the original pointer:
- intptr_t
- The following type designates an unsigned integer type with the property that any valid
- pointer to void can be converted to this type, then converted back to pointer to void,
- and the result will compare equal to the original pointer:
- uintptr_t
- These types are optional.
-<a name="7.20.1.5" href="#7.20.1.5"><b> 7.20.1.5 Greatest-width integer types</b></a>
-1 The following type designates a signed integer type capable of representing any value of
- any signed integer type:
- intmax_t
- The following type designates an unsigned integer type capable of representing any value
- of any unsigned integer type:
- uintmax_t
- These types are required.
-<a name="7.20.2" href="#7.20.2"><b> 7.20.2 Limits of specified-width integer types</b></a>
-1 The following object-like macros specify the minimum and maximum limits of the types
- declared in <a href="#7.20"><stdint.h></a>. Each macro name corresponds to a similar type name in
-<a name="7.20.1" href="#7.20.1"><b> 7.20.1.</b></a>
-2 Each instance of any defined macro shall be replaced by a constant expression suitable
- for use in #if preprocessing directives, and this expression shall have the same type as
- would an expression that is an object of the corresponding type converted according to
- the integer promotions. Its implementation-defined value shall be equal to or greater in
- magnitude (absolute value) than the corresponding value given below, with the same sign,
- except where stated to be exactly the given value.
-
-[<a name="#p290" href="p290">page 290</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.20.2.1" href="#7.20.2.1"><b> 7.20.2.1 Limits of exact-width integer types</b></a>
-1 -- minimum values of exact-width signed integer types
- INTN_MIN exactly -(2 N -1 )
- -- maximum values of exact-width signed integer types
- INTN_MAX exactly 2 N -1 - 1
- -- maximum values of exact-width unsigned integer types
- UINTN_MAX exactly 2 N - 1
-<a name="7.20.2.2" href="#7.20.2.2"><b> 7.20.2.2 Limits of minimum-width integer types</b></a>
-1 -- minimum values of minimum-width signed integer types
- INT_LEASTN_MIN -(2 N -1 - 1)
- -- maximum values of minimum-width signed integer types
- INT_LEASTN_MAX 2 N -1 - 1
- -- maximum values of minimum-width unsigned integer types
- UINT_LEASTN_MAX 2N - 1
-<a name="7.20.2.3" href="#7.20.2.3"><b> 7.20.2.3 Limits of fastest minimum-width integer types</b></a>
-1 -- minimum values of fastest minimum-width signed integer types
- INT_FASTN_MIN -(2 N -1 - 1)
- -- maximum values of fastest minimum-width signed integer types
- INT_FASTN_MAX 2 N -1 - 1
- -- maximum values of fastest minimum-width unsigned integer types
- UINT_FASTN_MAX 2N - 1
-<a name="7.20.2.4" href="#7.20.2.4"><b> 7.20.2.4 Limits of integer types capable of holding object pointers</b></a>
-1 -- minimum value of pointer-holding signed integer type
- INTPTR_MIN -(215 - 1)
- -- maximum value of pointer-holding signed integer type
- INTPTR_MAX 215 - 1
- -- maximum value of pointer-holding unsigned integer type
- UINTPTR_MAX 216 - 1
-
-
-
-[<a name="#p291" href="p291">page 291</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.20.2.5" href="#7.20.2.5"><b> 7.20.2.5 Limits of greatest-width integer types</b></a>
-1 -- minimum value of greatest-width signed integer type
- INTMAX_MIN -(263 - 1)
- -- maximum value of greatest-width signed integer type
- INTMAX_MAX 263 - 1
- -- maximum value of greatest-width unsigned integer type
- UINTMAX_MAX 264 - 1
-<a name="7.20.3" href="#7.20.3"><b> 7.20.3 Limits of other integer types</b></a>
-1 The following object-like macros specify the minimum and maximum limits of integer
- types corresponding to types defined in other standard headers.
-2 Each instance of these macros shall be replaced by a constant expression suitable for use
- in #if preprocessing directives, and this expression shall have the same type as would an
- expression that is an object of the corresponding type converted according to the integer
- promotions. Its implementation-defined value shall be equal to or greater in magnitude
- (absolute value) than the corresponding value given below, with the same sign. An
- implementation shall define only the macros corresponding to those typedef names it
- actually provides.252)
- -- limits of ptrdiff_t
- PTRDIFF_MIN -65535
- PTRDIFF_MAX +65535
- -- limits of sig_atomic_t
- SIG_ATOMIC_MIN see below
- SIG_ATOMIC_MAX see below
- -- limit of size_t
- SIZE_MAX 65535
- -- limits of wchar_t
- WCHAR_MIN see below
- WCHAR_MAX see below
- -- limits of wint_t
-
-
-
-
- 252) A freestanding implementation need not provide all of these types.
-
-[<a name="#p292" href="p292">page 292</a>] (<a href="#Contents">Contents</a>)
-
- WINT_MIN see below
- WINT_MAX see below
-3 If sig_atomic_t (see <a href="#7.14">7.14</a>) is defined as a signed integer type, the value of
- SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX
- shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
- type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
- SIG_ATOMIC_MAX shall be no less than 255.
-4 If wchar_t (see <a href="#7.19">7.19</a>) is defined as a signed integer type, the value of WCHAR_MIN
- shall be no greater than -127 and the value of WCHAR_MAX shall be no less than 127;
- otherwise, wchar_t is defined as an unsigned integer type, and the value of
- WCHAR_MIN shall be 0 and the value of WCHAR_MAX shall be no less than 255.253)
-5 If wint_t (see <a href="#7.28">7.28</a>) is defined as a signed integer type, the value of WINT_MIN shall
- be no greater than -32767 and the value of WINT_MAX shall be no less than 32767;
- otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
- shall be 0 and the value of WINT_MAX shall be no less than 65535.
-<a name="7.20.4" href="#7.20.4"><b> 7.20.4 Macros for integer constants</b></a>
-1 The following function-like macros expand to integer constants suitable for initializing
- objects that have integer types corresponding to types defined in <a href="#7.20"><stdint.h></a>. Each
- macro name corresponds to a similar type name in <a href="#7.20.1.2">7.20.1.2</a> or <a href="#7.20.1.5">7.20.1.5</a>.
-2 The argument in any instance of these macros shall be an unsuffixed integer constant (as
- defined in <a href="#6.4.4.1">6.4.4.1</a>) with a value that does not exceed the limits for the corresponding type.
-3 Each invocation of one of these macros shall expand to an integer constant expression
- suitable for use in #if preprocessing directives. The type of the expression shall have
- the same type as would an expression of the corresponding type converted according to
- the integer promotions. The value of the expression shall be that of the argument.
-<a name="7.20.4.1" href="#7.20.4.1"><b> 7.20.4.1 Macros for minimum-width integer constants</b></a>
-1 The macro INTN_C(value) shall expand to an integer constant expression
- corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
- to an integer constant expression corresponding to the type uint_leastN_t. For
- example, if uint_least64_t is a name for the type unsigned long long int,
- then UINT64_C(0x123) might expand to the integer constant 0x123ULL.
-
-
-
-
- 253) The values WCHAR_MIN and WCHAR_MAX do not necessarily correspond to members of the extended
- character set.
-
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-
-<a name="7.20.4.2" href="#7.20.4.2"><b> 7.20.4.2 Macros for greatest-width integer constants</b></a>
-1 The following macro expands to an integer constant expression having the value specified
- by its argument and the type intmax_t:
- INTMAX_C(value)
- The following macro expands to an integer constant expression having the value specified
- by its argument and the type uintmax_t:
- UINTMAX_C(value)
-
-
-
-
-[<a name="#p294" href="p294">page 294</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.21" href="#7.21"><b> 7.21 Input/output <stdio.h></b></a>
-<a name="7.21.1" href="#7.21.1"><b> 7.21.1 Introduction</b></a>
-1 The header <a href="#7.21"><stdio.h></a> defines several macros, and declares three types and many
- functions for performing input and output.
-2 The types declared are size_t (described in <a href="#7.19">7.19</a>);
- FILE
- which is an object type capable of recording all the information needed to control a
- stream, including its file position indicator, a pointer to its associated buffer (if any), an
- error indicator that records whether a read/write error has occurred, and an end-of-file
- indicator that records whether the end of the file has been reached; and
- fpos_t
- which is a complete object type other than an array type capable of recording all the
- information needed to specify uniquely every position within a file.
-3 The macros are NULL (described in <a href="#7.19">7.19</a>);
- _IOFBF
- _IOLBF
- _IONBF
- which expand to integer constant expressions with distinct values, suitable for use as the
- third argument to the setvbuf function;
- BUFSIZ
- which expands to an integer constant expression that is the size of the buffer used by the
- setbuf function;
- EOF
- which expands to an integer constant expression, with type int and a negative value, that
- is returned by several functions to indicate end-of-file, that is, no more input from a
- stream;
- FOPEN_MAX
- which expands to an integer constant expression that is the minimum number of files that
- the implementation guarantees can be open simultaneously;
- FILENAME_MAX
- which expands to an integer constant expression that is the size needed for an array of
- char large enough to hold the longest file name string that the implementation
-
-
-
-[<a name="#p295" href="p295">page 295</a>] (<a href="#Contents">Contents</a>)
-
- guarantees can be opened;254)
- L_tmpnam
- which expands to an integer constant expression that is the size needed for an array of
- char large enough to hold a temporary file name string generated by the tmpnam
- function;
- SEEK_CUR
- SEEK_END
- SEEK_SET
- which expand to integer constant expressions with distinct values, suitable for use as the
- third argument to the fseek function;
- TMP_MAX
- which expands to an integer constant expression that is the minimum number of unique
- file names that can be generated by the tmpnam function;
- stderr
- stdin
- stdout
- which are expressions of type ''pointer to FILE'' that point to the FILE objects
- associated, respectively, with the standard error, input, and output streams.
-4 The header <a href="#7.28"><wchar.h></a> declares a number of functions useful for wide character input
- and output. The wide character input/output functions described in that subclause
- provide operations analogous to most of those described here, except that the
- fundamental units internal to the program are wide characters. The external
- representation (in the file) is a sequence of ''generalized'' multibyte characters, as
- described further in <a href="#7.21.3">7.21.3</a>.
-5 The input/output functions are given the following collective terms:
- -- The wide character input functions -- those functions described in <a href="#7.28">7.28</a> that perform
- input into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar,
- fwscanf, wscanf, vfwscanf, and vwscanf.
- -- The wide character output functions -- those functions described in <a href="#7.28">7.28</a> that perform
- output from wide characters and wide strings: fputwc, fputws, putwc,
- putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
-
-
- 254) If the implementation imposes no practical limit on the length of file name strings, the value of
- FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
- string. Of course, file name string contents are subject to other system-specific constraints; therefore
- all possible strings of length FILENAME_MAX cannot be expected to be opened successfully.
-
-[<a name="#p296" href="p296">page 296</a>] (<a href="#Contents">Contents</a>)
-
- -- The wide character input/output functions -- the union of the ungetwc function, the
- wide character input functions, and the wide character output functions.
- -- The byte input/output functions -- those functions described in this subclause that
- perform input/output: fgetc, fgets, fprintf, fputc, fputs, fread,
- fscanf, fwrite, getc, getchar, printf, putc, putchar, puts, scanf,
- ungetc, vfprintf, vfscanf, vprintf, and vscanf.
- Forward references: files (<a href="#7.21.3">7.21.3</a>), the fseek function (<a href="#7.21.9.2">7.21.9.2</a>), streams (<a href="#7.21.2">7.21.2</a>), the
- tmpnam function (<a href="#7.21.4.4">7.21.4.4</a>), <a href="#7.28"><wchar.h></a> (<a href="#7.28">7.28</a>).
-<a name="7.21.2" href="#7.21.2"><b> 7.21.2 Streams</b></a>
-1 Input and output, whether to or from physical devices such as terminals and tape drives,
- or whether to or from files supported on structured storage devices, are mapped into
- logical data streams, whose properties are more uniform than their various inputs and
- outputs. Two forms of mapping are supported, for text streams and for binary
- streams.255)
-2 A text stream is an ordered sequence of characters composed into lines, each line
- consisting of zero or more characters plus a terminating new-line character. Whether the
- last line requires a terminating new-line character is implementation-defined. Characters
- may have to be added, altered, or deleted on input and output to conform to differing
- conventions for representing text in the host environment. Thus, there need not be a one-
- to-one correspondence between the characters in a stream and those in the external
- representation. Data read in from a text stream will necessarily compare equal to the data
- that were earlier written out to that stream only if: the data consist only of printing
- characters and the control characters horizontal tab and new-line; no new-line character is
- immediately preceded by space characters; and the last character is a new-line character.
- Whether space characters that are written out immediately before a new-line character
- appear when read in is implementation-defined.
-3 A binary stream is an ordered sequence of characters that can transparently record
- internal data. Data read in from a binary stream shall compare equal to the data that were
- earlier written out to that stream, under the same implementation. Such a stream may,
- however, have an implementation-defined number of null characters appended to the end
- of the stream.
-4 Each stream has an orientation. After a stream is associated with an external file, but
- before any operations are performed on it, the stream is without orientation. Once a wide
- character input/output function has been applied to a stream without orientation, the
-
-
- 255) An implementation need not distinguish between text streams and binary streams. In such an
- implementation, there need be no new-line characters in a text stream nor any limit to the length of a
- line.
-
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-
- stream becomes a wide-oriented stream. Similarly, once a byte input/output function has
- been applied to a stream without orientation, the stream becomes a byte-oriented stream.
- Only a call to the freopen function or the fwide function can otherwise alter the
- orientation of a stream. (A successful call to freopen removes any orientation.)256)
-5 Byte input/output functions shall not be applied to a wide-oriented stream and wide
- character input/output functions shall not be applied to a byte-oriented stream. The
- remaining stream operations do not affect, and are not affected by, a stream's orientation,
- except for the following additional restrictions:
- -- Binary wide-oriented streams have the file-positioning restrictions ascribed to both
- text and binary streams.
- -- For wide-oriented streams, after a successful call to a file-positioning function that
- leaves the file position indicator prior to the end-of-file, a wide character output
- function can overwrite a partial multibyte character; any file contents beyond the
- byte(s) written are henceforth indeterminate.
-6 Each wide-oriented stream has an associated mbstate_t object that stores the current
- parse state of the stream. A successful call to fgetpos stores a representation of the
- value of this mbstate_t object as part of the value of the fpos_t object. A later
- successful call to fsetpos using the same stored fpos_t value restores the value of
- the associated mbstate_t object as well as the position within the controlled stream.
- Environmental limits
-7 An implementation shall support text files with lines containing at least 254 characters,
- including the terminating new-line character. The value of the macro BUFSIZ shall be at
- least 256.
- Forward references: the freopen function (<a href="#7.21.5.4">7.21.5.4</a>), the fwide function (<a href="#7.28.3.5">7.28.3.5</a>),
- mbstate_t (<a href="#7.29.1">7.29.1</a>), the fgetpos function (<a href="#7.21.9.1">7.21.9.1</a>), the fsetpos function
- (<a href="#7.21.9.3">7.21.9.3</a>).
-
-
-
-
- 256) The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
-
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-
-<a name="7.21.3" href="#7.21.3"><b> 7.21.3 Files</b></a>
-1 A stream is associated with an external file (which may be a physical device) by opening
- a file, which may involve creating a new file. Creating an existing file causes its former
- contents to be discarded, if necessary. If a file can support positioning requests (such as a
- disk file, as opposed to a terminal), then a file position indicator associated with the
- stream is positioned at the start (character number zero) of the file, unless the file is
- opened with append mode in which case it is implementation-defined whether the file
- position indicator is initially positioned at the beginning or the end of the file. The file
- position indicator is maintained by subsequent reads, writes, and positioning requests, to
- facilitate an orderly progression through the file.
-2 Binary files are not truncated, except as defined in <a href="#7.21.5.3">7.21.5.3</a>. Whether a write on a text
- stream causes the associated file to be truncated beyond that point is implementation-
- defined.
-3 When a stream is unbuffered, characters are intended to appear from the source or at the
- destination as soon as possible. Otherwise characters may be accumulated and
- transmitted to or from the host environment as a block. When a stream is fully buffered,
- characters are intended to be transmitted to or from the host environment as a block when
- a buffer is filled. When a stream is line buffered, characters are intended to be
- transmitted to or from the host environment as a block when a new-line character is
- encountered. Furthermore, characters are intended to be transmitted as a block to the host
- environment when a buffer is filled, when input is requested on an unbuffered stream, or
- when input is requested on a line buffered stream that requires the transmission of
- characters from the host environment. Support for these characteristics is
- implementation-defined, and may be affected via the setbuf and setvbuf functions.
-4 A file may be disassociated from a controlling stream by closing the file. Output streams
- are flushed (any unwritten buffer contents are transmitted to the host environment) before
- the stream is disassociated from the file. The value of a pointer to a FILE object is
- indeterminate after the associated file is closed (including the standard text streams).
- Whether a file of zero length (on which no characters have been written by an output
- stream) actually exists is implementation-defined.
-5 The file may be subsequently reopened, by the same or another program execution, and
- its contents reclaimed or modified (if it can be repositioned at its start). If the main
- function returns to its original caller, or if the exit function is called, all open files are
- closed (hence all output streams are flushed) before program termination. Other paths to
- program termination, such as calling the abort function, need not close all files
- properly.
-6 The address of the FILE object used to control a stream may be significant; a copy of a
- FILE object need not serve in place of the original.
-
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-
-7 At program startup, three text streams are predefined and need not be opened explicitly
- -- standard input (for reading conventional input), standard output (for writing
- conventional output), and standard error (for writing diagnostic output). As initially
- opened, the standard error stream is not fully buffered; the standard input and standard
- output streams are fully buffered if and only if the stream can be determined not to refer
- to an interactive device.
-8 Functions that open additional (nontemporary) files require a file name, which is a string.
- The rules for composing valid file names are implementation-defined. Whether the same
- file can be simultaneously open multiple times is also implementation-defined.
-9 Although both text and binary wide-oriented streams are conceptually sequences of wide
- characters, the external file associated with a wide-oriented stream is a sequence of
- multibyte characters, generalized as follows:
- -- Multibyte encodings within files may contain embedded null bytes (unlike multibyte
- encodings valid for use internal to the program).
- -- A file need not begin nor end in the initial shift state.257)
-10 Moreover, the encodings used for multibyte characters may differ among files. Both the
- nature and choice of such encodings are implementation-defined.
-11 The wide character input functions read multibyte characters from the stream and convert
- them to wide characters as if they were read by successive calls to the fgetwc function.
- Each conversion occurs as if by a call to the mbrtowc function, with the conversion state
- described by the stream's own mbstate_t object. The byte input functions read
- characters from the stream as if by successive calls to the fgetc function.
-12 The wide character output functions convert wide characters to multibyte characters and
- write them to the stream as if they were written by successive calls to the fputwc
- function. Each conversion occurs as if by a call to the wcrtomb function, with the
- conversion state described by the stream's own mbstate_t object. The byte output
- functions write characters to the stream as if by successive calls to the fputc function.
-13 In some cases, some of the byte input/output functions also perform conversions between
- multibyte characters and wide characters. These conversions also occur as if by calls to
- the mbrtowc and wcrtomb functions.
-14 An encoding error occurs if the character sequence presented to the underlying
- mbrtowc function does not form a valid (generalized) multibyte character, or if the code
- value passed to the underlying wcrtomb does not correspond to a valid (generalized)
-
-
- 257) Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END), has
- undefined behavior for a binary stream (because of possible trailing null characters) or for any stream
- with state-dependent encoding that does not assuredly end in the initial shift state.
-
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-
- multibyte character. The wide character input/output functions and the byte input/output
- functions store the value of the macro EILSEQ in errno if and only if an encoding error
- occurs.
- Environmental limits
-15 The value of FOPEN_MAX shall be at least eight, including the three standard text
- streams.
- Forward references: the exit function (<a href="#7.22.4.4">7.22.4.4</a>), the fgetc function (<a href="#7.21.7.1">7.21.7.1</a>), the
- fopen function (<a href="#7.21.5.3">7.21.5.3</a>), the fputc function (<a href="#7.21.7.3">7.21.7.3</a>), the setbuf function
- (<a href="#7.21.5.5">7.21.5.5</a>), the setvbuf function (<a href="#7.21.5.6">7.21.5.6</a>), the fgetwc function (<a href="#7.28.3.1">7.28.3.1</a>), the
- fputwc function (<a href="#7.28.3.3">7.28.3.3</a>), conversion state (<a href="#7.28.6">7.28.6</a>), the mbrtowc function
- (<a href="#7.28.6.3.2">7.28.6.3.2</a>), the wcrtomb function (<a href="#7.28.6.3.3">7.28.6.3.3</a>).
-<a name="7.21.4" href="#7.21.4"><b> 7.21.4 Operations on files</b></a>
-<a name="7.21.4.1" href="#7.21.4.1"><b> 7.21.4.1 The remove function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int remove(const char *filename);
- Description
-2 The remove function causes the file whose name is the string pointed to by filename
- to be no longer accessible by that name. A subsequent attempt to open that file using that
- name will fail, unless it is created anew. If the file is open, the behavior of the remove
- function is implementation-defined.
- Returns
-3 The remove function returns zero if the operation succeeds, nonzero if it fails.
-<a name="7.21.4.2" href="#7.21.4.2"><b> 7.21.4.2 The rename function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int rename(const char *old, const char *new);
- Description
-2 The rename function causes the file whose name is the string pointed to by old to be
- henceforth known by the name given by the string pointed to by new. The file named
- old is no longer accessible by that name. If a file named by the string pointed to by new
- exists prior to the call to the rename function, the behavior is implementation-defined.
-
-
-
-
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-
- Returns
-3 The rename function returns zero if the operation succeeds, nonzero if it fails,258) in
- which case if the file existed previously it is still known by its original name.
-<a name="7.21.4.3" href="#7.21.4.3"><b> 7.21.4.3 The tmpfile function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- FILE *tmpfile(void);
- Description
-2 The tmpfile function creates a temporary binary file that is different from any other
- existing file and that will automatically be removed when it is closed or at program
- termination. If the program terminates abnormally, whether an open temporary file is
- removed is implementation-defined. The file is opened for update with "wb+" mode.
- Recommended practice
-3 It should be possible to open at least TMP_MAX temporary files during the lifetime of the
- program (this limit may be shared with tmpnam) and there should be no limit on the
- number simultaneously open other than this limit and any limit on the number of open
- files (FOPEN_MAX).
- Returns
-4 The tmpfile function returns a pointer to the stream of the file that it created. If the file
- cannot be created, the tmpfile function returns a null pointer.
- Forward references: the fopen function (<a href="#7.21.5.3">7.21.5.3</a>).
-<a name="7.21.4.4" href="#7.21.4.4"><b> 7.21.4.4 The tmpnam function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- char *tmpnam(char *s);
- Description
-2 The tmpnam function generates a string that is a valid file name and that is not the same
- as the name of an existing file.259) The function is potentially capable of generating at
-
-
- 258) Among the reasons the implementation may cause the rename function to fail are that the file is open
- or that it is necessary to copy its contents to effectuate its renaming.
- 259) Files created using strings generated by the tmpnam function are temporary only in the sense that
- their names should not collide with those generated by conventional naming rules for the
- implementation. It is still necessary to use the remove function to remove such files when their use
- is ended, and before program termination.
-
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-
- least TMP_MAX different strings, but any or all of them may already be in use by existing
- files and thus not be suitable return values.
-3 The tmpnam function generates a different string each time it is called.
-4 Calls to the tmpnam function with a null pointer argument may introduce data races with
- each other. The implementation shall behave as if no library function calls the tmpnam
- function.
- Returns
-5 If no suitable string can be generated, the tmpnam function returns a null pointer.
- Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an
- internal static object and returns a pointer to that object (subsequent calls to the tmpnam
- function may modify the same object). If the argument is not a null pointer, it is assumed
- to point to an array of at least L_tmpnam chars; the tmpnam function writes its result
- in that array and returns the argument as its value.
- Environmental limits
-6 The value of the macro TMP_MAX shall be at least 25.
-<a name="7.21.5" href="#7.21.5"><b> 7.21.5 File access functions</b></a>
-<a name="7.21.5.1" href="#7.21.5.1"><b> 7.21.5.1 The fclose function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int fclose(FILE *stream);
- Description
-2 A successful call to the fclose function causes the stream pointed to by stream to be
- flushed and the associated file to be closed. Any unwritten buffered data for the stream
- are delivered to the host environment to be written to the file; any unread buffered data
- are discarded. Whether or not the call succeeds, the stream is disassociated from the file
- and any buffer set by the setbuf or setvbuf function is disassociated from the stream
- (and deallocated if it was automatically allocated).
- Returns
-3 The fclose function returns zero if the stream was successfully closed, or EOF if any
- errors were detected.
-
-
-
-
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-
-<a name="7.21.5.2" href="#7.21.5.2"><b> 7.21.5.2 The fflush function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int fflush(FILE *stream);
- Description
-2 If stream points to an output stream or an update stream in which the most recent
- operation was not input, the fflush function causes any unwritten data for that stream
- to be delivered to the host environment to be written to the file; otherwise, the behavior is
- undefined.
-3 If stream is a null pointer, the fflush function performs this flushing action on all
- streams for which the behavior is defined above.
- Returns
-4 The fflush function sets the error indicator for the stream and returns EOF if a write
- error occurs, otherwise it returns zero.
- Forward references: the fopen function (<a href="#7.21.5.3">7.21.5.3</a>).
-<a name="7.21.5.3" href="#7.21.5.3"><b> 7.21.5.3 The fopen function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- FILE *fopen(const char * restrict filename,
- const char * restrict mode);
- Description
-2 The fopen function opens the file whose name is the string pointed to by filename,
- and associates a stream with it.
-3 The argument mode points to a string. If the string is one of the following, the file is
- open in the indicated mode. Otherwise, the behavior is undefined.260)
- r open text file for reading
- w truncate to zero length or create text file for writing
- wx create text file for writing
- a append; open or create text file for writing at end-of-file
- rb open binary file for reading
- wb truncate to zero length or create binary file for writing
-
-
- 260) If the string begins with one of the above sequences, the implementation might choose to ignore the
- remaining characters, or it might use them to select different kinds of a file (some of which might not
- conform to the properties in <a href="#7.21.2">7.21.2</a>).
-
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-
- wbx create binary file for writing
- ab append; open or create binary file for writing at end-of-file
- r+ open text file for update (reading and writing)
- w+ truncate to zero length or create text file for update
- w+x create text file for update
- a+ append; open or create text file for update, writing at end-of-file
- r+b or rb+ open binary file for update (reading and writing)
- w+b or wb+ truncate to zero length or create binary file for update
- w+bx or wb+x create binary file for update
- a+b or ab+ append; open or create binary file for update, writing at end-of-file
-4 Opening a file with read mode ('r' as the first character in the mode argument) fails if
- the file does not exist or cannot be read.
-5 Opening a file with exclusive mode ('x' as the last character in the mode argument)
- fails if the file already exists or cannot be created. Otherwise, the file is created with
- exclusive (also known as non-shared) access to the extent that the underlying system
- supports exclusive access.
-6 Opening a file with append mode ('a' as the first character in the mode argument)
- causes all subsequent writes to the file to be forced to the then current end-of-file,
- regardless of intervening calls to the fseek function. In some implementations, opening
- a binary file with append mode ('b' as the second or third character in the above list of
- mode argument values) may initially position the file position indicator for the stream
- beyond the last data written, because of null character padding.
-7 When a file is opened with update mode ('+' as the second or third character in the
- above list of mode argument values), both input and output may be performed on the
- associated stream. However, output shall not be directly followed by input without an
- intervening call to the fflush function or to a file positioning function (fseek,
- fsetpos, or rewind), and input shall not be directly followed by output without an
- intervening call to a file positioning function, unless the input operation encounters end-
- of-file. Opening (or creating) a text file with update mode may instead open (or create) a
- binary stream in some implementations.
-8 When opened, a stream is fully buffered if and only if it can be determined not to refer to
- an interactive device. The error and end-of-file indicators for the stream are cleared.
- Returns
-9 The fopen function returns a pointer to the object controlling the stream. If the open
- operation fails, fopen returns a null pointer.
- Forward references: file positioning functions (<a href="#7.21.9">7.21.9</a>).
-
-
-
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-
-<a name="7.21.5.4" href="#7.21.5.4"><b> 7.21.5.4 The freopen function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- FILE *freopen(const char * restrict filename,
- const char * restrict mode,
- FILE * restrict stream);
- Description
-2 The freopen function opens the file whose name is the string pointed to by filename
- and associates the stream pointed to by stream with it. The mode argument is used just
- as in the fopen function.261)
-3 If filename is a null pointer, the freopen function attempts to change the mode of
- the stream to that specified by mode, as if the name of the file currently associated with
- the stream had been used. It is implementation-defined which changes of mode are
- permitted (if any), and under what circumstances.
-4 The freopen function first attempts to close any file that is associated with the specified
- stream. Failure to close the file is ignored. The error and end-of-file indicators for the
- stream are cleared.
- Returns
-5 The freopen function returns a null pointer if the open operation fails. Otherwise,
- freopen returns the value of stream.
-<a name="7.21.5.5" href="#7.21.5.5"><b> 7.21.5.5 The setbuf function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- void setbuf(FILE * restrict stream,
- char * restrict buf);
- Description
-2 Except that it returns no value, the setbuf function is equivalent to the setvbuf
- function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
- is a null pointer), with the value _IONBF for mode.
-
-
-
-
- 261) The primary use of the freopen function is to change the file associated with a standard text stream
- (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value
- returned by the fopen function may be assigned.
-
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-
- Returns
-3 The setbuf function returns no value.
- Forward references: the setvbuf function (<a href="#7.21.5.6">7.21.5.6</a>).
-<a name="7.21.5.6" href="#7.21.5.6"><b> 7.21.5.6 The setvbuf function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int setvbuf(FILE * restrict stream,
- char * restrict buf,
- int mode, size_t size);
- Description
-2 The setvbuf function may be used only after the stream pointed to by stream has
- been associated with an open file and before any other operation (other than an
- unsuccessful call to setvbuf) is performed on the stream. The argument mode
- determines how stream will be buffered, as follows: _IOFBF causes input/output to be
- fully buffered; _IOLBF causes input/output to be line buffered; _IONBF causes
- input/output to be unbuffered. If buf is not a null pointer, the array it points to may be
- used instead of a buffer allocated by the setvbuf function262) and the argument size
- specifies the size of the array; otherwise, size may determine the size of a buffer
- allocated by the setvbuf function. The contents of the array at any time are
- indeterminate.
- Returns
-3 The setvbuf function returns zero on success, or nonzero if an invalid value is given
- for mode or if the request cannot be honored.
-
-
-
-
- 262) The buffer has to have a lifetime at least as great as the open stream, so the stream should be closed
- before a buffer that has automatic storage duration is deallocated upon block exit.
-
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-
-<a name="7.21.6" href="#7.21.6"><b> 7.21.6 Formatted input/output functions</b></a>
-1 The formatted input/output functions shall behave as if there is a sequence point after the
- actions associated with each specifier.263)
-<a name="7.21.6.1" href="#7.21.6.1"><b> 7.21.6.1 The fprintf function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int fprintf(FILE * restrict stream,
- const char * restrict format, ...);
- Description
-2 The fprintf function writes output to the stream pointed to by stream, under control
- of the string pointed to by format that specifies how subsequent arguments are
- converted for output. If there are insufficient arguments for the format, the behavior is
- undefined. If the format is exhausted while arguments remain, the excess arguments are
- evaluated (as always) but are otherwise ignored. The fprintf function returns when
- the end of the format string is encountered.
-3 The format shall be a multibyte character sequence, beginning and ending in its initial
- shift state. The format is composed of zero or more directives: ordinary multibyte
- characters (not %), which are copied unchanged to the output stream; and conversion
- specifications, each of which results in fetching zero or more subsequent arguments,
- converting them, if applicable, according to the corresponding conversion specifier, and
- then writing the result to the output stream.
-4 Each conversion specification is introduced by the character %. After the %, the following
- appear in sequence:
- -- Zero or more flags (in any order) that modify the meaning of the conversion
- specification.
- -- An optional minimum field width. If the converted value has fewer characters than the
- field width, it is padded with spaces (by default) on the left (or right, if the left
- adjustment flag, described later, has been given) to the field width. The field width
- takes the form of an asterisk * (described later) or a nonnegative decimal integer.264)
- -- An optional precision that gives the minimum number of digits to appear for the d, i,
- o, u, x, and X conversions, the number of digits to appear after the decimal-point
- character for a, A, e, E, f, and F conversions, the maximum number of significant
- digits for the g and G conversions, or the maximum number of bytes to be written for
-
-
- 263) The fprintf functions perform writes to memory for the %n specifier.
- 264) Note that 0 is taken as a flag, not as the beginning of a field width.
-
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-
- s conversions. The precision takes the form of a period (.) followed either by an
- asterisk * (described later) or by an optional decimal integer; if only the period is
- specified, the precision is taken as zero. If a precision appears with any other
- conversion specifier, the behavior is undefined.
- -- An optional length modifier that specifies the size of the argument.
- -- A conversion specifier character that specifies the type of conversion to be applied.
-5 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
- this case, an int argument supplies the field width or precision. The arguments
- specifying field width, or precision, or both, shall appear (in that order) before the
- argument (if any) to be converted. A negative field width argument is taken as a - flag
- followed by a positive field width. A negative precision argument is taken as if the
- precision were omitted.
-6 The flag characters and their meanings are:
- - The result of the conversion is left-justified within the field. (It is right-justified if
- this flag is not specified.)
- + The result of a signed conversion always begins with a plus or minus sign. (It
- begins with a sign only when a negative value is converted if this flag is not
- specified.)265)
- space If the first character of a signed conversion is not a sign, or if a signed conversion
- results in no characters, a space is prefixed to the result. If the space and + flags
- both appear, the space flag is ignored.
- # The result is converted to an ''alternative form''. For o conversion, it increases
- the precision, if and only if necessary, to force the first digit of the result to be a
- zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
- conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
- and G conversions, the result of converting a floating-point number always
- contains a decimal-point character, even if no digits follow it. (Normally, a
- decimal-point character appears in the result of these conversions only if a digit
- follows it.) For g and G conversions, trailing zeros are not removed from the
- result. For other conversions, the behavior is undefined.
- 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
- (following any indication of sign or base) are used to pad to the field width rather
- than performing space padding, except when converting an infinity or NaN. If the
- 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
-
-
- 265) The results of all floating conversions of a negative zero, and of negative values that round to zero,
- include a minus sign.
-
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-
- conversions, if a precision is specified, the 0 flag is ignored. For other
- conversions, the behavior is undefined.
-7 The length modifiers and their meanings are:
- hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- signed char or unsigned char argument (the argument will have
- been promoted according to the integer promotions, but its value shall be
- converted to signed char or unsigned char before printing); or that
- a following n conversion specifier applies to a pointer to a signed char
- argument.
- h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- short int or unsigned short int argument (the argument will
- have been promoted according to the integer promotions, but its value shall
- be converted to short int or unsigned short int before printing);
- or that a following n conversion specifier applies to a pointer to a short
- int argument.
- l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- long int or unsigned long int argument; that a following n
- conversion specifier applies to a pointer to a long int argument; that a
- following c conversion specifier applies to a wint_t argument; that a
- following s conversion specifier applies to a pointer to a wchar_t
- argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
- specifier.
- ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- long long int or unsigned long long int argument; or that a
- following n conversion specifier applies to a pointer to a long long int
- argument.
- j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
- an intmax_t or uintmax_t argument; or that a following n conversion
- specifier applies to a pointer to an intmax_t argument.
- z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- size_t or the corresponding signed integer type argument; or that a
- following n conversion specifier applies to a pointer to a signed integer type
- corresponding to size_t argument.
- t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- ptrdiff_t or the corresponding unsigned integer type argument; or that a
- following n conversion specifier applies to a pointer to a ptrdiff_t
- argument.
-
-
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-
- L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
- applies to a long double argument.
- If a length modifier appears with any conversion specifier other than as specified above,
- the behavior is undefined.
-8 The conversion specifiers and their meanings are:
- d,i The int argument is converted to signed decimal in the style [-]dddd. The
- precision specifies the minimum number of digits to appear; if the value
- being converted can be represented in fewer digits, it is expanded with
- leading zeros. The default precision is 1. The result of converting a zero
- value with a precision of zero is no characters.
- o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
- decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
- letters abcdef are used for x conversion and the letters ABCDEF for X
- conversion. The precision specifies the minimum number of digits to appear;
- if the value being converted can be represented in fewer digits, it is expanded
- with leading zeros. The default precision is 1. The result of converting a
- zero value with a precision of zero is no characters.
- f,F A double argument representing a floating-point number is converted to
- decimal notation in the style [-]ddd.ddd, where the number of digits after
- the decimal-point character is equal to the precision specification. If the
- precision is missing, it is taken as 6; if the precision is zero and the # flag is
- not specified, no decimal-point character appears. If a decimal-point
- character appears, at least one digit appears before it. The value is rounded to
- the appropriate number of digits.
- A double argument representing an infinity is converted in one of the styles
- [-]inf or [-]infinity -- which style is implementation-defined. A
- double argument representing a NaN is converted in one of the styles
- [-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
- any n-char-sequence, is implementation-defined. The F conversion specifier
- produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
- respectively.266)
- e,E A double argument representing a floating-point number is converted in the
- style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
- argument is nonzero) before the decimal-point character and the number of
- digits after it is equal to the precision; if the precision is missing, it is taken as
-
-
- 266) When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning;
- the # and 0 flag characters have no effect.
-
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-
- 6; if the precision is zero and the # flag is not specified, no decimal-point
- character appears. The value is rounded to the appropriate number of digits.
- The E conversion specifier produces a number with E instead of e
- introducing the exponent. The exponent always contains at least two digits,
- and only as many more digits as necessary to represent the exponent. If the
- value is zero, the exponent is zero.
- A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
-g,G A double argument representing a floating-point number is converted in
- style f or e (or in style F or E in the case of a G conversion specifier),
- depending on the value converted and the precision. Let P equal the
- precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
- Then, if a conversion with style E would have an exponent of X:
- -- if P > X >= -4, the conversion is with style f (or F) and precision
- P - (X + 1).
- -- otherwise, the conversion is with style e (or E) and precision P - 1.
- Finally, unless the # flag is used, any trailing zeros are removed from the
- fractional portion of the result and the decimal-point character is removed if
- there is no fractional portion remaining.
- A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
-a,A A double argument representing a floating-point number is converted in the
- style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
- nonzero if the argument is a normalized floating-point number and is
- otherwise unspecified) before the decimal-point character267) and the number
- of hexadecimal digits after it is equal to the precision; if the precision is
- missing and FLT_RADIX is a power of 2, then the precision is sufficient for
- an exact representation of the value; if the precision is missing and
- FLT_RADIX is not a power of 2, then the precision is sufficient to
-
-
-
-
-267) Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so
- that subsequent digits align to nibble (4-bit) boundaries.
-
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-
- distinguish268) values of type double, except that trailing zeros may be
- omitted; if the precision is zero and the # flag is not specified, no decimal-
- point character appears. The letters abcdef are used for a conversion and
- the letters ABCDEF for A conversion. The A conversion specifier produces a
- number with X and P instead of x and p. The exponent always contains at
- least one digit, and only as many more digits as necessary to represent the
- decimal exponent of 2. If the value is zero, the exponent is zero.
- A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
-c If no l length modifier is present, the int argument is converted to an
- unsigned char, and the resulting character is written.
- If an l length modifier is present, the wint_t argument is converted as if by
- an ls conversion specification with no precision and an argument that points
- to the initial element of a two-element array of wchar_t, the first element
- containing the wint_t argument to the lc conversion specification and the
- second a null wide character.
-s If no l length modifier is present, the argument shall be a pointer to the initial
- element of an array of character type.269) Characters from the array are
- written up to (but not including) the terminating null character. If the
- precision is specified, no more than that many bytes are written. If the
- precision is not specified or is greater than the size of the array, the array shall
- contain a null character.
- If an l length modifier is present, the argument shall be a pointer to the initial
- element of an array of wchar_t type. Wide characters from the array are
- converted to multibyte characters (each as if by a call to the wcrtomb
- function, with the conversion state described by an mbstate_t object
- initialized to zero before the first wide character is converted) up to and
- including a terminating null wide character. The resulting multibyte
- characters are written up to (but not including) the terminating null character
- (byte). If no precision is specified, the array shall contain a null wide
- character. If a precision is specified, no more than that many bytes are
- written (including shift sequences, if any), and the array shall contain a null
- wide character if, to equal the multibyte character sequence length given by
-
-268) The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
- FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
- might suffice depending on the implementation's scheme for determining the digit to the left of the
- decimal-point character.
-269) No special provisions are made for multibyte characters.
-
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-
- the precision, the function would need to access a wide character one past the
- end of the array. In no case is a partial multibyte character written.270)
- p The argument shall be a pointer to void. The value of the pointer is
- converted to a sequence of printing characters, in an implementation-defined
- manner.
- n The argument shall be a pointer to signed integer into which is written the
- number of characters written to the output stream so far by this call to
- fprintf. No argument is converted, but one is consumed. If the conversion
- specification includes any flags, a field width, or a precision, the behavior is
- undefined.
- % A % character is written. No argument is converted. The complete
- conversion specification shall be %%.
-9 If a conversion specification is invalid, the behavior is undefined.271) If any argument is
- not the correct type for the corresponding conversion specification, the behavior is
- undefined.
-10 In no case does a nonexistent or small field width cause truncation of a field; if the result
- of a conversion is wider than the field width, the field is expanded to contain the
- conversion result.
-11 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
- to a hexadecimal floating number with the given precision.
- Recommended practice
-12 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
- representable in the given precision, the result should be one of the two adjacent numbers
- in hexadecimal floating style with the given precision, with the extra stipulation that the
- error should have a correct sign for the current rounding direction.
-13 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
- DECIMAL_DIG, then the result should be correctly rounded.272) If the number of
- significant decimal digits is more than DECIMAL_DIG but the source value is exactly
- representable with DECIMAL_DIG digits, then the result should be an exact
- representation with trailing zeros. Otherwise, the source value is bounded by two
- adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
-
-
- 270) Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
- 271) See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
- 272) For binary-to-decimal conversion, the result format's values are the numbers representable with the
- given format specifier. The number of significant digits is determined by the format specifier, and in
- the case of fixed-point conversion by the source value as well.
-
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-
- of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
- the error should have a correct sign for the current rounding direction.
- Returns
-14 The fprintf function returns the number of characters transmitted, or a negative value
- if an output or encoding error occurred.
- Environmental limits
-15 The number of characters that can be produced by any single conversion shall be at least
- 4095.
-16 EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
- places:
- #include <a href="#7.12"><math.h></a>
- #include <a href="#7.21"><stdio.h></a>
- /* ... */
- char *weekday, *month; // pointers to strings
- int day, hour, min;
- fprintf(stdout, "%s, %s %d, %.2d:%.2d\n",
- weekday, month, day, hour, min);
- fprintf(stdout, "pi = %.5f\n", 4 * atan(<a href="#1.0">1.0</a>));
-
-17 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the
- members of the extended character set that consist of more than one byte each consist of exactly two bytes,
- the first of which is denoted here by a and the second by an uppercase letter.
-18 Given the following wide string with length seven,
- static wchar_t wstr[] = L" X Yabc Z W";
- the seven calls
- fprintf(stdout, "|1234567890123|\n");
- fprintf(stdout, "|%13ls|\n", wstr);
- fprintf(stdout, "|%-13.9ls|\n", wstr);
- fprintf(stdout, "|%13.10ls|\n", wstr);
- fprintf(stdout, "|%13.11ls|\n", wstr);
- fprintf(stdout, "|%13.15ls|\n", &wstr[2]);
- fprintf(stdout, "|%13lc|\n", (wint_t) wstr[5]);
- will print the following seven lines:
- |1234567890123|
- | X Yabc Z W|
- | X Yabc Z |
- | X Yabc Z|
- | X Yabc Z W|
- | abc Z W|
- | Z|
-
- Forward references: conversion state (<a href="#7.28.6">7.28.6</a>), the wcrtomb function (<a href="#7.28.6.3.3">7.28.6.3.3</a>).
-
-
-
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-
-<a name="7.21.6.2" href="#7.21.6.2"><b> 7.21.6.2 The fscanf function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int fscanf(FILE * restrict stream,
- const char * restrict format, ...);
- Description
-2 The fscanf function reads input from the stream pointed to by stream, under control
- of the string pointed to by format that specifies the admissible input sequences and how
- they are to be converted for assignment, using subsequent arguments as pointers to the
- objects to receive the converted input. If there are insufficient arguments for the format,
- the behavior is undefined. If the format is exhausted while arguments remain, the excess
- arguments are evaluated (as always) but are otherwise ignored.
-3 The format shall be a multibyte character sequence, beginning and ending in its initial
- shift state. The format is composed of zero or more directives: one or more white-space
- characters, an ordinary multibyte character (neither % nor a white-space character), or a
- conversion specification. Each conversion specification is introduced by the character %.
- After the %, the following appear in sequence:
- -- An optional assignment-suppressing character *.
- -- An optional decimal integer greater than zero that specifies the maximum field width
- (in characters).
- -- An optional length modifier that specifies the size of the receiving object.
- -- A conversion specifier character that specifies the type of conversion to be applied.
-4 The fscanf function executes each directive of the format in turn. When all directives
- have been executed, or if a directive fails (as detailed below), the function returns.
- Failures are described as input failures (due to the occurrence of an encoding error or the
- unavailability of input characters), or matching failures (due to inappropriate input).
-5 A directive composed of white-space character(s) is executed by reading input up to the
- first non-white-space character (which remains unread), or until no more characters can
- be read.
-6 A directive that is an ordinary multibyte character is executed by reading the next
- characters of the stream. If any of those characters differ from the ones composing the
- directive, the directive fails and the differing and subsequent characters remain unread.
- Similarly, if end-of-file, an encoding error, or a read error prevents a character from being
- read, the directive fails.
-7 A directive that is a conversion specification defines a set of matching input sequences, as
- described below for each specifier. A conversion specification is executed in the
-
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-
- following steps:
-8 Input white-space characters (as specified by the isspace function) are skipped, unless
- the specification includes a [, c, or n specifier.273)
-9 An input item is read from the stream, unless the specification includes an n specifier. An
- input item is defined as the longest sequence of input characters which does not exceed
- any specified field width and which is, or is a prefix of, a matching input sequence.274)
- The first character, if any, after the input item remains unread. If the length of the input
- item is zero, the execution of the directive fails; this condition is a matching failure unless
- end-of-file, an encoding error, or a read error prevented input from the stream, in which
- case it is an input failure.
-10 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
- count of input characters) is converted to a type appropriate to the conversion specifier. If
- the input item is not a matching sequence, the execution of the directive fails: this
- condition is a matching failure. Unless assignment suppression was indicated by a *, the
- result of the conversion is placed in the object pointed to by the first argument following
- the format argument that has not already received a conversion result. If this object
- does not have an appropriate type, or if the result of the conversion cannot be represented
- in the object, the behavior is undefined.
-11 The length modifiers and their meanings are:
- hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to signed char or unsigned char.
- h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to short int or unsigned short
- int.
- l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to long int or unsigned long
- int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
- an argument with type pointer to double; or that a following c, s, or [
- conversion specifier applies to an argument with type pointer to wchar_t.
- ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to long long int or unsigned
- long long int.
-
-
-
- 273) These white-space characters are not counted against a specified field width.
- 274) fscanf pushes back at most one input character onto the input stream. Therefore, some sequences
- that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.
-
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-
- j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to intmax_t or uintmax_t.
- z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to size_t or the corresponding signed
- integer type.
- t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to ptrdiff_t or the corresponding
- unsigned integer type.
- L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
- applies to an argument with type pointer to long double.
- If a length modifier appears with any conversion specifier other than as specified above,
- the behavior is undefined.
-12 The conversion specifiers and their meanings are:
- d Matches an optionally signed decimal integer, whose format is the same as
- expected for the subject sequence of the strtol function with the value 10
- for the base argument. The corresponding argument shall be a pointer to
- signed integer.
- i Matches an optionally signed integer, whose format is the same as expected
- for the subject sequence of the strtol function with the value 0 for the
- base argument. The corresponding argument shall be a pointer to signed
- integer.
- o Matches an optionally signed octal integer, whose format is the same as
- expected for the subject sequence of the strtoul function with the value 8
- for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
- u Matches an optionally signed decimal integer, whose format is the same as
- expected for the subject sequence of the strtoul function with the value 10
- for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
- x Matches an optionally signed hexadecimal integer, whose format is the same
- as expected for the subject sequence of the strtoul function with the value
- 16 for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
- a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
- format is the same as expected for the subject sequence of the strtod
- function. The corresponding argument shall be a pointer to floating.
-
-
-[<a name="#p318" href="p318">page 318</a>] (<a href="#Contents">Contents</a>)
-
-c Matches a sequence of characters of exactly the number specified by the field
- width (1 if no field width is present in the directive).275)
- If no l length modifier is present, the corresponding argument shall be a
- pointer to the initial element of a character array large enough to accept the
- sequence. No null character is added.
- If an l length modifier is present, the input shall be a sequence of multibyte
- characters that begins in the initial shift state. Each multibyte character in the
- sequence is converted to a wide character as if by a call to the mbrtowc
- function, with the conversion state described by an mbstate_t object
- initialized to zero before the first multibyte character is converted. The
- corresponding argument shall be a pointer to the initial element of an array of
- wchar_t large enough to accept the resulting sequence of wide characters.
- No null wide character is added.
-s Matches a sequence of non-white-space characters.275)
- If no l length modifier is present, the corresponding argument shall be a
- pointer to the initial element of a character array large enough to accept the
- sequence and a terminating null character, which will be added automatically.
- If an l length modifier is present, the input shall be a sequence of multibyte
- characters that begins in the initial shift state. Each multibyte character is
- converted to a wide character as if by a call to the mbrtowc function, with
- the conversion state described by an mbstate_t object initialized to zero
- before the first multibyte character is converted. The corresponding argument
- shall be a pointer to the initial element of an array of wchar_t large enough
- to accept the sequence and the terminating null wide character, which will be
- added automatically.
-[ Matches a nonempty sequence of characters from a set of expected characters
- (the scanset).275)
- If no l length modifier is present, the corresponding argument shall be a
- pointer to the initial element of a character array large enough to accept the
- sequence and a terminating null character, which will be added automatically.
- If an l length modifier is present, the input shall be a sequence of multibyte
- characters that begins in the initial shift state. Each multibyte character is
- converted to a wide character as if by a call to the mbrtowc function, with
- the conversion state described by an mbstate_t object initialized to zero
-
-275) No special provisions are made for multibyte characters in the matching rules used by the c, s, and [
- conversion specifiers -- the extent of the input field is determined on a byte-by-byte basis. The
- resulting field is nevertheless a sequence of multibyte characters that begins in the initial shift state.
-
-[<a name="#p319" href="p319">page 319</a>] (<a href="#Contents">Contents</a>)
-
- before the first multibyte character is converted. The corresponding argument
- shall be a pointer to the initial element of an array of wchar_t large enough
- to accept the sequence and the terminating null wide character, which will be
- added automatically.
- The conversion specifier includes all subsequent characters in the format
- string, up to and including the matching right bracket (]). The characters
- between the brackets (the scanlist) compose the scanset, unless the character
- after the left bracket is a circumflex (^), in which case the scanset contains all
- characters that do not appear in the scanlist between the circumflex and the
- right bracket. If the conversion specifier begins with [] or [^], the right
- bracket character is in the scanlist and the next following right bracket
- character is the matching right bracket that ends the specification; otherwise
- the first following right bracket character is the one that ends the
- specification. If a - character is in the scanlist and is not the first, nor the
- second where the first character is a ^, nor the last character, the behavior is
- implementation-defined.
- p Matches an implementation-defined set of sequences, which should be the
- same as the set of sequences that may be produced by the %p conversion of
- the fprintf function. The corresponding argument shall be a pointer to a
- pointer to void. The input item is converted to a pointer value in an
- implementation-defined manner. If the input item is a value converted earlier
- during the same program execution, the pointer that results shall compare
- equal to that value; otherwise the behavior of the %p conversion is undefined.
- n No input is consumed. The corresponding argument shall be a pointer to
- signed integer into which is to be written the number of characters read from
- the input stream so far by this call to the fscanf function. Execution of a
- %n directive does not increment the assignment count returned at the
- completion of execution of the fscanf function. No argument is converted,
- but one is consumed. If the conversion specification includes an assignment-
- suppressing character or a field width, the behavior is undefined.
- % Matches a single % character; no conversion or assignment occurs. The
- complete conversion specification shall be %%.
-13 If a conversion specification is invalid, the behavior is undefined.276)
-14 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
- respectively, a, e, f, g, and x.
-
-
-
- 276) See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
-
-[<a name="#p320" href="p320">page 320</a>] (<a href="#Contents">Contents</a>)
-
-15 Trailing white space (including new-line characters) is left unread unless matched by a
- directive. The success of literal matches and suppressed assignments is not directly
- determinable other than via the %n directive.
- Returns
-16 The fscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the function returns the
- number of input items assigned, which can be fewer than provided for, or even zero, in
- the event of an early matching failure.
-17 EXAMPLE 1 The call:
- #include <a href="#7.21"><stdio.h></a>
- /* ... */
- int n, i; float x; char name[50];
- n = fscanf(stdin, "%d%f%s", &i, &x, name);
- with the input line:
- 25 54.32E-1 thompson
- will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
- thompson\0.
-
-18 EXAMPLE 2 The call:
- #include <a href="#7.21"><stdio.h></a>
- /* ... */
- int i; float x; char name[50];
- fscanf(stdin, "%2d%f%*d %[0123456789]", &i, &x, name);
- with input:
- 56789 0123 56a72
- will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the
- sequence 56\0. The next character read from the input stream will be a.
-
-19 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
- #include <a href="#7.21"><stdio.h></a>
- /* ... */
- int count; float quant; char units[21], item[21];
- do {
- count = fscanf(stdin, "%f%20s of %20s", &quant, units, item);
- fscanf(stdin,"%*[^\n]");
- } while (!feof(stdin) && !ferror(stdin));
-20 If the stdin stream contains the following lines:
- 2 quarts of oil
- -12.8degrees Celsius
- lots of luck
- 10.0LBS of
- dirt
- 100ergs of energy
-
-[<a name="#p321" href="p321">page 321</a>] (<a href="#Contents">Contents</a>)
-
- the execution of the above example will be analogous to the following assignments:
- quant = 2; strcpy(units, "quarts"); strcpy(item, "oil");
- count = 3;
- quant = -12.8; strcpy(units, "degrees");
- count = 2; // "C" fails to match "o"
- count = 0; // "l" fails to match "%f"
- quant = 10.0; strcpy(units, "LBS"); strcpy(item, "dirt");
- count = 3;
- count = 0; // "100e" fails to match "%f"
- count = EOF;
-
-21 EXAMPLE 4 In:
- #include <a href="#7.21"><stdio.h></a>
- /* ... */
- int d1, d2, n1, n2, i;
- i = sscanf("123", "%d%n%n%d", &d1, &n1, &n2, &d2);
- the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure the value
- of 3 is also assigned to n2. The value of d2 is not affected. The value 1 is assigned to i.
-
-22 EXAMPLE 5 In these examples, multibyte characters do have a state-dependent encoding, and the
- members of the extended character set that consist of more than one byte each consist of exactly two bytes,
- the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as
- such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes
- entry into the alternate shift state.
-23 After the call:
- #include <a href="#7.21"><stdio.h></a>
- /* ... */
- char str[50];
- fscanf(stdin, "a%s", str);
- with the input line:
- a(uparrow) X Y(downarrow) bc
- str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte
- characters, in the more general case) appears to be a single-byte white-space character.
-24 In contrast, after the call:
- #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.19"><stddef.h></a>
- /* ... */
- wchar_t wstr[50];
- fscanf(stdin, "a%ls", wstr);
- with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
- terminating null wide character.
-25 However, the call:
-
-
-
-
-[<a name="#p322" href="p322">page 322</a>] (<a href="#Contents">Contents</a>)
-
- #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.19"><stddef.h></a>
- /* ... */
- wchar_t wstr[50];
- fscanf(stdin, "a(uparrow) X(downarrow)%ls", wstr);
- with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
- string.
-26 Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte
- character Y, after the call:
- #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.19"><stddef.h></a>
- /* ... */
- wchar_t wstr[50];
- fscanf(stdin, "a(uparrow) Y(downarrow)%ls", wstr);
- with the same input line, zero will again be returned, but stdin will be left with a partially consumed
- multibyte character.
-
- Forward references: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>), the
- strtol, strtoll, strtoul, and strtoull functions (<a href="#7.22.1.4">7.22.1.4</a>), conversion state
- (<a href="#7.28.6">7.28.6</a>), the wcrtomb function (<a href="#7.28.6.3.3">7.28.6.3.3</a>).
-<a name="7.21.6.3" href="#7.21.6.3"><b> 7.21.6.3 The printf function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int printf(const char * restrict format, ...);
- Description
-2 The printf function is equivalent to fprintf with the argument stdout interposed
- before the arguments to printf.
- Returns
-3 The printf function returns the number of characters transmitted, or a negative value if
- an output or encoding error occurred.
-<a name="7.21.6.4" href="#7.21.6.4"><b> 7.21.6.4 The scanf function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int scanf(const char * restrict format, ...);
- Description
-2 The scanf function is equivalent to fscanf with the argument stdin interposed
- before the arguments to scanf.
-
-
-
-[<a name="#p323" href="p323">page 323</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The scanf function returns the value of the macro EOF if an input failure occurs before
- the first conversion (if any) has completed. Otherwise, the scanf function returns the
- number of input items assigned, which can be fewer than provided for, or even zero, in
- the event of an early matching failure.
-<a name="7.21.6.5" href="#7.21.6.5"><b> 7.21.6.5 The snprintf function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int snprintf(char * restrict s, size_t n,
- const char * restrict format, ...);
- Description
-2 The snprintf function is equivalent to fprintf, except that the output is written into
- an array (specified by argument s) rather than to a stream. If n is zero, nothing is written,
- and s may be a null pointer. Otherwise, output characters beyond the n-1st are
- discarded rather than being written to the array, and a null character is written at the end
- of the characters actually written into the array. If copying takes place between objects
- that overlap, the behavior is undefined.
- Returns
-3 The snprintf function returns the number of characters that would have been written
- had n been sufficiently large, not counting the terminating null character, or a negative
- value if an encoding error occurred. Thus, the null-terminated output has been
- completely written if and only if the returned value is nonnegative and less than n.
-<a name="7.21.6.6" href="#7.21.6.6"><b> 7.21.6.6 The sprintf function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int sprintf(char * restrict s,
- const char * restrict format, ...);
- Description
-2 The sprintf function is equivalent to fprintf, except that the output is written into
- an array (specified by the argument s) rather than to a stream. A null character is written
- at the end of the characters written; it is not counted as part of the returned value. If
- copying takes place between objects that overlap, the behavior is undefined.
- Returns
-3 The sprintf function returns the number of characters written in the array, not
- counting the terminating null character, or a negative value if an encoding error occurred.
-
-[<a name="#p324" href="p324">page 324</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.21.6.7" href="#7.21.6.7"><b> 7.21.6.7 The sscanf function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int sscanf(const char * restrict s,
- const char * restrict format, ...);
- Description
-2 The sscanf function is equivalent to fscanf, except that input is obtained from a
- string (specified by the argument s) rather than from a stream. Reaching the end of the
- string is equivalent to encountering end-of-file for the fscanf function. If copying
- takes place between objects that overlap, the behavior is undefined.
- Returns
-3 The sscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the sscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
-<a name="7.21.6.8" href="#7.21.6.8"><b> 7.21.6.8 The vfprintf function</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- int vfprintf(FILE * restrict stream,
- const char * restrict format,
- va_list arg);
- Description
-2 The vfprintf function is equivalent to fprintf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vfprintf function does not invoke the
- va_end macro.277)
- Returns
-3 The vfprintf function returns the number of characters transmitted, or a negative
- value if an output or encoding error occurred.
-4 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
-
-
-
-
- 277) As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
- vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
-
-[<a name="#p325" href="p325">page 325</a>] (<a href="#Contents">Contents</a>)
-
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- void error(char *function_name, char *format, ...)
- {
- va_list args;
- va_start(args, format);
- // print out name of function causing error
- fprintf(stderr, "ERROR in %s: ", function_name);
- // print out remainder of message
- vfprintf(stderr, format, args);
- va_end(args);
- }
-
-<a name="7.21.6.9" href="#7.21.6.9"><b> 7.21.6.9 The vfscanf function</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- int vfscanf(FILE * restrict stream,
- const char * restrict format,
- va_list arg);
- Description
-2 The vfscanf function is equivalent to fscanf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vfscanf function does not invoke the
- va_end macro.277)
- Returns
-3 The vfscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the vfscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
-<a name="7.21.6.10" href="#7.21.6.10"><b> 7.21.6.10 The vprintf function</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- int vprintf(const char * restrict format,
- va_list arg);
- Description
-2 The vprintf function is equivalent to printf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
-
-[<a name="#p326" href="p326">page 326</a>] (<a href="#Contents">Contents</a>)
-
- possibly subsequent va_arg calls). The vprintf function does not invoke the
- va_end macro.277)
- Returns
-3 The vprintf function returns the number of characters transmitted, or a negative value
- if an output or encoding error occurred.
-<a name="7.21.6.11" href="#7.21.6.11"><b> 7.21.6.11 The vscanf function</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- int vscanf(const char * restrict format,
- va_list arg);
- Description
-2 The vscanf function is equivalent to scanf, with the variable argument list replaced
- by arg, which shall have been initialized by the va_start macro (and possibly
- subsequent va_arg calls). The vscanf function does not invoke the va_end
- macro.277)
- Returns
-3 The vscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the vscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
-<a name="7.21.6.12" href="#7.21.6.12"><b> 7.21.6.12 The vsnprintf function</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- int vsnprintf(char * restrict s, size_t n,
- const char * restrict format,
- va_list arg);
- Description
-2 The vsnprintf function is equivalent to snprintf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vsnprintf function does not invoke the
- va_end macro.277) If copying takes place between objects that overlap, the behavior is
- undefined.
-
-
-
-[<a name="#p327" href="p327">page 327</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The vsnprintf function returns the number of characters that would have been written
- had n been sufficiently large, not counting the terminating null character, or a negative
- value if an encoding error occurred. Thus, the null-terminated output has been
- completely written if and only if the returned value is nonnegative and less than n.
-<a name="7.21.6.13" href="#7.21.6.13"><b> 7.21.6.13 The vsprintf function</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- int vsprintf(char * restrict s,
- const char * restrict format,
- va_list arg);
- Description
-2 The vsprintf function is equivalent to sprintf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vsprintf function does not invoke the
- va_end macro.277) If copying takes place between objects that overlap, the behavior is
- undefined.
- Returns
-3 The vsprintf function returns the number of characters written in the array, not
- counting the terminating null character, or a negative value if an encoding error occurred.
-<a name="7.21.6.14" href="#7.21.6.14"><b> 7.21.6.14 The vsscanf function</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- int vsscanf(const char * restrict s,
- const char * restrict format,
- va_list arg);
- Description
-2 The vsscanf function is equivalent to sscanf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vsscanf function does not invoke the
- va_end macro.277)
- Returns
-3 The vsscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the vsscanf function
-[<a name="#p328" href="p328">page 328</a>] (<a href="#Contents">Contents</a>)
-
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
-<a name="7.21.7" href="#7.21.7"><b> 7.21.7 Character input/output functions</b></a>
-<a name="7.21.7.1" href="#7.21.7.1"><b> 7.21.7.1 The fgetc function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int fgetc(FILE *stream);
- Description
-2 If the end-of-file indicator for the input stream pointed to by stream is not set and a
- next character is present, the fgetc function obtains that character as an unsigned
- char converted to an int and advances the associated file position indicator for the
- stream (if defined).
- Returns
-3 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
- of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the
- fgetc function returns the next character from the input stream pointed to by stream.
- If a read error occurs, the error indicator for the stream is set and the fgetc function
- returns EOF.278)
-<a name="7.21.7.2" href="#7.21.7.2"><b> 7.21.7.2 The fgets function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- char *fgets(char * restrict s, int n,
- FILE * restrict stream);
- Description
-2 The fgets function reads at most one less than the number of characters specified by n
- from the stream pointed to by stream into the array pointed to by s. No additional
- characters are read after a new-line character (which is retained) or after end-of-file. A
- null character is written immediately after the last character read into the array.
- Returns
-3 The fgets function returns s if successful. If end-of-file is encountered and no
- characters have been read into the array, the contents of the array remain unchanged and a
- null pointer is returned. If a read error occurs during the operation, the array contents are
- indeterminate and a null pointer is returned.
-
- 278) An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
-
-[<a name="#p329" href="p329">page 329</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.21.7.3" href="#7.21.7.3"><b> 7.21.7.3 The fputc function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int fputc(int c, FILE *stream);
- Description
-2 The fputc function writes the character specified by c (converted to an unsigned
- char) to the output stream pointed to by stream, at the position indicated by the
- associated file position indicator for the stream (if defined), and advances the indicator
- appropriately. If the file cannot support positioning requests, or if the stream was opened
- with append mode, the character is appended to the output stream.
- Returns
-3 The fputc function returns the character written. If a write error occurs, the error
- indicator for the stream is set and fputc returns EOF.
-<a name="7.21.7.4" href="#7.21.7.4"><b> 7.21.7.4 The fputs function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int fputs(const char * restrict s,
- FILE * restrict stream);
- Description
-2 The fputs function writes the string pointed to by s to the stream pointed to by
- stream. The terminating null character is not written.
- Returns
-3 The fputs function returns EOF if a write error occurs; otherwise it returns a
- nonnegative value.
-<a name="7.21.7.5" href="#7.21.7.5"><b> 7.21.7.5 The getc function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int getc(FILE *stream);
- Description
-2 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it
- may evaluate stream more than once, so the argument should never be an expression
- with side effects.
-
-
-
-
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-
- Returns
-3 The getc function returns the next character from the input stream pointed to by
- stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
- getc returns EOF. If a read error occurs, the error indicator for the stream is set and
- getc returns EOF.
-<a name="7.21.7.6" href="#7.21.7.6"><b> 7.21.7.6 The getchar function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int getchar(void);
- Description
-2 The getchar function is equivalent to getc with the argument stdin.
- Returns
-3 The getchar function returns the next character from the input stream pointed to by
- stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
- getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
- getchar returns EOF.
-<a name="7.21.7.7" href="#7.21.7.7"><b> 7.21.7.7 The putc function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int putc(int c, FILE *stream);
- Description
-2 The putc function is equivalent to fputc, except that if it is implemented as a macro, it
- may evaluate stream more than once, so that argument should never be an expression
- with side effects.
- Returns
-3 The putc function returns the character written. If a write error occurs, the error
- indicator for the stream is set and putc returns EOF.
-<a name="7.21.7.8" href="#7.21.7.8"><b> 7.21.7.8 The putchar function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int putchar(int c);
- Description
-2 The putchar function is equivalent to putc with the second argument stdout.
-
-
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-
- Returns
-3 The putchar function returns the character written. If a write error occurs, the error
- indicator for the stream is set and putchar returns EOF.
-<a name="7.21.7.9" href="#7.21.7.9"><b> 7.21.7.9 The puts function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int puts(const char *s);
- Description
-2 The puts function writes the string pointed to by s to the stream pointed to by stdout,
- and appends a new-line character to the output. The terminating null character is not
- written.
- Returns
-3 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
- value.
-<a name="7.21.7.10" href="#7.21.7.10"><b> 7.21.7.10 The ungetc function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int ungetc(int c, FILE *stream);
- Description
-2 The ungetc function pushes the character specified by c (converted to an unsigned
- char) back onto the input stream pointed to by stream. Pushed-back characters will be
- returned by subsequent reads on that stream in the reverse order of their pushing. A
- successful intervening call (with the stream pointed to by stream) to a file positioning
- function (fseek, fsetpos, or rewind) discards any pushed-back characters for the
- stream. The external storage corresponding to the stream is unchanged.
-3 One character of pushback is guaranteed. If the ungetc function is called too many
- times on the same stream without an intervening read or file positioning operation on that
- stream, the operation may fail.
-4 If the value of c equals that of the macro EOF, the operation fails and the input stream is
- unchanged.
-5 A successful call to the ungetc function clears the end-of-file indicator for the stream.
- The value of the file position indicator for the stream after reading or discarding all
- pushed-back characters shall be the same as it was before the characters were pushed
- back. For a text stream, the value of its file position indicator after a successful call to the
- ungetc function is unspecified until all pushed-back characters are read or discarded.
-
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-
- For a binary stream, its file position indicator is decremented by each successful call to
- the ungetc function; if its value was zero before a call, it is indeterminate after the
- call.279)
- Returns
-6 The ungetc function returns the character pushed back after conversion, or EOF if the
- operation fails.
- Forward references: file positioning functions (<a href="#7.21.9">7.21.9</a>).
-<a name="7.21.8" href="#7.21.8"><b> 7.21.8 Direct input/output functions</b></a>
-<a name="7.21.8.1" href="#7.21.8.1"><b> 7.21.8.1 The fread function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- size_t fread(void * restrict ptr,
- size_t size, size_t nmemb,
- FILE * restrict stream);
- Description
-2 The fread function reads, into the array pointed to by ptr, up to nmemb elements
- whose size is specified by size, from the stream pointed to by stream. For each
- object, size calls are made to the fgetc function and the results stored, in the order
- read, in an array of unsigned char exactly overlaying the object. The file position
- indicator for the stream (if defined) is advanced by the number of characters successfully
- read. If an error occurs, the resulting value of the file position indicator for the stream is
- indeterminate. If a partial element is read, its value is indeterminate.
- Returns
-3 The fread function returns the number of elements successfully read, which may be
- less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
- fread returns zero and the contents of the array and the state of the stream remain
- unchanged.
-
-
-
-
- 279) See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
-
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-
-<a name="7.21.8.2" href="#7.21.8.2"><b> 7.21.8.2 The fwrite function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- size_t fwrite(const void * restrict ptr,
- size_t size, size_t nmemb,
- FILE * restrict stream);
- Description
-2 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements
- whose size is specified by size, to the stream pointed to by stream. For each object,
- size calls are made to the fputc function, taking the values (in order) from an array of
- unsigned char exactly overlaying the object. The file position indicator for the
- stream (if defined) is advanced by the number of characters successfully written. If an
- error occurs, the resulting value of the file position indicator for the stream is
- indeterminate.
- Returns
-3 The fwrite function returns the number of elements successfully written, which will be
- less than nmemb only if a write error is encountered. If size or nmemb is zero,
- fwrite returns zero and the state of the stream remains unchanged.
-<a name="7.21.9" href="#7.21.9"><b> 7.21.9 File positioning functions</b></a>
-<a name="7.21.9.1" href="#7.21.9.1"><b> 7.21.9.1 The fgetpos function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int fgetpos(FILE * restrict stream,
- fpos_t * restrict pos);
- Description
-2 The fgetpos function stores the current values of the parse state (if any) and file
- position indicator for the stream pointed to by stream in the object pointed to by pos.
- The values stored contain unspecified information usable by the fsetpos function for
- repositioning the stream to its position at the time of the call to the fgetpos function.
- Returns
-3 If successful, the fgetpos function returns zero; on failure, the fgetpos function
- returns nonzero and stores an implementation-defined positive value in errno.
- Forward references: the fsetpos function (<a href="#7.21.9.3">7.21.9.3</a>).
-
-
-
-
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-
-<a name="7.21.9.2" href="#7.21.9.2"><b> 7.21.9.2 The fseek function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int fseek(FILE *stream, long int offset, int whence);
- Description
-2 The fseek function sets the file position indicator for the stream pointed to by stream.
- If a read or write error occurs, the error indicator for the stream is set and fseek fails.
-3 For a binary stream, the new position, measured in characters from the beginning of the
- file, is obtained by adding offset to the position specified by whence. The specified
- position is the beginning of the file if whence is SEEK_SET, the current value of the file
- position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
- meaningfully support fseek calls with a whence value of SEEK_END.
-4 For a text stream, either offset shall be zero, or offset shall be a value returned by
- an earlier successful call to the ftell function on a stream associated with the same file
- and whence shall be SEEK_SET.
-5 After determining the new position, a successful call to the fseek function undoes any
- effects of the ungetc function on the stream, clears the end-of-file indicator for the
- stream, and then establishes the new position. After a successful fseek call, the next
- operation on an update stream may be either input or output.
- Returns
-6 The fseek function returns nonzero only for a request that cannot be satisfied.
- Forward references: the ftell function (<a href="#7.21.9.4">7.21.9.4</a>).
-<a name="7.21.9.3" href="#7.21.9.3"><b> 7.21.9.3 The fsetpos function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int fsetpos(FILE *stream, const fpos_t *pos);
- Description
-2 The fsetpos function sets the mbstate_t object (if any) and file position indicator
- for the stream pointed to by stream according to the value of the object pointed to by
- pos, which shall be a value obtained from an earlier successful call to the fgetpos
- function on a stream associated with the same file. If a read or write error occurs, the
- error indicator for the stream is set and fsetpos fails.
-3 A successful call to the fsetpos function undoes any effects of the ungetc function
- on the stream, clears the end-of-file indicator for the stream, and then establishes the new
- parse state and position. After a successful fsetpos call, the next operation on an
-
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-
- update stream may be either input or output.
- Returns
-4 If successful, the fsetpos function returns zero; on failure, the fsetpos function
- returns nonzero and stores an implementation-defined positive value in errno.
-<a name="7.21.9.4" href="#7.21.9.4"><b> 7.21.9.4 The ftell function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- long int ftell(FILE *stream);
- Description
-2 The ftell function obtains the current value of the file position indicator for the stream
- pointed to by stream. For a binary stream, the value is the number of characters from
- the beginning of the file. For a text stream, its file position indicator contains unspecified
- information, usable by the fseek function for returning the file position indicator for the
- stream to its position at the time of the ftell call; the difference between two such
- return values is not necessarily a meaningful measure of the number of characters written
- or read.
- Returns
-3 If successful, the ftell function returns the current value of the file position indicator
- for the stream. On failure, the ftell function returns -1L and stores an
- implementation-defined positive value in errno.
-<a name="7.21.9.5" href="#7.21.9.5"><b> 7.21.9.5 The rewind function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- void rewind(FILE *stream);
- Description
-2 The rewind function sets the file position indicator for the stream pointed to by
- stream to the beginning of the file. It is equivalent to
- (void)fseek(stream, 0L, SEEK_SET)
- except that the error indicator for the stream is also cleared.
- Returns
-3 The rewind function returns no value.
-
-
-
-
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-
-<a name="7.21.10" href="#7.21.10"><b> 7.21.10 Error-handling functions</b></a>
-<a name="7.21.10.1" href="#7.21.10.1"><b> 7.21.10.1 The clearerr function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- void clearerr(FILE *stream);
- Description
-2 The clearerr function clears the end-of-file and error indicators for the stream pointed
- to by stream.
- Returns
-3 The clearerr function returns no value.
-<a name="7.21.10.2" href="#7.21.10.2"><b> 7.21.10.2 The feof function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int feof(FILE *stream);
- Description
-2 The feof function tests the end-of-file indicator for the stream pointed to by stream.
- Returns
-3 The feof function returns nonzero if and only if the end-of-file indicator is set for
- stream.
-<a name="7.21.10.3" href="#7.21.10.3"><b> 7.21.10.3 The ferror function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- int ferror(FILE *stream);
- Description
-2 The ferror function tests the error indicator for the stream pointed to by stream.
- Returns
-3 The ferror function returns nonzero if and only if the error indicator is set for
- stream.
-
-
-
-
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-
-<a name="7.21.10.4" href="#7.21.10.4"><b> 7.21.10.4 The perror function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- void perror(const char *s);
- Description
-2 The perror function maps the error number in the integer expression errno to an
- error message. It writes a sequence of characters to the standard error stream thus: first
- (if s is not a null pointer and the character pointed to by s is not the null character), the
- string pointed to by s followed by a colon (:) and a space; then an appropriate error
- message string followed by a new-line character. The contents of the error message
- strings are the same as those returned by the strerror function with argument errno.
- Returns
-3 The perror function returns no value.
- Forward references: the strerror function (<a href="#7.23.6.2">7.23.6.2</a>).
-
-
-
-
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-
-<a name="7.22" href="#7.22"><b> 7.22 General utilities <stdlib.h></b></a>
-1 The header <a href="#7.22"><stdlib.h></a> declares five types and several functions of general utility, and
- defines several macros.280)
-2 The types declared are size_t and wchar_t (both described in <a href="#7.19">7.19</a>),
- div_t
- which is a structure type that is the type of the value returned by the div function,
- ldiv_t
- which is a structure type that is the type of the value returned by the ldiv function, and
- lldiv_t
- which is a structure type that is the type of the value returned by the lldiv function.
-3 The macros defined are NULL (described in <a href="#7.19">7.19</a>);
- EXIT_FAILURE
- and
- EXIT_SUCCESS
- which expand to integer constant expressions that can be used as the argument to the
- exit function to return unsuccessful or successful termination status, respectively, to the
- host environment;
- RAND_MAX
- which expands to an integer constant expression that is the maximum value returned by
- the rand function; and
- MB_CUR_MAX
- which expands to a positive integer expression with type size_t that is the maximum
- number of bytes in a multibyte character for the extended character set specified by the
- current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX.
-
-
-
-
- 280) See ''future library directions'' (<a href="#7.30.10">7.30.10</a>).
-
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-
-<a name="7.22.1" href="#7.22.1"><b> 7.22.1 Numeric conversion functions</b></a>
-1 The functions atof, atoi, atol, and atoll need not affect the value of the integer
- expression errno on an error. If the value of the result cannot be represented, the
- behavior is undefined.
-<a name="7.22.1.1" href="#7.22.1.1"><b> 7.22.1.1 The atof function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- double atof(const char *nptr);
- Description
-2 The atof function converts the initial portion of the string pointed to by nptr to
- double representation. Except for the behavior on error, it is equivalent to
- strtod(nptr, (char **)NULL)
- Returns
-3 The atof function returns the converted value.
- Forward references: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
-<a name="7.22.1.2" href="#7.22.1.2"><b> 7.22.1.2 The atoi, atol, and atoll functions</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- int atoi(const char *nptr);
- long int atol(const char *nptr);
- long long int atoll(const char *nptr);
- Description
-2 The atoi, atol, and atoll functions convert the initial portion of the string pointed
- to by nptr to int, long int, and long long int representation, respectively.
- Except for the behavior on error, they are equivalent to
- atoi: (int)strtol(nptr, (char **)NULL, 10)
- atol: strtol(nptr, (char **)NULL, 10)
- atoll: strtoll(nptr, (char **)NULL, 10)
- Returns
-3 The atoi, atol, and atoll functions return the converted value.
- Forward references: the strtol, strtoll, strtoul, and strtoull functions
- (<a href="#7.22.1.4">7.22.1.4</a>).
-
-
-
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-
-<a name="7.22.1.3" href="#7.22.1.3"><b> 7.22.1.3 The strtod, strtof, and strtold functions</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- double strtod(const char * restrict nptr,
- char ** restrict endptr);
- float strtof(const char * restrict nptr,
- char ** restrict endptr);
- long double strtold(const char * restrict nptr,
- char ** restrict endptr);
- Description
-2 The strtod, strtof, and strtold functions convert the initial portion of the string
- pointed to by nptr to double, float, and long double representation,
- respectively. First, they decompose the input string into three parts: an initial, possibly
- empty, sequence of white-space characters (as specified by the isspace function), a
- subject sequence resembling a floating-point constant or representing an infinity or NaN;
- and a final string of one or more unrecognized characters, including the terminating null
- character of the input string. Then, they attempt to convert the subject sequence to a
- floating-point number, and return the result.
-3 The expected form of the subject sequence is an optional plus or minus sign, then one of
- the following:
- -- a nonempty sequence of decimal digits optionally containing a decimal-point
- character, then an optional exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
- -- a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
- decimal-point character, then an optional binary exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
- -- INF or INFINITY, ignoring case
- -- NAN or NAN(n-char-sequenceopt), ignoring case in the NAN part, where:
- n-char-sequence:
- digit
- nondigit
- n-char-sequence digit
- n-char-sequence nondigit
- The subject sequence is defined as the longest initial subsequence of the input string,
- starting with the first non-white-space character, that is of the expected form. The subject
- sequence contains no characters if the input string is not of the expected form.
-4 If the subject sequence has the expected form for a floating-point number, the sequence of
- characters starting with the first digit or the decimal-point character (whichever occurs
- first) is interpreted as a floating constant according to the rules of <a href="#6.4.4.2">6.4.4.2</a>, except that the
-[<a name="#p341" href="p341">page 341</a>] (<a href="#Contents">Contents</a>)
-
- decimal-point character is used in place of a period, and that if neither an exponent part
- nor a decimal-point character appears in a decimal floating point number, or if a binary
- exponent part does not appear in a hexadecimal floating point number, an exponent part
- of the appropriate type with value zero is assumed to follow the last digit in the string. If
- the subject sequence begins with a minus sign, the sequence is interpreted as negated.281)
- A character sequence INF or INFINITY is interpreted as an infinity, if representable in
- the return type, else like a floating constant that is too large for the range of the return
- type. A character sequence NAN or NAN(n-char-sequenceopt), is interpreted as a quiet
- NaN, if supported in the return type, else like a subject sequence part that does not have
- the expected form; the meaning of the n-char sequences is implementation-defined.282) A
- pointer to the final string is stored in the object pointed to by endptr, provided that
- endptr is not a null pointer.
-5 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
- value resulting from the conversion is correctly rounded.
-6 In other than the "C" locale, additional locale-specific subject sequence forms may be
- accepted.
-7 If the subject sequence is empty or does not have the expected form, no conversion is
- performed; the value of nptr is stored in the object pointed to by endptr, provided
- that endptr is not a null pointer.
- Recommended practice
-8 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
- the result is not exactly representable, the result should be one of the two numbers in the
- appropriate internal format that are adjacent to the hexadecimal floating source value,
- with the extra stipulation that the error should have a correct sign for the current rounding
- direction.
-9 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
- <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
- sequence D has the decimal form and more than DECIMAL_DIG significant digits,
- consider the two bounding, adjacent decimal strings L and U, both having
- DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
- The result should be one of the (equal or adjacent) values that would be obtained by
- correctly rounding L and U according to the current rounding direction, with the extra
-
- 281) It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
- negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
- methods may yield different results if rounding is toward positive or negative infinity. In either case,
- the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
- 282) An implementation may use the n-char sequence to determine extra information to be represented in
- the NaN's significand.
-
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-
- stipulation that the error with respect to D should have a correct sign for the current
- rounding direction.283)
- Returns
-10 The functions return the converted value, if any. If no conversion could be performed,
- zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
- plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
- return type and sign of the value), and the value of the macro ERANGE is stored in
- errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
- no greater than the smallest normalized positive number in the return type; whether
- errno acquires the value ERANGE is implementation-defined.
-<a name="7.22.1.4" href="#7.22.1.4"><b> 7.22.1.4 The strtol, strtoll, strtoul, and strtoull functions</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- long int strtol(
- const char * restrict nptr,
- char ** restrict endptr,
- int base);
- long long int strtoll(
- const char * restrict nptr,
- char ** restrict endptr,
- int base);
- unsigned long int strtoul(
- const char * restrict nptr,
- char ** restrict endptr,
- int base);
- unsigned long long int strtoull(
- const char * restrict nptr,
- char ** restrict endptr,
- int base);
- Description
-2 The strtol, strtoll, strtoul, and strtoull functions convert the initial
- portion of the string pointed to by nptr to long int, long long int, unsigned
- long int, and unsigned long long int representation, respectively. First,
- they decompose the input string into three parts: an initial, possibly empty, sequence of
- white-space characters (as specified by the isspace function), a subject sequence
-
-
- 283) DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
- to the same internal floating value, but if not will round to adjacent values.
-
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-
- resembling an integer represented in some radix determined by the value of base, and a
- final string of one or more unrecognized characters, including the terminating null
- character of the input string. Then, they attempt to convert the subject sequence to an
- integer, and return the result.
-3 If the value of base is zero, the expected form of the subject sequence is that of an
- integer constant as described in <a href="#6.4.4.1">6.4.4.1</a>, optionally preceded by a plus or minus sign, but
- not including an integer suffix. If the value of base is between 2 and 36 (inclusive), the
- expected form of the subject sequence is a sequence of letters and digits representing an
- integer with the radix specified by base, optionally preceded by a plus or minus sign,
- but not including an integer suffix. The letters from a (or A) through z (or Z) are
- ascribed the values 10 through 35; only letters and digits whose ascribed values are less
- than that of base are permitted. If the value of base is 16, the characters 0x or 0X may
- optionally precede the sequence of letters and digits, following the sign if present.
-4 The subject sequence is defined as the longest initial subsequence of the input string,
- starting with the first non-white-space character, that is of the expected form. The subject
- sequence contains no characters if the input string is empty or consists entirely of white
- space, or if the first non-white-space character is other than a sign or a permissible letter
- or digit.
-5 If the subject sequence has the expected form and the value of base is zero, the sequence
- of characters starting with the first digit is interpreted as an integer constant according to
- the rules of <a href="#6.4.4.1">6.4.4.1</a>. If the subject sequence has the expected form and the value of base
- is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
- as given above. If the subject sequence begins with a minus sign, the value resulting from
- the conversion is negated (in the return type). A pointer to the final string is stored in the
- object pointed to by endptr, provided that endptr is not a null pointer.
-6 In other than the "C" locale, additional locale-specific subject sequence forms may be
- accepted.
-7 If the subject sequence is empty or does not have the expected form, no conversion is
- performed; the value of nptr is stored in the object pointed to by endptr, provided
- that endptr is not a null pointer.
- Returns
-8 The strtol, strtoll, strtoul, and strtoull functions return the converted
- value, if any. If no conversion could be performed, zero is returned. If the correct value
- is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
- LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
- and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
-
-
-
-
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-
-<a name="7.22.2" href="#7.22.2"><b> 7.22.2 Pseudo-random sequence generation functions</b></a>
-<a name="7.22.2.1" href="#7.22.2.1"><b> 7.22.2.1 The rand function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- int rand(void);
- Description
-2 The rand function computes a sequence of pseudo-random integers in the range 0 to
- RAND_MAX.284)
-3 The rand function is not required to avoid data races. The implementation shall behave
- as if no library function calls the rand function.
- Returns
-4 The rand function returns a pseudo-random integer.
- Environmental limits
-5 The value of the RAND_MAX macro shall be at least 32767.
-<a name="7.22.2.2" href="#7.22.2.2"><b> 7.22.2.2 The srand function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- void srand(unsigned int seed);
- Description
-2 The srand function uses the argument as a seed for a new sequence of pseudo-random
- numbers to be returned by subsequent calls to rand. If srand is then called with the
- same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
- called before any calls to srand have been made, the same sequence shall be generated
- as when srand is first called with a seed value of 1.
-3 The implementation shall behave as if no library function calls the srand function.
- Returns
-4 The srand function returns no value.
-
-
-
-
- 284) There are no guarantees as to the quality of the random sequence produced and some implementations
- are known to produce sequences with distressingly non-random low-order bits. Applications with
- particular requirements should use a generator that is known to be sufficient for their needs.
-
-[<a name="#p345" href="p345">page 345</a>] (<a href="#Contents">Contents</a>)
-
-5 EXAMPLE The following functions define a portable implementation of rand and srand.
- static unsigned long int next = 1;
- int rand(void) // RAND_MAX assumed to be 32767
- {
- next = next * 1103515245 + 12345;
- return (unsigned int)(next/65536) % 32768;
- }
- void srand(unsigned int seed)
- {
- next = seed;
- }
-
-<a name="7.22.3" href="#7.22.3"><b> 7.22.3 Memory management functions</b></a>
-1 The order and contiguity of storage allocated by successive calls to the
- aligned_alloc, calloc, malloc, and realloc functions is unspecified. The
- pointer returned if the allocation succeeds is suitably aligned so that it may be assigned to
- a pointer to any type of object with a fundamental alignment requirement and then used
- to access such an object or an array of such objects in the space allocated (until the space
- is explicitly deallocated). The lifetime of an allocated object extends from the allocation
- until the deallocation. Each such allocation shall yield a pointer to an object disjoint from
- any other object. The pointer returned points to the start (lowest byte address) of the
- allocated space. If the space cannot be allocated, a null pointer is returned. If the size of
- the space requested is zero, the behavior is implementation-defined: either a null pointer
- is returned, or the behavior is as if the size were some nonzero value, except that the
- returned pointer shall not be used to access an object.
-<a name="7.22.3.1" href="#7.22.3.1"><b> 7.22.3.1 The aligned_alloc function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- void *aligned_alloc(size_t alignment, size_t size);
- Description
-2 The aligned_alloc function allocates space for an object whose alignment is
- specified by alignment, whose size is specified by size, and whose value is
- indeterminate. The value of alignment shall be a valid alignment supported by the
- implementation and the value of size shall be an integral multiple of alignment.
- Returns
-3 The aligned_alloc function returns either a null pointer or a pointer to the allocated
- space.
-
-
-
-
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-
-<a name="7.22.3.2" href="#7.22.3.2"><b> 7.22.3.2 The calloc function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- void *calloc(size_t nmemb, size_t size);
- Description
-2 The calloc function allocates space for an array of nmemb objects, each of whose size
- is size. The space is initialized to all bits zero.285)
- Returns
-3 The calloc function returns either a null pointer or a pointer to the allocated space.
-<a name="7.22.3.3" href="#7.22.3.3"><b> 7.22.3.3 The free function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- void free(void *ptr);
- Description
-2 The free function causes the space pointed to by ptr to be deallocated, that is, made
- available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
- the argument does not match a pointer earlier returned by a memory management
- function, or if the space has been deallocated by a call to free or realloc, the
- behavior is undefined.
- Returns
-3 The free function returns no value.
-<a name="7.22.3.4" href="#7.22.3.4"><b> 7.22.3.4 The malloc function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- void *malloc(size_t size);
- Description
-2 The malloc function allocates space for an object whose size is specified by size and
- whose value is indeterminate.
-
-
-
-
- 285) Note that this need not be the same as the representation of floating-point zero or a null pointer
- constant.
-
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-
- Returns
-3 The malloc function returns either a null pointer or a pointer to the allocated space.
-<a name="7.22.3.5" href="#7.22.3.5"><b> 7.22.3.5 The realloc function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- void *realloc(void *ptr, size_t size);
- Description
-2 The realloc function deallocates the old object pointed to by ptr and returns a
- pointer to a new object that has the size specified by size. The contents of the new
- object shall be the same as that of the old object prior to deallocation, up to the lesser of
- the new and old sizes. Any bytes in the new object beyond the size of the old object have
- indeterminate values.
-3 If ptr is a null pointer, the realloc function behaves like the malloc function for the
- specified size. Otherwise, if ptr does not match a pointer earlier returned by a memory
- management function, or if the space has been deallocated by a call to the free or
- realloc function, the behavior is undefined. If memory for the new object cannot be
- allocated, the old object is not deallocated and its value is unchanged.
- Returns
-4 The realloc function returns a pointer to the new object (which may have the same
- value as a pointer to the old object), or a null pointer if the new object could not be
- allocated.
-<a name="7.22.4" href="#7.22.4"><b> 7.22.4 Communication with the environment</b></a>
-<a name="7.22.4.1" href="#7.22.4.1"><b> 7.22.4.1 The abort function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- _Noreturn void abort(void);
- Description
-2 The abort function causes abnormal program termination to occur, unless the signal
- SIGABRT is being caught and the signal handler does not return. Whether open streams
- with unwritten buffered data are flushed, open streams are closed, or temporary files are
- removed is implementation-defined. An implementation-defined form of the status
- unsuccessful termination is returned to the host environment by means of the function
- call raise(SIGABRT).
-
-
-
-
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-
- Returns
-3 The abort function does not return to its caller.
-<a name="7.22.4.2" href="#7.22.4.2"><b> 7.22.4.2 The atexit function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- int atexit(void (*func)(void));
- Description
-2 The atexit function registers the function pointed to by func, to be called without
- arguments at normal program termination.286)
- Environmental limits
-3 The implementation shall support the registration of at least 32 functions.
- Returns
-4 The atexit function returns zero if the registration succeeds, nonzero if it fails.
- Forward references: the at_quick_exit function (<a href="#7.22.4.3">7.22.4.3</a>), the exit function
- (<a href="#7.22.4.4">7.22.4.4</a>).
-<a name="7.22.4.3" href="#7.22.4.3"><b> 7.22.4.3 The at_quick_exit function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- int at_quick_exit(void (*func)(void));
- Description
-2 The at_quick_exit function registers the function pointed to by func, to be called
- without arguments should quick_exit be called.287)
- Environmental limits
-3 The implementation shall support the registration of at least 32 functions.
- Returns
-4 The at_quick_exit function returns zero if the registration succeeds, nonzero if it
- fails.
- Forward references: the quick_exit function (<a href="#7.22.4.7">7.22.4.7</a>).
-
- 286) The atexit function registrations are distinct from the at_quick_exit registrations, so
- applications may need to call both registration functions with the same argument.
- 287) The at_quick_exit function registrations are distinct from the atexit registrations, so
- applications may need to call both registration functions with the same argument.
-
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-
-<a name="7.22.4.4" href="#7.22.4.4"><b> 7.22.4.4 The exit function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- _Noreturn void exit(int status);
- Description
-2 The exit function causes normal program termination to occur. No functions registered
- by the at_quick_exit function are called. If a program calls the exit function
- more than once, or calls the quick_exit function in addition to the exit function, the
- behavior is undefined.
-3 First, all functions registered by the atexit function are called, in the reverse order of
- their registration,288) except that a function is called after any previously registered
- functions that had already been called at the time it was registered. If, during the call to
- any such function, a call to the longjmp function is made that would terminate the call
- to the registered function, the behavior is undefined.
-4 Next, all open streams with unwritten buffered data are flushed, all open streams are
- closed, and all files created by the tmpfile function are removed.
-5 Finally, control is returned to the host environment. If the value of status is zero or
- EXIT_SUCCESS, an implementation-defined form of the status successful termination is
- returned. If the value of status is EXIT_FAILURE, an implementation-defined form
- of the status unsuccessful termination is returned. Otherwise the status returned is
- implementation-defined.
- Returns
-6 The exit function cannot return to its caller.
-<a name="7.22.4.5" href="#7.22.4.5"><b> 7.22.4.5 The _Exit function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- _Noreturn void _Exit(int status);
- Description
-2 The _Exit function causes normal program termination to occur and control to be
- returned to the host environment. No functions registered by the atexit function, the
- at_quick_exit function, or signal handlers registered by the signal function are
- called. The status returned to the host environment is determined in the same way as for
-
-
- 288) Each function is called as many times as it was registered, and in the correct order with respect to
- other registered functions.
-
-[<a name="#p350" href="p350">page 350</a>] (<a href="#Contents">Contents</a>)
-
- the exit function (<a href="#7.22.4.4">7.22.4.4</a>). Whether open streams with unwritten buffered data are
- flushed, open streams are closed, or temporary files are removed is implementation-
- defined.
- Returns
-3 The _Exit function cannot return to its caller.
-<a name="7.22.4.6" href="#7.22.4.6"><b> 7.22.4.6 The getenv function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- char *getenv(const char *name);
- Description
-2 The getenv function searches an environment list, provided by the host environment,
- for a string that matches the string pointed to by name. The set of environment names
- and the method for altering the environment list are implementation-defined. The
- getenv function need not avoid data races with other threads of execution that modify
- the environment list.289)
-3 The implementation shall behave as if no library function calls the getenv function.
- Returns
-4 The getenv function returns a pointer to a string associated with the matched list
- member. The string pointed to shall not be modified by the program, but may be
- overwritten by a subsequent call to the getenv function. If the specified name cannot
- be found, a null pointer is returned.
-<a name="7.22.4.7" href="#7.22.4.7"><b> 7.22.4.7 The quick_exit function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- _Noreturn void quick_exit(int status);
- Description
-2 The quick_exit function causes normal program termination to occur. No functions
- registered by the atexit function or signal handlers registered by the signal function
- are called. If a program calls the quick_exit function more than once, or calls the
- exit function in addition to the quick_exit function, the behavior is undefined.
-3 The quick_exit function first calls all functions registered by the at_quick_exit
- function, in the reverse order of their registration,290) except that a function is called after
-
-
- 289) Many implementations provide non-standard functions that modify the environment list.
-
-[<a name="#p351" href="p351">page 351</a>] (<a href="#Contents">Contents</a>)
-
- any previously registered functions that had already been called at the time it was
- registered. If, during the call to any such function, a call to the longjmp function is
- made that would terminate the call to the registered function, the behavior is undefined.
-4 Then control is returned to the host environment by means of the function call
- _Exit(status).
- Returns
-5 The quick_exit function cannot return to its caller.
-<a name="7.22.4.8" href="#7.22.4.8"><b> 7.22.4.8 The system function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- int system(const char *string);
- Description
-2 If string is a null pointer, the system function determines whether the host
- environment has a command processor. If string is not a null pointer, the system
- function passes the string pointed to by string to that command processor to be
- executed in a manner which the implementation shall document; this might then cause the
- program calling system to behave in a non-conforming manner or to terminate.
- Returns
-3 If the argument is a null pointer, the system function returns nonzero only if a
- command processor is available. If the argument is not a null pointer, and the system
- function does return, it returns an implementation-defined value.
-<a name="7.22.5" href="#7.22.5"><b> 7.22.5 Searching and sorting utilities</b></a>
-1 These utilities make use of a comparison function to search or sort arrays of unspecified
- type. Where an argument declared as size_t nmemb specifies the length of the array
- for a function, nmemb can have the value zero on a call to that function; the comparison
- function is not called, a search finds no matching element, and sorting performs no
- rearrangement. Pointer arguments on such a call shall still have valid values, as described
- in <a href="#7.1.4">7.1.4</a>.
-2 The implementation shall ensure that the second argument of the comparison function
- (when called from bsearch), or both arguments (when called from qsort), are
- pointers to elements of the array.291) The first argument when called from bsearch
- shall equal key.
-
-
-
- 290) Each function is called as many times as it was registered, and in the correct order with respect to
- other registered functions.
-
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-
-3 The comparison function shall not alter the contents of the array. The implementation
- may reorder elements of the array between calls to the comparison function, but shall not
- alter the contents of any individual element.
-4 When the same objects (consisting of size bytes, irrespective of their current positions
- in the array) are passed more than once to the comparison function, the results shall be
- consistent with one another. That is, for qsort they shall define a total ordering on the
- array, and for bsearch the same object shall always compare the same way with the
- key.
-5 A sequence point occurs immediately before and immediately after each call to the
- comparison function, and also between any call to the comparison function and any
- movement of the objects passed as arguments to that call.
-<a name="7.22.5.1" href="#7.22.5.1"><b> 7.22.5.1 The bsearch function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- void *bsearch(const void *key, const void *base,
- size_t nmemb, size_t size,
- int (*compar)(const void *, const void *));
- Description
-2 The bsearch function searches an array of nmemb objects, the initial element of which
- is pointed to by base, for an element that matches the object pointed to by key. The
- size of each element of the array is specified by size.
-3 The comparison function pointed to by compar is called with two arguments that point
- to the key object and to an array element, in that order. The function shall return an
- integer less than, equal to, or greater than zero if the key object is considered,
- respectively, to be less than, to match, or to be greater than the array element. The array
- shall consist of: all the elements that compare less than, all the elements that compare
- equal to, and all the elements that compare greater than the key object, in that order.292)
- Returns
-4 The bsearch function returns a pointer to a matching element of the array, or a null
- pointer if no match is found. If two elements compare as equal, which element is
-
-
- 291) That is, if the value passed is p, then the following expressions are always nonzero:
- ((char *)p - (char *)base) % size == 0
- (char *)p >= (char *)base
- (char *)p < (char *)base + nmemb * size
-
- 292) In practice, the entire array is sorted according to the comparison function.
-
-[<a name="#p353" href="p353">page 353</a>] (<a href="#Contents">Contents</a>)
-
- matched is unspecified.
-<a name="7.22.5.2" href="#7.22.5.2"><b> 7.22.5.2 The qsort function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- void qsort(void *base, size_t nmemb, size_t size,
- int (*compar)(const void *, const void *));
- Description
-2 The qsort function sorts an array of nmemb objects, the initial element of which is
- pointed to by base. The size of each object is specified by size.
-3 The contents of the array are sorted into ascending order according to a comparison
- function pointed to by compar, which is called with two arguments that point to the
- objects being compared. The function shall return an integer less than, equal to, or
- greater than zero if the first argument is considered to be respectively less than, equal to,
- or greater than the second.
-4 If two elements compare as equal, their order in the resulting sorted array is unspecified.
- Returns
-5 The qsort function returns no value.
-<a name="7.22.6" href="#7.22.6"><b> 7.22.6 Integer arithmetic functions</b></a>
-<a name="7.22.6.1" href="#7.22.6.1"><b> 7.22.6.1 The abs, labs and llabs functions</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- int abs(int j);
- long int labs(long int j);
- long long int llabs(long long int j);
- Description
-2 The abs, labs, and llabs functions compute the absolute value of an integer j. If the
- result cannot be represented, the behavior is undefined.293)
- Returns
-3 The abs, labs, and llabs, functions return the absolute value.
-
-
-
-
- 293) The absolute value of the most negative number cannot be represented in two's complement.
-
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-
-<a name="7.22.6.2" href="#7.22.6.2"><b> 7.22.6.2 The div, ldiv, and lldiv functions</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- div_t div(int numer, int denom);
- ldiv_t ldiv(long int numer, long int denom);
- lldiv_t lldiv(long long int numer, long long int denom);
- Description
-2 The div, ldiv, and lldiv, functions compute numer / denom and numer %
- denom in a single operation.
- Returns
-3 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
- lldiv_t, respectively, comprising both the quotient and the remainder. The structures
- shall contain (in either order) the members quot (the quotient) and rem (the remainder),
- each of which has the same type as the arguments numer and denom. If either part of
- the result cannot be represented, the behavior is undefined.
-<a name="7.22.7" href="#7.22.7"><b> 7.22.7 Multibyte/wide character conversion functions</b></a>
-1 The behavior of the multibyte character functions is affected by the LC_CTYPE category
- of the current locale. For a state-dependent encoding, each function is placed into its
- initial conversion state at program startup and can be returned to that state by a call for
- which its character pointer argument, s, is a null pointer. Subsequent calls with s as
- other than a null pointer cause the internal conversion state of the function to be altered as
- necessary. A call with s as a null pointer causes these functions to return a nonzero value
- if encodings have state dependency, and zero otherwise.294) Changing the LC_CTYPE
- category causes the conversion state of these functions to be indeterminate.
-<a name="7.22.7.1" href="#7.22.7.1"><b> 7.22.7.1 The mblen function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- int mblen(const char *s, size_t n);
- Description
-2 If s is not a null pointer, the mblen function determines the number of bytes contained
- in the multibyte character pointed to by s. Except that the conversion state of the
- mbtowc function is not affected, it is equivalent to
-
-
-
- 294) If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
- character codes, but are grouped with an adjacent multibyte character.
-
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-
- mbtowc((wchar_t *)0, (const char *)0, 0);
- mbtowc((wchar_t *)0, s, n);
-3 The implementation shall behave as if no library function calls the mblen function.
- Returns
-4 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte
- character encodings, respectively, do or do not have state-dependent encodings. If s is
- not a null pointer, the mblen function either returns 0 (if s points to the null character),
- or returns the number of bytes that are contained in the multibyte character (if the next n
- or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid
- multibyte character).
- Forward references: the mbtowc function (<a href="#7.22.7.2">7.22.7.2</a>).
-<a name="7.22.7.2" href="#7.22.7.2"><b> 7.22.7.2 The mbtowc function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- int mbtowc(wchar_t * restrict pwc,
- const char * restrict s,
- size_t n);
- Description
-2 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with
- the byte pointed to by s to determine the number of bytes needed to complete the next
- multibyte character (including any shift sequences). If the function determines that the
- next multibyte character is complete and valid, it determines the value of the
- corresponding wide character and then, if pwc is not a null pointer, stores that value in
- the object pointed to by pwc. If the corresponding wide character is the null wide
- character, the function is left in the initial conversion state.
-3 The implementation shall behave as if no library function calls the mbtowc function.
- Returns
-4 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte
- character encodings, respectively, do or do not have state-dependent encodings. If s is
- not a null pointer, the mbtowc function either returns 0 (if s points to the null character),
- or returns the number of bytes that are contained in the converted multibyte character (if
- the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not
- form a valid multibyte character).
-5 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
- macro.
-
-
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-
-<a name="7.22.7.3" href="#7.22.7.3"><b> 7.22.7.3 The wctomb function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- int wctomb(char *s, wchar_t wc);
- Description
-2 The wctomb function determines the number of bytes needed to represent the multibyte
- character corresponding to the wide character given by wc (including any shift
- sequences), and stores the multibyte character representation in the array whose first
- element is pointed to by s (if s is not a null pointer). At most MB_CUR_MAX characters
- are stored. If wc is a null wide character, a null byte is stored, preceded by any shift
- sequence needed to restore the initial shift state, and the function is left in the initial
- conversion state.
-3 The implementation shall behave as if no library function calls the wctomb function.
- Returns
-4 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte
- character encodings, respectively, do or do not have state-dependent encodings. If s is
- not a null pointer, the wctomb function returns -1 if the value of wc does not correspond
- to a valid multibyte character, or returns the number of bytes that are contained in the
- multibyte character corresponding to the value of wc.
-5 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
-<a name="7.22.8" href="#7.22.8"><b> 7.22.8 Multibyte/wide string conversion functions</b></a>
-1 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
- the current locale.
-<a name="7.22.8.1" href="#7.22.8.1"><b> 7.22.8.1 The mbstowcs function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- size_t mbstowcs(wchar_t * restrict pwcs,
- const char * restrict s,
- size_t n);
- Description
-2 The mbstowcs function converts a sequence of multibyte characters that begins in the
- initial shift state from the array pointed to by s into a sequence of corresponding wide
- characters and stores not more than n wide characters into the array pointed to by pwcs.
- No multibyte characters that follow a null character (which is converted into a null wide
- character) will be examined or converted. Each multibyte character is converted as if by
- a call to the mbtowc function, except that the conversion state of the mbtowc function is
-[<a name="#p357" href="p357">page 357</a>] (<a href="#Contents">Contents</a>)
-
- not affected.
-3 No more than n elements will be modified in the array pointed to by pwcs. If copying
- takes place between objects that overlap, the behavior is undefined.
- Returns
-4 If an invalid multibyte character is encountered, the mbstowcs function returns
- (size_t)(-1). Otherwise, the mbstowcs function returns the number of array
- elements modified, not including a terminating null wide character, if any.295)
-<a name="7.22.8.2" href="#7.22.8.2"><b> 7.22.8.2 The wcstombs function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- size_t wcstombs(char * restrict s,
- const wchar_t * restrict pwcs,
- size_t n);
- Description
-2 The wcstombs function converts a sequence of wide characters from the array pointed
- to by pwcs into a sequence of corresponding multibyte characters that begins in the
- initial shift state, and stores these multibyte characters into the array pointed to by s,
- stopping if a multibyte character would exceed the limit of n total bytes or if a null
- character is stored. Each wide character is converted as if by a call to the wctomb
- function, except that the conversion state of the wctomb function is not affected.
-3 No more than n bytes will be modified in the array pointed to by s. If copying takes place
- between objects that overlap, the behavior is undefined.
- Returns
-4 If a wide character is encountered that does not correspond to a valid multibyte character,
- the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
- returns the number of bytes modified, not including a terminating null character, if
- any.295)
-
-
-
-
- 295) The array will not be null-terminated if the value returned is n.
-
-[<a name="#p358" href="p358">page 358</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.23" href="#7.23"><b> 7.23 String handling <string.h></b></a>
-<a name="7.23.1" href="#7.23.1"><b> 7.23.1 String function conventions</b></a>
-1 The header <a href="#7.23"><string.h></a> declares one type and several functions, and defines one
- macro useful for manipulating arrays of character type and other objects treated as arrays
- of character type.296) The type is size_t and the macro is NULL (both described in
-<a name="7.19)" href="#7.19)"><b> 7.19). Various methods are used for determining the lengths of the arrays, but in all cases</b></a>
- a char * or void * argument points to the initial (lowest addressed) character of the
- array. If an array is accessed beyond the end of an object, the behavior is undefined.
-2 Where an argument declared as size_t n specifies the length of the array for a
- function, n can have the value zero on a call to that function. Unless explicitly stated
- otherwise in the description of a particular function in this subclause, pointer arguments
- on such a call shall still have valid values, as described in <a href="#7.1.4">7.1.4</a>. On such a call, a
- function that locates a character finds no occurrence, a function that compares two
- character sequences returns zero, and a function that copies characters copies zero
- characters.
-3 For all functions in this subclause, each character shall be interpreted as if it had the type
- unsigned char (and therefore every possible object representation is valid and has a
- different value).
-<a name="7.23.2" href="#7.23.2"><b> 7.23.2 Copying functions</b></a>
-<a name="7.23.2.1" href="#7.23.2.1"><b> 7.23.2.1 The memcpy function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- void *memcpy(void * restrict s1,
- const void * restrict s2,
- size_t n);
- Description
-2 The memcpy function copies n characters from the object pointed to by s2 into the
- object pointed to by s1. If copying takes place between objects that overlap, the behavior
- is undefined.
- Returns
-3 The memcpy function returns the value of s1.
-
-
-
-
- 296) See ''future library directions'' (<a href="#7.30.11">7.30.11</a>).
-
-[<a name="#p359" href="p359">page 359</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.23.2.2" href="#7.23.2.2"><b> 7.23.2.2 The memmove function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- void *memmove(void *s1, const void *s2, size_t n);
- Description
-2 The memmove function copies n characters from the object pointed to by s2 into the
- object pointed to by s1. Copying takes place as if the n characters from the object
- pointed to by s2 are first copied into a temporary array of n characters that does not
- overlap the objects pointed to by s1 and s2, and then the n characters from the
- temporary array are copied into the object pointed to by s1.
- Returns
-3 The memmove function returns the value of s1.
-<a name="7.23.2.3" href="#7.23.2.3"><b> 7.23.2.3 The strcpy function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- char *strcpy(char * restrict s1,
- const char * restrict s2);
- Description
-2 The strcpy function copies the string pointed to by s2 (including the terminating null
- character) into the array pointed to by s1. If copying takes place between objects that
- overlap, the behavior is undefined.
- Returns
-3 The strcpy function returns the value of s1.
-<a name="7.23.2.4" href="#7.23.2.4"><b> 7.23.2.4 The strncpy function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- char *strncpy(char * restrict s1,
- const char * restrict s2,
- size_t n);
- Description
-2 The strncpy function copies not more than n characters (characters that follow a null
- character are not copied) from the array pointed to by s2 to the array pointed to by
-
-
-
-
-[<a name="#p360" href="p360">page 360</a>] (<a href="#Contents">Contents</a>)
-
- s1.297) If copying takes place between objects that overlap, the behavior is undefined.
-3 If the array pointed to by s2 is a string that is shorter than n characters, null characters
- are appended to the copy in the array pointed to by s1, until n characters in all have been
- written.
- Returns
-4 The strncpy function returns the value of s1.
-<a name="7.23.3" href="#7.23.3"><b> 7.23.3 Concatenation functions</b></a>
-<a name="7.23.3.1" href="#7.23.3.1"><b> 7.23.3.1 The strcat function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- char *strcat(char * restrict s1,
- const char * restrict s2);
- Description
-2 The strcat function appends a copy of the string pointed to by s2 (including the
- terminating null character) to the end of the string pointed to by s1. The initial character
- of s2 overwrites the null character at the end of s1. If copying takes place between
- objects that overlap, the behavior is undefined.
- Returns
-3 The strcat function returns the value of s1.
-<a name="7.23.3.2" href="#7.23.3.2"><b> 7.23.3.2 The strncat function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- char *strncat(char * restrict s1,
- const char * restrict s2,
- size_t n);
- Description
-2 The strncat function appends not more than n characters (a null character and
- characters that follow it are not appended) from the array pointed to by s2 to the end of
- the string pointed to by s1. The initial character of s2 overwrites the null character at the
- end of s1. A terminating null character is always appended to the result.298) If copying
-
- 297) Thus, if there is no null character in the first n characters of the array pointed to by s2, the result will
- not be null-terminated.
- 298) Thus, the maximum number of characters that can end up in the array pointed to by s1 is
- strlen(s1)+n+1.
-
-[<a name="#p361" href="p361">page 361</a>] (<a href="#Contents">Contents</a>)
-
- takes place between objects that overlap, the behavior is undefined.
- Returns
-3 The strncat function returns the value of s1.
- Forward references: the strlen function (<a href="#7.23.6.3">7.23.6.3</a>).
-<a name="7.23.4" href="#7.23.4"><b> 7.23.4 Comparison functions</b></a>
-1 The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
- and strncmp is determined by the sign of the difference between the values of the first
- pair of characters (both interpreted as unsigned char) that differ in the objects being
- compared.
-<a name="7.23.4.1" href="#7.23.4.1"><b> 7.23.4.1 The memcmp function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- int memcmp(const void *s1, const void *s2, size_t n);
- Description
-2 The memcmp function compares the first n characters of the object pointed to by s1 to
- the first n characters of the object pointed to by s2.299)
- Returns
-3 The memcmp function returns an integer greater than, equal to, or less than zero,
- accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
- pointed to by s2.
-<a name="7.23.4.2" href="#7.23.4.2"><b> 7.23.4.2 The strcmp function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- int strcmp(const char *s1, const char *s2);
- Description
-2 The strcmp function compares the string pointed to by s1 to the string pointed to by
- s2.
- Returns
-3 The strcmp function returns an integer greater than, equal to, or less than zero,
- accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
-
- 299) The contents of ''holes'' used as padding for purposes of alignment within structure objects are
- indeterminate. Strings shorter than their allocated space and unions may also cause problems in
- comparison.
-
-[<a name="#p362" href="p362">page 362</a>] (<a href="#Contents">Contents</a>)
-
- pointed to by s2.
-<a name="7.23.4.3" href="#7.23.4.3"><b> 7.23.4.3 The strcoll function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- int strcoll(const char *s1, const char *s2);
- Description
-2 The strcoll function compares the string pointed to by s1 to the string pointed to by
- s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
- Returns
-3 The strcoll function returns an integer greater than, equal to, or less than zero,
- accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
- pointed to by s2 when both are interpreted as appropriate to the current locale.
-<a name="7.23.4.4" href="#7.23.4.4"><b> 7.23.4.4 The strncmp function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- int strncmp(const char *s1, const char *s2, size_t n);
- Description
-2 The strncmp function compares not more than n characters (characters that follow a
- null character are not compared) from the array pointed to by s1 to the array pointed to
- by s2.
- Returns
-3 The strncmp function returns an integer greater than, equal to, or less than zero,
- accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
- to, or less than the possibly null-terminated array pointed to by s2.
-<a name="7.23.4.5" href="#7.23.4.5"><b> 7.23.4.5 The strxfrm function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- size_t strxfrm(char * restrict s1,
- const char * restrict s2,
- size_t n);
- Description
-2 The strxfrm function transforms the string pointed to by s2 and places the resulting
- string into the array pointed to by s1. The transformation is such that if the strcmp
- function is applied to two transformed strings, it returns a value greater than, equal to, or
-
-[<a name="#p363" href="p363">page 363</a>] (<a href="#Contents">Contents</a>)
-
- less than zero, corresponding to the result of the strcoll function applied to the same
- two original strings. No more than n characters are placed into the resulting array
- pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
- be a null pointer. If copying takes place between objects that overlap, the behavior is
- undefined.
- Returns
-3 The strxfrm function returns the length of the transformed string (not including the
- terminating null character). If the value returned is n or more, the contents of the array
- pointed to by s1 are indeterminate.
-4 EXAMPLE The value of the following expression is the size of the array needed to hold the
- transformation of the string pointed to by s.
- 1 + strxfrm(NULL, s, 0)
-
-<a name="7.23.5" href="#7.23.5"><b> 7.23.5 Search functions</b></a>
-<a name="7.23.5.1" href="#7.23.5.1"><b> 7.23.5.1 The memchr function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- void *memchr(const void *s, int c, size_t n);
- Description
-2 The memchr function locates the first occurrence of c (converted to an unsigned
- char) in the initial n characters (each interpreted as unsigned char) of the object
- pointed to by s.
- Returns
-3 The memchr function returns a pointer to the located character, or a null pointer if the
- character does not occur in the object.
-<a name="7.23.5.2" href="#7.23.5.2"><b> 7.23.5.2 The strchr function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- char *strchr(const char *s, int c);
- Description
-2 The strchr function locates the first occurrence of c (converted to a char) in the
- string pointed to by s. The terminating null character is considered to be part of the
- string.
- Returns
-3 The strchr function returns a pointer to the located character, or a null pointer if the
- character does not occur in the string.
-[<a name="#p364" href="p364">page 364</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.23.5.3" href="#7.23.5.3"><b> 7.23.5.3 The strcspn function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- size_t strcspn(const char *s1, const char *s2);
- Description
-2 The strcspn function computes the length of the maximum initial segment of the string
- pointed to by s1 which consists entirely of characters not from the string pointed to by
- s2.
- Returns
-3 The strcspn function returns the length of the segment.
-<a name="7.23.5.4" href="#7.23.5.4"><b> 7.23.5.4 The strpbrk function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- char *strpbrk(const char *s1, const char *s2);
- Description
-2 The strpbrk function locates the first occurrence in the string pointed to by s1 of any
- character from the string pointed to by s2.
- Returns
-3 The strpbrk function returns a pointer to the character, or a null pointer if no character
- from s2 occurs in s1.
-<a name="7.23.5.5" href="#7.23.5.5"><b> 7.23.5.5 The strrchr function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- char *strrchr(const char *s, int c);
- Description
-2 The strrchr function locates the last occurrence of c (converted to a char) in the
- string pointed to by s. The terminating null character is considered to be part of the
- string.
- Returns
-3 The strrchr function returns a pointer to the character, or a null pointer if c does not
- occur in the string.
-
-
-
-
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-
-<a name="7.23.5.6" href="#7.23.5.6"><b> 7.23.5.6 The strspn function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- size_t strspn(const char *s1, const char *s2);
- Description
-2 The strspn function computes the length of the maximum initial segment of the string
- pointed to by s1 which consists entirely of characters from the string pointed to by s2.
- Returns
-3 The strspn function returns the length of the segment.
-<a name="7.23.5.7" href="#7.23.5.7"><b> 7.23.5.7 The strstr function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- char *strstr(const char *s1, const char *s2);
- Description
-2 The strstr function locates the first occurrence in the string pointed to by s1 of the
- sequence of characters (excluding the terminating null character) in the string pointed to
- by s2.
- Returns
-3 The strstr function returns a pointer to the located string, or a null pointer if the string
- is not found. If s2 points to a string with zero length, the function returns s1.
-<a name="7.23.5.8" href="#7.23.5.8"><b> 7.23.5.8 The strtok function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- char *strtok(char * restrict s1,
- const char * restrict s2);
- Description
-2 A sequence of calls to the strtok function breaks the string pointed to by s1 into a
- sequence of tokens, each of which is delimited by a character from the string pointed to
- by s2. The first call in the sequence has a non-null first argument; subsequent calls in the
- sequence have a null first argument. The separator string pointed to by s2 may be
- different from call to call.
-3 The first call in the sequence searches the string pointed to by s1 for the first character
- that is not contained in the current separator string pointed to by s2. If no such character
- is found, then there are no tokens in the string pointed to by s1 and the strtok function
-
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-
- returns a null pointer. If such a character is found, it is the start of the first token.
-4 The strtok function then searches from there for a character that is contained in the
- current separator string. If no such character is found, the current token extends to the
- end of the string pointed to by s1, and subsequent searches for a token will return a null
- pointer. If such a character is found, it is overwritten by a null character, which
- terminates the current token. The strtok function saves a pointer to the following
- character, from which the next search for a token will start.
-5 Each subsequent call, with a null pointer as the value of the first argument, starts
- searching from the saved pointer and behaves as described above.
-6 The strtok function is not required to avoid data races. The implementation shall
- behave as if no library function calls the strtok function.
- Returns
-7 The strtok function returns a pointer to the first character of a token, or a null pointer
- if there is no token.
-8 EXAMPLE
- #include <a href="#7.23"><string.h></a>
- static char str[] = "?a???b,,,#c";
- char *t;
- t = strtok(str, "?"); // t points to the token "a"
- t = strtok(NULL, ","); // t points to the token "??b"
- t = strtok(NULL, "#,"); // t points to the token "c"
- t = strtok(NULL, "?"); // t is a null pointer
-
-<a name="7.23.6" href="#7.23.6"><b> 7.23.6 Miscellaneous functions</b></a>
-<a name="7.23.6.1" href="#7.23.6.1"><b> 7.23.6.1 The memset function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- void *memset(void *s, int c, size_t n);
- Description
-2 The memset function copies the value of c (converted to an unsigned char) into
- each of the first n characters of the object pointed to by s.
- Returns
-3 The memset function returns the value of s.
-
-
-
-
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-
-<a name="7.23.6.2" href="#7.23.6.2"><b> 7.23.6.2 The strerror function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- char *strerror(int errnum);
- Description
-2 The strerror function maps the number in errnum to a message string. Typically,
- the values for errnum come from errno, but strerror shall map any value of type
- int to a message.
-3 The strerror function is not required to avoid data races. The implementation shall
- behave as if no library function calls the strerror function.
- Returns
-4 The strerror function returns a pointer to the string, the contents of which are locale-
- specific. The array pointed to shall not be modified by the program, but may be
- overwritten by a subsequent call to the strerror function.
-<a name="7.23.6.3" href="#7.23.6.3"><b> 7.23.6.3 The strlen function</b></a>
- Synopsis
-1 #include <a href="#7.23"><string.h></a>
- size_t strlen(const char *s);
- Description
-2 The strlen function computes the length of the string pointed to by s.
- Returns
-3 The strlen function returns the number of characters that precede the terminating null
- character.
-
-
-
-
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-
-<a name="7.24" href="#7.24"><b> 7.24 Type-generic math <tgmath.h></b></a>
-1 The header <a href="#7.24"><tgmath.h></a> includes the headers <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> and
- defines several type-generic macros.
-2 Of the <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> functions without an f (float) or l (long
- double) suffix, several have one or more parameters whose corresponding real type is
- double. For each such function, except modf, there is a corresponding type-generic
- macro.300) The parameters whose corresponding real type is double in the function
- synopsis are generic parameters. Use of the macro invokes a function whose
- corresponding real type and type domain are determined by the arguments for the generic
- parameters.301)
-3 Use of the macro invokes a function whose generic parameters have the corresponding
- real type determined as follows:
- -- First, if any argument for generic parameters has type long double, the type
- determined is long double.
- -- Otherwise, if any argument for generic parameters has type double or is of integer
- type, the type determined is double.
- -- Otherwise, the type determined is float.
-4 For each unsuffixed function in <a href="#7.12"><math.h></a> for which there is a function in
- <a href="#7.3"><complex.h></a> with the same name except for a c prefix, the corresponding type-
- generic macro (for both functions) has the same name as the function in <a href="#7.12"><math.h></a>. The
- corresponding type-generic macro for fabs and cabs is fabs.
-
-
-
-
- 300) Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to
- make available the corresponding ordinary function.
- 301) If the type of the argument is not compatible with the type of the parameter for the selected function,
- the behavior is undefined.
-
-[<a name="#p369" href="p369">page 369</a>] (<a href="#Contents">Contents</a>)
-
- <a href="#7.12"><math.h></a> <a href="#7.3"><complex.h></a> type-generic
- function function macro
- acos cacos acos
- asin casin asin
- atan catan atan
- acosh cacosh acosh
- asinh casinh asinh
- atanh catanh atanh
- cos ccos cos
- sin csin sin
- tan ctan tan
- cosh ccosh cosh
- sinh csinh sinh
- tanh ctanh tanh
- exp cexp exp
- log clog log
- pow cpow pow
- sqrt csqrt sqrt
- fabs cabs fabs
- If at least one argument for a generic parameter is complex, then use of the macro invokes
- a complex function; otherwise, use of the macro invokes a real function.
-5 For each unsuffixed function in <a href="#7.12"><math.h></a> without a c-prefixed counterpart in
- <a href="#7.3"><complex.h></a> (except modf), the corresponding type-generic macro has the same
- name as the function. These type-generic macros are:
- atan2 fma llround remainder
- cbrt fmax log10 remquo
- ceil fmin log1p rint
- copysign fmod log2 round
- erf frexp logb scalbn
- erfc hypot lrint scalbln
- exp2 ilogb lround tgamma
- expm1 ldexp nearbyint trunc
- fdim lgamma nextafter
- floor llrint nexttoward
- If all arguments for generic parameters are real, then use of the macro invokes a real
- function; otherwise, use of the macro results in undefined behavior.
-
-
-
-
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-
-6 For each unsuffixed function in <a href="#7.3"><complex.h></a> that is not a c-prefixed counterpart to a
- function in <a href="#7.12"><math.h></a>, the corresponding type-generic macro has the same name as the
- function. These type-generic macros are:
- carg conj creal
- cimag cproj
- Use of the macro with any real or complex argument invokes a complex function.
-7 EXAMPLE With the declarations
- #include <a href="#7.24"><tgmath.h></a>
- int n;
- float f;
- double d;
- long double ld;
- float complex fc;
- double complex dc;
- long double complex ldc;
- functions invoked by use of type-generic macros are shown in the following table:
- macro use invokes
- exp(n) exp(n), the function
- acosh(f) acoshf(f)
- sin(d) sin(d), the function
- atan(ld) atanl(ld)
- log(fc) clogf(fc)
- sqrt(dc) csqrt(dc)
- pow(ldc, f) cpowl(ldc, f)
- remainder(n, n) remainder(n, n), the function
- nextafter(d, f) nextafter(d, f), the function
- nexttoward(f, ld) nexttowardf(f, ld)
- copysign(n, ld) copysignl(n, ld)
- ceil(fc) undefined behavior
- rint(dc) undefined behavior
- fmax(ldc, ld) undefined behavior
- carg(n) carg(n), the function
- cproj(f) cprojf(f)
- creal(d) creal(d), the function
- cimag(ld) cimagl(ld)
- fabs(fc) cabsf(fc)
- carg(dc) carg(dc), the function
- cproj(ldc) cprojl(ldc)
-
-
-
-
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-
-<a name="7.25" href="#7.25"><b> 7.25 Threads <threads.h></b></a>
-<a name="7.25.1" href="#7.25.1"><b> 7.25.1 Introduction</b></a>
-1 The header <a href="#7.25"><threads.h></a> defines macros, and declares types, enumeration constants,
- and functions that support multiple threads of execution.
-2 Implementations that define the macro __STDC_NO_THREADS__ need not provide
- this header nor support any of its facilities.
-3 The macros are
- ONCE_FLAG_INIT
- which expands to a value that can be used to initialize an object of type once_flag;
- and
- TSS_DTOR_ITERATIONS
- which expands to an integer constant expression representing the maximum number of
- times that destructors will be called when a thread terminates.
-4 The types are
- cnd_t
- which is a complete object type that holds an identifier for a condition variable;
- thrd_t
- which is a complete object type that holds an identifier for a thread;
- tss_t
- which is a complete object type that holds an identifier for a thread-specific storage
- pointer;
- mtx_t
- which is a complete object type that holds an identifier for a mutex;
- tss_dtor_t
- which is the function pointer type void (*)(void*), used for a destructor for a
- thread-specific storage pointer;
- thrd_start_t
- which is the function pointer type int (*)(void*) that is passed to thrd_create
- to create a new thread;
- once_flag
- which is a complete object type that holds a flag for use by call_once; and
-
-
-[<a name="#p372" href="p372">page 372</a>] (<a href="#Contents">Contents</a>)
-
- xtime
- which is a structure type that holds a time specified in seconds and nanoseconds. The
- structure shall contain at least the following members, in any order.
- time_t sec;
- long nsec;
-5 The enumeration constants are
- mtx_plain
- which is passed to mtx_init to create a mutex object that supports neither timeout nor
- test and return;
- mtx_recursive
- which is passed to mtx_init to create a mutex object that supports recursive locking;
- mtx_timed
- which is passed to mtx_init to create a mutex object that supports timeout;
- mtx_try
- which is passed to mtx_init to create a mutex object that supports test and return;
- thrd_timeout
- which is returned by a timed wait function to indicate that the time specified in the call
- was reached without acquiring the requested resource;
- thrd_success
- which is returned by a function to indicate that the requested operation succeeded;
- thrd_busy
- which is returned by a function to indicate that the requested operation failed because a
- resource requested by a test and return function is already in use;
- thrd_error
- which is returned by a function to indicate that the requested operation failed; and
- thrd_nomem
- which is returned by a function to indicate that the requested operation failed because it
- was unable to allocate memory.
-
-
-
-
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-
-<a name="7.25.2" href="#7.25.2"><b> 7.25.2 Initialization functions</b></a>
-<a name="7.25.2.1" href="#7.25.2.1"><b> 7.25.2.1 The call_once function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- void call_once(once_flag *flag, void (*func)(void));
- Description
-2 The call_once function uses the once_flag pointed to by flag to ensure that
- func is called exactly once, the first time the call_once function is called with that
- value of flag. Completion of an effective call to the call_once function synchronizes
- with all subsequent calls to the call_once function with the same value of flag.
- Returns
-3 The call_once function returns no value.
-<a name="7.25.3" href="#7.25.3"><b> 7.25.3 Condition variable functions</b></a>
-<a name="7.25.3.1" href="#7.25.3.1"><b> 7.25.3.1 The cnd_broadcast function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int cnd_broadcast(cnd_t *cond);
- Description
-2 The cnd_broadcast function unblocks all of the threads that are blocked on the
- condition variable pointed to by cond at the time of the call. If no threads are blocked
- on the condition variable pointed to by cond at the time of the call, the function does
- nothing.
- Returns
-3 The cnd_broadcast function returns thrd_success on success, or thrd_error
- if the request could not be honored.
-<a name="7.25.3.2" href="#7.25.3.2"><b> 7.25.3.2 The cnd_destroy function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- void cnd_destroy(cnd_t *cond);
- Description
-2 The cnd_destroy function releases all resources used by the condition variable
- pointed to by cond. The cnd_destroy function requires that no threads be blocked
- waiting for the condition variable pointed to by cond.
-
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-
- Returns
-3 The cnd_destroy function returns no value.
-<a name="7.25.3.3" href="#7.25.3.3"><b> 7.25.3.3 The cnd_init function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int cnd_init(cnd_t *cond);
- Description
-2 The cnd_init function creates a condition variable. If it succeeds it sets the variable
- pointed to by cond to a value that uniquely identifies the newly created condition
- variable. A thread that calls cnd_wait on a newly created condition variable will
- block.
- Returns
-3 The cnd_init function returns thrd_success on success, or thrd_nomem if no
- memory could be allocated for the newly created condition, or thrd_error if the
- request could not be honored.
-<a name="7.25.3.4" href="#7.25.3.4"><b> 7.25.3.4 The cnd_signal function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int cnd_signal(cnd_t *cond);
- Description
-2 The cnd_signal function unblocks one of the threads that are blocked on the
- condition variable pointed to by cond at the time of the call. If no threads are blocked
- on the condition variable at the time of the call, the function does nothing and return
- success.
- Returns
-3 The cnd_signal function returns thrd_success on success or thrd_error if
- the request could not be honored.
-<a name="7.25.3.5" href="#7.25.3.5"><b> 7.25.3.5 The cnd_timedwait function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
- const xtime *xt);
-
-
-
-
-[<a name="#p375" href="p375">page 375</a>] (<a href="#Contents">Contents</a>)
-
- Description
-2 The cnd_timedwait function atomically unlocks the mutex pointed to by mtx and
- endeavors to block until the condition variable pointed to by cond is signaled by a call to
- cnd_signal or to cnd_broadcast, or until after the time specified by the xtime
- object pointed to by xt. When the calling thread becomes unblocked it locks the variable
- pointed to by mtx before it returns. The cnd_timedwait function requires that the
- mutex pointed to by mtx be locked by the calling thread.
- Returns
-3 The cnd_timedwait function returns thrd_success upon success, or
- thrd_timeout if the time specified in the call was reached without acquiring the
- requested resource, or thrd_error if the request could not be honored.
-<a name="7.25.3.6" href="#7.25.3.6"><b> 7.25.3.6 The cnd_wait function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int cnd_wait(cnd_t *cond, mtx_t *mtx);
- Description
-2 The cnd_wait function atomically unlocks the mutex pointed to by mtx and endeavors
- to block until the condition variable pointed to by cond is signaled by a call to
- cnd_signal or to cnd_broadcast. When the calling thread becomes unblocked it
- locks the mutex pointed to by mtx before it returns. If the mutex pointed to by mtx is
- not locked by the calling thread, the cnd_wait function will act as if the abort
- function is called.
- Returns
-3 The cnd_wait function returns thrd_success on success or thrd_error if the
- request could not be honored.
-<a name="7.25.4" href="#7.25.4"><b> 7.25.4 Mutex functions</b></a>
-<a name="7.25.4.1" href="#7.25.4.1"><b> 7.25.4.1 The mtx_destroy function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- void mtx_destroy(mtx_t *mtx);
- Description
-2 The mtx_destroy function releases any resources used by the mutex pointed to by
- mtx. No threads can be blocked waiting for the mutex pointed to by mtx.
-
-
-
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-
- Returns
-3 The mtx_destroy function returns no value.
-<a name="7.25.4.2" href="#7.25.4.2"><b> 7.25.4.2 The mtx_init function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int mtx_init(mtx_t *mtx, int type);
- Description
-2 The mtx_init function creates a mutex object with properties indicated by type,
- which must have one of the six values:
- mtx_plain for a simple non-recursive mutex,
- mtx_timed for a non-recursive mutex that supports timeout,
- mtx_try for a non-recursive mutex that supports test and return,
- mtx_plain | mtx_recursive for a simple recursive mutex,
- mtx_timed | mtx_recursive for a recursive mutex that supports timeout, or
- mtx_try | mtx_recursive for a recursive mutex that supports test and return.
-3 If the mtx_init function succeeds, it sets the mutex pointed to by mtx to a value that
- uniquely identifies the newly created mutex.
- Returns
-4 The mtx_init function returns thrd_success on success, or thrd_error if the
- request could not be honored.
-<a name="7.25.4.3" href="#7.25.4.3"><b> 7.25.4.3 The mtx_lock function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int mtx_lock(mtx_t *mtx);
- Description
-2 The mtx_lock function blocks until it locks the mutex pointed to by mtx. If the mutex
- is non-recursive, it shall not be locked by the calling thread. Prior calls to mtx_unlock
- on the same mutex shall synchronize with this operation.
- Returns
-3 The mtx_lock function returns thrd_success on success, or thrd_busy if the
- resource requested is already in use, or thrd_error if the request could not be
- honored.
-
-
-
-
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-
-<a name="7.25.4.4" href="#7.25.4.4"><b> 7.25.4.4 The mtx_timedlock function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int mtx_timedlock(mtx_t *mtx, const xtime *xt);
- Description
-2 The mtx_timedlock function endeavors to block until it locks the mutex pointed to by
- mtx or until the time specified by the xtime object xt has passed. The specified mutex
- shall support timeout. Prior calls to mtx_unlock on the same mutex shall synchronize
- with this operation. *
- Returns
-3 The mtx_timedlock function returns thrd_success on success, or thrd_busy
- if the resource requested is already in use, or thrd_timeout if the time specified was
- reached without acquiring the requested resource, or thrd_error if the request could
- not be honored.
-<a name="7.25.4.5" href="#7.25.4.5"><b> 7.25.4.5 The mtx_trylock function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int mtx_trylock(mtx_t *mtx);
- Description
-2 The mtx_trylock function endeavors to lock the mutex pointed to by mtx. The
- specified mutex shall support either test and return or timeout. If the mutex is already
- locked, the function returns without blocking. Prior calls to mtx_unlock on the same
- mutex shall synchronize with this operation. *
- Returns
-3 The mtx_trylock function returns thrd_success on success, or thrd_busy if
- the resource requested is already in use, or thrd_error if the request could not be
- honored.
-<a name="7.25.4.6" href="#7.25.4.6"><b> 7.25.4.6 The mtx_unlock function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int mtx_unlock(mtx_t *mtx);
- Description
-2 The mtx_unlock function unlocks the mutex pointed to by mtx. The mutex pointed to
- by mtx shall be locked by the calling thread.
-
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-
- Returns
-3 The mtx_unlock function returns thrd_success on success or thrd_error if
- the request could not be honored.
-<a name="7.25.5" href="#7.25.5"><b> 7.25.5 Thread functions</b></a>
-<a name="7.25.5.1" href="#7.25.5.1"><b> 7.25.5.1 The thrd_create function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int thrd_create(thrd_t *thr, thrd_start_t func,
- void *arg);
- Description
-2 The thrd_create function creates a new thread executing func(arg). If the
- thrd_create function succeeds, it sets the thread thr to a value that uniquely
- identifies the newly created thread.
- Returns
-3 The thrd_create function returns thrd_success on success, or thrd_nomem if
- no memory could be allocated for the thread requested, or thrd_error if the request
- could not be honored.
-<a name="7.25.5.2" href="#7.25.5.2"><b> 7.25.5.2 The thrd_current function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- thrd_t thrd_current(void);
- Description
-2 The thrd_current function identifies the thread that called it.
- Returns
-3 The thrd_current function returns a value that uniquely identifies the thread that
- called it.
-<a name="7.25.5.3" href="#7.25.5.3"><b> 7.25.5.3 The thrd_detach function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int thrd_detach(thrd_t thr);
- Description
-2 The thrd_detach function tells the operating system to dispose of any resources
- allocated to the thread identified by thr when that thread terminates. The value of the
-
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-
- thread identified by thr value shall not have been set by a call to thrd_join or
- thrd_detach.
- Returns
-3 The thrd_detach function returns thrd_success on success or thrd_error if
- the request could not be honored.
-<a name="7.25.5.4" href="#7.25.5.4"><b> 7.25.5.4 The thrd_equal function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int thrd_equal(thrd_t thr0, thrd_t thr1);
- Description
-2 The thrd_equal function will determine whether the thread identified by thr0 refers
- to the thread identified by thr1.
- Returns
-3 The thrd_equal function returns zero if the thread thr0 and the thread thr1 refer to
- different threads. Otherwise the thrd_equal function returns a nonzero value.
-<a name="7.25.5.5" href="#7.25.5.5"><b> 7.25.5.5 The thrd_exit function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- void thrd_exit(int res);
- Description
-2 The thrd_exit function terminates execution of the calling thread and sets its result
- code to res.
- Returns
-3 The thrd_exit function returns no value.
-<a name="7.25.5.6" href="#7.25.5.6"><b> 7.25.5.6 The thrd_join function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int thrd_join(thrd_t thr, int *res);
- Description
-2 The thrd_join function blocks until the thread identified by thr has terminated. If
- the parameter res is not a null pointer, it stores the thread's result code in the integer
- pointed to by res. The value of the thread identified by thr shall not have been set by a
- call to thrd_join or thrd_detach.
-
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-
- Returns
-3 The thrd_join function returns thrd_success on success or thrd_error if the
- request could not be honored.
-<a name="7.25.5.7" href="#7.25.5.7"><b> 7.25.5.7 The thrd_sleep function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- void thrd_sleep(const xtime *xt);
- Description
-2 The thrd_sleep function suspends execution of the calling thread until after the time
- specified by the xtime object pointed to by xt.
- Returns
-3 The thrd_sleep function returns no value.
-<a name="7.25.5.8" href="#7.25.5.8"><b> 7.25.5.8 The thrd_yield function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- void thrd_yield(void);
- Description
-2 The thrd_yield function endeavors to permit other threads to run, even if the current
- thread would ordinarily continue to run.
- Returns
-3 The thrd_yield function returns no value.
-<a name="7.25.6" href="#7.25.6"><b> 7.25.6 Thread-specific storage functions</b></a>
-<a name="7.25.6.1" href="#7.25.6.1"><b> 7.25.6.1 The tss_create function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int tss_create(tss_t *key, tss_dtor_t dtor);
- Description
-2 The tss_create function creates a thread-specific storage pointer with destructor
- dtor, which may be null.
- Returns
-3 If the tss_create function is successful, it sets the thread-specific storage pointed to
- by key to a value that uniquely identifies the newly created pointer and returns
- thrd_success; otherwise, thrd_error is returned and the thread-specific storage
-[<a name="#p381" href="p381">page 381</a>] (<a href="#Contents">Contents</a>)
-
- pointed to by key is set to an undefined value.
-<a name="7.25.6.2" href="#7.25.6.2"><b> 7.25.6.2 The tss_delete function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- void tss_delete(tss_t key);
- Description
-2 The tss_delete function releases any resources used by the thread-specific storage
- identified by key.
- Returns
-3 The tss_delete function returns no value.
-<a name="7.25.6.3" href="#7.25.6.3"><b> 7.25.6.3 The tss_get function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- void *tss_get(tss_t key);
- Description
-2 The tss_get function returns the value for the current thread held in the thread-specific
- storage identified by key.
- Returns
-3 The tss_get function returns the value for the current thread if successful, or zero if
- unsuccessful.
-<a name="7.25.6.4" href="#7.25.6.4"><b> 7.25.6.4 The tss_set function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int tss_set(tss_t key, void *val);
- Description
-2 The tss_set function sets the value for the current thread held in the thread-specific
- storage identified by key to val.
- Returns
-3 The tss_set function returns thrd_success on success or thrd_error if the
- request could not be honored.
-
-
-
-
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-
-<a name="7.25.7" href="#7.25.7"><b> 7.25.7 Time functions</b></a>
-<a name="7.25.7.1" href="#7.25.7.1"><b> 7.25.7.1 The xtime_get function</b></a>
- Synopsis
-1 #include <a href="#7.25"><threads.h></a>
- int xtime_get(xtime *xt, int base);
- Description
-2 The xtime_get function sets the xtime object pointed to by xt to hold the current
- time based on the time base base.
- Returns
-3 If the xtime_get function is successful it returns the nonzero value base, which must
- be TIME_UTC; otherwise, it returns zero.302)
-
-
-
-
- 302) Although an xtime object describes times with nanosecond resolution, the actual resolution in an
- xtime object is system dependent.
-
-[<a name="#p383" href="p383">page 383</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.26" href="#7.26"><b> 7.26 Date and time <time.h></b></a>
-<a name="7.26.1" href="#7.26.1"><b> 7.26.1 Components of time</b></a>
-1 The header <a href="#7.26"><time.h></a> defines two macros, and declares several types and functions for
- manipulating time. Many functions deal with a calendar time that represents the current
- date (according to the Gregorian calendar) and time. Some functions deal with local
- time, which is the calendar time expressed for some specific time zone, and with Daylight
- Saving Time, which is a temporary change in the algorithm for determining local time.
- The local time zone and Daylight Saving Time are implementation-defined.
-2 The macros defined are NULL (described in <a href="#7.19">7.19</a>); and
- CLOCKS_PER_SEC
- which expands to an expression with type clock_t (described below) that is the
- number per second of the value returned by the clock function.
-3 The types declared are size_t (described in <a href="#7.19">7.19</a>);
- clock_t
- and
- time_t
- which are arithmetic types capable of representing times; and
- struct tm
- which holds the components of a calendar time, called the broken-down time.
-4 The range and precision of times representable in clock_t and time_t are
- implementation-defined. The tm structure shall contain at least the following members,
- in any order. The semantics of the members and their normal ranges are expressed in the
- comments.303)
- int tm_sec; // seconds after the minute -- [0, 60]
- int tm_min; // minutes after the hour -- [0, 59]
- int tm_hour; // hours since midnight -- [0, 23]
- int tm_mday; // day of the month -- [1, 31]
- int tm_mon; // months since January -- [0, 11]
- int tm_year; // years since 1900
- int tm_wday; // days since Sunday -- [0, 6]
- int tm_yday; // days since January 1 -- [0, 365]
- int tm_isdst; // Daylight Saving Time flag
-
-
-
- 303) The range [0, 60] for tm_sec allows for a positive leap second.
-
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-
- The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight
- Saving Time is not in effect, and negative if the information is not available.
-<a name="7.26.2" href="#7.26.2"><b> 7.26.2 Time manipulation functions</b></a>
-<a name="7.26.2.1" href="#7.26.2.1"><b> 7.26.2.1 The clock function</b></a>
- Synopsis
-1 #include <a href="#7.26"><time.h></a>
- clock_t clock(void);
- Description
-2 The clock function determines the processor time used.
- Returns
-3 The clock function returns the implementation's best approximation to the processor
- time used by the program since the beginning of an implementation-defined era related
- only to the program invocation. To determine the time in seconds, the value returned by
- the clock function should be divided by the value of the macro CLOCKS_PER_SEC. If
- the processor time used is not available or its value cannot be represented, the function
- returns the value (clock_t)(-1).304)
-<a name="7.26.2.2" href="#7.26.2.2"><b> 7.26.2.2 The difftime function</b></a>
- Synopsis
-1 #include <a href="#7.26"><time.h></a>
- double difftime(time_t time1, time_t time0);
- Description
-2 The difftime function computes the difference between two calendar times: time1 -
- time0.
- Returns
-3 The difftime function returns the difference expressed in seconds as a double.
-
-
-
-
- 304) In order to measure the time spent in a program, the clock function should be called at the start of
- the program and its return value subtracted from the value returned by subsequent calls.
-
-[<a name="#p385" href="p385">page 385</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.26.2.3" href="#7.26.2.3"><b> 7.26.2.3 The mktime function</b></a>
- Synopsis
-1 #include <a href="#7.26"><time.h></a>
- time_t mktime(struct tm *timeptr);
- Description
-2 The mktime function converts the broken-down time, expressed as local time, in the
- structure pointed to by timeptr into a calendar time value with the same encoding as
- that of the values returned by the time function. The original values of the tm_wday
- and tm_yday components of the structure are ignored, and the original values of the
- other components are not restricted to the ranges indicated above.305) On successful
- completion, the values of the tm_wday and tm_yday components of the structure are
- set appropriately, and the other components are set to represent the specified calendar
- time, but with their values forced to the ranges indicated above; the final value of
- tm_mday is not set until tm_mon and tm_year are determined.
- Returns
-3 The mktime function returns the specified calendar time encoded as a value of type
- time_t. If the calendar time cannot be represented, the function returns the value
- (time_t)(-1).
-4 EXAMPLE What day of the week is July 4, 2001?
- #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.26"><time.h></a>
- static const char *const wday[] = {
- "Sunday", "Monday", "Tuesday", "Wednesday",
- "Thursday", "Friday", "Saturday", "-unknown-"
- };
- struct tm time_str;
- /* ... */
-
-
-
-
- 305) Thus, a positive or zero value for tm_isdst causes the mktime function to presume initially that
- Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value
- causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time.
-
-[<a name="#p386" href="p386">page 386</a>] (<a href="#Contents">Contents</a>)
-
- time_str.tm_year = 2001 - 1900;
- time_str.tm_mon = 7 - 1;
- time_str.tm_mday = 4;
- time_str.tm_hour = 0;
- time_str.tm_min = 0;
- time_str.tm_sec = 1;
- time_str.tm_isdst = -1;
- if (mktime(&time_str) == (time_t)(-1))
- time_str.tm_wday = 7;
- printf("%s\n", wday[time_str.tm_wday]);
-
-<a name="7.26.2.4" href="#7.26.2.4"><b> 7.26.2.4 The time function</b></a>
- Synopsis
-1 #include <a href="#7.26"><time.h></a>
- time_t time(time_t *timer);
- Description
-2 The time function determines the current calendar time. The encoding of the value is
- unspecified.
- Returns
-3 The time function returns the implementation's best approximation to the current
- calendar time. The value (time_t)(-1) is returned if the calendar time is not
- available. If timer is not a null pointer, the return value is also assigned to the object it
- points to.
-<a name="7.26.3" href="#7.26.3"><b> 7.26.3 Time conversion functions</b></a>
-1 Except for the strftime function, these functions each return a pointer to one of two
- types of static objects: a broken-down time structure or an array of char. Execution of
- any of the functions that return a pointer to one of these object types may overwrite the
- information in any object of the same type pointed to by the value returned from any
- previous call to any of them and the functions are not required to avoid data races. The
- implementation shall behave as if no other library functions call these functions.
-<a name="7.26.3.1" href="#7.26.3.1"><b> 7.26.3.1 The asctime function</b></a>
- Synopsis
-1 #include <a href="#7.26"><time.h></a>
- char *asctime(const struct tm *timeptr);
- Description
-2 The asctime function converts the broken-down time in the structure pointed to by
- timeptr into a string in the form
- Sun Sep 16 01:03:52 1973\n\0
-
-[<a name="#p387" href="p387">page 387</a>] (<a href="#Contents">Contents</a>)
-
- using the equivalent of the following algorithm.
- char *asctime(const struct tm *timeptr)
- {
- static const char wday_name[7][3] = {
- "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
- };
- static const char mon_name[12][3] = {
- "Jan", "Feb", "Mar", "Apr", "May", "Jun",
- "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
- };
- static char result[26];
- sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
- wday_name[timeptr->tm_wday],
- mon_name[timeptr->tm_mon],
- timeptr->tm_mday, timeptr->tm_hour,
- timeptr->tm_min, timeptr->tm_sec,
- 1900 + timeptr->tm_year);
- return result;
- }
-3 If any of the fields of the broken-down time contain values that are outside their normal
- ranges,306) the behavior of the asctime function is undefined. Likewise, if the
- calculated year exceeds four digits or is less than the year 1000, the behavior is
- undefined.
- Returns
-4 The asctime function returns a pointer to the string.
-<a name="7.26.3.2" href="#7.26.3.2"><b> 7.26.3.2 The ctime function</b></a>
- Synopsis
-1 #include <a href="#7.26"><time.h></a>
- char *ctime(const time_t *timer);
- Description
-2 The ctime function converts the calendar time pointed to by timer to local time in the
- form of a string. It is equivalent to
- asctime(localtime(timer))
-
-
-
- 306) See <a href="#7.26.1">7.26.1</a>.
-
-[<a name="#p388" href="p388">page 388</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The ctime function returns the pointer returned by the asctime function with that
- broken-down time as argument.
- Forward references: the localtime function (<a href="#7.26.3.4">7.26.3.4</a>).
-<a name="7.26.3.3" href="#7.26.3.3"><b> 7.26.3.3 The gmtime function</b></a>
- Synopsis
-1 #include <a href="#7.26"><time.h></a>
- struct tm *gmtime(const time_t *timer);
- Description
-2 The gmtime function converts the calendar time pointed to by timer into a broken-
- down time, expressed as UTC.
- Returns
-3 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
- specified time cannot be converted to UTC.
-<a name="7.26.3.4" href="#7.26.3.4"><b> 7.26.3.4 The localtime function</b></a>
- Synopsis
-1 #include <a href="#7.26"><time.h></a>
- struct tm *localtime(const time_t *timer);
- Description
-2 The localtime function converts the calendar time pointed to by timer into a
- broken-down time, expressed as local time.
- Returns
-3 The localtime function returns a pointer to the broken-down time, or a null pointer if
- the specified time cannot be converted to local time.
-<a name="7.26.3.5" href="#7.26.3.5"><b> 7.26.3.5 The strftime function</b></a>
- Synopsis
-1 #include <a href="#7.26"><time.h></a>
- size_t strftime(char * restrict s,
- size_t maxsize,
- const char * restrict format,
- const struct tm * restrict timeptr);
-
-
-
-
-[<a name="#p389" href="p389">page 389</a>] (<a href="#Contents">Contents</a>)
-
- Description
-2 The strftime function places characters into the array pointed to by s as controlled by
- the string pointed to by format. The format shall be a multibyte character sequence,
- beginning and ending in its initial shift state. The format string consists of zero or
- more conversion specifiers and ordinary multibyte characters. A conversion specifier
- consists of a % character, possibly followed by an E or O modifier character (described
- below), followed by a character that determines the behavior of the conversion specifier.
- All ordinary multibyte characters (including the terminating null character) are copied
- unchanged into the array. If copying takes place between objects that overlap, the
- behavior is undefined. No more than maxsize characters are placed into the array.
-3 Each conversion specifier is replaced by appropriate characters as described in the
- following list. The appropriate characters are determined using the LC_TIME category
- of the current locale and by the values of zero or more members of the broken-down time
- structure pointed to by timeptr, as specified in brackets in the description. If any of
- the specified values is outside the normal range, the characters stored are unspecified.
- %a is replaced by the locale's abbreviated weekday name. [tm_wday]
- %A is replaced by the locale's full weekday name. [tm_wday]
- %b is replaced by the locale's abbreviated month name. [tm_mon]
- %B is replaced by the locale's full month name. [tm_mon]
- %c is replaced by the locale's appropriate date and time representation. [all specified
- in <a href="#7.26.1">7.26.1</a>]
- %C is replaced by the year divided by 100 and truncated to an integer, as a decimal
- number (00-99). [tm_year]
- %d is replaced by the day of the month as a decimal number (01-31). [tm_mday]
- %D is equivalent to ''%m/%d/%y''. [tm_mon, tm_mday, tm_year]
- %e is replaced by the day of the month as a decimal number (1-31); a single digit is
- preceded by a space. [tm_mday]
- %F is equivalent to ''%Y-%m-%d'' (the ISO 8601 date format). [tm_year, tm_mon,
- tm_mday]
- %g is replaced by the last 2 digits of the week-based year (see below) as a decimal
- number (00-99). [tm_year, tm_wday, tm_yday]
- %G is replaced by the week-based year (see below) as a decimal number (e.g., 1997).
- [tm_year, tm_wday, tm_yday]
- %h is equivalent to ''%b''. [tm_mon]
- %H is replaced by the hour (24-hour clock) as a decimal number (00-23). [tm_hour]
- %I is replaced by the hour (12-hour clock) as a decimal number (01-12). [tm_hour]
- %j is replaced by the day of the year as a decimal number (001-366). [tm_yday]
- %m is replaced by the month as a decimal number (01-12). [tm_mon]
- %M is replaced by the minute as a decimal number (00-59). [tm_min]
- %n is replaced by a new-line character.
-
-[<a name="#p390" href="p390">page 390</a>] (<a href="#Contents">Contents</a>)
-
- %p is replaced by the locale's equivalent of the AM/PM designations associated with a
- 12-hour clock. [tm_hour]
- %r is replaced by the locale's 12-hour clock time. [tm_hour, tm_min, tm_sec]
- %R is equivalent to ''%H:%M''. [tm_hour, tm_min]
- %S is replaced by the second as a decimal number (00-60). [tm_sec]
- %t is replaced by a horizontal-tab character.
- %T is equivalent to ''%H:%M:%S'' (the ISO 8601 time format). [tm_hour, tm_min,
- tm_sec]
- %u is replaced by the ISO 8601 weekday as a decimal number (1-7), where Monday
- is 1. [tm_wday]
- %U is replaced by the week number of the year (the first Sunday as the first day of week
- 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
- %V is replaced by the ISO 8601 week number (see below) as a decimal number
- (01-53). [tm_year, tm_wday, tm_yday]
- %w is replaced by the weekday as a decimal number (0-6), where Sunday is 0.
- [tm_wday]
- %W is replaced by the week number of the year (the first Monday as the first day of
- week 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
- %x is replaced by the locale's appropriate date representation. [all specified in <a href="#7.26.1">7.26.1</a>]
- %X is replaced by the locale's appropriate time representation. [all specified in <a href="#7.26.1">7.26.1</a>]
- %y is replaced by the last 2 digits of the year as a decimal number (00-99).
- [tm_year]
- %Y is replaced by the year as a decimal number (e.g., 1997). [tm_year]
- %z is replaced by the offset from UTC in the ISO 8601 format ''-0430'' (meaning 4
- hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
- zone is determinable. [tm_isdst]
- %Z is replaced by the locale's time zone name or abbreviation, or by no characters if no
- time zone is determinable. [tm_isdst]
- %% is replaced by %.
-4 Some conversion specifiers can be modified by the inclusion of an E or O modifier
- character to indicate an alternative format or specification. If the alternative format or
- specification does not exist for the current locale, the modifier is ignored.
- %Ec is replaced by the locale's alternative date and time representation.
- %EC is replaced by the name of the base year (period) in the locale's alternative
- representation.
- %Ex is replaced by the locale's alternative date representation.
- %EX is replaced by the locale's alternative time representation.
- %Ey is replaced by the offset from %EC (year only) in the locale's alternative
- representation.
- %EY is replaced by the locale's full alternative year representation.
-
-[<a name="#p391" href="p391">page 391</a>] (<a href="#Contents">Contents</a>)
-
- %Od is replaced by the day of the month, using the locale's alternative numeric symbols
- (filled as needed with leading zeros, or with leading spaces if there is no alternative
- symbol for zero).
- %Oe is replaced by the day of the month, using the locale's alternative numeric symbols
- (filled as needed with leading spaces).
- %OH is replaced by the hour (24-hour clock), using the locale's alternative numeric
- symbols.
- %OI is replaced by the hour (12-hour clock), using the locale's alternative numeric
- symbols.
- %Om is replaced by the month, using the locale's alternative numeric symbols.
- %OM is replaced by the minutes, using the locale's alternative numeric symbols.
- %OS is replaced by the seconds, using the locale's alternative numeric symbols.
- %Ou is replaced by the ISO 8601 weekday as a number in the locale's alternative
- representation, where Monday is 1.
- %OU is replaced by the week number, using the locale's alternative numeric symbols.
- %OV is replaced by the ISO 8601 week number, using the locale's alternative numeric
- symbols.
- %Ow is replaced by the weekday as a number, using the locale's alternative numeric
- symbols.
- %OW is replaced by the week number of the year, using the locale's alternative numeric
- symbols.
- %Oy is replaced by the last 2 digits of the year, using the locale's alternative numeric
- symbols.
-5 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system,
- weeks begin on a Monday and week 1 of the year is the week that includes January 4th,
- which is also the week that includes the first Thursday of the year, and is also the first
- week that contains at least four days in the year. If the first Monday of January is the
- 2nd, 3rd, or 4th, the preceding days are part of the last week of the preceding year; thus,
- for Saturday 2nd January 1999, %G is replaced by 1998 and %V is replaced by 53. If
- December 29th, 30th, or 31st is a Monday, it and any following days are part of week 1 of
- the following year. Thus, for Tuesday 30th December 1997, %G is replaced by 1998 and
- %V is replaced by 01.
-6 If a conversion specifier is not one of the above, the behavior is undefined.
-7 In the "C" locale, the E and O modifiers are ignored and the replacement strings for the
- following specifiers are:
- %a the first three characters of %A.
- %A one of ''Sunday'', ''Monday'', ... , ''Saturday''.
- %b the first three characters of %B.
- %B one of ''January'', ''February'', ... , ''December''.
- %c equivalent to ''%a %b %e %T %Y''.
-[<a name="#p392" href="p392">page 392</a>] (<a href="#Contents">Contents</a>)
-
- %p one of ''AM'' or ''PM''.
- %r equivalent to ''%I:%M:%S %p''.
- %x equivalent to ''%m/%d/%y''.
- %X equivalent to %T.
- %Z implementation-defined.
- Returns
-8 If the total number of resulting characters including the terminating null character is not
- more than maxsize, the strftime function returns the number of characters placed
- into the array pointed to by s not including the terminating null character. Otherwise,
- zero is returned and the contents of the array are indeterminate.
-
-
-
-
-[<a name="#p393" href="p393">page 393</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.27" href="#7.27"><b> 7.27 Unicode utilities <uchar.h></b></a>
-1 The header <a href="#7.27"><uchar.h></a> declares types and functions for manipulating Unicode
- characters.
-2 The types declared are mbstate_t (described in <a href="#7.29.1">7.29.1</a>) and size_t (described in
-<a name="7.19);" href="#7.19);"><b> 7.19);</b></a>
- char16_t
- which is an unsigned integer type used for 16-bit characters and is the same type as
- uint_least16_t (described in <a href="#7.20.1.2">7.20.1.2</a>); and
- char32_t
- which is an unsigned integer type used for 32-bit characters and is the same type as
- uint_least32_t (also described in <a href="#7.20.1.2">7.20.1.2</a>).
-<a name="7.27.1" href="#7.27.1"><b> 7.27.1 Restartable multibyte/wide character conversion functions</b></a>
-1 These functions have a parameter, ps, of type pointer to mbstate_t that points to an
- object that can completely describe the current conversion state of the associated
- multibyte character sequence, which the functions alter as necessary. If ps is a null
- pointer, each function uses its own internal mbstate_t object instead, which is
- initialized at program startup to the initial conversion state; the functions are not required
- to avoid data races in this case. The implementation behaves as if no library function
- calls these functions with a null pointer for ps.
-<a name="7.27.1.1" href="#7.27.1.1"><b> 7.27.1.1 The mbrtoc16 function</b></a>
- Synopsis
-1 #include <a href="#7.27"><uchar.h></a>
- size_t mbrtoc16(char16_t * restrict pc16,
- const char * restrict s, size_t n,
- mbstate_t * restrict ps);
- Description
-2 If s is a null pointer, the mbrtoc16 function is equivalent to the call:
- mbrtoc16(NULL, "", 1, ps)
- In this case, the values of the parameters pc16 and n are ignored.
-3 If s is not a null pointer, the mbrtoc16 function inspects at most n bytes beginning with
- the byte pointed to by s to determine the number of bytes needed to complete the next
- multibyte character (including any shift sequences). If the function determines that the
- next multibyte character is complete and valid, it determines the values of the
- corresponding wide characters and then, if pc16 is not a null pointer, stores the value of
- the first (or only) such character in the object pointed to by pc16. Subsequent calls will
-[<a name="#p394" href="p394">page 394</a>] (<a href="#Contents">Contents</a>)
-
- store successive wide characters without consuming any additional input until all the
- characters have been stored. If the corresponding wide character is the null wide
- character, the resulting state described is the initial conversion state.
- Returns
-4 The mbrtoc16 function returns the first of the following that applies (given the current
- conversion state):
- 0 if the next n or fewer bytes complete the multibyte character that
- corresponds to the null wide character (which is the value stored).
- between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
- character (which is the value stored); the value returned is the number
- of bytes that complete the multibyte character.
- (size_t)(-3) if the next character resulting from a previous call has been stored (no
- bytes from the input have been consumed by this call).
- (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
- multibyte character, and all n bytes have been processed (no value is
- stored).307)
- (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
- do not contribute to a complete and valid multibyte character (no
- value is stored); the value of the macro EILSEQ is stored in errno,
- and the conversion state is unspecified.
-<a name="7.27.1.2" href="#7.27.1.2"><b> 7.27.1.2 The c16rtomb function</b></a>
- Synopsis
-1 #include <a href="#7.27"><uchar.h></a>
- size_t c16rtomb(char * restrict s, char16_t c16,
- mbstate_t * restrict ps);
- Description
-2 If s is a null pointer, the c16rtomb function is equivalent to the call
- c16rtomb(buf, L'\0', ps)
- where buf is an internal buffer.
-3 If s is not a null pointer, the c16rtomb function determines the number of bytes needed
- to represent the multibyte character that corresponds to the wide character given by c16
- (including any shift sequences), and stores the multibyte character representation in the
-
- 307) When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
- sequence of redundant shift sequences (for implementations with state-dependent encodings).
-
-[<a name="#p395" href="p395">page 395</a>] (<a href="#Contents">Contents</a>)
-
- array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
- c16 is a null wide character, a null byte is stored, preceded by any shift sequence needed
- to restore the initial shift state; the resulting state described is the initial conversion state.
- Returns
-4 The c16rtomb function returns the number of bytes stored in the array object (including
- any shift sequences). When c16 is not a valid wide character, an encoding error occurs:
- the function stores the value of the macro EILSEQ in errno and returns
- (size_t)(-1); the conversion state is unspecified.
-<a name="7.27.1.3" href="#7.27.1.3"><b> 7.27.1.3 The mbrtoc32 function</b></a>
- Synopsis
-1 #include <a href="#7.27"><uchar.h></a>
- size_t mbrtoc32(char32_t * restrict pc32,
- const char * restrict s, size_t n,
- mbstate_t * restrict ps);
- Description
-2 If s is a null pointer, the mbrtoc32 function is equivalent to the call:
- mbrtoc32(NULL, "", 1, ps)
- In this case, the values of the parameters pc32 and n are ignored.
-3 If s is not a null pointer, the mbrtoc32 function inspects at most n bytes beginning with
- the byte pointed to by s to determine the number of bytes needed to complete the next
- multibyte character (including any shift sequences). If the function determines that the
- next multibyte character is complete and valid, it determines the values of the
- corresponding wide characters and then, if pc32 is not a null pointer, stores the value of
- the first (or only) such character in the object pointed to by pc32. Subsequent calls will
- store successive wide characters without consuming any additional input until all the
- characters have been stored. If the corresponding wide character is the null wide
- character, the resulting state described is the initial conversion state.
- Returns
-4 The mbrtoc32 function returns the first of the following that applies (given the current
- conversion state):
- 0 if the next n or fewer bytes complete the multibyte character that
- corresponds to the null wide character (which is the value stored).
- between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
- character (which is the value stored); the value returned is the number
- of bytes that complete the multibyte character.
-
-
-[<a name="#p396" href="p396">page 396</a>] (<a href="#Contents">Contents</a>)
-
- (size_t)(-3) if the next character resulting from a previous call has been stored (no
- bytes from the input have been consumed by this call).
- (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
- multibyte character, and all n bytes have been processed (no value is
- stored).308)
- (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
- do not contribute to a complete and valid multibyte character (no
- value is stored); the value of the macro EILSEQ is stored in errno,
- and the conversion state is unspecified.
-<a name="7.27.1.4" href="#7.27.1.4"><b> 7.27.1.4 The c32rtomb function</b></a>
- Synopsis
-1 #include <a href="#7.27"><uchar.h></a>
- size_t c32rtomb(char * restrict s, char32_t c32,
- mbstate_t * restrict ps);
- Description
-2 If s is a null pointer, the c32rtomb function is equivalent to the call
- c32rtomb(buf, L'\0', ps)
- where buf is an internal buffer.
-3 If s is not a null pointer, the c32rtomb function determines the number of bytes needed
- to represent the multibyte character that corresponds to the wide character given by c32
- (including any shift sequences), and stores the multibyte character representation in the
- array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
- c32 is a null wide character, a null byte is stored, preceded by any shift sequence needed
- to restore the initial shift state; the resulting state described is the initial conversion state.
- Returns
-4 The c32rtomb function returns the number of bytes stored in the array object (including
- any shift sequences). When c32 is not a valid wide character, an encoding error occurs:
- the function stores the value of the macro EILSEQ in errno and returns
- (size_t)(-1); the conversion state is unspecified.
-
-
-
-
- 308) When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
- sequence of redundant shift sequences (for implementations with state-dependent encodings).
-
-[<a name="#p397" href="p397">page 397</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.28" href="#7.28"><b> 7.28 Extended multibyte and wide character utilities <wchar.h></b></a>
-<a name="7.28.1" href="#7.28.1"><b> 7.28.1 Introduction</b></a>
-1 The header <a href="#7.28"><wchar.h></a> defines four macros, and declares four data types, one tag, and
- many functions.309)
-2 The types declared are wchar_t and size_t (both described in <a href="#7.19">7.19</a>);
- mbstate_t
- which is a complete object type other than an array type that can hold the conversion state
- information necessary to convert between sequences of multibyte characters and wide
- characters;
- wint_t
- which is an integer type unchanged by default argument promotions that can hold any
- value corresponding to members of the extended character set, as well as at least one
- value that does not correspond to any member of the extended character set (see WEOF
- below);310) and
- struct tm
- which is declared as an incomplete structure type (the contents are described in <a href="#7.26.1">7.26.1</a>).
-3 The macros defined are NULL (described in <a href="#7.19">7.19</a>); WCHAR_MIN and WCHAR_MAX
- (described in <a href="#7.20.3">7.20.3</a>); and
- WEOF
- which expands to a constant expression of type wint_t whose value does not
- correspond to any member of the extended character set.311) It is accepted (and returned)
- by several functions in this subclause to indicate end-of-file, that is, no more input from a
- stream. It is also used as a wide character value that does not correspond to any member
- of the extended character set.
-4 The functions declared are grouped as follows:
- -- Functions that perform input and output of wide characters, or multibyte characters,
- or both;
- -- Functions that provide wide string numeric conversion;
- -- Functions that perform general wide string manipulation;
-
-
- 309) See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
- 310) wchar_t and wint_t can be the same integer type.
- 311) The value of the macro WEOF may differ from that of EOF and need not be negative.
-
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-
- -- Functions for wide string date and time conversion; and
- -- Functions that provide extended capabilities for conversion between multibyte and
- wide character sequences.
-5 Unless explicitly stated otherwise, if the execution of a function described in this
- subclause causes copying to take place between objects that overlap, the behavior is
- undefined.
-<a name="7.28.2" href="#7.28.2"><b> 7.28.2 Formatted wide character input/output functions</b></a>
-1 The formatted wide character input/output functions shall behave as if there is a sequence
- point after the actions associated with each specifier.312)
-<a name="7.28.2.1" href="#7.28.2.1"><b> 7.28.2.1 The fwprintf function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int fwprintf(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- Description
-2 The fwprintf function writes output to the stream pointed to by stream, under
- control of the wide string pointed to by format that specifies how subsequent arguments
- are converted for output. If there are insufficient arguments for the format, the behavior
- is undefined. If the format is exhausted while arguments remain, the excess arguments
- are evaluated (as always) but are otherwise ignored. The fwprintf function returns
- when the end of the format string is encountered.
-3 The format is composed of zero or more directives: ordinary wide characters (not %),
- which are copied unchanged to the output stream; and conversion specifications, each of
- which results in fetching zero or more subsequent arguments, converting them, if
- applicable, according to the corresponding conversion specifier, and then writing the
- result to the output stream.
-4 Each conversion specification is introduced by the wide character %. After the %, the
- following appear in sequence:
- -- Zero or more flags (in any order) that modify the meaning of the conversion
- specification.
- -- An optional minimum field width. If the converted value has fewer wide characters
- than the field width, it is padded with spaces (by default) on the left (or right, if the
-
-
- 312) The fwprintf functions perform writes to memory for the %n specifier.
-
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-
- left adjustment flag, described later, has been given) to the field width. The field
- width takes the form of an asterisk * (described later) or a nonnegative decimal
- integer.313)
- -- An optional precision that gives the minimum number of digits to appear for the d, i,
- o, u, x, and X conversions, the number of digits to appear after the decimal-point
- wide character for a, A, e, E, f, and F conversions, the maximum number of
- significant digits for the g and G conversions, or the maximum number of wide
- characters to be written for s conversions. The precision takes the form of a period
- (.) followed either by an asterisk * (described later) or by an optional decimal
- integer; if only the period is specified, the precision is taken as zero. If a precision
- appears with any other conversion specifier, the behavior is undefined.
- -- An optional length modifier that specifies the size of the argument.
- -- A conversion specifier wide character that specifies the type of conversion to be
- applied.
-5 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
- this case, an int argument supplies the field width or precision. The arguments
- specifying field width, or precision, or both, shall appear (in that order) before the
- argument (if any) to be converted. A negative field width argument is taken as a - flag
- followed by a positive field width. A negative precision argument is taken as if the
- precision were omitted.
-6 The flag wide characters and their meanings are:
- - The result of the conversion is left-justified within the field. (It is right-justified if
- this flag is not specified.)
- + The result of a signed conversion always begins with a plus or minus sign. (It
- begins with a sign only when a negative value is converted if this flag is not
- specified.)314)
- space If the first wide character of a signed conversion is not a sign, or if a signed
- conversion results in no wide characters, a space is prefixed to the result. If the
- space and + flags both appear, the space flag is ignored.
- # The result is converted to an ''alternative form''. For o conversion, it increases
- the precision, if and only if necessary, to force the first digit of the result to be a
- zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
- conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
-
-
- 313) Note that 0 is taken as a flag, not as the beginning of a field width.
- 314) The results of all floating conversions of a negative zero, and of negative values that round to zero,
- include a minus sign.
-
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-
- and G conversions, the result of converting a floating-point number always
- contains a decimal-point wide character, even if no digits follow it. (Normally, a
- decimal-point wide character appears in the result of these conversions only if a
- digit follows it.) For g and G conversions, trailing zeros are not removed from the
- result. For other conversions, the behavior is undefined.
- 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
- (following any indication of sign or base) are used to pad to the field width rather
- than performing space padding, except when converting an infinity or NaN. If the
- 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
- conversions, if a precision is specified, the 0 flag is ignored. For other
- conversions, the behavior is undefined.
-7 The length modifiers and their meanings are:
- hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- signed char or unsigned char argument (the argument will have
- been promoted according to the integer promotions, but its value shall be
- converted to signed char or unsigned char before printing); or that
- a following n conversion specifier applies to a pointer to a signed char
- argument.
- h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- short int or unsigned short int argument (the argument will
- have been promoted according to the integer promotions, but its value shall
- be converted to short int or unsigned short int before printing);
- or that a following n conversion specifier applies to a pointer to a short
- int argument.
- l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- long int or unsigned long int argument; that a following n
- conversion specifier applies to a pointer to a long int argument; that a
- following c conversion specifier applies to a wint_t argument; that a
- following s conversion specifier applies to a pointer to a wchar_t
- argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
- specifier.
- ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- long long int or unsigned long long int argument; or that a
- following n conversion specifier applies to a pointer to a long long int
- argument.
- j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
- an intmax_t or uintmax_t argument; or that a following n conversion
- specifier applies to a pointer to an intmax_t argument.
-
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-
- z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- size_t or the corresponding signed integer type argument; or that a
- following n conversion specifier applies to a pointer to a signed integer type
- corresponding to size_t argument.
- t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- ptrdiff_t or the corresponding unsigned integer type argument; or that a
- following n conversion specifier applies to a pointer to a ptrdiff_t
- argument.
- L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
- applies to a long double argument.
- If a length modifier appears with any conversion specifier other than as specified above,
- the behavior is undefined.
-8 The conversion specifiers and their meanings are:
- d,i The int argument is converted to signed decimal in the style [-]dddd. The
- precision specifies the minimum number of digits to appear; if the value
- being converted can be represented in fewer digits, it is expanded with
- leading zeros. The default precision is 1. The result of converting a zero
- value with a precision of zero is no wide characters.
- o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
- decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
- letters abcdef are used for x conversion and the letters ABCDEF for X
- conversion. The precision specifies the minimum number of digits to appear;
- if the value being converted can be represented in fewer digits, it is expanded
- with leading zeros. The default precision is 1. The result of converting a
- zero value with a precision of zero is no wide characters.
- f,F A double argument representing a floating-point number is converted to
- decimal notation in the style [-]ddd.ddd, where the number of digits after
- the decimal-point wide character is equal to the precision specification. If the
- precision is missing, it is taken as 6; if the precision is zero and the # flag is
- not specified, no decimal-point wide character appears. If a decimal-point
- wide character appears, at least one digit appears before it. The value is
- rounded to the appropriate number of digits.
- A double argument representing an infinity is converted in one of the styles
- [-]inf or [-]infinity -- which style is implementation-defined. A
- double argument representing a NaN is converted in one of the styles
- [-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
- any n-wchar-sequence, is implementation-defined. The F conversion
- specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
-
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-
- nan, respectively.315)
-e,E A double argument representing a floating-point number is converted in the
- style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
- argument is nonzero) before the decimal-point wide character and the number
- of digits after it is equal to the precision; if the precision is missing, it is taken
- as 6; if the precision is zero and the # flag is not specified, no decimal-point
- wide character appears. The value is rounded to the appropriate number of
- digits. The E conversion specifier produces a number with E instead of e
- introducing the exponent. The exponent always contains at least two digits,
- and only as many more digits as necessary to represent the exponent. If the
- value is zero, the exponent is zero.
- A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
-g,G A double argument representing a floating-point number is converted in
- style f or e (or in style F or E in the case of a G conversion specifier),
- depending on the value converted and the precision. Let P equal the
- precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
- Then, if a conversion with style E would have an exponent of X:
- -- if P > X >= -4, the conversion is with style f (or F) and precision
- P - (X + 1).
- -- otherwise, the conversion is with style e (or E) and precision P - 1.
- Finally, unless the # flag is used, any trailing zeros are removed from the
- fractional portion of the result and the decimal-point wide character is
- removed if there is no fractional portion remaining.
- A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
-a,A A double argument representing a floating-point number is converted in the
- style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
- nonzero if the argument is a normalized floating-point number and is
- otherwise unspecified) before the decimal-point wide character316) and the
- number of hexadecimal digits after it is equal to the precision; if the precision
- is missing and FLT_RADIX is a power of 2, then the precision is sufficient
-
-
-315) When applied to infinite and NaN values, the -, +, and space flag wide characters have their usual
- meaning; the # and 0 flag wide characters have no effect.
-316) Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide
- character so that subsequent digits align to nibble (4-bit) boundaries.
-
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-
- for an exact representation of the value; if the precision is missing and
- FLT_RADIX is not a power of 2, then the precision is sufficient to
- distinguish317) values of type double, except that trailing zeros may be
- omitted; if the precision is zero and the # flag is not specified, no decimal-
- point wide character appears. The letters abcdef are used for a conversion
- and the letters ABCDEF for A conversion. The A conversion specifier
- produces a number with X and P instead of x and p. The exponent always
- contains at least one digit, and only as many more digits as necessary to
- represent the decimal exponent of 2. If the value is zero, the exponent is
- zero.
- A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
-c If no l length modifier is present, the int argument is converted to a wide
- character as if by calling btowc and the resulting wide character is written.
- If an l length modifier is present, the wint_t argument is converted to
- wchar_t and written.
-s If no l length modifier is present, the argument shall be a pointer to the initial
- element of a character array containing a multibyte character sequence
- beginning in the initial shift state. Characters from the array are converted as
- if by repeated calls to the mbrtowc function, with the conversion state
- described by an mbstate_t object initialized to zero before the first
- multibyte character is converted, and written up to (but not including) the
- terminating null wide character. If the precision is specified, no more than
- that many wide characters are written. If the precision is not specified or is
- greater than the size of the converted array, the converted array shall contain a
- null wide character.
- If an l length modifier is present, the argument shall be a pointer to the initial
- element of an array of wchar_t type. Wide characters from the array are
- written up to (but not including) a terminating null wide character. If the
- precision is specified, no more than that many wide characters are written. If
- the precision is not specified or is greater than the size of the array, the array
- shall contain a null wide character.
-p The argument shall be a pointer to void. The value of the pointer is
- converted to a sequence of printing wide characters, in an implementation-
-
-317) The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
- FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
- might suffice depending on the implementation's scheme for determining the digit to the left of the
- decimal-point wide character.
-
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-
- defined manner.
- n The argument shall be a pointer to signed integer into which is written the
- number of wide characters written to the output stream so far by this call to
- fwprintf. No argument is converted, but one is consumed. If the
- conversion specification includes any flags, a field width, or a precision, the
- behavior is undefined.
- % A % wide character is written. No argument is converted. The complete
- conversion specification shall be %%.
-9 If a conversion specification is invalid, the behavior is undefined.318) If any argument is
- not the correct type for the corresponding conversion specification, the behavior is
- undefined.
-10 In no case does a nonexistent or small field width cause truncation of a field; if the result
- of a conversion is wider than the field width, the field is expanded to contain the
- conversion result.
-11 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
- to a hexadecimal floating number with the given precision.
- Recommended practice
-12 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
- representable in the given precision, the result should be one of the two adjacent numbers
- in hexadecimal floating style with the given precision, with the extra stipulation that the
- error should have a correct sign for the current rounding direction.
-13 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
- DECIMAL_DIG, then the result should be correctly rounded.319) If the number of
- significant decimal digits is more than DECIMAL_DIG but the source value is exactly
- representable with DECIMAL_DIG digits, then the result should be an exact
- representation with trailing zeros. Otherwise, the source value is bounded by two
- adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
- of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
- the error should have a correct sign for the current rounding direction.
- Returns
-14 The fwprintf function returns the number of wide characters transmitted, or a negative
- value if an output or encoding error occurred.
-
- 318) See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
- 319) For binary-to-decimal conversion, the result format's values are the numbers representable with the
- given format specifier. The number of significant digits is determined by the format specifier, and in
- the case of fixed-point conversion by the source value as well.
-
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-
- Environmental limits
-15 The number of wide characters that can be produced by any single conversion shall be at
- least 4095.
-16 EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
- places:
- #include <a href="#7.12"><math.h></a>
- #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- /* ... */
- wchar_t *weekday, *month; // pointers to wide strings
- int day, hour, min;
- fwprintf(stdout, L"%ls, %ls %d, %.2d:%.2d\n",
- weekday, month, day, hour, min);
- fwprintf(stdout, L"pi = %.5f\n", 4 * atan(<a href="#1.0">1.0</a>));
-
- Forward references: the btowc function (<a href="#7.28.6.1.1">7.28.6.1.1</a>), the mbrtowc function
- (<a href="#7.28.6.3.2">7.28.6.3.2</a>).
-<a name="7.28.2.2" href="#7.28.2.2"><b> 7.28.2.2 The fwscanf function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int fwscanf(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- Description
-2 The fwscanf function reads input from the stream pointed to by stream, under
- control of the wide string pointed to by format that specifies the admissible input
- sequences and how they are to be converted for assignment, using subsequent arguments
- as pointers to the objects to receive the converted input. If there are insufficient
- arguments for the format, the behavior is undefined. If the format is exhausted while
- arguments remain, the excess arguments are evaluated (as always) but are otherwise
- ignored.
-3 The format is composed of zero or more directives: one or more white-space wide
- characters, an ordinary wide character (neither % nor a white-space wide character), or a
- conversion specification. Each conversion specification is introduced by the wide
- character %. After the %, the following appear in sequence:
- -- An optional assignment-suppressing wide character *.
- -- An optional decimal integer greater than zero that specifies the maximum field width
- (in wide characters).
-
-
-
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-
- -- An optional length modifier that specifies the size of the receiving object.
- -- A conversion specifier wide character that specifies the type of conversion to be
- applied.
-4 The fwscanf function executes each directive of the format in turn. When all directives
- have been executed, or if a directive fails (as detailed below), the function returns.
- Failures are described as input failures (due to the occurrence of an encoding error or the
- unavailability of input characters), or matching failures (due to inappropriate input).
-5 A directive composed of white-space wide character(s) is executed by reading input up to
- the first non-white-space wide character (which remains unread), or until no more wide
- characters can be read.
-6 A directive that is an ordinary wide character is executed by reading the next wide
- character of the stream. If that wide character differs from the directive, the directive
- fails and the differing and subsequent wide characters remain unread. Similarly, if end-
- of-file, an encoding error, or a read error prevents a wide character from being read, the
- directive fails.
-7 A directive that is a conversion specification defines a set of matching input sequences, as
- described below for each specifier. A conversion specification is executed in the
- following steps:
-8 Input white-space wide characters (as specified by the iswspace function) are skipped,
- unless the specification includes a [, c, or n specifier.320)
-9 An input item is read from the stream, unless the specification includes an n specifier. An
- input item is defined as the longest sequence of input wide characters which does not
- exceed any specified field width and which is, or is a prefix of, a matching input
- sequence.321) The first wide character, if any, after the input item remains unread. If the
- length of the input item is zero, the execution of the directive fails; this condition is a
- matching failure unless end-of-file, an encoding error, or a read error prevented input
- from the stream, in which case it is an input failure.
-10 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
- count of input wide characters) is converted to a type appropriate to the conversion
- specifier. If the input item is not a matching sequence, the execution of the directive fails:
- this condition is a matching failure. Unless assignment suppression was indicated by a *,
- the result of the conversion is placed in the object pointed to by the first argument
- following the format argument that has not already received a conversion result. If this
-
-
- 320) These white-space wide characters are not counted against a specified field width.
- 321) fwscanf pushes back at most one input wide character onto the input stream. Therefore, some
- sequences that are acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
-
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-
- object does not have an appropriate type, or if the result of the conversion cannot be
- represented in the object, the behavior is undefined.
-11 The length modifiers and their meanings are:
- hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to signed char or unsigned char.
- h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to short int or unsigned short
- int.
- l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to long int or unsigned long
- int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
- an argument with type pointer to double; or that a following c, s, or [
- conversion specifier applies to an argument with type pointer to wchar_t.
- ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to long long int or unsigned
- long long int.
- j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to intmax_t or uintmax_t.
- z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to size_t or the corresponding signed
- integer type.
- t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to ptrdiff_t or the corresponding
- unsigned integer type.
- L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
- applies to an argument with type pointer to long double.
- If a length modifier appears with any conversion specifier other than as specified above,
- the behavior is undefined.
-12 The conversion specifiers and their meanings are:
- d Matches an optionally signed decimal integer, whose format is the same as
- expected for the subject sequence of the wcstol function with the value 10
- for the base argument. The corresponding argument shall be a pointer to
- signed integer.
- i Matches an optionally signed integer, whose format is the same as expected
- for the subject sequence of the wcstol function with the value 0 for the
- base argument. The corresponding argument shall be a pointer to signed
-
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-
- integer.
-o Matches an optionally signed octal integer, whose format is the same as
- expected for the subject sequence of the wcstoul function with the value 8
- for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
-u Matches an optionally signed decimal integer, whose format is the same as
- expected for the subject sequence of the wcstoul function with the value 10
- for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
-x Matches an optionally signed hexadecimal integer, whose format is the same
- as expected for the subject sequence of the wcstoul function with the value
- 16 for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
-a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
- format is the same as expected for the subject sequence of the wcstod
- function. The corresponding argument shall be a pointer to floating.
-c Matches a sequence of wide characters of exactly the number specified by the
- field width (1 if no field width is present in the directive).
- If no l length modifier is present, characters from the input field are
- converted as if by repeated calls to the wcrtomb function, with the
- conversion state described by an mbstate_t object initialized to zero
- before the first wide character is converted. The corresponding argument
- shall be a pointer to the initial element of a character array large enough to
- accept the sequence. No null character is added.
- If an l length modifier is present, the corresponding argument shall be a
- pointer to the initial element of an array of wchar_t large enough to accept
- the sequence. No null wide character is added.
-s Matches a sequence of non-white-space wide characters.
- If no l length modifier is present, characters from the input field are
- converted as if by repeated calls to the wcrtomb function, with the
- conversion state described by an mbstate_t object initialized to zero
- before the first wide character is converted. The corresponding argument
- shall be a pointer to the initial element of a character array large enough to
- accept the sequence and a terminating null character, which will be added
- automatically.
- If an l length modifier is present, the corresponding argument shall be a
- pointer to the initial element of an array of wchar_t large enough to accept
-
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-
- the sequence and the terminating null wide character, which will be added
- automatically.
-[ Matches a nonempty sequence of wide characters from a set of expected
- characters (the scanset).
- If no l length modifier is present, characters from the input field are
- converted as if by repeated calls to the wcrtomb function, with the
- conversion state described by an mbstate_t object initialized to zero
- before the first wide character is converted. The corresponding argument
- shall be a pointer to the initial element of a character array large enough to
- accept the sequence and a terminating null character, which will be added
- automatically.
- If an l length modifier is present, the corresponding argument shall be a
- pointer to the initial element of an array of wchar_t large enough to accept
- the sequence and the terminating null wide character, which will be added
- automatically.
- The conversion specifier includes all subsequent wide characters in the
- format string, up to and including the matching right bracket (]). The wide
- characters between the brackets (the scanlist) compose the scanset, unless the
- wide character after the left bracket is a circumflex (^), in which case the
- scanset contains all wide characters that do not appear in the scanlist between
- the circumflex and the right bracket. If the conversion specifier begins with
- [] or [^], the right bracket wide character is in the scanlist and the next
- following right bracket wide character is the matching right bracket that ends
- the specification; otherwise the first following right bracket wide character is
- the one that ends the specification. If a - wide character is in the scanlist and
- is not the first, nor the second where the first wide character is a ^, nor the
- last character, the behavior is implementation-defined.
-p Matches an implementation-defined set of sequences, which should be the
- same as the set of sequences that may be produced by the %p conversion of
- the fwprintf function. The corresponding argument shall be a pointer to a
- pointer to void. The input item is converted to a pointer value in an
- implementation-defined manner. If the input item is a value converted earlier
- during the same program execution, the pointer that results shall compare
- equal to that value; otherwise the behavior of the %p conversion is undefined.
-n No input is consumed. The corresponding argument shall be a pointer to
- signed integer into which is to be written the number of wide characters read
- from the input stream so far by this call to the fwscanf function. Execution
- of a %n directive does not increment the assignment count returned at the
- completion of execution of the fwscanf function. No argument is
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-
- converted, but one is consumed. If the conversion specification includes an
- assignment-suppressing wide character or a field width, the behavior is
- undefined.
- % Matches a single % wide character; no conversion or assignment occurs. The
- complete conversion specification shall be %%.
-13 If a conversion specification is invalid, the behavior is undefined.322)
-14 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
- respectively, a, e, f, g, and x.
-15 Trailing white space (including new-line wide characters) is left unread unless matched
- by a directive. The success of literal matches and suppressed assignments is not directly
- determinable other than via the %n directive.
- Returns
-16 The fwscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the function returns the
- number of input items assigned, which can be fewer than provided for, or even zero, in
- the event of an early matching failure.
-17 EXAMPLE 1 The call:
- #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- /* ... */
- int n, i; float x; wchar_t name[50];
- n = fwscanf(stdin, L"%d%f%ls", &i, &x, name);
- with the input line:
- 25 54.32E-1 thompson
- will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
- thompson\0.
-
-18 EXAMPLE 2 The call:
- #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- /* ... */
- int i; float x; double y;
- fwscanf(stdin, L"%2d%f%*d %lf", &i, &x, &y);
- with input:
- 56789 0123 56a72
- will assign to i the value 56 and to x the value 789.0, will skip past 0123, and will assign to y the value
- 56.0. The next wide character read from the input stream will be a.
-
-
- 322) See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
-
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-
- Forward references: the wcstod, wcstof, and wcstold functions (<a href="#7.28.4.1.1">7.28.4.1.1</a>), the
- wcstol, wcstoll, wcstoul, and wcstoull functions (<a href="#7.28.4.1.2">7.28.4.1.2</a>), the wcrtomb
- function (<a href="#7.28.6.3.3">7.28.6.3.3</a>).
-<a name="7.28.2.3" href="#7.28.2.3"><b> 7.28.2.3 The swprintf function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- int swprintf(wchar_t * restrict s,
- size_t n,
- const wchar_t * restrict format, ...);
- Description
-2 The swprintf function is equivalent to fwprintf, except that the argument s
- specifies an array of wide characters into which the generated output is to be written,
- rather than written to a stream. No more than n wide characters are written, including a
- terminating null wide character, which is always added (unless n is zero).
- Returns
-3 The swprintf function returns the number of wide characters written in the array, not
- counting the terminating null wide character, or a negative value if an encoding error
- occurred or if n or more wide characters were requested to be written.
-<a name="7.28.2.4" href="#7.28.2.4"><b> 7.28.2.4 The swscanf function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- int swscanf(const wchar_t * restrict s,
- const wchar_t * restrict format, ...);
- Description
-2 The swscanf function is equivalent to fwscanf, except that the argument s specifies a
- wide string from which the input is to be obtained, rather than from a stream. Reaching
- the end of the wide string is equivalent to encountering end-of-file for the fwscanf
- function.
- Returns
-3 The swscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the swscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
-
-
-
-
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-
-<a name="7.28.2.5" href="#7.28.2.5"><b> 7.28.2.5 The vfwprintf function</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int vfwprintf(FILE * restrict stream,
- const wchar_t * restrict format,
- va_list arg);
- Description
-2 The vfwprintf function is equivalent to fwprintf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vfwprintf function does not invoke the
- va_end macro.323)
- Returns
-3 The vfwprintf function returns the number of wide characters transmitted, or a
- negative value if an output or encoding error occurred.
-4 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting
- routine.
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- void error(char *function_name, wchar_t *format, ...)
- {
- va_list args;
- va_start(args, format);
- // print out name of function causing error
- fwprintf(stderr, L"ERROR in %s: ", function_name);
- // print out remainder of message
- vfwprintf(stderr, format, args);
- va_end(args);
- }
-
-
-
-
- 323) As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
- invoke the va_arg macro, the value of arg after the return is indeterminate.
-
-[<a name="#p413" href="p413">page 413</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.28.2.6" href="#7.28.2.6"><b> 7.28.2.6 The vfwscanf function</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int vfwscanf(FILE * restrict stream,
- const wchar_t * restrict format,
- va_list arg);
- Description
-2 The vfwscanf function is equivalent to fwscanf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vfwscanf function does not invoke the
- va_end macro.323)
- Returns
-3 The vfwscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the vfwscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
-<a name="7.28.2.7" href="#7.28.2.7"><b> 7.28.2.7 The vswprintf function</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int vswprintf(wchar_t * restrict s,
- size_t n,
- const wchar_t * restrict format,
- va_list arg);
- Description
-2 The vswprintf function is equivalent to swprintf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vswprintf function does not invoke the
- va_end macro.323)
- Returns
-3 The vswprintf function returns the number of wide characters written in the array, not
- counting the terminating null wide character, or a negative value if an encoding error
- occurred or if n or more wide characters were requested to be generated.
-
-
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-
-<a name="7.28.2.8" href="#7.28.2.8"><b> 7.28.2.8 The vswscanf function</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int vswscanf(const wchar_t * restrict s,
- const wchar_t * restrict format,
- va_list arg);
- Description
-2 The vswscanf function is equivalent to swscanf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vswscanf function does not invoke the
- va_end macro.323)
- Returns
-3 The vswscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the vswscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
-<a name="7.28.2.9" href="#7.28.2.9"><b> 7.28.2.9 The vwprintf function</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int vwprintf(const wchar_t * restrict format,
- va_list arg);
- Description
-2 The vwprintf function is equivalent to wprintf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vwprintf function does not invoke the
- va_end macro.323)
- Returns
-3 The vwprintf function returns the number of wide characters transmitted, or a negative
- value if an output or encoding error occurred.
-
-
-
-
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-
-<a name="7.28.2.10" href="#7.28.2.10"><b> 7.28.2.10 The vwscanf function</b></a>
- Synopsis
-1 #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int vwscanf(const wchar_t * restrict format,
- va_list arg);
- Description
-2 The vwscanf function is equivalent to wscanf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vwscanf function does not invoke the
- va_end macro.323)
- Returns
-3 The vwscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the vwscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
-<a name="7.28.2.11" href="#7.28.2.11"><b> 7.28.2.11 The wprintf function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- int wprintf(const wchar_t * restrict format, ...);
- Description
-2 The wprintf function is equivalent to fwprintf with the argument stdout
- interposed before the arguments to wprintf.
- Returns
-3 The wprintf function returns the number of wide characters transmitted, or a negative
- value if an output or encoding error occurred.
-<a name="7.28.2.12" href="#7.28.2.12"><b> 7.28.2.12 The wscanf function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- int wscanf(const wchar_t * restrict format, ...);
- Description
-2 The wscanf function is equivalent to fwscanf with the argument stdin interposed
- before the arguments to wscanf.
-
-
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-
- Returns
-3 The wscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the wscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
-<a name="7.28.3" href="#7.28.3"><b> 7.28.3 Wide character input/output functions</b></a>
-<a name="7.28.3.1" href="#7.28.3.1"><b> 7.28.3.1 The fgetwc function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- wint_t fgetwc(FILE *stream);
- Description
-2 If the end-of-file indicator for the input stream pointed to by stream is not set and a
- next wide character is present, the fgetwc function obtains that wide character as a
- wchar_t converted to a wint_t and advances the associated file position indicator for
- the stream (if defined).
- Returns
-3 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
- of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
- the fgetwc function returns the next wide character from the input stream pointed to by
- stream. If a read error occurs, the error indicator for the stream is set and the fgetwc
- function returns WEOF. If an encoding error occurs (including too few bytes), the value of
- the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.324)
-<a name="7.28.3.2" href="#7.28.3.2"><b> 7.28.3.2 The fgetws function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- wchar_t *fgetws(wchar_t * restrict s,
- int n, FILE * restrict stream);
- Description
-2 The fgetws function reads at most one less than the number of wide characters
- specified by n from the stream pointed to by stream into the array pointed to by s. No
-
-
- 324) An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
- Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
-
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-
- additional wide characters are read after a new-line wide character (which is retained) or
- after end-of-file. A null wide character is written immediately after the last wide
- character read into the array.
- Returns
-3 The fgetws function returns s if successful. If end-of-file is encountered and no
- characters have been read into the array, the contents of the array remain unchanged and a
- null pointer is returned. If a read or encoding error occurs during the operation, the array
- contents are indeterminate and a null pointer is returned.
-<a name="7.28.3.3" href="#7.28.3.3"><b> 7.28.3.3 The fputwc function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- wint_t fputwc(wchar_t c, FILE *stream);
- Description
-2 The fputwc function writes the wide character specified by c to the output stream
- pointed to by stream, at the position indicated by the associated file position indicator
- for the stream (if defined), and advances the indicator appropriately. If the file cannot
- support positioning requests, or if the stream was opened with append mode, the
- character is appended to the output stream.
- Returns
-3 The fputwc function returns the wide character written. If a write error occurs, the
- error indicator for the stream is set and fputwc returns WEOF. If an encoding error
- occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
-<a name="7.28.3.4" href="#7.28.3.4"><b> 7.28.3.4 The fputws function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int fputws(const wchar_t * restrict s,
- FILE * restrict stream);
- Description
-2 The fputws function writes the wide string pointed to by s to the stream pointed to by
- stream. The terminating null wide character is not written.
- Returns
-3 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
- returns a nonnegative value.
-
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-
-<a name="7.28.3.5" href="#7.28.3.5"><b> 7.28.3.5 The fwide function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int fwide(FILE *stream, int mode);
- Description
-2 The fwide function determines the orientation of the stream pointed to by stream. If
- mode is greater than zero, the function first attempts to make the stream wide oriented. If
- mode is less than zero, the function first attempts to make the stream byte oriented.325)
- Otherwise, mode is zero and the function does not alter the orientation of the stream.
- Returns
-3 The fwide function returns a value greater than zero if, after the call, the stream has
- wide orientation, a value less than zero if the stream has byte orientation, or zero if the
- stream has no orientation.
-<a name="7.28.3.6" href="#7.28.3.6"><b> 7.28.3.6 The getwc function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- wint_t getwc(FILE *stream);
- Description
-2 The getwc function is equivalent to fgetwc, except that if it is implemented as a
- macro, it may evaluate stream more than once, so the argument should never be an
- expression with side effects.
- Returns
-3 The getwc function returns the next wide character from the input stream pointed to by
- stream, or WEOF.
-<a name="7.28.3.7" href="#7.28.3.7"><b> 7.28.3.7 The getwchar function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- wint_t getwchar(void);
-
-
-
-
- 325) If the orientation of the stream has already been determined, fwide does not change it.
-
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-
- Description
-2 The getwchar function is equivalent to getwc with the argument stdin.
- Returns
-3 The getwchar function returns the next wide character from the input stream pointed to
- by stdin, or WEOF.
-<a name="7.28.3.8" href="#7.28.3.8"><b> 7.28.3.8 The putwc function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- wint_t putwc(wchar_t c, FILE *stream);
- Description
-2 The putwc function is equivalent to fputwc, except that if it is implemented as a
- macro, it may evaluate stream more than once, so that argument should never be an
- expression with side effects.
- Returns
-3 The putwc function returns the wide character written, or WEOF.
-<a name="7.28.3.9" href="#7.28.3.9"><b> 7.28.3.9 The putwchar function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- wint_t putwchar(wchar_t c);
- Description
-2 The putwchar function is equivalent to putwc with the second argument stdout.
- Returns
-3 The putwchar function returns the character written, or WEOF.
-<a name="7.28.3.10" href="#7.28.3.10"><b> 7.28.3.10 The ungetwc function</b></a>
- Synopsis
-1 #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- wint_t ungetwc(wint_t c, FILE *stream);
- Description
-2 The ungetwc function pushes the wide character specified by c back onto the input
- stream pointed to by stream. Pushed-back wide characters will be returned by
- subsequent reads on that stream in the reverse order of their pushing. A successful
-
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-
- intervening call (with the stream pointed to by stream) to a file positioning function
- (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the
- stream. The external storage corresponding to the stream is unchanged.
-3 One wide character of pushback is guaranteed, even if the call to the ungetwc function
- follows just after a call to a formatted wide character input function fwscanf,
- vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times
- on the same stream without an intervening read or file positioning operation on that
- stream, the operation may fail.
-4 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
- unchanged.
-5 A successful call to the ungetwc function clears the end-of-file indicator for the stream.
- The value of the file position indicator for the stream after reading or discarding all
- pushed-back wide characters is the same as it was before the wide characters were pushed
- back. For a text or binary stream, the value of its file position indicator after a successful
- call to the ungetwc function is unspecified until all pushed-back wide characters are
- read or discarded.
- Returns
-6 The ungetwc function returns the wide character pushed back, or WEOF if the operation
- fails.
-<a name="7.28.4" href="#7.28.4"><b> 7.28.4 General wide string utilities</b></a>
-1 The header <a href="#7.28"><wchar.h></a> declares a number of functions useful for wide string
- manipulation. Various methods are used for determining the lengths of the arrays, but in
- all cases a wchar_t * argument points to the initial (lowest addressed) element of the
- array. If an array is accessed beyond the end of an object, the behavior is undefined.
-2 Where an argument declared as size_t n determines the length of the array for a
- function, n can have the value zero on a call to that function. Unless explicitly stated
- otherwise in the description of a particular function in this subclause, pointer arguments
- on such a call shall still have valid values, as described in <a href="#7.1.4">7.1.4</a>. On such a call, a
- function that locates a wide character finds no occurrence, a function that compares two
- wide character sequences returns zero, and a function that copies wide characters copies
- zero wide characters.
-
-
-
-
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-
-<a name="7.28.4.1" href="#7.28.4.1"><b> 7.28.4.1 Wide string numeric conversion functions</b></a>
-<a name="7.28.4.1.1" href="#7.28.4.1.1"><b> 7.28.4.1.1 The wcstod, wcstof, and wcstold functions</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- double wcstod(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr);
- float wcstof(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr);
- long double wcstold(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr);
- Description
-2 The wcstod, wcstof, and wcstold functions convert the initial portion of the wide
- string pointed to by nptr to double, float, and long double representation,
- respectively. First, they decompose the input string into three parts: an initial, possibly
- empty, sequence of white-space wide characters (as specified by the iswspace
- function), a subject sequence resembling a floating-point constant or representing an
- infinity or NaN; and a final wide string of one or more unrecognized wide characters,
- including the terminating null wide character of the input wide string. Then, they attempt
- to convert the subject sequence to a floating-point number, and return the result.
-3 The expected form of the subject sequence is an optional plus or minus sign, then one of
- the following:
- -- a nonempty sequence of decimal digits optionally containing a decimal-point wide
- character, then an optional exponent part as defined for the corresponding single-byte
- characters in <a href="#6.4.4.2">6.4.4.2</a>;
- -- a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
- decimal-point wide character, then an optional binary exponent part as defined in
- <a href="#6.4.4.2">6.4.4.2</a>;
- -- INF or INFINITY, or any other wide string equivalent except for case
- -- NAN or NAN(n-wchar-sequenceopt), or any other wide string equivalent except for
- case in the NAN part, where:
- n-wchar-sequence:
- digit
- nondigit
- n-wchar-sequence digit
- n-wchar-sequence nondigit
- The subject sequence is defined as the longest initial subsequence of the input wide
- string, starting with the first non-white-space wide character, that is of the expected form.
-[<a name="#p422" href="p422">page 422</a>] (<a href="#Contents">Contents</a>)
-
- The subject sequence contains no wide characters if the input wide string is not of the
- expected form.
-4 If the subject sequence has the expected form for a floating-point number, the sequence of
- wide characters starting with the first digit or the decimal-point wide character
- (whichever occurs first) is interpreted as a floating constant according to the rules of
- <a href="#6.4.4.2">6.4.4.2</a>, except that the decimal-point wide character is used in place of a period, and that
- if neither an exponent part nor a decimal-point wide character appears in a decimal
- floating point number, or if a binary exponent part does not appear in a hexadecimal
- floating point number, an exponent part of the appropriate type with value zero is
- assumed to follow the last digit in the string. If the subject sequence begins with a minus
- sign, the sequence is interpreted as negated.326) A wide character sequence INF or
- INFINITY is interpreted as an infinity, if representable in the return type, else like a
- floating constant that is too large for the range of the return type. A wide character
- sequence NAN or NAN(n-wchar-sequenceopt) is interpreted as a quiet NaN, if supported
- in the return type, else like a subject sequence part that does not have the expected form;
- the meaning of the n-wchar sequences is implementation-defined.327) A pointer to the
- final wide string is stored in the object pointed to by endptr, provided that endptr is
- not a null pointer.
-5 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
- value resulting from the conversion is correctly rounded.
-6 In other than the "C" locale, additional locale-specific subject sequence forms may be
- accepted.
-7 If the subject sequence is empty or does not have the expected form, no conversion is
- performed; the value of nptr is stored in the object pointed to by endptr, provided
- that endptr is not a null pointer.
- Recommended practice
-8 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
- the result is not exactly representable, the result should be one of the two numbers in the
- appropriate internal format that are adjacent to the hexadecimal floating source value,
- with the extra stipulation that the error should have a correct sign for the current rounding
- direction.
-
-
-
- 326) It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
- negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
- methods may yield different results if rounding is toward positive or negative infinity. In either case,
- the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
- 327) An implementation may use the n-wchar sequence to determine extra information to be represented in
- the NaN's significand.
-
-[<a name="#p423" href="p423">page 423</a>] (<a href="#Contents">Contents</a>)
-
-9 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
- <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
- sequence D has the decimal form and more than DECIMAL_DIG significant digits,
- consider the two bounding, adjacent decimal strings L and U, both having
- DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
- The result should be one of the (equal or adjacent) values that would be obtained by
- correctly rounding L and U according to the current rounding direction, with the extra
- stipulation that the error with respect to D should have a correct sign for the current
- rounding direction.328)
- Returns
-10 The functions return the converted value, if any. If no conversion could be performed,
- zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
- plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
- return type and sign of the value), and the value of the macro ERANGE is stored in
- errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
- no greater than the smallest normalized positive number in the return type; whether
- errno acquires the value ERANGE is implementation-defined.
-
-
-
-
- 328) DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
- to the same internal floating value, but if not will round to adjacent values.
-
-[<a name="#p424" href="p424">page 424</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.28.4.1.2" href="#7.28.4.1.2"><b> 7.28.4.1.2 The wcstol, wcstoll, wcstoul, and wcstoull functions</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- long int wcstol(
- const wchar_t * restrict nptr,
- wchar_t ** restrict endptr,
- int base);
- long long int wcstoll(
- const wchar_t * restrict nptr,
- wchar_t ** restrict endptr,
- int base);
- unsigned long int wcstoul(
- const wchar_t * restrict nptr,
- wchar_t ** restrict endptr,
- int base);
- unsigned long long int wcstoull(
- const wchar_t * restrict nptr,
- wchar_t ** restrict endptr,
- int base);
- Description
-2 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial
- portion of the wide string pointed to by nptr to long int, long long int,
- unsigned long int, and unsigned long long int representation,
- respectively. First, they decompose the input string into three parts: an initial, possibly
- empty, sequence of white-space wide characters (as specified by the iswspace
- function), a subject sequence resembling an integer represented in some radix determined
- by the value of base, and a final wide string of one or more unrecognized wide
- characters, including the terminating null wide character of the input wide string. Then,
- they attempt to convert the subject sequence to an integer, and return the result.
-3 If the value of base is zero, the expected form of the subject sequence is that of an
- integer constant as described for the corresponding single-byte characters in <a href="#6.4.4.1">6.4.4.1</a>,
- optionally preceded by a plus or minus sign, but not including an integer suffix. If the
- value of base is between 2 and 36 (inclusive), the expected form of the subject sequence
- is a sequence of letters and digits representing an integer with the radix specified by
- base, optionally preceded by a plus or minus sign, but not including an integer suffix.
- The letters from a (or A) through z (or Z) are ascribed the values 10 through 35; only
- letters and digits whose ascribed values are less than that of base are permitted. If the
- value of base is 16, the wide characters 0x or 0X may optionally precede the sequence
- of letters and digits, following the sign if present.
-
-[<a name="#p425" href="p425">page 425</a>] (<a href="#Contents">Contents</a>)
-
-4 The subject sequence is defined as the longest initial subsequence of the input wide
- string, starting with the first non-white-space wide character, that is of the expected form.
- The subject sequence contains no wide characters if the input wide string is empty or
- consists entirely of white space, or if the first non-white-space wide character is other
- than a sign or a permissible letter or digit.
-5 If the subject sequence has the expected form and the value of base is zero, the sequence
- of wide characters starting with the first digit is interpreted as an integer constant
- according to the rules of <a href="#6.4.4.1">6.4.4.1</a>. If the subject sequence has the expected form and the
- value of base is between 2 and 36, it is used as the base for conversion, ascribing to each
- letter its value as given above. If the subject sequence begins with a minus sign, the value
- resulting from the conversion is negated (in the return type). A pointer to the final wide
- string is stored in the object pointed to by endptr, provided that endptr is not a null
- pointer.
-6 In other than the "C" locale, additional locale-specific subject sequence forms may be
- accepted.
-7 If the subject sequence is empty or does not have the expected form, no conversion is
- performed; the value of nptr is stored in the object pointed to by endptr, provided
- that endptr is not a null pointer.
- Returns
-8 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
- value, if any. If no conversion could be performed, zero is returned. If the correct value
- is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
- LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
- sign of the value, if any), and the value of the macro ERANGE is stored in errno.
-<a name="7.28.4.2" href="#7.28.4.2"><b> 7.28.4.2 Wide string copying functions</b></a>
-<a name="7.28.4.2.1" href="#7.28.4.2.1"><b> 7.28.4.2.1 The wcscpy function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- wchar_t *wcscpy(wchar_t * restrict s1,
- const wchar_t * restrict s2);
- Description
-2 The wcscpy function copies the wide string pointed to by s2 (including the terminating
- null wide character) into the array pointed to by s1.
- Returns
-3 The wcscpy function returns the value of s1.
-
-
-[<a name="#p426" href="p426">page 426</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.28.4.2.2" href="#7.28.4.2.2"><b> 7.28.4.2.2 The wcsncpy function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- wchar_t *wcsncpy(wchar_t * restrict s1,
- const wchar_t * restrict s2,
- size_t n);
- Description
-2 The wcsncpy function copies not more than n wide characters (those that follow a null
- wide character are not copied) from the array pointed to by s2 to the array pointed to by
- s1.329)
-3 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null
- wide characters are appended to the copy in the array pointed to by s1, until n wide
- characters in all have been written.
- Returns
-4 The wcsncpy function returns the value of s1.
-<a name="7.28.4.2.3" href="#7.28.4.2.3"><b> 7.28.4.2.3 The wmemcpy function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- wchar_t *wmemcpy(wchar_t * restrict s1,
- const wchar_t * restrict s2,
- size_t n);
- Description
-2 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
- object pointed to by s1.
- Returns
-3 The wmemcpy function returns the value of s1.
-
-
-
-
- 329) Thus, if there is no null wide character in the first n wide characters of the array pointed to by s2, the
- result will not be null-terminated.
-
-[<a name="#p427" href="p427">page 427</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.28.4.2.4" href="#7.28.4.2.4"><b> 7.28.4.2.4 The wmemmove function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
- size_t n);
- Description
-2 The wmemmove function copies n wide characters from the object pointed to by s2 to
- the object pointed to by s1. Copying takes place as if the n wide characters from the
- object pointed to by s2 are first copied into a temporary array of n wide characters that
- does not overlap the objects pointed to by s1 or s2, and then the n wide characters from
- the temporary array are copied into the object pointed to by s1.
- Returns
-3 The wmemmove function returns the value of s1.
-<a name="7.28.4.3" href="#7.28.4.3"><b> 7.28.4.3 Wide string concatenation functions</b></a>
-<a name="7.28.4.3.1" href="#7.28.4.3.1"><b> 7.28.4.3.1 The wcscat function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- wchar_t *wcscat(wchar_t * restrict s1,
- const wchar_t * restrict s2);
- Description
-2 The wcscat function appends a copy of the wide string pointed to by s2 (including the
- terminating null wide character) to the end of the wide string pointed to by s1. The initial
- wide character of s2 overwrites the null wide character at the end of s1.
- Returns
-3 The wcscat function returns the value of s1.
-<a name="7.28.4.3.2" href="#7.28.4.3.2"><b> 7.28.4.3.2 The wcsncat function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- wchar_t *wcsncat(wchar_t * restrict s1,
- const wchar_t * restrict s2,
- size_t n);
- Description
-2 The wcsncat function appends not more than n wide characters (a null wide character
- and those that follow it are not appended) from the array pointed to by s2 to the end of
-
-[<a name="#p428" href="p428">page 428</a>] (<a href="#Contents">Contents</a>)
-
- the wide string pointed to by s1. The initial wide character of s2 overwrites the null
- wide character at the end of s1. A terminating null wide character is always appended to
- the result.330)
- Returns
-3 The wcsncat function returns the value of s1.
-<a name="7.28.4.4" href="#7.28.4.4"><b> 7.28.4.4 Wide string comparison functions</b></a>
-1 Unless explicitly stated otherwise, the functions described in this subclause order two
- wide characters the same way as two integers of the underlying integer type designated
- by wchar_t.
-<a name="7.28.4.4.1" href="#7.28.4.4.1"><b> 7.28.4.4.1 The wcscmp function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- int wcscmp(const wchar_t *s1, const wchar_t *s2);
- Description
-2 The wcscmp function compares the wide string pointed to by s1 to the wide string
- pointed to by s2.
- Returns
-3 The wcscmp function returns an integer greater than, equal to, or less than zero,
- accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
- wide string pointed to by s2.
-<a name="7.28.4.4.2" href="#7.28.4.4.2"><b> 7.28.4.4.2 The wcscoll function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- int wcscoll(const wchar_t *s1, const wchar_t *s2);
- Description
-2 The wcscoll function compares the wide string pointed to by s1 to the wide string
- pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the
- current locale.
- Returns
-3 The wcscoll function returns an integer greater than, equal to, or less than zero,
- accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
-
-
- 330) Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is
- wcslen(s1)+n+1.
-
-[<a name="#p429" href="p429">page 429</a>] (<a href="#Contents">Contents</a>)
-
- wide string pointed to by s2 when both are interpreted as appropriate to the current
- locale.
-<a name="7.28.4.4.3" href="#7.28.4.4.3"><b> 7.28.4.4.3 The wcsncmp function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- int wcsncmp(const wchar_t *s1, const wchar_t *s2,
- size_t n);
- Description
-2 The wcsncmp function compares not more than n wide characters (those that follow a
- null wide character are not compared) from the array pointed to by s1 to the array
- pointed to by s2.
- Returns
-3 The wcsncmp function returns an integer greater than, equal to, or less than zero,
- accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
- to, or less than the possibly null-terminated array pointed to by s2.
-<a name="7.28.4.4.4" href="#7.28.4.4.4"><b> 7.28.4.4.4 The wcsxfrm function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- size_t wcsxfrm(wchar_t * restrict s1,
- const wchar_t * restrict s2,
- size_t n);
- Description
-2 The wcsxfrm function transforms the wide string pointed to by s2 and places the
- resulting wide string into the array pointed to by s1. The transformation is such that if
- the wcscmp function is applied to two transformed wide strings, it returns a value greater
- than, equal to, or less than zero, corresponding to the result of the wcscoll function
- applied to the same two original wide strings. No more than n wide characters are placed
- into the resulting array pointed to by s1, including the terminating null wide character. If
- n is zero, s1 is permitted to be a null pointer.
- Returns
-3 The wcsxfrm function returns the length of the transformed wide string (not including
- the terminating null wide character). If the value returned is n or greater, the contents of
- the array pointed to by s1 are indeterminate.
-4 EXAMPLE The value of the following expression is the length of the array needed to hold the
- transformation of the wide string pointed to by s:
-
-
-[<a name="#p430" href="p430">page 430</a>] (<a href="#Contents">Contents</a>)
-
- 1 + wcsxfrm(NULL, s, 0)
-
-<a name="7.28.4.4.5" href="#7.28.4.4.5"><b> 7.28.4.4.5 The wmemcmp function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- int wmemcmp(const wchar_t *s1, const wchar_t *s2,
- size_t n);
- Description
-2 The wmemcmp function compares the first n wide characters of the object pointed to by
- s1 to the first n wide characters of the object pointed to by s2.
- Returns
-3 The wmemcmp function returns an integer greater than, equal to, or less than zero,
- accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
- pointed to by s2.
-<a name="7.28.4.5" href="#7.28.4.5"><b> 7.28.4.5 Wide string search functions</b></a>
-<a name="7.28.4.5.1" href="#7.28.4.5.1"><b> 7.28.4.5.1 The wcschr function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- wchar_t *wcschr(const wchar_t *s, wchar_t c);
- Description
-2 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
- The terminating null wide character is considered to be part of the wide string.
- Returns
-3 The wcschr function returns a pointer to the located wide character, or a null pointer if
- the wide character does not occur in the wide string.
-<a name="7.28.4.5.2" href="#7.28.4.5.2"><b> 7.28.4.5.2 The wcscspn function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
- Description
-2 The wcscspn function computes the length of the maximum initial segment of the wide
- string pointed to by s1 which consists entirely of wide characters not from the wide
- string pointed to by s2.
-
-
-
-[<a name="#p431" href="p431">page 431</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The wcscspn function returns the length of the segment.
-<a name="7.28.4.5.3" href="#7.28.4.5.3"><b> 7.28.4.5.3 The wcspbrk function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
- Description
-2 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
- any wide character from the wide string pointed to by s2.
- Returns
-3 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
- no wide character from s2 occurs in s1.
-<a name="7.28.4.5.4" href="#7.28.4.5.4"><b> 7.28.4.5.4 The wcsrchr function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
- Description
-2 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
- s. The terminating null wide character is considered to be part of the wide string.
- Returns
-3 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
- not occur in the wide string.
-<a name="7.28.4.5.5" href="#7.28.4.5.5"><b> 7.28.4.5.5 The wcsspn function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
- Description
-2 The wcsspn function computes the length of the maximum initial segment of the wide
- string pointed to by s1 which consists entirely of wide characters from the wide string
- pointed to by s2.
- Returns
-3 The wcsspn function returns the length of the segment.
-
-
-[<a name="#p432" href="p432">page 432</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.28.4.5.6" href="#7.28.4.5.6"><b> 7.28.4.5.6 The wcsstr function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
- Description
-2 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
- the sequence of wide characters (excluding the terminating null wide character) in the
- wide string pointed to by s2.
- Returns
-3 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
- wide string is not found. If s2 points to a wide string with zero length, the function
- returns s1.
-<a name="7.28.4.5.7" href="#7.28.4.5.7"><b> 7.28.4.5.7 The wcstok function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- wchar_t *wcstok(wchar_t * restrict s1,
- const wchar_t * restrict s2,
- wchar_t ** restrict ptr);
- Description
-2 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
- a sequence of tokens, each of which is delimited by a wide character from the wide string
- pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
- which the wcstok function stores information necessary for it to continue scanning the
- same wide string.
-3 The first call in a sequence has a non-null first argument and stores an initial value in the
- object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
- the object pointed to by ptr is required to have the value stored by the previous call in
- the sequence, which is then updated. The separator wide string pointed to by s2 may be
- different from call to call.
-4 The first call in the sequence searches the wide string pointed to by s1 for the first wide
- character that is not contained in the current separator wide string pointed to by s2. If no
- such wide character is found, then there are no tokens in the wide string pointed to by s1
- and the wcstok function returns a null pointer. If such a wide character is found, it is
- the start of the first token.
-5 The wcstok function then searches from there for a wide character that is contained in
- the current separator wide string. If no such wide character is found, the current token
-[<a name="#p433" href="p433">page 433</a>] (<a href="#Contents">Contents</a>)
-
- extends to the end of the wide string pointed to by s1, and subsequent searches in the
- same wide string for a token return a null pointer. If such a wide character is found, it is
- overwritten by a null wide character, which terminates the current token.
-6 In all cases, the wcstok function stores sufficient information in the pointer pointed to
- by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
- value for ptr, shall start searching just past the element overwritten by a null wide
- character (if any).
- Returns
-7 The wcstok function returns a pointer to the first wide character of a token, or a null
- pointer if there is no token.
-8 EXAMPLE
- #include <a href="#7.28"><wchar.h></a>
- static wchar_t str1[] = L"?a???b,,,#c";
- static wchar_t str2[] = L"\t \t";
- wchar_t *t, *ptr1, *ptr2;
- t = wcstok(str1, L"?", &ptr1); // t points to the token L"a"
- t = wcstok(NULL, L",", &ptr1); // t points to the token L"??b"
- t = wcstok(str2, L" \t", &ptr2); // t is a null pointer
- t = wcstok(NULL, L"#,", &ptr1); // t points to the token L"c"
- t = wcstok(NULL, L"?", &ptr1); // t is a null pointer
-
-<a name="7.28.4.5.8" href="#7.28.4.5.8"><b> 7.28.4.5.8 The wmemchr function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- wchar_t *wmemchr(const wchar_t *s, wchar_t c,
- size_t n);
- Description
-2 The wmemchr function locates the first occurrence of c in the initial n wide characters of
- the object pointed to by s.
- Returns
-3 The wmemchr function returns a pointer to the located wide character, or a null pointer if
- the wide character does not occur in the object.
-
-
-
-
-[<a name="#p434" href="p434">page 434</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.28.4.6" href="#7.28.4.6"><b> 7.28.4.6 Miscellaneous functions</b></a>
-<a name="7.28.4.6.1" href="#7.28.4.6.1"><b> 7.28.4.6.1 The wcslen function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- size_t wcslen(const wchar_t *s);
- Description
-2 The wcslen function computes the length of the wide string pointed to by s.
- Returns
-3 The wcslen function returns the number of wide characters that precede the terminating
- null wide character.
-<a name="7.28.4.6.2" href="#7.28.4.6.2"><b> 7.28.4.6.2 The wmemset function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
- Description
-2 The wmemset function copies the value of c into each of the first n wide characters of
- the object pointed to by s.
- Returns
-3 The wmemset function returns the value of s.
-<a name="7.28.5" href="#7.28.5"><b> 7.28.5 Wide character time conversion functions</b></a>
-<a name="7.28.5.1" href="#7.28.5.1"><b> 7.28.5.1 The wcsftime function</b></a>
- Synopsis
-1 #include <a href="#7.26"><time.h></a>
- #include <a href="#7.28"><wchar.h></a>
- size_t wcsftime(wchar_t * restrict s,
- size_t maxsize,
- const wchar_t * restrict format,
- const struct tm * restrict timeptr);
- Description
-2 The wcsftime function is equivalent to the strftime function, except that:
- -- The argument s points to the initial element of an array of wide characters into which
- the generated output is to be placed.
-
-
-[<a name="#p435" href="p435">page 435</a>] (<a href="#Contents">Contents</a>)
-
- -- The argument maxsize indicates the limiting number of wide characters.
- -- The argument format is a wide string and the conversion specifiers are replaced by
- corresponding sequences of wide characters.
- -- The return value indicates the number of wide characters.
- Returns
-3 If the total number of resulting wide characters including the terminating null wide
- character is not more than maxsize, the wcsftime function returns the number of
- wide characters placed into the array pointed to by s not including the terminating null
- wide character. Otherwise, zero is returned and the contents of the array are
- indeterminate.
-<a name="7.28.6" href="#7.28.6"><b> 7.28.6 Extended multibyte/wide character conversion utilities</b></a>
-1 The header <a href="#7.28"><wchar.h></a> declares an extended set of functions useful for conversion
- between multibyte characters and wide characters.
-2 Most of the following functions -- those that are listed as ''restartable'', <a href="#7.28.6.3">7.28.6.3</a> and
- <a href="#7.28.6.4">7.28.6.4</a> -- take as a last argument a pointer to an object of type mbstate_t that is used
- to describe the current conversion state from a particular multibyte character sequence to
- a wide character sequence (or the reverse) under the rules of a particular setting for the
- LC_CTYPE category of the current locale.
-3 The initial conversion state corresponds, for a conversion in either direction, to the
- beginning of a new multibyte character in the initial shift state. A zero-valued
- mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
- valued mbstate_t object can be used to initiate conversion involving any multibyte
- character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
- been altered by any of the functions described in this subclause, and is then used with a
- different multibyte character sequence, or in the other conversion direction, or with a
- different LC_CTYPE category setting than on earlier function calls, the behavior is
- undefined.331)
-4 On entry, each function takes the described conversion state (either internal or pointed to
- by an argument) as current. The conversion state described by the referenced object is
- altered as needed to track the shift state, and the position within a multibyte character, for
- the associated multibyte character sequence.
-
-
-
-
- 331) Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and
- mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
- character string.
-
-[<a name="#p436" href="p436">page 436</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.28.6.1" href="#7.28.6.1"><b> 7.28.6.1 Single-byte/wide character conversion functions</b></a>
-<a name="7.28.6.1.1" href="#7.28.6.1.1"><b> 7.28.6.1.1 The btowc function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a> *
- wint_t btowc(int c);
- Description
-2 The btowc function determines whether c constitutes a valid single-byte character in the
- initial shift state.
- Returns
-3 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
- does not constitute a valid single-byte character in the initial shift state. Otherwise, it
- returns the wide character representation of that character.
-<a name="7.28.6.1.2" href="#7.28.6.1.2"><b> 7.28.6.1.2 The wctob function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a> *
- int wctob(wint_t c);
- Description
-2 The wctob function determines whether c corresponds to a member of the extended
- character set whose multibyte character representation is a single byte when in the initial
- shift state.
- Returns
-3 The wctob function returns EOF if c does not correspond to a multibyte character with
- length one in the initial shift state. Otherwise, it returns the single-byte representation of
- that character as an unsigned char converted to an int.
-<a name="7.28.6.2" href="#7.28.6.2"><b> 7.28.6.2 Conversion state functions</b></a>
-<a name="7.28.6.2.1" href="#7.28.6.2.1"><b> 7.28.6.2.1 The mbsinit function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- int mbsinit(const mbstate_t *ps);
- Description
-2 If ps is not a null pointer, the mbsinit function determines whether the referenced
- mbstate_t object describes an initial conversion state.
-
-
-
-[<a name="#p437" href="p437">page 437</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-3 The mbsinit function returns nonzero if ps is a null pointer or if the referenced object
- describes an initial conversion state; otherwise, it returns zero.
-<a name="7.28.6.3" href="#7.28.6.3"><b> 7.28.6.3 Restartable multibyte/wide character conversion functions</b></a>
-1 These functions differ from the corresponding multibyte character functions of <a href="#7.22.7">7.22.7</a>
- (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type
- pointer to mbstate_t that points to an object that can completely describe the current
- conversion state of the associated multibyte character sequence. If ps is a null pointer,
- each function uses its own internal mbstate_t object instead, which is initialized at
- program startup to the initial conversion state; the functions are not required to avoid data
- races in this case. The implementation behaves as if no library function calls these
- functions with a null pointer for ps.
-2 Also unlike their corresponding functions, the return value does not represent whether the
- encoding is state-dependent.
-<a name="7.28.6.3.1" href="#7.28.6.3.1"><b> 7.28.6.3.1 The mbrlen function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- size_t mbrlen(const char * restrict s,
- size_t n,
- mbstate_t * restrict ps);
- Description
-2 The mbrlen function is equivalent to the call:
- mbrtowc(NULL, s, n, ps != NULL ? ps : &internal)
- where internal is the mbstate_t object for the mbrlen function, except that the
- expression designated by ps is evaluated only once.
- Returns
-3 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
- or (size_t)(-1).
- Forward references: the mbrtowc function (<a href="#7.28.6.3.2">7.28.6.3.2</a>).
-
-
-
-
-[<a name="#p438" href="p438">page 438</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.28.6.3.2" href="#7.28.6.3.2"><b> 7.28.6.3.2 The mbrtowc function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- size_t mbrtowc(wchar_t * restrict pwc,
- const char * restrict s,
- size_t n,
- mbstate_t * restrict ps);
- Description
-2 If s is a null pointer, the mbrtowc function is equivalent to the call:
- mbrtowc(NULL, "", 1, ps)
- In this case, the values of the parameters pwc and n are ignored.
-3 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with
- the byte pointed to by s to determine the number of bytes needed to complete the next
- multibyte character (including any shift sequences). If the function determines that the
- next multibyte character is complete and valid, it determines the value of the
- corresponding wide character and then, if pwc is not a null pointer, stores that value in
- the object pointed to by pwc. If the corresponding wide character is the null wide
- character, the resulting state described is the initial conversion state.
- Returns
-4 The mbrtowc function returns the first of the following that applies (given the current
- conversion state):
- 0 if the next n or fewer bytes complete the multibyte character that
- corresponds to the null wide character (which is the value stored).
- between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
- character (which is the value stored); the value returned is the number
- of bytes that complete the multibyte character.
- (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
- multibyte character, and all n bytes have been processed (no value is
- stored).332)
- (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
- do not contribute to a complete and valid multibyte character (no
- value is stored); the value of the macro EILSEQ is stored in errno,
- and the conversion state is unspecified.
-
- 332) When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
- sequence of redundant shift sequences (for implementations with state-dependent encodings).
-
-[<a name="#p439" href="p439">page 439</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.28.6.3.3" href="#7.28.6.3.3"><b> 7.28.6.3.3 The wcrtomb function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- size_t wcrtomb(char * restrict s,
- wchar_t wc,
- mbstate_t * restrict ps);
- Description
-2 If s is a null pointer, the wcrtomb function is equivalent to the call
- wcrtomb(buf, L'\0', ps)
- where buf is an internal buffer.
-3 If s is not a null pointer, the wcrtomb function determines the number of bytes needed
- to represent the multibyte character that corresponds to the wide character given by wc
- (including any shift sequences), and stores the multibyte character representation in the
- array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
- wc is a null wide character, a null byte is stored, preceded by any shift sequence needed
- to restore the initial shift state; the resulting state described is the initial conversion state.
- Returns
-4 The wcrtomb function returns the number of bytes stored in the array object (including
- any shift sequences). When wc is not a valid wide character, an encoding error occurs:
- the function stores the value of the macro EILSEQ in errno and returns
- (size_t)(-1); the conversion state is unspecified.
-<a name="7.28.6.4" href="#7.28.6.4"><b> 7.28.6.4 Restartable multibyte/wide string conversion functions</b></a>
-1 These functions differ from the corresponding multibyte string functions of <a href="#7.22.8">7.22.8</a>
- (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to
- mbstate_t that points to an object that can completely describe the current conversion
- state of the associated multibyte character sequence. If ps is a null pointer, each function
- uses its own internal mbstate_t object instead, which is initialized at program startup
- to the initial conversion state; the functions are not required to avoid data races in this
- case. The implementation behaves as if no library function calls these functions with a
- null pointer for ps.
-2 Also unlike their corresponding functions, the conversion source parameter, src, has a
- pointer-to-pointer type. When the function is storing the results of conversions (that is,
- when dst is not a null pointer), the pointer object pointed to by this parameter is updated
- to reflect the amount of the source processed by that invocation.
-
-
-
-
-[<a name="#p440" href="p440">page 440</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.28.6.4.1" href="#7.28.6.4.1"><b> 7.28.6.4.1 The mbsrtowcs function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- size_t mbsrtowcs(wchar_t * restrict dst,
- const char ** restrict src,
- size_t len,
- mbstate_t * restrict ps);
- Description
-2 The mbsrtowcs function converts a sequence of multibyte characters that begins in the
- conversion state described by the object pointed to by ps, from the array indirectly
- pointed to by src into a sequence of corresponding wide characters. If dst is not a null
- pointer, the converted characters are stored into the array pointed to by dst. Conversion
- continues up to and including a terminating null character, which is also stored.
- Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
- not form a valid multibyte character, or (if dst is not a null pointer) when len wide
- characters have been stored into the array pointed to by dst.333) Each conversion takes
- place as if by a call to the mbrtowc function.
-3 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
- pointer (if conversion stopped due to reaching a terminating null character) or the address
- just past the last multibyte character converted (if any). If conversion stopped due to
- reaching a terminating null character and if dst is not a null pointer, the resulting state
- described is the initial conversion state.
- Returns
-4 If the input conversion encounters a sequence of bytes that do not form a valid multibyte
- character, an encoding error occurs: the mbsrtowcs function stores the value of the
- macro EILSEQ in errno and returns (size_t)(-1); the conversion state is
- unspecified. Otherwise, it returns the number of multibyte characters successfully
- converted, not including the terminating null character (if any).
-
-
-
-
- 333) Thus, the value of len is ignored if dst is a null pointer.
-
-[<a name="#p441" href="p441">page 441</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.28.6.4.2" href="#7.28.6.4.2"><b> 7.28.6.4.2 The wcsrtombs function</b></a>
- Synopsis
-1 #include <a href="#7.28"><wchar.h></a>
- size_t wcsrtombs(char * restrict dst,
- const wchar_t ** restrict src,
- size_t len,
- mbstate_t * restrict ps);
- Description
-2 The wcsrtombs function converts a sequence of wide characters from the array
- indirectly pointed to by src into a sequence of corresponding multibyte characters that
- begins in the conversion state described by the object pointed to by ps. If dst is not a
- null pointer, the converted characters are then stored into the array pointed to by dst.
- Conversion continues up to and including a terminating null wide character, which is also
- stored. Conversion stops earlier in two cases: when a wide character is reached that does
- not correspond to a valid multibyte character, or (if dst is not a null pointer) when the
- next multibyte character would exceed the limit of len total bytes to be stored into the
- array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb
- function.334)
-3 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
- pointer (if conversion stopped due to reaching a terminating null wide character) or the
- address just past the last wide character converted (if any). If conversion stopped due to
- reaching a terminating null wide character, the resulting state described is the initial
- conversion state.
- Returns
-4 If conversion stops because a wide character is reached that does not correspond to a
- valid multibyte character, an encoding error occurs: the wcsrtombs function stores the
- value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion
- state is unspecified. Otherwise, it returns the number of bytes in the resulting multibyte
- character sequence, not including the terminating null character (if any).
-
-
-
-
- 334) If conversion stops because a terminating null wide character has been reached, the bytes stored
- include those necessary to reach the initial shift state immediately before the null byte.
-
-[<a name="#p442" href="p442">page 442</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.29" href="#7.29"><b> 7.29 Wide character classification and mapping utilities <wctype.h></b></a>
-<a name="7.29.1" href="#7.29.1"><b> 7.29.1 Introduction</b></a>
-1 The header <a href="#7.29"><wctype.h></a> defines one macro, and declares three data types and many
- functions.335)
-2 The types declared are
- wint_t
- described in <a href="#7.28.1">7.28.1</a>;
- wctrans_t
- which is a scalar type that can hold values which represent locale-specific character
- mappings; and
- wctype_t
- which is a scalar type that can hold values which represent locale-specific character
- classifications.
-3 The macro defined is WEOF (described in <a href="#7.28.1">7.28.1</a>).
-4 The functions declared are grouped as follows:
- -- Functions that provide wide character classification;
- -- Extensible functions that provide wide character classification;
- -- Functions that provide wide character case mapping;
- -- Extensible functions that provide wide character mapping.
-5 For all functions described in this subclause that accept an argument of type wint_t, the
- value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If
- this argument has any other value, the behavior is undefined.
-6 The behavior of these functions is affected by the LC_CTYPE category of the current
- locale.
-
-
-
-
- 335) See ''future library directions'' (<a href="#7.30.13">7.30.13</a>).
-
-[<a name="#p443" href="p443">page 443</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.29.2" href="#7.29.2"><b> 7.29.2 Wide character classification utilities</b></a>
-1 The header <a href="#7.29"><wctype.h></a> declares several functions useful for classifying wide
- characters.
-2 The term printing wide character refers to a member of a locale-specific set of wide
- characters, each of which occupies at least one printing position on a display device. The
- term control wide character refers to a member of a locale-specific set of wide characters
- that are not printing wide characters.
-<a name="7.29.2.1" href="#7.29.2.1"><b> 7.29.2.1 Wide character classification functions</b></a>
-1 The functions in this subclause return nonzero (true) if and only if the value of the
- argument wc conforms to that in the description of the function.
-2 Each of the following functions returns true for each wide character that corresponds (as
- if by a call to the wctob function) to a single-byte character for which the corresponding
- character classification function from <a href="#7.4.1">7.4.1</a> returns true, except that the iswgraph and
- iswpunct functions may differ with respect to wide characters other than L' ' that are
- both printing and white-space wide characters.336)
- Forward references: the wctob function (<a href="#7.28.6.1.2">7.28.6.1.2</a>).
-<a name="7.29.2.1.1" href="#7.29.2.1.1"><b> 7.29.2.1.1 The iswalnum function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- int iswalnum(wint_t wc);
- Description
-2 The iswalnum function tests for any wide character for which iswalpha or
- iswdigit is true.
-<a name="7.29.2.1.2" href="#7.29.2.1.2"><b> 7.29.2.1.2 The iswalpha function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- int iswalpha(wint_t wc);
- Description
-2 The iswalpha function tests for any wide character for which iswupper or
- iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
-
- 336) For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call
- iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true
- (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc)
- && iswspace(wc) is true, but not both.
-
-[<a name="#p444" href="p444">page 444</a>] (<a href="#Contents">Contents</a>)
-
- wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
- is true.337)
-<a name="7.29.2.1.3" href="#7.29.2.1.3"><b> 7.29.2.1.3 The iswblank function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- int iswblank(wint_t wc);
- Description
-2 The iswblank function tests for any wide character that is a standard blank wide
- character or is one of a locale-specific set of wide characters for which iswspace is true
- and that is used to separate words within a line of text. The standard blank wide
- characters are the following: space (L' '), and horizontal tab (L'\t'). In the "C"
- locale, iswblank returns true only for the standard blank characters.
-<a name="7.29.2.1.4" href="#7.29.2.1.4"><b> 7.29.2.1.4 The iswcntrl function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- int iswcntrl(wint_t wc);
- Description
-2 The iswcntrl function tests for any control wide character.
-<a name="7.29.2.1.5" href="#7.29.2.1.5"><b> 7.29.2.1.5 The iswdigit function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- int iswdigit(wint_t wc);
- Description
-2 The iswdigit function tests for any wide character that corresponds to a decimal-digit
- character (as defined in <a href="#5.2.1">5.2.1</a>).
-<a name="7.29.2.1.6" href="#7.29.2.1.6"><b> 7.29.2.1.6 The iswgraph function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- int iswgraph(wint_t wc);
-
-
-
-
- 337) The functions iswlower and iswupper test true or false separately for each of these additional
- wide characters; all four combinations are possible.
-
-[<a name="#p445" href="p445">page 445</a>] (<a href="#Contents">Contents</a>)
-
- Description
-2 The iswgraph function tests for any wide character for which iswprint is true and
- iswspace is false.338)
-<a name="7.29.2.1.7" href="#7.29.2.1.7"><b> 7.29.2.1.7 The iswlower function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- int iswlower(wint_t wc);
- Description
-2 The iswlower function tests for any wide character that corresponds to a lowercase
- letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
- iswdigit, iswpunct, or iswspace is true.
-<a name="7.29.2.1.8" href="#7.29.2.1.8"><b> 7.29.2.1.8 The iswprint function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- int iswprint(wint_t wc);
- Description
-2 The iswprint function tests for any printing wide character.
-<a name="7.29.2.1.9" href="#7.29.2.1.9"><b> 7.29.2.1.9 The iswpunct function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- int iswpunct(wint_t wc);
- Description
-2 The iswpunct function tests for any printing wide character that is one of a locale-
- specific set of punctuation wide characters for which neither iswspace nor iswalnum
- is true.338)
-<a name="7.29.2.1.10" href="#7.29.2.1.10"><b> 7.29.2.1.10 The iswspace function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- int iswspace(wint_t wc);
-
-
-
- 338) Note that the behavior of the iswgraph and iswpunct functions may differ from their
- corresponding functions in <a href="#7.4.1">7.4.1</a> with respect to printing, white-space, single-byte execution
- characters other than ' '.
-
-[<a name="#p446" href="p446">page 446</a>] (<a href="#Contents">Contents</a>)
-
- Description
-2 The iswspace function tests for any wide character that corresponds to a locale-specific
- set of white-space wide characters for which none of iswalnum, iswgraph, or
- iswpunct is true.
-<a name="7.29.2.1.11" href="#7.29.2.1.11"><b> 7.29.2.1.11 The iswupper function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- int iswupper(wint_t wc);
- Description
-2 The iswupper function tests for any wide character that corresponds to an uppercase
- letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
- iswdigit, iswpunct, or iswspace is true.
-<a name="7.29.2.1.12" href="#7.29.2.1.12"><b> 7.29.2.1.12 The iswxdigit function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- int iswxdigit(wint_t wc);
- Description
-2 The iswxdigit function tests for any wide character that corresponds to a
- hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
-<a name="7.29.2.2" href="#7.29.2.2"><b> 7.29.2.2 Extensible wide character classification functions</b></a>
-1 The functions wctype and iswctype provide extensible wide character classification
- as well as testing equivalent to that performed by the functions described in the previous
- subclause (<a href="#7.29.2.1">7.29.2.1</a>).
-<a name="7.29.2.2.1" href="#7.29.2.2.1"><b> 7.29.2.2.1 The iswctype function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- int iswctype(wint_t wc, wctype_t desc);
- Description
-2 The iswctype function determines whether the wide character wc has the property
- described by desc. The current setting of the LC_CTYPE category shall be the same as
- during the call to wctype that returned the value desc.
-3 Each of the following expressions has a truth-value equivalent to the call to the wide
- character classification function (<a href="#7.29.2.1">7.29.2.1</a>) in the comment that follows the expression:
-
-
-[<a name="#p447" href="p447">page 447</a>] (<a href="#Contents">Contents</a>)
-
- iswctype(wc, wctype("alnum")) // iswalnum(wc)
- iswctype(wc, wctype("alpha")) // iswalpha(wc)
- iswctype(wc, wctype("blank")) // iswblank(wc)
- iswctype(wc, wctype("cntrl")) // iswcntrl(wc)
- iswctype(wc, wctype("digit")) // iswdigit(wc)
- iswctype(wc, wctype("graph")) // iswgraph(wc)
- iswctype(wc, wctype("lower")) // iswlower(wc)
- iswctype(wc, wctype("print")) // iswprint(wc)
- iswctype(wc, wctype("punct")) // iswpunct(wc)
- iswctype(wc, wctype("space")) // iswspace(wc)
- iswctype(wc, wctype("upper")) // iswupper(wc)
- iswctype(wc, wctype("xdigit")) // iswxdigit(wc)
- Returns
-4 The iswctype function returns nonzero (true) if and only if the value of the wide
- character wc has the property described by desc.
- Forward references: the wctype function (<a href="#7.29.2.2.2">7.29.2.2.2</a>).
-<a name="7.29.2.2.2" href="#7.29.2.2.2"><b> 7.29.2.2.2 The wctype function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- wctype_t wctype(const char *property);
- Description
-2 The wctype function constructs a value with type wctype_t that describes a class of
- wide characters identified by the string argument property.
-3 The strings listed in the description of the iswctype function shall be valid in all
- locales as property arguments to the wctype function.
- Returns
-4 If property identifies a valid class of wide characters according to the LC_CTYPE
- category of the current locale, the wctype function returns a nonzero value that is valid
- as the second argument to the iswctype function; otherwise, it returns zero.
-
-
-
-
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-
-<a name="7.29.3" href="#7.29.3"><b> 7.29.3 Wide character case mapping utilities</b></a>
-1 The header <a href="#7.29"><wctype.h></a> declares several functions useful for mapping wide characters.
-<a name="7.29.3.1" href="#7.29.3.1"><b> 7.29.3.1 Wide character case mapping functions</b></a>
-<a name="7.29.3.1.1" href="#7.29.3.1.1"><b> 7.29.3.1.1 The towlower function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- wint_t towlower(wint_t wc);
- Description
-2 The towlower function converts an uppercase letter to a corresponding lowercase letter.
- Returns
-3 If the argument is a wide character for which iswupper is true and there are one or
- more corresponding wide characters, as specified by the current locale, for which
- iswlower is true, the towlower function returns one of the corresponding wide
- characters (always the same one for any given locale); otherwise, the argument is
- returned unchanged.
-<a name="7.29.3.1.2" href="#7.29.3.1.2"><b> 7.29.3.1.2 The towupper function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- wint_t towupper(wint_t wc);
- Description
-2 The towupper function converts a lowercase letter to a corresponding uppercase letter.
- Returns
-3 If the argument is a wide character for which iswlower is true and there are one or
- more corresponding wide characters, as specified by the current locale, for which
- iswupper is true, the towupper function returns one of the corresponding wide
- characters (always the same one for any given locale); otherwise, the argument is
- returned unchanged.
-<a name="7.29.3.2" href="#7.29.3.2"><b> 7.29.3.2 Extensible wide character case mapping functions</b></a>
-1 The functions wctrans and towctrans provide extensible wide character mapping as
- well as case mapping equivalent to that performed by the functions described in the
- previous subclause (<a href="#7.29.3.1">7.29.3.1</a>).
-
-
-
-
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-
-<a name="7.29.3.2.1" href="#7.29.3.2.1"><b> 7.29.3.2.1 The towctrans function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- wint_t towctrans(wint_t wc, wctrans_t desc);
- Description
-2 The towctrans function maps the wide character wc using the mapping described by
- desc. The current setting of the LC_CTYPE category shall be the same as during the call
- to wctrans that returned the value desc.
-3 Each of the following expressions behaves the same as the call to the wide character case
- mapping function (<a href="#7.29.3.1">7.29.3.1</a>) in the comment that follows the expression:
- towctrans(wc, wctrans("tolower")) // towlower(wc)
- towctrans(wc, wctrans("toupper")) // towupper(wc)
- Returns
-4 The towctrans function returns the mapped value of wc using the mapping described
- by desc.
-<a name="7.29.3.2.2" href="#7.29.3.2.2"><b> 7.29.3.2.2 The wctrans function</b></a>
- Synopsis
-1 #include <a href="#7.29"><wctype.h></a>
- wctrans_t wctrans(const char *property);
- Description
-2 The wctrans function constructs a value with type wctrans_t that describes a
- mapping between wide characters identified by the string argument property.
-3 The strings listed in the description of the towctrans function shall be valid in all
- locales as property arguments to the wctrans function.
- Returns
-4 If property identifies a valid mapping of wide characters according to the LC_CTYPE
- category of the current locale, the wctrans function returns a nonzero value that is valid
- as the second argument to the towctrans function; otherwise, it returns zero.
-
-
-
-
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-
-<a name="7.30" href="#7.30"><b> 7.30 Future library directions</b></a>
-1 The following names are grouped under individual headers for convenience. All external
- names described below are reserved no matter what headers are included by the program.
-<a name="7.30.1" href="#7.30.1"><b> 7.30.1 Complex arithmetic <complex.h></b></a>
-1 The function names
- cerf cexpm1 clog2
- cerfc clog10 clgamma
- cexp2 clog1p ctgamma
- and the same names suffixed with f or l may be added to the declarations in the
- <a href="#7.3"><complex.h></a> header.
-<a name="7.30.2" href="#7.30.2"><b> 7.30.2 Character handling <ctype.h></b></a>
-1 Function names that begin with either is or to, and a lowercase letter may be added to
- the declarations in the <a href="#7.4"><ctype.h></a> header.
-<a name="7.30.3" href="#7.30.3"><b> 7.30.3 Errors <errno.h></b></a>
-1 Macros that begin with E and a digit or E and an uppercase letter may be added to the
- declarations in the <a href="#7.5"><errno.h></a> header.
-<a name="7.30.4" href="#7.30.4"><b> 7.30.4 Format conversion of integer types <inttypes.h></b></a>
-1 Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
- added to the macros defined in the <a href="#7.8"><inttypes.h></a> header.
-<a name="7.30.5" href="#7.30.5"><b> 7.30.5 Localization <locale.h></b></a>
-1 Macros that begin with LC_ and an uppercase letter may be added to the definitions in
- the <a href="#7.11"><locale.h></a> header.
-<a name="7.30.6" href="#7.30.6"><b> 7.30.6 Signal handling <signal.h></b></a>
-1 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
- letter may be added to the definitions in the <a href="#7.14"><signal.h></a> header.
-<a name="7.30.7" href="#7.30.7"><b> 7.30.7 Boolean type and values <stdbool.h></b></a>
-1 The ability to undefine and perhaps then redefine the macros bool, true, and false is
- an obsolescent feature.
-<a name="7.30.8" href="#7.30.8"><b> 7.30.8 Integer types <stdint.h></b></a>
-1 Typedef names beginning with int or uint and ending with _t may be added to the
- types defined in the <a href="#7.20"><stdint.h></a> header. Macro names beginning with INT or UINT
- and ending with _MAX, _MIN, or _C may be added to the macros defined in the
- <a href="#7.20"><stdint.h></a> header.
-
-[<a name="#p451" href="p451">page 451</a>] (<a href="#Contents">Contents</a>)
-
-<a name="7.30.9" href="#7.30.9"><b> 7.30.9 Input/output <stdio.h></b></a>
-1 Lowercase letters may be added to the conversion specifiers and length modifiers in
- fprintf and fscanf. Other characters may be used in extensions.
-2 The use of ungetc on a binary stream where the file position indicator is zero prior to
- the call is an obsolescent feature.
-<a name="7.30.10" href="#7.30.10"><b> 7.30.10 General utilities <stdlib.h></b></a>
-1 Function names that begin with str and a lowercase letter may be added to the
- declarations in the <a href="#7.22"><stdlib.h></a> header.
-<a name="7.30.11" href="#7.30.11"><b> 7.30.11 String handling <string.h></b></a>
-1 Function names that begin with str, mem, or wcs and a lowercase letter may be added
- to the declarations in the <a href="#7.23"><string.h></a> header.
-<a name="7.30.12" href="#7.30.12"><b> 7.30.12 Extended multibyte and wide character utilities <wchar.h></b></a>
-1 Function names that begin with wcs and a lowercase letter may be added to the
- declarations in the <a href="#7.28"><wchar.h></a> header.
-2 Lowercase letters may be added to the conversion specifiers and length modifiers in
- fwprintf and fwscanf. Other characters may be used in extensions.
-<a name="7.30.13" href="#7.30.13"><b> 7.30.13 Wide character classification and mapping utilities</b></a>
- <a href="#7.29"><wctype.h></a>
-1 Function names that begin with is or to and a lowercase letter may be added to the
- declarations in the <a href="#7.29"><wctype.h></a> header.
-
-
-
-
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-
-<a name="A" href="#A"><b> Annex A</b></a>
- (informative)
- Language syntax summary
-1 NOTE The notation is described in <a href="#6.1">6.1</a>.
-
-<a name="A.1" href="#A.1"><b> A.1 Lexical grammar</b></a>
-<a name="A.1.1" href="#A.1.1"><b> A.1.1 Lexical elements</b></a>
- (<a href="#6.4">6.4</a>) token:
- keyword
- identifier
- constant
- string-literal
- punctuator
- (<a href="#6.4">6.4</a>) preprocessing-token:
- header-name
- identifier
- pp-number
- character-constant
- string-literal
- punctuator
- each non-white-space character that cannot be one of the above
-
-
-
-
-[<a name="#p453" href="p453">page 453</a>] (<a href="#Contents">Contents</a>)
-
-<a name="A.1.2" href="#A.1.2"><b>A.1.2 Keywords</b></a>
-(<a href="#6.4.1">6.4.1</a>) keyword: one of
- alignof goto union
- auto if unsigned
- break inline void
- case int volatile
- char long while
- const register _Alignas
- continue restrict _Atomic
- default return _Bool
- do short _Complex
- double signed _Generic
- else sizeof _Imaginary
- enum static _Noreturn
- extern struct _Static_assert
- float switch _Thread_local
- for typedef
-<a name="A.1.3" href="#A.1.3"><b>A.1.3 Identifiers</b></a>
-(<a href="#6.4.2.1">6.4.2.1</a>) identifier:
- identifier-nondigit
- identifier identifier-nondigit
- identifier digit
-(<a href="#6.4.2.1">6.4.2.1</a>) identifier-nondigit:
- nondigit
- universal-character-name
- other implementation-defined characters
-(<a href="#6.4.2.1">6.4.2.1</a>) nondigit: one of
- _ a b c d e f g h i j k l m
- n o p q r s t u v w x y z
- A B C D E F G H I J K L M
- N O P Q R S T U V W X Y Z
-(<a href="#6.4.2.1">6.4.2.1</a>) digit: one of
- 0 1 2 3 4 5 6 7 8 9
-
-
-
-
-[<a name="#p454" href="p454">page 454</a>] (<a href="#Contents">Contents</a>)
-
-<a name="A.1.4" href="#A.1.4"><b>A.1.4 Universal character names</b></a>
-(<a href="#6.4.3">6.4.3</a>) universal-character-name:
- \u hex-quad
- \U hex-quad hex-quad
-(<a href="#6.4.3">6.4.3</a>) hex-quad:
- hexadecimal-digit hexadecimal-digit
- hexadecimal-digit hexadecimal-digit
-<a name="A.1.5" href="#A.1.5"><b>A.1.5 Constants</b></a>
-(<a href="#6.4.4">6.4.4</a>) constant:
- integer-constant
- floating-constant
- enumeration-constant
- character-constant
-(<a href="#6.4.4.1">6.4.4.1</a>) integer-constant:
- decimal-constant integer-suffixopt
- octal-constant integer-suffixopt
- hexadecimal-constant integer-suffixopt
-(<a href="#6.4.4.1">6.4.4.1</a>) decimal-constant:
- nonzero-digit
- decimal-constant digit
-(<a href="#6.4.4.1">6.4.4.1</a>) octal-constant:
- 0
- octal-constant octal-digit
-(<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-constant:
- hexadecimal-prefix hexadecimal-digit
- hexadecimal-constant hexadecimal-digit
-(<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-prefix: one of
- 0x 0X
-(<a href="#6.4.4.1">6.4.4.1</a>) nonzero-digit: one of
- 1 2 3 4 5 6 7 8 9
-(<a href="#6.4.4.1">6.4.4.1</a>) octal-digit: one of
- 0 1 2 3 4 5 6 7
-
-
-
-
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-
-(<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-digit: one of
- 0 1 2 3 4 5 6 7 8 9
- a b c d e f
- A B C D E F
-(<a href="#6.4.4.1">6.4.4.1</a>) integer-suffix:
- unsigned-suffix long-suffixopt
- unsigned-suffix long-long-suffix
- long-suffix unsigned-suffixopt
- long-long-suffix unsigned-suffixopt
-(<a href="#6.4.4.1">6.4.4.1</a>) unsigned-suffix: one of
- u U
-(<a href="#6.4.4.1">6.4.4.1</a>) long-suffix: one of
- l L
-(<a href="#6.4.4.1">6.4.4.1</a>) long-long-suffix: one of
- ll LL
-(<a href="#6.4.4.2">6.4.4.2</a>) floating-constant:
- decimal-floating-constant
- hexadecimal-floating-constant
-(<a href="#6.4.4.2">6.4.4.2</a>) decimal-floating-constant:
- fractional-constant exponent-partopt floating-suffixopt
- digit-sequence exponent-part floating-suffixopt
-(<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-floating-constant:
- hexadecimal-prefix hexadecimal-fractional-constant
- binary-exponent-part floating-suffixopt
- hexadecimal-prefix hexadecimal-digit-sequence
- binary-exponent-part floating-suffixopt
-(<a href="#6.4.4.2">6.4.4.2</a>) fractional-constant:
- digit-sequenceopt . digit-sequence
- digit-sequence .
-(<a href="#6.4.4.2">6.4.4.2</a>) exponent-part:
- e signopt digit-sequence
- E signopt digit-sequence
-(<a href="#6.4.4.2">6.4.4.2</a>) sign: one of
- + -
-
-
-
-[<a name="#p456" href="p456">page 456</a>] (<a href="#Contents">Contents</a>)
-
-(<a href="#6.4.4.2">6.4.4.2</a>) digit-sequence:
- digit
- digit-sequence digit
-(<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-fractional-constant:
- hexadecimal-digit-sequenceopt .
- hexadecimal-digit-sequence
- hexadecimal-digit-sequence .
-(<a href="#6.4.4.2">6.4.4.2</a>) binary-exponent-part:
- p signopt digit-sequence
- P signopt digit-sequence
-(<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-digit-sequence:
- hexadecimal-digit
- hexadecimal-digit-sequence hexadecimal-digit
-(<a href="#6.4.4.2">6.4.4.2</a>) floating-suffix: one of
- f l F L
-(<a href="#6.4.4.3">6.4.4.3</a>) enumeration-constant:
- identifier
-(<a href="#6.4.4.4">6.4.4.4</a>) character-constant:
- ' c-char-sequence '
- L' c-char-sequence '
- u' c-char-sequence '
- U' c-char-sequence '
-(<a href="#6.4.4.4">6.4.4.4</a>) c-char-sequence:
- c-char
- c-char-sequence c-char
-(<a href="#6.4.4.4">6.4.4.4</a>) c-char:
- any member of the source character set except
- the single-quote ', backslash \, or new-line character
- escape-sequence
-(<a href="#6.4.4.4">6.4.4.4</a>) escape-sequence:
- simple-escape-sequence
- octal-escape-sequence
- hexadecimal-escape-sequence
- universal-character-name
-
-
-
-
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-
-(<a href="#6.4.4.4">6.4.4.4</a>) simple-escape-sequence: one of
- \' \" \? \\
- \a \b \f \n \r \t \v
-(<a href="#6.4.4.4">6.4.4.4</a>) octal-escape-sequence:
- \ octal-digit
- \ octal-digit octal-digit
- \ octal-digit octal-digit octal-digit
-(<a href="#6.4.4.4">6.4.4.4</a>) hexadecimal-escape-sequence:
- \x hexadecimal-digit
- hexadecimal-escape-sequence hexadecimal-digit
-<a name="A.1.6" href="#A.1.6"><b>A.1.6 String literals</b></a>
-(<a href="#6.4.5">6.4.5</a>) string-literal:
- encoding-prefixopt " s-char-sequenceopt "
-(<a href="#6.4.5">6.4.5</a>) encoding-prefix:
- u8
- u
- U
- L
-(<a href="#6.4.5">6.4.5</a>) s-char-sequence:
- s-char
- s-char-sequence s-char
-(<a href="#6.4.5">6.4.5</a>) s-char:
- any member of the source character set except
- the double-quote ", backslash \, or new-line character
- escape-sequence
-<a name="A.1.7" href="#A.1.7"><b>A.1.7 Punctuators</b></a>
-(<a href="#6.4.6">6.4.6</a>) punctuator: one of
- [ ] ( ) { } . ->
- ++ -- & * + - ~ !
- / % << >> < > <= >= == != ^ | && ||
- ? : ; ...
- = *= /= %= += -= <<= >>= &= ^= |=
- , # ##
- <: :> <% %> %: %:%:
-
-
-
-
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-
-<a name="A.1.8" href="#A.1.8"><b>A.1.8 Header names</b></a>
-(<a href="#6.4.7">6.4.7</a>) header-name:
- < h-char-sequence >
- " q-char-sequence "
-(<a href="#6.4.7">6.4.7</a>) h-char-sequence:
- h-char
- h-char-sequence h-char
-(<a href="#6.4.7">6.4.7</a>) h-char:
- any member of the source character set except
- the new-line character and >
-(<a href="#6.4.7">6.4.7</a>) q-char-sequence:
- q-char
- q-char-sequence q-char
-(<a href="#6.4.7">6.4.7</a>) q-char:
- any member of the source character set except
- the new-line character and "
-<a name="A.1.9" href="#A.1.9"><b>A.1.9 Preprocessing numbers</b></a>
-(<a href="#6.4.8">6.4.8</a>) pp-number:
- digit
- . digit
- pp-number digit
- pp-number identifier-nondigit
- pp-number e sign
- pp-number E sign
- pp-number p sign
- pp-number P sign
- pp-number .
-
-
-
-
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-
-<a name="A.2" href="#A.2"><b>A.2 Phrase structure grammar</b></a>
-<a name="A.2.1" href="#A.2.1"><b>A.2.1 Expressions</b></a>
-(<a href="#6.5.1">6.5.1</a>) primary-expression:
- identifier
- constant
- string-literal
- ( expression )
- generic-selection
-(<a href="#6.5.1.1">6.5.1.1</a>) generic-selection:
- _Generic ( assignment-expression , generic-assoc-list )
-(<a href="#6.5.1.1">6.5.1.1</a>) generic-assoc-list:
- generic-association
- generic-assoc-list , generic-association
-(<a href="#6.5.1.1">6.5.1.1</a>) generic-association:
- type-name : assignment-expression
- default : assignment-expression
-(<a href="#6.5.2">6.5.2</a>) postfix-expression:
- primary-expression
- postfix-expression [ expression ]
- postfix-expression ( argument-expression-listopt )
- postfix-expression . identifier
- postfix-expression -> identifier
- postfix-expression ++
- postfix-expression --
- ( type-name ) { initializer-list }
- ( type-name ) { initializer-list , }
-(<a href="#6.5.2">6.5.2</a>) argument-expression-list:
- assignment-expression
- argument-expression-list , assignment-expression
-(<a href="#6.5.3">6.5.3</a>) unary-expression:
- postfix-expression
- ++ unary-expression
- -- unary-expression
- unary-operator cast-expression
- sizeof unary-expression
- sizeof ( type-name )
- alignof ( type-name )
-
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-
-(<a href="#6.5.3">6.5.3</a>) unary-operator: one of
- & * + - ~ !
-(<a href="#6.5.4">6.5.4</a>) cast-expression:
- unary-expression
- ( type-name ) cast-expression
-(<a href="#6.5.5">6.5.5</a>) multiplicative-expression:
- cast-expression
- multiplicative-expression * cast-expression
- multiplicative-expression / cast-expression
- multiplicative-expression % cast-expression
-(<a href="#6.5.6">6.5.6</a>) additive-expression:
- multiplicative-expression
- additive-expression + multiplicative-expression
- additive-expression - multiplicative-expression
-(<a href="#6.5.7">6.5.7</a>) shift-expression:
- additive-expression
- shift-expression << additive-expression
- shift-expression >> additive-expression
-(<a href="#6.5.8">6.5.8</a>) relational-expression:
- shift-expression
- relational-expression < shift-expression
- relational-expression > shift-expression
- relational-expression <= shift-expression
- relational-expression >= shift-expression
-(<a href="#6.5.9">6.5.9</a>) equality-expression:
- relational-expression
- equality-expression == relational-expression
- equality-expression != relational-expression
-(<a href="#6.5.10">6.5.10</a>) AND-expression:
- equality-expression
- AND-expression & equality-expression
-(<a href="#6.5.11">6.5.11</a>) exclusive-OR-expression:
- AND-expression
- exclusive-OR-expression ^ AND-expression
-
-
-
-
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-
-(<a href="#6.5.12">6.5.12</a>) inclusive-OR-expression:
- exclusive-OR-expression
- inclusive-OR-expression | exclusive-OR-expression
-(<a href="#6.5.13">6.5.13</a>) logical-AND-expression:
- inclusive-OR-expression
- logical-AND-expression && inclusive-OR-expression
-(<a href="#6.5.14">6.5.14</a>) logical-OR-expression:
- logical-AND-expression
- logical-OR-expression || logical-AND-expression
-(<a href="#6.5.15">6.5.15</a>) conditional-expression:
- logical-OR-expression
- logical-OR-expression ? expression : conditional-expression
-(<a href="#6.5.16">6.5.16</a>) assignment-expression:
- conditional-expression
- unary-expression assignment-operator assignment-expression
-(<a href="#6.5.16">6.5.16</a>) assignment-operator: one of
- = *= /= %= += -= <<= >>= &= ^= |=
-(<a href="#6.5.17">6.5.17</a>) expression:
- assignment-expression
- expression , assignment-expression
-(<a href="#6.6">6.6</a>) constant-expression:
- conditional-expression
-<a name="A.2.2" href="#A.2.2"><b>A.2.2 Declarations</b></a>
-(<a href="#6.7">6.7</a>) declaration:
- declaration-specifiers init-declarator-listopt ;
- static_assert-declaration *
-(<a href="#6.7">6.7</a>) declaration-specifiers:
- storage-class-specifier declaration-specifiersopt
- type-specifier declaration-specifiersopt
- type-qualifier declaration-specifiersopt
- function-specifier declaration-specifiersopt
- alignment-specifier declaration-specifiersopt
-(<a href="#6.7">6.7</a>) init-declarator-list:
- init-declarator
- init-declarator-list , init-declarator
-
-
-[<a name="#p462" href="p462">page 462</a>] (<a href="#Contents">Contents</a>)
-
-(<a href="#6.7">6.7</a>) init-declarator:
- declarator
- declarator = initializer
-(<a href="#6.7.1">6.7.1</a>) storage-class-specifier:
- typedef
- extern
- static
- _Thread_local
- auto
- register
-(<a href="#6.7.2">6.7.2</a>) type-specifier:
- void
- char
- short
- int
- long
- float
- double
- signed
- unsigned
- _Bool
- _Complex
- _Atomic ( type-name )
- struct-or-union-specifier
- enum-specifier
- typedef-name
-(<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union-specifier:
- struct-or-union identifieropt { struct-declaration-list }
- struct-or-union identifier
-(<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union:
- struct
- union
-(<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration-list:
- struct-declaration
- struct-declaration-list struct-declaration
-(<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration:
- specifier-qualifier-list struct-declarator-listopt ;
- static_assert-declaration
-
-[<a name="#p463" href="p463">page 463</a>] (<a href="#Contents">Contents</a>)
-
-(<a href="#6.7.2.1">6.7.2.1</a>) specifier-qualifier-list:
- type-specifier specifier-qualifier-listopt
- type-qualifier specifier-qualifier-listopt
-(<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator-list:
- struct-declarator
- struct-declarator-list , struct-declarator
-(<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator:
- declarator
- declaratoropt : constant-expression
-(<a href="#6.7.2.2">6.7.2.2</a>) enum-specifier:
- enum identifieropt { enumerator-list }
- enum identifieropt { enumerator-list , }
- enum identifier
-(<a href="#6.7.2.2">6.7.2.2</a>) enumerator-list:
- enumerator
- enumerator-list , enumerator
-(<a href="#6.7.2.2">6.7.2.2</a>) enumerator:
- enumeration-constant
- enumeration-constant = constant-expression
-(<a href="#6.7.3">6.7.3</a>) type-qualifier:
- const
- restrict
- volatile
- _Atomic
-(<a href="#6.7.4">6.7.4</a>) function-specifier:
- inline
- _Noreturn
-(<a href="#6.7.5">6.7.5</a>) alignment-specifier:
- _Alignas ( type-name )
- _Alignas ( constant-expression )
-(<a href="#6.7.6">6.7.6</a>) declarator:
- pointeropt direct-declarator
-
-
-
-
-[<a name="#p464" href="p464">page 464</a>] (<a href="#Contents">Contents</a>)
-
-(<a href="#6.7.6">6.7.6</a>) direct-declarator:
- identifier
- ( declarator )
- direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
- direct-declarator [ static type-qualifier-listopt assignment-expression ]
- direct-declarator [ type-qualifier-list static assignment-expression ]
- direct-declarator [ type-qualifier-listopt * ]
- direct-declarator ( parameter-type-list )
- direct-declarator ( identifier-listopt )
-(<a href="#6.7.6">6.7.6</a>) pointer:
- * type-qualifier-listopt
- * type-qualifier-listopt pointer
-(<a href="#6.7.6">6.7.6</a>) type-qualifier-list:
- type-qualifier
- type-qualifier-list type-qualifier
-(<a href="#6.7.6">6.7.6</a>) parameter-type-list:
- parameter-list
- parameter-list , ...
-(<a href="#6.7.6">6.7.6</a>) parameter-list:
- parameter-declaration
- parameter-list , parameter-declaration
-(<a href="#6.7.6">6.7.6</a>) parameter-declaration:
- declaration-specifiers declarator
- declaration-specifiers abstract-declaratoropt
-(<a href="#6.7.6">6.7.6</a>) identifier-list:
- identifier
- identifier-list , identifier
-(<a href="#6.7.7">6.7.7</a>) type-name:
- specifier-qualifier-list abstract-declaratoropt
-(<a href="#6.7.7">6.7.7</a>) abstract-declarator:
- pointer
- pointeropt direct-abstract-declarator
-
-
-
-
-[<a name="#p465" href="p465">page 465</a>] (<a href="#Contents">Contents</a>)
-
-(<a href="#6.7.7">6.7.7</a>) direct-abstract-declarator:
- ( abstract-declarator )
- direct-abstract-declaratoropt [ type-qualifier-listopt
- assignment-expressionopt ]
- direct-abstract-declaratoropt [ static type-qualifier-listopt
- assignment-expression ]
- direct-abstract-declaratoropt [ type-qualifier-list static
- assignment-expression ]
- direct-abstract-declaratoropt [ * ]
- direct-abstract-declaratoropt ( parameter-type-listopt )
-(<a href="#6.7.8">6.7.8</a>) typedef-name:
- identifier
-(<a href="#6.7.9">6.7.9</a>) initializer:
- assignment-expression
- { initializer-list }
- { initializer-list , }
-(<a href="#6.7.9">6.7.9</a>) initializer-list:
- designationopt initializer
- initializer-list , designationopt initializer
-(<a href="#6.7.9">6.7.9</a>) designation:
- designator-list =
-(<a href="#6.7.9">6.7.9</a>) designator-list:
- designator
- designator-list designator
-(<a href="#6.7.9">6.7.9</a>) designator:
- [ constant-expression ]
- . identifier
-(<a href="#6.7.10">6.7.10</a>) static_assert-declaration:
- _Static_assert ( constant-expression , string-literal ) ;
-
-
-
-
-[<a name="#p466" href="p466">page 466</a>] (<a href="#Contents">Contents</a>)
-
-<a name="A.2.3" href="#A.2.3"><b>A.2.3 Statements</b></a>
-(<a href="#6.8">6.8</a>) statement:
- labeled-statement
- compound-statement
- expression-statement
- selection-statement
- iteration-statement
- jump-statement
-(<a href="#6.8.1">6.8.1</a>) labeled-statement:
- identifier : statement
- case constant-expression : statement
- default : statement
-(<a href="#6.8.2">6.8.2</a>) compound-statement:
- { block-item-listopt }
-(<a href="#6.8.2">6.8.2</a>) block-item-list:
- block-item
- block-item-list block-item
-(<a href="#6.8.2">6.8.2</a>) block-item:
- declaration
- statement
-(<a href="#6.8.3">6.8.3</a>) expression-statement:
- expressionopt ;
-(<a href="#6.8.4">6.8.4</a>) selection-statement:
- if ( expression ) statement
- if ( expression ) statement else statement
- switch ( expression ) statement
-(<a href="#6.8.5">6.8.5</a>) iteration-statement:
- while ( expression ) statement
- do statement while ( expression ) ;
- for ( expressionopt ; expressionopt ; expressionopt ) statement
- for ( declaration expressionopt ; expressionopt ) statement
-(<a href="#6.8.6">6.8.6</a>) jump-statement:
- goto identifier ;
- continue ;
- break ;
- return expressionopt ;
-
-[<a name="#p467" href="p467">page 467</a>] (<a href="#Contents">Contents</a>)
-
-<a name="A.2.4" href="#A.2.4"><b>A.2.4 External definitions</b></a>
-(<a href="#6.9">6.9</a>) translation-unit:
- external-declaration
- translation-unit external-declaration
-(<a href="#6.9">6.9</a>) external-declaration:
- function-definition
- declaration
-(<a href="#6.9.1">6.9.1</a>) function-definition:
- declaration-specifiers declarator declaration-listopt compound-statement
-(<a href="#6.9.1">6.9.1</a>) declaration-list:
- declaration
- declaration-list declaration
-<a name="A.3" href="#A.3"><b>A.3 Preprocessing directives</b></a>
-(<a href="#6.10">6.10</a>) preprocessing-file:
- groupopt
-(<a href="#6.10">6.10</a>) group:
- group-part
- group group-part
-(<a href="#6.10">6.10</a>) group-part:
- if-section
- control-line
- text-line
- # non-directive
-(<a href="#6.10">6.10</a>) if-section:
- if-group elif-groupsopt else-groupopt endif-line
-(<a href="#6.10">6.10</a>) if-group:
- # if constant-expression new-line groupopt
- # ifdef identifier new-line groupopt
- # ifndef identifier new-line groupopt
-(<a href="#6.10">6.10</a>) elif-groups:
- elif-group
- elif-groups elif-group
-(<a href="#6.10">6.10</a>) elif-group:
- # elif constant-expression new-line groupopt
-
-
-[<a name="#p468" href="p468">page 468</a>] (<a href="#Contents">Contents</a>)
-
-(<a href="#6.10">6.10</a>) else-group:
- # else new-line groupopt
-(<a href="#6.10">6.10</a>) endif-line:
- # endif new-line
-(<a href="#6.10">6.10</a>) control-line:
- # include pp-tokens new-line
- # define identifier replacement-list new-line
- # define identifier lparen identifier-listopt )
- replacement-list new-line
- # define identifier lparen ... ) replacement-list new-line
- # define identifier lparen identifier-list , ... )
- replacement-list new-line
- # undef identifier new-line
- # line pp-tokens new-line
- # error pp-tokensopt new-line
- # pragma pp-tokensopt new-line
- # new-line
-(<a href="#6.10">6.10</a>) text-line:
- pp-tokensopt new-line
-(<a href="#6.10">6.10</a>) non-directive:
- pp-tokens new-line
-(<a href="#6.10">6.10</a>) lparen:
- a ( character not immediately preceded by white-space
-(<a href="#6.10">6.10</a>) replacement-list:
- pp-tokensopt
-(<a href="#6.10">6.10</a>) pp-tokens:
- preprocessing-token
- pp-tokens preprocessing-token
-(<a href="#6.10">6.10</a>) new-line:
- the new-line character
-
-
-
-
-[<a name="#p469" href="p469">page 469</a>] (<a href="#Contents">Contents</a>)
-
-<a name="B" href="#B"><b> Annex B</b></a>
- (informative)
- Library summary
-<a name="B.1" href="#B.1"><b>B.1 Diagnostics <assert.h></b></a>
- NDEBUG
- static_assert
- void assert(scalar expression);
-<a name="B.2" href="#B.2"><b>B.2 Complex <complex.h></b></a>
- __STDC_NO_COMPLEX__ imaginary
- complex _Imaginary_I
- _Complex_I I
- #pragma STDC CX_LIMITED_RANGE on-off-switch
- double complex cacos(double complex z);
- float complex cacosf(float complex z);
- long double complex cacosl(long double complex z);
- double complex casin(double complex z);
- float complex casinf(float complex z);
- long double complex casinl(long double complex z);
- double complex catan(double complex z);
- float complex catanf(float complex z);
- long double complex catanl(long double complex z);
- double complex ccos(double complex z);
- float complex ccosf(float complex z);
- long double complex ccosl(long double complex z);
- double complex csin(double complex z);
- float complex csinf(float complex z);
- long double complex csinl(long double complex z);
- double complex ctan(double complex z);
- float complex ctanf(float complex z);
- long double complex ctanl(long double complex z);
- double complex cacosh(double complex z);
- float complex cacoshf(float complex z);
- long double complex cacoshl(long double complex z);
- double complex casinh(double complex z);
- float complex casinhf(float complex z);
- long double complex casinhl(long double complex z);
-
-[<a name="#p470" href="p470">page 470</a>] (<a href="#Contents">Contents</a>)
-
- double complex catanh(double complex z);
- float complex catanhf(float complex z);
- long double complex catanhl(long double complex z);
- double complex ccosh(double complex z);
- float complex ccoshf(float complex z);
- long double complex ccoshl(long double complex z);
- double complex csinh(double complex z);
- float complex csinhf(float complex z);
- long double complex csinhl(long double complex z);
- double complex ctanh(double complex z);
- float complex ctanhf(float complex z);
- long double complex ctanhl(long double complex z);
- double complex cexp(double complex z);
- float complex cexpf(float complex z);
- long double complex cexpl(long double complex z);
- double complex clog(double complex z);
- float complex clogf(float complex z);
- long double complex clogl(long double complex z);
- double cabs(double complex z);
- float cabsf(float complex z);
- long double cabsl(long double complex z);
- double complex cpow(double complex x, double complex y);
- float complex cpowf(float complex x, float complex y);
- long double complex cpowl(long double complex x,
- long double complex y);
- double complex csqrt(double complex z);
- float complex csqrtf(float complex z);
- long double complex csqrtl(long double complex z);
- double carg(double complex z);
- float cargf(float complex z);
- long double cargl(long double complex z);
- double cimag(double complex z);
- float cimagf(float complex z);
- long double cimagl(long double complex z);
- double complex CMPLX(double x, double y);
- float complex CMPLXF(float x, float y);
- long double complex CMPLXL(long double x, long double y);
- double complex conj(double complex z);
- float complex conjf(float complex z);
- long double complex conjl(long double complex z);
- double complex cproj(double complex z);
-
-[<a name="#p471" href="p471">page 471</a>] (<a href="#Contents">Contents</a>)
-
- float complex cprojf(float complex z);
- long double complex cprojl(long double complex z);
- double creal(double complex z);
- float crealf(float complex z);
- long double creall(long double complex z);
-<a name="B.3" href="#B.3"><b>B.3 Character handling <ctype.h></b></a>
- int isalnum(int c);
- int isalpha(int c);
- int isblank(int c);
- int iscntrl(int c);
- int isdigit(int c);
- int isgraph(int c);
- int islower(int c);
- int isprint(int c);
- int ispunct(int c);
- int isspace(int c);
- int isupper(int c);
- int isxdigit(int c);
- int tolower(int c);
- int toupper(int c);
-<a name="B.4" href="#B.4"><b>B.4 Errors <errno.h></b></a>
- EDOM EILSEQ ERANGE errno
- __STDC_WANT_LIB_EXT1__
- errno_t
-<a name="B.5" href="#B.5"><b>B.5 Floating-point environment <fenv.h></b></a>
- fenv_t FE_OVERFLOW FE_TOWARDZERO
- fexcept_t FE_UNDERFLOW FE_UPWARD
- FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
- FE_INEXACT FE_DOWNWARD
- FE_INVALID FE_TONEAREST
- #pragma STDC FENV_ACCESS on-off-switch
- int feclearexcept(int excepts);
- int fegetexceptflag(fexcept_t *flagp, int excepts);
- int feraiseexcept(int excepts);
- int fesetexceptflag(const fexcept_t *flagp,
- int excepts);
- int fetestexcept(int excepts);
-
-[<a name="#p472" href="p472">page 472</a>] (<a href="#Contents">Contents</a>)
-
- int fegetround(void);
- int fesetround(int round);
- int fegetenv(fenv_t *envp);
- int feholdexcept(fenv_t *envp);
- int fesetenv(const fenv_t *envp);
- int feupdateenv(const fenv_t *envp);
-<a name="B.6" href="#B.6"><b>B.6 Characteristics of floating types <float.h></b></a>
- FLT_ROUNDS DBL_DIG FLT_MAX
- FLT_EVAL_METHOD LDBL_DIG DBL_MAX
- FLT_HAS_SUBNORM FLT_MIN_EXP LDBL_MAX
- DBL_HAS_SUBNORM DBL_MIN_EXP FLT_EPSILON
- LDBL_HAS_SUBNORM LDBL_MIN_EXP DBL_EPSILON
- FLT_RADIX FLT_MIN_10_EXP LDBL_EPSILON
- FLT_MANT_DIG DBL_MIN_10_EXP FLT_MIN
- DBL_MANT_DIG LDBL_MIN_10_EXP DBL_MIN
- LDBL_MANT_DIG FLT_MAX_EXP LDBL_MIN
- FLT_DECIMAL_DIG DBL_MAX_EXP FLT_TRUE_MIN
- DBL_DECIMAL_DIG LDBL_MAX_EXP DBL_TRUE_MIN
- LDBL_DECIMAL_DIG FLT_MAX_10_EXP LDBL_TRUE_MIN
- DECIMAL_DIG DBL_MAX_10_EXP
- FLT_DIG LDBL_MAX_10_EXP
-<a name="B.7" href="#B.7"><b>B.7 Format conversion of integer types <inttypes.h></b></a>
- imaxdiv_t
- PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
- PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
- PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
- PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
- PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
- PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
- SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
- SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
- SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
- SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
- SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
- intmax_t imaxabs(intmax_t j);
- imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
- intmax_t strtoimax(const char * restrict nptr,
- char ** restrict endptr, int base);
-
-[<a name="#p473" href="p473">page 473</a>] (<a href="#Contents">Contents</a>)
-
- uintmax_t strtoumax(const char * restrict nptr,
- char ** restrict endptr, int base);
- intmax_t wcstoimax(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
- uintmax_t wcstoumax(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
-<a name="B.8" href="#B.8"><b>B.8 Alternative spellings <iso646.h></b></a>
- and bitor not_eq xor
- and_eq compl or xor_eq
- bitand not or_eq
-<a name="B.9" href="#B.9"><b>B.9 Sizes of integer types <limits.h></b></a>
- CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
- SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
- SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
- UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
- CHAR_MIN USHRT_MAX LONG_MAX
-<a name="B.10" href="#B.10"><b>B.10 Localization <locale.h></b></a>
- struct lconv LC_ALL LC_CTYPE LC_NUMERIC
- NULL LC_COLLATE LC_MONETARY LC_TIME
- char *setlocale(int category, const char *locale);
- struct lconv *localeconv(void);
-<a name="B.11" href="#B.11"><b>B.11 Mathematics <math.h></b></a>
- float_t FP_INFINITE FP_FAST_FMAL
- double_t FP_NAN FP_ILOGB0
- HUGE_VAL FP_NORMAL FP_ILOGBNAN
- HUGE_VALF FP_SUBNORMAL MATH_ERRNO
- HUGE_VALL FP_ZERO MATH_ERREXCEPT
- INFINITY FP_FAST_FMA math_errhandling
- NAN FP_FAST_FMAF
- #pragma STDC FP_CONTRACT on-off-switch
- int fpclassify(real-floating x);
- int isfinite(real-floating x);
- int isinf(real-floating x);
- int isnan(real-floating x);
- int isnormal(real-floating x);
- int signbit(real-floating x);
-[<a name="#p474" href="p474">page 474</a>] (<a href="#Contents">Contents</a>)
-
- double acos(double x);
- float acosf(float x);
- long double acosl(long double x);
- double asin(double x);
- float asinf(float x);
- long double asinl(long double x);
- double atan(double x);
- float atanf(float x);
- long double atanl(long double x);
- double atan2(double y, double x);
- float atan2f(float y, float x);
- long double atan2l(long double y, long double x);
- double cos(double x);
- float cosf(float x);
- long double cosl(long double x);
- double sin(double x);
- float sinf(float x);
- long double sinl(long double x);
- double tan(double x);
- float tanf(float x);
- long double tanl(long double x);
- double acosh(double x);
- float acoshf(float x);
- long double acoshl(long double x);
- double asinh(double x);
- float asinhf(float x);
- long double asinhl(long double x);
- double atanh(double x);
- float atanhf(float x);
- long double atanhl(long double x);
- double cosh(double x);
- float coshf(float x);
- long double coshl(long double x);
- double sinh(double x);
- float sinhf(float x);
- long double sinhl(long double x);
- double tanh(double x);
- float tanhf(float x);
- long double tanhl(long double x);
- double exp(double x);
- float expf(float x);
-
-[<a name="#p475" href="p475">page 475</a>] (<a href="#Contents">Contents</a>)
-
- long double expl(long double x);
- double exp2(double x);
- float exp2f(float x);
- long double exp2l(long double x);
- double expm1(double x);
- float expm1f(float x);
- long double expm1l(long double x);
- double frexp(double value, int *exp);
- float frexpf(float value, int *exp);
- long double frexpl(long double value, int *exp);
- int ilogb(double x);
- int ilogbf(float x);
- int ilogbl(long double x);
- double ldexp(double x, int exp);
- float ldexpf(float x, int exp);
- long double ldexpl(long double x, int exp);
- double log(double x);
- float logf(float x);
- long double logl(long double x);
- double log10(double x);
- float log10f(float x);
- long double log10l(long double x);
- double log1p(double x);
- float log1pf(float x);
- long double log1pl(long double x);
- double log2(double x);
- float log2f(float x);
- long double log2l(long double x);
- double logb(double x);
- float logbf(float x);
- long double logbl(long double x);
- double modf(double value, double *iptr);
- float modff(float value, float *iptr);
- long double modfl(long double value, long double *iptr);
- double scalbn(double x, int n);
- float scalbnf(float x, int n);
- long double scalbnl(long double x, int n);
- double scalbln(double x, long int n);
- float scalblnf(float x, long int n);
- long double scalblnl(long double x, long int n);
- double cbrt(double x);
-
-[<a name="#p476" href="p476">page 476</a>] (<a href="#Contents">Contents</a>)
-
- float cbrtf(float x);
- long double cbrtl(long double x);
- double fabs(double x);
- float fabsf(float x);
- long double fabsl(long double x);
- double hypot(double x, double y);
- float hypotf(float x, float y);
- long double hypotl(long double x, long double y);
- double pow(double x, double y);
- float powf(float x, float y);
- long double powl(long double x, long double y);
- double sqrt(double x);
- float sqrtf(float x);
- long double sqrtl(long double x);
- double erf(double x);
- float erff(float x);
- long double erfl(long double x);
- double erfc(double x);
- float erfcf(float x);
- long double erfcl(long double x);
- double lgamma(double x);
- float lgammaf(float x);
- long double lgammal(long double x);
- double tgamma(double x);
- float tgammaf(float x);
- long double tgammal(long double x);
- double ceil(double x);
- float ceilf(float x);
- long double ceill(long double x);
- double floor(double x);
- float floorf(float x);
- long double floorl(long double x);
- double nearbyint(double x);
- float nearbyintf(float x);
- long double nearbyintl(long double x);
- double rint(double x);
- float rintf(float x);
- long double rintl(long double x);
- long int lrint(double x);
- long int lrintf(float x);
- long int lrintl(long double x);
-
-[<a name="#p477" href="p477">page 477</a>] (<a href="#Contents">Contents</a>)
-
- long long int llrint(double x);
- long long int llrintf(float x);
- long long int llrintl(long double x);
- double round(double x);
- float roundf(float x);
- long double roundl(long double x);
- long int lround(double x);
- long int lroundf(float x);
- long int lroundl(long double x);
- long long int llround(double x);
- long long int llroundf(float x);
- long long int llroundl(long double x);
- double trunc(double x);
- float truncf(float x);
- long double truncl(long double x);
- double fmod(double x, double y);
- float fmodf(float x, float y);
- long double fmodl(long double x, long double y);
- double remainder(double x, double y);
- float remainderf(float x, float y);
- long double remainderl(long double x, long double y);
- double remquo(double x, double y, int *quo);
- float remquof(float x, float y, int *quo);
- long double remquol(long double x, long double y,
- int *quo);
- double copysign(double x, double y);
- float copysignf(float x, float y);
- long double copysignl(long double x, long double y);
- double nan(const char *tagp);
- float nanf(const char *tagp);
- long double nanl(const char *tagp);
- double nextafter(double x, double y);
- float nextafterf(float x, float y);
- long double nextafterl(long double x, long double y);
- double nexttoward(double x, long double y);
- float nexttowardf(float x, long double y);
- long double nexttowardl(long double x, long double y);
- double fdim(double x, double y);
- float fdimf(float x, float y);
- long double fdiml(long double x, long double y);
- double fmax(double x, double y);
-
-[<a name="#p478" href="p478">page 478</a>] (<a href="#Contents">Contents</a>)
-
- float fmaxf(float x, float y);
- long double fmaxl(long double x, long double y);
- double fmin(double x, double y);
- float fminf(float x, float y);
- long double fminl(long double x, long double y);
- double fma(double x, double y, double z);
- float fmaf(float x, float y, float z);
- long double fmal(long double x, long double y,
- long double z);
- int isgreater(real-floating x, real-floating y);
- int isgreaterequal(real-floating x, real-floating y);
- int isless(real-floating x, real-floating y);
- int islessequal(real-floating x, real-floating y);
- int islessgreater(real-floating x, real-floating y);
- int isunordered(real-floating x, real-floating y);
-<a name="B.12" href="#B.12"><b>B.12 Nonlocal jumps <setjmp.h></b></a>
- jmp_buf
- int setjmp(jmp_buf env);
- _Noreturn void longjmp(jmp_buf env, int val);
-<a name="B.13" href="#B.13"><b>B.13 Signal handling <signal.h></b></a>
- sig_atomic_t SIG_IGN SIGILL SIGTERM
- SIG_DFL SIGABRT SIGINT
- SIG_ERR SIGFPE SIGSEGV
- void (*signal(int sig, void (*func)(int)))(int);
- int raise(int sig);
-
-
-
-
-[<a name="#p479" href="p479">page 479</a>] (<a href="#Contents">Contents</a>)
-
-<a name="B.14" href="#B.14"><b>B.14 Alignment <stdalign.h></b></a>
- alignas
- __alignas_is_defined
-<a name="B.15" href="#B.15"><b>B.15 Variable arguments <stdarg.h></b></a>
- va_list
- type va_arg(va_list ap, type);
- void va_copy(va_list dest, va_list src);
- void va_end(va_list ap);
- void va_start(va_list ap, parmN);
-<a name="B.16" href="#B.16"><b>B.16 Atomics <stdatomic.h></b></a>
- ATOMIC_CHAR_LOCK_FREE atomic_uint
- ATOMIC_CHAR16_T_LOCK_FREE atomic_long
- ATOMIC_CHAR32_T_LOCK_FREE atomic_ulong
- ATOMIC_WCHAR_T_LOCK_FREE atomic_llong
- ATOMIC_SHORT_LOCK_FREE atomic_ullong
- ATOMIC_INT_LOCK_FREE atomic_char16_t
- ATOMIC_LONG_LOCK_FREE atomic_char32_t
- ATOMIC_LLONG_LOCK_FREE atomic_wchar_t
- ATOMIC_ADDRESS_LOCK_FREE atomic_int_least8_t
- ATOMIC_FLAG_INIT atomic_uint_least8_t
- memory_order atomic_int_least16_t
- atomic_flag atomic_uint_least16_t
- atomic_bool atomic_int_least32_t
- atomic_address atomic_uint_least32_t
- memory_order_relaxed atomic_int_least64_t
- memory_order_consume atomic_uint_least64_t
- memory_order_acquire atomic_int_fast8_t
- memory_order_release atomic_uint_fast8_t
- memory_order_acq_rel atomic_int_fast16_t
- memory_order_seq_cst atomic_uint_fast16_t
- atomic_char atomic_int_fast32_t
- atomic_schar atomic_uint_fast32_t
- atomic_uchar atomic_int_fast64_t
- atomic_short atomic_uint_fast64_t
- atomic_ushort atomic_intptr_t
- atomic_int atomic_uintptr_t
-
-
-
-[<a name="#p480" href="p480">page 480</a>] (<a href="#Contents">Contents</a>)
-
- atomic_size_t atomic_intmax_t
- atomic_ptrdiff_t atomic_uintmax_t
- #define ATOMIC_VAR_INIT(C value)
- void atomic_init(volatile A *obj, C value);
- type kill_dependency(type y);
- void atomic_thread_fence(memory_order order);
- void atomic_signal_fence(memory_order order);
- _Bool atomic_is_lock_free(atomic_type const volatile *obj);
- void atomic_store(volatile A *object, C desired);
- void atomic_store_explicit(volatile A *object,
- C desired, memory_order order);
- C atomic_load(volatile A *object);
- C atomic_load_explicit(volatile A *object,
- memory_order order);
- C atomic_exchange(volatile A *object, C desired);
- C atomic_exchange_explicit(volatile A *object,
- C desired, memory_order order);
- _Bool atomic_compare_exchange_strong(volatile A *object,
- C *expected, C desired);
- _Bool atomic_compare_exchange_strong_explicit(
- volatile A *object, C *expected, C desired,
- memory_order success, memory_order failure);
- _Bool atomic_compare_exchange_weak(volatile A *object,
- C *expected, C desired);
- _Bool atomic_compare_exchange_weak_explicit(
- volatile A *object, C *expected, C desired,
- memory_order success, memory_order failure);
- C atomic_fetch_key(volatile A *object, M operand);
- C atomic_fetch_key_explicit(volatile A *object,
- M operand, memory_order order);
- bool atomic_flag_test_and_set(
- volatile atomic_flag *object);
- bool atomic_flag_test_and_set_explicit(
- volatile atomic_flag *object, memory_order order);
- void atomic_flag_clear(volatile atomic_flag *object);
- void atomic_flag_clear_explicit(
- volatile atomic_flag *object, memory_order order);
-
-
-
-
-[<a name="#p481" href="p481">page 481</a>] (<a href="#Contents">Contents</a>)
-
-<a name="B.17" href="#B.17"><b>B.17 Boolean type and values <stdbool.h></b></a>
- bool
- true
- false
- __bool_true_false_are_defined
-<a name="B.18" href="#B.18"><b>B.18 Common definitions <stddef.h></b></a>
- ptrdiff_t max_align_t NULL
- size_t wchar_t
- offsetof(type, member-designator)
- __STDC_WANT_LIB_EXT1__
- rsize_t
-<a name="B.19" href="#B.19"><b>B.19 Integer types <stdint.h></b></a>
- intN_t INT_LEASTN_MIN PTRDIFF_MAX
- uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
- int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
- uint_leastN_t INT_FASTN_MIN SIZE_MAX
- int_fastN_t INT_FASTN_MAX WCHAR_MIN
- uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
- intptr_t INTPTR_MIN WINT_MIN
- uintptr_t INTPTR_MAX WINT_MAX
- intmax_t UINTPTR_MAX INTN_C(value)
- uintmax_t INTMAX_MIN UINTN_C(value)
- INTN_MIN INTMAX_MAX INTMAX_C(value)
- INTN_MAX UINTMAX_MAX UINTMAX_C(value)
- UINTN_MAX PTRDIFF_MIN
- __STDC_WANT_LIB_EXT1__
- RSIZE_MAX
-
-
-
-
-[<a name="#p482" href="p482">page 482</a>] (<a href="#Contents">Contents</a>)
-
-<a name="B.20" href="#B.20"><b>B.20 Input/output <stdio.h></b></a>
- size_t _IOLBF FILENAME_MAX TMP_MAX
- FILE _IONBF L_tmpnam stderr
- fpos_t BUFSIZ SEEK_CUR stdin
- NULL EOF SEEK_END stdout
- _IOFBF FOPEN_MAX SEEK_SET
- int remove(const char *filename);
- int rename(const char *old, const char *new);
- FILE *tmpfile(void);
- char *tmpnam(char *s);
- int fclose(FILE *stream);
- int fflush(FILE *stream);
- FILE *fopen(const char * restrict filename,
- const char * restrict mode);
- FILE *freopen(const char * restrict filename,
- const char * restrict mode,
- FILE * restrict stream);
- void setbuf(FILE * restrict stream,
- char * restrict buf);
- int setvbuf(FILE * restrict stream,
- char * restrict buf,
- int mode, size_t size);
- int fprintf(FILE * restrict stream,
- const char * restrict format, ...);
- int fscanf(FILE * restrict stream,
- const char * restrict format, ...);
- int printf(const char * restrict format, ...);
- int scanf(const char * restrict format, ...);
- int snprintf(char * restrict s, size_t n,
- const char * restrict format, ...);
- int sprintf(char * restrict s,
- const char * restrict format, ...);
- int sscanf(const char * restrict s,
- const char * restrict format, ...);
- int vfprintf(FILE * restrict stream,
- const char * restrict format, va_list arg);
- int vfscanf(FILE * restrict stream,
- const char * restrict format, va_list arg);
- int vprintf(const char * restrict format, va_list arg);
- int vscanf(const char * restrict format, va_list arg);
-
-[<a name="#p483" href="p483">page 483</a>] (<a href="#Contents">Contents</a>)
-
- int vsnprintf(char * restrict s, size_t n,
- const char * restrict format, va_list arg);
- int vsprintf(char * restrict s,
- const char * restrict format, va_list arg);
- int vsscanf(const char * restrict s,
- const char * restrict format, va_list arg);
- int fgetc(FILE *stream);
- char *fgets(char * restrict s, int n,
- FILE * restrict stream);
- int fputc(int c, FILE *stream);
- int fputs(const char * restrict s,
- FILE * restrict stream);
- int getc(FILE *stream);
- int getchar(void);
- int putc(int c, FILE *stream);
- int putchar(int c);
- int puts(const char *s);
- int ungetc(int c, FILE *stream);
- size_t fread(void * restrict ptr,
- size_t size, size_t nmemb,
- FILE * restrict stream);
- size_t fwrite(const void * restrict ptr,
- size_t size, size_t nmemb,
- FILE * restrict stream);
- int fgetpos(FILE * restrict stream,
- fpos_t * restrict pos);
- int fseek(FILE *stream, long int offset, int whence);
- int fsetpos(FILE *stream, const fpos_t *pos);
- long int ftell(FILE *stream);
- void rewind(FILE *stream);
- void clearerr(FILE *stream);
- int feof(FILE *stream);
- int ferror(FILE *stream);
- void perror(const char *s);
- __STDC_WANT_LIB_EXT1__
- L_tmpnam_s TMP_MAX_S errno_t rsize_t
- errno_t tmpfile_s(FILE * restrict * restrict streamptr);
- errno_t tmpnam_s(char *s, rsize_t maxsize);
-
-
-
-[<a name="#p484" href="p484">page 484</a>] (<a href="#Contents">Contents</a>)
-
- errno_t fopen_s(FILE * restrict * restrict streamptr,
- const char * restrict filename,
- const char * restrict mode);
- errno_t freopen_s(FILE * restrict * restrict newstreamptr,
- const char * restrict filename,
- const char * restrict mode,
- FILE * restrict stream);
- int fprintf_s(FILE * restrict stream,
- const char * restrict format, ...);
- int fscanf_s(FILE * restrict stream,
- const char * restrict format, ...);
- int printf_s(const char * restrict format, ...);
- int scanf_s(const char * restrict format, ...);
- int snprintf_s(char * restrict s, rsize_t n,
- const char * restrict format, ...);
- int sprintf_s(char * restrict s, rsize_t n,
- const char * restrict format, ...);
- int sscanf_s(const char * restrict s,
- const char * restrict format, ...);
- int vfprintf_s(FILE * restrict stream,
- const char * restrict format,
- va_list arg);
- int vfscanf_s(FILE * restrict stream,
- const char * restrict format,
- va_list arg);
- int vprintf_s(const char * restrict format,
- va_list arg);
- int vscanf_s(const char * restrict format,
- va_list arg);
- int vsnprintf_s(char * restrict s, rsize_t n,
- const char * restrict format,
- va_list arg);
- int vsprintf_s(char * restrict s, rsize_t n,
- const char * restrict format,
- va_list arg);
- int vsscanf_s(const char * restrict s,
- const char * restrict format,
- va_list arg);
- char *gets_s(char *s, rsize_t n);
-
-
-
-[<a name="#p485" href="p485">page 485</a>] (<a href="#Contents">Contents</a>)
-
-<a name="B.21" href="#B.21"><b>B.21 General utilities <stdlib.h></b></a>
- size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
- wchar_t lldiv_t EXIT_SUCCESS
- div_t NULL RAND_MAX
- double atof(const char *nptr);
- int atoi(const char *nptr);
- long int atol(const char *nptr);
- long long int atoll(const char *nptr);
- double strtod(const char * restrict nptr,
- char ** restrict endptr);
- float strtof(const char * restrict nptr,
- char ** restrict endptr);
- long double strtold(const char * restrict nptr,
- char ** restrict endptr);
- long int strtol(const char * restrict nptr,
- char ** restrict endptr, int base);
- long long int strtoll(const char * restrict nptr,
- char ** restrict endptr, int base);
- unsigned long int strtoul(
- const char * restrict nptr,
- char ** restrict endptr, int base);
- unsigned long long int strtoull(
- const char * restrict nptr,
- char ** restrict endptr, int base);
- int rand(void);
- void srand(unsigned int seed);
- void *aligned_alloc(size_t alignment, size_t size);
- void *calloc(size_t nmemb, size_t size);
- void free(void *ptr);
- void *malloc(size_t size);
- void *realloc(void *ptr, size_t size);
- _Noreturn void abort(void);
- int atexit(void (*func)(void));
- int at_quick_exit(void (*func)(void));
- _Noreturn void exit(int status);
- _Noreturn void _Exit(int status);
- char *getenv(const char *name);
- _Noreturn void quick_exit(int status);
- int system(const char *string);
-
-
-[<a name="#p486" href="p486">page 486</a>] (<a href="#Contents">Contents</a>)
-
- void *bsearch(const void *key, const void *base,
- size_t nmemb, size_t size,
- int (*compar)(const void *, const void *));
- void qsort(void *base, size_t nmemb, size_t size,
- int (*compar)(const void *, const void *));
- int abs(int j);
- long int labs(long int j);
- long long int llabs(long long int j);
- div_t div(int numer, int denom);
- ldiv_t ldiv(long int numer, long int denom);
- lldiv_t lldiv(long long int numer,
- long long int denom);
- int mblen(const char *s, size_t n);
- int mbtowc(wchar_t * restrict pwc,
- const char * restrict s, size_t n);
- int wctomb(char *s, wchar_t wchar);
- size_t mbstowcs(wchar_t * restrict pwcs,
- const char * restrict s, size_t n);
- size_t wcstombs(char * restrict s,
- const wchar_t * restrict pwcs, size_t n);
- __STDC_WANT_LIB_EXT1__
- errno_t
- rsize_t
- constraint_handler_t
- constraint_handler_t set_constraint_handler_s(
- constraint_handler_t handler);
- void abort_handler_s(
- const char * restrict msg,
- void * restrict ptr,
- errno_t error);
- void ignore_handler_s(
- const char * restrict msg,
- void * restrict ptr,
- errno_t error);
- errno_t getenv_s(size_t * restrict len,
- char * restrict value, rsize_t maxsize,
- const char * restrict name);
-
-
-
-
-[<a name="#p487" href="p487">page 487</a>] (<a href="#Contents">Contents</a>)
-
- void *bsearch_s(const void *key, const void *base,
- rsize_t nmemb, rsize_t size,
- int (*compar)(const void *k, const void *y,
- void *context),
- void *context);
- errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
- int (*compar)(const void *x, const void *y,
- void *context),
- void *context);
- errno_t wctomb_s(int * restrict status,
- char * restrict s,
- rsize_t smax,
- wchar_t wc);
- errno_t mbstowcs_s(size_t * restrict retval,
- wchar_t * restrict dst, rsize_t dstmax,
- const char * restrict src, rsize_t len);
- errno_t wcstombs_s(size_t * restrict retval,
- char * restrict dst, rsize_t dstmax,
- const wchar_t * restrict src, rsize_t len);
-<a name="B.22" href="#B.22"><b>B.22 String handling <string.h></b></a>
- size_t
- NULL
- void *memcpy(void * restrict s1,
- const void * restrict s2, size_t n);
- void *memmove(void *s1, const void *s2, size_t n);
- char *strcpy(char * restrict s1,
- const char * restrict s2);
- char *strncpy(char * restrict s1,
- const char * restrict s2, size_t n);
- char *strcat(char * restrict s1,
- const char * restrict s2);
- char *strncat(char * restrict s1,
- const char * restrict s2, size_t n);
- int memcmp(const void *s1, const void *s2, size_t n);
- int strcmp(const char *s1, const char *s2);
- int strcoll(const char *s1, const char *s2);
- int strncmp(const char *s1, const char *s2, size_t n);
- size_t strxfrm(char * restrict s1,
- const char * restrict s2, size_t n);
- void *memchr(const void *s, int c, size_t n);
-[<a name="#p488" href="p488">page 488</a>] (<a href="#Contents">Contents</a>)
-
- char *strchr(const char *s, int c);
- size_t strcspn(const char *s1, const char *s2);
- char *strpbrk(const char *s1, const char *s2);
- char *strrchr(const char *s, int c);
- size_t strspn(const char *s1, const char *s2);
- char *strstr(const char *s1, const char *s2);
- char *strtok(char * restrict s1,
- const char * restrict s2);
- void *memset(void *s, int c, size_t n);
- char *strerror(int errnum);
- size_t strlen(const char *s);
- __STDC_WANT_LIB_EXT1__
- errno_t
- rsize_t
- errno_t memcpy_s(void * restrict s1, rsize_t s1max,
- const void * restrict s2, rsize_t n);
- errno_t memmove_s(void *s1, rsize_t s1max,
- const void *s2, rsize_t n);
- errno_t strcpy_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2);
- errno_t strncpy_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2,
- rsize_t n);
- errno_t strcat_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2);
- errno_t strncat_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2,
- rsize_t n);
- char *strtok_s(char * restrict s1,
- rsize_t * restrict s1max,
- const char * restrict s2,
- char ** restrict ptr);
- errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
- errno_t strerror_s(char *s, rsize_t maxsize,
- errno_t errnum);
- size_t strerrorlen_s(errno_t errnum);
-
-[<a name="#p489" href="p489">page 489</a>] (<a href="#Contents">Contents</a>)
-
- size_t strnlen_s(const char *s, size_t maxsize);
-<a name="B.23" href="#B.23"><b>B.23 Type-generic math <tgmath.h></b></a>
- acos sqrt fmod nextafter
- asin fabs frexp nexttoward
- atan atan2 hypot remainder
- acosh cbrt ilogb remquo
- asinh ceil ldexp rint
- atanh copysign lgamma round
- cos erf llrint scalbn
- sin erfc llround scalbln
- tan exp2 log10 tgamma
- cosh expm1 log1p trunc
- sinh fdim log2 carg
- tanh floor logb cimag
- exp fma lrint conj
- log fmax lround cproj
- pow fmin nearbyint creal
-<a name="B.24" href="#B.24"><b>B.24 Threads <threads.h></b></a>
- ONCE_FLAG_INIT mtx_plain
- TSS_DTOR_ITERATIONS mtx_recursive
- cnd_t mtx_timed
- thrd_t mtx_try
- tss_t thrd_timeout
- mtx_t thrd_success
- tss_dtor_t thrd_busy
- thrd_start_t thrd_error
- once_flag thrd_nomem
- xtime
- void call_once(once_flag *flag, void (*func)(void));
- int cnd_broadcast(cnd_t *cond);
- void cnd_destroy(cnd_t *cond);
- int cnd_init(cnd_t *cond);
- int cnd_signal(cnd_t *cond);
- int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
- const xtime *xt);
- int cnd_wait(cnd_t *cond, mtx_t *mtx);
- void mtx_destroy(mtx_t *mtx);
- int mtx_init(mtx_t *mtx, int type);
- int mtx_lock(mtx_t *mtx);
-[<a name="#p490" href="p490">page 490</a>] (<a href="#Contents">Contents</a>)
-
- int mtx_timedlock(mtx_t *mtx, const xtime *xt);
- int mtx_trylock(mtx_t *mtx);
- int mtx_unlock(mtx_t *mtx);
- int thrd_create(thrd_t *thr, thrd_start_t func,
- void *arg);
- thrd_t thrd_current(void);
- int thrd_detach(thrd_t thr);
- int thrd_equal(thrd_t thr0, thrd_t thr1);
- void thrd_exit(int res);
- int thrd_join(thrd_t thr, int *res);
- void thrd_sleep(const xtime *xt);
- void thrd_yield(void);
- int tss_create(tss_t *key, tss_dtor_t dtor);
- void tss_delete(tss_t key);
- void *tss_get(tss_t key);
- int tss_set(tss_t key, void *val);
- int xtime_get(xtime *xt, int base);
-<a name="B.25" href="#B.25"><b>B.25 Date and time <time.h></b></a>
- NULL size_t time_t
- CLOCKS_PER_SEC clock_t struct tm
- clock_t clock(void);
- double difftime(time_t time1, time_t time0);
- time_t mktime(struct tm *timeptr);
- time_t time(time_t *timer);
- char *asctime(const struct tm *timeptr);
- char *ctime(const time_t *timer);
- struct tm *gmtime(const time_t *timer);
- struct tm *localtime(const time_t *timer);
- size_t strftime(char * restrict s,
- size_t maxsize,
- const char * restrict format,
- const struct tm * restrict timeptr);
- __STDC_WANT_LIB_EXT1__
- errno_t
- rsize_t
- errno_t asctime_s(char *s, rsize_t maxsize,
- const struct tm *timeptr);
-
-
-
-[<a name="#p491" href="p491">page 491</a>] (<a href="#Contents">Contents</a>)
-
- errno_t ctime_s(char *s, rsize_t maxsize,
- const time_t *timer);
- struct tm *gmtime_s(const time_t * restrict timer,
- struct tm * restrict result);
- struct tm *localtime_s(const time_t * restrict timer,
- struct tm * restrict result);
-<a name="B.26" href="#B.26"><b>B.26 Unicode utilities <uchar.h></b></a>
- mbstate_t size_t char16_t char32_t
- size_t mbrtoc16(char16_t * restrict pc16,
- const char * restrict s, size_t n,
- mbstate_t * restrict ps);
- size_t c16rtomb(char * restrict s, char16_t c16,
- mbstate_t * restrict ps);
- size_t mbrtoc32(char32_t * restrict pc32,
- const char * restrict s, size_t n,
- mbstate_t * restrict ps);
- size_t c32rtomb(char * restrict s, char32_t c32,
- mbstate_t * restrict ps);
-<a name="B.27" href="#B.27"><b>B.27 Extended multibyte/wide character utilities <wchar.h></b></a>
- wchar_t wint_t WCHAR_MAX
- size_t struct tm WCHAR_MIN
- mbstate_t NULL WEOF
- int fwprintf(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- int fwscanf(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- int swprintf(wchar_t * restrict s, size_t n,
- const wchar_t * restrict format, ...);
- int swscanf(const wchar_t * restrict s,
- const wchar_t * restrict format, ...);
- int vfwprintf(FILE * restrict stream,
- const wchar_t * restrict format, va_list arg);
- int vfwscanf(FILE * restrict stream,
- const wchar_t * restrict format, va_list arg);
- int vswprintf(wchar_t * restrict s, size_t n,
- const wchar_t * restrict format, va_list arg);
-
-
-
-[<a name="#p492" href="p492">page 492</a>] (<a href="#Contents">Contents</a>)
-
- int vswscanf(const wchar_t * restrict s,
- const wchar_t * restrict format, va_list arg);
- int vwprintf(const wchar_t * restrict format,
- va_list arg);
- int vwscanf(const wchar_t * restrict format,
- va_list arg);
- int wprintf(const wchar_t * restrict format, ...);
- int wscanf(const wchar_t * restrict format, ...);
- wint_t fgetwc(FILE *stream);
- wchar_t *fgetws(wchar_t * restrict s, int n,
- FILE * restrict stream);
- wint_t fputwc(wchar_t c, FILE *stream);
- int fputws(const wchar_t * restrict s,
- FILE * restrict stream);
- int fwide(FILE *stream, int mode);
- wint_t getwc(FILE *stream);
- wint_t getwchar(void);
- wint_t putwc(wchar_t c, FILE *stream);
- wint_t putwchar(wchar_t c);
- wint_t ungetwc(wint_t c, FILE *stream);
- double wcstod(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr);
- float wcstof(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr);
- long double wcstold(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr);
- long int wcstol(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
- long long int wcstoll(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
- unsigned long int wcstoul(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
- unsigned long long int wcstoull(
- const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
- wchar_t *wcscpy(wchar_t * restrict s1,
- const wchar_t * restrict s2);
- wchar_t *wcsncpy(wchar_t * restrict s1,
- const wchar_t * restrict s2, size_t n);
-
-
-
-[<a name="#p493" href="p493">page 493</a>] (<a href="#Contents">Contents</a>)
-
- wchar_t *wmemcpy(wchar_t * restrict s1,
- const wchar_t * restrict s2, size_t n);
- wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
- size_t n);
- wchar_t *wcscat(wchar_t * restrict s1,
- const wchar_t * restrict s2);
- wchar_t *wcsncat(wchar_t * restrict s1,
- const wchar_t * restrict s2, size_t n);
- int wcscmp(const wchar_t *s1, const wchar_t *s2);
- int wcscoll(const wchar_t *s1, const wchar_t *s2);
- int wcsncmp(const wchar_t *s1, const wchar_t *s2,
- size_t n);
- size_t wcsxfrm(wchar_t * restrict s1,
- const wchar_t * restrict s2, size_t n);
- int wmemcmp(const wchar_t *s1, const wchar_t *s2,
- size_t n);
- wchar_t *wcschr(const wchar_t *s, wchar_t c);
- size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
- wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
- wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
- size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
- wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
- wchar_t *wcstok(wchar_t * restrict s1,
- const wchar_t * restrict s2,
- wchar_t ** restrict ptr);
- wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
- size_t wcslen(const wchar_t *s);
- wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
- size_t wcsftime(wchar_t * restrict s, size_t maxsize,
- const wchar_t * restrict format,
- const struct tm * restrict timeptr);
- wint_t btowc(int c);
- int wctob(wint_t c);
- int mbsinit(const mbstate_t *ps);
- size_t mbrlen(const char * restrict s, size_t n,
- mbstate_t * restrict ps);
- size_t mbrtowc(wchar_t * restrict pwc,
- const char * restrict s, size_t n,
- mbstate_t * restrict ps);
-
-
-
-[<a name="#p494" href="p494">page 494</a>] (<a href="#Contents">Contents</a>)
-
- size_t wcrtomb(char * restrict s, wchar_t wc,
- mbstate_t * restrict ps);
- size_t mbsrtowcs(wchar_t * restrict dst,
- const char ** restrict src, size_t len,
- mbstate_t * restrict ps);
- size_t wcsrtombs(char * restrict dst,
- const wchar_t ** restrict src, size_t len,
- mbstate_t * restrict ps);
- __STDC_WANT_LIB_EXT1__
- errno_t
- rsize_t
- int fwprintf_s(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- int fwscanf_s(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- int snwprintf_s(wchar_t * restrict s,
- rsize_t n,
- const wchar_t * restrict format, ...);
- int swprintf_s(wchar_t * restrict s, rsize_t n,
- const wchar_t * restrict format, ...);
- int swscanf_s(const wchar_t * restrict s,
- const wchar_t * restrict format, ...);
- int vfwprintf_s(FILE * restrict stream,
- const wchar_t * restrict format,
- va_list arg);
- int vfwscanf_s(FILE * restrict stream,
- const wchar_t * restrict format, va_list arg);
- int vsnwprintf_s(wchar_t * restrict s,
- rsize_t n,
- const wchar_t * restrict format,
- va_list arg);
- int vswprintf_s(wchar_t * restrict s,
- rsize_t n,
- const wchar_t * restrict format,
- va_list arg);
- int vswscanf_s(const wchar_t * restrict s,
- const wchar_t * restrict format,
- va_list arg);
-
-
-
-[<a name="#p495" href="p495">page 495</a>] (<a href="#Contents">Contents</a>)
-
- int vwprintf_s(const wchar_t * restrict format,
- va_list arg);
- int vwscanf_s(const wchar_t * restrict format,
- va_list arg);
- int wprintf_s(const wchar_t * restrict format, ...);
- int wscanf_s(const wchar_t * restrict format, ...);
- errno_t wcscpy_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2);
- errno_t wcsncpy_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2,
- rsize_t n);
- errno_t wmemcpy_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2,
- rsize_t n);
- errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
- const wchar_t *s2, rsize_t n);
- errno_t wcscat_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2);
- errno_t wcsncat_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2,
- rsize_t n);
- wchar_t *wcstok_s(wchar_t * restrict s1,
- rsize_t * restrict s1max,
- const wchar_t * restrict s2,
- wchar_t ** restrict ptr);
- size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
- errno_t wcrtomb_s(size_t * restrict retval,
- char * restrict s, rsize_t smax,
- wchar_t wc, mbstate_t * restrict ps);
- errno_t mbsrtowcs_s(size_t * restrict retval,
- wchar_t * restrict dst, rsize_t dstmax,
- const char ** restrict src, rsize_t len,
- mbstate_t * restrict ps);
-
-
-
-
-[<a name="#p496" href="p496">page 496</a>] (<a href="#Contents">Contents</a>)
-
- errno_t wcsrtombs_s(size_t * restrict retval,
- char * restrict dst, rsize_t dstmax,
- const wchar_t ** restrict src, rsize_t len,
- mbstate_t * restrict ps);
-<a name="B.28" href="#B.28"><b>B.28 Wide character classification and mapping utilities <wctype.h></b></a>
- wint_t wctrans_t wctype_t WEOF
- int iswalnum(wint_t wc);
- int iswalpha(wint_t wc);
- int iswblank(wint_t wc);
- int iswcntrl(wint_t wc);
- int iswdigit(wint_t wc);
- int iswgraph(wint_t wc);
- int iswlower(wint_t wc);
- int iswprint(wint_t wc);
- int iswpunct(wint_t wc);
- int iswspace(wint_t wc);
- int iswupper(wint_t wc);
- int iswxdigit(wint_t wc);
- int iswctype(wint_t wc, wctype_t desc);
- wctype_t wctype(const char *property);
- wint_t towlower(wint_t wc);
- wint_t towupper(wint_t wc);
- wint_t towctrans(wint_t wc, wctrans_t desc);
- wctrans_t wctrans(const char *property);
-
-
-
-
-[<a name="#p497" href="p497">page 497</a>] (<a href="#Contents">Contents</a>)
-
-<a name="C" href="#C"><b> Annex C</b></a>
- (informative)
- Sequence points
-1 The following are the sequence points described in <a href="#5.1.2.3">5.1.2.3</a>:
- -- Between the evaluations of the function designator and actual arguments in a function
- call and the actual call. (<a href="#6.5.2.2">6.5.2.2</a>).
- -- Between the evaluations of the first and second operands of the following operators:
- logical AND && (<a href="#6.5.13">6.5.13</a>); logical OR || (<a href="#6.5.14">6.5.14</a>); comma , (<a href="#6.5.17">6.5.17</a>).
- -- Between the evaluations of the first operand of the conditional ? : operator and
- whichever of the second and third operands is evaluated (<a href="#6.5.15">6.5.15</a>).
- -- The end of a full declarator: declarators (<a href="#6.7.6">6.7.6</a>);
- -- Between the evaluation of a full expression and the next full expression to be
- evaluated. The following are full expressions: an initializer that is not part of a
- compound literal (<a href="#6.7.9">6.7.9</a>); the expression in an expression statement (<a href="#6.8.3">6.8.3</a>); the
- controlling expression of a selection statement (if or switch) (<a href="#6.8.4">6.8.4</a>); the
- controlling expression of a while or do statement (<a href="#6.8.5">6.8.5</a>); each of the (optional)
- expressions of a for statement (<a href="#6.8.5.3">6.8.5.3</a>); the (optional) expression in a return
- statement (<a href="#6.8.6.4">6.8.6.4</a>).
- -- Immediately before a library function returns (<a href="#7.1.4">7.1.4</a>).
- -- After the actions associated with each formatted input/output function conversion
- specifier (<a href="#7.21.6">7.21.6</a>, <a href="#7.28.2">7.28.2</a>).
- -- Immediately before and immediately after each call to a comparison function, and
- also between any call to a comparison function and any movement of the objects
- passed as arguments to that call (<a href="#7.22.5">7.22.5</a>).
-
-
-
-
-[<a name="#p498" href="p498">page 498</a>] (<a href="#Contents">Contents</a>)
-
-<a name="D" href="#D"><b> Annex D</b></a>
- (normative)
- Universal character names for identifiers
-1 This clause lists the hexadecimal code values that are valid in universal character names
- in identifiers.
-2 This table is reproduced unchanged from ISO/IEC TR 10176:1998, produced by ISO/IEC
- JTC 1/SC 22/WG 20, except for the omission of ranges that are part of the basic character
- sets.
- Latin: 00AA, 00BA, 00C0-00D6, 00D8-00F6, 00F8-01F5, 01FA-0217,
- 0250-02A8, 1E00-1E9B, 1EA0-1EF9, 207F
- Greek: 0386, 0388-038A, 038C, 038E-03A1, 03A3-03CE, 03D0-03D6,
- 03DA, 03DC, 03DE, 03E0, 03E2-03F3, 1F00-1F15, 1F18-1F1D,
- 1F20-1F45, 1F48-1F4D, 1F50-1F57, 1F59, 1F5B, 1F5D,
- 1F5F-1F7D, 1F80-1FB4, 1FB6-1FBC, 1FC2-1FC4, 1FC6-1FCC,
- 1FD0-1FD3, 1FD6-1FDB, 1FE0-1FEC, 1FF2-1FF4, 1FF6-1FFC
- Cyrillic: 0401-040C, 040E-044F, 0451-045C, 045E-0481, 0490-04C4,
- 04C7-04C8, 04CB-04CC, 04D0-04EB, 04EE-04F5, 04F8-04F9
- Armenian: 0531-0556, 0561-0587
- Hebrew: 05B0-05B9, 05BB-05BD, 05BF, 05C1-05C2, 05D0-05EA,
- 05F0-05F2
- Arabic: 0621-063A, 0640-0652, 0670-06B7, 06BA-06BE, 06C0-06CE,
- 06D0-06DC, 06E5-06E8, 06EA-06ED
- Devanagari: 0901-0903, 0905-0939, 093E-094D, 0950-0952, 0958-0963
- Bengali: 0981-0983, 0985-098C, 098F-0990, 0993-09A8, 09AA-09B0,
- 09B2, 09B6-09B9, 09BE-09C4, 09C7-09C8, 09CB-09CD,
- 09DC-09DD, 09DF-09E3, 09F0-09F1
- Gurmukhi: 0A02, 0A05-0A0A, 0A0F-0A10, 0A13-0A28, 0A2A-0A30,
- 0A32-0A33, 0A35-0A36, 0A38-0A39, 0A3E-0A42, 0A47-0A48,
- 0A4B-0A4D, 0A59-0A5C, 0A5E, 0A74
- Gujarati: 0A81-0A83, 0A85-0A8B, 0A8D, 0A8F-0A91, 0A93-0AA8,
- 0AAA-0AB0, 0AB2-0AB3, 0AB5-0AB9, 0ABD-0AC5,
- 0AC7-0AC9, 0ACB-0ACD, 0AD0, 0AE0
- Oriya: 0B01-0B03, 0B05-0B0C, 0B0F-0B10, 0B13-0B28, 0B2A-0B30,
- 0B32-0B33, 0B36-0B39, 0B3E-0B43, 0B47-0B48, 0B4B-0B4D,
-[<a name="#p499" href="p499">page 499</a>] (<a href="#Contents">Contents</a>)
-
- 0B5C-0B5D, 0B5F-0B61
-Tamil: 0B82-0B83, 0B85-0B8A, 0B8E-0B90, 0B92-0B95, 0B99-0B9A,
- 0B9C, 0B9E-0B9F, 0BA3-0BA4, 0BA8-0BAA, 0BAE-0BB5,
- 0BB7-0BB9, 0BBE-0BC2, 0BC6-0BC8, 0BCA-0BCD
-Telugu: 0C01-0C03, 0C05-0C0C, 0C0E-0C10, 0C12-0C28, 0C2A-0C33,
- 0C35-0C39, 0C3E-0C44, 0C46-0C48, 0C4A-0C4D, 0C60-0C61
-Kannada: 0C82-0C83, 0C85-0C8C, 0C8E-0C90, 0C92-0CA8, 0CAA-0CB3,
- 0CB5-0CB9, 0CBE-0CC4, 0CC6-0CC8, 0CCA-0CCD, 0CDE,
- 0CE0-0CE1
-Malayalam: 0D02-0D03, 0D05-0D0C, 0D0E-0D10, 0D12-0D28, 0D2A-0D39,
- 0D3E-0D43, 0D46-0D48, 0D4A-0D4D, 0D60-0D61
-Thai: 0E01-0E3A, 0E40-0E5B
-Lao: 0E81-0E82, 0E84, 0E87-0E88, 0E8A, 0E8D, 0E94-0E97,
- 0E99-0E9F, 0EA1-0EA3, 0EA5, 0EA7, 0EAA-0EAB,
- 0EAD-0EAE, 0EB0-0EB9, 0EBB-0EBD, 0EC0-0EC4, 0EC6,
- 0EC8-0ECD, 0EDC-0EDD
-Tibetan: 0F00, 0F18-0F19, 0F35, 0F37, 0F39, 0F3E-0F47, 0F49-0F69,
- 0F71-0F84, 0F86-0F8B, 0F90-0F95, 0F97, 0F99-0FAD,
- 0FB1-0FB7, 0FB9
-Georgian: 10A0-10C5, 10D0-10F6
-Hiragana: 3041-3093, 309B-309C
-Katakana: 30A1-30F6, 30FB-30FC
-Bopomofo: 3105-312C
-CJK Unified Ideographs: 4E00-9FA5
-Hangul: AC00-D7A3
-Digits: 0660-0669, 06F0-06F9, 0966-096F, 09E6-09EF, 0A66-0A6F,
- 0AE6-0AEF, 0B66-0B6F, 0BE7-0BEF, 0C66-0C6F, 0CE6-0CEF,
- 0D66-0D6F, 0E50-0E59, 0ED0-0ED9, 0F20-0F33
-Special characters: 00B5, 00B7, 02B0-02B8, 02BB, 02BD-02C1, 02D0-02D1,
- 02E0-02E4, 037A, 0559, 093D, 0B3D, 1FBE, 203F-2040, 2102,
- 2107, 210A-2113, 2115, 2118-211D, 2124, 2126, 2128, 212A-2131,
- 2133-2138, 2160-2182, 3005-3007, 3021-3029
-
-
-
-
-[<a name="#p500" href="p500">page 500</a>] (<a href="#Contents">Contents</a>)
-
-<a name="E" href="#E"><b> Annex E</b></a>
- (informative)
- Implementation limits
-1 The contents of the header <a href="#7.10"><limits.h></a> are given below, in alphabetical order. The
- minimum magnitudes shown shall be replaced by implementation-defined magnitudes
- with the same sign. The values shall all be constant expressions suitable for use in #if
- preprocessing directives. The components are described further in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
- #define CHAR_BIT 8
- #define CHAR_MAX UCHAR_MAX or SCHAR_MAX
- #define CHAR_MIN 0 or SCHAR_MIN
- #define INT_MAX +32767
- #define INT_MIN -32767
- #define LONG_MAX +2147483647
- #define LONG_MIN -2147483647
- #define LLONG_MAX +9223372036854775807
- #define LLONG_MIN -9223372036854775807
- #define MB_LEN_MAX 1
- #define SCHAR_MAX +127
- #define SCHAR_MIN -127
- #define SHRT_MAX +32767
- #define SHRT_MIN -32767
- #define UCHAR_MAX 255
- #define USHRT_MAX 65535
- #define UINT_MAX 65535
- #define ULONG_MAX 4294967295
- #define ULLONG_MAX 18446744073709551615
-2 The contents of the header <a href="#7.7"><float.h></a> are given below. All integer values, except
- FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing
- directives; all floating values shall be constant expressions. The components are
- described further in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
-3 The values given in the following list shall be replaced by implementation-defined
- expressions:
- #define FLT_EVAL_METHOD
- #define FLT_ROUNDS
-4 The values given in the following list shall be replaced by implementation-defined
- constant expressions that are greater or equal in magnitude (absolute value) to those
- shown, with the same sign:
-[<a name="#p501" href="p501">page 501</a>] (<a href="#Contents">Contents</a>)
-
- #define DLB_DECIMAL_DIG 10
- #define DBL_DIG 10
- #define DBL_MANT_DIG
- #define DBL_MAX_10_EXP +37
- #define DBL_MAX_EXP
- #define DBL_MIN_10_EXP -37
- #define DBL_MIN_EXP
- #define DECIMAL_DIG 10
- #define FLT_DECIMAL_DIG 6
- #define FLT_DIG 6
- #define FLT_MANT_DIG
- #define FLT_MAX_10_EXP +37
- #define FLT_MAX_EXP
- #define FLT_MIN_10_EXP -37
- #define FLT_MIN_EXP
- #define FLT_RADIX 2
- #define LDLB_DECIMAL_DIG 10
- #define LDBL_DIG 10
- #define LDBL_MANT_DIG
- #define LDBL_MAX_10_EXP +37
- #define LDBL_MAX_EXP
- #define LDBL_MIN_10_EXP -37
- #define LDBL_MIN_EXP
-5 The values given in the following list shall be replaced by implementation-defined
- constant expressions with values that are greater than or equal to those shown:
- #define DBL_MAX 1E+37
- #define FLT_MAX 1E+37
- #define LDBL_MAX 1E+37
-6 The values given in the following list shall be replaced by implementation-defined
- constant expressions with (positive) values that are less than or equal to those shown:
- #define DBL_EPSILON 1E-9
- #define DBL_MIN 1E-37
- #define FLT_EPSILON 1E-5
- #define FLT_MIN 1E-37
- #define LDBL_EPSILON 1E-9
- #define LDBL_MIN 1E-37
-
-
-
-
-[<a name="#p502" href="p502">page 502</a>] (<a href="#Contents">Contents</a>)
-
-<a name="F" href="#F"><b> Annex F</b></a>
- (normative)
- IEC 60559 floating-point arithmetic
-<a name="F.1" href="#F.1"><b> F.1 Introduction</b></a>
-1 This annex specifies C language support for the IEC 60559 floating-point standard. The
- IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
- microprocessor systems, second edition (IEC 60559:1989), previously designated
- IEC 559:1989 and as IEEE Standard for Binary Floating-Point Arithmetic
- (ANSI/IEEE 754-1985). IEEE Standard for Radix-Independent Floating-Point
- Arithmetic (ANSI/IEEE 854-1987) generalizes the binary standard to remove
- dependencies on radix and word length. IEC 60559 generally refers to the floating-point
- standard, as in IEC 60559 operation, IEC 60559 format, etc. An implementation that
- defines __STDC_IEC_559__ shall conform to the specifications in this annex.339)
- Where a binding between the C language and IEC 60559 is indicated, the
- IEC 60559-specified behavior is adopted by reference, unless stated otherwise. Since
- negative and positive infinity are representable in IEC 60559 formats, all real numbers lie
- within the range of representable values.
-<a name="F.2" href="#F.2"><b> F.2 Types</b></a>
-1 The C floating types match the IEC 60559 formats as follows:
- -- The float type matches the IEC 60559 single format.
- -- The double type matches the IEC 60559 double format.
- -- The long double type matches an IEC 60559 extended format,340) else a
- non-IEC 60559 extended format, else the IEC 60559 double format.
- Any non-IEC 60559 extended format used for the long double type shall have more
- precision than IEC 60559 double and at least the range of IEC 60559 double.341)
-
-
-
-
- 339) Implementations that do not define __STDC_IEC_559__ are not required to conform to these
- specifications.
- 340) ''Extended'' is IEC 60559's double-extended data format. Extended refers to both the common 80-bit
- and quadruple 128-bit IEC 60559 formats.
- 341) A non-IEC 60559 long double type is required to provide infinity and NaNs, as its values include
- all double values.
-
-[<a name="#p503" href="p503">page 503</a>] (<a href="#Contents">Contents</a>)
-
- Recommended practice
-2 The long double type should match an IEC 60559 extended format.
-<a name="F.2.1" href="#F.2.1"><b> F.2.1 Infinities, signed zeros, and NaNs</b></a>
-1 This specification does not define the behavior of signaling NaNs.342) It generally uses
- the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
- functions in <a href="#7.12"><math.h></a> provide designations for IEC 60559 NaNs and infinities.
-<a name="F.3" href="#F.3"><b> F.3 Operators and functions</b></a>
-1 C operators and functions provide IEC 60559 required and recommended facilities as
- listed below.
- -- The +, -, *, and / operators provide the IEC 60559 add, subtract, multiply, and
- divide operations.
- -- The sqrt functions in <a href="#7.12"><math.h></a> provide the IEC 60559 square root operation.
- -- The remainder functions in <a href="#7.12"><math.h></a> provide the IEC 60559 remainder
- operation. The remquo functions in <a href="#7.12"><math.h></a> provide the same operation but
- with additional information.
- -- The rint functions in <a href="#7.12"><math.h></a> provide the IEC 60559 operation that rounds a
- floating-point number to an integer value (in the same precision). The nearbyint
- functions in <a href="#7.12"><math.h></a> provide the nearbyinteger function recommended in the
- Appendix to ANSI/IEEE 854.
- -- The conversions for floating types provide the IEC 60559 conversions between
- floating-point precisions.
- -- The conversions from integer to floating types provide the IEC 60559 conversions
- from integer to floating point.
- -- The conversions from floating to integer types provide IEC 60559-like conversions
- but always round toward zero.
- -- The lrint and llrint functions in <a href="#7.12"><math.h></a> provide the IEC 60559
- conversions, which honor the directed rounding mode, from floating point to the
- long int and long long int integer formats. The lrint and llrint
- functions can be used to implement IEC 60559 conversions from floating to other
- integer formats.
- -- The translation time conversion of floating constants and the strtod, strtof,
- strtold, fprintf, fscanf, and related library functions in <a href="#7.22"><stdlib.h></a>,
-
-
- 342) Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are
- sufficient for closure of the arithmetic.
-
-[<a name="#p504" href="p504">page 504</a>] (<a href="#Contents">Contents</a>)
-
- <a href="#7.21"><stdio.h></a>, and <a href="#7.28"><wchar.h></a> provide IEC 60559 binary-decimal conversions. The
- strtold function in <a href="#7.22"><stdlib.h></a> provides the conv function recommended in the
- Appendix to ANSI/IEEE 854.
--- The relational and equality operators provide IEC 60559 comparisons. IEC 60559
- identifies a need for additional comparison predicates to facilitate writing code that
- accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
- isless, islessequal, islessgreater, and isunordered) in <a href="#7.12"><math.h></a>
- supplement the language operators to address this need. The islessgreater and
- isunordered macros provide respectively a quiet version of the <> predicate and
- the unordered predicate recommended in the Appendix to IEC 60559.
--- The feclearexcept, feraiseexcept, and fetestexcept functions in
- <a href="#7.6"><fenv.h></a> provide the facility to test and alter the IEC 60559 floating-point
- exception status flags. The fegetexceptflag and fesetexceptflag
- functions in <a href="#7.6"><fenv.h></a> provide the facility to save and restore all five status flags at
- one time. These functions are used in conjunction with the type fexcept_t and the
- floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
- FE_UNDERFLOW, FE_OVERFLOW, FE_INVALID) also in <a href="#7.6"><fenv.h></a>.
--- The fegetround and fesetround functions in <a href="#7.6"><fenv.h></a> provide the facility
- to select among the IEC 60559 directed rounding modes represented by the rounding
- direction macros in <a href="#7.6"><fenv.h></a> (FE_TONEAREST, FE_UPWARD, FE_DOWNWARD,
- FE_TOWARDZERO) and the values 0, 1, 2, and 3 of FLT_ROUNDS are the
- IEC 60559 directed rounding modes.
--- The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
- <a href="#7.6"><fenv.h></a> provide a facility to manage the floating-point environment, comprising
- the IEC 60559 status flags and control modes.
--- The copysign functions in <a href="#7.12"><math.h></a> provide the copysign function
- recommended in the Appendix to IEC 60559.
--- The fabs functions in <a href="#7.12"><math.h></a> provide the abs function recommended in the
- Appendix to IEC 60559.
--- The unary minus (-) operator provides the unary minus (-) operation recommended
- in the Appendix to IEC 60559.
--- The scalbn and scalbln functions in <a href="#7.12"><math.h></a> provide the scalb function
- recommended in the Appendix to IEC 60559.
--- The logb functions in <a href="#7.12"><math.h></a> provide the logb function recommended in the
- Appendix to IEC 60559, but following the newer specifications in ANSI/IEEE 854.
--- The nextafter and nexttoward functions in <a href="#7.12"><math.h></a> provide the nextafter
- function recommended in the Appendix to IEC 60559 (but with a minor change to
-
-[<a name="#p505" href="p505">page 505</a>] (<a href="#Contents">Contents</a>)
-
- better handle signed zeros).
- -- The isfinite macro in <a href="#7.12"><math.h></a> provides the finite function recommended in
- the Appendix to IEC 60559.
- -- The isnan macro in <a href="#7.12"><math.h></a> provides the isnan function recommended in the
- Appendix to IEC 60559.
- -- The signbit macro and the fpclassify macro in <a href="#7.12"><math.h></a>, used in
- conjunction with the number classification macros (FP_NAN, FP_INFINITE,
- FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
- function recommended in the Appendix to IEC 60559 (except that the classification
- macros defined in <a href="#7.12.3">7.12.3</a> do not distinguish signaling from quiet NaNs).
-<a name="F.4" href="#F.4"><b> F.4 Floating to integer conversion</b></a>
-1 If the integer type is _Bool, <a href="#6.3.1.2">6.3.1.2</a> applies and no floating-point exceptions are raised
- (even for NaN). Otherwise, if the floating value is infinite or NaN or if the integral part
- of the floating value exceeds the range of the integer type, then the ''invalid'' floating-
- point exception is raised and the resulting value is unspecified. Otherwise, the resulting
- value is determined by <a href="#6.3.1.4">6.3.1.4</a>. Conversion of an integral floating value that does not
- exceed the range of the integer type raises no floating-point exceptions; whether
- conversion of a non-integral floating value raises the ''inexact'' floating-point exception is
- unspecified.343)
-<a name="F.5" href="#F.5"><b> F.5 Binary-decimal conversion</b></a>
-1 Conversion from the widest supported IEC 60559 format to decimal with
- DECIMAL_DIG digits and back is the identity function.344)
-2 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
- particular, conversion between any supported IEC 60559 format and decimal with
- DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
- rounding mode), which assures that conversion from the widest supported IEC 60559
- format to decimal with DECIMAL_DIG digits and back is the identity function.
-
-
-
- 343) ANSI/IEEE 854, but not IEC 60559 (ANSI/IEEE 754), directly specifies that floating-to-integer
- conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those
- cases where it matters, library functions can be used to effect such conversions with or without raising
- the ''inexact'' floating-point exception. See rint, lrint, llrint, and nearbyint in
- <a href="#7.12"><math.h></a>.
- 344) If the minimum-width IEC 60559 extended format (64 bits of precision) is supported,
- DECIMAL_DIG shall be at least 21. If IEC 60559 double (53 bits of precision) is the widest
- IEC 60559 format supported, then DECIMAL_DIG shall be at least 17. (By contrast, LDBL_DIG and
- DBL_DIG are 18 and 15, respectively, for these formats.)
-
-[<a name="#p506" href="p506">page 506</a>] (<a href="#Contents">Contents</a>)
-
-3 Functions such as strtod that convert character sequences to floating types honor the
- rounding direction. Hence, if the rounding direction might be upward or downward, the
- implementation cannot convert a minus-signed sequence by negating the converted
- unsigned sequence.
-<a name="F.6" href="#F.6"><b> F.6 The return statement</b></a>
- If the return expression is evaluated in a floating-point format different from the return
- type, the expression is converted to the return type of the function and the resulting value
- is returned to the caller.
-<a name="F.7" href="#F.7"><b> F.7 Contracted expressions</b></a>
-1 A contracted expression is correctly rounded (once) and treats infinities, NaNs, signed
- zeros, subnormals, and the rounding directions in a manner consistent with the basic
- arithmetic operations covered by IEC 60559.
- Recommended practice
-2 A contracted expression should raise floating-point exceptions in a manner generally
- consistent with the basic arithmetic operations.
-<a name="F.8" href="#F.8"><b> F.8 Floating-point environment</b></a>
-1 The floating-point environment defined in <a href="#7.6"><fenv.h></a> includes the IEC 60559 floating-
- point exception status flags and directed-rounding control modes. It includes also
- IEC 60559 dynamic rounding precision and trap enablement modes, if the
- implementation supports them.345)
-<a name="F.8.1" href="#F.8.1"><b> F.8.1 Environment management</b></a>
-1 IEC 60559 requires that floating-point operations implicitly raise floating-point exception
- status flags, and that rounding control modes can be set explicitly to affect result values of
- floating-point operations. When the state for the FENV_ACCESS pragma (defined in
- <a href="#7.6"><fenv.h></a>) is ''on'', these changes to the floating-point state are treated as side effects
- which respect sequence points.346)
-
-
-
-
- 345) This specification does not require dynamic rounding precision nor trap enablement modes.
- 346) If the state for the FENV_ACCESS pragma is ''off'', the implementation is free to assume the floating-
- point control modes will be the default ones and the floating-point status flags will not be tested,
- which allows certain optimizations (see <a href="#F.9">F.9</a>).
-
-[<a name="#p507" href="p507">page 507</a>] (<a href="#Contents">Contents</a>)
-
-<a name="F.8.2" href="#F.8.2"><b> F.8.2 Translation</b></a>
-1 During translation the IEC 60559 default modes are in effect:
- -- The rounding direction mode is rounding to nearest.
- -- The rounding precision mode (if supported) is set so that results are not shortened.
- -- Trapping or stopping (if supported) is disabled on all floating-point exceptions.
- Recommended practice
-2 The implementation should produce a diagnostic message for each translation-time
- floating-point exception, other than ''inexact'';347) the implementation should then
- proceed with the translation of the program.
-<a name="F.8.3" href="#F.8.3"><b> F.8.3 Execution</b></a>
-1 At program startup the floating-point environment is initialized as prescribed by
- IEC 60559:
- -- All floating-point exception status flags are cleared.
- -- The rounding direction mode is rounding to nearest.
- -- The dynamic rounding precision mode (if supported) is set so that results are not
- shortened.
- -- Trapping or stopping (if supported) is disabled on all floating-point exceptions.
-<a name="F.8.4" href="#F.8.4"><b> F.8.4 Constant expressions</b></a>
-1 An arithmetic constant expression of floating type, other than one in an initializer for an
- object that has static or thread storage duration, is evaluated (as if) during execution; thus,
- it is affected by any operative floating-point control modes and raises floating-point
- exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma
- is ''on'').348)
-2 EXAMPLE
-
-
-
- 347) As floating constants are converted to appropriate internal representations at translation time, their
- conversion is subject to default rounding modes and raises no execution-time floating-point exceptions
- (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example
- strtod, provide execution-time conversion of numeric strings.
- 348) Where the state for the FENV_ACCESS pragma is ''on'', results of inexact expressions like <a href="#1.0">1.0</a>/3.0
- are affected by rounding modes set at execution time, and expressions such as 0.0/0.0 and
- <a href="#1.0">1.0</a>/0.0 generate execution-time floating-point exceptions. The programmer can achieve the
- efficiency of translation-time evaluation through static initialization, such as
- const static double one_third = <a href="#1.0">1.0</a>/3.0;
-
-
-[<a name="#p508" href="p508">page 508</a>] (<a href="#Contents">Contents</a>)
-
- #include <a href="#7.6"><fenv.h></a>
- #pragma STDC FENV_ACCESS ON
- void f(void)
- {
- float w[] = { 0.0/0.0 }; // raises an exception
- static float x = 0.0/0.0; // does not raise an exception
- float y = 0.0/0.0; // raises an exception
- double z = 0.0/0.0; // raises an exception
- /* ... */
- }
-3 For the static initialization, the division is done at translation time, raising no (execution-time) floating-
- point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at
- execution time.
-
-<a name="F.8.5" href="#F.8.5"><b> F.8.5 Initialization</b></a>
-1 All computation for automatic initialization is done (as if) at execution time; thus, it is
- affected by any operative modes and raises floating-point exceptions as required by
- IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation
- for initialization of objects that have static or thread storage duration is done (as if) at
- translation time.
-2 EXAMPLE
- #include <a href="#7.6"><fenv.h></a>
- #pragma STDC FENV_ACCESS ON
- void f(void)
- {
- float u[] = { 1.1e75 }; // raises exceptions
- static float v = 1.1e75; // does not raise exceptions
- float w = 1.1e75; // raises exceptions
- double x = 1.1e75; // may raise exceptions
- float y = 1.1e75f; // may raise exceptions
- long double z = 1.1e75; // does not raise exceptions
- /* ... */
- }
-3 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is
- done at translation time. The automatic initialization of u and w require an execution-time conversion to
- float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations
- of x and y entail execution-time conversion; however, in some expression evaluation methods, the
- conversions is not to a narrower format, in which case no floating-point exception is raised.349) The
- automatic initialization of z entails execution-time conversion, but not to a narrower format, so no floating-
- point exception is raised. Note that the conversions of the floating constants 1.1e75 and 1.1e75f to
-
-
-
- 349) Use of float_t and double_t variables increases the likelihood of translation-time computation.
- For example, the automatic initialization
- double_t x = 1.1e75;
- could be done at translation time, regardless of the expression evaluation method.
-
-[<a name="#p509" href="p509">page 509</a>] (<a href="#Contents">Contents</a>)
-
- their internal representations occur at translation time in all cases.
-
-<a name="F.8.6" href="#F.8.6"><b> F.8.6 Changing the environment</b></a>
-1 Operations defined in <a href="#6.5">6.5</a> and functions and macros defined for the standard libraries
- change floating-point status flags and control modes just as indicated by their
- specifications (including conformance to IEC 60559). They do not change flags or modes
- (so as to be detectable by the user) in any other cases.
-2 If the argument to the feraiseexcept function in <a href="#7.6"><fenv.h></a> represents IEC 60559
- valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
- ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
- before ''inexact''.
-<a name="F.9" href="#F.9"><b> F.9 Optimization</b></a>
-1 This section identifies code transformations that might subvert IEC 60559-specified
- behavior, and others that do not.
-<a name="F.9.1" href="#F.9.1"><b> F.9.1 Global transformations</b></a>
-1 Floating-point arithmetic operations and external function calls may entail side effects
- which optimization shall honor, at least where the state of the FENV_ACCESS pragma is
- ''on''. The flags and modes in the floating-point environment may be regarded as global
- variables; floating-point operations (+, *, etc.) implicitly read the modes and write the
- flags.
-2 Concern about side effects may inhibit code motion and removal of seemingly useless
- code. For example, in
- #include <a href="#7.6"><fenv.h></a>
- #pragma STDC FENV_ACCESS ON
- void f(double x)
- {
- /* ... */
- for (i = 0; i < n; i++) x + 1;
- /* ... */
- }
- x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
- body might not execute (maybe 0 >= n), x + 1 cannot be moved out of the loop. (Of
- course these optimizations are valid if the implementation can rule out the nettlesome
- cases.)
-3 This specification does not require support for trap handlers that maintain information
- about the order or count of floating-point exceptions. Therefore, between function calls,
- floating-point exceptions need not be precise: the actual order and number of occurrences
- of floating-point exceptions (> 1) may vary from what the source code expresses. Thus,
-[<a name="#p510" href="p510">page 510</a>] (<a href="#Contents">Contents</a>)
-
- the preceding loop could be treated as
- if (0 < n) x + 1;
-<a name="F.9.2" href="#F.9.2"><b> F.9.2 Expression transformations</b></a>
-1 x/2 (<->) x x 0.5 Although similar transformations involving inexact constants
- generally do not yield numerically equivalent expressions, if the
- constants are exact then such transformations can be made on
- IEC 60559 machines and others that round perfectly.
- 1 x x and x/1 (->) x The expressions 1 x x, x/1, and x are equivalent (on IEC 60559
- machines, among others).350)
- x/x (->) <a href="#1.0">1.0</a> The expressions x/x and <a href="#1.0">1.0</a> are not equivalent if x can be zero,
- infinite, or NaN.
- x - y (<->) x + (-y) The expressions x - y, x + (-y), and (-y) + x are equivalent (on
- IEC 60559 machines, among others).
- x - y (<->) -(y - x) The expressions x - y and -(y - x) are not equivalent because 1 - 1
- is +0 but -(1 - 1) is -0 (in the default rounding direction).351)
- x - x (->) 0.0 The expressions x - x and 0.0 are not equivalent if x is a NaN or
- infinite.
- 0 x x (->) 0.0 The expressions 0 x x and 0.0 are not equivalent if x is a NaN,
- infinite, or -0.
- x+0(->) x The expressions x + 0 and x are not equivalent if x is -0, because
- (-0) + (+0) yields +0 (in the default rounding direction), not -0.
- x-0(->) x (+0) - (+0) yields -0 when rounding is downward (toward -(inf)), but
- +0 otherwise, and (-0) - (+0) always yields -0; so, if the state of the
- FENV_ACCESS pragma is ''off'', promising default rounding, then
- the implementation can replace x - 0 by x, even if x might be zero.
- -x (<->) 0 - x The expressions -x and 0 - x are not equivalent if x is +0, because
- -(+0) yields -0, but 0 - (+0) yields +0 (unless rounding is
- downward).
-
- 350) Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
- other transformations that remove arithmetic operators.
- 351) IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
- Examples include:
- 1/(1/ (+-) (inf)) is (+-) (inf)
- and
- conj(csqrt(z)) is csqrt(conj(z)),
- for complex z.
-
-[<a name="#p511" href="p511">page 511</a>] (<a href="#Contents">Contents</a>)
-
-<a name="F.9.3" href="#F.9.3"><b> F.9.3 Relational operators</b></a>
-1 x != x (->) false The expression x != x is true if x is a NaN.
- x = x (->) true The expression x = x is false if x is a NaN.
- x < y (->) isless(x,y) (and similarly for <=, >, >=) Though numerically equal, these
- expressions are not equivalent because of side effects when x or y is a
- NaN and the state of the FENV_ACCESS pragma is ''on''. This
- transformation, which would be desirable if extra code were required
- to cause the ''invalid'' floating-point exception for unordered cases,
- could be performed provided the state of the FENV_ACCESS pragma
- is ''off''.
- The sense of relational operators shall be maintained. This includes handling unordered
- cases as expressed by the source code.
-2 EXAMPLE
- // calls g and raises ''invalid'' if a and b are unordered
- if (a < b)
- f();
- else
- g();
- is not equivalent to
- // calls f and raises ''invalid'' if a and b are unordered
- if (a >= b)
- g();
- else
- f();
- nor to
- // calls f without raising ''invalid'' if a and b are unordered
- if (isgreaterequal(a,b))
- g();
- else
- f();
- nor, unless the state of the FENV_ACCESS pragma is ''off'', to
- // calls g without raising ''invalid'' if a and b are unordered
- if (isless(a,b))
- f();
- else
- g();
- but is equivalent to
-
-
-
-
-[<a name="#p512" href="p512">page 512</a>] (<a href="#Contents">Contents</a>)
-
- if (!(a < b))
- g();
- else
- f();
-
-<a name="F.9.4" href="#F.9.4"><b> F.9.4 Constant arithmetic</b></a>
-1 The implementation shall honor floating-point exceptions raised by execution-time
- constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See <a href="#F.8.4">F.8.4</a>
- and <a href="#F.8.5">F.8.5</a>.) An operation on constants that raises no floating-point exception can be
- folded during translation, except, if the state of the FENV_ACCESS pragma is ''on'', a
- further check is required to assure that changing the rounding direction to downward does
- not alter the sign of the result,352) and implementations that support dynamic rounding
- precision modes shall assure further that the result of the operation raises no floating-
- point exception when converted to the semantic type of the operation.
-<a name="F.10" href="#F.10"><b> F.10 Mathematics <math.h></b></a>
-1 This subclause contains specifications of <a href="#7.12"><math.h></a> facilities that are particularly suited
- for IEC 60559 implementations.
-2 The Standard C macro HUGE_VAL and its float and long double analogs,
- HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive
- infinities.
-3 Special cases for functions in <a href="#7.12"><math.h></a> are covered directly or indirectly by
- IEC 60559. The functions that IEC 60559 specifies directly are identified in <a href="#F.3">F.3</a>. The
- other functions in <a href="#7.12"><math.h></a> treat infinities, NaNs, signed zeros, subnormals, and
- (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags
- in a manner consistent with the basic arithmetic operations covered by IEC 60559.
-4 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
- nonzero value.
-5 The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in
- subsequent subclauses of this annex.
-6 The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of
- rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value
- whose magnitude is too large.
-7 The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially
- subnormal or zero) and suffers loss of accuracy.353)
-
-
- 352) 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
- 353) IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on
- when the floating-point exception is raised.
-
-[<a name="#p513" href="p513">page 513</a>] (<a href="#Contents">Contents</a>)
-
-8 Whether or when library functions raise the ''inexact'' floating-point exception is
- unspecified, unless explicitly specified otherwise.
-9 Whether or when library functions raise an undeserved ''underflow'' floating-point
- exception is unspecified.354) Otherwise, as implied by <a href="#F.8.6">F.8.6</a>, the <a href="#7.12"><math.h></a> functions do
- not raise spurious floating-point exceptions (detectable by the user), other than the
- ''inexact'' floating-point exception.
-10 Whether the functions honor the rounding direction mode is implementation-defined,
- unless explicitly specified otherwise.
-11 Functions with a NaN argument return a NaN result and raise no floating-point exception,
- except where stated otherwise.
-12 The specifications in the following subclauses append to the definitions in <a href="#7.12"><math.h></a>.
- For families of functions, the specifications apply to all of the functions even though only
- the principal function is shown. Unless otherwise specified, where the symbol ''(+-)''
- occurs in both an argument and the result, the result has the same sign as the argument.
- Recommended practice
-13 If a function with one or more NaN arguments returns a NaN result, the result should be
- the same as one of the NaN arguments (after possible type conversion), except perhaps
- for the sign.
-<a name="F.10.1" href="#F.10.1"><b> F.10.1 Trigonometric functions</b></a>
-<a name="F.10.1.1" href="#F.10.1.1"><b> F.10.1.1 The acos functions</b></a>
-1 -- acos(1) returns +0.
- -- acos(x) returns a NaN and raises the ''invalid'' floating-point exception for
- | x | > 1.
-<a name="F.10.1.2" href="#F.10.1.2"><b> F.10.1.2 The asin functions</b></a>
-1 -- asin((+-)0) returns (+-)0.
- -- asin(x) returns a NaN and raises the ''invalid'' floating-point exception for
- | x | > 1.
-
-
-
-
- 354) It is intended that undeserved ''underflow'' and ''inexact'' floating-point exceptions are raised only if
- avoiding them would be too costly.
-
-[<a name="#p514" href="p514">page 514</a>] (<a href="#Contents">Contents</a>)
-
-<a name="F.10.1.3" href="#F.10.1.3"><b> F.10.1.3 The atan functions</b></a>
-1 -- atan((+-)0) returns (+-)0.
- -- atan((+-)(inf)) returns (+-)pi /2.
-<a name="F.10.1.4" href="#F.10.1.4"><b> F.10.1.4 The atan2 functions</b></a>
-1 -- atan2((+-)0, -0) returns (+-)pi .355)
- -- atan2((+-)0, +0) returns (+-)0.
- -- atan2((+-)0, x) returns (+-)pi for x < 0.
- -- atan2((+-)0, x) returns (+-)0 for x > 0.
- -- atan2(y, (+-)0) returns -pi /2 for y < 0.
- -- atan2(y, (+-)0) returns pi /2 for y > 0.
- -- atan2((+-)y, -(inf)) returns (+-)pi for finite y > 0.
- -- atan2((+-)y, +(inf)) returns (+-)0 for finite y > 0.
- -- atan2((+-)(inf), x) returns (+-)pi /2 for finite x.
- -- atan2((+-)(inf), -(inf)) returns (+-)3pi /4.
- -- atan2((+-)(inf), +(inf)) returns (+-)pi /4.
-<a name="F.10.1.5" href="#F.10.1.5"><b> F.10.1.5 The cos functions</b></a>
-1 -- cos((+-)0) returns 1.
- -- cos((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
-<a name="F.10.1.6" href="#F.10.1.6"><b> F.10.1.6 The sin functions</b></a>
-1 -- sin((+-)0) returns (+-)0.
- -- sin((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
-<a name="F.10.1.7" href="#F.10.1.7"><b> F.10.1.7 The tan functions</b></a>
-1 -- tan((+-)0) returns (+-)0.
- -- tan((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
-
-
-
-
- 355) atan2(0, 0) does not raise the ''invalid'' floating-point exception, nor does atan2( y , 0) raise
- the ''divide-by-zero'' floating-point exception.
-
-[<a name="#p515" href="p515">page 515</a>] (<a href="#Contents">Contents</a>)
-
-<a name="F.10.2" href="#F.10.2"><b> F.10.2 Hyperbolic functions</b></a>
-<a name="F.10.2.1" href="#F.10.2.1"><b> F.10.2.1 The acosh functions</b></a>
-1 -- acosh(1) returns +0.
- -- acosh(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 1.
- -- acosh(+(inf)) returns +(inf).
-<a name="F.10.2.2" href="#F.10.2.2"><b> F.10.2.2 The asinh functions</b></a>
-1 -- asinh((+-)0) returns (+-)0.
- -- asinh((+-)(inf)) returns (+-)(inf).
-<a name="F.10.2.3" href="#F.10.2.3"><b> F.10.2.3 The atanh functions</b></a>
-1 -- atanh((+-)0) returns (+-)0.
- -- atanh((+-)1) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
- -- atanh(x) returns a NaN and raises the ''invalid'' floating-point exception for
- | x | > 1.
-<a name="F.10.2.4" href="#F.10.2.4"><b> F.10.2.4 The cosh functions</b></a>
-1 -- cosh((+-)0) returns 1.
- -- cosh((+-)(inf)) returns +(inf).
-<a name="F.10.2.5" href="#F.10.2.5"><b> F.10.2.5 The sinh functions</b></a>
-1 -- sinh((+-)0) returns (+-)0.
- -- sinh((+-)(inf)) returns (+-)(inf).
-<a name="F.10.2.6" href="#F.10.2.6"><b> F.10.2.6 The tanh functions</b></a>
-1 -- tanh((+-)0) returns (+-)0.
- -- tanh((+-)(inf)) returns (+-)1.
-<a name="F.10.3" href="#F.10.3"><b> F.10.3 Exponential and logarithmic functions</b></a>
-<a name="F.10.3.1" href="#F.10.3.1"><b> F.10.3.1 The exp functions</b></a>
-1 -- exp((+-)0) returns 1.
- -- exp(-(inf)) returns +0.
- -- exp(+(inf)) returns +(inf).
-
-
-
-
-[<a name="#p516" href="p516">page 516</a>] (<a href="#Contents">Contents</a>)
-
-<a name="F.10.3.2" href="#F.10.3.2"><b> F.10.3.2 The exp2 functions</b></a>
-1 -- exp2((+-)0) returns 1.
- -- exp2(-(inf)) returns +0.
- -- exp2(+(inf)) returns +(inf).
-<a name="F.10.3.3" href="#F.10.3.3"><b> F.10.3.3 The expm1 functions</b></a>
-1 -- expm1((+-)0) returns (+-)0.
- -- expm1(-(inf)) returns -1.
- -- expm1(+(inf)) returns +(inf).
-<a name="F.10.3.4" href="#F.10.3.4"><b> F.10.3.4 The frexp functions</b></a>
-1 -- frexp((+-)0, exp) returns (+-)0, and stores 0 in the object pointed to by exp.
- -- frexp((+-)(inf), exp) returns (+-)(inf), and stores an unspecified value in the object
- pointed to by exp.
- -- frexp(NaN, exp) stores an unspecified value in the object pointed to by exp
- (and returns a NaN).
-2 frexp raises no floating-point exceptions.
-3 When the radix of the argument is a power of 2, the returned value is exact and is
- independent of the current rounding direction mode.
-4 On a binary system, the body of the frexp function might be
- {
- *exp = (value == 0) ? 0 : (int)(1 + logb(value));
- return scalbn(value, -(*exp));
- }
-<a name="F.10.3.5" href="#F.10.3.5"><b> F.10.3.5 The ilogb functions</b></a>
-1 When the correct result is representable in the range of the return type, the returned value
- is exact and is independent of the current rounding direction mode.
-2 If the correct result is outside the range of the return type, the numeric result is
- unspecified and the ''invalid'' floating-point exception is raised.
-
-
-
-
-[<a name="#p517" href="p517">page 517</a>] (<a href="#Contents">Contents</a>)
-
-<a name="F.10.3.6" href="#F.10.3.6"><b> F.10.3.6 The ldexp functions</b></a>
-1 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
-<a name="F.10.3.7" href="#F.10.3.7"><b> F.10.3.7 The log functions</b></a>
-1 -- log((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
- -- log(1) returns +0.
- -- log(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
- -- log(+(inf)) returns +(inf).
-<a name="F.10.3.8" href="#F.10.3.8"><b> F.10.3.8 The log10 functions</b></a>
-1 -- log10((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
- -- log10(1) returns +0.
- -- log10(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
- -- log10(+(inf)) returns +(inf).
-<a name="F.10.3.9" href="#F.10.3.9"><b> F.10.3.9 The log1p functions</b></a>
-1 -- log1p((+-)0) returns (+-)0.
- -- log1p(-1) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
- -- log1p(x) returns a NaN and raises the ''invalid'' floating-point exception for
- x < -1.
- -- log1p(+(inf)) returns +(inf).
-<a name="F.10.3.10" href="#F.10.3.10"><b> F.10.3.10 The log2 functions</b></a>
-1 -- log2((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
- -- log2(1) returns +0.
- -- log2(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
- -- log2(+(inf)) returns +(inf).
-<a name="F.10.3.11" href="#F.10.3.11"><b> F.10.3.11 The logb functions</b></a>
-1 -- logb((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
- -- logb((+-)(inf)) returns +(inf).
-2 The returned value is exact and is independent of the current rounding direction mode.
-
-
-
-
-[<a name="#p518" href="p518">page 518</a>] (<a href="#Contents">Contents</a>)
-
-<a name="F.10.3.12" href="#F.10.3.12"><b> F.10.3.12 The modf functions</b></a>
-1 -- modf((+-)x, iptr) returns a result with the same sign as x.
- -- modf((+-)(inf), iptr) returns (+-)0 and stores (+-)(inf) in the object pointed to by iptr.
- -- modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
- NaN).
-2 The returned values are exact and are independent of the current rounding direction
- mode.
-3 modf behaves as though implemented by
- #include <a href="#7.12"><math.h></a>
- #include <a href="#7.6"><fenv.h></a>
- #pragma STDC FENV_ACCESS ON
- double modf(double value, double *iptr)
- {
- int save_round = fegetround();
- fesetround(FE_TOWARDZERO);
- *iptr = nearbyint(value);
- fesetround(save_round);
- return copysign(
- isinf(value) ? 0.0 :
- value - (*iptr), value);
- }
-<a name="F.10.3.13" href="#F.10.3.13"><b> F.10.3.13 The scalbn and scalbln functions</b></a>
-1 -- scalbn((+-)0, n) returns (+-)0.
- -- scalbn(x, 0) returns x.
- -- scalbn((+-)(inf), n) returns (+-)(inf).
-<a name="F.10.4" href="#F.10.4"><b> F.10.4 Power and absolute value functions</b></a>
-<a name="F.10.4.1" href="#F.10.4.1"><b> F.10.4.1 The cbrt functions</b></a>
-1 -- cbrt((+-)0) returns (+-)0.
- -- cbrt((+-)(inf)) returns (+-)(inf).
-
-
-
-
-[<a name="#p519" href="p519">page 519</a>] (<a href="#Contents">Contents</a>)
-
-<a name="F.10.4.2" href="#F.10.4.2"><b> F.10.4.2 The fabs functions</b></a>
-1 -- fabs((+-)0) returns +0.
- -- fabs((+-)(inf)) returns +(inf).
-2 The returned value is exact and is independent of the current rounding direction mode.
-<a name="F.10.4.3" href="#F.10.4.3"><b> F.10.4.3 The hypot functions</b></a>
-1 -- hypot(x, y), hypot(y, x), and hypot(x, -y) are equivalent.
- -- hypot(x, (+-)0) is equivalent to fabs(x).
- -- hypot((+-)(inf), y) returns +(inf), even if y is a NaN.
-<a name="F.10.4.4" href="#F.10.4.4"><b> F.10.4.4 The pow functions</b></a>
-1 -- pow((+-)0, y) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception
- for y an odd integer < 0.
- -- pow((+-)0, y) returns +(inf) and raises the ''divide-by-zero'' floating-point exception
- for y < 0 and not an odd integer.
- -- pow((+-)0, y) returns (+-)0 for y an odd integer > 0.
- -- pow((+-)0, y) returns +0 for y > 0 and not an odd integer.
- -- pow(-1, (+-)(inf)) returns 1.
- -- pow(+1, y) returns 1 for any y, even a NaN.
- -- pow(x, (+-)0) returns 1 for any x, even a NaN.
- -- pow(x, y) returns a NaN and raises the ''invalid'' floating-point exception for
- finite x < 0 and finite non-integer y.
- -- pow(x, -(inf)) returns +(inf) for | x | < 1.
- -- pow(x, -(inf)) returns +0 for | x | > 1.
- -- pow(x, +(inf)) returns +0 for | x | < 1.
- -- pow(x, +(inf)) returns +(inf) for | x | > 1.
- -- pow(-(inf), y) returns -0 for y an odd integer < 0.
- -- pow(-(inf), y) returns +0 for y < 0 and not an odd integer.
- -- pow(-(inf), y) returns -(inf) for y an odd integer > 0.
- -- pow(-(inf), y) returns +(inf) for y > 0 and not an odd integer.
- -- pow(+(inf), y) returns +0 for y < 0.
- -- pow(+(inf), y) returns +(inf) for y > 0.
-
-
-[<a name="#p520" href="p520">page 520</a>] (<a href="#Contents">Contents</a>)
-
-<a name="F.10.4.5" href="#F.10.4.5"><b> F.10.4.5 The sqrt functions</b></a>
-1 sqrt is fully specified as a basic arithmetic operation in IEC 60559. The returned value
- is dependent on the current rounding direction mode.
-<a name="F.10.5" href="#F.10.5"><b> F.10.5 Error and gamma functions</b></a>
-<a name="F.10.5.1" href="#F.10.5.1"><b> F.10.5.1 The erf functions</b></a>
-1 -- erf((+-)0) returns (+-)0.
- -- erf((+-)(inf)) returns (+-)1.
-<a name="F.10.5.2" href="#F.10.5.2"><b> F.10.5.2 The erfc functions</b></a>
-1 -- erfc(-(inf)) returns 2.
- -- erfc(+(inf)) returns +0.
-<a name="F.10.5.3" href="#F.10.5.3"><b> F.10.5.3 The lgamma functions</b></a>
-1 -- lgamma(1) returns +0.
- -- lgamma(2) returns +0.
- -- lgamma(x) returns +(inf) and raises the ''divide-by-zero'' floating-point exception for
- x a negative integer or zero.
- -- lgamma(-(inf)) returns +(inf).
- -- lgamma(+(inf)) returns +(inf).
-<a name="F.10.5.4" href="#F.10.5.4"><b> F.10.5.4 The tgamma functions</b></a>
-1 -- tgamma((+-)0) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
- -- tgamma(x) returns a NaN and raises the ''invalid'' floating-point exception for x a
- negative integer.
- -- tgamma(-(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
- -- tgamma(+(inf)) returns +(inf).
-<a name="F.10.6" href="#F.10.6"><b> F.10.6 Nearest integer functions</b></a>
-<a name="F.10.6.1" href="#F.10.6.1"><b> F.10.6.1 The ceil functions</b></a>
-1 -- ceil((+-)0) returns (+-)0.
- -- ceil((+-)(inf)) returns (+-)(inf).
-2 The returned value is exact and is independent of the current rounding direction mode.
-3 The double version of ceil behaves as though implemented by
-
-
-
-[<a name="#p521" href="p521">page 521</a>] (<a href="#Contents">Contents</a>)
-
- #include <a href="#7.12"><math.h></a>
- #include <a href="#7.6"><fenv.h></a>
- #pragma STDC FENV_ACCESS ON
- double ceil(double x)
- {
- double result;
- int save_round = fegetround();
- fesetround(FE_UPWARD);
- result = rint(x); // or nearbyint instead of rint
- fesetround(save_round);
- return result;
- }
-<a name="F.10.6.2" href="#F.10.6.2"><b> F.10.6.2 The floor functions</b></a>
-1 -- floor((+-)0) returns (+-)0.
- -- floor((+-)(inf)) returns (+-)(inf).
-2 The returned value is exact and is independent of the current rounding direction mode.
-3 See the sample implementation for ceil in <a href="#F.10.6.1">F.10.6.1</a>.
-<a name="F.10.6.3" href="#F.10.6.3"><b> F.10.6.3 The nearbyint functions</b></a>
-1 The nearbyint functions use IEC 60559 rounding according to the current rounding
- direction. They do not raise the ''inexact'' floating-point exception if the result differs in
- value from the argument.
- -- nearbyint((+-)0) returns (+-)0 (for all rounding directions).
- -- nearbyint((+-)(inf)) returns (+-)(inf) (for all rounding directions).
-<a name="F.10.6.4" href="#F.10.6.4"><b> F.10.6.4 The rint functions</b></a>
-1 The rint functions differ from the nearbyint functions only in that they do raise the
- ''inexact'' floating-point exception if the result differs in value from the argument.
-<a name="F.10.6.5" href="#F.10.6.5"><b> F.10.6.5 The lrint and llrint functions</b></a>
-1 The lrint and llrint functions provide floating-to-integer conversion as prescribed
- by IEC 60559. They round according to the current rounding direction. If the rounded
- value is outside the range of the return type, the numeric result is unspecified and the
- ''invalid'' floating-point exception is raised. When they raise no other floating-point
- exception and the result differs from the argument, they raise the ''inexact'' floating-point
- exception.
-
-
-
-
-[<a name="#p522" href="p522">page 522</a>] (<a href="#Contents">Contents</a>)
-
-<a name="F.10.6.6" href="#F.10.6.6"><b> F.10.6.6 The round functions</b></a>
-1 -- round((+-)0) returns (+-)0.
- -- round((+-)(inf)) returns (+-)(inf).
-2 The double version of round behaves as though implemented by
- #include <a href="#7.12"><math.h></a>
- #include <a href="#7.6"><fenv.h></a>
- #pragma STDC FENV_ACCESS ON
- double round(double x)
- {
- double result;
- fenv_t save_env;
- feholdexcept(&save_env);
- result = rint(x);
- if (fetestexcept(FE_INEXACT)) {
- fesetround(FE_TOWARDZERO);
- result = rint(copysign(0.5 + fabs(x), x));
- }
- feupdateenv(&save_env);
- return result;
- }
- The round functions may, but are not required to, raise the ''inexact'' floating-point
- exception for non-integer numeric arguments, as this implementation does.
-<a name="F.10.6.7" href="#F.10.6.7"><b> F.10.6.7 The lround and llround functions</b></a>
-1 The lround and llround functions differ from the lrint and llrint functions
- with the default rounding direction just in that the lround and llround functions
- round halfway cases away from zero and need not raise the ''inexact'' floating-point
- exception for non-integer arguments that round to within the range of the return type.
-<a name="F.10.6.8" href="#F.10.6.8"><b> F.10.6.8 The trunc functions</b></a>
-1 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
- rounding direction). The returned value is exact.
- -- trunc((+-)0) returns (+-)0.
- -- trunc((+-)(inf)) returns (+-)(inf).
-
-
-
-
-[<a name="#p523" href="p523">page 523</a>] (<a href="#Contents">Contents</a>)
-
-<a name="F.10.7" href="#F.10.7"><b> F.10.7 Remainder functions</b></a>
-<a name="F.10.7.1" href="#F.10.7.1"><b> F.10.7.1 The fmod functions</b></a>
-1 -- fmod((+-)0, y) returns (+-)0 for y not zero.
- -- fmod(x, y) returns a NaN and raises the ''invalid'' floating-point exception for x
- infinite or y zero.
- -- fmod(x, (+-)(inf)) returns x for x not infinite.
-2 When subnormal results are supported, the returned value is exact and is independent of
- the current rounding direction mode.
-3 The double version of fmod behaves as though implemented by
- #include <a href="#7.12"><math.h></a>
- #include <a href="#7.6"><fenv.h></a>
- #pragma STDC FENV_ACCESS ON
- double fmod(double x, double y)
- {
- double result;
- result = remainder(fabs(x), (y = fabs(y)));
- if (signbit(result)) result += y;
- return copysign(result, x);
- }
-<a name="F.10.7.2" href="#F.10.7.2"><b> F.10.7.2 The remainder functions</b></a>
-1 The remainder functions are fully specified as a basic arithmetic operation in
- IEC 60559.
-2 When subnormal results are supported, the returned value is exact and is independent of
- the current rounding direction mode.
-<a name="F.10.7.3" href="#F.10.7.3"><b> F.10.7.3 The remquo functions</b></a>
-1 The remquo functions follow the specifications for the remainder functions. They
- have no further specifications special to IEC 60559 implementations.
-2 When subnormal results are supported, the returned value is exact and is independent of
- the current rounding direction mode.
-
-
-
-
-[<a name="#p524" href="p524">page 524</a>] (<a href="#Contents">Contents</a>)
-
-<a name="F.10.8" href="#F.10.8"><b> F.10.8 Manipulation functions</b></a>
-<a name="F.10.8.1" href="#F.10.8.1"><b> F.10.8.1 The copysign functions</b></a>
-1 copysign is specified in the Appendix to IEC 60559.
-2 The returned value is exact and is independent of the current rounding direction mode.
-<a name="F.10.8.2" href="#F.10.8.2"><b> F.10.8.2 The nan functions</b></a>
-1 All IEC 60559 implementations support quiet NaNs, in all floating formats.
-2 The returned value is exact and is independent of the current rounding direction mode.
-<a name="F.10.8.3" href="#F.10.8.3"><b> F.10.8.3 The nextafter functions</b></a>
-1 -- nextafter(x, y) raises the ''overflow'' and ''inexact'' floating-point exceptions
- for x finite and the function value infinite.
- -- nextafter(x, y) raises the ''underflow'' and ''inexact'' floating-point
- exceptions for the function value subnormal or zero and x != y.
-2 Even though underflow or overflow can occur, the returned value is independent of the
- current rounding direction mode.
-<a name="F.10.8.4" href="#F.10.8.4"><b> F.10.8.4 The nexttoward functions</b></a>
-1 No additional requirements beyond those on nextafter.
-2 Even though underflow or overflow can occur, the returned value is independent of the
- current rounding direction mode.
-<a name="F.10.9" href="#F.10.9"><b> F.10.9 Maximum, minimum, and positive difference functions</b></a>
-<a name="F.10.9.1" href="#F.10.9.1"><b> F.10.9.1 The fdim functions</b></a>
-1 No additional requirements.
-<a name="F.10.9.2" href="#F.10.9.2"><b> F.10.9.2 The fmax functions</b></a>
-1 If just one argument is a NaN, the fmax functions return the other argument (if both
- arguments are NaNs, the functions return a NaN).
-2 The returned value is exact and is independent of the current rounding direction mode.
-3 The body of the fmax function might be356)
- { return (isgreaterequal(x, y) ||
- isnan(y)) ? x : y; }
-
-
-
- 356) Ideally, fmax would be sensitive to the sign of zero, for example fmax(-0.0, +0.0) would
- return +0; however, implementation in software might be impractical.
-
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-
-<a name="F.10.9.3" href="#F.10.9.3"><b> F.10.9.3 The fmin functions</b></a>
-1 The fmin functions are analogous to the fmax functions (see <a href="#F.10.9.2">F.10.9.2</a>).
-2 The returned value is exact and is independent of the current rounding direction mode.
-<a name="F.10.10" href="#F.10.10"><b> F.10.10 Floating multiply-add</b></a>
-<a name="F.10.10.1" href="#F.10.10.1"><b> F.10.10.1 The fma functions</b></a>
-1 -- fma(x, y, z) computes xy + z, correctly rounded once.
- -- fma(x, y, z) returns a NaN and optionally raises the ''invalid'' floating-point
- exception if one of x and y is infinite, the other is zero, and z is a NaN.
- -- fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if
- one of x and y is infinite, the other is zero, and z is not a NaN.
- -- fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if x
- times y is an exact infinity and z is also an infinity but with the opposite sign.
-<a name="F.10.11" href="#F.10.11"><b> F.10.11 Comparison macros</b></a>
-1 Relational operators and their corresponding comparison macros (<a href="#7.12.14">7.12.14</a>) produce
- equivalent result values, even if argument values are represented in wider formats. Thus,
- comparison macro arguments represented in formats wider than their semantic types are
- not converted to the semantic types, unless the wide evaluation method converts operands
- of relational operators to their semantic types. The standard wide evaluation methods
- characterized by FLT_EVAL_METHOD equal to 1 or 2 (<a href="#5.2.4.2.2">5.2.4.2.2</a>), do not convert
- operands of relational operators to their semantic types.
-
-
-
-
-[<a name="#p526" href="p526">page 526</a>] (<a href="#Contents">Contents</a>)
-
-<a name="G" href="#G"><b> Annex G</b></a>
- (informative)
- IEC 60559-compatible complex arithmetic
-<a name="G.1" href="#G.1"><b> G.1 Introduction</b></a>
-1 This annex supplements <a href="#F">annex F</a> to specify complex arithmetic for compatibility with
- IEC 60559 real floating-point arithmetic. Although these specifications have been
- carefully designed, there is little existing practice to validate the design decisions.
- Therefore, these specifications are not normative, but should be viewed more as
- recommended practice. An implementation that defines
- __STDC_IEC_559_COMPLEX__ should conform to the specifications in this annex.
-<a name="G.2" href="#G.2"><b> G.2 Types</b></a>
-1 There is a new keyword _Imaginary, which is used to specify imaginary types. It is
- used as a type specifier within declaration specifiers in the same way as _Complex is
- (thus, _Imaginary float is a valid type name).
-2 There are three imaginary types, designated as float _Imaginary, double
- _Imaginary, and long double _Imaginary. The imaginary types (along with
- the real floating and complex types) are floating types.
-3 For imaginary types, the corresponding real type is given by deleting the keyword
- _Imaginary from the type name.
-4 Each imaginary type has the same representation and alignment requirements as the
- corresponding real type. The value of an object of imaginary type is the value of the real
- representation times the imaginary unit.
-5 The imaginary type domain comprises the imaginary types.
-<a name="G.3" href="#G.3"><b> G.3 Conventions</b></a>
-1 A complex or imaginary value with at least one infinite part is regarded as an infinity
- (even if its other part is a NaN). A complex or imaginary value is a finite number if each
- of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
- a zero if each of its parts is a zero.
-
-
-
-
-[<a name="#p527" href="p527">page 527</a>] (<a href="#Contents">Contents</a>)
-
-<a name="G.4" href="#G.4"><b> G.4 Conversions</b></a>
-<a name="G.4.1" href="#G.4.1"><b> G.4.1 Imaginary types</b></a>
-1 Conversions among imaginary types follow rules analogous to those for real floating
- types.
-<a name="G.4.2" href="#G.4.2"><b> G.4.2 Real and imaginary</b></a>
-1 When a value of imaginary type is converted to a real type other than _Bool,357) the
- result is a positive zero.
-2 When a value of real type is converted to an imaginary type, the result is a positive
- imaginary zero.
-<a name="G.4.3" href="#G.4.3"><b> G.4.3 Imaginary and complex</b></a>
-1 When a value of imaginary type is converted to a complex type, the real part of the
- complex result value is a positive zero and the imaginary part of the complex result value
- is determined by the conversion rules for the corresponding real types.
-2 When a value of complex type is converted to an imaginary type, the real part of the
- complex value is discarded and the value of the imaginary part is converted according to
- the conversion rules for the corresponding real types.
-<a name="G.5" href="#G.5"><b> G.5 Binary operators</b></a>
-1 The following subclauses supplement <a href="#6.5">6.5</a> in order to specify the type of the result for an
- operation with an imaginary operand.
-2 For most operand types, the value of the result of a binary operator with an imaginary or
- complex operand is completely determined, with reference to real arithmetic, by the usual
- mathematical formula. For some operand types, the usual mathematical formula is
- problematic because of its treatment of infinities and because of undue overflow or
- underflow; in these cases the result satisfies certain properties (specified in <a href="#G.5.1">G.5.1</a>), but is
- not completely determined.
-
-
-
-
- 357) See <a href="#6.3.1.2">6.3.1.2</a>.
-
-[<a name="#p528" href="p528">page 528</a>] (<a href="#Contents">Contents</a>)
-
-<a name="G.5.1" href="#G.5.1"><b> G.5.1 Multiplicative operators</b></a>
- Semantics
-1 If one operand has real type and the other operand has imaginary type, then the result has
- imaginary type. If both operands have imaginary type, then the result has real type. (If
- either operand has complex type, then the result has complex type.)
-2 If the operands are not both complex, then the result and floating-point exception
- behavior of the * operator is defined by the usual mathematical formula:
- * u iv u + iv
-
- x xu i(xv) (xu) + i(xv)
-
- iy i(yu) -yv (-yv) + i(yu)
-
- x + iy (xu) + i(yu) (-yv) + i(xv)
-3 If the second operand is not complex, then the result and floating-point exception
- behavior of the / operator is defined by the usual mathematical formula:
- / u iv
-
- x x/u i(-x/v)
-
- iy i(y/u) y/v
-
- x + iy (x/u) + i(y/u) (y/v) + i(-x/v)
-4 The * and / operators satisfy the following infinity properties for all real, imaginary, and
- complex operands:358)
- -- if one operand is an infinity and the other operand is a nonzero finite number or an
- infinity, then the result of the * operator is an infinity;
- -- if the first operand is an infinity and the second operand is a finite number, then the
- result of the / operator is an infinity;
- -- if the first operand is a finite number and the second operand is an infinity, then the
- result of the / operator is a zero;
-
-
-
-
- 358) These properties are already implied for those cases covered in the tables, but are required for all cases
- (at least where the state for CX_LIMITED_RANGE is ''off'').
-
-[<a name="#p529" href="p529">page 529</a>] (<a href="#Contents">Contents</a>)
-
- -- if the first operand is a nonzero finite number or an infinity and the second operand is
- a zero, then the result of the / operator is an infinity.
-5 If both operands of the * operator are complex or if the second operand of the / operator
- is complex, the operator raises floating-point exceptions if appropriate for the calculation
- of the parts of the result, and may raise spurious floating-point exceptions.
-6 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
- that the imaginary unit I has imaginary type (see <a href="#G.6">G.6</a>).
- #include <a href="#7.12"><math.h></a>
- #include <a href="#7.3"><complex.h></a>
- /* Multiply z * w ... */
- double complex _Cmultd(double complex z, double complex w)
- {
- #pragma STDC FP_CONTRACT OFF
- double a, b, c, d, ac, bd, ad, bc, x, y;
- a = creal(z); b = cimag(z);
- c = creal(w); d = cimag(w);
- ac = a * c; bd = b * d;
- ad = a * d; bc = b * c;
- x = ac - bd; y = ad + bc;
- if (isnan(x) && isnan(y)) {
- /* Recover infinities that computed as NaN+iNaN ... */
- int recalc = 0;
- if ( isinf(a) || isinf(b) ) { // z is infinite
- /* "Box" the infinity and change NaNs in the other factor to 0 */
- a = copysign(isinf(a) ? <a href="#1.0">1.0</a> : 0.0, a);
- b = copysign(isinf(b) ? <a href="#1.0">1.0</a> : 0.0, b);
- if (isnan(c)) c = copysign(0.0, c);
- if (isnan(d)) d = copysign(0.0, d);
- recalc = 1;
- }
- if ( isinf(c) || isinf(d) ) { // w is infinite
- /* "Box" the infinity and change NaNs in the other factor to 0 */
- c = copysign(isinf(c) ? <a href="#1.0">1.0</a> : 0.0, c);
- d = copysign(isinf(d) ? <a href="#1.0">1.0</a> : 0.0, d);
- if (isnan(a)) a = copysign(0.0, a);
- if (isnan(b)) b = copysign(0.0, b);
- recalc = 1;
- }
- if (!recalc && (isinf(ac) || isinf(bd) ||
- isinf(ad) || isinf(bc))) {
- /* Recover infinities from overflow by changing NaNs to 0 ... */
- if (isnan(a)) a = copysign(0.0, a);
- if (isnan(b)) b = copysign(0.0, b);
- if (isnan(c)) c = copysign(0.0, c);
- if (isnan(d)) d = copysign(0.0, d);
- recalc = 1;
- }
- if (recalc) {
-
-[<a name="#p530" href="p530">page 530</a>] (<a href="#Contents">Contents</a>)
-
- x = INFINITY * ( a * c - b * d );
- y = INFINITY * ( a * d + b * c );
- }
- }
- return x + I * y;
- }
-7 This implementation achieves the required treatment of infinities at the cost of only one isnan test in
- ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur.
-
-8 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
- #include <a href="#7.12"><math.h></a>
- #include <a href="#7.3"><complex.h></a>
- /* Divide z / w ... */
- double complex _Cdivd(double complex z, double complex w)
- {
- #pragma STDC FP_CONTRACT OFF
- double a, b, c, d, logbw, denom, x, y;
- int ilogbw = 0;
- a = creal(z); b = cimag(z);
- c = creal(w); d = cimag(w);
- logbw = logb(fmax(fabs(c), fabs(d)));
- if (isfinite(logbw)) {
- ilogbw = (int)logbw;
- c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
- }
- denom = c * c + d * d;
- x = scalbn((a * c + b * d) / denom, -ilogbw);
- y = scalbn((b * c - a * d) / denom, -ilogbw);
- /* Recover infinities and zeros that computed as NaN+iNaN; */
- /* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
- if (isnan(x) && isnan(y)) {
- if ((denom == 0.0) &&
- (!isnan(a) || !isnan(b))) {
- x = copysign(INFINITY, c) * a;
- y = copysign(INFINITY, c) * b;
- }
- else if ((isinf(a) || isinf(b)) &&
- isfinite(c) && isfinite(d)) {
- a = copysign(isinf(a) ? <a href="#1.0">1.0</a> : 0.0, a);
- b = copysign(isinf(b) ? <a href="#1.0">1.0</a> : 0.0, b);
- x = INFINITY * ( a * c + b * d );
- y = INFINITY * ( b * c - a * d );
- }
- else if (isinf(logbw) &&
- isfinite(a) && isfinite(b)) {
- c = copysign(isinf(c) ? <a href="#1.0">1.0</a> : 0.0, c);
- d = copysign(isinf(d) ? <a href="#1.0">1.0</a> : 0.0, d);
- x = 0.0 * ( a * c + b * d );
- y = 0.0 * ( b * c - a * d );
-
-[<a name="#p531" href="p531">page 531</a>] (<a href="#Contents">Contents</a>)
-
- }
- }
- return x + I * y;
- }
-9 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
- for multiplication. In the spirit of the multiplication example above, this code does not defend against
- overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
- with division, provides better roundoff characteristics.
-
-<a name="G.5.2" href="#G.5.2"><b> G.5.2 Additive operators</b></a>
- Semantics
-1 If both operands have imaginary type, then the result has imaginary type. (If one operand
- has real type and the other operand has imaginary type, or if either operand has complex
- type, then the result has complex type.)
-2 In all cases the result and floating-point exception behavior of a + or - operator is defined
- by the usual mathematical formula:
- + or - u iv u + iv
-
- x x(+-)u x (+-) iv (x (+-) u) (+-) iv
-
- iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)
-
- x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)
-<a name="G.6" href="#G.6"><b> G.6 Complex arithmetic <complex.h></b></a>
-1 The macros
- imaginary
- and
- _Imaginary_I
- are defined, respectively, as _Imaginary and a constant expression of type const
- float _Imaginary with the value of the imaginary unit. The macro
- I
- is defined to be _Imaginary_I (not _Complex_I as stated in <a href="#7.3">7.3</a>). Notwithstanding
- the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and then perhaps redefine the macro
- imaginary.
-2 This subclause contains specifications for the <a href="#7.3"><complex.h></a> functions that are
- particularly suited to IEC 60559 implementations. For families of functions, the
- specifications apply to all of the functions even though only the principal function is
-
-[<a name="#p532" href="p532">page 532</a>] (<a href="#Contents">Contents</a>)
-
- shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument
- and the result, the result has the same sign as the argument.
-3 The functions are continuous onto both sides of their branch cuts, taking into account the
- sign of zero. For example, csqrt(-2 (+-) i0) = (+-)isqrt:2. -
-4 Since complex and imaginary values are composed of real values, each function may be
- regarded as computing real values from real values. Except as noted, the functions treat
- real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
- manner consistent with the specifications for real functions in F.10.359)
-5 The functions cimag, conj, cproj, and creal are fully specified for all
- implementations, including IEC 60559 ones, in <a href="#7.3.9">7.3.9</a>. These functions raise no floating-
- point exceptions.
-6 Each of the functions cabs and carg is specified by a formula in terms of a real
- function (whose special cases are covered in <a href="#F">annex F</a>):
- cabs(x + iy) = hypot(x, y)
- carg(x + iy) = atan2(y, x)
-7 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
- a formula in terms of other complex functions (whose special cases are specified below):
- casin(z) = -i casinh(iz)
- catan(z) = -i catanh(iz)
- ccos(z) = ccosh(iz)
- csin(z) = -i csinh(iz)
- ctan(z) = -i ctanh(iz)
-8 For the other functions, the following subclauses specify behavior for special cases,
- including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For
- families of functions, the specifications apply to all of the functions even though only the
- principal function is shown. For a function f satisfying f (conj(z)) = conj( f (z)), the
- specifications for the upper half-plane imply the specifications for the lower half-plane; if
- the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the
- specifications for the first quadrant imply the specifications for the other three quadrants.
-9 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
-
-
-
-
- 359) As noted in <a href="#G.3">G.3</a>, a complex value with at least one infinite part is regarded as an infinity even if its
- other part is a NaN.
-
-[<a name="#p533" href="p533">page 533</a>] (<a href="#Contents">Contents</a>)
-
-<a name="G.6.1" href="#G.6.1"><b> G.6.1 Trigonometric functions</b></a>
-<a name="G.6.1.1" href="#G.6.1.1"><b> G.6.1.1 The cacos functions</b></a>
-1 -- cacos(conj(z)) = conj(cacos(z)).
- -- cacos((+-)0 + i0) returns pi /2 - i0.
- -- cacos((+-)0 + iNaN) returns pi /2 + iNaN.
- -- cacos(x + i (inf)) returns pi /2 - i (inf), for finite x.
- -- cacos(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for nonzero finite x.
- -- cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.
- -- cacos(+(inf) + iy) returns +0 - i (inf), for positive-signed finite y.
- -- cacos(-(inf) + i (inf)) returns 3pi /4 - i (inf).
- -- cacos(+(inf) + i (inf)) returns pi /4 - i (inf).
- -- cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
- result is unspecified).
- -- cacos(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite y.
- -- cacos(NaN + i (inf)) returns NaN - i (inf).
- -- cacos(NaN + iNaN) returns NaN + iNaN.
-<a name="G.6.2" href="#G.6.2"><b> G.6.2 Hyperbolic functions</b></a>
-<a name="G.6.2.1" href="#G.6.2.1"><b> G.6.2.1 The cacosh functions</b></a>
-1 -- cacosh(conj(z)) = conj(cacosh(z)).
- -- cacosh((+-)0 + i0) returns +0 + ipi /2.
- -- cacosh(x + i (inf)) returns +(inf) + ipi /2, for finite x.
- -- cacosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
- floating-point exception, for finite x.
- -- cacosh(-(inf) + iy) returns +(inf) + ipi , for positive-signed finite y.
- -- cacosh(+(inf) + iy) returns +(inf) + i0, for positive-signed finite y.
- -- cacosh(-(inf) + i (inf)) returns +(inf) + i3pi /4.
- -- cacosh(+(inf) + i (inf)) returns +(inf) + ipi /4.
- -- cacosh((+-)(inf) + iNaN) returns +(inf) + iNaN.
-
-
-[<a name="#p534" href="p534">page 534</a>] (<a href="#Contents">Contents</a>)
-
- -- cacosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
- floating-point exception, for finite y.
- -- cacosh(NaN + i (inf)) returns +(inf) + iNaN.
- -- cacosh(NaN + iNaN) returns NaN + iNaN.
-<a name="G.6.2.2" href="#G.6.2.2"><b> G.6.2.2 The casinh functions</b></a>
-1 -- casinh(conj(z)) = conj(casinh(z)) and casinh is odd.
- -- casinh(+0 + i0) returns 0 + i0.
- -- casinh(x + i (inf)) returns +(inf) + ipi /2 for positive-signed finite x.
- -- casinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
- floating-point exception, for finite x.
- -- casinh(+(inf) + iy) returns +(inf) + i0 for positive-signed finite y.
- -- casinh(+(inf) + i (inf)) returns +(inf) + ipi /4.
- -- casinh(+(inf) + iNaN) returns +(inf) + iNaN.
- -- casinh(NaN + i0) returns NaN + i0.
- -- casinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
- floating-point exception, for finite nonzero y.
- -- casinh(NaN + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result
- is unspecified).
- -- casinh(NaN + iNaN) returns NaN + iNaN.
-<a name="G.6.2.3" href="#G.6.2.3"><b> G.6.2.3 The catanh functions</b></a>
-1 -- catanh(conj(z)) = conj(catanh(z)) and catanh is odd.
- -- catanh(+0 + i0) returns +0 + i0.
- -- catanh(+0 + iNaN) returns +0 + iNaN.
- -- catanh(+1 + i0) returns +(inf) + i0 and raises the ''divide-by-zero'' floating-point
- exception.
- -- catanh(x + i (inf)) returns +0 + ipi /2, for finite positive-signed x.
- -- catanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
- floating-point exception, for nonzero finite x.
- -- catanh(+(inf) + iy) returns +0 + ipi /2, for finite positive-signed y.
- -- catanh(+(inf) + i (inf)) returns +0 + ipi /2.
- -- catanh(+(inf) + iNaN) returns +0 + iNaN.
-
-[<a name="#p535" href="p535">page 535</a>] (<a href="#Contents">Contents</a>)
-
- -- catanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
- floating-point exception, for finite y.
- -- catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is
- unspecified).
- -- catanh(NaN + iNaN) returns NaN + iNaN.
-<a name="G.6.2.4" href="#G.6.2.4"><b> G.6.2.4 The ccosh functions</b></a>
-1 -- ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
- -- ccosh(+0 + i0) returns 1 + i0.
- -- ccosh(+0 + i (inf)) returns NaN (+-) i0 (where the sign of the imaginary part of the
- result is unspecified) and raises the ''invalid'' floating-point exception.
- -- ccosh(+0 + iNaN) returns NaN (+-) i0 (where the sign of the imaginary part of the
- result is unspecified).
- -- ccosh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
- exception, for finite nonzero x.
- -- ccosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite nonzero x.
- -- ccosh(+(inf) + i0) returns +(inf) + i0.
- -- ccosh(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
- -- ccosh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
- unspecified) and raises the ''invalid'' floating-point exception.
- -- ccosh(+(inf) + iNaN) returns +(inf) + iNaN.
- -- ccosh(NaN + i0) returns NaN (+-) i0 (where the sign of the imaginary part of the
- result is unspecified).
- -- ccosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for all nonzero numbers y.
- -- ccosh(NaN + iNaN) returns NaN + iNaN.
-<a name="G.6.2.5" href="#G.6.2.5"><b> G.6.2.5 The csinh functions</b></a>
-1 -- csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
- -- csinh(+0 + i0) returns +0 + i0.
- -- csinh(+0 + i (inf)) returns (+-)0 + iNaN (where the sign of the real part of the result is
- unspecified) and raises the ''invalid'' floating-point exception.
- -- csinh(+0 + iNaN) returns (+-)0 + iNaN (where the sign of the real part of the result is
- unspecified).
-[<a name="#p536" href="p536">page 536</a>] (<a href="#Contents">Contents</a>)
-
- -- csinh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
- exception, for positive finite x.
- -- csinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite nonzero x.
- -- csinh(+(inf) + i0) returns +(inf) + i0.
- -- csinh(+(inf) + iy) returns +(inf) cis(y), for positive finite y.
- -- csinh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
- unspecified) and raises the ''invalid'' floating-point exception.
- -- csinh(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
- is unspecified).
- -- csinh(NaN + i0) returns NaN + i0.
- -- csinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for all nonzero numbers y.
- -- csinh(NaN + iNaN) returns NaN + iNaN.
-<a name="G.6.2.6" href="#G.6.2.6"><b> G.6.2.6 The ctanh functions</b></a>
-1 -- ctanh(conj(z)) = conj(ctanh(z))and ctanh is odd.
- -- ctanh(+0 + i0) returns +0 + i0.
- -- ctanh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
- exception, for finite x.
- -- ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite x.
- -- ctanh(+(inf) + iy) returns 1 + i0 sin(2y), for positive-signed finite y.
- -- ctanh(+(inf) + i (inf)) returns 1 (+-) i0 (where the sign of the imaginary part of the result
- is unspecified).
- -- ctanh(+(inf) + iNaN) returns 1 (+-) i0 (where the sign of the imaginary part of the
- result is unspecified).
- -- ctanh(NaN + i0) returns NaN + i0.
- -- ctanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for all nonzero numbers y.
- -- ctanh(NaN + iNaN) returns NaN + iNaN.
-
-
-
-
-[<a name="#p537" href="p537">page 537</a>] (<a href="#Contents">Contents</a>)
-
-<a name="G.6.3" href="#G.6.3"><b> G.6.3 Exponential and logarithmic functions</b></a>
-<a name="G.6.3.1" href="#G.6.3.1"><b> G.6.3.1 The cexp functions</b></a>
-1 -- cexp(conj(z)) = conj(cexp(z)).
- -- cexp((+-)0 + i0) returns 1 + i0.
- -- cexp(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
- exception, for finite x.
- -- cexp(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite x.
- -- cexp(+(inf) + i0) returns +(inf) + i0.
- -- cexp(-(inf) + iy) returns +0 cis(y), for finite y.
- -- cexp(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
- -- cexp(-(inf) + i (inf)) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts of
- the result are unspecified).
- -- cexp(+(inf) + i (inf)) returns (+-)(inf) + iNaN and raises the ''invalid'' floating-point
- exception (where the sign of the real part of the result is unspecified).
- -- cexp(-(inf) + iNaN) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts
- of the result are unspecified).
- -- cexp(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
- is unspecified).
- -- cexp(NaN + i0) returns NaN + i0.
- -- cexp(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for all nonzero numbers y.
- -- cexp(NaN + iNaN) returns NaN + iNaN.
-<a name="G.6.3.2" href="#G.6.3.2"><b> G.6.3.2 The clog functions</b></a>
-1 -- clog(conj(z)) = conj(clog(z)).
- -- clog(-0 + i0) returns -(inf) + ipi and raises the ''divide-by-zero'' floating-point
- exception.
- -- clog(+0 + i0) returns -(inf) + i0 and raises the ''divide-by-zero'' floating-point
- exception.
- -- clog(x + i (inf)) returns +(inf) + ipi /2, for finite x.
- -- clog(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite x.
-
-[<a name="#p538" href="p538">page 538</a>] (<a href="#Contents">Contents</a>)
-
- -- clog(-(inf) + iy) returns +(inf) + ipi , for finite positive-signed y.
- -- clog(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
- -- clog(-(inf) + i (inf)) returns +(inf) + i3pi /4.
- -- clog(+(inf) + i (inf)) returns +(inf) + ipi /4.
- -- clog((+-)(inf) + iNaN) returns +(inf) + iNaN.
- -- clog(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite y.
- -- clog(NaN + i (inf)) returns +(inf) + iNaN.
- -- clog(NaN + iNaN) returns NaN + iNaN.
-<a name="G.6.4" href="#G.6.4"><b> G.6.4 Power and absolute-value functions</b></a>
-<a name="G.6.4.1" href="#G.6.4.1"><b> G.6.4.1 The cpow functions</b></a>
-1 The cpow functions raise floating-point exceptions if appropriate for the calculation of
- the parts of the result, and may raise spurious exceptions.360)
-<a name="G.6.4.2" href="#G.6.4.2"><b> G.6.4.2 The csqrt functions</b></a>
-1 -- csqrt(conj(z)) = conj(csqrt(z)).
- -- csqrt((+-)0 + i0) returns +0 + i0.
- -- csqrt(x + i (inf)) returns +(inf) + i (inf), for all x (including NaN).
- -- csqrt(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite x.
- -- csqrt(-(inf) + iy) returns +0 + i (inf), for finite positive-signed y.
- -- csqrt(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
- -- csqrt(-(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
- result is unspecified).
- -- csqrt(+(inf) + iNaN) returns +(inf) + iNaN.
- -- csqrt(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite y.
- -- csqrt(NaN + iNaN) returns NaN + iNaN.
-
-
-
-
- 360) This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding
- implementations that treat special cases more carefully.
-
-[<a name="#p539" href="p539">page 539</a>] (<a href="#Contents">Contents</a>)
-
-<a name="G.7" href="#G.7"><b> G.7 Type-generic math <tgmath.h></b></a>
-1 Type-generic macros that accept complex arguments also accept imaginary arguments. If
- an argument is imaginary, the macro expands to an expression whose type is real,
- imaginary, or complex, as appropriate for the particular function: if the argument is
- imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the
- types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and
- the types of the others are complex.
-2 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh,
- sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real
- functions:
- cos(iy) = cosh(y)
- sin(iy) = i sinh(y)
- tan(iy) = i tanh(y)
- cosh(iy) = cos(y)
- sinh(iy) = i sin(y)
- tanh(iy) = i tan(y)
- asin(iy) = i asinh(y)
- atan(iy) = i atanh(y)
- asinh(iy) = i asin(y)
- atanh(iy) = i atan(y)
-
-
-
-
-[<a name="#p540" href="p540">page 540</a>] (<a href="#Contents">Contents</a>)
-
-<a name="H" href="#H"><b> Annex H</b></a>
- (informative)
- Language independent arithmetic
-<a name="H.1" href="#H.1"><b> H.1 Introduction</b></a>
-1 This annex documents the extent to which the C language supports the ISO/IEC 10967-1
- standard for language-independent arithmetic (LIA-1). LIA-1 is more general than
- IEC 60559 (<a href="#F">annex F</a>) in that it covers integer and diverse floating-point arithmetics.
-<a name="H.2" href="#H.2"><b> H.2 Types</b></a>
-1 The relevant C arithmetic types meet the requirements of LIA-1 types if an
- implementation adds notification of exceptional arithmetic operations and meets the 1
- unit in the last place (ULP) accuracy requirement (LIA-1 subclause <a href="#5.2.8">5.2.8</a>).
-<a name="H.2.1" href="#H.2.1"><b> H.2.1 Boolean type</b></a>
-1 The LIA-1 data type Boolean is implemented by the C data type bool with values of
- true and false, all from <a href="#7.18"><stdbool.h></a>.
-<a name="H.2.2" href="#H.2.2"><b> H.2.2 Integer types</b></a>
-1 The signed C integer types int, long int, long long int, and the corresponding
- unsigned types are compatible with LIA-1. If an implementation adds support for the
- LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are
- LIA-1 conformant types. C's unsigned integer types are ''modulo'' in the LIA-1 sense
- in that overflows or out-of-bounds results silently wrap. An implementation that defines
- signed integer types as also being modulo need not detect integer overflow, in which case,
- only integer divide-by-zero need be detected.
-2 The parameters for the integer data types can be accessed by the following:
- maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
- ULLONG_MAX
- minint INT_MIN, LONG_MIN, LLONG_MIN
-3 The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
- is always 0 for the unsigned types, and is not provided for those types.
-
-
-
-
-[<a name="#p541" href="p541">page 541</a>] (<a href="#Contents">Contents</a>)
-
-<a name="H.2.2.1" href="#H.2.2.1"><b> H.2.2.1 Integer operations</b></a>
-1 The integer operations on integer types are the following:
- addI x + y
- subI x - y
- mulI x * y
- divI, divtI x / y
- remI, remtI x % y
- negI -x
- absI abs(x), labs(x), llabs(x)
- eqI x == y
- neqI x != y
- lssI x < y
- leqI x <= y
- gtrI x > y
- geqI x >= y
- where x and y are expressions of the same integer type.
-<a name="H.2.3" href="#H.2.3"><b> H.2.3 Floating-point types</b></a>
-1 The C floating-point types float, double, and long double are compatible with
- LIA-1. If an implementation adds support for the LIA-1 exceptional values
- ''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
- with LIA-1. An implementation that uses IEC 60559 floating-point formats and
- operations (see <a href="#F">annex F</a>) along with IEC 60559 status flags and traps has LIA-1
- conformant types.
-<a name="H.2.3.1" href="#H.2.3.1"><b> H.2.3.1 Floating-point parameters</b></a>
-1 The parameters for a floating point data type can be accessed by the following:
- r FLT_RADIX
- p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
- emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
- emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
-2 The derived constants for the floating point types are accessed by the following:
-
-
-[<a name="#p542" href="p542">page 542</a>] (<a href="#Contents">Contents</a>)
-
- fmax FLT_MAX, DBL_MAX, LDBL_MAX
- fminN FLT_MIN, DBL_MIN, LDBL_MIN
- epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
- rnd_style FLT_ROUNDS
-<a name="H.2.3.2" href="#H.2.3.2"><b> H.2.3.2 Floating-point operations</b></a>
-1 The floating-point operations on floating-point types are the following:
- addF x + y
- subF x - y
- mulF x * y
- divF x / y
- negF -x
- absF fabsf(x), fabs(x), fabsl(x)
- exponentF 1.f+logbf(x), <a href="#1.0">1.0</a>+logb(x), 1.L+logbl(x)
- scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
- scalblnf(x, li), scalbln(x, li), scalblnl(x, li)
- intpartF modff(x, &y), modf(x, &y), modfl(x, &y)
- fractpartF modff(x, &y), modf(x, &y), modfl(x, &y)
- eqF x == y
- neqF x != y
- lssF x < y
- leqF x <= y
- gtrF x > y
- geqF x >= y
- where x and y are expressions of the same floating point type, n is of type int, and li
- is of type long int.
-<a name="H.2.3.3" href="#H.2.3.3"><b> H.2.3.3 Rounding styles</b></a>
-1 The C Standard requires all floating types to use the same radix and rounding style, so
- that only one identifier for each is provided to map to LIA-1.
-2 The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
- truncate FLT_ROUNDS == 0
-
-
-[<a name="#p543" href="p543">page 543</a>] (<a href="#Contents">Contents</a>)
-
- nearest FLT_ROUNDS == 1
- other FLT_ROUNDS != 0 && FLT_ROUNDS != 1
- provided that an implementation extends FLT_ROUNDS to cover the rounding style used
- in all relevant LIA-1 operations, not just addition as in C.
-<a name="H.2.4" href="#H.2.4"><b> H.2.4 Type conversions</b></a>
-1 The LIA-1 type conversions are the following type casts:
- cvtI' (->) I (int)i, (long int)i, (long long int)i,
- (unsigned int)i, (unsigned long int)i,
- (unsigned long long int)i
- cvtF (->) I (int)x, (long int)x, (long long int)x,
- (unsigned int)x, (unsigned long int)x,
- (unsigned long long int)x
- cvtI (->) F (float)i, (double)i, (long double)i
- cvtF' (->) F (float)x, (double)x, (long double)x
-2 In the above conversions from floating to integer, the use of (cast)x can be replaced with
- (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
- (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer
- conversion functions, lrint(), llrint(), lround(), and llround(), can be
- used. They all meet LIA-1's requirements on floating to integer rounding for in-range
- values. For out-of-range values, the conversions shall silently wrap for the modulo types.
-3 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
- fmod( fabs(rint(x)), 65536.0 ) or (0.0 <= (y = fmod( rint(x),
- 65536.0 )) ? y : 65536.0 + y) will compute an integer value in the range 0.0
- to 65535.0 which can then be cast to unsigned short int. But, the
- remainder() function is not useful for doing silent wrapping to signed integer types,
- e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
- range -32767.0 to +32768.0 which is not, in general, in the range of signed short
- int.
-4 C's conversions (casts) from floating-point to floating-point can meet LIA-1
- requirements if an implementation uses round-to-nearest (IEC 60559 default).
-5 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
- implementation uses round-to-nearest.
-
-
-
-
-[<a name="#p544" href="p544">page 544</a>] (<a href="#Contents">Contents</a>)
-
-<a name="H.3" href="#H.3"><b> H.3 Notification</b></a>
-1 Notification is the process by which a user or program is informed that an exceptional
- arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
- allows an implementation to cause a notification to occur when any arithmetic operation
- returns an exceptional value as defined in LIA-1 clause 5.
-<a name="H.3.1" href="#H.3.1"><b> H.3.1 Notification alternatives</b></a>
-1 LIA-1 requires at least the following two alternatives for handling of notifications:
- setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and-
- resume.
-2 An implementation need only support a given notification alternative for the entire
- program. An implementation may support the ability to switch between notification
- alternatives during execution, but is not required to do so. An implementation can
- provide separate selection for each kind of notification, but this is not required.
-3 C allows an implementation to provide notification. C's SIGFPE (for traps) and
- FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
- can provide LIA-1 notification.
-4 C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
- provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
- math library function calls. User-provided signal handlers for SIGFPE allow for trap-
- and-resume behavior with the same constraint.
-<a name="H.3.1.1" href="#H.3.1.1"><b> H.3.1.1 Indicators</b></a>
-1 C's <a href="#7.6"><fenv.h></a> status flags are compatible with the LIA-1 indicators.
-2 The following mapping is for floating-point types:
- undefined FE_INVALID, FE_DIVBYZERO
- floating_overflow FE_OVERFLOW
- underflow FE_UNDERFLOW
-3 The floating-point indicator interrogation and manipulation operations are:
- set_indicators feraiseexcept(i)
- clear_indicators feclearexcept(i)
- test_indicators fetestexcept(i)
- current_indicators fetestexcept(FE_ALL_EXCEPT)
- where i is an expression of type int representing a subset of the LIA-1 indicators.
-4 C allows an implementation to provide the following LIA-1 required behavior: at
- program termination if any indicator is set the implementation shall send an unambiguous
-[<a name="#p545" href="p545">page 545</a>] (<a href="#Contents">Contents</a>)
-
- and ''hard to ignore'' message (see LIA-1 subclause <a href="#6.1.2">6.1.2</a>)
-5 LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
- This documentation makes that distinction because <a href="#7.6"><fenv.h></a> covers only the floating-
- point indicators.
-<a name="H.3.1.2" href="#H.3.1.2"><b> H.3.1.2 Traps</b></a>
-1 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
- math library functions (which are not permitted to invoke a user's signal handler for
- SIGFPE). An implementation can provide an alternative of notification through
- termination with a ''hard-to-ignore'' message (see LIA-1 subclause <a href="#6.1.3">6.1.3</a>).
-2 LIA-1 does not require that traps be precise.
-3 C does require that SIGFPE be the signal corresponding to arithmetic exceptions, if there
- is any signal raised for them.
-4 C supports signal handlers for SIGFPE and allows trapping of arithmetic exceptions.
- When arithmetic exceptions do trap, C's signal-handler mechanism allows trap-and-
- terminate (either default implementation behavior or user replacement for it) or trap-and-
- resume, at the programmer's option.
-
-
-
-
-[<a name="#p546" href="p546">page 546</a>] (<a href="#Contents">Contents</a>)
-
-<a name="I" href="#I"><b> Annex I</b></a>
- (informative)
- Common warnings
-1 An implementation may generate warnings in many situations, none of which are
- specified as part of this International Standard. The following are a few of the more
- common situations.
-2 -- A new struct or union type appears in a function prototype (<a href="#6.2.1">6.2.1</a>, <a href="#6.7.2.3">6.7.2.3</a>).
- -- A block with initialization of an object that has automatic storage duration is jumped
- into (<a href="#6.2.4">6.2.4</a>).
- -- An implicit narrowing conversion is encountered, such as the assignment of a long
- int or a double to an int, or a pointer to void to a pointer to any type other than
- a character type (<a href="#6.3">6.3</a>).
- -- A hexadecimal floating constant cannot be represented exactly in its evaluation format
- (<a href="#6.4.4.2">6.4.4.2</a>).
- -- An integer character constant includes more than one character or a wide character
- constant includes more than one multibyte character (<a href="#6.4.4.4">6.4.4.4</a>).
- -- The characters /* are found in a comment (<a href="#6.4.7">6.4.7</a>).
- -- An ''unordered'' binary operator (not comma, &&, or ||) contains a side effect to an
- lvalue in one operand, and a side effect to, or an access to the value of, the identical
- lvalue in the other operand (<a href="#6.5">6.5</a>).
- -- A function is called but no prototype has been supplied (<a href="#6.5.2.2">6.5.2.2</a>).
- -- The arguments in a function call do not agree in number and type with those of the
- parameters in a function definition that is not a prototype (<a href="#6.5.2.2">6.5.2.2</a>).
- -- An object is defined but not used (<a href="#6.7">6.7</a>).
- -- A value is given to an object of an enumerated type other than by assignment of an
- enumeration constant that is a member of that type, or an enumeration object that has
- the same type, or the value of a function that returns the same enumerated type
- (<a href="#6.7.2.2">6.7.2.2</a>).
- -- An aggregate has a partly bracketed initialization (<a href="#6.7.8">6.7.8</a>).
- -- A statement cannot be reached (<a href="#6.8">6.8</a>).
- -- A statement with no apparent effect is encountered (<a href="#6.8">6.8</a>).
- -- A constant expression is used as the controlling expression of a selection statement
- (<a href="#6.8.4">6.8.4</a>).
-[<a name="#p547" href="p547">page 547</a>] (<a href="#Contents">Contents</a>)
-
--- An incorrectly formed preprocessing group is encountered while skipping a
- preprocessing group (<a href="#6.10.1">6.10.1</a>).
--- An unrecognized #pragma directive is encountered (<a href="#6.10.6">6.10.6</a>).
-
-
-
-
-[<a name="#p548" href="p548">page 548</a>] (<a href="#Contents">Contents</a>)
-
-<a name="J" href="#J"><b> Annex J</b></a>
- (informative)
- Portability issues
-1 This annex collects some information about portability that appears in this International
- Standard.
-<a name="J.1" href="#J.1"><b> J.1 Unspecified behavior</b></a>
-1 The following are unspecified:
- -- The manner and timing of static initialization (<a href="#5.1.2">5.1.2</a>).
- -- The termination status returned to the hosted environment if the return type of main
- is not compatible with int (<a href="#5.1.2.2.3">5.1.2.2.3</a>).
- -- The behavior of the display device if a printing character is written when the active
- position is at the final position of a line (<a href="#5.2.2">5.2.2</a>).
- -- The behavior of the display device if a backspace character is written when the active
- position is at the initial position of a line (<a href="#5.2.2">5.2.2</a>).
- -- The behavior of the display device if a horizontal tab character is written when the
- active position is at or past the last defined horizontal tabulation position (<a href="#5.2.2">5.2.2</a>).
- -- The behavior of the display device if a vertical tab character is written when the active
- position is at or past the last defined vertical tabulation position (<a href="#5.2.2">5.2.2</a>).
- -- How an extended source character that does not correspond to a universal character
- name counts toward the significant initial characters in an external identifier (<a href="#5.2.4.1">5.2.4.1</a>).
- -- Many aspects of the representations of types (<a href="#6.2.6">6.2.6</a>).
- -- The value of padding bytes when storing values in structures or unions (<a href="#6.2.6.1">6.2.6.1</a>).
- -- The values of bytes that correspond to union members other than the one last stored
- into (<a href="#6.2.6.1">6.2.6.1</a>).
- -- The representation used when storing a value in an object that has more than one
- object representation for that value (<a href="#6.2.6.1">6.2.6.1</a>).
- -- The values of any padding bits in integer representations (<a href="#6.2.6.2">6.2.6.2</a>).
- -- Whether certain operators can generate negative zeros and whether a negative zero
- becomes a normal zero when stored in an object (<a href="#6.2.6.2">6.2.6.2</a>).
- -- Whether two string literals result in distinct arrays (<a href="#6.4.5">6.4.5</a>).
- -- The order in which subexpressions are evaluated and the order in which side effects
- take place, except as specified for the function-call (), &&, ||, ? :, and comma
-[<a name="#p549" href="p549">page 549</a>] (<a href="#Contents">Contents</a>)
-
- operators (<a href="#6.5">6.5</a>).
--- The order in which the function designator, arguments, and subexpressions within the
- arguments are evaluated in a function call (<a href="#6.5.2.2">6.5.2.2</a>).
--- The order of side effects among compound literal initialization list expressions
- (<a href="#6.5.2.5">6.5.2.5</a>).
--- The order in which the operands of an assignment operator are evaluated (<a href="#6.5.16">6.5.16</a>).
--- The alignment of the addressable storage unit allocated to hold a bit-field (<a href="#6.7.2.1">6.7.2.1</a>).
--- Whether a call to an inline function uses the inline definition or the external definition
- of the function (<a href="#6.7.4">6.7.4</a>).
--- Whether or not a size expression is evaluated when it is part of the operand of a
- sizeof operator and changing the value of the size expression would not affect the
- result of the operator (<a href="#6.7.6.2">6.7.6.2</a>).
--- The order in which any side effects occur among the initialization list expressions in
- an initializer (<a href="#6.7.9">6.7.9</a>).
--- The layout of storage for function parameters (<a href="#6.9.1">6.9.1</a>).
--- When a fully expanded macro replacement list contains a function-like macro name
- as its last preprocessing token and the next preprocessing token from the source file is
- a (, and the fully expanded replacement of that macro ends with the name of the first
- macro and the next preprocessing token from the source file is again a (, whether that
- is considered a nested replacement (<a href="#6.10.3">6.10.3</a>).
--- The order in which # and ## operations are evaluated during macro substitution
- (<a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>).
--- The state of the floating-point status flags when execution passes from a part of the
- program translated with FENV_ACCESS ''off'' to a part translated with
- FENV_ACCESS ''on'' (<a href="#7.6.1">7.6.1</a>).
--- The order in which feraiseexcept raises floating-point exceptions, except as
- stated in <a href="#F.8.6">F.8.6</a> (<a href="#7.6.2.3">7.6.2.3</a>).
--- Whether math_errhandling is a macro or an identifier with external linkage
- (<a href="#7.12">7.12</a>).
--- The results of the frexp functions when the specified value is not a floating-point
- number (<a href="#7.12.6.4">7.12.6.4</a>).
--- The numeric result of the ilogb functions when the correct value is outside the
- range of the return type (<a href="#7.12.6.5">7.12.6.5</a>, <a href="#F.10.3.5">F.10.3.5</a>).
--- The result of rounding when the value is out of range (<a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.10.6.5">F.10.6.5</a>).
-
-
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-
--- The value stored by the remquo functions in the object pointed to by quo when y is
- zero (<a href="#7.12.10.3">7.12.10.3</a>).
--- Whether a comparison macro argument that is represented in a format wider than its
- semantic type is converted to the semantic type (<a href="#7.12.14">7.12.14</a>).
--- Whether setjmp is a macro or an identifier with external linkage (<a href="#7.13">7.13</a>).
--- Whether va_copy and va_end are macros or identifiers with external linkage
- (<a href="#7.16.1">7.16.1</a>).
--- The hexadecimal digit before the decimal point when a non-normalized floating-point
- number is printed with an a or A conversion specifier (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>).
--- The value of the file position indicator after a successful call to the ungetc function
- for a text stream, or the ungetwc function for any stream, until all pushed-back
- characters are read or discarded (<a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.28.3.10">7.28.3.10</a>).
--- The details of the value stored by the fgetpos function (<a href="#7.21.9.1">7.21.9.1</a>).
--- The details of the value returned by the ftell function for a text stream (<a href="#7.21.9.4">7.21.9.4</a>).
--- Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold
- functions convert a minus-signed sequence to a negative number directly or by
- negating the value resulting from converting the corresponding unsigned sequence
- (<a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.28.4.1.1">7.28.4.1.1</a>).
--- The order and contiguity of storage allocated by successive calls to the calloc,
- malloc, and realloc functions (<a href="#7.22.3">7.22.3</a>).
--- The amount of storage allocated by a successful call to the calloc, malloc, or
- realloc function when 0 bytes was requested (<a href="#7.22.3">7.22.3</a>).
--- Which of two elements that compare as equal is matched by the bsearch function
- (<a href="#7.22.5.1">7.22.5.1</a>).
--- The order of two elements that compare as equal in an array sorted by the qsort
- function (<a href="#7.22.5.2">7.22.5.2</a>).
--- The encoding of the calendar time returned by the time function (<a href="#7.26.2.4">7.26.2.4</a>).
--- The characters stored by the strftime or wcsftime function if any of the time
- values being converted is outside the normal range (<a href="#7.26.3.5">7.26.3.5</a>, <a href="#7.28.5.1">7.28.5.1</a>).
--- The conversion state after an encoding error occurs (<a href="#7.28.6.3.2">7.28.6.3.2</a>, <a href="#7.28.6.3.3">7.28.6.3.3</a>, <a href="#7.28.6.4.1">7.28.6.4.1</a>,
- <a href="#7.28.6.4.2">7.28.6.4.2</a>,
--- The resulting value when the ''invalid'' floating-point exception is raised during
- IEC 60559 floating to integer conversion (<a href="#F.4">F.4</a>).
-
-
-
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-
- -- Whether conversion of non-integer IEC 60559 floating values to integer raises the
- ''inexact'' floating-point exception (<a href="#F.4">F.4</a>).
- -- Whether or when library functions in <a href="#7.12"><math.h></a> raise the ''inexact'' floating-point
- exception in an IEC 60559 conformant implementation (<a href="#F.10">F.10</a>).
- -- Whether or when library functions in <a href="#7.12"><math.h></a> raise an undeserved ''underflow''
- floating-point exception in an IEC 60559 conformant implementation (<a href="#F.10">F.10</a>).
- -- The exponent value stored by frexp for a NaN or infinity (<a href="#F.10.3.4">F.10.3.4</a>).
- -- The numeric result returned by the lrint, llrint, lround, and llround
- functions if the rounded value is outside the range of the return type (<a href="#F.10.6.5">F.10.6.5</a>,
- <a href="#F.10.6.7">F.10.6.7</a>).
- -- The sign of one part of the complex result of several math functions for certain
- exceptional values in IEC 60559 compatible implementations (<a href="#G.6.1.1">G.6.1.1</a>, <a href="#G.6.2.2">G.6.2.2</a>,
- <a href="#G.6.2.3">G.6.2.3</a>, <a href="#G.6.2.4">G.6.2.4</a>, <a href="#G.6.2.5">G.6.2.5</a>, <a href="#G.6.2.6">G.6.2.6</a>, <a href="#G.6.3.1">G.6.3.1</a>, <a href="#G.6.4.2">G.6.4.2</a>).
-<a name="J.2" href="#J.2"><b> J.2 Undefined behavior</b></a>
-1 The behavior is undefined in the following circumstances:
- -- A ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated
- (clause 4).
- -- A nonempty source file does not end in a new-line character which is not immediately
- preceded by a backslash character or ends in a partial preprocessing token or
- comment (<a href="#5.1.1.2">5.1.1.2</a>).
- -- Token concatenation produces a character sequence matching the syntax of a
- universal character name (<a href="#5.1.1.2">5.1.1.2</a>).
- -- A program in a hosted environment does not define a function named main using one
- of the specified forms (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
- -- The execution of a program contains a data race (<a href="#5.1.2.4">5.1.2.4</a>).
- -- A character not in the basic source character set is encountered in a source file, except
- in an identifier, a character constant, a string literal, a header name, a comment, or a
- preprocessing token that is never converted to a token (<a href="#5.2.1">5.2.1</a>).
- -- An identifier, comment, string literal, character constant, or header name contains an
- invalid multibyte character or does not begin and end in the initial shift state (<a href="#5.2.1.2">5.2.1.2</a>).
- -- The same identifier has both internal and external linkage in the same translation unit
- (<a href="#6.2.2">6.2.2</a>).
- -- An object is referred to outside of its lifetime (<a href="#6.2.4">6.2.4</a>).
-
-
-
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-
--- The value of a pointer to an object whose lifetime has ended is used (<a href="#6.2.4">6.2.4</a>).
--- The value of an object with automatic storage duration is used while it is
- indeterminate (<a href="#6.2.4">6.2.4</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.8">6.8</a>).
--- A trap representation is read by an lvalue expression that does not have character type
- (<a href="#6.2.6.1">6.2.6.1</a>).
--- A trap representation is produced by a side effect that modifies any part of the object
- using an lvalue expression that does not have character type (<a href="#6.2.6.1">6.2.6.1</a>).
--- The operands to certain operators are such that they could produce a negative zero
- result, but the implementation does not support negative zeros (<a href="#6.2.6.2">6.2.6.2</a>).
--- Two declarations of the same object or function specify types that are not compatible
- (<a href="#6.2.7">6.2.7</a>).
--- A program requires the formation of a composite type from a variable length array
- type whose size is specified by an expression that is not evaluated (<a href="#6.2.7">6.2.7</a>).
--- Conversion to or from an integer type produces a value outside the range that can be
- represented (<a href="#6.3.1.4">6.3.1.4</a>).
--- Demotion of one real floating type to another produces a value outside the range that
- can be represented (<a href="#6.3.1.5">6.3.1.5</a>).
--- An lvalue does not designate an object when evaluated (<a href="#6.3.2.1">6.3.2.1</a>).
--- A non-array lvalue with an incomplete type is used in a context that requires the value
- of the designated object (<a href="#6.3.2.1">6.3.2.1</a>).
--- An lvalue designating an object of automatic storage duration that could have been
- declared with the register storage class is used in a context that requires the value
- of the designated object, but the object is uninitialized. (<a href="#6.3.2.1">6.3.2.1</a>).
--- An lvalue having array type is converted to a pointer to the initial element of the
- array, and the array object has register storage class (<a href="#6.3.2.1">6.3.2.1</a>).
--- An attempt is made to use the value of a void expression, or an implicit or explicit
- conversion (except to void) is applied to a void expression (<a href="#6.3.2.2">6.3.2.2</a>).
--- Conversion of a pointer to an integer type produces a value outside the range that can
- be represented (<a href="#6.3.2.3">6.3.2.3</a>).
--- Conversion between two pointer types produces a result that is incorrectly aligned
- (<a href="#6.3.2.3">6.3.2.3</a>).
--- A pointer is used to call a function whose type is not compatible with the referenced
- type (<a href="#6.3.2.3">6.3.2.3</a>).
-
-
-
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-
--- An unmatched ' or " character is encountered on a logical source line during
- tokenization (<a href="#6.4">6.4</a>).
--- A reserved keyword token is used in translation phase 7 or 8 for some purpose other
- than as a keyword (<a href="#6.4.1">6.4.1</a>).
--- A universal character name in an identifier does not designate a character whose
- encoding falls into one of the specified ranges (<a href="#6.4.2.1">6.4.2.1</a>).
--- The initial character of an identifier is a universal character name designating a digit
- (<a href="#6.4.2.1">6.4.2.1</a>).
--- Two identifiers differ only in nonsignificant characters (<a href="#6.4.2.1">6.4.2.1</a>).
--- The identifier __func__ is explicitly declared (<a href="#6.4.2.2">6.4.2.2</a>).
--- The program attempts to modify a string literal (<a href="#6.4.5">6.4.5</a>).
--- The characters ', \, ", //, or /* occur in the sequence between the < and >
- delimiters, or the characters ', \, //, or /* occur in the sequence between the "
- delimiters, in a header name preprocessing token (<a href="#6.4.7">6.4.7</a>).
--- A side effect on a scalar object is unsequenced relative to either a different side effect
- on the same scalar object or a value computation using the value of the same scalar
- object (<a href="#6.5">6.5</a>).
--- An exceptional condition occurs during the evaluation of an expression (<a href="#6.5">6.5</a>).
--- An object has its stored value accessed other than by an lvalue of an allowable type
- (<a href="#6.5">6.5</a>).
--- For a call to a function without a function prototype in scope, the number of
- arguments does not equal the number of parameters (<a href="#6.5.2.2">6.5.2.2</a>).
--- For call to a function without a function prototype in scope where the function is
- defined with a function prototype, either the prototype ends with an ellipsis or the
- types of the arguments after promotion are not compatible with the types of the
- parameters (<a href="#6.5.2.2">6.5.2.2</a>).
--- For a call to a function without a function prototype in scope where the function is not
- defined with a function prototype, the types of the arguments after promotion are not
- compatible with those of the parameters after promotion (with certain exceptions)
- (<a href="#6.5.2.2">6.5.2.2</a>).
--- A function is defined with a type that is not compatible with the type (of the
- expression) pointed to by the expression that denotes the called function (<a href="#6.5.2.2">6.5.2.2</a>).
--- A member of an _Atomic-qualified structure or union is accessed (<a href="#6.5.2.3">6.5.2.3</a>).
--- The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
-
-
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-
--- A pointer is converted to other than an integer or pointer type (<a href="#6.5.4">6.5.4</a>).
--- The value of the second operand of the / or % operator is zero (<a href="#6.5.5">6.5.5</a>).
--- Addition or subtraction of a pointer into, or just beyond, an array object and an
- integer type produces a result that does not point into, or just beyond, the same array
- object (<a href="#6.5.6">6.5.6</a>).
--- Addition or subtraction of a pointer into, or just beyond, an array object and an
- integer type produces a result that points just beyond the array object and is used as
- the operand of a unary * operator that is evaluated (<a href="#6.5.6">6.5.6</a>).
--- Pointers that do not point into, or just beyond, the same array object are subtracted
- (<a href="#6.5.6">6.5.6</a>).
--- An array subscript is out of range, even if an object is apparently accessible with the
- given subscript (as in the lvalue expression a[1][7] given the declaration int
- a[4][5]) (<a href="#6.5.6">6.5.6</a>).
--- The result of subtracting two pointers is not representable in an object of type
- ptrdiff_t (<a href="#6.5.6">6.5.6</a>).
--- An expression is shifted by a negative number or by an amount greater than or equal
- to the width of the promoted expression (<a href="#6.5.7">6.5.7</a>).
--- An expression having signed promoted type is left-shifted and either the value of the
- expression is negative or the result of shifting would be not be representable in the
- promoted type (<a href="#6.5.7">6.5.7</a>).
--- Pointers that do not point to the same aggregate or union (nor just beyond the same
- array object) are compared using relational operators (<a href="#6.5.8">6.5.8</a>).
--- An object is assigned to an inexactly overlapping object or to an exactly overlapping
- object with incompatible type (<a href="#6.5.16.1">6.5.16.1</a>).
--- An expression that is required to be an integer constant expression does not have an
- integer type; has operands that are not integer constants, enumeration constants,
- character constants, sizeof expressions whose results are integer constants, or
- immediately-cast floating constants; or contains casts (outside operands to sizeof
- operators) other than conversions of arithmetic types to integer types (<a href="#6.6">6.6</a>).
--- A constant expression in an initializer is not, or does not evaluate to, one of the
- following: an arithmetic constant expression, a null pointer constant, an address
- constant, or an address constant for a complete object type plus or minus an integer
- constant expression (<a href="#6.6">6.6</a>).
--- An arithmetic constant expression does not have arithmetic type; has operands that
- are not integer constants, floating constants, enumeration constants, character
- constants, or sizeof expressions; or contains casts (outside operands to sizeof
-
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-
- operators) other than conversions of arithmetic types to arithmetic types (<a href="#6.6">6.6</a>).
--- The value of an object is accessed by an array-subscript [], member-access . or ->,
- address &, or indirection * operator or a pointer cast in creating an address constant
- (<a href="#6.6">6.6</a>).
--- An identifier for an object is declared with no linkage and the type of the object is
- incomplete after its declarator, or after its init-declarator if it has an initializer (<a href="#6.7">6.7</a>).
--- A function is declared at block scope with an explicit storage-class specifier other
- than extern (<a href="#6.7.1">6.7.1</a>).
--- A structure or union is defined as containing no named members, no anonymous
- structures, and no anonymous unions (<a href="#6.7.2.1">6.7.2.1</a>).
--- An attempt is made to access, or generate a pointer to just past, a flexible array
- member of a structure when the referenced object provides no elements for that array
- (<a href="#6.7.2.1">6.7.2.1</a>).
--- When the complete type is needed, an incomplete structure or union type is not
- completed in the same scope by another declaration of the tag that defines the content
- (<a href="#6.7.2.3">6.7.2.3</a>).
--- An attempt is made to modify an object defined with a const-qualified type through
- use of an lvalue with non-const-qualified type (<a href="#6.7.3">6.7.3</a>).
--- An attempt is made to refer to an object defined with a volatile-qualified type through
- use of an lvalue with non-volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
--- An attempt is made to refer to an object defined with an _Atomic-qualified type
- through use of an lvalue with non-_Atomic-qualified type (<a href="#6.7.3">6.7.3</a>).
--- The specification of a function type includes any type qualifiers (<a href="#6.7.3">6.7.3</a>).
--- Two qualified types that are required to be compatible do not have the identically
- qualified version of a compatible type (<a href="#6.7.3">6.7.3</a>).
--- An object which has been modified is accessed through a restrict-qualified pointer to
- a const-qualified type, or through a restrict-qualified pointer and another pointer that
- are not both based on the same object (<a href="#6.7.3.1">6.7.3.1</a>).
--- A restrict-qualified pointer is assigned a value based on another restricted pointer
- whose associated block neither began execution before the block associated with this
- pointer, nor ended before the assignment (<a href="#6.7.3.1">6.7.3.1</a>).
--- A function with external linkage is declared with an inline function specifier, but is
- not also defined in the same translation unit (<a href="#6.7.4">6.7.4</a>).
--- A function declared with a _Noreturn function specifier returns to its caller (<a href="#6.7.4">6.7.4</a>).
-
-
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-
--- The definition of an object has an alignment specifier and another declaration of that
- object has a different alignment specifier (<a href="#6.7.5">6.7.5</a>).
--- Declarations of an object in different translation units have different alignment
- specifiers (<a href="#6.7.5">6.7.5</a>).
--- Two pointer types that are required to be compatible are not identically qualified, or
- are not pointers to compatible types (<a href="#6.7.6.1">6.7.6.1</a>).
--- The size expression in an array declaration is not a constant expression and evaluates
- at program execution time to a nonpositive value (<a href="#6.7.6.2">6.7.6.2</a>).
--- In a context requiring two array types to be compatible, they do not have compatible
- element types, or their size specifiers evaluate to unequal values (<a href="#6.7.6.2">6.7.6.2</a>).
--- A declaration of an array parameter includes the keyword static within the [ and
- ] and the corresponding argument does not provide access to the first element of an
- array with at least the specified number of elements (<a href="#6.7.6.3">6.7.6.3</a>).
--- A storage-class specifier or type qualifier modifies the keyword void as a function
- parameter type list (<a href="#6.7.6.3">6.7.6.3</a>).
--- In a context requiring two function types to be compatible, they do not have
- compatible return types, or their parameters disagree in use of the ellipsis terminator
- or the number and type of parameters (after default argument promotion, when there
- is no parameter type list or when one type is specified by a function definition with an
- identifier list) (<a href="#6.7.6.3">6.7.6.3</a>).
--- The value of an unnamed member of a structure or union is used (<a href="#6.7.9">6.7.9</a>).
--- The initializer for a scalar is neither a single expression nor a single expression
- enclosed in braces (<a href="#6.7.9">6.7.9</a>).
--- The initializer for a structure or union object that has automatic storage duration is
- neither an initializer list nor a single expression that has compatible structure or union
- type (<a href="#6.7.9">6.7.9</a>).
--- The initializer for an aggregate or union, other than an array initialized by a string
- literal, is not a brace-enclosed list of initializers for its elements or members (<a href="#6.7.9">6.7.9</a>).
--- An identifier with external linkage is used, but in the program there does not exist
- exactly one external definition for the identifier, or the identifier is not used and there
- exist multiple external definitions for the identifier (<a href="#6.9">6.9</a>).
--- A function definition includes an identifier list, but the types of the parameters are not
- declared in a following declaration list (<a href="#6.9.1">6.9.1</a>).
--- An adjusted parameter type in a function definition is not a complete object type
- (<a href="#6.9.1">6.9.1</a>).
-
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-
--- A function that accepts a variable number of arguments is defined without a
- parameter type list that ends with the ellipsis notation (<a href="#6.9.1">6.9.1</a>).
--- The } that terminates a function is reached, and the value of the function call is used
- by the caller (<a href="#6.9.1">6.9.1</a>).
--- An identifier for an object with internal linkage and an incomplete type is declared
- with a tentative definition (<a href="#6.9.2">6.9.2</a>).
--- The token defined is generated during the expansion of a #if or #elif
- preprocessing directive, or the use of the defined unary operator does not match
- one of the two specified forms prior to macro replacement (<a href="#6.10.1">6.10.1</a>).
--- The #include preprocessing directive that results after expansion does not match
- one of the two header name forms (<a href="#6.10.2">6.10.2</a>).
--- The character sequence in an #include preprocessing directive does not start with a
- letter (<a href="#6.10.2">6.10.2</a>).
--- There are sequences of preprocessing tokens within the list of macro arguments that
- would otherwise act as preprocessing directives (<a href="#6.10.3">6.10.3</a>).
--- The result of the preprocessing operator # is not a valid character string literal
- (<a href="#6.10.3.2">6.10.3.2</a>).
--- The result of the preprocessing operator ## is not a valid preprocessing token
- (<a href="#6.10.3.3">6.10.3.3</a>).
--- The #line preprocessing directive that results after expansion does not match one of
- the two well-defined forms, or its digit sequence specifies zero or a number greater
- than 2147483647 (<a href="#6.10.4">6.10.4</a>).
--- A non-STDC #pragma preprocessing directive that is documented as causing
- translation failure or some other form of undefined behavior is encountered (<a href="#6.10.6">6.10.6</a>).
--- A #pragma STDC preprocessing directive does not match one of the well-defined
- forms (<a href="#6.10.6">6.10.6</a>).
--- The name of a predefined macro, or the identifier defined, is the subject of a
- #define or #undef preprocessing directive (<a href="#6.10.8">6.10.8</a>).
--- An attempt is made to copy an object to an overlapping object by use of a library
- function, other than as explicitly allowed (e.g., memmove) (clause 7).
--- A file with the same name as one of the standard headers, not provided as part of the
- implementation, is placed in any of the standard places that are searched for included
- source files (<a href="#7.1.2">7.1.2</a>).
--- A header is included within an external declaration or definition (<a href="#7.1.2">7.1.2</a>).
-
-
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-
--- A function, object, type, or macro that is specified as being declared or defined by
- some standard header is used before any header that declares or defines it is included
- (<a href="#7.1.2">7.1.2</a>).
--- A standard header is included while a macro is defined with the same name as a
- keyword (<a href="#7.1.2">7.1.2</a>).
--- The program attempts to declare a library function itself, rather than via a standard
- header, but the declaration does not have external linkage (<a href="#7.1.2">7.1.2</a>).
--- The program declares or defines a reserved identifier, other than as allowed by <a href="#7.1.4">7.1.4</a>
- (<a href="#7.1.3">7.1.3</a>).
--- The program removes the definition of a macro whose name begins with an
- underscore and either an uppercase letter or another underscore (<a href="#7.1.3">7.1.3</a>).
--- An argument to a library function has an invalid value or a type not expected by a
- function with variable number of arguments (<a href="#7.1.4">7.1.4</a>).
--- The pointer passed to a library function array parameter does not have a value such
- that all address computations and object accesses are valid (<a href="#7.1.4">7.1.4</a>).
--- The macro definition of assert is suppressed in order to access an actual function
- (<a href="#7.2">7.2</a>).
--- The argument to the assert macro does not have a scalar type (<a href="#7.2">7.2</a>).
--- The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in
- any context other than outside all external declarations or preceding all explicit
- declarations and statements inside a compound statement (<a href="#7.3.4">7.3.4</a>, <a href="#7.6.1">7.6.1</a>, <a href="#7.12.2">7.12.2</a>).
--- The value of an argument to a character handling function is neither equal to the value
- of EOF nor representable as an unsigned char (<a href="#7.4">7.4</a>).
--- A macro definition of errno is suppressed in order to access an actual object, or the
- program defines an identifier with the name errno (<a href="#7.5">7.5</a>).
--- Part of the program tests floating-point status flags, sets floating-point control modes,
- or runs under non-default mode settings, but was translated with the state for the
- FENV_ACCESS pragma ''off'' (<a href="#7.6.1">7.6.1</a>).
--- The exception-mask argument for one of the functions that provide access to the
- floating-point status flags has a nonzero value not obtained by bitwise OR of the
- floating-point exception macros (<a href="#7.6.2">7.6.2</a>).
--- The fesetexceptflag function is used to set floating-point status flags that were
- not specified in the call to the fegetexceptflag function that provided the value
- of the corresponding fexcept_t object (<a href="#7.6.2.4">7.6.2.4</a>).
-
-
-
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-
--- The argument to fesetenv or feupdateenv is neither an object set by a call to
- fegetenv or feholdexcept, nor is it an environment macro (<a href="#7.6.4.3">7.6.4.3</a>, <a href="#7.6.4.4">7.6.4.4</a>).
--- The value of the result of an integer arithmetic or conversion function cannot be
- represented (<a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.8.2.2">7.8.2.2</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.22.6.1">7.22.6.1</a>, <a href="#7.22.6.2">7.22.6.2</a>, <a href="#7.22.1">7.22.1</a>).
--- The program modifies the string pointed to by the value returned by the setlocale
- function (<a href="#7.11.1.1">7.11.1.1</a>).
--- The program modifies the structure pointed to by the value returned by the
- localeconv function (<a href="#7.11.2.1">7.11.2.1</a>).
--- A macro definition of math_errhandling is suppressed or the program defines
- an identifier with the name math_errhandling (<a href="#7.12">7.12</a>).
--- An argument to a floating-point classification or comparison macro is not of real
- floating type (<a href="#7.12.3">7.12.3</a>, <a href="#7.12.14">7.12.14</a>).
--- A macro definition of setjmp is suppressed in order to access an actual function, or
- the program defines an external identifier with the name setjmp (<a href="#7.13">7.13</a>).
--- An invocation of the setjmp macro occurs other than in an allowed context
- (<a href="#7.13.2.1">7.13.2.1</a>).
--- The longjmp function is invoked to restore a nonexistent environment (<a href="#7.13.2.1">7.13.2.1</a>).
--- After a longjmp, there is an attempt to access the value of an object of automatic
- storage duration that does not have volatile-qualified type, local to the function
- containing the invocation of the corresponding setjmp macro, that was changed
- between the setjmp invocation and longjmp call (<a href="#7.13.2.1">7.13.2.1</a>).
--- The program specifies an invalid pointer to a signal handler function (<a href="#7.14.1.1">7.14.1.1</a>).
--- A signal handler returns when the signal corresponded to a computational exception
- (<a href="#7.14.1.1">7.14.1.1</a>).
--- A signal occurs as the result of calling the abort or raise function, and the signal
- handler calls the raise function (<a href="#7.14.1.1">7.14.1.1</a>).
--- A signal occurs other than as the result of calling the abort or raise function, and
- the signal handler refers to an object with static storage duration other than by
- assigning a value to an object declared as volatile sig_atomic_t, or calls any
- function in the standard library other than the abort function, the _Exit function,
- the quick_exit function, or the signal function (for the same signal number)
- (<a href="#7.14.1.1">7.14.1.1</a>).
--- The value of errno is referred to after a signal occurred other than as the result of
- calling the abort or raise function and the corresponding signal handler obtained
- a SIG_ERR return from a call to the signal function (<a href="#7.14.1.1">7.14.1.1</a>).
-
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-
--- A signal is generated by an asynchronous signal handler (<a href="#7.14.1.1">7.14.1.1</a>).
--- A function with a variable number of arguments attempts to access its varying
- arguments other than through a properly declared and initialized va_list object, or
- before the va_start macro is invoked (<a href="#7.16">7.16</a>, <a href="#7.16.1.1">7.16.1.1</a>, <a href="#7.16.1.4">7.16.1.4</a>).
--- The macro va_arg is invoked using the parameter ap that was passed to a function
- that invoked the macro va_arg with the same parameter (<a href="#7.16">7.16</a>).
--- A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in
- order to access an actual function, or the program defines an external identifier with
- the name va_copy or va_end (<a href="#7.16.1">7.16.1</a>).
--- The va_start or va_copy macro is invoked without a corresponding invocation
- of the va_end macro in the same function, or vice versa (<a href="#7.16.1">7.16.1</a>, <a href="#7.16.1.2">7.16.1.2</a>, <a href="#7.16.1.3">7.16.1.3</a>,
- <a href="#7.16.1.4">7.16.1.4</a>).
--- The type parameter to the va_arg macro is not such that a pointer to an object of
- that type can be obtained simply by postfixing a * (<a href="#7.16.1.1">7.16.1.1</a>).
--- The va_arg macro is invoked when there is no actual next argument, or with a
- specified type that is not compatible with the promoted type of the actual next
- argument, with certain exceptions (<a href="#7.16.1.1">7.16.1.1</a>).
--- The va_copy or va_start macro is called to initialize a va_list that was
- previously initialized by either macro without an intervening invocation of the
- va_end macro for the same va_list (<a href="#7.16.1.2">7.16.1.2</a>, <a href="#7.16.1.4">7.16.1.4</a>).
--- The parameter parmN of a va_start macro is declared with the register
- storage class, with a function or array type, or with a type that is not compatible with
- the type that results after application of the default argument promotions (<a href="#7.16.1.4">7.16.1.4</a>).
--- The member designator parameter of an offsetof macro is an invalid right
- operand of the . operator for the type parameter, or designates a bit-field (<a href="#7.19">7.19</a>).
--- The argument in an instance of one of the integer-constant macros is not a decimal,
- octal, or hexadecimal constant, or it has a value that exceeds the limits for the
- corresponding type (<a href="#7.20.4">7.20.4</a>).
--- A byte input/output function is applied to a wide-oriented stream, or a wide character
- input/output function is applied to a byte-oriented stream (<a href="#7.21.2">7.21.2</a>).
--- Use is made of any portion of a file beyond the most recent wide character written to
- a wide-oriented stream (<a href="#7.21.2">7.21.2</a>).
--- The value of a pointer to a FILE object is used after the associated file is closed
- (<a href="#7.21.3">7.21.3</a>).
--- The stream for the fflush function points to an input stream or to an update stream
- in which the most recent operation was input (<a href="#7.21.5.2">7.21.5.2</a>).
-[<a name="#p561" href="p561">page 561</a>] (<a href="#Contents">Contents</a>)
-
--- The string pointed to by the mode argument in a call to the fopen function does not
- exactly match one of the specified character sequences (<a href="#7.21.5.3">7.21.5.3</a>).
--- An output operation on an update stream is followed by an input operation without an
- intervening call to the fflush function or a file positioning function, or an input
- operation on an update stream is followed by an output operation with an intervening
- call to a file positioning function (<a href="#7.21.5.3">7.21.5.3</a>).
--- An attempt is made to use the contents of the array that was supplied in a call to the
- setvbuf function (<a href="#7.21.5.6">7.21.5.6</a>).
--- There are insufficient arguments for the format in a call to one of the formatted
- input/output functions, or an argument does not have an appropriate type (<a href="#7.21.6.1">7.21.6.1</a>,
- <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>).
--- The format in a call to one of the formatted input/output functions or to the
- strftime or wcsftime function is not a valid multibyte character sequence that
- begins and ends in its initial shift state (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.26.3.5">7.26.3.5</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>,
- <a href="#7.28.5.1">7.28.5.1</a>).
--- In a call to one of the formatted output functions, a precision appears with a
- conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>).
--- A conversion specification for a formatted output function uses an asterisk to denote
- an argument-supplied field width or precision, but the corresponding argument is not
- provided (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>).
--- A conversion specification for a formatted output function uses a # or 0 flag with a
- conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>).
--- A conversion specification for one of the formatted input/output functions uses a
- length modifier with a conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>,
- <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>).
--- An s conversion specifier is encountered by one of the formatted output functions,
- and the argument is missing the null terminator (unless a precision is specified that
- does not require null termination) (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>).
--- An n conversion specification for one of the formatted input/output functions includes
- any flags, an assignment-suppressing character, a field width, or a precision (<a href="#7.21.6.1">7.21.6.1</a>,
- <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>).
--- A % conversion specifier is encountered by one of the formatted input/output
- functions, but the complete conversion specification is not exactly %% (<a href="#7.21.6.1">7.21.6.1</a>,
- <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>).
--- An invalid conversion specification is found in the format for one of the formatted
- input/output functions, or the strftime or wcsftime function (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
-
-[<a name="#p562" href="p562">page 562</a>] (<a href="#Contents">Contents</a>)
-
- <a href="#7.26.3.5">7.26.3.5</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>, <a href="#7.28.5.1">7.28.5.1</a>).
--- The number of characters transmitted by a formatted output function is greater than
- INT_MAX (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.3">7.21.6.3</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.10">7.21.6.10</a>).
--- The result of a conversion by one of the formatted input functions cannot be
- represented in the corresponding object, or the receiving object does not have an
- appropriate type (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>).
--- A c, s, or [ conversion specifier is encountered by one of the formatted input
- functions, and the array pointed to by the corresponding argument is not large enough
- to accept the input sequence (and a null terminator if the conversion specifier is s or
- [) (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>).
--- A c, s, or [ conversion specifier with an l qualifier is encountered by one of the
- formatted input functions, but the input is not a valid multibyte character sequence
- that begins in the initial shift state (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>).
--- The input item for a %p conversion by one of the formatted input functions is not a
- value converted earlier during the same program execution (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>).
--- The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf,
- vsscanf, vfwprintf, vfwscanf, vswprintf, vswscanf, vwprintf, or
- vwscanf function is called with an improperly initialized va_list argument, or
- the argument is used (other than in an invocation of va_end) after the function
- returns (<a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.10">7.21.6.10</a>, <a href="#7.21.6.11">7.21.6.11</a>, <a href="#7.21.6.12">7.21.6.12</a>, <a href="#7.21.6.13">7.21.6.13</a>, <a href="#7.21.6.14">7.21.6.14</a>,
- <a href="#7.28.2.5">7.28.2.5</a>, <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.2.7">7.28.2.7</a>, <a href="#7.28.2.8">7.28.2.8</a>, <a href="#7.28.2.9">7.28.2.9</a>, <a href="#7.28.2.10">7.28.2.10</a>).
--- The contents of the array supplied in a call to the fgets or fgetws function are
- used after a read error occurred (<a href="#7.21.7.2">7.21.7.2</a>, <a href="#7.28.3.2">7.28.3.2</a>).
--- The file position indicator for a binary stream is used after a call to the ungetc
- function where its value was zero before the call (<a href="#7.21.7.10">7.21.7.10</a>).
--- The file position indicator for a stream is used after an error occurred during a call to
- the fread or fwrite function (<a href="#7.21.8.1">7.21.8.1</a>, <a href="#7.21.8.2">7.21.8.2</a>).
--- A partial element read by a call to the fread function is used (<a href="#7.21.8.1">7.21.8.1</a>).
--- The fseek function is called for a text stream with a nonzero offset and either the
- offset was not returned by a previous successful call to the ftell function on a
- stream associated with the same file or whence is not SEEK_SET (<a href="#7.21.9.2">7.21.9.2</a>).
--- The fsetpos function is called to set a position that was not returned by a previous
- successful call to the fgetpos function on a stream associated with the same file
- (<a href="#7.21.9.3">7.21.9.3</a>).
--- A non-null pointer returned by a call to the calloc, malloc, or realloc function
- with a zero requested size is used to access an object (<a href="#7.22.3">7.22.3</a>).
-
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-
--- The value of a pointer that refers to space deallocated by a call to the free or
- realloc function is used (<a href="#7.22.3">7.22.3</a>).
--- The alignment requested of the aligned_alloc function is not valid or not
- supported by the implementation, or the size requested is not an integral multiple of
- the alignment (<a href="#7.22.3.1">7.22.3.1</a>).
--- The pointer argument to the free or realloc function does not match a pointer
- earlier returned by a memory management function, or the space has been deallocated
- by a call to free or realloc (<a href="#7.22.3.3">7.22.3.3</a>, <a href="#7.22.3.5">7.22.3.5</a>).
--- The value of the object allocated by the malloc function is used (<a href="#7.22.3.4">7.22.3.4</a>).
--- The value of any bytes in a new object allocated by the realloc function beyond
- the size of the old object are used (<a href="#7.22.3.5">7.22.3.5</a>).
--- The program calls the exit or quick_exit function more than once, or calls both
- functions (<a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.7">7.22.4.7</a>).
--- During the call to a function registered with the atexit or at_quick_exit
- function, a call is made to the longjmp function that would terminate the call to the
- registered function (<a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.7">7.22.4.7</a>).
--- The string set up by the getenv or strerror function is modified by the program
- (<a href="#7.22.4.6">7.22.4.6</a>, <a href="#7.23.6.2">7.23.6.2</a>).
--- A command is executed through the system function in a way that is documented as
- causing termination or some other form of undefined behavior (<a href="#7.22.4.8">7.22.4.8</a>).
--- A searching or sorting utility function is called with an invalid pointer argument, even
- if the number of elements is zero (<a href="#7.22.5">7.22.5</a>).
--- The comparison function called by a searching or sorting utility function alters the
- contents of the array being searched or sorted, or returns ordering values
- inconsistently (<a href="#7.22.5">7.22.5</a>).
--- The array being searched by the bsearch function does not have its elements in
- proper order (<a href="#7.22.5.1">7.22.5.1</a>).
--- The current conversion state is used by a multibyte/wide character conversion
- function after changing the LC_CTYPE category (<a href="#7.22.7">7.22.7</a>).
--- A string or wide string utility function is instructed to access an array beyond the end
- of an object (<a href="#7.23.1">7.23.1</a>, <a href="#7.28.4">7.28.4</a>).
--- A string or wide string utility function is called with an invalid pointer argument, even
- if the length is zero (<a href="#7.23.1">7.23.1</a>, <a href="#7.28.4">7.28.4</a>).
--- The contents of the destination array are used after a call to the strxfrm,
- strftime, wcsxfrm, or wcsftime function in which the specified length was
-
-[<a name="#p564" href="p564">page 564</a>] (<a href="#Contents">Contents</a>)
-
- too small to hold the entire null-terminated result (<a href="#7.23.4.5">7.23.4.5</a>, <a href="#7.26.3.5">7.26.3.5</a>, <a href="#7.28.4.4.4">7.28.4.4.4</a>,
- <a href="#7.28.5.1">7.28.5.1</a>).
--- The first argument in the very first call to the strtok or wcstok is a null pointer
- (<a href="#7.23.5.8">7.23.5.8</a>, <a href="#7.28.4.5.7">7.28.4.5.7</a>).
--- The type of an argument to a type-generic macro is not compatible with the type of
- the corresponding parameter of the selected function (<a href="#7.24">7.24</a>).
--- A complex argument is supplied for a generic parameter of a type-generic macro that
- has no corresponding complex function (<a href="#7.24">7.24</a>).
--- At least one field of the broken-down time passed to asctime contains a value
- outside its normal range, or the calculated year exceeds four digits or is less than the
- year 1000 (<a href="#7.26.3.1">7.26.3.1</a>).
--- The argument corresponding to an s specifier without an l qualifier in a call to the
- fwprintf function does not point to a valid multibyte character sequence that
- begins in the initial shift state (<a href="#7.28.2.11">7.28.2.11</a>).
--- In a call to the wcstok function, the object pointed to by ptr does not have the
- value stored by the previous call for the same wide string (<a href="#7.28.4.5.7">7.28.4.5.7</a>).
--- An mbstate_t object is used inappropriately (<a href="#7.28.6">7.28.6</a>).
--- The value of an argument of type wint_t to a wide character classification or case
- mapping function is neither equal to the value of WEOF nor representable as a
- wchar_t (<a href="#7.29.1">7.29.1</a>).
--- The iswctype function is called using a different LC_CTYPE category from the
- one in effect for the call to the wctype function that returned the description
- (<a href="#7.29.2.2.1">7.29.2.2.1</a>).
--- The towctrans function is called using a different LC_CTYPE category from the
- one in effect for the call to the wctrans function that returned the description
- (<a href="#7.29.3.2.1">7.29.3.2.1</a>).
-
-
-
-
-[<a name="#p565" href="p565">page 565</a>] (<a href="#Contents">Contents</a>)
-
-<a name="J.3" href="#J.3"><b> J.3 Implementation-defined behavior</b></a>
-1 A conforming implementation is required to document its choice of behavior in each of
- the areas listed in this subclause. The following are implementation-defined:
-<a name="J.3.1" href="#J.3.1"><b> J.3.1 Translation</b></a>
-1 -- How a diagnostic is identified (<a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a>).
- -- Whether each nonempty sequence of white-space characters other than new-line is
- retained or replaced by one space character in translation phase 3 (<a href="#5.1.1.2">5.1.1.2</a>).
-<a name="J.3.2" href="#J.3.2"><b> J.3.2 Environment</b></a>
-1 -- The mapping between physical source file multibyte characters and the source
- character set in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>).
- -- The name and type of the function called at program startup in a freestanding
- environment (<a href="#5.1.2.1">5.1.2.1</a>).
- -- The effect of program termination in a freestanding environment (<a href="#5.1.2.1">5.1.2.1</a>).
- -- An alternative manner in which the main function may be defined (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
- -- The values given to the strings pointed to by the argv argument to main (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
- -- What constitutes an interactive device (<a href="#5.1.2.3">5.1.2.3</a>).
- -- Whether a program can have more than one thread of execution in a freestanding
- environment (<a href="#5.1.2.4">5.1.2.4</a>).
- -- The set of signals, their semantics, and their default handling (<a href="#7.14">7.14</a>).
- -- Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
- computational exception (<a href="#7.14.1.1">7.14.1.1</a>).
- -- Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
- program startup (<a href="#7.14.1.1">7.14.1.1</a>).
- -- The set of environment names and the method for altering the environment list used
- by the getenv function (<a href="#7.22.4.6">7.22.4.6</a>).
- -- The manner of execution of the string by the system function (<a href="#7.22.4.8">7.22.4.8</a>).
-
-
-
-
-[<a name="#p566" href="p566">page 566</a>] (<a href="#Contents">Contents</a>)
-
-<a name="J.3.3" href="#J.3.3"><b> J.3.3 Identifiers</b></a>
-1 -- Which additional multibyte characters may appear in identifiers and their
- correspondence to universal character names (<a href="#6.4.2">6.4.2</a>).
- -- The number of significant initial characters in an identifier (<a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2">6.4.2</a>).
-<a name="J.3.4" href="#J.3.4"><b> J.3.4 Characters</b></a>
-1 -- The number of bits in a byte (<a href="#3.6">3.6</a>).
- -- The values of the members of the execution character set (<a href="#5.2.1">5.2.1</a>).
- -- The unique value of the member of the execution character set produced for each of
- the standard alphabetic escape sequences (<a href="#5.2.2">5.2.2</a>).
- -- The value of a char object into which has been stored any character other than a
- member of the basic execution character set (<a href="#6.2.5">6.2.5</a>).
- -- Which of signed char or unsigned char has the same range, representation,
- and behavior as ''plain'' char (<a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>).
- -- The mapping of members of the source character set (in character constants and string
- literals) to members of the execution character set (<a href="#6.4.4.4">6.4.4.4</a>, <a href="#5.1.1.2">5.1.1.2</a>).
- -- The value of an integer character constant containing more than one character or
- containing a character or escape sequence that does not map to a single-byte
- execution character (<a href="#6.4.4.4">6.4.4.4</a>).
- -- The value of a wide character constant containing more than one multibyte character
- or a single multibyte character that maps to multiple members of the extended
- execution character set, or containing a multibyte character or escape sequence not
- represented in the extended execution character set (<a href="#6.4.4.4">6.4.4.4</a>).
- -- The current locale used to convert a wide character constant consisting of a single
- multibyte character that maps to a member of the extended execution character set
- into a corresponding wide character code (<a href="#6.4.4.4">6.4.4.4</a>).
- -- Whether differently-prefixed wide string literal tokens can be concatenated and, if so,
- the treatment of the resulting multibyte character sequence (<a href="#6.4.5">6.4.5</a>).
- -- The current locale used to convert a wide string literal into corresponding wide
- character codes (<a href="#6.4.5">6.4.5</a>).
- -- The value of a string literal containing a multibyte character or escape sequence not
- represented in the execution character set (<a href="#6.4.5">6.4.5</a>).
- -- The encoding of any of wchar_t, char16_t, and char32_t where the
- corresponding standard encoding macro (__STDC_ISO_10646__,
- __STDC_UTF_16__, or __STDC_UTF_32__) is not defined (<a href="#6.10.8.2">6.10.8.2</a>).
-
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-
-<a name="J.3.5" href="#J.3.5"><b> J.3.5 Integers</b></a>
-1 -- Any extended integer types that exist in the implementation (<a href="#6.2.5">6.2.5</a>).
- -- Whether signed integer types are represented using sign and magnitude, two's
- complement, or ones' complement, and whether the extraordinary value is a trap
- representation or an ordinary value (<a href="#6.2.6.2">6.2.6.2</a>).
- -- The rank of any extended integer type relative to another extended integer type with
- the same precision (<a href="#6.3.1.1">6.3.1.1</a>).
- -- The result of, or the signal raised by, converting an integer to a signed integer type
- when the value cannot be represented in an object of that type (<a href="#6.3.1.3">6.3.1.3</a>).
- -- The results of some bitwise operations on signed integers (<a href="#6.5">6.5</a>).
-<a name="J.3.6" href="#J.3.6"><b> J.3.6 Floating point</b></a>
-1 -- The accuracy of the floating-point operations and of the library functions in
- <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
- -- The accuracy of the conversions between floating-point internal representations and
- string representations performed by the library functions in <a href="#7.21"><stdio.h></a>,
- <a href="#7.22"><stdlib.h></a>, and <a href="#7.28"><wchar.h></a> (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
- -- The rounding behaviors characterized by non-standard values of FLT_ROUNDS
- (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
- -- The evaluation methods characterized by non-standard negative values of
- FLT_EVAL_METHOD (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
- -- The direction of rounding when an integer is converted to a floating-point number that
- cannot exactly represent the original value (<a href="#6.3.1.4">6.3.1.4</a>).
- -- The direction of rounding when a floating-point number is converted to a narrower
- floating-point number (<a href="#6.3.1.5">6.3.1.5</a>).
- -- How the nearest representable value or the larger or smaller representable value
- immediately adjacent to the nearest representable value is chosen for certain floating
- constants (<a href="#6.4.4.2">6.4.4.2</a>).
- -- Whether and how floating expressions are contracted when not disallowed by the
- FP_CONTRACT pragma (<a href="#6.5">6.5</a>).
- -- The default state for the FENV_ACCESS pragma (<a href="#7.6.1">7.6.1</a>).
- -- Additional floating-point exceptions, rounding modes, environments, and
- classifications, and their macro names (<a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>).
- -- The default state for the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>).
-
-
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-
-<a name="J.3.7" href="#J.3.7"><b> J.3.7 Arrays and pointers</b></a>
-1 -- The result of converting a pointer to an integer or vice versa (<a href="#6.3.2.3">6.3.2.3</a>).
- -- The size of the result of subtracting two pointers to elements of the same array
- (<a href="#6.5.6">6.5.6</a>).
-<a name="J.3.8" href="#J.3.8"><b> J.3.8 Hints</b></a>
-1 -- The extent to which suggestions made by using the register storage-class
- specifier are effective (<a href="#6.7.1">6.7.1</a>).
- -- The extent to which suggestions made by using the inline function specifier are
- effective (<a href="#6.7.4">6.7.4</a>).
-<a name="J.3.9" href="#J.3.9"><b> J.3.9 Structures, unions, enumerations, and bit-fields</b></a>
-1 -- Whether a ''plain'' int bit-field is treated as a signed int bit-field or as an
- unsigned int bit-field (<a href="#6.7.2">6.7.2</a>, <a href="#6.7.2.1">6.7.2.1</a>).
- -- Allowable bit-field types other than _Bool, signed int, and unsigned int
- (<a href="#6.7.2.1">6.7.2.1</a>).
- -- Whether a bit-field can straddle a storage-unit boundary (<a href="#6.7.2.1">6.7.2.1</a>).
- -- The order of allocation of bit-fields within a unit (<a href="#6.7.2.1">6.7.2.1</a>).
- -- The alignment of non-bit-field members of structures (<a href="#6.7.2.1">6.7.2.1</a>). This should present
- no problem unless binary data written by one implementation is read by another.
- -- The integer type compatible with each enumerated type (<a href="#6.7.2.2">6.7.2.2</a>).
-<a name="J.3.10" href="#J.3.10"><b> J.3.10 Qualifiers</b></a>
-1 -- What constitutes an access to an object that has volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
-<a name="J.3.11" href="#J.3.11"><b> J.3.11 Preprocessing directives</b></a>
-1 -- The locations within #pragma directives where header name preprocessing tokens
- are recognized (<a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>).
- -- How sequences in both forms of header names are mapped to headers or external
- source file names (<a href="#6.4.7">6.4.7</a>).
- -- Whether the value of a character constant in a constant expression that controls
- conditional inclusion matches the value of the same character constant in the
- execution character set (<a href="#6.10.1">6.10.1</a>).
- -- Whether the value of a single-character character constant in a constant expression
- that controls conditional inclusion may have a negative value (<a href="#6.10.1">6.10.1</a>).
- -- The places that are searched for an included < > delimited header, and how the places
- are specified or the header is identified (<a href="#6.10.2">6.10.2</a>).
-[<a name="#p569" href="p569">page 569</a>] (<a href="#Contents">Contents</a>)
-
- -- How the named source file is searched for in an included " " delimited header
- (<a href="#6.10.2">6.10.2</a>).
- -- The method by which preprocessing tokens (possibly resulting from macro
- expansion) in a #include directive are combined into a header name (<a href="#6.10.2">6.10.2</a>).
- -- The nesting limit for #include processing (<a href="#6.10.2">6.10.2</a>).
- -- Whether the # operator inserts a \ character before the \ character that begins a
- universal character name in a character constant or string literal (<a href="#6.10.3.2">6.10.3.2</a>).
- -- The behavior on each recognized non-STDC #pragma directive (<a href="#6.10.6">6.10.6</a>).
- -- The definitions for __DATE__ and __TIME__ when respectively, the date and
- time of translation are not available (<a href="#6.10.8.1">6.10.8.1</a>).
-<a name="J.3.12" href="#J.3.12"><b> J.3.12 Library functions</b></a>
-1 -- Any library facilities available to a freestanding program, other than the minimal set
- required by clause 4 (<a href="#5.1.2.1">5.1.2.1</a>).
- -- The format of the diagnostic printed by the assert macro (<a href="#7.2.1.1">7.2.1.1</a>).
- -- The representation of the floating-point status flags stored by the
- fegetexceptflag function (<a href="#7.6.2.2">7.6.2.2</a>).
- -- Whether the feraiseexcept function raises the ''inexact'' floating-point
- exception in addition to the ''overflow'' or ''underflow'' floating-point exception
- (<a href="#7.6.2.3">7.6.2.3</a>).
- -- Strings other than "C" and "" that may be passed as the second argument to the
- setlocale function (<a href="#7.11.1.1">7.11.1.1</a>).
- -- The types defined for float_t and double_t when the value of the
- FLT_EVAL_METHOD macro is less than 0 (<a href="#7.12">7.12</a>).
- -- Domain errors for the mathematics functions, other than those required by this
- International Standard (<a href="#7.12.1">7.12.1</a>).
- -- The values returned by the mathematics functions on domain errors or pole errors
- (<a href="#7.12.1">7.12.1</a>).
- -- The values returned by the mathematics functions on underflow range errors, whether
- errno is set to the value of the macro ERANGE when the integer expression
- math_errhandling & MATH_ERRNO is nonzero, and whether the ''underflow''
- floating-point exception is raised when the integer expression math_errhandling
- & MATH_ERREXCEPT is nonzero. (<a href="#7.12.1">7.12.1</a>).
- -- Whether a domain error occurs or zero is returned when an fmod function has a
- second argument of zero (<a href="#7.12.10.1">7.12.10.1</a>).
-
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-
--- Whether a domain error occurs or zero is returned when a remainder function has
- a second argument of zero (<a href="#7.12.10.2">7.12.10.2</a>).
--- The base-2 logarithm of the modulus used by the remquo functions in reducing the
- quotient (<a href="#7.12.10.3">7.12.10.3</a>).
--- Whether a domain error occurs or zero is returned when a remquo function has a
- second argument of zero (<a href="#7.12.10.3">7.12.10.3</a>).
--- Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call
- of a signal handler, and, if not, the blocking of signals that is performed (<a href="#7.14.1.1">7.14.1.1</a>).
--- The null pointer constant to which the macro NULL expands (<a href="#7.19">7.19</a>).
--- Whether the last line of a text stream requires a terminating new-line character
- (<a href="#7.21.2">7.21.2</a>).
--- Whether space characters that are written out to a text stream immediately before a
- new-line character appear when read in (<a href="#7.21.2">7.21.2</a>).
--- The number of null characters that may be appended to data written to a binary
- stream (<a href="#7.21.2">7.21.2</a>).
--- Whether the file position indicator of an append-mode stream is initially positioned at
- the beginning or end of the file (<a href="#7.21.3">7.21.3</a>).
--- Whether a write on a text stream causes the associated file to be truncated beyond that
- point (<a href="#7.21.3">7.21.3</a>).
--- The characteristics of file buffering (<a href="#7.21.3">7.21.3</a>).
--- Whether a zero-length file actually exists (<a href="#7.21.3">7.21.3</a>).
--- The rules for composing valid file names (<a href="#7.21.3">7.21.3</a>).
--- Whether the same file can be simultaneously open multiple times (<a href="#7.21.3">7.21.3</a>).
--- The nature and choice of encodings used for multibyte characters in files (<a href="#7.21.3">7.21.3</a>).
--- The effect of the remove function on an open file (<a href="#7.21.4.1">7.21.4.1</a>).
--- The effect if a file with the new name exists prior to a call to the rename function
- (<a href="#7.21.4.2">7.21.4.2</a>).
--- Whether an open temporary file is removed upon abnormal program termination
- (<a href="#7.21.4.3">7.21.4.3</a>).
--- Which changes of mode are permitted (if any), and under what circumstances
- (<a href="#7.21.5.4">7.21.5.4</a>).
--- The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
- sequence printed for a NaN (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>).
-
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-
--- The output for %p conversion in the fprintf or fwprintf function (<a href="#7.21.6.1">7.21.6.1</a>,
- <a href="#7.28.2.1">7.28.2.1</a>).
--- The interpretation of a - character that is neither the first nor the last character, nor
- the second where a ^ character is the first, in the scanlist for %[ conversion in the
- fscanf or fwscanf function (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>).
--- The set of sequences matched by a %p conversion and the interpretation of the
- corresponding input item in the fscanf or fwscanf function (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>).
--- The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
- functions on failure (<a href="#7.21.9.1">7.21.9.1</a>, <a href="#7.21.9.3">7.21.9.3</a>, <a href="#7.21.9.4">7.21.9.4</a>).
--- The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
- converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold
- function (<a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.28.4.1.1">7.28.4.1.1</a>).
--- Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
- function sets errno to ERANGE when underflow occurs (<a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.28.4.1.1">7.28.4.1.1</a>).
--- Whether the calloc, malloc, and realloc functions return a null pointer or a
- pointer to an allocated object when the size requested is zero (<a href="#7.22.3">7.22.3</a>).
--- Whether open streams with unwritten buffered data are flushed, open streams are
- closed, or temporary files are removed when the abort or _Exit function is called
- (<a href="#7.22.4.1">7.22.4.1</a>, <a href="#7.22.4.5">7.22.4.5</a>).
--- The termination status returned to the host environment by the abort, exit,
- _Exit, or quick_exit function (<a href="#7.22.4.1">7.22.4.1</a>, <a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>).
--- The value returned by the system function when its argument is not a null pointer
- (<a href="#7.22.4.8">7.22.4.8</a>).
--- The local time zone and Daylight Saving Time (<a href="#7.26.1">7.26.1</a>).
--- The range and precision of times representable in clock_t and time_t (<a href="#7.26">7.26</a>).
--- The era for the clock function (<a href="#7.26.2.1">7.26.2.1</a>).
--- The replacement string for the %Z specifier to the strftime, and wcsftime
- functions in the "C" locale (<a href="#7.26.3.5">7.26.3.5</a>, <a href="#7.28.5.1">7.28.5.1</a>).
--- Whether the functions in <a href="#7.12"><math.h></a> honor the rounding direction mode in an
- IEC 60559 conformant implementation, unless explicitly specified otherwise (<a href="#F.10">F.10</a>).
-
-
-
-
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-
-<a name="J.3.13" href="#J.3.13"><b> J.3.13 Architecture</b></a>
-1 -- The values or expressions assigned to the macros specified in the headers
- <a href="#7.7"><float.h></a>, <a href="#7.10"><limits.h></a>, and <a href="#7.20"><stdint.h></a> (<a href="#5.2.4.2">5.2.4.2</a>, <a href="#7.20.2">7.20.2</a>, <a href="#7.20.3">7.20.3</a>).
- -- The result of attempting to indirectly access an object with automatic or thread
- storage duration from a thread other than the one with which it is associated (<a href="#6.2.4">6.2.4</a>).
- -- The number, order, and encoding of bytes in any object (when not explicitly specified
- in this International Standard) (<a href="#6.2.6.1">6.2.6.1</a>).
- -- Whether any extended alignments are supported and the contexts in which they are
- supported (<a href="#6.2.8">6.2.8</a>).
- -- Valid alignment values other than those returned by an alignof expression for
- fundamental types, if any (<a href="#6.2.8">6.2.8</a>).
- -- The value of the result of the sizeof and alignof operators (<a href="#6.5.3.4">6.5.3.4</a>).
-<a name="J.4" href="#J.4"><b> J.4 Locale-specific behavior</b></a>
-1 The following characteristics of a hosted environment are locale-specific and are required
- to be documented by the implementation:
- -- Additional members of the source and execution character sets beyond the basic
- character set (<a href="#5.2.1">5.2.1</a>).
- -- The presence, meaning, and representation of additional multibyte characters in the
- execution character set beyond the basic character set (<a href="#5.2.1.2">5.2.1.2</a>).
- -- The shift states used for the encoding of multibyte characters (<a href="#5.2.1.2">5.2.1.2</a>).
- -- The direction of writing of successive printing characters (<a href="#5.2.2">5.2.2</a>).
- -- The decimal-point character (<a href="#7.1.1">7.1.1</a>).
- -- The set of printing characters (<a href="#7.4">7.4</a>, <a href="#7.29.2">7.29.2</a>).
- -- The set of control characters (<a href="#7.4">7.4</a>, <a href="#7.29.2">7.29.2</a>).
- -- The sets of characters tested for by the isalpha, isblank, islower, ispunct,
- isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
- iswspace, or iswupper functions (<a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>, <a href="#7.4.1.10">7.4.1.10</a>,
- <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.29.2.1.2">7.29.2.1.2</a>, <a href="#7.29.2.1.3">7.29.2.1.3</a>, <a href="#7.29.2.1.7">7.29.2.1.7</a>, <a href="#7.29.2.1.9">7.29.2.1.9</a>, <a href="#7.29.2.1.10">7.29.2.1.10</a>, <a href="#7.29.2.1.11">7.29.2.1.11</a>).
- -- The native environment (<a href="#7.11.1.1">7.11.1.1</a>).
- -- Additional subject sequences accepted by the numeric conversion functions (<a href="#7.22.1">7.22.1</a>,
- <a href="#7.28.4.1">7.28.4.1</a>).
- -- The collation sequence of the execution character set (<a href="#7.23.4.3">7.23.4.3</a>, <a href="#7.28.4.4.2">7.28.4.4.2</a>).
-
-
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-
- -- The contents of the error message strings set up by the strerror function
- (<a href="#7.23.6.2">7.23.6.2</a>).
- -- The formats for time and date (<a href="#7.26.3.5">7.26.3.5</a>, <a href="#7.28.5.1">7.28.5.1</a>).
- -- Character mappings that are supported by the towctrans function (<a href="#7.29.1">7.29.1</a>).
- -- Character classifications that are supported by the iswctype function (<a href="#7.29.1">7.29.1</a>).
-<a name="J.5" href="#J.5"><b> J.5 Common extensions</b></a>
-1 The following extensions are widely used in many systems, but are not portable to all
- implementations. The inclusion of any extension that may cause a strictly conforming
- program to become invalid renders an implementation nonconforming. Examples of such
- extensions are new keywords, extra library functions declared in standard headers, or
- predefined macros with names that do not begin with an underscore.
-<a name="J.5.1" href="#J.5.1"><b> J.5.1 Environment arguments</b></a>
-1 In a hosted environment, the main function receives a third argument, char *envp[],
- that points to a null-terminated array of pointers to char, each of which points to a string
- that provides information about the environment for this execution of the program
- (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
-<a name="J.5.2" href="#J.5.2"><b> J.5.2 Specialized identifiers</b></a>
-1 Characters other than the underscore _, letters, and digits, that are not part of the basic
- source character set (such as the dollar sign $, or characters in national character sets)
- may appear in an identifier (<a href="#6.4.2">6.4.2</a>).
-<a name="J.5.3" href="#J.5.3"><b> J.5.3 Lengths and cases of identifiers</b></a>
-1 All characters in identifiers (with or without external linkage) are significant (<a href="#6.4.2">6.4.2</a>).
-<a name="J.5.4" href="#J.5.4"><b> J.5.4 Scopes of identifiers</b></a>
-1 A function identifier, or the identifier of an object the declaration of which contains the
- keyword extern, has file scope (<a href="#6.2.1">6.2.1</a>).
-<a name="J.5.5" href="#J.5.5"><b> J.5.5 Writable string literals</b></a>
-1 String literals are modifiable (in which case, identical string literals should denote distinct
- objects) (<a href="#6.4.5">6.4.5</a>).
-
-
-
-
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-
-<a name="J.5.6" href="#J.5.6"><b> J.5.6 Other arithmetic types</b></a>
-1 Additional arithmetic types, such as __int128 or double double, and their
- appropriate conversions are defined (<a href="#6.2.5">6.2.5</a>, <a href="#6.3.1">6.3.1</a>). Additional floating types may have
- more range or precision than long double, may be used for evaluating expressions of
- other floating types, and may be used to define float_t or double_t.
-<a name="J.5.7" href="#J.5.7"><b> J.5.7 Function pointer casts</b></a>
-1 A pointer to an object or to void may be cast to a pointer to a function, allowing data to
- be invoked as a function (<a href="#6.5.4">6.5.4</a>).
-2 A pointer to a function may be cast to a pointer to an object or to void, allowing a
- function to be inspected or modified (for example, by a debugger) (<a href="#6.5.4">6.5.4</a>).
-<a name="J.5.8" href="#J.5.8"><b> J.5.8 Extended bit-field types</b></a>
-1 A bit-field may be declared with a type other than _Bool, unsigned int, or
- signed int, with an appropriate maximum width (<a href="#6.7.2.1">6.7.2.1</a>).
-<a name="J.5.9" href="#J.5.9"><b> J.5.9 The fortran keyword</b></a>
-1 The fortran function specifier may be used in a function declaration to indicate that
- calls suitable for FORTRAN should be generated, or that a different representation for the
- external name is to be generated (<a href="#6.7.4">6.7.4</a>).
-<a name="J.5.10" href="#J.5.10"><b> J.5.10 The asm keyword</b></a>
-1 The asm keyword may be used to insert assembly language directly into the translator
- output (<a href="#6.8">6.8</a>). The most common implementation is via a statement of the form:
- asm ( character-string-literal );
-<a name="J.5.11" href="#J.5.11"><b> J.5.11 Multiple external definitions</b></a>
-1 There may be more than one external definition for the identifier of an object, with or
- without the explicit use of the keyword extern; if the definitions disagree, or more than
- one is initialized, the behavior is undefined (<a href="#6.9.2">6.9.2</a>).
-<a name="J.5.12" href="#J.5.12"><b> J.5.12 Predefined macro names</b></a>
-1 Macro names that do not begin with an underscore, describing the translation and
- execution environments, are defined by the implementation before translation begins
- (<a href="#6.10.8">6.10.8</a>).
-
-
-
-
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-
-<a name="J.5.13" href="#J.5.13"><b> J.5.13 Floating-point status flags</b></a>
-1 If any floating-point status flags are set on normal termination after all calls to functions
- registered by the atexit function have been made (see <a href="#7.22.4.4">7.22.4.4</a>), the implementation
- writes some diagnostics indicating the fact to the stderr stream, if it is still open,
-<a name="J.5.14" href="#J.5.14"><b> J.5.14 Extra arguments for signal handlers</b></a>
-1 Handlers for specific signals are called with extra arguments in addition to the signal
- number (<a href="#7.14.1.1">7.14.1.1</a>).
-<a name="J.5.15" href="#J.5.15"><b> J.5.15 Additional stream types and file-opening modes</b></a>
-1 Additional mappings from files to streams are supported (<a href="#7.21.2">7.21.2</a>).
-2 Additional file-opening modes may be specified by characters appended to the mode
- argument of the fopen function (<a href="#7.21.5.3">7.21.5.3</a>).
-<a name="J.5.16" href="#J.5.16"><b> J.5.16 Defined file position indicator</b></a>
-1 The file position indicator is decremented by each successful call to the ungetc or
- ungetwc function for a text stream, except if its value was zero before a call (<a href="#7.21.7.10">7.21.7.10</a>,
-<a name="7.28.3.10)" href="#7.28.3.10)"><b> 7.28.3.10).</b></a>
-<a name="J.5.17" href="#J.5.17"><b> J.5.17 Math error reporting</b></a>
-1 Functions declared in <a href="#7.3"><complex.h></a> and <a href="#7.12"><math.h></a> raise SIGFPE to report errors
- instead of, or in addition to, setting errno or raising floating-point exceptions (<a href="#7.3">7.3</a>,
-<a name="7.12)" href="#7.12)"><b> 7.12).</b></a>
-
-
-
-
-[<a name="#p576" href="p576">page 576</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K" href="#K"><b> Annex K</b></a>
- (normative)
- Bounds-checking interfaces
-<a name="K.1" href="#K.1"><b> K.1 Background</b></a>
-1 Traditionally, the C Library has contained many functions that trust the programmer to
- provide output character arrays big enough to hold the result being produced. Not only
- do these functions not check that the arrays are big enough, they frequently lack the
- information needed to perform such checks. While it is possible to write safe, robust, and
- error-free code using the existing library, the library tends to promote programming styles
- that lead to mysterious failures if a result is too big for the provided array.
-2 A common programming style is to declare character arrays large enough to handle most
- practical cases. However, if these arrays are not large enough to handle the resulting
- strings, data can be written past the end of the array overwriting other data and program
- structures. The program never gets any indication that a problem exists, and so never has
- a chance to recover or to fail gracefully.
-3 Worse, this style of programming has compromised the security of computers and
- networks. Buffer overflows can often be exploited to run arbitrary code with the
- permissions of the vulnerable (defective) program.
-4 If the programmer writes runtime checks to verify lengths before calling library
- functions, then those runtime checks frequently duplicate work done inside the library
- functions, which discover string lengths as a side effect of doing their job.
-5 This annex provides alternative library functions that promote safer, more secure
- programming. The alternative functions verify that output buffers are large enough for
- the intended result and return a failure indicator if they are not. Data is never written past
- the end of an array. All string results are null terminated.
-6 This annex also addresses another problem that complicates writing robust code:
- functions that are not reentrant because they return pointers to static objects owned by the
- function. Such functions can be troublesome since a previously returned result can
- change if the function is called again, perhaps by another thread.
-
-
-
-
-[<a name="#p577" href="p577">page 577</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.2" href="#K.2"><b> K.2 Scope</b></a>
-1 This annex specifies a series of optional extensions that can be useful in the mitigation of
- security vulnerabilities in programs, and comprise new functions, macros, and types
- declared or defined in existing standard headers.
-2 An implementation that defines __STDC_LIB_EXT1__ shall conform to the
- specifications in this annex.361)
-3 Subclause <a href="#K.3">K.3</a> should be read as if it were merged into the parallel structure of named
- subclauses of clause 7.
-<a name="K.3" href="#K.3"><b> K.3 Library</b></a>
-<a name="K.3.1" href="#K.3.1"><b> K.3.1 Introduction</b></a>
-<a name="K.3.1.1" href="#K.3.1.1"><b> K.3.1.1 Standard headers</b></a>
-1 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are not
- declared or defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
- defined as a macro which expands to the integer constant 0 at the point in the source file
- where the appropriate header is first included.
-2 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are
- declared and defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
- defined as a macro which expands to the integer constant 1 at the point in the source file
- where the appropriate header is first included.362)
-3 It is implementation-defined whether the functions, macros, and types declared or defined
- in <a href="#K.3">K.3</a> and its subclauses are declared or defined by their respective headers if
- __STDC_WANT_LIB_EXT1__ is not defined as a macro at the point in the source file
- where the appropriate header is first included.363)
-4 Within a preprocessing translation unit, __STDC_WANT_LIB_EXT1__ shall be
- defined identically for all inclusions of any headers from subclause <a href="#K.3">K.3</a>. If
- __STDC_WANT_LIB_EXT1__ is defined differently for any such inclusion, the
- implementation shall issue a diagnostic as if a preprocessor error directive were used.
-
-
- 361) Implementations that do not define __STDC_LIB_EXT1__ are not required to conform to these
- specifications.
- 362) Future revisions of this International Standard may define meanings for other values of
- __STDC_WANT_LIB_EXT1__.
- 363) Subclause <a href="#7.1.3">7.1.3</a> reserves certain names and patterns of names that an implementation may use in
- headers. All other names are not reserved, and a conforming implementation is not permitted to use
- them. While some of the names defined in <a href="#K.3">K.3</a> and its subclauses are reserved, others are not. If an
- unreserved name is defined in a header when __STDC_WANT_LIB_EXT1__ is defined as 0, the
- implementation is not conforming.
-
-[<a name="#p578" href="p578">page 578</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.1.2" href="#K.3.1.2"><b> K.3.1.2 Reserved identifiers</b></a>
-1 Each macro name in any of the following subclauses is reserved for use as specified if it
- is defined by any of its associated headers when included; unless explicitly stated
- otherwise (see <a href="#7.1.4">7.1.4</a>).
-2 All identifiers with external linkage in any of the following subclauses are reserved for
- use as identifiers with external linkage if any of them are used by the program. None of
- them are reserved if none of them are used.
-3 Each identifier with file scope listed in any of the following subclauses is reserved for use
- as a macro name and as an identifier with file scope in the same name space if it is
- defined by any of its associated headers when included.
-<a name="K.3.1.3" href="#K.3.1.3"><b> K.3.1.3 Use of errno</b></a>
-1 An implementation may set errno for the functions defined in this annex, but is not
- required to.
-<a name="K.3.1.4" href="#K.3.1.4"><b> K.3.1.4 Runtime-constraint violations</b></a>
-1 Most functions in this annex include as part of their specification a list of runtime-
- constraints. These runtime-constraints are requirements on the program using the
- library.364)
-2 Implementations shall verify that the runtime-constraints for a function are not violated
- by the program. If a runtime-constraint is violated, the implementation shall call the
- currently registered runtime-constraint handler (see set_constraint_handler_s
- in <a href="#7.22"><stdlib.h></a>). Multiple runtime-constraint violations in the same call to a library
- function result in only one call to the runtime-constraint handler. It is unspecified which
- one of the multiple runtime-constraint violations cause the handler to be called.
-3 If the runtime-constraints section for a function states an action to be performed when a
- runtime-constraint violation occurs, the function shall perform the action before calling
- the runtime-constraint handler. If the runtime-constraints section lists actions that are
- prohibited when a runtime-constraint violation occurs, then such actions are prohibited to
- the function both before calling the handler and after the handler returns.
-4 The runtime-constraint handler might not return. If the handler does return, the library
- function whose runtime-constraint was violated shall return some indication of failure as
- given by the returns section in the function's specification.
-
-
-
- 364) Although runtime-constraints replace many cases of undefined behavior, undefined behavior still
- exists in this annex. Implementations are free to detect any case of undefined behavior and treat it as a
- runtime-constraint violation by calling the runtime-constraint handler. This license comes directly
- from the definition of undefined behavior.
-
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-
-<a name="K.3.2" href="#K.3.2"><b> K.3.2 Errors <errno.h></b></a>
-1 The header <a href="#7.5"><errno.h></a> defines a type.
-2 The type is
- errno_t
- which is type int.365)
-<a name="K.3.3" href="#K.3.3"><b> K.3.3 Common definitions <stddef.h></b></a>
-1 The header <a href="#7.19"><stddef.h></a> defines a type.
-2 The type is
- rsize_t
- which is the type size_t.366)
-<a name="K.3.4" href="#K.3.4"><b> K.3.4 Integer types <stdint.h></b></a>
-1 The header <a href="#7.20"><stdint.h></a> defines a macro.
-2 The macro is
- RSIZE_MAX
- which expands to a value367) of type size_t. Functions that have parameters of type
- rsize_t consider it a runtime-constraint violation if the values of those parameters are
- greater than RSIZE_MAX.
- Recommended practice
-3 Extremely large object sizes are frequently a sign that an object's size was calculated
- incorrectly. For example, negative numbers appear as very large positive numbers when
- converted to an unsigned type like size_t. Also, some implementations do not support
- objects as large as the maximum value that can be represented by type size_t.
-4 For those reasons, it is sometimes beneficial to restrict the range of object sizes to detect
- programming errors. For implementations targeting machines with large address spaces,
- it is recommended that RSIZE_MAX be defined as the smaller of the size of the largest
- object supported or (SIZE_MAX >> 1), even if this limit is smaller than the size of
- some legitimate, but very large, objects. Implementations targeting machines with small
- address spaces may wish to define RSIZE_MAX as SIZE_MAX, which means that there
-
- 365) As a matter of programming style, errno_t may be used as the type of something that deals only
- with the values that might be found in errno. For example, a function which returns the value of
- errno might be declared as having the return type errno_t.
- 366) See the description of the RSIZE_MAX macro in <a href="#7.20"><stdint.h></a>.
- 367) The macro RSIZE_MAX need not expand to a constant expression.
-
-[<a name="#p580" href="p580">page 580</a>] (<a href="#Contents">Contents</a>)
-
- is no object size that is considered a runtime-constraint violation.
-<a name="K.3.5" href="#K.3.5"><b> K.3.5 Input/output <stdio.h></b></a>
-1 The header <a href="#7.21"><stdio.h></a> defines several macros and two types.
-2 The macros are
- L_tmpnam_s
- which expands to an integer constant expression that is the size needed for an array of
- char large enough to hold a temporary file name string generated by the tmpnam_s
- function;
- TMP_MAX_S
- which expands to an integer constant expression that is the maximum number of unique
- file names that can be generated by the tmpnam_s function.
-3 The types are
- errno_t
- which is type int; and
- rsize_t
- which is the type size_t.
-<a name="K.3.5.1" href="#K.3.5.1"><b> K.3.5.1 Operations on files</b></a>
-<a name="K.3.5.1.1" href="#K.3.5.1.1"><b> K.3.5.1.1 The tmpfile_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.21"><stdio.h></a>
- errno_t tmpfile_s(FILE * restrict * restrict streamptr);
- Runtime-constraints
-2 streamptr shall not be a null pointer.
-3 If there is a runtime-constraint violation, tmpfile_s does not attempt to create a file.
- Description
-4 The tmpfile_s function creates a temporary binary file that is different from any other
- existing file and that will automatically be removed when it is closed or at program
- termination. If the program terminates abnormally, whether an open temporary file is
- removed is implementation-defined. The file is opened for update with "wb+" mode
- with the meaning that mode has in the fopen_s function (including the mode's effect
- on exclusive access and file permissions).
-
-
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-
-5 If the file was created successfully, then the pointer to FILE pointed to by streamptr
- will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
- to FILE pointed to by streamptr will be set to a null pointer.
- Recommended practice
- It should be possible to open at least TMP_MAX_S temporary files during the lifetime of
- the program (this limit may be shared with tmpnam_s) and there should be no limit on
- the number simultaneously open other than this limit and any limit on the number of open
- files (FOPEN_MAX).
- Returns
-6 The tmpfile_s function returns zero if it created the file. If it did not create the file or
- there was a runtime-constraint violation, tmpfile_s returns a nonzero value.
-<a name="K.3.5.1.2" href="#K.3.5.1.2"><b> K.3.5.1.2 The tmpnam_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.21"><stdio.h></a>
- errno_t tmpnam_s(char *s, rsize_t maxsize);
- Runtime-constraints
-2 s shall not be a null pointer. maxsize shall be less than or equal to RSIZE_MAX.
- maxsize shall be greater than the length of the generated file name string.
- Description
-3 The tmpnam_s function generates a string that is a valid file name and that is not the
- same as the name of an existing file.368) The function is potentially capable of generating
- TMP_MAX_S different strings, but any or all of them may already be in use by existing
- files and thus not be suitable return values. The lengths of these strings shall be less than
- the value of the L_tmpnam_s macro.
-4 The tmpnam_s function generates a different string each time it is called.
-5 It is assumed that s points to an array of at least maxsize characters. This array will be
- set to generated string, as specified below.
-
-
-
- 368) Files created using strings generated by the tmpnam_s function are temporary only in the sense that
- their names should not collide with those generated by conventional naming rules for the
- implementation. It is still necessary to use the remove function to remove such files when their use
- is ended, and before program termination. Implementations should take care in choosing the patterns
- used for names returned by tmpnam_s. For example, making a thread id part of the names avoids the
- race condition and possible conflict when multiple programs run simultaneously by the same user
- generate the same temporary file names.
-
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-
-6 The implementation shall behave as if no library function except tmpnam calls the
- tmpnam_s function.369)
- Recommended practice
-7 After a program obtains a file name using the tmpnam_s function and before the
- program creates a file with that name, the possibility exists that someone else may create
- a file with that same name. To avoid this race condition, the tmpfile_s function
- should be used instead of tmpnam_s when possible. One situation that requires the use
- of the tmpnam_s function is when the program needs to create a temporary directory
- rather than a temporary file.
- Returns
-8 If no suitable string can be generated, or if there is a runtime-constraint violation, the
- tmpnam_s function writes a null character to s[0] (only if s is not null and maxsize
- is greater than zero) and returns a nonzero value.
-9 Otherwise, the tmpnam_s function writes the string in the array pointed to by s and
- returns zero.
- Environmental limits
-10 The value of the macro TMP_MAX_S shall be at least 25.
-<a name="K.3.5.2" href="#K.3.5.2"><b> K.3.5.2 File access functions</b></a>
-<a name="K.3.5.2.1" href="#K.3.5.2.1"><b> K.3.5.2.1 The fopen_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.21"><stdio.h></a>
- errno_t fopen_s(FILE * restrict * restrict streamptr,
- const char * restrict filename,
- const char * restrict mode);
- Runtime-constraints
-2 None of streamptr, filename, or mode shall be a null pointer.
-3 If there is a runtime-constraint violation, fopen_s does not attempt to open a file.
- Furthermore, if streamptr is not a null pointer, fopen_s sets *streamptr to the
- null pointer.
-
-
-
-
- 369) An implementation may have tmpnam call tmpnam_s (perhaps so there is only one naming
- convention for temporary files), but this is not required.
-
-[<a name="#p583" href="p583">page 583</a>] (<a href="#Contents">Contents</a>)
-
- Description
-4 The fopen_s function opens the file whose name is the string pointed to by
- filename, and associates a stream with it.
-5 The mode string shall be as described for fopen, with the addition that modes starting
- with the character 'w' or 'a' may be preceded by the character 'u', see below:
- uw truncate to zero length or create text file for writing, default
- permissions
- uwx create text file for writing, default permissions
- ua append; open or create text file for writing at end-of-file, default
- permissions
- uwb truncate to zero length or create binary file for writing, default
- permissions
- uwbx create binary file for writing, default permissions
- uab append; open or create binary file for writing at end-of-file, default
- permissions
- uw+ truncate to zero length or create text file for update, default
- permissions
- uw+x create text file for update, default permissions
- ua+ append; open or create text file for update, writing at end-of-file,
- default permissions
- uw+b or uwb+ truncate to zero length or create binary file for update, default
- permissions
- uw+bx or uwb+x create binary file for update, default permissions
- ua+b or uab+ append; open or create binary file for update, writing at end-of-file,
- default permissions
-6 Opening a file with exclusive mode ('x' as the last character in the mode argument)
- fails if the file already exists or cannot be created.
-7 To the extent that the underlying system supports the concepts, files opened for writing
- shall be opened with exclusive (also known as non-shared) access. If the file is being
- created, and the first character of the mode string is not 'u', to the extent that the
- underlying system supports it, the file shall have a file permission that prevents other
- users on the system from accessing the file. If the file is being created and first character
- of the mode string is 'u', then by the time the file has been closed, it shall have the
- system default file access permissions.370)
-8 If the file was opened successfully, then the pointer to FILE pointed to by streamptr
- will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
-
-
- 370) These are the same permissions that the file would have been created with by fopen.
-
-[<a name="#p584" href="p584">page 584</a>] (<a href="#Contents">Contents</a>)
-
- to FILE pointed to by streamptr will be set to a null pointer.
- Returns
-9 The fopen_s function returns zero if it opened the file. If it did not open the file or if
- there was a runtime-constraint violation, fopen_s returns a nonzero value.
-<a name="K.3.5.2.2" href="#K.3.5.2.2"><b> K.3.5.2.2 The freopen_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.21"><stdio.h></a>
- errno_t freopen_s(FILE * restrict * restrict newstreamptr,
- const char * restrict filename,
- const char * restrict mode,
- FILE * restrict stream);
- Runtime-constraints
-2 None of newstreamptr, mode, and stream shall be a null pointer.
-3 If there is a runtime-constraint violation, freopen_s neither attempts to close any file
- associated with stream nor attempts to open a file. Furthermore, if newstreamptr is
- not a null pointer, fopen_s sets *newstreamptr to the null pointer.
- Description
-4 The freopen_s function opens the file whose name is the string pointed to by
- filename and associates the stream pointed to by stream with it. The mode
- argument has the same meaning as in the fopen_s function (including the mode's effect
- on exclusive access and file permissions).
-5 If filename is a null pointer, the freopen_s function attempts to change the mode of
- the stream to that specified by mode, as if the name of the file currently associated with
- the stream had been used. It is implementation-defined which changes of mode are
- permitted (if any), and under what circumstances.
-6 The freopen_s function first attempts to close any file that is associated with stream.
- Failure to close the file is ignored. The error and end-of-file indicators for the stream are
- cleared.
-7 If the file was opened successfully, then the pointer to FILE pointed to by
- newstreamptr will be set to the value of stream. Otherwise, the pointer to FILE
- pointed to by newstreamptr will be set to a null pointer.
- Returns
-8 The freopen_s function returns zero if it opened the file. If it did not open the file or
- there was a runtime-constraint violation, freopen_s returns a nonzero value.
-
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-
-<a name="K.3.5.3" href="#K.3.5.3"><b> K.3.5.3 Formatted input/output functions</b></a>
-1 Unless explicitly stated otherwise, if the execution of a function described in this
- subclause causes copying to take place between objects that overlap, the objects take on
- unspecified values.
-<a name="K.3.5.3.1" href="#K.3.5.3.1"><b> K.3.5.3.1 The fprintf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.21"><stdio.h></a>
- int fprintf_s(FILE * restrict stream,
- const char * restrict format, ...);
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. The %n specifier371) (modified or
- not by flags, field width, or precision) shall not appear in the string pointed to by
- format. Any argument to fprintf_s corresponding to a %s specifier shall not be a
- null pointer.
-3 If there is a runtime-constraint violation,372) the fprintf_s function does not attempt
- to produce further output, and it is unspecified to what extent fprintf_s produced
- output before discovering the runtime-constraint violation.
- Description
-4 The fprintf_s function is equivalent to the fprintf function except for the explicit
- runtime-constraints listed above.
- Returns
-5 The fprintf_s function returns the number of characters transmitted, or a negative
- value if an output error, encoding error, or runtime-constraint violation occurred.
-
-
-
-
- 371) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
- 372) Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
- implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
- constraint violation.
-
-[<a name="#p586" href="p586">page 586</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.5.3.2" href="#K.3.5.3.2"><b> K.3.5.3.2 The fscanf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.21"><stdio.h></a>
- int fscanf_s(FILE * restrict stream,
- const char * restrict format, ...);
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. Any argument indirected though in
- order to store converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation,373) the fscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent fscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The fscanf_s function is equivalent to fscanf except that the c, s, and [ conversion
- specifiers apply to a pair of arguments (unless assignment suppression is indicated by a
- *). The first of these arguments is the same as for fscanf. That argument is
- immediately followed in the argument list by the second argument, which has type
- rsize_t and gives the number of elements in the array pointed to by the first argument
- of the pair. If the first argument points to a scalar object, it is considered to be an array of
- one element.374)
-5 A matching failure occurs if the number of elements in a receiving object is insufficient to
- hold the converted input (including any trailing null character).
- Returns
-6 The fscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
-
- 373) Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
- implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
- constraint violation.
- 374) If the format is known at translation time, an implementation may issue a diagnostic for any argument
- used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
- argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
- the format is not known at translation time. For example, an implementation may issue a diagnostic
- for each argument after format that has of type pointer to one of char, signed char,
- unsigned char, or void that is not followed by an argument of a type compatible with
- rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
- using the hh length modifier, a length argument must follow the pointer argument. Another useful
- diagnostic could flag any non-pointer argument following format that did not have a type
- compatible with rsize_t.
-
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-
- fscanf_s function returns the number of input items assigned, which can be fewer than
- provided for, or even zero, in the event of an early matching failure.
-7 EXAMPLE 1 The call:
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.21"><stdio.h></a>
- /* ... */
- int n, i; float x; char name[50];
- n = fscanf_s(stdin, "%d%f%s", &i, &x, name, (rsize_t) 50);
- with the input line:
- 25 54.32E-1 thompson
- will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
- thompson\0.
-
-8 EXAMPLE 2 The call:
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.21"><stdio.h></a>
- /* ... */
- int n; char s[5];
- n = fscanf_s(stdin, "%s", s, sizeof s);
- with the input line:
- hello
- will assign to n the value 0 since a matching failure occurred because the sequence hello\0 requires an
- array of six characters to store it.
-
-<a name="K.3.5.3.3" href="#K.3.5.3.3"><b> K.3.5.3.3 The printf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.21"><stdio.h></a>
- int printf_s(const char * restrict format, ...);
- Runtime-constraints
-2 format shall not be a null pointer. The %n specifier375) (modified or not by flags, field
- width, or precision) shall not appear in the string pointed to by format. Any argument
- to printf_s corresponding to a %s specifier shall not be a null pointer.
-3 If there is a runtime-constraint violation, the printf_s function does not attempt to
- produce further output, and it is unspecified to what extent printf_s produced output
- before discovering the runtime-constraint violation.
-
-
- 375) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
-
-[<a name="#p588" href="p588">page 588</a>] (<a href="#Contents">Contents</a>)
-
- Description
-4 The printf_s function is equivalent to the printf function except for the explicit
- runtime-constraints listed above.
- Returns
-5 The printf_s function returns the number of characters transmitted, or a negative
- value if an output error, encoding error, or runtime-constraint violation occurred.
-<a name="K.3.5.3.4" href="#K.3.5.3.4"><b> K.3.5.3.4 The scanf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.21"><stdio.h></a>
- int scanf_s(const char * restrict format, ...);
- Runtime-constraints
-2 format shall not be a null pointer. Any argument indirected though in order to store
- converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the scanf_s function does not attempt to
- perform further input, and it is unspecified to what extent scanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The scanf_s function is equivalent to fscanf_s with the argument stdin
- interposed before the arguments to scanf_s.
- Returns
-5 The scanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- scanf_s function returns the number of input items assigned, which can be fewer than
- provided for, or even zero, in the event of an early matching failure.
-<a name="K.3.5.3.5" href="#K.3.5.3.5"><b> K.3.5.3.5 The snprintf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.21"><stdio.h></a>
- int snprintf_s(char * restrict s, rsize_t n,
- const char * restrict format, ...);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The %n specifier376) (modified or not by flags, field width, or
- precision) shall not appear in the string pointed to by format. Any argument to
-[<a name="#p589" href="p589">page 589</a>] (<a href="#Contents">Contents</a>)
-
- snprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
- error shall occur.
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the snprintf_s function sets s[0] to the
- null character.
- Description
-4 The snprintf_s function is equivalent to the snprintf function except for the
- explicit runtime-constraints listed above.
-5 The snprintf_s function, unlike sprintf_s, will truncate the result to fit within the
- array pointed to by s.
- Returns
-6 The snprintf_s function returns the number of characters that would have been
- written had n been sufficiently large, not counting the terminating null character, or a
- negative value if a runtime-constraint violation occurred. Thus, the null-terminated
- output has been completely written if and only if the returned value is nonnegative and
- less than n.
-<a name="K.3.5.3.6" href="#K.3.5.3.6"><b> K.3.5.3.6 The sprintf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.21"><stdio.h></a>
- int sprintf_s(char * restrict s, rsize_t n,
- const char * restrict format, ...);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The number of characters (including the trailing null) required for the
- result to be written to the array pointed to by s shall not be greater than n. The %n
- specifier377) (modified or not by flags, field width, or precision) shall not appear in the
- string pointed to by format. Any argument to sprintf_s corresponding to a %s
- specifier shall not be a null pointer. No encoding error shall occur.
-
-
-
- 376) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
- 377) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
-
-[<a name="#p590" href="p590">page 590</a>] (<a href="#Contents">Contents</a>)
-
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the sprintf_s function sets s[0] to the
- null character.
- Description
-4 The sprintf_s function is equivalent to the sprintf function except for the
- parameter n and the explicit runtime-constraints listed above.
-5 The sprintf_s function, unlike snprintf_s, treats a result too big for the array
- pointed to by s as a runtime-constraint violation.
- Returns
-6 If no runtime-constraint violation occurred, the sprintf_s function returns the number
- of characters written in the array, not counting the terminating null character. If an
- encoding error occurred, sprintf_s returns a negative value. If any other runtime-
- constraint violation occurred, sprintf_s returns zero.
-<a name="K.3.5.3.7" href="#K.3.5.3.7"><b> K.3.5.3.7 The sscanf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.21"><stdio.h></a>
- int sscanf_s(const char * restrict s,
- const char * restrict format, ...);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. Any argument indirected though in order
- to store converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the sscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent sscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The sscanf_s function is equivalent to fscanf_s, except that input is obtained from
- a string (specified by the argument s) rather than from a stream. Reaching the end of the
- string is equivalent to encountering end-of-file for the fscanf_s function. If copying
- takes place between objects that overlap, the objects take on unspecified values.
- Returns
-5 The sscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- sscanf_s function returns the number of input items assigned, which can be fewer than
- provided for, or even zero, in the event of an early matching failure.
-
-[<a name="#p591" href="p591">page 591</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.5.3.8" href="#K.3.5.3.8"><b> K.3.5.3.8 The vfprintf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- int vfprintf_s(FILE * restrict stream,
- const char * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. The %n specifier378) (modified or
- not by flags, field width, or precision) shall not appear in the string pointed to by
- format. Any argument to vfprintf_s corresponding to a %s specifier shall not be a
- null pointer.
-3 If there is a runtime-constraint violation, the vfprintf_s function does not attempt to
- produce further output, and it is unspecified to what extent vfprintf_s produced
- output before discovering the runtime-constraint violation.
- Description
-4 The vfprintf_s function is equivalent to the vfprintf function except for the
- explicit runtime-constraints listed above.
- Returns
-5 The vfprintf_s function returns the number of characters transmitted, or a negative
- value if an output error, encoding error, or runtime-constraint violation occurred.
-<a name="K.3.5.3.9" href="#K.3.5.3.9"><b> K.3.5.3.9 The vfscanf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- int vfscanf_s(FILE * restrict stream,
- const char * restrict format,
- va_list arg);
-
-
-
-
- 378) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
-
-[<a name="#p592" href="p592">page 592</a>] (<a href="#Contents">Contents</a>)
-
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. Any argument indirected though in
- order to store converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vfscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent vfscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The vfscanf_s function is equivalent to fscanf_s, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vfscanf_s function does not invoke the
- va_end macro.379)
- Returns
-5 The vfscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- vfscanf_s function returns the number of input items assigned, which can be fewer
- than provided for, or even zero, in the event of an early matching failure.
-<a name="K.3.5.3.10" href="#K.3.5.3.10"><b> K.3.5.3.10 The vprintf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- int vprintf_s(const char * restrict format,
- va_list arg);
- Runtime-constraints
-2 format shall not be a null pointer. The %n specifier380) (modified or not by flags, field
- width, or precision) shall not appear in the string pointed to by format. Any argument
- to vprintf_s corresponding to a %s specifier shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vprintf_s function does not attempt to
- produce further output, and it is unspecified to what extent vprintf_s produced output
- before discovering the runtime-constraint violation.
-
- 379) As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
- vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
- indeterminate.
- 380) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
-
-[<a name="#p593" href="p593">page 593</a>] (<a href="#Contents">Contents</a>)
-
- Description
-4 The vprintf_s function is equivalent to the vprintf function except for the explicit
- runtime-constraints listed above.
- Returns
-5 The vprintf_s function returns the number of characters transmitted, or a negative
- value if an output error, encoding error, or runtime-constraint violation occurred.
-<a name="K.3.5.3.11" href="#K.3.5.3.11"><b> K.3.5.3.11 The vscanf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- int vscanf_s(const char * restrict format,
- va_list arg);
- Runtime-constraints
-2 format shall not be a null pointer. Any argument indirected though in order to store
- converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent vscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The vscanf_s function is equivalent to scanf_s, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vscanf_s function does not invoke the
- va_end macro.381)
- Returns
-5 The vscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- vscanf_s function returns the number of input items assigned, which can be fewer than
- provided for, or even zero, in the event of an early matching failure.
-
-
-
-
- 381) As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
- vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
- indeterminate.
-
-[<a name="#p594" href="p594">page 594</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.5.3.12" href="#K.3.5.3.12"><b> K.3.5.3.12 The vsnprintf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- int vsnprintf_s(char * restrict s, rsize_t n,
- const char * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The %n specifier382) (modified or not by flags, field width, or
- precision) shall not appear in the string pointed to by format. Any argument to
- vsnprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
- error shall occur.
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the vsnprintf_s function sets s[0] to the
- null character.
- Description
-4 The vsnprintf_s function is equivalent to the vsnprintf function except for the
- explicit runtime-constraints listed above.
-5 The vsnprintf_s function, unlike vsprintf_s, will truncate the result to fit within
- the array pointed to by s.
- Returns
-6 The vsnprintf_s function returns the number of characters that would have been
- written had n been sufficiently large, not counting the terminating null character, or a
- negative value if a runtime-constraint violation occurred. Thus, the null-terminated
- output has been completely written if and only if the returned value is nonnegative and
- less than n.
-
-
-
-
- 382) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
-
-[<a name="#p595" href="p595">page 595</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.5.3.13" href="#K.3.5.3.13"><b> K.3.5.3.13 The vsprintf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- int vsprintf_s(char * restrict s, rsize_t n,
- const char * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The number of characters (including the trailing null) required for the
- result to be written to the array pointed to by s shall not be greater than n. The %n
- specifier383) (modified or not by flags, field width, or precision) shall not appear in the
- string pointed to by format. Any argument to vsprintf_s corresponding to a %s
- specifier shall not be a null pointer. No encoding error shall occur.
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the vsprintf_s function sets s[0] to the
- null character.
- Description
-4 The vsprintf_s function is equivalent to the vsprintf function except for the
- parameter n and the explicit runtime-constraints listed above.
-5 The vsprintf_s function, unlike vsnprintf_s, treats a result too big for the array
- pointed to by s as a runtime-constraint violation.
- Returns
-6 If no runtime-constraint violation occurred, the vsprintf_s function returns the
- number of characters written in the array, not counting the terminating null character. If
- an encoding error occurred, vsprintf_s returns a negative value. If any other
- runtime-constraint violation occurred, vsprintf_s returns zero.
-
-
-
-
- 383) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
-
-[<a name="#p596" href="p596">page 596</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.5.3.14" href="#K.3.5.3.14"><b> K.3.5.3.14 The vsscanf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- int vsscanf_s(const char * restrict s,
- const char * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. Any argument indirected though in order
- to store converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vsscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent vsscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The vsscanf_s function is equivalent to sscanf_s, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vsscanf_s function does not invoke the
- va_end macro.384)
- Returns
-5 The vsscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- vscanf_s function returns the number of input items assigned, which can be fewer than
- provided for, or even zero, in the event of an early matching failure.
-<a name="K.3.5.4" href="#K.3.5.4"><b> K.3.5.4 Character input/output functions</b></a>
-<a name="K.3.5.4.1" href="#K.3.5.4.1"><b> K.3.5.4.1 The gets_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.21"><stdio.h></a>
- char *gets_s(char *s, rsize_t n);
-
-
-
-
- 384) As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
- vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
- indeterminate.
-
-[<a name="#p597" href="p597">page 597</a>] (<a href="#Contents">Contents</a>)
-
- Runtime-constraints
-2 s shall not be a null pointer. n shall neither be equal to zero nor be greater than
- RSIZE_MAX. A new-line character, end-of-file, or read error shall occur within reading
- n-1 characters from stdin.385)
-3 If there is a runtime-constraint violation, s[0] is set to the null character, and characters
- are read and discarded from stdin until a new-line character is read, or end-of-file or a
- read error occurs.
- Description
-4 The gets_s function reads at most one less than the number of characters specified by n
- from the stream pointed to by stdin, into the array pointed to by s. No additional
- characters are read after a new-line character (which is discarded) or after end-of-file.
- The discarded new-line character does not count towards number of characters read. A
- null character is written immediately after the last character read into the array.
-5 If end-of-file is encountered and no characters have been read into the array, or if a read
- error occurs during the operation, then s[0] is set to the null character, and the other
- elements of s take unspecified values.
- Recommended practice
-6 The fgets function allows properly-written programs to safely process input lines too
- long to store in the result array. In general this requires that callers of fgets pay
- attention to the presence or absence of a new-line character in the result array. Consider
- using fgets (along with any needed processing based on new-line characters) instead of
- gets_s.
- Returns
-7 The gets_s function returns s if successful. If there was a runtime-constraint violation,
- or if end-of-file is encountered and no characters have been read into the array, or if a
- read error occurs during the operation, then a null pointer is returned.
-
-
-
-
- 385) The gets_s function, unlike the historical gets function, makes it a runtime-constraint violation for
- a line of input to overflow the buffer to store it. Unlike the fgets function, gets_s maintains a
- one-to-one relationship between input lines and successful calls to gets_s. Programs that use gets
- expect such a relationship.
-
-[<a name="#p598" href="p598">page 598</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.6" href="#K.3.6"><b> K.3.6 General utilities <stdlib.h></b></a>
-1 The header <a href="#7.22"><stdlib.h></a> defines three types.
-2 The types are
- errno_t
- which is type int; and
- rsize_t
- which is the type size_t; and
- constraint_handler_t
- which has the following definition
- typedef void (*constraint_handler_t)(
- const char * restrict msg,
- void * restrict ptr,
- errno_t error);
-<a name="K.3.6.1" href="#K.3.6.1"><b> K.3.6.1 Runtime-constraint handling</b></a>
-<a name="K.3.6.1.1" href="#K.3.6.1.1"><b> K.3.6.1.1 The set_constraint_handler_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.22"><stdlib.h></a>
- constraint_handler_t set_constraint_handler_s(
- constraint_handler_t handler);
- Description
-2 The set_constraint_handler_s function sets the runtime-constraint handler to
- be handler. The runtime-constraint handler is the function to be called when a library
- function detects a runtime-constraint violation. Only the most recent handler registered
- with set_constraint_handler_s is called when a runtime-constraint violation
- occurs.
-3 When the handler is called, it is passed the following arguments in the following order:
- 1. A pointer to a character string describing the runtime-constraint violation.
- 2. A null pointer or a pointer to an implementation defined object.
- 3. If the function calling the handler has a return type declared as errno_t, the
- return value of the function is passed. Otherwise, a positive value of type
- errno_t is passed.
-
-
-
-[<a name="#p599" href="p599">page 599</a>] (<a href="#Contents">Contents</a>)
-
-4 The implementation has a default constraint handler that is used if no calls to the
- set_constraint_handler_s function have been made. The behavior of the
- default handler is implementation-defined, and it may cause the program to exit or abort.
-5 If the handler argument to set_constraint_handler_s is a null pointer, the
- implementation default handler becomes the current constraint handler.
- Returns
-6 The set_constraint_handler_s function returns a pointer to the previously
- registered handler.386)
-<a name="K.3.6.1.2" href="#K.3.6.1.2"><b> K.3.6.1.2 The abort_handler_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.22"><stdlib.h></a>
- void abort_handler_s(
- const char * restrict msg,
- void * restrict ptr,
- errno_t error);
- Description
-2 A pointer to the abort_handler_s function shall be a suitable argument to the
- set_constraint_handler_s function.
-3 The abort_handler_s function writes a message on the standard error stream in an
- implementation-defined format. The message shall include the string pointed to by msg.
- The abort_handler_s function then calls the abort function.387)
- Returns
-4 The abort_handler_s function does not return to its caller.
-
-
-
-
- 386) If the previous handler was registered by calling set_constraint_handler_s with a null
- pointer argument, a pointer to the implementation default handler is returned (not NULL).
- 387) Many implementations invoke a debugger when the abort function is called.
-
-[<a name="#p600" href="p600">page 600</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.6.1.3" href="#K.3.6.1.3"><b> K.3.6.1.3 The ignore_handler_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.22"><stdlib.h></a>
- void ignore_handler_s(
- const char * restrict msg,
- void * restrict ptr,
- errno_t error);
- Description
-2 A pointer to the ignore_handler_s function shall be a suitable argument to the
- set_constraint_handler_s function.
-3 The ignore_handler_s function simply returns to its caller.388)
- Returns
-4 The ignore_handler_s function returns no value.
-<a name="K.3.6.2" href="#K.3.6.2"><b> K.3.6.2 Communication with the environment</b></a>
-<a name="K.3.6.2.1" href="#K.3.6.2.1"><b> K.3.6.2.1 The getenv_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.22"><stdlib.h></a>
- errno_t getenv_s(size_t * restrict len,
- char * restrict value, rsize_t maxsize,
- const char * restrict name);
- Runtime-constraints
-2 name shall not be a null pointer. maxsize shall neither equal zero nor be greater than
- RSIZE_MAX. If maxsize is not equal to zero, then value shall not be a null pointer.
-3 If there is a runtime-constraint violation, the integer pointed to by len is set to 0 (if len
- is not null), and the environment list is not searched.
- Description
-4 The getenv_s function searches an environment list, provided by the host environment,
- for a string that matches the string pointed to by name.
-
-
- 388) If the runtime-constraint handler is set to the ignore_handler_s function, any library function in
- which a runtime-constraint violation occurs will return to its caller. The caller can determine whether
- a runtime-constraint violation occurred based on the library function's specification (usually, the
- library function returns a nonzero errno_t).
-
-[<a name="#p601" href="p601">page 601</a>] (<a href="#Contents">Contents</a>)
-
-5 If that name is found then getenv_s performs the following actions. If len is not a
- null pointer, the length of the string associated with the matched list member is stored in
- the integer pointed to by len. If the length of the associated string is less than maxsize,
- then the associated string is copied to the array pointed to by value.
-6 If that name is not found then getenv_s performs the following actions. If len is not
- a null pointer, zero is stored in the integer pointed to by len. If maxsize is greater than
- zero, then value[0] is set to the null character.
-7 The set of environment names and the method for altering the environment list are
- implementation-defined.
- Returns
-8 The getenv_s function returns zero if the specified name is found and the associated
- string was successfully stored in value. Otherwise, a nonzero value is returned.
-<a name="K.3.6.3" href="#K.3.6.3"><b> K.3.6.3 Searching and sorting utilities</b></a>
-1 These utilities make use of a comparison function to search or sort arrays of unspecified
- type. Where an argument declared as size_t nmemb specifies the length of the array
- for a function, if nmemb has the value zero on a call to that function, then the comparison
- function is not called, a search finds no matching element, sorting performs no
- rearrangement, and the pointer to the array may be null.
-2 The implementation shall ensure that the second argument of the comparison function
- (when called from bsearch_s), or both arguments (when called from qsort_s), are
- pointers to elements of the array.389) The first argument when called from bsearch_s
- shall equal key.
-3 The comparison function shall not alter the contents of either the array or search key. The
- implementation may reorder elements of the array between calls to the comparison
- function, but shall not otherwise alter the contents of any individual element.
-4 When the same objects (consisting of size bytes, irrespective of their current positions
- in the array) are passed more than once to the comparison function, the results shall be
- consistent with one another. That is, for qsort_s they shall define a total ordering on
- the array, and for bsearch_s the same object shall always compare the same way with
- the key.
-
-
-
-
- 389) That is, if the value passed is p, then the following expressions are always valid and nonzero:
- ((char *)p - (char *)base) % size == 0
- (char *)p >= (char *)base
- (char *)p < (char *)base + nmemb * size
-
-
-[<a name="#p602" href="p602">page 602</a>] (<a href="#Contents">Contents</a>)
-
-5 A sequence point occurs immediately before and immediately after each call to the
- comparison function, and also between any call to the comparison function and any
- movement of the objects passed as arguments to that call.
-<a name="K.3.6.3.1" href="#K.3.6.3.1"><b> K.3.6.3.1 The bsearch_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.22"><stdlib.h></a>
- void *bsearch_s(const void *key, const void *base,
- rsize_t nmemb, rsize_t size,
- int (*compar)(const void *k, const void *y,
- void *context),
- void *context);
- Runtime-constraints
-2 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
- zero, then none of key, base, or compar shall be a null pointer.
-3 If there is a runtime-constraint violation, the bsearch_s function does not search the
- array.
- Description
-4 The bsearch_s function searches an array of nmemb objects, the initial element of
- which is pointed to by base, for an element that matches the object pointed to by key.
- The size of each element of the array is specified by size.
-5 The comparison function pointed to by compar is called with three arguments. The first
- two point to the key object and to an array element, in that order. The function shall
- return an integer less than, equal to, or greater than zero if the key object is considered,
- respectively, to be less than, to match, or to be greater than the array element. The array
- shall consist of: all the elements that compare less than, all the elements that compare
- equal to, and all the elements that compare greater than the key object, in that order.390)
- The third argument to the comparison function is the context argument passed to
- bsearch_s. The sole use of context by bsearch_s is to pass it to the comparison
- function.391)
-
-
-
-
- 390) In practice, this means that the entire array has been sorted according to the comparison function.
- 391) The context argument is for the use of the comparison function in performing its duties. For
- example, it might specify a collating sequence used by the comparison function.
-
-[<a name="#p603" href="p603">page 603</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-6 The bsearch_s function returns a pointer to a matching element of the array, or a null
- pointer if no match is found or there is a runtime-constraint violation. If two elements
- compare as equal, which element is matched is unspecified.
-<a name="K.3.6.3.2" href="#K.3.6.3.2"><b> K.3.6.3.2 The qsort_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.22"><stdlib.h></a>
- errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
- int (*compar)(const void *x, const void *y,
- void *context),
- void *context);
- Runtime-constraints
-2 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
- zero, then neither base nor compar shall be a null pointer.
-3 If there is a runtime-constraint violation, the qsort_s function does not sort the array.
- Description
-4 The qsort_s function sorts an array of nmemb objects, the initial element of which is
- pointed to by base. The size of each object is specified by size.
-5 The contents of the array are sorted into ascending order according to a comparison
- function pointed to by compar, which is called with three arguments. The first two
- point to the objects being compared. The function shall return an integer less than, equal
- to, or greater than zero if the first argument is considered to be respectively less than,
- equal to, or greater than the second. The third argument to the comparison function is the
- context argument passed to qsort_s. The sole use of context by qsort_s is to
- pass it to the comparison function.392)
-6 If two elements compare as equal, their relative order in the resulting sorted array is
- unspecified.
- Returns
-7 The qsort_s function returns zero if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-
-
-
-
- 392) The context argument is for the use of the comparison function in performing its duties. For
- example, it might specify a collating sequence used by the comparison function.
-
-[<a name="#p604" href="p604">page 604</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.6.4" href="#K.3.6.4"><b> K.3.6.4 Multibyte/wide character conversion functions</b></a>
-1 The behavior of the multibyte character functions is affected by the LC_CTYPE category
- of the current locale. For a state-dependent encoding, each function is placed into its
- initial conversion state by a call for which its character pointer argument, s, is a null
- pointer. Subsequent calls with s as other than a null pointer cause the internal conversion
- state of the function to be altered as necessary. A call with s as a null pointer causes
- these functions to set the int pointed to by their status argument to a nonzero value if
- encodings have state dependency, and zero otherwise.393) Changing the LC_CTYPE
- category causes the conversion state of these functions to be indeterminate.
-<a name="K.3.6.4.1" href="#K.3.6.4.1"><b> K.3.6.4.1 The wctomb_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.22"><stdlib.h></a>
- errno_t wctomb_s(int * restrict status,
- char * restrict s,
- rsize_t smax,
- wchar_t wc);
- Runtime-constraints
-2 Let n denote the number of bytes needed to represent the multibyte character
- corresponding to the wide character given by wc (including any shift sequences).
-3 If s is not a null pointer, then smax shall not be less than n, and smax shall not be
- greater than RSIZE_MAX. If s is a null pointer, then smax shall equal zero.
-4 If there is a runtime-constraint violation, wctomb_s does not modify the int pointed to
- by status, and if s is not a null pointer, no more than smax elements in the array
- pointed to by s will be accessed.
- Description
-5 The wctomb_s function determines n and stores the multibyte character representation
- of wc in the array whose first element is pointed to by s (if s is not a null pointer). The
- number of characters stored never exceeds MB_CUR_MAX or smax. If wc is a null wide
- character, a null byte is stored, preceded by any shift sequence needed to restore the
- initial shift state, and the function is left in the initial conversion state.
-6 The implementation shall behave as if no library function calls the wctomb_s function.
-
-
-
- 393) If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
- character codes, but are grouped with an adjacent multibyte character.
-
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-
-7 If s is a null pointer, the wctomb_s function stores into the int pointed to by status a
- nonzero or zero value, if multibyte character encodings, respectively, do or do not have
- state-dependent encodings.
-8 If s is not a null pointer, the wctomb_s function stores into the int pointed to by
- status either n or -1 if wc, respectively, does or does not correspond to a valid
- multibyte character.
-9 In no case will the int pointed to by status be set to a value greater than the
- MB_CUR_MAX macro.
- Returns
-10 The wctomb_s function returns zero if successful, and a nonzero value if there was a
- runtime-constraint violation or wc did not correspond to a valid multibyte character.
-<a name="K.3.6.5" href="#K.3.6.5"><b> K.3.6.5 Multibyte/wide string conversion functions</b></a>
-1 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
- the current locale.
-<a name="K.3.6.5.1" href="#K.3.6.5.1"><b> K.3.6.5.1 The mbstowcs_s function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- errno_t mbstowcs_s(size_t * restrict retval,
- wchar_t * restrict dst, rsize_t dstmax,
- const char * restrict src, rsize_t len);
- Runtime-constraints
-2 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
- neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
- then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
- zero. If dst is not a null pointer and len is not less than dstmax, then a null character
- shall occur within the first dstmax multibyte characters of the array pointed to by src.
-3 If there is a runtime-constraint violation, then mbstowcs_s does the following. If
- retval is not a null pointer, then mbstowcs_s sets *retval to (size_t)(-1). If
- dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
- then mbstowcs_s sets dst[0] to the null wide character.
- Description
-4 The mbstowcs_s function converts a sequence of multibyte characters that begins in
- the initial shift state from the array pointed to by src into a sequence of corresponding
- wide characters. If dst is not a null pointer, the converted characters are stored into the
- array pointed to by dst. Conversion continues up to and including a terminating null
- character, which is also stored. Conversion stops earlier in two cases: when a sequence of
-[<a name="#p606" href="p606">page 606</a>] (<a href="#Contents">Contents</a>)
-
- bytes is encountered that does not form a valid multibyte character, or (if dst is not a
- null pointer) when len wide characters have been stored into the array pointed to by
- dst.394) If dst is not a null pointer and no null wide character was stored into the array
- pointed to by dst, then dst[len] is set to the null wide character. Each conversion
- takes place as if by a call to the mbrtowc function.
-5 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
- sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
- the mbstowcs_s function stores the value (size_t)(-1) into *retval.
- Otherwise, the mbstowcs_s function stores into *retval the number of multibyte
- characters successfully converted, not including the terminating null character (if any).
-6 All elements following the terminating null wide character (if any) written by
- mbstowcs_s in the array of dstmax wide characters pointed to by dst take
- unspecified values when mbstowcs_s returns.395)
-7 If copying takes place between objects that overlap, the objects take on unspecified
- values.
- Returns
-8 The mbstowcs_s function returns zero if no runtime-constraint violation and no
- encoding error occurred. Otherwise, a nonzero value is returned.
-<a name="K.3.6.5.2" href="#K.3.6.5.2"><b> K.3.6.5.2 The wcstombs_s function</b></a>
- Synopsis
-1 #include <a href="#7.22"><stdlib.h></a>
- errno_t wcstombs_s(size_t * restrict retval,
- char * restrict dst, rsize_t dstmax,
- const wchar_t * restrict src, rsize_t len);
- Runtime-constraints
-2 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
- neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
- then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
- zero. If dst is not a null pointer and len is not less than dstmax, then the conversion
- shall have been stopped (see below) because a terminating null wide character was
- reached or because an encoding error occurred.
-
-
-
-
- 394) Thus, the value of len is ignored if dst is a null pointer.
- 395) This allows an implementation to attempt converting the multibyte string before discovering a
- terminating null character did not occur where required.
-
-[<a name="#p607" href="p607">page 607</a>] (<a href="#Contents">Contents</a>)
-
-3 If there is a runtime-constraint violation, then wcstombs_s does the following. If
- retval is not a null pointer, then wcstombs_s sets *retval to (size_t)(-1). If
- dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
- then wcstombs_s sets dst[0] to the null character.
- Description
-4 The wcstombs_s function converts a sequence of wide characters from the array
- pointed to by src into a sequence of corresponding multibyte characters that begins in
- the initial shift state. If dst is not a null pointer, the converted characters are then stored
- into the array pointed to by dst. Conversion continues up to and including a terminating
- null wide character, which is also stored. Conversion stops earlier in two cases:
- -- when a wide character is reached that does not correspond to a valid multibyte
- character;
- -- (if dst is not a null pointer) when the next multibyte character would exceed the
- limit of n total bytes to be stored into the array pointed to by dst. If the wide
- character being converted is the null wide character, then n is the lesser of len or
- dstmax. Otherwise, n is the lesser of len or dstmax-1.
- If the conversion stops without converting a null wide character and dst is not a null
- pointer, then a null character is stored into the array pointed to by dst immediately
- following any multibyte characters already stored. Each conversion takes place as if by a
- call to the wcrtomb function.396)
-5 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
- wide character that does not correspond to a valid multibyte character, an encoding error
- occurs: the wcstombs_s function stores the value (size_t)(-1) into *retval.
- Otherwise, the wcstombs_s function stores into *retval the number of bytes in the
- resulting multibyte character sequence, not including the terminating null character (if
- any).
-6 All elements following the terminating null character (if any) written by wcstombs_s
- in the array of dstmax elements pointed to by dst take unspecified values when
- wcstombs_s returns.397)
-7 If copying takes place between objects that overlap, the objects take on unspecified
- values.
-
-
- 396) If conversion stops because a terminating null wide character has been reached, the bytes stored
- include those necessary to reach the initial shift state immediately before the null byte. However, if
- the conversion stops before a terminating null wide character has been reached, the result will be null
- terminated, but might not end in the initial shift state.
- 397) When len is not less than dstmax, the implementation might fill the array before discovering a
- runtime-constraint violation.
-
-[<a name="#p608" href="p608">page 608</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-8 The wcstombs_s function returns zero if no runtime-constraint violation and no
- encoding error occurred. Otherwise, a nonzero value is returned.
-<a name="K.3.7" href="#K.3.7"><b> K.3.7 String handling <string.h></b></a>
-1 The header <a href="#7.23"><string.h></a> defines two types.
-2 The types are
- errno_t
- which is type int; and
- rsize_t
- which is the type size_t.
-<a name="K.3.7.1" href="#K.3.7.1"><b> K.3.7.1 Copying functions</b></a>
-<a name="K.3.7.1.1" href="#K.3.7.1.1"><b> K.3.7.1.1 The memcpy_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.23"><string.h></a>
- errno_t memcpy_s(void * restrict s1, rsize_t s1max,
- const void * restrict s2, rsize_t n);
- Runtime-constraints
-2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
- objects that overlap.
-3 If there is a runtime-constraint violation, the memcpy_s function stores zeros in the first
- s1max characters of the object pointed to by s1 if s1 is not a null pointer and s1max is
- not greater than RSIZE_MAX.
- Description
-4 The memcpy_s function copies n characters from the object pointed to by s2 into the
- object pointed to by s1.
- Returns
-5 The memcpy_s function returns zero if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-
-
-
-
-[<a name="#p609" href="p609">page 609</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.7.1.2" href="#K.3.7.1.2"><b> K.3.7.1.2 The memmove_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.23"><string.h></a>
- errno_t memmove_s(void *s1, rsize_t s1max,
- const void *s2, rsize_t n);
- Runtime-constraints
-2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. n shall not be greater than s1max.
-3 If there is a runtime-constraint violation, the memmove_s function stores zeros in the
- first s1max characters of the object pointed to by s1 if s1 is not a null pointer and
- s1max is not greater than RSIZE_MAX.
- Description
-4 The memmove_s function copies n characters from the object pointed to by s2 into the
- object pointed to by s1. This copying takes place as if the n characters from the object
- pointed to by s2 are first copied into a temporary array of n characters that does not
- overlap the objects pointed to by s1 or s2, and then the n characters from the temporary
- array are copied into the object pointed to by s1.
- Returns
-5 The memmove_s function returns zero if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-<a name="K.3.7.1.3" href="#K.3.7.1.3"><b> K.3.7.1.3 The strcpy_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.23"><string.h></a>
- errno_t strcpy_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2);
- Runtime-constraints
-2 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
- s1max shall not equal zero. s1max shall be greater than strnlen_s(s2, s1max).
- Copying shall not take place between objects that overlap.
-3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then strcpy_s sets s1[0] to the
- null character.
-
-[<a name="#p610" href="p610">page 610</a>] (<a href="#Contents">Contents</a>)
-
- Description
-4 The strcpy_s function copies the string pointed to by s2 (including the terminating
- null character) into the array pointed to by s1.
-5 All elements following the terminating null character (if any) written by strcpy_s in
- the array of s1max characters pointed to by s1 take unspecified values when
- strcpy_s returns.398)
- Returns
-6 The strcpy_s function returns zero399) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-<a name="K.3.7.1.4" href="#K.3.7.1.4"><b> K.3.7.1.4 The strncpy_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.23"><string.h></a>
- errno_t strncpy_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2,
- rsize_t n);
- Runtime-constraints
-2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
- shall be greater than strnlen_s(s2, s1max). Copying shall not take place between
- objects that overlap.
-3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then strncpy_s sets s1[0] to the
- null character.
- Description
-4 The strncpy_s function copies not more than n successive characters (characters that
- follow a null character are not copied) from the array pointed to by s2 to the array
- pointed to by s1. If no null character was copied from s2, then s1[n] is set to a null
- character.
-
-
- 398) This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
- any of those characters are null. Such an approach might write a character to every element of s1
- before discovering that the first element should be set to the null character.
- 399) A zero return value implies that all of the requested characters from the string pointed to by s2 fit
- within the array pointed to by s1 and that the result in s1 is null terminated.
-
-[<a name="#p611" href="p611">page 611</a>] (<a href="#Contents">Contents</a>)
-
-5 All elements following the terminating null character (if any) written by strncpy_s in
- the array of s1max characters pointed to by s1 take unspecified values when
- strncpy_s returns.400)
- Returns
-6 The strncpy_s function returns zero401) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-7 EXAMPLE 1 The strncpy_s function can be used to copy a string without the danger that the result
- will not be null terminated or that characters will be written past the end of the destination array.
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.23"><string.h></a>
- /* ... */
- char src1[100] = "hello";
- char src2[7] = {'g', 'o', 'o', 'd', 'b', 'y', 'e'};
- char dst1[6], dst2[5], dst3[5];
- int r1, r2, r3;
- r1 = strncpy_s(dst1, 6, src1, 100);
- r2 = strncpy_s(dst2, 5, src2, 7);
- r3 = strncpy_s(dst3, 5, src2, 4);
- The first call will assign to r1 the value zero and to dst1 the sequence hello\0.
- The second call will assign to r2 a nonzero value and to dst2 the sequence \0.
- The third call will assign to r3 the value zero and to dst3 the sequence good\0.
-
-<a name="K.3.7.2" href="#K.3.7.2"><b> K.3.7.2 Concatenation functions</b></a>
-<a name="K.3.7.2.1" href="#K.3.7.2.1"><b> K.3.7.2.1 The strcat_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.23"><string.h></a>
- errno_t strcat_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2);
- Runtime-constraints
-2 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
- strcat_s.
-
-
-
-
- 400) This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
- any of those characters are null. Such an approach might write a character to every element of s1
- before discovering that the first element should be set to the null character.
- 401) A zero return value implies that all of the requested characters from the string pointed to by s2 fit
- within the array pointed to by s1 and that the result in s1 is null terminated.
-
-[<a name="#p612" href="p612">page 612</a>] (<a href="#Contents">Contents</a>)
-
-3 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
- s1max shall not equal zero. m shall not equal zero.402) m shall be greater than
- strnlen_s(s2, m). Copying shall not take place between objects that overlap.
-4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then strcat_s sets s1[0] to the
- null character.
- Description
-5 The strcat_s function appends a copy of the string pointed to by s2 (including the
- terminating null character) to the end of the string pointed to by s1. The initial character
- from s2 overwrites the null character at the end of s1.
-6 All elements following the terminating null character (if any) written by strcat_s in
- the array of s1max characters pointed to by s1 take unspecified values when
- strcat_s returns.403)
- Returns
-7 The strcat_s function returns zero404) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-<a name="K.3.7.2.2" href="#K.3.7.2.2"><b> K.3.7.2.2 The strncat_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.23"><string.h></a>
- errno_t strncat_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2,
- rsize_t n);
- Runtime-constraints
-2 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
- strncat_s.
-3 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.405) If n is not less
-
-
- 402) Zero means that s1 was not null terminated upon entry to strcat_s.
- 403) This allows an implementation to append characters from s2 to s1 while simultaneously checking if
- any of those characters are null. Such an approach might write a character to every element of s1
- before discovering that the first element should be set to the null character.
- 404) A zero return value implies that all of the requested characters from the string pointed to by s2 were
- appended to the string pointed to by s1 and that the result in s1 is null terminated.
-
-[<a name="#p613" href="p613">page 613</a>] (<a href="#Contents">Contents</a>)
-
- than m, then m shall be greater than strnlen_s(s2, m). Copying shall not take
- place between objects that overlap.
-4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then strncat_s sets s1[0] to the
- null character.
- Description
-5 The strncat_s function appends not more than n successive characters (characters
- that follow a null character are not copied) from the array pointed to by s2 to the end of
- the string pointed to by s1. The initial character from s2 overwrites the null character at
- the end of s1. If no null character was copied from s2, then s1[s1max-m+n] is set to
- a null character.
-6 All elements following the terminating null character (if any) written by strncat_s in
- the array of s1max characters pointed to by s1 take unspecified values when
- strncat_s returns.406)
- Returns
-7 The strncat_s function returns zero407) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-8 EXAMPLE 1 The strncat_s function can be used to copy a string without the danger that the result
- will not be null terminated or that characters will be written past the end of the destination array.
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.23"><string.h></a>
- /* ... */
- char s1[100] = "good";
- char s2[6] = "hello";
- char s3[6] = "hello";
- char s4[7] = "abc";
- char s5[1000] = "bye";
- int r1, r2, r3, r4;
- r1 = strncat_s(s1, 100, s5, 1000);
- r2 = strncat_s(s2, 6, "", 1);
- r3 = strncat_s(s3, 6, "X", 2);
- r4 = strncat_s(s4, 7, "defghijklmn", 3);
- After the first call r1 will have the value zero and s1 will contain the sequence goodbye\0.
-
-
-
- 405) Zero means that s1 was not null terminated upon entry to strncat_s.
- 406) This allows an implementation to append characters from s2 to s1 while simultaneously checking if
- any of those characters are null. Such an approach might write a character to every element of s1
- before discovering that the first element should be set to the null character.
- 407) A zero return value implies that all of the requested characters from the string pointed to by s2 were
- appended to the string pointed to by s1 and that the result in s1 is null terminated.
-
-[<a name="#p614" href="p614">page 614</a>] (<a href="#Contents">Contents</a>)
-
- After the second call r2 will have the value zero and s2 will contain the sequence hello\0.
- After the third call r3 will have a nonzero value and s3 will contain the sequence \0.
- After the fourth call r4 will have the value zero and s4 will contain the sequence abcdef\0.
-
-<a name="K.3.7.3" href="#K.3.7.3"><b> K.3.7.3 Search functions</b></a>
-<a name="K.3.7.3.1" href="#K.3.7.3.1"><b> K.3.7.3.1 The strtok_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.23"><string.h></a>
- char *strtok_s(char * restrict s1,
- rsize_t * restrict s1max,
- const char * restrict s2,
- char ** restrict ptr);
- Runtime-constraints
-2 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
- shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
- The end of the token found shall occur within the first *s1max characters of s1 for the
- first call, and shall occur within the first *s1max characters of where searching resumes
- on subsequent calls.
-3 If there is a runtime-constraint violation, the strtok_s function does not indirect
- through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
- Description
-4 A sequence of calls to the strtok_s function breaks the string pointed to by s1 into a
- sequence of tokens, each of which is delimited by a character from the string pointed to
- by s2. The fourth argument points to a caller-provided char pointer into which the
- strtok_s function stores information necessary for it to continue scanning the same
- string.
-5 The first call in a sequence has a non-null first argument and s1max points to an object
- whose value is the number of elements in the character array pointed to by the first
- argument. The first call stores an initial value in the object pointed to by ptr and
- updates the value pointed to by s1max to reflect the number of elements that remain in
- relation to ptr. Subsequent calls in the sequence have a null first argument and the
- objects pointed to by s1max and ptr are required to have the values stored by the
- previous call in the sequence, which are then updated. The separator string pointed to by
- s2 may be different from call to call.
-6 The first call in the sequence searches the string pointed to by s1 for the first character
- that is not contained in the current separator string pointed to by s2. If no such character
- is found, then there are no tokens in the string pointed to by s1 and the strtok_s
- function returns a null pointer. If such a character is found, it is the start of the first token.
-[<a name="#p615" href="p615">page 615</a>] (<a href="#Contents">Contents</a>)
-
-7 The strtok_s function then searches from there for the first character in s1 that is
- contained in the current separator string. If no such character is found, the current token
- extends to the end of the string pointed to by s1, and subsequent searches in the same
- string for a token return a null pointer. If such a character is found, it is overwritten by a
- null character, which terminates the current token.
-8 In all cases, the strtok_s function stores sufficient information in the pointer pointed
- to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
- value for ptr, shall start searching just past the element overwritten by a null character
- (if any).
- Returns
-9 The strtok_s function returns a pointer to the first character of a token, or a null
- pointer if there is no token or there is a runtime-constraint violation.
-10 EXAMPLE
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.23"><string.h></a>
- static char str1[] = "?a???b,,,#c";
- static char str2[] = "\t \t";
- char *t, *ptr1, *ptr2;
- rsize_t max1 = sizeof(str1);
- rsize_t max2 = sizeof(str2);
- t = strtok_s(str1, &max1, "?", &ptr1); // t points to the token "a"
- t = strtok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
- t = strtok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
- t = strtok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
- t = strtok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
-
-<a name="K.3.7.4" href="#K.3.7.4"><b> K.3.7.4 Miscellaneous functions</b></a>
-<a name="K.3.7.4.1" href="#K.3.7.4.1"><b> K.3.7.4.1 The memset_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.23"><string.h></a>
- errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
- Runtime-constraints
-2 s shall not be a null pointer. Neither smax nor n shall be greater than RSIZE_MAX. n
- shall not be greater than smax.
-3 If there is a runtime-constraint violation, then if s is not a null pointer and smax is not
- greater than RSIZE_MAX, the memset_s function stores the value of c (converted to an
- unsigned char) into each of the first smax characters of the object pointed to by s.
-
-
-
-[<a name="#p616" href="p616">page 616</a>] (<a href="#Contents">Contents</a>)
-
- Description
-4 The memset_s function copies the value of c (converted to an unsigned char) into
- each of the first n characters of the object pointed to by s. Unlike memset, any call to
- the memset_s function shall be evaluated strictly according to the rules of the abstract
- machine as described in (<a href="#5.1.2.3">5.1.2.3</a>). That is, any call to the memset_s function shall
- assume that the memory indicated by s and n may be accessible in the future and thus
- must contain the values indicated by c.
- Returns
-5 The memset_s function returns zero if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-<a name="K.3.7.4.2" href="#K.3.7.4.2"><b> K.3.7.4.2 The strerror_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.23"><string.h></a>
- errno_t strerror_s(char *s, rsize_t maxsize,
- errno_t errnum);
- Runtime-constraints
-2 s shall not be a null pointer. maxsize shall not be greater than RSIZE_MAX.
- maxsize shall not equal zero.
-3 If there is a runtime-constraint violation, then the array (if any) pointed to by s is not
- modified.
- Description
-4 The strerror_s function maps the number in errnum to a locale-specific message
- string. Typically, the values for errnum come from errno, but strerror_s shall
- map any value of type int to a message.
-5 If the length of the desired string is less than maxsize, then the string is copied to the
- array pointed to by s.
-6 Otherwise, if maxsize is greater than zero, then maxsize-1 characters are copied
- from the string to the array pointed to by s and then s[maxsize-1] is set to the null
- character. Then, if maxsize is greater than 3, then s[maxsize-2],
- s[maxsize-3], and s[maxsize-4] are set to the character period (.).
- Returns
-7 The strerror_s function returns zero if the length of the desired string was less than
- maxsize and there was no runtime-constraint violation. Otherwise, the strerror_s
- function returns a nonzero value.
-
-[<a name="#p617" href="p617">page 617</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.7.4.3" href="#K.3.7.4.3"><b> K.3.7.4.3 The strerrorlen_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.23"><string.h></a>
- size_t strerrorlen_s(errno_t errnum);
- Description
-2 The strerrorlen_s function calculates the length of the (untruncated) locale-specific
- message string that the strerror_s function maps to errnum.
- Returns
-3 The strerrorlen_s function returns the number of characters (not including the null
- character) in the full message string.
-<a name="K.3.7.4.4" href="#K.3.7.4.4"><b> K.3.7.4.4 The strnlen_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.23"><string.h></a>
- size_t strnlen_s(const char *s, size_t maxsize);
- Description
-2 The strnlen_s function computes the length of the string pointed to by s.
- Returns
-3 If s is a null pointer,408) then the strnlen_s function returns zero.
-4 Otherwise, the strnlen_s function returns the number of characters that precede the
- terminating null character. If there is no null character in the first maxsize characters of
- s then strnlen_s returns maxsize. At most the first maxsize characters of s shall
- be accessed by strnlen_s.
-
-
-
-
- 408) Note that the strnlen_s function has no runtime-constraints. This lack of runtime-constraints
- along with the values returned for a null pointer or an unterminated string argument make
- strnlen_s useful in algorithms that gracefully handle such exceptional data.
-
-[<a name="#p618" href="p618">page 618</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.8" href="#K.3.8"><b> K.3.8 Date and time <time.h></b></a>
-1 The header <a href="#7.26"><time.h></a> defines two types.
-2 The types are
- errno_t
- which is type int; and
- rsize_t
- which is the type size_t.
-<a name="K.3.8.1" href="#K.3.8.1"><b> K.3.8.1 Components of time</b></a>
-1 A broken-down time is normalized if the values of the members of the tm structure are in
- their normal rages.409)
-<a name="K.3.8.2" href="#K.3.8.2"><b> K.3.8.2 Time conversion functions</b></a>
-1 Like the strftime function, the asctime_s and ctime_s functions do not return a
- pointer to a static object, and other library functions are permitted to call them.
-<a name="K.3.8.2.1" href="#K.3.8.2.1"><b> K.3.8.2.1 The asctime_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.26"><time.h></a>
- errno_t asctime_s(char *s, rsize_t maxsize,
- const struct tm *timeptr);
- Runtime-constraints
-2 Neither s nor timeptr shall be a null pointer. maxsize shall not be less than 26 and
- shall not be greater than RSIZE_MAX. The broken-down time pointed to by timeptr
- shall be normalized. The calendar year represented by the broken-down time pointed to
- by timeptr shall not be less than calendar year 0 and shall not be greater than calendar
- year 9999.
-3 If there is a runtime-constraint violation, there is no attempt to convert the time, and
- s[0] is set to a null character if s is not a null pointer and maxsize is not zero and is
- not greater than RSIZE_MAX.
- Description
-4 The asctime_s function converts the normalized broken-down time in the structure
- pointed to by timeptr into a 26 character (including the null character) string in the
-
-
- 409) The normal ranges are defined in <a href="#7.26.1">7.26.1</a>.
-
-[<a name="#p619" href="p619">page 619</a>] (<a href="#Contents">Contents</a>)
-
- form
- Sun Sep 16 01:03:52 1973\n\0
- The fields making up this string are (in order):
- 1. The name of the day of the week represented by timeptr->tm_wday using the
- following three character weekday names: Sun, Mon, Tue, Wed, Thu, Fri, and Sat.
- 2. The character space.
- 3. The name of the month represented by timeptr->tm_mon using the following
- three character month names: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct,
- Nov, and Dec.
- 4. The character space.
- 5. The value of timeptr->tm_mday as if printed using the fprintf format
- "%2d".
- 6. The character space.
- 7. The value of timeptr->tm_hour as if printed using the fprintf format
- "%.2d".
- 8. The character colon.
- 9. The value of timeptr->tm_min as if printed using the fprintf format
- "%.2d".
- 10. The character colon.
- 11. The value of timeptr->tm_sec as if printed using the fprintf format
- "%.2d".
- 12. The character space.
- 13. The value of timeptr->tm_year + 1900 as if printed using the fprintf
- format "%4d".
- 14. The character new line.
- 15. The null character.
- Recommended practice
- The strftime function allows more flexible formatting and supports locale-specific
- behavior. If you do not require the exact form of the result string produced by the
- asctime_s function, consider using the strftime function instead.
- Returns
-5 The asctime_s function returns zero if the time was successfully converted and stored
- into the array pointed to by s. Otherwise, it returns a nonzero value.
-[<a name="#p620" href="p620">page 620</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.8.2.2" href="#K.3.8.2.2"><b> K.3.8.2.2 The ctime_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.26"><time.h></a>
- errno_t ctime_s(char *s, rsize_t maxsize,
- const time_t *timer);
- Runtime-constraints
-2 Neither s nor timer shall be a null pointer. maxsize shall not be less than 26 and
- shall not be greater than RSIZE_MAX.
-3 If there is a runtime-constraint violation, s[0] is set to a null character if s is not a null
- pointer and maxsize is not equal zero and is not greater than RSIZE_MAX.
- Description
-4 The ctime_s function converts the calendar time pointed to by timer to local time in
- the form of a string. It is equivalent to
- asctime_s(s, maxsize, localtime_s(timer))
- Recommended practice
- The strftime function allows more flexible formatting and supports locale-specific
- behavior. If you do not require the exact form of the result string produced by the
- ctime_s function, consider using the strftime function instead.
- Returns
-5 The ctime_s function returns zero if the time was successfully converted and stored
- into the array pointed to by s. Otherwise, it returns a nonzero value.
-<a name="K.3.8.2.3" href="#K.3.8.2.3"><b> K.3.8.2.3 The gmtime_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.26"><time.h></a>
- struct tm *gmtime_s(const time_t * restrict timer,
- struct tm * restrict result);
- Runtime-constraints
-2 Neither timer nor result shall be a null pointer.
-3 If there is a runtime-constraint violation, there is no attempt to convert the time.
- Description
-4 The gmtime_s function converts the calendar time pointed to by timer into a broken-
- down time, expressed as UTC. The broken-down time is stored in the structure pointed
-[<a name="#p621" href="p621">page 621</a>] (<a href="#Contents">Contents</a>)
-
- to by result.
- Returns
-5 The gmtime_s function returns result, or a null pointer if the specified time cannot
- be converted to UTC or there is a runtime-constraint violation.
-<a name="K.3.8.2.4" href="#K.3.8.2.4"><b> K.3.8.2.4 The localtime_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.26"><time.h></a>
- struct tm *localtime_s(const time_t * restrict timer,
- struct tm * restrict result);
- Runtime-constraints
-2 Neither timer nor result shall be a null pointer.
-3 If there is a runtime-constraint violation, there is no attempt to convert the time.
- Description
-4 The localtime_s function converts the calendar time pointed to by timer into a
- broken-down time, expressed as local time. The broken-down time is stored in the
- structure pointed to by result.
- Returns
-5 The localtime_s function returns result, or a null pointer if the specified time
- cannot be converted to local time or there is a runtime-constraint violation.
-<a name="K.3.9" href="#K.3.9"><b> K.3.9 Extended multibyte and wide character utilities <wchar.h></b></a>
-1 The header <a href="#7.28"><wchar.h></a> defines two types.
-2 The types are
- errno_t
- which is type int; and
- rsize_t
- which is the type size_t.
-3 Unless explicitly stated otherwise, if the execution of a function described in this
- subclause causes copying to take place between objects that overlap, the objects take on
- unspecified values.
-
-
-
-
-[<a name="#p622" href="p622">page 622</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.9.1" href="#K.3.9.1"><b> K.3.9.1 Formatted wide character input/output functions</b></a>
-<a name="K.3.9.1.1" href="#K.3.9.1.1"><b> K.3.9.1.1 The fwprintf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- int fwprintf_s(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. The %n specifier410) (modified or
- not by flags, field width, or precision) shall not appear in the wide string pointed to by
- format. Any argument to fwprintf_s corresponding to a %s specifier shall not be a
- null pointer.
-3 If there is a runtime-constraint violation, the fwprintf_s function does not attempt to
- produce further output, and it is unspecified to what extent fwprintf_s produced
- output before discovering the runtime-constraint violation.
- Description
-4 The fwprintf_s function is equivalent to the fwprintf function except for the
- explicit runtime-constraints listed above.
- Returns
-5 The fwprintf_s function returns the number of wide characters transmitted, or a
- negative value if an output error, encoding error, or runtime-constraint violation occurred.
-<a name="K.3.9.1.2" href="#K.3.9.1.2"><b> K.3.9.1.2 The fwscanf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int fwscanf_s(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. Any argument indirected though in
- order to store converted input shall not be a null pointer.
-
-
- 410) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
-
-[<a name="#p623" href="p623">page 623</a>] (<a href="#Contents">Contents</a>)
-
-3 If there is a runtime-constraint violation, the fwscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent fwscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The fwscanf_s function is equivalent to fwscanf except that the c, s, and [
- conversion specifiers apply to a pair of arguments (unless assignment suppression is
- indicated by a *). The first of these arguments is the same as for fwscanf. That
- argument is immediately followed in the argument list by the second argument, which has
- type size_t and gives the number of elements in the array pointed to by the first
- argument of the pair. If the first argument points to a scalar object, it is considered to be
- an array of one element.411)
-5 A matching failure occurs if the number of elements in a receiving object is insufficient to
- hold the converted input (including any trailing null character).
- Returns
-6 The fwscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- fwscanf_s function returns the number of input items assigned, which can be fewer
- than provided for, or even zero, in the event of an early matching failure.
-<a name="K.3.9.1.3" href="#K.3.9.1.3"><b> K.3.9.1.3 The snwprintf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- int snwprintf_s(wchar_t * restrict s,
- rsize_t n,
- const wchar_t * restrict format, ...);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The %n specifier412) (modified or not by flags, field width, or
-
- 411) If the format is known at translation time, an implementation may issue a diagnostic for any argument
- used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
- argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
- the format is not known at translation time. For example, an implementation may issue a diagnostic
- for each argument after format that has of type pointer to one of char, signed char,
- unsigned char, or void that is not followed by an argument of a type compatible with
- rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
- using the hh length modifier, a length argument must follow the pointer argument. Another useful
- diagnostic could flag any non-pointer argument following format that did not have a type
- compatible with rsize_t.
-
-[<a name="#p624" href="p624">page 624</a>] (<a href="#Contents">Contents</a>)
-
- precision) shall not appear in the wide string pointed to by format. Any argument to
- snwprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
- error shall occur.
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the snwprintf_s function sets s[0] to the
- null wide character.
- Description
-4 The snwprintf_s function is equivalent to the swprintf function except for the
- explicit runtime-constraints listed above.
-5 The snwprintf_s function, unlike swprintf_s, will truncate the result to fit within
- the array pointed to by s.
- Returns
-6 The snwprintf_s function returns the number of wide characters that would have
- been written had n been sufficiently large, not counting the terminating wide null
- character, or a negative value if a runtime-constraint violation occurred. Thus, the null-
- terminated output has been completely written if and only if the returned value is
- nonnegative and less than n.
-<a name="K.3.9.1.4" href="#K.3.9.1.4"><b> K.3.9.1.4 The swprintf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- int swprintf_s(wchar_t * restrict s, rsize_t n,
- const wchar_t * restrict format, ...);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The number of wide characters (including the trailing null) required
- for the result to be written to the array pointed to by s shall not be greater than n. The %n
- specifier413) (modified or not by flags, field width, or precision) shall not appear in the
- wide string pointed to by format. Any argument to swprintf_s corresponding to a
- %s specifier shall not be a null pointer. No encoding error shall occur.
-
-
- 412) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
- 413) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
-
-[<a name="#p625" href="p625">page 625</a>] (<a href="#Contents">Contents</a>)
-
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the swprintf_s function sets s[0] to the
- null wide character.
- Description
-4 The swprintf_s function is equivalent to the swprintf function except for the
- explicit runtime-constraints listed above.
-5 The swprintf_s function, unlike snwprintf_s, treats a result too big for the array
- pointed to by s as a runtime-constraint violation.
- Returns
-6 If no runtime-constraint violation occurred, the swprintf_s function returns the
- number of wide characters written in the array, not counting the terminating null wide
- character. If an encoding error occurred or if n or more wide characters are requested to
- be written, swprintf_s returns a negative value. If any other runtime-constraint
- violation occurred, swprintf_s returns zero.
-<a name="K.3.9.1.5" href="#K.3.9.1.5"><b> K.3.9.1.5 The swscanf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- int swscanf_s(const wchar_t * restrict s,
- const wchar_t * restrict format, ...);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. Any argument indirected though in order
- to store converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the swscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent swscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The swscanf_s function is equivalent to fwscanf_s, except that the argument s
- specifies a wide string from which the input is to be obtained, rather than from a stream.
- Reaching the end of the wide string is equivalent to encountering end-of-file for the
- fwscanf_s function.
- Returns
-5 The swscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- swscanf_s function returns the number of input items assigned, which can be fewer
- than provided for, or even zero, in the event of an early matching failure.
-[<a name="#p626" href="p626">page 626</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.9.1.6" href="#K.3.9.1.6"><b> K.3.9.1.6 The vfwprintf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int vfwprintf_s(FILE * restrict stream,
- const wchar_t * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. The %n specifier414) (modified or
- not by flags, field width, or precision) shall not appear in the wide string pointed to by
- format. Any argument to vfwprintf_s corresponding to a %s specifier shall not be
- a null pointer.
-3 If there is a runtime-constraint violation, the vfwprintf_s function does not attempt
- to produce further output, and it is unspecified to what extent vfwprintf_s produced
- output before discovering the runtime-constraint violation.
- Description
-4 The vfwprintf_s function is equivalent to the vfwprintf function except for the
- explicit runtime-constraints listed above.
- Returns
-5 The vfwprintf_s function returns the number of wide characters transmitted, or a
- negative value if an output error, encoding error, or runtime-constraint violation occurred.
-<a name="K.3.9.1.7" href="#K.3.9.1.7"><b> K.3.9.1.7 The vfwscanf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.21"><stdio.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int vfwscanf_s(FILE * restrict stream,
- const wchar_t * restrict format, va_list arg);
-
-
-
- 414) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
-
-[<a name="#p627" href="p627">page 627</a>] (<a href="#Contents">Contents</a>)
-
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. Any argument indirected though in
- order to store converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vfwscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent vfwscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The vfwscanf_s function is equivalent to fwscanf_s, with the variable argument
- list replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vfwscanf_s function does not invoke the
- va_end macro.415)
- Returns
-5 The vfwscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- vfwscanf_s function returns the number of input items assigned, which can be fewer
- than provided for, or even zero, in the event of an early matching failure.
-<a name="K.3.9.1.8" href="#K.3.9.1.8"><b> K.3.9.1.8 The vsnwprintf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int vsnwprintf_s(wchar_t * restrict s,
- rsize_t n,
- const wchar_t * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The %n specifier416) (modified or not by flags, field width, or
- precision) shall not appear in the wide string pointed to by format. Any argument to
- vsnwprintf_s corresponding to a %s specifier shall not be a null pointer. No
- encoding error shall occur.
-
- 415) As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
- value of arg after the return is indeterminate.
- 416) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
-
-[<a name="#p628" href="p628">page 628</a>] (<a href="#Contents">Contents</a>)
-
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the vsnwprintf_s function sets s[0] to
- the null wide character.
- Description
-4 The vsnwprintf_s function is equivalent to the vswprintf function except for the
- explicit runtime-constraints listed above.
-5 The vsnwprintf_s function, unlike vswprintf_s, will truncate the result to fit
- within the array pointed to by s.
- Returns
-6 The vsnwprintf_s function returns the number of wide characters that would have
- been written had n been sufficiently large, not counting the terminating null character, or
- a negative value if a runtime-constraint violation occurred. Thus, the null-terminated
- output has been completely written if and only if the returned value is nonnegative and
- less than n.
-<a name="K.3.9.1.9" href="#K.3.9.1.9"><b> K.3.9.1.9 The vswprintf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int vswprintf_s(wchar_t * restrict s,
- rsize_t n,
- const wchar_t * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The number of wide characters (including the trailing null) required
- for the result to be written to the array pointed to by s shall not be greater than n. The %n
- specifier417) (modified or not by flags, field width, or precision) shall not appear in the
- wide string pointed to by format. Any argument to vswprintf_s corresponding to a
- %s specifier shall not be a null pointer. No encoding error shall occur.
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the vswprintf_s function sets s[0] to the
- null wide character.
-
- 417) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
-
-[<a name="#p629" href="p629">page 629</a>] (<a href="#Contents">Contents</a>)
-
- Description
-4 The vswprintf_s function is equivalent to the vswprintf function except for the
- explicit runtime-constraints listed above.
-5 The vswprintf_s function, unlike vsnwprintf_s, treats a result too big for the
- array pointed to by s as a runtime-constraint violation.
- Returns
-6 If no runtime-constraint violation occurred, the vswprintf_s function returns the
- number of wide characters written in the array, not counting the terminating null wide
- character. If an encoding error occurred or if n or more wide characters are requested to
- be written, vswprintf_s returns a negative value. If any other runtime-constraint
- violation occurred, vswprintf_s returns zero.
-<a name="K.3.9.1.10" href="#K.3.9.1.10"><b> K.3.9.1.10 The vswscanf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int vswscanf_s(const wchar_t * restrict s,
- const wchar_t * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. Any argument indirected though in order
- to store converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vswscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent vswscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The vswscanf_s function is equivalent to swscanf_s, with the variable argument
- list replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vswscanf_s function does not invoke the
- va_end macro.418)
-
-
-
-
- 418) As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
- value of arg after the return is indeterminate.
-
-[<a name="#p630" href="p630">page 630</a>] (<a href="#Contents">Contents</a>)
-
- Returns
-5 The vswscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- vswscanf_s function returns the number of input items assigned, which can be fewer
- than provided for, or even zero, in the event of an early matching failure.
-<a name="K.3.9.1.11" href="#K.3.9.1.11"><b> K.3.9.1.11 The vwprintf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int vwprintf_s(const wchar_t * restrict format,
- va_list arg);
- Runtime-constraints
-2 format shall not be a null pointer. The %n specifier419) (modified or not by flags, field
- width, or precision) shall not appear in the wide string pointed to by format. Any
- argument to vwprintf_s corresponding to a %s specifier shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vwprintf_s function does not attempt to
- produce further output, and it is unspecified to what extent vwprintf_s produced
- output before discovering the runtime-constraint violation.
- Description
-4 The vwprintf_s function is equivalent to the vwprintf function except for the
- explicit runtime-constraints listed above.
- Returns
-5 The vwprintf_s function returns the number of wide characters transmitted, or a
- negative value if an output error, encoding error, or runtime-constraint violation occurred.
-
-
-
-
- 419) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
-
-[<a name="#p631" href="p631">page 631</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.9.1.12" href="#K.3.9.1.12"><b> K.3.9.1.12 The vwscanf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.16"><stdarg.h></a>
- #include <a href="#7.28"><wchar.h></a>
- int vwscanf_s(const wchar_t * restrict format,
- va_list arg);
- Runtime-constraints
-2 format shall not be a null pointer. Any argument indirected though in order to store
- converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vwscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent vwscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The vwscanf_s function is equivalent to wscanf_s, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vwscanf_s function does not invoke the
- va_end macro.420)
- Returns
-5 The vwscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- vwscanf_s function returns the number of input items assigned, which can be fewer
- than provided for, or even zero, in the event of an early matching failure.
-<a name="K.3.9.1.13" href="#K.3.9.1.13"><b> K.3.9.1.13 The wprintf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- int wprintf_s(const wchar_t * restrict format, ...);
- Runtime-constraints
-2 format shall not be a null pointer. The %n specifier421) (modified or not by flags, field
-
- 420) As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
- value of arg after the return is indeterminate.
- 421) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
-
-[<a name="#p632" href="p632">page 632</a>] (<a href="#Contents">Contents</a>)
-
- width, or precision) shall not appear in the wide string pointed to by format. Any
- argument to wprintf_s corresponding to a %s specifier shall not be a null pointer.
-3 If there is a runtime-constraint violation, the wprintf_s function does not attempt to
- produce further output, and it is unspecified to what extent wprintf_s produced output
- before discovering the runtime-constraint violation.
- Description
-4 The wprintf_s function is equivalent to the wprintf function except for the explicit
- runtime-constraints listed above.
- Returns
-5 The wprintf_s function returns the number of wide characters transmitted, or a
- negative value if an output error, encoding error, or runtime-constraint violation occurred.
-<a name="K.3.9.1.14" href="#K.3.9.1.14"><b> K.3.9.1.14 The wscanf_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- int wscanf_s(const wchar_t * restrict format, ...);
- Runtime-constraints
-2 format shall not be a null pointer. Any argument indirected though in order to store
- converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the wscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent wscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The wscanf_s function is equivalent to fwscanf_s with the argument stdin
- interposed before the arguments to wscanf_s.
- Returns
-5 The wscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- wscanf_s function returns the number of input items assigned, which can be fewer than
- provided for, or even zero, in the event of an early matching failure.
-
-
-
-
-[<a name="#p633" href="p633">page 633</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.9.2" href="#K.3.9.2"><b> K.3.9.2 General wide string utilities</b></a>
-<a name="K.3.9.2.1" href="#K.3.9.2.1"><b> K.3.9.2.1 Wide string copying functions</b></a>
-<a name="K.3.9.2.1.1" href="#K.3.9.2.1.1"><b> K.3.9.2.1.1 The wcscpy_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- errno_t wcscpy_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2);
- Runtime-constraints
-2 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
- s1max shall not equal zero. s1max shall be greater than wcsnlen_s(s2, s1max).
- Copying shall not take place between objects that overlap.
-3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then wcscpy_s sets s1[0] to the
- null wide character.
- Description
-4 The wcscpy_s function copies the wide string pointed to by s2 (including the
- terminating null wide character) into the array pointed to by s1.
-5 All elements following the terminating null wide character (if any) written by
- wcscpy_s in the array of s1max wide characters pointed to by s1 take unspecified
- values when wcscpy_s returns.422)
- Returns
-6 The wcscpy_s function returns zero423) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-
-
-
-
- 422) This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
- if any of those wide characters are null. Such an approach might write a wide character to every
- element of s1 before discovering that the first element should be set to the null wide character.
- 423) A zero return value implies that all of the requested wide characters from the string pointed to by s2
- fit within the array pointed to by s1 and that the result in s1 is null terminated.
-
-[<a name="#p634" href="p634">page 634</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.9.2.1.2" href="#K.3.9.2.1.2"><b> K.3.9.2.1.2 The wcsncpy_s function</b></a>
- Synopsis
-7 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- errno_t wcsncpy_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2,
- rsize_t n);
- Runtime-constraints
-8 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
- shall be greater than wcsnlen_s(s2, s1max). Copying shall not take place between
- objects that overlap.
-9 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then wcsncpy_s sets s1[0] to the
- null wide character.
- Description
-10 The wcsncpy_s function copies not more than n successive wide characters (wide
- characters that follow a null wide character are not copied) from the array pointed to by
- s2 to the array pointed to by s1. If no null wide character was copied from s2, then
- s1[n] is set to a null wide character.
-11 All elements following the terminating null wide character (if any) written by
- wcsncpy_s in the array of s1max wide characters pointed to by s1 take unspecified
- values when wcsncpy_s returns.424)
- Returns
-12 The wcsncpy_s function returns zero425) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-13 EXAMPLE 1 The wcsncpy_s function can be used to copy a wide string without the danger that the
- result will not be null terminated or that wide characters will be written past the end of the destination
- array.
-
-
-
-
- 424) This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
- if any of those wide characters are null. Such an approach might write a wide character to every
- element of s1 before discovering that the first element should be set to the null wide character.
- 425) A zero return value implies that all of the requested wide characters from the string pointed to by s2
- fit within the array pointed to by s1 and that the result in s1 is null terminated.
-
-[<a name="#p635" href="p635">page 635</a>] (<a href="#Contents">Contents</a>)
-
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- /* ... */
- wchar_t src1[100] = L"hello";
- wchar_t src2[7] = {L'g', L'o', L'o', L'd', L'b', L'y', L'e'};
- wchar_t dst1[6], dst2[5], dst3[5];
- int r1, r2, r3;
- r1 = wcsncpy_s(dst1, 6, src1, 100);
- r2 = wcsncpy_s(dst2, 5, src2, 7);
- r3 = wcsncpy_s(dst3, 5, src2, 4);
- The first call will assign to r1 the value zero and to dst1 the sequence of wide characters hello\0.
- The second call will assign to r2 a nonzero value and to dst2 the sequence of wide characters \0.
- The third call will assign to r3 the value zero and to dst3 the sequence of wide characters good\0.
-
-<a name="K.3.9.2.1.3" href="#K.3.9.2.1.3"><b> K.3.9.2.1.3 The wmemcpy_s function</b></a>
- Synopsis
-14 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- errno_t wmemcpy_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2,
- rsize_t n);
- Runtime-constraints
-15 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
- objects that overlap.
-16 If there is a runtime-constraint violation, the wmemcpy_s function stores zeros in the
- first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
- s1max is not greater than RSIZE_MAX.
- Description
-17 The wmemcpy_s function copies n successive wide characters from the object pointed
- to by s2 into the object pointed to by s1.
- Returns
-18 The wmemcpy_s function returns zero if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-
-
-
-
-[<a name="#p636" href="p636">page 636</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.9.2.1.4" href="#K.3.9.2.1.4"><b> K.3.9.2.1.4 The wmemmove_s function</b></a>
- Synopsis
-19 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
- const wchar_t *s2, rsize_t n);
- Runtime-constraints
-20 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. n shall not be greater than s1max.
-21 If there is a runtime-constraint violation, the wmemmove_s function stores zeros in the
- first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
- s1max is not greater than RSIZE_MAX.
- Description
-22 The wmemmove_s function copies n successive wide characters from the object pointed
- to by s2 into the object pointed to by s1. This copying takes place as if the n wide
- characters from the object pointed to by s2 are first copied into a temporary array of n
- wide characters that does not overlap the objects pointed to by s1 or s2, and then the n
- wide characters from the temporary array are copied into the object pointed to by s1.
- Returns
-23 The wmemmove_s function returns zero if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-<a name="K.3.9.2.2" href="#K.3.9.2.2"><b> K.3.9.2.2 Wide string concatenation functions</b></a>
-<a name="K.3.9.2.2.1" href="#K.3.9.2.2.1"><b> K.3.9.2.2.1 The wcscat_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- errno_t wcscat_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2);
- Runtime-constraints
-2 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
- wcscat_s.
-3 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
- s1max shall not equal zero. m shall not equal zero.426) m shall be greater than
- wcsnlen_s(s2, m). Copying shall not take place between objects that overlap.
-
-[<a name="#p637" href="p637">page 637</a>] (<a href="#Contents">Contents</a>)
-
-4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then wcscat_s sets s1[0] to the
- null wide character.
- Description
-5 The wcscat_s function appends a copy of the wide string pointed to by s2 (including
- the terminating null wide character) to the end of the wide string pointed to by s1. The
- initial wide character from s2 overwrites the null wide character at the end of s1.
-6 All elements following the terminating null wide character (if any) written by
- wcscat_s in the array of s1max wide characters pointed to by s1 take unspecified
- values when wcscat_s returns.427)
- Returns
-7 The wcscat_s function returns zero428) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-<a name="K.3.9.2.2.2" href="#K.3.9.2.2.2"><b> K.3.9.2.2.2 The wcsncat_s function</b></a>
- Synopsis
-8 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- errno_t wcsncat_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2,
- rsize_t n);
- Runtime-constraints
-9 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
- wcsncat_s.
-10 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.429) If n is not less
- than m, then m shall be greater than wcsnlen_s(s2, m). Copying shall not take
- place between objects that overlap.
-
-
- 426) Zero means that s1 was not null terminated upon entry to wcscat_s.
- 427) This allows an implementation to append wide characters from s2 to s1 while simultaneously
- checking if any of those wide characters are null. Such an approach might write a wide character to
- every element of s1 before discovering that the first element should be set to the null wide character.
- 428) A zero return value implies that all of the requested wide characters from the wide string pointed to by
- s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
- 429) Zero means that s1 was not null terminated upon entry to wcsncat_s.
-
-[<a name="#p638" href="p638">page 638</a>] (<a href="#Contents">Contents</a>)
-
-11 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then wcsncat_s sets s1[0] to the
- null wide character.
- Description
-12 The wcsncat_s function appends not more than n successive wide characters (wide
- characters that follow a null wide character are not copied) from the array pointed to by
- s2 to the end of the wide string pointed to by s1. The initial wide character from s2
- overwrites the null wide character at the end of s1. If no null wide character was copied
- from s2, then s1[s1max-m+n] is set to a null wide character.
-13 All elements following the terminating null wide character (if any) written by
- wcsncat_s in the array of s1max wide characters pointed to by s1 take unspecified
- values when wcsncat_s returns.430)
- Returns
-14 The wcsncat_s function returns zero431) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-15 EXAMPLE 1 The wcsncat_s function can be used to copy a wide string without the danger that the
- result will not be null terminated or that wide characters will be written past the end of the destination
- array.
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- /* ... */
- wchar_t s1[100] = L"good";
- wchar_t s2[6] = L"hello";
- wchar_t s3[6] = L"hello";
- wchar_t s4[7] = L"abc";
- wchar_t s5[1000] = L"bye";
- int r1, r2, r3, r4;
- r1 = wcsncat_s(s1, 100, s5, 1000);
- r2 = wcsncat_s(s2, 6, L"", 1);
- r3 = wcsncat_s(s3, 6, L"X", 2);
- r4 = wcsncat_s(s4, 7, L"defghijklmn", 3);
- After the first call r1 will have the value zero and s1 will be the wide character sequence goodbye\0.
- After the second call r2 will have the value zero and s2 will be the wide character sequence hello\0.
- After the third call r3 will have a nonzero value and s3 will be the wide character sequence \0.
- After the fourth call r4 will have the value zero and s4 will be the wide character sequence abcdef\0.
-
-
-
-
- 430) This allows an implementation to append wide characters from s2 to s1 while simultaneously
- checking if any of those wide characters are null. Such an approach might write a wide character to
- every element of s1 before discovering that the first element should be set to the null wide character.
- 431) A zero return value implies that all of the requested wide characters from the wide string pointed to by
- s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
-
-[<a name="#p639" href="p639">page 639</a>] (<a href="#Contents">Contents</a>)
-
-<a name="K.3.9.2.3" href="#K.3.9.2.3"><b> K.3.9.2.3 Wide string search functions</b></a>
-<a name="K.3.9.2.3.1" href="#K.3.9.2.3.1"><b> K.3.9.2.3.1 The wcstok_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- wchar_t *wcstok_s(wchar_t * restrict s1,
- rsize_t * restrict s1max,
- const wchar_t * restrict s2,
- wchar_t ** restrict ptr);
- Runtime-constraints
-2 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
- shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
- The end of the token found shall occur within the first *s1max wide characters of s1 for
- the first call, and shall occur within the first *s1max wide characters of where searching
- resumes on subsequent calls.
-3 If there is a runtime-constraint violation, the wcstok_s function does not indirect
- through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
- Description
-4 A sequence of calls to the wcstok_s function breaks the wide string pointed to by s1
- into a sequence of tokens, each of which is delimited by a wide character from the wide
- string pointed to by s2. The fourth argument points to a caller-provided wchar_t
- pointer into which the wcstok_s function stores information necessary for it to
- continue scanning the same wide string.
-5 The first call in a sequence has a non-null first argument and s1max points to an object
- whose value is the number of elements in the wide character array pointed to by the first
- argument. The first call stores an initial value in the object pointed to by ptr and
- updates the value pointed to by s1max to reflect the number of elements that remain in
- relation to ptr. Subsequent calls in the sequence have a null first argument and the
- objects pointed to by s1max and ptr are required to have the values stored by the
- previous call in the sequence, which are then updated. The separator wide string pointed
- to by s2 may be different from call to call.
-6 The first call in the sequence searches the wide string pointed to by s1 for the first wide
- character that is not contained in the current separator wide string pointed to by s2. If no
- such wide character is found, then there are no tokens in the wide string pointed to by s1
- and the wcstok_s function returns a null pointer. If such a wide character is found, it is
- the start of the first token.
-
-
-[<a name="#p640" href="p640">page 640</a>] (<a href="#Contents">Contents</a>)
-
-7 The wcstok_s function then searches from there for the first wide character in s1 that
- is contained in the current separator wide string. If no such wide character is found, the
- current token extends to the end of the wide string pointed to by s1, and subsequent
- searches in the same wide string for a token return a null pointer. If such a wide character
- is found, it is overwritten by a null wide character, which terminates the current token.
-8 In all cases, the wcstok_s function stores sufficient information in the pointer pointed
- to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
- value for ptr, shall start searching just past the element overwritten by a null wide
- character (if any).
- Returns
-9 The wcstok_s function returns a pointer to the first wide character of a token, or a null
- pointer if there is no token or there is a runtime-constraint violation.
-10 EXAMPLE
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- static wchar_t str1[] = L"?a???b,,,#c";
- static wchar_t str2[] = L"\t \t";
- wchar_t *t, *ptr1, *ptr2;
- rsize_t max1 = wcslen(str1)+1;
- rsize_t max2 = wcslen(str2)+1;
- t = wcstok_s(str1, &max1, "?", &ptr1); // t points to the token "a"
- t = wcstok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
- t = wcstok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
- t = wcstok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
- t = wcstok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
-
-<a name="K.3.9.2.4" href="#K.3.9.2.4"><b> K.3.9.2.4 Miscellaneous functions</b></a>
-<a name="K.3.9.2.4.1" href="#K.3.9.2.4.1"><b> K.3.9.2.4.1 The wcsnlen_s function</b></a>
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <a href="#7.28"><wchar.h></a>
- size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
- Description
-2 The wcsnlen_s function computes the length of the wide string pointed to by s.
- Returns
-3 If s is a null pointer,432) then the wcsnlen_s function returns zero.
-4 Otherwise, the wcsnlen_s function returns the number of wide characters that precede
- the terminating null wide character. If there is no null wide character in the first
- maxsize wide characters of s then wcsnlen_s returns maxsize. At most the first
-
-[<a name="#p641" href="p641">page 641</a>] (<a href="#Contents">Contents</a>)
-
- maxsize wide characters of s shall be accessed by wcsnlen_s.
-<a name="K.3.9.3" href="#K.3.9.3"><b> K.3.9.3 Extended multibyte/wide character conversion utilities</b></a>
-<a name="K.3.9.3.1" href="#K.3.9.3.1"><b> K.3.9.3.1 Restartable multibyte/wide character conversion functions</b></a>
-1 Unlike wcrtomb, wcrtomb_s does not permit the ps parameter (the pointer to the
- conversion state) to be a null pointer.
-<a name="K.3.9.3.1.1" href="#K.3.9.3.1.1"><b> K.3.9.3.1.1 The wcrtomb_s function</b></a>
- Synopsis
-2 #include <a href="#7.28"><wchar.h></a>
- errno_t wcrtomb_s(size_t * restrict retval,
- char * restrict s, rsize_t smax,
- wchar_t wc, mbstate_t * restrict ps);
- Runtime-constraints
-3 Neither retval nor ps shall be a null pointer. If s is not a null pointer, then smax
- shall not equal zero and shall not be greater than RSIZE_MAX. If s is not a null pointer,
- then smax shall be not be less than the number of bytes to be stored in the array pointed
- to by s. If s is a null pointer, then smax shall equal zero.
-4 If there is a runtime-constraint violation, then wcrtomb_s does the following. If s is
- not a null pointer and smax is greater than zero and not greater than RSIZE_MAX, then
- wcrtomb_s sets s[0] to the null character. If retval is not a null pointer, then
- wcrtomb_s sets *retval to (size_t)(-1).
- Description
-5 If s is a null pointer, the wcrtomb_s function is equivalent to the call
- wcrtomb_s(&retval, buf, sizeof buf, L'\0', ps)
- where retval and buf are internal variables of the appropriate types, and the size of
- buf is greater than MB_CUR_MAX.
-6 If s is not a null pointer, the wcrtomb_s function determines the number of bytes
- needed to represent the multibyte character that corresponds to the wide character given
- by wc (including any shift sequences), and stores the multibyte character representation
- in the array whose first element is pointed to by s. At most MB_CUR_MAX bytes are
- stored. If wc is a null wide character, a null byte is stored, preceded by any shift
- sequence needed to restore the initial shift state; the resulting state described is the initial
- conversion state.
-
- 432) Note that the wcsnlen_s function has no runtime-constraints. This lack of runtime-constraints
- along with the values returned for a null pointer or an unterminated wide string argument make
- wcsnlen_s useful in algorithms that gracefully handle such exceptional data.
-
-[<a name="#p642" href="p642">page 642</a>] (<a href="#Contents">Contents</a>)
-
-7 If wc does not correspond to a valid multibyte character, an encoding error occurs: the
- wcrtomb_s function stores the value (size_t)(-1) into *retval and the
- conversion state is unspecified. Otherwise, the wcrtomb_s function stores into
- *retval the number of bytes (including any shift sequences) stored in the array pointed
- to by s.
- Returns
-8 The wcrtomb_s function returns zero if no runtime-constraint violation and no
- encoding error occurred. Otherwise, a nonzero value is returned.
-<a name="K.3.9.3.2" href="#K.3.9.3.2"><b> K.3.9.3.2 Restartable multibyte/wide string conversion functions</b></a>
-1 Unlike mbsrtowcs and wcsrtombs, mbsrtowcs_s and wcsrtombs_s do not
- permit the ps parameter (the pointer to the conversion state) to be a null pointer.
-<a name="K.3.9.3.2.1" href="#K.3.9.3.2.1"><b> K.3.9.3.2.1 The mbsrtowcs_s function</b></a>
- Synopsis
-2 #include <a href="#7.28"><wchar.h></a>
- errno_t mbsrtowcs_s(size_t * restrict retval,
- wchar_t * restrict dst, rsize_t dstmax,
- const char ** restrict src, rsize_t len,
- mbstate_t * restrict ps);
- Runtime-constraints
-3 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
- then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
- pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
- not equal zero. If dst is not a null pointer and len is not less than dstmax, then a null
- character shall occur within the first dstmax multibyte characters of the array pointed to
- by *src.
-4 If there is a runtime-constraint violation, then mbsrtowcs_s does the following. If
- retval is not a null pointer, then mbsrtowcs_s sets *retval to (size_t)(-1).
- If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
- then mbsrtowcs_s sets dst[0] to the null wide character.
- Description
-5 The mbsrtowcs_s function converts a sequence of multibyte characters that begins in
- the conversion state described by the object pointed to by ps, from the array indirectly
- pointed to by src into a sequence of corresponding wide characters. If dst is not a null
- pointer, the converted characters are stored into the array pointed to by dst. Conversion
- continues up to and including a terminating null character, which is also stored.
- Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
- not form a valid multibyte character, or (if dst is not a null pointer) when len wide
-[<a name="#p643" href="p643">page 643</a>] (<a href="#Contents">Contents</a>)
-
- characters have been stored into the array pointed to by dst.433) If dst is not a null
- pointer and no null wide character was stored into the array pointed to by dst, then
- dst[len] is set to the null wide character. Each conversion takes place as if by a call
- to the mbrtowc function.
-6 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
- pointer (if conversion stopped due to reaching a terminating null character) or the address
- just past the last multibyte character converted (if any). If conversion stopped due to
- reaching a terminating null character and if dst is not a null pointer, the resulting state
- described is the initial conversion state.
-7 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
- sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
- the mbsrtowcs_s function stores the value (size_t)(-1) into *retval and the
- conversion state is unspecified. Otherwise, the mbsrtowcs_s function stores into
- *retval the number of multibyte characters successfully converted, not including the
- terminating null character (if any).
-8 All elements following the terminating null wide character (if any) written by
- mbsrtowcs_s in the array of dstmax wide characters pointed to by dst take
- unspecified values when mbsrtowcs_s returns.434)
-9 If copying takes place between objects that overlap, the objects take on unspecified
- values.
- Returns
-10 The mbsrtowcs_s function returns zero if no runtime-constraint violation and no
- encoding error occurred. Otherwise, a nonzero value is returned.
-<a name="K.3.9.3.2.2" href="#K.3.9.3.2.2"><b> K.3.9.3.2.2 The wcsrtombs_s function</b></a>
- Synopsis
-11 #include <a href="#7.28"><wchar.h></a>
- errno_t wcsrtombs_s(size_t * restrict retval,
- char * restrict dst, rsize_t dstmax,
- const wchar_t ** restrict src, rsize_t len,
- mbstate_t * restrict ps);
-
-
-
-
- 433) Thus, the value of len is ignored if dst is a null pointer.
- 434) This allows an implementation to attempt converting the multibyte string before discovering a
- terminating null character did not occur where required.
-
-[<a name="#p644" href="p644">page 644</a>] (<a href="#Contents">Contents</a>)
-
- Runtime-constraints
-12 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
- then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
- pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
- not equal zero. If dst is not a null pointer and len is not less than dstmax, then the
- conversion shall have been stopped (see below) because a terminating null wide character
- was reached or because an encoding error occurred.
-13 If there is a runtime-constraint violation, then wcsrtombs_s does the following. If
- retval is not a null pointer, then wcsrtombs_s sets *retval to (size_t)(-1).
- If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
- then wcsrtombs_s sets dst[0] to the null character.
- Description
-14 The wcsrtombs_s function converts a sequence of wide characters from the array
- indirectly pointed to by src into a sequence of corresponding multibyte characters that
- begins in the conversion state described by the object pointed to by ps. If dst is not a
- null pointer, the converted characters are then stored into the array pointed to by dst.
- Conversion continues up to and including a terminating null wide character, which is also
- stored. Conversion stops earlier in two cases:
- -- when a wide character is reached that does not correspond to a valid multibyte
- character;
- -- (if dst is not a null pointer) when the next multibyte character would exceed the
- limit of n total bytes to be stored into the array pointed to by dst. If the wide
- character being converted is the null wide character, then n is the lesser of len or
- dstmax. Otherwise, n is the lesser of len or dstmax-1.
- If the conversion stops without converting a null wide character and dst is not a null
- pointer, then a null character is stored into the array pointed to by dst immediately
- following any multibyte characters already stored. Each conversion takes place as if by a
- call to the wcrtomb function.435)
-15 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
- pointer (if conversion stopped due to reaching a terminating null wide character) or the
- address just past the last wide character converted (if any). If conversion stopped due to
- reaching a terminating null wide character, the resulting state described is the initial
- conversion state.
-
-
- 435) If conversion stops because a terminating null wide character has been reached, the bytes stored
- include those necessary to reach the initial shift state immediately before the null byte. However, if
- the conversion stops before a terminating null wide character has been reached, the result will be null
- terminated, but might not end in the initial shift state.
-
-[<a name="#p645" href="p645">page 645</a>] (<a href="#Contents">Contents</a>)
-
-16 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
- wide character that does not correspond to a valid multibyte character, an encoding error
- occurs: the wcsrtombs_s function stores the value (size_t)(-1) into *retval
- and the conversion state is unspecified. Otherwise, the wcsrtombs_s function stores
- into *retval the number of bytes in the resulting multibyte character sequence, not
- including the terminating null character (if any).
-17 All elements following the terminating null character (if any) written by wcsrtombs_s
- in the array of dstmax elements pointed to by dst take unspecified values when
- wcsrtombs_s returns.436)
-18 If copying takes place between objects that overlap, the objects take on unspecified
- values.
- Returns
-19 The wcsrtombs_s function returns zero if no runtime-constraint violation and no
- encoding error occurred. Otherwise, a nonzero value is returned.
-
-
-
-
- 436) When len is not less than dstmax, the implementation might fill the array before discovering a
- runtime-constraint violation.
-
-[<a name="#p646" href="p646">page 646</a>] (<a href="#Contents">Contents</a>)
-
-<a name="L" href="#L"><b> Annex L</b></a>
- (normative)
- Analyzability
-<a name="L.1" href="#L.1"><b> L.1 Scope</b></a>
-1 This annex specifies optional behavior that can aid in the analyzability of C programs.
-2 An implementation that defines __STDC_ANALYZABLE__ shall conform to the
- specifications in this annex.437)
-<a name="L.2" href="#L.2"><b> L.2 Definitions</b></a>
-<a name="L.2.1" href="#L.2.1"><b> L.2.1</b></a>
-1 out-of-bounds store
- an (attempted) access (<a href="#3.1">3.1</a>) that, at run time, for a given computational state, would
- modify (or, for an object declared volatile, fetch) one or more bytes that lie outside
- the bounds permitted by this Standard.
-<a name="L.2.2" href="#L.2.2"><b> L.2.2</b></a>
-1 bounded undefined behavior
- undefined behavior (<a href="#3.4.3">3.4.3</a>) that does not perform an out-of-bounds store.
-2 NOTE 1 The behavior might perform a trap.
-
-3 NOTE 2 Any values produced or stored might be indeterminate values.
-
-<a name="L.2.3" href="#L.2.3"><b> L.2.3</b></a>
-1 critical undefined behavior
- undefined behavior that is not bounded undefined behavior.
-2 NOTE The behavior might perform an out-of-bounds store or perform a trap.
-
-
-
-
- 437) Implementations that do not define __STDC_ANALYZABLE__ are not required to conform to these
- specifications.
-
-[<a name="#p647" href="p647">page 647</a>] (<a href="#Contents">Contents</a>)
-
-<a name="L.3" href="#L.3"><b> L.3 Requirements</b></a>
-1 If the program performs a trap (<a href="#3.19.5">3.19.5</a>), the implementation is permitted to invoke a
- runtime-constraint handler. Any such semantics are implementation-defined.
-2 All undefined behavior shall be limited to bounded undefined behavior, except for the
- following which are permitted to result in critical undefined behavior:
- -- An object is referred to outside of its lifetime (<a href="#6.2.4">6.2.4</a>).
- -- An lvalue does not designate an object when evaluated (<a href="#6.3.2.1">6.3.2.1</a>).
- -- A pointer is used to call a function whose type is not compatible with the referenced
- type (<a href="#6.3.2.3">6.3.2.3</a>).
- -- The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
- -- Addition or subtraction of a pointer into, or just beyond, an array object and an
- integer type produces a result that points just beyond the array object and is used as
- the operand of a unary * operator that is evaluated (<a href="#6.5.6">6.5.6</a>).
- -- An argument to a library function has an invalid value or a type not expected by a
- function with variable number of arguments (<a href="#7.1.4">7.1.4</a>).
- -- The value of a pointer that refers to space deallocated by a call to the free or realloc
- function is used (<a href="#7.22.3">7.22.3</a>).
- -- A string or wide string utility function is instructed to access an array beyond the end
- of an object (<a href="#7.23.1">7.23.1</a>, <a href="#7.28.4">7.28.4</a>).
-
-
-
-
-[<a name="#p648" href="p648">page 648</a>] (<a href="#Contents">Contents</a>)
-
-
-<a name="Bibliography" href="#Bibliography"><b> Bibliography</b></a>
- 1. ''The C Reference Manual'' by Dennis M. Ritchie, a version of which was
- published in The C Programming Language by Brian W. Kernighan and Dennis
- M. Ritchie, Prentice-Hall, Inc., (1978). Copyright owned by AT&T.
- 2. 1984 /usr/group Standard by the /usr/group Standards Committee, Santa Clara,
- California, USA, November 1984.
- 3. ANSI X3/TR-1-82 (1982), American National Dictionary for Information
- Processing Systems, Information Processing Systems Technical Report.
- 4. ANSI/IEEE 754-1985, American National Standard for Binary Floating-Point
- Arithmetic.
- 5. ANSI/IEEE 854-1988, American National Standard for Radix-Independent
- Floating-Point Arithmetic.
- 6. IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems,
- second edition (previously designated IEC 559:1989).
- 7. ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and
- symbols for use in the physical sciences and technology.
- 8. ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for
- information interchange.
- 9. ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1:
- Fundamental terms.
- 10. ISO 4217:1995, Codes for the representation of currencies and funds.
- 11. ISO 8601:1988, Data elements and interchange formats -- Information
- interchange -- Representation of dates and times.
- 12. ISO/IEC 9899:1990, Programming languages -- C.
- 13. ISO/IEC 9899/COR1:1994, Technical Corrigendum 1.
- 14. ISO/IEC 9899/COR2:1996, Technical Corrigendum 2.
- 15. ISO/IEC 9899/AMD1:1995, Amendment 1 to ISO/IEC 9899:1990 C Integrity.
- 16. ISO/IEC 9899:1999, Programming languages -- C.
- 17. ISO/IEC 9899:1999/Cor.1:2001, Technical Corrigendum 1.
- 18. ISO/IEC 9899:1999/Cor.2:2004, Technical Corrigendum 2.
- 19. ISO/IEC 9899:1999/Cor.3:2007, Technical Corrigendum 3.
-
-
-
-[<a name="#p649" href="p649">page 649</a>] (<a href="#Contents">Contents</a>)
-
- 20. ISO/IEC 9945-2:1993, Information technology -- Portable Operating System
- Interface (POSIX) -- Part 2: Shell and Utilities.
- 21. ISO/IEC TR 10176:1998, Information technology -- Guidelines for the
- preparation of programming language standards.
- 22. ISO/IEC 10646-1:1993, Information technology -- Universal Multiple-Octet
- Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
- 23. ISO/IEC 10646-1/COR1:1996, Technical Corrigendum 1 to
- ISO/IEC 10646-1:1993.
- 24. ISO/IEC 10646-1/COR2:1998, Technical Corrigendum 2 to
- ISO/IEC 10646-1:1993.
- 25. ISO/IEC 10646-1/AMD1:1996, Amendment 1 to ISO/IEC 10646-1:1993
- Transformation Format for 16 planes of group 00 (UTF-16).
- 26. ISO/IEC 10646-1/AMD2:1996, Amendment 2 to ISO/IEC 10646-1:1993 UCS
- Transformation Format 8 (UTF-8).
- 27. ISO/IEC 10646-1/AMD3:1996, Amendment 3 to ISO/IEC 10646-1:1993.
- 28. ISO/IEC 10646-1/AMD4:1996, Amendment 4 to ISO/IEC 10646-1:1993.
- 29. ISO/IEC 10646-1/AMD5:1998, Amendment 5 to ISO/IEC 10646-1:1993 Hangul
- syllables.
- 30. ISO/IEC 10646-1/AMD6:1997, Amendment 6 to ISO/IEC 10646-1:1993
- Tibetan.
- 31. ISO/IEC 10646-1/AMD7:1997, Amendment 7 to ISO/IEC 10646-1:1993 33
- additional characters.
- 32. ISO/IEC 10646-1/AMD8:1997, Amendment 8 to ISO/IEC 10646-1:1993.
- 33. ISO/IEC 10646-1/AMD9:1997, Amendment 9 to ISO/IEC 10646-1:1993
- Identifiers for characters.
- 34. ISO/IEC 10646-1/AMD10:1998, Amendment 10 to ISO/IEC 10646-1:1993
- Ethiopic.
- 35. ISO/IEC 10646-1/AMD11:1998, Amendment 11 to ISO/IEC 10646-1:1993
- Unified Canadian Aboriginal Syllabics.
- 36. ISO/IEC 10646-1/AMD12:1998, Amendment 12 to ISO/IEC 10646-1:1993
- Cherokee.
- 37. ISO/IEC 10967-1:1994, Information technology -- Language independent
- arithmetic -- Part 1: Integer and floating point arithmetic.
-
-
-[<a name="#p650" href="p650">page 650</a>] (<a href="#Contents">Contents</a>)
-
- 38. ISO/IEC TR 19769:2004, Information technology -- Programming languages,
- their environments and system software interfaces -- Extensions for the
- programming language C to support new character data types.
- 39. ISO/IEC TR 24731-1:2007, Information technology -- Programming languages,
- their environments and system software interfaces -- Extensions to the C library
- -- Part 1: Bounds-checking interfaces.
-
-
-
-
-[<a name="#p651" href="p651">page 651</a>] (<a href="#Contents">Contents</a>)
-
-
-
-[<a name="#p652" href="p652">page 652</a>] (<a href="#Contents">Contents</a>)
-
-
-<a name="Index" href="#Index"><b>Index</b></a>
-[^ x ^], <a href="#3.20">3.20</a> , (comma operator), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.17">6.5.17</a>
- , (comma punctuator), <a href="#6.5.2">6.5.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.7.2.2">6.7.2.2</a>,
-[_ x _], <a href="#3.21">3.21</a> <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.9">6.7.9</a>
-! (logical negation operator), <a href="#6.5.3.3">6.5.3.3</a> - (subtraction operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a>
-!= (inequality operator), <a href="#6.5.9">6.5.9</a> - (unary minus operator), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a>
-# operator, <a href="#6.10.3.2">6.10.3.2</a> -- (postfix decrement operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a>
-# preprocessing directive, <a href="#6.10.7">6.10.7</a> -- (prefix decrement operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a>
-# punctuator, <a href="#6.10">6.10</a> -= (subtraction assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
-## operator, <a href="#6.10.3.3">6.10.3.3</a> -> (structure/union pointer operator), <a href="#6.5.2.3">6.5.2.3</a>
-#define preprocessing directive, <a href="#6.10.3">6.10.3</a> . (structure/union member operator), <a href="#6.3.2.1">6.3.2.1</a>,
-#elif preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#6.5.2.3">6.5.2.3</a>
-#else preprocessing directive, <a href="#6.10.1">6.10.1</a> . punctuator, <a href="#6.7.9">6.7.9</a>
-#endif preprocessing directive, <a href="#6.10.1">6.10.1</a> ... (ellipsis punctuator), <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.10.3">6.10.3</a>
-#error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> / (division operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a>
-#if preprocessing directive, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, /* */ (comment delimiters), <a href="#6.4.9">6.4.9</a>
- <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a> // (comment delimiter), <a href="#6.4.9">6.4.9</a>
-#ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a> /= (division assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
-#ifndef preprocessing directive, <a href="#6.10.1">6.10.1</a> : (colon punctuator), <a href="#6.7.2.1">6.7.2.1</a>
-#include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</a>, :> (alternative spelling of ]), <a href="#6.4.6">6.4.6</a>
- <a href="#6.10.2">6.10.2</a> ; (semicolon punctuator), <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.8.3">6.8.3</a>,
-#line preprocessing directive, <a href="#6.10.4">6.10.4</a> <a href="#6.8.5">6.8.5</a>, <a href="#6.8.6">6.8.6</a>
-#pragma preprocessing directive, <a href="#6.10.6">6.10.6</a> < (less-than operator), <a href="#6.5.8">6.5.8</a>
-#undef preprocessing directive, <a href="#6.10.3.5">6.10.3.5</a>, <a href="#7.1.3">7.1.3</a>, <% (alternative spelling of {), <a href="#6.4.6">6.4.6</a>
- <a href="#7.1.4">7.1.4</a> <: (alternative spelling of [), <a href="#6.4.6">6.4.6</a>
-% (remainder operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a> << (left-shift operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a>
-%: (alternative spelling of #), <a href="#6.4.6">6.4.6</a> <<= (left-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
-%:%: (alternative spelling of ##), <a href="#6.4.6">6.4.6</a> <= (less-than-or-equal-to operator), <a href="#6.5.8">6.5.8</a>
-%= (remainder assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.2"><assert.h></a> header, <a href="#7.2">7.2</a>
-%> (alternative spelling of }), <a href="#6.4.6">6.4.6</a> <a href="#7.3"><complex.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>,
-& (address operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#7.3">7.3</a>, <a href="#7.24">7.24</a>, <a href="#7.30.1">7.30.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
-& (bitwise AND operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.10">6.5.10</a> <a href="#7.4"><ctype.h></a> header, <a href="#7.4">7.4</a>, <a href="#7.30.2">7.30.2</a>
-&& (logical AND operator), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.13">6.5.13</a> <a href="#7.5"><errno.h></a> header, <a href="#7.5">7.5</a>, <a href="#7.30.3">7.30.3</a>, <a href="#K.3.2">K.3.2</a>
-&= (bitwise AND assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.6"><fenv.h></a> header, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F">F</a>,
-' ' (space character), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#H">H</a>
- <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.29.2.1.3">7.29.2.1.3</a> <a href="#7.7"><float.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.22.1.3">7.22.1.3</a>,
-( ) (cast operator), <a href="#6.5.4">6.5.4</a> <a href="#7.28.4.1.1">7.28.4.1.1</a>
-( ) (function-call operator), <a href="#6.5.2.2">6.5.2.2</a> <a href="#7.8"><inttypes.h></a> header, <a href="#7.8">7.8</a>, <a href="#7.30.4">7.30.4</a>
-( ) (parentheses punctuator), <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a> <a href="#7.9"><iso646.h></a> header, <a href="#4">4</a>, <a href="#7.9">7.9</a>
-( ){ } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a> <a href="#7.10"><limits.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a>
-* (asterisk punctuator), <a href="#6.7.6.1">6.7.6.1</a>, <a href="#6.7.6.2">6.7.6.2</a> <a href="#7.11"><locale.h></a> header, <a href="#7.11">7.11</a>, <a href="#7.30.5">7.30.5</a>
-* (indirection operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#7.12"><math.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.24">7.24</a>, <a href="#F">F</a>,
-* (multiplication operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#F.10">F.10</a>, <a href="#J.5.17">J.5.17</a>
- <a href="#G.5.1">G.5.1</a> <a href="#7.13"><setjmp.h></a> header, <a href="#7.13">7.13</a>
-*= (multiplication assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.14"><signal.h></a> header, <a href="#7.14">7.14</a>, <a href="#7.30.6">7.30.6</a>
-+ (addition operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>, <a href="#7.15"><stdalign.h></a> header, <a href="#4">4</a>, <a href="#7.15">7.15</a>
- <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a> <a href="#7.16"><stdarg.h></a> header, <a href="#4">4</a>, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#7.16">7.16</a>
-+ (unary plus operator), <a href="#6.5.3.3">6.5.3.3</a> <a href="#7.17"><stdatomic.h></a> header, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.17">7.17</a>
-++ (postfix increment operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a> <a href="#7.18"><stdbool.h></a> header, <a href="#4">4</a>, <a href="#7.18">7.18</a>, <a href="#7.30.7">7.30.7</a>, <a href="#H">H</a>
-++ (prefix increment operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a> <a href="#7.19"><stddef.h></a> header, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>,
-+= (addition assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
-[<a name="#p653" href="p653">page 653</a>] (<a href="#Contents">Contents</a>)
-
- <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.19">7.19</a>, <a href="#K.3.3">K.3.3</a> \x hexadecimal digits (hexadecimal-character
-<a href="#7.20"><stdint.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>, escape sequence), <a href="#6.4.4.4">6.4.4.4</a>
- <a href="#7.20">7.20</a>, <a href="#7.30.8">7.30.8</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a> ^ (bitwise exclusive OR operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.11">6.5.11</a>
-<a href="#7.21"><stdio.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21">7.21</a>, <a href="#7.30.9">7.30.9</a>, <a href="#F">F</a>, ^= (bitwise exclusive OR assignment operator),
- <a href="#K.3.5">K.3.5</a> <a href="#6.5.16.2">6.5.16.2</a>
-<a href="#7.22"><stdlib.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.22">7.22</a>, <a href="#7.30.10">7.30.10</a>, <a href="#F">F</a>, __alignas_is_defined macro, <a href="#7.15">7.15</a>
- <a href="#K.3.1.4">K.3.1.4</a>, <a href="#K.3.6">K.3.6</a> __bool_true_false_are_defined
-<a href="#7.23"><string.h></a> header, <a href="#7.23">7.23</a>, <a href="#7.30.11">7.30.11</a>, <a href="#K.3.7">K.3.7</a> macro, <a href="#7.18">7.18</a>
-<a href="#7.24"><tgmath.h></a> header, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> __cplusplus macro, <a href="#6.10.8">6.10.8</a>
-<a href="#7.25"><threads.h></a> header, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.25">7.25</a> __DATE__ macro, <a href="#6.10.8.1">6.10.8.1</a>
-<a href="#7.26"><time.h></a> header, <a href="#7.26">7.26</a>, <a href="#K.3.8">K.3.8</a> __FILE__ macro, <a href="#6.10.8.1">6.10.8.1</a>, <a href="#7.2.1.1">7.2.1.1</a>
-<a href="#7.27"><uchar.h></a> header, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.27">7.27</a> __func__ identifier, <a href="#6.4.2.2">6.4.2.2</a>, <a href="#7.2.1.1">7.2.1.1</a>
-<a href="#7.28"><wchar.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.28">7.28</a>, __LINE__ macro, <a href="#6.10.8.1">6.10.8.1</a>, <a href="#7.2.1.1">7.2.1.1</a>
- <a href="#7.30.12">7.30.12</a>, <a href="#F">F</a>, <a href="#K.3.9">K.3.9</a> __STDC_, <a href="#6.11.9">6.11.9</a>
-<a href="#7.29"><wctype.h></a> header, <a href="#7.29">7.29</a>, <a href="#7.30.13">7.30.13</a> __STDC__ macro, <a href="#6.10.8.1">6.10.8.1</a>
-= (equal-sign punctuator), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.9">6.7.9</a> __STDC_ANALYZABLE__ macro, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#L.1">L.1</a>
-= (simple assignment operator), <a href="#6.5.16.1">6.5.16.1</a> __STDC_HOSTED__ macro, <a href="#6.10.8.1">6.10.8.1</a>
-== (equality operator), <a href="#6.5.9">6.5.9</a> __STDC_IEC_559__ macro, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#F.1">F.1</a>
-> (greater-than operator), <a href="#6.5.8">6.5.8</a> __STDC_IEC_559_COMPLEX__ macro,
->= (greater-than-or-equal-to operator), <a href="#6.5.8">6.5.8</a> <a href="#6.10.8.3">6.10.8.3</a>, <a href="#G.1">G.1</a>
->> (right-shift operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a> __STDC_ISO_10646__ macro, <a href="#6.10.8.2">6.10.8.2</a>
->>= (right-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a> __STDC_LIB_EXT1__ macro, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#K.2">K.2</a>
-? : (conditional operator), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.15">6.5.15</a> __STDC_MB_MIGHT_NEQ_WC__ macro,
-?? (trigraph sequences), <a href="#5.2.1.1">5.2.1.1</a> <a href="#6.10.8.2">6.10.8.2</a>, <a href="#7.19">7.19</a>
-[ ] (array subscript operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> __STDC_NO_COMPLEX__ macro, <a href="#6.10.8.3">6.10.8.3</a>,
-[ ] (brackets punctuator), <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.7.9">6.7.9</a> <a href="#7.3.1">7.3.1</a>
-\ (backslash character), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a> __STDC_NO_THREADS__ macro, <a href="#6.10.8.3">6.10.8.3</a>,
-\ (escape character), <a href="#6.4.4.4">6.4.4.4</a> <a href="#7.17.1">7.17.1</a>, <a href="#7.25.1">7.25.1</a>
-\" (double-quote escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, __STDC_NO_VLA__ macro, <a href="#6.10.8.3">6.10.8.3</a>
- <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</a> __STDC_UTF_16__ macro, <a href="#6.10.8.2">6.10.8.2</a>
-\\ (backslash escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a> __STDC_UTF_32__ macro, <a href="#6.10.8.2">6.10.8.2</a>
-\' (single-quote escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> __STDC_VERSION__ macro, <a href="#6.10.8.1">6.10.8.1</a>
-\0 (null character), <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> __STDC_WANT_LIB_EXT1__ macro, <a href="#K.3.1.1">K.3.1.1</a>
- padding of binary stream, <a href="#7.21.2">7.21.2</a> __TIME__ macro, <a href="#6.10.8.1">6.10.8.1</a>
-\? (question-mark escape sequence), <a href="#6.4.4.4">6.4.4.4</a> __VA_ARGS__ identifier, <a href="#6.10.3">6.10.3</a>, <a href="#6.10.3.1">6.10.3.1</a>
-\a (alert escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> _Alignas, <a href="#6.7.5">6.7.5</a>
-\b (backspace escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> _Atomic type qualifier, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>
-\f (form-feed escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, _Atomic-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.5.2.3">6.5.2.3</a>,
- <a href="#7.4.1.10">7.4.1.10</a> <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.16.2">6.5.16.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>
-\n (new-line escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, _Bool type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.2">6.3.1.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.17.1">7.17.1</a>,
- <a href="#7.4.1.10">7.4.1.10</a> <a href="#F.4">F.4</a>
-\octal digits (octal-character escape sequence), _Bool type conversions, <a href="#6.3.1.2">6.3.1.2</a>
- <a href="#6.4.4.4">6.4.4.4</a> _Complex types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a>
-\r (carriage-return escape sequence), <a href="#5.2.2">5.2.2</a>, _Complex_I macro, <a href="#7.3.1">7.3.1</a>
- <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a> _Exit function, <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>
-\t (horizontal-tab escape sequence), <a href="#5.2.2">5.2.2</a>, _Imaginary keyword, <a href="#G.2">G.2</a>
- <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.29.2.1.3">7.29.2.1.3</a> _Imaginary types, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a>
-\U (universal character names), <a href="#6.4.3">6.4.3</a> _Imaginary_I macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a>
-\u (universal character names), <a href="#6.4.3">6.4.3</a> _IOFBF macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.5">7.21.5.5</a>, <a href="#7.21.5.6">7.21.5.6</a>
-\v (vertical-tab escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, _IOLBF macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.6">7.21.5.6</a>
- <a href="#7.4.1.10">7.4.1.10</a> _IONBF macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.5">7.21.5.5</a>, <a href="#7.21.5.6">7.21.5.6</a>
-
-[<a name="#p654" href="p654">page 654</a>] (<a href="#Contents">Contents</a>)
-
-_Noreturn, <a href="#6.7.4">6.7.4</a> alignment specifier, <a href="#6.7.5">6.7.5</a>
-_Pragma operator, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a> alignof operator, <a href="#6.5.3">6.5.3</a>, <a href="#6.5.3.4">6.5.3.4</a>
-_Static_assert, <a href="#6.7.10">6.7.10</a>, <a href="#7.2">7.2</a> allocated storage, order and contiguity, <a href="#7.22.3">7.22.3</a>
-_Thread_local storage-class specifier, <a href="#6.2.4">6.2.4</a>, and macro, <a href="#7.9">7.9</a>
- <a href="#6.7.1">6.7.1</a> AND operators
-{ } (braces punctuator), <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.9">6.7.9</a>, bitwise (&), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.10">6.5.10</a>
- <a href="#6.8.2">6.8.2</a> bitwise assignment (&=), <a href="#6.5.16.2">6.5.16.2</a>
-{ } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a> logical (&&), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.13">6.5.13</a>
-| (bitwise inclusive OR operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a> and_eq macro, <a href="#7.9">7.9</a>
-|= (bitwise inclusive OR assignment operator), anonymous structure, <a href="#6.7.2.1">6.7.2.1</a>
- <a href="#6.5.16.2">6.5.16.2</a> anonymous union, <a href="#6.7.2.1">6.7.2.1</a>
-|| (logical OR operator), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.14">6.5.14</a> ANSI/IEEE 754, <a href="#F.1">F.1</a>
-~ (bitwise complement operator), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.3.3">6.5.3.3</a> ANSI/IEEE 854, <a href="#F.1">F.1</a>
- argc (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a>
-abort function, <a href="#7.2.1.1">7.2.1.1</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.21.3">7.21.3</a>, argument, <a href="#3.3">3.3</a>
- <a href="#7.22.4.1">7.22.4.1</a>, <a href="#7.25.3.6">7.25.3.6</a>, <a href="#K.3.6.1.2">K.3.6.1.2</a> array, <a href="#6.9.1">6.9.1</a>
-abort_handler_s function, <a href="#K.3.6.1.2">K.3.6.1.2</a> default promotions, <a href="#6.5.2.2">6.5.2.2</a>
-abs function, <a href="#7.22.6.1">7.22.6.1</a> function, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a>
-absolute-value functions macro, substitution, <a href="#6.10.3.1">6.10.3.1</a>
- complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a> argument, complex, <a href="#7.3.9.1">7.3.9.1</a>
- integer, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.22.6.1">7.22.6.1</a> argv (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a>
- real, <a href="#7.12.7">7.12.7</a>, <a href="#F.10.4">F.10.4</a> arithmetic constant expression, <a href="#6.6">6.6</a>
-abstract declarator, <a href="#6.7.7">6.7.7</a> arithmetic conversions, usual, see usual arithmetic
-abstract machine, <a href="#5.1.2.3">5.1.2.3</a> conversions
-access, <a href="#3.1">3.1</a>, <a href="#6.7.3">6.7.3</a>, <a href="#L.2.1">L.2.1</a> arithmetic operators
-accuracy, see floating-point accuracy additive, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a>
-acos functions, <a href="#7.12.4.1">7.12.4.1</a>, <a href="#F.10.1.1">F.10.1.1</a> bitwise, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.3.3">6.5.3.3</a>, <a href="#6.5.10">6.5.10</a>, <a href="#6.5.11">6.5.11</a>, <a href="#6.5.12">6.5.12</a>
-acos type-generic macro, <a href="#7.24">7.24</a> increment and decrement, <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.3.1">6.5.3.1</a>
-acosh functions, <a href="#7.12.5.1">7.12.5.1</a>, <a href="#F.10.2.1">F.10.2.1</a> multiplicative, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
-acosh type-generic macro, <a href="#7.24">7.24</a> shift, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a>
-acquire fence, <a href="#7.17.4">7.17.4</a> unary, <a href="#6.5.3.3">6.5.3.3</a>
-acquire operation, <a href="#5.1.2.4">5.1.2.4</a> arithmetic types, <a href="#6.2.5">6.2.5</a>
-active position, <a href="#5.2.2">5.2.2</a> arithmetic, pointer, <a href="#6.5.6">6.5.6</a>
-actual argument, <a href="#3.3">3.3</a> array
-actual parameter (deprecated), <a href="#3.3">3.3</a> argument, <a href="#6.9.1">6.9.1</a>
-addition assignment operator (+=), <a href="#6.5.16.2">6.5.16.2</a> declarator, <a href="#6.7.6.2">6.7.6.2</a>
-addition operator (+), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>, initialization, <a href="#6.7.9">6.7.9</a>
- <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a> multidimensional, <a href="#6.5.2.1">6.5.2.1</a>
-additive expressions, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a> parameter, <a href="#6.9.1">6.9.1</a>
-address constant, <a href="#6.6">6.6</a> storage order, <a href="#6.5.2.1">6.5.2.1</a>
-address operator (&), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> subscript operator ([ ]), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>
-address-free, <a href="#7.17.5">7.17.5</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
-aggregate initialization, <a href="#6.7.9">6.7.9</a> type, <a href="#6.2.5">6.2.5</a>
-aggregate types, <a href="#6.2.5">6.2.5</a> type conversion, <a href="#6.3.2.1">6.3.2.1</a>
-alert escape sequence (\a), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> variable length, <a href="#6.7.6">6.7.6</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.10.8.3">6.10.8.3</a>
-aliasing, <a href="#6.5">6.5</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
-alignas macro, <a href="#7.15">7.15</a> as-if rule, <a href="#5.1.2.3">5.1.2.3</a>
-aligned_alloc function, <a href="#7.22.3">7.22.3</a>, <a href="#7.22.3.1">7.22.3.1</a> ASCII code set, <a href="#5.2.1.1">5.2.1.1</a>
-alignment, <a href="#3.2">3.2</a>, <a href="#6.2.8">6.2.8</a>, <a href="#7.22.3.1">7.22.3.1</a> asctime function, <a href="#7.26.3.1">7.26.3.1</a>
- pointer, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.3">6.3.2.3</a> asctime_s function, <a href="#K.3.8.2">K.3.8.2</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a>
- structure/union member, <a href="#6.7.2.1">6.7.2.1</a> asin functions, <a href="#7.12.4.2">7.12.4.2</a>, <a href="#F.10.1.2">F.10.1.2</a>
-
-[<a name="#p655" href="p655">page 655</a>] (<a href="#Contents">Contents</a>)
-
-asin type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> atomic_is_lock_free generic function,
-asinh functions, <a href="#7.12.5.2">7.12.5.2</a>, <a href="#F.10.2.2">F.10.2.2</a> <a href="#7.17.5.1">7.17.5.1</a>
-asinh type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> ATOMIC_LLONG_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
-asm keyword, <a href="#J.5.10">J.5.10</a> atomic_load generic functions, <a href="#7.17.7.2">7.17.7.2</a>
-assert macro, <a href="#7.2.1.1">7.2.1.1</a> ATOMIC_LONG_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
-assert.h header, <a href="#7.2">7.2</a> ATOMIC_SHORT_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
-assignment atomic_signal_fence function, <a href="#7.17.4.2">7.17.4.2</a>
- compound, <a href="#6.5.16.2">6.5.16.2</a> atomic_store generic functions, <a href="#7.17.7.1">7.17.7.1</a>
- conversion, <a href="#6.5.16.1">6.5.16.1</a> atomic_thread_fence function, <a href="#7.17.4.1">7.17.4.1</a>
- expression, <a href="#6.5.16">6.5.16</a> ATOMIC_VAR_INIT macro, <a href="#7.17.2.1">7.17.2.1</a>
- operators, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.16">6.5.16</a> ATOMIC_WCHAR_T_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
- simple, <a href="#6.5.16.1">6.5.16.1</a> atomics header, <a href="#7.17">7.17</a>
-associativity of operators, <a href="#6.5">6.5</a> auto storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a>
-asterisk punctuator (*), <a href="#6.7.6.1">6.7.6.1</a>, <a href="#6.7.6.2">6.7.6.2</a> automatic storage duration, <a href="#5.2.3">5.2.3</a>, <a href="#6.2.4">6.2.4</a>
-at_quick_exit function, <a href="#7.22.4.2">7.22.4.2</a>, <a href="#7.22.4.3">7.22.4.3</a>,
- <a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a> backslash character (\), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>
-atan functions, <a href="#7.12.4.3">7.12.4.3</a>, <a href="#F.10.1.3">F.10.1.3</a> backslash escape sequence (\\), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a>
-atan type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> backspace escape sequence (\b), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
-atan2 functions, <a href="#7.12.4.4">7.12.4.4</a>, <a href="#F.10.1.4">F.10.1.4</a> basic character set, <a href="#3.6">3.6</a>, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1">5.2.1</a>
-atan2 type-generic macro, <a href="#7.24">7.24</a> basic types, <a href="#6.2.5">6.2.5</a>
-atanh functions, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#F.10.2.3">F.10.2.3</a> behavior, <a href="#3.4">3.4</a>
-atanh type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> binary streams, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.2">7.21.9.2</a>,
-atexit function, <a href="#7.22.4.2">7.22.4.2</a>, <a href="#7.22.4.3">7.22.4.3</a>, <a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.21.9.4">7.21.9.4</a>
- <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>, <a href="#J.5.13">J.5.13</a> bit, <a href="#3.5">3.5</a>
-atof function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.1">7.22.1.1</a> high order, <a href="#3.6">3.6</a>
-atoi function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.2">7.22.1.2</a> low order, <a href="#3.6">3.6</a>
-atol function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.2">7.22.1.2</a> bit-field, <a href="#6.7.2.1">6.7.2.1</a>
-atoll function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.2">7.22.1.2</a> bitand macro, <a href="#7.9">7.9</a>
-atomic lock-free macros, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.5">7.17.5</a> bitor macro, <a href="#7.9">7.9</a>
-atomic operations, <a href="#5.1.2.4">5.1.2.4</a> bitwise operators, <a href="#6.5">6.5</a>
-atomic types, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.17.6">7.17.6</a> AND, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.10">6.5.10</a>
-atomic_address type, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.6">7.17.6</a> AND assignment (&=), <a href="#6.5.16.2">6.5.16.2</a>
-ATOMIC_ADDRESS_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a> complement (~), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.3.3">6.5.3.3</a>
-atomic_bool type, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.6">7.17.6</a> exclusive OR, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.11">6.5.11</a>
-ATOMIC_CHAR16_T_LOCK_FREE macro, exclusive OR assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
- <a href="#7.17.1">7.17.1</a> inclusive OR, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a>
-ATOMIC_CHAR32_T_LOCK_FREE macro, inclusive OR assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
- <a href="#7.17.1">7.17.1</a> shift, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a>
-ATOMIC_CHAR_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a> blank character, <a href="#7.4.1.3">7.4.1.3</a>
-atomic_compare_exchange generic block, <a href="#6.8">6.8</a>, <a href="#6.8.2">6.8.2</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a>
- functions, <a href="#7.17.7.4">7.17.7.4</a> block scope, <a href="#6.2.1">6.2.1</a>
-atomic_exchange generic functions, <a href="#7.17.7.3">7.17.7.3</a> block structure, <a href="#6.2.1">6.2.1</a>
-atomic_fetch and modify generic functions, bold type convention, <a href="#6.1">6.1</a>
- <a href="#7.17.7.5">7.17.7.5</a> bool macro, <a href="#7.18">7.18</a>
-atomic_flag type, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.8">7.17.8</a> boolean type, <a href="#6.3.1.2">6.3.1.2</a>
-atomic_flag_clear functions, <a href="#7.17.8.2">7.17.8.2</a> boolean type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.2">6.3.1.2</a>
-ATOMIC_FLAG_INIT macro, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.8">7.17.8</a> bounded undefined behavior, <a href="#L.2.2">L.2.2</a>
-atomic_flag_test_and_set functions, braces punctuator ({ }), <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.9">6.7.9</a>,
- <a href="#7.17.8.1">7.17.8.1</a> <a href="#6.8.2">6.8.2</a>
-atomic_init generic function, <a href="#7.17.2.2">7.17.2.2</a> brackets operator ([ ]), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>
-ATOMIC_INT_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a> brackets punctuator ([ ]), <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.7.9">6.7.9</a>
-
-[<a name="#p656" href="p656">page 656</a>] (<a href="#Contents">Contents</a>)
-
-branch cuts, <a href="#7.3.3">7.3.3</a> type-generic macro for, <a href="#7.24">7.24</a>
-break statement, <a href="#6.8.6.3">6.8.6.3</a> ccosh functions, <a href="#7.3.6.4">7.3.6.4</a>, <a href="#G.6.2.4">G.6.2.4</a>
-broken-down time, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.2.3">7.26.2.3</a>, <a href="#7.26.3">7.26.3</a>, type-generic macro for, <a href="#7.24">7.24</a>
- <a href="#7.26.3.1">7.26.3.1</a>, <a href="#7.26.3.3">7.26.3.3</a>, <a href="#7.26.3.4">7.26.3.4</a>, <a href="#7.26.3.5">7.26.3.5</a>, ceil functions, <a href="#7.12.9.1">7.12.9.1</a>, <a href="#F.10.6.1">F.10.6.1</a>
- <a href="#K.3.8.2.1">K.3.8.2.1</a>, <a href="#K.3.8.2.3">K.3.8.2.3</a>, <a href="#K.3.8.2.4">K.3.8.2.4</a> ceil type-generic macro, <a href="#7.24">7.24</a>
-bsearch function, <a href="#7.22.5">7.22.5</a>, <a href="#7.22.5.1">7.22.5.1</a> cerf function, <a href="#7.30.1">7.30.1</a>
-bsearch_s function, <a href="#K.3.6.3">K.3.6.3</a>, <a href="#K.3.6.3.1">K.3.6.3.1</a> cerfc function, <a href="#7.30.1">7.30.1</a>
-btowc function, <a href="#7.28.6.1.1">7.28.6.1.1</a> cexp functions, <a href="#7.3.7.1">7.3.7.1</a>, <a href="#G.6.3.1">G.6.3.1</a>
-BUFSIZ macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.5.5">7.21.5.5</a> type-generic macro for, <a href="#7.24">7.24</a>
-byte, <a href="#3.6">3.6</a>, <a href="#6.5.3.4">6.5.3.4</a> cexp2 function, <a href="#7.30.1">7.30.1</a>
-byte input/output functions, <a href="#7.21.1">7.21.1</a> cexpm1 function, <a href="#7.30.1">7.30.1</a>
-byte-oriented stream, <a href="#7.21.2">7.21.2</a> char type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#K.3.5.3.2">K.3.5.3.2</a>,
- <a href="#K.3.9.1.2">K.3.9.1.2</a>
-C program, <a href="#5.1.1.1">5.1.1.1</a> char type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
-c16rtomb function, <a href="#7.27.1.2">7.27.1.2</a> <a href="#6.3.1.8">6.3.1.8</a>
-c32rtomb function, <a href="#7.27.1.4">7.27.1.4</a> char16_t type, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.10.8.2">6.10.8.2</a>, <a href="#7.27">7.27</a>
-cabs functions, <a href="#7.3.8.1">7.3.8.1</a>, <a href="#G.6">G.6</a> char32_t type, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.10.8.2">6.10.8.2</a>, <a href="#7.27">7.27</a>
- type-generic macro for, <a href="#7.24">7.24</a> CHAR_BIT macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.7.2.1">6.7.2.1</a>
-cacos functions, <a href="#7.3.5.1">7.3.5.1</a>, <a href="#G.6.1.1">G.6.1.1</a> CHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
- type-generic macro for, <a href="#7.24">7.24</a> CHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
-cacosh functions, <a href="#7.3.6.1">7.3.6.1</a>, <a href="#G.6.2.1">G.6.2.1</a> character, <a href="#3.7">3.7</a>, <a href="#3.7.1">3.7.1</a>
- type-generic macro for, <a href="#7.24">7.24</a> character array initialization, <a href="#6.7.9">6.7.9</a>
-calendar time, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.2.2">7.26.2.2</a>, <a href="#7.26.2.3">7.26.2.3</a>, <a href="#7.26.2.4">7.26.2.4</a>, character case mapping functions, <a href="#7.4.2">7.4.2</a>
- <a href="#7.26.3.2">7.26.3.2</a>, <a href="#7.26.3.3">7.26.3.3</a>, <a href="#7.26.3.4">7.26.3.4</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>, wide character, <a href="#7.29.3.1">7.29.3.1</a>
- <a href="#K.3.8.2.3">K.3.8.2.3</a>, <a href="#K.3.8.2.4">K.3.8.2.4</a> extensible, <a href="#7.29.3.2">7.29.3.2</a>
-call by value, <a href="#6.5.2.2">6.5.2.2</a> character classification functions, <a href="#7.4.1">7.4.1</a>
-call_once function, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.2.1">7.25.2.1</a> wide character, <a href="#7.29.2.1">7.29.2.1</a>
-calloc function, <a href="#7.22.3">7.22.3</a>, <a href="#7.22.3.2">7.22.3.2</a> extensible, <a href="#7.29.2.2">7.29.2.2</a>
-carg functions, <a href="#7.3.9.1">7.3.9.1</a>, <a href="#G.6">G.6</a> character constant, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>
-carg type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> character display semantics, <a href="#5.2.2">5.2.2</a>
-carriage-return escape sequence (\r), <a href="#5.2.2">5.2.2</a>, character handling header, <a href="#7.4">7.4</a>, <a href="#7.11.1.1">7.11.1.1</a>
- <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a> character input/output functions, <a href="#7.21.7">7.21.7</a>, <a href="#K.3.5.4">K.3.5.4</a>
-carries a dependency, <a href="#5.1.2.4">5.1.2.4</a> wide character, <a href="#7.28.3">7.28.3</a>
-case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> character sets, <a href="#5.2.1">5.2.1</a>
-case mapping functions character string literal, see string literal
- character, <a href="#7.4.2">7.4.2</a> character type conversion, <a href="#6.3.1.1">6.3.1.1</a>
- wide character, <a href="#7.29.3.1">7.29.3.1</a> character types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.9">6.7.9</a>
- extensible, <a href="#7.29.3.2">7.29.3.2</a> cimag functions, <a href="#7.3.9.2">7.3.9.2</a>, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#G.6">G.6</a>
-casin functions, <a href="#7.3.5.2">7.3.5.2</a>, <a href="#G.6">G.6</a> cimag type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a>
- type-generic macro for, <a href="#7.24">7.24</a> cis function, <a href="#G.6">G.6</a>
-casinh functions, <a href="#7.3.6.2">7.3.6.2</a>, <a href="#G.6.2.2">G.6.2.2</a> classification functions
- type-generic macro for, <a href="#7.24">7.24</a> character, <a href="#7.4.1">7.4.1</a>
-cast expression, <a href="#6.5.4">6.5.4</a> floating-point, <a href="#7.12.3">7.12.3</a>
-cast operator (( )), <a href="#6.5.4">6.5.4</a> wide character, <a href="#7.29.2.1">7.29.2.1</a>
-catan functions, <a href="#7.3.5.3">7.3.5.3</a>, <a href="#G.6">G.6</a> extensible, <a href="#7.29.2.2">7.29.2.2</a>
- type-generic macro for, <a href="#7.24">7.24</a> clearerr function, <a href="#7.21.10.1">7.21.10.1</a>
-catanh functions, <a href="#7.3.6.3">7.3.6.3</a>, <a href="#G.6.2.3">G.6.2.3</a> clgamma function, <a href="#7.30.1">7.30.1</a>
- type-generic macro for, <a href="#7.24">7.24</a> clock function, <a href="#7.26.2.1">7.26.2.1</a>
-cbrt functions, <a href="#7.12.7.1">7.12.7.1</a>, <a href="#F.10.4.1">F.10.4.1</a> clock_t type, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.2.1">7.26.2.1</a>
-cbrt type-generic macro, <a href="#7.24">7.24</a> CLOCKS_PER_SEC macro, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.2.1">7.26.2.1</a>
-ccos functions, <a href="#7.3.5.4">7.3.5.4</a>, <a href="#G.6">G.6</a> clog functions, <a href="#7.3.7.2">7.3.7.2</a>, <a href="#G.6.3.2">G.6.3.2</a>
-
-[<a name="#p657" href="p657">page 657</a>] (<a href="#Contents">Contents</a>)
-
- type-generic macro for, <a href="#7.24">7.24</a> string, <a href="#7.23.3">7.23.3</a>, <a href="#K.3.7.2">K.3.7.2</a>
-clog10 function, <a href="#7.30.1">7.30.1</a> wide string, <a href="#7.28.4.3">7.28.4.3</a>, <a href="#K.3.9.2.2">K.3.9.2.2</a>
-clog1p function, <a href="#7.30.1">7.30.1</a> concatenation, preprocessing, see preprocessing
-clog2 function, <a href="#7.30.1">7.30.1</a> concatenation
-CMPLX macros, <a href="#7.3.9.3">7.3.9.3</a> conceptual models, <a href="#5.1">5.1</a>
-cnd_broadcast function, <a href="#7.25.3.1">7.25.3.1</a>, <a href="#7.25.3.5">7.25.3.5</a>, conditional features, <a href="#4">4</a>, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.10.8.3">6.10.8.3</a>,
- <a href="#7.25.3.6">7.25.3.6</a> <a href="#7.1.2">7.1.2</a>, <a href="#F.1">F.1</a>, <a href="#G.1">G.1</a>, <a href="#K.2">K.2</a>, <a href="#L.1">L.1</a>
-cnd_destroy function, <a href="#7.25.3.2">7.25.3.2</a> conditional inclusion, <a href="#6.10.1">6.10.1</a>
-cnd_init function, <a href="#7.25.3.3">7.25.3.3</a> conditional operator (? :), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.15">6.5.15</a>
-cnd_signal function, <a href="#7.25.3.4">7.25.3.4</a>, <a href="#7.25.3.5">7.25.3.5</a>, conflict, <a href="#5.1.2.4">5.1.2.4</a>
- <a href="#7.25.3.6">7.25.3.6</a> conformance, <a href="#4">4</a>
-cnd_t type, <a href="#7.25.1">7.25.1</a> conj functions, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a>
-cnd_timedwait function, <a href="#7.25.3.5">7.25.3.5</a> conj type-generic macro, <a href="#7.24">7.24</a>
-cnd_wait function, <a href="#7.25.3.3">7.25.3.3</a>, <a href="#7.25.3.6">7.25.3.6</a> const type qualifier, <a href="#6.7.3">6.7.3</a>
-collating sequences, <a href="#5.2.1">5.2.1</a> const-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.7.3">6.7.3</a>
-colon punctuator (:), <a href="#6.7.2.1">6.7.2.1</a> constant expression, <a href="#6.6">6.6</a>, <a href="#F.8.4">F.8.4</a>
-comma operator (,), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.17">6.5.17</a> constants, <a href="#6.4.4">6.4.4</a>
-comma punctuator (,), <a href="#6.5.2">6.5.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.7.2.2">6.7.2.2</a>, as primary expression, <a href="#6.5.1">6.5.1</a>
- <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.9">6.7.9</a> character, <a href="#6.4.4.4">6.4.4.4</a>
-command processor, <a href="#7.22.4.8">7.22.4.8</a> enumeration, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
-comment delimiters (/* */ and //), <a href="#6.4.9">6.4.9</a> floating, <a href="#6.4.4.2">6.4.4.2</a>
-comments, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.4.9">6.4.9</a> hexadecimal, <a href="#6.4.4.1">6.4.4.1</a>
-common extensions, <a href="#J.5">J.5</a> integer, <a href="#6.4.4.1">6.4.4.1</a>
-common initial sequence, <a href="#6.5.2.3">6.5.2.3</a> octal, <a href="#6.4.4.1">6.4.4.1</a>
-common real type, <a href="#6.3.1.8">6.3.1.8</a> constraint, <a href="#3.8">3.8</a>, <a href="#4">4</a>
-common warnings, <a href="#I">I</a> constraint_handler_t type, <a href="#K.3.6">K.3.6</a>
-comparison functions, <a href="#7.22.5">7.22.5</a>, <a href="#7.22.5.1">7.22.5.1</a>, <a href="#7.22.5.2">7.22.5.2</a>, consume operation, <a href="#5.1.2.4">5.1.2.4</a>
- <a href="#K.3.6.3">K.3.6.3</a>, <a href="#K.3.6.3.1">K.3.6.3.1</a>, <a href="#K.3.6.3.2">K.3.6.3.2</a> content of structure/union/enumeration, <a href="#6.7.2.3">6.7.2.3</a>
- string, <a href="#7.23.4">7.23.4</a> contiguity of allocated storage, <a href="#7.22.3">7.22.3</a>
- wide string, <a href="#7.28.4.4">7.28.4.4</a> continue statement, <a href="#6.8.6.2">6.8.6.2</a>
-comparison macros, <a href="#7.12.14">7.12.14</a> contracted expression, <a href="#6.5">6.5</a>, <a href="#7.12.2">7.12.2</a>, <a href="#F.7">F.7</a>
-comparison, pointer, <a href="#6.5.8">6.5.8</a> control character, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a>
-compatible type, <a href="#6.2.7">6.2.7</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.6">6.7.6</a> control wide character, <a href="#7.29.2">7.29.2</a>
-compl macro, <a href="#7.9">7.9</a> conversion, <a href="#6.3">6.3</a>
-complement operator (~), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.3.3">6.5.3.3</a> arithmetic operands, <a href="#6.3.1">6.3.1</a>
-complete type, <a href="#6.2.5">6.2.5</a> array argument, <a href="#6.9.1">6.9.1</a>
-complex macro, <a href="#7.3.1">7.3.1</a> array parameter, <a href="#6.9.1">6.9.1</a>
-complex numbers, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a> arrays, <a href="#6.3.2.1">6.3.2.1</a>
-complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, <a href="#6.3.1.7">6.3.1.7</a> boolean, <a href="#6.3.1.2">6.3.1.2</a>
-complex type domain, <a href="#6.2.5">6.2.5</a> boolean, characters, and integers, <a href="#6.3.1.1">6.3.1.1</a>
-complex types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#G">G</a> by assignment, <a href="#6.5.16.1">6.5.16.1</a>
-complex.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, by return statement, <a href="#6.8.6.4">6.8.6.4</a>
- <a href="#7.3">7.3</a>, <a href="#7.24">7.24</a>, <a href="#7.30.1">7.30.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a> complex types, <a href="#6.3.1.6">6.3.1.6</a>
-compliance, see conformance explicit, <a href="#6.3">6.3</a>
-components of time, <a href="#7.26.1">7.26.1</a>, <a href="#K.3.8.1">K.3.8.1</a> function, <a href="#6.3.2.1">6.3.2.1</a>
-composite type, <a href="#6.2.7">6.2.7</a> function argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a>
-compound assignment, <a href="#6.5.16.2">6.5.16.2</a> function designators, <a href="#6.3.2.1">6.3.2.1</a>
-compound literals, <a href="#6.5.2.5">6.5.2.5</a> function parameter, <a href="#6.9.1">6.9.1</a>
-compound statement, <a href="#6.8.2">6.8.2</a> imaginary, <a href="#G.4.1">G.4.1</a>
-compound-literal operator (( ){ }), <a href="#6.5.2.5">6.5.2.5</a> imaginary and complex, <a href="#G.4.3">G.4.3</a>
-concatenation functions implicit, <a href="#6.3">6.3</a>
-
-[<a name="#p658" href="p658">page 658</a>] (<a href="#Contents">Contents</a>)
-
- lvalues, <a href="#6.3.2.1">6.3.2.1</a> csinh functions, <a href="#7.3.6.5">7.3.6.5</a>, <a href="#G.6.2.5">G.6.2.5</a>
- pointer, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a> type-generic macro for, <a href="#7.24">7.24</a>
- real and complex, <a href="#6.3.1.7">6.3.1.7</a> csqrt functions, <a href="#7.3.8.3">7.3.8.3</a>, <a href="#G.6.4.2">G.6.4.2</a>
- real and imaginary, <a href="#G.4.2">G.4.2</a> type-generic macro for, <a href="#7.24">7.24</a>
- real floating and integer, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> ctan functions, <a href="#7.3.5.6">7.3.5.6</a>, <a href="#G.6">G.6</a>
- real floating types, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#F.3">F.3</a> type-generic macro for, <a href="#7.24">7.24</a>
- signed and unsigned integers, <a href="#6.3.1.3">6.3.1.3</a> ctanh functions, <a href="#7.3.6.6">7.3.6.6</a>, <a href="#G.6.2.6">G.6.2.6</a>
- usual arithmetic, see usual arithmetic type-generic macro for, <a href="#7.24">7.24</a>
- conversions ctgamma function, <a href="#7.30.1">7.30.1</a>
- void type, <a href="#6.3.2.2">6.3.2.2</a> ctime function, <a href="#7.26.3.2">7.26.3.2</a>
-conversion functions ctime_s function, <a href="#K.3.8.2">K.3.8.2</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>
- multibyte/wide character, <a href="#7.22.7">7.22.7</a>, <a href="#K.3.6.4">K.3.6.4</a> ctype.h header, <a href="#7.4">7.4</a>, <a href="#7.30.2">7.30.2</a>
- extended, <a href="#7.28.6">7.28.6</a>, <a href="#K.3.9.3">K.3.9.3</a> current object, <a href="#6.7.9">6.7.9</a>
- restartable, <a href="#7.27.1">7.27.1</a>, <a href="#7.28.6.3">7.28.6.3</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a> CX_LIMITED_RANGE pragma, <a href="#6.10.6">6.10.6</a>, <a href="#7.3.4">7.3.4</a>
- multibyte/wide string, <a href="#7.22.8">7.22.8</a>, <a href="#K.3.6.5">K.3.6.5</a>
- restartable, <a href="#7.28.6.4">7.28.6.4</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a> data race, <a href="#5.1.2.4">5.1.2.4</a>, <a href="#7.1.4">7.1.4</a>, <a href="#7.22.2.1">7.22.2.1</a>, <a href="#7.22.4.6">7.22.4.6</a>,
- numeric, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a> <a href="#7.23.5.8">7.23.5.8</a>, <a href="#7.23.6.2">7.23.6.2</a>, <a href="#7.26.3">7.26.3</a>, <a href="#7.27.1">7.27.1</a>, <a href="#7.28.6.3">7.28.6.3</a>,
- wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.28.4.1">7.28.4.1</a> <a href="#7.28.6.4">7.28.6.4</a>
- single byte/wide character, <a href="#7.28.6.1">7.28.6.1</a> data stream, see streams
- time, <a href="#7.26.3">7.26.3</a>, <a href="#K.3.8.2">K.3.8.2</a> date and time header, <a href="#7.26">7.26</a>, <a href="#K.3.8">K.3.8</a>
- wide character, <a href="#7.28.5">7.28.5</a> Daylight Saving Time, <a href="#7.26.1">7.26.1</a>
-conversion specifier, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, DBL_DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- <a href="#7.28.2.2">7.28.2.2</a> DBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-conversion state, <a href="#7.22.7">7.22.7</a>, <a href="#7.27.1">7.27.1</a>, <a href="#7.27.1.1">7.27.1.1</a>, DBL_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- <a href="#7.27.1.2">7.27.1.2</a>, <a href="#7.27.1.3">7.27.1.3</a>, <a href="#7.27.1.4">7.27.1.4</a>, <a href="#7.28.6">7.28.6</a>, DBL_HAS_SUBNORM macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- <a href="#7.28.6.2.1">7.28.6.2.1</a>, <a href="#7.28.6.3">7.28.6.3</a>, <a href="#7.28.6.3.2">7.28.6.3.2</a>, <a href="#7.28.6.3.3">7.28.6.3.3</a>, DBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- <a href="#7.28.6.4">7.28.6.4</a>, <a href="#7.28.6.4.1">7.28.6.4.1</a>, <a href="#7.28.6.4.2">7.28.6.4.2</a>, <a href="#K.3.6.4">K.3.6.4</a>, DBL_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- <a href="#K.3.9.3.1">K.3.9.3.1</a>, <a href="#K.3.9.3.1.1">K.3.9.3.1.1</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a>, <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a>, DBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- <a href="#K.3.9.3.2.2">K.3.9.3.2.2</a> DBL_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-conversion state functions, <a href="#7.28.6.2">7.28.6.2</a> DBL_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-copying functions DBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- string, <a href="#7.23.2">7.23.2</a>, <a href="#K.3.7.1">K.3.7.1</a> DBL_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- wide string, <a href="#7.28.4.2">7.28.4.2</a>, <a href="#K.3.9.2.1">K.3.9.2.1</a> DBL_TRUE_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-copysign functions, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#7.12.11.1">7.12.11.1</a>, <a href="#F.3">F.3</a>, decimal constant, <a href="#6.4.4.1">6.4.4.1</a>
- <a href="#F.10.8.1">F.10.8.1</a> decimal digit, <a href="#5.2.1">5.2.1</a>
-copysign type-generic macro, <a href="#7.24">7.24</a> decimal-point character, <a href="#7.1.1">7.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
-correctly rounded result, <a href="#3.9">3.9</a> DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21.6.1">7.21.6.1</a>,
-corresponding real type, <a href="#6.2.5">6.2.5</a> <a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.4.1.1">7.28.4.1.1</a>, <a href="#F.5">F.5</a>
-cos functions, <a href="#7.12.4.5">7.12.4.5</a>, <a href="#F.10.1.5">F.10.1.5</a> declaration specifiers, <a href="#6.7">6.7</a>
-cos type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> declarations, <a href="#6.7">6.7</a>
-cosh functions, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#F.10.2.4">F.10.2.4</a> function, <a href="#6.7.6.3">6.7.6.3</a>
-cosh type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> pointer, <a href="#6.7.6.1">6.7.6.1</a>
-cpow functions, <a href="#7.3.8.2">7.3.8.2</a>, <a href="#G.6.4.1">G.6.4.1</a> structure/union, <a href="#6.7.2.1">6.7.2.1</a>
- type-generic macro for, <a href="#7.24">7.24</a> typedef, <a href="#6.7.8">6.7.8</a>
-cproj functions, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#G.6">G.6</a> declarator, <a href="#6.7.6">6.7.6</a>
-cproj type-generic macro, <a href="#7.24">7.24</a> abstract, <a href="#6.7.7">6.7.7</a>
-creal functions, <a href="#7.3.9.6">7.3.9.6</a>, <a href="#G.6">G.6</a> declarator type derivation, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.6">6.7.6</a>
-creal type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> decrement operators, see arithmetic operators,
-critical undefined behavior, <a href="#L.2.3">L.2.3</a> increment and decrement
-csin functions, <a href="#7.3.5.5">7.3.5.5</a>, <a href="#G.6">G.6</a> default argument promotions, <a href="#6.5.2.2">6.5.2.2</a>
- type-generic macro for, <a href="#7.24">7.24</a> default initialization, <a href="#6.7.9">6.7.9</a>
-
-[<a name="#p659" href="p659">page 659</a>] (<a href="#Contents">Contents</a>)
-
-default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> elif preprocessing directive, <a href="#6.10.1">6.10.1</a>
-define preprocessing directive, <a href="#6.10.3">6.10.3</a> ellipsis punctuator (...), <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.10.3">6.10.3</a>
-defined operator, <a href="#6.10.1">6.10.1</a>, <a href="#6.10.8">6.10.8</a> else preprocessing directive, <a href="#6.10.1">6.10.1</a>
-definition, <a href="#6.7">6.7</a> else statement, <a href="#6.8.4.1">6.8.4.1</a>
- function, <a href="#6.9.1">6.9.1</a> empty statement, <a href="#6.8.3">6.8.3</a>
-dependency-ordered before, <a href="#5.1.2.4">5.1.2.4</a> encoding error, <a href="#7.21.3">7.21.3</a>, <a href="#7.27.1.1">7.27.1.1</a>, <a href="#7.27.1.2">7.27.1.2</a>,
-derived declarator types, <a href="#6.2.5">6.2.5</a> <a href="#7.27.1.3">7.27.1.3</a>, <a href="#7.27.1.4">7.27.1.4</a>, <a href="#7.28.3.1">7.28.3.1</a>, <a href="#7.28.3.3">7.28.3.3</a>,
-derived types, <a href="#6.2.5">6.2.5</a> <a href="#7.28.6.3.2">7.28.6.3.2</a>, <a href="#7.28.6.3.3">7.28.6.3.3</a>, <a href="#7.28.6.4.1">7.28.6.4.1</a>, <a href="#7.28.6.4.2">7.28.6.4.2</a>,
-designated initializer, <a href="#6.7.9">6.7.9</a> <a href="#K.3.6.5.1">K.3.6.5.1</a>, <a href="#K.3.6.5.2">K.3.6.5.2</a>, <a href="#K.3.9.3.1.1">K.3.9.3.1.1</a>, <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a>,
-destringizing, <a href="#6.10.9">6.10.9</a> <a href="#K.3.9.3.2.2">K.3.9.3.2.2</a>
-device input/output, <a href="#5.1.2.3">5.1.2.3</a> end-of-file, <a href="#7.28.1">7.28.1</a>
-diagnostic message, <a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a> end-of-file indicator, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.1">7.21.7.1</a>,
-diagnostics, <a href="#5.1.1.3">5.1.1.3</a> <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.7.6">7.21.7.6</a>, <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.2">7.21.9.2</a>,
-diagnostics header, <a href="#7.2">7.2</a> <a href="#7.21.9.3">7.21.9.3</a>, <a href="#7.21.10.1">7.21.10.1</a>, <a href="#7.21.10.2">7.21.10.2</a>, <a href="#7.28.3.1">7.28.3.1</a>,
-difftime function, <a href="#7.26.2.2">7.26.2.2</a> <a href="#7.28.3.10">7.28.3.10</a>
-digit, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> end-of-file macro, see EOF macro
-digraphs, <a href="#6.4.6">6.4.6</a> end-of-line indicator, <a href="#5.2.1">5.2.1</a>
-direct input/output functions, <a href="#7.21.8">7.21.8</a> endif preprocessing directive, <a href="#6.10.1">6.10.1</a>
-display device, <a href="#5.2.2">5.2.2</a> enum type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.2.2">6.7.2.2</a>
-div function, <a href="#7.22.6.2">7.22.6.2</a> enumerated type, <a href="#6.2.5">6.2.5</a>
-div_t type, <a href="#7.22">7.22</a> enumeration, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.2">6.7.2.2</a>
-division assignment operator (/=), <a href="#6.5.16.2">6.5.16.2</a> enumeration constant, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
-division operator (/), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a> enumeration content, <a href="#6.7.2.3">6.7.2.3</a>
-do statement, <a href="#6.8.5.2">6.8.5.2</a> enumeration members, <a href="#6.7.2.2">6.7.2.2</a>
-documentation of implementation, <a href="#4">4</a> enumeration specifiers, <a href="#6.7.2.2">6.7.2.2</a>
-domain error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.4.1">7.12.4.1</a>, <a href="#7.12.4.2">7.12.4.2</a>, <a href="#7.12.4.4">7.12.4.4</a>, enumeration tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
- <a href="#7.12.5.1">7.12.5.1</a>, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#7.12.6.7">7.12.6.7</a>, enumerator, <a href="#6.7.2.2">6.7.2.2</a>
- <a href="#7.12.6.8">7.12.6.8</a>, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#7.12.6.11">7.12.6.11</a>, environment, <a href="#5">5</a>
- <a href="#7.12.7.4">7.12.7.4</a>, <a href="#7.12.7.5">7.12.7.5</a>, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#7.12.9.5">7.12.9.5</a>, environment functions, <a href="#7.22.4">7.22.4</a>, <a href="#K.3.6.2">K.3.6.2</a>
- <a href="#7.12.9.7">7.12.9.7</a>, <a href="#7.12.10.1">7.12.10.1</a>, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.10.3">7.12.10.3</a> environment list, <a href="#7.22.4.6">7.22.4.6</a>, <a href="#K.3.6.2.1">K.3.6.2.1</a>
-dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> environmental considerations, <a href="#5.2">5.2</a>
-double _Complex type, <a href="#6.2.5">6.2.5</a> environmental limits, <a href="#5.2.4">5.2.4</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.21.2">7.21.2</a>,
-double _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.4.4">7.21.4.4</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.22.2.1">7.22.2.1</a>, <a href="#7.22.4.2">7.22.4.2</a>,
- <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a> <a href="#7.22.4.3">7.22.4.3</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a>
-double _Imaginary type, <a href="#G.2">G.2</a> EOF macro, <a href="#7.4">7.4</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.1">7.21.5.1</a>, <a href="#7.21.5.2">7.21.5.2</a>,
-double type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.21.6.7">7.21.6.7</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.11">7.21.6.11</a>,
- <a href="#7.28.2.2">7.28.2.2</a>, <a href="#F.2">F.2</a> <a href="#7.21.6.14">7.21.6.14</a>, <a href="#7.21.7.1">7.21.7.1</a>, <a href="#7.21.7.3">7.21.7.3</a>, <a href="#7.21.7.4">7.21.7.4</a>,
-double type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>, <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.7.6">7.21.7.6</a>, <a href="#7.21.7.8">7.21.7.8</a>, <a href="#7.21.7.9">7.21.7.9</a>,
- <a href="#6.3.1.8">6.3.1.8</a> <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.28.1">7.28.1</a>, <a href="#7.28.2.2">7.28.2.2</a>, <a href="#7.28.2.4">7.28.2.4</a>,
-double-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a> <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.2.8">7.28.2.8</a>, <a href="#7.28.2.10">7.28.2.10</a>, <a href="#7.28.2.12">7.28.2.12</a>,
-double-quote escape sequence (\"), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.28.3.4">7.28.3.4</a>, <a href="#7.28.6.1.1">7.28.6.1.1</a>, <a href="#7.28.6.1.2">7.28.6.1.2</a>, <a href="#K.3.5.3.7">K.3.5.3.7</a>,
- <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</a> <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a>,
-double_t type, <a href="#7.12">7.12</a>, <a href="#J.5.6">J.5.6</a> <a href="#K.3.9.1.5">K.3.9.1.5</a>, <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a>,
- <a href="#K.3.9.1.14">K.3.9.1.14</a>
-EDOM macro, <a href="#7.5">7.5</a>, <a href="#7.12.1">7.12.1</a>, see also domain error equal-sign punctuator (=), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.9">6.7.9</a>
-effective type, <a href="#6.5">6.5</a> equal-to operator, see equality operator
-EILSEQ macro, <a href="#7.5">7.5</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.27.1.1">7.27.1.1</a>, <a href="#7.27.1.2">7.27.1.2</a>, equality expressions, <a href="#6.5.9">6.5.9</a>
- <a href="#7.27.1.3">7.27.1.3</a>, <a href="#7.27.1.4">7.27.1.4</a>, <a href="#7.28.3.1">7.28.3.1</a>, <a href="#7.28.3.3">7.28.3.3</a>, equality operator (==), <a href="#6.5.9">6.5.9</a>
- <a href="#7.28.6.3.2">7.28.6.3.2</a>, <a href="#7.28.6.3.3">7.28.6.3.3</a>, <a href="#7.28.6.4.1">7.28.6.4.1</a>, <a href="#7.28.6.4.2">7.28.6.4.2</a>, ERANGE macro, <a href="#7.5">7.5</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.12.1">7.12.1</a>,
- see also encoding error <a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.28.4.1.1">7.28.4.1.1</a>, <a href="#7.28.4.1.2">7.28.4.1.2</a>, see
-element type, <a href="#6.2.5">6.2.5</a> also range error, pole error
-
-[<a name="#p660" href="p660">page 660</a>] (<a href="#Contents">Contents</a>)
-
-erf functions, <a href="#7.12.8.1">7.12.8.1</a>, <a href="#F.10.5.1">F.10.5.1</a> exp type-generic macro, <a href="#7.24">7.24</a>
-erf type-generic macro, <a href="#7.24">7.24</a> exp2 functions, <a href="#7.12.6.2">7.12.6.2</a>, <a href="#F.10.3.2">F.10.3.2</a>
-erfc functions, <a href="#7.12.8.2">7.12.8.2</a>, <a href="#F.10.5.2">F.10.5.2</a> exp2 type-generic macro, <a href="#7.24">7.24</a>
-erfc type-generic macro, <a href="#7.24">7.24</a> explicit conversion, <a href="#6.3">6.3</a>
-errno macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.3.2">7.3.2</a>, <a href="#7.5">7.5</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, expm1 functions, <a href="#7.12.6.3">7.12.6.3</a>, <a href="#F.10.3.3">F.10.3.3</a>
- <a href="#7.12.1">7.12.1</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.9.3">7.21.9.3</a>, <a href="#7.21.10.4">7.21.10.4</a>, expm1 type-generic macro, <a href="#7.24">7.24</a>
- <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.23.6.2">7.23.6.2</a>, <a href="#7.27.1.1">7.27.1.1</a>, exponent part, <a href="#6.4.4.2">6.4.4.2</a>
- <a href="#7.27.1.2">7.27.1.2</a>, <a href="#7.27.1.3">7.27.1.3</a>, <a href="#7.27.1.4">7.27.1.4</a>, <a href="#7.28.3.1">7.28.3.1</a>, exponential functions
- <a href="#7.28.3.3">7.28.3.3</a>, <a href="#7.28.4.1.1">7.28.4.1.1</a>, <a href="#7.28.4.1.2">7.28.4.1.2</a>, <a href="#7.28.6.3.2">7.28.6.3.2</a>, complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a>
- <a href="#7.28.6.3.3">7.28.6.3.3</a>, <a href="#7.28.6.4.1">7.28.6.4.1</a>, <a href="#7.28.6.4.2">7.28.6.4.2</a>, <a href="#J.5.17">J.5.17</a>, real, <a href="#7.12.6">7.12.6</a>, <a href="#F.10.3">F.10.3</a>
- <a href="#K.3.1.3">K.3.1.3</a>, <a href="#K.3.7.4.2">K.3.7.4.2</a> expression, <a href="#6.5">6.5</a>
-errno.h header, <a href="#7.5">7.5</a>, <a href="#7.30.3">7.30.3</a>, <a href="#K.3.2">K.3.2</a> assignment, <a href="#6.5.16">6.5.16</a>
-errno_t type, <a href="#K.3.2">K.3.2</a>, <a href="#K.3.5">K.3.5</a>, <a href="#K.3.6">K.3.6</a>, <a href="#K.3.6.1.1">K.3.6.1.1</a>, cast, <a href="#6.5.4">6.5.4</a>
- <a href="#K.3.7">K.3.7</a>, <a href="#K.3.8">K.3.8</a>, <a href="#K.3.9">K.3.9</a> constant, <a href="#6.6">6.6</a>
-error evaluation, <a href="#5.1.2.3">5.1.2.3</a>
- domain, see domain error full, <a href="#6.8">6.8</a>
- encoding, see encoding error order of evaluation, see order of evaluation
- pole, see pole error parenthesized, <a href="#6.5.1">6.5.1</a>
- range, see range error primary, <a href="#6.5.1">6.5.1</a>
-error conditions, <a href="#7.12.1">7.12.1</a> unary, <a href="#6.5.3">6.5.3</a>
-error functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.10.5">F.10.5</a> expression statement, <a href="#6.8.3">6.8.3</a>
-error indicator, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.1">7.21.7.1</a>, extended alignment, <a href="#6.2.8">6.2.8</a>
- <a href="#7.21.7.3">7.21.7.3</a>, <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.7.6">7.21.7.6</a>, <a href="#7.21.7.7">7.21.7.7</a>, extended character set, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#5.2.1.2">5.2.1.2</a>
- <a href="#7.21.7.8">7.21.7.8</a>, <a href="#7.21.9.2">7.21.9.2</a>, <a href="#7.21.10.1">7.21.10.1</a>, <a href="#7.21.10.3">7.21.10.3</a>, extended characters, <a href="#5.2.1">5.2.1</a>
- <a href="#7.28.3.1">7.28.3.1</a>, <a href="#7.28.3.3">7.28.3.3</a> extended integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.4.4.1">6.4.4.1</a>,
-error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> <a href="#7.20">7.20</a>
-error-handling functions, <a href="#7.21.10">7.21.10</a>, <a href="#7.23.6.2">7.23.6.2</a>, extended multibyte/wide character conversion
- <a href="#K.3.7.4.2">K.3.7.4.2</a>, <a href="#K.3.7.4.3">K.3.7.4.3</a> utilities, <a href="#7.28.6">7.28.6</a>, <a href="#K.3.9.3">K.3.9.3</a>
-escape character (\), <a href="#6.4.4.4">6.4.4.4</a> extensible wide character case mapping functions,
-escape sequences, <a href="#5.2.1">5.2.1</a>, <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.11.4">6.11.4</a> <a href="#7.29.3.2">7.29.3.2</a>
-evaluation format, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#7.12">7.12</a> extensible wide character classification functions,
-evaluation method, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#F.8.5">F.8.5</a> <a href="#7.29.2.2">7.29.2.2</a>
-evaluation of expression, <a href="#5.1.2.3">5.1.2.3</a> extern storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.7.1">6.7.1</a>
-evaluation order, see order of evaluation external definition, <a href="#6.9">6.9</a>
-exceptional condition, <a href="#6.5">6.5</a> external identifiers, underscore, <a href="#7.1.3">7.1.3</a>
-excess precision, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, external linkage, <a href="#6.2.2">6.2.2</a>
- <a href="#6.8.6.4">6.8.6.4</a> external name, <a href="#6.4.2.1">6.4.2.1</a>
-excess range, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> external object definitions, <a href="#6.9.2">6.9.2</a>
-exclusive OR operators
- bitwise (^), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.11">6.5.11</a> fabs functions, <a href="#7.12.7.2">7.12.7.2</a>, <a href="#F.3">F.3</a>, <a href="#F.10.4.2">F.10.4.2</a>
- bitwise assignment (^=), <a href="#6.5.16.2">6.5.16.2</a> fabs type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a>
-executable program, <a href="#5.1.1.1">5.1.1.1</a> false macro, <a href="#7.18">7.18</a>
-execution character set, <a href="#5.2.1">5.2.1</a> fclose function, <a href="#7.21.5.1">7.21.5.1</a>
-execution environment, <a href="#5">5</a>, <a href="#5.1.2">5.1.2</a>, see also fdim functions, <a href="#7.12.12.1">7.12.12.1</a>, <a href="#F.10.9.1">F.10.9.1</a>
- environmental limits fdim type-generic macro, <a href="#7.24">7.24</a>
-execution sequence, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.8">6.8</a> FE_ALL_EXCEPT macro, <a href="#7.6">7.6</a>
-exit function, <a href="#5.1.2.2.3">5.1.2.2.3</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.22">7.22</a>, <a href="#7.22.4.4">7.22.4.4</a>, FE_DFL_ENV macro, <a href="#7.6">7.6</a>
- <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a> FE_DIVBYZERO macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
-EXIT_FAILURE macro, <a href="#7.22">7.22</a>, <a href="#7.22.4.4">7.22.4.4</a> FE_DOWNWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
-EXIT_SUCCESS macro, <a href="#7.22">7.22</a>, <a href="#7.22.4.4">7.22.4.4</a> FE_INEXACT macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
-exp functions, <a href="#7.12.6.1">7.12.6.1</a>, <a href="#F.10.3.1">F.10.3.1</a> FE_INVALID macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
-
-[<a name="#p661" href="p661">page 661</a>] (<a href="#Contents">Contents</a>)
-
-FE_OVERFLOW macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> float _Complex type, <a href="#6.2.5">6.2.5</a>
-FE_TONEAREST macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> float _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>,
-FE_TOWARDZERO macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
-FE_UNDERFLOW macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> float _Imaginary type, <a href="#G.2">G.2</a>
-FE_UPWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> float type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#F.2">F.2</a>
-feclearexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.1">7.6.2.1</a>, <a href="#F.3">F.3</a> float type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>,
-fegetenv function, <a href="#7.6.4.1">7.6.4.1</a>, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a> <a href="#6.3.1.8">6.3.1.8</a>
-fegetexceptflag function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.2">7.6.2.2</a>, <a href="#F.3">F.3</a> float.h header, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.22.1.3">7.22.1.3</a>,
-fegetround function, <a href="#7.6">7.6</a>, <a href="#7.6.3.1">7.6.3.1</a>, <a href="#F.3">F.3</a> <a href="#7.28.4.1.1">7.28.4.1.1</a>
-feholdexcept function, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.6.4.3">7.6.4.3</a>, float_t type, <a href="#7.12">7.12</a>, <a href="#J.5.6">J.5.6</a>
- <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a> floating constant, <a href="#6.4.4.2">6.4.4.2</a>
-fence, <a href="#5.1.2.4">5.1.2.4</a> floating suffix, f or <a href="#F">F</a>, <a href="#6.4.4.2">6.4.4.2</a>
-fences, <a href="#7.17.4">7.17.4</a> floating type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>,
-fenv.h header, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F">F</a>, <a href="#H">H</a> <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a>
-FENV_ACCESS pragma, <a href="#6.10.6">6.10.6</a>, <a href="#7.6.1">7.6.1</a>, <a href="#F.8">F.8</a>, <a href="#F.9">F.9</a>, floating types, <a href="#6.2.5">6.2.5</a>, <a href="#6.11.1">6.11.1</a>
- <a href="#F.10">F.10</a> floating-point accuracy, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.5">6.5</a>,
-fenv_t type, <a href="#7.6">7.6</a> <a href="#7.22.1.3">7.22.1.3</a>, <a href="#F.5">F.5</a>, see also contracted expression
-feof function, <a href="#7.21.10.2">7.21.10.2</a> floating-point arithmetic functions, <a href="#7.12">7.12</a>, <a href="#F.10">F.10</a>
-feraiseexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.3">7.6.2.3</a>, <a href="#F.3">F.3</a> floating-point classification functions, <a href="#7.12.3">7.12.3</a>
-ferror function, <a href="#7.21.10.3">7.21.10.3</a> floating-point control mode, <a href="#7.6">7.6</a>, <a href="#F.8.6">F.8.6</a>
-fesetenv function, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#F.3">F.3</a> floating-point environment, <a href="#7.6">7.6</a>, <a href="#F.8">F.8</a>, <a href="#F.8.6">F.8.6</a>
-fesetexceptflag function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.4">7.6.2.4</a>, <a href="#F.3">F.3</a> floating-point exception, <a href="#7.6">7.6</a>, <a href="#7.6.2">7.6.2</a>, <a href="#F.10">F.10</a>
-fesetround function, <a href="#7.6">7.6</a>, <a href="#7.6.3.2">7.6.3.2</a>, <a href="#F.3">F.3</a> floating-point number, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.2.5">6.2.5</a>
-fetestexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.5">7.6.2.5</a>, <a href="#F.3">F.3</a> floating-point rounding mode, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-feupdateenv function, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a> floating-point status flag, <a href="#7.6">7.6</a>, <a href="#F.8.6">F.8.6</a>
-fexcept_t type, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> floor functions, <a href="#7.12.9.2">7.12.9.2</a>, <a href="#F.10.6.2">F.10.6.2</a>
-fflush function, <a href="#7.21.5.2">7.21.5.2</a>, <a href="#7.21.5.3">7.21.5.3</a> floor type-generic macro, <a href="#7.24">7.24</a>
-fgetc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.7.1">7.21.7.1</a>, FLT_DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.8.1">7.21.8.1</a> FLT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-fgetpos function, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.9.1">7.21.9.1</a>, <a href="#7.21.9.3">7.21.9.3</a> FLT_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-fgets function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.2">7.21.7.2</a>, <a href="#K.3.5.4.1">K.3.5.4.1</a> FLT_EVAL_METHOD macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.6">6.6</a>, <a href="#7.12">7.12</a>,
-fgetwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.28.3.1">7.28.3.1</a>, <a href="#F.10.11">F.10.11</a>
- <a href="#7.28.3.6">7.28.3.6</a> FLT_HAS_SUBNORM macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-fgetws function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3.2">7.28.3.2</a> FLT_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-field width, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a> FLT_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-file, <a href="#7.21.3">7.21.3</a> FLT_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- access functions, <a href="#7.21.5">7.21.5</a>, <a href="#K.3.5.2">K.3.5.2</a> FLT_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- name, <a href="#7.21.3">7.21.3</a> FLT_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- operations, <a href="#7.21.4">7.21.4</a>, <a href="#K.3.5.1">K.3.5.1</a> FLT_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- position indicator, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.3">7.21.3</a>, FLT_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.1">7.21.7.1</a>, <a href="#7.21.7.3">7.21.7.3</a>, <a href="#7.21.7.10">7.21.7.10</a>, FLT_RADIX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.22.1.3">7.22.1.3</a>,
- <a href="#7.21.8.1">7.21.8.1</a>, <a href="#7.21.8.2">7.21.8.2</a>, <a href="#7.21.9.1">7.21.9.1</a>, <a href="#7.21.9.2">7.21.9.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.4.1.1">7.28.4.1.1</a>
- <a href="#7.21.9.3">7.21.9.3</a>, <a href="#7.21.9.4">7.21.9.4</a>, <a href="#7.21.9.5">7.21.9.5</a>, <a href="#7.28.3.1">7.28.3.1</a>, FLT_ROUNDS macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
- <a href="#7.28.3.3">7.28.3.3</a>, <a href="#7.28.3.10">7.28.3.10</a> FLT_TRUE_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- positioning functions, <a href="#7.21.9">7.21.9</a> fma functions, <a href="#7.12">7.12</a>, <a href="#7.12.13.1">7.12.13.1</a>, <a href="#F.10.10.1">F.10.10.1</a>
-file scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.9">6.9</a> fma type-generic macro, <a href="#7.24">7.24</a>
-FILE type, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> fmax functions, <a href="#7.12.12.2">7.12.12.2</a>, <a href="#F.10.9.2">F.10.9.2</a>
-FILENAME_MAX macro, <a href="#7.21.1">7.21.1</a> fmax type-generic macro, <a href="#7.24">7.24</a>
-flags, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>, see also floating-point fmin functions, <a href="#7.12.12.3">7.12.12.3</a>, <a href="#F.10.9.3">F.10.9.3</a>
- status flag fmin type-generic macro, <a href="#7.24">7.24</a>
-flexible array member, <a href="#6.7.2.1">6.7.2.1</a> fmod functions, <a href="#7.12.10.1">7.12.10.1</a>, <a href="#F.10.7.1">F.10.7.1</a>
-
-[<a name="#p662" href="p662">page 662</a>] (<a href="#Contents">Contents</a>)
-
-fmod type-generic macro, <a href="#7.24">7.24</a> fscanf_s function, <a href="#K.3.5.3.2">K.3.5.3.2</a>, <a href="#K.3.5.3.4">K.3.5.3.4</a>,
-fopen function, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.5.4">7.21.5.4</a>, <a href="#K.3.5.2.1">K.3.5.2.1</a> <a href="#K.3.5.3.7">K.3.5.3.7</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>
-FOPEN_MAX macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.4.3">7.21.4.3</a>, fseek function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.10">7.21.7.10</a>,
- <a href="#K.3.5.1.1">K.3.5.1.1</a> <a href="#7.21.9.2">7.21.9.2</a>, <a href="#7.21.9.4">7.21.9.4</a>, <a href="#7.21.9.5">7.21.9.5</a>, <a href="#7.28.3.10">7.28.3.10</a>
-fopen_s function, <a href="#K.3.5.1.1">K.3.5.1.1</a>, <a href="#K.3.5.2.1">K.3.5.2.1</a>, fsetpos function, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.10">7.21.7.10</a>,
- <a href="#K.3.5.2.2">K.3.5.2.2</a> <a href="#7.21.9.1">7.21.9.1</a>, <a href="#7.21.9.3">7.21.9.3</a>, <a href="#7.28.3.10">7.28.3.10</a>
-for statement, <a href="#6.8.5">6.8.5</a>, <a href="#6.8.5.3">6.8.5.3</a> ftell function, <a href="#7.21.9.2">7.21.9.2</a>, <a href="#7.21.9.4">7.21.9.4</a>
-form-feed character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a> full declarator, <a href="#6.7.6">6.7.6</a>
-form-feed escape sequence (\f), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, full expression, <a href="#6.8">6.8</a>
- <a href="#7.4.1.10">7.4.1.10</a> fully buffered stream, <a href="#7.21.3">7.21.3</a>
-formal argument (deprecated), <a href="#3.16">3.16</a> function
-formal parameter, <a href="#3.16">3.16</a> argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a>
-formatted input/output functions, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.6">7.21.6</a>, body, <a href="#6.9.1">6.9.1</a>
- <a href="#K.3.5.3">K.3.5.3</a> call, <a href="#6.5.2.2">6.5.2.2</a>
- wide character, <a href="#7.28.2">7.28.2</a>, <a href="#K.3.9.1">K.3.9.1</a> library, <a href="#7.1.4">7.1.4</a>
-fortran keyword, <a href="#J.5.9">J.5.9</a> declarator, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.11.6">6.11.6</a>
-forward reference, <a href="#3.11">3.11</a> definition, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.9.1">6.9.1</a>, <a href="#6.11.7">6.11.7</a>
-FP_CONTRACT pragma, <a href="#6.5">6.5</a>, <a href="#6.10.6">6.10.6</a>, <a href="#7.12.2">7.12.2</a>, see designator, <a href="#6.3.2.1">6.3.2.1</a>
- also contracted expression image, <a href="#5.2.3">5.2.3</a>
-FP_FAST_FMA macro, <a href="#7.12">7.12</a> inline, <a href="#6.7.4">6.7.4</a>
-FP_FAST_FMAF macro, <a href="#7.12">7.12</a> library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.4">7.1.4</a>
-FP_FAST_FMAL macro, <a href="#7.12">7.12</a> name length, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a>
-FP_ILOGB0 macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a> no-return, <a href="#6.7.4">6.7.4</a>
-FP_ILOGBNAN macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a> parameter, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.9.1">6.9.1</a>
-FP_INFINITE macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> prototype, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#6.2.1">6.2.1</a>, <a href="#6.2.7">6.2.7</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>,
-FP_NAN macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.9.1">6.9.1</a>, <a href="#6.11.6">6.11.6</a>, <a href="#6.11.7">6.11.7</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.12">7.12</a>
-FP_NORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> prototype scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.7.6.2">6.7.6.2</a>
-FP_SUBNORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> recursive call, <a href="#6.5.2.2">6.5.2.2</a>
-FP_ZERO macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a> return, <a href="#6.8.6.4">6.8.6.4</a>, <a href="#F.6">F.6</a>
-fpclassify macro, <a href="#7.12.3.1">7.12.3.1</a>, <a href="#F.3">F.3</a> scope, <a href="#6.2.1">6.2.1</a>
-fpos_t type, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a> type, <a href="#6.2.5">6.2.5</a>
-fprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.1">7.21.6.1</a>, type conversion, <a href="#6.3.2.1">6.3.2.1</a>
- <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.21.6.3">7.21.6.3</a>, <a href="#7.21.6.5">7.21.6.5</a>, <a href="#7.21.6.6">7.21.6.6</a>, function specifiers, <a href="#6.7.4">6.7.4</a>
- <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.28.2.2">7.28.2.2</a>, <a href="#F.3">F.3</a>, <a href="#K.3.5.3.1">K.3.5.3.1</a> function type, <a href="#6.2.5">6.2.5</a>
-fprintf_s function, <a href="#K.3.5.3.1">K.3.5.3.1</a> function-call operator (( )), <a href="#6.5.2.2">6.5.2.2</a>
-fputc function, <a href="#5.2.2">5.2.2</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.7.3">7.21.7.3</a>, function-like macro, <a href="#6.10.3">6.10.3</a>
- <a href="#7.21.7.7">7.21.7.7</a>, <a href="#7.21.8.2">7.21.8.2</a> fundamental alignment, <a href="#6.2.8">6.2.8</a>
-fputs function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.4">7.21.7.4</a> future directions
-fputwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.28.3.3">7.28.3.3</a>, language, <a href="#6.11">6.11</a>
- <a href="#7.28.3.8">7.28.3.8</a> library, <a href="#7.30">7.30</a>
-fputws function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3.4">7.28.3.4</a> fwide function, <a href="#7.21.2">7.21.2</a>, <a href="#7.28.3.5">7.28.3.5</a>
-fread function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.8.1">7.21.8.1</a> fwprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
-free function, <a href="#7.22.3.3">7.22.3.3</a>, <a href="#7.22.3.5">7.22.3.5</a> <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>, <a href="#7.28.2.3">7.28.2.3</a>, <a href="#7.28.2.5">7.28.2.5</a>,
-freestanding execution environment, <a href="#4">4</a>, <a href="#5.1.2">5.1.2</a>, <a href="#7.28.2.11">7.28.2.11</a>, <a href="#K.3.9.1.1">K.3.9.1.1</a>
- <a href="#5.1.2.1">5.1.2.1</a> fwprintf_s function, <a href="#K.3.9.1.1">K.3.9.1.1</a>
-freopen function, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.5.4">7.21.5.4</a> fwrite function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.8.2">7.21.8.2</a>
-freopen_s function, <a href="#K.3.5.2.2">K.3.5.2.2</a> fwscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.2.2">7.28.2.2</a>,
-frexp functions, <a href="#7.12.6.4">7.12.6.4</a>, <a href="#F.10.3.4">F.10.3.4</a> <a href="#7.28.2.4">7.28.2.4</a>, <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.2.12">7.28.2.12</a>, <a href="#7.28.3.10">7.28.3.10</a>,
-frexp type-generic macro, <a href="#7.24">7.24</a> <a href="#K.3.9.1.2">K.3.9.1.2</a>
-fscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, fwscanf_s function, <a href="#K.3.9.1.2">K.3.9.1.2</a>, <a href="#K.3.9.1.5">K.3.9.1.5</a>,
- <a href="#7.21.6.4">7.21.6.4</a>, <a href="#7.21.6.7">7.21.6.7</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#F.3">F.3</a>, <a href="#K.3.5.3.2">K.3.5.3.2</a> <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.14">K.3.9.1.14</a>
-
-[<a name="#p663" href="p663">page 663</a>] (<a href="#Contents">Contents</a>)
-
-gamma functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.10.5">F.10.5</a> name spaces, <a href="#6.2.3">6.2.3</a>
-general utilities, <a href="#7.22">7.22</a>, <a href="#K.3.6">K.3.6</a> reserved, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a>, <a href="#K.3.1.2">K.3.1.2</a>
- wide string, <a href="#7.28.4">7.28.4</a>, <a href="#K.3.9.2">K.3.9.2</a> scope, <a href="#6.2.1">6.2.1</a>
-general wide string utilities, <a href="#7.28.4">7.28.4</a>, <a href="#K.3.9.2">K.3.9.2</a> type, <a href="#6.2.5">6.2.5</a>
-generic parameters, <a href="#7.24">7.24</a> identifier list, <a href="#6.7.6">6.7.6</a>
-generic selection, <a href="#6.5.1.1">6.5.1.1</a> identifier nondigit, <a href="#6.4.2.1">6.4.2.1</a>
-getc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.5">7.21.7.5</a>, <a href="#7.21.7.6">7.21.7.6</a> IEC 559, <a href="#F.1">F.1</a>
-getchar function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.6">7.21.7.6</a> IEC 60559, <a href="#2">2</a>, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.3.3">7.3.3</a>,
-getenv function, <a href="#7.22.4.6">7.22.4.6</a> <a href="#7.6">7.6</a>, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.14">7.12.14</a>, <a href="#F">F</a>, <a href="#G">G</a>,
-getenv_s function, <a href="#K.3.6.2.1">K.3.6.2.1</a> <a href="#H.1">H.1</a>
-gets function, <a href="#K.3.5.4.1">K.3.5.4.1</a> IEEE 754, <a href="#F.1">F.1</a>
-gets_s function, <a href="#K.3.5.4.1">K.3.5.4.1</a> IEEE 854, <a href="#F.1">F.1</a>
-getwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3.6">7.28.3.6</a>, <a href="#7.28.3.7">7.28.3.7</a> IEEE floating-point arithmetic standard, see
-getwchar function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3.7">7.28.3.7</a> IEC 60559, ANSI/IEEE 754,
-gmtime function, <a href="#7.26.3.3">7.26.3.3</a> ANSI/IEEE 854
-gmtime_s function, <a href="#K.3.8.2.3">K.3.8.2.3</a> if preprocessing directive, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>,
-goto statement, <a href="#6.2.1">6.2.1</a>, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.6.1">6.8.6.1</a> <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a>
-graphic characters, <a href="#5.2.1">5.2.1</a> if statement, <a href="#6.8.4.1">6.8.4.1</a>
-greater-than operator (>), <a href="#6.5.8">6.5.8</a> ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a>
-greater-than-or-equal-to operator (>=), <a href="#6.5.8">6.5.8</a> ifndef preprocessing directive, <a href="#6.10.1">6.10.1</a>
- ignore_handler_s function, <a href="#K.3.6.1.3">K.3.6.1.3</a>
-happens before, <a href="#5.1.2.4">5.1.2.4</a> ilogb functions, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#F.10.3.5">F.10.3.5</a>
-header, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.2">7.1.2</a>, see also standard headers ilogb type-generic macro, <a href="#7.24">7.24</a>
-header names, <a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>, <a href="#6.10.2">6.10.2</a> imaginary macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a>
-hexadecimal constant, <a href="#6.4.4.1">6.4.4.1</a> imaginary numbers, <a href="#G">G</a>
-hexadecimal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.4.4.4">6.4.4.4</a> imaginary type domain, <a href="#G.2">G.2</a>
-hexadecimal prefix, <a href="#6.4.4.1">6.4.4.1</a> imaginary types, <a href="#G">G</a>
-hexadecimal-character escape sequence imaxabs function, <a href="#7.8.2.1">7.8.2.1</a>
- (\x hexadecimal digits), <a href="#6.4.4.4">6.4.4.4</a> imaxdiv function, <a href="#7.8">7.8</a>, <a href="#7.8.2.2">7.8.2.2</a>
-high-order bit, <a href="#3.6">3.6</a> imaxdiv_t type, <a href="#7.8">7.8</a>
-horizontal-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a> implementation, <a href="#3.12">3.12</a>
-horizontal-tab escape sequence (\r), <a href="#7.29.2.1.3">7.29.2.1.3</a> implementation limit, <a href="#3.13">3.13</a>, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.4.2.1">6.4.2.1</a>,
-horizontal-tab escape sequence (\t), <a href="#5.2.2">5.2.2</a>, <a href="#6.7.6">6.7.6</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#E">E</a>, see also environmental
- <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.10">7.4.1.10</a> limits
-hosted execution environment, <a href="#4">4</a>, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.2">5.1.2.2</a> implementation-defined behavior, <a href="#3.4.1">3.4.1</a>, <a href="#4">4</a>, <a href="#J.3">J.3</a>
-HUGE_VAL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.22.1.3">7.22.1.3</a>, implementation-defined value, <a href="#3.19.1">3.19.1</a>
- <a href="#7.28.4.1.1">7.28.4.1.1</a>, <a href="#F.10">F.10</a> implicit conversion, <a href="#6.3">6.3</a>
-HUGE_VALF macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.22.1.3">7.22.1.3</a>, implicit initialization, <a href="#6.7.9">6.7.9</a>
- <a href="#7.28.4.1.1">7.28.4.1.1</a>, <a href="#F.10">F.10</a> include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.2">6.10.2</a>
-HUGE_VALL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.22.1.3">7.22.1.3</a>, inclusive OR operators
- <a href="#7.28.4.1.1">7.28.4.1.1</a>, <a href="#F.10">F.10</a> bitwise (|), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a>
-hyperbolic functions bitwise assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
- complex, <a href="#7.3.6">7.3.6</a>, <a href="#G.6.2">G.6.2</a> incomplete type, <a href="#6.2.5">6.2.5</a>
- real, <a href="#7.12.5">7.12.5</a>, <a href="#F.10.2">F.10.2</a> increment operators, see arithmetic operators,
-hypot functions, <a href="#7.12.7.3">7.12.7.3</a>, <a href="#F.10.4.3">F.10.4.3</a> increment and decrement
-hypot type-generic macro, <a href="#7.24">7.24</a> indeterminate value, <a href="#3.19.2">3.19.2</a>
- indeterminately sequenced, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5.2.2">6.5.2.2</a>,
-I macro, <a href="#7.3.1">7.3.1</a>, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#G.6">G.6</a> <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.16.2">6.5.16.2</a>, see also sequenced before,
-identifier, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.5.1">6.5.1</a> unsequenced
- linkage, see linkage indirection operator (*), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>
- maximum length, <a href="#6.4.2.1">6.4.2.1</a> inequality operator (!=), <a href="#6.5.9">6.5.9</a>
-
-[<a name="#p664" href="p664">page 664</a>] (<a href="#Contents">Contents</a>)
-
-infinitary, <a href="#7.12.1">7.12.1</a> extended, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#7.20">7.20</a>
-INFINITY macro, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</a> inter-thread happens before, <a href="#5.1.2.4">5.1.2.4</a>
-initial position, <a href="#5.2.2">5.2.2</a> interactive device, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.5.3">7.21.5.3</a>
-initial shift state, <a href="#5.2.1.2">5.2.1.2</a> internal linkage, <a href="#6.2.2">6.2.2</a>
-initialization, <a href="#5.1.2">5.1.2</a>, <a href="#6.2.4">6.2.4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.5">6.5.2.5</a>, <a href="#6.7.9">6.7.9</a>, internal name, <a href="#6.4.2.1">6.4.2.1</a>
- <a href="#F.8.5">F.8.5</a> interrupt, <a href="#5.2.3">5.2.3</a>
- in blocks, <a href="#6.8">6.8</a> INTMAX_C macro, <a href="#7.20.4.2">7.20.4.2</a>
-initializer, <a href="#6.7.9">6.7.9</a> INTMAX_MAX macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.20.2.5">7.20.2.5</a>
- permitted form, <a href="#6.6">6.6</a> INTMAX_MIN macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.20.2.5">7.20.2.5</a>
- string literal, <a href="#6.3.2.1">6.3.2.1</a> intmax_t type, <a href="#7.20.1.5">7.20.1.5</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
-inline, <a href="#6.7.4">6.7.4</a> <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>
-inner scope, <a href="#6.2.1">6.2.1</a> INTN_C macros, <a href="#7.20.4.1">7.20.4.1</a>
-input failure, <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.2.8">7.28.2.8</a>, <a href="#7.28.2.10">7.28.2.10</a>, INTN_MAX macros, <a href="#7.20.2.1">7.20.2.1</a>
- <a href="#K.3.5.3.2">K.3.5.3.2</a>, <a href="#K.3.5.3.4">K.3.5.3.4</a>, <a href="#K.3.5.3.7">K.3.5.3.7</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>, INTN_MIN macros, <a href="#7.20.2.1">7.20.2.1</a>
- <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a>, <a href="#K.3.9.1.5">K.3.9.1.5</a>, intN_t types, <a href="#7.20.1.1">7.20.1.1</a>
- <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a>, <a href="#K.3.9.1.14">K.3.9.1.14</a> INTPTR_MAX macro, <a href="#7.20.2.4">7.20.2.4</a>
-input/output functions INTPTR_MIN macro, <a href="#7.20.2.4">7.20.2.4</a>
- character, <a href="#7.21.7">7.21.7</a>, <a href="#K.3.5.4">K.3.5.4</a> intptr_t type, <a href="#7.20.1.4">7.20.1.4</a>
- direct, <a href="#7.21.8">7.21.8</a> inttypes.h header, <a href="#7.8">7.8</a>, <a href="#7.30.4">7.30.4</a>
- formatted, <a href="#7.21.6">7.21.6</a>, <a href="#K.3.5.3">K.3.5.3</a> isalnum function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.9">7.4.1.9</a>, <a href="#7.4.1.10">7.4.1.10</a>
- wide character, <a href="#7.28.2">7.28.2</a>, <a href="#K.3.9.1">K.3.9.1</a> isalpha function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.2">7.4.1.2</a>
- wide character, <a href="#7.28.3">7.28.3</a> isblank function, <a href="#7.4.1.3">7.4.1.3</a>
- formatted, <a href="#7.28.2">7.28.2</a>, <a href="#K.3.9.1">K.3.9.1</a> iscntrl function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.4">7.4.1.4</a>, <a href="#7.4.1.7">7.4.1.7</a>,
-input/output header, <a href="#7.21">7.21</a>, <a href="#K.3.5">K.3.5</a> <a href="#7.4.1.11">7.4.1.11</a>
-input/output, device, <a href="#5.1.2.3">5.1.2.3</a> isdigit function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.5">7.4.1.5</a>,
-int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.7.2">6.7.2</a> <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.11.1.1">7.11.1.1</a>
-int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>, isfinite macro, <a href="#7.12.3.2">7.12.3.2</a>, <a href="#F.3">F.3</a>
- <a href="#6.3.1.8">6.3.1.8</a> isgraph function, <a href="#7.4.1.6">7.4.1.6</a>
-INT_FASTN_MAX macros, <a href="#7.20.2.3">7.20.2.3</a> isgreater macro, <a href="#7.12.14.1">7.12.14.1</a>, <a href="#F.3">F.3</a>
-INT_FASTN_MIN macros, <a href="#7.20.2.3">7.20.2.3</a> isgreaterequal macro, <a href="#7.12.14.2">7.12.14.2</a>, <a href="#F.3">F.3</a>
-int_fastN_t types, <a href="#7.20.1.3">7.20.1.3</a> isinf macro, <a href="#7.12.3.3">7.12.3.3</a>
-INT_LEASTN_MAX macros, <a href="#7.20.2.2">7.20.2.2</a> isless macro, <a href="#7.12.14.3">7.12.14.3</a>, <a href="#F.3">F.3</a>
-INT_LEASTN_MIN macros, <a href="#7.20.2.2">7.20.2.2</a> islessequal macro, <a href="#7.12.14.4">7.12.14.4</a>, <a href="#F.3">F.3</a>
-int_leastN_t types, <a href="#7.20.1.2">7.20.1.2</a> islessgreater macro, <a href="#7.12.14.5">7.12.14.5</a>, <a href="#F.3">F.3</a>
-INT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a> islower function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.2.1">7.4.2.1</a>,
-INT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a> <a href="#7.4.2.2">7.4.2.2</a>
-integer arithmetic functions, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.8.2.2">7.8.2.2</a>, isnan macro, <a href="#7.12.3.4">7.12.3.4</a>, <a href="#F.3">F.3</a>
- <a href="#7.22.6">7.22.6</a> isnormal macro, <a href="#7.12.3.5">7.12.3.5</a>
-integer character constant, <a href="#6.4.4.4">6.4.4.4</a> ISO 31-11, <a href="#2">2</a>, <a href="#3">3</a>
-integer constant, <a href="#6.4.4.1">6.4.4.1</a> ISO 4217, <a href="#2">2</a>, <a href="#7.11.2.1">7.11.2.1</a>
-integer constant expression, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.6">6.6</a>, <a href="#6.7.2.1">6.7.2.1</a>, ISO 8601, <a href="#2">2</a>, <a href="#7.26.3.5">7.26.3.5</a>
- <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.7.10">6.7.10</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#6.10.1">6.10.1</a>, ISO/IEC 10646, <a href="#2">2</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.4.3">6.4.3</a>, <a href="#6.10.8.2">6.10.8.2</a>
- <a href="#7.1.4">7.1.4</a> ISO/IEC 10976-1, <a href="#H.1">H.1</a>
-integer conversion rank, <a href="#6.3.1.1">6.3.1.1</a> ISO/IEC 2382-1, <a href="#2">2</a>, <a href="#3">3</a>
-integer promotions, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.3.1.1">6.3.1.1</a>, ISO/IEC 646, <a href="#2">2</a>, <a href="#5.2.1.1">5.2.1.1</a>
- <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.3.3">6.5.3.3</a>, <a href="#6.5.7">6.5.7</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#7.20.2">7.20.2</a>, <a href="#7.20.3">7.20.3</a>, ISO/IEC 9945-2, <a href="#7.11">7.11</a>
- <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a> ISO/IEC TR 10176, <a href="#D">D</a>
-integer suffix, <a href="#6.4.4.1">6.4.4.1</a> iso646.h header, <a href="#4">4</a>, <a href="#7.9">7.9</a>
-integer type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>, isprint function, <a href="#5.2.2">5.2.2</a>, <a href="#7.4.1.8">7.4.1.8</a>
- <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> ispunct function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>,
-integer types, <a href="#6.2.5">6.2.5</a>, <a href="#7.20">7.20</a> <a href="#7.4.1.11">7.4.1.11</a>
-
-[<a name="#p665" href="p665">page 665</a>] (<a href="#Contents">Contents</a>)
-
-isspace function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>, Latin alphabet, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
- <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22.1.3">7.22.1.3</a>, LC_ALL macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
- <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.28.2.2">7.28.2.2</a> LC_COLLATE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.4.3">7.23.4.3</a>,
-isunordered macro, <a href="#7.12.14.6">7.12.14.6</a>, <a href="#F.3">F.3</a> <a href="#7.28.4.4.2">7.28.4.4.2</a>
-isupper function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.4.2.1">7.4.2.1</a>, LC_CTYPE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.22">7.22</a>, <a href="#7.22.7">7.22.7</a>,
- <a href="#7.4.2.2">7.4.2.2</a> <a href="#7.22.8">7.22.8</a>, <a href="#7.28.6">7.28.6</a>, <a href="#7.29.1">7.29.1</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a>, <a href="#7.29.2.2.2">7.29.2.2.2</a>,
-iswalnum function, <a href="#7.29.2.1.1">7.29.2.1.1</a>, <a href="#7.29.2.1.9">7.29.2.1.9</a>, <a href="#7.29.3.2.1">7.29.3.2.1</a>, <a href="#7.29.3.2.2">7.29.3.2.2</a>, <a href="#K.3.6.4">K.3.6.4</a>, <a href="#K.3.6.5">K.3.6.5</a>
- <a href="#7.29.2.1.10">7.29.2.1.10</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a> LC_MONETARY macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
-iswalpha function, <a href="#7.29.2.1.1">7.29.2.1.1</a>, <a href="#7.29.2.1.2">7.29.2.1.2</a>, LC_NUMERIC macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
- <a href="#7.29.2.2.1">7.29.2.2.1</a> LC_TIME macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.26.3.5">7.26.3.5</a>
-iswblank function, <a href="#7.29.2.1.3">7.29.2.1.3</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a> lconv structure type, <a href="#7.11">7.11</a>
-iswcntrl function, <a href="#7.29.2.1.2">7.29.2.1.2</a>, <a href="#7.29.2.1.4">7.29.2.1.4</a>, LDBL_DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- <a href="#7.29.2.1.7">7.29.2.1.7</a>, <a href="#7.29.2.1.11">7.29.2.1.11</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a> LDBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-iswctype function, <a href="#7.29.2.2.1">7.29.2.2.1</a>, <a href="#7.29.2.2.2">7.29.2.2.2</a> LDBL_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-iswdigit function, <a href="#7.29.2.1.1">7.29.2.1.1</a>, <a href="#7.29.2.1.2">7.29.2.1.2</a>, LDBL_HAS_SUBNORM macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- <a href="#7.29.2.1.5">7.29.2.1.5</a>, <a href="#7.29.2.1.7">7.29.2.1.7</a>, <a href="#7.29.2.1.11">7.29.2.1.11</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a> LDBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-iswgraph function, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.1.6">7.29.2.1.6</a>, LDBL_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- <a href="#7.29.2.1.10">7.29.2.1.10</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a> LDBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-iswlower function, <a href="#7.29.2.1.2">7.29.2.1.2</a>, <a href="#7.29.2.1.7">7.29.2.1.7</a>, LDBL_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- <a href="#7.29.2.2.1">7.29.2.2.1</a>, <a href="#7.29.3.1.1">7.29.3.1.1</a>, <a href="#7.29.3.1.2">7.29.3.1.2</a> LDBL_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-iswprint function, <a href="#7.29.2.1.6">7.29.2.1.6</a>, <a href="#7.29.2.1.8">7.29.2.1.8</a>, LDBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- <a href="#7.29.2.2.1">7.29.2.2.1</a> LDBL_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-iswpunct function, <a href="#7.29.2.1">7.29.2.1</a>, <a href="#7.29.2.1.2">7.29.2.1.2</a>, LDBL_TRUE_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- <a href="#7.29.2.1.7">7.29.2.1.7</a>, <a href="#7.29.2.1.9">7.29.2.1.9</a>, <a href="#7.29.2.1.10">7.29.2.1.10</a>, ldexp functions, <a href="#7.12.6.6">7.12.6.6</a>, <a href="#F.10.3.6">F.10.3.6</a>
- <a href="#7.29.2.1.11">7.29.2.1.11</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a> ldexp type-generic macro, <a href="#7.24">7.24</a>
-iswspace function, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>, ldiv function, <a href="#7.22.6.2">7.22.6.2</a>
- <a href="#7.28.4.1.1">7.28.4.1.1</a>, <a href="#7.28.4.1.2">7.28.4.1.2</a>, <a href="#7.29.2.1.2">7.29.2.1.2</a>, <a href="#7.29.2.1.6">7.29.2.1.6</a>, ldiv_t type, <a href="#7.22">7.22</a>
- <a href="#7.29.2.1.7">7.29.2.1.7</a>, <a href="#7.29.2.1.9">7.29.2.1.9</a>, <a href="#7.29.2.1.10">7.29.2.1.10</a>, leading underscore in identifiers, <a href="#7.1.3">7.1.3</a>
- <a href="#7.29.2.1.11">7.29.2.1.11</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a> left-shift assignment operator (<<=), <a href="#6.5.16.2">6.5.16.2</a>
-iswupper function, <a href="#7.29.2.1.2">7.29.2.1.2</a>, <a href="#7.29.2.1.11">7.29.2.1.11</a>, left-shift operator (<<), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a>
- <a href="#7.29.2.2.1">7.29.2.2.1</a>, <a href="#7.29.3.1.1">7.29.3.1.1</a>, <a href="#7.29.3.1.2">7.29.3.1.2</a> length
-iswxdigit function, <a href="#7.29.2.1.12">7.29.2.1.12</a>, <a href="#7.29.2.2.1">7.29.2.2.1</a> external name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a>
-isxdigit function, <a href="#7.4.1.12">7.4.1.12</a>, <a href="#7.11.1.1">7.11.1.1</a> function name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a>
-italic type convention, <a href="#3">3</a>, <a href="#6.1">6.1</a> identifier, <a href="#6.4.2.1">6.4.2.1</a>
-iteration statements, <a href="#6.8.5">6.8.5</a> internal name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
- length function, <a href="#7.22.7.1">7.22.7.1</a>, <a href="#7.23.6.3">7.23.6.3</a>, <a href="#7.28.4.6.1">7.28.4.6.1</a>,
-jmp_buf type, <a href="#7.13">7.13</a> <a href="#7.28.6.3.1">7.28.6.3.1</a>, <a href="#K.3.7.4.4">K.3.7.4.4</a>, <a href="#K.3.9.2.4.1">K.3.9.2.4.1</a>
-jump statements, <a href="#6.8.6">6.8.6</a> length modifier, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>,
- <a href="#7.28.2.2">7.28.2.2</a>
-keywords, <a href="#6.4.1">6.4.1</a>, <a href="#G.2">G.2</a>, <a href="#J.5.9">J.5.9</a>, <a href="#J.5.10">J.5.10</a> less-than operator (<), <a href="#6.5.8">6.5.8</a>
-kill_dependency macro, <a href="#5.1.2.4">5.1.2.4</a>, <a href="#7.17.3.1">7.17.3.1</a> less-than-or-equal-to operator (<=), <a href="#6.5.8">6.5.8</a>
-known constant size, <a href="#6.2.5">6.2.5</a> letter, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a>
- lexical elements, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>
-L_tmpnam macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.4.4">7.21.4.4</a> lgamma functions, <a href="#7.12.8.3">7.12.8.3</a>, <a href="#F.10.5.3">F.10.5.3</a>
-L_tmpnam_s macro, <a href="#K.3.5">K.3.5</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a> lgamma type-generic macro, <a href="#7.24">7.24</a>
-label name, <a href="#6.2.1">6.2.1</a>, <a href="#6.2.3">6.2.3</a> library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7">7</a>, <a href="#K.3">K.3</a>
-labeled statement, <a href="#6.8.1">6.8.1</a> future directions, <a href="#7.30">7.30</a>
-labs function, <a href="#7.22.6.1">7.22.6.1</a> summary, <a href="#B">B</a>
-language, <a href="#6">6</a> terms, <a href="#7.1.1">7.1.1</a>
- future directions, <a href="#6.11">6.11</a> use of functions, <a href="#7.1.4">7.1.4</a>
- syntax summary, <a href="#A">A</a> lifetime, <a href="#6.2.4">6.2.4</a>
-
-[<a name="#p666" href="p666">page 666</a>] (<a href="#Contents">Contents</a>)
-
-limits long double _Complex type conversion,
- environmental, see environmental limits <a href="#6.3.1.6">6.3.1.6</a>, <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
- implementation, see implementation limits long double _Imaginary type, <a href="#G.2">G.2</a>
- numerical, see numerical limits long double suffix, l or <a href="#L">L</a>, <a href="#6.4.4.2">6.4.4.2</a>
- translation, see translation limits long double type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>,
-limits.h header, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a> <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>, <a href="#F.2">F.2</a>
-line buffered stream, <a href="#7.21.3">7.21.3</a> long double type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>,
-line number, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8.1">6.10.8.1</a> <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
-line preprocessing directive, <a href="#6.10.4">6.10.4</a> long int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.21.6.1">7.21.6.1</a>,
-lines, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#7.21.2">7.21.2</a> <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>
- preprocessing directive, <a href="#6.10">6.10</a> long int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>,
-linkage, <a href="#6.2.2">6.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.4">6.7.4</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.9">6.9</a>, <a href="#6.9.2">6.9.2</a>, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
- <a href="#6.11.2">6.11.2</a> long integer suffix, l or <a href="#L">L</a>, <a href="#6.4.4.1">6.4.4.1</a>
-llabs function, <a href="#7.22.6.1">7.22.6.1</a> long long int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>,
-lldiv function, <a href="#7.22.6.2">7.22.6.2</a> <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>
-lldiv_t type, <a href="#7.22">7.22</a> long long int type conversion, <a href="#6.3.1.1">6.3.1.1</a>,
-LLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
- <a href="#7.28.4.1.2">7.28.4.1.2</a> long long integer suffix, ll or LL, <a href="#6.4.4.1">6.4.4.1</a>
-LLONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>, LONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.28.4.1.2">7.28.4.1.2</a>
- <a href="#7.28.4.1.2">7.28.4.1.2</a> LONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.28.4.1.2">7.28.4.1.2</a>
-llrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.10.6.5">F.10.6.5</a> longjmp function, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.13.2.1">7.13.2.1</a>, <a href="#7.22.4.4">7.22.4.4</a>,
-llrint type-generic macro, <a href="#7.24">7.24</a> <a href="#7.22.4.7">7.22.4.7</a>
-llround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.10.6.7">F.10.6.7</a> loop body, <a href="#6.8.5">6.8.5</a>
-llround type-generic macro, <a href="#7.24">7.24</a> low-order bit, <a href="#3.6">3.6</a>
-local time, <a href="#7.26.1">7.26.1</a> lowercase letter, <a href="#5.2.1">5.2.1</a>
-locale, <a href="#3.4.2">3.4.2</a> lrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.10.6.5">F.10.6.5</a>
-locale-specific behavior, <a href="#3.4.2">3.4.2</a>, <a href="#J.4">J.4</a> lrint type-generic macro, <a href="#7.24">7.24</a>
-locale.h header, <a href="#7.11">7.11</a>, <a href="#7.30.5">7.30.5</a> lround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.10.6.7">F.10.6.7</a>
-localeconv function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a> lround type-generic macro, <a href="#7.24">7.24</a>
-localization, <a href="#7.11">7.11</a> lvalue, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.1">6.5.1</a>, <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.3.1">6.5.3.1</a>, <a href="#6.5.16">6.5.16</a>
-localtime function, <a href="#7.26.3.4">7.26.3.4</a>
-localtime_s function, <a href="#K.3.8.2.4">K.3.8.2.4</a> macro argument substitution, <a href="#6.10.3.1">6.10.3.1</a>
-log functions, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#F.10.3.7">F.10.3.7</a> macro definition
-log type-generic macro, <a href="#7.24">7.24</a> library function, <a href="#7.1.4">7.1.4</a>
-log10 functions, <a href="#7.12.6.8">7.12.6.8</a>, <a href="#F.10.3.8">F.10.3.8</a> macro invocation, <a href="#6.10.3">6.10.3</a>
-log10 type-generic macro, <a href="#7.24">7.24</a> macro name, <a href="#6.10.3">6.10.3</a>
-log1p functions, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#F.10.3.9">F.10.3.9</a> length, <a href="#5.2.4.1">5.2.4.1</a>
-log1p type-generic macro, <a href="#7.24">7.24</a> predefined, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a>
-log2 functions, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#F.10.3.10">F.10.3.10</a> redefinition, <a href="#6.10.3">6.10.3</a>
-log2 type-generic macro, <a href="#7.24">7.24</a> scope, <a href="#6.10.3.5">6.10.3.5</a>
-logarithmic functions macro parameter, <a href="#6.10.3">6.10.3</a>
- complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a> macro preprocessor, <a href="#6.10">6.10</a>
- real, <a href="#7.12.6">7.12.6</a>, <a href="#F.10.3">F.10.3</a> macro replacement, <a href="#6.10.3">6.10.3</a>
-logb functions, <a href="#7.12.6.11">7.12.6.11</a>, <a href="#F.3">F.3</a>, <a href="#F.10.3.11">F.10.3.11</a> magnitude, complex, <a href="#7.3.8.1">7.3.8.1</a>
-logb type-generic macro, <a href="#7.24">7.24</a> main function, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#5.1.2.2.3">5.1.2.2.3</a>, <a href="#6.7.3.1">6.7.3.1</a>, <a href="#6.7.4">6.7.4</a>,
-logical operators <a href="#7.21.3">7.21.3</a>
- AND (&&), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.13">6.5.13</a> malloc function, <a href="#7.22.3">7.22.3</a>, <a href="#7.22.3.4">7.22.3.4</a>, <a href="#7.22.3.5">7.22.3.5</a>
- negation (!), <a href="#6.5.3.3">6.5.3.3</a> manipulation functions
- OR (||), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.14">6.5.14</a> complex, <a href="#7.3.9">7.3.9</a>
-logical source lines, <a href="#5.1.1.2">5.1.1.2</a> real, <a href="#7.12.11">7.12.11</a>, <a href="#F.10.8">F.10.8</a>
-long double _Complex type, <a href="#6.2.5">6.2.5</a> matching failure, <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.2.8">7.28.2.8</a>, <a href="#7.28.2.10">7.28.2.10</a>,
-
-[<a name="#p667" href="p667">page 667</a>] (<a href="#Contents">Contents</a>)
-
- <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a> modification order, <a href="#5.1.2.4">5.1.2.4</a>
-math.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.24">7.24</a>, <a href="#F">F</a>, modulus functions, <a href="#7.12.6.12">7.12.6.12</a>
- <a href="#F.10">F.10</a>, <a href="#J.5.17">J.5.17</a> modulus, complex, <a href="#7.3.8.1">7.3.8.1</a>
-MATH_ERREXCEPT macro, <a href="#7.12">7.12</a>, <a href="#F.10">F.10</a> mtx_destroy function, <a href="#7.25.4.1">7.25.4.1</a>
-math_errhandling macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.12">7.12</a>, <a href="#F.10">F.10</a> mtx_init function, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.4.2">7.25.4.2</a>
-MATH_ERRNO macro, <a href="#7.12">7.12</a> mtx_lock function, <a href="#7.25.4.3">7.25.4.3</a>
-max_align_t type, <a href="#7.19">7.19</a> mtx_t type, <a href="#7.25.1">7.25.1</a>
-maximum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.10.9">F.10.9</a> mtx_timedlock function, <a href="#7.25.4.4">7.25.4.4</a>
-MB_CUR_MAX macro, <a href="#7.1.1">7.1.1</a>, <a href="#7.22">7.22</a>, <a href="#7.22.7.2">7.22.7.2</a>, mtx_trylock function, <a href="#7.25.4.5">7.25.4.5</a>
- <a href="#7.22.7.3">7.22.7.3</a>, <a href="#7.27.1.2">7.27.1.2</a>, <a href="#7.27.1.4">7.27.1.4</a>, <a href="#7.28.6.3.3">7.28.6.3.3</a>, mtx_unlock function, <a href="#7.25.4.3">7.25.4.3</a>, <a href="#7.25.4.4">7.25.4.4</a>,
- <a href="#K.3.6.4.1">K.3.6.4.1</a>, <a href="#K.3.9.3.1.1">K.3.9.3.1.1</a> <a href="#7.25.4.5">7.25.4.5</a>, <a href="#7.25.4.6">7.25.4.6</a>
-MB_LEN_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.1.1">7.1.1</a>, <a href="#7.22">7.22</a> multibyte character, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1.2">5.2.1.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
-mblen function, <a href="#7.22.7.1">7.22.7.1</a>, <a href="#7.28.6.3">7.28.6.3</a> multibyte conversion functions
-mbrlen function, <a href="#7.28.6.3.1">7.28.6.3.1</a> wide character, <a href="#7.22.7">7.22.7</a>, <a href="#K.3.6.4">K.3.6.4</a>
-mbrtoc16 function, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.27.1.1">7.27.1.1</a> extended, <a href="#7.28.6">7.28.6</a>, <a href="#K.3.9.3">K.3.9.3</a>
-mbrtoc32 function, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.27.1.3">7.27.1.3</a> restartable, <a href="#7.27.1">7.27.1</a>, <a href="#7.28.6.3">7.28.6.3</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a>
-mbrtowc function, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, wide string, <a href="#7.22.8">7.22.8</a>, <a href="#K.3.6.5">K.3.6.5</a>
- <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>, <a href="#7.28.6.3.1">7.28.6.3.1</a>, <a href="#7.28.6.3.2">7.28.6.3.2</a>, restartable, <a href="#7.28.6.4">7.28.6.4</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a>
- <a href="#7.28.6.4.1">7.28.6.4.1</a>, <a href="#K.3.6.5.1">K.3.6.5.1</a>, <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a> multibyte string, <a href="#7.1.1">7.1.1</a>
-mbsinit function, <a href="#7.28.6.2.1">7.28.6.2.1</a> multibyte/wide character conversion functions,
-mbsrtowcs function, <a href="#7.28.6.4.1">7.28.6.4.1</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a> <a href="#7.22.7">7.22.7</a>, <a href="#K.3.6.4">K.3.6.4</a>
-mbsrtowcs_s function, <a href="#K.3.9.3.2">K.3.9.3.2</a>, <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a> extended, <a href="#7.28.6">7.28.6</a>, <a href="#K.3.9.3">K.3.9.3</a>
-mbstate_t type, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.1">7.21.6.1</a>, restartable, <a href="#7.27.1">7.27.1</a>, <a href="#7.28.6.3">7.28.6.3</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a>
- <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.27">7.27</a>, <a href="#7.27.1">7.27.1</a>, <a href="#7.28.1">7.28.1</a>, <a href="#7.28.2.1">7.28.2.1</a>, multibyte/wide string conversion functions,
- <a href="#7.28.2.2">7.28.2.2</a>, <a href="#7.28.6">7.28.6</a>, <a href="#7.28.6.2.1">7.28.6.2.1</a>, <a href="#7.28.6.3">7.28.6.3</a>, <a href="#7.22.8">7.22.8</a>, <a href="#K.3.6.5">K.3.6.5</a>
- <a href="#7.28.6.3.1">7.28.6.3.1</a>, <a href="#7.28.6.4">7.28.6.4</a> restartable, <a href="#7.28.6.4">7.28.6.4</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a>
-mbstowcs function, <a href="#6.4.5">6.4.5</a>, <a href="#7.22.8.1">7.22.8.1</a>, <a href="#7.28.6.4">7.28.6.4</a> multidimensional array, <a href="#6.5.2.1">6.5.2.1</a>
-mbstowcs_s function, <a href="#K.3.6.5.1">K.3.6.5.1</a> multiplication assignment operator (*=), <a href="#6.5.16.2">6.5.16.2</a>
-mbtowc function, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.22.7.1">7.22.7.1</a>, <a href="#7.22.7.2">7.22.7.2</a>, multiplication operator (*), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>,
- <a href="#7.22.8.1">7.22.8.1</a>, <a href="#7.28.6.3">7.28.6.3</a> <a href="#G.5.1">G.5.1</a>
-member access operators (. and ->), <a href="#6.5.2.3">6.5.2.3</a> multiplicative expressions, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
-member alignment, <a href="#6.7.2.1">6.7.2.1</a>
-memchr function, <a href="#7.23.5.1">7.23.5.1</a> n-char sequence, <a href="#7.22.1.3">7.22.1.3</a>
-memcmp function, <a href="#7.23.4">7.23.4</a>, <a href="#7.23.4.1">7.23.4.1</a> n-wchar sequence, <a href="#7.28.4.1.1">7.28.4.1.1</a>
-memcpy function, <a href="#7.23.2.1">7.23.2.1</a> name
-memcpy_s function, <a href="#K.3.7.1.1">K.3.7.1.1</a> external, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a>
-memmove function, <a href="#7.23.2.2">7.23.2.2</a> file, <a href="#7.21.3">7.21.3</a>
-memmove_s function, <a href="#K.3.7.1.2">K.3.7.1.2</a> internal, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
-memory location, <a href="#3.14">3.14</a> label, <a href="#6.2.3">6.2.3</a>
-memory management functions, <a href="#7.22.3">7.22.3</a> structure/union member, <a href="#6.2.3">6.2.3</a>
-memory_order type, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.3">7.17.3</a> name spaces, <a href="#6.2.3">6.2.3</a>
-memset function, <a href="#7.23.6.1">7.23.6.1</a>, <a href="#K.3.7.4.1">K.3.7.4.1</a> named label, <a href="#6.8.1">6.8.1</a>
-memset_s function, <a href="#K.3.7.4.1">K.3.7.4.1</a> NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-minimum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.10.9">F.10.9</a> nan functions, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#F.2.1">F.2.1</a>, <a href="#F.10.8.2">F.10.8.2</a>
-minus operator, unary, <a href="#6.5.3.3">6.5.3.3</a> NAN macro, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</a>
-miscellaneous functions NDEBUG macro, <a href="#7.2">7.2</a>
- string, <a href="#7.23.6">7.23.6</a>, <a href="#K.3.7.4">K.3.7.4</a> nearbyint functions, <a href="#7.12.9.3">7.12.9.3</a>, <a href="#7.12.9.4">7.12.9.4</a>, <a href="#F.3">F.3</a>,
- wide string, <a href="#7.28.4.6">7.28.4.6</a>, <a href="#K.3.9.2.4">K.3.9.2.4</a> <a href="#F.10.6.3">F.10.6.3</a>
-mktime function, <a href="#7.26.2.3">7.26.2.3</a> nearbyint type-generic macro, <a href="#7.24">7.24</a>
-modf functions, <a href="#7.12.6.12">7.12.6.12</a>, <a href="#F.10.3.12">F.10.3.12</a> nearest integer functions, <a href="#7.12.9">7.12.9</a>, <a href="#F.10.6">F.10.6</a>
-modifiable lvalue, <a href="#6.3.2.1">6.3.2.1</a> negation operator (!), <a href="#6.5.3.3">6.5.3.3</a>
-
-[<a name="#p668" href="p668">page 668</a>] (<a href="#Contents">Contents</a>)
-
-negative zero, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.12.11.1">7.12.11.1</a> operator, <a href="#6.4.6">6.4.6</a>
-new-line character, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>, <a href="#6.10.4">6.10.4</a> operators, <a href="#6.5">6.5</a>
-new-line escape sequence (\n), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, additive, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.6">6.5.6</a>
- <a href="#7.4.1.10">7.4.1.10</a> alignof, <a href="#6.5.3.4">6.5.3.4</a>
-nextafter functions, <a href="#7.12.11.3">7.12.11.3</a>, <a href="#7.12.11.4">7.12.11.4</a>, <a href="#F.3">F.3</a>, assignment, <a href="#6.5.16">6.5.16</a>
- <a href="#F.10.8.3">F.10.8.3</a> associativity, <a href="#6.5">6.5</a>
-nextafter type-generic macro, <a href="#7.24">7.24</a> equality, <a href="#6.5.9">6.5.9</a>
-nexttoward functions, <a href="#7.12.11.4">7.12.11.4</a>, <a href="#F.3">F.3</a>, <a href="#F.10.8.4">F.10.8.4</a> multiplicative, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
-nexttoward type-generic macro, <a href="#7.24">7.24</a> postfix, <a href="#6.5.2">6.5.2</a>
-no linkage, <a href="#6.2.2">6.2.2</a> precedence, <a href="#6.5">6.5</a>
-no-return function, <a href="#6.7.4">6.7.4</a> preprocessing, <a href="#6.10.1">6.10.1</a>, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>, <a href="#6.10.9">6.10.9</a>
-non-stop floating-point control mode, <a href="#7.6.4.2">7.6.4.2</a> relational, <a href="#6.5.8">6.5.8</a>
-nongraphic characters, <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> shift, <a href="#6.5.7">6.5.7</a>
-nonlocal jumps header, <a href="#7.13">7.13</a> sizeof, <a href="#6.5.3.4">6.5.3.4</a>
-norm, complex, <a href="#7.3.8.1">7.3.8.1</a> unary, <a href="#6.5.3">6.5.3</a>
-normalized broken-down time, <a href="#K.3.8.1">K.3.8.1</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a> unary arithmetic, <a href="#6.5.3.3">6.5.3.3</a>
-not macro, <a href="#7.9">7.9</a> optional features, see conditional features
-not-equal-to operator, see inequality operator or macro, <a href="#7.9">7.9</a>
-not_eq macro, <a href="#7.9">7.9</a> OR operators
-null character (\0), <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> bitwise exclusive (^), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.11">6.5.11</a>
- padding of binary stream, <a href="#7.21.2">7.21.2</a> bitwise exclusive assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
-NULL macro, <a href="#7.11">7.11</a>, <a href="#7.19">7.19</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.22">7.22</a>, <a href="#7.23.1">7.23.1</a>, bitwise inclusive (|), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.12">6.5.12</a>
- <a href="#7.26.1">7.26.1</a>, <a href="#7.28.1">7.28.1</a> bitwise inclusive assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
-null pointer, <a href="#6.3.2.3">6.3.2.3</a> logical (||), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.14">6.5.14</a>
-null pointer constant, <a href="#6.3.2.3">6.3.2.3</a> or_eq macro, <a href="#7.9">7.9</a>
-null preprocessing directive, <a href="#6.10.7">6.10.7</a> order of allocated storage, <a href="#7.22.3">7.22.3</a>
-null statement, <a href="#6.8.3">6.8.3</a> order of evaluation, <a href="#6.5">6.5</a>, <a href="#6.5.16">6.5.16</a>, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>,
-null wide character, <a href="#7.1.1">7.1.1</a> see also sequence points
-number classification macros, <a href="#7.12">7.12</a>, <a href="#7.12.3.1">7.12.3.1</a> ordinary identifier name space, <a href="#6.2.3">6.2.3</a>
-numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a> orientation of stream, <a href="#7.21.2">7.21.2</a>, <a href="#7.28.3.5">7.28.3.5</a>
- wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.28.4.1">7.28.4.1</a> out-of-bounds store, <a href="#L.2.1">L.2.1</a>
-numerical limits, <a href="#5.2.4.2">5.2.4.2</a> outer scope, <a href="#6.2.1">6.2.1</a>
- over-aligned, <a href="#6.2.8">6.2.8</a>
-object, <a href="#3.15">3.15</a>
-object representation, <a href="#6.2.6.1">6.2.6.1</a> padding
-object type, <a href="#6.2.5">6.2.5</a> binary stream, <a href="#7.21.2">7.21.2</a>
-object-like macro, <a href="#6.10.3">6.10.3</a> bits, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.20.1.1">7.20.1.1</a>
-observable behavior, <a href="#5.1.2.3">5.1.2.3</a> structure/union, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.7.2.1">6.7.2.1</a>
-obsolescence, <a href="#6.11">6.11</a>, <a href="#7.30">7.30</a> parameter, <a href="#3.16">3.16</a>
-octal constant, <a href="#6.4.4.1">6.4.4.1</a> array, <a href="#6.9.1">6.9.1</a>
-octal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.4">6.4.4.4</a> ellipsis, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.10.3">6.10.3</a>
-octal-character escape sequence (\octal digits), function, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.9.1">6.9.1</a>
- <a href="#6.4.4.4">6.4.4.4</a> macro, <a href="#6.10.3">6.10.3</a>
-offsetof macro, <a href="#7.19">7.19</a> main function, <a href="#5.1.2.2.1">5.1.2.2.1</a>
-on-off switch, <a href="#6.10.6">6.10.6</a> program, <a href="#5.1.2.2.1">5.1.2.2.1</a>
-once_flag type, <a href="#7.25.1">7.25.1</a> parameter type list, <a href="#6.7.6.3">6.7.6.3</a>
-ONCE_FLAG_INIT macro, <a href="#7.25.1">7.25.1</a> parentheses punctuator (( )), <a href="#6.7.6.3">6.7.6.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a>
-ones' complement, <a href="#6.2.6.2">6.2.6.2</a> parenthesized expression, <a href="#6.5.1">6.5.1</a>
-operand, <a href="#6.4.6">6.4.6</a>, <a href="#6.5">6.5</a> parse state, <a href="#7.21.2">7.21.2</a>
-operating system, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#7.22.4.8">7.22.4.8</a> perform a trap, <a href="#3.19.5">3.19.5</a>
-operations on files, <a href="#7.21.4">7.21.4</a>, <a href="#K.3.5.1">K.3.5.1</a> permitted form of initializer, <a href="#6.6">6.6</a>
-
-[<a name="#p669" href="p669">page 669</a>] (<a href="#Contents">Contents</a>)
-
-perror function, <a href="#7.21.10.4">7.21.10.4</a> PRIcLEASTN macros, <a href="#7.8.1">7.8.1</a>
-phase angle, complex, <a href="#7.3.9.1">7.3.9.1</a> PRIcMAX macros, <a href="#7.8.1">7.8.1</a>
-physical source lines, <a href="#5.1.1.2">5.1.1.2</a> PRIcN macros, <a href="#7.8.1">7.8.1</a>
-placemarker, <a href="#6.10.3.3">6.10.3.3</a> PRIcPTR macros, <a href="#7.8.1">7.8.1</a>
-plus operator, unary, <a href="#6.5.3.3">6.5.3.3</a> primary expression, <a href="#6.5.1">6.5.1</a>
-pointer arithmetic, <a href="#6.5.6">6.5.6</a> printf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.3">7.21.6.3</a>, <a href="#7.21.6.10">7.21.6.10</a>,
-pointer comparison, <a href="#6.5.8">6.5.8</a> <a href="#K.3.5.3.3">K.3.5.3.3</a>
-pointer declarator, <a href="#6.7.6.1">6.7.6.1</a> printf_s function, <a href="#K.3.5.3.3">K.3.5.3.3</a>
-pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> printing character, <a href="#5.2.2">5.2.2</a>, <a href="#7.4">7.4</a>, <a href="#7.4.1.8">7.4.1.8</a>
-pointer to function, <a href="#6.5.2.2">6.5.2.2</a> printing wide character, <a href="#7.29.2">7.29.2</a>
-pointer type, <a href="#6.2.5">6.2.5</a> program diagnostics, <a href="#7.2.1">7.2.1</a>
-pointer type conversion, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a> program execution, <a href="#5.1.2.2.2">5.1.2.2.2</a>, <a href="#5.1.2.3">5.1.2.3</a>
-pointer, null, <a href="#6.3.2.3">6.3.2.3</a> program file, <a href="#5.1.1.1">5.1.1.1</a>
-pole error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#7.12.6.8">7.12.6.8</a>, program image, <a href="#5.1.1.2">5.1.1.2</a>
- <a href="#7.12.6.9">7.12.6.9</a>, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#7.12.6.11">7.12.6.11</a>, <a href="#7.12.7.4">7.12.7.4</a>, program name (argv[0]), <a href="#5.1.2.2.1">5.1.2.2.1</a>
- <a href="#7.12.8.3">7.12.8.3</a>, <a href="#7.12.8.4">7.12.8.4</a> program parameters, <a href="#5.1.2.2.1">5.1.2.2.1</a>
-portability, <a href="#4">4</a>, <a href="#J">J</a> program startup, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#5.1.2.2.1">5.1.2.2.1</a>
-position indicator, file, see file position indicator program structure, <a href="#5.1.1.1">5.1.1.1</a>
-positive difference, <a href="#7.12.12.1">7.12.12.1</a> program termination, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#5.1.2.2.3">5.1.2.2.3</a>,
-positive difference functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.10.9">F.10.9</a> <a href="#5.1.2.3">5.1.2.3</a>
-postfix decrement operator (--), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a> program, conforming, <a href="#4">4</a>
-postfix expressions, <a href="#6.5.2">6.5.2</a> program, strictly conforming, <a href="#4">4</a>
-postfix increment operator (++), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a> promotions
-pow functions, <a href="#7.12.7.4">7.12.7.4</a>, <a href="#F.10.4.4">F.10.4.4</a> default argument, <a href="#6.5.2.2">6.5.2.2</a>
-pow type-generic macro, <a href="#7.24">7.24</a> integer, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.3.1.1">6.3.1.1</a>
-power functions prototype, see function prototype
- complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a> pseudo-random sequence functions, <a href="#7.22.2">7.22.2</a>
- real, <a href="#7.12.7">7.12.7</a>, <a href="#F.10.4">F.10.4</a> PTRDIFF_MAX macro, <a href="#7.20.3">7.20.3</a>
-pp-number, <a href="#6.4.8">6.4.8</a> PTRDIFF_MIN macro, <a href="#7.20.3">7.20.3</a>
-pragma operator, <a href="#6.10.9">6.10.9</a> ptrdiff_t type, <a href="#7.17.1">7.17.1</a>, <a href="#7.19">7.19</a>, <a href="#7.20.3">7.20.3</a>, <a href="#7.21.6.1">7.21.6.1</a>,
-pragma preprocessing directive, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a> <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>
-precedence of operators, <a href="#6.5">6.5</a> punctuators, <a href="#6.4.6">6.4.6</a>
-precedence of syntax rules, <a href="#5.1.1.2">5.1.1.2</a> putc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.7">7.21.7.7</a>, <a href="#7.21.7.8">7.21.7.8</a>
-precision, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a> putchar function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.8">7.21.7.8</a>
- excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> puts function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.9">7.21.7.9</a>
-predefined macro names, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a> putwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3.8">7.28.3.8</a>, <a href="#7.28.3.9">7.28.3.9</a>
-prefix decrement operator (--), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a> putwchar function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3.9">7.28.3.9</a>
-prefix increment operator (++), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a>
-preprocessing concatenation, <a href="#6.10.3.3">6.10.3.3</a> qsort function, <a href="#7.22.5">7.22.5</a>, <a href="#7.22.5.2">7.22.5.2</a>
-preprocessing directives, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10">6.10</a> qsort_s function, <a href="#K.3.6.3">K.3.6.3</a>, <a href="#K.3.6.3.2">K.3.6.3.2</a>
-preprocessing file, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.10">6.10</a> qualified types, <a href="#6.2.5">6.2.5</a>
-preprocessing numbers, <a href="#6.4">6.4</a>, <a href="#6.4.8">6.4.8</a> qualified version of type, <a href="#6.2.5">6.2.5</a>
-preprocessing operators question-mark escape sequence (\?), <a href="#6.4.4.4">6.4.4.4</a>
- #, <a href="#6.10.3.2">6.10.3.2</a> quick_exit function, <a href="#7.22.4.3">7.22.4.3</a>, <a href="#7.22.4.4">7.22.4.4</a>,
- ##, <a href="#6.10.3.3">6.10.3.3</a> <a href="#7.22.4.7">7.22.4.7</a>
- _Pragma, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a> quiet NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- defined, <a href="#6.10.1">6.10.1</a>
-preprocessing tokens, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a> raise function, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.14.2.1">7.14.2.1</a>, <a href="#7.22.4.1">7.22.4.1</a>
-preprocessing translation unit, <a href="#5.1.1.1">5.1.1.1</a> rand function, <a href="#7.22">7.22</a>, <a href="#7.22.2.1">7.22.2.1</a>, <a href="#7.22.2.2">7.22.2.2</a>
-preprocessor, <a href="#6.10">6.10</a> RAND_MAX macro, <a href="#7.22">7.22</a>, <a href="#7.22.2.1">7.22.2.1</a>
-PRIcFASTN macros, <a href="#7.8.1">7.8.1</a> range
-
-[<a name="#p670" href="p670">page 670</a>] (<a href="#Contents">Contents</a>)
-
- excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> rewind function, <a href="#7.21.5.3">7.21.5.3</a>, <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.5">7.21.9.5</a>,
-range error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#7.12.5.5">7.12.5.5</a>, <a href="#7.12.6.1">7.12.6.1</a>, <a href="#7.28.3.10">7.28.3.10</a>
- <a href="#7.12.6.2">7.12.6.2</a>, <a href="#7.12.6.3">7.12.6.3</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#7.12.6.6">7.12.6.6</a>, right-shift assignment operator (>>=), <a href="#6.5.16.2">6.5.16.2</a>
- <a href="#7.12.6.13">7.12.6.13</a>, <a href="#7.12.7.3">7.12.7.3</a>, <a href="#7.12.7.4">7.12.7.4</a>, <a href="#7.12.8.2">7.12.8.2</a>, right-shift operator (>>), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.7">6.5.7</a>
- <a href="#7.12.8.3">7.12.8.3</a>, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.12.9.7">7.12.9.7</a>, rint functions, <a href="#7.12.9.4">7.12.9.4</a>, <a href="#F.3">F.3</a>, <a href="#F.10.6.4">F.10.6.4</a>
- <a href="#7.12.11.3">7.12.11.3</a>, <a href="#7.12.12.1">7.12.12.1</a>, <a href="#7.12.13.1">7.12.13.1</a> rint type-generic macro, <a href="#7.24">7.24</a>
-rank, see integer conversion rank round functions, <a href="#7.12.9.6">7.12.9.6</a>, <a href="#F.10.6.6">F.10.6.6</a>
-read-modify-write operations, <a href="#5.1.2.4">5.1.2.4</a> round type-generic macro, <a href="#7.24">7.24</a>
-real floating type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, rounding mode, floating point, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- <a href="#6.3.1.7">6.3.1.7</a>, <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> RSIZE_MAX macro, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a>,
-real floating types, <a href="#6.2.5">6.2.5</a> <a href="#K.3.5.3.5">K.3.5.3.5</a>, <a href="#K.3.5.3.6">K.3.5.3.6</a>, <a href="#K.3.5.3.12">K.3.5.3.12</a>, <a href="#K.3.5.3.13">K.3.5.3.13</a>,
-real type domain, <a href="#6.2.5">6.2.5</a> <a href="#K.3.5.4.1">K.3.5.4.1</a>, <a href="#K.3.6.2.1">K.3.6.2.1</a>, <a href="#K.3.6.3.1">K.3.6.3.1</a>, <a href="#K.3.6.3.2">K.3.6.3.2</a>,
-real types, <a href="#6.2.5">6.2.5</a> <a href="#K.3.6.4.1">K.3.6.4.1</a>, <a href="#K.3.6.5.1">K.3.6.5.1</a>, <a href="#K.3.6.5.2">K.3.6.5.2</a>, <a href="#K.3.7.1.1">K.3.7.1.1</a>,
-real-floating, <a href="#7.12.3">7.12.3</a> <a href="#K.3.7.1.2">K.3.7.1.2</a>, <a href="#K.3.7.1.3">K.3.7.1.3</a>, <a href="#K.3.7.1.4">K.3.7.1.4</a>, <a href="#K.3.7.2.1">K.3.7.2.1</a>,
-realloc function, <a href="#7.22.3">7.22.3</a>, <a href="#7.22.3.5">7.22.3.5</a> <a href="#K.3.7.2.2">K.3.7.2.2</a>, <a href="#K.3.7.3.1">K.3.7.3.1</a>, <a href="#K.3.7.4.1">K.3.7.4.1</a>, <a href="#K.3.7.4.2">K.3.7.4.2</a>,
-recommended practice, <a href="#3.17">3.17</a> <a href="#K.3.8.2.1">K.3.8.2.1</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>, <a href="#K.3.9.1.3">K.3.9.1.3</a>, <a href="#K.3.9.1.4">K.3.9.1.4</a>,
-recursion, <a href="#6.5.2.2">6.5.2.2</a> <a href="#K.3.9.1.8">K.3.9.1.8</a>, <a href="#K.3.9.1.9">K.3.9.1.9</a>, <a href="#K.3.9.2.1.1">K.3.9.2.1.1</a>, <a href="#K.3.9.2.1.2">K.3.9.2.1.2</a>,
-recursive function call, <a href="#6.5.2.2">6.5.2.2</a> <a href="#K.3.9.2.1.3">K.3.9.2.1.3</a>, <a href="#K.3.9.2.1.4">K.3.9.2.1.4</a>, <a href="#K.3.9.2.2.1">K.3.9.2.2.1</a>,
-redefinition of macro, <a href="#6.10.3">6.10.3</a> <a href="#K.3.9.2.2.2">K.3.9.2.2.2</a>, <a href="#K.3.9.2.3.1">K.3.9.2.3.1</a>, <a href="#K.3.9.3.1.1">K.3.9.3.1.1</a>,
-reentrancy, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a> <a href="#K.3.9.3.2.1">K.3.9.3.2.1</a>, <a href="#K.3.9.3.2.2">K.3.9.3.2.2</a>
- library functions, <a href="#7.1.4">7.1.4</a> rsize_t type, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a>, <a href="#K.3.5">K.3.5</a>, <a href="#K.3.5.3.2">K.3.5.3.2</a>,
-referenced type, <a href="#6.2.5">6.2.5</a> <a href="#K.3.6">K.3.6</a>, <a href="#K.3.7">K.3.7</a>, <a href="#K.3.8">K.3.8</a>, <a href="#K.3.9">K.3.9</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a>
-register storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a> runtime-constraint, <a href="#3.18">3.18</a>
-relational expressions, <a href="#6.5.8">6.5.8</a> Runtime-constraint handling functions, <a href="#K.3.6.1">K.3.6.1</a>
-relaxed atomic operations, <a href="#5.1.2.4">5.1.2.4</a> rvalue, <a href="#6.3.2.1">6.3.2.1</a>
-release fence, <a href="#7.17.4">7.17.4</a>
-release operation, <a href="#5.1.2.4">5.1.2.4</a> same scope, <a href="#6.2.1">6.2.1</a>
-release sequence, <a href="#5.1.2.4">5.1.2.4</a> save calling environment function, <a href="#7.13.1">7.13.1</a>
-reliability of data, interrupted, <a href="#5.1.2.3">5.1.2.3</a> scalar types, <a href="#6.2.5">6.2.5</a>
-remainder assignment operator (%=), <a href="#6.5.16.2">6.5.16.2</a> scalbln function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.10.3.13">F.10.3.13</a>
-remainder functions, <a href="#7.12.10">7.12.10</a>, <a href="#F.10.7">F.10.7</a> scalbln type-generic macro, <a href="#7.24">7.24</a>
-remainder functions, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.10.3">7.12.10.3</a>, <a href="#F.3">F.3</a>, scalbn function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.10.3.13">F.10.3.13</a>
- <a href="#F.10.7.2">F.10.7.2</a> scalbn type-generic macro, <a href="#7.24">7.24</a>
-remainder operator (%), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.5">6.5.5</a> scanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.4">7.21.6.4</a>, <a href="#7.21.6.11">7.21.6.11</a>
-remainder type-generic macro, <a href="#7.24">7.24</a> scanf_s function, <a href="#K.3.5.3.4">K.3.5.3.4</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>
-remove function, <a href="#7.21.4.1">7.21.4.1</a>, <a href="#7.21.4.4">7.21.4.4</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a> scanlist, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>
-remquo functions, <a href="#7.12.10.3">7.12.10.3</a>, <a href="#F.3">F.3</a>, <a href="#F.10.7.3">F.10.7.3</a> scanset, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>
-remquo type-generic macro, <a href="#7.24">7.24</a> SCHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
-rename function, <a href="#7.21.4.2">7.21.4.2</a> SCHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
-representations of types, <a href="#6.2.6">6.2.6</a> SCNcFASTN macros, <a href="#7.8.1">7.8.1</a>
- pointer, <a href="#6.2.5">6.2.5</a> SCNcLEASTN macros, <a href="#7.8.1">7.8.1</a>
-rescanning and replacement, <a href="#6.10.3.4">6.10.3.4</a> SCNcMAX macros, <a href="#7.8.1">7.8.1</a>
-reserved identifiers, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a>, <a href="#K.3.1.2">K.3.1.2</a> SCNcN macros, <a href="#7.8.1">7.8.1</a>
-restartable multibyte/wide character conversion SCNcPTR macros, <a href="#7.8.1">7.8.1</a>
- functions, <a href="#7.27.1">7.27.1</a>, <a href="#7.28.6.3">7.28.6.3</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a> scope of identifier, <a href="#6.2.1">6.2.1</a>, <a href="#6.9.2">6.9.2</a>
-restartable multibyte/wide string conversion search functions
- functions, <a href="#7.28.6.4">7.28.6.4</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a> string, <a href="#7.23.5">7.23.5</a>, <a href="#K.3.7.3">K.3.7.3</a>
-restore calling environment function, <a href="#7.13.2">7.13.2</a> utility, <a href="#7.22.5">7.22.5</a>, <a href="#K.3.6.3">K.3.6.3</a>
-restrict type qualifier, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.3.1">6.7.3.1</a> wide string, <a href="#7.28.4.5">7.28.4.5</a>, <a href="#K.3.9.2.3">K.3.9.2.3</a>
-restrict-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a> SEEK_CUR macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.9.2">7.21.9.2</a>
-return statement, <a href="#6.8.6.4">6.8.6.4</a>, <a href="#F.6">F.6</a> SEEK_END macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.9.2">7.21.9.2</a>
-
-[<a name="#p671" href="p671">page 671</a>] (<a href="#Contents">Contents</a>)
-
-SEEK_SET macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.9.2">7.21.9.2</a> signal function, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.22.4.5">7.22.4.5</a>, <a href="#7.22.4.7">7.22.4.7</a>
-selection statements, <a href="#6.8.4">6.8.4</a> signal handler, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.14.2.1">7.14.2.1</a>
-self-referential structure, <a href="#6.7.2.3">6.7.2.3</a> signal handling functions, <a href="#7.14.1">7.14.1</a>
-semicolon punctuator (;), <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.8.3">6.8.3</a>, signal.h header, <a href="#7.14">7.14</a>, <a href="#7.30.6">7.30.6</a>
- <a href="#6.8.5">6.8.5</a>, <a href="#6.8.6">6.8.6</a> signaling NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#F.2.1">F.2.1</a>
-separate compilation, <a href="#5.1.1.1">5.1.1.1</a> signals, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a>, <a href="#7.14.1">7.14.1</a>
-separate translation, <a href="#5.1.1.1">5.1.1.1</a> signbit macro, <a href="#7.12.3.6">7.12.3.6</a>, <a href="#F.3">F.3</a>
-sequence points, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.13">6.5.13</a>, <a href="#6.5.14">6.5.14</a>, signed char type, <a href="#6.2.5">6.2.5</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
- <a href="#6.5.15">6.5.15</a>, <a href="#6.5.17">6.5.17</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.3.1">6.7.3.1</a>, <a href="#6.7.6">6.7.6</a>, <a href="#6.8">6.8</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>, <a href="#K.3.5.3.2">K.3.5.3.2</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a>
- <a href="#7.1.4">7.1.4</a>, <a href="#7.21.6">7.21.6</a>, <a href="#7.22.5">7.22.5</a>, <a href="#7.28.2">7.28.2</a>, <a href="#C">C</a>, <a href="#K.3.6.3">K.3.6.3</a> signed character, <a href="#6.3.1.1">6.3.1.1</a>
-sequenced after, see sequenced before signed integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a>
-sequenced before, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.2.4">6.5.2.4</a>, signed type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
- <a href="#6.5.16">6.5.16</a>, see also indeterminately sequenced, <a href="#6.3.1.8">6.3.1.8</a>
- unsequenced signed types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>
-sequencing of statements, <a href="#6.8">6.8</a> significand part, <a href="#6.4.4.2">6.4.4.2</a>
-set_constraint_handler_s function, SIGSEGV macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>
- <a href="#K.3.1.4">K.3.1.4</a>, <a href="#K.3.6.1.1">K.3.6.1.1</a>, <a href="#K.3.6.1.2">K.3.6.1.2</a>, <a href="#K.3.6.1.3">K.3.6.1.3</a> SIGTERM macro, <a href="#7.14">7.14</a>
-setbuf function, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.5.1">7.21.5.1</a>, <a href="#7.21.5.5">7.21.5.5</a> simple assignment operator (=), <a href="#6.5.16.1">6.5.16.1</a>
-setjmp macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.13.2.1">7.13.2.1</a> sin functions, <a href="#7.12.4.6">7.12.4.6</a>, <a href="#F.10.1.6">F.10.1.6</a>
-setjmp.h header, <a href="#7.13">7.13</a> sin type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a>
-setlocale function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a> single-byte character, <a href="#3.7.1">3.7.1</a>, <a href="#5.2.1.2">5.2.1.2</a>
-setvbuf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.5.1">7.21.5.1</a>, single-byte/wide character conversion functions,
- <a href="#7.21.5.5">7.21.5.5</a>, <a href="#7.21.5.6">7.21.5.6</a> <a href="#7.28.6.1">7.28.6.1</a>
-shall, <a href="#4">4</a> single-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a>
-shift expressions, <a href="#6.5.7">6.5.7</a> single-quote escape sequence (\'), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>
-shift sequence, <a href="#7.1.1">7.1.1</a> singularity, <a href="#7.12.1">7.12.1</a>
-shift states, <a href="#5.2.1.2">5.2.1.2</a> sinh functions, <a href="#7.12.5.5">7.12.5.5</a>, <a href="#F.10.2.5">F.10.2.5</a>
-short identifier, character, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.3">6.4.3</a> sinh type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a>
-short int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.21.6.1">7.21.6.1</a>, SIZE_MAX macro, <a href="#7.20.3">7.20.3</a>
- <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a> size_t type, <a href="#6.2.8">6.2.8</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#7.19">7.19</a>, <a href="#7.20.3">7.20.3</a>, <a href="#7.21.1">7.21.1</a>,
-short int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22">7.22</a>, <a href="#7.23.1">7.23.1</a>, <a href="#7.26.1">7.26.1</a>, <a href="#7.27">7.27</a>,
- <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a> <a href="#7.28.1">7.28.1</a>, <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a>,
-SHRT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a> <a href="#K.3.5">K.3.5</a>, <a href="#K.3.6">K.3.6</a>, <a href="#K.3.7">K.3.7</a>, <a href="#K.3.8">K.3.8</a>, <a href="#K.3.9">K.3.9</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a>
-SHRT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a> sizeof operator, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3">6.5.3</a>, <a href="#6.5.3.4">6.5.3.4</a>
-side effects, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.3.2.2">6.3.2.2</a>, <a href="#6.5">6.5</a>, <a href="#6.5.2.4">6.5.2.4</a>, snprintf function, <a href="#7.21.6.5">7.21.6.5</a>, <a href="#7.21.6.12">7.21.6.12</a>,
- <a href="#6.5.16">6.5.16</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.8.3">6.8.3</a>, <a href="#7.6">7.6</a>, <a href="#7.6.1">7.6.1</a>, <a href="#7.21.7.5">7.21.7.5</a>, <a href="#K.3.5.3.5">K.3.5.3.5</a>
- <a href="#7.21.7.7">7.21.7.7</a>, <a href="#7.28.3.6">7.28.3.6</a>, <a href="#7.28.3.8">7.28.3.8</a>, <a href="#F.8.1">F.8.1</a>, <a href="#F.9.1">F.9.1</a>, snprintf_s function, <a href="#K.3.5.3.5">K.3.5.3.5</a>, <a href="#K.3.5.3.6">K.3.5.3.6</a>
- <a href="#F.9.3">F.9.3</a> snwprintf_s function, <a href="#K.3.9.1.3">K.3.9.1.3</a>, <a href="#K.3.9.1.4">K.3.9.1.4</a>
-SIG_ATOMIC_MAX macro, <a href="#7.20.3">7.20.3</a> sorting utility functions, <a href="#7.22.5">7.22.5</a>, <a href="#K.3.6.3">K.3.6.3</a>
-SIG_ATOMIC_MIN macro, <a href="#7.20.3">7.20.3</a> source character set, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>
-sig_atomic_t type, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, source file, <a href="#5.1.1.1">5.1.1.1</a>
- <a href="#7.20.3">7.20.3</a> name, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8.1">6.10.8.1</a>
-SIG_DFL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> source file inclusion, <a href="#6.10.2">6.10.2</a>
-SIG_ERR macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> source lines, <a href="#5.1.1.2">5.1.1.2</a>
-SIG_IGN macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> source text, <a href="#5.1.1.2">5.1.1.2</a>
-SIGABRT macro, <a href="#7.14">7.14</a>, <a href="#7.22.4.1">7.22.4.1</a> space character (' '), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#7.4.1.3">7.4.1.3</a>,
-SIGFPE macro, <a href="#7.12.1">7.12.1</a>, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#J.5.17">J.5.17</a> <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.29.2.1.3">7.29.2.1.3</a>
-SIGILL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sprintf function, <a href="#7.21.6.6">7.21.6.6</a>, <a href="#7.21.6.13">7.21.6.13</a>, <a href="#K.3.5.3.6">K.3.5.3.6</a>
-SIGINT macro, <a href="#7.14">7.14</a> sprintf_s function, <a href="#K.3.5.3.5">K.3.5.3.5</a>, <a href="#K.3.5.3.6">K.3.5.3.6</a>
-sign and magnitude, <a href="#6.2.6.2">6.2.6.2</a> sqrt functions, <a href="#7.12.7.5">7.12.7.5</a>, <a href="#F.3">F.3</a>, <a href="#F.10.4.5">F.10.4.5</a>
-sign bit, <a href="#6.2.6.2">6.2.6.2</a> sqrt type-generic macro, <a href="#7.24">7.24</a>
-
-[<a name="#p672" href="p672">page 672</a>] (<a href="#Contents">Contents</a>)
-
-srand function, <a href="#7.22.2.2">7.22.2.2</a> expression, <a href="#6.8.3">6.8.3</a>
-sscanf function, <a href="#7.21.6.7">7.21.6.7</a>, <a href="#7.21.6.14">7.21.6.14</a> for, <a href="#6.8.5.3">6.8.5.3</a>
-sscanf_s function, <a href="#K.3.5.3.7">K.3.5.3.7</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a> goto, <a href="#6.8.6.1">6.8.6.1</a>
-standard error stream, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.10.4">7.21.10.4</a> if, <a href="#6.8.4.1">6.8.4.1</a>
-standard headers, <a href="#4">4</a>, <a href="#7.1.2">7.1.2</a> iteration, <a href="#6.8.5">6.8.5</a>
- <a href="#7.2"><assert.h></a>, <a href="#7.2">7.2</a> jump, <a href="#6.8.6">6.8.6</a>
- <a href="#7.3"><complex.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.3">7.3</a>, labeled, <a href="#6.8.1">6.8.1</a>
- <a href="#7.24">7.24</a>, <a href="#7.30.1">7.30.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a> null, <a href="#6.8.3">6.8.3</a>
- <a href="#7.4"><ctype.h></a>, <a href="#7.4">7.4</a>, <a href="#7.30.2">7.30.2</a> return, <a href="#6.8.6.4">6.8.6.4</a>, <a href="#F.6">F.6</a>
- <a href="#7.5"><errno.h></a>, <a href="#7.5">7.5</a>, <a href="#7.30.3">7.30.3</a>, <a href="#K.3.2">K.3.2</a> selection, <a href="#6.8.4">6.8.4</a>
- <a href="#7.6"><fenv.h></a>, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F">F</a>, <a href="#H">H</a> sequencing, <a href="#6.8">6.8</a>
- <a href="#7.7"><float.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.22.1.3">7.22.1.3</a>, switch, <a href="#6.8.4.2">6.8.4.2</a>
- <a href="#7.28.4.1.1">7.28.4.1.1</a> while, <a href="#6.8.5.1">6.8.5.1</a>
- <a href="#7.8"><inttypes.h></a>, <a href="#7.8">7.8</a>, <a href="#7.30.4">7.30.4</a> static assertions, <a href="#6.7.10">6.7.10</a>
- <a href="#7.9"><iso646.h></a>, <a href="#4">4</a>, <a href="#7.9">7.9</a> static storage duration, <a href="#6.2.4">6.2.4</a>
- <a href="#7.10"><limits.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a> static storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.2.4">6.2.4</a>, <a href="#6.7.1">6.7.1</a>
- <a href="#7.11"><locale.h></a>, <a href="#7.11">7.11</a>, <a href="#7.30.5">7.30.5</a> static, in array declarators, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.7.6.3">6.7.6.3</a>
- <a href="#7.12"><math.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.24">7.24</a>, <a href="#F">F</a>, <a href="#F.10">F.10</a>, static_assert declaration, <a href="#6.7.10">6.7.10</a>
- <a href="#J.5.17">J.5.17</a> static_assert macro, <a href="#7.2">7.2</a>
- <a href="#7.13"><setjmp.h></a>, <a href="#7.13">7.13</a> stdalign.h header, <a href="#4">4</a>, <a href="#7.15">7.15</a>
- <a href="#7.14"><signal.h></a>, <a href="#7.14">7.14</a>, <a href="#7.30.6">7.30.6</a> stdarg.h header, <a href="#4">4</a>, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#7.16">7.16</a>
- <a href="#7.15"><stdalign.h></a>, <a href="#4">4</a>, <a href="#7.15">7.15</a> stdatomic.h header, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.17">7.17</a>
- <a href="#7.16"><stdarg.h></a>, <a href="#4">4</a>, <a href="#6.7.6.3">6.7.6.3</a>, <a href="#7.16">7.16</a> stdbool.h header, <a href="#4">4</a>, <a href="#7.18">7.18</a>, <a href="#7.30.7">7.30.7</a>, <a href="#H">H</a>
- <a href="#7.17"><stdatomic.h></a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.17">7.17</a> STDC, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a>
- <a href="#7.18"><stdbool.h></a>, <a href="#4">4</a>, <a href="#7.18">7.18</a>, <a href="#7.30.7">7.30.7</a>, <a href="#H">H</a> stddef.h header, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>,
- <a href="#7.19"><stddef.h></a>, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.19">7.19</a>, <a href="#K.3.3">K.3.3</a>
- <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.19">7.19</a>, <a href="#K.3.3">K.3.3</a> stderr macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.3">7.21.3</a>
- <a href="#7.20"><stdint.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>, <a href="#7.20">7.20</a>, stdin macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.4">7.21.6.4</a>,
- <a href="#7.30.8">7.30.8</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a> <a href="#7.21.7.6">7.21.7.6</a>, <a href="#7.28.2.12">7.28.2.12</a>, <a href="#7.28.3.7">7.28.3.7</a>, <a href="#K.3.5.3.4">K.3.5.3.4</a>,
- <a href="#7.21"><stdio.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21">7.21</a>, <a href="#7.30.9">7.30.9</a>, <a href="#F">F</a>, <a href="#K.3.5">K.3.5</a> <a href="#K.3.5.4.1">K.3.5.4.1</a>, <a href="#K.3.9.1.14">K.3.9.1.14</a>
- <a href="#7.22"><stdlib.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.22">7.22</a>, <a href="#7.30.10">7.30.10</a>, <a href="#F">F</a>, stdint.h header, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>, <a href="#7.20">7.20</a>,
- <a href="#K.3.1.4">K.3.1.4</a>, <a href="#K.3.6">K.3.6</a> <a href="#7.30.8">7.30.8</a>, <a href="#K.3.3">K.3.3</a>, <a href="#K.3.4">K.3.4</a>
- <a href="#7.23"><string.h></a>, <a href="#7.23">7.23</a>, <a href="#7.30.11">7.30.11</a>, <a href="#K.3.7">K.3.7</a> stdio.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21">7.21</a>, <a href="#7.30.9">7.30.9</a>, <a href="#F">F</a>, <a href="#K.3.5">K.3.5</a>
- <a href="#7.24"><tgmath.h></a>, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> stdlib.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.22">7.22</a>, <a href="#7.30.10">7.30.10</a>, <a href="#F">F</a>,
- <a href="#7.25"><threads.h></a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.25">7.25</a> <a href="#K.3.1.4">K.3.1.4</a>, <a href="#K.3.6">K.3.6</a>
- <a href="#7.26"><time.h></a>, <a href="#7.26">7.26</a>, <a href="#K.3.8">K.3.8</a> stdout macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.3">7.21.6.3</a>,
- <a href="#7.27"><uchar.h></a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.27">7.27</a> <a href="#7.21.7.8">7.21.7.8</a>, <a href="#7.21.7.9">7.21.7.9</a>, <a href="#7.28.2.11">7.28.2.11</a>, <a href="#7.28.3.9">7.28.3.9</a>
- <a href="#7.28"><wchar.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.28">7.28</a>, <a href="#7.30.12">7.30.12</a>, storage duration, <a href="#6.2.4">6.2.4</a>
- <a href="#F">F</a>, <a href="#K.3.9">K.3.9</a> storage order of array, <a href="#6.5.2.1">6.5.2.1</a>
- <a href="#7.29"><wctype.h></a>, <a href="#7.29">7.29</a>, <a href="#7.30.13">7.30.13</a> storage unit (bit-field), <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.7.2.1">6.7.2.1</a>
-standard input stream, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> storage-class specifiers, <a href="#6.7.1">6.7.1</a>, <a href="#6.11.5">6.11.5</a>
-standard integer types, <a href="#6.2.5">6.2.5</a> strcat function, <a href="#7.23.3.1">7.23.3.1</a>
-standard output stream, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> strcat_s function, <a href="#K.3.7.2.1">K.3.7.2.1</a>
-standard signed integer types, <a href="#6.2.5">6.2.5</a> strchr function, <a href="#7.23.5.2">7.23.5.2</a>
-state-dependent encoding, <a href="#5.2.1.2">5.2.1.2</a>, <a href="#7.22.7">7.22.7</a>, <a href="#K.3.6.4">K.3.6.4</a> strcmp function, <a href="#7.23.4">7.23.4</a>, <a href="#7.23.4.2">7.23.4.2</a>
-statements, <a href="#6.8">6.8</a> strcoll function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.4.3">7.23.4.3</a>, <a href="#7.23.4.5">7.23.4.5</a>
- break, <a href="#6.8.6.3">6.8.6.3</a> strcpy function, <a href="#7.23.2.3">7.23.2.3</a>
- compound, <a href="#6.8.2">6.8.2</a> strcpy_s function, <a href="#K.3.7.1.3">K.3.7.1.3</a>
- continue, <a href="#6.8.6.2">6.8.6.2</a> strcspn function, <a href="#7.23.5.3">7.23.5.3</a>
- do, <a href="#6.8.5.2">6.8.5.2</a> streams, <a href="#7.21.2">7.21.2</a>, <a href="#7.22.4.4">7.22.4.4</a>
- else, <a href="#6.8.4.1">6.8.4.1</a> fully buffered, <a href="#7.21.3">7.21.3</a>
-
-[<a name="#p673" href="p673">page 673</a>] (<a href="#Contents">Contents</a>)
-
- line buffered, <a href="#7.21.3">7.21.3</a> strtoumax function, <a href="#7.8.2.3">7.8.2.3</a>
- orientation, <a href="#7.21.2">7.21.2</a> struct hack, see flexible array member
- standard error, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> struct lconv, <a href="#7.11">7.11</a>
- standard input, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> struct tm, <a href="#7.26.1">7.26.1</a>
- standard output, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> structure
- unbuffered, <a href="#7.21.3">7.21.3</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
-strerror function, <a href="#7.21.10.4">7.21.10.4</a>, <a href="#7.23.6.2">7.23.6.2</a> content, <a href="#6.7.2.3">6.7.2.3</a>
-strerror_s function, <a href="#K.3.7.4.2">K.3.7.4.2</a>, <a href="#K.3.7.4.3">K.3.7.4.3</a> dot operator (.), <a href="#6.5.2.3">6.5.2.3</a>
-strerrorlen_s function, <a href="#K.3.7.4.3">K.3.7.4.3</a> initialization, <a href="#6.7.9">6.7.9</a>
-strftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.26.3">7.26.3</a>, <a href="#7.26.3.5">7.26.3.5</a>, member alignment, <a href="#6.7.2.1">6.7.2.1</a>
- <a href="#7.28.5.1">7.28.5.1</a>, <a href="#K.3.8.2">K.3.8.2</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a> member name space, <a href="#6.2.3">6.2.3</a>
-stricter, <a href="#6.2.8">6.2.8</a> member operator (.), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a>
-strictly conforming program, <a href="#4">4</a> pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a>
-string, <a href="#7.1.1">7.1.1</a> specifier, <a href="#6.7.2.1">6.7.2.1</a>
- comparison functions, <a href="#7.23.4">7.23.4</a> tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
- concatenation functions, <a href="#7.23.3">7.23.3</a>, <a href="#K.3.7.2">K.3.7.2</a> type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a>
- conversion functions, <a href="#7.11.1.1">7.11.1.1</a> strxfrm function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.4.5">7.23.4.5</a>
- copying functions, <a href="#7.23.2">7.23.2</a>, <a href="#K.3.7.1">K.3.7.1</a> subnormal floating-point numbers, <a href="#5.2.4.2.2">5.2.4.2.2</a>
- library function conventions, <a href="#7.23.1">7.23.1</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
- literal, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.5.1">6.5.1</a>, <a href="#6.7.9">6.7.9</a> subtraction assignment operator (-=), <a href="#6.5.16.2">6.5.16.2</a>
- miscellaneous functions, <a href="#7.23.6">7.23.6</a>, <a href="#K.3.7.4">K.3.7.4</a> subtraction operator (-), <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a>
- numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a> suffix
- search functions, <a href="#7.23.5">7.23.5</a>, <a href="#K.3.7.3">K.3.7.3</a> floating constant, <a href="#6.4.4.2">6.4.4.2</a>
-string handling header, <a href="#7.23">7.23</a>, <a href="#K.3.7">K.3.7</a> integer constant, <a href="#6.4.4.1">6.4.4.1</a>
-string.h header, <a href="#7.23">7.23</a>, <a href="#7.30.11">7.30.11</a>, <a href="#K.3.7">K.3.7</a> switch body, <a href="#6.8.4.2">6.8.4.2</a>
-stringizing, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.9">6.10.9</a> switch case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
-strlen function, <a href="#7.23.6.3">7.23.6.3</a> switch default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
-strncat function, <a href="#7.23.3.2">7.23.3.2</a> switch statement, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
-strncat_s function, <a href="#K.3.7.2.2">K.3.7.2.2</a> swprintf function, <a href="#7.28.2.3">7.28.2.3</a>, <a href="#7.28.2.7">7.28.2.7</a>,
-strncmp function, <a href="#7.23.4">7.23.4</a>, <a href="#7.23.4.4">7.23.4.4</a> <a href="#K.3.9.1.3">K.3.9.1.3</a>, <a href="#K.3.9.1.4">K.3.9.1.4</a>
-strncpy function, <a href="#7.23.2.4">7.23.2.4</a> swprintf_s function, <a href="#K.3.9.1.3">K.3.9.1.3</a>, <a href="#K.3.9.1.4">K.3.9.1.4</a>
-strncpy_s function, <a href="#K.3.7.1.4">K.3.7.1.4</a> swscanf function, <a href="#7.28.2.4">7.28.2.4</a>, <a href="#7.28.2.8">7.28.2.8</a>
-strnlen_s function, <a href="#K.3.7.4.4">K.3.7.4.4</a> swscanf_s function, <a href="#K.3.9.1.5">K.3.9.1.5</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>
-stronger, <a href="#6.2.8">6.2.8</a> symbols, <a href="#3">3</a>
-strpbrk function, <a href="#7.23.5.4">7.23.5.4</a> synchronization operation, <a href="#5.1.2.4">5.1.2.4</a>
-strrchr function, <a href="#7.23.5.5">7.23.5.5</a> synchronize with, <a href="#5.1.2.4">5.1.2.4</a>
-strspn function, <a href="#7.23.5.6">7.23.5.6</a> syntactic categories, <a href="#6.1">6.1</a>
-strstr function, <a href="#7.23.5.7">7.23.5.7</a> syntax notation, <a href="#6.1">6.1</a>
-strtod function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22.1.3">7.22.1.3</a>, syntax rule precedence, <a href="#5.1.1.2">5.1.1.2</a>
- <a href="#7.28.2.2">7.28.2.2</a>, <a href="#F.3">F.3</a> syntax summary, language, <a href="#A">A</a>
-strtof function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.22.1.3">7.22.1.3</a>, <a href="#F.3">F.3</a> system function, <a href="#7.22.4.8">7.22.4.8</a>
-strtoimax function, <a href="#7.8.2.3">7.8.2.3</a>
-strtok function, <a href="#7.23.5.8">7.23.5.8</a> tab characters, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
-strtok_s function, <a href="#K.3.7.3.1">K.3.7.3.1</a> tag compatibility, <a href="#6.2.7">6.2.7</a>
-strtol function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22.1.2">7.22.1.2</a>, tag name space, <a href="#6.2.3">6.2.3</a>
- <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.28.2.2">7.28.2.2</a> tags, <a href="#6.7.2.3">6.7.2.3</a>
-strtold function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.22.1.3">7.22.1.3</a>, <a href="#F.3">F.3</a> tan functions, <a href="#7.12.4.7">7.12.4.7</a>, <a href="#F.10.1.7">F.10.1.7</a>
-strtoll function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1.2">7.22.1.2</a>, <a href="#7.22.1.4">7.22.1.4</a> tan type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a>
-strtoul function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22.1.2">7.22.1.2</a>, tanh functions, <a href="#7.12.5.6">7.12.5.6</a>, <a href="#F.10.2.6">F.10.2.6</a>
- <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.28.2.2">7.28.2.2</a> tanh type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a>
-strtoull function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1.2">7.22.1.2</a>, <a href="#7.22.1.4">7.22.1.4</a> temporary lifetime, <a href="#6.2.4">6.2.4</a>
-
-[<a name="#p674" href="p674">page 674</a>] (<a href="#Contents">Contents</a>)
-
-tentative definition, <a href="#6.9.2">6.9.2</a> towlower function, <a href="#7.29.3.1.1">7.29.3.1.1</a>, <a href="#7.29.3.2.1">7.29.3.2.1</a>
-terms, <a href="#3">3</a> towupper function, <a href="#7.29.3.1.2">7.29.3.1.2</a>, <a href="#7.29.3.2.1">7.29.3.2.1</a>
-text streams, <a href="#7.21.2">7.21.2</a>, <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.2">7.21.9.2</a>, <a href="#7.21.9.4">7.21.9.4</a> translation environment, <a href="#5">5</a>, <a href="#5.1.1">5.1.1</a>
-tgamma functions, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#F.10.5.4">F.10.5.4</a> translation limits, <a href="#5.2.4.1">5.2.4.1</a>
-tgamma type-generic macro, <a href="#7.24">7.24</a> translation phases, <a href="#5.1.1.2">5.1.1.2</a>
-tgmath.h header, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> translation unit, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.9">6.9</a>
-thrd_create function, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.5.1">7.25.5.1</a> trap, see perform a trap
-thrd_current function, <a href="#7.25.5.2">7.25.5.2</a> trap representation, <a href="#3.19.4">3.19.4</a>, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.2.6.2">6.2.6.2</a>,
-thrd_detach function, <a href="#7.25.5.3">7.25.5.3</a>, <a href="#7.25.5.6">7.25.5.6</a> <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.5.2.3">6.5.2.3</a>
-thrd_equal function, <a href="#7.25.5.4">7.25.5.4</a> trigonometric functions
-thrd_exit function, <a href="#7.25.5.5">7.25.5.5</a> complex, <a href="#7.3.5">7.3.5</a>, <a href="#G.6.1">G.6.1</a>
-thrd_join function, <a href="#7.25.5.3">7.25.5.3</a>, <a href="#7.25.5.6">7.25.5.6</a> real, <a href="#7.12.4">7.12.4</a>, <a href="#F.10.1">F.10.1</a>
-thrd_sleep function, <a href="#7.25.5.7">7.25.5.7</a> trigraph sequences, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1.1">5.2.1.1</a>
-thrd_start_t type, <a href="#7.25.1">7.25.1</a> true macro, <a href="#7.18">7.18</a>
-thrd_t type, <a href="#7.25.1">7.25.1</a> trunc functions, <a href="#7.12.9.8">7.12.9.8</a>, <a href="#F.10.6.8">F.10.6.8</a>
-thrd_yield function, <a href="#7.25.5.8">7.25.5.8</a> trunc type-generic macro, <a href="#7.24">7.24</a>
-thread of execution, <a href="#5.1.2.4">5.1.2.4</a>, <a href="#7.1.4">7.1.4</a>, <a href="#7.6">7.6</a>, <a href="#7.22.4.6">7.22.4.6</a> truncation, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#7.12.9.8">7.12.9.8</a>, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.5.3">7.21.5.3</a>
-thread storage duration, <a href="#6.2.4">6.2.4</a>, <a href="#7.6">7.6</a> truncation toward zero, <a href="#6.5.5">6.5.5</a>
-threads header, <a href="#7.25">7.25</a> tss_create function, <a href="#7.25.6.1">7.25.6.1</a>
-threads.h header, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.25">7.25</a> tss_delete function, <a href="#7.25.6.2">7.25.6.2</a>
-time TSS_DTOR_ITERATIONS macro, <a href="#7.25.1">7.25.1</a>
- broken down, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.2.3">7.26.2.3</a>, <a href="#7.26.3">7.26.3</a>, <a href="#7.26.3.1">7.26.3.1</a>, tss_dtor_t type, <a href="#7.25.1">7.25.1</a>
- <a href="#7.26.3.3">7.26.3.3</a>, <a href="#7.26.3.4">7.26.3.4</a>, <a href="#7.26.3.5">7.26.3.5</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a>, tss_get function, <a href="#7.25.6.3">7.25.6.3</a>
- <a href="#K.3.8.2.3">K.3.8.2.3</a>, <a href="#K.3.8.2.4">K.3.8.2.4</a> tss_set function, <a href="#7.25.6.4">7.25.6.4</a>
- calendar, <a href="#7.26.1">7.26.1</a>, <a href="#7.26.2.2">7.26.2.2</a>, <a href="#7.26.2.3">7.26.2.3</a>, <a href="#7.26.2.4">7.26.2.4</a>, tss_t type, <a href="#7.25.1">7.25.1</a>
- <a href="#7.26.3.2">7.26.3.2</a>, <a href="#7.26.3.3">7.26.3.3</a>, <a href="#7.26.3.4">7.26.3.4</a>, <a href="#K.3.8.2.2">K.3.8.2.2</a>, two's complement, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.20.1.1">7.20.1.1</a>
- <a href="#K.3.8.2.3">K.3.8.2.3</a>, <a href="#K.3.8.2.4">K.3.8.2.4</a> type category, <a href="#6.2.5">6.2.5</a>
- components, <a href="#7.26.1">7.26.1</a>, <a href="#K.3.8.1">K.3.8.1</a> type conversion, <a href="#6.3">6.3</a>
- conversion functions, <a href="#7.26.3">7.26.3</a>, <a href="#K.3.8.2">K.3.8.2</a> type definitions, <a href="#6.7.8">6.7.8</a>
- wide character, <a href="#7.28.5">7.28.5</a> type domain, <a href="#6.2.5">6.2.5</a>, <a href="#G.2">G.2</a>
- local, <a href="#7.26.1">7.26.1</a> type names, <a href="#6.7.7">6.7.7</a>
- manipulation functions, <a href="#7.26.2">7.26.2</a> type punning, <a href="#6.5.2.3">6.5.2.3</a>
- normalized broken down, <a href="#K.3.8.1">K.3.8.1</a>, <a href="#K.3.8.2.1">K.3.8.2.1</a> type qualifiers, <a href="#6.7.3">6.7.3</a>
-time function, <a href="#7.26.2.4">7.26.2.4</a> type specifiers, <a href="#6.7.2">6.7.2</a>
-time.h header, <a href="#7.26">7.26</a>, <a href="#K.3.8">K.3.8</a> type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a>
-time_t type, <a href="#7.26.1">7.26.1</a> typedef declaration, <a href="#6.7.8">6.7.8</a>
-TIME_UTC macro, <a href="#7.25.7.1">7.25.7.1</a> typedef storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.7.8">6.7.8</a>
-tm structure type, <a href="#7.26.1">7.26.1</a>, <a href="#7.28.1">7.28.1</a>, <a href="#K.3.8.1">K.3.8.1</a> types, <a href="#6.2.5">6.2.5</a>
-TMP_MAX macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.21.4.4">7.21.4.4</a> _Atomic qualified, <a href="#6.2.5">6.2.5</a>, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.5.2.3">6.5.2.3</a>,
-TMP_MAX_S macro, <a href="#K.3.5">K.3.5</a>, <a href="#K.3.5.1.1">K.3.5.1.1</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a> <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.16.2">6.5.16.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>
-tmpfile function, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.22.4.4">7.22.4.4</a> atomic, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.17.6">7.17.6</a>
-tmpfile_s function, <a href="#K.3.5.1.1">K.3.5.1.1</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a> character, <a href="#6.7.9">6.7.9</a>
-tmpnam function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.21.4.4">7.21.4.4</a>, compatible, <a href="#6.2.7">6.2.7</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.6">6.7.6</a>
- <a href="#K.3.5.1.2">K.3.5.1.2</a> complex, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a>
-tmpnam_s function, <a href="#K.3.5">K.3.5</a>, <a href="#K.3.5.1.1">K.3.5.1.1</a>, <a href="#K.3.5.1.2">K.3.5.1.2</a> composite, <a href="#6.2.7">6.2.7</a>
-token, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, see also preprocessing tokens const qualified, <a href="#6.7.3">6.7.3</a>
-token concatenation, <a href="#6.10.3.3">6.10.3.3</a> conversions, <a href="#6.3">6.3</a>
-token pasting, <a href="#6.10.3.3">6.10.3.3</a> imaginary, <a href="#G">G</a>
-tolower function, <a href="#7.4.2.1">7.4.2.1</a> restrict qualified, <a href="#6.7.3">6.7.3</a>
-toupper function, <a href="#7.4.2.2">7.4.2.2</a> volatile qualified, <a href="#6.7.3">6.7.3</a>
-towctrans function, <a href="#7.29.3.2.1">7.29.3.2.1</a>, <a href="#7.29.3.2.2">7.29.3.2.2</a>
-
-[<a name="#p675" href="p675">page 675</a>] (<a href="#Contents">Contents</a>)
-
-uchar.h header, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#7.27">7.27</a> universal character name, <a href="#6.4.3">6.4.3</a>
-UCHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a> unnormalized floating-point numbers, <a href="#5.2.4.2.2">5.2.4.2.2</a>
-UINT_FASTN_MAX macros, <a href="#7.20.2.3">7.20.2.3</a> unqualified type, <a href="#6.2.5">6.2.5</a>
-uint_fastN_t types, <a href="#7.20.1.3">7.20.1.3</a> unqualified version of type, <a href="#6.2.5">6.2.5</a>
-uint_least16_t type, <a href="#7.27">7.27</a> unsequenced, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a>, <a href="#6.5.16">6.5.16</a>, see also
-uint_least32_t type, <a href="#7.27">7.27</a> indeterminately sequenced, sequenced
-UINT_LEASTN_MAX macros, <a href="#7.20.2.2">7.20.2.2</a> before
-uint_leastN_t types, <a href="#7.20.1.2">7.20.1.2</a> unsigned char type, <a href="#K.3.5.3.2">K.3.5.3.2</a>, <a href="#K.3.9.1.2">K.3.9.1.2</a>
-UINT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a> unsigned integer suffix, u or <a href="#U">U</a>, <a href="#6.4.4.1">6.4.4.1</a>
-UINTMAX_C macro, <a href="#7.20.4.2">7.20.4.2</a> unsigned integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a>
-UINTMAX_MAX macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.20.2.5">7.20.2.5</a> unsigned type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>,
-uintmax_t type, <a href="#7.20.1.5">7.20.1.5</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
- <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a> unsigned types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>,
-UINTN_C macros, <a href="#7.20.4.1">7.20.4.1</a> <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>
-UINTN_MAX macros, <a href="#7.20.2.1">7.20.2.1</a> unspecified behavior, <a href="#3.4.4">3.4.4</a>, <a href="#4">4</a>, <a href="#J.1">J.1</a>
-uintN_t types, <a href="#7.20.1.1">7.20.1.1</a> unspecified value, <a href="#3.19.3">3.19.3</a>
-UINTPTR_MAX macro, <a href="#7.20.2.4">7.20.2.4</a> uppercase letter, <a href="#5.2.1">5.2.1</a>
-uintptr_t type, <a href="#7.20.1.4">7.20.1.4</a> use of library functions, <a href="#7.1.4">7.1.4</a>
-ULLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>, USHRT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
- <a href="#7.28.4.1.2">7.28.4.1.2</a> usual arithmetic conversions, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.5.5">6.5.5</a>, <a href="#6.5.6">6.5.6</a>,
-ULONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.22.1.4">7.22.1.4</a>, <a href="#6.5.8">6.5.8</a>, <a href="#6.5.9">6.5.9</a>, <a href="#6.5.10">6.5.10</a>, <a href="#6.5.11">6.5.11</a>, <a href="#6.5.12">6.5.12</a>, <a href="#6.5.15">6.5.15</a>
- <a href="#7.28.4.1.2">7.28.4.1.2</a> UTF-16, <a href="#6.10.8.2">6.10.8.2</a>
-unary arithmetic operators, <a href="#6.5.3.3">6.5.3.3</a> UTF-32, <a href="#6.10.8.2">6.10.8.2</a>
-unary expression, <a href="#6.5.3">6.5.3</a> UTF-8 string literal, see string literal
-unary minus operator (-), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a> utilities, general, <a href="#7.22">7.22</a>, <a href="#K.3.6">K.3.6</a>
-unary operators, <a href="#6.5.3">6.5.3</a> wide string, <a href="#7.28.4">7.28.4</a>, <a href="#K.3.9.2">K.3.9.2</a>
-unary plus operator (+), <a href="#6.5.3.3">6.5.3.3</a>
-unbuffered stream, <a href="#7.21.3">7.21.3</a> va_arg macro, <a href="#7.16">7.16</a>, <a href="#7.16.1">7.16.1</a>, <a href="#7.16.1.1">7.16.1.1</a>, <a href="#7.16.1.2">7.16.1.2</a>,
-undef preprocessing directive, <a href="#6.10.3.5">6.10.3.5</a>, <a href="#7.1.3">7.1.3</a>, <a href="#7.16.1.4">7.16.1.4</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.10">7.21.6.10</a>,
- <a href="#7.1.4">7.1.4</a> <a href="#7.21.6.11">7.21.6.11</a>, <a href="#7.21.6.12">7.21.6.12</a>, <a href="#7.21.6.13">7.21.6.13</a>, <a href="#7.21.6.14">7.21.6.14</a>,
-undefined behavior, <a href="#3.4.3">3.4.3</a>, <a href="#4">4</a>, <a href="#J.2">J.2</a> <a href="#7.28.2.5">7.28.2.5</a>, <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.2.7">7.28.2.7</a>, <a href="#7.28.2.8">7.28.2.8</a>,
-underscore character, <a href="#6.4.2.1">6.4.2.1</a> <a href="#7.28.2.9">7.28.2.9</a>, <a href="#7.28.2.10">7.28.2.10</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>,
-underscore, leading, in identifier, <a href="#7.1.3">7.1.3</a> <a href="#K.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a>
-ungetc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.10">7.21.7.10</a>, <a href="#7.21.9.2">7.21.9.2</a>, va_copy macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.16">7.16</a>, <a href="#7.16.1">7.16.1</a>, <a href="#7.16.1.1">7.16.1.1</a>,
- <a href="#7.21.9.3">7.21.9.3</a> <a href="#7.16.1.2">7.16.1.2</a>, <a href="#7.16.1.3">7.16.1.3</a>
-ungetwc function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3.10">7.28.3.10</a> va_end macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.16">7.16</a>, <a href="#7.16.1">7.16.1</a>, <a href="#7.16.1.3">7.16.1.3</a>,
-Unicode, <a href="#7.27">7.27</a>, see also char16_t type, <a href="#7.16.1.4">7.16.1.4</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.10">7.21.6.10</a>,
- char32_t type, wchar_t type <a href="#7.21.6.11">7.21.6.11</a>, <a href="#7.21.6.12">7.21.6.12</a>, <a href="#7.21.6.13">7.21.6.13</a>, <a href="#7.21.6.14">7.21.6.14</a>,
-Unicode required set, <a href="#6.10.8.2">6.10.8.2</a> <a href="#7.28.2.5">7.28.2.5</a>, <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.2.7">7.28.2.7</a>, <a href="#7.28.2.8">7.28.2.8</a>,
-union <a href="#7.28.2.9">7.28.2.9</a>, <a href="#7.28.2.10">7.28.2.10</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>,
- arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a> <a href="#K.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.7">K.3.9.1.7</a>, <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a>
- content, <a href="#6.7.2.3">6.7.2.3</a> va_list type, <a href="#7.16">7.16</a>, <a href="#7.16.1.3">7.16.1.3</a>
- dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> va_start macro, <a href="#7.16">7.16</a>, <a href="#7.16.1">7.16.1</a>, <a href="#7.16.1.1">7.16.1.1</a>,
- initialization, <a href="#6.7.9">6.7.9</a> <a href="#7.16.1.2">7.16.1.2</a>, <a href="#7.16.1.3">7.16.1.3</a>, <a href="#7.16.1.4">7.16.1.4</a>, <a href="#7.21.6.8">7.21.6.8</a>,
- member alignment, <a href="#6.7.2.1">6.7.2.1</a> <a href="#7.21.6.9">7.21.6.9</a>, <a href="#7.21.6.10">7.21.6.10</a>, <a href="#7.21.6.11">7.21.6.11</a>, <a href="#7.21.6.12">7.21.6.12</a>,
- member name space, <a href="#6.2.3">6.2.3</a> <a href="#7.21.6.13">7.21.6.13</a>, <a href="#7.21.6.14">7.21.6.14</a>, <a href="#7.28.2.5">7.28.2.5</a>, <a href="#7.28.2.6">7.28.2.6</a>,
- member operator (.), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a> <a href="#7.28.2.7">7.28.2.7</a>, <a href="#7.28.2.8">7.28.2.8</a>, <a href="#7.28.2.9">7.28.2.9</a>, <a href="#7.28.2.10">7.28.2.10</a>,
- pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a>, <a href="#K.3.9.1.7">K.3.9.1.7</a>,
- specifier, <a href="#6.7.2.1">6.7.2.1</a> <a href="#K.3.9.1.10">K.3.9.1.10</a>, <a href="#K.3.9.1.12">K.3.9.1.12</a>
- tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a> value, <a href="#3.19">3.19</a>
- type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a> value bits, <a href="#6.2.6.2">6.2.6.2</a>
-
-[<a name="#p676" href="p676">page 676</a>] (<a href="#Contents">Contents</a>)
-
-variable arguments, <a href="#6.10.3">6.10.3</a>, <a href="#7.16">7.16</a> vswscanf function, <a href="#7.28.2.8">7.28.2.8</a>
-variable arguments header, <a href="#7.16">7.16</a> vswscanf_s function, <a href="#K.3.9.1.10">K.3.9.1.10</a>
-variable length array, <a href="#6.7.6">6.7.6</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.10.8.3">6.10.8.3</a> vwprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.2.9">7.28.2.9</a>, <a href="#K.3.9.1.11">K.3.9.1.11</a>
-variably modified type, <a href="#6.7.6">6.7.6</a>, <a href="#6.7.6.2">6.7.6.2</a>, <a href="#6.10.8.3">6.10.8.3</a> vwprintf_s function, <a href="#K.3.9.1.11">K.3.9.1.11</a>
-vertical-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a> vwscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.2.10">7.28.2.10</a>, <a href="#7.28.3.10">7.28.3.10</a>
-vertical-tab escape sequence (\v), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, vwscanf_s function, <a href="#K.3.9.1.12">K.3.9.1.12</a>
- <a href="#7.4.1.10">7.4.1.10</a>
-vfprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#K.3.5.3.8">K.3.5.3.8</a> warnings, <a href="#I">I</a>
-vfprintf_s function, <a href="#K.3.5.3.8">K.3.5.3.8</a>, <a href="#K.3.5.3.9">K.3.5.3.9</a>, wchar.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.28">7.28</a>, <a href="#7.30.12">7.30.12</a>,
- <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a> <a href="#F">F</a>, <a href="#K.3.9">K.3.9</a>
-vfscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.9">7.21.6.9</a> WCHAR_MAX macro, <a href="#7.20.3">7.20.3</a>, <a href="#7.28.1">7.28.1</a>
-vfscanf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, WCHAR_MIN macro, <a href="#7.20.3">7.20.3</a>, <a href="#7.28.1">7.28.1</a>
- <a href="#K.3.5.3.14">K.3.5.3.14</a> wchar_t type, <a href="#3.7.3">3.7.3</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.7.9">6.7.9</a>, <a href="#6.10.8.2">6.10.8.2</a>, <a href="#7.19">7.19</a>,
-vfwprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.2.5">7.28.2.5</a>, <a href="#K.3.9.1.6">K.3.9.1.6</a> <a href="#7.20.3">7.20.3</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.22">7.22</a>, <a href="#7.28.1">7.28.1</a>,
-vfwprintf_s function, <a href="#K.3.9.1.6">K.3.9.1.6</a> <a href="#7.28.2.1">7.28.2.1</a>, <a href="#7.28.2.2">7.28.2.2</a>
-vfwscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.2.6">7.28.2.6</a>, <a href="#7.28.3.10">7.28.3.10</a> wcrtomb function, <a href="#7.21.3">7.21.3</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>,
-vfwscanf_s function, <a href="#K.3.9.1.7">K.3.9.1.7</a> <a href="#7.28.6.3.3">7.28.6.3.3</a>, <a href="#7.28.6.4.2">7.28.6.4.2</a>, <a href="#K.3.6.5.2">K.3.6.5.2</a>, <a href="#K.3.9.3.1">K.3.9.3.1</a>,
-visibility of identifier, <a href="#6.2.1">6.2.1</a> <a href="#K.3.9.3.2.2">K.3.9.3.2.2</a>
-visible sequence of side effects, <a href="#5.1.2.4">5.1.2.4</a> wcrtomb_s function, <a href="#K.3.9.3.1">K.3.9.3.1</a>, <a href="#K.3.9.3.1.1">K.3.9.3.1.1</a>
-visible side effect, <a href="#5.1.2.4">5.1.2.4</a> wcscat function, <a href="#7.28.4.3.1">7.28.4.3.1</a>
-VLA, see variable length array wcscat_s function, <a href="#K.3.9.2.2.1">K.3.9.2.2.1</a>
-void expression, <a href="#6.3.2.2">6.3.2.2</a> wcschr function, <a href="#7.28.4.5.1">7.28.4.5.1</a>
-void function parameter, <a href="#6.7.6.3">6.7.6.3</a> wcscmp function, <a href="#7.28.4.4.1">7.28.4.4.1</a>, <a href="#7.28.4.4.4">7.28.4.4.4</a>
-void type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.2">6.3.2.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#K.3.5.3.2">K.3.5.3.2</a>, wcscoll function, <a href="#7.28.4.4.2">7.28.4.4.2</a>, <a href="#7.28.4.4.4">7.28.4.4.4</a>
- <a href="#K.3.9.1.2">K.3.9.1.2</a> wcscpy function, <a href="#7.28.4.2.1">7.28.4.2.1</a>
-void type conversion, <a href="#6.3.2.2">6.3.2.2</a> wcscpy_s function, <a href="#K.3.9.2.1.1">K.3.9.2.1.1</a>
-volatile storage, <a href="#5.1.2.3">5.1.2.3</a> wcscspn function, <a href="#7.28.4.5.2">7.28.4.5.2</a>
-volatile type qualifier, <a href="#6.7.3">6.7.3</a> wcsftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.28.5.1">7.28.5.1</a>
-volatile-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a> wcslen function, <a href="#7.28.4.6.1">7.28.4.6.1</a>
-vprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.10">7.21.6.10</a>, wcsncat function, <a href="#7.28.4.3.2">7.28.4.3.2</a>
- <a href="#K.3.5.3.10">K.3.5.3.10</a> wcsncat_s function, <a href="#K.3.9.2.2.2">K.3.9.2.2.2</a>
-vprintf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.10">K.3.5.3.10</a>, wcsncmp function, <a href="#7.28.4.4.3">7.28.4.4.3</a>
- <a href="#K.3.5.3.11">K.3.5.3.11</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a> wcsncpy function, <a href="#7.28.4.2.2">7.28.4.2.2</a>
-vscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.11">7.21.6.11</a> wcsncpy_s function, <a href="#K.3.9.2.1.2">K.3.9.2.1.2</a>
-vscanf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, wcsnlen_s function, <a href="#K.3.9.2.4.1">K.3.9.2.4.1</a>
- <a href="#K.3.5.3.14">K.3.5.3.14</a> wcspbrk function, <a href="#7.28.4.5.3">7.28.4.5.3</a>
-vsnprintf function, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.12">7.21.6.12</a>, wcsrchr function, <a href="#7.28.4.5.4">7.28.4.5.4</a>
- <a href="#K.3.5.3.12">K.3.5.3.12</a> wcsrtombs function, <a href="#7.28.6.4.2">7.28.6.4.2</a>, <a href="#K.3.9.3.2">K.3.9.3.2</a>
-vsnprintf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, wcsrtombs_s function, <a href="#K.3.9.3.2">K.3.9.3.2</a>, <a href="#K.3.9.3.2.2">K.3.9.3.2.2</a>
- <a href="#K.3.5.3.12">K.3.5.3.12</a>, <a href="#K.3.5.3.13">K.3.5.3.13</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a> wcsspn function, <a href="#7.28.4.5.5">7.28.4.5.5</a>
-vsnwprintf_s function, <a href="#K.3.9.1.8">K.3.9.1.8</a>, <a href="#K.3.9.1.9">K.3.9.1.9</a> wcsstr function, <a href="#7.28.4.5.6">7.28.4.5.6</a>
-vsprintf function, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.13">7.21.6.13</a>, wcstod function, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>
- <a href="#K.3.5.3.13">K.3.5.3.13</a> wcstod function, <a href="#7.28.4.1.1">7.28.4.1.1</a>
-vsprintf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, wcstof function, <a href="#7.28.4.1.1">7.28.4.1.1</a>
- <a href="#K.3.5.3.12">K.3.5.3.12</a>, <a href="#K.3.5.3.13">K.3.5.3.13</a>, <a href="#K.3.5.3.14">K.3.5.3.14</a> wcstoimax function, <a href="#7.8.2.4">7.8.2.4</a>
-vsscanf function, <a href="#7.21.6.8">7.21.6.8</a>, <a href="#7.21.6.14">7.21.6.14</a> wcstok function, <a href="#7.28.4.5.7">7.28.4.5.7</a>
-vsscanf_s function, <a href="#K.3.5.3.9">K.3.5.3.9</a>, <a href="#K.3.5.3.11">K.3.5.3.11</a>, wcstok_s function, <a href="#K.3.9.2.3.1">K.3.9.2.3.1</a>
- <a href="#K.3.5.3.14">K.3.5.3.14</a> wcstol function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>,
-vswprintf function, <a href="#7.28.2.7">7.28.2.7</a>, <a href="#K.3.9.1.8">K.3.9.1.8</a>, <a href="#7.28.4.1.2">7.28.4.1.2</a>
- <a href="#K.3.9.1.9">K.3.9.1.9</a> wcstold function, <a href="#7.28.4.1.1">7.28.4.1.1</a>
-vswprintf_s function, <a href="#K.3.9.1.8">K.3.9.1.8</a>, <a href="#K.3.9.1.9">K.3.9.1.9</a> wcstoll function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.28.4.1.2">7.28.4.1.2</a>
-
-[<a name="#p677" href="p677">page 677</a>] (<a href="#Contents">Contents</a>)
-
-wcstombs function, <a href="#7.22.8.2">7.22.8.2</a>, <a href="#7.28.6.4">7.28.6.4</a> <a href="#7.29.1">7.29.1</a>
-wcstombs_s function, <a href="#K.3.6.5.2">K.3.6.5.2</a> wmemchr function, <a href="#7.28.4.5.8">7.28.4.5.8</a>
-wcstoul function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>, wmemcmp function, <a href="#7.28.4.4.5">7.28.4.4.5</a>
- <a href="#7.28.4.1.2">7.28.4.1.2</a> wmemcpy function, <a href="#7.28.4.2.3">7.28.4.2.3</a>
-wcstoull function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.28.4.1.2">7.28.4.1.2</a> wmemcpy_s function, <a href="#K.3.9.2.1.3">K.3.9.2.1.3</a>
-wcstoumax function, <a href="#7.8.2.4">7.8.2.4</a> wmemmove function, <a href="#7.28.4.2.4">7.28.4.2.4</a>
-wcsxfrm function, <a href="#7.28.4.4.4">7.28.4.4.4</a> wmemmove_s function, <a href="#K.3.9.2.1.4">K.3.9.2.1.4</a>
-wctob function, <a href="#7.28.6.1.2">7.28.6.1.2</a>, <a href="#7.29.2.1">7.29.2.1</a> wmemset function, <a href="#7.28.4.6.2">7.28.4.6.2</a>
-wctomb function, <a href="#7.22.7.3">7.22.7.3</a>, <a href="#7.22.8.2">7.22.8.2</a>, <a href="#7.28.6.3">7.28.6.3</a> wprintf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.2.9">7.28.2.9</a>, <a href="#7.28.2.11">7.28.2.11</a>,
-wctomb_s function, <a href="#K.3.6.4.1">K.3.6.4.1</a> <a href="#K.3.9.1.13">K.3.9.1.13</a>
-wctrans function, <a href="#7.29.3.2.1">7.29.3.2.1</a>, <a href="#7.29.3.2.2">7.29.3.2.2</a> wprintf_s function, <a href="#K.3.9.1.13">K.3.9.1.13</a>
-wctrans_t type, <a href="#7.29.1">7.29.1</a>, <a href="#7.29.3.2.2">7.29.3.2.2</a> wscanf function, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.2.10">7.28.2.10</a>, <a href="#7.28.2.12">7.28.2.12</a>,
-wctype function, <a href="#7.29.2.2.1">7.29.2.2.1</a>, <a href="#7.29.2.2.2">7.29.2.2.2</a> <a href="#7.28.3.10">7.28.3.10</a>
-wctype.h header, <a href="#7.29">7.29</a>, <a href="#7.30.13">7.30.13</a> wscanf_s function, <a href="#K.3.9.1.12">K.3.9.1.12</a>, <a href="#K.3.9.1.14">K.3.9.1.14</a>
-wctype_t type, <a href="#7.29.1">7.29.1</a>, <a href="#7.29.2.2.2">7.29.2.2.2</a>
-weaker, <a href="#6.2.8">6.2.8</a> xor macro, <a href="#7.9">7.9</a>
-WEOF macro, <a href="#7.28.1">7.28.1</a>, <a href="#7.28.3.1">7.28.3.1</a>, <a href="#7.28.3.3">7.28.3.3</a>, <a href="#7.28.3.6">7.28.3.6</a>, xor_eq macro, <a href="#7.9">7.9</a>
- <a href="#7.28.3.7">7.28.3.7</a>, <a href="#7.28.3.8">7.28.3.8</a>, <a href="#7.28.3.9">7.28.3.9</a>, <a href="#7.28.3.10">7.28.3.10</a>, xtime type, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.3.5">7.25.3.5</a>, <a href="#7.25.4.4">7.25.4.4</a>, <a href="#7.25.5.7">7.25.5.7</a>,
- <a href="#7.28.6.1.1">7.28.6.1.1</a>, <a href="#7.29.1">7.29.1</a> <a href="#7.25.7.1">7.25.7.1</a>
-while statement, <a href="#6.8.5.1">6.8.5.1</a> xtime_get function, <a href="#7.25.7.1">7.25.7.1</a>
-white space, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>, <a href="#7.4.1.10">7.4.1.10</a>,
- <a href="#7.29.2.1.10">7.29.2.1.10</a>
-white-space characters, <a href="#6.4">6.4</a>
-wide character, <a href="#3.7.3">3.7.3</a>
- case mapping functions, <a href="#7.29.3.1">7.29.3.1</a>
- extensible, <a href="#7.29.3.2">7.29.3.2</a>
- classification functions, <a href="#7.29.2.1">7.29.2.1</a>
- extensible, <a href="#7.29.2.2">7.29.2.2</a>
- constant, <a href="#6.4.4.4">6.4.4.4</a>
- formatted input/output functions, <a href="#7.28.2">7.28.2</a>,
- <a href="#K.3.9.1">K.3.9.1</a>
- input functions, <a href="#7.21.1">7.21.1</a>
- input/output functions, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3">7.28.3</a>
- output functions, <a href="#7.21.1">7.21.1</a>
- single-byte conversion functions, <a href="#7.28.6.1">7.28.6.1</a>
-wide string, <a href="#7.1.1">7.1.1</a>
-wide string comparison functions, <a href="#7.28.4.4">7.28.4.4</a>
-wide string concatenation functions, <a href="#7.28.4.3">7.28.4.3</a>,
- <a href="#K.3.9.2.2">K.3.9.2.2</a>
-wide string copying functions, <a href="#7.28.4.2">7.28.4.2</a>, <a href="#K.3.9.2.1">K.3.9.2.1</a>
-wide string literal, see string literal
-wide string miscellaneous functions, <a href="#7.28.4.6">7.28.4.6</a>,
- <a href="#K.3.9.2.4">K.3.9.2.4</a>
-wide string numeric conversion functions, <a href="#7.8.2.4">7.8.2.4</a>,
- <a href="#7.28.4.1">7.28.4.1</a>
-wide string search functions, <a href="#7.28.4.5">7.28.4.5</a>, <a href="#K.3.9.2.3">K.3.9.2.3</a>
-wide-oriented stream, <a href="#7.21.2">7.21.2</a>
-width, <a href="#6.2.6.2">6.2.6.2</a>
-WINT_MAX macro, <a href="#7.20.3">7.20.3</a>
-WINT_MIN macro, <a href="#7.20.3">7.20.3</a>
-wint_t type, <a href="#7.20.3">7.20.3</a>, <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.1">7.28.1</a>, <a href="#7.28.2.1">7.28.2.1</a>,
-
-[<a name="#p678" href="p678">page 678</a>] (<a href="#Contents">Contents</a>)
-</pre></body></html>
+++ /dev/null
-N1516 Committee Draft -- October 4, 2010 ISO/IEC 9899:201x
-
-
-
-
-INTERNATIONAL STANDARD (C)ISO/IEC ISO/IEC 9899:201x
-
-
-
-
-Programming languages -- C
-
-
- ABSTRACT
-
-
-
- (Cover sheet to be provided by ISO Secretariat.)
-
-This International Standard specifies the form and establishes the interpretation of
-programs expressed in the programming language C. Its purpose is to promote
-portability, reliability, maintainability, and efficient execution of C language programs on
-a variety of computing systems.
-
-Clauses are included that detail the C language itself and the contents of the C language
-execution library. Annexes summarize aspects of both of them, and enumerate factors
-that influence the portability of C programs.
-
-Although this International Standard is intended to guide knowledgeable C language
-programmers as well as implementors of C language translation systems, the document
-itself is not designed to serve as a tutorial.
-
-Recipients of this draft are invited to submit, with their comments, notification of any
-relevant patent rights of which they are aware and to provide supporting documentation.
-
-Changes from the previous draft (N1494) are indicated by ''diff marks'' in the right
-margin: deleted text is marked with ''*'', new or changed text with '' ''.
-
-
-
-
-[page i]
-
-
-
-[page ii]
-
-Contents
-Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii
-Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
-1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
-2. Normative references . . . . . . . . . . . . . . . . . . . . . . . 2
-3. Terms, definitions, and symbols . . . . . . . . . . . . . . . . . . . 3
-4. Conformance . . . . . . . . . . . . . . . . . . . . . . . . . . 8
-5. Environment . . . . . . . . . . . . . . . . . . . . . . . . . . 10
- 5.1 Conceptual models . . . . . . . . . . . . . . . . . . . . . 10
- 5.1.1 Translation environment . . . . . . . . . . . . . . . . 10
- 5.1.2 Execution environments . . . . . . . . . . . . . . . . 12
- 5.2 Environmental considerations . . . . . . . . . . . . . . . . . 22
- 5.2.1 Character sets . . . . . . . . . . . . . . . . . . . . 22
- 5.2.2 Character display semantics . . . . . . . . . . . . . . 24
- 5.2.3 Signals and interrupts . . . . . . . . . . . . . . . . . 25
- 5.2.4 Environmental limits . . . . . . . . . . . . . . . . . 25
-6. Language . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
- 6.1 Notation . . . . . . . . . . . . . . . . . . . . . . . . . . 35
- 6.2 Concepts . . . . . . . . . . . . . . . . . . . . . . . . . 35
- 6.2.1 Scopes of identifiers . . . . . . . . . . . . . . . . . 35
- 6.2.2 Linkages of identifiers . . . . . . . . . . . . . . . . . 36
- 6.2.3 Name spaces of identifiers . . . . . . . . . . . . . . . 37
- 6.2.4 Storage durations of objects . . . . . . . . . . . . . . 38
- 6.2.5 Types . . . . . . . . . . . . . . . . . . . . . . . 39
- 6.2.6 Representations of types . . . . . . . . . . . . . . . . 44
- 6.2.7 Compatible type and composite type . . . . . . . . . . . 47
- 6.2.8 Alignment of objects . . . . . . . . . . . . . . . . . 48
- 6.3 Conversions . . . . . . . . . . . . . . . . . . . . . . . . 50
- 6.3.1 Arithmetic operands . . . . . . . . . . . . . . . . . 50
- 6.3.2 Other operands . . . . . . . . . . . . . . . . . . . 54
- 6.4 Lexical elements . . . . . . . . . . . . . . . . . . . . . . 57
- 6.4.1 Keywords . . . . . . . . . . . . . . . . . . . . . . 58
- 6.4.2 Identifiers . . . . . . . . . . . . . . . . . . . . . . 59
- 6.4.3 Universal character names . . . . . . . . . . . . . . . 61
- 6.4.4 Constants . . . . . . . . . . . . . . . . . . . . . . 62
- 6.4.5 String literals . . . . . . . . . . . . . . . . . . . . 70
- 6.4.6 Punctuators . . . . . . . . . . . . . . . . . . . . . 72
- 6.4.7 Header names . . . . . . . . . . . . . . . . . . . . 73
- 6.4.8 Preprocessing numbers . . . . . . . . . . . . . . . . 74
- 6.4.9 Comments . . . . . . . . . . . . . . . . . . . . . 75
-
-
-[page iii]
-
- 6.5 Expressions . . . . . . . . . . . . . . . . . . . . . . . . 76
- 6.5.1 Primary expressions . . . . . . . . . . . . . . . . . 78
- 6.5.2 Postfix operators . . . . . . . . . . . . . . . . . . . 79
- 6.5.3 Unary operators . . . . . . . . . . . . . . . . . . . 88
- 6.5.4 Cast operators . . . . . . . . . . . . . . . . . . . . 91
- 6.5.5 Multiplicative operators . . . . . . . . . . . . . . . . 92
- 6.5.6 Additive operators . . . . . . . . . . . . . . . . . . 92
- 6.5.7 Bitwise shift operators . . . . . . . . . . . . . . . . . 94
- 6.5.8 Relational operators . . . . . . . . . . . . . . . . . . 95
- 6.5.9 Equality operators . . . . . . . . . . . . . . . . . . 96
- 6.5.10 Bitwise AND operator . . . . . . . . . . . . . . . . . 97
- 6.5.11 Bitwise exclusive OR operator . . . . . . . . . . . . . 98
- 6.5.12 Bitwise inclusive OR operator . . . . . . . . . . . . . . 98
- 6.5.13 Logical AND operator . . . . . . . . . . . . . . . . . 99
- 6.5.14 Logical OR operator . . . . . . . . . . . . . . . . . 99
- 6.5.15 Conditional operator . . . . . . . . . . . . . . . . . 100
- 6.5.16 Assignment operators . . . . . . . . . . . . . . . . . 101
- 6.5.17 Comma operator . . . . . . . . . . . . . . . . . . . 104
- 6.6 Constant expressions . . . . . . . . . . . . . . . . . . . . . 105
- 6.7 Declarations . . . . . . . . . . . . . . . . . . . . . . . . 107
- 6.7.1 Storage-class specifiers . . . . . . . . . . . . . . . . 108
- 6.7.2 Type specifiers . . . . . . . . . . . . . . . . . . . . 109
- 6.7.3 Type qualifiers . . . . . . . . . . . . . . . . . . . . 119
- 6.7.4 Function specifiers . . . . . . . . . . . . . . . . . . 123
- 6.7.5 Alignment specifier . . . . . . . . . . . . . . . . . . 125
- 6.7.6 Declarators . . . . . . . . . . . . . . . . . . . . . 126
- 6.7.7 Type names . . . . . . . . . . . . . . . . . . . . . 134
- 6.7.8 Type definitions . . . . . . . . . . . . . . . . . . . 135
- 6.7.9 Initialization . . . . . . . . . . . . . . . . . . . . 137
- 6.7.10 Static assertions . . . . . . . . . . . . . . . . . . . 143
- 6.8 Statements and blocks . . . . . . . . . . . . . . . . . . . . 144
- 6.8.1 Labeled statements . . . . . . . . . . . . . . . . . . 144
- 6.8.2 Compound statement . . . . . . . . . . . . . . . . . 145
- 6.8.3 Expression and null statements . . . . . . . . . . . . . 145
- 6.8.4 Selection statements . . . . . . . . . . . . . . . . . 146
- 6.8.5 Iteration statements . . . . . . . . . . . . . . . . . . 148
- 6.8.6 Jump statements . . . . . . . . . . . . . . . . . . . 149
- 6.9 External definitions . . . . . . . . . . . . . . . . . . . . . 153
- 6.9.1 Function definitions . . . . . . . . . . . . . . . . . . 154
- 6.9.2 External object definitions . . . . . . . . . . . . . . . 156
- 6.10 Preprocessing directives . . . . . . . . . . . . . . . . . . . 158
- 6.10.1 Conditional inclusion . . . . . . . . . . . . . . . . . 160
- 6.10.2 Source file inclusion . . . . . . . . . . . . . . . . . 162
- 6.10.3 Macro replacement . . . . . . . . . . . . . . . . . . 164
-
-
-[page iv]
-
- 6.10.4 Line control . . . . . . . . . . . . . . . . . . . . . 171
- 6.10.5 Error directive . . . . . . . . . . . . . . . . . . . . 172
- 6.10.6 Pragma directive . . . . . . . . . . . . . . . . . . . 172
- 6.10.7 Null directive . . . . . . . . . . . . . . . . . . . . 173
- 6.10.8 Predefined macro names . . . . . . . . . . . . . . . . 173
- 6.10.9 Pragma operator . . . . . . . . . . . . . . . . . . . 175
- 6.11 Future language directions . . . . . . . . . . . . . . . . . . 177
- 6.11.1 Floating types . . . . . . . . . . . . . . . . . . . . 177
- 6.11.2 Linkages of identifiers . . . . . . . . . . . . . . . . . 177
- 6.11.3 External names . . . . . . . . . . . . . . . . . . . 177
- 6.11.4 Character escape sequences . . . . . . . . . . . . . . 177
- 6.11.5 Storage-class specifiers . . . . . . . . . . . . . . . . 177
- 6.11.6 Function declarators . . . . . . . . . . . . . . . . . 177
- 6.11.7 Function definitions . . . . . . . . . . . . . . . . . . 177
- 6.11.8 Pragma directives . . . . . . . . . . . . . . . . . . 177
- 6.11.9 Predefined macro names . . . . . . . . . . . . . . . . 177
-7. Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
- 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 178
- 7.1.1 Definitions of terms . . . . . . . . . . . . . . . . . . 178
- 7.1.2 Standard headers . . . . . . . . . . . . . . . . . . . 179
- 7.1.3 Reserved identifiers . . . . . . . . . . . . . . . . . . 180
- 7.1.4 Use of library functions . . . . . . . . . . . . . . . . 181
- 7.2 Diagnostics <assert.h> . . . . . . . . . . . . . . . . . . 184
- 7.2.1 Program diagnostics . . . . . . . . . . . . . . . . . 184
- 7.3 Complex arithmetic <complex.h> . . . . . . . . . . . . . . 186
- 7.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . 186
- 7.3.2 Conventions . . . . . . . . . . . . . . . . . . . . . 187
- 7.3.3 Branch cuts . . . . . . . . . . . . . . . . . . . . . 187
- 7.3.4 The CX_LIMITED_RANGE pragma . . . . . . . . . . . 187
- 7.3.5 Trigonometric functions . . . . . . . . . . . . . . . . 188
- 7.3.6 Hyperbolic functions . . . . . . . . . . . . . . . . . 190
- 7.3.7 Exponential and logarithmic functions . . . . . . . . . . 192
- 7.3.8 Power and absolute-value functions . . . . . . . . . . . 193
- 7.3.9 Manipulation functions . . . . . . . . . . . . . . . . 194
- 7.4 Character handling <ctype.h> . . . . . . . . . . . . . . . . 198
- 7.4.1 Character classification functions . . . . . . . . . . . . 198
- 7.4.2 Character case mapping functions . . . . . . . . . . . . 201
- 7.5 Errors <errno.h> . . . . . . . . . . . . . . . . . . . . . 203
- 7.6 Floating-point environment <fenv.h> . . . . . . . . . . . . . 204
- 7.6.1 The FENV_ACCESS pragma . . . . . . . . . . . . . . 206
- 7.6.2 Floating-point exceptions . . . . . . . . . . . . . . . 207
- 7.6.3 Rounding . . . . . . . . . . . . . . . . . . . . . . 210
- 7.6.4 Environment . . . . . . . . . . . . . . . . . . . . 211
- 7.7 Characteristics of floating types <float.h> . . . . . . . . . . . 214
-
-[page v]
-
- 7.8 Format conversion of integer types <inttypes.h> . . . . . . . . 215
- 7.8.1 Macros for format specifiers . . . . . . . . . . . . . . 215
- 7.8.2 Functions for greatest-width integer types . . . . . . . . . 216
- 7.9 Alternative spellings <iso646.h> . . . . . . . . . . . . . . . 219
- 7.10 Sizes of integer types <limits.h> . . . . . . . . . . . . . . 220
- 7.11 Localization <locale.h> . . . . . . . . . . . . . . . . . . 221
- 7.11.1 Locale control . . . . . . . . . . . . . . . . . . . . 222
- 7.11.2 Numeric formatting convention inquiry . . . . . . . . . . 223
- 7.12 Mathematics <math.h> . . . . . . . . . . . . . . . . . . . 229
- 7.12.1 Treatment of error conditions . . . . . . . . . . . . . . 231
- 7.12.2 The FP_CONTRACT pragma . . . . . . . . . . . . . . 233
- 7.12.3 Classification macros . . . . . . . . . . . . . . . . . 233
- 7.12.4 Trigonometric functions . . . . . . . . . . . . . . . . 236
- 7.12.5 Hyperbolic functions . . . . . . . . . . . . . . . . . 238
- 7.12.6 Exponential and logarithmic functions . . . . . . . . . . 240
- 7.12.7 Power and absolute-value functions . . . . . . . . . . . 245
- 7.12.8 Error and gamma functions . . . . . . . . . . . . . . . 247
- 7.12.9 Nearest integer functions . . . . . . . . . . . . . . . . 249
- 7.12.10 Remainder functions . . . . . . . . . . . . . . . . . 252
- 7.12.11 Manipulation functions . . . . . . . . . . . . . . . . 253
- 7.12.12 Maximum, minimum, and positive difference functions . . . 255
- 7.12.13 Floating multiply-add . . . . . . . . . . . . . . . . . 256
- 7.12.14 Comparison macros . . . . . . . . . . . . . . . . . . 257
- 7.13 Nonlocal jumps <setjmp.h> . . . . . . . . . . . . . . . . 260
- 7.13.1 Save calling environment . . . . . . . . . . . . . . . 260
- 7.13.2 Restore calling environment . . . . . . . . . . . . . . 261
- 7.14 Signal handling <signal.h> . . . . . . . . . . . . . . . . . 263
- 7.14.1 Specify signal handling . . . . . . . . . . . . . . . . 264
- 7.14.2 Send signal . . . . . . . . . . . . . . . . . . . . . 265
- 7.15 Alignment <stdalign.h> . . . . . . . . . . . . . . . . . 266
- 7.16 Variable arguments <stdarg.h> . . . . . . . . . . . . . . . 267
- 7.16.1 Variable argument list access macros . . . . . . . . . . . 267
- 7.17 Atomics <stdatomic.h> . . . . . . . . . . . . . . . . . . 271
- 7.17.1 Introduction . . . . . . . . . . . . . . . . . . . . . 271
- 7.17.2 Initialization . . . . . . . . . . . . . . . . . . . . 272
- 7.17.3 Order and consistency . . . . . . . . . . . . . . . . . 273
- 7.17.4 Fences . . . . . . . . . . . . . . . . . . . . . . . 276
- 7.17.5 Lock-free property . . . . . . . . . . . . . . . . . . 277
- 7.17.6 Atomic integer and address types . . . . . . . . . . . . 278
- 7.17.7 Operations on atomic types . . . . . . . . . . . . . . . 280
- 7.17.8 Atomic flag type and operations . . . . . . . . . . . . . 283
- 7.18 Boolean type and values <stdbool.h> . . . . . . . . . . . . 285
- 7.19 Common definitions <stddef.h> . . . . . . . . . . . . . . . 286
- 7.20 Integer types <stdint.h> . . . . . . . . . . . . . . . . . . 288
-
-
-[page vi]
-
- 7.20.1 Integer types . . . . . . . . . . . . . . . . . . . . 288
- 7.20.2 Limits of specified-width integer types . . . . . . . . . . 290
- 7.20.3 Limits of other integer types . . . . . . . . . . . . . . 292
- 7.20.4 Macros for integer constants . . . . . . . . . . . . . . 293
- 7.21 Input/output <stdio.h> . . . . . . . . . . . . . . . . . . 295
- 7.21.1 Introduction . . . . . . . . . . . . . . . . . . . . . 295
- 7.21.2 Streams . . . . . . . . . . . . . . . . . . . . . . 297
- 7.21.3 Files . . . . . . . . . . . . . . . . . . . . . . . . 299
- 7.21.4 Operations on files . . . . . . . . . . . . . . . . . . 301
- 7.21.5 File access functions . . . . . . . . . . . . . . . . . 303
- 7.21.6 Formatted input/output functions . . . . . . . . . . . . 308
- 7.21.7 Character input/output functions . . . . . . . . . . . . . 329
- 7.21.8 Direct input/output functions . . . . . . . . . . . . . . 333
- 7.21.9 File positioning functions . . . . . . . . . . . . . . . 334
- 7.21.10 Error-handling functions . . . . . . . . . . . . . . . . 337
- 7.22 General utilities <stdlib.h> . . . . . . . . . . . . . . . . 339
- 7.22.1 Numeric conversion functions . . . . . . . . . . . . . . 340
- 7.22.2 Pseudo-random sequence generation functions . . . . . . . 345
- 7.22.3 Memory management functions . . . . . . . . . . . . . 346
- 7.22.4 Communication with the environment . . . . . . . . . . 348
- 7.22.5 Searching and sorting utilities . . . . . . . . . . . . . . 352
- 7.22.6 Integer arithmetic functions . . . . . . . . . . . . . . 354
- 7.22.7 Multibyte/wide character conversion functions . . . . . . . 355
- 7.22.8 Multibyte/wide string conversion functions . . . . . . . . 357
- 7.23 String handling <string.h> . . . . . . . . . . . . . . . . . 359
- 7.23.1 String function conventions . . . . . . . . . . . . . . . 359
- 7.23.2 Copying functions . . . . . . . . . . . . . . . . . . 359
- 7.23.3 Concatenation functions . . . . . . . . . . . . . . . . 361
- 7.23.4 Comparison functions . . . . . . . . . . . . . . . . . 362
- 7.23.5 Search functions . . . . . . . . . . . . . . . . . . . 364
- 7.23.6 Miscellaneous functions . . . . . . . . . . . . . . . . 367
- 7.24 Type-generic math <tgmath.h> . . . . . . . . . . . . . . . 369
- 7.25 Threads <threads.h> . . . . . . . . . . . . . . . . . . . 372
- 7.25.1 Introduction . . . . . . . . . . . . . . . . . . . . . 372
- 7.25.2 Initialization functions . . . . . . . . . . . . . . . . . 374
- 7.25.3 Condition variable functions . . . . . . . . . . . . . . 374
- 7.25.4 Mutex functions . . . . . . . . . . . . . . . . . . . 376
- 7.25.5 Thread functions . . . . . . . . . . . . . . . . . . . 379
- 7.25.6 Thread-specific storage functions . . . . . . . . . . . . 381
- 7.25.7 Time functions . . . . . . . . . . . . . . . . . . . . 383
- 7.26 Date and time <time.h> . . . . . . . . . . . . . . . . . . 384
- 7.26.1 Components of time . . . . . . . . . . . . . . . . . 384
- 7.26.2 Time manipulation functions . . . . . . . . . . . . . . 385
- 7.26.3 Time conversion functions . . . . . . . . . . . . . . . 387
-
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-[page vii]
-
- 7.27 Unicode utilities <uchar.h> . . . . . . . . . . . . . . . . . 394
- 7.27.1 Restartable multibyte/wide character conversion functions . . 394
- 7.28 Extended multibyte and wide character utilities <wchar.h> . . . . . 398
- 7.28.1 Introduction . . . . . . . . . . . . . . . . . . . . . 398
- 7.28.2 Formatted wide character input/output functions . . . . . . 399
- 7.28.3 Wide character input/output functions . . . . . . . . . . 417
- 7.28.4 General wide string utilities . . . . . . . . . . . . . . 421
- 7.28.4.1 Wide string numeric conversion functions . . . . . 422
- 7.28.4.2 Wide string copying functions . . . . . . . . . . 426
- 7.28.4.3 Wide string concatenation functions . . . . . . . 428
- 7.28.4.4 Wide string comparison functions . . . . . . . . 429
- 7.28.4.5 Wide string search functions . . . . . . . . . . 431
- 7.28.4.6 Miscellaneous functions . . . . . . . . . . . . 435
- 7.28.5 Wide character time conversion functions . . . . . . . . . 435
- 7.28.6 Extended multibyte/wide character conversion utilities . . . . 436
- 7.28.6.1 Single-byte/wide character conversion functions . . . 437
- 7.28.6.2 Conversion state functions . . . . . . . . . . . 437
- 7.28.6.3 Restartable multibyte/wide character conversion
- functions . . . . . . . . . . . . . . . . . . 438
- 7.28.6.4 Restartable multibyte/wide string conversion
- functions . . . . . . . . . . . . . . . . . . 440
- 7.29 Wide character classification and mapping utilities <wctype.h> . . . 443
- 7.29.1 Introduction . . . . . . . . . . . . . . . . . . . . . 443
- 7.29.2 Wide character classification utilities . . . . . . . . . . . 444
- 7.29.2.1 Wide character classification functions . . . . . . 444
- 7.29.2.2 Extensible wide character classification
- functions . . . . . . . . . . . . . . . . . . 447
- 7.29.3 Wide character case mapping utilities . . . . . . . . . . . 449
- 7.29.3.1 Wide character case mapping functions . . . . . . 449
- 7.29.3.2 Extensible wide character case mapping
- functions . . . . . . . . . . . . . . . . . . 449
- 7.30 Future library directions . . . . . . . . . . . . . . . . . . . 451
- 7.30.1 Complex arithmetic <complex.h> . . . . . . . . . . . 451
- 7.30.2 Character handling <ctype.h> . . . . . . . . . . . . 451
- 7.30.3 Errors <errno.h> . . . . . . . . . . . . . . . . . 451
- 7.30.4 Format conversion of integer types <inttypes.h> . . . . 451
- 7.30.5 Localization <locale.h> . . . . . . . . . . . . . . 451
- 7.30.6 Signal handling <signal.h> . . . . . . . . . . . . . 451
- 7.30.7 Boolean type and values <stdbool.h> . . . . . . . . . 451
- 7.30.8 Integer types <stdint.h> . . . . . . . . . . . . . . 451
- 7.30.9 Input/output <stdio.h> . . . . . . . . . . . . . . . 452
- 7.30.10 General utilities <stdlib.h> . . . . . . . . . . . . . 452
- 7.30.11 String handling <string.h> . . . . . . . . . . . . . 452
-
-
-
-[page viii]
-
- 7.30.12 Extended multibyte and wide character utilities
- <wchar.h> . . . . . . . . . . . . . . . . . . . . 452
- 7.30.13 Wide character classification and mapping utilities
- <wctype.h> . . . . . . . . . . . . . . . . . . . . 452
-Annex A (informative) Language syntax summary . . . . . . . . . . . . 453
- A.1 Lexical grammar . . . . . . . . . . . . . . . . . . . . . . 453
- A.2 Phrase structure grammar . . . . . . . . . . . . . . . . . . . 460
- A.3 Preprocessing directives . . . . . . . . . . . . . . . . . . . 468
-Annex B (informative) Library summary . . . . . . . . . . . . . . . . 470
- B.1 Diagnostics <assert.h> . . . . . . . . . . . . . . . . . . 470
- B.2 Complex <complex.h> . . . . . . . . . . . . . . . . . . . 470
- B.3 Character handling <ctype.h> . . . . . . . . . . . . . . . . 472
- B.4 Errors <errno.h> . . . . . . . . . . . . . . . . . . . . . 472
- B.5 Floating-point environment <fenv.h> . . . . . . . . . . . . . 472
- B.6 Characteristics of floating types <float.h> . . . . . . . . . . . 473
- B.7 Format conversion of integer types <inttypes.h> . . . . . . . . 473
- B.8 Alternative spellings <iso646.h> . . . . . . . . . . . . . . . 474
- B.9 Sizes of integer types <limits.h> . . . . . . . . . . . . . . 474
- B.10 Localization <locale.h> . . . . . . . . . . . . . . . . . . 474
- B.11 Mathematics <math.h> . . . . . . . . . . . . . . . . . . . 474
- B.12 Nonlocal jumps <setjmp.h> . . . . . . . . . . . . . . . . 479
- B.13 Signal handling <signal.h> . . . . . . . . . . . . . . . . . 479
- B.14 Alignment <stdalign.h> . . . . . . . . . . . . . . . . . 480
- B.15 Variable arguments <stdarg.h> . . . . . . . . . . . . . . . 480
- B.16 Atomics <stdatomic.h> . . . . . . . . . . . . . . . . . . 480
- B.17 Boolean type and values <stdbool.h> . . . . . . . . . . . . 482
- B.18 Common definitions <stddef.h> . . . . . . . . . . . . . . . 482
- B.19 Integer types <stdint.h> . . . . . . . . . . . . . . . . . . 482
- B.20 Input/output <stdio.h> . . . . . . . . . . . . . . . . . . 483
- B.21 General utilities <stdlib.h> . . . . . . . . . . . . . . . . 486
- B.22 String handling <string.h> . . . . . . . . . . . . . . . . . 488
- B.23 Type-generic math <tgmath.h> . . . . . . . . . . . . . . . 490
- B.24 Threads <threads.h> . . . . . . . . . . . . . . . . . . . 490
- B.25 Date and time <time.h> . . . . . . . . . . . . . . . . . . 491
- B.26 Unicode utilities <uchar.h> . . . . . . . . . . . . . . . . . 492
- B.27 Extended multibyte/wide character utilities <wchar.h> . . . . . . 492
- B.28 Wide character classification and mapping utilities <wctype.h> . . . 497
-Annex C (informative) Sequence points . . . . . . . . . . . . . . . . . 498
-Annex D (normative) Universal character names for identifiers . . . . . . . 499
-Annex E (informative) Implementation limits . . . . . . . . . . . . . . 501
-Annex F (normative) IEC 60559 floating-point arithmetic . . . . . . . . . . 503
- F.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 503
-
-[page ix]
-
- F.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 503
- F.3 Operators and functions . . . . . . . . . . . . . . . . . . . 504
- F.4 Floating to integer conversion . . . . . . . . . . . . . . . . . 506
- F.5 Binary-decimal conversion . . . . . . . . . . . . . . . . . . 506
- F.6 The return statement . . . . . . . . . . . . . . . . . . . . 507
- F.7 Contracted expressions . . . . . . . . . . . . . . . . . . . . 507
- F.8 Floating-point environment . . . . . . . . . . . . . . . . . . 507
- F.9 Optimization . . . . . . . . . . . . . . . . . . . . . . . . 510
- F.10 Mathematics <math.h> . . . . . . . . . . . . . . . . . . . 513
- F.10.1 Trigonometric functions . . . . . . . . . . . . . . . . 514
- F.10.2 Hyperbolic functions . . . . . . . . . . . . . . . . . 516
- F.10.3 Exponential and logarithmic functions . . . . . . . . . . 516
- F.10.4 Power and absolute value functions . . . . . . . . . . . 519
- F.10.5 Error and gamma functions . . . . . . . . . . . . . . . 521
- F.10.6 Nearest integer functions . . . . . . . . . . . . . . . . 521
- F.10.7 Remainder functions . . . . . . . . . . . . . . . . . 524
- F.10.8 Manipulation functions . . . . . . . . . . . . . . . . 525
- F.10.9 Maximum, minimum, and positive difference functions . . . 525
- F.10.10 Floating multiply-add . . . . . . . . . . . . . . . . . 526
- F.10.11 Comparison macros . . . . . . . . . . . . . . . . . . 526
-Annex G (informative) IEC 60559-compatible complex arithmetic . . . . . . 527
- G.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 527
- G.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 527
- G.3 Conventions . . . . . . . . . . . . . . . . . . . . . . . . 527
- G.4 Conversions . . . . . . . . . . . . . . . . . . . . . . . . 528
- G.4.1 Imaginary types . . . . . . . . . . . . . . . . . . . 528
- G.4.2 Real and imaginary . . . . . . . . . . . . . . . . . . 528
- G.4.3 Imaginary and complex . . . . . . . . . . . . . . . . 528
- G.5 Binary operators . . . . . . . . . . . . . . . . . . . . . . 528
- G.5.1 Multiplicative operators . . . . . . . . . . . . . . . . 529
- G.5.2 Additive operators . . . . . . . . . . . . . . . . . . 532
- G.6 Complex arithmetic <complex.h> . . . . . . . . . . . . . . 532
- G.6.1 Trigonometric functions . . . . . . . . . . . . . . . . 534
- G.6.2 Hyperbolic functions . . . . . . . . . . . . . . . . . 534
- G.6.3 Exponential and logarithmic functions . . . . . . . . . . 538
- G.6.4 Power and absolute-value functions . . . . . . . . . . . 539
- G.7 Type-generic math <tgmath.h> . . . . . . . . . . . . . . . 540
-Annex H (informative) Language independent arithmetic . . . . . . . . . . 541
- H.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 541
- H.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 541
- H.3 Notification . . . . . . . . . . . . . . . . . . . . . . . . 545
-Annex I (informative) Common warnings . . . . . . . . . . . . . . . . 547
-
-
-[page x]
-
-Annex J (informative) Portability issues . . . . . . . . . . . . . . . . . 549
- J.1 Unspecified behavior . . . . . . . . . . . . . . . . . . . . . 549
- J.2 Undefined behavior . . . . . . . . . . . . . . . . . . . . . 552
- J.3 Implementation-defined behavior . . . . . . . . . . . . . . . . 566
- J.4 Locale-specific behavior . . . . . . . . . . . . . . . . . . . 573
- J.5 Common extensions . . . . . . . . . . . . . . . . . . . . . 574
-Annex K (normative) Bounds-checking interfaces . . . . . . . . . . . . . 577
- K.1 Background . . . . . . . . . . . . . . . . . . . . . . . . 577
- K.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 578
- K.3 Library . . . . . . . . . . . . . . . . . . . . . . . . . . 578
- K.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . 578
- K.3.1.1 Standard headers . . . . . . . . . . . . . . . 578
- K.3.1.2 Reserved identifiers . . . . . . . . . . . . . . 579
- K.3.1.3 Use of errno . . . . . . . . . . . . . . . . . 579
- K.3.1.4 Runtime-constraint violations . . . . . . . . . . 579
- K.3.2 Errors <errno.h> . . . . . . . . . . . . . . . . . 580
- K.3.3 Common definitions <stddef.h> . . . . . . . . . . . 580
- K.3.4 Integer types <stdint.h> . . . . . . . . . . . . . . 580
- K.3.5 Input/output <stdio.h> . . . . . . . . . . . . . . . 581
- K.3.5.1 Operations on files . . . . . . . . . . . . . . 581
- K.3.5.2 File access functions . . . . . . . . . . . . . . 583
- K.3.5.3 Formatted input/output functions . . . . . . . . . 586
- K.3.5.4 Character input/output functions . . . . . . . . . 597
- K.3.6 General utilities <stdlib.h> . . . . . . . . . . . . . 599
- K.3.6.1 Runtime-constraint handling . . . . . . . . . . 599
- K.3.6.2 Communication with the environment . . . . . . . 601
- K.3.6.3 Searching and sorting utilities . . . . . . . . . . 602
- K.3.6.4 Multibyte/wide character conversion functions . . . 605
- K.3.6.5 Multibyte/wide string conversion functions . . . . . 606
- K.3.7 String handling <string.h> . . . . . . . . . . . . . 609
- K.3.7.1 Copying functions . . . . . . . . . . . . . . 609
- K.3.7.2 Concatenation functions . . . . . . . . . . . . 612
- K.3.7.3 Search functions . . . . . . . . . . . . . . . 615
- K.3.7.4 Miscellaneous functions . . . . . . . . . . . . 616
- K.3.8 Date and time <time.h> . . . . . . . . . . . . . . . 619
- K.3.8.1 Components of time . . . . . . . . . . . . . . 619
- K.3.8.2 Time conversion functions . . . . . . . . . . . 619
- K.3.9 Extended multibyte and wide character utilities
- <wchar.h> . . . . . . . . . . . . . . . . . . . . 622
- K.3.9.1 Formatted wide character input/output functions . . . 623
- K.3.9.2 General wide string utilities . . . . . . . . . . . 634
- K.3.9.3 Extended multibyte/wide character conversion
- utilities . . . . . . . . . . . . . . . . . . . 642
-
-
-[page xi]
-
-Annex L (normative) Analyzability . . . . . . . . . . . . . . . . . . 647
- L.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 647
- L.2 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 647
- L.3 Requirements . . . . . . . . . . . . . . . . . . . . . . . . 648
-Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . 649
-Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 653
-
-
-
-
-[page xii]
-
- Foreword
-1 ISO (the International Organization for Standardization) and IEC (the International
- Electrotechnical Commission) form the specialized system for worldwide
- standardization. National bodies that are member of ISO or IEC participate in the
- development of International Standards through technical committees established by the
- respective organization to deal with particular fields of technical activity. ISO and IEC
- technical committees collaborate in fields of mutual interest. Other international
- organizations, governmental and non-governmental, in liaison with ISO and IEC, also
- take part in the work.
-2 International Standards are drafted in accordance with the rules given in the ISO/IEC
- Directives, Part 2. This International Standard was drafted in accordance with the fifth
- edition (2004).
-3 In the field of information technology, ISO and IEC have established a joint technical
- committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
- committee are circulated to national bodies for voting. Publication as an International
- Standard requires approval by at least 75% of the national bodies casting a vote.
-4 Attention is drawn to the possibility that some of the elements of this document may be
- the subject of patent rights. ISO and IEC shall not be held responsible for identifying any
- or all such patent rights.
-5 This International Standard was prepared by Joint Technical Committee ISO/IEC JTC 1,
- Information technology, Subcommittee SC 22, Programming languages, their
- environments and system software interfaces. The Working Group responsible for this
- standard (WG 14) maintains a site on the World Wide Web at http://www.open-
- std.org/JTC1/SC22/WG14/ containing additional information relevant to this
- standard such as a Rationale for many of the decisions made during its preparation and a
- log of Defect Reports and Responses.
-6 This third edition cancels and replaces the second edition, ISO/IEC 9899:1999, as
- corrected by ISO/IEC 9899:1999/Cor 1:2001, ISO/IEC 9899:1999/Cor 2:2004, and
- ISO/IEC 9899:1999/Cor 3:2007. Major changes from the previous edition include:
- -- conditional (optional) features (including some that were previously mandatory)
- -- support for multiple threads of execution including an improved memory sequencing
- model, atomic objects, and thread-local storage (<stdatomic.h> and
- <threads.h>)
- -- additional floating-point characteristic macros (<float.h>)
- -- querying and specifying alignment of objects (<stdalign.h>, <stdlib.h>)
- -- Unicode characters and strings (<uchar.h>) (originally specified in
- ISO/IEC TR 19769:2004)
- -- type-generic expressions
-
-
-[page xiii]
-
- -- static assertions
- -- anonymous structures and unions
- -- no-return functions
- -- macros to create complex numbers (<complex.h>)
- -- support for opening files for exclusive access
- -- removed the gets function (<stdio.h>)
- -- added the aligned_alloc, at_quick_exit, and quick_exit functions
- (<stdlib.h>)
- -- (conditional) support for bounds-checking interfaces (originally specified in
- ISO/IEC TR 24731-1:2007)
- -- (conditional) support for analyzability
-7 Major changes in the second edition included:
- -- restricted character set support via digraphs and <iso646.h> (originally specified
- in AMD1)
- -- wide character library support in <wchar.h> and <wctype.h> (originally
- specified in AMD1)
- -- more precise aliasing rules via effective type
- -- restricted pointers
- -- variable length arrays
- -- flexible array members
- -- static and type qualifiers in parameter array declarators
- -- complex (and imaginary) support in <complex.h>
- -- type-generic math macros in <tgmath.h>
- -- the long long int type and library functions
- -- increased minimum translation limits
- -- additional floating-point characteristics in <float.h>
- -- remove implicit int
- -- reliable integer division
- -- universal character names (\u and \U)
- -- extended identifiers
- -- hexadecimal floating-point constants and %a and %A printf/scanf conversion
- specifiers
-
-
-
-[page xiv]
-
--- compound literals
--- designated initializers
--- // comments
--- extended integer types and library functions in <inttypes.h> and <stdint.h>
--- remove implicit function declaration
--- preprocessor arithmetic done in intmax_t/uintmax_t
--- mixed declarations and code
--- new block scopes for selection and iteration statements
--- integer constant type rules
--- integer promotion rules
--- macros with a variable number of arguments
--- the vscanf family of functions in <stdio.h> and <wchar.h>
--- additional math library functions in <math.h>
--- treatment of error conditions by math library functions (math_errhandling)
--- floating-point environment access in <fenv.h>
--- IEC 60559 (also known as IEC 559 or IEEE arithmetic) support
--- trailing comma allowed in enum declaration
--- %lf conversion specifier allowed in printf
--- inline functions
--- the snprintf family of functions in <stdio.h>
--- boolean type in <stdbool.h>
--- idempotent type qualifiers
--- empty macro arguments
--- new structure type compatibility rules (tag compatibility)
--- additional predefined macro names
--- _Pragma preprocessing operator
--- standard pragmas
--- __func__ predefined identifier
--- va_copy macro
--- additional strftime conversion specifiers
--- LIA compatibility annex
-
-
-[page xv]
-
- -- deprecate ungetc at the beginning of a binary file
- -- remove deprecation of aliased array parameters
- -- conversion of array to pointer not limited to lvalues
- -- relaxed constraints on aggregate and union initialization
- -- relaxed restrictions on portable header names
- -- return without expression not permitted in function that returns a value (and vice
- versa)
-8 Annexes D, F, K, and L form a normative part of this standard; annexes A, B, C, E, G, H,
- I, J, the bibliography, and the index are for information only. In accordance with Part 2 of
- the ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples
- are also for information only.
-
-
-
-
-[page xvi]
-
- Introduction
-1 With the introduction of new devices and extended character sets, new features may be
- added to this International Standard. Subclauses in the language and library clauses warn
- implementors and programmers of usages which, though valid in themselves, may
- conflict with future additions.
-2 Certain features are obsolescent, which means that they may be considered for
- withdrawal in future revisions of this International Standard. They are retained because
- of their widespread use, but their use in new implementations (for implementation
- features) or new programs (for language [6.11] or library features [7.30]) is discouraged.
-3 This International Standard is divided into four major subdivisions:
- -- preliminary elements (clauses 1-4);
- -- the characteristics of environments that translate and execute C programs (clause 5);
- -- the language syntax, constraints, and semantics (clause 6);
- -- the library facilities (clause 7).
-4 Examples are provided to illustrate possible forms of the constructions described.
- Footnotes are provided to emphasize consequences of the rules described in that
- subclause or elsewhere in this International Standard. References are used to refer to
- other related subclauses. Recommendations are provided to give advice or guidance to
- implementors. Annexes provide additional information and summarize the information
- contained in this International Standard. A bibliography lists documents that were
- referred to during the preparation of the standard.
-5 The language clause (clause 6) is derived from ''The C Reference Manual''.
-6 The library clause (clause 7) is based on the 1984 /usr/group Standard.
-
-
-
-
-[page xvii]
-
-
-
-[page xviii]
-
-
-
- Programming languages -- C
-
-
-
- 1. Scope
-1 This International Standard specifies the form and establishes the interpretation of
- programs written in the C programming language.1) It specifies
- -- the representation of C programs;
- -- the syntax and constraints of the C language;
- -- the semantic rules for interpreting C programs;
- -- the representation of input data to be processed by C programs;
- -- the representation of output data produced by C programs;
- -- the restrictions and limits imposed by a conforming implementation of C.
-2 This International Standard does not specify
- -- the mechanism by which C programs are transformed for use by a data-processing
- system;
- -- the mechanism by which C programs are invoked for use by a data-processing
- system;
- -- the mechanism by which input data are transformed for use by a C program;
- -- the mechanism by which output data are transformed after being produced by a C
- program;
- -- the size or complexity of a program and its data that will exceed the capacity of any
- specific data-processing system or the capacity of a particular processor;
- -- all minimal requirements of a data-processing system that is capable of supporting a
- conforming implementation.
-
-
- 1) This International Standard is designed to promote the portability of C programs among a variety of
- data-processing systems. It is intended for use by implementors and programmers.
-
-[page 1]
-
-
- 2. Normative references
-1 The following referenced documents are indispensable for the application of this
- document. For dated references, only the edition cited applies. For undated references,
- the latest edition of the referenced document (including any amendments) applies.
-2 ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and symbols for
- use in the physical sciences and technology.
-3 ISO/IEC 646, Information technology -- ISO 7-bit coded character set for information
- interchange.
-4 ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1: Fundamental
- terms.
-5 ISO 4217, Codes for the representation of currencies and funds.
-6 ISO 8601, Data elements and interchange formats -- Information interchange --
- Representation of dates and times.
-7 ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded
- Character Set (UCS).
-8 IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems (previously
- designated IEC 559:1989).
-
-
-
-
-[page 2]
-
-
- 3. Terms, definitions, and symbols
-1 For the purposes of this International Standard, the following definitions apply. Other
- terms are defined where they appear in italic type or on the left side of a syntax rule.
- Terms explicitly defined in this International Standard are not to be presumed to refer
- implicitly to similar terms defined elsewhere. Terms not defined in this International
- Standard are to be interpreted according to ISO/IEC 2382-1. Mathematical symbols not
- defined in this International Standard are to be interpreted according to ISO 31-11.
- 3.1
-1 access
- <execution-time action> to read or modify the value of an object
-2 NOTE 1 Where only one of these two actions is meant, ''read'' or ''modify'' is used.
-
-3 NOTE 2 ''Modify'' includes the case where the new value being stored is the same as the previous value.
-
-4 NOTE 3 Expressions that are not evaluated do not access objects.
-
- 3.2
-1 alignment
- requirement that objects of a particular type be located on storage boundaries with
- addresses that are particular multiples of a byte address
- 3.3
-1 argument
- actual argument
- actual parameter (deprecated)
- expression in the comma-separated list bounded by the parentheses in a function call
- expression, or a sequence of preprocessing tokens in the comma-separated list bounded
- by the parentheses in a function-like macro invocation
- 3.4
-1 behavior
- external appearance or action
- 3.4.1
-1 implementation-defined behavior
- unspecified behavior where each implementation documents how the choice is made
-2 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
- when a signed integer is shifted right.
-
- 3.4.2
-1 locale-specific behavior
- behavior that depends on local conventions of nationality, culture, and language that each
- implementation documents
-
-
-[page 3]
-
-2 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
- characters other than the 26 lowercase Latin letters.
-
- 3.4.3
-1 undefined behavior
- behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
- for which this International Standard imposes no requirements
-2 NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable
- results, to behaving during translation or program execution in a documented manner characteristic of the
- environment (with or without the issuance of a diagnostic message), to terminating a translation or
- execution (with the issuance of a diagnostic message).
-
-3 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
-
- 3.4.4
-1 unspecified behavior
- use of an unspecified value, or other behavior where this International Standard provides
- two or more possibilities and imposes no further requirements on which is chosen in any
- instance
-2 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
- evaluated.
-
- 3.5
-1 bit
- unit of data storage in the execution environment large enough to hold an object that may
- have one of two values
-2 NOTE It need not be possible to express the address of each individual bit of an object.
-
- 3.6
-1 byte
- addressable unit of data storage large enough to hold any member of the basic character
- set of the execution environment
-2 NOTE 1 It is possible to express the address of each individual byte of an object uniquely.
-
-3 NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
- defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order
- bit.
-
- 3.7
-1 character
- <abstract> member of a set of elements used for the organization, control, or
- representation of data
- 3.7.1
-1 character
- single-byte character
- <C> bit representation that fits in a byte
-[page 4]
-
- 3.7.2
-1 multibyte character
- sequence of one or more bytes representing a member of the extended character set of
- either the source or the execution environment
-2 NOTE The extended character set is a superset of the basic character set.
-
- 3.7.3
-1 wide character
- bit representation that fits in an object of type wchar_t, capable of representing any
- character in the current locale
- 3.8
-1 constraint
- restriction, either syntactic or semantic, by which the exposition of language elements is
- to be interpreted
- 3.9
-1 correctly rounded result
- representation in the result format that is nearest in value, subject to the current rounding
- mode, to what the result would be given unlimited range and precision
- 3.10
-1 diagnostic message
- message belonging to an implementation-defined subset of the implementation's message
- output
- 3.11
-1 forward reference
- reference to a later subclause of this International Standard that contains additional
- information relevant to this subclause
- 3.12
-1 implementation
- particular set of software, running in a particular translation environment under particular
- control options, that performs translation of programs for, and supports execution of
- functions in, a particular execution environment
- 3.13
-1 implementation limit
- restriction imposed upon programs by the implementation
- 3.14
-1 memory location
- either an object of scalar type, or a maximal sequence of adjacent bit-fields all having
- nonzero width
-
-[page 5]
-
-2 NOTE 1 Two threads of execution can update and access separate memory locations without interfering
- with each other.
-
-3 NOTE 2 A bit-field and an adjacent non-bit-field member are in separate memory locations. The same
- applies to two bit-fields, if one is declared inside a nested structure declaration and the other is not, or if the
- two are separated by a zero-length bit-field declaration, or if they are separated by a non-bit-field member
- declaration. It is not safe to concurrently update two non-atomic bit-fields in the same structure if all
- members declared between them are also (non-zero-length) bit-fields, no matter what the sizes of those
- intervening bit-fields happen to be.
-
-4 EXAMPLE A structure declared as
- struct {
- char a;
- int b:5, c:11, :0, d:8;
- struct { int ee:8; } e;
- }
- contains four separate memory locations: The member a, and bit-fields d and e.ee are each separate
- memory locations, and can be modified concurrently without interfering with each other. The bit-fields b
- and c together constitute the fourth memory location. The bit-fields b and c cannot be concurrently
- modified, but b and a, for example, can be.
-
- 3.15
-1 object
- region of data storage in the execution environment, the contents of which can represent
- values
-2 NOTE When referenced, an object may be interpreted as having a particular type; see 6.3.2.1.
-
- 3.16
-1 parameter
- formal parameter
- formal argument (deprecated)
- object declared as part of a function declaration or definition that acquires a value on
- entry to the function, or an identifier from the comma-separated list bounded by the
- parentheses immediately following the macro name in a function-like macro definition
- 3.17
-1 recommended practice
- specification that is strongly recommended as being in keeping with the intent of the
- standard, but that may be impractical for some implementations
- 3.18
-1 runtime-constraint
- requirement on a program when calling a library function
-2 NOTE 1 Despite the similar terms, a runtime-constraint is not a kind of constraint as defined by 3.8, and
- need not be diagnosed at translation time.
-
-3 NOTE 2 Implementations that support the extensions in annex K are required to verify that the runtime-
- constraints for a library function are not violated by the program; see K.3.1.4.
-
-[page 6]
-
- 3.19
-1 value
- precise meaning of the contents of an object when interpreted as having a specific type
- 3.19.1
-1 implementation-defined value
- unspecified value where each implementation documents how the choice is made
- 3.19.2
-1 indeterminate value
- either an unspecified value or a trap representation
- 3.19.3
-1 unspecified value
- valid value of the relevant type where this International Standard imposes no
- requirements on which value is chosen in any instance
-2 NOTE An unspecified value cannot be a trap representation.
-
- 3.19.4
-1 trap representation
- an object representation that need not represent a value of the object type
- 3.19.5
-1 perform a trap
- interrupt execution of the program such that no further operations are performed
-2 NOTE In this International Standard, when the word ''trap'' is not immediately followed by
- ''representation'', this is the intended usage.2)
-
- 3.20
-1 [^ x^]
- ceiling of x: the least integer greater than or equal to x
-2 EXAMPLE [^2.4^] is 3, [^-2.4^] is -2.
-
- 3.21
-1 [_ x_]
- floor of x: the greatest integer less than or equal to x
-2 EXAMPLE [_2.4_] is 2, [_-2.4_] is -3.
-
-
-
-
- 2) For example, ''Trapping or stopping (if supported) is disabled...'' (F.8.2). Note that fetching a trap
- representation might perform a trap but is not required to (see 6.2.6.1).
-
-[page 7]
-
-
- 4. Conformance
-1 In this International Standard, ''shall'' is to be interpreted as a requirement on an
- implementation or on a program; conversely, ''shall not'' is to be interpreted as a
- prohibition.
-2 If a ''shall'' or ''shall not'' requirement that appears outside of a constraint or runtime-
- constraint is violated, the behavior is undefined. Undefined behavior is otherwise
- indicated in this International Standard by the words ''undefined behavior'' or by the
- omission of any explicit definition of behavior. There is no difference in emphasis among
- these three; they all describe ''behavior that is undefined''.
-3 A program that is correct in all other aspects, operating on correct data, containing
- unspecified behavior shall be a correct program and act in accordance with 5.1.2.3.
-4 The implementation shall not successfully translate a preprocessing translation unit
- containing a #error preprocessing directive unless it is part of a group skipped by
- conditional inclusion.
-5 A strictly conforming program shall use only those features of the language and library
- specified in this International Standard.3) It shall not produce output dependent on any
- unspecified, undefined, or implementation-defined behavior, and shall not exceed any
- minimum implementation limit.
-6 The two forms of conforming implementation are hosted and freestanding. A conforming
- hosted implementation shall accept any strictly conforming program. A conforming
- freestanding implementation shall accept any strictly conforming program that does not
- use complex types and in which the use of the features specified in the library clause
- (clause 7) is confined to the contents of the standard headers <float.h>,
- <iso646.h>, <limits.h>, <stdalign.h>, <stdarg.h>, <stdbool.h>,
- <stddef.h>, and <stdint.h>. A conforming implementation may have extensions
- (including additional library functions), provided they do not alter the behavior of any
- strictly conforming program.4)
-
-
-
- 3) A strictly conforming program can use conditional features (see 6.10.8.3) provided the use is guarded
- by an appropriate conditional inclusion preprocessing directive using the related macro. For example:
- #ifdef __STDC_IEC_559__ /* FE_UPWARD defined */
- /* ... */
- fesetround(FE_UPWARD);
- /* ... */
- #endif
-
- 4) This implies that a conforming implementation reserves no identifiers other than those explicitly
- reserved in this International Standard.
-
-[page 8]
-
-7 A conforming program is one that is acceptable to a conforming implementation.5)
-8 An implementation shall be accompanied by a document that defines all implementation-
- defined and locale-specific characteristics and all extensions.
- Forward references: conditional inclusion (6.10.1), error directive (6.10.5),
- characteristics of floating types <float.h> (7.7), alternative spellings <iso646.h>
- (7.9), sizes of integer types <limits.h> (7.10), alignment <stdalign.h> (7.15),
- variable arguments <stdarg.h> (7.16), boolean type and values <stdbool.h>
- (7.18), common definitions <stddef.h> (7.19), integer types <stdint.h> (7.20).
-
-
-
-
- 5) Strictly conforming programs are intended to be maximally portable among conforming
- implementations. Conforming programs may depend upon nonportable features of a conforming
- implementation.
-
-[page 9]
-
-
- 5. Environment
-1 An implementation translates C source files and executes C programs in two data-
- processing-system environments, which will be called the translation environment and
- the execution environment in this International Standard. Their characteristics define and
- constrain the results of executing conforming C programs constructed according to the
- syntactic and semantic rules for conforming implementations.
- Forward references: In this clause, only a few of many possible forward references
- have been noted.
- 5.1 Conceptual models
- 5.1.1 Translation environment
- 5.1.1.1 Program structure
-1 A C program need not all be translated at the same time. The text of the program is kept
- in units called source files, (or preprocessing files) in this International Standard. A
- source file together with all the headers and source files included via the preprocessing
- directive #include is known as a preprocessing translation unit. After preprocessing, a
- preprocessing translation unit is called a translation unit. Previously translated translation
- units may be preserved individually or in libraries. The separate translation units of a
- program communicate by (for example) calls to functions whose identifiers have external
- linkage, manipulation of objects whose identifiers have external linkage, or manipulation
- of data files. Translation units may be separately translated and then later linked to
- produce an executable program.
- Forward references: linkages of identifiers (6.2.2), external definitions (6.9),
- preprocessing directives (6.10).
- 5.1.1.2 Translation phases
-1 The precedence among the syntax rules of translation is specified by the following
- phases.6)
- 1. Physical source file multibyte characters are mapped, in an implementation-
- defined manner, to the source character set (introducing new-line characters for
- end-of-line indicators) if necessary. Trigraph sequences are replaced by
- corresponding single-character internal representations.
-
-
-
- 6) Implementations shall behave as if these separate phases occur, even though many are typically folded
- together in practice. Source files, translation units, and translated translation units need not
- necessarily be stored as files, nor need there be any one-to-one correspondence between these entities
- and any external representation. The description is conceptual only, and does not specify any
- particular implementation.
-
-[page 10]
-
- 2. Each instance of a backslash character (\) immediately followed by a new-line
- character is deleted, splicing physical source lines to form logical source lines.
- Only the last backslash on any physical source line shall be eligible for being part
- of such a splice. A source file that is not empty shall end in a new-line character,
- which shall not be immediately preceded by a backslash character before any such
- splicing takes place.
- 3. The source file is decomposed into preprocessing tokens7) and sequences of
- white-space characters (including comments). A source file shall not end in a
- partial preprocessing token or in a partial comment. Each comment is replaced by
- one space character. New-line characters are retained. Whether each nonempty
- sequence of white-space characters other than new-line is retained or replaced by
- one space character is implementation-defined.
- 4. Preprocessing directives are executed, macro invocations are expanded, and
- _Pragma unary operator expressions are executed. If a character sequence that
- matches the syntax of a universal character name is produced by token
- concatenation (6.10.3.3), the behavior is undefined. A #include preprocessing
- directive causes the named header or source file to be processed from phase 1
- through phase 4, recursively. All preprocessing directives are then deleted.
- 5. Each source character set member and escape sequence in character constants and
- string literals is converted to the corresponding member of the execution character
- set; if there is no corresponding member, it is converted to an implementation-
- defined member other than the null (wide) character.8)
- 6. Adjacent string literal tokens are concatenated.
- 7. White-space characters separating tokens are no longer significant. Each
- preprocessing token is converted into a token. The resulting tokens are
- syntactically and semantically analyzed and translated as a translation unit.
- 8. All external object and function references are resolved. Library components are
- linked to satisfy external references to functions and objects not defined in the
- current translation. All such translator output is collected into a program image
- which contains information needed for execution in its execution environment.
-Forward references: universal character names (6.4.3), lexical elements (6.4),
-preprocessing directives (6.10), trigraph sequences (5.2.1.1), external definitions (6.9).
-
-
-
-7) As described in 6.4, the process of dividing a source file's characters into preprocessing tokens is
- context-dependent. For example, see the handling of < within a #include preprocessing directive.
-8) An implementation need not convert all non-corresponding source characters to the same execution
- character.
-
-[page 11]
-
- 5.1.1.3 Diagnostics
-1 A conforming implementation shall produce at least one diagnostic message (identified in
- an implementation-defined manner) if a preprocessing translation unit or translation unit
- contains a violation of any syntax rule or constraint, even if the behavior is also explicitly
- specified as undefined or implementation-defined. Diagnostic messages need not be
- produced in other circumstances.9)
-2 EXAMPLE An implementation shall issue a diagnostic for the translation unit:
- char i;
- int i;
- because in those cases where wording in this International Standard describes the behavior for a construct
- as being both a constraint error and resulting in undefined behavior, the constraint error shall be diagnosed.
-
- 5.1.2 Execution environments
-1 Two execution environments are defined: freestanding and hosted. In both cases,
- program startup occurs when a designated C function is called by the execution
- environment. All objects with static storage duration shall be initialized (set to their
- initial values) before program startup. The manner and timing of such initialization are
- otherwise unspecified. Program termination returns control to the execution
- environment.
- Forward references: storage durations of objects (6.2.4), initialization (6.7.9).
- 5.1.2.1 Freestanding environment
-1 In a freestanding environment (in which C program execution may take place without any
- benefit of an operating system), the name and type of the function called at program
- startup are implementation-defined. Any library facilities available to a freestanding
- program, other than the minimal set required by clause 4, are implementation-defined.
-2 The effect of program termination in a freestanding environment is implementation-
- defined.
- 5.1.2.2 Hosted environment
-1 A hosted environment need not be provided, but shall conform to the following
- specifications if present.
-
-
-
-
- 9) The intent is that an implementation should identify the nature of, and where possible localize, each
- violation. Of course, an implementation is free to produce any number of diagnostics as long as a
- valid program is still correctly translated. It may also successfully translate an invalid program.
-
-[page 12]
-
- 5.1.2.2.1 Program startup
-1 The function called at program startup is named main. The implementation declares no
- prototype for this function. It shall be defined with a return type of int and with no
- parameters:
- int main(void) { /* ... */ }
- or with two parameters (referred to here as argc and argv, though any names may be
- used, as they are local to the function in which they are declared):
- int main(int argc, char *argv[]) { /* ... */ }
- or equivalent;10) or in some other implementation-defined manner.
-2 If they are declared, the parameters to the main function shall obey the following
- constraints:
- -- The value of argc shall be nonnegative.
- -- argv[argc] shall be a null pointer.
- -- If the value of argc is greater than zero, the array members argv[0] through
- argv[argc-1] inclusive shall contain pointers to strings, which are given
- implementation-defined values by the host environment prior to program startup. The
- intent is to supply to the program information determined prior to program startup
- from elsewhere in the hosted environment. If the host environment is not capable of
- supplying strings with letters in both uppercase and lowercase, the implementation
- shall ensure that the strings are received in lowercase.
- -- If the value of argc is greater than zero, the string pointed to by argv[0]
- represents the program name; argv[0][0] shall be the null character if the
- program name is not available from the host environment. If the value of argc is
- greater than one, the strings pointed to by argv[1] through argv[argc-1]
- represent the program parameters.
- -- The parameters argc and argv and the strings pointed to by the argv array shall
- be modifiable by the program, and retain their last-stored values between program
- startup and program termination.
- 5.1.2.2.2 Program execution
-1 In a hosted environment, a program may use all the functions, macros, type definitions,
- and objects described in the library clause (clause 7).
-
-
-
-
- 10) Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as
- char ** argv, and so on.
-
-[page 13]
-
- 5.1.2.2.3 Program termination
-1 If the return type of the main function is a type compatible with int, a return from the
- initial call to the main function is equivalent to calling the exit function with the value
- returned by the main function as its argument;11) reaching the } that terminates the
- main function returns a value of 0. If the return type is not compatible with int, the
- termination status returned to the host environment is unspecified.
- Forward references: definition of terms (7.1.1), the exit function (7.22.4.4).
- 5.1.2.3 Program execution
-1 The semantic descriptions in this International Standard describe the behavior of an
- abstract machine in which issues of optimization are irrelevant.
-2 Accessing a volatile object, modifying an object, modifying a file, or calling a function
- that does any of those operations are all side effects,12) which are changes in the state of
- the execution environment. Evaluation of an expression in general includes both value
- computations and initiation of side effects. Value computation for an lvalue expression
- includes determining the identity of the designated object.
-3 Sequenced before is an asymmetric, transitive, pair-wise relation between evaluations
- executed by a single thread, which induces a partial order among those evaluations.
- Given any two evaluations A and B, if A is sequenced before B, then the execution of A
- shall precede the execution of B. (Conversely, if A is sequenced before B, then B is
- sequenced after A.) If A is not sequenced before or after B, then A and B are
- unsequenced. Evaluations A and B are indeterminately sequenced when A is sequenced
- either before or after B, but it is unspecified which.13) The presence of a sequence point
- between the evaluation of expressions A and B implies that every value computation and
- side effect associated with A is sequenced before every value computation and side effect
- associated with B. (A summary of the sequence points is given in annex C.)
-4 In the abstract machine, all expressions are evaluated as specified by the semantics. An
- actual implementation need not evaluate part of an expression if it can deduce that its
- value is not used and that no needed side effects are produced (including any caused by
-
- 11) In accordance with 6.2.4, the lifetimes of objects with automatic storage duration declared in main
- will have ended in the former case, even where they would not have in the latter.
- 12) The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status
- flags and control modes. Floating-point operations implicitly set the status flags; modes affect result
- values of floating-point operations. Implementations that support such floating-point state are
- required to regard changes to it as side effects -- see annex F for details. The floating-point
- environment library <fenv.h> provides a programming facility for indicating when these side
- effects matter, freeing the implementations in other cases.
- 13) The executions of unsequenced evaluations can interleave. Indeterminately sequenced evaluations
- cannot interleave, but can be executed in any order.
-
-[page 14]
-
- calling a function or accessing a volatile object).
-5 When the processing of the abstract machine is interrupted by receipt of a signal, the
- values of objects that are neither lock-free atomic objects nor of type volatile
- sig_atomic_t are unspecified, and the value of any object that is modified by the
- handler that is neither a lock-free atomic object nor of type volatile
- sig_atomic_t becomes undefined.
-6 The least requirements on a conforming implementation are:
- -- Accesses to volatile objects are evaluated strictly according to the rules of the abstract
- machine.
- -- At program termination, all data written into files shall be identical to the result that
- execution of the program according to the abstract semantics would have produced.
- -- The input and output dynamics of interactive devices shall take place as specified in
- 7.21.3. The intent of these requirements is that unbuffered or line-buffered output
- appear as soon as possible, to ensure that prompting messages actually appear prior to
- a program waiting for input.
- This is the observable behavior of the program.
-7 What constitutes an interactive device is implementation-defined.
-8 More stringent correspondences between abstract and actual semantics may be defined by
- each implementation.
-9 EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual
- semantics: at every sequence point, the values of the actual objects would agree with those specified by the
- abstract semantics. The keyword volatile would then be redundant.
-10 Alternatively, an implementation might perform various optimizations within each translation unit, such
- that the actual semantics would agree with the abstract semantics only when making function calls across
- translation unit boundaries. In such an implementation, at the time of each function entry and function
- return where the calling function and the called function are in different translation units, the values of all
- externally linked objects and of all objects accessible via pointers therein would agree with the abstract
- semantics. Furthermore, at the time of each such function entry the values of the parameters of the called
- function and of all objects accessible via pointers therein would agree with the abstract semantics. In this
- type of implementation, objects referred to by interrupt service routines activated by the signal function
- would require explicit specification of volatile storage, as well as other implementation-defined
- restrictions.
-
-11 EXAMPLE 2 In executing the fragment
- char c1, c2;
- /* ... */
- c1 = c1 + c2;
- the ''integer promotions'' require that the abstract machine promote the value of each variable to int size
- and then add the two ints and truncate the sum. Provided the addition of two chars can be done without
- overflow, or with overflow wrapping silently to produce the correct result, the actual execution need only
- produce the same result, possibly omitting the promotions.
-
-[page 15]
-
-12 EXAMPLE 3 Similarly, in the fragment
- float f1, f2;
- double d;
- /* ... */
- f1 = f2 * d;
- the multiplication may be executed using single-precision arithmetic if the implementation can ascertain
- that the result would be the same as if it were executed using double-precision arithmetic (for example, if d
- were replaced by the constant 2.0, which has type double).
-
-13 EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate
- semantics. Values are independent of whether they are represented in a register or in memory. For
- example, an implicit spilling of a register is not permitted to alter the value. Also, an explicit store and load
- is required to round to the precision of the storage type. In particular, casts and assignments are required to
- perform their specified conversion. For the fragment
- double d1, d2;
- float f;
- d1 = f = expression;
- d2 = (float) expression;
- the values assigned to d1 and d2 are required to have been converted to float.
-
-14 EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in
- precision as well as range. The implementation cannot generally apply the mathematical associative rules
- for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of
- overflow and underflow. Likewise, implementations cannot generally replace decimal constants in order to
- rearrange expressions. In the following fragment, rearrangements suggested by mathematical rules for real
- numbers are often not valid (see F.9).
- double x, y, z;
- /* ... */
- x = (x * y) * z; // not equivalent to x *= y * z;
- z = (x - y) + y ; // not equivalent to z = x;
- z = x + x * y; // not equivalent to z = x * (1.0 + y);
- y = x / 5.0; // not equivalent to y = x * 0.2;
-
-15 EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
- int a, b;
- /* ... */
- a = a + 32760 + b + 5;
- the expression statement behaves exactly the same as
- a = (((a + 32760) + b) + 5);
- due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is
- next added to b, and that result is then added to 5 which results in the value assigned to a. On a machine in
- which overflows produce an explicit trap and in which the range of values representable by an int is
- [-32768, +32767], the implementation cannot rewrite this expression as
- a = ((a + b) + 32765);
- since if the values for a and b were, respectively, -32754 and -15, the sum a + b would produce a trap
- while the original expression would not; nor can the expression be rewritten either as
-
-
-[page 16]
-
- a = ((a + 32765) + b);
- or
- a = (a + (b + 32765));
- since the values for a and b might have been, respectively, 4 and -8 or -17 and 12. However, on a machine
- in which overflow silently generates some value and where positive and negative overflows cancel, the
- above expression statement can be rewritten by the implementation in any of the above ways because the
- same result will occur.
-
-16 EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the
- following fragment
- #include <stdio.h>
- int sum;
- char *p;
- /* ... */
- sum = sum * 10 - '0' + (*p++ = getchar());
- the expression statement is grouped as if it were written as
- sum = (((sum * 10) - '0') + ((*(p++)) = (getchar())));
- but the actual increment of p can occur at any time between the previous sequence point and the next
- sequence point (the ;), and the call to getchar can occur at any point prior to the need of its returned
- value.
-
- Forward references: expressions (6.5), type qualifiers (6.7.3), statements (6.8), the
- signal function (7.14), files (7.21.3).
- 5.1.2.4 Multi-threaded executions and data races
-1 Under a hosted implementation, a program can have more than one thread of execution
- (or thread) running concurrently. The execution of each thread proceeds as defined by
- the remainder of this standard. The execution of the entire program consists of an
- execution of all of its threads.14) Under a freestanding implementation, it is
- implementation-defined whether a program can have more than one thread of execution.
-2 The value of an object visible to a thread T at a particular point is the initial value of the
- object, a value stored in the object by T , or a value stored in the object by another thread,
- according to the rules below.
-3 NOTE 1 In some cases, there may instead be undefined behavior. Much of this section is motivated by
- the desire to support atomic operations with explicit and detailed visibility constraints. However, it also
- implicitly supports a simpler view for more restricted programs.
-
-4 Two expression evaluations conflict if one of them modifies a memory location and the
- other one accesses or modifies the same memory location.
-
-
-
-
- 14) The execution can usually be viewed as an interleaving of all of the threads. However, some kinds of
- atomic operations, for example, allow executions inconsistent with a simple interleaving as described
- below.
-
-[page 17]
-
-5 The library defines a number of atomic operations (7.17) and operations on mutexes
- (7.25.4) that are specially identified as synchronization operations. These operations play
- a special role in making assignments in one thread visible to another. A synchronization
- operation on one or more memory locations is either an acquire operation, a release
- operation, both an acquire and release operation, or a consume operation. A
- synchronization operation without an associated memory location is a fence and can be
- either an acquire fence, a release fence, or both an acquire and release fence. In addition,
- there are relaxed atomic operations, which are not synchronization operations, and
- atomic read-modify-write operations, which have special characteristics.
-6 NOTE 2 For example, a call that acquires a mutex will perform an acquire operation on the locations
- composing the mutex. Correspondingly, a call that releases the same mutex will perform a release
- operation on those same locations. Informally, performing a release operation on A forces prior side effects
- on other memory locations to become visible to other threads that later perform an acquire or consume
- operation on A. We do not include relaxed atomic operations as synchronization operations although, like
- synchronization operations, they cannot contribute to data races.
-
-7 All modifications to a particular atomic object M occur in some particular total order,
- called the modification order of M. If A and B are modifications of an atomic object M,
- and A happens before B, then A shall precede B in the modification order of M, which is
- defined below.
-8 NOTE 3 This states that the modification orders must respect the ''happens before'' relation.
-
-9 NOTE 4 There is a separate order for each atomic object. There is no requirement that these can be
- combined into a single total order for all objects. In general this will be impossible since different threads
- may observe modifications to different variables in inconsistent orders.
-
-10 A release sequence on an atomic object M is a maximal contiguous sub-sequence of side
- effects in the modification order of M, where the first operation is a release and every
- subsequent operation either is performed by the same thread that performed the release or
- is an atomic read-modify-write operation.
-11 Certain library calls synchronize with other library calls performed by another thread. In
- particular, an atomic operation A that performs a release operation on an object M
- synchronizes with an atomic operation B that performs an acquire operation on M and
- reads a value written by any side effect in the release sequence headed by A.
-12 NOTE 5 Except in the specified cases, reading a later value does not necessarily ensure visibility as
- described below. Such a requirement would sometimes interfere with efficient implementation.
-
-13 NOTE 6 The specifications of the synchronization operations define when one reads the value written by
- another. For atomic variables, the definition is clear. All operations on a given mutex occur in a single total
- order. Each mutex acquisition ''reads the value written'' by the last mutex release.
-
-14 An evaluation A carries a dependency 15) to an evaluation B if:
-
-
- 15) The ''carries a dependency'' relation is a subset of the ''sequenced before'' relation, and is similarly
- strictly intra-thread.
-
-[page 18]
-
- -- the value of A is used as an operand of B, unless:
- o B is an invocation of the kill_dependency macro,
-
- o A is the left operand of a && or || operator,
-
- o A is the left operand of a ? : operator, or
-
- o A is the left operand of a , operator;
- or
- -- A writes a scalar object or bit-field M, B reads from M the value written by A, and A
- is sequenced before B, or
- -- for some evaluation X, A carries a dependency to X and X carries a dependency to B.
-15 An evaluation A is dependency-ordered before16) an evaluation B if:
- -- A performs a release operation on an atomic object M, and B performs a consume
- operation on M and reads a value written by any side effect in the release sequence
- headed by A, or
- -- for some evaluation X, A is dependency-ordered before X and X carries a
- dependency to B.
-16 An evaluation A inter-thread happens before an evaluation B if A synchronizes with B, A
- is dependency-ordered before B, or, for some evaluation X:
- -- A synchronizes with X and X is sequenced before B,
- -- A is sequenced before X and X inter-thread happens before B, or
- -- A inter-thread happens before X and X inter-thread happens before B.
-17 NOTE 7 The ''inter-thread happens before'' relation describes arbitrary concatenations of ''sequenced
- before'', ''synchronizes with'', and ''dependency-ordered before'' relationships, with two exceptions. The
- first exception is that a concatenation is not permitted to end with ''dependency-ordered before'' followed
- by ''sequenced before''. The reason for this limitation is that a consume operation participating in a
- ''dependency-ordered before'' relationship provides ordering only with respect to operations to which this
- consume operation actually carries a dependency. The reason that this limitation applies only to the end of
- such a concatenation is that any subsequent release operation will provide the required ordering for a prior
- consume operation. The second exception is that a concatenation is not permitted to consist entirely of
- ''sequenced before''. The reasons for this limitation are (1) to permit ''inter-thread happens before'' to be
- transitively closed and (2) the ''happens before'' relation, defined below, provides for relationships
- consisting entirely of ''sequenced before''.
-
-18 An evaluation A happens before an evaluation B if A is sequenced before B or A inter-
- thread happens before B.
-
-
-
- 16) The ''dependency-ordered before'' relation is analogous to the ''synchronizes with'' relation, but uses
- release/consume in place of release/acquire.
-
-[page 19]
-
-19 A visible side effect A on an object M with respect to a value computation B of M
- satisfies the conditions:
- -- A happens before B, and
- -- there is no other side effect X to M such that A happens before X and X happens
- before B.
- The value of a non-atomic scalar object M, as determined by evaluation B, shall be the
- value stored by the visible side effect A.
-20 NOTE 8 If there is ambiguity about which side effect to a non-atomic object is visible, then there is a data
- race and the behavior is undefined.
-
-21 NOTE 9 This states that operations on ordinary variables are not visibly reordered. This is not actually
- detectable without data races, but it is necessary to ensure that data races, as defined here, and with suitable
- restrictions on the use of atomics, correspond to data races in a simple interleaved (sequentially consistent)
- execution.
-
-22 The visible sequence of side effects on an atomic object M, with respect to a value
- computation B of M, is a maximal contiguous sub-sequence of side effects in the
- modification order of M, where the first side effect is visible with respect to B, and for
- every subsequent side effect, it is not the case that B happens before it. The value of an
- atomic object M, as determined by evaluation B, shall be the value stored by some
- operation in the visible sequence of M with respect to B. Furthermore, if a value
- computation A of an atomic object M happens before a value computation B of M, and
- the value computed by A corresponds to the value stored by side effect X, then the value
- computed by B shall either equal the value computed by A, or be the value stored by side
- effect Y , where Y follows X in the modification order of M.
-23 NOTE 10 This effectively disallows compiler reordering of atomic operations to a single object, even if
- both operations are ''relaxed'' loads. By doing so, we effectively make the ''cache coherence'' guarantee
- provided by most hardware available to C atomic operations.
-
-24 NOTE 11 The visible sequence depends on the ''happens before'' relation, which in turn depends on the
- values observed by loads of atomics, which we are restricting here. The intended reading is that there must
- exist an association of atomic loads with modifications they observe that, together with suitably chosen
- modification orders and the ''happens before'' relation derived as described above, satisfy the resulting
- constraints as imposed here.
-
-25 The execution of a program contains a data race if it contains two conflicting actions in
- different threads, at least one of which is not atomic, and neither happens before the
- other. Any such data race results in undefined behavior.
-26 NOTE 12 It can be shown that programs that correctly use simple mutexes and
- memory_order_seq_cst operations to prevent all data races, and use no other synchronization
- operations, behave as though the operations executed by their constituent threads were simply interleaved,
- with each value computation of an object being the last value stored in that interleaving. This is normally
- referred to as ''sequential consistency''. However, this applies only to data-race-free programs, and data-
- race-free programs cannot observe most program transformations that do not change single-threaded
- program semantics. In fact, most single-threaded program transformations continue to be allowed, since
- any program that behaves differently as a result must contain undefined behavior.
-
-[page 20]
-
-27 NOTE 13 Compiler transformations that introduce assignments to a potentially shared memory location
- that would not be modified by the abstract machine are generally precluded by this standard, since such an
- assignment might overwrite another assignment by a different thread in cases in which an abstract machine
- execution would not have encountered a data race. This includes implementations of data member
- assignment that overwrite adjacent members in separate memory locations. We also generally preclude
- reordering of atomic loads in cases in which the atomics in question may alias, since this may violate the
- "visible sequence" rules.
-
-28 NOTE 14 Transformations that introduce a speculative read of a potentially shared memory location may
- not preserve the semantics of the program as defined in this standard, since they potentially introduce a data
- race. However, they are typically valid in the context of an optimizing compiler that targets a specific
- machine with well-defined semantics for data races. They would be invalid for a hypothetical machine that
- is not tolerant of races or provides hardware race detection.
-
-
-
-
-[page 21]
-
- 5.2 Environmental considerations
- 5.2.1 Character sets
-1 Two sets of characters and their associated collating sequences shall be defined: the set in
- which source files are written (the source character set), and the set interpreted in the
- execution environment (the execution character set). Each set is further divided into a
- basic character set, whose contents are given by this subclause, and a set of zero or more
- locale-specific members (which are not members of the basic character set) called
- extended characters. The combined set is also called the extended character set. The
- values of the members of the execution character set are implementation-defined.
-2 In a character constant or string literal, members of the execution character set shall be
- represented by corresponding members of the source character set or by escape
- sequences consisting of the backslash \ followed by one or more characters. A byte with
- all bits set to 0, called the null character, shall exist in the basic execution character set; it
- is used to terminate a character string.
-3 Both the basic source and basic execution character sets shall have the following
- members: the 26 uppercase letters of the Latin alphabet
- A B C D E F G H I J K L M
- N O P Q R S T U V W X Y Z
- the 26 lowercase letters of the Latin alphabet
- a b c d e f g h i j k l m
- n o p q r s t u v w x y z
- the 10 decimal digits
- 0 1 2 3 4 5 6 7 8 9
- the following 29 graphic characters
- ! " # % & ' ( ) * + , - . / :
- ; < = > ? [ \ ] ^ _ { | } ~
- the space character, and control characters representing horizontal tab, vertical tab, and
- form feed. The representation of each member of the source and execution basic
- character sets shall fit in a byte. In both the source and execution basic character sets, the
- value of each character after 0 in the above list of decimal digits shall be one greater than
- the value of the previous. In source files, there shall be some way of indicating the end of
- each line of text; this International Standard treats such an end-of-line indicator as if it
- were a single new-line character. In the basic execution character set, there shall be
- control characters representing alert, backspace, carriage return, and new line. If any
- other characters are encountered in a source file (except in an identifier, a character
- constant, a string literal, a header name, a comment, or a preprocessing token that is never
-
-[page 22]
-
- converted to a token), the behavior is undefined.
-4 A letter is an uppercase letter or a lowercase letter as defined above; in this International
- Standard the term does not include other characters that are letters in other alphabets.
-5 The universal character name construct provides a way to name other characters.
- Forward references: universal character names (6.4.3), character constants (6.4.4.4),
- preprocessing directives (6.10), string literals (6.4.5), comments (6.4.9), string (7.1.1).
- 5.2.1.1 Trigraph sequences
-1 Before any other processing takes place, each occurrence of one of the following
- sequences of three characters (called trigraph sequences17)) is replaced with the
- corresponding single character.
- ??= # ??) ] ??! |
- ??( [ ??' ^ ??> }
- ??/ \ ??< { ??- ~
- No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
- above is not changed.
-2 EXAMPLE 1
- ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)
- becomes
- #define arraycheck(a, b) a[b] || b[a]
-
-3 EXAMPLE 2 The following source line
- printf("Eh???/n");
- becomes (after replacement of the trigraph sequence ??/)
- printf("Eh?\n");
-
- 5.2.1.2 Multibyte characters
-1 The source character set may contain multibyte characters, used to represent members of
- the extended character set. The execution character set may also contain multibyte
- characters, which need not have the same encoding as for the source character set. For
- both character sets, the following shall hold:
- -- The basic character set shall be present and each character shall be encoded as a
- single byte.
- -- The presence, meaning, and representation of any additional members is locale-
- specific.
-
- 17) The trigraph sequences enable the input of characters that are not defined in the Invariant Code Set as
- described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
-
-[page 23]
-
- -- A multibyte character set may have a state-dependent encoding, wherein each
- sequence of multibyte characters begins in an initial shift state and enters other
- locale-specific shift states when specific multibyte characters are encountered in the
- sequence. While in the initial shift state, all single-byte characters retain their usual
- interpretation and do not alter the shift state. The interpretation for subsequent bytes
- in the sequence is a function of the current shift state.
- -- A byte with all bits zero shall be interpreted as a null character independent of shift
- state. Such a byte shall not occur as part of any other multibyte character.
-2 For source files, the following shall hold:
- -- An identifier, comment, string literal, character constant, or header name shall begin
- and end in the initial shift state.
- -- An identifier, comment, string literal, character constant, or header name shall consist
- of a sequence of valid multibyte characters.
- 5.2.2 Character display semantics
-1 The active position is that location on a display device where the next character output by
- the fputc function would appear. The intent of writing a printing character (as defined
- by the isprint function) to a display device is to display a graphic representation of
- that character at the active position and then advance the active position to the next
- position on the current line. The direction of writing is locale-specific. If the active
- position is at the final position of a line (if there is one), the behavior of the display device
- is unspecified.
-2 Alphabetic escape sequences representing nongraphic characters in the execution
- character set are intended to produce actions on display devices as follows:
- \a (alert) Produces an audible or visible alert without changing the active position.
- \b (backspace) Moves the active position to the previous position on the current line. If
- the active position is at the initial position of a line, the behavior of the display
- device is unspecified.
- \f ( form feed) Moves the active position to the initial position at the start of the next
- logical page.
- \n (new line) Moves the active position to the initial position of the next line.
- \r (carriage return) Moves the active position to the initial position of the current line.
- \t (horizontal tab) Moves the active position to the next horizontal tabulation position
- on the current line. If the active position is at or past the last defined horizontal
- tabulation position, the behavior of the display device is unspecified.
- \v (vertical tab) Moves the active position to the initial position of the next vertical
- tabulation position. If the active position is at or past the last defined vertical
-[page 24]
-
- tabulation position, the behavior of the display device is unspecified.
-3 Each of these escape sequences shall produce a unique implementation-defined value
- which can be stored in a single char object. The external representations in a text file
- need not be identical to the internal representations, and are outside the scope of this
- International Standard.
- Forward references: the isprint function (7.4.1.8), the fputc function (7.21.7.3).
- 5.2.3 Signals and interrupts
-1 Functions shall be implemented such that they may be interrupted at any time by a signal,
- or may be called by a signal handler, or both, with no alteration to earlier, but still active,
- invocations' control flow (after the interruption), function return values, or objects with
- automatic storage duration. All such objects shall be maintained outside the function
- image (the instructions that compose the executable representation of a function) on a
- per-invocation basis.
- 5.2.4 Environmental limits
-1 Both the translation and execution environments constrain the implementation of
- language translators and libraries. The following summarizes the language-related
- environmental limits on a conforming implementation; the library-related limits are
- discussed in clause 7.
- 5.2.4.1 Translation limits
-1 The implementation shall be able to translate and execute at least one program that
- contains at least one instance of every one of the following limits:18)
- -- 127 nesting levels of blocks
- -- 63 nesting levels of conditional inclusion
- -- 12 pointer, array, and function declarators (in any combinations) modifying an
- arithmetic, structure, union, or void type in a declaration
- -- 63 nesting levels of parenthesized declarators within a full declarator
- -- 63 nesting levels of parenthesized expressions within a full expression
- -- 63 significant initial characters in an internal identifier or a macro name (each
- universal character name or extended source character is considered a single
- character)
- -- 31 significant initial characters in an external identifier (each universal character name
- specifying a short identifier of 0000FFFF or less is considered 6 characters, each
-
-
- 18) Implementations should avoid imposing fixed translation limits whenever possible.
-
-[page 25]
-
- universal character name specifying a short identifier of 00010000 or more is
- considered 10 characters, and each extended source character is considered the same
- number of characters as the corresponding universal character name, if any)19)
- -- 4095 external identifiers in one translation unit
- -- 511 identifiers with block scope declared in one block
- -- 4095 macro identifiers simultaneously defined in one preprocessing translation unit
- -- 127 parameters in one function definition
- -- 127 arguments in one function call
- -- 127 parameters in one macro definition
- -- 127 arguments in one macro invocation
- -- 4095 characters in a logical source line
- -- 4095 characters in a string literal (after concatenation)
- -- 65535 bytes in an object (in a hosted environment only)
- -- 15 nesting levels for #included files
- -- 1023 case labels for a switch statement (excluding those for any nested switch
- statements)
- -- 1023 members in a single structure or union
- -- 1023 enumeration constants in a single enumeration
- -- 63 levels of nested structure or union definitions in a single struct-declaration-list
- 5.2.4.2 Numerical limits
-1 An implementation is required to document all the limits specified in this subclause,
- which are specified in the headers <limits.h> and <float.h>. Additional limits are
- specified in <stdint.h>.
- Forward references: integer types <stdint.h> (7.20).
- 5.2.4.2.1 Sizes of integer types <limits.h>
-1 The values given below shall be replaced by constant expressions suitable for use in #if
- preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the
- following shall be replaced by expressions that have the same type as would an
- expression that is an object of the corresponding type converted according to the integer
- promotions. Their implementation-defined values shall be equal or greater in magnitude
-
-
- 19) See ''future language directions'' (6.11.3).
-
-[page 26]
-
-(absolute value) to those shown, with the same sign.
--- number of bits for smallest object that is not a bit-field (byte)
- CHAR_BIT 8
--- minimum value for an object of type signed char
- SCHAR_MIN -127 // -(27 - 1)
--- maximum value for an object of type signed char
- SCHAR_MAX +127 // 27 - 1
--- maximum value for an object of type unsigned char
- UCHAR_MAX 255 // 28 - 1
--- minimum value for an object of type char
- CHAR_MIN see below
--- maximum value for an object of type char
- CHAR_MAX see below
--- maximum number of bytes in a multibyte character, for any supported locale
- MB_LEN_MAX 1
--- minimum value for an object of type short int
- SHRT_MIN -32767 // -(215 - 1)
--- maximum value for an object of type short int
- SHRT_MAX +32767 // 215 - 1
--- maximum value for an object of type unsigned short int
- USHRT_MAX 65535 // 216 - 1
--- minimum value for an object of type int
- INT_MIN -32767 // -(215 - 1)
--- maximum value for an object of type int
- INT_MAX +32767 // 215 - 1
--- maximum value for an object of type unsigned int
- UINT_MAX 65535 // 216 - 1
--- minimum value for an object of type long int
- LONG_MIN -2147483647 // -(231 - 1)
--- maximum value for an object of type long int
- LONG_MAX +2147483647 // 231 - 1
--- maximum value for an object of type unsigned long int
- ULONG_MAX 4294967295 // 232 - 1
-
-
-[page 27]
-
- -- minimum value for an object of type long long int
- LLONG_MIN -9223372036854775807 // -(263 - 1)
- -- maximum value for an object of type long long int
- LLONG_MAX +9223372036854775807 // 263 - 1
- -- maximum value for an object of type unsigned long long int
- ULLONG_MAX 18446744073709551615 // 264 - 1
-2 If the value of an object of type char is treated as a signed integer when used in an
- expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the
- value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of
- CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of
- UCHAR_MAX.20) The value UCHAR_MAX shall equal 2CHAR_BIT - 1.
- Forward references: representations of types (6.2.6), conditional inclusion (6.10.1).
- 5.2.4.2.2 Characteristics of floating types <float.h>
-1 The characteristics of floating types are defined in terms of a model that describes a
- representation of floating-point numbers and values that provide information about an
- implementation's floating-point arithmetic.21) The following parameters are used to
- define the model for each floating-point type:
- s sign ((+-)1)
- b base or radix of exponent representation (an integer > 1)
- e exponent (an integer between a minimum emin and a maximum emax )
- p precision (the number of base-b digits in the significand)
- fk nonnegative integers less than b (the significand digits)
-2 A floating-point number (x) is defined by the following model:
- p
- x = sb e (Sum) f k b-k ,
- k=1
- emin <= e <= emax
-
-3 In addition to normalized floating-point numbers ( f 1 > 0 if x != 0), floating types may be
- able to contain other kinds of floating-point numbers, such as subnormal floating-point
- numbers (x != 0, e = emin , f 1 = 0) and unnormalized floating-point numbers (x != 0,
- e > emin , f 1 = 0), and values that are not floating-point numbers, such as infinities and
- NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates
- through almost every arithmetic operation without raising a floating-point exception; a
- signaling NaN generally raises a floating-point exception when occurring as an
-
-
- 20) See 6.2.5.
- 21) The floating-point model is intended to clarify the description of each floating-point characteristic and
- does not require the floating-point arithmetic of the implementation to be identical.
-
-[page 28]
-
- arithmetic operand.22)
-4 An implementation may give zero and non-numeric values (such as infinities and NaNs) a
- sign or may leave them unsigned. Wherever such values are unsigned, any requirement
- in this International Standard to retrieve the sign shall produce an unspecified sign, and
- any requirement to set the sign shall be ignored.
-5 The minimum range of representable values for a floating type is the most negative finite
- floating-point number representable in that type through the most positive finite floating-
- point number representable in that type. In addition, if negative infinity is representable
- in a type, the range of that type is extended to all negative real numbers; likewise, if
- positive infinity is representable in a type, the range of that type is extended to all positive
- real numbers.
-6 The accuracy of the floating-point operations (+, -, *, /) and of the library functions in
- <math.h> and <complex.h> that return floating-point results is implementation-
- defined, as is the accuracy of the conversion between floating-point internal
- representations and string representations performed by the library functions in
- <stdio.h>, <stdlib.h>, and <wchar.h>. The implementation may state that the
- accuracy is unknown.
-7 All integer values in the <float.h> header, except FLT_ROUNDS, shall be constant
- expressions suitable for use in #if preprocessing directives; all floating values shall be
- constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
- and FLT_ROUNDS have separate names for all three floating-point types. The floating-
- point model representation is provided for all values except FLT_EVAL_METHOD and
- FLT_ROUNDS.
-8 The rounding mode for floating-point addition is characterized by the implementation-
- defined value of FLT_ROUNDS:23)
- -1 indeterminable
- 0 toward zero
- 1 to nearest
- 2 toward positive infinity
- 3 toward negative infinity
- All other values for FLT_ROUNDS characterize implementation-defined rounding
- behavior.
-
-
- 22) IEC 60559:1989 specifies quiet and signaling NaNs. For implementations that do not support
- IEC 60559:1989, the terms quiet NaN and signaling NaN are intended to apply to encodings with
- similar behavior.
- 23) Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
- the function fesetround in <fenv.h>.
-
-[page 29]
-
-9 Except for assignment and cast (which remove all extra range and precision), the values
- yielded by operators with floating operands and values subject to the usual arithmetic
- conversions and of floating constants are evaluated to a format whose range and precision
- may be greater than required by the type. The use of evaluation formats is characterized
- by the implementation-defined value of FLT_EVAL_METHOD:24)
- -1 indeterminable;
- 0 evaluate all operations and constants just to the range and precision of the
- type;
- 1 evaluate operations and constants of type float and double to the
- range and precision of the double type, evaluate long double
- operations and constants to the range and precision of the long double
- type;
- 2 evaluate all operations and constants to the range and precision of the
- long double type.
- All other negative values for FLT_EVAL_METHOD characterize implementation-defined
- behavior.
-10 The presence or absence of subnormal numbers is characterized by the implementation-
- defined values of FLT_HAS_SUBNORM, DBL_HAS_SUBNORM, and
- LDBL_HAS_SUBNORM:
- -1 indeterminable25)
- 0 absent26) (type does not support subnormal numbers)
- 1 present (type does support subnormal numbers)
-11 The values given in the following list shall be replaced by constant expressions with
- implementation-defined values that are greater or equal in magnitude (absolute value) to
- those shown, with the same sign:
- -- radix of exponent representation, b
- FLT_RADIX 2
-
-
-
-
- 24) The evaluation method determines evaluation formats of expressions involving all floating types, not
- just real types. For example, if FLT_EVAL_METHOD is 1, then the product of two float
- _Complex operands is represented in the double _Complex format, and its parts are evaluated to
- double.
- 25) Characterization as indeterminable is intended if floating-point operations do not consistently interpret
- subnormal representations as zero, nor as nonzero.
- 26) Characterization as absent is intended if no floating-point operations produce subnormal results from
- non-subnormal inputs, even if the type format includes representations of subnormal numbers.
-
-[page 30]
-
--- number of base-FLT_RADIX digits in the floating-point significand, p
- FLT_MANT_DIG
- DBL_MANT_DIG
- LDBL_MANT_DIG
--- number of decimal digits, n, such that any floating-point number with p radix b digits
- can be rounded to a floating-point number with n decimal digits and back again
- without change to the value,
- { p log10 b if b is a power of 10
- {
- { [^1 + p log10 b^] otherwise
- FLT_DECIMAL_DIG 6
- DBL_DECIMAL_DIG 10
- LDBL_DECIMAL_DIG 10
--- number of decimal digits, n, such that any floating-point number in the widest
- supported floating type with pmax radix b digits can be rounded to a floating-point
- number with n decimal digits and back again without change to the value,
- { pmax log10 b if b is a power of 10
- {
- { [^1 + pmax log10 b^] otherwise
- DECIMAL_DIG 10
--- number of decimal digits, q, such that any floating-point number with q decimal digits
- can be rounded into a floating-point number with p radix b digits and back again
- without change to the q decimal digits,
- { p log10 b if b is a power of 10
- {
- { [_( p - 1) log10 b_] otherwise
- FLT_DIG 6
- DBL_DIG 10
- LDBL_DIG 10
--- minimum negative integer such that FLT_RADIX raised to one less than that power is
- a normalized floating-point number, emin
- FLT_MIN_EXP
- DBL_MIN_EXP
- LDBL_MIN_EXP
-
-
-
-
-[page 31]
-
- -- minimum negative integer such that 10 raised to that power is in the range of
- normalized floating-point numbers, [^log10 b emin -1 ^]
- [ ]
- FLT_MIN_10_EXP -37
- DBL_MIN_10_EXP -37
- LDBL_MIN_10_EXP -37
- -- maximum integer such that FLT_RADIX raised to one less than that power is a
- representable finite floating-point number, emax
- FLT_MAX_EXP
- DBL_MAX_EXP
- LDBL_MAX_EXP
- -- maximum integer such that 10 raised to that power is in the range of representable
- finite floating-point numbers, [_log10 ((1 - b- p )b emax )_]
- FLT_MAX_10_EXP +37
- DBL_MAX_10_EXP +37
- LDBL_MAX_10_EXP +37
-12 The values given in the following list shall be replaced by constant expressions with
- implementation-defined values that are greater than or equal to those shown:
- -- maximum representable finite floating-point number, (1 - b- p )b emax
- FLT_MAX 1E+37
- DBL_MAX 1E+37
- LDBL_MAX 1E+37
-13 The values given in the following list shall be replaced by constant expressions with
- implementation-defined (positive) values that are less than or equal to those shown:
- -- the difference between 1 and the least value greater than 1 that is representable in the
- given floating point type, b1- p
- FLT_EPSILON 1E-5
- DBL_EPSILON 1E-9
- LDBL_EPSILON 1E-9
- -- minimum normalized positive floating-point number, b emin -1
- FLT_MIN 1E-37
- DBL_MIN 1E-37
- LDBL_MIN 1E-37
-
-
-
-
-[page 32]
-
- -- minimum positive floating-point number27)
- FLT_TRUE_MIN 1E-37
- DBL_TRUE_MIN 1E-37
- LDBL_TRUE_MIN 1E-37
- Recommended practice
-14 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
- should be the identity function.
-15 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
- requirements of this International Standard, and the appropriate values in a <float.h> header for type
- float:
- 6
- x = s16e (Sum) f k 16-k ,
- k=1
- -31 <= e <= +32
-
- FLT_RADIX 16
- FLT_MANT_DIG 6
- FLT_EPSILON 9.53674316E-07F
- FLT_DECIMAL_DIG 9
- FLT_DIG 6
- FLT_MIN_EXP -31
- FLT_MIN 2.93873588E-39F
- FLT_MIN_10_EXP -38
- FLT_MAX_EXP +32
- FLT_MAX 3.40282347E+38F
- FLT_MAX_10_EXP +38
-
-16 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
- single-precision and double-precision numbers in IEC 60559,28) and the appropriate values in a
- <float.h> header for types float and double:
- 24
- x f = s2e (Sum) f k 2-k ,
- k=1
- -125 <= e <= +128
-
- 53
- x d = s2e (Sum) f k 2-k ,
- k=1
- -1021 <= e <= +1024
-
- FLT_RADIX 2
- DECIMAL_DIG 17
- FLT_MANT_DIG 24
- FLT_EPSILON 1.19209290E-07F // decimal constant
- FLT_EPSILON 0X1P-23F // hex constant
- FLT_DECIMAL_DIG 9
-
-
- 27) If the presence or absence of subnormal numbers is indeterminable, then the value is intended to be a
- positive number no greater than the minimum normalized positive number for the type.
- 28) The floating-point model in that standard sums powers of b from zero, so the values of the exponent
- limits are one less than shown here.
-
-[page 33]
-
- FLT_DIG 6
- FLT_MIN_EXP -125
- FLT_MIN 1.17549435E-38F // decimal constant
- FLT_MIN 0X1P-126F // hex constant
- FLT_TRUE_MIN 1.40129846E-45F // decimal constant
- FLT_TRUE_MIN 0X1P-149F // hex constant
- FLT_HAS_SUBNORM 1
- FLT_MIN_10_EXP -37
- FLT_MAX_EXP +128
- FLT_MAX 3.40282347E+38F // decimal constant
- FLT_MAX 0X1.fffffeP127F // hex constant
- FLT_MAX_10_EXP +38
- DBL_MANT_DIG 53
- DBL_EPSILON 2.2204460492503131E-16 // decimal constant
- DBL_EPSILON 0X1P-52 // hex constant
- DBL_DECIMAL_DIG 17
- DBL_DIG 15
- DBL_MIN_EXP -1021
- DBL_MIN 2.2250738585072014E-308 // decimal constant
- DBL_MIN 0X1P-1022 // hex constant
- DBL_TRUE_MIN 4.9406564584124654E-324 // decimal constant
- DBL_TRUE_MIN 0X1P-1074 // hex constant
- DBL_HAS_SUBNORM 1
- DBL_MIN_10_EXP -307
- DBL_MAX_EXP +1024
- DBL_MAX 1.7976931348623157E+308 // decimal constant
- DBL_MAX 0X1.fffffffffffffP1023 // hex constant
- DBL_MAX_10_EXP +308
-If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
-example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
-precision), then DECIMAL_DIG would be 21.
-
-Forward references: conditional inclusion (6.10.1), complex arithmetic
-<complex.h> (7.3), extended multibyte and wide character utilities <wchar.h>
-(7.28), floating-point environment <fenv.h> (7.6), general utilities <stdlib.h>
-(7.22), input/output <stdio.h> (7.21), mathematics <math.h> (7.12).
-
-
-
-
-[page 34]
-
-
- 6. Language
- 6.1 Notation
-1 In the syntax notation used in this clause, syntactic categories (nonterminals) are
- indicated by italic type, and literal words and character set members (terminals) by bold
- type. A colon (:) following a nonterminal introduces its definition. Alternative
- definitions are listed on separate lines, except when prefaced by the words ''one of''. An
- optional symbol is indicated by the subscript ''opt'', so that
- { expressionopt }
- indicates an optional expression enclosed in braces.
-2 When syntactic categories are referred to in the main text, they are not italicized and
- words are separated by spaces instead of hyphens.
-3 A summary of the language syntax is given in annex A.
- 6.2 Concepts
- 6.2.1 Scopes of identifiers
-1 An identifier can denote an object; a function; a tag or a member of a structure, union, or
- enumeration; a typedef name; a label name; a macro name; or a macro parameter. The
- same identifier can denote different entities at different points in the program. A member
- of an enumeration is called an enumeration constant. Macro names and macro
- parameters are not considered further here, because prior to the semantic phase of
- program translation any occurrences of macro names in the source file are replaced by the
- preprocessing token sequences that constitute their macro definitions.
-2 For each different entity that an identifier designates, the identifier is visible (i.e., can be
- used) only within a region of program text called its scope. Different entities designated
- by the same identifier either have different scopes, or are in different name spaces. There
- are four kinds of scopes: function, file, block, and function prototype. (A function
- prototype is a declaration of a function that declares the types of its parameters.)
-3 A label name is the only kind of identifier that has function scope. It can be used (in a
- goto statement) anywhere in the function in which it appears, and is declared implicitly
- by its syntactic appearance (followed by a : and a statement).
-4 Every other identifier has scope determined by the placement of its declaration (in a
- declarator or type specifier). If the declarator or type specifier that declares the identifier
- appears outside of any block or list of parameters, the identifier has file scope, which
- terminates at the end of the translation unit. If the declarator or type specifier that
- declares the identifier appears inside a block or within the list of parameter declarations in
- a function definition, the identifier has block scope, which terminates at the end of the
- associated block. If the declarator or type specifier that declares the identifier appears
-
-[page 35]
-
- within the list of parameter declarations in a function prototype (not part of a function
- definition), the identifier has function prototype scope, which terminates at the end of the
- function declarator. If an identifier designates two different entities in the same name
- space, the scopes might overlap. If so, the scope of one entity (the inner scope) will end
- strictly before the scope of the other entity (the outer scope). Within the inner scope, the
- identifier designates the entity declared in the inner scope; the entity declared in the outer
- scope is hidden (and not visible) within the inner scope.
-5 Unless explicitly stated otherwise, where this International Standard uses the term
- ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the
- entity in the relevant name space whose declaration is visible at the point the identifier
- occurs.
-6 Two identifiers have the same scope if and only if their scopes terminate at the same
- point.
-7 Structure, union, and enumeration tags have scope that begins just after the appearance of
- the tag in a type specifier that declares the tag. Each enumeration constant has scope that
- begins just after the appearance of its defining enumerator in an enumerator list. Any
- other identifier has scope that begins just after the completion of its declarator.
-8 As a special case, a type name (which is not a declaration of an identifier) is considered to
- have a scope that begins just after the place within the type name where the omitted
- identifier would appear were it not omitted.
- Forward references: declarations (6.7), function calls (6.5.2.2), function definitions
- (6.9.1), identifiers (6.4.2), macro replacement (6.10.3), name spaces of identifiers (6.2.3),
- source file inclusion (6.10.2), statements (6.8).
- 6.2.2 Linkages of identifiers
-1 An identifier declared in different scopes or in the same scope more than once can be
- made to refer to the same object or function by a process called linkage.29) There are
- three kinds of linkage: external, internal, and none.
-2 In the set of translation units and libraries that constitutes an entire program, each
- declaration of a particular identifier with external linkage denotes the same object or
- function. Within one translation unit, each declaration of an identifier with internal
- linkage denotes the same object or function. Each declaration of an identifier with no
- linkage denotes a unique entity.
-3 If the declaration of a file scope identifier for an object or a function contains the storage-
- class specifier static, the identifier has internal linkage.30)
-
-
-
- 29) There is no linkage between different identifiers.
-
-[page 36]
-
-4 For an identifier declared with the storage-class specifier extern in a scope in which a
- prior declaration of that identifier is visible,31) if the prior declaration specifies internal or
- external linkage, the linkage of the identifier at the later declaration is the same as the
- linkage specified at the prior declaration. If no prior declaration is visible, or if the prior
- declaration specifies no linkage, then the identifier has external linkage.
-5 If the declaration of an identifier for a function has no storage-class specifier, its linkage
- is determined exactly as if it were declared with the storage-class specifier extern. If
- the declaration of an identifier for an object has file scope and no storage-class specifier,
- its linkage is external.
-6 The following identifiers have no linkage: an identifier declared to be anything other than
- an object or a function; an identifier declared to be a function parameter; a block scope
- identifier for an object declared without the storage-class specifier extern.
-7 If, within a translation unit, the same identifier appears with both internal and external
- linkage, the behavior is undefined.
- Forward references: declarations (6.7), expressions (6.5), external definitions (6.9),
- statements (6.8).
- 6.2.3 Name spaces of identifiers
-1 If more than one declaration of a particular identifier is visible at any point in a
- translation unit, the syntactic context disambiguates uses that refer to different entities.
- Thus, there are separate name spaces for various categories of identifiers, as follows:
- -- label names (disambiguated by the syntax of the label declaration and use);
- -- the tags of structures, unions, and enumerations (disambiguated by following any32)
- of the keywords struct, union, or enum);
- -- the members of structures or unions; each structure or union has a separate name
- space for its members (disambiguated by the type of the expression used to access the
- member via the . or -> operator);
- -- all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
- enumeration constants).
- Forward references: enumeration specifiers (6.7.2.2), labeled statements (6.8.1),
- structure and union specifiers (6.7.2.1), structure and union members (6.5.2.3), tags
- (6.7.2.3), the goto statement (6.8.6.1).
-
- 30) A function declaration can contain the storage-class specifier static only if it is at file scope; see
- 6.7.1.
- 31) As specified in 6.2.1, the later declaration might hide the prior declaration.
- 32) There is only one name space for tags even though three are possible.
-
-[page 37]
-
- 6.2.4 Storage durations of objects
-1 An object has a storage duration that determines its lifetime. There are four storage
- durations: static, thread, automatic, and allocated. Allocated storage is described in
- 7.22.3.
-2 The lifetime of an object is the portion of program execution during which storage is
- guaranteed to be reserved for it. An object exists, has a constant address,33) and retains
- its last-stored value throughout its lifetime.34) If an object is referred to outside of its
- lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
- the object it points to (or just past) reaches the end of its lifetime.
-3 An object whose identifier is declared without the storage-class specifier
- _Thread_local, and either with external or internal linkage or with the storage-class
- specifier static, has static storage duration. Its lifetime is the entire execution of the
- program and its stored value is initialized only once, prior to program startup.
-4 An object whose identifier is declared with the storage-class specifier _Thread_local
- has thread storage duration. Its lifetime is the entire execution of the thread for which it
- is created, and its stored value is initialized when the thread is started. There is a distinct
- object per thread, and use of the declared name in an expression refers to the object
- associated with the thread evaluating the expression. The result of attempting to
- indirectly access an object with thread storage duration from a thread other than the one
- with which the object is associated is implementation-defined.
-5 An object whose identifier is declared with no linkage and without the storage-class
- specifier static has automatic storage duration, as do some compound literals. The
- result of attempting to indirectly access an object with automatic storage duration from a
- thread other than the one with which the object is associated is implementation-defined.
-6 For such an object that does not have a variable length array type, its lifetime extends
- from entry into the block with which it is associated until execution of that block ends in
- any way. (Entering an enclosed block or calling a function suspends, but does not end,
- execution of the current block.) If the block is entered recursively, a new instance of the
- object is created each time. The initial value of the object is indeterminate. If an
- initialization is specified for the object, it is performed each time the declaration or
- compound literal is reached in the execution of the block; otherwise, the value becomes
- indeterminate each time the declaration is reached.
-
-
-
- 33) The term ''constant address'' means that two pointers to the object constructed at possibly different
- times will compare equal. The address may be different during two different executions of the same
- program.
- 34) In the case of a volatile object, the last store need not be explicit in the program.
-
-[page 38]
-
-7 For such an object that does have a variable length array type, its lifetime extends from
- the declaration of the object until execution of the program leaves the scope of the
- declaration.35) If the scope is entered recursively, a new instance of the object is created
- each time. The initial value of the object is indeterminate.
-8 A non-lvalue expression with structure or union type, where the structure or union
- contains a member with array type (including, recursively, members of all contained
- structures and unions) refers to an object with automatic storage duration and temporary
- lifetime.36) Its lifetime begins when the expression is evaluated and its initial value is the
- value of the expression. Its lifetime ends when the evaluation of the containing full
- expression or full declarator ends. Any attempt to modify an object with temporary
- lifetime results in undefined behavior.
- Forward references: array declarators (6.7.6.2), compound literals (6.5.2.5), declarators
- (6.7.6), function calls (6.5.2.2), initialization (6.7.9), statements (6.8).
- 6.2.5 Types
-1 The meaning of a value stored in an object or returned by a function is determined by the
- type of the expression used to access it. (An identifier declared to be an object is the
- simplest such expression; the type is specified in the declaration of the identifier.) Types
- are partitioned into object types (types that describe objects) and function types (types
- that describe functions). At various points within a translation unit an object type may be
- incomplete (lacking sufficient information to determine the size of objects of that type) or
- complete (having sufficient information).37)
-2 An object declared as type _Bool is large enough to store the values 0 and 1.
-3 An object declared as type char is large enough to store any member of the basic
- execution character set. If a member of the basic execution character set is stored in a
- char object, its value is guaranteed to be nonnegative. If any other character is stored in
- a char object, the resulting value is implementation-defined but shall be within the range
- of values that can be represented in that type.
-4 There are five standard signed integer types, designated as signed char, short
- int, int, long int, and long long int. (These and other types may be
- designated in several additional ways, as described in 6.7.2.) There may also be
- implementation-defined extended signed integer types.38) The standard and extended
- signed integer types are collectively called signed integer types.39)
-
- 35) Leaving the innermost block containing the declaration, or jumping to a point in that block or an
- embedded block prior to the declaration, leaves the scope of the declaration.
- 36) The address of such an object is taken implicitly when an array member is accessed.
- 37) A type may be incomplete or complete throughout an entire translation unit, or it may change states at
- different points within a translation unit.
-
-[page 39]
-
-5 An object declared as type signed char occupies the same amount of storage as a
- ''plain'' char object. A ''plain'' int object has the natural size suggested by the
- architecture of the execution environment (large enough to contain any value in the range
- INT_MIN to INT_MAX as defined in the header <limits.h>).
-6 For each of the signed integer types, there is a corresponding (but different) unsigned
- integer type (designated with the keyword unsigned) that uses the same amount of
- storage (including sign information) and has the same alignment requirements. The type
- _Bool and the unsigned integer types that correspond to the standard signed integer
- types are the standard unsigned integer types. The unsigned integer types that
- correspond to the extended signed integer types are the extended unsigned integer types.
- The standard and extended unsigned integer types are collectively called unsigned integer
- types.40)
-7 The standard signed integer types and standard unsigned integer types are collectively
- called the standard integer types, the extended signed integer types and extended
- unsigned integer types are collectively called the extended integer types.
-8 For any two integer types with the same signedness and different integer conversion rank
- (see 6.3.1.1), the range of values of the type with smaller integer conversion rank is a
- subrange of the values of the other type.
-9 The range of nonnegative values of a signed integer type is a subrange of the
- corresponding unsigned integer type, and the representation of the same value in each
- type is the same.41) A computation involving unsigned operands can never overflow,
- because a result that cannot be represented by the resulting unsigned integer type is
- reduced modulo the number that is one greater than the largest value that can be
- represented by the resulting type.
-10 There are three real floating types, designated as float, double, and long
- double.42) The set of values of the type float is a subset of the set of values of the
- type double; the set of values of the type double is a subset of the set of values of the
- type long double.
-
-
- 38) Implementation-defined keywords shall have the form of an identifier reserved for any use as
- described in 7.1.3.
- 39) Therefore, any statement in this Standard about signed integer types also applies to the extended
- signed integer types.
- 40) Therefore, any statement in this Standard about unsigned integer types also applies to the extended
- unsigned integer types.
- 41) The same representation and alignment requirements are meant to imply interchangeability as
- arguments to functions, return values from functions, and members of unions.
- 42) See ''future language directions'' (6.11.1).
-
-[page 40]
-
-11 There are three complex types, designated as float _Complex, double
- _Complex, and long double _Complex.43) (Complex types are a conditional
- feature that implementations need not support; see 6.10.8.3.) The real floating and
- complex types are collectively called the floating types.
-12 For each floating type there is a corresponding real type, which is always a real floating
- type. For real floating types, it is the same type. For complex types, it is the type given
- by deleting the keyword _Complex from the type name.
-13 Each complex type has the same representation and alignment requirements as an array
- type containing exactly two elements of the corresponding real type; the first element is
- equal to the real part, and the second element to the imaginary part, of the complex
- number.
-14 The type char, the signed and unsigned integer types, and the floating types are
- collectively called the basic types. The basic types are complete object types. Even if the
- implementation defines two or more basic types to have the same representation, they are
- nevertheless different types.44)
-15 The three types char, signed char, and unsigned char are collectively called
- the character types. The implementation shall define char to have the same range,
- representation, and behavior as either signed char or unsigned char.45)
-16 An enumeration comprises a set of named integer constant values. Each distinct
- enumeration constitutes a different enumerated type.
-17 The type char, the signed and unsigned integer types, and the enumerated types are
- collectively called integer types. The integer and real floating types are collectively called
- real types.
-18 Integer and floating types are collectively called arithmetic types. Each arithmetic type
- belongs to one type domain: the real type domain comprises the real types, the complex
- type domain comprises the complex types.
-19 The void type comprises an empty set of values; it is an incomplete object type that
- cannot be completed.
-
-
-
- 43) A specification for imaginary types is in informative annex G.
- 44) An implementation may define new keywords that provide alternative ways to designate a basic (or
- any other) type; this does not violate the requirement that all basic types be different.
- Implementation-defined keywords shall have the form of an identifier reserved for any use as
- described in 7.1.3.
- 45) CHAR_MIN, defined in <limits.h>, will have one of the values 0 or SCHAR_MIN, and this can be
- used to distinguish the two options. Irrespective of the choice made, char is a separate type from the
- other two and is not compatible with either.
-
-[page 41]
-
-20 Any number of derived types can be constructed from the object and function types, as
- follows:
- -- An array type describes a contiguously allocated nonempty set of objects with a
- particular member object type, called the element type. The element type shall be
- complete whenever the array type is specified. Array types are characterized by their
- element type and by the number of elements in the array. An array type is said to be
- derived from its element type, and if its element type is T , the array type is sometimes
- called ''array of T ''. The construction of an array type from an element type is called
- ''array type derivation''.
- -- A structure type describes a sequentially allocated nonempty set of member objects
- (and, in certain circumstances, an incomplete array), each of which has an optionally
- specified name and possibly distinct type.
- -- A union type describes an overlapping nonempty set of member objects, each of
- which has an optionally specified name and possibly distinct type.
- -- A function type describes a function with specified return type. A function type is
- characterized by its return type and the number and types of its parameters. A
- function type is said to be derived from its return type, and if its return type is T , the
- function type is sometimes called ''function returning T ''. The construction of a
- function type from a return type is called ''function type derivation''.
- -- A pointer type may be derived from a function type or an object type, called the
- referenced type. A pointer type describes an object whose value provides a reference
- to an entity of the referenced type. A pointer type derived from the referenced type T
- is sometimes called ''pointer to T ''. The construction of a pointer type from a
- referenced type is called ''pointer type derivation''. A pointer type is a complete
- object type.
- These methods of constructing derived types can be applied recursively.
-21 Arithmetic types and pointer types are collectively called scalar types. Array and
- structure types are collectively called aggregate types.46)
-22 An array type of unknown size is an incomplete type. It is completed, for an identifier of
- that type, by specifying the size in a later declaration (with internal or external linkage).
- A structure or union type of unknown content (as described in 6.7.2.3) is an incomplete
- type. It is completed, for all declarations of that type, by declaring the same structure or
- union tag with its defining content later in the same scope.
-
-
-
-
- 46) Note that aggregate type does not include union type because an object with union type can only
- contain one member at a time.
-
-[page 42]
-
-23 A type has known constant size if the type is not incomplete and is not a variable length
- array type.
-24 Array, function, and pointer types are collectively called derived declarator types. A
- declarator type derivation from a type T is the construction of a derived declarator type
- from T by the application of an array-type, a function-type, or a pointer-type derivation to
- T.
-25 A type is characterized by its type category, which is either the outermost derivation of a
- derived type (as noted above in the construction of derived types), or the type itself if the
- type consists of no derived types.
-26 Any type so far mentioned is an unqualified type. Each unqualified type has several
- qualified versions of its type,47) corresponding to the combinations of one, two, or all
- three of the const, volatile, and restrict qualifiers. The qualified or unqualified
- versions of a type are distinct types that belong to the same type category and have the
- same representation and alignment requirements.48) A derived type is not qualified by the
- qualifiers (if any) of the type from which it is derived.
-27 Further, there is the _Atomic qualifier, which may combine with volatile and
- restrict. The size, representation, and alignment of an _Atomic-qualified type need
- not be the same as those of the corresponding unqualified type. (Atomic types are a
- conditional feature that implementations need not support; see 6.10.8.3.)
-28 A pointer to void shall have the same representation and alignment requirements as a
- pointer to a character type.48) Similarly, pointers to qualified or unqualified versions of
- compatible types shall have the same representation and alignment requirements. All
- pointers to structure types shall have the same representation and alignment requirements
- as each other. All pointers to union types shall have the same representation and
- alignment requirements as each other. Pointers to other types need not have the same
- representation or alignment requirements.
-29 EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is
- pointer, not a floating type. The const-qualified version of this type is designated as ''float * const''
- whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const-
- qualified float'' and is a pointer to a qualified type.
-
-30 EXAMPLE 2 The type designated as ''struct tag (*[5])(float)'' has type ''array of pointer to
- function returning struct tag''. The array has length five and the function has a single parameter of type
- float. Its type category is array.
-
- Forward references: compatible type and composite type (6.2.7), declarations (6.7).
-
-
-
- 47) See 6.7.3 regarding qualified array and function types.
- 48) The same representation and alignment requirements are meant to imply interchangeability as
- arguments to functions, return values from functions, and members of unions.
-
-[page 43]
-
- 6.2.6 Representations of types
- 6.2.6.1 General
-1 The representations of all types are unspecified except as stated in this subclause.
-2 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes,
- the number, order, and encoding of which are either explicitly specified or
- implementation-defined.
-3 Values stored in unsigned bit-fields and objects of type unsigned char shall be
- represented using a pure binary notation.49)
-4 Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT
- bits, where n is the size of an object of that type, in bytes. The value may be copied into
- an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is
- called the object representation of the value. Values stored in bit-fields consist of m bits,
- where m is the size specified for the bit-field. The object representation is the set of m
- bits the bit-field comprises in the addressable storage unit holding it. Two values (other
- than NaNs) with the same object representation compare equal, but values that compare
- equal may have different object representations.
-5 Certain object representations need not represent a value of the object type. If the stored
- value of an object has such a representation and is read by an lvalue expression that does
- not have character type, the behavior is undefined. If such a representation is produced
- by a side effect that modifies all or any part of the object by an lvalue expression that
- does not have character type, the behavior is undefined.50) Such a representation is called
- a trap representation.
-6 When a value is stored in an object of structure or union type, including in a member
- object, the bytes of the object representation that correspond to any padding bytes take
- unspecified values.51) The value of a structure or union object is never a trap
- representation, even though the value of a member of the structure or union object may be
- a trap representation.
-7 When a value is stored in a member of an object of union type, the bytes of the object
- representation that do not correspond to that member but do correspond to other members
-
- 49) A positional representation for integers that uses the binary digits 0 and 1, in which the values
- represented by successive bits are additive, begin with 1, and are multiplied by successive integral
- powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
- Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
- type unsigned char range from 0 to 2
- CHAR_BIT
- - 1.
- 50) Thus, an automatic variable can be initialized to a trap representation without causing undefined
- behavior, but the value of the variable cannot be used until a proper value is stored in it.
- 51) Thus, for example, structure assignment need not copy any padding bits.
-
-[page 44]
-
- take unspecified values.
-8 Where an operator is applied to a value that has more than one object representation,
- which object representation is used shall not affect the value of the result.52) Where a
- value is stored in an object using a type that has more than one object representation for
- that value, it is unspecified which representation is used, but a trap representation shall
- not be generated.
-9 Loads and stores of objects with _Atomic-qualified types are done with
- memory_order_seq_cst semantics.
- Forward references: declarations (6.7), expressions (6.5), lvalues, arrays, and function
- designators (6.3.2.1), order and consistency (7.17.3).
- 6.2.6.2 Integer types
-1 For unsigned integer types other than unsigned char, the bits of the object
- representation shall be divided into two groups: value bits and padding bits (there need
- not be any of the latter). If there are N value bits, each bit shall represent a different
- power of 2 between 1 and 2 N -1 , so that objects of that type shall be capable of
- representing values from 0 to 2 N - 1 using a pure binary representation; this shall be
- known as the value representation. The values of any padding bits are unspecified.53)
-2 For signed integer types, the bits of the object representation shall be divided into three
- groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
- signed char shall not have any padding bits. There shall be exactly one sign bit.
- Each bit that is a value bit shall have the same value as the same bit in the object
- representation of the corresponding unsigned type (if there are M value bits in the signed
- type and N in the unsigned type, then M <= N ). If the sign bit is zero, it shall not affect
- the resulting value. If the sign bit is one, the value shall be modified in one of the
- following ways:
- -- the corresponding value with sign bit 0 is negated (sign and magnitude);
- -- the sign bit has the value -(2 M ) (two's complement);
-
-
- 52) It is possible for objects x and y with the same effective type T to have the same value when they are
- accessed as objects of type T, but to have different values in other contexts. In particular, if == is
- defined for type T, then x == y does not imply that memcmp(&x, &y, sizeof (T)) == 0.
- Furthermore, x == y does not necessarily imply that x and y have the same value; other operations
- on values of type T may distinguish between them.
- 53) Some combinations of padding bits might generate trap representations, for example, if one padding
- bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
- representation other than as part of an exceptional condition such as an overflow, and this cannot occur
- with unsigned types. All other combinations of padding bits are alternative object representations of
- the value specified by the value bits.
-
-[page 45]
-
- -- the sign bit has the value -(2 M - 1) (ones' complement).
- Which of these applies is implementation-defined, as is whether the value with sign bit 1
- and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones'
- complement), is a trap representation or a normal value. In the case of sign and
- magnitude and ones' complement, if this representation is a normal value it is called a
- negative zero.
-3 If the implementation supports negative zeros, they shall be generated only by:
- -- the &, |, ^, ~, <<, and >> operators with operands that produce such a value;
- -- the +, -, *, /, and % operators where one operand is a negative zero and the result is
- zero;
- -- compound assignment operators based on the above cases.
- It is unspecified whether these cases actually generate a negative zero or a normal zero,
- and whether a negative zero becomes a normal zero when stored in an object.
-4 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
- and >> operators with operands that would produce such a value is undefined.
-5 The values of any padding bits are unspecified.54) A valid (non-trap) object representation
- of a signed integer type where the sign bit is zero is a valid object representation of the
- corresponding unsigned type, and shall represent the same value. For any integer type,
- the object representation where all the bits are zero shall be a representation of the value
- zero in that type.
-6 The precision of an integer type is the number of bits it uses to represent values,
- excluding any sign and padding bits. The width of an integer type is the same but
- including any sign bit; thus for unsigned integer types the two values are the same, while
- for signed integer types the width is one greater than the precision.
-
-
-
-
- 54) Some combinations of padding bits might generate trap representations, for example, if one padding
- bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
- representation other than as part of an exceptional condition such as an overflow. All other
- combinations of padding bits are alternative object representations of the value specified by the value
- bits.
-
-[page 46]
-
- 6.2.7 Compatible type and composite type
-1 Two types have compatible type if their types are the same. Additional rules for
- determining whether two types are compatible are described in 6.7.2 for type specifiers,
- in 6.7.3 for type qualifiers, and in 6.7.6 for declarators.55) Moreover, two structure,
- union, or enumerated types declared in separate translation units are compatible if their
- tags and members satisfy the following requirements: If one is declared with a tag, the
- other shall be declared with the same tag. If both are completed anywhere within their
- respective translation units, then the following additional requirements apply: there shall
- be a one-to-one correspondence between their members such that each pair of
- corresponding members are declared with compatible types, and such that if one member
- of a corresponding pair is declared with a name, the other member is declared with the
- same name. For two structures, corresponding members shall be declared in the same
- order. For two structures or unions, corresponding bit-fields shall have the same widths.
- For two enumerations, corresponding members shall have the same values.
-2 All declarations that refer to the same object or function shall have compatible type;
- otherwise, the behavior is undefined.
-3 A composite type can be constructed from two types that are compatible; it is a type that
- is compatible with both of the two types and satisfies the following conditions:
- -- If both types are array types, the following rules are applied:
- o If one type is an array of known constant size, the composite type is an array of
- that size.
- o Otherwise, if one type is a variable length array whose size is specified by an
- expression that is not evaluated, the behavior is undefined.
- o Otherwise, if one type is a variable length array whose size is specified, the
- composite type is a variable length array of that size.
- o Otherwise, if one type is a variable length array of unspecified size, the composite
- type is a variable length array of unspecified size.
- o Otherwise, both types are arrays of unknown size and the composite type is an
- array of unknown size.
- The element type of the composite type is the composite type of the two element
- types.
- -- If only one type is a function type with a parameter type list (a function prototype),
- the composite type is a function prototype with the parameter type list.
-
-
-
- 55) Two types need not be identical to be compatible.
-
-[page 47]
-
- -- If both types are function types with parameter type lists, the type of each parameter
- in the composite parameter type list is the composite type of the corresponding
- parameters.
- These rules apply recursively to the types from which the two types are derived.
-4 For an identifier with internal or external linkage declared in a scope in which a prior
- declaration of that identifier is visible,56) if the prior declaration specifies internal or
- external linkage, the type of the identifier at the later declaration becomes the composite
- type.
- Forward references: array declarators (6.7.6.2).
-5 EXAMPLE Given the following two file scope declarations:
- int f(int (*)(), double (*)[3]);
- int f(int (*)(char *), double (*)[]);
- The resulting composite type for the function is:
- int f(int (*)(char *), double (*)[3]);
-
- 6.2.8 Alignment of objects
-1 Complete object types have alignment requirements which place restrictions on the
- addresses at which objects of that type may be allocated. An alignment is an
- implementation-defined integer value representing the number of bytes between
- successive addresses at which a given object can be allocated. An object type imposes an
- alignment requirement on every object of that type: stricter alignment can be requested
- using the _Alignas keyword.
-2 A fundamental alignment is represented by an alignment less than or equal to the greatest
- alignment supported by the implementation in all contexts, which is equal to
- alignof(max_align_t).
-3 An extended alignment is represented by an alignment greater than
- alignof(max_align_t). It is implementation-defined whether any extended
- alignments are supported and the contexts in which they are supported. A type having an
- extended alignment requirement is an over-aligned type.57)
-4 Alignments are represented as values of the type size_t. Valid alignments include only
- those values returned by an alignof expression for fundamental types, plus an
- additional implementation-defined set of values, which may be empty. Every valid
- alignment value shall be an integral power of two.
-
-
- 56) As specified in 6.2.1, the later declaration might hide the prior declaration.
- 57) Every over-aligned type is, or contains, a structure or union type with a member to which an extended
- alignment has been applied.
-
-[page 48]
-
-5 Alignments have an order from weaker to stronger or stricter alignments. Stricter
- alignments have larger alignment values. An address that satisfies an alignment
- requirement also satisfies any weaker valid alignment requirement.
-6 The alignment requirement of a complete type can be queried using an alignof
- expression. The types char, signed char, and unsigned char shall have the
- weakest alignment requirement.
-7 Comparing alignments is meaningful and provides the obvious results:
- -- Two alignments are equal when their numeric values are equal.
- -- Two alignments are different when their numeric values are not equal.
- -- When an alignment is larger than another it represents a stricter alignment.
-
-
-
-
-[page 49]
-
- 6.3 Conversions
-1 Several operators convert operand values from one type to another automatically. This
- subclause specifies the result required from such an implicit conversion, as well as those
- that result from a cast operation (an explicit conversion). The list in 6.3.1.8 summarizes
- the conversions performed by most ordinary operators; it is supplemented as required by
- the discussion of each operator in 6.5.
-2 Conversion of an operand value to a compatible type causes no change to the value or the
- representation.
- Forward references: cast operators (6.5.4).
- 6.3.1 Arithmetic operands
- 6.3.1.1 Boolean, characters, and integers
-1 Every integer type has an integer conversion rank defined as follows:
- -- No two signed integer types shall have the same rank, even if they have the same
- representation.
- -- The rank of a signed integer type shall be greater than the rank of any signed integer
- type with less precision.
- -- The rank of long long int shall be greater than the rank of long int, which
- shall be greater than the rank of int, which shall be greater than the rank of short
- int, which shall be greater than the rank of signed char.
- -- The rank of any unsigned integer type shall equal the rank of the corresponding
- signed integer type, if any.
- -- The rank of any standard integer type shall be greater than the rank of any extended
- integer type with the same width.
- -- The rank of char shall equal the rank of signed char and unsigned char.
- -- The rank of _Bool shall be less than the rank of all other standard integer types.
- -- The rank of any enumerated type shall equal the rank of the compatible integer type
- (see 6.7.2.2).
- -- The rank of any extended signed integer type relative to another extended signed
- integer type with the same precision is implementation-defined, but still subject to the
- other rules for determining the integer conversion rank.
- -- For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has
- greater rank than T3, then T1 has greater rank than T3.
-2 The following may be used in an expression wherever an int or unsigned int may
- be used:
-
-[page 50]
-
- -- An object or expression with an integer type (other than int or unsigned int)
- whose integer conversion rank is less than or equal to the rank of int and
- unsigned int.
- -- A bit-field of type _Bool, int, signed int, or unsigned int.
- If an int can represent all values of the original type (as restricted by the width, for a
- bit-field), the value is converted to an int; otherwise, it is converted to an unsigned
- int. These are called the integer promotions.58) All other types are unchanged by the
- integer promotions.
-3 The integer promotions preserve value including sign. As discussed earlier, whether a
- ''plain'' char is treated as signed is implementation-defined.
- Forward references: enumeration specifiers (6.7.2.2), structure and union specifiers
- (6.7.2.1).
- 6.3.1.2 Boolean type
-1 When any scalar value is converted to _Bool, the result is 0 if the value compares equal
- to 0; otherwise, the result is 1.59)
- 6.3.1.3 Signed and unsigned integers
-1 When a value with integer type is converted to another integer type other than _Bool, if
- the value can be represented by the new type, it is unchanged.
-2 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or
- subtracting one more than the maximum value that can be represented in the new type
- until the value is in the range of the new type.60)
-3 Otherwise, the new type is signed and the value cannot be represented in it; either the
- result is implementation-defined or an implementation-defined signal is raised.
- 6.3.1.4 Real floating and integer
-1 When a finite value of real floating type is converted to an integer type other than _Bool,
- the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
- the integral part cannot be represented by the integer type, the behavior is undefined.61)
-
-
- 58) The integer promotions are applied only: as part of the usual arithmetic conversions, to certain
- argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the
- shift operators, as specified by their respective subclauses.
- 59) NaNs do not compare equal to 0 and thus convert to 1.
- 60) The rules describe arithmetic on the mathematical value, not the value of a given type of expression.
- 61) The remaindering operation performed when a value of integer type is converted to unsigned type
- need not be performed when a value of real floating type is converted to unsigned type. Thus, the
- range of portable real floating values is (-1, Utype_MAX+1).
-
-[page 51]
-
-2 When a value of integer type is converted to a real floating type, if the value being
- converted can be represented exactly in the new type, it is unchanged. If the value being
- converted is in the range of values that can be represented but cannot be represented
- exactly, the result is either the nearest higher or nearest lower representable value, chosen
- in an implementation-defined manner. If the value being converted is outside the range of
- values that can be represented, the behavior is undefined.
- 6.3.1.5 Real floating types
-1 When a float is promoted to double or long double, or a double is promoted
- to long double, its value is unchanged (if the source value is represented in the
- precision and range of its type).
-2 When a double is demoted to float, a long double is demoted to double or
- float, or a value being represented in greater precision and range than required by its
- semantic type (see 6.3.1.8) is explicitly converted (including to its own type), if the value
- being converted can be represented exactly in the new type, it is unchanged. If the value
- being converted is in the range of values that can be represented but cannot be
- represented exactly, the result is either the nearest higher or nearest lower representable
- value, chosen in an implementation-defined manner. If the value being converted is
- outside the range of values that can be represented, the behavior is undefined.
- 6.3.1.6 Complex types
-1 When a value of complex type is converted to another complex type, both the real and
- imaginary parts follow the conversion rules for the corresponding real types.
- 6.3.1.7 Real and complex
-1 When a value of real type is converted to a complex type, the real part of the complex
- result value is determined by the rules of conversion to the corresponding real type and
- the imaginary part of the complex result value is a positive zero or an unsigned zero.
-2 When a value of complex type is converted to a real type, the imaginary part of the
- complex value is discarded and the value of the real part is converted according to the
- conversion rules for the corresponding real type.
- 6.3.1.8 Usual arithmetic conversions
-1 Many operators that expect operands of arithmetic type cause conversions and yield result
- types in a similar way. The purpose is to determine a common real type for the operands
- and result. For the specified operands, each operand is converted, without change of type
- domain, to a type whose corresponding real type is the common real type. Unless
- explicitly stated otherwise, the common real type is also the corresponding real type of
- the result, whose type domain is the type domain of the operands if they are the same,
- and complex otherwise. This pattern is called the usual arithmetic conversions:
-
-
-[page 52]
-
- First, if the corresponding real type of either operand is long double, the other
- operand is converted, without change of type domain, to a type whose
- corresponding real type is long double.
- Otherwise, if the corresponding real type of either operand is double, the other
- operand is converted, without change of type domain, to a type whose
- corresponding real type is double.
- Otherwise, if the corresponding real type of either operand is float, the other
- operand is converted, without change of type domain, to a type whose
- corresponding real type is float.62)
- Otherwise, the integer promotions are performed on both operands. Then the
- following rules are applied to the promoted operands:
- If both operands have the same type, then no further conversion is needed.
- Otherwise, if both operands have signed integer types or both have unsigned
- integer types, the operand with the type of lesser integer conversion rank is
- converted to the type of the operand with greater rank.
- Otherwise, if the operand that has unsigned integer type has rank greater or
- equal to the rank of the type of the other operand, then the operand with
- signed integer type is converted to the type of the operand with unsigned
- integer type.
- Otherwise, if the type of the operand with signed integer type can represent
- all of the values of the type of the operand with unsigned integer type, then
- the operand with unsigned integer type is converted to the type of the
- operand with signed integer type.
- Otherwise, both operands are converted to the unsigned integer type
- corresponding to the type of the operand with signed integer type.
-2 The values of floating operands and of the results of floating expressions may be
- represented in greater precision and range than that required by the type; the types are not
- changed thereby.63)
-
-
-
-
- 62) For example, addition of a double _Complex and a float entails just the conversion of the
- float operand to double (and yields a double _Complex result).
- 63) The cast and assignment operators are still required to perform their specified conversions as
- described in 6.3.1.4 and 6.3.1.5.
-
-[page 53]
-
- 6.3.2 Other operands
- 6.3.2.1 Lvalues, arrays, and function designators
-1 An lvalue is an expression (with an object type other than void) that potentially
- designates an object;64) if an lvalue does not designate an object when it is evaluated, the
- behavior is undefined. When an object is said to have a particular type, the type is
- specified by the lvalue used to designate the object. A modifiable lvalue is an lvalue that
- does not have array type, does not have an incomplete type, does not have a const-
- qualified type, and if it is a structure or union, does not have any member (including,
- recursively, any member or element of all contained aggregates or unions) with a const-
- qualified type.
-2 Except when it is the operand of the sizeof operator, the unary & operator, the ++
- operator, the -- operator, or the left operand of the . operator or an assignment operator,
- an lvalue that does not have array type is converted to the value stored in the designated
- object (and is no longer an lvalue). If the lvalue has qualified type, the value has the
- unqualified version of the type of the lvalue; otherwise, the value has the type of the
- lvalue. If the lvalue has an incomplete type and does not have array type, the behavior is
- undefined. If the lvalue designates an object of automatic storage duration that could
- have been declared with the register storage class (never had its address taken), and
- that object is uninitialized (not declared with an initializer and no assignment to it has
- been performed prior to use), the behavior is undefined.
-3 Except when it is the operand of the sizeof operator or the unary & operator, or is a
- string literal used to initialize an array, an expression that has type ''array of type'' is
- converted to an expression with type ''pointer to type'' that points to the initial element of
- the array object and is not an lvalue. If the array object has register storage class, the
- behavior is undefined.
-4 A function designator is an expression that has function type. Except when it is the
- operand of the sizeof operator65) or the unary & operator, a function designator with
- type ''function returning type'' is converted to an expression that has type ''pointer to
- function returning type''.
- Forward references: address and indirection operators (6.5.3.2), assignment operators
-
- 64) The name ''lvalue'' comes originally from the assignment expression E1 = E2, in which the left
- operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
- object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described
- as the ''value of an expression''.
- An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
- expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.
- 65) Because this conversion does not occur, the operand of the sizeof operator remains a function
- designator and violates the constraint in 6.5.3.4.
-
-[page 54]
-
- (6.5.16), common definitions <stddef.h> (7.19), initialization (6.7.9), postfix
- increment and decrement operators (6.5.2.4), prefix increment and decrement operators
- (6.5.3.1), the sizeof operator (6.5.3.4), structure and union members (6.5.2.3).
- 6.3.2.2 void
-1 The (nonexistent) value of a void expression (an expression that has type void) shall not
- be used in any way, and implicit or explicit conversions (except to void) shall not be
- applied to such an expression. If an expression of any other type is evaluated as a void
- expression, its value or designator is discarded. (A void expression is evaluated for its
- side effects.)
- 6.3.2.3 Pointers
-1 A pointer to void may be converted to or from a pointer to any object type. A pointer to
- any object type may be converted to a pointer to void and back again; the result shall
- compare equal to the original pointer.
-2 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to
- the q-qualified version of the type; the values stored in the original and converted pointers
- shall compare equal.
-3 An integer constant expression with the value 0, or such an expression cast to type
- void *, is called a null pointer constant.66) If a null pointer constant is converted to a
- pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal
- to a pointer to any object or function.
-4 Conversion of a null pointer to another pointer type yields a null pointer of that type.
- Any two null pointers shall compare equal.
-5 An integer may be converted to any pointer type. Except as previously specified, the
- result is implementation-defined, might not be correctly aligned, might not point to an
- entity of the referenced type, and might be a trap representation.67)
-6 Any pointer type may be converted to an integer type. Except as previously specified, the
- result is implementation-defined. If the result cannot be represented in the integer type,
- the behavior is undefined. The result need not be in the range of values of any integer
- type.
-7 A pointer to an object type may be converted to a pointer to a different object type. If the
- resulting pointer is not correctly aligned68) for the referenced type, the behavior is
- undefined. Otherwise, when converted back again, the result shall compare equal to the
-
-
- 66) The macro NULL is defined in <stddef.h> (and other headers) as a null pointer constant; see 7.19.
- 67) The mapping functions for converting a pointer to an integer or an integer to a pointer are intended to
- be consistent with the addressing structure of the execution environment.
-
-[page 55]
-
- original pointer. When a pointer to an object is converted to a pointer to a character type,
- the result points to the lowest addressed byte of the object. Successive increments of the
- result, up to the size of the object, yield pointers to the remaining bytes of the object.
-8 A pointer to a function of one type may be converted to a pointer to a function of another
- type and back again; the result shall compare equal to the original pointer. If a converted
- pointer is used to call a function whose type is not compatible with the referenced type,
- the behavior is undefined.
- Forward references: cast operators (6.5.4), equality operators (6.5.9), integer types
- capable of holding object pointers (7.20.1.4), simple assignment (6.5.16.1).
-
-
-
-
- 68) In general, the concept ''correctly aligned'' is transitive: if a pointer to type A is correctly aligned for a
- pointer to type B, which in turn is correctly aligned for a pointer to type C, then a pointer to type A is
- correctly aligned for a pointer to type C.
-
-[page 56]
-
- 6.4 Lexical elements
- Syntax
-1 token:
- keyword
- identifier
- constant
- string-literal
- punctuator
- preprocessing-token:
- header-name
- identifier
- pp-number
- character-constant
- string-literal
- punctuator
- each non-white-space character that cannot be one of the above
- Constraints
-2 Each preprocessing token that is converted to a token shall have the lexical form of a
- keyword, an identifier, a constant, a string literal, or a punctuator.
- Semantics
-3 A token is the minimal lexical element of the language in translation phases 7 and 8. The
- categories of tokens are: keywords, identifiers, constants, string literals, and punctuators.
- A preprocessing token is the minimal lexical element of the language in translation
- phases 3 through 6. The categories of preprocessing tokens are: header names,
- identifiers, preprocessing numbers, character constants, string literals, punctuators, and
- single non-white-space characters that do not lexically match the other preprocessing
- token categories.69) If a ' or a " character matches the last category, the behavior is
- undefined. Preprocessing tokens can be separated by white space; this consists of
- comments (described later), or white-space characters (space, horizontal tab, new-line,
- vertical tab, and form-feed), or both. As described in 6.10, in certain circumstances
- during translation phase 4, white space (or the absence thereof) serves as more than
- preprocessing token separation. White space may appear within a preprocessing token
- only as part of a header name or between the quotation characters in a character constant
- or string literal.
-
-
-
- 69) An additional category, placemarkers, is used internally in translation phase 4 (see 6.10.3.3); it cannot
- occur in source files.
-
-[page 57]
-
-4 If the input stream has been parsed into preprocessing tokens up to a given character, the
- next preprocessing token is the longest sequence of characters that could constitute a
- preprocessing token. There is one exception to this rule: header name preprocessing
- tokens are recognized only within #include preprocessing directives and in
- implementation-defined locations within #pragma directives. In such contexts, a
- sequence of characters that could be either a header name or a string literal is recognized
- as the former.
-5 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a
- valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex
- might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program
- fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or
- not E is a macro name.
-
-6 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
- increment operators, even though the parse x ++ + ++ y might yield a correct expression.
-
- Forward references: character constants (6.4.4.4), comments (6.4.9), expressions (6.5),
- floating constants (6.4.4.2), header names (6.4.7), macro replacement (6.10.3), postfix
- increment and decrement operators (6.5.2.4), prefix increment and decrement operators
- (6.5.3.1), preprocessing directives (6.10), preprocessing numbers (6.4.8), string literals
- (6.4.5).
- 6.4.1 Keywords
- Syntax
-1 keyword: one of
- alignof goto union
- auto if unsigned
- break inline void
- case int volatile
- char long while
- const register _Alignas
- continue restrict _Atomic
- default return _Bool
- do short _Complex
- double signed _Generic
- else sizeof _Imaginary
- enum static _Noreturn
- extern struct _Static_assert
- float switch _Thread_local
- for typedef
- Semantics
-2 The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as
- keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
-[page 58]
-
- specifying imaginary types.70)
- 6.4.2 Identifiers
- 6.4.2.1 General
- Syntax
-1 identifier:
- identifier-nondigit
- identifier identifier-nondigit
- identifier digit
- identifier-nondigit:
- nondigit
- universal-character-name
- other implementation-defined characters
- nondigit: one of
- _ a b c d e f g h i j k l m
- n o p q r s t u v w x y z
- A B C D E F G H I J K L M
- N O P Q R S T U V W X Y Z
- digit: one of
- 0 1 2 3 4 5 6 7 8 9
- Semantics
-2 An identifier is a sequence of nondigit characters (including the underscore _, the
- lowercase and uppercase Latin letters, and other characters) and digits, which designates
- one or more entities as described in 6.2.1. Lowercase and uppercase letters are distinct.
- There is no specific limit on the maximum length of an identifier.
-3 Each universal character name in an identifier shall designate a character whose encoding
- in ISO/IEC 10646 falls into one of the ranges specified in annex D.71) The initial
- character shall not be a universal character name designating a digit. An implementation
- may allow multibyte characters that are not part of the basic source character set to
- appear in identifiers; which characters and their correspondence to universal character
- names is implementation-defined.
-
-
-
- 70) One possible specification for imaginary types appears in annex G.
- 71) On systems in which linkers cannot accept extended characters, an encoding of the universal character
- name may be used in forming valid external identifiers. For example, some otherwise unused
- character or sequence of characters may be used to encode the \u in a universal character name.
- Extended characters may produce a long external identifier.
-
-[page 59]
-
-4 When preprocessing tokens are converted to tokens during translation phase 7, if a
- preprocessing token could be converted to either a keyword or an identifier, it is converted
- to a keyword.
- Implementation limits
-5 As discussed in 5.2.4.1, an implementation may limit the number of significant initial
- characters in an identifier; the limit for an external name (an identifier that has external
- linkage) may be more restrictive than that for an internal name (a macro name or an
- identifier that does not have external linkage). The number of significant characters in an
- identifier is implementation-defined.
-6 Any identifiers that differ in a significant character are different identifiers. If two
- identifiers differ only in nonsignificant characters, the behavior is undefined.
- Forward references: universal character names (6.4.3), macro replacement (6.10.3).
- 6.4.2.2 Predefined identifiers
- Semantics
-1 The identifier __func__ shall be implicitly declared by the translator as if,
- immediately following the opening brace of each function definition, the declaration
- static const char __func__[] = "function-name";
- appeared, where function-name is the name of the lexically-enclosing function.72)
-2 This name is encoded as if the implicit declaration had been written in the source
- character set and then translated into the execution character set as indicated in translation
- phase 5.
-3 EXAMPLE Consider the code fragment:
- #include <stdio.h>
- void myfunc(void)
- {
- printf("%s\n", __func__);
- /* ... */
- }
- Each time the function is called, it will print to the standard output stream:
- myfunc
-
- Forward references: function definitions (6.9.1).
-
-
-
-
- 72) Since the name __func__ is reserved for any use by the implementation (7.1.3), if any other
- identifier is explicitly declared using the name __func__, the behavior is undefined.
-
-[page 60]
-
- 6.4.3 Universal character names
- Syntax
-1 universal-character-name:
- \u hex-quad
- \U hex-quad hex-quad
- hex-quad:
- hexadecimal-digit hexadecimal-digit
- hexadecimal-digit hexadecimal-digit
- Constraints
-2 A universal character name shall not specify a character whose short identifier is less than
- 00A0 other than 0024 ($), 0040 (@), or 0060 ('), nor one in the range D800 through
- DFFF inclusive.73)
- Description
-3 Universal character names may be used in identifiers, character constants, and string
- literals to designate characters that are not in the basic character set.
- Semantics
-4 The universal character name \Unnnnnnnn designates the character whose eight-digit
- short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.74) Similarly, the universal
- character name \unnnn designates the character whose four-digit short identifier is nnnn
- (and whose eight-digit short identifier is 0000nnnn).
-
-
-
-
- 73) The disallowed characters are the characters in the basic character set and the code positions reserved
- by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by
- UTF-16).
-
- 74) Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
-
-[page 61]
-
- 6.4.4 Constants
- Syntax
-1 constant:
- integer-constant
- floating-constant
- enumeration-constant
- character-constant
- Constraints
-2 Each constant shall have a type and the value of a constant shall be in the range of
- representable values for its type.
- Semantics
-3 Each constant has a type, determined by its form and value, as detailed later.
- 6.4.4.1 Integer constants
- Syntax
-1 integer-constant:
- decimal-constant integer-suffixopt
- octal-constant integer-suffixopt
- hexadecimal-constant integer-suffixopt
- decimal-constant:
- nonzero-digit
- decimal-constant digit
- octal-constant:
- 0
- octal-constant octal-digit
- hexadecimal-constant:
- hexadecimal-prefix hexadecimal-digit
- hexadecimal-constant hexadecimal-digit
- hexadecimal-prefix: one of
- 0x 0X
- nonzero-digit: one of
- 1 2 3 4 5 6 7 8 9
- octal-digit: one of
- 0 1 2 3 4 5 6 7
-
-
-
-
-[page 62]
-
- hexadecimal-digit: one of
- 0 1 2 3 4 5 6 7 8 9
- a b c d e f
- A B C D E F
- integer-suffix:
- unsigned-suffix long-suffixopt
- unsigned-suffix long-long-suffix
- long-suffix unsigned-suffixopt
- long-long-suffix unsigned-suffixopt
- unsigned-suffix: one of
- u U
- long-suffix: one of
- l L
- long-long-suffix: one of
- ll LL
- Description
-2 An integer constant begins with a digit, but has no period or exponent part. It may have a
- prefix that specifies its base and a suffix that specifies its type.
-3 A decimal constant begins with a nonzero digit and consists of a sequence of decimal
- digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
- digits 0 through 7 only. A hexadecimal constant consists of the prefix 0x or 0X followed
- by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
- 10 through 15 respectively.
- Semantics
-4 The value of a decimal constant is computed base 10; that of an octal constant, base 8;
- that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
-5 The type of an integer constant is the first of the corresponding list in which its value can
- be represented.
-
-
-
-
-[page 63]
-
- Octal or Hexadecimal
- Suffix Decimal Constant Constant
-
- none int int
- long int unsigned int
- long long int long int
- unsigned long int
- long long int
- unsigned long long int
-
- u or U unsigned int unsigned int
- unsigned long int unsigned long int
- unsigned long long int unsigned long long int
-
- l or L long int long int
- long long int unsigned long int
- long long int
- unsigned long long int
-
- Both u or U unsigned long int unsigned long int
- and l or L unsigned long long int unsigned long long int
-
- ll or LL long long int long long int
- unsigned long long int
-
- Both u or U unsigned long long int unsigned long long int
- and ll or LL
-6 If an integer constant cannot be represented by any type in its list, it may have an
- extended integer type, if the extended integer type can represent its value. If all of the
- types in the list for the constant are signed, the extended integer type shall be signed. If
- all of the types in the list for the constant are unsigned, the extended integer type shall be
- unsigned. If the list contains both signed and unsigned types, the extended integer type
- may be signed or unsigned. If an integer constant cannot be represented by any type in
- its list and has no extended integer type, then the integer constant has no type.
-
-
-
-
-[page 64]
-
- 6.4.4.2 Floating constants
- Syntax
-1 floating-constant:
- decimal-floating-constant
- hexadecimal-floating-constant
- decimal-floating-constant:
- fractional-constant exponent-partopt floating-suffixopt
- digit-sequence exponent-part floating-suffixopt
- hexadecimal-floating-constant:
- hexadecimal-prefix hexadecimal-fractional-constant
- binary-exponent-part floating-suffixopt
- hexadecimal-prefix hexadecimal-digit-sequence
- binary-exponent-part floating-suffixopt
- fractional-constant:
- digit-sequenceopt . digit-sequence
- digit-sequence .
- exponent-part:
- e signopt digit-sequence
- E signopt digit-sequence
- sign: one of
- + -
- digit-sequence:
- digit
- digit-sequence digit
- hexadecimal-fractional-constant:
- hexadecimal-digit-sequenceopt .
- hexadecimal-digit-sequence
- hexadecimal-digit-sequence .
- binary-exponent-part:
- p signopt digit-sequence
- P signopt digit-sequence
- hexadecimal-digit-sequence:
- hexadecimal-digit
- hexadecimal-digit-sequence hexadecimal-digit
- floating-suffix: one of
- f l F L
-
-[page 65]
-
- Description
-2 A floating constant has a significand part that may be followed by an exponent part and a
- suffix that specifies its type. The components of the significand part may include a digit
- sequence representing the whole-number part, followed by a period (.), followed by a
- digit sequence representing the fraction part. The components of the exponent part are an
- e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
- Either the whole-number part or the fraction part has to be present; for decimal floating
- constants, either the period or the exponent part has to be present.
- Semantics
-3 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
- digit sequence in the exponent part is interpreted as a decimal integer. For decimal
- floating constants, the exponent indicates the power of 10 by which the significand part is
- to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
- by which the significand part is to be scaled. For decimal floating constants, and also for
- hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
- the nearest representable value, or the larger or smaller representable value immediately
- adjacent to the nearest representable value, chosen in an implementation-defined manner.
- For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
- correctly rounded.
-4 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
- type float. If suffixed by the letter l or L, it has type long double.
-5 Floating constants are converted to internal format as if at translation-time. The
- conversion of a floating constant shall not raise an exceptional condition or a floating-
- point exception at execution time.
- Recommended practice
-6 The implementation should produce a diagnostic message if a hexadecimal constant
- cannot be represented exactly in its evaluation format; the implementation should then
- proceed with the translation of the program.
-7 The translation-time conversion of floating constants should match the execution-time
- conversion of character strings by library functions, such as strtod, given matching
- inputs suitable for both conversions, the same result format, and default execution-time
- rounding.75)
-
-
-
-
- 75) The specification for the library functions recommends more accurate conversion than required for
- floating constants (see 7.22.1.3).
-
-[page 66]
-
- 6.4.4.3 Enumeration constants
- Syntax
-1 enumeration-constant:
- identifier
- Semantics
-2 An identifier declared as an enumeration constant has type int.
- Forward references: enumeration specifiers (6.7.2.2).
- 6.4.4.4 Character constants
- Syntax
-1 character-constant:
- ' c-char-sequence '
- L' c-char-sequence '
- u' c-char-sequence '
- U' c-char-sequence '
- c-char-sequence:
- c-char
- c-char-sequence c-char
- c-char:
- any member of the source character set except
- the single-quote ', backslash \, or new-line character
- escape-sequence
- escape-sequence:
- simple-escape-sequence
- octal-escape-sequence
- hexadecimal-escape-sequence
- universal-character-name
- simple-escape-sequence: one of
- \' \" \? \\
- \a \b \f \n \r \t \v
- octal-escape-sequence:
- \ octal-digit
- \ octal-digit octal-digit
- \ octal-digit octal-digit octal-digit
-
-
-
-
-[page 67]
-
- hexadecimal-escape-sequence:
- \x hexadecimal-digit
- hexadecimal-escape-sequence hexadecimal-digit
- Description
-2 An integer character constant is a sequence of one or more multibyte characters enclosed
- in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
- letter L, u, or U. With a few exceptions detailed later, the elements of the sequence are
- any members of the source character set; they are mapped in an implementation-defined
- manner to members of the execution character set.
-3 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
- arbitrary integer values are representable according to the following table of escape
- sequences:
- single quote ' \'
- double quote " \"
- question mark ? \?
- backslash \ \\
- octal character \octal digits
- hexadecimal character \x hexadecimal digits
-4 The double-quote " and question-mark ? are representable either by themselves or by the
- escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
- shall be represented, respectively, by the escape sequences \' and \\.
-5 The octal digits that follow the backslash in an octal escape sequence are taken to be part
- of the construction of a single character for an integer character constant or of a single
- wide character for a wide character constant. The numerical value of the octal integer so
- formed specifies the value of the desired character or wide character.
-6 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
- sequence are taken to be part of the construction of a single character for an integer
- character constant or of a single wide character for a wide character constant. The
- numerical value of the hexadecimal integer so formed specifies the value of the desired
- character or wide character.
-7 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
- constitute the escape sequence.
-8 In addition, characters not in the basic character set are representable by universal
- character names and certain nongraphic characters are representable by escape sequences
- consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
- and \v.76)
-
-
-
-[page 68]
-
- Constraints
-9 The value of an octal or hexadecimal escape sequence shall be in the range of
- representable values for the corresponding type:
- Prefix Corresponding Type
- none unsigned char
- L the unsigned type corresponding to wchar_t
- u char16_t
- U char32_t
- Semantics
-10 An integer character constant has type int. The value of an integer character constant
- containing a single character that maps to a single-byte execution character is the
- numerical value of the representation of the mapped character interpreted as an integer.
- The value of an integer character constant containing more than one character (e.g.,
- 'ab'), or containing a character or escape sequence that does not map to a single-byte
- execution character, is implementation-defined. If an integer character constant contains
- a single character or escape sequence, its value is the one that results when an object with
- type char whose value is that of the single character or escape sequence is converted to
- type int.
-11 A wide character constant prefixed by the letter L has type wchar_t, an integer type
- defined in the <stddef.h> header; a wide character constant prefixed by the letter u or
- U has type char16_t or char32_t, respectively, unsigned integer types defined in the
- <uchar.h> header. The value of a wide character constant containing a single
- multibyte character that maps to a single member of the extended execution character set
- is the wide character corresponding to that multibyte character, as defined by the
- mbtowc, mbrtoc16, or mbrtoc32 function as appropriate for its type, with an
- implementation-defined current locale. The value of a wide character constant containing
- more than one multibyte character or a single multibyte character that maps to multiple
- members of the extended execution character set, or containing a multibyte character or
- escape sequence not represented in the extended execution character set, is
- implementation-defined.
-12 EXAMPLE 1 The construction '\0' is commonly used to represent the null character.
-
-13 EXAMPLE 2 Consider implementations that use two's-complement representation for integers and eight
- bits for objects that have type char. In an implementation in which type char has the same range of
- values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
- same range of values as unsigned char, the character constant '\xFF' has the value +255.
-
-
-
-
- 76) The semantics of these characters were discussed in 5.2.2. If any other character follows a backslash,
- the result is not a token and a diagnostic is required. See ''future language directions'' (6.11.4).
-
-[page 69]
-
-14 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
- specifies an integer character constant containing only one character, since a hexadecimal escape sequence
- is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
- two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
- escape sequence is terminated after three octal digits. (The value of this two-character integer character
- constant is implementation-defined.)
-
-15 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
- L'\1234' specifies the implementation-defined value that results from the combination of the values
- 0123 and '4'.
-
- Forward references: common definitions <stddef.h> (7.19), the mbtowc function
- (7.22.7.2), Unicode utilities <uchar.h> (7.27).
- 6.4.5 String literals
- Syntax
-1 string-literal:
- encoding-prefixopt " s-char-sequenceopt "
- encoding-prefix:
- u8
- u
- U
- L
- s-char-sequence:
- s-char
- s-char-sequence s-char
- s-char:
- any member of the source character set except
- the double-quote ", backslash \, or new-line character
- escape-sequence
- Constraints
-2 A sequence of adjacent string literal tokens shall not include both a wide string literal and
- a UTF-8 string literal.
- Description
-3 A character string literal is a sequence of zero or more multibyte characters enclosed in
- double-quotes, as in "xyz". A UTF-8 string literal is the same, except prefixed by u8.
- A wide string literal is the same, except prefixed by the letter L, u, or U.
-4 The same considerations apply to each element of the sequence in a string literal as if it
- were in an integer character constant (for a character or UTF-8 string literal) or a wide
- character constant (for a wide string literal), except that the single-quote ' is
- representable either by itself or by the escape sequence \', but the double-quote " shall
-[page 70]
-
- be represented by the escape sequence \".
- Semantics
-5 In translation phase 6, the multibyte character sequences specified by any sequence of
- adjacent character and identically-prefixed string literal tokens are concatenated into a
- single multibyte character sequence. If any of the tokens has an encoding prefix, the
- resulting multibyte character sequence is treated as having the same prefix; otherwise, it
- is treated as a character string literal. Whether differently-prefixed wide string literal
- tokens can be concatenated and, if so, the treatment of the resulting multibyte character
- sequence are implementation-defined.
-6 In translation phase 7, a byte or code of value zero is appended to each multibyte
- character sequence that results from a string literal or literals.77) The multibyte character
- sequence is then used to initialize an array of static storage duration and length just
- sufficient to contain the sequence. For character string literals, the array elements have
- type char, and are initialized with the individual bytes of the multibyte character
- sequence. For UTF-8 string literals, the array elements have type char, and are
- initialized with the characters of the multibyte character sequence, as encoded in UTF-8.
- For wide string literals prefixed by the letter L, the array elements have type wchar_t
- and are initialized with the sequence of wide characters corresponding to the multibyte
- character sequence, as defined by the mbstowcs function with an implementation-
- defined current locale. For wide string literals prefixed by the letter u or U, the array
- elements have type char16_t or char32_t, respectively, and are initialized with the
- sequence of wide characters corresponding to the multibyte character sequence, as
- defined by successive calls to the mbrtoc16, or mbrtoc32 function as appropriate for
- its type, with an implementation-defined current locale. The value of a string literal
- containing a multibyte character or escape sequence not represented in the execution
- character set is implementation-defined.
-7 It is unspecified whether these arrays are distinct provided their elements have the
- appropriate values. If the program attempts to modify such an array, the behavior is
- undefined.
-8 EXAMPLE 1 This pair of adjacent character string literals
- "\x12" "3"
- produces a single character string literal containing the two characters whose values are '\x12' and '3',
- because escape sequences are converted into single members of the execution character set just prior to
- adjacent string literal concatenation.
-
-9 EXAMPLE 2 Each of the sequences of adjacent string literal tokens
-
-
-
- 77) A string literal need not be a string (see 7.1.1), because a null character may be embedded in it by a
- \0 escape sequence.
-
-[page 71]
-
- "a" "b" L"c"
- "a" L"b" "c"
- L"a" "b" L"c"
- L"a" L"b" L"c"
- is equivalent to the string literal
- L"abc"
- Likewise, each of the sequences
- "a" "b" u"c"
- "a" u"b" "c"
- u"a" "b" u"c"
- u"a" u"b" u"c"
- is equivalent to
- u"abc"
-
- Forward references: common definitions <stddef.h> (7.19), the mbstowcs
- function (7.22.8.1), Unicode utilities <uchar.h> (7.27).
- 6.4.6 Punctuators
- Syntax
-1 punctuator: one of
- [ ] ( ) { } . ->
- ++ -- & * + - ~ !
- / % << >> < > <= >= == != ^ | && ||
- ? : ; ...
- = *= /= %= += -= <<= >>= &= ^= |=
- , # ##
- <: :> <% %> %: %:%:
- Semantics
-2 A punctuator is a symbol that has independent syntactic and semantic significance.
- Depending on context, it may specify an operation to be performed (which in turn may
- yield a value or a function designator, produce a side effect, or some combination thereof)
- in which case it is known as an operator (other forms of operator also exist in some
- contexts). An operand is an entity on which an operator acts.
-
-
-
-
-[page 72]
-
-3 In all aspects of the language, the six tokens78)
- <: :> <% %> %: %:%:
- behave, respectively, the same as the six tokens
- [ ] { } # ##
- except for their spelling.79)
- Forward references: expressions (6.5), declarations (6.7), preprocessing directives
- (6.10), statements (6.8).
- 6.4.7 Header names
- Syntax
-1 header-name:
- < h-char-sequence >
- " q-char-sequence "
- h-char-sequence:
- h-char
- h-char-sequence h-char
- h-char:
- any member of the source character set except
- the new-line character and >
- q-char-sequence:
- q-char
- q-char-sequence q-char
- q-char:
- any member of the source character set except
- the new-line character and "
- Semantics
-2 The sequences in both forms of header names are mapped in an implementation-defined
- manner to headers or external source file names as specified in 6.10.2.
-3 If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters,
- the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the
-
-
-
-
- 78) These tokens are sometimes called ''digraphs''.
- 79) Thus [ and <: behave differently when ''stringized'' (see 6.10.3.2), but can otherwise be freely
- interchanged.
-
-[page 73]
-
- sequence between the " delimiters, the behavior is undefined.80) Header name
- preprocessing tokens are recognized only within #include preprocessing directives and
- in implementation-defined locations within #pragma directives.81)
-4 EXAMPLE The following sequence of characters:
- 0x3<1/a.h>1e2
- #include <1/a.h>
- #define const.member@$
- forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
- by a { on the left and a } on the right).
- {0x3}{<}{1}{/}{a}{.}{h}{>}{1e2}
- {#}{include} {<1/a.h>}
- {#}{define} {const}{.}{member}{@}{$}
-
- Forward references: source file inclusion (6.10.2).
- 6.4.8 Preprocessing numbers
- Syntax
-1 pp-number:
- digit
- . digit
- pp-number digit
- pp-number identifier-nondigit
- pp-number e sign
- pp-number E sign
- pp-number p sign
- pp-number P sign
- pp-number .
- Description
-2 A preprocessing number begins with a digit optionally preceded by a period (.) and may
- be followed by valid identifier characters and the character sequences e+, e-, E+, E-,
- p+, p-, P+, or P-.
-3 Preprocessing number tokens lexically include all floating and integer constant tokens.
- Semantics
-4 A preprocessing number does not have type or a value; it acquires both after a successful
- conversion (as part of translation phase 7) to a floating constant token or an integer
- constant token.
-
-
- 80) Thus, sequences of characters that resemble escape sequences cause undefined behavior.
- 81) For an example of a header name preprocessing token used in a #pragma directive, see 6.10.9.
-
-[page 74]
-
- 6.4.9 Comments
-1 Except within a character constant, a string literal, or a comment, the characters /*
- introduce a comment. The contents of such a comment are examined only to identify
- multibyte characters and to find the characters */ that terminate it.82)
-2 Except within a character constant, a string literal, or a comment, the characters //
- introduce a comment that includes all multibyte characters up to, but not including, the
- next new-line character. The contents of such a comment are examined only to identify
- multibyte characters and to find the terminating new-line character.
-3 EXAMPLE
- "a//b" // four-character string literal
- #include "//e" // undefined behavior
- // */ // comment, not syntax error
- f = g/**//h; // equivalent to f = g / h;
- //\
- i(); // part of a two-line comment
- /\
- / j(); // part of a two-line comment
- #define glue(x,y) x##y
- glue(/,/) k(); // syntax error, not comment
- /*//*/ l(); // equivalent to l();
- m = n//**/o
- + p; // equivalent to m = n + p;
-
-
-
-
- 82) Thus, /* ... */ comments do not nest.
-
-[page 75]
-
- 6.5 Expressions
-1 An expression is a sequence of operators and operands that specifies computation of a
- value, or that designates an object or a function, or that generates side effects, or that
- performs a combination thereof. The value computations of the operands of an operator
- are sequenced before the value computation of the result of the operator.
-2 If a side effect on a scalar object is unsequenced relative to either a different side effect
- on the same scalar object or a value computation using the value of the same scalar
- object, the behavior is undefined. If there are multiple allowable orderings of the
- subexpressions of an expression, the behavior is undefined if such an unsequenced side
- effect occurs in any of the orderings.83)
-3 The grouping of operators and operands is indicated by the syntax.84) Except as specified
- later, side effects and value computations of subexpressions are unsequenced.85)
-4 Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |,
- collectively described as bitwise operators) are required to have operands that have
- integer type. These operators yield values that depend on the internal representations of
- integers, and have implementation-defined and undefined aspects for signed types.
-5 If an exceptional condition occurs during the evaluation of an expression (that is, if the
- result is not mathematically defined or not in the range of representable values for its
- type), the behavior is undefined.
-
-
-
- 83) This paragraph renders undefined statement expressions such as
- i = ++i + 1;
- a[i++] = i;
- while allowing
- i = i + 1;
- a[i] = i;
-
- 84) The syntax specifies the precedence of operators in the evaluation of an expression, which is the same
- as the order of the major subclauses of this subclause, highest precedence first. Thus, for example, the
- expressions allowed as the operands of the binary + operator (6.5.6) are those expressions defined in
- 6.5.1 through 6.5.6. The exceptions are cast expressions (6.5.4) as operands of unary operators
- (6.5.3), and an operand contained between any of the following pairs of operators: grouping
- parentheses () (6.5.1), subscripting brackets [] (6.5.2.1), function-call parentheses () (6.5.2.2), and
- the conditional operator ? : (6.5.15).
- Within each major subclause, the operators have the same precedence. Left- or right-associativity is
- indicated in each subclause by the syntax for the expressions discussed therein.
- 85) In an expression that is evaluated more than once during the execution of a program, unsequenced and
- indeterminately sequenced evaluations of its subexpressions need not be performed consistently in
- different evaluations.
-
-[page 76]
-
-6 The effective type of an object for an access to its stored value is the declared type of the
- object, if any.86) If a value is stored into an object having no declared type through an
- lvalue having a type that is not a character type, then the type of the lvalue becomes the
- effective type of the object for that access and for subsequent accesses that do not modify
- the stored value. If a value is copied into an object having no declared type using
- memcpy or memmove, or is copied as an array of character type, then the effective type
- of the modified object for that access and for subsequent accesses that do not modify the
- value is the effective type of the object from which the value is copied, if it has one. For
- all other accesses to an object having no declared type, the effective type of the object is
- simply the type of the lvalue used for the access.
-7 An object shall have its stored value accessed only by an lvalue expression that has one of
- the following types:87)
- -- a type compatible with the effective type of the object,
- -- a qualified version of a type compatible with the effective type of the object,
- -- a type that is the signed or unsigned type corresponding to the effective type of the
- object,
- -- a type that is the signed or unsigned type corresponding to a qualified version of the
- effective type of the object,
- -- an aggregate or union type that includes one of the aforementioned types among its
- members (including, recursively, a member of a subaggregate or contained union), or
- -- a character type.
-8 A floating expression may be contracted, that is, evaluated as though it were a single
- operation, thereby omitting rounding errors implied by the source code and the
- expression evaluation method.88) The FP_CONTRACT pragma in <math.h> provides a
- way to disallow contracted expressions. Otherwise, whether and how expressions are
- contracted is implementation-defined.89)
- Forward references: the FP_CONTRACT pragma (7.12.2), copying functions (7.23.2).
-
-
- 86) Allocated objects have no declared type.
- 87) The intent of this list is to specify those circumstances in which an object may or may not be aliased.
- 88) The intermediate operations in the contracted expression are evaluated as if to infinite precision and
- range, while the final operation is rounded to the format determined by the expression evaluation
- method. A contracted expression might also omit the raising of floating-point exceptions.
- 89) This license is specifically intended to allow implementations to exploit fast machine instructions that
- combine multiple C operators. As contractions potentially undermine predictability, and can even
- decrease accuracy for containing expressions, their use needs to be well-defined and clearly
- documented.
-
-[page 77]
-
- 6.5.1 Primary expressions
- Syntax
-1 primary-expression:
- identifier
- constant
- string-literal
- ( expression )
- generic-selection
- Semantics
-2 An identifier is a primary expression, provided it has been declared as designating an
- object (in which case it is an lvalue) or a function (in which case it is a function
- designator).90)
-3 A constant is a primary expression. Its type depends on its form and value, as detailed in
- 6.4.4.
-4 A string literal is a primary expression. It is an lvalue with type as detailed in 6.4.5.
-5 A parenthesized expression is a primary expression. Its type and value are identical to
- those of the unparenthesized expression. It is an lvalue, a function designator, or a void
- expression if the unparenthesized expression is, respectively, an lvalue, a function
- designator, or a void expression.
- Forward references: declarations (6.7).
- 6.5.1.1 Generic selection
- Syntax
-1 generic-selection:
- _Generic ( assignment-expression , generic-assoc-list )
- generic-assoc-list:
- generic-association
- generic-assoc-list , generic-association
- generic-association:
- type-name : assignment-expression
- default : assignment-expression
- Constraints
-2 A generic selection shall have no more than one default generic association. The type
- name in a generic association shall specify a complete object type other than a variably
-
- 90) Thus, an undeclared identifier is a violation of the syntax.
-
-[page 78]
-
- modified type. No two generic associations in the same generic selection shall specify
- compatible types. The controlling expression of a generic selection shall have type
- compatible with at most one of the types named in its generic association list. If a
- generic selection has no default generic association, its controlling expression shall
- have type compatible with exactly one of the types named in its generic association list.
- Semantics
-3 The controlling expression of a generic selection is not evaluated. If a generic selection
- has a generic association with a type name that is compatible with the type of the
- controlling expression, then the result expression of the generic selection is the
- expression in that generic association. Otherwise, the result expression of the generic
- selection is the expression in the default generic association. None of the expressions
- from any other generic association of the generic selection is evaluated.
-4 The type and value of a generic selection are identical to those of its result expression. It
- is an lvalue, a function designator, or a void expression if its result expression is,
- respectively, an lvalue, a function designator, or a void expression.
-5 EXAMPLE The cbrt type-generic macro could be implemented as follows:
- #define cbrt(X) _Generic((X), \
- long double: cbrtl, \
- default: cbrt, \
- float: cbrtf \
- )(X)
-
- 6.5.2 Postfix operators
- Syntax
-1 postfix-expression:
- primary-expression
- postfix-expression [ expression ]
- postfix-expression ( argument-expression-listopt )
- postfix-expression . identifier
- postfix-expression -> identifier
- postfix-expression ++
- postfix-expression --
- ( type-name ) { initializer-list }
- ( type-name ) { initializer-list , }
- argument-expression-list:
- assignment-expression
- argument-expression-list , assignment-expression
-
-
-
-
-[page 79]
-
- 6.5.2.1 Array subscripting
- Constraints
-1 One of the expressions shall have type ''pointer to complete object type'', the other
- expression shall have integer type, and the result has type ''type''.
- Semantics
-2 A postfix expression followed by an expression in square brackets [] is a subscripted
- designation of an element of an array object. The definition of the subscript operator []
- is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that
- apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the
- initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th
- element of E1 (counting from zero).
-3 Successive subscript operators designate an element of a multidimensional array object.
- If E is an n-dimensional array (n >= 2) with dimensions i x j x . . . x k, then E (used as
- other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with
- dimensions j x . . . x k. If the unary * operator is applied to this pointer explicitly, or
- implicitly as a result of subscripting, the result is the referenced (n - 1)-dimensional
- array, which itself is converted into a pointer if used as other than an lvalue. It follows
- from this that arrays are stored in row-major order (last subscript varies fastest).
-4 EXAMPLE Consider the array object defined by the declaration
- int x[3][5];
- Here x is a 3 x 5 array of ints; more precisely, x is an array of three element objects, each of which is an
- array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
- a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually
- entails multiplying i by the size of the object to which the pointer points, namely an array of five int
- objects. The results are added and indirection is applied to yield an array of five ints. When used in the
- expression x[i][j], that array is in turn converted to a pointer to the first of the ints, so x[i][j]
- yields an int.
-
- Forward references: additive operators (6.5.6), address and indirection operators
- (6.5.3.2), array declarators (6.7.6.2).
- 6.5.2.2 Function calls
- Constraints
-1 The expression that denotes the called function91) shall have type pointer to function
- returning void or returning a complete object type other than an array type.
-2 If the expression that denotes the called function has a type that includes a prototype, the
- number of arguments shall agree with the number of parameters. Each argument shall
-
-
- 91) Most often, this is the result of converting an identifier that is a function designator.
-
-[page 80]
-
- have a type such that its value may be assigned to an object with the unqualified version
- of the type of its corresponding parameter.
- Semantics
-3 A postfix expression followed by parentheses () containing a possibly empty, comma-
- separated list of expressions is a function call. The postfix expression denotes the called
- function. The list of expressions specifies the arguments to the function.
-4 An argument may be an expression of any complete object type. In preparing for the call
- to a function, the arguments are evaluated, and each parameter is assigned the value of the
- corresponding argument.92)
-5 If the expression that denotes the called function has type pointer to function returning an
- object type, the function call expression has the same type as that object type, and has the
- value determined as specified in 6.8.6.4. Otherwise, the function call has type void.
-6 If the expression that denotes the called function has a type that does not include a
- prototype, the integer promotions are performed on each argument, and arguments that
- have type float are promoted to double. These are called the default argument
- promotions. If the number of arguments does not equal the number of parameters, the
- behavior is undefined. If the function is defined with a type that includes a prototype, and
- either the prototype ends with an ellipsis (, ...) or the types of the arguments after
- promotion are not compatible with the types of the parameters, the behavior is undefined.
- If the function is defined with a type that does not include a prototype, and the types of
- the arguments after promotion are not compatible with those of the parameters after
- promotion, the behavior is undefined, except for the following cases:
- -- one promoted type is a signed integer type, the other promoted type is the
- corresponding unsigned integer type, and the value is representable in both types;
- -- both types are pointers to qualified or unqualified versions of a character type or
- void.
-7 If the expression that denotes the called function has a type that does include a prototype,
- the arguments are implicitly converted, as if by assignment, to the types of the
- corresponding parameters, taking the type of each parameter to be the unqualified version
- of its declared type. The ellipsis notation in a function prototype declarator causes
- argument type conversion to stop after the last declared parameter. The default argument
- promotions are performed on trailing arguments.
-
-
-
- 92) A function may change the values of its parameters, but these changes cannot affect the values of the
- arguments. On the other hand, it is possible to pass a pointer to an object, and the function may
- change the value of the object pointed to. A parameter declared to have array or function type is
- adjusted to have a pointer type as described in 6.9.1.
-
-[page 81]
-
-8 No other conversions are performed implicitly; in particular, the number and types of
- arguments are not compared with those of the parameters in a function definition that
- does not include a function prototype declarator.
-9 If the function is defined with a type that is not compatible with the type (of the
- expression) pointed to by the expression that denotes the called function, the behavior is
- undefined.
-10 There is a sequence point after the evaluations of the function designator and the actual
- arguments but before the actual call. Every evaluation in the calling function (including
- other function calls) that is not otherwise specifically sequenced before or after the
- execution of the body of the called function is indeterminately sequenced with respect to
- the execution of the called function.93)
-11 Recursive function calls shall be permitted, both directly and indirectly through any chain
- of other functions.
-12 EXAMPLE In the function call
- (*pf[f1()]) (f2(), f3() + f4())
- the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before
- the function pointed to by pf[f1()] is called.
-
- Forward references: function declarators (including prototypes) (6.7.6.3), function
- definitions (6.9.1), the return statement (6.8.6.4), simple assignment (6.5.16.1).
- 6.5.2.3 Structure and union members
- Constraints
-1 The first operand of the . operator shall have a qualified or unqualified structure or union
- type, and the second operand shall name a member of that type.
-2 The first operand of the -> operator shall have type ''pointer to qualified or unqualified
- structure'' or ''pointer to qualified or unqualified union'', and the second operand shall
- name a member of the type pointed to.
- Semantics
-3 A postfix expression followed by the . operator and an identifier designates a member of
- a structure or union object. The value is that of the named member,94) and is an lvalue if
- the first expression is an lvalue. If the first expression has qualified type, the result has
- the so-qualified version of the type of the designated member.
-
- 93) In other words, function executions do not ''interleave'' with each other.
- 94) If the member used to access the contents of a union object is not the same as the member last used to
- store a value in the object, the appropriate part of the object representation of the value is reinterpreted
- as an object representation in the new type as described in 6.2.6 (a process sometimes called ''type
- punning''). This might be a trap representation.
-
-[page 82]
-
-4 A postfix expression followed by the -> operator and an identifier designates a member
- of a structure or union object. The value is that of the named member of the object to
- which the first expression points, and is an lvalue.95) If the first expression is a pointer to
- a qualified type, the result has the so-qualified version of the type of the designated
- member.
-5 Accessing a member of an _Atomic-qualified structure or union object results in
- undefined behavior.96)
-6 One special guarantee is made in order to simplify the use of unions: if a union contains
- several structures that share a common initial sequence (see below), and if the union
- object currently contains one of these structures, it is permitted to inspect the common
- initial part of any of them anywhere that a declaration of the completed type of the union
- is visible. Two structures share a common initial sequence if corresponding members
- have compatible types (and, for bit-fields, the same widths) for a sequence of one or more
- initial members.
-7 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or
- union, f().x is a valid postfix expression but is not an lvalue.
-
-8 EXAMPLE 2 In:
- struct s { int i; const int ci; };
- struct s s;
- const struct s cs;
- volatile struct s vs;
- the various members have the types:
- s.i int
- s.ci const int
- cs.i const int
- cs.ci const int
- vs.i volatile int
- vs.ci volatile const int
-
-
-
-
- 95) If &E is a valid pointer expression (where & is the ''address-of '' operator, which generates a pointer to
- its operand), the expression (&E)->MOS is the same as E.MOS.
- 96) A data race would occur if access to the entire structure or union in one thread conflicts with access to
- a member from another thread, where at least one access is a modification. Such a data race results in
- undefined behavior.
-
-[page 83]
-
-9 EXAMPLE 3 The following is a valid fragment:
- union {
- struct {
- int alltypes;
- } n;
- struct {
- int type;
- int intnode;
- } ni;
- struct {
- int type;
- double doublenode;
- } nf;
- } u;
- u.nf.type = 1;
- u.nf.doublenode = 3.14;
- /* ... */
- if (u.n.alltypes == 1)
- if (sin(u.nf.doublenode) == 0.0)
- /* ... */
- The following is not a valid fragment (because the union type is not visible within function f):
- struct t1 { int m; };
- struct t2 { int m; };
- int f(struct t1 *p1, struct t2 *p2)
- {
- if (p1->m < 0)
- p2->m = -p2->m;
- return p1->m;
- }
- int g()
- {
- union {
- struct t1 s1;
- struct t2 s2;
- } u;
- /* ... */
- return f(&u.s1, &u.s2);
- }
-
- Forward references: address and indirection operators (6.5.3.2), structure and union
- specifiers (6.7.2.1).
-
-
-
-
-[page 84]
-
- 6.5.2.4 Postfix increment and decrement operators
- Constraints
-1 The operand of the postfix increment or decrement operator shall have qualified or
- unqualified real or pointer type and shall be a modifiable lvalue.
- Semantics
-2 The result of the postfix ++ operator is the value of the operand. As a side effect, the
- value of the operand object is incremented (that is, the value 1 of the appropriate type is
- added to it). See the discussions of additive operators and compound assignment for
- information on constraints, types, and conversions and the effects of operations on
- pointers. The value computation of the result is sequenced before the side effect of
- updating the stored value of the operand. With respect to an indeterminately-sequenced
- function call, the operation of postfix ++ is a single evaluation. Postfix ++ on an object
- with _Atomic-qualified type is a read-modify-write operation with
- 97)
- memory_order_seq_cst memory order semantics.
-3 The postfix -- operator is analogous to the postfix ++ operator, except that the value of
- the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
- it).
- Forward references: additive operators (6.5.6), compound assignment (6.5.16.2).
- 6.5.2.5 Compound literals
- Constraints
-1 The type name shall specify a complete object type or an array of unknown size, but not a
- variable length array type.
-2 All the constraints for initializer lists in 6.7.9 also apply to compound literals.
- Semantics
-3 A postfix expression that consists of a parenthesized type name followed by a brace-
- enclosed list of initializers is a compound literal. It provides an unnamed object whose
- value is given by the initializer list.98)
-
-
- 97) Where a pointer to an atomic object can be formed, this is equivalent to the following code sequence
- where T is the type of E:
- T tmp;
- T result = E;
- do {
- tmp = result + 1;
- } while (!atomic_compare_exchange_strong(&E, &result, tmp));
- with result being the result of the operation.
-
-[page 85]
-
-4 If the type name specifies an array of unknown size, the size is determined by the
- initializer list as specified in 6.7.9, and the type of the compound literal is that of the
- completed array type. Otherwise (when the type name specifies an object type), the type
- of the compound literal is that specified by the type name. In either case, the result is an
- lvalue.
-5 The value of the compound literal is that of an unnamed object initialized by the
- initializer list. If the compound literal occurs outside the body of a function, the object
- has static storage duration; otherwise, it has automatic storage duration associated with
- the enclosing block.
-6 All the semantic rules for initializer lists in 6.7.9 also apply to compound literals.99)
-7 String literals, and compound literals with const-qualified types, need not designate
- distinct objects.100)
-8 EXAMPLE 1 The file scope definition
- int *p = (int []){2, 4};
- initializes p to point to the first element of an array of two ints, the first having the value two and the
- second, four. The expressions in this compound literal are required to be constant. The unnamed object
- has static storage duration.
-
-9 EXAMPLE 2 In contrast, in
- void f(void)
- {
- int *p;
- /*...*/
- p = (int [2]){*p};
- /*...*/
- }
- p is assigned the address of the first element of an array of two ints, the first having the value previously
- pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
- unnamed object has automatic storage duration.
-
-10 EXAMPLE 3 Initializers with designations can be combined with compound literals. Structure objects
- created using compound literals can be passed to functions without depending on member order:
- drawline((struct point){.x=1, .y=1},
- (struct point){.x=3, .y=4});
- Or, if drawline instead expected pointers to struct point:
-
-
-
- 98) Note that this differs from a cast expression. For example, a cast specifies a conversion to scalar types
- or void only, and the result of a cast expression is not an lvalue.
- 99) For example, subobjects without explicit initializers are initialized to zero.
- 100) This allows implementations to share storage for string literals and constant compound literals with
- the same or overlapping representations.
-
-[page 86]
-
- drawline(&(struct point){.x=1, .y=1},
- &(struct point){.x=3, .y=4});
-
-11 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
- (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}
-
-12 EXAMPLE 5 The following three expressions have different meanings:
- "/tmp/fileXXXXXX"
- (char []){"/tmp/fileXXXXXX"}
- (const char []){"/tmp/fileXXXXXX"}
- The first always has static storage duration and has type array of char, but need not be modifiable; the last
- two have automatic storage duration when they occur within the body of a function, and the first of these
- two is modifiable.
-
-13 EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory
- and can even be shared. For example,
- (const char []){"abc"} == "abc"
- might yield 1 if the literals' storage is shared.
-
-14 EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly
- linked object. For example, there is no way to write a self-referential compound literal that could be used
- as the function argument in place of the named object endless_zeros below:
- struct int_list { int car; struct int_list *cdr; };
- struct int_list endless_zeros = {0, &endless_zeros};
- eval(endless_zeros);
-
-15 EXAMPLE 8 Each compound literal creates only a single object in a given scope:
- struct s { int i; };
- int f (void)
- {
- struct s *p = 0, *q;
- int j = 0;
- again:
- q = p, p = &((struct s){ j++ });
- if (j < 2) goto again;
- return p == q && q->i == 1;
- }
- The function f() always returns the value 1.
-16 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
- lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
- have an indeterminate value, which would result in undefined behavior.
-
- Forward references: type names (6.7.7), initialization (6.7.9).
-
-
-
-
-[page 87]
-
- 6.5.3 Unary operators
- Syntax
-1 unary-expression:
- postfix-expression
- ++ unary-expression
- -- unary-expression
- unary-operator cast-expression
- sizeof unary-expression
- sizeof ( type-name )
- alignof ( type-name )
- unary-operator: one of
- & * + - ~ !
- 6.5.3.1 Prefix increment and decrement operators
- Constraints
-1 The operand of the prefix increment or decrement operator shall have qualified or
- unqualified real or pointer type and shall be a modifiable lvalue.
- Semantics
-2 The value of the operand of the prefix ++ operator is incremented. The result is the new
- value of the operand after incrementation. The expression ++E is equivalent to (E+=1).
- See the discussions of additive operators and compound assignment for information on
- constraints, types, side effects, and conversions and the effects of operations on pointers.
-3 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
- operand is decremented.
- Forward references: additive operators (6.5.6), compound assignment (6.5.16.2).
- 6.5.3.2 Address and indirection operators
- Constraints
-1 The operand of the unary & operator shall be either a function designator, the result of a
- [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is
- not declared with the register storage-class specifier.
-2 The operand of the unary * operator shall have pointer type.
- Semantics
-3 The unary & operator yields the address of its operand. If the operand has type ''type'',
- the result has type ''pointer to type''. If the operand is the result of a unary * operator,
- neither that operator nor the & operator is evaluated and the result is as if both were
- omitted, except that the constraints on the operators still apply and the result is not an
-
-[page 88]
-
- lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor
- the unary * that is implied by the [] is evaluated and the result is as if the & operator
- were removed and the [] operator were changed to a + operator. Otherwise, the result is
- a pointer to the object or function designated by its operand.
-4 The unary * operator denotes indirection. If the operand points to a function, the result is
- a function designator; if it points to an object, the result is an lvalue designating the
- object. If the operand has type ''pointer to type'', the result has type ''type''. If an
- invalid value has been assigned to the pointer, the behavior of the unary * operator is
- undefined.101)
- Forward references: storage-class specifiers (6.7.1), structure and union specifiers
- (6.7.2.1).
- 6.5.3.3 Unary arithmetic operators
- Constraints
-1 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
- integer type; of the ! operator, scalar type.
- Semantics
-2 The result of the unary + operator is the value of its (promoted) operand. The integer
- promotions are performed on the operand, and the result has the promoted type.
-3 The result of the unary - operator is the negative of its (promoted) operand. The integer
- promotions are performed on the operand, and the result has the promoted type.
-4 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is,
- each bit in the result is set if and only if the corresponding bit in the converted operand is
- not set). The integer promotions are performed on the operand, and the result has the
- promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent
- to the maximum value representable in that type minus E.
-5 The result of the logical negation operator ! is 0 if the value of its operand compares
- unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int.
- The expression !E is equivalent to (0==E).
-
-
-
- 101) Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). It is
- always true that if E is a function designator or an lvalue that is a valid operand of the unary &
- operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of
- an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points.
- Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an
- address inappropriately aligned for the type of object pointed to, and the address of an object after the
- end of its lifetime.
-
-[page 89]
-
- 6.5.3.4 The sizeof and alignof operators
- Constraints
-1 The sizeof operator shall not be applied to an expression that has function type or an
- incomplete type, to the parenthesized name of such a type, or to an expression that
- designates a bit-field member. The alignof operator shall not be applied to a function
- type or an incomplete type.
- Semantics
-2 The sizeof operator yields the size (in bytes) of its operand, which may be an
- expression or the parenthesized name of a type. The size is determined from the type of
- the operand. The result is an integer. If the type of the operand is a variable length array
- type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an
- integer constant.
-3 The alignof operator yields the alignment requirement of its operand type. The result
- is an integer constant. When applied to an array type, the result is the alignment
- requirement of the element type.
-4 When sizeof is applied to an operand that has type char, unsigned char, or
- signed char, (or a qualified version thereof) the result is 1. When applied to an
- operand that has array type, the result is the total number of bytes in the array.102) When
- applied to an operand that has structure or union type, the result is the total number of
- bytes in such an object, including internal and trailing padding.
-5 The value of the result of both operators is implementation-defined, and its type (an
- unsigned integer type) is size_t, defined in <stddef.h> (and other headers).
-6 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage
- allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to
- allocate and return a pointer to void. For example:
- extern void *alloc(size_t);
- double *dp = alloc(sizeof *dp);
- The implementation of the alloc function should ensure that its return value is aligned suitably for
- conversion to a pointer to double.
-
-7 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
- sizeof array / sizeof array[0]
-
-8 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a
- function:
- #include <stddef.h>
-
-
-
- 102) When applied to a parameter declared to have array or function type, the sizeof operator yields the
- size of the adjusted (pointer) type (see 6.9.1).
-
-[page 90]
-
- size_t fsize3(int n)
- {
- char b[n+3]; // variable length array
- return sizeof b; // execution time sizeof
- }
- int main()
- {
- size_t size;
- size = fsize3(10); // fsize3 returns 13
- return 0;
- }
-
- Forward references: common definitions <stddef.h> (7.19), declarations (6.7),
- structure and union specifiers (6.7.2.1), type names (6.7.7), array declarators (6.7.6.2).
- 6.5.4 Cast operators
- Syntax
-1 cast-expression:
- unary-expression
- ( type-name ) cast-expression
- Constraints
-2 Unless the type name specifies a void type, the type name shall specify qualified or
- unqualified scalar type and the operand shall have scalar type.
-3 Conversions that involve pointers, other than where permitted by the constraints of
- 6.5.16.1, shall be specified by means of an explicit cast.
-4 A pointer type shall not be converted to any floating type. A floating type shall not be
- converted to any pointer type.
- Semantics
-5 Preceding an expression by a parenthesized type name converts the value of the
- expression to the named type. This construction is called a cast.103) A cast that specifies
- no conversion has no effect on the type or value of an expression.
-6 If the value of the expression is represented with greater precision or range than required
- by the type named by the cast (6.3.1.8), then the cast specifies a conversion even if the
- type of the expression is the same as the named type.
- Forward references: equality operators (6.5.9), function declarators (including
- prototypes) (6.7.6.3), simple assignment (6.5.16.1), type names (6.7.7).
-
-
-
- 103) A cast does not yield an lvalue. Thus, a cast to a qualified type has the same effect as a cast to the
- unqualified version of the type.
-
-[page 91]
-
- 6.5.5 Multiplicative operators
- Syntax
-1 multiplicative-expression:
- cast-expression
- multiplicative-expression * cast-expression
- multiplicative-expression / cast-expression
- multiplicative-expression % cast-expression
- Constraints
-2 Each of the operands shall have arithmetic type. The operands of the % operator shall
- have integer type.
- Semantics
-3 The usual arithmetic conversions are performed on the operands.
-4 The result of the binary * operator is the product of the operands.
-5 The result of the / operator is the quotient from the division of the first operand by the
- second; the result of the % operator is the remainder. In both operations, if the value of
- the second operand is zero, the behavior is undefined.
-6 When integers are divided, the result of the / operator is the algebraic quotient with any
- fractional part discarded.104) If the quotient a/b is representable, the expression
- (a/b)*b + a%b shall equal a; otherwise, the behavior of both a/b and a%b is
- undefined.
- 6.5.6 Additive operators
- Syntax
-1 additive-expression:
- multiplicative-expression
- additive-expression + multiplicative-expression
- additive-expression - multiplicative-expression
- Constraints
-2 For addition, either both operands shall have arithmetic type, or one operand shall be a
- pointer to a complete object type and the other shall have integer type. (Incrementing is
- equivalent to adding 1.)
-3 For subtraction, one of the following shall hold:
-
-
-
-
- 104) This is often called ''truncation toward zero''.
-
-[page 92]
-
- -- both operands have arithmetic type;
- -- both operands are pointers to qualified or unqualified versions of compatible complete
- object types; or
- -- the left operand is a pointer to a complete object type and the right operand has
- integer type.
- (Decrementing is equivalent to subtracting 1.)
- Semantics
-4 If both operands have arithmetic type, the usual arithmetic conversions are performed on
- them.
-5 The result of the binary + operator is the sum of the operands.
-6 The result of the binary - operator is the difference resulting from the subtraction of the
- second operand from the first.
-7 For the purposes of these operators, a pointer to an object that is not an element of an
- array behaves the same as a pointer to the first element of an array of length one with the
- type of the object as its element type.
-8 When an expression that has integer type is added to or subtracted from a pointer, the
- result has the type of the pointer operand. If the pointer operand points to an element of
- an array object, and the array is large enough, the result points to an element offset from
- the original element such that the difference of the subscripts of the resulting and original
- array elements equals the integer expression. In other words, if the expression P points to
- the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
- (P)-N (where N has the value n) point to, respectively, the i+n-th and i-n-th elements of
- the array object, provided they exist. Moreover, if the expression P points to the last
- element of an array object, the expression (P)+1 points one past the last element of the
- array object, and if the expression Q points one past the last element of an array object,
- the expression (Q)-1 points to the last element of the array object. If both the pointer
- operand and the result point to elements of the same array object, or one past the last
- element of the array object, the evaluation shall not produce an overflow; otherwise, the
- behavior is undefined. If the result points one past the last element of the array object, it
- shall not be used as the operand of a unary * operator that is evaluated.
-9 When two pointers are subtracted, both shall point to elements of the same array object,
- or one past the last element of the array object; the result is the difference of the
- subscripts of the two array elements. The size of the result is implementation-defined,
- and its type (a signed integer type) is ptrdiff_t defined in the <stddef.h> header.
- If the result is not representable in an object of that type, the behavior is undefined. In
- other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of
- an array object, the expression (P)-(Q) has the value i-j provided the value fits in an
-
-[page 93]
-
- object of type ptrdiff_t. Moreover, if the expression P points either to an element of
- an array object or one past the last element of an array object, and the expression Q points
- to the last element of the same array object, the expression ((Q)+1)-(P) has the same
- value as ((Q)-(P))+1 and as -((P)-((Q)+1)), and has the value zero if the
- expression P points one past the last element of the array object, even though the
- expression (Q)+1 does not point to an element of the array object.105)
-10 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
- {
- int n = 4, m = 3;
- int a[n][m];
- int (*p)[m] = a; // p == &a[0]
- p += 1; // p == &a[1]
- (*p)[2] = 99; // a[1][2] == 99
- n = p - a; // n == 1
- }
-11 If array a in the above example were declared to be an array of known constant size, and pointer p were
- declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
- the same.
-
- Forward references: array declarators (6.7.6.2), common definitions <stddef.h>
- (7.19).
- 6.5.7 Bitwise shift operators
- Syntax
-1 shift-expression:
- additive-expression
- shift-expression << additive-expression
- shift-expression >> additive-expression
- Constraints
-2 Each of the operands shall have integer type.
- Semantics
-3 The integer promotions are performed on each of the operands. The type of the result is
- that of the promoted left operand. If the value of the right operand is negative or is
-
- 105) Another way to approach pointer arithmetic is first to convert the pointer(s) to character pointer(s): In
- this scheme the integer expression added to or subtracted from the converted pointer is first multiplied
- by the size of the object originally pointed to, and the resulting pointer is converted back to the
- original type. For pointer subtraction, the result of the difference between the character pointers is
- similarly divided by the size of the object originally pointed to.
- When viewed in this way, an implementation need only provide one extra byte (which may overlap
- another object in the program) just after the end of the object in order to satisfy the ''one past the last
- element'' requirements.
-
-[page 94]
-
- greater than or equal to the width of the promoted left operand, the behavior is undefined.
-4 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with
- zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo
- one more than the maximum value representable in the result type. If E1 has a signed
- type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is
- the resulting value; otherwise, the behavior is undefined.
-5 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
- or if E1 has a signed type and a nonnegative value, the value of the result is the integral
- part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
- resulting value is implementation-defined.
- 6.5.8 Relational operators
- Syntax
-1 relational-expression:
- shift-expression
- relational-expression < shift-expression
- relational-expression > shift-expression
- relational-expression <= shift-expression
- relational-expression >= shift-expression
- Constraints
-2 One of the following shall hold:
- -- both operands have real type; or
- -- both operands are pointers to qualified or unqualified versions of compatible object
- types.
- Semantics
-3 If both of the operands have arithmetic type, the usual arithmetic conversions are
- performed.
-4 For the purposes of these operators, a pointer to an object that is not an element of an
- array behaves the same as a pointer to the first element of an array of length one with the
- type of the object as its element type.
-5 When two pointers are compared, the result depends on the relative locations in the
- address space of the objects pointed to. If two pointers to object types both point to the
- same object, or both point one past the last element of the same array object, they
- compare equal. If the objects pointed to are members of the same aggregate object,
- pointers to structure members declared later compare greater than pointers to members
- declared earlier in the structure, and pointers to array elements with larger subscript
- values compare greater than pointers to elements of the same array with lower subscript
-
-[page 95]
-
- values. All pointers to members of the same union object compare equal. If the
- expression P points to an element of an array object and the expression Q points to the
- last element of the same array object, the pointer expression Q+1 compares greater than
- P. In all other cases, the behavior is undefined.
-6 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
- (greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is
- false.106) The result has type int.
- 6.5.9 Equality operators
- Syntax
-1 equality-expression:
- relational-expression
- equality-expression == relational-expression
- equality-expression != relational-expression
- Constraints
-2 One of the following shall hold:
- -- both operands have arithmetic type;
- -- both operands are pointers to qualified or unqualified versions of compatible types;
- -- one operand is a pointer to an object type and the other is a pointer to a qualified or
- unqualified version of void; or
- -- one operand is a pointer and the other is a null pointer constant.
- Semantics
-3 The == (equal to) and != (not equal to) operators are analogous to the relational
- operators except for their lower precedence.107) Each of the operators yields 1 if the
- specified relation is true and 0 if it is false. The result has type int. For any pair of
- operands, exactly one of the relations is true.
-4 If both of the operands have arithmetic type, the usual arithmetic conversions are
- performed. Values of complex types are equal if and only if both their real parts are equal
- and also their imaginary parts are equal. Any two values of arithmetic types from
- different type domains are equal if and only if the results of their conversions to the
- (complex) result type determined by the usual arithmetic conversions are equal.
-
-
-
- 106) The expression a<b<c is not interpreted as in ordinary mathematics. As the syntax indicates, it
- means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
- 107) Because of the precedences, a<b == c<d is 1 whenever a<b and c<d have the same truth-value.
-
-[page 96]
-
-5 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a
- null pointer constant, the null pointer constant is converted to the type of the pointer. If
- one operand is a pointer to an object type and the other is a pointer to a qualified or
- unqualified version of void, the former is converted to the type of the latter.
-6 Two pointers compare equal if and only if both are null pointers, both are pointers to the
- same object (including a pointer to an object and a subobject at its beginning) or function,
- both are pointers to one past the last element of the same array object, or one is a pointer
- to one past the end of one array object and the other is a pointer to the start of a different
- array object that happens to immediately follow the first array object in the address
- space.108)
-7 For the purposes of these operators, a pointer to an object that is not an element of an
- array behaves the same as a pointer to the first element of an array of length one with the
- type of the object as its element type.
- 6.5.10 Bitwise AND operator
- Syntax
-1 AND-expression:
- equality-expression
- AND-expression & equality-expression
- Constraints
-2 Each of the operands shall have integer type.
- Semantics
-3 The usual arithmetic conversions are performed on the operands.
-4 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
- the result is set if and only if each of the corresponding bits in the converted operands is
- set).
-
-
-
-
- 108) Two objects may be adjacent in memory because they are adjacent elements of a larger array or
- adjacent members of a structure with no padding between them, or because the implementation chose
- to place them so, even though they are unrelated. If prior invalid pointer operations (such as accesses
- outside array bounds) produced undefined behavior, subsequent comparisons also produce undefined
- behavior.
-
-[page 97]
-
- 6.5.11 Bitwise exclusive OR operator
- Syntax
-1 exclusive-OR-expression:
- AND-expression
- exclusive-OR-expression ^ AND-expression
- Constraints
-2 Each of the operands shall have integer type.
- Semantics
-3 The usual arithmetic conversions are performed on the operands.
-4 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
- in the result is set if and only if exactly one of the corresponding bits in the converted
- operands is set).
- 6.5.12 Bitwise inclusive OR operator
- Syntax
-1 inclusive-OR-expression:
- exclusive-OR-expression
- inclusive-OR-expression | exclusive-OR-expression
- Constraints
-2 Each of the operands shall have integer type.
- Semantics
-3 The usual arithmetic conversions are performed on the operands.
-4 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
- the result is set if and only if at least one of the corresponding bits in the converted
- operands is set).
-
-
-
-
-[page 98]
-
- 6.5.13 Logical AND operator
- Syntax
-1 logical-AND-expression:
- inclusive-OR-expression
- logical-AND-expression && inclusive-OR-expression
- Constraints
-2 Each of the operands shall have scalar type.
- Semantics
-3 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
- yields 0. The result has type int.
-4 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
- if the second operand is evaluated, there is a sequence point between the evaluations of
- the first and second operands. If the first operand compares equal to 0, the second
- operand is not evaluated.
- 6.5.14 Logical OR operator
- Syntax
-1 logical-OR-expression:
- logical-AND-expression
- logical-OR-expression || logical-AND-expression
- Constraints
-2 Each of the operands shall have scalar type.
- Semantics
-3 The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it
- yields 0. The result has type int.
-4 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; if the
- second operand is evaluated, there is a sequence point between the evaluations of the first
- and second operands. If the first operand compares unequal to 0, the second operand is
- not evaluated.
-
-
-
-
-[page 99]
-
- 6.5.15 Conditional operator
- Syntax
-1 conditional-expression:
- logical-OR-expression
- logical-OR-expression ? expression : conditional-expression
- Constraints
-2 The first operand shall have scalar type.
-3 One of the following shall hold for the second and third operands:
- -- both operands have arithmetic type;
- -- both operands have the same structure or union type;
- -- both operands have void type;
- -- both operands are pointers to qualified or unqualified versions of compatible types;
- -- one operand is a pointer and the other is a null pointer constant; or
- -- one operand is a pointer to an object type and the other is a pointer to a qualified or
- unqualified version of void.
- Semantics
-4 The first operand is evaluated; there is a sequence point between its evaluation and the
- evaluation of the second or third operand (whichever is evaluated). The second operand
- is evaluated only if the first compares unequal to 0; the third operand is evaluated only if
- the first compares equal to 0; the result is the value of the second or third operand
- (whichever is evaluated), converted to the type described below.109)
-5 If both the second and third operands have arithmetic type, the result type that would be
- determined by the usual arithmetic conversions, were they applied to those two operands,
- is the type of the result. If both the operands have structure or union type, the result has
- that type. If both operands have void type, the result has void type.
-6 If both the second and third operands are pointers or one is a null pointer constant and the
- other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
- of the types referenced by both operands. Furthermore, if both operands are pointers to
- compatible types or to differently qualified versions of compatible types, the result type is
- a pointer to an appropriately qualified version of the composite type; if one operand is a
- null pointer constant, the result has the type of the other operand; otherwise, one operand
- is a pointer to void or a qualified version of void, in which case the result type is a
- pointer to an appropriately qualified version of void.
-
- 109) A conditional expression does not yield an lvalue.
-
-[page 100]
-
-7 EXAMPLE The common type that results when the second and third operands are pointers is determined
- in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two
- pointers have compatible types.
-8 Given the declarations
- const void *c_vp;
- void *vp;
- const int *c_ip;
- volatile int *v_ip;
- int *ip;
- const char *c_cp;
- the third column in the following table is the common type that is the result of a conditional expression in
- which the first two columns are the second and third operands (in either order):
- c_vp c_ip const void *
- v_ip 0 volatile int *
- c_ip v_ip const volatile int *
- vp c_cp const void *
- ip c_ip const int *
- vp ip void *
-
- 6.5.16 Assignment operators
- Syntax
-1 assignment-expression:
- conditional-expression
- unary-expression assignment-operator assignment-expression
- assignment-operator: one of
- = *= /= %= += -= <<= >>= &= ^= |=
- Constraints
-2 An assignment operator shall have a modifiable lvalue as its left operand.
- Semantics
-3 An assignment operator stores a value in the object designated by the left operand. An
- assignment expression has the value of the left operand after the assignment,110) but is not
- an lvalue. The type of an assignment expression is the type of the left operand unless the
- left operand has qualified type, in which case it is the unqualified version of the type of
- the left operand. The side effect of updating the stored value of the left operand is
- sequenced after the value computations of the left and right operands. The evaluations of
- the operands are unsequenced.
-
-
-
-
- 110) The implementation is permitted to read the object to determine the value but is not required to, even
- when the object has volatile-qualified type.
-
-[page 101]
-
- 6.5.16.1 Simple assignment
- Constraints
-1 One of the following shall hold:111)
- -- the left operand has qualified or unqualified arithmetic type and the right has
- arithmetic type;
- -- the left operand has a qualified or unqualified version of a structure or union type
- compatible with the type of the right;
- -- both operands are pointers to qualified or unqualified versions of compatible types,
- and the type pointed to by the left has all the qualifiers of the type pointed to by the
- right;
- -- one operand is a pointer to an object type and the other is a pointer to a qualified or
- unqualified version of void, and the type pointed to by the left has all the qualifiers
- of the type pointed to by the right;
- -- the left operand is a pointer and the right is a null pointer constant; or
- -- the left operand has type _Bool and the right is a pointer.
- Semantics
-2 In simple assignment (=), the value of the right operand is converted to the type of the
- assignment expression and replaces the value stored in the object designated by the left
- operand.
-3 If the value being stored in an object is read from another object that overlaps in any way
- the storage of the first object, then the overlap shall be exact and the two objects shall
- have qualified or unqualified versions of a compatible type; otherwise, the behavior is
- undefined.
-4 EXAMPLE 1 In the program fragment
- int f(void);
- char c;
- /* ... */
- if ((c = f()) == -1)
- /* ... */
- the int value returned by the function may be truncated when stored in the char, and then converted back
- to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
- values as unsigned char (and char is narrower than int), the result of the conversion cannot be
-
-
-
- 111) The asymmetric appearance of these constraints with respect to type qualifiers is due to the conversion
- (specified in 6.3.2.1) that changes lvalues to ''the value of the expression'' and thus removes any type
- qualifiers that were applied to the type category of the expression (for example, it removes const but
- not volatile from the type int volatile * const).
-
-[page 102]
-
- negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
- variable c should be declared as int.
-
-5 EXAMPLE 2 In the fragment:
- char c;
- int i;
- long l;
- l = (c = i);
- the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
- of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
- that is, long int type.
-
-6 EXAMPLE 3 Consider the fragment:
- const char **cpp;
- char *p;
- const char c = 'A';
- cpp = &p; // constraint violation
- *cpp = &c; // valid
- *p = 0; // valid
- The first assignment is unsafe because it would allow the following valid code to attempt to change the
- value of the const object c.
-
- 6.5.16.2 Compound assignment
- Constraints
-1 For the operators += and -= only, either the left operand shall be a pointer to a complete
- object type and the right shall have integer type, or the left operand shall have qualified or
- unqualified arithmetic type and the right shall have arithmetic type.
-2 For the other operators, each operand shall have arithmetic type consistent with those
- allowed by the corresponding binary operator.
- Semantics
-3 A compound assignment of the form E1 op = E2 is equivalent to the simple assignment
- expression E1 = E1 op (E2), except that the lvalue E1 is evaluated only once, and with
- respect to an indeterminately-sequenced function call, the operation of a compound
- assignment is a single evaluation. If E1 has an _Atomic-qualified type, compound
- assignment is a read-modify-write operation with memory_order_seq_cst memory
- order semantics.112)
-
-
-
-
-[page 103]
-
- 6.5.17 Comma operator
- Syntax
-1 expression:
- assignment-expression
- expression , assignment-expression
- Semantics
-2 The left operand of a comma operator is evaluated as a void expression; there is a
- sequence point between its evaluation and that of the right operand. Then the right
- operand is evaluated; the result has its type and value.113)
-3 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot
- appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists
- of initializers). On the other hand, it can be used within a parenthesized expression or within the second
- expression of a conditional operator in such contexts. In the function call
- f(a, (t=3, t+2), c)
- the function has three arguments, the second of which has the value 5.
-
- Forward references: initialization (6.7.9).
-
-
-
-
- 112) Where a pointer to an atomic object can be formed, this is equivalent to the following code sequence
- where T is the type of E1:
- T tmp = E1;
- T result;
- do {
- result = tmp op (E2);
- } while (!atomic_compare_exchange_strong(&E1, &tmp, result));
- with result being the result of the operation.
- 113) A comma operator does not yield an lvalue.
-
-[page 104]
-
- 6.6 Constant expressions
- Syntax
-1 constant-expression:
- conditional-expression
- Description
-2 A constant expression can be evaluated during translation rather than runtime, and
- accordingly may be used in any place that a constant may be.
- Constraints
-3 Constant expressions shall not contain assignment, increment, decrement, function-call,
- or comma operators, except when they are contained within a subexpression that is not
- evaluated.114)
-4 Each constant expression shall evaluate to a constant that is in the range of representable
- values for its type.
- Semantics
-5 An expression that evaluates to a constant is required in several contexts. If a floating
- expression is evaluated in the translation environment, the arithmetic precision and range
- shall be at least as great as if the expression were being evaluated in the execution
- environment.115)
-6 An integer constant expression116) shall have integer type and shall only have operands
- that are integer constants, enumeration constants, character constants, sizeof
- expressions whose results are integer constants, and floating constants that are the
- immediate operands of casts. Cast operators in an integer constant expression shall only
- convert arithmetic types to integer types, except as part of an operand to the sizeof
- operator.
-7 More latitude is permitted for constant expressions in initializers. Such a constant
- expression shall be, or evaluate to, one of the following:
- -- an arithmetic constant expression,
-
-
-
- 114) The operand of a sizeof operator is usually not evaluated (6.5.3.4).
- 115) The use of evaluation formats as characterized by FLT_EVAL_METHOD also applies to evaluation in
- the translation environment.
- 116) An integer constant expression is required in a number of contexts such as the size of a bit-field
- member of a structure, the value of an enumeration constant, and the size of a non-variable length
- array. Further constraints that apply to the integer constant expressions used in conditional-inclusion
- preprocessing directives are discussed in 6.10.1.
-
-[page 105]
-
- -- a null pointer constant,
- -- an address constant, or
- -- an address constant for a complete object type plus or minus an integer constant
- expression.
-8 An arithmetic constant expression shall have arithmetic type and shall only have
- operands that are integer constants, floating constants, enumeration constants, character
- constants, and sizeof expressions. Cast operators in an arithmetic constant expression
- shall only convert arithmetic types to arithmetic types, except as part of an operand to a
- sizeof operator whose result is an integer constant.
-9 An address constant is a null pointer, a pointer to an lvalue designating an object of static
- storage duration, or a pointer to a function designator; it shall be created explicitly using
- the unary & operator or an integer constant cast to pointer type, or implicitly by the use of
- an expression of array or function type. The array-subscript [] and member-access .
- and -> operators, the address & and indirection * unary operators, and pointer casts may
- be used in the creation of an address constant, but the value of an object shall not be
- accessed by use of these operators.
-10 An implementation may accept other forms of constant expressions.
-11 The semantic rules for the evaluation of a constant expression are the same as for
- nonconstant expressions.117)
- Forward references: array declarators (6.7.6.2), initialization (6.7.9).
-
-
-
-
- 117) Thus, in the following initialization,
- static int i = 2 || 1 / 0;
- the expression is a valid integer constant expression with value one.
-
-[page 106]
-
- 6.7 Declarations
- Syntax
-1 declaration:
- declaration-specifiers init-declarator-listopt ;
- static_assert-declaration *
- declaration-specifiers:
- storage-class-specifier declaration-specifiersopt
- type-specifier declaration-specifiersopt
- type-qualifier declaration-specifiersopt
- function-specifier declaration-specifiersopt
- alignment-specifier declaration-specifiersopt
- init-declarator-list:
- init-declarator
- init-declarator-list , init-declarator
- init-declarator:
- declarator
- declarator = initializer
- Constraints
-2 A declaration other than a static_assert declaration shall declare at least a declarator
- (other than the parameters of a function or the members of a structure or union), a tag, or
- the members of an enumeration.
-3 If an identifier has no linkage, there shall be no more than one declaration of the identifier
- (in a declarator or type specifier) with the same scope and in the same name space, except
- that a typedef name can be redefined to denote the same type as it currently does and tags
- may be redeclared as specified in 6.7.2.3.
-4 All declarations in the same scope that refer to the same object or function shall specify
- compatible types.
- Semantics
-5 A declaration specifies the interpretation and attributes of a set of identifiers. A definition
- of an identifier is a declaration for that identifier that:
- -- for an object, causes storage to be reserved for that object;
- -- for a function, includes the function body;118)
-
-
-
- 118) Function definitions have a different syntax, described in 6.9.1.
-
-[page 107]
-
- -- for an enumeration constant or typedef name, is the (only) declaration of the
- identifier.
-6 The declaration specifiers consist of a sequence of specifiers that indicate the linkage,
- storage duration, and part of the type of the entities that the declarators denote. The init-
- declarator-list is a comma-separated sequence of declarators, each of which may have
- additional type information, or an initializer, or both. The declarators contain the
- identifiers (if any) being declared.
-7 If an identifier for an object is declared with no linkage, the type for the object shall be *
- complete by the end of its declarator, or by the end of its init-declarator if it has an
- initializer; in the case of function parameters (including in prototypes), it is the adjusted
- type (see 6.7.6.3) that is required to be complete.
- Forward references: declarators (6.7.6), enumeration specifiers (6.7.2.2), initialization
- (6.7.9), type names (6.7.7), type qualifiers (6.7.3).
- 6.7.1 Storage-class specifiers
- Syntax
-1 storage-class-specifier:
- typedef
- extern
- static
- _Thread_local
- auto
- register
- Constraints
-2 At most, one storage-class specifier may be given in the declaration specifiers in a
- declaration, except that _Thread_local may appear with static or extern.119)
-3 In the declaration of an object with block scope, if the declaration specifiers include
- _Thread_local, they shall also include either static or extern. If
- _Thread_local appears in any declaration of an object, it shall be present in every
- declaration of that object.
- Semantics
-4 The typedef specifier is called a ''storage-class specifier'' for syntactic convenience
- only; it is discussed in 6.7.8. The meanings of the various linkages and storage durations
- were discussed in 6.2.2 and 6.2.4.
-
-
-
- 119) See ''future language directions'' (6.11.5).
-
-[page 108]
-
-5 A declaration of an identifier for an object with storage-class specifier register
- suggests that access to the object be as fast as possible. The extent to which such
- suggestions are effective is implementation-defined.120)
-6 The declaration of an identifier for a function that has block scope shall have no explicit
- storage-class specifier other than extern.
-7 If an aggregate or union object is declared with a storage-class specifier other than
- typedef, the properties resulting from the storage-class specifier, except with respect to
- linkage, also apply to the members of the object, and so on recursively for any aggregate
- or union member objects.
- Forward references: type definitions (6.7.8).
- 6.7.2 Type specifiers
- Syntax
-1 type-specifier:
- void
- char
- short
- int
- long
- float
- double
- signed
- unsigned
- _Bool
- _Complex
- _Atomic ( type-name )
- struct-or-union-specifier
- enum-specifier
- typedef-name
- Constraints
-2 At least one type specifier shall be given in the declaration specifiers in each declaration,
- and in the specifier-qualifier list in each struct declaration and type name. Each list of
-
-
- 120) The implementation may treat any register declaration simply as an auto declaration. However,
- whether or not addressable storage is actually used, the address of any part of an object declared with
- storage-class specifier register cannot be computed, either explicitly (by use of the unary &
- operator as discussed in 6.5.3.2) or implicitly (by converting an array name to a pointer as discussed in
- 6.3.2.1). Thus, the only operator that can be applied to an array declared with storage-class specifier
- register is sizeof.
-
-[page 109]
-
- type specifiers shall be one of the following multisets (delimited by commas, when there
- is more than one multiset per item); the type specifiers may occur in any order, possibly
- intermixed with the other declaration specifiers.
- -- void
- -- char
- -- signed char
- -- unsigned char
- -- short, signed short, short int, or signed short int
- -- unsigned short, or unsigned short int
- -- int, signed, or signed int
- -- unsigned, or unsigned int
- -- long, signed long, long int, or signed long int
- -- unsigned long, or unsigned long int
- -- long long, signed long long, long long int, or
- signed long long int
- -- unsigned long long, or unsigned long long int
- -- float
- -- double
- -- long double
- -- _Bool
- -- float _Complex
- -- double _Complex
- -- long double _Complex
- -- _Atomic ( type-name )
- -- struct or union specifier
- -- enum specifier
- -- typedef name
-3 The type specifier _Complex shall not be used if the implementation does not support
- complex types; likewise, _Atomic shall not be used if the implementation does not
- support atomic types (see 6.10.8.3).
-
-
-
-[page 110]
-
- Semantics
-4 The _Atomic form of type specifier designates the _Atomic-qualified version of the
- named type.
-5 Specifiers for structures, unions, and enumerations are discussed in 6.7.2.1 through
- 6.7.2.3. Declarations of typedef names are discussed in 6.7.8. The characteristics of the
- other types are discussed in 6.2.5.
-6 Each of the comma-separated multisets designates the same type, except that for bit-
- fields, it is implementation-defined whether the specifier int designates the same type as
- signed int or the same type as unsigned int.
- Forward references: enumeration specifiers (6.7.2.2), structure and union specifiers
- (6.7.2.1), tags (6.7.2.3), type definitions (6.7.8).
- 6.7.2.1 Structure and union specifiers
- Syntax
-1 struct-or-union-specifier:
- struct-or-union identifieropt { struct-declaration-list }
- struct-or-union identifier
- struct-or-union:
- struct
- union
- struct-declaration-list:
- struct-declaration
- struct-declaration-list struct-declaration
- struct-declaration:
- specifier-qualifier-list struct-declarator-listopt ;
- static_assert-declaration
- specifier-qualifier-list:
- type-specifier specifier-qualifier-listopt
- type-qualifier specifier-qualifier-listopt
- struct-declarator-list:
- struct-declarator
- struct-declarator-list , struct-declarator
- struct-declarator:
- declarator
- declaratoropt : constant-expression
-
-
-
-[page 111]
-
- Constraints
-2 A struct-declaration that does not declare an anonymous structure or anonymous union
- shall contain a struct-declarator-list.
-3 A structure or union shall not contain a member with incomplete or function type (hence,
- a structure shall not contain an instance of itself, but may contain a pointer to an instance
- of itself), except that the last member of a structure with more than one named member
- may have incomplete array type; such a structure (and any union containing, possibly
- recursively, a member that is such a structure) shall not be a member of a structure or an
- element of an array.
-4 The expression that specifies the width of a bit-field shall be an integer constant
- expression with a nonnegative value that does not exceed the width of an object of the
- type that would be specified were the colon and expression omitted.121) If the value is
- zero, the declaration shall have no declarator.
-5 A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed
- int, unsigned int, or some other implementation-defined type.
- Semantics
-6 As discussed in 6.2.5, a structure is a type consisting of a sequence of members, whose
- storage is allocated in an ordered sequence, and a union is a type consisting of a sequence
- of members whose storage overlap.
-7 Structure and union specifiers have the same form. The keywords struct and union
- indicate that the type being specified is, respectively, a structure type or a union type.
-8 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
- within a translation unit. The struct-declaration-list is a sequence of declarations for the
- members of the structure or union. If the struct-declaration-list contains no named
- members, no anonymous structures, and no anonymous unions, the behavior is undefined.
- The type is incomplete until immediately after the } that terminates the list, and complete
- thereafter.
-9 A member of a structure or union may have any complete object type other than a
- variably modified type.122) In addition, a member may be declared to consist of a
- specified number of bits (including a sign bit, if any). Such a member is called a
- bit-field;123) its width is preceded by a colon.
-
-
-
- 121) While the number of bits in a _Bool object is at least CHAR_BIT, the width (number of sign and
- value bits) of a _Bool may be just 1 bit.
- 122) A structure or union cannot contain a member with a variably modified type because member names
- are not ordinary identifiers as defined in 6.2.3.
-
-[page 112]
-
-10 A bit-field is interpreted as a signed or unsigned integer type consisting of the specified
- number of bits.124) If the value 0 or 1 is stored into a nonzero-width bit-field of type
- _Bool, the value of the bit-field shall compare equal to the value stored; a _Bool bit-
- field has the semantics of a _Bool.
-11 An implementation may allocate any addressable storage unit large enough to hold a bit-
- field. If enough space remains, a bit-field that immediately follows another bit-field in a
- structure shall be packed into adjacent bits of the same unit. If insufficient space remains,
- whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is
- implementation-defined. The order of allocation of bit-fields within a unit (high-order to
- low-order or low-order to high-order) is implementation-defined. The alignment of the
- addressable storage unit is unspecified.
-12 A bit-field declaration with no declarator, but only a colon and a width, indicates an
- unnamed bit-field.125) As a special case, a bit-field structure member with a width of 0
- indicates that no further bit-field is to be packed into the unit in which the previous bit-
- field, if any, was placed.
-13 An unnamed member of structure type with no tag is called an anonymous structure; an
- unnamed member of union type with no tag is called an anonymous union. The members
- of an anonymous structure or union are considered to be members of the containing
- structure or union. This applies recursively if the containing structure or union is also
- anonymous.
-14 Each non-bit-field member of a structure or union object is aligned in an implementation-
- defined manner appropriate to its type.
-15 Within a structure object, the non-bit-field members and the units in which bit-fields
- reside have addresses that increase in the order in which they are declared. A pointer to a
- structure object, suitably converted, points to its initial member (or if that member is a
- bit-field, then to the unit in which it resides), and vice versa. There may be unnamed
- padding within a structure object, but not at its beginning.
-16 The size of a union is sufficient to contain the largest of its members. The value of at
- most one of the members can be stored in a union object at any time. A pointer to a
- union object, suitably converted, points to each of its members (or if a member is a bit-
- field, then to the unit in which it resides), and vice versa.
-
-
- 123) The unary & (address-of) operator cannot be applied to a bit-field object; thus, there are no pointers to
- or arrays of bit-field objects.
- 124) As specified in 6.7.2 above, if the actual type specifier used is int or a typedef-name defined as int,
- then it is implementation-defined whether the bit-field is signed or unsigned.
- 125) An unnamed bit-field structure member is useful for padding to conform to externally imposed
- layouts.
-
-[page 113]
-
-17 There may be unnamed padding at the end of a structure or union.
-18 As a special case, the last element of a structure with more than one named member may
- have an incomplete array type; this is called a flexible array member. In most situations,
- the flexible array member is ignored. In particular, the size of the structure is as if the
- flexible array member were omitted except that it may have more trailing padding than
- the omission would imply. However, when a . (or ->) operator has a left operand that is
- (a pointer to) a structure with a flexible array member and the right operand names that
- member, it behaves as if that member were replaced with the longest array (with the same
- element type) that would not make the structure larger than the object being accessed; the
- offset of the array shall remain that of the flexible array member, even if this would differ
- from that of the replacement array. If this array would have no elements, it behaves as if
- it had one element but the behavior is undefined if any attempt is made to access that
- element or to generate a pointer one past it.
-19 EXAMPLE 1 The following illustrates anonymous structures and unions:
- struct v {
- union { // anonymous union
- struct { int i, j; }; // anonymous structure
- struct { long k, l; } w;
- };
- int m;
- } v1;
- v1.i = 2; // valid
- v1.k = 3; // invalid: inner structure is not anonymous
- v1.w.k = 5; // valid
-
-20 EXAMPLE 2 After the declaration:
- struct s { int n; double d[]; };
- the structure struct s has a flexible array member d. A typical way to use this is:
- int m = /* some value */;
- struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));
- and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
- p had been declared as:
- struct { int n; double d[m]; } *p;
- (there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
- not be the same).
-21 Following the above declaration:
- struct s t1 = { 0 }; // valid
- struct s t2 = { 1, { 4.2 }}; // invalid
- t1.n = 4; // valid
- t1.d[0] = 4.2; // might be undefined behavior
- The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
- contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
-
-[page 114]
-
- sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)
- in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming
- code.
-22 After the further declaration:
- struct ss { int n; };
- the expressions:
- sizeof (struct s) >= sizeof (struct ss)
- sizeof (struct s) >= offsetof(struct s, d)
- are always equal to 1.
-23 If sizeof (double) is 8, then after the following code is executed:
- struct s *s1;
- struct s *s2;
- s1 = malloc(sizeof (struct s) + 64);
- s2 = malloc(sizeof (struct s) + 46);
- and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
- purposes, as if the identifiers had been declared as:
- struct { int n; double d[8]; } *s1;
- struct { int n; double d[5]; } *s2;
-24 Following the further successful assignments:
- s1 = malloc(sizeof (struct s) + 10);
- s2 = malloc(sizeof (struct s) + 6);
- they then behave as if the declarations were:
- struct { int n; double d[1]; } *s1, *s2;
- and:
- double *dp;
- dp = &(s1->d[0]); // valid
- *dp = 42; // valid
- dp = &(s2->d[0]); // valid
- *dp = 42; // undefined behavior
-25 The assignment:
- *s1 = *s2;
- only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes
- of the structure, they might be copied or simply overwritten with indeterminate values.
-
- Forward references: declarators (6.7.6), tags (6.7.2.3).
-
-
-
-
-[page 115]
-
- 6.7.2.2 Enumeration specifiers
- Syntax
-1 enum-specifier:
- enum identifieropt { enumerator-list }
- enum identifieropt { enumerator-list , }
- enum identifier
- enumerator-list:
- enumerator
- enumerator-list , enumerator
- enumerator:
- enumeration-constant
- enumeration-constant = constant-expression
- Constraints
-2 The expression that defines the value of an enumeration constant shall be an integer
- constant expression that has a value representable as an int.
- Semantics
-3 The identifiers in an enumerator list are declared as constants that have type int and
- may appear wherever such are permitted.126) An enumerator with = defines its
- enumeration constant as the value of the constant expression. If the first enumerator has
- no =, the value of its enumeration constant is 0. Each subsequent enumerator with no =
- defines its enumeration constant as the value of the constant expression obtained by
- adding 1 to the value of the previous enumeration constant. (The use of enumerators with
- = may produce enumeration constants with values that duplicate other values in the same
- enumeration.) The enumerators of an enumeration are also known as its members.
-4 Each enumerated type shall be compatible with char, a signed integer type, or an
- unsigned integer type. The choice of type is implementation-defined,127) but shall be
- capable of representing the values of all the members of the enumeration. The
- enumerated type is incomplete until immediately after the } that terminates the list of
- enumerator declarations, and complete thereafter.
-
-
-
-
- 126) Thus, the identifiers of enumeration constants declared in the same scope shall all be distinct from
- each other and from other identifiers declared in ordinary declarators.
- 127) An implementation may delay the choice of which integer type until all enumeration constants have
- been seen.
-
-[page 116]
-
-5 EXAMPLE The following fragment:
- enum hue { chartreuse, burgundy, claret=20, winedark };
- enum hue col, *cp;
- col = claret;
- cp = &col;
- if (*cp != burgundy)
- /* ... */
- makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
- pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
-
- Forward references: tags (6.7.2.3).
- 6.7.2.3 Tags
- Constraints
-1 A specific type shall have its content defined at most once.
-2 Where two declarations that use the same tag declare the same type, they shall both use
- the same choice of struct, union, or enum.
-3 A type specifier of the form
- enum identifier
- without an enumerator list shall only appear after the type it specifies is complete.
- Semantics
-4 All declarations of structure, union, or enumerated types that have the same scope and
- use the same tag declare the same type. Irrespective of whether there is a tag or what
- other declarations of the type are in the same translation unit, the type is incomplete128)
- until immediately after the closing brace of the list defining the content, and complete
- thereafter.
-5 Two declarations of structure, union, or enumerated types which are in different scopes or
- use different tags declare distinct types. Each declaration of a structure, union, or
- enumerated type which does not include a tag declares a distinct type.
-6 A type specifier of the form
-
-
-
-
- 128) An incomplete type may only by used when the size of an object of that type is not needed. It is not
- needed, for example, when a typedef name is declared to be a specifier for a structure or union, or
- when a pointer to or a function returning a structure or union is being declared. (See incomplete types
- in 6.2.5.) The specification has to be complete before such a function is called or defined.
-
-[page 117]
-
- struct-or-union identifieropt { struct-declaration-list }
- or
- enum identifieropt { enumerator-list }
- or
- enum identifieropt { enumerator-list , }
- declares a structure, union, or enumerated type. The list defines the structure content,
- union content, or enumeration content. If an identifier is provided,129) the type specifier
- also declares the identifier to be the tag of that type.
-7 A declaration of the form
- struct-or-union identifier ;
- specifies a structure or union type and declares the identifier as a tag of that type.130)
-8 If a type specifier of the form
- struct-or-union identifier
- occurs other than as part of one of the above forms, and no other declaration of the
- identifier as a tag is visible, then it declares an incomplete structure or union type, and
- declares the identifier as the tag of that type.130)
-9 If a type specifier of the form
- struct-or-union identifier
- or
- enum identifier
- occurs other than as part of one of the above forms, and a declaration of the identifier as a
- tag is visible, then it specifies the same type as that other declaration, and does not
- redeclare the tag.
-10 EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
- struct tnode {
- int count;
- struct tnode *left, *right;
- };
- specifies a structure that contains an integer and two pointers to objects of the same type. Once this
- declaration has been given, the declaration
-
-
-
-
- 129) If there is no identifier, the type can, within the translation unit, only be referred to by the declaration
- of which it is a part. Of course, when the declaration is of a typedef name, subsequent declarations
- can make use of that typedef name to declare objects having the specified structure, union, or
- enumerated type.
- 130) A similar construction with enum does not exist.
-
-[page 118]
-
- struct tnode s, *sp;
- declares s to be an object of the given type and sp to be a pointer to an object of the given type. With
- these declarations, the expression sp->left refers to the left struct tnode pointer of the object to
- which sp points; the expression s.right->count designates the count member of the right struct
- tnode pointed to from s.
-11 The following alternative formulation uses the typedef mechanism:
- typedef struct tnode TNODE;
- struct tnode {
- int count;
- TNODE *left, *right;
- };
- TNODE s, *sp;
-
-12 EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential
- structures, the declarations
- struct s1 { struct s2 *s2p; /* ... */ }; // D1
- struct s2 { struct s1 *s1p; /* ... */ }; // D2
- specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
- declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
- D2. To eliminate this context sensitivity, the declaration
- struct s2;
- may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then
- completes the specification of the new type.
-
- Forward references: declarators (6.7.6), type definitions (6.7.8).
- 6.7.3 Type qualifiers
- Syntax
-1 type-qualifier:
- const
- restrict
- volatile
- _Atomic
- Constraints
-2 Types other than pointer types whose referenced type is an object type shall not be
- restrict-qualified.
- Semantics
-3 The properties associated with qualified types are meaningful only for expressions that
- are lvalues.131)
-4 If the same qualifier appears more than once in the same specifier-qualifier-list, either
- directly or via one or more typedefs, the behavior is the same as if it appeared only
- once.
-[page 119]
-
-5 If an attempt is made to modify an object defined with a const-qualified type through use
- of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is
- made to refer to an object defined with a volatile-qualified type through use of an lvalue
- with non-volatile-qualified type, the behavior is undefined.132) If an attempt is made to
- refer to an object defined with an _Atomic-qualified type through use of an lvalue with
- non-_Atomic-qualified type, the behavior is undefined.
-6 An object that has volatile-qualified type may be modified in ways unknown to the
- implementation or have other unknown side effects. Therefore any expression referring
- to such an object shall be evaluated strictly according to the rules of the abstract machine,
- as described in 5.1.2.3. Furthermore, at every sequence point the value last stored in the
- object shall agree with that prescribed by the abstract machine, except as modified by the
- unknown factors mentioned previously.133) What constitutes an access to an object that
- has volatile-qualified type is implementation-defined.
-7 An object that is accessed through a restrict-qualified pointer has a special association
- with that pointer. This association, defined in 6.7.3.1 below, requires that all accesses to
- that object use, directly or indirectly, the value of that particular pointer.134) The intended
- use of the restrict qualifier (like the register storage class) is to promote
- optimization, and deleting all instances of the qualifier from all preprocessing translation
- units composing a conforming program does not change its meaning (i.e., observable
- behavior).
-8 If the specification of an array type includes any type qualifiers, the element type is so-
- qualified, not the array type. If the specification of a function type includes any type
- qualifiers, the behavior is undefined.135)
-9 For two qualified types to be compatible, both shall have the identically qualified version
- of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers
- does not affect the specified type.
-
- 131) The implementation may place a const object that is not volatile in a read-only region of
- storage. Moreover, the implementation need not allocate storage for such an object if its address is
- never used.
- 132) This applies to those objects that behave as if they were defined with qualified types, even if they are
- never actually defined as objects in the program (such as an object at a memory-mapped input/output
- address).
- 133) A volatile declaration may be used to describe an object corresponding to a memory-mapped
- input/output port or an object accessed by an asynchronously interrupting function. Actions on
- objects so declared shall not be ''optimized out'' by an implementation or reordered except as
- permitted by the rules for evaluating expressions.
- 134) For example, a statement that assigns a value returned by malloc to a single pointer establishes this
- association between the allocated object and the pointer.
- 135) Both of these can occur through the use of typedefs.
-
-[page 120]
-
-10 EXAMPLE 1 An object declared
- extern const volatile int real_time_clock;
- may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
-
-11 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers
- modify an aggregate type:
- const struct s { int mem; } cs = { 1 };
- struct s ncs; // the object ncs is modifiable
- typedef int A[2][3];
- const A a = {{4, 5, 6}, {7, 8, 9}}; // array of array of const int
- int *pi;
- const int *pci;
- ncs = cs; // valid
- cs = ncs; // violates modifiable lvalue constraint for =
- pi = &ncs.mem; // valid
- pi = &cs.mem; // violates type constraints for =
- pci = &cs.mem; // valid
- pi = a[0]; // invalid: a[0] has type ''const int *''
-
- 6.7.3.1 Formal definition of restrict
-1 Let D be a declaration of an ordinary identifier that provides a means of designating an
- object P as a restrict-qualified pointer to type T.
-2 If D appears inside a block and does not have storage class extern, let B denote the
- block. If D appears in the list of parameter declarations of a function definition, let B
- denote the associated block. Otherwise, let B denote the block of main (or the block of
- whatever function is called at program startup in a freestanding environment).
-3 In what follows, a pointer expression E is said to be based on object P if (at some
- sequence point in the execution of B prior to the evaluation of E) modifying P to point to
- a copy of the array object into which it formerly pointed would change the value of E.136)
- Note that ''based'' is defined only for expressions with pointer types.
-4 During each execution of B, let L be any lvalue that has &L based on P. If L is used to
- access the value of the object X that it designates, and X is also modified (by any means),
- then the following requirements apply: T shall not be const-qualified. Every other lvalue
- used to access the value of X shall also have its address based on P. Every access that
- modifies X shall be considered also to modify P, for the purposes of this subclause. If P
- is assigned the value of a pointer expression E that is based on another restricted pointer
- object P2, associated with block B2, then either the execution of B2 shall begin before
-
-
- 136) In other words, E depends on the value of P itself rather than on the value of an object referenced
- indirectly through P. For example, if identifier p has type (int **restrict), then the pointer
- expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer
- expressions *p and p[1] are not.
-
-[page 121]
-
- the execution of B, or the execution of B2 shall end prior to the assignment. If these
- requirements are not met, then the behavior is undefined.
-5 Here an execution of B means that portion of the execution of the program that would
- correspond to the lifetime of an object with scalar type and automatic storage duration
- associated with B.
-6 A translator is free to ignore any or all aliasing implications of uses of restrict.
-7 EXAMPLE 1 The file scope declarations
- int * restrict a;
- int * restrict b;
- extern int c[];
- assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
- program, then it is never accessed using either of the other two.
-
-8 EXAMPLE 2 The function parameter declarations in the following example
- void f(int n, int * restrict p, int * restrict q)
- {
- while (n-- > 0)
- *p++ = *q++;
- }
- assert that, during each execution of the function, if an object is accessed through one of the pointer
- parameters, then it is not also accessed through the other.
-9 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence
- analysis of function f without examining any of the calls of f in the program. The cost is that the
- programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the
- second call of f in g has undefined behavior because each of d[1] through d[49] is accessed through
- both p and q.
- void g(void)
- {
- extern int d[100];
- f(50, d + 50, d); // valid
- f(50, d + 1, d); // undefined behavior
- }
-
-10 EXAMPLE 3 The function parameter declarations
- void h(int n, int * restrict p, int * restrict q, int * restrict r)
- {
- int i;
- for (i = 0; i < n; i++)
- p[i] = q[i] + r[i];
- }
- illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
- are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
- modified within function h.
-
-11 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a
- function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments
-
-[page 122]
-
- between restricted pointers declared in nested blocks have defined behavior.
- {
- int * restrict p1;
- int * restrict q1;
- p1 = q1; // undefined behavior
- {
- int * restrict p2 = p1; // valid
- int * restrict q2 = q1; // valid
- p1 = q2; // undefined behavior
- p2 = q2; // undefined behavior
- }
- }
-12 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more
- precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For
- example, this permits new_vector to return a vector.
- typedef struct { int n; float * restrict v; } vector;
- vector new_vector(int n)
- {
- vector t;
- t.n = n;
- t.v = malloc(n * sizeof (float));
- return t;
- }
-
- 6.7.4 Function specifiers
- Syntax
-1 function-specifier:
- inline
- _Noreturn
- Constraints
-2 Function specifiers shall be used only in the declaration of an identifier for a function.
-3 An inline definition of a function with external linkage shall not contain a definition of a
- modifiable object with static or thread storage duration, and shall not contain a reference
- to an identifier with internal linkage.
-4 In a hosted environment, no function specifier(s) shall appear in a declaration of main.
- Semantics
-5 A function specifier may appear more than once; the behavior is the same as if it
- appeared only once.
-6 A function declared with an inline function specifier is an inline function. Making a
- function an inline function suggests that calls to the function be as fast as possible.137)
- The extent to which such suggestions are effective is implementation-defined.138)
-
-[page 123]
-
-7 Any function with internal linkage can be an inline function. For a function with external
- linkage, the following restrictions apply: If a function is declared with an inline
- function specifier, then it shall also be defined in the same translation unit. If all of the
- file scope declarations for a function in a translation unit include the inline function
- specifier without extern, then the definition in that translation unit is an inline
- definition. An inline definition does not provide an external definition for the function,
- and does not forbid an external definition in another translation unit. An inline definition
- provides an alternative to an external definition, which a translator may use to implement
- any call to the function in the same translation unit. It is unspecified whether a call to the
- function uses the inline definition or the external definition.139)
-8 A function declared with a _Noreturn function specifier shall not return to its caller.
- Recommended practice
-9 The implementation should produce a diagnostic message for a function declared with a
- _Noreturn function specifier that appears to be capable of returning to its caller.
-10 EXAMPLE 1 The declaration of an inline function with external linkage can result in either an external
- definition, or a definition available for use only within the translation unit. A file scope declaration with
- extern creates an external definition. The following example shows an entire translation unit.
- inline double fahr(double t)
- {
- return (9.0 * t) / 5.0 + 32.0;
- }
- inline double cels(double t)
- {
- return (5.0 * (t - 32.0)) / 9.0;
- }
- extern double fahr(double); // creates an external definition
-
-
-
-
- 137) By using, for example, an alternative to the usual function call mechanism, such as ''inline
- substitution''. Inline substitution is not textual substitution, nor does it create a new function.
- Therefore, for example, the expansion of a macro used within the body of the function uses the
- definition it had at the point the function body appears, and not where the function is called; and
- identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a
- single address, regardless of the number of inline definitions that occur in addition to the external
- definition.
- 138) For example, an implementation might never perform inline substitution, or might only perform inline
- substitutions to calls in the scope of an inline declaration.
- 139) Since an inline definition is distinct from the corresponding external definition and from any other
- corresponding inline definitions in other translation units, all corresponding objects with static storage
- duration are also distinct in each of the definitions.
-
-[page 124]
-
- double convert(int is_fahr, double temp)
- {
- /* A translator may perform inline substitutions */
- return is_fahr ? cels(temp) : fahr(temp);
- }
-11 Note that the definition of fahr is an external definition because fahr is also declared with extern, but
- the definition of cels is an inline definition. Because cels has external linkage and is referenced, an
- external definition has to appear in another translation unit (see 6.9); the inline definition and the external
- definition are distinct and either may be used for the call.
-
-12 EXAMPLE 2
- _Noreturn void f () {
- abort(); // ok
- }
- _Noreturn void g (int i) { // causes undefined behavior if i <= 0
- if (i > 0) abort();
- }
-
- Forward references: function definitions (6.9.1).
- 6.7.5 Alignment specifier
- Syntax
-1 alignment-specifier:
- _Alignas ( type-name )
- _Alignas ( constant-expression )
- Constraints
-2 An alignment attribute shall not be specified in a declaration of a typedef, or a bit-field, or
- a function, or a parameter, or an object declared with the register storage-class
- specifier.
-3 The constant expression shall be an integer constant expression. It shall evaluate to a
- valid fundamental alignment, or to a valid extended alignment supported by the
- implementation in the context in which it appears, or to zero.
-4 The combined effect of all alignment attributes in a declaration shall not specify an
- alignment that is less strict than the alignment that would otherwise be required for the
- type of the object or field being declared.
- Semantics
-5 The first form is equivalent to _Alignas(alignof(type-name)).
-6 The alignment requirement of the declared object or field is taken to be the specified
- alignment. An alignment specification of zero has no effect.140) When multiple
- alignment specifiers occur in a declaration, the effective alignment requirement is the
- strictest specified alignment.
-
-[page 125]
-
-7 If the definition of an object has an alignment specifier, any other declaration of that
- object shall either specify equivalent alignment or have no alignment specifier. If the
- definition of an object does not have an alignment specifier, any other declaration of that
- object shall also have no alignment specifier. If declarations of an object in different
- translation units have different alignment specifiers, the behavior is undefined.
- 6.7.6 Declarators
- Syntax
-1 declarator:
- pointeropt direct-declarator
- direct-declarator:
- identifier
- ( declarator )
- direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
- direct-declarator [ static type-qualifier-listopt assignment-expression ]
- direct-declarator [ type-qualifier-list static assignment-expression ]
- direct-declarator [ type-qualifier-listopt * ]
- direct-declarator ( parameter-type-list )
- direct-declarator ( identifier-listopt )
- pointer:
- * type-qualifier-listopt
- * type-qualifier-listopt pointer
- type-qualifier-list:
- type-qualifier
- type-qualifier-list type-qualifier
- parameter-type-list:
- parameter-list
- parameter-list , ...
- parameter-list:
- parameter-declaration
- parameter-list , parameter-declaration
- parameter-declaration:
- declaration-specifiers declarator
- declaration-specifiers abstract-declaratoropt
-
-
-
- 140) An alignment specification of zero also does not affect other alignment specifications in the same
- declaration.
-
-[page 126]
-
- identifier-list:
- identifier
- identifier-list , identifier
- Semantics
-2 Each declarator declares one identifier, and asserts that when an operand of the same
- form as the declarator appears in an expression, it designates a function or object with the
- scope, storage duration, and type indicated by the declaration specifiers.
-3 A full declarator is a declarator that is not part of another declarator. The end of a full
- declarator is a sequence point. If, in the nested sequence of declarators in a full
- declarator, there is a declarator specifying a variable length array type, the type specified
- by the full declarator is said to be variably modified. Furthermore, any type derived by
- declarator type derivation from a variably modified type is itself variably modified.
-4 In the following subclauses, consider a declaration
- T D1
- where T contains the declaration specifiers that specify a type T (such as int) and D1 is
- a declarator that contains an identifier ident. The type specified for the identifier ident in
- the various forms of declarator is described inductively using this notation.
-5 If, in the declaration ''T D1'', D1 has the form
- identifier
- then the type specified for ident is T .
-6 If, in the declaration ''T D1'', D1 has the form
- ( D )
- then ident has the type specified by the declaration ''T D''. Thus, a declarator in
- parentheses is identical to the unparenthesized declarator, but the binding of complicated
- declarators may be altered by parentheses.
- Implementation limits
-7 As discussed in 5.2.4.1, an implementation may limit the number of pointer, array, and
- function declarators that modify an arithmetic, structure, union, or void type, either
- directly or via one or more typedefs.
- Forward references: array declarators (6.7.6.2), type definitions (6.7.8).
-
-
-
-
-[page 127]
-
- 6.7.6.1 Pointer declarators
- Semantics
-1 If, in the declaration ''T D1'', D1 has the form
- * type-qualifier-listopt D
- and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
- T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list
- pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer.
-2 For two pointer types to be compatible, both shall be identically qualified and both shall
- be pointers to compatible types.
-3 EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer
- to a constant value'' and a ''constant pointer to a variable value''.
- const int *ptr_to_constant;
- int *const constant_ptr;
- The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
- but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
- int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
- same location.
-4 The declaration of the constant pointer constant_ptr may be clarified by including a definition for the
- type ''pointer to int''.
- typedef int *int_ptr;
- const int_ptr constant_ptr;
- declares constant_ptr as an object that has type ''const-qualified pointer to int''.
-
- 6.7.6.2 Array declarators
- Constraints
-1 In addition to optional type qualifiers and the keyword static, the [ and ] may delimit
- an expression or *. If they delimit an expression (which specifies the size of an array), the
- expression shall have an integer type. If the expression is a constant expression, it shall
- have a value greater than zero. The element type shall not be an incomplete or function
- type. The optional type qualifiers and the keyword static shall appear only in a
- declaration of a function parameter with an array type, and then only in the outermost
- array type derivation.
-2 An ordinary identifier (as defined in 6.2.3) that has a variably modified type shall have
- either block scope and no linkage or function prototype scope. If an identifier is declared
- to be an object with static or thread storage duration, it shall not have a variable length
- array type.
-
-
-
-
-[page 128]
-
- Semantics
-3 If, in the declaration ''T D1'', D1 has one of the forms:
- D[ type-qualifier-listopt assignment-expressionopt ]
- D[ static type-qualifier-listopt assignment-expression ]
- D[ type-qualifier-list static assignment-expression ]
- D[ type-qualifier-listopt * ]
- and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
- T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.141)
- (See 6.7.6.3 for the meaning of the optional type qualifiers and the keyword static.)
-4 If the size is not present, the array type is an incomplete type. If the size is * instead of
- being an expression, the array type is a variable length array type of unspecified size,
- which can only be used in declarations or type names with function prototype scope;142)
- such arrays are nonetheless complete types. If the size is an integer constant expression
- and the element type has a known constant size, the array type is not a variable length
- array type; otherwise, the array type is a variable length array type. (Variable length
- arrays are a conditional feature that implementations need not support; see 6.10.8.3.)
-5 If the size is an expression that is not an integer constant expression: if it occurs in a
- declaration at function prototype scope, it is treated as if it were replaced by *; otherwise,
- each time it is evaluated it shall have a value greater than zero. The size of each instance
- of a variable length array type does not change during its lifetime. Where a size
- expression is part of the operand of a sizeof operator and changing the value of the
- size expression would not affect the result of the operator, it is unspecified whether or not
- the size expression is evaluated.
-6 For two array types to be compatible, both shall have compatible element types, and if
- both size specifiers are present, and are integer constant expressions, then both size
- specifiers shall have the same constant value. If the two array types are used in a context
- which requires them to be compatible, it is undefined behavior if the two size specifiers
- evaluate to unequal values.
-7 EXAMPLE 1
- float fa[11], *afp[17];
- declares an array of float numbers and an array of pointers to float numbers.
-
-8 EXAMPLE 2 Note the distinction between the declarations
-
-
-
-
- 141) When several ''array of'' specifications are adjacent, a multidimensional array is declared.
- 142) Thus, * can be used only in function declarations that are not definitions (see 6.7.6.3).
-
-[page 129]
-
- extern int *x;
- extern int y[];
- The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
- (an incomplete type), the storage for which is defined elsewhere.
-
-9 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
- extern int n;
- extern int m;
- void fcompat(void)
- {
- int a[n][6][m];
- int (*p)[4][n+1];
- int c[n][n][6][m];
- int (*r)[n][n][n+1];
- p = a; // invalid: not compatible because 4 != 6
- r = c; // compatible, but defined behavior only if
- // n == 6 and m == n+1
- }
-
-10 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or
- function prototype scope. Array objects declared with the _Thread_local, static, or extern
- storage-class specifier cannot have a variable length array (VLA) type. However, an object declared with
- the static storage-class specifier can have a VM type (that is, a pointer to a VLA type). Finally, all
- identifiers declared with a VM type have to be ordinary identifiers and cannot, therefore, be members of
- structures or unions.
- extern int n;
- int A[n]; // invalid: file scope VLA
- extern int (*p2)[n]; // invalid: file scope VM
- int B[100]; // valid: file scope but not VM
- void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
- void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
- {
- typedef int VLA[m][m]; // valid: block scope typedef VLA
- struct tag {
- int (*y)[n]; // invalid: y not ordinary identifier
- int z[n]; // invalid: z not ordinary identifier
- };
- int D[m]; // valid: auto VLA
- static int E[m]; // invalid: static block scope VLA
- extern int F[m]; // invalid: F has linkage and is VLA
- int (*s)[m]; // valid: auto pointer to VLA
- extern int (*r)[m]; // invalid: r has linkage and points to VLA
- static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
- }
-
- Forward references: function declarators (6.7.6.3), function definitions (6.9.1),
- initialization (6.7.9).
-
-
-
-[page 130]
-
- 6.7.6.3 Function declarators (including prototypes)
- Constraints
-1 A function declarator shall not specify a return type that is a function type or an array
- type.
-2 The only storage-class specifier that shall occur in a parameter declaration is register.
-3 An identifier list in a function declarator that is not part of a definition of that function
- shall be empty.
-4 After adjustment, the parameters in a parameter type list in a function declarator that is
- part of a definition of that function shall not have incomplete type.
- Semantics
-5 If, in the declaration ''T D1'', D1 has the form
- D( parameter-type-list )
- or
- D( identifier-listopt )
- and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
- T '', then the type specified for ident is ''derived-declarator-type-list function returning
- T ''.
-6 A parameter type list specifies the types of, and may declare identifiers for, the
- parameters of the function.
-7 A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to
- type'', where the type qualifiers (if any) are those specified within the [ and ] of the
- array type derivation. If the keyword static also appears within the [ and ] of the
- array type derivation, then for each call to the function, the value of the corresponding
- actual argument shall provide access to the first element of an array with at least as many
- elements as specified by the size expression.
-8 A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to
- function returning type'', as in 6.3.2.1.
-9 If the list terminates with an ellipsis (, ...), no information about the number or types
- of the parameters after the comma is supplied.143)
-10 The special case of an unnamed parameter of type void as the only item in the list
- specifies that the function has no parameters.
-
-
-
- 143) The macros defined in the <stdarg.h> header (7.16) may be used to access arguments that
- correspond to the ellipsis.
-
-[page 131]
-
-11 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a
- parameter name, it shall be taken as a typedef name.
-12 If the function declarator is not part of a definition of that function, parameters may have
- incomplete type and may use the [*] notation in their sequences of declarator specifiers
- to specify variable length array types.
-13 The storage-class specifier in the declaration specifiers for a parameter declaration, if
- present, is ignored unless the declared parameter is one of the members of the parameter
- type list for a function definition.
-14 An identifier list declares only the identifiers of the parameters of the function. An empty
- list in a function declarator that is part of a definition of that function specifies that the
- function has no parameters. The empty list in a function declarator that is not part of a
- definition of that function specifies that no information about the number or types of the
- parameters is supplied.144)
-15 For two function types to be compatible, both shall specify compatible return types.145)
- Moreover, the parameter type lists, if both are present, shall agree in the number of
- parameters and in use of the ellipsis terminator; corresponding parameters shall have
- compatible types. If one type has a parameter type list and the other type is specified by a
- function declarator that is not part of a function definition and that contains an empty
- identifier list, the parameter list shall not have an ellipsis terminator and the type of each
- parameter shall be compatible with the type that results from the application of the
- default argument promotions. If one type has a parameter type list and the other type is
- specified by a function definition that contains a (possibly empty) identifier list, both shall
- agree in the number of parameters, and the type of each prototype parameter shall be
- compatible with the type that results from the application of the default argument
- promotions to the type of the corresponding identifier. (In the determination of type
- compatibility and of a composite type, each parameter declared with function or array
- type is taken as having the adjusted type and each parameter declared with qualified type
- is taken as having the unqualified version of its declared type.)
-16 EXAMPLE 1 The declaration
- int f(void), *fip(), (*pfi)();
- declares a function f with no parameters returning an int, a function fip with no parameter specification
- returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an
- int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the
- declaration suggests, and the same construction in an expression requires, the calling of a function fip,
- and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the
- extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function
-
-
- 144) See ''future language directions'' (6.11.6).
- 145) If both function types are ''old style'', parameter types are not compared.
-
-[page 132]
-
- designator, which is then used to call the function; it returns an int.
-17 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the
- declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either
- internal or external linkage (depending on what file scope declarations for these identifiers are visible), and
- the identifier of the pointer pfi has block scope and no linkage.
-
-18 EXAMPLE 2 The declaration
- int (*apfi[3])(int *x, int *y);
- declares an array apfi of three pointers to functions returning int. Each of these functions has two
- parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and
- go out of scope at the end of the declaration of apfi.
-
-19 EXAMPLE 3 The declaration
- int (*fpfi(int (*)(long), int))(int, ...);
- declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two
- parameters: a pointer to a function returning an int (with one parameter of type long int), and an int.
- The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more
- additional arguments of any type.
-
-20 EXAMPLE 4 The following prototype has a variably modified parameter.
- void addscalar(int n, int m,
- double a[n][n*m+300], double x);
- int main()
- {
- double b[4][308];
- addscalar(4, 2, b, 2.17);
- return 0;
- }
- void addscalar(int n, int m,
- double a[n][n*m+300], double x)
- {
- for (int i = 0; i < n; i++)
- for (int j = 0, k = n*m+300; j < k; j++)
- // a is a pointer to a VLA with n*m+300 elements
- a[i][j] += x;
- }
-
-21 EXAMPLE 5 The following are all compatible function prototype declarators.
- double maximum(int n, int m, double a[n][m]);
- double maximum(int n, int m, double a[*][*]);
- double maximum(int n, int m, double a[ ][*]);
- double maximum(int n, int m, double a[ ][m]);
- as are:
- void f(double (* restrict a)[5]);
- void f(double a[restrict][5]);
- void f(double a[restrict 3][5]);
- void f(double a[restrict static 3][5]);
-
-
-[page 133]
-
- (Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
- non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
-
- Forward references: function definitions (6.9.1), type names (6.7.7).
- 6.7.7 Type names
- Syntax
-1 type-name:
- specifier-qualifier-list abstract-declaratoropt
- abstract-declarator:
- pointer
- pointeropt direct-abstract-declarator
- direct-abstract-declarator:
- ( abstract-declarator )
- direct-abstract-declaratoropt [ type-qualifier-listopt
- assignment-expressionopt ]
- direct-abstract-declaratoropt [ static type-qualifier-listopt
- assignment-expression ]
- direct-abstract-declaratoropt [ type-qualifier-list static
- assignment-expression ]
- direct-abstract-declaratoropt [ * ]
- direct-abstract-declaratoropt ( parameter-type-listopt )
- Semantics
-2 In several contexts, it is necessary to specify a type. This is accomplished using a type
- name, which is syntactically a declaration for a function or an object of that type that
- omits the identifier.146)
-3 EXAMPLE The constructions
- (a) int
- (b) int *
- (c) int *[3]
- (d) int (*)[3]
- (e) int (*)[*]
- (f) int *()
- (g) int (*)(void)
- (h) int (*const [])(unsigned int, ...)
- name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
- array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
- with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
-
-
- 146) As indicated by the syntax, empty parentheses in a type name are interpreted as ''function with no
- parameter specification'', rather than redundant parentheses around the omitted identifier.
-
-[page 134]
-
- returning an int, and (h) array of an unspecified number of constant pointers to functions, each with one
- parameter that has type unsigned int and an unspecified number of other parameters, returning an
- int.
-
- 6.7.8 Type definitions
- Syntax
-1 typedef-name:
- identifier
- Constraints
-2 If a typedef name specifies a variably modified type then it shall have block scope.
- Semantics
-3 In a declaration whose storage-class specifier is typedef, each declarator defines an
- identifier to be a typedef name that denotes the type specified for the identifier in the way
- described in 6.7.6. Any array size expressions associated with variable length array
- declarators are evaluated each time the declaration of the typedef name is reached in the
- order of execution. A typedef declaration does not introduce a new type, only a
- synonym for the type so specified. That is, in the following declarations:
- typedef T type_ident;
- type_ident D;
- type_ident is defined as a typedef name with the type specified by the declaration
- specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
- type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
- typedef name shares the same name space as other identifiers declared in ordinary
- declarators.
-4 EXAMPLE 1 After
- typedef int MILES, KLICKSP();
- typedef struct { double hi, lo; } range;
- the constructions
- MILES distance;
- extern KLICKSP *metricp;
- range x;
- range z, *zp;
- are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
- parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
- such a structure. The object distance has a type compatible with any other int object.
-
-5 EXAMPLE 2 After the declarations
- typedef struct s1 { int x; } t1, *tp1;
- typedef struct s2 { int x; } t2, *tp2;
- type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
-
-[page 135]
-
- s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
-
-6 EXAMPLE 3 The following obscure constructions
- typedef signed int t;
- typedef int plain;
- struct tag {
- unsigned t:4;
- const t:5;
- plain r:5;
- };
- declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
- with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
- qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
- [-16, +15], and one named r that contains values in one of the ranges [0, 31], [-15, +15], or [-16, +15].
- (The choice of range is implementation-defined.) The first two bit-field declarations differ in that
- unsigned is a type specifier (which forces t to be the name of a structure member), while const is a
- type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed
- in an inner scope by
- t f(t (t));
- long t;
- then a function f is declared with type ''function returning signed int with one unnamed parameter
- with type pointer to function returning signed int with one unnamed parameter with type signed
- int'', and an identifier t with type long int.
-
-7 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the
- following declarations of the signal function specify exactly the same type, the first without making use
- of any typedef names.
- typedef void fv(int), (*pfv)(int);
- void (*signal(int, void (*)(int)))(int);
- fv *signal(int, fv *);
- pfv signal(int, pfv);
-
-8 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the
- time the typedef name is defined, not each time it is used:
- void copyt(int n)
- {
- typedef int B[n]; // B is n ints, n evaluated now
- n += 1;
- B a; // a is n ints, n without += 1
- int b[n]; // a and b are different sizes
- for (int i = 1; i < n; i++)
- a[i-1] = b[i];
- }
-
-
-
-
-[page 136]
-
- 6.7.9 Initialization
- Syntax
-1 initializer:
- assignment-expression
- { initializer-list }
- { initializer-list , }
- initializer-list:
- designationopt initializer
- initializer-list , designationopt initializer
- designation:
- designator-list =
- designator-list:
- designator
- designator-list designator
- designator:
- [ constant-expression ]
- . identifier
- Constraints
-2 No initializer shall attempt to provide a value for an object not contained within the entity
- being initialized.
-3 The type of the entity to be initialized shall be an array of unknown size or a complete
- object type that is not a variable length array type.
-4 All the expressions in an initializer for an object that has static or thread storage duration
- shall be constant expressions or string literals.
-5 If the declaration of an identifier has block scope, and the identifier has external or
- internal linkage, the declaration shall have no initializer for the identifier.
-6 If a designator has the form
- [ constant-expression ]
- then the current object (defined below) shall have array type and the expression shall be
- an integer constant expression. If the array is of unknown size, any nonnegative value is
- valid.
-7 If a designator has the form
- . identifier
- then the current object (defined below) shall have structure or union type and the
- identifier shall be the name of a member of that type.
-[page 137]
-
- Semantics
-8 An initializer specifies the initial value stored in an object.
-9 Except where explicitly stated otherwise, for the purposes of this subclause unnamed
- members of objects of structure and union type do not participate in initialization.
- Unnamed members of structure objects have indeterminate value even after initialization.
-10 If an object that has automatic storage duration is not initialized explicitly, its value is
- indeterminate. If an object that has static or thread storage duration is not initialized
- explicitly, then:
- -- if it has pointer type, it is initialized to a null pointer;
- -- if it has arithmetic type, it is initialized to (positive or unsigned) zero;
- -- if it is an aggregate, every member is initialized (recursively) according to these rules,
- and any padding is initialized to zero bits;
- -- if it is a union, the first named member is initialized (recursively) according to these
- rules, and any padding is initialized to zero bits;
-11 The initializer for a scalar shall be a single expression, optionally enclosed in braces. The
- initial value of the object is that of the expression (after conversion); the same type
- constraints and conversions as for simple assignment apply, taking the type of the scalar
- to be the unqualified version of its declared type.
-12 The rest of this subclause deals with initializers for objects that have aggregate or union
- type.
-13 The initializer for a structure or union object that has automatic storage duration shall be
- either an initializer list as described below, or a single expression that has compatible
- structure or union type. In the latter case, the initial value of the object, including
- unnamed members, is that of the expression.
-14 An array of character type may be initialized by a character string literal or UTF-8 string
- literal, optionally enclosed in braces. Successive bytes of the string literal (including the
- terminating null character if there is room or if the array is of unknown size) initialize the
- elements of the array.
-15 An array with element type compatible with a qualified or unqualified version of
- wchar_t may be initialized by a wide string literal, optionally enclosed in braces.
- Successive wide characters of the wide string literal (including the terminating null wide
- character if there is room or if the array is of unknown size) initialize the elements of the
- array.
-16 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-
- enclosed list of initializers for the elements or named members.
-
-
-[page 138]
-
-17 Each brace-enclosed initializer list has an associated current object. When no
- designations are present, subobjects of the current object are initialized in order according
- to the type of the current object: array elements in increasing subscript order, structure
- members in declaration order, and the first named member of a union.147) In contrast, a
- designation causes the following initializer to begin initialization of the subobject
- described by the designator. Initialization then continues forward in order, beginning
- with the next subobject after that described by the designator.148)
-18 Each designator list begins its description with the current object associated with the
- closest surrounding brace pair. Each item in the designator list (in order) specifies a
- particular member of its current object and changes the current object for the next
- designator (if any) to be that member.149) The current object that results at the end of the
- designator list is the subobject to be initialized by the following initializer.
-19 The initialization shall occur in initializer list order, each initializer provided for a
- particular subobject overriding any previously listed initializer for the same subobject;150)
- all subobjects that are not initialized explicitly shall be initialized implicitly the same as
- objects that have static storage duration.
-20 If the aggregate or union contains elements or members that are aggregates or unions,
- these rules apply recursively to the subaggregates or contained unions. If the initializer of
- a subaggregate or contained union begins with a left brace, the initializers enclosed by
- that brace and its matching right brace initialize the elements or members of the
- subaggregate or the contained union. Otherwise, only enough initializers from the list are
- taken to account for the elements or members of the subaggregate or the first member of
- the contained union; any remaining initializers are left to initialize the next element or
- member of the aggregate of which the current subaggregate or contained union is a part.
-21 If there are fewer initializers in a brace-enclosed list than there are elements or members
- of an aggregate, or fewer characters in a string literal used to initialize an array of known
- size than there are elements in the array, the remainder of the aggregate shall be
- initialized implicitly the same as objects that have static storage duration.
-
-
-
- 147) If the initializer list for a subaggregate or contained union does not begin with a left brace, its
- subobjects are initialized as usual, but the subaggregate or contained union does not become the
- current object: current objects are associated only with brace-enclosed initializer lists.
- 148) After a union member is initialized, the next object is not the next member of the union; instead, it is
- the next subobject of an object containing the union.
- 149) Thus, a designator can only specify a strict subobject of the aggregate or union that is associated with
- the surrounding brace pair. Note, too, that each separate designator list is independent.
- 150) Any initializer for the subobject which is overridden and so not used to initialize that subobject might
- not be evaluated at all.
-
-[page 139]
-
-22 If an array of unknown size is initialized, its size is determined by the largest indexed
- element with an explicit initializer. The array type is completed at the end of its
- initializer list.
-23 The order in which any side effects occur among the initialization list expressions is
- unspecified.151)
-24 EXAMPLE 1 Provided that <complex.h> has been #included, the declarations
- int i = 3.5;
- double complex c = 5 + 3 * I;
- define and initialize i with the value 3 and c with the value 5.0 + i3.0.
-
-25 EXAMPLE 2 The declaration
- int x[] = { 1, 3, 5 };
- defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
- and there are three initializers.
-
-26 EXAMPLE 3 The declaration
- int y[4][3] = {
- { 1, 3, 5 },
- { 2, 4, 6 },
- { 3, 5, 7 },
- };
- is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
- y[0]), namely y[0][0], y[0][1], and y[0][2]. Likewise the next two lines initialize y[1] and
- y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
- been achieved by
- int y[4][3] = {
- 1, 3, 5, 2, 4, 6, 3, 5, 7
- };
- The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
- next three are taken successively for y[1] and y[2].
-
-27 EXAMPLE 4 The declaration
- int z[4][3] = {
- { 1 }, { 2 }, { 3 }, { 4 }
- };
- initializes the first column of z as specified and initializes the rest with zeros.
-
-28 EXAMPLE 5 The declaration
- struct { int a[3], b; } w[] = { { 1 }, 2 };
- is a definition with an inconsistently bracketed initialization. It defines an array with two element
- structures: w[0].a[0] is 1 and w[1].a[0] is 2; all the other elements are zero.
-
-
-
- 151) In particular, the evaluation order need not be the same as the order of subobject initialization.
-
-[page 140]
-
-29 EXAMPLE 6 The declaration
- short q[4][3][2] = {
- { 1 },
- { 2, 3 },
- { 4, 5, 6 }
- };
- contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
- object: q[0][0][0] is 1, q[1][0][0] is 2, q[1][0][1] is 3, and 4, 5, and 6 initialize
- q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
- q[0][0] does not begin with a left brace, so up to six items from the current list may be used. There is
- only one, so the values for the remaining five elements are initialized with zero. Likewise, the initializers
- for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their
- respective two-dimensional subaggregates. If there had been more than six items in any of the lists, a
- diagnostic message would have been issued. The same initialization result could have been achieved by:
- short q[4][3][2] = {
- 1, 0, 0, 0, 0, 0,
- 2, 3, 0, 0, 0, 0,
- 4, 5, 6
- };
- or by:
- short q[4][3][2] = {
- {
- { 1 },
- },
- {
- { 2, 3 },
- },
- {
- { 4, 5 },
- { 6 },
- }
- };
- in a fully bracketed form.
-30 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
- cause confusion.
-
-31 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the
- declaration
- typedef int A[]; // OK - declared with block scope
- the declaration
- A a = { 1, 2 }, b = { 3, 4, 5 };
- is identical to
- int a[] = { 1, 2 }, b[] = { 3, 4, 5 };
- due to the rules for incomplete types.
-
-
-
-[page 141]
-
-32 EXAMPLE 8 The declaration
- char s[] = "abc", t[3] = "abc";
- defines ''plain'' char array objects s and t whose elements are initialized with character string literals.
- This declaration is identical to
- char s[] = { 'a', 'b', 'c', '\0' },
- t[] = { 'a', 'b', 'c' };
- The contents of the arrays are modifiable. On the other hand, the declaration
- char *p = "abc";
- defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char''
- with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to
- modify the contents of the array, the behavior is undefined.
-
-33 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using
- designators:
- enum { member_one, member_two };
- const char *nm[] = {
- [member_two] = "member two",
- [member_one] = "member one",
- };
-
-34 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
- div_t answer = { .quot = 2, .rem = -1 };
-
-35 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
- might be misunderstood:
- struct { int a[3], b; } w[] =
- { [0].a = {1}, [1].a[0] = 2 };
-
-36 EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator:
- int a[MAX] = {
- 1, 3, 5, 7, 9, [MAX-5] = 8, 6, 4, 2, 0
- };
-37 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less
- than ten, some of the values provided by the first five initializers will be overridden by the second five.
-
-38 EXAMPLE 13 Any member of a union can be initialized:
- union { /* ... */ } u = { .any_member = 42 };
-
- Forward references: common definitions <stddef.h> (7.19).
-
-
-
-
-[page 142]
-
- 6.7.10 Static assertions
- Syntax
-1 static_assert-declaration:
- _Static_assert ( constant-expression , string-literal ) ;
- Constraints
-2 The constant expression shall compare unequal to 0.
- Semantics
-3 The constant expression shall be an integer constant expression. If the value of the
- constant expression compares unequal to 0, the declaration has no effect. Otherwise, the
- constraint is violated and the implementation shall produce a diagnostic message that
- includes the text of the string literal, except that characters not in the basic source
- character set are not required to appear in the message.
- Forward references: diagnostics (7.2).
-
-
-
-
-[page 143]
-
- 6.8 Statements and blocks
- Syntax
-1 statement:
- labeled-statement
- compound-statement
- expression-statement
- selection-statement
- iteration-statement
- jump-statement
- Semantics
-2 A statement specifies an action to be performed. Except as indicated, statements are
- executed in sequence.
-3 A block allows a set of declarations and statements to be grouped into one syntactic unit.
- The initializers of objects that have automatic storage duration, and the variable length
- array declarators of ordinary identifiers with block scope, are evaluated and the values are
- stored in the objects (including storing an indeterminate value in objects without an
- initializer) each time the declaration is reached in the order of execution, as if it were a
- statement, and within each declaration in the order that declarators appear.
-4 A full expression is an expression that is not part of another expression or of a declarator.
- Each of the following is a full expression: an initializer that is not part of a compound
- literal; the expression in an expression statement; the controlling expression of a selection
- statement (if or switch); the controlling expression of a while or do statement; each
- of the (optional) expressions of a for statement; the (optional) expression in a return
- statement. There is a sequence point between the evaluation of a full expression and the
- evaluation of the next full expression to be evaluated.
- Forward references: expression and null statements (6.8.3), selection statements
- (6.8.4), iteration statements (6.8.5), the return statement (6.8.6.4).
- 6.8.1 Labeled statements
- Syntax
-1 labeled-statement:
- identifier : statement
- case constant-expression : statement
- default : statement
- Constraints
-2 A case or default label shall appear only in a switch statement. Further
- constraints on such labels are discussed under the switch statement.
-
-[page 144]
-
-3 Label names shall be unique within a function.
- Semantics
-4 Any statement may be preceded by a prefix that declares an identifier as a label name.
- Labels in themselves do not alter the flow of control, which continues unimpeded across
- them.
- Forward references: the goto statement (6.8.6.1), the switch statement (6.8.4.2).
- 6.8.2 Compound statement
- Syntax
-1 compound-statement:
- { block-item-listopt }
- block-item-list:
- block-item
- block-item-list block-item
- block-item:
- declaration
- statement
- Semantics
-2 A compound statement is a block.
- 6.8.3 Expression and null statements
- Syntax
-1 expression-statement:
- expressionopt ;
- Semantics
-2 The expression in an expression statement is evaluated as a void expression for its side
- effects.152)
-3 A null statement (consisting of just a semicolon) performs no operations.
-4 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the
- discarding of its value may be made explicit by converting the expression to a void expression by means of
- a cast:
- int p(int);
- /* ... */
- (void)p(0);
-
-
-
- 152) Such as assignments, and function calls which have side effects.
-
-[page 145]
-
-5 EXAMPLE 2 In the program fragment
- char *s;
- /* ... */
- while (*s++ != '\0')
- ;
- a null statement is used to supply an empty loop body to the iteration statement.
-
-6 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
- statement.
- while (loop1) {
- /* ... */
- while (loop2) {
- /* ... */
- if (want_out)
- goto end_loop1;
- /* ... */
- }
- /* ... */
- end_loop1: ;
- }
-
- Forward references: iteration statements (6.8.5).
- 6.8.4 Selection statements
- Syntax
-1 selection-statement:
- if ( expression ) statement
- if ( expression ) statement else statement
- switch ( expression ) statement
- Semantics
-2 A selection statement selects among a set of statements depending on the value of a
- controlling expression.
-3 A selection statement is a block whose scope is a strict subset of the scope of its
- enclosing block. Each associated substatement is also a block whose scope is a strict
- subset of the scope of the selection statement.
- 6.8.4.1 The if statement
- Constraints
-1 The controlling expression of an if statement shall have scalar type.
- Semantics
-2 In both forms, the first substatement is executed if the expression compares unequal to 0.
- In the else form, the second substatement is executed if the expression compares equal
-
-
-[page 146]
-
- to 0. If the first substatement is reached via a label, the second substatement is not
- executed.
-3 An else is associated with the lexically nearest preceding if that is allowed by the
- syntax.
- 6.8.4.2 The switch statement
- Constraints
-1 The controlling expression of a switch statement shall have integer type.
-2 If a switch statement has an associated case or default label within the scope of an
- identifier with a variably modified type, the entire switch statement shall be within the
- scope of that identifier.153)
-3 The expression of each case label shall be an integer constant expression and no two of
- the case constant expressions in the same switch statement shall have the same value
- after conversion. There may be at most one default label in a switch statement.
- (Any enclosed switch statement may have a default label or case constant
- expressions with values that duplicate case constant expressions in the enclosing
- switch statement.)
- Semantics
-4 A switch statement causes control to jump to, into, or past the statement that is the
- switch body, depending on the value of a controlling expression, and on the presence of a
- default label and the values of any case labels on or in the switch body. A case or
- default label is accessible only within the closest enclosing switch statement.
-5 The integer promotions are performed on the controlling expression. The constant
- expression in each case label is converted to the promoted type of the controlling
- expression. If a converted value matches that of the promoted controlling expression,
- control jumps to the statement following the matched case label. Otherwise, if there is
- a default label, control jumps to the labeled statement. If no converted case constant
- expression matches and there is no default label, no part of the switch body is
- executed.
- Implementation limits
-6 As discussed in 5.2.4.1, the implementation may limit the number of case values in a
- switch statement.
-
-
-
-
- 153) That is, the declaration either precedes the switch statement, or it follows the last case or
- default label associated with the switch that is in the block containing the declaration.
-
-[page 147]
-
-7 EXAMPLE In the artificial program fragment
- switch (expr)
- {
- int i = 4;
- f(i);
- case 0:
- i = 17;
- /* falls through into default code */
- default:
- printf("%d\n", i);
- }
- the object whose identifier is i exists with automatic storage duration (within the block) but is never
- initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
- access an indeterminate value. Similarly, the call to the function f cannot be reached.
-
- 6.8.5 Iteration statements
- Syntax
-1 iteration-statement:
- while ( expression ) statement
- do statement while ( expression ) ;
- for ( expressionopt ; expressionopt ; expressionopt ) statement
- for ( declaration expressionopt ; expressionopt ) statement
- Constraints
-2 The controlling expression of an iteration statement shall have scalar type.
-3 The declaration part of a for statement shall only declare identifiers for objects having
- storage class auto or register.
- Semantics
-4 An iteration statement causes a statement called the loop body to be executed repeatedly
- until the controlling expression compares equal to 0. The repetition occurs regardless of
- whether the loop body is entered from the iteration statement or by a jump.154)
-5 An iteration statement is a block whose scope is a strict subset of the scope of its
- enclosing block. The loop body is also a block whose scope is a strict subset of the scope
- of the iteration statement.
-6 An iteration statement that performs no input/output operations, does not access volatile
- objects, and performs no synchronization or atomic operations in its body, controlling
- expression, or (in the case of a for statement) its expression-3, may be assumed by the
- implementation to terminate.155)
-
- 154) Code jumped over is not executed. In particular, the controlling expression of a for or while
- statement is not evaluated before entering the loop body, nor is clause-1 of a for statement.
-
-[page 148]
-
- 6.8.5.1 The while statement
-1 The evaluation of the controlling expression takes place before each execution of the loop
- body.
- 6.8.5.2 The do statement
-1 The evaluation of the controlling expression takes place after each execution of the loop
- body.
- 6.8.5.3 The for statement
-1 The statement
- for ( clause-1 ; expression-2 ; expression-3 ) statement
- behaves as follows: The expression expression-2 is the controlling expression that is
- evaluated before each execution of the loop body. The expression expression-3 is
- evaluated as a void expression after each execution of the loop body. If clause-1 is a
- declaration, the scope of any identifiers it declares is the remainder of the declaration and
- the entire loop, including the other two expressions; it is reached in the order of execution
- before the first evaluation of the controlling expression. If clause-1 is an expression, it is
- evaluated as a void expression before the first evaluation of the controlling expression.156)
-2 Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a
- nonzero constant.
- 6.8.6 Jump statements
- Syntax
-1 jump-statement:
- goto identifier ;
- continue ;
- break ;
- return expressionopt ;
- Semantics
-2 A jump statement causes an unconditional jump to another place.
-
-
-
-
- 155) This is intended to allow compiler transformations such as removal of empty loops even when
- termination cannot be proven.
- 156) Thus, clause-1 specifies initialization for the loop, possibly declaring one or more variables for use in
- the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration,
- such that execution of the loop continues until the expression compares equal to 0; and expression-3
- specifies an operation (such as incrementing) that is performed after each iteration.
-
-[page 149]
-
- 6.8.6.1 The goto statement
- Constraints
-1 The identifier in a goto statement shall name a label located somewhere in the enclosing
- function. A goto statement shall not jump from outside the scope of an identifier having
- a variably modified type to inside the scope of that identifier.
- Semantics
-2 A goto statement causes an unconditional jump to the statement prefixed by the named
- label in the enclosing function.
-3 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The
- following outline presents one possible approach to a problem based on these three assumptions:
- 1. The general initialization code accesses objects only visible to the current function.
- 2. The general initialization code is too large to warrant duplication.
- 3. The code to determine the next operation is at the head of the loop. (To allow it to be reached by
- continue statements, for example.)
- /* ... */
- goto first_time;
- for (;;) {
- // determine next operation
- /* ... */
- if (need to reinitialize) {
- // reinitialize-only code
- /* ... */
- first_time:
- // general initialization code
- /* ... */
- continue;
- }
- // handle other operations
- /* ... */
- }
-
-
-
-
-[page 150]
-
-4 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably
- modified types. A jump within the scope, however, is permitted.
- goto lab3; // invalid: going INTO scope of VLA.
- {
- double a[n];
- a[j] = 4.4;
- lab3:
- a[j] = 3.3;
- goto lab4; // valid: going WITHIN scope of VLA.
- a[j] = 5.5;
- lab4:
- a[j] = 6.6;
- }
- goto lab4; // invalid: going INTO scope of VLA.
-
- 6.8.6.2 The continue statement
- Constraints
-1 A continue statement shall appear only in or as a loop body.
- Semantics
-2 A continue statement causes a jump to the loop-continuation portion of the smallest
- enclosing iteration statement; that is, to the end of the loop body. More precisely, in each
- of the statements
- while (/* ... */) { do { for (/* ... */) {
- /* ... */ /* ... */ /* ... */
- continue; continue; continue;
- /* ... */ /* ... */ /* ... */
- contin: ; contin: ; contin: ;
- } } while (/* ... */); }
- unless the continue statement shown is in an enclosed iteration statement (in which
- case it is interpreted within that statement), it is equivalent to goto contin;.157)
- 6.8.6.3 The break statement
- Constraints
-1 A break statement shall appear only in or as a switch body or loop body.
- Semantics
-2 A break statement terminates execution of the smallest enclosing switch or iteration
- statement.
-
-
-
- 157) Following the contin: label is a null statement.
-
-[page 151]
-
- 6.8.6.4 The return statement
- Constraints
-1 A return statement with an expression shall not appear in a function whose return type
- is void. A return statement without an expression shall only appear in a function
- whose return type is void.
- Semantics
-2 A return statement terminates execution of the current function and returns control to
- its caller. A function may have any number of return statements.
-3 If a return statement with an expression is executed, the value of the expression is
- returned to the caller as the value of the function call expression. If the expression has a
- type different from the return type of the function in which it appears, the value is
- converted as if by assignment to an object having the return type of the function.158)
-4 EXAMPLE In:
- struct s { double i; } f(void);
- union {
- struct {
- int f1;
- struct s f2;
- } u1;
- struct {
- struct s f3;
- int f4;
- } u2;
- } g;
- struct s f(void)
- {
- return g.u1.f2;
- }
- /* ... */
- g.u2.f3 = f();
- there is no undefined behavior, although there would be if the assignment were done directly (without using
- a function call to fetch the value).
-
-
-
-
- 158) The return statement is not an assignment. The overlap restriction of subclause 6.5.16.1 does not
- apply to the case of function return. The representation of floating-point values may have wider range
- or precision than implied by the type; a cast may be used to remove this extra range and precision.
-
-[page 152]
-
- 6.9 External definitions
- Syntax
-1 translation-unit:
- external-declaration
- translation-unit external-declaration
- external-declaration:
- function-definition
- declaration
- Constraints
-2 The storage-class specifiers auto and register shall not appear in the declaration
- specifiers in an external declaration.
-3 There shall be no more than one external definition for each identifier declared with
- internal linkage in a translation unit. Moreover, if an identifier declared with internal
- linkage is used in an expression (other than as a part of the operand of a sizeof
- operator whose result is an integer constant), there shall be exactly one external definition
- for the identifier in the translation unit.
- Semantics
-4 As discussed in 5.1.1.1, the unit of program text after preprocessing is a translation unit,
- which consists of a sequence of external declarations. These are described as ''external''
- because they appear outside any function (and hence have file scope). As discussed in
- 6.7, a declaration that also causes storage to be reserved for an object or a function named
- by the identifier is a definition.
-5 An external definition is an external declaration that is also a definition of a function
- (other than an inline definition) or an object. If an identifier declared with external
- linkage is used in an expression (other than as part of the operand of a sizeof operator
- whose result is an integer constant), somewhere in the entire program there shall be
- exactly one external definition for the identifier; otherwise, there shall be no more than
- one.159)
-
-
-
-
- 159) Thus, if an identifier declared with external linkage is not used in an expression, there need be no
- external definition for it.
-
-[page 153]
-
- 6.9.1 Function definitions
- Syntax
-1 function-definition:
- declaration-specifiers declarator declaration-listopt compound-statement
- declaration-list:
- declaration
- declaration-list declaration
- Constraints
-2 The identifier declared in a function definition (which is the name of the function) shall
- have a function type, as specified by the declarator portion of the function definition.160)
-3 The return type of a function shall be void or a complete object type other than array
- type.
-4 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
- static.
-5 If the declarator includes a parameter type list, the declaration of each parameter shall
- include an identifier, except for the special case of a parameter list consisting of a single
- parameter of type void, in which case there shall not be an identifier. No declaration list
- shall follow.
-6 If the declarator includes an identifier list, each declaration in the declaration list shall
- have at least one declarator, those declarators shall declare only identifiers from the
- identifier list, and every identifier in the identifier list shall be declared. An identifier
- declared as a typedef name shall not be redeclared as a parameter. The declarations in the
- declaration list shall contain no storage-class specifier other than register and no
- initializations.
-
-
-
- 160) The intent is that the type category in a function definition cannot be inherited from a typedef:
- typedef int F(void); // type F is ''function with no parameters
- // returning int''
- F f, g; // f and g both have type compatible with F
- F f { /* ... */ } // WRONG: syntax/constraint error
- F g() { /* ... */ } // WRONG: declares that g returns a function
- int f(void) { /* ... */ } // RIGHT: f has type compatible with F
- int g() { /* ... */ } // RIGHT: g has type compatible with F
- F *e(void) { /* ... */ } // e returns a pointer to a function
- F *((e))(void) { /* ... */ } // same: parentheses irrelevant
- int (*fp)(void); // fp points to a function that has type F
- F *Fp; // Fp points to a function that has type F
-
-
-[page 154]
-
- Semantics
-7 The declarator in a function definition specifies the name of the function being defined
- and the identifiers of its parameters. If the declarator includes a parameter type list, the
- list also specifies the types of all the parameters; such a declarator also serves as a
- function prototype for later calls to the same function in the same translation unit. If the
- declarator includes an identifier list,161) the types of the parameters shall be declared in a
- following declaration list. In either case, the type of each parameter is adjusted as
- described in 6.7.6.3 for a parameter type list; the resulting type shall be a complete object
- type.
-8 If a function that accepts a variable number of arguments is defined without a parameter
- type list that ends with the ellipsis notation, the behavior is undefined.
-9 Each parameter has automatic storage duration; its identifier is an lvalue.162) The layout
- of the storage for parameters is unspecified.
-10 On entry to the function, the size expressions of each variably modified parameter are
- evaluated and the value of each argument expression is converted to the type of the
- corresponding parameter as if by assignment. (Array expressions and function
- designators as arguments were converted to pointers before the call.)
-11 After all parameters have been assigned, the compound statement that constitutes the
- body of the function definition is executed.
-12 If the } that terminates a function is reached, and the value of the function call is used by
- the caller, the behavior is undefined.
-13 EXAMPLE 1 In the following:
- extern int max(int a, int b)
- {
- return a > b ? a : b;
- }
- extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
- function declarator; and
- { return a > b ? a : b; }
- is the function body. The following similar definition uses the identifier-list form for the parameter
- declarations:
-
-
-
-
- 161) See ''future language directions'' (6.11.7).
- 162) A parameter identifier cannot be redeclared in the function body except in an enclosed block.
-
-[page 155]
-
- extern int max(a, b)
- int a, b;
- {
- return a > b ? a : b;
- }
- Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
- that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
- to the function, whereas the second form does not.
-
-14 EXAMPLE 2 To pass one function to another, one might say
- int f(void);
- /* ... */
- g(f);
- Then the definition of g might read
- void g(int (*funcp)(void))
- {
- /* ... */
- (*funcp)(); /* or funcp(); ... */
- }
- or, equivalently,
- void g(int func(void))
- {
- /* ... */
- func(); /* or (*func)(); ... */
- }
-
- 6.9.2 External object definitions
- Semantics
-1 If the declaration of an identifier for an object has file scope and an initializer, the
- declaration is an external definition for the identifier.
-2 A declaration of an identifier for an object that has file scope without an initializer, and
- without a storage-class specifier or with the storage-class specifier static, constitutes a
- tentative definition. If a translation unit contains one or more tentative definitions for an
- identifier, and the translation unit contains no external definition for that identifier, then
- the behavior is exactly as if the translation unit contains a file scope declaration of that
- identifier, with the composite type as of the end of the translation unit, with an initializer
- equal to 0.
-3 If the declaration of an identifier for an object is a tentative definition and has internal
- linkage, the declared type shall not be an incomplete type.
-
-
-
-
-[page 156]
-
-4 EXAMPLE 1
- int i1 = 1; // definition, external linkage
- static int i2 = 2; // definition, internal linkage
- extern int i3 = 3; // definition, external linkage
- int i4; // tentative definition, external linkage
- static int i5; // tentative definition, internal linkage
- int i1; // valid tentative definition, refers to previous
- int i2; // 6.2.2 renders undefined, linkage disagreement
- int i3; // valid tentative definition, refers to previous
- int i4; // valid tentative definition, refers to previous
- int i5; // 6.2.2 renders undefined, linkage disagreement
- extern int i1; // refers to previous, whose linkage is external
- extern int i2; // refers to previous, whose linkage is internal
- extern int i3; // refers to previous, whose linkage is external
- extern int i4; // refers to previous, whose linkage is external
- extern int i5; // refers to previous, whose linkage is internal
-
-5 EXAMPLE 2 If at the end of the translation unit containing
- int i[];
- the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to
- zero on program startup.
-
-
-
-
-[page 157]
-
- 6.10 Preprocessing directives
- Syntax
-1 preprocessing-file:
- groupopt
- group:
- group-part
- group group-part
- group-part:
- if-section
- control-line
- text-line
- # non-directive
- if-section:
- if-group elif-groupsopt else-groupopt endif-line
- if-group:
- # if constant-expression new-line groupopt
- # ifdef identifier new-line groupopt
- # ifndef identifier new-line groupopt
- elif-groups:
- elif-group
- elif-groups elif-group
- elif-group:
- # elif constant-expression new-line groupopt
- else-group:
- # else new-line groupopt
- endif-line:
- # endif new-line
-
-
-
-
-[page 158]
-
- control-line:
- # include pp-tokens new-line
- # define identifier replacement-list new-line
- # define identifier lparen identifier-listopt )
- replacement-list new-line
- # define identifier lparen ... ) replacement-list new-line
- # define identifier lparen identifier-list , ... )
- replacement-list new-line
- # undef identifier new-line
- # line pp-tokens new-line
- # error pp-tokensopt new-line
- # pragma pp-tokensopt new-line
- # new-line
- text-line:
- pp-tokensopt new-line
- non-directive:
- pp-tokens new-line
- lparen:
- a ( character not immediately preceded by white-space
- replacement-list:
- pp-tokensopt
- pp-tokens:
- preprocessing-token
- pp-tokens preprocessing-token
- new-line:
- the new-line character
- Description
-2 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the
- following constraints: The first token in the sequence is a # preprocessing token that (at
- the start of translation phase 4) is either the first character in the source file (optionally
- after white space containing no new-line characters) or that follows white space
- containing at least one new-line character. The last token in the sequence is the first new-
- line character that follows the first token in the sequence.163) A new-line character ends
- the preprocessing directive even if it occurs within what would otherwise be an
-
- 163) Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic
- significance, as all white space is equivalent except in certain situations during preprocessing (see the
- # character string literal creation operator in 6.10.3.2, for example).
-
-[page 159]
-
- invocation of a function-like macro.
-3 A text line shall not begin with a # preprocessing token. A non-directive shall not begin
- with any of the directive names appearing in the syntax.
-4 When in a group that is skipped (6.10.1), the directive syntax is relaxed to allow any
- sequence of preprocessing tokens to occur between the directive name and the following
- new-line character.
- Constraints
-5 The only white-space characters that shall appear between preprocessing tokens within a
- preprocessing directive (from just after the introducing # preprocessing token through
- just before the terminating new-line character) are space and horizontal-tab (including
- spaces that have replaced comments or possibly other white-space characters in
- translation phase 3).
- Semantics
-6 The implementation can process and skip sections of source files conditionally, include
- other source files, and replace macros. These capabilities are called preprocessing,
- because conceptually they occur before translation of the resulting translation unit.
-7 The preprocessing tokens within a preprocessing directive are not subject to macro
- expansion unless otherwise stated.
-8 EXAMPLE In:
- #define EMPTY
- EMPTY # include <file.h>
- the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
- begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
- replaced.
-
- 6.10.1 Conditional inclusion
- Constraints
-1 The expression that controls conditional inclusion shall be an integer constant expression
- except that: identifiers (including those lexically identical to keywords) are interpreted as
- described below;164) and it may contain unary operator expressions of the form
- defined identifier
- or
- defined ( identifier )
- which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is
-
-
- 164) Because the controlling constant expression is evaluated during translation phase 4, all identifiers
- either are or are not macro names -- there simply are no keywords, enumeration constants, etc.
-
-[page 160]
-
- predefined or if it has been the subject of a #define preprocessing directive without an
- intervening #undef directive with the same subject identifier), 0 if it is not.
-2 Each preprocessing token that remains (in the list of preprocessing tokens that will
- become the controlling expression) after all macro replacements have occurred shall be in
- the lexical form of a token (6.4).
- Semantics
-3 Preprocessing directives of the forms
- # if constant-expression new-line groupopt
- # elif constant-expression new-line groupopt
- check whether the controlling constant expression evaluates to nonzero.
-4 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
- the controlling constant expression are replaced (except for those macro names modified
- by the defined unary operator), just as in normal text. If the token defined is
- generated as a result of this replacement process or use of the defined unary operator
- does not match one of the two specified forms prior to macro replacement, the behavior is
- undefined. After all replacements due to macro expansion and the defined unary
- operator have been performed, all remaining identifiers (including those lexically
- identical to keywords) are replaced with the pp-number 0, and then each preprocessing
- token is converted into a token. The resulting tokens compose the controlling constant
- expression which is evaluated according to the rules of 6.6. For the purposes of this
- token conversion and evaluation, all signed integer types and all unsigned integer types
- act as if they have the same representation as, respectively, the types intmax_t and
- uintmax_t defined in the header <stdint.h>.165) This includes interpreting
- character constants, which may involve converting escape sequences into execution
- character set members. Whether the numeric value for these character constants matches
- the value obtained when an identical character constant occurs in an expression (other
- than within a #if or #elif directive) is implementation-defined.166) Also, whether a
- single-character character constant may have a negative value is implementation-defined.
-
-
-
-
- 165) Thus, on an implementation where INT_MAX is 0x7FFF and UINT_MAX is 0xFFFF, the constant
- 0x8000 is signed and positive within a #if expression even though it would be unsigned in
- translation phase 7.
- 166) Thus, the constant expression in the following #if directive and if statement is not guaranteed to
- evaluate to the same value in these two contexts.
- #if 'z' - 'a' == 25
- if ('z' - 'a' == 25)
-
-
-[page 161]
-
-5 Preprocessing directives of the forms
- # ifdef identifier new-line groupopt
- # ifndef identifier new-line groupopt
- check whether the identifier is or is not currently defined as a macro name. Their
- conditions are equivalent to #if defined identifier and #if !defined identifier
- respectively.
-6 Each directive's condition is checked in order. If it evaluates to false (zero), the group
- that it controls is skipped: directives are processed only through the name that determines
- the directive in order to keep track of the level of nested conditionals; the rest of the
- directives' preprocessing tokens are ignored, as are the other preprocessing tokens in the
- group. Only the first group whose control condition evaluates to true (nonzero) is
- processed. If none of the conditions evaluates to true, and there is a #else directive, the
- group controlled by the #else is processed; lacking a #else directive, all the groups
- until the #endif are skipped.167)
- Forward references: macro replacement (6.10.3), source file inclusion (6.10.2), largest
- integer types (7.20.1.5).
- 6.10.2 Source file inclusion
- Constraints
-1 A #include directive shall identify a header or source file that can be processed by the
- implementation.
- Semantics
-2 A preprocessing directive of the form
- # include <h-char-sequence> new-line
- searches a sequence of implementation-defined places for a header identified uniquely by
- the specified sequence between the < and > delimiters, and causes the replacement of that
- directive by the entire contents of the header. How the places are specified or the header
- identified is implementation-defined.
-3 A preprocessing directive of the form
- # include "q-char-sequence" new-line
- causes the replacement of that directive by the entire contents of the source file identified
- by the specified sequence between the " delimiters. The named source file is searched
-
-
- 167) As indicated by the syntax, a preprocessing token shall not follow a #else or #endif directive
- before the terminating new-line character. However, comments may appear anywhere in a source file,
- including within a preprocessing directive.
-
-[page 162]
-
- for in an implementation-defined manner. If this search is not supported, or if the search
- fails, the directive is reprocessed as if it read
- # include <h-char-sequence> new-line
- with the identical contained sequence (including > characters, if any) from the original
- directive.
-4 A preprocessing directive of the form
- # include pp-tokens new-line
- (that does not match one of the two previous forms) is permitted. The preprocessing
- tokens after include in the directive are processed just as in normal text. (Each
- identifier currently defined as a macro name is replaced by its replacement list of
- preprocessing tokens.) The directive resulting after all replacements shall match one of
- the two previous forms.168) The method by which a sequence of preprocessing tokens
- between a < and a > preprocessing token pair or a pair of " characters is combined into a
- single header name preprocessing token is implementation-defined.
-5 The implementation shall provide unique mappings for sequences consisting of one or
- more nondigits or digits (6.4.2.1) followed by a period (.) and a single nondigit. The
- first character shall not be a digit. The implementation may ignore distinctions of
- alphabetical case and restrict the mapping to eight significant characters before the
- period.
-6 A #include preprocessing directive may appear in a source file that has been read
- because of a #include directive in another file, up to an implementation-defined
- nesting limit (see 5.2.4.1).
-7 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
- #include <stdio.h>
- #include "myprog.h"
-
-
-
-
- 168) Note that adjacent string literals are not concatenated into a single string literal (see the translation
- phases in 5.1.1.2); thus, an expansion that results in two string literals is an invalid directive.
-
-[page 163]
-
-8 EXAMPLE 2 This illustrates macro-replaced #include directives:
- #if VERSION == 1
- #define INCFILE "vers1.h"
- #elif VERSION == 2
- #define INCFILE "vers2.h" // and so on
- #else
- #define INCFILE "versN.h"
- #endif
- #include INCFILE
-
- Forward references: macro replacement (6.10.3).
- 6.10.3 Macro replacement
- Constraints
-1 Two replacement lists are identical if and only if the preprocessing tokens in both have
- the same number, ordering, spelling, and white-space separation, where all white-space
- separations are considered identical.
-2 An identifier currently defined as an object-like macro shall not be redefined by another
- #define preprocessing directive unless the second definition is an object-like macro
- definition and the two replacement lists are identical. Likewise, an identifier currently
- defined as a function-like macro shall not be redefined by another #define
- preprocessing directive unless the second definition is a function-like macro definition
- that has the same number and spelling of parameters, and the two replacement lists are
- identical.
-3 There shall be white-space between the identifier and the replacement list in the definition
- of an object-like macro.
-4 If the identifier-list in the macro definition does not end with an ellipsis, the number of
- arguments (including those arguments consisting of no preprocessing tokens) in an
- invocation of a function-like macro shall equal the number of parameters in the macro
- definition. Otherwise, there shall be more arguments in the invocation than there are
- parameters in the macro definition (excluding the ...). There shall exist a )
- preprocessing token that terminates the invocation.
-5 The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like
- macro that uses the ellipsis notation in the parameters.
-6 A parameter identifier in a function-like macro shall be uniquely declared within its
- scope.
- Semantics
-7 The identifier immediately following the define is called the macro name. There is one
- name space for macro names. Any white-space characters preceding or following the
- replacement list of preprocessing tokens are not considered part of the replacement list
-
-[page 164]
-
- for either form of macro.
-8 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
- a preprocessing directive could begin, the identifier is not subject to macro replacement.
-9 A preprocessing directive of the form
- # define identifier replacement-list new-line
- defines an object-like macro that causes each subsequent instance of the macro name169)
- to be replaced by the replacement list of preprocessing tokens that constitute the
- remainder of the directive. The replacement list is then rescanned for more macro names
- as specified below.
-10 A preprocessing directive of the form
- # define identifier lparen identifier-listopt ) replacement-list new-line
- # define identifier lparen ... ) replacement-list new-line
- # define identifier lparen identifier-list , ... ) replacement-list new-line
- defines a function-like macro with parameters, whose use is similar syntactically to a
- function call. The parameters are specified by the optional list of identifiers, whose scope
- extends from their declaration in the identifier list until the new-line character that
- terminates the #define preprocessing directive. Each subsequent instance of the
- function-like macro name followed by a ( as the next preprocessing token introduces the
- sequence of preprocessing tokens that is replaced by the replacement list in the definition
- (an invocation of the macro). The replaced sequence of preprocessing tokens is
- terminated by the matching ) preprocessing token, skipping intervening matched pairs of
- left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
- tokens making up an invocation of a function-like macro, new-line is considered a normal
- white-space character.
-11 The sequence of preprocessing tokens bounded by the outside-most matching parentheses
- forms the list of arguments for the function-like macro. The individual arguments within
- the list are separated by comma preprocessing tokens, but comma preprocessing tokens
- between matching inner parentheses do not separate arguments. If there are sequences of
- preprocessing tokens within the list of arguments that would otherwise act as
- preprocessing directives,170) the behavior is undefined.
-12 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
- including any separating comma preprocessing tokens, are merged to form a single item:
-
-
- 169) Since, by macro-replacement time, all character constants and string literals are preprocessing tokens,
- not sequences possibly containing identifier-like subsequences (see 5.1.1.2, translation phases), they
- are never scanned for macro names or parameters.
- 170) Despite the name, a non-directive is a preprocessing directive.
-
-[page 165]
-
- the variable arguments. The number of arguments so combined is such that, following
- merger, the number of arguments is one more than the number of parameters in the macro
- definition (excluding the ...).
- 6.10.3.1 Argument substitution
-1 After the arguments for the invocation of a function-like macro have been identified,
- argument substitution takes place. A parameter in the replacement list, unless preceded
- by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
- replaced by the corresponding argument after all macros contained therein have been
- expanded. Before being substituted, each argument's preprocessing tokens are
- completely macro replaced as if they formed the rest of the preprocessing file; no other
- preprocessing tokens are available.
-2 An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
- were a parameter, and the variable arguments shall form the preprocessing tokens used to
- replace it.
- 6.10.3.2 The # operator
- Constraints
-1 Each # preprocessing token in the replacement list for a function-like macro shall be
- followed by a parameter as the next preprocessing token in the replacement list.
- Semantics
-2 If, in the replacement list, a parameter is immediately preceded by a # preprocessing
- token, both are replaced by a single character string literal preprocessing token that
- contains the spelling of the preprocessing token sequence for the corresponding
- argument. Each occurrence of white space between the argument's preprocessing tokens
- becomes a single space character in the character string literal. White space before the
- first preprocessing token and after the last preprocessing token composing the argument
- is deleted. Otherwise, the original spelling of each preprocessing token in the argument
- is retained in the character string literal, except for special handling for producing the
- spelling of string literals and character constants: a \ character is inserted before each "
- and \ character of a character constant or string literal (including the delimiting "
- characters), except that it is implementation-defined whether a \ character is inserted
- before the \ character beginning a universal character name. If the replacement that
- results is not a valid character string literal, the behavior is undefined. The character
- string literal corresponding to an empty argument is "". The order of evaluation of # and
- ## operators is unspecified.
-
-
-
-
-[page 166]
-
- 6.10.3.3 The ## operator
- Constraints
-1 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
- list for either form of macro definition.
- Semantics
-2 If, in the replacement list of a function-like macro, a parameter is immediately preceded
- or followed by a ## preprocessing token, the parameter is replaced by the corresponding
- argument's preprocessing token sequence; however, if an argument consists of no
- preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
- instead.171)
-3 For both object-like and function-like macro invocations, before the replacement list is
- reexamined for more macro names to replace, each instance of a ## preprocessing token
- in the replacement list (not from an argument) is deleted and the preceding preprocessing
- token is concatenated with the following preprocessing token. Placemarker
- preprocessing tokens are handled specially: concatenation of two placemarkers results in
- a single placemarker preprocessing token, and concatenation of a placemarker with a
- non-placemarker preprocessing token results in the non-placemarker preprocessing token.
- If the result is not a valid preprocessing token, the behavior is undefined. The resulting
- token is available for further macro replacement. The order of evaluation of ## operators
- is unspecified.
-4 EXAMPLE In the following fragment:
- #define hash_hash # ## #
- #define mkstr(a) # a
- #define in_between(a) mkstr(a)
- #define join(c, d) in_between(c hash_hash d)
- char p[] = join(x, y); // equivalent to
- // char p[] = "x ## y";
- The expansion produces, at various stages:
- join(x, y)
- in_between(x hash_hash y)
- in_between(x ## y)
- mkstr(x ## y)
- "x ## y"
- In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
- this new token is not the ## operator.
-
-
- 171) Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
- exist only within translation phase 4.
-
-[page 167]
-
- 6.10.3.4 Rescanning and further replacement
-1 After all parameters in the replacement list have been substituted and # and ##
- processing has taken place, all placemarker preprocessing tokens are removed. The
- resulting preprocessing token sequence is then rescanned, along with all subsequent
- preprocessing tokens of the source file, for more macro names to replace.
-2 If the name of the macro being replaced is found during this scan of the replacement list
- (not including the rest of the source file's preprocessing tokens), it is not replaced.
- Furthermore, if any nested replacements encounter the name of the macro being replaced,
- it is not replaced. These nonreplaced macro name preprocessing tokens are no longer
- available for further replacement even if they are later (re)examined in contexts in which
- that macro name preprocessing token would otherwise have been replaced.
-3 The resulting completely macro-replaced preprocessing token sequence is not processed
- as a preprocessing directive even if it resembles one, but all pragma unary operator
- expressions within it are then processed as specified in 6.10.9 below.
- 6.10.3.5 Scope of macro definitions
-1 A macro definition lasts (independent of block structure) until a corresponding #undef
- directive is encountered or (if none is encountered) until the end of the preprocessing
- translation unit. Macro definitions have no significance after translation phase 4.
-2 A preprocessing directive of the form
- # undef identifier new-line
- causes the specified identifier no longer to be defined as a macro name. It is ignored if
- the specified identifier is not currently defined as a macro name.
-3 EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
- #define TABSIZE 100
- int table[TABSIZE];
-
-4 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments.
- It has the advantages of working for any compatible types of the arguments and of generating in-line code
- without the overhead of function calling. It has the disadvantages of evaluating one or the other of its
- arguments a second time (including side effects) and generating more code than a function if invoked
- several times. It also cannot have its address taken, as it has none.
- #define max(a, b) ((a) > (b) ? (a) : (b))
- The parentheses ensure that the arguments and the resulting expression are bound properly.
-
-
-
-
-[page 168]
-
-5 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
- #define x 3
- #define f(a) f(x * (a))
- #undef x
- #define x 2
- #define g f
- #define z z[0]
- #define h g(~
- #define m(a) a(w)
- #define w 0,1
- #define t(a) a
- #define p() int
- #define q(x) x
- #define r(x,y) x ## y
- #define str(x) # x
- f(y+1) + f(f(z)) % t(t(g)(0) + t)(1);
- g(x+(3,4)-w) | h 5) & m
- (f)^m(m);
- p() i[q()] = { q(1), r(2,3), r(4,), r(,5), r(,) };
- char c[2][6] = { str(hello), str() };
- results in
- f(2 * (y+1)) + f(2 * (f(2 * (z[0])))) % f(2 * (0)) + t(1);
- f(2 * (2+(3,4)-0,1)) | f(2 * (~ 5)) & f(2 * (0,1))^m(0,1);
- int i[] = { 1, 23, 4, 5, };
- char c[2][6] = { "hello", "" };
-
-6 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the
- sequence
- #define str(s) # s
- #define xstr(s) str(s)
- #define debug(s, t) printf("x" # s "= %d, x" # t "= %s", \
- x ## s, x ## t)
- #define INCFILE(n) vers ## n
- #define glue(a, b) a ## b
- #define xglue(a, b) glue(a, b)
- #define HIGHLOW "hello"
- #define LOW LOW ", world"
- debug(1, 2);
- fputs(str(strncmp("abc\0d", "abc", '\4') // this goes away
- == 0) str(: @\n), s);
- #include xstr(INCFILE(2).h)
- glue(HIGH, LOW);
- xglue(HIGH, LOW)
- results in
-
-
-
-
-[page 169]
-
- printf("x" "1" "= %d, x" "2" "= %s", x1, x2);
- fputs(
- "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0" ": @\n",
- s);
- #include "vers2.h" (after macro replacement, before file access)
- "hello";
- "hello" ", world"
- or, after concatenation of the character string literals,
- printf("x1= %d, x2= %s", x1, x2);
- fputs(
- "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0: @\n",
- s);
- #include "vers2.h" (after macro replacement, before file access)
- "hello";
- "hello, world"
- Space around the # and ## tokens in the macro definition is optional.
-
-7 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
- #define t(x,y,z) x ## y ## z
- int j[] = { t(1,2,3), t(,4,5), t(6,,7), t(8,9,),
- t(10,,), t(,11,), t(,,12), t(,,) };
- results in
- int j[] = { 123, 45, 67, 89,
- 10, 11, 12, };
-
-8 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
- #define OBJ_LIKE (1-1)
- #define OBJ_LIKE /* white space */ (1-1) /* other */
- #define FUNC_LIKE(a) ( a )
- #define FUNC_LIKE( a )( /* note the white space */ \
- a /* other stuff on this line
- */ )
- But the following redefinitions are invalid:
- #define OBJ_LIKE (0) // different token sequence
- #define OBJ_LIKE (1 - 1) // different white space
- #define FUNC_LIKE(b) ( a ) // different parameter usage
- #define FUNC_LIKE(b) ( b ) // different parameter spelling
-
-9 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
- #define debug(...) fprintf(stderr, __VA_ARGS__)
- #define showlist(...) puts(#__VA_ARGS__)
- #define report(test, ...) ((test)?puts(#test):\
- printf(__VA_ARGS__))
- debug("Flag");
- debug("X = %d\n", x);
- showlist(The first, second, and third items.);
- report(x>y, "x is %d but y is %d", x, y);
-
-
-[page 170]
-
- results in
- fprintf(stderr, "Flag" );
- fprintf(stderr, "X = %d\n", x );
- puts( "The first, second, and third items." );
- ((x>y)?puts("x>y"):
- printf("x is %d but y is %d", x, y));
-
- 6.10.4 Line control
- Constraints
-1 The string literal of a #line directive, if present, shall be a character string literal.
- Semantics
-2 The line number of the current source line is one greater than the number of new-line
- characters read or introduced in translation phase 1 (5.1.1.2) while processing the source
- file to the current token.
-3 A preprocessing directive of the form
- # line digit-sequence new-line
- causes the implementation to behave as if the following sequence of source lines begins
- with a source line that has a line number as specified by the digit sequence (interpreted as
- a decimal integer). The digit sequence shall not specify zero, nor a number greater than
- 2147483647.
-4 A preprocessing directive of the form
- # line digit-sequence "s-char-sequenceopt" new-line
- sets the presumed line number similarly and changes the presumed name of the source
- file to be the contents of the character string literal.
-5 A preprocessing directive of the form
- # line pp-tokens new-line
- (that does not match one of the two previous forms) is permitted. The preprocessing
- tokens after line on the directive are processed just as in normal text (each identifier
- currently defined as a macro name is replaced by its replacement list of preprocessing
- tokens). The directive resulting after all replacements shall match one of the two
- previous forms and is then processed as appropriate.
-
-
-
-
-[page 171]
-
- 6.10.5 Error directive
- Semantics
-1 A preprocessing directive of the form
- # error pp-tokensopt new-line
- causes the implementation to produce a diagnostic message that includes the specified
- sequence of preprocessing tokens.
- 6.10.6 Pragma directive
- Semantics
-1 A preprocessing directive of the form
- # pragma pp-tokensopt new-line
- where the preprocessing token STDC does not immediately follow pragma in the
- directive (prior to any macro replacement)172) causes the implementation to behave in an
- implementation-defined manner. The behavior might cause translation to fail or cause the
- translator or the resulting program to behave in a non-conforming manner. Any such
- pragma that is not recognized by the implementation is ignored.
-2 If the preprocessing token STDC does immediately follow pragma in the directive (prior
- to any macro replacement), then no macro replacement is performed on the directive, and
- the directive shall have one of the following forms173) whose meanings are described
- elsewhere:
- #pragma STDC FP_CONTRACT on-off-switch
- #pragma STDC FENV_ACCESS on-off-switch
- #pragma STDC CX_LIMITED_RANGE on-off-switch
- on-off-switch: one of
- ON OFF DEFAULT
- Forward references: the FP_CONTRACT pragma (7.12.2), the FENV_ACCESS pragma
- (7.6.1), the CX_LIMITED_RANGE pragma (7.3.4).
-
-
-
-
- 172) An implementation is not required to perform macro replacement in pragmas, but it is permitted
- except for in standard pragmas (where STDC immediately follows pragma). If the result of macro
- replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still
- implementation-defined; an implementation is permitted to behave as if it were the standard pragma,
- but is not required to.
- 173) See ''future language directions'' (6.11.8).
-
-[page 172]
-
- 6.10.7 Null directive
- Semantics
-1 A preprocessing directive of the form
- # new-line
- has no effect.
- 6.10.8 Predefined macro names
-1 The values of the predefined macros listed in the following subclauses174) (except for
- __FILE__ and __LINE__) remain constant throughout the translation unit.
-2 None of these macro names, nor the identifier defined, shall be the subject of a
- #define or a #undef preprocessing directive. Any other predefined macro names
- shall begin with a leading underscore followed by an uppercase letter or a second
- underscore.
-3 The implementation shall not predefine the macro __cplusplus, nor shall it define it
- in any standard header.
- Forward references: standard headers (7.1.2).
- 6.10.8.1 Mandatory macros
-1 The following macro names shall be defined by the implementation:
- __DATE__ The date of translation of the preprocessing translation unit: a character
- string literal of the form "Mmm dd yyyy", where the names of the
- months are the same as those generated by the asctime function, and the
- first character of dd is a space character if the value is less than 10. If the
- date of translation is not available, an implementation-defined valid date
- shall be supplied.
- __FILE__ The presumed name of the current source file (a character string literal).175)
- __LINE__ The presumed line number (within the current source file) of the current
- source line (an integer constant).175)
- __STDC__ The integer constant 1, intended to indicate a conforming implementation.
- __STDC_HOSTED__ The integer constant 1 if the implementation is a hosted
- implementation or the integer constant 0 if it is not.
-
-
-
-
- 174) See ''future language directions'' (6.11.9).
- 175) The presumed source file name and line number can be changed by the #line directive.
-
-[page 173]
-
- __STDC_VERSION__ The integer constant 201ymmL.176)
- __TIME__ The time of translation of the preprocessing translation unit: a character
- string literal of the form "hh:mm:ss" as in the time generated by the
- asctime function. If the time of translation is not available, an
- implementation-defined valid time shall be supplied.
- Forward references: the asctime function (7.26.3.1).
- 6.10.8.2 Environment macros
-1 The following macro names are conditionally defined by the implementation:
- __STDC_ISO_10646__ An integer constant of the form yyyymmL (for example,
- 199712L). If this symbol is defined, then every character in the Unicode
- required set, when stored in an object of type wchar_t, has the same
- value as the short identifier of that character. The Unicode required set
- consists of all the characters that are defined by ISO/IEC 10646, along with
- all amendments and technical corrigenda, as of the specified year and
- month. If some other encoding is used, the macro shall not be defined and
- the actual encoding used is implementation-defined.
- __STDC_MB_MIGHT_NEQ_WC__ The integer constant 1, intended to indicate that, in
- the encoding for wchar_t, a member of the basic character set need not
- have a code value equal to its value when used as the lone character in an
- integer character constant.
- __STDC_UTF_16__ The integer constant 1, intended to indicate that values of type
- char16_t are UTF-16 encoded. If some other encoding is used, the
- macro shall not be defined and the actual encoding used is implementation-
- defined.
- __STDC_UTF_32__ The integer constant 1, intended to indicate that values of type
- char32_t are UTF-32 encoded. If some other encoding is used, the
- macro shall not be defined and the actual encoding used is implementation-
- defined.
- Forward references: common definitions (7.19), unicode utilities (7.27).
-
-
-
-
- 176) This macro was not specified in ISO/IEC 9899:1990 and was specified as 199409L in
- ISO/IEC 9899/AMD1:1995 and as 199901L in ISO/IEC 9899:1999. The intention is that this will
- remain an integer constant of type long int that is increased with each revision of this International
- Standard.
-
-[page 174]
-
- 6.10.8.3 Conditional feature macros
-1 The following macro names are conditionally defined by the implementation:
- __STDC_ANALYZABLE__ The integer constant 1, intended to indicate conformance to
- the specifications in annex L (Analyzability).
- __STDC_IEC_559__ The integer constant 1, intended to indicate conformance to the
- specifications in annex F (IEC 60559 floating-point arithmetic).
- __STDC_IEC_559_COMPLEX__ The integer constant 1, intended to indicate
- adherence to the specifications in informative annex G (IEC 60559
- compatible complex arithmetic).
- __STDC_LIB_EXT1__ The integer constant 201ymmL, intended to indicate support
- for the extensions defined in annex K (Bounds-checking interfaces).177)
- __STDC_NO_COMPLEX__ The integer constant 1, intended to indicate that the
- implementation does not support complex types or the <complex.h>
- header.
- __STDC_NO_THREADS__ The integer constant 1, intended to indicate that the
- implementation does not support atomic types (including the _Atomic
- type qualifier and the <stdatomic.h> header) or the <threads.h>
- header.
- __STDC_NO_VLA__ The integer constant 1, intended to indicate that the
- implementation does not support variable length arrays or variably
- modified types.
- 6.10.9 Pragma operator
- Semantics
-1 A unary operator expression of the form:
- _Pragma ( string-literal )
- is processed as follows: The string literal is destringized by deleting the L prefix, if
- present, deleting the leading and trailing double-quotes, replacing each escape sequence
- \" by a double-quote, and replacing each escape sequence \\ by a single backslash. The
- resulting sequence of characters is processed through translation phase 3 to produce
- preprocessing tokens that are executed as if they were the pp-tokens in a pragma
- directive. The original four preprocessing tokens in the unary operator expression are
- removed.
-
-
- 177) The intention is that this will remain an integer constant of type long int that is increased with
- each revision of this International Standard.
-
-[page 175]
-
-2 EXAMPLE A directive of the form:
- #pragma listing on "..\listing.dir"
- can also be expressed as:
- _Pragma ( "listing on \"..\\listing.dir\"" )
- The latter form is processed in the same way whether it appears literally as shown, or results from macro
- replacement, as in:
- #define LISTING(x) PRAGMA(listing on #x)
- #define PRAGMA(x) _Pragma(#x)
- LISTING ( ..\listing.dir )
-
-
-
-
-[page 176]
-
- 6.11 Future language directions
- 6.11.1 Floating types
-1 Future standardization may include additional floating-point types, including those with
- greater range, precision, or both than long double.
- 6.11.2 Linkages of identifiers
-1 Declaring an identifier with internal linkage at file scope without the static storage-
- class specifier is an obsolescent feature.
- 6.11.3 External names
-1 Restriction of the significance of an external name to fewer than 255 characters
- (considering each universal character name or extended source character as a single
- character) is an obsolescent feature that is a concession to existing implementations.
- 6.11.4 Character escape sequences
-1 Lowercase letters as escape sequences are reserved for future standardization. Other
- characters may be used in extensions.
- 6.11.5 Storage-class specifiers
-1 The placement of a storage-class specifier other than at the beginning of the declaration
- specifiers in a declaration is an obsolescent feature.
- 6.11.6 Function declarators
-1 The use of function declarators with empty parentheses (not prototype-format parameter
- type declarators) is an obsolescent feature.
- 6.11.7 Function definitions
-1 The use of function definitions with separate parameter identifier and declaration lists
- (not prototype-format parameter type and identifier declarators) is an obsolescent feature.
- 6.11.8 Pragma directives
-1 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
- 6.11.9 Predefined macro names
-1 Macro names beginning with __STDC_ are reserved for future standardization.
-
-
-
-
-[page 177]
-
-
- 7. Library
- 7.1 Introduction
- 7.1.1 Definitions of terms
-1 A string is a contiguous sequence of characters terminated by and including the first null
- character. The term multibyte string is sometimes used instead to emphasize special
- processing given to multibyte characters contained in the string or to avoid confusion
- with a wide string. A pointer to a string is a pointer to its initial (lowest addressed)
- character. The length of a string is the number of bytes preceding the null character and
- the value of a string is the sequence of the values of the contained characters, in order.
-2 The decimal-point character is the character used by functions that convert floating-point
- numbers to or from character sequences to denote the beginning of the fractional part of
- such character sequences.178) It is represented in the text and examples by a period, but
- may be changed by the setlocale function.
-3 A null wide character is a wide character with code value zero.
-4 A wide string is a contiguous sequence of wide characters terminated by and including
- the first null wide character. A pointer to a wide string is a pointer to its initial (lowest
- addressed) wide character. The length of a wide string is the number of wide characters
- preceding the null wide character and the value of a wide string is the sequence of code
- values of the contained wide characters, in order.
-5 A shift sequence is a contiguous sequence of bytes within a multibyte string that
- (potentially) causes a change in shift state (see 5.2.1.2). A shift sequence shall not have a
- corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
- character.179)
- Forward references: character handling (7.4), the setlocale function (7.11.1.1).
-
-
-
-
- 178) The functions that make use of the decimal-point character are the numeric conversion functions
- (7.22.1, 7.28.4.1) and the formatted input/output functions (7.21.6, 7.28.2).
- 179) For state-dependent encodings, the values for MB_CUR_MAX and MB_LEN_MAX shall thus be large
- enough to count all the bytes in any complete multibyte character plus at least one adjacent shift
- sequence of maximum length. Whether these counts provide for more than one shift sequence is the
- implementation's choice.
-
-[page 178]
-
- 7.1.2 Standard headers
-1 Each library function is declared, with a type that includes a prototype, in a header,180)
- whose contents are made available by the #include preprocessing directive. The
- header declares a set of related functions, plus any necessary types and additional macros
- needed to facilitate their use. Declarations of types described in this clause shall not
- include type qualifiers, unless explicitly stated otherwise.
-2 The standard headers are181)
- <assert.h> <iso646.h> <stdarg.h> <string.h>
- <complex.h> <limits.h> <stdatomic.h> <tgmath.h>
- <ctype.h> <locale.h> <stdbool.h> <threads.h>
- <errno.h> <math.h> <stddef.h> <time.h>
- <fenv.h> <setjmp.h> <stdint.h> <uchar.h>
- <float.h> <signal.h> <stdio.h> <wchar.h>
- <inttypes.h> <stdalign.h> <stdlib.h> <wctype.h>
-3 If a file with the same name as one of the above < and > delimited sequences, not
- provided as part of the implementation, is placed in any of the standard places that are
- searched for included source files, the behavior is undefined.
-4 Standard headers may be included in any order; each may be included more than once in
- a given scope, with no effect different from being included only once, except that the
- effect of including <assert.h> depends on the definition of NDEBUG (see 7.2). If
- used, a header shall be included outside of any external declaration or definition, and it
- shall first be included before the first reference to any of the functions or objects it
- declares, or to any of the types or macros it defines. However, if an identifier is declared
- or defined in more than one header, the second and subsequent associated headers may be
- included after the initial reference to the identifier. The program shall not have any
- macros with names lexically identical to keywords currently defined prior to the
- inclusion.
-5 Any definition of an object-like macro described in this clause shall expand to code that is
- fully protected by parentheses where necessary, so that it groups in an arbitrary
- expression as if it were a single identifier.
-6 Any declaration of a library function shall have external linkage.
-
-
-
-
- 180) A header is not necessarily a source file, nor are the < and > delimited sequences in header names
- necessarily valid source file names.
- 181) The headers <complex.h>, <stdatomic.h>, and <threads.h> are conditional features that
- implementations need not support; see 6.10.8.3.
-
-[page 179]
-
-7 A summary of the contents of the standard headers is given in annex B.
- Forward references: diagnostics (7.2).
- 7.1.3 Reserved identifiers
-1 Each header declares or defines all identifiers listed in its associated subclause, and
- optionally declares or defines identifiers listed in its associated future library directions
- subclause and identifiers which are always reserved either for any use or for use as file
- scope identifiers.
- -- All identifiers that begin with an underscore and either an uppercase letter or another
- underscore are always reserved for any use.
- -- All identifiers that begin with an underscore are always reserved for use as identifiers
- with file scope in both the ordinary and tag name spaces.
- -- Each macro name in any of the following subclauses (including the future library
- directions) is reserved for use as specified if any of its associated headers is included;
- unless explicitly stated otherwise (see 7.1.4).
- -- All identifiers with external linkage in any of the following subclauses (including the
- future library directions) and errno are always reserved for use as identifiers with
- external linkage.182)
- -- Each identifier with file scope listed in any of the following subclauses (including the
- future library directions) is reserved for use as a macro name and as an identifier with
- file scope in the same name space if any of its associated headers is included.
-2 No other identifiers are reserved. If the program declares or defines an identifier in a
- context in which it is reserved (other than as allowed by 7.1.4), or defines a reserved
- identifier as a macro name, the behavior is undefined.
-3 If the program removes (with #undef) any macro definition of an identifier in the first
- group listed above, the behavior is undefined.
-
-
-
-
- 182) The list of reserved identifiers with external linkage includes math_errhandling, setjmp,
- va_copy, and va_end.
-
-[page 180]
-
- 7.1.4 Use of library functions
-1 Each of the following statements applies unless explicitly stated otherwise in the detailed
- descriptions that follow: If an argument to a function has an invalid value (such as a value
- outside the domain of the function, or a pointer outside the address space of the program,
- or a null pointer, or a pointer to non-modifiable storage when the corresponding
- parameter is not const-qualified) or a type (after promotion) not expected by a function
- with variable number of arguments, the behavior is undefined. If a function argument is
- described as being an array, the pointer actually passed to the function shall have a value
- such that all address computations and accesses to objects (that would be valid if the
- pointer did point to the first element of such an array) are in fact valid. Any function
- declared in a header may be additionally implemented as a function-like macro defined in
- the header, so if a library function is declared explicitly when its header is included, one
- of the techniques shown below can be used to ensure the declaration is not affected by
- such a macro. Any macro definition of a function can be suppressed locally by enclosing
- the name of the function in parentheses, because the name is then not followed by the left
- parenthesis that indicates expansion of a macro function name. For the same syntactic
- reason, it is permitted to take the address of a library function even if it is also defined as
- a macro.183) The use of #undef to remove any macro definition will also ensure that an
- actual function is referred to. Any invocation of a library function that is implemented as
- a macro shall expand to code that evaluates each of its arguments exactly once, fully
- protected by parentheses where necessary, so it is generally safe to use arbitrary
- expressions as arguments.184) Likewise, those function-like macros described in the
- following subclauses may be invoked in an expression anywhere a function with a
- compatible return type could be called.185) All object-like macros listed as expanding to
-
-
- 183) This means that an implementation shall provide an actual function for each library function, even if it
- also provides a macro for that function.
- 184) Such macros might not contain the sequence points that the corresponding function calls do.
- 185) Because external identifiers and some macro names beginning with an underscore are reserved,
- implementations may provide special semantics for such names. For example, the identifier
- _BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
- appropriate header could specify
- #define abs(x) _BUILTIN_abs(x)
- for a compiler whose code generator will accept it.
- In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
- function may write
- #undef abs
- whether the implementation's header provides a macro implementation of abs or a built-in
- implementation. The prototype for the function, which precedes and is hidden by any macro
- definition, is thereby revealed also.
-
-[page 181]
-
- integer constant expressions shall additionally be suitable for use in #if preprocessing
- directives.
-2 Provided that a library function can be declared without reference to any type defined in a
- header, it is also permissible to declare the function and use it without including its
- associated header.
-3 There is a sequence point immediately before a library function returns.
-4 The functions in the standard library are not guaranteed to be reentrant and may modify
- objects with static or thread storage duration.186)
-5 Unless explicitly stated otherwise in the detailed descriptions that follow, library
- functions shall prevent data races as follows: A library function shall not directly or
- indirectly access objects accessible by threads other than the current thread unless the
- objects are accessed directly or indirectly via the function's arguments. A library
- function shall not directly or indirectly modify objects accessible by threads other than
- the current thread unless the objects are accessed directly or indirectly via the function's
- non-const arguments.187) Implementations may share their own internal objects between
- threads if the objects are not visible to users and are protected against data races.
-6 Unless otherwise specified, library functions shall perform all operations solely within the
- current thread if those operations have effects that are visible to users.188)
-7 EXAMPLE The function atoi may be used in any of several ways:
- -- by use of its associated header (possibly generating a macro expansion)
- #include <stdlib.h>
- const char *str;
- /* ... */
- i = atoi(str);
- -- by use of its associated header (assuredly generating a true function reference)
-
-
-
-
- 186) Thus, a signal handler cannot, in general, call standard library functions.
- 187) This means, for example, that an implementation is not permitted to use a static object for internal
- purposes without synchronization because it could cause a data race even in programs that do not
- explicitly share objects between threads.
- 188) This allows implementations to parallelize operations if there are no visible side effects.
-
-[page 182]
-
- #include <stdlib.h>
- #undef atoi
- const char *str;
- /* ... */
- i = atoi(str);
- or
- #include <stdlib.h>
- const char *str;
- /* ... */
- i = (atoi)(str);
--- by explicit declaration
- extern int atoi(const char *);
- const char *str;
- /* ... */
- i = atoi(str);
-
-
-
-
-[page 183]
-
- 7.2 Diagnostics <assert.h>
-1 The header <assert.h> defines the assert and static_assert macros and
- refers to another macro,
- NDEBUG
- which is not defined by <assert.h>. If NDEBUG is defined as a macro name at the
- point in the source file where <assert.h> is included, the assert macro is defined
- simply as
- #define assert(ignore) ((void)0)
- The assert macro is redefined according to the current state of NDEBUG each time that
- <assert.h> is included.
-2 The assert macro shall be implemented as a macro, not as an actual function. If the
- macro definition is suppressed in order to access an actual function, the behavior is
- undefined.
-3 The macro
- static_assert
- expands to _Static_assert.
- 7.2.1 Program diagnostics
- 7.2.1.1 The assert macro
- Synopsis
-1 #include <assert.h>
- void assert(scalar expression);
- Description
-2 The assert macro puts diagnostic tests into programs; it expands to a void expression.
- When it is executed, if expression (which shall have a scalar type) is false (that is,
- compares equal to 0), the assert macro writes information about the particular call that
- failed (including the text of the argument, the name of the source file, the source line
- number, and the name of the enclosing function -- the latter are respectively the values of
- the preprocessing macros __FILE__ and __LINE__ and of the identifier
- __func__) on the standard error stream in an implementation-defined format.189) It
- then calls the abort function.
-
-
-
- 189) The message written might be of the form:
- Assertion failed: expression, function abc, file xyz, line nnn.
-
-
-[page 184]
-
- Returns
-3 The assert macro returns no value.
- Forward references: the abort function (7.22.4.1).
-
-
-
-
-[page 185]
-
- 7.3 Complex arithmetic <complex.h>
- 7.3.1 Introduction
-1 The header <complex.h> defines macros and declares functions that support complex
- arithmetic.190)
-2 Implementations that define the macro __STDC_NO_COMPLEX__ need not provide
- this header nor support any of its facilities.
-3 Each synopsis specifies a family of functions consisting of a principal function with one
- or more double complex parameters and a double complex or double return
- value; and other functions with the same name but with f and l suffixes which are
- corresponding functions with float and long double parameters and return values.
-4 The macro
- complex
- expands to _Complex; the macro
- _Complex_I
- expands to a constant expression of type const float _Complex, with the value of
- the imaginary unit.191)
-5 The macros
- imaginary
- and
- _Imaginary_I
- are defined if and only if the implementation supports imaginary types;192) if defined,
- they expand to _Imaginary and a constant expression of type const float
- _Imaginary with the value of the imaginary unit.
-6 The macro
- I
- expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
- defined, I shall expand to _Complex_I.
-7 Notwithstanding the provisions of 7.1.3, a program may undefine and perhaps then
- redefine the macros complex, imaginary, and I.
-
- 190) See ''future library directions'' (7.30.1).
- 191) The imaginary unit is a number i such that i 2 = -1.
- 192) A specification for imaginary types is in informative annex G.
-
-[page 186]
-
- Forward references: IEC 60559-compatible complex arithmetic (annex G).
- 7.3.2 Conventions
-1 Values are interpreted as radians, not degrees. An implementation may set errno but is
- not required to.
- 7.3.3 Branch cuts
-1 Some of the functions below have branch cuts, across which the function is
- discontinuous. For implementations with a signed zero (including all IEC 60559
- implementations) that follow the specifications of annex G, the sign of zero distinguishes
- one side of a cut from another so the function is continuous (except for format
- limitations) as the cut is approached from either side. For example, for the square root
- function, which has a branch cut along the negative real axis, the top of the cut, with
- imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with
- imaginary part -0, maps to the negative imaginary axis.
-2 Implementations that do not support a signed zero (see annex F) cannot distinguish the
- sides of branch cuts. These implementations shall map a cut so the function is continuous
- as the cut is approached coming around the finite endpoint of the cut in a counter
- clockwise direction. (Branch cuts for the functions specified here have just one finite
- endpoint.) For example, for the square root function, coming counter clockwise around
- the finite endpoint of the cut along the negative real axis approaches the cut from above,
- so the cut maps to the positive imaginary axis.
- 7.3.4 The CX_LIMITED_RANGE pragma
- Synopsis
-1 #include <complex.h>
- #pragma STDC CX_LIMITED_RANGE on-off-switch
- Description
-2 The usual mathematical formulas for complex multiply, divide, and absolute value are
- problematic because of their treatment of infinities and because of undue overflow and
- underflow. The CX_LIMITED_RANGE pragma can be used to inform the
- implementation that (where the state is ''on'') the usual mathematical formulas are
- acceptable.193) The pragma can occur either outside external declarations or preceding all
- explicit declarations and statements inside a compound statement. When outside external
- declarations, the pragma takes effect from its occurrence until another
- CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit.
- When inside a compound statement, the pragma takes effect from its occurrence until
- another CX_LIMITED_RANGE pragma is encountered (including within a nested
- compound statement), or until the end of the compound statement; at the end of a
- compound statement the state for the pragma is restored to its condition just before the
-
-[page 187]
-
- compound statement. If this pragma is used in any other context, the behavior is
- undefined. The default state for the pragma is ''off''.
- 7.3.5 Trigonometric functions
- 7.3.5.1 The cacos functions
- Synopsis
-1 #include <complex.h>
- double complex cacos(double complex z);
- float complex cacosf(float complex z);
- long double complex cacosl(long double complex z);
- Description
-2 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
- interval [-1, +1] along the real axis.
- Returns
-3 The cacos functions return the complex arc cosine value, in the range of a strip
- mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
- real axis.
- 7.3.5.2 The casin functions
- Synopsis
-1 #include <complex.h>
- double complex casin(double complex z);
- float complex casinf(float complex z);
- long double complex casinl(long double complex z);
- Description
-2 The casin functions compute the complex arc sine of z, with branch cuts outside the
- interval [-1, +1] along the real axis.
- Returns
-3 The casin functions return the complex arc sine value, in the range of a strip
- mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
-
- 193) The purpose of the pragma is to allow the implementation to use the formulas:
- (x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
- (x + iy) / (u + iv) = [(xu + yv) + i(yu - xv)]/(u2 + v 2 )
- | x + iy | = sqrt: x 2 + y 2
- -----
- where the programmer can determine they are safe.
-
-[page 188]
-
- along the real axis.
- 7.3.5.3 The catan functions
- Synopsis
-1 #include <complex.h>
- double complex catan(double complex z);
- float complex catanf(float complex z);
- long double complex catanl(long double complex z);
- Description
-2 The catan functions compute the complex arc tangent of z, with branch cuts outside the
- interval [-i, +i] along the imaginary axis.
- Returns
-3 The catan functions return the complex arc tangent value, in the range of a strip
- mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
- along the real axis.
- 7.3.5.4 The ccos functions
- Synopsis
-1 #include <complex.h>
- double complex ccos(double complex z);
- float complex ccosf(float complex z);
- long double complex ccosl(long double complex z);
- Description
-2 The ccos functions compute the complex cosine of z.
- Returns
-3 The ccos functions return the complex cosine value.
- 7.3.5.5 The csin functions
- Synopsis
-1 #include <complex.h>
- double complex csin(double complex z);
- float complex csinf(float complex z);
- long double complex csinl(long double complex z);
- Description
-2 The csin functions compute the complex sine of z.
-
-
-
-[page 189]
-
- Returns
-3 The csin functions return the complex sine value.
- 7.3.5.6 The ctan functions
- Synopsis
-1 #include <complex.h>
- double complex ctan(double complex z);
- float complex ctanf(float complex z);
- long double complex ctanl(long double complex z);
- Description
-2 The ctan functions compute the complex tangent of z.
- Returns
-3 The ctan functions return the complex tangent value.
- 7.3.6 Hyperbolic functions
- 7.3.6.1 The cacosh functions
- Synopsis
-1 #include <complex.h>
- double complex cacosh(double complex z);
- float complex cacoshf(float complex z);
- long double complex cacoshl(long double complex z);
- Description
-2 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch
- cut at values less than 1 along the real axis.
- Returns
-3 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
- half-strip of non-negative values along the real axis and in the interval [-ipi , +ipi ] along
- the imaginary axis.
- 7.3.6.2 The casinh functions
- Synopsis
-1 #include <complex.h>
- double complex casinh(double complex z);
- float complex casinhf(float complex z);
- long double complex casinhl(long double complex z);
-
-
-
-[page 190]
-
- Description
-2 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts
- outside the interval [-i, +i] along the imaginary axis.
- Returns
-3 The casinh functions return the complex arc hyperbolic sine value, in the range of a
- strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
- along the imaginary axis.
- 7.3.6.3 The catanh functions
- Synopsis
-1 #include <complex.h>
- double complex catanh(double complex z);
- float complex catanhf(float complex z);
- long double complex catanhl(long double complex z);
- Description
-2 The catanh functions compute the complex arc hyperbolic tangent of z, with branch
- cuts outside the interval [-1, +1] along the real axis.
- Returns
-3 The catanh functions return the complex arc hyperbolic tangent value, in the range of a
- strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
- along the imaginary axis.
- 7.3.6.4 The ccosh functions
- Synopsis
-1 #include <complex.h>
- double complex ccosh(double complex z);
- float complex ccoshf(float complex z);
- long double complex ccoshl(long double complex z);
- Description
-2 The ccosh functions compute the complex hyperbolic cosine of z.
- Returns
-3 The ccosh functions return the complex hyperbolic cosine value.
-
-
-
-
-[page 191]
-
- 7.3.6.5 The csinh functions
- Synopsis
-1 #include <complex.h>
- double complex csinh(double complex z);
- float complex csinhf(float complex z);
- long double complex csinhl(long double complex z);
- Description
-2 The csinh functions compute the complex hyperbolic sine of z.
- Returns
-3 The csinh functions return the complex hyperbolic sine value.
- 7.3.6.6 The ctanh functions
- Synopsis
-1 #include <complex.h>
- double complex ctanh(double complex z);
- float complex ctanhf(float complex z);
- long double complex ctanhl(long double complex z);
- Description
-2 The ctanh functions compute the complex hyperbolic tangent of z.
- Returns
-3 The ctanh functions return the complex hyperbolic tangent value.
- 7.3.7 Exponential and logarithmic functions
- 7.3.7.1 The cexp functions
- Synopsis
-1 #include <complex.h>
- double complex cexp(double complex z);
- float complex cexpf(float complex z);
- long double complex cexpl(long double complex z);
- Description
-2 The cexp functions compute the complex base-e exponential of z.
- Returns
-3 The cexp functions return the complex base-e exponential value.
-
-
-
-[page 192]
-
- 7.3.7.2 The clog functions
- Synopsis
-1 #include <complex.h>
- double complex clog(double complex z);
- float complex clogf(float complex z);
- long double complex clogl(long double complex z);
- Description
-2 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
- cut along the negative real axis.
- Returns
-3 The clog functions return the complex natural logarithm value, in the range of a strip
- mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
- imaginary axis.
- 7.3.8 Power and absolute-value functions
- 7.3.8.1 The cabs functions
- Synopsis
-1 #include <complex.h>
- double cabs(double complex z);
- float cabsf(float complex z);
- long double cabsl(long double complex z);
- Description
-2 The cabs functions compute the complex absolute value (also called norm, modulus, or
- magnitude) of z.
- Returns
-3 The cabs functions return the complex absolute value.
- 7.3.8.2 The cpow functions
- Synopsis
-1 #include <complex.h>
- double complex cpow(double complex x, double complex y);
- float complex cpowf(float complex x, float complex y);
- long double complex cpowl(long double complex x,
- long double complex y);
-
-
-
-
-[page 193]
-
- Description
-2 The cpow functions compute the complex power function xy , with a branch cut for the
- first parameter along the negative real axis.
- Returns
-3 The cpow functions return the complex power function value.
- 7.3.8.3 The csqrt functions
- Synopsis
-1 #include <complex.h>
- double complex csqrt(double complex z);
- float complex csqrtf(float complex z);
- long double complex csqrtl(long double complex z);
- Description
-2 The csqrt functions compute the complex square root of z, with a branch cut along the
- negative real axis.
- Returns
-3 The csqrt functions return the complex square root value, in the range of the right half-
- plane (including the imaginary axis).
- 7.3.9 Manipulation functions
- 7.3.9.1 The carg functions
- Synopsis
-1 #include <complex.h>
- double carg(double complex z);
- float cargf(float complex z);
- long double cargl(long double complex z);
- Description
-2 The carg functions compute the argument (also called phase angle) of z, with a branch
- cut along the negative real axis.
- Returns
-3 The carg functions return the value of the argument in the interval [-pi , +pi ].
-
-
-
-
-[page 194]
-
- 7.3.9.2 The cimag functions
- Synopsis
-1 #include <complex.h>
- double cimag(double complex z);
- float cimagf(float complex z);
- long double cimagl(long double complex z);
- Description
-2 The cimag functions compute the imaginary part of z.194)
- Returns
-3 The cimag functions return the imaginary part value (as a real).
- 7.3.9.3 The CMPLX macros
- Synopsis
-1 #include <complex.h>
- double complex CMPLX(double x, double y);
- float complex CMPLXF(float x, float y);
- long double complex CMPLXL(long double x, long double y);
- Description
-2 The CMPLX macros expand to an expression of the specified complex type, with the real
- part having the (converted) value of x and the imaginary part having the (converted)
- value of y.
- Recommended practice
-3 The resulting expression should be suitable for use as an initializer for an object with
- static or thread storage duration, provided both arguments are likewise suitable.
- Returns
-4 The CMPLX macros return the complex value x + i y.
-5 NOTE These macros act as if the implementation supported imaginary types and the definitions were:
- #define CMPLX(x, y) ((double complex)((double)(x) + \
- _Imaginary_I * (double)(y)))
- #define CMPLXF(x, y) ((float complex)((float)(x) + \
- _Imaginary_I * (float)(y)))
- #define CMPLXL(x, y) ((long double complex)((long double)(x) + \
- _Imaginary_I * (long double)(y)))
-
-
-
-
- 194) For a variable z of complex type, z == creal(z) + cimag(z)*I.
-
-[page 195]
-
- 7.3.9.4 The conj functions
- Synopsis
-1 #include <complex.h>
- double complex conj(double complex z);
- float complex conjf(float complex z);
- long double complex conjl(long double complex z);
- Description
-2 The conj functions compute the complex conjugate of z, by reversing the sign of its
- imaginary part.
- Returns
-3 The conj functions return the complex conjugate value.
- 7.3.9.5 The cproj functions
- Synopsis
-1 #include <complex.h>
- double complex cproj(double complex z);
- float complex cprojf(float complex z);
- long double complex cprojl(long double complex z);
- Description
-2 The cproj functions compute a projection of z onto the Riemann sphere: z projects to
- z except that all complex infinities (even those with one infinite part and one NaN part)
- project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is
- equivalent to
- INFINITY + I * copysign(0.0, cimag(z))
- Returns
-3 The cproj functions return the value of the projection onto the Riemann sphere.
- 7.3.9.6 The creal functions
- Synopsis
-1 #include <complex.h>
- double creal(double complex z);
- float crealf(float complex z);
- long double creall(long double complex z);
- Description
-2 The creal functions compute the real part of z.195)
-
-
-[page 196]
-
- Returns
-3 The creal functions return the real part value.
-
-
-
-
- 195) For a variable z of complex type, z == creal(z) + cimag(z)*I.
-
-[page 197]
-
- 7.4 Character handling <ctype.h>
-1 The header <ctype.h> declares several functions useful for classifying and mapping
- characters.196) In all cases the argument is an int, the value of which shall be
- representable as an unsigned char or shall equal the value of the macro EOF. If the
- argument has any other value, the behavior is undefined.
-2 The behavior of these functions is affected by the current locale. Those functions that
- have locale-specific aspects only when not in the "C" locale are noted below.
-3 The term printing character refers to a member of a locale-specific set of characters, each
- of which occupies one printing position on a display device; the term control character
- refers to a member of a locale-specific set of characters that are not printing
- characters.197) All letters and digits are printing characters.
- Forward references: EOF (7.21.1), localization (7.11).
- 7.4.1 Character classification functions
-1 The functions in this subclause return nonzero (true) if and only if the value of the
- argument c conforms to that in the description of the function.
- 7.4.1.1 The isalnum function
- Synopsis
-1 #include <ctype.h>
- int isalnum(int c);
- Description
-2 The isalnum function tests for any character for which isalpha or isdigit is true.
- 7.4.1.2 The isalpha function
- Synopsis
-1 #include <ctype.h>
- int isalpha(int c);
- Description
-2 The isalpha function tests for any character for which isupper or islower is true,
- or any character that is one of a locale-specific set of alphabetic characters for which
-
-
-
- 196) See ''future library directions'' (7.30.2).
- 197) In an implementation that uses the seven-bit US ASCII character set, the printing characters are those
- whose values lie from 0x20 (space) through 0x7E (tilde); the control characters are those whose
- values lie from 0 (NUL) through 0x1F (US), and the character 0x7F (DEL).
-
-[page 198]
-
- none of iscntrl, isdigit, ispunct, or isspace is true.198) In the "C" locale,
- isalpha returns true only for the characters for which isupper or islower is true.
- 7.4.1.3 The isblank function
- Synopsis
-1 #include <ctype.h>
- int isblank(int c);
- Description
-2 The isblank function tests for any character that is a standard blank character or is one
- of a locale-specific set of characters for which isspace is true and that is used to
- separate words within a line of text. The standard blank characters are the following:
- space (' '), and horizontal tab ('\t'). In the "C" locale, isblank returns true only
- for the standard blank characters.
- 7.4.1.4 The iscntrl function
- Synopsis
-1 #include <ctype.h>
- int iscntrl(int c);
- Description
-2 The iscntrl function tests for any control character.
- 7.4.1.5 The isdigit function
- Synopsis
-1 #include <ctype.h>
- int isdigit(int c);
- Description
-2 The isdigit function tests for any decimal-digit character (as defined in 5.2.1).
- 7.4.1.6 The isgraph function
- Synopsis
-1 #include <ctype.h>
- int isgraph(int c);
-
-
-
-
- 198) The functions islower and isupper test true or false separately for each of these additional
- characters; all four combinations are possible.
-
-[page 199]
-
- Description
-2 The isgraph function tests for any printing character except space (' ').
- 7.4.1.7 The islower function
- Synopsis
-1 #include <ctype.h>
- int islower(int c);
- Description
-2 The islower function tests for any character that is a lowercase letter or is one of a
- locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
- isspace is true. In the "C" locale, islower returns true only for the lowercase
- letters (as defined in 5.2.1).
- 7.4.1.8 The isprint function
- Synopsis
-1 #include <ctype.h>
- int isprint(int c);
- Description
-2 The isprint function tests for any printing character including space (' ').
- 7.4.1.9 The ispunct function
- Synopsis
-1 #include <ctype.h>
- int ispunct(int c);
- Description
-2 The ispunct function tests for any printing character that is one of a locale-specific set
- of punctuation characters for which neither isspace nor isalnum is true. In the "C"
- locale, ispunct returns true for every printing character for which neither isspace
- nor isalnum is true.
- 7.4.1.10 The isspace function
- Synopsis
-1 #include <ctype.h>
- int isspace(int c);
- Description
-2 The isspace function tests for any character that is a standard white-space character or
- is one of a locale-specific set of characters for which isalnum is false. The standard
-
-[page 200]
-
- white-space characters are the following: space (' '), form feed ('\f'), new-line
- ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
- "C" locale, isspace returns true only for the standard white-space characters.
- 7.4.1.11 The isupper function
- Synopsis
-1 #include <ctype.h>
- int isupper(int c);
- Description
-2 The isupper function tests for any character that is an uppercase letter or is one of a
- locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
- isspace is true. In the "C" locale, isupper returns true only for the uppercase
- letters (as defined in 5.2.1).
- 7.4.1.12 The isxdigit function
- Synopsis
-1 #include <ctype.h>
- int isxdigit(int c);
- Description
-2 The isxdigit function tests for any hexadecimal-digit character (as defined in 6.4.4.1).
- 7.4.2 Character case mapping functions
- 7.4.2.1 The tolower function
- Synopsis
-1 #include <ctype.h>
- int tolower(int c);
- Description
-2 The tolower function converts an uppercase letter to a corresponding lowercase letter.
- Returns
-3 If the argument is a character for which isupper is true and there are one or more
- corresponding characters, as specified by the current locale, for which islower is true,
- the tolower function returns one of the corresponding characters (always the same one
- for any given locale); otherwise, the argument is returned unchanged.
-
-
-
-
-[page 201]
-
- 7.4.2.2 The toupper function
- Synopsis
-1 #include <ctype.h>
- int toupper(int c);
- Description
-2 The toupper function converts a lowercase letter to a corresponding uppercase letter.
- Returns
-3 If the argument is a character for which islower is true and there are one or more
- corresponding characters, as specified by the current locale, for which isupper is true,
- the toupper function returns one of the corresponding characters (always the same one
- for any given locale); otherwise, the argument is returned unchanged.
-
-
-
-
-[page 202]
-
- 7.5 Errors <errno.h>
-1 The header <errno.h> defines several macros, all relating to the reporting of error
- conditions.
-2 The macros are
- EDOM
- EILSEQ
- ERANGE
- which expand to integer constant expressions with type int, distinct positive values, and
- which are suitable for use in #if preprocessing directives; and
- errno
- which expands to a modifiable lvalue199) that has type int and thread local storage
- duration, the value of which is set to a positive error number by several library functions.
- If a macro definition is suppressed in order to access an actual object, or a program
- defines an identifier with the name errno, the behavior is undefined.
-3 The value of errno in the initial thread is zero at program startup (the initial value of
- errno in other threads is an indeterminate value), but is never set to zero by any library
- function.200) The value of errno may be set to nonzero by a library function call
- whether or not there is an error, provided the use of errno is not documented in the
- description of the function in this International Standard.
-4 Additional macro definitions, beginning with E and a digit or E and an uppercase
- letter,201) may also be specified by the implementation.
-
-
-
-
- 199) The macro errno need not be the identifier of an object. It might expand to a modifiable lvalue
- resulting from a function call (for example, *errno()).
- 200) Thus, a program that uses errno for error checking should set it to zero before a library function call,
- then inspect it before a subsequent library function call. Of course, a library function can save the
- value of errno on entry and then set it to zero, as long as the original value is restored if errno's
- value is still zero just before the return.
- 201) See ''future library directions'' (7.30.3).
-
-[page 203]
-
- 7.6 Floating-point environment <fenv.h>
-1 The header <fenv.h> defines several macros, and declares types and functions that
- provide access to the floating-point environment. The floating-point environment refers
- collectively to any floating-point status flags and control modes supported by the
- implementation.202) A floating-point status flag is a system variable whose value is set
- (but never cleared) when a floating-point exception is raised, which occurs as a side effect
- of exceptional floating-point arithmetic to provide auxiliary information.203) A floating-
- point control mode is a system variable whose value may be set by the user to affect the
- subsequent behavior of floating-point arithmetic.
-2 The floating-point environment has thread storage duration. The initial state for a
- thread's floating-point environment is the current state of the floating-point environment
- of the thread that creates it at the time of creation.
-3 Certain programming conventions support the intended model of use for the floating-
- point environment:204)
- -- a function call does not alter its caller's floating-point control modes, clear its caller's
- floating-point status flags, nor depend on the state of its caller's floating-point status
- flags unless the function is so documented;
- -- a function call is assumed to require default floating-point control modes, unless its
- documentation promises otherwise;
- -- a function call is assumed to have the potential for raising floating-point exceptions,
- unless its documentation promises otherwise.
-4 The type
- fenv_t
- represents the entire floating-point environment.
-5 The type
- fexcept_t
- represents the floating-point status flags collectively, including any status the
- implementation associates with the flags.
-
-
- 202) This header is designed to support the floating-point exception status flags and directed-rounding
- control modes required by IEC 60559, and other similar floating-point state information. Also it is
- designed to facilitate code portability among all systems.
- 203) A floating-point status flag is not an object and can be set more than once within an expression.
- 204) With these conventions, a programmer can safely assume default floating-point control modes (or be
- unaware of them). The responsibilities associated with accessing the floating-point environment fall
- on the programmer or program that does so explicitly.
-
-[page 204]
-
-6 Each of the macros
- FE_DIVBYZERO
- FE_INEXACT
- FE_INVALID
- FE_OVERFLOW
- FE_UNDERFLOW
- is defined if and only if the implementation supports the floating-point exception by
- means of the functions in 7.6.2.205) Additional implementation-defined floating-point
- exceptions, with macro definitions beginning with FE_ and an uppercase letter, may also
- be specified by the implementation. The defined macros expand to integer constant
- expressions with values such that bitwise ORs of all combinations of the macros result in
- distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
- zero.206)
-7 The macro
- FE_ALL_EXCEPT
- is simply the bitwise OR of all floating-point exception macros defined by the
- implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
-8 Each of the macros
- FE_DOWNWARD
- FE_TONEAREST
- FE_TOWARDZERO
- FE_UPWARD
- is defined if and only if the implementation supports getting and setting the represented
- rounding direction by means of the fegetround and fesetround functions.
- Additional implementation-defined rounding directions, with macro definitions beginning
- with FE_ and an uppercase letter, may also be specified by the implementation. The
- defined macros expand to integer constant expressions whose values are distinct
- nonnegative values.207)
-9 The macro
-
-
-
- 205) The implementation supports an exception if there are circumstances where a call to at least one of the
- functions in 7.6.2, using the macro as the appropriate argument, will succeed. It is not necessary for
- all the functions to succeed all the time.
- 206) The macros should be distinct powers of two.
- 207) Even though the rounding direction macros may expand to constants corresponding to the values of
- FLT_ROUNDS, they are not required to do so.
-
-[page 205]
-
- FE_DFL_ENV
- represents the default floating-point environment -- the one installed at program startup
- -- and has type ''pointer to const-qualified fenv_t''. It can be used as an argument to
- <fenv.h> functions that manage the floating-point environment.
-10 Additional implementation-defined environments, with macro definitions beginning with
- FE_ and an uppercase letter, and having type ''pointer to const-qualified fenv_t'', may
- also be specified by the implementation.
- 7.6.1 The FENV_ACCESS pragma
- Synopsis
-1 #include <fenv.h>
- #pragma STDC FENV_ACCESS on-off-switch
- Description
-2 The FENV_ACCESS pragma provides a means to inform the implementation when a
- program might access the floating-point environment to test floating-point status flags or
- run under non-default floating-point control modes.208) The pragma shall occur either
- outside external declarations or preceding all explicit declarations and statements inside a
- compound statement. When outside external declarations, the pragma takes effect from
- its occurrence until another FENV_ACCESS pragma is encountered, or until the end of
- the translation unit. When inside a compound statement, the pragma takes effect from its
- occurrence until another FENV_ACCESS pragma is encountered (including within a
- nested compound statement), or until the end of the compound statement; at the end of a
- compound statement the state for the pragma is restored to its condition just before the
- compound statement. If this pragma is used in any other context, the behavior is
- undefined. If part of a program tests floating-point status flags, sets floating-point control
- modes, or runs under non-default mode settings, but was translated with the state for the
- FENV_ACCESS pragma ''off'', the behavior is undefined. The default state (''on'' or
- ''off'') for the pragma is implementation-defined. (When execution passes from a part of
- the program translated with FENV_ACCESS ''off'' to a part translated with
- FENV_ACCESS ''on'', the state of the floating-point status flags is unspecified and the
- floating-point control modes have their default settings.)
-
-
-
-
- 208) The purpose of the FENV_ACCESS pragma is to allow certain optimizations that could subvert flag
- tests and mode changes (e.g., global common subexpression elimination, code motion, and constant
- folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default
- modes are in effect and the flags are not tested.
-
-[page 206]
-
-3 EXAMPLE
- #include <fenv.h>
- void f(double x)
- {
- #pragma STDC FENV_ACCESS ON
- void g(double);
- void h(double);
- /* ... */
- g(x + 1);
- h(x + 1);
- /* ... */
- }
-4 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
- x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
- contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.209)
-
- 7.6.2 Floating-point exceptions
-1 The following functions provide access to the floating-point status flags.210) The int
- input argument for the functions represents a subset of floating-point exceptions, and can
- be zero or the bitwise OR of one or more floating-point exception macros, for example
- FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
- functions is undefined.
- 7.6.2.1 The feclearexcept function
- Synopsis
-1 #include <fenv.h>
- int feclearexcept(int excepts);
- Description
-2 The feclearexcept function attempts to clear the supported floating-point exceptions
- represented by its argument.
- Returns
-3 The feclearexcept function returns zero if the excepts argument is zero or if all
- the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
-
-
- 209) The side effects impose a temporal ordering that requires two evaluations of x + 1. On the other
- hand, without the #pragma STDC FENV_ACCESS ON pragma, and assuming the default state is
- ''off'', just one evaluation of x + 1 would suffice.
- 210) The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
- abstraction of flags that are either set or clear. An implementation may endow floating-point status
- flags with more information -- for example, the address of the code which first raised the floating-
- point exception; the functions fegetexceptflag and fesetexceptflag deal with the full
- content of flags.
-
-[page 207]
-
- 7.6.2.2 The fegetexceptflag function
- Synopsis
-1 #include <fenv.h>
- int fegetexceptflag(fexcept_t *flagp,
- int excepts);
- Description
-2 The fegetexceptflag function attempts to store an implementation-defined
- representation of the states of the floating-point status flags indicated by the argument
- excepts in the object pointed to by the argument flagp.
- Returns
-3 The fegetexceptflag function returns zero if the representation was successfully
- stored. Otherwise, it returns a nonzero value.
- 7.6.2.3 The feraiseexcept function
- Synopsis
-1 #include <fenv.h>
- int feraiseexcept(int excepts);
- Description
-2 The feraiseexcept function attempts to raise the supported floating-point exceptions
- represented by its argument.211) The order in which these floating-point exceptions are
- raised is unspecified, except as stated in F.8.6. Whether the feraiseexcept function
- additionally raises the ''inexact'' floating-point exception whenever it raises the
- ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
- Returns
-3 The feraiseexcept function returns zero if the excepts argument is zero or if all
- the specified exceptions were successfully raised. Otherwise, it returns a nonzero value.
-
-
-
-
- 211) The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations.
- Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
- in F.8.6 is in the same spirit.
-
-[page 208]
-
- 7.6.2.4 The fesetexceptflag function
- Synopsis
-1 #include <fenv.h>
- int fesetexceptflag(const fexcept_t *flagp,
- int excepts);
- Description
-2 The fesetexceptflag function attempts to set the floating-point status flags
- indicated by the argument excepts to the states stored in the object pointed to by
- flagp. The value of *flagp shall have been set by a previous call to
- fegetexceptflag whose second argument represented at least those floating-point
- exceptions represented by the argument excepts. This function does not raise floating-
- point exceptions, but only sets the state of the flags.
- Returns
-3 The fesetexceptflag function returns zero if the excepts argument is zero or if
- all the specified flags were successfully set to the appropriate state. Otherwise, it returns
- a nonzero value.
- 7.6.2.5 The fetestexcept function
- Synopsis
-1 #include <fenv.h>
- int fetestexcept(int excepts);
- Description
-2 The fetestexcept function determines which of a specified subset of the floating-
- point exception flags are currently set. The excepts argument specifies the floating-
- point status flags to be queried.212)
- Returns
-3 The fetestexcept function returns the value of the bitwise OR of the floating-point
- exception macros corresponding to the currently set floating-point exceptions included in
- excepts.
-4 EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set:
-
-
-
-
- 212) This mechanism allows testing several floating-point exceptions with just one function call.
-
-[page 209]
-
- #include <fenv.h>
- /* ... */
- {
- #pragma STDC FENV_ACCESS ON
- int set_excepts;
- feclearexcept(FE_INVALID | FE_OVERFLOW);
- // maybe raise exceptions
- set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
- if (set_excepts & FE_INVALID) f();
- if (set_excepts & FE_OVERFLOW) g();
- /* ... */
- }
-
- 7.6.3 Rounding
-1 The fegetround and fesetround functions provide control of rounding direction
- modes.
- 7.6.3.1 The fegetround function
- Synopsis
-1 #include <fenv.h>
- int fegetround(void);
- Description
-2 The fegetround function gets the current rounding direction.
- Returns
-3 The fegetround function returns the value of the rounding direction macro
- representing the current rounding direction or a negative value if there is no such
- rounding direction macro or the current rounding direction is not determinable.
- 7.6.3.2 The fesetround function
- Synopsis
-1 #include <fenv.h>
- int fesetround(int round);
- Description
-2 The fesetround function establishes the rounding direction represented by its
- argument round. If the argument is not equal to the value of a rounding direction macro,
- the rounding direction is not changed.
- Returns
-3 The fesetround function returns zero if and only if the requested rounding direction
- was established.
-
-
-[page 210]
-
-4 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the
- rounding direction fails.
- #include <fenv.h>
- #include <assert.h>
- void f(int round_dir)
- {
- #pragma STDC FENV_ACCESS ON
- int save_round;
- int setround_ok;
- save_round = fegetround();
- setround_ok = fesetround(round_dir);
- assert(setround_ok == 0);
- /* ... */
- fesetround(save_round);
- /* ... */
- }
-
- 7.6.4 Environment
-1 The functions in this section manage the floating-point environment -- status flags and
- control modes -- as one entity.
- 7.6.4.1 The fegetenv function
- Synopsis
-1 #include <fenv.h>
- int fegetenv(fenv_t *envp);
- Description
-2 The fegetenv function attempts to store the current floating-point environment in the
- object pointed to by envp.
- Returns
-3 The fegetenv function returns zero if the environment was successfully stored.
- Otherwise, it returns a nonzero value.
- 7.6.4.2 The feholdexcept function
- Synopsis
-1 #include <fenv.h>
- int feholdexcept(fenv_t *envp);
- Description
-2 The feholdexcept function saves the current floating-point environment in the object
- pointed to by envp, clears the floating-point status flags, and then installs a non-stop
- (continue on floating-point exceptions) mode, if available, for all floating-point
- exceptions.213)
-
-[page 211]
-
- Returns
-3 The feholdexcept function returns zero if and only if non-stop floating-point
- exception handling was successfully installed.
- 7.6.4.3 The fesetenv function
- Synopsis
-1 #include <fenv.h>
- int fesetenv(const fenv_t *envp);
- Description
-2 The fesetenv function attempts to establish the floating-point environment represented
- by the object pointed to by envp. The argument envp shall point to an object set by a
- call to fegetenv or feholdexcept, or equal a floating-point environment macro.
- Note that fesetenv merely installs the state of the floating-point status flags
- represented through its argument, and does not raise these floating-point exceptions.
- Returns
-3 The fesetenv function returns zero if the environment was successfully established.
- Otherwise, it returns a nonzero value.
- 7.6.4.4 The feupdateenv function
- Synopsis
-1 #include <fenv.h>
- int feupdateenv(const fenv_t *envp);
- Description
-2 The feupdateenv function attempts to save the currently raised floating-point
- exceptions in its automatic storage, install the floating-point environment represented by
- the object pointed to by envp, and then raise the saved floating-point exceptions. The
- argument envp shall point to an object set by a call to feholdexcept or fegetenv,
- or equal a floating-point environment macro.
- Returns
-3 The feupdateenv function returns zero if all the actions were successfully carried out.
- Otherwise, it returns a nonzero value.
-
-
-
-
- 213) IEC 60559 systems have a default non-stop mode, and typically at least one other mode for trap
- handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For
- such systems, the feholdexcept function can be used in conjunction with the feupdateenv
- function to write routines that hide spurious floating-point exceptions from their callers.
-
-[page 212]
-
-4 EXAMPLE Hide spurious underflow floating-point exceptions:
- #include <fenv.h>
- double f(double x)
- {
- #pragma STDC FENV_ACCESS ON
- double result;
- fenv_t save_env;
- if (feholdexcept(&save_env))
- return /* indication of an environmental problem */;
- // compute result
- if (/* test spurious underflow */)
- if (feclearexcept(FE_UNDERFLOW))
- return /* indication of an environmental problem */;
- if (feupdateenv(&save_env))
- return /* indication of an environmental problem */;
- return result;
- }
-
-
-
-
-[page 213]
-
- 7.7 Characteristics of floating types <float.h>
-1 The header <float.h> defines several macros that expand to various limits and
- parameters of the standard floating-point types.
-2 The macros, their meanings, and the constraints (or restrictions) on their values are listed
- in 5.2.4.2.2.
-
-
-
-
-[page 214]
-
- 7.8 Format conversion of integer types <inttypes.h>
-1 The header <inttypes.h> includes the header <stdint.h> and extends it with
- additional facilities provided by hosted implementations.
-2 It declares functions for manipulating greatest-width integers and converting numeric
- character strings to greatest-width integers, and it declares the type
- imaxdiv_t
- which is a structure type that is the type of the value returned by the imaxdiv function.
- For each type declared in <stdint.h>, it defines corresponding macros for conversion
- specifiers for use with the formatted input/output functions.214)
- Forward references: integer types <stdint.h> (7.20), formatted input/output
- functions (7.21.6), formatted wide character input/output functions (7.28.2).
- 7.8.1 Macros for format specifiers
-1 Each of the following object-like macros expands to a character string literal containing a
- conversion specifier, possibly modified by a length modifier, suitable for use within the
- format argument of a formatted input/output function when converting the corresponding
- integer type. These macro names have the general form of PRI (character string literals
- for the fprintf and fwprintf family) or SCN (character string literals for the
- fscanf and fwscanf family),215) followed by the conversion specifier, followed by a
- name corresponding to a similar type name in 7.20.1. In these names, N represents the
- width of the type as described in 7.20.1. For example, PRIdFAST32 can be used in a
- format string to print the value of an integer of type int_fast32_t.
-2 The fprintf macros for signed integers are:
- PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
- PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
-3 The fprintf macros for unsigned integers are:
- PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
- PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
- PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
- PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
-4 The fscanf macros for signed integers are:
-
-
-
- 214) See ''future library directions'' (7.30.4).
- 215) Separate macros are given for use with fprintf and fscanf functions because, in the general case,
- different format specifiers may be required for fprintf and fscanf, even when the type is the
- same.
-
-[page 215]
-
- SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
- SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
-5 The fscanf macros for unsigned integers are:
- SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
- SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
- SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
-6 For each type that the implementation provides in <stdint.h>, the corresponding
- fprintf macros shall be defined and the corresponding fscanf macros shall be
- defined unless the implementation does not have a suitable fscanf length modifier for
- the type.
-7 EXAMPLE
- #include <inttypes.h>
- #include <wchar.h>
- int main(void)
- {
- uintmax_t i = UINTMAX_MAX; // this type always exists
- wprintf(L"The largest integer value is %020"
- PRIxMAX "\n", i);
- return 0;
- }
-
- 7.8.2 Functions for greatest-width integer types
- 7.8.2.1 The imaxabs function
- Synopsis
-1 #include <inttypes.h>
- intmax_t imaxabs(intmax_t j);
- Description
-2 The imaxabs function computes the absolute value of an integer j. If the result cannot
- be represented, the behavior is undefined.216)
- Returns
-3 The imaxabs function returns the absolute value.
-
-
-
-
- 216) The absolute value of the most negative number cannot be represented in two's complement.
-
-[page 216]
-
- 7.8.2.2 The imaxdiv function
- Synopsis
-1 #include <inttypes.h>
- imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
- Description
-2 The imaxdiv function computes numer / denom and numer % denom in a single
- operation.
- Returns
-3 The imaxdiv function returns a structure of type imaxdiv_t comprising both the
- quotient and the remainder. The structure shall contain (in either order) the members
- quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
- either part of the result cannot be represented, the behavior is undefined.
- 7.8.2.3 The strtoimax and strtoumax functions
- Synopsis
-1 #include <inttypes.h>
- intmax_t strtoimax(const char * restrict nptr,
- char ** restrict endptr, int base);
- uintmax_t strtoumax(const char * restrict nptr,
- char ** restrict endptr, int base);
- Description
-2 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll,
- strtoul, and strtoull functions, except that the initial portion of the string is
- converted to intmax_t and uintmax_t representation, respectively.
- Returns
-3 The strtoimax and strtoumax functions return the converted value, if any. If no
- conversion could be performed, zero is returned. If the correct value is outside the range
- of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned
- (according to the return type and sign of the value, if any), and the value of the macro
- ERANGE is stored in errno.
- Forward references: the strtol, strtoll, strtoul, and strtoull functions
- (7.22.1.4).
-
-
-
-
-[page 217]
-
- 7.8.2.4 The wcstoimax and wcstoumax functions
- Synopsis
-1 #include <stddef.h> // for wchar_t
- #include <inttypes.h>
- intmax_t wcstoimax(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
- uintmax_t wcstoumax(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
- Description
-2 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll,
- wcstoul, and wcstoull functions except that the initial portion of the wide string is
- converted to intmax_t and uintmax_t representation, respectively.
- Returns
-3 The wcstoimax function returns the converted value, if any. If no conversion could be
- performed, zero is returned. If the correct value is outside the range of representable
- values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the
- return type and sign of the value, if any), and the value of the macro ERANGE is stored in
- errno.
- Forward references: the wcstol, wcstoll, wcstoul, and wcstoull functions
- (7.28.4.1.2).
-
-
-
-
-[page 218]
-
- 7.9 Alternative spellings <iso646.h>
-1 The header <iso646.h> defines the following eleven macros (on the left) that expand
- to the corresponding tokens (on the right):
- and &&
- and_eq &=
- bitand &
- bitor |
- compl ~
- not !
- not_eq !=
- or ||
- or_eq |=
- xor ^
- xor_eq ^=
-
-
-
-
-[page 219]
-
- 7.10 Sizes of integer types <limits.h>
-1 The header <limits.h> defines several macros that expand to various limits and
- parameters of the standard integer types.
-2 The macros, their meanings, and the constraints (or restrictions) on their values are listed
- in 5.2.4.2.1.
-
-
-
-
-[page 220]
-
- 7.11 Localization <locale.h>
-1 The header <locale.h> declares two functions, one type, and defines several macros.
-2 The type is
- struct lconv
- which contains members related to the formatting of numeric values. The structure shall
- contain at least the following members, in any order. The semantics of the members and
- their normal ranges are explained in 7.11.2.1. In the "C" locale, the members shall have
- the values specified in the comments.
- char *decimal_point; // "."
- char *thousands_sep; // ""
- char *grouping; // ""
- char *mon_decimal_point; // ""
- char *mon_thousands_sep; // ""
- char *mon_grouping; // ""
- char *positive_sign; // ""
- char *negative_sign; // ""
- char *currency_symbol; // ""
- char frac_digits; // CHAR_MAX
- char p_cs_precedes; // CHAR_MAX
- char n_cs_precedes; // CHAR_MAX
- char p_sep_by_space; // CHAR_MAX
- char n_sep_by_space; // CHAR_MAX
- char p_sign_posn; // CHAR_MAX
- char n_sign_posn; // CHAR_MAX
- char *int_curr_symbol; // ""
- char int_frac_digits; // CHAR_MAX
- char int_p_cs_precedes; // CHAR_MAX
- char int_n_cs_precedes; // CHAR_MAX
- char int_p_sep_by_space; // CHAR_MAX
- char int_n_sep_by_space; // CHAR_MAX
- char int_p_sign_posn; // CHAR_MAX
- char int_n_sign_posn; // CHAR_MAX
-
-
-
-
-[page 221]
-
-3 The macros defined are NULL (described in 7.19); and
- LC_ALL
- LC_COLLATE
- LC_CTYPE
- LC_MONETARY
- LC_NUMERIC
- LC_TIME
- which expand to integer constant expressions with distinct values, suitable for use as the
- first argument to the setlocale function.217) Additional macro definitions, beginning
- with the characters LC_ and an uppercase letter,218) may also be specified by the
- implementation.
- 7.11.1 Locale control
- 7.11.1.1 The setlocale function
- Synopsis
-1 #include <locale.h>
- char *setlocale(int category, const char *locale);
- Description
-2 The setlocale function selects the appropriate portion of the program's locale as
- specified by the category and locale arguments. The setlocale function may be
- used to change or query the program's entire current locale or portions thereof. The value
- LC_ALL for category names the program's entire locale; the other values for
- category name only a portion of the program's locale. LC_COLLATE affects the
- behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of
- the character handling functions219) and the multibyte and wide character functions.
- LC_MONETARY affects the monetary formatting information returned by the
- localeconv function. LC_NUMERIC affects the decimal-point character for the
- formatted input/output functions and the string conversion functions, as well as the
- nonmonetary formatting information returned by the localeconv function. LC_TIME
- affects the behavior of the strftime and wcsftime functions.
-3 A value of "C" for locale specifies the minimal environment for C translation; a value
- of "" for locale specifies the locale-specific native environment. Other
- implementation-defined strings may be passed as the second argument to setlocale.
-
- 217) ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.
- 218) See ''future library directions'' (7.30.5).
- 219) The only functions in 7.4 whose behavior is not affected by the current locale are isdigit and
- isxdigit.
-
-[page 222]
-
-4 At program startup, the equivalent of
- setlocale(LC_ALL, "C");
- is executed.
-5 A call to the setlocale function may introduce a data race with other calls to the
- setlocale function or with calls to functions that are affected by the current locale.
- The implementation shall behave as if no library function calls the setlocale function.
- Returns
-6 If a pointer to a string is given for locale and the selection can be honored, the
- setlocale function returns a pointer to the string associated with the specified
- category for the new locale. If the selection cannot be honored, the setlocale
- function returns a null pointer and the program's locale is not changed.
-7 A null pointer for locale causes the setlocale function to return a pointer to the
- string associated with the category for the program's current locale; the program's
- locale is not changed.220)
-8 The pointer to string returned by the setlocale function is such that a subsequent call
- with that string value and its associated category will restore that part of the program's
- locale. The string pointed to shall not be modified by the program, but may be
- overwritten by a subsequent call to the setlocale function.
- Forward references: formatted input/output functions (7.21.6), multibyte/wide
- character conversion functions (7.22.7), multibyte/wide string conversion functions
- (7.22.8), numeric conversion functions (7.22.1), the strcoll function (7.23.4.3), the
- strftime function (7.26.3.5), the strxfrm function (7.23.4.5).
- 7.11.2 Numeric formatting convention inquiry
- 7.11.2.1 The localeconv function
- Synopsis
-1 #include <locale.h>
- struct lconv *localeconv(void);
- Description
-2 The localeconv function sets the components of an object with type struct lconv
- with values appropriate for the formatting of numeric quantities (monetary and otherwise)
- according to the rules of the current locale.
-
-
-
- 220) The implementation shall arrange to encode in a string the various categories due to a heterogeneous
- locale when category has the value LC_ALL.
-
-[page 223]
-
-3 The members of the structure with type char * are pointers to strings, any of which
- (except decimal_point) can point to "", to indicate that the value is not available in
- the current locale or is of zero length. Apart from grouping and mon_grouping, the
- strings shall start and end in the initial shift state. The members with type char are
- nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not
- available in the current locale. The members include the following:
- char *decimal_point
- The decimal-point character used to format nonmonetary quantities.
- char *thousands_sep
- The character used to separate groups of digits before the decimal-point
- character in formatted nonmonetary quantities.
- char *grouping
- A string whose elements indicate the size of each group of digits in
- formatted nonmonetary quantities.
- char *mon_decimal_point
- The decimal-point used to format monetary quantities.
- char *mon_thousands_sep
- The separator for groups of digits before the decimal-point in formatted
- monetary quantities.
- char *mon_grouping
- A string whose elements indicate the size of each group of digits in
- formatted monetary quantities.
- char *positive_sign
- The string used to indicate a nonnegative-valued formatted monetary
- quantity.
- char *negative_sign
- The string used to indicate a negative-valued formatted monetary quantity.
- char *currency_symbol
- The local currency symbol applicable to the current locale.
- char frac_digits
- The number of fractional digits (those after the decimal-point) to be
- displayed in a locally formatted monetary quantity.
- char p_cs_precedes
- Set to 1 or 0 if the currency_symbol respectively precedes or
- succeeds the value for a nonnegative locally formatted monetary quantity.
-
-
-
-[page 224]
-
-char n_cs_precedes
- Set to 1 or 0 if the currency_symbol respectively precedes or
- succeeds the value for a negative locally formatted monetary quantity.
-char p_sep_by_space
- Set to a value indicating the separation of the currency_symbol, the
- sign string, and the value for a nonnegative locally formatted monetary
- quantity.
-char n_sep_by_space
- Set to a value indicating the separation of the currency_symbol, the
- sign string, and the value for a negative locally formatted monetary
- quantity.
-char p_sign_posn
- Set to a value indicating the positioning of the positive_sign for a
- nonnegative locally formatted monetary quantity.
-char n_sign_posn
- Set to a value indicating the positioning of the negative_sign for a
- negative locally formatted monetary quantity.
-char *int_curr_symbol
- The international currency symbol applicable to the current locale. The
- first three characters contain the alphabetic international currency symbol
- in accordance with those specified in ISO 4217. The fourth character
- (immediately preceding the null character) is the character used to separate
- the international currency symbol from the monetary quantity.
-char int_frac_digits
- The number of fractional digits (those after the decimal-point) to be
- displayed in an internationally formatted monetary quantity.
-char int_p_cs_precedes
- Set to 1 or 0 if the int_curr_symbol respectively precedes or
- succeeds the value for a nonnegative internationally formatted monetary
- quantity.
-char int_n_cs_precedes
- Set to 1 or 0 if the int_curr_symbol respectively precedes or
- succeeds the value for a negative internationally formatted monetary
- quantity.
-char int_p_sep_by_space
- Set to a value indicating the separation of the int_curr_symbol, the
- sign string, and the value for a nonnegative internationally formatted
- monetary quantity.
-[page 225]
-
- char int_n_sep_by_space
- Set to a value indicating the separation of the int_curr_symbol, the
- sign string, and the value for a negative internationally formatted monetary
- quantity.
- char int_p_sign_posn
- Set to a value indicating the positioning of the positive_sign for a
- nonnegative internationally formatted monetary quantity.
- char int_n_sign_posn
- Set to a value indicating the positioning of the negative_sign for a
- negative internationally formatted monetary quantity.
-4 The elements of grouping and mon_grouping are interpreted according to the
- following:
- CHAR_MAX No further grouping is to be performed.
- 0 The previous element is to be repeatedly used for the remainder of the
- digits.
- other The integer value is the number of digits that compose the current group.
- The next element is examined to determine the size of the next group of
- digits before the current group.
-5 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space,
- and int_n_sep_by_space are interpreted according to the following:
- 0 No space separates the currency symbol and value.
- 1 If the currency symbol and sign string are adjacent, a space separates them from the
- value; otherwise, a space separates the currency symbol from the value.
- 2 If the currency symbol and sign string are adjacent, a space separates them;
- otherwise, a space separates the sign string from the value.
- For int_p_sep_by_space and int_n_sep_by_space, the fourth character of
- int_curr_symbol is used instead of a space.
-6 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and
- int_n_sign_posn are interpreted according to the following:
- 0 Parentheses surround the quantity and currency symbol.
- 1 The sign string precedes the quantity and currency symbol.
- 2 The sign string succeeds the quantity and currency symbol.
- 3 The sign string immediately precedes the currency symbol.
- 4 The sign string immediately succeeds the currency symbol.
-
-
-[page 226]
-
-7 The implementation shall behave as if no library function calls the localeconv
- function.
- Returns
-8 The localeconv function returns a pointer to the filled-in object. The structure
- pointed to by the return value shall not be modified by the program, but may be
- overwritten by a subsequent call to the localeconv function. In addition, calls to the
- setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may
- overwrite the contents of the structure.
-9 EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format
- monetary quantities.
- Local format International format
-
- Country Positive Negative Positive Negative
-
- Country1 1.234,56 mk -1.234,56 mk FIM 1.234,56 FIM -1.234,56
- Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234
- Country3 fl. 1.234,56 fl. -1.234,56 NLG 1.234,56 NLG -1.234,56
- Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C
-10 For these four countries, the respective values for the monetary members of the structure returned by
- localeconv could be:
- Country1 Country2 Country3 Country4
-
- mon_decimal_point "," "" "," "."
- mon_thousands_sep "." "." "." ","
- mon_grouping "\3" "\3" "\3" "\3"
- positive_sign "" "" "" ""
- negative_sign "-" "-" "-" "C"
- currency_symbol "mk" "L." "\u0192" "SFrs."
- frac_digits 2 0 2 2
- p_cs_precedes 0 1 1 1
- n_cs_precedes 0 1 1 1
- p_sep_by_space 1 0 1 0
- n_sep_by_space 1 0 2 0
- p_sign_posn 1 1 1 1
- n_sign_posn 1 1 4 2
- int_curr_symbol "FIM " "ITL " "NLG " "CHF "
- int_frac_digits 2 0 2 2
- int_p_cs_precedes 1 1 1 1
- int_n_cs_precedes 1 1 1 1
- int_p_sep_by_space 1 1 1 1
- int_n_sep_by_space 2 1 2 1
- int_p_sign_posn 1 1 1 1
- int_n_sign_posn 4 1 4 2
-
-
-
-
-[page 227]
-
-11 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
- affect the formatted value.
- p_sep_by_space
-
- p_cs_precedes p_sign_posn 0 1 2
-
- 0 0 (1.25$) (1.25 $) (1.25$)
- 1 +1.25$ +1.25 $ + 1.25$
- 2 1.25$+ 1.25 $+ 1.25$ +
- 3 1.25+$ 1.25 +$ 1.25+ $
- 4 1.25$+ 1.25 $+ 1.25$ +
-
- 1 0 ($1.25) ($ 1.25) ($1.25)
- 1 +$1.25 +$ 1.25 + $1.25
- 2 $1.25+ $ 1.25+ $1.25 +
- 3 +$1.25 +$ 1.25 + $1.25
- 4 $+1.25 $+ 1.25 $ +1.25
-
-
-
-
-[page 228]
-
- 7.12 Mathematics <math.h>
-1 The header <math.h> declares two types and many mathematical functions and defines
- several macros. Most synopses specify a family of functions consisting of a principal
- function with one or more double parameters, a double return value, or both; and
- other functions with the same name but with f and l suffixes, which are corresponding
- functions with float and long double parameters, return values, or both.221)
- Integer arithmetic functions and conversion functions are discussed later.
-2 The types
- float_t
- double_t
- are floating types at least as wide as float and double, respectively, and such that
- double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
- float_t and double_t are float and double, respectively; if
- FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
- 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
- otherwise implementation-defined.222)
-3 The macro
- HUGE_VAL
- expands to a positive double constant expression, not necessarily representable as a
- float. The macros
- HUGE_VALF
- HUGE_VALL
- are respectively float and long double analogs of HUGE_VAL.223)
-4 The macro
- INFINITY
- expands to a constant expression of type float representing positive or unsigned
- infinity, if available; else to a positive constant of type float that overflows at
-
-
-
- 221) Particularly on systems with wide expression evaluation, a <math.h> function might pass arguments
- and return values in wider format than the synopsis prototype indicates.
- 222) The types float_t and double_t are intended to be the implementation's most efficient types at
- least as wide as float and double, respectively. For FLT_EVAL_METHOD equal 0, 1, or 2, the
- type float_t is the narrowest type used by the implementation to evaluate floating expressions.
- 223) HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
- supports infinities.
-
-[page 229]
-
- translation time.224)
-5 The macro
- NAN
- is defined if and only if the implementation supports quiet NaNs for the float type. It
- expands to a constant expression of type float representing a quiet NaN.
-6 The number classification macros
- FP_INFINITE
- FP_NAN
- FP_NORMAL
- FP_SUBNORMAL
- FP_ZERO
- represent the mutually exclusive kinds of floating-point values. They expand to integer
- constant expressions with distinct values. Additional implementation-defined floating-
- point classifications, with macro definitions beginning with FP_ and an uppercase letter,
- may also be specified by the implementation.
-7 The macro
- FP_FAST_FMA
- is optionally defined. If defined, it indicates that the fma function generally executes
- about as fast as, or faster than, a multiply and an add of double operands.225) The
- macros
- FP_FAST_FMAF
- FP_FAST_FMAL
- are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
- these macros expand to the integer constant 1.
-8 The macros
- FP_ILOGB0
- FP_ILOGBNAN
- expand to integer constant expressions whose values are returned by ilogb(x) if x is
- zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
- -INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
-
-
- 224) In this case, using INFINITY will violate the constraint in 6.4.4 and thus require a diagnostic.
- 225) Typically, the FP_FAST_FMA macro is defined if and only if the fma function is implemented
- directly with a hardware multiply-add instruction. Software implementations are expected to be
- substantially slower.
-
-[page 230]
-
-9 The macros
- MATH_ERRNO
- MATH_ERREXCEPT
- expand to the integer constants 1 and 2, respectively; the macro
- math_errhandling
- expands to an expression that has type int and the value MATH_ERRNO,
- MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is
- constant for the duration of the program. It is unspecified whether
- math_errhandling is a macro or an identifier with external linkage. If a macro
- definition is suppressed or a program defines an identifier with the name
- math_errhandling, the behavior is undefined. If the expression
- math_errhandling & MATH_ERREXCEPT can be nonzero, the implementation
- shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in
- <fenv.h>.
- 7.12.1 Treatment of error conditions
-1 The behavior of each of the functions in <math.h> is specified for all representable
- values of its input arguments, except where stated otherwise. Each function shall execute
- as if it were a single operation without raising SIGFPE and without generating any of the
- exceptions ''invalid'', ''divide-by-zero'', or ''overflow'' except to reflect the result of the
- function.
-2 For all functions, a domain error occurs if an input argument is outside the domain over
- which the mathematical function is defined. The description of each function lists any
- required domain errors; an implementation may define additional domain errors, provided
- that such errors are consistent with the mathematical definition of the function.226) On a
- domain error, the function returns an implementation-defined value; if the integer
- expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
- errno acquires the value EDOM; if the integer expression math_errhandling &
- MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised.
-3 Similarly, a pole error (also known as a singularity or infinitary) occurs if the
- mathematical function has an exact infinite result as the finite input argument(s) are
- approached in the limit (for example, log(0.0)). The description of each function lists
- any required pole errors; an implementation may define additional pole errors, provided
- that such errors are consistent with the mathematical definition of the function. On a pole
- error, the function returns an implementation-defined value; if the integer expression
-
-
- 226) In an implementation that supports infinities, this allows an infinity as an argument to be a domain
- error if the mathematical domain of the function does not include the infinity.
-
-[page 231]
-
- math_errhandling & MATH_ERRNO is nonzero, the integer expression errno
- acquires the value ERANGE; if the integer expression math_errhandling &
- MATH_ERREXCEPT is nonzero, the ''divide-by-zero'' floating-point exception is raised.
-4 Likewise, a range error occurs if the mathematical result of the function cannot be
- represented in an object of the specified type, due to extreme magnitude.
-5 A floating result overflows if the magnitude of the mathematical result is finite but so
- large that the mathematical result cannot be represented without extraordinary roundoff
- error in an object of the specified type. If a floating result overflows and default rounding
- is in effect, then the function returns the value of the macro HUGE_VAL, HUGE_VALF, or
- HUGE_VALL according to the return type, with the same sign as the correct value of the
- function; if the integer expression math_errhandling & MATH_ERRNO is nonzero,
- the integer expression errno acquires the value ERANGE; if the integer expression
- math_errhandling & MATH_ERREXCEPT is nonzero, the ''overflow'' floating-
- point exception is raised.
-6 The result underflows if the magnitude of the mathematical result is so small that the
- mathematical result cannot be represented, without extraordinary roundoff error, in an
- object of the specified type.227) If the result underflows, the function returns an
- implementation-defined value whose magnitude is no greater than the smallest
- normalized positive number in the specified type; if the integer expression
- math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the
- value ERANGE is implementation-defined; if the integer expression
- math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow''
- floating-point exception is raised is implementation-defined.
-7 If a domain, pole, or range error occurs and the integer expression
- math_errhandling & MATH_ERRNO is zero,228) then errno shall either be set to
- the value corresponding to the error or left unmodified. If no such error occurs, errno
- shall be left unmodified regardless of the setting of math_errhandling.
-
-
-
-
- 227) The term underflow here is intended to encompass both ''gradual underflow'' as in IEC 60559 and
- also ''flush-to-zero'' underflow.
- 228) Math errors are being indicated by the floating-point exception flags rather than by errno.
-
-[page 232]
-
- 7.12.2 The FP_CONTRACT pragma
- Synopsis
-1 #include <math.h>
- #pragma STDC FP_CONTRACT on-off-switch
- Description
-2 The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
- state is ''off'') the implementation to contract expressions (6.5). Each pragma can occur
- either outside external declarations or preceding all explicit declarations and statements
- inside a compound statement. When outside external declarations, the pragma takes
- effect from its occurrence until another FP_CONTRACT pragma is encountered, or until
- the end of the translation unit. When inside a compound statement, the pragma takes
- effect from its occurrence until another FP_CONTRACT pragma is encountered
- (including within a nested compound statement), or until the end of the compound
- statement; at the end of a compound statement the state for the pragma is restored to its
- condition just before the compound statement. If this pragma is used in any other
- context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
- implementation-defined.
- 7.12.3 Classification macros
-1 In the synopses in this subclause, real-floating indicates that the argument shall be an
- expression of real floating type.
- 7.12.3.1 The fpclassify macro
- Synopsis
-1 #include <math.h>
- int fpclassify(real-floating x);
- Description
-2 The fpclassify macro classifies its argument value as NaN, infinite, normal,
- subnormal, zero, or into another implementation-defined category. First, an argument
- represented in a format wider than its semantic type is converted to its semantic type.
- Then classification is based on the type of the argument.229)
- Returns
-3 The fpclassify macro returns the value of the number classification macro
- appropriate to the value of its argument.
-
-
- 229) Since an expression can be evaluated with more range and precision than its type has, it is important to
- know the type that classification is based on. For example, a normal long double value might
- become subnormal when converted to double, and zero when converted to float.
-
-[page 233]
-
- 7.12.3.2 The isfinite macro
- Synopsis
-1 #include <math.h>
- int isfinite(real-floating x);
- Description
-2 The isfinite macro determines whether its argument has a finite value (zero,
- subnormal, or normal, and not infinite or NaN). First, an argument represented in a
- format wider than its semantic type is converted to its semantic type. Then determination
- is based on the type of the argument.
- Returns
-3 The isfinite macro returns a nonzero value if and only if its argument has a finite
- value.
- 7.12.3.3 The isinf macro
- Synopsis
-1 #include <math.h>
- int isinf(real-floating x);
- Description
-2 The isinf macro determines whether its argument value is an infinity (positive or
- negative). First, an argument represented in a format wider than its semantic type is
- converted to its semantic type. Then determination is based on the type of the argument.
- Returns
-3 The isinf macro returns a nonzero value if and only if its argument has an infinite
- value.
- 7.12.3.4 The isnan macro
- Synopsis
-1 #include <math.h>
- int isnan(real-floating x);
- Description
-2 The isnan macro determines whether its argument value is a NaN. First, an argument
- represented in a format wider than its semantic type is converted to its semantic type.
- Then determination is based on the type of the argument.230)
-
-
- 230) For the isnan macro, the type for determination does not matter unless the implementation supports
- NaNs in the evaluation type but not in the semantic type.
-
-[page 234]
-
- Returns
-3 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
- 7.12.3.5 The isnormal macro
- Synopsis
-1 #include <math.h>
- int isnormal(real-floating x);
- Description
-2 The isnormal macro determines whether its argument value is normal (neither zero,
- subnormal, infinite, nor NaN). First, an argument represented in a format wider than its
- semantic type is converted to its semantic type. Then determination is based on the type
- of the argument.
- Returns
-3 The isnormal macro returns a nonzero value if and only if its argument has a normal
- value.
- 7.12.3.6 The signbit macro
- Synopsis
-1 #include <math.h>
- int signbit(real-floating x);
- Description
-2 The signbit macro determines whether the sign of its argument value is negative.231)
- Returns
-3 The signbit macro returns a nonzero value if and only if the sign of its argument value
- is negative.
-
-
-
-
- 231) The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is
- unsigned, it is treated as positive.
-
-[page 235]
-
- 7.12.4 Trigonometric functions
- 7.12.4.1 The acos functions
- Synopsis
-1 #include <math.h>
- double acos(double x);
- float acosf(float x);
- long double acosl(long double x);
- Description
-2 The acos functions compute the principal value of the arc cosine of x. A domain error
- occurs for arguments not in the interval [-1, +1].
- Returns
-3 The acos functions return arccos x in the interval [0, pi ] radians.
- 7.12.4.2 The asin functions
- Synopsis
-1 #include <math.h>
- double asin(double x);
- float asinf(float x);
- long double asinl(long double x);
- Description
-2 The asin functions compute the principal value of the arc sine of x. A domain error
- occurs for arguments not in the interval [-1, +1].
- Returns
-3 The asin functions return arcsin x in the interval [-pi /2, +pi /2] radians.
- 7.12.4.3 The atan functions
- Synopsis
-1 #include <math.h>
- double atan(double x);
- float atanf(float x);
- long double atanl(long double x);
- Description
-2 The atan functions compute the principal value of the arc tangent of x.
-
-
-
-
-[page 236]
-
- Returns
-3 The atan functions return arctan x in the interval [-pi /2, +pi /2] radians.
- 7.12.4.4 The atan2 functions
- Synopsis
-1 #include <math.h>
- double atan2(double y, double x);
- float atan2f(float y, float x);
- long double atan2l(long double y, long double x);
- Description
-2 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
- arguments to determine the quadrant of the return value. A domain error may occur if
- both arguments are zero.
- Returns
-3 The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
- 7.12.4.5 The cos functions
- Synopsis
-1 #include <math.h>
- double cos(double x);
- float cosf(float x);
- long double cosl(long double x);
- Description
-2 The cos functions compute the cosine of x (measured in radians).
- Returns
-3 The cos functions return cos x.
- 7.12.4.6 The sin functions
- Synopsis
-1 #include <math.h>
- double sin(double x);
- float sinf(float x);
- long double sinl(long double x);
- Description
-2 The sin functions compute the sine of x (measured in radians).
-
-
-
-[page 237]
-
- Returns
-3 The sin functions return sin x.
- 7.12.4.7 The tan functions
- Synopsis
-1 #include <math.h>
- double tan(double x);
- float tanf(float x);
- long double tanl(long double x);
- Description
-2 The tan functions return the tangent of x (measured in radians).
- Returns
-3 The tan functions return tan x.
- 7.12.5 Hyperbolic functions
- 7.12.5.1 The acosh functions
- Synopsis
-1 #include <math.h>
- double acosh(double x);
- float acoshf(float x);
- long double acoshl(long double x);
- Description
-2 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
- error occurs for arguments less than 1.
- Returns
-3 The acosh functions return arcosh x in the interval [0, +(inf)].
- 7.12.5.2 The asinh functions
- Synopsis
-1 #include <math.h>
- double asinh(double x);
- float asinhf(float x);
- long double asinhl(long double x);
- Description
-2 The asinh functions compute the arc hyperbolic sine of x.
-
-
-[page 238]
-
- Returns
-3 The asinh functions return arsinh x.
- 7.12.5.3 The atanh functions
- Synopsis
-1 #include <math.h>
- double atanh(double x);
- float atanhf(float x);
- long double atanhl(long double x);
- Description
-2 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
- for arguments not in the interval [-1, +1]. A pole error may occur if the argument equals
- -1 or +1.
- Returns
-3 The atanh functions return artanh x.
- 7.12.5.4 The cosh functions
- Synopsis
-1 #include <math.h>
- double cosh(double x);
- float coshf(float x);
- long double coshl(long double x);
- Description
-2 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
- magnitude of x is too large.
- Returns
-3 The cosh functions return cosh x.
- 7.12.5.5 The sinh functions
- Synopsis
-1 #include <math.h>
- double sinh(double x);
- float sinhf(float x);
- long double sinhl(long double x);
- Description
-2 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
- magnitude of x is too large.
-[page 239]
-
- Returns
-3 The sinh functions return sinh x.
- 7.12.5.6 The tanh functions
- Synopsis
-1 #include <math.h>
- double tanh(double x);
- float tanhf(float x);
- long double tanhl(long double x);
- Description
-2 The tanh functions compute the hyperbolic tangent of x.
- Returns
-3 The tanh functions return tanh x.
- 7.12.6 Exponential and logarithmic functions
- 7.12.6.1 The exp functions
- Synopsis
-1 #include <math.h>
- double exp(double x);
- float expf(float x);
- long double expl(long double x);
- Description
-2 The exp functions compute the base-e exponential of x. A range error occurs if the
- magnitude of x is too large.
- Returns
-3 The exp functions return ex .
- 7.12.6.2 The exp2 functions
- Synopsis
-1 #include <math.h>
- double exp2(double x);
- float exp2f(float x);
- long double exp2l(long double x);
- Description
-2 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
- magnitude of x is too large.
-
-[page 240]
-
- Returns
-3 The exp2 functions return 2x .
- 7.12.6.3 The expm1 functions
- Synopsis
-1 #include <math.h>
- double expm1(double x);
- float expm1f(float x);
- long double expm1l(long double x);
- Description
-2 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
- error occurs if x is too large.232)
- Returns
-3 The expm1 functions return ex - 1.
- 7.12.6.4 The frexp functions
- Synopsis
-1 #include <math.h>
- double frexp(double value, int *exp);
- float frexpf(float value, int *exp);
- long double frexpl(long double value, int *exp);
- Description
-2 The frexp functions break a floating-point number into a normalized fraction and an
- integral power of 2. They store the integer in the int object pointed to by exp.
- Returns
-3 If value is not a floating-point number or if the integral power of 2 is outside the range
- of int, the results are unspecified. Otherwise, the frexp functions return the value x,
- such that x has a magnitude in the interval [1/2, 1) or zero, and value equals x x 2*exp .
- If value is zero, both parts of the result are zero.
-
-
-
-
- 232) For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1.
-
-[page 241]
-
- 7.12.6.5 The ilogb functions
- Synopsis
-1 #include <math.h>
- int ilogb(double x);
- int ilogbf(float x);
- int ilogbl(long double x);
- Description
-2 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
- compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
- a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
- the corresponding logb function and casting the returned value to type int. A domain
- error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
- the range of the return type, the numeric result is unspecified.
- Returns
-3 The ilogb functions return the exponent of x as a signed int value.
- Forward references: the logb functions (7.12.6.11).
- 7.12.6.6 The ldexp functions
- Synopsis
-1 #include <math.h>
- double ldexp(double x, int exp);
- float ldexpf(float x, int exp);
- long double ldexpl(long double x, int exp);
- Description
-2 The ldexp functions multiply a floating-point number by an integral power of 2. A
- range error may occur.
- Returns
-3 The ldexp functions return x x 2exp .
- 7.12.6.7 The log functions
- Synopsis
-1 #include <math.h>
- double log(double x);
- float logf(float x);
- long double logl(long double x);
-
-
-
-[page 242]
-
- Description
-2 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
- the argument is negative. A pole error may occur if the argument is zero.
- Returns
-3 The log functions return loge x.
- 7.12.6.8 The log10 functions
- Synopsis
-1 #include <math.h>
- double log10(double x);
- float log10f(float x);
- long double log10l(long double x);
- Description
-2 The log10 functions compute the base-10 (common) logarithm of x. A domain error
- occurs if the argument is negative. A pole error may occur if the argument is zero.
- Returns
-3 The log10 functions return log10 x.
- 7.12.6.9 The log1p functions
- Synopsis
-1 #include <math.h>
- double log1p(double x);
- float log1pf(float x);
- long double log1pl(long double x);
- Description
-2 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.233)
- A domain error occurs if the argument is less than -1. A pole error may occur if the
- argument equals -1.
- Returns
-3 The log1p functions return loge (1 + x).
-
-
-
-
- 233) For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x).
-
-[page 243]
-
- 7.12.6.10 The log2 functions
- Synopsis
-1 #include <math.h>
- double log2(double x);
- float log2f(float x);
- long double log2l(long double x);
- Description
-2 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
- argument is less than zero. A pole error may occur if the argument is zero.
- Returns
-3 The log2 functions return log2 x.
- 7.12.6.11 The logb functions
- Synopsis
-1 #include <math.h>
- double logb(double x);
- float logbf(float x);
- long double logbl(long double x);
- Description
-2 The logb functions extract the exponent of x, as a signed integer value in floating-point
- format. If x is subnormal it is treated as though it were normalized; thus, for positive
- finite x,
- 1 <= x x FLT_RADIX-logb(x) < FLT_RADIX
- A domain error or pole error may occur if the argument is zero.
- Returns
-3 The logb functions return the signed exponent of x.
- 7.12.6.12 The modf functions
- Synopsis
-1 #include <math.h>
- double modf(double value, double *iptr);
- float modff(float value, float *iptr);
- long double modfl(long double value, long double *iptr);
- Description
-2 The modf functions break the argument value into integral and fractional parts, each of
- which has the same type and sign as the argument. They store the integral part (in
-[page 244]
-
- floating-point format) in the object pointed to by iptr.
- Returns
-3 The modf functions return the signed fractional part of value.
- 7.12.6.13 The scalbn and scalbln functions
- Synopsis
-1 #include <math.h>
- double scalbn(double x, int n);
- float scalbnf(float x, int n);
- long double scalbnl(long double x, int n);
- double scalbln(double x, long int n);
- float scalblnf(float x, long int n);
- long double scalblnl(long double x, long int n);
- Description
-2 The scalbn and scalbln functions compute x x FLT_RADIXn efficiently, not
- normally by computing FLT_RADIXn explicitly. A range error may occur.
- Returns
-3 The scalbn and scalbln functions return x x FLT_RADIXn .
- 7.12.7 Power and absolute-value functions
- 7.12.7.1 The cbrt functions
- Synopsis
-1 #include <math.h>
- double cbrt(double x);
- float cbrtf(float x);
- long double cbrtl(long double x);
- Description
-2 The cbrt functions compute the real cube root of x.
- Returns
-3 The cbrt functions return x1/3 .
-
-
-
-
-[page 245]
-
- 7.12.7.2 The fabs functions
- Synopsis
-1 #include <math.h>
- double fabs(double x);
- float fabsf(float x);
- long double fabsl(long double x);
- Description
-2 The fabs functions compute the absolute value of a floating-point number x.
- Returns
-3 The fabs functions return | x |.
- 7.12.7.3 The hypot functions
- Synopsis
-1 #include <math.h>
- double hypot(double x, double y);
- float hypotf(float x, float y);
- long double hypotl(long double x, long double y);
- Description
-2 The hypot functions compute the square root of the sum of the squares of x and y,
- without undue overflow or underflow. A range error may occur.
-3 Returns
-4 The hypot functions return sqrt:x2 + y2 .
- -
- -----
- 7.12.7.4 The pow functions
- Synopsis
-1 #include <math.h>
- double pow(double x, double y);
- float powf(float x, float y);
- long double powl(long double x, long double y);
- Description
-2 The pow functions compute x raised to the power y. A domain error occurs if x is finite
- and negative and y is finite and not an integer value. A range error may occur. A domain
- error may occur if x is zero and y is zero. A domain error or pole error may occur if x is
- zero and y is less than zero.
-
-
-
-
-[page 246]
-
- Returns
-3 The pow functions return xy .
- 7.12.7.5 The sqrt functions
- Synopsis
-1 #include <math.h>
- double sqrt(double x);
- float sqrtf(float x);
- long double sqrtl(long double x);
- Description
-2 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
- the argument is less than zero.
- Returns
-3 The sqrt functions return sqrt:x.
- -
- -
- 7.12.8 Error and gamma functions
- 7.12.8.1 The erf functions
- Synopsis
-1 #include <math.h>
- double erf(double x);
- float erff(float x);
- long double erfl(long double x);
- Description
-2 The erf functions compute the error function of x.
- Returns
-3 2 x
- (integral) e-t dt.
- 2
- The erf functions return erf x =
- sqrt:pi
- -
- - 0
-
- 7.12.8.2 The erfc functions
- Synopsis
-1 #include <math.h>
- double erfc(double x);
- float erfcf(float x);
- long double erfcl(long double x);
- Description
-2 The erfc functions compute the complementary error function of x. A range error
- occurs if x is too large.
-[page 247]
-
- Returns
-3 2 (inf)
- (integral) e-t dt.
- 2
- The erfc functions return erfc x = 1 - erf x =
- sqrt:pi
- -
- - x
-
- 7.12.8.3 The lgamma functions
- Synopsis
-1 #include <math.h>
- double lgamma(double x);
- float lgammaf(float x);
- long double lgammal(long double x);
- Description
-2 The lgamma functions compute the natural logarithm of the absolute value of gamma of
- x. A range error occurs if x is too large. A pole error may occur if x is a negative integer
- or zero.
- Returns
-3 The lgamma functions return loge | (Gamma)(x) |.
- 7.12.8.4 The tgamma functions
- Synopsis
-1 #include <math.h>
- double tgamma(double x);
- float tgammaf(float x);
- long double tgammal(long double x);
- Description
-2 The tgamma functions compute the gamma function of x. A domain error or pole error
- may occur if x is a negative integer or zero. A range error occurs if the magnitude of x is
- too large and may occur if the magnitude of x is too small.
- Returns
-3 The tgamma functions return (Gamma)(x).
-
-
-
-
-[page 248]
-
- 7.12.9 Nearest integer functions
- 7.12.9.1 The ceil functions
- Synopsis
-1 #include <math.h>
- double ceil(double x);
- float ceilf(float x);
- long double ceill(long double x);
- Description
-2 The ceil functions compute the smallest integer value not less than x.
- Returns
-3 The ceil functions return [^x^], expressed as a floating-point number.
- 7.12.9.2 The floor functions
- Synopsis
-1 #include <math.h>
- double floor(double x);
- float floorf(float x);
- long double floorl(long double x);
- Description
-2 The floor functions compute the largest integer value not greater than x.
- Returns
-3 The floor functions return [_x_], expressed as a floating-point number.
- 7.12.9.3 The nearbyint functions
- Synopsis
-1 #include <math.h>
- double nearbyint(double x);
- float nearbyintf(float x);
- long double nearbyintl(long double x);
- Description
-2 The nearbyint functions round their argument to an integer value in floating-point
- format, using the current rounding direction and without raising the ''inexact'' floating-
- point exception.
-
-
-
-
-[page 249]
-
- Returns
-3 The nearbyint functions return the rounded integer value.
- 7.12.9.4 The rint functions
- Synopsis
-1 #include <math.h>
- double rint(double x);
- float rintf(float x);
- long double rintl(long double x);
- Description
-2 The rint functions differ from the nearbyint functions (7.12.9.3) only in that the
- rint functions may raise the ''inexact'' floating-point exception if the result differs in
- value from the argument.
- Returns
-3 The rint functions return the rounded integer value.
- 7.12.9.5 The lrint and llrint functions
- Synopsis
-1 #include <math.h>
- long int lrint(double x);
- long int lrintf(float x);
- long int lrintl(long double x);
- long long int llrint(double x);
- long long int llrintf(float x);
- long long int llrintl(long double x);
- Description
-2 The lrint and llrint functions round their argument to the nearest integer value,
- rounding according to the current rounding direction. If the rounded value is outside the
- range of the return type, the numeric result is unspecified and a domain error or range
- error may occur.
- Returns
-3 The lrint and llrint functions return the rounded integer value.
-
-
-
-
-[page 250]
-
- 7.12.9.6 The round functions
- Synopsis
-1 #include <math.h>
- double round(double x);
- float roundf(float x);
- long double roundl(long double x);
- Description
-2 The round functions round their argument to the nearest integer value in floating-point
- format, rounding halfway cases away from zero, regardless of the current rounding
- direction.
- Returns
-3 The round functions return the rounded integer value.
- 7.12.9.7 The lround and llround functions
- Synopsis
-1 #include <math.h>
- long int lround(double x);
- long int lroundf(float x);
- long int lroundl(long double x);
- long long int llround(double x);
- long long int llroundf(float x);
- long long int llroundl(long double x);
- Description
-2 The lround and llround functions round their argument to the nearest integer value,
- rounding halfway cases away from zero, regardless of the current rounding direction. If
- the rounded value is outside the range of the return type, the numeric result is unspecified
- and a domain error or range error may occur.
- Returns
-3 The lround and llround functions return the rounded integer value.
- 7.12.9.8 The trunc functions
- Synopsis
-1 #include <math.h>
- double trunc(double x);
- float truncf(float x);
- long double truncl(long double x);
-
-
-[page 251]
-
- Description
-2 The trunc functions round their argument to the integer value, in floating format,
- nearest to but no larger in magnitude than the argument.
- Returns
-3 The trunc functions return the truncated integer value.
- 7.12.10 Remainder functions
- 7.12.10.1 The fmod functions
- Synopsis
-1 #include <math.h>
- double fmod(double x, double y);
- float fmodf(float x, float y);
- long double fmodl(long double x, long double y);
- Description
-2 The fmod functions compute the floating-point remainder of x/y.
- Returns
-3 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
- the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
- whether a domain error occurs or the fmod functions return zero is implementation-
- defined.
- 7.12.10.2 The remainder functions
- Synopsis
-1 #include <math.h>
- double remainder(double x, double y);
- float remainderf(float x, float y);
- long double remainderl(long double x, long double y);
- Description
-2 The remainder functions compute the remainder x REM y required by IEC 60559.234)
-
-
-
-
- 234) ''When y != 0, the remainder r = x REM y is defined regardless of the rounding mode by the
- mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever
- | n - x/y | = 1/2, then n is even. If r = 0, its sign shall be that of x.'' This definition is applicable for
- all implementations.
-
-[page 252]
-
- Returns
-3 The remainder functions return x REM y. If y is zero, whether a domain error occurs
- or the functions return zero is implementation defined.
- 7.12.10.3 The remquo functions
- Synopsis
-1 #include <math.h>
- double remquo(double x, double y, int *quo);
- float remquof(float x, float y, int *quo);
- long double remquol(long double x, long double y,
- int *quo);
- Description
-2 The remquo functions compute the same remainder as the remainder functions. In
- the object pointed to by quo they store a value whose sign is the sign of x/y and whose
- magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where
- n is an implementation-defined integer greater than or equal to 3.
- Returns
-3 The remquo functions return x REM y. If y is zero, the value stored in the object
- pointed to by quo is unspecified and whether a domain error occurs or the functions
- return zero is implementation defined.
- 7.12.11 Manipulation functions
- 7.12.11.1 The copysign functions
- Synopsis
-1 #include <math.h>
- double copysign(double x, double y);
- float copysignf(float x, float y);
- long double copysignl(long double x, long double y);
- Description
-2 The copysign functions produce a value with the magnitude of x and the sign of y.
- They produce a NaN (with the sign of y) if x is a NaN. On implementations that
- represent a signed zero but do not treat negative zero consistently in arithmetic
- operations, the copysign functions regard the sign of zero as positive.
- Returns
-3 The copysign functions return a value with the magnitude of x and the sign of y.
-
-
-
-[page 253]
-
- 7.12.11.2 The nan functions
- Synopsis
-1 #include <math.h>
- double nan(const char *tagp);
- float nanf(const char *tagp);
- long double nanl(const char *tagp);
- Description
-2 The call nan("n-char-sequence") is equivalent to strtod("NAN(n-char-
- sequence)", (char**) NULL); the call nan("") is equivalent to
- strtod("NAN()", (char**) NULL). If tagp does not point to an n-char
- sequence or an empty string, the call is equivalent to strtod("NAN", (char**)
- NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof
- and strtold.
- Returns
-3 The nan functions return a quiet NaN, if available, with content indicated through tagp.
- If the implementation does not support quiet NaNs, the functions return zero.
- Forward references: the strtod, strtof, and strtold functions (7.22.1.3).
- 7.12.11.3 The nextafter functions
- Synopsis
-1 #include <math.h>
- double nextafter(double x, double y);
- float nextafterf(float x, float y);
- long double nextafterl(long double x, long double y);
- Description
-2 The nextafter functions determine the next representable value, in the type of the
- function, after x in the direction of y, where x and y are first converted to the type of the
- function.235) The nextafter functions return y if x equals y. A range error may occur
- if the magnitude of x is the largest finite value representable in the type and the result is
- infinite or not representable in the type.
- Returns
-3 The nextafter functions return the next representable value in the specified format
- after x in the direction of y.
-
-
- 235) The argument values are converted to the type of the function, even by a macro implementation of the
- function.
-
-[page 254]
-
- 7.12.11.4 The nexttoward functions
- Synopsis
-1 #include <math.h>
- double nexttoward(double x, long double y);
- float nexttowardf(float x, long double y);
- long double nexttowardl(long double x, long double y);
- Description
-2 The nexttoward functions are equivalent to the nextafter functions except that the
- second parameter has type long double and the functions return y converted to the
- type of the function if x equals y.236)
- 7.12.12 Maximum, minimum, and positive difference functions
- 7.12.12.1 The fdim functions
- Synopsis
-1 #include <math.h>
- double fdim(double x, double y);
- float fdimf(float x, float y);
- long double fdiml(long double x, long double y);
- Description
-2 The fdim functions determine the positive difference between their arguments:
- {x - y if x > y
- {
- {+0 if x <= y
- A range error may occur.
- Returns
-3 The fdim functions return the positive difference value.
- 7.12.12.2 The fmax functions
- Synopsis
-1 #include <math.h>
- double fmax(double x, double y);
- float fmaxf(float x, float y);
- long double fmaxl(long double x, long double y);
-
-
-
- 236) The result of the nexttoward functions is determined in the type of the function, without loss of
- range or precision in a floating second argument.
-
-[page 255]
-
- Description
-2 The fmax functions determine the maximum numeric value of their arguments.237)
- Returns
-3 The fmax functions return the maximum numeric value of their arguments.
- 7.12.12.3 The fmin functions
- Synopsis
-1 #include <math.h>
- double fmin(double x, double y);
- float fminf(float x, float y);
- long double fminl(long double x, long double y);
- Description
-2 The fmin functions determine the minimum numeric value of their arguments.238)
- Returns
-3 The fmin functions return the minimum numeric value of their arguments.
- 7.12.13 Floating multiply-add
- 7.12.13.1 The fma functions
- Synopsis
-1 #include <math.h>
- double fma(double x, double y, double z);
- float fmaf(float x, float y, float z);
- long double fmal(long double x, long double y,
- long double z);
- Description
-2 The fma functions compute (x x y) + z, rounded as one ternary operation: they compute
- the value (as if) to infinite precision and round once to the result format, according to the
- current rounding mode. A range error may occur.
- Returns
-3 The fma functions return (x x y) + z, rounded as one ternary operation.
-
-
-
-
- 237) NaN arguments are treated as missing data: if one argument is a NaN and the other numeric, then the
- fmax functions choose the numeric value. See F.10.9.2.
- 238) The fmin functions are analogous to the fmax functions in their treatment of NaNs.
-
-[page 256]
-
- 7.12.14 Comparison macros
-1 The relational and equality operators support the usual mathematical relationships
- between numeric values. For any ordered pair of numeric values exactly one of the
- relationships -- less, greater, and equal -- is true. Relational operators may raise the
- ''invalid'' floating-point exception when argument values are NaNs. For a NaN and a
- numeric value, or for two NaNs, just the unordered relationship is true.239) The following
- subclauses provide macros that are quiet (non floating-point exception raising) versions
- of the relational operators, and other comparison macros that facilitate writing efficient
- code that accounts for NaNs without suffering the ''invalid'' floating-point exception. In
- the synopses in this subclause, real-floating indicates that the argument shall be an
- expression of real floating type (both arguments need not have the same type).240)
- 7.12.14.1 The isgreater macro
- Synopsis
-1 #include <math.h>
- int isgreater(real-floating x, real-floating y);
- Description
-2 The isgreater macro determines whether its first argument is greater than its second
- argument. The value of isgreater(x, y) is always equal to (x) > (y); however,
- unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point
- exception when x and y are unordered.
- Returns
-3 The isgreater macro returns the value of (x) > (y).
- 7.12.14.2 The isgreaterequal macro
- Synopsis
-1 #include <math.h>
- int isgreaterequal(real-floating x, real-floating y);
- Description
-2 The isgreaterequal macro determines whether its first argument is greater than or
- equal to its second argument. The value of isgreaterequal(x, y) is always equal
- to (x) >= (y); however, unlike (x) >= (y), isgreaterequal(x, y) does
-
-
- 239) IEC 60559 requires that the built-in relational operators raise the ''invalid'' floating-point exception if
- the operands compare unordered, as an error indicator for programs written without consideration of
- NaNs; the result in these cases is false.
- 240) Whether an argument represented in a format wider than its semantic type is converted to the semantic
- type is unspecified.
-
-[page 257]
-
- not raise the ''invalid'' floating-point exception when x and y are unordered.
- Returns
-3 The isgreaterequal macro returns the value of (x) >= (y).
- 7.12.14.3 The isless macro
- Synopsis
-1 #include <math.h>
- int isless(real-floating x, real-floating y);
- Description
-2 The isless macro determines whether its first argument is less than its second
- argument. The value of isless(x, y) is always equal to (x) < (y); however,
- unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point
- exception when x and y are unordered.
- Returns
-3 The isless macro returns the value of (x) < (y).
- 7.12.14.4 The islessequal macro
- Synopsis
-1 #include <math.h>
- int islessequal(real-floating x, real-floating y);
- Description
-2 The islessequal macro determines whether its first argument is less than or equal to
- its second argument. The value of islessequal(x, y) is always equal to
- (x) <= (y); however, unlike (x) <= (y), islessequal(x, y) does not raise
- the ''invalid'' floating-point exception when x and y are unordered.
- Returns
-3 The islessequal macro returns the value of (x) <= (y).
- 7.12.14.5 The islessgreater macro
- Synopsis
-1 #include <math.h>
- int islessgreater(real-floating x, real-floating y);
- Description
-2 The islessgreater macro determines whether its first argument is less than or
- greater than its second argument. The islessgreater(x, y) macro is similar to
- (x) < (y) || (x) > (y); however, islessgreater(x, y) does not raise
-
-[page 258]
-
- the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x
- and y twice).
- Returns
-3 The islessgreater macro returns the value of (x) < (y) || (x) > (y).
- 7.12.14.6 The isunordered macro
- Synopsis
-1 #include <math.h>
- int isunordered(real-floating x, real-floating y);
- Description
-2 The isunordered macro determines whether its arguments are unordered.
- Returns
-3 The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
-
-
-
-
-[page 259]
-
- 7.13 Nonlocal jumps <setjmp.h>
-1 The header <setjmp.h> defines the macro setjmp, and declares one function and
- one type, for bypassing the normal function call and return discipline.241)
-2 The type declared is
- jmp_buf
- which is an array type suitable for holding the information needed to restore a calling
- environment. The environment of a call to the setjmp macro consists of information
- sufficient for a call to the longjmp function to return execution to the correct block and
- invocation of that block, were it called recursively. It does not include the state of the
- floating-point status flags, of open files, or of any other component of the abstract
- machine.
-3 It is unspecified whether setjmp is a macro or an identifier declared with external
- linkage. If a macro definition is suppressed in order to access an actual function, or a
- program defines an external identifier with the name setjmp, the behavior is undefined.
- 7.13.1 Save calling environment
- 7.13.1.1 The setjmp macro
- Synopsis
-1 #include <setjmp.h>
- int setjmp(jmp_buf env);
- Description
-2 The setjmp macro saves its calling environment in its jmp_buf argument for later use
- by the longjmp function.
- Returns
-3 If the return is from a direct invocation, the setjmp macro returns the value zero. If the
- return is from a call to the longjmp function, the setjmp macro returns a nonzero
- value.
- Environmental limits
-4 An invocation of the setjmp macro shall appear only in one of the following contexts:
- -- the entire controlling expression of a selection or iteration statement;
- -- one operand of a relational or equality operator with the other operand an integer
- constant expression, with the resulting expression being the entire controlling
-
-
- 241) These functions are useful for dealing with unusual conditions encountered in a low-level function of
- a program.
-
-[page 260]
-
- expression of a selection or iteration statement;
- -- the operand of a unary ! operator with the resulting expression being the entire
- controlling expression of a selection or iteration statement; or
- -- the entire expression of an expression statement (possibly cast to void).
-5 If the invocation appears in any other context, the behavior is undefined.
- 7.13.2 Restore calling environment
- 7.13.2.1 The longjmp function
- Synopsis
-1 #include <setjmp.h>
- _Noreturn void longjmp(jmp_buf env, int val);
- Description
-2 The longjmp function restores the environment saved by the most recent invocation of
- the setjmp macro in the same invocation of the program with the corresponding
- jmp_buf argument. If there has been no such invocation, or if the function containing
- the invocation of the setjmp macro has terminated execution242) in the interim, or if the
- invocation of the setjmp macro was within the scope of an identifier with variably
- modified type and execution has left that scope in the interim, the behavior is undefined.
-3 All accessible objects have values, and all other components of the abstract machine243)
- have state, as of the time the longjmp function was called, except that the values of
- objects of automatic storage duration that are local to the function containing the
- invocation of the corresponding setjmp macro that do not have volatile-qualified type
- and have been changed between the setjmp invocation and longjmp call are
- indeterminate.
- Returns
-4 After longjmp is completed, program execution continues as if the corresponding
- invocation of the setjmp macro had just returned the value specified by val. The
- longjmp function cannot cause the setjmp macro to return the value 0; if val is 0,
- the setjmp macro returns the value 1.
-5 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation
- might cause memory associated with a variable length array object to be squandered.
-
-
-
-
- 242) For example, by executing a return statement or because another longjmp call has caused a
- transfer to a setjmp invocation in a function earlier in the set of nested calls.
- 243) This includes, but is not limited to, the floating-point status flags and the state of open files.
-
-[page 261]
-
- #include <setjmp.h>
- jmp_buf buf;
- void g(int n);
- void h(int n);
- int n = 6;
- void f(void)
- {
- int x[n]; // valid: f is not terminated
- setjmp(buf);
- g(n);
- }
- void g(int n)
- {
- int a[n]; // a may remain allocated
- h(n);
- }
- void h(int n)
- {
- int b[n]; // b may remain allocated
- longjmp(buf, 2); // might cause memory loss
- }
-
-
-
-
-[page 262]
-
- 7.14 Signal handling <signal.h>
-1 The header <signal.h> declares a type and two functions and defines several macros,
- for handling various signals (conditions that may be reported during program execution).
-2 The type defined is
- sig_atomic_t
- which is the (possibly volatile-qualified) integer type of an object that can be accessed as
- an atomic entity, even in the presence of asynchronous interrupts.
-3 The macros defined are
- SIG_DFL
- SIG_ERR
- SIG_IGN
- which expand to constant expressions with distinct values that have type compatible with
- the second argument to, and the return value of, the signal function, and whose values
- compare unequal to the address of any declarable function; and the following, which
- expand to positive integer constant expressions with type int and distinct values that are
- the signal numbers, each corresponding to the specified condition:
- SIGABRT abnormal termination, such as is initiated by the abort function
- SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
- resulting in overflow
- SIGILL detection of an invalid function image, such as an invalid instruction
- SIGINT receipt of an interactive attention signal
- SIGSEGV an invalid access to storage
- SIGTERM a termination request sent to the program
-4 An implementation need not generate any of these signals, except as a result of explicit
- calls to the raise function. Additional signals and pointers to undeclarable functions,
- with macro definitions beginning, respectively, with the letters SIG and an uppercase
- letter or with SIG_ and an uppercase letter,244) may also be specified by the
- implementation. The complete set of signals, their semantics, and their default handling
- is implementation-defined; all signal numbers shall be positive.
-
-
-
-
- 244) See ''future library directions'' (7.30.6). The names of the signal numbers reflect the following terms
- (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
- and termination.
-
-[page 263]
-
- 7.14.1 Specify signal handling
- 7.14.1.1 The signal function
- Synopsis
-1 #include <signal.h>
- void (*signal(int sig, void (*func)(int)))(int);
- Description
-2 The signal function chooses one of three ways in which receipt of the signal number
- sig is to be subsequently handled. If the value of func is SIG_DFL, default handling
- for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored.
- Otherwise, func shall point to a function to be called when that signal occurs. An
- invocation of such a function because of a signal, or (recursively) of any further functions
- called by that invocation (other than functions in the standard library), is called a signal
- handler.
-3 When a signal occurs and func points to a function, it is implementation-defined
- whether the equivalent of signal(sig, SIG_DFL); is executed or the
- implementation prevents some implementation-defined set of signals (at least including
- sig) from occurring until the current signal handling has completed; in the case of
- SIGILL, the implementation may alternatively define that no action is taken. Then the
- equivalent of (*func)(sig); is executed. If and when the function returns, if the
- value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined
- value corresponding to a computational exception, the behavior is undefined; otherwise
- the program will resume execution at the point it was interrupted.
-4 If the signal occurs as the result of calling the abort or raise function, the signal
- handler shall not call the raise function.
-5 If the signal occurs other than as the result of calling the abort or raise function, the
- behavior is undefined if the signal handler refers to any object with static or thread
- storage duration other than by assigning a value to an object declared as volatile
- sig_atomic_t, or the signal handler calls any function in the standard library other
- than the abort function, the _Exit function, the quick_exit function, or the
- signal function with the first argument equal to the signal number corresponding to the
- signal that caused the invocation of the handler. Furthermore, if such a call to the
- signal function results in a SIG_ERR return, the value of errno is indeterminate.245)
-6 At program startup, the equivalent of
- signal(sig, SIG_IGN);
-
-
- 245) If any signal is generated by an asynchronous signal handler, the behavior is undefined.
-
-[page 264]
-
- may be executed for some signals selected in an implementation-defined manner; the
- equivalent of
- signal(sig, SIG_DFL);
- is executed for all other signals defined by the implementation.
-7 The implementation shall behave as if no library function calls the signal function.
- Returns
-8 If the request can be honored, the signal function returns the value of func for the
- most recent successful call to signal for the specified signal sig. Otherwise, a value of
- SIG_ERR is returned and a positive value is stored in errno.
- Forward references: the abort function (7.22.4.1), the exit function (7.22.4.4), the
- _Exit function (7.22.4.5), the quick_exit function (7.22.4.7).
- 7.14.2 Send signal
- 7.14.2.1 The raise function
- Synopsis
-1 #include <signal.h>
- int raise(int sig);
- Description
-2 The raise function carries out the actions described in 7.14.1.1 for the signal sig. If a
- signal handler is called, the raise function shall not return until after the signal handler
- does.
- Returns
-3 The raise function returns zero if successful, nonzero if unsuccessful.
-
-
-
-
-[page 265]
-
- 7.15 Alignment <stdalign.h>
-1 The header <stdalign.h> defines two macros.
-2 The macro
- alignas
- expands to _Alignas.
-3 The remaining macro is suitable for use in #if preprocessing directives. It is
- __alignas_is_defined
- which expands to the integer constant 1.
-
-
-
-
-[page 266]
-
- 7.16 Variable arguments <stdarg.h>
-1 The header <stdarg.h> declares a type and defines four macros, for advancing
- through a list of arguments whose number and types are not known to the called function
- when it is translated.
-2 A function may be called with a variable number of arguments of varying types. As
- described in 6.9.1, its parameter list contains one or more parameters. The rightmost
- parameter plays a special role in the access mechanism, and will be designated parmN in
- this description.
-3 The type declared is
- va_list
- which is a complete object type suitable for holding information needed by the macros
- va_start, va_arg, va_end, and va_copy. If access to the varying arguments is
- desired, the called function shall declare an object (generally referred to as ap in this
- subclause) having type va_list. The object ap may be passed as an argument to
- another function; if that function invokes the va_arg macro with parameter ap, the
- value of ap in the calling function is indeterminate and shall be passed to the va_end
- macro prior to any further reference to ap.246)
- 7.16.1 Variable argument list access macros
-1 The va_start and va_arg macros described in this subclause shall be implemented
- as macros, not functions. It is unspecified whether va_copy and va_end are macros or
- identifiers declared with external linkage. If a macro definition is suppressed in order to
- access an actual function, or a program defines an external identifier with the same name,
- the behavior is undefined. Each invocation of the va_start and va_copy macros
- shall be matched by a corresponding invocation of the va_end macro in the same
- function.
- 7.16.1.1 The va_arg macro
- Synopsis
-1 #include <stdarg.h>
- type va_arg(va_list ap, type);
- Description
-2 The va_arg macro expands to an expression that has the specified type and the value of
- the next argument in the call. The parameter ap shall have been initialized by the
- va_start or va_copy macro (without an intervening invocation of the va_end
-
- 246) It is permitted to create a pointer to a va_list and pass that pointer to another function, in which
- case the original function may make further use of the original list after the other function returns.
-
-[page 267]
-
- macro for the same ap). Each invocation of the va_arg macro modifies ap so that the
- values of successive arguments are returned in turn. The parameter type shall be a type
- name specified such that the type of a pointer to an object that has the specified type can
- be obtained simply by postfixing a * to type. If there is no actual next argument, or if
- type is not compatible with the type of the actual next argument (as promoted according
- to the default argument promotions), the behavior is undefined, except for the following
- cases:
- -- one type is a signed integer type, the other type is the corresponding unsigned integer
- type, and the value is representable in both types;
- -- one type is pointer to void and the other is a pointer to a character type.
- Returns
-3 The first invocation of the va_arg macro after that of the va_start macro returns the
- value of the argument after that specified by parmN . Successive invocations return the
- values of the remaining arguments in succession.
- 7.16.1.2 The va_copy macro
- Synopsis
-1 #include <stdarg.h>
- void va_copy(va_list dest, va_list src);
- Description
-2 The va_copy macro initializes dest as a copy of src, as if the va_start macro had
- been applied to dest followed by the same sequence of uses of the va_arg macro as
- had previously been used to reach the present state of src. Neither the va_copy nor
- va_start macro shall be invoked to reinitialize dest without an intervening
- invocation of the va_end macro for the same dest.
- Returns
-3 The va_copy macro returns no value.
- 7.16.1.3 The va_end macro
- Synopsis
-1 #include <stdarg.h>
- void va_end(va_list ap);
- Description
-2 The va_end macro facilitates a normal return from the function whose variable
- argument list was referred to by the expansion of the va_start macro, or the function
- containing the expansion of the va_copy macro, that initialized the va_list ap. The
- va_end macro may modify ap so that it is no longer usable (without being reinitialized
-
-[page 268]
-
- by the va_start or va_copy macro). If there is no corresponding invocation of the
- va_start or va_copy macro, or if the va_end macro is not invoked before the
- return, the behavior is undefined.
- Returns
-3 The va_end macro returns no value.
- 7.16.1.4 The va_start macro
- Synopsis
-1 #include <stdarg.h>
- void va_start(va_list ap, parmN);
- Description
-2 The va_start macro shall be invoked before any access to the unnamed arguments.
-3 The va_start macro initializes ap for subsequent use by the va_arg and va_end
- macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap
- without an intervening invocation of the va_end macro for the same ap.
-4 The parameter parmN is the identifier of the rightmost parameter in the variable
- parameter list in the function definition (the one just before the , ...). If the parameter
- parmN is declared with the register storage class, with a function or array type, or
- with a type that is not compatible with the type that results after application of the default
- argument promotions, the behavior is undefined.
- Returns
-5 The va_start macro returns no value.
-6 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not
- more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of
- pointers is specified by the first argument to f1.
- #include <stdarg.h>
- #define MAXARGS 31
- void f1(int n_ptrs, ...)
- {
- va_list ap;
- char *array[MAXARGS];
- int ptr_no = 0;
-
-
-
-
-[page 269]
-
- if (n_ptrs > MAXARGS)
- n_ptrs = MAXARGS;
- va_start(ap, n_ptrs);
- while (ptr_no < n_ptrs)
- array[ptr_no++] = va_arg(ap, char *);
- va_end(ap);
- f2(n_ptrs, array);
- }
- Each call to f1 is required to have visible the definition of the function or a declaration such as
- void f1(int, ...);
-
-7 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the
- indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list
- is gathered again and passed to function f4.
- #include <stdarg.h>
- #define MAXARGS 31
- void f3(int n_ptrs, int f4_after, ...)
- {
- va_list ap, ap_save;
- char *array[MAXARGS];
- int ptr_no = 0;
- if (n_ptrs > MAXARGS)
- n_ptrs = MAXARGS;
- va_start(ap, f4_after);
- while (ptr_no < n_ptrs) {
- array[ptr_no++] = va_arg(ap, char *);
- if (ptr_no == f4_after)
- va_copy(ap_save, ap);
- }
- va_end(ap);
- f2(n_ptrs, array);
- // Now process the saved copy.
- n_ptrs -= f4_after;
- ptr_no = 0;
- while (ptr_no < n_ptrs)
- array[ptr_no++] = va_arg(ap_save, char *);
- va_end(ap_save);
- f4(n_ptrs, array);
- }
-
-
-
-
-[page 270]
-
- 7.17 Atomics <stdatomic.h>
- 7.17.1 Introduction
-1 The header <stdatomic.h> defines several macros and declares several types and
- functions for performing atomic operations on data shared between threads.
-2 Implementations that define the macro __STDC_NO_THREADS__ need not provide
- this header nor support any of its facilities.
-3 The macros defined are the atomic lock-free macros
- ATOMIC_CHAR_LOCK_FREE
- ATOMIC_CHAR16_T_LOCK_FREE
- ATOMIC_CHAR32_T_LOCK_FREE
- ATOMIC_WCHAR_T_LOCK_FREE
- ATOMIC_SHORT_LOCK_FREE
- ATOMIC_INT_LOCK_FREE
- ATOMIC_LONG_LOCK_FREE
- ATOMIC_LLONG_LOCK_FREE
- ATOMIC_ADDRESS_LOCK_FREE
- which indicate the lock-free property of the corresponding atomic types (both signed and
- unsigned); and
- ATOMIC_FLAG_INIT
- which expands to an initializer for an object of type atomic_flag.
-4 The types include
- memory_order
- which is an enumerated type whose enumerators identify memory ordering constraints;
- atomic_flag
- which is a structure type representing a lock-free, primitive atomic flag;
- atomic_bool
- which is a structure type representing the atomic analog of the type _Bool;
- atomic_address
- which is a structure type representing the atomic analog of a pointer type; and several
- atomic analogs of integer types.
-5 In the following operation definitions:
- -- An A refers to one of the atomic types.
-
-
-[page 271]
-
- -- A C refers to its corresponding non-atomic type. The atomic_address atomic
- type corresponds to the void * non-atomic type.
- -- An M refers to the type of the other argument for arithmetic operations. For atomic
- integer types, M is C. For atomic address types, M is ptrdiff_t.
- -- The functions not ending in _explicit have the same semantics as the
- corresponding _explicit function with memory_order_seq_cst for the
- memory_order argument.
- 6 NOTE Many operations are volatile-qualified. The ''volatile as device register'' semantics have not
- changed in the standard. This qualification means that volatility is preserved when applying these
- operations to volatile objects.
-
- 7.17.2 Initialization
- 7.17.2.1 The ATOMIC_VAR_INIT macro
- Synopsis
-1 #include <stdatomic.h>
- #define ATOMIC_VAR_INIT(C value)
- Description
-2 The ATOMIC_VAR_INIT macro expands to a token sequence suitable for initializing an
- atomic object of a type that is initialization-compatible with value. An atomic object
- with automatic storage duration that is not explicitly initialized using
- ATOMIC_VAR_INIT is initially in an indeterminate state; however, the default (zero)
- initialization for objects with static or thread-local storage duration is guaranteed to
- produce a valid state.
-3 Concurrent access to the variable being initialized, even via an atomic operation,
- constitutes a data race.
-4 EXAMPLE
- atomic_int guide = ATOMIC_VAR_INIT(42);
-
- 7.17.2.2 The atomic_init generic function
- Synopsis
-1 #include <stdatomic.h>
- void atomic_init(volatile A *obj, C value);
- Description
-2 The atomic_init generic function initializes the atomic object pointed to by obj to
- the value value, while also initializing any additional state that the implementation
- might need to carry for the atomic object.
-
-
-
-[page 272]
-
-3 Although this function initializes an atomic object, it does not avoid data races;
- concurrent access to the variable being initialized, even via an atomic operation,
- constitutes a data race.
- Returns
-4 The atomic_init generic function returns no value.
-5 EXAMPLE
- atomic_int guide;
- atomic_init(&guide, 42);
-
- 7.17.3 Order and consistency
-1 The enumerated type memory_order specifies the detailed regular (non-atomic)
- memory synchronization operations as defined in 5.1.2.4 and may provide for operation
- ordering. Its enumeration constants are as follows:
- memory_order_relaxed
- memory_order_consume
- memory_order_acquire
- memory_order_release
- memory_order_acq_rel
- memory_order_seq_cst
-2 For memory_order_relaxed, no operation orders memory.
-3 For memory_order_release, memory_order_acq_rel, and
- memory_order_seq_cst, a store operation performs a release operation on the
- affected memory location.
-4 For memory_order_acquire, memory_order_acq_rel, and
- memory_order_seq_cst, a load operation performs an acquire operation on the
- affected memory location.
-5 For memory_order_consume, a load operation performs a consume operation on the
- affected memory location.
-6 For memory_order_seq_cst, there shall be a single total order S on all operations,
- consistent with the ''happens before'' order and modification orders for all affected
- locations, such that each memory_order_seq_cst operation that loads a value
- observes either the last preceding modification according to this order S, or the result of
- an operation that is not memory_order_seq_cst.
-7 NOTE 1 Although it is not explicitly required that S include lock operations, it can always be extended to
- an order that does include lock and unlock operations, since the ordering between those is already included
- in the ''happens before'' ordering.
-
-8 NOTE 2 Atomic operations specifying memory_order_relaxed are relaxed only with respect to
- memory ordering. Implementations must still guarantee that any given atomic access to a particular atomic
-
-[page 273]
-
- object be indivisible with respect to all other atomic accesses to that object.
-
-9 For an atomic operation B that reads the value of an atomic object M, if there is a
- memory_order_seq_cst fence X sequenced before B, then B observes either the
- last memory_order_seq_cst modification of M preceding X in the total order S or
- a later modification of M in its modification order.
-10 For atomic operations A and B on an atomic object M, where A modifies M and B takes
- its value, if there is a memory_order_seq_cst fence X such that A is sequenced
- before X and B follows X in S, then B observes either the effects of A or a later
- modification of M in its modification order.
-11 For atomic operations A and B on an atomic object M, where A modifies M and B takes
- its value, if there are memory_order_seq_cst fences X and Y such that A is
- sequenced before X, Y is sequenced before B, and X precedes Y in S, then B observes
- either the effects of A or a later modification of M in its modification order.
-12 Atomic read-modify-write operations shall always read the last value (in the modification
- order) stored before the write associated with the read-modify-write operation.
-13 An atomic store shall only store a value that has been computed from constants and
- program input values by a finite sequence of program evaluations, such that each
- evaluation observes the values of variables as computed by the last prior assignment in
- the sequence.247) The ordering of evaluations in this sequence shall be such that
- -- If an evaluation B observes a value computed by A in a different thread, then B does
- not happen before A.
- -- If an evaluation A is included in the sequence, then all evaluations that assign to the
- same variable and happen before A are also included.
-14 NOTE 3 The second requirement disallows ''out-of-thin-air'', or ''speculative'' stores of atomics when
- relaxed atomics are used. Since unordered operations are involved, evaluations may appear in this
- sequence out of thread order. For example, with x and y initially zero,
- // Thread 1:
- r1 = atomic_load_explicit(&y, memory_order_relaxed);
- atomic_store_explicit(&x, r1, memory_order_relaxed);
-
- // Thread 2:
- r2 = atomic_load_explicit(&x, memory_order_relaxed);
- atomic_store_explicit(&y, 42, memory_order_relaxed);
- is allowed to produce r1 == 42 && r2 == 42. The sequence of evaluations justifying this consists of:
-
-
-
-
- 247) Among other implications, atomic variables shall not decay.
-
-[page 274]
-
- atomic_store_explicit(&y, 42, memory_order_relaxed);
- r1 = atomic_load_explicit(&y, memory_order_relaxed);
- atomic_store_explicit(&x, r1, memory_order_relaxed);
- r2 = atomic_load_explicit(&x, memory_order_relaxed);
- On the other hand,
- // Thread 1:
- r1 = atomic_load_explicit(&y, memory_order_relaxed);
- atomic_store_explicit(&x, r1, memory_order_relaxed);
-
- // Thread 2:
- r2 = atomic_load_explicit(&x, memory_order_relaxed);
- atomic_store_explicit(&y, r2, memory_order_relaxed);
- is not allowed to produce r1 == 42 && r2 = 42, since there is no sequence of evaluations that results
- in the computation of 42. In the absence of ''relaxed'' operations and read-modify-write operations with
- weaker than memory_order_acq_rel ordering, the second requirement has no impact.
-
- Recommended practice
-15 The requirements do not forbid r1 == 42 && r2 == 42 in the following example,
- with x and y initially zero:
- // Thread 1:
- r1 = atomic_load_explicit(&x, memory_order_relaxed);
- if (r1 == 42)
- atomic_store_explicit(&y, r1, memory_order_relaxed);
-
- // Thread 2:
- r2 = atomic_load_explicit(&y, memory_order_relaxed);
- if (r2 == 42)
- atomic_store_explicit(&x, 42, memory_order_relaxed);
- However, this is not useful behavior, and implementations should not allow it.
-16 Implementations should make atomic stores visible to atomic loads within a reasonable
- amount of time.
- 7.17.3.1 The kill_dependency macro
- Synopsis
-1 #include <stdatomic.h>
- type kill_dependency(type y);
- Description
-2 The kill_dependency macro terminates a dependency chain; the argument does not
- carry a dependency to the return value.
-
-
-
-[page 275]
-
- Returns
-3 The kill_dependency macro returns the value of y.
- 7.17.4 Fences
-1 This subclause introduces synchronization primitives called fences. Fences can have
- acquire semantics, release semantics, or both. A fence with acquire semantics is called
- an acquire fence; a fence with release semantics is called a release fence.
-2 A release fence A synchronizes with an acquire fence B if there exist atomic operations
- X and Y , both operating on some atomic object M, such that A is sequenced before X, X
- modifies M, Y is sequenced before B, and Y reads the value written by X or a value
- written by any side effect in the hypothetical release sequence X would head if it were a
- release operation.
-3 A release fence A synchronizes with an atomic operation B that performs an acquire
- operation on an atomic object M if there exists an atomic operation X such that A is
- sequenced before X, X modifies M, and B reads the value written by X or a value written
- by any side effect in the hypothetical release sequence X would head if it were a release
- operation.
-4 An atomic operation A that is a release operation on an atomic object M synchronizes
- with an acquire fence B if there exists some atomic operation X on M such that X is
- sequenced before B and reads the value written by A or a value written by any side effect
- in the release sequence headed by A.
- 7.17.4.1 The atomic_thread_fence function
- Synopsis
-1 #include <stdatomic.h>
- void atomic_thread_fence(memory_order order);
- Description
-2 Depending on the value of order, this operation:
- -- has no effects, if order == memory_order_relaxed;
- -- is an acquire fence, if order == memory_order_acquire or order ==
- memory_order_consume;
- -- is a release fence, if order == memory_order_release;
- -- is both an acquire fence and a release fence, if order ==
- memory_order_acq_rel;
- -- is a sequentially consistent acquire and release fence, if order ==
- memory_order_seq_cst.
-
-
-[page 276]
-
- Returns
-3 The atomic_thread_fence function returns no value.
- 7.17.4.2 The atomic_signal_fence function
- Synopsis
-1 #include <stdatomic.h>
- void atomic_signal_fence(memory_order order);
- Description
-2 Equivalent to atomic_thread_fence(order), except that ''synchronizes with''
- relationships are established only between a thread and a signal handler executed in the
- same thread.
-3 NOTE 1 The atomic_signal_fence function can be used to specify the order in which actions
- performed by the thread become visible to the signal handler.
-
-4 NOTE 2 Compiler optimizations and reorderings of loads and stores are inhibited in the same way as with
- atomic_thread_fence, but the hardware fence instructions that atomic_thread_fence would
- have inserted are not emitted.
-
- Returns
-5 The atomic_signal_fence function returns no value.
- 7.17.5 Lock-free property
-1 The atomic lock-free macros indicate the lock-free property of integer and address atomic
- types. A value of 0 indicates that the type is never lock-free; a value of 1 indicates that
- the type is sometimes lock-free; a value of 2 indicates that the type is always lock-free.
-2 NOTE Operations that are lock-free should also be address-free. That is, atomic operations on the same
- memory location via two different addresses will communicate atomically. The implementation should not
- depend on any per-process state. This restriction enables communication via memory mapped into a
- process more than once and memory shared between two processes.
-
- 7.17.5.1 The atomic_is_lock_free generic function
- Synopsis
-1 #include <stdatomic.h>
- _Bool atomic_is_lock_free(atomic_type const volatile *obj);
- Description
-2 The atomic_is_lock_free generic function indicates whether or not the object
- pointed to by obj is lock-free. atomic_type can be any atomic type.
- Returns
-3 The atomic_is_lock_free generic function returns nonzero (true) if and only if the
- object's operations are lock-free. The result of a lock-free query on one object cannot be
-
-[page 277]
-
- inferred from the result of a lock-free query on another object.
- 7.17.6 Atomic integer and address types
-1 For each line in the following table, the atomic type name is declared as the
- corresponding direct type.
-
-
-
-
-[page 278]
-
-
-
- Atomic type name Direct type
- atomic_char _Atomic char
- atomic_schar _Atomic signed char
- atomic_uchar _Atomic unsigned char
- atomic_short _Atomic short
- atomic_ushort _Atomic unsigned short
- atomic_int _Atomic int
- atomic_uint _Atomic unsigned int
- atomic_long _Atomic long
- atomic_ulong _Atomic unsigned long
- atomic_llong _Atomic long long
- atomic_ullong _Atomic unsigned long long
- atomic_char16_t _Atomic char16_t
- atomic_char32_t _Atomic char32_t
- atomic_wchar_t _Atomic wchar_t
- atomic_int_least8_t _Atomic int_least8_t
- atomic_uint_least8_t _Atomic uint_least8_t
- atomic_int_least16_t _Atomic int_least16_t
- atomic_uint_least16_t _Atomic uint_least16_t
- atomic_int_least32_t _Atomic int_least32_t
- atomic_uint_least32_t _Atomic uint_least32_t
- atomic_int_least64_t _Atomic int_least64_t
- atomic_uint_least64_t _Atomic uint_least64_t
- atomic_int_fast8_t _Atomic int_fast8_t
- atomic_uint_fast8_t _Atomic uint_fast8_t
- atomic_int_fast16_t _Atomic int_fast16_t
- atomic_uint_fast16_t _Atomic uint_fast16_t
- atomic_int_fast32_t _Atomic int_fast32_t
- atomic_uint_fast32_t _Atomic uint_fast32_t
- atomic_int_fast64_t _Atomic int_fast64_t
- atomic_uint_fast64_t _Atomic uint_fast64_t
- atomic_intptr_t _Atomic intptr_t
- atomic_uintptr_t _Atomic uintptr_t
- atomic_size_t _Atomic size_t
- atomic_ptrdiff_t _Atomic ptrdiff_t
- atomic_intmax_t _Atomic intmax_t
- atomic_uintmax_t _Atomic uintmax_t
-2 The semantics of the operations on these types are defined in 7.17.7.
-
-
-
-[page 279]
-
-3 The atomic_bool type provides an atomic boolean.
-4 The atomic_address type provides atomic void * operations. The unit of
- addition/subtraction shall be one byte.
-5 NOTE The representation of atomic integer and address types need not have the same size as their
- corresponding regular types. They should have the same size whenever possible, as it eases effort required
- to port existing code.
-
- 7.17.7 Operations on atomic types
-1 There are only a few kinds of operations on atomic types, though there are many
- instances of those kinds. This subclause specifies each general kind.
- 7.17.7.1 The atomic_store generic functions
- Synopsis
-1 #include <stdatomic.h>
- void atomic_store(volatile A *object, C desired);
- void atomic_store_explicit(volatile A *object,
- C desired, memory_order order);
- Description
-2 The order argument shall not be memory_order_acquire,
- memory_order_consume, nor memory_order_acq_rel. Atomically replace the
- value pointed to by object with the value of desired. Memory is affected according
- to the value of order.
- Returns
-3 The atomic_store generic functions return no value.
- 7.17.7.2 The atomic_load generic functions
- Synopsis
-1 #include <stdatomic.h>
- C atomic_load(volatile A *object);
- C atomic_load_explicit(volatile A *object,
- memory_order order);
- Description
-2 The order argument shall not be memory_order_release nor
- memory_order_acq_rel. Memory is affected according to the value of order.
- Returns
- Atomically returns the value pointed to by object.
-
-
-
-[page 280]
-
- 7.17.7.3 The atomic_exchange generic functions
- Synopsis
-1 #include <stdatomic.h>
- C atomic_exchange(volatile A *object, C desired);
- C atomic_exchange_explicit(volatile A *object,
- C desired, memory_order order);
- Description
-2 Atomically replace the value pointed to by object with desired. Memory is affected
- according to the value of order. These operations are read-modify-write operations
- (5.1.2.4).
- Returns
-3 Atomically returns the value pointed to by object immediately before the effects.
- 7.17.7.4 The atomic_compare_exchange generic functions
- Synopsis
-1 #include <stdatomic.h>
- _Bool atomic_compare_exchange_strong(volatile A *object,
- C *expected, C desired);
- _Bool atomic_compare_exchange_strong_explicit(
- volatile A *object, C *expected, C desired,
- memory_order success, memory_order failure);
- _Bool atomic_compare_exchange_weak(volatile A *object,
- C *expected, C desired);
- _Bool atomic_compare_exchange_weak_explicit(
- volatile A *object, C *expected, C desired,
- memory_order success, memory_order failure);
- Description
-2 The failure argument shall not be memory_order_release nor
- memory_order_acq_rel. The failure argument shall be no stronger than the
- success argument. Atomically, compares the value pointed to by object for equality
- with that in expected, and if true, replaces the value pointed to by object with
- desired, and if false, updates the value in expected with the value pointed to by
- object. Further, if the comparison is true, memory is affected according to the value of
- success, and if the comparison is false, memory is affected according to the value of
- failure. These operations are atomic read-modify-write operations (5.1.2.4).
-3 NOTE 1 The effect of the compare-and-exchange operations is
-
-
-
-
-[page 281]
-
- if (*object == *expected)
- *object = desired;
- else
- *expected = *object;
-
-4 The weak compare-and-exchange operations may fail spuriously, that is, return zero
- while leaving the value pointed to by expected unchanged.
-5 NOTE 2 This spurious failure enables implementation of compare-and-exchange on a broader class of
- machines, e.g. load-locked store-conditional machines.
-
-6 EXAMPLE A consequence of spurious failure is that nearly all uses of weak compare-and-exchange will
- be in a loop.
- exp = atomic_load(&cur);
- do {
- des = function(exp);
- } while (!atomic_compare_exchange_weak(&cur, &exp, des));
- When a compare-and-exchange is in a loop, the weak version will yield better performance on some
- platforms. When a weak compare-and-exchange would require a loop and a strong one would not, the
- strong one is preferable.
-
- Returns
-7 The result of the comparison.
- 7.17.7.5 The atomic_fetch and modify generic functions
-1 The following operations perform arithmetic and bitwise computations. All of these
- operations are applicable to an object of any atomic integer type. Only addition and
- subtraction are applicable to atomic_address. None of these operations is applicable
- to atomic_bool. The key, operator, and computation correspondence is:
-
-
- key op computation
- add + addition
- sub - subtraction
- or | bitwise inclusive or
- xor ^ bitwise exclusive or
- and & bitwise and
- Synopsis
-2 #include <stdatomic.h>
- C atomic_fetch_key(volatile A *object, M operand);
- C atomic_fetch_key_explicit(volatile A *object,
- M operand, memory_order order);
- Description
-3 Atomically replaces the value pointed to by object with the result of the computation
- applied to the value pointed to by object and the given operand. Memory is affected
-[page 282]
-
- according to the value of order. These operations are atomic read-modify-write
- operations (5.1.2.4). For signed integer types, arithmetic is defined to use two's-
- complement representation. There are no undefined results. For address types, the result
- may be an undefined address, but the operations otherwise have no undefined behavior.
- Returns
-4 Atomically, the value pointed to by object immediately before the effects.
-5 NOTE The operation of the atomic_fetch and modify generic functions are nearly equivalent to the
- operation of the corresponding op= compound assignment operators. The only differences are that the
- compound assignment operators are not guaranteed to operate atomically, and the value yielded by a
- compound assignment operator is the updated value of the object, whereas the value returned by the
- atomic_fetch and modify generic functions is the previous value of the atomic object.
-
- 7.17.8 Atomic flag type and operations
-1 The atomic_flag type provides the classic test-and-set functionality. It has two
- states, set and clear.
-2 Operations on an object of type atomic_flag shall be lock free.
-3 NOTE Hence the operations should also be address-free. No other type requires lock-free operations, so
- the atomic_flag type is the minimum hardware-implemented type needed to conform to this
- International standard. The remaining types can be emulated with atomic_flag, though with less than
- ideal properties.
-
-4 The macro ATOMIC_FLAG_INIT may be used to initialize an atomic_flag to the
- clear state. An atomic_flag that is not explicitly initialized with
- ATOMIC_FLAG_INIT is initially in an indeterminate state.
-5 EXAMPLE
- atomic_flag guard = ATOMIC_FLAG_INIT;
-
- 7.17.8.1 The atomic_flag_test_and_set functions
- Synopsis
-1 #include <stdatomic.h>
- bool atomic_flag_test_and_set(
- volatile atomic_flag *object);
- bool atomic_flag_test_and_set_explicit(
- volatile atomic_flag *object, memory_order order);
- Description
-2 Atomically sets the value pointed to by object to true. Memory is affected according
- to the value of order. These operations are atomic read-modify-write operations
- (5.1.2.4).
-
-
-
-
-[page 283]
-
- Returns
-3 Atomically, the value of the object immediately before the effects.
- 7.17.8.2 The atomic_flag_clear functions
- Synopsis
-1 #include <stdatomic.h>
- void atomic_flag_clear(volatile atomic_flag *object);
- void atomic_flag_clear_explicit(
- volatile atomic_flag *object, memory_order order);
- Description
-2 The order argument shall not be memory_order_acquire nor
- memory_order_acq_rel. Atomically sets the value pointed to by object to false.
- Memory is affected according to the value of order.
- Returns
-3 The atomic_flag_clear functions return no value.
-
-
-
-
-[page 284]
-
- 7.18 Boolean type and values <stdbool.h>
-1 The header <stdbool.h> defines four macros.
-2 The macro
- bool
- expands to _Bool.
-3 The remaining three macros are suitable for use in #if preprocessing directives. They
- are
- true
- which expands to the integer constant 1,
- false
- which expands to the integer constant 0, and
- __bool_true_false_are_defined
- which expands to the integer constant 1.
-4 Notwithstanding the provisions of 7.1.3, a program may undefine and perhaps then
- redefine the macros bool, true, and false.248)
-
-
-
-
- 248) See ''future library directions'' (7.30.7).
-
-[page 285]
-
- 7.19 Common definitions <stddef.h>
-1 The header <stddef.h> defines the following macros and declares the following types.
- Some are also defined in other headers, as noted in their respective subclauses.
-2 The types are
- ptrdiff_t
- which is the signed integer type of the result of subtracting two pointers;
- size_t
- which is the unsigned integer type of the result of the sizeof operator;
- max_align_t
- which is an object type whose alignment is as great as is supported by the implementation
- in all contexts; and
- wchar_t
- which is an integer type whose range of values can represent distinct codes for all
- members of the largest extended character set specified among the supported locales; the
- null character shall have the code value zero. Each member of the basic character set
- shall have a code value equal to its value when used as the lone character in an integer
- character constant if an implementation does not define
- __STDC_MB_MIGHT_NEQ_WC__.
-3 The macros are
- NULL
- which expands to an implementation-defined null pointer constant; and
- offsetof(type, member-designator)
- which expands to an integer constant expression that has type size_t, the value of
- which is the offset in bytes, to the structure member (designated by member-designator),
- from the beginning of its structure (designated by type). The type and member designator
- shall be such that given
- static type t;
- then the expression &(t.member-designator) evaluates to an address constant. (If the
- specified member is a bit-field, the behavior is undefined.)
- Recommended practice
-4 The types used for size_t and ptrdiff_t should not have an integer conversion rank
- greater than that of signed long int unless the implementation supports objects
- large enough to make this necessary.
-
-[page 286]
-
-Forward references: localization (7.11).
-
-
-
-
-[page 287]
-
- 7.20 Integer types <stdint.h>
-1 The header <stdint.h> declares sets of integer types having specified widths, and
- defines corresponding sets of macros.249) It also defines macros that specify limits of
- integer types corresponding to types defined in other standard headers.
-2 Types are defined in the following categories:
- -- integer types having certain exact widths;
- -- integer types having at least certain specified widths;
- -- fastest integer types having at least certain specified widths;
- -- integer types wide enough to hold pointers to objects;
- -- integer types having greatest width.
- (Some of these types may denote the same type.)
-3 Corresponding macros specify limits of the declared types and construct suitable
- constants.
-4 For each type described herein that the implementation provides,250) <stdint.h> shall
- declare that typedef name and define the associated macros. Conversely, for each type
- described herein that the implementation does not provide, <stdint.h> shall not
- declare that typedef name nor shall it define the associated macros. An implementation
- shall provide those types described as ''required'', but need not provide any of the others
- (described as ''optional'').
- 7.20.1 Integer types
-1 When typedef names differing only in the absence or presence of the initial u are defined,
- they shall denote corresponding signed and unsigned types as described in 6.2.5; an
- implementation providing one of these corresponding types shall also provide the other.
-2 In the following descriptions, the symbol N represents an unsigned decimal integer with
- no leading zeros (e.g., 8 or 24, but not 04 or 048).
-
-
-
-
- 249) See ''future library directions'' (7.30.8).
- 250) Some of these types may denote implementation-defined extended integer types.
-
-[page 288]
-
- 7.20.1.1 Exact-width integer types
-1 The typedef name intN_t designates a signed integer type with width N , no padding
- bits, and a two's complement representation. Thus, int8_t denotes such a signed
- integer type with a width of exactly 8 bits.
-2 The typedef name uintN_t designates an unsigned integer type with width N and no
- padding bits. Thus, uint24_t denotes such an unsigned integer type with a width of
- exactly 24 bits.
-3 These types are optional. However, if an implementation provides integer types with
- widths of 8, 16, 32, or 64 bits, no padding bits, and (for the signed types) that have a
- two's complement representation, it shall define the corresponding typedef names.
- 7.20.1.2 Minimum-width integer types
-1 The typedef name int_leastN_t designates a signed integer type with a width of at
- least N , such that no signed integer type with lesser size has at least the specified width.
- Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits.
-2 The typedef name uint_leastN_t designates an unsigned integer type with a width
- of at least N , such that no unsigned integer type with lesser size has at least the specified
- width. Thus, uint_least16_t denotes an unsigned integer type with a width of at
- least 16 bits.
-3 The following types are required:
- int_least8_t uint_least8_t
- int_least16_t uint_least16_t
- int_least32_t uint_least32_t
- int_least64_t uint_least64_t
- All other types of this form are optional.
- 7.20.1.3 Fastest minimum-width integer types
-1 Each of the following types designates an integer type that is usually fastest251) to operate
- with among all integer types that have at least the specified width.
-2 The typedef name int_fastN_t designates the fastest signed integer type with a width
- of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer
- type with a width of at least N .
-
-
-
-
- 251) The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear
- grounds for choosing one type over another, it will simply pick some integer type satisfying the
- signedness and width requirements.
-
-[page 289]
-
-3 The following types are required:
- int_fast8_t uint_fast8_t
- int_fast16_t uint_fast16_t
- int_fast32_t uint_fast32_t
- int_fast64_t uint_fast64_t
- All other types of this form are optional.
- 7.20.1.4 Integer types capable of holding object pointers
-1 The following type designates a signed integer type with the property that any valid
- pointer to void can be converted to this type, then converted back to pointer to void,
- and the result will compare equal to the original pointer:
- intptr_t
- The following type designates an unsigned integer type with the property that any valid
- pointer to void can be converted to this type, then converted back to pointer to void,
- and the result will compare equal to the original pointer:
- uintptr_t
- These types are optional.
- 7.20.1.5 Greatest-width integer types
-1 The following type designates a signed integer type capable of representing any value of
- any signed integer type:
- intmax_t
- The following type designates an unsigned integer type capable of representing any value
- of any unsigned integer type:
- uintmax_t
- These types are required.
- 7.20.2 Limits of specified-width integer types
-1 The following object-like macros specify the minimum and maximum limits of the types
- declared in <stdint.h>. Each macro name corresponds to a similar type name in
- 7.20.1.
-2 Each instance of any defined macro shall be replaced by a constant expression suitable
- for use in #if preprocessing directives, and this expression shall have the same type as
- would an expression that is an object of the corresponding type converted according to
- the integer promotions. Its implementation-defined value shall be equal to or greater in
- magnitude (absolute value) than the corresponding value given below, with the same sign,
- except where stated to be exactly the given value.
-
-[page 290]
-
- 7.20.2.1 Limits of exact-width integer types
-1 -- minimum values of exact-width signed integer types
- INTN_MIN exactly -(2 N -1 )
- -- maximum values of exact-width signed integer types
- INTN_MAX exactly 2 N -1 - 1
- -- maximum values of exact-width unsigned integer types
- UINTN_MAX exactly 2 N - 1
- 7.20.2.2 Limits of minimum-width integer types
-1 -- minimum values of minimum-width signed integer types
- INT_LEASTN_MIN -(2 N -1 - 1)
- -- maximum values of minimum-width signed integer types
- INT_LEASTN_MAX 2 N -1 - 1
- -- maximum values of minimum-width unsigned integer types
- UINT_LEASTN_MAX 2N - 1
- 7.20.2.3 Limits of fastest minimum-width integer types
-1 -- minimum values of fastest minimum-width signed integer types
- INT_FASTN_MIN -(2 N -1 - 1)
- -- maximum values of fastest minimum-width signed integer types
- INT_FASTN_MAX 2 N -1 - 1
- -- maximum values of fastest minimum-width unsigned integer types
- UINT_FASTN_MAX 2N - 1
- 7.20.2.4 Limits of integer types capable of holding object pointers
-1 -- minimum value of pointer-holding signed integer type
- INTPTR_MIN -(215 - 1)
- -- maximum value of pointer-holding signed integer type
- INTPTR_MAX 215 - 1
- -- maximum value of pointer-holding unsigned integer type
- UINTPTR_MAX 216 - 1
-
-
-
-[page 291]
-
- 7.20.2.5 Limits of greatest-width integer types
-1 -- minimum value of greatest-width signed integer type
- INTMAX_MIN -(263 - 1)
- -- maximum value of greatest-width signed integer type
- INTMAX_MAX 263 - 1
- -- maximum value of greatest-width unsigned integer type
- UINTMAX_MAX 264 - 1
- 7.20.3 Limits of other integer types
-1 The following object-like macros specify the minimum and maximum limits of integer
- types corresponding to types defined in other standard headers.
-2 Each instance of these macros shall be replaced by a constant expression suitable for use
- in #if preprocessing directives, and this expression shall have the same type as would an
- expression that is an object of the corresponding type converted according to the integer
- promotions. Its implementation-defined value shall be equal to or greater in magnitude
- (absolute value) than the corresponding value given below, with the same sign. An
- implementation shall define only the macros corresponding to those typedef names it
- actually provides.252)
- -- limits of ptrdiff_t
- PTRDIFF_MIN -65535
- PTRDIFF_MAX +65535
- -- limits of sig_atomic_t
- SIG_ATOMIC_MIN see below
- SIG_ATOMIC_MAX see below
- -- limit of size_t
- SIZE_MAX 65535
- -- limits of wchar_t
- WCHAR_MIN see below
- WCHAR_MAX see below
- -- limits of wint_t
-
-
-
-
- 252) A freestanding implementation need not provide all of these types.
-
-[page 292]
-
- WINT_MIN see below
- WINT_MAX see below
-3 If sig_atomic_t (see 7.14) is defined as a signed integer type, the value of
- SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX
- shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
- type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
- SIG_ATOMIC_MAX shall be no less than 255.
-4 If wchar_t (see 7.19) is defined as a signed integer type, the value of WCHAR_MIN
- shall be no greater than -127 and the value of WCHAR_MAX shall be no less than 127;
- otherwise, wchar_t is defined as an unsigned integer type, and the value of
- WCHAR_MIN shall be 0 and the value of WCHAR_MAX shall be no less than 255.253)
-5 If wint_t (see 7.28) is defined as a signed integer type, the value of WINT_MIN shall
- be no greater than -32767 and the value of WINT_MAX shall be no less than 32767;
- otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
- shall be 0 and the value of WINT_MAX shall be no less than 65535.
- 7.20.4 Macros for integer constants
-1 The following function-like macros expand to integer constants suitable for initializing
- objects that have integer types corresponding to types defined in <stdint.h>. Each
- macro name corresponds to a similar type name in 7.20.1.2 or 7.20.1.5.
-2 The argument in any instance of these macros shall be an unsuffixed integer constant (as
- defined in 6.4.4.1) with a value that does not exceed the limits for the corresponding type.
-3 Each invocation of one of these macros shall expand to an integer constant expression
- suitable for use in #if preprocessing directives. The type of the expression shall have
- the same type as would an expression of the corresponding type converted according to
- the integer promotions. The value of the expression shall be that of the argument.
- 7.20.4.1 Macros for minimum-width integer constants
-1 The macro INTN_C(value) shall expand to an integer constant expression
- corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
- to an integer constant expression corresponding to the type uint_leastN_t. For
- example, if uint_least64_t is a name for the type unsigned long long int,
- then UINT64_C(0x123) might expand to the integer constant 0x123ULL.
-
-
-
-
- 253) The values WCHAR_MIN and WCHAR_MAX do not necessarily correspond to members of the extended
- character set.
-
-[page 293]
-
- 7.20.4.2 Macros for greatest-width integer constants
-1 The following macro expands to an integer constant expression having the value specified
- by its argument and the type intmax_t:
- INTMAX_C(value)
- The following macro expands to an integer constant expression having the value specified
- by its argument and the type uintmax_t:
- UINTMAX_C(value)
-
-
-
-
-[page 294]
-
- 7.21 Input/output <stdio.h>
- 7.21.1 Introduction
-1 The header <stdio.h> defines several macros, and declares three types and many
- functions for performing input and output.
-2 The types declared are size_t (described in 7.19);
- FILE
- which is an object type capable of recording all the information needed to control a
- stream, including its file position indicator, a pointer to its associated buffer (if any), an
- error indicator that records whether a read/write error has occurred, and an end-of-file
- indicator that records whether the end of the file has been reached; and
- fpos_t
- which is a complete object type other than an array type capable of recording all the
- information needed to specify uniquely every position within a file.
-3 The macros are NULL (described in 7.19);
- _IOFBF
- _IOLBF
- _IONBF
- which expand to integer constant expressions with distinct values, suitable for use as the
- third argument to the setvbuf function;
- BUFSIZ
- which expands to an integer constant expression that is the size of the buffer used by the
- setbuf function;
- EOF
- which expands to an integer constant expression, with type int and a negative value, that
- is returned by several functions to indicate end-of-file, that is, no more input from a
- stream;
- FOPEN_MAX
- which expands to an integer constant expression that is the minimum number of files that
- the implementation guarantees can be open simultaneously;
- FILENAME_MAX
- which expands to an integer constant expression that is the size needed for an array of
- char large enough to hold the longest file name string that the implementation
-
-
-
-[page 295]
-
- guarantees can be opened;254)
- L_tmpnam
- which expands to an integer constant expression that is the size needed for an array of
- char large enough to hold a temporary file name string generated by the tmpnam
- function;
- SEEK_CUR
- SEEK_END
- SEEK_SET
- which expand to integer constant expressions with distinct values, suitable for use as the
- third argument to the fseek function;
- TMP_MAX
- which expands to an integer constant expression that is the minimum number of unique
- file names that can be generated by the tmpnam function;
- stderr
- stdin
- stdout
- which are expressions of type ''pointer to FILE'' that point to the FILE objects
- associated, respectively, with the standard error, input, and output streams.
-4 The header <wchar.h> declares a number of functions useful for wide character input
- and output. The wide character input/output functions described in that subclause
- provide operations analogous to most of those described here, except that the
- fundamental units internal to the program are wide characters. The external
- representation (in the file) is a sequence of ''generalized'' multibyte characters, as
- described further in 7.21.3.
-5 The input/output functions are given the following collective terms:
- -- The wide character input functions -- those functions described in 7.28 that perform
- input into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar,
- fwscanf, wscanf, vfwscanf, and vwscanf.
- -- The wide character output functions -- those functions described in 7.28 that perform
- output from wide characters and wide strings: fputwc, fputws, putwc,
- putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
-
-
- 254) If the implementation imposes no practical limit on the length of file name strings, the value of
- FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
- string. Of course, file name string contents are subject to other system-specific constraints; therefore
- all possible strings of length FILENAME_MAX cannot be expected to be opened successfully.
-
-[page 296]
-
- -- The wide character input/output functions -- the union of the ungetwc function, the
- wide character input functions, and the wide character output functions.
- -- The byte input/output functions -- those functions described in this subclause that
- perform input/output: fgetc, fgets, fprintf, fputc, fputs, fread,
- fscanf, fwrite, getc, getchar, printf, putc, putchar, puts, scanf,
- ungetc, vfprintf, vfscanf, vprintf, and vscanf.
- Forward references: files (7.21.3), the fseek function (7.21.9.2), streams (7.21.2), the
- tmpnam function (7.21.4.4), <wchar.h> (7.28).
- 7.21.2 Streams
-1 Input and output, whether to or from physical devices such as terminals and tape drives,
- or whether to or from files supported on structured storage devices, are mapped into
- logical data streams, whose properties are more uniform than their various inputs and
- outputs. Two forms of mapping are supported, for text streams and for binary
- streams.255)
-2 A text stream is an ordered sequence of characters composed into lines, each line
- consisting of zero or more characters plus a terminating new-line character. Whether the
- last line requires a terminating new-line character is implementation-defined. Characters
- may have to be added, altered, or deleted on input and output to conform to differing
- conventions for representing text in the host environment. Thus, there need not be a one-
- to-one correspondence between the characters in a stream and those in the external
- representation. Data read in from a text stream will necessarily compare equal to the data
- that were earlier written out to that stream only if: the data consist only of printing
- characters and the control characters horizontal tab and new-line; no new-line character is
- immediately preceded by space characters; and the last character is a new-line character.
- Whether space characters that are written out immediately before a new-line character
- appear when read in is implementation-defined.
-3 A binary stream is an ordered sequence of characters that can transparently record
- internal data. Data read in from a binary stream shall compare equal to the data that were
- earlier written out to that stream, under the same implementation. Such a stream may,
- however, have an implementation-defined number of null characters appended to the end
- of the stream.
-4 Each stream has an orientation. After a stream is associated with an external file, but
- before any operations are performed on it, the stream is without orientation. Once a wide
- character input/output function has been applied to a stream without orientation, the
-
-
- 255) An implementation need not distinguish between text streams and binary streams. In such an
- implementation, there need be no new-line characters in a text stream nor any limit to the length of a
- line.
-
-[page 297]
-
- stream becomes a wide-oriented stream. Similarly, once a byte input/output function has
- been applied to a stream without orientation, the stream becomes a byte-oriented stream.
- Only a call to the freopen function or the fwide function can otherwise alter the
- orientation of a stream. (A successful call to freopen removes any orientation.)256)
-5 Byte input/output functions shall not be applied to a wide-oriented stream and wide
- character input/output functions shall not be applied to a byte-oriented stream. The
- remaining stream operations do not affect, and are not affected by, a stream's orientation,
- except for the following additional restrictions:
- -- Binary wide-oriented streams have the file-positioning restrictions ascribed to both
- text and binary streams.
- -- For wide-oriented streams, after a successful call to a file-positioning function that
- leaves the file position indicator prior to the end-of-file, a wide character output
- function can overwrite a partial multibyte character; any file contents beyond the
- byte(s) written are henceforth indeterminate.
-6 Each wide-oriented stream has an associated mbstate_t object that stores the current
- parse state of the stream. A successful call to fgetpos stores a representation of the
- value of this mbstate_t object as part of the value of the fpos_t object. A later
- successful call to fsetpos using the same stored fpos_t value restores the value of
- the associated mbstate_t object as well as the position within the controlled stream.
- Environmental limits
-7 An implementation shall support text files with lines containing at least 254 characters,
- including the terminating new-line character. The value of the macro BUFSIZ shall be at
- least 256.
- Forward references: the freopen function (7.21.5.4), the fwide function (7.28.3.5),
- mbstate_t (7.29.1), the fgetpos function (7.21.9.1), the fsetpos function
- (7.21.9.3).
-
-
-
-
- 256) The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
-
-[page 298]
-
- 7.21.3 Files
-1 A stream is associated with an external file (which may be a physical device) by opening
- a file, which may involve creating a new file. Creating an existing file causes its former
- contents to be discarded, if necessary. If a file can support positioning requests (such as a
- disk file, as opposed to a terminal), then a file position indicator associated with the
- stream is positioned at the start (character number zero) of the file, unless the file is
- opened with append mode in which case it is implementation-defined whether the file
- position indicator is initially positioned at the beginning or the end of the file. The file
- position indicator is maintained by subsequent reads, writes, and positioning requests, to
- facilitate an orderly progression through the file.
-2 Binary files are not truncated, except as defined in 7.21.5.3. Whether a write on a text
- stream causes the associated file to be truncated beyond that point is implementation-
- defined.
-3 When a stream is unbuffered, characters are intended to appear from the source or at the
- destination as soon as possible. Otherwise characters may be accumulated and
- transmitted to or from the host environment as a block. When a stream is fully buffered,
- characters are intended to be transmitted to or from the host environment as a block when
- a buffer is filled. When a stream is line buffered, characters are intended to be
- transmitted to or from the host environment as a block when a new-line character is
- encountered. Furthermore, characters are intended to be transmitted as a block to the host
- environment when a buffer is filled, when input is requested on an unbuffered stream, or
- when input is requested on a line buffered stream that requires the transmission of
- characters from the host environment. Support for these characteristics is
- implementation-defined, and may be affected via the setbuf and setvbuf functions.
-4 A file may be disassociated from a controlling stream by closing the file. Output streams
- are flushed (any unwritten buffer contents are transmitted to the host environment) before
- the stream is disassociated from the file. The value of a pointer to a FILE object is
- indeterminate after the associated file is closed (including the standard text streams).
- Whether a file of zero length (on which no characters have been written by an output
- stream) actually exists is implementation-defined.
-5 The file may be subsequently reopened, by the same or another program execution, and
- its contents reclaimed or modified (if it can be repositioned at its start). If the main
- function returns to its original caller, or if the exit function is called, all open files are
- closed (hence all output streams are flushed) before program termination. Other paths to
- program termination, such as calling the abort function, need not close all files
- properly.
-6 The address of the FILE object used to control a stream may be significant; a copy of a
- FILE object need not serve in place of the original.
-
-[page 299]
-
-7 At program startup, three text streams are predefined and need not be opened explicitly
- -- standard input (for reading conventional input), standard output (for writing
- conventional output), and standard error (for writing diagnostic output). As initially
- opened, the standard error stream is not fully buffered; the standard input and standard
- output streams are fully buffered if and only if the stream can be determined not to refer
- to an interactive device.
-8 Functions that open additional (nontemporary) files require a file name, which is a string.
- The rules for composing valid file names are implementation-defined. Whether the same
- file can be simultaneously open multiple times is also implementation-defined.
-9 Although both text and binary wide-oriented streams are conceptually sequences of wide
- characters, the external file associated with a wide-oriented stream is a sequence of
- multibyte characters, generalized as follows:
- -- Multibyte encodings within files may contain embedded null bytes (unlike multibyte
- encodings valid for use internal to the program).
- -- A file need not begin nor end in the initial shift state.257)
-10 Moreover, the encodings used for multibyte characters may differ among files. Both the
- nature and choice of such encodings are implementation-defined.
-11 The wide character input functions read multibyte characters from the stream and convert
- them to wide characters as if they were read by successive calls to the fgetwc function.
- Each conversion occurs as if by a call to the mbrtowc function, with the conversion state
- described by the stream's own mbstate_t object. The byte input functions read
- characters from the stream as if by successive calls to the fgetc function.
-12 The wide character output functions convert wide characters to multibyte characters and
- write them to the stream as if they were written by successive calls to the fputwc
- function. Each conversion occurs as if by a call to the wcrtomb function, with the
- conversion state described by the stream's own mbstate_t object. The byte output
- functions write characters to the stream as if by successive calls to the fputc function.
-13 In some cases, some of the byte input/output functions also perform conversions between
- multibyte characters and wide characters. These conversions also occur as if by calls to
- the mbrtowc and wcrtomb functions.
-14 An encoding error occurs if the character sequence presented to the underlying
- mbrtowc function does not form a valid (generalized) multibyte character, or if the code
- value passed to the underlying wcrtomb does not correspond to a valid (generalized)
-
-
- 257) Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END), has
- undefined behavior for a binary stream (because of possible trailing null characters) or for any stream
- with state-dependent encoding that does not assuredly end in the initial shift state.
-
-[page 300]
-
- multibyte character. The wide character input/output functions and the byte input/output
- functions store the value of the macro EILSEQ in errno if and only if an encoding error
- occurs.
- Environmental limits
-15 The value of FOPEN_MAX shall be at least eight, including the three standard text
- streams.
- Forward references: the exit function (7.22.4.4), the fgetc function (7.21.7.1), the
- fopen function (7.21.5.3), the fputc function (7.21.7.3), the setbuf function
- (7.21.5.5), the setvbuf function (7.21.5.6), the fgetwc function (7.28.3.1), the
- fputwc function (7.28.3.3), conversion state (7.28.6), the mbrtowc function
- (7.28.6.3.2), the wcrtomb function (7.28.6.3.3).
- 7.21.4 Operations on files
- 7.21.4.1 The remove function
- Synopsis
-1 #include <stdio.h>
- int remove(const char *filename);
- Description
-2 The remove function causes the file whose name is the string pointed to by filename
- to be no longer accessible by that name. A subsequent attempt to open that file using that
- name will fail, unless it is created anew. If the file is open, the behavior of the remove
- function is implementation-defined.
- Returns
-3 The remove function returns zero if the operation succeeds, nonzero if it fails.
- 7.21.4.2 The rename function
- Synopsis
-1 #include <stdio.h>
- int rename(const char *old, const char *new);
- Description
-2 The rename function causes the file whose name is the string pointed to by old to be
- henceforth known by the name given by the string pointed to by new. The file named
- old is no longer accessible by that name. If a file named by the string pointed to by new
- exists prior to the call to the rename function, the behavior is implementation-defined.
-
-
-
-
-[page 301]
-
- Returns
-3 The rename function returns zero if the operation succeeds, nonzero if it fails,258) in
- which case if the file existed previously it is still known by its original name.
- 7.21.4.3 The tmpfile function
- Synopsis
-1 #include <stdio.h>
- FILE *tmpfile(void);
- Description
-2 The tmpfile function creates a temporary binary file that is different from any other
- existing file and that will automatically be removed when it is closed or at program
- termination. If the program terminates abnormally, whether an open temporary file is
- removed is implementation-defined. The file is opened for update with "wb+" mode.
- Recommended practice
-3 It should be possible to open at least TMP_MAX temporary files during the lifetime of the
- program (this limit may be shared with tmpnam) and there should be no limit on the
- number simultaneously open other than this limit and any limit on the number of open
- files (FOPEN_MAX).
- Returns
-4 The tmpfile function returns a pointer to the stream of the file that it created. If the file
- cannot be created, the tmpfile function returns a null pointer.
- Forward references: the fopen function (7.21.5.3).
- 7.21.4.4 The tmpnam function
- Synopsis
-1 #include <stdio.h>
- char *tmpnam(char *s);
- Description
-2 The tmpnam function generates a string that is a valid file name and that is not the same
- as the name of an existing file.259) The function is potentially capable of generating at
-
-
- 258) Among the reasons the implementation may cause the rename function to fail are that the file is open
- or that it is necessary to copy its contents to effectuate its renaming.
- 259) Files created using strings generated by the tmpnam function are temporary only in the sense that
- their names should not collide with those generated by conventional naming rules for the
- implementation. It is still necessary to use the remove function to remove such files when their use
- is ended, and before program termination.
-
-[page 302]
-
- least TMP_MAX different strings, but any or all of them may already be in use by existing
- files and thus not be suitable return values.
-3 The tmpnam function generates a different string each time it is called.
-4 Calls to the tmpnam function with a null pointer argument may introduce data races with
- each other. The implementation shall behave as if no library function calls the tmpnam
- function.
- Returns
-5 If no suitable string can be generated, the tmpnam function returns a null pointer.
- Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an
- internal static object and returns a pointer to that object (subsequent calls to the tmpnam
- function may modify the same object). If the argument is not a null pointer, it is assumed
- to point to an array of at least L_tmpnam chars; the tmpnam function writes its result
- in that array and returns the argument as its value.
- Environmental limits
-6 The value of the macro TMP_MAX shall be at least 25.
- 7.21.5 File access functions
- 7.21.5.1 The fclose function
- Synopsis
-1 #include <stdio.h>
- int fclose(FILE *stream);
- Description
-2 A successful call to the fclose function causes the stream pointed to by stream to be
- flushed and the associated file to be closed. Any unwritten buffered data for the stream
- are delivered to the host environment to be written to the file; any unread buffered data
- are discarded. Whether or not the call succeeds, the stream is disassociated from the file
- and any buffer set by the setbuf or setvbuf function is disassociated from the stream
- (and deallocated if it was automatically allocated).
- Returns
-3 The fclose function returns zero if the stream was successfully closed, or EOF if any
- errors were detected.
-
-
-
-
-[page 303]
-
- 7.21.5.2 The fflush function
- Synopsis
-1 #include <stdio.h>
- int fflush(FILE *stream);
- Description
-2 If stream points to an output stream or an update stream in which the most recent
- operation was not input, the fflush function causes any unwritten data for that stream
- to be delivered to the host environment to be written to the file; otherwise, the behavior is
- undefined.
-3 If stream is a null pointer, the fflush function performs this flushing action on all
- streams for which the behavior is defined above.
- Returns
-4 The fflush function sets the error indicator for the stream and returns EOF if a write
- error occurs, otherwise it returns zero.
- Forward references: the fopen function (7.21.5.3).
- 7.21.5.3 The fopen function
- Synopsis
-1 #include <stdio.h>
- FILE *fopen(const char * restrict filename,
- const char * restrict mode);
- Description
-2 The fopen function opens the file whose name is the string pointed to by filename,
- and associates a stream with it.
-3 The argument mode points to a string. If the string is one of the following, the file is
- open in the indicated mode. Otherwise, the behavior is undefined.260)
- r open text file for reading
- w truncate to zero length or create text file for writing
- wx create text file for writing
- a append; open or create text file for writing at end-of-file
- rb open binary file for reading
- wb truncate to zero length or create binary file for writing
-
-
- 260) If the string begins with one of the above sequences, the implementation might choose to ignore the
- remaining characters, or it might use them to select different kinds of a file (some of which might not
- conform to the properties in 7.21.2).
-
-[page 304]
-
- wbx create binary file for writing
- ab append; open or create binary file for writing at end-of-file
- r+ open text file for update (reading and writing)
- w+ truncate to zero length or create text file for update
- w+x create text file for update
- a+ append; open or create text file for update, writing at end-of-file
- r+b or rb+ open binary file for update (reading and writing)
- w+b or wb+ truncate to zero length or create binary file for update
- w+bx or wb+x create binary file for update
- a+b or ab+ append; open or create binary file for update, writing at end-of-file
-4 Opening a file with read mode ('r' as the first character in the mode argument) fails if
- the file does not exist or cannot be read.
-5 Opening a file with exclusive mode ('x' as the last character in the mode argument)
- fails if the file already exists or cannot be created. Otherwise, the file is created with
- exclusive (also known as non-shared) access to the extent that the underlying system
- supports exclusive access.
-6 Opening a file with append mode ('a' as the first character in the mode argument)
- causes all subsequent writes to the file to be forced to the then current end-of-file,
- regardless of intervening calls to the fseek function. In some implementations, opening
- a binary file with append mode ('b' as the second or third character in the above list of
- mode argument values) may initially position the file position indicator for the stream
- beyond the last data written, because of null character padding.
-7 When a file is opened with update mode ('+' as the second or third character in the
- above list of mode argument values), both input and output may be performed on the
- associated stream. However, output shall not be directly followed by input without an
- intervening call to the fflush function or to a file positioning function (fseek,
- fsetpos, or rewind), and input shall not be directly followed by output without an
- intervening call to a file positioning function, unless the input operation encounters end-
- of-file. Opening (or creating) a text file with update mode may instead open (or create) a
- binary stream in some implementations.
-8 When opened, a stream is fully buffered if and only if it can be determined not to refer to
- an interactive device. The error and end-of-file indicators for the stream are cleared.
- Returns
-9 The fopen function returns a pointer to the object controlling the stream. If the open
- operation fails, fopen returns a null pointer.
- Forward references: file positioning functions (7.21.9).
-
-
-
-[page 305]
-
- 7.21.5.4 The freopen function
- Synopsis
-1 #include <stdio.h>
- FILE *freopen(const char * restrict filename,
- const char * restrict mode,
- FILE * restrict stream);
- Description
-2 The freopen function opens the file whose name is the string pointed to by filename
- and associates the stream pointed to by stream with it. The mode argument is used just
- as in the fopen function.261)
-3 If filename is a null pointer, the freopen function attempts to change the mode of
- the stream to that specified by mode, as if the name of the file currently associated with
- the stream had been used. It is implementation-defined which changes of mode are
- permitted (if any), and under what circumstances.
-4 The freopen function first attempts to close any file that is associated with the specified
- stream. Failure to close the file is ignored. The error and end-of-file indicators for the
- stream are cleared.
- Returns
-5 The freopen function returns a null pointer if the open operation fails. Otherwise,
- freopen returns the value of stream.
- 7.21.5.5 The setbuf function
- Synopsis
-1 #include <stdio.h>
- void setbuf(FILE * restrict stream,
- char * restrict buf);
- Description
-2 Except that it returns no value, the setbuf function is equivalent to the setvbuf
- function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
- is a null pointer), with the value _IONBF for mode.
-
-
-
-
- 261) The primary use of the freopen function is to change the file associated with a standard text stream
- (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value
- returned by the fopen function may be assigned.
-
-[page 306]
-
- Returns
-3 The setbuf function returns no value.
- Forward references: the setvbuf function (7.21.5.6).
- 7.21.5.6 The setvbuf function
- Synopsis
-1 #include <stdio.h>
- int setvbuf(FILE * restrict stream,
- char * restrict buf,
- int mode, size_t size);
- Description
-2 The setvbuf function may be used only after the stream pointed to by stream has
- been associated with an open file and before any other operation (other than an
- unsuccessful call to setvbuf) is performed on the stream. The argument mode
- determines how stream will be buffered, as follows: _IOFBF causes input/output to be
- fully buffered; _IOLBF causes input/output to be line buffered; _IONBF causes
- input/output to be unbuffered. If buf is not a null pointer, the array it points to may be
- used instead of a buffer allocated by the setvbuf function262) and the argument size
- specifies the size of the array; otherwise, size may determine the size of a buffer
- allocated by the setvbuf function. The contents of the array at any time are
- indeterminate.
- Returns
-3 The setvbuf function returns zero on success, or nonzero if an invalid value is given
- for mode or if the request cannot be honored.
-
-
-
-
- 262) The buffer has to have a lifetime at least as great as the open stream, so the stream should be closed
- before a buffer that has automatic storage duration is deallocated upon block exit.
-
-[page 307]
-
- 7.21.6 Formatted input/output functions
-1 The formatted input/output functions shall behave as if there is a sequence point after the
- actions associated with each specifier.263)
- 7.21.6.1 The fprintf function
- Synopsis
-1 #include <stdio.h>
- int fprintf(FILE * restrict stream,
- const char * restrict format, ...);
- Description
-2 The fprintf function writes output to the stream pointed to by stream, under control
- of the string pointed to by format that specifies how subsequent arguments are
- converted for output. If there are insufficient arguments for the format, the behavior is
- undefined. If the format is exhausted while arguments remain, the excess arguments are
- evaluated (as always) but are otherwise ignored. The fprintf function returns when
- the end of the format string is encountered.
-3 The format shall be a multibyte character sequence, beginning and ending in its initial
- shift state. The format is composed of zero or more directives: ordinary multibyte
- characters (not %), which are copied unchanged to the output stream; and conversion
- specifications, each of which results in fetching zero or more subsequent arguments,
- converting them, if applicable, according to the corresponding conversion specifier, and
- then writing the result to the output stream.
-4 Each conversion specification is introduced by the character %. After the %, the following
- appear in sequence:
- -- Zero or more flags (in any order) that modify the meaning of the conversion
- specification.
- -- An optional minimum field width. If the converted value has fewer characters than the
- field width, it is padded with spaces (by default) on the left (or right, if the left
- adjustment flag, described later, has been given) to the field width. The field width
- takes the form of an asterisk * (described later) or a nonnegative decimal integer.264)
- -- An optional precision that gives the minimum number of digits to appear for the d, i,
- o, u, x, and X conversions, the number of digits to appear after the decimal-point
- character for a, A, e, E, f, and F conversions, the maximum number of significant
- digits for the g and G conversions, or the maximum number of bytes to be written for
-
-
- 263) The fprintf functions perform writes to memory for the %n specifier.
- 264) Note that 0 is taken as a flag, not as the beginning of a field width.
-
-[page 308]
-
- s conversions. The precision takes the form of a period (.) followed either by an
- asterisk * (described later) or by an optional decimal integer; if only the period is
- specified, the precision is taken as zero. If a precision appears with any other
- conversion specifier, the behavior is undefined.
- -- An optional length modifier that specifies the size of the argument.
- -- A conversion specifier character that specifies the type of conversion to be applied.
-5 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
- this case, an int argument supplies the field width or precision. The arguments
- specifying field width, or precision, or both, shall appear (in that order) before the
- argument (if any) to be converted. A negative field width argument is taken as a - flag
- followed by a positive field width. A negative precision argument is taken as if the
- precision were omitted.
-6 The flag characters and their meanings are:
- - The result of the conversion is left-justified within the field. (It is right-justified if
- this flag is not specified.)
- + The result of a signed conversion always begins with a plus or minus sign. (It
- begins with a sign only when a negative value is converted if this flag is not
- specified.)265)
- space If the first character of a signed conversion is not a sign, or if a signed conversion
- results in no characters, a space is prefixed to the result. If the space and + flags
- both appear, the space flag is ignored.
- # The result is converted to an ''alternative form''. For o conversion, it increases
- the precision, if and only if necessary, to force the first digit of the result to be a
- zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
- conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
- and G conversions, the result of converting a floating-point number always
- contains a decimal-point character, even if no digits follow it. (Normally, a
- decimal-point character appears in the result of these conversions only if a digit
- follows it.) For g and G conversions, trailing zeros are not removed from the
- result. For other conversions, the behavior is undefined.
- 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
- (following any indication of sign or base) are used to pad to the field width rather
- than performing space padding, except when converting an infinity or NaN. If the
- 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
-
-
- 265) The results of all floating conversions of a negative zero, and of negative values that round to zero,
- include a minus sign.
-
-[page 309]
-
- conversions, if a precision is specified, the 0 flag is ignored. For other
- conversions, the behavior is undefined.
-7 The length modifiers and their meanings are:
- hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- signed char or unsigned char argument (the argument will have
- been promoted according to the integer promotions, but its value shall be
- converted to signed char or unsigned char before printing); or that
- a following n conversion specifier applies to a pointer to a signed char
- argument.
- h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- short int or unsigned short int argument (the argument will
- have been promoted according to the integer promotions, but its value shall
- be converted to short int or unsigned short int before printing);
- or that a following n conversion specifier applies to a pointer to a short
- int argument.
- l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- long int or unsigned long int argument; that a following n
- conversion specifier applies to a pointer to a long int argument; that a
- following c conversion specifier applies to a wint_t argument; that a
- following s conversion specifier applies to a pointer to a wchar_t
- argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
- specifier.
- ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- long long int or unsigned long long int argument; or that a
- following n conversion specifier applies to a pointer to a long long int
- argument.
- j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
- an intmax_t or uintmax_t argument; or that a following n conversion
- specifier applies to a pointer to an intmax_t argument.
- z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- size_t or the corresponding signed integer type argument; or that a
- following n conversion specifier applies to a pointer to a signed integer type
- corresponding to size_t argument.
- t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- ptrdiff_t or the corresponding unsigned integer type argument; or that a
- following n conversion specifier applies to a pointer to a ptrdiff_t
- argument.
-
-
-[page 310]
-
- L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
- applies to a long double argument.
- If a length modifier appears with any conversion specifier other than as specified above,
- the behavior is undefined.
-8 The conversion specifiers and their meanings are:
- d,i The int argument is converted to signed decimal in the style [-]dddd. The
- precision specifies the minimum number of digits to appear; if the value
- being converted can be represented in fewer digits, it is expanded with
- leading zeros. The default precision is 1. The result of converting a zero
- value with a precision of zero is no characters.
- o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
- decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
- letters abcdef are used for x conversion and the letters ABCDEF for X
- conversion. The precision specifies the minimum number of digits to appear;
- if the value being converted can be represented in fewer digits, it is expanded
- with leading zeros. The default precision is 1. The result of converting a
- zero value with a precision of zero is no characters.
- f,F A double argument representing a floating-point number is converted to
- decimal notation in the style [-]ddd.ddd, where the number of digits after
- the decimal-point character is equal to the precision specification. If the
- precision is missing, it is taken as 6; if the precision is zero and the # flag is
- not specified, no decimal-point character appears. If a decimal-point
- character appears, at least one digit appears before it. The value is rounded to
- the appropriate number of digits.
- A double argument representing an infinity is converted in one of the styles
- [-]inf or [-]infinity -- which style is implementation-defined. A
- double argument representing a NaN is converted in one of the styles
- [-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
- any n-char-sequence, is implementation-defined. The F conversion specifier
- produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
- respectively.266)
- e,E A double argument representing a floating-point number is converted in the
- style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
- argument is nonzero) before the decimal-point character and the number of
- digits after it is equal to the precision; if the precision is missing, it is taken as
-
-
- 266) When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning;
- the # and 0 flag characters have no effect.
-
-[page 311]
-
- 6; if the precision is zero and the # flag is not specified, no decimal-point
- character appears. The value is rounded to the appropriate number of digits.
- The E conversion specifier produces a number with E instead of e
- introducing the exponent. The exponent always contains at least two digits,
- and only as many more digits as necessary to represent the exponent. If the
- value is zero, the exponent is zero.
- A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
-g,G A double argument representing a floating-point number is converted in
- style f or e (or in style F or E in the case of a G conversion specifier),
- depending on the value converted and the precision. Let P equal the
- precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
- Then, if a conversion with style E would have an exponent of X:
- -- if P > X >= -4, the conversion is with style f (or F) and precision
- P - (X + 1).
- -- otherwise, the conversion is with style e (or E) and precision P - 1.
- Finally, unless the # flag is used, any trailing zeros are removed from the
- fractional portion of the result and the decimal-point character is removed if
- there is no fractional portion remaining.
- A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
-a,A A double argument representing a floating-point number is converted in the
- style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
- nonzero if the argument is a normalized floating-point number and is
- otherwise unspecified) before the decimal-point character267) and the number
- of hexadecimal digits after it is equal to the precision; if the precision is
- missing and FLT_RADIX is a power of 2, then the precision is sufficient for
- an exact representation of the value; if the precision is missing and
- FLT_RADIX is not a power of 2, then the precision is sufficient to
-
-
-
-
-267) Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so
- that subsequent digits align to nibble (4-bit) boundaries.
-
-[page 312]
-
- distinguish268) values of type double, except that trailing zeros may be
- omitted; if the precision is zero and the # flag is not specified, no decimal-
- point character appears. The letters abcdef are used for a conversion and
- the letters ABCDEF for A conversion. The A conversion specifier produces a
- number with X and P instead of x and p. The exponent always contains at
- least one digit, and only as many more digits as necessary to represent the
- decimal exponent of 2. If the value is zero, the exponent is zero.
- A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
-c If no l length modifier is present, the int argument is converted to an
- unsigned char, and the resulting character is written.
- If an l length modifier is present, the wint_t argument is converted as if by
- an ls conversion specification with no precision and an argument that points
- to the initial element of a two-element array of wchar_t, the first element
- containing the wint_t argument to the lc conversion specification and the
- second a null wide character.
-s If no l length modifier is present, the argument shall be a pointer to the initial
- element of an array of character type.269) Characters from the array are
- written up to (but not including) the terminating null character. If the
- precision is specified, no more than that many bytes are written. If the
- precision is not specified or is greater than the size of the array, the array shall
- contain a null character.
- If an l length modifier is present, the argument shall be a pointer to the initial
- element of an array of wchar_t type. Wide characters from the array are
- converted to multibyte characters (each as if by a call to the wcrtomb
- function, with the conversion state described by an mbstate_t object
- initialized to zero before the first wide character is converted) up to and
- including a terminating null wide character. The resulting multibyte
- characters are written up to (but not including) the terminating null character
- (byte). If no precision is specified, the array shall contain a null wide
- character. If a precision is specified, no more than that many bytes are
- written (including shift sequences, if any), and the array shall contain a null
- wide character if, to equal the multibyte character sequence length given by
-
-268) The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
- FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
- might suffice depending on the implementation's scheme for determining the digit to the left of the
- decimal-point character.
-269) No special provisions are made for multibyte characters.
-
-[page 313]
-
- the precision, the function would need to access a wide character one past the
- end of the array. In no case is a partial multibyte character written.270)
- p The argument shall be a pointer to void. The value of the pointer is
- converted to a sequence of printing characters, in an implementation-defined
- manner.
- n The argument shall be a pointer to signed integer into which is written the
- number of characters written to the output stream so far by this call to
- fprintf. No argument is converted, but one is consumed. If the conversion
- specification includes any flags, a field width, or a precision, the behavior is
- undefined.
- % A % character is written. No argument is converted. The complete
- conversion specification shall be %%.
-9 If a conversion specification is invalid, the behavior is undefined.271) If any argument is
- not the correct type for the corresponding conversion specification, the behavior is
- undefined.
-10 In no case does a nonexistent or small field width cause truncation of a field; if the result
- of a conversion is wider than the field width, the field is expanded to contain the
- conversion result.
-11 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
- to a hexadecimal floating number with the given precision.
- Recommended practice
-12 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
- representable in the given precision, the result should be one of the two adjacent numbers
- in hexadecimal floating style with the given precision, with the extra stipulation that the
- error should have a correct sign for the current rounding direction.
-13 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
- DECIMAL_DIG, then the result should be correctly rounded.272) If the number of
- significant decimal digits is more than DECIMAL_DIG but the source value is exactly
- representable with DECIMAL_DIG digits, then the result should be an exact
- representation with trailing zeros. Otherwise, the source value is bounded by two
- adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
-
-
- 270) Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
- 271) See ''future library directions'' (7.30.9).
- 272) For binary-to-decimal conversion, the result format's values are the numbers representable with the
- given format specifier. The number of significant digits is determined by the format specifier, and in
- the case of fixed-point conversion by the source value as well.
-
-[page 314]
-
- of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
- the error should have a correct sign for the current rounding direction.
- Returns
-14 The fprintf function returns the number of characters transmitted, or a negative value
- if an output or encoding error occurred.
- Environmental limits
-15 The number of characters that can be produced by any single conversion shall be at least
- 4095.
-16 EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
- places:
- #include <math.h>
- #include <stdio.h>
- /* ... */
- char *weekday, *month; // pointers to strings
- int day, hour, min;
- fprintf(stdout, "%s, %s %d, %.2d:%.2d\n",
- weekday, month, day, hour, min);
- fprintf(stdout, "pi = %.5f\n", 4 * atan(1.0));
-
-17 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the
- members of the extended character set that consist of more than one byte each consist of exactly two bytes,
- the first of which is denoted here by a and the second by an uppercase letter.
-18 Given the following wide string with length seven,
- static wchar_t wstr[] = L" X Yabc Z W";
- the seven calls
- fprintf(stdout, "|1234567890123|\n");
- fprintf(stdout, "|%13ls|\n", wstr);
- fprintf(stdout, "|%-13.9ls|\n", wstr);
- fprintf(stdout, "|%13.10ls|\n", wstr);
- fprintf(stdout, "|%13.11ls|\n", wstr);
- fprintf(stdout, "|%13.15ls|\n", &wstr[2]);
- fprintf(stdout, "|%13lc|\n", (wint_t) wstr[5]);
- will print the following seven lines:
- |1234567890123|
- | X Yabc Z W|
- | X Yabc Z |
- | X Yabc Z|
- | X Yabc Z W|
- | abc Z W|
- | Z|
-
- Forward references: conversion state (7.28.6), the wcrtomb function (7.28.6.3.3).
-
-
-
-[page 315]
-
- 7.21.6.2 The fscanf function
- Synopsis
-1 #include <stdio.h>
- int fscanf(FILE * restrict stream,
- const char * restrict format, ...);
- Description
-2 The fscanf function reads input from the stream pointed to by stream, under control
- of the string pointed to by format that specifies the admissible input sequences and how
- they are to be converted for assignment, using subsequent arguments as pointers to the
- objects to receive the converted input. If there are insufficient arguments for the format,
- the behavior is undefined. If the format is exhausted while arguments remain, the excess
- arguments are evaluated (as always) but are otherwise ignored.
-3 The format shall be a multibyte character sequence, beginning and ending in its initial
- shift state. The format is composed of zero or more directives: one or more white-space
- characters, an ordinary multibyte character (neither % nor a white-space character), or a
- conversion specification. Each conversion specification is introduced by the character %.
- After the %, the following appear in sequence:
- -- An optional assignment-suppressing character *.
- -- An optional decimal integer greater than zero that specifies the maximum field width
- (in characters).
- -- An optional length modifier that specifies the size of the receiving object.
- -- A conversion specifier character that specifies the type of conversion to be applied.
-4 The fscanf function executes each directive of the format in turn. When all directives
- have been executed, or if a directive fails (as detailed below), the function returns.
- Failures are described as input failures (due to the occurrence of an encoding error or the
- unavailability of input characters), or matching failures (due to inappropriate input).
-5 A directive composed of white-space character(s) is executed by reading input up to the
- first non-white-space character (which remains unread), or until no more characters can
- be read.
-6 A directive that is an ordinary multibyte character is executed by reading the next
- characters of the stream. If any of those characters differ from the ones composing the
- directive, the directive fails and the differing and subsequent characters remain unread.
- Similarly, if end-of-file, an encoding error, or a read error prevents a character from being
- read, the directive fails.
-7 A directive that is a conversion specification defines a set of matching input sequences, as
- described below for each specifier. A conversion specification is executed in the
-
-[page 316]
-
- following steps:
-8 Input white-space characters (as specified by the isspace function) are skipped, unless
- the specification includes a [, c, or n specifier.273)
-9 An input item is read from the stream, unless the specification includes an n specifier. An
- input item is defined as the longest sequence of input characters which does not exceed
- any specified field width and which is, or is a prefix of, a matching input sequence.274)
- The first character, if any, after the input item remains unread. If the length of the input
- item is zero, the execution of the directive fails; this condition is a matching failure unless
- end-of-file, an encoding error, or a read error prevented input from the stream, in which
- case it is an input failure.
-10 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
- count of input characters) is converted to a type appropriate to the conversion specifier. If
- the input item is not a matching sequence, the execution of the directive fails: this
- condition is a matching failure. Unless assignment suppression was indicated by a *, the
- result of the conversion is placed in the object pointed to by the first argument following
- the format argument that has not already received a conversion result. If this object
- does not have an appropriate type, or if the result of the conversion cannot be represented
- in the object, the behavior is undefined.
-11 The length modifiers and their meanings are:
- hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to signed char or unsigned char.
- h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to short int or unsigned short
- int.
- l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to long int or unsigned long
- int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
- an argument with type pointer to double; or that a following c, s, or [
- conversion specifier applies to an argument with type pointer to wchar_t.
- ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to long long int or unsigned
- long long int.
-
-
-
- 273) These white-space characters are not counted against a specified field width.
- 274) fscanf pushes back at most one input character onto the input stream. Therefore, some sequences
- that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.
-
-[page 317]
-
- j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to intmax_t or uintmax_t.
- z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to size_t or the corresponding signed
- integer type.
- t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to ptrdiff_t or the corresponding
- unsigned integer type.
- L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
- applies to an argument with type pointer to long double.
- If a length modifier appears with any conversion specifier other than as specified above,
- the behavior is undefined.
-12 The conversion specifiers and their meanings are:
- d Matches an optionally signed decimal integer, whose format is the same as
- expected for the subject sequence of the strtol function with the value 10
- for the base argument. The corresponding argument shall be a pointer to
- signed integer.
- i Matches an optionally signed integer, whose format is the same as expected
- for the subject sequence of the strtol function with the value 0 for the
- base argument. The corresponding argument shall be a pointer to signed
- integer.
- o Matches an optionally signed octal integer, whose format is the same as
- expected for the subject sequence of the strtoul function with the value 8
- for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
- u Matches an optionally signed decimal integer, whose format is the same as
- expected for the subject sequence of the strtoul function with the value 10
- for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
- x Matches an optionally signed hexadecimal integer, whose format is the same
- as expected for the subject sequence of the strtoul function with the value
- 16 for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
- a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
- format is the same as expected for the subject sequence of the strtod
- function. The corresponding argument shall be a pointer to floating.
-
-
-[page 318]
-
-c Matches a sequence of characters of exactly the number specified by the field
- width (1 if no field width is present in the directive).275)
- If no l length modifier is present, the corresponding argument shall be a
- pointer to the initial element of a character array large enough to accept the
- sequence. No null character is added.
- If an l length modifier is present, the input shall be a sequence of multibyte
- characters that begins in the initial shift state. Each multibyte character in the
- sequence is converted to a wide character as if by a call to the mbrtowc
- function, with the conversion state described by an mbstate_t object
- initialized to zero before the first multibyte character is converted. The
- corresponding argument shall be a pointer to the initial element of an array of
- wchar_t large enough to accept the resulting sequence of wide characters.
- No null wide character is added.
-s Matches a sequence of non-white-space characters.275)
- If no l length modifier is present, the corresponding argument shall be a
- pointer to the initial element of a character array large enough to accept the
- sequence and a terminating null character, which will be added automatically.
- If an l length modifier is present, the input shall be a sequence of multibyte
- characters that begins in the initial shift state. Each multibyte character is
- converted to a wide character as if by a call to the mbrtowc function, with
- the conversion state described by an mbstate_t object initialized to zero
- before the first multibyte character is converted. The corresponding argument
- shall be a pointer to the initial element of an array of wchar_t large enough
- to accept the sequence and the terminating null wide character, which will be
- added automatically.
-[ Matches a nonempty sequence of characters from a set of expected characters
- (the scanset).275)
- If no l length modifier is present, the corresponding argument shall be a
- pointer to the initial element of a character array large enough to accept the
- sequence and a terminating null character, which will be added automatically.
- If an l length modifier is present, the input shall be a sequence of multibyte
- characters that begins in the initial shift state. Each multibyte character is
- converted to a wide character as if by a call to the mbrtowc function, with
- the conversion state described by an mbstate_t object initialized to zero
-
-275) No special provisions are made for multibyte characters in the matching rules used by the c, s, and [
- conversion specifiers -- the extent of the input field is determined on a byte-by-byte basis. The
- resulting field is nevertheless a sequence of multibyte characters that begins in the initial shift state.
-
-[page 319]
-
- before the first multibyte character is converted. The corresponding argument
- shall be a pointer to the initial element of an array of wchar_t large enough
- to accept the sequence and the terminating null wide character, which will be
- added automatically.
- The conversion specifier includes all subsequent characters in the format
- string, up to and including the matching right bracket (]). The characters
- between the brackets (the scanlist) compose the scanset, unless the character
- after the left bracket is a circumflex (^), in which case the scanset contains all
- characters that do not appear in the scanlist between the circumflex and the
- right bracket. If the conversion specifier begins with [] or [^], the right
- bracket character is in the scanlist and the next following right bracket
- character is the matching right bracket that ends the specification; otherwise
- the first following right bracket character is the one that ends the
- specification. If a - character is in the scanlist and is not the first, nor the
- second where the first character is a ^, nor the last character, the behavior is
- implementation-defined.
- p Matches an implementation-defined set of sequences, which should be the
- same as the set of sequences that may be produced by the %p conversion of
- the fprintf function. The corresponding argument shall be a pointer to a
- pointer to void. The input item is converted to a pointer value in an
- implementation-defined manner. If the input item is a value converted earlier
- during the same program execution, the pointer that results shall compare
- equal to that value; otherwise the behavior of the %p conversion is undefined.
- n No input is consumed. The corresponding argument shall be a pointer to
- signed integer into which is to be written the number of characters read from
- the input stream so far by this call to the fscanf function. Execution of a
- %n directive does not increment the assignment count returned at the
- completion of execution of the fscanf function. No argument is converted,
- but one is consumed. If the conversion specification includes an assignment-
- suppressing character or a field width, the behavior is undefined.
- % Matches a single % character; no conversion or assignment occurs. The
- complete conversion specification shall be %%.
-13 If a conversion specification is invalid, the behavior is undefined.276)
-14 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
- respectively, a, e, f, g, and x.
-
-
-
- 276) See ''future library directions'' (7.30.9).
-
-[page 320]
-
-15 Trailing white space (including new-line characters) is left unread unless matched by a
- directive. The success of literal matches and suppressed assignments is not directly
- determinable other than via the %n directive.
- Returns
-16 The fscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the function returns the
- number of input items assigned, which can be fewer than provided for, or even zero, in
- the event of an early matching failure.
-17 EXAMPLE 1 The call:
- #include <stdio.h>
- /* ... */
- int n, i; float x; char name[50];
- n = fscanf(stdin, "%d%f%s", &i, &x, name);
- with the input line:
- 25 54.32E-1 thompson
- will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
- thompson\0.
-
-18 EXAMPLE 2 The call:
- #include <stdio.h>
- /* ... */
- int i; float x; char name[50];
- fscanf(stdin, "%2d%f%*d %[0123456789]", &i, &x, name);
- with input:
- 56789 0123 56a72
- will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the
- sequence 56\0. The next character read from the input stream will be a.
-
-19 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
- #include <stdio.h>
- /* ... */
- int count; float quant; char units[21], item[21];
- do {
- count = fscanf(stdin, "%f%20s of %20s", &quant, units, item);
- fscanf(stdin,"%*[^\n]");
- } while (!feof(stdin) && !ferror(stdin));
-20 If the stdin stream contains the following lines:
- 2 quarts of oil
- -12.8degrees Celsius
- lots of luck
- 10.0LBS of
- dirt
- 100ergs of energy
-
-[page 321]
-
- the execution of the above example will be analogous to the following assignments:
- quant = 2; strcpy(units, "quarts"); strcpy(item, "oil");
- count = 3;
- quant = -12.8; strcpy(units, "degrees");
- count = 2; // "C" fails to match "o"
- count = 0; // "l" fails to match "%f"
- quant = 10.0; strcpy(units, "LBS"); strcpy(item, "dirt");
- count = 3;
- count = 0; // "100e" fails to match "%f"
- count = EOF;
-
-21 EXAMPLE 4 In:
- #include <stdio.h>
- /* ... */
- int d1, d2, n1, n2, i;
- i = sscanf("123", "%d%n%n%d", &d1, &n1, &n2, &d2);
- the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure the value
- of 3 is also assigned to n2. The value of d2 is not affected. The value 1 is assigned to i.
-
-22 EXAMPLE 5 In these examples, multibyte characters do have a state-dependent encoding, and the
- members of the extended character set that consist of more than one byte each consist of exactly two bytes,
- the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as
- such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes
- entry into the alternate shift state.
-23 After the call:
- #include <stdio.h>
- /* ... */
- char str[50];
- fscanf(stdin, "a%s", str);
- with the input line:
- a(uparrow) X Y(downarrow) bc
- str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte
- characters, in the more general case) appears to be a single-byte white-space character.
-24 In contrast, after the call:
- #include <stdio.h>
- #include <stddef.h>
- /* ... */
- wchar_t wstr[50];
- fscanf(stdin, "a%ls", wstr);
- with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
- terminating null wide character.
-25 However, the call:
-
-
-
-
-[page 322]
-
- #include <stdio.h>
- #include <stddef.h>
- /* ... */
- wchar_t wstr[50];
- fscanf(stdin, "a(uparrow) X(downarrow)%ls", wstr);
- with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
- string.
-26 Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte
- character Y, after the call:
- #include <stdio.h>
- #include <stddef.h>
- /* ... */
- wchar_t wstr[50];
- fscanf(stdin, "a(uparrow) Y(downarrow)%ls", wstr);
- with the same input line, zero will again be returned, but stdin will be left with a partially consumed
- multibyte character.
-
- Forward references: the strtod, strtof, and strtold functions (7.22.1.3), the
- strtol, strtoll, strtoul, and strtoull functions (7.22.1.4), conversion state
- (7.28.6), the wcrtomb function (7.28.6.3.3).
- 7.21.6.3 The printf function
- Synopsis
-1 #include <stdio.h>
- int printf(const char * restrict format, ...);
- Description
-2 The printf function is equivalent to fprintf with the argument stdout interposed
- before the arguments to printf.
- Returns
-3 The printf function returns the number of characters transmitted, or a negative value if
- an output or encoding error occurred.
- 7.21.6.4 The scanf function
- Synopsis
-1 #include <stdio.h>
- int scanf(const char * restrict format, ...);
- Description
-2 The scanf function is equivalent to fscanf with the argument stdin interposed
- before the arguments to scanf.
-
-
-
-[page 323]
-
- Returns
-3 The scanf function returns the value of the macro EOF if an input failure occurs before
- the first conversion (if any) has completed. Otherwise, the scanf function returns the
- number of input items assigned, which can be fewer than provided for, or even zero, in
- the event of an early matching failure.
- 7.21.6.5 The snprintf function
- Synopsis
-1 #include <stdio.h>
- int snprintf(char * restrict s, size_t n,
- const char * restrict format, ...);
- Description
-2 The snprintf function is equivalent to fprintf, except that the output is written into
- an array (specified by argument s) rather than to a stream. If n is zero, nothing is written,
- and s may be a null pointer. Otherwise, output characters beyond the n-1st are
- discarded rather than being written to the array, and a null character is written at the end
- of the characters actually written into the array. If copying takes place between objects
- that overlap, the behavior is undefined.
- Returns
-3 The snprintf function returns the number of characters that would have been written
- had n been sufficiently large, not counting the terminating null character, or a negative
- value if an encoding error occurred. Thus, the null-terminated output has been
- completely written if and only if the returned value is nonnegative and less than n.
- 7.21.6.6 The sprintf function
- Synopsis
-1 #include <stdio.h>
- int sprintf(char * restrict s,
- const char * restrict format, ...);
- Description
-2 The sprintf function is equivalent to fprintf, except that the output is written into
- an array (specified by the argument s) rather than to a stream. A null character is written
- at the end of the characters written; it is not counted as part of the returned value. If
- copying takes place between objects that overlap, the behavior is undefined.
- Returns
-3 The sprintf function returns the number of characters written in the array, not
- counting the terminating null character, or a negative value if an encoding error occurred.
-
-[page 324]
-
- 7.21.6.7 The sscanf function
- Synopsis
-1 #include <stdio.h>
- int sscanf(const char * restrict s,
- const char * restrict format, ...);
- Description
-2 The sscanf function is equivalent to fscanf, except that input is obtained from a
- string (specified by the argument s) rather than from a stream. Reaching the end of the
- string is equivalent to encountering end-of-file for the fscanf function. If copying
- takes place between objects that overlap, the behavior is undefined.
- Returns
-3 The sscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the sscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
- 7.21.6.8 The vfprintf function
- Synopsis
-1 #include <stdarg.h>
- #include <stdio.h>
- int vfprintf(FILE * restrict stream,
- const char * restrict format,
- va_list arg);
- Description
-2 The vfprintf function is equivalent to fprintf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vfprintf function does not invoke the
- va_end macro.277)
- Returns
-3 The vfprintf function returns the number of characters transmitted, or a negative
- value if an output or encoding error occurred.
-4 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
-
-
-
-
- 277) As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
- vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
-
-[page 325]
-
- #include <stdarg.h>
- #include <stdio.h>
- void error(char *function_name, char *format, ...)
- {
- va_list args;
- va_start(args, format);
- // print out name of function causing error
- fprintf(stderr, "ERROR in %s: ", function_name);
- // print out remainder of message
- vfprintf(stderr, format, args);
- va_end(args);
- }
-
- 7.21.6.9 The vfscanf function
- Synopsis
-1 #include <stdarg.h>
- #include <stdio.h>
- int vfscanf(FILE * restrict stream,
- const char * restrict format,
- va_list arg);
- Description
-2 The vfscanf function is equivalent to fscanf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vfscanf function does not invoke the
- va_end macro.277)
- Returns
-3 The vfscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the vfscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
- 7.21.6.10 The vprintf function
- Synopsis
-1 #include <stdarg.h>
- #include <stdio.h>
- int vprintf(const char * restrict format,
- va_list arg);
- Description
-2 The vprintf function is equivalent to printf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
-
-[page 326]
-
- possibly subsequent va_arg calls). The vprintf function does not invoke the
- va_end macro.277)
- Returns
-3 The vprintf function returns the number of characters transmitted, or a negative value
- if an output or encoding error occurred.
- 7.21.6.11 The vscanf function
- Synopsis
-1 #include <stdarg.h>
- #include <stdio.h>
- int vscanf(const char * restrict format,
- va_list arg);
- Description
-2 The vscanf function is equivalent to scanf, with the variable argument list replaced
- by arg, which shall have been initialized by the va_start macro (and possibly
- subsequent va_arg calls). The vscanf function does not invoke the va_end
- macro.277)
- Returns
-3 The vscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the vscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
- 7.21.6.12 The vsnprintf function
- Synopsis
-1 #include <stdarg.h>
- #include <stdio.h>
- int vsnprintf(char * restrict s, size_t n,
- const char * restrict format,
- va_list arg);
- Description
-2 The vsnprintf function is equivalent to snprintf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vsnprintf function does not invoke the
- va_end macro.277) If copying takes place between objects that overlap, the behavior is
- undefined.
-
-
-
-[page 327]
-
- Returns
-3 The vsnprintf function returns the number of characters that would have been written
- had n been sufficiently large, not counting the terminating null character, or a negative
- value if an encoding error occurred. Thus, the null-terminated output has been
- completely written if and only if the returned value is nonnegative and less than n.
- 7.21.6.13 The vsprintf function
- Synopsis
-1 #include <stdarg.h>
- #include <stdio.h>
- int vsprintf(char * restrict s,
- const char * restrict format,
- va_list arg);
- Description
-2 The vsprintf function is equivalent to sprintf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vsprintf function does not invoke the
- va_end macro.277) If copying takes place between objects that overlap, the behavior is
- undefined.
- Returns
-3 The vsprintf function returns the number of characters written in the array, not
- counting the terminating null character, or a negative value if an encoding error occurred.
- 7.21.6.14 The vsscanf function
- Synopsis
-1 #include <stdarg.h>
- #include <stdio.h>
- int vsscanf(const char * restrict s,
- const char * restrict format,
- va_list arg);
- Description
-2 The vsscanf function is equivalent to sscanf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vsscanf function does not invoke the
- va_end macro.277)
- Returns
-3 The vsscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the vsscanf function
-[page 328]
-
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
- 7.21.7 Character input/output functions
- 7.21.7.1 The fgetc function
- Synopsis
-1 #include <stdio.h>
- int fgetc(FILE *stream);
- Description
-2 If the end-of-file indicator for the input stream pointed to by stream is not set and a
- next character is present, the fgetc function obtains that character as an unsigned
- char converted to an int and advances the associated file position indicator for the
- stream (if defined).
- Returns
-3 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
- of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the
- fgetc function returns the next character from the input stream pointed to by stream.
- If a read error occurs, the error indicator for the stream is set and the fgetc function
- returns EOF.278)
- 7.21.7.2 The fgets function
- Synopsis
-1 #include <stdio.h>
- char *fgets(char * restrict s, int n,
- FILE * restrict stream);
- Description
-2 The fgets function reads at most one less than the number of characters specified by n
- from the stream pointed to by stream into the array pointed to by s. No additional
- characters are read after a new-line character (which is retained) or after end-of-file. A
- null character is written immediately after the last character read into the array.
- Returns
-3 The fgets function returns s if successful. If end-of-file is encountered and no
- characters have been read into the array, the contents of the array remain unchanged and a
- null pointer is returned. If a read error occurs during the operation, the array contents are
- indeterminate and a null pointer is returned.
-
- 278) An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
-
-[page 329]
-
- 7.21.7.3 The fputc function
- Synopsis
-1 #include <stdio.h>
- int fputc(int c, FILE *stream);
- Description
-2 The fputc function writes the character specified by c (converted to an unsigned
- char) to the output stream pointed to by stream, at the position indicated by the
- associated file position indicator for the stream (if defined), and advances the indicator
- appropriately. If the file cannot support positioning requests, or if the stream was opened
- with append mode, the character is appended to the output stream.
- Returns
-3 The fputc function returns the character written. If a write error occurs, the error
- indicator for the stream is set and fputc returns EOF.
- 7.21.7.4 The fputs function
- Synopsis
-1 #include <stdio.h>
- int fputs(const char * restrict s,
- FILE * restrict stream);
- Description
-2 The fputs function writes the string pointed to by s to the stream pointed to by
- stream. The terminating null character is not written.
- Returns
-3 The fputs function returns EOF if a write error occurs; otherwise it returns a
- nonnegative value.
- 7.21.7.5 The getc function
- Synopsis
-1 #include <stdio.h>
- int getc(FILE *stream);
- Description
-2 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it
- may evaluate stream more than once, so the argument should never be an expression
- with side effects.
-
-
-
-
-[page 330]
-
- Returns
-3 The getc function returns the next character from the input stream pointed to by
- stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
- getc returns EOF. If a read error occurs, the error indicator for the stream is set and
- getc returns EOF.
- 7.21.7.6 The getchar function
- Synopsis
-1 #include <stdio.h>
- int getchar(void);
- Description
-2 The getchar function is equivalent to getc with the argument stdin.
- Returns
-3 The getchar function returns the next character from the input stream pointed to by
- stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
- getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
- getchar returns EOF.
- 7.21.7.7 The putc function
- Synopsis
-1 #include <stdio.h>
- int putc(int c, FILE *stream);
- Description
-2 The putc function is equivalent to fputc, except that if it is implemented as a macro, it
- may evaluate stream more than once, so that argument should never be an expression
- with side effects.
- Returns
-3 The putc function returns the character written. If a write error occurs, the error
- indicator for the stream is set and putc returns EOF.
- 7.21.7.8 The putchar function
- Synopsis
-1 #include <stdio.h>
- int putchar(int c);
- Description
-2 The putchar function is equivalent to putc with the second argument stdout.
-
-
-[page 331]
-
- Returns
-3 The putchar function returns the character written. If a write error occurs, the error
- indicator for the stream is set and putchar returns EOF.
- 7.21.7.9 The puts function
- Synopsis
-1 #include <stdio.h>
- int puts(const char *s);
- Description
-2 The puts function writes the string pointed to by s to the stream pointed to by stdout,
- and appends a new-line character to the output. The terminating null character is not
- written.
- Returns
-3 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
- value.
- 7.21.7.10 The ungetc function
- Synopsis
-1 #include <stdio.h>
- int ungetc(int c, FILE *stream);
- Description
-2 The ungetc function pushes the character specified by c (converted to an unsigned
- char) back onto the input stream pointed to by stream. Pushed-back characters will be
- returned by subsequent reads on that stream in the reverse order of their pushing. A
- successful intervening call (with the stream pointed to by stream) to a file positioning
- function (fseek, fsetpos, or rewind) discards any pushed-back characters for the
- stream. The external storage corresponding to the stream is unchanged.
-3 One character of pushback is guaranteed. If the ungetc function is called too many
- times on the same stream without an intervening read or file positioning operation on that
- stream, the operation may fail.
-4 If the value of c equals that of the macro EOF, the operation fails and the input stream is
- unchanged.
-5 A successful call to the ungetc function clears the end-of-file indicator for the stream.
- The value of the file position indicator for the stream after reading or discarding all
- pushed-back characters shall be the same as it was before the characters were pushed
- back. For a text stream, the value of its file position indicator after a successful call to the
- ungetc function is unspecified until all pushed-back characters are read or discarded.
-
-[page 332]
-
- For a binary stream, its file position indicator is decremented by each successful call to
- the ungetc function; if its value was zero before a call, it is indeterminate after the
- call.279)
- Returns
-6 The ungetc function returns the character pushed back after conversion, or EOF if the
- operation fails.
- Forward references: file positioning functions (7.21.9).
- 7.21.8 Direct input/output functions
- 7.21.8.1 The fread function
- Synopsis
-1 #include <stdio.h>
- size_t fread(void * restrict ptr,
- size_t size, size_t nmemb,
- FILE * restrict stream);
- Description
-2 The fread function reads, into the array pointed to by ptr, up to nmemb elements
- whose size is specified by size, from the stream pointed to by stream. For each
- object, size calls are made to the fgetc function and the results stored, in the order
- read, in an array of unsigned char exactly overlaying the object. The file position
- indicator for the stream (if defined) is advanced by the number of characters successfully
- read. If an error occurs, the resulting value of the file position indicator for the stream is
- indeterminate. If a partial element is read, its value is indeterminate.
- Returns
-3 The fread function returns the number of elements successfully read, which may be
- less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
- fread returns zero and the contents of the array and the state of the stream remain
- unchanged.
-
-
-
-
- 279) See ''future library directions'' (7.30.9).
-
-[page 333]
-
- 7.21.8.2 The fwrite function
- Synopsis
-1 #include <stdio.h>
- size_t fwrite(const void * restrict ptr,
- size_t size, size_t nmemb,
- FILE * restrict stream);
- Description
-2 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements
- whose size is specified by size, to the stream pointed to by stream. For each object,
- size calls are made to the fputc function, taking the values (in order) from an array of
- unsigned char exactly overlaying the object. The file position indicator for the
- stream (if defined) is advanced by the number of characters successfully written. If an
- error occurs, the resulting value of the file position indicator for the stream is
- indeterminate.
- Returns
-3 The fwrite function returns the number of elements successfully written, which will be
- less than nmemb only if a write error is encountered. If size or nmemb is zero,
- fwrite returns zero and the state of the stream remains unchanged.
- 7.21.9 File positioning functions
- 7.21.9.1 The fgetpos function
- Synopsis
-1 #include <stdio.h>
- int fgetpos(FILE * restrict stream,
- fpos_t * restrict pos);
- Description
-2 The fgetpos function stores the current values of the parse state (if any) and file
- position indicator for the stream pointed to by stream in the object pointed to by pos.
- The values stored contain unspecified information usable by the fsetpos function for
- repositioning the stream to its position at the time of the call to the fgetpos function.
- Returns
-3 If successful, the fgetpos function returns zero; on failure, the fgetpos function
- returns nonzero and stores an implementation-defined positive value in errno.
- Forward references: the fsetpos function (7.21.9.3).
-
-
-
-
-[page 334]
-
- 7.21.9.2 The fseek function
- Synopsis
-1 #include <stdio.h>
- int fseek(FILE *stream, long int offset, int whence);
- Description
-2 The fseek function sets the file position indicator for the stream pointed to by stream.
- If a read or write error occurs, the error indicator for the stream is set and fseek fails.
-3 For a binary stream, the new position, measured in characters from the beginning of the
- file, is obtained by adding offset to the position specified by whence. The specified
- position is the beginning of the file if whence is SEEK_SET, the current value of the file
- position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
- meaningfully support fseek calls with a whence value of SEEK_END.
-4 For a text stream, either offset shall be zero, or offset shall be a value returned by
- an earlier successful call to the ftell function on a stream associated with the same file
- and whence shall be SEEK_SET.
-5 After determining the new position, a successful call to the fseek function undoes any
- effects of the ungetc function on the stream, clears the end-of-file indicator for the
- stream, and then establishes the new position. After a successful fseek call, the next
- operation on an update stream may be either input or output.
- Returns
-6 The fseek function returns nonzero only for a request that cannot be satisfied.
- Forward references: the ftell function (7.21.9.4).
- 7.21.9.3 The fsetpos function
- Synopsis
-1 #include <stdio.h>
- int fsetpos(FILE *stream, const fpos_t *pos);
- Description
-2 The fsetpos function sets the mbstate_t object (if any) and file position indicator
- for the stream pointed to by stream according to the value of the object pointed to by
- pos, which shall be a value obtained from an earlier successful call to the fgetpos
- function on a stream associated with the same file. If a read or write error occurs, the
- error indicator for the stream is set and fsetpos fails.
-3 A successful call to the fsetpos function undoes any effects of the ungetc function
- on the stream, clears the end-of-file indicator for the stream, and then establishes the new
- parse state and position. After a successful fsetpos call, the next operation on an
-
-[page 335]
-
- update stream may be either input or output.
- Returns
-4 If successful, the fsetpos function returns zero; on failure, the fsetpos function
- returns nonzero and stores an implementation-defined positive value in errno.
- 7.21.9.4 The ftell function
- Synopsis
-1 #include <stdio.h>
- long int ftell(FILE *stream);
- Description
-2 The ftell function obtains the current value of the file position indicator for the stream
- pointed to by stream. For a binary stream, the value is the number of characters from
- the beginning of the file. For a text stream, its file position indicator contains unspecified
- information, usable by the fseek function for returning the file position indicator for the
- stream to its position at the time of the ftell call; the difference between two such
- return values is not necessarily a meaningful measure of the number of characters written
- or read.
- Returns
-3 If successful, the ftell function returns the current value of the file position indicator
- for the stream. On failure, the ftell function returns -1L and stores an
- implementation-defined positive value in errno.
- 7.21.9.5 The rewind function
- Synopsis
-1 #include <stdio.h>
- void rewind(FILE *stream);
- Description
-2 The rewind function sets the file position indicator for the stream pointed to by
- stream to the beginning of the file. It is equivalent to
- (void)fseek(stream, 0L, SEEK_SET)
- except that the error indicator for the stream is also cleared.
- Returns
-3 The rewind function returns no value.
-
-
-
-
-[page 336]
-
- 7.21.10 Error-handling functions
- 7.21.10.1 The clearerr function
- Synopsis
-1 #include <stdio.h>
- void clearerr(FILE *stream);
- Description
-2 The clearerr function clears the end-of-file and error indicators for the stream pointed
- to by stream.
- Returns
-3 The clearerr function returns no value.
- 7.21.10.2 The feof function
- Synopsis
-1 #include <stdio.h>
- int feof(FILE *stream);
- Description
-2 The feof function tests the end-of-file indicator for the stream pointed to by stream.
- Returns
-3 The feof function returns nonzero if and only if the end-of-file indicator is set for
- stream.
- 7.21.10.3 The ferror function
- Synopsis
-1 #include <stdio.h>
- int ferror(FILE *stream);
- Description
-2 The ferror function tests the error indicator for the stream pointed to by stream.
- Returns
-3 The ferror function returns nonzero if and only if the error indicator is set for
- stream.
-
-
-
-
-[page 337]
-
- 7.21.10.4 The perror function
- Synopsis
-1 #include <stdio.h>
- void perror(const char *s);
- Description
-2 The perror function maps the error number in the integer expression errno to an
- error message. It writes a sequence of characters to the standard error stream thus: first
- (if s is not a null pointer and the character pointed to by s is not the null character), the
- string pointed to by s followed by a colon (:) and a space; then an appropriate error
- message string followed by a new-line character. The contents of the error message
- strings are the same as those returned by the strerror function with argument errno.
- Returns
-3 The perror function returns no value.
- Forward references: the strerror function (7.23.6.2).
-
-
-
-
-[page 338]
-
- 7.22 General utilities <stdlib.h>
-1 The header <stdlib.h> declares five types and several functions of general utility, and
- defines several macros.280)
-2 The types declared are size_t and wchar_t (both described in 7.19),
- div_t
- which is a structure type that is the type of the value returned by the div function,
- ldiv_t
- which is a structure type that is the type of the value returned by the ldiv function, and
- lldiv_t
- which is a structure type that is the type of the value returned by the lldiv function.
-3 The macros defined are NULL (described in 7.19);
- EXIT_FAILURE
- and
- EXIT_SUCCESS
- which expand to integer constant expressions that can be used as the argument to the
- exit function to return unsuccessful or successful termination status, respectively, to the
- host environment;
- RAND_MAX
- which expands to an integer constant expression that is the maximum value returned by
- the rand function; and
- MB_CUR_MAX
- which expands to a positive integer expression with type size_t that is the maximum
- number of bytes in a multibyte character for the extended character set specified by the
- current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX.
-
-
-
-
- 280) See ''future library directions'' (7.30.10).
-
-[page 339]
-
- 7.22.1 Numeric conversion functions
-1 The functions atof, atoi, atol, and atoll need not affect the value of the integer
- expression errno on an error. If the value of the result cannot be represented, the
- behavior is undefined.
- 7.22.1.1 The atof function
- Synopsis
-1 #include <stdlib.h>
- double atof(const char *nptr);
- Description
-2 The atof function converts the initial portion of the string pointed to by nptr to
- double representation. Except for the behavior on error, it is equivalent to
- strtod(nptr, (char **)NULL)
- Returns
-3 The atof function returns the converted value.
- Forward references: the strtod, strtof, and strtold functions (7.22.1.3).
- 7.22.1.2 The atoi, atol, and atoll functions
- Synopsis
-1 #include <stdlib.h>
- int atoi(const char *nptr);
- long int atol(const char *nptr);
- long long int atoll(const char *nptr);
- Description
-2 The atoi, atol, and atoll functions convert the initial portion of the string pointed
- to by nptr to int, long int, and long long int representation, respectively.
- Except for the behavior on error, they are equivalent to
- atoi: (int)strtol(nptr, (char **)NULL, 10)
- atol: strtol(nptr, (char **)NULL, 10)
- atoll: strtoll(nptr, (char **)NULL, 10)
- Returns
-3 The atoi, atol, and atoll functions return the converted value.
- Forward references: the strtol, strtoll, strtoul, and strtoull functions
- (7.22.1.4).
-
-
-
-[page 340]
-
- 7.22.1.3 The strtod, strtof, and strtold functions
- Synopsis
-1 #include <stdlib.h>
- double strtod(const char * restrict nptr,
- char ** restrict endptr);
- float strtof(const char * restrict nptr,
- char ** restrict endptr);
- long double strtold(const char * restrict nptr,
- char ** restrict endptr);
- Description
-2 The strtod, strtof, and strtold functions convert the initial portion of the string
- pointed to by nptr to double, float, and long double representation,
- respectively. First, they decompose the input string into three parts: an initial, possibly
- empty, sequence of white-space characters (as specified by the isspace function), a
- subject sequence resembling a floating-point constant or representing an infinity or NaN;
- and a final string of one or more unrecognized characters, including the terminating null
- character of the input string. Then, they attempt to convert the subject sequence to a
- floating-point number, and return the result.
-3 The expected form of the subject sequence is an optional plus or minus sign, then one of
- the following:
- -- a nonempty sequence of decimal digits optionally containing a decimal-point
- character, then an optional exponent part as defined in 6.4.4.2;
- -- a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
- decimal-point character, then an optional binary exponent part as defined in 6.4.4.2;
- -- INF or INFINITY, ignoring case
- -- NAN or NAN(n-char-sequenceopt), ignoring case in the NAN part, where:
- n-char-sequence:
- digit
- nondigit
- n-char-sequence digit
- n-char-sequence nondigit
- The subject sequence is defined as the longest initial subsequence of the input string,
- starting with the first non-white-space character, that is of the expected form. The subject
- sequence contains no characters if the input string is not of the expected form.
-4 If the subject sequence has the expected form for a floating-point number, the sequence of
- characters starting with the first digit or the decimal-point character (whichever occurs
- first) is interpreted as a floating constant according to the rules of 6.4.4.2, except that the
-[page 341]
-
- decimal-point character is used in place of a period, and that if neither an exponent part
- nor a decimal-point character appears in a decimal floating point number, or if a binary
- exponent part does not appear in a hexadecimal floating point number, an exponent part
- of the appropriate type with value zero is assumed to follow the last digit in the string. If
- the subject sequence begins with a minus sign, the sequence is interpreted as negated.281)
- A character sequence INF or INFINITY is interpreted as an infinity, if representable in
- the return type, else like a floating constant that is too large for the range of the return
- type. A character sequence NAN or NAN(n-char-sequenceopt), is interpreted as a quiet
- NaN, if supported in the return type, else like a subject sequence part that does not have
- the expected form; the meaning of the n-char sequences is implementation-defined.282) A
- pointer to the final string is stored in the object pointed to by endptr, provided that
- endptr is not a null pointer.
-5 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
- value resulting from the conversion is correctly rounded.
-6 In other than the "C" locale, additional locale-specific subject sequence forms may be
- accepted.
-7 If the subject sequence is empty or does not have the expected form, no conversion is
- performed; the value of nptr is stored in the object pointed to by endptr, provided
- that endptr is not a null pointer.
- Recommended practice
-8 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
- the result is not exactly representable, the result should be one of the two numbers in the
- appropriate internal format that are adjacent to the hexadecimal floating source value,
- with the extra stipulation that the error should have a correct sign for the current rounding
- direction.
-9 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
- <float.h>) significant digits, the result should be correctly rounded. If the subject
- sequence D has the decimal form and more than DECIMAL_DIG significant digits,
- consider the two bounding, adjacent decimal strings L and U, both having
- DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
- The result should be one of the (equal or adjacent) values that would be obtained by
- correctly rounding L and U according to the current rounding direction, with the extra
-
- 281) It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
- negating the value resulting from converting the corresponding unsigned sequence (see F.5); the two
- methods may yield different results if rounding is toward positive or negative infinity. In either case,
- the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
- 282) An implementation may use the n-char sequence to determine extra information to be represented in
- the NaN's significand.
-
-[page 342]
-
- stipulation that the error with respect to D should have a correct sign for the current
- rounding direction.283)
- Returns
-10 The functions return the converted value, if any. If no conversion could be performed,
- zero is returned. If the correct value overflows and default rounding is in effect (7.12.1),
- plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
- return type and sign of the value), and the value of the macro ERANGE is stored in
- errno. If the result underflows (7.12.1), the functions return a value whose magnitude is
- no greater than the smallest normalized positive number in the return type; whether
- errno acquires the value ERANGE is implementation-defined.
- 7.22.1.4 The strtol, strtoll, strtoul, and strtoull functions
- Synopsis
-1 #include <stdlib.h>
- long int strtol(
- const char * restrict nptr,
- char ** restrict endptr,
- int base);
- long long int strtoll(
- const char * restrict nptr,
- char ** restrict endptr,
- int base);
- unsigned long int strtoul(
- const char * restrict nptr,
- char ** restrict endptr,
- int base);
- unsigned long long int strtoull(
- const char * restrict nptr,
- char ** restrict endptr,
- int base);
- Description
-2 The strtol, strtoll, strtoul, and strtoull functions convert the initial
- portion of the string pointed to by nptr to long int, long long int, unsigned
- long int, and unsigned long long int representation, respectively. First,
- they decompose the input string into three parts: an initial, possibly empty, sequence of
- white-space characters (as specified by the isspace function), a subject sequence
-
-
- 283) DECIMAL_DIG, defined in <float.h>, should be sufficiently large that L and U will usually round
- to the same internal floating value, but if not will round to adjacent values.
-
-[page 343]
-
- resembling an integer represented in some radix determined by the value of base, and a
- final string of one or more unrecognized characters, including the terminating null
- character of the input string. Then, they attempt to convert the subject sequence to an
- integer, and return the result.
-3 If the value of base is zero, the expected form of the subject sequence is that of an
- integer constant as described in 6.4.4.1, optionally preceded by a plus or minus sign, but
- not including an integer suffix. If the value of base is between 2 and 36 (inclusive), the
- expected form of the subject sequence is a sequence of letters and digits representing an
- integer with the radix specified by base, optionally preceded by a plus or minus sign,
- but not including an integer suffix. The letters from a (or A) through z (or Z) are
- ascribed the values 10 through 35; only letters and digits whose ascribed values are less
- than that of base are permitted. If the value of base is 16, the characters 0x or 0X may
- optionally precede the sequence of letters and digits, following the sign if present.
-4 The subject sequence is defined as the longest initial subsequence of the input string,
- starting with the first non-white-space character, that is of the expected form. The subject
- sequence contains no characters if the input string is empty or consists entirely of white
- space, or if the first non-white-space character is other than a sign or a permissible letter
- or digit.
-5 If the subject sequence has the expected form and the value of base is zero, the sequence
- of characters starting with the first digit is interpreted as an integer constant according to
- the rules of 6.4.4.1. If the subject sequence has the expected form and the value of base
- is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
- as given above. If the subject sequence begins with a minus sign, the value resulting from
- the conversion is negated (in the return type). A pointer to the final string is stored in the
- object pointed to by endptr, provided that endptr is not a null pointer.
-6 In other than the "C" locale, additional locale-specific subject sequence forms may be
- accepted.
-7 If the subject sequence is empty or does not have the expected form, no conversion is
- performed; the value of nptr is stored in the object pointed to by endptr, provided
- that endptr is not a null pointer.
- Returns
-8 The strtol, strtoll, strtoul, and strtoull functions return the converted
- value, if any. If no conversion could be performed, zero is returned. If the correct value
- is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
- LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
- and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
-
-
-
-
-[page 344]
-
- 7.22.2 Pseudo-random sequence generation functions
- 7.22.2.1 The rand function
- Synopsis
-1 #include <stdlib.h>
- int rand(void);
- Description
-2 The rand function computes a sequence of pseudo-random integers in the range 0 to
- RAND_MAX.284)
-3 The rand function is not required to avoid data races. The implementation shall behave
- as if no library function calls the rand function.
- Returns
-4 The rand function returns a pseudo-random integer.
- Environmental limits
-5 The value of the RAND_MAX macro shall be at least 32767.
- 7.22.2.2 The srand function
- Synopsis
-1 #include <stdlib.h>
- void srand(unsigned int seed);
- Description
-2 The srand function uses the argument as a seed for a new sequence of pseudo-random
- numbers to be returned by subsequent calls to rand. If srand is then called with the
- same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
- called before any calls to srand have been made, the same sequence shall be generated
- as when srand is first called with a seed value of 1.
-3 The implementation shall behave as if no library function calls the srand function.
- Returns
-4 The srand function returns no value.
-
-
-
-
- 284) There are no guarantees as to the quality of the random sequence produced and some implementations
- are known to produce sequences with distressingly non-random low-order bits. Applications with
- particular requirements should use a generator that is known to be sufficient for their needs.
-
-[page 345]
-
-5 EXAMPLE The following functions define a portable implementation of rand and srand.
- static unsigned long int next = 1;
- int rand(void) // RAND_MAX assumed to be 32767
- {
- next = next * 1103515245 + 12345;
- return (unsigned int)(next/65536) % 32768;
- }
- void srand(unsigned int seed)
- {
- next = seed;
- }
-
- 7.22.3 Memory management functions
-1 The order and contiguity of storage allocated by successive calls to the
- aligned_alloc, calloc, malloc, and realloc functions is unspecified. The
- pointer returned if the allocation succeeds is suitably aligned so that it may be assigned to
- a pointer to any type of object with a fundamental alignment requirement and then used
- to access such an object or an array of such objects in the space allocated (until the space
- is explicitly deallocated). The lifetime of an allocated object extends from the allocation
- until the deallocation. Each such allocation shall yield a pointer to an object disjoint from
- any other object. The pointer returned points to the start (lowest byte address) of the
- allocated space. If the space cannot be allocated, a null pointer is returned. If the size of
- the space requested is zero, the behavior is implementation-defined: either a null pointer
- is returned, or the behavior is as if the size were some nonzero value, except that the
- returned pointer shall not be used to access an object.
- 7.22.3.1 The aligned_alloc function
- Synopsis
-1 #include <stdlib.h>
- void *aligned_alloc(size_t alignment, size_t size);
- Description
-2 The aligned_alloc function allocates space for an object whose alignment is
- specified by alignment, whose size is specified by size, and whose value is
- indeterminate. The value of alignment shall be a valid alignment supported by the
- implementation and the value of size shall be an integral multiple of alignment.
- Returns
-3 The aligned_alloc function returns either a null pointer or a pointer to the allocated
- space.
-
-
-
-
-[page 346]
-
- 7.22.3.2 The calloc function
- Synopsis
-1 #include <stdlib.h>
- void *calloc(size_t nmemb, size_t size);
- Description
-2 The calloc function allocates space for an array of nmemb objects, each of whose size
- is size. The space is initialized to all bits zero.285)
- Returns
-3 The calloc function returns either a null pointer or a pointer to the allocated space.
- 7.22.3.3 The free function
- Synopsis
-1 #include <stdlib.h>
- void free(void *ptr);
- Description
-2 The free function causes the space pointed to by ptr to be deallocated, that is, made
- available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
- the argument does not match a pointer earlier returned by a memory management
- function, or if the space has been deallocated by a call to free or realloc, the
- behavior is undefined.
- Returns
-3 The free function returns no value.
- 7.22.3.4 The malloc function
- Synopsis
-1 #include <stdlib.h>
- void *malloc(size_t size);
- Description
-2 The malloc function allocates space for an object whose size is specified by size and
- whose value is indeterminate.
-
-
-
-
- 285) Note that this need not be the same as the representation of floating-point zero or a null pointer
- constant.
-
-[page 347]
-
- Returns
-3 The malloc function returns either a null pointer or a pointer to the allocated space.
- 7.22.3.5 The realloc function
- Synopsis
-1 #include <stdlib.h>
- void *realloc(void *ptr, size_t size);
- Description
-2 The realloc function deallocates the old object pointed to by ptr and returns a
- pointer to a new object that has the size specified by size. The contents of the new
- object shall be the same as that of the old object prior to deallocation, up to the lesser of
- the new and old sizes. Any bytes in the new object beyond the size of the old object have
- indeterminate values.
-3 If ptr is a null pointer, the realloc function behaves like the malloc function for the
- specified size. Otherwise, if ptr does not match a pointer earlier returned by a memory
- management function, or if the space has been deallocated by a call to the free or
- realloc function, the behavior is undefined. If memory for the new object cannot be
- allocated, the old object is not deallocated and its value is unchanged.
- Returns
-4 The realloc function returns a pointer to the new object (which may have the same
- value as a pointer to the old object), or a null pointer if the new object could not be
- allocated.
- 7.22.4 Communication with the environment
- 7.22.4.1 The abort function
- Synopsis
-1 #include <stdlib.h>
- _Noreturn void abort(void);
- Description
-2 The abort function causes abnormal program termination to occur, unless the signal
- SIGABRT is being caught and the signal handler does not return. Whether open streams
- with unwritten buffered data are flushed, open streams are closed, or temporary files are
- removed is implementation-defined. An implementation-defined form of the status
- unsuccessful termination is returned to the host environment by means of the function
- call raise(SIGABRT).
-
-
-
-
-[page 348]
-
- Returns
-3 The abort function does not return to its caller.
- 7.22.4.2 The atexit function
- Synopsis
-1 #include <stdlib.h>
- int atexit(void (*func)(void));
- Description
-2 The atexit function registers the function pointed to by func, to be called without
- arguments at normal program termination.286)
- Environmental limits
-3 The implementation shall support the registration of at least 32 functions.
- Returns
-4 The atexit function returns zero if the registration succeeds, nonzero if it fails.
- Forward references: the at_quick_exit function (7.22.4.3), the exit function
- (7.22.4.4).
- 7.22.4.3 The at_quick_exit function
- Synopsis
-1 #include <stdlib.h>
- int at_quick_exit(void (*func)(void));
- Description
-2 The at_quick_exit function registers the function pointed to by func, to be called
- without arguments should quick_exit be called.287)
- Environmental limits
-3 The implementation shall support the registration of at least 32 functions.
- Returns
-4 The at_quick_exit function returns zero if the registration succeeds, nonzero if it
- fails.
- Forward references: the quick_exit function (7.22.4.7).
-
- 286) The atexit function registrations are distinct from the at_quick_exit registrations, so
- applications may need to call both registration functions with the same argument.
- 287) The at_quick_exit function registrations are distinct from the atexit registrations, so
- applications may need to call both registration functions with the same argument.
-
-[page 349]
-
- 7.22.4.4 The exit function
- Synopsis
-1 #include <stdlib.h>
- _Noreturn void exit(int status);
- Description
-2 The exit function causes normal program termination to occur. No functions registered
- by the at_quick_exit function are called. If a program calls the exit function
- more than once, or calls the quick_exit function in addition to the exit function, the
- behavior is undefined.
-3 First, all functions registered by the atexit function are called, in the reverse order of
- their registration,288) except that a function is called after any previously registered
- functions that had already been called at the time it was registered. If, during the call to
- any such function, a call to the longjmp function is made that would terminate the call
- to the registered function, the behavior is undefined.
-4 Next, all open streams with unwritten buffered data are flushed, all open streams are
- closed, and all files created by the tmpfile function are removed.
-5 Finally, control is returned to the host environment. If the value of status is zero or
- EXIT_SUCCESS, an implementation-defined form of the status successful termination is
- returned. If the value of status is EXIT_FAILURE, an implementation-defined form
- of the status unsuccessful termination is returned. Otherwise the status returned is
- implementation-defined.
- Returns
-6 The exit function cannot return to its caller.
- 7.22.4.5 The _Exit function
- Synopsis
-1 #include <stdlib.h>
- _Noreturn void _Exit(int status);
- Description
-2 The _Exit function causes normal program termination to occur and control to be
- returned to the host environment. No functions registered by the atexit function, the
- at_quick_exit function, or signal handlers registered by the signal function are
- called. The status returned to the host environment is determined in the same way as for
-
-
- 288) Each function is called as many times as it was registered, and in the correct order with respect to
- other registered functions.
-
-[page 350]
-
- the exit function (7.22.4.4). Whether open streams with unwritten buffered data are
- flushed, open streams are closed, or temporary files are removed is implementation-
- defined.
- Returns
-3 The _Exit function cannot return to its caller.
- 7.22.4.6 The getenv function
- Synopsis
-1 #include <stdlib.h>
- char *getenv(const char *name);
- Description
-2 The getenv function searches an environment list, provided by the host environment,
- for a string that matches the string pointed to by name. The set of environment names
- and the method for altering the environment list are implementation-defined. The
- getenv function need not avoid data races with other threads of execution that modify
- the environment list.289)
-3 The implementation shall behave as if no library function calls the getenv function.
- Returns
-4 The getenv function returns a pointer to a string associated with the matched list
- member. The string pointed to shall not be modified by the program, but may be
- overwritten by a subsequent call to the getenv function. If the specified name cannot
- be found, a null pointer is returned.
- 7.22.4.7 The quick_exit function
- Synopsis
-1 #include <stdlib.h>
- _Noreturn void quick_exit(int status);
- Description
-2 The quick_exit function causes normal program termination to occur. No functions
- registered by the atexit function or signal handlers registered by the signal function
- are called. If a program calls the quick_exit function more than once, or calls the
- exit function in addition to the quick_exit function, the behavior is undefined.
-3 The quick_exit function first calls all functions registered by the at_quick_exit
- function, in the reverse order of their registration,290) except that a function is called after
-
-
- 289) Many implementations provide non-standard functions that modify the environment list.
-
-[page 351]
-
- any previously registered functions that had already been called at the time it was
- registered. If, during the call to any such function, a call to the longjmp function is
- made that would terminate the call to the registered function, the behavior is undefined.
-4 Then control is returned to the host environment by means of the function call
- _Exit(status).
- Returns
-5 The quick_exit function cannot return to its caller.
- 7.22.4.8 The system function
- Synopsis
-1 #include <stdlib.h>
- int system(const char *string);
- Description
-2 If string is a null pointer, the system function determines whether the host
- environment has a command processor. If string is not a null pointer, the system
- function passes the string pointed to by string to that command processor to be
- executed in a manner which the implementation shall document; this might then cause the
- program calling system to behave in a non-conforming manner or to terminate.
- Returns
-3 If the argument is a null pointer, the system function returns nonzero only if a
- command processor is available. If the argument is not a null pointer, and the system
- function does return, it returns an implementation-defined value.
- 7.22.5 Searching and sorting utilities
-1 These utilities make use of a comparison function to search or sort arrays of unspecified
- type. Where an argument declared as size_t nmemb specifies the length of the array
- for a function, nmemb can have the value zero on a call to that function; the comparison
- function is not called, a search finds no matching element, and sorting performs no
- rearrangement. Pointer arguments on such a call shall still have valid values, as described
- in 7.1.4.
-2 The implementation shall ensure that the second argument of the comparison function
- (when called from bsearch), or both arguments (when called from qsort), are
- pointers to elements of the array.291) The first argument when called from bsearch
- shall equal key.
-
-
-
- 290) Each function is called as many times as it was registered, and in the correct order with respect to
- other registered functions.
-
-[page 352]
-
-3 The comparison function shall not alter the contents of the array. The implementation
- may reorder elements of the array between calls to the comparison function, but shall not
- alter the contents of any individual element.
-4 When the same objects (consisting of size bytes, irrespective of their current positions
- in the array) are passed more than once to the comparison function, the results shall be
- consistent with one another. That is, for qsort they shall define a total ordering on the
- array, and for bsearch the same object shall always compare the same way with the
- key.
-5 A sequence point occurs immediately before and immediately after each call to the
- comparison function, and also between any call to the comparison function and any
- movement of the objects passed as arguments to that call.
- 7.22.5.1 The bsearch function
- Synopsis
-1 #include <stdlib.h>
- void *bsearch(const void *key, const void *base,
- size_t nmemb, size_t size,
- int (*compar)(const void *, const void *));
- Description
-2 The bsearch function searches an array of nmemb objects, the initial element of which
- is pointed to by base, for an element that matches the object pointed to by key. The
- size of each element of the array is specified by size.
-3 The comparison function pointed to by compar is called with two arguments that point
- to the key object and to an array element, in that order. The function shall return an
- integer less than, equal to, or greater than zero if the key object is considered,
- respectively, to be less than, to match, or to be greater than the array element. The array
- shall consist of: all the elements that compare less than, all the elements that compare
- equal to, and all the elements that compare greater than the key object, in that order.292)
- Returns
-4 The bsearch function returns a pointer to a matching element of the array, or a null
- pointer if no match is found. If two elements compare as equal, which element is
-
-
- 291) That is, if the value passed is p, then the following expressions are always nonzero:
- ((char *)p - (char *)base) % size == 0
- (char *)p >= (char *)base
- (char *)p < (char *)base + nmemb * size
-
- 292) In practice, the entire array is sorted according to the comparison function.
-
-[page 353]
-
- matched is unspecified.
- 7.22.5.2 The qsort function
- Synopsis
-1 #include <stdlib.h>
- void qsort(void *base, size_t nmemb, size_t size,
- int (*compar)(const void *, const void *));
- Description
-2 The qsort function sorts an array of nmemb objects, the initial element of which is
- pointed to by base. The size of each object is specified by size.
-3 The contents of the array are sorted into ascending order according to a comparison
- function pointed to by compar, which is called with two arguments that point to the
- objects being compared. The function shall return an integer less than, equal to, or
- greater than zero if the first argument is considered to be respectively less than, equal to,
- or greater than the second.
-4 If two elements compare as equal, their order in the resulting sorted array is unspecified.
- Returns
-5 The qsort function returns no value.
- 7.22.6 Integer arithmetic functions
- 7.22.6.1 The abs, labs and llabs functions
- Synopsis
-1 #include <stdlib.h>
- int abs(int j);
- long int labs(long int j);
- long long int llabs(long long int j);
- Description
-2 The abs, labs, and llabs functions compute the absolute value of an integer j. If the
- result cannot be represented, the behavior is undefined.293)
- Returns
-3 The abs, labs, and llabs, functions return the absolute value.
-
-
-
-
- 293) The absolute value of the most negative number cannot be represented in two's complement.
-
-[page 354]
-
- 7.22.6.2 The div, ldiv, and lldiv functions
- Synopsis
-1 #include <stdlib.h>
- div_t div(int numer, int denom);
- ldiv_t ldiv(long int numer, long int denom);
- lldiv_t lldiv(long long int numer, long long int denom);
- Description
-2 The div, ldiv, and lldiv, functions compute numer / denom and numer %
- denom in a single operation.
- Returns
-3 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
- lldiv_t, respectively, comprising both the quotient and the remainder. The structures
- shall contain (in either order) the members quot (the quotient) and rem (the remainder),
- each of which has the same type as the arguments numer and denom. If either part of
- the result cannot be represented, the behavior is undefined.
- 7.22.7 Multibyte/wide character conversion functions
-1 The behavior of the multibyte character functions is affected by the LC_CTYPE category
- of the current locale. For a state-dependent encoding, each function is placed into its
- initial conversion state at program startup and can be returned to that state by a call for
- which its character pointer argument, s, is a null pointer. Subsequent calls with s as
- other than a null pointer cause the internal conversion state of the function to be altered as
- necessary. A call with s as a null pointer causes these functions to return a nonzero value
- if encodings have state dependency, and zero otherwise.294) Changing the LC_CTYPE
- category causes the conversion state of these functions to be indeterminate.
- 7.22.7.1 The mblen function
- Synopsis
-1 #include <stdlib.h>
- int mblen(const char *s, size_t n);
- Description
-2 If s is not a null pointer, the mblen function determines the number of bytes contained
- in the multibyte character pointed to by s. Except that the conversion state of the
- mbtowc function is not affected, it is equivalent to
-
-
-
- 294) If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
- character codes, but are grouped with an adjacent multibyte character.
-
-[page 355]
-
- mbtowc((wchar_t *)0, (const char *)0, 0);
- mbtowc((wchar_t *)0, s, n);
-3 The implementation shall behave as if no library function calls the mblen function.
- Returns
-4 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte
- character encodings, respectively, do or do not have state-dependent encodings. If s is
- not a null pointer, the mblen function either returns 0 (if s points to the null character),
- or returns the number of bytes that are contained in the multibyte character (if the next n
- or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid
- multibyte character).
- Forward references: the mbtowc function (7.22.7.2).
- 7.22.7.2 The mbtowc function
- Synopsis
-1 #include <stdlib.h>
- int mbtowc(wchar_t * restrict pwc,
- const char * restrict s,
- size_t n);
- Description
-2 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with
- the byte pointed to by s to determine the number of bytes needed to complete the next
- multibyte character (including any shift sequences). If the function determines that the
- next multibyte character is complete and valid, it determines the value of the
- corresponding wide character and then, if pwc is not a null pointer, stores that value in
- the object pointed to by pwc. If the corresponding wide character is the null wide
- character, the function is left in the initial conversion state.
-3 The implementation shall behave as if no library function calls the mbtowc function.
- Returns
-4 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte
- character encodings, respectively, do or do not have state-dependent encodings. If s is
- not a null pointer, the mbtowc function either returns 0 (if s points to the null character),
- or returns the number of bytes that are contained in the converted multibyte character (if
- the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not
- form a valid multibyte character).
-5 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
- macro.
-
-
-[page 356]
-
- 7.22.7.3 The wctomb function
- Synopsis
-1 #include <stdlib.h>
- int wctomb(char *s, wchar_t wc);
- Description
-2 The wctomb function determines the number of bytes needed to represent the multibyte
- character corresponding to the wide character given by wc (including any shift
- sequences), and stores the multibyte character representation in the array whose first
- element is pointed to by s (if s is not a null pointer). At most MB_CUR_MAX characters
- are stored. If wc is a null wide character, a null byte is stored, preceded by any shift
- sequence needed to restore the initial shift state, and the function is left in the initial
- conversion state.
-3 The implementation shall behave as if no library function calls the wctomb function.
- Returns
-4 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte
- character encodings, respectively, do or do not have state-dependent encodings. If s is
- not a null pointer, the wctomb function returns -1 if the value of wc does not correspond
- to a valid multibyte character, or returns the number of bytes that are contained in the
- multibyte character corresponding to the value of wc.
-5 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
- 7.22.8 Multibyte/wide string conversion functions
-1 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
- the current locale.
- 7.22.8.1 The mbstowcs function
- Synopsis
-1 #include <stdlib.h>
- size_t mbstowcs(wchar_t * restrict pwcs,
- const char * restrict s,
- size_t n);
- Description
-2 The mbstowcs function converts a sequence of multibyte characters that begins in the
- initial shift state from the array pointed to by s into a sequence of corresponding wide
- characters and stores not more than n wide characters into the array pointed to by pwcs.
- No multibyte characters that follow a null character (which is converted into a null wide
- character) will be examined or converted. Each multibyte character is converted as if by
- a call to the mbtowc function, except that the conversion state of the mbtowc function is
-[page 357]
-
- not affected.
-3 No more than n elements will be modified in the array pointed to by pwcs. If copying
- takes place between objects that overlap, the behavior is undefined.
- Returns
-4 If an invalid multibyte character is encountered, the mbstowcs function returns
- (size_t)(-1). Otherwise, the mbstowcs function returns the number of array
- elements modified, not including a terminating null wide character, if any.295)
- 7.22.8.2 The wcstombs function
- Synopsis
-1 #include <stdlib.h>
- size_t wcstombs(char * restrict s,
- const wchar_t * restrict pwcs,
- size_t n);
- Description
-2 The wcstombs function converts a sequence of wide characters from the array pointed
- to by pwcs into a sequence of corresponding multibyte characters that begins in the
- initial shift state, and stores these multibyte characters into the array pointed to by s,
- stopping if a multibyte character would exceed the limit of n total bytes or if a null
- character is stored. Each wide character is converted as if by a call to the wctomb
- function, except that the conversion state of the wctomb function is not affected.
-3 No more than n bytes will be modified in the array pointed to by s. If copying takes place
- between objects that overlap, the behavior is undefined.
- Returns
-4 If a wide character is encountered that does not correspond to a valid multibyte character,
- the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
- returns the number of bytes modified, not including a terminating null character, if
- any.295)
-
-
-
-
- 295) The array will not be null-terminated if the value returned is n.
-
-[page 358]
-
- 7.23 String handling <string.h>
- 7.23.1 String function conventions
-1 The header <string.h> declares one type and several functions, and defines one
- macro useful for manipulating arrays of character type and other objects treated as arrays
- of character type.296) The type is size_t and the macro is NULL (both described in
- 7.19). Various methods are used for determining the lengths of the arrays, but in all cases
- a char * or void * argument points to the initial (lowest addressed) character of the
- array. If an array is accessed beyond the end of an object, the behavior is undefined.
-2 Where an argument declared as size_t n specifies the length of the array for a
- function, n can have the value zero on a call to that function. Unless explicitly stated
- otherwise in the description of a particular function in this subclause, pointer arguments
- on such a call shall still have valid values, as described in 7.1.4. On such a call, a
- function that locates a character finds no occurrence, a function that compares two
- character sequences returns zero, and a function that copies characters copies zero
- characters.
-3 For all functions in this subclause, each character shall be interpreted as if it had the type
- unsigned char (and therefore every possible object representation is valid and has a
- different value).
- 7.23.2 Copying functions
- 7.23.2.1 The memcpy function
- Synopsis
-1 #include <string.h>
- void *memcpy(void * restrict s1,
- const void * restrict s2,
- size_t n);
- Description
-2 The memcpy function copies n characters from the object pointed to by s2 into the
- object pointed to by s1. If copying takes place between objects that overlap, the behavior
- is undefined.
- Returns
-3 The memcpy function returns the value of s1.
-
-
-
-
- 296) See ''future library directions'' (7.30.11).
-
-[page 359]
-
- 7.23.2.2 The memmove function
- Synopsis
-1 #include <string.h>
- void *memmove(void *s1, const void *s2, size_t n);
- Description
-2 The memmove function copies n characters from the object pointed to by s2 into the
- object pointed to by s1. Copying takes place as if the n characters from the object
- pointed to by s2 are first copied into a temporary array of n characters that does not
- overlap the objects pointed to by s1 and s2, and then the n characters from the
- temporary array are copied into the object pointed to by s1.
- Returns
-3 The memmove function returns the value of s1.
- 7.23.2.3 The strcpy function
- Synopsis
-1 #include <string.h>
- char *strcpy(char * restrict s1,
- const char * restrict s2);
- Description
-2 The strcpy function copies the string pointed to by s2 (including the terminating null
- character) into the array pointed to by s1. If copying takes place between objects that
- overlap, the behavior is undefined.
- Returns
-3 The strcpy function returns the value of s1.
- 7.23.2.4 The strncpy function
- Synopsis
-1 #include <string.h>
- char *strncpy(char * restrict s1,
- const char * restrict s2,
- size_t n);
- Description
-2 The strncpy function copies not more than n characters (characters that follow a null
- character are not copied) from the array pointed to by s2 to the array pointed to by
-
-
-
-
-[page 360]
-
- s1.297) If copying takes place between objects that overlap, the behavior is undefined.
-3 If the array pointed to by s2 is a string that is shorter than n characters, null characters
- are appended to the copy in the array pointed to by s1, until n characters in all have been
- written.
- Returns
-4 The strncpy function returns the value of s1.
- 7.23.3 Concatenation functions
- 7.23.3.1 The strcat function
- Synopsis
-1 #include <string.h>
- char *strcat(char * restrict s1,
- const char * restrict s2);
- Description
-2 The strcat function appends a copy of the string pointed to by s2 (including the
- terminating null character) to the end of the string pointed to by s1. The initial character
- of s2 overwrites the null character at the end of s1. If copying takes place between
- objects that overlap, the behavior is undefined.
- Returns
-3 The strcat function returns the value of s1.
- 7.23.3.2 The strncat function
- Synopsis
-1 #include <string.h>
- char *strncat(char * restrict s1,
- const char * restrict s2,
- size_t n);
- Description
-2 The strncat function appends not more than n characters (a null character and
- characters that follow it are not appended) from the array pointed to by s2 to the end of
- the string pointed to by s1. The initial character of s2 overwrites the null character at the
- end of s1. A terminating null character is always appended to the result.298) If copying
-
- 297) Thus, if there is no null character in the first n characters of the array pointed to by s2, the result will
- not be null-terminated.
- 298) Thus, the maximum number of characters that can end up in the array pointed to by s1 is
- strlen(s1)+n+1.
-
-[page 361]
-
- takes place between objects that overlap, the behavior is undefined.
- Returns
-3 The strncat function returns the value of s1.
- Forward references: the strlen function (7.23.6.3).
- 7.23.4 Comparison functions
-1 The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
- and strncmp is determined by the sign of the difference between the values of the first
- pair of characters (both interpreted as unsigned char) that differ in the objects being
- compared.
- 7.23.4.1 The memcmp function
- Synopsis
-1 #include <string.h>
- int memcmp(const void *s1, const void *s2, size_t n);
- Description
-2 The memcmp function compares the first n characters of the object pointed to by s1 to
- the first n characters of the object pointed to by s2.299)
- Returns
-3 The memcmp function returns an integer greater than, equal to, or less than zero,
- accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
- pointed to by s2.
- 7.23.4.2 The strcmp function
- Synopsis
-1 #include <string.h>
- int strcmp(const char *s1, const char *s2);
- Description
-2 The strcmp function compares the string pointed to by s1 to the string pointed to by
- s2.
- Returns
-3 The strcmp function returns an integer greater than, equal to, or less than zero,
- accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
-
- 299) The contents of ''holes'' used as padding for purposes of alignment within structure objects are
- indeterminate. Strings shorter than their allocated space and unions may also cause problems in
- comparison.
-
-[page 362]
-
- pointed to by s2.
- 7.23.4.3 The strcoll function
- Synopsis
-1 #include <string.h>
- int strcoll(const char *s1, const char *s2);
- Description
-2 The strcoll function compares the string pointed to by s1 to the string pointed to by
- s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
- Returns
-3 The strcoll function returns an integer greater than, equal to, or less than zero,
- accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
- pointed to by s2 when both are interpreted as appropriate to the current locale.
- 7.23.4.4 The strncmp function
- Synopsis
-1 #include <string.h>
- int strncmp(const char *s1, const char *s2, size_t n);
- Description
-2 The strncmp function compares not more than n characters (characters that follow a
- null character are not compared) from the array pointed to by s1 to the array pointed to
- by s2.
- Returns
-3 The strncmp function returns an integer greater than, equal to, or less than zero,
- accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
- to, or less than the possibly null-terminated array pointed to by s2.
- 7.23.4.5 The strxfrm function
- Synopsis
-1 #include <string.h>
- size_t strxfrm(char * restrict s1,
- const char * restrict s2,
- size_t n);
- Description
-2 The strxfrm function transforms the string pointed to by s2 and places the resulting
- string into the array pointed to by s1. The transformation is such that if the strcmp
- function is applied to two transformed strings, it returns a value greater than, equal to, or
-
-[page 363]
-
- less than zero, corresponding to the result of the strcoll function applied to the same
- two original strings. No more than n characters are placed into the resulting array
- pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
- be a null pointer. If copying takes place between objects that overlap, the behavior is
- undefined.
- Returns
-3 The strxfrm function returns the length of the transformed string (not including the
- terminating null character). If the value returned is n or more, the contents of the array
- pointed to by s1 are indeterminate.
-4 EXAMPLE The value of the following expression is the size of the array needed to hold the
- transformation of the string pointed to by s.
- 1 + strxfrm(NULL, s, 0)
-
- 7.23.5 Search functions
- 7.23.5.1 The memchr function
- Synopsis
-1 #include <string.h>
- void *memchr(const void *s, int c, size_t n);
- Description
-2 The memchr function locates the first occurrence of c (converted to an unsigned
- char) in the initial n characters (each interpreted as unsigned char) of the object
- pointed to by s.
- Returns
-3 The memchr function returns a pointer to the located character, or a null pointer if the
- character does not occur in the object.
- 7.23.5.2 The strchr function
- Synopsis
-1 #include <string.h>
- char *strchr(const char *s, int c);
- Description
-2 The strchr function locates the first occurrence of c (converted to a char) in the
- string pointed to by s. The terminating null character is considered to be part of the
- string.
- Returns
-3 The strchr function returns a pointer to the located character, or a null pointer if the
- character does not occur in the string.
-[page 364]
-
- 7.23.5.3 The strcspn function
- Synopsis
-1 #include <string.h>
- size_t strcspn(const char *s1, const char *s2);
- Description
-2 The strcspn function computes the length of the maximum initial segment of the string
- pointed to by s1 which consists entirely of characters not from the string pointed to by
- s2.
- Returns
-3 The strcspn function returns the length of the segment.
- 7.23.5.4 The strpbrk function
- Synopsis
-1 #include <string.h>
- char *strpbrk(const char *s1, const char *s2);
- Description
-2 The strpbrk function locates the first occurrence in the string pointed to by s1 of any
- character from the string pointed to by s2.
- Returns
-3 The strpbrk function returns a pointer to the character, or a null pointer if no character
- from s2 occurs in s1.
- 7.23.5.5 The strrchr function
- Synopsis
-1 #include <string.h>
- char *strrchr(const char *s, int c);
- Description
-2 The strrchr function locates the last occurrence of c (converted to a char) in the
- string pointed to by s. The terminating null character is considered to be part of the
- string.
- Returns
-3 The strrchr function returns a pointer to the character, or a null pointer if c does not
- occur in the string.
-
-
-
-
-[page 365]
-
- 7.23.5.6 The strspn function
- Synopsis
-1 #include <string.h>
- size_t strspn(const char *s1, const char *s2);
- Description
-2 The strspn function computes the length of the maximum initial segment of the string
- pointed to by s1 which consists entirely of characters from the string pointed to by s2.
- Returns
-3 The strspn function returns the length of the segment.
- 7.23.5.7 The strstr function
- Synopsis
-1 #include <string.h>
- char *strstr(const char *s1, const char *s2);
- Description
-2 The strstr function locates the first occurrence in the string pointed to by s1 of the
- sequence of characters (excluding the terminating null character) in the string pointed to
- by s2.
- Returns
-3 The strstr function returns a pointer to the located string, or a null pointer if the string
- is not found. If s2 points to a string with zero length, the function returns s1.
- 7.23.5.8 The strtok function
- Synopsis
-1 #include <string.h>
- char *strtok(char * restrict s1,
- const char * restrict s2);
- Description
-2 A sequence of calls to the strtok function breaks the string pointed to by s1 into a
- sequence of tokens, each of which is delimited by a character from the string pointed to
- by s2. The first call in the sequence has a non-null first argument; subsequent calls in the
- sequence have a null first argument. The separator string pointed to by s2 may be
- different from call to call.
-3 The first call in the sequence searches the string pointed to by s1 for the first character
- that is not contained in the current separator string pointed to by s2. If no such character
- is found, then there are no tokens in the string pointed to by s1 and the strtok function
-
-[page 366]
-
- returns a null pointer. If such a character is found, it is the start of the first token.
-4 The strtok function then searches from there for a character that is contained in the
- current separator string. If no such character is found, the current token extends to the
- end of the string pointed to by s1, and subsequent searches for a token will return a null
- pointer. If such a character is found, it is overwritten by a null character, which
- terminates the current token. The strtok function saves a pointer to the following
- character, from which the next search for a token will start.
-5 Each subsequent call, with a null pointer as the value of the first argument, starts
- searching from the saved pointer and behaves as described above.
-6 The strtok function is not required to avoid data races. The implementation shall
- behave as if no library function calls the strtok function.
- Returns
-7 The strtok function returns a pointer to the first character of a token, or a null pointer
- if there is no token.
-8 EXAMPLE
- #include <string.h>
- static char str[] = "?a???b,,,#c";
- char *t;
- t = strtok(str, "?"); // t points to the token "a"
- t = strtok(NULL, ","); // t points to the token "??b"
- t = strtok(NULL, "#,"); // t points to the token "c"
- t = strtok(NULL, "?"); // t is a null pointer
-
- 7.23.6 Miscellaneous functions
- 7.23.6.1 The memset function
- Synopsis
-1 #include <string.h>
- void *memset(void *s, int c, size_t n);
- Description
-2 The memset function copies the value of c (converted to an unsigned char) into
- each of the first n characters of the object pointed to by s.
- Returns
-3 The memset function returns the value of s.
-
-
-
-
-[page 367]
-
- 7.23.6.2 The strerror function
- Synopsis
-1 #include <string.h>
- char *strerror(int errnum);
- Description
-2 The strerror function maps the number in errnum to a message string. Typically,
- the values for errnum come from errno, but strerror shall map any value of type
- int to a message.
-3 The strerror function is not required to avoid data races. The implementation shall
- behave as if no library function calls the strerror function.
- Returns
-4 The strerror function returns a pointer to the string, the contents of which are locale-
- specific. The array pointed to shall not be modified by the program, but may be
- overwritten by a subsequent call to the strerror function.
- 7.23.6.3 The strlen function
- Synopsis
-1 #include <string.h>
- size_t strlen(const char *s);
- Description
-2 The strlen function computes the length of the string pointed to by s.
- Returns
-3 The strlen function returns the number of characters that precede the terminating null
- character.
-
-
-
-
-[page 368]
-
- 7.24 Type-generic math <tgmath.h>
-1 The header <tgmath.h> includes the headers <math.h> and <complex.h> and
- defines several type-generic macros.
-2 Of the <math.h> and <complex.h> functions without an f (float) or l (long
- double) suffix, several have one or more parameters whose corresponding real type is
- double. For each such function, except modf, there is a corresponding type-generic
- macro.300) The parameters whose corresponding real type is double in the function
- synopsis are generic parameters. Use of the macro invokes a function whose
- corresponding real type and type domain are determined by the arguments for the generic
- parameters.301)
-3 Use of the macro invokes a function whose generic parameters have the corresponding
- real type determined as follows:
- -- First, if any argument for generic parameters has type long double, the type
- determined is long double.
- -- Otherwise, if any argument for generic parameters has type double or is of integer
- type, the type determined is double.
- -- Otherwise, the type determined is float.
-4 For each unsuffixed function in <math.h> for which there is a function in
- <complex.h> with the same name except for a c prefix, the corresponding type-
- generic macro (for both functions) has the same name as the function in <math.h>. The
- corresponding type-generic macro for fabs and cabs is fabs.
-
-
-
-
- 300) Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to
- make available the corresponding ordinary function.
- 301) If the type of the argument is not compatible with the type of the parameter for the selected function,
- the behavior is undefined.
-
-[page 369]
-
- <math.h> <complex.h> type-generic
- function function macro
- acos cacos acos
- asin casin asin
- atan catan atan
- acosh cacosh acosh
- asinh casinh asinh
- atanh catanh atanh
- cos ccos cos
- sin csin sin
- tan ctan tan
- cosh ccosh cosh
- sinh csinh sinh
- tanh ctanh tanh
- exp cexp exp
- log clog log
- pow cpow pow
- sqrt csqrt sqrt
- fabs cabs fabs
- If at least one argument for a generic parameter is complex, then use of the macro invokes
- a complex function; otherwise, use of the macro invokes a real function.
-5 For each unsuffixed function in <math.h> without a c-prefixed counterpart in
- <complex.h> (except modf), the corresponding type-generic macro has the same
- name as the function. These type-generic macros are:
- atan2 fma llround remainder
- cbrt fmax log10 remquo
- ceil fmin log1p rint
- copysign fmod log2 round
- erf frexp logb scalbn
- erfc hypot lrint scalbln
- exp2 ilogb lround tgamma
- expm1 ldexp nearbyint trunc
- fdim lgamma nextafter
- floor llrint nexttoward
- If all arguments for generic parameters are real, then use of the macro invokes a real
- function; otherwise, use of the macro results in undefined behavior.
-
-
-
-
-[page 370]
-
-6 For each unsuffixed function in <complex.h> that is not a c-prefixed counterpart to a
- function in <math.h>, the corresponding type-generic macro has the same name as the
- function. These type-generic macros are:
- carg conj creal
- cimag cproj
- Use of the macro with any real or complex argument invokes a complex function.
-7 EXAMPLE With the declarations
- #include <tgmath.h>
- int n;
- float f;
- double d;
- long double ld;
- float complex fc;
- double complex dc;
- long double complex ldc;
- functions invoked by use of type-generic macros are shown in the following table:
- macro use invokes
- exp(n) exp(n), the function
- acosh(f) acoshf(f)
- sin(d) sin(d), the function
- atan(ld) atanl(ld)
- log(fc) clogf(fc)
- sqrt(dc) csqrt(dc)
- pow(ldc, f) cpowl(ldc, f)
- remainder(n, n) remainder(n, n), the function
- nextafter(d, f) nextafter(d, f), the function
- nexttoward(f, ld) nexttowardf(f, ld)
- copysign(n, ld) copysignl(n, ld)
- ceil(fc) undefined behavior
- rint(dc) undefined behavior
- fmax(ldc, ld) undefined behavior
- carg(n) carg(n), the function
- cproj(f) cprojf(f)
- creal(d) creal(d), the function
- cimag(ld) cimagl(ld)
- fabs(fc) cabsf(fc)
- carg(dc) carg(dc), the function
- cproj(ldc) cprojl(ldc)
-
-
-
-
-[page 371]
-
- 7.25 Threads <threads.h>
- 7.25.1 Introduction
-1 The header <threads.h> defines macros, and declares types, enumeration constants,
- and functions that support multiple threads of execution.
-2 Implementations that define the macro __STDC_NO_THREADS__ need not provide
- this header nor support any of its facilities.
-3 The macros are
- ONCE_FLAG_INIT
- which expands to a value that can be used to initialize an object of type once_flag;
- and
- TSS_DTOR_ITERATIONS
- which expands to an integer constant expression representing the maximum number of
- times that destructors will be called when a thread terminates.
-4 The types are
- cnd_t
- which is a complete object type that holds an identifier for a condition variable;
- thrd_t
- which is a complete object type that holds an identifier for a thread;
- tss_t
- which is a complete object type that holds an identifier for a thread-specific storage
- pointer;
- mtx_t
- which is a complete object type that holds an identifier for a mutex;
- tss_dtor_t
- which is the function pointer type void (*)(void*), used for a destructor for a
- thread-specific storage pointer;
- thrd_start_t
- which is the function pointer type int (*)(void*) that is passed to thrd_create
- to create a new thread;
- once_flag
- which is a complete object type that holds a flag for use by call_once; and
-
-
-[page 372]
-
- xtime
- which is a structure type that holds a time specified in seconds and nanoseconds. The
- structure shall contain at least the following members, in any order.
- time_t sec;
- long nsec;
-5 The enumeration constants are
- mtx_plain
- which is passed to mtx_init to create a mutex object that supports neither timeout nor
- test and return;
- mtx_recursive
- which is passed to mtx_init to create a mutex object that supports recursive locking;
- mtx_timed
- which is passed to mtx_init to create a mutex object that supports timeout;
- mtx_try
- which is passed to mtx_init to create a mutex object that supports test and return;
- thrd_timeout
- which is returned by a timed wait function to indicate that the time specified in the call
- was reached without acquiring the requested resource;
- thrd_success
- which is returned by a function to indicate that the requested operation succeeded;
- thrd_busy
- which is returned by a function to indicate that the requested operation failed because a
- resource requested by a test and return function is already in use;
- thrd_error
- which is returned by a function to indicate that the requested operation failed; and
- thrd_nomem
- which is returned by a function to indicate that the requested operation failed because it
- was unable to allocate memory.
-
-
-
-
-[page 373]
-
- 7.25.2 Initialization functions
- 7.25.2.1 The call_once function
- Synopsis
-1 #include <threads.h>
- void call_once(once_flag *flag, void (*func)(void));
- Description
-2 The call_once function uses the once_flag pointed to by flag to ensure that
- func is called exactly once, the first time the call_once function is called with that
- value of flag. Completion of an effective call to the call_once function synchronizes
- with all subsequent calls to the call_once function with the same value of flag.
- Returns
-3 The call_once function returns no value.
- 7.25.3 Condition variable functions
- 7.25.3.1 The cnd_broadcast function
- Synopsis
-1 #include <threads.h>
- int cnd_broadcast(cnd_t *cond);
- Description
-2 The cnd_broadcast function unblocks all of the threads that are blocked on the
- condition variable pointed to by cond at the time of the call. If no threads are blocked
- on the condition variable pointed to by cond at the time of the call, the function does
- nothing.
- Returns
-3 The cnd_broadcast function returns thrd_success on success, or thrd_error
- if the request could not be honored.
- 7.25.3.2 The cnd_destroy function
- Synopsis
-1 #include <threads.h>
- void cnd_destroy(cnd_t *cond);
- Description
-2 The cnd_destroy function releases all resources used by the condition variable
- pointed to by cond. The cnd_destroy function requires that no threads be blocked
- waiting for the condition variable pointed to by cond.
-
-[page 374]
-
- Returns
-3 The cnd_destroy function returns no value.
- 7.25.3.3 The cnd_init function
- Synopsis
-1 #include <threads.h>
- int cnd_init(cnd_t *cond);
- Description
-2 The cnd_init function creates a condition variable. If it succeeds it sets the variable
- pointed to by cond to a value that uniquely identifies the newly created condition
- variable. A thread that calls cnd_wait on a newly created condition variable will
- block.
- Returns
-3 The cnd_init function returns thrd_success on success, or thrd_nomem if no
- memory could be allocated for the newly created condition, or thrd_error if the
- request could not be honored.
- 7.25.3.4 The cnd_signal function
- Synopsis
-1 #include <threads.h>
- int cnd_signal(cnd_t *cond);
- Description
-2 The cnd_signal function unblocks one of the threads that are blocked on the
- condition variable pointed to by cond at the time of the call. If no threads are blocked
- on the condition variable at the time of the call, the function does nothing and return
- success.
- Returns
-3 The cnd_signal function returns thrd_success on success or thrd_error if
- the request could not be honored.
- 7.25.3.5 The cnd_timedwait function
- Synopsis
-1 #include <threads.h>
- int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
- const xtime *xt);
-
-
-
-
-[page 375]
-
- Description
-2 The cnd_timedwait function atomically unlocks the mutex pointed to by mtx and
- endeavors to block until the condition variable pointed to by cond is signaled by a call to
- cnd_signal or to cnd_broadcast, or until after the time specified by the xtime
- object pointed to by xt. When the calling thread becomes unblocked it locks the variable
- pointed to by mtx before it returns. The cnd_timedwait function requires that the
- mutex pointed to by mtx be locked by the calling thread.
- Returns
-3 The cnd_timedwait function returns thrd_success upon success, or
- thrd_timeout if the time specified in the call was reached without acquiring the
- requested resource, or thrd_error if the request could not be honored.
- 7.25.3.6 The cnd_wait function
- Synopsis
-1 #include <threads.h>
- int cnd_wait(cnd_t *cond, mtx_t *mtx);
- Description
-2 The cnd_wait function atomically unlocks the mutex pointed to by mtx and endeavors
- to block until the condition variable pointed to by cond is signaled by a call to
- cnd_signal or to cnd_broadcast. When the calling thread becomes unblocked it
- locks the mutex pointed to by mtx before it returns. If the mutex pointed to by mtx is
- not locked by the calling thread, the cnd_wait function will act as if the abort
- function is called.
- Returns
-3 The cnd_wait function returns thrd_success on success or thrd_error if the
- request could not be honored.
- 7.25.4 Mutex functions
- 7.25.4.1 The mtx_destroy function
- Synopsis
-1 #include <threads.h>
- void mtx_destroy(mtx_t *mtx);
- Description
-2 The mtx_destroy function releases any resources used by the mutex pointed to by
- mtx. No threads can be blocked waiting for the mutex pointed to by mtx.
-
-
-
-[page 376]
-
- Returns
-3 The mtx_destroy function returns no value.
- 7.25.4.2 The mtx_init function
- Synopsis
-1 #include <threads.h>
- int mtx_init(mtx_t *mtx, int type);
- Description
-2 The mtx_init function creates a mutex object with properties indicated by type,
- which must have one of the six values:
- mtx_plain for a simple non-recursive mutex,
- mtx_timed for a non-recursive mutex that supports timeout,
- mtx_try for a non-recursive mutex that supports test and return,
- mtx_plain | mtx_recursive for a simple recursive mutex,
- mtx_timed | mtx_recursive for a recursive mutex that supports timeout, or
- mtx_try | mtx_recursive for a recursive mutex that supports test and return.
-3 If the mtx_init function succeeds, it sets the mutex pointed to by mtx to a value that
- uniquely identifies the newly created mutex.
- Returns
-4 The mtx_init function returns thrd_success on success, or thrd_error if the
- request could not be honored.
- 7.25.4.3 The mtx_lock function
- Synopsis
-1 #include <threads.h>
- int mtx_lock(mtx_t *mtx);
- Description
-2 The mtx_lock function blocks until it locks the mutex pointed to by mtx. If the mutex
- is non-recursive, it shall not be locked by the calling thread. Prior calls to mtx_unlock
- on the same mutex shall synchronize with this operation.
- Returns
-3 The mtx_lock function returns thrd_success on success, or thrd_busy if the
- resource requested is already in use, or thrd_error if the request could not be
- honored.
-
-
-
-
-[page 377]
-
- 7.25.4.4 The mtx_timedlock function
- Synopsis
-1 #include <threads.h>
- int mtx_timedlock(mtx_t *mtx, const xtime *xt);
- Description
-2 The mtx_timedlock function endeavors to block until it locks the mutex pointed to by
- mtx or until the time specified by the xtime object xt has passed. The specified mutex
- shall support timeout. Prior calls to mtx_unlock on the same mutex shall synchronize
- with this operation. *
- Returns
-3 The mtx_timedlock function returns thrd_success on success, or thrd_busy
- if the resource requested is already in use, or thrd_timeout if the time specified was
- reached without acquiring the requested resource, or thrd_error if the request could
- not be honored.
- 7.25.4.5 The mtx_trylock function
- Synopsis
-1 #include <threads.h>
- int mtx_trylock(mtx_t *mtx);
- Description
-2 The mtx_trylock function endeavors to lock the mutex pointed to by mtx. The
- specified mutex shall support either test and return or timeout. If the mutex is already
- locked, the function returns without blocking. Prior calls to mtx_unlock on the same
- mutex shall synchronize with this operation. *
- Returns
-3 The mtx_trylock function returns thrd_success on success, or thrd_busy if
- the resource requested is already in use, or thrd_error if the request could not be
- honored.
- 7.25.4.6 The mtx_unlock function
- Synopsis
-1 #include <threads.h>
- int mtx_unlock(mtx_t *mtx);
- Description
-2 The mtx_unlock function unlocks the mutex pointed to by mtx. The mutex pointed to
- by mtx shall be locked by the calling thread.
-
-[page 378]
-
- Returns
-3 The mtx_unlock function returns thrd_success on success or thrd_error if
- the request could not be honored.
- 7.25.5 Thread functions
- 7.25.5.1 The thrd_create function
- Synopsis
-1 #include <threads.h>
- int thrd_create(thrd_t *thr, thrd_start_t func,
- void *arg);
- Description
-2 The thrd_create function creates a new thread executing func(arg). If the
- thrd_create function succeeds, it sets the thread thr to a value that uniquely
- identifies the newly created thread.
- Returns
-3 The thrd_create function returns thrd_success on success, or thrd_nomem if
- no memory could be allocated for the thread requested, or thrd_error if the request
- could not be honored.
- 7.25.5.2 The thrd_current function
- Synopsis
-1 #include <threads.h>
- thrd_t thrd_current(void);
- Description
-2 The thrd_current function identifies the thread that called it.
- Returns
-3 The thrd_current function returns a value that uniquely identifies the thread that
- called it.
- 7.25.5.3 The thrd_detach function
- Synopsis
-1 #include <threads.h>
- int thrd_detach(thrd_t thr);
- Description
-2 The thrd_detach function tells the operating system to dispose of any resources
- allocated to the thread identified by thr when that thread terminates. The value of the
-
-[page 379]
-
- thread identified by thr value shall not have been set by a call to thrd_join or
- thrd_detach.
- Returns
-3 The thrd_detach function returns thrd_success on success or thrd_error if
- the request could not be honored.
- 7.25.5.4 The thrd_equal function
- Synopsis
-1 #include <threads.h>
- int thrd_equal(thrd_t thr0, thrd_t thr1);
- Description
-2 The thrd_equal function will determine whether the thread identified by thr0 refers
- to the thread identified by thr1.
- Returns
-3 The thrd_equal function returns zero if the thread thr0 and the thread thr1 refer to
- different threads. Otherwise the thrd_equal function returns a nonzero value.
- 7.25.5.5 The thrd_exit function
- Synopsis
-1 #include <threads.h>
- void thrd_exit(int res);
- Description
-2 The thrd_exit function terminates execution of the calling thread and sets its result
- code to res.
- Returns
-3 The thrd_exit function returns no value.
- 7.25.5.6 The thrd_join function
- Synopsis
-1 #include <threads.h>
- int thrd_join(thrd_t thr, int *res);
- Description
-2 The thrd_join function blocks until the thread identified by thr has terminated. If
- the parameter res is not a null pointer, it stores the thread's result code in the integer
- pointed to by res. The value of the thread identified by thr shall not have been set by a
- call to thrd_join or thrd_detach.
-
-[page 380]
-
- Returns
-3 The thrd_join function returns thrd_success on success or thrd_error if the
- request could not be honored.
- 7.25.5.7 The thrd_sleep function
- Synopsis
-1 #include <threads.h>
- void thrd_sleep(const xtime *xt);
- Description
-2 The thrd_sleep function suspends execution of the calling thread until after the time
- specified by the xtime object pointed to by xt.
- Returns
-3 The thrd_sleep function returns no value.
- 7.25.5.8 The thrd_yield function
- Synopsis
-1 #include <threads.h>
- void thrd_yield(void);
- Description
-2 The thrd_yield function endeavors to permit other threads to run, even if the current
- thread would ordinarily continue to run.
- Returns
-3 The thrd_yield function returns no value.
- 7.25.6 Thread-specific storage functions
- 7.25.6.1 The tss_create function
- Synopsis
-1 #include <threads.h>
- int tss_create(tss_t *key, tss_dtor_t dtor);
- Description
-2 The tss_create function creates a thread-specific storage pointer with destructor
- dtor, which may be null.
- Returns
-3 If the tss_create function is successful, it sets the thread-specific storage pointed to
- by key to a value that uniquely identifies the newly created pointer and returns
- thrd_success; otherwise, thrd_error is returned and the thread-specific storage
-[page 381]
-
- pointed to by key is set to an undefined value.
- 7.25.6.2 The tss_delete function
- Synopsis
-1 #include <threads.h>
- void tss_delete(tss_t key);
- Description
-2 The tss_delete function releases any resources used by the thread-specific storage
- identified by key.
- Returns
-3 The tss_delete function returns no value.
- 7.25.6.3 The tss_get function
- Synopsis
-1 #include <threads.h>
- void *tss_get(tss_t key);
- Description
-2 The tss_get function returns the value for the current thread held in the thread-specific
- storage identified by key.
- Returns
-3 The tss_get function returns the value for the current thread if successful, or zero if
- unsuccessful.
- 7.25.6.4 The tss_set function
- Synopsis
-1 #include <threads.h>
- int tss_set(tss_t key, void *val);
- Description
-2 The tss_set function sets the value for the current thread held in the thread-specific
- storage identified by key to val.
- Returns
-3 The tss_set function returns thrd_success on success or thrd_error if the
- request could not be honored.
-
-
-
-
-[page 382]
-
- 7.25.7 Time functions
- 7.25.7.1 The xtime_get function
- Synopsis
-1 #include <threads.h>
- int xtime_get(xtime *xt, int base);
- Description
-2 The xtime_get function sets the xtime object pointed to by xt to hold the current
- time based on the time base base.
- Returns
-3 If the xtime_get function is successful it returns the nonzero value base, which must
- be TIME_UTC; otherwise, it returns zero.302)
-
-
-
-
- 302) Although an xtime object describes times with nanosecond resolution, the actual resolution in an
- xtime object is system dependent.
-
-[page 383]
-
- 7.26 Date and time <time.h>
- 7.26.1 Components of time
-1 The header <time.h> defines two macros, and declares several types and functions for
- manipulating time. Many functions deal with a calendar time that represents the current
- date (according to the Gregorian calendar) and time. Some functions deal with local
- time, which is the calendar time expressed for some specific time zone, and with Daylight
- Saving Time, which is a temporary change in the algorithm for determining local time.
- The local time zone and Daylight Saving Time are implementation-defined.
-2 The macros defined are NULL (described in 7.19); and
- CLOCKS_PER_SEC
- which expands to an expression with type clock_t (described below) that is the
- number per second of the value returned by the clock function.
-3 The types declared are size_t (described in 7.19);
- clock_t
- and
- time_t
- which are arithmetic types capable of representing times; and
- struct tm
- which holds the components of a calendar time, called the broken-down time.
-4 The range and precision of times representable in clock_t and time_t are
- implementation-defined. The tm structure shall contain at least the following members,
- in any order. The semantics of the members and their normal ranges are expressed in the
- comments.303)
- int tm_sec; // seconds after the minute -- [0, 60]
- int tm_min; // minutes after the hour -- [0, 59]
- int tm_hour; // hours since midnight -- [0, 23]
- int tm_mday; // day of the month -- [1, 31]
- int tm_mon; // months since January -- [0, 11]
- int tm_year; // years since 1900
- int tm_wday; // days since Sunday -- [0, 6]
- int tm_yday; // days since January 1 -- [0, 365]
- int tm_isdst; // Daylight Saving Time flag
-
-
-
- 303) The range [0, 60] for tm_sec allows for a positive leap second.
-
-[page 384]
-
- The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight
- Saving Time is not in effect, and negative if the information is not available.
- 7.26.2 Time manipulation functions
- 7.26.2.1 The clock function
- Synopsis
-1 #include <time.h>
- clock_t clock(void);
- Description
-2 The clock function determines the processor time used.
- Returns
-3 The clock function returns the implementation's best approximation to the processor
- time used by the program since the beginning of an implementation-defined era related
- only to the program invocation. To determine the time in seconds, the value returned by
- the clock function should be divided by the value of the macro CLOCKS_PER_SEC. If
- the processor time used is not available or its value cannot be represented, the function
- returns the value (clock_t)(-1).304)
- 7.26.2.2 The difftime function
- Synopsis
-1 #include <time.h>
- double difftime(time_t time1, time_t time0);
- Description
-2 The difftime function computes the difference between two calendar times: time1 -
- time0.
- Returns
-3 The difftime function returns the difference expressed in seconds as a double.
-
-
-
-
- 304) In order to measure the time spent in a program, the clock function should be called at the start of
- the program and its return value subtracted from the value returned by subsequent calls.
-
-[page 385]
-
- 7.26.2.3 The mktime function
- Synopsis
-1 #include <time.h>
- time_t mktime(struct tm *timeptr);
- Description
-2 The mktime function converts the broken-down time, expressed as local time, in the
- structure pointed to by timeptr into a calendar time value with the same encoding as
- that of the values returned by the time function. The original values of the tm_wday
- and tm_yday components of the structure are ignored, and the original values of the
- other components are not restricted to the ranges indicated above.305) On successful
- completion, the values of the tm_wday and tm_yday components of the structure are
- set appropriately, and the other components are set to represent the specified calendar
- time, but with their values forced to the ranges indicated above; the final value of
- tm_mday is not set until tm_mon and tm_year are determined.
- Returns
-3 The mktime function returns the specified calendar time encoded as a value of type
- time_t. If the calendar time cannot be represented, the function returns the value
- (time_t)(-1).
-4 EXAMPLE What day of the week is July 4, 2001?
- #include <stdio.h>
- #include <time.h>
- static const char *const wday[] = {
- "Sunday", "Monday", "Tuesday", "Wednesday",
- "Thursday", "Friday", "Saturday", "-unknown-"
- };
- struct tm time_str;
- /* ... */
-
-
-
-
- 305) Thus, a positive or zero value for tm_isdst causes the mktime function to presume initially that
- Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value
- causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time.
-
-[page 386]
-
- time_str.tm_year = 2001 - 1900;
- time_str.tm_mon = 7 - 1;
- time_str.tm_mday = 4;
- time_str.tm_hour = 0;
- time_str.tm_min = 0;
- time_str.tm_sec = 1;
- time_str.tm_isdst = -1;
- if (mktime(&time_str) == (time_t)(-1))
- time_str.tm_wday = 7;
- printf("%s\n", wday[time_str.tm_wday]);
-
- 7.26.2.4 The time function
- Synopsis
-1 #include <time.h>
- time_t time(time_t *timer);
- Description
-2 The time function determines the current calendar time. The encoding of the value is
- unspecified.
- Returns
-3 The time function returns the implementation's best approximation to the current
- calendar time. The value (time_t)(-1) is returned if the calendar time is not
- available. If timer is not a null pointer, the return value is also assigned to the object it
- points to.
- 7.26.3 Time conversion functions
-1 Except for the strftime function, these functions each return a pointer to one of two
- types of static objects: a broken-down time structure or an array of char. Execution of
- any of the functions that return a pointer to one of these object types may overwrite the
- information in any object of the same type pointed to by the value returned from any
- previous call to any of them and the functions are not required to avoid data races. The
- implementation shall behave as if no other library functions call these functions.
- 7.26.3.1 The asctime function
- Synopsis
-1 #include <time.h>
- char *asctime(const struct tm *timeptr);
- Description
-2 The asctime function converts the broken-down time in the structure pointed to by
- timeptr into a string in the form
- Sun Sep 16 01:03:52 1973\n\0
-
-[page 387]
-
- using the equivalent of the following algorithm.
- char *asctime(const struct tm *timeptr)
- {
- static const char wday_name[7][3] = {
- "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
- };
- static const char mon_name[12][3] = {
- "Jan", "Feb", "Mar", "Apr", "May", "Jun",
- "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
- };
- static char result[26];
- sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
- wday_name[timeptr->tm_wday],
- mon_name[timeptr->tm_mon],
- timeptr->tm_mday, timeptr->tm_hour,
- timeptr->tm_min, timeptr->tm_sec,
- 1900 + timeptr->tm_year);
- return result;
- }
-3 If any of the fields of the broken-down time contain values that are outside their normal
- ranges,306) the behavior of the asctime function is undefined. Likewise, if the
- calculated year exceeds four digits or is less than the year 1000, the behavior is
- undefined.
- Returns
-4 The asctime function returns a pointer to the string.
- 7.26.3.2 The ctime function
- Synopsis
-1 #include <time.h>
- char *ctime(const time_t *timer);
- Description
-2 The ctime function converts the calendar time pointed to by timer to local time in the
- form of a string. It is equivalent to
- asctime(localtime(timer))
-
-
-
- 306) See 7.26.1.
-
-[page 388]
-
- Returns
-3 The ctime function returns the pointer returned by the asctime function with that
- broken-down time as argument.
- Forward references: the localtime function (7.26.3.4).
- 7.26.3.3 The gmtime function
- Synopsis
-1 #include <time.h>
- struct tm *gmtime(const time_t *timer);
- Description
-2 The gmtime function converts the calendar time pointed to by timer into a broken-
- down time, expressed as UTC.
- Returns
-3 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
- specified time cannot be converted to UTC.
- 7.26.3.4 The localtime function
- Synopsis
-1 #include <time.h>
- struct tm *localtime(const time_t *timer);
- Description
-2 The localtime function converts the calendar time pointed to by timer into a
- broken-down time, expressed as local time.
- Returns
-3 The localtime function returns a pointer to the broken-down time, or a null pointer if
- the specified time cannot be converted to local time.
- 7.26.3.5 The strftime function
- Synopsis
-1 #include <time.h>
- size_t strftime(char * restrict s,
- size_t maxsize,
- const char * restrict format,
- const struct tm * restrict timeptr);
-
-
-
-
-[page 389]
-
- Description
-2 The strftime function places characters into the array pointed to by s as controlled by
- the string pointed to by format. The format shall be a multibyte character sequence,
- beginning and ending in its initial shift state. The format string consists of zero or
- more conversion specifiers and ordinary multibyte characters. A conversion specifier
- consists of a % character, possibly followed by an E or O modifier character (described
- below), followed by a character that determines the behavior of the conversion specifier.
- All ordinary multibyte characters (including the terminating null character) are copied
- unchanged into the array. If copying takes place between objects that overlap, the
- behavior is undefined. No more than maxsize characters are placed into the array.
-3 Each conversion specifier is replaced by appropriate characters as described in the
- following list. The appropriate characters are determined using the LC_TIME category
- of the current locale and by the values of zero or more members of the broken-down time
- structure pointed to by timeptr, as specified in brackets in the description. If any of
- the specified values is outside the normal range, the characters stored are unspecified.
- %a is replaced by the locale's abbreviated weekday name. [tm_wday]
- %A is replaced by the locale's full weekday name. [tm_wday]
- %b is replaced by the locale's abbreviated month name. [tm_mon]
- %B is replaced by the locale's full month name. [tm_mon]
- %c is replaced by the locale's appropriate date and time representation. [all specified
- in 7.26.1]
- %C is replaced by the year divided by 100 and truncated to an integer, as a decimal
- number (00-99). [tm_year]
- %d is replaced by the day of the month as a decimal number (01-31). [tm_mday]
- %D is equivalent to ''%m/%d/%y''. [tm_mon, tm_mday, tm_year]
- %e is replaced by the day of the month as a decimal number (1-31); a single digit is
- preceded by a space. [tm_mday]
- %F is equivalent to ''%Y-%m-%d'' (the ISO 8601 date format). [tm_year, tm_mon,
- tm_mday]
- %g is replaced by the last 2 digits of the week-based year (see below) as a decimal
- number (00-99). [tm_year, tm_wday, tm_yday]
- %G is replaced by the week-based year (see below) as a decimal number (e.g., 1997).
- [tm_year, tm_wday, tm_yday]
- %h is equivalent to ''%b''. [tm_mon]
- %H is replaced by the hour (24-hour clock) as a decimal number (00-23). [tm_hour]
- %I is replaced by the hour (12-hour clock) as a decimal number (01-12). [tm_hour]
- %j is replaced by the day of the year as a decimal number (001-366). [tm_yday]
- %m is replaced by the month as a decimal number (01-12). [tm_mon]
- %M is replaced by the minute as a decimal number (00-59). [tm_min]
- %n is replaced by a new-line character.
-
-[page 390]
-
- %p is replaced by the locale's equivalent of the AM/PM designations associated with a
- 12-hour clock. [tm_hour]
- %r is replaced by the locale's 12-hour clock time. [tm_hour, tm_min, tm_sec]
- %R is equivalent to ''%H:%M''. [tm_hour, tm_min]
- %S is replaced by the second as a decimal number (00-60). [tm_sec]
- %t is replaced by a horizontal-tab character.
- %T is equivalent to ''%H:%M:%S'' (the ISO 8601 time format). [tm_hour, tm_min,
- tm_sec]
- %u is replaced by the ISO 8601 weekday as a decimal number (1-7), where Monday
- is 1. [tm_wday]
- %U is replaced by the week number of the year (the first Sunday as the first day of week
- 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
- %V is replaced by the ISO 8601 week number (see below) as a decimal number
- (01-53). [tm_year, tm_wday, tm_yday]
- %w is replaced by the weekday as a decimal number (0-6), where Sunday is 0.
- [tm_wday]
- %W is replaced by the week number of the year (the first Monday as the first day of
- week 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
- %x is replaced by the locale's appropriate date representation. [all specified in 7.26.1]
- %X is replaced by the locale's appropriate time representation. [all specified in 7.26.1]
- %y is replaced by the last 2 digits of the year as a decimal number (00-99).
- [tm_year]
- %Y is replaced by the year as a decimal number (e.g., 1997). [tm_year]
- %z is replaced by the offset from UTC in the ISO 8601 format ''-0430'' (meaning 4
- hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
- zone is determinable. [tm_isdst]
- %Z is replaced by the locale's time zone name or abbreviation, or by no characters if no
- time zone is determinable. [tm_isdst]
- %% is replaced by %.
-4 Some conversion specifiers can be modified by the inclusion of an E or O modifier
- character to indicate an alternative format or specification. If the alternative format or
- specification does not exist for the current locale, the modifier is ignored.
- %Ec is replaced by the locale's alternative date and time representation.
- %EC is replaced by the name of the base year (period) in the locale's alternative
- representation.
- %Ex is replaced by the locale's alternative date representation.
- %EX is replaced by the locale's alternative time representation.
- %Ey is replaced by the offset from %EC (year only) in the locale's alternative
- representation.
- %EY is replaced by the locale's full alternative year representation.
-
-[page 391]
-
- %Od is replaced by the day of the month, using the locale's alternative numeric symbols
- (filled as needed with leading zeros, or with leading spaces if there is no alternative
- symbol for zero).
- %Oe is replaced by the day of the month, using the locale's alternative numeric symbols
- (filled as needed with leading spaces).
- %OH is replaced by the hour (24-hour clock), using the locale's alternative numeric
- symbols.
- %OI is replaced by the hour (12-hour clock), using the locale's alternative numeric
- symbols.
- %Om is replaced by the month, using the locale's alternative numeric symbols.
- %OM is replaced by the minutes, using the locale's alternative numeric symbols.
- %OS is replaced by the seconds, using the locale's alternative numeric symbols.
- %Ou is replaced by the ISO 8601 weekday as a number in the locale's alternative
- representation, where Monday is 1.
- %OU is replaced by the week number, using the locale's alternative numeric symbols.
- %OV is replaced by the ISO 8601 week number, using the locale's alternative numeric
- symbols.
- %Ow is replaced by the weekday as a number, using the locale's alternative numeric
- symbols.
- %OW is replaced by the week number of the year, using the locale's alternative numeric
- symbols.
- %Oy is replaced by the last 2 digits of the year, using the locale's alternative numeric
- symbols.
-5 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system,
- weeks begin on a Monday and week 1 of the year is the week that includes January 4th,
- which is also the week that includes the first Thursday of the year, and is also the first
- week that contains at least four days in the year. If the first Monday of January is the
- 2nd, 3rd, or 4th, the preceding days are part of the last week of the preceding year; thus,
- for Saturday 2nd January 1999, %G is replaced by 1998 and %V is replaced by 53. If
- December 29th, 30th, or 31st is a Monday, it and any following days are part of week 1 of
- the following year. Thus, for Tuesday 30th December 1997, %G is replaced by 1998 and
- %V is replaced by 01.
-6 If a conversion specifier is not one of the above, the behavior is undefined.
-7 In the "C" locale, the E and O modifiers are ignored and the replacement strings for the
- following specifiers are:
- %a the first three characters of %A.
- %A one of ''Sunday'', ''Monday'', ... , ''Saturday''.
- %b the first three characters of %B.
- %B one of ''January'', ''February'', ... , ''December''.
- %c equivalent to ''%a %b %e %T %Y''.
-[page 392]
-
- %p one of ''AM'' or ''PM''.
- %r equivalent to ''%I:%M:%S %p''.
- %x equivalent to ''%m/%d/%y''.
- %X equivalent to %T.
- %Z implementation-defined.
- Returns
-8 If the total number of resulting characters including the terminating null character is not
- more than maxsize, the strftime function returns the number of characters placed
- into the array pointed to by s not including the terminating null character. Otherwise,
- zero is returned and the contents of the array are indeterminate.
-
-
-
-
-[page 393]
-
- 7.27 Unicode utilities <uchar.h>
-1 The header <uchar.h> declares types and functions for manipulating Unicode
- characters.
-2 The types declared are mbstate_t (described in 7.29.1) and size_t (described in
- 7.19);
- char16_t
- which is an unsigned integer type used for 16-bit characters and is the same type as
- uint_least16_t (described in 7.20.1.2); and
- char32_t
- which is an unsigned integer type used for 32-bit characters and is the same type as
- uint_least32_t (also described in 7.20.1.2).
- 7.27.1 Restartable multibyte/wide character conversion functions
-1 These functions have a parameter, ps, of type pointer to mbstate_t that points to an
- object that can completely describe the current conversion state of the associated
- multibyte character sequence, which the functions alter as necessary. If ps is a null
- pointer, each function uses its own internal mbstate_t object instead, which is
- initialized at program startup to the initial conversion state; the functions are not required
- to avoid data races in this case. The implementation behaves as if no library function
- calls these functions with a null pointer for ps.
- 7.27.1.1 The mbrtoc16 function
- Synopsis
-1 #include <uchar.h>
- size_t mbrtoc16(char16_t * restrict pc16,
- const char * restrict s, size_t n,
- mbstate_t * restrict ps);
- Description
-2 If s is a null pointer, the mbrtoc16 function is equivalent to the call:
- mbrtoc16(NULL, "", 1, ps)
- In this case, the values of the parameters pc16 and n are ignored.
-3 If s is not a null pointer, the mbrtoc16 function inspects at most n bytes beginning with
- the byte pointed to by s to determine the number of bytes needed to complete the next
- multibyte character (including any shift sequences). If the function determines that the
- next multibyte character is complete and valid, it determines the values of the
- corresponding wide characters and then, if pc16 is not a null pointer, stores the value of
- the first (or only) such character in the object pointed to by pc16. Subsequent calls will
-[page 394]
-
- store successive wide characters without consuming any additional input until all the
- characters have been stored. If the corresponding wide character is the null wide
- character, the resulting state described is the initial conversion state.
- Returns
-4 The mbrtoc16 function returns the first of the following that applies (given the current
- conversion state):
- 0 if the next n or fewer bytes complete the multibyte character that
- corresponds to the null wide character (which is the value stored).
- between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
- character (which is the value stored); the value returned is the number
- of bytes that complete the multibyte character.
- (size_t)(-3) if the next character resulting from a previous call has been stored (no
- bytes from the input have been consumed by this call).
- (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
- multibyte character, and all n bytes have been processed (no value is
- stored).307)
- (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
- do not contribute to a complete and valid multibyte character (no
- value is stored); the value of the macro EILSEQ is stored in errno,
- and the conversion state is unspecified.
- 7.27.1.2 The c16rtomb function
- Synopsis
-1 #include <uchar.h>
- size_t c16rtomb(char * restrict s, char16_t c16,
- mbstate_t * restrict ps);
- Description
-2 If s is a null pointer, the c16rtomb function is equivalent to the call
- c16rtomb(buf, L'\0', ps)
- where buf is an internal buffer.
-3 If s is not a null pointer, the c16rtomb function determines the number of bytes needed
- to represent the multibyte character that corresponds to the wide character given by c16
- (including any shift sequences), and stores the multibyte character representation in the
-
- 307) When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
- sequence of redundant shift sequences (for implementations with state-dependent encodings).
-
-[page 395]
-
- array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
- c16 is a null wide character, a null byte is stored, preceded by any shift sequence needed
- to restore the initial shift state; the resulting state described is the initial conversion state.
- Returns
-4 The c16rtomb function returns the number of bytes stored in the array object (including
- any shift sequences). When c16 is not a valid wide character, an encoding error occurs:
- the function stores the value of the macro EILSEQ in errno and returns
- (size_t)(-1); the conversion state is unspecified.
- 7.27.1.3 The mbrtoc32 function
- Synopsis
-1 #include <uchar.h>
- size_t mbrtoc32(char32_t * restrict pc32,
- const char * restrict s, size_t n,
- mbstate_t * restrict ps);
- Description
-2 If s is a null pointer, the mbrtoc32 function is equivalent to the call:
- mbrtoc32(NULL, "", 1, ps)
- In this case, the values of the parameters pc32 and n are ignored.
-3 If s is not a null pointer, the mbrtoc32 function inspects at most n bytes beginning with
- the byte pointed to by s to determine the number of bytes needed to complete the next
- multibyte character (including any shift sequences). If the function determines that the
- next multibyte character is complete and valid, it determines the values of the
- corresponding wide characters and then, if pc32 is not a null pointer, stores the value of
- the first (or only) such character in the object pointed to by pc32. Subsequent calls will
- store successive wide characters without consuming any additional input until all the
- characters have been stored. If the corresponding wide character is the null wide
- character, the resulting state described is the initial conversion state.
- Returns
-4 The mbrtoc32 function returns the first of the following that applies (given the current
- conversion state):
- 0 if the next n or fewer bytes complete the multibyte character that
- corresponds to the null wide character (which is the value stored).
- between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
- character (which is the value stored); the value returned is the number
- of bytes that complete the multibyte character.
-
-
-[page 396]
-
- (size_t)(-3) if the next character resulting from a previous call has been stored (no
- bytes from the input have been consumed by this call).
- (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
- multibyte character, and all n bytes have been processed (no value is
- stored).308)
- (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
- do not contribute to a complete and valid multibyte character (no
- value is stored); the value of the macro EILSEQ is stored in errno,
- and the conversion state is unspecified.
- 7.27.1.4 The c32rtomb function
- Synopsis
-1 #include <uchar.h>
- size_t c32rtomb(char * restrict s, char32_t c32,
- mbstate_t * restrict ps);
- Description
-2 If s is a null pointer, the c32rtomb function is equivalent to the call
- c32rtomb(buf, L'\0', ps)
- where buf is an internal buffer.
-3 If s is not a null pointer, the c32rtomb function determines the number of bytes needed
- to represent the multibyte character that corresponds to the wide character given by c32
- (including any shift sequences), and stores the multibyte character representation in the
- array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
- c32 is a null wide character, a null byte is stored, preceded by any shift sequence needed
- to restore the initial shift state; the resulting state described is the initial conversion state.
- Returns
-4 The c32rtomb function returns the number of bytes stored in the array object (including
- any shift sequences). When c32 is not a valid wide character, an encoding error occurs:
- the function stores the value of the macro EILSEQ in errno and returns
- (size_t)(-1); the conversion state is unspecified.
-
-
-
-
- 308) When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
- sequence of redundant shift sequences (for implementations with state-dependent encodings).
-
-[page 397]
-
- 7.28 Extended multibyte and wide character utilities <wchar.h>
- 7.28.1 Introduction
-1 The header <wchar.h> defines four macros, and declares four data types, one tag, and
- many functions.309)
-2 The types declared are wchar_t and size_t (both described in 7.19);
- mbstate_t
- which is a complete object type other than an array type that can hold the conversion state
- information necessary to convert between sequences of multibyte characters and wide
- characters;
- wint_t
- which is an integer type unchanged by default argument promotions that can hold any
- value corresponding to members of the extended character set, as well as at least one
- value that does not correspond to any member of the extended character set (see WEOF
- below);310) and
- struct tm
- which is declared as an incomplete structure type (the contents are described in 7.26.1).
-3 The macros defined are NULL (described in 7.19); WCHAR_MIN and WCHAR_MAX
- (described in 7.20.3); and
- WEOF
- which expands to a constant expression of type wint_t whose value does not
- correspond to any member of the extended character set.311) It is accepted (and returned)
- by several functions in this subclause to indicate end-of-file, that is, no more input from a
- stream. It is also used as a wide character value that does not correspond to any member
- of the extended character set.
-4 The functions declared are grouped as follows:
- -- Functions that perform input and output of wide characters, or multibyte characters,
- or both;
- -- Functions that provide wide string numeric conversion;
- -- Functions that perform general wide string manipulation;
-
-
- 309) See ''future library directions'' (7.30.12).
- 310) wchar_t and wint_t can be the same integer type.
- 311) The value of the macro WEOF may differ from that of EOF and need not be negative.
-
-[page 398]
-
- -- Functions for wide string date and time conversion; and
- -- Functions that provide extended capabilities for conversion between multibyte and
- wide character sequences.
-5 Unless explicitly stated otherwise, if the execution of a function described in this
- subclause causes copying to take place between objects that overlap, the behavior is
- undefined.
- 7.28.2 Formatted wide character input/output functions
-1 The formatted wide character input/output functions shall behave as if there is a sequence
- point after the actions associated with each specifier.312)
- 7.28.2.1 The fwprintf function
- Synopsis
-1 #include <stdio.h>
- #include <wchar.h>
- int fwprintf(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- Description
-2 The fwprintf function writes output to the stream pointed to by stream, under
- control of the wide string pointed to by format that specifies how subsequent arguments
- are converted for output. If there are insufficient arguments for the format, the behavior
- is undefined. If the format is exhausted while arguments remain, the excess arguments
- are evaluated (as always) but are otherwise ignored. The fwprintf function returns
- when the end of the format string is encountered.
-3 The format is composed of zero or more directives: ordinary wide characters (not %),
- which are copied unchanged to the output stream; and conversion specifications, each of
- which results in fetching zero or more subsequent arguments, converting them, if
- applicable, according to the corresponding conversion specifier, and then writing the
- result to the output stream.
-4 Each conversion specification is introduced by the wide character %. After the %, the
- following appear in sequence:
- -- Zero or more flags (in any order) that modify the meaning of the conversion
- specification.
- -- An optional minimum field width. If the converted value has fewer wide characters
- than the field width, it is padded with spaces (by default) on the left (or right, if the
-
-
- 312) The fwprintf functions perform writes to memory for the %n specifier.
-
-[page 399]
-
- left adjustment flag, described later, has been given) to the field width. The field
- width takes the form of an asterisk * (described later) or a nonnegative decimal
- integer.313)
- -- An optional precision that gives the minimum number of digits to appear for the d, i,
- o, u, x, and X conversions, the number of digits to appear after the decimal-point
- wide character for a, A, e, E, f, and F conversions, the maximum number of
- significant digits for the g and G conversions, or the maximum number of wide
- characters to be written for s conversions. The precision takes the form of a period
- (.) followed either by an asterisk * (described later) or by an optional decimal
- integer; if only the period is specified, the precision is taken as zero. If a precision
- appears with any other conversion specifier, the behavior is undefined.
- -- An optional length modifier that specifies the size of the argument.
- -- A conversion specifier wide character that specifies the type of conversion to be
- applied.
-5 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
- this case, an int argument supplies the field width or precision. The arguments
- specifying field width, or precision, or both, shall appear (in that order) before the
- argument (if any) to be converted. A negative field width argument is taken as a - flag
- followed by a positive field width. A negative precision argument is taken as if the
- precision were omitted.
-6 The flag wide characters and their meanings are:
- - The result of the conversion is left-justified within the field. (It is right-justified if
- this flag is not specified.)
- + The result of a signed conversion always begins with a plus or minus sign. (It
- begins with a sign only when a negative value is converted if this flag is not
- specified.)314)
- space If the first wide character of a signed conversion is not a sign, or if a signed
- conversion results in no wide characters, a space is prefixed to the result. If the
- space and + flags both appear, the space flag is ignored.
- # The result is converted to an ''alternative form''. For o conversion, it increases
- the precision, if and only if necessary, to force the first digit of the result to be a
- zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
- conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
-
-
- 313) Note that 0 is taken as a flag, not as the beginning of a field width.
- 314) The results of all floating conversions of a negative zero, and of negative values that round to zero,
- include a minus sign.
-
-[page 400]
-
- and G conversions, the result of converting a floating-point number always
- contains a decimal-point wide character, even if no digits follow it. (Normally, a
- decimal-point wide character appears in the result of these conversions only if a
- digit follows it.) For g and G conversions, trailing zeros are not removed from the
- result. For other conversions, the behavior is undefined.
- 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
- (following any indication of sign or base) are used to pad to the field width rather
- than performing space padding, except when converting an infinity or NaN. If the
- 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
- conversions, if a precision is specified, the 0 flag is ignored. For other
- conversions, the behavior is undefined.
-7 The length modifiers and their meanings are:
- hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- signed char or unsigned char argument (the argument will have
- been promoted according to the integer promotions, but its value shall be
- converted to signed char or unsigned char before printing); or that
- a following n conversion specifier applies to a pointer to a signed char
- argument.
- h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- short int or unsigned short int argument (the argument will
- have been promoted according to the integer promotions, but its value shall
- be converted to short int or unsigned short int before printing);
- or that a following n conversion specifier applies to a pointer to a short
- int argument.
- l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- long int or unsigned long int argument; that a following n
- conversion specifier applies to a pointer to a long int argument; that a
- following c conversion specifier applies to a wint_t argument; that a
- following s conversion specifier applies to a pointer to a wchar_t
- argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
- specifier.
- ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- long long int or unsigned long long int argument; or that a
- following n conversion specifier applies to a pointer to a long long int
- argument.
- j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
- an intmax_t or uintmax_t argument; or that a following n conversion
- specifier applies to a pointer to an intmax_t argument.
-
-[page 401]
-
- z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- size_t or the corresponding signed integer type argument; or that a
- following n conversion specifier applies to a pointer to a signed integer type
- corresponding to size_t argument.
- t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
- ptrdiff_t or the corresponding unsigned integer type argument; or that a
- following n conversion specifier applies to a pointer to a ptrdiff_t
- argument.
- L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
- applies to a long double argument.
- If a length modifier appears with any conversion specifier other than as specified above,
- the behavior is undefined.
-8 The conversion specifiers and their meanings are:
- d,i The int argument is converted to signed decimal in the style [-]dddd. The
- precision specifies the minimum number of digits to appear; if the value
- being converted can be represented in fewer digits, it is expanded with
- leading zeros. The default precision is 1. The result of converting a zero
- value with a precision of zero is no wide characters.
- o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
- decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
- letters abcdef are used for x conversion and the letters ABCDEF for X
- conversion. The precision specifies the minimum number of digits to appear;
- if the value being converted can be represented in fewer digits, it is expanded
- with leading zeros. The default precision is 1. The result of converting a
- zero value with a precision of zero is no wide characters.
- f,F A double argument representing a floating-point number is converted to
- decimal notation in the style [-]ddd.ddd, where the number of digits after
- the decimal-point wide character is equal to the precision specification. If the
- precision is missing, it is taken as 6; if the precision is zero and the # flag is
- not specified, no decimal-point wide character appears. If a decimal-point
- wide character appears, at least one digit appears before it. The value is
- rounded to the appropriate number of digits.
- A double argument representing an infinity is converted in one of the styles
- [-]inf or [-]infinity -- which style is implementation-defined. A
- double argument representing a NaN is converted in one of the styles
- [-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
- any n-wchar-sequence, is implementation-defined. The F conversion
- specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
-
-[page 402]
-
- nan, respectively.315)
-e,E A double argument representing a floating-point number is converted in the
- style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
- argument is nonzero) before the decimal-point wide character and the number
- of digits after it is equal to the precision; if the precision is missing, it is taken
- as 6; if the precision is zero and the # flag is not specified, no decimal-point
- wide character appears. The value is rounded to the appropriate number of
- digits. The E conversion specifier produces a number with E instead of e
- introducing the exponent. The exponent always contains at least two digits,
- and only as many more digits as necessary to represent the exponent. If the
- value is zero, the exponent is zero.
- A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
-g,G A double argument representing a floating-point number is converted in
- style f or e (or in style F or E in the case of a G conversion specifier),
- depending on the value converted and the precision. Let P equal the
- precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
- Then, if a conversion with style E would have an exponent of X:
- -- if P > X >= -4, the conversion is with style f (or F) and precision
- P - (X + 1).
- -- otherwise, the conversion is with style e (or E) and precision P - 1.
- Finally, unless the # flag is used, any trailing zeros are removed from the
- fractional portion of the result and the decimal-point wide character is
- removed if there is no fractional portion remaining.
- A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
-a,A A double argument representing a floating-point number is converted in the
- style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
- nonzero if the argument is a normalized floating-point number and is
- otherwise unspecified) before the decimal-point wide character316) and the
- number of hexadecimal digits after it is equal to the precision; if the precision
- is missing and FLT_RADIX is a power of 2, then the precision is sufficient
-
-
-315) When applied to infinite and NaN values, the -, +, and space flag wide characters have their usual
- meaning; the # and 0 flag wide characters have no effect.
-316) Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide
- character so that subsequent digits align to nibble (4-bit) boundaries.
-
-[page 403]
-
- for an exact representation of the value; if the precision is missing and
- FLT_RADIX is not a power of 2, then the precision is sufficient to
- distinguish317) values of type double, except that trailing zeros may be
- omitted; if the precision is zero and the # flag is not specified, no decimal-
- point wide character appears. The letters abcdef are used for a conversion
- and the letters ABCDEF for A conversion. The A conversion specifier
- produces a number with X and P instead of x and p. The exponent always
- contains at least one digit, and only as many more digits as necessary to
- represent the decimal exponent of 2. If the value is zero, the exponent is
- zero.
- A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
-c If no l length modifier is present, the int argument is converted to a wide
- character as if by calling btowc and the resulting wide character is written.
- If an l length modifier is present, the wint_t argument is converted to
- wchar_t and written.
-s If no l length modifier is present, the argument shall be a pointer to the initial
- element of a character array containing a multibyte character sequence
- beginning in the initial shift state. Characters from the array are converted as
- if by repeated calls to the mbrtowc function, with the conversion state
- described by an mbstate_t object initialized to zero before the first
- multibyte character is converted, and written up to (but not including) the
- terminating null wide character. If the precision is specified, no more than
- that many wide characters are written. If the precision is not specified or is
- greater than the size of the converted array, the converted array shall contain a
- null wide character.
- If an l length modifier is present, the argument shall be a pointer to the initial
- element of an array of wchar_t type. Wide characters from the array are
- written up to (but not including) a terminating null wide character. If the
- precision is specified, no more than that many wide characters are written. If
- the precision is not specified or is greater than the size of the array, the array
- shall contain a null wide character.
-p The argument shall be a pointer to void. The value of the pointer is
- converted to a sequence of printing wide characters, in an implementation-
-
-317) The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
- FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
- might suffice depending on the implementation's scheme for determining the digit to the left of the
- decimal-point wide character.
-
-[page 404]
-
- defined manner.
- n The argument shall be a pointer to signed integer into which is written the
- number of wide characters written to the output stream so far by this call to
- fwprintf. No argument is converted, but one is consumed. If the
- conversion specification includes any flags, a field width, or a precision, the
- behavior is undefined.
- % A % wide character is written. No argument is converted. The complete
- conversion specification shall be %%.
-9 If a conversion specification is invalid, the behavior is undefined.318) If any argument is
- not the correct type for the corresponding conversion specification, the behavior is
- undefined.
-10 In no case does a nonexistent or small field width cause truncation of a field; if the result
- of a conversion is wider than the field width, the field is expanded to contain the
- conversion result.
-11 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
- to a hexadecimal floating number with the given precision.
- Recommended practice
-12 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
- representable in the given precision, the result should be one of the two adjacent numbers
- in hexadecimal floating style with the given precision, with the extra stipulation that the
- error should have a correct sign for the current rounding direction.
-13 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
- DECIMAL_DIG, then the result should be correctly rounded.319) If the number of
- significant decimal digits is more than DECIMAL_DIG but the source value is exactly
- representable with DECIMAL_DIG digits, then the result should be an exact
- representation with trailing zeros. Otherwise, the source value is bounded by two
- adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
- of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
- the error should have a correct sign for the current rounding direction.
- Returns
-14 The fwprintf function returns the number of wide characters transmitted, or a negative
- value if an output or encoding error occurred.
-
- 318) See ''future library directions'' (7.30.12).
- 319) For binary-to-decimal conversion, the result format's values are the numbers representable with the
- given format specifier. The number of significant digits is determined by the format specifier, and in
- the case of fixed-point conversion by the source value as well.
-
-[page 405]
-
- Environmental limits
-15 The number of wide characters that can be produced by any single conversion shall be at
- least 4095.
-16 EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
- places:
- #include <math.h>
- #include <stdio.h>
- #include <wchar.h>
- /* ... */
- wchar_t *weekday, *month; // pointers to wide strings
- int day, hour, min;
- fwprintf(stdout, L"%ls, %ls %d, %.2d:%.2d\n",
- weekday, month, day, hour, min);
- fwprintf(stdout, L"pi = %.5f\n", 4 * atan(1.0));
-
- Forward references: the btowc function (7.28.6.1.1), the mbrtowc function
- (7.28.6.3.2).
- 7.28.2.2 The fwscanf function
- Synopsis
-1 #include <stdio.h>
- #include <wchar.h>
- int fwscanf(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- Description
-2 The fwscanf function reads input from the stream pointed to by stream, under
- control of the wide string pointed to by format that specifies the admissible input
- sequences and how they are to be converted for assignment, using subsequent arguments
- as pointers to the objects to receive the converted input. If there are insufficient
- arguments for the format, the behavior is undefined. If the format is exhausted while
- arguments remain, the excess arguments are evaluated (as always) but are otherwise
- ignored.
-3 The format is composed of zero or more directives: one or more white-space wide
- characters, an ordinary wide character (neither % nor a white-space wide character), or a
- conversion specification. Each conversion specification is introduced by the wide
- character %. After the %, the following appear in sequence:
- -- An optional assignment-suppressing wide character *.
- -- An optional decimal integer greater than zero that specifies the maximum field width
- (in wide characters).
-
-
-
-[page 406]
-
- -- An optional length modifier that specifies the size of the receiving object.
- -- A conversion specifier wide character that specifies the type of conversion to be
- applied.
-4 The fwscanf function executes each directive of the format in turn. When all directives
- have been executed, or if a directive fails (as detailed below), the function returns.
- Failures are described as input failures (due to the occurrence of an encoding error or the
- unavailability of input characters), or matching failures (due to inappropriate input).
-5 A directive composed of white-space wide character(s) is executed by reading input up to
- the first non-white-space wide character (which remains unread), or until no more wide
- characters can be read.
-6 A directive that is an ordinary wide character is executed by reading the next wide
- character of the stream. If that wide character differs from the directive, the directive
- fails and the differing and subsequent wide characters remain unread. Similarly, if end-
- of-file, an encoding error, or a read error prevents a wide character from being read, the
- directive fails.
-7 A directive that is a conversion specification defines a set of matching input sequences, as
- described below for each specifier. A conversion specification is executed in the
- following steps:
-8 Input white-space wide characters (as specified by the iswspace function) are skipped,
- unless the specification includes a [, c, or n specifier.320)
-9 An input item is read from the stream, unless the specification includes an n specifier. An
- input item is defined as the longest sequence of input wide characters which does not
- exceed any specified field width and which is, or is a prefix of, a matching input
- sequence.321) The first wide character, if any, after the input item remains unread. If the
- length of the input item is zero, the execution of the directive fails; this condition is a
- matching failure unless end-of-file, an encoding error, or a read error prevented input
- from the stream, in which case it is an input failure.
-10 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
- count of input wide characters) is converted to a type appropriate to the conversion
- specifier. If the input item is not a matching sequence, the execution of the directive fails:
- this condition is a matching failure. Unless assignment suppression was indicated by a *,
- the result of the conversion is placed in the object pointed to by the first argument
- following the format argument that has not already received a conversion result. If this
-
-
- 320) These white-space wide characters are not counted against a specified field width.
- 321) fwscanf pushes back at most one input wide character onto the input stream. Therefore, some
- sequences that are acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
-
-[page 407]
-
- object does not have an appropriate type, or if the result of the conversion cannot be
- represented in the object, the behavior is undefined.
-11 The length modifiers and their meanings are:
- hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to signed char or unsigned char.
- h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to short int or unsigned short
- int.
- l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to long int or unsigned long
- int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
- an argument with type pointer to double; or that a following c, s, or [
- conversion specifier applies to an argument with type pointer to wchar_t.
- ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to long long int or unsigned
- long long int.
- j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to intmax_t or uintmax_t.
- z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to size_t or the corresponding signed
- integer type.
- t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to ptrdiff_t or the corresponding
- unsigned integer type.
- L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
- applies to an argument with type pointer to long double.
- If a length modifier appears with any conversion specifier other than as specified above,
- the behavior is undefined.
-12 The conversion specifiers and their meanings are:
- d Matches an optionally signed decimal integer, whose format is the same as
- expected for the subject sequence of the wcstol function with the value 10
- for the base argument. The corresponding argument shall be a pointer to
- signed integer.
- i Matches an optionally signed integer, whose format is the same as expected
- for the subject sequence of the wcstol function with the value 0 for the
- base argument. The corresponding argument shall be a pointer to signed
-
-[page 408]
-
- integer.
-o Matches an optionally signed octal integer, whose format is the same as
- expected for the subject sequence of the wcstoul function with the value 8
- for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
-u Matches an optionally signed decimal integer, whose format is the same as
- expected for the subject sequence of the wcstoul function with the value 10
- for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
-x Matches an optionally signed hexadecimal integer, whose format is the same
- as expected for the subject sequence of the wcstoul function with the value
- 16 for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
-a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
- format is the same as expected for the subject sequence of the wcstod
- function. The corresponding argument shall be a pointer to floating.
-c Matches a sequence of wide characters of exactly the number specified by the
- field width (1 if no field width is present in the directive).
- If no l length modifier is present, characters from the input field are
- converted as if by repeated calls to the wcrtomb function, with the
- conversion state described by an mbstate_t object initialized to zero
- before the first wide character is converted. The corresponding argument
- shall be a pointer to the initial element of a character array large enough to
- accept the sequence. No null character is added.
- If an l length modifier is present, the corresponding argument shall be a
- pointer to the initial element of an array of wchar_t large enough to accept
- the sequence. No null wide character is added.
-s Matches a sequence of non-white-space wide characters.
- If no l length modifier is present, characters from the input field are
- converted as if by repeated calls to the wcrtomb function, with the
- conversion state described by an mbstate_t object initialized to zero
- before the first wide character is converted. The corresponding argument
- shall be a pointer to the initial element of a character array large enough to
- accept the sequence and a terminating null character, which will be added
- automatically.
- If an l length modifier is present, the corresponding argument shall be a
- pointer to the initial element of an array of wchar_t large enough to accept
-
-[page 409]
-
- the sequence and the terminating null wide character, which will be added
- automatically.
-[ Matches a nonempty sequence of wide characters from a set of expected
- characters (the scanset).
- If no l length modifier is present, characters from the input field are
- converted as if by repeated calls to the wcrtomb function, with the
- conversion state described by an mbstate_t object initialized to zero
- before the first wide character is converted. The corresponding argument
- shall be a pointer to the initial element of a character array large enough to
- accept the sequence and a terminating null character, which will be added
- automatically.
- If an l length modifier is present, the corresponding argument shall be a
- pointer to the initial element of an array of wchar_t large enough to accept
- the sequence and the terminating null wide character, which will be added
- automatically.
- The conversion specifier includes all subsequent wide characters in the
- format string, up to and including the matching right bracket (]). The wide
- characters between the brackets (the scanlist) compose the scanset, unless the
- wide character after the left bracket is a circumflex (^), in which case the
- scanset contains all wide characters that do not appear in the scanlist between
- the circumflex and the right bracket. If the conversion specifier begins with
- [] or [^], the right bracket wide character is in the scanlist and the next
- following right bracket wide character is the matching right bracket that ends
- the specification; otherwise the first following right bracket wide character is
- the one that ends the specification. If a - wide character is in the scanlist and
- is not the first, nor the second where the first wide character is a ^, nor the
- last character, the behavior is implementation-defined.
-p Matches an implementation-defined set of sequences, which should be the
- same as the set of sequences that may be produced by the %p conversion of
- the fwprintf function. The corresponding argument shall be a pointer to a
- pointer to void. The input item is converted to a pointer value in an
- implementation-defined manner. If the input item is a value converted earlier
- during the same program execution, the pointer that results shall compare
- equal to that value; otherwise the behavior of the %p conversion is undefined.
-n No input is consumed. The corresponding argument shall be a pointer to
- signed integer into which is to be written the number of wide characters read
- from the input stream so far by this call to the fwscanf function. Execution
- of a %n directive does not increment the assignment count returned at the
- completion of execution of the fwscanf function. No argument is
-[page 410]
-
- converted, but one is consumed. If the conversion specification includes an
- assignment-suppressing wide character or a field width, the behavior is
- undefined.
- % Matches a single % wide character; no conversion or assignment occurs. The
- complete conversion specification shall be %%.
-13 If a conversion specification is invalid, the behavior is undefined.322)
-14 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
- respectively, a, e, f, g, and x.
-15 Trailing white space (including new-line wide characters) is left unread unless matched
- by a directive. The success of literal matches and suppressed assignments is not directly
- determinable other than via the %n directive.
- Returns
-16 The fwscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the function returns the
- number of input items assigned, which can be fewer than provided for, or even zero, in
- the event of an early matching failure.
-17 EXAMPLE 1 The call:
- #include <stdio.h>
- #include <wchar.h>
- /* ... */
- int n, i; float x; wchar_t name[50];
- n = fwscanf(stdin, L"%d%f%ls", &i, &x, name);
- with the input line:
- 25 54.32E-1 thompson
- will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
- thompson\0.
-
-18 EXAMPLE 2 The call:
- #include <stdio.h>
- #include <wchar.h>
- /* ... */
- int i; float x; double y;
- fwscanf(stdin, L"%2d%f%*d %lf", &i, &x, &y);
- with input:
- 56789 0123 56a72
- will assign to i the value 56 and to x the value 789.0, will skip past 0123, and will assign to y the value
- 56.0. The next wide character read from the input stream will be a.
-
-
- 322) See ''future library directions'' (7.30.12).
-
-[page 411]
-
- Forward references: the wcstod, wcstof, and wcstold functions (7.28.4.1.1), the
- wcstol, wcstoll, wcstoul, and wcstoull functions (7.28.4.1.2), the wcrtomb
- function (7.28.6.3.3).
- 7.28.2.3 The swprintf function
- Synopsis
-1 #include <wchar.h>
- int swprintf(wchar_t * restrict s,
- size_t n,
- const wchar_t * restrict format, ...);
- Description
-2 The swprintf function is equivalent to fwprintf, except that the argument s
- specifies an array of wide characters into which the generated output is to be written,
- rather than written to a stream. No more than n wide characters are written, including a
- terminating null wide character, which is always added (unless n is zero).
- Returns
-3 The swprintf function returns the number of wide characters written in the array, not
- counting the terminating null wide character, or a negative value if an encoding error
- occurred or if n or more wide characters were requested to be written.
- 7.28.2.4 The swscanf function
- Synopsis
-1 #include <wchar.h>
- int swscanf(const wchar_t * restrict s,
- const wchar_t * restrict format, ...);
- Description
-2 The swscanf function is equivalent to fwscanf, except that the argument s specifies a
- wide string from which the input is to be obtained, rather than from a stream. Reaching
- the end of the wide string is equivalent to encountering end-of-file for the fwscanf
- function.
- Returns
-3 The swscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the swscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
-
-
-
-
-[page 412]
-
- 7.28.2.5 The vfwprintf function
- Synopsis
-1 #include <stdarg.h>
- #include <stdio.h>
- #include <wchar.h>
- int vfwprintf(FILE * restrict stream,
- const wchar_t * restrict format,
- va_list arg);
- Description
-2 The vfwprintf function is equivalent to fwprintf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vfwprintf function does not invoke the
- va_end macro.323)
- Returns
-3 The vfwprintf function returns the number of wide characters transmitted, or a
- negative value if an output or encoding error occurred.
-4 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting
- routine.
- #include <stdarg.h>
- #include <stdio.h>
- #include <wchar.h>
- void error(char *function_name, wchar_t *format, ...)
- {
- va_list args;
- va_start(args, format);
- // print out name of function causing error
- fwprintf(stderr, L"ERROR in %s: ", function_name);
- // print out remainder of message
- vfwprintf(stderr, format, args);
- va_end(args);
- }
-
-
-
-
- 323) As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
- invoke the va_arg macro, the value of arg after the return is indeterminate.
-
-[page 413]
-
- 7.28.2.6 The vfwscanf function
- Synopsis
-1 #include <stdarg.h>
- #include <stdio.h>
- #include <wchar.h>
- int vfwscanf(FILE * restrict stream,
- const wchar_t * restrict format,
- va_list arg);
- Description
-2 The vfwscanf function is equivalent to fwscanf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vfwscanf function does not invoke the
- va_end macro.323)
- Returns
-3 The vfwscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the vfwscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
- 7.28.2.7 The vswprintf function
- Synopsis
-1 #include <stdarg.h>
- #include <wchar.h>
- int vswprintf(wchar_t * restrict s,
- size_t n,
- const wchar_t * restrict format,
- va_list arg);
- Description
-2 The vswprintf function is equivalent to swprintf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vswprintf function does not invoke the
- va_end macro.323)
- Returns
-3 The vswprintf function returns the number of wide characters written in the array, not
- counting the terminating null wide character, or a negative value if an encoding error
- occurred or if n or more wide characters were requested to be generated.
-
-
-[page 414]
-
- 7.28.2.8 The vswscanf function
- Synopsis
-1 #include <stdarg.h>
- #include <wchar.h>
- int vswscanf(const wchar_t * restrict s,
- const wchar_t * restrict format,
- va_list arg);
- Description
-2 The vswscanf function is equivalent to swscanf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vswscanf function does not invoke the
- va_end macro.323)
- Returns
-3 The vswscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the vswscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
- 7.28.2.9 The vwprintf function
- Synopsis
-1 #include <stdarg.h>
- #include <wchar.h>
- int vwprintf(const wchar_t * restrict format,
- va_list arg);
- Description
-2 The vwprintf function is equivalent to wprintf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vwprintf function does not invoke the
- va_end macro.323)
- Returns
-3 The vwprintf function returns the number of wide characters transmitted, or a negative
- value if an output or encoding error occurred.
-
-
-
-
-[page 415]
-
- 7.28.2.10 The vwscanf function
- Synopsis
-1 #include <stdarg.h>
- #include <wchar.h>
- int vwscanf(const wchar_t * restrict format,
- va_list arg);
- Description
-2 The vwscanf function is equivalent to wscanf, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vwscanf function does not invoke the
- va_end macro.323)
- Returns
-3 The vwscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the vwscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
- 7.28.2.11 The wprintf function
- Synopsis
-1 #include <wchar.h>
- int wprintf(const wchar_t * restrict format, ...);
- Description
-2 The wprintf function is equivalent to fwprintf with the argument stdout
- interposed before the arguments to wprintf.
- Returns
-3 The wprintf function returns the number of wide characters transmitted, or a negative
- value if an output or encoding error occurred.
- 7.28.2.12 The wscanf function
- Synopsis
-1 #include <wchar.h>
- int wscanf(const wchar_t * restrict format, ...);
- Description
-2 The wscanf function is equivalent to fwscanf with the argument stdin interposed
- before the arguments to wscanf.
-
-
-[page 416]
-
- Returns
-3 The wscanf function returns the value of the macro EOF if an input failure occurs
- before the first conversion (if any) has completed. Otherwise, the wscanf function
- returns the number of input items assigned, which can be fewer than provided for, or even
- zero, in the event of an early matching failure.
- 7.28.3 Wide character input/output functions
- 7.28.3.1 The fgetwc function
- Synopsis
-1 #include <stdio.h>
- #include <wchar.h>
- wint_t fgetwc(FILE *stream);
- Description
-2 If the end-of-file indicator for the input stream pointed to by stream is not set and a
- next wide character is present, the fgetwc function obtains that wide character as a
- wchar_t converted to a wint_t and advances the associated file position indicator for
- the stream (if defined).
- Returns
-3 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
- of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
- the fgetwc function returns the next wide character from the input stream pointed to by
- stream. If a read error occurs, the error indicator for the stream is set and the fgetwc
- function returns WEOF. If an encoding error occurs (including too few bytes), the value of
- the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.324)
- 7.28.3.2 The fgetws function
- Synopsis
-1 #include <stdio.h>
- #include <wchar.h>
- wchar_t *fgetws(wchar_t * restrict s,
- int n, FILE * restrict stream);
- Description
-2 The fgetws function reads at most one less than the number of wide characters
- specified by n from the stream pointed to by stream into the array pointed to by s. No
-
-
- 324) An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
- Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
-
-[page 417]
-
- additional wide characters are read after a new-line wide character (which is retained) or
- after end-of-file. A null wide character is written immediately after the last wide
- character read into the array.
- Returns
-3 The fgetws function returns s if successful. If end-of-file is encountered and no
- characters have been read into the array, the contents of the array remain unchanged and a
- null pointer is returned. If a read or encoding error occurs during the operation, the array
- contents are indeterminate and a null pointer is returned.
- 7.28.3.3 The fputwc function
- Synopsis
-1 #include <stdio.h>
- #include <wchar.h>
- wint_t fputwc(wchar_t c, FILE *stream);
- Description
-2 The fputwc function writes the wide character specified by c to the output stream
- pointed to by stream, at the position indicated by the associated file position indicator
- for the stream (if defined), and advances the indicator appropriately. If the file cannot
- support positioning requests, or if the stream was opened with append mode, the
- character is appended to the output stream.
- Returns
-3 The fputwc function returns the wide character written. If a write error occurs, the
- error indicator for the stream is set and fputwc returns WEOF. If an encoding error
- occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
- 7.28.3.4 The fputws function
- Synopsis
-1 #include <stdio.h>
- #include <wchar.h>
- int fputws(const wchar_t * restrict s,
- FILE * restrict stream);
- Description
-2 The fputws function writes the wide string pointed to by s to the stream pointed to by
- stream. The terminating null wide character is not written.
- Returns
-3 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
- returns a nonnegative value.
-
-[page 418]
-
- 7.28.3.5 The fwide function
- Synopsis
-1 #include <stdio.h>
- #include <wchar.h>
- int fwide(FILE *stream, int mode);
- Description
-2 The fwide function determines the orientation of the stream pointed to by stream. If
- mode is greater than zero, the function first attempts to make the stream wide oriented. If
- mode is less than zero, the function first attempts to make the stream byte oriented.325)
- Otherwise, mode is zero and the function does not alter the orientation of the stream.
- Returns
-3 The fwide function returns a value greater than zero if, after the call, the stream has
- wide orientation, a value less than zero if the stream has byte orientation, or zero if the
- stream has no orientation.
- 7.28.3.6 The getwc function
- Synopsis
-1 #include <stdio.h>
- #include <wchar.h>
- wint_t getwc(FILE *stream);
- Description
-2 The getwc function is equivalent to fgetwc, except that if it is implemented as a
- macro, it may evaluate stream more than once, so the argument should never be an
- expression with side effects.
- Returns
-3 The getwc function returns the next wide character from the input stream pointed to by
- stream, or WEOF.
- 7.28.3.7 The getwchar function
- Synopsis
-1 #include <wchar.h>
- wint_t getwchar(void);
-
-
-
-
- 325) If the orientation of the stream has already been determined, fwide does not change it.
-
-[page 419]
-
- Description
-2 The getwchar function is equivalent to getwc with the argument stdin.
- Returns
-3 The getwchar function returns the next wide character from the input stream pointed to
- by stdin, or WEOF.
- 7.28.3.8 The putwc function
- Synopsis
-1 #include <stdio.h>
- #include <wchar.h>
- wint_t putwc(wchar_t c, FILE *stream);
- Description
-2 The putwc function is equivalent to fputwc, except that if it is implemented as a
- macro, it may evaluate stream more than once, so that argument should never be an
- expression with side effects.
- Returns
-3 The putwc function returns the wide character written, or WEOF.
- 7.28.3.9 The putwchar function
- Synopsis
-1 #include <wchar.h>
- wint_t putwchar(wchar_t c);
- Description
-2 The putwchar function is equivalent to putwc with the second argument stdout.
- Returns
-3 The putwchar function returns the character written, or WEOF.
- 7.28.3.10 The ungetwc function
- Synopsis
-1 #include <stdio.h>
- #include <wchar.h>
- wint_t ungetwc(wint_t c, FILE *stream);
- Description
-2 The ungetwc function pushes the wide character specified by c back onto the input
- stream pointed to by stream. Pushed-back wide characters will be returned by
- subsequent reads on that stream in the reverse order of their pushing. A successful
-
-[page 420]
-
- intervening call (with the stream pointed to by stream) to a file positioning function
- (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the
- stream. The external storage corresponding to the stream is unchanged.
-3 One wide character of pushback is guaranteed, even if the call to the ungetwc function
- follows just after a call to a formatted wide character input function fwscanf,
- vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times
- on the same stream without an intervening read or file positioning operation on that
- stream, the operation may fail.
-4 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
- unchanged.
-5 A successful call to the ungetwc function clears the end-of-file indicator for the stream.
- The value of the file position indicator for the stream after reading or discarding all
- pushed-back wide characters is the same as it was before the wide characters were pushed
- back. For a text or binary stream, the value of its file position indicator after a successful
- call to the ungetwc function is unspecified until all pushed-back wide characters are
- read or discarded.
- Returns
-6 The ungetwc function returns the wide character pushed back, or WEOF if the operation
- fails.
- 7.28.4 General wide string utilities
-1 The header <wchar.h> declares a number of functions useful for wide string
- manipulation. Various methods are used for determining the lengths of the arrays, but in
- all cases a wchar_t * argument points to the initial (lowest addressed) element of the
- array. If an array is accessed beyond the end of an object, the behavior is undefined.
-2 Where an argument declared as size_t n determines the length of the array for a
- function, n can have the value zero on a call to that function. Unless explicitly stated
- otherwise in the description of a particular function in this subclause, pointer arguments
- on such a call shall still have valid values, as described in 7.1.4. On such a call, a
- function that locates a wide character finds no occurrence, a function that compares two
- wide character sequences returns zero, and a function that copies wide characters copies
- zero wide characters.
-
-
-
-
-[page 421]
-
- 7.28.4.1 Wide string numeric conversion functions
- 7.28.4.1.1 The wcstod, wcstof, and wcstold functions
- Synopsis
-1 #include <wchar.h>
- double wcstod(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr);
- float wcstof(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr);
- long double wcstold(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr);
- Description
-2 The wcstod, wcstof, and wcstold functions convert the initial portion of the wide
- string pointed to by nptr to double, float, and long double representation,
- respectively. First, they decompose the input string into three parts: an initial, possibly
- empty, sequence of white-space wide characters (as specified by the iswspace
- function), a subject sequence resembling a floating-point constant or representing an
- infinity or NaN; and a final wide string of one or more unrecognized wide characters,
- including the terminating null wide character of the input wide string. Then, they attempt
- to convert the subject sequence to a floating-point number, and return the result.
-3 The expected form of the subject sequence is an optional plus or minus sign, then one of
- the following:
- -- a nonempty sequence of decimal digits optionally containing a decimal-point wide
- character, then an optional exponent part as defined for the corresponding single-byte
- characters in 6.4.4.2;
- -- a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
- decimal-point wide character, then an optional binary exponent part as defined in
- 6.4.4.2;
- -- INF or INFINITY, or any other wide string equivalent except for case
- -- NAN or NAN(n-wchar-sequenceopt), or any other wide string equivalent except for
- case in the NAN part, where:
- n-wchar-sequence:
- digit
- nondigit
- n-wchar-sequence digit
- n-wchar-sequence nondigit
- The subject sequence is defined as the longest initial subsequence of the input wide
- string, starting with the first non-white-space wide character, that is of the expected form.
-[page 422]
-
- The subject sequence contains no wide characters if the input wide string is not of the
- expected form.
-4 If the subject sequence has the expected form for a floating-point number, the sequence of
- wide characters starting with the first digit or the decimal-point wide character
- (whichever occurs first) is interpreted as a floating constant according to the rules of
- 6.4.4.2, except that the decimal-point wide character is used in place of a period, and that
- if neither an exponent part nor a decimal-point wide character appears in a decimal
- floating point number, or if a binary exponent part does not appear in a hexadecimal
- floating point number, an exponent part of the appropriate type with value zero is
- assumed to follow the last digit in the string. If the subject sequence begins with a minus
- sign, the sequence is interpreted as negated.326) A wide character sequence INF or
- INFINITY is interpreted as an infinity, if representable in the return type, else like a
- floating constant that is too large for the range of the return type. A wide character
- sequence NAN or NAN(n-wchar-sequenceopt) is interpreted as a quiet NaN, if supported
- in the return type, else like a subject sequence part that does not have the expected form;
- the meaning of the n-wchar sequences is implementation-defined.327) A pointer to the
- final wide string is stored in the object pointed to by endptr, provided that endptr is
- not a null pointer.
-5 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
- value resulting from the conversion is correctly rounded.
-6 In other than the "C" locale, additional locale-specific subject sequence forms may be
- accepted.
-7 If the subject sequence is empty or does not have the expected form, no conversion is
- performed; the value of nptr is stored in the object pointed to by endptr, provided
- that endptr is not a null pointer.
- Recommended practice
-8 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
- the result is not exactly representable, the result should be one of the two numbers in the
- appropriate internal format that are adjacent to the hexadecimal floating source value,
- with the extra stipulation that the error should have a correct sign for the current rounding
- direction.
-
-
-
- 326) It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
- negating the value resulting from converting the corresponding unsigned sequence (see F.5); the two
- methods may yield different results if rounding is toward positive or negative infinity. In either case,
- the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
- 327) An implementation may use the n-wchar sequence to determine extra information to be represented in
- the NaN's significand.
-
-[page 423]
-
-9 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
- <float.h>) significant digits, the result should be correctly rounded. If the subject
- sequence D has the decimal form and more than DECIMAL_DIG significant digits,
- consider the two bounding, adjacent decimal strings L and U, both having
- DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
- The result should be one of the (equal or adjacent) values that would be obtained by
- correctly rounding L and U according to the current rounding direction, with the extra
- stipulation that the error with respect to D should have a correct sign for the current
- rounding direction.328)
- Returns
-10 The functions return the converted value, if any. If no conversion could be performed,
- zero is returned. If the correct value overflows and default rounding is in effect (7.12.1),
- plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
- return type and sign of the value), and the value of the macro ERANGE is stored in
- errno. If the result underflows (7.12.1), the functions return a value whose magnitude is
- no greater than the smallest normalized positive number in the return type; whether
- errno acquires the value ERANGE is implementation-defined.
-
-
-
-
- 328) DECIMAL_DIG, defined in <float.h>, should be sufficiently large that L and U will usually round
- to the same internal floating value, but if not will round to adjacent values.
-
-[page 424]
-
- 7.28.4.1.2 The wcstol, wcstoll, wcstoul, and wcstoull functions
- Synopsis
-1 #include <wchar.h>
- long int wcstol(
- const wchar_t * restrict nptr,
- wchar_t ** restrict endptr,
- int base);
- long long int wcstoll(
- const wchar_t * restrict nptr,
- wchar_t ** restrict endptr,
- int base);
- unsigned long int wcstoul(
- const wchar_t * restrict nptr,
- wchar_t ** restrict endptr,
- int base);
- unsigned long long int wcstoull(
- const wchar_t * restrict nptr,
- wchar_t ** restrict endptr,
- int base);
- Description
-2 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial
- portion of the wide string pointed to by nptr to long int, long long int,
- unsigned long int, and unsigned long long int representation,
- respectively. First, they decompose the input string into three parts: an initial, possibly
- empty, sequence of white-space wide characters (as specified by the iswspace
- function), a subject sequence resembling an integer represented in some radix determined
- by the value of base, and a final wide string of one or more unrecognized wide
- characters, including the terminating null wide character of the input wide string. Then,
- they attempt to convert the subject sequence to an integer, and return the result.
-3 If the value of base is zero, the expected form of the subject sequence is that of an
- integer constant as described for the corresponding single-byte characters in 6.4.4.1,
- optionally preceded by a plus or minus sign, but not including an integer suffix. If the
- value of base is between 2 and 36 (inclusive), the expected form of the subject sequence
- is a sequence of letters and digits representing an integer with the radix specified by
- base, optionally preceded by a plus or minus sign, but not including an integer suffix.
- The letters from a (or A) through z (or Z) are ascribed the values 10 through 35; only
- letters and digits whose ascribed values are less than that of base are permitted. If the
- value of base is 16, the wide characters 0x or 0X may optionally precede the sequence
- of letters and digits, following the sign if present.
-
-[page 425]
-
-4 The subject sequence is defined as the longest initial subsequence of the input wide
- string, starting with the first non-white-space wide character, that is of the expected form.
- The subject sequence contains no wide characters if the input wide string is empty or
- consists entirely of white space, or if the first non-white-space wide character is other
- than a sign or a permissible letter or digit.
-5 If the subject sequence has the expected form and the value of base is zero, the sequence
- of wide characters starting with the first digit is interpreted as an integer constant
- according to the rules of 6.4.4.1. If the subject sequence has the expected form and the
- value of base is between 2 and 36, it is used as the base for conversion, ascribing to each
- letter its value as given above. If the subject sequence begins with a minus sign, the value
- resulting from the conversion is negated (in the return type). A pointer to the final wide
- string is stored in the object pointed to by endptr, provided that endptr is not a null
- pointer.
-6 In other than the "C" locale, additional locale-specific subject sequence forms may be
- accepted.
-7 If the subject sequence is empty or does not have the expected form, no conversion is
- performed; the value of nptr is stored in the object pointed to by endptr, provided
- that endptr is not a null pointer.
- Returns
-8 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
- value, if any. If no conversion could be performed, zero is returned. If the correct value
- is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
- LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
- sign of the value, if any), and the value of the macro ERANGE is stored in errno.
- 7.28.4.2 Wide string copying functions
- 7.28.4.2.1 The wcscpy function
- Synopsis
-1 #include <wchar.h>
- wchar_t *wcscpy(wchar_t * restrict s1,
- const wchar_t * restrict s2);
- Description
-2 The wcscpy function copies the wide string pointed to by s2 (including the terminating
- null wide character) into the array pointed to by s1.
- Returns
-3 The wcscpy function returns the value of s1.
-
-
-[page 426]
-
- 7.28.4.2.2 The wcsncpy function
- Synopsis
-1 #include <wchar.h>
- wchar_t *wcsncpy(wchar_t * restrict s1,
- const wchar_t * restrict s2,
- size_t n);
- Description
-2 The wcsncpy function copies not more than n wide characters (those that follow a null
- wide character are not copied) from the array pointed to by s2 to the array pointed to by
- s1.329)
-3 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null
- wide characters are appended to the copy in the array pointed to by s1, until n wide
- characters in all have been written.
- Returns
-4 The wcsncpy function returns the value of s1.
- 7.28.4.2.3 The wmemcpy function
- Synopsis
-1 #include <wchar.h>
- wchar_t *wmemcpy(wchar_t * restrict s1,
- const wchar_t * restrict s2,
- size_t n);
- Description
-2 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
- object pointed to by s1.
- Returns
-3 The wmemcpy function returns the value of s1.
-
-
-
-
- 329) Thus, if there is no null wide character in the first n wide characters of the array pointed to by s2, the
- result will not be null-terminated.
-
-[page 427]
-
- 7.28.4.2.4 The wmemmove function
- Synopsis
-1 #include <wchar.h>
- wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
- size_t n);
- Description
-2 The wmemmove function copies n wide characters from the object pointed to by s2 to
- the object pointed to by s1. Copying takes place as if the n wide characters from the
- object pointed to by s2 are first copied into a temporary array of n wide characters that
- does not overlap the objects pointed to by s1 or s2, and then the n wide characters from
- the temporary array are copied into the object pointed to by s1.
- Returns
-3 The wmemmove function returns the value of s1.
- 7.28.4.3 Wide string concatenation functions
- 7.28.4.3.1 The wcscat function
- Synopsis
-1 #include <wchar.h>
- wchar_t *wcscat(wchar_t * restrict s1,
- const wchar_t * restrict s2);
- Description
-2 The wcscat function appends a copy of the wide string pointed to by s2 (including the
- terminating null wide character) to the end of the wide string pointed to by s1. The initial
- wide character of s2 overwrites the null wide character at the end of s1.
- Returns
-3 The wcscat function returns the value of s1.
- 7.28.4.3.2 The wcsncat function
- Synopsis
-1 #include <wchar.h>
- wchar_t *wcsncat(wchar_t * restrict s1,
- const wchar_t * restrict s2,
- size_t n);
- Description
-2 The wcsncat function appends not more than n wide characters (a null wide character
- and those that follow it are not appended) from the array pointed to by s2 to the end of
-
-[page 428]
-
- the wide string pointed to by s1. The initial wide character of s2 overwrites the null
- wide character at the end of s1. A terminating null wide character is always appended to
- the result.330)
- Returns
-3 The wcsncat function returns the value of s1.
- 7.28.4.4 Wide string comparison functions
-1 Unless explicitly stated otherwise, the functions described in this subclause order two
- wide characters the same way as two integers of the underlying integer type designated
- by wchar_t.
- 7.28.4.4.1 The wcscmp function
- Synopsis
-1 #include <wchar.h>
- int wcscmp(const wchar_t *s1, const wchar_t *s2);
- Description
-2 The wcscmp function compares the wide string pointed to by s1 to the wide string
- pointed to by s2.
- Returns
-3 The wcscmp function returns an integer greater than, equal to, or less than zero,
- accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
- wide string pointed to by s2.
- 7.28.4.4.2 The wcscoll function
- Synopsis
-1 #include <wchar.h>
- int wcscoll(const wchar_t *s1, const wchar_t *s2);
- Description
-2 The wcscoll function compares the wide string pointed to by s1 to the wide string
- pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the
- current locale.
- Returns
-3 The wcscoll function returns an integer greater than, equal to, or less than zero,
- accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
-
-
- 330) Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is
- wcslen(s1)+n+1.
-
-[page 429]
-
- wide string pointed to by s2 when both are interpreted as appropriate to the current
- locale.
- 7.28.4.4.3 The wcsncmp function
- Synopsis
-1 #include <wchar.h>
- int wcsncmp(const wchar_t *s1, const wchar_t *s2,
- size_t n);
- Description
-2 The wcsncmp function compares not more than n wide characters (those that follow a
- null wide character are not compared) from the array pointed to by s1 to the array
- pointed to by s2.
- Returns
-3 The wcsncmp function returns an integer greater than, equal to, or less than zero,
- accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
- to, or less than the possibly null-terminated array pointed to by s2.
- 7.28.4.4.4 The wcsxfrm function
- Synopsis
-1 #include <wchar.h>
- size_t wcsxfrm(wchar_t * restrict s1,
- const wchar_t * restrict s2,
- size_t n);
- Description
-2 The wcsxfrm function transforms the wide string pointed to by s2 and places the
- resulting wide string into the array pointed to by s1. The transformation is such that if
- the wcscmp function is applied to two transformed wide strings, it returns a value greater
- than, equal to, or less than zero, corresponding to the result of the wcscoll function
- applied to the same two original wide strings. No more than n wide characters are placed
- into the resulting array pointed to by s1, including the terminating null wide character. If
- n is zero, s1 is permitted to be a null pointer.
- Returns
-3 The wcsxfrm function returns the length of the transformed wide string (not including
- the terminating null wide character). If the value returned is n or greater, the contents of
- the array pointed to by s1 are indeterminate.
-4 EXAMPLE The value of the following expression is the length of the array needed to hold the
- transformation of the wide string pointed to by s:
-
-
-[page 430]
-
- 1 + wcsxfrm(NULL, s, 0)
-
- 7.28.4.4.5 The wmemcmp function
- Synopsis
-1 #include <wchar.h>
- int wmemcmp(const wchar_t *s1, const wchar_t *s2,
- size_t n);
- Description
-2 The wmemcmp function compares the first n wide characters of the object pointed to by
- s1 to the first n wide characters of the object pointed to by s2.
- Returns
-3 The wmemcmp function returns an integer greater than, equal to, or less than zero,
- accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
- pointed to by s2.
- 7.28.4.5 Wide string search functions
- 7.28.4.5.1 The wcschr function
- Synopsis
-1 #include <wchar.h>
- wchar_t *wcschr(const wchar_t *s, wchar_t c);
- Description
-2 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
- The terminating null wide character is considered to be part of the wide string.
- Returns
-3 The wcschr function returns a pointer to the located wide character, or a null pointer if
- the wide character does not occur in the wide string.
- 7.28.4.5.2 The wcscspn function
- Synopsis
-1 #include <wchar.h>
- size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
- Description
-2 The wcscspn function computes the length of the maximum initial segment of the wide
- string pointed to by s1 which consists entirely of wide characters not from the wide
- string pointed to by s2.
-
-
-
-[page 431]
-
- Returns
-3 The wcscspn function returns the length of the segment.
- 7.28.4.5.3 The wcspbrk function
- Synopsis
-1 #include <wchar.h>
- wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
- Description
-2 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
- any wide character from the wide string pointed to by s2.
- Returns
-3 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
- no wide character from s2 occurs in s1.
- 7.28.4.5.4 The wcsrchr function
- Synopsis
-1 #include <wchar.h>
- wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
- Description
-2 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
- s. The terminating null wide character is considered to be part of the wide string.
- Returns
-3 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
- not occur in the wide string.
- 7.28.4.5.5 The wcsspn function
- Synopsis
-1 #include <wchar.h>
- size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
- Description
-2 The wcsspn function computes the length of the maximum initial segment of the wide
- string pointed to by s1 which consists entirely of wide characters from the wide string
- pointed to by s2.
- Returns
-3 The wcsspn function returns the length of the segment.
-
-
-[page 432]
-
- 7.28.4.5.6 The wcsstr function
- Synopsis
-1 #include <wchar.h>
- wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
- Description
-2 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
- the sequence of wide characters (excluding the terminating null wide character) in the
- wide string pointed to by s2.
- Returns
-3 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
- wide string is not found. If s2 points to a wide string with zero length, the function
- returns s1.
- 7.28.4.5.7 The wcstok function
- Synopsis
-1 #include <wchar.h>
- wchar_t *wcstok(wchar_t * restrict s1,
- const wchar_t * restrict s2,
- wchar_t ** restrict ptr);
- Description
-2 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
- a sequence of tokens, each of which is delimited by a wide character from the wide string
- pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
- which the wcstok function stores information necessary for it to continue scanning the
- same wide string.
-3 The first call in a sequence has a non-null first argument and stores an initial value in the
- object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
- the object pointed to by ptr is required to have the value stored by the previous call in
- the sequence, which is then updated. The separator wide string pointed to by s2 may be
- different from call to call.
-4 The first call in the sequence searches the wide string pointed to by s1 for the first wide
- character that is not contained in the current separator wide string pointed to by s2. If no
- such wide character is found, then there are no tokens in the wide string pointed to by s1
- and the wcstok function returns a null pointer. If such a wide character is found, it is
- the start of the first token.
-5 The wcstok function then searches from there for a wide character that is contained in
- the current separator wide string. If no such wide character is found, the current token
-[page 433]
-
- extends to the end of the wide string pointed to by s1, and subsequent searches in the
- same wide string for a token return a null pointer. If such a wide character is found, it is
- overwritten by a null wide character, which terminates the current token.
-6 In all cases, the wcstok function stores sufficient information in the pointer pointed to
- by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
- value for ptr, shall start searching just past the element overwritten by a null wide
- character (if any).
- Returns
-7 The wcstok function returns a pointer to the first wide character of a token, or a null
- pointer if there is no token.
-8 EXAMPLE
- #include <wchar.h>
- static wchar_t str1[] = L"?a???b,,,#c";
- static wchar_t str2[] = L"\t \t";
- wchar_t *t, *ptr1, *ptr2;
- t = wcstok(str1, L"?", &ptr1); // t points to the token L"a"
- t = wcstok(NULL, L",", &ptr1); // t points to the token L"??b"
- t = wcstok(str2, L" \t", &ptr2); // t is a null pointer
- t = wcstok(NULL, L"#,", &ptr1); // t points to the token L"c"
- t = wcstok(NULL, L"?", &ptr1); // t is a null pointer
-
- 7.28.4.5.8 The wmemchr function
- Synopsis
-1 #include <wchar.h>
- wchar_t *wmemchr(const wchar_t *s, wchar_t c,
- size_t n);
- Description
-2 The wmemchr function locates the first occurrence of c in the initial n wide characters of
- the object pointed to by s.
- Returns
-3 The wmemchr function returns a pointer to the located wide character, or a null pointer if
- the wide character does not occur in the object.
-
-
-
-
-[page 434]
-
- 7.28.4.6 Miscellaneous functions
- 7.28.4.6.1 The wcslen function
- Synopsis
-1 #include <wchar.h>
- size_t wcslen(const wchar_t *s);
- Description
-2 The wcslen function computes the length of the wide string pointed to by s.
- Returns
-3 The wcslen function returns the number of wide characters that precede the terminating
- null wide character.
- 7.28.4.6.2 The wmemset function
- Synopsis
-1 #include <wchar.h>
- wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
- Description
-2 The wmemset function copies the value of c into each of the first n wide characters of
- the object pointed to by s.
- Returns
-3 The wmemset function returns the value of s.
- 7.28.5 Wide character time conversion functions
- 7.28.5.1 The wcsftime function
- Synopsis
-1 #include <time.h>
- #include <wchar.h>
- size_t wcsftime(wchar_t * restrict s,
- size_t maxsize,
- const wchar_t * restrict format,
- const struct tm * restrict timeptr);
- Description
-2 The wcsftime function is equivalent to the strftime function, except that:
- -- The argument s points to the initial element of an array of wide characters into which
- the generated output is to be placed.
-
-
-[page 435]
-
- -- The argument maxsize indicates the limiting number of wide characters.
- -- The argument format is a wide string and the conversion specifiers are replaced by
- corresponding sequences of wide characters.
- -- The return value indicates the number of wide characters.
- Returns
-3 If the total number of resulting wide characters including the terminating null wide
- character is not more than maxsize, the wcsftime function returns the number of
- wide characters placed into the array pointed to by s not including the terminating null
- wide character. Otherwise, zero is returned and the contents of the array are
- indeterminate.
- 7.28.6 Extended multibyte/wide character conversion utilities
-1 The header <wchar.h> declares an extended set of functions useful for conversion
- between multibyte characters and wide characters.
-2 Most of the following functions -- those that are listed as ''restartable'', 7.28.6.3 and
- 7.28.6.4 -- take as a last argument a pointer to an object of type mbstate_t that is used
- to describe the current conversion state from a particular multibyte character sequence to
- a wide character sequence (or the reverse) under the rules of a particular setting for the
- LC_CTYPE category of the current locale.
-3 The initial conversion state corresponds, for a conversion in either direction, to the
- beginning of a new multibyte character in the initial shift state. A zero-valued
- mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
- valued mbstate_t object can be used to initiate conversion involving any multibyte
- character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
- been altered by any of the functions described in this subclause, and is then used with a
- different multibyte character sequence, or in the other conversion direction, or with a
- different LC_CTYPE category setting than on earlier function calls, the behavior is
- undefined.331)
-4 On entry, each function takes the described conversion state (either internal or pointed to
- by an argument) as current. The conversion state described by the referenced object is
- altered as needed to track the shift state, and the position within a multibyte character, for
- the associated multibyte character sequence.
-
-
-
-
- 331) Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and
- mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
- character string.
-
-[page 436]
-
- 7.28.6.1 Single-byte/wide character conversion functions
- 7.28.6.1.1 The btowc function
- Synopsis
-1 #include <wchar.h> *
- wint_t btowc(int c);
- Description
-2 The btowc function determines whether c constitutes a valid single-byte character in the
- initial shift state.
- Returns
-3 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
- does not constitute a valid single-byte character in the initial shift state. Otherwise, it
- returns the wide character representation of that character.
- 7.28.6.1.2 The wctob function
- Synopsis
-1 #include <wchar.h> *
- int wctob(wint_t c);
- Description
-2 The wctob function determines whether c corresponds to a member of the extended
- character set whose multibyte character representation is a single byte when in the initial
- shift state.
- Returns
-3 The wctob function returns EOF if c does not correspond to a multibyte character with
- length one in the initial shift state. Otherwise, it returns the single-byte representation of
- that character as an unsigned char converted to an int.
- 7.28.6.2 Conversion state functions
- 7.28.6.2.1 The mbsinit function
- Synopsis
-1 #include <wchar.h>
- int mbsinit(const mbstate_t *ps);
- Description
-2 If ps is not a null pointer, the mbsinit function determines whether the referenced
- mbstate_t object describes an initial conversion state.
-
-
-
-[page 437]
-
- Returns
-3 The mbsinit function returns nonzero if ps is a null pointer or if the referenced object
- describes an initial conversion state; otherwise, it returns zero.
- 7.28.6.3 Restartable multibyte/wide character conversion functions
-1 These functions differ from the corresponding multibyte character functions of 7.22.7
- (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type
- pointer to mbstate_t that points to an object that can completely describe the current
- conversion state of the associated multibyte character sequence. If ps is a null pointer,
- each function uses its own internal mbstate_t object instead, which is initialized at
- program startup to the initial conversion state; the functions are not required to avoid data
- races in this case. The implementation behaves as if no library function calls these
- functions with a null pointer for ps.
-2 Also unlike their corresponding functions, the return value does not represent whether the
- encoding is state-dependent.
- 7.28.6.3.1 The mbrlen function
- Synopsis
-1 #include <wchar.h>
- size_t mbrlen(const char * restrict s,
- size_t n,
- mbstate_t * restrict ps);
- Description
-2 The mbrlen function is equivalent to the call:
- mbrtowc(NULL, s, n, ps != NULL ? ps : &internal)
- where internal is the mbstate_t object for the mbrlen function, except that the
- expression designated by ps is evaluated only once.
- Returns
-3 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
- or (size_t)(-1).
- Forward references: the mbrtowc function (7.28.6.3.2).
-
-
-
-
-[page 438]
-
- 7.28.6.3.2 The mbrtowc function
- Synopsis
-1 #include <wchar.h>
- size_t mbrtowc(wchar_t * restrict pwc,
- const char * restrict s,
- size_t n,
- mbstate_t * restrict ps);
- Description
-2 If s is a null pointer, the mbrtowc function is equivalent to the call:
- mbrtowc(NULL, "", 1, ps)
- In this case, the values of the parameters pwc and n are ignored.
-3 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with
- the byte pointed to by s to determine the number of bytes needed to complete the next
- multibyte character (including any shift sequences). If the function determines that the
- next multibyte character is complete and valid, it determines the value of the
- corresponding wide character and then, if pwc is not a null pointer, stores that value in
- the object pointed to by pwc. If the corresponding wide character is the null wide
- character, the resulting state described is the initial conversion state.
- Returns
-4 The mbrtowc function returns the first of the following that applies (given the current
- conversion state):
- 0 if the next n or fewer bytes complete the multibyte character that
- corresponds to the null wide character (which is the value stored).
- between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
- character (which is the value stored); the value returned is the number
- of bytes that complete the multibyte character.
- (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
- multibyte character, and all n bytes have been processed (no value is
- stored).332)
- (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
- do not contribute to a complete and valid multibyte character (no
- value is stored); the value of the macro EILSEQ is stored in errno,
- and the conversion state is unspecified.
-
- 332) When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
- sequence of redundant shift sequences (for implementations with state-dependent encodings).
-
-[page 439]
-
- 7.28.6.3.3 The wcrtomb function
- Synopsis
-1 #include <wchar.h>
- size_t wcrtomb(char * restrict s,
- wchar_t wc,
- mbstate_t * restrict ps);
- Description
-2 If s is a null pointer, the wcrtomb function is equivalent to the call
- wcrtomb(buf, L'\0', ps)
- where buf is an internal buffer.
-3 If s is not a null pointer, the wcrtomb function determines the number of bytes needed
- to represent the multibyte character that corresponds to the wide character given by wc
- (including any shift sequences), and stores the multibyte character representation in the
- array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
- wc is a null wide character, a null byte is stored, preceded by any shift sequence needed
- to restore the initial shift state; the resulting state described is the initial conversion state.
- Returns
-4 The wcrtomb function returns the number of bytes stored in the array object (including
- any shift sequences). When wc is not a valid wide character, an encoding error occurs:
- the function stores the value of the macro EILSEQ in errno and returns
- (size_t)(-1); the conversion state is unspecified.
- 7.28.6.4 Restartable multibyte/wide string conversion functions
-1 These functions differ from the corresponding multibyte string functions of 7.22.8
- (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to
- mbstate_t that points to an object that can completely describe the current conversion
- state of the associated multibyte character sequence. If ps is a null pointer, each function
- uses its own internal mbstate_t object instead, which is initialized at program startup
- to the initial conversion state; the functions are not required to avoid data races in this
- case. The implementation behaves as if no library function calls these functions with a
- null pointer for ps.
-2 Also unlike their corresponding functions, the conversion source parameter, src, has a
- pointer-to-pointer type. When the function is storing the results of conversions (that is,
- when dst is not a null pointer), the pointer object pointed to by this parameter is updated
- to reflect the amount of the source processed by that invocation.
-
-
-
-
-[page 440]
-
- 7.28.6.4.1 The mbsrtowcs function
- Synopsis
-1 #include <wchar.h>
- size_t mbsrtowcs(wchar_t * restrict dst,
- const char ** restrict src,
- size_t len,
- mbstate_t * restrict ps);
- Description
-2 The mbsrtowcs function converts a sequence of multibyte characters that begins in the
- conversion state described by the object pointed to by ps, from the array indirectly
- pointed to by src into a sequence of corresponding wide characters. If dst is not a null
- pointer, the converted characters are stored into the array pointed to by dst. Conversion
- continues up to and including a terminating null character, which is also stored.
- Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
- not form a valid multibyte character, or (if dst is not a null pointer) when len wide
- characters have been stored into the array pointed to by dst.333) Each conversion takes
- place as if by a call to the mbrtowc function.
-3 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
- pointer (if conversion stopped due to reaching a terminating null character) or the address
- just past the last multibyte character converted (if any). If conversion stopped due to
- reaching a terminating null character and if dst is not a null pointer, the resulting state
- described is the initial conversion state.
- Returns
-4 If the input conversion encounters a sequence of bytes that do not form a valid multibyte
- character, an encoding error occurs: the mbsrtowcs function stores the value of the
- macro EILSEQ in errno and returns (size_t)(-1); the conversion state is
- unspecified. Otherwise, it returns the number of multibyte characters successfully
- converted, not including the terminating null character (if any).
-
-
-
-
- 333) Thus, the value of len is ignored if dst is a null pointer.
-
-[page 441]
-
- 7.28.6.4.2 The wcsrtombs function
- Synopsis
-1 #include <wchar.h>
- size_t wcsrtombs(char * restrict dst,
- const wchar_t ** restrict src,
- size_t len,
- mbstate_t * restrict ps);
- Description
-2 The wcsrtombs function converts a sequence of wide characters from the array
- indirectly pointed to by src into a sequence of corresponding multibyte characters that
- begins in the conversion state described by the object pointed to by ps. If dst is not a
- null pointer, the converted characters are then stored into the array pointed to by dst.
- Conversion continues up to and including a terminating null wide character, which is also
- stored. Conversion stops earlier in two cases: when a wide character is reached that does
- not correspond to a valid multibyte character, or (if dst is not a null pointer) when the
- next multibyte character would exceed the limit of len total bytes to be stored into the
- array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb
- function.334)
-3 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
- pointer (if conversion stopped due to reaching a terminating null wide character) or the
- address just past the last wide character converted (if any). If conversion stopped due to
- reaching a terminating null wide character, the resulting state described is the initial
- conversion state.
- Returns
-4 If conversion stops because a wide character is reached that does not correspond to a
- valid multibyte character, an encoding error occurs: the wcsrtombs function stores the
- value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion
- state is unspecified. Otherwise, it returns the number of bytes in the resulting multibyte
- character sequence, not including the terminating null character (if any).
-
-
-
-
- 334) If conversion stops because a terminating null wide character has been reached, the bytes stored
- include those necessary to reach the initial shift state immediately before the null byte.
-
-[page 442]
-
- 7.29 Wide character classification and mapping utilities <wctype.h>
- 7.29.1 Introduction
-1 The header <wctype.h> defines one macro, and declares three data types and many
- functions.335)
-2 The types declared are
- wint_t
- described in 7.28.1;
- wctrans_t
- which is a scalar type that can hold values which represent locale-specific character
- mappings; and
- wctype_t
- which is a scalar type that can hold values which represent locale-specific character
- classifications.
-3 The macro defined is WEOF (described in 7.28.1).
-4 The functions declared are grouped as follows:
- -- Functions that provide wide character classification;
- -- Extensible functions that provide wide character classification;
- -- Functions that provide wide character case mapping;
- -- Extensible functions that provide wide character mapping.
-5 For all functions described in this subclause that accept an argument of type wint_t, the
- value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If
- this argument has any other value, the behavior is undefined.
-6 The behavior of these functions is affected by the LC_CTYPE category of the current
- locale.
-
-
-
-
- 335) See ''future library directions'' (7.30.13).
-
-[page 443]
-
- 7.29.2 Wide character classification utilities
-1 The header <wctype.h> declares several functions useful for classifying wide
- characters.
-2 The term printing wide character refers to a member of a locale-specific set of wide
- characters, each of which occupies at least one printing position on a display device. The
- term control wide character refers to a member of a locale-specific set of wide characters
- that are not printing wide characters.
- 7.29.2.1 Wide character classification functions
-1 The functions in this subclause return nonzero (true) if and only if the value of the
- argument wc conforms to that in the description of the function.
-2 Each of the following functions returns true for each wide character that corresponds (as
- if by a call to the wctob function) to a single-byte character for which the corresponding
- character classification function from 7.4.1 returns true, except that the iswgraph and
- iswpunct functions may differ with respect to wide characters other than L' ' that are
- both printing and white-space wide characters.336)
- Forward references: the wctob function (7.28.6.1.2).
- 7.29.2.1.1 The iswalnum function
- Synopsis
-1 #include <wctype.h>
- int iswalnum(wint_t wc);
- Description
-2 The iswalnum function tests for any wide character for which iswalpha or
- iswdigit is true.
- 7.29.2.1.2 The iswalpha function
- Synopsis
-1 #include <wctype.h>
- int iswalpha(wint_t wc);
- Description
-2 The iswalpha function tests for any wide character for which iswupper or
- iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
-
- 336) For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call
- iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true
- (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc)
- && iswspace(wc) is true, but not both.
-
-[page 444]
-
- wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
- is true.337)
- 7.29.2.1.3 The iswblank function
- Synopsis
-1 #include <wctype.h>
- int iswblank(wint_t wc);
- Description
-2 The iswblank function tests for any wide character that is a standard blank wide
- character or is one of a locale-specific set of wide characters for which iswspace is true
- and that is used to separate words within a line of text. The standard blank wide
- characters are the following: space (L' '), and horizontal tab (L'\t'). In the "C"
- locale, iswblank returns true only for the standard blank characters.
- 7.29.2.1.4 The iswcntrl function
- Synopsis
-1 #include <wctype.h>
- int iswcntrl(wint_t wc);
- Description
-2 The iswcntrl function tests for any control wide character.
- 7.29.2.1.5 The iswdigit function
- Synopsis
-1 #include <wctype.h>
- int iswdigit(wint_t wc);
- Description
-2 The iswdigit function tests for any wide character that corresponds to a decimal-digit
- character (as defined in 5.2.1).
- 7.29.2.1.6 The iswgraph function
- Synopsis
-1 #include <wctype.h>
- int iswgraph(wint_t wc);
-
-
-
-
- 337) The functions iswlower and iswupper test true or false separately for each of these additional
- wide characters; all four combinations are possible.
-
-[page 445]
-
- Description
-2 The iswgraph function tests for any wide character for which iswprint is true and
- iswspace is false.338)
- 7.29.2.1.7 The iswlower function
- Synopsis
-1 #include <wctype.h>
- int iswlower(wint_t wc);
- Description
-2 The iswlower function tests for any wide character that corresponds to a lowercase
- letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
- iswdigit, iswpunct, or iswspace is true.
- 7.29.2.1.8 The iswprint function
- Synopsis
-1 #include <wctype.h>
- int iswprint(wint_t wc);
- Description
-2 The iswprint function tests for any printing wide character.
- 7.29.2.1.9 The iswpunct function
- Synopsis
-1 #include <wctype.h>
- int iswpunct(wint_t wc);
- Description
-2 The iswpunct function tests for any printing wide character that is one of a locale-
- specific set of punctuation wide characters for which neither iswspace nor iswalnum
- is true.338)
- 7.29.2.1.10 The iswspace function
- Synopsis
-1 #include <wctype.h>
- int iswspace(wint_t wc);
-
-
-
- 338) Note that the behavior of the iswgraph and iswpunct functions may differ from their
- corresponding functions in 7.4.1 with respect to printing, white-space, single-byte execution
- characters other than ' '.
-
-[page 446]
-
- Description
-2 The iswspace function tests for any wide character that corresponds to a locale-specific
- set of white-space wide characters for which none of iswalnum, iswgraph, or
- iswpunct is true.
- 7.29.2.1.11 The iswupper function
- Synopsis
-1 #include <wctype.h>
- int iswupper(wint_t wc);
- Description
-2 The iswupper function tests for any wide character that corresponds to an uppercase
- letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
- iswdigit, iswpunct, or iswspace is true.
- 7.29.2.1.12 The iswxdigit function
- Synopsis
-1 #include <wctype.h>
- int iswxdigit(wint_t wc);
- Description
-2 The iswxdigit function tests for any wide character that corresponds to a
- hexadecimal-digit character (as defined in 6.4.4.1).
- 7.29.2.2 Extensible wide character classification functions
-1 The functions wctype and iswctype provide extensible wide character classification
- as well as testing equivalent to that performed by the functions described in the previous
- subclause (7.29.2.1).
- 7.29.2.2.1 The iswctype function
- Synopsis
-1 #include <wctype.h>
- int iswctype(wint_t wc, wctype_t desc);
- Description
-2 The iswctype function determines whether the wide character wc has the property
- described by desc. The current setting of the LC_CTYPE category shall be the same as
- during the call to wctype that returned the value desc.
-3 Each of the following expressions has a truth-value equivalent to the call to the wide
- character classification function (7.29.2.1) in the comment that follows the expression:
-
-
-[page 447]
-
- iswctype(wc, wctype("alnum")) // iswalnum(wc)
- iswctype(wc, wctype("alpha")) // iswalpha(wc)
- iswctype(wc, wctype("blank")) // iswblank(wc)
- iswctype(wc, wctype("cntrl")) // iswcntrl(wc)
- iswctype(wc, wctype("digit")) // iswdigit(wc)
- iswctype(wc, wctype("graph")) // iswgraph(wc)
- iswctype(wc, wctype("lower")) // iswlower(wc)
- iswctype(wc, wctype("print")) // iswprint(wc)
- iswctype(wc, wctype("punct")) // iswpunct(wc)
- iswctype(wc, wctype("space")) // iswspace(wc)
- iswctype(wc, wctype("upper")) // iswupper(wc)
- iswctype(wc, wctype("xdigit")) // iswxdigit(wc)
- Returns
-4 The iswctype function returns nonzero (true) if and only if the value of the wide
- character wc has the property described by desc.
- Forward references: the wctype function (7.29.2.2.2).
- 7.29.2.2.2 The wctype function
- Synopsis
-1 #include <wctype.h>
- wctype_t wctype(const char *property);
- Description
-2 The wctype function constructs a value with type wctype_t that describes a class of
- wide characters identified by the string argument property.
-3 The strings listed in the description of the iswctype function shall be valid in all
- locales as property arguments to the wctype function.
- Returns
-4 If property identifies a valid class of wide characters according to the LC_CTYPE
- category of the current locale, the wctype function returns a nonzero value that is valid
- as the second argument to the iswctype function; otherwise, it returns zero.
-
-
-
-
-[page 448]
-
- 7.29.3 Wide character case mapping utilities
-1 The header <wctype.h> declares several functions useful for mapping wide characters.
- 7.29.3.1 Wide character case mapping functions
- 7.29.3.1.1 The towlower function
- Synopsis
-1 #include <wctype.h>
- wint_t towlower(wint_t wc);
- Description
-2 The towlower function converts an uppercase letter to a corresponding lowercase letter.
- Returns
-3 If the argument is a wide character for which iswupper is true and there are one or
- more corresponding wide characters, as specified by the current locale, for which
- iswlower is true, the towlower function returns one of the corresponding wide
- characters (always the same one for any given locale); otherwise, the argument is
- returned unchanged.
- 7.29.3.1.2 The towupper function
- Synopsis
-1 #include <wctype.h>
- wint_t towupper(wint_t wc);
- Description
-2 The towupper function converts a lowercase letter to a corresponding uppercase letter.
- Returns
-3 If the argument is a wide character for which iswlower is true and there are one or
- more corresponding wide characters, as specified by the current locale, for which
- iswupper is true, the towupper function returns one of the corresponding wide
- characters (always the same one for any given locale); otherwise, the argument is
- returned unchanged.
- 7.29.3.2 Extensible wide character case mapping functions
-1 The functions wctrans and towctrans provide extensible wide character mapping as
- well as case mapping equivalent to that performed by the functions described in the
- previous subclause (7.29.3.1).
-
-
-
-
-[page 449]
-
- 7.29.3.2.1 The towctrans function
- Synopsis
-1 #include <wctype.h>
- wint_t towctrans(wint_t wc, wctrans_t desc);
- Description
-2 The towctrans function maps the wide character wc using the mapping described by
- desc. The current setting of the LC_CTYPE category shall be the same as during the call
- to wctrans that returned the value desc.
-3 Each of the following expressions behaves the same as the call to the wide character case
- mapping function (7.29.3.1) in the comment that follows the expression:
- towctrans(wc, wctrans("tolower")) // towlower(wc)
- towctrans(wc, wctrans("toupper")) // towupper(wc)
- Returns
-4 The towctrans function returns the mapped value of wc using the mapping described
- by desc.
- 7.29.3.2.2 The wctrans function
- Synopsis
-1 #include <wctype.h>
- wctrans_t wctrans(const char *property);
- Description
-2 The wctrans function constructs a value with type wctrans_t that describes a
- mapping between wide characters identified by the string argument property.
-3 The strings listed in the description of the towctrans function shall be valid in all
- locales as property arguments to the wctrans function.
- Returns
-4 If property identifies a valid mapping of wide characters according to the LC_CTYPE
- category of the current locale, the wctrans function returns a nonzero value that is valid
- as the second argument to the towctrans function; otherwise, it returns zero.
-
-
-
-
-[page 450]
-
- 7.30 Future library directions
-1 The following names are grouped under individual headers for convenience. All external
- names described below are reserved no matter what headers are included by the program.
- 7.30.1 Complex arithmetic <complex.h>
-1 The function names
- cerf cexpm1 clog2
- cerfc clog10 clgamma
- cexp2 clog1p ctgamma
- and the same names suffixed with f or l may be added to the declarations in the
- <complex.h> header.
- 7.30.2 Character handling <ctype.h>
-1 Function names that begin with either is or to, and a lowercase letter may be added to
- the declarations in the <ctype.h> header.
- 7.30.3 Errors <errno.h>
-1 Macros that begin with E and a digit or E and an uppercase letter may be added to the
- declarations in the <errno.h> header.
- 7.30.4 Format conversion of integer types <inttypes.h>
-1 Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
- added to the macros defined in the <inttypes.h> header.
- 7.30.5 Localization <locale.h>
-1 Macros that begin with LC_ and an uppercase letter may be added to the definitions in
- the <locale.h> header.
- 7.30.6 Signal handling <signal.h>
-1 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
- letter may be added to the definitions in the <signal.h> header.
- 7.30.7 Boolean type and values <stdbool.h>
-1 The ability to undefine and perhaps then redefine the macros bool, true, and false is
- an obsolescent feature.
- 7.30.8 Integer types <stdint.h>
-1 Typedef names beginning with int or uint and ending with _t may be added to the
- types defined in the <stdint.h> header. Macro names beginning with INT or UINT
- and ending with _MAX, _MIN, or _C may be added to the macros defined in the
- <stdint.h> header.
-
-[page 451]
-
- 7.30.9 Input/output <stdio.h>
-1 Lowercase letters may be added to the conversion specifiers and length modifiers in
- fprintf and fscanf. Other characters may be used in extensions.
-2 The use of ungetc on a binary stream where the file position indicator is zero prior to
- the call is an obsolescent feature.
- 7.30.10 General utilities <stdlib.h>
-1 Function names that begin with str and a lowercase letter may be added to the
- declarations in the <stdlib.h> header.
- 7.30.11 String handling <string.h>
-1 Function names that begin with str, mem, or wcs and a lowercase letter may be added
- to the declarations in the <string.h> header.
- 7.30.12 Extended multibyte and wide character utilities <wchar.h>
-1 Function names that begin with wcs and a lowercase letter may be added to the
- declarations in the <wchar.h> header.
-2 Lowercase letters may be added to the conversion specifiers and length modifiers in
- fwprintf and fwscanf. Other characters may be used in extensions.
- 7.30.13 Wide character classification and mapping utilities
- <wctype.h>
-1 Function names that begin with is or to and a lowercase letter may be added to the
- declarations in the <wctype.h> header.
-
-
-
-
-[page 452]
-
- Annex A
- (informative)
- Language syntax summary
-1 NOTE The notation is described in 6.1.
-
- A.1 Lexical grammar
- A.1.1 Lexical elements
- (6.4) token:
- keyword
- identifier
- constant
- string-literal
- punctuator
- (6.4) preprocessing-token:
- header-name
- identifier
- pp-number
- character-constant
- string-literal
- punctuator
- each non-white-space character that cannot be one of the above
-
-
-
-
-[page 453]
-
-A.1.2 Keywords
-(6.4.1) keyword: one of
- alignof goto union
- auto if unsigned
- break inline void
- case int volatile
- char long while
- const register _Alignas
- continue restrict _Atomic
- default return _Bool
- do short _Complex
- double signed _Generic
- else sizeof _Imaginary
- enum static _Noreturn
- extern struct _Static_assert
- float switch _Thread_local
- for typedef
-A.1.3 Identifiers
-(6.4.2.1) identifier:
- identifier-nondigit
- identifier identifier-nondigit
- identifier digit
-(6.4.2.1) identifier-nondigit:
- nondigit
- universal-character-name
- other implementation-defined characters
-(6.4.2.1) nondigit: one of
- _ a b c d e f g h i j k l m
- n o p q r s t u v w x y z
- A B C D E F G H I J K L M
- N O P Q R S T U V W X Y Z
-(6.4.2.1) digit: one of
- 0 1 2 3 4 5 6 7 8 9
-
-
-
-
-[page 454]
-
-A.1.4 Universal character names
-(6.4.3) universal-character-name:
- \u hex-quad
- \U hex-quad hex-quad
-(6.4.3) hex-quad:
- hexadecimal-digit hexadecimal-digit
- hexadecimal-digit hexadecimal-digit
-A.1.5 Constants
-(6.4.4) constant:
- integer-constant
- floating-constant
- enumeration-constant
- character-constant
-(6.4.4.1) integer-constant:
- decimal-constant integer-suffixopt
- octal-constant integer-suffixopt
- hexadecimal-constant integer-suffixopt
-(6.4.4.1) decimal-constant:
- nonzero-digit
- decimal-constant digit
-(6.4.4.1) octal-constant:
- 0
- octal-constant octal-digit
-(6.4.4.1) hexadecimal-constant:
- hexadecimal-prefix hexadecimal-digit
- hexadecimal-constant hexadecimal-digit
-(6.4.4.1) hexadecimal-prefix: one of
- 0x 0X
-(6.4.4.1) nonzero-digit: one of
- 1 2 3 4 5 6 7 8 9
-(6.4.4.1) octal-digit: one of
- 0 1 2 3 4 5 6 7
-
-
-
-
-[page 455]
-
-(6.4.4.1) hexadecimal-digit: one of
- 0 1 2 3 4 5 6 7 8 9
- a b c d e f
- A B C D E F
-(6.4.4.1) integer-suffix:
- unsigned-suffix long-suffixopt
- unsigned-suffix long-long-suffix
- long-suffix unsigned-suffixopt
- long-long-suffix unsigned-suffixopt
-(6.4.4.1) unsigned-suffix: one of
- u U
-(6.4.4.1) long-suffix: one of
- l L
-(6.4.4.1) long-long-suffix: one of
- ll LL
-(6.4.4.2) floating-constant:
- decimal-floating-constant
- hexadecimal-floating-constant
-(6.4.4.2) decimal-floating-constant:
- fractional-constant exponent-partopt floating-suffixopt
- digit-sequence exponent-part floating-suffixopt
-(6.4.4.2) hexadecimal-floating-constant:
- hexadecimal-prefix hexadecimal-fractional-constant
- binary-exponent-part floating-suffixopt
- hexadecimal-prefix hexadecimal-digit-sequence
- binary-exponent-part floating-suffixopt
-(6.4.4.2) fractional-constant:
- digit-sequenceopt . digit-sequence
- digit-sequence .
-(6.4.4.2) exponent-part:
- e signopt digit-sequence
- E signopt digit-sequence
-(6.4.4.2) sign: one of
- + -
-
-
-
-[page 456]
-
-(6.4.4.2) digit-sequence:
- digit
- digit-sequence digit
-(6.4.4.2) hexadecimal-fractional-constant:
- hexadecimal-digit-sequenceopt .
- hexadecimal-digit-sequence
- hexadecimal-digit-sequence .
-(6.4.4.2) binary-exponent-part:
- p signopt digit-sequence
- P signopt digit-sequence
-(6.4.4.2) hexadecimal-digit-sequence:
- hexadecimal-digit
- hexadecimal-digit-sequence hexadecimal-digit
-(6.4.4.2) floating-suffix: one of
- f l F L
-(6.4.4.3) enumeration-constant:
- identifier
-(6.4.4.4) character-constant:
- ' c-char-sequence '
- L' c-char-sequence '
- u' c-char-sequence '
- U' c-char-sequence '
-(6.4.4.4) c-char-sequence:
- c-char
- c-char-sequence c-char
-(6.4.4.4) c-char:
- any member of the source character set except
- the single-quote ', backslash \, or new-line character
- escape-sequence
-(6.4.4.4) escape-sequence:
- simple-escape-sequence
- octal-escape-sequence
- hexadecimal-escape-sequence
- universal-character-name
-
-
-
-
-[page 457]
-
-(6.4.4.4) simple-escape-sequence: one of
- \' \" \? \\
- \a \b \f \n \r \t \v
-(6.4.4.4) octal-escape-sequence:
- \ octal-digit
- \ octal-digit octal-digit
- \ octal-digit octal-digit octal-digit
-(6.4.4.4) hexadecimal-escape-sequence:
- \x hexadecimal-digit
- hexadecimal-escape-sequence hexadecimal-digit
-A.1.6 String literals
-(6.4.5) string-literal:
- encoding-prefixopt " s-char-sequenceopt "
-(6.4.5) encoding-prefix:
- u8
- u
- U
- L
-(6.4.5) s-char-sequence:
- s-char
- s-char-sequence s-char
-(6.4.5) s-char:
- any member of the source character set except
- the double-quote ", backslash \, or new-line character
- escape-sequence
-A.1.7 Punctuators
-(6.4.6) punctuator: one of
- [ ] ( ) { } . ->
- ++ -- & * + - ~ !
- / % << >> < > <= >= == != ^ | && ||
- ? : ; ...
- = *= /= %= += -= <<= >>= &= ^= |=
- , # ##
- <: :> <% %> %: %:%:
-
-
-
-
-[page 458]
-
-A.1.8 Header names
-(6.4.7) header-name:
- < h-char-sequence >
- " q-char-sequence "
-(6.4.7) h-char-sequence:
- h-char
- h-char-sequence h-char
-(6.4.7) h-char:
- any member of the source character set except
- the new-line character and >
-(6.4.7) q-char-sequence:
- q-char
- q-char-sequence q-char
-(6.4.7) q-char:
- any member of the source character set except
- the new-line character and "
-A.1.9 Preprocessing numbers
-(6.4.8) pp-number:
- digit
- . digit
- pp-number digit
- pp-number identifier-nondigit
- pp-number e sign
- pp-number E sign
- pp-number p sign
- pp-number P sign
- pp-number .
-
-
-
-
-[page 459]
-
-A.2 Phrase structure grammar
-A.2.1 Expressions
-(6.5.1) primary-expression:
- identifier
- constant
- string-literal
- ( expression )
- generic-selection
-(6.5.1.1) generic-selection:
- _Generic ( assignment-expression , generic-assoc-list )
-(6.5.1.1) generic-assoc-list:
- generic-association
- generic-assoc-list , generic-association
-(6.5.1.1) generic-association:
- type-name : assignment-expression
- default : assignment-expression
-(6.5.2) postfix-expression:
- primary-expression
- postfix-expression [ expression ]
- postfix-expression ( argument-expression-listopt )
- postfix-expression . identifier
- postfix-expression -> identifier
- postfix-expression ++
- postfix-expression --
- ( type-name ) { initializer-list }
- ( type-name ) { initializer-list , }
-(6.5.2) argument-expression-list:
- assignment-expression
- argument-expression-list , assignment-expression
-(6.5.3) unary-expression:
- postfix-expression
- ++ unary-expression
- -- unary-expression
- unary-operator cast-expression
- sizeof unary-expression
- sizeof ( type-name )
- alignof ( type-name )
-
-[page 460]
-
-(6.5.3) unary-operator: one of
- & * + - ~ !
-(6.5.4) cast-expression:
- unary-expression
- ( type-name ) cast-expression
-(6.5.5) multiplicative-expression:
- cast-expression
- multiplicative-expression * cast-expression
- multiplicative-expression / cast-expression
- multiplicative-expression % cast-expression
-(6.5.6) additive-expression:
- multiplicative-expression
- additive-expression + multiplicative-expression
- additive-expression - multiplicative-expression
-(6.5.7) shift-expression:
- additive-expression
- shift-expression << additive-expression
- shift-expression >> additive-expression
-(6.5.8) relational-expression:
- shift-expression
- relational-expression < shift-expression
- relational-expression > shift-expression
- relational-expression <= shift-expression
- relational-expression >= shift-expression
-(6.5.9) equality-expression:
- relational-expression
- equality-expression == relational-expression
- equality-expression != relational-expression
-(6.5.10) AND-expression:
- equality-expression
- AND-expression & equality-expression
-(6.5.11) exclusive-OR-expression:
- AND-expression
- exclusive-OR-expression ^ AND-expression
-
-
-
-
-[page 461]
-
-(6.5.12) inclusive-OR-expression:
- exclusive-OR-expression
- inclusive-OR-expression | exclusive-OR-expression
-(6.5.13) logical-AND-expression:
- inclusive-OR-expression
- logical-AND-expression && inclusive-OR-expression
-(6.5.14) logical-OR-expression:
- logical-AND-expression
- logical-OR-expression || logical-AND-expression
-(6.5.15) conditional-expression:
- logical-OR-expression
- logical-OR-expression ? expression : conditional-expression
-(6.5.16) assignment-expression:
- conditional-expression
- unary-expression assignment-operator assignment-expression
-(6.5.16) assignment-operator: one of
- = *= /= %= += -= <<= >>= &= ^= |=
-(6.5.17) expression:
- assignment-expression
- expression , assignment-expression
-(6.6) constant-expression:
- conditional-expression
-A.2.2 Declarations
-(6.7) declaration:
- declaration-specifiers init-declarator-listopt ;
- static_assert-declaration *
-(6.7) declaration-specifiers:
- storage-class-specifier declaration-specifiersopt
- type-specifier declaration-specifiersopt
- type-qualifier declaration-specifiersopt
- function-specifier declaration-specifiersopt
- alignment-specifier declaration-specifiersopt
-(6.7) init-declarator-list:
- init-declarator
- init-declarator-list , init-declarator
-
-
-[page 462]
-
-(6.7) init-declarator:
- declarator
- declarator = initializer
-(6.7.1) storage-class-specifier:
- typedef
- extern
- static
- _Thread_local
- auto
- register
-(6.7.2) type-specifier:
- void
- char
- short
- int
- long
- float
- double
- signed
- unsigned
- _Bool
- _Complex
- _Atomic ( type-name )
- struct-or-union-specifier
- enum-specifier
- typedef-name
-(6.7.2.1) struct-or-union-specifier:
- struct-or-union identifieropt { struct-declaration-list }
- struct-or-union identifier
-(6.7.2.1) struct-or-union:
- struct
- union
-(6.7.2.1) struct-declaration-list:
- struct-declaration
- struct-declaration-list struct-declaration
-(6.7.2.1) struct-declaration:
- specifier-qualifier-list struct-declarator-listopt ;
- static_assert-declaration
-
-[page 463]
-
-(6.7.2.1) specifier-qualifier-list:
- type-specifier specifier-qualifier-listopt
- type-qualifier specifier-qualifier-listopt
-(6.7.2.1) struct-declarator-list:
- struct-declarator
- struct-declarator-list , struct-declarator
-(6.7.2.1) struct-declarator:
- declarator
- declaratoropt : constant-expression
-(6.7.2.2) enum-specifier:
- enum identifieropt { enumerator-list }
- enum identifieropt { enumerator-list , }
- enum identifier
-(6.7.2.2) enumerator-list:
- enumerator
- enumerator-list , enumerator
-(6.7.2.2) enumerator:
- enumeration-constant
- enumeration-constant = constant-expression
-(6.7.3) type-qualifier:
- const
- restrict
- volatile
- _Atomic
-(6.7.4) function-specifier:
- inline
- _Noreturn
-(6.7.5) alignment-specifier:
- _Alignas ( type-name )
- _Alignas ( constant-expression )
-(6.7.6) declarator:
- pointeropt direct-declarator
-
-
-
-
-[page 464]
-
-(6.7.6) direct-declarator:
- identifier
- ( declarator )
- direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
- direct-declarator [ static type-qualifier-listopt assignment-expression ]
- direct-declarator [ type-qualifier-list static assignment-expression ]
- direct-declarator [ type-qualifier-listopt * ]
- direct-declarator ( parameter-type-list )
- direct-declarator ( identifier-listopt )
-(6.7.6) pointer:
- * type-qualifier-listopt
- * type-qualifier-listopt pointer
-(6.7.6) type-qualifier-list:
- type-qualifier
- type-qualifier-list type-qualifier
-(6.7.6) parameter-type-list:
- parameter-list
- parameter-list , ...
-(6.7.6) parameter-list:
- parameter-declaration
- parameter-list , parameter-declaration
-(6.7.6) parameter-declaration:
- declaration-specifiers declarator
- declaration-specifiers abstract-declaratoropt
-(6.7.6) identifier-list:
- identifier
- identifier-list , identifier
-(6.7.7) type-name:
- specifier-qualifier-list abstract-declaratoropt
-(6.7.7) abstract-declarator:
- pointer
- pointeropt direct-abstract-declarator
-
-
-
-
-[page 465]
-
-(6.7.7) direct-abstract-declarator:
- ( abstract-declarator )
- direct-abstract-declaratoropt [ type-qualifier-listopt
- assignment-expressionopt ]
- direct-abstract-declaratoropt [ static type-qualifier-listopt
- assignment-expression ]
- direct-abstract-declaratoropt [ type-qualifier-list static
- assignment-expression ]
- direct-abstract-declaratoropt [ * ]
- direct-abstract-declaratoropt ( parameter-type-listopt )
-(6.7.8) typedef-name:
- identifier
-(6.7.9) initializer:
- assignment-expression
- { initializer-list }
- { initializer-list , }
-(6.7.9) initializer-list:
- designationopt initializer
- initializer-list , designationopt initializer
-(6.7.9) designation:
- designator-list =
-(6.7.9) designator-list:
- designator
- designator-list designator
-(6.7.9) designator:
- [ constant-expression ]
- . identifier
-(6.7.10) static_assert-declaration:
- _Static_assert ( constant-expression , string-literal ) ;
-
-
-
-
-[page 466]
-
-A.2.3 Statements
-(6.8) statement:
- labeled-statement
- compound-statement
- expression-statement
- selection-statement
- iteration-statement
- jump-statement
-(6.8.1) labeled-statement:
- identifier : statement
- case constant-expression : statement
- default : statement
-(6.8.2) compound-statement:
- { block-item-listopt }
-(6.8.2) block-item-list:
- block-item
- block-item-list block-item
-(6.8.2) block-item:
- declaration
- statement
-(6.8.3) expression-statement:
- expressionopt ;
-(6.8.4) selection-statement:
- if ( expression ) statement
- if ( expression ) statement else statement
- switch ( expression ) statement
-(6.8.5) iteration-statement:
- while ( expression ) statement
- do statement while ( expression ) ;
- for ( expressionopt ; expressionopt ; expressionopt ) statement
- for ( declaration expressionopt ; expressionopt ) statement
-(6.8.6) jump-statement:
- goto identifier ;
- continue ;
- break ;
- return expressionopt ;
-
-[page 467]
-
-A.2.4 External definitions
-(6.9) translation-unit:
- external-declaration
- translation-unit external-declaration
-(6.9) external-declaration:
- function-definition
- declaration
-(6.9.1) function-definition:
- declaration-specifiers declarator declaration-listopt compound-statement
-(6.9.1) declaration-list:
- declaration
- declaration-list declaration
-A.3 Preprocessing directives
-(6.10) preprocessing-file:
- groupopt
-(6.10) group:
- group-part
- group group-part
-(6.10) group-part:
- if-section
- control-line
- text-line
- # non-directive
-(6.10) if-section:
- if-group elif-groupsopt else-groupopt endif-line
-(6.10) if-group:
- # if constant-expression new-line groupopt
- # ifdef identifier new-line groupopt
- # ifndef identifier new-line groupopt
-(6.10) elif-groups:
- elif-group
- elif-groups elif-group
-(6.10) elif-group:
- # elif constant-expression new-line groupopt
-
-
-[page 468]
-
-(6.10) else-group:
- # else new-line groupopt
-(6.10) endif-line:
- # endif new-line
-(6.10) control-line:
- # include pp-tokens new-line
- # define identifier replacement-list new-line
- # define identifier lparen identifier-listopt )
- replacement-list new-line
- # define identifier lparen ... ) replacement-list new-line
- # define identifier lparen identifier-list , ... )
- replacement-list new-line
- # undef identifier new-line
- # line pp-tokens new-line
- # error pp-tokensopt new-line
- # pragma pp-tokensopt new-line
- # new-line
-(6.10) text-line:
- pp-tokensopt new-line
-(6.10) non-directive:
- pp-tokens new-line
-(6.10) lparen:
- a ( character not immediately preceded by white-space
-(6.10) replacement-list:
- pp-tokensopt
-(6.10) pp-tokens:
- preprocessing-token
- pp-tokens preprocessing-token
-(6.10) new-line:
- the new-line character
-
-
-
-
-[page 469]
-
- Annex B
- (informative)
- Library summary
-B.1 Diagnostics <assert.h>
- NDEBUG
- static_assert
- void assert(scalar expression);
-B.2 Complex <complex.h>
- __STDC_NO_COMPLEX__ imaginary
- complex _Imaginary_I
- _Complex_I I
- #pragma STDC CX_LIMITED_RANGE on-off-switch
- double complex cacos(double complex z);
- float complex cacosf(float complex z);
- long double complex cacosl(long double complex z);
- double complex casin(double complex z);
- float complex casinf(float complex z);
- long double complex casinl(long double complex z);
- double complex catan(double complex z);
- float complex catanf(float complex z);
- long double complex catanl(long double complex z);
- double complex ccos(double complex z);
- float complex ccosf(float complex z);
- long double complex ccosl(long double complex z);
- double complex csin(double complex z);
- float complex csinf(float complex z);
- long double complex csinl(long double complex z);
- double complex ctan(double complex z);
- float complex ctanf(float complex z);
- long double complex ctanl(long double complex z);
- double complex cacosh(double complex z);
- float complex cacoshf(float complex z);
- long double complex cacoshl(long double complex z);
- double complex casinh(double complex z);
- float complex casinhf(float complex z);
- long double complex casinhl(long double complex z);
-
-[page 470]
-
- double complex catanh(double complex z);
- float complex catanhf(float complex z);
- long double complex catanhl(long double complex z);
- double complex ccosh(double complex z);
- float complex ccoshf(float complex z);
- long double complex ccoshl(long double complex z);
- double complex csinh(double complex z);
- float complex csinhf(float complex z);
- long double complex csinhl(long double complex z);
- double complex ctanh(double complex z);
- float complex ctanhf(float complex z);
- long double complex ctanhl(long double complex z);
- double complex cexp(double complex z);
- float complex cexpf(float complex z);
- long double complex cexpl(long double complex z);
- double complex clog(double complex z);
- float complex clogf(float complex z);
- long double complex clogl(long double complex z);
- double cabs(double complex z);
- float cabsf(float complex z);
- long double cabsl(long double complex z);
- double complex cpow(double complex x, double complex y);
- float complex cpowf(float complex x, float complex y);
- long double complex cpowl(long double complex x,
- long double complex y);
- double complex csqrt(double complex z);
- float complex csqrtf(float complex z);
- long double complex csqrtl(long double complex z);
- double carg(double complex z);
- float cargf(float complex z);
- long double cargl(long double complex z);
- double cimag(double complex z);
- float cimagf(float complex z);
- long double cimagl(long double complex z);
- double complex CMPLX(double x, double y);
- float complex CMPLXF(float x, float y);
- long double complex CMPLXL(long double x, long double y);
- double complex conj(double complex z);
- float complex conjf(float complex z);
- long double complex conjl(long double complex z);
- double complex cproj(double complex z);
-
-[page 471]
-
- float complex cprojf(float complex z);
- long double complex cprojl(long double complex z);
- double creal(double complex z);
- float crealf(float complex z);
- long double creall(long double complex z);
-B.3 Character handling <ctype.h>
- int isalnum(int c);
- int isalpha(int c);
- int isblank(int c);
- int iscntrl(int c);
- int isdigit(int c);
- int isgraph(int c);
- int islower(int c);
- int isprint(int c);
- int ispunct(int c);
- int isspace(int c);
- int isupper(int c);
- int isxdigit(int c);
- int tolower(int c);
- int toupper(int c);
-B.4 Errors <errno.h>
- EDOM EILSEQ ERANGE errno
- __STDC_WANT_LIB_EXT1__
- errno_t
-B.5 Floating-point environment <fenv.h>
- fenv_t FE_OVERFLOW FE_TOWARDZERO
- fexcept_t FE_UNDERFLOW FE_UPWARD
- FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
- FE_INEXACT FE_DOWNWARD
- FE_INVALID FE_TONEAREST
- #pragma STDC FENV_ACCESS on-off-switch
- int feclearexcept(int excepts);
- int fegetexceptflag(fexcept_t *flagp, int excepts);
- int feraiseexcept(int excepts);
- int fesetexceptflag(const fexcept_t *flagp,
- int excepts);
- int fetestexcept(int excepts);
-
-[page 472]
-
- int fegetround(void);
- int fesetround(int round);
- int fegetenv(fenv_t *envp);
- int feholdexcept(fenv_t *envp);
- int fesetenv(const fenv_t *envp);
- int feupdateenv(const fenv_t *envp);
-B.6 Characteristics of floating types <float.h>
- FLT_ROUNDS DBL_DIG FLT_MAX
- FLT_EVAL_METHOD LDBL_DIG DBL_MAX
- FLT_HAS_SUBNORM FLT_MIN_EXP LDBL_MAX
- DBL_HAS_SUBNORM DBL_MIN_EXP FLT_EPSILON
- LDBL_HAS_SUBNORM LDBL_MIN_EXP DBL_EPSILON
- FLT_RADIX FLT_MIN_10_EXP LDBL_EPSILON
- FLT_MANT_DIG DBL_MIN_10_EXP FLT_MIN
- DBL_MANT_DIG LDBL_MIN_10_EXP DBL_MIN
- LDBL_MANT_DIG FLT_MAX_EXP LDBL_MIN
- FLT_DECIMAL_DIG DBL_MAX_EXP FLT_TRUE_MIN
- DBL_DECIMAL_DIG LDBL_MAX_EXP DBL_TRUE_MIN
- LDBL_DECIMAL_DIG FLT_MAX_10_EXP LDBL_TRUE_MIN
- DECIMAL_DIG DBL_MAX_10_EXP
- FLT_DIG LDBL_MAX_10_EXP
-B.7 Format conversion of integer types <inttypes.h>
- imaxdiv_t
- PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
- PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
- PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
- PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
- PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
- PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
- SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
- SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
- SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
- SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
- SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
- intmax_t imaxabs(intmax_t j);
- imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
- intmax_t strtoimax(const char * restrict nptr,
- char ** restrict endptr, int base);
-
-[page 473]
-
- uintmax_t strtoumax(const char * restrict nptr,
- char ** restrict endptr, int base);
- intmax_t wcstoimax(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
- uintmax_t wcstoumax(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
-B.8 Alternative spellings <iso646.h>
- and bitor not_eq xor
- and_eq compl or xor_eq
- bitand not or_eq
-B.9 Sizes of integer types <limits.h>
- CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
- SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
- SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
- UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
- CHAR_MIN USHRT_MAX LONG_MAX
-B.10 Localization <locale.h>
- struct lconv LC_ALL LC_CTYPE LC_NUMERIC
- NULL LC_COLLATE LC_MONETARY LC_TIME
- char *setlocale(int category, const char *locale);
- struct lconv *localeconv(void);
-B.11 Mathematics <math.h>
- float_t FP_INFINITE FP_FAST_FMAL
- double_t FP_NAN FP_ILOGB0
- HUGE_VAL FP_NORMAL FP_ILOGBNAN
- HUGE_VALF FP_SUBNORMAL MATH_ERRNO
- HUGE_VALL FP_ZERO MATH_ERREXCEPT
- INFINITY FP_FAST_FMA math_errhandling
- NAN FP_FAST_FMAF
- #pragma STDC FP_CONTRACT on-off-switch
- int fpclassify(real-floating x);
- int isfinite(real-floating x);
- int isinf(real-floating x);
- int isnan(real-floating x);
- int isnormal(real-floating x);
- int signbit(real-floating x);
-[page 474]
-
- double acos(double x);
- float acosf(float x);
- long double acosl(long double x);
- double asin(double x);
- float asinf(float x);
- long double asinl(long double x);
- double atan(double x);
- float atanf(float x);
- long double atanl(long double x);
- double atan2(double y, double x);
- float atan2f(float y, float x);
- long double atan2l(long double y, long double x);
- double cos(double x);
- float cosf(float x);
- long double cosl(long double x);
- double sin(double x);
- float sinf(float x);
- long double sinl(long double x);
- double tan(double x);
- float tanf(float x);
- long double tanl(long double x);
- double acosh(double x);
- float acoshf(float x);
- long double acoshl(long double x);
- double asinh(double x);
- float asinhf(float x);
- long double asinhl(long double x);
- double atanh(double x);
- float atanhf(float x);
- long double atanhl(long double x);
- double cosh(double x);
- float coshf(float x);
- long double coshl(long double x);
- double sinh(double x);
- float sinhf(float x);
- long double sinhl(long double x);
- double tanh(double x);
- float tanhf(float x);
- long double tanhl(long double x);
- double exp(double x);
- float expf(float x);
-
-[page 475]
-
- long double expl(long double x);
- double exp2(double x);
- float exp2f(float x);
- long double exp2l(long double x);
- double expm1(double x);
- float expm1f(float x);
- long double expm1l(long double x);
- double frexp(double value, int *exp);
- float frexpf(float value, int *exp);
- long double frexpl(long double value, int *exp);
- int ilogb(double x);
- int ilogbf(float x);
- int ilogbl(long double x);
- double ldexp(double x, int exp);
- float ldexpf(float x, int exp);
- long double ldexpl(long double x, int exp);
- double log(double x);
- float logf(float x);
- long double logl(long double x);
- double log10(double x);
- float log10f(float x);
- long double log10l(long double x);
- double log1p(double x);
- float log1pf(float x);
- long double log1pl(long double x);
- double log2(double x);
- float log2f(float x);
- long double log2l(long double x);
- double logb(double x);
- float logbf(float x);
- long double logbl(long double x);
- double modf(double value, double *iptr);
- float modff(float value, float *iptr);
- long double modfl(long double value, long double *iptr);
- double scalbn(double x, int n);
- float scalbnf(float x, int n);
- long double scalbnl(long double x, int n);
- double scalbln(double x, long int n);
- float scalblnf(float x, long int n);
- long double scalblnl(long double x, long int n);
- double cbrt(double x);
-
-[page 476]
-
- float cbrtf(float x);
- long double cbrtl(long double x);
- double fabs(double x);
- float fabsf(float x);
- long double fabsl(long double x);
- double hypot(double x, double y);
- float hypotf(float x, float y);
- long double hypotl(long double x, long double y);
- double pow(double x, double y);
- float powf(float x, float y);
- long double powl(long double x, long double y);
- double sqrt(double x);
- float sqrtf(float x);
- long double sqrtl(long double x);
- double erf(double x);
- float erff(float x);
- long double erfl(long double x);
- double erfc(double x);
- float erfcf(float x);
- long double erfcl(long double x);
- double lgamma(double x);
- float lgammaf(float x);
- long double lgammal(long double x);
- double tgamma(double x);
- float tgammaf(float x);
- long double tgammal(long double x);
- double ceil(double x);
- float ceilf(float x);
- long double ceill(long double x);
- double floor(double x);
- float floorf(float x);
- long double floorl(long double x);
- double nearbyint(double x);
- float nearbyintf(float x);
- long double nearbyintl(long double x);
- double rint(double x);
- float rintf(float x);
- long double rintl(long double x);
- long int lrint(double x);
- long int lrintf(float x);
- long int lrintl(long double x);
-
-[page 477]
-
- long long int llrint(double x);
- long long int llrintf(float x);
- long long int llrintl(long double x);
- double round(double x);
- float roundf(float x);
- long double roundl(long double x);
- long int lround(double x);
- long int lroundf(float x);
- long int lroundl(long double x);
- long long int llround(double x);
- long long int llroundf(float x);
- long long int llroundl(long double x);
- double trunc(double x);
- float truncf(float x);
- long double truncl(long double x);
- double fmod(double x, double y);
- float fmodf(float x, float y);
- long double fmodl(long double x, long double y);
- double remainder(double x, double y);
- float remainderf(float x, float y);
- long double remainderl(long double x, long double y);
- double remquo(double x, double y, int *quo);
- float remquof(float x, float y, int *quo);
- long double remquol(long double x, long double y,
- int *quo);
- double copysign(double x, double y);
- float copysignf(float x, float y);
- long double copysignl(long double x, long double y);
- double nan(const char *tagp);
- float nanf(const char *tagp);
- long double nanl(const char *tagp);
- double nextafter(double x, double y);
- float nextafterf(float x, float y);
- long double nextafterl(long double x, long double y);
- double nexttoward(double x, long double y);
- float nexttowardf(float x, long double y);
- long double nexttowardl(long double x, long double y);
- double fdim(double x, double y);
- float fdimf(float x, float y);
- long double fdiml(long double x, long double y);
- double fmax(double x, double y);
-
-[page 478]
-
- float fmaxf(float x, float y);
- long double fmaxl(long double x, long double y);
- double fmin(double x, double y);
- float fminf(float x, float y);
- long double fminl(long double x, long double y);
- double fma(double x, double y, double z);
- float fmaf(float x, float y, float z);
- long double fmal(long double x, long double y,
- long double z);
- int isgreater(real-floating x, real-floating y);
- int isgreaterequal(real-floating x, real-floating y);
- int isless(real-floating x, real-floating y);
- int islessequal(real-floating x, real-floating y);
- int islessgreater(real-floating x, real-floating y);
- int isunordered(real-floating x, real-floating y);
-B.12 Nonlocal jumps <setjmp.h>
- jmp_buf
- int setjmp(jmp_buf env);
- _Noreturn void longjmp(jmp_buf env, int val);
-B.13 Signal handling <signal.h>
- sig_atomic_t SIG_IGN SIGILL SIGTERM
- SIG_DFL SIGABRT SIGINT
- SIG_ERR SIGFPE SIGSEGV
- void (*signal(int sig, void (*func)(int)))(int);
- int raise(int sig);
-
-
-
-
-[page 479]
-
-B.14 Alignment <stdalign.h>
- alignas
- __alignas_is_defined
-B.15 Variable arguments <stdarg.h>
- va_list
- type va_arg(va_list ap, type);
- void va_copy(va_list dest, va_list src);
- void va_end(va_list ap);
- void va_start(va_list ap, parmN);
-B.16 Atomics <stdatomic.h>
- ATOMIC_CHAR_LOCK_FREE atomic_uint
- ATOMIC_CHAR16_T_LOCK_FREE atomic_long
- ATOMIC_CHAR32_T_LOCK_FREE atomic_ulong
- ATOMIC_WCHAR_T_LOCK_FREE atomic_llong
- ATOMIC_SHORT_LOCK_FREE atomic_ullong
- ATOMIC_INT_LOCK_FREE atomic_char16_t
- ATOMIC_LONG_LOCK_FREE atomic_char32_t
- ATOMIC_LLONG_LOCK_FREE atomic_wchar_t
- ATOMIC_ADDRESS_LOCK_FREE atomic_int_least8_t
- ATOMIC_FLAG_INIT atomic_uint_least8_t
- memory_order atomic_int_least16_t
- atomic_flag atomic_uint_least16_t
- atomic_bool atomic_int_least32_t
- atomic_address atomic_uint_least32_t
- memory_order_relaxed atomic_int_least64_t
- memory_order_consume atomic_uint_least64_t
- memory_order_acquire atomic_int_fast8_t
- memory_order_release atomic_uint_fast8_t
- memory_order_acq_rel atomic_int_fast16_t
- memory_order_seq_cst atomic_uint_fast16_t
- atomic_char atomic_int_fast32_t
- atomic_schar atomic_uint_fast32_t
- atomic_uchar atomic_int_fast64_t
- atomic_short atomic_uint_fast64_t
- atomic_ushort atomic_intptr_t
- atomic_int atomic_uintptr_t
-
-
-
-[page 480]
-
- atomic_size_t atomic_intmax_t
- atomic_ptrdiff_t atomic_uintmax_t
- #define ATOMIC_VAR_INIT(C value)
- void atomic_init(volatile A *obj, C value);
- type kill_dependency(type y);
- void atomic_thread_fence(memory_order order);
- void atomic_signal_fence(memory_order order);
- _Bool atomic_is_lock_free(atomic_type const volatile *obj);
- void atomic_store(volatile A *object, C desired);
- void atomic_store_explicit(volatile A *object,
- C desired, memory_order order);
- C atomic_load(volatile A *object);
- C atomic_load_explicit(volatile A *object,
- memory_order order);
- C atomic_exchange(volatile A *object, C desired);
- C atomic_exchange_explicit(volatile A *object,
- C desired, memory_order order);
- _Bool atomic_compare_exchange_strong(volatile A *object,
- C *expected, C desired);
- _Bool atomic_compare_exchange_strong_explicit(
- volatile A *object, C *expected, C desired,
- memory_order success, memory_order failure);
- _Bool atomic_compare_exchange_weak(volatile A *object,
- C *expected, C desired);
- _Bool atomic_compare_exchange_weak_explicit(
- volatile A *object, C *expected, C desired,
- memory_order success, memory_order failure);
- C atomic_fetch_key(volatile A *object, M operand);
- C atomic_fetch_key_explicit(volatile A *object,
- M operand, memory_order order);
- bool atomic_flag_test_and_set(
- volatile atomic_flag *object);
- bool atomic_flag_test_and_set_explicit(
- volatile atomic_flag *object, memory_order order);
- void atomic_flag_clear(volatile atomic_flag *object);
- void atomic_flag_clear_explicit(
- volatile atomic_flag *object, memory_order order);
-
-
-
-
-[page 481]
-
-B.17 Boolean type and values <stdbool.h>
- bool
- true
- false
- __bool_true_false_are_defined
-B.18 Common definitions <stddef.h>
- ptrdiff_t max_align_t NULL
- size_t wchar_t
- offsetof(type, member-designator)
- __STDC_WANT_LIB_EXT1__
- rsize_t
-B.19 Integer types <stdint.h>
- intN_t INT_LEASTN_MIN PTRDIFF_MAX
- uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
- int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
- uint_leastN_t INT_FASTN_MIN SIZE_MAX
- int_fastN_t INT_FASTN_MAX WCHAR_MIN
- uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
- intptr_t INTPTR_MIN WINT_MIN
- uintptr_t INTPTR_MAX WINT_MAX
- intmax_t UINTPTR_MAX INTN_C(value)
- uintmax_t INTMAX_MIN UINTN_C(value)
- INTN_MIN INTMAX_MAX INTMAX_C(value)
- INTN_MAX UINTMAX_MAX UINTMAX_C(value)
- UINTN_MAX PTRDIFF_MIN
- __STDC_WANT_LIB_EXT1__
- RSIZE_MAX
-
-
-
-
-[page 482]
-
-B.20 Input/output <stdio.h>
- size_t _IOLBF FILENAME_MAX TMP_MAX
- FILE _IONBF L_tmpnam stderr
- fpos_t BUFSIZ SEEK_CUR stdin
- NULL EOF SEEK_END stdout
- _IOFBF FOPEN_MAX SEEK_SET
- int remove(const char *filename);
- int rename(const char *old, const char *new);
- FILE *tmpfile(void);
- char *tmpnam(char *s);
- int fclose(FILE *stream);
- int fflush(FILE *stream);
- FILE *fopen(const char * restrict filename,
- const char * restrict mode);
- FILE *freopen(const char * restrict filename,
- const char * restrict mode,
- FILE * restrict stream);
- void setbuf(FILE * restrict stream,
- char * restrict buf);
- int setvbuf(FILE * restrict stream,
- char * restrict buf,
- int mode, size_t size);
- int fprintf(FILE * restrict stream,
- const char * restrict format, ...);
- int fscanf(FILE * restrict stream,
- const char * restrict format, ...);
- int printf(const char * restrict format, ...);
- int scanf(const char * restrict format, ...);
- int snprintf(char * restrict s, size_t n,
- const char * restrict format, ...);
- int sprintf(char * restrict s,
- const char * restrict format, ...);
- int sscanf(const char * restrict s,
- const char * restrict format, ...);
- int vfprintf(FILE * restrict stream,
- const char * restrict format, va_list arg);
- int vfscanf(FILE * restrict stream,
- const char * restrict format, va_list arg);
- int vprintf(const char * restrict format, va_list arg);
- int vscanf(const char * restrict format, va_list arg);
-
-[page 483]
-
- int vsnprintf(char * restrict s, size_t n,
- const char * restrict format, va_list arg);
- int vsprintf(char * restrict s,
- const char * restrict format, va_list arg);
- int vsscanf(const char * restrict s,
- const char * restrict format, va_list arg);
- int fgetc(FILE *stream);
- char *fgets(char * restrict s, int n,
- FILE * restrict stream);
- int fputc(int c, FILE *stream);
- int fputs(const char * restrict s,
- FILE * restrict stream);
- int getc(FILE *stream);
- int getchar(void);
- int putc(int c, FILE *stream);
- int putchar(int c);
- int puts(const char *s);
- int ungetc(int c, FILE *stream);
- size_t fread(void * restrict ptr,
- size_t size, size_t nmemb,
- FILE * restrict stream);
- size_t fwrite(const void * restrict ptr,
- size_t size, size_t nmemb,
- FILE * restrict stream);
- int fgetpos(FILE * restrict stream,
- fpos_t * restrict pos);
- int fseek(FILE *stream, long int offset, int whence);
- int fsetpos(FILE *stream, const fpos_t *pos);
- long int ftell(FILE *stream);
- void rewind(FILE *stream);
- void clearerr(FILE *stream);
- int feof(FILE *stream);
- int ferror(FILE *stream);
- void perror(const char *s);
- __STDC_WANT_LIB_EXT1__
- L_tmpnam_s TMP_MAX_S errno_t rsize_t
- errno_t tmpfile_s(FILE * restrict * restrict streamptr);
- errno_t tmpnam_s(char *s, rsize_t maxsize);
-
-
-
-[page 484]
-
- errno_t fopen_s(FILE * restrict * restrict streamptr,
- const char * restrict filename,
- const char * restrict mode);
- errno_t freopen_s(FILE * restrict * restrict newstreamptr,
- const char * restrict filename,
- const char * restrict mode,
- FILE * restrict stream);
- int fprintf_s(FILE * restrict stream,
- const char * restrict format, ...);
- int fscanf_s(FILE * restrict stream,
- const char * restrict format, ...);
- int printf_s(const char * restrict format, ...);
- int scanf_s(const char * restrict format, ...);
- int snprintf_s(char * restrict s, rsize_t n,
- const char * restrict format, ...);
- int sprintf_s(char * restrict s, rsize_t n,
- const char * restrict format, ...);
- int sscanf_s(const char * restrict s,
- const char * restrict format, ...);
- int vfprintf_s(FILE * restrict stream,
- const char * restrict format,
- va_list arg);
- int vfscanf_s(FILE * restrict stream,
- const char * restrict format,
- va_list arg);
- int vprintf_s(const char * restrict format,
- va_list arg);
- int vscanf_s(const char * restrict format,
- va_list arg);
- int vsnprintf_s(char * restrict s, rsize_t n,
- const char * restrict format,
- va_list arg);
- int vsprintf_s(char * restrict s, rsize_t n,
- const char * restrict format,
- va_list arg);
- int vsscanf_s(const char * restrict s,
- const char * restrict format,
- va_list arg);
- char *gets_s(char *s, rsize_t n);
-
-
-
-[page 485]
-
-B.21 General utilities <stdlib.h>
- size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
- wchar_t lldiv_t EXIT_SUCCESS
- div_t NULL RAND_MAX
- double atof(const char *nptr);
- int atoi(const char *nptr);
- long int atol(const char *nptr);
- long long int atoll(const char *nptr);
- double strtod(const char * restrict nptr,
- char ** restrict endptr);
- float strtof(const char * restrict nptr,
- char ** restrict endptr);
- long double strtold(const char * restrict nptr,
- char ** restrict endptr);
- long int strtol(const char * restrict nptr,
- char ** restrict endptr, int base);
- long long int strtoll(const char * restrict nptr,
- char ** restrict endptr, int base);
- unsigned long int strtoul(
- const char * restrict nptr,
- char ** restrict endptr, int base);
- unsigned long long int strtoull(
- const char * restrict nptr,
- char ** restrict endptr, int base);
- int rand(void);
- void srand(unsigned int seed);
- void *aligned_alloc(size_t alignment, size_t size);
- void *calloc(size_t nmemb, size_t size);
- void free(void *ptr);
- void *malloc(size_t size);
- void *realloc(void *ptr, size_t size);
- _Noreturn void abort(void);
- int atexit(void (*func)(void));
- int at_quick_exit(void (*func)(void));
- _Noreturn void exit(int status);
- _Noreturn void _Exit(int status);
- char *getenv(const char *name);
- _Noreturn void quick_exit(int status);
- int system(const char *string);
-
-
-[page 486]
-
- void *bsearch(const void *key, const void *base,
- size_t nmemb, size_t size,
- int (*compar)(const void *, const void *));
- void qsort(void *base, size_t nmemb, size_t size,
- int (*compar)(const void *, const void *));
- int abs(int j);
- long int labs(long int j);
- long long int llabs(long long int j);
- div_t div(int numer, int denom);
- ldiv_t ldiv(long int numer, long int denom);
- lldiv_t lldiv(long long int numer,
- long long int denom);
- int mblen(const char *s, size_t n);
- int mbtowc(wchar_t * restrict pwc,
- const char * restrict s, size_t n);
- int wctomb(char *s, wchar_t wchar);
- size_t mbstowcs(wchar_t * restrict pwcs,
- const char * restrict s, size_t n);
- size_t wcstombs(char * restrict s,
- const wchar_t * restrict pwcs, size_t n);
- __STDC_WANT_LIB_EXT1__
- errno_t
- rsize_t
- constraint_handler_t
- constraint_handler_t set_constraint_handler_s(
- constraint_handler_t handler);
- void abort_handler_s(
- const char * restrict msg,
- void * restrict ptr,
- errno_t error);
- void ignore_handler_s(
- const char * restrict msg,
- void * restrict ptr,
- errno_t error);
- errno_t getenv_s(size_t * restrict len,
- char * restrict value, rsize_t maxsize,
- const char * restrict name);
-
-
-
-
-[page 487]
-
- void *bsearch_s(const void *key, const void *base,
- rsize_t nmemb, rsize_t size,
- int (*compar)(const void *k, const void *y,
- void *context),
- void *context);
- errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
- int (*compar)(const void *x, const void *y,
- void *context),
- void *context);
- errno_t wctomb_s(int * restrict status,
- char * restrict s,
- rsize_t smax,
- wchar_t wc);
- errno_t mbstowcs_s(size_t * restrict retval,
- wchar_t * restrict dst, rsize_t dstmax,
- const char * restrict src, rsize_t len);
- errno_t wcstombs_s(size_t * restrict retval,
- char * restrict dst, rsize_t dstmax,
- const wchar_t * restrict src, rsize_t len);
-B.22 String handling <string.h>
- size_t
- NULL
- void *memcpy(void * restrict s1,
- const void * restrict s2, size_t n);
- void *memmove(void *s1, const void *s2, size_t n);
- char *strcpy(char * restrict s1,
- const char * restrict s2);
- char *strncpy(char * restrict s1,
- const char * restrict s2, size_t n);
- char *strcat(char * restrict s1,
- const char * restrict s2);
- char *strncat(char * restrict s1,
- const char * restrict s2, size_t n);
- int memcmp(const void *s1, const void *s2, size_t n);
- int strcmp(const char *s1, const char *s2);
- int strcoll(const char *s1, const char *s2);
- int strncmp(const char *s1, const char *s2, size_t n);
- size_t strxfrm(char * restrict s1,
- const char * restrict s2, size_t n);
- void *memchr(const void *s, int c, size_t n);
-[page 488]
-
- char *strchr(const char *s, int c);
- size_t strcspn(const char *s1, const char *s2);
- char *strpbrk(const char *s1, const char *s2);
- char *strrchr(const char *s, int c);
- size_t strspn(const char *s1, const char *s2);
- char *strstr(const char *s1, const char *s2);
- char *strtok(char * restrict s1,
- const char * restrict s2);
- void *memset(void *s, int c, size_t n);
- char *strerror(int errnum);
- size_t strlen(const char *s);
- __STDC_WANT_LIB_EXT1__
- errno_t
- rsize_t
- errno_t memcpy_s(void * restrict s1, rsize_t s1max,
- const void * restrict s2, rsize_t n);
- errno_t memmove_s(void *s1, rsize_t s1max,
- const void *s2, rsize_t n);
- errno_t strcpy_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2);
- errno_t strncpy_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2,
- rsize_t n);
- errno_t strcat_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2);
- errno_t strncat_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2,
- rsize_t n);
- char *strtok_s(char * restrict s1,
- rsize_t * restrict s1max,
- const char * restrict s2,
- char ** restrict ptr);
- errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
- errno_t strerror_s(char *s, rsize_t maxsize,
- errno_t errnum);
- size_t strerrorlen_s(errno_t errnum);
-
-[page 489]
-
- size_t strnlen_s(const char *s, size_t maxsize);
-B.23 Type-generic math <tgmath.h>
- acos sqrt fmod nextafter
- asin fabs frexp nexttoward
- atan atan2 hypot remainder
- acosh cbrt ilogb remquo
- asinh ceil ldexp rint
- atanh copysign lgamma round
- cos erf llrint scalbn
- sin erfc llround scalbln
- tan exp2 log10 tgamma
- cosh expm1 log1p trunc
- sinh fdim log2 carg
- tanh floor logb cimag
- exp fma lrint conj
- log fmax lround cproj
- pow fmin nearbyint creal
-B.24 Threads <threads.h>
- ONCE_FLAG_INIT mtx_plain
- TSS_DTOR_ITERATIONS mtx_recursive
- cnd_t mtx_timed
- thrd_t mtx_try
- tss_t thrd_timeout
- mtx_t thrd_success
- tss_dtor_t thrd_busy
- thrd_start_t thrd_error
- once_flag thrd_nomem
- xtime
- void call_once(once_flag *flag, void (*func)(void));
- int cnd_broadcast(cnd_t *cond);
- void cnd_destroy(cnd_t *cond);
- int cnd_init(cnd_t *cond);
- int cnd_signal(cnd_t *cond);
- int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
- const xtime *xt);
- int cnd_wait(cnd_t *cond, mtx_t *mtx);
- void mtx_destroy(mtx_t *mtx);
- int mtx_init(mtx_t *mtx, int type);
- int mtx_lock(mtx_t *mtx);
-[page 490]
-
- int mtx_timedlock(mtx_t *mtx, const xtime *xt);
- int mtx_trylock(mtx_t *mtx);
- int mtx_unlock(mtx_t *mtx);
- int thrd_create(thrd_t *thr, thrd_start_t func,
- void *arg);
- thrd_t thrd_current(void);
- int thrd_detach(thrd_t thr);
- int thrd_equal(thrd_t thr0, thrd_t thr1);
- void thrd_exit(int res);
- int thrd_join(thrd_t thr, int *res);
- void thrd_sleep(const xtime *xt);
- void thrd_yield(void);
- int tss_create(tss_t *key, tss_dtor_t dtor);
- void tss_delete(tss_t key);
- void *tss_get(tss_t key);
- int tss_set(tss_t key, void *val);
- int xtime_get(xtime *xt, int base);
-B.25 Date and time <time.h>
- NULL size_t time_t
- CLOCKS_PER_SEC clock_t struct tm
- clock_t clock(void);
- double difftime(time_t time1, time_t time0);
- time_t mktime(struct tm *timeptr);
- time_t time(time_t *timer);
- char *asctime(const struct tm *timeptr);
- char *ctime(const time_t *timer);
- struct tm *gmtime(const time_t *timer);
- struct tm *localtime(const time_t *timer);
- size_t strftime(char * restrict s,
- size_t maxsize,
- const char * restrict format,
- const struct tm * restrict timeptr);
- __STDC_WANT_LIB_EXT1__
- errno_t
- rsize_t
- errno_t asctime_s(char *s, rsize_t maxsize,
- const struct tm *timeptr);
-
-
-
-[page 491]
-
- errno_t ctime_s(char *s, rsize_t maxsize,
- const time_t *timer);
- struct tm *gmtime_s(const time_t * restrict timer,
- struct tm * restrict result);
- struct tm *localtime_s(const time_t * restrict timer,
- struct tm * restrict result);
-B.26 Unicode utilities <uchar.h>
- mbstate_t size_t char16_t char32_t
- size_t mbrtoc16(char16_t * restrict pc16,
- const char * restrict s, size_t n,
- mbstate_t * restrict ps);
- size_t c16rtomb(char * restrict s, char16_t c16,
- mbstate_t * restrict ps);
- size_t mbrtoc32(char32_t * restrict pc32,
- const char * restrict s, size_t n,
- mbstate_t * restrict ps);
- size_t c32rtomb(char * restrict s, char32_t c32,
- mbstate_t * restrict ps);
-B.27 Extended multibyte/wide character utilities <wchar.h>
- wchar_t wint_t WCHAR_MAX
- size_t struct tm WCHAR_MIN
- mbstate_t NULL WEOF
- int fwprintf(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- int fwscanf(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- int swprintf(wchar_t * restrict s, size_t n,
- const wchar_t * restrict format, ...);
- int swscanf(const wchar_t * restrict s,
- const wchar_t * restrict format, ...);
- int vfwprintf(FILE * restrict stream,
- const wchar_t * restrict format, va_list arg);
- int vfwscanf(FILE * restrict stream,
- const wchar_t * restrict format, va_list arg);
- int vswprintf(wchar_t * restrict s, size_t n,
- const wchar_t * restrict format, va_list arg);
-
-
-
-[page 492]
-
- int vswscanf(const wchar_t * restrict s,
- const wchar_t * restrict format, va_list arg);
- int vwprintf(const wchar_t * restrict format,
- va_list arg);
- int vwscanf(const wchar_t * restrict format,
- va_list arg);
- int wprintf(const wchar_t * restrict format, ...);
- int wscanf(const wchar_t * restrict format, ...);
- wint_t fgetwc(FILE *stream);
- wchar_t *fgetws(wchar_t * restrict s, int n,
- FILE * restrict stream);
- wint_t fputwc(wchar_t c, FILE *stream);
- int fputws(const wchar_t * restrict s,
- FILE * restrict stream);
- int fwide(FILE *stream, int mode);
- wint_t getwc(FILE *stream);
- wint_t getwchar(void);
- wint_t putwc(wchar_t c, FILE *stream);
- wint_t putwchar(wchar_t c);
- wint_t ungetwc(wint_t c, FILE *stream);
- double wcstod(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr);
- float wcstof(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr);
- long double wcstold(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr);
- long int wcstol(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
- long long int wcstoll(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
- unsigned long int wcstoul(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
- unsigned long long int wcstoull(
- const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
- wchar_t *wcscpy(wchar_t * restrict s1,
- const wchar_t * restrict s2);
- wchar_t *wcsncpy(wchar_t * restrict s1,
- const wchar_t * restrict s2, size_t n);
-
-
-
-[page 493]
-
- wchar_t *wmemcpy(wchar_t * restrict s1,
- const wchar_t * restrict s2, size_t n);
- wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
- size_t n);
- wchar_t *wcscat(wchar_t * restrict s1,
- const wchar_t * restrict s2);
- wchar_t *wcsncat(wchar_t * restrict s1,
- const wchar_t * restrict s2, size_t n);
- int wcscmp(const wchar_t *s1, const wchar_t *s2);
- int wcscoll(const wchar_t *s1, const wchar_t *s2);
- int wcsncmp(const wchar_t *s1, const wchar_t *s2,
- size_t n);
- size_t wcsxfrm(wchar_t * restrict s1,
- const wchar_t * restrict s2, size_t n);
- int wmemcmp(const wchar_t *s1, const wchar_t *s2,
- size_t n);
- wchar_t *wcschr(const wchar_t *s, wchar_t c);
- size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
- wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
- wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
- size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
- wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
- wchar_t *wcstok(wchar_t * restrict s1,
- const wchar_t * restrict s2,
- wchar_t ** restrict ptr);
- wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
- size_t wcslen(const wchar_t *s);
- wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
- size_t wcsftime(wchar_t * restrict s, size_t maxsize,
- const wchar_t * restrict format,
- const struct tm * restrict timeptr);
- wint_t btowc(int c);
- int wctob(wint_t c);
- int mbsinit(const mbstate_t *ps);
- size_t mbrlen(const char * restrict s, size_t n,
- mbstate_t * restrict ps);
- size_t mbrtowc(wchar_t * restrict pwc,
- const char * restrict s, size_t n,
- mbstate_t * restrict ps);
-
-
-
-[page 494]
-
- size_t wcrtomb(char * restrict s, wchar_t wc,
- mbstate_t * restrict ps);
- size_t mbsrtowcs(wchar_t * restrict dst,
- const char ** restrict src, size_t len,
- mbstate_t * restrict ps);
- size_t wcsrtombs(char * restrict dst,
- const wchar_t ** restrict src, size_t len,
- mbstate_t * restrict ps);
- __STDC_WANT_LIB_EXT1__
- errno_t
- rsize_t
- int fwprintf_s(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- int fwscanf_s(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- int snwprintf_s(wchar_t * restrict s,
- rsize_t n,
- const wchar_t * restrict format, ...);
- int swprintf_s(wchar_t * restrict s, rsize_t n,
- const wchar_t * restrict format, ...);
- int swscanf_s(const wchar_t * restrict s,
- const wchar_t * restrict format, ...);
- int vfwprintf_s(FILE * restrict stream,
- const wchar_t * restrict format,
- va_list arg);
- int vfwscanf_s(FILE * restrict stream,
- const wchar_t * restrict format, va_list arg);
- int vsnwprintf_s(wchar_t * restrict s,
- rsize_t n,
- const wchar_t * restrict format,
- va_list arg);
- int vswprintf_s(wchar_t * restrict s,
- rsize_t n,
- const wchar_t * restrict format,
- va_list arg);
- int vswscanf_s(const wchar_t * restrict s,
- const wchar_t * restrict format,
- va_list arg);
-
-
-
-[page 495]
-
- int vwprintf_s(const wchar_t * restrict format,
- va_list arg);
- int vwscanf_s(const wchar_t * restrict format,
- va_list arg);
- int wprintf_s(const wchar_t * restrict format, ...);
- int wscanf_s(const wchar_t * restrict format, ...);
- errno_t wcscpy_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2);
- errno_t wcsncpy_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2,
- rsize_t n);
- errno_t wmemcpy_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2,
- rsize_t n);
- errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
- const wchar_t *s2, rsize_t n);
- errno_t wcscat_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2);
- errno_t wcsncat_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2,
- rsize_t n);
- wchar_t *wcstok_s(wchar_t * restrict s1,
- rsize_t * restrict s1max,
- const wchar_t * restrict s2,
- wchar_t ** restrict ptr);
- size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
- errno_t wcrtomb_s(size_t * restrict retval,
- char * restrict s, rsize_t smax,
- wchar_t wc, mbstate_t * restrict ps);
- errno_t mbsrtowcs_s(size_t * restrict retval,
- wchar_t * restrict dst, rsize_t dstmax,
- const char ** restrict src, rsize_t len,
- mbstate_t * restrict ps);
-
-
-
-
-[page 496]
-
- errno_t wcsrtombs_s(size_t * restrict retval,
- char * restrict dst, rsize_t dstmax,
- const wchar_t ** restrict src, rsize_t len,
- mbstate_t * restrict ps);
-B.28 Wide character classification and mapping utilities <wctype.h>
- wint_t wctrans_t wctype_t WEOF
- int iswalnum(wint_t wc);
- int iswalpha(wint_t wc);
- int iswblank(wint_t wc);
- int iswcntrl(wint_t wc);
- int iswdigit(wint_t wc);
- int iswgraph(wint_t wc);
- int iswlower(wint_t wc);
- int iswprint(wint_t wc);
- int iswpunct(wint_t wc);
- int iswspace(wint_t wc);
- int iswupper(wint_t wc);
- int iswxdigit(wint_t wc);
- int iswctype(wint_t wc, wctype_t desc);
- wctype_t wctype(const char *property);
- wint_t towlower(wint_t wc);
- wint_t towupper(wint_t wc);
- wint_t towctrans(wint_t wc, wctrans_t desc);
- wctrans_t wctrans(const char *property);
-
-
-
-
-[page 497]
-
- Annex C
- (informative)
- Sequence points
-1 The following are the sequence points described in 5.1.2.3:
- -- Between the evaluations of the function designator and actual arguments in a function
- call and the actual call. (6.5.2.2).
- -- Between the evaluations of the first and second operands of the following operators:
- logical AND && (6.5.13); logical OR || (6.5.14); comma , (6.5.17).
- -- Between the evaluations of the first operand of the conditional ? : operator and
- whichever of the second and third operands is evaluated (6.5.15).
- -- The end of a full declarator: declarators (6.7.6);
- -- Between the evaluation of a full expression and the next full expression to be
- evaluated. The following are full expressions: an initializer that is not part of a
- compound literal (6.7.9); the expression in an expression statement (6.8.3); the
- controlling expression of a selection statement (if or switch) (6.8.4); the
- controlling expression of a while or do statement (6.8.5); each of the (optional)
- expressions of a for statement (6.8.5.3); the (optional) expression in a return
- statement (6.8.6.4).
- -- Immediately before a library function returns (7.1.4).
- -- After the actions associated with each formatted input/output function conversion
- specifier (7.21.6, 7.28.2).
- -- Immediately before and immediately after each call to a comparison function, and
- also between any call to a comparison function and any movement of the objects
- passed as arguments to that call (7.22.5).
-
-
-
-
-[page 498]
-
- Annex D
- (normative)
- Universal character names for identifiers
-1 This clause lists the hexadecimal code values that are valid in universal character names
- in identifiers.
-2 This table is reproduced unchanged from ISO/IEC TR 10176:1998, produced by ISO/IEC
- JTC 1/SC 22/WG 20, except for the omission of ranges that are part of the basic character
- sets.
- Latin: 00AA, 00BA, 00C0-00D6, 00D8-00F6, 00F8-01F5, 01FA-0217,
- 0250-02A8, 1E00-1E9B, 1EA0-1EF9, 207F
- Greek: 0386, 0388-038A, 038C, 038E-03A1, 03A3-03CE, 03D0-03D6,
- 03DA, 03DC, 03DE, 03E0, 03E2-03F3, 1F00-1F15, 1F18-1F1D,
- 1F20-1F45, 1F48-1F4D, 1F50-1F57, 1F59, 1F5B, 1F5D,
- 1F5F-1F7D, 1F80-1FB4, 1FB6-1FBC, 1FC2-1FC4, 1FC6-1FCC,
- 1FD0-1FD3, 1FD6-1FDB, 1FE0-1FEC, 1FF2-1FF4, 1FF6-1FFC
- Cyrillic: 0401-040C, 040E-044F, 0451-045C, 045E-0481, 0490-04C4,
- 04C7-04C8, 04CB-04CC, 04D0-04EB, 04EE-04F5, 04F8-04F9
- Armenian: 0531-0556, 0561-0587
- Hebrew: 05B0-05B9, 05BB-05BD, 05BF, 05C1-05C2, 05D0-05EA,
- 05F0-05F2
- Arabic: 0621-063A, 0640-0652, 0670-06B7, 06BA-06BE, 06C0-06CE,
- 06D0-06DC, 06E5-06E8, 06EA-06ED
- Devanagari: 0901-0903, 0905-0939, 093E-094D, 0950-0952, 0958-0963
- Bengali: 0981-0983, 0985-098C, 098F-0990, 0993-09A8, 09AA-09B0,
- 09B2, 09B6-09B9, 09BE-09C4, 09C7-09C8, 09CB-09CD,
- 09DC-09DD, 09DF-09E3, 09F0-09F1
- Gurmukhi: 0A02, 0A05-0A0A, 0A0F-0A10, 0A13-0A28, 0A2A-0A30,
- 0A32-0A33, 0A35-0A36, 0A38-0A39, 0A3E-0A42, 0A47-0A48,
- 0A4B-0A4D, 0A59-0A5C, 0A5E, 0A74
- Gujarati: 0A81-0A83, 0A85-0A8B, 0A8D, 0A8F-0A91, 0A93-0AA8,
- 0AAA-0AB0, 0AB2-0AB3, 0AB5-0AB9, 0ABD-0AC5,
- 0AC7-0AC9, 0ACB-0ACD, 0AD0, 0AE0
- Oriya: 0B01-0B03, 0B05-0B0C, 0B0F-0B10, 0B13-0B28, 0B2A-0B30,
- 0B32-0B33, 0B36-0B39, 0B3E-0B43, 0B47-0B48, 0B4B-0B4D,
-[page 499]
-
- 0B5C-0B5D, 0B5F-0B61
-Tamil: 0B82-0B83, 0B85-0B8A, 0B8E-0B90, 0B92-0B95, 0B99-0B9A,
- 0B9C, 0B9E-0B9F, 0BA3-0BA4, 0BA8-0BAA, 0BAE-0BB5,
- 0BB7-0BB9, 0BBE-0BC2, 0BC6-0BC8, 0BCA-0BCD
-Telugu: 0C01-0C03, 0C05-0C0C, 0C0E-0C10, 0C12-0C28, 0C2A-0C33,
- 0C35-0C39, 0C3E-0C44, 0C46-0C48, 0C4A-0C4D, 0C60-0C61
-Kannada: 0C82-0C83, 0C85-0C8C, 0C8E-0C90, 0C92-0CA8, 0CAA-0CB3,
- 0CB5-0CB9, 0CBE-0CC4, 0CC6-0CC8, 0CCA-0CCD, 0CDE,
- 0CE0-0CE1
-Malayalam: 0D02-0D03, 0D05-0D0C, 0D0E-0D10, 0D12-0D28, 0D2A-0D39,
- 0D3E-0D43, 0D46-0D48, 0D4A-0D4D, 0D60-0D61
-Thai: 0E01-0E3A, 0E40-0E5B
-Lao: 0E81-0E82, 0E84, 0E87-0E88, 0E8A, 0E8D, 0E94-0E97,
- 0E99-0E9F, 0EA1-0EA3, 0EA5, 0EA7, 0EAA-0EAB,
- 0EAD-0EAE, 0EB0-0EB9, 0EBB-0EBD, 0EC0-0EC4, 0EC6,
- 0EC8-0ECD, 0EDC-0EDD
-Tibetan: 0F00, 0F18-0F19, 0F35, 0F37, 0F39, 0F3E-0F47, 0F49-0F69,
- 0F71-0F84, 0F86-0F8B, 0F90-0F95, 0F97, 0F99-0FAD,
- 0FB1-0FB7, 0FB9
-Georgian: 10A0-10C5, 10D0-10F6
-Hiragana: 3041-3093, 309B-309C
-Katakana: 30A1-30F6, 30FB-30FC
-Bopomofo: 3105-312C
-CJK Unified Ideographs: 4E00-9FA5
-Hangul: AC00-D7A3
-Digits: 0660-0669, 06F0-06F9, 0966-096F, 09E6-09EF, 0A66-0A6F,
- 0AE6-0AEF, 0B66-0B6F, 0BE7-0BEF, 0C66-0C6F, 0CE6-0CEF,
- 0D66-0D6F, 0E50-0E59, 0ED0-0ED9, 0F20-0F33
-Special characters: 00B5, 00B7, 02B0-02B8, 02BB, 02BD-02C1, 02D0-02D1,
- 02E0-02E4, 037A, 0559, 093D, 0B3D, 1FBE, 203F-2040, 2102,
- 2107, 210A-2113, 2115, 2118-211D, 2124, 2126, 2128, 212A-2131,
- 2133-2138, 2160-2182, 3005-3007, 3021-3029
-
-
-
-
-[page 500]
-
- Annex E
- (informative)
- Implementation limits
-1 The contents of the header <limits.h> are given below, in alphabetical order. The
- minimum magnitudes shown shall be replaced by implementation-defined magnitudes
- with the same sign. The values shall all be constant expressions suitable for use in #if
- preprocessing directives. The components are described further in 5.2.4.2.1.
- #define CHAR_BIT 8
- #define CHAR_MAX UCHAR_MAX or SCHAR_MAX
- #define CHAR_MIN 0 or SCHAR_MIN
- #define INT_MAX +32767
- #define INT_MIN -32767
- #define LONG_MAX +2147483647
- #define LONG_MIN -2147483647
- #define LLONG_MAX +9223372036854775807
- #define LLONG_MIN -9223372036854775807
- #define MB_LEN_MAX 1
- #define SCHAR_MAX +127
- #define SCHAR_MIN -127
- #define SHRT_MAX +32767
- #define SHRT_MIN -32767
- #define UCHAR_MAX 255
- #define USHRT_MAX 65535
- #define UINT_MAX 65535
- #define ULONG_MAX 4294967295
- #define ULLONG_MAX 18446744073709551615
-2 The contents of the header <float.h> are given below. All integer values, except
- FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing
- directives; all floating values shall be constant expressions. The components are
- described further in 5.2.4.2.2.
-3 The values given in the following list shall be replaced by implementation-defined
- expressions:
- #define FLT_EVAL_METHOD
- #define FLT_ROUNDS
-4 The values given in the following list shall be replaced by implementation-defined
- constant expressions that are greater or equal in magnitude (absolute value) to those
- shown, with the same sign:
-[page 501]
-
- #define DLB_DECIMAL_DIG 10
- #define DBL_DIG 10
- #define DBL_MANT_DIG
- #define DBL_MAX_10_EXP +37
- #define DBL_MAX_EXP
- #define DBL_MIN_10_EXP -37
- #define DBL_MIN_EXP
- #define DECIMAL_DIG 10
- #define FLT_DECIMAL_DIG 6
- #define FLT_DIG 6
- #define FLT_MANT_DIG
- #define FLT_MAX_10_EXP +37
- #define FLT_MAX_EXP
- #define FLT_MIN_10_EXP -37
- #define FLT_MIN_EXP
- #define FLT_RADIX 2
- #define LDLB_DECIMAL_DIG 10
- #define LDBL_DIG 10
- #define LDBL_MANT_DIG
- #define LDBL_MAX_10_EXP +37
- #define LDBL_MAX_EXP
- #define LDBL_MIN_10_EXP -37
- #define LDBL_MIN_EXP
-5 The values given in the following list shall be replaced by implementation-defined
- constant expressions with values that are greater than or equal to those shown:
- #define DBL_MAX 1E+37
- #define FLT_MAX 1E+37
- #define LDBL_MAX 1E+37
-6 The values given in the following list shall be replaced by implementation-defined
- constant expressions with (positive) values that are less than or equal to those shown:
- #define DBL_EPSILON 1E-9
- #define DBL_MIN 1E-37
- #define FLT_EPSILON 1E-5
- #define FLT_MIN 1E-37
- #define LDBL_EPSILON 1E-9
- #define LDBL_MIN 1E-37
-
-
-
-
-[page 502]
-
- Annex F
- (normative)
- IEC 60559 floating-point arithmetic
- F.1 Introduction
-1 This annex specifies C language support for the IEC 60559 floating-point standard. The
- IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
- microprocessor systems, second edition (IEC 60559:1989), previously designated
- IEC 559:1989 and as IEEE Standard for Binary Floating-Point Arithmetic
- (ANSI/IEEE 754-1985). IEEE Standard for Radix-Independent Floating-Point
- Arithmetic (ANSI/IEEE 854-1987) generalizes the binary standard to remove
- dependencies on radix and word length. IEC 60559 generally refers to the floating-point
- standard, as in IEC 60559 operation, IEC 60559 format, etc. An implementation that
- defines __STDC_IEC_559__ shall conform to the specifications in this annex.339)
- Where a binding between the C language and IEC 60559 is indicated, the
- IEC 60559-specified behavior is adopted by reference, unless stated otherwise. Since
- negative and positive infinity are representable in IEC 60559 formats, all real numbers lie
- within the range of representable values.
- F.2 Types
-1 The C floating types match the IEC 60559 formats as follows:
- -- The float type matches the IEC 60559 single format.
- -- The double type matches the IEC 60559 double format.
- -- The long double type matches an IEC 60559 extended format,340) else a
- non-IEC 60559 extended format, else the IEC 60559 double format.
- Any non-IEC 60559 extended format used for the long double type shall have more
- precision than IEC 60559 double and at least the range of IEC 60559 double.341)
-
-
-
-
- 339) Implementations that do not define __STDC_IEC_559__ are not required to conform to these
- specifications.
- 340) ''Extended'' is IEC 60559's double-extended data format. Extended refers to both the common 80-bit
- and quadruple 128-bit IEC 60559 formats.
- 341) A non-IEC 60559 long double type is required to provide infinity and NaNs, as its values include
- all double values.
-
-[page 503]
-
- Recommended practice
-2 The long double type should match an IEC 60559 extended format.
- F.2.1 Infinities, signed zeros, and NaNs
-1 This specification does not define the behavior of signaling NaNs.342) It generally uses
- the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
- functions in <math.h> provide designations for IEC 60559 NaNs and infinities.
- F.3 Operators and functions
-1 C operators and functions provide IEC 60559 required and recommended facilities as
- listed below.
- -- The +, -, *, and / operators provide the IEC 60559 add, subtract, multiply, and
- divide operations.
- -- The sqrt functions in <math.h> provide the IEC 60559 square root operation.
- -- The remainder functions in <math.h> provide the IEC 60559 remainder
- operation. The remquo functions in <math.h> provide the same operation but
- with additional information.
- -- The rint functions in <math.h> provide the IEC 60559 operation that rounds a
- floating-point number to an integer value (in the same precision). The nearbyint
- functions in <math.h> provide the nearbyinteger function recommended in the
- Appendix to ANSI/IEEE 854.
- -- The conversions for floating types provide the IEC 60559 conversions between
- floating-point precisions.
- -- The conversions from integer to floating types provide the IEC 60559 conversions
- from integer to floating point.
- -- The conversions from floating to integer types provide IEC 60559-like conversions
- but always round toward zero.
- -- The lrint and llrint functions in <math.h> provide the IEC 60559
- conversions, which honor the directed rounding mode, from floating point to the
- long int and long long int integer formats. The lrint and llrint
- functions can be used to implement IEC 60559 conversions from floating to other
- integer formats.
- -- The translation time conversion of floating constants and the strtod, strtof,
- strtold, fprintf, fscanf, and related library functions in <stdlib.h>,
-
-
- 342) Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are
- sufficient for closure of the arithmetic.
-
-[page 504]
-
- <stdio.h>, and <wchar.h> provide IEC 60559 binary-decimal conversions. The
- strtold function in <stdlib.h> provides the conv function recommended in the
- Appendix to ANSI/IEEE 854.
--- The relational and equality operators provide IEC 60559 comparisons. IEC 60559
- identifies a need for additional comparison predicates to facilitate writing code that
- accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
- isless, islessequal, islessgreater, and isunordered) in <math.h>
- supplement the language operators to address this need. The islessgreater and
- isunordered macros provide respectively a quiet version of the <> predicate and
- the unordered predicate recommended in the Appendix to IEC 60559.
--- The feclearexcept, feraiseexcept, and fetestexcept functions in
- <fenv.h> provide the facility to test and alter the IEC 60559 floating-point
- exception status flags. The fegetexceptflag and fesetexceptflag
- functions in <fenv.h> provide the facility to save and restore all five status flags at
- one time. These functions are used in conjunction with the type fexcept_t and the
- floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
- FE_UNDERFLOW, FE_OVERFLOW, FE_INVALID) also in <fenv.h>.
--- The fegetround and fesetround functions in <fenv.h> provide the facility
- to select among the IEC 60559 directed rounding modes represented by the rounding
- direction macros in <fenv.h> (FE_TONEAREST, FE_UPWARD, FE_DOWNWARD,
- FE_TOWARDZERO) and the values 0, 1, 2, and 3 of FLT_ROUNDS are the
- IEC 60559 directed rounding modes.
--- The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
- <fenv.h> provide a facility to manage the floating-point environment, comprising
- the IEC 60559 status flags and control modes.
--- The copysign functions in <math.h> provide the copysign function
- recommended in the Appendix to IEC 60559.
--- The fabs functions in <math.h> provide the abs function recommended in the
- Appendix to IEC 60559.
--- The unary minus (-) operator provides the unary minus (-) operation recommended
- in the Appendix to IEC 60559.
--- The scalbn and scalbln functions in <math.h> provide the scalb function
- recommended in the Appendix to IEC 60559.
--- The logb functions in <math.h> provide the logb function recommended in the
- Appendix to IEC 60559, but following the newer specifications in ANSI/IEEE 854.
--- The nextafter and nexttoward functions in <math.h> provide the nextafter
- function recommended in the Appendix to IEC 60559 (but with a minor change to
-
-[page 505]
-
- better handle signed zeros).
- -- The isfinite macro in <math.h> provides the finite function recommended in
- the Appendix to IEC 60559.
- -- The isnan macro in <math.h> provides the isnan function recommended in the
- Appendix to IEC 60559.
- -- The signbit macro and the fpclassify macro in <math.h>, used in
- conjunction with the number classification macros (FP_NAN, FP_INFINITE,
- FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
- function recommended in the Appendix to IEC 60559 (except that the classification
- macros defined in 7.12.3 do not distinguish signaling from quiet NaNs).
- F.4 Floating to integer conversion
-1 If the integer type is _Bool, 6.3.1.2 applies and no floating-point exceptions are raised
- (even for NaN). Otherwise, if the floating value is infinite or NaN or if the integral part
- of the floating value exceeds the range of the integer type, then the ''invalid'' floating-
- point exception is raised and the resulting value is unspecified. Otherwise, the resulting
- value is determined by 6.3.1.4. Conversion of an integral floating value that does not
- exceed the range of the integer type raises no floating-point exceptions; whether
- conversion of a non-integral floating value raises the ''inexact'' floating-point exception is
- unspecified.343)
- F.5 Binary-decimal conversion
-1 Conversion from the widest supported IEC 60559 format to decimal with
- DECIMAL_DIG digits and back is the identity function.344)
-2 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
- particular, conversion between any supported IEC 60559 format and decimal with
- DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
- rounding mode), which assures that conversion from the widest supported IEC 60559
- format to decimal with DECIMAL_DIG digits and back is the identity function.
-
-
-
- 343) ANSI/IEEE 854, but not IEC 60559 (ANSI/IEEE 754), directly specifies that floating-to-integer
- conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those
- cases where it matters, library functions can be used to effect such conversions with or without raising
- the ''inexact'' floating-point exception. See rint, lrint, llrint, and nearbyint in
- <math.h>.
- 344) If the minimum-width IEC 60559 extended format (64 bits of precision) is supported,
- DECIMAL_DIG shall be at least 21. If IEC 60559 double (53 bits of precision) is the widest
- IEC 60559 format supported, then DECIMAL_DIG shall be at least 17. (By contrast, LDBL_DIG and
- DBL_DIG are 18 and 15, respectively, for these formats.)
-
-[page 506]
-
-3 Functions such as strtod that convert character sequences to floating types honor the
- rounding direction. Hence, if the rounding direction might be upward or downward, the
- implementation cannot convert a minus-signed sequence by negating the converted
- unsigned sequence.
- F.6 The return statement
- If the return expression is evaluated in a floating-point format different from the return
- type, the expression is converted to the return type of the function and the resulting value
- is returned to the caller.
- F.7 Contracted expressions
-1 A contracted expression is correctly rounded (once) and treats infinities, NaNs, signed
- zeros, subnormals, and the rounding directions in a manner consistent with the basic
- arithmetic operations covered by IEC 60559.
- Recommended practice
-2 A contracted expression should raise floating-point exceptions in a manner generally
- consistent with the basic arithmetic operations.
- F.8 Floating-point environment
-1 The floating-point environment defined in <fenv.h> includes the IEC 60559 floating-
- point exception status flags and directed-rounding control modes. It includes also
- IEC 60559 dynamic rounding precision and trap enablement modes, if the
- implementation supports them.345)
- F.8.1 Environment management
-1 IEC 60559 requires that floating-point operations implicitly raise floating-point exception
- status flags, and that rounding control modes can be set explicitly to affect result values of
- floating-point operations. When the state for the FENV_ACCESS pragma (defined in
- <fenv.h>) is ''on'', these changes to the floating-point state are treated as side effects
- which respect sequence points.346)
-
-
-
-
- 345) This specification does not require dynamic rounding precision nor trap enablement modes.
- 346) If the state for the FENV_ACCESS pragma is ''off'', the implementation is free to assume the floating-
- point control modes will be the default ones and the floating-point status flags will not be tested,
- which allows certain optimizations (see F.9).
-
-[page 507]
-
- F.8.2 Translation
-1 During translation the IEC 60559 default modes are in effect:
- -- The rounding direction mode is rounding to nearest.
- -- The rounding precision mode (if supported) is set so that results are not shortened.
- -- Trapping or stopping (if supported) is disabled on all floating-point exceptions.
- Recommended practice
-2 The implementation should produce a diagnostic message for each translation-time
- floating-point exception, other than ''inexact'';347) the implementation should then
- proceed with the translation of the program.
- F.8.3 Execution
-1 At program startup the floating-point environment is initialized as prescribed by
- IEC 60559:
- -- All floating-point exception status flags are cleared.
- -- The rounding direction mode is rounding to nearest.
- -- The dynamic rounding precision mode (if supported) is set so that results are not
- shortened.
- -- Trapping or stopping (if supported) is disabled on all floating-point exceptions.
- F.8.4 Constant expressions
-1 An arithmetic constant expression of floating type, other than one in an initializer for an
- object that has static or thread storage duration, is evaluated (as if) during execution; thus,
- it is affected by any operative floating-point control modes and raises floating-point
- exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma
- is ''on'').348)
-2 EXAMPLE
-
-
-
- 347) As floating constants are converted to appropriate internal representations at translation time, their
- conversion is subject to default rounding modes and raises no execution-time floating-point exceptions
- (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example
- strtod, provide execution-time conversion of numeric strings.
- 348) Where the state for the FENV_ACCESS pragma is ''on'', results of inexact expressions like 1.0/3.0
- are affected by rounding modes set at execution time, and expressions such as 0.0/0.0 and
- 1.0/0.0 generate execution-time floating-point exceptions. The programmer can achieve the
- efficiency of translation-time evaluation through static initialization, such as
- const static double one_third = 1.0/3.0;
-
-
-[page 508]
-
- #include <fenv.h>
- #pragma STDC FENV_ACCESS ON
- void f(void)
- {
- float w[] = { 0.0/0.0 }; // raises an exception
- static float x = 0.0/0.0; // does not raise an exception
- float y = 0.0/0.0; // raises an exception
- double z = 0.0/0.0; // raises an exception
- /* ... */
- }
-3 For the static initialization, the division is done at translation time, raising no (execution-time) floating-
- point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at
- execution time.
-
- F.8.5 Initialization
-1 All computation for automatic initialization is done (as if) at execution time; thus, it is
- affected by any operative modes and raises floating-point exceptions as required by
- IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation
- for initialization of objects that have static or thread storage duration is done (as if) at
- translation time.
-2 EXAMPLE
- #include <fenv.h>
- #pragma STDC FENV_ACCESS ON
- void f(void)
- {
- float u[] = { 1.1e75 }; // raises exceptions
- static float v = 1.1e75; // does not raise exceptions
- float w = 1.1e75; // raises exceptions
- double x = 1.1e75; // may raise exceptions
- float y = 1.1e75f; // may raise exceptions
- long double z = 1.1e75; // does not raise exceptions
- /* ... */
- }
-3 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is
- done at translation time. The automatic initialization of u and w require an execution-time conversion to
- float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations
- of x and y entail execution-time conversion; however, in some expression evaluation methods, the
- conversions is not to a narrower format, in which case no floating-point exception is raised.349) The
- automatic initialization of z entails execution-time conversion, but not to a narrower format, so no floating-
- point exception is raised. Note that the conversions of the floating constants 1.1e75 and 1.1e75f to
-
-
-
- 349) Use of float_t and double_t variables increases the likelihood of translation-time computation.
- For example, the automatic initialization
- double_t x = 1.1e75;
- could be done at translation time, regardless of the expression evaluation method.
-
-[page 509]
-
- their internal representations occur at translation time in all cases.
-
- F.8.6 Changing the environment
-1 Operations defined in 6.5 and functions and macros defined for the standard libraries
- change floating-point status flags and control modes just as indicated by their
- specifications (including conformance to IEC 60559). They do not change flags or modes
- (so as to be detectable by the user) in any other cases.
-2 If the argument to the feraiseexcept function in <fenv.h> represents IEC 60559
- valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
- ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
- before ''inexact''.
- F.9 Optimization
-1 This section identifies code transformations that might subvert IEC 60559-specified
- behavior, and others that do not.
- F.9.1 Global transformations
-1 Floating-point arithmetic operations and external function calls may entail side effects
- which optimization shall honor, at least where the state of the FENV_ACCESS pragma is
- ''on''. The flags and modes in the floating-point environment may be regarded as global
- variables; floating-point operations (+, *, etc.) implicitly read the modes and write the
- flags.
-2 Concern about side effects may inhibit code motion and removal of seemingly useless
- code. For example, in
- #include <fenv.h>
- #pragma STDC FENV_ACCESS ON
- void f(double x)
- {
- /* ... */
- for (i = 0; i < n; i++) x + 1;
- /* ... */
- }
- x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
- body might not execute (maybe 0 >= n), x + 1 cannot be moved out of the loop. (Of
- course these optimizations are valid if the implementation can rule out the nettlesome
- cases.)
-3 This specification does not require support for trap handlers that maintain information
- about the order or count of floating-point exceptions. Therefore, between function calls,
- floating-point exceptions need not be precise: the actual order and number of occurrences
- of floating-point exceptions (> 1) may vary from what the source code expresses. Thus,
-[page 510]
-
- the preceding loop could be treated as
- if (0 < n) x + 1;
- F.9.2 Expression transformations
-1 x/2 (<->) x x 0.5 Although similar transformations involving inexact constants
- generally do not yield numerically equivalent expressions, if the
- constants are exact then such transformations can be made on
- IEC 60559 machines and others that round perfectly.
- 1 x x and x/1 (->) x The expressions 1 x x, x/1, and x are equivalent (on IEC 60559
- machines, among others).350)
- x/x (->) 1.0 The expressions x/x and 1.0 are not equivalent if x can be zero,
- infinite, or NaN.
- x - y (<->) x + (-y) The expressions x - y, x + (-y), and (-y) + x are equivalent (on
- IEC 60559 machines, among others).
- x - y (<->) -(y - x) The expressions x - y and -(y - x) are not equivalent because 1 - 1
- is +0 but -(1 - 1) is -0 (in the default rounding direction).351)
- x - x (->) 0.0 The expressions x - x and 0.0 are not equivalent if x is a NaN or
- infinite.
- 0 x x (->) 0.0 The expressions 0 x x and 0.0 are not equivalent if x is a NaN,
- infinite, or -0.
- x+0(->) x The expressions x + 0 and x are not equivalent if x is -0, because
- (-0) + (+0) yields +0 (in the default rounding direction), not -0.
- x-0(->) x (+0) - (+0) yields -0 when rounding is downward (toward -(inf)), but
- +0 otherwise, and (-0) - (+0) always yields -0; so, if the state of the
- FENV_ACCESS pragma is ''off'', promising default rounding, then
- the implementation can replace x - 0 by x, even if x might be zero.
- -x (<->) 0 - x The expressions -x and 0 - x are not equivalent if x is +0, because
- -(+0) yields -0, but 0 - (+0) yields +0 (unless rounding is
- downward).
-
- 350) Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
- other transformations that remove arithmetic operators.
- 351) IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
- Examples include:
- 1/(1/ (+-) (inf)) is (+-) (inf)
- and
- conj(csqrt(z)) is csqrt(conj(z)),
- for complex z.
-
-[page 511]
-
- F.9.3 Relational operators
-1 x != x (->) false The expression x != x is true if x is a NaN.
- x = x (->) true The expression x = x is false if x is a NaN.
- x < y (->) isless(x,y) (and similarly for <=, >, >=) Though numerically equal, these
- expressions are not equivalent because of side effects when x or y is a
- NaN and the state of the FENV_ACCESS pragma is ''on''. This
- transformation, which would be desirable if extra code were required
- to cause the ''invalid'' floating-point exception for unordered cases,
- could be performed provided the state of the FENV_ACCESS pragma
- is ''off''.
- The sense of relational operators shall be maintained. This includes handling unordered
- cases as expressed by the source code.
-2 EXAMPLE
- // calls g and raises ''invalid'' if a and b are unordered
- if (a < b)
- f();
- else
- g();
- is not equivalent to
- // calls f and raises ''invalid'' if a and b are unordered
- if (a >= b)
- g();
- else
- f();
- nor to
- // calls f without raising ''invalid'' if a and b are unordered
- if (isgreaterequal(a,b))
- g();
- else
- f();
- nor, unless the state of the FENV_ACCESS pragma is ''off'', to
- // calls g without raising ''invalid'' if a and b are unordered
- if (isless(a,b))
- f();
- else
- g();
- but is equivalent to
-
-
-
-
-[page 512]
-
- if (!(a < b))
- g();
- else
- f();
-
- F.9.4 Constant arithmetic
-1 The implementation shall honor floating-point exceptions raised by execution-time
- constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See F.8.4
- and F.8.5.) An operation on constants that raises no floating-point exception can be
- folded during translation, except, if the state of the FENV_ACCESS pragma is ''on'', a
- further check is required to assure that changing the rounding direction to downward does
- not alter the sign of the result,352) and implementations that support dynamic rounding
- precision modes shall assure further that the result of the operation raises no floating-
- point exception when converted to the semantic type of the operation.
- F.10 Mathematics <math.h>
-1 This subclause contains specifications of <math.h> facilities that are particularly suited
- for IEC 60559 implementations.
-2 The Standard C macro HUGE_VAL and its float and long double analogs,
- HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive
- infinities.
-3 Special cases for functions in <math.h> are covered directly or indirectly by
- IEC 60559. The functions that IEC 60559 specifies directly are identified in F.3. The
- other functions in <math.h> treat infinities, NaNs, signed zeros, subnormals, and
- (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags
- in a manner consistent with the basic arithmetic operations covered by IEC 60559.
-4 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
- nonzero value.
-5 The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in
- subsequent subclauses of this annex.
-6 The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of
- rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value
- whose magnitude is too large.
-7 The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially
- subnormal or zero) and suffers loss of accuracy.353)
-
-
- 352) 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
- 353) IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on
- when the floating-point exception is raised.
-
-[page 513]
-
-8 Whether or when library functions raise the ''inexact'' floating-point exception is
- unspecified, unless explicitly specified otherwise.
-9 Whether or when library functions raise an undeserved ''underflow'' floating-point
- exception is unspecified.354) Otherwise, as implied by F.8.6, the <math.h> functions do
- not raise spurious floating-point exceptions (detectable by the user), other than the
- ''inexact'' floating-point exception.
-10 Whether the functions honor the rounding direction mode is implementation-defined,
- unless explicitly specified otherwise.
-11 Functions with a NaN argument return a NaN result and raise no floating-point exception,
- except where stated otherwise.
-12 The specifications in the following subclauses append to the definitions in <math.h>.
- For families of functions, the specifications apply to all of the functions even though only
- the principal function is shown. Unless otherwise specified, where the symbol ''(+-)''
- occurs in both an argument and the result, the result has the same sign as the argument.
- Recommended practice
-13 If a function with one or more NaN arguments returns a NaN result, the result should be
- the same as one of the NaN arguments (after possible type conversion), except perhaps
- for the sign.
- F.10.1 Trigonometric functions
- F.10.1.1 The acos functions
-1 -- acos(1) returns +0.
- -- acos(x) returns a NaN and raises the ''invalid'' floating-point exception for
- | x | > 1.
- F.10.1.2 The asin functions
-1 -- asin((+-)0) returns (+-)0.
- -- asin(x) returns a NaN and raises the ''invalid'' floating-point exception for
- | x | > 1.
-
-
-
-
- 354) It is intended that undeserved ''underflow'' and ''inexact'' floating-point exceptions are raised only if
- avoiding them would be too costly.
-
-[page 514]
-
- F.10.1.3 The atan functions
-1 -- atan((+-)0) returns (+-)0.
- -- atan((+-)(inf)) returns (+-)pi /2.
- F.10.1.4 The atan2 functions
-1 -- atan2((+-)0, -0) returns (+-)pi .355)
- -- atan2((+-)0, +0) returns (+-)0.
- -- atan2((+-)0, x) returns (+-)pi for x < 0.
- -- atan2((+-)0, x) returns (+-)0 for x > 0.
- -- atan2(y, (+-)0) returns -pi /2 for y < 0.
- -- atan2(y, (+-)0) returns pi /2 for y > 0.
- -- atan2((+-)y, -(inf)) returns (+-)pi for finite y > 0.
- -- atan2((+-)y, +(inf)) returns (+-)0 for finite y > 0.
- -- atan2((+-)(inf), x) returns (+-)pi /2 for finite x.
- -- atan2((+-)(inf), -(inf)) returns (+-)3pi /4.
- -- atan2((+-)(inf), +(inf)) returns (+-)pi /4.
- F.10.1.5 The cos functions
-1 -- cos((+-)0) returns 1.
- -- cos((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
- F.10.1.6 The sin functions
-1 -- sin((+-)0) returns (+-)0.
- -- sin((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
- F.10.1.7 The tan functions
-1 -- tan((+-)0) returns (+-)0.
- -- tan((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
-
-
-
-
- 355) atan2(0, 0) does not raise the ''invalid'' floating-point exception, nor does atan2( y , 0) raise
- the ''divide-by-zero'' floating-point exception.
-
-[page 515]
-
- F.10.2 Hyperbolic functions
- F.10.2.1 The acosh functions
-1 -- acosh(1) returns +0.
- -- acosh(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 1.
- -- acosh(+(inf)) returns +(inf).
- F.10.2.2 The asinh functions
-1 -- asinh((+-)0) returns (+-)0.
- -- asinh((+-)(inf)) returns (+-)(inf).
- F.10.2.3 The atanh functions
-1 -- atanh((+-)0) returns (+-)0.
- -- atanh((+-)1) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
- -- atanh(x) returns a NaN and raises the ''invalid'' floating-point exception for
- | x | > 1.
- F.10.2.4 The cosh functions
-1 -- cosh((+-)0) returns 1.
- -- cosh((+-)(inf)) returns +(inf).
- F.10.2.5 The sinh functions
-1 -- sinh((+-)0) returns (+-)0.
- -- sinh((+-)(inf)) returns (+-)(inf).
- F.10.2.6 The tanh functions
-1 -- tanh((+-)0) returns (+-)0.
- -- tanh((+-)(inf)) returns (+-)1.
- F.10.3 Exponential and logarithmic functions
- F.10.3.1 The exp functions
-1 -- exp((+-)0) returns 1.
- -- exp(-(inf)) returns +0.
- -- exp(+(inf)) returns +(inf).
-
-
-
-
-[page 516]
-
- F.10.3.2 The exp2 functions
-1 -- exp2((+-)0) returns 1.
- -- exp2(-(inf)) returns +0.
- -- exp2(+(inf)) returns +(inf).
- F.10.3.3 The expm1 functions
-1 -- expm1((+-)0) returns (+-)0.
- -- expm1(-(inf)) returns -1.
- -- expm1(+(inf)) returns +(inf).
- F.10.3.4 The frexp functions
-1 -- frexp((+-)0, exp) returns (+-)0, and stores 0 in the object pointed to by exp.
- -- frexp((+-)(inf), exp) returns (+-)(inf), and stores an unspecified value in the object
- pointed to by exp.
- -- frexp(NaN, exp) stores an unspecified value in the object pointed to by exp
- (and returns a NaN).
-2 frexp raises no floating-point exceptions.
-3 When the radix of the argument is a power of 2, the returned value is exact and is
- independent of the current rounding direction mode.
-4 On a binary system, the body of the frexp function might be
- {
- *exp = (value == 0) ? 0 : (int)(1 + logb(value));
- return scalbn(value, -(*exp));
- }
- F.10.3.5 The ilogb functions
-1 When the correct result is representable in the range of the return type, the returned value
- is exact and is independent of the current rounding direction mode.
-2 If the correct result is outside the range of the return type, the numeric result is
- unspecified and the ''invalid'' floating-point exception is raised.
-
-
-
-
-[page 517]
-
- F.10.3.6 The ldexp functions
-1 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
- F.10.3.7 The log functions
-1 -- log((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
- -- log(1) returns +0.
- -- log(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
- -- log(+(inf)) returns +(inf).
- F.10.3.8 The log10 functions
-1 -- log10((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
- -- log10(1) returns +0.
- -- log10(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
- -- log10(+(inf)) returns +(inf).
- F.10.3.9 The log1p functions
-1 -- log1p((+-)0) returns (+-)0.
- -- log1p(-1) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
- -- log1p(x) returns a NaN and raises the ''invalid'' floating-point exception for
- x < -1.
- -- log1p(+(inf)) returns +(inf).
- F.10.3.10 The log2 functions
-1 -- log2((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
- -- log2(1) returns +0.
- -- log2(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
- -- log2(+(inf)) returns +(inf).
- F.10.3.11 The logb functions
-1 -- logb((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
- -- logb((+-)(inf)) returns +(inf).
-2 The returned value is exact and is independent of the current rounding direction mode.
-
-
-
-
-[page 518]
-
- F.10.3.12 The modf functions
-1 -- modf((+-)x, iptr) returns a result with the same sign as x.
- -- modf((+-)(inf), iptr) returns (+-)0 and stores (+-)(inf) in the object pointed to by iptr.
- -- modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
- NaN).
-2 The returned values are exact and are independent of the current rounding direction
- mode.
-3 modf behaves as though implemented by
- #include <math.h>
- #include <fenv.h>
- #pragma STDC FENV_ACCESS ON
- double modf(double value, double *iptr)
- {
- int save_round = fegetround();
- fesetround(FE_TOWARDZERO);
- *iptr = nearbyint(value);
- fesetround(save_round);
- return copysign(
- isinf(value) ? 0.0 :
- value - (*iptr), value);
- }
- F.10.3.13 The scalbn and scalbln functions
-1 -- scalbn((+-)0, n) returns (+-)0.
- -- scalbn(x, 0) returns x.
- -- scalbn((+-)(inf), n) returns (+-)(inf).
- F.10.4 Power and absolute value functions
- F.10.4.1 The cbrt functions
-1 -- cbrt((+-)0) returns (+-)0.
- -- cbrt((+-)(inf)) returns (+-)(inf).
-
-
-
-
-[page 519]
-
- F.10.4.2 The fabs functions
-1 -- fabs((+-)0) returns +0.
- -- fabs((+-)(inf)) returns +(inf).
-2 The returned value is exact and is independent of the current rounding direction mode.
- F.10.4.3 The hypot functions
-1 -- hypot(x, y), hypot(y, x), and hypot(x, -y) are equivalent.
- -- hypot(x, (+-)0) is equivalent to fabs(x).
- -- hypot((+-)(inf), y) returns +(inf), even if y is a NaN.
- F.10.4.4 The pow functions
-1 -- pow((+-)0, y) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception
- for y an odd integer < 0.
- -- pow((+-)0, y) returns +(inf) and raises the ''divide-by-zero'' floating-point exception
- for y < 0 and not an odd integer.
- -- pow((+-)0, y) returns (+-)0 for y an odd integer > 0.
- -- pow((+-)0, y) returns +0 for y > 0 and not an odd integer.
- -- pow(-1, (+-)(inf)) returns 1.
- -- pow(+1, y) returns 1 for any y, even a NaN.
- -- pow(x, (+-)0) returns 1 for any x, even a NaN.
- -- pow(x, y) returns a NaN and raises the ''invalid'' floating-point exception for
- finite x < 0 and finite non-integer y.
- -- pow(x, -(inf)) returns +(inf) for | x | < 1.
- -- pow(x, -(inf)) returns +0 for | x | > 1.
- -- pow(x, +(inf)) returns +0 for | x | < 1.
- -- pow(x, +(inf)) returns +(inf) for | x | > 1.
- -- pow(-(inf), y) returns -0 for y an odd integer < 0.
- -- pow(-(inf), y) returns +0 for y < 0 and not an odd integer.
- -- pow(-(inf), y) returns -(inf) for y an odd integer > 0.
- -- pow(-(inf), y) returns +(inf) for y > 0 and not an odd integer.
- -- pow(+(inf), y) returns +0 for y < 0.
- -- pow(+(inf), y) returns +(inf) for y > 0.
-
-
-[page 520]
-
- F.10.4.5 The sqrt functions
-1 sqrt is fully specified as a basic arithmetic operation in IEC 60559. The returned value
- is dependent on the current rounding direction mode.
- F.10.5 Error and gamma functions
- F.10.5.1 The erf functions
-1 -- erf((+-)0) returns (+-)0.
- -- erf((+-)(inf)) returns (+-)1.
- F.10.5.2 The erfc functions
-1 -- erfc(-(inf)) returns 2.
- -- erfc(+(inf)) returns +0.
- F.10.5.3 The lgamma functions
-1 -- lgamma(1) returns +0.
- -- lgamma(2) returns +0.
- -- lgamma(x) returns +(inf) and raises the ''divide-by-zero'' floating-point exception for
- x a negative integer or zero.
- -- lgamma(-(inf)) returns +(inf).
- -- lgamma(+(inf)) returns +(inf).
- F.10.5.4 The tgamma functions
-1 -- tgamma((+-)0) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
- -- tgamma(x) returns a NaN and raises the ''invalid'' floating-point exception for x a
- negative integer.
- -- tgamma(-(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
- -- tgamma(+(inf)) returns +(inf).
- F.10.6 Nearest integer functions
- F.10.6.1 The ceil functions
-1 -- ceil((+-)0) returns (+-)0.
- -- ceil((+-)(inf)) returns (+-)(inf).
-2 The returned value is exact and is independent of the current rounding direction mode.
-3 The double version of ceil behaves as though implemented by
-
-
-
-[page 521]
-
- #include <math.h>
- #include <fenv.h>
- #pragma STDC FENV_ACCESS ON
- double ceil(double x)
- {
- double result;
- int save_round = fegetround();
- fesetround(FE_UPWARD);
- result = rint(x); // or nearbyint instead of rint
- fesetround(save_round);
- return result;
- }
- F.10.6.2 The floor functions
-1 -- floor((+-)0) returns (+-)0.
- -- floor((+-)(inf)) returns (+-)(inf).
-2 The returned value is exact and is independent of the current rounding direction mode.
-3 See the sample implementation for ceil in F.10.6.1.
- F.10.6.3 The nearbyint functions
-1 The nearbyint functions use IEC 60559 rounding according to the current rounding
- direction. They do not raise the ''inexact'' floating-point exception if the result differs in
- value from the argument.
- -- nearbyint((+-)0) returns (+-)0 (for all rounding directions).
- -- nearbyint((+-)(inf)) returns (+-)(inf) (for all rounding directions).
- F.10.6.4 The rint functions
-1 The rint functions differ from the nearbyint functions only in that they do raise the
- ''inexact'' floating-point exception if the result differs in value from the argument.
- F.10.6.5 The lrint and llrint functions
-1 The lrint and llrint functions provide floating-to-integer conversion as prescribed
- by IEC 60559. They round according to the current rounding direction. If the rounded
- value is outside the range of the return type, the numeric result is unspecified and the
- ''invalid'' floating-point exception is raised. When they raise no other floating-point
- exception and the result differs from the argument, they raise the ''inexact'' floating-point
- exception.
-
-
-
-
-[page 522]
-
- F.10.6.6 The round functions
-1 -- round((+-)0) returns (+-)0.
- -- round((+-)(inf)) returns (+-)(inf).
-2 The double version of round behaves as though implemented by
- #include <math.h>
- #include <fenv.h>
- #pragma STDC FENV_ACCESS ON
- double round(double x)
- {
- double result;
- fenv_t save_env;
- feholdexcept(&save_env);
- result = rint(x);
- if (fetestexcept(FE_INEXACT)) {
- fesetround(FE_TOWARDZERO);
- result = rint(copysign(0.5 + fabs(x), x));
- }
- feupdateenv(&save_env);
- return result;
- }
- The round functions may, but are not required to, raise the ''inexact'' floating-point
- exception for non-integer numeric arguments, as this implementation does.
- F.10.6.7 The lround and llround functions
-1 The lround and llround functions differ from the lrint and llrint functions
- with the default rounding direction just in that the lround and llround functions
- round halfway cases away from zero and need not raise the ''inexact'' floating-point
- exception for non-integer arguments that round to within the range of the return type.
- F.10.6.8 The trunc functions
-1 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
- rounding direction). The returned value is exact.
- -- trunc((+-)0) returns (+-)0.
- -- trunc((+-)(inf)) returns (+-)(inf).
-
-
-
-
-[page 523]
-
- F.10.7 Remainder functions
- F.10.7.1 The fmod functions
-1 -- fmod((+-)0, y) returns (+-)0 for y not zero.
- -- fmod(x, y) returns a NaN and raises the ''invalid'' floating-point exception for x
- infinite or y zero.
- -- fmod(x, (+-)(inf)) returns x for x not infinite.
-2 When subnormal results are supported, the returned value is exact and is independent of
- the current rounding direction mode.
-3 The double version of fmod behaves as though implemented by
- #include <math.h>
- #include <fenv.h>
- #pragma STDC FENV_ACCESS ON
- double fmod(double x, double y)
- {
- double result;
- result = remainder(fabs(x), (y = fabs(y)));
- if (signbit(result)) result += y;
- return copysign(result, x);
- }
- F.10.7.2 The remainder functions
-1 The remainder functions are fully specified as a basic arithmetic operation in
- IEC 60559.
-2 When subnormal results are supported, the returned value is exact and is independent of
- the current rounding direction mode.
- F.10.7.3 The remquo functions
-1 The remquo functions follow the specifications for the remainder functions. They
- have no further specifications special to IEC 60559 implementations.
-2 When subnormal results are supported, the returned value is exact and is independent of
- the current rounding direction mode.
-
-
-
-
-[page 524]
-
- F.10.8 Manipulation functions
- F.10.8.1 The copysign functions
-1 copysign is specified in the Appendix to IEC 60559.
-2 The returned value is exact and is independent of the current rounding direction mode.
- F.10.8.2 The nan functions
-1 All IEC 60559 implementations support quiet NaNs, in all floating formats.
-2 The returned value is exact and is independent of the current rounding direction mode.
- F.10.8.3 The nextafter functions
-1 -- nextafter(x, y) raises the ''overflow'' and ''inexact'' floating-point exceptions
- for x finite and the function value infinite.
- -- nextafter(x, y) raises the ''underflow'' and ''inexact'' floating-point
- exceptions for the function value subnormal or zero and x != y.
-2 Even though underflow or overflow can occur, the returned value is independent of the
- current rounding direction mode.
- F.10.8.4 The nexttoward functions
-1 No additional requirements beyond those on nextafter.
-2 Even though underflow or overflow can occur, the returned value is independent of the
- current rounding direction mode.
- F.10.9 Maximum, minimum, and positive difference functions
- F.10.9.1 The fdim functions
-1 No additional requirements.
- F.10.9.2 The fmax functions
-1 If just one argument is a NaN, the fmax functions return the other argument (if both
- arguments are NaNs, the functions return a NaN).
-2 The returned value is exact and is independent of the current rounding direction mode.
-3 The body of the fmax function might be356)
- { return (isgreaterequal(x, y) ||
- isnan(y)) ? x : y; }
-
-
-
- 356) Ideally, fmax would be sensitive to the sign of zero, for example fmax(-0.0, +0.0) would
- return +0; however, implementation in software might be impractical.
-
-[page 525]
-
- F.10.9.3 The fmin functions
-1 The fmin functions are analogous to the fmax functions (see F.10.9.2).
-2 The returned value is exact and is independent of the current rounding direction mode.
- F.10.10 Floating multiply-add
- F.10.10.1 The fma functions
-1 -- fma(x, y, z) computes xy + z, correctly rounded once.
- -- fma(x, y, z) returns a NaN and optionally raises the ''invalid'' floating-point
- exception if one of x and y is infinite, the other is zero, and z is a NaN.
- -- fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if
- one of x and y is infinite, the other is zero, and z is not a NaN.
- -- fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if x
- times y is an exact infinity and z is also an infinity but with the opposite sign.
- F.10.11 Comparison macros
-1 Relational operators and their corresponding comparison macros (7.12.14) produce
- equivalent result values, even if argument values are represented in wider formats. Thus,
- comparison macro arguments represented in formats wider than their semantic types are
- not converted to the semantic types, unless the wide evaluation method converts operands
- of relational operators to their semantic types. The standard wide evaluation methods
- characterized by FLT_EVAL_METHOD equal to 1 or 2 (5.2.4.2.2), do not convert
- operands of relational operators to their semantic types.
-
-
-
-
-[page 526]
-
- Annex G
- (informative)
- IEC 60559-compatible complex arithmetic
- G.1 Introduction
-1 This annex supplements annex F to specify complex arithmetic for compatibility with
- IEC 60559 real floating-point arithmetic. Although these specifications have been
- carefully designed, there is little existing practice to validate the design decisions.
- Therefore, these specifications are not normative, but should be viewed more as
- recommended practice. An implementation that defines
- __STDC_IEC_559_COMPLEX__ should conform to the specifications in this annex.
- G.2 Types
-1 There is a new keyword _Imaginary, which is used to specify imaginary types. It is
- used as a type specifier within declaration specifiers in the same way as _Complex is
- (thus, _Imaginary float is a valid type name).
-2 There are three imaginary types, designated as float _Imaginary, double
- _Imaginary, and long double _Imaginary. The imaginary types (along with
- the real floating and complex types) are floating types.
-3 For imaginary types, the corresponding real type is given by deleting the keyword
- _Imaginary from the type name.
-4 Each imaginary type has the same representation and alignment requirements as the
- corresponding real type. The value of an object of imaginary type is the value of the real
- representation times the imaginary unit.
-5 The imaginary type domain comprises the imaginary types.
- G.3 Conventions
-1 A complex or imaginary value with at least one infinite part is regarded as an infinity
- (even if its other part is a NaN). A complex or imaginary value is a finite number if each
- of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
- a zero if each of its parts is a zero.
-
-
-
-
-[page 527]
-
- G.4 Conversions
- G.4.1 Imaginary types
-1 Conversions among imaginary types follow rules analogous to those for real floating
- types.
- G.4.2 Real and imaginary
-1 When a value of imaginary type is converted to a real type other than _Bool,357) the
- result is a positive zero.
-2 When a value of real type is converted to an imaginary type, the result is a positive
- imaginary zero.
- G.4.3 Imaginary and complex
-1 When a value of imaginary type is converted to a complex type, the real part of the
- complex result value is a positive zero and the imaginary part of the complex result value
- is determined by the conversion rules for the corresponding real types.
-2 When a value of complex type is converted to an imaginary type, the real part of the
- complex value is discarded and the value of the imaginary part is converted according to
- the conversion rules for the corresponding real types.
- G.5 Binary operators
-1 The following subclauses supplement 6.5 in order to specify the type of the result for an
- operation with an imaginary operand.
-2 For most operand types, the value of the result of a binary operator with an imaginary or
- complex operand is completely determined, with reference to real arithmetic, by the usual
- mathematical formula. For some operand types, the usual mathematical formula is
- problematic because of its treatment of infinities and because of undue overflow or
- underflow; in these cases the result satisfies certain properties (specified in G.5.1), but is
- not completely determined.
-
-
-
-
- 357) See 6.3.1.2.
-
-[page 528]
-
- G.5.1 Multiplicative operators
- Semantics
-1 If one operand has real type and the other operand has imaginary type, then the result has
- imaginary type. If both operands have imaginary type, then the result has real type. (If
- either operand has complex type, then the result has complex type.)
-2 If the operands are not both complex, then the result and floating-point exception
- behavior of the * operator is defined by the usual mathematical formula:
- * u iv u + iv
-
- x xu i(xv) (xu) + i(xv)
-
- iy i(yu) -yv (-yv) + i(yu)
-
- x + iy (xu) + i(yu) (-yv) + i(xv)
-3 If the second operand is not complex, then the result and floating-point exception
- behavior of the / operator is defined by the usual mathematical formula:
- / u iv
-
- x x/u i(-x/v)
-
- iy i(y/u) y/v
-
- x + iy (x/u) + i(y/u) (y/v) + i(-x/v)
-4 The * and / operators satisfy the following infinity properties for all real, imaginary, and
- complex operands:358)
- -- if one operand is an infinity and the other operand is a nonzero finite number or an
- infinity, then the result of the * operator is an infinity;
- -- if the first operand is an infinity and the second operand is a finite number, then the
- result of the / operator is an infinity;
- -- if the first operand is a finite number and the second operand is an infinity, then the
- result of the / operator is a zero;
-
-
-
-
- 358) These properties are already implied for those cases covered in the tables, but are required for all cases
- (at least where the state for CX_LIMITED_RANGE is ''off'').
-
-[page 529]
-
- -- if the first operand is a nonzero finite number or an infinity and the second operand is
- a zero, then the result of the / operator is an infinity.
-5 If both operands of the * operator are complex or if the second operand of the / operator
- is complex, the operator raises floating-point exceptions if appropriate for the calculation
- of the parts of the result, and may raise spurious floating-point exceptions.
-6 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
- that the imaginary unit I has imaginary type (see G.6).
- #include <math.h>
- #include <complex.h>
- /* Multiply z * w ... */
- double complex _Cmultd(double complex z, double complex w)
- {
- #pragma STDC FP_CONTRACT OFF
- double a, b, c, d, ac, bd, ad, bc, x, y;
- a = creal(z); b = cimag(z);
- c = creal(w); d = cimag(w);
- ac = a * c; bd = b * d;
- ad = a * d; bc = b * c;
- x = ac - bd; y = ad + bc;
- if (isnan(x) && isnan(y)) {
- /* Recover infinities that computed as NaN+iNaN ... */
- int recalc = 0;
- if ( isinf(a) || isinf(b) ) { // z is infinite
- /* "Box" the infinity and change NaNs in the other factor to 0 */
- a = copysign(isinf(a) ? 1.0 : 0.0, a);
- b = copysign(isinf(b) ? 1.0 : 0.0, b);
- if (isnan(c)) c = copysign(0.0, c);
- if (isnan(d)) d = copysign(0.0, d);
- recalc = 1;
- }
- if ( isinf(c) || isinf(d) ) { // w is infinite
- /* "Box" the infinity and change NaNs in the other factor to 0 */
- c = copysign(isinf(c) ? 1.0 : 0.0, c);
- d = copysign(isinf(d) ? 1.0 : 0.0, d);
- if (isnan(a)) a = copysign(0.0, a);
- if (isnan(b)) b = copysign(0.0, b);
- recalc = 1;
- }
- if (!recalc && (isinf(ac) || isinf(bd) ||
- isinf(ad) || isinf(bc))) {
- /* Recover infinities from overflow by changing NaNs to 0 ... */
- if (isnan(a)) a = copysign(0.0, a);
- if (isnan(b)) b = copysign(0.0, b);
- if (isnan(c)) c = copysign(0.0, c);
- if (isnan(d)) d = copysign(0.0, d);
- recalc = 1;
- }
- if (recalc) {
-
-[page 530]
-
- x = INFINITY * ( a * c - b * d );
- y = INFINITY * ( a * d + b * c );
- }
- }
- return x + I * y;
- }
-7 This implementation achieves the required treatment of infinities at the cost of only one isnan test in
- ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur.
-
-8 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
- #include <math.h>
- #include <complex.h>
- /* Divide z / w ... */
- double complex _Cdivd(double complex z, double complex w)
- {
- #pragma STDC FP_CONTRACT OFF
- double a, b, c, d, logbw, denom, x, y;
- int ilogbw = 0;
- a = creal(z); b = cimag(z);
- c = creal(w); d = cimag(w);
- logbw = logb(fmax(fabs(c), fabs(d)));
- if (isfinite(logbw)) {
- ilogbw = (int)logbw;
- c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
- }
- denom = c * c + d * d;
- x = scalbn((a * c + b * d) / denom, -ilogbw);
- y = scalbn((b * c - a * d) / denom, -ilogbw);
- /* Recover infinities and zeros that computed as NaN+iNaN; */
- /* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
- if (isnan(x) && isnan(y)) {
- if ((denom == 0.0) &&
- (!isnan(a) || !isnan(b))) {
- x = copysign(INFINITY, c) * a;
- y = copysign(INFINITY, c) * b;
- }
- else if ((isinf(a) || isinf(b)) &&
- isfinite(c) && isfinite(d)) {
- a = copysign(isinf(a) ? 1.0 : 0.0, a);
- b = copysign(isinf(b) ? 1.0 : 0.0, b);
- x = INFINITY * ( a * c + b * d );
- y = INFINITY * ( b * c - a * d );
- }
- else if (isinf(logbw) &&
- isfinite(a) && isfinite(b)) {
- c = copysign(isinf(c) ? 1.0 : 0.0, c);
- d = copysign(isinf(d) ? 1.0 : 0.0, d);
- x = 0.0 * ( a * c + b * d );
- y = 0.0 * ( b * c - a * d );
-
-[page 531]
-
- }
- }
- return x + I * y;
- }
-9 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
- for multiplication. In the spirit of the multiplication example above, this code does not defend against
- overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
- with division, provides better roundoff characteristics.
-
- G.5.2 Additive operators
- Semantics
-1 If both operands have imaginary type, then the result has imaginary type. (If one operand
- has real type and the other operand has imaginary type, or if either operand has complex
- type, then the result has complex type.)
-2 In all cases the result and floating-point exception behavior of a + or - operator is defined
- by the usual mathematical formula:
- + or - u iv u + iv
-
- x x(+-)u x (+-) iv (x (+-) u) (+-) iv
-
- iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)
-
- x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)
- G.6 Complex arithmetic <complex.h>
-1 The macros
- imaginary
- and
- _Imaginary_I
- are defined, respectively, as _Imaginary and a constant expression of type const
- float _Imaginary with the value of the imaginary unit. The macro
- I
- is defined to be _Imaginary_I (not _Complex_I as stated in 7.3). Notwithstanding
- the provisions of 7.1.3, a program may undefine and then perhaps redefine the macro
- imaginary.
-2 This subclause contains specifications for the <complex.h> functions that are
- particularly suited to IEC 60559 implementations. For families of functions, the
- specifications apply to all of the functions even though only the principal function is
-
-[page 532]
-
- shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument
- and the result, the result has the same sign as the argument.
-3 The functions are continuous onto both sides of their branch cuts, taking into account the
- sign of zero. For example, csqrt(-2 (+-) i0) = (+-)isqrt:2. -
-4 Since complex and imaginary values are composed of real values, each function may be
- regarded as computing real values from real values. Except as noted, the functions treat
- real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
- manner consistent with the specifications for real functions in F.10.359)
-5 The functions cimag, conj, cproj, and creal are fully specified for all
- implementations, including IEC 60559 ones, in 7.3.9. These functions raise no floating-
- point exceptions.
-6 Each of the functions cabs and carg is specified by a formula in terms of a real
- function (whose special cases are covered in annex F):
- cabs(x + iy) = hypot(x, y)
- carg(x + iy) = atan2(y, x)
-7 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
- a formula in terms of other complex functions (whose special cases are specified below):
- casin(z) = -i casinh(iz)
- catan(z) = -i catanh(iz)
- ccos(z) = ccosh(iz)
- csin(z) = -i csinh(iz)
- ctan(z) = -i ctanh(iz)
-8 For the other functions, the following subclauses specify behavior for special cases,
- including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For
- families of functions, the specifications apply to all of the functions even though only the
- principal function is shown. For a function f satisfying f (conj(z)) = conj( f (z)), the
- specifications for the upper half-plane imply the specifications for the lower half-plane; if
- the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the
- specifications for the first quadrant imply the specifications for the other three quadrants.
-9 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
-
-
-
-
- 359) As noted in G.3, a complex value with at least one infinite part is regarded as an infinity even if its
- other part is a NaN.
-
-[page 533]
-
- G.6.1 Trigonometric functions
- G.6.1.1 The cacos functions
-1 -- cacos(conj(z)) = conj(cacos(z)).
- -- cacos((+-)0 + i0) returns pi /2 - i0.
- -- cacos((+-)0 + iNaN) returns pi /2 + iNaN.
- -- cacos(x + i (inf)) returns pi /2 - i (inf), for finite x.
- -- cacos(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for nonzero finite x.
- -- cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.
- -- cacos(+(inf) + iy) returns +0 - i (inf), for positive-signed finite y.
- -- cacos(-(inf) + i (inf)) returns 3pi /4 - i (inf).
- -- cacos(+(inf) + i (inf)) returns pi /4 - i (inf).
- -- cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
- result is unspecified).
- -- cacos(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite y.
- -- cacos(NaN + i (inf)) returns NaN - i (inf).
- -- cacos(NaN + iNaN) returns NaN + iNaN.
- G.6.2 Hyperbolic functions
- G.6.2.1 The cacosh functions
-1 -- cacosh(conj(z)) = conj(cacosh(z)).
- -- cacosh((+-)0 + i0) returns +0 + ipi /2.
- -- cacosh(x + i (inf)) returns +(inf) + ipi /2, for finite x.
- -- cacosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
- floating-point exception, for finite x.
- -- cacosh(-(inf) + iy) returns +(inf) + ipi , for positive-signed finite y.
- -- cacosh(+(inf) + iy) returns +(inf) + i0, for positive-signed finite y.
- -- cacosh(-(inf) + i (inf)) returns +(inf) + i3pi /4.
- -- cacosh(+(inf) + i (inf)) returns +(inf) + ipi /4.
- -- cacosh((+-)(inf) + iNaN) returns +(inf) + iNaN.
-
-
-[page 534]
-
- -- cacosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
- floating-point exception, for finite y.
- -- cacosh(NaN + i (inf)) returns +(inf) + iNaN.
- -- cacosh(NaN + iNaN) returns NaN + iNaN.
- G.6.2.2 The casinh functions
-1 -- casinh(conj(z)) = conj(casinh(z)) and casinh is odd.
- -- casinh(+0 + i0) returns 0 + i0.
- -- casinh(x + i (inf)) returns +(inf) + ipi /2 for positive-signed finite x.
- -- casinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
- floating-point exception, for finite x.
- -- casinh(+(inf) + iy) returns +(inf) + i0 for positive-signed finite y.
- -- casinh(+(inf) + i (inf)) returns +(inf) + ipi /4.
- -- casinh(+(inf) + iNaN) returns +(inf) + iNaN.
- -- casinh(NaN + i0) returns NaN + i0.
- -- casinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
- floating-point exception, for finite nonzero y.
- -- casinh(NaN + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result
- is unspecified).
- -- casinh(NaN + iNaN) returns NaN + iNaN.
- G.6.2.3 The catanh functions
-1 -- catanh(conj(z)) = conj(catanh(z)) and catanh is odd.
- -- catanh(+0 + i0) returns +0 + i0.
- -- catanh(+0 + iNaN) returns +0 + iNaN.
- -- catanh(+1 + i0) returns +(inf) + i0 and raises the ''divide-by-zero'' floating-point
- exception.
- -- catanh(x + i (inf)) returns +0 + ipi /2, for finite positive-signed x.
- -- catanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
- floating-point exception, for nonzero finite x.
- -- catanh(+(inf) + iy) returns +0 + ipi /2, for finite positive-signed y.
- -- catanh(+(inf) + i (inf)) returns +0 + ipi /2.
- -- catanh(+(inf) + iNaN) returns +0 + iNaN.
-
-[page 535]
-
- -- catanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
- floating-point exception, for finite y.
- -- catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is
- unspecified).
- -- catanh(NaN + iNaN) returns NaN + iNaN.
- G.6.2.4 The ccosh functions
-1 -- ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
- -- ccosh(+0 + i0) returns 1 + i0.
- -- ccosh(+0 + i (inf)) returns NaN (+-) i0 (where the sign of the imaginary part of the
- result is unspecified) and raises the ''invalid'' floating-point exception.
- -- ccosh(+0 + iNaN) returns NaN (+-) i0 (where the sign of the imaginary part of the
- result is unspecified).
- -- ccosh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
- exception, for finite nonzero x.
- -- ccosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite nonzero x.
- -- ccosh(+(inf) + i0) returns +(inf) + i0.
- -- ccosh(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
- -- ccosh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
- unspecified) and raises the ''invalid'' floating-point exception.
- -- ccosh(+(inf) + iNaN) returns +(inf) + iNaN.
- -- ccosh(NaN + i0) returns NaN (+-) i0 (where the sign of the imaginary part of the
- result is unspecified).
- -- ccosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for all nonzero numbers y.
- -- ccosh(NaN + iNaN) returns NaN + iNaN.
- G.6.2.5 The csinh functions
-1 -- csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
- -- csinh(+0 + i0) returns +0 + i0.
- -- csinh(+0 + i (inf)) returns (+-)0 + iNaN (where the sign of the real part of the result is
- unspecified) and raises the ''invalid'' floating-point exception.
- -- csinh(+0 + iNaN) returns (+-)0 + iNaN (where the sign of the real part of the result is
- unspecified).
-[page 536]
-
- -- csinh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
- exception, for positive finite x.
- -- csinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite nonzero x.
- -- csinh(+(inf) + i0) returns +(inf) + i0.
- -- csinh(+(inf) + iy) returns +(inf) cis(y), for positive finite y.
- -- csinh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
- unspecified) and raises the ''invalid'' floating-point exception.
- -- csinh(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
- is unspecified).
- -- csinh(NaN + i0) returns NaN + i0.
- -- csinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for all nonzero numbers y.
- -- csinh(NaN + iNaN) returns NaN + iNaN.
- G.6.2.6 The ctanh functions
-1 -- ctanh(conj(z)) = conj(ctanh(z))and ctanh is odd.
- -- ctanh(+0 + i0) returns +0 + i0.
- -- ctanh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
- exception, for finite x.
- -- ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite x.
- -- ctanh(+(inf) + iy) returns 1 + i0 sin(2y), for positive-signed finite y.
- -- ctanh(+(inf) + i (inf)) returns 1 (+-) i0 (where the sign of the imaginary part of the result
- is unspecified).
- -- ctanh(+(inf) + iNaN) returns 1 (+-) i0 (where the sign of the imaginary part of the
- result is unspecified).
- -- ctanh(NaN + i0) returns NaN + i0.
- -- ctanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for all nonzero numbers y.
- -- ctanh(NaN + iNaN) returns NaN + iNaN.
-
-
-
-
-[page 537]
-
- G.6.3 Exponential and logarithmic functions
- G.6.3.1 The cexp functions
-1 -- cexp(conj(z)) = conj(cexp(z)).
- -- cexp((+-)0 + i0) returns 1 + i0.
- -- cexp(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
- exception, for finite x.
- -- cexp(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite x.
- -- cexp(+(inf) + i0) returns +(inf) + i0.
- -- cexp(-(inf) + iy) returns +0 cis(y), for finite y.
- -- cexp(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
- -- cexp(-(inf) + i (inf)) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts of
- the result are unspecified).
- -- cexp(+(inf) + i (inf)) returns (+-)(inf) + iNaN and raises the ''invalid'' floating-point
- exception (where the sign of the real part of the result is unspecified).
- -- cexp(-(inf) + iNaN) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts
- of the result are unspecified).
- -- cexp(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
- is unspecified).
- -- cexp(NaN + i0) returns NaN + i0.
- -- cexp(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for all nonzero numbers y.
- -- cexp(NaN + iNaN) returns NaN + iNaN.
- G.6.3.2 The clog functions
-1 -- clog(conj(z)) = conj(clog(z)).
- -- clog(-0 + i0) returns -(inf) + ipi and raises the ''divide-by-zero'' floating-point
- exception.
- -- clog(+0 + i0) returns -(inf) + i0 and raises the ''divide-by-zero'' floating-point
- exception.
- -- clog(x + i (inf)) returns +(inf) + ipi /2, for finite x.
- -- clog(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite x.
-
-[page 538]
-
- -- clog(-(inf) + iy) returns +(inf) + ipi , for finite positive-signed y.
- -- clog(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
- -- clog(-(inf) + i (inf)) returns +(inf) + i3pi /4.
- -- clog(+(inf) + i (inf)) returns +(inf) + ipi /4.
- -- clog((+-)(inf) + iNaN) returns +(inf) + iNaN.
- -- clog(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite y.
- -- clog(NaN + i (inf)) returns +(inf) + iNaN.
- -- clog(NaN + iNaN) returns NaN + iNaN.
- G.6.4 Power and absolute-value functions
- G.6.4.1 The cpow functions
-1 The cpow functions raise floating-point exceptions if appropriate for the calculation of
- the parts of the result, and may raise spurious exceptions.360)
- G.6.4.2 The csqrt functions
-1 -- csqrt(conj(z)) = conj(csqrt(z)).
- -- csqrt((+-)0 + i0) returns +0 + i0.
- -- csqrt(x + i (inf)) returns +(inf) + i (inf), for all x (including NaN).
- -- csqrt(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite x.
- -- csqrt(-(inf) + iy) returns +0 + i (inf), for finite positive-signed y.
- -- csqrt(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
- -- csqrt(-(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
- result is unspecified).
- -- csqrt(+(inf) + iNaN) returns +(inf) + iNaN.
- -- csqrt(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
- point exception, for finite y.
- -- csqrt(NaN + iNaN) returns NaN + iNaN.
-
-
-
-
- 360) This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding
- implementations that treat special cases more carefully.
-
-[page 539]
-
- G.7 Type-generic math <tgmath.h>
-1 Type-generic macros that accept complex arguments also accept imaginary arguments. If
- an argument is imaginary, the macro expands to an expression whose type is real,
- imaginary, or complex, as appropriate for the particular function: if the argument is
- imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the
- types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and
- the types of the others are complex.
-2 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh,
- sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real
- functions:
- cos(iy) = cosh(y)
- sin(iy) = i sinh(y)
- tan(iy) = i tanh(y)
- cosh(iy) = cos(y)
- sinh(iy) = i sin(y)
- tanh(iy) = i tan(y)
- asin(iy) = i asinh(y)
- atan(iy) = i atanh(y)
- asinh(iy) = i asin(y)
- atanh(iy) = i atan(y)
-
-
-
-
-[page 540]
-
- Annex H
- (informative)
- Language independent arithmetic
- H.1 Introduction
-1 This annex documents the extent to which the C language supports the ISO/IEC 10967-1
- standard for language-independent arithmetic (LIA-1). LIA-1 is more general than
- IEC 60559 (annex F) in that it covers integer and diverse floating-point arithmetics.
- H.2 Types
-1 The relevant C arithmetic types meet the requirements of LIA-1 types if an
- implementation adds notification of exceptional arithmetic operations and meets the 1
- unit in the last place (ULP) accuracy requirement (LIA-1 subclause 5.2.8).
- H.2.1 Boolean type
-1 The LIA-1 data type Boolean is implemented by the C data type bool with values of
- true and false, all from <stdbool.h>.
- H.2.2 Integer types
-1 The signed C integer types int, long int, long long int, and the corresponding
- unsigned types are compatible with LIA-1. If an implementation adds support for the
- LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are
- LIA-1 conformant types. C's unsigned integer types are ''modulo'' in the LIA-1 sense
- in that overflows or out-of-bounds results silently wrap. An implementation that defines
- signed integer types as also being modulo need not detect integer overflow, in which case,
- only integer divide-by-zero need be detected.
-2 The parameters for the integer data types can be accessed by the following:
- maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
- ULLONG_MAX
- minint INT_MIN, LONG_MIN, LLONG_MIN
-3 The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
- is always 0 for the unsigned types, and is not provided for those types.
-
-
-
-
-[page 541]
-
- H.2.2.1 Integer operations
-1 The integer operations on integer types are the following:
- addI x + y
- subI x - y
- mulI x * y
- divI, divtI x / y
- remI, remtI x % y
- negI -x
- absI abs(x), labs(x), llabs(x)
- eqI x == y
- neqI x != y
- lssI x < y
- leqI x <= y
- gtrI x > y
- geqI x >= y
- where x and y are expressions of the same integer type.
- H.2.3 Floating-point types
-1 The C floating-point types float, double, and long double are compatible with
- LIA-1. If an implementation adds support for the LIA-1 exceptional values
- ''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
- with LIA-1. An implementation that uses IEC 60559 floating-point formats and
- operations (see annex F) along with IEC 60559 status flags and traps has LIA-1
- conformant types.
- H.2.3.1 Floating-point parameters
-1 The parameters for a floating point data type can be accessed by the following:
- r FLT_RADIX
- p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
- emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
- emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
-2 The derived constants for the floating point types are accessed by the following:
-
-
-[page 542]
-
- fmax FLT_MAX, DBL_MAX, LDBL_MAX
- fminN FLT_MIN, DBL_MIN, LDBL_MIN
- epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
- rnd_style FLT_ROUNDS
- H.2.3.2 Floating-point operations
-1 The floating-point operations on floating-point types are the following:
- addF x + y
- subF x - y
- mulF x * y
- divF x / y
- negF -x
- absF fabsf(x), fabs(x), fabsl(x)
- exponentF 1.f+logbf(x), 1.0+logb(x), 1.L+logbl(x)
- scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
- scalblnf(x, li), scalbln(x, li), scalblnl(x, li)
- intpartF modff(x, &y), modf(x, &y), modfl(x, &y)
- fractpartF modff(x, &y), modf(x, &y), modfl(x, &y)
- eqF x == y
- neqF x != y
- lssF x < y
- leqF x <= y
- gtrF x > y
- geqF x >= y
- where x and y are expressions of the same floating point type, n is of type int, and li
- is of type long int.
- H.2.3.3 Rounding styles
-1 The C Standard requires all floating types to use the same radix and rounding style, so
- that only one identifier for each is provided to map to LIA-1.
-2 The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
- truncate FLT_ROUNDS == 0
-
-
-[page 543]
-
- nearest FLT_ROUNDS == 1
- other FLT_ROUNDS != 0 && FLT_ROUNDS != 1
- provided that an implementation extends FLT_ROUNDS to cover the rounding style used
- in all relevant LIA-1 operations, not just addition as in C.
- H.2.4 Type conversions
-1 The LIA-1 type conversions are the following type casts:
- cvtI' (->) I (int)i, (long int)i, (long long int)i,
- (unsigned int)i, (unsigned long int)i,
- (unsigned long long int)i
- cvtF (->) I (int)x, (long int)x, (long long int)x,
- (unsigned int)x, (unsigned long int)x,
- (unsigned long long int)x
- cvtI (->) F (float)i, (double)i, (long double)i
- cvtF' (->) F (float)x, (double)x, (long double)x
-2 In the above conversions from floating to integer, the use of (cast)x can be replaced with
- (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
- (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer
- conversion functions, lrint(), llrint(), lround(), and llround(), can be
- used. They all meet LIA-1's requirements on floating to integer rounding for in-range
- values. For out-of-range values, the conversions shall silently wrap for the modulo types.
-3 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
- fmod( fabs(rint(x)), 65536.0 ) or (0.0 <= (y = fmod( rint(x),
- 65536.0 )) ? y : 65536.0 + y) will compute an integer value in the range 0.0
- to 65535.0 which can then be cast to unsigned short int. But, the
- remainder() function is not useful for doing silent wrapping to signed integer types,
- e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
- range -32767.0 to +32768.0 which is not, in general, in the range of signed short
- int.
-4 C's conversions (casts) from floating-point to floating-point can meet LIA-1
- requirements if an implementation uses round-to-nearest (IEC 60559 default).
-5 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
- implementation uses round-to-nearest.
-
-
-
-
-[page 544]
-
- H.3 Notification
-1 Notification is the process by which a user or program is informed that an exceptional
- arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
- allows an implementation to cause a notification to occur when any arithmetic operation
- returns an exceptional value as defined in LIA-1 clause 5.
- H.3.1 Notification alternatives
-1 LIA-1 requires at least the following two alternatives for handling of notifications:
- setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and-
- resume.
-2 An implementation need only support a given notification alternative for the entire
- program. An implementation may support the ability to switch between notification
- alternatives during execution, but is not required to do so. An implementation can
- provide separate selection for each kind of notification, but this is not required.
-3 C allows an implementation to provide notification. C's SIGFPE (for traps) and
- FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
- can provide LIA-1 notification.
-4 C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
- provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
- math library function calls. User-provided signal handlers for SIGFPE allow for trap-
- and-resume behavior with the same constraint.
- H.3.1.1 Indicators
-1 C's <fenv.h> status flags are compatible with the LIA-1 indicators.
-2 The following mapping is for floating-point types:
- undefined FE_INVALID, FE_DIVBYZERO
- floating_overflow FE_OVERFLOW
- underflow FE_UNDERFLOW
-3 The floating-point indicator interrogation and manipulation operations are:
- set_indicators feraiseexcept(i)
- clear_indicators feclearexcept(i)
- test_indicators fetestexcept(i)
- current_indicators fetestexcept(FE_ALL_EXCEPT)
- where i is an expression of type int representing a subset of the LIA-1 indicators.
-4 C allows an implementation to provide the following LIA-1 required behavior: at
- program termination if any indicator is set the implementation shall send an unambiguous
-[page 545]
-
- and ''hard to ignore'' message (see LIA-1 subclause 6.1.2)
-5 LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
- This documentation makes that distinction because <fenv.h> covers only the floating-
- point indicators.
- H.3.1.2 Traps
-1 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
- math library functions (which are not permitted to invoke a user's signal handler for
- SIGFPE). An implementation can provide an alternative of notification through
- termination with a ''hard-to-ignore'' message (see LIA-1 subclause 6.1.3).
-2 LIA-1 does not require that traps be precise.
-3 C does require that SIGFPE be the signal corresponding to arithmetic exceptions, if there
- is any signal raised for them.
-4 C supports signal handlers for SIGFPE and allows trapping of arithmetic exceptions.
- When arithmetic exceptions do trap, C's signal-handler mechanism allows trap-and-
- terminate (either default implementation behavior or user replacement for it) or trap-and-
- resume, at the programmer's option.
-
-
-
-
-[page 546]
-
- Annex I
- (informative)
- Common warnings
-1 An implementation may generate warnings in many situations, none of which are
- specified as part of this International Standard. The following are a few of the more
- common situations.
-2 -- A new struct or union type appears in a function prototype (6.2.1, 6.7.2.3).
- -- A block with initialization of an object that has automatic storage duration is jumped
- into (6.2.4).
- -- An implicit narrowing conversion is encountered, such as the assignment of a long
- int or a double to an int, or a pointer to void to a pointer to any type other than
- a character type (6.3).
- -- A hexadecimal floating constant cannot be represented exactly in its evaluation format
- (6.4.4.2).
- -- An integer character constant includes more than one character or a wide character
- constant includes more than one multibyte character (6.4.4.4).
- -- The characters /* are found in a comment (6.4.7).
- -- An ''unordered'' binary operator (not comma, &&, or ||) contains a side effect to an
- lvalue in one operand, and a side effect to, or an access to the value of, the identical
- lvalue in the other operand (6.5).
- -- A function is called but no prototype has been supplied (6.5.2.2).
- -- The arguments in a function call do not agree in number and type with those of the
- parameters in a function definition that is not a prototype (6.5.2.2).
- -- An object is defined but not used (6.7).
- -- A value is given to an object of an enumerated type other than by assignment of an
- enumeration constant that is a member of that type, or an enumeration object that has
- the same type, or the value of a function that returns the same enumerated type
- (6.7.2.2).
- -- An aggregate has a partly bracketed initialization (6.7.8).
- -- A statement cannot be reached (6.8).
- -- A statement with no apparent effect is encountered (6.8).
- -- A constant expression is used as the controlling expression of a selection statement
- (6.8.4).
-[page 547]
-
--- An incorrectly formed preprocessing group is encountered while skipping a
- preprocessing group (6.10.1).
--- An unrecognized #pragma directive is encountered (6.10.6).
-
-
-
-
-[page 548]
-
- Annex J
- (informative)
- Portability issues
-1 This annex collects some information about portability that appears in this International
- Standard.
- J.1 Unspecified behavior
-1 The following are unspecified:
- -- The manner and timing of static initialization (5.1.2).
- -- The termination status returned to the hosted environment if the return type of main
- is not compatible with int (5.1.2.2.3).
- -- The behavior of the display device if a printing character is written when the active
- position is at the final position of a line (5.2.2).
- -- The behavior of the display device if a backspace character is written when the active
- position is at the initial position of a line (5.2.2).
- -- The behavior of the display device if a horizontal tab character is written when the
- active position is at or past the last defined horizontal tabulation position (5.2.2).
- -- The behavior of the display device if a vertical tab character is written when the active
- position is at or past the last defined vertical tabulation position (5.2.2).
- -- How an extended source character that does not correspond to a universal character
- name counts toward the significant initial characters in an external identifier (5.2.4.1).
- -- Many aspects of the representations of types (6.2.6).
- -- The value of padding bytes when storing values in structures or unions (6.2.6.1).
- -- The values of bytes that correspond to union members other than the one last stored
- into (6.2.6.1).
- -- The representation used when storing a value in an object that has more than one
- object representation for that value (6.2.6.1).
- -- The values of any padding bits in integer representations (6.2.6.2).
- -- Whether certain operators can generate negative zeros and whether a negative zero
- becomes a normal zero when stored in an object (6.2.6.2).
- -- Whether two string literals result in distinct arrays (6.4.5).
- -- The order in which subexpressions are evaluated and the order in which side effects
- take place, except as specified for the function-call (), &&, ||, ? :, and comma
-[page 549]
-
- operators (6.5).
--- The order in which the function designator, arguments, and subexpressions within the
- arguments are evaluated in a function call (6.5.2.2).
--- The order of side effects among compound literal initialization list expressions
- (6.5.2.5).
--- The order in which the operands of an assignment operator are evaluated (6.5.16).
--- The alignment of the addressable storage unit allocated to hold a bit-field (6.7.2.1).
--- Whether a call to an inline function uses the inline definition or the external definition
- of the function (6.7.4).
--- Whether or not a size expression is evaluated when it is part of the operand of a
- sizeof operator and changing the value of the size expression would not affect the
- result of the operator (6.7.6.2).
--- The order in which any side effects occur among the initialization list expressions in
- an initializer (6.7.9).
--- The layout of storage for function parameters (6.9.1).
--- When a fully expanded macro replacement list contains a function-like macro name
- as its last preprocessing token and the next preprocessing token from the source file is
- a (, and the fully expanded replacement of that macro ends with the name of the first
- macro and the next preprocessing token from the source file is again a (, whether that
- is considered a nested replacement (6.10.3).
--- The order in which # and ## operations are evaluated during macro substitution
- (6.10.3.2, 6.10.3.3).
--- The state of the floating-point status flags when execution passes from a part of the
- program translated with FENV_ACCESS ''off'' to a part translated with
- FENV_ACCESS ''on'' (7.6.1).
--- The order in which feraiseexcept raises floating-point exceptions, except as
- stated in F.8.6 (7.6.2.3).
--- Whether math_errhandling is a macro or an identifier with external linkage
- (7.12).
--- The results of the frexp functions when the specified value is not a floating-point
- number (7.12.6.4).
--- The numeric result of the ilogb functions when the correct value is outside the
- range of the return type (7.12.6.5, F.10.3.5).
--- The result of rounding when the value is out of range (7.12.9.5, 7.12.9.7, F.10.6.5).
-
-
-[page 550]
-
--- The value stored by the remquo functions in the object pointed to by quo when y is
- zero (7.12.10.3).
--- Whether a comparison macro argument that is represented in a format wider than its
- semantic type is converted to the semantic type (7.12.14).
--- Whether setjmp is a macro or an identifier with external linkage (7.13).
--- Whether va_copy and va_end are macros or identifiers with external linkage
- (7.16.1).
--- The hexadecimal digit before the decimal point when a non-normalized floating-point
- number is printed with an a or A conversion specifier (7.21.6.1, 7.28.2.1).
--- The value of the file position indicator after a successful call to the ungetc function
- for a text stream, or the ungetwc function for any stream, until all pushed-back
- characters are read or discarded (7.21.7.10, 7.28.3.10).
--- The details of the value stored by the fgetpos function (7.21.9.1).
--- The details of the value returned by the ftell function for a text stream (7.21.9.4).
--- Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold
- functions convert a minus-signed sequence to a negative number directly or by
- negating the value resulting from converting the corresponding unsigned sequence
- (7.22.1.3, 7.28.4.1.1).
--- The order and contiguity of storage allocated by successive calls to the calloc,
- malloc, and realloc functions (7.22.3).
--- The amount of storage allocated by a successful call to the calloc, malloc, or
- realloc function when 0 bytes was requested (7.22.3).
--- Which of two elements that compare as equal is matched by the bsearch function
- (7.22.5.1).
--- The order of two elements that compare as equal in an array sorted by the qsort
- function (7.22.5.2).
--- The encoding of the calendar time returned by the time function (7.26.2.4).
--- The characters stored by the strftime or wcsftime function if any of the time
- values being converted is outside the normal range (7.26.3.5, 7.28.5.1).
--- The conversion state after an encoding error occurs (7.28.6.3.2, 7.28.6.3.3, 7.28.6.4.1,
- 7.28.6.4.2,
--- The resulting value when the ''invalid'' floating-point exception is raised during
- IEC 60559 floating to integer conversion (F.4).
-
-
-
-[page 551]
-
- -- Whether conversion of non-integer IEC 60559 floating values to integer raises the
- ''inexact'' floating-point exception (F.4).
- -- Whether or when library functions in <math.h> raise the ''inexact'' floating-point
- exception in an IEC 60559 conformant implementation (F.10).
- -- Whether or when library functions in <math.h> raise an undeserved ''underflow''
- floating-point exception in an IEC 60559 conformant implementation (F.10).
- -- The exponent value stored by frexp for a NaN or infinity (F.10.3.4).
- -- The numeric result returned by the lrint, llrint, lround, and llround
- functions if the rounded value is outside the range of the return type (F.10.6.5,
- F.10.6.7).
- -- The sign of one part of the complex result of several math functions for certain
- exceptional values in IEC 60559 compatible implementations (G.6.1.1, G.6.2.2,
- G.6.2.3, G.6.2.4, G.6.2.5, G.6.2.6, G.6.3.1, G.6.4.2).
- J.2 Undefined behavior
-1 The behavior is undefined in the following circumstances:
- -- A ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated
- (clause 4).
- -- A nonempty source file does not end in a new-line character which is not immediately
- preceded by a backslash character or ends in a partial preprocessing token or
- comment (5.1.1.2).
- -- Token concatenation produces a character sequence matching the syntax of a
- universal character name (5.1.1.2).
- -- A program in a hosted environment does not define a function named main using one
- of the specified forms (5.1.2.2.1).
- -- The execution of a program contains a data race (5.1.2.4).
- -- A character not in the basic source character set is encountered in a source file, except
- in an identifier, a character constant, a string literal, a header name, a comment, or a
- preprocessing token that is never converted to a token (5.2.1).
- -- An identifier, comment, string literal, character constant, or header name contains an
- invalid multibyte character or does not begin and end in the initial shift state (5.2.1.2).
- -- The same identifier has both internal and external linkage in the same translation unit
- (6.2.2).
- -- An object is referred to outside of its lifetime (6.2.4).
-
-
-
-[page 552]
-
--- The value of a pointer to an object whose lifetime has ended is used (6.2.4).
--- The value of an object with automatic storage duration is used while it is
- indeterminate (6.2.4, 6.7.9, 6.8).
--- A trap representation is read by an lvalue expression that does not have character type
- (6.2.6.1).
--- A trap representation is produced by a side effect that modifies any part of the object
- using an lvalue expression that does not have character type (6.2.6.1).
--- The operands to certain operators are such that they could produce a negative zero
- result, but the implementation does not support negative zeros (6.2.6.2).
--- Two declarations of the same object or function specify types that are not compatible
- (6.2.7).
--- A program requires the formation of a composite type from a variable length array
- type whose size is specified by an expression that is not evaluated (6.2.7).
--- Conversion to or from an integer type produces a value outside the range that can be
- represented (6.3.1.4).
--- Demotion of one real floating type to another produces a value outside the range that
- can be represented (6.3.1.5).
--- An lvalue does not designate an object when evaluated (6.3.2.1).
--- A non-array lvalue with an incomplete type is used in a context that requires the value
- of the designated object (6.3.2.1).
--- An lvalue designating an object of automatic storage duration that could have been
- declared with the register storage class is used in a context that requires the value
- of the designated object, but the object is uninitialized. (6.3.2.1).
--- An lvalue having array type is converted to a pointer to the initial element of the
- array, and the array object has register storage class (6.3.2.1).
--- An attempt is made to use the value of a void expression, or an implicit or explicit
- conversion (except to void) is applied to a void expression (6.3.2.2).
--- Conversion of a pointer to an integer type produces a value outside the range that can
- be represented (6.3.2.3).
--- Conversion between two pointer types produces a result that is incorrectly aligned
- (6.3.2.3).
--- A pointer is used to call a function whose type is not compatible with the referenced
- type (6.3.2.3).
-
-
-
-[page 553]
-
--- An unmatched ' or " character is encountered on a logical source line during
- tokenization (6.4).
--- A reserved keyword token is used in translation phase 7 or 8 for some purpose other
- than as a keyword (6.4.1).
--- A universal character name in an identifier does not designate a character whose
- encoding falls into one of the specified ranges (6.4.2.1).
--- The initial character of an identifier is a universal character name designating a digit
- (6.4.2.1).
--- Two identifiers differ only in nonsignificant characters (6.4.2.1).
--- The identifier __func__ is explicitly declared (6.4.2.2).
--- The program attempts to modify a string literal (6.4.5).
--- The characters ', \, ", //, or /* occur in the sequence between the < and >
- delimiters, or the characters ', \, //, or /* occur in the sequence between the "
- delimiters, in a header name preprocessing token (6.4.7).
--- A side effect on a scalar object is unsequenced relative to either a different side effect
- on the same scalar object or a value computation using the value of the same scalar
- object (6.5).
--- An exceptional condition occurs during the evaluation of an expression (6.5).
--- An object has its stored value accessed other than by an lvalue of an allowable type
- (6.5).
--- For a call to a function without a function prototype in scope, the number of
- arguments does not equal the number of parameters (6.5.2.2).
--- For call to a function without a function prototype in scope where the function is
- defined with a function prototype, either the prototype ends with an ellipsis or the
- types of the arguments after promotion are not compatible with the types of the
- parameters (6.5.2.2).
--- For a call to a function without a function prototype in scope where the function is not
- defined with a function prototype, the types of the arguments after promotion are not
- compatible with those of the parameters after promotion (with certain exceptions)
- (6.5.2.2).
--- A function is defined with a type that is not compatible with the type (of the
- expression) pointed to by the expression that denotes the called function (6.5.2.2).
--- A member of an _Atomic-qualified structure or union is accessed (6.5.2.3).
--- The operand of the unary * operator has an invalid value (6.5.3.2).
-
-
-[page 554]
-
--- A pointer is converted to other than an integer or pointer type (6.5.4).
--- The value of the second operand of the / or % operator is zero (6.5.5).
--- Addition or subtraction of a pointer into, or just beyond, an array object and an
- integer type produces a result that does not point into, or just beyond, the same array
- object (6.5.6).
--- Addition or subtraction of a pointer into, or just beyond, an array object and an
- integer type produces a result that points just beyond the array object and is used as
- the operand of a unary * operator that is evaluated (6.5.6).
--- Pointers that do not point into, or just beyond, the same array object are subtracted
- (6.5.6).
--- An array subscript is out of range, even if an object is apparently accessible with the
- given subscript (as in the lvalue expression a[1][7] given the declaration int
- a[4][5]) (6.5.6).
--- The result of subtracting two pointers is not representable in an object of type
- ptrdiff_t (6.5.6).
--- An expression is shifted by a negative number or by an amount greater than or equal
- to the width of the promoted expression (6.5.7).
--- An expression having signed promoted type is left-shifted and either the value of the
- expression is negative or the result of shifting would be not be representable in the
- promoted type (6.5.7).
--- Pointers that do not point to the same aggregate or union (nor just beyond the same
- array object) are compared using relational operators (6.5.8).
--- An object is assigned to an inexactly overlapping object or to an exactly overlapping
- object with incompatible type (6.5.16.1).
--- An expression that is required to be an integer constant expression does not have an
- integer type; has operands that are not integer constants, enumeration constants,
- character constants, sizeof expressions whose results are integer constants, or
- immediately-cast floating constants; or contains casts (outside operands to sizeof
- operators) other than conversions of arithmetic types to integer types (6.6).
--- A constant expression in an initializer is not, or does not evaluate to, one of the
- following: an arithmetic constant expression, a null pointer constant, an address
- constant, or an address constant for a complete object type plus or minus an integer
- constant expression (6.6).
--- An arithmetic constant expression does not have arithmetic type; has operands that
- are not integer constants, floating constants, enumeration constants, character
- constants, or sizeof expressions; or contains casts (outside operands to sizeof
-
-[page 555]
-
- operators) other than conversions of arithmetic types to arithmetic types (6.6).
--- The value of an object is accessed by an array-subscript [], member-access . or ->,
- address &, or indirection * operator or a pointer cast in creating an address constant
- (6.6).
--- An identifier for an object is declared with no linkage and the type of the object is
- incomplete after its declarator, or after its init-declarator if it has an initializer (6.7).
--- A function is declared at block scope with an explicit storage-class specifier other
- than extern (6.7.1).
--- A structure or union is defined as containing no named members, no anonymous
- structures, and no anonymous unions (6.7.2.1).
--- An attempt is made to access, or generate a pointer to just past, a flexible array
- member of a structure when the referenced object provides no elements for that array
- (6.7.2.1).
--- When the complete type is needed, an incomplete structure or union type is not
- completed in the same scope by another declaration of the tag that defines the content
- (6.7.2.3).
--- An attempt is made to modify an object defined with a const-qualified type through
- use of an lvalue with non-const-qualified type (6.7.3).
--- An attempt is made to refer to an object defined with a volatile-qualified type through
- use of an lvalue with non-volatile-qualified type (6.7.3).
--- An attempt is made to refer to an object defined with an _Atomic-qualified type
- through use of an lvalue with non-_Atomic-qualified type (6.7.3).
--- The specification of a function type includes any type qualifiers (6.7.3).
--- Two qualified types that are required to be compatible do not have the identically
- qualified version of a compatible type (6.7.3).
--- An object which has been modified is accessed through a restrict-qualified pointer to
- a const-qualified type, or through a restrict-qualified pointer and another pointer that
- are not both based on the same object (6.7.3.1).
--- A restrict-qualified pointer is assigned a value based on another restricted pointer
- whose associated block neither began execution before the block associated with this
- pointer, nor ended before the assignment (6.7.3.1).
--- A function with external linkage is declared with an inline function specifier, but is
- not also defined in the same translation unit (6.7.4).
--- A function declared with a _Noreturn function specifier returns to its caller (6.7.4).
-
-
-[page 556]
-
--- The definition of an object has an alignment specifier and another declaration of that
- object has a different alignment specifier (6.7.5).
--- Declarations of an object in different translation units have different alignment
- specifiers (6.7.5).
--- Two pointer types that are required to be compatible are not identically qualified, or
- are not pointers to compatible types (6.7.6.1).
--- The size expression in an array declaration is not a constant expression and evaluates
- at program execution time to a nonpositive value (6.7.6.2).
--- In a context requiring two array types to be compatible, they do not have compatible
- element types, or their size specifiers evaluate to unequal values (6.7.6.2).
--- A declaration of an array parameter includes the keyword static within the [ and
- ] and the corresponding argument does not provide access to the first element of an
- array with at least the specified number of elements (6.7.6.3).
--- A storage-class specifier or type qualifier modifies the keyword void as a function
- parameter type list (6.7.6.3).
--- In a context requiring two function types to be compatible, they do not have
- compatible return types, or their parameters disagree in use of the ellipsis terminator
- or the number and type of parameters (after default argument promotion, when there
- is no parameter type list or when one type is specified by a function definition with an
- identifier list) (6.7.6.3).
--- The value of an unnamed member of a structure or union is used (6.7.9).
--- The initializer for a scalar is neither a single expression nor a single expression
- enclosed in braces (6.7.9).
--- The initializer for a structure or union object that has automatic storage duration is
- neither an initializer list nor a single expression that has compatible structure or union
- type (6.7.9).
--- The initializer for an aggregate or union, other than an array initialized by a string
- literal, is not a brace-enclosed list of initializers for its elements or members (6.7.9).
--- An identifier with external linkage is used, but in the program there does not exist
- exactly one external definition for the identifier, or the identifier is not used and there
- exist multiple external definitions for the identifier (6.9).
--- A function definition includes an identifier list, but the types of the parameters are not
- declared in a following declaration list (6.9.1).
--- An adjusted parameter type in a function definition is not a complete object type
- (6.9.1).
-
-[page 557]
-
--- A function that accepts a variable number of arguments is defined without a
- parameter type list that ends with the ellipsis notation (6.9.1).
--- The } that terminates a function is reached, and the value of the function call is used
- by the caller (6.9.1).
--- An identifier for an object with internal linkage and an incomplete type is declared
- with a tentative definition (6.9.2).
--- The token defined is generated during the expansion of a #if or #elif
- preprocessing directive, or the use of the defined unary operator does not match
- one of the two specified forms prior to macro replacement (6.10.1).
--- The #include preprocessing directive that results after expansion does not match
- one of the two header name forms (6.10.2).
--- The character sequence in an #include preprocessing directive does not start with a
- letter (6.10.2).
--- There are sequences of preprocessing tokens within the list of macro arguments that
- would otherwise act as preprocessing directives (6.10.3).
--- The result of the preprocessing operator # is not a valid character string literal
- (6.10.3.2).
--- The result of the preprocessing operator ## is not a valid preprocessing token
- (6.10.3.3).
--- The #line preprocessing directive that results after expansion does not match one of
- the two well-defined forms, or its digit sequence specifies zero or a number greater
- than 2147483647 (6.10.4).
--- A non-STDC #pragma preprocessing directive that is documented as causing
- translation failure or some other form of undefined behavior is encountered (6.10.6).
--- A #pragma STDC preprocessing directive does not match one of the well-defined
- forms (6.10.6).
--- The name of a predefined macro, or the identifier defined, is the subject of a
- #define or #undef preprocessing directive (6.10.8).
--- An attempt is made to copy an object to an overlapping object by use of a library
- function, other than as explicitly allowed (e.g., memmove) (clause 7).
--- A file with the same name as one of the standard headers, not provided as part of the
- implementation, is placed in any of the standard places that are searched for included
- source files (7.1.2).
--- A header is included within an external declaration or definition (7.1.2).
-
-
-[page 558]
-
--- A function, object, type, or macro that is specified as being declared or defined by
- some standard header is used before any header that declares or defines it is included
- (7.1.2).
--- A standard header is included while a macro is defined with the same name as a
- keyword (7.1.2).
--- The program attempts to declare a library function itself, rather than via a standard
- header, but the declaration does not have external linkage (7.1.2).
--- The program declares or defines a reserved identifier, other than as allowed by 7.1.4
- (7.1.3).
--- The program removes the definition of a macro whose name begins with an
- underscore and either an uppercase letter or another underscore (7.1.3).
--- An argument to a library function has an invalid value or a type not expected by a
- function with variable number of arguments (7.1.4).
--- The pointer passed to a library function array parameter does not have a value such
- that all address computations and object accesses are valid (7.1.4).
--- The macro definition of assert is suppressed in order to access an actual function
- (7.2).
--- The argument to the assert macro does not have a scalar type (7.2).
--- The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in
- any context other than outside all external declarations or preceding all explicit
- declarations and statements inside a compound statement (7.3.4, 7.6.1, 7.12.2).
--- The value of an argument to a character handling function is neither equal to the value
- of EOF nor representable as an unsigned char (7.4).
--- A macro definition of errno is suppressed in order to access an actual object, or the
- program defines an identifier with the name errno (7.5).
--- Part of the program tests floating-point status flags, sets floating-point control modes,
- or runs under non-default mode settings, but was translated with the state for the
- FENV_ACCESS pragma ''off'' (7.6.1).
--- The exception-mask argument for one of the functions that provide access to the
- floating-point status flags has a nonzero value not obtained by bitwise OR of the
- floating-point exception macros (7.6.2).
--- The fesetexceptflag function is used to set floating-point status flags that were
- not specified in the call to the fegetexceptflag function that provided the value
- of the corresponding fexcept_t object (7.6.2.4).
-
-
-
-[page 559]
-
--- The argument to fesetenv or feupdateenv is neither an object set by a call to
- fegetenv or feholdexcept, nor is it an environment macro (7.6.4.3, 7.6.4.4).
--- The value of the result of an integer arithmetic or conversion function cannot be
- represented (7.8.2.1, 7.8.2.2, 7.8.2.3, 7.8.2.4, 7.22.6.1, 7.22.6.2, 7.22.1).
--- The program modifies the string pointed to by the value returned by the setlocale
- function (7.11.1.1).
--- The program modifies the structure pointed to by the value returned by the
- localeconv function (7.11.2.1).
--- A macro definition of math_errhandling is suppressed or the program defines
- an identifier with the name math_errhandling (7.12).
--- An argument to a floating-point classification or comparison macro is not of real
- floating type (7.12.3, 7.12.14).
--- A macro definition of setjmp is suppressed in order to access an actual function, or
- the program defines an external identifier with the name setjmp (7.13).
--- An invocation of the setjmp macro occurs other than in an allowed context
- (7.13.2.1).
--- The longjmp function is invoked to restore a nonexistent environment (7.13.2.1).
--- After a longjmp, there is an attempt to access the value of an object of automatic
- storage duration that does not have volatile-qualified type, local to the function
- containing the invocation of the corresponding setjmp macro, that was changed
- between the setjmp invocation and longjmp call (7.13.2.1).
--- The program specifies an invalid pointer to a signal handler function (7.14.1.1).
--- A signal handler returns when the signal corresponded to a computational exception
- (7.14.1.1).
--- A signal occurs as the result of calling the abort or raise function, and the signal
- handler calls the raise function (7.14.1.1).
--- A signal occurs other than as the result of calling the abort or raise function, and
- the signal handler refers to an object with static storage duration other than by
- assigning a value to an object declared as volatile sig_atomic_t, or calls any
- function in the standard library other than the abort function, the _Exit function,
- the quick_exit function, or the signal function (for the same signal number)
- (7.14.1.1).
--- The value of errno is referred to after a signal occurred other than as the result of
- calling the abort or raise function and the corresponding signal handler obtained
- a SIG_ERR return from a call to the signal function (7.14.1.1).
-
-[page 560]
-
--- A signal is generated by an asynchronous signal handler (7.14.1.1).
--- A function with a variable number of arguments attempts to access its varying
- arguments other than through a properly declared and initialized va_list object, or
- before the va_start macro is invoked (7.16, 7.16.1.1, 7.16.1.4).
--- The macro va_arg is invoked using the parameter ap that was passed to a function
- that invoked the macro va_arg with the same parameter (7.16).
--- A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in
- order to access an actual function, or the program defines an external identifier with
- the name va_copy or va_end (7.16.1).
--- The va_start or va_copy macro is invoked without a corresponding invocation
- of the va_end macro in the same function, or vice versa (7.16.1, 7.16.1.2, 7.16.1.3,
- 7.16.1.4).
--- The type parameter to the va_arg macro is not such that a pointer to an object of
- that type can be obtained simply by postfixing a * (7.16.1.1).
--- The va_arg macro is invoked when there is no actual next argument, or with a
- specified type that is not compatible with the promoted type of the actual next
- argument, with certain exceptions (7.16.1.1).
--- The va_copy or va_start macro is called to initialize a va_list that was
- previously initialized by either macro without an intervening invocation of the
- va_end macro for the same va_list (7.16.1.2, 7.16.1.4).
--- The parameter parmN of a va_start macro is declared with the register
- storage class, with a function or array type, or with a type that is not compatible with
- the type that results after application of the default argument promotions (7.16.1.4).
--- The member designator parameter of an offsetof macro is an invalid right
- operand of the . operator for the type parameter, or designates a bit-field (7.19).
--- The argument in an instance of one of the integer-constant macros is not a decimal,
- octal, or hexadecimal constant, or it has a value that exceeds the limits for the
- corresponding type (7.20.4).
--- A byte input/output function is applied to a wide-oriented stream, or a wide character
- input/output function is applied to a byte-oriented stream (7.21.2).
--- Use is made of any portion of a file beyond the most recent wide character written to
- a wide-oriented stream (7.21.2).
--- The value of a pointer to a FILE object is used after the associated file is closed
- (7.21.3).
--- The stream for the fflush function points to an input stream or to an update stream
- in which the most recent operation was input (7.21.5.2).
-[page 561]
-
--- The string pointed to by the mode argument in a call to the fopen function does not
- exactly match one of the specified character sequences (7.21.5.3).
--- An output operation on an update stream is followed by an input operation without an
- intervening call to the fflush function or a file positioning function, or an input
- operation on an update stream is followed by an output operation with an intervening
- call to a file positioning function (7.21.5.3).
--- An attempt is made to use the contents of the array that was supplied in a call to the
- setvbuf function (7.21.5.6).
--- There are insufficient arguments for the format in a call to one of the formatted
- input/output functions, or an argument does not have an appropriate type (7.21.6.1,
- 7.21.6.2, 7.28.2.1, 7.28.2.2).
--- The format in a call to one of the formatted input/output functions or to the
- strftime or wcsftime function is not a valid multibyte character sequence that
- begins and ends in its initial shift state (7.21.6.1, 7.21.6.2, 7.26.3.5, 7.28.2.1, 7.28.2.2,
- 7.28.5.1).
--- In a call to one of the formatted output functions, a precision appears with a
- conversion specifier other than those described (7.21.6.1, 7.28.2.1).
--- A conversion specification for a formatted output function uses an asterisk to denote
- an argument-supplied field width or precision, but the corresponding argument is not
- provided (7.21.6.1, 7.28.2.1).
--- A conversion specification for a formatted output function uses a # or 0 flag with a
- conversion specifier other than those described (7.21.6.1, 7.28.2.1).
--- A conversion specification for one of the formatted input/output functions uses a
- length modifier with a conversion specifier other than those described (7.21.6.1,
- 7.21.6.2, 7.28.2.1, 7.28.2.2).
--- An s conversion specifier is encountered by one of the formatted output functions,
- and the argument is missing the null terminator (unless a precision is specified that
- does not require null termination) (7.21.6.1, 7.28.2.1).
--- An n conversion specification for one of the formatted input/output functions includes
- any flags, an assignment-suppressing character, a field width, or a precision (7.21.6.1,
- 7.21.6.2, 7.28.2.1, 7.28.2.2).
--- A % conversion specifier is encountered by one of the formatted input/output
- functions, but the complete conversion specification is not exactly %% (7.21.6.1,
- 7.21.6.2, 7.28.2.1, 7.28.2.2).
--- An invalid conversion specification is found in the format for one of the formatted
- input/output functions, or the strftime or wcsftime function (7.21.6.1, 7.21.6.2,
-
-[page 562]
-
- 7.26.3.5, 7.28.2.1, 7.28.2.2, 7.28.5.1).
--- The number of characters transmitted by a formatted output function is greater than
- INT_MAX (7.21.6.1, 7.21.6.3, 7.21.6.8, 7.21.6.10).
--- The result of a conversion by one of the formatted input functions cannot be
- represented in the corresponding object, or the receiving object does not have an
- appropriate type (7.21.6.2, 7.28.2.2).
--- A c, s, or [ conversion specifier is encountered by one of the formatted input
- functions, and the array pointed to by the corresponding argument is not large enough
- to accept the input sequence (and a null terminator if the conversion specifier is s or
- [) (7.21.6.2, 7.28.2.2).
--- A c, s, or [ conversion specifier with an l qualifier is encountered by one of the
- formatted input functions, but the input is not a valid multibyte character sequence
- that begins in the initial shift state (7.21.6.2, 7.28.2.2).
--- The input item for a %p conversion by one of the formatted input functions is not a
- value converted earlier during the same program execution (7.21.6.2, 7.28.2.2).
--- The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf,
- vsscanf, vfwprintf, vfwscanf, vswprintf, vswscanf, vwprintf, or
- vwscanf function is called with an improperly initialized va_list argument, or
- the argument is used (other than in an invocation of va_end) after the function
- returns (7.21.6.8, 7.21.6.9, 7.21.6.10, 7.21.6.11, 7.21.6.12, 7.21.6.13, 7.21.6.14,
- 7.28.2.5, 7.28.2.6, 7.28.2.7, 7.28.2.8, 7.28.2.9, 7.28.2.10).
--- The contents of the array supplied in a call to the fgets or fgetws function are
- used after a read error occurred (7.21.7.2, 7.28.3.2).
--- The file position indicator for a binary stream is used after a call to the ungetc
- function where its value was zero before the call (7.21.7.10).
--- The file position indicator for a stream is used after an error occurred during a call to
- the fread or fwrite function (7.21.8.1, 7.21.8.2).
--- A partial element read by a call to the fread function is used (7.21.8.1).
--- The fseek function is called for a text stream with a nonzero offset and either the
- offset was not returned by a previous successful call to the ftell function on a
- stream associated with the same file or whence is not SEEK_SET (7.21.9.2).
--- The fsetpos function is called to set a position that was not returned by a previous
- successful call to the fgetpos function on a stream associated with the same file
- (7.21.9.3).
--- A non-null pointer returned by a call to the calloc, malloc, or realloc function
- with a zero requested size is used to access an object (7.22.3).
-
-[page 563]
-
--- The value of a pointer that refers to space deallocated by a call to the free or
- realloc function is used (7.22.3).
--- The alignment requested of the aligned_alloc function is not valid or not
- supported by the implementation, or the size requested is not an integral multiple of
- the alignment (7.22.3.1).
--- The pointer argument to the free or realloc function does not match a pointer
- earlier returned by a memory management function, or the space has been deallocated
- by a call to free or realloc (7.22.3.3, 7.22.3.5).
--- The value of the object allocated by the malloc function is used (7.22.3.4).
--- The value of any bytes in a new object allocated by the realloc function beyond
- the size of the old object are used (7.22.3.5).
--- The program calls the exit or quick_exit function more than once, or calls both
- functions (7.22.4.4, 7.22.4.7).
--- During the call to a function registered with the atexit or at_quick_exit
- function, a call is made to the longjmp function that would terminate the call to the
- registered function (7.22.4.4, 7.22.4.7).
--- The string set up by the getenv or strerror function is modified by the program
- (7.22.4.6, 7.23.6.2).
--- A command is executed through the system function in a way that is documented as
- causing termination or some other form of undefined behavior (7.22.4.8).
--- A searching or sorting utility function is called with an invalid pointer argument, even
- if the number of elements is zero (7.22.5).
--- The comparison function called by a searching or sorting utility function alters the
- contents of the array being searched or sorted, or returns ordering values
- inconsistently (7.22.5).
--- The array being searched by the bsearch function does not have its elements in
- proper order (7.22.5.1).
--- The current conversion state is used by a multibyte/wide character conversion
- function after changing the LC_CTYPE category (7.22.7).
--- A string or wide string utility function is instructed to access an array beyond the end
- of an object (7.23.1, 7.28.4).
--- A string or wide string utility function is called with an invalid pointer argument, even
- if the length is zero (7.23.1, 7.28.4).
--- The contents of the destination array are used after a call to the strxfrm,
- strftime, wcsxfrm, or wcsftime function in which the specified length was
-
-[page 564]
-
- too small to hold the entire null-terminated result (7.23.4.5, 7.26.3.5, 7.28.4.4.4,
- 7.28.5.1).
--- The first argument in the very first call to the strtok or wcstok is a null pointer
- (7.23.5.8, 7.28.4.5.7).
--- The type of an argument to a type-generic macro is not compatible with the type of
- the corresponding parameter of the selected function (7.24).
--- A complex argument is supplied for a generic parameter of a type-generic macro that
- has no corresponding complex function (7.24).
--- At least one field of the broken-down time passed to asctime contains a value
- outside its normal range, or the calculated year exceeds four digits or is less than the
- year 1000 (7.26.3.1).
--- The argument corresponding to an s specifier without an l qualifier in a call to the
- fwprintf function does not point to a valid multibyte character sequence that
- begins in the initial shift state (7.28.2.11).
--- In a call to the wcstok function, the object pointed to by ptr does not have the
- value stored by the previous call for the same wide string (7.28.4.5.7).
--- An mbstate_t object is used inappropriately (7.28.6).
--- The value of an argument of type wint_t to a wide character classification or case
- mapping function is neither equal to the value of WEOF nor representable as a
- wchar_t (7.29.1).
--- The iswctype function is called using a different LC_CTYPE category from the
- one in effect for the call to the wctype function that returned the description
- (7.29.2.2.1).
--- The towctrans function is called using a different LC_CTYPE category from the
- one in effect for the call to the wctrans function that returned the description
- (7.29.3.2.1).
-
-
-
-
-[page 565]
-
- J.3 Implementation-defined behavior
-1 A conforming implementation is required to document its choice of behavior in each of
- the areas listed in this subclause. The following are implementation-defined:
- J.3.1 Translation
-1 -- How a diagnostic is identified (3.10, 5.1.1.3).
- -- Whether each nonempty sequence of white-space characters other than new-line is
- retained or replaced by one space character in translation phase 3 (5.1.1.2).
- J.3.2 Environment
-1 -- The mapping between physical source file multibyte characters and the source
- character set in translation phase 1 (5.1.1.2).
- -- The name and type of the function called at program startup in a freestanding
- environment (5.1.2.1).
- -- The effect of program termination in a freestanding environment (5.1.2.1).
- -- An alternative manner in which the main function may be defined (5.1.2.2.1).
- -- The values given to the strings pointed to by the argv argument to main (5.1.2.2.1).
- -- What constitutes an interactive device (5.1.2.3).
- -- Whether a program can have more than one thread of execution in a freestanding
- environment (5.1.2.4).
- -- The set of signals, their semantics, and their default handling (7.14).
- -- Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
- computational exception (7.14.1.1).
- -- Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
- program startup (7.14.1.1).
- -- The set of environment names and the method for altering the environment list used
- by the getenv function (7.22.4.6).
- -- The manner of execution of the string by the system function (7.22.4.8).
-
-
-
-
-[page 566]
-
- J.3.3 Identifiers
-1 -- Which additional multibyte characters may appear in identifiers and their
- correspondence to universal character names (6.4.2).
- -- The number of significant initial characters in an identifier (5.2.4.1, 6.4.2).
- J.3.4 Characters
-1 -- The number of bits in a byte (3.6).
- -- The values of the members of the execution character set (5.2.1).
- -- The unique value of the member of the execution character set produced for each of
- the standard alphabetic escape sequences (5.2.2).
- -- The value of a char object into which has been stored any character other than a
- member of the basic execution character set (6.2.5).
- -- Which of signed char or unsigned char has the same range, representation,
- and behavior as ''plain'' char (6.2.5, 6.3.1.1).
- -- The mapping of members of the source character set (in character constants and string
- literals) to members of the execution character set (6.4.4.4, 5.1.1.2).
- -- The value of an integer character constant containing more than one character or
- containing a character or escape sequence that does not map to a single-byte
- execution character (6.4.4.4).
- -- The value of a wide character constant containing more than one multibyte character
- or a single multibyte character that maps to multiple members of the extended
- execution character set, or containing a multibyte character or escape sequence not
- represented in the extended execution character set (6.4.4.4).
- -- The current locale used to convert a wide character constant consisting of a single
- multibyte character that maps to a member of the extended execution character set
- into a corresponding wide character code (6.4.4.4).
- -- Whether differently-prefixed wide string literal tokens can be concatenated and, if so,
- the treatment of the resulting multibyte character sequence (6.4.5).
- -- The current locale used to convert a wide string literal into corresponding wide
- character codes (6.4.5).
- -- The value of a string literal containing a multibyte character or escape sequence not
- represented in the execution character set (6.4.5).
- -- The encoding of any of wchar_t, char16_t, and char32_t where the
- corresponding standard encoding macro (__STDC_ISO_10646__,
- __STDC_UTF_16__, or __STDC_UTF_32__) is not defined (6.10.8.2).
-
-[page 567]
-
- J.3.5 Integers
-1 -- Any extended integer types that exist in the implementation (6.2.5).
- -- Whether signed integer types are represented using sign and magnitude, two's
- complement, or ones' complement, and whether the extraordinary value is a trap
- representation or an ordinary value (6.2.6.2).
- -- The rank of any extended integer type relative to another extended integer type with
- the same precision (6.3.1.1).
- -- The result of, or the signal raised by, converting an integer to a signed integer type
- when the value cannot be represented in an object of that type (6.3.1.3).
- -- The results of some bitwise operations on signed integers (6.5).
- J.3.6 Floating point
-1 -- The accuracy of the floating-point operations and of the library functions in
- <math.h> and <complex.h> that return floating-point results (5.2.4.2.2).
- -- The accuracy of the conversions between floating-point internal representations and
- string representations performed by the library functions in <stdio.h>,
- <stdlib.h>, and <wchar.h> (5.2.4.2.2).
- -- The rounding behaviors characterized by non-standard values of FLT_ROUNDS
- (5.2.4.2.2).
- -- The evaluation methods characterized by non-standard negative values of
- FLT_EVAL_METHOD (5.2.4.2.2).
- -- The direction of rounding when an integer is converted to a floating-point number that
- cannot exactly represent the original value (6.3.1.4).
- -- The direction of rounding when a floating-point number is converted to a narrower
- floating-point number (6.3.1.5).
- -- How the nearest representable value or the larger or smaller representable value
- immediately adjacent to the nearest representable value is chosen for certain floating
- constants (6.4.4.2).
- -- Whether and how floating expressions are contracted when not disallowed by the
- FP_CONTRACT pragma (6.5).
- -- The default state for the FENV_ACCESS pragma (7.6.1).
- -- Additional floating-point exceptions, rounding modes, environments, and
- classifications, and their macro names (7.6, 7.12).
- -- The default state for the FP_CONTRACT pragma (7.12.2).
-
-
-[page 568]
-
- J.3.7 Arrays and pointers
-1 -- The result of converting a pointer to an integer or vice versa (6.3.2.3).
- -- The size of the result of subtracting two pointers to elements of the same array
- (6.5.6).
- J.3.8 Hints
-1 -- The extent to which suggestions made by using the register storage-class
- specifier are effective (6.7.1).
- -- The extent to which suggestions made by using the inline function specifier are
- effective (6.7.4).
- J.3.9 Structures, unions, enumerations, and bit-fields
-1 -- Whether a ''plain'' int bit-field is treated as a signed int bit-field or as an
- unsigned int bit-field (6.7.2, 6.7.2.1).
- -- Allowable bit-field types other than _Bool, signed int, and unsigned int
- (6.7.2.1).
- -- Whether a bit-field can straddle a storage-unit boundary (6.7.2.1).
- -- The order of allocation of bit-fields within a unit (6.7.2.1).
- -- The alignment of non-bit-field members of structures (6.7.2.1). This should present
- no problem unless binary data written by one implementation is read by another.
- -- The integer type compatible with each enumerated type (6.7.2.2).
- J.3.10 Qualifiers
-1 -- What constitutes an access to an object that has volatile-qualified type (6.7.3).
- J.3.11 Preprocessing directives
-1 -- The locations within #pragma directives where header name preprocessing tokens
- are recognized (6.4, 6.4.7).
- -- How sequences in both forms of header names are mapped to headers or external
- source file names (6.4.7).
- -- Whether the value of a character constant in a constant expression that controls
- conditional inclusion matches the value of the same character constant in the
- execution character set (6.10.1).
- -- Whether the value of a single-character character constant in a constant expression
- that controls conditional inclusion may have a negative value (6.10.1).
- -- The places that are searched for an included < > delimited header, and how the places
- are specified or the header is identified (6.10.2).
-[page 569]
-
- -- How the named source file is searched for in an included " " delimited header
- (6.10.2).
- -- The method by which preprocessing tokens (possibly resulting from macro
- expansion) in a #include directive are combined into a header name (6.10.2).
- -- The nesting limit for #include processing (6.10.2).
- -- Whether the # operator inserts a \ character before the \ character that begins a
- universal character name in a character constant or string literal (6.10.3.2).
- -- The behavior on each recognized non-STDC #pragma directive (6.10.6).
- -- The definitions for __DATE__ and __TIME__ when respectively, the date and
- time of translation are not available (6.10.8.1).
- J.3.12 Library functions
-1 -- Any library facilities available to a freestanding program, other than the minimal set
- required by clause 4 (5.1.2.1).
- -- The format of the diagnostic printed by the assert macro (7.2.1.1).
- -- The representation of the floating-point status flags stored by the
- fegetexceptflag function (7.6.2.2).
- -- Whether the feraiseexcept function raises the ''inexact'' floating-point
- exception in addition to the ''overflow'' or ''underflow'' floating-point exception
- (7.6.2.3).
- -- Strings other than "C" and "" that may be passed as the second argument to the
- setlocale function (7.11.1.1).
- -- The types defined for float_t and double_t when the value of the
- FLT_EVAL_METHOD macro is less than 0 (7.12).
- -- Domain errors for the mathematics functions, other than those required by this
- International Standard (7.12.1).
- -- The values returned by the mathematics functions on domain errors or pole errors
- (7.12.1).
- -- The values returned by the mathematics functions on underflow range errors, whether
- errno is set to the value of the macro ERANGE when the integer expression
- math_errhandling & MATH_ERRNO is nonzero, and whether the ''underflow''
- floating-point exception is raised when the integer expression math_errhandling
- & MATH_ERREXCEPT is nonzero. (7.12.1).
- -- Whether a domain error occurs or zero is returned when an fmod function has a
- second argument of zero (7.12.10.1).
-
-[page 570]
-
--- Whether a domain error occurs or zero is returned when a remainder function has
- a second argument of zero (7.12.10.2).
--- The base-2 logarithm of the modulus used by the remquo functions in reducing the
- quotient (7.12.10.3).
--- Whether a domain error occurs or zero is returned when a remquo function has a
- second argument of zero (7.12.10.3).
--- Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call
- of a signal handler, and, if not, the blocking of signals that is performed (7.14.1.1).
--- The null pointer constant to which the macro NULL expands (7.19).
--- Whether the last line of a text stream requires a terminating new-line character
- (7.21.2).
--- Whether space characters that are written out to a text stream immediately before a
- new-line character appear when read in (7.21.2).
--- The number of null characters that may be appended to data written to a binary
- stream (7.21.2).
--- Whether the file position indicator of an append-mode stream is initially positioned at
- the beginning or end of the file (7.21.3).
--- Whether a write on a text stream causes the associated file to be truncated beyond that
- point (7.21.3).
--- The characteristics of file buffering (7.21.3).
--- Whether a zero-length file actually exists (7.21.3).
--- The rules for composing valid file names (7.21.3).
--- Whether the same file can be simultaneously open multiple times (7.21.3).
--- The nature and choice of encodings used for multibyte characters in files (7.21.3).
--- The effect of the remove function on an open file (7.21.4.1).
--- The effect if a file with the new name exists prior to a call to the rename function
- (7.21.4.2).
--- Whether an open temporary file is removed upon abnormal program termination
- (7.21.4.3).
--- Which changes of mode are permitted (if any), and under what circumstances
- (7.21.5.4).
--- The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
- sequence printed for a NaN (7.21.6.1, 7.28.2.1).
-
-[page 571]
-
--- The output for %p conversion in the fprintf or fwprintf function (7.21.6.1,
- 7.28.2.1).
--- The interpretation of a - character that is neither the first nor the last character, nor
- the second where a ^ character is the first, in the scanlist for %[ conversion in the
- fscanf or fwscanf function (7.21.6.2, 7.28.2.1).
--- The set of sequences matched by a %p conversion and the interpretation of the
- corresponding input item in the fscanf or fwscanf function (7.21.6.2, 7.28.2.2).
--- The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
- functions on failure (7.21.9.1, 7.21.9.3, 7.21.9.4).
--- The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
- converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold
- function (7.22.1.3, 7.28.4.1.1).
--- Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
- function sets errno to ERANGE when underflow occurs (7.22.1.3, 7.28.4.1.1).
--- Whether the calloc, malloc, and realloc functions return a null pointer or a
- pointer to an allocated object when the size requested is zero (7.22.3).
--- Whether open streams with unwritten buffered data are flushed, open streams are
- closed, or temporary files are removed when the abort or _Exit function is called
- (7.22.4.1, 7.22.4.5).
--- The termination status returned to the host environment by the abort, exit,
- _Exit, or quick_exit function (7.22.4.1, 7.22.4.4, 7.22.4.5, 7.22.4.7).
--- The value returned by the system function when its argument is not a null pointer
- (7.22.4.8).
--- The local time zone and Daylight Saving Time (7.26.1).
--- The range and precision of times representable in clock_t and time_t (7.26).
--- The era for the clock function (7.26.2.1).
--- The replacement string for the %Z specifier to the strftime, and wcsftime
- functions in the "C" locale (7.26.3.5, 7.28.5.1).
--- Whether the functions in <math.h> honor the rounding direction mode in an
- IEC 60559 conformant implementation, unless explicitly specified otherwise (F.10).
-
-
-
-
-[page 572]
-
- J.3.13 Architecture
-1 -- The values or expressions assigned to the macros specified in the headers
- <float.h>, <limits.h>, and <stdint.h> (5.2.4.2, 7.20.2, 7.20.3).
- -- The result of attempting to indirectly access an object with automatic or thread
- storage duration from a thread other than the one with which it is associated (6.2.4).
- -- The number, order, and encoding of bytes in any object (when not explicitly specified
- in this International Standard) (6.2.6.1).
- -- Whether any extended alignments are supported and the contexts in which they are
- supported (6.2.8).
- -- Valid alignment values other than those returned by an alignof expression for
- fundamental types, if any (6.2.8).
- -- The value of the result of the sizeof and alignof operators (6.5.3.4).
- J.4 Locale-specific behavior
-1 The following characteristics of a hosted environment are locale-specific and are required
- to be documented by the implementation:
- -- Additional members of the source and execution character sets beyond the basic
- character set (5.2.1).
- -- The presence, meaning, and representation of additional multibyte characters in the
- execution character set beyond the basic character set (5.2.1.2).
- -- The shift states used for the encoding of multibyte characters (5.2.1.2).
- -- The direction of writing of successive printing characters (5.2.2).
- -- The decimal-point character (7.1.1).
- -- The set of printing characters (7.4, 7.29.2).
- -- The set of control characters (7.4, 7.29.2).
- -- The sets of characters tested for by the isalpha, isblank, islower, ispunct,
- isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
- iswspace, or iswupper functions (7.4.1.2, 7.4.1.3, 7.4.1.7, 7.4.1.9, 7.4.1.10,
- 7.4.1.11, 7.29.2.1.2, 7.29.2.1.3, 7.29.2.1.7, 7.29.2.1.9, 7.29.2.1.10, 7.29.2.1.11).
- -- The native environment (7.11.1.1).
- -- Additional subject sequences accepted by the numeric conversion functions (7.22.1,
- 7.28.4.1).
- -- The collation sequence of the execution character set (7.23.4.3, 7.28.4.4.2).
-
-
-[page 573]
-
- -- The contents of the error message strings set up by the strerror function
- (7.23.6.2).
- -- The formats for time and date (7.26.3.5, 7.28.5.1).
- -- Character mappings that are supported by the towctrans function (7.29.1).
- -- Character classifications that are supported by the iswctype function (7.29.1).
- J.5 Common extensions
-1 The following extensions are widely used in many systems, but are not portable to all
- implementations. The inclusion of any extension that may cause a strictly conforming
- program to become invalid renders an implementation nonconforming. Examples of such
- extensions are new keywords, extra library functions declared in standard headers, or
- predefined macros with names that do not begin with an underscore.
- J.5.1 Environment arguments
-1 In a hosted environment, the main function receives a third argument, char *envp[],
- that points to a null-terminated array of pointers to char, each of which points to a string
- that provides information about the environment for this execution of the program
- (5.1.2.2.1).
- J.5.2 Specialized identifiers
-1 Characters other than the underscore _, letters, and digits, that are not part of the basic
- source character set (such as the dollar sign $, or characters in national character sets)
- may appear in an identifier (6.4.2).
- J.5.3 Lengths and cases of identifiers
-1 All characters in identifiers (with or without external linkage) are significant (6.4.2).
- J.5.4 Scopes of identifiers
-1 A function identifier, or the identifier of an object the declaration of which contains the
- keyword extern, has file scope (6.2.1).
- J.5.5 Writable string literals
-1 String literals are modifiable (in which case, identical string literals should denote distinct
- objects) (6.4.5).
-
-
-
-
-[page 574]
-
- J.5.6 Other arithmetic types
-1 Additional arithmetic types, such as __int128 or double double, and their
- appropriate conversions are defined (6.2.5, 6.3.1). Additional floating types may have
- more range or precision than long double, may be used for evaluating expressions of
- other floating types, and may be used to define float_t or double_t.
- J.5.7 Function pointer casts
-1 A pointer to an object or to void may be cast to a pointer to a function, allowing data to
- be invoked as a function (6.5.4).
-2 A pointer to a function may be cast to a pointer to an object or to void, allowing a
- function to be inspected or modified (for example, by a debugger) (6.5.4).
- J.5.8 Extended bit-field types
-1 A bit-field may be declared with a type other than _Bool, unsigned int, or
- signed int, with an appropriate maximum width (6.7.2.1).
- J.5.9 The fortran keyword
-1 The fortran function specifier may be used in a function declaration to indicate that
- calls suitable for FORTRAN should be generated, or that a different representation for the
- external name is to be generated (6.7.4).
- J.5.10 The asm keyword
-1 The asm keyword may be used to insert assembly language directly into the translator
- output (6.8). The most common implementation is via a statement of the form:
- asm ( character-string-literal );
- J.5.11 Multiple external definitions
-1 There may be more than one external definition for the identifier of an object, with or
- without the explicit use of the keyword extern; if the definitions disagree, or more than
- one is initialized, the behavior is undefined (6.9.2).
- J.5.12 Predefined macro names
-1 Macro names that do not begin with an underscore, describing the translation and
- execution environments, are defined by the implementation before translation begins
- (6.10.8).
-
-
-
-
-[page 575]
-
- J.5.13 Floating-point status flags
-1 If any floating-point status flags are set on normal termination after all calls to functions
- registered by the atexit function have been made (see 7.22.4.4), the implementation
- writes some diagnostics indicating the fact to the stderr stream, if it is still open,
- J.5.14 Extra arguments for signal handlers
-1 Handlers for specific signals are called with extra arguments in addition to the signal
- number (7.14.1.1).
- J.5.15 Additional stream types and file-opening modes
-1 Additional mappings from files to streams are supported (7.21.2).
-2 Additional file-opening modes may be specified by characters appended to the mode
- argument of the fopen function (7.21.5.3).
- J.5.16 Defined file position indicator
-1 The file position indicator is decremented by each successful call to the ungetc or
- ungetwc function for a text stream, except if its value was zero before a call (7.21.7.10,
- 7.28.3.10).
- J.5.17 Math error reporting
-1 Functions declared in <complex.h> and <math.h> raise SIGFPE to report errors
- instead of, or in addition to, setting errno or raising floating-point exceptions (7.3,
- 7.12).
-
-
-
-
-[page 576]
-
- Annex K
- (normative)
- Bounds-checking interfaces
- K.1 Background
-1 Traditionally, the C Library has contained many functions that trust the programmer to
- provide output character arrays big enough to hold the result being produced. Not only
- do these functions not check that the arrays are big enough, they frequently lack the
- information needed to perform such checks. While it is possible to write safe, robust, and
- error-free code using the existing library, the library tends to promote programming styles
- that lead to mysterious failures if a result is too big for the provided array.
-2 A common programming style is to declare character arrays large enough to handle most
- practical cases. However, if these arrays are not large enough to handle the resulting
- strings, data can be written past the end of the array overwriting other data and program
- structures. The program never gets any indication that a problem exists, and so never has
- a chance to recover or to fail gracefully.
-3 Worse, this style of programming has compromised the security of computers and
- networks. Buffer overflows can often be exploited to run arbitrary code with the
- permissions of the vulnerable (defective) program.
-4 If the programmer writes runtime checks to verify lengths before calling library
- functions, then those runtime checks frequently duplicate work done inside the library
- functions, which discover string lengths as a side effect of doing their job.
-5 This annex provides alternative library functions that promote safer, more secure
- programming. The alternative functions verify that output buffers are large enough for
- the intended result and return a failure indicator if they are not. Data is never written past
- the end of an array. All string results are null terminated.
-6 This annex also addresses another problem that complicates writing robust code:
- functions that are not reentrant because they return pointers to static objects owned by the
- function. Such functions can be troublesome since a previously returned result can
- change if the function is called again, perhaps by another thread.
-
-
-
-
-[page 577]
-
- K.2 Scope
-1 This annex specifies a series of optional extensions that can be useful in the mitigation of
- security vulnerabilities in programs, and comprise new functions, macros, and types
- declared or defined in existing standard headers.
-2 An implementation that defines __STDC_LIB_EXT1__ shall conform to the
- specifications in this annex.361)
-3 Subclause K.3 should be read as if it were merged into the parallel structure of named
- subclauses of clause 7.
- K.3 Library
- K.3.1 Introduction
- K.3.1.1 Standard headers
-1 The functions, macros, and types declared or defined in K.3 and its subclauses are not
- declared or defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
- defined as a macro which expands to the integer constant 0 at the point in the source file
- where the appropriate header is first included.
-2 The functions, macros, and types declared or defined in K.3 and its subclauses are
- declared and defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
- defined as a macro which expands to the integer constant 1 at the point in the source file
- where the appropriate header is first included.362)
-3 It is implementation-defined whether the functions, macros, and types declared or defined
- in K.3 and its subclauses are declared or defined by their respective headers if
- __STDC_WANT_LIB_EXT1__ is not defined as a macro at the point in the source file
- where the appropriate header is first included.363)
-4 Within a preprocessing translation unit, __STDC_WANT_LIB_EXT1__ shall be
- defined identically for all inclusions of any headers from subclause K.3. If
- __STDC_WANT_LIB_EXT1__ is defined differently for any such inclusion, the
- implementation shall issue a diagnostic as if a preprocessor error directive were used.
-
-
- 361) Implementations that do not define __STDC_LIB_EXT1__ are not required to conform to these
- specifications.
- 362) Future revisions of this International Standard may define meanings for other values of
- __STDC_WANT_LIB_EXT1__.
- 363) Subclause 7.1.3 reserves certain names and patterns of names that an implementation may use in
- headers. All other names are not reserved, and a conforming implementation is not permitted to use
- them. While some of the names defined in K.3 and its subclauses are reserved, others are not. If an
- unreserved name is defined in a header when __STDC_WANT_LIB_EXT1__ is defined as 0, the
- implementation is not conforming.
-
-[page 578]
-
- K.3.1.2 Reserved identifiers
-1 Each macro name in any of the following subclauses is reserved for use as specified if it
- is defined by any of its associated headers when included; unless explicitly stated
- otherwise (see 7.1.4).
-2 All identifiers with external linkage in any of the following subclauses are reserved for
- use as identifiers with external linkage if any of them are used by the program. None of
- them are reserved if none of them are used.
-3 Each identifier with file scope listed in any of the following subclauses is reserved for use
- as a macro name and as an identifier with file scope in the same name space if it is
- defined by any of its associated headers when included.
- K.3.1.3 Use of errno
-1 An implementation may set errno for the functions defined in this annex, but is not
- required to.
- K.3.1.4 Runtime-constraint violations
-1 Most functions in this annex include as part of their specification a list of runtime-
- constraints. These runtime-constraints are requirements on the program using the
- library.364)
-2 Implementations shall verify that the runtime-constraints for a function are not violated
- by the program. If a runtime-constraint is violated, the implementation shall call the
- currently registered runtime-constraint handler (see set_constraint_handler_s
- in <stdlib.h>). Multiple runtime-constraint violations in the same call to a library
- function result in only one call to the runtime-constraint handler. It is unspecified which
- one of the multiple runtime-constraint violations cause the handler to be called.
-3 If the runtime-constraints section for a function states an action to be performed when a
- runtime-constraint violation occurs, the function shall perform the action before calling
- the runtime-constraint handler. If the runtime-constraints section lists actions that are
- prohibited when a runtime-constraint violation occurs, then such actions are prohibited to
- the function both before calling the handler and after the handler returns.
-4 The runtime-constraint handler might not return. If the handler does return, the library
- function whose runtime-constraint was violated shall return some indication of failure as
- given by the returns section in the function's specification.
-
-
-
- 364) Although runtime-constraints replace many cases of undefined behavior, undefined behavior still
- exists in this annex. Implementations are free to detect any case of undefined behavior and treat it as a
- runtime-constraint violation by calling the runtime-constraint handler. This license comes directly
- from the definition of undefined behavior.
-
-[page 579]
-
- K.3.2 Errors <errno.h>
-1 The header <errno.h> defines a type.
-2 The type is
- errno_t
- which is type int.365)
- K.3.3 Common definitions <stddef.h>
-1 The header <stddef.h> defines a type.
-2 The type is
- rsize_t
- which is the type size_t.366)
- K.3.4 Integer types <stdint.h>
-1 The header <stdint.h> defines a macro.
-2 The macro is
- RSIZE_MAX
- which expands to a value367) of type size_t. Functions that have parameters of type
- rsize_t consider it a runtime-constraint violation if the values of those parameters are
- greater than RSIZE_MAX.
- Recommended practice
-3 Extremely large object sizes are frequently a sign that an object's size was calculated
- incorrectly. For example, negative numbers appear as very large positive numbers when
- converted to an unsigned type like size_t. Also, some implementations do not support
- objects as large as the maximum value that can be represented by type size_t.
-4 For those reasons, it is sometimes beneficial to restrict the range of object sizes to detect
- programming errors. For implementations targeting machines with large address spaces,
- it is recommended that RSIZE_MAX be defined as the smaller of the size of the largest
- object supported or (SIZE_MAX >> 1), even if this limit is smaller than the size of
- some legitimate, but very large, objects. Implementations targeting machines with small
- address spaces may wish to define RSIZE_MAX as SIZE_MAX, which means that there
-
- 365) As a matter of programming style, errno_t may be used as the type of something that deals only
- with the values that might be found in errno. For example, a function which returns the value of
- errno might be declared as having the return type errno_t.
- 366) See the description of the RSIZE_MAX macro in <stdint.h>.
- 367) The macro RSIZE_MAX need not expand to a constant expression.
-
-[page 580]
-
- is no object size that is considered a runtime-constraint violation.
- K.3.5 Input/output <stdio.h>
-1 The header <stdio.h> defines several macros and two types.
-2 The macros are
- L_tmpnam_s
- which expands to an integer constant expression that is the size needed for an array of
- char large enough to hold a temporary file name string generated by the tmpnam_s
- function;
- TMP_MAX_S
- which expands to an integer constant expression that is the maximum number of unique
- file names that can be generated by the tmpnam_s function.
-3 The types are
- errno_t
- which is type int; and
- rsize_t
- which is the type size_t.
- K.3.5.1 Operations on files
- K.3.5.1.1 The tmpfile_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdio.h>
- errno_t tmpfile_s(FILE * restrict * restrict streamptr);
- Runtime-constraints
-2 streamptr shall not be a null pointer.
-3 If there is a runtime-constraint violation, tmpfile_s does not attempt to create a file.
- Description
-4 The tmpfile_s function creates a temporary binary file that is different from any other
- existing file and that will automatically be removed when it is closed or at program
- termination. If the program terminates abnormally, whether an open temporary file is
- removed is implementation-defined. The file is opened for update with "wb+" mode
- with the meaning that mode has in the fopen_s function (including the mode's effect
- on exclusive access and file permissions).
-
-
-[page 581]
-
-5 If the file was created successfully, then the pointer to FILE pointed to by streamptr
- will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
- to FILE pointed to by streamptr will be set to a null pointer.
- Recommended practice
- It should be possible to open at least TMP_MAX_S temporary files during the lifetime of
- the program (this limit may be shared with tmpnam_s) and there should be no limit on
- the number simultaneously open other than this limit and any limit on the number of open
- files (FOPEN_MAX).
- Returns
-6 The tmpfile_s function returns zero if it created the file. If it did not create the file or
- there was a runtime-constraint violation, tmpfile_s returns a nonzero value.
- K.3.5.1.2 The tmpnam_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdio.h>
- errno_t tmpnam_s(char *s, rsize_t maxsize);
- Runtime-constraints
-2 s shall not be a null pointer. maxsize shall be less than or equal to RSIZE_MAX.
- maxsize shall be greater than the length of the generated file name string.
- Description
-3 The tmpnam_s function generates a string that is a valid file name and that is not the
- same as the name of an existing file.368) The function is potentially capable of generating
- TMP_MAX_S different strings, but any or all of them may already be in use by existing
- files and thus not be suitable return values. The lengths of these strings shall be less than
- the value of the L_tmpnam_s macro.
-4 The tmpnam_s function generates a different string each time it is called.
-5 It is assumed that s points to an array of at least maxsize characters. This array will be
- set to generated string, as specified below.
-
-
-
- 368) Files created using strings generated by the tmpnam_s function are temporary only in the sense that
- their names should not collide with those generated by conventional naming rules for the
- implementation. It is still necessary to use the remove function to remove such files when their use
- is ended, and before program termination. Implementations should take care in choosing the patterns
- used for names returned by tmpnam_s. For example, making a thread id part of the names avoids the
- race condition and possible conflict when multiple programs run simultaneously by the same user
- generate the same temporary file names.
-
-[page 582]
-
-6 The implementation shall behave as if no library function except tmpnam calls the
- tmpnam_s function.369)
- Recommended practice
-7 After a program obtains a file name using the tmpnam_s function and before the
- program creates a file with that name, the possibility exists that someone else may create
- a file with that same name. To avoid this race condition, the tmpfile_s function
- should be used instead of tmpnam_s when possible. One situation that requires the use
- of the tmpnam_s function is when the program needs to create a temporary directory
- rather than a temporary file.
- Returns
-8 If no suitable string can be generated, or if there is a runtime-constraint violation, the
- tmpnam_s function writes a null character to s[0] (only if s is not null and maxsize
- is greater than zero) and returns a nonzero value.
-9 Otherwise, the tmpnam_s function writes the string in the array pointed to by s and
- returns zero.
- Environmental limits
-10 The value of the macro TMP_MAX_S shall be at least 25.
- K.3.5.2 File access functions
- K.3.5.2.1 The fopen_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdio.h>
- errno_t fopen_s(FILE * restrict * restrict streamptr,
- const char * restrict filename,
- const char * restrict mode);
- Runtime-constraints
-2 None of streamptr, filename, or mode shall be a null pointer.
-3 If there is a runtime-constraint violation, fopen_s does not attempt to open a file.
- Furthermore, if streamptr is not a null pointer, fopen_s sets *streamptr to the
- null pointer.
-
-
-
-
- 369) An implementation may have tmpnam call tmpnam_s (perhaps so there is only one naming
- convention for temporary files), but this is not required.
-
-[page 583]
-
- Description
-4 The fopen_s function opens the file whose name is the string pointed to by
- filename, and associates a stream with it.
-5 The mode string shall be as described for fopen, with the addition that modes starting
- with the character 'w' or 'a' may be preceded by the character 'u', see below:
- uw truncate to zero length or create text file for writing, default
- permissions
- uwx create text file for writing, default permissions
- ua append; open or create text file for writing at end-of-file, default
- permissions
- uwb truncate to zero length or create binary file for writing, default
- permissions
- uwbx create binary file for writing, default permissions
- uab append; open or create binary file for writing at end-of-file, default
- permissions
- uw+ truncate to zero length or create text file for update, default
- permissions
- uw+x create text file for update, default permissions
- ua+ append; open or create text file for update, writing at end-of-file,
- default permissions
- uw+b or uwb+ truncate to zero length or create binary file for update, default
- permissions
- uw+bx or uwb+x create binary file for update, default permissions
- ua+b or uab+ append; open or create binary file for update, writing at end-of-file,
- default permissions
-6 Opening a file with exclusive mode ('x' as the last character in the mode argument)
- fails if the file already exists or cannot be created.
-7 To the extent that the underlying system supports the concepts, files opened for writing
- shall be opened with exclusive (also known as non-shared) access. If the file is being
- created, and the first character of the mode string is not 'u', to the extent that the
- underlying system supports it, the file shall have a file permission that prevents other
- users on the system from accessing the file. If the file is being created and first character
- of the mode string is 'u', then by the time the file has been closed, it shall have the
- system default file access permissions.370)
-8 If the file was opened successfully, then the pointer to FILE pointed to by streamptr
- will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
-
-
- 370) These are the same permissions that the file would have been created with by fopen.
-
-[page 584]
-
- to FILE pointed to by streamptr will be set to a null pointer.
- Returns
-9 The fopen_s function returns zero if it opened the file. If it did not open the file or if
- there was a runtime-constraint violation, fopen_s returns a nonzero value.
- K.3.5.2.2 The freopen_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdio.h>
- errno_t freopen_s(FILE * restrict * restrict newstreamptr,
- const char * restrict filename,
- const char * restrict mode,
- FILE * restrict stream);
- Runtime-constraints
-2 None of newstreamptr, mode, and stream shall be a null pointer.
-3 If there is a runtime-constraint violation, freopen_s neither attempts to close any file
- associated with stream nor attempts to open a file. Furthermore, if newstreamptr is
- not a null pointer, fopen_s sets *newstreamptr to the null pointer.
- Description
-4 The freopen_s function opens the file whose name is the string pointed to by
- filename and associates the stream pointed to by stream with it. The mode
- argument has the same meaning as in the fopen_s function (including the mode's effect
- on exclusive access and file permissions).
-5 If filename is a null pointer, the freopen_s function attempts to change the mode of
- the stream to that specified by mode, as if the name of the file currently associated with
- the stream had been used. It is implementation-defined which changes of mode are
- permitted (if any), and under what circumstances.
-6 The freopen_s function first attempts to close any file that is associated with stream.
- Failure to close the file is ignored. The error and end-of-file indicators for the stream are
- cleared.
-7 If the file was opened successfully, then the pointer to FILE pointed to by
- newstreamptr will be set to the value of stream. Otherwise, the pointer to FILE
- pointed to by newstreamptr will be set to a null pointer.
- Returns
-8 The freopen_s function returns zero if it opened the file. If it did not open the file or
- there was a runtime-constraint violation, freopen_s returns a nonzero value.
-
-[page 585]
-
- K.3.5.3 Formatted input/output functions
-1 Unless explicitly stated otherwise, if the execution of a function described in this
- subclause causes copying to take place between objects that overlap, the objects take on
- unspecified values.
- K.3.5.3.1 The fprintf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdio.h>
- int fprintf_s(FILE * restrict stream,
- const char * restrict format, ...);
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. The %n specifier371) (modified or
- not by flags, field width, or precision) shall not appear in the string pointed to by
- format. Any argument to fprintf_s corresponding to a %s specifier shall not be a
- null pointer.
-3 If there is a runtime-constraint violation,372) the fprintf_s function does not attempt
- to produce further output, and it is unspecified to what extent fprintf_s produced
- output before discovering the runtime-constraint violation.
- Description
-4 The fprintf_s function is equivalent to the fprintf function except for the explicit
- runtime-constraints listed above.
- Returns
-5 The fprintf_s function returns the number of characters transmitted, or a negative
- value if an output error, encoding error, or runtime-constraint violation occurred.
-
-
-
-
- 371) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
- 372) Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
- implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
- constraint violation.
-
-[page 586]
-
- K.3.5.3.2 The fscanf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdio.h>
- int fscanf_s(FILE * restrict stream,
- const char * restrict format, ...);
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. Any argument indirected though in
- order to store converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation,373) the fscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent fscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The fscanf_s function is equivalent to fscanf except that the c, s, and [ conversion
- specifiers apply to a pair of arguments (unless assignment suppression is indicated by a
- *). The first of these arguments is the same as for fscanf. That argument is
- immediately followed in the argument list by the second argument, which has type
- rsize_t and gives the number of elements in the array pointed to by the first argument
- of the pair. If the first argument points to a scalar object, it is considered to be an array of
- one element.374)
-5 A matching failure occurs if the number of elements in a receiving object is insufficient to
- hold the converted input (including any trailing null character).
- Returns
-6 The fscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
-
- 373) Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
- implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
- constraint violation.
- 374) If the format is known at translation time, an implementation may issue a diagnostic for any argument
- used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
- argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
- the format is not known at translation time. For example, an implementation may issue a diagnostic
- for each argument after format that has of type pointer to one of char, signed char,
- unsigned char, or void that is not followed by an argument of a type compatible with
- rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
- using the hh length modifier, a length argument must follow the pointer argument. Another useful
- diagnostic could flag any non-pointer argument following format that did not have a type
- compatible with rsize_t.
-
-[page 587]
-
- fscanf_s function returns the number of input items assigned, which can be fewer than
- provided for, or even zero, in the event of an early matching failure.
-7 EXAMPLE 1 The call:
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdio.h>
- /* ... */
- int n, i; float x; char name[50];
- n = fscanf_s(stdin, "%d%f%s", &i, &x, name, (rsize_t) 50);
- with the input line:
- 25 54.32E-1 thompson
- will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
- thompson\0.
-
-8 EXAMPLE 2 The call:
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdio.h>
- /* ... */
- int n; char s[5];
- n = fscanf_s(stdin, "%s", s, sizeof s);
- with the input line:
- hello
- will assign to n the value 0 since a matching failure occurred because the sequence hello\0 requires an
- array of six characters to store it.
-
- K.3.5.3.3 The printf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdio.h>
- int printf_s(const char * restrict format, ...);
- Runtime-constraints
-2 format shall not be a null pointer. The %n specifier375) (modified or not by flags, field
- width, or precision) shall not appear in the string pointed to by format. Any argument
- to printf_s corresponding to a %s specifier shall not be a null pointer.
-3 If there is a runtime-constraint violation, the printf_s function does not attempt to
- produce further output, and it is unspecified to what extent printf_s produced output
- before discovering the runtime-constraint violation.
-
-
- 375) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
-
-[page 588]
-
- Description
-4 The printf_s function is equivalent to the printf function except for the explicit
- runtime-constraints listed above.
- Returns
-5 The printf_s function returns the number of characters transmitted, or a negative
- value if an output error, encoding error, or runtime-constraint violation occurred.
- K.3.5.3.4 The scanf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdio.h>
- int scanf_s(const char * restrict format, ...);
- Runtime-constraints
-2 format shall not be a null pointer. Any argument indirected though in order to store
- converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the scanf_s function does not attempt to
- perform further input, and it is unspecified to what extent scanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The scanf_s function is equivalent to fscanf_s with the argument stdin
- interposed before the arguments to scanf_s.
- Returns
-5 The scanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- scanf_s function returns the number of input items assigned, which can be fewer than
- provided for, or even zero, in the event of an early matching failure.
- K.3.5.3.5 The snprintf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdio.h>
- int snprintf_s(char * restrict s, rsize_t n,
- const char * restrict format, ...);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The %n specifier376) (modified or not by flags, field width, or
- precision) shall not appear in the string pointed to by format. Any argument to
-[page 589]
-
- snprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
- error shall occur.
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the snprintf_s function sets s[0] to the
- null character.
- Description
-4 The snprintf_s function is equivalent to the snprintf function except for the
- explicit runtime-constraints listed above.
-5 The snprintf_s function, unlike sprintf_s, will truncate the result to fit within the
- array pointed to by s.
- Returns
-6 The snprintf_s function returns the number of characters that would have been
- written had n been sufficiently large, not counting the terminating null character, or a
- negative value if a runtime-constraint violation occurred. Thus, the null-terminated
- output has been completely written if and only if the returned value is nonnegative and
- less than n.
- K.3.5.3.6 The sprintf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdio.h>
- int sprintf_s(char * restrict s, rsize_t n,
- const char * restrict format, ...);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The number of characters (including the trailing null) required for the
- result to be written to the array pointed to by s shall not be greater than n. The %n
- specifier377) (modified or not by flags, field width, or precision) shall not appear in the
- string pointed to by format. Any argument to sprintf_s corresponding to a %s
- specifier shall not be a null pointer. No encoding error shall occur.
-
-
-
- 376) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
- 377) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
-
-[page 590]
-
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the sprintf_s function sets s[0] to the
- null character.
- Description
-4 The sprintf_s function is equivalent to the sprintf function except for the
- parameter n and the explicit runtime-constraints listed above.
-5 The sprintf_s function, unlike snprintf_s, treats a result too big for the array
- pointed to by s as a runtime-constraint violation.
- Returns
-6 If no runtime-constraint violation occurred, the sprintf_s function returns the number
- of characters written in the array, not counting the terminating null character. If an
- encoding error occurred, sprintf_s returns a negative value. If any other runtime-
- constraint violation occurred, sprintf_s returns zero.
- K.3.5.3.7 The sscanf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdio.h>
- int sscanf_s(const char * restrict s,
- const char * restrict format, ...);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. Any argument indirected though in order
- to store converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the sscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent sscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The sscanf_s function is equivalent to fscanf_s, except that input is obtained from
- a string (specified by the argument s) rather than from a stream. Reaching the end of the
- string is equivalent to encountering end-of-file for the fscanf_s function. If copying
- takes place between objects that overlap, the objects take on unspecified values.
- Returns
-5 The sscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- sscanf_s function returns the number of input items assigned, which can be fewer than
- provided for, or even zero, in the event of an early matching failure.
-
-[page 591]
-
- K.3.5.3.8 The vfprintf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdarg.h>
- #include <stdio.h>
- int vfprintf_s(FILE * restrict stream,
- const char * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. The %n specifier378) (modified or
- not by flags, field width, or precision) shall not appear in the string pointed to by
- format. Any argument to vfprintf_s corresponding to a %s specifier shall not be a
- null pointer.
-3 If there is a runtime-constraint violation, the vfprintf_s function does not attempt to
- produce further output, and it is unspecified to what extent vfprintf_s produced
- output before discovering the runtime-constraint violation.
- Description
-4 The vfprintf_s function is equivalent to the vfprintf function except for the
- explicit runtime-constraints listed above.
- Returns
-5 The vfprintf_s function returns the number of characters transmitted, or a negative
- value if an output error, encoding error, or runtime-constraint violation occurred.
- K.3.5.3.9 The vfscanf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdarg.h>
- #include <stdio.h>
- int vfscanf_s(FILE * restrict stream,
- const char * restrict format,
- va_list arg);
-
-
-
-
- 378) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
-
-[page 592]
-
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. Any argument indirected though in
- order to store converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vfscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent vfscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The vfscanf_s function is equivalent to fscanf_s, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vfscanf_s function does not invoke the
- va_end macro.379)
- Returns
-5 The vfscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- vfscanf_s function returns the number of input items assigned, which can be fewer
- than provided for, or even zero, in the event of an early matching failure.
- K.3.5.3.10 The vprintf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdarg.h>
- #include <stdio.h>
- int vprintf_s(const char * restrict format,
- va_list arg);
- Runtime-constraints
-2 format shall not be a null pointer. The %n specifier380) (modified or not by flags, field
- width, or precision) shall not appear in the string pointed to by format. Any argument
- to vprintf_s corresponding to a %s specifier shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vprintf_s function does not attempt to
- produce further output, and it is unspecified to what extent vprintf_s produced output
- before discovering the runtime-constraint violation.
-
- 379) As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
- vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
- indeterminate.
- 380) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
-
-[page 593]
-
- Description
-4 The vprintf_s function is equivalent to the vprintf function except for the explicit
- runtime-constraints listed above.
- Returns
-5 The vprintf_s function returns the number of characters transmitted, or a negative
- value if an output error, encoding error, or runtime-constraint violation occurred.
- K.3.5.3.11 The vscanf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdarg.h>
- #include <stdio.h>
- int vscanf_s(const char * restrict format,
- va_list arg);
- Runtime-constraints
-2 format shall not be a null pointer. Any argument indirected though in order to store
- converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent vscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The vscanf_s function is equivalent to scanf_s, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vscanf_s function does not invoke the
- va_end macro.381)
- Returns
-5 The vscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- vscanf_s function returns the number of input items assigned, which can be fewer than
- provided for, or even zero, in the event of an early matching failure.
-
-
-
-
- 381) As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
- vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
- indeterminate.
-
-[page 594]
-
- K.3.5.3.12 The vsnprintf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdarg.h>
- #include <stdio.h>
- int vsnprintf_s(char * restrict s, rsize_t n,
- const char * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The %n specifier382) (modified or not by flags, field width, or
- precision) shall not appear in the string pointed to by format. Any argument to
- vsnprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
- error shall occur.
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the vsnprintf_s function sets s[0] to the
- null character.
- Description
-4 The vsnprintf_s function is equivalent to the vsnprintf function except for the
- explicit runtime-constraints listed above.
-5 The vsnprintf_s function, unlike vsprintf_s, will truncate the result to fit within
- the array pointed to by s.
- Returns
-6 The vsnprintf_s function returns the number of characters that would have been
- written had n been sufficiently large, not counting the terminating null character, or a
- negative value if a runtime-constraint violation occurred. Thus, the null-terminated
- output has been completely written if and only if the returned value is nonnegative and
- less than n.
-
-
-
-
- 382) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
-
-[page 595]
-
- K.3.5.3.13 The vsprintf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdarg.h>
- #include <stdio.h>
- int vsprintf_s(char * restrict s, rsize_t n,
- const char * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The number of characters (including the trailing null) required for the
- result to be written to the array pointed to by s shall not be greater than n. The %n
- specifier383) (modified or not by flags, field width, or precision) shall not appear in the
- string pointed to by format. Any argument to vsprintf_s corresponding to a %s
- specifier shall not be a null pointer. No encoding error shall occur.
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the vsprintf_s function sets s[0] to the
- null character.
- Description
-4 The vsprintf_s function is equivalent to the vsprintf function except for the
- parameter n and the explicit runtime-constraints listed above.
-5 The vsprintf_s function, unlike vsnprintf_s, treats a result too big for the array
- pointed to by s as a runtime-constraint violation.
- Returns
-6 If no runtime-constraint violation occurred, the vsprintf_s function returns the
- number of characters written in the array, not counting the terminating null character. If
- an encoding error occurred, vsprintf_s returns a negative value. If any other
- runtime-constraint violation occurred, vsprintf_s returns zero.
-
-
-
-
- 383) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
- at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
- format string was %%n.
-
-[page 596]
-
- K.3.5.3.14 The vsscanf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdarg.h>
- #include <stdio.h>
- int vsscanf_s(const char * restrict s,
- const char * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. Any argument indirected though in order
- to store converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vsscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent vsscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The vsscanf_s function is equivalent to sscanf_s, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vsscanf_s function does not invoke the
- va_end macro.384)
- Returns
-5 The vsscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- vscanf_s function returns the number of input items assigned, which can be fewer than
- provided for, or even zero, in the event of an early matching failure.
- K.3.5.4 Character input/output functions
- K.3.5.4.1 The gets_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdio.h>
- char *gets_s(char *s, rsize_t n);
-
-
-
-
- 384) As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
- vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
- indeterminate.
-
-[page 597]
-
- Runtime-constraints
-2 s shall not be a null pointer. n shall neither be equal to zero nor be greater than
- RSIZE_MAX. A new-line character, end-of-file, or read error shall occur within reading
- n-1 characters from stdin.385)
-3 If there is a runtime-constraint violation, s[0] is set to the null character, and characters
- are read and discarded from stdin until a new-line character is read, or end-of-file or a
- read error occurs.
- Description
-4 The gets_s function reads at most one less than the number of characters specified by n
- from the stream pointed to by stdin, into the array pointed to by s. No additional
- characters are read after a new-line character (which is discarded) or after end-of-file.
- The discarded new-line character does not count towards number of characters read. A
- null character is written immediately after the last character read into the array.
-5 If end-of-file is encountered and no characters have been read into the array, or if a read
- error occurs during the operation, then s[0] is set to the null character, and the other
- elements of s take unspecified values.
- Recommended practice
-6 The fgets function allows properly-written programs to safely process input lines too
- long to store in the result array. In general this requires that callers of fgets pay
- attention to the presence or absence of a new-line character in the result array. Consider
- using fgets (along with any needed processing based on new-line characters) instead of
- gets_s.
- Returns
-7 The gets_s function returns s if successful. If there was a runtime-constraint violation,
- or if end-of-file is encountered and no characters have been read into the array, or if a
- read error occurs during the operation, then a null pointer is returned.
-
-
-
-
- 385) The gets_s function, unlike the historical gets function, makes it a runtime-constraint violation for
- a line of input to overflow the buffer to store it. Unlike the fgets function, gets_s maintains a
- one-to-one relationship between input lines and successful calls to gets_s. Programs that use gets
- expect such a relationship.
-
-[page 598]
-
- K.3.6 General utilities <stdlib.h>
-1 The header <stdlib.h> defines three types.
-2 The types are
- errno_t
- which is type int; and
- rsize_t
- which is the type size_t; and
- constraint_handler_t
- which has the following definition
- typedef void (*constraint_handler_t)(
- const char * restrict msg,
- void * restrict ptr,
- errno_t error);
- K.3.6.1 Runtime-constraint handling
- K.3.6.1.1 The set_constraint_handler_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdlib.h>
- constraint_handler_t set_constraint_handler_s(
- constraint_handler_t handler);
- Description
-2 The set_constraint_handler_s function sets the runtime-constraint handler to
- be handler. The runtime-constraint handler is the function to be called when a library
- function detects a runtime-constraint violation. Only the most recent handler registered
- with set_constraint_handler_s is called when a runtime-constraint violation
- occurs.
-3 When the handler is called, it is passed the following arguments in the following order:
- 1. A pointer to a character string describing the runtime-constraint violation.
- 2. A null pointer or a pointer to an implementation defined object.
- 3. If the function calling the handler has a return type declared as errno_t, the
- return value of the function is passed. Otherwise, a positive value of type
- errno_t is passed.
-
-
-
-[page 599]
-
-4 The implementation has a default constraint handler that is used if no calls to the
- set_constraint_handler_s function have been made. The behavior of the
- default handler is implementation-defined, and it may cause the program to exit or abort.
-5 If the handler argument to set_constraint_handler_s is a null pointer, the
- implementation default handler becomes the current constraint handler.
- Returns
-6 The set_constraint_handler_s function returns a pointer to the previously
- registered handler.386)
- K.3.6.1.2 The abort_handler_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdlib.h>
- void abort_handler_s(
- const char * restrict msg,
- void * restrict ptr,
- errno_t error);
- Description
-2 A pointer to the abort_handler_s function shall be a suitable argument to the
- set_constraint_handler_s function.
-3 The abort_handler_s function writes a message on the standard error stream in an
- implementation-defined format. The message shall include the string pointed to by msg.
- The abort_handler_s function then calls the abort function.387)
- Returns
-4 The abort_handler_s function does not return to its caller.
-
-
-
-
- 386) If the previous handler was registered by calling set_constraint_handler_s with a null
- pointer argument, a pointer to the implementation default handler is returned (not NULL).
- 387) Many implementations invoke a debugger when the abort function is called.
-
-[page 600]
-
- K.3.6.1.3 The ignore_handler_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdlib.h>
- void ignore_handler_s(
- const char * restrict msg,
- void * restrict ptr,
- errno_t error);
- Description
-2 A pointer to the ignore_handler_s function shall be a suitable argument to the
- set_constraint_handler_s function.
-3 The ignore_handler_s function simply returns to its caller.388)
- Returns
-4 The ignore_handler_s function returns no value.
- K.3.6.2 Communication with the environment
- K.3.6.2.1 The getenv_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdlib.h>
- errno_t getenv_s(size_t * restrict len,
- char * restrict value, rsize_t maxsize,
- const char * restrict name);
- Runtime-constraints
-2 name shall not be a null pointer. maxsize shall neither equal zero nor be greater than
- RSIZE_MAX. If maxsize is not equal to zero, then value shall not be a null pointer.
-3 If there is a runtime-constraint violation, the integer pointed to by len is set to 0 (if len
- is not null), and the environment list is not searched.
- Description
-4 The getenv_s function searches an environment list, provided by the host environment,
- for a string that matches the string pointed to by name.
-
-
- 388) If the runtime-constraint handler is set to the ignore_handler_s function, any library function in
- which a runtime-constraint violation occurs will return to its caller. The caller can determine whether
- a runtime-constraint violation occurred based on the library function's specification (usually, the
- library function returns a nonzero errno_t).
-
-[page 601]
-
-5 If that name is found then getenv_s performs the following actions. If len is not a
- null pointer, the length of the string associated with the matched list member is stored in
- the integer pointed to by len. If the length of the associated string is less than maxsize,
- then the associated string is copied to the array pointed to by value.
-6 If that name is not found then getenv_s performs the following actions. If len is not
- a null pointer, zero is stored in the integer pointed to by len. If maxsize is greater than
- zero, then value[0] is set to the null character.
-7 The set of environment names and the method for altering the environment list are
- implementation-defined.
- Returns
-8 The getenv_s function returns zero if the specified name is found and the associated
- string was successfully stored in value. Otherwise, a nonzero value is returned.
- K.3.6.3 Searching and sorting utilities
-1 These utilities make use of a comparison function to search or sort arrays of unspecified
- type. Where an argument declared as size_t nmemb specifies the length of the array
- for a function, if nmemb has the value zero on a call to that function, then the comparison
- function is not called, a search finds no matching element, sorting performs no
- rearrangement, and the pointer to the array may be null.
-2 The implementation shall ensure that the second argument of the comparison function
- (when called from bsearch_s), or both arguments (when called from qsort_s), are
- pointers to elements of the array.389) The first argument when called from bsearch_s
- shall equal key.
-3 The comparison function shall not alter the contents of either the array or search key. The
- implementation may reorder elements of the array between calls to the comparison
- function, but shall not otherwise alter the contents of any individual element.
-4 When the same objects (consisting of size bytes, irrespective of their current positions
- in the array) are passed more than once to the comparison function, the results shall be
- consistent with one another. That is, for qsort_s they shall define a total ordering on
- the array, and for bsearch_s the same object shall always compare the same way with
- the key.
-
-
-
-
- 389) That is, if the value passed is p, then the following expressions are always valid and nonzero:
- ((char *)p - (char *)base) % size == 0
- (char *)p >= (char *)base
- (char *)p < (char *)base + nmemb * size
-
-
-[page 602]
-
-5 A sequence point occurs immediately before and immediately after each call to the
- comparison function, and also between any call to the comparison function and any
- movement of the objects passed as arguments to that call.
- K.3.6.3.1 The bsearch_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdlib.h>
- void *bsearch_s(const void *key, const void *base,
- rsize_t nmemb, rsize_t size,
- int (*compar)(const void *k, const void *y,
- void *context),
- void *context);
- Runtime-constraints
-2 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
- zero, then none of key, base, or compar shall be a null pointer.
-3 If there is a runtime-constraint violation, the bsearch_s function does not search the
- array.
- Description
-4 The bsearch_s function searches an array of nmemb objects, the initial element of
- which is pointed to by base, for an element that matches the object pointed to by key.
- The size of each element of the array is specified by size.
-5 The comparison function pointed to by compar is called with three arguments. The first
- two point to the key object and to an array element, in that order. The function shall
- return an integer less than, equal to, or greater than zero if the key object is considered,
- respectively, to be less than, to match, or to be greater than the array element. The array
- shall consist of: all the elements that compare less than, all the elements that compare
- equal to, and all the elements that compare greater than the key object, in that order.390)
- The third argument to the comparison function is the context argument passed to
- bsearch_s. The sole use of context by bsearch_s is to pass it to the comparison
- function.391)
-
-
-
-
- 390) In practice, this means that the entire array has been sorted according to the comparison function.
- 391) The context argument is for the use of the comparison function in performing its duties. For
- example, it might specify a collating sequence used by the comparison function.
-
-[page 603]
-
- Returns
-6 The bsearch_s function returns a pointer to a matching element of the array, or a null
- pointer if no match is found or there is a runtime-constraint violation. If two elements
- compare as equal, which element is matched is unspecified.
- K.3.6.3.2 The qsort_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdlib.h>
- errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
- int (*compar)(const void *x, const void *y,
- void *context),
- void *context);
- Runtime-constraints
-2 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
- zero, then neither base nor compar shall be a null pointer.
-3 If there is a runtime-constraint violation, the qsort_s function does not sort the array.
- Description
-4 The qsort_s function sorts an array of nmemb objects, the initial element of which is
- pointed to by base. The size of each object is specified by size.
-5 The contents of the array are sorted into ascending order according to a comparison
- function pointed to by compar, which is called with three arguments. The first two
- point to the objects being compared. The function shall return an integer less than, equal
- to, or greater than zero if the first argument is considered to be respectively less than,
- equal to, or greater than the second. The third argument to the comparison function is the
- context argument passed to qsort_s. The sole use of context by qsort_s is to
- pass it to the comparison function.392)
-6 If two elements compare as equal, their relative order in the resulting sorted array is
- unspecified.
- Returns
-7 The qsort_s function returns zero if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-
-
-
-
- 392) The context argument is for the use of the comparison function in performing its duties. For
- example, it might specify a collating sequence used by the comparison function.
-
-[page 604]
-
- K.3.6.4 Multibyte/wide character conversion functions
-1 The behavior of the multibyte character functions is affected by the LC_CTYPE category
- of the current locale. For a state-dependent encoding, each function is placed into its
- initial conversion state by a call for which its character pointer argument, s, is a null
- pointer. Subsequent calls with s as other than a null pointer cause the internal conversion
- state of the function to be altered as necessary. A call with s as a null pointer causes
- these functions to set the int pointed to by their status argument to a nonzero value if
- encodings have state dependency, and zero otherwise.393) Changing the LC_CTYPE
- category causes the conversion state of these functions to be indeterminate.
- K.3.6.4.1 The wctomb_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdlib.h>
- errno_t wctomb_s(int * restrict status,
- char * restrict s,
- rsize_t smax,
- wchar_t wc);
- Runtime-constraints
-2 Let n denote the number of bytes needed to represent the multibyte character
- corresponding to the wide character given by wc (including any shift sequences).
-3 If s is not a null pointer, then smax shall not be less than n, and smax shall not be
- greater than RSIZE_MAX. If s is a null pointer, then smax shall equal zero.
-4 If there is a runtime-constraint violation, wctomb_s does not modify the int pointed to
- by status, and if s is not a null pointer, no more than smax elements in the array
- pointed to by s will be accessed.
- Description
-5 The wctomb_s function determines n and stores the multibyte character representation
- of wc in the array whose first element is pointed to by s (if s is not a null pointer). The
- number of characters stored never exceeds MB_CUR_MAX or smax. If wc is a null wide
- character, a null byte is stored, preceded by any shift sequence needed to restore the
- initial shift state, and the function is left in the initial conversion state.
-6 The implementation shall behave as if no library function calls the wctomb_s function.
-
-
-
- 393) If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
- character codes, but are grouped with an adjacent multibyte character.
-
-[page 605]
-
-7 If s is a null pointer, the wctomb_s function stores into the int pointed to by status a
- nonzero or zero value, if multibyte character encodings, respectively, do or do not have
- state-dependent encodings.
-8 If s is not a null pointer, the wctomb_s function stores into the int pointed to by
- status either n or -1 if wc, respectively, does or does not correspond to a valid
- multibyte character.
-9 In no case will the int pointed to by status be set to a value greater than the
- MB_CUR_MAX macro.
- Returns
-10 The wctomb_s function returns zero if successful, and a nonzero value if there was a
- runtime-constraint violation or wc did not correspond to a valid multibyte character.
- K.3.6.5 Multibyte/wide string conversion functions
-1 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
- the current locale.
- K.3.6.5.1 The mbstowcs_s function
- Synopsis
-1 #include <stdlib.h>
- errno_t mbstowcs_s(size_t * restrict retval,
- wchar_t * restrict dst, rsize_t dstmax,
- const char * restrict src, rsize_t len);
- Runtime-constraints
-2 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
- neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
- then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
- zero. If dst is not a null pointer and len is not less than dstmax, then a null character
- shall occur within the first dstmax multibyte characters of the array pointed to by src.
-3 If there is a runtime-constraint violation, then mbstowcs_s does the following. If
- retval is not a null pointer, then mbstowcs_s sets *retval to (size_t)(-1). If
- dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
- then mbstowcs_s sets dst[0] to the null wide character.
- Description
-4 The mbstowcs_s function converts a sequence of multibyte characters that begins in
- the initial shift state from the array pointed to by src into a sequence of corresponding
- wide characters. If dst is not a null pointer, the converted characters are stored into the
- array pointed to by dst. Conversion continues up to and including a terminating null
- character, which is also stored. Conversion stops earlier in two cases: when a sequence of
-[page 606]
-
- bytes is encountered that does not form a valid multibyte character, or (if dst is not a
- null pointer) when len wide characters have been stored into the array pointed to by
- dst.394) If dst is not a null pointer and no null wide character was stored into the array
- pointed to by dst, then dst[len] is set to the null wide character. Each conversion
- takes place as if by a call to the mbrtowc function.
-5 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
- sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
- the mbstowcs_s function stores the value (size_t)(-1) into *retval.
- Otherwise, the mbstowcs_s function stores into *retval the number of multibyte
- characters successfully converted, not including the terminating null character (if any).
-6 All elements following the terminating null wide character (if any) written by
- mbstowcs_s in the array of dstmax wide characters pointed to by dst take
- unspecified values when mbstowcs_s returns.395)
-7 If copying takes place between objects that overlap, the objects take on unspecified
- values.
- Returns
-8 The mbstowcs_s function returns zero if no runtime-constraint violation and no
- encoding error occurred. Otherwise, a nonzero value is returned.
- K.3.6.5.2 The wcstombs_s function
- Synopsis
-1 #include <stdlib.h>
- errno_t wcstombs_s(size_t * restrict retval,
- char * restrict dst, rsize_t dstmax,
- const wchar_t * restrict src, rsize_t len);
- Runtime-constraints
-2 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
- neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
- then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
- zero. If dst is not a null pointer and len is not less than dstmax, then the conversion
- shall have been stopped (see below) because a terminating null wide character was
- reached or because an encoding error occurred.
-
-
-
-
- 394) Thus, the value of len is ignored if dst is a null pointer.
- 395) This allows an implementation to attempt converting the multibyte string before discovering a
- terminating null character did not occur where required.
-
-[page 607]
-
-3 If there is a runtime-constraint violation, then wcstombs_s does the following. If
- retval is not a null pointer, then wcstombs_s sets *retval to (size_t)(-1). If
- dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
- then wcstombs_s sets dst[0] to the null character.
- Description
-4 The wcstombs_s function converts a sequence of wide characters from the array
- pointed to by src into a sequence of corresponding multibyte characters that begins in
- the initial shift state. If dst is not a null pointer, the converted characters are then stored
- into the array pointed to by dst. Conversion continues up to and including a terminating
- null wide character, which is also stored. Conversion stops earlier in two cases:
- -- when a wide character is reached that does not correspond to a valid multibyte
- character;
- -- (if dst is not a null pointer) when the next multibyte character would exceed the
- limit of n total bytes to be stored into the array pointed to by dst. If the wide
- character being converted is the null wide character, then n is the lesser of len or
- dstmax. Otherwise, n is the lesser of len or dstmax-1.
- If the conversion stops without converting a null wide character and dst is not a null
- pointer, then a null character is stored into the array pointed to by dst immediately
- following any multibyte characters already stored. Each conversion takes place as if by a
- call to the wcrtomb function.396)
-5 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
- wide character that does not correspond to a valid multibyte character, an encoding error
- occurs: the wcstombs_s function stores the value (size_t)(-1) into *retval.
- Otherwise, the wcstombs_s function stores into *retval the number of bytes in the
- resulting multibyte character sequence, not including the terminating null character (if
- any).
-6 All elements following the terminating null character (if any) written by wcstombs_s
- in the array of dstmax elements pointed to by dst take unspecified values when
- wcstombs_s returns.397)
-7 If copying takes place between objects that overlap, the objects take on unspecified
- values.
-
-
- 396) If conversion stops because a terminating null wide character has been reached, the bytes stored
- include those necessary to reach the initial shift state immediately before the null byte. However, if
- the conversion stops before a terminating null wide character has been reached, the result will be null
- terminated, but might not end in the initial shift state.
- 397) When len is not less than dstmax, the implementation might fill the array before discovering a
- runtime-constraint violation.
-
-[page 608]
-
- Returns
-8 The wcstombs_s function returns zero if no runtime-constraint violation and no
- encoding error occurred. Otherwise, a nonzero value is returned.
- K.3.7 String handling <string.h>
-1 The header <string.h> defines two types.
-2 The types are
- errno_t
- which is type int; and
- rsize_t
- which is the type size_t.
- K.3.7.1 Copying functions
- K.3.7.1.1 The memcpy_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <string.h>
- errno_t memcpy_s(void * restrict s1, rsize_t s1max,
- const void * restrict s2, rsize_t n);
- Runtime-constraints
-2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
- objects that overlap.
-3 If there is a runtime-constraint violation, the memcpy_s function stores zeros in the first
- s1max characters of the object pointed to by s1 if s1 is not a null pointer and s1max is
- not greater than RSIZE_MAX.
- Description
-4 The memcpy_s function copies n characters from the object pointed to by s2 into the
- object pointed to by s1.
- Returns
-5 The memcpy_s function returns zero if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-
-
-
-
-[page 609]
-
- K.3.7.1.2 The memmove_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <string.h>
- errno_t memmove_s(void *s1, rsize_t s1max,
- const void *s2, rsize_t n);
- Runtime-constraints
-2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. n shall not be greater than s1max.
-3 If there is a runtime-constraint violation, the memmove_s function stores zeros in the
- first s1max characters of the object pointed to by s1 if s1 is not a null pointer and
- s1max is not greater than RSIZE_MAX.
- Description
-4 The memmove_s function copies n characters from the object pointed to by s2 into the
- object pointed to by s1. This copying takes place as if the n characters from the object
- pointed to by s2 are first copied into a temporary array of n characters that does not
- overlap the objects pointed to by s1 or s2, and then the n characters from the temporary
- array are copied into the object pointed to by s1.
- Returns
-5 The memmove_s function returns zero if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
- K.3.7.1.3 The strcpy_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <string.h>
- errno_t strcpy_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2);
- Runtime-constraints
-2 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
- s1max shall not equal zero. s1max shall be greater than strnlen_s(s2, s1max).
- Copying shall not take place between objects that overlap.
-3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then strcpy_s sets s1[0] to the
- null character.
-
-[page 610]
-
- Description
-4 The strcpy_s function copies the string pointed to by s2 (including the terminating
- null character) into the array pointed to by s1.
-5 All elements following the terminating null character (if any) written by strcpy_s in
- the array of s1max characters pointed to by s1 take unspecified values when
- strcpy_s returns.398)
- Returns
-6 The strcpy_s function returns zero399) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
- K.3.7.1.4 The strncpy_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <string.h>
- errno_t strncpy_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2,
- rsize_t n);
- Runtime-constraints
-2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
- shall be greater than strnlen_s(s2, s1max). Copying shall not take place between
- objects that overlap.
-3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then strncpy_s sets s1[0] to the
- null character.
- Description
-4 The strncpy_s function copies not more than n successive characters (characters that
- follow a null character are not copied) from the array pointed to by s2 to the array
- pointed to by s1. If no null character was copied from s2, then s1[n] is set to a null
- character.
-
-
- 398) This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
- any of those characters are null. Such an approach might write a character to every element of s1
- before discovering that the first element should be set to the null character.
- 399) A zero return value implies that all of the requested characters from the string pointed to by s2 fit
- within the array pointed to by s1 and that the result in s1 is null terminated.
-
-[page 611]
-
-5 All elements following the terminating null character (if any) written by strncpy_s in
- the array of s1max characters pointed to by s1 take unspecified values when
- strncpy_s returns.400)
- Returns
-6 The strncpy_s function returns zero401) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-7 EXAMPLE 1 The strncpy_s function can be used to copy a string without the danger that the result
- will not be null terminated or that characters will be written past the end of the destination array.
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <string.h>
- /* ... */
- char src1[100] = "hello";
- char src2[7] = {'g', 'o', 'o', 'd', 'b', 'y', 'e'};
- char dst1[6], dst2[5], dst3[5];
- int r1, r2, r3;
- r1 = strncpy_s(dst1, 6, src1, 100);
- r2 = strncpy_s(dst2, 5, src2, 7);
- r3 = strncpy_s(dst3, 5, src2, 4);
- The first call will assign to r1 the value zero and to dst1 the sequence hello\0.
- The second call will assign to r2 a nonzero value and to dst2 the sequence \0.
- The third call will assign to r3 the value zero and to dst3 the sequence good\0.
-
- K.3.7.2 Concatenation functions
- K.3.7.2.1 The strcat_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <string.h>
- errno_t strcat_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2);
- Runtime-constraints
-2 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
- strcat_s.
-
-
-
-
- 400) This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
- any of those characters are null. Such an approach might write a character to every element of s1
- before discovering that the first element should be set to the null character.
- 401) A zero return value implies that all of the requested characters from the string pointed to by s2 fit
- within the array pointed to by s1 and that the result in s1 is null terminated.
-
-[page 612]
-
-3 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
- s1max shall not equal zero. m shall not equal zero.402) m shall be greater than
- strnlen_s(s2, m). Copying shall not take place between objects that overlap.
-4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then strcat_s sets s1[0] to the
- null character.
- Description
-5 The strcat_s function appends a copy of the string pointed to by s2 (including the
- terminating null character) to the end of the string pointed to by s1. The initial character
- from s2 overwrites the null character at the end of s1.
-6 All elements following the terminating null character (if any) written by strcat_s in
- the array of s1max characters pointed to by s1 take unspecified values when
- strcat_s returns.403)
- Returns
-7 The strcat_s function returns zero404) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
- K.3.7.2.2 The strncat_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <string.h>
- errno_t strncat_s(char * restrict s1,
- rsize_t s1max,
- const char * restrict s2,
- rsize_t n);
- Runtime-constraints
-2 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
- strncat_s.
-3 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.405) If n is not less
-
-
- 402) Zero means that s1 was not null terminated upon entry to strcat_s.
- 403) This allows an implementation to append characters from s2 to s1 while simultaneously checking if
- any of those characters are null. Such an approach might write a character to every element of s1
- before discovering that the first element should be set to the null character.
- 404) A zero return value implies that all of the requested characters from the string pointed to by s2 were
- appended to the string pointed to by s1 and that the result in s1 is null terminated.
-
-[page 613]
-
- than m, then m shall be greater than strnlen_s(s2, m). Copying shall not take
- place between objects that overlap.
-4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then strncat_s sets s1[0] to the
- null character.
- Description
-5 The strncat_s function appends not more than n successive characters (characters
- that follow a null character are not copied) from the array pointed to by s2 to the end of
- the string pointed to by s1. The initial character from s2 overwrites the null character at
- the end of s1. If no null character was copied from s2, then s1[s1max-m+n] is set to
- a null character.
-6 All elements following the terminating null character (if any) written by strncat_s in
- the array of s1max characters pointed to by s1 take unspecified values when
- strncat_s returns.406)
- Returns
-7 The strncat_s function returns zero407) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-8 EXAMPLE 1 The strncat_s function can be used to copy a string without the danger that the result
- will not be null terminated or that characters will be written past the end of the destination array.
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <string.h>
- /* ... */
- char s1[100] = "good";
- char s2[6] = "hello";
- char s3[6] = "hello";
- char s4[7] = "abc";
- char s5[1000] = "bye";
- int r1, r2, r3, r4;
- r1 = strncat_s(s1, 100, s5, 1000);
- r2 = strncat_s(s2, 6, "", 1);
- r3 = strncat_s(s3, 6, "X", 2);
- r4 = strncat_s(s4, 7, "defghijklmn", 3);
- After the first call r1 will have the value zero and s1 will contain the sequence goodbye\0.
-
-
-
- 405) Zero means that s1 was not null terminated upon entry to strncat_s.
- 406) This allows an implementation to append characters from s2 to s1 while simultaneously checking if
- any of those characters are null. Such an approach might write a character to every element of s1
- before discovering that the first element should be set to the null character.
- 407) A zero return value implies that all of the requested characters from the string pointed to by s2 were
- appended to the string pointed to by s1 and that the result in s1 is null terminated.
-
-[page 614]
-
- After the second call r2 will have the value zero and s2 will contain the sequence hello\0.
- After the third call r3 will have a nonzero value and s3 will contain the sequence \0.
- After the fourth call r4 will have the value zero and s4 will contain the sequence abcdef\0.
-
- K.3.7.3 Search functions
- K.3.7.3.1 The strtok_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <string.h>
- char *strtok_s(char * restrict s1,
- rsize_t * restrict s1max,
- const char * restrict s2,
- char ** restrict ptr);
- Runtime-constraints
-2 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
- shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
- The end of the token found shall occur within the first *s1max characters of s1 for the
- first call, and shall occur within the first *s1max characters of where searching resumes
- on subsequent calls.
-3 If there is a runtime-constraint violation, the strtok_s function does not indirect
- through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
- Description
-4 A sequence of calls to the strtok_s function breaks the string pointed to by s1 into a
- sequence of tokens, each of which is delimited by a character from the string pointed to
- by s2. The fourth argument points to a caller-provided char pointer into which the
- strtok_s function stores information necessary for it to continue scanning the same
- string.
-5 The first call in a sequence has a non-null first argument and s1max points to an object
- whose value is the number of elements in the character array pointed to by the first
- argument. The first call stores an initial value in the object pointed to by ptr and
- updates the value pointed to by s1max to reflect the number of elements that remain in
- relation to ptr. Subsequent calls in the sequence have a null first argument and the
- objects pointed to by s1max and ptr are required to have the values stored by the
- previous call in the sequence, which are then updated. The separator string pointed to by
- s2 may be different from call to call.
-6 The first call in the sequence searches the string pointed to by s1 for the first character
- that is not contained in the current separator string pointed to by s2. If no such character
- is found, then there are no tokens in the string pointed to by s1 and the strtok_s
- function returns a null pointer. If such a character is found, it is the start of the first token.
-[page 615]
-
-7 The strtok_s function then searches from there for the first character in s1 that is
- contained in the current separator string. If no such character is found, the current token
- extends to the end of the string pointed to by s1, and subsequent searches in the same
- string for a token return a null pointer. If such a character is found, it is overwritten by a
- null character, which terminates the current token.
-8 In all cases, the strtok_s function stores sufficient information in the pointer pointed
- to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
- value for ptr, shall start searching just past the element overwritten by a null character
- (if any).
- Returns
-9 The strtok_s function returns a pointer to the first character of a token, or a null
- pointer if there is no token or there is a runtime-constraint violation.
-10 EXAMPLE
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <string.h>
- static char str1[] = "?a???b,,,#c";
- static char str2[] = "\t \t";
- char *t, *ptr1, *ptr2;
- rsize_t max1 = sizeof(str1);
- rsize_t max2 = sizeof(str2);
- t = strtok_s(str1, &max1, "?", &ptr1); // t points to the token "a"
- t = strtok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
- t = strtok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
- t = strtok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
- t = strtok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
-
- K.3.7.4 Miscellaneous functions
- K.3.7.4.1 The memset_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <string.h>
- errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
- Runtime-constraints
-2 s shall not be a null pointer. Neither smax nor n shall be greater than RSIZE_MAX. n
- shall not be greater than smax.
-3 If there is a runtime-constraint violation, then if s is not a null pointer and smax is not
- greater than RSIZE_MAX, the memset_s function stores the value of c (converted to an
- unsigned char) into each of the first smax characters of the object pointed to by s.
-
-
-
-[page 616]
-
- Description
-4 The memset_s function copies the value of c (converted to an unsigned char) into
- each of the first n characters of the object pointed to by s. Unlike memset, any call to
- the memset_s function shall be evaluated strictly according to the rules of the abstract
- machine as described in (5.1.2.3). That is, any call to the memset_s function shall
- assume that the memory indicated by s and n may be accessible in the future and thus
- must contain the values indicated by c.
- Returns
-5 The memset_s function returns zero if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
- K.3.7.4.2 The strerror_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <string.h>
- errno_t strerror_s(char *s, rsize_t maxsize,
- errno_t errnum);
- Runtime-constraints
-2 s shall not be a null pointer. maxsize shall not be greater than RSIZE_MAX.
- maxsize shall not equal zero.
-3 If there is a runtime-constraint violation, then the array (if any) pointed to by s is not
- modified.
- Description
-4 The strerror_s function maps the number in errnum to a locale-specific message
- string. Typically, the values for errnum come from errno, but strerror_s shall
- map any value of type int to a message.
-5 If the length of the desired string is less than maxsize, then the string is copied to the
- array pointed to by s.
-6 Otherwise, if maxsize is greater than zero, then maxsize-1 characters are copied
- from the string to the array pointed to by s and then s[maxsize-1] is set to the null
- character. Then, if maxsize is greater than 3, then s[maxsize-2],
- s[maxsize-3], and s[maxsize-4] are set to the character period (.).
- Returns
-7 The strerror_s function returns zero if the length of the desired string was less than
- maxsize and there was no runtime-constraint violation. Otherwise, the strerror_s
- function returns a nonzero value.
-
-[page 617]
-
- K.3.7.4.3 The strerrorlen_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <string.h>
- size_t strerrorlen_s(errno_t errnum);
- Description
-2 The strerrorlen_s function calculates the length of the (untruncated) locale-specific
- message string that the strerror_s function maps to errnum.
- Returns
-3 The strerrorlen_s function returns the number of characters (not including the null
- character) in the full message string.
- K.3.7.4.4 The strnlen_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <string.h>
- size_t strnlen_s(const char *s, size_t maxsize);
- Description
-2 The strnlen_s function computes the length of the string pointed to by s.
- Returns
-3 If s is a null pointer,408) then the strnlen_s function returns zero.
-4 Otherwise, the strnlen_s function returns the number of characters that precede the
- terminating null character. If there is no null character in the first maxsize characters of
- s then strnlen_s returns maxsize. At most the first maxsize characters of s shall
- be accessed by strnlen_s.
-
-
-
-
- 408) Note that the strnlen_s function has no runtime-constraints. This lack of runtime-constraints
- along with the values returned for a null pointer or an unterminated string argument make
- strnlen_s useful in algorithms that gracefully handle such exceptional data.
-
-[page 618]
-
- K.3.8 Date and time <time.h>
-1 The header <time.h> defines two types.
-2 The types are
- errno_t
- which is type int; and
- rsize_t
- which is the type size_t.
- K.3.8.1 Components of time
-1 A broken-down time is normalized if the values of the members of the tm structure are in
- their normal rages.409)
- K.3.8.2 Time conversion functions
-1 Like the strftime function, the asctime_s and ctime_s functions do not return a
- pointer to a static object, and other library functions are permitted to call them.
- K.3.8.2.1 The asctime_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <time.h>
- errno_t asctime_s(char *s, rsize_t maxsize,
- const struct tm *timeptr);
- Runtime-constraints
-2 Neither s nor timeptr shall be a null pointer. maxsize shall not be less than 26 and
- shall not be greater than RSIZE_MAX. The broken-down time pointed to by timeptr
- shall be normalized. The calendar year represented by the broken-down time pointed to
- by timeptr shall not be less than calendar year 0 and shall not be greater than calendar
- year 9999.
-3 If there is a runtime-constraint violation, there is no attempt to convert the time, and
- s[0] is set to a null character if s is not a null pointer and maxsize is not zero and is
- not greater than RSIZE_MAX.
- Description
-4 The asctime_s function converts the normalized broken-down time in the structure
- pointed to by timeptr into a 26 character (including the null character) string in the
-
-
- 409) The normal ranges are defined in 7.26.1.
-
-[page 619]
-
- form
- Sun Sep 16 01:03:52 1973\n\0
- The fields making up this string are (in order):
- 1. The name of the day of the week represented by timeptr->tm_wday using the
- following three character weekday names: Sun, Mon, Tue, Wed, Thu, Fri, and Sat.
- 2. The character space.
- 3. The name of the month represented by timeptr->tm_mon using the following
- three character month names: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct,
- Nov, and Dec.
- 4. The character space.
- 5. The value of timeptr->tm_mday as if printed using the fprintf format
- "%2d".
- 6. The character space.
- 7. The value of timeptr->tm_hour as if printed using the fprintf format
- "%.2d".
- 8. The character colon.
- 9. The value of timeptr->tm_min as if printed using the fprintf format
- "%.2d".
- 10. The character colon.
- 11. The value of timeptr->tm_sec as if printed using the fprintf format
- "%.2d".
- 12. The character space.
- 13. The value of timeptr->tm_year + 1900 as if printed using the fprintf
- format "%4d".
- 14. The character new line.
- 15. The null character.
- Recommended practice
- The strftime function allows more flexible formatting and supports locale-specific
- behavior. If you do not require the exact form of the result string produced by the
- asctime_s function, consider using the strftime function instead.
- Returns
-5 The asctime_s function returns zero if the time was successfully converted and stored
- into the array pointed to by s. Otherwise, it returns a nonzero value.
-[page 620]
-
- K.3.8.2.2 The ctime_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <time.h>
- errno_t ctime_s(char *s, rsize_t maxsize,
- const time_t *timer);
- Runtime-constraints
-2 Neither s nor timer shall be a null pointer. maxsize shall not be less than 26 and
- shall not be greater than RSIZE_MAX.
-3 If there is a runtime-constraint violation, s[0] is set to a null character if s is not a null
- pointer and maxsize is not equal zero and is not greater than RSIZE_MAX.
- Description
-4 The ctime_s function converts the calendar time pointed to by timer to local time in
- the form of a string. It is equivalent to
- asctime_s(s, maxsize, localtime_s(timer))
- Recommended practice
- The strftime function allows more flexible formatting and supports locale-specific
- behavior. If you do not require the exact form of the result string produced by the
- ctime_s function, consider using the strftime function instead.
- Returns
-5 The ctime_s function returns zero if the time was successfully converted and stored
- into the array pointed to by s. Otherwise, it returns a nonzero value.
- K.3.8.2.3 The gmtime_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <time.h>
- struct tm *gmtime_s(const time_t * restrict timer,
- struct tm * restrict result);
- Runtime-constraints
-2 Neither timer nor result shall be a null pointer.
-3 If there is a runtime-constraint violation, there is no attempt to convert the time.
- Description
-4 The gmtime_s function converts the calendar time pointed to by timer into a broken-
- down time, expressed as UTC. The broken-down time is stored in the structure pointed
-[page 621]
-
- to by result.
- Returns
-5 The gmtime_s function returns result, or a null pointer if the specified time cannot
- be converted to UTC or there is a runtime-constraint violation.
- K.3.8.2.4 The localtime_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <time.h>
- struct tm *localtime_s(const time_t * restrict timer,
- struct tm * restrict result);
- Runtime-constraints
-2 Neither timer nor result shall be a null pointer.
-3 If there is a runtime-constraint violation, there is no attempt to convert the time.
- Description
-4 The localtime_s function converts the calendar time pointed to by timer into a
- broken-down time, expressed as local time. The broken-down time is stored in the
- structure pointed to by result.
- Returns
-5 The localtime_s function returns result, or a null pointer if the specified time
- cannot be converted to local time or there is a runtime-constraint violation.
- K.3.9 Extended multibyte and wide character utilities <wchar.h>
-1 The header <wchar.h> defines two types.
-2 The types are
- errno_t
- which is type int; and
- rsize_t
- which is the type size_t.
-3 Unless explicitly stated otherwise, if the execution of a function described in this
- subclause causes copying to take place between objects that overlap, the objects take on
- unspecified values.
-
-
-
-
-[page 622]
-
- K.3.9.1 Formatted wide character input/output functions
- K.3.9.1.1 The fwprintf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- int fwprintf_s(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. The %n specifier410) (modified or
- not by flags, field width, or precision) shall not appear in the wide string pointed to by
- format. Any argument to fwprintf_s corresponding to a %s specifier shall not be a
- null pointer.
-3 If there is a runtime-constraint violation, the fwprintf_s function does not attempt to
- produce further output, and it is unspecified to what extent fwprintf_s produced
- output before discovering the runtime-constraint violation.
- Description
-4 The fwprintf_s function is equivalent to the fwprintf function except for the
- explicit runtime-constraints listed above.
- Returns
-5 The fwprintf_s function returns the number of wide characters transmitted, or a
- negative value if an output error, encoding error, or runtime-constraint violation occurred.
- K.3.9.1.2 The fwscanf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdio.h>
- #include <wchar.h>
- int fwscanf_s(FILE * restrict stream,
- const wchar_t * restrict format, ...);
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. Any argument indirected though in
- order to store converted input shall not be a null pointer.
-
-
- 410) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
-
-[page 623]
-
-3 If there is a runtime-constraint violation, the fwscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent fwscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The fwscanf_s function is equivalent to fwscanf except that the c, s, and [
- conversion specifiers apply to a pair of arguments (unless assignment suppression is
- indicated by a *). The first of these arguments is the same as for fwscanf. That
- argument is immediately followed in the argument list by the second argument, which has
- type size_t and gives the number of elements in the array pointed to by the first
- argument of the pair. If the first argument points to a scalar object, it is considered to be
- an array of one element.411)
-5 A matching failure occurs if the number of elements in a receiving object is insufficient to
- hold the converted input (including any trailing null character).
- Returns
-6 The fwscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- fwscanf_s function returns the number of input items assigned, which can be fewer
- than provided for, or even zero, in the event of an early matching failure.
- K.3.9.1.3 The snwprintf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- int snwprintf_s(wchar_t * restrict s,
- rsize_t n,
- const wchar_t * restrict format, ...);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The %n specifier412) (modified or not by flags, field width, or
-
- 411) If the format is known at translation time, an implementation may issue a diagnostic for any argument
- used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
- argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
- the format is not known at translation time. For example, an implementation may issue a diagnostic
- for each argument after format that has of type pointer to one of char, signed char,
- unsigned char, or void that is not followed by an argument of a type compatible with
- rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
- using the hh length modifier, a length argument must follow the pointer argument. Another useful
- diagnostic could flag any non-pointer argument following format that did not have a type
- compatible with rsize_t.
-
-[page 624]
-
- precision) shall not appear in the wide string pointed to by format. Any argument to
- snwprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
- error shall occur.
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the snwprintf_s function sets s[0] to the
- null wide character.
- Description
-4 The snwprintf_s function is equivalent to the swprintf function except for the
- explicit runtime-constraints listed above.
-5 The snwprintf_s function, unlike swprintf_s, will truncate the result to fit within
- the array pointed to by s.
- Returns
-6 The snwprintf_s function returns the number of wide characters that would have
- been written had n been sufficiently large, not counting the terminating wide null
- character, or a negative value if a runtime-constraint violation occurred. Thus, the null-
- terminated output has been completely written if and only if the returned value is
- nonnegative and less than n.
- K.3.9.1.4 The swprintf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- int swprintf_s(wchar_t * restrict s, rsize_t n,
- const wchar_t * restrict format, ...);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The number of wide characters (including the trailing null) required
- for the result to be written to the array pointed to by s shall not be greater than n. The %n
- specifier413) (modified or not by flags, field width, or precision) shall not appear in the
- wide string pointed to by format. Any argument to swprintf_s corresponding to a
- %s specifier shall not be a null pointer. No encoding error shall occur.
-
-
- 412) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
- 413) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
-
-[page 625]
-
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the swprintf_s function sets s[0] to the
- null wide character.
- Description
-4 The swprintf_s function is equivalent to the swprintf function except for the
- explicit runtime-constraints listed above.
-5 The swprintf_s function, unlike snwprintf_s, treats a result too big for the array
- pointed to by s as a runtime-constraint violation.
- Returns
-6 If no runtime-constraint violation occurred, the swprintf_s function returns the
- number of wide characters written in the array, not counting the terminating null wide
- character. If an encoding error occurred or if n or more wide characters are requested to
- be written, swprintf_s returns a negative value. If any other runtime-constraint
- violation occurred, swprintf_s returns zero.
- K.3.9.1.5 The swscanf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- int swscanf_s(const wchar_t * restrict s,
- const wchar_t * restrict format, ...);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. Any argument indirected though in order
- to store converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the swscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent swscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The swscanf_s function is equivalent to fwscanf_s, except that the argument s
- specifies a wide string from which the input is to be obtained, rather than from a stream.
- Reaching the end of the wide string is equivalent to encountering end-of-file for the
- fwscanf_s function.
- Returns
-5 The swscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- swscanf_s function returns the number of input items assigned, which can be fewer
- than provided for, or even zero, in the event of an early matching failure.
-[page 626]
-
- K.3.9.1.6 The vfwprintf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdarg.h>
- #include <stdio.h>
- #include <wchar.h>
- int vfwprintf_s(FILE * restrict stream,
- const wchar_t * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. The %n specifier414) (modified or
- not by flags, field width, or precision) shall not appear in the wide string pointed to by
- format. Any argument to vfwprintf_s corresponding to a %s specifier shall not be
- a null pointer.
-3 If there is a runtime-constraint violation, the vfwprintf_s function does not attempt
- to produce further output, and it is unspecified to what extent vfwprintf_s produced
- output before discovering the runtime-constraint violation.
- Description
-4 The vfwprintf_s function is equivalent to the vfwprintf function except for the
- explicit runtime-constraints listed above.
- Returns
-5 The vfwprintf_s function returns the number of wide characters transmitted, or a
- negative value if an output error, encoding error, or runtime-constraint violation occurred.
- K.3.9.1.7 The vfwscanf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdarg.h>
- #include <stdio.h>
- #include <wchar.h>
- int vfwscanf_s(FILE * restrict stream,
- const wchar_t * restrict format, va_list arg);
-
-
-
- 414) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
-
-[page 627]
-
- Runtime-constraints
-2 Neither stream nor format shall be a null pointer. Any argument indirected though in
- order to store converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vfwscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent vfwscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The vfwscanf_s function is equivalent to fwscanf_s, with the variable argument
- list replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vfwscanf_s function does not invoke the
- va_end macro.415)
- Returns
-5 The vfwscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- vfwscanf_s function returns the number of input items assigned, which can be fewer
- than provided for, or even zero, in the event of an early matching failure.
- K.3.9.1.8 The vsnwprintf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdarg.h>
- #include <wchar.h>
- int vsnwprintf_s(wchar_t * restrict s,
- rsize_t n,
- const wchar_t * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The %n specifier416) (modified or not by flags, field width, or
- precision) shall not appear in the wide string pointed to by format. Any argument to
- vsnwprintf_s corresponding to a %s specifier shall not be a null pointer. No
- encoding error shall occur.
-
- 415) As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
- value of arg after the return is indeterminate.
- 416) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
-
-[page 628]
-
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the vsnwprintf_s function sets s[0] to
- the null wide character.
- Description
-4 The vsnwprintf_s function is equivalent to the vswprintf function except for the
- explicit runtime-constraints listed above.
-5 The vsnwprintf_s function, unlike vswprintf_s, will truncate the result to fit
- within the array pointed to by s.
- Returns
-6 The vsnwprintf_s function returns the number of wide characters that would have
- been written had n been sufficiently large, not counting the terminating null character, or
- a negative value if a runtime-constraint violation occurred. Thus, the null-terminated
- output has been completely written if and only if the returned value is nonnegative and
- less than n.
- K.3.9.1.9 The vswprintf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdarg.h>
- #include <wchar.h>
- int vswprintf_s(wchar_t * restrict s,
- rsize_t n,
- const wchar_t * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
- than RSIZE_MAX. The number of wide characters (including the trailing null) required
- for the result to be written to the array pointed to by s shall not be greater than n. The %n
- specifier417) (modified or not by flags, field width, or precision) shall not appear in the
- wide string pointed to by format. Any argument to vswprintf_s corresponding to a
- %s specifier shall not be a null pointer. No encoding error shall occur.
-3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
- than zero and less than RSIZE_MAX, then the vswprintf_s function sets s[0] to the
- null wide character.
-
- 417) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
-
-[page 629]
-
- Description
-4 The vswprintf_s function is equivalent to the vswprintf function except for the
- explicit runtime-constraints listed above.
-5 The vswprintf_s function, unlike vsnwprintf_s, treats a result too big for the
- array pointed to by s as a runtime-constraint violation.
- Returns
-6 If no runtime-constraint violation occurred, the vswprintf_s function returns the
- number of wide characters written in the array, not counting the terminating null wide
- character. If an encoding error occurred or if n or more wide characters are requested to
- be written, vswprintf_s returns a negative value. If any other runtime-constraint
- violation occurred, vswprintf_s returns zero.
- K.3.9.1.10 The vswscanf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdarg.h>
- #include <wchar.h>
- int vswscanf_s(const wchar_t * restrict s,
- const wchar_t * restrict format,
- va_list arg);
- Runtime-constraints
-2 Neither s nor format shall be a null pointer. Any argument indirected though in order
- to store converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vswscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent vswscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The vswscanf_s function is equivalent to swscanf_s, with the variable argument
- list replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vswscanf_s function does not invoke the
- va_end macro.418)
-
-
-
-
- 418) As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
- value of arg after the return is indeterminate.
-
-[page 630]
-
- Returns
-5 The vswscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- vswscanf_s function returns the number of input items assigned, which can be fewer
- than provided for, or even zero, in the event of an early matching failure.
- K.3.9.1.11 The vwprintf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdarg.h>
- #include <wchar.h>
- int vwprintf_s(const wchar_t * restrict format,
- va_list arg);
- Runtime-constraints
-2 format shall not be a null pointer. The %n specifier419) (modified or not by flags, field
- width, or precision) shall not appear in the wide string pointed to by format. Any
- argument to vwprintf_s corresponding to a %s specifier shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vwprintf_s function does not attempt to
- produce further output, and it is unspecified to what extent vwprintf_s produced
- output before discovering the runtime-constraint violation.
- Description
-4 The vwprintf_s function is equivalent to the vwprintf function except for the
- explicit runtime-constraints listed above.
- Returns
-5 The vwprintf_s function returns the number of wide characters transmitted, or a
- negative value if an output error, encoding error, or runtime-constraint violation occurred.
-
-
-
-
- 419) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
-
-[page 631]
-
- K.3.9.1.12 The vwscanf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <stdarg.h>
- #include <wchar.h>
- int vwscanf_s(const wchar_t * restrict format,
- va_list arg);
- Runtime-constraints
-2 format shall not be a null pointer. Any argument indirected though in order to store
- converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the vwscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent vwscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The vwscanf_s function is equivalent to wscanf_s, with the variable argument list
- replaced by arg, which shall have been initialized by the va_start macro (and
- possibly subsequent va_arg calls). The vwscanf_s function does not invoke the
- va_end macro.420)
- Returns
-5 The vwscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- vwscanf_s function returns the number of input items assigned, which can be fewer
- than provided for, or even zero, in the event of an early matching failure.
- K.3.9.1.13 The wprintf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- int wprintf_s(const wchar_t * restrict format, ...);
- Runtime-constraints
-2 format shall not be a null pointer. The %n specifier421) (modified or not by flags, field
-
- 420) As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
- value of arg after the return is indeterminate.
- 421) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
- string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
- example, if the entire format string was L"%%n".
-
-[page 632]
-
- width, or precision) shall not appear in the wide string pointed to by format. Any
- argument to wprintf_s corresponding to a %s specifier shall not be a null pointer.
-3 If there is a runtime-constraint violation, the wprintf_s function does not attempt to
- produce further output, and it is unspecified to what extent wprintf_s produced output
- before discovering the runtime-constraint violation.
- Description
-4 The wprintf_s function is equivalent to the wprintf function except for the explicit
- runtime-constraints listed above.
- Returns
-5 The wprintf_s function returns the number of wide characters transmitted, or a
- negative value if an output error, encoding error, or runtime-constraint violation occurred.
- K.3.9.1.14 The wscanf_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- int wscanf_s(const wchar_t * restrict format, ...);
- Runtime-constraints
-2 format shall not be a null pointer. Any argument indirected though in order to store
- converted input shall not be a null pointer.
-3 If there is a runtime-constraint violation, the wscanf_s function does not attempt to
- perform further input, and it is unspecified to what extent wscanf_s performed input
- before discovering the runtime-constraint violation.
- Description
-4 The wscanf_s function is equivalent to fwscanf_s with the argument stdin
- interposed before the arguments to wscanf_s.
- Returns
-5 The wscanf_s function returns the value of the macro EOF if an input failure occurs
- before any conversion or if there is a runtime-constraint violation. Otherwise, the
- wscanf_s function returns the number of input items assigned, which can be fewer than
- provided for, or even zero, in the event of an early matching failure.
-
-
-
-
-[page 633]
-
- K.3.9.2 General wide string utilities
- K.3.9.2.1 Wide string copying functions
- K.3.9.2.1.1 The wcscpy_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- errno_t wcscpy_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2);
- Runtime-constraints
-2 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
- s1max shall not equal zero. s1max shall be greater than wcsnlen_s(s2, s1max).
- Copying shall not take place between objects that overlap.
-3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then wcscpy_s sets s1[0] to the
- null wide character.
- Description
-4 The wcscpy_s function copies the wide string pointed to by s2 (including the
- terminating null wide character) into the array pointed to by s1.
-5 All elements following the terminating null wide character (if any) written by
- wcscpy_s in the array of s1max wide characters pointed to by s1 take unspecified
- values when wcscpy_s returns.422)
- Returns
-6 The wcscpy_s function returns zero423) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-
-
-
-
- 422) This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
- if any of those wide characters are null. Such an approach might write a wide character to every
- element of s1 before discovering that the first element should be set to the null wide character.
- 423) A zero return value implies that all of the requested wide characters from the string pointed to by s2
- fit within the array pointed to by s1 and that the result in s1 is null terminated.
-
-[page 634]
-
- K.3.9.2.1.2 The wcsncpy_s function
- Synopsis
-7 #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- errno_t wcsncpy_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2,
- rsize_t n);
- Runtime-constraints
-8 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
- shall be greater than wcsnlen_s(s2, s1max). Copying shall not take place between
- objects that overlap.
-9 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then wcsncpy_s sets s1[0] to the
- null wide character.
- Description
-10 The wcsncpy_s function copies not more than n successive wide characters (wide
- characters that follow a null wide character are not copied) from the array pointed to by
- s2 to the array pointed to by s1. If no null wide character was copied from s2, then
- s1[n] is set to a null wide character.
-11 All elements following the terminating null wide character (if any) written by
- wcsncpy_s in the array of s1max wide characters pointed to by s1 take unspecified
- values when wcsncpy_s returns.424)
- Returns
-12 The wcsncpy_s function returns zero425) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-13 EXAMPLE 1 The wcsncpy_s function can be used to copy a wide string without the danger that the
- result will not be null terminated or that wide characters will be written past the end of the destination
- array.
-
-
-
-
- 424) This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
- if any of those wide characters are null. Such an approach might write a wide character to every
- element of s1 before discovering that the first element should be set to the null wide character.
- 425) A zero return value implies that all of the requested wide characters from the string pointed to by s2
- fit within the array pointed to by s1 and that the result in s1 is null terminated.
-
-[page 635]
-
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- /* ... */
- wchar_t src1[100] = L"hello";
- wchar_t src2[7] = {L'g', L'o', L'o', L'd', L'b', L'y', L'e'};
- wchar_t dst1[6], dst2[5], dst3[5];
- int r1, r2, r3;
- r1 = wcsncpy_s(dst1, 6, src1, 100);
- r2 = wcsncpy_s(dst2, 5, src2, 7);
- r3 = wcsncpy_s(dst3, 5, src2, 4);
- The first call will assign to r1 the value zero and to dst1 the sequence of wide characters hello\0.
- The second call will assign to r2 a nonzero value and to dst2 the sequence of wide characters \0.
- The third call will assign to r3 the value zero and to dst3 the sequence of wide characters good\0.
-
- K.3.9.2.1.3 The wmemcpy_s function
- Synopsis
-14 #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- errno_t wmemcpy_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2,
- rsize_t n);
- Runtime-constraints
-15 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
- objects that overlap.
-16 If there is a runtime-constraint violation, the wmemcpy_s function stores zeros in the
- first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
- s1max is not greater than RSIZE_MAX.
- Description
-17 The wmemcpy_s function copies n successive wide characters from the object pointed
- to by s2 into the object pointed to by s1.
- Returns
-18 The wmemcpy_s function returns zero if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-
-
-
-
-[page 636]
-
- K.3.9.2.1.4 The wmemmove_s function
- Synopsis
-19 #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
- const wchar_t *s2, rsize_t n);
- Runtime-constraints
-20 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. n shall not be greater than s1max.
-21 If there is a runtime-constraint violation, the wmemmove_s function stores zeros in the
- first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
- s1max is not greater than RSIZE_MAX.
- Description
-22 The wmemmove_s function copies n successive wide characters from the object pointed
- to by s2 into the object pointed to by s1. This copying takes place as if the n wide
- characters from the object pointed to by s2 are first copied into a temporary array of n
- wide characters that does not overlap the objects pointed to by s1 or s2, and then the n
- wide characters from the temporary array are copied into the object pointed to by s1.
- Returns
-23 The wmemmove_s function returns zero if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
- K.3.9.2.2 Wide string concatenation functions
- K.3.9.2.2.1 The wcscat_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- errno_t wcscat_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2);
- Runtime-constraints
-2 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
- wcscat_s.
-3 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
- s1max shall not equal zero. m shall not equal zero.426) m shall be greater than
- wcsnlen_s(s2, m). Copying shall not take place between objects that overlap.
-
-[page 637]
-
-4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then wcscat_s sets s1[0] to the
- null wide character.
- Description
-5 The wcscat_s function appends a copy of the wide string pointed to by s2 (including
- the terminating null wide character) to the end of the wide string pointed to by s1. The
- initial wide character from s2 overwrites the null wide character at the end of s1.
-6 All elements following the terminating null wide character (if any) written by
- wcscat_s in the array of s1max wide characters pointed to by s1 take unspecified
- values when wcscat_s returns.427)
- Returns
-7 The wcscat_s function returns zero428) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
- K.3.9.2.2.2 The wcsncat_s function
- Synopsis
-8 #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- errno_t wcsncat_s(wchar_t * restrict s1,
- rsize_t s1max,
- const wchar_t * restrict s2,
- rsize_t n);
- Runtime-constraints
-9 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
- wcsncat_s.
-10 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
- RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.429) If n is not less
- than m, then m shall be greater than wcsnlen_s(s2, m). Copying shall not take
- place between objects that overlap.
-
-
- 426) Zero means that s1 was not null terminated upon entry to wcscat_s.
- 427) This allows an implementation to append wide characters from s2 to s1 while simultaneously
- checking if any of those wide characters are null. Such an approach might write a wide character to
- every element of s1 before discovering that the first element should be set to the null wide character.
- 428) A zero return value implies that all of the requested wide characters from the wide string pointed to by
- s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
- 429) Zero means that s1 was not null terminated upon entry to wcsncat_s.
-
-[page 638]
-
-11 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
- greater than zero and not greater than RSIZE_MAX, then wcsncat_s sets s1[0] to the
- null wide character.
- Description
-12 The wcsncat_s function appends not more than n successive wide characters (wide
- characters that follow a null wide character are not copied) from the array pointed to by
- s2 to the end of the wide string pointed to by s1. The initial wide character from s2
- overwrites the null wide character at the end of s1. If no null wide character was copied
- from s2, then s1[s1max-m+n] is set to a null wide character.
-13 All elements following the terminating null wide character (if any) written by
- wcsncat_s in the array of s1max wide characters pointed to by s1 take unspecified
- values when wcsncat_s returns.430)
- Returns
-14 The wcsncat_s function returns zero431) if there was no runtime-constraint violation.
- Otherwise, a nonzero value is returned.
-15 EXAMPLE 1 The wcsncat_s function can be used to copy a wide string without the danger that the
- result will not be null terminated or that wide characters will be written past the end of the destination
- array.
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- /* ... */
- wchar_t s1[100] = L"good";
- wchar_t s2[6] = L"hello";
- wchar_t s3[6] = L"hello";
- wchar_t s4[7] = L"abc";
- wchar_t s5[1000] = L"bye";
- int r1, r2, r3, r4;
- r1 = wcsncat_s(s1, 100, s5, 1000);
- r2 = wcsncat_s(s2, 6, L"", 1);
- r3 = wcsncat_s(s3, 6, L"X", 2);
- r4 = wcsncat_s(s4, 7, L"defghijklmn", 3);
- After the first call r1 will have the value zero and s1 will be the wide character sequence goodbye\0.
- After the second call r2 will have the value zero and s2 will be the wide character sequence hello\0.
- After the third call r3 will have a nonzero value and s3 will be the wide character sequence \0.
- After the fourth call r4 will have the value zero and s4 will be the wide character sequence abcdef\0.
-
-
-
-
- 430) This allows an implementation to append wide characters from s2 to s1 while simultaneously
- checking if any of those wide characters are null. Such an approach might write a wide character to
- every element of s1 before discovering that the first element should be set to the null wide character.
- 431) A zero return value implies that all of the requested wide characters from the wide string pointed to by
- s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
-
-[page 639]
-
- K.3.9.2.3 Wide string search functions
- K.3.9.2.3.1 The wcstok_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- wchar_t *wcstok_s(wchar_t * restrict s1,
- rsize_t * restrict s1max,
- const wchar_t * restrict s2,
- wchar_t ** restrict ptr);
- Runtime-constraints
-2 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
- shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
- The end of the token found shall occur within the first *s1max wide characters of s1 for
- the first call, and shall occur within the first *s1max wide characters of where searching
- resumes on subsequent calls.
-3 If there is a runtime-constraint violation, the wcstok_s function does not indirect
- through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
- Description
-4 A sequence of calls to the wcstok_s function breaks the wide string pointed to by s1
- into a sequence of tokens, each of which is delimited by a wide character from the wide
- string pointed to by s2. The fourth argument points to a caller-provided wchar_t
- pointer into which the wcstok_s function stores information necessary for it to
- continue scanning the same wide string.
-5 The first call in a sequence has a non-null first argument and s1max points to an object
- whose value is the number of elements in the wide character array pointed to by the first
- argument. The first call stores an initial value in the object pointed to by ptr and
- updates the value pointed to by s1max to reflect the number of elements that remain in
- relation to ptr. Subsequent calls in the sequence have a null first argument and the
- objects pointed to by s1max and ptr are required to have the values stored by the
- previous call in the sequence, which are then updated. The separator wide string pointed
- to by s2 may be different from call to call.
-6 The first call in the sequence searches the wide string pointed to by s1 for the first wide
- character that is not contained in the current separator wide string pointed to by s2. If no
- such wide character is found, then there are no tokens in the wide string pointed to by s1
- and the wcstok_s function returns a null pointer. If such a wide character is found, it is
- the start of the first token.
-
-
-[page 640]
-
-7 The wcstok_s function then searches from there for the first wide character in s1 that
- is contained in the current separator wide string. If no such wide character is found, the
- current token extends to the end of the wide string pointed to by s1, and subsequent
- searches in the same wide string for a token return a null pointer. If such a wide character
- is found, it is overwritten by a null wide character, which terminates the current token.
-8 In all cases, the wcstok_s function stores sufficient information in the pointer pointed
- to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
- value for ptr, shall start searching just past the element overwritten by a null wide
- character (if any).
- Returns
-9 The wcstok_s function returns a pointer to the first wide character of a token, or a null
- pointer if there is no token or there is a runtime-constraint violation.
-10 EXAMPLE
- #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- static wchar_t str1[] = L"?a???b,,,#c";
- static wchar_t str2[] = L"\t \t";
- wchar_t *t, *ptr1, *ptr2;
- rsize_t max1 = wcslen(str1)+1;
- rsize_t max2 = wcslen(str2)+1;
- t = wcstok_s(str1, &max1, "?", &ptr1); // t points to the token "a"
- t = wcstok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
- t = wcstok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
- t = wcstok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
- t = wcstok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
-
- K.3.9.2.4 Miscellaneous functions
- K.3.9.2.4.1 The wcsnlen_s function
- Synopsis
-1 #define __STDC_WANT_LIB_EXT1__ 1
- #include <wchar.h>
- size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
- Description
-2 The wcsnlen_s function computes the length of the wide string pointed to by s.
- Returns
-3 If s is a null pointer,432) then the wcsnlen_s function returns zero.
-4 Otherwise, the wcsnlen_s function returns the number of wide characters that precede
- the terminating null wide character. If there is no null wide character in the first
- maxsize wide characters of s then wcsnlen_s returns maxsize. At most the first
-
-[page 641]
-
- maxsize wide characters of s shall be accessed by wcsnlen_s.
- K.3.9.3 Extended multibyte/wide character conversion utilities
- K.3.9.3.1 Restartable multibyte/wide character conversion functions
-1 Unlike wcrtomb, wcrtomb_s does not permit the ps parameter (the pointer to the
- conversion state) to be a null pointer.
- K.3.9.3.1.1 The wcrtomb_s function
- Synopsis
-2 #include <wchar.h>
- errno_t wcrtomb_s(size_t * restrict retval,
- char * restrict s, rsize_t smax,
- wchar_t wc, mbstate_t * restrict ps);
- Runtime-constraints
-3 Neither retval nor ps shall be a null pointer. If s is not a null pointer, then smax
- shall not equal zero and shall not be greater than RSIZE_MAX. If s is not a null pointer,
- then smax shall be not be less than the number of bytes to be stored in the array pointed
- to by s. If s is a null pointer, then smax shall equal zero.
-4 If there is a runtime-constraint violation, then wcrtomb_s does the following. If s is
- not a null pointer and smax is greater than zero and not greater than RSIZE_MAX, then
- wcrtomb_s sets s[0] to the null character. If retval is not a null pointer, then
- wcrtomb_s sets *retval to (size_t)(-1).
- Description
-5 If s is a null pointer, the wcrtomb_s function is equivalent to the call
- wcrtomb_s(&retval, buf, sizeof buf, L'\0', ps)
- where retval and buf are internal variables of the appropriate types, and the size of
- buf is greater than MB_CUR_MAX.
-6 If s is not a null pointer, the wcrtomb_s function determines the number of bytes
- needed to represent the multibyte character that corresponds to the wide character given
- by wc (including any shift sequences), and stores the multibyte character representation
- in the array whose first element is pointed to by s. At most MB_CUR_MAX bytes are
- stored. If wc is a null wide character, a null byte is stored, preceded by any shift
- sequence needed to restore the initial shift state; the resulting state described is the initial
- conversion state.
-
- 432) Note that the wcsnlen_s function has no runtime-constraints. This lack of runtime-constraints
- along with the values returned for a null pointer or an unterminated wide string argument make
- wcsnlen_s useful in algorithms that gracefully handle such exceptional data.
-
-[page 642]
-
-7 If wc does not correspond to a valid multibyte character, an encoding error occurs: the
- wcrtomb_s function stores the value (size_t)(-1) into *retval and the
- conversion state is unspecified. Otherwise, the wcrtomb_s function stores into
- *retval the number of bytes (including any shift sequences) stored in the array pointed
- to by s.
- Returns
-8 The wcrtomb_s function returns zero if no runtime-constraint violation and no
- encoding error occurred. Otherwise, a nonzero value is returned.
- K.3.9.3.2 Restartable multibyte/wide string conversion functions
-1 Unlike mbsrtowcs and wcsrtombs, mbsrtowcs_s and wcsrtombs_s do not
- permit the ps parameter (the pointer to the conversion state) to be a null pointer.
- K.3.9.3.2.1 The mbsrtowcs_s function
- Synopsis
-2 #include <wchar.h>
- errno_t mbsrtowcs_s(size_t * restrict retval,
- wchar_t * restrict dst, rsize_t dstmax,
- const char ** restrict src, rsize_t len,
- mbstate_t * restrict ps);
- Runtime-constraints
-3 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
- then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
- pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
- not equal zero. If dst is not a null pointer and len is not less than dstmax, then a null
- character shall occur within the first dstmax multibyte characters of the array pointed to
- by *src.
-4 If there is a runtime-constraint violation, then mbsrtowcs_s does the following. If
- retval is not a null pointer, then mbsrtowcs_s sets *retval to (size_t)(-1).
- If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
- then mbsrtowcs_s sets dst[0] to the null wide character.
- Description
-5 The mbsrtowcs_s function converts a sequence of multibyte characters that begins in
- the conversion state described by the object pointed to by ps, from the array indirectly
- pointed to by src into a sequence of corresponding wide characters. If dst is not a null
- pointer, the converted characters are stored into the array pointed to by dst. Conversion
- continues up to and including a terminating null character, which is also stored.
- Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
- not form a valid multibyte character, or (if dst is not a null pointer) when len wide
-[page 643]
-
- characters have been stored into the array pointed to by dst.433) If dst is not a null
- pointer and no null wide character was stored into the array pointed to by dst, then
- dst[len] is set to the null wide character. Each conversion takes place as if by a call
- to the mbrtowc function.
-6 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
- pointer (if conversion stopped due to reaching a terminating null character) or the address
- just past the last multibyte character converted (if any). If conversion stopped due to
- reaching a terminating null character and if dst is not a null pointer, the resulting state
- described is the initial conversion state.
-7 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
- sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
- the mbsrtowcs_s function stores the value (size_t)(-1) into *retval and the
- conversion state is unspecified. Otherwise, the mbsrtowcs_s function stores into
- *retval the number of multibyte characters successfully converted, not including the
- terminating null character (if any).
-8 All elements following the terminating null wide character (if any) written by
- mbsrtowcs_s in the array of dstmax wide characters pointed to by dst take
- unspecified values when mbsrtowcs_s returns.434)
-9 If copying takes place between objects that overlap, the objects take on unspecified
- values.
- Returns
-10 The mbsrtowcs_s function returns zero if no runtime-constraint violation and no
- encoding error occurred. Otherwise, a nonzero value is returned.
- K.3.9.3.2.2 The wcsrtombs_s function
- Synopsis
-11 #include <wchar.h>
- errno_t wcsrtombs_s(size_t * restrict retval,
- char * restrict dst, rsize_t dstmax,
- const wchar_t ** restrict src, rsize_t len,
- mbstate_t * restrict ps);
-
-
-
-
- 433) Thus, the value of len is ignored if dst is a null pointer.
- 434) This allows an implementation to attempt converting the multibyte string before discovering a
- terminating null character did not occur where required.
-
-[page 644]
-
- Runtime-constraints
-12 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
- then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
- pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
- not equal zero. If dst is not a null pointer and len is not less than dstmax, then the
- conversion shall have been stopped (see below) because a terminating null wide character
- was reached or because an encoding error occurred.
-13 If there is a runtime-constraint violation, then wcsrtombs_s does the following. If
- retval is not a null pointer, then wcsrtombs_s sets *retval to (size_t)(-1).
- If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
- then wcsrtombs_s sets dst[0] to the null character.
- Description
-14 The wcsrtombs_s function converts a sequence of wide characters from the array
- indirectly pointed to by src into a sequence of corresponding multibyte characters that
- begins in the conversion state described by the object pointed to by ps. If dst is not a
- null pointer, the converted characters are then stored into the array pointed to by dst.
- Conversion continues up to and including a terminating null wide character, which is also
- stored. Conversion stops earlier in two cases:
- -- when a wide character is reached that does not correspond to a valid multibyte
- character;
- -- (if dst is not a null pointer) when the next multibyte character would exceed the
- limit of n total bytes to be stored into the array pointed to by dst. If the wide
- character being converted is the null wide character, then n is the lesser of len or
- dstmax. Otherwise, n is the lesser of len or dstmax-1.
- If the conversion stops without converting a null wide character and dst is not a null
- pointer, then a null character is stored into the array pointed to by dst immediately
- following any multibyte characters already stored. Each conversion takes place as if by a
- call to the wcrtomb function.435)
-15 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
- pointer (if conversion stopped due to reaching a terminating null wide character) or the
- address just past the last wide character converted (if any). If conversion stopped due to
- reaching a terminating null wide character, the resulting state described is the initial
- conversion state.
-
-
- 435) If conversion stops because a terminating null wide character has been reached, the bytes stored
- include those necessary to reach the initial shift state immediately before the null byte. However, if
- the conversion stops before a terminating null wide character has been reached, the result will be null
- terminated, but might not end in the initial shift state.
-
-[page 645]
-
-16 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
- wide character that does not correspond to a valid multibyte character, an encoding error
- occurs: the wcsrtombs_s function stores the value (size_t)(-1) into *retval
- and the conversion state is unspecified. Otherwise, the wcsrtombs_s function stores
- into *retval the number of bytes in the resulting multibyte character sequence, not
- including the terminating null character (if any).
-17 All elements following the terminating null character (if any) written by wcsrtombs_s
- in the array of dstmax elements pointed to by dst take unspecified values when
- wcsrtombs_s returns.436)
-18 If copying takes place between objects that overlap, the objects take on unspecified
- values.
- Returns
-19 The wcsrtombs_s function returns zero if no runtime-constraint violation and no
- encoding error occurred. Otherwise, a nonzero value is returned.
-
-
-
-
- 436) When len is not less than dstmax, the implementation might fill the array before discovering a
- runtime-constraint violation.
-
-[page 646]
-
- Annex L
- (normative)
- Analyzability
- L.1 Scope
-1 This annex specifies optional behavior that can aid in the analyzability of C programs.
-2 An implementation that defines __STDC_ANALYZABLE__ shall conform to the
- specifications in this annex.437)
- L.2 Definitions
- L.2.1
-1 out-of-bounds store
- an (attempted) access (3.1) that, at run time, for a given computational state, would
- modify (or, for an object declared volatile, fetch) one or more bytes that lie outside
- the bounds permitted by this Standard.
- L.2.2
-1 bounded undefined behavior
- undefined behavior (3.4.3) that does not perform an out-of-bounds store.
-2 NOTE 1 The behavior might perform a trap.
-
-3 NOTE 2 Any values produced or stored might be indeterminate values.
-
- L.2.3
-1 critical undefined behavior
- undefined behavior that is not bounded undefined behavior.
-2 NOTE The behavior might perform an out-of-bounds store or perform a trap.
-
-
-
-
- 437) Implementations that do not define __STDC_ANALYZABLE__ are not required to conform to these
- specifications.
-
-[page 647]
-
- L.3 Requirements
-1 If the program performs a trap (3.19.5), the implementation is permitted to invoke a
- runtime-constraint handler. Any such semantics are implementation-defined.
-2 All undefined behavior shall be limited to bounded undefined behavior, except for the
- following which are permitted to result in critical undefined behavior:
- -- An object is referred to outside of its lifetime (6.2.4).
- -- An lvalue does not designate an object when evaluated (6.3.2.1).
- -- A pointer is used to call a function whose type is not compatible with the referenced
- type (6.3.2.3).
- -- The operand of the unary * operator has an invalid value (6.5.3.2).
- -- Addition or subtraction of a pointer into, or just beyond, an array object and an
- integer type produces a result that points just beyond the array object and is used as
- the operand of a unary * operator that is evaluated (6.5.6).
- -- An argument to a library function has an invalid value or a type not expected by a
- function with variable number of arguments (7.1.4).
- -- The value of a pointer that refers to space deallocated by a call to the free or realloc
- function is used (7.22.3).
- -- A string or wide string utility function is instructed to access an array beyond the end
- of an object (7.23.1, 7.28.4).
-
-
-
-
-[page 648]
-
-
- Bibliography
- 1. ''The C Reference Manual'' by Dennis M. Ritchie, a version of which was
- published in The C Programming Language by Brian W. Kernighan and Dennis
- M. Ritchie, Prentice-Hall, Inc., (1978). Copyright owned by AT&T.
- 2. 1984 /usr/group Standard by the /usr/group Standards Committee, Santa Clara,
- California, USA, November 1984.
- 3. ANSI X3/TR-1-82 (1982), American National Dictionary for Information
- Processing Systems, Information Processing Systems Technical Report.
- 4. ANSI/IEEE 754-1985, American National Standard for Binary Floating-Point
- Arithmetic.
- 5. ANSI/IEEE 854-1988, American National Standard for Radix-Independent
- Floating-Point Arithmetic.
- 6. IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems,
- second edition (previously designated IEC 559:1989).
- 7. ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and
- symbols for use in the physical sciences and technology.
- 8. ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for
- information interchange.
- 9. ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1:
- Fundamental terms.
- 10. ISO 4217:1995, Codes for the representation of currencies and funds.
- 11. ISO 8601:1988, Data elements and interchange formats -- Information
- interchange -- Representation of dates and times.
- 12. ISO/IEC 9899:1990, Programming languages -- C.
- 13. ISO/IEC 9899/COR1:1994, Technical Corrigendum 1.
- 14. ISO/IEC 9899/COR2:1996, Technical Corrigendum 2.
- 15. ISO/IEC 9899/AMD1:1995, Amendment 1 to ISO/IEC 9899:1990 C Integrity.
- 16. ISO/IEC 9899:1999, Programming languages -- C.
- 17. ISO/IEC 9899:1999/Cor.1:2001, Technical Corrigendum 1.
- 18. ISO/IEC 9899:1999/Cor.2:2004, Technical Corrigendum 2.
- 19. ISO/IEC 9899:1999/Cor.3:2007, Technical Corrigendum 3.
-
-
-
-[page 649]
-
- 20. ISO/IEC 9945-2:1993, Information technology -- Portable Operating System
- Interface (POSIX) -- Part 2: Shell and Utilities.
- 21. ISO/IEC TR 10176:1998, Information technology -- Guidelines for the
- preparation of programming language standards.
- 22. ISO/IEC 10646-1:1993, Information technology -- Universal Multiple-Octet
- Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
- 23. ISO/IEC 10646-1/COR1:1996, Technical Corrigendum 1 to
- ISO/IEC 10646-1:1993.
- 24. ISO/IEC 10646-1/COR2:1998, Technical Corrigendum 2 to
- ISO/IEC 10646-1:1993.
- 25. ISO/IEC 10646-1/AMD1:1996, Amendment 1 to ISO/IEC 10646-1:1993
- Transformation Format for 16 planes of group 00 (UTF-16).
- 26. ISO/IEC 10646-1/AMD2:1996, Amendment 2 to ISO/IEC 10646-1:1993 UCS
- Transformation Format 8 (UTF-8).
- 27. ISO/IEC 10646-1/AMD3:1996, Amendment 3 to ISO/IEC 10646-1:1993.
- 28. ISO/IEC 10646-1/AMD4:1996, Amendment 4 to ISO/IEC 10646-1:1993.
- 29. ISO/IEC 10646-1/AMD5:1998, Amendment 5 to ISO/IEC 10646-1:1993 Hangul
- syllables.
- 30. ISO/IEC 10646-1/AMD6:1997, Amendment 6 to ISO/IEC 10646-1:1993
- Tibetan.
- 31. ISO/IEC 10646-1/AMD7:1997, Amendment 7 to ISO/IEC 10646-1:1993 33
- additional characters.
- 32. ISO/IEC 10646-1/AMD8:1997, Amendment 8 to ISO/IEC 10646-1:1993.
- 33. ISO/IEC 10646-1/AMD9:1997, Amendment 9 to ISO/IEC 10646-1:1993
- Identifiers for characters.
- 34. ISO/IEC 10646-1/AMD10:1998, Amendment 10 to ISO/IEC 10646-1:1993
- Ethiopic.
- 35. ISO/IEC 10646-1/AMD11:1998, Amendment 11 to ISO/IEC 10646-1:1993
- Unified Canadian Aboriginal Syllabics.
- 36. ISO/IEC 10646-1/AMD12:1998, Amendment 12 to ISO/IEC 10646-1:1993
- Cherokee.
- 37. ISO/IEC 10967-1:1994, Information technology -- Language independent
- arithmetic -- Part 1: Integer and floating point arithmetic.
-
-
-[page 650]
-
- 38. ISO/IEC TR 19769:2004, Information technology -- Programming languages,
- their environments and system software interfaces -- Extensions for the
- programming language C to support new character data types.
- 39. ISO/IEC TR 24731-1:2007, Information technology -- Programming languages,
- their environments and system software interfaces -- Extensions to the C library
- -- Part 1: Bounds-checking interfaces.
-
-
-
-
-[page 651]
-
-
-
-[page 652]
-
-
-Index
-[^ x ^], 3.20 , (comma operator), 5.1.2.4, 6.5.17
- , (comma punctuator), 6.5.2, 6.7, 6.7.2.1, 6.7.2.2,
-[_ x _], 3.21 6.7.2.3, 6.7.9
-! (logical negation operator), 6.5.3.3 - (subtraction operator), 6.2.6.2, 6.5.6, F.3, G.5.2
-!= (inequality operator), 6.5.9 - (unary minus operator), 6.5.3.3, F.3
-# operator, 6.10.3.2 -- (postfix decrement operator), 6.3.2.1, 6.5.2.4
-# preprocessing directive, 6.10.7 -- (prefix decrement operator), 6.3.2.1, 6.5.3.1
-# punctuator, 6.10 -= (subtraction assignment operator), 6.5.16.2
-## operator, 6.10.3.3 -> (structure/union pointer operator), 6.5.2.3
-#define preprocessing directive, 6.10.3 . (structure/union member operator), 6.3.2.1,
-#elif preprocessing directive, 6.10.1 6.5.2.3
-#else preprocessing directive, 6.10.1 . punctuator, 6.7.9
-#endif preprocessing directive, 6.10.1 ... (ellipsis punctuator), 6.5.2.2, 6.7.6.3, 6.10.3
-#error preprocessing directive, 4, 6.10.5 / (division operator), 6.2.6.2, 6.5.5, F.3, G.5.1
-#if preprocessing directive, 5.2.4.2.1, 5.2.4.2.2, /* */ (comment delimiters), 6.4.9
- 6.10.1, 7.1.4 // (comment delimiter), 6.4.9
-#ifdef preprocessing directive, 6.10.1 /= (division assignment operator), 6.5.16.2
-#ifndef preprocessing directive, 6.10.1 : (colon punctuator), 6.7.2.1
-#include preprocessing directive, 5.1.1.2, :> (alternative spelling of ]), 6.4.6
- 6.10.2 ; (semicolon punctuator), 6.7, 6.7.2.1, 6.8.3,
-#line preprocessing directive, 6.10.4 6.8.5, 6.8.6
-#pragma preprocessing directive, 6.10.6 < (less-than operator), 6.5.8
-#undef preprocessing directive, 6.10.3.5, 7.1.3, <% (alternative spelling of {), 6.4.6
- 7.1.4 <: (alternative spelling of [), 6.4.6
-% (remainder operator), 6.2.6.2, 6.5.5 << (left-shift operator), 6.2.6.2, 6.5.7
-%: (alternative spelling of #), 6.4.6 <<= (left-shift assignment operator), 6.5.16.2
-%:%: (alternative spelling of ##), 6.4.6 <= (less-than-or-equal-to operator), 6.5.8
-%= (remainder assignment operator), 6.5.16.2 <assert.h> header, 7.2
-%> (alternative spelling of }), 6.4.6 <complex.h> header, 5.2.4.2.2, 6.10.8.3, 7.1.2,
-& (address operator), 6.3.2.1, 6.5.3.2 7.3, 7.24, 7.30.1, G.6, J.5.17
-& (bitwise AND operator), 6.2.6.2, 6.5.10 <ctype.h> header, 7.4, 7.30.2
-&& (logical AND operator), 5.1.2.4, 6.5.13 <errno.h> header, 7.5, 7.30.3, K.3.2
-&= (bitwise AND assignment operator), 6.5.16.2 <fenv.h> header, 5.1.2.3, 5.2.4.2.2, 7.6, 7.12, F,
-' ' (space character), 5.1.1.2, 5.2.1, 6.4, 7.4.1.3, H
- 7.4.1.10, 7.29.2.1.3 <float.h> header, 4, 5.2.4.2.2, 7.7, 7.22.1.3,
-( ) (cast operator), 6.5.4 7.28.4.1.1
-( ) (function-call operator), 6.5.2.2 <inttypes.h> header, 7.8, 7.30.4
-( ) (parentheses punctuator), 6.7.6.3, 6.8.4, 6.8.5 <iso646.h> header, 4, 7.9
-( ){ } (compound-literal operator), 6.5.2.5 <limits.h> header, 4, 5.2.4.2.1, 6.2.5, 7.10
-* (asterisk punctuator), 6.7.6.1, 6.7.6.2 <locale.h> header, 7.11, 7.30.5
-* (indirection operator), 6.5.2.1, 6.5.3.2 <math.h> header, 5.2.4.2.2, 6.5, 7.12, 7.24, F,
-* (multiplication operator), 6.2.6.2, 6.5.5, F.3, F.10, J.5.17
- G.5.1 <setjmp.h> header, 7.13
-*= (multiplication assignment operator), 6.5.16.2 <signal.h> header, 7.14, 7.30.6
-+ (addition operator), 6.2.6.2, 6.5.2.1, 6.5.3.2, <stdalign.h> header, 4, 7.15
- 6.5.6, F.3, G.5.2 <stdarg.h> header, 4, 6.7.6.3, 7.16
-+ (unary plus operator), 6.5.3.3 <stdatomic.h> header, 6.10.8.3, 7.1.2, 7.17
-++ (postfix increment operator), 6.3.2.1, 6.5.2.4 <stdbool.h> header, 4, 7.18, 7.30.7, H
-++ (prefix increment operator), 6.3.2.1, 6.5.3.1 <stddef.h> header, 4, 6.3.2.1, 6.3.2.3, 6.4.4.4,
-+= (addition assignment operator), 6.5.16.2
-[page 653]
-
- 6.4.5, 6.5.3.4, 6.5.6, 7.19, K.3.3 \x hexadecimal digits (hexadecimal-character
-<stdint.h> header, 4, 5.2.4.2, 6.10.1, 7.8, escape sequence), 6.4.4.4
- 7.20, 7.30.8, K.3.3, K.3.4 ^ (bitwise exclusive OR operator), 6.2.6.2, 6.5.11
-<stdio.h> header, 5.2.4.2.2, 7.21, 7.30.9, F, ^= (bitwise exclusive OR assignment operator),
- K.3.5 6.5.16.2
-<stdlib.h> header, 5.2.4.2.2, 7.22, 7.30.10, F, __alignas_is_defined macro, 7.15
- K.3.1.4, K.3.6 __bool_true_false_are_defined
-<string.h> header, 7.23, 7.30.11, K.3.7 macro, 7.18
-<tgmath.h> header, 7.24, G.7 __cplusplus macro, 6.10.8
-<threads.h> header, 6.10.8.3, 7.1.2, 7.25 __DATE__ macro, 6.10.8.1
-<time.h> header, 7.26, K.3.8 __FILE__ macro, 6.10.8.1, 7.2.1.1
-<uchar.h> header, 6.4.4.4, 6.4.5, 7.27 __func__ identifier, 6.4.2.2, 7.2.1.1
-<wchar.h> header, 5.2.4.2.2, 7.21.1, 7.28, __LINE__ macro, 6.10.8.1, 7.2.1.1
- 7.30.12, F, K.3.9 __STDC_, 6.11.9
-<wctype.h> header, 7.29, 7.30.13 __STDC__ macro, 6.10.8.1
-= (equal-sign punctuator), 6.7, 6.7.2.2, 6.7.9 __STDC_ANALYZABLE__ macro, 6.10.8.3, L.1
-= (simple assignment operator), 6.5.16.1 __STDC_HOSTED__ macro, 6.10.8.1
-== (equality operator), 6.5.9 __STDC_IEC_559__ macro, 6.10.8.3, F.1
-> (greater-than operator), 6.5.8 __STDC_IEC_559_COMPLEX__ macro,
->= (greater-than-or-equal-to operator), 6.5.8 6.10.8.3, G.1
->> (right-shift operator), 6.2.6.2, 6.5.7 __STDC_ISO_10646__ macro, 6.10.8.2
->>= (right-shift assignment operator), 6.5.16.2 __STDC_LIB_EXT1__ macro, 6.10.8.3, K.2
-? : (conditional operator), 5.1.2.4, 6.5.15 __STDC_MB_MIGHT_NEQ_WC__ macro,
-?? (trigraph sequences), 5.2.1.1 6.10.8.2, 7.19
-[ ] (array subscript operator), 6.5.2.1, 6.5.3.2 __STDC_NO_COMPLEX__ macro, 6.10.8.3,
-[ ] (brackets punctuator), 6.7.6.2, 6.7.9 7.3.1
-\ (backslash character), 5.1.1.2, 5.2.1, 6.4.4.4 __STDC_NO_THREADS__ macro, 6.10.8.3,
-\ (escape character), 6.4.4.4 7.17.1, 7.25.1
-\" (double-quote escape sequence), 6.4.4.4, __STDC_NO_VLA__ macro, 6.10.8.3
- 6.4.5, 6.10.9 __STDC_UTF_16__ macro, 6.10.8.2
-\\ (backslash escape sequence), 6.4.4.4, 6.10.9 __STDC_UTF_32__ macro, 6.10.8.2
-\' (single-quote escape sequence), 6.4.4.4, 6.4.5 __STDC_VERSION__ macro, 6.10.8.1
-\0 (null character), 5.2.1, 6.4.4.4, 6.4.5 __STDC_WANT_LIB_EXT1__ macro, K.3.1.1
- padding of binary stream, 7.21.2 __TIME__ macro, 6.10.8.1
-\? (question-mark escape sequence), 6.4.4.4 __VA_ARGS__ identifier, 6.10.3, 6.10.3.1
-\a (alert escape sequence), 5.2.2, 6.4.4.4 _Alignas, 6.7.5
-\b (backspace escape sequence), 5.2.2, 6.4.4.4 _Atomic type qualifier, 6.7.2, 6.7.3
-\f (form-feed escape sequence), 5.2.2, 6.4.4.4, _Atomic-qualified type, 6.2.5, 6.2.6.1, 6.5.2.3,
- 7.4.1.10 6.5.2.4, 6.5.16.2, 6.7.2, 6.7.3
-\n (new-line escape sequence), 5.2.2, 6.4.4.4, _Bool type, 6.2.5, 6.3.1.1, 6.3.1.2, 6.7.2, 7.17.1,
- 7.4.1.10 F.4
-\octal digits (octal-character escape sequence), _Bool type conversions, 6.3.1.2
- 6.4.4.4 _Complex types, 6.2.5, 6.7.2, 7.3.1, G
-\r (carriage-return escape sequence), 5.2.2, _Complex_I macro, 7.3.1
- 6.4.4.4, 7.4.1.10 _Exit function, 7.22.4.5, 7.22.4.7
-\t (horizontal-tab escape sequence), 5.2.2, _Imaginary keyword, G.2
- 6.4.4.4, 7.4.1.3, 7.4.1.10, 7.29.2.1.3 _Imaginary types, 7.3.1, G
-\U (universal character names), 6.4.3 _Imaginary_I macro, 7.3.1, G.6
-\u (universal character names), 6.4.3 _IOFBF macro, 7.21.1, 7.21.5.5, 7.21.5.6
-\v (vertical-tab escape sequence), 5.2.2, 6.4.4.4, _IOLBF macro, 7.21.1, 7.21.5.6
- 7.4.1.10 _IONBF macro, 7.21.1, 7.21.5.5, 7.21.5.6
-
-[page 654]
-
-_Noreturn, 6.7.4 alignment specifier, 6.7.5
-_Pragma operator, 5.1.1.2, 6.10.9 alignof operator, 6.5.3, 6.5.3.4
-_Static_assert, 6.7.10, 7.2 allocated storage, order and contiguity, 7.22.3
-_Thread_local storage-class specifier, 6.2.4, and macro, 7.9
- 6.7.1 AND operators
-{ } (braces punctuator), 6.7.2.2, 6.7.2.3, 6.7.9, bitwise (&), 6.2.6.2, 6.5.10
- 6.8.2 bitwise assignment (&=), 6.5.16.2
-{ } (compound-literal operator), 6.5.2.5 logical (&&), 5.1.2.4, 6.5.13
-| (bitwise inclusive OR operator), 6.2.6.2, 6.5.12 and_eq macro, 7.9
-|= (bitwise inclusive OR assignment operator), anonymous structure, 6.7.2.1
- 6.5.16.2 anonymous union, 6.7.2.1
-|| (logical OR operator), 5.1.2.4, 6.5.14 ANSI/IEEE 754, F.1
-~ (bitwise complement operator), 6.2.6.2, 6.5.3.3 ANSI/IEEE 854, F.1
- argc (main function parameter), 5.1.2.2.1
-abort function, 7.2.1.1, 7.14.1.1, 7.21.3, argument, 3.3
- 7.22.4.1, 7.25.3.6, K.3.6.1.2 array, 6.9.1
-abort_handler_s function, K.3.6.1.2 default promotions, 6.5.2.2
-abs function, 7.22.6.1 function, 6.5.2.2, 6.9.1
-absolute-value functions macro, substitution, 6.10.3.1
- complex, 7.3.8, G.6.4 argument, complex, 7.3.9.1
- integer, 7.8.2.1, 7.22.6.1 argv (main function parameter), 5.1.2.2.1
- real, 7.12.7, F.10.4 arithmetic constant expression, 6.6
-abstract declarator, 6.7.7 arithmetic conversions, usual, see usual arithmetic
-abstract machine, 5.1.2.3 conversions
-access, 3.1, 6.7.3, L.2.1 arithmetic operators
-accuracy, see floating-point accuracy additive, 6.2.6.2, 6.5.6, G.5.2
-acos functions, 7.12.4.1, F.10.1.1 bitwise, 6.2.6.2, 6.5.3.3, 6.5.10, 6.5.11, 6.5.12
-acos type-generic macro, 7.24 increment and decrement, 6.5.2.4, 6.5.3.1
-acosh functions, 7.12.5.1, F.10.2.1 multiplicative, 6.2.6.2, 6.5.5, G.5.1
-acosh type-generic macro, 7.24 shift, 6.2.6.2, 6.5.7
-acquire fence, 7.17.4 unary, 6.5.3.3
-acquire operation, 5.1.2.4 arithmetic types, 6.2.5
-active position, 5.2.2 arithmetic, pointer, 6.5.6
-actual argument, 3.3 array
-actual parameter (deprecated), 3.3 argument, 6.9.1
-addition assignment operator (+=), 6.5.16.2 declarator, 6.7.6.2
-addition operator (+), 6.2.6.2, 6.5.2.1, 6.5.3.2, initialization, 6.7.9
- 6.5.6, F.3, G.5.2 multidimensional, 6.5.2.1
-additive expressions, 6.5.6, G.5.2 parameter, 6.9.1
-address constant, 6.6 storage order, 6.5.2.1
-address operator (&), 6.3.2.1, 6.5.3.2 subscript operator ([ ]), 6.5.2.1, 6.5.3.2
-address-free, 7.17.5 subscripting, 6.5.2.1
-aggregate initialization, 6.7.9 type, 6.2.5
-aggregate types, 6.2.5 type conversion, 6.3.2.1
-alert escape sequence (\a), 5.2.2, 6.4.4.4 variable length, 6.7.6, 6.7.6.2, 6.10.8.3
-aliasing, 6.5 arrow operator (->), 6.5.2.3
-alignas macro, 7.15 as-if rule, 5.1.2.3
-aligned_alloc function, 7.22.3, 7.22.3.1 ASCII code set, 5.2.1.1
-alignment, 3.2, 6.2.8, 7.22.3.1 asctime function, 7.26.3.1
- pointer, 6.2.5, 6.3.2.3 asctime_s function, K.3.8.2, K.3.8.2.1
- structure/union member, 6.7.2.1 asin functions, 7.12.4.2, F.10.1.2
-
-[page 655]
-
-asin type-generic macro, 7.24, G.7 atomic_is_lock_free generic function,
-asinh functions, 7.12.5.2, F.10.2.2 7.17.5.1
-asinh type-generic macro, 7.24, G.7 ATOMIC_LLONG_LOCK_FREE macro, 7.17.1
-asm keyword, J.5.10 atomic_load generic functions, 7.17.7.2
-assert macro, 7.2.1.1 ATOMIC_LONG_LOCK_FREE macro, 7.17.1
-assert.h header, 7.2 ATOMIC_SHORT_LOCK_FREE macro, 7.17.1
-assignment atomic_signal_fence function, 7.17.4.2
- compound, 6.5.16.2 atomic_store generic functions, 7.17.7.1
- conversion, 6.5.16.1 atomic_thread_fence function, 7.17.4.1
- expression, 6.5.16 ATOMIC_VAR_INIT macro, 7.17.2.1
- operators, 6.3.2.1, 6.5.16 ATOMIC_WCHAR_T_LOCK_FREE macro, 7.17.1
- simple, 6.5.16.1 atomics header, 7.17
-associativity of operators, 6.5 auto storage-class specifier, 6.7.1, 6.9
-asterisk punctuator (*), 6.7.6.1, 6.7.6.2 automatic storage duration, 5.2.3, 6.2.4
-at_quick_exit function, 7.22.4.2, 7.22.4.3,
- 7.22.4.4, 7.22.4.5, 7.22.4.7 backslash character (\), 5.1.1.2, 5.2.1, 6.4.4.4
-atan functions, 7.12.4.3, F.10.1.3 backslash escape sequence (\\), 6.4.4.4, 6.10.9
-atan type-generic macro, 7.24, G.7 backspace escape sequence (\b), 5.2.2, 6.4.4.4
-atan2 functions, 7.12.4.4, F.10.1.4 basic character set, 3.6, 3.7.2, 5.2.1
-atan2 type-generic macro, 7.24 basic types, 6.2.5
-atanh functions, 7.12.5.3, F.10.2.3 behavior, 3.4
-atanh type-generic macro, 7.24, G.7 binary streams, 7.21.2, 7.21.7.10, 7.21.9.2,
-atexit function, 7.22.4.2, 7.22.4.3, 7.22.4.4, 7.21.9.4
- 7.22.4.5, 7.22.4.7, J.5.13 bit, 3.5
-atof function, 7.22.1, 7.22.1.1 high order, 3.6
-atoi function, 7.22.1, 7.22.1.2 low order, 3.6
-atol function, 7.22.1, 7.22.1.2 bit-field, 6.7.2.1
-atoll function, 7.22.1, 7.22.1.2 bitand macro, 7.9
-atomic lock-free macros, 7.17.1, 7.17.5 bitor macro, 7.9
-atomic operations, 5.1.2.4 bitwise operators, 6.5
-atomic types, 5.1.2.3, 6.10.8.3, 7.17.6 AND, 6.2.6.2, 6.5.10
-atomic_address type, 7.17.1, 7.17.6 AND assignment (&=), 6.5.16.2
-ATOMIC_ADDRESS_LOCK_FREE macro, 7.17.1 complement (~), 6.2.6.2, 6.5.3.3
-atomic_bool type, 7.17.1, 7.17.6 exclusive OR, 6.2.6.2, 6.5.11
-ATOMIC_CHAR16_T_LOCK_FREE macro, exclusive OR assignment (^=), 6.5.16.2
- 7.17.1 inclusive OR, 6.2.6.2, 6.5.12
-ATOMIC_CHAR32_T_LOCK_FREE macro, inclusive OR assignment (|=), 6.5.16.2
- 7.17.1 shift, 6.2.6.2, 6.5.7
-ATOMIC_CHAR_LOCK_FREE macro, 7.17.1 blank character, 7.4.1.3
-atomic_compare_exchange generic block, 6.8, 6.8.2, 6.8.4, 6.8.5
- functions, 7.17.7.4 block scope, 6.2.1
-atomic_exchange generic functions, 7.17.7.3 block structure, 6.2.1
-atomic_fetch and modify generic functions, bold type convention, 6.1
- 7.17.7.5 bool macro, 7.18
-atomic_flag type, 7.17.1, 7.17.8 boolean type, 6.3.1.2
-atomic_flag_clear functions, 7.17.8.2 boolean type conversion, 6.3.1.1, 6.3.1.2
-ATOMIC_FLAG_INIT macro, 7.17.1, 7.17.8 bounded undefined behavior, L.2.2
-atomic_flag_test_and_set functions, braces punctuator ({ }), 6.7.2.2, 6.7.2.3, 6.7.9,
- 7.17.8.1 6.8.2
-atomic_init generic function, 7.17.2.2 brackets operator ([ ]), 6.5.2.1, 6.5.3.2
-ATOMIC_INT_LOCK_FREE macro, 7.17.1 brackets punctuator ([ ]), 6.7.6.2, 6.7.9
-
-[page 656]
-
-branch cuts, 7.3.3 type-generic macro for, 7.24
-break statement, 6.8.6.3 ccosh functions, 7.3.6.4, G.6.2.4
-broken-down time, 7.26.1, 7.26.2.3, 7.26.3, type-generic macro for, 7.24
- 7.26.3.1, 7.26.3.3, 7.26.3.4, 7.26.3.5, ceil functions, 7.12.9.1, F.10.6.1
- K.3.8.2.1, K.3.8.2.3, K.3.8.2.4 ceil type-generic macro, 7.24
-bsearch function, 7.22.5, 7.22.5.1 cerf function, 7.30.1
-bsearch_s function, K.3.6.3, K.3.6.3.1 cerfc function, 7.30.1
-btowc function, 7.28.6.1.1 cexp functions, 7.3.7.1, G.6.3.1
-BUFSIZ macro, 7.21.1, 7.21.2, 7.21.5.5 type-generic macro for, 7.24
-byte, 3.6, 6.5.3.4 cexp2 function, 7.30.1
-byte input/output functions, 7.21.1 cexpm1 function, 7.30.1
-byte-oriented stream, 7.21.2 char type, 6.2.5, 6.3.1.1, 6.7.2, K.3.5.3.2,
- K.3.9.1.2
-C program, 5.1.1.1 char type conversion, 6.3.1.1, 6.3.1.3, 6.3.1.4,
-c16rtomb function, 7.27.1.2 6.3.1.8
-c32rtomb function, 7.27.1.4 char16_t type, 6.4.4.4, 6.4.5, 6.10.8.2, 7.27
-cabs functions, 7.3.8.1, G.6 char32_t type, 6.4.4.4, 6.4.5, 6.10.8.2, 7.27
- type-generic macro for, 7.24 CHAR_BIT macro, 5.2.4.2.1, 6.7.2.1
-cacos functions, 7.3.5.1, G.6.1.1 CHAR_MAX macro, 5.2.4.2.1, 7.11.2.1
- type-generic macro for, 7.24 CHAR_MIN macro, 5.2.4.2.1
-cacosh functions, 7.3.6.1, G.6.2.1 character, 3.7, 3.7.1
- type-generic macro for, 7.24 character array initialization, 6.7.9
-calendar time, 7.26.1, 7.26.2.2, 7.26.2.3, 7.26.2.4, character case mapping functions, 7.4.2
- 7.26.3.2, 7.26.3.3, 7.26.3.4, K.3.8.2.2, wide character, 7.29.3.1
- K.3.8.2.3, K.3.8.2.4 extensible, 7.29.3.2
-call by value, 6.5.2.2 character classification functions, 7.4.1
-call_once function, 7.25.1, 7.25.2.1 wide character, 7.29.2.1
-calloc function, 7.22.3, 7.22.3.2 extensible, 7.29.2.2
-carg functions, 7.3.9.1, G.6 character constant, 5.1.1.2, 5.2.1, 6.4.4.4
-carg type-generic macro, 7.24, G.7 character display semantics, 5.2.2
-carriage-return escape sequence (\r), 5.2.2, character handling header, 7.4, 7.11.1.1
- 6.4.4.4, 7.4.1.10 character input/output functions, 7.21.7, K.3.5.4
-carries a dependency, 5.1.2.4 wide character, 7.28.3
-case label, 6.8.1, 6.8.4.2 character sets, 5.2.1
-case mapping functions character string literal, see string literal
- character, 7.4.2 character type conversion, 6.3.1.1
- wide character, 7.29.3.1 character types, 6.2.5, 6.7.9
- extensible, 7.29.3.2 cimag functions, 7.3.9.2, 7.3.9.5, G.6
-casin functions, 7.3.5.2, G.6 cimag type-generic macro, 7.24, G.7
- type-generic macro for, 7.24 cis function, G.6
-casinh functions, 7.3.6.2, G.6.2.2 classification functions
- type-generic macro for, 7.24 character, 7.4.1
-cast expression, 6.5.4 floating-point, 7.12.3
-cast operator (( )), 6.5.4 wide character, 7.29.2.1
-catan functions, 7.3.5.3, G.6 extensible, 7.29.2.2
- type-generic macro for, 7.24 clearerr function, 7.21.10.1
-catanh functions, 7.3.6.3, G.6.2.3 clgamma function, 7.30.1
- type-generic macro for, 7.24 clock function, 7.26.2.1
-cbrt functions, 7.12.7.1, F.10.4.1 clock_t type, 7.26.1, 7.26.2.1
-cbrt type-generic macro, 7.24 CLOCKS_PER_SEC macro, 7.26.1, 7.26.2.1
-ccos functions, 7.3.5.4, G.6 clog functions, 7.3.7.2, G.6.3.2
-
-[page 657]
-
- type-generic macro for, 7.24 string, 7.23.3, K.3.7.2
-clog10 function, 7.30.1 wide string, 7.28.4.3, K.3.9.2.2
-clog1p function, 7.30.1 concatenation, preprocessing, see preprocessing
-clog2 function, 7.30.1 concatenation
-CMPLX macros, 7.3.9.3 conceptual models, 5.1
-cnd_broadcast function, 7.25.3.1, 7.25.3.5, conditional features, 4, 6.2.5, 6.7.6.2, 6.10.8.3,
- 7.25.3.6 7.1.2, F.1, G.1, K.2, L.1
-cnd_destroy function, 7.25.3.2 conditional inclusion, 6.10.1
-cnd_init function, 7.25.3.3 conditional operator (? :), 5.1.2.4, 6.5.15
-cnd_signal function, 7.25.3.4, 7.25.3.5, conflict, 5.1.2.4
- 7.25.3.6 conformance, 4
-cnd_t type, 7.25.1 conj functions, 7.3.9.4, G.6
-cnd_timedwait function, 7.25.3.5 conj type-generic macro, 7.24
-cnd_wait function, 7.25.3.3, 7.25.3.6 const type qualifier, 6.7.3
-collating sequences, 5.2.1 const-qualified type, 6.2.5, 6.3.2.1, 6.7.3
-colon punctuator (:), 6.7.2.1 constant expression, 6.6, F.8.4
-comma operator (,), 5.1.2.4, 6.5.17 constants, 6.4.4
-comma punctuator (,), 6.5.2, 6.7, 6.7.2.1, 6.7.2.2, as primary expression, 6.5.1
- 6.7.2.3, 6.7.9 character, 6.4.4.4
-command processor, 7.22.4.8 enumeration, 6.2.1, 6.4.4.3
-comment delimiters (/* */ and //), 6.4.9 floating, 6.4.4.2
-comments, 5.1.1.2, 6.4, 6.4.9 hexadecimal, 6.4.4.1
-common extensions, J.5 integer, 6.4.4.1
-common initial sequence, 6.5.2.3 octal, 6.4.4.1
-common real type, 6.3.1.8 constraint, 3.8, 4
-common warnings, I constraint_handler_t type, K.3.6
-comparison functions, 7.22.5, 7.22.5.1, 7.22.5.2, consume operation, 5.1.2.4
- K.3.6.3, K.3.6.3.1, K.3.6.3.2 content of structure/union/enumeration, 6.7.2.3
- string, 7.23.4 contiguity of allocated storage, 7.22.3
- wide string, 7.28.4.4 continue statement, 6.8.6.2
-comparison macros, 7.12.14 contracted expression, 6.5, 7.12.2, F.7
-comparison, pointer, 6.5.8 control character, 5.2.1, 7.4
-compatible type, 6.2.7, 6.7.2, 6.7.3, 6.7.6 control wide character, 7.29.2
-compl macro, 7.9 conversion, 6.3
-complement operator (~), 6.2.6.2, 6.5.3.3 arithmetic operands, 6.3.1
-complete type, 6.2.5 array argument, 6.9.1
-complex macro, 7.3.1 array parameter, 6.9.1
-complex numbers, 6.2.5, G arrays, 6.3.2.1
-complex type conversion, 6.3.1.6, 6.3.1.7 boolean, 6.3.1.2
-complex type domain, 6.2.5 boolean, characters, and integers, 6.3.1.1
-complex types, 6.2.5, 6.7.2, 6.10.8.3, G by assignment, 6.5.16.1
-complex.h header, 5.2.4.2.2, 6.10.8.3, 7.1.2, by return statement, 6.8.6.4
- 7.3, 7.24, 7.30.1, G.6, J.5.17 complex types, 6.3.1.6
-compliance, see conformance explicit, 6.3
-components of time, 7.26.1, K.3.8.1 function, 6.3.2.1
-composite type, 6.2.7 function argument, 6.5.2.2, 6.9.1
-compound assignment, 6.5.16.2 function designators, 6.3.2.1
-compound literals, 6.5.2.5 function parameter, 6.9.1
-compound statement, 6.8.2 imaginary, G.4.1
-compound-literal operator (( ){ }), 6.5.2.5 imaginary and complex, G.4.3
-concatenation functions implicit, 6.3
-
-[page 658]
-
- lvalues, 6.3.2.1 csinh functions, 7.3.6.5, G.6.2.5
- pointer, 6.3.2.1, 6.3.2.3 type-generic macro for, 7.24
- real and complex, 6.3.1.7 csqrt functions, 7.3.8.3, G.6.4.2
- real and imaginary, G.4.2 type-generic macro for, 7.24
- real floating and integer, 6.3.1.4, F.3, F.4 ctan functions, 7.3.5.6, G.6
- real floating types, 6.3.1.5, F.3 type-generic macro for, 7.24
- signed and unsigned integers, 6.3.1.3 ctanh functions, 7.3.6.6, G.6.2.6
- usual arithmetic, see usual arithmetic type-generic macro for, 7.24
- conversions ctgamma function, 7.30.1
- void type, 6.3.2.2 ctime function, 7.26.3.2
-conversion functions ctime_s function, K.3.8.2, K.3.8.2.2
- multibyte/wide character, 7.22.7, K.3.6.4 ctype.h header, 7.4, 7.30.2
- extended, 7.28.6, K.3.9.3 current object, 6.7.9
- restartable, 7.27.1, 7.28.6.3, K.3.9.3.1 CX_LIMITED_RANGE pragma, 6.10.6, 7.3.4
- multibyte/wide string, 7.22.8, K.3.6.5
- restartable, 7.28.6.4, K.3.9.3.2 data race, 5.1.2.4, 7.1.4, 7.22.2.1, 7.22.4.6,
- numeric, 7.8.2.3, 7.22.1 7.23.5.8, 7.23.6.2, 7.26.3, 7.27.1, 7.28.6.3,
- wide string, 7.8.2.4, 7.28.4.1 7.28.6.4
- single byte/wide character, 7.28.6.1 data stream, see streams
- time, 7.26.3, K.3.8.2 date and time header, 7.26, K.3.8
- wide character, 7.28.5 Daylight Saving Time, 7.26.1
-conversion specifier, 7.21.6.1, 7.21.6.2, 7.28.2.1, DBL_DECIMAL_DIG macro, 5.2.4.2.2
- 7.28.2.2 DBL_DIG macro, 5.2.4.2.2
-conversion state, 7.22.7, 7.27.1, 7.27.1.1, DBL_EPSILON macro, 5.2.4.2.2
- 7.27.1.2, 7.27.1.3, 7.27.1.4, 7.28.6, DBL_HAS_SUBNORM macro, 5.2.4.2.2
- 7.28.6.2.1, 7.28.6.3, 7.28.6.3.2, 7.28.6.3.3, DBL_MANT_DIG macro, 5.2.4.2.2
- 7.28.6.4, 7.28.6.4.1, 7.28.6.4.2, K.3.6.4, DBL_MAX macro, 5.2.4.2.2
- K.3.9.3.1, K.3.9.3.1.1, K.3.9.3.2, K.3.9.3.2.1, DBL_MAX_10_EXP macro, 5.2.4.2.2
- K.3.9.3.2.2 DBL_MAX_EXP macro, 5.2.4.2.2
-conversion state functions, 7.28.6.2 DBL_MIN macro, 5.2.4.2.2
-copying functions DBL_MIN_10_EXP macro, 5.2.4.2.2
- string, 7.23.2, K.3.7.1 DBL_MIN_EXP macro, 5.2.4.2.2
- wide string, 7.28.4.2, K.3.9.2.1 DBL_TRUE_MIN macro, 5.2.4.2.2
-copysign functions, 7.3.9.5, 7.12.11.1, F.3, decimal constant, 6.4.4.1
- F.10.8.1 decimal digit, 5.2.1
-copysign type-generic macro, 7.24 decimal-point character, 7.1.1, 7.11.2.1
-correctly rounded result, 3.9 DECIMAL_DIG macro, 5.2.4.2.2, 7.21.6.1,
-corresponding real type, 6.2.5 7.22.1.3, 7.28.2.1, 7.28.4.1.1, F.5
-cos functions, 7.12.4.5, F.10.1.5 declaration specifiers, 6.7
-cos type-generic macro, 7.24, G.7 declarations, 6.7
-cosh functions, 7.12.5.4, F.10.2.4 function, 6.7.6.3
-cosh type-generic macro, 7.24, G.7 pointer, 6.7.6.1
-cpow functions, 7.3.8.2, G.6.4.1 structure/union, 6.7.2.1
- type-generic macro for, 7.24 typedef, 6.7.8
-cproj functions, 7.3.9.5, G.6 declarator, 6.7.6
-cproj type-generic macro, 7.24 abstract, 6.7.7
-creal functions, 7.3.9.6, G.6 declarator type derivation, 6.2.5, 6.7.6
-creal type-generic macro, 7.24, G.7 decrement operators, see arithmetic operators,
-critical undefined behavior, L.2.3 increment and decrement
-csin functions, 7.3.5.5, G.6 default argument promotions, 6.5.2.2
- type-generic macro for, 7.24 default initialization, 6.7.9
-
-[page 659]
-
-default label, 6.8.1, 6.8.4.2 elif preprocessing directive, 6.10.1
-define preprocessing directive, 6.10.3 ellipsis punctuator (...), 6.5.2.2, 6.7.6.3, 6.10.3
-defined operator, 6.10.1, 6.10.8 else preprocessing directive, 6.10.1
-definition, 6.7 else statement, 6.8.4.1
- function, 6.9.1 empty statement, 6.8.3
-dependency-ordered before, 5.1.2.4 encoding error, 7.21.3, 7.27.1.1, 7.27.1.2,
-derived declarator types, 6.2.5 7.27.1.3, 7.27.1.4, 7.28.3.1, 7.28.3.3,
-derived types, 6.2.5 7.28.6.3.2, 7.28.6.3.3, 7.28.6.4.1, 7.28.6.4.2,
-designated initializer, 6.7.9 K.3.6.5.1, K.3.6.5.2, K.3.9.3.1.1, K.3.9.3.2.1,
-destringizing, 6.10.9 K.3.9.3.2.2
-device input/output, 5.1.2.3 end-of-file, 7.28.1
-diagnostic message, 3.10, 5.1.1.3 end-of-file indicator, 7.21.1, 7.21.5.3, 7.21.7.1,
-diagnostics, 5.1.1.3 7.21.7.5, 7.21.7.6, 7.21.7.10, 7.21.9.2,
-diagnostics header, 7.2 7.21.9.3, 7.21.10.1, 7.21.10.2, 7.28.3.1,
-difftime function, 7.26.2.2 7.28.3.10
-digit, 5.2.1, 7.4 end-of-file macro, see EOF macro
-digraphs, 6.4.6 end-of-line indicator, 5.2.1
-direct input/output functions, 7.21.8 endif preprocessing directive, 6.10.1
-display device, 5.2.2 enum type, 6.2.5, 6.7.2, 6.7.2.2
-div function, 7.22.6.2 enumerated type, 6.2.5
-div_t type, 7.22 enumeration, 6.2.5, 6.7.2.2
-division assignment operator (/=), 6.5.16.2 enumeration constant, 6.2.1, 6.4.4.3
-division operator (/), 6.2.6.2, 6.5.5, F.3, G.5.1 enumeration content, 6.7.2.3
-do statement, 6.8.5.2 enumeration members, 6.7.2.2
-documentation of implementation, 4 enumeration specifiers, 6.7.2.2
-domain error, 7.12.1, 7.12.4.1, 7.12.4.2, 7.12.4.4, enumeration tag, 6.2.3, 6.7.2.3
- 7.12.5.1, 7.12.5.3, 7.12.6.5, 7.12.6.7, enumerator, 6.7.2.2
- 7.12.6.8, 7.12.6.9, 7.12.6.10, 7.12.6.11, environment, 5
- 7.12.7.4, 7.12.7.5, 7.12.8.4, 7.12.9.5, environment functions, 7.22.4, K.3.6.2
- 7.12.9.7, 7.12.10.1, 7.12.10.2, 7.12.10.3 environment list, 7.22.4.6, K.3.6.2.1
-dot operator (.), 6.5.2.3 environmental considerations, 5.2
-double _Complex type, 6.2.5 environmental limits, 5.2.4, 7.13.1.1, 7.21.2,
-double _Complex type conversion, 6.3.1.6, 7.21.3, 7.21.4.4, 7.21.6.1, 7.22.2.1, 7.22.4.2,
- 6.3.1.7, 6.3.1.8 7.22.4.3, 7.28.2.1, K.3.5.1.2
-double _Imaginary type, G.2 EOF macro, 7.4, 7.21.1, 7.21.5.1, 7.21.5.2,
-double type, 6.2.5, 6.4.4.2, 6.7.2, 7.21.6.2, 7.21.6.2, 7.21.6.7, 7.21.6.9, 7.21.6.11,
- 7.28.2.2, F.2 7.21.6.14, 7.21.7.1, 7.21.7.3, 7.21.7.4,
-double type conversion, 6.3.1.4, 6.3.1.5, 6.3.1.7, 7.21.7.5, 7.21.7.6, 7.21.7.8, 7.21.7.9,
- 6.3.1.8 7.21.7.10, 7.28.1, 7.28.2.2, 7.28.2.4,
-double-precision arithmetic, 5.1.2.3 7.28.2.6, 7.28.2.8, 7.28.2.10, 7.28.2.12,
-double-quote escape sequence (\"), 6.4.4.4, 7.28.3.4, 7.28.6.1.1, 7.28.6.1.2, K.3.5.3.7,
- 6.4.5, 6.10.9 K.3.5.3.9, K.3.5.3.11, K.3.5.3.14, K.3.9.1.2,
-double_t type, 7.12, J.5.6 K.3.9.1.5, K.3.9.1.7, K.3.9.1.10, K.3.9.1.12,
- K.3.9.1.14
-EDOM macro, 7.5, 7.12.1, see also domain error equal-sign punctuator (=), 6.7, 6.7.2.2, 6.7.9
-effective type, 6.5 equal-to operator, see equality operator
-EILSEQ macro, 7.5, 7.21.3, 7.27.1.1, 7.27.1.2, equality expressions, 6.5.9
- 7.27.1.3, 7.27.1.4, 7.28.3.1, 7.28.3.3, equality operator (==), 6.5.9
- 7.28.6.3.2, 7.28.6.3.3, 7.28.6.4.1, 7.28.6.4.2, ERANGE macro, 7.5, 7.8.2.3, 7.8.2.4, 7.12.1,
- see also encoding error 7.22.1.3, 7.22.1.4, 7.28.4.1.1, 7.28.4.1.2, see
-element type, 6.2.5 also range error, pole error
-
-[page 660]
-
-erf functions, 7.12.8.1, F.10.5.1 exp type-generic macro, 7.24
-erf type-generic macro, 7.24 exp2 functions, 7.12.6.2, F.10.3.2
-erfc functions, 7.12.8.2, F.10.5.2 exp2 type-generic macro, 7.24
-erfc type-generic macro, 7.24 explicit conversion, 6.3
-errno macro, 7.1.3, 7.3.2, 7.5, 7.8.2.3, 7.8.2.4, expm1 functions, 7.12.6.3, F.10.3.3
- 7.12.1, 7.14.1.1, 7.21.3, 7.21.9.3, 7.21.10.4, expm1 type-generic macro, 7.24
- 7.22.1, 7.22.1.3, 7.22.1.4, 7.23.6.2, 7.27.1.1, exponent part, 6.4.4.2
- 7.27.1.2, 7.27.1.3, 7.27.1.4, 7.28.3.1, exponential functions
- 7.28.3.3, 7.28.4.1.1, 7.28.4.1.2, 7.28.6.3.2, complex, 7.3.7, G.6.3
- 7.28.6.3.3, 7.28.6.4.1, 7.28.6.4.2, J.5.17, real, 7.12.6, F.10.3
- K.3.1.3, K.3.7.4.2 expression, 6.5
-errno.h header, 7.5, 7.30.3, K.3.2 assignment, 6.5.16
-errno_t type, K.3.2, K.3.5, K.3.6, K.3.6.1.1, cast, 6.5.4
- K.3.7, K.3.8, K.3.9 constant, 6.6
-error evaluation, 5.1.2.3
- domain, see domain error full, 6.8
- encoding, see encoding error order of evaluation, see order of evaluation
- pole, see pole error parenthesized, 6.5.1
- range, see range error primary, 6.5.1
-error conditions, 7.12.1 unary, 6.5.3
-error functions, 7.12.8, F.10.5 expression statement, 6.8.3
-error indicator, 7.21.1, 7.21.5.3, 7.21.7.1, extended alignment, 6.2.8
- 7.21.7.3, 7.21.7.5, 7.21.7.6, 7.21.7.7, extended character set, 3.7.2, 5.2.1, 5.2.1.2
- 7.21.7.8, 7.21.9.2, 7.21.10.1, 7.21.10.3, extended characters, 5.2.1
- 7.28.3.1, 7.28.3.3 extended integer types, 6.2.5, 6.3.1.1, 6.4.4.1,
-error preprocessing directive, 4, 6.10.5 7.20
-error-handling functions, 7.21.10, 7.23.6.2, extended multibyte/wide character conversion
- K.3.7.4.2, K.3.7.4.3 utilities, 7.28.6, K.3.9.3
-escape character (\), 6.4.4.4 extensible wide character case mapping functions,
-escape sequences, 5.2.1, 5.2.2, 6.4.4.4, 6.11.4 7.29.3.2
-evaluation format, 5.2.4.2.2, 6.4.4.2, 7.12 extensible wide character classification functions,
-evaluation method, 5.2.4.2.2, 6.5, F.8.5 7.29.2.2
-evaluation of expression, 5.1.2.3 extern storage-class specifier, 6.2.2, 6.7.1
-evaluation order, see order of evaluation external definition, 6.9
-exceptional condition, 6.5 external identifiers, underscore, 7.1.3
-excess precision, 5.2.4.2.2, 6.3.1.5, 6.3.1.8, external linkage, 6.2.2
- 6.8.6.4 external name, 6.4.2.1
-excess range, 5.2.4.2.2, 6.3.1.5, 6.3.1.8, 6.8.6.4 external object definitions, 6.9.2
-exclusive OR operators
- bitwise (^), 6.2.6.2, 6.5.11 fabs functions, 7.12.7.2, F.3, F.10.4.2
- bitwise assignment (^=), 6.5.16.2 fabs type-generic macro, 7.24, G.7
-executable program, 5.1.1.1 false macro, 7.18
-execution character set, 5.2.1 fclose function, 7.21.5.1
-execution environment, 5, 5.1.2, see also fdim functions, 7.12.12.1, F.10.9.1
- environmental limits fdim type-generic macro, 7.24
-execution sequence, 5.1.2.3, 6.8 FE_ALL_EXCEPT macro, 7.6
-exit function, 5.1.2.2.3, 7.21.3, 7.22, 7.22.4.4, FE_DFL_ENV macro, 7.6
- 7.22.4.5, 7.22.4.7 FE_DIVBYZERO macro, 7.6, 7.12, F.3
-EXIT_FAILURE macro, 7.22, 7.22.4.4 FE_DOWNWARD macro, 7.6, F.3
-EXIT_SUCCESS macro, 7.22, 7.22.4.4 FE_INEXACT macro, 7.6, F.3
-exp functions, 7.12.6.1, F.10.3.1 FE_INVALID macro, 7.6, 7.12, F.3
-
-[page 661]
-
-FE_OVERFLOW macro, 7.6, 7.12, F.3 float _Complex type, 6.2.5
-FE_TONEAREST macro, 7.6, F.3 float _Complex type conversion, 6.3.1.6,
-FE_TOWARDZERO macro, 7.6, F.3 6.3.1.7, 6.3.1.8
-FE_UNDERFLOW macro, 7.6, F.3 float _Imaginary type, G.2
-FE_UPWARD macro, 7.6, F.3 float type, 6.2.5, 6.4.4.2, 6.7.2, F.2
-feclearexcept function, 7.6.2, 7.6.2.1, F.3 float type conversion, 6.3.1.4, 6.3.1.5, 6.3.1.7,
-fegetenv function, 7.6.4.1, 7.6.4.3, 7.6.4.4, F.3 6.3.1.8
-fegetexceptflag function, 7.6.2, 7.6.2.2, F.3 float.h header, 4, 5.2.4.2.2, 7.7, 7.22.1.3,
-fegetround function, 7.6, 7.6.3.1, F.3 7.28.4.1.1
-feholdexcept function, 7.6.4.2, 7.6.4.3, float_t type, 7.12, J.5.6
- 7.6.4.4, F.3 floating constant, 6.4.4.2
-fence, 5.1.2.4 floating suffix, f or F, 6.4.4.2
-fences, 7.17.4 floating type conversion, 6.3.1.4, 6.3.1.5, 6.3.1.7,
-fenv.h header, 5.1.2.3, 5.2.4.2.2, 7.6, 7.12, F, H F.3, F.4
-FENV_ACCESS pragma, 6.10.6, 7.6.1, F.8, F.9, floating types, 6.2.5, 6.11.1
- F.10 floating-point accuracy, 5.2.4.2.2, 6.4.4.2, 6.5,
-fenv_t type, 7.6 7.22.1.3, F.5, see also contracted expression
-feof function, 7.21.10.2 floating-point arithmetic functions, 7.12, F.10
-feraiseexcept function, 7.6.2, 7.6.2.3, F.3 floating-point classification functions, 7.12.3
-ferror function, 7.21.10.3 floating-point control mode, 7.6, F.8.6
-fesetenv function, 7.6.4.3, F.3 floating-point environment, 7.6, F.8, F.8.6
-fesetexceptflag function, 7.6.2, 7.6.2.4, F.3 floating-point exception, 7.6, 7.6.2, F.10
-fesetround function, 7.6, 7.6.3.2, F.3 floating-point number, 5.2.4.2.2, 6.2.5
-fetestexcept function, 7.6.2, 7.6.2.5, F.3 floating-point rounding mode, 5.2.4.2.2
-feupdateenv function, 7.6.4.2, 7.6.4.4, F.3 floating-point status flag, 7.6, F.8.6
-fexcept_t type, 7.6, F.3 floor functions, 7.12.9.2, F.10.6.2
-fflush function, 7.21.5.2, 7.21.5.3 floor type-generic macro, 7.24
-fgetc function, 7.21.1, 7.21.3, 7.21.7.1, FLT_DECIMAL_DIG macro, 5.2.4.2.2
- 7.21.7.5, 7.21.8.1 FLT_DIG macro, 5.2.4.2.2
-fgetpos function, 7.21.2, 7.21.9.1, 7.21.9.3 FLT_EPSILON macro, 5.2.4.2.2
-fgets function, 7.21.1, 7.21.7.2, K.3.5.4.1 FLT_EVAL_METHOD macro, 5.2.4.2.2, 6.6, 7.12,
-fgetwc function, 7.21.1, 7.21.3, 7.28.3.1, F.10.11
- 7.28.3.6 FLT_HAS_SUBNORM macro, 5.2.4.2.2
-fgetws function, 7.21.1, 7.28.3.2 FLT_MANT_DIG macro, 5.2.4.2.2
-field width, 7.21.6.1, 7.28.2.1 FLT_MAX macro, 5.2.4.2.2
-file, 7.21.3 FLT_MAX_10_EXP macro, 5.2.4.2.2
- access functions, 7.21.5, K.3.5.2 FLT_MAX_EXP macro, 5.2.4.2.2
- name, 7.21.3 FLT_MIN macro, 5.2.4.2.2
- operations, 7.21.4, K.3.5.1 FLT_MIN_10_EXP macro, 5.2.4.2.2
- position indicator, 7.21.1, 7.21.2, 7.21.3, FLT_MIN_EXP macro, 5.2.4.2.2
- 7.21.5.3, 7.21.7.1, 7.21.7.3, 7.21.7.10, FLT_RADIX macro, 5.2.4.2.2, 7.21.6.1, 7.22.1.3,
- 7.21.8.1, 7.21.8.2, 7.21.9.1, 7.21.9.2, 7.28.2.1, 7.28.4.1.1
- 7.21.9.3, 7.21.9.4, 7.21.9.5, 7.28.3.1, FLT_ROUNDS macro, 5.2.4.2.2, 7.6, F.3
- 7.28.3.3, 7.28.3.10 FLT_TRUE_MIN macro, 5.2.4.2.2
- positioning functions, 7.21.9 fma functions, 7.12, 7.12.13.1, F.10.10.1
-file scope, 6.2.1, 6.9 fma type-generic macro, 7.24
-FILE type, 7.21.1, 7.21.3 fmax functions, 7.12.12.2, F.10.9.2
-FILENAME_MAX macro, 7.21.1 fmax type-generic macro, 7.24
-flags, 7.21.6.1, 7.28.2.1, see also floating-point fmin functions, 7.12.12.3, F.10.9.3
- status flag fmin type-generic macro, 7.24
-flexible array member, 6.7.2.1 fmod functions, 7.12.10.1, F.10.7.1
-
-[page 662]
-
-fmod type-generic macro, 7.24 fscanf_s function, K.3.5.3.2, K.3.5.3.4,
-fopen function, 7.21.5.3, 7.21.5.4, K.3.5.2.1 K.3.5.3.7, K.3.5.3.9
-FOPEN_MAX macro, 7.21.1, 7.21.3, 7.21.4.3, fseek function, 7.21.1, 7.21.5.3, 7.21.7.10,
- K.3.5.1.1 7.21.9.2, 7.21.9.4, 7.21.9.5, 7.28.3.10
-fopen_s function, K.3.5.1.1, K.3.5.2.1, fsetpos function, 7.21.2, 7.21.5.3, 7.21.7.10,
- K.3.5.2.2 7.21.9.1, 7.21.9.3, 7.28.3.10
-for statement, 6.8.5, 6.8.5.3 ftell function, 7.21.9.2, 7.21.9.4
-form-feed character, 5.2.1, 6.4 full declarator, 6.7.6
-form-feed escape sequence (\f), 5.2.2, 6.4.4.4, full expression, 6.8
- 7.4.1.10 fully buffered stream, 7.21.3
-formal argument (deprecated), 3.16 function
-formal parameter, 3.16 argument, 6.5.2.2, 6.9.1
-formatted input/output functions, 7.11.1.1, 7.21.6, body, 6.9.1
- K.3.5.3 call, 6.5.2.2
- wide character, 7.28.2, K.3.9.1 library, 7.1.4
-fortran keyword, J.5.9 declarator, 6.7.6.3, 6.11.6
-forward reference, 3.11 definition, 6.7.6.3, 6.9.1, 6.11.7
-FP_CONTRACT pragma, 6.5, 6.10.6, 7.12.2, see designator, 6.3.2.1
- also contracted expression image, 5.2.3
-FP_FAST_FMA macro, 7.12 inline, 6.7.4
-FP_FAST_FMAF macro, 7.12 library, 5.1.1.1, 7.1.4
-FP_FAST_FMAL macro, 7.12 name length, 5.2.4.1, 6.4.2.1, 6.11.3
-FP_ILOGB0 macro, 7.12, 7.12.6.5 no-return, 6.7.4
-FP_ILOGBNAN macro, 7.12, 7.12.6.5 parameter, 5.1.2.2.1, 6.5.2.2, 6.7, 6.9.1
-FP_INFINITE macro, 7.12, F.3 prototype, 5.1.2.2.1, 6.2.1, 6.2.7, 6.5.2.2, 6.7,
-FP_NAN macro, 7.12, F.3 6.7.6.3, 6.9.1, 6.11.6, 6.11.7, 7.1.2, 7.12
-FP_NORMAL macro, 7.12, F.3 prototype scope, 6.2.1, 6.7.6.2
-FP_SUBNORMAL macro, 7.12, F.3 recursive call, 6.5.2.2
-FP_ZERO macro, 7.12, F.3 return, 6.8.6.4, F.6
-fpclassify macro, 7.12.3.1, F.3 scope, 6.2.1
-fpos_t type, 7.21.1, 7.21.2 type, 6.2.5
-fprintf function, 7.8.1, 7.21.1, 7.21.6.1, type conversion, 6.3.2.1
- 7.21.6.2, 7.21.6.3, 7.21.6.5, 7.21.6.6, function specifiers, 6.7.4
- 7.21.6.8, 7.28.2.2, F.3, K.3.5.3.1 function type, 6.2.5
-fprintf_s function, K.3.5.3.1 function-call operator (( )), 6.5.2.2
-fputc function, 5.2.2, 7.21.1, 7.21.3, 7.21.7.3, function-like macro, 6.10.3
- 7.21.7.7, 7.21.8.2 fundamental alignment, 6.2.8
-fputs function, 7.21.1, 7.21.7.4 future directions
-fputwc function, 7.21.1, 7.21.3, 7.28.3.3, language, 6.11
- 7.28.3.8 library, 7.30
-fputws function, 7.21.1, 7.28.3.4 fwide function, 7.21.2, 7.28.3.5
-fread function, 7.21.1, 7.21.8.1 fwprintf function, 7.8.1, 7.21.1, 7.21.6.2,
-free function, 7.22.3.3, 7.22.3.5 7.28.2.1, 7.28.2.2, 7.28.2.3, 7.28.2.5,
-freestanding execution environment, 4, 5.1.2, 7.28.2.11, K.3.9.1.1
- 5.1.2.1 fwprintf_s function, K.3.9.1.1
-freopen function, 7.21.2, 7.21.5.4 fwrite function, 7.21.1, 7.21.8.2
-freopen_s function, K.3.5.2.2 fwscanf function, 7.8.1, 7.21.1, 7.28.2.2,
-frexp functions, 7.12.6.4, F.10.3.4 7.28.2.4, 7.28.2.6, 7.28.2.12, 7.28.3.10,
-frexp type-generic macro, 7.24 K.3.9.1.2
-fscanf function, 7.8.1, 7.21.1, 7.21.6.2, fwscanf_s function, K.3.9.1.2, K.3.9.1.5,
- 7.21.6.4, 7.21.6.7, 7.21.6.9, F.3, K.3.5.3.2 K.3.9.1.7, K.3.9.1.14
-
-[page 663]
-
-gamma functions, 7.12.8, F.10.5 name spaces, 6.2.3
-general utilities, 7.22, K.3.6 reserved, 6.4.1, 7.1.3, K.3.1.2
- wide string, 7.28.4, K.3.9.2 scope, 6.2.1
-general wide string utilities, 7.28.4, K.3.9.2 type, 6.2.5
-generic parameters, 7.24 identifier list, 6.7.6
-generic selection, 6.5.1.1 identifier nondigit, 6.4.2.1
-getc function, 7.21.1, 7.21.7.5, 7.21.7.6 IEC 559, F.1
-getchar function, 7.21.1, 7.21.7.6 IEC 60559, 2, 5.1.2.3, 5.2.4.2.2, 6.10.8.3, 7.3.3,
-getenv function, 7.22.4.6 7.6, 7.6.4.2, 7.12.1, 7.12.10.2, 7.12.14, F, G,
-getenv_s function, K.3.6.2.1 H.1
-gets function, K.3.5.4.1 IEEE 754, F.1
-gets_s function, K.3.5.4.1 IEEE 854, F.1
-getwc function, 7.21.1, 7.28.3.6, 7.28.3.7 IEEE floating-point arithmetic standard, see
-getwchar function, 7.21.1, 7.28.3.7 IEC 60559, ANSI/IEEE 754,
-gmtime function, 7.26.3.3 ANSI/IEEE 854
-gmtime_s function, K.3.8.2.3 if preprocessing directive, 5.2.4.2.1, 5.2.4.2.2,
-goto statement, 6.2.1, 6.8.1, 6.8.6.1 6.10.1, 7.1.4
-graphic characters, 5.2.1 if statement, 6.8.4.1
-greater-than operator (>), 6.5.8 ifdef preprocessing directive, 6.10.1
-greater-than-or-equal-to operator (>=), 6.5.8 ifndef preprocessing directive, 6.10.1
- ignore_handler_s function, K.3.6.1.3
-happens before, 5.1.2.4 ilogb functions, 7.12, 7.12.6.5, F.10.3.5
-header, 5.1.1.1, 7.1.2, see also standard headers ilogb type-generic macro, 7.24
-header names, 6.4, 6.4.7, 6.10.2 imaginary macro, 7.3.1, G.6
-hexadecimal constant, 6.4.4.1 imaginary numbers, G
-hexadecimal digit, 6.4.4.1, 6.4.4.2, 6.4.4.4 imaginary type domain, G.2
-hexadecimal prefix, 6.4.4.1 imaginary types, G
-hexadecimal-character escape sequence imaxabs function, 7.8.2.1
- (\x hexadecimal digits), 6.4.4.4 imaxdiv function, 7.8, 7.8.2.2
-high-order bit, 3.6 imaxdiv_t type, 7.8
-horizontal-tab character, 5.2.1, 6.4 implementation, 3.12
-horizontal-tab escape sequence (\r), 7.29.2.1.3 implementation limit, 3.13, 4, 5.2.4.2, 6.4.2.1,
-horizontal-tab escape sequence (\t), 5.2.2, 6.7.6, 6.8.4.2, E, see also environmental
- 6.4.4.4, 7.4.1.3, 7.4.1.10 limits
-hosted execution environment, 4, 5.1.2, 5.1.2.2 implementation-defined behavior, 3.4.1, 4, J.3
-HUGE_VAL macro, 7.12, 7.12.1, 7.22.1.3, implementation-defined value, 3.19.1
- 7.28.4.1.1, F.10 implicit conversion, 6.3
-HUGE_VALF macro, 7.12, 7.12.1, 7.22.1.3, implicit initialization, 6.7.9
- 7.28.4.1.1, F.10 include preprocessing directive, 5.1.1.2, 6.10.2
-HUGE_VALL macro, 7.12, 7.12.1, 7.22.1.3, inclusive OR operators
- 7.28.4.1.1, F.10 bitwise (|), 6.2.6.2, 6.5.12
-hyperbolic functions bitwise assignment (|=), 6.5.16.2
- complex, 7.3.6, G.6.2 incomplete type, 6.2.5
- real, 7.12.5, F.10.2 increment operators, see arithmetic operators,
-hypot functions, 7.12.7.3, F.10.4.3 increment and decrement
-hypot type-generic macro, 7.24 indeterminate value, 3.19.2
- indeterminately sequenced, 5.1.2.3, 6.5.2.2,
-I macro, 7.3.1, 7.3.9.5, G.6 6.5.2.4, 6.5.16.2, see also sequenced before,
-identifier, 6.4.2.1, 6.5.1 unsequenced
- linkage, see linkage indirection operator (*), 6.5.2.1, 6.5.3.2
- maximum length, 6.4.2.1 inequality operator (!=), 6.5.9
-
-[page 664]
-
-infinitary, 7.12.1 extended, 6.2.5, 6.3.1.1, 6.4.4.1, 7.20
-INFINITY macro, 7.3.9.5, 7.12, F.2.1 inter-thread happens before, 5.1.2.4
-initial position, 5.2.2 interactive device, 5.1.2.3, 7.21.3, 7.21.5.3
-initial shift state, 5.2.1.2 internal linkage, 6.2.2
-initialization, 5.1.2, 6.2.4, 6.3.2.1, 6.5.2.5, 6.7.9, internal name, 6.4.2.1
- F.8.5 interrupt, 5.2.3
- in blocks, 6.8 INTMAX_C macro, 7.20.4.2
-initializer, 6.7.9 INTMAX_MAX macro, 7.8.2.3, 7.8.2.4, 7.20.2.5
- permitted form, 6.6 INTMAX_MIN macro, 7.8.2.3, 7.8.2.4, 7.20.2.5
- string literal, 6.3.2.1 intmax_t type, 7.20.1.5, 7.21.6.1, 7.21.6.2,
-inline, 6.7.4 7.28.2.1, 7.28.2.2
-inner scope, 6.2.1 INTN_C macros, 7.20.4.1
-input failure, 7.28.2.6, 7.28.2.8, 7.28.2.10, INTN_MAX macros, 7.20.2.1
- K.3.5.3.2, K.3.5.3.4, K.3.5.3.7, K.3.5.3.9, INTN_MIN macros, 7.20.2.1
- K.3.5.3.11, K.3.5.3.14, K.3.9.1.2, K.3.9.1.5, intN_t types, 7.20.1.1
- K.3.9.1.7, K.3.9.1.10, K.3.9.1.12, K.3.9.1.14 INTPTR_MAX macro, 7.20.2.4
-input/output functions INTPTR_MIN macro, 7.20.2.4
- character, 7.21.7, K.3.5.4 intptr_t type, 7.20.1.4
- direct, 7.21.8 inttypes.h header, 7.8, 7.30.4
- formatted, 7.21.6, K.3.5.3 isalnum function, 7.4.1.1, 7.4.1.9, 7.4.1.10
- wide character, 7.28.2, K.3.9.1 isalpha function, 7.4.1.1, 7.4.1.2
- wide character, 7.28.3 isblank function, 7.4.1.3
- formatted, 7.28.2, K.3.9.1 iscntrl function, 7.4.1.2, 7.4.1.4, 7.4.1.7,
-input/output header, 7.21, K.3.5 7.4.1.11
-input/output, device, 5.1.2.3 isdigit function, 7.4.1.1, 7.4.1.2, 7.4.1.5,
-int type, 6.2.5, 6.3.1.1, 6.3.1.3, 6.4.4.1, 6.7.2 7.4.1.7, 7.4.1.11, 7.11.1.1
-int type conversion, 6.3.1.1, 6.3.1.3, 6.3.1.4, isfinite macro, 7.12.3.2, F.3
- 6.3.1.8 isgraph function, 7.4.1.6
-INT_FASTN_MAX macros, 7.20.2.3 isgreater macro, 7.12.14.1, F.3
-INT_FASTN_MIN macros, 7.20.2.3 isgreaterequal macro, 7.12.14.2, F.3
-int_fastN_t types, 7.20.1.3 isinf macro, 7.12.3.3
-INT_LEASTN_MAX macros, 7.20.2.2 isless macro, 7.12.14.3, F.3
-INT_LEASTN_MIN macros, 7.20.2.2 islessequal macro, 7.12.14.4, F.3
-int_leastN_t types, 7.20.1.2 islessgreater macro, 7.12.14.5, F.3
-INT_MAX macro, 5.2.4.2.1, 7.12, 7.12.6.5 islower function, 7.4.1.2, 7.4.1.7, 7.4.2.1,
-INT_MIN macro, 5.2.4.2.1, 7.12 7.4.2.2
-integer arithmetic functions, 7.8.2.1, 7.8.2.2, isnan macro, 7.12.3.4, F.3
- 7.22.6 isnormal macro, 7.12.3.5
-integer character constant, 6.4.4.4 ISO 31-11, 2, 3
-integer constant, 6.4.4.1 ISO 4217, 2, 7.11.2.1
-integer constant expression, 6.3.2.3, 6.6, 6.7.2.1, ISO 8601, 2, 7.26.3.5
- 6.7.2.2, 6.7.6.2, 6.7.9, 6.7.10, 6.8.4.2, 6.10.1, ISO/IEC 10646, 2, 6.4.2.1, 6.4.3, 6.10.8.2
- 7.1.4 ISO/IEC 10976-1, H.1
-integer conversion rank, 6.3.1.1 ISO/IEC 2382-1, 2, 3
-integer promotions, 5.1.2.3, 5.2.4.2.1, 6.3.1.1, ISO/IEC 646, 2, 5.2.1.1
- 6.5.2.2, 6.5.3.3, 6.5.7, 6.8.4.2, 7.20.2, 7.20.3, ISO/IEC 9945-2, 7.11
- 7.21.6.1, 7.28.2.1 ISO/IEC TR 10176, D
-integer suffix, 6.4.4.1 iso646.h header, 4, 7.9
-integer type conversion, 6.3.1.1, 6.3.1.3, 6.3.1.4, isprint function, 5.2.2, 7.4.1.8
- F.3, F.4 ispunct function, 7.4.1.2, 7.4.1.7, 7.4.1.9,
-integer types, 6.2.5, 7.20 7.4.1.11
-
-[page 665]
-
-isspace function, 7.4.1.2, 7.4.1.7, 7.4.1.9, Latin alphabet, 5.2.1, 6.4.2.1
- 7.4.1.10, 7.4.1.11, 7.21.6.2, 7.22.1.3, LC_ALL macro, 7.11, 7.11.1.1, 7.11.2.1
- 7.22.1.4, 7.28.2.2 LC_COLLATE macro, 7.11, 7.11.1.1, 7.23.4.3,
-isunordered macro, 7.12.14.6, F.3 7.28.4.4.2
-isupper function, 7.4.1.2, 7.4.1.11, 7.4.2.1, LC_CTYPE macro, 7.11, 7.11.1.1, 7.22, 7.22.7,
- 7.4.2.2 7.22.8, 7.28.6, 7.29.1, 7.29.2.2.1, 7.29.2.2.2,
-iswalnum function, 7.29.2.1.1, 7.29.2.1.9, 7.29.3.2.1, 7.29.3.2.2, K.3.6.4, K.3.6.5
- 7.29.2.1.10, 7.29.2.2.1 LC_MONETARY macro, 7.11, 7.11.1.1, 7.11.2.1
-iswalpha function, 7.29.2.1.1, 7.29.2.1.2, LC_NUMERIC macro, 7.11, 7.11.1.1, 7.11.2.1
- 7.29.2.2.1 LC_TIME macro, 7.11, 7.11.1.1, 7.26.3.5
-iswblank function, 7.29.2.1.3, 7.29.2.2.1 lconv structure type, 7.11
-iswcntrl function, 7.29.2.1.2, 7.29.2.1.4, LDBL_DECIMAL_DIG macro, 5.2.4.2.2
- 7.29.2.1.7, 7.29.2.1.11, 7.29.2.2.1 LDBL_DIG macro, 5.2.4.2.2
-iswctype function, 7.29.2.2.1, 7.29.2.2.2 LDBL_EPSILON macro, 5.2.4.2.2
-iswdigit function, 7.29.2.1.1, 7.29.2.1.2, LDBL_HAS_SUBNORM macro, 5.2.4.2.2
- 7.29.2.1.5, 7.29.2.1.7, 7.29.2.1.11, 7.29.2.2.1 LDBL_MANT_DIG macro, 5.2.4.2.2
-iswgraph function, 7.29.2.1, 7.29.2.1.6, LDBL_MAX macro, 5.2.4.2.2
- 7.29.2.1.10, 7.29.2.2.1 LDBL_MAX_10_EXP macro, 5.2.4.2.2
-iswlower function, 7.29.2.1.2, 7.29.2.1.7, LDBL_MAX_EXP macro, 5.2.4.2.2
- 7.29.2.2.1, 7.29.3.1.1, 7.29.3.1.2 LDBL_MIN macro, 5.2.4.2.2
-iswprint function, 7.29.2.1.6, 7.29.2.1.8, LDBL_MIN_10_EXP macro, 5.2.4.2.2
- 7.29.2.2.1 LDBL_MIN_EXP macro, 5.2.4.2.2
-iswpunct function, 7.29.2.1, 7.29.2.1.2, LDBL_TRUE_MIN macro, 5.2.4.2.2
- 7.29.2.1.7, 7.29.2.1.9, 7.29.2.1.10, ldexp functions, 7.12.6.6, F.10.3.6
- 7.29.2.1.11, 7.29.2.2.1 ldexp type-generic macro, 7.24
-iswspace function, 7.21.6.2, 7.28.2.2, ldiv function, 7.22.6.2
- 7.28.4.1.1, 7.28.4.1.2, 7.29.2.1.2, 7.29.2.1.6, ldiv_t type, 7.22
- 7.29.2.1.7, 7.29.2.1.9, 7.29.2.1.10, leading underscore in identifiers, 7.1.3
- 7.29.2.1.11, 7.29.2.2.1 left-shift assignment operator (<<=), 6.5.16.2
-iswupper function, 7.29.2.1.2, 7.29.2.1.11, left-shift operator (<<), 6.2.6.2, 6.5.7
- 7.29.2.2.1, 7.29.3.1.1, 7.29.3.1.2 length
-iswxdigit function, 7.29.2.1.12, 7.29.2.2.1 external name, 5.2.4.1, 6.4.2.1, 6.11.3
-isxdigit function, 7.4.1.12, 7.11.1.1 function name, 5.2.4.1, 6.4.2.1, 6.11.3
-italic type convention, 3, 6.1 identifier, 6.4.2.1
-iteration statements, 6.8.5 internal name, 5.2.4.1, 6.4.2.1
- length function, 7.22.7.1, 7.23.6.3, 7.28.4.6.1,
-jmp_buf type, 7.13 7.28.6.3.1, K.3.7.4.4, K.3.9.2.4.1
-jump statements, 6.8.6 length modifier, 7.21.6.1, 7.21.6.2, 7.28.2.1,
- 7.28.2.2
-keywords, 6.4.1, G.2, J.5.9, J.5.10 less-than operator (<), 6.5.8
-kill_dependency macro, 5.1.2.4, 7.17.3.1 less-than-or-equal-to operator (<=), 6.5.8
-known constant size, 6.2.5 letter, 5.2.1, 7.4
- lexical elements, 5.1.1.2, 6.4
-L_tmpnam macro, 7.21.1, 7.21.4.4 lgamma functions, 7.12.8.3, F.10.5.3
-L_tmpnam_s macro, K.3.5, K.3.5.1.2 lgamma type-generic macro, 7.24
-label name, 6.2.1, 6.2.3 library, 5.1.1.1, 7, K.3
-labeled statement, 6.8.1 future directions, 7.30
-labs function, 7.22.6.1 summary, B
-language, 6 terms, 7.1.1
- future directions, 6.11 use of functions, 7.1.4
- syntax summary, A lifetime, 6.2.4
-
-[page 666]
-
-limits long double _Complex type conversion,
- environmental, see environmental limits 6.3.1.6, 6.3.1.7, 6.3.1.8
- implementation, see implementation limits long double _Imaginary type, G.2
- numerical, see numerical limits long double suffix, l or L, 6.4.4.2
- translation, see translation limits long double type, 6.2.5, 6.4.4.2, 6.7.2,
-limits.h header, 4, 5.2.4.2.1, 6.2.5, 7.10 7.21.6.1, 7.21.6.2, 7.28.2.1, 7.28.2.2, F.2
-line buffered stream, 7.21.3 long double type conversion, 6.3.1.4, 6.3.1.5,
-line number, 6.10.4, 6.10.8.1 6.3.1.7, 6.3.1.8
-line preprocessing directive, 6.10.4 long int type, 6.2.5, 6.3.1.1, 6.7.2, 7.21.6.1,
-lines, 5.1.1.2, 7.21.2 7.21.6.2, 7.28.2.1, 7.28.2.2
- preprocessing directive, 6.10 long int type conversion, 6.3.1.1, 6.3.1.3,
-linkage, 6.2.2, 6.7, 6.7.4, 6.7.6.2, 6.9, 6.9.2, 6.3.1.4, 6.3.1.8
- 6.11.2 long integer suffix, l or L, 6.4.4.1
-llabs function, 7.22.6.1 long long int type, 6.2.5, 6.3.1.1, 6.7.2,
-lldiv function, 7.22.6.2 7.21.6.1, 7.21.6.2, 7.28.2.1, 7.28.2.2
-lldiv_t type, 7.22 long long int type conversion, 6.3.1.1,
-LLONG_MAX macro, 5.2.4.2.1, 7.22.1.4, 6.3.1.3, 6.3.1.4, 6.3.1.8
- 7.28.4.1.2 long long integer suffix, ll or LL, 6.4.4.1
-LLONG_MIN macro, 5.2.4.2.1, 7.22.1.4, LONG_MAX macro, 5.2.4.2.1, 7.22.1.4, 7.28.4.1.2
- 7.28.4.1.2 LONG_MIN macro, 5.2.4.2.1, 7.22.1.4, 7.28.4.1.2
-llrint functions, 7.12.9.5, F.3, F.10.6.5 longjmp function, 7.13.1.1, 7.13.2.1, 7.22.4.4,
-llrint type-generic macro, 7.24 7.22.4.7
-llround functions, 7.12.9.7, F.10.6.7 loop body, 6.8.5
-llround type-generic macro, 7.24 low-order bit, 3.6
-local time, 7.26.1 lowercase letter, 5.2.1
-locale, 3.4.2 lrint functions, 7.12.9.5, F.3, F.10.6.5
-locale-specific behavior, 3.4.2, J.4 lrint type-generic macro, 7.24
-locale.h header, 7.11, 7.30.5 lround functions, 7.12.9.7, F.10.6.7
-localeconv function, 7.11.1.1, 7.11.2.1 lround type-generic macro, 7.24
-localization, 7.11 lvalue, 6.3.2.1, 6.5.1, 6.5.2.4, 6.5.3.1, 6.5.16
-localtime function, 7.26.3.4
-localtime_s function, K.3.8.2.4 macro argument substitution, 6.10.3.1
-log functions, 7.12.6.7, F.10.3.7 macro definition
-log type-generic macro, 7.24 library function, 7.1.4
-log10 functions, 7.12.6.8, F.10.3.8 macro invocation, 6.10.3
-log10 type-generic macro, 7.24 macro name, 6.10.3
-log1p functions, 7.12.6.9, F.10.3.9 length, 5.2.4.1
-log1p type-generic macro, 7.24 predefined, 6.10.8, 6.11.9
-log2 functions, 7.12.6.10, F.10.3.10 redefinition, 6.10.3
-log2 type-generic macro, 7.24 scope, 6.10.3.5
-logarithmic functions macro parameter, 6.10.3
- complex, 7.3.7, G.6.3 macro preprocessor, 6.10
- real, 7.12.6, F.10.3 macro replacement, 6.10.3
-logb functions, 7.12.6.11, F.3, F.10.3.11 magnitude, complex, 7.3.8.1
-logb type-generic macro, 7.24 main function, 5.1.2.2.1, 5.1.2.2.3, 6.7.3.1, 6.7.4,
-logical operators 7.21.3
- AND (&&), 5.1.2.4, 6.5.13 malloc function, 7.22.3, 7.22.3.4, 7.22.3.5
- negation (!), 6.5.3.3 manipulation functions
- OR (||), 5.1.2.4, 6.5.14 complex, 7.3.9
-logical source lines, 5.1.1.2 real, 7.12.11, F.10.8
-long double _Complex type, 6.2.5 matching failure, 7.28.2.6, 7.28.2.8, 7.28.2.10,
-
-[page 667]
-
- K.3.9.1.7, K.3.9.1.10, K.3.9.1.12 modification order, 5.1.2.4
-math.h header, 5.2.4.2.2, 6.5, 7.12, 7.24, F, modulus functions, 7.12.6.12
- F.10, J.5.17 modulus, complex, 7.3.8.1
-MATH_ERREXCEPT macro, 7.12, F.10 mtx_destroy function, 7.25.4.1
-math_errhandling macro, 7.1.3, 7.12, F.10 mtx_init function, 7.25.1, 7.25.4.2
-MATH_ERRNO macro, 7.12 mtx_lock function, 7.25.4.3
-max_align_t type, 7.19 mtx_t type, 7.25.1
-maximum functions, 7.12.12, F.10.9 mtx_timedlock function, 7.25.4.4
-MB_CUR_MAX macro, 7.1.1, 7.22, 7.22.7.2, mtx_trylock function, 7.25.4.5
- 7.22.7.3, 7.27.1.2, 7.27.1.4, 7.28.6.3.3, mtx_unlock function, 7.25.4.3, 7.25.4.4,
- K.3.6.4.1, K.3.9.3.1.1 7.25.4.5, 7.25.4.6
-MB_LEN_MAX macro, 5.2.4.2.1, 7.1.1, 7.22 multibyte character, 3.7.2, 5.2.1.2, 6.4.4.4
-mblen function, 7.22.7.1, 7.28.6.3 multibyte conversion functions
-mbrlen function, 7.28.6.3.1 wide character, 7.22.7, K.3.6.4
-mbrtoc16 function, 6.4.4.4, 6.4.5, 7.27.1.1 extended, 7.28.6, K.3.9.3
-mbrtoc32 function, 6.4.4.4, 6.4.5, 7.27.1.3 restartable, 7.27.1, 7.28.6.3, K.3.9.3.1
-mbrtowc function, 7.21.3, 7.21.6.1, 7.21.6.2, wide string, 7.22.8, K.3.6.5
- 7.28.2.1, 7.28.2.2, 7.28.6.3.1, 7.28.6.3.2, restartable, 7.28.6.4, K.3.9.3.2
- 7.28.6.4.1, K.3.6.5.1, K.3.9.3.2.1 multibyte string, 7.1.1
-mbsinit function, 7.28.6.2.1 multibyte/wide character conversion functions,
-mbsrtowcs function, 7.28.6.4.1, K.3.9.3.2 7.22.7, K.3.6.4
-mbsrtowcs_s function, K.3.9.3.2, K.3.9.3.2.1 extended, 7.28.6, K.3.9.3
-mbstate_t type, 7.21.2, 7.21.3, 7.21.6.1, restartable, 7.27.1, 7.28.6.3, K.3.9.3.1
- 7.21.6.2, 7.27, 7.27.1, 7.28.1, 7.28.2.1, multibyte/wide string conversion functions,
- 7.28.2.2, 7.28.6, 7.28.6.2.1, 7.28.6.3, 7.22.8, K.3.6.5
- 7.28.6.3.1, 7.28.6.4 restartable, 7.28.6.4, K.3.9.3.2
-mbstowcs function, 6.4.5, 7.22.8.1, 7.28.6.4 multidimensional array, 6.5.2.1
-mbstowcs_s function, K.3.6.5.1 multiplication assignment operator (*=), 6.5.16.2
-mbtowc function, 6.4.4.4, 7.22.7.1, 7.22.7.2, multiplication operator (*), 6.2.6.2, 6.5.5, F.3,
- 7.22.8.1, 7.28.6.3 G.5.1
-member access operators (. and ->), 6.5.2.3 multiplicative expressions, 6.5.5, G.5.1
-member alignment, 6.7.2.1
-memchr function, 7.23.5.1 n-char sequence, 7.22.1.3
-memcmp function, 7.23.4, 7.23.4.1 n-wchar sequence, 7.28.4.1.1
-memcpy function, 7.23.2.1 name
-memcpy_s function, K.3.7.1.1 external, 5.2.4.1, 6.4.2.1, 6.11.3
-memmove function, 7.23.2.2 file, 7.21.3
-memmove_s function, K.3.7.1.2 internal, 5.2.4.1, 6.4.2.1
-memory location, 3.14 label, 6.2.3
-memory management functions, 7.22.3 structure/union member, 6.2.3
-memory_order type, 7.17.1, 7.17.3 name spaces, 6.2.3
-memset function, 7.23.6.1, K.3.7.4.1 named label, 6.8.1
-memset_s function, K.3.7.4.1 NaN, 5.2.4.2.2
-minimum functions, 7.12.12, F.10.9 nan functions, 7.12.11.2, F.2.1, F.10.8.2
-minus operator, unary, 6.5.3.3 NAN macro, 7.12, F.2.1
-miscellaneous functions NDEBUG macro, 7.2
- string, 7.23.6, K.3.7.4 nearbyint functions, 7.12.9.3, 7.12.9.4, F.3,
- wide string, 7.28.4.6, K.3.9.2.4 F.10.6.3
-mktime function, 7.26.2.3 nearbyint type-generic macro, 7.24
-modf functions, 7.12.6.12, F.10.3.12 nearest integer functions, 7.12.9, F.10.6
-modifiable lvalue, 6.3.2.1 negation operator (!), 6.5.3.3
-
-[page 668]
-
-negative zero, 6.2.6.2, 7.12.11.1 operator, 6.4.6
-new-line character, 5.1.1.2, 5.2.1, 6.4, 6.10, 6.10.4 operators, 6.5
-new-line escape sequence (\n), 5.2.2, 6.4.4.4, additive, 6.2.6.2, 6.5.6
- 7.4.1.10 alignof, 6.5.3.4
-nextafter functions, 7.12.11.3, 7.12.11.4, F.3, assignment, 6.5.16
- F.10.8.3 associativity, 6.5
-nextafter type-generic macro, 7.24 equality, 6.5.9
-nexttoward functions, 7.12.11.4, F.3, F.10.8.4 multiplicative, 6.2.6.2, 6.5.5, G.5.1
-nexttoward type-generic macro, 7.24 postfix, 6.5.2
-no linkage, 6.2.2 precedence, 6.5
-no-return function, 6.7.4 preprocessing, 6.10.1, 6.10.3.2, 6.10.3.3, 6.10.9
-non-stop floating-point control mode, 7.6.4.2 relational, 6.5.8
-nongraphic characters, 5.2.2, 6.4.4.4 shift, 6.5.7
-nonlocal jumps header, 7.13 sizeof, 6.5.3.4
-norm, complex, 7.3.8.1 unary, 6.5.3
-normalized broken-down time, K.3.8.1, K.3.8.2.1 unary arithmetic, 6.5.3.3
-not macro, 7.9 optional features, see conditional features
-not-equal-to operator, see inequality operator or macro, 7.9
-not_eq macro, 7.9 OR operators
-null character (\0), 5.2.1, 6.4.4.4, 6.4.5 bitwise exclusive (^), 6.2.6.2, 6.5.11
- padding of binary stream, 7.21.2 bitwise exclusive assignment (^=), 6.5.16.2
-NULL macro, 7.11, 7.19, 7.21.1, 7.22, 7.23.1, bitwise inclusive (|), 6.2.6.2, 6.5.12
- 7.26.1, 7.28.1 bitwise inclusive assignment (|=), 6.5.16.2
-null pointer, 6.3.2.3 logical (||), 5.1.2.4, 6.5.14
-null pointer constant, 6.3.2.3 or_eq macro, 7.9
-null preprocessing directive, 6.10.7 order of allocated storage, 7.22.3
-null statement, 6.8.3 order of evaluation, 6.5, 6.5.16, 6.10.3.2, 6.10.3.3,
-null wide character, 7.1.1 see also sequence points
-number classification macros, 7.12, 7.12.3.1 ordinary identifier name space, 6.2.3
-numeric conversion functions, 7.8.2.3, 7.22.1 orientation of stream, 7.21.2, 7.28.3.5
- wide string, 7.8.2.4, 7.28.4.1 out-of-bounds store, L.2.1
-numerical limits, 5.2.4.2 outer scope, 6.2.1
- over-aligned, 6.2.8
-object, 3.15
-object representation, 6.2.6.1 padding
-object type, 6.2.5 binary stream, 7.21.2
-object-like macro, 6.10.3 bits, 6.2.6.2, 7.20.1.1
-observable behavior, 5.1.2.3 structure/union, 6.2.6.1, 6.7.2.1
-obsolescence, 6.11, 7.30 parameter, 3.16
-octal constant, 6.4.4.1 array, 6.9.1
-octal digit, 6.4.4.1, 6.4.4.4 ellipsis, 6.7.6.3, 6.10.3
-octal-character escape sequence (\octal digits), function, 6.5.2.2, 6.7, 6.9.1
- 6.4.4.4 macro, 6.10.3
-offsetof macro, 7.19 main function, 5.1.2.2.1
-on-off switch, 6.10.6 program, 5.1.2.2.1
-once_flag type, 7.25.1 parameter type list, 6.7.6.3
-ONCE_FLAG_INIT macro, 7.25.1 parentheses punctuator (( )), 6.7.6.3, 6.8.4, 6.8.5
-ones' complement, 6.2.6.2 parenthesized expression, 6.5.1
-operand, 6.4.6, 6.5 parse state, 7.21.2
-operating system, 5.1.2.1, 7.22.4.8 perform a trap, 3.19.5
-operations on files, 7.21.4, K.3.5.1 permitted form of initializer, 6.6
-
-[page 669]
-
-perror function, 7.21.10.4 PRIcLEASTN macros, 7.8.1
-phase angle, complex, 7.3.9.1 PRIcMAX macros, 7.8.1
-physical source lines, 5.1.1.2 PRIcN macros, 7.8.1
-placemarker, 6.10.3.3 PRIcPTR macros, 7.8.1
-plus operator, unary, 6.5.3.3 primary expression, 6.5.1
-pointer arithmetic, 6.5.6 printf function, 7.21.1, 7.21.6.3, 7.21.6.10,
-pointer comparison, 6.5.8 K.3.5.3.3
-pointer declarator, 6.7.6.1 printf_s function, K.3.5.3.3
-pointer operator (->), 6.5.2.3 printing character, 5.2.2, 7.4, 7.4.1.8
-pointer to function, 6.5.2.2 printing wide character, 7.29.2
-pointer type, 6.2.5 program diagnostics, 7.2.1
-pointer type conversion, 6.3.2.1, 6.3.2.3 program execution, 5.1.2.2.2, 5.1.2.3
-pointer, null, 6.3.2.3 program file, 5.1.1.1
-pole error, 7.12.1, 7.12.5.3, 7.12.6.7, 7.12.6.8, program image, 5.1.1.2
- 7.12.6.9, 7.12.6.10, 7.12.6.11, 7.12.7.4, program name (argv[0]), 5.1.2.2.1
- 7.12.8.3, 7.12.8.4 program parameters, 5.1.2.2.1
-portability, 4, J program startup, 5.1.2, 5.1.2.1, 5.1.2.2.1
-position indicator, file, see file position indicator program structure, 5.1.1.1
-positive difference, 7.12.12.1 program termination, 5.1.2, 5.1.2.1, 5.1.2.2.3,
-positive difference functions, 7.12.12, F.10.9 5.1.2.3
-postfix decrement operator (--), 6.3.2.1, 6.5.2.4 program, conforming, 4
-postfix expressions, 6.5.2 program, strictly conforming, 4
-postfix increment operator (++), 6.3.2.1, 6.5.2.4 promotions
-pow functions, 7.12.7.4, F.10.4.4 default argument, 6.5.2.2
-pow type-generic macro, 7.24 integer, 5.1.2.3, 6.3.1.1
-power functions prototype, see function prototype
- complex, 7.3.8, G.6.4 pseudo-random sequence functions, 7.22.2
- real, 7.12.7, F.10.4 PTRDIFF_MAX macro, 7.20.3
-pp-number, 6.4.8 PTRDIFF_MIN macro, 7.20.3
-pragma operator, 6.10.9 ptrdiff_t type, 7.17.1, 7.19, 7.20.3, 7.21.6.1,
-pragma preprocessing directive, 6.10.6, 6.11.8 7.21.6.2, 7.28.2.1, 7.28.2.2
-precedence of operators, 6.5 punctuators, 6.4.6
-precedence of syntax rules, 5.1.1.2 putc function, 7.21.1, 7.21.7.7, 7.21.7.8
-precision, 6.2.6.2, 6.3.1.1, 7.21.6.1, 7.28.2.1 putchar function, 7.21.1, 7.21.7.8
- excess, 5.2.4.2.2, 6.3.1.5, 6.3.1.8, 6.8.6.4 puts function, 7.21.1, 7.21.7.9
-predefined macro names, 6.10.8, 6.11.9 putwc function, 7.21.1, 7.28.3.8, 7.28.3.9
-prefix decrement operator (--), 6.3.2.1, 6.5.3.1 putwchar function, 7.21.1, 7.28.3.9
-prefix increment operator (++), 6.3.2.1, 6.5.3.1
-preprocessing concatenation, 6.10.3.3 qsort function, 7.22.5, 7.22.5.2
-preprocessing directives, 5.1.1.2, 6.10 qsort_s function, K.3.6.3, K.3.6.3.2
-preprocessing file, 5.1.1.1, 6.10 qualified types, 6.2.5
-preprocessing numbers, 6.4, 6.4.8 qualified version of type, 6.2.5
-preprocessing operators question-mark escape sequence (\?), 6.4.4.4
- #, 6.10.3.2 quick_exit function, 7.22.4.3, 7.22.4.4,
- ##, 6.10.3.3 7.22.4.7
- _Pragma, 5.1.1.2, 6.10.9 quiet NaN, 5.2.4.2.2
- defined, 6.10.1
-preprocessing tokens, 5.1.1.2, 6.4, 6.10 raise function, 7.14, 7.14.1.1, 7.14.2.1, 7.22.4.1
-preprocessing translation unit, 5.1.1.1 rand function, 7.22, 7.22.2.1, 7.22.2.2
-preprocessor, 6.10 RAND_MAX macro, 7.22, 7.22.2.1
-PRIcFASTN macros, 7.8.1 range
-
-[page 670]
-
- excess, 5.2.4.2.2, 6.3.1.5, 6.3.1.8, 6.8.6.4 rewind function, 7.21.5.3, 7.21.7.10, 7.21.9.5,
-range error, 7.12.1, 7.12.5.4, 7.12.5.5, 7.12.6.1, 7.28.3.10
- 7.12.6.2, 7.12.6.3, 7.12.6.5, 7.12.6.6, right-shift assignment operator (>>=), 6.5.16.2
- 7.12.6.13, 7.12.7.3, 7.12.7.4, 7.12.8.2, right-shift operator (>>), 6.2.6.2, 6.5.7
- 7.12.8.3, 7.12.8.4, 7.12.9.5, 7.12.9.7, rint functions, 7.12.9.4, F.3, F.10.6.4
- 7.12.11.3, 7.12.12.1, 7.12.13.1 rint type-generic macro, 7.24
-rank, see integer conversion rank round functions, 7.12.9.6, F.10.6.6
-read-modify-write operations, 5.1.2.4 round type-generic macro, 7.24
-real floating type conversion, 6.3.1.4, 6.3.1.5, rounding mode, floating point, 5.2.4.2.2
- 6.3.1.7, F.3, F.4 RSIZE_MAX macro, K.3.3, K.3.4, K.3.5.1.2,
-real floating types, 6.2.5 K.3.5.3.5, K.3.5.3.6, K.3.5.3.12, K.3.5.3.13,
-real type domain, 6.2.5 K.3.5.4.1, K.3.6.2.1, K.3.6.3.1, K.3.6.3.2,
-real types, 6.2.5 K.3.6.4.1, K.3.6.5.1, K.3.6.5.2, K.3.7.1.1,
-real-floating, 7.12.3 K.3.7.1.2, K.3.7.1.3, K.3.7.1.4, K.3.7.2.1,
-realloc function, 7.22.3, 7.22.3.5 K.3.7.2.2, K.3.7.3.1, K.3.7.4.1, K.3.7.4.2,
-recommended practice, 3.17 K.3.8.2.1, K.3.8.2.2, K.3.9.1.3, K.3.9.1.4,
-recursion, 6.5.2.2 K.3.9.1.8, K.3.9.1.9, K.3.9.2.1.1, K.3.9.2.1.2,
-recursive function call, 6.5.2.2 K.3.9.2.1.3, K.3.9.2.1.4, K.3.9.2.2.1,
-redefinition of macro, 6.10.3 K.3.9.2.2.2, K.3.9.2.3.1, K.3.9.3.1.1,
-reentrancy, 5.1.2.3, 5.2.3 K.3.9.3.2.1, K.3.9.3.2.2
- library functions, 7.1.4 rsize_t type, K.3.3, K.3.4, K.3.5, K.3.5.3.2,
-referenced type, 6.2.5 K.3.6, K.3.7, K.3.8, K.3.9, K.3.9.1.2
-register storage-class specifier, 6.7.1, 6.9 runtime-constraint, 3.18
-relational expressions, 6.5.8 Runtime-constraint handling functions, K.3.6.1
-relaxed atomic operations, 5.1.2.4 rvalue, 6.3.2.1
-release fence, 7.17.4
-release operation, 5.1.2.4 same scope, 6.2.1
-release sequence, 5.1.2.4 save calling environment function, 7.13.1
-reliability of data, interrupted, 5.1.2.3 scalar types, 6.2.5
-remainder assignment operator (%=), 6.5.16.2 scalbln function, 7.12.6.13, F.3, F.10.3.13
-remainder functions, 7.12.10, F.10.7 scalbln type-generic macro, 7.24
-remainder functions, 7.12.10.2, 7.12.10.3, F.3, scalbn function, 7.12.6.13, F.3, F.10.3.13
- F.10.7.2 scalbn type-generic macro, 7.24
-remainder operator (%), 6.2.6.2, 6.5.5 scanf function, 7.21.1, 7.21.6.4, 7.21.6.11
-remainder type-generic macro, 7.24 scanf_s function, K.3.5.3.4, K.3.5.3.11
-remove function, 7.21.4.1, 7.21.4.4, K.3.5.1.2 scanlist, 7.21.6.2, 7.28.2.2
-remquo functions, 7.12.10.3, F.3, F.10.7.3 scanset, 7.21.6.2, 7.28.2.2
-remquo type-generic macro, 7.24 SCHAR_MAX macro, 5.2.4.2.1
-rename function, 7.21.4.2 SCHAR_MIN macro, 5.2.4.2.1
-representations of types, 6.2.6 SCNcFASTN macros, 7.8.1
- pointer, 6.2.5 SCNcLEASTN macros, 7.8.1
-rescanning and replacement, 6.10.3.4 SCNcMAX macros, 7.8.1
-reserved identifiers, 6.4.1, 7.1.3, K.3.1.2 SCNcN macros, 7.8.1
-restartable multibyte/wide character conversion SCNcPTR macros, 7.8.1
- functions, 7.27.1, 7.28.6.3, K.3.9.3.1 scope of identifier, 6.2.1, 6.9.2
-restartable multibyte/wide string conversion search functions
- functions, 7.28.6.4, K.3.9.3.2 string, 7.23.5, K.3.7.3
-restore calling environment function, 7.13.2 utility, 7.22.5, K.3.6.3
-restrict type qualifier, 6.7.3, 6.7.3.1 wide string, 7.28.4.5, K.3.9.2.3
-restrict-qualified type, 6.2.5, 6.7.3 SEEK_CUR macro, 7.21.1, 7.21.9.2
-return statement, 6.8.6.4, F.6 SEEK_END macro, 7.21.1, 7.21.9.2
-
-[page 671]
-
-SEEK_SET macro, 7.21.1, 7.21.9.2 signal function, 7.14.1.1, 7.22.4.5, 7.22.4.7
-selection statements, 6.8.4 signal handler, 5.1.2.3, 5.2.3, 7.14.1.1, 7.14.2.1
-self-referential structure, 6.7.2.3 signal handling functions, 7.14.1
-semicolon punctuator (;), 6.7, 6.7.2.1, 6.8.3, signal.h header, 7.14, 7.30.6
- 6.8.5, 6.8.6 signaling NaN, 5.2.4.2.2, F.2.1
-separate compilation, 5.1.1.1 signals, 5.1.2.3, 5.2.3, 7.14.1
-separate translation, 5.1.1.1 signbit macro, 7.12.3.6, F.3
-sequence points, 5.1.2.3, 6.5.2.2, 6.5.13, 6.5.14, signed char type, 6.2.5, 7.21.6.1, 7.21.6.2,
- 6.5.15, 6.5.17, 6.7.3, 6.7.3.1, 6.7.6, 6.8, 7.28.2.1, 7.28.2.2, K.3.5.3.2, K.3.9.1.2
- 7.1.4, 7.21.6, 7.22.5, 7.28.2, C, K.3.6.3 signed character, 6.3.1.1
-sequenced after, see sequenced before signed integer types, 6.2.5, 6.3.1.3, 6.4.4.1
-sequenced before, 5.1.2.3, 6.5, 6.5.2.2, 6.5.2.4, signed type conversion, 6.3.1.1, 6.3.1.3, 6.3.1.4,
- 6.5.16, see also indeterminately sequenced, 6.3.1.8
- unsequenced signed types, 6.2.5, 6.7.2
-sequencing of statements, 6.8 significand part, 6.4.4.2
-set_constraint_handler_s function, SIGSEGV macro, 7.14, 7.14.1.1
- K.3.1.4, K.3.6.1.1, K.3.6.1.2, K.3.6.1.3 SIGTERM macro, 7.14
-setbuf function, 7.21.3, 7.21.5.1, 7.21.5.5 simple assignment operator (=), 6.5.16.1
-setjmp macro, 7.1.3, 7.13.1.1, 7.13.2.1 sin functions, 7.12.4.6, F.10.1.6
-setjmp.h header, 7.13 sin type-generic macro, 7.24, G.7
-setlocale function, 7.11.1.1, 7.11.2.1 single-byte character, 3.7.1, 5.2.1.2
-setvbuf function, 7.21.1, 7.21.3, 7.21.5.1, single-byte/wide character conversion functions,
- 7.21.5.5, 7.21.5.6 7.28.6.1
-shall, 4 single-precision arithmetic, 5.1.2.3
-shift expressions, 6.5.7 single-quote escape sequence (\'), 6.4.4.4, 6.4.5
-shift sequence, 7.1.1 singularity, 7.12.1
-shift states, 5.2.1.2 sinh functions, 7.12.5.5, F.10.2.5
-short identifier, character, 5.2.4.1, 6.4.3 sinh type-generic macro, 7.24, G.7
-short int type, 6.2.5, 6.3.1.1, 6.7.2, 7.21.6.1, SIZE_MAX macro, 7.20.3
- 7.21.6.2, 7.28.2.1, 7.28.2.2 size_t type, 6.2.8, 6.5.3.4, 7.19, 7.20.3, 7.21.1,
-short int type conversion, 6.3.1.1, 6.3.1.3, 7.21.6.1, 7.21.6.2, 7.22, 7.23.1, 7.26.1, 7.27,
- 6.3.1.4, 6.3.1.8 7.28.1, 7.28.2.1, 7.28.2.2, K.3.3, K.3.4,
-SHRT_MAX macro, 5.2.4.2.1 K.3.5, K.3.6, K.3.7, K.3.8, K.3.9, K.3.9.1.2
-SHRT_MIN macro, 5.2.4.2.1 sizeof operator, 6.3.2.1, 6.5.3, 6.5.3.4
-side effects, 5.1.2.3, 6.2.6.1, 6.3.2.2, 6.5, 6.5.2.4, snprintf function, 7.21.6.5, 7.21.6.12,
- 6.5.16, 6.7.9, 6.8.3, 7.6, 7.6.1, 7.21.7.5, K.3.5.3.5
- 7.21.7.7, 7.28.3.6, 7.28.3.8, F.8.1, F.9.1, snprintf_s function, K.3.5.3.5, K.3.5.3.6
- F.9.3 snwprintf_s function, K.3.9.1.3, K.3.9.1.4
-SIG_ATOMIC_MAX macro, 7.20.3 sorting utility functions, 7.22.5, K.3.6.3
-SIG_ATOMIC_MIN macro, 7.20.3 source character set, 5.1.1.2, 5.2.1
-sig_atomic_t type, 5.1.2.3, 7.14, 7.14.1.1, source file, 5.1.1.1
- 7.20.3 name, 6.10.4, 6.10.8.1
-SIG_DFL macro, 7.14, 7.14.1.1 source file inclusion, 6.10.2
-SIG_ERR macro, 7.14, 7.14.1.1 source lines, 5.1.1.2
-SIG_IGN macro, 7.14, 7.14.1.1 source text, 5.1.1.2
-SIGABRT macro, 7.14, 7.22.4.1 space character (' '), 5.1.1.2, 5.2.1, 6.4, 7.4.1.3,
-SIGFPE macro, 7.12.1, 7.14, 7.14.1.1, J.5.17 7.4.1.10, 7.29.2.1.3
-SIGILL macro, 7.14, 7.14.1.1 sprintf function, 7.21.6.6, 7.21.6.13, K.3.5.3.6
-SIGINT macro, 7.14 sprintf_s function, K.3.5.3.5, K.3.5.3.6
-sign and magnitude, 6.2.6.2 sqrt functions, 7.12.7.5, F.3, F.10.4.5
-sign bit, 6.2.6.2 sqrt type-generic macro, 7.24
-
-[page 672]
-
-srand function, 7.22.2.2 expression, 6.8.3
-sscanf function, 7.21.6.7, 7.21.6.14 for, 6.8.5.3
-sscanf_s function, K.3.5.3.7, K.3.5.3.14 goto, 6.8.6.1
-standard error stream, 7.21.1, 7.21.3, 7.21.10.4 if, 6.8.4.1
-standard headers, 4, 7.1.2 iteration, 6.8.5
- <assert.h>, 7.2 jump, 6.8.6
- <complex.h>, 5.2.4.2.2, 6.10.8.3, 7.1.2, 7.3, labeled, 6.8.1
- 7.24, 7.30.1, G.6, J.5.17 null, 6.8.3
- <ctype.h>, 7.4, 7.30.2 return, 6.8.6.4, F.6
- <errno.h>, 7.5, 7.30.3, K.3.2 selection, 6.8.4
- <fenv.h>, 5.1.2.3, 5.2.4.2.2, 7.6, 7.12, F, H sequencing, 6.8
- <float.h>, 4, 5.2.4.2.2, 7.7, 7.22.1.3, switch, 6.8.4.2
- 7.28.4.1.1 while, 6.8.5.1
- <inttypes.h>, 7.8, 7.30.4 static assertions, 6.7.10
- <iso646.h>, 4, 7.9 static storage duration, 6.2.4
- <limits.h>, 4, 5.2.4.2.1, 6.2.5, 7.10 static storage-class specifier, 6.2.2, 6.2.4, 6.7.1
- <locale.h>, 7.11, 7.30.5 static, in array declarators, 6.7.6.2, 6.7.6.3
- <math.h>, 5.2.4.2.2, 6.5, 7.12, 7.24, F, F.10, static_assert declaration, 6.7.10
- J.5.17 static_assert macro, 7.2
- <setjmp.h>, 7.13 stdalign.h header, 4, 7.15
- <signal.h>, 7.14, 7.30.6 stdarg.h header, 4, 6.7.6.3, 7.16
- <stdalign.h>, 4, 7.15 stdatomic.h header, 6.10.8.3, 7.1.2, 7.17
- <stdarg.h>, 4, 6.7.6.3, 7.16 stdbool.h header, 4, 7.18, 7.30.7, H
- <stdatomic.h>, 6.10.8.3, 7.1.2, 7.17 STDC, 6.10.6, 6.11.8
- <stdbool.h>, 4, 7.18, 7.30.7, H stddef.h header, 4, 6.3.2.1, 6.3.2.3, 6.4.4.4,
- <stddef.h>, 4, 6.3.2.1, 6.3.2.3, 6.4.4.4, 6.4.5, 6.5.3.4, 6.5.6, 7.19, K.3.3
- 6.4.5, 6.5.3.4, 6.5.6, 7.19, K.3.3 stderr macro, 7.21.1, 7.21.2, 7.21.3
- <stdint.h>, 4, 5.2.4.2, 6.10.1, 7.8, 7.20, stdin macro, 7.21.1, 7.21.2, 7.21.3, 7.21.6.4,
- 7.30.8, K.3.3, K.3.4 7.21.7.6, 7.28.2.12, 7.28.3.7, K.3.5.3.4,
- <stdio.h>, 5.2.4.2.2, 7.21, 7.30.9, F, K.3.5 K.3.5.4.1, K.3.9.1.14
- <stdlib.h>, 5.2.4.2.2, 7.22, 7.30.10, F, stdint.h header, 4, 5.2.4.2, 6.10.1, 7.8, 7.20,
- K.3.1.4, K.3.6 7.30.8, K.3.3, K.3.4
- <string.h>, 7.23, 7.30.11, K.3.7 stdio.h header, 5.2.4.2.2, 7.21, 7.30.9, F, K.3.5
- <tgmath.h>, 7.24, G.7 stdlib.h header, 5.2.4.2.2, 7.22, 7.30.10, F,
- <threads.h>, 6.10.8.3, 7.1.2, 7.25 K.3.1.4, K.3.6
- <time.h>, 7.26, K.3.8 stdout macro, 7.21.1, 7.21.2, 7.21.3, 7.21.6.3,
- <uchar.h>, 6.4.4.4, 6.4.5, 7.27 7.21.7.8, 7.21.7.9, 7.28.2.11, 7.28.3.9
- <wchar.h>, 5.2.4.2.2, 7.21.1, 7.28, 7.30.12, storage duration, 6.2.4
- F, K.3.9 storage order of array, 6.5.2.1
- <wctype.h>, 7.29, 7.30.13 storage unit (bit-field), 6.2.6.1, 6.7.2.1
-standard input stream, 7.21.1, 7.21.3 storage-class specifiers, 6.7.1, 6.11.5
-standard integer types, 6.2.5 strcat function, 7.23.3.1
-standard output stream, 7.21.1, 7.21.3 strcat_s function, K.3.7.2.1
-standard signed integer types, 6.2.5 strchr function, 7.23.5.2
-state-dependent encoding, 5.2.1.2, 7.22.7, K.3.6.4 strcmp function, 7.23.4, 7.23.4.2
-statements, 6.8 strcoll function, 7.11.1.1, 7.23.4.3, 7.23.4.5
- break, 6.8.6.3 strcpy function, 7.23.2.3
- compound, 6.8.2 strcpy_s function, K.3.7.1.3
- continue, 6.8.6.2 strcspn function, 7.23.5.3
- do, 6.8.5.2 streams, 7.21.2, 7.22.4.4
- else, 6.8.4.1 fully buffered, 7.21.3
-
-[page 673]
-
- line buffered, 7.21.3 strtoumax function, 7.8.2.3
- orientation, 7.21.2 struct hack, see flexible array member
- standard error, 7.21.1, 7.21.3 struct lconv, 7.11
- standard input, 7.21.1, 7.21.3 struct tm, 7.26.1
- standard output, 7.21.1, 7.21.3 structure
- unbuffered, 7.21.3 arrow operator (->), 6.5.2.3
-strerror function, 7.21.10.4, 7.23.6.2 content, 6.7.2.3
-strerror_s function, K.3.7.4.2, K.3.7.4.3 dot operator (.), 6.5.2.3
-strerrorlen_s function, K.3.7.4.3 initialization, 6.7.9
-strftime function, 7.11.1.1, 7.26.3, 7.26.3.5, member alignment, 6.7.2.1
- 7.28.5.1, K.3.8.2, K.3.8.2.1, K.3.8.2.2 member name space, 6.2.3
-stricter, 6.2.8 member operator (.), 6.3.2.1, 6.5.2.3
-strictly conforming program, 4 pointer operator (->), 6.5.2.3
-string, 7.1.1 specifier, 6.7.2.1
- comparison functions, 7.23.4 tag, 6.2.3, 6.7.2.3
- concatenation functions, 7.23.3, K.3.7.2 type, 6.2.5, 6.7.2.1
- conversion functions, 7.11.1.1 strxfrm function, 7.11.1.1, 7.23.4.5
- copying functions, 7.23.2, K.3.7.1 subnormal floating-point numbers, 5.2.4.2.2
- library function conventions, 7.23.1 subscripting, 6.5.2.1
- literal, 5.1.1.2, 5.2.1, 6.3.2.1, 6.4.5, 6.5.1, 6.7.9 subtraction assignment operator (-=), 6.5.16.2
- miscellaneous functions, 7.23.6, K.3.7.4 subtraction operator (-), 6.2.6.2, 6.5.6, F.3, G.5.2
- numeric conversion functions, 7.8.2.3, 7.22.1 suffix
- search functions, 7.23.5, K.3.7.3 floating constant, 6.4.4.2
-string handling header, 7.23, K.3.7 integer constant, 6.4.4.1
-string.h header, 7.23, 7.30.11, K.3.7 switch body, 6.8.4.2
-stringizing, 6.10.3.2, 6.10.9 switch case label, 6.8.1, 6.8.4.2
-strlen function, 7.23.6.3 switch default label, 6.8.1, 6.8.4.2
-strncat function, 7.23.3.2 switch statement, 6.8.1, 6.8.4.2
-strncat_s function, K.3.7.2.2 swprintf function, 7.28.2.3, 7.28.2.7,
-strncmp function, 7.23.4, 7.23.4.4 K.3.9.1.3, K.3.9.1.4
-strncpy function, 7.23.2.4 swprintf_s function, K.3.9.1.3, K.3.9.1.4
-strncpy_s function, K.3.7.1.4 swscanf function, 7.28.2.4, 7.28.2.8
-strnlen_s function, K.3.7.4.4 swscanf_s function, K.3.9.1.5, K.3.9.1.10
-stronger, 6.2.8 symbols, 3
-strpbrk function, 7.23.5.4 synchronization operation, 5.1.2.4
-strrchr function, 7.23.5.5 synchronize with, 5.1.2.4
-strspn function, 7.23.5.6 syntactic categories, 6.1
-strstr function, 7.23.5.7 syntax notation, 6.1
-strtod function, 7.12.11.2, 7.21.6.2, 7.22.1.3, syntax rule precedence, 5.1.1.2
- 7.28.2.2, F.3 syntax summary, language, A
-strtof function, 7.12.11.2, 7.22.1.3, F.3 system function, 7.22.4.8
-strtoimax function, 7.8.2.3
-strtok function, 7.23.5.8 tab characters, 5.2.1, 6.4
-strtok_s function, K.3.7.3.1 tag compatibility, 6.2.7
-strtol function, 7.8.2.3, 7.21.6.2, 7.22.1.2, tag name space, 6.2.3
- 7.22.1.4, 7.28.2.2 tags, 6.7.2.3
-strtold function, 7.12.11.2, 7.22.1.3, F.3 tan functions, 7.12.4.7, F.10.1.7
-strtoll function, 7.8.2.3, 7.22.1.2, 7.22.1.4 tan type-generic macro, 7.24, G.7
-strtoul function, 7.8.2.3, 7.21.6.2, 7.22.1.2, tanh functions, 7.12.5.6, F.10.2.6
- 7.22.1.4, 7.28.2.2 tanh type-generic macro, 7.24, G.7
-strtoull function, 7.8.2.3, 7.22.1.2, 7.22.1.4 temporary lifetime, 6.2.4
-
-[page 674]
-
-tentative definition, 6.9.2 towlower function, 7.29.3.1.1, 7.29.3.2.1
-terms, 3 towupper function, 7.29.3.1.2, 7.29.3.2.1
-text streams, 7.21.2, 7.21.7.10, 7.21.9.2, 7.21.9.4 translation environment, 5, 5.1.1
-tgamma functions, 7.12.8.4, F.10.5.4 translation limits, 5.2.4.1
-tgamma type-generic macro, 7.24 translation phases, 5.1.1.2
-tgmath.h header, 7.24, G.7 translation unit, 5.1.1.1, 6.9
-thrd_create function, 7.25.1, 7.25.5.1 trap, see perform a trap
-thrd_current function, 7.25.5.2 trap representation, 3.19.4, 6.2.6.1, 6.2.6.2,
-thrd_detach function, 7.25.5.3, 7.25.5.6 6.3.2.3, 6.5.2.3
-thrd_equal function, 7.25.5.4 trigonometric functions
-thrd_exit function, 7.25.5.5 complex, 7.3.5, G.6.1
-thrd_join function, 7.25.5.3, 7.25.5.6 real, 7.12.4, F.10.1
-thrd_sleep function, 7.25.5.7 trigraph sequences, 5.1.1.2, 5.2.1.1
-thrd_start_t type, 7.25.1 true macro, 7.18
-thrd_t type, 7.25.1 trunc functions, 7.12.9.8, F.10.6.8
-thrd_yield function, 7.25.5.8 trunc type-generic macro, 7.24
-thread of execution, 5.1.2.4, 7.1.4, 7.6, 7.22.4.6 truncation, 6.3.1.4, 7.12.9.8, 7.21.3, 7.21.5.3
-thread storage duration, 6.2.4, 7.6 truncation toward zero, 6.5.5
-threads header, 7.25 tss_create function, 7.25.6.1
-threads.h header, 6.10.8.3, 7.1.2, 7.25 tss_delete function, 7.25.6.2
-time TSS_DTOR_ITERATIONS macro, 7.25.1
- broken down, 7.26.1, 7.26.2.3, 7.26.3, 7.26.3.1, tss_dtor_t type, 7.25.1
- 7.26.3.3, 7.26.3.4, 7.26.3.5, K.3.8.2.1, tss_get function, 7.25.6.3
- K.3.8.2.3, K.3.8.2.4 tss_set function, 7.25.6.4
- calendar, 7.26.1, 7.26.2.2, 7.26.2.3, 7.26.2.4, tss_t type, 7.25.1
- 7.26.3.2, 7.26.3.3, 7.26.3.4, K.3.8.2.2, two's complement, 6.2.6.2, 7.20.1.1
- K.3.8.2.3, K.3.8.2.4 type category, 6.2.5
- components, 7.26.1, K.3.8.1 type conversion, 6.3
- conversion functions, 7.26.3, K.3.8.2 type definitions, 6.7.8
- wide character, 7.28.5 type domain, 6.2.5, G.2
- local, 7.26.1 type names, 6.7.7
- manipulation functions, 7.26.2 type punning, 6.5.2.3
- normalized broken down, K.3.8.1, K.3.8.2.1 type qualifiers, 6.7.3
-time function, 7.26.2.4 type specifiers, 6.7.2
-time.h header, 7.26, K.3.8 type-generic macro, 7.24, G.7
-time_t type, 7.26.1 typedef declaration, 6.7.8
-TIME_UTC macro, 7.25.7.1 typedef storage-class specifier, 6.7.1, 6.7.8
-tm structure type, 7.26.1, 7.28.1, K.3.8.1 types, 6.2.5
-TMP_MAX macro, 7.21.1, 7.21.4.3, 7.21.4.4 _Atomic qualified, 6.2.5, 6.2.6.1, 6.5.2.3,
-TMP_MAX_S macro, K.3.5, K.3.5.1.1, K.3.5.1.2 6.5.2.4, 6.5.16.2, 6.7.2, 6.7.3
-tmpfile function, 7.21.4.3, 7.22.4.4 atomic, 5.1.2.3, 6.10.8.3, 7.17.6
-tmpfile_s function, K.3.5.1.1, K.3.5.1.2 character, 6.7.9
-tmpnam function, 7.21.1, 7.21.4.3, 7.21.4.4, compatible, 6.2.7, 6.7.2, 6.7.3, 6.7.6
- K.3.5.1.2 complex, 6.2.5, G
-tmpnam_s function, K.3.5, K.3.5.1.1, K.3.5.1.2 composite, 6.2.7
-token, 5.1.1.2, 6.4, see also preprocessing tokens const qualified, 6.7.3
-token concatenation, 6.10.3.3 conversions, 6.3
-token pasting, 6.10.3.3 imaginary, G
-tolower function, 7.4.2.1 restrict qualified, 6.7.3
-toupper function, 7.4.2.2 volatile qualified, 6.7.3
-towctrans function, 7.29.3.2.1, 7.29.3.2.2
-
-[page 675]
-
-uchar.h header, 6.4.4.4, 6.4.5, 7.27 universal character name, 6.4.3
-UCHAR_MAX macro, 5.2.4.2.1 unnormalized floating-point numbers, 5.2.4.2.2
-UINT_FASTN_MAX macros, 7.20.2.3 unqualified type, 6.2.5
-uint_fastN_t types, 7.20.1.3 unqualified version of type, 6.2.5
-uint_least16_t type, 7.27 unsequenced, 5.1.2.3, 6.5, 6.5.16, see also
-uint_least32_t type, 7.27 indeterminately sequenced, sequenced
-UINT_LEASTN_MAX macros, 7.20.2.2 before
-uint_leastN_t types, 7.20.1.2 unsigned char type, K.3.5.3.2, K.3.9.1.2
-UINT_MAX macro, 5.2.4.2.1 unsigned integer suffix, u or U, 6.4.4.1
-UINTMAX_C macro, 7.20.4.2 unsigned integer types, 6.2.5, 6.3.1.3, 6.4.4.1
-UINTMAX_MAX macro, 7.8.2.3, 7.8.2.4, 7.20.2.5 unsigned type conversion, 6.3.1.1, 6.3.1.3,
-uintmax_t type, 7.20.1.5, 7.21.6.1, 7.21.6.2, 6.3.1.4, 6.3.1.8
- 7.28.2.1, 7.28.2.2 unsigned types, 6.2.5, 6.7.2, 7.21.6.1, 7.21.6.2,
-UINTN_C macros, 7.20.4.1 7.28.2.1, 7.28.2.2
-UINTN_MAX macros, 7.20.2.1 unspecified behavior, 3.4.4, 4, J.1
-uintN_t types, 7.20.1.1 unspecified value, 3.19.3
-UINTPTR_MAX macro, 7.20.2.4 uppercase letter, 5.2.1
-uintptr_t type, 7.20.1.4 use of library functions, 7.1.4
-ULLONG_MAX macro, 5.2.4.2.1, 7.22.1.4, USHRT_MAX macro, 5.2.4.2.1
- 7.28.4.1.2 usual arithmetic conversions, 6.3.1.8, 6.5.5, 6.5.6,
-ULONG_MAX macro, 5.2.4.2.1, 7.22.1.4, 6.5.8, 6.5.9, 6.5.10, 6.5.11, 6.5.12, 6.5.15
- 7.28.4.1.2 UTF-16, 6.10.8.2
-unary arithmetic operators, 6.5.3.3 UTF-32, 6.10.8.2
-unary expression, 6.5.3 UTF-8 string literal, see string literal
-unary minus operator (-), 6.5.3.3, F.3 utilities, general, 7.22, K.3.6
-unary operators, 6.5.3 wide string, 7.28.4, K.3.9.2
-unary plus operator (+), 6.5.3.3
-unbuffered stream, 7.21.3 va_arg macro, 7.16, 7.16.1, 7.16.1.1, 7.16.1.2,
-undef preprocessing directive, 6.10.3.5, 7.1.3, 7.16.1.4, 7.21.6.8, 7.21.6.9, 7.21.6.10,
- 7.1.4 7.21.6.11, 7.21.6.12, 7.21.6.13, 7.21.6.14,
-undefined behavior, 3.4.3, 4, J.2 7.28.2.5, 7.28.2.6, 7.28.2.7, 7.28.2.8,
-underscore character, 6.4.2.1 7.28.2.9, 7.28.2.10, K.3.5.3.9, K.3.5.3.11,
-underscore, leading, in identifier, 7.1.3 K.3.5.3.14, K.3.9.1.7, K.3.9.1.10, K.3.9.1.12
-ungetc function, 7.21.1, 7.21.7.10, 7.21.9.2, va_copy macro, 7.1.3, 7.16, 7.16.1, 7.16.1.1,
- 7.21.9.3 7.16.1.2, 7.16.1.3
-ungetwc function, 7.21.1, 7.28.3.10 va_end macro, 7.1.3, 7.16, 7.16.1, 7.16.1.3,
-Unicode, 7.27, see also char16_t type, 7.16.1.4, 7.21.6.8, 7.21.6.9, 7.21.6.10,
- char32_t type, wchar_t type 7.21.6.11, 7.21.6.12, 7.21.6.13, 7.21.6.14,
-Unicode required set, 6.10.8.2 7.28.2.5, 7.28.2.6, 7.28.2.7, 7.28.2.8,
-union 7.28.2.9, 7.28.2.10, K.3.5.3.9, K.3.5.3.11,
- arrow operator (->), 6.5.2.3 K.3.5.3.14, K.3.9.1.7, K.3.9.1.10, K.3.9.1.12
- content, 6.7.2.3 va_list type, 7.16, 7.16.1.3
- dot operator (.), 6.5.2.3 va_start macro, 7.16, 7.16.1, 7.16.1.1,
- initialization, 6.7.9 7.16.1.2, 7.16.1.3, 7.16.1.4, 7.21.6.8,
- member alignment, 6.7.2.1 7.21.6.9, 7.21.6.10, 7.21.6.11, 7.21.6.12,
- member name space, 6.2.3 7.21.6.13, 7.21.6.14, 7.28.2.5, 7.28.2.6,
- member operator (.), 6.3.2.1, 6.5.2.3 7.28.2.7, 7.28.2.8, 7.28.2.9, 7.28.2.10,
- pointer operator (->), 6.5.2.3 K.3.5.3.9, K.3.5.3.11, K.3.5.3.14, K.3.9.1.7,
- specifier, 6.7.2.1 K.3.9.1.10, K.3.9.1.12
- tag, 6.2.3, 6.7.2.3 value, 3.19
- type, 6.2.5, 6.7.2.1 value bits, 6.2.6.2
-
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-variable arguments, 6.10.3, 7.16 vswscanf function, 7.28.2.8
-variable arguments header, 7.16 vswscanf_s function, K.3.9.1.10
-variable length array, 6.7.6, 6.7.6.2, 6.10.8.3 vwprintf function, 7.21.1, 7.28.2.9, K.3.9.1.11
-variably modified type, 6.7.6, 6.7.6.2, 6.10.8.3 vwprintf_s function, K.3.9.1.11
-vertical-tab character, 5.2.1, 6.4 vwscanf function, 7.21.1, 7.28.2.10, 7.28.3.10
-vertical-tab escape sequence (\v), 5.2.2, 6.4.4.4, vwscanf_s function, K.3.9.1.12
- 7.4.1.10
-vfprintf function, 7.21.1, 7.21.6.8, K.3.5.3.8 warnings, I
-vfprintf_s function, K.3.5.3.8, K.3.5.3.9, wchar.h header, 5.2.4.2.2, 7.21.1, 7.28, 7.30.12,
- K.3.5.3.11, K.3.5.3.14 F, K.3.9
-vfscanf function, 7.21.1, 7.21.6.8, 7.21.6.9 WCHAR_MAX macro, 7.20.3, 7.28.1
-vfscanf_s function, K.3.5.3.9, K.3.5.3.11, WCHAR_MIN macro, 7.20.3, 7.28.1
- K.3.5.3.14 wchar_t type, 3.7.3, 6.4.5, 6.7.9, 6.10.8.2, 7.19,
-vfwprintf function, 7.21.1, 7.28.2.5, K.3.9.1.6 7.20.3, 7.21.6.1, 7.21.6.2, 7.22, 7.28.1,
-vfwprintf_s function, K.3.9.1.6 7.28.2.1, 7.28.2.2
-vfwscanf function, 7.21.1, 7.28.2.6, 7.28.3.10 wcrtomb function, 7.21.3, 7.21.6.2, 7.28.2.2,
-vfwscanf_s function, K.3.9.1.7 7.28.6.3.3, 7.28.6.4.2, K.3.6.5.2, K.3.9.3.1,
-visibility of identifier, 6.2.1 K.3.9.3.2.2
-visible sequence of side effects, 5.1.2.4 wcrtomb_s function, K.3.9.3.1, K.3.9.3.1.1
-visible side effect, 5.1.2.4 wcscat function, 7.28.4.3.1
-VLA, see variable length array wcscat_s function, K.3.9.2.2.1
-void expression, 6.3.2.2 wcschr function, 7.28.4.5.1
-void function parameter, 6.7.6.3 wcscmp function, 7.28.4.4.1, 7.28.4.4.4
-void type, 6.2.5, 6.3.2.2, 6.7.2, K.3.5.3.2, wcscoll function, 7.28.4.4.2, 7.28.4.4.4
- K.3.9.1.2 wcscpy function, 7.28.4.2.1
-void type conversion, 6.3.2.2 wcscpy_s function, K.3.9.2.1.1
-volatile storage, 5.1.2.3 wcscspn function, 7.28.4.5.2
-volatile type qualifier, 6.7.3 wcsftime function, 7.11.1.1, 7.28.5.1
-volatile-qualified type, 6.2.5, 6.7.3 wcslen function, 7.28.4.6.1
-vprintf function, 7.21.1, 7.21.6.8, 7.21.6.10, wcsncat function, 7.28.4.3.2
- K.3.5.3.10 wcsncat_s function, K.3.9.2.2.2
-vprintf_s function, K.3.5.3.9, K.3.5.3.10, wcsncmp function, 7.28.4.4.3
- K.3.5.3.11, K.3.5.3.14 wcsncpy function, 7.28.4.2.2
-vscanf function, 7.21.1, 7.21.6.8, 7.21.6.11 wcsncpy_s function, K.3.9.2.1.2
-vscanf_s function, K.3.5.3.9, K.3.5.3.11, wcsnlen_s function, K.3.9.2.4.1
- K.3.5.3.14 wcspbrk function, 7.28.4.5.3
-vsnprintf function, 7.21.6.8, 7.21.6.12, wcsrchr function, 7.28.4.5.4
- K.3.5.3.12 wcsrtombs function, 7.28.6.4.2, K.3.9.3.2
-vsnprintf_s function, K.3.5.3.9, K.3.5.3.11, wcsrtombs_s function, K.3.9.3.2, K.3.9.3.2.2
- K.3.5.3.12, K.3.5.3.13, K.3.5.3.14 wcsspn function, 7.28.4.5.5
-vsnwprintf_s function, K.3.9.1.8, K.3.9.1.9 wcsstr function, 7.28.4.5.6
-vsprintf function, 7.21.6.8, 7.21.6.13, wcstod function, 7.21.6.2, 7.28.2.2
- K.3.5.3.13 wcstod function, 7.28.4.1.1
-vsprintf_s function, K.3.5.3.9, K.3.5.3.11, wcstof function, 7.28.4.1.1
- K.3.5.3.12, K.3.5.3.13, K.3.5.3.14 wcstoimax function, 7.8.2.4
-vsscanf function, 7.21.6.8, 7.21.6.14 wcstok function, 7.28.4.5.7
-vsscanf_s function, K.3.5.3.9, K.3.5.3.11, wcstok_s function, K.3.9.2.3.1
- K.3.5.3.14 wcstol function, 7.8.2.4, 7.21.6.2, 7.28.2.2,
-vswprintf function, 7.28.2.7, K.3.9.1.8, 7.28.4.1.2
- K.3.9.1.9 wcstold function, 7.28.4.1.1
-vswprintf_s function, K.3.9.1.8, K.3.9.1.9 wcstoll function, 7.8.2.4, 7.28.4.1.2
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-wcstombs function, 7.22.8.2, 7.28.6.4 7.29.1
-wcstombs_s function, K.3.6.5.2 wmemchr function, 7.28.4.5.8
-wcstoul function, 7.8.2.4, 7.21.6.2, 7.28.2.2, wmemcmp function, 7.28.4.4.5
- 7.28.4.1.2 wmemcpy function, 7.28.4.2.3
-wcstoull function, 7.8.2.4, 7.28.4.1.2 wmemcpy_s function, K.3.9.2.1.3
-wcstoumax function, 7.8.2.4 wmemmove function, 7.28.4.2.4
-wcsxfrm function, 7.28.4.4.4 wmemmove_s function, K.3.9.2.1.4
-wctob function, 7.28.6.1.2, 7.29.2.1 wmemset function, 7.28.4.6.2
-wctomb function, 7.22.7.3, 7.22.8.2, 7.28.6.3 wprintf function, 7.21.1, 7.28.2.9, 7.28.2.11,
-wctomb_s function, K.3.6.4.1 K.3.9.1.13
-wctrans function, 7.29.3.2.1, 7.29.3.2.2 wprintf_s function, K.3.9.1.13
-wctrans_t type, 7.29.1, 7.29.3.2.2 wscanf function, 7.21.1, 7.28.2.10, 7.28.2.12,
-wctype function, 7.29.2.2.1, 7.29.2.2.2 7.28.3.10
-wctype.h header, 7.29, 7.30.13 wscanf_s function, K.3.9.1.12, K.3.9.1.14
-wctype_t type, 7.29.1, 7.29.2.2.2
-weaker, 6.2.8 xor macro, 7.9
-WEOF macro, 7.28.1, 7.28.3.1, 7.28.3.3, 7.28.3.6, xor_eq macro, 7.9
- 7.28.3.7, 7.28.3.8, 7.28.3.9, 7.28.3.10, xtime type, 7.25.1, 7.25.3.5, 7.25.4.4, 7.25.5.7,
- 7.28.6.1.1, 7.29.1 7.25.7.1
-while statement, 6.8.5.1 xtime_get function, 7.25.7.1
-white space, 5.1.1.2, 6.4, 6.10, 7.4.1.10,
- 7.29.2.1.10
-white-space characters, 6.4
-wide character, 3.7.3
- case mapping functions, 7.29.3.1
- extensible, 7.29.3.2
- classification functions, 7.29.2.1
- extensible, 7.29.2.2
- constant, 6.4.4.4
- formatted input/output functions, 7.28.2,
- K.3.9.1
- input functions, 7.21.1
- input/output functions, 7.21.1, 7.28.3
- output functions, 7.21.1
- single-byte conversion functions, 7.28.6.1
-wide string, 7.1.1
-wide string comparison functions, 7.28.4.4
-wide string concatenation functions, 7.28.4.3,
- K.3.9.2.2
-wide string copying functions, 7.28.4.2, K.3.9.2.1
-wide string literal, see string literal
-wide string miscellaneous functions, 7.28.4.6,
- K.3.9.2.4
-wide string numeric conversion functions, 7.8.2.4,
- 7.28.4.1
-wide string search functions, 7.28.4.5, K.3.9.2.3
-wide-oriented stream, 7.21.2
-width, 6.2.6.2
-WINT_MAX macro, 7.20.3
-WINT_MIN macro, 7.20.3
-wint_t type, 7.20.3, 7.21.6.1, 7.28.1, 7.28.2.1,
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projects / c-standard / commitdiff