1 <html><head><title>N1516 Committee Draft -- October 4, 2010 ISO/IEC 9899:201x</title></head><body><pre>
2 N1516 Committee Draft -- October 4, 2010 ISO/IEC 9899:201x
7 INTERNATIONAL STANDARD (C)ISO/IEC ISO/IEC 9899:201x
12 Programming languages -- C
19 (Cover sheet to be provided by ISO Secretariat.)
21 This International Standard specifies the form and establishes the interpretation of
22 programs expressed in the programming language C. Its purpose is to promote
23 portability, reliability, maintainability, and efficient execution of C language programs on
24 a variety of computing systems.
26 Clauses are included that detail the C language itself and the contents of the C language
27 execution library. Annexes summarize aspects of both of them, and enumerate factors
28 that influence the portability of C programs.
30 Although this International Standard is intended to guide knowledgeable C language
31 programmers as well as implementors of C language translation systems, the document
32 itself is not designed to serve as a tutorial.
34 Recipients of this draft are invited to submit, with their comments, notification of any
35 relevant patent rights of which they are aware and to provide supporting documentation.
37 Changes from the previous draft (N1494) are indicated by ''diff marks'' in the right
38 margin: deleted text is marked with ''*'', new or changed text with '' ''.
49 <a name="Contents" href="#Contents">Contents</a>
50 <a href="#Foreword">Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii</a>
51 <a href="#Introduction">Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii</a>
52 <a href="#1">1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1</a>
53 <a href="#2">2. Normative references . . . . . . . . . . . . . . . . . . . . . . . 2</a>
54 <a href="#3">3. Terms, definitions, and symbols . . . . . . . . . . . . . . . . . . . 3</a>
55 <a href="#4">4. Conformance . . . . . . . . . . . . . . . . . . . . . . . . . . 8</a>
56 <a href="#5">5. Environment . . . . . . . . . . . . . . . . . . . . . . . . . . 10</a>
57 <a href="#5.1"> 5.1 Conceptual models . . . . . . . . . . . . . . . . . . . . . 10</a>
58 <a href="#5.1.1"> 5.1.1 Translation environment . . . . . . . . . . . . . . . . 10</a>
59 <a href="#5.1.2"> 5.1.2 Execution environments . . . . . . . . . . . . . . . . 12</a>
60 <a href="#5.2"> 5.2 Environmental considerations . . . . . . . . . . . . . . . . . 22</a>
61 <a href="#5.2.1"> 5.2.1 Character sets . . . . . . . . . . . . . . . . . . . . 22</a>
62 <a href="#5.2.2"> 5.2.2 Character display semantics . . . . . . . . . . . . . . 24</a>
63 <a href="#5.2.3"> 5.2.3 Signals and interrupts . . . . . . . . . . . . . . . . . 25</a>
64 <a href="#5.2.4"> 5.2.4 Environmental limits . . . . . . . . . . . . . . . . . 25</a>
65 <a href="#6">6. Language . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35</a>
66 <a href="#6.1"> 6.1 Notation . . . . . . . . . . . . . . . . . . . . . . . . . . 35</a>
67 <a href="#6.2"> 6.2 Concepts . . . . . . . . . . . . . . . . . . . . . . . . . 35</a>
68 <a href="#6.2.1"> 6.2.1 Scopes of identifiers . . . . . . . . . . . . . . . . . 35</a>
69 <a href="#6.2.2"> 6.2.2 Linkages of identifiers . . . . . . . . . . . . . . . . . 36</a>
70 <a href="#6.2.3"> 6.2.3 Name spaces of identifiers . . . . . . . . . . . . . . . 37</a>
71 <a href="#6.2.4"> 6.2.4 Storage durations of objects . . . . . . . . . . . . . . 38</a>
72 <a href="#6.2.5"> 6.2.5 Types . . . . . . . . . . . . . . . . . . . . . . . 39</a>
73 <a href="#6.2.6"> 6.2.6 Representations of types . . . . . . . . . . . . . . . . 44</a>
74 <a href="#6.2.7"> 6.2.7 Compatible type and composite type . . . . . . . . . . . 47</a>
75 <a href="#6.2.8"> 6.2.8 Alignment of objects . . . . . . . . . . . . . . . . . 48</a>
76 <a href="#6.3"> 6.3 Conversions . . . . . . . . . . . . . . . . . . . . . . . . 50</a>
77 <a href="#6.3.1"> 6.3.1 Arithmetic operands . . . . . . . . . . . . . . . . . 50</a>
78 <a href="#6.3.2"> 6.3.2 Other operands . . . . . . . . . . . . . . . . . . . 54</a>
79 <a href="#6.4"> 6.4 Lexical elements . . . . . . . . . . . . . . . . . . . . . . 57</a>
80 <a href="#6.4.1"> 6.4.1 Keywords . . . . . . . . . . . . . . . . . . . . . . 58</a>
81 <a href="#6.4.2"> 6.4.2 Identifiers . . . . . . . . . . . . . . . . . . . . . . 59</a>
82 <a href="#6.4.3"> 6.4.3 Universal character names . . . . . . . . . . . . . . . 61</a>
83 <a href="#6.4.4"> 6.4.4 Constants . . . . . . . . . . . . . . . . . . . . . . 62</a>
84 <a href="#6.4.5"> 6.4.5 String literals . . . . . . . . . . . . . . . . . . . . 70</a>
85 <a href="#6.4.6"> 6.4.6 Punctuators . . . . . . . . . . . . . . . . . . . . . 72</a>
86 <a href="#6.4.7"> 6.4.7 Header names . . . . . . . . . . . . . . . . . . . . 73</a>
87 <a href="#6.4.8"> 6.4.8 Preprocessing numbers . . . . . . . . . . . . . . . . 74</a>
88 <a href="#6.4.9"> 6.4.9 Comments . . . . . . . . . . . . . . . . . . . . . 75</a>
93 <a href="#6.5"> 6.5 Expressions . . . . . . . . . . . . . . . . . . . . . . . . 76</a>
94 <a href="#6.5.1"> 6.5.1 Primary expressions . . . . . . . . . . . . . . . . . 78</a>
95 <a href="#6.5.2"> 6.5.2 Postfix operators . . . . . . . . . . . . . . . . . . . 79</a>
96 <a href="#6.5.3"> 6.5.3 Unary operators . . . . . . . . . . . . . . . . . . . 88</a>
97 <a href="#6.5.4"> 6.5.4 Cast operators . . . . . . . . . . . . . . . . . . . . 91</a>
98 <a href="#6.5.5"> 6.5.5 Multiplicative operators . . . . . . . . . . . . . . . . 92</a>
99 <a href="#6.5.6"> 6.5.6 Additive operators . . . . . . . . . . . . . . . . . . 92</a>
100 <a href="#6.5.7"> 6.5.7 Bitwise shift operators . . . . . . . . . . . . . . . . . 94</a>
101 <a href="#6.5.8"> 6.5.8 Relational operators . . . . . . . . . . . . . . . . . . 95</a>
102 <a href="#6.5.9"> 6.5.9 Equality operators . . . . . . . . . . . . . . . . . . 96</a>
103 <a href="#6.5.10"> 6.5.10 Bitwise AND operator . . . . . . . . . . . . . . . . . 97</a>
104 <a href="#6.5.11"> 6.5.11 Bitwise exclusive OR operator . . . . . . . . . . . . . 98</a>
105 <a href="#6.5.12"> 6.5.12 Bitwise inclusive OR operator . . . . . . . . . . . . . . 98</a>
106 <a href="#6.5.13"> 6.5.13 Logical AND operator . . . . . . . . . . . . . . . . . 99</a>
107 <a href="#6.5.14"> 6.5.14 Logical OR operator . . . . . . . . . . . . . . . . . 99</a>
108 <a href="#6.5.15"> 6.5.15 Conditional operator . . . . . . . . . . . . . . . . . 100</a>
109 <a href="#6.5.16"> 6.5.16 Assignment operators . . . . . . . . . . . . . . . . . 101</a>
110 <a href="#6.5.17"> 6.5.17 Comma operator . . . . . . . . . . . . . . . . . . . 104</a>
111 <a href="#6.6"> 6.6 Constant expressions . . . . . . . . . . . . . . . . . . . . . 105</a>
112 <a href="#6.7"> 6.7 Declarations . . . . . . . . . . . . . . . . . . . . . . . . 107</a>
113 <a href="#6.7.1"> 6.7.1 Storage-class specifiers . . . . . . . . . . . . . . . . 108</a>
114 <a href="#6.7.2"> 6.7.2 Type specifiers . . . . . . . . . . . . . . . . . . . . 109</a>
115 <a href="#6.7.3"> 6.7.3 Type qualifiers . . . . . . . . . . . . . . . . . . . . 119</a>
116 <a href="#6.7.4"> 6.7.4 Function specifiers . . . . . . . . . . . . . . . . . . 123</a>
117 <a href="#6.7.5"> 6.7.5 Alignment specifier . . . . . . . . . . . . . . . . . . 125</a>
118 <a href="#6.7.6"> 6.7.6 Declarators . . . . . . . . . . . . . . . . . . . . . 126</a>
119 <a href="#6.7.7"> 6.7.7 Type names . . . . . . . . . . . . . . . . . . . . . 134</a>
120 <a href="#6.7.8"> 6.7.8 Type definitions . . . . . . . . . . . . . . . . . . . 135</a>
121 <a href="#6.7.9"> 6.7.9 Initialization . . . . . . . . . . . . . . . . . . . . 137</a>
122 <a href="#6.7.10"> 6.7.10 Static assertions . . . . . . . . . . . . . . . . . . . 143</a>
123 <a href="#6.8"> 6.8 Statements and blocks . . . . . . . . . . . . . . . . . . . . 144</a>
124 <a href="#6.8.1"> 6.8.1 Labeled statements . . . . . . . . . . . . . . . . . . 144</a>
125 <a href="#6.8.2"> 6.8.2 Compound statement . . . . . . . . . . . . . . . . . 145</a>
126 <a href="#6.8.3"> 6.8.3 Expression and null statements . . . . . . . . . . . . . 145</a>
127 <a href="#6.8.4"> 6.8.4 Selection statements . . . . . . . . . . . . . . . . . 146</a>
128 <a href="#6.8.5"> 6.8.5 Iteration statements . . . . . . . . . . . . . . . . . . 148</a>
129 <a href="#6.8.6"> 6.8.6 Jump statements . . . . . . . . . . . . . . . . . . . 149</a>
130 <a href="#6.9"> 6.9 External definitions . . . . . . . . . . . . . . . . . . . . . 153</a>
131 <a href="#6.9.1"> 6.9.1 Function definitions . . . . . . . . . . . . . . . . . . 154</a>
132 <a href="#6.9.2"> 6.9.2 External object definitions . . . . . . . . . . . . . . . 156</a>
133 <a href="#6.10"> 6.10 Preprocessing directives . . . . . . . . . . . . . . . . . . . 158</a>
134 <a href="#6.10.1"> 6.10.1 Conditional inclusion . . . . . . . . . . . . . . . . . 160</a>
135 <a href="#6.10.2"> 6.10.2 Source file inclusion . . . . . . . . . . . . . . . . . 162</a>
136 <a href="#6.10.3"> 6.10.3 Macro replacement . . . . . . . . . . . . . . . . . . 164</a>
141 <a href="#6.10.4"> 6.10.4 Line control . . . . . . . . . . . . . . . . . . . . . 171</a>
142 <a href="#6.10.5"> 6.10.5 Error directive . . . . . . . . . . . . . . . . . . . . 172</a>
143 <a href="#6.10.6"> 6.10.6 Pragma directive . . . . . . . . . . . . . . . . . . . 172</a>
144 <a href="#6.10.7"> 6.10.7 Null directive . . . . . . . . . . . . . . . . . . . . 173</a>
145 <a href="#6.10.8"> 6.10.8 Predefined macro names . . . . . . . . . . . . . . . . 173</a>
146 <a href="#6.10.9"> 6.10.9 Pragma operator . . . . . . . . . . . . . . . . . . . 175</a>
147 <a href="#6.11"> 6.11 Future language directions . . . . . . . . . . . . . . . . . . 177</a>
148 <a href="#6.11.1"> 6.11.1 Floating types . . . . . . . . . . . . . . . . . . . . 177</a>
149 <a href="#6.11.2"> 6.11.2 Linkages of identifiers . . . . . . . . . . . . . . . . . 177</a>
150 <a href="#6.11.3"> 6.11.3 External names . . . . . . . . . . . . . . . . . . . 177</a>
151 <a href="#6.11.4"> 6.11.4 Character escape sequences . . . . . . . . . . . . . . 177</a>
152 <a href="#6.11.5"> 6.11.5 Storage-class specifiers . . . . . . . . . . . . . . . . 177</a>
153 <a href="#6.11.6"> 6.11.6 Function declarators . . . . . . . . . . . . . . . . . 177</a>
154 <a href="#6.11.7"> 6.11.7 Function definitions . . . . . . . . . . . . . . . . . . 177</a>
155 <a href="#6.11.8"> 6.11.8 Pragma directives . . . . . . . . . . . . . . . . . . 177</a>
156 <a href="#6.11.9"> 6.11.9 Predefined macro names . . . . . . . . . . . . . . . . 177</a>
157 <a href="#7">7. Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178</a>
158 <a href="#7.1"> 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 178</a>
159 <a href="#7.1.1"> 7.1.1 Definitions of terms . . . . . . . . . . . . . . . . . . 178</a>
160 <a href="#7.1.2"> 7.1.2 Standard headers . . . . . . . . . . . . . . . . . . . 179</a>
161 <a href="#7.1.3"> 7.1.3 Reserved identifiers . . . . . . . . . . . . . . . . . . 180</a>
162 <a href="#7.1.4"> 7.1.4 Use of library functions . . . . . . . . . . . . . . . . 181</a>
163 <a href="#7.2"> 7.2 Diagnostics <assert.h> . . . . . . . . . . . . . . . . . . 184</a>
164 <a href="#7.2.1"> 7.2.1 Program diagnostics . . . . . . . . . . . . . . . . . 184</a>
165 <a href="#7.3"> 7.3 Complex arithmetic <complex.h> . . . . . . . . . . . . . . 186</a>
166 <a href="#7.3.1"> 7.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . 186</a>
167 <a href="#7.3.2"> 7.3.2 Conventions . . . . . . . . . . . . . . . . . . . . . 187</a>
168 <a href="#7.3.3"> 7.3.3 Branch cuts . . . . . . . . . . . . . . . . . . . . . 187</a>
169 <a href="#7.3.4"> 7.3.4 The CX_LIMITED_RANGE pragma . . . . . . . . . . . 187</a>
170 <a href="#7.3.5"> 7.3.5 Trigonometric functions . . . . . . . . . . . . . . . . 188</a>
171 <a href="#7.3.6"> 7.3.6 Hyperbolic functions . . . . . . . . . . . . . . . . . 190</a>
172 <a href="#7.3.7"> 7.3.7 Exponential and logarithmic functions . . . . . . . . . . 192</a>
173 <a href="#7.3.8"> 7.3.8 Power and absolute-value functions . . . . . . . . . . . 193</a>
174 <a href="#7.3.9"> 7.3.9 Manipulation functions . . . . . . . . . . . . . . . . 194</a>
175 <a href="#7.4"> 7.4 Character handling <ctype.h> . . . . . . . . . . . . . . . . 198</a>
176 <a href="#7.4.1"> 7.4.1 Character classification functions . . . . . . . . . . . . 198</a>
177 <a href="#7.4.2"> 7.4.2 Character case mapping functions . . . . . . . . . . . . 201</a>
178 <a href="#7.5"> 7.5 Errors <errno.h> . . . . . . . . . . . . . . . . . . . . . 203</a>
179 <a href="#7.6"> 7.6 Floating-point environment <fenv.h> . . . . . . . . . . . . . 204</a>
180 <a href="#7.6.1"> 7.6.1 The FENV_ACCESS pragma . . . . . . . . . . . . . . 206</a>
181 <a href="#7.6.2"> 7.6.2 Floating-point exceptions . . . . . . . . . . . . . . . 207</a>
182 <a href="#7.6.3"> 7.6.3 Rounding . . . . . . . . . . . . . . . . . . . . . . 210</a>
183 <a href="#7.6.4"> 7.6.4 Environment . . . . . . . . . . . . . . . . . . . . 211</a>
184 <a href="#7.7"> 7.7 Characteristics of floating types <float.h> . . . . . . . . . . . 214</a>
188 <a href="#7.8"> 7.8 Format conversion of integer types <inttypes.h> . . . . . . . . 215</a>
189 <a href="#7.8.1"> 7.8.1 Macros for format specifiers . . . . . . . . . . . . . . 215</a>
190 <a href="#7.8.2"> 7.8.2 Functions for greatest-width integer types . . . . . . . . . 216</a>
191 <a href="#7.9"> 7.9 Alternative spellings <iso646.h> . . . . . . . . . . . . . . . 219</a>
192 <a href="#7.10"> 7.10 Sizes of integer types <limits.h> . . . . . . . . . . . . . . 220</a>
193 <a href="#7.11"> 7.11 Localization <locale.h> . . . . . . . . . . . . . . . . . . 221</a>
194 <a href="#7.11.1"> 7.11.1 Locale control . . . . . . . . . . . . . . . . . . . . 222</a>
195 <a href="#7.11.2"> 7.11.2 Numeric formatting convention inquiry . . . . . . . . . . 223</a>
196 <a href="#7.12"> 7.12 Mathematics <math.h> . . . . . . . . . . . . . . . . . . . 229</a>
197 <a href="#7.12.1"> 7.12.1 Treatment of error conditions . . . . . . . . . . . . . . 231</a>
198 <a href="#7.12.2"> 7.12.2 The FP_CONTRACT pragma . . . . . . . . . . . . . . 233</a>
199 <a href="#7.12.3"> 7.12.3 Classification macros . . . . . . . . . . . . . . . . . 233</a>
200 <a href="#7.12.4"> 7.12.4 Trigonometric functions . . . . . . . . . . . . . . . . 236</a>
201 <a href="#7.12.5"> 7.12.5 Hyperbolic functions . . . . . . . . . . . . . . . . . 238</a>
202 <a href="#7.12.6"> 7.12.6 Exponential and logarithmic functions . . . . . . . . . . 240</a>
203 <a href="#7.12.7"> 7.12.7 Power and absolute-value functions . . . . . . . . . . . 245</a>
204 <a href="#7.12.8"> 7.12.8 Error and gamma functions . . . . . . . . . . . . . . . 247</a>
205 <a href="#7.12.9"> 7.12.9 Nearest integer functions . . . . . . . . . . . . . . . . 249</a>
206 <a href="#7.12.10"> 7.12.10 Remainder functions . . . . . . . . . . . . . . . . . 252</a>
207 <a href="#7.12.11"> 7.12.11 Manipulation functions . . . . . . . . . . . . . . . . 253</a>
208 <a href="#7.12.12"> 7.12.12 Maximum, minimum, and positive difference functions . . . 255</a>
209 <a href="#7.12.13"> 7.12.13 Floating multiply-add . . . . . . . . . . . . . . . . . 256</a>
210 <a href="#7.12.14"> 7.12.14 Comparison macros . . . . . . . . . . . . . . . . . . 257</a>
211 <a href="#7.13"> 7.13 Nonlocal jumps <setjmp.h> . . . . . . . . . . . . . . . . 260</a>
212 <a href="#7.13.1"> 7.13.1 Save calling environment . . . . . . . . . . . . . . . 260</a>
213 <a href="#7.13.2"> 7.13.2 Restore calling environment . . . . . . . . . . . . . . 261</a>
214 <a href="#7.14"> 7.14 Signal handling <signal.h> . . . . . . . . . . . . . . . . . 263</a>
215 <a href="#7.14.1"> 7.14.1 Specify signal handling . . . . . . . . . . . . . . . . 264</a>
216 <a href="#7.14.2"> 7.14.2 Send signal . . . . . . . . . . . . . . . . . . . . . 265</a>
217 <a href="#7.15"> 7.15 Alignment <stdalign.h> . . . . . . . . . . . . . . . . . 266</a>
218 <a href="#7.16"> 7.16 Variable arguments <stdarg.h> . . . . . . . . . . . . . . . 267</a>
219 <a href="#7.16.1"> 7.16.1 Variable argument list access macros . . . . . . . . . . . 267</a>
220 <a href="#7.17"> 7.17 Atomics <stdatomic.h> . . . . . . . . . . . . . . . . . . 271</a>
221 <a href="#7.17.1"> 7.17.1 Introduction . . . . . . . . . . . . . . . . . . . . . 271</a>
222 <a href="#7.17.2"> 7.17.2 Initialization . . . . . . . . . . . . . . . . . . . . 272</a>
223 <a href="#7.17.3"> 7.17.3 Order and consistency . . . . . . . . . . . . . . . . . 273</a>
224 <a href="#7.17.4"> 7.17.4 Fences . . . . . . . . . . . . . . . . . . . . . . . 276</a>
225 <a href="#7.17.5"> 7.17.5 Lock-free property . . . . . . . . . . . . . . . . . . 277</a>
226 <a href="#7.17.6"> 7.17.6 Atomic integer and address types . . . . . . . . . . . . 278</a>
227 <a href="#7.17.7"> 7.17.7 Operations on atomic types . . . . . . . . . . . . . . . 280</a>
228 <a href="#7.17.8"> 7.17.8 Atomic flag type and operations . . . . . . . . . . . . . 283</a>
229 <a href="#7.18"> 7.18 Boolean type and values <stdbool.h> . . . . . . . . . . . . 285</a>
230 <a href="#7.19"> 7.19 Common definitions <stddef.h> . . . . . . . . . . . . . . . 286</a>
231 <a href="#7.20"> 7.20 Integer types <stdint.h> . . . . . . . . . . . . . . . . . . 288</a>
236 <a href="#7.20.1"> 7.20.1 Integer types . . . . . . . . . . . . . . . . . . . . 288</a>
237 <a href="#7.20.2"> 7.20.2 Limits of specified-width integer types . . . . . . . . . . 290</a>
238 <a href="#7.20.3"> 7.20.3 Limits of other integer types . . . . . . . . . . . . . . 292</a>
239 <a href="#7.20.4"> 7.20.4 Macros for integer constants . . . . . . . . . . . . . . 293</a>
240 <a href="#7.21"> 7.21 Input/output <stdio.h> . . . . . . . . . . . . . . . . . . 295</a>
241 <a href="#7.21.1"> 7.21.1 Introduction . . . . . . . . . . . . . . . . . . . . . 295</a>
242 <a href="#7.21.2"> 7.21.2 Streams . . . . . . . . . . . . . . . . . . . . . . 297</a>
243 <a href="#7.21.3"> 7.21.3 Files . . . . . . . . . . . . . . . . . . . . . . . . 299</a>
244 <a href="#7.21.4"> 7.21.4 Operations on files . . . . . . . . . . . . . . . . . . 301</a>
245 <a href="#7.21.5"> 7.21.5 File access functions . . . . . . . . . . . . . . . . . 303</a>
246 <a href="#7.21.6"> 7.21.6 Formatted input/output functions . . . . . . . . . . . . 308</a>
247 <a href="#7.21.7"> 7.21.7 Character input/output functions . . . . . . . . . . . . . 329</a>
248 <a href="#7.21.8"> 7.21.8 Direct input/output functions . . . . . . . . . . . . . . 333</a>
249 <a href="#7.21.9"> 7.21.9 File positioning functions . . . . . . . . . . . . . . . 334</a>
250 <a href="#7.21.10"> 7.21.10 Error-handling functions . . . . . . . . . . . . . . . . 337</a>
251 <a href="#7.22"> 7.22 General utilities <stdlib.h> . . . . . . . . . . . . . . . . 339</a>
252 <a href="#7.22.1"> 7.22.1 Numeric conversion functions . . . . . . . . . . . . . . 340</a>
253 <a href="#7.22.2"> 7.22.2 Pseudo-random sequence generation functions . . . . . . . 345</a>
254 <a href="#7.22.3"> 7.22.3 Memory management functions . . . . . . . . . . . . . 346</a>
255 <a href="#7.22.4"> 7.22.4 Communication with the environment . . . . . . . . . . 348</a>
256 <a href="#7.22.5"> 7.22.5 Searching and sorting utilities . . . . . . . . . . . . . . 352</a>
257 <a href="#7.22.6"> 7.22.6 Integer arithmetic functions . . . . . . . . . . . . . . 354</a>
258 <a href="#7.22.7"> 7.22.7 Multibyte/wide character conversion functions . . . . . . . 355</a>
259 <a href="#7.22.8"> 7.22.8 Multibyte/wide string conversion functions . . . . . . . . 357</a>
260 <a href="#7.23"> 7.23 String handling <string.h> . . . . . . . . . . . . . . . . . 359</a>
261 <a href="#7.23.1"> 7.23.1 String function conventions . . . . . . . . . . . . . . . 359</a>
262 <a href="#7.23.2"> 7.23.2 Copying functions . . . . . . . . . . . . . . . . . . 359</a>
263 <a href="#7.23.3"> 7.23.3 Concatenation functions . . . . . . . . . . . . . . . . 361</a>
264 <a href="#7.23.4"> 7.23.4 Comparison functions . . . . . . . . . . . . . . . . . 362</a>
265 <a href="#7.23.5"> 7.23.5 Search functions . . . . . . . . . . . . . . . . . . . 364</a>
266 <a href="#7.23.6"> 7.23.6 Miscellaneous functions . . . . . . . . . . . . . . . . 367</a>
267 <a href="#7.24"> 7.24 Type-generic math <tgmath.h> . . . . . . . . . . . . . . . 369</a>
268 <a href="#7.25"> 7.25 Threads <threads.h> . . . . . . . . . . . . . . . . . . . 372</a>
269 <a href="#7.25.1"> 7.25.1 Introduction . . . . . . . . . . . . . . . . . . . . . 372</a>
270 <a href="#7.25.2"> 7.25.2 Initialization functions . . . . . . . . . . . . . . . . . 374</a>
271 <a href="#7.25.3"> 7.25.3 Condition variable functions . . . . . . . . . . . . . . 374</a>
272 <a href="#7.25.4"> 7.25.4 Mutex functions . . . . . . . . . . . . . . . . . . . 376</a>
273 <a href="#7.25.5"> 7.25.5 Thread functions . . . . . . . . . . . . . . . . . . . 379</a>
274 <a href="#7.25.6"> 7.25.6 Thread-specific storage functions . . . . . . . . . . . . 381</a>
275 <a href="#7.25.7"> 7.25.7 Time functions . . . . . . . . . . . . . . . . . . . . 383</a>
276 <a href="#7.26"> 7.26 Date and time <time.h> . . . . . . . . . . . . . . . . . . 384</a>
277 <a href="#7.26.1"> 7.26.1 Components of time . . . . . . . . . . . . . . . . . 384</a>
278 <a href="#7.26.2"> 7.26.2 Time manipulation functions . . . . . . . . . . . . . . 385</a>
279 <a href="#7.26.3"> 7.26.3 Time conversion functions . . . . . . . . . . . . . . . 387</a>
284 <a href="#7.27"> 7.27 Unicode utilities <uchar.h> . . . . . . . . . . . . . . . . . 394</a>
285 <a href="#7.27.1"> 7.27.1 Restartable multibyte/wide character conversion functions . . 394</a>
286 <a href="#7.28"> 7.28 Extended multibyte and wide character utilities <wchar.h> . . . . . 398</a>
287 <a href="#7.28.1"> 7.28.1 Introduction . . . . . . . . . . . . . . . . . . . . . 398</a>
288 <a href="#7.28.2"> 7.28.2 Formatted wide character input/output functions . . . . . . 399</a>
289 <a href="#7.28.3"> 7.28.3 Wide character input/output functions . . . . . . . . . . 417</a>
290 <a href="#7.28.4"> 7.28.4 General wide string utilities . . . . . . . . . . . . . . 421</a>
291 <a href="#7.28.4.1"> 7.28.4.1 Wide string numeric conversion functions . . . . . 422</a>
292 <a href="#7.28.4.2"> 7.28.4.2 Wide string copying functions . . . . . . . . . . 426</a>
293 <a href="#7.28.4.3"> 7.28.4.3 Wide string concatenation functions . . . . . . . 428</a>
294 <a href="#7.28.4.4"> 7.28.4.4 Wide string comparison functions . . . . . . . . 429</a>
295 <a href="#7.28.4.5"> 7.28.4.5 Wide string search functions . . . . . . . . . . 431</a>
296 <a href="#7.28.4.6"> 7.28.4.6 Miscellaneous functions . . . . . . . . . . . . 435</a>
297 <a href="#7.28.5"> 7.28.5 Wide character time conversion functions . . . . . . . . . 435</a>
298 <a href="#7.28.6"> 7.28.6 Extended multibyte/wide character conversion utilities . . . . 436</a>
299 <a href="#7.28.6.1"> 7.28.6.1 Single-byte/wide character conversion functions . . . 437</a>
300 <a href="#7.28.6.2"> 7.28.6.2 Conversion state functions . . . . . . . . . . . 437</a>
301 <a href="#7.28.6.3"> 7.28.6.3 Restartable multibyte/wide character conversion
302 functions . . . . . . . . . . . . . . . . . . 438</a>
303 <a href="#7.28.6.4"> 7.28.6.4 Restartable multibyte/wide string conversion
304 functions . . . . . . . . . . . . . . . . . . 440</a>
305 <a href="#7.29"> 7.29 Wide character classification and mapping utilities <wctype.h> . . . 443</a>
306 <a href="#7.29.1"> 7.29.1 Introduction . . . . . . . . . . . . . . . . . . . . . 443</a>
307 <a href="#7.29.2"> 7.29.2 Wide character classification utilities . . . . . . . . . . . 444</a>
308 <a href="#7.29.2.1"> 7.29.2.1 Wide character classification functions . . . . . . 444</a>
309 <a href="#7.29.2.2"> 7.29.2.2 Extensible wide character classification
310 functions . . . . . . . . . . . . . . . . . . 447</a>
311 <a href="#7.29.3"> 7.29.3 Wide character case mapping utilities . . . . . . . . . . . 449</a>
312 <a href="#7.29.3.1"> 7.29.3.1 Wide character case mapping functions . . . . . . 449</a>
313 <a href="#7.29.3.2"> 7.29.3.2 Extensible wide character case mapping
314 functions . . . . . . . . . . . . . . . . . . 449</a>
315 <a href="#7.30"> 7.30 Future library directions . . . . . . . . . . . . . . . . . . . 451</a>
316 <a href="#7.30.1"> 7.30.1 Complex arithmetic <complex.h> . . . . . . . . . . . 451</a>
317 <a href="#7.30.2"> 7.30.2 Character handling <ctype.h> . . . . . . . . . . . . 451</a>
318 <a href="#7.30.3"> 7.30.3 Errors <errno.h> . . . . . . . . . . . . . . . . . 451</a>
319 <a href="#7.30.4"> 7.30.4 Format conversion of integer types <inttypes.h> . . . . 451</a>
320 <a href="#7.30.5"> 7.30.5 Localization <locale.h> . . . . . . . . . . . . . . 451</a>
321 <a href="#7.30.6"> 7.30.6 Signal handling <signal.h> . . . . . . . . . . . . . 451</a>
322 <a href="#7.30.7"> 7.30.7 Boolean type and values <stdbool.h> . . . . . . . . . 451</a>
323 <a href="#7.30.8"> 7.30.8 Integer types <stdint.h> . . . . . . . . . . . . . . 451</a>
324 <a href="#7.30.9"> 7.30.9 Input/output <stdio.h> . . . . . . . . . . . . . . . 452</a>
325 <a href="#7.30.10"> 7.30.10 General utilities <stdlib.h> . . . . . . . . . . . . . 452</a>
326 <a href="#7.30.11"> 7.30.11 String handling <string.h> . . . . . . . . . . . . . 452</a>
332 <a href="#7.30.12"> 7.30.12 Extended multibyte and wide character utilities
333 <wchar.h> . . . . . . . . . . . . . . . . . . . . 452</a>
334 <a href="#7.30.13"> 7.30.13 Wide character classification and mapping utilities
335 <wctype.h> . . . . . . . . . . . . . . . . . . . . 452</a>
336 <a href="#A">Annex A (informative) Language syntax summary . . . . . . . . . . . . 453</a>
337 <a href="#A.1"> A.1 Lexical grammar . . . . . . . . . . . . . . . . . . . . . . 453</a>
338 <a href="#A.2"> A.2 Phrase structure grammar . . . . . . . . . . . . . . . . . . . 460</a>
339 <a href="#A.3"> A.3 Preprocessing directives . . . . . . . . . . . . . . . . . . . 468</a>
340 <a href="#B">Annex B (informative) Library summary . . . . . . . . . . . . . . . . 470</a>
341 <a href="#B.1"> B.1 Diagnostics <assert.h> . . . . . . . . . . . . . . . . . . 470</a>
342 <a href="#B.2"> B.2 Complex <complex.h> . . . . . . . . . . . . . . . . . . . 470</a>
343 <a href="#B.3"> B.3 Character handling <ctype.h> . . . . . . . . . . . . . . . . 472</a>
344 <a href="#B.4"> B.4 Errors <errno.h> . . . . . . . . . . . . . . . . . . . . . 472</a>
345 <a href="#B.5"> B.5 Floating-point environment <fenv.h> . . . . . . . . . . . . . 472</a>
346 <a href="#B.6"> B.6 Characteristics of floating types <float.h> . . . . . . . . . . . 473</a>
347 <a href="#B.7"> B.7 Format conversion of integer types <inttypes.h> . . . . . . . . 473</a>
348 <a href="#B.8"> B.8 Alternative spellings <iso646.h> . . . . . . . . . . . . . . . 474</a>
349 <a href="#B.9"> B.9 Sizes of integer types <limits.h> . . . . . . . . . . . . . . 474</a>
350 <a href="#B.10"> B.10 Localization <locale.h> . . . . . . . . . . . . . . . . . . 474</a>
351 <a href="#B.11"> B.11 Mathematics <math.h> . . . . . . . . . . . . . . . . . . . 474</a>
352 <a href="#B.12"> B.12 Nonlocal jumps <setjmp.h> . . . . . . . . . . . . . . . . 479</a>
353 <a href="#B.13"> B.13 Signal handling <signal.h> . . . . . . . . . . . . . . . . . 479</a>
354 <a href="#B.14"> B.14 Alignment <stdalign.h> . . . . . . . . . . . . . . . . . 480</a>
355 <a href="#B.15"> B.15 Variable arguments <stdarg.h> . . . . . . . . . . . . . . . 480</a>
356 <a href="#B.16"> B.16 Atomics <stdatomic.h> . . . . . . . . . . . . . . . . . . 480</a>
357 <a href="#B.17"> B.17 Boolean type and values <stdbool.h> . . . . . . . . . . . . 482</a>
358 <a href="#B.18"> B.18 Common definitions <stddef.h> . . . . . . . . . . . . . . . 482</a>
359 <a href="#B.19"> B.19 Integer types <stdint.h> . . . . . . . . . . . . . . . . . . 482</a>
360 <a href="#B.20"> B.20 Input/output <stdio.h> . . . . . . . . . . . . . . . . . . 483</a>
361 <a href="#B.21"> B.21 General utilities <stdlib.h> . . . . . . . . . . . . . . . . 486</a>
362 <a href="#B.22"> B.22 String handling <string.h> . . . . . . . . . . . . . . . . . 488</a>
363 <a href="#B.23"> B.23 Type-generic math <tgmath.h> . . . . . . . . . . . . . . . 490</a>
364 <a href="#B.24"> B.24 Threads <threads.h> . . . . . . . . . . . . . . . . . . . 490</a>
365 <a href="#B.25"> B.25 Date and time <time.h> . . . . . . . . . . . . . . . . . . 491</a>
366 <a href="#B.26"> B.26 Unicode utilities <uchar.h> . . . . . . . . . . . . . . . . . 492</a>
367 <a href="#B.27"> B.27 Extended multibyte/wide character utilities <wchar.h> . . . . . . 492</a>
368 <a href="#B.28"> B.28 Wide character classification and mapping utilities <wctype.h> . . . 497</a>
369 <a href="#C">Annex C (informative) Sequence points . . . . . . . . . . . . . . . . . 498</a>
370 <a href="#D">Annex D (normative) Universal character names for identifiers . . . . . . . 499</a>
371 <a href="#E">Annex E (informative) Implementation limits . . . . . . . . . . . . . . 501</a>
372 <a href="#F">Annex F (normative) IEC 60559 floating-point arithmetic . . . . . . . . . . 503</a>
373 <a href="#F.1"> F.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 503</a>
377 <a href="#F.2"> F.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 503</a>
378 <a href="#F.3"> F.3 Operators and functions . . . . . . . . . . . . . . . . . . . 504</a>
379 <a href="#F.4"> F.4 Floating to integer conversion . . . . . . . . . . . . . . . . . 506</a>
380 <a href="#F.5"> F.5 Binary-decimal conversion . . . . . . . . . . . . . . . . . . 506</a>
381 <a href="#F.6"> F.6 The return statement . . . . . . . . . . . . . . . . . . . . 507</a>
382 <a href="#F.7"> F.7 Contracted expressions . . . . . . . . . . . . . . . . . . . . 507</a>
383 <a href="#F.8"> F.8 Floating-point environment . . . . . . . . . . . . . . . . . . 507</a>
384 <a href="#F.9"> F.9 Optimization . . . . . . . . . . . . . . . . . . . . . . . . 510</a>
385 <a href="#F.10"> F.10 Mathematics <math.h> . . . . . . . . . . . . . . . . . . . 513</a>
386 <a href="#F.10.1"> F.10.1 Trigonometric functions . . . . . . . . . . . . . . . . 514</a>
387 <a href="#F.10.2"> F.10.2 Hyperbolic functions . . . . . . . . . . . . . . . . . 516</a>
388 <a href="#F.10.3"> F.10.3 Exponential and logarithmic functions . . . . . . . . . . 516</a>
389 <a href="#F.10.4"> F.10.4 Power and absolute value functions . . . . . . . . . . . 519</a>
390 <a href="#F.10.5"> F.10.5 Error and gamma functions . . . . . . . . . . . . . . . 521</a>
391 <a href="#F.10.6"> F.10.6 Nearest integer functions . . . . . . . . . . . . . . . . 521</a>
392 <a href="#F.10.7"> F.10.7 Remainder functions . . . . . . . . . . . . . . . . . 524</a>
393 <a href="#F.10.8"> F.10.8 Manipulation functions . . . . . . . . . . . . . . . . 525</a>
394 <a href="#F.10.9"> F.10.9 Maximum, minimum, and positive difference functions . . . 525</a>
395 <a href="#F.10.10"> F.10.10 Floating multiply-add . . . . . . . . . . . . . . . . . 526</a>
396 <a href="#F.10.11"> F.10.11 Comparison macros . . . . . . . . . . . . . . . . . . 526</a>
397 <a href="#G">Annex G (informative) IEC 60559-compatible complex arithmetic . . . . . . 527</a>
398 <a href="#G.1"> G.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 527</a>
399 <a href="#G.2"> G.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 527</a>
400 <a href="#G.3"> G.3 Conventions . . . . . . . . . . . . . . . . . . . . . . . . 527</a>
401 <a href="#G.4"> G.4 Conversions . . . . . . . . . . . . . . . . . . . . . . . . 528</a>
402 <a href="#G.4.1"> G.4.1 Imaginary types . . . . . . . . . . . . . . . . . . . 528</a>
403 <a href="#G.4.2"> G.4.2 Real and imaginary . . . . . . . . . . . . . . . . . . 528</a>
404 <a href="#G.4.3"> G.4.3 Imaginary and complex . . . . . . . . . . . . . . . . 528</a>
405 <a href="#G.5"> G.5 Binary operators . . . . . . . . . . . . . . . . . . . . . . 528</a>
406 <a href="#G.5.1"> G.5.1 Multiplicative operators . . . . . . . . . . . . . . . . 529</a>
407 <a href="#G.5.2"> G.5.2 Additive operators . . . . . . . . . . . . . . . . . . 532</a>
408 <a href="#G.6"> G.6 Complex arithmetic <complex.h> . . . . . . . . . . . . . . 532</a>
409 <a href="#G.6.1"> G.6.1 Trigonometric functions . . . . . . . . . . . . . . . . 534</a>
410 <a href="#G.6.2"> G.6.2 Hyperbolic functions . . . . . . . . . . . . . . . . . 534</a>
411 <a href="#G.6.3"> G.6.3 Exponential and logarithmic functions . . . . . . . . . . 538</a>
412 <a href="#G.6.4"> G.6.4 Power and absolute-value functions . . . . . . . . . . . 539</a>
413 <a href="#G.7"> G.7 Type-generic math <tgmath.h> . . . . . . . . . . . . . . . 540</a>
414 <a href="#H">Annex H (informative) Language independent arithmetic . . . . . . . . . . 541</a>
415 <a href="#H.1"> H.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 541</a>
416 <a href="#H.2"> H.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 541</a>
417 <a href="#H.3"> H.3 Notification . . . . . . . . . . . . . . . . . . . . . . . . 545</a>
418 <a href="#I">Annex I (informative) Common warnings . . . . . . . . . . . . . . . . 547</a>
423 <a href="#J">Annex J (informative) Portability issues . . . . . . . . . . . . . . . . . 549</a>
424 <a href="#J.1"> J.1 Unspecified behavior . . . . . . . . . . . . . . . . . . . . . 549</a>
425 <a href="#J.2"> J.2 Undefined behavior . . . . . . . . . . . . . . . . . . . . . 552</a>
426 <a href="#J.3"> J.3 Implementation-defined behavior . . . . . . . . . . . . . . . . 566</a>
427 <a href="#J.4"> J.4 Locale-specific behavior . . . . . . . . . . . . . . . . . . . 573</a>
428 <a href="#J.5"> J.5 Common extensions . . . . . . . . . . . . . . . . . . . . . 574</a>
429 <a href="#K">Annex K (normative) Bounds-checking interfaces . . . . . . . . . . . . . 577</a>
430 <a href="#K.1"> K.1 Background . . . . . . . . . . . . . . . . . . . . . . . . 577</a>
431 <a href="#K.2"> K.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 578</a>
432 <a href="#K.3"> K.3 Library . . . . . . . . . . . . . . . . . . . . . . . . . . 578</a>
433 <a href="#K.3.1"> K.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . 578</a>
434 <a href="#K.3.1.1"> K.3.1.1 Standard headers . . . . . . . . . . . . . . . 578</a>
435 <a href="#K.3.1.2"> K.3.1.2 Reserved identifiers . . . . . . . . . . . . . . 579</a>
436 <a href="#K.3.1.3"> K.3.1.3 Use of errno . . . . . . . . . . . . . . . . . 579</a>
437 <a href="#K.3.1.4"> K.3.1.4 Runtime-constraint violations . . . . . . . . . . 579</a>
438 <a href="#K.3.2"> K.3.2 Errors <errno.h> . . . . . . . . . . . . . . . . . 580</a>
439 <a href="#K.3.3"> K.3.3 Common definitions <stddef.h> . . . . . . . . . . . 580</a>
440 <a href="#K.3.4"> K.3.4 Integer types <stdint.h> . . . . . . . . . . . . . . 580</a>
441 <a href="#K.3.5"> K.3.5 Input/output <stdio.h> . . . . . . . . . . . . . . . 581</a>
442 <a href="#K.3.5.1"> K.3.5.1 Operations on files . . . . . . . . . . . . . . 581</a>
443 <a href="#K.3.5.2"> K.3.5.2 File access functions . . . . . . . . . . . . . . 583</a>
444 <a href="#K.3.5.3"> K.3.5.3 Formatted input/output functions . . . . . . . . . 586</a>
445 <a href="#K.3.5.4"> K.3.5.4 Character input/output functions . . . . . . . . . 597</a>
446 <a href="#K.3.6"> K.3.6 General utilities <stdlib.h> . . . . . . . . . . . . . 599</a>
447 <a href="#K.3.6.1"> K.3.6.1 Runtime-constraint handling . . . . . . . . . . 599</a>
448 <a href="#K.3.6.2"> K.3.6.2 Communication with the environment . . . . . . . 601</a>
449 <a href="#K.3.6.3"> K.3.6.3 Searching and sorting utilities . . . . . . . . . . 602</a>
450 <a href="#K.3.6.4"> K.3.6.4 Multibyte/wide character conversion functions . . . 605</a>
451 <a href="#K.3.6.5"> K.3.6.5 Multibyte/wide string conversion functions . . . . . 606</a>
452 <a href="#K.3.7"> K.3.7 String handling <string.h> . . . . . . . . . . . . . 609</a>
453 <a href="#K.3.7.1"> K.3.7.1 Copying functions . . . . . . . . . . . . . . 609</a>
454 <a href="#K.3.7.2"> K.3.7.2 Concatenation functions . . . . . . . . . . . . 612</a>
455 <a href="#K.3.7.3"> K.3.7.3 Search functions . . . . . . . . . . . . . . . 615</a>
456 <a href="#K.3.7.4"> K.3.7.4 Miscellaneous functions . . . . . . . . . . . . 616</a>
457 <a href="#K.3.8"> K.3.8 Date and time <time.h> . . . . . . . . . . . . . . . 619</a>
458 <a href="#K.3.8.1"> K.3.8.1 Components of time . . . . . . . . . . . . . . 619</a>
459 <a href="#K.3.8.2"> K.3.8.2 Time conversion functions . . . . . . . . . . . 619</a>
460 <a href="#K.3.9"> K.3.9 Extended multibyte and wide character utilities
461 <wchar.h> . . . . . . . . . . . . . . . . . . . . 622</a>
462 <a href="#K.3.9.1"> K.3.9.1 Formatted wide character input/output functions . . . 623</a>
463 <a href="#K.3.9.2"> K.3.9.2 General wide string utilities . . . . . . . . . . . 634</a>
464 <a href="#K.3.9.3"> K.3.9.3 Extended multibyte/wide character conversion
465 utilities . . . . . . . . . . . . . . . . . . . 642</a>
470 <a href="#L">Annex L (normative) Analyzability . . . . . . . . . . . . . . . . . . 647</a>
471 <a href="#L.1"> L.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 647</a>
472 <a href="#L.2"> L.2 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 647</a>
473 <a href="#L.3"> L.3 Requirements . . . . . . . . . . . . . . . . . . . . . . . . 648</a>
474 <a href="#Bibliography">Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . 649</a>
475 <a href="#Index">Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 653</a>
480 [<a name="#pxii" href="pxii">page xii</a>] (<a href="#Contents">Contents</a>)
482 <a name="Foreword" href="#Foreword"><b> Foreword</b></a>
483 1 ISO (the International Organization for Standardization) and IEC (the International
484 Electrotechnical Commission) form the specialized system for worldwide
485 standardization. National bodies that are member of ISO or IEC participate in the
486 development of International Standards through technical committees established by the
487 respective organization to deal with particular fields of technical activity. ISO and IEC
488 technical committees collaborate in fields of mutual interest. Other international
489 organizations, governmental and non-governmental, in liaison with ISO and IEC, also
490 take part in the work.
491 2 International Standards are drafted in accordance with the rules given in the ISO/IEC
492 Directives, Part 2. This International Standard was drafted in accordance with the fifth
494 3 In the field of information technology, ISO and IEC have established a joint technical
495 committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
496 committee are circulated to national bodies for voting. Publication as an International
497 Standard requires approval by at least 75% of the national bodies casting a vote.
498 4 Attention is drawn to the possibility that some of the elements of this document may be
499 the subject of patent rights. ISO and IEC shall not be held responsible for identifying any
500 or all such patent rights.
501 5 This International Standard was prepared by Joint Technical Committee ISO/IEC JTC 1,
502 Information technology, Subcommittee SC 22, Programming languages, their
503 environments and system software interfaces. The Working Group responsible for this
504 standard (WG 14) maintains a site on the World Wide Web at http://www.open-
505 std.org/JTC1/SC22/WG14/ containing additional information relevant to this
506 standard such as a Rationale for many of the decisions made during its preparation and a
507 log of Defect Reports and Responses.
508 6 This third edition cancels and replaces the second edition, ISO/IEC 9899:1999, as
509 corrected by ISO/IEC 9899:1999/Cor 1:2001, ISO/IEC 9899:1999/Cor 2:2004, and
510 ISO/IEC 9899:1999/Cor 3:2007. Major changes from the previous edition include:
511 -- conditional (optional) features (including some that were previously mandatory)
512 -- support for multiple threads of execution including an improved memory sequencing
513 model, atomic objects, and thread-local storage (<a href="#7.17"><stdatomic.h></a> and
514 <a href="#7.25"><threads.h></a>)
515 -- additional floating-point characteristic macros (<a href="#7.7"><float.h></a>)
516 -- querying and specifying alignment of objects (<a href="#7.15"><stdalign.h></a>, <a href="#7.22"><stdlib.h></a>)
517 -- Unicode characters and strings (<a href="#7.27"><uchar.h></a>) (originally specified in
518 ISO/IEC TR 19769:2004)
519 -- type-generic expressions
522 [<a name="#pxiii" href="pxiii">page xiii</a>] (<a href="#Contents">Contents</a>)
525 -- anonymous structures and unions
526 -- no-return functions
527 -- macros to create complex numbers (<a href="#7.3"><complex.h></a>)
528 -- support for opening files for exclusive access
529 -- removed the gets function (<a href="#7.21"><stdio.h></a>)
530 -- added the aligned_alloc, at_quick_exit, and quick_exit functions
531 (<a href="#7.22"><stdlib.h></a>)
532 -- (conditional) support for bounds-checking interfaces (originally specified in
533 ISO/IEC TR 24731-1:2007)
534 -- (conditional) support for analyzability
535 7 Major changes in the second edition included:
536 -- restricted character set support via digraphs and <a href="#7.9"><iso646.h></a> (originally specified
538 -- wide character library support in <a href="#7.28"><wchar.h></a> and <a href="#7.29"><wctype.h></a> (originally
540 -- more precise aliasing rules via effective type
541 -- restricted pointers
542 -- variable length arrays
543 -- flexible array members
544 -- static and type qualifiers in parameter array declarators
545 -- complex (and imaginary) support in <a href="#7.3"><complex.h></a>
546 -- type-generic math macros in <a href="#7.24"><tgmath.h></a>
547 -- the long long int type and library functions
548 -- increased minimum translation limits
549 -- additional floating-point characteristics in <a href="#7.7"><float.h></a>
550 -- remove implicit int
551 -- reliable integer division
552 -- universal character names (\u and \U)
553 -- extended identifiers
554 -- hexadecimal floating-point constants and %a and %A printf/scanf conversion
559 [<a name="#pxiv" href="pxiv">page xiv</a>] (<a href="#Contents">Contents</a>)
562 -- designated initializers
564 -- extended integer types and library functions in <a href="#7.8"><inttypes.h></a> and <a href="#7.20"><stdint.h></a>
565 -- remove implicit function declaration
566 -- preprocessor arithmetic done in intmax_t/uintmax_t
567 -- mixed declarations and code
568 -- new block scopes for selection and iteration statements
569 -- integer constant type rules
570 -- integer promotion rules
571 -- macros with a variable number of arguments
572 -- the vscanf family of functions in <a href="#7.21"><stdio.h></a> and <a href="#7.28"><wchar.h></a>
573 -- additional math library functions in <a href="#7.12"><math.h></a>
574 -- treatment of error conditions by math library functions (math_errhandling)
575 -- floating-point environment access in <a href="#7.6"><fenv.h></a>
576 -- IEC 60559 (also known as IEC 559 or IEEE arithmetic) support
577 -- trailing comma allowed in enum declaration
578 -- %lf conversion specifier allowed in printf
580 -- the snprintf family of functions in <a href="#7.21"><stdio.h></a>
581 -- boolean type in <a href="#7.18"><stdbool.h></a>
582 -- idempotent type qualifiers
583 -- empty macro arguments
584 -- new structure type compatibility rules (tag compatibility)
585 -- additional predefined macro names
586 -- _Pragma preprocessing operator
588 -- __func__ predefined identifier
590 -- additional strftime conversion specifiers
591 -- LIA compatibility annex
594 [<a name="#pxv" href="pxv">page xv</a>] (<a href="#Contents">Contents</a>)
596 -- deprecate ungetc at the beginning of a binary file
597 -- remove deprecation of aliased array parameters
598 -- conversion of array to pointer not limited to lvalues
599 -- relaxed constraints on aggregate and union initialization
600 -- relaxed restrictions on portable header names
601 -- return without expression not permitted in function that returns a value (and vice
603 8 Annexes D, F, K, and L form a normative part of this standard; annexes A, B, C, E, G, H,
604 I, J, the bibliography, and the index are for information only. In accordance with Part 2 of
605 the ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples
606 are also for information only.
611 [<a name="#pxvi" href="pxvi">page xvi</a>] (<a href="#Contents">Contents</a>)
613 <a name="Introduction" href="#Introduction"><b> Introduction</b></a>
614 1 With the introduction of new devices and extended character sets, new features may be
615 added to this International Standard. Subclauses in the language and library clauses warn
616 implementors and programmers of usages which, though valid in themselves, may
617 conflict with future additions.
618 2 Certain features are obsolescent, which means that they may be considered for
619 withdrawal in future revisions of this International Standard. They are retained because
620 of their widespread use, but their use in new implementations (for implementation
621 features) or new programs (for language [6.11] or library features [7.30]) is discouraged.
622 3 This International Standard is divided into four major subdivisions:
623 -- preliminary elements (clauses 1-4);
624 -- the characteristics of environments that translate and execute C programs (clause 5);
625 -- the language syntax, constraints, and semantics (clause 6);
626 -- the library facilities (clause 7).
627 4 Examples are provided to illustrate possible forms of the constructions described.
628 Footnotes are provided to emphasize consequences of the rules described in that
629 subclause or elsewhere in this International Standard. References are used to refer to
630 other related subclauses. Recommendations are provided to give advice or guidance to
631 implementors. Annexes provide additional information and summarize the information
632 contained in this International Standard. A bibliography lists documents that were
633 referred to during the preparation of the standard.
634 5 The language clause (clause 6) is derived from ''The C Reference Manual''.
635 6 The library clause (clause 7) is based on the 1984 /usr/group Standard.
640 [<a name="#pxvii" href="pxvii">page xvii</a>] (<a href="#Contents">Contents</a>)
644 [<a name="#pxviii" href="pxviii">page xviii</a>] (<a href="#Contents">Contents</a>)
648 Programming languages -- C
652 <a name="1" href="#1"><b> 1. Scope</b></a>
653 1 This International Standard specifies the form and establishes the interpretation of
654 programs written in the C programming language.1) It specifies
655 -- the representation of C programs;
656 -- the syntax and constraints of the C language;
657 -- the semantic rules for interpreting C programs;
658 -- the representation of input data to be processed by C programs;
659 -- the representation of output data produced by C programs;
660 -- the restrictions and limits imposed by a conforming implementation of C.
661 2 This International Standard does not specify
662 -- the mechanism by which C programs are transformed for use by a data-processing
664 -- the mechanism by which C programs are invoked for use by a data-processing
666 -- the mechanism by which input data are transformed for use by a C program;
667 -- the mechanism by which output data are transformed after being produced by a C
669 -- the size or complexity of a program and its data that will exceed the capacity of any
670 specific data-processing system or the capacity of a particular processor;
671 -- all minimal requirements of a data-processing system that is capable of supporting a
672 conforming implementation.
675 1) This International Standard is designed to promote the portability of C programs among a variety of
676 data-processing systems. It is intended for use by implementors and programmers.
678 [<a name="#p1" href="p1">page 1</a>] (<a href="#Contents">Contents</a>)
681 <a name="2" href="#2"><b> 2. Normative references</b></a>
682 1 The following referenced documents are indispensable for the application of this
683 document. For dated references, only the edition cited applies. For undated references,
684 the latest edition of the referenced document (including any amendments) applies.
685 2 ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and symbols for
686 use in the physical sciences and technology.
687 3 ISO/IEC 646, Information technology -- ISO 7-bit coded character set for information
689 4 ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1: Fundamental
691 5 ISO 4217, Codes for the representation of currencies and funds.
692 6 ISO 8601, Data elements and interchange formats -- Information interchange --
693 Representation of dates and times.
694 7 ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded
696 8 IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems (previously
697 designated IEC 559:1989).
702 [<a name="#p2" href="p2">page 2</a>] (<a href="#Contents">Contents</a>)
705 <a name="3" href="#3"><b> 3. Terms, definitions, and symbols</b></a>
706 1 For the purposes of this International Standard, the following definitions apply. Other
707 terms are defined where they appear in italic type or on the left side of a syntax rule.
708 Terms explicitly defined in this International Standard are not to be presumed to refer
709 implicitly to similar terms defined elsewhere. Terms not defined in this International
710 Standard are to be interpreted according to ISO/IEC 2382-1. Mathematical symbols not
711 defined in this International Standard are to be interpreted according to ISO 31-11.
712 <a name="3.1" href="#3.1"><b> 3.1</b></a>
714 <execution-time action> to read or modify the value of an object
715 2 NOTE 1 Where only one of these two actions is meant, ''read'' or ''modify'' is used.
717 3 NOTE 2 ''Modify'' includes the case where the new value being stored is the same as the previous value.
719 4 NOTE 3 Expressions that are not evaluated do not access objects.
721 <a name="3.2" href="#3.2"><b> 3.2</b></a>
723 requirement that objects of a particular type be located on storage boundaries with
724 addresses that are particular multiples of a byte address
725 <a name="3.3" href="#3.3"><b> 3.3</b></a>
728 actual parameter (deprecated)
729 expression in the comma-separated list bounded by the parentheses in a function call
730 expression, or a sequence of preprocessing tokens in the comma-separated list bounded
731 by the parentheses in a function-like macro invocation
732 <a name="3.4" href="#3.4"><b> 3.4</b></a>
734 external appearance or action
735 <a name="3.4.1" href="#3.4.1"><b> 3.4.1</b></a>
736 1 implementation-defined behavior
737 unspecified behavior where each implementation documents how the choice is made
738 2 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
739 when a signed integer is shifted right.
741 <a name="3.4.2" href="#3.4.2"><b> 3.4.2</b></a>
742 1 locale-specific behavior
743 behavior that depends on local conventions of nationality, culture, and language that each
744 implementation documents
747 [<a name="#p3" href="p3">page 3</a>] (<a href="#Contents">Contents</a>)
749 2 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
750 characters other than the 26 lowercase Latin letters.
752 <a name="3.4.3" href="#3.4.3"><b> 3.4.3</b></a>
754 behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
755 for which this International Standard imposes no requirements
756 2 NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable
757 results, to behaving during translation or program execution in a documented manner characteristic of the
758 environment (with or without the issuance of a diagnostic message), to terminating a translation or
759 execution (with the issuance of a diagnostic message).
761 3 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
763 <a name="3.4.4" href="#3.4.4"><b> 3.4.4</b></a>
764 1 unspecified behavior
765 use of an unspecified value, or other behavior where this International Standard provides
766 two or more possibilities and imposes no further requirements on which is chosen in any
768 2 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
771 <a name="3.5" href="#3.5"><b> 3.5</b></a>
773 unit of data storage in the execution environment large enough to hold an object that may
774 have one of two values
775 2 NOTE It need not be possible to express the address of each individual bit of an object.
777 <a name="3.6" href="#3.6"><b> 3.6</b></a>
779 addressable unit of data storage large enough to hold any member of the basic character
780 set of the execution environment
781 2 NOTE 1 It is possible to express the address of each individual byte of an object uniquely.
783 3 NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
784 defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order
787 <a name="3.7" href="#3.7"><b> 3.7</b></a>
789 <abstract> member of a set of elements used for the organization, control, or
790 representation of data
791 <a name="3.7.1" href="#3.7.1"><b> 3.7.1</b></a>
793 single-byte character
794 <C> bit representation that fits in a byte
795 [<a name="#p4" href="p4">page 4</a>] (<a href="#Contents">Contents</a>)
797 <a name="3.7.2" href="#3.7.2"><b> 3.7.2</b></a>
798 1 multibyte character
799 sequence of one or more bytes representing a member of the extended character set of
800 either the source or the execution environment
801 2 NOTE The extended character set is a superset of the basic character set.
803 <a name="3.7.3" href="#3.7.3"><b> 3.7.3</b></a>
805 bit representation that fits in an object of type wchar_t, capable of representing any
806 character in the current locale
807 <a name="3.8" href="#3.8"><b> 3.8</b></a>
809 restriction, either syntactic or semantic, by which the exposition of language elements is
811 <a name="3.9" href="#3.9"><b> 3.9</b></a>
812 1 correctly rounded result
813 representation in the result format that is nearest in value, subject to the current rounding
814 mode, to what the result would be given unlimited range and precision
815 <a name="3.10" href="#3.10"><b> 3.10</b></a>
817 message belonging to an implementation-defined subset of the implementation's message
819 <a name="3.11" href="#3.11"><b> 3.11</b></a>
821 reference to a later subclause of this International Standard that contains additional
822 information relevant to this subclause
823 <a name="3.12" href="#3.12"><b> 3.12</b></a>
825 particular set of software, running in a particular translation environment under particular
826 control options, that performs translation of programs for, and supports execution of
827 functions in, a particular execution environment
828 <a name="3.13" href="#3.13"><b> 3.13</b></a>
829 1 implementation limit
830 restriction imposed upon programs by the implementation
831 <a name="3.14" href="#3.14"><b> 3.14</b></a>
833 either an object of scalar type, or a maximal sequence of adjacent bit-fields all having
836 [<a name="#p5" href="p5">page 5</a>] (<a href="#Contents">Contents</a>)
838 2 NOTE 1 Two threads of execution can update and access separate memory locations without interfering
841 3 NOTE 2 A bit-field and an adjacent non-bit-field member are in separate memory locations. The same
842 applies to two bit-fields, if one is declared inside a nested structure declaration and the other is not, or if the
843 two are separated by a zero-length bit-field declaration, or if they are separated by a non-bit-field member
844 declaration. It is not safe to concurrently update two non-atomic bit-fields in the same structure if all
845 members declared between them are also (non-zero-length) bit-fields, no matter what the sizes of those
846 intervening bit-fields happen to be.
848 4 EXAMPLE A structure declared as
851 int b:5, c:11, :0, d:8;
852 struct { int ee:8; } e;
854 contains four separate memory locations: The member a, and bit-fields d and e.ee are each separate
855 memory locations, and can be modified concurrently without interfering with each other. The bit-fields b
856 and c together constitute the fourth memory location. The bit-fields b and c cannot be concurrently
857 modified, but b and a, for example, can be.
859 <a name="3.15" href="#3.15"><b> 3.15</b></a>
861 region of data storage in the execution environment, the contents of which can represent
863 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>.
865 <a name="3.16" href="#3.16"><b> 3.16</b></a>
868 formal argument (deprecated)
869 object declared as part of a function declaration or definition that acquires a value on
870 entry to the function, or an identifier from the comma-separated list bounded by the
871 parentheses immediately following the macro name in a function-like macro definition
872 <a name="3.17" href="#3.17"><b> 3.17</b></a>
873 1 recommended practice
874 specification that is strongly recommended as being in keeping with the intent of the
875 standard, but that may be impractical for some implementations
876 <a name="3.18" href="#3.18"><b> 3.18</b></a>
878 requirement on a program when calling a library function
879 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
880 need not be diagnosed at translation time.
882 3 NOTE 2 Implementations that support the extensions in <a href="#K">annex K</a> are required to verify that the runtime-
883 constraints for a library function are not violated by the program; see <a href="#K.3.1.4">K.3.1.4</a>.
885 [<a name="#p6" href="p6">page 6</a>] (<a href="#Contents">Contents</a>)
887 <a name="3.19" href="#3.19"><b> 3.19</b></a>
889 precise meaning of the contents of an object when interpreted as having a specific type
890 <a name="3.19.1" href="#3.19.1"><b> 3.19.1</b></a>
891 1 implementation-defined value
892 unspecified value where each implementation documents how the choice is made
893 <a name="3.19.2" href="#3.19.2"><b> 3.19.2</b></a>
894 1 indeterminate value
895 either an unspecified value or a trap representation
896 <a name="3.19.3" href="#3.19.3"><b> 3.19.3</b></a>
898 valid value of the relevant type where this International Standard imposes no
899 requirements on which value is chosen in any instance
900 2 NOTE An unspecified value cannot be a trap representation.
902 <a name="3.19.4" href="#3.19.4"><b> 3.19.4</b></a>
903 1 trap representation
904 an object representation that need not represent a value of the object type
905 <a name="3.19.5" href="#3.19.5"><b> 3.19.5</b></a>
907 interrupt execution of the program such that no further operations are performed
908 2 NOTE In this International Standard, when the word ''trap'' is not immediately followed by
909 ''representation'', this is the intended usage.2)
911 <a name="3.20" href="#3.20"><b> 3.20</b></a>
913 ceiling of x: the least integer greater than or equal to x
914 2 EXAMPLE [^2.4^] is 3, [^-2.4^] is -2.
916 <a name="3.21" href="#3.21"><b> 3.21</b></a>
918 floor of x: the greatest integer less than or equal to x
919 2 EXAMPLE [_2.4_] is 2, [_-2.4_] is -3.
924 2) For example, ''Trapping or stopping (if supported) is disabled...'' (<a href="#F.8.2">F.8.2</a>). Note that fetching a trap
925 representation might perform a trap but is not required to (see <a href="#6.2.6.1">6.2.6.1</a>).
927 [<a name="#p7" href="p7">page 7</a>] (<a href="#Contents">Contents</a>)
930 <a name="4" href="#4"><b> 4. Conformance</b></a>
931 1 In this International Standard, ''shall'' is to be interpreted as a requirement on an
932 implementation or on a program; conversely, ''shall not'' is to be interpreted as a
934 2 If a ''shall'' or ''shall not'' requirement that appears outside of a constraint or runtime-
935 constraint is violated, the behavior is undefined. Undefined behavior is otherwise
936 indicated in this International Standard by the words ''undefined behavior'' or by the
937 omission of any explicit definition of behavior. There is no difference in emphasis among
938 these three; they all describe ''behavior that is undefined''.
939 3 A program that is correct in all other aspects, operating on correct data, containing
940 unspecified behavior shall be a correct program and act in accordance with <a href="#5.1.2.3">5.1.2.3</a>.
941 4 The implementation shall not successfully translate a preprocessing translation unit
942 containing a #error preprocessing directive unless it is part of a group skipped by
943 conditional inclusion.
944 5 A strictly conforming program shall use only those features of the language and library
945 specified in this International Standard.3) It shall not produce output dependent on any
946 unspecified, undefined, or implementation-defined behavior, and shall not exceed any
947 minimum implementation limit.
948 6 The two forms of conforming implementation are hosted and freestanding. A conforming
949 hosted implementation shall accept any strictly conforming program. A conforming
950 freestanding implementation shall accept any strictly conforming program that does not
951 use complex types and in which the use of the features specified in the library clause
952 (clause 7) is confined to the contents of the standard headers <a href="#7.7"><float.h></a>,
953 <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>,
954 <a href="#7.19"><stddef.h></a>, and <a href="#7.20"><stdint.h></a>. A conforming implementation may have extensions
955 (including additional library functions), provided they do not alter the behavior of any
956 strictly conforming program.4)
960 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
961 by an appropriate conditional inclusion preprocessing directive using the related macro. For example:
962 #ifdef __STDC_IEC_559__ /* FE_UPWARD defined */
964 fesetround(FE_UPWARD);
968 4) This implies that a conforming implementation reserves no identifiers other than those explicitly
969 reserved in this International Standard.
971 [<a name="#p8" href="p8">page 8</a>] (<a href="#Contents">Contents</a>)
973 7 A conforming program is one that is acceptable to a conforming implementation.5)
974 8 An implementation shall be accompanied by a document that defines all implementation-
975 defined and locale-specific characteristics and all extensions.
976 Forward references: conditional inclusion (<a href="#6.10.1">6.10.1</a>), error directive (<a href="#6.10.5">6.10.5</a>),
977 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>
978 (<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>),
979 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>
980 (<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>).
985 5) Strictly conforming programs are intended to be maximally portable among conforming
986 implementations. Conforming programs may depend upon nonportable features of a conforming
989 [<a name="#p9" href="p9">page 9</a>] (<a href="#Contents">Contents</a>)
992 <a name="5" href="#5"><b> 5. Environment</b></a>
993 1 An implementation translates C source files and executes C programs in two data-
994 processing-system environments, which will be called the translation environment and
995 the execution environment in this International Standard. Their characteristics define and
996 constrain the results of executing conforming C programs constructed according to the
997 syntactic and semantic rules for conforming implementations.
998 Forward references: In this clause, only a few of many possible forward references
1000 <a name="5.1" href="#5.1"><b> 5.1 Conceptual models</b></a>
1001 <a name="5.1.1" href="#5.1.1"><b> 5.1.1 Translation environment</b></a>
1002 <a name="5.1.1.1" href="#5.1.1.1"><b> 5.1.1.1 Program structure</b></a>
1003 1 A C program need not all be translated at the same time. The text of the program is kept
1004 in units called source files, (or preprocessing files) in this International Standard. A
1005 source file together with all the headers and source files included via the preprocessing
1006 directive #include is known as a preprocessing translation unit. After preprocessing, a
1007 preprocessing translation unit is called a translation unit. Previously translated translation
1008 units may be preserved individually or in libraries. The separate translation units of a
1009 program communicate by (for example) calls to functions whose identifiers have external
1010 linkage, manipulation of objects whose identifiers have external linkage, or manipulation
1011 of data files. Translation units may be separately translated and then later linked to
1012 produce an executable program.
1013 Forward references: linkages of identifiers (<a href="#6.2.2">6.2.2</a>), external definitions (<a href="#6.9">6.9</a>),
1014 preprocessing directives (<a href="#6.10">6.10</a>).
1015 <a name="5.1.1.2" href="#5.1.1.2"><b> 5.1.1.2 Translation phases</b></a>
1016 1 The precedence among the syntax rules of translation is specified by the following
1018 1. Physical source file multibyte characters are mapped, in an implementation-
1019 defined manner, to the source character set (introducing new-line characters for
1020 end-of-line indicators) if necessary. Trigraph sequences are replaced by
1021 corresponding single-character internal representations.
1025 6) Implementations shall behave as if these separate phases occur, even though many are typically folded
1026 together in practice. Source files, translation units, and translated translation units need not
1027 necessarily be stored as files, nor need there be any one-to-one correspondence between these entities
1028 and any external representation. The description is conceptual only, and does not specify any
1029 particular implementation.
1031 [<a name="#p10" href="p10">page 10</a>] (<a href="#Contents">Contents</a>)
1033 2. Each instance of a backslash character (\) immediately followed by a new-line
1034 character is deleted, splicing physical source lines to form logical source lines.
1035 Only the last backslash on any physical source line shall be eligible for being part
1036 of such a splice. A source file that is not empty shall end in a new-line character,
1037 which shall not be immediately preceded by a backslash character before any such
1038 splicing takes place.
1039 3. The source file is decomposed into preprocessing tokens7) and sequences of
1040 white-space characters (including comments). A source file shall not end in a
1041 partial preprocessing token or in a partial comment. Each comment is replaced by
1042 one space character. New-line characters are retained. Whether each nonempty
1043 sequence of white-space characters other than new-line is retained or replaced by
1044 one space character is implementation-defined.
1045 4. Preprocessing directives are executed, macro invocations are expanded, and
1046 _Pragma unary operator expressions are executed. If a character sequence that
1047 matches the syntax of a universal character name is produced by token
1048 concatenation (<a href="#6.10.3.3">6.10.3.3</a>), the behavior is undefined. A #include preprocessing
1049 directive causes the named header or source file to be processed from phase 1
1050 through phase 4, recursively. All preprocessing directives are then deleted.
1051 5. Each source character set member and escape sequence in character constants and
1052 string literals is converted to the corresponding member of the execution character
1053 set; if there is no corresponding member, it is converted to an implementation-
1054 defined member other than the null (wide) character.8)
1055 6. Adjacent string literal tokens are concatenated.
1056 7. White-space characters separating tokens are no longer significant. Each
1057 preprocessing token is converted into a token. The resulting tokens are
1058 syntactically and semantically analyzed and translated as a translation unit.
1059 8. All external object and function references are resolved. Library components are
1060 linked to satisfy external references to functions and objects not defined in the
1061 current translation. All such translator output is collected into a program image
1062 which contains information needed for execution in its execution environment.
1063 Forward references: universal character names (<a href="#6.4.3">6.4.3</a>), lexical elements (<a href="#6.4">6.4</a>),
1064 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>).
1068 7) As described in <a href="#6.4">6.4</a>, the process of dividing a source file's characters into preprocessing tokens is
1069 context-dependent. For example, see the handling of < within a #include preprocessing directive.
1070 8) An implementation need not convert all non-corresponding source characters to the same execution
1073 [<a name="#p11" href="p11">page 11</a>] (<a href="#Contents">Contents</a>)
1075 <a name="5.1.1.3" href="#5.1.1.3"><b> 5.1.1.3 Diagnostics</b></a>
1076 1 A conforming implementation shall produce at least one diagnostic message (identified in
1077 an implementation-defined manner) if a preprocessing translation unit or translation unit
1078 contains a violation of any syntax rule or constraint, even if the behavior is also explicitly
1079 specified as undefined or implementation-defined. Diagnostic messages need not be
1080 produced in other circumstances.9)
1081 2 EXAMPLE An implementation shall issue a diagnostic for the translation unit:
1084 because in those cases where wording in this International Standard describes the behavior for a construct
1085 as being both a constraint error and resulting in undefined behavior, the constraint error shall be diagnosed.
1087 <a name="5.1.2" href="#5.1.2"><b> 5.1.2 Execution environments</b></a>
1088 1 Two execution environments are defined: freestanding and hosted. In both cases,
1089 program startup occurs when a designated C function is called by the execution
1090 environment. All objects with static storage duration shall be initialized (set to their
1091 initial values) before program startup. The manner and timing of such initialization are
1092 otherwise unspecified. Program termination returns control to the execution
1094 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>).
1095 <a name="5.1.2.1" href="#5.1.2.1"><b> 5.1.2.1 Freestanding environment</b></a>
1096 1 In a freestanding environment (in which C program execution may take place without any
1097 benefit of an operating system), the name and type of the function called at program
1098 startup are implementation-defined. Any library facilities available to a freestanding
1099 program, other than the minimal set required by clause 4, are implementation-defined.
1100 2 The effect of program termination in a freestanding environment is implementation-
1102 <a name="5.1.2.2" href="#5.1.2.2"><b> 5.1.2.2 Hosted environment</b></a>
1103 1 A hosted environment need not be provided, but shall conform to the following
1104 specifications if present.
1109 9) The intent is that an implementation should identify the nature of, and where possible localize, each
1110 violation. Of course, an implementation is free to produce any number of diagnostics as long as a
1111 valid program is still correctly translated. It may also successfully translate an invalid program.
1113 [<a name="#p12" href="p12">page 12</a>] (<a href="#Contents">Contents</a>)
1115 <a name="5.1.2.2.1" href="#5.1.2.2.1"><b> 5.1.2.2.1 Program startup</b></a>
1116 1 The function called at program startup is named main. The implementation declares no
1117 prototype for this function. It shall be defined with a return type of int and with no
1119 int main(void) { /* ... */ }
1120 or with two parameters (referred to here as argc and argv, though any names may be
1121 used, as they are local to the function in which they are declared):
1122 int main(int argc, char *argv[]) { /* ... */ }
1123 or equivalent;10) or in some other implementation-defined manner.
1124 2 If they are declared, the parameters to the main function shall obey the following
1126 -- The value of argc shall be nonnegative.
1127 -- argv[argc] shall be a null pointer.
1128 -- If the value of argc is greater than zero, the array members argv[0] through
1129 argv[argc-1] inclusive shall contain pointers to strings, which are given
1130 implementation-defined values by the host environment prior to program startup. The
1131 intent is to supply to the program information determined prior to program startup
1132 from elsewhere in the hosted environment. If the host environment is not capable of
1133 supplying strings with letters in both uppercase and lowercase, the implementation
1134 shall ensure that the strings are received in lowercase.
1135 -- If the value of argc is greater than zero, the string pointed to by argv[0]
1136 represents the program name; argv[0][0] shall be the null character if the
1137 program name is not available from the host environment. If the value of argc is
1138 greater than one, the strings pointed to by argv[1] through argv[argc-1]
1139 represent the program parameters.
1140 -- The parameters argc and argv and the strings pointed to by the argv array shall
1141 be modifiable by the program, and retain their last-stored values between program
1142 startup and program termination.
1143 <a name="5.1.2.2.2" href="#5.1.2.2.2"><b> 5.1.2.2.2 Program execution</b></a>
1144 1 In a hosted environment, a program may use all the functions, macros, type definitions,
1145 and objects described in the library clause (clause 7).
1150 10) Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as
1151 char ** argv, and so on.
1153 [<a name="#p13" href="p13">page 13</a>] (<a href="#Contents">Contents</a>)
1155 <a name="5.1.2.2.3" href="#5.1.2.2.3"><b> 5.1.2.2.3 Program termination</b></a>
1156 1 If the return type of the main function is a type compatible with int, a return from the
1157 initial call to the main function is equivalent to calling the exit function with the value
1158 returned by the main function as its argument;11) reaching the } that terminates the
1159 main function returns a value of 0. If the return type is not compatible with int, the
1160 termination status returned to the host environment is unspecified.
1161 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>).
1162 <a name="5.1.2.3" href="#5.1.2.3"><b> 5.1.2.3 Program execution</b></a>
1163 1 The semantic descriptions in this International Standard describe the behavior of an
1164 abstract machine in which issues of optimization are irrelevant.
1165 2 Accessing a volatile object, modifying an object, modifying a file, or calling a function
1166 that does any of those operations are all side effects,12) which are changes in the state of
1167 the execution environment. Evaluation of an expression in general includes both value
1168 computations and initiation of side effects. Value computation for an lvalue expression
1169 includes determining the identity of the designated object.
1170 3 Sequenced before is an asymmetric, transitive, pair-wise relation between evaluations
1171 executed by a single thread, which induces a partial order among those evaluations.
1172 Given any two evaluations A and B, if A is sequenced before B, then the execution of A
1173 shall precede the execution of B. (Conversely, if A is sequenced before B, then B is
1174 sequenced after A.) If A is not sequenced before or after B, then A and B are
1175 unsequenced. Evaluations A and B are indeterminately sequenced when A is sequenced
1176 either before or after B, but it is unspecified which.13) The presence of a sequence point
1177 between the evaluation of expressions A and B implies that every value computation and
1178 side effect associated with A is sequenced before every value computation and side effect
1179 associated with B. (A summary of the sequence points is given in <a href="#C">annex C</a>.)
1180 4 In the abstract machine, all expressions are evaluated as specified by the semantics. An
1181 actual implementation need not evaluate part of an expression if it can deduce that its
1182 value is not used and that no needed side effects are produced (including any caused by
1184 11) In accordance with <a href="#6.2.4">6.2.4</a>, the lifetimes of objects with automatic storage duration declared in main
1185 will have ended in the former case, even where they would not have in the latter.
1186 12) The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status
1187 flags and control modes. Floating-point operations implicitly set the status flags; modes affect result
1188 values of floating-point operations. Implementations that support such floating-point state are
1189 required to regard changes to it as side effects -- see <a href="#F">annex F</a> for details. The floating-point
1190 environment library <a href="#7.6"><fenv.h></a> provides a programming facility for indicating when these side
1191 effects matter, freeing the implementations in other cases.
1192 13) The executions of unsequenced evaluations can interleave. Indeterminately sequenced evaluations
1193 cannot interleave, but can be executed in any order.
1195 [<a name="#p14" href="p14">page 14</a>] (<a href="#Contents">Contents</a>)
1197 calling a function or accessing a volatile object).
1198 5 When the processing of the abstract machine is interrupted by receipt of a signal, the
1199 values of objects that are neither lock-free atomic objects nor of type volatile
1200 sig_atomic_t are unspecified, and the value of any object that is modified by the
1201 handler that is neither a lock-free atomic object nor of type volatile
1202 sig_atomic_t becomes undefined.
1203 6 The least requirements on a conforming implementation are:
1204 -- Accesses to volatile objects are evaluated strictly according to the rules of the abstract
1206 -- At program termination, all data written into files shall be identical to the result that
1207 execution of the program according to the abstract semantics would have produced.
1208 -- The input and output dynamics of interactive devices shall take place as specified in
1209 <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>
1210 appear as soon as possible, to ensure that prompting messages actually appear prior to
1211 a program waiting for input.
1212 This is the observable behavior of the program.
1213 7 What constitutes an interactive device is implementation-defined.
1214 8 More stringent correspondences between abstract and actual semantics may be defined by
1215 each implementation.
1216 9 EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual
1217 semantics: at every sequence point, the values of the actual objects would agree with those specified by the
1218 abstract semantics. The keyword volatile would then be redundant.
1219 10 Alternatively, an implementation might perform various optimizations within each translation unit, such
1220 that the actual semantics would agree with the abstract semantics only when making function calls across
1221 translation unit boundaries. In such an implementation, at the time of each function entry and function
1222 return where the calling function and the called function are in different translation units, the values of all
1223 externally linked objects and of all objects accessible via pointers therein would agree with the abstract
1224 semantics. Furthermore, at the time of each such function entry the values of the parameters of the called
1225 function and of all objects accessible via pointers therein would agree with the abstract semantics. In this
1226 type of implementation, objects referred to by interrupt service routines activated by the signal function
1227 would require explicit specification of volatile storage, as well as other implementation-defined
1230 11 EXAMPLE 2 In executing the fragment
1234 the ''integer promotions'' require that the abstract machine promote the value of each variable to int size
1235 and then add the two ints and truncate the sum. Provided the addition of two chars can be done without
1236 overflow, or with overflow wrapping silently to produce the correct result, the actual execution need only
1237 produce the same result, possibly omitting the promotions.
1239 [<a name="#p15" href="p15">page 15</a>] (<a href="#Contents">Contents</a>)
1241 12 EXAMPLE 3 Similarly, in the fragment
1246 the multiplication may be executed using single-precision arithmetic if the implementation can ascertain
1247 that the result would be the same as if it were executed using double-precision arithmetic (for example, if d
1248 were replaced by the constant <a href="#2.0">2.0</a>, which has type double).
1250 13 EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate
1251 semantics. Values are independent of whether they are represented in a register or in memory. For
1252 example, an implicit spilling of a register is not permitted to alter the value. Also, an explicit store and load
1253 is required to round to the precision of the storage type. In particular, casts and assignments are required to
1254 perform their specified conversion. For the fragment
1257 d1 = f = expression;
1258 d2 = (float) expression;
1259 the values assigned to d1 and d2 are required to have been converted to float.
1261 14 EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in
1262 precision as well as range. The implementation cannot generally apply the mathematical associative rules
1263 for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of
1264 overflow and underflow. Likewise, implementations cannot generally replace decimal constants in order to
1265 rearrange expressions. In the following fragment, rearrangements suggested by mathematical rules for real
1266 numbers are often not valid (see <a href="#F.9">F.9</a>).
1269 x = (x * y) * z; // not equivalent to x *= y * z;
1270 z = (x - y) + y ; // not equivalent to z = x;
1271 z = x + x * y; // not equivalent to z = x * (<a href="#1.0">1.0</a> + y);
1272 y = x / <a href="#5.0">5.0</a>; // not equivalent to y = x * 0.2;
1274 15 EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
1277 a = a + 32760 + b + 5;
1278 the expression statement behaves exactly the same as
1279 a = (((a + 32760) + b) + 5);
1280 due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is
1281 next added to b, and that result is then added to 5 which results in the value assigned to a. On a machine in
1282 which overflows produce an explicit trap and in which the range of values representable by an int is
1283 [-32768, +32767], the implementation cannot rewrite this expression as
1284 a = ((a + b) + 32765);
1285 since if the values for a and b were, respectively, -32754 and -15, the sum a + b would produce a trap
1286 while the original expression would not; nor can the expression be rewritten either as
1289 [<a name="#p16" href="p16">page 16</a>] (<a href="#Contents">Contents</a>)
1291 a = ((a + 32765) + b);
1293 a = (a + (b + 32765));
1294 since the values for a and b might have been, respectively, 4 and -8 or -17 and 12. However, on a machine
1295 in which overflow silently generates some value and where positive and negative overflows cancel, the
1296 above expression statement can be rewritten by the implementation in any of the above ways because the
1297 same result will occur.
1299 16 EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the
1301 #include <a href="#7.21"><stdio.h></a>
1305 sum = sum * 10 - '0' + (*p++ = getchar());
1306 the expression statement is grouped as if it were written as
1307 sum = (((sum * 10) - '0') + ((*(p++)) = (getchar())));
1308 but the actual increment of p can occur at any time between the previous sequence point and the next
1309 sequence point (the ;), and the call to getchar can occur at any point prior to the need of its returned
1312 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
1313 signal function (<a href="#7.14">7.14</a>), files (<a href="#7.21.3">7.21.3</a>).
1314 <a name="5.1.2.4" href="#5.1.2.4"><b> 5.1.2.4 Multi-threaded executions and data races</b></a>
1315 1 Under a hosted implementation, a program can have more than one thread of execution
1316 (or thread) running concurrently. The execution of each thread proceeds as defined by
1317 the remainder of this standard. The execution of the entire program consists of an
1318 execution of all of its threads.14) Under a freestanding implementation, it is
1319 implementation-defined whether a program can have more than one thread of execution.
1320 2 The value of an object visible to a thread T at a particular point is the initial value of the
1321 object, a value stored in the object by T , or a value stored in the object by another thread,
1322 according to the rules below.
1323 3 NOTE 1 In some cases, there may instead be undefined behavior. Much of this section is motivated by
1324 the desire to support atomic operations with explicit and detailed visibility constraints. However, it also
1325 implicitly supports a simpler view for more restricted programs.
1327 4 Two expression evaluations conflict if one of them modifies a memory location and the
1328 other one accesses or modifies the same memory location.
1333 14) The execution can usually be viewed as an interleaving of all of the threads. However, some kinds of
1334 atomic operations, for example, allow executions inconsistent with a simple interleaving as described
1337 [<a name="#p17" href="p17">page 17</a>] (<a href="#Contents">Contents</a>)
1339 5 The library defines a number of atomic operations (<a href="#7.17">7.17</a>) and operations on mutexes
1340 (<a href="#7.25.4">7.25.4</a>) that are specially identified as synchronization operations. These operations play
1341 a special role in making assignments in one thread visible to another. A synchronization
1342 operation on one or more memory locations is either an acquire operation, a release
1343 operation, both an acquire and release operation, or a consume operation. A
1344 synchronization operation without an associated memory location is a fence and can be
1345 either an acquire fence, a release fence, or both an acquire and release fence. In addition,
1346 there are relaxed atomic operations, which are not synchronization operations, and
1347 atomic read-modify-write operations, which have special characteristics.
1348 6 NOTE 2 For example, a call that acquires a mutex will perform an acquire operation on the locations
1349 composing the mutex. Correspondingly, a call that releases the same mutex will perform a release
1350 operation on those same locations. Informally, performing a release operation on A forces prior side effects
1351 on other memory locations to become visible to other threads that later perform an acquire or consume
1352 operation on A. We do not include relaxed atomic operations as synchronization operations although, like
1353 synchronization operations, they cannot contribute to data races.
1355 7 All modifications to a particular atomic object M occur in some particular total order,
1356 called the modification order of M. If A and B are modifications of an atomic object M,
1357 and A happens before B, then A shall precede B in the modification order of M, which is
1359 8 NOTE 3 This states that the modification orders must respect the ''happens before'' relation.
1361 9 NOTE 4 There is a separate order for each atomic object. There is no requirement that these can be
1362 combined into a single total order for all objects. In general this will be impossible since different threads
1363 may observe modifications to different variables in inconsistent orders.
1365 10 A release sequence on an atomic object M is a maximal contiguous sub-sequence of side
1366 effects in the modification order of M, where the first operation is a release and every
1367 subsequent operation either is performed by the same thread that performed the release or
1368 is an atomic read-modify-write operation.
1369 11 Certain library calls synchronize with other library calls performed by another thread. In
1370 particular, an atomic operation A that performs a release operation on an object M
1371 synchronizes with an atomic operation B that performs an acquire operation on M and
1372 reads a value written by any side effect in the release sequence headed by A.
1373 12 NOTE 5 Except in the specified cases, reading a later value does not necessarily ensure visibility as
1374 described below. Such a requirement would sometimes interfere with efficient implementation.
1376 13 NOTE 6 The specifications of the synchronization operations define when one reads the value written by
1377 another. For atomic variables, the definition is clear. All operations on a given mutex occur in a single total
1378 order. Each mutex acquisition ''reads the value written'' by the last mutex release.
1380 14 An evaluation A carries a dependency 15) to an evaluation B if:
1383 15) The ''carries a dependency'' relation is a subset of the ''sequenced before'' relation, and is similarly
1384 strictly intra-thread.
1386 [<a name="#p18" href="p18">page 18</a>] (<a href="#Contents">Contents</a>)
1388 -- the value of A is used as an operand of B, unless:
1389 o B is an invocation of the kill_dependency macro,
1391 o A is the left operand of a && or || operator,
1393 o A is the left operand of a ? : operator, or
1395 o A is the left operand of a , operator;
1397 -- A writes a scalar object or bit-field M, B reads from M the value written by A, and A
1398 is sequenced before B, or
1399 -- for some evaluation X, A carries a dependency to X and X carries a dependency to B.
1400 15 An evaluation A is dependency-ordered before16) an evaluation B if:
1401 -- A performs a release operation on an atomic object M, and B performs a consume
1402 operation on M and reads a value written by any side effect in the release sequence
1404 -- for some evaluation X, A is dependency-ordered before X and X carries a
1406 16 An evaluation A inter-thread happens before an evaluation B if A synchronizes with B, A
1407 is dependency-ordered before B, or, for some evaluation X:
1408 -- A synchronizes with X and X is sequenced before B,
1409 -- A is sequenced before X and X inter-thread happens before B, or
1410 -- A inter-thread happens before X and X inter-thread happens before B.
1411 17 NOTE 7 The ''inter-thread happens before'' relation describes arbitrary concatenations of ''sequenced
1412 before'', ''synchronizes with'', and ''dependency-ordered before'' relationships, with two exceptions. The
1413 first exception is that a concatenation is not permitted to end with ''dependency-ordered before'' followed
1414 by ''sequenced before''. The reason for this limitation is that a consume operation participating in a
1415 ''dependency-ordered before'' relationship provides ordering only with respect to operations to which this
1416 consume operation actually carries a dependency. The reason that this limitation applies only to the end of
1417 such a concatenation is that any subsequent release operation will provide the required ordering for a prior
1418 consume operation. The second exception is that a concatenation is not permitted to consist entirely of
1419 ''sequenced before''. The reasons for this limitation are (1) to permit ''inter-thread happens before'' to be
1420 transitively closed and (2) the ''happens before'' relation, defined below, provides for relationships
1421 consisting entirely of ''sequenced before''.
1423 18 An evaluation A happens before an evaluation B if A is sequenced before B or A inter-
1424 thread happens before B.
1428 16) The ''dependency-ordered before'' relation is analogous to the ''synchronizes with'' relation, but uses
1429 release/consume in place of release/acquire.
1431 [<a name="#p19" href="p19">page 19</a>] (<a href="#Contents">Contents</a>)
1433 19 A visible side effect A on an object M with respect to a value computation B of M
1434 satisfies the conditions:
1435 -- A happens before B, and
1436 -- there is no other side effect X to M such that A happens before X and X happens
1438 The value of a non-atomic scalar object M, as determined by evaluation B, shall be the
1439 value stored by the visible side effect A.
1440 20 NOTE 8 If there is ambiguity about which side effect to a non-atomic object is visible, then there is a data
1441 race and the behavior is undefined.
1443 21 NOTE 9 This states that operations on ordinary variables are not visibly reordered. This is not actually
1444 detectable without data races, but it is necessary to ensure that data races, as defined here, and with suitable
1445 restrictions on the use of atomics, correspond to data races in a simple interleaved (sequentially consistent)
1448 22 The visible sequence of side effects on an atomic object M, with respect to a value
1449 computation B of M, is a maximal contiguous sub-sequence of side effects in the
1450 modification order of M, where the first side effect is visible with respect to B, and for
1451 every subsequent side effect, it is not the case that B happens before it. The value of an
1452 atomic object M, as determined by evaluation B, shall be the value stored by some
1453 operation in the visible sequence of M with respect to B. Furthermore, if a value
1454 computation A of an atomic object M happens before a value computation B of M, and
1455 the value computed by A corresponds to the value stored by side effect X, then the value
1456 computed by B shall either equal the value computed by A, or be the value stored by side
1457 effect Y , where Y follows X in the modification order of M.
1458 23 NOTE 10 This effectively disallows compiler reordering of atomic operations to a single object, even if
1459 both operations are ''relaxed'' loads. By doing so, we effectively make the ''cache coherence'' guarantee
1460 provided by most hardware available to C atomic operations.
1462 24 NOTE 11 The visible sequence depends on the ''happens before'' relation, which in turn depends on the
1463 values observed by loads of atomics, which we are restricting here. The intended reading is that there must
1464 exist an association of atomic loads with modifications they observe that, together with suitably chosen
1465 modification orders and the ''happens before'' relation derived as described above, satisfy the resulting
1466 constraints as imposed here.
1468 25 The execution of a program contains a data race if it contains two conflicting actions in
1469 different threads, at least one of which is not atomic, and neither happens before the
1470 other. Any such data race results in undefined behavior.
1471 26 NOTE 12 It can be shown that programs that correctly use simple mutexes and
1472 memory_order_seq_cst operations to prevent all data races, and use no other synchronization
1473 operations, behave as though the operations executed by their constituent threads were simply interleaved,
1474 with each value computation of an object being the last value stored in that interleaving. This is normally
1475 referred to as ''sequential consistency''. However, this applies only to data-race-free programs, and data-
1476 race-free programs cannot observe most program transformations that do not change single-threaded
1477 program semantics. In fact, most single-threaded program transformations continue to be allowed, since
1478 any program that behaves differently as a result must contain undefined behavior.
1480 [<a name="#p20" href="p20">page 20</a>] (<a href="#Contents">Contents</a>)
1482 27 NOTE 13 Compiler transformations that introduce assignments to a potentially shared memory location
1483 that would not be modified by the abstract machine are generally precluded by this standard, since such an
1484 assignment might overwrite another assignment by a different thread in cases in which an abstract machine
1485 execution would not have encountered a data race. This includes implementations of data member
1486 assignment that overwrite adjacent members in separate memory locations. We also generally preclude
1487 reordering of atomic loads in cases in which the atomics in question may alias, since this may violate the
1488 "visible sequence" rules.
1490 28 NOTE 14 Transformations that introduce a speculative read of a potentially shared memory location may
1491 not preserve the semantics of the program as defined in this standard, since they potentially introduce a data
1492 race. However, they are typically valid in the context of an optimizing compiler that targets a specific
1493 machine with well-defined semantics for data races. They would be invalid for a hypothetical machine that
1494 is not tolerant of races or provides hardware race detection.
1499 [<a name="#p21" href="p21">page 21</a>] (<a href="#Contents">Contents</a>)
1501 <a name="5.2" href="#5.2"><b> 5.2 Environmental considerations</b></a>
1502 <a name="5.2.1" href="#5.2.1"><b> 5.2.1 Character sets</b></a>
1503 1 Two sets of characters and their associated collating sequences shall be defined: the set in
1504 which source files are written (the source character set), and the set interpreted in the
1505 execution environment (the execution character set). Each set is further divided into a
1506 basic character set, whose contents are given by this subclause, and a set of zero or more
1507 locale-specific members (which are not members of the basic character set) called
1508 extended characters. The combined set is also called the extended character set. The
1509 values of the members of the execution character set are implementation-defined.
1510 2 In a character constant or string literal, members of the execution character set shall be
1511 represented by corresponding members of the source character set or by escape
1512 sequences consisting of the backslash \ followed by one or more characters. A byte with
1513 all bits set to 0, called the null character, shall exist in the basic execution character set; it
1514 is used to terminate a character string.
1515 3 Both the basic source and basic execution character sets shall have the following
1516 members: the 26 uppercase letters of the Latin alphabet
1517 A B C D E F G H I J K L M
1518 N O P Q R S T U V W X Y Z
1519 the 26 lowercase letters of the Latin alphabet
1520 a b c d e f g h i j k l m
1521 n o p q r s t u v w x y z
1522 the 10 decimal digits
1524 the following 29 graphic characters
1525 ! " # % & ' ( ) * + , - . / :
1526 ; < = > ? [ \ ] ^ _ { | } ~
1527 the space character, and control characters representing horizontal tab, vertical tab, and
1528 form feed. The representation of each member of the source and execution basic
1529 character sets shall fit in a byte. In both the source and execution basic character sets, the
1530 value of each character after 0 in the above list of decimal digits shall be one greater than
1531 the value of the previous. In source files, there shall be some way of indicating the end of
1532 each line of text; this International Standard treats such an end-of-line indicator as if it
1533 were a single new-line character. In the basic execution character set, there shall be
1534 control characters representing alert, backspace, carriage return, and new line. If any
1535 other characters are encountered in a source file (except in an identifier, a character
1536 constant, a string literal, a header name, a comment, or a preprocessing token that is never
1538 [<a name="#p22" href="p22">page 22</a>] (<a href="#Contents">Contents</a>)
1540 converted to a token), the behavior is undefined.
1541 4 A letter is an uppercase letter or a lowercase letter as defined above; in this International
1542 Standard the term does not include other characters that are letters in other alphabets.
1543 5 The universal character name construct provides a way to name other characters.
1544 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>),
1545 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>).
1546 <a name="5.2.1.1" href="#5.2.1.1"><b> 5.2.1.1 Trigraph sequences</b></a>
1547 1 Before any other processing takes place, each occurrence of one of the following
1548 sequences of three characters (called trigraph sequences17)) is replaced with the
1549 corresponding single character.
1551 ??( [ ??' ^ ??> }
1552 ??/ \ ??< { ??- ~
1553 No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
1554 above is not changed.
1556 ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)
1558 #define arraycheck(a, b) a[b] || b[a]
1560 3 EXAMPLE 2 The following source line
1562 becomes (after replacement of the trigraph sequence ??/)
1565 <a name="5.2.1.2" href="#5.2.1.2"><b> 5.2.1.2 Multibyte characters</b></a>
1566 1 The source character set may contain multibyte characters, used to represent members of
1567 the extended character set. The execution character set may also contain multibyte
1568 characters, which need not have the same encoding as for the source character set. For
1569 both character sets, the following shall hold:
1570 -- The basic character set shall be present and each character shall be encoded as a
1572 -- The presence, meaning, and representation of any additional members is locale-
1575 17) The trigraph sequences enable the input of characters that are not defined in the Invariant Code Set as
1576 described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
1578 [<a name="#p23" href="p23">page 23</a>] (<a href="#Contents">Contents</a>)
1580 -- A multibyte character set may have a state-dependent encoding, wherein each
1581 sequence of multibyte characters begins in an initial shift state and enters other
1582 locale-specific shift states when specific multibyte characters are encountered in the
1583 sequence. While in the initial shift state, all single-byte characters retain their usual
1584 interpretation and do not alter the shift state. The interpretation for subsequent bytes
1585 in the sequence is a function of the current shift state.
1586 -- A byte with all bits zero shall be interpreted as a null character independent of shift
1587 state. Such a byte shall not occur as part of any other multibyte character.
1588 2 For source files, the following shall hold:
1589 -- An identifier, comment, string literal, character constant, or header name shall begin
1590 and end in the initial shift state.
1591 -- An identifier, comment, string literal, character constant, or header name shall consist
1592 of a sequence of valid multibyte characters.
1593 <a name="5.2.2" href="#5.2.2"><b> 5.2.2 Character display semantics</b></a>
1594 1 The active position is that location on a display device where the next character output by
1595 the fputc function would appear. The intent of writing a printing character (as defined
1596 by the isprint function) to a display device is to display a graphic representation of
1597 that character at the active position and then advance the active position to the next
1598 position on the current line. The direction of writing is locale-specific. If the active
1599 position is at the final position of a line (if there is one), the behavior of the display device
1601 2 Alphabetic escape sequences representing nongraphic characters in the execution
1602 character set are intended to produce actions on display devices as follows:
1603 \a (alert) Produces an audible or visible alert without changing the active position.
1604 \b (backspace) Moves the active position to the previous position on the current line. If
1605 the active position is at the initial position of a line, the behavior of the display
1606 device is unspecified.
1607 \f ( form feed) Moves the active position to the initial position at the start of the next
1609 \n (new line) Moves the active position to the initial position of the next line.
1610 \r (carriage return) Moves the active position to the initial position of the current line.
1611 \t (horizontal tab) Moves the active position to the next horizontal tabulation position
1612 on the current line. If the active position is at or past the last defined horizontal
1613 tabulation position, the behavior of the display device is unspecified.
1614 \v (vertical tab) Moves the active position to the initial position of the next vertical
1615 tabulation position. If the active position is at or past the last defined vertical
1616 [<a name="#p24" href="p24">page 24</a>] (<a href="#Contents">Contents</a>)
1618 tabulation position, the behavior of the display device is unspecified.
1619 3 Each of these escape sequences shall produce a unique implementation-defined value
1620 which can be stored in a single char object. The external representations in a text file
1621 need not be identical to the internal representations, and are outside the scope of this
1622 International Standard.
1623 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>).
1624 <a name="5.2.3" href="#5.2.3"><b> 5.2.3 Signals and interrupts</b></a>
1625 1 Functions shall be implemented such that they may be interrupted at any time by a signal,
1626 or may be called by a signal handler, or both, with no alteration to earlier, but still active,
1627 invocations' control flow (after the interruption), function return values, or objects with
1628 automatic storage duration. All such objects shall be maintained outside the function
1629 image (the instructions that compose the executable representation of a function) on a
1630 per-invocation basis.
1631 <a name="5.2.4" href="#5.2.4"><b> 5.2.4 Environmental limits</b></a>
1632 1 Both the translation and execution environments constrain the implementation of
1633 language translators and libraries. The following summarizes the language-related
1634 environmental limits on a conforming implementation; the library-related limits are
1635 discussed in clause 7.
1636 <a name="5.2.4.1" href="#5.2.4.1"><b> 5.2.4.1 Translation limits</b></a>
1637 1 The implementation shall be able to translate and execute at least one program that
1638 contains at least one instance of every one of the following limits:18)
1639 -- 127 nesting levels of blocks
1640 -- 63 nesting levels of conditional inclusion
1641 -- 12 pointer, array, and function declarators (in any combinations) modifying an
1642 arithmetic, structure, union, or void type in a declaration
1643 -- 63 nesting levels of parenthesized declarators within a full declarator
1644 -- 63 nesting levels of parenthesized expressions within a full expression
1645 -- 63 significant initial characters in an internal identifier or a macro name (each
1646 universal character name or extended source character is considered a single
1648 -- 31 significant initial characters in an external identifier (each universal character name
1649 specifying a short identifier of 0000FFFF or less is considered 6 characters, each
1652 18) Implementations should avoid imposing fixed translation limits whenever possible.
1654 [<a name="#p25" href="p25">page 25</a>] (<a href="#Contents">Contents</a>)
1656 universal character name specifying a short identifier of 00010000 or more is
1657 considered 10 characters, and each extended source character is considered the same
1658 number of characters as the corresponding universal character name, if any)19)
1659 -- 4095 external identifiers in one translation unit
1660 -- 511 identifiers with block scope declared in one block
1661 -- 4095 macro identifiers simultaneously defined in one preprocessing translation unit
1662 -- 127 parameters in one function definition
1663 -- 127 arguments in one function call
1664 -- 127 parameters in one macro definition
1665 -- 127 arguments in one macro invocation
1666 -- 4095 characters in a logical source line
1667 -- 4095 characters in a string literal (after concatenation)
1668 -- 65535 bytes in an object (in a hosted environment only)
1669 -- 15 nesting levels for #included files
1670 -- 1023 case labels for a switch statement (excluding those for any nested switch
1672 -- 1023 members in a single structure or union
1673 -- 1023 enumeration constants in a single enumeration
1674 -- 63 levels of nested structure or union definitions in a single struct-declaration-list
1675 <a name="5.2.4.2" href="#5.2.4.2"><b> 5.2.4.2 Numerical limits</b></a>
1676 1 An implementation is required to document all the limits specified in this subclause,
1677 which are specified in the headers <a href="#7.10"><limits.h></a> and <a href="#7.7"><float.h></a>. Additional limits are
1678 specified in <a href="#7.20"><stdint.h></a>.
1679 Forward references: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>).
1680 <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>
1681 1 The values given below shall be replaced by constant expressions suitable for use in #if
1682 preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the
1683 following shall be replaced by expressions that have the same type as would an
1684 expression that is an object of the corresponding type converted according to the integer
1685 promotions. Their implementation-defined values shall be equal or greater in magnitude
1688 19) See ''future language directions'' (<a href="#6.11.3">6.11.3</a>).
1690 [<a name="#p26" href="p26">page 26</a>] (<a href="#Contents">Contents</a>)
1692 (absolute value) to those shown, with the same sign.
1693 -- number of bits for smallest object that is not a bit-field (byte)
1695 -- minimum value for an object of type signed char
1696 SCHAR_MIN -127 // -(27 - 1)
1697 -- maximum value for an object of type signed char
1698 SCHAR_MAX +127 // 27 - 1
1699 -- maximum value for an object of type unsigned char
1700 UCHAR_MAX 255 // 28 - 1
1701 -- minimum value for an object of type char
1703 -- maximum value for an object of type char
1705 -- maximum number of bytes in a multibyte character, for any supported locale
1707 -- minimum value for an object of type short int
1708 SHRT_MIN -32767 // -(215 - 1)
1709 -- maximum value for an object of type short int
1710 SHRT_MAX +32767 // 215 - 1
1711 -- maximum value for an object of type unsigned short int
1712 USHRT_MAX 65535 // 216 - 1
1713 -- minimum value for an object of type int
1714 INT_MIN -32767 // -(215 - 1)
1715 -- maximum value for an object of type int
1716 INT_MAX +32767 // 215 - 1
1717 -- maximum value for an object of type unsigned int
1718 UINT_MAX 65535 // 216 - 1
1719 -- minimum value for an object of type long int
1720 LONG_MIN -2147483647 // -(231 - 1)
1721 -- maximum value for an object of type long int
1722 LONG_MAX +2147483647 // 231 - 1
1723 -- maximum value for an object of type unsigned long int
1724 ULONG_MAX 4294967295 // 232 - 1
1727 [<a name="#p27" href="p27">page 27</a>] (<a href="#Contents">Contents</a>)
1729 -- minimum value for an object of type long long int
1730 LLONG_MIN -9223372036854775807 // -(263 - 1)
1731 -- maximum value for an object of type long long int
1732 LLONG_MAX +9223372036854775807 // 263 - 1
1733 -- maximum value for an object of type unsigned long long int
1734 ULLONG_MAX 18446744073709551615 // 264 - 1
1735 2 If the value of an object of type char is treated as a signed integer when used in an
1736 expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the
1737 value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of
1738 CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of
1739 UCHAR_MAX.20) The value UCHAR_MAX shall equal 2CHAR_BIT - 1.
1740 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>).
1741 <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>
1742 1 The characteristics of floating types are defined in terms of a model that describes a
1743 representation of floating-point numbers and values that provide information about an
1744 implementation's floating-point arithmetic.21) The following parameters are used to
1745 define the model for each floating-point type:
1747 b base or radix of exponent representation (an integer > 1)
1748 e exponent (an integer between a minimum emin and a maximum emax )
1749 p precision (the number of base-b digits in the significand)
1750 fk nonnegative integers less than b (the significand digits)
1751 2 A floating-point number (x) is defined by the following model:
1753 x = sb e (Sum) f k b-k ,
1755 emin <= e <= emax
1757 3 In addition to normalized floating-point numbers ( f 1 > 0 if x != 0), floating types may be
1758 able to contain other kinds of floating-point numbers, such as subnormal floating-point
1759 numbers (x != 0, e = emin , f 1 = 0) and unnormalized floating-point numbers (x != 0,
1760 e > emin , f 1 = 0), and values that are not floating-point numbers, such as infinities and
1761 NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates
1762 through almost every arithmetic operation without raising a floating-point exception; a
1763 signaling NaN generally raises a floating-point exception when occurring as an
1766 20) See <a href="#6.2.5">6.2.5</a>.
1767 21) The floating-point model is intended to clarify the description of each floating-point characteristic and
1768 does not require the floating-point arithmetic of the implementation to be identical.
1770 [<a name="#p28" href="p28">page 28</a>] (<a href="#Contents">Contents</a>)
1772 arithmetic operand.22)
1773 4 An implementation may give zero and non-numeric values (such as infinities and NaNs) a
1774 sign or may leave them unsigned. Wherever such values are unsigned, any requirement
1775 in this International Standard to retrieve the sign shall produce an unspecified sign, and
1776 any requirement to set the sign shall be ignored.
1777 5 The minimum range of representable values for a floating type is the most negative finite
1778 floating-point number representable in that type through the most positive finite floating-
1779 point number representable in that type. In addition, if negative infinity is representable
1780 in a type, the range of that type is extended to all negative real numbers; likewise, if
1781 positive infinity is representable in a type, the range of that type is extended to all positive
1783 6 The accuracy of the floating-point operations (+, -, *, /) and of the library functions in
1784 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results is implementation-
1785 defined, as is the accuracy of the conversion between floating-point internal
1786 representations and string representations performed by the library functions in
1787 <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
1788 accuracy is unknown.
1789 7 All integer values in the <a href="#7.7"><float.h></a> header, except FLT_ROUNDS, shall be constant
1790 expressions suitable for use in #if preprocessing directives; all floating values shall be
1791 constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
1792 and FLT_ROUNDS have separate names for all three floating-point types. The floating-
1793 point model representation is provided for all values except FLT_EVAL_METHOD and
1795 8 The rounding mode for floating-point addition is characterized by the implementation-
1796 defined value of FLT_ROUNDS:23)
1800 2 toward positive infinity
1801 3 toward negative infinity
1802 All other values for FLT_ROUNDS characterize implementation-defined rounding
1806 22) IEC 60559:1989 specifies quiet and signaling NaNs. For implementations that do not support
1807 IEC 60559:1989, the terms quiet NaN and signaling NaN are intended to apply to encodings with
1809 23) Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
1810 the function fesetround in <a href="#7.6"><fenv.h></a>.
1812 [<a name="#p29" href="p29">page 29</a>] (<a href="#Contents">Contents</a>)
1814 9 Except for assignment and cast (which remove all extra range and precision), the values
1815 yielded by operators with floating operands and values subject to the usual arithmetic
1816 conversions and of floating constants are evaluated to a format whose range and precision
1817 may be greater than required by the type. The use of evaluation formats is characterized
1818 by the implementation-defined value of FLT_EVAL_METHOD:24)
1820 0 evaluate all operations and constants just to the range and precision of the
1822 1 evaluate operations and constants of type float and double to the
1823 range and precision of the double type, evaluate long double
1824 operations and constants to the range and precision of the long double
1826 2 evaluate all operations and constants to the range and precision of the
1828 All other negative values for FLT_EVAL_METHOD characterize implementation-defined
1830 10 The presence or absence of subnormal numbers is characterized by the implementation-
1831 defined values of FLT_HAS_SUBNORM, DBL_HAS_SUBNORM, and
1833 -1 indeterminable25)
1834 0 absent26) (type does not support subnormal numbers)
1835 1 present (type does support subnormal numbers)
1836 11 The values given in the following list shall be replaced by constant expressions with
1837 implementation-defined values that are greater or equal in magnitude (absolute value) to
1838 those shown, with the same sign:
1839 -- radix of exponent representation, b
1845 24) The evaluation method determines evaluation formats of expressions involving all floating types, not
1846 just real types. For example, if FLT_EVAL_METHOD is 1, then the product of two float
1847 _Complex operands is represented in the double _Complex format, and its parts are evaluated to
1849 25) Characterization as indeterminable is intended if floating-point operations do not consistently interpret
1850 subnormal representations as zero, nor as nonzero.
1851 26) Characterization as absent is intended if no floating-point operations produce subnormal results from
1852 non-subnormal inputs, even if the type format includes representations of subnormal numbers.
1854 [<a name="#p30" href="p30">page 30</a>] (<a href="#Contents">Contents</a>)
1856 -- number of base-FLT_RADIX digits in the floating-point significand, p
1860 -- number of decimal digits, n, such that any floating-point number with p radix b digits
1861 can be rounded to a floating-point number with n decimal digits and back again
1862 without change to the value,
1863 { p log10 b if b is a power of 10
1865 { [^1 + p log10 b^] otherwise
1869 -- number of decimal digits, n, such that any floating-point number in the widest
1870 supported floating type with pmax radix b digits can be rounded to a floating-point
1871 number with n decimal digits and back again without change to the value,
1872 { pmax log10 b if b is a power of 10
1874 { [^1 + pmax log10 b^] otherwise
1876 -- number of decimal digits, q, such that any floating-point number with q decimal digits
1877 can be rounded into a floating-point number with p radix b digits and back again
1878 without change to the q decimal digits,
1879 { p log10 b if b is a power of 10
1881 { [_( p - 1) log10 b_] otherwise
1885 -- minimum negative integer such that FLT_RADIX raised to one less than that power is
1886 a normalized floating-point number, emin
1894 [<a name="#p31" href="p31">page 31</a>] (<a href="#Contents">Contents</a>)
1896 -- minimum negative integer such that 10 raised to that power is in the range of
1897 normalized floating-point numbers, [^log10 b emin -1 ^]
1902 -- maximum integer such that FLT_RADIX raised to one less than that power is a
1903 representable finite floating-point number, emax
1907 -- maximum integer such that 10 raised to that power is in the range of representable
1908 finite floating-point numbers, [_log10 ((1 - b- p )b emax )_]
1912 12 The values given in the following list shall be replaced by constant expressions with
1913 implementation-defined values that are greater than or equal to those shown:
1914 -- maximum representable finite floating-point number, (1 - b- p )b emax
1918 13 The values given in the following list shall be replaced by constant expressions with
1919 implementation-defined (positive) values that are less than or equal to those shown:
1920 -- the difference between 1 and the least value greater than 1 that is representable in the
1921 given floating point type, b1- p
1925 -- minimum normalized positive floating-point number, b emin -1
1933 [<a name="#p32" href="p32">page 32</a>] (<a href="#Contents">Contents</a>)
1935 -- minimum positive floating-point number27)
1939 Recommended practice
1940 14 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
1941 should be the identity function.
1942 15 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
1943 requirements of this International Standard, and the appropriate values in a <a href="#7.7"><float.h></a> header for type
1946 x = s16e (Sum) f k 16-k ,
1948 -31 <= e <= +32
1952 FLT_EPSILON 9.53674316E-07F
1956 FLT_MIN 2.93873588E-39F
1959 FLT_MAX 3.40282347E+38F
1962 16 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
1963 single-precision and double-precision numbers in IEC 60559,28) and the appropriate values in a
1964 <a href="#7.7"><float.h></a> header for types float and double:
1966 x f = s2e (Sum) f k 2-k ,
1968 -125 <= e <= +128
1971 x d = s2e (Sum) f k 2-k ,
1973 -1021 <= e <= +1024
1978 FLT_EPSILON 1.19209290E-07F // decimal constant
1979 FLT_EPSILON 0X1P-23F // hex constant
1983 27) If the presence or absence of subnormal numbers is indeterminable, then the value is intended to be a
1984 positive number no greater than the minimum normalized positive number for the type.
1985 28) The floating-point model in that standard sums powers of b from zero, so the values of the exponent
1986 limits are one less than shown here.
1988 [<a name="#p33" href="p33">page 33</a>] (<a href="#Contents">Contents</a>)
1992 FLT_MIN 1.17549435E-38F // decimal constant
1993 FLT_MIN 0X1P-126F // hex constant
1994 FLT_TRUE_MIN 1.40129846E-45F // decimal constant
1995 FLT_TRUE_MIN 0X1P-149F // hex constant
1999 FLT_MAX 3.40282347E+38F // decimal constant
2000 FLT_MAX 0X1.fffffeP127F // hex constant
2003 DBL_EPSILON 2.2204460492503131E-16 // decimal constant
2004 DBL_EPSILON 0X1P-52 // hex constant
2008 DBL_MIN 2.2250738585072014E-308 // decimal constant
2009 DBL_MIN 0X1P-1022 // hex constant
2010 DBL_TRUE_MIN 4.9406564584124654E-324 // decimal constant
2011 DBL_TRUE_MIN 0X1P-1074 // hex constant
2015 DBL_MAX 1.7976931348623157E+308 // decimal constant
2016 DBL_MAX 0X1.fffffffffffffP1023 // hex constant
2018 If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
2019 example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
2020 precision), then DECIMAL_DIG would be 21.
2022 Forward references: conditional inclusion (<a href="#6.10.1">6.10.1</a>), complex arithmetic
2023 <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>
2024 (<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>
2025 (<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>).
2030 [<a name="#p34" href="p34">page 34</a>] (<a href="#Contents">Contents</a>)
2033 <a name="6" href="#6"><b> 6. Language</b></a>
2034 <a name="6.1" href="#6.1"><b> 6.1 Notation</b></a>
2035 1 In the syntax notation used in this clause, syntactic categories (nonterminals) are
2036 indicated by italic type, and literal words and character set members (terminals) by bold
2037 type. A colon (:) following a nonterminal introduces its definition. Alternative
2038 definitions are listed on separate lines, except when prefaced by the words ''one of''. An
2039 optional symbol is indicated by the subscript ''opt'', so that
2041 indicates an optional expression enclosed in braces.
2042 2 When syntactic categories are referred to in the main text, they are not italicized and
2043 words are separated by spaces instead of hyphens.
2044 3 A summary of the language syntax is given in <a href="#A">annex A</a>.
2045 <a name="6.2" href="#6.2"><b> 6.2 Concepts</b></a>
2046 <a name="6.2.1" href="#6.2.1"><b> 6.2.1 Scopes of identifiers</b></a>
2047 1 An identifier can denote an object; a function; a tag or a member of a structure, union, or
2048 enumeration; a typedef name; a label name; a macro name; or a macro parameter. The
2049 same identifier can denote different entities at different points in the program. A member
2050 of an enumeration is called an enumeration constant. Macro names and macro
2051 parameters are not considered further here, because prior to the semantic phase of
2052 program translation any occurrences of macro names in the source file are replaced by the
2053 preprocessing token sequences that constitute their macro definitions.
2054 2 For each different entity that an identifier designates, the identifier is visible (i.e., can be
2055 used) only within a region of program text called its scope. Different entities designated
2056 by the same identifier either have different scopes, or are in different name spaces. There
2057 are four kinds of scopes: function, file, block, and function prototype. (A function
2058 prototype is a declaration of a function that declares the types of its parameters.)
2059 3 A label name is the only kind of identifier that has function scope. It can be used (in a
2060 goto statement) anywhere in the function in which it appears, and is declared implicitly
2061 by its syntactic appearance (followed by a : and a statement).
2062 4 Every other identifier has scope determined by the placement of its declaration (in a
2063 declarator or type specifier). If the declarator or type specifier that declares the identifier
2064 appears outside of any block or list of parameters, the identifier has file scope, which
2065 terminates at the end of the translation unit. If the declarator or type specifier that
2066 declares the identifier appears inside a block or within the list of parameter declarations in
2067 a function definition, the identifier has block scope, which terminates at the end of the
2068 associated block. If the declarator or type specifier that declares the identifier appears
2070 [<a name="#p35" href="p35">page 35</a>] (<a href="#Contents">Contents</a>)
2072 within the list of parameter declarations in a function prototype (not part of a function
2073 definition), the identifier has function prototype scope, which terminates at the end of the
2074 function declarator. If an identifier designates two different entities in the same name
2075 space, the scopes might overlap. If so, the scope of one entity (the inner scope) will end
2076 strictly before the scope of the other entity (the outer scope). Within the inner scope, the
2077 identifier designates the entity declared in the inner scope; the entity declared in the outer
2078 scope is hidden (and not visible) within the inner scope.
2079 5 Unless explicitly stated otherwise, where this International Standard uses the term
2080 ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the
2081 entity in the relevant name space whose declaration is visible at the point the identifier
2083 6 Two identifiers have the same scope if and only if their scopes terminate at the same
2085 7 Structure, union, and enumeration tags have scope that begins just after the appearance of
2086 the tag in a type specifier that declares the tag. Each enumeration constant has scope that
2087 begins just after the appearance of its defining enumerator in an enumerator list. Any
2088 other identifier has scope that begins just after the completion of its declarator.
2089 8 As a special case, a type name (which is not a declaration of an identifier) is considered to
2090 have a scope that begins just after the place within the type name where the omitted
2091 identifier would appear were it not omitted.
2092 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
2093 (<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>),
2094 source file inclusion (<a href="#6.10.2">6.10.2</a>), statements (<a href="#6.8">6.8</a>).
2095 <a name="6.2.2" href="#6.2.2"><b> 6.2.2 Linkages of identifiers</b></a>
2096 1 An identifier declared in different scopes or in the same scope more than once can be
2097 made to refer to the same object or function by a process called linkage.29) There are
2098 three kinds of linkage: external, internal, and none.
2099 2 In the set of translation units and libraries that constitutes an entire program, each
2100 declaration of a particular identifier with external linkage denotes the same object or
2101 function. Within one translation unit, each declaration of an identifier with internal
2102 linkage denotes the same object or function. Each declaration of an identifier with no
2103 linkage denotes a unique entity.
2104 3 If the declaration of a file scope identifier for an object or a function contains the storage-
2105 class specifier static, the identifier has internal linkage.30)
2109 29) There is no linkage between different identifiers.
2111 [<a name="#p36" href="p36">page 36</a>] (<a href="#Contents">Contents</a>)
2113 4 For an identifier declared with the storage-class specifier extern in a scope in which a
2114 prior declaration of that identifier is visible,31) if the prior declaration specifies internal or
2115 external linkage, the linkage of the identifier at the later declaration is the same as the
2116 linkage specified at the prior declaration. If no prior declaration is visible, or if the prior
2117 declaration specifies no linkage, then the identifier has external linkage.
2118 5 If the declaration of an identifier for a function has no storage-class specifier, its linkage
2119 is determined exactly as if it were declared with the storage-class specifier extern. If
2120 the declaration of an identifier for an object has file scope and no storage-class specifier,
2121 its linkage is external.
2122 6 The following identifiers have no linkage: an identifier declared to be anything other than
2123 an object or a function; an identifier declared to be a function parameter; a block scope
2124 identifier for an object declared without the storage-class specifier extern.
2125 7 If, within a translation unit, the same identifier appears with both internal and external
2126 linkage, the behavior is undefined.
2127 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>),
2128 statements (<a href="#6.8">6.8</a>).
2129 <a name="6.2.3" href="#6.2.3"><b> 6.2.3 Name spaces of identifiers</b></a>
2130 1 If more than one declaration of a particular identifier is visible at any point in a
2131 translation unit, the syntactic context disambiguates uses that refer to different entities.
2132 Thus, there are separate name spaces for various categories of identifiers, as follows:
2133 -- label names (disambiguated by the syntax of the label declaration and use);
2134 -- the tags of structures, unions, and enumerations (disambiguated by following any32)
2135 of the keywords struct, union, or enum);
2136 -- the members of structures or unions; each structure or union has a separate name
2137 space for its members (disambiguated by the type of the expression used to access the
2138 member via the . or -> operator);
2139 -- all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
2140 enumeration constants).
2141 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>),
2142 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
2143 (<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>).
2145 30) A function declaration can contain the storage-class specifier static only if it is at file scope; see
2146 <a name="6.7.1" href="#6.7.1"><b> 6.7.1.</b></a>
2147 31) As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
2148 32) There is only one name space for tags even though three are possible.
2150 [<a name="#p37" href="p37">page 37</a>] (<a href="#Contents">Contents</a>)
2152 <a name="6.2.4" href="#6.2.4"><b> 6.2.4 Storage durations of objects</b></a>
2153 1 An object has a storage duration that determines its lifetime. There are four storage
2154 durations: static, thread, automatic, and allocated. Allocated storage is described in
2155 <a name="7.22.3" href="#7.22.3"><b> 7.22.3.</b></a>
2156 2 The lifetime of an object is the portion of program execution during which storage is
2157 guaranteed to be reserved for it. An object exists, has a constant address,33) and retains
2158 its last-stored value throughout its lifetime.34) If an object is referred to outside of its
2159 lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
2160 the object it points to (or just past) reaches the end of its lifetime.
2161 3 An object whose identifier is declared without the storage-class specifier
2162 _Thread_local, and either with external or internal linkage or with the storage-class
2163 specifier static, has static storage duration. Its lifetime is the entire execution of the
2164 program and its stored value is initialized only once, prior to program startup.
2165 4 An object whose identifier is declared with the storage-class specifier _Thread_local
2166 has thread storage duration. Its lifetime is the entire execution of the thread for which it
2167 is created, and its stored value is initialized when the thread is started. There is a distinct
2168 object per thread, and use of the declared name in an expression refers to the object
2169 associated with the thread evaluating the expression. The result of attempting to
2170 indirectly access an object with thread storage duration from a thread other than the one
2171 with which the object is associated is implementation-defined.
2172 5 An object whose identifier is declared with no linkage and without the storage-class
2173 specifier static has automatic storage duration, as do some compound literals. The
2174 result of attempting to indirectly access an object with automatic storage duration from a
2175 thread other than the one with which the object is associated is implementation-defined.
2176 6 For such an object that does not have a variable length array type, its lifetime extends
2177 from entry into the block with which it is associated until execution of that block ends in
2178 any way. (Entering an enclosed block or calling a function suspends, but does not end,
2179 execution of the current block.) If the block is entered recursively, a new instance of the
2180 object is created each time. The initial value of the object is indeterminate. If an
2181 initialization is specified for the object, it is performed each time the declaration or
2182 compound literal is reached in the execution of the block; otherwise, the value becomes
2183 indeterminate each time the declaration is reached.
2187 33) The term ''constant address'' means that two pointers to the object constructed at possibly different
2188 times will compare equal. The address may be different during two different executions of the same
2190 34) In the case of a volatile object, the last store need not be explicit in the program.
2192 [<a name="#p38" href="p38">page 38</a>] (<a href="#Contents">Contents</a>)
2194 7 For such an object that does have a variable length array type, its lifetime extends from
2195 the declaration of the object until execution of the program leaves the scope of the
2196 declaration.35) If the scope is entered recursively, a new instance of the object is created
2197 each time. The initial value of the object is indeterminate.
2198 8 A non-lvalue expression with structure or union type, where the structure or union
2199 contains a member with array type (including, recursively, members of all contained
2200 structures and unions) refers to an object with automatic storage duration and temporary
2201 lifetime.36) Its lifetime begins when the expression is evaluated and its initial value is the
2202 value of the expression. Its lifetime ends when the evaluation of the containing full
2203 expression or full declarator ends. Any attempt to modify an object with temporary
2204 lifetime results in undefined behavior.
2205 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
2206 (<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>).
2207 <a name="6.2.5" href="#6.2.5"><b> 6.2.5 Types</b></a>
2208 1 The meaning of a value stored in an object or returned by a function is determined by the
2209 type of the expression used to access it. (An identifier declared to be an object is the
2210 simplest such expression; the type is specified in the declaration of the identifier.) Types
2211 are partitioned into object types (types that describe objects) and function types (types
2212 that describe functions). At various points within a translation unit an object type may be
2213 incomplete (lacking sufficient information to determine the size of objects of that type) or
2214 complete (having sufficient information).37)
2215 2 An object declared as type _Bool is large enough to store the values 0 and 1.
2216 3 An object declared as type char is large enough to store any member of the basic
2217 execution character set. If a member of the basic execution character set is stored in a
2218 char object, its value is guaranteed to be nonnegative. If any other character is stored in
2219 a char object, the resulting value is implementation-defined but shall be within the range
2220 of values that can be represented in that type.
2221 4 There are five standard signed integer types, designated as signed char, short
2222 int, int, long int, and long long int. (These and other types may be
2223 designated in several additional ways, as described in <a href="#6.7.2">6.7.2</a>.) There may also be
2224 implementation-defined extended signed integer types.38) The standard and extended
2225 signed integer types are collectively called signed integer types.39)
2227 35) Leaving the innermost block containing the declaration, or jumping to a point in that block or an
2228 embedded block prior to the declaration, leaves the scope of the declaration.
2229 36) The address of such an object is taken implicitly when an array member is accessed.
2230 37) A type may be incomplete or complete throughout an entire translation unit, or it may change states at
2231 different points within a translation unit.
2233 [<a name="#p39" href="p39">page 39</a>] (<a href="#Contents">Contents</a>)
2235 5 An object declared as type signed char occupies the same amount of storage as a
2236 ''plain'' char object. A ''plain'' int object has the natural size suggested by the
2237 architecture of the execution environment (large enough to contain any value in the range
2238 INT_MIN to INT_MAX as defined in the header <a href="#7.10"><limits.h></a>).
2239 6 For each of the signed integer types, there is a corresponding (but different) unsigned
2240 integer type (designated with the keyword unsigned) that uses the same amount of
2241 storage (including sign information) and has the same alignment requirements. The type
2242 _Bool and the unsigned integer types that correspond to the standard signed integer
2243 types are the standard unsigned integer types. The unsigned integer types that
2244 correspond to the extended signed integer types are the extended unsigned integer types.
2245 The standard and extended unsigned integer types are collectively called unsigned integer
2247 7 The standard signed integer types and standard unsigned integer types are collectively
2248 called the standard integer types, the extended signed integer types and extended
2249 unsigned integer types are collectively called the extended integer types.
2250 8 For any two integer types with the same signedness and different integer conversion rank
2251 (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
2252 subrange of the values of the other type.
2253 9 The range of nonnegative values of a signed integer type is a subrange of the
2254 corresponding unsigned integer type, and the representation of the same value in each
2255 type is the same.41) A computation involving unsigned operands can never overflow,
2256 because a result that cannot be represented by the resulting unsigned integer type is
2257 reduced modulo the number that is one greater than the largest value that can be
2258 represented by the resulting type.
2259 10 There are three real floating types, designated as float, double, and long
2260 double.42) The set of values of the type float is a subset of the set of values of the
2261 type double; the set of values of the type double is a subset of the set of values of the
2265 38) Implementation-defined keywords shall have the form of an identifier reserved for any use as
2266 described in <a href="#7.1.3">7.1.3</a>.
2267 39) Therefore, any statement in this Standard about signed integer types also applies to the extended
2268 signed integer types.
2269 40) Therefore, any statement in this Standard about unsigned integer types also applies to the extended
2270 unsigned integer types.
2271 41) The same representation and alignment requirements are meant to imply interchangeability as
2272 arguments to functions, return values from functions, and members of unions.
2273 42) See ''future language directions'' (<a href="#6.11.1">6.11.1</a>).
2275 [<a name="#p40" href="p40">page 40</a>] (<a href="#Contents">Contents</a>)
2277 11 There are three complex types, designated as float _Complex, double
2278 _Complex, and long double _Complex.43) (Complex types are a conditional
2279 feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.) The real floating and
2280 complex types are collectively called the floating types.
2281 12 For each floating type there is a corresponding real type, which is always a real floating
2282 type. For real floating types, it is the same type. For complex types, it is the type given
2283 by deleting the keyword _Complex from the type name.
2284 13 Each complex type has the same representation and alignment requirements as an array
2285 type containing exactly two elements of the corresponding real type; the first element is
2286 equal to the real part, and the second element to the imaginary part, of the complex
2288 14 The type char, the signed and unsigned integer types, and the floating types are
2289 collectively called the basic types. The basic types are complete object types. Even if the
2290 implementation defines two or more basic types to have the same representation, they are
2291 nevertheless different types.44)
2292 15 The three types char, signed char, and unsigned char are collectively called
2293 the character types. The implementation shall define char to have the same range,
2294 representation, and behavior as either signed char or unsigned char.45)
2295 16 An enumeration comprises a set of named integer constant values. Each distinct
2296 enumeration constitutes a different enumerated type.
2297 17 The type char, the signed and unsigned integer types, and the enumerated types are
2298 collectively called integer types. The integer and real floating types are collectively called
2300 18 Integer and floating types are collectively called arithmetic types. Each arithmetic type
2301 belongs to one type domain: the real type domain comprises the real types, the complex
2302 type domain comprises the complex types.
2303 19 The void type comprises an empty set of values; it is an incomplete object type that
2304 cannot be completed.
2308 43) A specification for imaginary types is in informative <a href="#G">annex G</a>.
2309 44) An implementation may define new keywords that provide alternative ways to designate a basic (or
2310 any other) type; this does not violate the requirement that all basic types be different.
2311 Implementation-defined keywords shall have the form of an identifier reserved for any use as
2312 described in <a href="#7.1.3">7.1.3</a>.
2313 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
2314 used to distinguish the two options. Irrespective of the choice made, char is a separate type from the
2315 other two and is not compatible with either.
2317 [<a name="#p41" href="p41">page 41</a>] (<a href="#Contents">Contents</a>)
2319 20 Any number of derived types can be constructed from the object and function types, as
2321 -- An array type describes a contiguously allocated nonempty set of objects with a
2322 particular member object type, called the element type. The element type shall be
2323 complete whenever the array type is specified. Array types are characterized by their
2324 element type and by the number of elements in the array. An array type is said to be
2325 derived from its element type, and if its element type is T , the array type is sometimes
2326 called ''array of T ''. The construction of an array type from an element type is called
2327 ''array type derivation''.
2328 -- A structure type describes a sequentially allocated nonempty set of member objects
2329 (and, in certain circumstances, an incomplete array), each of which has an optionally
2330 specified name and possibly distinct type.
2331 -- A union type describes an overlapping nonempty set of member objects, each of
2332 which has an optionally specified name and possibly distinct type.
2333 -- A function type describes a function with specified return type. A function type is
2334 characterized by its return type and the number and types of its parameters. A
2335 function type is said to be derived from its return type, and if its return type is T , the
2336 function type is sometimes called ''function returning T ''. The construction of a
2337 function type from a return type is called ''function type derivation''.
2338 -- A pointer type may be derived from a function type or an object type, called the
2339 referenced type. A pointer type describes an object whose value provides a reference
2340 to an entity of the referenced type. A pointer type derived from the referenced type T
2341 is sometimes called ''pointer to T ''. The construction of a pointer type from a
2342 referenced type is called ''pointer type derivation''. A pointer type is a complete
2344 These methods of constructing derived types can be applied recursively.
2345 21 Arithmetic types and pointer types are collectively called scalar types. Array and
2346 structure types are collectively called aggregate types.46)
2347 22 An array type of unknown size is an incomplete type. It is completed, for an identifier of
2348 that type, by specifying the size in a later declaration (with internal or external linkage).
2349 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
2350 type. It is completed, for all declarations of that type, by declaring the same structure or
2351 union tag with its defining content later in the same scope.
2356 46) Note that aggregate type does not include union type because an object with union type can only
2357 contain one member at a time.
2359 [<a name="#p42" href="p42">page 42</a>] (<a href="#Contents">Contents</a>)
2361 23 A type has known constant size if the type is not incomplete and is not a variable length
2363 24 Array, function, and pointer types are collectively called derived declarator types. A
2364 declarator type derivation from a type T is the construction of a derived declarator type
2365 from T by the application of an array-type, a function-type, or a pointer-type derivation to
2367 25 A type is characterized by its type category, which is either the outermost derivation of a
2368 derived type (as noted above in the construction of derived types), or the type itself if the
2369 type consists of no derived types.
2370 26 Any type so far mentioned is an unqualified type. Each unqualified type has several
2371 qualified versions of its type,47) corresponding to the combinations of one, two, or all
2372 three of the const, volatile, and restrict qualifiers. The qualified or unqualified
2373 versions of a type are distinct types that belong to the same type category and have the
2374 same representation and alignment requirements.48) A derived type is not qualified by the
2375 qualifiers (if any) of the type from which it is derived.
2376 27 Further, there is the _Atomic qualifier, which may combine with volatile and
2377 restrict. The size, representation, and alignment of an _Atomic-qualified type need
2378 not be the same as those of the corresponding unqualified type. (Atomic types are a
2379 conditional feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.)
2380 28 A pointer to void shall have the same representation and alignment requirements as a
2381 pointer to a character type.48) Similarly, pointers to qualified or unqualified versions of
2382 compatible types shall have the same representation and alignment requirements. All
2383 pointers to structure types shall have the same representation and alignment requirements
2384 as each other. All pointers to union types shall have the same representation and
2385 alignment requirements as each other. Pointers to other types need not have the same
2386 representation or alignment requirements.
2387 29 EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is
2388 pointer, not a floating type. The const-qualified version of this type is designated as ''float * const''
2389 whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const-
2390 qualified float'' and is a pointer to a qualified type.
2392 30 EXAMPLE 2 The type designated as ''struct tag (*[5])(float)'' has type ''array of pointer to
2393 function returning struct tag''. The array has length five and the function has a single parameter of type
2394 float. Its type category is array.
2396 Forward references: compatible type and composite type (<a href="#6.2.7">6.2.7</a>), declarations (<a href="#6.7">6.7</a>).
2400 47) See <a href="#6.7.3">6.7.3</a> regarding qualified array and function types.
2401 48) The same representation and alignment requirements are meant to imply interchangeability as
2402 arguments to functions, return values from functions, and members of unions.
2404 [<a name="#p43" href="p43">page 43</a>] (<a href="#Contents">Contents</a>)
2406 <a name="6.2.6" href="#6.2.6"><b> 6.2.6 Representations of types</b></a>
2407 <a name="6.2.6.1" href="#6.2.6.1"><b> 6.2.6.1 General</b></a>
2408 1 The representations of all types are unspecified except as stated in this subclause.
2409 2 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes,
2410 the number, order, and encoding of which are either explicitly specified or
2411 implementation-defined.
2412 3 Values stored in unsigned bit-fields and objects of type unsigned char shall be
2413 represented using a pure binary notation.49)
2414 4 Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT
2415 bits, where n is the size of an object of that type, in bytes. The value may be copied into
2416 an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is
2417 called the object representation of the value. Values stored in bit-fields consist of m bits,
2418 where m is the size specified for the bit-field. The object representation is the set of m
2419 bits the bit-field comprises in the addressable storage unit holding it. Two values (other
2420 than NaNs) with the same object representation compare equal, but values that compare
2421 equal may have different object representations.
2422 5 Certain object representations need not represent a value of the object type. If the stored
2423 value of an object has such a representation and is read by an lvalue expression that does
2424 not have character type, the behavior is undefined. If such a representation is produced
2425 by a side effect that modifies all or any part of the object by an lvalue expression that
2426 does not have character type, the behavior is undefined.50) Such a representation is called
2427 a trap representation.
2428 6 When a value is stored in an object of structure or union type, including in a member
2429 object, the bytes of the object representation that correspond to any padding bytes take
2430 unspecified values.51) The value of a structure or union object is never a trap
2431 representation, even though the value of a member of the structure or union object may be
2432 a trap representation.
2433 7 When a value is stored in a member of an object of union type, the bytes of the object
2434 representation that do not correspond to that member but do correspond to other members
2436 49) A positional representation for integers that uses the binary digits 0 and 1, in which the values
2437 represented by successive bits are additive, begin with 1, and are multiplied by successive integral
2438 powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
2439 Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
2440 type unsigned char range from 0 to 2
2443 50) Thus, an automatic variable can be initialized to a trap representation without causing undefined
2444 behavior, but the value of the variable cannot be used until a proper value is stored in it.
2445 51) Thus, for example, structure assignment need not copy any padding bits.
2447 [<a name="#p44" href="p44">page 44</a>] (<a href="#Contents">Contents</a>)
2449 take unspecified values.
2450 8 Where an operator is applied to a value that has more than one object representation,
2451 which object representation is used shall not affect the value of the result.52) Where a
2452 value is stored in an object using a type that has more than one object representation for
2453 that value, it is unspecified which representation is used, but a trap representation shall
2455 9 Loads and stores of objects with _Atomic-qualified types are done with
2456 memory_order_seq_cst semantics.
2457 Forward references: declarations (<a href="#6.7">6.7</a>), expressions (<a href="#6.5">6.5</a>), lvalues, arrays, and function
2458 designators (<a href="#6.3.2.1">6.3.2.1</a>), order and consistency (<a href="#7.17.3">7.17.3</a>).
2459 <a name="6.2.6.2" href="#6.2.6.2"><b> 6.2.6.2 Integer types</b></a>
2460 1 For unsigned integer types other than unsigned char, the bits of the object
2461 representation shall be divided into two groups: value bits and padding bits (there need
2462 not be any of the latter). If there are N value bits, each bit shall represent a different
2463 power of 2 between 1 and 2 N -1 , so that objects of that type shall be capable of
2464 representing values from 0 to 2 N - 1 using a pure binary representation; this shall be
2465 known as the value representation. The values of any padding bits are unspecified.53)
2466 2 For signed integer types, the bits of the object representation shall be divided into three
2467 groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
2468 signed char shall not have any padding bits. There shall be exactly one sign bit.
2469 Each bit that is a value bit shall have the same value as the same bit in the object
2470 representation of the corresponding unsigned type (if there are M value bits in the signed
2471 type and N in the unsigned type, then M <= N ). If the sign bit is zero, it shall not affect
2472 the resulting value. If the sign bit is one, the value shall be modified in one of the
2474 -- the corresponding value with sign bit 0 is negated (sign and magnitude);
2475 -- the sign bit has the value -(2 M ) (two's complement);
2478 52) It is possible for objects x and y with the same effective type T to have the same value when they are
2479 accessed as objects of type T, but to have different values in other contexts. In particular, if == is
2480 defined for type T, then x == y does not imply that memcmp(&x, &y, sizeof (T)) == 0.
2481 Furthermore, x == y does not necessarily imply that x and y have the same value; other operations
2482 on values of type T may distinguish between them.
2483 53) Some combinations of padding bits might generate trap representations, for example, if one padding
2484 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2485 representation other than as part of an exceptional condition such as an overflow, and this cannot occur
2486 with unsigned types. All other combinations of padding bits are alternative object representations of
2487 the value specified by the value bits.
2489 [<a name="#p45" href="p45">page 45</a>] (<a href="#Contents">Contents</a>)
2491 -- the sign bit has the value -(2 M - 1) (ones' complement).
2492 Which of these applies is implementation-defined, as is whether the value with sign bit 1
2493 and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones'
2494 complement), is a trap representation or a normal value. In the case of sign and
2495 magnitude and ones' complement, if this representation is a normal value it is called a
2497 3 If the implementation supports negative zeros, they shall be generated only by:
2498 -- the &, |, ^, ~, <<, and >> operators with operands that produce such a value;
2499 -- the +, -, *, /, and % operators where one operand is a negative zero and the result is
2501 -- compound assignment operators based on the above cases.
2502 It is unspecified whether these cases actually generate a negative zero or a normal zero,
2503 and whether a negative zero becomes a normal zero when stored in an object.
2504 4 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
2505 and >> operators with operands that would produce such a value is undefined.
2506 5 The values of any padding bits are unspecified.54) A valid (non-trap) object representation
2507 of a signed integer type where the sign bit is zero is a valid object representation of the
2508 corresponding unsigned type, and shall represent the same value. For any integer type,
2509 the object representation where all the bits are zero shall be a representation of the value
2511 6 The precision of an integer type is the number of bits it uses to represent values,
2512 excluding any sign and padding bits. The width of an integer type is the same but
2513 including any sign bit; thus for unsigned integer types the two values are the same, while
2514 for signed integer types the width is one greater than the precision.
2519 54) Some combinations of padding bits might generate trap representations, for example, if one padding
2520 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2521 representation other than as part of an exceptional condition such as an overflow. All other
2522 combinations of padding bits are alternative object representations of the value specified by the value
2525 [<a name="#p46" href="p46">page 46</a>] (<a href="#Contents">Contents</a>)
2527 <a name="6.2.7" href="#6.2.7"><b> 6.2.7 Compatible type and composite type</b></a>
2528 1 Two types have compatible type if their types are the same. Additional rules for
2529 determining whether two types are compatible are described in <a href="#6.7.2">6.7.2</a> for type specifiers,
2530 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,
2531 union, or enumerated types declared in separate translation units are compatible if their
2532 tags and members satisfy the following requirements: If one is declared with a tag, the
2533 other shall be declared with the same tag. If both are completed anywhere within their
2534 respective translation units, then the following additional requirements apply: there shall
2535 be a one-to-one correspondence between their members such that each pair of
2536 corresponding members are declared with compatible types, and such that if one member
2537 of a corresponding pair is declared with a name, the other member is declared with the
2538 same name. For two structures, corresponding members shall be declared in the same
2539 order. For two structures or unions, corresponding bit-fields shall have the same widths.
2540 For two enumerations, corresponding members shall have the same values.
2541 2 All declarations that refer to the same object or function shall have compatible type;
2542 otherwise, the behavior is undefined.
2543 3 A composite type can be constructed from two types that are compatible; it is a type that
2544 is compatible with both of the two types and satisfies the following conditions:
2545 -- If both types are array types, the following rules are applied:
2546 o If one type is an array of known constant size, the composite type is an array of
2548 o Otherwise, if one type is a variable length array whose size is specified by an
2549 expression that is not evaluated, the behavior is undefined.
2550 o Otherwise, if one type is a variable length array whose size is specified, the
2551 composite type is a variable length array of that size.
2552 o Otherwise, if one type is a variable length array of unspecified size, the composite
2553 type is a variable length array of unspecified size.
2554 o Otherwise, both types are arrays of unknown size and the composite type is an
2555 array of unknown size.
2556 The element type of the composite type is the composite type of the two element
2558 -- If only one type is a function type with a parameter type list (a function prototype),
2559 the composite type is a function prototype with the parameter type list.
2563 55) Two types need not be identical to be compatible.
2565 [<a name="#p47" href="p47">page 47</a>] (<a href="#Contents">Contents</a>)
2567 -- If both types are function types with parameter type lists, the type of each parameter
2568 in the composite parameter type list is the composite type of the corresponding
2570 These rules apply recursively to the types from which the two types are derived.
2571 4 For an identifier with internal or external linkage declared in a scope in which a prior
2572 declaration of that identifier is visible,56) if the prior declaration specifies internal or
2573 external linkage, the type of the identifier at the later declaration becomes the composite
2575 Forward references: array declarators (<a href="#6.7.6.2">6.7.6.2</a>).
2576 5 EXAMPLE Given the following two file scope declarations:
2577 int f(int (*)(), double (*)[3]);
2578 int f(int (*)(char *), double (*)[]);
2579 The resulting composite type for the function is:
2580 int f(int (*)(char *), double (*)[3]);
2582 <a name="6.2.8" href="#6.2.8"><b> 6.2.8 Alignment of objects</b></a>
2583 1 Complete object types have alignment requirements which place restrictions on the
2584 addresses at which objects of that type may be allocated. An alignment is an
2585 implementation-defined integer value representing the number of bytes between
2586 successive addresses at which a given object can be allocated. An object type imposes an
2587 alignment requirement on every object of that type: stricter alignment can be requested
2588 using the _Alignas keyword.
2589 2 A fundamental alignment is represented by an alignment less than or equal to the greatest
2590 alignment supported by the implementation in all contexts, which is equal to
2591 alignof(max_align_t).
2592 3 An extended alignment is represented by an alignment greater than
2593 alignof(max_align_t). It is implementation-defined whether any extended
2594 alignments are supported and the contexts in which they are supported. A type having an
2595 extended alignment requirement is an over-aligned type.57)
2596 4 Alignments are represented as values of the type size_t. Valid alignments include only
2597 those values returned by an alignof expression for fundamental types, plus an
2598 additional implementation-defined set of values, which may be empty. Every valid
2599 alignment value shall be an integral power of two.
2602 56) As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
2603 57) Every over-aligned type is, or contains, a structure or union type with a member to which an extended
2604 alignment has been applied.
2606 [<a name="#p48" href="p48">page 48</a>] (<a href="#Contents">Contents</a>)
2608 5 Alignments have an order from weaker to stronger or stricter alignments. Stricter
2609 alignments have larger alignment values. An address that satisfies an alignment
2610 requirement also satisfies any weaker valid alignment requirement.
2611 6 The alignment requirement of a complete type can be queried using an alignof
2612 expression. The types char, signed char, and unsigned char shall have the
2613 weakest alignment requirement.
2614 7 Comparing alignments is meaningful and provides the obvious results:
2615 -- Two alignments are equal when their numeric values are equal.
2616 -- Two alignments are different when their numeric values are not equal.
2617 -- When an alignment is larger than another it represents a stricter alignment.
2622 [<a name="#p49" href="p49">page 49</a>] (<a href="#Contents">Contents</a>)
2624 <a name="6.3" href="#6.3"><b> 6.3 Conversions</b></a>
2625 1 Several operators convert operand values from one type to another automatically. This
2626 subclause specifies the result required from such an implicit conversion, as well as those
2627 that result from a cast operation (an explicit conversion). The list in <a href="#6.3.1.8">6.3.1.8</a> summarizes
2628 the conversions performed by most ordinary operators; it is supplemented as required by
2629 the discussion of each operator in <a href="#6.5">6.5</a>.
2630 2 Conversion of an operand value to a compatible type causes no change to the value or the
2632 Forward references: cast operators (<a href="#6.5.4">6.5.4</a>).
2633 <a name="6.3.1" href="#6.3.1"><b> 6.3.1 Arithmetic operands</b></a>
2634 <a name="6.3.1.1" href="#6.3.1.1"><b> 6.3.1.1 Boolean, characters, and integers</b></a>
2635 1 Every integer type has an integer conversion rank defined as follows:
2636 -- No two signed integer types shall have the same rank, even if they have the same
2638 -- The rank of a signed integer type shall be greater than the rank of any signed integer
2639 type with less precision.
2640 -- The rank of long long int shall be greater than the rank of long int, which
2641 shall be greater than the rank of int, which shall be greater than the rank of short
2642 int, which shall be greater than the rank of signed char.
2643 -- The rank of any unsigned integer type shall equal the rank of the corresponding
2644 signed integer type, if any.
2645 -- The rank of any standard integer type shall be greater than the rank of any extended
2646 integer type with the same width.
2647 -- The rank of char shall equal the rank of signed char and unsigned char.
2648 -- The rank of _Bool shall be less than the rank of all other standard integer types.
2649 -- The rank of any enumerated type shall equal the rank of the compatible integer type
2650 (see <a href="#6.7.2.2">6.7.2.2</a>).
2651 -- The rank of any extended signed integer type relative to another extended signed
2652 integer type with the same precision is implementation-defined, but still subject to the
2653 other rules for determining the integer conversion rank.
2654 -- For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has
2655 greater rank than T3, then T1 has greater rank than T3.
2656 2 The following may be used in an expression wherever an int or unsigned int may
2659 [<a name="#p50" href="p50">page 50</a>] (<a href="#Contents">Contents</a>)
2661 -- An object or expression with an integer type (other than int or unsigned int)
2662 whose integer conversion rank is less than or equal to the rank of int and
2664 -- A bit-field of type _Bool, int, signed int, or unsigned int.
2665 If an int can represent all values of the original type (as restricted by the width, for a
2666 bit-field), the value is converted to an int; otherwise, it is converted to an unsigned
2667 int. These are called the integer promotions.58) All other types are unchanged by the
2669 3 The integer promotions preserve value including sign. As discussed earlier, whether a
2670 ''plain'' char is treated as signed is implementation-defined.
2671 Forward references: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
2672 (<a href="#6.7.2.1">6.7.2.1</a>).
2673 <a name="6.3.1.2" href="#6.3.1.2"><b> 6.3.1.2 Boolean type</b></a>
2674 1 When any scalar value is converted to _Bool, the result is 0 if the value compares equal
2675 to 0; otherwise, the result is 1.59)
2676 <a name="6.3.1.3" href="#6.3.1.3"><b> 6.3.1.3 Signed and unsigned integers</b></a>
2677 1 When a value with integer type is converted to another integer type other than _Bool, if
2678 the value can be represented by the new type, it is unchanged.
2679 2 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or
2680 subtracting one more than the maximum value that can be represented in the new type
2681 until the value is in the range of the new type.60)
2682 3 Otherwise, the new type is signed and the value cannot be represented in it; either the
2683 result is implementation-defined or an implementation-defined signal is raised.
2684 <a name="6.3.1.4" href="#6.3.1.4"><b> 6.3.1.4 Real floating and integer</b></a>
2685 1 When a finite value of real floating type is converted to an integer type other than _Bool,
2686 the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
2687 the integral part cannot be represented by the integer type, the behavior is undefined.61)
2690 58) The integer promotions are applied only: as part of the usual arithmetic conversions, to certain
2691 argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the
2692 shift operators, as specified by their respective subclauses.
2693 59) NaNs do not compare equal to 0 and thus convert to 1.
2694 60) The rules describe arithmetic on the mathematical value, not the value of a given type of expression.
2695 61) The remaindering operation performed when a value of integer type is converted to unsigned type
2696 need not be performed when a value of real floating type is converted to unsigned type. Thus, the
2697 range of portable real floating values is (-1, Utype_MAX+1).
2699 [<a name="#p51" href="p51">page 51</a>] (<a href="#Contents">Contents</a>)
2701 2 When a value of integer type is converted to a real floating type, if the value being
2702 converted can be represented exactly in the new type, it is unchanged. If the value being
2703 converted is in the range of values that can be represented but cannot be represented
2704 exactly, the result is either the nearest higher or nearest lower representable value, chosen
2705 in an implementation-defined manner. If the value being converted is outside the range of
2706 values that can be represented, the behavior is undefined.
2707 <a name="6.3.1.5" href="#6.3.1.5"><b> 6.3.1.5 Real floating types</b></a>
2708 1 When a float is promoted to double or long double, or a double is promoted
2709 to long double, its value is unchanged (if the source value is represented in the
2710 precision and range of its type).
2711 2 When a double is demoted to float, a long double is demoted to double or
2712 float, or a value being represented in greater precision and range than required by its
2713 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
2714 being converted can be represented exactly in the new type, it is unchanged. If the value
2715 being converted is in the range of values that can be represented but cannot be
2716 represented exactly, the result is either the nearest higher or nearest lower representable
2717 value, chosen in an implementation-defined manner. If the value being converted is
2718 outside the range of values that can be represented, the behavior is undefined.
2719 <a name="6.3.1.6" href="#6.3.1.6"><b> 6.3.1.6 Complex types</b></a>
2720 1 When a value of complex type is converted to another complex type, both the real and
2721 imaginary parts follow the conversion rules for the corresponding real types.
2722 <a name="6.3.1.7" href="#6.3.1.7"><b> 6.3.1.7 Real and complex</b></a>
2723 1 When a value of real type is converted to a complex type, the real part of the complex
2724 result value is determined by the rules of conversion to the corresponding real type and
2725 the imaginary part of the complex result value is a positive zero or an unsigned zero.
2726 2 When a value of complex type is converted to a real type, the imaginary part of the
2727 complex value is discarded and the value of the real part is converted according to the
2728 conversion rules for the corresponding real type.
2729 <a name="6.3.1.8" href="#6.3.1.8"><b> 6.3.1.8 Usual arithmetic conversions</b></a>
2730 1 Many operators that expect operands of arithmetic type cause conversions and yield result
2731 types in a similar way. The purpose is to determine a common real type for the operands
2732 and result. For the specified operands, each operand is converted, without change of type
2733 domain, to a type whose corresponding real type is the common real type. Unless
2734 explicitly stated otherwise, the common real type is also the corresponding real type of
2735 the result, whose type domain is the type domain of the operands if they are the same,
2736 and complex otherwise. This pattern is called the usual arithmetic conversions:
2739 [<a name="#p52" href="p52">page 52</a>] (<a href="#Contents">Contents</a>)
2741 First, if the corresponding real type of either operand is long double, the other
2742 operand is converted, without change of type domain, to a type whose
2743 corresponding real type is long double.
2744 Otherwise, if the corresponding real type of either operand is double, the other
2745 operand is converted, without change of type domain, to a type whose
2746 corresponding real type is double.
2747 Otherwise, if the corresponding real type of either operand is float, the other
2748 operand is converted, without change of type domain, to a type whose
2749 corresponding real type is float.62)
2750 Otherwise, the integer promotions are performed on both operands. Then the
2751 following rules are applied to the promoted operands:
2752 If both operands have the same type, then no further conversion is needed.
2753 Otherwise, if both operands have signed integer types or both have unsigned
2754 integer types, the operand with the type of lesser integer conversion rank is
2755 converted to the type of the operand with greater rank.
2756 Otherwise, if the operand that has unsigned integer type has rank greater or
2757 equal to the rank of the type of the other operand, then the operand with
2758 signed integer type is converted to the type of the operand with unsigned
2760 Otherwise, if the type of the operand with signed integer type can represent
2761 all of the values of the type of the operand with unsigned integer type, then
2762 the operand with unsigned integer type is converted to the type of the
2763 operand with signed integer type.
2764 Otherwise, both operands are converted to the unsigned integer type
2765 corresponding to the type of the operand with signed integer type.
2766 2 The values of floating operands and of the results of floating expressions may be
2767 represented in greater precision and range than that required by the type; the types are not
2773 62) For example, addition of a double _Complex and a float entails just the conversion of the
2774 float operand to double (and yields a double _Complex result).
2775 63) The cast and assignment operators are still required to perform their specified conversions as
2776 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>.
2778 [<a name="#p53" href="p53">page 53</a>] (<a href="#Contents">Contents</a>)
2780 <a name="6.3.2" href="#6.3.2"><b> 6.3.2 Other operands</b></a>
2781 <a name="6.3.2.1" href="#6.3.2.1"><b> 6.3.2.1 Lvalues, arrays, and function designators</b></a>
2782 1 An lvalue is an expression (with an object type other than void) that potentially
2783 designates an object;64) if an lvalue does not designate an object when it is evaluated, the
2784 behavior is undefined. When an object is said to have a particular type, the type is
2785 specified by the lvalue used to designate the object. A modifiable lvalue is an lvalue that
2786 does not have array type, does not have an incomplete type, does not have a const-
2787 qualified type, and if it is a structure or union, does not have any member (including,
2788 recursively, any member or element of all contained aggregates or unions) with a const-
2790 2 Except when it is the operand of the sizeof operator, the unary & operator, the ++
2791 operator, the -- operator, or the left operand of the . operator or an assignment operator,
2792 an lvalue that does not have array type is converted to the value stored in the designated
2793 object (and is no longer an lvalue). If the lvalue has qualified type, the value has the
2794 unqualified version of the type of the lvalue; otherwise, the value has the type of the
2795 lvalue. If the lvalue has an incomplete type and does not have array type, the behavior is
2796 undefined. If the lvalue designates an object of automatic storage duration that could
2797 have been declared with the register storage class (never had its address taken), and
2798 that object is uninitialized (not declared with an initializer and no assignment to it has
2799 been performed prior to use), the behavior is undefined.
2800 3 Except when it is the operand of the sizeof operator or the unary & operator, or is a
2801 string literal used to initialize an array, an expression that has type ''array of type'' is
2802 converted to an expression with type ''pointer to type'' that points to the initial element of
2803 the array object and is not an lvalue. If the array object has register storage class, the
2804 behavior is undefined.
2805 4 A function designator is an expression that has function type. Except when it is the
2806 operand of the sizeof operator65) or the unary & operator, a function designator with
2807 type ''function returning type'' is converted to an expression that has type ''pointer to
2808 function returning type''.
2809 Forward references: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), assignment operators
2811 64) The name ''lvalue'' comes originally from the assignment expression E1 = E2, in which the left
2812 operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
2813 object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described
2814 as the ''value of an expression''.
2815 An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
2816 expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.
2817 65) Because this conversion does not occur, the operand of the sizeof operator remains a function
2818 designator and violates the constraint in <a href="#6.5.3.4">6.5.3.4</a>.
2820 [<a name="#p54" href="p54">page 54</a>] (<a href="#Contents">Contents</a>)
2822 (<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
2823 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2824 (<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>).
2825 <a href="#6.3.2.2">6.3.2.2</a> void
2826 1 The (nonexistent) value of a void expression (an expression that has type void) shall not
2827 be used in any way, and implicit or explicit conversions (except to void) shall not be
2828 applied to such an expression. If an expression of any other type is evaluated as a void
2829 expression, its value or designator is discarded. (A void expression is evaluated for its
2831 <a name="6.3.2.3" href="#6.3.2.3"><b> 6.3.2.3 Pointers</b></a>
2832 1 A pointer to void may be converted to or from a pointer to any object type. A pointer to
2833 any object type may be converted to a pointer to void and back again; the result shall
2834 compare equal to the original pointer.
2835 2 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to
2836 the q-qualified version of the type; the values stored in the original and converted pointers
2837 shall compare equal.
2838 3 An integer constant expression with the value 0, or such an expression cast to type
2839 void *, is called a null pointer constant.66) If a null pointer constant is converted to a
2840 pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal
2841 to a pointer to any object or function.
2842 4 Conversion of a null pointer to another pointer type yields a null pointer of that type.
2843 Any two null pointers shall compare equal.
2844 5 An integer may be converted to any pointer type. Except as previously specified, the
2845 result is implementation-defined, might not be correctly aligned, might not point to an
2846 entity of the referenced type, and might be a trap representation.67)
2847 6 Any pointer type may be converted to an integer type. Except as previously specified, the
2848 result is implementation-defined. If the result cannot be represented in the integer type,
2849 the behavior is undefined. The result need not be in the range of values of any integer
2851 7 A pointer to an object type may be converted to a pointer to a different object type. If the
2852 resulting pointer is not correctly aligned68) for the referenced type, the behavior is
2853 undefined. Otherwise, when converted back again, the result shall compare equal to the
2856 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>.
2857 67) The mapping functions for converting a pointer to an integer or an integer to a pointer are intended to
2858 be consistent with the addressing structure of the execution environment.
2860 [<a name="#p55" href="p55">page 55</a>] (<a href="#Contents">Contents</a>)
2862 original pointer. When a pointer to an object is converted to a pointer to a character type,
2863 the result points to the lowest addressed byte of the object. Successive increments of the
2864 result, up to the size of the object, yield pointers to the remaining bytes of the object.
2865 8 A pointer to a function of one type may be converted to a pointer to a function of another
2866 type and back again; the result shall compare equal to the original pointer. If a converted
2867 pointer is used to call a function whose type is not compatible with the referenced type,
2868 the behavior is undefined.
2869 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
2870 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>).
2875 68) In general, the concept ''correctly aligned'' is transitive: if a pointer to type A is correctly aligned for a
2876 pointer to type B, which in turn is correctly aligned for a pointer to type C, then a pointer to type A is
2877 correctly aligned for a pointer to type C.
2879 [<a name="#p56" href="p56">page 56</a>] (<a href="#Contents">Contents</a>)
2881 <a name="6.4" href="#6.4"><b> 6.4 Lexical elements</b></a>
2889 preprocessing-token:
2896 each non-white-space character that cannot be one of the above
2898 2 Each preprocessing token that is converted to a token shall have the lexical form of a
2899 keyword, an identifier, a constant, a string literal, or a punctuator.
2901 3 A token is the minimal lexical element of the language in translation phases 7 and 8. The
2902 categories of tokens are: keywords, identifiers, constants, string literals, and punctuators.
2903 A preprocessing token is the minimal lexical element of the language in translation
2904 phases 3 through 6. The categories of preprocessing tokens are: header names,
2905 identifiers, preprocessing numbers, character constants, string literals, punctuators, and
2906 single non-white-space characters that do not lexically match the other preprocessing
2907 token categories.69) If a ' or a " character matches the last category, the behavior is
2908 undefined. Preprocessing tokens can be separated by white space; this consists of
2909 comments (described later), or white-space characters (space, horizontal tab, new-line,
2910 vertical tab, and form-feed), or both. As described in <a href="#6.10">6.10</a>, in certain circumstances
2911 during translation phase 4, white space (or the absence thereof) serves as more than
2912 preprocessing token separation. White space may appear within a preprocessing token
2913 only as part of a header name or between the quotation characters in a character constant
2918 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
2919 occur in source files.
2921 [<a name="#p57" href="p57">page 57</a>] (<a href="#Contents">Contents</a>)
2923 4 If the input stream has been parsed into preprocessing tokens up to a given character, the
2924 next preprocessing token is the longest sequence of characters that could constitute a
2925 preprocessing token. There is one exception to this rule: header name preprocessing
2926 tokens are recognized only within #include preprocessing directives and in
2927 implementation-defined locations within #pragma directives. In such contexts, a
2928 sequence of characters that could be either a header name or a string literal is recognized
2930 5 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a
2931 valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex
2932 might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program
2933 fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or
2934 not E is a macro name.
2936 6 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
2937 increment operators, even though the parse x ++ + ++ y might yield a correct expression.
2939 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>),
2940 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
2941 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2942 (<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
2943 (<a href="#6.4.5">6.4.5</a>).
2944 <a name="6.4.1" href="#6.4.1"><b> 6.4.1 Keywords</b></a>
2952 const register _Alignas
2953 continue restrict _Atomic
2954 default return _Bool
2956 double signed _Generic
2957 else sizeof _Imaginary
2958 enum static _Noreturn
2959 extern struct _Static_assert
2960 float switch _Thread_local
2963 2 The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as
2964 keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
2965 [<a name="#p58" href="p58">page 58</a>] (<a href="#Contents">Contents</a>)
2967 specifying imaginary types.70)
2968 <a name="6.4.2" href="#6.4.2"><b> 6.4.2 Identifiers</b></a>
2969 <a name="6.4.2.1" href="#6.4.2.1"><b> 6.4.2.1 General</b></a>
2973 identifier identifier-nondigit
2975 identifier-nondigit:
2977 universal-character-name
2978 other implementation-defined characters
2980 _ a b c d e f g h i j k l m
2981 n o p q r s t u v w x y z
2982 A B C D E F G H I J K L M
2983 N O P Q R S T U V W X Y Z
2987 2 An identifier is a sequence of nondigit characters (including the underscore _, the
2988 lowercase and uppercase Latin letters, and other characters) and digits, which designates
2989 one or more entities as described in <a href="#6.2.1">6.2.1</a>. Lowercase and uppercase letters are distinct.
2990 There is no specific limit on the maximum length of an identifier.
2991 3 Each universal character name in an identifier shall designate a character whose encoding
2992 in ISO/IEC 10646 falls into one of the ranges specified in <a href="#D">annex D</a>.71) The initial
2993 character shall not be a universal character name designating a digit. An implementation
2994 may allow multibyte characters that are not part of the basic source character set to
2995 appear in identifiers; which characters and their correspondence to universal character
2996 names is implementation-defined.
3000 70) One possible specification for imaginary types appears in <a href="#G">annex G</a>.
3001 71) On systems in which linkers cannot accept extended characters, an encoding of the universal character
3002 name may be used in forming valid external identifiers. For example, some otherwise unused
3003 character or sequence of characters may be used to encode the \u in a universal character name.
3004 Extended characters may produce a long external identifier.
3006 [<a name="#p59" href="p59">page 59</a>] (<a href="#Contents">Contents</a>)
3008 4 When preprocessing tokens are converted to tokens during translation phase 7, if a
3009 preprocessing token could be converted to either a keyword or an identifier, it is converted
3011 Implementation limits
3012 5 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of significant initial
3013 characters in an identifier; the limit for an external name (an identifier that has external
3014 linkage) may be more restrictive than that for an internal name (a macro name or an
3015 identifier that does not have external linkage). The number of significant characters in an
3016 identifier is implementation-defined.
3017 6 Any identifiers that differ in a significant character are different identifiers. If two
3018 identifiers differ only in nonsignificant characters, the behavior is undefined.
3019 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>).
3020 <a name="6.4.2.2" href="#6.4.2.2"><b> 6.4.2.2 Predefined identifiers</b></a>
3022 1 The identifier __func__ shall be implicitly declared by the translator as if,
3023 immediately following the opening brace of each function definition, the declaration
3024 static const char __func__[] = "function-name";
3025 appeared, where function-name is the name of the lexically-enclosing function.72)
3026 2 This name is encoded as if the implicit declaration had been written in the source
3027 character set and then translated into the execution character set as indicated in translation
3029 3 EXAMPLE Consider the code fragment:
3030 #include <a href="#7.21"><stdio.h></a>
3033 printf("%s\n", __func__);
3036 Each time the function is called, it will print to the standard output stream:
3039 Forward references: function definitions (<a href="#6.9.1">6.9.1</a>).
3044 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
3045 identifier is explicitly declared using the name __func__, the behavior is undefined.
3047 [<a name="#p60" href="p60">page 60</a>] (<a href="#Contents">Contents</a>)
3049 <a name="6.4.3" href="#6.4.3"><b> 6.4.3 Universal character names</b></a>
3051 1 universal-character-name:
3053 \U hex-quad hex-quad
3055 hexadecimal-digit hexadecimal-digit
3056 hexadecimal-digit hexadecimal-digit
3058 2 A universal character name shall not specify a character whose short identifier is less than
3059 00A0 other than 0024 ($), 0040 (@), or 0060 ('), nor one in the range D800 through
3062 3 Universal character names may be used in identifiers, character constants, and string
3063 literals to designate characters that are not in the basic character set.
3065 4 The universal character name \Unnnnnnnn designates the character whose eight-digit
3066 short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.74) Similarly, the universal
3067 character name \unnnn designates the character whose four-digit short identifier is nnnn
3068 (and whose eight-digit short identifier is 0000nnnn).
3073 73) The disallowed characters are the characters in the basic character set and the code positions reserved
3074 by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by
3077 74) Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
3079 [<a name="#p61" href="p61">page 61</a>] (<a href="#Contents">Contents</a>)
3081 <a name="6.4.4" href="#6.4.4"><b> 6.4.4 Constants</b></a>
3086 enumeration-constant
3089 2 Each constant shall have a type and the value of a constant shall be in the range of
3090 representable values for its type.
3092 3 Each constant has a type, determined by its form and value, as detailed later.
3093 <a name="6.4.4.1" href="#6.4.4.1"><b> 6.4.4.1 Integer constants</b></a>
3096 decimal-constant integer-suffixopt
3097 octal-constant integer-suffixopt
3098 hexadecimal-constant integer-suffixopt
3101 decimal-constant digit
3104 octal-constant octal-digit
3105 hexadecimal-constant:
3106 hexadecimal-prefix hexadecimal-digit
3107 hexadecimal-constant hexadecimal-digit
3108 hexadecimal-prefix: one of
3110 nonzero-digit: one of
3118 [<a name="#p62" href="p62">page 62</a>] (<a href="#Contents">Contents</a>)
3120 hexadecimal-digit: one of
3125 unsigned-suffix long-suffixopt
3126 unsigned-suffix long-long-suffix
3127 long-suffix unsigned-suffixopt
3128 long-long-suffix unsigned-suffixopt
3129 unsigned-suffix: one of
3133 long-long-suffix: one of
3136 2 An integer constant begins with a digit, but has no period or exponent part. It may have a
3137 prefix that specifies its base and a suffix that specifies its type.
3138 3 A decimal constant begins with a nonzero digit and consists of a sequence of decimal
3139 digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
3140 digits 0 through 7 only. A hexadecimal constant consists of the prefix 0x or 0X followed
3141 by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
3142 10 through 15 respectively.
3144 4 The value of a decimal constant is computed base 10; that of an octal constant, base 8;
3145 that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
3146 5 The type of an integer constant is the first of the corresponding list in which its value can
3152 [<a name="#p63" href="p63">page 63</a>] (<a href="#Contents">Contents</a>)
3154 Octal or Hexadecimal
3155 Suffix Decimal Constant Constant
3158 long int unsigned int
3159 long long int long int
3162 unsigned long long int
3164 u or U unsigned int unsigned int
3165 unsigned long int unsigned long int
3166 unsigned long long int unsigned long long int
3168 l or L long int long int
3169 long long int unsigned long int
3171 unsigned long long int
3173 Both u or U unsigned long int unsigned long int
3174 and l or L unsigned long long int unsigned long long int
3176 ll or LL long long int long long int
3177 unsigned long long int
3179 Both u or U unsigned long long int unsigned long long int
3181 6 If an integer constant cannot be represented by any type in its list, it may have an
3182 extended integer type, if the extended integer type can represent its value. If all of the
3183 types in the list for the constant are signed, the extended integer type shall be signed. If
3184 all of the types in the list for the constant are unsigned, the extended integer type shall be
3185 unsigned. If the list contains both signed and unsigned types, the extended integer type
3186 may be signed or unsigned. If an integer constant cannot be represented by any type in
3187 its list and has no extended integer type, then the integer constant has no type.
3192 [<a name="#p64" href="p64">page 64</a>] (<a href="#Contents">Contents</a>)
3194 <a name="6.4.4.2" href="#6.4.4.2"><b> 6.4.4.2 Floating constants</b></a>
3196 1 floating-constant:
3197 decimal-floating-constant
3198 hexadecimal-floating-constant
3199 decimal-floating-constant:
3200 fractional-constant exponent-partopt floating-suffixopt
3201 digit-sequence exponent-part floating-suffixopt
3202 hexadecimal-floating-constant:
3203 hexadecimal-prefix hexadecimal-fractional-constant
3204 binary-exponent-part floating-suffixopt
3205 hexadecimal-prefix hexadecimal-digit-sequence
3206 binary-exponent-part floating-suffixopt
3207 fractional-constant:
3208 digit-sequenceopt . digit-sequence
3211 e signopt digit-sequence
3212 E signopt digit-sequence
3217 digit-sequence digit
3218 hexadecimal-fractional-constant:
3219 hexadecimal-digit-sequenceopt .
3220 hexadecimal-digit-sequence
3221 hexadecimal-digit-sequence .
3222 binary-exponent-part:
3223 p signopt digit-sequence
3224 P signopt digit-sequence
3225 hexadecimal-digit-sequence:
3227 hexadecimal-digit-sequence hexadecimal-digit
3228 floating-suffix: one of
3231 [<a name="#p65" href="p65">page 65</a>] (<a href="#Contents">Contents</a>)
3234 2 A floating constant has a significand part that may be followed by an exponent part and a
3235 suffix that specifies its type. The components of the significand part may include a digit
3236 sequence representing the whole-number part, followed by a period (.), followed by a
3237 digit sequence representing the fraction part. The components of the exponent part are an
3238 e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
3239 Either the whole-number part or the fraction part has to be present; for decimal floating
3240 constants, either the period or the exponent part has to be present.
3242 3 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
3243 digit sequence in the exponent part is interpreted as a decimal integer. For decimal
3244 floating constants, the exponent indicates the power of 10 by which the significand part is
3245 to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
3246 by which the significand part is to be scaled. For decimal floating constants, and also for
3247 hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
3248 the nearest representable value, or the larger or smaller representable value immediately
3249 adjacent to the nearest representable value, chosen in an implementation-defined manner.
3250 For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
3252 4 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
3253 type float. If suffixed by the letter l or L, it has type long double.
3254 5 Floating constants are converted to internal format as if at translation-time. The
3255 conversion of a floating constant shall not raise an exceptional condition or a floating-
3256 point exception at execution time.
3257 Recommended practice
3258 6 The implementation should produce a diagnostic message if a hexadecimal constant
3259 cannot be represented exactly in its evaluation format; the implementation should then
3260 proceed with the translation of the program.
3261 7 The translation-time conversion of floating constants should match the execution-time
3262 conversion of character strings by library functions, such as strtod, given matching
3263 inputs suitable for both conversions, the same result format, and default execution-time
3269 75) The specification for the library functions recommends more accurate conversion than required for
3270 floating constants (see <a href="#7.22.1.3">7.22.1.3</a>).
3272 [<a name="#p66" href="p66">page 66</a>] (<a href="#Contents">Contents</a>)
3274 <a name="6.4.4.3" href="#6.4.4.3"><b> 6.4.4.3 Enumeration constants</b></a>
3276 1 enumeration-constant:
3279 2 An identifier declared as an enumeration constant has type int.
3280 Forward references: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>).
3281 <a name="6.4.4.4" href="#6.4.4.4"><b> 6.4.4.4 Character constants</b></a>
3283 1 character-constant:
3285 L' c-char-sequence '
3286 u' c-char-sequence '
3287 U' c-char-sequence '
3290 c-char-sequence c-char
3292 any member of the source character set except
3293 the single-quote ', backslash \, or new-line character
3296 simple-escape-sequence
3297 octal-escape-sequence
3298 hexadecimal-escape-sequence
3299 universal-character-name
3300 simple-escape-sequence: one of
3302 \a \b \f \n \r \t \v
3303 octal-escape-sequence:
3305 \ octal-digit octal-digit
3306 \ octal-digit octal-digit octal-digit
3311 [<a name="#p67" href="p67">page 67</a>] (<a href="#Contents">Contents</a>)
3313 hexadecimal-escape-sequence:
3314 \x hexadecimal-digit
3315 hexadecimal-escape-sequence hexadecimal-digit
3317 2 An integer character constant is a sequence of one or more multibyte characters enclosed
3318 in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
3319 letter L, u, or U. With a few exceptions detailed later, the elements of the sequence are
3320 any members of the source character set; they are mapped in an implementation-defined
3321 manner to members of the execution character set.
3322 3 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
3323 arbitrary integer values are representable according to the following table of escape
3329 octal character \octal digits
3330 hexadecimal character \x hexadecimal digits
3331 4 The double-quote " and question-mark ? are representable either by themselves or by the
3332 escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
3333 shall be represented, respectively, by the escape sequences \' and \\.
3334 5 The octal digits that follow the backslash in an octal escape sequence are taken to be part
3335 of the construction of a single character for an integer character constant or of a single
3336 wide character for a wide character constant. The numerical value of the octal integer so
3337 formed specifies the value of the desired character or wide character.
3338 6 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
3339 sequence are taken to be part of the construction of a single character for an integer
3340 character constant or of a single wide character for a wide character constant. The
3341 numerical value of the hexadecimal integer so formed specifies the value of the desired
3342 character or wide character.
3343 7 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
3344 constitute the escape sequence.
3345 8 In addition, characters not in the basic character set are representable by universal
3346 character names and certain nongraphic characters are representable by escape sequences
3347 consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
3352 [<a name="#p68" href="p68">page 68</a>] (<a href="#Contents">Contents</a>)
3355 9 The value of an octal or hexadecimal escape sequence shall be in the range of
3356 representable values for the corresponding type:
3357 Prefix Corresponding Type
3359 L the unsigned type corresponding to wchar_t
3363 10 An integer character constant has type int. The value of an integer character constant
3364 containing a single character that maps to a single-byte execution character is the
3365 numerical value of the representation of the mapped character interpreted as an integer.
3366 The value of an integer character constant containing more than one character (e.g.,
3367 'ab'), or containing a character or escape sequence that does not map to a single-byte
3368 execution character, is implementation-defined. If an integer character constant contains
3369 a single character or escape sequence, its value is the one that results when an object with
3370 type char whose value is that of the single character or escape sequence is converted to
3372 11 A wide character constant prefixed by the letter L has type wchar_t, an integer type
3373 defined in the <a href="#7.19"><stddef.h></a> header; a wide character constant prefixed by the letter u or
3374 U has type char16_t or char32_t, respectively, unsigned integer types defined in the
3375 <a href="#7.27"><uchar.h></a> header. The value of a wide character constant containing a single
3376 multibyte character that maps to a single member of the extended execution character set
3377 is the wide character corresponding to that multibyte character, as defined by the
3378 mbtowc, mbrtoc16, or mbrtoc32 function as appropriate for its type, with an
3379 implementation-defined current locale. The value of a wide character constant containing
3380 more than one multibyte character or a single multibyte character that maps to multiple
3381 members of the extended execution character set, or containing a multibyte character or
3382 escape sequence not represented in the extended execution character set, is
3383 implementation-defined.
3384 12 EXAMPLE 1 The construction '\0' is commonly used to represent the null character.
3386 13 EXAMPLE 2 Consider implementations that use two's-complement representation for integers and eight
3387 bits for objects that have type char. In an implementation in which type char has the same range of
3388 values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
3389 same range of values as unsigned char, the character constant '\xFF' has the value +255.
3394 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,
3395 the result is not a token and a diagnostic is required. See ''future language directions'' (<a href="#6.11.4">6.11.4</a>).
3397 [<a name="#p69" href="p69">page 69</a>] (<a href="#Contents">Contents</a>)
3399 14 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
3400 specifies an integer character constant containing only one character, since a hexadecimal escape sequence
3401 is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
3402 two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
3403 escape sequence is terminated after three octal digits. (The value of this two-character integer character
3404 constant is implementation-defined.)
3406 15 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
3407 L'\1234' specifies the implementation-defined value that results from the combination of the values
3410 Forward references: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbtowc function
3411 (<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>).
3412 <a name="6.4.5" href="#6.4.5"><b> 6.4.5 String literals</b></a>
3415 encoding-prefixopt " s-char-sequenceopt "
3423 s-char-sequence s-char
3425 any member of the source character set except
3426 the double-quote ", backslash \, or new-line character
3429 2 A sequence of adjacent string literal tokens shall not include both a wide string literal and
3430 a UTF-8 string literal.
3432 3 A character string literal is a sequence of zero or more multibyte characters enclosed in
3433 double-quotes, as in "xyz". A UTF-8 string literal is the same, except prefixed by u8.
3434 A wide string literal is the same, except prefixed by the letter L, u, or U.
3435 4 The same considerations apply to each element of the sequence in a string literal as if it
3436 were in an integer character constant (for a character or UTF-8 string literal) or a wide
3437 character constant (for a wide string literal), except that the single-quote ' is
3438 representable either by itself or by the escape sequence \', but the double-quote " shall
3439 [<a name="#p70" href="p70">page 70</a>] (<a href="#Contents">Contents</a>)
3441 be represented by the escape sequence \".
3443 5 In translation phase 6, the multibyte character sequences specified by any sequence of
3444 adjacent character and identically-prefixed string literal tokens are concatenated into a
3445 single multibyte character sequence. If any of the tokens has an encoding prefix, the
3446 resulting multibyte character sequence is treated as having the same prefix; otherwise, it
3447 is treated as a character string literal. Whether differently-prefixed wide string literal
3448 tokens can be concatenated and, if so, the treatment of the resulting multibyte character
3449 sequence are implementation-defined.
3450 6 In translation phase 7, a byte or code of value zero is appended to each multibyte
3451 character sequence that results from a string literal or literals.77) The multibyte character
3452 sequence is then used to initialize an array of static storage duration and length just
3453 sufficient to contain the sequence. For character string literals, the array elements have
3454 type char, and are initialized with the individual bytes of the multibyte character
3455 sequence. For UTF-8 string literals, the array elements have type char, and are
3456 initialized with the characters of the multibyte character sequence, as encoded in UTF-8.
3457 For wide string literals prefixed by the letter L, the array elements have type wchar_t
3458 and are initialized with the sequence of wide characters corresponding to the multibyte
3459 character sequence, as defined by the mbstowcs function with an implementation-
3460 defined current locale. For wide string literals prefixed by the letter u or U, the array
3461 elements have type char16_t or char32_t, respectively, and are initialized with the
3462 sequence of wide characters corresponding to the multibyte character sequence, as
3463 defined by successive calls to the mbrtoc16, or mbrtoc32 function as appropriate for
3464 its type, with an implementation-defined current locale. The value of a string literal
3465 containing a multibyte character or escape sequence not represented in the execution
3466 character set is implementation-defined.
3467 7 It is unspecified whether these arrays are distinct provided their elements have the
3468 appropriate values. If the program attempts to modify such an array, the behavior is
3470 8 EXAMPLE 1 This pair of adjacent character string literals
3472 produces a single character string literal containing the two characters whose values are '\x12' and '3',
3473 because escape sequences are converted into single members of the execution character set just prior to
3474 adjacent string literal concatenation.
3476 9 EXAMPLE 2 Each of the sequences of adjacent string literal tokens
3480 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
3483 [<a name="#p71" href="p71">page 71</a>] (<a href="#Contents">Contents</a>)
3489 is equivalent to the string literal
3491 Likewise, each of the sequences
3499 Forward references: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbstowcs
3500 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>).
3501 <a name="6.4.6" href="#6.4.6"><b> 6.4.6 Punctuators</b></a>
3503 1 punctuator: one of
3505 ++ -- & * + - ~ !
3506 / % << >> < > <= >= == != ^ | && ||
3508 = *= /= %= += -= <<= >>= &= ^= |=
3510 <: :> <% %> %: %:%:
3512 2 A punctuator is a symbol that has independent syntactic and semantic significance.
3513 Depending on context, it may specify an operation to be performed (which in turn may
3514 yield a value or a function designator, produce a side effect, or some combination thereof)
3515 in which case it is known as an operator (other forms of operator also exist in some
3516 contexts). An operand is an entity on which an operator acts.
3521 [<a name="#p72" href="p72">page 72</a>] (<a href="#Contents">Contents</a>)
3523 3 In all aspects of the language, the six tokens78)
3524 <: :> <% %> %: %:%:
3525 behave, respectively, the same as the six tokens
3527 except for their spelling.79)
3528 Forward references: expressions (<a href="#6.5">6.5</a>), declarations (<a href="#6.7">6.7</a>), preprocessing directives
3529 (<a href="#6.10">6.10</a>), statements (<a href="#6.8">6.8</a>).
3530 <a name="6.4.7" href="#6.4.7"><b> 6.4.7 Header names</b></a>
3533 < h-char-sequence >
3537 h-char-sequence h-char
3539 any member of the source character set except
3540 the new-line character and >
3543 q-char-sequence q-char
3545 any member of the source character set except
3546 the new-line character and "
3548 2 The sequences in both forms of header names are mapped in an implementation-defined
3549 manner to headers or external source file names as specified in <a href="#6.10.2">6.10.2</a>.
3550 3 If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters,
3551 the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the
3556 78) These tokens are sometimes called ''digraphs''.
3557 79) Thus [ and <: behave differently when ''stringized'' (see <a href="#6.10.3.2">6.10.3.2</a>), but can otherwise be freely
3560 [<a name="#p73" href="p73">page 73</a>] (<a href="#Contents">Contents</a>)
3562 sequence between the " delimiters, the behavior is undefined.80) Header name
3563 preprocessing tokens are recognized only within #include preprocessing directives and
3564 in implementation-defined locations within #pragma directives.81)
3565 4 EXAMPLE The following sequence of characters:
3567 #include <1/a.h>
3568 #define const.member@$
3569 forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
3570 by a { on the left and a } on the right).
3571 {0x3}{<}{1}{/}{a}{.}{h}{>}{1e2}
3572 {#}{include} {<1/a.h>}
3573 {#}{define} {const}{.}{member}{@}{$}
3575 Forward references: source file inclusion (<a href="#6.10.2">6.10.2</a>).
3576 <a name="6.4.8" href="#6.4.8"><b> 6.4.8 Preprocessing numbers</b></a>
3582 pp-number identifier-nondigit
3589 2 A preprocessing number begins with a digit optionally preceded by a period (.) and may
3590 be followed by valid identifier characters and the character sequences e+, e-, E+, E-,
3592 3 Preprocessing number tokens lexically include all floating and integer constant tokens.
3594 4 A preprocessing number does not have type or a value; it acquires both after a successful
3595 conversion (as part of translation phase 7) to a floating constant token or an integer
3599 80) Thus, sequences of characters that resemble escape sequences cause undefined behavior.
3600 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>.
3602 [<a name="#p74" href="p74">page 74</a>] (<a href="#Contents">Contents</a>)
3604 <a name="6.4.9" href="#6.4.9"><b> 6.4.9 Comments</b></a>
3605 1 Except within a character constant, a string literal, or a comment, the characters /*
3606 introduce a comment. The contents of such a comment are examined only to identify
3607 multibyte characters and to find the characters */ that terminate it.82)
3608 2 Except within a character constant, a string literal, or a comment, the characters //
3609 introduce a comment that includes all multibyte characters up to, but not including, the
3610 next new-line character. The contents of such a comment are examined only to identify
3611 multibyte characters and to find the terminating new-line character.
3613 "a//b" // four-character string literal
3614 #include "//e" // undefined behavior
3615 // */ // comment, not syntax error
3616 f = g/**//h; // equivalent to f = g / h;
3618 i(); // part of a two-line comment
3620 / j(); // part of a two-line comment
3621 #define glue(x,y) x##y
3622 glue(/,/) k(); // syntax error, not comment
3623 /*//*/ l(); // equivalent to l();
3625 + p; // equivalent to m = n + p;
3630 82) Thus, /* ... */ comments do not nest.
3632 [<a name="#p75" href="p75">page 75</a>] (<a href="#Contents">Contents</a>)
3634 <a name="6.5" href="#6.5"><b> 6.5 Expressions</b></a>
3635 1 An expression is a sequence of operators and operands that specifies computation of a
3636 value, or that designates an object or a function, or that generates side effects, or that
3637 performs a combination thereof. The value computations of the operands of an operator
3638 are sequenced before the value computation of the result of the operator.
3639 2 If a side effect on a scalar object is unsequenced relative to either a different side effect
3640 on the same scalar object or a value computation using the value of the same scalar
3641 object, the behavior is undefined. If there are multiple allowable orderings of the
3642 subexpressions of an expression, the behavior is undefined if such an unsequenced side
3643 effect occurs in any of the orderings.83)
3644 3 The grouping of operators and operands is indicated by the syntax.84) Except as specified
3645 later, side effects and value computations of subexpressions are unsequenced.85)
3646 4 Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |,
3647 collectively described as bitwise operators) are required to have operands that have
3648 integer type. These operators yield values that depend on the internal representations of
3649 integers, and have implementation-defined and undefined aspects for signed types.
3650 5 If an exceptional condition occurs during the evaluation of an expression (that is, if the
3651 result is not mathematically defined or not in the range of representable values for its
3652 type), the behavior is undefined.
3656 83) This paragraph renders undefined statement expressions such as
3663 84) The syntax specifies the precedence of operators in the evaluation of an expression, which is the same
3664 as the order of the major subclauses of this subclause, highest precedence first. Thus, for example, the
3665 expressions allowed as the operands of the binary + operator (<a href="#6.5.6">6.5.6</a>) are those expressions defined in
3666 <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
3667 (<a href="#6.5.3">6.5.3</a>), and an operand contained between any of the following pairs of operators: grouping
3668 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
3669 the conditional operator ? : (<a href="#6.5.15">6.5.15</a>).
3670 Within each major subclause, the operators have the same precedence. Left- or right-associativity is
3671 indicated in each subclause by the syntax for the expressions discussed therein.
3672 85) In an expression that is evaluated more than once during the execution of a program, unsequenced and
3673 indeterminately sequenced evaluations of its subexpressions need not be performed consistently in
3674 different evaluations.
3676 [<a name="#p76" href="p76">page 76</a>] (<a href="#Contents">Contents</a>)
3678 6 The effective type of an object for an access to its stored value is the declared type of the
3679 object, if any.86) If a value is stored into an object having no declared type through an
3680 lvalue having a type that is not a character type, then the type of the lvalue becomes the
3681 effective type of the object for that access and for subsequent accesses that do not modify
3682 the stored value. If a value is copied into an object having no declared type using
3683 memcpy or memmove, or is copied as an array of character type, then the effective type
3684 of the modified object for that access and for subsequent accesses that do not modify the
3685 value is the effective type of the object from which the value is copied, if it has one. For
3686 all other accesses to an object having no declared type, the effective type of the object is
3687 simply the type of the lvalue used for the access.
3688 7 An object shall have its stored value accessed only by an lvalue expression that has one of
3689 the following types:87)
3690 -- a type compatible with the effective type of the object,
3691 -- a qualified version of a type compatible with the effective type of the object,
3692 -- a type that is the signed or unsigned type corresponding to the effective type of the
3694 -- a type that is the signed or unsigned type corresponding to a qualified version of the
3695 effective type of the object,
3696 -- an aggregate or union type that includes one of the aforementioned types among its
3697 members (including, recursively, a member of a subaggregate or contained union), or
3698 -- a character type.
3699 8 A floating expression may be contracted, that is, evaluated as though it were a single
3700 operation, thereby omitting rounding errors implied by the source code and the
3701 expression evaluation method.88) The FP_CONTRACT pragma in <a href="#7.12"><math.h></a> provides a
3702 way to disallow contracted expressions. Otherwise, whether and how expressions are
3703 contracted is implementation-defined.89)
3704 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>).
3707 86) Allocated objects have no declared type.
3708 87) The intent of this list is to specify those circumstances in which an object may or may not be aliased.
3709 88) The intermediate operations in the contracted expression are evaluated as if to infinite precision and
3710 range, while the final operation is rounded to the format determined by the expression evaluation
3711 method. A contracted expression might also omit the raising of floating-point exceptions.
3712 89) This license is specifically intended to allow implementations to exploit fast machine instructions that
3713 combine multiple C operators. As contractions potentially undermine predictability, and can even
3714 decrease accuracy for containing expressions, their use needs to be well-defined and clearly
3717 [<a name="#p77" href="p77">page 77</a>] (<a href="#Contents">Contents</a>)
3719 <a name="6.5.1" href="#6.5.1"><b> 6.5.1 Primary expressions</b></a>
3721 1 primary-expression:
3728 2 An identifier is a primary expression, provided it has been declared as designating an
3729 object (in which case it is an lvalue) or a function (in which case it is a function
3731 3 A constant is a primary expression. Its type depends on its form and value, as detailed in
3732 <a name="6.4.4" href="#6.4.4"><b> 6.4.4.</b></a>
3733 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>.
3734 5 A parenthesized expression is a primary expression. Its type and value are identical to
3735 those of the unparenthesized expression. It is an lvalue, a function designator, or a void
3736 expression if the unparenthesized expression is, respectively, an lvalue, a function
3737 designator, or a void expression.
3738 Forward references: declarations (<a href="#6.7">6.7</a>).
3739 <a name="6.5.1.1" href="#6.5.1.1"><b> 6.5.1.1 Generic selection</b></a>
3741 1 generic-selection:
3742 _Generic ( assignment-expression , generic-assoc-list )
3745 generic-assoc-list , generic-association
3746 generic-association:
3747 type-name : assignment-expression
3748 default : assignment-expression
3750 2 A generic selection shall have no more than one default generic association. The type
3751 name in a generic association shall specify a complete object type other than a variably
3753 90) Thus, an undeclared identifier is a violation of the syntax.
3755 [<a name="#p78" href="p78">page 78</a>] (<a href="#Contents">Contents</a>)
3757 modified type. No two generic associations in the same generic selection shall specify
3758 compatible types. The controlling expression of a generic selection shall have type
3759 compatible with at most one of the types named in its generic association list. If a
3760 generic selection has no default generic association, its controlling expression shall
3761 have type compatible with exactly one of the types named in its generic association list.
3763 3 The controlling expression of a generic selection is not evaluated. If a generic selection
3764 has a generic association with a type name that is compatible with the type of the
3765 controlling expression, then the result expression of the generic selection is the
3766 expression in that generic association. Otherwise, the result expression of the generic
3767 selection is the expression in the default generic association. None of the expressions
3768 from any other generic association of the generic selection is evaluated.
3769 4 The type and value of a generic selection are identical to those of its result expression. It
3770 is an lvalue, a function designator, or a void expression if its result expression is,
3771 respectively, an lvalue, a function designator, or a void expression.
3772 5 EXAMPLE The cbrt type-generic macro could be implemented as follows:
3773 #define cbrt(X) _Generic((X), \
3774 long double: cbrtl, \
3779 <a name="6.5.2" href="#6.5.2"><b> 6.5.2 Postfix operators</b></a>
3781 1 postfix-expression:
3783 postfix-expression [ expression ]
3784 postfix-expression ( argument-expression-listopt )
3785 postfix-expression . identifier
3786 postfix-expression -> identifier
3787 postfix-expression ++
3788 postfix-expression --
3789 ( type-name ) { initializer-list }
3790 ( type-name ) { initializer-list , }
3791 argument-expression-list:
3792 assignment-expression
3793 argument-expression-list , assignment-expression
3798 [<a name="#p79" href="p79">page 79</a>] (<a href="#Contents">Contents</a>)
3800 <a name="6.5.2.1" href="#6.5.2.1"><b> 6.5.2.1 Array subscripting</b></a>
3802 1 One of the expressions shall have type ''pointer to complete object type'', the other
3803 expression shall have integer type, and the result has type ''type''.
3805 2 A postfix expression followed by an expression in square brackets [] is a subscripted
3806 designation of an element of an array object. The definition of the subscript operator []
3807 is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that
3808 apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the
3809 initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th
3810 element of E1 (counting from zero).
3811 3 Successive subscript operators designate an element of a multidimensional array object.
3812 If E is an n-dimensional array (n >= 2) with dimensions i x j x . . . x k, then E (used as
3813 other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with
3814 dimensions j x . . . x k. If the unary * operator is applied to this pointer explicitly, or
3815 implicitly as a result of subscripting, the result is the referenced (n - 1)-dimensional
3816 array, which itself is converted into a pointer if used as other than an lvalue. It follows
3817 from this that arrays are stored in row-major order (last subscript varies fastest).
3818 4 EXAMPLE Consider the array object defined by the declaration
3820 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
3821 array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
3822 a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually
3823 entails multiplying i by the size of the object to which the pointer points, namely an array of five int
3824 objects. The results are added and indirection is applied to yield an array of five ints. When used in the
3825 expression x[i][j], that array is in turn converted to a pointer to the first of the ints, so x[i][j]
3828 Forward references: additive operators (<a href="#6.5.6">6.5.6</a>), address and indirection operators
3829 (<a href="#6.5.3.2">6.5.3.2</a>), array declarators (<a href="#6.7.6.2">6.7.6.2</a>).
3830 <a name="6.5.2.2" href="#6.5.2.2"><b> 6.5.2.2 Function calls</b></a>
3832 1 The expression that denotes the called function91) shall have type pointer to function
3833 returning void or returning a complete object type other than an array type.
3834 2 If the expression that denotes the called function has a type that includes a prototype, the
3835 number of arguments shall agree with the number of parameters. Each argument shall
3838 91) Most often, this is the result of converting an identifier that is a function designator.
3840 [<a name="#p80" href="p80">page 80</a>] (<a href="#Contents">Contents</a>)
3842 have a type such that its value may be assigned to an object with the unqualified version
3843 of the type of its corresponding parameter.
3845 3 A postfix expression followed by parentheses () containing a possibly empty, comma-
3846 separated list of expressions is a function call. The postfix expression denotes the called
3847 function. The list of expressions specifies the arguments to the function.
3848 4 An argument may be an expression of any complete object type. In preparing for the call
3849 to a function, the arguments are evaluated, and each parameter is assigned the value of the
3850 corresponding argument.92)
3851 5 If the expression that denotes the called function has type pointer to function returning an
3852 object type, the function call expression has the same type as that object type, and has the
3853 value determined as specified in <a href="#6.8.6.4">6.8.6.4</a>. Otherwise, the function call has type void.
3854 6 If the expression that denotes the called function has a type that does not include a
3855 prototype, the integer promotions are performed on each argument, and arguments that
3856 have type float are promoted to double. These are called the default argument
3857 promotions. If the number of arguments does not equal the number of parameters, the
3858 behavior is undefined. If the function is defined with a type that includes a prototype, and
3859 either the prototype ends with an ellipsis (, ...) or the types of the arguments after
3860 promotion are not compatible with the types of the parameters, the behavior is undefined.
3861 If the function is defined with a type that does not include a prototype, and the types of
3862 the arguments after promotion are not compatible with those of the parameters after
3863 promotion, the behavior is undefined, except for the following cases:
3864 -- one promoted type is a signed integer type, the other promoted type is the
3865 corresponding unsigned integer type, and the value is representable in both types;
3866 -- both types are pointers to qualified or unqualified versions of a character type or
3868 7 If the expression that denotes the called function has a type that does include a prototype,
3869 the arguments are implicitly converted, as if by assignment, to the types of the
3870 corresponding parameters, taking the type of each parameter to be the unqualified version
3871 of its declared type. The ellipsis notation in a function prototype declarator causes
3872 argument type conversion to stop after the last declared parameter. The default argument
3873 promotions are performed on trailing arguments.
3877 92) A function may change the values of its parameters, but these changes cannot affect the values of the
3878 arguments. On the other hand, it is possible to pass a pointer to an object, and the function may
3879 change the value of the object pointed to. A parameter declared to have array or function type is
3880 adjusted to have a pointer type as described in <a href="#6.9.1">6.9.1</a>.
3882 [<a name="#p81" href="p81">page 81</a>] (<a href="#Contents">Contents</a>)
3884 8 No other conversions are performed implicitly; in particular, the number and types of
3885 arguments are not compared with those of the parameters in a function definition that
3886 does not include a function prototype declarator.
3887 9 If the function is defined with a type that is not compatible with the type (of the
3888 expression) pointed to by the expression that denotes the called function, the behavior is
3890 10 There is a sequence point after the evaluations of the function designator and the actual
3891 arguments but before the actual call. Every evaluation in the calling function (including
3892 other function calls) that is not otherwise specifically sequenced before or after the
3893 execution of the body of the called function is indeterminately sequenced with respect to
3894 the execution of the called function.93)
3895 11 Recursive function calls shall be permitted, both directly and indirectly through any chain
3897 12 EXAMPLE In the function call
3898 (*pf[f1()]) (f2(), f3() + f4())
3899 the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before
3900 the function pointed to by pf[f1()] is called.
3902 Forward references: function declarators (including prototypes) (<a href="#6.7.6.3">6.7.6.3</a>), function
3903 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>).
3904 <a name="6.5.2.3" href="#6.5.2.3"><b> 6.5.2.3 Structure and union members</b></a>
3906 1 The first operand of the . operator shall have a qualified or unqualified structure or union
3907 type, and the second operand shall name a member of that type.
3908 2 The first operand of the -> operator shall have type ''pointer to qualified or unqualified
3909 structure'' or ''pointer to qualified or unqualified union'', and the second operand shall
3910 name a member of the type pointed to.
3912 3 A postfix expression followed by the . operator and an identifier designates a member of
3913 a structure or union object. The value is that of the named member,94) and is an lvalue if
3914 the first expression is an lvalue. If the first expression has qualified type, the result has
3915 the so-qualified version of the type of the designated member.
3917 93) In other words, function executions do not ''interleave'' with each other.
3918 94) If the member used to access the contents of a union object is not the same as the member last used to
3919 store a value in the object, the appropriate part of the object representation of the value is reinterpreted
3920 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
3921 punning''). This might be a trap representation.
3923 [<a name="#p82" href="p82">page 82</a>] (<a href="#Contents">Contents</a>)
3925 4 A postfix expression followed by the -> operator and an identifier designates a member
3926 of a structure or union object. The value is that of the named member of the object to
3927 which the first expression points, and is an lvalue.95) If the first expression is a pointer to
3928 a qualified type, the result has the so-qualified version of the type of the designated
3930 5 Accessing a member of an _Atomic-qualified structure or union object results in
3931 undefined behavior.96)
3932 6 One special guarantee is made in order to simplify the use of unions: if a union contains
3933 several structures that share a common initial sequence (see below), and if the union
3934 object currently contains one of these structures, it is permitted to inspect the common
3935 initial part of any of them anywhere that a declaration of the completed type of the union
3936 is visible. Two structures share a common initial sequence if corresponding members
3937 have compatible types (and, for bit-fields, the same widths) for a sequence of one or more
3939 7 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or
3940 union, f().x is a valid postfix expression but is not an lvalue.
3943 struct s { int i; const int ci; };
3946 volatile struct s vs;
3947 the various members have the types:
3953 vs.ci volatile const int
3958 95) If &E is a valid pointer expression (where & is the ''address-of '' operator, which generates a pointer to
3959 its operand), the expression (&E)->MOS is the same as E.MOS.
3960 96) A data race would occur if access to the entire structure or union in one thread conflicts with access to
3961 a member from another thread, where at least one access is a modification. Such a data race results in
3964 [<a name="#p83" href="p83">page 83</a>] (<a href="#Contents">Contents</a>)
3966 9 EXAMPLE 3 The following is a valid fragment:
3981 u.nf.doublenode = <a href="#3.14">3.14</a>;
3983 if (u.n.alltypes == 1)
3984 if (sin(u.nf.doublenode) == 0.0)
3986 The following is not a valid fragment (because the union type is not visible within function f):
3987 struct t1 { int m; };
3988 struct t2 { int m; };
3989 int f(struct t1 *p1, struct t2 *p2)
3991 if (p1->m < 0)
3992 p2->m = -p2->m;
4002 return f(&u.s1, &u.s2);
4005 Forward references: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), structure and union
4006 specifiers (<a href="#6.7.2.1">6.7.2.1</a>).
4011 [<a name="#p84" href="p84">page 84</a>] (<a href="#Contents">Contents</a>)
4013 <a name="6.5.2.4" href="#6.5.2.4"><b> 6.5.2.4 Postfix increment and decrement operators</b></a>
4015 1 The operand of the postfix increment or decrement operator shall have qualified or
4016 unqualified real or pointer type and shall be a modifiable lvalue.
4018 2 The result of the postfix ++ operator is the value of the operand. As a side effect, the
4019 value of the operand object is incremented (that is, the value 1 of the appropriate type is
4020 added to it). See the discussions of additive operators and compound assignment for
4021 information on constraints, types, and conversions and the effects of operations on
4022 pointers. The value computation of the result is sequenced before the side effect of
4023 updating the stored value of the operand. With respect to an indeterminately-sequenced
4024 function call, the operation of postfix ++ is a single evaluation. Postfix ++ on an object
4025 with _Atomic-qualified type is a read-modify-write operation with
4027 memory_order_seq_cst memory order semantics.
4028 3 The postfix -- operator is analogous to the postfix ++ operator, except that the value of
4029 the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
4031 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>).
4032 <a name="6.5.2.5" href="#6.5.2.5"><b> 6.5.2.5 Compound literals</b></a>
4034 1 The type name shall specify a complete object type or an array of unknown size, but not a
4035 variable length array type.
4036 2 All the constraints for initializer lists in <a href="#6.7.9">6.7.9</a> also apply to compound literals.
4038 3 A postfix expression that consists of a parenthesized type name followed by a brace-
4039 enclosed list of initializers is a compound literal. It provides an unnamed object whose
4040 value is given by the initializer list.98)
4043 97) Where a pointer to an atomic object can be formed, this is equivalent to the following code sequence
4044 where T is the type of E:
4049 } while (!atomic_compare_exchange_strong(&E, &result, tmp));
4050 with result being the result of the operation.
4052 [<a name="#p85" href="p85">page 85</a>] (<a href="#Contents">Contents</a>)
4054 4 If the type name specifies an array of unknown size, the size is determined by the
4055 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
4056 completed array type. Otherwise (when the type name specifies an object type), the type
4057 of the compound literal is that specified by the type name. In either case, the result is an
4059 5 The value of the compound literal is that of an unnamed object initialized by the
4060 initializer list. If the compound literal occurs outside the body of a function, the object
4061 has static storage duration; otherwise, it has automatic storage duration associated with
4062 the enclosing block.
4063 6 All the semantic rules for initializer lists in <a href="#6.7.9">6.7.9</a> also apply to compound literals.99)
4064 7 String literals, and compound literals with const-qualified types, need not designate
4065 distinct objects.100)
4066 8 EXAMPLE 1 The file scope definition
4067 int *p = (int []){2, 4};
4068 initializes p to point to the first element of an array of two ints, the first having the value two and the
4069 second, four. The expressions in this compound literal are required to be constant. The unnamed object
4070 has static storage duration.
4072 9 EXAMPLE 2 In contrast, in
4080 p is assigned the address of the first element of an array of two ints, the first having the value previously
4081 pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
4082 unnamed object has automatic storage duration.
4084 10 EXAMPLE 3 Initializers with designations can be combined with compound literals. Structure objects
4085 created using compound literals can be passed to functions without depending on member order:
4086 drawline((struct point){.x=1, .y=1},
4087 (struct point){.x=3, .y=4});
4088 Or, if drawline instead expected pointers to struct point:
4092 98) Note that this differs from a cast expression. For example, a cast specifies a conversion to scalar types
4093 or void only, and the result of a cast expression is not an lvalue.
4094 99) For example, subobjects without explicit initializers are initialized to zero.
4095 100) This allows implementations to share storage for string literals and constant compound literals with
4096 the same or overlapping representations.
4098 [<a name="#p86" href="p86">page 86</a>] (<a href="#Contents">Contents</a>)
4100 drawline(&(struct point){.x=1, .y=1},
4101 &(struct point){.x=3, .y=4});
4103 11 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
4104 (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}
4106 12 EXAMPLE 5 The following three expressions have different meanings:
4108 (char []){"/tmp/fileXXXXXX"}
4109 (const char []){"/tmp/fileXXXXXX"}
4110 The first always has static storage duration and has type array of char, but need not be modifiable; the last
4111 two have automatic storage duration when they occur within the body of a function, and the first of these
4114 13 EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory
4115 and can even be shared. For example,
4116 (const char []){"abc"} == "abc"
4117 might yield 1 if the literals' storage is shared.
4119 14 EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly
4120 linked object. For example, there is no way to write a self-referential compound literal that could be used
4121 as the function argument in place of the named object endless_zeros below:
4122 struct int_list { int car; struct int_list *cdr; };
4123 struct int_list endless_zeros = {0, &endless_zeros};
4124 eval(endless_zeros);
4126 15 EXAMPLE 8 Each compound literal creates only a single object in a given scope:
4127 struct s { int i; };
4130 struct s *p = 0, *q;
4133 q = p, p = &((struct s){ j++ });
4134 if (j < 2) goto again;
4135 return p == q && q->i == 1;
4137 The function f() always returns the value 1.
4138 16 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
4139 lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
4140 have an indeterminate value, which would result in undefined behavior.
4142 Forward references: type names (<a href="#6.7.7">6.7.7</a>), initialization (<a href="#6.7.9">6.7.9</a>).
4147 [<a name="#p87" href="p87">page 87</a>] (<a href="#Contents">Contents</a>)
4149 <a name="6.5.3" href="#6.5.3"><b> 6.5.3 Unary operators</b></a>
4155 unary-operator cast-expression
4156 sizeof unary-expression
4157 sizeof ( type-name )
4158 alignof ( type-name )
4159 unary-operator: one of
4161 <a name="6.5.3.1" href="#6.5.3.1"><b> 6.5.3.1 Prefix increment and decrement operators</b></a>
4163 1 The operand of the prefix increment or decrement operator shall have qualified or
4164 unqualified real or pointer type and shall be a modifiable lvalue.
4166 2 The value of the operand of the prefix ++ operator is incremented. The result is the new
4167 value of the operand after incrementation. The expression ++E is equivalent to (E+=1).
4168 See the discussions of additive operators and compound assignment for information on
4169 constraints, types, side effects, and conversions and the effects of operations on pointers.
4170 3 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
4171 operand is decremented.
4172 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>).
4173 <a name="6.5.3.2" href="#6.5.3.2"><b> 6.5.3.2 Address and indirection operators</b></a>
4175 1 The operand of the unary & operator shall be either a function designator, the result of a
4176 [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is
4177 not declared with the register storage-class specifier.
4178 2 The operand of the unary * operator shall have pointer type.
4180 3 The unary & operator yields the address of its operand. If the operand has type ''type'',
4181 the result has type ''pointer to type''. If the operand is the result of a unary * operator,
4182 neither that operator nor the & operator is evaluated and the result is as if both were
4183 omitted, except that the constraints on the operators still apply and the result is not an
4185 [<a name="#p88" href="p88">page 88</a>] (<a href="#Contents">Contents</a>)
4187 lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor
4188 the unary * that is implied by the [] is evaluated and the result is as if the & operator
4189 were removed and the [] operator were changed to a + operator. Otherwise, the result is
4190 a pointer to the object or function designated by its operand.
4191 4 The unary * operator denotes indirection. If the operand points to a function, the result is
4192 a function designator; if it points to an object, the result is an lvalue designating the
4193 object. If the operand has type ''pointer to type'', the result has type ''type''. If an
4194 invalid value has been assigned to the pointer, the behavior of the unary * operator is
4196 Forward references: storage-class specifiers (<a href="#6.7.1">6.7.1</a>), structure and union specifiers
4197 (<a href="#6.7.2.1">6.7.2.1</a>).
4198 <a name="6.5.3.3" href="#6.5.3.3"><b> 6.5.3.3 Unary arithmetic operators</b></a>
4200 1 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
4201 integer type; of the ! operator, scalar type.
4203 2 The result of the unary + operator is the value of its (promoted) operand. The integer
4204 promotions are performed on the operand, and the result has the promoted type.
4205 3 The result of the unary - operator is the negative of its (promoted) operand. The integer
4206 promotions are performed on the operand, and the result has the promoted type.
4207 4 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is,
4208 each bit in the result is set if and only if the corresponding bit in the converted operand is
4209 not set). The integer promotions are performed on the operand, and the result has the
4210 promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent
4211 to the maximum value representable in that type minus E.
4212 5 The result of the logical negation operator ! is 0 if the value of its operand compares
4213 unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int.
4214 The expression !E is equivalent to (0==E).
4218 101) Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). It is
4219 always true that if E is a function designator or an lvalue that is a valid operand of the unary &
4220 operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of
4221 an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points.
4222 Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an
4223 address inappropriately aligned for the type of object pointed to, and the address of an object after the
4224 end of its lifetime.
4226 [<a name="#p89" href="p89">page 89</a>] (<a href="#Contents">Contents</a>)
4228 <a name="6.5.3.4" href="#6.5.3.4"><b> 6.5.3.4 The sizeof and alignof operators</b></a>
4230 1 The sizeof operator shall not be applied to an expression that has function type or an
4231 incomplete type, to the parenthesized name of such a type, or to an expression that
4232 designates a bit-field member. The alignof operator shall not be applied to a function
4233 type or an incomplete type.
4235 2 The sizeof operator yields the size (in bytes) of its operand, which may be an
4236 expression or the parenthesized name of a type. The size is determined from the type of
4237 the operand. The result is an integer. If the type of the operand is a variable length array
4238 type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an
4240 3 The alignof operator yields the alignment requirement of its operand type. The result
4241 is an integer constant. When applied to an array type, the result is the alignment
4242 requirement of the element type.
4243 4 When sizeof is applied to an operand that has type char, unsigned char, or
4244 signed char, (or a qualified version thereof) the result is 1. When applied to an
4245 operand that has array type, the result is the total number of bytes in the array.102) When
4246 applied to an operand that has structure or union type, the result is the total number of
4247 bytes in such an object, including internal and trailing padding.
4248 5 The value of the result of both operators is implementation-defined, and its type (an
4249 unsigned integer type) is size_t, defined in <a href="#7.19"><stddef.h></a> (and other headers).
4250 6 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage
4251 allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to
4252 allocate and return a pointer to void. For example:
4253 extern void *alloc(size_t);
4254 double *dp = alloc(sizeof *dp);
4255 The implementation of the alloc function should ensure that its return value is aligned suitably for
4256 conversion to a pointer to double.
4258 7 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
4259 sizeof array / sizeof array[0]
4261 8 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a
4263 #include <a href="#7.19"><stddef.h></a>
4267 102) When applied to a parameter declared to have array or function type, the sizeof operator yields the
4268 size of the adjusted (pointer) type (see <a href="#6.9.1">6.9.1</a>).
4270 [<a name="#p90" href="p90">page 90</a>] (<a href="#Contents">Contents</a>)
4272 size_t fsize3(int n)
4274 char b[n+3]; // variable length array
4275 return sizeof b; // execution time sizeof
4280 size = fsize3(10); // fsize3 returns 13
4284 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>),
4285 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>).
4286 <a name="6.5.4" href="#6.5.4"><b> 6.5.4 Cast operators</b></a>
4290 ( type-name ) cast-expression
4292 2 Unless the type name specifies a void type, the type name shall specify qualified or
4293 unqualified scalar type and the operand shall have scalar type.
4294 3 Conversions that involve pointers, other than where permitted by the constraints of
4295 <a href="#6.5.16.1">6.5.16.1</a>, shall be specified by means of an explicit cast.
4296 4 A pointer type shall not be converted to any floating type. A floating type shall not be
4297 converted to any pointer type.
4299 5 Preceding an expression by a parenthesized type name converts the value of the
4300 expression to the named type. This construction is called a cast.103) A cast that specifies
4301 no conversion has no effect on the type or value of an expression.
4302 6 If the value of the expression is represented with greater precision or range than required
4303 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
4304 type of the expression is the same as the named type.
4305 Forward references: equality operators (<a href="#6.5.9">6.5.9</a>), function declarators (including
4306 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>).
4310 103) A cast does not yield an lvalue. Thus, a cast to a qualified type has the same effect as a cast to the
4311 unqualified version of the type.
4313 [<a name="#p91" href="p91">page 91</a>] (<a href="#Contents">Contents</a>)
4315 <a name="6.5.5" href="#6.5.5"><b> 6.5.5 Multiplicative operators</b></a>
4317 1 multiplicative-expression:
4319 multiplicative-expression * cast-expression
4320 multiplicative-expression / cast-expression
4321 multiplicative-expression % cast-expression
4323 2 Each of the operands shall have arithmetic type. The operands of the % operator shall
4326 3 The usual arithmetic conversions are performed on the operands.
4327 4 The result of the binary * operator is the product of the operands.
4328 5 The result of the / operator is the quotient from the division of the first operand by the
4329 second; the result of the % operator is the remainder. In both operations, if the value of
4330 the second operand is zero, the behavior is undefined.
4331 6 When integers are divided, the result of the / operator is the algebraic quotient with any
4332 fractional part discarded.104) If the quotient a/b is representable, the expression
4333 (a/b)*b + a%b shall equal a; otherwise, the behavior of both a/b and a%b is
4335 <a name="6.5.6" href="#6.5.6"><b> 6.5.6 Additive operators</b></a>
4337 1 additive-expression:
4338 multiplicative-expression
4339 additive-expression + multiplicative-expression
4340 additive-expression - multiplicative-expression
4342 2 For addition, either both operands shall have arithmetic type, or one operand shall be a
4343 pointer to a complete object type and the other shall have integer type. (Incrementing is
4344 equivalent to adding 1.)
4345 3 For subtraction, one of the following shall hold:
4350 104) This is often called ''truncation toward zero''.
4352 [<a name="#p92" href="p92">page 92</a>] (<a href="#Contents">Contents</a>)
4354 -- both operands have arithmetic type;
4355 -- both operands are pointers to qualified or unqualified versions of compatible complete
4357 -- the left operand is a pointer to a complete object type and the right operand has
4359 (Decrementing is equivalent to subtracting 1.)
4361 4 If both operands have arithmetic type, the usual arithmetic conversions are performed on
4363 5 The result of the binary + operator is the sum of the operands.
4364 6 The result of the binary - operator is the difference resulting from the subtraction of the
4365 second operand from the first.
4366 7 For the purposes of these operators, a pointer to an object that is not an element of an
4367 array behaves the same as a pointer to the first element of an array of length one with the
4368 type of the object as its element type.
4369 8 When an expression that has integer type is added to or subtracted from a pointer, the
4370 result has the type of the pointer operand. If the pointer operand points to an element of
4371 an array object, and the array is large enough, the result points to an element offset from
4372 the original element such that the difference of the subscripts of the resulting and original
4373 array elements equals the integer expression. In other words, if the expression P points to
4374 the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
4375 (P)-N (where N has the value n) point to, respectively, the i+n-th and i-n-th elements of
4376 the array object, provided they exist. Moreover, if the expression P points to the last
4377 element of an array object, the expression (P)+1 points one past the last element of the
4378 array object, and if the expression Q points one past the last element of an array object,
4379 the expression (Q)-1 points to the last element of the array object. If both the pointer
4380 operand and the result point to elements of the same array object, or one past the last
4381 element of the array object, the evaluation shall not produce an overflow; otherwise, the
4382 behavior is undefined. If the result points one past the last element of the array object, it
4383 shall not be used as the operand of a unary * operator that is evaluated.
4384 9 When two pointers are subtracted, both shall point to elements of the same array object,
4385 or one past the last element of the array object; the result is the difference of the
4386 subscripts of the two array elements. The size of the result is implementation-defined,
4387 and its type (a signed integer type) is ptrdiff_t defined in the <a href="#7.19"><stddef.h></a> header.
4388 If the result is not representable in an object of that type, the behavior is undefined. In
4389 other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of
4390 an array object, the expression (P)-(Q) has the value i-j provided the value fits in an
4392 [<a name="#p93" href="p93">page 93</a>] (<a href="#Contents">Contents</a>)
4394 object of type ptrdiff_t. Moreover, if the expression P points either to an element of
4395 an array object or one past the last element of an array object, and the expression Q points
4396 to the last element of the same array object, the expression ((Q)+1)-(P) has the same
4397 value as ((Q)-(P))+1 and as -((P)-((Q)+1)), and has the value zero if the
4398 expression P points one past the last element of the array object, even though the
4399 expression (Q)+1 does not point to an element of the array object.105)
4400 10 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
4404 int (*p)[m] = a; // p == &a[0]
4405 p += 1; // p == &a[1]
4406 (*p)[2] = 99; // a[1][2] == 99
4407 n = p - a; // n == 1
4409 11 If array a in the above example were declared to be an array of known constant size, and pointer p were
4410 declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
4413 Forward references: array declarators (<a href="#6.7.6.2">6.7.6.2</a>), common definitions <a href="#7.19"><stddef.h></a>
4414 (<a href="#7.19">7.19</a>).
4415 <a name="6.5.7" href="#6.5.7"><b> 6.5.7 Bitwise shift operators</b></a>
4419 shift-expression << additive-expression
4420 shift-expression >> additive-expression
4422 2 Each of the operands shall have integer type.
4424 3 The integer promotions are performed on each of the operands. The type of the result is
4425 that of the promoted left operand. If the value of the right operand is negative or is
4427 105) Another way to approach pointer arithmetic is first to convert the pointer(s) to character pointer(s): In
4428 this scheme the integer expression added to or subtracted from the converted pointer is first multiplied
4429 by the size of the object originally pointed to, and the resulting pointer is converted back to the
4430 original type. For pointer subtraction, the result of the difference between the character pointers is
4431 similarly divided by the size of the object originally pointed to.
4432 When viewed in this way, an implementation need only provide one extra byte (which may overlap
4433 another object in the program) just after the end of the object in order to satisfy the ''one past the last
4434 element'' requirements.
4436 [<a name="#p94" href="p94">page 94</a>] (<a href="#Contents">Contents</a>)
4438 greater than or equal to the width of the promoted left operand, the behavior is undefined.
4439 4 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with
4440 zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo
4441 one more than the maximum value representable in the result type. If E1 has a signed
4442 type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is
4443 the resulting value; otherwise, the behavior is undefined.
4444 5 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
4445 or if E1 has a signed type and a nonnegative value, the value of the result is the integral
4446 part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
4447 resulting value is implementation-defined.
4448 <a name="6.5.8" href="#6.5.8"><b> 6.5.8 Relational operators</b></a>
4450 1 relational-expression:
4452 relational-expression < shift-expression
4453 relational-expression > shift-expression
4454 relational-expression <= shift-expression
4455 relational-expression >= shift-expression
4457 2 One of the following shall hold:
4458 -- both operands have real type; or
4459 -- both operands are pointers to qualified or unqualified versions of compatible object
4462 3 If both of the operands have arithmetic type, the usual arithmetic conversions are
4464 4 For the purposes of these operators, a pointer to an object that is not an element of an
4465 array behaves the same as a pointer to the first element of an array of length one with the
4466 type of the object as its element type.
4467 5 When two pointers are compared, the result depends on the relative locations in the
4468 address space of the objects pointed to. If two pointers to object types both point to the
4469 same object, or both point one past the last element of the same array object, they
4470 compare equal. If the objects pointed to are members of the same aggregate object,
4471 pointers to structure members declared later compare greater than pointers to members
4472 declared earlier in the structure, and pointers to array elements with larger subscript
4473 values compare greater than pointers to elements of the same array with lower subscript
4475 [<a name="#p95" href="p95">page 95</a>] (<a href="#Contents">Contents</a>)
4477 values. All pointers to members of the same union object compare equal. If the
4478 expression P points to an element of an array object and the expression Q points to the
4479 last element of the same array object, the pointer expression Q+1 compares greater than
4480 P. In all other cases, the behavior is undefined.
4481 6 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
4482 (greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is
4483 false.106) The result has type int.
4484 <a name="6.5.9" href="#6.5.9"><b> 6.5.9 Equality operators</b></a>
4486 1 equality-expression:
4487 relational-expression
4488 equality-expression == relational-expression
4489 equality-expression != relational-expression
4491 2 One of the following shall hold:
4492 -- both operands have arithmetic type;
4493 -- both operands are pointers to qualified or unqualified versions of compatible types;
4494 -- one operand is a pointer to an object type and the other is a pointer to a qualified or
4495 unqualified version of void; or
4496 -- one operand is a pointer and the other is a null pointer constant.
4498 3 The == (equal to) and != (not equal to) operators are analogous to the relational
4499 operators except for their lower precedence.107) Each of the operators yields 1 if the
4500 specified relation is true and 0 if it is false. The result has type int. For any pair of
4501 operands, exactly one of the relations is true.
4502 4 If both of the operands have arithmetic type, the usual arithmetic conversions are
4503 performed. Values of complex types are equal if and only if both their real parts are equal
4504 and also their imaginary parts are equal. Any two values of arithmetic types from
4505 different type domains are equal if and only if the results of their conversions to the
4506 (complex) result type determined by the usual arithmetic conversions are equal.
4510 106) The expression a<b<c is not interpreted as in ordinary mathematics. As the syntax indicates, it
4511 means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
4512 107) Because of the precedences, a<b == c<d is 1 whenever a<b and c<d have the same truth-value.
4514 [<a name="#p96" href="p96">page 96</a>] (<a href="#Contents">Contents</a>)
4516 5 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a
4517 null pointer constant, the null pointer constant is converted to the type of the pointer. If
4518 one operand is a pointer to an object type and the other is a pointer to a qualified or
4519 unqualified version of void, the former is converted to the type of the latter.
4520 6 Two pointers compare equal if and only if both are null pointers, both are pointers to the
4521 same object (including a pointer to an object and a subobject at its beginning) or function,
4522 both are pointers to one past the last element of the same array object, or one is a pointer
4523 to one past the end of one array object and the other is a pointer to the start of a different
4524 array object that happens to immediately follow the first array object in the address
4526 7 For the purposes of these operators, a pointer to an object that is not an element of an
4527 array behaves the same as a pointer to the first element of an array of length one with the
4528 type of the object as its element type.
4529 <a name="6.5.10" href="#6.5.10"><b> 6.5.10 Bitwise AND operator</b></a>
4533 AND-expression & equality-expression
4535 2 Each of the operands shall have integer type.
4537 3 The usual arithmetic conversions are performed on the operands.
4538 4 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
4539 the result is set if and only if each of the corresponding bits in the converted operands is
4545 108) Two objects may be adjacent in memory because they are adjacent elements of a larger array or
4546 adjacent members of a structure with no padding between them, or because the implementation chose
4547 to place them so, even though they are unrelated. If prior invalid pointer operations (such as accesses
4548 outside array bounds) produced undefined behavior, subsequent comparisons also produce undefined
4551 [<a name="#p97" href="p97">page 97</a>] (<a href="#Contents">Contents</a>)
4553 <a name="6.5.11" href="#6.5.11"><b> 6.5.11 Bitwise exclusive OR operator</b></a>
4555 1 exclusive-OR-expression:
4557 exclusive-OR-expression ^ AND-expression
4559 2 Each of the operands shall have integer type.
4561 3 The usual arithmetic conversions are performed on the operands.
4562 4 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
4563 in the result is set if and only if exactly one of the corresponding bits in the converted
4565 <a name="6.5.12" href="#6.5.12"><b> 6.5.12 Bitwise inclusive OR operator</b></a>
4567 1 inclusive-OR-expression:
4568 exclusive-OR-expression
4569 inclusive-OR-expression | exclusive-OR-expression
4571 2 Each of the operands shall have integer type.
4573 3 The usual arithmetic conversions are performed on the operands.
4574 4 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
4575 the result is set if and only if at least one of the corresponding bits in the converted
4581 [<a name="#p98" href="p98">page 98</a>] (<a href="#Contents">Contents</a>)
4583 <a name="6.5.13" href="#6.5.13"><b> 6.5.13 Logical AND operator</b></a>
4585 1 logical-AND-expression:
4586 inclusive-OR-expression
4587 logical-AND-expression && inclusive-OR-expression
4589 2 Each of the operands shall have scalar type.
4591 3 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
4592 yields 0. The result has type int.
4593 4 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
4594 if the second operand is evaluated, there is a sequence point between the evaluations of
4595 the first and second operands. If the first operand compares equal to 0, the second
4596 operand is not evaluated.
4597 <a name="6.5.14" href="#6.5.14"><b> 6.5.14 Logical OR operator</b></a>
4599 1 logical-OR-expression:
4600 logical-AND-expression
4601 logical-OR-expression || logical-AND-expression
4603 2 Each of the operands shall have scalar type.
4605 3 The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it
4606 yields 0. The result has type int.
4607 4 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; if the
4608 second operand is evaluated, there is a sequence point between the evaluations of the first
4609 and second operands. If the first operand compares unequal to 0, the second operand is
4615 [<a name="#p99" href="p99">page 99</a>] (<a href="#Contents">Contents</a>)
4617 <a name="6.5.15" href="#6.5.15"><b> 6.5.15 Conditional operator</b></a>
4619 1 conditional-expression:
4620 logical-OR-expression
4621 logical-OR-expression ? expression : conditional-expression
4623 2 The first operand shall have scalar type.
4624 3 One of the following shall hold for the second and third operands:
4625 -- both operands have arithmetic type;
4626 -- both operands have the same structure or union type;
4627 -- both operands have void type;
4628 -- both operands are pointers to qualified or unqualified versions of compatible types;
4629 -- one operand is a pointer and the other is a null pointer constant; or
4630 -- one operand is a pointer to an object type and the other is a pointer to a qualified or
4631 unqualified version of void.
4633 4 The first operand is evaluated; there is a sequence point between its evaluation and the
4634 evaluation of the second or third operand (whichever is evaluated). The second operand
4635 is evaluated only if the first compares unequal to 0; the third operand is evaluated only if
4636 the first compares equal to 0; the result is the value of the second or third operand
4637 (whichever is evaluated), converted to the type described below.109)
4638 5 If both the second and third operands have arithmetic type, the result type that would be
4639 determined by the usual arithmetic conversions, were they applied to those two operands,
4640 is the type of the result. If both the operands have structure or union type, the result has
4641 that type. If both operands have void type, the result has void type.
4642 6 If both the second and third operands are pointers or one is a null pointer constant and the
4643 other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
4644 of the types referenced by both operands. Furthermore, if both operands are pointers to
4645 compatible types or to differently qualified versions of compatible types, the result type is
4646 a pointer to an appropriately qualified version of the composite type; if one operand is a
4647 null pointer constant, the result has the type of the other operand; otherwise, one operand
4648 is a pointer to void or a qualified version of void, in which case the result type is a
4649 pointer to an appropriately qualified version of void.
4651 109) A conditional expression does not yield an lvalue.
4653 [<a name="#p100" href="p100">page 100</a>] (<a href="#Contents">Contents</a>)
4655 7 EXAMPLE The common type that results when the second and third operands are pointers is determined
4656 in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two
4657 pointers have compatible types.
4658 8 Given the declarations
4665 the third column in the following table is the common type that is the result of a conditional expression in
4666 which the first two columns are the second and third operands (in either order):
4667 c_vp c_ip const void *
4668 v_ip 0 volatile int *
4669 c_ip v_ip const volatile int *
4670 vp c_cp const void *
4674 <a name="6.5.16" href="#6.5.16"><b> 6.5.16 Assignment operators</b></a>
4676 1 assignment-expression:
4677 conditional-expression
4678 unary-expression assignment-operator assignment-expression
4679 assignment-operator: one of
4680 = *= /= %= += -= <<= >>= &= ^= |=
4682 2 An assignment operator shall have a modifiable lvalue as its left operand.
4684 3 An assignment operator stores a value in the object designated by the left operand. An
4685 assignment expression has the value of the left operand after the assignment,110) but is not
4686 an lvalue. The type of an assignment expression is the type of the left operand unless the
4687 left operand has qualified type, in which case it is the unqualified version of the type of
4688 the left operand. The side effect of updating the stored value of the left operand is
4689 sequenced after the value computations of the left and right operands. The evaluations of
4690 the operands are unsequenced.
4695 110) The implementation is permitted to read the object to determine the value but is not required to, even
4696 when the object has volatile-qualified type.
4698 [<a name="#p101" href="p101">page 101</a>] (<a href="#Contents">Contents</a>)
4700 <a name="6.5.16.1" href="#6.5.16.1"><b> 6.5.16.1 Simple assignment</b></a>
4702 1 One of the following shall hold:111)
4703 -- the left operand has qualified or unqualified arithmetic type and the right has
4705 -- the left operand has a qualified or unqualified version of a structure or union type
4706 compatible with the type of the right;
4707 -- both operands are pointers to qualified or unqualified versions of compatible types,
4708 and the type pointed to by the left has all the qualifiers of the type pointed to by the
4710 -- one operand is a pointer to an object type and the other is a pointer to a qualified or
4711 unqualified version of void, and the type pointed to by the left has all the qualifiers
4712 of the type pointed to by the right;
4713 -- the left operand is a pointer and the right is a null pointer constant; or
4714 -- the left operand has type _Bool and the right is a pointer.
4716 2 In simple assignment (=), the value of the right operand is converted to the type of the
4717 assignment expression and replaces the value stored in the object designated by the left
4719 3 If the value being stored in an object is read from another object that overlaps in any way
4720 the storage of the first object, then the overlap shall be exact and the two objects shall
4721 have qualified or unqualified versions of a compatible type; otherwise, the behavior is
4723 4 EXAMPLE 1 In the program fragment
4727 if ((c = f()) == -1)
4729 the int value returned by the function may be truncated when stored in the char, and then converted back
4730 to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
4731 values as unsigned char (and char is narrower than int), the result of the conversion cannot be
4735 111) The asymmetric appearance of these constraints with respect to type qualifiers is due to the conversion
4736 (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
4737 qualifiers that were applied to the type category of the expression (for example, it removes const but
4738 not volatile from the type int volatile * const).
4740 [<a name="#p102" href="p102">page 102</a>] (<a href="#Contents">Contents</a>)
4742 negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
4743 variable c should be declared as int.
4745 5 EXAMPLE 2 In the fragment:
4750 the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
4751 of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
4752 that is, long int type.
4754 6 EXAMPLE 3 Consider the fragment:
4758 cpp = &p; // constraint violation
4759 *cpp = &c; // valid
4761 The first assignment is unsafe because it would allow the following valid code to attempt to change the
4762 value of the const object c.
4764 <a name="6.5.16.2" href="#6.5.16.2"><b> 6.5.16.2 Compound assignment</b></a>
4766 1 For the operators += and -= only, either the left operand shall be a pointer to a complete
4767 object type and the right shall have integer type, or the left operand shall have qualified or
4768 unqualified arithmetic type and the right shall have arithmetic type.
4769 2 For the other operators, each operand shall have arithmetic type consistent with those
4770 allowed by the corresponding binary operator.
4772 3 A compound assignment of the form E1 op = E2 is equivalent to the simple assignment
4773 expression E1 = E1 op (E2), except that the lvalue E1 is evaluated only once, and with
4774 respect to an indeterminately-sequenced function call, the operation of a compound
4775 assignment is a single evaluation. If E1 has an _Atomic-qualified type, compound
4776 assignment is a read-modify-write operation with memory_order_seq_cst memory
4777 order semantics.112)
4782 [<a name="#p103" href="p103">page 103</a>] (<a href="#Contents">Contents</a>)
4784 <a name="6.5.17" href="#6.5.17"><b> 6.5.17 Comma operator</b></a>
4787 assignment-expression
4788 expression , assignment-expression
4790 2 The left operand of a comma operator is evaluated as a void expression; there is a
4791 sequence point between its evaluation and that of the right operand. Then the right
4792 operand is evaluated; the result has its type and value.113)
4793 3 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot
4794 appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists
4795 of initializers). On the other hand, it can be used within a parenthesized expression or within the second
4796 expression of a conditional operator in such contexts. In the function call
4798 the function has three arguments, the second of which has the value 5.
4800 Forward references: initialization (<a href="#6.7.9">6.7.9</a>).
4805 112) Where a pointer to an atomic object can be formed, this is equivalent to the following code sequence
4806 where T is the type of E1:
4810 result = tmp op (E2);
4811 } while (!atomic_compare_exchange_strong(&E1, &tmp, result));
4812 with result being the result of the operation.
4813 113) A comma operator does not yield an lvalue.
4815 [<a name="#p104" href="p104">page 104</a>] (<a href="#Contents">Contents</a>)
4817 <a name="6.6" href="#6.6"><b> 6.6 Constant expressions</b></a>
4819 1 constant-expression:
4820 conditional-expression
4822 2 A constant expression can be evaluated during translation rather than runtime, and
4823 accordingly may be used in any place that a constant may be.
4825 3 Constant expressions shall not contain assignment, increment, decrement, function-call,
4826 or comma operators, except when they are contained within a subexpression that is not
4828 4 Each constant expression shall evaluate to a constant that is in the range of representable
4829 values for its type.
4831 5 An expression that evaluates to a constant is required in several contexts. If a floating
4832 expression is evaluated in the translation environment, the arithmetic precision and range
4833 shall be at least as great as if the expression were being evaluated in the execution
4835 6 An integer constant expression116) shall have integer type and shall only have operands
4836 that are integer constants, enumeration constants, character constants, sizeof
4837 expressions whose results are integer constants, and floating constants that are the
4838 immediate operands of casts. Cast operators in an integer constant expression shall only
4839 convert arithmetic types to integer types, except as part of an operand to the sizeof
4841 7 More latitude is permitted for constant expressions in initializers. Such a constant
4842 expression shall be, or evaluate to, one of the following:
4843 -- an arithmetic constant expression,
4847 114) The operand of a sizeof operator is usually not evaluated (<a href="#6.5.3.4">6.5.3.4</a>).
4848 115) The use of evaluation formats as characterized by FLT_EVAL_METHOD also applies to evaluation in
4849 the translation environment.
4850 116) An integer constant expression is required in a number of contexts such as the size of a bit-field
4851 member of a structure, the value of an enumeration constant, and the size of a non-variable length
4852 array. Further constraints that apply to the integer constant expressions used in conditional-inclusion
4853 preprocessing directives are discussed in <a href="#6.10.1">6.10.1</a>.
4855 [<a name="#p105" href="p105">page 105</a>] (<a href="#Contents">Contents</a>)
4857 -- a null pointer constant,
4858 -- an address constant, or
4859 -- an address constant for a complete object type plus or minus an integer constant
4861 8 An arithmetic constant expression shall have arithmetic type and shall only have
4862 operands that are integer constants, floating constants, enumeration constants, character
4863 constants, and sizeof expressions. Cast operators in an arithmetic constant expression
4864 shall only convert arithmetic types to arithmetic types, except as part of an operand to a
4865 sizeof operator whose result is an integer constant.
4866 9 An address constant is a null pointer, a pointer to an lvalue designating an object of static
4867 storage duration, or a pointer to a function designator; it shall be created explicitly using
4868 the unary & operator or an integer constant cast to pointer type, or implicitly by the use of
4869 an expression of array or function type. The array-subscript [] and member-access .
4870 and -> operators, the address & and indirection * unary operators, and pointer casts may
4871 be used in the creation of an address constant, but the value of an object shall not be
4872 accessed by use of these operators.
4873 10 An implementation may accept other forms of constant expressions.
4874 11 The semantic rules for the evaluation of a constant expression are the same as for
4875 nonconstant expressions.117)
4876 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>).
4881 117) Thus, in the following initialization,
4882 static int i = 2 || 1 / 0;
4883 the expression is a valid integer constant expression with value one.
4885 [<a name="#p106" href="p106">page 106</a>] (<a href="#Contents">Contents</a>)
4887 <a name="6.7" href="#6.7"><b> 6.7 Declarations</b></a>
4890 declaration-specifiers init-declarator-listopt ;
4891 static_assert-declaration *
4892 declaration-specifiers:
4893 storage-class-specifier declaration-specifiersopt
4894 type-specifier declaration-specifiersopt
4895 type-qualifier declaration-specifiersopt
4896 function-specifier declaration-specifiersopt
4897 alignment-specifier declaration-specifiersopt
4898 init-declarator-list:
4900 init-declarator-list , init-declarator
4903 declarator = initializer
4905 2 A declaration other than a static_assert declaration shall declare at least a declarator
4906 (other than the parameters of a function or the members of a structure or union), a tag, or
4907 the members of an enumeration.
4908 3 If an identifier has no linkage, there shall be no more than one declaration of the identifier
4909 (in a declarator or type specifier) with the same scope and in the same name space, except
4910 that a typedef name can be redefined to denote the same type as it currently does and tags
4911 may be redeclared as specified in <a href="#6.7.2.3">6.7.2.3</a>.
4912 4 All declarations in the same scope that refer to the same object or function shall specify
4915 5 A declaration specifies the interpretation and attributes of a set of identifiers. A definition
4916 of an identifier is a declaration for that identifier that:
4917 -- for an object, causes storage to be reserved for that object;
4918 -- for a function, includes the function body;118)
4922 118) Function definitions have a different syntax, described in <a href="#6.9.1">6.9.1</a>.
4924 [<a name="#p107" href="p107">page 107</a>] (<a href="#Contents">Contents</a>)
4926 -- for an enumeration constant or typedef name, is the (only) declaration of the
4928 6 The declaration specifiers consist of a sequence of specifiers that indicate the linkage,
4929 storage duration, and part of the type of the entities that the declarators denote. The init-
4930 declarator-list is a comma-separated sequence of declarators, each of which may have
4931 additional type information, or an initializer, or both. The declarators contain the
4932 identifiers (if any) being declared.
4933 7 If an identifier for an object is declared with no linkage, the type for the object shall be *
4934 complete by the end of its declarator, or by the end of its init-declarator if it has an
4935 initializer; in the case of function parameters (including in prototypes), it is the adjusted
4936 type (see <a href="#6.7.6.3">6.7.6.3</a>) that is required to be complete.
4937 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
4938 (<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>).
4939 <a name="6.7.1" href="#6.7.1"><b> 6.7.1 Storage-class specifiers</b></a>
4941 1 storage-class-specifier:
4949 2 At most, one storage-class specifier may be given in the declaration specifiers in a
4950 declaration, except that _Thread_local may appear with static or extern.119)
4951 3 In the declaration of an object with block scope, if the declaration specifiers include
4952 _Thread_local, they shall also include either static or extern. If
4953 _Thread_local appears in any declaration of an object, it shall be present in every
4954 declaration of that object.
4956 4 The typedef specifier is called a ''storage-class specifier'' for syntactic convenience
4957 only; it is discussed in <a href="#6.7.8">6.7.8</a>. The meanings of the various linkages and storage durations
4958 were discussed in <a href="#6.2.2">6.2.2</a> and <a href="#6.2.4">6.2.4</a>.
4962 119) See ''future language directions'' (<a href="#6.11.5">6.11.5</a>).
4964 [<a name="#p108" href="p108">page 108</a>] (<a href="#Contents">Contents</a>)
4966 5 A declaration of an identifier for an object with storage-class specifier register
4967 suggests that access to the object be as fast as possible. The extent to which such
4968 suggestions are effective is implementation-defined.120)
4969 6 The declaration of an identifier for a function that has block scope shall have no explicit
4970 storage-class specifier other than extern.
4971 7 If an aggregate or union object is declared with a storage-class specifier other than
4972 typedef, the properties resulting from the storage-class specifier, except with respect to
4973 linkage, also apply to the members of the object, and so on recursively for any aggregate
4974 or union member objects.
4975 Forward references: type definitions (<a href="#6.7.8">6.7.8</a>).
4976 <a name="6.7.2" href="#6.7.2"><b> 6.7.2 Type specifiers</b></a>
4990 _Atomic ( type-name )
4991 struct-or-union-specifier
4995 2 At least one type specifier shall be given in the declaration specifiers in each declaration,
4996 and in the specifier-qualifier list in each struct declaration and type name. Each list of
4999 120) The implementation may treat any register declaration simply as an auto declaration. However,
5000 whether or not addressable storage is actually used, the address of any part of an object declared with
5001 storage-class specifier register cannot be computed, either explicitly (by use of the unary &
5002 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
5003 <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
5006 [<a name="#p109" href="p109">page 109</a>] (<a href="#Contents">Contents</a>)
5008 type specifiers shall be one of the following multisets (delimited by commas, when there
5009 is more than one multiset per item); the type specifiers may occur in any order, possibly
5010 intermixed with the other declaration specifiers.
5015 -- short, signed short, short int, or signed short int
5016 -- unsigned short, or unsigned short int
5017 -- int, signed, or signed int
5018 -- unsigned, or unsigned int
5019 -- long, signed long, long int, or signed long int
5020 -- unsigned long, or unsigned long int
5021 -- long long, signed long long, long long int, or
5022 signed long long int
5023 -- unsigned long long, or unsigned long long int
5030 -- long double _Complex
5031 -- _Atomic ( type-name )
5032 -- struct or union specifier
5035 3 The type specifier _Complex shall not be used if the implementation does not support
5036 complex types; likewise, _Atomic shall not be used if the implementation does not
5037 support atomic types (see <a href="#6.10.8.3">6.10.8.3</a>).
5041 [<a name="#p110" href="p110">page 110</a>] (<a href="#Contents">Contents</a>)
5044 4 The _Atomic form of type specifier designates the _Atomic-qualified version of the
5046 5 Specifiers for structures, unions, and enumerations are discussed in <a href="#6.7.2.1">6.7.2.1</a> through
5047 <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>
5048 other types are discussed in <a href="#6.2.5">6.2.5</a>.
5049 6 Each of the comma-separated multisets designates the same type, except that for bit-
5050 fields, it is implementation-defined whether the specifier int designates the same type as
5051 signed int or the same type as unsigned int.
5052 Forward references: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
5053 (<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>).
5054 <a name="6.7.2.1" href="#6.7.2.1"><b> 6.7.2.1 Structure and union specifiers</b></a>
5056 1 struct-or-union-specifier:
5057 struct-or-union identifieropt { struct-declaration-list }
5058 struct-or-union identifier
5062 struct-declaration-list:
5064 struct-declaration-list struct-declaration
5066 specifier-qualifier-list struct-declarator-listopt ;
5067 static_assert-declaration
5068 specifier-qualifier-list:
5069 type-specifier specifier-qualifier-listopt
5070 type-qualifier specifier-qualifier-listopt
5071 struct-declarator-list:
5073 struct-declarator-list , struct-declarator
5076 declaratoropt : constant-expression
5080 [<a name="#p111" href="p111">page 111</a>] (<a href="#Contents">Contents</a>)
5083 2 A struct-declaration that does not declare an anonymous structure or anonymous union
5084 shall contain a struct-declarator-list.
5085 3 A structure or union shall not contain a member with incomplete or function type (hence,
5086 a structure shall not contain an instance of itself, but may contain a pointer to an instance
5087 of itself), except that the last member of a structure with more than one named member
5088 may have incomplete array type; such a structure (and any union containing, possibly
5089 recursively, a member that is such a structure) shall not be a member of a structure or an
5090 element of an array.
5091 4 The expression that specifies the width of a bit-field shall be an integer constant
5092 expression with a nonnegative value that does not exceed the width of an object of the
5093 type that would be specified were the colon and expression omitted.121) If the value is
5094 zero, the declaration shall have no declarator.
5095 5 A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed
5096 int, unsigned int, or some other implementation-defined type.
5098 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
5099 storage is allocated in an ordered sequence, and a union is a type consisting of a sequence
5100 of members whose storage overlap.
5101 7 Structure and union specifiers have the same form. The keywords struct and union
5102 indicate that the type being specified is, respectively, a structure type or a union type.
5103 8 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
5104 within a translation unit. The struct-declaration-list is a sequence of declarations for the
5105 members of the structure or union. If the struct-declaration-list contains no named
5106 members, no anonymous structures, and no anonymous unions, the behavior is undefined.
5107 The type is incomplete until immediately after the } that terminates the list, and complete
5109 9 A member of a structure or union may have any complete object type other than a
5110 variably modified type.122) In addition, a member may be declared to consist of a
5111 specified number of bits (including a sign bit, if any). Such a member is called a
5112 bit-field;123) its width is preceded by a colon.
5116 121) While the number of bits in a _Bool object is at least CHAR_BIT, the width (number of sign and
5117 value bits) of a _Bool may be just 1 bit.
5118 122) A structure or union cannot contain a member with a variably modified type because member names
5119 are not ordinary identifiers as defined in <a href="#6.2.3">6.2.3</a>.
5121 [<a name="#p112" href="p112">page 112</a>] (<a href="#Contents">Contents</a>)
5123 10 A bit-field is interpreted as a signed or unsigned integer type consisting of the specified
5124 number of bits.124) If the value 0 or 1 is stored into a nonzero-width bit-field of type
5125 _Bool, the value of the bit-field shall compare equal to the value stored; a _Bool bit-
5126 field has the semantics of a _Bool.
5127 11 An implementation may allocate any addressable storage unit large enough to hold a bit-
5128 field. If enough space remains, a bit-field that immediately follows another bit-field in a
5129 structure shall be packed into adjacent bits of the same unit. If insufficient space remains,
5130 whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is
5131 implementation-defined. The order of allocation of bit-fields within a unit (high-order to
5132 low-order or low-order to high-order) is implementation-defined. The alignment of the
5133 addressable storage unit is unspecified.
5134 12 A bit-field declaration with no declarator, but only a colon and a width, indicates an
5135 unnamed bit-field.125) As a special case, a bit-field structure member with a width of 0
5136 indicates that no further bit-field is to be packed into the unit in which the previous bit-
5137 field, if any, was placed.
5138 13 An unnamed member of structure type with no tag is called an anonymous structure; an
5139 unnamed member of union type with no tag is called an anonymous union. The members
5140 of an anonymous structure or union are considered to be members of the containing
5141 structure or union. This applies recursively if the containing structure or union is also
5143 14 Each non-bit-field member of a structure or union object is aligned in an implementation-
5144 defined manner appropriate to its type.
5145 15 Within a structure object, the non-bit-field members and the units in which bit-fields
5146 reside have addresses that increase in the order in which they are declared. A pointer to a
5147 structure object, suitably converted, points to its initial member (or if that member is a
5148 bit-field, then to the unit in which it resides), and vice versa. There may be unnamed
5149 padding within a structure object, but not at its beginning.
5150 16 The size of a union is sufficient to contain the largest of its members. The value of at
5151 most one of the members can be stored in a union object at any time. A pointer to a
5152 union object, suitably converted, points to each of its members (or if a member is a bit-
5153 field, then to the unit in which it resides), and vice versa.
5156 123) The unary & (address-of) operator cannot be applied to a bit-field object; thus, there are no pointers to
5157 or arrays of bit-field objects.
5158 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,
5159 then it is implementation-defined whether the bit-field is signed or unsigned.
5160 125) An unnamed bit-field structure member is useful for padding to conform to externally imposed
5163 [<a name="#p113" href="p113">page 113</a>] (<a href="#Contents">Contents</a>)
5165 17 There may be unnamed padding at the end of a structure or union.
5166 18 As a special case, the last element of a structure with more than one named member may
5167 have an incomplete array type; this is called a flexible array member. In most situations,
5168 the flexible array member is ignored. In particular, the size of the structure is as if the
5169 flexible array member were omitted except that it may have more trailing padding than
5170 the omission would imply. However, when a . (or ->) operator has a left operand that is
5171 (a pointer to) a structure with a flexible array member and the right operand names that
5172 member, it behaves as if that member were replaced with the longest array (with the same
5173 element type) that would not make the structure larger than the object being accessed; the
5174 offset of the array shall remain that of the flexible array member, even if this would differ
5175 from that of the replacement array. If this array would have no elements, it behaves as if
5176 it had one element but the behavior is undefined if any attempt is made to access that
5177 element or to generate a pointer one past it.
5178 19 EXAMPLE 1 The following illustrates anonymous structures and unions:
5180 union { // anonymous union
5181 struct { int i, j; }; // anonymous structure
5182 struct { long k, l; } w;
5187 v1.k = 3; // invalid: inner structure is not anonymous
5188 v1.w.k = 5; // valid
5190 20 EXAMPLE 2 After the declaration:
5191 struct s { int n; double d[]; };
5192 the structure struct s has a flexible array member d. A typical way to use this is:
5193 int m = /* some value */;
5194 struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));
5195 and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
5196 p had been declared as:
5197 struct { int n; double d[m]; } *p;
5198 (there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
5200 21 Following the above declaration:
5201 struct s t1 = { 0 }; // valid
5202 struct s t2 = { 1, { <a href="#4.2">4.2</a> }}; // invalid
5204 t1.d[0] = <a href="#4.2">4.2</a>; // might be undefined behavior
5205 The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
5206 contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
5208 [<a name="#p114" href="p114">page 114</a>] (<a href="#Contents">Contents</a>)
5210 sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)
5211 in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming
5213 22 After the further declaration:
5214 struct ss { int n; };
5216 sizeof (struct s) >= sizeof (struct ss)
5217 sizeof (struct s) >= offsetof(struct s, d)
5218 are always equal to 1.
5219 23 If sizeof (double) is 8, then after the following code is executed:
5222 s1 = malloc(sizeof (struct s) + 64);
5223 s2 = malloc(sizeof (struct s) + 46);
5224 and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
5225 purposes, as if the identifiers had been declared as:
5226 struct { int n; double d[8]; } *s1;
5227 struct { int n; double d[5]; } *s2;
5228 24 Following the further successful assignments:
5229 s1 = malloc(sizeof (struct s) + 10);
5230 s2 = malloc(sizeof (struct s) + 6);
5231 they then behave as if the declarations were:
5232 struct { int n; double d[1]; } *s1, *s2;
5235 dp = &(s1->d[0]); // valid
5237 dp = &(s2->d[0]); // valid
5238 *dp = 42; // undefined behavior
5241 only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes
5242 of the structure, they might be copied or simply overwritten with indeterminate values.
5244 Forward references: declarators (<a href="#6.7.6">6.7.6</a>), tags (<a href="#6.7.2.3">6.7.2.3</a>).
5249 [<a name="#p115" href="p115">page 115</a>] (<a href="#Contents">Contents</a>)
5251 <a name="6.7.2.2" href="#6.7.2.2"><b> 6.7.2.2 Enumeration specifiers</b></a>
5254 enum identifieropt { enumerator-list }
5255 enum identifieropt { enumerator-list , }
5259 enumerator-list , enumerator
5261 enumeration-constant
5262 enumeration-constant = constant-expression
5264 2 The expression that defines the value of an enumeration constant shall be an integer
5265 constant expression that has a value representable as an int.
5267 3 The identifiers in an enumerator list are declared as constants that have type int and
5268 may appear wherever such are permitted.126) An enumerator with = defines its
5269 enumeration constant as the value of the constant expression. If the first enumerator has
5270 no =, the value of its enumeration constant is 0. Each subsequent enumerator with no =
5271 defines its enumeration constant as the value of the constant expression obtained by
5272 adding 1 to the value of the previous enumeration constant. (The use of enumerators with
5273 = may produce enumeration constants with values that duplicate other values in the same
5274 enumeration.) The enumerators of an enumeration are also known as its members.
5275 4 Each enumerated type shall be compatible with char, a signed integer type, or an
5276 unsigned integer type. The choice of type is implementation-defined,127) but shall be
5277 capable of representing the values of all the members of the enumeration. The
5278 enumerated type is incomplete until immediately after the } that terminates the list of
5279 enumerator declarations, and complete thereafter.
5284 126) Thus, the identifiers of enumeration constants declared in the same scope shall all be distinct from
5285 each other and from other identifiers declared in ordinary declarators.
5286 127) An implementation may delay the choice of which integer type until all enumeration constants have
5289 [<a name="#p116" href="p116">page 116</a>] (<a href="#Contents">Contents</a>)
5291 5 EXAMPLE The following fragment:
5292 enum hue { chartreuse, burgundy, claret=20, winedark };
5296 if (*cp != burgundy)
5298 makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
5299 pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
5301 Forward references: tags (<a href="#6.7.2.3">6.7.2.3</a>).
5302 <a name="6.7.2.3" href="#6.7.2.3"><b> 6.7.2.3 Tags</b></a>
5304 1 A specific type shall have its content defined at most once.
5305 2 Where two declarations that use the same tag declare the same type, they shall both use
5306 the same choice of struct, union, or enum.
5307 3 A type specifier of the form
5309 without an enumerator list shall only appear after the type it specifies is complete.
5311 4 All declarations of structure, union, or enumerated types that have the same scope and
5312 use the same tag declare the same type. Irrespective of whether there is a tag or what
5313 other declarations of the type are in the same translation unit, the type is incomplete128)
5314 until immediately after the closing brace of the list defining the content, and complete
5316 5 Two declarations of structure, union, or enumerated types which are in different scopes or
5317 use different tags declare distinct types. Each declaration of a structure, union, or
5318 enumerated type which does not include a tag declares a distinct type.
5319 6 A type specifier of the form
5324 128) An incomplete type may only by used when the size of an object of that type is not needed. It is not
5325 needed, for example, when a typedef name is declared to be a specifier for a structure or union, or
5326 when a pointer to or a function returning a structure or union is being declared. (See incomplete types
5327 in <a href="#6.2.5">6.2.5</a>.) The specification has to be complete before such a function is called or defined.
5329 [<a name="#p117" href="p117">page 117</a>] (<a href="#Contents">Contents</a>)
5331 struct-or-union identifieropt { struct-declaration-list }
5333 enum identifieropt { enumerator-list }
5335 enum identifieropt { enumerator-list , }
5336 declares a structure, union, or enumerated type. The list defines the structure content,
5337 union content, or enumeration content. If an identifier is provided,129) the type specifier
5338 also declares the identifier to be the tag of that type.
5339 7 A declaration of the form
5340 struct-or-union identifier ;
5341 specifies a structure or union type and declares the identifier as a tag of that type.130)
5342 8 If a type specifier of the form
5343 struct-or-union identifier
5344 occurs other than as part of one of the above forms, and no other declaration of the
5345 identifier as a tag is visible, then it declares an incomplete structure or union type, and
5346 declares the identifier as the tag of that type.130)
5347 9 If a type specifier of the form
5348 struct-or-union identifier
5351 occurs other than as part of one of the above forms, and a declaration of the identifier as a
5352 tag is visible, then it specifies the same type as that other declaration, and does not
5354 10 EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
5357 struct tnode *left, *right;
5359 specifies a structure that contains an integer and two pointers to objects of the same type. Once this
5360 declaration has been given, the declaration
5365 129) If there is no identifier, the type can, within the translation unit, only be referred to by the declaration
5366 of which it is a part. Of course, when the declaration is of a typedef name, subsequent declarations
5367 can make use of that typedef name to declare objects having the specified structure, union, or
5369 130) A similar construction with enum does not exist.
5371 [<a name="#p118" href="p118">page 118</a>] (<a href="#Contents">Contents</a>)
5373 struct tnode s, *sp;
5374 declares s to be an object of the given type and sp to be a pointer to an object of the given type. With
5375 these declarations, the expression sp->left refers to the left struct tnode pointer of the object to
5376 which sp points; the expression s.right->count designates the count member of the right struct
5377 tnode pointed to from s.
5378 11 The following alternative formulation uses the typedef mechanism:
5379 typedef struct tnode TNODE;
5382 TNODE *left, *right;
5386 12 EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential
5387 structures, the declarations
5388 struct s1 { struct s2 *s2p; /* ... */ }; // D1
5389 struct s2 { struct s1 *s1p; /* ... */ }; // D2
5390 specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
5391 declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
5392 D2. To eliminate this context sensitivity, the declaration
5394 may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then
5395 completes the specification of the new type.
5397 Forward references: declarators (<a href="#6.7.6">6.7.6</a>), type definitions (<a href="#6.7.8">6.7.8</a>).
5398 <a name="6.7.3" href="#6.7.3"><b> 6.7.3 Type qualifiers</b></a>
5406 2 Types other than pointer types whose referenced type is an object type shall not be
5409 3 The properties associated with qualified types are meaningful only for expressions that
5411 4 If the same qualifier appears more than once in the same specifier-qualifier-list, either
5412 directly or via one or more typedefs, the behavior is the same as if it appeared only
5414 [<a name="#p119" href="p119">page 119</a>] (<a href="#Contents">Contents</a>)
5416 5 If an attempt is made to modify an object defined with a const-qualified type through use
5417 of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is
5418 made to refer to an object defined with a volatile-qualified type through use of an lvalue
5419 with non-volatile-qualified type, the behavior is undefined.132) If an attempt is made to
5420 refer to an object defined with an _Atomic-qualified type through use of an lvalue with
5421 non-_Atomic-qualified type, the behavior is undefined.
5422 6 An object that has volatile-qualified type may be modified in ways unknown to the
5423 implementation or have other unknown side effects. Therefore any expression referring
5424 to such an object shall be evaluated strictly according to the rules of the abstract machine,
5425 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
5426 object shall agree with that prescribed by the abstract machine, except as modified by the
5427 unknown factors mentioned previously.133) What constitutes an access to an object that
5428 has volatile-qualified type is implementation-defined.
5429 7 An object that is accessed through a restrict-qualified pointer has a special association
5430 with that pointer. This association, defined in <a href="#6.7.3.1">6.7.3.1</a> below, requires that all accesses to
5431 that object use, directly or indirectly, the value of that particular pointer.134) The intended
5432 use of the restrict qualifier (like the register storage class) is to promote
5433 optimization, and deleting all instances of the qualifier from all preprocessing translation
5434 units composing a conforming program does not change its meaning (i.e., observable
5436 8 If the specification of an array type includes any type qualifiers, the element type is so-
5437 qualified, not the array type. If the specification of a function type includes any type
5438 qualifiers, the behavior is undefined.135)
5439 9 For two qualified types to be compatible, both shall have the identically qualified version
5440 of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers
5441 does not affect the specified type.
5443 131) The implementation may place a const object that is not volatile in a read-only region of
5444 storage. Moreover, the implementation need not allocate storage for such an object if its address is
5446 132) This applies to those objects that behave as if they were defined with qualified types, even if they are
5447 never actually defined as objects in the program (such as an object at a memory-mapped input/output
5449 133) A volatile declaration may be used to describe an object corresponding to a memory-mapped
5450 input/output port or an object accessed by an asynchronously interrupting function. Actions on
5451 objects so declared shall not be ''optimized out'' by an implementation or reordered except as
5452 permitted by the rules for evaluating expressions.
5453 134) For example, a statement that assigns a value returned by malloc to a single pointer establishes this
5454 association between the allocated object and the pointer.
5455 135) Both of these can occur through the use of typedefs.
5457 [<a name="#p120" href="p120">page 120</a>] (<a href="#Contents">Contents</a>)
5459 10 EXAMPLE 1 An object declared
5460 extern const volatile int real_time_clock;
5461 may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
5463 11 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers
5464 modify an aggregate type:
5465 const struct s { int mem; } cs = { 1 };
5466 struct s ncs; // the object ncs is modifiable
5467 typedef int A[2][3];
5468 const A a = {{4, 5, 6}, {7, 8, 9}}; // array of array of const int
5472 cs = ncs; // violates modifiable lvalue constraint for =
5473 pi = &ncs.mem; // valid
5474 pi = &cs.mem; // violates type constraints for =
5475 pci = &cs.mem; // valid
5476 pi = a[0]; // invalid: a[0] has type ''const int *''
5478 <a name="6.7.3.1" href="#6.7.3.1"><b> 6.7.3.1 Formal definition of restrict</b></a>
5479 1 Let D be a declaration of an ordinary identifier that provides a means of designating an
5480 object P as a restrict-qualified pointer to type T.
5481 2 If D appears inside a block and does not have storage class extern, let B denote the
5482 block. If D appears in the list of parameter declarations of a function definition, let B
5483 denote the associated block. Otherwise, let B denote the block of main (or the block of
5484 whatever function is called at program startup in a freestanding environment).
5485 3 In what follows, a pointer expression E is said to be based on object P if (at some
5486 sequence point in the execution of B prior to the evaluation of E) modifying P to point to
5487 a copy of the array object into which it formerly pointed would change the value of E.136)
5488 Note that ''based'' is defined only for expressions with pointer types.
5489 4 During each execution of B, let L be any lvalue that has &L based on P. If L is used to
5490 access the value of the object X that it designates, and X is also modified (by any means),
5491 then the following requirements apply: T shall not be const-qualified. Every other lvalue
5492 used to access the value of X shall also have its address based on P. Every access that
5493 modifies X shall be considered also to modify P, for the purposes of this subclause. If P
5494 is assigned the value of a pointer expression E that is based on another restricted pointer
5495 object P2, associated with block B2, then either the execution of B2 shall begin before
5498 136) In other words, E depends on the value of P itself rather than on the value of an object referenced
5499 indirectly through P. For example, if identifier p has type (int **restrict), then the pointer
5500 expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer
5501 expressions *p and p[1] are not.
5503 [<a name="#p121" href="p121">page 121</a>] (<a href="#Contents">Contents</a>)
5505 the execution of B, or the execution of B2 shall end prior to the assignment. If these
5506 requirements are not met, then the behavior is undefined.
5507 5 Here an execution of B means that portion of the execution of the program that would
5508 correspond to the lifetime of an object with scalar type and automatic storage duration
5510 6 A translator is free to ignore any or all aliasing implications of uses of restrict.
5511 7 EXAMPLE 1 The file scope declarations
5515 assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
5516 program, then it is never accessed using either of the other two.
5518 8 EXAMPLE 2 The function parameter declarations in the following example
5519 void f(int n, int * restrict p, int * restrict q)
5524 assert that, during each execution of the function, if an object is accessed through one of the pointer
5525 parameters, then it is not also accessed through the other.
5526 9 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence
5527 analysis of function f without examining any of the calls of f in the program. The cost is that the
5528 programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the
5529 second call of f in g has undefined behavior because each of d[1] through d[49] is accessed through
5534 f(50, d + 50, d); // valid
5535 f(50, d + 1, d); // undefined behavior
5538 10 EXAMPLE 3 The function parameter declarations
5539 void h(int n, int * restrict p, int * restrict q, int * restrict r)
5542 for (i = 0; i < n; i++)
5545 illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
5546 are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
5547 modified within function h.
5549 11 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a
5550 function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments
5552 [<a name="#p122" href="p122">page 122</a>] (<a href="#Contents">Contents</a>)
5554 between restricted pointers declared in nested blocks have defined behavior.
5558 p1 = q1; // undefined behavior
5560 int * restrict p2 = p1; // valid
5561 int * restrict q2 = q1; // valid
5562 p1 = q2; // undefined behavior
5563 p2 = q2; // undefined behavior
5566 12 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more
5567 precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For
5568 example, this permits new_vector to return a vector.
5569 typedef struct { int n; float * restrict v; } vector;
5570 vector new_vector(int n)
5574 t.v = malloc(n * sizeof (float));
5578 <a name="6.7.4" href="#6.7.4"><b> 6.7.4 Function specifiers</b></a>
5580 1 function-specifier:
5584 2 Function specifiers shall be used only in the declaration of an identifier for a function.
5585 3 An inline definition of a function with external linkage shall not contain a definition of a
5586 modifiable object with static or thread storage duration, and shall not contain a reference
5587 to an identifier with internal linkage.
5588 4 In a hosted environment, no function specifier(s) shall appear in a declaration of main.
5590 5 A function specifier may appear more than once; the behavior is the same as if it
5592 6 A function declared with an inline function specifier is an inline function. Making a
5593 function an inline function suggests that calls to the function be as fast as possible.137)
5594 The extent to which such suggestions are effective is implementation-defined.138)
5596 [<a name="#p123" href="p123">page 123</a>] (<a href="#Contents">Contents</a>)
5598 7 Any function with internal linkage can be an inline function. For a function with external
5599 linkage, the following restrictions apply: If a function is declared with an inline
5600 function specifier, then it shall also be defined in the same translation unit. If all of the
5601 file scope declarations for a function in a translation unit include the inline function
5602 specifier without extern, then the definition in that translation unit is an inline
5603 definition. An inline definition does not provide an external definition for the function,
5604 and does not forbid an external definition in another translation unit. An inline definition
5605 provides an alternative to an external definition, which a translator may use to implement
5606 any call to the function in the same translation unit. It is unspecified whether a call to the
5607 function uses the inline definition or the external definition.139)
5608 8 A function declared with a _Noreturn function specifier shall not return to its caller.
5609 Recommended practice
5610 9 The implementation should produce a diagnostic message for a function declared with a
5611 _Noreturn function specifier that appears to be capable of returning to its caller.
5612 10 EXAMPLE 1 The declaration of an inline function with external linkage can result in either an external
5613 definition, or a definition available for use only within the translation unit. A file scope declaration with
5614 extern creates an external definition. The following example shows an entire translation unit.
5615 inline double fahr(double t)
5617 return (<a href="#9.0">9.0</a> * t) / <a href="#5.0">5.0</a> + 32.0;
5619 inline double cels(double t)
5621 return (<a href="#5.0">5.0</a> * (t - 32.0)) / <a href="#9.0">9.0</a>;
5623 extern double fahr(double); // creates an external definition
5628 137) By using, for example, an alternative to the usual function call mechanism, such as ''inline
5629 substitution''. Inline substitution is not textual substitution, nor does it create a new function.
5630 Therefore, for example, the expansion of a macro used within the body of the function uses the
5631 definition it had at the point the function body appears, and not where the function is called; and
5632 identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a
5633 single address, regardless of the number of inline definitions that occur in addition to the external
5635 138) For example, an implementation might never perform inline substitution, or might only perform inline
5636 substitutions to calls in the scope of an inline declaration.
5637 139) Since an inline definition is distinct from the corresponding external definition and from any other
5638 corresponding inline definitions in other translation units, all corresponding objects with static storage
5639 duration are also distinct in each of the definitions.
5641 [<a name="#p124" href="p124">page 124</a>] (<a href="#Contents">Contents</a>)
5643 double convert(int is_fahr, double temp)
5645 /* A translator may perform inline substitutions */
5646 return is_fahr ? cels(temp) : fahr(temp);
5648 11 Note that the definition of fahr is an external definition because fahr is also declared with extern, but
5649 the definition of cels is an inline definition. Because cels has external linkage and is referenced, an
5650 external definition has to appear in another translation unit (see <a href="#6.9">6.9</a>); the inline definition and the external
5651 definition are distinct and either may be used for the call.
5654 _Noreturn void f () {
5657 _Noreturn void g (int i) { // causes undefined behavior if i <= 0
5658 if (i > 0) abort();
5661 Forward references: function definitions (<a href="#6.9.1">6.9.1</a>).
5662 <a name="6.7.5" href="#6.7.5"><b> 6.7.5 Alignment specifier</b></a>
5664 1 alignment-specifier:
5665 _Alignas ( type-name )
5666 _Alignas ( constant-expression )
5668 2 An alignment attribute shall not be specified in a declaration of a typedef, or a bit-field, or
5669 a function, or a parameter, or an object declared with the register storage-class
5671 3 The constant expression shall be an integer constant expression. It shall evaluate to a
5672 valid fundamental alignment, or to a valid extended alignment supported by the
5673 implementation in the context in which it appears, or to zero.
5674 4 The combined effect of all alignment attributes in a declaration shall not specify an
5675 alignment that is less strict than the alignment that would otherwise be required for the
5676 type of the object or field being declared.
5678 5 The first form is equivalent to _Alignas(alignof(type-name)).
5679 6 The alignment requirement of the declared object or field is taken to be the specified
5680 alignment. An alignment specification of zero has no effect.140) When multiple
5681 alignment specifiers occur in a declaration, the effective alignment requirement is the
5682 strictest specified alignment.
5684 [<a name="#p125" href="p125">page 125</a>] (<a href="#Contents">Contents</a>)
5686 7 If the definition of an object has an alignment specifier, any other declaration of that
5687 object shall either specify equivalent alignment or have no alignment specifier. If the
5688 definition of an object does not have an alignment specifier, any other declaration of that
5689 object shall also have no alignment specifier. If declarations of an object in different
5690 translation units have different alignment specifiers, the behavior is undefined.
5691 <a name="6.7.6" href="#6.7.6"><b> 6.7.6 Declarators</b></a>
5694 pointeropt direct-declarator
5698 direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
5699 direct-declarator [ static type-qualifier-listopt assignment-expression ]
5700 direct-declarator [ type-qualifier-list static assignment-expression ]
5701 direct-declarator [ type-qualifier-listopt * ]
5702 direct-declarator ( parameter-type-list )
5703 direct-declarator ( identifier-listopt )
5705 * type-qualifier-listopt
5706 * type-qualifier-listopt pointer
5707 type-qualifier-list:
5709 type-qualifier-list type-qualifier
5710 parameter-type-list:
5712 parameter-list , ...
5714 parameter-declaration
5715 parameter-list , parameter-declaration
5716 parameter-declaration:
5717 declaration-specifiers declarator
5718 declaration-specifiers abstract-declaratoropt
5722 140) An alignment specification of zero also does not affect other alignment specifications in the same
5725 [<a name="#p126" href="p126">page 126</a>] (<a href="#Contents">Contents</a>)
5729 identifier-list , identifier
5731 2 Each declarator declares one identifier, and asserts that when an operand of the same
5732 form as the declarator appears in an expression, it designates a function or object with the
5733 scope, storage duration, and type indicated by the declaration specifiers.
5734 3 A full declarator is a declarator that is not part of another declarator. The end of a full
5735 declarator is a sequence point. If, in the nested sequence of declarators in a full
5736 declarator, there is a declarator specifying a variable length array type, the type specified
5737 by the full declarator is said to be variably modified. Furthermore, any type derived by
5738 declarator type derivation from a variably modified type is itself variably modified.
5739 4 In the following subclauses, consider a declaration
5741 where T contains the declaration specifiers that specify a type T (such as int) and D1 is
5742 a declarator that contains an identifier ident. The type specified for the identifier ident in
5743 the various forms of declarator is described inductively using this notation.
5744 5 If, in the declaration ''T D1'', D1 has the form
5746 then the type specified for ident is T .
5747 6 If, in the declaration ''T D1'', D1 has the form
5749 then ident has the type specified by the declaration ''T D''. Thus, a declarator in
5750 parentheses is identical to the unparenthesized declarator, but the binding of complicated
5751 declarators may be altered by parentheses.
5752 Implementation limits
5753 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
5754 function declarators that modify an arithmetic, structure, union, or void type, either
5755 directly or via one or more typedefs.
5756 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>).
5761 [<a name="#p127" href="p127">page 127</a>] (<a href="#Contents">Contents</a>)
5763 <a name="6.7.6.1" href="#6.7.6.1"><b> 6.7.6.1 Pointer declarators</b></a>
5765 1 If, in the declaration ''T D1'', D1 has the form
5766 * type-qualifier-listopt D
5767 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5768 T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list
5769 pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer.
5770 2 For two pointer types to be compatible, both shall be identically qualified and both shall
5771 be pointers to compatible types.
5772 3 EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer
5773 to a constant value'' and a ''constant pointer to a variable value''.
5774 const int *ptr_to_constant;
5775 int *const constant_ptr;
5776 The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
5777 but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
5778 int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
5780 4 The declaration of the constant pointer constant_ptr may be clarified by including a definition for the
5781 type ''pointer to int''.
5782 typedef int *int_ptr;
5783 const int_ptr constant_ptr;
5784 declares constant_ptr as an object that has type ''const-qualified pointer to int''.
5786 <a name="6.7.6.2" href="#6.7.6.2"><b> 6.7.6.2 Array declarators</b></a>
5788 1 In addition to optional type qualifiers and the keyword static, the [ and ] may delimit
5789 an expression or *. If they delimit an expression (which specifies the size of an array), the
5790 expression shall have an integer type. If the expression is a constant expression, it shall
5791 have a value greater than zero. The element type shall not be an incomplete or function
5792 type. The optional type qualifiers and the keyword static shall appear only in a
5793 declaration of a function parameter with an array type, and then only in the outermost
5794 array type derivation.
5795 2 An ordinary identifier (as defined in <a href="#6.2.3">6.2.3</a>) that has a variably modified type shall have
5796 either block scope and no linkage or function prototype scope. If an identifier is declared
5797 to be an object with static or thread storage duration, it shall not have a variable length
5803 [<a name="#p128" href="p128">page 128</a>] (<a href="#Contents">Contents</a>)
5806 3 If, in the declaration ''T D1'', D1 has one of the forms:
5807 D[ type-qualifier-listopt assignment-expressionopt ]
5808 D[ static type-qualifier-listopt assignment-expression ]
5809 D[ type-qualifier-list static assignment-expression ]
5810 D[ type-qualifier-listopt * ]
5811 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5812 T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.141)
5813 (See <a href="#6.7.6.3">6.7.6.3</a> for the meaning of the optional type qualifiers and the keyword static.)
5814 4 If the size is not present, the array type is an incomplete type. If the size is * instead of
5815 being an expression, the array type is a variable length array type of unspecified size,
5816 which can only be used in declarations or type names with function prototype scope;142)
5817 such arrays are nonetheless complete types. If the size is an integer constant expression
5818 and the element type has a known constant size, the array type is not a variable length
5819 array type; otherwise, the array type is a variable length array type. (Variable length
5820 arrays are a conditional feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.)
5821 5 If the size is an expression that is not an integer constant expression: if it occurs in a
5822 declaration at function prototype scope, it is treated as if it were replaced by *; otherwise,
5823 each time it is evaluated it shall have a value greater than zero. The size of each instance
5824 of a variable length array type does not change during its lifetime. Where a size
5825 expression is part of the operand of a sizeof operator and changing the value of the
5826 size expression would not affect the result of the operator, it is unspecified whether or not
5827 the size expression is evaluated.
5828 6 For two array types to be compatible, both shall have compatible element types, and if
5829 both size specifiers are present, and are integer constant expressions, then both size
5830 specifiers shall have the same constant value. If the two array types are used in a context
5831 which requires them to be compatible, it is undefined behavior if the two size specifiers
5832 evaluate to unequal values.
5834 float fa[11], *afp[17];
5835 declares an array of float numbers and an array of pointers to float numbers.
5837 8 EXAMPLE 2 Note the distinction between the declarations
5842 141) When several ''array of'' specifications are adjacent, a multidimensional array is declared.
5843 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>).
5845 [<a name="#p129" href="p129">page 129</a>] (<a href="#Contents">Contents</a>)
5849 The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
5850 (an incomplete type), the storage for which is defined elsewhere.
5852 9 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
5860 int (*r)[n][n][n+1];
5861 p = a; // invalid: not compatible because 4 != 6
5862 r = c; // compatible, but defined behavior only if
5863 // n == 6 and m == n+1
5866 10 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or
5867 function prototype scope. Array objects declared with the _Thread_local, static, or extern
5868 storage-class specifier cannot have a variable length array (VLA) type. However, an object declared with
5869 the static storage-class specifier can have a VM type (that is, a pointer to a VLA type). Finally, all
5870 identifiers declared with a VM type have to be ordinary identifiers and cannot, therefore, be members of
5871 structures or unions.
5873 int A[n]; // invalid: file scope VLA
5874 extern int (*p2)[n]; // invalid: file scope VM
5875 int B[100]; // valid: file scope but not VM
5876 void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
5877 void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
5879 typedef int VLA[m][m]; // valid: block scope typedef VLA
5881 int (*y)[n]; // invalid: y not ordinary identifier
5882 int z[n]; // invalid: z not ordinary identifier
5884 int D[m]; // valid: auto VLA
5885 static int E[m]; // invalid: static block scope VLA
5886 extern int F[m]; // invalid: F has linkage and is VLA
5887 int (*s)[m]; // valid: auto pointer to VLA
5888 extern int (*r)[m]; // invalid: r has linkage and points to VLA
5889 static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
5892 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>),
5893 initialization (<a href="#6.7.9">6.7.9</a>).
5897 [<a name="#p130" href="p130">page 130</a>] (<a href="#Contents">Contents</a>)
5899 <a name="6.7.6.3" href="#6.7.6.3"><b> 6.7.6.3 Function declarators (including prototypes)</b></a>
5901 1 A function declarator shall not specify a return type that is a function type or an array
5903 2 The only storage-class specifier that shall occur in a parameter declaration is register.
5904 3 An identifier list in a function declarator that is not part of a definition of that function
5906 4 After adjustment, the parameters in a parameter type list in a function declarator that is
5907 part of a definition of that function shall not have incomplete type.
5909 5 If, in the declaration ''T D1'', D1 has the form
5910 D( parameter-type-list )
5912 D( identifier-listopt )
5913 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5914 T '', then the type specified for ident is ''derived-declarator-type-list function returning
5916 6 A parameter type list specifies the types of, and may declare identifiers for, the
5917 parameters of the function.
5918 7 A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to
5919 type'', where the type qualifiers (if any) are those specified within the [ and ] of the
5920 array type derivation. If the keyword static also appears within the [ and ] of the
5921 array type derivation, then for each call to the function, the value of the corresponding
5922 actual argument shall provide access to the first element of an array with at least as many
5923 elements as specified by the size expression.
5924 8 A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to
5925 function returning type'', as in <a href="#6.3.2.1">6.3.2.1</a>.
5926 9 If the list terminates with an ellipsis (, ...), no information about the number or types
5927 of the parameters after the comma is supplied.143)
5928 10 The special case of an unnamed parameter of type void as the only item in the list
5929 specifies that the function has no parameters.
5933 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
5934 correspond to the ellipsis.
5936 [<a name="#p131" href="p131">page 131</a>] (<a href="#Contents">Contents</a>)
5938 11 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a
5939 parameter name, it shall be taken as a typedef name.
5940 12 If the function declarator is not part of a definition of that function, parameters may have
5941 incomplete type and may use the [*] notation in their sequences of declarator specifiers
5942 to specify variable length array types.
5943 13 The storage-class specifier in the declaration specifiers for a parameter declaration, if
5944 present, is ignored unless the declared parameter is one of the members of the parameter
5945 type list for a function definition.
5946 14 An identifier list declares only the identifiers of the parameters of the function. An empty
5947 list in a function declarator that is part of a definition of that function specifies that the
5948 function has no parameters. The empty list in a function declarator that is not part of a
5949 definition of that function specifies that no information about the number or types of the
5950 parameters is supplied.144)
5951 15 For two function types to be compatible, both shall specify compatible return types.145)
5952 Moreover, the parameter type lists, if both are present, shall agree in the number of
5953 parameters and in use of the ellipsis terminator; corresponding parameters shall have
5954 compatible types. If one type has a parameter type list and the other type is specified by a
5955 function declarator that is not part of a function definition and that contains an empty
5956 identifier list, the parameter list shall not have an ellipsis terminator and the type of each
5957 parameter shall be compatible with the type that results from the application of the
5958 default argument promotions. If one type has a parameter type list and the other type is
5959 specified by a function definition that contains a (possibly empty) identifier list, both shall
5960 agree in the number of parameters, and the type of each prototype parameter shall be
5961 compatible with the type that results from the application of the default argument
5962 promotions to the type of the corresponding identifier. (In the determination of type
5963 compatibility and of a composite type, each parameter declared with function or array
5964 type is taken as having the adjusted type and each parameter declared with qualified type
5965 is taken as having the unqualified version of its declared type.)
5966 16 EXAMPLE 1 The declaration
5967 int f(void), *fip(), (*pfi)();
5968 declares a function f with no parameters returning an int, a function fip with no parameter specification
5969 returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an
5970 int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the
5971 declaration suggests, and the same construction in an expression requires, the calling of a function fip,
5972 and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the
5973 extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function
5976 144) See ''future language directions'' (<a href="#6.11.6">6.11.6</a>).
5977 145) If both function types are ''old style'', parameter types are not compared.
5979 [<a name="#p132" href="p132">page 132</a>] (<a href="#Contents">Contents</a>)
5981 designator, which is then used to call the function; it returns an int.
5982 17 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the
5983 declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either
5984 internal or external linkage (depending on what file scope declarations for these identifiers are visible), and
5985 the identifier of the pointer pfi has block scope and no linkage.
5987 18 EXAMPLE 2 The declaration
5988 int (*apfi[3])(int *x, int *y);
5989 declares an array apfi of three pointers to functions returning int. Each of these functions has two
5990 parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and
5991 go out of scope at the end of the declaration of apfi.
5993 19 EXAMPLE 3 The declaration
5994 int (*fpfi(int (*)(long), int))(int, ...);
5995 declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two
5996 parameters: a pointer to a function returning an int (with one parameter of type long int), and an int.
5997 The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more
5998 additional arguments of any type.
6000 20 EXAMPLE 4 The following prototype has a variably modified parameter.
6001 void addscalar(int n, int m,
6002 double a[n][n*m+300], double x);
6006 addscalar(4, 2, b, <a href="#2.17">2.17</a>);
6009 void addscalar(int n, int m,
6010 double a[n][n*m+300], double x)
6012 for (int i = 0; i < n; i++)
6013 for (int j = 0, k = n*m+300; j < k; j++)
6014 // a is a pointer to a VLA with n*m+300 elements
6018 21 EXAMPLE 5 The following are all compatible function prototype declarators.
6019 double maximum(int n, int m, double a[n][m]);
6020 double maximum(int n, int m, double a[*][*]);
6021 double maximum(int n, int m, double a[ ][*]);
6022 double maximum(int n, int m, double a[ ][m]);
6024 void f(double (* restrict a)[5]);
6025 void f(double a[restrict][5]);
6026 void f(double a[restrict 3][5]);
6027 void f(double a[restrict static 3][5]);
6030 [<a name="#p133" href="p133">page 133</a>] (<a href="#Contents">Contents</a>)
6032 (Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
6033 non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
6035 Forward references: function definitions (<a href="#6.9.1">6.9.1</a>), type names (<a href="#6.7.7">6.7.7</a>).
6036 <a name="6.7.7" href="#6.7.7"><b> 6.7.7 Type names</b></a>
6039 specifier-qualifier-list abstract-declaratoropt
6040 abstract-declarator:
6042 pointeropt direct-abstract-declarator
6043 direct-abstract-declarator:
6044 ( abstract-declarator )
6045 direct-abstract-declaratoropt [ type-qualifier-listopt
6046 assignment-expressionopt ]
6047 direct-abstract-declaratoropt [ static type-qualifier-listopt
6048 assignment-expression ]
6049 direct-abstract-declaratoropt [ type-qualifier-list static
6050 assignment-expression ]
6051 direct-abstract-declaratoropt [ * ]
6052 direct-abstract-declaratoropt ( parameter-type-listopt )
6054 2 In several contexts, it is necessary to specify a type. This is accomplished using a type
6055 name, which is syntactically a declaration for a function or an object of that type that
6056 omits the identifier.146)
6057 3 EXAMPLE The constructions
6065 (h) int (*const [])(unsigned int, ...)
6066 name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
6067 array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
6068 with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
6071 146) As indicated by the syntax, empty parentheses in a type name are interpreted as ''function with no
6072 parameter specification'', rather than redundant parentheses around the omitted identifier.
6074 [<a name="#p134" href="p134">page 134</a>] (<a href="#Contents">Contents</a>)
6076 returning an int, and (h) array of an unspecified number of constant pointers to functions, each with one
6077 parameter that has type unsigned int and an unspecified number of other parameters, returning an
6080 <a name="6.7.8" href="#6.7.8"><b> 6.7.8 Type definitions</b></a>
6085 2 If a typedef name specifies a variably modified type then it shall have block scope.
6087 3 In a declaration whose storage-class specifier is typedef, each declarator defines an
6088 identifier to be a typedef name that denotes the type specified for the identifier in the way
6089 described in <a href="#6.7.6">6.7.6</a>. Any array size expressions associated with variable length array
6090 declarators are evaluated each time the declaration of the typedef name is reached in the
6091 order of execution. A typedef declaration does not introduce a new type, only a
6092 synonym for the type so specified. That is, in the following declarations:
6093 typedef T type_ident;
6095 type_ident is defined as a typedef name with the type specified by the declaration
6096 specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
6097 type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
6098 typedef name shares the same name space as other identifiers declared in ordinary
6101 typedef int MILES, KLICKSP();
6102 typedef struct { double hi, lo; } range;
6105 extern KLICKSP *metricp;
6108 are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
6109 parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
6110 such a structure. The object distance has a type compatible with any other int object.
6112 5 EXAMPLE 2 After the declarations
6113 typedef struct s1 { int x; } t1, *tp1;
6114 typedef struct s2 { int x; } t2, *tp2;
6115 type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
6117 [<a name="#p135" href="p135">page 135</a>] (<a href="#Contents">Contents</a>)
6119 s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
6121 6 EXAMPLE 3 The following obscure constructions
6122 typedef signed int t;
6129 declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
6130 with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
6131 qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
6132 [-16, +15], and one named r that contains values in one of the ranges [0, 31], [-15, +15], or [-16, +15].
6133 (The choice of range is implementation-defined.) The first two bit-field declarations differ in that
6134 unsigned is a type specifier (which forces t to be the name of a structure member), while const is a
6135 type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed
6136 in an inner scope by
6139 then a function f is declared with type ''function returning signed int with one unnamed parameter
6140 with type pointer to function returning signed int with one unnamed parameter with type signed
6141 int'', and an identifier t with type long int.
6143 7 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the
6144 following declarations of the signal function specify exactly the same type, the first without making use
6145 of any typedef names.
6146 typedef void fv(int), (*pfv)(int);
6147 void (*signal(int, void (*)(int)))(int);
6148 fv *signal(int, fv *);
6149 pfv signal(int, pfv);
6151 8 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the
6152 time the typedef name is defined, not each time it is used:
6155 typedef int B[n]; // B is n ints, n evaluated now
6157 B a; // a is n ints, n without += 1
6158 int b[n]; // a and b are different sizes
6159 for (int i = 1; i < n; i++)
6166 [<a name="#p136" href="p136">page 136</a>] (<a href="#Contents">Contents</a>)
6168 <a name="6.7.9" href="#6.7.9"><b> 6.7.9 Initialization</b></a>
6171 assignment-expression
6172 { initializer-list }
6173 { initializer-list , }
6175 designationopt initializer
6176 initializer-list , designationopt initializer
6181 designator-list designator
6183 [ constant-expression ]
6186 2 No initializer shall attempt to provide a value for an object not contained within the entity
6188 3 The type of the entity to be initialized shall be an array of unknown size or a complete
6189 object type that is not a variable length array type.
6190 4 All the expressions in an initializer for an object that has static or thread storage duration
6191 shall be constant expressions or string literals.
6192 5 If the declaration of an identifier has block scope, and the identifier has external or
6193 internal linkage, the declaration shall have no initializer for the identifier.
6194 6 If a designator has the form
6195 [ constant-expression ]
6196 then the current object (defined below) shall have array type and the expression shall be
6197 an integer constant expression. If the array is of unknown size, any nonnegative value is
6199 7 If a designator has the form
6201 then the current object (defined below) shall have structure or union type and the
6202 identifier shall be the name of a member of that type.
6203 [<a name="#p137" href="p137">page 137</a>] (<a href="#Contents">Contents</a>)
6206 8 An initializer specifies the initial value stored in an object.
6207 9 Except where explicitly stated otherwise, for the purposes of this subclause unnamed
6208 members of objects of structure and union type do not participate in initialization.
6209 Unnamed members of structure objects have indeterminate value even after initialization.
6210 10 If an object that has automatic storage duration is not initialized explicitly, its value is
6211 indeterminate. If an object that has static or thread storage duration is not initialized
6213 -- if it has pointer type, it is initialized to a null pointer;
6214 -- if it has arithmetic type, it is initialized to (positive or unsigned) zero;
6215 -- if it is an aggregate, every member is initialized (recursively) according to these rules,
6216 and any padding is initialized to zero bits;
6217 -- if it is a union, the first named member is initialized (recursively) according to these
6218 rules, and any padding is initialized to zero bits;
6219 11 The initializer for a scalar shall be a single expression, optionally enclosed in braces. The
6220 initial value of the object is that of the expression (after conversion); the same type
6221 constraints and conversions as for simple assignment apply, taking the type of the scalar
6222 to be the unqualified version of its declared type.
6223 12 The rest of this subclause deals with initializers for objects that have aggregate or union
6225 13 The initializer for a structure or union object that has automatic storage duration shall be
6226 either an initializer list as described below, or a single expression that has compatible
6227 structure or union type. In the latter case, the initial value of the object, including
6228 unnamed members, is that of the expression.
6229 14 An array of character type may be initialized by a character string literal or UTF-8 string
6230 literal, optionally enclosed in braces. Successive bytes of the string literal (including the
6231 terminating null character if there is room or if the array is of unknown size) initialize the
6232 elements of the array.
6233 15 An array with element type compatible with a qualified or unqualified version of
6234 wchar_t may be initialized by a wide string literal, optionally enclosed in braces.
6235 Successive wide characters of the wide string literal (including the terminating null wide
6236 character if there is room or if the array is of unknown size) initialize the elements of the
6238 16 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-
6239 enclosed list of initializers for the elements or named members.
6242 [<a name="#p138" href="p138">page 138</a>] (<a href="#Contents">Contents</a>)
6244 17 Each brace-enclosed initializer list has an associated current object. When no
6245 designations are present, subobjects of the current object are initialized in order according
6246 to the type of the current object: array elements in increasing subscript order, structure
6247 members in declaration order, and the first named member of a union.147) In contrast, a
6248 designation causes the following initializer to begin initialization of the subobject
6249 described by the designator. Initialization then continues forward in order, beginning
6250 with the next subobject after that described by the designator.148)
6251 18 Each designator list begins its description with the current object associated with the
6252 closest surrounding brace pair. Each item in the designator list (in order) specifies a
6253 particular member of its current object and changes the current object for the next
6254 designator (if any) to be that member.149) The current object that results at the end of the
6255 designator list is the subobject to be initialized by the following initializer.
6256 19 The initialization shall occur in initializer list order, each initializer provided for a
6257 particular subobject overriding any previously listed initializer for the same subobject;150)
6258 all subobjects that are not initialized explicitly shall be initialized implicitly the same as
6259 objects that have static storage duration.
6260 20 If the aggregate or union contains elements or members that are aggregates or unions,
6261 these rules apply recursively to the subaggregates or contained unions. If the initializer of
6262 a subaggregate or contained union begins with a left brace, the initializers enclosed by
6263 that brace and its matching right brace initialize the elements or members of the
6264 subaggregate or the contained union. Otherwise, only enough initializers from the list are
6265 taken to account for the elements or members of the subaggregate or the first member of
6266 the contained union; any remaining initializers are left to initialize the next element or
6267 member of the aggregate of which the current subaggregate or contained union is a part.
6268 21 If there are fewer initializers in a brace-enclosed list than there are elements or members
6269 of an aggregate, or fewer characters in a string literal used to initialize an array of known
6270 size than there are elements in the array, the remainder of the aggregate shall be
6271 initialized implicitly the same as objects that have static storage duration.
6275 147) If the initializer list for a subaggregate or contained union does not begin with a left brace, its
6276 subobjects are initialized as usual, but the subaggregate or contained union does not become the
6277 current object: current objects are associated only with brace-enclosed initializer lists.
6278 148) After a union member is initialized, the next object is not the next member of the union; instead, it is
6279 the next subobject of an object containing the union.
6280 149) Thus, a designator can only specify a strict subobject of the aggregate or union that is associated with
6281 the surrounding brace pair. Note, too, that each separate designator list is independent.
6282 150) Any initializer for the subobject which is overridden and so not used to initialize that subobject might
6283 not be evaluated at all.
6285 [<a name="#p139" href="p139">page 139</a>] (<a href="#Contents">Contents</a>)
6287 22 If an array of unknown size is initialized, its size is determined by the largest indexed
6288 element with an explicit initializer. The array type is completed at the end of its
6290 23 The order in which any side effects occur among the initialization list expressions is
6292 24 EXAMPLE 1 Provided that <a href="#7.3"><complex.h></a> has been #included, the declarations
6293 int i = <a href="#3.5">3.5</a>;
6294 double complex c = 5 + 3 * I;
6295 define and initialize i with the value 3 and c with the value <a href="#5.0">5.0</a> + i3.0.
6297 25 EXAMPLE 2 The declaration
6298 int x[] = { 1, 3, 5 };
6299 defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
6300 and there are three initializers.
6302 26 EXAMPLE 3 The declaration
6308 is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
6309 y[0]), namely y[0][0], y[0][1], and y[0][2]. Likewise the next two lines initialize y[1] and
6310 y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
6313 1, 3, 5, 2, 4, 6, 3, 5, 7
6315 The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
6316 next three are taken successively for y[1] and y[2].
6318 27 EXAMPLE 4 The declaration
6320 { 1 }, { 2 }, { 3 }, { 4 }
6322 initializes the first column of z as specified and initializes the rest with zeros.
6324 28 EXAMPLE 5 The declaration
6325 struct { int a[3], b; } w[] = { { 1 }, 2 };
6326 is a definition with an inconsistently bracketed initialization. It defines an array with two element
6327 structures: w[0].a[0] is 1 and w[1].a[0] is 2; all the other elements are zero.
6331 151) In particular, the evaluation order need not be the same as the order of subobject initialization.
6333 [<a name="#p140" href="p140">page 140</a>] (<a href="#Contents">Contents</a>)
6335 29 EXAMPLE 6 The declaration
6336 short q[4][3][2] = {
6341 contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
6342 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
6343 q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
6344 q[0][0] does not begin with a left brace, so up to six items from the current list may be used. There is
6345 only one, so the values for the remaining five elements are initialized with zero. Likewise, the initializers
6346 for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their
6347 respective two-dimensional subaggregates. If there had been more than six items in any of the lists, a
6348 diagnostic message would have been issued. The same initialization result could have been achieved by:
6349 short q[4][3][2] = {
6355 short q[4][3][2] = {
6367 in a fully bracketed form.
6368 30 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
6371 31 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the
6373 typedef int A[]; // OK - declared with block scope
6375 A a = { 1, 2 }, b = { 3, 4, 5 };
6377 int a[] = { 1, 2 }, b[] = { 3, 4, 5 };
6378 due to the rules for incomplete types.
6382 [<a name="#p141" href="p141">page 141</a>] (<a href="#Contents">Contents</a>)
6384 32 EXAMPLE 8 The declaration
6385 char s[] = "abc", t[3] = "abc";
6386 defines ''plain'' char array objects s and t whose elements are initialized with character string literals.
6387 This declaration is identical to
6388 char s[] = { 'a', 'b', 'c', '\0' },
6389 t[] = { 'a', 'b', 'c' };
6390 The contents of the arrays are modifiable. On the other hand, the declaration
6392 defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char''
6393 with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to
6394 modify the contents of the array, the behavior is undefined.
6396 33 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using
6398 enum { member_one, member_two };
6399 const char *nm[] = {
6400 [member_two] = "member two",
6401 [member_one] = "member one",
6404 34 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
6405 div_t answer = { .quot = 2, .rem = -1 };
6407 35 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
6408 might be misunderstood:
6409 struct { int a[3], b; } w[] =
6410 { [0].a = {1}, [1].a[0] = 2 };
6412 36 EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator:
6414 1, 3, 5, 7, 9, [MAX-5] = 8, 6, 4, 2, 0
6416 37 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less
6417 than ten, some of the values provided by the first five initializers will be overridden by the second five.
6419 38 EXAMPLE 13 Any member of a union can be initialized:
6420 union { /* ... */ } u = { .any_member = 42 };
6422 Forward references: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>).
6427 [<a name="#p142" href="p142">page 142</a>] (<a href="#Contents">Contents</a>)
6429 <a name="6.7.10" href="#6.7.10"><b> 6.7.10 Static assertions</b></a>
6431 1 static_assert-declaration:
6432 _Static_assert ( constant-expression , string-literal ) ;
6434 2 The constant expression shall compare unequal to 0.
6436 3 The constant expression shall be an integer constant expression. If the value of the
6437 constant expression compares unequal to 0, the declaration has no effect. Otherwise, the
6438 constraint is violated and the implementation shall produce a diagnostic message that
6439 includes the text of the string literal, except that characters not in the basic source
6440 character set are not required to appear in the message.
6441 Forward references: diagnostics (<a href="#7.2">7.2</a>).
6446 [<a name="#p143" href="p143">page 143</a>] (<a href="#Contents">Contents</a>)
6448 <a name="6.8" href="#6.8"><b> 6.8 Statements and blocks</b></a>
6453 expression-statement
6458 2 A statement specifies an action to be performed. Except as indicated, statements are
6459 executed in sequence.
6460 3 A block allows a set of declarations and statements to be grouped into one syntactic unit.
6461 The initializers of objects that have automatic storage duration, and the variable length
6462 array declarators of ordinary identifiers with block scope, are evaluated and the values are
6463 stored in the objects (including storing an indeterminate value in objects without an
6464 initializer) each time the declaration is reached in the order of execution, as if it were a
6465 statement, and within each declaration in the order that declarators appear.
6466 4 A full expression is an expression that is not part of another expression or of a declarator.
6467 Each of the following is a full expression: an initializer that is not part of a compound
6468 literal; the expression in an expression statement; the controlling expression of a selection
6469 statement (if or switch); the controlling expression of a while or do statement; each
6470 of the (optional) expressions of a for statement; the (optional) expression in a return
6471 statement. There is a sequence point between the evaluation of a full expression and the
6472 evaluation of the next full expression to be evaluated.
6473 Forward references: expression and null statements (<a href="#6.8.3">6.8.3</a>), selection statements
6474 (<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>).
6475 <a name="6.8.1" href="#6.8.1"><b> 6.8.1 Labeled statements</b></a>
6477 1 labeled-statement:
6478 identifier : statement
6479 case constant-expression : statement
6482 2 A case or default label shall appear only in a switch statement. Further
6483 constraints on such labels are discussed under the switch statement.
6485 [<a name="#p144" href="p144">page 144</a>] (<a href="#Contents">Contents</a>)
6487 3 Label names shall be unique within a function.
6489 4 Any statement may be preceded by a prefix that declares an identifier as a label name.
6490 Labels in themselves do not alter the flow of control, which continues unimpeded across
6492 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>).
6493 <a name="6.8.2" href="#6.8.2"><b> 6.8.2 Compound statement</b></a>
6495 1 compound-statement:
6496 { block-item-listopt }
6499 block-item-list block-item
6504 2 A compound statement is a block.
6505 <a name="6.8.3" href="#6.8.3"><b> 6.8.3 Expression and null statements</b></a>
6507 1 expression-statement:
6510 2 The expression in an expression statement is evaluated as a void expression for its side
6512 3 A null statement (consisting of just a semicolon) performs no operations.
6513 4 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the
6514 discarding of its value may be made explicit by converting the expression to a void expression by means of
6522 152) Such as assignments, and function calls which have side effects.
6524 [<a name="#p145" href="p145">page 145</a>] (<a href="#Contents">Contents</a>)
6526 5 EXAMPLE 2 In the program fragment
6529 while (*s++ != '\0')
6531 a null statement is used to supply an empty loop body to the iteration statement.
6533 6 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
6547 Forward references: iteration statements (<a href="#6.8.5">6.8.5</a>).
6548 <a name="6.8.4" href="#6.8.4"><b> 6.8.4 Selection statements</b></a>
6550 1 selection-statement:
6551 if ( expression ) statement
6552 if ( expression ) statement else statement
6553 switch ( expression ) statement
6555 2 A selection statement selects among a set of statements depending on the value of a
6556 controlling expression.
6557 3 A selection statement is a block whose scope is a strict subset of the scope of its
6558 enclosing block. Each associated substatement is also a block whose scope is a strict
6559 subset of the scope of the selection statement.
6560 <a name="6.8.4.1" href="#6.8.4.1"><b> 6.8.4.1 The if statement</b></a>
6562 1 The controlling expression of an if statement shall have scalar type.
6564 2 In both forms, the first substatement is executed if the expression compares unequal to 0.
6565 In the else form, the second substatement is executed if the expression compares equal
6568 [<a name="#p146" href="p146">page 146</a>] (<a href="#Contents">Contents</a>)
6570 to 0. If the first substatement is reached via a label, the second substatement is not
6572 3 An else is associated with the lexically nearest preceding if that is allowed by the
6574 <a name="6.8.4.2" href="#6.8.4.2"><b> 6.8.4.2 The switch statement</b></a>
6576 1 The controlling expression of a switch statement shall have integer type.
6577 2 If a switch statement has an associated case or default label within the scope of an
6578 identifier with a variably modified type, the entire switch statement shall be within the
6579 scope of that identifier.153)
6580 3 The expression of each case label shall be an integer constant expression and no two of
6581 the case constant expressions in the same switch statement shall have the same value
6582 after conversion. There may be at most one default label in a switch statement.
6583 (Any enclosed switch statement may have a default label or case constant
6584 expressions with values that duplicate case constant expressions in the enclosing
6587 4 A switch statement causes control to jump to, into, or past the statement that is the
6588 switch body, depending on the value of a controlling expression, and on the presence of a
6589 default label and the values of any case labels on or in the switch body. A case or
6590 default label is accessible only within the closest enclosing switch statement.
6591 5 The integer promotions are performed on the controlling expression. The constant
6592 expression in each case label is converted to the promoted type of the controlling
6593 expression. If a converted value matches that of the promoted controlling expression,
6594 control jumps to the statement following the matched case label. Otherwise, if there is
6595 a default label, control jumps to the labeled statement. If no converted case constant
6596 expression matches and there is no default label, no part of the switch body is
6598 Implementation limits
6599 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
6605 153) That is, the declaration either precedes the switch statement, or it follows the last case or
6606 default label associated with the switch that is in the block containing the declaration.
6608 [<a name="#p147" href="p147">page 147</a>] (<a href="#Contents">Contents</a>)
6610 7 EXAMPLE In the artificial program fragment
6617 /* falls through into default code */
6621 the object whose identifier is i exists with automatic storage duration (within the block) but is never
6622 initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
6623 access an indeterminate value. Similarly, the call to the function f cannot be reached.
6625 <a name="6.8.5" href="#6.8.5"><b> 6.8.5 Iteration statements</b></a>
6627 1 iteration-statement:
6628 while ( expression ) statement
6629 do statement while ( expression ) ;
6630 for ( expressionopt ; expressionopt ; expressionopt ) statement
6631 for ( declaration expressionopt ; expressionopt ) statement
6633 2 The controlling expression of an iteration statement shall have scalar type.
6634 3 The declaration part of a for statement shall only declare identifiers for objects having
6635 storage class auto or register.
6637 4 An iteration statement causes a statement called the loop body to be executed repeatedly
6638 until the controlling expression compares equal to 0. The repetition occurs regardless of
6639 whether the loop body is entered from the iteration statement or by a jump.154)
6640 5 An iteration statement is a block whose scope is a strict subset of the scope of its
6641 enclosing block. The loop body is also a block whose scope is a strict subset of the scope
6642 of the iteration statement.
6643 6 An iteration statement that performs no input/output operations, does not access volatile
6644 objects, and performs no synchronization or atomic operations in its body, controlling
6645 expression, or (in the case of a for statement) its expression-3, may be assumed by the
6646 implementation to terminate.155)
6648 154) Code jumped over is not executed. In particular, the controlling expression of a for or while
6649 statement is not evaluated before entering the loop body, nor is clause-1 of a for statement.
6651 [<a name="#p148" href="p148">page 148</a>] (<a href="#Contents">Contents</a>)
6653 <a name="6.8.5.1" href="#6.8.5.1"><b> 6.8.5.1 The while statement</b></a>
6654 1 The evaluation of the controlling expression takes place before each execution of the loop
6656 <a name="6.8.5.2" href="#6.8.5.2"><b> 6.8.5.2 The do statement</b></a>
6657 1 The evaluation of the controlling expression takes place after each execution of the loop
6659 <a name="6.8.5.3" href="#6.8.5.3"><b> 6.8.5.3 The for statement</b></a>
6661 for ( clause-1 ; expression-2 ; expression-3 ) statement
6662 behaves as follows: The expression expression-2 is the controlling expression that is
6663 evaluated before each execution of the loop body. The expression expression-3 is
6664 evaluated as a void expression after each execution of the loop body. If clause-1 is a
6665 declaration, the scope of any identifiers it declares is the remainder of the declaration and
6666 the entire loop, including the other two expressions; it is reached in the order of execution
6667 before the first evaluation of the controlling expression. If clause-1 is an expression, it is
6668 evaluated as a void expression before the first evaluation of the controlling expression.156)
6669 2 Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a
6671 <a name="6.8.6" href="#6.8.6"><b> 6.8.6 Jump statements</b></a>
6677 return expressionopt ;
6679 2 A jump statement causes an unconditional jump to another place.
6684 155) This is intended to allow compiler transformations such as removal of empty loops even when
6685 termination cannot be proven.
6686 156) Thus, clause-1 specifies initialization for the loop, possibly declaring one or more variables for use in
6687 the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration,
6688 such that execution of the loop continues until the expression compares equal to 0; and expression-3
6689 specifies an operation (such as incrementing) that is performed after each iteration.
6691 [<a name="#p149" href="p149">page 149</a>] (<a href="#Contents">Contents</a>)
6693 <a name="6.8.6.1" href="#6.8.6.1"><b> 6.8.6.1 The goto statement</b></a>
6695 1 The identifier in a goto statement shall name a label located somewhere in the enclosing
6696 function. A goto statement shall not jump from outside the scope of an identifier having
6697 a variably modified type to inside the scope of that identifier.
6699 2 A goto statement causes an unconditional jump to the statement prefixed by the named
6700 label in the enclosing function.
6701 3 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The
6702 following outline presents one possible approach to a problem based on these three assumptions:
6703 1. The general initialization code accesses objects only visible to the current function.
6704 2. The general initialization code is too large to warrant duplication.
6705 3. The code to determine the next operation is at the head of the loop. (To allow it to be reached by
6706 continue statements, for example.)
6710 // determine next operation
6712 if (need to reinitialize) {
6713 // reinitialize-only code
6716 // general initialization code
6720 // handle other operations
6727 [<a name="#p150" href="p150">page 150</a>] (<a href="#Contents">Contents</a>)
6729 4 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably
6730 modified types. A jump within the scope, however, is permitted.
6731 goto lab3; // invalid: going INTO scope of VLA.
6734 a[j] = <a href="#4.4">4.4</a>;
6736 a[j] = <a href="#3.3">3.3</a>;
6737 goto lab4; // valid: going WITHIN scope of VLA.
6738 a[j] = <a href="#5.5">5.5</a>;
6740 a[j] = <a href="#6.6">6.6</a>;
6742 goto lab4; // invalid: going INTO scope of VLA.
6744 <a name="6.8.6.2" href="#6.8.6.2"><b> 6.8.6.2 The continue statement</b></a>
6746 1 A continue statement shall appear only in or as a loop body.
6748 2 A continue statement causes a jump to the loop-continuation portion of the smallest
6749 enclosing iteration statement; that is, to the end of the loop body. More precisely, in each
6751 while (/* ... */) { do { for (/* ... */) {
6752 /* ... */ /* ... */ /* ... */
6753 continue; continue; continue;
6754 /* ... */ /* ... */ /* ... */
6755 contin: ; contin: ; contin: ;
6756 } } while (/* ... */); }
6757 unless the continue statement shown is in an enclosed iteration statement (in which
6758 case it is interpreted within that statement), it is equivalent to goto contin;.157)
6759 <a name="6.8.6.3" href="#6.8.6.3"><b> 6.8.6.3 The break statement</b></a>
6761 1 A break statement shall appear only in or as a switch body or loop body.
6763 2 A break statement terminates execution of the smallest enclosing switch or iteration
6768 157) Following the contin: label is a null statement.
6770 [<a name="#p151" href="p151">page 151</a>] (<a href="#Contents">Contents</a>)
6772 <a name="6.8.6.4" href="#6.8.6.4"><b> 6.8.6.4 The return statement</b></a>
6774 1 A return statement with an expression shall not appear in a function whose return type
6775 is void. A return statement without an expression shall only appear in a function
6776 whose return type is void.
6778 2 A return statement terminates execution of the current function and returns control to
6779 its caller. A function may have any number of return statements.
6780 3 If a return statement with an expression is executed, the value of the expression is
6781 returned to the caller as the value of the function call expression. If the expression has a
6782 type different from the return type of the function in which it appears, the value is
6783 converted as if by assignment to an object having the return type of the function.158)
6785 struct s { double i; } f(void);
6802 there is no undefined behavior, although there would be if the assignment were done directly (without using
6803 a function call to fetch the value).
6808 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
6809 apply to the case of function return. The representation of floating-point values may have wider range
6810 or precision than implied by the type; a cast may be used to remove this extra range and precision.
6812 [<a name="#p152" href="p152">page 152</a>] (<a href="#Contents">Contents</a>)
6814 <a name="6.9" href="#6.9"><b> 6.9 External definitions</b></a>
6817 external-declaration
6818 translation-unit external-declaration
6819 external-declaration:
6823 2 The storage-class specifiers auto and register shall not appear in the declaration
6824 specifiers in an external declaration.
6825 3 There shall be no more than one external definition for each identifier declared with
6826 internal linkage in a translation unit. Moreover, if an identifier declared with internal
6827 linkage is used in an expression (other than as a part of the operand of a sizeof
6828 operator whose result is an integer constant), there shall be exactly one external definition
6829 for the identifier in the translation unit.
6831 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,
6832 which consists of a sequence of external declarations. These are described as ''external''
6833 because they appear outside any function (and hence have file scope). As discussed in
6834 <a href="#6.7">6.7</a>, a declaration that also causes storage to be reserved for an object or a function named
6835 by the identifier is a definition.
6836 5 An external definition is an external declaration that is also a definition of a function
6837 (other than an inline definition) or an object. If an identifier declared with external
6838 linkage is used in an expression (other than as part of the operand of a sizeof operator
6839 whose result is an integer constant), somewhere in the entire program there shall be
6840 exactly one external definition for the identifier; otherwise, there shall be no more than
6846 159) Thus, if an identifier declared with external linkage is not used in an expression, there need be no
6847 external definition for it.
6849 [<a name="#p153" href="p153">page 153</a>] (<a href="#Contents">Contents</a>)
6851 <a name="6.9.1" href="#6.9.1"><b> 6.9.1 Function definitions</b></a>
6853 1 function-definition:
6854 declaration-specifiers declarator declaration-listopt compound-statement
6857 declaration-list declaration
6859 2 The identifier declared in a function definition (which is the name of the function) shall
6860 have a function type, as specified by the declarator portion of the function definition.160)
6861 3 The return type of a function shall be void or a complete object type other than array
6863 4 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
6865 5 If the declarator includes a parameter type list, the declaration of each parameter shall
6866 include an identifier, except for the special case of a parameter list consisting of a single
6867 parameter of type void, in which case there shall not be an identifier. No declaration list
6869 6 If the declarator includes an identifier list, each declaration in the declaration list shall
6870 have at least one declarator, those declarators shall declare only identifiers from the
6871 identifier list, and every identifier in the identifier list shall be declared. An identifier
6872 declared as a typedef name shall not be redeclared as a parameter. The declarations in the
6873 declaration list shall contain no storage-class specifier other than register and no
6878 160) The intent is that the type category in a function definition cannot be inherited from a typedef:
6879 typedef int F(void); // type F is ''function with no parameters
6881 F f, g; // f and g both have type compatible with F
6882 F f { /* ... */ } // WRONG: syntax/constraint error
6883 F g() { /* ... */ } // WRONG: declares that g returns a function
6884 int f(void) { /* ... */ } // RIGHT: f has type compatible with F
6885 int g() { /* ... */ } // RIGHT: g has type compatible with F
6886 F *e(void) { /* ... */ } // e returns a pointer to a function
6887 F *((e))(void) { /* ... */ } // same: parentheses irrelevant
6888 int (*fp)(void); // fp points to a function that has type F
6889 F *Fp; // Fp points to a function that has type F
6892 [<a name="#p154" href="p154">page 154</a>] (<a href="#Contents">Contents</a>)
6895 7 The declarator in a function definition specifies the name of the function being defined
6896 and the identifiers of its parameters. If the declarator includes a parameter type list, the
6897 list also specifies the types of all the parameters; such a declarator also serves as a
6898 function prototype for later calls to the same function in the same translation unit. If the
6899 declarator includes an identifier list,161) the types of the parameters shall be declared in a
6900 following declaration list. In either case, the type of each parameter is adjusted as
6901 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
6903 8 If a function that accepts a variable number of arguments is defined without a parameter
6904 type list that ends with the ellipsis notation, the behavior is undefined.
6905 9 Each parameter has automatic storage duration; its identifier is an lvalue.162) The layout
6906 of the storage for parameters is unspecified.
6907 10 On entry to the function, the size expressions of each variably modified parameter are
6908 evaluated and the value of each argument expression is converted to the type of the
6909 corresponding parameter as if by assignment. (Array expressions and function
6910 designators as arguments were converted to pointers before the call.)
6911 11 After all parameters have been assigned, the compound statement that constitutes the
6912 body of the function definition is executed.
6913 12 If the } that terminates a function is reached, and the value of the function call is used by
6914 the caller, the behavior is undefined.
6915 13 EXAMPLE 1 In the following:
6916 extern int max(int a, int b)
6918 return a > b ? a : b;
6920 extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
6921 function declarator; and
6922 { return a > b ? a : b; }
6923 is the function body. The following similar definition uses the identifier-list form for the parameter
6929 161) See ''future language directions'' (<a href="#6.11.7">6.11.7</a>).
6930 162) A parameter identifier cannot be redeclared in the function body except in an enclosed block.
6932 [<a name="#p155" href="p155">page 155</a>] (<a href="#Contents">Contents</a>)
6934 extern int max(a, b)
6937 return a > b ? a : b;
6939 Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
6940 that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
6941 to the function, whereas the second form does not.
6943 14 EXAMPLE 2 To pass one function to another, one might say
6947 Then the definition of g might read
6948 void g(int (*funcp)(void))
6951 (*funcp)(); /* or funcp(); ... */
6954 void g(int func(void))
6957 func(); /* or (*func)(); ... */
6960 <a name="6.9.2" href="#6.9.2"><b> 6.9.2 External object definitions</b></a>
6962 1 If the declaration of an identifier for an object has file scope and an initializer, the
6963 declaration is an external definition for the identifier.
6964 2 A declaration of an identifier for an object that has file scope without an initializer, and
6965 without a storage-class specifier or with the storage-class specifier static, constitutes a
6966 tentative definition. If a translation unit contains one or more tentative definitions for an
6967 identifier, and the translation unit contains no external definition for that identifier, then
6968 the behavior is exactly as if the translation unit contains a file scope declaration of that
6969 identifier, with the composite type as of the end of the translation unit, with an initializer
6971 3 If the declaration of an identifier for an object is a tentative definition and has internal
6972 linkage, the declared type shall not be an incomplete type.
6977 [<a name="#p156" href="p156">page 156</a>] (<a href="#Contents">Contents</a>)
6980 int i1 = 1; // definition, external linkage
6981 static int i2 = 2; // definition, internal linkage
6982 extern int i3 = 3; // definition, external linkage
6983 int i4; // tentative definition, external linkage
6984 static int i5; // tentative definition, internal linkage
6985 int i1; // valid tentative definition, refers to previous
6986 int i2; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
6987 int i3; // valid tentative definition, refers to previous
6988 int i4; // valid tentative definition, refers to previous
6989 int i5; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
6990 extern int i1; // refers to previous, whose linkage is external
6991 extern int i2; // refers to previous, whose linkage is internal
6992 extern int i3; // refers to previous, whose linkage is external
6993 extern int i4; // refers to previous, whose linkage is external
6994 extern int i5; // refers to previous, whose linkage is internal
6996 5 EXAMPLE 2 If at the end of the translation unit containing
6998 the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to
6999 zero on program startup.
7004 [<a name="#p157" href="p157">page 157</a>] (<a href="#Contents">Contents</a>)
7006 <a name="6.10" href="#6.10"><b> 6.10 Preprocessing directives</b></a>
7008 1 preprocessing-file:
7019 if-group elif-groupsopt else-groupopt endif-line
7021 # if constant-expression new-line groupopt
7022 # ifdef identifier new-line groupopt
7023 # ifndef identifier new-line groupopt
7026 elif-groups elif-group
7028 # elif constant-expression new-line groupopt
7030 # else new-line groupopt
7037 [<a name="#p158" href="p158">page 158</a>] (<a href="#Contents">Contents</a>)
7040 # include pp-tokens new-line
7041 # define identifier replacement-list new-line
7042 # define identifier lparen identifier-listopt )
7043 replacement-list new-line
7044 # define identifier lparen ... ) replacement-list new-line
7045 # define identifier lparen identifier-list , ... )
7046 replacement-list new-line
7047 # undef identifier new-line
7048 # line pp-tokens new-line
7049 # error pp-tokensopt new-line
7050 # pragma pp-tokensopt new-line
7053 pp-tokensopt new-line
7057 a ( character not immediately preceded by white-space
7062 pp-tokens preprocessing-token
7064 the new-line character
7066 2 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the
7067 following constraints: The first token in the sequence is a # preprocessing token that (at
7068 the start of translation phase 4) is either the first character in the source file (optionally
7069 after white space containing no new-line characters) or that follows white space
7070 containing at least one new-line character. The last token in the sequence is the first new-
7071 line character that follows the first token in the sequence.163) A new-line character ends
7072 the preprocessing directive even if it occurs within what would otherwise be an
7074 163) Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic
7075 significance, as all white space is equivalent except in certain situations during preprocessing (see the
7076 # character string literal creation operator in <a href="#6.10.3.2">6.10.3.2</a>, for example).
7078 [<a name="#p159" href="p159">page 159</a>] (<a href="#Contents">Contents</a>)
7080 invocation of a function-like macro.
7081 3 A text line shall not begin with a # preprocessing token. A non-directive shall not begin
7082 with any of the directive names appearing in the syntax.
7083 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
7084 sequence of preprocessing tokens to occur between the directive name and the following
7087 5 The only white-space characters that shall appear between preprocessing tokens within a
7088 preprocessing directive (from just after the introducing # preprocessing token through
7089 just before the terminating new-line character) are space and horizontal-tab (including
7090 spaces that have replaced comments or possibly other white-space characters in
7091 translation phase 3).
7093 6 The implementation can process and skip sections of source files conditionally, include
7094 other source files, and replace macros. These capabilities are called preprocessing,
7095 because conceptually they occur before translation of the resulting translation unit.
7096 7 The preprocessing tokens within a preprocessing directive are not subject to macro
7097 expansion unless otherwise stated.
7100 EMPTY # include <file.h>
7101 the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
7102 begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
7105 <a name="6.10.1" href="#6.10.1"><b> 6.10.1 Conditional inclusion</b></a>
7107 1 The expression that controls conditional inclusion shall be an integer constant expression
7108 except that: identifiers (including those lexically identical to keywords) are interpreted as
7109 described below;164) and it may contain unary operator expressions of the form
7112 defined ( identifier )
7113 which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is
7116 164) Because the controlling constant expression is evaluated during translation phase 4, all identifiers
7117 either are or are not macro names -- there simply are no keywords, enumeration constants, etc.
7119 [<a name="#p160" href="p160">page 160</a>] (<a href="#Contents">Contents</a>)
7121 predefined or if it has been the subject of a #define preprocessing directive without an
7122 intervening #undef directive with the same subject identifier), 0 if it is not.
7123 2 Each preprocessing token that remains (in the list of preprocessing tokens that will
7124 become the controlling expression) after all macro replacements have occurred shall be in
7125 the lexical form of a token (<a href="#6.4">6.4</a>).
7127 3 Preprocessing directives of the forms
7128 # if constant-expression new-line groupopt
7129 # elif constant-expression new-line groupopt
7130 check whether the controlling constant expression evaluates to nonzero.
7131 4 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
7132 the controlling constant expression are replaced (except for those macro names modified
7133 by the defined unary operator), just as in normal text. If the token defined is
7134 generated as a result of this replacement process or use of the defined unary operator
7135 does not match one of the two specified forms prior to macro replacement, the behavior is
7136 undefined. After all replacements due to macro expansion and the defined unary
7137 operator have been performed, all remaining identifiers (including those lexically
7138 identical to keywords) are replaced with the pp-number 0, and then each preprocessing
7139 token is converted into a token. The resulting tokens compose the controlling constant
7140 expression which is evaluated according to the rules of <a href="#6.6">6.6</a>. For the purposes of this
7141 token conversion and evaluation, all signed integer types and all unsigned integer types
7142 act as if they have the same representation as, respectively, the types intmax_t and
7143 uintmax_t defined in the header <a href="#7.20"><stdint.h></a>.165) This includes interpreting
7144 character constants, which may involve converting escape sequences into execution
7145 character set members. Whether the numeric value for these character constants matches
7146 the value obtained when an identical character constant occurs in an expression (other
7147 than within a #if or #elif directive) is implementation-defined.166) Also, whether a
7148 single-character character constant may have a negative value is implementation-defined.
7153 165) Thus, on an implementation where INT_MAX is 0x7FFF and UINT_MAX is 0xFFFF, the constant
7154 0x8000 is signed and positive within a #if expression even though it would be unsigned in
7155 translation phase 7.
7156 166) Thus, the constant expression in the following #if directive and if statement is not guaranteed to
7157 evaluate to the same value in these two contexts.
7159 if ('z' - 'a' == 25)
7162 [<a name="#p161" href="p161">page 161</a>] (<a href="#Contents">Contents</a>)
7164 5 Preprocessing directives of the forms
7165 # ifdef identifier new-line groupopt
7166 # ifndef identifier new-line groupopt
7167 check whether the identifier is or is not currently defined as a macro name. Their
7168 conditions are equivalent to #if defined identifier and #if !defined identifier
7170 6 Each directive's condition is checked in order. If it evaluates to false (zero), the group
7171 that it controls is skipped: directives are processed only through the name that determines
7172 the directive in order to keep track of the level of nested conditionals; the rest of the
7173 directives' preprocessing tokens are ignored, as are the other preprocessing tokens in the
7174 group. Only the first group whose control condition evaluates to true (nonzero) is
7175 processed. If none of the conditions evaluates to true, and there is a #else directive, the
7176 group controlled by the #else is processed; lacking a #else directive, all the groups
7177 until the #endif are skipped.167)
7178 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
7179 integer types (<a href="#7.20.1.5">7.20.1.5</a>).
7180 <a name="6.10.2" href="#6.10.2"><b> 6.10.2 Source file inclusion</b></a>
7182 1 A #include directive shall identify a header or source file that can be processed by the
7185 2 A preprocessing directive of the form
7186 # include <h-char-sequence> new-line
7187 searches a sequence of implementation-defined places for a header identified uniquely by
7188 the specified sequence between the < and > delimiters, and causes the replacement of that
7189 directive by the entire contents of the header. How the places are specified or the header
7190 identified is implementation-defined.
7191 3 A preprocessing directive of the form
7192 # include "q-char-sequence" new-line
7193 causes the replacement of that directive by the entire contents of the source file identified
7194 by the specified sequence between the " delimiters. The named source file is searched
7197 167) As indicated by the syntax, a preprocessing token shall not follow a #else or #endif directive
7198 before the terminating new-line character. However, comments may appear anywhere in a source file,
7199 including within a preprocessing directive.
7201 [<a name="#p162" href="p162">page 162</a>] (<a href="#Contents">Contents</a>)
7203 for in an implementation-defined manner. If this search is not supported, or if the search
7204 fails, the directive is reprocessed as if it read
7205 # include <h-char-sequence> new-line
7206 with the identical contained sequence (including > characters, if any) from the original
7208 4 A preprocessing directive of the form
7209 # include pp-tokens new-line
7210 (that does not match one of the two previous forms) is permitted. The preprocessing
7211 tokens after include in the directive are processed just as in normal text. (Each
7212 identifier currently defined as a macro name is replaced by its replacement list of
7213 preprocessing tokens.) The directive resulting after all replacements shall match one of
7214 the two previous forms.168) The method by which a sequence of preprocessing tokens
7215 between a < and a > preprocessing token pair or a pair of " characters is combined into a
7216 single header name preprocessing token is implementation-defined.
7217 5 The implementation shall provide unique mappings for sequences consisting of one or
7218 more nondigits or digits (<a href="#6.4.2.1">6.4.2.1</a>) followed by a period (.) and a single nondigit. The
7219 first character shall not be a digit. The implementation may ignore distinctions of
7220 alphabetical case and restrict the mapping to eight significant characters before the
7222 6 A #include preprocessing directive may appear in a source file that has been read
7223 because of a #include directive in another file, up to an implementation-defined
7224 nesting limit (see <a href="#5.2.4.1">5.2.4.1</a>).
7225 7 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
7226 #include <a href="#7.21"><stdio.h></a>
7232 168) Note that adjacent string literals are not concatenated into a single string literal (see the translation
7233 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.
7235 [<a name="#p163" href="p163">page 163</a>] (<a href="#Contents">Contents</a>)
7237 8 EXAMPLE 2 This illustrates macro-replaced #include directives:
7239 #define INCFILE "vers1.h"
7241 #define INCFILE "vers2.h" // and so on
7243 #define INCFILE "versN.h"
7247 Forward references: macro replacement (<a href="#6.10.3">6.10.3</a>).
7248 <a name="6.10.3" href="#6.10.3"><b> 6.10.3 Macro replacement</b></a>
7250 1 Two replacement lists are identical if and only if the preprocessing tokens in both have
7251 the same number, ordering, spelling, and white-space separation, where all white-space
7252 separations are considered identical.
7253 2 An identifier currently defined as an object-like macro shall not be redefined by another
7254 #define preprocessing directive unless the second definition is an object-like macro
7255 definition and the two replacement lists are identical. Likewise, an identifier currently
7256 defined as a function-like macro shall not be redefined by another #define
7257 preprocessing directive unless the second definition is a function-like macro definition
7258 that has the same number and spelling of parameters, and the two replacement lists are
7260 3 There shall be white-space between the identifier and the replacement list in the definition
7261 of an object-like macro.
7262 4 If the identifier-list in the macro definition does not end with an ellipsis, the number of
7263 arguments (including those arguments consisting of no preprocessing tokens) in an
7264 invocation of a function-like macro shall equal the number of parameters in the macro
7265 definition. Otherwise, there shall be more arguments in the invocation than there are
7266 parameters in the macro definition (excluding the ...). There shall exist a )
7267 preprocessing token that terminates the invocation.
7268 5 The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like
7269 macro that uses the ellipsis notation in the parameters.
7270 6 A parameter identifier in a function-like macro shall be uniquely declared within its
7273 7 The identifier immediately following the define is called the macro name. There is one
7274 name space for macro names. Any white-space characters preceding or following the
7275 replacement list of preprocessing tokens are not considered part of the replacement list
7277 [<a name="#p164" href="p164">page 164</a>] (<a href="#Contents">Contents</a>)
7279 for either form of macro.
7280 8 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
7281 a preprocessing directive could begin, the identifier is not subject to macro replacement.
7282 9 A preprocessing directive of the form
7283 # define identifier replacement-list new-line
7284 defines an object-like macro that causes each subsequent instance of the macro name169)
7285 to be replaced by the replacement list of preprocessing tokens that constitute the
7286 remainder of the directive. The replacement list is then rescanned for more macro names
7288 10 A preprocessing directive of the form
7289 # define identifier lparen identifier-listopt ) replacement-list new-line
7290 # define identifier lparen ... ) replacement-list new-line
7291 # define identifier lparen identifier-list , ... ) replacement-list new-line
7292 defines a function-like macro with parameters, whose use is similar syntactically to a
7293 function call. The parameters are specified by the optional list of identifiers, whose scope
7294 extends from their declaration in the identifier list until the new-line character that
7295 terminates the #define preprocessing directive. Each subsequent instance of the
7296 function-like macro name followed by a ( as the next preprocessing token introduces the
7297 sequence of preprocessing tokens that is replaced by the replacement list in the definition
7298 (an invocation of the macro). The replaced sequence of preprocessing tokens is
7299 terminated by the matching ) preprocessing token, skipping intervening matched pairs of
7300 left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
7301 tokens making up an invocation of a function-like macro, new-line is considered a normal
7302 white-space character.
7303 11 The sequence of preprocessing tokens bounded by the outside-most matching parentheses
7304 forms the list of arguments for the function-like macro. The individual arguments within
7305 the list are separated by comma preprocessing tokens, but comma preprocessing tokens
7306 between matching inner parentheses do not separate arguments. If there are sequences of
7307 preprocessing tokens within the list of arguments that would otherwise act as
7308 preprocessing directives,170) the behavior is undefined.
7309 12 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
7310 including any separating comma preprocessing tokens, are merged to form a single item:
7313 169) Since, by macro-replacement time, all character constants and string literals are preprocessing tokens,
7314 not sequences possibly containing identifier-like subsequences (see <a href="#5.1.1.2">5.1.1.2</a>, translation phases), they
7315 are never scanned for macro names or parameters.
7316 170) Despite the name, a non-directive is a preprocessing directive.
7318 [<a name="#p165" href="p165">page 165</a>] (<a href="#Contents">Contents</a>)
7320 the variable arguments. The number of arguments so combined is such that, following
7321 merger, the number of arguments is one more than the number of parameters in the macro
7322 definition (excluding the ...).
7323 <a name="6.10.3.1" href="#6.10.3.1"><b> 6.10.3.1 Argument substitution</b></a>
7324 1 After the arguments for the invocation of a function-like macro have been identified,
7325 argument substitution takes place. A parameter in the replacement list, unless preceded
7326 by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
7327 replaced by the corresponding argument after all macros contained therein have been
7328 expanded. Before being substituted, each argument's preprocessing tokens are
7329 completely macro replaced as if they formed the rest of the preprocessing file; no other
7330 preprocessing tokens are available.
7331 2 An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
7332 were a parameter, and the variable arguments shall form the preprocessing tokens used to
7334 <a name="6.10.3.2" href="#6.10.3.2"><b> 6.10.3.2 The # operator</b></a>
7336 1 Each # preprocessing token in the replacement list for a function-like macro shall be
7337 followed by a parameter as the next preprocessing token in the replacement list.
7339 2 If, in the replacement list, a parameter is immediately preceded by a # preprocessing
7340 token, both are replaced by a single character string literal preprocessing token that
7341 contains the spelling of the preprocessing token sequence for the corresponding
7342 argument. Each occurrence of white space between the argument's preprocessing tokens
7343 becomes a single space character in the character string literal. White space before the
7344 first preprocessing token and after the last preprocessing token composing the argument
7345 is deleted. Otherwise, the original spelling of each preprocessing token in the argument
7346 is retained in the character string literal, except for special handling for producing the
7347 spelling of string literals and character constants: a \ character is inserted before each "
7348 and \ character of a character constant or string literal (including the delimiting "
7349 characters), except that it is implementation-defined whether a \ character is inserted
7350 before the \ character beginning a universal character name. If the replacement that
7351 results is not a valid character string literal, the behavior is undefined. The character
7352 string literal corresponding to an empty argument is "". The order of evaluation of # and
7353 ## operators is unspecified.
7358 [<a name="#p166" href="p166">page 166</a>] (<a href="#Contents">Contents</a>)
7360 <a name="6.10.3.3" href="#6.10.3.3"><b> 6.10.3.3 The ## operator</b></a>
7362 1 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
7363 list for either form of macro definition.
7365 2 If, in the replacement list of a function-like macro, a parameter is immediately preceded
7366 or followed by a ## preprocessing token, the parameter is replaced by the corresponding
7367 argument's preprocessing token sequence; however, if an argument consists of no
7368 preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
7370 3 For both object-like and function-like macro invocations, before the replacement list is
7371 reexamined for more macro names to replace, each instance of a ## preprocessing token
7372 in the replacement list (not from an argument) is deleted and the preceding preprocessing
7373 token is concatenated with the following preprocessing token. Placemarker
7374 preprocessing tokens are handled specially: concatenation of two placemarkers results in
7375 a single placemarker preprocessing token, and concatenation of a placemarker with a
7376 non-placemarker preprocessing token results in the non-placemarker preprocessing token.
7377 If the result is not a valid preprocessing token, the behavior is undefined. The resulting
7378 token is available for further macro replacement. The order of evaluation of ## operators
7380 4 EXAMPLE In the following fragment:
7381 #define hash_hash # ## #
7382 #define mkstr(a) # a
7383 #define in_between(a) mkstr(a)
7384 #define join(c, d) in_between(c hash_hash d)
7385 char p[] = join(x, y); // equivalent to
7386 // char p[] = "x ## y";
7387 The expansion produces, at various stages:
7389 in_between(x hash_hash y)
7393 In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
7394 this new token is not the ## operator.
7397 171) Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
7398 exist only within translation phase 4.
7400 [<a name="#p167" href="p167">page 167</a>] (<a href="#Contents">Contents</a>)
7402 <a name="6.10.3.4" href="#6.10.3.4"><b> 6.10.3.4 Rescanning and further replacement</b></a>
7403 1 After all parameters in the replacement list have been substituted and # and ##
7404 processing has taken place, all placemarker preprocessing tokens are removed. The
7405 resulting preprocessing token sequence is then rescanned, along with all subsequent
7406 preprocessing tokens of the source file, for more macro names to replace.
7407 2 If the name of the macro being replaced is found during this scan of the replacement list
7408 (not including the rest of the source file's preprocessing tokens), it is not replaced.
7409 Furthermore, if any nested replacements encounter the name of the macro being replaced,
7410 it is not replaced. These nonreplaced macro name preprocessing tokens are no longer
7411 available for further replacement even if they are later (re)examined in contexts in which
7412 that macro name preprocessing token would otherwise have been replaced.
7413 3 The resulting completely macro-replaced preprocessing token sequence is not processed
7414 as a preprocessing directive even if it resembles one, but all pragma unary operator
7415 expressions within it are then processed as specified in <a href="#6.10.9">6.10.9</a> below.
7416 <a name="6.10.3.5" href="#6.10.3.5"><b> 6.10.3.5 Scope of macro definitions</b></a>
7417 1 A macro definition lasts (independent of block structure) until a corresponding #undef
7418 directive is encountered or (if none is encountered) until the end of the preprocessing
7419 translation unit. Macro definitions have no significance after translation phase 4.
7420 2 A preprocessing directive of the form
7421 # undef identifier new-line
7422 causes the specified identifier no longer to be defined as a macro name. It is ignored if
7423 the specified identifier is not currently defined as a macro name.
7424 3 EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
7428 4 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments.
7429 It has the advantages of working for any compatible types of the arguments and of generating in-line code
7430 without the overhead of function calling. It has the disadvantages of evaluating one or the other of its
7431 arguments a second time (including side effects) and generating more code than a function if invoked
7432 several times. It also cannot have its address taken, as it has none.
7433 #define max(a, b) ((a) > (b) ? (a) : (b))
7434 The parentheses ensure that the arguments and the resulting expression are bound properly.
7439 [<a name="#p168" href="p168">page 168</a>] (<a href="#Contents">Contents</a>)
7441 5 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
7443 #define f(a) f(x * (a))
7454 #define r(x,y) x ## y
7456 f(y+1) + f(f(z)) % t(t(g)(0) + t)(1);
7457 g(x+(3,4)-w) | h 5) & m
7459 p() i[q()] = { q(1), r(2,3), r(4,), r(,5), r(,) };
7460 char c[2][6] = { str(hello), str() };
7462 f(2 * (y+1)) + f(2 * (f(2 * (z[0])))) % f(2 * (0)) + t(1);
7463 f(2 * (2+(3,4)-0,1)) | f(2 * (~ 5)) & f(2 * (0,1))^m(0,1);
7464 int i[] = { 1, 23, 4, 5, };
7465 char c[2][6] = { "hello", "" };
7467 6 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the
7470 #define xstr(s) str(s)
7471 #define debug(s, t) printf("x" # s "= %d, x" # t "= %s", \
7473 #define INCFILE(n) vers ## n
7474 #define glue(a, b) a ## b
7475 #define xglue(a, b) glue(a, b)
7476 #define HIGHLOW "hello"
7477 #define LOW LOW ", world"
7479 fputs(str(strncmp("abc\0d", "abc", '\4') // this goes away
7480 == 0) str(: @\n), s);
7481 #include xstr(INCFILE(2).h)
7489 [<a name="#p169" href="p169">page 169</a>] (<a href="#Contents">Contents</a>)
7491 printf("x" "1" "= %d, x" "2" "= %s", x1, x2);
7493 "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0" ": @\n",
7495 #include "vers2.h" (after macro replacement, before file access)
7498 or, after concatenation of the character string literals,
7499 printf("x1= %d, x2= %s", x1, x2);
7501 "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0: @\n",
7503 #include "vers2.h" (after macro replacement, before file access)
7506 Space around the # and ## tokens in the macro definition is optional.
7508 7 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
7509 #define t(x,y,z) x ## y ## z
7510 int j[] = { t(1,2,3), t(,4,5), t(6,,7), t(8,9,),
7511 t(10,,), t(,11,), t(,,12), t(,,) };
7513 int j[] = { 123, 45, 67, 89,
7516 8 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
7517 #define OBJ_LIKE (1-1)
7518 #define OBJ_LIKE /* white space */ (1-1) /* other */
7519 #define FUNC_LIKE(a) ( a )
7520 #define FUNC_LIKE( a )( /* note the white space */ \
7521 a /* other stuff on this line
7523 But the following redefinitions are invalid:
7524 #define OBJ_LIKE (0) // different token sequence
7525 #define OBJ_LIKE (1 - 1) // different white space
7526 #define FUNC_LIKE(b) ( a ) // different parameter usage
7527 #define FUNC_LIKE(b) ( b ) // different parameter spelling
7529 9 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
7530 #define debug(...) fprintf(stderr, __VA_ARGS__)
7531 #define showlist(...) puts(#__VA_ARGS__)
7532 #define report(test, ...) ((test)?puts(#test):\
7533 printf(__VA_ARGS__))
7535 debug("X = %d\n", x);
7536 showlist(The first, second, and third items.);
7537 report(x>y, "x is %d but y is %d", x, y);
7540 [<a name="#p170" href="p170">page 170</a>] (<a href="#Contents">Contents</a>)
7543 fprintf(stderr, "Flag" );
7544 fprintf(stderr, "X = %d\n", x );
7545 puts( "The first, second, and third items." );
7546 ((x>y)?puts("x>y"):
7547 printf("x is %d but y is %d", x, y));
7549 <a name="6.10.4" href="#6.10.4"><b> 6.10.4 Line control</b></a>
7551 1 The string literal of a #line directive, if present, shall be a character string literal.
7553 2 The line number of the current source line is one greater than the number of new-line
7554 characters read or introduced in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>) while processing the source
7555 file to the current token.
7556 3 A preprocessing directive of the form
7557 # line digit-sequence new-line
7558 causes the implementation to behave as if the following sequence of source lines begins
7559 with a source line that has a line number as specified by the digit sequence (interpreted as
7560 a decimal integer). The digit sequence shall not specify zero, nor a number greater than
7562 4 A preprocessing directive of the form
7563 # line digit-sequence "s-char-sequenceopt" new-line
7564 sets the presumed line number similarly and changes the presumed name of the source
7565 file to be the contents of the character string literal.
7566 5 A preprocessing directive of the form
7567 # line pp-tokens new-line
7568 (that does not match one of the two previous forms) is permitted. The preprocessing
7569 tokens after line on the directive are processed just as in normal text (each identifier
7570 currently defined as a macro name is replaced by its replacement list of preprocessing
7571 tokens). The directive resulting after all replacements shall match one of the two
7572 previous forms and is then processed as appropriate.
7577 [<a name="#p171" href="p171">page 171</a>] (<a href="#Contents">Contents</a>)
7579 <a name="6.10.5" href="#6.10.5"><b> 6.10.5 Error directive</b></a>
7581 1 A preprocessing directive of the form
7582 # error pp-tokensopt new-line
7583 causes the implementation to produce a diagnostic message that includes the specified
7584 sequence of preprocessing tokens.
7585 <a name="6.10.6" href="#6.10.6"><b> 6.10.6 Pragma directive</b></a>
7587 1 A preprocessing directive of the form
7588 # pragma pp-tokensopt new-line
7589 where the preprocessing token STDC does not immediately follow pragma in the
7590 directive (prior to any macro replacement)172) causes the implementation to behave in an
7591 implementation-defined manner. The behavior might cause translation to fail or cause the
7592 translator or the resulting program to behave in a non-conforming manner. Any such
7593 pragma that is not recognized by the implementation is ignored.
7594 2 If the preprocessing token STDC does immediately follow pragma in the directive (prior
7595 to any macro replacement), then no macro replacement is performed on the directive, and
7596 the directive shall have one of the following forms173) whose meanings are described
7598 #pragma STDC FP_CONTRACT on-off-switch
7599 #pragma STDC FENV_ACCESS on-off-switch
7600 #pragma STDC CX_LIMITED_RANGE on-off-switch
7601 on-off-switch: one of
7603 Forward references: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), the FENV_ACCESS pragma
7604 (<a href="#7.6.1">7.6.1</a>), the CX_LIMITED_RANGE pragma (<a href="#7.3.4">7.3.4</a>).
7609 172) An implementation is not required to perform macro replacement in pragmas, but it is permitted
7610 except for in standard pragmas (where STDC immediately follows pragma). If the result of macro
7611 replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still
7612 implementation-defined; an implementation is permitted to behave as if it were the standard pragma,
7613 but is not required to.
7614 173) See ''future language directions'' (<a href="#6.11.8">6.11.8</a>).
7616 [<a name="#p172" href="p172">page 172</a>] (<a href="#Contents">Contents</a>)
7618 <a name="6.10.7" href="#6.10.7"><b> 6.10.7 Null directive</b></a>
7620 1 A preprocessing directive of the form
7623 <a name="6.10.8" href="#6.10.8"><b> 6.10.8 Predefined macro names</b></a>
7624 1 The values of the predefined macros listed in the following subclauses174) (except for
7625 __FILE__ and __LINE__) remain constant throughout the translation unit.
7626 2 None of these macro names, nor the identifier defined, shall be the subject of a
7627 #define or a #undef preprocessing directive. Any other predefined macro names
7628 shall begin with a leading underscore followed by an uppercase letter or a second
7630 3 The implementation shall not predefine the macro __cplusplus, nor shall it define it
7631 in any standard header.
7632 Forward references: standard headers (<a href="#7.1.2">7.1.2</a>).
7633 <a name="6.10.8.1" href="#6.10.8.1"><b> 6.10.8.1 Mandatory macros</b></a>
7634 1 The following macro names shall be defined by the implementation:
7635 __DATE__ The date of translation of the preprocessing translation unit: a character
7636 string literal of the form "Mmm dd yyyy", where the names of the
7637 months are the same as those generated by the asctime function, and the
7638 first character of dd is a space character if the value is less than 10. If the
7639 date of translation is not available, an implementation-defined valid date
7641 __FILE__ The presumed name of the current source file (a character string literal).175)
7642 __LINE__ The presumed line number (within the current source file) of the current
7643 source line (an integer constant).175)
7644 __STDC__ The integer constant 1, intended to indicate a conforming implementation.
7645 __STDC_HOSTED__ The integer constant 1 if the implementation is a hosted
7646 implementation or the integer constant 0 if it is not.
7651 174) See ''future language directions'' (<a href="#6.11.9">6.11.9</a>).
7652 175) The presumed source file name and line number can be changed by the #line directive.
7654 [<a name="#p173" href="p173">page 173</a>] (<a href="#Contents">Contents</a>)
7656 __STDC_VERSION__ The integer constant 201ymmL.176)
7657 __TIME__ The time of translation of the preprocessing translation unit: a character
7658 string literal of the form "hh:mm:ss" as in the time generated by the
7659 asctime function. If the time of translation is not available, an
7660 implementation-defined valid time shall be supplied.
7661 Forward references: the asctime function (<a href="#7.26.3.1">7.26.3.1</a>).
7662 <a name="6.10.8.2" href="#6.10.8.2"><b> 6.10.8.2 Environment macros</b></a>
7663 1 The following macro names are conditionally defined by the implementation:
7664 __STDC_ISO_10646__ An integer constant of the form yyyymmL (for example,
7665 199712L). If this symbol is defined, then every character in the Unicode
7666 required set, when stored in an object of type wchar_t, has the same
7667 value as the short identifier of that character. The Unicode required set
7668 consists of all the characters that are defined by ISO/IEC 10646, along with
7669 all amendments and technical corrigenda, as of the specified year and
7670 month. If some other encoding is used, the macro shall not be defined and
7671 the actual encoding used is implementation-defined.
7672 __STDC_MB_MIGHT_NEQ_WC__ The integer constant 1, intended to indicate that, in
7673 the encoding for wchar_t, a member of the basic character set need not
7674 have a code value equal to its value when used as the lone character in an
7675 integer character constant.
7676 __STDC_UTF_16__ The integer constant 1, intended to indicate that values of type
7677 char16_t are UTF-16 encoded. If some other encoding is used, the
7678 macro shall not be defined and the actual encoding used is implementation-
7680 __STDC_UTF_32__ The integer constant 1, intended to indicate that values of type
7681 char32_t are UTF-32 encoded. If some other encoding is used, the
7682 macro shall not be defined and the actual encoding used is implementation-
7684 Forward references: common definitions (<a href="#7.19">7.19</a>), unicode utilities (<a href="#7.27">7.27</a>).
7689 176) This macro was not specified in ISO/IEC 9899:1990 and was specified as 199409L in
7690 ISO/IEC 9899/AMD1:1995 and as 199901L in ISO/IEC 9899:1999. The intention is that this will
7691 remain an integer constant of type long int that is increased with each revision of this International
7694 [<a name="#p174" href="p174">page 174</a>] (<a href="#Contents">Contents</a>)
7696 <a name="6.10.8.3" href="#6.10.8.3"><b> 6.10.8.3 Conditional feature macros</b></a>
7697 1 The following macro names are conditionally defined by the implementation:
7698 __STDC_ANALYZABLE__ The integer constant 1, intended to indicate conformance to
7699 the specifications in <a href="#L">annex L</a> (Analyzability).
7700 __STDC_IEC_559__ The integer constant 1, intended to indicate conformance to the
7701 specifications in <a href="#F">annex F</a> (IEC 60559 floating-point arithmetic).
7702 __STDC_IEC_559_COMPLEX__ The integer constant 1, intended to indicate
7703 adherence to the specifications in informative <a href="#G">annex G</a> (IEC 60559
7704 compatible complex arithmetic).
7705 __STDC_LIB_EXT1__ The integer constant 201ymmL, intended to indicate support
7706 for the extensions defined in <a href="#K">annex K</a> (Bounds-checking interfaces).177)
7707 __STDC_NO_COMPLEX__ The integer constant 1, intended to indicate that the
7708 implementation does not support complex types or the <a href="#7.3"><complex.h></a>
7710 __STDC_NO_THREADS__ The integer constant 1, intended to indicate that the
7711 implementation does not support atomic types (including the _Atomic
7712 type qualifier and the <a href="#7.17"><stdatomic.h></a> header) or the <a href="#7.25"><threads.h></a>
7714 __STDC_NO_VLA__ The integer constant 1, intended to indicate that the
7715 implementation does not support variable length arrays or variably
7717 <a name="6.10.9" href="#6.10.9"><b> 6.10.9 Pragma operator</b></a>
7719 1 A unary operator expression of the form:
7720 _Pragma ( string-literal )
7721 is processed as follows: The string literal is destringized by deleting the L prefix, if
7722 present, deleting the leading and trailing double-quotes, replacing each escape sequence
7723 \" by a double-quote, and replacing each escape sequence \\ by a single backslash. The
7724 resulting sequence of characters is processed through translation phase 3 to produce
7725 preprocessing tokens that are executed as if they were the pp-tokens in a pragma
7726 directive. The original four preprocessing tokens in the unary operator expression are
7730 177) The intention is that this will remain an integer constant of type long int that is increased with
7731 each revision of this International Standard.
7733 [<a name="#p175" href="p175">page 175</a>] (<a href="#Contents">Contents</a>)
7735 2 EXAMPLE A directive of the form:
7736 #pragma listing on "..\listing.dir"
7737 can also be expressed as:
7738 _Pragma ( "listing on \"..\\listing.dir\"" )
7739 The latter form is processed in the same way whether it appears literally as shown, or results from macro
7741 #define LISTING(x) PRAGMA(listing on #x)
7742 #define PRAGMA(x) _Pragma(#x)
7743 LISTING ( ..\listing.dir )
7748 [<a name="#p176" href="p176">page 176</a>] (<a href="#Contents">Contents</a>)
7750 <a name="6.11" href="#6.11"><b> 6.11 Future language directions</b></a>
7751 <a name="6.11.1" href="#6.11.1"><b> 6.11.1 Floating types</b></a>
7752 1 Future standardization may include additional floating-point types, including those with
7753 greater range, precision, or both than long double.
7754 <a name="6.11.2" href="#6.11.2"><b> 6.11.2 Linkages of identifiers</b></a>
7755 1 Declaring an identifier with internal linkage at file scope without the static storage-
7756 class specifier is an obsolescent feature.
7757 <a name="6.11.3" href="#6.11.3"><b> 6.11.3 External names</b></a>
7758 1 Restriction of the significance of an external name to fewer than 255 characters
7759 (considering each universal character name or extended source character as a single
7760 character) is an obsolescent feature that is a concession to existing implementations.
7761 <a name="6.11.4" href="#6.11.4"><b> 6.11.4 Character escape sequences</b></a>
7762 1 Lowercase letters as escape sequences are reserved for future standardization. Other
7763 characters may be used in extensions.
7764 <a name="6.11.5" href="#6.11.5"><b> 6.11.5 Storage-class specifiers</b></a>
7765 1 The placement of a storage-class specifier other than at the beginning of the declaration
7766 specifiers in a declaration is an obsolescent feature.
7767 <a name="6.11.6" href="#6.11.6"><b> 6.11.6 Function declarators</b></a>
7768 1 The use of function declarators with empty parentheses (not prototype-format parameter
7769 type declarators) is an obsolescent feature.
7770 <a name="6.11.7" href="#6.11.7"><b> 6.11.7 Function definitions</b></a>
7771 1 The use of function definitions with separate parameter identifier and declaration lists
7772 (not prototype-format parameter type and identifier declarators) is an obsolescent feature.
7773 <a name="6.11.8" href="#6.11.8"><b> 6.11.8 Pragma directives</b></a>
7774 1 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
7775 <a name="6.11.9" href="#6.11.9"><b> 6.11.9 Predefined macro names</b></a>
7776 1 Macro names beginning with __STDC_ are reserved for future standardization.
7781 [<a name="#p177" href="p177">page 177</a>] (<a href="#Contents">Contents</a>)
7784 <a name="7" href="#7"><b> 7. Library</b></a>
7785 <a name="7.1" href="#7.1"><b> 7.1 Introduction</b></a>
7786 <a name="7.1.1" href="#7.1.1"><b> 7.1.1 Definitions of terms</b></a>
7787 1 A string is a contiguous sequence of characters terminated by and including the first null
7788 character. The term multibyte string is sometimes used instead to emphasize special
7789 processing given to multibyte characters contained in the string or to avoid confusion
7790 with a wide string. A pointer to a string is a pointer to its initial (lowest addressed)
7791 character. The length of a string is the number of bytes preceding the null character and
7792 the value of a string is the sequence of the values of the contained characters, in order.
7793 2 The decimal-point character is the character used by functions that convert floating-point
7794 numbers to or from character sequences to denote the beginning of the fractional part of
7795 such character sequences.178) It is represented in the text and examples by a period, but
7796 may be changed by the setlocale function.
7797 3 A null wide character is a wide character with code value zero.
7798 4 A wide string is a contiguous sequence of wide characters terminated by and including
7799 the first null wide character. A pointer to a wide string is a pointer to its initial (lowest
7800 addressed) wide character. The length of a wide string is the number of wide characters
7801 preceding the null wide character and the value of a wide string is the sequence of code
7802 values of the contained wide characters, in order.
7803 5 A shift sequence is a contiguous sequence of bytes within a multibyte string that
7804 (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
7805 corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
7807 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>).
7812 178) The functions that make use of the decimal-point character are the numeric conversion functions
7813 (<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>).
7814 179) For state-dependent encodings, the values for MB_CUR_MAX and MB_LEN_MAX shall thus be large
7815 enough to count all the bytes in any complete multibyte character plus at least one adjacent shift
7816 sequence of maximum length. Whether these counts provide for more than one shift sequence is the
7817 implementation's choice.
7819 [<a name="#p178" href="p178">page 178</a>] (<a href="#Contents">Contents</a>)
7821 <a name="7.1.2" href="#7.1.2"><b> 7.1.2 Standard headers</b></a>
7822 1 Each library function is declared, with a type that includes a prototype, in a header,180)
7823 whose contents are made available by the #include preprocessing directive. The
7824 header declares a set of related functions, plus any necessary types and additional macros
7825 needed to facilitate their use. Declarations of types described in this clause shall not
7826 include type qualifiers, unless explicitly stated otherwise.
7827 2 The standard headers are181)
7828 <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>
7829 <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>
7830 <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>
7831 <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>
7832 <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>
7833 <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>
7834 <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>
7835 3 If a file with the same name as one of the above < and > delimited sequences, not
7836 provided as part of the implementation, is placed in any of the standard places that are
7837 searched for included source files, the behavior is undefined.
7838 4 Standard headers may be included in any order; each may be included more than once in
7839 a given scope, with no effect different from being included only once, except that the
7840 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
7841 used, a header shall be included outside of any external declaration or definition, and it
7842 shall first be included before the first reference to any of the functions or objects it
7843 declares, or to any of the types or macros it defines. However, if an identifier is declared
7844 or defined in more than one header, the second and subsequent associated headers may be
7845 included after the initial reference to the identifier. The program shall not have any
7846 macros with names lexically identical to keywords currently defined prior to the
7848 5 Any definition of an object-like macro described in this clause shall expand to code that is
7849 fully protected by parentheses where necessary, so that it groups in an arbitrary
7850 expression as if it were a single identifier.
7851 6 Any declaration of a library function shall have external linkage.
7856 180) A header is not necessarily a source file, nor are the < and > delimited sequences in header names
7857 necessarily valid source file names.
7858 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
7859 implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.
7861 [<a name="#p179" href="p179">page 179</a>] (<a href="#Contents">Contents</a>)
7863 7 A summary of the contents of the standard headers is given in <a href="#B">annex B</a>.
7864 Forward references: diagnostics (<a href="#7.2">7.2</a>).
7865 <a name="7.1.3" href="#7.1.3"><b> 7.1.3 Reserved identifiers</b></a>
7866 1 Each header declares or defines all identifiers listed in its associated subclause, and
7867 optionally declares or defines identifiers listed in its associated future library directions
7868 subclause and identifiers which are always reserved either for any use or for use as file
7870 -- All identifiers that begin with an underscore and either an uppercase letter or another
7871 underscore are always reserved for any use.
7872 -- All identifiers that begin with an underscore are always reserved for use as identifiers
7873 with file scope in both the ordinary and tag name spaces.
7874 -- Each macro name in any of the following subclauses (including the future library
7875 directions) is reserved for use as specified if any of its associated headers is included;
7876 unless explicitly stated otherwise (see <a href="#7.1.4">7.1.4</a>).
7877 -- All identifiers with external linkage in any of the following subclauses (including the
7878 future library directions) and errno are always reserved for use as identifiers with
7879 external linkage.182)
7880 -- Each identifier with file scope listed in any of the following subclauses (including the
7881 future library directions) is reserved for use as a macro name and as an identifier with
7882 file scope in the same name space if any of its associated headers is included.
7883 2 No other identifiers are reserved. If the program declares or defines an identifier in a
7884 context in which it is reserved (other than as allowed by <a href="#7.1.4">7.1.4</a>), or defines a reserved
7885 identifier as a macro name, the behavior is undefined.
7886 3 If the program removes (with #undef) any macro definition of an identifier in the first
7887 group listed above, the behavior is undefined.
7892 182) The list of reserved identifiers with external linkage includes math_errhandling, setjmp,
7893 va_copy, and va_end.
7895 [<a name="#p180" href="p180">page 180</a>] (<a href="#Contents">Contents</a>)
7897 <a name="7.1.4" href="#7.1.4"><b> 7.1.4 Use of library functions</b></a>
7898 1 Each of the following statements applies unless explicitly stated otherwise in the detailed
7899 descriptions that follow: If an argument to a function has an invalid value (such as a value
7900 outside the domain of the function, or a pointer outside the address space of the program,
7901 or a null pointer, or a pointer to non-modifiable storage when the corresponding
7902 parameter is not const-qualified) or a type (after promotion) not expected by a function
7903 with variable number of arguments, the behavior is undefined. If a function argument is
7904 described as being an array, the pointer actually passed to the function shall have a value
7905 such that all address computations and accesses to objects (that would be valid if the
7906 pointer did point to the first element of such an array) are in fact valid. Any function
7907 declared in a header may be additionally implemented as a function-like macro defined in
7908 the header, so if a library function is declared explicitly when its header is included, one
7909 of the techniques shown below can be used to ensure the declaration is not affected by
7910 such a macro. Any macro definition of a function can be suppressed locally by enclosing
7911 the name of the function in parentheses, because the name is then not followed by the left
7912 parenthesis that indicates expansion of a macro function name. For the same syntactic
7913 reason, it is permitted to take the address of a library function even if it is also defined as
7914 a macro.183) The use of #undef to remove any macro definition will also ensure that an
7915 actual function is referred to. Any invocation of a library function that is implemented as
7916 a macro shall expand to code that evaluates each of its arguments exactly once, fully
7917 protected by parentheses where necessary, so it is generally safe to use arbitrary
7918 expressions as arguments.184) Likewise, those function-like macros described in the
7919 following subclauses may be invoked in an expression anywhere a function with a
7920 compatible return type could be called.185) All object-like macros listed as expanding to
7923 183) This means that an implementation shall provide an actual function for each library function, even if it
7924 also provides a macro for that function.
7925 184) Such macros might not contain the sequence points that the corresponding function calls do.
7926 185) Because external identifiers and some macro names beginning with an underscore are reserved,
7927 implementations may provide special semantics for such names. For example, the identifier
7928 _BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
7929 appropriate header could specify
7930 #define abs(x) _BUILTIN_abs(x)
7931 for a compiler whose code generator will accept it.
7932 In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
7935 whether the implementation's header provides a macro implementation of abs or a built-in
7936 implementation. The prototype for the function, which precedes and is hidden by any macro
7937 definition, is thereby revealed also.
7939 [<a name="#p181" href="p181">page 181</a>] (<a href="#Contents">Contents</a>)
7941 integer constant expressions shall additionally be suitable for use in #if preprocessing
7943 2 Provided that a library function can be declared without reference to any type defined in a
7944 header, it is also permissible to declare the function and use it without including its
7946 3 There is a sequence point immediately before a library function returns.
7947 4 The functions in the standard library are not guaranteed to be reentrant and may modify
7948 objects with static or thread storage duration.186)
7949 5 Unless explicitly stated otherwise in the detailed descriptions that follow, library
7950 functions shall prevent data races as follows: A library function shall not directly or
7951 indirectly access objects accessible by threads other than the current thread unless the
7952 objects are accessed directly or indirectly via the function's arguments. A library
7953 function shall not directly or indirectly modify objects accessible by threads other than
7954 the current thread unless the objects are accessed directly or indirectly via the function's
7955 non-const arguments.187) Implementations may share their own internal objects between
7956 threads if the objects are not visible to users and are protected against data races.
7957 6 Unless otherwise specified, library functions shall perform all operations solely within the
7958 current thread if those operations have effects that are visible to users.188)
7959 7 EXAMPLE The function atoi may be used in any of several ways:
7960 -- by use of its associated header (possibly generating a macro expansion)
7961 #include <a href="#7.22"><stdlib.h></a>
7965 -- by use of its associated header (assuredly generating a true function reference)
7970 186) Thus, a signal handler cannot, in general, call standard library functions.
7971 187) This means, for example, that an implementation is not permitted to use a static object for internal
7972 purposes without synchronization because it could cause a data race even in programs that do not
7973 explicitly share objects between threads.
7974 188) This allows implementations to parallelize operations if there are no visible side effects.
7976 [<a name="#p182" href="p182">page 182</a>] (<a href="#Contents">Contents</a>)
7978 #include <a href="#7.22"><stdlib.h></a>
7984 #include <a href="#7.22"><stdlib.h></a>
7988 -- by explicit declaration
7989 extern int atoi(const char *);
7997 [<a name="#p183" href="p183">page 183</a>] (<a href="#Contents">Contents</a>)
7999 <a name="7.2" href="#7.2"><b> 7.2 Diagnostics <assert.h></b></a>
8000 1 The header <a href="#7.2"><assert.h></a> defines the assert and static_assert macros and
8001 refers to another macro,
8003 which is not defined by <a href="#7.2"><assert.h></a>. If NDEBUG is defined as a macro name at the
8004 point in the source file where <a href="#7.2"><assert.h></a> is included, the assert macro is defined
8006 #define assert(ignore) ((void)0)
8007 The assert macro is redefined according to the current state of NDEBUG each time that
8008 <a href="#7.2"><assert.h></a> is included.
8009 2 The assert macro shall be implemented as a macro, not as an actual function. If the
8010 macro definition is suppressed in order to access an actual function, the behavior is
8014 expands to _Static_assert.
8015 <a name="7.2.1" href="#7.2.1"><b> 7.2.1 Program diagnostics</b></a>
8016 <a name="7.2.1.1" href="#7.2.1.1"><b> 7.2.1.1 The assert macro</b></a>
8018 1 #include <a href="#7.2"><assert.h></a>
8019 void assert(scalar expression);
8021 2 The assert macro puts diagnostic tests into programs; it expands to a void expression.
8022 When it is executed, if expression (which shall have a scalar type) is false (that is,
8023 compares equal to 0), the assert macro writes information about the particular call that
8024 failed (including the text of the argument, the name of the source file, the source line
8025 number, and the name of the enclosing function -- the latter are respectively the values of
8026 the preprocessing macros __FILE__ and __LINE__ and of the identifier
8027 __func__) on the standard error stream in an implementation-defined format.189) It
8028 then calls the abort function.
8032 189) The message written might be of the form:
8033 Assertion failed: expression, function abc, file xyz, line nnn.
8036 [<a name="#p184" href="p184">page 184</a>] (<a href="#Contents">Contents</a>)
8039 3 The assert macro returns no value.
8040 Forward references: the abort function (<a href="#7.22.4.1">7.22.4.1</a>).
8045 [<a name="#p185" href="p185">page 185</a>] (<a href="#Contents">Contents</a>)
8047 <a name="7.3" href="#7.3"><b> 7.3 Complex arithmetic <complex.h></b></a>
8048 <a name="7.3.1" href="#7.3.1"><b> 7.3.1 Introduction</b></a>
8049 1 The header <a href="#7.3"><complex.h></a> defines macros and declares functions that support complex
8051 2 Implementations that define the macro __STDC_NO_COMPLEX__ need not provide
8052 this header nor support any of its facilities.
8053 3 Each synopsis specifies a family of functions consisting of a principal function with one
8054 or more double complex parameters and a double complex or double return
8055 value; and other functions with the same name but with f and l suffixes which are
8056 corresponding functions with float and long double parameters and return values.
8059 expands to _Complex; the macro
8061 expands to a constant expression of type const float _Complex, with the value of
8062 the imaginary unit.191)
8067 are defined if and only if the implementation supports imaginary types;192) if defined,
8068 they expand to _Imaginary and a constant expression of type const float
8069 _Imaginary with the value of the imaginary unit.
8072 expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
8073 defined, I shall expand to _Complex_I.
8074 7 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
8075 redefine the macros complex, imaginary, and I.
8077 190) See ''future library directions'' (<a href="#7.30.1">7.30.1</a>).
8078 191) The imaginary unit is a number i such that i 2 = -1.
8079 192) A specification for imaginary types is in informative <a href="#G">annex G</a>.
8081 [<a name="#p186" href="p186">page 186</a>] (<a href="#Contents">Contents</a>)
8083 Forward references: IEC 60559-compatible complex arithmetic (<a href="#G">annex G</a>).
8084 <a name="7.3.2" href="#7.3.2"><b> 7.3.2 Conventions</b></a>
8085 1 Values are interpreted as radians, not degrees. An implementation may set errno but is
8087 <a name="7.3.3" href="#7.3.3"><b> 7.3.3 Branch cuts</b></a>
8088 1 Some of the functions below have branch cuts, across which the function is
8089 discontinuous. For implementations with a signed zero (including all IEC 60559
8090 implementations) that follow the specifications of <a href="#G">annex G</a>, the sign of zero distinguishes
8091 one side of a cut from another so the function is continuous (except for format
8092 limitations) as the cut is approached from either side. For example, for the square root
8093 function, which has a branch cut along the negative real axis, the top of the cut, with
8094 imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with
8095 imaginary part -0, maps to the negative imaginary axis.
8096 2 Implementations that do not support a signed zero (see <a href="#F">annex F</a>) cannot distinguish the
8097 sides of branch cuts. These implementations shall map a cut so the function is continuous
8098 as the cut is approached coming around the finite endpoint of the cut in a counter
8099 clockwise direction. (Branch cuts for the functions specified here have just one finite
8100 endpoint.) For example, for the square root function, coming counter clockwise around
8101 the finite endpoint of the cut along the negative real axis approaches the cut from above,
8102 so the cut maps to the positive imaginary axis.
8103 <a name="7.3.4" href="#7.3.4"><b> 7.3.4 The CX_LIMITED_RANGE pragma</b></a>
8105 1 #include <a href="#7.3"><complex.h></a>
8106 #pragma STDC CX_LIMITED_RANGE on-off-switch
8108 2 The usual mathematical formulas for complex multiply, divide, and absolute value are
8109 problematic because of their treatment of infinities and because of undue overflow and
8110 underflow. The CX_LIMITED_RANGE pragma can be used to inform the
8111 implementation that (where the state is ''on'') the usual mathematical formulas are
8112 acceptable.193) The pragma can occur either outside external declarations or preceding all
8113 explicit declarations and statements inside a compound statement. When outside external
8114 declarations, the pragma takes effect from its occurrence until another
8115 CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit.
8116 When inside a compound statement, the pragma takes effect from its occurrence until
8117 another CX_LIMITED_RANGE pragma is encountered (including within a nested
8118 compound statement), or until the end of the compound statement; at the end of a
8119 compound statement the state for the pragma is restored to its condition just before the
8121 [<a name="#p187" href="p187">page 187</a>] (<a href="#Contents">Contents</a>)
8123 compound statement. If this pragma is used in any other context, the behavior is
8124 undefined. The default state for the pragma is ''off''.
8125 <a name="7.3.5" href="#7.3.5"><b> 7.3.5 Trigonometric functions</b></a>
8126 <a name="7.3.5.1" href="#7.3.5.1"><b> 7.3.5.1 The cacos functions</b></a>
8128 1 #include <a href="#7.3"><complex.h></a>
8129 double complex cacos(double complex z);
8130 float complex cacosf(float complex z);
8131 long double complex cacosl(long double complex z);
8133 2 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
8134 interval [-1, +1] along the real axis.
8136 3 The cacos functions return the complex arc cosine value, in the range of a strip
8137 mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
8139 <a name="7.3.5.2" href="#7.3.5.2"><b> 7.3.5.2 The casin functions</b></a>
8141 1 #include <a href="#7.3"><complex.h></a>
8142 double complex casin(double complex z);
8143 float complex casinf(float complex z);
8144 long double complex casinl(long double complex z);
8146 2 The casin functions compute the complex arc sine of z, with branch cuts outside the
8147 interval [-1, +1] along the real axis.
8149 3 The casin functions return the complex arc sine value, in the range of a strip
8150 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
8152 193) The purpose of the pragma is to allow the implementation to use the formulas:
8153 (x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
8154 (x + iy) / (u + iv) = [(xu + yv) + i(yu - xv)]/(u2 + v 2 )
8155 | x + iy | = sqrt: x 2 + y 2
8157 where the programmer can determine they are safe.
8159 [<a name="#p188" href="p188">page 188</a>] (<a href="#Contents">Contents</a>)
8161 along the real axis.
8162 <a name="7.3.5.3" href="#7.3.5.3"><b> 7.3.5.3 The catan functions</b></a>
8164 1 #include <a href="#7.3"><complex.h></a>
8165 double complex catan(double complex z);
8166 float complex catanf(float complex z);
8167 long double complex catanl(long double complex z);
8169 2 The catan functions compute the complex arc tangent of z, with branch cuts outside the
8170 interval [-i, +i] along the imaginary axis.
8172 3 The catan functions return the complex arc tangent value, in the range of a strip
8173 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
8174 along the real axis.
8175 <a name="7.3.5.4" href="#7.3.5.4"><b> 7.3.5.4 The ccos functions</b></a>
8177 1 #include <a href="#7.3"><complex.h></a>
8178 double complex ccos(double complex z);
8179 float complex ccosf(float complex z);
8180 long double complex ccosl(long double complex z);
8182 2 The ccos functions compute the complex cosine of z.
8184 3 The ccos functions return the complex cosine value.
8185 <a name="7.3.5.5" href="#7.3.5.5"><b> 7.3.5.5 The csin functions</b></a>
8187 1 #include <a href="#7.3"><complex.h></a>
8188 double complex csin(double complex z);
8189 float complex csinf(float complex z);
8190 long double complex csinl(long double complex z);
8192 2 The csin functions compute the complex sine of z.
8196 [<a name="#p189" href="p189">page 189</a>] (<a href="#Contents">Contents</a>)
8199 3 The csin functions return the complex sine value.
8200 <a name="7.3.5.6" href="#7.3.5.6"><b> 7.3.5.6 The ctan functions</b></a>
8202 1 #include <a href="#7.3"><complex.h></a>
8203 double complex ctan(double complex z);
8204 float complex ctanf(float complex z);
8205 long double complex ctanl(long double complex z);
8207 2 The ctan functions compute the complex tangent of z.
8209 3 The ctan functions return the complex tangent value.
8210 <a name="7.3.6" href="#7.3.6"><b> 7.3.6 Hyperbolic functions</b></a>
8211 <a name="7.3.6.1" href="#7.3.6.1"><b> 7.3.6.1 The cacosh functions</b></a>
8213 1 #include <a href="#7.3"><complex.h></a>
8214 double complex cacosh(double complex z);
8215 float complex cacoshf(float complex z);
8216 long double complex cacoshl(long double complex z);
8218 2 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch
8219 cut at values less than 1 along the real axis.
8221 3 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
8222 half-strip of non-negative values along the real axis and in the interval [-ipi , +ipi ] along
8224 <a name="7.3.6.2" href="#7.3.6.2"><b> 7.3.6.2 The casinh functions</b></a>
8226 1 #include <a href="#7.3"><complex.h></a>
8227 double complex casinh(double complex z);
8228 float complex casinhf(float complex z);
8229 long double complex casinhl(long double complex z);
8233 [<a name="#p190" href="p190">page 190</a>] (<a href="#Contents">Contents</a>)
8236 2 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts
8237 outside the interval [-i, +i] along the imaginary axis.
8239 3 The casinh functions return the complex arc hyperbolic sine value, in the range of a
8240 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
8241 along the imaginary axis.
8242 <a name="7.3.6.3" href="#7.3.6.3"><b> 7.3.6.3 The catanh functions</b></a>
8244 1 #include <a href="#7.3"><complex.h></a>
8245 double complex catanh(double complex z);
8246 float complex catanhf(float complex z);
8247 long double complex catanhl(long double complex z);
8249 2 The catanh functions compute the complex arc hyperbolic tangent of z, with branch
8250 cuts outside the interval [-1, +1] along the real axis.
8252 3 The catanh functions return the complex arc hyperbolic tangent value, in the range of a
8253 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
8254 along the imaginary axis.
8255 <a name="7.3.6.4" href="#7.3.6.4"><b> 7.3.6.4 The ccosh functions</b></a>
8257 1 #include <a href="#7.3"><complex.h></a>
8258 double complex ccosh(double complex z);
8259 float complex ccoshf(float complex z);
8260 long double complex ccoshl(long double complex z);
8262 2 The ccosh functions compute the complex hyperbolic cosine of z.
8264 3 The ccosh functions return the complex hyperbolic cosine value.
8269 [<a name="#p191" href="p191">page 191</a>] (<a href="#Contents">Contents</a>)
8271 <a name="7.3.6.5" href="#7.3.6.5"><b> 7.3.6.5 The csinh functions</b></a>
8273 1 #include <a href="#7.3"><complex.h></a>
8274 double complex csinh(double complex z);
8275 float complex csinhf(float complex z);
8276 long double complex csinhl(long double complex z);
8278 2 The csinh functions compute the complex hyperbolic sine of z.
8280 3 The csinh functions return the complex hyperbolic sine value.
8281 <a name="7.3.6.6" href="#7.3.6.6"><b> 7.3.6.6 The ctanh functions</b></a>
8283 1 #include <a href="#7.3"><complex.h></a>
8284 double complex ctanh(double complex z);
8285 float complex ctanhf(float complex z);
8286 long double complex ctanhl(long double complex z);
8288 2 The ctanh functions compute the complex hyperbolic tangent of z.
8290 3 The ctanh functions return the complex hyperbolic tangent value.
8291 <a name="7.3.7" href="#7.3.7"><b> 7.3.7 Exponential and logarithmic functions</b></a>
8292 <a name="7.3.7.1" href="#7.3.7.1"><b> 7.3.7.1 The cexp functions</b></a>
8294 1 #include <a href="#7.3"><complex.h></a>
8295 double complex cexp(double complex z);
8296 float complex cexpf(float complex z);
8297 long double complex cexpl(long double complex z);
8299 2 The cexp functions compute the complex base-e exponential of z.
8301 3 The cexp functions return the complex base-e exponential value.
8305 [<a name="#p192" href="p192">page 192</a>] (<a href="#Contents">Contents</a>)
8307 <a name="7.3.7.2" href="#7.3.7.2"><b> 7.3.7.2 The clog functions</b></a>
8309 1 #include <a href="#7.3"><complex.h></a>
8310 double complex clog(double complex z);
8311 float complex clogf(float complex z);
8312 long double complex clogl(long double complex z);
8314 2 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
8315 cut along the negative real axis.
8317 3 The clog functions return the complex natural logarithm value, in the range of a strip
8318 mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
8320 <a name="7.3.8" href="#7.3.8"><b> 7.3.8 Power and absolute-value functions</b></a>
8321 <a name="7.3.8.1" href="#7.3.8.1"><b> 7.3.8.1 The cabs functions</b></a>
8323 1 #include <a href="#7.3"><complex.h></a>
8324 double cabs(double complex z);
8325 float cabsf(float complex z);
8326 long double cabsl(long double complex z);
8328 2 The cabs functions compute the complex absolute value (also called norm, modulus, or
8331 3 The cabs functions return the complex absolute value.
8332 <a name="7.3.8.2" href="#7.3.8.2"><b> 7.3.8.2 The cpow functions</b></a>
8334 1 #include <a href="#7.3"><complex.h></a>
8335 double complex cpow(double complex x, double complex y);
8336 float complex cpowf(float complex x, float complex y);
8337 long double complex cpowl(long double complex x,
8338 long double complex y);
8343 [<a name="#p193" href="p193">page 193</a>] (<a href="#Contents">Contents</a>)
8346 2 The cpow functions compute the complex power function xy , with a branch cut for the
8347 first parameter along the negative real axis.
8349 3 The cpow functions return the complex power function value.
8350 <a name="7.3.8.3" href="#7.3.8.3"><b> 7.3.8.3 The csqrt functions</b></a>
8352 1 #include <a href="#7.3"><complex.h></a>
8353 double complex csqrt(double complex z);
8354 float complex csqrtf(float complex z);
8355 long double complex csqrtl(long double complex z);
8357 2 The csqrt functions compute the complex square root of z, with a branch cut along the
8360 3 The csqrt functions return the complex square root value, in the range of the right half-
8361 plane (including the imaginary axis).
8362 <a name="7.3.9" href="#7.3.9"><b> 7.3.9 Manipulation functions</b></a>
8363 <a name="7.3.9.1" href="#7.3.9.1"><b> 7.3.9.1 The carg functions</b></a>
8365 1 #include <a href="#7.3"><complex.h></a>
8366 double carg(double complex z);
8367 float cargf(float complex z);
8368 long double cargl(long double complex z);
8370 2 The carg functions compute the argument (also called phase angle) of z, with a branch
8371 cut along the negative real axis.
8373 3 The carg functions return the value of the argument in the interval [-pi , +pi ].
8378 [<a name="#p194" href="p194">page 194</a>] (<a href="#Contents">Contents</a>)
8380 <a name="7.3.9.2" href="#7.3.9.2"><b> 7.3.9.2 The cimag functions</b></a>
8382 1 #include <a href="#7.3"><complex.h></a>
8383 double cimag(double complex z);
8384 float cimagf(float complex z);
8385 long double cimagl(long double complex z);
8387 2 The cimag functions compute the imaginary part of z.194)
8389 3 The cimag functions return the imaginary part value (as a real).
8390 <a name="7.3.9.3" href="#7.3.9.3"><b> 7.3.9.3 The CMPLX macros</b></a>
8392 1 #include <a href="#7.3"><complex.h></a>
8393 double complex CMPLX(double x, double y);
8394 float complex CMPLXF(float x, float y);
8395 long double complex CMPLXL(long double x, long double y);
8397 2 The CMPLX macros expand to an expression of the specified complex type, with the real
8398 part having the (converted) value of x and the imaginary part having the (converted)
8400 Recommended practice
8401 3 The resulting expression should be suitable for use as an initializer for an object with
8402 static or thread storage duration, provided both arguments are likewise suitable.
8404 4 The CMPLX macros return the complex value x + i y.
8405 5 NOTE These macros act as if the implementation supported imaginary types and the definitions were:
8406 #define CMPLX(x, y) ((double complex)((double)(x) + \
8407 _Imaginary_I * (double)(y)))
8408 #define CMPLXF(x, y) ((float complex)((float)(x) + \
8409 _Imaginary_I * (float)(y)))
8410 #define CMPLXL(x, y) ((long double complex)((long double)(x) + \
8411 _Imaginary_I * (long double)(y)))
8416 194) For a variable z of complex type, z == creal(z) + cimag(z)*I.
8418 [<a name="#p195" href="p195">page 195</a>] (<a href="#Contents">Contents</a>)
8420 <a name="7.3.9.4" href="#7.3.9.4"><b> 7.3.9.4 The conj functions</b></a>
8422 1 #include <a href="#7.3"><complex.h></a>
8423 double complex conj(double complex z);
8424 float complex conjf(float complex z);
8425 long double complex conjl(long double complex z);
8427 2 The conj functions compute the complex conjugate of z, by reversing the sign of its
8430 3 The conj functions return the complex conjugate value.
8431 <a name="7.3.9.5" href="#7.3.9.5"><b> 7.3.9.5 The cproj functions</b></a>
8433 1 #include <a href="#7.3"><complex.h></a>
8434 double complex cproj(double complex z);
8435 float complex cprojf(float complex z);
8436 long double complex cprojl(long double complex z);
8438 2 The cproj functions compute a projection of z onto the Riemann sphere: z projects to
8439 z except that all complex infinities (even those with one infinite part and one NaN part)
8440 project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is
8442 INFINITY + I * copysign(0.0, cimag(z))
8444 3 The cproj functions return the value of the projection onto the Riemann sphere.
8445 <a name="7.3.9.6" href="#7.3.9.6"><b> 7.3.9.6 The creal functions</b></a>
8447 1 #include <a href="#7.3"><complex.h></a>
8448 double creal(double complex z);
8449 float crealf(float complex z);
8450 long double creall(long double complex z);
8452 2 The creal functions compute the real part of z.195)
8455 [<a name="#p196" href="p196">page 196</a>] (<a href="#Contents">Contents</a>)
8458 3 The creal functions return the real part value.
8463 195) For a variable z of complex type, z == creal(z) + cimag(z)*I.
8465 [<a name="#p197" href="p197">page 197</a>] (<a href="#Contents">Contents</a>)
8467 <a name="7.4" href="#7.4"><b> 7.4 Character handling <ctype.h></b></a>
8468 1 The header <a href="#7.4"><ctype.h></a> declares several functions useful for classifying and mapping
8469 characters.196) In all cases the argument is an int, the value of which shall be
8470 representable as an unsigned char or shall equal the value of the macro EOF. If the
8471 argument has any other value, the behavior is undefined.
8472 2 The behavior of these functions is affected by the current locale. Those functions that
8473 have locale-specific aspects only when not in the "C" locale are noted below.
8474 3 The term printing character refers to a member of a locale-specific set of characters, each
8475 of which occupies one printing position on a display device; the term control character
8476 refers to a member of a locale-specific set of characters that are not printing
8477 characters.197) All letters and digits are printing characters.
8478 Forward references: EOF (<a href="#7.21.1">7.21.1</a>), localization (<a href="#7.11">7.11</a>).
8479 <a name="7.4.1" href="#7.4.1"><b> 7.4.1 Character classification functions</b></a>
8480 1 The functions in this subclause return nonzero (true) if and only if the value of the
8481 argument c conforms to that in the description of the function.
8482 <a name="7.4.1.1" href="#7.4.1.1"><b> 7.4.1.1 The isalnum function</b></a>
8484 1 #include <a href="#7.4"><ctype.h></a>
8487 2 The isalnum function tests for any character for which isalpha or isdigit is true.
8488 <a name="7.4.1.2" href="#7.4.1.2"><b> 7.4.1.2 The isalpha function</b></a>
8490 1 #include <a href="#7.4"><ctype.h></a>
8493 2 The isalpha function tests for any character for which isupper or islower is true,
8494 or any character that is one of a locale-specific set of alphabetic characters for which
8498 196) See ''future library directions'' (<a href="#7.30.2">7.30.2</a>).
8499 197) In an implementation that uses the seven-bit US ASCII character set, the printing characters are those
8500 whose values lie from 0x20 (space) through 0x7E (tilde); the control characters are those whose
8501 values lie from 0 (NUL) through 0x1F (US), and the character 0x7F (DEL).
8503 [<a name="#p198" href="p198">page 198</a>] (<a href="#Contents">Contents</a>)
8505 none of iscntrl, isdigit, ispunct, or isspace is true.198) In the "C" locale,
8506 isalpha returns true only for the characters for which isupper or islower is true.
8507 <a name="7.4.1.3" href="#7.4.1.3"><b> 7.4.1.3 The isblank function</b></a>
8509 1 #include <a href="#7.4"><ctype.h></a>
8512 2 The isblank function tests for any character that is a standard blank character or is one
8513 of a locale-specific set of characters for which isspace is true and that is used to
8514 separate words within a line of text. The standard blank characters are the following:
8515 space (' '), and horizontal tab ('\t'). In the "C" locale, isblank returns true only
8516 for the standard blank characters.
8517 <a name="7.4.1.4" href="#7.4.1.4"><b> 7.4.1.4 The iscntrl function</b></a>
8519 1 #include <a href="#7.4"><ctype.h></a>
8522 2 The iscntrl function tests for any control character.
8523 <a name="7.4.1.5" href="#7.4.1.5"><b> 7.4.1.5 The isdigit function</b></a>
8525 1 #include <a href="#7.4"><ctype.h></a>
8528 2 The isdigit function tests for any decimal-digit character (as defined in <a href="#5.2.1">5.2.1</a>).
8529 <a name="7.4.1.6" href="#7.4.1.6"><b> 7.4.1.6 The isgraph function</b></a>
8531 1 #include <a href="#7.4"><ctype.h></a>
8537 198) The functions islower and isupper test true or false separately for each of these additional
8538 characters; all four combinations are possible.
8540 [<a name="#p199" href="p199">page 199</a>] (<a href="#Contents">Contents</a>)
8543 2 The isgraph function tests for any printing character except space (' ').
8544 <a name="7.4.1.7" href="#7.4.1.7"><b> 7.4.1.7 The islower function</b></a>
8546 1 #include <a href="#7.4"><ctype.h></a>
8549 2 The islower function tests for any character that is a lowercase letter or is one of a
8550 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
8551 isspace is true. In the "C" locale, islower returns true only for the lowercase
8552 letters (as defined in <a href="#5.2.1">5.2.1</a>).
8553 <a name="7.4.1.8" href="#7.4.1.8"><b> 7.4.1.8 The isprint function</b></a>
8555 1 #include <a href="#7.4"><ctype.h></a>
8558 2 The isprint function tests for any printing character including space (' ').
8559 <a name="7.4.1.9" href="#7.4.1.9"><b> 7.4.1.9 The ispunct function</b></a>
8561 1 #include <a href="#7.4"><ctype.h></a>
8564 2 The ispunct function tests for any printing character that is one of a locale-specific set
8565 of punctuation characters for which neither isspace nor isalnum is true. In the "C"
8566 locale, ispunct returns true for every printing character for which neither isspace
8567 nor isalnum is true.
8568 <a name="7.4.1.10" href="#7.4.1.10"><b> 7.4.1.10 The isspace function</b></a>
8570 1 #include <a href="#7.4"><ctype.h></a>
8573 2 The isspace function tests for any character that is a standard white-space character or
8574 is one of a locale-specific set of characters for which isalnum is false. The standard
8576 [<a name="#p200" href="p200">page 200</a>] (<a href="#Contents">Contents</a>)
8578 white-space characters are the following: space (' '), form feed ('\f'), new-line
8579 ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
8580 "C" locale, isspace returns true only for the standard white-space characters.
8581 <a name="7.4.1.11" href="#7.4.1.11"><b> 7.4.1.11 The isupper function</b></a>
8583 1 #include <a href="#7.4"><ctype.h></a>
8586 2 The isupper function tests for any character that is an uppercase letter or is one of a
8587 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
8588 isspace is true. In the "C" locale, isupper returns true only for the uppercase
8589 letters (as defined in <a href="#5.2.1">5.2.1</a>).
8590 <a name="7.4.1.12" href="#7.4.1.12"><b> 7.4.1.12 The isxdigit function</b></a>
8592 1 #include <a href="#7.4"><ctype.h></a>
8593 int isxdigit(int c);
8595 2 The isxdigit function tests for any hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
8596 <a name="7.4.2" href="#7.4.2"><b> 7.4.2 Character case mapping functions</b></a>
8597 <a name="7.4.2.1" href="#7.4.2.1"><b> 7.4.2.1 The tolower function</b></a>
8599 1 #include <a href="#7.4"><ctype.h></a>
8602 2 The tolower function converts an uppercase letter to a corresponding lowercase letter.
8604 3 If the argument is a character for which isupper is true and there are one or more
8605 corresponding characters, as specified by the current locale, for which islower is true,
8606 the tolower function returns one of the corresponding characters (always the same one
8607 for any given locale); otherwise, the argument is returned unchanged.
8612 [<a name="#p201" href="p201">page 201</a>] (<a href="#Contents">Contents</a>)
8614 <a name="7.4.2.2" href="#7.4.2.2"><b> 7.4.2.2 The toupper function</b></a>
8616 1 #include <a href="#7.4"><ctype.h></a>
8619 2 The toupper function converts a lowercase letter to a corresponding uppercase letter.
8621 3 If the argument is a character for which islower is true and there are one or more
8622 corresponding characters, as specified by the current locale, for which isupper is true,
8623 the toupper function returns one of the corresponding characters (always the same one
8624 for any given locale); otherwise, the argument is returned unchanged.
8629 [<a name="#p202" href="p202">page 202</a>] (<a href="#Contents">Contents</a>)
8631 <a name="7.5" href="#7.5"><b> 7.5 Errors <errno.h></b></a>
8632 1 The header <a href="#7.5"><errno.h></a> defines several macros, all relating to the reporting of error
8638 which expand to integer constant expressions with type int, distinct positive values, and
8639 which are suitable for use in #if preprocessing directives; and
8641 which expands to a modifiable lvalue199) that has type int and thread local storage
8642 duration, the value of which is set to a positive error number by several library functions.
8643 If a macro definition is suppressed in order to access an actual object, or a program
8644 defines an identifier with the name errno, the behavior is undefined.
8645 3 The value of errno in the initial thread is zero at program startup (the initial value of
8646 errno in other threads is an indeterminate value), but is never set to zero by any library
8647 function.200) The value of errno may be set to nonzero by a library function call
8648 whether or not there is an error, provided the use of errno is not documented in the
8649 description of the function in this International Standard.
8650 4 Additional macro definitions, beginning with E and a digit or E and an uppercase
8651 letter,201) may also be specified by the implementation.
8656 199) The macro errno need not be the identifier of an object. It might expand to a modifiable lvalue
8657 resulting from a function call (for example, *errno()).
8658 200) Thus, a program that uses errno for error checking should set it to zero before a library function call,
8659 then inspect it before a subsequent library function call. Of course, a library function can save the
8660 value of errno on entry and then set it to zero, as long as the original value is restored if errno's
8661 value is still zero just before the return.
8662 201) See ''future library directions'' (<a href="#7.30.3">7.30.3</a>).
8664 [<a name="#p203" href="p203">page 203</a>] (<a href="#Contents">Contents</a>)
8666 <a name="7.6" href="#7.6"><b> 7.6 Floating-point environment <fenv.h></b></a>
8667 1 The header <a href="#7.6"><fenv.h></a> defines several macros, and declares types and functions that
8668 provide access to the floating-point environment. The floating-point environment refers
8669 collectively to any floating-point status flags and control modes supported by the
8670 implementation.202) A floating-point status flag is a system variable whose value is set
8671 (but never cleared) when a floating-point exception is raised, which occurs as a side effect
8672 of exceptional floating-point arithmetic to provide auxiliary information.203) A floating-
8673 point control mode is a system variable whose value may be set by the user to affect the
8674 subsequent behavior of floating-point arithmetic.
8675 2 The floating-point environment has thread storage duration. The initial state for a
8676 thread's floating-point environment is the current state of the floating-point environment
8677 of the thread that creates it at the time of creation.
8678 3 Certain programming conventions support the intended model of use for the floating-
8679 point environment:204)
8680 -- a function call does not alter its caller's floating-point control modes, clear its caller's
8681 floating-point status flags, nor depend on the state of its caller's floating-point status
8682 flags unless the function is so documented;
8683 -- a function call is assumed to require default floating-point control modes, unless its
8684 documentation promises otherwise;
8685 -- a function call is assumed to have the potential for raising floating-point exceptions,
8686 unless its documentation promises otherwise.
8689 represents the entire floating-point environment.
8692 represents the floating-point status flags collectively, including any status the
8693 implementation associates with the flags.
8696 202) This header is designed to support the floating-point exception status flags and directed-rounding
8697 control modes required by IEC 60559, and other similar floating-point state information. Also it is
8698 designed to facilitate code portability among all systems.
8699 203) A floating-point status flag is not an object and can be set more than once within an expression.
8700 204) With these conventions, a programmer can safely assume default floating-point control modes (or be
8701 unaware of them). The responsibilities associated with accessing the floating-point environment fall
8702 on the programmer or program that does so explicitly.
8704 [<a name="#p204" href="p204">page 204</a>] (<a href="#Contents">Contents</a>)
8706 6 Each of the macros
8712 is defined if and only if the implementation supports the floating-point exception by
8713 means of the functions in 7.6.2.205) Additional implementation-defined floating-point
8714 exceptions, with macro definitions beginning with FE_ and an uppercase letter, may also
8715 be specified by the implementation. The defined macros expand to integer constant
8716 expressions with values such that bitwise ORs of all combinations of the macros result in
8717 distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
8721 is simply the bitwise OR of all floating-point exception macros defined by the
8722 implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
8723 8 Each of the macros
8728 is defined if and only if the implementation supports getting and setting the represented
8729 rounding direction by means of the fegetround and fesetround functions.
8730 Additional implementation-defined rounding directions, with macro definitions beginning
8731 with FE_ and an uppercase letter, may also be specified by the implementation. The
8732 defined macros expand to integer constant expressions whose values are distinct
8733 nonnegative values.207)
8738 205) The implementation supports an exception if there are circumstances where a call to at least one of the
8739 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
8740 all the functions to succeed all the time.
8741 206) The macros should be distinct powers of two.
8742 207) Even though the rounding direction macros may expand to constants corresponding to the values of
8743 FLT_ROUNDS, they are not required to do so.
8745 [<a name="#p205" href="p205">page 205</a>] (<a href="#Contents">Contents</a>)
8748 represents the default floating-point environment -- the one installed at program startup
8749 -- and has type ''pointer to const-qualified fenv_t''. It can be used as an argument to
8750 <a href="#7.6"><fenv.h></a> functions that manage the floating-point environment.
8751 10 Additional implementation-defined environments, with macro definitions beginning with
8752 FE_ and an uppercase letter, and having type ''pointer to const-qualified fenv_t'', may
8753 also be specified by the implementation.
8754 <a name="7.6.1" href="#7.6.1"><b> 7.6.1 The FENV_ACCESS pragma</b></a>
8756 1 #include <a href="#7.6"><fenv.h></a>
8757 #pragma STDC FENV_ACCESS on-off-switch
8759 2 The FENV_ACCESS pragma provides a means to inform the implementation when a
8760 program might access the floating-point environment to test floating-point status flags or
8761 run under non-default floating-point control modes.208) The pragma shall occur either
8762 outside external declarations or preceding all explicit declarations and statements inside a
8763 compound statement. When outside external declarations, the pragma takes effect from
8764 its occurrence until another FENV_ACCESS pragma is encountered, or until the end of
8765 the translation unit. When inside a compound statement, the pragma takes effect from its
8766 occurrence until another FENV_ACCESS pragma is encountered (including within a
8767 nested compound statement), or until the end of the compound statement; at the end of a
8768 compound statement the state for the pragma is restored to its condition just before the
8769 compound statement. If this pragma is used in any other context, the behavior is
8770 undefined. If part of a program tests floating-point status flags, sets floating-point control
8771 modes, or runs under non-default mode settings, but was translated with the state for the
8772 FENV_ACCESS pragma ''off'', the behavior is undefined. The default state (''on'' or
8773 ''off'') for the pragma is implementation-defined. (When execution passes from a part of
8774 the program translated with FENV_ACCESS ''off'' to a part translated with
8775 FENV_ACCESS ''on'', the state of the floating-point status flags is unspecified and the
8776 floating-point control modes have their default settings.)
8781 208) The purpose of the FENV_ACCESS pragma is to allow certain optimizations that could subvert flag
8782 tests and mode changes (e.g., global common subexpression elimination, code motion, and constant
8783 folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default
8784 modes are in effect and the flags are not tested.
8786 [<a name="#p206" href="p206">page 206</a>] (<a href="#Contents">Contents</a>)
8789 #include <a href="#7.6"><fenv.h></a>
8792 #pragma STDC FENV_ACCESS ON
8800 4 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
8801 x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
8802 contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.209)
8804 <a name="7.6.2" href="#7.6.2"><b> 7.6.2 Floating-point exceptions</b></a>
8805 1 The following functions provide access to the floating-point status flags.210) The int
8806 input argument for the functions represents a subset of floating-point exceptions, and can
8807 be zero or the bitwise OR of one or more floating-point exception macros, for example
8808 FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
8809 functions is undefined.
8810 <a name="7.6.2.1" href="#7.6.2.1"><b> 7.6.2.1 The feclearexcept function</b></a>
8812 1 #include <a href="#7.6"><fenv.h></a>
8813 int feclearexcept(int excepts);
8815 2 The feclearexcept function attempts to clear the supported floating-point exceptions
8816 represented by its argument.
8818 3 The feclearexcept function returns zero if the excepts argument is zero or if all
8819 the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
8822 209) The side effects impose a temporal ordering that requires two evaluations of x + 1. On the other
8823 hand, without the #pragma STDC FENV_ACCESS ON pragma, and assuming the default state is
8824 ''off'', just one evaluation of x + 1 would suffice.
8825 210) The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
8826 abstraction of flags that are either set or clear. An implementation may endow floating-point status
8827 flags with more information -- for example, the address of the code which first raised the floating-
8828 point exception; the functions fegetexceptflag and fesetexceptflag deal with the full
8831 [<a name="#p207" href="p207">page 207</a>] (<a href="#Contents">Contents</a>)
8833 <a name="7.6.2.2" href="#7.6.2.2"><b> 7.6.2.2 The fegetexceptflag function</b></a>
8835 1 #include <a href="#7.6"><fenv.h></a>
8836 int fegetexceptflag(fexcept_t *flagp,
8839 2 The fegetexceptflag function attempts to store an implementation-defined
8840 representation of the states of the floating-point status flags indicated by the argument
8841 excepts in the object pointed to by the argument flagp.
8843 3 The fegetexceptflag function returns zero if the representation was successfully
8844 stored. Otherwise, it returns a nonzero value.
8845 <a name="7.6.2.3" href="#7.6.2.3"><b> 7.6.2.3 The feraiseexcept function</b></a>
8847 1 #include <a href="#7.6"><fenv.h></a>
8848 int feraiseexcept(int excepts);
8850 2 The feraiseexcept function attempts to raise the supported floating-point exceptions
8851 represented by its argument.211) The order in which these floating-point exceptions are
8852 raised is unspecified, except as stated in <a href="#F.8.6">F.8.6</a>. Whether the feraiseexcept function
8853 additionally raises the ''inexact'' floating-point exception whenever it raises the
8854 ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
8856 3 The feraiseexcept function returns zero if the excepts argument is zero or if all
8857 the specified exceptions were successfully raised. Otherwise, it returns a nonzero value.
8862 211) The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations.
8863 Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
8864 in <a href="#F.8.6">F.8.6</a> is in the same spirit.
8866 [<a name="#p208" href="p208">page 208</a>] (<a href="#Contents">Contents</a>)
8868 <a name="7.6.2.4" href="#7.6.2.4"><b> 7.6.2.4 The fesetexceptflag function</b></a>
8870 1 #include <a href="#7.6"><fenv.h></a>
8871 int fesetexceptflag(const fexcept_t *flagp,
8874 2 The fesetexceptflag function attempts to set the floating-point status flags
8875 indicated by the argument excepts to the states stored in the object pointed to by
8876 flagp. The value of *flagp shall have been set by a previous call to
8877 fegetexceptflag whose second argument represented at least those floating-point
8878 exceptions represented by the argument excepts. This function does not raise floating-
8879 point exceptions, but only sets the state of the flags.
8881 3 The fesetexceptflag function returns zero if the excepts argument is zero or if
8882 all the specified flags were successfully set to the appropriate state. Otherwise, it returns
8884 <a name="7.6.2.5" href="#7.6.2.5"><b> 7.6.2.5 The fetestexcept function</b></a>
8886 1 #include <a href="#7.6"><fenv.h></a>
8887 int fetestexcept(int excepts);
8889 2 The fetestexcept function determines which of a specified subset of the floating-
8890 point exception flags are currently set. The excepts argument specifies the floating-
8891 point status flags to be queried.212)
8893 3 The fetestexcept function returns the value of the bitwise OR of the floating-point
8894 exception macros corresponding to the currently set floating-point exceptions included in
8896 4 EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set:
8901 212) This mechanism allows testing several floating-point exceptions with just one function call.
8903 [<a name="#p209" href="p209">page 209</a>] (<a href="#Contents">Contents</a>)
8905 #include <a href="#7.6"><fenv.h></a>
8908 #pragma STDC FENV_ACCESS ON
8910 feclearexcept(FE_INVALID | FE_OVERFLOW);
8911 // maybe raise exceptions
8912 set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
8913 if (set_excepts & FE_INVALID) f();
8914 if (set_excepts & FE_OVERFLOW) g();
8918 <a name="7.6.3" href="#7.6.3"><b> 7.6.3 Rounding</b></a>
8919 1 The fegetround and fesetround functions provide control of rounding direction
8921 <a name="7.6.3.1" href="#7.6.3.1"><b> 7.6.3.1 The fegetround function</b></a>
8923 1 #include <a href="#7.6"><fenv.h></a>
8924 int fegetround(void);
8926 2 The fegetround function gets the current rounding direction.
8928 3 The fegetround function returns the value of the rounding direction macro
8929 representing the current rounding direction or a negative value if there is no such
8930 rounding direction macro or the current rounding direction is not determinable.
8931 <a name="7.6.3.2" href="#7.6.3.2"><b> 7.6.3.2 The fesetround function</b></a>
8933 1 #include <a href="#7.6"><fenv.h></a>
8934 int fesetround(int round);
8936 2 The fesetround function establishes the rounding direction represented by its
8937 argument round. If the argument is not equal to the value of a rounding direction macro,
8938 the rounding direction is not changed.
8940 3 The fesetround function returns zero if and only if the requested rounding direction
8944 [<a name="#p210" href="p210">page 210</a>] (<a href="#Contents">Contents</a>)
8946 4 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the
8947 rounding direction fails.
8948 #include <a href="#7.6"><fenv.h></a>
8949 #include <a href="#7.2"><assert.h></a>
8950 void f(int round_dir)
8952 #pragma STDC FENV_ACCESS ON
8955 save_round = fegetround();
8956 setround_ok = fesetround(round_dir);
8957 assert(setround_ok == 0);
8959 fesetround(save_round);
8963 <a name="7.6.4" href="#7.6.4"><b> 7.6.4 Environment</b></a>
8964 1 The functions in this section manage the floating-point environment -- status flags and
8965 control modes -- as one entity.
8966 <a name="7.6.4.1" href="#7.6.4.1"><b> 7.6.4.1 The fegetenv function</b></a>
8968 1 #include <a href="#7.6"><fenv.h></a>
8969 int fegetenv(fenv_t *envp);
8971 2 The fegetenv function attempts to store the current floating-point environment in the
8972 object pointed to by envp.
8974 3 The fegetenv function returns zero if the environment was successfully stored.
8975 Otherwise, it returns a nonzero value.
8976 <a name="7.6.4.2" href="#7.6.4.2"><b> 7.6.4.2 The feholdexcept function</b></a>
8978 1 #include <a href="#7.6"><fenv.h></a>
8979 int feholdexcept(fenv_t *envp);
8981 2 The feholdexcept function saves the current floating-point environment in the object
8982 pointed to by envp, clears the floating-point status flags, and then installs a non-stop
8983 (continue on floating-point exceptions) mode, if available, for all floating-point
8986 [<a name="#p211" href="p211">page 211</a>] (<a href="#Contents">Contents</a>)
8989 3 The feholdexcept function returns zero if and only if non-stop floating-point
8990 exception handling was successfully installed.
8991 <a name="7.6.4.3" href="#7.6.4.3"><b> 7.6.4.3 The fesetenv function</b></a>
8993 1 #include <a href="#7.6"><fenv.h></a>
8994 int fesetenv(const fenv_t *envp);
8996 2 The fesetenv function attempts to establish the floating-point environment represented
8997 by the object pointed to by envp. The argument envp shall point to an object set by a
8998 call to fegetenv or feholdexcept, or equal a floating-point environment macro.
8999 Note that fesetenv merely installs the state of the floating-point status flags
9000 represented through its argument, and does not raise these floating-point exceptions.
9002 3 The fesetenv function returns zero if the environment was successfully established.
9003 Otherwise, it returns a nonzero value.
9004 <a name="7.6.4.4" href="#7.6.4.4"><b> 7.6.4.4 The feupdateenv function</b></a>
9006 1 #include <a href="#7.6"><fenv.h></a>
9007 int feupdateenv(const fenv_t *envp);
9009 2 The feupdateenv function attempts to save the currently raised floating-point
9010 exceptions in its automatic storage, install the floating-point environment represented by
9011 the object pointed to by envp, and then raise the saved floating-point exceptions. The
9012 argument envp shall point to an object set by a call to feholdexcept or fegetenv,
9013 or equal a floating-point environment macro.
9015 3 The feupdateenv function returns zero if all the actions were successfully carried out.
9016 Otherwise, it returns a nonzero value.
9021 213) IEC 60559 systems have a default non-stop mode, and typically at least one other mode for trap
9022 handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For
9023 such systems, the feholdexcept function can be used in conjunction with the feupdateenv
9024 function to write routines that hide spurious floating-point exceptions from their callers.
9026 [<a name="#p212" href="p212">page 212</a>] (<a href="#Contents">Contents</a>)
9028 4 EXAMPLE Hide spurious underflow floating-point exceptions:
9029 #include <a href="#7.6"><fenv.h></a>
9032 #pragma STDC FENV_ACCESS ON
9035 if (feholdexcept(&save_env))
9036 return /* indication of an environmental problem */;
9038 if (/* test spurious underflow */)
9039 if (feclearexcept(FE_UNDERFLOW))
9040 return /* indication of an environmental problem */;
9041 if (feupdateenv(&save_env))
9042 return /* indication of an environmental problem */;
9049 [<a name="#p213" href="p213">page 213</a>] (<a href="#Contents">Contents</a>)
9051 <a name="7.7" href="#7.7"><b> 7.7 Characteristics of floating types <float.h></b></a>
9052 1 The header <a href="#7.7"><float.h></a> defines several macros that expand to various limits and
9053 parameters of the standard floating-point types.
9054 2 The macros, their meanings, and the constraints (or restrictions) on their values are listed
9055 in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
9060 [<a name="#p214" href="p214">page 214</a>] (<a href="#Contents">Contents</a>)
9062 <a name="7.8" href="#7.8"><b> 7.8 Format conversion of integer types <inttypes.h></b></a>
9063 1 The header <a href="#7.8"><inttypes.h></a> includes the header <a href="#7.20"><stdint.h></a> and extends it with
9064 additional facilities provided by hosted implementations.
9065 2 It declares functions for manipulating greatest-width integers and converting numeric
9066 character strings to greatest-width integers, and it declares the type
9068 which is a structure type that is the type of the value returned by the imaxdiv function.
9069 For each type declared in <a href="#7.20"><stdint.h></a>, it defines corresponding macros for conversion
9070 specifiers for use with the formatted input/output functions.214)
9071 Forward references: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>), formatted input/output
9072 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>).
9073 <a name="7.8.1" href="#7.8.1"><b> 7.8.1 Macros for format specifiers</b></a>
9074 1 Each of the following object-like macros expands to a character string literal containing a
9075 conversion specifier, possibly modified by a length modifier, suitable for use within the
9076 format argument of a formatted input/output function when converting the corresponding
9077 integer type. These macro names have the general form of PRI (character string literals
9078 for the fprintf and fwprintf family) or SCN (character string literals for the
9079 fscanf and fwscanf family),215) followed by the conversion specifier, followed by a
9080 name corresponding to a similar type name in <a href="#7.20.1">7.20.1</a>. In these names, N represents the
9081 width of the type as described in <a href="#7.20.1">7.20.1</a>. For example, PRIdFAST32 can be used in a
9082 format string to print the value of an integer of type int_fast32_t.
9083 2 The fprintf macros for signed integers are:
9084 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
9085 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
9086 3 The fprintf macros for unsigned integers are:
9087 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
9088 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
9089 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
9090 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
9091 4 The fscanf macros for signed integers are:
9095 214) See ''future library directions'' (<a href="#7.30.4">7.30.4</a>).
9096 215) Separate macros are given for use with fprintf and fscanf functions because, in the general case,
9097 different format specifiers may be required for fprintf and fscanf, even when the type is the
9100 [<a name="#p215" href="p215">page 215</a>] (<a href="#Contents">Contents</a>)
9102 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
9103 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
9104 5 The fscanf macros for unsigned integers are:
9105 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
9106 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
9107 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
9108 6 For each type that the implementation provides in <a href="#7.20"><stdint.h></a>, the corresponding
9109 fprintf macros shall be defined and the corresponding fscanf macros shall be
9110 defined unless the implementation does not have a suitable fscanf length modifier for
9113 #include <a href="#7.8"><inttypes.h></a>
9114 #include <a href="#7.28"><wchar.h></a>
9117 uintmax_t i = UINTMAX_MAX; // this type always exists
9118 wprintf(L"The largest integer value is %020"
9123 <a name="7.8.2" href="#7.8.2"><b> 7.8.2 Functions for greatest-width integer types</b></a>
9124 <a name="7.8.2.1" href="#7.8.2.1"><b> 7.8.2.1 The imaxabs function</b></a>
9126 1 #include <a href="#7.8"><inttypes.h></a>
9127 intmax_t imaxabs(intmax_t j);
9129 2 The imaxabs function computes the absolute value of an integer j. If the result cannot
9130 be represented, the behavior is undefined.216)
9132 3 The imaxabs function returns the absolute value.
9137 216) The absolute value of the most negative number cannot be represented in two's complement.
9139 [<a name="#p216" href="p216">page 216</a>] (<a href="#Contents">Contents</a>)
9141 <a name="7.8.2.2" href="#7.8.2.2"><b> 7.8.2.2 The imaxdiv function</b></a>
9143 1 #include <a href="#7.8"><inttypes.h></a>
9144 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
9146 2 The imaxdiv function computes numer / denom and numer % denom in a single
9149 3 The imaxdiv function returns a structure of type imaxdiv_t comprising both the
9150 quotient and the remainder. The structure shall contain (in either order) the members
9151 quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
9152 either part of the result cannot be represented, the behavior is undefined.
9153 <a name="7.8.2.3" href="#7.8.2.3"><b> 7.8.2.3 The strtoimax and strtoumax functions</b></a>
9155 1 #include <a href="#7.8"><inttypes.h></a>
9156 intmax_t strtoimax(const char * restrict nptr,
9157 char ** restrict endptr, int base);
9158 uintmax_t strtoumax(const char * restrict nptr,
9159 char ** restrict endptr, int base);
9161 2 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll,
9162 strtoul, and strtoull functions, except that the initial portion of the string is
9163 converted to intmax_t and uintmax_t representation, respectively.
9165 3 The strtoimax and strtoumax functions return the converted value, if any. If no
9166 conversion could be performed, zero is returned. If the correct value is outside the range
9167 of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned
9168 (according to the return type and sign of the value, if any), and the value of the macro
9169 ERANGE is stored in errno.
9170 Forward references: the strtol, strtoll, strtoul, and strtoull functions
9171 (<a href="#7.22.1.4">7.22.1.4</a>).
9176 [<a name="#p217" href="p217">page 217</a>] (<a href="#Contents">Contents</a>)
9178 <a name="7.8.2.4" href="#7.8.2.4"><b> 7.8.2.4 The wcstoimax and wcstoumax functions</b></a>
9180 1 #include <a href="#7.19"><stddef.h></a> // for wchar_t
9181 #include <a href="#7.8"><inttypes.h></a>
9182 intmax_t wcstoimax(const wchar_t * restrict nptr,
9183 wchar_t ** restrict endptr, int base);
9184 uintmax_t wcstoumax(const wchar_t * restrict nptr,
9185 wchar_t ** restrict endptr, int base);
9187 2 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll,
9188 wcstoul, and wcstoull functions except that the initial portion of the wide string is
9189 converted to intmax_t and uintmax_t representation, respectively.
9191 3 The wcstoimax function returns the converted value, if any. If no conversion could be
9192 performed, zero is returned. If the correct value is outside the range of representable
9193 values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the
9194 return type and sign of the value, if any), and the value of the macro ERANGE is stored in
9196 Forward references: the wcstol, wcstoll, wcstoul, and wcstoull functions
9197 (<a href="#7.28.4.1.2">7.28.4.1.2</a>).
9202 [<a name="#p218" href="p218">page 218</a>] (<a href="#Contents">Contents</a>)
9204 <a name="7.9" href="#7.9"><b> 7.9 Alternative spellings <iso646.h></b></a>
9205 1 The header <a href="#7.9"><iso646.h></a> defines the following eleven macros (on the left) that expand
9206 to the corresponding tokens (on the right):
9222 [<a name="#p219" href="p219">page 219</a>] (<a href="#Contents">Contents</a>)
9224 <a name="7.10" href="#7.10"><b> 7.10 Sizes of integer types <limits.h></b></a>
9225 1 The header <a href="#7.10"><limits.h></a> defines several macros that expand to various limits and
9226 parameters of the standard integer types.
9227 2 The macros, their meanings, and the constraints (or restrictions) on their values are listed
9228 in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
9233 [<a name="#p220" href="p220">page 220</a>] (<a href="#Contents">Contents</a>)
9235 <a name="7.11" href="#7.11"><b> 7.11 Localization <locale.h></b></a>
9236 1 The header <a href="#7.11"><locale.h></a> declares two functions, one type, and defines several macros.
9239 which contains members related to the formatting of numeric values. The structure shall
9240 contain at least the following members, in any order. The semantics of the members and
9241 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
9242 the values specified in the comments.
9243 char *decimal_point; // "."
9244 char *thousands_sep; // ""
9245 char *grouping; // ""
9246 char *mon_decimal_point; // ""
9247 char *mon_thousands_sep; // ""
9248 char *mon_grouping; // ""
9249 char *positive_sign; // ""
9250 char *negative_sign; // ""
9251 char *currency_symbol; // ""
9252 char frac_digits; // CHAR_MAX
9253 char p_cs_precedes; // CHAR_MAX
9254 char n_cs_precedes; // CHAR_MAX
9255 char p_sep_by_space; // CHAR_MAX
9256 char n_sep_by_space; // CHAR_MAX
9257 char p_sign_posn; // CHAR_MAX
9258 char n_sign_posn; // CHAR_MAX
9259 char *int_curr_symbol; // ""
9260 char int_frac_digits; // CHAR_MAX
9261 char int_p_cs_precedes; // CHAR_MAX
9262 char int_n_cs_precedes; // CHAR_MAX
9263 char int_p_sep_by_space; // CHAR_MAX
9264 char int_n_sep_by_space; // CHAR_MAX
9265 char int_p_sign_posn; // CHAR_MAX
9266 char int_n_sign_posn; // CHAR_MAX
9271 [<a name="#p221" href="p221">page 221</a>] (<a href="#Contents">Contents</a>)
9273 3 The macros defined are NULL (described in <a href="#7.19">7.19</a>); and
9280 which expand to integer constant expressions with distinct values, suitable for use as the
9281 first argument to the setlocale function.217) Additional macro definitions, beginning
9282 with the characters LC_ and an uppercase letter,218) may also be specified by the
9284 <a name="7.11.1" href="#7.11.1"><b> 7.11.1 Locale control</b></a>
9285 <a name="7.11.1.1" href="#7.11.1.1"><b> 7.11.1.1 The setlocale function</b></a>
9287 1 #include <a href="#7.11"><locale.h></a>
9288 char *setlocale(int category, const char *locale);
9290 2 The setlocale function selects the appropriate portion of the program's locale as
9291 specified by the category and locale arguments. The setlocale function may be
9292 used to change or query the program's entire current locale or portions thereof. The value
9293 LC_ALL for category names the program's entire locale; the other values for
9294 category name only a portion of the program's locale. LC_COLLATE affects the
9295 behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of
9296 the character handling functions219) and the multibyte and wide character functions.
9297 LC_MONETARY affects the monetary formatting information returned by the
9298 localeconv function. LC_NUMERIC affects the decimal-point character for the
9299 formatted input/output functions and the string conversion functions, as well as the
9300 nonmonetary formatting information returned by the localeconv function. LC_TIME
9301 affects the behavior of the strftime and wcsftime functions.
9302 3 A value of "C" for locale specifies the minimal environment for C translation; a value
9303 of "" for locale specifies the locale-specific native environment. Other
9304 implementation-defined strings may be passed as the second argument to setlocale.
9306 217) ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.
9307 218) See ''future library directions'' (<a href="#7.30.5">7.30.5</a>).
9308 219) The only functions in <a href="#7.4">7.4</a> whose behavior is not affected by the current locale are isdigit and
9311 [<a name="#p222" href="p222">page 222</a>] (<a href="#Contents">Contents</a>)
9313 4 At program startup, the equivalent of
9314 setlocale(LC_ALL, "C");
9316 5 A call to the setlocale function may introduce a data race with other calls to the
9317 setlocale function or with calls to functions that are affected by the current locale.
9318 The implementation shall behave as if no library function calls the setlocale function.
9320 6 If a pointer to a string is given for locale and the selection can be honored, the
9321 setlocale function returns a pointer to the string associated with the specified
9322 category for the new locale. If the selection cannot be honored, the setlocale
9323 function returns a null pointer and the program's locale is not changed.
9324 7 A null pointer for locale causes the setlocale function to return a pointer to the
9325 string associated with the category for the program's current locale; the program's
9326 locale is not changed.220)
9327 8 The pointer to string returned by the setlocale function is such that a subsequent call
9328 with that string value and its associated category will restore that part of the program's
9329 locale. The string pointed to shall not be modified by the program, but may be
9330 overwritten by a subsequent call to the setlocale function.
9331 Forward references: formatted input/output functions (<a href="#7.21.6">7.21.6</a>), multibyte/wide
9332 character conversion functions (<a href="#7.22.7">7.22.7</a>), multibyte/wide string conversion functions
9333 (<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
9334 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>).
9335 <a name="7.11.2" href="#7.11.2"><b> 7.11.2 Numeric formatting convention inquiry</b></a>
9336 <a name="7.11.2.1" href="#7.11.2.1"><b> 7.11.2.1 The localeconv function</b></a>
9338 1 #include <a href="#7.11"><locale.h></a>
9339 struct lconv *localeconv(void);
9341 2 The localeconv function sets the components of an object with type struct lconv
9342 with values appropriate for the formatting of numeric quantities (monetary and otherwise)
9343 according to the rules of the current locale.
9347 220) The implementation shall arrange to encode in a string the various categories due to a heterogeneous
9348 locale when category has the value LC_ALL.
9350 [<a name="#p223" href="p223">page 223</a>] (<a href="#Contents">Contents</a>)
9352 3 The members of the structure with type char * are pointers to strings, any of which
9353 (except decimal_point) can point to "", to indicate that the value is not available in
9354 the current locale or is of zero length. Apart from grouping and mon_grouping, the
9355 strings shall start and end in the initial shift state. The members with type char are
9356 nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not
9357 available in the current locale. The members include the following:
9359 The decimal-point character used to format nonmonetary quantities.
9361 The character used to separate groups of digits before the decimal-point
9362 character in formatted nonmonetary quantities.
9364 A string whose elements indicate the size of each group of digits in
9365 formatted nonmonetary quantities.
9366 char *mon_decimal_point
9367 The decimal-point used to format monetary quantities.
9368 char *mon_thousands_sep
9369 The separator for groups of digits before the decimal-point in formatted
9370 monetary quantities.
9372 A string whose elements indicate the size of each group of digits in
9373 formatted monetary quantities.
9375 The string used to indicate a nonnegative-valued formatted monetary
9378 The string used to indicate a negative-valued formatted monetary quantity.
9379 char *currency_symbol
9380 The local currency symbol applicable to the current locale.
9382 The number of fractional digits (those after the decimal-point) to be
9383 displayed in a locally formatted monetary quantity.
9385 Set to 1 or 0 if the currency_symbol respectively precedes or
9386 succeeds the value for a nonnegative locally formatted monetary quantity.
9390 [<a name="#p224" href="p224">page 224</a>] (<a href="#Contents">Contents</a>)
9393 Set to 1 or 0 if the currency_symbol respectively precedes or
9394 succeeds the value for a negative locally formatted monetary quantity.
9396 Set to a value indicating the separation of the currency_symbol, the
9397 sign string, and the value for a nonnegative locally formatted monetary
9400 Set to a value indicating the separation of the currency_symbol, the
9401 sign string, and the value for a negative locally formatted monetary
9404 Set to a value indicating the positioning of the positive_sign for a
9405 nonnegative locally formatted monetary quantity.
9407 Set to a value indicating the positioning of the negative_sign for a
9408 negative locally formatted monetary quantity.
9409 char *int_curr_symbol
9410 The international currency symbol applicable to the current locale. The
9411 first three characters contain the alphabetic international currency symbol
9412 in accordance with those specified in ISO 4217. The fourth character
9413 (immediately preceding the null character) is the character used to separate
9414 the international currency symbol from the monetary quantity.
9415 char int_frac_digits
9416 The number of fractional digits (those after the decimal-point) to be
9417 displayed in an internationally formatted monetary quantity.
9418 char int_p_cs_precedes
9419 Set to 1 or 0 if the int_curr_symbol respectively precedes or
9420 succeeds the value for a nonnegative internationally formatted monetary
9422 char int_n_cs_precedes
9423 Set to 1 or 0 if the int_curr_symbol respectively precedes or
9424 succeeds the value for a negative internationally formatted monetary
9426 char int_p_sep_by_space
9427 Set to a value indicating the separation of the int_curr_symbol, the
9428 sign string, and the value for a nonnegative internationally formatted
9430 [<a name="#p225" href="p225">page 225</a>] (<a href="#Contents">Contents</a>)
9432 char int_n_sep_by_space
9433 Set to a value indicating the separation of the int_curr_symbol, the
9434 sign string, and the value for a negative internationally formatted monetary
9436 char int_p_sign_posn
9437 Set to a value indicating the positioning of the positive_sign for a
9438 nonnegative internationally formatted monetary quantity.
9439 char int_n_sign_posn
9440 Set to a value indicating the positioning of the negative_sign for a
9441 negative internationally formatted monetary quantity.
9442 4 The elements of grouping and mon_grouping are interpreted according to the
9444 CHAR_MAX No further grouping is to be performed.
9445 0 The previous element is to be repeatedly used for the remainder of the
9447 other The integer value is the number of digits that compose the current group.
9448 The next element is examined to determine the size of the next group of
9449 digits before the current group.
9450 5 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space,
9451 and int_n_sep_by_space are interpreted according to the following:
9452 0 No space separates the currency symbol and value.
9453 1 If the currency symbol and sign string are adjacent, a space separates them from the
9454 value; otherwise, a space separates the currency symbol from the value.
9455 2 If the currency symbol and sign string are adjacent, a space separates them;
9456 otherwise, a space separates the sign string from the value.
9457 For int_p_sep_by_space and int_n_sep_by_space, the fourth character of
9458 int_curr_symbol is used instead of a space.
9459 6 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and
9460 int_n_sign_posn are interpreted according to the following:
9461 0 Parentheses surround the quantity and currency symbol.
9462 1 The sign string precedes the quantity and currency symbol.
9463 2 The sign string succeeds the quantity and currency symbol.
9464 3 The sign string immediately precedes the currency symbol.
9465 4 The sign string immediately succeeds the currency symbol.
9468 [<a name="#p226" href="p226">page 226</a>] (<a href="#Contents">Contents</a>)
9470 7 The implementation shall behave as if no library function calls the localeconv
9473 8 The localeconv function returns a pointer to the filled-in object. The structure
9474 pointed to by the return value shall not be modified by the program, but may be
9475 overwritten by a subsequent call to the localeconv function. In addition, calls to the
9476 setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may
9477 overwrite the contents of the structure.
9478 9 EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format
9479 monetary quantities.
9480 Local format International format
9482 Country Positive Negative Positive Negative
9484 Country1 1.234,56 mk -1.234,56 mk FIM 1.234,56 FIM -1.234,56
9485 Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234
9486 Country3 fl. 1.234,56 fl. -1.234,56 NLG 1.234,56 NLG -1.234,56
9487 Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C
9488 10 For these four countries, the respective values for the monetary members of the structure returned by
9489 localeconv could be:
9490 Country1 Country2 Country3 Country4
9492 mon_decimal_point "," "" "," "."
9493 mon_thousands_sep "." "." "." ","
9494 mon_grouping "\3" "\3" "\3" "\3"
9495 positive_sign "" "" "" ""
9496 negative_sign "-" "-" "-" "C"
9497 currency_symbol "mk" "L." "\u0192" "SFrs."
9499 p_cs_precedes 0 1 1 1
9500 n_cs_precedes 0 1 1 1
9501 p_sep_by_space 1 0 1 0
9502 n_sep_by_space 1 0 2 0
9505 int_curr_symbol "FIM " "ITL " "NLG " "CHF "
9506 int_frac_digits 2 0 2 2
9507 int_p_cs_precedes 1 1 1 1
9508 int_n_cs_precedes 1 1 1 1
9509 int_p_sep_by_space 1 1 1 1
9510 int_n_sep_by_space 2 1 2 1
9511 int_p_sign_posn 1 1 1 1
9512 int_n_sign_posn 4 1 4 2
9517 [<a name="#p227" href="p227">page 227</a>] (<a href="#Contents">Contents</a>)
9519 11 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
9520 affect the formatted value.
9523 p_cs_precedes p_sign_posn 0 1 2
9525 0 0 (<a href="#1.25">1.25</a>$) (<a href="#1.25">1.25</a> $) (<a href="#1.25">1.25</a>$)
9526 1 +1.25$ +1.25 $ + <a href="#1.25">1.25</a>$
9527 2 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +
9528 3 <a href="#1.25">1.25</a>+$ <a href="#1.25">1.25</a> +$ <a href="#1.25">1.25</a>+ $
9529 4 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +
9531 1 0 ($1.25) ($ <a href="#1.25">1.25</a>) ($1.25)
9532 1 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
9533 2 $1.25+ $ <a href="#1.25">1.25</a>+ $1.25 +
9534 3 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
9535 4 $+1.25 $+ <a href="#1.25">1.25</a> $ +1.25
9540 [<a name="#p228" href="p228">page 228</a>] (<a href="#Contents">Contents</a>)
9542 <a name="7.12" href="#7.12"><b> 7.12 Mathematics <math.h></b></a>
9543 1 The header <a href="#7.12"><math.h></a> declares two types and many mathematical functions and defines
9544 several macros. Most synopses specify a family of functions consisting of a principal
9545 function with one or more double parameters, a double return value, or both; and
9546 other functions with the same name but with f and l suffixes, which are corresponding
9547 functions with float and long double parameters, return values, or both.221)
9548 Integer arithmetic functions and conversion functions are discussed later.
9552 are floating types at least as wide as float and double, respectively, and such that
9553 double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
9554 float_t and double_t are float and double, respectively; if
9555 FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
9556 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
9557 otherwise implementation-defined.222)
9560 expands to a positive double constant expression, not necessarily representable as a
9564 are respectively float and long double analogs of HUGE_VAL.223)
9567 expands to a constant expression of type float representing positive or unsigned
9568 infinity, if available; else to a positive constant of type float that overflows at
9572 221) Particularly on systems with wide expression evaluation, a <a href="#7.12"><math.h></a> function might pass arguments
9573 and return values in wider format than the synopsis prototype indicates.
9574 222) The types float_t and double_t are intended to be the implementation's most efficient types at
9575 least as wide as float and double, respectively. For FLT_EVAL_METHOD equal 0, 1, or 2, the
9576 type float_t is the narrowest type used by the implementation to evaluate floating expressions.
9577 223) HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
9578 supports infinities.
9580 [<a name="#p229" href="p229">page 229</a>] (<a href="#Contents">Contents</a>)
9582 translation time.224)
9585 is defined if and only if the implementation supports quiet NaNs for the float type. It
9586 expands to a constant expression of type float representing a quiet NaN.
9587 6 The number classification macros
9593 represent the mutually exclusive kinds of floating-point values. They expand to integer
9594 constant expressions with distinct values. Additional implementation-defined floating-
9595 point classifications, with macro definitions beginning with FP_ and an uppercase letter,
9596 may also be specified by the implementation.
9599 is optionally defined. If defined, it indicates that the fma function generally executes
9600 about as fast as, or faster than, a multiply and an add of double operands.225) The
9604 are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
9605 these macros expand to the integer constant 1.
9609 expand to integer constant expressions whose values are returned by ilogb(x) if x is
9610 zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
9611 -INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
9614 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.
9615 225) Typically, the FP_FAST_FMA macro is defined if and only if the fma function is implemented
9616 directly with a hardware multiply-add instruction. Software implementations are expected to be
9617 substantially slower.
9619 [<a name="#p230" href="p230">page 230</a>] (<a href="#Contents">Contents</a>)
9624 expand to the integer constants 1 and 2, respectively; the macro
9626 expands to an expression that has type int and the value MATH_ERRNO,
9627 MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is
9628 constant for the duration of the program. It is unspecified whether
9629 math_errhandling is a macro or an identifier with external linkage. If a macro
9630 definition is suppressed or a program defines an identifier with the name
9631 math_errhandling, the behavior is undefined. If the expression
9632 math_errhandling & MATH_ERREXCEPT can be nonzero, the implementation
9633 shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in
9634 <a href="#7.6"><fenv.h></a>.
9635 <a name="7.12.1" href="#7.12.1"><b> 7.12.1 Treatment of error conditions</b></a>
9636 1 The behavior of each of the functions in <a href="#7.12"><math.h></a> is specified for all representable
9637 values of its input arguments, except where stated otherwise. Each function shall execute
9638 as if it were a single operation without raising SIGFPE and without generating any of the
9639 exceptions ''invalid'', ''divide-by-zero'', or ''overflow'' except to reflect the result of the
9641 2 For all functions, a domain error occurs if an input argument is outside the domain over
9642 which the mathematical function is defined. The description of each function lists any
9643 required domain errors; an implementation may define additional domain errors, provided
9644 that such errors are consistent with the mathematical definition of the function.226) On a
9645 domain error, the function returns an implementation-defined value; if the integer
9646 expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
9647 errno acquires the value EDOM; if the integer expression math_errhandling &
9648 MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised.
9649 3 Similarly, a pole error (also known as a singularity or infinitary) occurs if the
9650 mathematical function has an exact infinite result as the finite input argument(s) are
9651 approached in the limit (for example, log(0.0)). The description of each function lists
9652 any required pole errors; an implementation may define additional pole errors, provided
9653 that such errors are consistent with the mathematical definition of the function. On a pole
9654 error, the function returns an implementation-defined value; if the integer expression
9657 226) In an implementation that supports infinities, this allows an infinity as an argument to be a domain
9658 error if the mathematical domain of the function does not include the infinity.
9660 [<a name="#p231" href="p231">page 231</a>] (<a href="#Contents">Contents</a>)
9662 math_errhandling & MATH_ERRNO is nonzero, the integer expression errno
9663 acquires the value ERANGE; if the integer expression math_errhandling &
9664 MATH_ERREXCEPT is nonzero, the ''divide-by-zero'' floating-point exception is raised.
9665 4 Likewise, a range error occurs if the mathematical result of the function cannot be
9666 represented in an object of the specified type, due to extreme magnitude.
9667 5 A floating result overflows if the magnitude of the mathematical result is finite but so
9668 large that the mathematical result cannot be represented without extraordinary roundoff
9669 error in an object of the specified type. If a floating result overflows and default rounding
9670 is in effect, then the function returns the value of the macro HUGE_VAL, HUGE_VALF, or
9671 HUGE_VALL according to the return type, with the same sign as the correct value of the
9672 function; if the integer expression math_errhandling & MATH_ERRNO is nonzero,
9673 the integer expression errno acquires the value ERANGE; if the integer expression
9674 math_errhandling & MATH_ERREXCEPT is nonzero, the ''overflow'' floating-
9675 point exception is raised.
9676 6 The result underflows if the magnitude of the mathematical result is so small that the
9677 mathematical result cannot be represented, without extraordinary roundoff error, in an
9678 object of the specified type.227) If the result underflows, the function returns an
9679 implementation-defined value whose magnitude is no greater than the smallest
9680 normalized positive number in the specified type; if the integer expression
9681 math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the
9682 value ERANGE is implementation-defined; if the integer expression
9683 math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow''
9684 floating-point exception is raised is implementation-defined.
9685 7 If a domain, pole, or range error occurs and the integer expression
9686 math_errhandling & MATH_ERRNO is zero,228) then errno shall either be set to
9687 the value corresponding to the error or left unmodified. If no such error occurs, errno
9688 shall be left unmodified regardless of the setting of math_errhandling.
9693 227) The term underflow here is intended to encompass both ''gradual underflow'' as in IEC 60559 and
9694 also ''flush-to-zero'' underflow.
9695 228) Math errors are being indicated by the floating-point exception flags rather than by errno.
9697 [<a name="#p232" href="p232">page 232</a>] (<a href="#Contents">Contents</a>)
9699 <a name="7.12.2" href="#7.12.2"><b> 7.12.2 The FP_CONTRACT pragma</b></a>
9701 1 #include <a href="#7.12"><math.h></a>
9702 #pragma STDC FP_CONTRACT on-off-switch
9704 2 The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
9705 state is ''off'') the implementation to contract expressions (<a href="#6.5">6.5</a>). Each pragma can occur
9706 either outside external declarations or preceding all explicit declarations and statements
9707 inside a compound statement. When outside external declarations, the pragma takes
9708 effect from its occurrence until another FP_CONTRACT pragma is encountered, or until
9709 the end of the translation unit. When inside a compound statement, the pragma takes
9710 effect from its occurrence until another FP_CONTRACT pragma is encountered
9711 (including within a nested compound statement), or until the end of the compound
9712 statement; at the end of a compound statement the state for the pragma is restored to its
9713 condition just before the compound statement. If this pragma is used in any other
9714 context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
9715 implementation-defined.
9716 <a name="7.12.3" href="#7.12.3"><b> 7.12.3 Classification macros</b></a>
9717 1 In the synopses in this subclause, real-floating indicates that the argument shall be an
9718 expression of real floating type.
9719 <a name="7.12.3.1" href="#7.12.3.1"><b> 7.12.3.1 The fpclassify macro</b></a>
9721 1 #include <a href="#7.12"><math.h></a>
9722 int fpclassify(real-floating x);
9724 2 The fpclassify macro classifies its argument value as NaN, infinite, normal,
9725 subnormal, zero, or into another implementation-defined category. First, an argument
9726 represented in a format wider than its semantic type is converted to its semantic type.
9727 Then classification is based on the type of the argument.229)
9729 3 The fpclassify macro returns the value of the number classification macro
9730 appropriate to the value of its argument.
9733 229) Since an expression can be evaluated with more range and precision than its type has, it is important to
9734 know the type that classification is based on. For example, a normal long double value might
9735 become subnormal when converted to double, and zero when converted to float.
9737 [<a name="#p233" href="p233">page 233</a>] (<a href="#Contents">Contents</a>)
9739 <a name="7.12.3.2" href="#7.12.3.2"><b> 7.12.3.2 The isfinite macro</b></a>
9741 1 #include <a href="#7.12"><math.h></a>
9742 int isfinite(real-floating x);
9744 2 The isfinite macro determines whether its argument has a finite value (zero,
9745 subnormal, or normal, and not infinite or NaN). First, an argument represented in a
9746 format wider than its semantic type is converted to its semantic type. Then determination
9747 is based on the type of the argument.
9749 3 The isfinite macro returns a nonzero value if and only if its argument has a finite
9751 <a name="7.12.3.3" href="#7.12.3.3"><b> 7.12.3.3 The isinf macro</b></a>
9753 1 #include <a href="#7.12"><math.h></a>
9754 int isinf(real-floating x);
9756 2 The isinf macro determines whether its argument value is an infinity (positive or
9757 negative). First, an argument represented in a format wider than its semantic type is
9758 converted to its semantic type. Then determination is based on the type of the argument.
9760 3 The isinf macro returns a nonzero value if and only if its argument has an infinite
9762 <a name="7.12.3.4" href="#7.12.3.4"><b> 7.12.3.4 The isnan macro</b></a>
9764 1 #include <a href="#7.12"><math.h></a>
9765 int isnan(real-floating x);
9767 2 The isnan macro determines whether its argument value is a NaN. First, an argument
9768 represented in a format wider than its semantic type is converted to its semantic type.
9769 Then determination is based on the type of the argument.230)
9772 230) For the isnan macro, the type for determination does not matter unless the implementation supports
9773 NaNs in the evaluation type but not in the semantic type.
9775 [<a name="#p234" href="p234">page 234</a>] (<a href="#Contents">Contents</a>)
9778 3 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
9779 <a name="7.12.3.5" href="#7.12.3.5"><b> 7.12.3.5 The isnormal macro</b></a>
9781 1 #include <a href="#7.12"><math.h></a>
9782 int isnormal(real-floating x);
9784 2 The isnormal macro determines whether its argument value is normal (neither zero,
9785 subnormal, infinite, nor NaN). First, an argument represented in a format wider than its
9786 semantic type is converted to its semantic type. Then determination is based on the type
9789 3 The isnormal macro returns a nonzero value if and only if its argument has a normal
9791 <a name="7.12.3.6" href="#7.12.3.6"><b> 7.12.3.6 The signbit macro</b></a>
9793 1 #include <a href="#7.12"><math.h></a>
9794 int signbit(real-floating x);
9796 2 The signbit macro determines whether the sign of its argument value is negative.231)
9798 3 The signbit macro returns a nonzero value if and only if the sign of its argument value
9804 231) The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is
9805 unsigned, it is treated as positive.
9807 [<a name="#p235" href="p235">page 235</a>] (<a href="#Contents">Contents</a>)
9809 <a name="7.12.4" href="#7.12.4"><b> 7.12.4 Trigonometric functions</b></a>
9810 <a name="7.12.4.1" href="#7.12.4.1"><b> 7.12.4.1 The acos functions</b></a>
9812 1 #include <a href="#7.12"><math.h></a>
9813 double acos(double x);
9814 float acosf(float x);
9815 long double acosl(long double x);
9817 2 The acos functions compute the principal value of the arc cosine of x. A domain error
9818 occurs for arguments not in the interval [-1, +1].
9820 3 The acos functions return arccos x in the interval [0, pi ] radians.
9821 <a name="7.12.4.2" href="#7.12.4.2"><b> 7.12.4.2 The asin functions</b></a>
9823 1 #include <a href="#7.12"><math.h></a>
9824 double asin(double x);
9825 float asinf(float x);
9826 long double asinl(long double x);
9828 2 The asin functions compute the principal value of the arc sine of x. A domain error
9829 occurs for arguments not in the interval [-1, +1].
9831 3 The asin functions return arcsin x in the interval [-pi /2, +pi /2] radians.
9832 <a name="7.12.4.3" href="#7.12.4.3"><b> 7.12.4.3 The atan functions</b></a>
9834 1 #include <a href="#7.12"><math.h></a>
9835 double atan(double x);
9836 float atanf(float x);
9837 long double atanl(long double x);
9839 2 The atan functions compute the principal value of the arc tangent of x.
9844 [<a name="#p236" href="p236">page 236</a>] (<a href="#Contents">Contents</a>)
9847 3 The atan functions return arctan x in the interval [-pi /2, +pi /2] radians.
9848 <a name="7.12.4.4" href="#7.12.4.4"><b> 7.12.4.4 The atan2 functions</b></a>
9850 1 #include <a href="#7.12"><math.h></a>
9851 double atan2(double y, double x);
9852 float atan2f(float y, float x);
9853 long double atan2l(long double y, long double x);
9855 2 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
9856 arguments to determine the quadrant of the return value. A domain error may occur if
9857 both arguments are zero.
9859 3 The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
9860 <a name="7.12.4.5" href="#7.12.4.5"><b> 7.12.4.5 The cos functions</b></a>
9862 1 #include <a href="#7.12"><math.h></a>
9863 double cos(double x);
9864 float cosf(float x);
9865 long double cosl(long double x);
9867 2 The cos functions compute the cosine of x (measured in radians).
9869 3 The cos functions return cos x.
9870 <a name="7.12.4.6" href="#7.12.4.6"><b> 7.12.4.6 The sin functions</b></a>
9872 1 #include <a href="#7.12"><math.h></a>
9873 double sin(double x);
9874 float sinf(float x);
9875 long double sinl(long double x);
9877 2 The sin functions compute the sine of x (measured in radians).
9881 [<a name="#p237" href="p237">page 237</a>] (<a href="#Contents">Contents</a>)
9884 3 The sin functions return sin x.
9885 <a name="7.12.4.7" href="#7.12.4.7"><b> 7.12.4.7 The tan functions</b></a>
9887 1 #include <a href="#7.12"><math.h></a>
9888 double tan(double x);
9889 float tanf(float x);
9890 long double tanl(long double x);
9892 2 The tan functions return the tangent of x (measured in radians).
9894 3 The tan functions return tan x.
9895 <a name="7.12.5" href="#7.12.5"><b> 7.12.5 Hyperbolic functions</b></a>
9896 <a name="7.12.5.1" href="#7.12.5.1"><b> 7.12.5.1 The acosh functions</b></a>
9898 1 #include <a href="#7.12"><math.h></a>
9899 double acosh(double x);
9900 float acoshf(float x);
9901 long double acoshl(long double x);
9903 2 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
9904 error occurs for arguments less than 1.
9906 3 The acosh functions return arcosh x in the interval [0, +(inf)].
9907 <a name="7.12.5.2" href="#7.12.5.2"><b> 7.12.5.2 The asinh functions</b></a>
9909 1 #include <a href="#7.12"><math.h></a>
9910 double asinh(double x);
9911 float asinhf(float x);
9912 long double asinhl(long double x);
9914 2 The asinh functions compute the arc hyperbolic sine of x.
9917 [<a name="#p238" href="p238">page 238</a>] (<a href="#Contents">Contents</a>)
9920 3 The asinh functions return arsinh x.
9921 <a name="7.12.5.3" href="#7.12.5.3"><b> 7.12.5.3 The atanh functions</b></a>
9923 1 #include <a href="#7.12"><math.h></a>
9924 double atanh(double x);
9925 float atanhf(float x);
9926 long double atanhl(long double x);
9928 2 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
9929 for arguments not in the interval [-1, +1]. A pole error may occur if the argument equals
9932 3 The atanh functions return artanh x.
9933 <a name="7.12.5.4" href="#7.12.5.4"><b> 7.12.5.4 The cosh functions</b></a>
9935 1 #include <a href="#7.12"><math.h></a>
9936 double cosh(double x);
9937 float coshf(float x);
9938 long double coshl(long double x);
9940 2 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
9941 magnitude of x is too large.
9943 3 The cosh functions return cosh x.
9944 <a name="7.12.5.5" href="#7.12.5.5"><b> 7.12.5.5 The sinh functions</b></a>
9946 1 #include <a href="#7.12"><math.h></a>
9947 double sinh(double x);
9948 float sinhf(float x);
9949 long double sinhl(long double x);
9951 2 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
9952 magnitude of x is too large.
9953 [<a name="#p239" href="p239">page 239</a>] (<a href="#Contents">Contents</a>)
9956 3 The sinh functions return sinh x.
9957 <a name="7.12.5.6" href="#7.12.5.6"><b> 7.12.5.6 The tanh functions</b></a>
9959 1 #include <a href="#7.12"><math.h></a>
9960 double tanh(double x);
9961 float tanhf(float x);
9962 long double tanhl(long double x);
9964 2 The tanh functions compute the hyperbolic tangent of x.
9966 3 The tanh functions return tanh x.
9967 <a name="7.12.6" href="#7.12.6"><b> 7.12.6 Exponential and logarithmic functions</b></a>
9968 <a name="7.12.6.1" href="#7.12.6.1"><b> 7.12.6.1 The exp functions</b></a>
9970 1 #include <a href="#7.12"><math.h></a>
9971 double exp(double x);
9972 float expf(float x);
9973 long double expl(long double x);
9975 2 The exp functions compute the base-e exponential of x. A range error occurs if the
9976 magnitude of x is too large.
9978 3 The exp functions return ex .
9979 <a name="7.12.6.2" href="#7.12.6.2"><b> 7.12.6.2 The exp2 functions</b></a>
9981 1 #include <a href="#7.12"><math.h></a>
9982 double exp2(double x);
9983 float exp2f(float x);
9984 long double exp2l(long double x);
9986 2 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
9987 magnitude of x is too large.
9989 [<a name="#p240" href="p240">page 240</a>] (<a href="#Contents">Contents</a>)
9992 3 The exp2 functions return 2x .
9993 <a name="7.12.6.3" href="#7.12.6.3"><b> 7.12.6.3 The expm1 functions</b></a>
9995 1 #include <a href="#7.12"><math.h></a>
9996 double expm1(double x);
9997 float expm1f(float x);
9998 long double expm1l(long double x);
10000 2 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
10001 error occurs if x is too large.232)
10003 3 The expm1 functions return ex - 1.
10004 <a name="7.12.6.4" href="#7.12.6.4"><b> 7.12.6.4 The frexp functions</b></a>
10006 1 #include <a href="#7.12"><math.h></a>
10007 double frexp(double value, int *exp);
10008 float frexpf(float value, int *exp);
10009 long double frexpl(long double value, int *exp);
10011 2 The frexp functions break a floating-point number into a normalized fraction and an
10012 integral power of 2. They store the integer in the int object pointed to by exp.
10014 3 If value is not a floating-point number or if the integral power of 2 is outside the range
10015 of int, the results are unspecified. Otherwise, the frexp functions return the value x,
10016 such that x has a magnitude in the interval [1/2, 1) or zero, and value equals x x 2*exp .
10017 If value is zero, both parts of the result are zero.
10022 232) For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1.
10024 [<a name="#p241" href="p241">page 241</a>] (<a href="#Contents">Contents</a>)
10026 <a name="7.12.6.5" href="#7.12.6.5"><b> 7.12.6.5 The ilogb functions</b></a>
10028 1 #include <a href="#7.12"><math.h></a>
10029 int ilogb(double x);
10030 int ilogbf(float x);
10031 int ilogbl(long double x);
10033 2 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
10034 compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
10035 a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
10036 the corresponding logb function and casting the returned value to type int. A domain
10037 error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
10038 the range of the return type, the numeric result is unspecified.
10040 3 The ilogb functions return the exponent of x as a signed int value.
10041 Forward references: the logb functions (<a href="#7.12.6.11">7.12.6.11</a>).
10042 <a name="7.12.6.6" href="#7.12.6.6"><b> 7.12.6.6 The ldexp functions</b></a>
10044 1 #include <a href="#7.12"><math.h></a>
10045 double ldexp(double x, int exp);
10046 float ldexpf(float x, int exp);
10047 long double ldexpl(long double x, int exp);
10049 2 The ldexp functions multiply a floating-point number by an integral power of 2. A
10050 range error may occur.
10052 3 The ldexp functions return x x 2exp .
10053 <a name="7.12.6.7" href="#7.12.6.7"><b> 7.12.6.7 The log functions</b></a>
10055 1 #include <a href="#7.12"><math.h></a>
10056 double log(double x);
10057 float logf(float x);
10058 long double logl(long double x);
10062 [<a name="#p242" href="p242">page 242</a>] (<a href="#Contents">Contents</a>)
10065 2 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
10066 the argument is negative. A pole error may occur if the argument is zero.
10068 3 The log functions return loge x.
10069 <a name="7.12.6.8" href="#7.12.6.8"><b> 7.12.6.8 The log10 functions</b></a>
10071 1 #include <a href="#7.12"><math.h></a>
10072 double log10(double x);
10073 float log10f(float x);
10074 long double log10l(long double x);
10076 2 The log10 functions compute the base-10 (common) logarithm of x. A domain error
10077 occurs if the argument is negative. A pole error may occur if the argument is zero.
10079 3 The log10 functions return log10 x.
10080 <a name="7.12.6.9" href="#7.12.6.9"><b> 7.12.6.9 The log1p functions</b></a>
10082 1 #include <a href="#7.12"><math.h></a>
10083 double log1p(double x);
10084 float log1pf(float x);
10085 long double log1pl(long double x);
10087 2 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.233)
10088 A domain error occurs if the argument is less than -1. A pole error may occur if the
10089 argument equals -1.
10091 3 The log1p functions return loge (1 + x).
10096 233) For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x).
10098 [<a name="#p243" href="p243">page 243</a>] (<a href="#Contents">Contents</a>)
10100 <a name="7.12.6.10" href="#7.12.6.10"><b> 7.12.6.10 The log2 functions</b></a>
10102 1 #include <a href="#7.12"><math.h></a>
10103 double log2(double x);
10104 float log2f(float x);
10105 long double log2l(long double x);
10107 2 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
10108 argument is less than zero. A pole error may occur if the argument is zero.
10110 3 The log2 functions return log2 x.
10111 <a name="7.12.6.11" href="#7.12.6.11"><b> 7.12.6.11 The logb functions</b></a>
10113 1 #include <a href="#7.12"><math.h></a>
10114 double logb(double x);
10115 float logbf(float x);
10116 long double logbl(long double x);
10118 2 The logb functions extract the exponent of x, as a signed integer value in floating-point
10119 format. If x is subnormal it is treated as though it were normalized; thus, for positive
10121 1 <= x x FLT_RADIX-logb(x) < FLT_RADIX
10122 A domain error or pole error may occur if the argument is zero.
10124 3 The logb functions return the signed exponent of x.
10125 <a name="7.12.6.12" href="#7.12.6.12"><b> 7.12.6.12 The modf functions</b></a>
10127 1 #include <a href="#7.12"><math.h></a>
10128 double modf(double value, double *iptr);
10129 float modff(float value, float *iptr);
10130 long double modfl(long double value, long double *iptr);
10132 2 The modf functions break the argument value into integral and fractional parts, each of
10133 which has the same type and sign as the argument. They store the integral part (in
10134 [<a name="#p244" href="p244">page 244</a>] (<a href="#Contents">Contents</a>)
10136 floating-point format) in the object pointed to by iptr.
10138 3 The modf functions return the signed fractional part of value.
10139 <a name="7.12.6.13" href="#7.12.6.13"><b> 7.12.6.13 The scalbn and scalbln functions</b></a>
10141 1 #include <a href="#7.12"><math.h></a>
10142 double scalbn(double x, int n);
10143 float scalbnf(float x, int n);
10144 long double scalbnl(long double x, int n);
10145 double scalbln(double x, long int n);
10146 float scalblnf(float x, long int n);
10147 long double scalblnl(long double x, long int n);
10149 2 The scalbn and scalbln functions compute x x FLT_RADIXn efficiently, not
10150 normally by computing FLT_RADIXn explicitly. A range error may occur.
10152 3 The scalbn and scalbln functions return x x FLT_RADIXn .
10153 <a name="7.12.7" href="#7.12.7"><b> 7.12.7 Power and absolute-value functions</b></a>
10154 <a name="7.12.7.1" href="#7.12.7.1"><b> 7.12.7.1 The cbrt functions</b></a>
10156 1 #include <a href="#7.12"><math.h></a>
10157 double cbrt(double x);
10158 float cbrtf(float x);
10159 long double cbrtl(long double x);
10161 2 The cbrt functions compute the real cube root of x.
10163 3 The cbrt functions return x1/3 .
10168 [<a name="#p245" href="p245">page 245</a>] (<a href="#Contents">Contents</a>)
10170 <a name="7.12.7.2" href="#7.12.7.2"><b> 7.12.7.2 The fabs functions</b></a>
10172 1 #include <a href="#7.12"><math.h></a>
10173 double fabs(double x);
10174 float fabsf(float x);
10175 long double fabsl(long double x);
10177 2 The fabs functions compute the absolute value of a floating-point number x.
10179 3 The fabs functions return | x |.
10180 <a name="7.12.7.3" href="#7.12.7.3"><b> 7.12.7.3 The hypot functions</b></a>
10182 1 #include <a href="#7.12"><math.h></a>
10183 double hypot(double x, double y);
10184 float hypotf(float x, float y);
10185 long double hypotl(long double x, long double y);
10187 2 The hypot functions compute the square root of the sum of the squares of x and y,
10188 without undue overflow or underflow. A range error may occur.
10190 4 The hypot functions return sqrt:x2 + y2 .
10193 <a name="7.12.7.4" href="#7.12.7.4"><b> 7.12.7.4 The pow functions</b></a>
10195 1 #include <a href="#7.12"><math.h></a>
10196 double pow(double x, double y);
10197 float powf(float x, float y);
10198 long double powl(long double x, long double y);
10200 2 The pow functions compute x raised to the power y. A domain error occurs if x is finite
10201 and negative and y is finite and not an integer value. A range error may occur. A domain
10202 error may occur if x is zero and y is zero. A domain error or pole error may occur if x is
10203 zero and y is less than zero.
10208 [<a name="#p246" href="p246">page 246</a>] (<a href="#Contents">Contents</a>)
10211 3 The pow functions return xy .
10212 <a name="7.12.7.5" href="#7.12.7.5"><b> 7.12.7.5 The sqrt functions</b></a>
10214 1 #include <a href="#7.12"><math.h></a>
10215 double sqrt(double x);
10216 float sqrtf(float x);
10217 long double sqrtl(long double x);
10219 2 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
10220 the argument is less than zero.
10222 3 The sqrt functions return sqrt:x.
10225 <a name="7.12.8" href="#7.12.8"><b> 7.12.8 Error and gamma functions</b></a>
10226 <a name="7.12.8.1" href="#7.12.8.1"><b> 7.12.8.1 The erf functions</b></a>
10228 1 #include <a href="#7.12"><math.h></a>
10229 double erf(double x);
10230 float erff(float x);
10231 long double erfl(long double x);
10233 2 The erf functions compute the error function of x.
10238 The erf functions return erf x =
10243 <a name="7.12.8.2" href="#7.12.8.2"><b> 7.12.8.2 The erfc functions</b></a>
10245 1 #include <a href="#7.12"><math.h></a>
10246 double erfc(double x);
10247 float erfcf(float x);
10248 long double erfcl(long double x);
10250 2 The erfc functions compute the complementary error function of x. A range error
10251 occurs if x is too large.
10252 [<a name="#p247" href="p247">page 247</a>] (<a href="#Contents">Contents</a>)
10258 The erfc functions return erfc x = 1 - erf x =
10263 <a name="7.12.8.3" href="#7.12.8.3"><b> 7.12.8.3 The lgamma functions</b></a>
10265 1 #include <a href="#7.12"><math.h></a>
10266 double lgamma(double x);
10267 float lgammaf(float x);
10268 long double lgammal(long double x);
10270 2 The lgamma functions compute the natural logarithm of the absolute value of gamma of
10271 x. A range error occurs if x is too large. A pole error may occur if x is a negative integer
10274 3 The lgamma functions return loge | (Gamma)(x) |.
10275 <a name="7.12.8.4" href="#7.12.8.4"><b> 7.12.8.4 The tgamma functions</b></a>
10277 1 #include <a href="#7.12"><math.h></a>
10278 double tgamma(double x);
10279 float tgammaf(float x);
10280 long double tgammal(long double x);
10282 2 The tgamma functions compute the gamma function of x. A domain error or pole error
10283 may occur if x is a negative integer or zero. A range error occurs if the magnitude of x is
10284 too large and may occur if the magnitude of x is too small.
10286 3 The tgamma functions return (Gamma)(x).
10291 [<a name="#p248" href="p248">page 248</a>] (<a href="#Contents">Contents</a>)
10293 <a name="7.12.9" href="#7.12.9"><b> 7.12.9 Nearest integer functions</b></a>
10294 <a name="7.12.9.1" href="#7.12.9.1"><b> 7.12.9.1 The ceil functions</b></a>
10296 1 #include <a href="#7.12"><math.h></a>
10297 double ceil(double x);
10298 float ceilf(float x);
10299 long double ceill(long double x);
10301 2 The ceil functions compute the smallest integer value not less than x.
10303 3 The ceil functions return [^x^], expressed as a floating-point number.
10304 <a name="7.12.9.2" href="#7.12.9.2"><b> 7.12.9.2 The floor functions</b></a>
10306 1 #include <a href="#7.12"><math.h></a>
10307 double floor(double x);
10308 float floorf(float x);
10309 long double floorl(long double x);
10311 2 The floor functions compute the largest integer value not greater than x.
10313 3 The floor functions return [_x_], expressed as a floating-point number.
10314 <a name="7.12.9.3" href="#7.12.9.3"><b> 7.12.9.3 The nearbyint functions</b></a>
10316 1 #include <a href="#7.12"><math.h></a>
10317 double nearbyint(double x);
10318 float nearbyintf(float x);
10319 long double nearbyintl(long double x);
10321 2 The nearbyint functions round their argument to an integer value in floating-point
10322 format, using the current rounding direction and without raising the ''inexact'' floating-
10328 [<a name="#p249" href="p249">page 249</a>] (<a href="#Contents">Contents</a>)
10331 3 The nearbyint functions return the rounded integer value.
10332 <a name="7.12.9.4" href="#7.12.9.4"><b> 7.12.9.4 The rint functions</b></a>
10334 1 #include <a href="#7.12"><math.h></a>
10335 double rint(double x);
10336 float rintf(float x);
10337 long double rintl(long double x);
10339 2 The rint functions differ from the nearbyint functions (<a href="#7.12.9.3">7.12.9.3</a>) only in that the
10340 rint functions may raise the ''inexact'' floating-point exception if the result differs in
10341 value from the argument.
10343 3 The rint functions return the rounded integer value.
10344 <a name="7.12.9.5" href="#7.12.9.5"><b> 7.12.9.5 The lrint and llrint functions</b></a>
10346 1 #include <a href="#7.12"><math.h></a>
10347 long int lrint(double x);
10348 long int lrintf(float x);
10349 long int lrintl(long double x);
10350 long long int llrint(double x);
10351 long long int llrintf(float x);
10352 long long int llrintl(long double x);
10354 2 The lrint and llrint functions round their argument to the nearest integer value,
10355 rounding according to the current rounding direction. If the rounded value is outside the
10356 range of the return type, the numeric result is unspecified and a domain error or range
10359 3 The lrint and llrint functions return the rounded integer value.
10364 [<a name="#p250" href="p250">page 250</a>] (<a href="#Contents">Contents</a>)
10366 <a name="7.12.9.6" href="#7.12.9.6"><b> 7.12.9.6 The round functions</b></a>
10368 1 #include <a href="#7.12"><math.h></a>
10369 double round(double x);
10370 float roundf(float x);
10371 long double roundl(long double x);
10373 2 The round functions round their argument to the nearest integer value in floating-point
10374 format, rounding halfway cases away from zero, regardless of the current rounding
10377 3 The round functions return the rounded integer value.
10378 <a name="7.12.9.7" href="#7.12.9.7"><b> 7.12.9.7 The lround and llround functions</b></a>
10380 1 #include <a href="#7.12"><math.h></a>
10381 long int lround(double x);
10382 long int lroundf(float x);
10383 long int lroundl(long double x);
10384 long long int llround(double x);
10385 long long int llroundf(float x);
10386 long long int llroundl(long double x);
10388 2 The lround and llround functions round their argument to the nearest integer value,
10389 rounding halfway cases away from zero, regardless of the current rounding direction. If
10390 the rounded value is outside the range of the return type, the numeric result is unspecified
10391 and a domain error or range error may occur.
10393 3 The lround and llround functions return the rounded integer value.
10394 <a name="7.12.9.8" href="#7.12.9.8"><b> 7.12.9.8 The trunc functions</b></a>
10396 1 #include <a href="#7.12"><math.h></a>
10397 double trunc(double x);
10398 float truncf(float x);
10399 long double truncl(long double x);
10402 [<a name="#p251" href="p251">page 251</a>] (<a href="#Contents">Contents</a>)
10405 2 The trunc functions round their argument to the integer value, in floating format,
10406 nearest to but no larger in magnitude than the argument.
10408 3 The trunc functions return the truncated integer value.
10409 <a name="7.12.10" href="#7.12.10"><b> 7.12.10 Remainder functions</b></a>
10410 <a name="7.12.10.1" href="#7.12.10.1"><b> 7.12.10.1 The fmod functions</b></a>
10412 1 #include <a href="#7.12"><math.h></a>
10413 double fmod(double x, double y);
10414 float fmodf(float x, float y);
10415 long double fmodl(long double x, long double y);
10417 2 The fmod functions compute the floating-point remainder of x/y.
10419 3 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
10420 the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
10421 whether a domain error occurs or the fmod functions return zero is implementation-
10423 <a name="7.12.10.2" href="#7.12.10.2"><b> 7.12.10.2 The remainder functions</b></a>
10425 1 #include <a href="#7.12"><math.h></a>
10426 double remainder(double x, double y);
10427 float remainderf(float x, float y);
10428 long double remainderl(long double x, long double y);
10430 2 The remainder functions compute the remainder x REM y required by IEC 60559.234)
10435 234) ''When y != 0, the remainder r = x REM y is defined regardless of the rounding mode by the
10436 mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever
10437 | n - x/y | = 1/2, then n is even. If r = 0, its sign shall be that of x.'' This definition is applicable for
10438 all implementations.
10440 [<a name="#p252" href="p252">page 252</a>] (<a href="#Contents">Contents</a>)
10443 3 The remainder functions return x REM y. If y is zero, whether a domain error occurs
10444 or the functions return zero is implementation defined.
10445 <a name="7.12.10.3" href="#7.12.10.3"><b> 7.12.10.3 The remquo functions</b></a>
10447 1 #include <a href="#7.12"><math.h></a>
10448 double remquo(double x, double y, int *quo);
10449 float remquof(float x, float y, int *quo);
10450 long double remquol(long double x, long double y,
10453 2 The remquo functions compute the same remainder as the remainder functions. In
10454 the object pointed to by quo they store a value whose sign is the sign of x/y and whose
10455 magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where
10456 n is an implementation-defined integer greater than or equal to 3.
10458 3 The remquo functions return x REM y. If y is zero, the value stored in the object
10459 pointed to by quo is unspecified and whether a domain error occurs or the functions
10460 return zero is implementation defined.
10461 <a name="7.12.11" href="#7.12.11"><b> 7.12.11 Manipulation functions</b></a>
10462 <a name="7.12.11.1" href="#7.12.11.1"><b> 7.12.11.1 The copysign functions</b></a>
10464 1 #include <a href="#7.12"><math.h></a>
10465 double copysign(double x, double y);
10466 float copysignf(float x, float y);
10467 long double copysignl(long double x, long double y);
10469 2 The copysign functions produce a value with the magnitude of x and the sign of y.
10470 They produce a NaN (with the sign of y) if x is a NaN. On implementations that
10471 represent a signed zero but do not treat negative zero consistently in arithmetic
10472 operations, the copysign functions regard the sign of zero as positive.
10474 3 The copysign functions return a value with the magnitude of x and the sign of y.
10478 [<a name="#p253" href="p253">page 253</a>] (<a href="#Contents">Contents</a>)
10480 <a name="7.12.11.2" href="#7.12.11.2"><b> 7.12.11.2 The nan functions</b></a>
10482 1 #include <a href="#7.12"><math.h></a>
10483 double nan(const char *tagp);
10484 float nanf(const char *tagp);
10485 long double nanl(const char *tagp);
10487 2 The call nan("n-char-sequence") is equivalent to strtod("NAN(n-char-
10488 sequence)", (char**) NULL); the call nan("") is equivalent to
10489 strtod("NAN()", (char**) NULL). If tagp does not point to an n-char
10490 sequence or an empty string, the call is equivalent to strtod("NAN", (char**)
10491 NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof
10494 3 The nan functions return a quiet NaN, if available, with content indicated through tagp.
10495 If the implementation does not support quiet NaNs, the functions return zero.
10496 Forward references: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
10497 <a name="7.12.11.3" href="#7.12.11.3"><b> 7.12.11.3 The nextafter functions</b></a>
10499 1 #include <a href="#7.12"><math.h></a>
10500 double nextafter(double x, double y);
10501 float nextafterf(float x, float y);
10502 long double nextafterl(long double x, long double y);
10504 2 The nextafter functions determine the next representable value, in the type of the
10505 function, after x in the direction of y, where x and y are first converted to the type of the
10506 function.235) The nextafter functions return y if x equals y. A range error may occur
10507 if the magnitude of x is the largest finite value representable in the type and the result is
10508 infinite or not representable in the type.
10510 3 The nextafter functions return the next representable value in the specified format
10511 after x in the direction of y.
10514 235) The argument values are converted to the type of the function, even by a macro implementation of the
10517 [<a name="#p254" href="p254">page 254</a>] (<a href="#Contents">Contents</a>)
10519 <a name="7.12.11.4" href="#7.12.11.4"><b> 7.12.11.4 The nexttoward functions</b></a>
10521 1 #include <a href="#7.12"><math.h></a>
10522 double nexttoward(double x, long double y);
10523 float nexttowardf(float x, long double y);
10524 long double nexttowardl(long double x, long double y);
10526 2 The nexttoward functions are equivalent to the nextafter functions except that the
10527 second parameter has type long double and the functions return y converted to the
10528 type of the function if x equals y.236)
10529 <a name="7.12.12" href="#7.12.12"><b> 7.12.12 Maximum, minimum, and positive difference functions</b></a>
10530 <a name="7.12.12.1" href="#7.12.12.1"><b> 7.12.12.1 The fdim functions</b></a>
10532 1 #include <a href="#7.12"><math.h></a>
10533 double fdim(double x, double y);
10534 float fdimf(float x, float y);
10535 long double fdiml(long double x, long double y);
10537 2 The fdim functions determine the positive difference between their arguments:
10541 A range error may occur.
10543 3 The fdim functions return the positive difference value.
10544 <a name="7.12.12.2" href="#7.12.12.2"><b> 7.12.12.2 The fmax functions</b></a>
10546 1 #include <a href="#7.12"><math.h></a>
10547 double fmax(double x, double y);
10548 float fmaxf(float x, float y);
10549 long double fmaxl(long double x, long double y);
10553 236) The result of the nexttoward functions is determined in the type of the function, without loss of
10554 range or precision in a floating second argument.
10556 [<a name="#p255" href="p255">page 255</a>] (<a href="#Contents">Contents</a>)
10559 2 The fmax functions determine the maximum numeric value of their arguments.237)
10561 3 The fmax functions return the maximum numeric value of their arguments.
10562 <a name="7.12.12.3" href="#7.12.12.3"><b> 7.12.12.3 The fmin functions</b></a>
10564 1 #include <a href="#7.12"><math.h></a>
10565 double fmin(double x, double y);
10566 float fminf(float x, float y);
10567 long double fminl(long double x, long double y);
10569 2 The fmin functions determine the minimum numeric value of their arguments.238)
10571 3 The fmin functions return the minimum numeric value of their arguments.
10572 <a name="7.12.13" href="#7.12.13"><b> 7.12.13 Floating multiply-add</b></a>
10573 <a name="7.12.13.1" href="#7.12.13.1"><b> 7.12.13.1 The fma functions</b></a>
10575 1 #include <a href="#7.12"><math.h></a>
10576 double fma(double x, double y, double z);
10577 float fmaf(float x, float y, float z);
10578 long double fmal(long double x, long double y,
10581 2 The fma functions compute (x x y) + z, rounded as one ternary operation: they compute
10582 the value (as if) to infinite precision and round once to the result format, according to the
10583 current rounding mode. A range error may occur.
10585 3 The fma functions return (x x y) + z, rounded as one ternary operation.
10590 237) NaN arguments are treated as missing data: if one argument is a NaN and the other numeric, then the
10591 fmax functions choose the numeric value. See <a href="#F.10.9.2">F.10.9.2</a>.
10592 238) The fmin functions are analogous to the fmax functions in their treatment of NaNs.
10594 [<a name="#p256" href="p256">page 256</a>] (<a href="#Contents">Contents</a>)
10596 <a name="7.12.14" href="#7.12.14"><b> 7.12.14 Comparison macros</b></a>
10597 1 The relational and equality operators support the usual mathematical relationships
10598 between numeric values. For any ordered pair of numeric values exactly one of the
10599 relationships -- less, greater, and equal -- is true. Relational operators may raise the
10600 ''invalid'' floating-point exception when argument values are NaNs. For a NaN and a
10601 numeric value, or for two NaNs, just the unordered relationship is true.239) The following
10602 subclauses provide macros that are quiet (non floating-point exception raising) versions
10603 of the relational operators, and other comparison macros that facilitate writing efficient
10604 code that accounts for NaNs without suffering the ''invalid'' floating-point exception. In
10605 the synopses in this subclause, real-floating indicates that the argument shall be an
10606 expression of real floating type (both arguments need not have the same type).240)
10607 <a name="7.12.14.1" href="#7.12.14.1"><b> 7.12.14.1 The isgreater macro</b></a>
10609 1 #include <a href="#7.12"><math.h></a>
10610 int isgreater(real-floating x, real-floating y);
10612 2 The isgreater macro determines whether its first argument is greater than its second
10613 argument. The value of isgreater(x, y) is always equal to (x) > (y); however,
10614 unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point
10615 exception when x and y are unordered.
10617 3 The isgreater macro returns the value of (x) > (y).
10618 <a name="7.12.14.2" href="#7.12.14.2"><b> 7.12.14.2 The isgreaterequal macro</b></a>
10620 1 #include <a href="#7.12"><math.h></a>
10621 int isgreaterequal(real-floating x, real-floating y);
10623 2 The isgreaterequal macro determines whether its first argument is greater than or
10624 equal to its second argument. The value of isgreaterequal(x, y) is always equal
10625 to (x) >= (y); however, unlike (x) >= (y), isgreaterequal(x, y) does
10628 239) IEC 60559 requires that the built-in relational operators raise the ''invalid'' floating-point exception if
10629 the operands compare unordered, as an error indicator for programs written without consideration of
10630 NaNs; the result in these cases is false.
10631 240) Whether an argument represented in a format wider than its semantic type is converted to the semantic
10632 type is unspecified.
10634 [<a name="#p257" href="p257">page 257</a>] (<a href="#Contents">Contents</a>)
10636 not raise the ''invalid'' floating-point exception when x and y are unordered.
10638 3 The isgreaterequal macro returns the value of (x) >= (y).
10639 <a name="7.12.14.3" href="#7.12.14.3"><b> 7.12.14.3 The isless macro</b></a>
10641 1 #include <a href="#7.12"><math.h></a>
10642 int isless(real-floating x, real-floating y);
10644 2 The isless macro determines whether its first argument is less than its second
10645 argument. The value of isless(x, y) is always equal to (x) < (y); however,
10646 unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point
10647 exception when x and y are unordered.
10649 3 The isless macro returns the value of (x) < (y).
10650 <a name="7.12.14.4" href="#7.12.14.4"><b> 7.12.14.4 The islessequal macro</b></a>
10652 1 #include <a href="#7.12"><math.h></a>
10653 int islessequal(real-floating x, real-floating y);
10655 2 The islessequal macro determines whether its first argument is less than or equal to
10656 its second argument. The value of islessequal(x, y) is always equal to
10657 (x) <= (y); however, unlike (x) <= (y), islessequal(x, y) does not raise
10658 the ''invalid'' floating-point exception when x and y are unordered.
10660 3 The islessequal macro returns the value of (x) <= (y).
10661 <a name="7.12.14.5" href="#7.12.14.5"><b> 7.12.14.5 The islessgreater macro</b></a>
10663 1 #include <a href="#7.12"><math.h></a>
10664 int islessgreater(real-floating x, real-floating y);
10666 2 The islessgreater macro determines whether its first argument is less than or
10667 greater than its second argument. The islessgreater(x, y) macro is similar to
10668 (x) < (y) || (x) > (y); however, islessgreater(x, y) does not raise
10670 [<a name="#p258" href="p258">page 258</a>] (<a href="#Contents">Contents</a>)
10672 the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x
10675 3 The islessgreater macro returns the value of (x) < (y) || (x) > (y).
10676 <a name="7.12.14.6" href="#7.12.14.6"><b> 7.12.14.6 The isunordered macro</b></a>
10678 1 #include <a href="#7.12"><math.h></a>
10679 int isunordered(real-floating x, real-floating y);
10681 2 The isunordered macro determines whether its arguments are unordered.
10683 3 The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
10688 [<a name="#p259" href="p259">page 259</a>] (<a href="#Contents">Contents</a>)
10690 <a name="7.13" href="#7.13"><b> 7.13 Nonlocal jumps <setjmp.h></b></a>
10691 1 The header <a href="#7.13"><setjmp.h></a> defines the macro setjmp, and declares one function and
10692 one type, for bypassing the normal function call and return discipline.241)
10693 2 The type declared is
10695 which is an array type suitable for holding the information needed to restore a calling
10696 environment. The environment of a call to the setjmp macro consists of information
10697 sufficient for a call to the longjmp function to return execution to the correct block and
10698 invocation of that block, were it called recursively. It does not include the state of the
10699 floating-point status flags, of open files, or of any other component of the abstract
10701 3 It is unspecified whether setjmp is a macro or an identifier declared with external
10702 linkage. If a macro definition is suppressed in order to access an actual function, or a
10703 program defines an external identifier with the name setjmp, the behavior is undefined.
10704 <a name="7.13.1" href="#7.13.1"><b> 7.13.1 Save calling environment</b></a>
10705 <a name="7.13.1.1" href="#7.13.1.1"><b> 7.13.1.1 The setjmp macro</b></a>
10707 1 #include <a href="#7.13"><setjmp.h></a>
10708 int setjmp(jmp_buf env);
10710 2 The setjmp macro saves its calling environment in its jmp_buf argument for later use
10711 by the longjmp function.
10713 3 If the return is from a direct invocation, the setjmp macro returns the value zero. If the
10714 return is from a call to the longjmp function, the setjmp macro returns a nonzero
10716 Environmental limits
10717 4 An invocation of the setjmp macro shall appear only in one of the following contexts:
10718 -- the entire controlling expression of a selection or iteration statement;
10719 -- one operand of a relational or equality operator with the other operand an integer
10720 constant expression, with the resulting expression being the entire controlling
10723 241) These functions are useful for dealing with unusual conditions encountered in a low-level function of
10726 [<a name="#p260" href="p260">page 260</a>] (<a href="#Contents">Contents</a>)
10728 expression of a selection or iteration statement;
10729 -- the operand of a unary ! operator with the resulting expression being the entire
10730 controlling expression of a selection or iteration statement; or
10731 -- the entire expression of an expression statement (possibly cast to void).
10732 5 If the invocation appears in any other context, the behavior is undefined.
10733 <a name="7.13.2" href="#7.13.2"><b> 7.13.2 Restore calling environment</b></a>
10734 <a name="7.13.2.1" href="#7.13.2.1"><b> 7.13.2.1 The longjmp function</b></a>
10736 1 #include <a href="#7.13"><setjmp.h></a>
10737 _Noreturn void longjmp(jmp_buf env, int val);
10739 2 The longjmp function restores the environment saved by the most recent invocation of
10740 the setjmp macro in the same invocation of the program with the corresponding
10741 jmp_buf argument. If there has been no such invocation, or if the function containing
10742 the invocation of the setjmp macro has terminated execution242) in the interim, or if the
10743 invocation of the setjmp macro was within the scope of an identifier with variably
10744 modified type and execution has left that scope in the interim, the behavior is undefined.
10745 3 All accessible objects have values, and all other components of the abstract machine243)
10746 have state, as of the time the longjmp function was called, except that the values of
10747 objects of automatic storage duration that are local to the function containing the
10748 invocation of the corresponding setjmp macro that do not have volatile-qualified type
10749 and have been changed between the setjmp invocation and longjmp call are
10752 4 After longjmp is completed, program execution continues as if the corresponding
10753 invocation of the setjmp macro had just returned the value specified by val. The
10754 longjmp function cannot cause the setjmp macro to return the value 0; if val is 0,
10755 the setjmp macro returns the value 1.
10756 5 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation
10757 might cause memory associated with a variable length array object to be squandered.
10762 242) For example, by executing a return statement or because another longjmp call has caused a
10763 transfer to a setjmp invocation in a function earlier in the set of nested calls.
10764 243) This includes, but is not limited to, the floating-point status flags and the state of open files.
10766 [<a name="#p261" href="p261">page 261</a>] (<a href="#Contents">Contents</a>)
10768 #include <a href="#7.13"><setjmp.h></a>
10775 int x[n]; // valid: f is not terminated
10781 int a[n]; // a may remain allocated
10786 int b[n]; // b may remain allocated
10787 longjmp(buf, 2); // might cause memory loss
10793 [<a name="#p262" href="p262">page 262</a>] (<a href="#Contents">Contents</a>)
10795 <a name="7.14" href="#7.14"><b> 7.14 Signal handling <signal.h></b></a>
10796 1 The header <a href="#7.14"><signal.h></a> declares a type and two functions and defines several macros,
10797 for handling various signals (conditions that may be reported during program execution).
10798 2 The type defined is
10800 which is the (possibly volatile-qualified) integer type of an object that can be accessed as
10801 an atomic entity, even in the presence of asynchronous interrupts.
10802 3 The macros defined are
10806 which expand to constant expressions with distinct values that have type compatible with
10807 the second argument to, and the return value of, the signal function, and whose values
10808 compare unequal to the address of any declarable function; and the following, which
10809 expand to positive integer constant expressions with type int and distinct values that are
10810 the signal numbers, each corresponding to the specified condition:
10811 SIGABRT abnormal termination, such as is initiated by the abort function
10812 SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
10813 resulting in overflow
10814 SIGILL detection of an invalid function image, such as an invalid instruction
10815 SIGINT receipt of an interactive attention signal
10816 SIGSEGV an invalid access to storage
10817 SIGTERM a termination request sent to the program
10818 4 An implementation need not generate any of these signals, except as a result of explicit
10819 calls to the raise function. Additional signals and pointers to undeclarable functions,
10820 with macro definitions beginning, respectively, with the letters SIG and an uppercase
10821 letter or with SIG_ and an uppercase letter,244) may also be specified by the
10822 implementation. The complete set of signals, their semantics, and their default handling
10823 is implementation-defined; all signal numbers shall be positive.
10828 244) See ''future library directions'' (<a href="#7.30.6">7.30.6</a>). The names of the signal numbers reflect the following terms
10829 (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
10832 [<a name="#p263" href="p263">page 263</a>] (<a href="#Contents">Contents</a>)
10834 <a name="7.14.1" href="#7.14.1"><b> 7.14.1 Specify signal handling</b></a>
10835 <a name="7.14.1.1" href="#7.14.1.1"><b> 7.14.1.1 The signal function</b></a>
10837 1 #include <a href="#7.14"><signal.h></a>
10838 void (*signal(int sig, void (*func)(int)))(int);
10840 2 The signal function chooses one of three ways in which receipt of the signal number
10841 sig is to be subsequently handled. If the value of func is SIG_DFL, default handling
10842 for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored.
10843 Otherwise, func shall point to a function to be called when that signal occurs. An
10844 invocation of such a function because of a signal, or (recursively) of any further functions
10845 called by that invocation (other than functions in the standard library), is called a signal
10847 3 When a signal occurs and func points to a function, it is implementation-defined
10848 whether the equivalent of signal(sig, SIG_DFL); is executed or the
10849 implementation prevents some implementation-defined set of signals (at least including
10850 sig) from occurring until the current signal handling has completed; in the case of
10851 SIGILL, the implementation may alternatively define that no action is taken. Then the
10852 equivalent of (*func)(sig); is executed. If and when the function returns, if the
10853 value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined
10854 value corresponding to a computational exception, the behavior is undefined; otherwise
10855 the program will resume execution at the point it was interrupted.
10856 4 If the signal occurs as the result of calling the abort or raise function, the signal
10857 handler shall not call the raise function.
10858 5 If the signal occurs other than as the result of calling the abort or raise function, the
10859 behavior is undefined if the signal handler refers to any object with static or thread
10860 storage duration other than by assigning a value to an object declared as volatile
10861 sig_atomic_t, or the signal handler calls any function in the standard library other
10862 than the abort function, the _Exit function, the quick_exit function, or the
10863 signal function with the first argument equal to the signal number corresponding to the
10864 signal that caused the invocation of the handler. Furthermore, if such a call to the
10865 signal function results in a SIG_ERR return, the value of errno is indeterminate.245)
10866 6 At program startup, the equivalent of
10867 signal(sig, SIG_IGN);
10870 245) If any signal is generated by an asynchronous signal handler, the behavior is undefined.
10872 [<a name="#p264" href="p264">page 264</a>] (<a href="#Contents">Contents</a>)
10874 may be executed for some signals selected in an implementation-defined manner; the
10876 signal(sig, SIG_DFL);
10877 is executed for all other signals defined by the implementation.
10878 7 The implementation shall behave as if no library function calls the signal function.
10880 8 If the request can be honored, the signal function returns the value of func for the
10881 most recent successful call to signal for the specified signal sig. Otherwise, a value of
10882 SIG_ERR is returned and a positive value is stored in errno.
10883 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
10884 _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>).
10885 <a name="7.14.2" href="#7.14.2"><b> 7.14.2 Send signal</b></a>
10886 <a name="7.14.2.1" href="#7.14.2.1"><b> 7.14.2.1 The raise function</b></a>
10888 1 #include <a href="#7.14"><signal.h></a>
10889 int raise(int sig);
10891 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
10892 signal handler is called, the raise function shall not return until after the signal handler
10895 3 The raise function returns zero if successful, nonzero if unsuccessful.
10900 [<a name="#p265" href="p265">page 265</a>] (<a href="#Contents">Contents</a>)
10902 <a name="7.15" href="#7.15"><b> 7.15 Alignment <stdalign.h></b></a>
10903 1 The header <a href="#7.15"><stdalign.h></a> defines two macros.
10906 expands to _Alignas.
10907 3 The remaining macro is suitable for use in #if preprocessing directives. It is
10908 __alignas_is_defined
10909 which expands to the integer constant 1.
10914 [<a name="#p266" href="p266">page 266</a>] (<a href="#Contents">Contents</a>)
10916 <a name="7.16" href="#7.16"><b> 7.16 Variable arguments <stdarg.h></b></a>
10917 1 The header <a href="#7.16"><stdarg.h></a> declares a type and defines four macros, for advancing
10918 through a list of arguments whose number and types are not known to the called function
10919 when it is translated.
10920 2 A function may be called with a variable number of arguments of varying types. As
10921 described in <a href="#6.9.1">6.9.1</a>, its parameter list contains one or more parameters. The rightmost
10922 parameter plays a special role in the access mechanism, and will be designated parmN in
10924 3 The type declared is
10926 which is a complete object type suitable for holding information needed by the macros
10927 va_start, va_arg, va_end, and va_copy. If access to the varying arguments is
10928 desired, the called function shall declare an object (generally referred to as ap in this
10929 subclause) having type va_list. The object ap may be passed as an argument to
10930 another function; if that function invokes the va_arg macro with parameter ap, the
10931 value of ap in the calling function is indeterminate and shall be passed to the va_end
10932 macro prior to any further reference to ap.246)
10933 <a name="7.16.1" href="#7.16.1"><b> 7.16.1 Variable argument list access macros</b></a>
10934 1 The va_start and va_arg macros described in this subclause shall be implemented
10935 as macros, not functions. It is unspecified whether va_copy and va_end are macros or
10936 identifiers declared with external linkage. If a macro definition is suppressed in order to
10937 access an actual function, or a program defines an external identifier with the same name,
10938 the behavior is undefined. Each invocation of the va_start and va_copy macros
10939 shall be matched by a corresponding invocation of the va_end macro in the same
10941 <a name="7.16.1.1" href="#7.16.1.1"><b> 7.16.1.1 The va_arg macro</b></a>
10943 1 #include <a href="#7.16"><stdarg.h></a>
10944 type va_arg(va_list ap, type);
10946 2 The va_arg macro expands to an expression that has the specified type and the value of
10947 the next argument in the call. The parameter ap shall have been initialized by the
10948 va_start or va_copy macro (without an intervening invocation of the va_end
10950 246) It is permitted to create a pointer to a va_list and pass that pointer to another function, in which
10951 case the original function may make further use of the original list after the other function returns.
10953 [<a name="#p267" href="p267">page 267</a>] (<a href="#Contents">Contents</a>)
10955 macro for the same ap). Each invocation of the va_arg macro modifies ap so that the
10956 values of successive arguments are returned in turn. The parameter type shall be a type
10957 name specified such that the type of a pointer to an object that has the specified type can
10958 be obtained simply by postfixing a * to type. If there is no actual next argument, or if
10959 type is not compatible with the type of the actual next argument (as promoted according
10960 to the default argument promotions), the behavior is undefined, except for the following
10962 -- one type is a signed integer type, the other type is the corresponding unsigned integer
10963 type, and the value is representable in both types;
10964 -- one type is pointer to void and the other is a pointer to a character type.
10966 3 The first invocation of the va_arg macro after that of the va_start macro returns the
10967 value of the argument after that specified by parmN . Successive invocations return the
10968 values of the remaining arguments in succession.
10969 <a name="7.16.1.2" href="#7.16.1.2"><b> 7.16.1.2 The va_copy macro</b></a>
10971 1 #include <a href="#7.16"><stdarg.h></a>
10972 void va_copy(va_list dest, va_list src);
10974 2 The va_copy macro initializes dest as a copy of src, as if the va_start macro had
10975 been applied to dest followed by the same sequence of uses of the va_arg macro as
10976 had previously been used to reach the present state of src. Neither the va_copy nor
10977 va_start macro shall be invoked to reinitialize dest without an intervening
10978 invocation of the va_end macro for the same dest.
10980 3 The va_copy macro returns no value.
10981 <a name="7.16.1.3" href="#7.16.1.3"><b> 7.16.1.3 The va_end macro</b></a>
10983 1 #include <a href="#7.16"><stdarg.h></a>
10984 void va_end(va_list ap);
10986 2 The va_end macro facilitates a normal return from the function whose variable
10987 argument list was referred to by the expansion of the va_start macro, or the function
10988 containing the expansion of the va_copy macro, that initialized the va_list ap. The
10989 va_end macro may modify ap so that it is no longer usable (without being reinitialized
10991 [<a name="#p268" href="p268">page 268</a>] (<a href="#Contents">Contents</a>)
10993 by the va_start or va_copy macro). If there is no corresponding invocation of the
10994 va_start or va_copy macro, or if the va_end macro is not invoked before the
10995 return, the behavior is undefined.
10997 3 The va_end macro returns no value.
10998 <a name="7.16.1.4" href="#7.16.1.4"><b> 7.16.1.4 The va_start macro</b></a>
11000 1 #include <a href="#7.16"><stdarg.h></a>
11001 void va_start(va_list ap, parmN);
11003 2 The va_start macro shall be invoked before any access to the unnamed arguments.
11004 3 The va_start macro initializes ap for subsequent use by the va_arg and va_end
11005 macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap
11006 without an intervening invocation of the va_end macro for the same ap.
11007 4 The parameter parmN is the identifier of the rightmost parameter in the variable
11008 parameter list in the function definition (the one just before the , ...). If the parameter
11009 parmN is declared with the register storage class, with a function or array type, or
11010 with a type that is not compatible with the type that results after application of the default
11011 argument promotions, the behavior is undefined.
11013 5 The va_start macro returns no value.
11014 6 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not
11015 more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of
11016 pointers is specified by the first argument to f1.
11017 #include <a href="#7.16"><stdarg.h></a>
11019 void f1(int n_ptrs, ...)
11022 char *array[MAXARGS];
11028 [<a name="#p269" href="p269">page 269</a>] (<a href="#Contents">Contents</a>)
11030 if (n_ptrs > MAXARGS)
11032 va_start(ap, n_ptrs);
11033 while (ptr_no < n_ptrs)
11034 array[ptr_no++] = va_arg(ap, char *);
11038 Each call to f1 is required to have visible the definition of the function or a declaration such as
11041 7 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the
11042 indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list
11043 is gathered again and passed to function f4.
11044 #include <a href="#7.16"><stdarg.h></a>
11046 void f3(int n_ptrs, int f4_after, ...)
11048 va_list ap, ap_save;
11049 char *array[MAXARGS];
11051 if (n_ptrs > MAXARGS)
11053 va_start(ap, f4_after);
11054 while (ptr_no < n_ptrs) {
11055 array[ptr_no++] = va_arg(ap, char *);
11056 if (ptr_no == f4_after)
11057 va_copy(ap_save, ap);
11061 // Now process the saved copy.
11062 n_ptrs -= f4_after;
11064 while (ptr_no < n_ptrs)
11065 array[ptr_no++] = va_arg(ap_save, char *);
11073 [<a name="#p270" href="p270">page 270</a>] (<a href="#Contents">Contents</a>)
11075 <a name="7.17" href="#7.17"><b> 7.17 Atomics <stdatomic.h></b></a>
11076 <a name="7.17.1" href="#7.17.1"><b> 7.17.1 Introduction</b></a>
11077 1 The header <a href="#7.17"><stdatomic.h></a> defines several macros and declares several types and
11078 functions for performing atomic operations on data shared between threads.
11079 2 Implementations that define the macro __STDC_NO_THREADS__ need not provide
11080 this header nor support any of its facilities.
11081 3 The macros defined are the atomic lock-free macros
11082 ATOMIC_CHAR_LOCK_FREE
11083 ATOMIC_CHAR16_T_LOCK_FREE
11084 ATOMIC_CHAR32_T_LOCK_FREE
11085 ATOMIC_WCHAR_T_LOCK_FREE
11086 ATOMIC_SHORT_LOCK_FREE
11087 ATOMIC_INT_LOCK_FREE
11088 ATOMIC_LONG_LOCK_FREE
11089 ATOMIC_LLONG_LOCK_FREE
11090 ATOMIC_ADDRESS_LOCK_FREE
11091 which indicate the lock-free property of the corresponding atomic types (both signed and
11094 which expands to an initializer for an object of type atomic_flag.
11095 4 The types include
11097 which is an enumerated type whose enumerators identify memory ordering constraints;
11099 which is a structure type representing a lock-free, primitive atomic flag;
11101 which is a structure type representing the atomic analog of the type _Bool;
11103 which is a structure type representing the atomic analog of a pointer type; and several
11104 atomic analogs of integer types.
11105 5 In the following operation definitions:
11106 -- An A refers to one of the atomic types.
11109 [<a name="#p271" href="p271">page 271</a>] (<a href="#Contents">Contents</a>)
11111 -- A C refers to its corresponding non-atomic type. The atomic_address atomic
11112 type corresponds to the void * non-atomic type.
11113 -- An M refers to the type of the other argument for arithmetic operations. For atomic
11114 integer types, M is C. For atomic address types, M is ptrdiff_t.
11115 -- The functions not ending in _explicit have the same semantics as the
11116 corresponding _explicit function with memory_order_seq_cst for the
11117 memory_order argument.
11118 6 NOTE Many operations are volatile-qualified. The ''volatile as device register'' semantics have not
11119 changed in the standard. This qualification means that volatility is preserved when applying these
11120 operations to volatile objects.
11122 <a name="7.17.2" href="#7.17.2"><b> 7.17.2 Initialization</b></a>
11123 <a name="7.17.2.1" href="#7.17.2.1"><b> 7.17.2.1 The ATOMIC_VAR_INIT macro</b></a>
11125 1 #include <a href="#7.17"><stdatomic.h></a>
11126 #define ATOMIC_VAR_INIT(C value)
11128 2 The ATOMIC_VAR_INIT macro expands to a token sequence suitable for initializing an
11129 atomic object of a type that is initialization-compatible with value. An atomic object
11130 with automatic storage duration that is not explicitly initialized using
11131 ATOMIC_VAR_INIT is initially in an indeterminate state; however, the default (zero)
11132 initialization for objects with static or thread-local storage duration is guaranteed to
11133 produce a valid state.
11134 3 Concurrent access to the variable being initialized, even via an atomic operation,
11135 constitutes a data race.
11137 atomic_int guide = ATOMIC_VAR_INIT(42);
11139 <a name="7.17.2.2" href="#7.17.2.2"><b> 7.17.2.2 The atomic_init generic function</b></a>
11141 1 #include <a href="#7.17"><stdatomic.h></a>
11142 void atomic_init(volatile A *obj, C value);
11144 2 The atomic_init generic function initializes the atomic object pointed to by obj to
11145 the value value, while also initializing any additional state that the implementation
11146 might need to carry for the atomic object.
11150 [<a name="#p272" href="p272">page 272</a>] (<a href="#Contents">Contents</a>)
11152 3 Although this function initializes an atomic object, it does not avoid data races;
11153 concurrent access to the variable being initialized, even via an atomic operation,
11154 constitutes a data race.
11156 4 The atomic_init generic function returns no value.
11159 atomic_init(&guide, 42);
11161 <a name="7.17.3" href="#7.17.3"><b> 7.17.3 Order and consistency</b></a>
11162 1 The enumerated type memory_order specifies the detailed regular (non-atomic)
11163 memory synchronization operations as defined in <a href="#5.1.2.4">5.1.2.4</a> and may provide for operation
11164 ordering. Its enumeration constants are as follows:
11165 memory_order_relaxed
11166 memory_order_consume
11167 memory_order_acquire
11168 memory_order_release
11169 memory_order_acq_rel
11170 memory_order_seq_cst
11171 2 For memory_order_relaxed, no operation orders memory.
11172 3 For memory_order_release, memory_order_acq_rel, and
11173 memory_order_seq_cst, a store operation performs a release operation on the
11174 affected memory location.
11175 4 For memory_order_acquire, memory_order_acq_rel, and
11176 memory_order_seq_cst, a load operation performs an acquire operation on the
11177 affected memory location.
11178 5 For memory_order_consume, a load operation performs a consume operation on the
11179 affected memory location.
11180 6 For memory_order_seq_cst, there shall be a single total order S on all operations,
11181 consistent with the ''happens before'' order and modification orders for all affected
11182 locations, such that each memory_order_seq_cst operation that loads a value
11183 observes either the last preceding modification according to this order S, or the result of
11184 an operation that is not memory_order_seq_cst.
11185 7 NOTE 1 Although it is not explicitly required that S include lock operations, it can always be extended to
11186 an order that does include lock and unlock operations, since the ordering between those is already included
11187 in the ''happens before'' ordering.
11189 8 NOTE 2 Atomic operations specifying memory_order_relaxed are relaxed only with respect to
11190 memory ordering. Implementations must still guarantee that any given atomic access to a particular atomic
11192 [<a name="#p273" href="p273">page 273</a>] (<a href="#Contents">Contents</a>)
11194 object be indivisible with respect to all other atomic accesses to that object.
11196 9 For an atomic operation B that reads the value of an atomic object M, if there is a
11197 memory_order_seq_cst fence X sequenced before B, then B observes either the
11198 last memory_order_seq_cst modification of M preceding X in the total order S or
11199 a later modification of M in its modification order.
11200 10 For atomic operations A and B on an atomic object M, where A modifies M and B takes
11201 its value, if there is a memory_order_seq_cst fence X such that A is sequenced
11202 before X and B follows X in S, then B observes either the effects of A or a later
11203 modification of M in its modification order.
11204 11 For atomic operations A and B on an atomic object M, where A modifies M and B takes
11205 its value, if there are memory_order_seq_cst fences X and Y such that A is
11206 sequenced before X, Y is sequenced before B, and X precedes Y in S, then B observes
11207 either the effects of A or a later modification of M in its modification order.
11208 12 Atomic read-modify-write operations shall always read the last value (in the modification
11209 order) stored before the write associated with the read-modify-write operation.
11210 13 An atomic store shall only store a value that has been computed from constants and
11211 program input values by a finite sequence of program evaluations, such that each
11212 evaluation observes the values of variables as computed by the last prior assignment in
11213 the sequence.247) The ordering of evaluations in this sequence shall be such that
11214 -- If an evaluation B observes a value computed by A in a different thread, then B does
11215 not happen before A.
11216 -- If an evaluation A is included in the sequence, then all evaluations that assign to the
11217 same variable and happen before A are also included.
11218 14 NOTE 3 The second requirement disallows ''out-of-thin-air'', or ''speculative'' stores of atomics when
11219 relaxed atomics are used. Since unordered operations are involved, evaluations may appear in this
11220 sequence out of thread order. For example, with x and y initially zero,
11222 r1 = atomic_load_explicit(&y, memory_order_relaxed);
11223 atomic_store_explicit(&x, r1, memory_order_relaxed);
11226 r2 = atomic_load_explicit(&x, memory_order_relaxed);
11227 atomic_store_explicit(&y, 42, memory_order_relaxed);
11228 is allowed to produce r1 == 42 && r2 == 42. The sequence of evaluations justifying this consists of:
11233 247) Among other implications, atomic variables shall not decay.
11235 [<a name="#p274" href="p274">page 274</a>] (<a href="#Contents">Contents</a>)
11237 atomic_store_explicit(&y, 42, memory_order_relaxed);
11238 r1 = atomic_load_explicit(&y, memory_order_relaxed);
11239 atomic_store_explicit(&x, r1, memory_order_relaxed);
11240 r2 = atomic_load_explicit(&x, memory_order_relaxed);
11243 r1 = atomic_load_explicit(&y, memory_order_relaxed);
11244 atomic_store_explicit(&x, r1, memory_order_relaxed);
11247 r2 = atomic_load_explicit(&x, memory_order_relaxed);
11248 atomic_store_explicit(&y, r2, memory_order_relaxed);
11249 is not allowed to produce r1 == 42 && r2 = 42, since there is no sequence of evaluations that results
11250 in the computation of 42. In the absence of ''relaxed'' operations and read-modify-write operations with
11251 weaker than memory_order_acq_rel ordering, the second requirement has no impact.
11253 Recommended practice
11254 15 The requirements do not forbid r1 == 42 && r2 == 42 in the following example,
11255 with x and y initially zero:
11257 r1 = atomic_load_explicit(&x, memory_order_relaxed);
11259 atomic_store_explicit(&y, r1, memory_order_relaxed);
11262 r2 = atomic_load_explicit(&y, memory_order_relaxed);
11264 atomic_store_explicit(&x, 42, memory_order_relaxed);
11265 However, this is not useful behavior, and implementations should not allow it.
11266 16 Implementations should make atomic stores visible to atomic loads within a reasonable
11268 <a name="7.17.3.1" href="#7.17.3.1"><b> 7.17.3.1 The kill_dependency macro</b></a>
11270 1 #include <a href="#7.17"><stdatomic.h></a>
11271 type kill_dependency(type y);
11273 2 The kill_dependency macro terminates a dependency chain; the argument does not
11274 carry a dependency to the return value.
11278 [<a name="#p275" href="p275">page 275</a>] (<a href="#Contents">Contents</a>)
11281 3 The kill_dependency macro returns the value of y.
11282 <a name="7.17.4" href="#7.17.4"><b> 7.17.4 Fences</b></a>
11283 1 This subclause introduces synchronization primitives called fences. Fences can have
11284 acquire semantics, release semantics, or both. A fence with acquire semantics is called
11285 an acquire fence; a fence with release semantics is called a release fence.
11286 2 A release fence A synchronizes with an acquire fence B if there exist atomic operations
11287 X and Y , both operating on some atomic object M, such that A is sequenced before X, X
11288 modifies M, Y is sequenced before B, and Y reads the value written by X or a value
11289 written by any side effect in the hypothetical release sequence X would head if it were a
11291 3 A release fence A synchronizes with an atomic operation B that performs an acquire
11292 operation on an atomic object M if there exists an atomic operation X such that A is
11293 sequenced before X, X modifies M, and B reads the value written by X or a value written
11294 by any side effect in the hypothetical release sequence X would head if it were a release
11296 4 An atomic operation A that is a release operation on an atomic object M synchronizes
11297 with an acquire fence B if there exists some atomic operation X on M such that X is
11298 sequenced before B and reads the value written by A or a value written by any side effect
11299 in the release sequence headed by A.
11300 <a name="7.17.4.1" href="#7.17.4.1"><b> 7.17.4.1 The atomic_thread_fence function</b></a>
11302 1 #include <a href="#7.17"><stdatomic.h></a>
11303 void atomic_thread_fence(memory_order order);
11305 2 Depending on the value of order, this operation:
11306 -- has no effects, if order == memory_order_relaxed;
11307 -- is an acquire fence, if order == memory_order_acquire or order ==
11308 memory_order_consume;
11309 -- is a release fence, if order == memory_order_release;
11310 -- is both an acquire fence and a release fence, if order ==
11311 memory_order_acq_rel;
11312 -- is a sequentially consistent acquire and release fence, if order ==
11313 memory_order_seq_cst.
11316 [<a name="#p276" href="p276">page 276</a>] (<a href="#Contents">Contents</a>)
11319 3 The atomic_thread_fence function returns no value.
11320 <a name="7.17.4.2" href="#7.17.4.2"><b> 7.17.4.2 The atomic_signal_fence function</b></a>
11322 1 #include <a href="#7.17"><stdatomic.h></a>
11323 void atomic_signal_fence(memory_order order);
11325 2 Equivalent to atomic_thread_fence(order), except that ''synchronizes with''
11326 relationships are established only between a thread and a signal handler executed in the
11328 3 NOTE 1 The atomic_signal_fence function can be used to specify the order in which actions
11329 performed by the thread become visible to the signal handler.
11331 4 NOTE 2 Compiler optimizations and reorderings of loads and stores are inhibited in the same way as with
11332 atomic_thread_fence, but the hardware fence instructions that atomic_thread_fence would
11333 have inserted are not emitted.
11336 5 The atomic_signal_fence function returns no value.
11337 <a name="7.17.5" href="#7.17.5"><b> 7.17.5 Lock-free property</b></a>
11338 1 The atomic lock-free macros indicate the lock-free property of integer and address atomic
11339 types. A value of 0 indicates that the type is never lock-free; a value of 1 indicates that
11340 the type is sometimes lock-free; a value of 2 indicates that the type is always lock-free.
11341 2 NOTE Operations that are lock-free should also be address-free. That is, atomic operations on the same
11342 memory location via two different addresses will communicate atomically. The implementation should not
11343 depend on any per-process state. This restriction enables communication via memory mapped into a
11344 process more than once and memory shared between two processes.
11346 <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>
11348 1 #include <a href="#7.17"><stdatomic.h></a>
11349 _Bool atomic_is_lock_free(atomic_type const volatile *obj);
11351 2 The atomic_is_lock_free generic function indicates whether or not the object
11352 pointed to by obj is lock-free. atomic_type can be any atomic type.
11354 3 The atomic_is_lock_free generic function returns nonzero (true) if and only if the
11355 object's operations are lock-free. The result of a lock-free query on one object cannot be
11357 [<a name="#p277" href="p277">page 277</a>] (<a href="#Contents">Contents</a>)
11359 inferred from the result of a lock-free query on another object.
11360 <a name="7.17.6" href="#7.17.6"><b> 7.17.6 Atomic integer and address types</b></a>
11361 1 For each line in the following table, the atomic type name is declared as the
11362 corresponding direct type.
11367 [<a name="#p278" href="p278">page 278</a>] (<a href="#Contents">Contents</a>)
11371 Atomic type name Direct type
11372 atomic_char _Atomic char
11373 atomic_schar _Atomic signed char
11374 atomic_uchar _Atomic unsigned char
11375 atomic_short _Atomic short
11376 atomic_ushort _Atomic unsigned short
11377 atomic_int _Atomic int
11378 atomic_uint _Atomic unsigned int
11379 atomic_long _Atomic long
11380 atomic_ulong _Atomic unsigned long
11381 atomic_llong _Atomic long long
11382 atomic_ullong _Atomic unsigned long long
11383 atomic_char16_t _Atomic char16_t
11384 atomic_char32_t _Atomic char32_t
11385 atomic_wchar_t _Atomic wchar_t
11386 atomic_int_least8_t _Atomic int_least8_t
11387 atomic_uint_least8_t _Atomic uint_least8_t
11388 atomic_int_least16_t _Atomic int_least16_t
11389 atomic_uint_least16_t _Atomic uint_least16_t
11390 atomic_int_least32_t _Atomic int_least32_t
11391 atomic_uint_least32_t _Atomic uint_least32_t
11392 atomic_int_least64_t _Atomic int_least64_t
11393 atomic_uint_least64_t _Atomic uint_least64_t
11394 atomic_int_fast8_t _Atomic int_fast8_t
11395 atomic_uint_fast8_t _Atomic uint_fast8_t
11396 atomic_int_fast16_t _Atomic int_fast16_t
11397 atomic_uint_fast16_t _Atomic uint_fast16_t
11398 atomic_int_fast32_t _Atomic int_fast32_t
11399 atomic_uint_fast32_t _Atomic uint_fast32_t
11400 atomic_int_fast64_t _Atomic int_fast64_t
11401 atomic_uint_fast64_t _Atomic uint_fast64_t
11402 atomic_intptr_t _Atomic intptr_t
11403 atomic_uintptr_t _Atomic uintptr_t
11404 atomic_size_t _Atomic size_t
11405 atomic_ptrdiff_t _Atomic ptrdiff_t
11406 atomic_intmax_t _Atomic intmax_t
11407 atomic_uintmax_t _Atomic uintmax_t
11408 2 The semantics of the operations on these types are defined in <a href="#7.17.7">7.17.7</a>.
11412 [<a name="#p279" href="p279">page 279</a>] (<a href="#Contents">Contents</a>)
11414 3 The atomic_bool type provides an atomic boolean.
11415 4 The atomic_address type provides atomic void * operations. The unit of
11416 addition/subtraction shall be one byte.
11417 5 NOTE The representation of atomic integer and address types need not have the same size as their
11418 corresponding regular types. They should have the same size whenever possible, as it eases effort required
11419 to port existing code.
11421 <a name="7.17.7" href="#7.17.7"><b> 7.17.7 Operations on atomic types</b></a>
11422 1 There are only a few kinds of operations on atomic types, though there are many
11423 instances of those kinds. This subclause specifies each general kind.
11424 <a name="7.17.7.1" href="#7.17.7.1"><b> 7.17.7.1 The atomic_store generic functions</b></a>
11426 1 #include <a href="#7.17"><stdatomic.h></a>
11427 void atomic_store(volatile A *object, C desired);
11428 void atomic_store_explicit(volatile A *object,
11429 C desired, memory_order order);
11431 2 The order argument shall not be memory_order_acquire,
11432 memory_order_consume, nor memory_order_acq_rel. Atomically replace the
11433 value pointed to by object with the value of desired. Memory is affected according
11434 to the value of order.
11436 3 The atomic_store generic functions return no value.
11437 <a name="7.17.7.2" href="#7.17.7.2"><b> 7.17.7.2 The atomic_load generic functions</b></a>
11439 1 #include <a href="#7.17"><stdatomic.h></a>
11440 C atomic_load(volatile A *object);
11441 C atomic_load_explicit(volatile A *object,
11442 memory_order order);
11444 2 The order argument shall not be memory_order_release nor
11445 memory_order_acq_rel. Memory is affected according to the value of order.
11447 Atomically returns the value pointed to by object.
11451 [<a name="#p280" href="p280">page 280</a>] (<a href="#Contents">Contents</a>)
11453 <a name="7.17.7.3" href="#7.17.7.3"><b> 7.17.7.3 The atomic_exchange generic functions</b></a>
11455 1 #include <a href="#7.17"><stdatomic.h></a>
11456 C atomic_exchange(volatile A *object, C desired);
11457 C atomic_exchange_explicit(volatile A *object,
11458 C desired, memory_order order);
11460 2 Atomically replace the value pointed to by object with desired. Memory is affected
11461 according to the value of order. These operations are read-modify-write operations
11462 (<a href="#5.1.2.4">5.1.2.4</a>).
11464 3 Atomically returns the value pointed to by object immediately before the effects.
11465 <a name="7.17.7.4" href="#7.17.7.4"><b> 7.17.7.4 The atomic_compare_exchange generic functions</b></a>
11467 1 #include <a href="#7.17"><stdatomic.h></a>
11468 _Bool atomic_compare_exchange_strong(volatile A *object,
11469 C *expected, C desired);
11470 _Bool atomic_compare_exchange_strong_explicit(
11471 volatile A *object, C *expected, C desired,
11472 memory_order success, memory_order failure);
11473 _Bool atomic_compare_exchange_weak(volatile A *object,
11474 C *expected, C desired);
11475 _Bool atomic_compare_exchange_weak_explicit(
11476 volatile A *object, C *expected, C desired,
11477 memory_order success, memory_order failure);
11479 2 The failure argument shall not be memory_order_release nor
11480 memory_order_acq_rel. The failure argument shall be no stronger than the
11481 success argument. Atomically, compares the value pointed to by object for equality
11482 with that in expected, and if true, replaces the value pointed to by object with
11483 desired, and if false, updates the value in expected with the value pointed to by
11484 object. Further, if the comparison is true, memory is affected according to the value of
11485 success, and if the comparison is false, memory is affected according to the value of
11486 failure. These operations are atomic read-modify-write operations (<a href="#5.1.2.4">5.1.2.4</a>).
11487 3 NOTE 1 The effect of the compare-and-exchange operations is
11492 [<a name="#p281" href="p281">page 281</a>] (<a href="#Contents">Contents</a>)
11494 if (*object == *expected)
11497 *expected = *object;
11499 4 The weak compare-and-exchange operations may fail spuriously, that is, return zero
11500 while leaving the value pointed to by expected unchanged.
11501 5 NOTE 2 This spurious failure enables implementation of compare-and-exchange on a broader class of
11502 machines, e.g. load-locked store-conditional machines.
11504 6 EXAMPLE A consequence of spurious failure is that nearly all uses of weak compare-and-exchange will
11506 exp = atomic_load(&cur);
11508 des = function(exp);
11509 } while (!atomic_compare_exchange_weak(&cur, &exp, des));
11510 When a compare-and-exchange is in a loop, the weak version will yield better performance on some
11511 platforms. When a weak compare-and-exchange would require a loop and a strong one would not, the
11512 strong one is preferable.
11515 7 The result of the comparison.
11516 <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>
11517 1 The following operations perform arithmetic and bitwise computations. All of these
11518 operations are applicable to an object of any atomic integer type. Only addition and
11519 subtraction are applicable to atomic_address. None of these operations is applicable
11520 to atomic_bool. The key, operator, and computation correspondence is:
11526 or | bitwise inclusive or
11527 xor ^ bitwise exclusive or
11528 and & bitwise and
11530 2 #include <a href="#7.17"><stdatomic.h></a>
11531 C atomic_fetch_key(volatile A *object, M operand);
11532 C atomic_fetch_key_explicit(volatile A *object,
11533 M operand, memory_order order);
11535 3 Atomically replaces the value pointed to by object with the result of the computation
11536 applied to the value pointed to by object and the given operand. Memory is affected
11537 [<a name="#p282" href="p282">page 282</a>] (<a href="#Contents">Contents</a>)
11539 according to the value of order. These operations are atomic read-modify-write
11540 operations (<a href="#5.1.2.4">5.1.2.4</a>). For signed integer types, arithmetic is defined to use two's-
11541 complement representation. There are no undefined results. For address types, the result
11542 may be an undefined address, but the operations otherwise have no undefined behavior.
11544 4 Atomically, the value pointed to by object immediately before the effects.
11545 5 NOTE The operation of the atomic_fetch and modify generic functions are nearly equivalent to the
11546 operation of the corresponding op= compound assignment operators. The only differences are that the
11547 compound assignment operators are not guaranteed to operate atomically, and the value yielded by a
11548 compound assignment operator is the updated value of the object, whereas the value returned by the
11549 atomic_fetch and modify generic functions is the previous value of the atomic object.
11551 <a name="7.17.8" href="#7.17.8"><b> 7.17.8 Atomic flag type and operations</b></a>
11552 1 The atomic_flag type provides the classic test-and-set functionality. It has two
11553 states, set and clear.
11554 2 Operations on an object of type atomic_flag shall be lock free.
11555 3 NOTE Hence the operations should also be address-free. No other type requires lock-free operations, so
11556 the atomic_flag type is the minimum hardware-implemented type needed to conform to this
11557 International standard. The remaining types can be emulated with atomic_flag, though with less than
11560 4 The macro ATOMIC_FLAG_INIT may be used to initialize an atomic_flag to the
11561 clear state. An atomic_flag that is not explicitly initialized with
11562 ATOMIC_FLAG_INIT is initially in an indeterminate state.
11564 atomic_flag guard = ATOMIC_FLAG_INIT;
11566 <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>
11568 1 #include <a href="#7.17"><stdatomic.h></a>
11569 bool atomic_flag_test_and_set(
11570 volatile atomic_flag *object);
11571 bool atomic_flag_test_and_set_explicit(
11572 volatile atomic_flag *object, memory_order order);
11574 2 Atomically sets the value pointed to by object to true. Memory is affected according
11575 to the value of order. These operations are atomic read-modify-write operations
11576 (<a href="#5.1.2.4">5.1.2.4</a>).
11581 [<a name="#p283" href="p283">page 283</a>] (<a href="#Contents">Contents</a>)
11584 3 Atomically, the value of the object immediately before the effects.
11585 <a name="7.17.8.2" href="#7.17.8.2"><b> 7.17.8.2 The atomic_flag_clear functions</b></a>
11587 1 #include <a href="#7.17"><stdatomic.h></a>
11588 void atomic_flag_clear(volatile atomic_flag *object);
11589 void atomic_flag_clear_explicit(
11590 volatile atomic_flag *object, memory_order order);
11592 2 The order argument shall not be memory_order_acquire nor
11593 memory_order_acq_rel. Atomically sets the value pointed to by object to false.
11594 Memory is affected according to the value of order.
11596 3 The atomic_flag_clear functions return no value.
11601 [<a name="#p284" href="p284">page 284</a>] (<a href="#Contents">Contents</a>)
11603 <a name="7.18" href="#7.18"><b> 7.18 Boolean type and values <stdbool.h></b></a>
11604 1 The header <a href="#7.18"><stdbool.h></a> defines four macros.
11608 3 The remaining three macros are suitable for use in #if preprocessing directives. They
11611 which expands to the integer constant 1,
11613 which expands to the integer constant 0, and
11614 __bool_true_false_are_defined
11615 which expands to the integer constant 1.
11616 4 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
11617 redefine the macros bool, true, and false.248)
11622 248) See ''future library directions'' (<a href="#7.30.7">7.30.7</a>).
11624 [<a name="#p285" href="p285">page 285</a>] (<a href="#Contents">Contents</a>)
11626 <a name="7.19" href="#7.19"><b> 7.19 Common definitions <stddef.h></b></a>
11627 1 The header <a href="#7.19"><stddef.h></a> defines the following macros and declares the following types.
11628 Some are also defined in other headers, as noted in their respective subclauses.
11631 which is the signed integer type of the result of subtracting two pointers;
11633 which is the unsigned integer type of the result of the sizeof operator;
11635 which is an object type whose alignment is as great as is supported by the implementation
11636 in all contexts; and
11638 which is an integer type whose range of values can represent distinct codes for all
11639 members of the largest extended character set specified among the supported locales; the
11640 null character shall have the code value zero. Each member of the basic character set
11641 shall have a code value equal to its value when used as the lone character in an integer
11642 character constant if an implementation does not define
11643 __STDC_MB_MIGHT_NEQ_WC__.
11646 which expands to an implementation-defined null pointer constant; and
11647 offsetof(type, member-designator)
11648 which expands to an integer constant expression that has type size_t, the value of
11649 which is the offset in bytes, to the structure member (designated by member-designator),
11650 from the beginning of its structure (designated by type). The type and member designator
11651 shall be such that given
11653 then the expression &(t.member-designator) evaluates to an address constant. (If the
11654 specified member is a bit-field, the behavior is undefined.)
11655 Recommended practice
11656 4 The types used for size_t and ptrdiff_t should not have an integer conversion rank
11657 greater than that of signed long int unless the implementation supports objects
11658 large enough to make this necessary.
11660 [<a name="#p286" href="p286">page 286</a>] (<a href="#Contents">Contents</a>)
11662 Forward references: localization (<a href="#7.11">7.11</a>).
11667 [<a name="#p287" href="p287">page 287</a>] (<a href="#Contents">Contents</a>)
11669 <a name="7.20" href="#7.20"><b> 7.20 Integer types <stdint.h></b></a>
11670 1 The header <a href="#7.20"><stdint.h></a> declares sets of integer types having specified widths, and
11671 defines corresponding sets of macros.249) It also defines macros that specify limits of
11672 integer types corresponding to types defined in other standard headers.
11673 2 Types are defined in the following categories:
11674 -- integer types having certain exact widths;
11675 -- integer types having at least certain specified widths;
11676 -- fastest integer types having at least certain specified widths;
11677 -- integer types wide enough to hold pointers to objects;
11678 -- integer types having greatest width.
11679 (Some of these types may denote the same type.)
11680 3 Corresponding macros specify limits of the declared types and construct suitable
11682 4 For each type described herein that the implementation provides,250) <a href="#7.20"><stdint.h></a> shall
11683 declare that typedef name and define the associated macros. Conversely, for each type
11684 described herein that the implementation does not provide, <a href="#7.20"><stdint.h></a> shall not
11685 declare that typedef name nor shall it define the associated macros. An implementation
11686 shall provide those types described as ''required'', but need not provide any of the others
11687 (described as ''optional'').
11688 <a name="7.20.1" href="#7.20.1"><b> 7.20.1 Integer types</b></a>
11689 1 When typedef names differing only in the absence or presence of the initial u are defined,
11690 they shall denote corresponding signed and unsigned types as described in <a href="#6.2.5">6.2.5</a>; an
11691 implementation providing one of these corresponding types shall also provide the other.
11692 2 In the following descriptions, the symbol N represents an unsigned decimal integer with
11693 no leading zeros (e.g., 8 or 24, but not 04 or 048).
11698 249) See ''future library directions'' (<a href="#7.30.8">7.30.8</a>).
11699 250) Some of these types may denote implementation-defined extended integer types.
11701 [<a name="#p288" href="p288">page 288</a>] (<a href="#Contents">Contents</a>)
11703 <a name="7.20.1.1" href="#7.20.1.1"><b> 7.20.1.1 Exact-width integer types</b></a>
11704 1 The typedef name intN_t designates a signed integer type with width N , no padding
11705 bits, and a two's complement representation. Thus, int8_t denotes such a signed
11706 integer type with a width of exactly 8 bits.
11707 2 The typedef name uintN_t designates an unsigned integer type with width N and no
11708 padding bits. Thus, uint24_t denotes such an unsigned integer type with a width of
11710 3 These types are optional. However, if an implementation provides integer types with
11711 widths of 8, 16, 32, or 64 bits, no padding bits, and (for the signed types) that have a
11712 two's complement representation, it shall define the corresponding typedef names.
11713 <a name="7.20.1.2" href="#7.20.1.2"><b> 7.20.1.2 Minimum-width integer types</b></a>
11714 1 The typedef name int_leastN_t designates a signed integer type with a width of at
11715 least N , such that no signed integer type with lesser size has at least the specified width.
11716 Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits.
11717 2 The typedef name uint_leastN_t designates an unsigned integer type with a width
11718 of at least N , such that no unsigned integer type with lesser size has at least the specified
11719 width. Thus, uint_least16_t denotes an unsigned integer type with a width of at
11721 3 The following types are required:
11722 int_least8_t uint_least8_t
11723 int_least16_t uint_least16_t
11724 int_least32_t uint_least32_t
11725 int_least64_t uint_least64_t
11726 All other types of this form are optional.
11727 <a name="7.20.1.3" href="#7.20.1.3"><b> 7.20.1.3 Fastest minimum-width integer types</b></a>
11728 1 Each of the following types designates an integer type that is usually fastest251) to operate
11729 with among all integer types that have at least the specified width.
11730 2 The typedef name int_fastN_t designates the fastest signed integer type with a width
11731 of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer
11732 type with a width of at least N .
11737 251) The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear
11738 grounds for choosing one type over another, it will simply pick some integer type satisfying the
11739 signedness and width requirements.
11741 [<a name="#p289" href="p289">page 289</a>] (<a href="#Contents">Contents</a>)
11743 3 The following types are required:
11744 int_fast8_t uint_fast8_t
11745 int_fast16_t uint_fast16_t
11746 int_fast32_t uint_fast32_t
11747 int_fast64_t uint_fast64_t
11748 All other types of this form are optional.
11749 <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>
11750 1 The following type designates a signed integer type with the property that any valid
11751 pointer to void can be converted to this type, then converted back to pointer to void,
11752 and the result will compare equal to the original pointer:
11754 The following type designates an unsigned integer type with the property that any valid
11755 pointer to void can be converted to this type, then converted back to pointer to void,
11756 and the result will compare equal to the original pointer:
11758 These types are optional.
11759 <a name="7.20.1.5" href="#7.20.1.5"><b> 7.20.1.5 Greatest-width integer types</b></a>
11760 1 The following type designates a signed integer type capable of representing any value of
11761 any signed integer type:
11763 The following type designates an unsigned integer type capable of representing any value
11764 of any unsigned integer type:
11766 These types are required.
11767 <a name="7.20.2" href="#7.20.2"><b> 7.20.2 Limits of specified-width integer types</b></a>
11768 1 The following object-like macros specify the minimum and maximum limits of the types
11769 declared in <a href="#7.20"><stdint.h></a>. Each macro name corresponds to a similar type name in
11770 <a name="7.20.1" href="#7.20.1"><b> 7.20.1.</b></a>
11771 2 Each instance of any defined macro shall be replaced by a constant expression suitable
11772 for use in #if preprocessing directives, and this expression shall have the same type as
11773 would an expression that is an object of the corresponding type converted according to
11774 the integer promotions. Its implementation-defined value shall be equal to or greater in
11775 magnitude (absolute value) than the corresponding value given below, with the same sign,
11776 except where stated to be exactly the given value.
11778 [<a name="#p290" href="p290">page 290</a>] (<a href="#Contents">Contents</a>)
11780 <a name="7.20.2.1" href="#7.20.2.1"><b> 7.20.2.1 Limits of exact-width integer types</b></a>
11781 1 -- minimum values of exact-width signed integer types
11782 INTN_MIN exactly -(2 N -1 )
11783 -- maximum values of exact-width signed integer types
11784 INTN_MAX exactly 2 N -1 - 1
11785 -- maximum values of exact-width unsigned integer types
11786 UINTN_MAX exactly 2 N - 1
11787 <a name="7.20.2.2" href="#7.20.2.2"><b> 7.20.2.2 Limits of minimum-width integer types</b></a>
11788 1 -- minimum values of minimum-width signed integer types
11789 INT_LEASTN_MIN -(2 N -1 - 1)
11790 -- maximum values of minimum-width signed integer types
11791 INT_LEASTN_MAX 2 N -1 - 1
11792 -- maximum values of minimum-width unsigned integer types
11793 UINT_LEASTN_MAX 2N - 1
11794 <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>
11795 1 -- minimum values of fastest minimum-width signed integer types
11796 INT_FASTN_MIN -(2 N -1 - 1)
11797 -- maximum values of fastest minimum-width signed integer types
11798 INT_FASTN_MAX 2 N -1 - 1
11799 -- maximum values of fastest minimum-width unsigned integer types
11800 UINT_FASTN_MAX 2N - 1
11801 <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>
11802 1 -- minimum value of pointer-holding signed integer type
11803 INTPTR_MIN -(215 - 1)
11804 -- maximum value of pointer-holding signed integer type
11806 -- maximum value of pointer-holding unsigned integer type
11807 UINTPTR_MAX 216 - 1
11811 [<a name="#p291" href="p291">page 291</a>] (<a href="#Contents">Contents</a>)
11813 <a name="7.20.2.5" href="#7.20.2.5"><b> 7.20.2.5 Limits of greatest-width integer types</b></a>
11814 1 -- minimum value of greatest-width signed integer type
11815 INTMAX_MIN -(263 - 1)
11816 -- maximum value of greatest-width signed integer type
11818 -- maximum value of greatest-width unsigned integer type
11819 UINTMAX_MAX 264 - 1
11820 <a name="7.20.3" href="#7.20.3"><b> 7.20.3 Limits of other integer types</b></a>
11821 1 The following object-like macros specify the minimum and maximum limits of integer
11822 types corresponding to types defined in other standard headers.
11823 2 Each instance of these macros shall be replaced by a constant expression suitable for use
11824 in #if preprocessing directives, and this expression shall have the same type as would an
11825 expression that is an object of the corresponding type converted according to the integer
11826 promotions. Its implementation-defined value shall be equal to or greater in magnitude
11827 (absolute value) than the corresponding value given below, with the same sign. An
11828 implementation shall define only the macros corresponding to those typedef names it
11829 actually provides.252)
11830 -- limits of ptrdiff_t
11833 -- limits of sig_atomic_t
11834 SIG_ATOMIC_MIN see below
11835 SIG_ATOMIC_MAX see below
11838 -- limits of wchar_t
11839 WCHAR_MIN see below
11840 WCHAR_MAX see below
11841 -- limits of wint_t
11846 252) A freestanding implementation need not provide all of these types.
11848 [<a name="#p292" href="p292">page 292</a>] (<a href="#Contents">Contents</a>)
11852 3 If sig_atomic_t (see <a href="#7.14">7.14</a>) is defined as a signed integer type, the value of
11853 SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX
11854 shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
11855 type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
11856 SIG_ATOMIC_MAX shall be no less than 255.
11857 4 If wchar_t (see <a href="#7.19">7.19</a>) is defined as a signed integer type, the value of WCHAR_MIN
11858 shall be no greater than -127 and the value of WCHAR_MAX shall be no less than 127;
11859 otherwise, wchar_t is defined as an unsigned integer type, and the value of
11860 WCHAR_MIN shall be 0 and the value of WCHAR_MAX shall be no less than 255.253)
11861 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
11862 be no greater than -32767 and the value of WINT_MAX shall be no less than 32767;
11863 otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
11864 shall be 0 and the value of WINT_MAX shall be no less than 65535.
11865 <a name="7.20.4" href="#7.20.4"><b> 7.20.4 Macros for integer constants</b></a>
11866 1 The following function-like macros expand to integer constants suitable for initializing
11867 objects that have integer types corresponding to types defined in <a href="#7.20"><stdint.h></a>. Each
11868 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>.
11869 2 The argument in any instance of these macros shall be an unsuffixed integer constant (as
11870 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.
11871 3 Each invocation of one of these macros shall expand to an integer constant expression
11872 suitable for use in #if preprocessing directives. The type of the expression shall have
11873 the same type as would an expression of the corresponding type converted according to
11874 the integer promotions. The value of the expression shall be that of the argument.
11875 <a name="7.20.4.1" href="#7.20.4.1"><b> 7.20.4.1 Macros for minimum-width integer constants</b></a>
11876 1 The macro INTN_C(value) shall expand to an integer constant expression
11877 corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
11878 to an integer constant expression corresponding to the type uint_leastN_t. For
11879 example, if uint_least64_t is a name for the type unsigned long long int,
11880 then UINT64_C(0x123) might expand to the integer constant 0x123ULL.
11885 253) The values WCHAR_MIN and WCHAR_MAX do not necessarily correspond to members of the extended
11888 [<a name="#p293" href="p293">page 293</a>] (<a href="#Contents">Contents</a>)
11890 <a name="7.20.4.2" href="#7.20.4.2"><b> 7.20.4.2 Macros for greatest-width integer constants</b></a>
11891 1 The following macro expands to an integer constant expression having the value specified
11892 by its argument and the type intmax_t:
11894 The following macro expands to an integer constant expression having the value specified
11895 by its argument and the type uintmax_t:
11901 [<a name="#p294" href="p294">page 294</a>] (<a href="#Contents">Contents</a>)
11903 <a name="7.21" href="#7.21"><b> 7.21 Input/output <stdio.h></b></a>
11904 <a name="7.21.1" href="#7.21.1"><b> 7.21.1 Introduction</b></a>
11905 1 The header <a href="#7.21"><stdio.h></a> defines several macros, and declares three types and many
11906 functions for performing input and output.
11907 2 The types declared are size_t (described in <a href="#7.19">7.19</a>);
11909 which is an object type capable of recording all the information needed to control a
11910 stream, including its file position indicator, a pointer to its associated buffer (if any), an
11911 error indicator that records whether a read/write error has occurred, and an end-of-file
11912 indicator that records whether the end of the file has been reached; and
11914 which is a complete object type other than an array type capable of recording all the
11915 information needed to specify uniquely every position within a file.
11916 3 The macros are NULL (described in <a href="#7.19">7.19</a>);
11920 which expand to integer constant expressions with distinct values, suitable for use as the
11921 third argument to the setvbuf function;
11923 which expands to an integer constant expression that is the size of the buffer used by the
11926 which expands to an integer constant expression, with type int and a negative value, that
11927 is returned by several functions to indicate end-of-file, that is, no more input from a
11930 which expands to an integer constant expression that is the minimum number of files that
11931 the implementation guarantees can be open simultaneously;
11933 which expands to an integer constant expression that is the size needed for an array of
11934 char large enough to hold the longest file name string that the implementation
11938 [<a name="#p295" href="p295">page 295</a>] (<a href="#Contents">Contents</a>)
11940 guarantees can be opened;254)
11942 which expands to an integer constant expression that is the size needed for an array of
11943 char large enough to hold a temporary file name string generated by the tmpnam
11948 which expand to integer constant expressions with distinct values, suitable for use as the
11949 third argument to the fseek function;
11951 which expands to an integer constant expression that is the minimum number of unique
11952 file names that can be generated by the tmpnam function;
11956 which are expressions of type ''pointer to FILE'' that point to the FILE objects
11957 associated, respectively, with the standard error, input, and output streams.
11958 4 The header <a href="#7.28"><wchar.h></a> declares a number of functions useful for wide character input
11959 and output. The wide character input/output functions described in that subclause
11960 provide operations analogous to most of those described here, except that the
11961 fundamental units internal to the program are wide characters. The external
11962 representation (in the file) is a sequence of ''generalized'' multibyte characters, as
11963 described further in <a href="#7.21.3">7.21.3</a>.
11964 5 The input/output functions are given the following collective terms:
11965 -- The wide character input functions -- those functions described in <a href="#7.28">7.28</a> that perform
11966 input into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar,
11967 fwscanf, wscanf, vfwscanf, and vwscanf.
11968 -- The wide character output functions -- those functions described in <a href="#7.28">7.28</a> that perform
11969 output from wide characters and wide strings: fputwc, fputws, putwc,
11970 putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
11973 254) If the implementation imposes no practical limit on the length of file name strings, the value of
11974 FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
11975 string. Of course, file name string contents are subject to other system-specific constraints; therefore
11976 all possible strings of length FILENAME_MAX cannot be expected to be opened successfully.
11978 [<a name="#p296" href="p296">page 296</a>] (<a href="#Contents">Contents</a>)
11980 -- The wide character input/output functions -- the union of the ungetwc function, the
11981 wide character input functions, and the wide character output functions.
11982 -- The byte input/output functions -- those functions described in this subclause that
11983 perform input/output: fgetc, fgets, fprintf, fputc, fputs, fread,
11984 fscanf, fwrite, getc, getchar, printf, putc, putchar, puts, scanf,
11985 ungetc, vfprintf, vfscanf, vprintf, and vscanf.
11986 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
11987 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>).
11988 <a name="7.21.2" href="#7.21.2"><b> 7.21.2 Streams</b></a>
11989 1 Input and output, whether to or from physical devices such as terminals and tape drives,
11990 or whether to or from files supported on structured storage devices, are mapped into
11991 logical data streams, whose properties are more uniform than their various inputs and
11992 outputs. Two forms of mapping are supported, for text streams and for binary
11994 2 A text stream is an ordered sequence of characters composed into lines, each line
11995 consisting of zero or more characters plus a terminating new-line character. Whether the
11996 last line requires a terminating new-line character is implementation-defined. Characters
11997 may have to be added, altered, or deleted on input and output to conform to differing
11998 conventions for representing text in the host environment. Thus, there need not be a one-
11999 to-one correspondence between the characters in a stream and those in the external
12000 representation. Data read in from a text stream will necessarily compare equal to the data
12001 that were earlier written out to that stream only if: the data consist only of printing
12002 characters and the control characters horizontal tab and new-line; no new-line character is
12003 immediately preceded by space characters; and the last character is a new-line character.
12004 Whether space characters that are written out immediately before a new-line character
12005 appear when read in is implementation-defined.
12006 3 A binary stream is an ordered sequence of characters that can transparently record
12007 internal data. Data read in from a binary stream shall compare equal to the data that were
12008 earlier written out to that stream, under the same implementation. Such a stream may,
12009 however, have an implementation-defined number of null characters appended to the end
12011 4 Each stream has an orientation. After a stream is associated with an external file, but
12012 before any operations are performed on it, the stream is without orientation. Once a wide
12013 character input/output function has been applied to a stream without orientation, the
12016 255) An implementation need not distinguish between text streams and binary streams. In such an
12017 implementation, there need be no new-line characters in a text stream nor any limit to the length of a
12020 [<a name="#p297" href="p297">page 297</a>] (<a href="#Contents">Contents</a>)
12022 stream becomes a wide-oriented stream. Similarly, once a byte input/output function has
12023 been applied to a stream without orientation, the stream becomes a byte-oriented stream.
12024 Only a call to the freopen function or the fwide function can otherwise alter the
12025 orientation of a stream. (A successful call to freopen removes any orientation.)256)
12026 5 Byte input/output functions shall not be applied to a wide-oriented stream and wide
12027 character input/output functions shall not be applied to a byte-oriented stream. The
12028 remaining stream operations do not affect, and are not affected by, a stream's orientation,
12029 except for the following additional restrictions:
12030 -- Binary wide-oriented streams have the file-positioning restrictions ascribed to both
12031 text and binary streams.
12032 -- For wide-oriented streams, after a successful call to a file-positioning function that
12033 leaves the file position indicator prior to the end-of-file, a wide character output
12034 function can overwrite a partial multibyte character; any file contents beyond the
12035 byte(s) written are henceforth indeterminate.
12036 6 Each wide-oriented stream has an associated mbstate_t object that stores the current
12037 parse state of the stream. A successful call to fgetpos stores a representation of the
12038 value of this mbstate_t object as part of the value of the fpos_t object. A later
12039 successful call to fsetpos using the same stored fpos_t value restores the value of
12040 the associated mbstate_t object as well as the position within the controlled stream.
12041 Environmental limits
12042 7 An implementation shall support text files with lines containing at least 254 characters,
12043 including the terminating new-line character. The value of the macro BUFSIZ shall be at
12045 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>),
12046 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
12047 (<a href="#7.21.9.3">7.21.9.3</a>).
12052 256) The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
12054 [<a name="#p298" href="p298">page 298</a>] (<a href="#Contents">Contents</a>)
12056 <a name="7.21.3" href="#7.21.3"><b> 7.21.3 Files</b></a>
12057 1 A stream is associated with an external file (which may be a physical device) by opening
12058 a file, which may involve creating a new file. Creating an existing file causes its former
12059 contents to be discarded, if necessary. If a file can support positioning requests (such as a
12060 disk file, as opposed to a terminal), then a file position indicator associated with the
12061 stream is positioned at the start (character number zero) of the file, unless the file is
12062 opened with append mode in which case it is implementation-defined whether the file
12063 position indicator is initially positioned at the beginning or the end of the file. The file
12064 position indicator is maintained by subsequent reads, writes, and positioning requests, to
12065 facilitate an orderly progression through the file.
12066 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
12067 stream causes the associated file to be truncated beyond that point is implementation-
12069 3 When a stream is unbuffered, characters are intended to appear from the source or at the
12070 destination as soon as possible. Otherwise characters may be accumulated and
12071 transmitted to or from the host environment as a block. When a stream is fully buffered,
12072 characters are intended to be transmitted to or from the host environment as a block when
12073 a buffer is filled. When a stream is line buffered, characters are intended to be
12074 transmitted to or from the host environment as a block when a new-line character is
12075 encountered. Furthermore, characters are intended to be transmitted as a block to the host
12076 environment when a buffer is filled, when input is requested on an unbuffered stream, or
12077 when input is requested on a line buffered stream that requires the transmission of
12078 characters from the host environment. Support for these characteristics is
12079 implementation-defined, and may be affected via the setbuf and setvbuf functions.
12080 4 A file may be disassociated from a controlling stream by closing the file. Output streams
12081 are flushed (any unwritten buffer contents are transmitted to the host environment) before
12082 the stream is disassociated from the file. The value of a pointer to a FILE object is
12083 indeterminate after the associated file is closed (including the standard text streams).
12084 Whether a file of zero length (on which no characters have been written by an output
12085 stream) actually exists is implementation-defined.
12086 5 The file may be subsequently reopened, by the same or another program execution, and
12087 its contents reclaimed or modified (if it can be repositioned at its start). If the main
12088 function returns to its original caller, or if the exit function is called, all open files are
12089 closed (hence all output streams are flushed) before program termination. Other paths to
12090 program termination, such as calling the abort function, need not close all files
12092 6 The address of the FILE object used to control a stream may be significant; a copy of a
12093 FILE object need not serve in place of the original.
12095 [<a name="#p299" href="p299">page 299</a>] (<a href="#Contents">Contents</a>)
12097 7 At program startup, three text streams are predefined and need not be opened explicitly
12098 -- standard input (for reading conventional input), standard output (for writing
12099 conventional output), and standard error (for writing diagnostic output). As initially
12100 opened, the standard error stream is not fully buffered; the standard input and standard
12101 output streams are fully buffered if and only if the stream can be determined not to refer
12102 to an interactive device.
12103 8 Functions that open additional (nontemporary) files require a file name, which is a string.
12104 The rules for composing valid file names are implementation-defined. Whether the same
12105 file can be simultaneously open multiple times is also implementation-defined.
12106 9 Although both text and binary wide-oriented streams are conceptually sequences of wide
12107 characters, the external file associated with a wide-oriented stream is a sequence of
12108 multibyte characters, generalized as follows:
12109 -- Multibyte encodings within files may contain embedded null bytes (unlike multibyte
12110 encodings valid for use internal to the program).
12111 -- A file need not begin nor end in the initial shift state.257)
12112 10 Moreover, the encodings used for multibyte characters may differ among files. Both the
12113 nature and choice of such encodings are implementation-defined.
12114 11 The wide character input functions read multibyte characters from the stream and convert
12115 them to wide characters as if they were read by successive calls to the fgetwc function.
12116 Each conversion occurs as if by a call to the mbrtowc function, with the conversion state
12117 described by the stream's own mbstate_t object. The byte input functions read
12118 characters from the stream as if by successive calls to the fgetc function.
12119 12 The wide character output functions convert wide characters to multibyte characters and
12120 write them to the stream as if they were written by successive calls to the fputwc
12121 function. Each conversion occurs as if by a call to the wcrtomb function, with the
12122 conversion state described by the stream's own mbstate_t object. The byte output
12123 functions write characters to the stream as if by successive calls to the fputc function.
12124 13 In some cases, some of the byte input/output functions also perform conversions between
12125 multibyte characters and wide characters. These conversions also occur as if by calls to
12126 the mbrtowc and wcrtomb functions.
12127 14 An encoding error occurs if the character sequence presented to the underlying
12128 mbrtowc function does not form a valid (generalized) multibyte character, or if the code
12129 value passed to the underlying wcrtomb does not correspond to a valid (generalized)
12132 257) Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END), has
12133 undefined behavior for a binary stream (because of possible trailing null characters) or for any stream
12134 with state-dependent encoding that does not assuredly end in the initial shift state.
12136 [<a name="#p300" href="p300">page 300</a>] (<a href="#Contents">Contents</a>)
12138 multibyte character. The wide character input/output functions and the byte input/output
12139 functions store the value of the macro EILSEQ in errno if and only if an encoding error
12141 Environmental limits
12142 15 The value of FOPEN_MAX shall be at least eight, including the three standard text
12144 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
12145 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
12146 (<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
12147 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
12148 (<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>).
12149 <a name="7.21.4" href="#7.21.4"><b> 7.21.4 Operations on files</b></a>
12150 <a name="7.21.4.1" href="#7.21.4.1"><b> 7.21.4.1 The remove function</b></a>
12152 1 #include <a href="#7.21"><stdio.h></a>
12153 int remove(const char *filename);
12155 2 The remove function causes the file whose name is the string pointed to by filename
12156 to be no longer accessible by that name. A subsequent attempt to open that file using that
12157 name will fail, unless it is created anew. If the file is open, the behavior of the remove
12158 function is implementation-defined.
12160 3 The remove function returns zero if the operation succeeds, nonzero if it fails.
12161 <a name="7.21.4.2" href="#7.21.4.2"><b> 7.21.4.2 The rename function</b></a>
12163 1 #include <a href="#7.21"><stdio.h></a>
12164 int rename(const char *old, const char *new);
12166 2 The rename function causes the file whose name is the string pointed to by old to be
12167 henceforth known by the name given by the string pointed to by new. The file named
12168 old is no longer accessible by that name. If a file named by the string pointed to by new
12169 exists prior to the call to the rename function, the behavior is implementation-defined.
12174 [<a name="#p301" href="p301">page 301</a>] (<a href="#Contents">Contents</a>)
12177 3 The rename function returns zero if the operation succeeds, nonzero if it fails,258) in
12178 which case if the file existed previously it is still known by its original name.
12179 <a name="7.21.4.3" href="#7.21.4.3"><b> 7.21.4.3 The tmpfile function</b></a>
12181 1 #include <a href="#7.21"><stdio.h></a>
12182 FILE *tmpfile(void);
12184 2 The tmpfile function creates a temporary binary file that is different from any other
12185 existing file and that will automatically be removed when it is closed or at program
12186 termination. If the program terminates abnormally, whether an open temporary file is
12187 removed is implementation-defined. The file is opened for update with "wb+" mode.
12188 Recommended practice
12189 3 It should be possible to open at least TMP_MAX temporary files during the lifetime of the
12190 program (this limit may be shared with tmpnam) and there should be no limit on the
12191 number simultaneously open other than this limit and any limit on the number of open
12194 4 The tmpfile function returns a pointer to the stream of the file that it created. If the file
12195 cannot be created, the tmpfile function returns a null pointer.
12196 Forward references: the fopen function (<a href="#7.21.5.3">7.21.5.3</a>).
12197 <a name="7.21.4.4" href="#7.21.4.4"><b> 7.21.4.4 The tmpnam function</b></a>
12199 1 #include <a href="#7.21"><stdio.h></a>
12200 char *tmpnam(char *s);
12202 2 The tmpnam function generates a string that is a valid file name and that is not the same
12203 as the name of an existing file.259) The function is potentially capable of generating at
12206 258) Among the reasons the implementation may cause the rename function to fail are that the file is open
12207 or that it is necessary to copy its contents to effectuate its renaming.
12208 259) Files created using strings generated by the tmpnam function are temporary only in the sense that
12209 their names should not collide with those generated by conventional naming rules for the
12210 implementation. It is still necessary to use the remove function to remove such files when their use
12211 is ended, and before program termination.
12213 [<a name="#p302" href="p302">page 302</a>] (<a href="#Contents">Contents</a>)
12215 least TMP_MAX different strings, but any or all of them may already be in use by existing
12216 files and thus not be suitable return values.
12217 3 The tmpnam function generates a different string each time it is called.
12218 4 Calls to the tmpnam function with a null pointer argument may introduce data races with
12219 each other. The implementation shall behave as if no library function calls the tmpnam
12222 5 If no suitable string can be generated, the tmpnam function returns a null pointer.
12223 Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an
12224 internal static object and returns a pointer to that object (subsequent calls to the tmpnam
12225 function may modify the same object). If the argument is not a null pointer, it is assumed
12226 to point to an array of at least L_tmpnam chars; the tmpnam function writes its result
12227 in that array and returns the argument as its value.
12228 Environmental limits
12229 6 The value of the macro TMP_MAX shall be at least 25.
12230 <a name="7.21.5" href="#7.21.5"><b> 7.21.5 File access functions</b></a>
12231 <a name="7.21.5.1" href="#7.21.5.1"><b> 7.21.5.1 The fclose function</b></a>
12233 1 #include <a href="#7.21"><stdio.h></a>
12234 int fclose(FILE *stream);
12236 2 A successful call to the fclose function causes the stream pointed to by stream to be
12237 flushed and the associated file to be closed. Any unwritten buffered data for the stream
12238 are delivered to the host environment to be written to the file; any unread buffered data
12239 are discarded. Whether or not the call succeeds, the stream is disassociated from the file
12240 and any buffer set by the setbuf or setvbuf function is disassociated from the stream
12241 (and deallocated if it was automatically allocated).
12243 3 The fclose function returns zero if the stream was successfully closed, or EOF if any
12244 errors were detected.
12249 [<a name="#p303" href="p303">page 303</a>] (<a href="#Contents">Contents</a>)
12251 <a name="7.21.5.2" href="#7.21.5.2"><b> 7.21.5.2 The fflush function</b></a>
12253 1 #include <a href="#7.21"><stdio.h></a>
12254 int fflush(FILE *stream);
12256 2 If stream points to an output stream or an update stream in which the most recent
12257 operation was not input, the fflush function causes any unwritten data for that stream
12258 to be delivered to the host environment to be written to the file; otherwise, the behavior is
12260 3 If stream is a null pointer, the fflush function performs this flushing action on all
12261 streams for which the behavior is defined above.
12263 4 The fflush function sets the error indicator for the stream and returns EOF if a write
12264 error occurs, otherwise it returns zero.
12265 Forward references: the fopen function (<a href="#7.21.5.3">7.21.5.3</a>).
12266 <a name="7.21.5.3" href="#7.21.5.3"><b> 7.21.5.3 The fopen function</b></a>
12268 1 #include <a href="#7.21"><stdio.h></a>
12269 FILE *fopen(const char * restrict filename,
12270 const char * restrict mode);
12272 2 The fopen function opens the file whose name is the string pointed to by filename,
12273 and associates a stream with it.
12274 3 The argument mode points to a string. If the string is one of the following, the file is
12275 open in the indicated mode. Otherwise, the behavior is undefined.260)
12276 r open text file for reading
12277 w truncate to zero length or create text file for writing
12278 wx create text file for writing
12279 a append; open or create text file for writing at end-of-file
12280 rb open binary file for reading
12281 wb truncate to zero length or create binary file for writing
12284 260) If the string begins with one of the above sequences, the implementation might choose to ignore the
12285 remaining characters, or it might use them to select different kinds of a file (some of which might not
12286 conform to the properties in <a href="#7.21.2">7.21.2</a>).
12288 [<a name="#p304" href="p304">page 304</a>] (<a href="#Contents">Contents</a>)
12290 wbx create binary file for writing
12291 ab append; open or create binary file for writing at end-of-file
12292 r+ open text file for update (reading and writing)
12293 w+ truncate to zero length or create text file for update
12294 w+x create text file for update
12295 a+ append; open or create text file for update, writing at end-of-file
12296 r+b or rb+ open binary file for update (reading and writing)
12297 w+b or wb+ truncate to zero length or create binary file for update
12298 w+bx or wb+x create binary file for update
12299 a+b or ab+ append; open or create binary file for update, writing at end-of-file
12300 4 Opening a file with read mode ('r' as the first character in the mode argument) fails if
12301 the file does not exist or cannot be read.
12302 5 Opening a file with exclusive mode ('x' as the last character in the mode argument)
12303 fails if the file already exists or cannot be created. Otherwise, the file is created with
12304 exclusive (also known as non-shared) access to the extent that the underlying system
12305 supports exclusive access.
12306 6 Opening a file with append mode ('a' as the first character in the mode argument)
12307 causes all subsequent writes to the file to be forced to the then current end-of-file,
12308 regardless of intervening calls to the fseek function. In some implementations, opening
12309 a binary file with append mode ('b' as the second or third character in the above list of
12310 mode argument values) may initially position the file position indicator for the stream
12311 beyond the last data written, because of null character padding.
12312 7 When a file is opened with update mode ('+' as the second or third character in the
12313 above list of mode argument values), both input and output may be performed on the
12314 associated stream. However, output shall not be directly followed by input without an
12315 intervening call to the fflush function or to a file positioning function (fseek,
12316 fsetpos, or rewind), and input shall not be directly followed by output without an
12317 intervening call to a file positioning function, unless the input operation encounters end-
12318 of-file. Opening (or creating) a text file with update mode may instead open (or create) a
12319 binary stream in some implementations.
12320 8 When opened, a stream is fully buffered if and only if it can be determined not to refer to
12321 an interactive device. The error and end-of-file indicators for the stream are cleared.
12323 9 The fopen function returns a pointer to the object controlling the stream. If the open
12324 operation fails, fopen returns a null pointer.
12325 Forward references: file positioning functions (<a href="#7.21.9">7.21.9</a>).
12329 [<a name="#p305" href="p305">page 305</a>] (<a href="#Contents">Contents</a>)
12331 <a name="7.21.5.4" href="#7.21.5.4"><b> 7.21.5.4 The freopen function</b></a>
12333 1 #include <a href="#7.21"><stdio.h></a>
12334 FILE *freopen(const char * restrict filename,
12335 const char * restrict mode,
12336 FILE * restrict stream);
12338 2 The freopen function opens the file whose name is the string pointed to by filename
12339 and associates the stream pointed to by stream with it. The mode argument is used just
12340 as in the fopen function.261)
12341 3 If filename is a null pointer, the freopen function attempts to change the mode of
12342 the stream to that specified by mode, as if the name of the file currently associated with
12343 the stream had been used. It is implementation-defined which changes of mode are
12344 permitted (if any), and under what circumstances.
12345 4 The freopen function first attempts to close any file that is associated with the specified
12346 stream. Failure to close the file is ignored. The error and end-of-file indicators for the
12347 stream are cleared.
12349 5 The freopen function returns a null pointer if the open operation fails. Otherwise,
12350 freopen returns the value of stream.
12351 <a name="7.21.5.5" href="#7.21.5.5"><b> 7.21.5.5 The setbuf function</b></a>
12353 1 #include <a href="#7.21"><stdio.h></a>
12354 void setbuf(FILE * restrict stream,
12355 char * restrict buf);
12357 2 Except that it returns no value, the setbuf function is equivalent to the setvbuf
12358 function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
12359 is a null pointer), with the value _IONBF for mode.
12364 261) The primary use of the freopen function is to change the file associated with a standard text stream
12365 (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value
12366 returned by the fopen function may be assigned.
12368 [<a name="#p306" href="p306">page 306</a>] (<a href="#Contents">Contents</a>)
12371 3 The setbuf function returns no value.
12372 Forward references: the setvbuf function (<a href="#7.21.5.6">7.21.5.6</a>).
12373 <a name="7.21.5.6" href="#7.21.5.6"><b> 7.21.5.6 The setvbuf function</b></a>
12375 1 #include <a href="#7.21"><stdio.h></a>
12376 int setvbuf(FILE * restrict stream,
12377 char * restrict buf,
12378 int mode, size_t size);
12380 2 The setvbuf function may be used only after the stream pointed to by stream has
12381 been associated with an open file and before any other operation (other than an
12382 unsuccessful call to setvbuf) is performed on the stream. The argument mode
12383 determines how stream will be buffered, as follows: _IOFBF causes input/output to be
12384 fully buffered; _IOLBF causes input/output to be line buffered; _IONBF causes
12385 input/output to be unbuffered. If buf is not a null pointer, the array it points to may be
12386 used instead of a buffer allocated by the setvbuf function262) and the argument size
12387 specifies the size of the array; otherwise, size may determine the size of a buffer
12388 allocated by the setvbuf function. The contents of the array at any time are
12391 3 The setvbuf function returns zero on success, or nonzero if an invalid value is given
12392 for mode or if the request cannot be honored.
12397 262) The buffer has to have a lifetime at least as great as the open stream, so the stream should be closed
12398 before a buffer that has automatic storage duration is deallocated upon block exit.
12400 [<a name="#p307" href="p307">page 307</a>] (<a href="#Contents">Contents</a>)
12402 <a name="7.21.6" href="#7.21.6"><b> 7.21.6 Formatted input/output functions</b></a>
12403 1 The formatted input/output functions shall behave as if there is a sequence point after the
12404 actions associated with each specifier.263)
12405 <a name="7.21.6.1" href="#7.21.6.1"><b> 7.21.6.1 The fprintf function</b></a>
12407 1 #include <a href="#7.21"><stdio.h></a>
12408 int fprintf(FILE * restrict stream,
12409 const char * restrict format, ...);
12411 2 The fprintf function writes output to the stream pointed to by stream, under control
12412 of the string pointed to by format that specifies how subsequent arguments are
12413 converted for output. If there are insufficient arguments for the format, the behavior is
12414 undefined. If the format is exhausted while arguments remain, the excess arguments are
12415 evaluated (as always) but are otherwise ignored. The fprintf function returns when
12416 the end of the format string is encountered.
12417 3 The format shall be a multibyte character sequence, beginning and ending in its initial
12418 shift state. The format is composed of zero or more directives: ordinary multibyte
12419 characters (not %), which are copied unchanged to the output stream; and conversion
12420 specifications, each of which results in fetching zero or more subsequent arguments,
12421 converting them, if applicable, according to the corresponding conversion specifier, and
12422 then writing the result to the output stream.
12423 4 Each conversion specification is introduced by the character %. After the %, the following
12424 appear in sequence:
12425 -- Zero or more flags (in any order) that modify the meaning of the conversion
12427 -- An optional minimum field width. If the converted value has fewer characters than the
12428 field width, it is padded with spaces (by default) on the left (or right, if the left
12429 adjustment flag, described later, has been given) to the field width. The field width
12430 takes the form of an asterisk * (described later) or a nonnegative decimal integer.264)
12431 -- An optional precision that gives the minimum number of digits to appear for the d, i,
12432 o, u, x, and X conversions, the number of digits to appear after the decimal-point
12433 character for a, A, e, E, f, and F conversions, the maximum number of significant
12434 digits for the g and G conversions, or the maximum number of bytes to be written for
12437 263) The fprintf functions perform writes to memory for the %n specifier.
12438 264) Note that 0 is taken as a flag, not as the beginning of a field width.
12440 [<a name="#p308" href="p308">page 308</a>] (<a href="#Contents">Contents</a>)
12442 s conversions. The precision takes the form of a period (.) followed either by an
12443 asterisk * (described later) or by an optional decimal integer; if only the period is
12444 specified, the precision is taken as zero. If a precision appears with any other
12445 conversion specifier, the behavior is undefined.
12446 -- An optional length modifier that specifies the size of the argument.
12447 -- A conversion specifier character that specifies the type of conversion to be applied.
12448 5 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
12449 this case, an int argument supplies the field width or precision. The arguments
12450 specifying field width, or precision, or both, shall appear (in that order) before the
12451 argument (if any) to be converted. A negative field width argument is taken as a - flag
12452 followed by a positive field width. A negative precision argument is taken as if the
12453 precision were omitted.
12454 6 The flag characters and their meanings are:
12455 - The result of the conversion is left-justified within the field. (It is right-justified if
12456 this flag is not specified.)
12457 + The result of a signed conversion always begins with a plus or minus sign. (It
12458 begins with a sign only when a negative value is converted if this flag is not
12460 space If the first character of a signed conversion is not a sign, or if a signed conversion
12461 results in no characters, a space is prefixed to the result. If the space and + flags
12462 both appear, the space flag is ignored.
12463 # The result is converted to an ''alternative form''. For o conversion, it increases
12464 the precision, if and only if necessary, to force the first digit of the result to be a
12465 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
12466 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
12467 and G conversions, the result of converting a floating-point number always
12468 contains a decimal-point character, even if no digits follow it. (Normally, a
12469 decimal-point character appears in the result of these conversions only if a digit
12470 follows it.) For g and G conversions, trailing zeros are not removed from the
12471 result. For other conversions, the behavior is undefined.
12472 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
12473 (following any indication of sign or base) are used to pad to the field width rather
12474 than performing space padding, except when converting an infinity or NaN. If the
12475 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
12478 265) The results of all floating conversions of a negative zero, and of negative values that round to zero,
12479 include a minus sign.
12481 [<a name="#p309" href="p309">page 309</a>] (<a href="#Contents">Contents</a>)
12483 conversions, if a precision is specified, the 0 flag is ignored. For other
12484 conversions, the behavior is undefined.
12485 7 The length modifiers and their meanings are:
12486 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12487 signed char or unsigned char argument (the argument will have
12488 been promoted according to the integer promotions, but its value shall be
12489 converted to signed char or unsigned char before printing); or that
12490 a following n conversion specifier applies to a pointer to a signed char
12492 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12493 short int or unsigned short int argument (the argument will
12494 have been promoted according to the integer promotions, but its value shall
12495 be converted to short int or unsigned short int before printing);
12496 or that a following n conversion specifier applies to a pointer to a short
12498 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12499 long int or unsigned long int argument; that a following n
12500 conversion specifier applies to a pointer to a long int argument; that a
12501 following c conversion specifier applies to a wint_t argument; that a
12502 following s conversion specifier applies to a pointer to a wchar_t
12503 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
12505 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12506 long long int or unsigned long long int argument; or that a
12507 following n conversion specifier applies to a pointer to a long long int
12509 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
12510 an intmax_t or uintmax_t argument; or that a following n conversion
12511 specifier applies to a pointer to an intmax_t argument.
12512 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12513 size_t or the corresponding signed integer type argument; or that a
12514 following n conversion specifier applies to a pointer to a signed integer type
12515 corresponding to size_t argument.
12516 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12517 ptrdiff_t or the corresponding unsigned integer type argument; or that a
12518 following n conversion specifier applies to a pointer to a ptrdiff_t
12522 [<a name="#p310" href="p310">page 310</a>] (<a href="#Contents">Contents</a>)
12524 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
12525 applies to a long double argument.
12526 If a length modifier appears with any conversion specifier other than as specified above,
12527 the behavior is undefined.
12528 8 The conversion specifiers and their meanings are:
12529 d,i The int argument is converted to signed decimal in the style [-]dddd. The
12530 precision specifies the minimum number of digits to appear; if the value
12531 being converted can be represented in fewer digits, it is expanded with
12532 leading zeros. The default precision is 1. The result of converting a zero
12533 value with a precision of zero is no characters.
12534 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
12535 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
12536 letters abcdef are used for x conversion and the letters ABCDEF for X
12537 conversion. The precision specifies the minimum number of digits to appear;
12538 if the value being converted can be represented in fewer digits, it is expanded
12539 with leading zeros. The default precision is 1. The result of converting a
12540 zero value with a precision of zero is no characters.
12541 f,F A double argument representing a floating-point number is converted to
12542 decimal notation in the style [-]ddd.ddd, where the number of digits after
12543 the decimal-point character is equal to the precision specification. If the
12544 precision is missing, it is taken as 6; if the precision is zero and the # flag is
12545 not specified, no decimal-point character appears. If a decimal-point
12546 character appears, at least one digit appears before it. The value is rounded to
12547 the appropriate number of digits.
12548 A double argument representing an infinity is converted in one of the styles
12549 [-]inf or [-]infinity -- which style is implementation-defined. A
12550 double argument representing a NaN is converted in one of the styles
12551 [-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
12552 any n-char-sequence, is implementation-defined. The F conversion specifier
12553 produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
12555 e,E A double argument representing a floating-point number is converted in the
12556 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
12557 argument is nonzero) before the decimal-point character and the number of
12558 digits after it is equal to the precision; if the precision is missing, it is taken as
12561 266) When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning;
12562 the # and 0 flag characters have no effect.
12564 [<a name="#p311" href="p311">page 311</a>] (<a href="#Contents">Contents</a>)
12566 6; if the precision is zero and the # flag is not specified, no decimal-point
12567 character appears. The value is rounded to the appropriate number of digits.
12568 The E conversion specifier produces a number with E instead of e
12569 introducing the exponent. The exponent always contains at least two digits,
12570 and only as many more digits as necessary to represent the exponent. If the
12571 value is zero, the exponent is zero.
12572 A double argument representing an infinity or NaN is converted in the style
12573 of an f or F conversion specifier.
12574 g,G A double argument representing a floating-point number is converted in
12575 style f or e (or in style F or E in the case of a G conversion specifier),
12576 depending on the value converted and the precision. Let P equal the
12577 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
12578 Then, if a conversion with style E would have an exponent of X:
12579 -- if P > X >= -4, the conversion is with style f (or F) and precision
12581 -- otherwise, the conversion is with style e (or E) and precision P - 1.
12582 Finally, unless the # flag is used, any trailing zeros are removed from the
12583 fractional portion of the result and the decimal-point character is removed if
12584 there is no fractional portion remaining.
12585 A double argument representing an infinity or NaN is converted in the style
12586 of an f or F conversion specifier.
12587 a,A A double argument representing a floating-point number is converted in the
12588 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
12589 nonzero if the argument is a normalized floating-point number and is
12590 otherwise unspecified) before the decimal-point character267) and the number
12591 of hexadecimal digits after it is equal to the precision; if the precision is
12592 missing and FLT_RADIX is a power of 2, then the precision is sufficient for
12593 an exact representation of the value; if the precision is missing and
12594 FLT_RADIX is not a power of 2, then the precision is sufficient to
12599 267) Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so
12600 that subsequent digits align to nibble (4-bit) boundaries.
12602 [<a name="#p312" href="p312">page 312</a>] (<a href="#Contents">Contents</a>)
12604 distinguish268) values of type double, except that trailing zeros may be
12605 omitted; if the precision is zero and the # flag is not specified, no decimal-
12606 point character appears. The letters abcdef are used for a conversion and
12607 the letters ABCDEF for A conversion. The A conversion specifier produces a
12608 number with X and P instead of x and p. The exponent always contains at
12609 least one digit, and only as many more digits as necessary to represent the
12610 decimal exponent of 2. If the value is zero, the exponent is zero.
12611 A double argument representing an infinity or NaN is converted in the style
12612 of an f or F conversion specifier.
12613 c If no l length modifier is present, the int argument is converted to an
12614 unsigned char, and the resulting character is written.
12615 If an l length modifier is present, the wint_t argument is converted as if by
12616 an ls conversion specification with no precision and an argument that points
12617 to the initial element of a two-element array of wchar_t, the first element
12618 containing the wint_t argument to the lc conversion specification and the
12619 second a null wide character.
12620 s If no l length modifier is present, the argument shall be a pointer to the initial
12621 element of an array of character type.269) Characters from the array are
12622 written up to (but not including) the terminating null character. If the
12623 precision is specified, no more than that many bytes are written. If the
12624 precision is not specified or is greater than the size of the array, the array shall
12625 contain a null character.
12626 If an l length modifier is present, the argument shall be a pointer to the initial
12627 element of an array of wchar_t type. Wide characters from the array are
12628 converted to multibyte characters (each as if by a call to the wcrtomb
12629 function, with the conversion state described by an mbstate_t object
12630 initialized to zero before the first wide character is converted) up to and
12631 including a terminating null wide character. The resulting multibyte
12632 characters are written up to (but not including) the terminating null character
12633 (byte). If no precision is specified, the array shall contain a null wide
12634 character. If a precision is specified, no more than that many bytes are
12635 written (including shift sequences, if any), and the array shall contain a null
12636 wide character if, to equal the multibyte character sequence length given by
12638 268) The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
12639 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
12640 might suffice depending on the implementation's scheme for determining the digit to the left of the
12641 decimal-point character.
12642 269) No special provisions are made for multibyte characters.
12644 [<a name="#p313" href="p313">page 313</a>] (<a href="#Contents">Contents</a>)
12646 the precision, the function would need to access a wide character one past the
12647 end of the array. In no case is a partial multibyte character written.270)
12648 p The argument shall be a pointer to void. The value of the pointer is
12649 converted to a sequence of printing characters, in an implementation-defined
12651 n The argument shall be a pointer to signed integer into which is written the
12652 number of characters written to the output stream so far by this call to
12653 fprintf. No argument is converted, but one is consumed. If the conversion
12654 specification includes any flags, a field width, or a precision, the behavior is
12656 % A % character is written. No argument is converted. The complete
12657 conversion specification shall be %%.
12658 9 If a conversion specification is invalid, the behavior is undefined.271) If any argument is
12659 not the correct type for the corresponding conversion specification, the behavior is
12661 10 In no case does a nonexistent or small field width cause truncation of a field; if the result
12662 of a conversion is wider than the field width, the field is expanded to contain the
12664 11 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
12665 to a hexadecimal floating number with the given precision.
12666 Recommended practice
12667 12 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
12668 representable in the given precision, the result should be one of the two adjacent numbers
12669 in hexadecimal floating style with the given precision, with the extra stipulation that the
12670 error should have a correct sign for the current rounding direction.
12671 13 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
12672 DECIMAL_DIG, then the result should be correctly rounded.272) If the number of
12673 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
12674 representable with DECIMAL_DIG digits, then the result should be an exact
12675 representation with trailing zeros. Otherwise, the source value is bounded by two
12676 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
12679 270) Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
12680 271) See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
12681 272) For binary-to-decimal conversion, the result format's values are the numbers representable with the
12682 given format specifier. The number of significant digits is determined by the format specifier, and in
12683 the case of fixed-point conversion by the source value as well.
12685 [<a name="#p314" href="p314">page 314</a>] (<a href="#Contents">Contents</a>)
12687 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
12688 the error should have a correct sign for the current rounding direction.
12690 14 The fprintf function returns the number of characters transmitted, or a negative value
12691 if an output or encoding error occurred.
12692 Environmental limits
12693 15 The number of characters that can be produced by any single conversion shall be at least
12695 16 EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
12697 #include <a href="#7.12"><math.h></a>
12698 #include <a href="#7.21"><stdio.h></a>
12700 char *weekday, *month; // pointers to strings
12701 int day, hour, min;
12702 fprintf(stdout, "%s, %s %d, %.2d:%.2d\n",
12703 weekday, month, day, hour, min);
12704 fprintf(stdout, "pi = %.5f\n", 4 * atan(<a href="#1.0">1.0</a>));
12706 17 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the
12707 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
12708 the first of which is denoted here by a and the second by an uppercase letter.
12709 18 Given the following wide string with length seven,
12710 static wchar_t wstr[] = L" X Yabc Z W";
12712 fprintf(stdout, "|1234567890123|\n");
12713 fprintf(stdout, "|%13ls|\n", wstr);
12714 fprintf(stdout, "|%-13.9ls|\n", wstr);
12715 fprintf(stdout, "|%13.10ls|\n", wstr);
12716 fprintf(stdout, "|%13.11ls|\n", wstr);
12717 fprintf(stdout, "|%13.15ls|\n", &wstr[2]);
12718 fprintf(stdout, "|%13lc|\n", (wint_t) wstr[5]);
12719 will print the following seven lines:
12728 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>).
12732 [<a name="#p315" href="p315">page 315</a>] (<a href="#Contents">Contents</a>)
12734 <a name="7.21.6.2" href="#7.21.6.2"><b> 7.21.6.2 The fscanf function</b></a>
12736 1 #include <a href="#7.21"><stdio.h></a>
12737 int fscanf(FILE * restrict stream,
12738 const char * restrict format, ...);
12740 2 The fscanf function reads input from the stream pointed to by stream, under control
12741 of the string pointed to by format that specifies the admissible input sequences and how
12742 they are to be converted for assignment, using subsequent arguments as pointers to the
12743 objects to receive the converted input. If there are insufficient arguments for the format,
12744 the behavior is undefined. If the format is exhausted while arguments remain, the excess
12745 arguments are evaluated (as always) but are otherwise ignored.
12746 3 The format shall be a multibyte character sequence, beginning and ending in its initial
12747 shift state. The format is composed of zero or more directives: one or more white-space
12748 characters, an ordinary multibyte character (neither % nor a white-space character), or a
12749 conversion specification. Each conversion specification is introduced by the character %.
12750 After the %, the following appear in sequence:
12751 -- An optional assignment-suppressing character *.
12752 -- An optional decimal integer greater than zero that specifies the maximum field width
12754 -- An optional length modifier that specifies the size of the receiving object.
12755 -- A conversion specifier character that specifies the type of conversion to be applied.
12756 4 The fscanf function executes each directive of the format in turn. When all directives
12757 have been executed, or if a directive fails (as detailed below), the function returns.
12758 Failures are described as input failures (due to the occurrence of an encoding error or the
12759 unavailability of input characters), or matching failures (due to inappropriate input).
12760 5 A directive composed of white-space character(s) is executed by reading input up to the
12761 first non-white-space character (which remains unread), or until no more characters can
12763 6 A directive that is an ordinary multibyte character is executed by reading the next
12764 characters of the stream. If any of those characters differ from the ones composing the
12765 directive, the directive fails and the differing and subsequent characters remain unread.
12766 Similarly, if end-of-file, an encoding error, or a read error prevents a character from being
12767 read, the directive fails.
12768 7 A directive that is a conversion specification defines a set of matching input sequences, as
12769 described below for each specifier. A conversion specification is executed in the
12771 [<a name="#p316" href="p316">page 316</a>] (<a href="#Contents">Contents</a>)
12774 8 Input white-space characters (as specified by the isspace function) are skipped, unless
12775 the specification includes a [, c, or n specifier.273)
12776 9 An input item is read from the stream, unless the specification includes an n specifier. An
12777 input item is defined as the longest sequence of input characters which does not exceed
12778 any specified field width and which is, or is a prefix of, a matching input sequence.274)
12779 The first character, if any, after the input item remains unread. If the length of the input
12780 item is zero, the execution of the directive fails; this condition is a matching failure unless
12781 end-of-file, an encoding error, or a read error prevented input from the stream, in which
12782 case it is an input failure.
12783 10 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
12784 count of input characters) is converted to a type appropriate to the conversion specifier. If
12785 the input item is not a matching sequence, the execution of the directive fails: this
12786 condition is a matching failure. Unless assignment suppression was indicated by a *, the
12787 result of the conversion is placed in the object pointed to by the first argument following
12788 the format argument that has not already received a conversion result. If this object
12789 does not have an appropriate type, or if the result of the conversion cannot be represented
12790 in the object, the behavior is undefined.
12791 11 The length modifiers and their meanings are:
12792 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12793 to an argument with type pointer to signed char or unsigned char.
12794 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12795 to an argument with type pointer to short int or unsigned short
12797 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12798 to an argument with type pointer to long int or unsigned long
12799 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
12800 an argument with type pointer to double; or that a following c, s, or [
12801 conversion specifier applies to an argument with type pointer to wchar_t.
12802 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12803 to an argument with type pointer to long long int or unsigned
12808 273) These white-space characters are not counted against a specified field width.
12809 274) fscanf pushes back at most one input character onto the input stream. Therefore, some sequences
12810 that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.
12812 [<a name="#p317" href="p317">page 317</a>] (<a href="#Contents">Contents</a>)
12814 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12815 to an argument with type pointer to intmax_t or uintmax_t.
12816 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12817 to an argument with type pointer to size_t or the corresponding signed
12819 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12820 to an argument with type pointer to ptrdiff_t or the corresponding
12821 unsigned integer type.
12822 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
12823 applies to an argument with type pointer to long double.
12824 If a length modifier appears with any conversion specifier other than as specified above,
12825 the behavior is undefined.
12826 12 The conversion specifiers and their meanings are:
12827 d Matches an optionally signed decimal integer, whose format is the same as
12828 expected for the subject sequence of the strtol function with the value 10
12829 for the base argument. The corresponding argument shall be a pointer to
12831 i Matches an optionally signed integer, whose format is the same as expected
12832 for the subject sequence of the strtol function with the value 0 for the
12833 base argument. The corresponding argument shall be a pointer to signed
12835 o Matches an optionally signed octal integer, whose format is the same as
12836 expected for the subject sequence of the strtoul function with the value 8
12837 for the base argument. The corresponding argument shall be a pointer to
12839 u Matches an optionally signed decimal integer, whose format is the same as
12840 expected for the subject sequence of the strtoul function with the value 10
12841 for the base argument. The corresponding argument shall be a pointer to
12843 x Matches an optionally signed hexadecimal integer, whose format is the same
12844 as expected for the subject sequence of the strtoul function with the value
12845 16 for the base argument. The corresponding argument shall be a pointer to
12847 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
12848 format is the same as expected for the subject sequence of the strtod
12849 function. The corresponding argument shall be a pointer to floating.
12852 [<a name="#p318" href="p318">page 318</a>] (<a href="#Contents">Contents</a>)
12854 c Matches a sequence of characters of exactly the number specified by the field
12855 width (1 if no field width is present in the directive).275)
12856 If no l length modifier is present, the corresponding argument shall be a
12857 pointer to the initial element of a character array large enough to accept the
12858 sequence. No null character is added.
12859 If an l length modifier is present, the input shall be a sequence of multibyte
12860 characters that begins in the initial shift state. Each multibyte character in the
12861 sequence is converted to a wide character as if by a call to the mbrtowc
12862 function, with the conversion state described by an mbstate_t object
12863 initialized to zero before the first multibyte character is converted. The
12864 corresponding argument shall be a pointer to the initial element of an array of
12865 wchar_t large enough to accept the resulting sequence of wide characters.
12866 No null wide character is added.
12867 s Matches a sequence of non-white-space characters.275)
12868 If no l length modifier is present, the corresponding argument shall be a
12869 pointer to the initial element of a character array large enough to accept the
12870 sequence and a terminating null character, which will be added automatically.
12871 If an l length modifier is present, the input shall be a sequence of multibyte
12872 characters that begins in the initial shift state. Each multibyte character is
12873 converted to a wide character as if by a call to the mbrtowc function, with
12874 the conversion state described by an mbstate_t object initialized to zero
12875 before the first multibyte character is converted. The corresponding argument
12876 shall be a pointer to the initial element of an array of wchar_t large enough
12877 to accept the sequence and the terminating null wide character, which will be
12878 added automatically.
12879 [ Matches a nonempty sequence of characters from a set of expected characters
12881 If no l length modifier is present, the corresponding argument shall be a
12882 pointer to the initial element of a character array large enough to accept the
12883 sequence and a terminating null character, which will be added automatically.
12884 If an l length modifier is present, the input shall be a sequence of multibyte
12885 characters that begins in the initial shift state. Each multibyte character is
12886 converted to a wide character as if by a call to the mbrtowc function, with
12887 the conversion state described by an mbstate_t object initialized to zero
12889 275) No special provisions are made for multibyte characters in the matching rules used by the c, s, and [
12890 conversion specifiers -- the extent of the input field is determined on a byte-by-byte basis. The
12891 resulting field is nevertheless a sequence of multibyte characters that begins in the initial shift state.
12893 [<a name="#p319" href="p319">page 319</a>] (<a href="#Contents">Contents</a>)
12895 before the first multibyte character is converted. The corresponding argument
12896 shall be a pointer to the initial element of an array of wchar_t large enough
12897 to accept the sequence and the terminating null wide character, which will be
12898 added automatically.
12899 The conversion specifier includes all subsequent characters in the format
12900 string, up to and including the matching right bracket (]). The characters
12901 between the brackets (the scanlist) compose the scanset, unless the character
12902 after the left bracket is a circumflex (^), in which case the scanset contains all
12903 characters that do not appear in the scanlist between the circumflex and the
12904 right bracket. If the conversion specifier begins with [] or [^], the right
12905 bracket character is in the scanlist and the next following right bracket
12906 character is the matching right bracket that ends the specification; otherwise
12907 the first following right bracket character is the one that ends the
12908 specification. If a - character is in the scanlist and is not the first, nor the
12909 second where the first character is a ^, nor the last character, the behavior is
12910 implementation-defined.
12911 p Matches an implementation-defined set of sequences, which should be the
12912 same as the set of sequences that may be produced by the %p conversion of
12913 the fprintf function. The corresponding argument shall be a pointer to a
12914 pointer to void. The input item is converted to a pointer value in an
12915 implementation-defined manner. If the input item is a value converted earlier
12916 during the same program execution, the pointer that results shall compare
12917 equal to that value; otherwise the behavior of the %p conversion is undefined.
12918 n No input is consumed. The corresponding argument shall be a pointer to
12919 signed integer into which is to be written the number of characters read from
12920 the input stream so far by this call to the fscanf function. Execution of a
12921 %n directive does not increment the assignment count returned at the
12922 completion of execution of the fscanf function. No argument is converted,
12923 but one is consumed. If the conversion specification includes an assignment-
12924 suppressing character or a field width, the behavior is undefined.
12925 % Matches a single % character; no conversion or assignment occurs. The
12926 complete conversion specification shall be %%.
12927 13 If a conversion specification is invalid, the behavior is undefined.276)
12928 14 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
12929 respectively, a, e, f, g, and x.
12933 276) See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
12935 [<a name="#p320" href="p320">page 320</a>] (<a href="#Contents">Contents</a>)
12937 15 Trailing white space (including new-line characters) is left unread unless matched by a
12938 directive. The success of literal matches and suppressed assignments is not directly
12939 determinable other than via the %n directive.
12941 16 The fscanf function returns the value of the macro EOF if an input failure occurs
12942 before the first conversion (if any) has completed. Otherwise, the function returns the
12943 number of input items assigned, which can be fewer than provided for, or even zero, in
12944 the event of an early matching failure.
12945 17 EXAMPLE 1 The call:
12946 #include <a href="#7.21"><stdio.h></a>
12948 int n, i; float x; char name[50];
12949 n = fscanf(stdin, "%d%f%s", &i, &x, name);
12950 with the input line:
12951 25 54.32E-1 thompson
12952 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
12955 18 EXAMPLE 2 The call:
12956 #include <a href="#7.21"><stdio.h></a>
12958 int i; float x; char name[50];
12959 fscanf(stdin, "%2d%f%*d %[0123456789]", &i, &x, name);
12962 will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the
12963 sequence 56\0. The next character read from the input stream will be a.
12965 19 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
12966 #include <a href="#7.21"><stdio.h></a>
12968 int count; float quant; char units[21], item[21];
12970 count = fscanf(stdin, "%f%20s of %20s", &quant, units, item);
12971 fscanf(stdin,"%*[^\n]");
12972 } while (!feof(stdin) && !ferror(stdin));
12973 20 If the stdin stream contains the following lines:
12975 -12.8degrees Celsius
12981 [<a name="#p321" href="p321">page 321</a>] (<a href="#Contents">Contents</a>)
12983 the execution of the above example will be analogous to the following assignments:
12984 quant = 2; strcpy(units, "quarts"); strcpy(item, "oil");
12986 quant = -12.8; strcpy(units, "degrees");
12987 count = 2; // "C" fails to match "o"
12988 count = 0; // "l" fails to match "%f"
12989 quant = 10.0; strcpy(units, "LBS"); strcpy(item, "dirt");
12991 count = 0; // "100e" fails to match "%f"
12995 #include <a href="#7.21"><stdio.h></a>
12997 int d1, d2, n1, n2, i;
12998 i = sscanf("123", "%d%n%n%d", &d1, &n1, &n2, &d2);
12999 the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure the value
13000 of 3 is also assigned to n2. The value of d2 is not affected. The value 1 is assigned to i.
13002 22 EXAMPLE 5 In these examples, multibyte characters do have a state-dependent encoding, and the
13003 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
13004 the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as
13005 such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes
13006 entry into the alternate shift state.
13008 #include <a href="#7.21"><stdio.h></a>
13011 fscanf(stdin, "a%s", str);
13012 with the input line:
13013 a(uparrow) X Y(downarrow) bc
13014 str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte
13015 characters, in the more general case) appears to be a single-byte white-space character.
13016 24 In contrast, after the call:
13017 #include <a href="#7.21"><stdio.h></a>
13018 #include <a href="#7.19"><stddef.h></a>
13021 fscanf(stdin, "a%ls", wstr);
13022 with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
13023 terminating null wide character.
13024 25 However, the call:
13029 [<a name="#p322" href="p322">page 322</a>] (<a href="#Contents">Contents</a>)
13031 #include <a href="#7.21"><stdio.h></a>
13032 #include <a href="#7.19"><stddef.h></a>
13035 fscanf(stdin, "a(uparrow) X(downarrow)%ls", wstr);
13036 with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
13038 26 Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte
13039 character Y, after the call:
13040 #include <a href="#7.21"><stdio.h></a>
13041 #include <a href="#7.19"><stddef.h></a>
13044 fscanf(stdin, "a(uparrow) Y(downarrow)%ls", wstr);
13045 with the same input line, zero will again be returned, but stdin will be left with a partially consumed
13046 multibyte character.
13048 Forward references: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>), the
13049 strtol, strtoll, strtoul, and strtoull functions (<a href="#7.22.1.4">7.22.1.4</a>), conversion state
13050 (<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>).
13051 <a name="7.21.6.3" href="#7.21.6.3"><b> 7.21.6.3 The printf function</b></a>
13053 1 #include <a href="#7.21"><stdio.h></a>
13054 int printf(const char * restrict format, ...);
13056 2 The printf function is equivalent to fprintf with the argument stdout interposed
13057 before the arguments to printf.
13059 3 The printf function returns the number of characters transmitted, or a negative value if
13060 an output or encoding error occurred.
13061 <a name="7.21.6.4" href="#7.21.6.4"><b> 7.21.6.4 The scanf function</b></a>
13063 1 #include <a href="#7.21"><stdio.h></a>
13064 int scanf(const char * restrict format, ...);
13066 2 The scanf function is equivalent to fscanf with the argument stdin interposed
13067 before the arguments to scanf.
13071 [<a name="#p323" href="p323">page 323</a>] (<a href="#Contents">Contents</a>)
13074 3 The scanf function returns the value of the macro EOF if an input failure occurs before
13075 the first conversion (if any) has completed. Otherwise, the scanf function returns the
13076 number of input items assigned, which can be fewer than provided for, or even zero, in
13077 the event of an early matching failure.
13078 <a name="7.21.6.5" href="#7.21.6.5"><b> 7.21.6.5 The snprintf function</b></a>
13080 1 #include <a href="#7.21"><stdio.h></a>
13081 int snprintf(char * restrict s, size_t n,
13082 const char * restrict format, ...);
13084 2 The snprintf function is equivalent to fprintf, except that the output is written into
13085 an array (specified by argument s) rather than to a stream. If n is zero, nothing is written,
13086 and s may be a null pointer. Otherwise, output characters beyond the n-1st are
13087 discarded rather than being written to the array, and a null character is written at the end
13088 of the characters actually written into the array. If copying takes place between objects
13089 that overlap, the behavior is undefined.
13091 3 The snprintf function returns the number of characters that would have been written
13092 had n been sufficiently large, not counting the terminating null character, or a negative
13093 value if an encoding error occurred. Thus, the null-terminated output has been
13094 completely written if and only if the returned value is nonnegative and less than n.
13095 <a name="7.21.6.6" href="#7.21.6.6"><b> 7.21.6.6 The sprintf function</b></a>
13097 1 #include <a href="#7.21"><stdio.h></a>
13098 int sprintf(char * restrict s,
13099 const char * restrict format, ...);
13101 2 The sprintf function is equivalent to fprintf, except that the output is written into
13102 an array (specified by the argument s) rather than to a stream. A null character is written
13103 at the end of the characters written; it is not counted as part of the returned value. If
13104 copying takes place between objects that overlap, the behavior is undefined.
13106 3 The sprintf function returns the number of characters written in the array, not
13107 counting the terminating null character, or a negative value if an encoding error occurred.
13109 [<a name="#p324" href="p324">page 324</a>] (<a href="#Contents">Contents</a>)
13111 <a name="7.21.6.7" href="#7.21.6.7"><b> 7.21.6.7 The sscanf function</b></a>
13113 1 #include <a href="#7.21"><stdio.h></a>
13114 int sscanf(const char * restrict s,
13115 const char * restrict format, ...);
13117 2 The sscanf function is equivalent to fscanf, except that input is obtained from a
13118 string (specified by the argument s) rather than from a stream. Reaching the end of the
13119 string is equivalent to encountering end-of-file for the fscanf function. If copying
13120 takes place between objects that overlap, the behavior is undefined.
13122 3 The sscanf function returns the value of the macro EOF if an input failure occurs
13123 before the first conversion (if any) has completed. Otherwise, the sscanf function
13124 returns the number of input items assigned, which can be fewer than provided for, or even
13125 zero, in the event of an early matching failure.
13126 <a name="7.21.6.8" href="#7.21.6.8"><b> 7.21.6.8 The vfprintf function</b></a>
13128 1 #include <a href="#7.16"><stdarg.h></a>
13129 #include <a href="#7.21"><stdio.h></a>
13130 int vfprintf(FILE * restrict stream,
13131 const char * restrict format,
13134 2 The vfprintf function is equivalent to fprintf, with the variable argument list
13135 replaced by arg, which shall have been initialized by the va_start macro (and
13136 possibly subsequent va_arg calls). The vfprintf function does not invoke the
13139 3 The vfprintf function returns the number of characters transmitted, or a negative
13140 value if an output or encoding error occurred.
13141 4 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
13146 277) As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
13147 vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
13149 [<a name="#p325" href="p325">page 325</a>] (<a href="#Contents">Contents</a>)
13151 #include <a href="#7.16"><stdarg.h></a>
13152 #include <a href="#7.21"><stdio.h></a>
13153 void error(char *function_name, char *format, ...)
13156 va_start(args, format);
13157 // print out name of function causing error
13158 fprintf(stderr, "ERROR in %s: ", function_name);
13159 // print out remainder of message
13160 vfprintf(stderr, format, args);
13164 <a name="7.21.6.9" href="#7.21.6.9"><b> 7.21.6.9 The vfscanf function</b></a>
13166 1 #include <a href="#7.16"><stdarg.h></a>
13167 #include <a href="#7.21"><stdio.h></a>
13168 int vfscanf(FILE * restrict stream,
13169 const char * restrict format,
13172 2 The vfscanf function is equivalent to fscanf, with the variable argument list
13173 replaced by arg, which shall have been initialized by the va_start macro (and
13174 possibly subsequent va_arg calls). The vfscanf function does not invoke the
13177 3 The vfscanf function returns the value of the macro EOF if an input failure occurs
13178 before the first conversion (if any) has completed. Otherwise, the vfscanf function
13179 returns the number of input items assigned, which can be fewer than provided for, or even
13180 zero, in the event of an early matching failure.
13181 <a name="7.21.6.10" href="#7.21.6.10"><b> 7.21.6.10 The vprintf function</b></a>
13183 1 #include <a href="#7.16"><stdarg.h></a>
13184 #include <a href="#7.21"><stdio.h></a>
13185 int vprintf(const char * restrict format,
13188 2 The vprintf function is equivalent to printf, with the variable argument list
13189 replaced by arg, which shall have been initialized by the va_start macro (and
13191 [<a name="#p326" href="p326">page 326</a>] (<a href="#Contents">Contents</a>)
13193 possibly subsequent va_arg calls). The vprintf function does not invoke the
13196 3 The vprintf function returns the number of characters transmitted, or a negative value
13197 if an output or encoding error occurred.
13198 <a name="7.21.6.11" href="#7.21.6.11"><b> 7.21.6.11 The vscanf function</b></a>
13200 1 #include <a href="#7.16"><stdarg.h></a>
13201 #include <a href="#7.21"><stdio.h></a>
13202 int vscanf(const char * restrict format,
13205 2 The vscanf function is equivalent to scanf, with the variable argument list replaced
13206 by arg, which shall have been initialized by the va_start macro (and possibly
13207 subsequent va_arg calls). The vscanf function does not invoke the va_end
13210 3 The vscanf function returns the value of the macro EOF if an input failure occurs
13211 before the first conversion (if any) has completed. Otherwise, the vscanf function
13212 returns the number of input items assigned, which can be fewer than provided for, or even
13213 zero, in the event of an early matching failure.
13214 <a name="7.21.6.12" href="#7.21.6.12"><b> 7.21.6.12 The vsnprintf function</b></a>
13216 1 #include <a href="#7.16"><stdarg.h></a>
13217 #include <a href="#7.21"><stdio.h></a>
13218 int vsnprintf(char * restrict s, size_t n,
13219 const char * restrict format,
13222 2 The vsnprintf function is equivalent to snprintf, with the variable argument list
13223 replaced by arg, which shall have been initialized by the va_start macro (and
13224 possibly subsequent va_arg calls). The vsnprintf function does not invoke the
13225 va_end macro.277) If copying takes place between objects that overlap, the behavior is
13230 [<a name="#p327" href="p327">page 327</a>] (<a href="#Contents">Contents</a>)
13233 3 The vsnprintf function returns the number of characters that would have been written
13234 had n been sufficiently large, not counting the terminating null character, or a negative
13235 value if an encoding error occurred. Thus, the null-terminated output has been
13236 completely written if and only if the returned value is nonnegative and less than n.
13237 <a name="7.21.6.13" href="#7.21.6.13"><b> 7.21.6.13 The vsprintf function</b></a>
13239 1 #include <a href="#7.16"><stdarg.h></a>
13240 #include <a href="#7.21"><stdio.h></a>
13241 int vsprintf(char * restrict s,
13242 const char * restrict format,
13245 2 The vsprintf function is equivalent to sprintf, with the variable argument list
13246 replaced by arg, which shall have been initialized by the va_start macro (and
13247 possibly subsequent va_arg calls). The vsprintf function does not invoke the
13248 va_end macro.277) If copying takes place between objects that overlap, the behavior is
13251 3 The vsprintf function returns the number of characters written in the array, not
13252 counting the terminating null character, or a negative value if an encoding error occurred.
13253 <a name="7.21.6.14" href="#7.21.6.14"><b> 7.21.6.14 The vsscanf function</b></a>
13255 1 #include <a href="#7.16"><stdarg.h></a>
13256 #include <a href="#7.21"><stdio.h></a>
13257 int vsscanf(const char * restrict s,
13258 const char * restrict format,
13261 2 The vsscanf function is equivalent to sscanf, with the variable argument list
13262 replaced by arg, which shall have been initialized by the va_start macro (and
13263 possibly subsequent va_arg calls). The vsscanf function does not invoke the
13266 3 The vsscanf function returns the value of the macro EOF if an input failure occurs
13267 before the first conversion (if any) has completed. Otherwise, the vsscanf function
13268 [<a name="#p328" href="p328">page 328</a>] (<a href="#Contents">Contents</a>)
13270 returns the number of input items assigned, which can be fewer than provided for, or even
13271 zero, in the event of an early matching failure.
13272 <a name="7.21.7" href="#7.21.7"><b> 7.21.7 Character input/output functions</b></a>
13273 <a name="7.21.7.1" href="#7.21.7.1"><b> 7.21.7.1 The fgetc function</b></a>
13275 1 #include <a href="#7.21"><stdio.h></a>
13276 int fgetc(FILE *stream);
13278 2 If the end-of-file indicator for the input stream pointed to by stream is not set and a
13279 next character is present, the fgetc function obtains that character as an unsigned
13280 char converted to an int and advances the associated file position indicator for the
13281 stream (if defined).
13283 3 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
13284 of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the
13285 fgetc function returns the next character from the input stream pointed to by stream.
13286 If a read error occurs, the error indicator for the stream is set and the fgetc function
13288 <a name="7.21.7.2" href="#7.21.7.2"><b> 7.21.7.2 The fgets function</b></a>
13290 1 #include <a href="#7.21"><stdio.h></a>
13291 char *fgets(char * restrict s, int n,
13292 FILE * restrict stream);
13294 2 The fgets function reads at most one less than the number of characters specified by n
13295 from the stream pointed to by stream into the array pointed to by s. No additional
13296 characters are read after a new-line character (which is retained) or after end-of-file. A
13297 null character is written immediately after the last character read into the array.
13299 3 The fgets function returns s if successful. If end-of-file is encountered and no
13300 characters have been read into the array, the contents of the array remain unchanged and a
13301 null pointer is returned. If a read error occurs during the operation, the array contents are
13302 indeterminate and a null pointer is returned.
13304 278) An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
13306 [<a name="#p329" href="p329">page 329</a>] (<a href="#Contents">Contents</a>)
13308 <a name="7.21.7.3" href="#7.21.7.3"><b> 7.21.7.3 The fputc function</b></a>
13310 1 #include <a href="#7.21"><stdio.h></a>
13311 int fputc(int c, FILE *stream);
13313 2 The fputc function writes the character specified by c (converted to an unsigned
13314 char) to the output stream pointed to by stream, at the position indicated by the
13315 associated file position indicator for the stream (if defined), and advances the indicator
13316 appropriately. If the file cannot support positioning requests, or if the stream was opened
13317 with append mode, the character is appended to the output stream.
13319 3 The fputc function returns the character written. If a write error occurs, the error
13320 indicator for the stream is set and fputc returns EOF.
13321 <a name="7.21.7.4" href="#7.21.7.4"><b> 7.21.7.4 The fputs function</b></a>
13323 1 #include <a href="#7.21"><stdio.h></a>
13324 int fputs(const char * restrict s,
13325 FILE * restrict stream);
13327 2 The fputs function writes the string pointed to by s to the stream pointed to by
13328 stream. The terminating null character is not written.
13330 3 The fputs function returns EOF if a write error occurs; otherwise it returns a
13332 <a name="7.21.7.5" href="#7.21.7.5"><b> 7.21.7.5 The getc function</b></a>
13334 1 #include <a href="#7.21"><stdio.h></a>
13335 int getc(FILE *stream);
13337 2 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it
13338 may evaluate stream more than once, so the argument should never be an expression
13344 [<a name="#p330" href="p330">page 330</a>] (<a href="#Contents">Contents</a>)
13347 3 The getc function returns the next character from the input stream pointed to by
13348 stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
13349 getc returns EOF. If a read error occurs, the error indicator for the stream is set and
13351 <a name="7.21.7.6" href="#7.21.7.6"><b> 7.21.7.6 The getchar function</b></a>
13353 1 #include <a href="#7.21"><stdio.h></a>
13356 2 The getchar function is equivalent to getc with the argument stdin.
13358 3 The getchar function returns the next character from the input stream pointed to by
13359 stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
13360 getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
13361 getchar returns EOF.
13362 <a name="7.21.7.7" href="#7.21.7.7"><b> 7.21.7.7 The putc function</b></a>
13364 1 #include <a href="#7.21"><stdio.h></a>
13365 int putc(int c, FILE *stream);
13367 2 The putc function is equivalent to fputc, except that if it is implemented as a macro, it
13368 may evaluate stream more than once, so that argument should never be an expression
13371 3 The putc function returns the character written. If a write error occurs, the error
13372 indicator for the stream is set and putc returns EOF.
13373 <a name="7.21.7.8" href="#7.21.7.8"><b> 7.21.7.8 The putchar function</b></a>
13375 1 #include <a href="#7.21"><stdio.h></a>
13376 int putchar(int c);
13378 2 The putchar function is equivalent to putc with the second argument stdout.
13381 [<a name="#p331" href="p331">page 331</a>] (<a href="#Contents">Contents</a>)
13384 3 The putchar function returns the character written. If a write error occurs, the error
13385 indicator for the stream is set and putchar returns EOF.
13386 <a name="7.21.7.9" href="#7.21.7.9"><b> 7.21.7.9 The puts function</b></a>
13388 1 #include <a href="#7.21"><stdio.h></a>
13389 int puts(const char *s);
13391 2 The puts function writes the string pointed to by s to the stream pointed to by stdout,
13392 and appends a new-line character to the output. The terminating null character is not
13395 3 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
13397 <a name="7.21.7.10" href="#7.21.7.10"><b> 7.21.7.10 The ungetc function</b></a>
13399 1 #include <a href="#7.21"><stdio.h></a>
13400 int ungetc(int c, FILE *stream);
13402 2 The ungetc function pushes the character specified by c (converted to an unsigned
13403 char) back onto the input stream pointed to by stream. Pushed-back characters will be
13404 returned by subsequent reads on that stream in the reverse order of their pushing. A
13405 successful intervening call (with the stream pointed to by stream) to a file positioning
13406 function (fseek, fsetpos, or rewind) discards any pushed-back characters for the
13407 stream. The external storage corresponding to the stream is unchanged.
13408 3 One character of pushback is guaranteed. If the ungetc function is called too many
13409 times on the same stream without an intervening read or file positioning operation on that
13410 stream, the operation may fail.
13411 4 If the value of c equals that of the macro EOF, the operation fails and the input stream is
13413 5 A successful call to the ungetc function clears the end-of-file indicator for the stream.
13414 The value of the file position indicator for the stream after reading or discarding all
13415 pushed-back characters shall be the same as it was before the characters were pushed
13416 back. For a text stream, the value of its file position indicator after a successful call to the
13417 ungetc function is unspecified until all pushed-back characters are read or discarded.
13419 [<a name="#p332" href="p332">page 332</a>] (<a href="#Contents">Contents</a>)
13421 For a binary stream, its file position indicator is decremented by each successful call to
13422 the ungetc function; if its value was zero before a call, it is indeterminate after the
13425 6 The ungetc function returns the character pushed back after conversion, or EOF if the
13427 Forward references: file positioning functions (<a href="#7.21.9">7.21.9</a>).
13428 <a name="7.21.8" href="#7.21.8"><b> 7.21.8 Direct input/output functions</b></a>
13429 <a name="7.21.8.1" href="#7.21.8.1"><b> 7.21.8.1 The fread function</b></a>
13431 1 #include <a href="#7.21"><stdio.h></a>
13432 size_t fread(void * restrict ptr,
13433 size_t size, size_t nmemb,
13434 FILE * restrict stream);
13436 2 The fread function reads, into the array pointed to by ptr, up to nmemb elements
13437 whose size is specified by size, from the stream pointed to by stream. For each
13438 object, size calls are made to the fgetc function and the results stored, in the order
13439 read, in an array of unsigned char exactly overlaying the object. The file position
13440 indicator for the stream (if defined) is advanced by the number of characters successfully
13441 read. If an error occurs, the resulting value of the file position indicator for the stream is
13442 indeterminate. If a partial element is read, its value is indeterminate.
13444 3 The fread function returns the number of elements successfully read, which may be
13445 less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
13446 fread returns zero and the contents of the array and the state of the stream remain
13452 279) See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
13454 [<a name="#p333" href="p333">page 333</a>] (<a href="#Contents">Contents</a>)
13456 <a name="7.21.8.2" href="#7.21.8.2"><b> 7.21.8.2 The fwrite function</b></a>
13458 1 #include <a href="#7.21"><stdio.h></a>
13459 size_t fwrite(const void * restrict ptr,
13460 size_t size, size_t nmemb,
13461 FILE * restrict stream);
13463 2 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements
13464 whose size is specified by size, to the stream pointed to by stream. For each object,
13465 size calls are made to the fputc function, taking the values (in order) from an array of
13466 unsigned char exactly overlaying the object. The file position indicator for the
13467 stream (if defined) is advanced by the number of characters successfully written. If an
13468 error occurs, the resulting value of the file position indicator for the stream is
13471 3 The fwrite function returns the number of elements successfully written, which will be
13472 less than nmemb only if a write error is encountered. If size or nmemb is zero,
13473 fwrite returns zero and the state of the stream remains unchanged.
13474 <a name="7.21.9" href="#7.21.9"><b> 7.21.9 File positioning functions</b></a>
13475 <a name="7.21.9.1" href="#7.21.9.1"><b> 7.21.9.1 The fgetpos function</b></a>
13477 1 #include <a href="#7.21"><stdio.h></a>
13478 int fgetpos(FILE * restrict stream,
13479 fpos_t * restrict pos);
13481 2 The fgetpos function stores the current values of the parse state (if any) and file
13482 position indicator for the stream pointed to by stream in the object pointed to by pos.
13483 The values stored contain unspecified information usable by the fsetpos function for
13484 repositioning the stream to its position at the time of the call to the fgetpos function.
13486 3 If successful, the fgetpos function returns zero; on failure, the fgetpos function
13487 returns nonzero and stores an implementation-defined positive value in errno.
13488 Forward references: the fsetpos function (<a href="#7.21.9.3">7.21.9.3</a>).
13493 [<a name="#p334" href="p334">page 334</a>] (<a href="#Contents">Contents</a>)
13495 <a name="7.21.9.2" href="#7.21.9.2"><b> 7.21.9.2 The fseek function</b></a>
13497 1 #include <a href="#7.21"><stdio.h></a>
13498 int fseek(FILE *stream, long int offset, int whence);
13500 2 The fseek function sets the file position indicator for the stream pointed to by stream.
13501 If a read or write error occurs, the error indicator for the stream is set and fseek fails.
13502 3 For a binary stream, the new position, measured in characters from the beginning of the
13503 file, is obtained by adding offset to the position specified by whence. The specified
13504 position is the beginning of the file if whence is SEEK_SET, the current value of the file
13505 position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
13506 meaningfully support fseek calls with a whence value of SEEK_END.
13507 4 For a text stream, either offset shall be zero, or offset shall be a value returned by
13508 an earlier successful call to the ftell function on a stream associated with the same file
13509 and whence shall be SEEK_SET.
13510 5 After determining the new position, a successful call to the fseek function undoes any
13511 effects of the ungetc function on the stream, clears the end-of-file indicator for the
13512 stream, and then establishes the new position. After a successful fseek call, the next
13513 operation on an update stream may be either input or output.
13515 6 The fseek function returns nonzero only for a request that cannot be satisfied.
13516 Forward references: the ftell function (<a href="#7.21.9.4">7.21.9.4</a>).
13517 <a name="7.21.9.3" href="#7.21.9.3"><b> 7.21.9.3 The fsetpos function</b></a>
13519 1 #include <a href="#7.21"><stdio.h></a>
13520 int fsetpos(FILE *stream, const fpos_t *pos);
13522 2 The fsetpos function sets the mbstate_t object (if any) and file position indicator
13523 for the stream pointed to by stream according to the value of the object pointed to by
13524 pos, which shall be a value obtained from an earlier successful call to the fgetpos
13525 function on a stream associated with the same file. If a read or write error occurs, the
13526 error indicator for the stream is set and fsetpos fails.
13527 3 A successful call to the fsetpos function undoes any effects of the ungetc function
13528 on the stream, clears the end-of-file indicator for the stream, and then establishes the new
13529 parse state and position. After a successful fsetpos call, the next operation on an
13531 [<a name="#p335" href="p335">page 335</a>] (<a href="#Contents">Contents</a>)
13533 update stream may be either input or output.
13535 4 If successful, the fsetpos function returns zero; on failure, the fsetpos function
13536 returns nonzero and stores an implementation-defined positive value in errno.
13537 <a name="7.21.9.4" href="#7.21.9.4"><b> 7.21.9.4 The ftell function</b></a>
13539 1 #include <a href="#7.21"><stdio.h></a>
13540 long int ftell(FILE *stream);
13542 2 The ftell function obtains the current value of the file position indicator for the stream
13543 pointed to by stream. For a binary stream, the value is the number of characters from
13544 the beginning of the file. For a text stream, its file position indicator contains unspecified
13545 information, usable by the fseek function for returning the file position indicator for the
13546 stream to its position at the time of the ftell call; the difference between two such
13547 return values is not necessarily a meaningful measure of the number of characters written
13550 3 If successful, the ftell function returns the current value of the file position indicator
13551 for the stream. On failure, the ftell function returns -1L and stores an
13552 implementation-defined positive value in errno.
13553 <a name="7.21.9.5" href="#7.21.9.5"><b> 7.21.9.5 The rewind function</b></a>
13555 1 #include <a href="#7.21"><stdio.h></a>
13556 void rewind(FILE *stream);
13558 2 The rewind function sets the file position indicator for the stream pointed to by
13559 stream to the beginning of the file. It is equivalent to
13560 (void)fseek(stream, 0L, SEEK_SET)
13561 except that the error indicator for the stream is also cleared.
13563 3 The rewind function returns no value.
13568 [<a name="#p336" href="p336">page 336</a>] (<a href="#Contents">Contents</a>)
13570 <a name="7.21.10" href="#7.21.10"><b> 7.21.10 Error-handling functions</b></a>
13571 <a name="7.21.10.1" href="#7.21.10.1"><b> 7.21.10.1 The clearerr function</b></a>
13573 1 #include <a href="#7.21"><stdio.h></a>
13574 void clearerr(FILE *stream);
13576 2 The clearerr function clears the end-of-file and error indicators for the stream pointed
13579 3 The clearerr function returns no value.
13580 <a name="7.21.10.2" href="#7.21.10.2"><b> 7.21.10.2 The feof function</b></a>
13582 1 #include <a href="#7.21"><stdio.h></a>
13583 int feof(FILE *stream);
13585 2 The feof function tests the end-of-file indicator for the stream pointed to by stream.
13587 3 The feof function returns nonzero if and only if the end-of-file indicator is set for
13589 <a name="7.21.10.3" href="#7.21.10.3"><b> 7.21.10.3 The ferror function</b></a>
13591 1 #include <a href="#7.21"><stdio.h></a>
13592 int ferror(FILE *stream);
13594 2 The ferror function tests the error indicator for the stream pointed to by stream.
13596 3 The ferror function returns nonzero if and only if the error indicator is set for
13602 [<a name="#p337" href="p337">page 337</a>] (<a href="#Contents">Contents</a>)
13604 <a name="7.21.10.4" href="#7.21.10.4"><b> 7.21.10.4 The perror function</b></a>
13606 1 #include <a href="#7.21"><stdio.h></a>
13607 void perror(const char *s);
13609 2 The perror function maps the error number in the integer expression errno to an
13610 error message. It writes a sequence of characters to the standard error stream thus: first
13611 (if s is not a null pointer and the character pointed to by s is not the null character), the
13612 string pointed to by s followed by a colon (:) and a space; then an appropriate error
13613 message string followed by a new-line character. The contents of the error message
13614 strings are the same as those returned by the strerror function with argument errno.
13616 3 The perror function returns no value.
13617 Forward references: the strerror function (<a href="#7.23.6.2">7.23.6.2</a>).
13622 [<a name="#p338" href="p338">page 338</a>] (<a href="#Contents">Contents</a>)
13624 <a name="7.22" href="#7.22"><b> 7.22 General utilities <stdlib.h></b></a>
13625 1 The header <a href="#7.22"><stdlib.h></a> declares five types and several functions of general utility, and
13626 defines several macros.280)
13627 2 The types declared are size_t and wchar_t (both described in <a href="#7.19">7.19</a>),
13629 which is a structure type that is the type of the value returned by the div function,
13631 which is a structure type that is the type of the value returned by the ldiv function, and
13633 which is a structure type that is the type of the value returned by the lldiv function.
13634 3 The macros defined are NULL (described in <a href="#7.19">7.19</a>);
13638 which expand to integer constant expressions that can be used as the argument to the
13639 exit function to return unsuccessful or successful termination status, respectively, to the
13642 which expands to an integer constant expression that is the maximum value returned by
13643 the rand function; and
13645 which expands to a positive integer expression with type size_t that is the maximum
13646 number of bytes in a multibyte character for the extended character set specified by the
13647 current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX.
13652 280) See ''future library directions'' (<a href="#7.30.10">7.30.10</a>).
13654 [<a name="#p339" href="p339">page 339</a>] (<a href="#Contents">Contents</a>)
13656 <a name="7.22.1" href="#7.22.1"><b> 7.22.1 Numeric conversion functions</b></a>
13657 1 The functions atof, atoi, atol, and atoll need not affect the value of the integer
13658 expression errno on an error. If the value of the result cannot be represented, the
13659 behavior is undefined.
13660 <a name="7.22.1.1" href="#7.22.1.1"><b> 7.22.1.1 The atof function</b></a>
13662 1 #include <a href="#7.22"><stdlib.h></a>
13663 double atof(const char *nptr);
13665 2 The atof function converts the initial portion of the string pointed to by nptr to
13666 double representation. Except for the behavior on error, it is equivalent to
13667 strtod(nptr, (char **)NULL)
13669 3 The atof function returns the converted value.
13670 Forward references: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
13671 <a name="7.22.1.2" href="#7.22.1.2"><b> 7.22.1.2 The atoi, atol, and atoll functions</b></a>
13673 1 #include <a href="#7.22"><stdlib.h></a>
13674 int atoi(const char *nptr);
13675 long int atol(const char *nptr);
13676 long long int atoll(const char *nptr);
13678 2 The atoi, atol, and atoll functions convert the initial portion of the string pointed
13679 to by nptr to int, long int, and long long int representation, respectively.
13680 Except for the behavior on error, they are equivalent to
13681 atoi: (int)strtol(nptr, (char **)NULL, 10)
13682 atol: strtol(nptr, (char **)NULL, 10)
13683 atoll: strtoll(nptr, (char **)NULL, 10)
13685 3 The atoi, atol, and atoll functions return the converted value.
13686 Forward references: the strtol, strtoll, strtoul, and strtoull functions
13687 (<a href="#7.22.1.4">7.22.1.4</a>).
13691 [<a name="#p340" href="p340">page 340</a>] (<a href="#Contents">Contents</a>)
13693 <a name="7.22.1.3" href="#7.22.1.3"><b> 7.22.1.3 The strtod, strtof, and strtold functions</b></a>
13695 1 #include <a href="#7.22"><stdlib.h></a>
13696 double strtod(const char * restrict nptr,
13697 char ** restrict endptr);
13698 float strtof(const char * restrict nptr,
13699 char ** restrict endptr);
13700 long double strtold(const char * restrict nptr,
13701 char ** restrict endptr);
13703 2 The strtod, strtof, and strtold functions convert the initial portion of the string
13704 pointed to by nptr to double, float, and long double representation,
13705 respectively. First, they decompose the input string into three parts: an initial, possibly
13706 empty, sequence of white-space characters (as specified by the isspace function), a
13707 subject sequence resembling a floating-point constant or representing an infinity or NaN;
13708 and a final string of one or more unrecognized characters, including the terminating null
13709 character of the input string. Then, they attempt to convert the subject sequence to a
13710 floating-point number, and return the result.
13711 3 The expected form of the subject sequence is an optional plus or minus sign, then one of
13713 -- a nonempty sequence of decimal digits optionally containing a decimal-point
13714 character, then an optional exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
13715 -- a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
13716 decimal-point character, then an optional binary exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
13717 -- INF or INFINITY, ignoring case
13718 -- NAN or NAN(n-char-sequenceopt), ignoring case in the NAN part, where:
13722 n-char-sequence digit
13723 n-char-sequence nondigit
13724 The subject sequence is defined as the longest initial subsequence of the input string,
13725 starting with the first non-white-space character, that is of the expected form. The subject
13726 sequence contains no characters if the input string is not of the expected form.
13727 4 If the subject sequence has the expected form for a floating-point number, the sequence of
13728 characters starting with the first digit or the decimal-point character (whichever occurs
13729 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
13730 [<a name="#p341" href="p341">page 341</a>] (<a href="#Contents">Contents</a>)
13732 decimal-point character is used in place of a period, and that if neither an exponent part
13733 nor a decimal-point character appears in a decimal floating point number, or if a binary
13734 exponent part does not appear in a hexadecimal floating point number, an exponent part
13735 of the appropriate type with value zero is assumed to follow the last digit in the string. If
13736 the subject sequence begins with a minus sign, the sequence is interpreted as negated.281)
13737 A character sequence INF or INFINITY is interpreted as an infinity, if representable in
13738 the return type, else like a floating constant that is too large for the range of the return
13739 type. A character sequence NAN or NAN(n-char-sequenceopt), is interpreted as a quiet
13740 NaN, if supported in the return type, else like a subject sequence part that does not have
13741 the expected form; the meaning of the n-char sequences is implementation-defined.282) A
13742 pointer to the final string is stored in the object pointed to by endptr, provided that
13743 endptr is not a null pointer.
13744 5 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
13745 value resulting from the conversion is correctly rounded.
13746 6 In other than the "C" locale, additional locale-specific subject sequence forms may be
13748 7 If the subject sequence is empty or does not have the expected form, no conversion is
13749 performed; the value of nptr is stored in the object pointed to by endptr, provided
13750 that endptr is not a null pointer.
13751 Recommended practice
13752 8 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
13753 the result is not exactly representable, the result should be one of the two numbers in the
13754 appropriate internal format that are adjacent to the hexadecimal floating source value,
13755 with the extra stipulation that the error should have a correct sign for the current rounding
13757 9 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
13758 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
13759 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
13760 consider the two bounding, adjacent decimal strings L and U, both having
13761 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
13762 The result should be one of the (equal or adjacent) values that would be obtained by
13763 correctly rounding L and U according to the current rounding direction, with the extra
13765 281) It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
13766 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
13767 methods may yield different results if rounding is toward positive or negative infinity. In either case,
13768 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
13769 282) An implementation may use the n-char sequence to determine extra information to be represented in
13770 the NaN's significand.
13772 [<a name="#p342" href="p342">page 342</a>] (<a href="#Contents">Contents</a>)
13774 stipulation that the error with respect to D should have a correct sign for the current
13775 rounding direction.283)
13777 10 The functions return the converted value, if any. If no conversion could be performed,
13778 zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
13779 plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
13780 return type and sign of the value), and the value of the macro ERANGE is stored in
13781 errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
13782 no greater than the smallest normalized positive number in the return type; whether
13783 errno acquires the value ERANGE is implementation-defined.
13784 <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>
13786 1 #include <a href="#7.22"><stdlib.h></a>
13788 const char * restrict nptr,
13789 char ** restrict endptr,
13791 long long int strtoll(
13792 const char * restrict nptr,
13793 char ** restrict endptr,
13795 unsigned long int strtoul(
13796 const char * restrict nptr,
13797 char ** restrict endptr,
13799 unsigned long long int strtoull(
13800 const char * restrict nptr,
13801 char ** restrict endptr,
13804 2 The strtol, strtoll, strtoul, and strtoull functions convert the initial
13805 portion of the string pointed to by nptr to long int, long long int, unsigned
13806 long int, and unsigned long long int representation, respectively. First,
13807 they decompose the input string into three parts: an initial, possibly empty, sequence of
13808 white-space characters (as specified by the isspace function), a subject sequence
13811 283) DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
13812 to the same internal floating value, but if not will round to adjacent values.
13814 [<a name="#p343" href="p343">page 343</a>] (<a href="#Contents">Contents</a>)
13816 resembling an integer represented in some radix determined by the value of base, and a
13817 final string of one or more unrecognized characters, including the terminating null
13818 character of the input string. Then, they attempt to convert the subject sequence to an
13819 integer, and return the result.
13820 3 If the value of base is zero, the expected form of the subject sequence is that of an
13821 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
13822 not including an integer suffix. If the value of base is between 2 and 36 (inclusive), the
13823 expected form of the subject sequence is a sequence of letters and digits representing an
13824 integer with the radix specified by base, optionally preceded by a plus or minus sign,
13825 but not including an integer suffix. The letters from a (or A) through z (or Z) are
13826 ascribed the values 10 through 35; only letters and digits whose ascribed values are less
13827 than that of base are permitted. If the value of base is 16, the characters 0x or 0X may
13828 optionally precede the sequence of letters and digits, following the sign if present.
13829 4 The subject sequence is defined as the longest initial subsequence of the input string,
13830 starting with the first non-white-space character, that is of the expected form. The subject
13831 sequence contains no characters if the input string is empty or consists entirely of white
13832 space, or if the first non-white-space character is other than a sign or a permissible letter
13834 5 If the subject sequence has the expected form and the value of base is zero, the sequence
13835 of characters starting with the first digit is interpreted as an integer constant according to
13836 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
13837 is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
13838 as given above. If the subject sequence begins with a minus sign, the value resulting from
13839 the conversion is negated (in the return type). A pointer to the final string is stored in the
13840 object pointed to by endptr, provided that endptr is not a null pointer.
13841 6 In other than the "C" locale, additional locale-specific subject sequence forms may be
13843 7 If the subject sequence is empty or does not have the expected form, no conversion is
13844 performed; the value of nptr is stored in the object pointed to by endptr, provided
13845 that endptr is not a null pointer.
13847 8 The strtol, strtoll, strtoul, and strtoull functions return the converted
13848 value, if any. If no conversion could be performed, zero is returned. If the correct value
13849 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
13850 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
13851 and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
13856 [<a name="#p344" href="p344">page 344</a>] (<a href="#Contents">Contents</a>)
13858 <a name="7.22.2" href="#7.22.2"><b> 7.22.2 Pseudo-random sequence generation functions</b></a>
13859 <a name="7.22.2.1" href="#7.22.2.1"><b> 7.22.2.1 The rand function</b></a>
13861 1 #include <a href="#7.22"><stdlib.h></a>
13864 2 The rand function computes a sequence of pseudo-random integers in the range 0 to
13866 3 The rand function is not required to avoid data races. The implementation shall behave
13867 as if no library function calls the rand function.
13869 4 The rand function returns a pseudo-random integer.
13870 Environmental limits
13871 5 The value of the RAND_MAX macro shall be at least 32767.
13872 <a name="7.22.2.2" href="#7.22.2.2"><b> 7.22.2.2 The srand function</b></a>
13874 1 #include <a href="#7.22"><stdlib.h></a>
13875 void srand(unsigned int seed);
13877 2 The srand function uses the argument as a seed for a new sequence of pseudo-random
13878 numbers to be returned by subsequent calls to rand. If srand is then called with the
13879 same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
13880 called before any calls to srand have been made, the same sequence shall be generated
13881 as when srand is first called with a seed value of 1.
13882 3 The implementation shall behave as if no library function calls the srand function.
13884 4 The srand function returns no value.
13889 284) There are no guarantees as to the quality of the random sequence produced and some implementations
13890 are known to produce sequences with distressingly non-random low-order bits. Applications with
13891 particular requirements should use a generator that is known to be sufficient for their needs.
13893 [<a name="#p345" href="p345">page 345</a>] (<a href="#Contents">Contents</a>)
13895 5 EXAMPLE The following functions define a portable implementation of rand and srand.
13896 static unsigned long int next = 1;
13897 int rand(void) // RAND_MAX assumed to be 32767
13899 next = next * 1103515245 + 12345;
13900 return (unsigned int)(next/65536) % 32768;
13902 void srand(unsigned int seed)
13907 <a name="7.22.3" href="#7.22.3"><b> 7.22.3 Memory management functions</b></a>
13908 1 The order and contiguity of storage allocated by successive calls to the
13909 aligned_alloc, calloc, malloc, and realloc functions is unspecified. The
13910 pointer returned if the allocation succeeds is suitably aligned so that it may be assigned to
13911 a pointer to any type of object with a fundamental alignment requirement and then used
13912 to access such an object or an array of such objects in the space allocated (until the space
13913 is explicitly deallocated). The lifetime of an allocated object extends from the allocation
13914 until the deallocation. Each such allocation shall yield a pointer to an object disjoint from
13915 any other object. The pointer returned points to the start (lowest byte address) of the
13916 allocated space. If the space cannot be allocated, a null pointer is returned. If the size of
13917 the space requested is zero, the behavior is implementation-defined: either a null pointer
13918 is returned, or the behavior is as if the size were some nonzero value, except that the
13919 returned pointer shall not be used to access an object.
13920 <a name="7.22.3.1" href="#7.22.3.1"><b> 7.22.3.1 The aligned_alloc function</b></a>
13922 1 #include <a href="#7.22"><stdlib.h></a>
13923 void *aligned_alloc(size_t alignment, size_t size);
13925 2 The aligned_alloc function allocates space for an object whose alignment is
13926 specified by alignment, whose size is specified by size, and whose value is
13927 indeterminate. The value of alignment shall be a valid alignment supported by the
13928 implementation and the value of size shall be an integral multiple of alignment.
13930 3 The aligned_alloc function returns either a null pointer or a pointer to the allocated
13936 [<a name="#p346" href="p346">page 346</a>] (<a href="#Contents">Contents</a>)
13938 <a name="7.22.3.2" href="#7.22.3.2"><b> 7.22.3.2 The calloc function</b></a>
13940 1 #include <a href="#7.22"><stdlib.h></a>
13941 void *calloc(size_t nmemb, size_t size);
13943 2 The calloc function allocates space for an array of nmemb objects, each of whose size
13944 is size. The space is initialized to all bits zero.285)
13946 3 The calloc function returns either a null pointer or a pointer to the allocated space.
13947 <a name="7.22.3.3" href="#7.22.3.3"><b> 7.22.3.3 The free function</b></a>
13949 1 #include <a href="#7.22"><stdlib.h></a>
13950 void free(void *ptr);
13952 2 The free function causes the space pointed to by ptr to be deallocated, that is, made
13953 available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
13954 the argument does not match a pointer earlier returned by a memory management
13955 function, or if the space has been deallocated by a call to free or realloc, the
13956 behavior is undefined.
13958 3 The free function returns no value.
13959 <a name="7.22.3.4" href="#7.22.3.4"><b> 7.22.3.4 The malloc function</b></a>
13961 1 #include <a href="#7.22"><stdlib.h></a>
13962 void *malloc(size_t size);
13964 2 The malloc function allocates space for an object whose size is specified by size and
13965 whose value is indeterminate.
13970 285) Note that this need not be the same as the representation of floating-point zero or a null pointer
13973 [<a name="#p347" href="p347">page 347</a>] (<a href="#Contents">Contents</a>)
13976 3 The malloc function returns either a null pointer or a pointer to the allocated space.
13977 <a name="7.22.3.5" href="#7.22.3.5"><b> 7.22.3.5 The realloc function</b></a>
13979 1 #include <a href="#7.22"><stdlib.h></a>
13980 void *realloc(void *ptr, size_t size);
13982 2 The realloc function deallocates the old object pointed to by ptr and returns a
13983 pointer to a new object that has the size specified by size. The contents of the new
13984 object shall be the same as that of the old object prior to deallocation, up to the lesser of
13985 the new and old sizes. Any bytes in the new object beyond the size of the old object have
13986 indeterminate values.
13987 3 If ptr is a null pointer, the realloc function behaves like the malloc function for the
13988 specified size. Otherwise, if ptr does not match a pointer earlier returned by a memory
13989 management function, or if the space has been deallocated by a call to the free or
13990 realloc function, the behavior is undefined. If memory for the new object cannot be
13991 allocated, the old object is not deallocated and its value is unchanged.
13993 4 The realloc function returns a pointer to the new object (which may have the same
13994 value as a pointer to the old object), or a null pointer if the new object could not be
13996 <a name="7.22.4" href="#7.22.4"><b> 7.22.4 Communication with the environment</b></a>
13997 <a name="7.22.4.1" href="#7.22.4.1"><b> 7.22.4.1 The abort function</b></a>
13999 1 #include <a href="#7.22"><stdlib.h></a>
14000 _Noreturn void abort(void);
14002 2 The abort function causes abnormal program termination to occur, unless the signal
14003 SIGABRT is being caught and the signal handler does not return. Whether open streams
14004 with unwritten buffered data are flushed, open streams are closed, or temporary files are
14005 removed is implementation-defined. An implementation-defined form of the status
14006 unsuccessful termination is returned to the host environment by means of the function
14007 call raise(SIGABRT).
14012 [<a name="#p348" href="p348">page 348</a>] (<a href="#Contents">Contents</a>)
14015 3 The abort function does not return to its caller.
14016 <a name="7.22.4.2" href="#7.22.4.2"><b> 7.22.4.2 The atexit function</b></a>
14018 1 #include <a href="#7.22"><stdlib.h></a>
14019 int atexit(void (*func)(void));
14021 2 The atexit function registers the function pointed to by func, to be called without
14022 arguments at normal program termination.286)
14023 Environmental limits
14024 3 The implementation shall support the registration of at least 32 functions.
14026 4 The atexit function returns zero if the registration succeeds, nonzero if it fails.
14027 Forward references: the at_quick_exit function (<a href="#7.22.4.3">7.22.4.3</a>), the exit function
14028 (<a href="#7.22.4.4">7.22.4.4</a>).
14029 <a name="7.22.4.3" href="#7.22.4.3"><b> 7.22.4.3 The at_quick_exit function</b></a>
14031 1 #include <a href="#7.22"><stdlib.h></a>
14032 int at_quick_exit(void (*func)(void));
14034 2 The at_quick_exit function registers the function pointed to by func, to be called
14035 without arguments should quick_exit be called.287)
14036 Environmental limits
14037 3 The implementation shall support the registration of at least 32 functions.
14039 4 The at_quick_exit function returns zero if the registration succeeds, nonzero if it
14041 Forward references: the quick_exit function (<a href="#7.22.4.7">7.22.4.7</a>).
14043 286) The atexit function registrations are distinct from the at_quick_exit registrations, so
14044 applications may need to call both registration functions with the same argument.
14045 287) The at_quick_exit function registrations are distinct from the atexit registrations, so
14046 applications may need to call both registration functions with the same argument.
14048 [<a name="#p349" href="p349">page 349</a>] (<a href="#Contents">Contents</a>)
14050 <a name="7.22.4.4" href="#7.22.4.4"><b> 7.22.4.4 The exit function</b></a>
14052 1 #include <a href="#7.22"><stdlib.h></a>
14053 _Noreturn void exit(int status);
14055 2 The exit function causes normal program termination to occur. No functions registered
14056 by the at_quick_exit function are called. If a program calls the exit function
14057 more than once, or calls the quick_exit function in addition to the exit function, the
14058 behavior is undefined.
14059 3 First, all functions registered by the atexit function are called, in the reverse order of
14060 their registration,288) except that a function is called after any previously registered
14061 functions that had already been called at the time it was registered. If, during the call to
14062 any such function, a call to the longjmp function is made that would terminate the call
14063 to the registered function, the behavior is undefined.
14064 4 Next, all open streams with unwritten buffered data are flushed, all open streams are
14065 closed, and all files created by the tmpfile function are removed.
14066 5 Finally, control is returned to the host environment. If the value of status is zero or
14067 EXIT_SUCCESS, an implementation-defined form of the status successful termination is
14068 returned. If the value of status is EXIT_FAILURE, an implementation-defined form
14069 of the status unsuccessful termination is returned. Otherwise the status returned is
14070 implementation-defined.
14072 6 The exit function cannot return to its caller.
14073 <a name="7.22.4.5" href="#7.22.4.5"><b> 7.22.4.5 The _Exit function</b></a>
14075 1 #include <a href="#7.22"><stdlib.h></a>
14076 _Noreturn void _Exit(int status);
14078 2 The _Exit function causes normal program termination to occur and control to be
14079 returned to the host environment. No functions registered by the atexit function, the
14080 at_quick_exit function, or signal handlers registered by the signal function are
14081 called. The status returned to the host environment is determined in the same way as for
14084 288) Each function is called as many times as it was registered, and in the correct order with respect to
14085 other registered functions.
14087 [<a name="#p350" href="p350">page 350</a>] (<a href="#Contents">Contents</a>)
14089 the exit function (<a href="#7.22.4.4">7.22.4.4</a>). Whether open streams with unwritten buffered data are
14090 flushed, open streams are closed, or temporary files are removed is implementation-
14093 3 The _Exit function cannot return to its caller.
14094 <a name="7.22.4.6" href="#7.22.4.6"><b> 7.22.4.6 The getenv function</b></a>
14096 1 #include <a href="#7.22"><stdlib.h></a>
14097 char *getenv(const char *name);
14099 2 The getenv function searches an environment list, provided by the host environment,
14100 for a string that matches the string pointed to by name. The set of environment names
14101 and the method for altering the environment list are implementation-defined. The
14102 getenv function need not avoid data races with other threads of execution that modify
14103 the environment list.289)
14104 3 The implementation shall behave as if no library function calls the getenv function.
14106 4 The getenv function returns a pointer to a string associated with the matched list
14107 member. The string pointed to shall not be modified by the program, but may be
14108 overwritten by a subsequent call to the getenv function. If the specified name cannot
14109 be found, a null pointer is returned.
14110 <a name="7.22.4.7" href="#7.22.4.7"><b> 7.22.4.7 The quick_exit function</b></a>
14112 1 #include <a href="#7.22"><stdlib.h></a>
14113 _Noreturn void quick_exit(int status);
14115 2 The quick_exit function causes normal program termination to occur. No functions
14116 registered by the atexit function or signal handlers registered by the signal function
14117 are called. If a program calls the quick_exit function more than once, or calls the
14118 exit function in addition to the quick_exit function, the behavior is undefined.
14119 3 The quick_exit function first calls all functions registered by the at_quick_exit
14120 function, in the reverse order of their registration,290) except that a function is called after
14123 289) Many implementations provide non-standard functions that modify the environment list.
14125 [<a name="#p351" href="p351">page 351</a>] (<a href="#Contents">Contents</a>)
14127 any previously registered functions that had already been called at the time it was
14128 registered. If, during the call to any such function, a call to the longjmp function is
14129 made that would terminate the call to the registered function, the behavior is undefined.
14130 4 Then control is returned to the host environment by means of the function call
14133 5 The quick_exit function cannot return to its caller.
14134 <a name="7.22.4.8" href="#7.22.4.8"><b> 7.22.4.8 The system function</b></a>
14136 1 #include <a href="#7.22"><stdlib.h></a>
14137 int system(const char *string);
14139 2 If string is a null pointer, the system function determines whether the host
14140 environment has a command processor. If string is not a null pointer, the system
14141 function passes the string pointed to by string to that command processor to be
14142 executed in a manner which the implementation shall document; this might then cause the
14143 program calling system to behave in a non-conforming manner or to terminate.
14145 3 If the argument is a null pointer, the system function returns nonzero only if a
14146 command processor is available. If the argument is not a null pointer, and the system
14147 function does return, it returns an implementation-defined value.
14148 <a name="7.22.5" href="#7.22.5"><b> 7.22.5 Searching and sorting utilities</b></a>
14149 1 These utilities make use of a comparison function to search or sort arrays of unspecified
14150 type. Where an argument declared as size_t nmemb specifies the length of the array
14151 for a function, nmemb can have the value zero on a call to that function; the comparison
14152 function is not called, a search finds no matching element, and sorting performs no
14153 rearrangement. Pointer arguments on such a call shall still have valid values, as described
14154 in <a href="#7.1.4">7.1.4</a>.
14155 2 The implementation shall ensure that the second argument of the comparison function
14156 (when called from bsearch), or both arguments (when called from qsort), are
14157 pointers to elements of the array.291) The first argument when called from bsearch
14162 290) Each function is called as many times as it was registered, and in the correct order with respect to
14163 other registered functions.
14165 [<a name="#p352" href="p352">page 352</a>] (<a href="#Contents">Contents</a>)
14167 3 The comparison function shall not alter the contents of the array. The implementation
14168 may reorder elements of the array between calls to the comparison function, but shall not
14169 alter the contents of any individual element.
14170 4 When the same objects (consisting of size bytes, irrespective of their current positions
14171 in the array) are passed more than once to the comparison function, the results shall be
14172 consistent with one another. That is, for qsort they shall define a total ordering on the
14173 array, and for bsearch the same object shall always compare the same way with the
14175 5 A sequence point occurs immediately before and immediately after each call to the
14176 comparison function, and also between any call to the comparison function and any
14177 movement of the objects passed as arguments to that call.
14178 <a name="7.22.5.1" href="#7.22.5.1"><b> 7.22.5.1 The bsearch function</b></a>
14180 1 #include <a href="#7.22"><stdlib.h></a>
14181 void *bsearch(const void *key, const void *base,
14182 size_t nmemb, size_t size,
14183 int (*compar)(const void *, const void *));
14185 2 The bsearch function searches an array of nmemb objects, the initial element of which
14186 is pointed to by base, for an element that matches the object pointed to by key. The
14187 size of each element of the array is specified by size.
14188 3 The comparison function pointed to by compar is called with two arguments that point
14189 to the key object and to an array element, in that order. The function shall return an
14190 integer less than, equal to, or greater than zero if the key object is considered,
14191 respectively, to be less than, to match, or to be greater than the array element. The array
14192 shall consist of: all the elements that compare less than, all the elements that compare
14193 equal to, and all the elements that compare greater than the key object, in that order.292)
14195 4 The bsearch function returns a pointer to a matching element of the array, or a null
14196 pointer if no match is found. If two elements compare as equal, which element is
14199 291) That is, if the value passed is p, then the following expressions are always nonzero:
14200 ((char *)p - (char *)base) % size == 0
14201 (char *)p >= (char *)base
14202 (char *)p < (char *)base + nmemb * size
14204 292) In practice, the entire array is sorted according to the comparison function.
14206 [<a name="#p353" href="p353">page 353</a>] (<a href="#Contents">Contents</a>)
14208 matched is unspecified.
14209 <a name="7.22.5.2" href="#7.22.5.2"><b> 7.22.5.2 The qsort function</b></a>
14211 1 #include <a href="#7.22"><stdlib.h></a>
14212 void qsort(void *base, size_t nmemb, size_t size,
14213 int (*compar)(const void *, const void *));
14215 2 The qsort function sorts an array of nmemb objects, the initial element of which is
14216 pointed to by base. The size of each object is specified by size.
14217 3 The contents of the array are sorted into ascending order according to a comparison
14218 function pointed to by compar, which is called with two arguments that point to the
14219 objects being compared. The function shall return an integer less than, equal to, or
14220 greater than zero if the first argument is considered to be respectively less than, equal to,
14221 or greater than the second.
14222 4 If two elements compare as equal, their order in the resulting sorted array is unspecified.
14224 5 The qsort function returns no value.
14225 <a name="7.22.6" href="#7.22.6"><b> 7.22.6 Integer arithmetic functions</b></a>
14226 <a name="7.22.6.1" href="#7.22.6.1"><b> 7.22.6.1 The abs, labs and llabs functions</b></a>
14228 1 #include <a href="#7.22"><stdlib.h></a>
14230 long int labs(long int j);
14231 long long int llabs(long long int j);
14233 2 The abs, labs, and llabs functions compute the absolute value of an integer j. If the
14234 result cannot be represented, the behavior is undefined.293)
14236 3 The abs, labs, and llabs, functions return the absolute value.
14241 293) The absolute value of the most negative number cannot be represented in two's complement.
14243 [<a name="#p354" href="p354">page 354</a>] (<a href="#Contents">Contents</a>)
14245 <a name="7.22.6.2" href="#7.22.6.2"><b> 7.22.6.2 The div, ldiv, and lldiv functions</b></a>
14247 1 #include <a href="#7.22"><stdlib.h></a>
14248 div_t div(int numer, int denom);
14249 ldiv_t ldiv(long int numer, long int denom);
14250 lldiv_t lldiv(long long int numer, long long int denom);
14252 2 The div, ldiv, and lldiv, functions compute numer / denom and numer %
14253 denom in a single operation.
14255 3 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
14256 lldiv_t, respectively, comprising both the quotient and the remainder. The structures
14257 shall contain (in either order) the members quot (the quotient) and rem (the remainder),
14258 each of which has the same type as the arguments numer and denom. If either part of
14259 the result cannot be represented, the behavior is undefined.
14260 <a name="7.22.7" href="#7.22.7"><b> 7.22.7 Multibyte/wide character conversion functions</b></a>
14261 1 The behavior of the multibyte character functions is affected by the LC_CTYPE category
14262 of the current locale. For a state-dependent encoding, each function is placed into its
14263 initial conversion state at program startup and can be returned to that state by a call for
14264 which its character pointer argument, s, is a null pointer. Subsequent calls with s as
14265 other than a null pointer cause the internal conversion state of the function to be altered as
14266 necessary. A call with s as a null pointer causes these functions to return a nonzero value
14267 if encodings have state dependency, and zero otherwise.294) Changing the LC_CTYPE
14268 category causes the conversion state of these functions to be indeterminate.
14269 <a name="7.22.7.1" href="#7.22.7.1"><b> 7.22.7.1 The mblen function</b></a>
14271 1 #include <a href="#7.22"><stdlib.h></a>
14272 int mblen(const char *s, size_t n);
14274 2 If s is not a null pointer, the mblen function determines the number of bytes contained
14275 in the multibyte character pointed to by s. Except that the conversion state of the
14276 mbtowc function is not affected, it is equivalent to
14280 294) If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
14281 character codes, but are grouped with an adjacent multibyte character.
14283 [<a name="#p355" href="p355">page 355</a>] (<a href="#Contents">Contents</a>)
14285 mbtowc((wchar_t *)0, (const char *)0, 0);
14286 mbtowc((wchar_t *)0, s, n);
14287 3 The implementation shall behave as if no library function calls the mblen function.
14289 4 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte
14290 character encodings, respectively, do or do not have state-dependent encodings. If s is
14291 not a null pointer, the mblen function either returns 0 (if s points to the null character),
14292 or returns the number of bytes that are contained in the multibyte character (if the next n
14293 or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid
14294 multibyte character).
14295 Forward references: the mbtowc function (<a href="#7.22.7.2">7.22.7.2</a>).
14296 <a name="7.22.7.2" href="#7.22.7.2"><b> 7.22.7.2 The mbtowc function</b></a>
14298 1 #include <a href="#7.22"><stdlib.h></a>
14299 int mbtowc(wchar_t * restrict pwc,
14300 const char * restrict s,
14303 2 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with
14304 the byte pointed to by s to determine the number of bytes needed to complete the next
14305 multibyte character (including any shift sequences). If the function determines that the
14306 next multibyte character is complete and valid, it determines the value of the
14307 corresponding wide character and then, if pwc is not a null pointer, stores that value in
14308 the object pointed to by pwc. If the corresponding wide character is the null wide
14309 character, the function is left in the initial conversion state.
14310 3 The implementation shall behave as if no library function calls the mbtowc function.
14312 4 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte
14313 character encodings, respectively, do or do not have state-dependent encodings. If s is
14314 not a null pointer, the mbtowc function either returns 0 (if s points to the null character),
14315 or returns the number of bytes that are contained in the converted multibyte character (if
14316 the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not
14317 form a valid multibyte character).
14318 5 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
14322 [<a name="#p356" href="p356">page 356</a>] (<a href="#Contents">Contents</a>)
14324 <a name="7.22.7.3" href="#7.22.7.3"><b> 7.22.7.3 The wctomb function</b></a>
14326 1 #include <a href="#7.22"><stdlib.h></a>
14327 int wctomb(char *s, wchar_t wc);
14329 2 The wctomb function determines the number of bytes needed to represent the multibyte
14330 character corresponding to the wide character given by wc (including any shift
14331 sequences), and stores the multibyte character representation in the array whose first
14332 element is pointed to by s (if s is not a null pointer). At most MB_CUR_MAX characters
14333 are stored. If wc is a null wide character, a null byte is stored, preceded by any shift
14334 sequence needed to restore the initial shift state, and the function is left in the initial
14336 3 The implementation shall behave as if no library function calls the wctomb function.
14338 4 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte
14339 character encodings, respectively, do or do not have state-dependent encodings. If s is
14340 not a null pointer, the wctomb function returns -1 if the value of wc does not correspond
14341 to a valid multibyte character, or returns the number of bytes that are contained in the
14342 multibyte character corresponding to the value of wc.
14343 5 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
14344 <a name="7.22.8" href="#7.22.8"><b> 7.22.8 Multibyte/wide string conversion functions</b></a>
14345 1 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
14346 the current locale.
14347 <a name="7.22.8.1" href="#7.22.8.1"><b> 7.22.8.1 The mbstowcs function</b></a>
14349 1 #include <a href="#7.22"><stdlib.h></a>
14350 size_t mbstowcs(wchar_t * restrict pwcs,
14351 const char * restrict s,
14354 2 The mbstowcs function converts a sequence of multibyte characters that begins in the
14355 initial shift state from the array pointed to by s into a sequence of corresponding wide
14356 characters and stores not more than n wide characters into the array pointed to by pwcs.
14357 No multibyte characters that follow a null character (which is converted into a null wide
14358 character) will be examined or converted. Each multibyte character is converted as if by
14359 a call to the mbtowc function, except that the conversion state of the mbtowc function is
14360 [<a name="#p357" href="p357">page 357</a>] (<a href="#Contents">Contents</a>)
14363 3 No more than n elements will be modified in the array pointed to by pwcs. If copying
14364 takes place between objects that overlap, the behavior is undefined.
14366 4 If an invalid multibyte character is encountered, the mbstowcs function returns
14367 (size_t)(-1). Otherwise, the mbstowcs function returns the number of array
14368 elements modified, not including a terminating null wide character, if any.295)
14369 <a name="7.22.8.2" href="#7.22.8.2"><b> 7.22.8.2 The wcstombs function</b></a>
14371 1 #include <a href="#7.22"><stdlib.h></a>
14372 size_t wcstombs(char * restrict s,
14373 const wchar_t * restrict pwcs,
14376 2 The wcstombs function converts a sequence of wide characters from the array pointed
14377 to by pwcs into a sequence of corresponding multibyte characters that begins in the
14378 initial shift state, and stores these multibyte characters into the array pointed to by s,
14379 stopping if a multibyte character would exceed the limit of n total bytes or if a null
14380 character is stored. Each wide character is converted as if by a call to the wctomb
14381 function, except that the conversion state of the wctomb function is not affected.
14382 3 No more than n bytes will be modified in the array pointed to by s. If copying takes place
14383 between objects that overlap, the behavior is undefined.
14385 4 If a wide character is encountered that does not correspond to a valid multibyte character,
14386 the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
14387 returns the number of bytes modified, not including a terminating null character, if
14393 295) The array will not be null-terminated if the value returned is n.
14395 [<a name="#p358" href="p358">page 358</a>] (<a href="#Contents">Contents</a>)
14397 <a name="7.23" href="#7.23"><b> 7.23 String handling <string.h></b></a>
14398 <a name="7.23.1" href="#7.23.1"><b> 7.23.1 String function conventions</b></a>
14399 1 The header <a href="#7.23"><string.h></a> declares one type and several functions, and defines one
14400 macro useful for manipulating arrays of character type and other objects treated as arrays
14401 of character type.296) The type is size_t and the macro is NULL (both described in
14402 <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>
14403 a char * or void * argument points to the initial (lowest addressed) character of the
14404 array. If an array is accessed beyond the end of an object, the behavior is undefined.
14405 2 Where an argument declared as size_t n specifies the length of the array for a
14406 function, n can have the value zero on a call to that function. Unless explicitly stated
14407 otherwise in the description of a particular function in this subclause, pointer arguments
14408 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
14409 function that locates a character finds no occurrence, a function that compares two
14410 character sequences returns zero, and a function that copies characters copies zero
14412 3 For all functions in this subclause, each character shall be interpreted as if it had the type
14413 unsigned char (and therefore every possible object representation is valid and has a
14415 <a name="7.23.2" href="#7.23.2"><b> 7.23.2 Copying functions</b></a>
14416 <a name="7.23.2.1" href="#7.23.2.1"><b> 7.23.2.1 The memcpy function</b></a>
14418 1 #include <a href="#7.23"><string.h></a>
14419 void *memcpy(void * restrict s1,
14420 const void * restrict s2,
14423 2 The memcpy function copies n characters from the object pointed to by s2 into the
14424 object pointed to by s1. If copying takes place between objects that overlap, the behavior
14427 3 The memcpy function returns the value of s1.
14432 296) See ''future library directions'' (<a href="#7.30.11">7.30.11</a>).
14434 [<a name="#p359" href="p359">page 359</a>] (<a href="#Contents">Contents</a>)
14436 <a name="7.23.2.2" href="#7.23.2.2"><b> 7.23.2.2 The memmove function</b></a>
14438 1 #include <a href="#7.23"><string.h></a>
14439 void *memmove(void *s1, const void *s2, size_t n);
14441 2 The memmove function copies n characters from the object pointed to by s2 into the
14442 object pointed to by s1. Copying takes place as if the n characters from the object
14443 pointed to by s2 are first copied into a temporary array of n characters that does not
14444 overlap the objects pointed to by s1 and s2, and then the n characters from the
14445 temporary array are copied into the object pointed to by s1.
14447 3 The memmove function returns the value of s1.
14448 <a name="7.23.2.3" href="#7.23.2.3"><b> 7.23.2.3 The strcpy function</b></a>
14450 1 #include <a href="#7.23"><string.h></a>
14451 char *strcpy(char * restrict s1,
14452 const char * restrict s2);
14454 2 The strcpy function copies the string pointed to by s2 (including the terminating null
14455 character) into the array pointed to by s1. If copying takes place between objects that
14456 overlap, the behavior is undefined.
14458 3 The strcpy function returns the value of s1.
14459 <a name="7.23.2.4" href="#7.23.2.4"><b> 7.23.2.4 The strncpy function</b></a>
14461 1 #include <a href="#7.23"><string.h></a>
14462 char *strncpy(char * restrict s1,
14463 const char * restrict s2,
14466 2 The strncpy function copies not more than n characters (characters that follow a null
14467 character are not copied) from the array pointed to by s2 to the array pointed to by
14472 [<a name="#p360" href="p360">page 360</a>] (<a href="#Contents">Contents</a>)
14474 s1.297) If copying takes place between objects that overlap, the behavior is undefined.
14475 3 If the array pointed to by s2 is a string that is shorter than n characters, null characters
14476 are appended to the copy in the array pointed to by s1, until n characters in all have been
14479 4 The strncpy function returns the value of s1.
14480 <a name="7.23.3" href="#7.23.3"><b> 7.23.3 Concatenation functions</b></a>
14481 <a name="7.23.3.1" href="#7.23.3.1"><b> 7.23.3.1 The strcat function</b></a>
14483 1 #include <a href="#7.23"><string.h></a>
14484 char *strcat(char * restrict s1,
14485 const char * restrict s2);
14487 2 The strcat function appends a copy of the string pointed to by s2 (including the
14488 terminating null character) to the end of the string pointed to by s1. The initial character
14489 of s2 overwrites the null character at the end of s1. If copying takes place between
14490 objects that overlap, the behavior is undefined.
14492 3 The strcat function returns the value of s1.
14493 <a name="7.23.3.2" href="#7.23.3.2"><b> 7.23.3.2 The strncat function</b></a>
14495 1 #include <a href="#7.23"><string.h></a>
14496 char *strncat(char * restrict s1,
14497 const char * restrict s2,
14500 2 The strncat function appends not more than n characters (a null character and
14501 characters that follow it are not appended) from the array pointed to by s2 to the end of
14502 the string pointed to by s1. The initial character of s2 overwrites the null character at the
14503 end of s1. A terminating null character is always appended to the result.298) If copying
14505 297) Thus, if there is no null character in the first n characters of the array pointed to by s2, the result will
14506 not be null-terminated.
14507 298) Thus, the maximum number of characters that can end up in the array pointed to by s1 is
14510 [<a name="#p361" href="p361">page 361</a>] (<a href="#Contents">Contents</a>)
14512 takes place between objects that overlap, the behavior is undefined.
14514 3 The strncat function returns the value of s1.
14515 Forward references: the strlen function (<a href="#7.23.6.3">7.23.6.3</a>).
14516 <a name="7.23.4" href="#7.23.4"><b> 7.23.4 Comparison functions</b></a>
14517 1 The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
14518 and strncmp is determined by the sign of the difference between the values of the first
14519 pair of characters (both interpreted as unsigned char) that differ in the objects being
14521 <a name="7.23.4.1" href="#7.23.4.1"><b> 7.23.4.1 The memcmp function</b></a>
14523 1 #include <a href="#7.23"><string.h></a>
14524 int memcmp(const void *s1, const void *s2, size_t n);
14526 2 The memcmp function compares the first n characters of the object pointed to by s1 to
14527 the first n characters of the object pointed to by s2.299)
14529 3 The memcmp function returns an integer greater than, equal to, or less than zero,
14530 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
14532 <a name="7.23.4.2" href="#7.23.4.2"><b> 7.23.4.2 The strcmp function</b></a>
14534 1 #include <a href="#7.23"><string.h></a>
14535 int strcmp(const char *s1, const char *s2);
14537 2 The strcmp function compares the string pointed to by s1 to the string pointed to by
14540 3 The strcmp function returns an integer greater than, equal to, or less than zero,
14541 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
14543 299) The contents of ''holes'' used as padding for purposes of alignment within structure objects are
14544 indeterminate. Strings shorter than their allocated space and unions may also cause problems in
14547 [<a name="#p362" href="p362">page 362</a>] (<a href="#Contents">Contents</a>)
14550 <a name="7.23.4.3" href="#7.23.4.3"><b> 7.23.4.3 The strcoll function</b></a>
14552 1 #include <a href="#7.23"><string.h></a>
14553 int strcoll(const char *s1, const char *s2);
14555 2 The strcoll function compares the string pointed to by s1 to the string pointed to by
14556 s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
14558 3 The strcoll function returns an integer greater than, equal to, or less than zero,
14559 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
14560 pointed to by s2 when both are interpreted as appropriate to the current locale.
14561 <a name="7.23.4.4" href="#7.23.4.4"><b> 7.23.4.4 The strncmp function</b></a>
14563 1 #include <a href="#7.23"><string.h></a>
14564 int strncmp(const char *s1, const char *s2, size_t n);
14566 2 The strncmp function compares not more than n characters (characters that follow a
14567 null character are not compared) from the array pointed to by s1 to the array pointed to
14570 3 The strncmp function returns an integer greater than, equal to, or less than zero,
14571 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
14572 to, or less than the possibly null-terminated array pointed to by s2.
14573 <a name="7.23.4.5" href="#7.23.4.5"><b> 7.23.4.5 The strxfrm function</b></a>
14575 1 #include <a href="#7.23"><string.h></a>
14576 size_t strxfrm(char * restrict s1,
14577 const char * restrict s2,
14580 2 The strxfrm function transforms the string pointed to by s2 and places the resulting
14581 string into the array pointed to by s1. The transformation is such that if the strcmp
14582 function is applied to two transformed strings, it returns a value greater than, equal to, or
14584 [<a name="#p363" href="p363">page 363</a>] (<a href="#Contents">Contents</a>)
14586 less than zero, corresponding to the result of the strcoll function applied to the same
14587 two original strings. No more than n characters are placed into the resulting array
14588 pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
14589 be a null pointer. If copying takes place between objects that overlap, the behavior is
14592 3 The strxfrm function returns the length of the transformed string (not including the
14593 terminating null character). If the value returned is n or more, the contents of the array
14594 pointed to by s1 are indeterminate.
14595 4 EXAMPLE The value of the following expression is the size of the array needed to hold the
14596 transformation of the string pointed to by s.
14597 1 + strxfrm(NULL, s, 0)
14599 <a name="7.23.5" href="#7.23.5"><b> 7.23.5 Search functions</b></a>
14600 <a name="7.23.5.1" href="#7.23.5.1"><b> 7.23.5.1 The memchr function</b></a>
14602 1 #include <a href="#7.23"><string.h></a>
14603 void *memchr(const void *s, int c, size_t n);
14605 2 The memchr function locates the first occurrence of c (converted to an unsigned
14606 char) in the initial n characters (each interpreted as unsigned char) of the object
14609 3 The memchr function returns a pointer to the located character, or a null pointer if the
14610 character does not occur in the object.
14611 <a name="7.23.5.2" href="#7.23.5.2"><b> 7.23.5.2 The strchr function</b></a>
14613 1 #include <a href="#7.23"><string.h></a>
14614 char *strchr(const char *s, int c);
14616 2 The strchr function locates the first occurrence of c (converted to a char) in the
14617 string pointed to by s. The terminating null character is considered to be part of the
14620 3 The strchr function returns a pointer to the located character, or a null pointer if the
14621 character does not occur in the string.
14622 [<a name="#p364" href="p364">page 364</a>] (<a href="#Contents">Contents</a>)
14624 <a name="7.23.5.3" href="#7.23.5.3"><b> 7.23.5.3 The strcspn function</b></a>
14626 1 #include <a href="#7.23"><string.h></a>
14627 size_t strcspn(const char *s1, const char *s2);
14629 2 The strcspn function computes the length of the maximum initial segment of the string
14630 pointed to by s1 which consists entirely of characters not from the string pointed to by
14633 3 The strcspn function returns the length of the segment.
14634 <a name="7.23.5.4" href="#7.23.5.4"><b> 7.23.5.4 The strpbrk function</b></a>
14636 1 #include <a href="#7.23"><string.h></a>
14637 char *strpbrk(const char *s1, const char *s2);
14639 2 The strpbrk function locates the first occurrence in the string pointed to by s1 of any
14640 character from the string pointed to by s2.
14642 3 The strpbrk function returns a pointer to the character, or a null pointer if no character
14643 from s2 occurs in s1.
14644 <a name="7.23.5.5" href="#7.23.5.5"><b> 7.23.5.5 The strrchr function</b></a>
14646 1 #include <a href="#7.23"><string.h></a>
14647 char *strrchr(const char *s, int c);
14649 2 The strrchr function locates the last occurrence of c (converted to a char) in the
14650 string pointed to by s. The terminating null character is considered to be part of the
14653 3 The strrchr function returns a pointer to the character, or a null pointer if c does not
14654 occur in the string.
14659 [<a name="#p365" href="p365">page 365</a>] (<a href="#Contents">Contents</a>)
14661 <a name="7.23.5.6" href="#7.23.5.6"><b> 7.23.5.6 The strspn function</b></a>
14663 1 #include <a href="#7.23"><string.h></a>
14664 size_t strspn(const char *s1, const char *s2);
14666 2 The strspn function computes the length of the maximum initial segment of the string
14667 pointed to by s1 which consists entirely of characters from the string pointed to by s2.
14669 3 The strspn function returns the length of the segment.
14670 <a name="7.23.5.7" href="#7.23.5.7"><b> 7.23.5.7 The strstr function</b></a>
14672 1 #include <a href="#7.23"><string.h></a>
14673 char *strstr(const char *s1, const char *s2);
14675 2 The strstr function locates the first occurrence in the string pointed to by s1 of the
14676 sequence of characters (excluding the terminating null character) in the string pointed to
14679 3 The strstr function returns a pointer to the located string, or a null pointer if the string
14680 is not found. If s2 points to a string with zero length, the function returns s1.
14681 <a name="7.23.5.8" href="#7.23.5.8"><b> 7.23.5.8 The strtok function</b></a>
14683 1 #include <a href="#7.23"><string.h></a>
14684 char *strtok(char * restrict s1,
14685 const char * restrict s2);
14687 2 A sequence of calls to the strtok function breaks the string pointed to by s1 into a
14688 sequence of tokens, each of which is delimited by a character from the string pointed to
14689 by s2. The first call in the sequence has a non-null first argument; subsequent calls in the
14690 sequence have a null first argument. The separator string pointed to by s2 may be
14691 different from call to call.
14692 3 The first call in the sequence searches the string pointed to by s1 for the first character
14693 that is not contained in the current separator string pointed to by s2. If no such character
14694 is found, then there are no tokens in the string pointed to by s1 and the strtok function
14696 [<a name="#p366" href="p366">page 366</a>] (<a href="#Contents">Contents</a>)
14698 returns a null pointer. If such a character is found, it is the start of the first token.
14699 4 The strtok function then searches from there for a character that is contained in the
14700 current separator string. If no such character is found, the current token extends to the
14701 end of the string pointed to by s1, and subsequent searches for a token will return a null
14702 pointer. If such a character is found, it is overwritten by a null character, which
14703 terminates the current token. The strtok function saves a pointer to the following
14704 character, from which the next search for a token will start.
14705 5 Each subsequent call, with a null pointer as the value of the first argument, starts
14706 searching from the saved pointer and behaves as described above.
14707 6 The strtok function is not required to avoid data races. The implementation shall
14708 behave as if no library function calls the strtok function.
14710 7 The strtok function returns a pointer to the first character of a token, or a null pointer
14711 if there is no token.
14713 #include <a href="#7.23"><string.h></a>
14714 static char str[] = "?a???b,,,#c";
14716 t = strtok(str, "?"); // t points to the token "a"
14717 t = strtok(NULL, ","); // t points to the token "??b"
14718 t = strtok(NULL, "#,"); // t points to the token "c"
14719 t = strtok(NULL, "?"); // t is a null pointer
14721 <a name="7.23.6" href="#7.23.6"><b> 7.23.6 Miscellaneous functions</b></a>
14722 <a name="7.23.6.1" href="#7.23.6.1"><b> 7.23.6.1 The memset function</b></a>
14724 1 #include <a href="#7.23"><string.h></a>
14725 void *memset(void *s, int c, size_t n);
14727 2 The memset function copies the value of c (converted to an unsigned char) into
14728 each of the first n characters of the object pointed to by s.
14730 3 The memset function returns the value of s.
14735 [<a name="#p367" href="p367">page 367</a>] (<a href="#Contents">Contents</a>)
14737 <a name="7.23.6.2" href="#7.23.6.2"><b> 7.23.6.2 The strerror function</b></a>
14739 1 #include <a href="#7.23"><string.h></a>
14740 char *strerror(int errnum);
14742 2 The strerror function maps the number in errnum to a message string. Typically,
14743 the values for errnum come from errno, but strerror shall map any value of type
14745 3 The strerror function is not required to avoid data races. The implementation shall
14746 behave as if no library function calls the strerror function.
14748 4 The strerror function returns a pointer to the string, the contents of which are locale-
14749 specific. The array pointed to shall not be modified by the program, but may be
14750 overwritten by a subsequent call to the strerror function.
14751 <a name="7.23.6.3" href="#7.23.6.3"><b> 7.23.6.3 The strlen function</b></a>
14753 1 #include <a href="#7.23"><string.h></a>
14754 size_t strlen(const char *s);
14756 2 The strlen function computes the length of the string pointed to by s.
14758 3 The strlen function returns the number of characters that precede the terminating null
14764 [<a name="#p368" href="p368">page 368</a>] (<a href="#Contents">Contents</a>)
14766 <a name="7.24" href="#7.24"><b> 7.24 Type-generic math <tgmath.h></b></a>
14767 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
14768 defines several type-generic macros.
14769 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
14770 double) suffix, several have one or more parameters whose corresponding real type is
14771 double. For each such function, except modf, there is a corresponding type-generic
14772 macro.300) The parameters whose corresponding real type is double in the function
14773 synopsis are generic parameters. Use of the macro invokes a function whose
14774 corresponding real type and type domain are determined by the arguments for the generic
14776 3 Use of the macro invokes a function whose generic parameters have the corresponding
14777 real type determined as follows:
14778 -- First, if any argument for generic parameters has type long double, the type
14779 determined is long double.
14780 -- Otherwise, if any argument for generic parameters has type double or is of integer
14781 type, the type determined is double.
14782 -- Otherwise, the type determined is float.
14783 4 For each unsuffixed function in <a href="#7.12"><math.h></a> for which there is a function in
14784 <a href="#7.3"><complex.h></a> with the same name except for a c prefix, the corresponding type-
14785 generic macro (for both functions) has the same name as the function in <a href="#7.12"><math.h></a>. The
14786 corresponding type-generic macro for fabs and cabs is fabs.
14791 300) Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to
14792 make available the corresponding ordinary function.
14793 301) If the type of the argument is not compatible with the type of the parameter for the selected function,
14794 the behavior is undefined.
14796 [<a name="#p369" href="p369">page 369</a>] (<a href="#Contents">Contents</a>)
14798 <a href="#7.12"><math.h></a> <a href="#7.3"><complex.h></a> type-generic
14799 function function macro
14817 If at least one argument for a generic parameter is complex, then use of the macro invokes
14818 a complex function; otherwise, use of the macro invokes a real function.
14819 5 For each unsuffixed function in <a href="#7.12"><math.h></a> without a c-prefixed counterpart in
14820 <a href="#7.3"><complex.h></a> (except modf), the corresponding type-generic macro has the same
14821 name as the function. These type-generic macros are:
14822 atan2 fma llround remainder
14823 cbrt fmax log10 remquo
14824 ceil fmin log1p rint
14825 copysign fmod log2 round
14826 erf frexp logb scalbn
14827 erfc hypot lrint scalbln
14828 exp2 ilogb lround tgamma
14829 expm1 ldexp nearbyint trunc
14830 fdim lgamma nextafter
14831 floor llrint nexttoward
14832 If all arguments for generic parameters are real, then use of the macro invokes a real
14833 function; otherwise, use of the macro results in undefined behavior.
14838 [<a name="#p370" href="p370">page 370</a>] (<a href="#Contents">Contents</a>)
14840 6 For each unsuffixed function in <a href="#7.3"><complex.h></a> that is not a c-prefixed counterpart to a
14841 function in <a href="#7.12"><math.h></a>, the corresponding type-generic macro has the same name as the
14842 function. These type-generic macros are:
14845 Use of the macro with any real or complex argument invokes a complex function.
14846 7 EXAMPLE With the declarations
14847 #include <a href="#7.24"><tgmath.h></a>
14854 long double complex ldc;
14855 functions invoked by use of type-generic macros are shown in the following table:
14857 exp(n) exp(n), the function
14859 sin(d) sin(d), the function
14863 pow(ldc, f) cpowl(ldc, f)
14864 remainder(n, n) remainder(n, n), the function
14865 nextafter(d, f) nextafter(d, f), the function
14866 nexttoward(f, ld) nexttowardf(f, ld)
14867 copysign(n, ld) copysignl(n, ld)
14868 ceil(fc) undefined behavior
14869 rint(dc) undefined behavior
14870 fmax(ldc, ld) undefined behavior
14871 carg(n) carg(n), the function
14873 creal(d) creal(d), the function
14874 cimag(ld) cimagl(ld)
14876 carg(dc) carg(dc), the function
14877 cproj(ldc) cprojl(ldc)
14882 [<a name="#p371" href="p371">page 371</a>] (<a href="#Contents">Contents</a>)
14884 <a name="7.25" href="#7.25"><b> 7.25 Threads <threads.h></b></a>
14885 <a name="7.25.1" href="#7.25.1"><b> 7.25.1 Introduction</b></a>
14886 1 The header <a href="#7.25"><threads.h></a> defines macros, and declares types, enumeration constants,
14887 and functions that support multiple threads of execution.
14888 2 Implementations that define the macro __STDC_NO_THREADS__ need not provide
14889 this header nor support any of its facilities.
14892 which expands to a value that can be used to initialize an object of type once_flag;
14894 TSS_DTOR_ITERATIONS
14895 which expands to an integer constant expression representing the maximum number of
14896 times that destructors will be called when a thread terminates.
14899 which is a complete object type that holds an identifier for a condition variable;
14901 which is a complete object type that holds an identifier for a thread;
14903 which is a complete object type that holds an identifier for a thread-specific storage
14906 which is a complete object type that holds an identifier for a mutex;
14908 which is the function pointer type void (*)(void*), used for a destructor for a
14909 thread-specific storage pointer;
14911 which is the function pointer type int (*)(void*) that is passed to thrd_create
14912 to create a new thread;
14914 which is a complete object type that holds a flag for use by call_once; and
14917 [<a name="#p372" href="p372">page 372</a>] (<a href="#Contents">Contents</a>)
14920 which is a structure type that holds a time specified in seconds and nanoseconds. The
14921 structure shall contain at least the following members, in any order.
14924 5 The enumeration constants are
14926 which is passed to mtx_init to create a mutex object that supports neither timeout nor
14929 which is passed to mtx_init to create a mutex object that supports recursive locking;
14931 which is passed to mtx_init to create a mutex object that supports timeout;
14933 which is passed to mtx_init to create a mutex object that supports test and return;
14935 which is returned by a timed wait function to indicate that the time specified in the call
14936 was reached without acquiring the requested resource;
14938 which is returned by a function to indicate that the requested operation succeeded;
14940 which is returned by a function to indicate that the requested operation failed because a
14941 resource requested by a test and return function is already in use;
14943 which is returned by a function to indicate that the requested operation failed; and
14945 which is returned by a function to indicate that the requested operation failed because it
14946 was unable to allocate memory.
14951 [<a name="#p373" href="p373">page 373</a>] (<a href="#Contents">Contents</a>)
14953 <a name="7.25.2" href="#7.25.2"><b> 7.25.2 Initialization functions</b></a>
14954 <a name="7.25.2.1" href="#7.25.2.1"><b> 7.25.2.1 The call_once function</b></a>
14956 1 #include <a href="#7.25"><threads.h></a>
14957 void call_once(once_flag *flag, void (*func)(void));
14959 2 The call_once function uses the once_flag pointed to by flag to ensure that
14960 func is called exactly once, the first time the call_once function is called with that
14961 value of flag. Completion of an effective call to the call_once function synchronizes
14962 with all subsequent calls to the call_once function with the same value of flag.
14964 3 The call_once function returns no value.
14965 <a name="7.25.3" href="#7.25.3"><b> 7.25.3 Condition variable functions</b></a>
14966 <a name="7.25.3.1" href="#7.25.3.1"><b> 7.25.3.1 The cnd_broadcast function</b></a>
14968 1 #include <a href="#7.25"><threads.h></a>
14969 int cnd_broadcast(cnd_t *cond);
14971 2 The cnd_broadcast function unblocks all of the threads that are blocked on the
14972 condition variable pointed to by cond at the time of the call. If no threads are blocked
14973 on the condition variable pointed to by cond at the time of the call, the function does
14976 3 The cnd_broadcast function returns thrd_success on success, or thrd_error
14977 if the request could not be honored.
14978 <a name="7.25.3.2" href="#7.25.3.2"><b> 7.25.3.2 The cnd_destroy function</b></a>
14980 1 #include <a href="#7.25"><threads.h></a>
14981 void cnd_destroy(cnd_t *cond);
14983 2 The cnd_destroy function releases all resources used by the condition variable
14984 pointed to by cond. The cnd_destroy function requires that no threads be blocked
14985 waiting for the condition variable pointed to by cond.
14987 [<a name="#p374" href="p374">page 374</a>] (<a href="#Contents">Contents</a>)
14990 3 The cnd_destroy function returns no value.
14991 <a name="7.25.3.3" href="#7.25.3.3"><b> 7.25.3.3 The cnd_init function</b></a>
14993 1 #include <a href="#7.25"><threads.h></a>
14994 int cnd_init(cnd_t *cond);
14996 2 The cnd_init function creates a condition variable. If it succeeds it sets the variable
14997 pointed to by cond to a value that uniquely identifies the newly created condition
14998 variable. A thread that calls cnd_wait on a newly created condition variable will
15001 3 The cnd_init function returns thrd_success on success, or thrd_nomem if no
15002 memory could be allocated for the newly created condition, or thrd_error if the
15003 request could not be honored.
15004 <a name="7.25.3.4" href="#7.25.3.4"><b> 7.25.3.4 The cnd_signal function</b></a>
15006 1 #include <a href="#7.25"><threads.h></a>
15007 int cnd_signal(cnd_t *cond);
15009 2 The cnd_signal function unblocks one of the threads that are blocked on the
15010 condition variable pointed to by cond at the time of the call. If no threads are blocked
15011 on the condition variable at the time of the call, the function does nothing and return
15014 3 The cnd_signal function returns thrd_success on success or thrd_error if
15015 the request could not be honored.
15016 <a name="7.25.3.5" href="#7.25.3.5"><b> 7.25.3.5 The cnd_timedwait function</b></a>
15018 1 #include <a href="#7.25"><threads.h></a>
15019 int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
15025 [<a name="#p375" href="p375">page 375</a>] (<a href="#Contents">Contents</a>)
15028 2 The cnd_timedwait function atomically unlocks the mutex pointed to by mtx and
15029 endeavors to block until the condition variable pointed to by cond is signaled by a call to
15030 cnd_signal or to cnd_broadcast, or until after the time specified by the xtime
15031 object pointed to by xt. When the calling thread becomes unblocked it locks the variable
15032 pointed to by mtx before it returns. The cnd_timedwait function requires that the
15033 mutex pointed to by mtx be locked by the calling thread.
15035 3 The cnd_timedwait function returns thrd_success upon success, or
15036 thrd_timeout if the time specified in the call was reached without acquiring the
15037 requested resource, or thrd_error if the request could not be honored.
15038 <a name="7.25.3.6" href="#7.25.3.6"><b> 7.25.3.6 The cnd_wait function</b></a>
15040 1 #include <a href="#7.25"><threads.h></a>
15041 int cnd_wait(cnd_t *cond, mtx_t *mtx);
15043 2 The cnd_wait function atomically unlocks the mutex pointed to by mtx and endeavors
15044 to block until the condition variable pointed to by cond is signaled by a call to
15045 cnd_signal or to cnd_broadcast. When the calling thread becomes unblocked it
15046 locks the mutex pointed to by mtx before it returns. If the mutex pointed to by mtx is
15047 not locked by the calling thread, the cnd_wait function will act as if the abort
15048 function is called.
15050 3 The cnd_wait function returns thrd_success on success or thrd_error if the
15051 request could not be honored.
15052 <a name="7.25.4" href="#7.25.4"><b> 7.25.4 Mutex functions</b></a>
15053 <a name="7.25.4.1" href="#7.25.4.1"><b> 7.25.4.1 The mtx_destroy function</b></a>
15055 1 #include <a href="#7.25"><threads.h></a>
15056 void mtx_destroy(mtx_t *mtx);
15058 2 The mtx_destroy function releases any resources used by the mutex pointed to by
15059 mtx. No threads can be blocked waiting for the mutex pointed to by mtx.
15063 [<a name="#p376" href="p376">page 376</a>] (<a href="#Contents">Contents</a>)
15066 3 The mtx_destroy function returns no value.
15067 <a name="7.25.4.2" href="#7.25.4.2"><b> 7.25.4.2 The mtx_init function</b></a>
15069 1 #include <a href="#7.25"><threads.h></a>
15070 int mtx_init(mtx_t *mtx, int type);
15072 2 The mtx_init function creates a mutex object with properties indicated by type,
15073 which must have one of the six values:
15074 mtx_plain for a simple non-recursive mutex,
15075 mtx_timed for a non-recursive mutex that supports timeout,
15076 mtx_try for a non-recursive mutex that supports test and return,
15077 mtx_plain | mtx_recursive for a simple recursive mutex,
15078 mtx_timed | mtx_recursive for a recursive mutex that supports timeout, or
15079 mtx_try | mtx_recursive for a recursive mutex that supports test and return.
15080 3 If the mtx_init function succeeds, it sets the mutex pointed to by mtx to a value that
15081 uniquely identifies the newly created mutex.
15083 4 The mtx_init function returns thrd_success on success, or thrd_error if the
15084 request could not be honored.
15085 <a name="7.25.4.3" href="#7.25.4.3"><b> 7.25.4.3 The mtx_lock function</b></a>
15087 1 #include <a href="#7.25"><threads.h></a>
15088 int mtx_lock(mtx_t *mtx);
15090 2 The mtx_lock function blocks until it locks the mutex pointed to by mtx. If the mutex
15091 is non-recursive, it shall not be locked by the calling thread. Prior calls to mtx_unlock
15092 on the same mutex shall synchronize with this operation.
15094 3 The mtx_lock function returns thrd_success on success, or thrd_busy if the
15095 resource requested is already in use, or thrd_error if the request could not be
15101 [<a name="#p377" href="p377">page 377</a>] (<a href="#Contents">Contents</a>)
15103 <a name="7.25.4.4" href="#7.25.4.4"><b> 7.25.4.4 The mtx_timedlock function</b></a>
15105 1 #include <a href="#7.25"><threads.h></a>
15106 int mtx_timedlock(mtx_t *mtx, const xtime *xt);
15108 2 The mtx_timedlock function endeavors to block until it locks the mutex pointed to by
15109 mtx or until the time specified by the xtime object xt has passed. The specified mutex
15110 shall support timeout. Prior calls to mtx_unlock on the same mutex shall synchronize
15111 with this operation. *
15113 3 The mtx_timedlock function returns thrd_success on success, or thrd_busy
15114 if the resource requested is already in use, or thrd_timeout if the time specified was
15115 reached without acquiring the requested resource, or thrd_error if the request could
15117 <a name="7.25.4.5" href="#7.25.4.5"><b> 7.25.4.5 The mtx_trylock function</b></a>
15119 1 #include <a href="#7.25"><threads.h></a>
15120 int mtx_trylock(mtx_t *mtx);
15122 2 The mtx_trylock function endeavors to lock the mutex pointed to by mtx. The
15123 specified mutex shall support either test and return or timeout. If the mutex is already
15124 locked, the function returns without blocking. Prior calls to mtx_unlock on the same
15125 mutex shall synchronize with this operation. *
15127 3 The mtx_trylock function returns thrd_success on success, or thrd_busy if
15128 the resource requested is already in use, or thrd_error if the request could not be
15130 <a name="7.25.4.6" href="#7.25.4.6"><b> 7.25.4.6 The mtx_unlock function</b></a>
15132 1 #include <a href="#7.25"><threads.h></a>
15133 int mtx_unlock(mtx_t *mtx);
15135 2 The mtx_unlock function unlocks the mutex pointed to by mtx. The mutex pointed to
15136 by mtx shall be locked by the calling thread.
15138 [<a name="#p378" href="p378">page 378</a>] (<a href="#Contents">Contents</a>)
15141 3 The mtx_unlock function returns thrd_success on success or thrd_error if
15142 the request could not be honored.
15143 <a name="7.25.5" href="#7.25.5"><b> 7.25.5 Thread functions</b></a>
15144 <a name="7.25.5.1" href="#7.25.5.1"><b> 7.25.5.1 The thrd_create function</b></a>
15146 1 #include <a href="#7.25"><threads.h></a>
15147 int thrd_create(thrd_t *thr, thrd_start_t func,
15150 2 The thrd_create function creates a new thread executing func(arg). If the
15151 thrd_create function succeeds, it sets the thread thr to a value that uniquely
15152 identifies the newly created thread.
15154 3 The thrd_create function returns thrd_success on success, or thrd_nomem if
15155 no memory could be allocated for the thread requested, or thrd_error if the request
15156 could not be honored.
15157 <a name="7.25.5.2" href="#7.25.5.2"><b> 7.25.5.2 The thrd_current function</b></a>
15159 1 #include <a href="#7.25"><threads.h></a>
15160 thrd_t thrd_current(void);
15162 2 The thrd_current function identifies the thread that called it.
15164 3 The thrd_current function returns a value that uniquely identifies the thread that
15166 <a name="7.25.5.3" href="#7.25.5.3"><b> 7.25.5.3 The thrd_detach function</b></a>
15168 1 #include <a href="#7.25"><threads.h></a>
15169 int thrd_detach(thrd_t thr);
15171 2 The thrd_detach function tells the operating system to dispose of any resources
15172 allocated to the thread identified by thr when that thread terminates. The value of the
15174 [<a name="#p379" href="p379">page 379</a>] (<a href="#Contents">Contents</a>)
15176 thread identified by thr value shall not have been set by a call to thrd_join or
15179 3 The thrd_detach function returns thrd_success on success or thrd_error if
15180 the request could not be honored.
15181 <a name="7.25.5.4" href="#7.25.5.4"><b> 7.25.5.4 The thrd_equal function</b></a>
15183 1 #include <a href="#7.25"><threads.h></a>
15184 int thrd_equal(thrd_t thr0, thrd_t thr1);
15186 2 The thrd_equal function will determine whether the thread identified by thr0 refers
15187 to the thread identified by thr1.
15189 3 The thrd_equal function returns zero if the thread thr0 and the thread thr1 refer to
15190 different threads. Otherwise the thrd_equal function returns a nonzero value.
15191 <a name="7.25.5.5" href="#7.25.5.5"><b> 7.25.5.5 The thrd_exit function</b></a>
15193 1 #include <a href="#7.25"><threads.h></a>
15194 void thrd_exit(int res);
15196 2 The thrd_exit function terminates execution of the calling thread and sets its result
15199 3 The thrd_exit function returns no value.
15200 <a name="7.25.5.6" href="#7.25.5.6"><b> 7.25.5.6 The thrd_join function</b></a>
15202 1 #include <a href="#7.25"><threads.h></a>
15203 int thrd_join(thrd_t thr, int *res);
15205 2 The thrd_join function blocks until the thread identified by thr has terminated. If
15206 the parameter res is not a null pointer, it stores the thread's result code in the integer
15207 pointed to by res. The value of the thread identified by thr shall not have been set by a
15208 call to thrd_join or thrd_detach.
15210 [<a name="#p380" href="p380">page 380</a>] (<a href="#Contents">Contents</a>)
15213 3 The thrd_join function returns thrd_success on success or thrd_error if the
15214 request could not be honored.
15215 <a name="7.25.5.7" href="#7.25.5.7"><b> 7.25.5.7 The thrd_sleep function</b></a>
15217 1 #include <a href="#7.25"><threads.h></a>
15218 void thrd_sleep(const xtime *xt);
15220 2 The thrd_sleep function suspends execution of the calling thread until after the time
15221 specified by the xtime object pointed to by xt.
15223 3 The thrd_sleep function returns no value.
15224 <a name="7.25.5.8" href="#7.25.5.8"><b> 7.25.5.8 The thrd_yield function</b></a>
15226 1 #include <a href="#7.25"><threads.h></a>
15227 void thrd_yield(void);
15229 2 The thrd_yield function endeavors to permit other threads to run, even if the current
15230 thread would ordinarily continue to run.
15232 3 The thrd_yield function returns no value.
15233 <a name="7.25.6" href="#7.25.6"><b> 7.25.6 Thread-specific storage functions</b></a>
15234 <a name="7.25.6.1" href="#7.25.6.1"><b> 7.25.6.1 The tss_create function</b></a>
15236 1 #include <a href="#7.25"><threads.h></a>
15237 int tss_create(tss_t *key, tss_dtor_t dtor);
15239 2 The tss_create function creates a thread-specific storage pointer with destructor
15240 dtor, which may be null.
15242 3 If the tss_create function is successful, it sets the thread-specific storage pointed to
15243 by key to a value that uniquely identifies the newly created pointer and returns
15244 thrd_success; otherwise, thrd_error is returned and the thread-specific storage
15245 [<a name="#p381" href="p381">page 381</a>] (<a href="#Contents">Contents</a>)
15247 pointed to by key is set to an undefined value.
15248 <a name="7.25.6.2" href="#7.25.6.2"><b> 7.25.6.2 The tss_delete function</b></a>
15250 1 #include <a href="#7.25"><threads.h></a>
15251 void tss_delete(tss_t key);
15253 2 The tss_delete function releases any resources used by the thread-specific storage
15256 3 The tss_delete function returns no value.
15257 <a name="7.25.6.3" href="#7.25.6.3"><b> 7.25.6.3 The tss_get function</b></a>
15259 1 #include <a href="#7.25"><threads.h></a>
15260 void *tss_get(tss_t key);
15262 2 The tss_get function returns the value for the current thread held in the thread-specific
15263 storage identified by key.
15265 3 The tss_get function returns the value for the current thread if successful, or zero if
15267 <a name="7.25.6.4" href="#7.25.6.4"><b> 7.25.6.4 The tss_set function</b></a>
15269 1 #include <a href="#7.25"><threads.h></a>
15270 int tss_set(tss_t key, void *val);
15272 2 The tss_set function sets the value for the current thread held in the thread-specific
15273 storage identified by key to val.
15275 3 The tss_set function returns thrd_success on success or thrd_error if the
15276 request could not be honored.
15281 [<a name="#p382" href="p382">page 382</a>] (<a href="#Contents">Contents</a>)
15283 <a name="7.25.7" href="#7.25.7"><b> 7.25.7 Time functions</b></a>
15284 <a name="7.25.7.1" href="#7.25.7.1"><b> 7.25.7.1 The xtime_get function</b></a>
15286 1 #include <a href="#7.25"><threads.h></a>
15287 int xtime_get(xtime *xt, int base);
15289 2 The xtime_get function sets the xtime object pointed to by xt to hold the current
15290 time based on the time base base.
15292 3 If the xtime_get function is successful it returns the nonzero value base, which must
15293 be TIME_UTC; otherwise, it returns zero.302)
15298 302) Although an xtime object describes times with nanosecond resolution, the actual resolution in an
15299 xtime object is system dependent.
15301 [<a name="#p383" href="p383">page 383</a>] (<a href="#Contents">Contents</a>)
15303 <a name="7.26" href="#7.26"><b> 7.26 Date and time <time.h></b></a>
15304 <a name="7.26.1" href="#7.26.1"><b> 7.26.1 Components of time</b></a>
15305 1 The header <a href="#7.26"><time.h></a> defines two macros, and declares several types and functions for
15306 manipulating time. Many functions deal with a calendar time that represents the current
15307 date (according to the Gregorian calendar) and time. Some functions deal with local
15308 time, which is the calendar time expressed for some specific time zone, and with Daylight
15309 Saving Time, which is a temporary change in the algorithm for determining local time.
15310 The local time zone and Daylight Saving Time are implementation-defined.
15311 2 The macros defined are NULL (described in <a href="#7.19">7.19</a>); and
15313 which expands to an expression with type clock_t (described below) that is the
15314 number per second of the value returned by the clock function.
15315 3 The types declared are size_t (described in <a href="#7.19">7.19</a>);
15319 which are arithmetic types capable of representing times; and
15321 which holds the components of a calendar time, called the broken-down time.
15322 4 The range and precision of times representable in clock_t and time_t are
15323 implementation-defined. The tm structure shall contain at least the following members,
15324 in any order. The semantics of the members and their normal ranges are expressed in the
15326 int tm_sec; // seconds after the minute -- [0, 60]
15327 int tm_min; // minutes after the hour -- [0, 59]
15328 int tm_hour; // hours since midnight -- [0, 23]
15329 int tm_mday; // day of the month -- [1, 31]
15330 int tm_mon; // months since January -- [0, 11]
15331 int tm_year; // years since 1900
15332 int tm_wday; // days since Sunday -- [0, 6]
15333 int tm_yday; // days since January 1 -- [0, 365]
15334 int tm_isdst; // Daylight Saving Time flag
15338 303) The range [0, 60] for tm_sec allows for a positive leap second.
15340 [<a name="#p384" href="p384">page 384</a>] (<a href="#Contents">Contents</a>)
15342 The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight
15343 Saving Time is not in effect, and negative if the information is not available.
15344 <a name="7.26.2" href="#7.26.2"><b> 7.26.2 Time manipulation functions</b></a>
15345 <a name="7.26.2.1" href="#7.26.2.1"><b> 7.26.2.1 The clock function</b></a>
15347 1 #include <a href="#7.26"><time.h></a>
15348 clock_t clock(void);
15350 2 The clock function determines the processor time used.
15352 3 The clock function returns the implementation's best approximation to the processor
15353 time used by the program since the beginning of an implementation-defined era related
15354 only to the program invocation. To determine the time in seconds, the value returned by
15355 the clock function should be divided by the value of the macro CLOCKS_PER_SEC. If
15356 the processor time used is not available or its value cannot be represented, the function
15357 returns the value (clock_t)(-1).304)
15358 <a name="7.26.2.2" href="#7.26.2.2"><b> 7.26.2.2 The difftime function</b></a>
15360 1 #include <a href="#7.26"><time.h></a>
15361 double difftime(time_t time1, time_t time0);
15363 2 The difftime function computes the difference between two calendar times: time1 -
15366 3 The difftime function returns the difference expressed in seconds as a double.
15371 304) In order to measure the time spent in a program, the clock function should be called at the start of
15372 the program and its return value subtracted from the value returned by subsequent calls.
15374 [<a name="#p385" href="p385">page 385</a>] (<a href="#Contents">Contents</a>)
15376 <a name="7.26.2.3" href="#7.26.2.3"><b> 7.26.2.3 The mktime function</b></a>
15378 1 #include <a href="#7.26"><time.h></a>
15379 time_t mktime(struct tm *timeptr);
15381 2 The mktime function converts the broken-down time, expressed as local time, in the
15382 structure pointed to by timeptr into a calendar time value with the same encoding as
15383 that of the values returned by the time function. The original values of the tm_wday
15384 and tm_yday components of the structure are ignored, and the original values of the
15385 other components are not restricted to the ranges indicated above.305) On successful
15386 completion, the values of the tm_wday and tm_yday components of the structure are
15387 set appropriately, and the other components are set to represent the specified calendar
15388 time, but with their values forced to the ranges indicated above; the final value of
15389 tm_mday is not set until tm_mon and tm_year are determined.
15391 3 The mktime function returns the specified calendar time encoded as a value of type
15392 time_t. If the calendar time cannot be represented, the function returns the value
15394 4 EXAMPLE What day of the week is July 4, 2001?
15395 #include <a href="#7.21"><stdio.h></a>
15396 #include <a href="#7.26"><time.h></a>
15397 static const char *const wday[] = {
15398 "Sunday", "Monday", "Tuesday", "Wednesday",
15399 "Thursday", "Friday", "Saturday", "-unknown-"
15401 struct tm time_str;
15407 305) Thus, a positive or zero value for tm_isdst causes the mktime function to presume initially that
15408 Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value
15409 causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time.
15411 [<a name="#p386" href="p386">page 386</a>] (<a href="#Contents">Contents</a>)
15413 time_str.tm_year = 2001 - 1900;
15414 time_str.tm_mon = 7 - 1;
15415 time_str.tm_mday = 4;
15416 time_str.tm_hour = 0;
15417 time_str.tm_min = 0;
15418 time_str.tm_sec = 1;
15419 time_str.tm_isdst = -1;
15420 if (mktime(&time_str) == (time_t)(-1))
15421 time_str.tm_wday = 7;
15422 printf("%s\n", wday[time_str.tm_wday]);
15424 <a name="7.26.2.4" href="#7.26.2.4"><b> 7.26.2.4 The time function</b></a>
15426 1 #include <a href="#7.26"><time.h></a>
15427 time_t time(time_t *timer);
15429 2 The time function determines the current calendar time. The encoding of the value is
15432 3 The time function returns the implementation's best approximation to the current
15433 calendar time. The value (time_t)(-1) is returned if the calendar time is not
15434 available. If timer is not a null pointer, the return value is also assigned to the object it
15436 <a name="7.26.3" href="#7.26.3"><b> 7.26.3 Time conversion functions</b></a>
15437 1 Except for the strftime function, these functions each return a pointer to one of two
15438 types of static objects: a broken-down time structure or an array of char. Execution of
15439 any of the functions that return a pointer to one of these object types may overwrite the
15440 information in any object of the same type pointed to by the value returned from any
15441 previous call to any of them and the functions are not required to avoid data races. The
15442 implementation shall behave as if no other library functions call these functions.
15443 <a name="7.26.3.1" href="#7.26.3.1"><b> 7.26.3.1 The asctime function</b></a>
15445 1 #include <a href="#7.26"><time.h></a>
15446 char *asctime(const struct tm *timeptr);
15448 2 The asctime function converts the broken-down time in the structure pointed to by
15449 timeptr into a string in the form
15450 Sun Sep 16 01:03:52 1973\n\0
15452 [<a name="#p387" href="p387">page 387</a>] (<a href="#Contents">Contents</a>)
15454 using the equivalent of the following algorithm.
15455 char *asctime(const struct tm *timeptr)
15457 static const char wday_name[7][3] = {
15458 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
15460 static const char mon_name[12][3] = {
15461 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
15462 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
15464 static char result[26];
15465 sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
15466 wday_name[timeptr->tm_wday],
15467 mon_name[timeptr->tm_mon],
15468 timeptr->tm_mday, timeptr->tm_hour,
15469 timeptr->tm_min, timeptr->tm_sec,
15470 1900 + timeptr->tm_year);
15473 3 If any of the fields of the broken-down time contain values that are outside their normal
15474 ranges,306) the behavior of the asctime function is undefined. Likewise, if the
15475 calculated year exceeds four digits or is less than the year 1000, the behavior is
15478 4 The asctime function returns a pointer to the string.
15479 <a name="7.26.3.2" href="#7.26.3.2"><b> 7.26.3.2 The ctime function</b></a>
15481 1 #include <a href="#7.26"><time.h></a>
15482 char *ctime(const time_t *timer);
15484 2 The ctime function converts the calendar time pointed to by timer to local time in the
15485 form of a string. It is equivalent to
15486 asctime(localtime(timer))
15490 306) See <a href="#7.26.1">7.26.1</a>.
15492 [<a name="#p388" href="p388">page 388</a>] (<a href="#Contents">Contents</a>)
15495 3 The ctime function returns the pointer returned by the asctime function with that
15496 broken-down time as argument.
15497 Forward references: the localtime function (<a href="#7.26.3.4">7.26.3.4</a>).
15498 <a name="7.26.3.3" href="#7.26.3.3"><b> 7.26.3.3 The gmtime function</b></a>
15500 1 #include <a href="#7.26"><time.h></a>
15501 struct tm *gmtime(const time_t *timer);
15503 2 The gmtime function converts the calendar time pointed to by timer into a broken-
15504 down time, expressed as UTC.
15506 3 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
15507 specified time cannot be converted to UTC.
15508 <a name="7.26.3.4" href="#7.26.3.4"><b> 7.26.3.4 The localtime function</b></a>
15510 1 #include <a href="#7.26"><time.h></a>
15511 struct tm *localtime(const time_t *timer);
15513 2 The localtime function converts the calendar time pointed to by timer into a
15514 broken-down time, expressed as local time.
15516 3 The localtime function returns a pointer to the broken-down time, or a null pointer if
15517 the specified time cannot be converted to local time.
15518 <a name="7.26.3.5" href="#7.26.3.5"><b> 7.26.3.5 The strftime function</b></a>
15520 1 #include <a href="#7.26"><time.h></a>
15521 size_t strftime(char * restrict s,
15523 const char * restrict format,
15524 const struct tm * restrict timeptr);
15529 [<a name="#p389" href="p389">page 389</a>] (<a href="#Contents">Contents</a>)
15532 2 The strftime function places characters into the array pointed to by s as controlled by
15533 the string pointed to by format. The format shall be a multibyte character sequence,
15534 beginning and ending in its initial shift state. The format string consists of zero or
15535 more conversion specifiers and ordinary multibyte characters. A conversion specifier
15536 consists of a % character, possibly followed by an E or O modifier character (described
15537 below), followed by a character that determines the behavior of the conversion specifier.
15538 All ordinary multibyte characters (including the terminating null character) are copied
15539 unchanged into the array. If copying takes place between objects that overlap, the
15540 behavior is undefined. No more than maxsize characters are placed into the array.
15541 3 Each conversion specifier is replaced by appropriate characters as described in the
15542 following list. The appropriate characters are determined using the LC_TIME category
15543 of the current locale and by the values of zero or more members of the broken-down time
15544 structure pointed to by timeptr, as specified in brackets in the description. If any of
15545 the specified values is outside the normal range, the characters stored are unspecified.
15546 %a is replaced by the locale's abbreviated weekday name. [tm_wday]
15547 %A is replaced by the locale's full weekday name. [tm_wday]
15548 %b is replaced by the locale's abbreviated month name. [tm_mon]
15549 %B is replaced by the locale's full month name. [tm_mon]
15550 %c is replaced by the locale's appropriate date and time representation. [all specified
15551 in <a href="#7.26.1">7.26.1</a>]
15552 %C is replaced by the year divided by 100 and truncated to an integer, as a decimal
15553 number (00-99). [tm_year]
15554 %d is replaced by the day of the month as a decimal number (01-31). [tm_mday]
15555 %D is equivalent to ''%m/%d/%y''. [tm_mon, tm_mday, tm_year]
15556 %e is replaced by the day of the month as a decimal number (1-31); a single digit is
15557 preceded by a space. [tm_mday]
15558 %F is equivalent to ''%Y-%m-%d'' (the ISO 8601 date format). [tm_year, tm_mon,
15560 %g is replaced by the last 2 digits of the week-based year (see below) as a decimal
15561 number (00-99). [tm_year, tm_wday, tm_yday]
15562 %G is replaced by the week-based year (see below) as a decimal number (e.g., 1997).
15563 [tm_year, tm_wday, tm_yday]
15564 %h is equivalent to ''%b''. [tm_mon]
15565 %H is replaced by the hour (24-hour clock) as a decimal number (00-23). [tm_hour]
15566 %I is replaced by the hour (12-hour clock) as a decimal number (01-12). [tm_hour]
15567 %j is replaced by the day of the year as a decimal number (001-366). [tm_yday]
15568 %m is replaced by the month as a decimal number (01-12). [tm_mon]
15569 %M is replaced by the minute as a decimal number (00-59). [tm_min]
15570 %n is replaced by a new-line character.
15572 [<a name="#p390" href="p390">page 390</a>] (<a href="#Contents">Contents</a>)
15574 %p is replaced by the locale's equivalent of the AM/PM designations associated with a
15575 12-hour clock. [tm_hour]
15576 %r is replaced by the locale's 12-hour clock time. [tm_hour, tm_min, tm_sec]
15577 %R is equivalent to ''%H:%M''. [tm_hour, tm_min]
15578 %S is replaced by the second as a decimal number (00-60). [tm_sec]
15579 %t is replaced by a horizontal-tab character.
15580 %T is equivalent to ''%H:%M:%S'' (the ISO 8601 time format). [tm_hour, tm_min,
15582 %u is replaced by the ISO 8601 weekday as a decimal number (1-7), where Monday
15584 %U is replaced by the week number of the year (the first Sunday as the first day of week
15585 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
15586 %V is replaced by the ISO 8601 week number (see below) as a decimal number
15587 (01-53). [tm_year, tm_wday, tm_yday]
15588 %w is replaced by the weekday as a decimal number (0-6), where Sunday is 0.
15590 %W is replaced by the week number of the year (the first Monday as the first day of
15591 week 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
15592 %x is replaced by the locale's appropriate date representation. [all specified in <a href="#7.26.1">7.26.1</a>]
15593 %X is replaced by the locale's appropriate time representation. [all specified in <a href="#7.26.1">7.26.1</a>]
15594 %y is replaced by the last 2 digits of the year as a decimal number (00-99).
15596 %Y is replaced by the year as a decimal number (e.g., 1997). [tm_year]
15597 %z is replaced by the offset from UTC in the ISO 8601 format ''-0430'' (meaning 4
15598 hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
15599 zone is determinable. [tm_isdst]
15600 %Z is replaced by the locale's time zone name or abbreviation, or by no characters if no
15601 time zone is determinable. [tm_isdst]
15602 %% is replaced by %.
15603 4 Some conversion specifiers can be modified by the inclusion of an E or O modifier
15604 character to indicate an alternative format or specification. If the alternative format or
15605 specification does not exist for the current locale, the modifier is ignored.
15606 %Ec is replaced by the locale's alternative date and time representation.
15607 %EC is replaced by the name of the base year (period) in the locale's alternative
15609 %Ex is replaced by the locale's alternative date representation.
15610 %EX is replaced by the locale's alternative time representation.
15611 %Ey is replaced by the offset from %EC (year only) in the locale's alternative
15613 %EY is replaced by the locale's full alternative year representation.
15615 [<a name="#p391" href="p391">page 391</a>] (<a href="#Contents">Contents</a>)
15617 %Od is replaced by the day of the month, using the locale's alternative numeric symbols
15618 (filled as needed with leading zeros, or with leading spaces if there is no alternative
15620 %Oe is replaced by the day of the month, using the locale's alternative numeric symbols
15621 (filled as needed with leading spaces).
15622 %OH is replaced by the hour (24-hour clock), using the locale's alternative numeric
15624 %OI is replaced by the hour (12-hour clock), using the locale's alternative numeric
15626 %Om is replaced by the month, using the locale's alternative numeric symbols.
15627 %OM is replaced by the minutes, using the locale's alternative numeric symbols.
15628 %OS is replaced by the seconds, using the locale's alternative numeric symbols.
15629 %Ou is replaced by the ISO 8601 weekday as a number in the locale's alternative
15630 representation, where Monday is 1.
15631 %OU is replaced by the week number, using the locale's alternative numeric symbols.
15632 %OV is replaced by the ISO 8601 week number, using the locale's alternative numeric
15634 %Ow is replaced by the weekday as a number, using the locale's alternative numeric
15636 %OW is replaced by the week number of the year, using the locale's alternative numeric
15638 %Oy is replaced by the last 2 digits of the year, using the locale's alternative numeric
15640 5 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system,
15641 weeks begin on a Monday and week 1 of the year is the week that includes January 4th,
15642 which is also the week that includes the first Thursday of the year, and is also the first
15643 week that contains at least four days in the year. If the first Monday of January is the
15644 2nd, 3rd, or 4th, the preceding days are part of the last week of the preceding year; thus,
15645 for Saturday 2nd January 1999, %G is replaced by 1998 and %V is replaced by 53. If
15646 December 29th, 30th, or 31st is a Monday, it and any following days are part of week 1 of
15647 the following year. Thus, for Tuesday 30th December 1997, %G is replaced by 1998 and
15648 %V is replaced by 01.
15649 6 If a conversion specifier is not one of the above, the behavior is undefined.
15650 7 In the "C" locale, the E and O modifiers are ignored and the replacement strings for the
15651 following specifiers are:
15652 %a the first three characters of %A.
15653 %A one of ''Sunday'', ''Monday'', ... , ''Saturday''.
15654 %b the first three characters of %B.
15655 %B one of ''January'', ''February'', ... , ''December''.
15656 %c equivalent to ''%a %b %e %T %Y''.
15657 [<a name="#p392" href="p392">page 392</a>] (<a href="#Contents">Contents</a>)
15659 %p one of ''AM'' or ''PM''.
15660 %r equivalent to ''%I:%M:%S %p''.
15661 %x equivalent to ''%m/%d/%y''.
15662 %X equivalent to %T.
15663 %Z implementation-defined.
15665 8 If the total number of resulting characters including the terminating null character is not
15666 more than maxsize, the strftime function returns the number of characters placed
15667 into the array pointed to by s not including the terminating null character. Otherwise,
15668 zero is returned and the contents of the array are indeterminate.
15673 [<a name="#p393" href="p393">page 393</a>] (<a href="#Contents">Contents</a>)
15675 <a name="7.27" href="#7.27"><b> 7.27 Unicode utilities <uchar.h></b></a>
15676 1 The header <a href="#7.27"><uchar.h></a> declares types and functions for manipulating Unicode
15678 2 The types declared are mbstate_t (described in <a href="#7.29.1">7.29.1</a>) and size_t (described in
15679 <a name="7.19);" href="#7.19);"><b> 7.19);</b></a>
15681 which is an unsigned integer type used for 16-bit characters and is the same type as
15682 uint_least16_t (described in <a href="#7.20.1.2">7.20.1.2</a>); and
15684 which is an unsigned integer type used for 32-bit characters and is the same type as
15685 uint_least32_t (also described in <a href="#7.20.1.2">7.20.1.2</a>).
15686 <a name="7.27.1" href="#7.27.1"><b> 7.27.1 Restartable multibyte/wide character conversion functions</b></a>
15687 1 These functions have a parameter, ps, of type pointer to mbstate_t that points to an
15688 object that can completely describe the current conversion state of the associated
15689 multibyte character sequence, which the functions alter as necessary. If ps is a null
15690 pointer, each function uses its own internal mbstate_t object instead, which is
15691 initialized at program startup to the initial conversion state; the functions are not required
15692 to avoid data races in this case. The implementation behaves as if no library function
15693 calls these functions with a null pointer for ps.
15694 <a name="7.27.1.1" href="#7.27.1.1"><b> 7.27.1.1 The mbrtoc16 function</b></a>
15696 1 #include <a href="#7.27"><uchar.h></a>
15697 size_t mbrtoc16(char16_t * restrict pc16,
15698 const char * restrict s, size_t n,
15699 mbstate_t * restrict ps);
15701 2 If s is a null pointer, the mbrtoc16 function is equivalent to the call:
15702 mbrtoc16(NULL, "", 1, ps)
15703 In this case, the values of the parameters pc16 and n are ignored.
15704 3 If s is not a null pointer, the mbrtoc16 function inspects at most n bytes beginning with
15705 the byte pointed to by s to determine the number of bytes needed to complete the next
15706 multibyte character (including any shift sequences). If the function determines that the
15707 next multibyte character is complete and valid, it determines the values of the
15708 corresponding wide characters and then, if pc16 is not a null pointer, stores the value of
15709 the first (or only) such character in the object pointed to by pc16. Subsequent calls will
15710 [<a name="#p394" href="p394">page 394</a>] (<a href="#Contents">Contents</a>)
15712 store successive wide characters without consuming any additional input until all the
15713 characters have been stored. If the corresponding wide character is the null wide
15714 character, the resulting state described is the initial conversion state.
15716 4 The mbrtoc16 function returns the first of the following that applies (given the current
15718 0 if the next n or fewer bytes complete the multibyte character that
15719 corresponds to the null wide character (which is the value stored).
15720 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
15721 character (which is the value stored); the value returned is the number
15722 of bytes that complete the multibyte character.
15723 (size_t)(-3) if the next character resulting from a previous call has been stored (no
15724 bytes from the input have been consumed by this call).
15725 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
15726 multibyte character, and all n bytes have been processed (no value is
15728 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
15729 do not contribute to a complete and valid multibyte character (no
15730 value is stored); the value of the macro EILSEQ is stored in errno,
15731 and the conversion state is unspecified.
15732 <a name="7.27.1.2" href="#7.27.1.2"><b> 7.27.1.2 The c16rtomb function</b></a>
15734 1 #include <a href="#7.27"><uchar.h></a>
15735 size_t c16rtomb(char * restrict s, char16_t c16,
15736 mbstate_t * restrict ps);
15738 2 If s is a null pointer, the c16rtomb function is equivalent to the call
15739 c16rtomb(buf, L'\0', ps)
15740 where buf is an internal buffer.
15741 3 If s is not a null pointer, the c16rtomb function determines the number of bytes needed
15742 to represent the multibyte character that corresponds to the wide character given by c16
15743 (including any shift sequences), and stores the multibyte character representation in the
15745 307) When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
15746 sequence of redundant shift sequences (for implementations with state-dependent encodings).
15748 [<a name="#p395" href="p395">page 395</a>] (<a href="#Contents">Contents</a>)
15750 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
15751 c16 is a null wide character, a null byte is stored, preceded by any shift sequence needed
15752 to restore the initial shift state; the resulting state described is the initial conversion state.
15754 4 The c16rtomb function returns the number of bytes stored in the array object (including
15755 any shift sequences). When c16 is not a valid wide character, an encoding error occurs:
15756 the function stores the value of the macro EILSEQ in errno and returns
15757 (size_t)(-1); the conversion state is unspecified.
15758 <a name="7.27.1.3" href="#7.27.1.3"><b> 7.27.1.3 The mbrtoc32 function</b></a>
15760 1 #include <a href="#7.27"><uchar.h></a>
15761 size_t mbrtoc32(char32_t * restrict pc32,
15762 const char * restrict s, size_t n,
15763 mbstate_t * restrict ps);
15765 2 If s is a null pointer, the mbrtoc32 function is equivalent to the call:
15766 mbrtoc32(NULL, "", 1, ps)
15767 In this case, the values of the parameters pc32 and n are ignored.
15768 3 If s is not a null pointer, the mbrtoc32 function inspects at most n bytes beginning with
15769 the byte pointed to by s to determine the number of bytes needed to complete the next
15770 multibyte character (including any shift sequences). If the function determines that the
15771 next multibyte character is complete and valid, it determines the values of the
15772 corresponding wide characters and then, if pc32 is not a null pointer, stores the value of
15773 the first (or only) such character in the object pointed to by pc32. Subsequent calls will
15774 store successive wide characters without consuming any additional input until all the
15775 characters have been stored. If the corresponding wide character is the null wide
15776 character, the resulting state described is the initial conversion state.
15778 4 The mbrtoc32 function returns the first of the following that applies (given the current
15780 0 if the next n or fewer bytes complete the multibyte character that
15781 corresponds to the null wide character (which is the value stored).
15782 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
15783 character (which is the value stored); the value returned is the number
15784 of bytes that complete the multibyte character.
15787 [<a name="#p396" href="p396">page 396</a>] (<a href="#Contents">Contents</a>)
15789 (size_t)(-3) if the next character resulting from a previous call has been stored (no
15790 bytes from the input have been consumed by this call).
15791 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
15792 multibyte character, and all n bytes have been processed (no value is
15794 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
15795 do not contribute to a complete and valid multibyte character (no
15796 value is stored); the value of the macro EILSEQ is stored in errno,
15797 and the conversion state is unspecified.
15798 <a name="7.27.1.4" href="#7.27.1.4"><b> 7.27.1.4 The c32rtomb function</b></a>
15800 1 #include <a href="#7.27"><uchar.h></a>
15801 size_t c32rtomb(char * restrict s, char32_t c32,
15802 mbstate_t * restrict ps);
15804 2 If s is a null pointer, the c32rtomb function is equivalent to the call
15805 c32rtomb(buf, L'\0', ps)
15806 where buf is an internal buffer.
15807 3 If s is not a null pointer, the c32rtomb function determines the number of bytes needed
15808 to represent the multibyte character that corresponds to the wide character given by c32
15809 (including any shift sequences), and stores the multibyte character representation in the
15810 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
15811 c32 is a null wide character, a null byte is stored, preceded by any shift sequence needed
15812 to restore the initial shift state; the resulting state described is the initial conversion state.
15814 4 The c32rtomb function returns the number of bytes stored in the array object (including
15815 any shift sequences). When c32 is not a valid wide character, an encoding error occurs:
15816 the function stores the value of the macro EILSEQ in errno and returns
15817 (size_t)(-1); the conversion state is unspecified.
15822 308) When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
15823 sequence of redundant shift sequences (for implementations with state-dependent encodings).
15825 [<a name="#p397" href="p397">page 397</a>] (<a href="#Contents">Contents</a>)
15827 <a name="7.28" href="#7.28"><b> 7.28 Extended multibyte and wide character utilities <wchar.h></b></a>
15828 <a name="7.28.1" href="#7.28.1"><b> 7.28.1 Introduction</b></a>
15829 1 The header <a href="#7.28"><wchar.h></a> defines four macros, and declares four data types, one tag, and
15830 many functions.309)
15831 2 The types declared are wchar_t and size_t (both described in <a href="#7.19">7.19</a>);
15833 which is a complete object type other than an array type that can hold the conversion state
15834 information necessary to convert between sequences of multibyte characters and wide
15837 which is an integer type unchanged by default argument promotions that can hold any
15838 value corresponding to members of the extended character set, as well as at least one
15839 value that does not correspond to any member of the extended character set (see WEOF
15842 which is declared as an incomplete structure type (the contents are described in <a href="#7.26.1">7.26.1</a>).
15843 3 The macros defined are NULL (described in <a href="#7.19">7.19</a>); WCHAR_MIN and WCHAR_MAX
15844 (described in <a href="#7.20.3">7.20.3</a>); and
15846 which expands to a constant expression of type wint_t whose value does not
15847 correspond to any member of the extended character set.311) It is accepted (and returned)
15848 by several functions in this subclause to indicate end-of-file, that is, no more input from a
15849 stream. It is also used as a wide character value that does not correspond to any member
15850 of the extended character set.
15851 4 The functions declared are grouped as follows:
15852 -- Functions that perform input and output of wide characters, or multibyte characters,
15854 -- Functions that provide wide string numeric conversion;
15855 -- Functions that perform general wide string manipulation;
15858 309) See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
15859 310) wchar_t and wint_t can be the same integer type.
15860 311) The value of the macro WEOF may differ from that of EOF and need not be negative.
15862 [<a name="#p398" href="p398">page 398</a>] (<a href="#Contents">Contents</a>)
15864 -- Functions for wide string date and time conversion; and
15865 -- Functions that provide extended capabilities for conversion between multibyte and
15866 wide character sequences.
15867 5 Unless explicitly stated otherwise, if the execution of a function described in this
15868 subclause causes copying to take place between objects that overlap, the behavior is
15870 <a name="7.28.2" href="#7.28.2"><b> 7.28.2 Formatted wide character input/output functions</b></a>
15871 1 The formatted wide character input/output functions shall behave as if there is a sequence
15872 point after the actions associated with each specifier.312)
15873 <a name="7.28.2.1" href="#7.28.2.1"><b> 7.28.2.1 The fwprintf function</b></a>
15875 1 #include <a href="#7.21"><stdio.h></a>
15876 #include <a href="#7.28"><wchar.h></a>
15877 int fwprintf(FILE * restrict stream,
15878 const wchar_t * restrict format, ...);
15880 2 The fwprintf function writes output to the stream pointed to by stream, under
15881 control of the wide string pointed to by format that specifies how subsequent arguments
15882 are converted for output. If there are insufficient arguments for the format, the behavior
15883 is undefined. If the format is exhausted while arguments remain, the excess arguments
15884 are evaluated (as always) but are otherwise ignored. The fwprintf function returns
15885 when the end of the format string is encountered.
15886 3 The format is composed of zero or more directives: ordinary wide characters (not %),
15887 which are copied unchanged to the output stream; and conversion specifications, each of
15888 which results in fetching zero or more subsequent arguments, converting them, if
15889 applicable, according to the corresponding conversion specifier, and then writing the
15890 result to the output stream.
15891 4 Each conversion specification is introduced by the wide character %. After the %, the
15892 following appear in sequence:
15893 -- Zero or more flags (in any order) that modify the meaning of the conversion
15895 -- An optional minimum field width. If the converted value has fewer wide characters
15896 than the field width, it is padded with spaces (by default) on the left (or right, if the
15899 312) The fwprintf functions perform writes to memory for the %n specifier.
15901 [<a name="#p399" href="p399">page 399</a>] (<a href="#Contents">Contents</a>)
15903 left adjustment flag, described later, has been given) to the field width. The field
15904 width takes the form of an asterisk * (described later) or a nonnegative decimal
15906 -- An optional precision that gives the minimum number of digits to appear for the d, i,
15907 o, u, x, and X conversions, the number of digits to appear after the decimal-point
15908 wide character for a, A, e, E, f, and F conversions, the maximum number of
15909 significant digits for the g and G conversions, or the maximum number of wide
15910 characters to be written for s conversions. The precision takes the form of a period
15911 (.) followed either by an asterisk * (described later) or by an optional decimal
15912 integer; if only the period is specified, the precision is taken as zero. If a precision
15913 appears with any other conversion specifier, the behavior is undefined.
15914 -- An optional length modifier that specifies the size of the argument.
15915 -- A conversion specifier wide character that specifies the type of conversion to be
15917 5 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
15918 this case, an int argument supplies the field width or precision. The arguments
15919 specifying field width, or precision, or both, shall appear (in that order) before the
15920 argument (if any) to be converted. A negative field width argument is taken as a - flag
15921 followed by a positive field width. A negative precision argument is taken as if the
15922 precision were omitted.
15923 6 The flag wide characters and their meanings are:
15924 - The result of the conversion is left-justified within the field. (It is right-justified if
15925 this flag is not specified.)
15926 + The result of a signed conversion always begins with a plus or minus sign. (It
15927 begins with a sign only when a negative value is converted if this flag is not
15929 space If the first wide character of a signed conversion is not a sign, or if a signed
15930 conversion results in no wide characters, a space is prefixed to the result. If the
15931 space and + flags both appear, the space flag is ignored.
15932 # The result is converted to an ''alternative form''. For o conversion, it increases
15933 the precision, if and only if necessary, to force the first digit of the result to be a
15934 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
15935 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
15938 313) Note that 0 is taken as a flag, not as the beginning of a field width.
15939 314) The results of all floating conversions of a negative zero, and of negative values that round to zero,
15940 include a minus sign.
15942 [<a name="#p400" href="p400">page 400</a>] (<a href="#Contents">Contents</a>)
15944 and G conversions, the result of converting a floating-point number always
15945 contains a decimal-point wide character, even if no digits follow it. (Normally, a
15946 decimal-point wide character appears in the result of these conversions only if a
15947 digit follows it.) For g and G conversions, trailing zeros are not removed from the
15948 result. For other conversions, the behavior is undefined.
15949 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
15950 (following any indication of sign or base) are used to pad to the field width rather
15951 than performing space padding, except when converting an infinity or NaN. If the
15952 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
15953 conversions, if a precision is specified, the 0 flag is ignored. For other
15954 conversions, the behavior is undefined.
15955 7 The length modifiers and their meanings are:
15956 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15957 signed char or unsigned char argument (the argument will have
15958 been promoted according to the integer promotions, but its value shall be
15959 converted to signed char or unsigned char before printing); or that
15960 a following n conversion specifier applies to a pointer to a signed char
15962 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15963 short int or unsigned short int argument (the argument will
15964 have been promoted according to the integer promotions, but its value shall
15965 be converted to short int or unsigned short int before printing);
15966 or that a following n conversion specifier applies to a pointer to a short
15968 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15969 long int or unsigned long int argument; that a following n
15970 conversion specifier applies to a pointer to a long int argument; that a
15971 following c conversion specifier applies to a wint_t argument; that a
15972 following s conversion specifier applies to a pointer to a wchar_t
15973 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
15975 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15976 long long int or unsigned long long int argument; or that a
15977 following n conversion specifier applies to a pointer to a long long int
15979 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
15980 an intmax_t or uintmax_t argument; or that a following n conversion
15981 specifier applies to a pointer to an intmax_t argument.
15983 [<a name="#p401" href="p401">page 401</a>] (<a href="#Contents">Contents</a>)
15985 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15986 size_t or the corresponding signed integer type argument; or that a
15987 following n conversion specifier applies to a pointer to a signed integer type
15988 corresponding to size_t argument.
15989 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15990 ptrdiff_t or the corresponding unsigned integer type argument; or that a
15991 following n conversion specifier applies to a pointer to a ptrdiff_t
15993 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
15994 applies to a long double argument.
15995 If a length modifier appears with any conversion specifier other than as specified above,
15996 the behavior is undefined.
15997 8 The conversion specifiers and their meanings are:
15998 d,i The int argument is converted to signed decimal in the style [-]dddd. The
15999 precision specifies the minimum number of digits to appear; if the value
16000 being converted can be represented in fewer digits, it is expanded with
16001 leading zeros. The default precision is 1. The result of converting a zero
16002 value with a precision of zero is no wide characters.
16003 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
16004 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
16005 letters abcdef are used for x conversion and the letters ABCDEF for X
16006 conversion. The precision specifies the minimum number of digits to appear;
16007 if the value being converted can be represented in fewer digits, it is expanded
16008 with leading zeros. The default precision is 1. The result of converting a
16009 zero value with a precision of zero is no wide characters.
16010 f,F A double argument representing a floating-point number is converted to
16011 decimal notation in the style [-]ddd.ddd, where the number of digits after
16012 the decimal-point wide character is equal to the precision specification. If the
16013 precision is missing, it is taken as 6; if the precision is zero and the # flag is
16014 not specified, no decimal-point wide character appears. If a decimal-point
16015 wide character appears, at least one digit appears before it. The value is
16016 rounded to the appropriate number of digits.
16017 A double argument representing an infinity is converted in one of the styles
16018 [-]inf or [-]infinity -- which style is implementation-defined. A
16019 double argument representing a NaN is converted in one of the styles
16020 [-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
16021 any n-wchar-sequence, is implementation-defined. The F conversion
16022 specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
16024 [<a name="#p402" href="p402">page 402</a>] (<a href="#Contents">Contents</a>)
16026 nan, respectively.315)
16027 e,E A double argument representing a floating-point number is converted in the
16028 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
16029 argument is nonzero) before the decimal-point wide character and the number
16030 of digits after it is equal to the precision; if the precision is missing, it is taken
16031 as 6; if the precision is zero and the # flag is not specified, no decimal-point
16032 wide character appears. The value is rounded to the appropriate number of
16033 digits. The E conversion specifier produces a number with E instead of e
16034 introducing the exponent. The exponent always contains at least two digits,
16035 and only as many more digits as necessary to represent the exponent. If the
16036 value is zero, the exponent is zero.
16037 A double argument representing an infinity or NaN is converted in the style
16038 of an f or F conversion specifier.
16039 g,G A double argument representing a floating-point number is converted in
16040 style f or e (or in style F or E in the case of a G conversion specifier),
16041 depending on the value converted and the precision. Let P equal the
16042 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
16043 Then, if a conversion with style E would have an exponent of X:
16044 -- if P > X >= -4, the conversion is with style f (or F) and precision
16046 -- otherwise, the conversion is with style e (or E) and precision P - 1.
16047 Finally, unless the # flag is used, any trailing zeros are removed from the
16048 fractional portion of the result and the decimal-point wide character is
16049 removed if there is no fractional portion remaining.
16050 A double argument representing an infinity or NaN is converted in the style
16051 of an f or F conversion specifier.
16052 a,A A double argument representing a floating-point number is converted in the
16053 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
16054 nonzero if the argument is a normalized floating-point number and is
16055 otherwise unspecified) before the decimal-point wide character316) and the
16056 number of hexadecimal digits after it is equal to the precision; if the precision
16057 is missing and FLT_RADIX is a power of 2, then the precision is sufficient
16060 315) When applied to infinite and NaN values, the -, +, and space flag wide characters have their usual
16061 meaning; the # and 0 flag wide characters have no effect.
16062 316) Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide
16063 character so that subsequent digits align to nibble (4-bit) boundaries.
16065 [<a name="#p403" href="p403">page 403</a>] (<a href="#Contents">Contents</a>)
16067 for an exact representation of the value; if the precision is missing and
16068 FLT_RADIX is not a power of 2, then the precision is sufficient to
16069 distinguish317) values of type double, except that trailing zeros may be
16070 omitted; if the precision is zero and the # flag is not specified, no decimal-
16071 point wide character appears. The letters abcdef are used for a conversion
16072 and the letters ABCDEF for A conversion. The A conversion specifier
16073 produces a number with X and P instead of x and p. The exponent always
16074 contains at least one digit, and only as many more digits as necessary to
16075 represent the decimal exponent of 2. If the value is zero, the exponent is
16077 A double argument representing an infinity or NaN is converted in the style
16078 of an f or F conversion specifier.
16079 c If no l length modifier is present, the int argument is converted to a wide
16080 character as if by calling btowc and the resulting wide character is written.
16081 If an l length modifier is present, the wint_t argument is converted to
16082 wchar_t and written.
16083 s If no l length modifier is present, the argument shall be a pointer to the initial
16084 element of a character array containing a multibyte character sequence
16085 beginning in the initial shift state. Characters from the array are converted as
16086 if by repeated calls to the mbrtowc function, with the conversion state
16087 described by an mbstate_t object initialized to zero before the first
16088 multibyte character is converted, and written up to (but not including) the
16089 terminating null wide character. If the precision is specified, no more than
16090 that many wide characters are written. If the precision is not specified or is
16091 greater than the size of the converted array, the converted array shall contain a
16092 null wide character.
16093 If an l length modifier is present, the argument shall be a pointer to the initial
16094 element of an array of wchar_t type. Wide characters from the array are
16095 written up to (but not including) a terminating null wide character. If the
16096 precision is specified, no more than that many wide characters are written. If
16097 the precision is not specified or is greater than the size of the array, the array
16098 shall contain a null wide character.
16099 p The argument shall be a pointer to void. The value of the pointer is
16100 converted to a sequence of printing wide characters, in an implementation-
16102 317) The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
16103 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
16104 might suffice depending on the implementation's scheme for determining the digit to the left of the
16105 decimal-point wide character.
16107 [<a name="#p404" href="p404">page 404</a>] (<a href="#Contents">Contents</a>)
16110 n The argument shall be a pointer to signed integer into which is written the
16111 number of wide characters written to the output stream so far by this call to
16112 fwprintf. No argument is converted, but one is consumed. If the
16113 conversion specification includes any flags, a field width, or a precision, the
16114 behavior is undefined.
16115 % A % wide character is written. No argument is converted. The complete
16116 conversion specification shall be %%.
16117 9 If a conversion specification is invalid, the behavior is undefined.318) If any argument is
16118 not the correct type for the corresponding conversion specification, the behavior is
16120 10 In no case does a nonexistent or small field width cause truncation of a field; if the result
16121 of a conversion is wider than the field width, the field is expanded to contain the
16123 11 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
16124 to a hexadecimal floating number with the given precision.
16125 Recommended practice
16126 12 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
16127 representable in the given precision, the result should be one of the two adjacent numbers
16128 in hexadecimal floating style with the given precision, with the extra stipulation that the
16129 error should have a correct sign for the current rounding direction.
16130 13 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
16131 DECIMAL_DIG, then the result should be correctly rounded.319) If the number of
16132 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
16133 representable with DECIMAL_DIG digits, then the result should be an exact
16134 representation with trailing zeros. Otherwise, the source value is bounded by two
16135 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
16136 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
16137 the error should have a correct sign for the current rounding direction.
16139 14 The fwprintf function returns the number of wide characters transmitted, or a negative
16140 value if an output or encoding error occurred.
16142 318) See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
16143 319) For binary-to-decimal conversion, the result format's values are the numbers representable with the
16144 given format specifier. The number of significant digits is determined by the format specifier, and in
16145 the case of fixed-point conversion by the source value as well.
16147 [<a name="#p405" href="p405">page 405</a>] (<a href="#Contents">Contents</a>)
16149 Environmental limits
16150 15 The number of wide characters that can be produced by any single conversion shall be at
16152 16 EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
16154 #include <a href="#7.12"><math.h></a>
16155 #include <a href="#7.21"><stdio.h></a>
16156 #include <a href="#7.28"><wchar.h></a>
16158 wchar_t *weekday, *month; // pointers to wide strings
16159 int day, hour, min;
16160 fwprintf(stdout, L"%ls, %ls %d, %.2d:%.2d\n",
16161 weekday, month, day, hour, min);
16162 fwprintf(stdout, L"pi = %.5f\n", 4 * atan(<a href="#1.0">1.0</a>));
16164 Forward references: the btowc function (<a href="#7.28.6.1.1">7.28.6.1.1</a>), the mbrtowc function
16165 (<a href="#7.28.6.3.2">7.28.6.3.2</a>).
16166 <a name="7.28.2.2" href="#7.28.2.2"><b> 7.28.2.2 The fwscanf function</b></a>
16168 1 #include <a href="#7.21"><stdio.h></a>
16169 #include <a href="#7.28"><wchar.h></a>
16170 int fwscanf(FILE * restrict stream,
16171 const wchar_t * restrict format, ...);
16173 2 The fwscanf function reads input from the stream pointed to by stream, under
16174 control of the wide string pointed to by format that specifies the admissible input
16175 sequences and how they are to be converted for assignment, using subsequent arguments
16176 as pointers to the objects to receive the converted input. If there are insufficient
16177 arguments for the format, the behavior is undefined. If the format is exhausted while
16178 arguments remain, the excess arguments are evaluated (as always) but are otherwise
16180 3 The format is composed of zero or more directives: one or more white-space wide
16181 characters, an ordinary wide character (neither % nor a white-space wide character), or a
16182 conversion specification. Each conversion specification is introduced by the wide
16183 character %. After the %, the following appear in sequence:
16184 -- An optional assignment-suppressing wide character *.
16185 -- An optional decimal integer greater than zero that specifies the maximum field width
16186 (in wide characters).
16190 [<a name="#p406" href="p406">page 406</a>] (<a href="#Contents">Contents</a>)
16192 -- An optional length modifier that specifies the size of the receiving object.
16193 -- A conversion specifier wide character that specifies the type of conversion to be
16195 4 The fwscanf function executes each directive of the format in turn. When all directives
16196 have been executed, or if a directive fails (as detailed below), the function returns.
16197 Failures are described as input failures (due to the occurrence of an encoding error or the
16198 unavailability of input characters), or matching failures (due to inappropriate input).
16199 5 A directive composed of white-space wide character(s) is executed by reading input up to
16200 the first non-white-space wide character (which remains unread), or until no more wide
16201 characters can be read.
16202 6 A directive that is an ordinary wide character is executed by reading the next wide
16203 character of the stream. If that wide character differs from the directive, the directive
16204 fails and the differing and subsequent wide characters remain unread. Similarly, if end-
16205 of-file, an encoding error, or a read error prevents a wide character from being read, the
16207 7 A directive that is a conversion specification defines a set of matching input sequences, as
16208 described below for each specifier. A conversion specification is executed in the
16210 8 Input white-space wide characters (as specified by the iswspace function) are skipped,
16211 unless the specification includes a [, c, or n specifier.320)
16212 9 An input item is read from the stream, unless the specification includes an n specifier. An
16213 input item is defined as the longest sequence of input wide characters which does not
16214 exceed any specified field width and which is, or is a prefix of, a matching input
16215 sequence.321) The first wide character, if any, after the input item remains unread. If the
16216 length of the input item is zero, the execution of the directive fails; this condition is a
16217 matching failure unless end-of-file, an encoding error, or a read error prevented input
16218 from the stream, in which case it is an input failure.
16219 10 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
16220 count of input wide characters) is converted to a type appropriate to the conversion
16221 specifier. If the input item is not a matching sequence, the execution of the directive fails:
16222 this condition is a matching failure. Unless assignment suppression was indicated by a *,
16223 the result of the conversion is placed in the object pointed to by the first argument
16224 following the format argument that has not already received a conversion result. If this
16227 320) These white-space wide characters are not counted against a specified field width.
16228 321) fwscanf pushes back at most one input wide character onto the input stream. Therefore, some
16229 sequences that are acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
16231 [<a name="#p407" href="p407">page 407</a>] (<a href="#Contents">Contents</a>)
16233 object does not have an appropriate type, or if the result of the conversion cannot be
16234 represented in the object, the behavior is undefined.
16235 11 The length modifiers and their meanings are:
16236 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16237 to an argument with type pointer to signed char or unsigned char.
16238 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16239 to an argument with type pointer to short int or unsigned short
16241 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16242 to an argument with type pointer to long int or unsigned long
16243 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
16244 an argument with type pointer to double; or that a following c, s, or [
16245 conversion specifier applies to an argument with type pointer to wchar_t.
16246 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16247 to an argument with type pointer to long long int or unsigned
16249 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16250 to an argument with type pointer to intmax_t or uintmax_t.
16251 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16252 to an argument with type pointer to size_t or the corresponding signed
16254 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16255 to an argument with type pointer to ptrdiff_t or the corresponding
16256 unsigned integer type.
16257 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
16258 applies to an argument with type pointer to long double.
16259 If a length modifier appears with any conversion specifier other than as specified above,
16260 the behavior is undefined.
16261 12 The conversion specifiers and their meanings are:
16262 d Matches an optionally signed decimal integer, whose format is the same as
16263 expected for the subject sequence of the wcstol function with the value 10
16264 for the base argument. The corresponding argument shall be a pointer to
16266 i Matches an optionally signed integer, whose format is the same as expected
16267 for the subject sequence of the wcstol function with the value 0 for the
16268 base argument. The corresponding argument shall be a pointer to signed
16270 [<a name="#p408" href="p408">page 408</a>] (<a href="#Contents">Contents</a>)
16273 o Matches an optionally signed octal integer, whose format is the same as
16274 expected for the subject sequence of the wcstoul function with the value 8
16275 for the base argument. The corresponding argument shall be a pointer to
16277 u Matches an optionally signed decimal integer, whose format is the same as
16278 expected for the subject sequence of the wcstoul function with the value 10
16279 for the base argument. The corresponding argument shall be a pointer to
16281 x Matches an optionally signed hexadecimal integer, whose format is the same
16282 as expected for the subject sequence of the wcstoul function with the value
16283 16 for the base argument. The corresponding argument shall be a pointer to
16285 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
16286 format is the same as expected for the subject sequence of the wcstod
16287 function. The corresponding argument shall be a pointer to floating.
16288 c Matches a sequence of wide characters of exactly the number specified by the
16289 field width (1 if no field width is present in the directive).
16290 If no l length modifier is present, characters from the input field are
16291 converted as if by repeated calls to the wcrtomb function, with the
16292 conversion state described by an mbstate_t object initialized to zero
16293 before the first wide character is converted. The corresponding argument
16294 shall be a pointer to the initial element of a character array large enough to
16295 accept the sequence. No null character is added.
16296 If an l length modifier is present, the corresponding argument shall be a
16297 pointer to the initial element of an array of wchar_t large enough to accept
16298 the sequence. No null wide character is added.
16299 s Matches a sequence of non-white-space wide characters.
16300 If no l length modifier is present, characters from the input field are
16301 converted as if by repeated calls to the wcrtomb function, with the
16302 conversion state described by an mbstate_t object initialized to zero
16303 before the first wide character is converted. The corresponding argument
16304 shall be a pointer to the initial element of a character array large enough to
16305 accept the sequence and a terminating null character, which will be added
16307 If an l length modifier is present, the corresponding argument shall be a
16308 pointer to the initial element of an array of wchar_t large enough to accept
16310 [<a name="#p409" href="p409">page 409</a>] (<a href="#Contents">Contents</a>)
16312 the sequence and the terminating null wide character, which will be added
16314 [ Matches a nonempty sequence of wide characters from a set of expected
16315 characters (the scanset).
16316 If no l length modifier is present, characters from the input field are
16317 converted as if by repeated calls to the wcrtomb function, with the
16318 conversion state described by an mbstate_t object initialized to zero
16319 before the first wide character is converted. The corresponding argument
16320 shall be a pointer to the initial element of a character array large enough to
16321 accept the sequence and a terminating null character, which will be added
16323 If an l length modifier is present, the corresponding argument shall be a
16324 pointer to the initial element of an array of wchar_t large enough to accept
16325 the sequence and the terminating null wide character, which will be added
16327 The conversion specifier includes all subsequent wide characters in the
16328 format string, up to and including the matching right bracket (]). The wide
16329 characters between the brackets (the scanlist) compose the scanset, unless the
16330 wide character after the left bracket is a circumflex (^), in which case the
16331 scanset contains all wide characters that do not appear in the scanlist between
16332 the circumflex and the right bracket. If the conversion specifier begins with
16333 [] or [^], the right bracket wide character is in the scanlist and the next
16334 following right bracket wide character is the matching right bracket that ends
16335 the specification; otherwise the first following right bracket wide character is
16336 the one that ends the specification. If a - wide character is in the scanlist and
16337 is not the first, nor the second where the first wide character is a ^, nor the
16338 last character, the behavior is implementation-defined.
16339 p Matches an implementation-defined set of sequences, which should be the
16340 same as the set of sequences that may be produced by the %p conversion of
16341 the fwprintf function. The corresponding argument shall be a pointer to a
16342 pointer to void. The input item is converted to a pointer value in an
16343 implementation-defined manner. If the input item is a value converted earlier
16344 during the same program execution, the pointer that results shall compare
16345 equal to that value; otherwise the behavior of the %p conversion is undefined.
16346 n No input is consumed. The corresponding argument shall be a pointer to
16347 signed integer into which is to be written the number of wide characters read
16348 from the input stream so far by this call to the fwscanf function. Execution
16349 of a %n directive does not increment the assignment count returned at the
16350 completion of execution of the fwscanf function. No argument is
16351 [<a name="#p410" href="p410">page 410</a>] (<a href="#Contents">Contents</a>)
16353 converted, but one is consumed. If the conversion specification includes an
16354 assignment-suppressing wide character or a field width, the behavior is
16356 % Matches a single % wide character; no conversion or assignment occurs. The
16357 complete conversion specification shall be %%.
16358 13 If a conversion specification is invalid, the behavior is undefined.322)
16359 14 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
16360 respectively, a, e, f, g, and x.
16361 15 Trailing white space (including new-line wide characters) is left unread unless matched
16362 by a directive. The success of literal matches and suppressed assignments is not directly
16363 determinable other than via the %n directive.
16365 16 The fwscanf function returns the value of the macro EOF if an input failure occurs
16366 before the first conversion (if any) has completed. Otherwise, the function returns the
16367 number of input items assigned, which can be fewer than provided for, or even zero, in
16368 the event of an early matching failure.
16369 17 EXAMPLE 1 The call:
16370 #include <a href="#7.21"><stdio.h></a>
16371 #include <a href="#7.28"><wchar.h></a>
16373 int n, i; float x; wchar_t name[50];
16374 n = fwscanf(stdin, L"%d%f%ls", &i, &x, name);
16375 with the input line:
16376 25 54.32E-1 thompson
16377 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
16380 18 EXAMPLE 2 The call:
16381 #include <a href="#7.21"><stdio.h></a>
16382 #include <a href="#7.28"><wchar.h></a>
16384 int i; float x; double y;
16385 fwscanf(stdin, L"%2d%f%*d %lf", &i, &x, &y);
16388 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
16389 56.0. The next wide character read from the input stream will be a.
16392 322) See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
16394 [<a name="#p411" href="p411">page 411</a>] (<a href="#Contents">Contents</a>)
16396 Forward references: the wcstod, wcstof, and wcstold functions (<a href="#7.28.4.1.1">7.28.4.1.1</a>), the
16397 wcstol, wcstoll, wcstoul, and wcstoull functions (<a href="#7.28.4.1.2">7.28.4.1.2</a>), the wcrtomb
16398 function (<a href="#7.28.6.3.3">7.28.6.3.3</a>).
16399 <a name="7.28.2.3" href="#7.28.2.3"><b> 7.28.2.3 The swprintf function</b></a>
16401 1 #include <a href="#7.28"><wchar.h></a>
16402 int swprintf(wchar_t * restrict s,
16404 const wchar_t * restrict format, ...);
16406 2 The swprintf function is equivalent to fwprintf, except that the argument s
16407 specifies an array of wide characters into which the generated output is to be written,
16408 rather than written to a stream. No more than n wide characters are written, including a
16409 terminating null wide character, which is always added (unless n is zero).
16411 3 The swprintf function returns the number of wide characters written in the array, not
16412 counting the terminating null wide character, or a negative value if an encoding error
16413 occurred or if n or more wide characters were requested to be written.
16414 <a name="7.28.2.4" href="#7.28.2.4"><b> 7.28.2.4 The swscanf function</b></a>
16416 1 #include <a href="#7.28"><wchar.h></a>
16417 int swscanf(const wchar_t * restrict s,
16418 const wchar_t * restrict format, ...);
16420 2 The swscanf function is equivalent to fwscanf, except that the argument s specifies a
16421 wide string from which the input is to be obtained, rather than from a stream. Reaching
16422 the end of the wide string is equivalent to encountering end-of-file for the fwscanf
16425 3 The swscanf function returns the value of the macro EOF if an input failure occurs
16426 before the first conversion (if any) has completed. Otherwise, the swscanf function
16427 returns the number of input items assigned, which can be fewer than provided for, or even
16428 zero, in the event of an early matching failure.
16433 [<a name="#p412" href="p412">page 412</a>] (<a href="#Contents">Contents</a>)
16435 <a name="7.28.2.5" href="#7.28.2.5"><b> 7.28.2.5 The vfwprintf function</b></a>
16437 1 #include <a href="#7.16"><stdarg.h></a>
16438 #include <a href="#7.21"><stdio.h></a>
16439 #include <a href="#7.28"><wchar.h></a>
16440 int vfwprintf(FILE * restrict stream,
16441 const wchar_t * restrict format,
16444 2 The vfwprintf function is equivalent to fwprintf, with the variable argument list
16445 replaced by arg, which shall have been initialized by the va_start macro (and
16446 possibly subsequent va_arg calls). The vfwprintf function does not invoke the
16449 3 The vfwprintf function returns the number of wide characters transmitted, or a
16450 negative value if an output or encoding error occurred.
16451 4 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting
16453 #include <a href="#7.16"><stdarg.h></a>
16454 #include <a href="#7.21"><stdio.h></a>
16455 #include <a href="#7.28"><wchar.h></a>
16456 void error(char *function_name, wchar_t *format, ...)
16459 va_start(args, format);
16460 // print out name of function causing error
16461 fwprintf(stderr, L"ERROR in %s: ", function_name);
16462 // print out remainder of message
16463 vfwprintf(stderr, format, args);
16470 323) As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
16471 invoke the va_arg macro, the value of arg after the return is indeterminate.
16473 [<a name="#p413" href="p413">page 413</a>] (<a href="#Contents">Contents</a>)
16475 <a name="7.28.2.6" href="#7.28.2.6"><b> 7.28.2.6 The vfwscanf function</b></a>
16477 1 #include <a href="#7.16"><stdarg.h></a>
16478 #include <a href="#7.21"><stdio.h></a>
16479 #include <a href="#7.28"><wchar.h></a>
16480 int vfwscanf(FILE * restrict stream,
16481 const wchar_t * restrict format,
16484 2 The vfwscanf function is equivalent to fwscanf, with the variable argument list
16485 replaced by arg, which shall have been initialized by the va_start macro (and
16486 possibly subsequent va_arg calls). The vfwscanf function does not invoke the
16489 3 The vfwscanf function returns the value of the macro EOF if an input failure occurs
16490 before the first conversion (if any) has completed. Otherwise, the vfwscanf function
16491 returns the number of input items assigned, which can be fewer than provided for, or even
16492 zero, in the event of an early matching failure.
16493 <a name="7.28.2.7" href="#7.28.2.7"><b> 7.28.2.7 The vswprintf function</b></a>
16495 1 #include <a href="#7.16"><stdarg.h></a>
16496 #include <a href="#7.28"><wchar.h></a>
16497 int vswprintf(wchar_t * restrict s,
16499 const wchar_t * restrict format,
16502 2 The vswprintf function is equivalent to swprintf, with the variable argument list
16503 replaced by arg, which shall have been initialized by the va_start macro (and
16504 possibly subsequent va_arg calls). The vswprintf function does not invoke the
16507 3 The vswprintf function returns the number of wide characters written in the array, not
16508 counting the terminating null wide character, or a negative value if an encoding error
16509 occurred or if n or more wide characters were requested to be generated.
16512 [<a name="#p414" href="p414">page 414</a>] (<a href="#Contents">Contents</a>)
16514 <a name="7.28.2.8" href="#7.28.2.8"><b> 7.28.2.8 The vswscanf function</b></a>
16516 1 #include <a href="#7.16"><stdarg.h></a>
16517 #include <a href="#7.28"><wchar.h></a>
16518 int vswscanf(const wchar_t * restrict s,
16519 const wchar_t * restrict format,
16522 2 The vswscanf function is equivalent to swscanf, with the variable argument list
16523 replaced by arg, which shall have been initialized by the va_start macro (and
16524 possibly subsequent va_arg calls). The vswscanf function does not invoke the
16527 3 The vswscanf function returns the value of the macro EOF if an input failure occurs
16528 before the first conversion (if any) has completed. Otherwise, the vswscanf function
16529 returns the number of input items assigned, which can be fewer than provided for, or even
16530 zero, in the event of an early matching failure.
16531 <a name="7.28.2.9" href="#7.28.2.9"><b> 7.28.2.9 The vwprintf function</b></a>
16533 1 #include <a href="#7.16"><stdarg.h></a>
16534 #include <a href="#7.28"><wchar.h></a>
16535 int vwprintf(const wchar_t * restrict format,
16538 2 The vwprintf function is equivalent to wprintf, with the variable argument list
16539 replaced by arg, which shall have been initialized by the va_start macro (and
16540 possibly subsequent va_arg calls). The vwprintf function does not invoke the
16543 3 The vwprintf function returns the number of wide characters transmitted, or a negative
16544 value if an output or encoding error occurred.
16549 [<a name="#p415" href="p415">page 415</a>] (<a href="#Contents">Contents</a>)
16551 <a name="7.28.2.10" href="#7.28.2.10"><b> 7.28.2.10 The vwscanf function</b></a>
16553 1 #include <a href="#7.16"><stdarg.h></a>
16554 #include <a href="#7.28"><wchar.h></a>
16555 int vwscanf(const wchar_t * restrict format,
16558 2 The vwscanf function is equivalent to wscanf, with the variable argument list
16559 replaced by arg, which shall have been initialized by the va_start macro (and
16560 possibly subsequent va_arg calls). The vwscanf function does not invoke the
16563 3 The vwscanf function returns the value of the macro EOF if an input failure occurs
16564 before the first conversion (if any) has completed. Otherwise, the vwscanf function
16565 returns the number of input items assigned, which can be fewer than provided for, or even
16566 zero, in the event of an early matching failure.
16567 <a name="7.28.2.11" href="#7.28.2.11"><b> 7.28.2.11 The wprintf function</b></a>
16569 1 #include <a href="#7.28"><wchar.h></a>
16570 int wprintf(const wchar_t * restrict format, ...);
16572 2 The wprintf function is equivalent to fwprintf with the argument stdout
16573 interposed before the arguments to wprintf.
16575 3 The wprintf function returns the number of wide characters transmitted, or a negative
16576 value if an output or encoding error occurred.
16577 <a name="7.28.2.12" href="#7.28.2.12"><b> 7.28.2.12 The wscanf function</b></a>
16579 1 #include <a href="#7.28"><wchar.h></a>
16580 int wscanf(const wchar_t * restrict format, ...);
16582 2 The wscanf function is equivalent to fwscanf with the argument stdin interposed
16583 before the arguments to wscanf.
16586 [<a name="#p416" href="p416">page 416</a>] (<a href="#Contents">Contents</a>)
16589 3 The wscanf function returns the value of the macro EOF if an input failure occurs
16590 before the first conversion (if any) has completed. Otherwise, the wscanf function
16591 returns the number of input items assigned, which can be fewer than provided for, or even
16592 zero, in the event of an early matching failure.
16593 <a name="7.28.3" href="#7.28.3"><b> 7.28.3 Wide character input/output functions</b></a>
16594 <a name="7.28.3.1" href="#7.28.3.1"><b> 7.28.3.1 The fgetwc function</b></a>
16596 1 #include <a href="#7.21"><stdio.h></a>
16597 #include <a href="#7.28"><wchar.h></a>
16598 wint_t fgetwc(FILE *stream);
16600 2 If the end-of-file indicator for the input stream pointed to by stream is not set and a
16601 next wide character is present, the fgetwc function obtains that wide character as a
16602 wchar_t converted to a wint_t and advances the associated file position indicator for
16603 the stream (if defined).
16605 3 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
16606 of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
16607 the fgetwc function returns the next wide character from the input stream pointed to by
16608 stream. If a read error occurs, the error indicator for the stream is set and the fgetwc
16609 function returns WEOF. If an encoding error occurs (including too few bytes), the value of
16610 the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.324)
16611 <a name="7.28.3.2" href="#7.28.3.2"><b> 7.28.3.2 The fgetws function</b></a>
16613 1 #include <a href="#7.21"><stdio.h></a>
16614 #include <a href="#7.28"><wchar.h></a>
16615 wchar_t *fgetws(wchar_t * restrict s,
16616 int n, FILE * restrict stream);
16618 2 The fgetws function reads at most one less than the number of wide characters
16619 specified by n from the stream pointed to by stream into the array pointed to by s. No
16622 324) An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
16623 Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
16625 [<a name="#p417" href="p417">page 417</a>] (<a href="#Contents">Contents</a>)
16627 additional wide characters are read after a new-line wide character (which is retained) or
16628 after end-of-file. A null wide character is written immediately after the last wide
16629 character read into the array.
16631 3 The fgetws function returns s if successful. If end-of-file is encountered and no
16632 characters have been read into the array, the contents of the array remain unchanged and a
16633 null pointer is returned. If a read or encoding error occurs during the operation, the array
16634 contents are indeterminate and a null pointer is returned.
16635 <a name="7.28.3.3" href="#7.28.3.3"><b> 7.28.3.3 The fputwc function</b></a>
16637 1 #include <a href="#7.21"><stdio.h></a>
16638 #include <a href="#7.28"><wchar.h></a>
16639 wint_t fputwc(wchar_t c, FILE *stream);
16641 2 The fputwc function writes the wide character specified by c to the output stream
16642 pointed to by stream, at the position indicated by the associated file position indicator
16643 for the stream (if defined), and advances the indicator appropriately. If the file cannot
16644 support positioning requests, or if the stream was opened with append mode, the
16645 character is appended to the output stream.
16647 3 The fputwc function returns the wide character written. If a write error occurs, the
16648 error indicator for the stream is set and fputwc returns WEOF. If an encoding error
16649 occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
16650 <a name="7.28.3.4" href="#7.28.3.4"><b> 7.28.3.4 The fputws function</b></a>
16652 1 #include <a href="#7.21"><stdio.h></a>
16653 #include <a href="#7.28"><wchar.h></a>
16654 int fputws(const wchar_t * restrict s,
16655 FILE * restrict stream);
16657 2 The fputws function writes the wide string pointed to by s to the stream pointed to by
16658 stream. The terminating null wide character is not written.
16660 3 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
16661 returns a nonnegative value.
16663 [<a name="#p418" href="p418">page 418</a>] (<a href="#Contents">Contents</a>)
16665 <a name="7.28.3.5" href="#7.28.3.5"><b> 7.28.3.5 The fwide function</b></a>
16667 1 #include <a href="#7.21"><stdio.h></a>
16668 #include <a href="#7.28"><wchar.h></a>
16669 int fwide(FILE *stream, int mode);
16671 2 The fwide function determines the orientation of the stream pointed to by stream. If
16672 mode is greater than zero, the function first attempts to make the stream wide oriented. If
16673 mode is less than zero, the function first attempts to make the stream byte oriented.325)
16674 Otherwise, mode is zero and the function does not alter the orientation of the stream.
16676 3 The fwide function returns a value greater than zero if, after the call, the stream has
16677 wide orientation, a value less than zero if the stream has byte orientation, or zero if the
16678 stream has no orientation.
16679 <a name="7.28.3.6" href="#7.28.3.6"><b> 7.28.3.6 The getwc function</b></a>
16681 1 #include <a href="#7.21"><stdio.h></a>
16682 #include <a href="#7.28"><wchar.h></a>
16683 wint_t getwc(FILE *stream);
16685 2 The getwc function is equivalent to fgetwc, except that if it is implemented as a
16686 macro, it may evaluate stream more than once, so the argument should never be an
16687 expression with side effects.
16689 3 The getwc function returns the next wide character from the input stream pointed to by
16691 <a name="7.28.3.7" href="#7.28.3.7"><b> 7.28.3.7 The getwchar function</b></a>
16693 1 #include <a href="#7.28"><wchar.h></a>
16694 wint_t getwchar(void);
16699 325) If the orientation of the stream has already been determined, fwide does not change it.
16701 [<a name="#p419" href="p419">page 419</a>] (<a href="#Contents">Contents</a>)
16704 2 The getwchar function is equivalent to getwc with the argument stdin.
16706 3 The getwchar function returns the next wide character from the input stream pointed to
16708 <a name="7.28.3.8" href="#7.28.3.8"><b> 7.28.3.8 The putwc function</b></a>
16710 1 #include <a href="#7.21"><stdio.h></a>
16711 #include <a href="#7.28"><wchar.h></a>
16712 wint_t putwc(wchar_t c, FILE *stream);
16714 2 The putwc function is equivalent to fputwc, except that if it is implemented as a
16715 macro, it may evaluate stream more than once, so that argument should never be an
16716 expression with side effects.
16718 3 The putwc function returns the wide character written, or WEOF.
16719 <a name="7.28.3.9" href="#7.28.3.9"><b> 7.28.3.9 The putwchar function</b></a>
16721 1 #include <a href="#7.28"><wchar.h></a>
16722 wint_t putwchar(wchar_t c);
16724 2 The putwchar function is equivalent to putwc with the second argument stdout.
16726 3 The putwchar function returns the character written, or WEOF.
16727 <a name="7.28.3.10" href="#7.28.3.10"><b> 7.28.3.10 The ungetwc function</b></a>
16729 1 #include <a href="#7.21"><stdio.h></a>
16730 #include <a href="#7.28"><wchar.h></a>
16731 wint_t ungetwc(wint_t c, FILE *stream);
16733 2 The ungetwc function pushes the wide character specified by c back onto the input
16734 stream pointed to by stream. Pushed-back wide characters will be returned by
16735 subsequent reads on that stream in the reverse order of their pushing. A successful
16737 [<a name="#p420" href="p420">page 420</a>] (<a href="#Contents">Contents</a>)
16739 intervening call (with the stream pointed to by stream) to a file positioning function
16740 (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the
16741 stream. The external storage corresponding to the stream is unchanged.
16742 3 One wide character of pushback is guaranteed, even if the call to the ungetwc function
16743 follows just after a call to a formatted wide character input function fwscanf,
16744 vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times
16745 on the same stream without an intervening read or file positioning operation on that
16746 stream, the operation may fail.
16747 4 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
16749 5 A successful call to the ungetwc function clears the end-of-file indicator for the stream.
16750 The value of the file position indicator for the stream after reading or discarding all
16751 pushed-back wide characters is the same as it was before the wide characters were pushed
16752 back. For a text or binary stream, the value of its file position indicator after a successful
16753 call to the ungetwc function is unspecified until all pushed-back wide characters are
16756 6 The ungetwc function returns the wide character pushed back, or WEOF if the operation
16758 <a name="7.28.4" href="#7.28.4"><b> 7.28.4 General wide string utilities</b></a>
16759 1 The header <a href="#7.28"><wchar.h></a> declares a number of functions useful for wide string
16760 manipulation. Various methods are used for determining the lengths of the arrays, but in
16761 all cases a wchar_t * argument points to the initial (lowest addressed) element of the
16762 array. If an array is accessed beyond the end of an object, the behavior is undefined.
16763 2 Where an argument declared as size_t n determines the length of the array for a
16764 function, n can have the value zero on a call to that function. Unless explicitly stated
16765 otherwise in the description of a particular function in this subclause, pointer arguments
16766 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
16767 function that locates a wide character finds no occurrence, a function that compares two
16768 wide character sequences returns zero, and a function that copies wide characters copies
16769 zero wide characters.
16774 [<a name="#p421" href="p421">page 421</a>] (<a href="#Contents">Contents</a>)
16776 <a name="7.28.4.1" href="#7.28.4.1"><b> 7.28.4.1 Wide string numeric conversion functions</b></a>
16777 <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>
16779 1 #include <a href="#7.28"><wchar.h></a>
16780 double wcstod(const wchar_t * restrict nptr,
16781 wchar_t ** restrict endptr);
16782 float wcstof(const wchar_t * restrict nptr,
16783 wchar_t ** restrict endptr);
16784 long double wcstold(const wchar_t * restrict nptr,
16785 wchar_t ** restrict endptr);
16787 2 The wcstod, wcstof, and wcstold functions convert the initial portion of the wide
16788 string pointed to by nptr to double, float, and long double representation,
16789 respectively. First, they decompose the input string into three parts: an initial, possibly
16790 empty, sequence of white-space wide characters (as specified by the iswspace
16791 function), a subject sequence resembling a floating-point constant or representing an
16792 infinity or NaN; and a final wide string of one or more unrecognized wide characters,
16793 including the terminating null wide character of the input wide string. Then, they attempt
16794 to convert the subject sequence to a floating-point number, and return the result.
16795 3 The expected form of the subject sequence is an optional plus or minus sign, then one of
16797 -- a nonempty sequence of decimal digits optionally containing a decimal-point wide
16798 character, then an optional exponent part as defined for the corresponding single-byte
16799 characters in <a href="#6.4.4.2">6.4.4.2</a>;
16800 -- a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
16801 decimal-point wide character, then an optional binary exponent part as defined in
16802 <a href="#6.4.4.2">6.4.4.2</a>;
16803 -- INF or INFINITY, or any other wide string equivalent except for case
16804 -- NAN or NAN(n-wchar-sequenceopt), or any other wide string equivalent except for
16805 case in the NAN part, where:
16809 n-wchar-sequence digit
16810 n-wchar-sequence nondigit
16811 The subject sequence is defined as the longest initial subsequence of the input wide
16812 string, starting with the first non-white-space wide character, that is of the expected form.
16813 [<a name="#p422" href="p422">page 422</a>] (<a href="#Contents">Contents</a>)
16815 The subject sequence contains no wide characters if the input wide string is not of the
16817 4 If the subject sequence has the expected form for a floating-point number, the sequence of
16818 wide characters starting with the first digit or the decimal-point wide character
16819 (whichever occurs first) is interpreted as a floating constant according to the rules of
16820 <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
16821 if neither an exponent part nor a decimal-point wide character appears in a decimal
16822 floating point number, or if a binary exponent part does not appear in a hexadecimal
16823 floating point number, an exponent part of the appropriate type with value zero is
16824 assumed to follow the last digit in the string. If the subject sequence begins with a minus
16825 sign, the sequence is interpreted as negated.326) A wide character sequence INF or
16826 INFINITY is interpreted as an infinity, if representable in the return type, else like a
16827 floating constant that is too large for the range of the return type. A wide character
16828 sequence NAN or NAN(n-wchar-sequenceopt) is interpreted as a quiet NaN, if supported
16829 in the return type, else like a subject sequence part that does not have the expected form;
16830 the meaning of the n-wchar sequences is implementation-defined.327) A pointer to the
16831 final wide string is stored in the object pointed to by endptr, provided that endptr is
16832 not a null pointer.
16833 5 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
16834 value resulting from the conversion is correctly rounded.
16835 6 In other than the "C" locale, additional locale-specific subject sequence forms may be
16837 7 If the subject sequence is empty or does not have the expected form, no conversion is
16838 performed; the value of nptr is stored in the object pointed to by endptr, provided
16839 that endptr is not a null pointer.
16840 Recommended practice
16841 8 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
16842 the result is not exactly representable, the result should be one of the two numbers in the
16843 appropriate internal format that are adjacent to the hexadecimal floating source value,
16844 with the extra stipulation that the error should have a correct sign for the current rounding
16849 326) It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
16850 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
16851 methods may yield different results if rounding is toward positive or negative infinity. In either case,
16852 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
16853 327) An implementation may use the n-wchar sequence to determine extra information to be represented in
16854 the NaN's significand.
16856 [<a name="#p423" href="p423">page 423</a>] (<a href="#Contents">Contents</a>)
16858 9 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
16859 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
16860 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
16861 consider the two bounding, adjacent decimal strings L and U, both having
16862 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
16863 The result should be one of the (equal or adjacent) values that would be obtained by
16864 correctly rounding L and U according to the current rounding direction, with the extra
16865 stipulation that the error with respect to D should have a correct sign for the current
16866 rounding direction.328)
16868 10 The functions return the converted value, if any. If no conversion could be performed,
16869 zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
16870 plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
16871 return type and sign of the value), and the value of the macro ERANGE is stored in
16872 errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
16873 no greater than the smallest normalized positive number in the return type; whether
16874 errno acquires the value ERANGE is implementation-defined.
16879 328) DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
16880 to the same internal floating value, but if not will round to adjacent values.
16882 [<a name="#p424" href="p424">page 424</a>] (<a href="#Contents">Contents</a>)
16884 <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>
16886 1 #include <a href="#7.28"><wchar.h></a>
16888 const wchar_t * restrict nptr,
16889 wchar_t ** restrict endptr,
16891 long long int wcstoll(
16892 const wchar_t * restrict nptr,
16893 wchar_t ** restrict endptr,
16895 unsigned long int wcstoul(
16896 const wchar_t * restrict nptr,
16897 wchar_t ** restrict endptr,
16899 unsigned long long int wcstoull(
16900 const wchar_t * restrict nptr,
16901 wchar_t ** restrict endptr,
16904 2 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial
16905 portion of the wide string pointed to by nptr to long int, long long int,
16906 unsigned long int, and unsigned long long int representation,
16907 respectively. First, they decompose the input string into three parts: an initial, possibly
16908 empty, sequence of white-space wide characters (as specified by the iswspace
16909 function), a subject sequence resembling an integer represented in some radix determined
16910 by the value of base, and a final wide string of one or more unrecognized wide
16911 characters, including the terminating null wide character of the input wide string. Then,
16912 they attempt to convert the subject sequence to an integer, and return the result.
16913 3 If the value of base is zero, the expected form of the subject sequence is that of an
16914 integer constant as described for the corresponding single-byte characters in <a href="#6.4.4.1">6.4.4.1</a>,
16915 optionally preceded by a plus or minus sign, but not including an integer suffix. If the
16916 value of base is between 2 and 36 (inclusive), the expected form of the subject sequence
16917 is a sequence of letters and digits representing an integer with the radix specified by
16918 base, optionally preceded by a plus or minus sign, but not including an integer suffix.
16919 The letters from a (or A) through z (or Z) are ascribed the values 10 through 35; only
16920 letters and digits whose ascribed values are less than that of base are permitted. If the
16921 value of base is 16, the wide characters 0x or 0X may optionally precede the sequence
16922 of letters and digits, following the sign if present.
16924 [<a name="#p425" href="p425">page 425</a>] (<a href="#Contents">Contents</a>)
16926 4 The subject sequence is defined as the longest initial subsequence of the input wide
16927 string, starting with the first non-white-space wide character, that is of the expected form.
16928 The subject sequence contains no wide characters if the input wide string is empty or
16929 consists entirely of white space, or if the first non-white-space wide character is other
16930 than a sign or a permissible letter or digit.
16931 5 If the subject sequence has the expected form and the value of base is zero, the sequence
16932 of wide characters starting with the first digit is interpreted as an integer constant
16933 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
16934 value of base is between 2 and 36, it is used as the base for conversion, ascribing to each
16935 letter its value as given above. If the subject sequence begins with a minus sign, the value
16936 resulting from the conversion is negated (in the return type). A pointer to the final wide
16937 string is stored in the object pointed to by endptr, provided that endptr is not a null
16939 6 In other than the "C" locale, additional locale-specific subject sequence forms may be
16941 7 If the subject sequence is empty or does not have the expected form, no conversion is
16942 performed; the value of nptr is stored in the object pointed to by endptr, provided
16943 that endptr is not a null pointer.
16945 8 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
16946 value, if any. If no conversion could be performed, zero is returned. If the correct value
16947 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
16948 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
16949 sign of the value, if any), and the value of the macro ERANGE is stored in errno.
16950 <a name="7.28.4.2" href="#7.28.4.2"><b> 7.28.4.2 Wide string copying functions</b></a>
16951 <a name="7.28.4.2.1" href="#7.28.4.2.1"><b> 7.28.4.2.1 The wcscpy function</b></a>
16953 1 #include <a href="#7.28"><wchar.h></a>
16954 wchar_t *wcscpy(wchar_t * restrict s1,
16955 const wchar_t * restrict s2);
16957 2 The wcscpy function copies the wide string pointed to by s2 (including the terminating
16958 null wide character) into the array pointed to by s1.
16960 3 The wcscpy function returns the value of s1.
16963 [<a name="#p426" href="p426">page 426</a>] (<a href="#Contents">Contents</a>)
16965 <a name="7.28.4.2.2" href="#7.28.4.2.2"><b> 7.28.4.2.2 The wcsncpy function</b></a>
16967 1 #include <a href="#7.28"><wchar.h></a>
16968 wchar_t *wcsncpy(wchar_t * restrict s1,
16969 const wchar_t * restrict s2,
16972 2 The wcsncpy function copies not more than n wide characters (those that follow a null
16973 wide character are not copied) from the array pointed to by s2 to the array pointed to by
16975 3 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null
16976 wide characters are appended to the copy in the array pointed to by s1, until n wide
16977 characters in all have been written.
16979 4 The wcsncpy function returns the value of s1.
16980 <a name="7.28.4.2.3" href="#7.28.4.2.3"><b> 7.28.4.2.3 The wmemcpy function</b></a>
16982 1 #include <a href="#7.28"><wchar.h></a>
16983 wchar_t *wmemcpy(wchar_t * restrict s1,
16984 const wchar_t * restrict s2,
16987 2 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
16988 object pointed to by s1.
16990 3 The wmemcpy function returns the value of s1.
16995 329) Thus, if there is no null wide character in the first n wide characters of the array pointed to by s2, the
16996 result will not be null-terminated.
16998 [<a name="#p427" href="p427">page 427</a>] (<a href="#Contents">Contents</a>)
17000 <a name="7.28.4.2.4" href="#7.28.4.2.4"><b> 7.28.4.2.4 The wmemmove function</b></a>
17002 1 #include <a href="#7.28"><wchar.h></a>
17003 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
17006 2 The wmemmove function copies n wide characters from the object pointed to by s2 to
17007 the object pointed to by s1. Copying takes place as if the n wide characters from the
17008 object pointed to by s2 are first copied into a temporary array of n wide characters that
17009 does not overlap the objects pointed to by s1 or s2, and then the n wide characters from
17010 the temporary array are copied into the object pointed to by s1.
17012 3 The wmemmove function returns the value of s1.
17013 <a name="7.28.4.3" href="#7.28.4.3"><b> 7.28.4.3 Wide string concatenation functions</b></a>
17014 <a name="7.28.4.3.1" href="#7.28.4.3.1"><b> 7.28.4.3.1 The wcscat function</b></a>
17016 1 #include <a href="#7.28"><wchar.h></a>
17017 wchar_t *wcscat(wchar_t * restrict s1,
17018 const wchar_t * restrict s2);
17020 2 The wcscat function appends a copy of the wide string pointed to by s2 (including the
17021 terminating null wide character) to the end of the wide string pointed to by s1. The initial
17022 wide character of s2 overwrites the null wide character at the end of s1.
17024 3 The wcscat function returns the value of s1.
17025 <a name="7.28.4.3.2" href="#7.28.4.3.2"><b> 7.28.4.3.2 The wcsncat function</b></a>
17027 1 #include <a href="#7.28"><wchar.h></a>
17028 wchar_t *wcsncat(wchar_t * restrict s1,
17029 const wchar_t * restrict s2,
17032 2 The wcsncat function appends not more than n wide characters (a null wide character
17033 and those that follow it are not appended) from the array pointed to by s2 to the end of
17035 [<a name="#p428" href="p428">page 428</a>] (<a href="#Contents">Contents</a>)
17037 the wide string pointed to by s1. The initial wide character of s2 overwrites the null
17038 wide character at the end of s1. A terminating null wide character is always appended to
17041 3 The wcsncat function returns the value of s1.
17042 <a name="7.28.4.4" href="#7.28.4.4"><b> 7.28.4.4 Wide string comparison functions</b></a>
17043 1 Unless explicitly stated otherwise, the functions described in this subclause order two
17044 wide characters the same way as two integers of the underlying integer type designated
17046 <a name="7.28.4.4.1" href="#7.28.4.4.1"><b> 7.28.4.4.1 The wcscmp function</b></a>
17048 1 #include <a href="#7.28"><wchar.h></a>
17049 int wcscmp(const wchar_t *s1, const wchar_t *s2);
17051 2 The wcscmp function compares the wide string pointed to by s1 to the wide string
17054 3 The wcscmp function returns an integer greater than, equal to, or less than zero,
17055 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
17056 wide string pointed to by s2.
17057 <a name="7.28.4.4.2" href="#7.28.4.4.2"><b> 7.28.4.4.2 The wcscoll function</b></a>
17059 1 #include <a href="#7.28"><wchar.h></a>
17060 int wcscoll(const wchar_t *s1, const wchar_t *s2);
17062 2 The wcscoll function compares the wide string pointed to by s1 to the wide string
17063 pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the
17066 3 The wcscoll function returns an integer greater than, equal to, or less than zero,
17067 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
17070 330) Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is
17073 [<a name="#p429" href="p429">page 429</a>] (<a href="#Contents">Contents</a>)
17075 wide string pointed to by s2 when both are interpreted as appropriate to the current
17077 <a name="7.28.4.4.3" href="#7.28.4.4.3"><b> 7.28.4.4.3 The wcsncmp function</b></a>
17079 1 #include <a href="#7.28"><wchar.h></a>
17080 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
17083 2 The wcsncmp function compares not more than n wide characters (those that follow a
17084 null wide character are not compared) from the array pointed to by s1 to the array
17087 3 The wcsncmp function returns an integer greater than, equal to, or less than zero,
17088 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
17089 to, or less than the possibly null-terminated array pointed to by s2.
17090 <a name="7.28.4.4.4" href="#7.28.4.4.4"><b> 7.28.4.4.4 The wcsxfrm function</b></a>
17092 1 #include <a href="#7.28"><wchar.h></a>
17093 size_t wcsxfrm(wchar_t * restrict s1,
17094 const wchar_t * restrict s2,
17097 2 The wcsxfrm function transforms the wide string pointed to by s2 and places the
17098 resulting wide string into the array pointed to by s1. The transformation is such that if
17099 the wcscmp function is applied to two transformed wide strings, it returns a value greater
17100 than, equal to, or less than zero, corresponding to the result of the wcscoll function
17101 applied to the same two original wide strings. No more than n wide characters are placed
17102 into the resulting array pointed to by s1, including the terminating null wide character. If
17103 n is zero, s1 is permitted to be a null pointer.
17105 3 The wcsxfrm function returns the length of the transformed wide string (not including
17106 the terminating null wide character). If the value returned is n or greater, the contents of
17107 the array pointed to by s1 are indeterminate.
17108 4 EXAMPLE The value of the following expression is the length of the array needed to hold the
17109 transformation of the wide string pointed to by s:
17112 [<a name="#p430" href="p430">page 430</a>] (<a href="#Contents">Contents</a>)
17114 1 + wcsxfrm(NULL, s, 0)
17116 <a name="7.28.4.4.5" href="#7.28.4.4.5"><b> 7.28.4.4.5 The wmemcmp function</b></a>
17118 1 #include <a href="#7.28"><wchar.h></a>
17119 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
17122 2 The wmemcmp function compares the first n wide characters of the object pointed to by
17123 s1 to the first n wide characters of the object pointed to by s2.
17125 3 The wmemcmp function returns an integer greater than, equal to, or less than zero,
17126 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
17128 <a name="7.28.4.5" href="#7.28.4.5"><b> 7.28.4.5 Wide string search functions</b></a>
17129 <a name="7.28.4.5.1" href="#7.28.4.5.1"><b> 7.28.4.5.1 The wcschr function</b></a>
17131 1 #include <a href="#7.28"><wchar.h></a>
17132 wchar_t *wcschr(const wchar_t *s, wchar_t c);
17134 2 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
17135 The terminating null wide character is considered to be part of the wide string.
17137 3 The wcschr function returns a pointer to the located wide character, or a null pointer if
17138 the wide character does not occur in the wide string.
17139 <a name="7.28.4.5.2" href="#7.28.4.5.2"><b> 7.28.4.5.2 The wcscspn function</b></a>
17141 1 #include <a href="#7.28"><wchar.h></a>
17142 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
17144 2 The wcscspn function computes the length of the maximum initial segment of the wide
17145 string pointed to by s1 which consists entirely of wide characters not from the wide
17146 string pointed to by s2.
17150 [<a name="#p431" href="p431">page 431</a>] (<a href="#Contents">Contents</a>)
17153 3 The wcscspn function returns the length of the segment.
17154 <a name="7.28.4.5.3" href="#7.28.4.5.3"><b> 7.28.4.5.3 The wcspbrk function</b></a>
17156 1 #include <a href="#7.28"><wchar.h></a>
17157 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
17159 2 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
17160 any wide character from the wide string pointed to by s2.
17162 3 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
17163 no wide character from s2 occurs in s1.
17164 <a name="7.28.4.5.4" href="#7.28.4.5.4"><b> 7.28.4.5.4 The wcsrchr function</b></a>
17166 1 #include <a href="#7.28"><wchar.h></a>
17167 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
17169 2 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
17170 s. The terminating null wide character is considered to be part of the wide string.
17172 3 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
17173 not occur in the wide string.
17174 <a name="7.28.4.5.5" href="#7.28.4.5.5"><b> 7.28.4.5.5 The wcsspn function</b></a>
17176 1 #include <a href="#7.28"><wchar.h></a>
17177 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
17179 2 The wcsspn function computes the length of the maximum initial segment of the wide
17180 string pointed to by s1 which consists entirely of wide characters from the wide string
17183 3 The wcsspn function returns the length of the segment.
17186 [<a name="#p432" href="p432">page 432</a>] (<a href="#Contents">Contents</a>)
17188 <a name="7.28.4.5.6" href="#7.28.4.5.6"><b> 7.28.4.5.6 The wcsstr function</b></a>
17190 1 #include <a href="#7.28"><wchar.h></a>
17191 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
17193 2 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
17194 the sequence of wide characters (excluding the terminating null wide character) in the
17195 wide string pointed to by s2.
17197 3 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
17198 wide string is not found. If s2 points to a wide string with zero length, the function
17200 <a name="7.28.4.5.7" href="#7.28.4.5.7"><b> 7.28.4.5.7 The wcstok function</b></a>
17202 1 #include <a href="#7.28"><wchar.h></a>
17203 wchar_t *wcstok(wchar_t * restrict s1,
17204 const wchar_t * restrict s2,
17205 wchar_t ** restrict ptr);
17207 2 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
17208 a sequence of tokens, each of which is delimited by a wide character from the wide string
17209 pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
17210 which the wcstok function stores information necessary for it to continue scanning the
17212 3 The first call in a sequence has a non-null first argument and stores an initial value in the
17213 object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
17214 the object pointed to by ptr is required to have the value stored by the previous call in
17215 the sequence, which is then updated. The separator wide string pointed to by s2 may be
17216 different from call to call.
17217 4 The first call in the sequence searches the wide string pointed to by s1 for the first wide
17218 character that is not contained in the current separator wide string pointed to by s2. If no
17219 such wide character is found, then there are no tokens in the wide string pointed to by s1
17220 and the wcstok function returns a null pointer. If such a wide character is found, it is
17221 the start of the first token.
17222 5 The wcstok function then searches from there for a wide character that is contained in
17223 the current separator wide string. If no such wide character is found, the current token
17224 [<a name="#p433" href="p433">page 433</a>] (<a href="#Contents">Contents</a>)
17226 extends to the end of the wide string pointed to by s1, and subsequent searches in the
17227 same wide string for a token return a null pointer. If such a wide character is found, it is
17228 overwritten by a null wide character, which terminates the current token.
17229 6 In all cases, the wcstok function stores sufficient information in the pointer pointed to
17230 by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
17231 value for ptr, shall start searching just past the element overwritten by a null wide
17232 character (if any).
17234 7 The wcstok function returns a pointer to the first wide character of a token, or a null
17235 pointer if there is no token.
17237 #include <a href="#7.28"><wchar.h></a>
17238 static wchar_t str1[] = L"?a???b,,,#c";
17239 static wchar_t str2[] = L"\t \t";
17240 wchar_t *t, *ptr1, *ptr2;
17241 t = wcstok(str1, L"?", &ptr1); // t points to the token L"a"
17242 t = wcstok(NULL, L",", &ptr1); // t points to the token L"??b"
17243 t = wcstok(str2, L" \t", &ptr2); // t is a null pointer
17244 t = wcstok(NULL, L"#,", &ptr1); // t points to the token L"c"
17245 t = wcstok(NULL, L"?", &ptr1); // t is a null pointer
17247 <a name="7.28.4.5.8" href="#7.28.4.5.8"><b> 7.28.4.5.8 The wmemchr function</b></a>
17249 1 #include <a href="#7.28"><wchar.h></a>
17250 wchar_t *wmemchr(const wchar_t *s, wchar_t c,
17253 2 The wmemchr function locates the first occurrence of c in the initial n wide characters of
17254 the object pointed to by s.
17256 3 The wmemchr function returns a pointer to the located wide character, or a null pointer if
17257 the wide character does not occur in the object.
17262 [<a name="#p434" href="p434">page 434</a>] (<a href="#Contents">Contents</a>)
17264 <a name="7.28.4.6" href="#7.28.4.6"><b> 7.28.4.6 Miscellaneous functions</b></a>
17265 <a name="7.28.4.6.1" href="#7.28.4.6.1"><b> 7.28.4.6.1 The wcslen function</b></a>
17267 1 #include <a href="#7.28"><wchar.h></a>
17268 size_t wcslen(const wchar_t *s);
17270 2 The wcslen function computes the length of the wide string pointed to by s.
17272 3 The wcslen function returns the number of wide characters that precede the terminating
17273 null wide character.
17274 <a name="7.28.4.6.2" href="#7.28.4.6.2"><b> 7.28.4.6.2 The wmemset function</b></a>
17276 1 #include <a href="#7.28"><wchar.h></a>
17277 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
17279 2 The wmemset function copies the value of c into each of the first n wide characters of
17280 the object pointed to by s.
17282 3 The wmemset function returns the value of s.
17283 <a name="7.28.5" href="#7.28.5"><b> 7.28.5 Wide character time conversion functions</b></a>
17284 <a name="7.28.5.1" href="#7.28.5.1"><b> 7.28.5.1 The wcsftime function</b></a>
17286 1 #include <a href="#7.26"><time.h></a>
17287 #include <a href="#7.28"><wchar.h></a>
17288 size_t wcsftime(wchar_t * restrict s,
17290 const wchar_t * restrict format,
17291 const struct tm * restrict timeptr);
17293 2 The wcsftime function is equivalent to the strftime function, except that:
17294 -- The argument s points to the initial element of an array of wide characters into which
17295 the generated output is to be placed.
17298 [<a name="#p435" href="p435">page 435</a>] (<a href="#Contents">Contents</a>)
17300 -- The argument maxsize indicates the limiting number of wide characters.
17301 -- The argument format is a wide string and the conversion specifiers are replaced by
17302 corresponding sequences of wide characters.
17303 -- The return value indicates the number of wide characters.
17305 3 If the total number of resulting wide characters including the terminating null wide
17306 character is not more than maxsize, the wcsftime function returns the number of
17307 wide characters placed into the array pointed to by s not including the terminating null
17308 wide character. Otherwise, zero is returned and the contents of the array are
17310 <a name="7.28.6" href="#7.28.6"><b> 7.28.6 Extended multibyte/wide character conversion utilities</b></a>
17311 1 The header <a href="#7.28"><wchar.h></a> declares an extended set of functions useful for conversion
17312 between multibyte characters and wide characters.
17313 2 Most of the following functions -- those that are listed as ''restartable'', <a href="#7.28.6.3">7.28.6.3</a> and
17314 <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
17315 to describe the current conversion state from a particular multibyte character sequence to
17316 a wide character sequence (or the reverse) under the rules of a particular setting for the
17317 LC_CTYPE category of the current locale.
17318 3 The initial conversion state corresponds, for a conversion in either direction, to the
17319 beginning of a new multibyte character in the initial shift state. A zero-valued
17320 mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
17321 valued mbstate_t object can be used to initiate conversion involving any multibyte
17322 character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
17323 been altered by any of the functions described in this subclause, and is then used with a
17324 different multibyte character sequence, or in the other conversion direction, or with a
17325 different LC_CTYPE category setting than on earlier function calls, the behavior is
17327 4 On entry, each function takes the described conversion state (either internal or pointed to
17328 by an argument) as current. The conversion state described by the referenced object is
17329 altered as needed to track the shift state, and the position within a multibyte character, for
17330 the associated multibyte character sequence.
17335 331) Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and
17336 mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
17339 [<a name="#p436" href="p436">page 436</a>] (<a href="#Contents">Contents</a>)
17341 <a name="7.28.6.1" href="#7.28.6.1"><b> 7.28.6.1 Single-byte/wide character conversion functions</b></a>
17342 <a name="7.28.6.1.1" href="#7.28.6.1.1"><b> 7.28.6.1.1 The btowc function</b></a>
17344 1 #include <a href="#7.28"><wchar.h></a> *
17345 wint_t btowc(int c);
17347 2 The btowc function determines whether c constitutes a valid single-byte character in the
17348 initial shift state.
17350 3 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
17351 does not constitute a valid single-byte character in the initial shift state. Otherwise, it
17352 returns the wide character representation of that character.
17353 <a name="7.28.6.1.2" href="#7.28.6.1.2"><b> 7.28.6.1.2 The wctob function</b></a>
17355 1 #include <a href="#7.28"><wchar.h></a> *
17356 int wctob(wint_t c);
17358 2 The wctob function determines whether c corresponds to a member of the extended
17359 character set whose multibyte character representation is a single byte when in the initial
17362 3 The wctob function returns EOF if c does not correspond to a multibyte character with
17363 length one in the initial shift state. Otherwise, it returns the single-byte representation of
17364 that character as an unsigned char converted to an int.
17365 <a name="7.28.6.2" href="#7.28.6.2"><b> 7.28.6.2 Conversion state functions</b></a>
17366 <a name="7.28.6.2.1" href="#7.28.6.2.1"><b> 7.28.6.2.1 The mbsinit function</b></a>
17368 1 #include <a href="#7.28"><wchar.h></a>
17369 int mbsinit(const mbstate_t *ps);
17371 2 If ps is not a null pointer, the mbsinit function determines whether the referenced
17372 mbstate_t object describes an initial conversion state.
17376 [<a name="#p437" href="p437">page 437</a>] (<a href="#Contents">Contents</a>)
17379 3 The mbsinit function returns nonzero if ps is a null pointer or if the referenced object
17380 describes an initial conversion state; otherwise, it returns zero.
17381 <a name="7.28.6.3" href="#7.28.6.3"><b> 7.28.6.3 Restartable multibyte/wide character conversion functions</b></a>
17382 1 These functions differ from the corresponding multibyte character functions of <a href="#7.22.7">7.22.7</a>
17383 (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type
17384 pointer to mbstate_t that points to an object that can completely describe the current
17385 conversion state of the associated multibyte character sequence. If ps is a null pointer,
17386 each function uses its own internal mbstate_t object instead, which is initialized at
17387 program startup to the initial conversion state; the functions are not required to avoid data
17388 races in this case. The implementation behaves as if no library function calls these
17389 functions with a null pointer for ps.
17390 2 Also unlike their corresponding functions, the return value does not represent whether the
17391 encoding is state-dependent.
17392 <a name="7.28.6.3.1" href="#7.28.6.3.1"><b> 7.28.6.3.1 The mbrlen function</b></a>
17394 1 #include <a href="#7.28"><wchar.h></a>
17395 size_t mbrlen(const char * restrict s,
17397 mbstate_t * restrict ps);
17399 2 The mbrlen function is equivalent to the call:
17400 mbrtowc(NULL, s, n, ps != NULL ? ps : &internal)
17401 where internal is the mbstate_t object for the mbrlen function, except that the
17402 expression designated by ps is evaluated only once.
17404 3 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
17406 Forward references: the mbrtowc function (<a href="#7.28.6.3.2">7.28.6.3.2</a>).
17411 [<a name="#p438" href="p438">page 438</a>] (<a href="#Contents">Contents</a>)
17413 <a name="7.28.6.3.2" href="#7.28.6.3.2"><b> 7.28.6.3.2 The mbrtowc function</b></a>
17415 1 #include <a href="#7.28"><wchar.h></a>
17416 size_t mbrtowc(wchar_t * restrict pwc,
17417 const char * restrict s,
17419 mbstate_t * restrict ps);
17421 2 If s is a null pointer, the mbrtowc function is equivalent to the call:
17422 mbrtowc(NULL, "", 1, ps)
17423 In this case, the values of the parameters pwc and n are ignored.
17424 3 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with
17425 the byte pointed to by s to determine the number of bytes needed to complete the next
17426 multibyte character (including any shift sequences). If the function determines that the
17427 next multibyte character is complete and valid, it determines the value of the
17428 corresponding wide character and then, if pwc is not a null pointer, stores that value in
17429 the object pointed to by pwc. If the corresponding wide character is the null wide
17430 character, the resulting state described is the initial conversion state.
17432 4 The mbrtowc function returns the first of the following that applies (given the current
17434 0 if the next n or fewer bytes complete the multibyte character that
17435 corresponds to the null wide character (which is the value stored).
17436 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
17437 character (which is the value stored); the value returned is the number
17438 of bytes that complete the multibyte character.
17439 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
17440 multibyte character, and all n bytes have been processed (no value is
17442 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
17443 do not contribute to a complete and valid multibyte character (no
17444 value is stored); the value of the macro EILSEQ is stored in errno,
17445 and the conversion state is unspecified.
17447 332) When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
17448 sequence of redundant shift sequences (for implementations with state-dependent encodings).
17450 [<a name="#p439" href="p439">page 439</a>] (<a href="#Contents">Contents</a>)
17452 <a name="7.28.6.3.3" href="#7.28.6.3.3"><b> 7.28.6.3.3 The wcrtomb function</b></a>
17454 1 #include <a href="#7.28"><wchar.h></a>
17455 size_t wcrtomb(char * restrict s,
17457 mbstate_t * restrict ps);
17459 2 If s is a null pointer, the wcrtomb function is equivalent to the call
17460 wcrtomb(buf, L'\0', ps)
17461 where buf is an internal buffer.
17462 3 If s is not a null pointer, the wcrtomb function determines the number of bytes needed
17463 to represent the multibyte character that corresponds to the wide character given by wc
17464 (including any shift sequences), and stores the multibyte character representation in the
17465 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
17466 wc is a null wide character, a null byte is stored, preceded by any shift sequence needed
17467 to restore the initial shift state; the resulting state described is the initial conversion state.
17469 4 The wcrtomb function returns the number of bytes stored in the array object (including
17470 any shift sequences). When wc is not a valid wide character, an encoding error occurs:
17471 the function stores the value of the macro EILSEQ in errno and returns
17472 (size_t)(-1); the conversion state is unspecified.
17473 <a name="7.28.6.4" href="#7.28.6.4"><b> 7.28.6.4 Restartable multibyte/wide string conversion functions</b></a>
17474 1 These functions differ from the corresponding multibyte string functions of <a href="#7.22.8">7.22.8</a>
17475 (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to
17476 mbstate_t that points to an object that can completely describe the current conversion
17477 state of the associated multibyte character sequence. If ps is a null pointer, each function
17478 uses its own internal mbstate_t object instead, which is initialized at program startup
17479 to the initial conversion state; the functions are not required to avoid data races in this
17480 case. The implementation behaves as if no library function calls these functions with a
17481 null pointer for ps.
17482 2 Also unlike their corresponding functions, the conversion source parameter, src, has a
17483 pointer-to-pointer type. When the function is storing the results of conversions (that is,
17484 when dst is not a null pointer), the pointer object pointed to by this parameter is updated
17485 to reflect the amount of the source processed by that invocation.
17490 [<a name="#p440" href="p440">page 440</a>] (<a href="#Contents">Contents</a>)
17492 <a name="7.28.6.4.1" href="#7.28.6.4.1"><b> 7.28.6.4.1 The mbsrtowcs function</b></a>
17494 1 #include <a href="#7.28"><wchar.h></a>
17495 size_t mbsrtowcs(wchar_t * restrict dst,
17496 const char ** restrict src,
17498 mbstate_t * restrict ps);
17500 2 The mbsrtowcs function converts a sequence of multibyte characters that begins in the
17501 conversion state described by the object pointed to by ps, from the array indirectly
17502 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
17503 pointer, the converted characters are stored into the array pointed to by dst. Conversion
17504 continues up to and including a terminating null character, which is also stored.
17505 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
17506 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
17507 characters have been stored into the array pointed to by dst.333) Each conversion takes
17508 place as if by a call to the mbrtowc function.
17509 3 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
17510 pointer (if conversion stopped due to reaching a terminating null character) or the address
17511 just past the last multibyte character converted (if any). If conversion stopped due to
17512 reaching a terminating null character and if dst is not a null pointer, the resulting state
17513 described is the initial conversion state.
17515 4 If the input conversion encounters a sequence of bytes that do not form a valid multibyte
17516 character, an encoding error occurs: the mbsrtowcs function stores the value of the
17517 macro EILSEQ in errno and returns (size_t)(-1); the conversion state is
17518 unspecified. Otherwise, it returns the number of multibyte characters successfully
17519 converted, not including the terminating null character (if any).
17524 333) Thus, the value of len is ignored if dst is a null pointer.
17526 [<a name="#p441" href="p441">page 441</a>] (<a href="#Contents">Contents</a>)
17528 <a name="7.28.6.4.2" href="#7.28.6.4.2"><b> 7.28.6.4.2 The wcsrtombs function</b></a>
17530 1 #include <a href="#7.28"><wchar.h></a>
17531 size_t wcsrtombs(char * restrict dst,
17532 const wchar_t ** restrict src,
17534 mbstate_t * restrict ps);
17536 2 The wcsrtombs function converts a sequence of wide characters from the array
17537 indirectly pointed to by src into a sequence of corresponding multibyte characters that
17538 begins in the conversion state described by the object pointed to by ps. If dst is not a
17539 null pointer, the converted characters are then stored into the array pointed to by dst.
17540 Conversion continues up to and including a terminating null wide character, which is also
17541 stored. Conversion stops earlier in two cases: when a wide character is reached that does
17542 not correspond to a valid multibyte character, or (if dst is not a null pointer) when the
17543 next multibyte character would exceed the limit of len total bytes to be stored into the
17544 array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb
17546 3 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
17547 pointer (if conversion stopped due to reaching a terminating null wide character) or the
17548 address just past the last wide character converted (if any). If conversion stopped due to
17549 reaching a terminating null wide character, the resulting state described is the initial
17552 4 If conversion stops because a wide character is reached that does not correspond to a
17553 valid multibyte character, an encoding error occurs: the wcsrtombs function stores the
17554 value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion
17555 state is unspecified. Otherwise, it returns the number of bytes in the resulting multibyte
17556 character sequence, not including the terminating null character (if any).
17561 334) If conversion stops because a terminating null wide character has been reached, the bytes stored
17562 include those necessary to reach the initial shift state immediately before the null byte.
17564 [<a name="#p442" href="p442">page 442</a>] (<a href="#Contents">Contents</a>)
17566 <a name="7.29" href="#7.29"><b> 7.29 Wide character classification and mapping utilities <wctype.h></b></a>
17567 <a name="7.29.1" href="#7.29.1"><b> 7.29.1 Introduction</b></a>
17568 1 The header <a href="#7.29"><wctype.h></a> defines one macro, and declares three data types and many
17570 2 The types declared are
17572 described in <a href="#7.28.1">7.28.1</a>;
17574 which is a scalar type that can hold values which represent locale-specific character
17577 which is a scalar type that can hold values which represent locale-specific character
17579 3 The macro defined is WEOF (described in <a href="#7.28.1">7.28.1</a>).
17580 4 The functions declared are grouped as follows:
17581 -- Functions that provide wide character classification;
17582 -- Extensible functions that provide wide character classification;
17583 -- Functions that provide wide character case mapping;
17584 -- Extensible functions that provide wide character mapping.
17585 5 For all functions described in this subclause that accept an argument of type wint_t, the
17586 value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If
17587 this argument has any other value, the behavior is undefined.
17588 6 The behavior of these functions is affected by the LC_CTYPE category of the current
17594 335) See ''future library directions'' (<a href="#7.30.13">7.30.13</a>).
17596 [<a name="#p443" href="p443">page 443</a>] (<a href="#Contents">Contents</a>)
17598 <a name="7.29.2" href="#7.29.2"><b> 7.29.2 Wide character classification utilities</b></a>
17599 1 The header <a href="#7.29"><wctype.h></a> declares several functions useful for classifying wide
17601 2 The term printing wide character refers to a member of a locale-specific set of wide
17602 characters, each of which occupies at least one printing position on a display device. The
17603 term control wide character refers to a member of a locale-specific set of wide characters
17604 that are not printing wide characters.
17605 <a name="7.29.2.1" href="#7.29.2.1"><b> 7.29.2.1 Wide character classification functions</b></a>
17606 1 The functions in this subclause return nonzero (true) if and only if the value of the
17607 argument wc conforms to that in the description of the function.
17608 2 Each of the following functions returns true for each wide character that corresponds (as
17609 if by a call to the wctob function) to a single-byte character for which the corresponding
17610 character classification function from <a href="#7.4.1">7.4.1</a> returns true, except that the iswgraph and
17611 iswpunct functions may differ with respect to wide characters other than L' ' that are
17612 both printing and white-space wide characters.336)
17613 Forward references: the wctob function (<a href="#7.28.6.1.2">7.28.6.1.2</a>).
17614 <a name="7.29.2.1.1" href="#7.29.2.1.1"><b> 7.29.2.1.1 The iswalnum function</b></a>
17616 1 #include <a href="#7.29"><wctype.h></a>
17617 int iswalnum(wint_t wc);
17619 2 The iswalnum function tests for any wide character for which iswalpha or
17621 <a name="7.29.2.1.2" href="#7.29.2.1.2"><b> 7.29.2.1.2 The iswalpha function</b></a>
17623 1 #include <a href="#7.29"><wctype.h></a>
17624 int iswalpha(wint_t wc);
17626 2 The iswalpha function tests for any wide character for which iswupper or
17627 iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
17629 336) For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call
17630 iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true
17631 (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc)
17632 && iswspace(wc) is true, but not both.
17634 [<a name="#p444" href="p444">page 444</a>] (<a href="#Contents">Contents</a>)
17636 wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
17638 <a name="7.29.2.1.3" href="#7.29.2.1.3"><b> 7.29.2.1.3 The iswblank function</b></a>
17640 1 #include <a href="#7.29"><wctype.h></a>
17641 int iswblank(wint_t wc);
17643 2 The iswblank function tests for any wide character that is a standard blank wide
17644 character or is one of a locale-specific set of wide characters for which iswspace is true
17645 and that is used to separate words within a line of text. The standard blank wide
17646 characters are the following: space (L' '), and horizontal tab (L'\t'). In the "C"
17647 locale, iswblank returns true only for the standard blank characters.
17648 <a name="7.29.2.1.4" href="#7.29.2.1.4"><b> 7.29.2.1.4 The iswcntrl function</b></a>
17650 1 #include <a href="#7.29"><wctype.h></a>
17651 int iswcntrl(wint_t wc);
17653 2 The iswcntrl function tests for any control wide character.
17654 <a name="7.29.2.1.5" href="#7.29.2.1.5"><b> 7.29.2.1.5 The iswdigit function</b></a>
17656 1 #include <a href="#7.29"><wctype.h></a>
17657 int iswdigit(wint_t wc);
17659 2 The iswdigit function tests for any wide character that corresponds to a decimal-digit
17660 character (as defined in <a href="#5.2.1">5.2.1</a>).
17661 <a name="7.29.2.1.6" href="#7.29.2.1.6"><b> 7.29.2.1.6 The iswgraph function</b></a>
17663 1 #include <a href="#7.29"><wctype.h></a>
17664 int iswgraph(wint_t wc);
17669 337) The functions iswlower and iswupper test true or false separately for each of these additional
17670 wide characters; all four combinations are possible.
17672 [<a name="#p445" href="p445">page 445</a>] (<a href="#Contents">Contents</a>)
17675 2 The iswgraph function tests for any wide character for which iswprint is true and
17676 iswspace is false.338)
17677 <a name="7.29.2.1.7" href="#7.29.2.1.7"><b> 7.29.2.1.7 The iswlower function</b></a>
17679 1 #include <a href="#7.29"><wctype.h></a>
17680 int iswlower(wint_t wc);
17682 2 The iswlower function tests for any wide character that corresponds to a lowercase
17683 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
17684 iswdigit, iswpunct, or iswspace is true.
17685 <a name="7.29.2.1.8" href="#7.29.2.1.8"><b> 7.29.2.1.8 The iswprint function</b></a>
17687 1 #include <a href="#7.29"><wctype.h></a>
17688 int iswprint(wint_t wc);
17690 2 The iswprint function tests for any printing wide character.
17691 <a name="7.29.2.1.9" href="#7.29.2.1.9"><b> 7.29.2.1.9 The iswpunct function</b></a>
17693 1 #include <a href="#7.29"><wctype.h></a>
17694 int iswpunct(wint_t wc);
17696 2 The iswpunct function tests for any printing wide character that is one of a locale-
17697 specific set of punctuation wide characters for which neither iswspace nor iswalnum
17699 <a name="7.29.2.1.10" href="#7.29.2.1.10"><b> 7.29.2.1.10 The iswspace function</b></a>
17701 1 #include <a href="#7.29"><wctype.h></a>
17702 int iswspace(wint_t wc);
17706 338) Note that the behavior of the iswgraph and iswpunct functions may differ from their
17707 corresponding functions in <a href="#7.4.1">7.4.1</a> with respect to printing, white-space, single-byte execution
17708 characters other than ' '.
17710 [<a name="#p446" href="p446">page 446</a>] (<a href="#Contents">Contents</a>)
17713 2 The iswspace function tests for any wide character that corresponds to a locale-specific
17714 set of white-space wide characters for which none of iswalnum, iswgraph, or
17716 <a name="7.29.2.1.11" href="#7.29.2.1.11"><b> 7.29.2.1.11 The iswupper function</b></a>
17718 1 #include <a href="#7.29"><wctype.h></a>
17719 int iswupper(wint_t wc);
17721 2 The iswupper function tests for any wide character that corresponds to an uppercase
17722 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
17723 iswdigit, iswpunct, or iswspace is true.
17724 <a name="7.29.2.1.12" href="#7.29.2.1.12"><b> 7.29.2.1.12 The iswxdigit function</b></a>
17726 1 #include <a href="#7.29"><wctype.h></a>
17727 int iswxdigit(wint_t wc);
17729 2 The iswxdigit function tests for any wide character that corresponds to a
17730 hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
17731 <a name="7.29.2.2" href="#7.29.2.2"><b> 7.29.2.2 Extensible wide character classification functions</b></a>
17732 1 The functions wctype and iswctype provide extensible wide character classification
17733 as well as testing equivalent to that performed by the functions described in the previous
17734 subclause (<a href="#7.29.2.1">7.29.2.1</a>).
17735 <a name="7.29.2.2.1" href="#7.29.2.2.1"><b> 7.29.2.2.1 The iswctype function</b></a>
17737 1 #include <a href="#7.29"><wctype.h></a>
17738 int iswctype(wint_t wc, wctype_t desc);
17740 2 The iswctype function determines whether the wide character wc has the property
17741 described by desc. The current setting of the LC_CTYPE category shall be the same as
17742 during the call to wctype that returned the value desc.
17743 3 Each of the following expressions has a truth-value equivalent to the call to the wide
17744 character classification function (<a href="#7.29.2.1">7.29.2.1</a>) in the comment that follows the expression:
17747 [<a name="#p447" href="p447">page 447</a>] (<a href="#Contents">Contents</a>)
17749 iswctype(wc, wctype("alnum")) // iswalnum(wc)
17750 iswctype(wc, wctype("alpha")) // iswalpha(wc)
17751 iswctype(wc, wctype("blank")) // iswblank(wc)
17752 iswctype(wc, wctype("cntrl")) // iswcntrl(wc)
17753 iswctype(wc, wctype("digit")) // iswdigit(wc)
17754 iswctype(wc, wctype("graph")) // iswgraph(wc)
17755 iswctype(wc, wctype("lower")) // iswlower(wc)
17756 iswctype(wc, wctype("print")) // iswprint(wc)
17757 iswctype(wc, wctype("punct")) // iswpunct(wc)
17758 iswctype(wc, wctype("space")) // iswspace(wc)
17759 iswctype(wc, wctype("upper")) // iswupper(wc)
17760 iswctype(wc, wctype("xdigit")) // iswxdigit(wc)
17762 4 The iswctype function returns nonzero (true) if and only if the value of the wide
17763 character wc has the property described by desc.
17764 Forward references: the wctype function (<a href="#7.29.2.2.2">7.29.2.2.2</a>).
17765 <a name="7.29.2.2.2" href="#7.29.2.2.2"><b> 7.29.2.2.2 The wctype function</b></a>
17767 1 #include <a href="#7.29"><wctype.h></a>
17768 wctype_t wctype(const char *property);
17770 2 The wctype function constructs a value with type wctype_t that describes a class of
17771 wide characters identified by the string argument property.
17772 3 The strings listed in the description of the iswctype function shall be valid in all
17773 locales as property arguments to the wctype function.
17775 4 If property identifies a valid class of wide characters according to the LC_CTYPE
17776 category of the current locale, the wctype function returns a nonzero value that is valid
17777 as the second argument to the iswctype function; otherwise, it returns zero.
17782 [<a name="#p448" href="p448">page 448</a>] (<a href="#Contents">Contents</a>)
17784 <a name="7.29.3" href="#7.29.3"><b> 7.29.3 Wide character case mapping utilities</b></a>
17785 1 The header <a href="#7.29"><wctype.h></a> declares several functions useful for mapping wide characters.
17786 <a name="7.29.3.1" href="#7.29.3.1"><b> 7.29.3.1 Wide character case mapping functions</b></a>
17787 <a name="7.29.3.1.1" href="#7.29.3.1.1"><b> 7.29.3.1.1 The towlower function</b></a>
17789 1 #include <a href="#7.29"><wctype.h></a>
17790 wint_t towlower(wint_t wc);
17792 2 The towlower function converts an uppercase letter to a corresponding lowercase letter.
17794 3 If the argument is a wide character for which iswupper is true and there are one or
17795 more corresponding wide characters, as specified by the current locale, for which
17796 iswlower is true, the towlower function returns one of the corresponding wide
17797 characters (always the same one for any given locale); otherwise, the argument is
17798 returned unchanged.
17799 <a name="7.29.3.1.2" href="#7.29.3.1.2"><b> 7.29.3.1.2 The towupper function</b></a>
17801 1 #include <a href="#7.29"><wctype.h></a>
17802 wint_t towupper(wint_t wc);
17804 2 The towupper function converts a lowercase letter to a corresponding uppercase letter.
17806 3 If the argument is a wide character for which iswlower is true and there are one or
17807 more corresponding wide characters, as specified by the current locale, for which
17808 iswupper is true, the towupper function returns one of the corresponding wide
17809 characters (always the same one for any given locale); otherwise, the argument is
17810 returned unchanged.
17811 <a name="7.29.3.2" href="#7.29.3.2"><b> 7.29.3.2 Extensible wide character case mapping functions</b></a>
17812 1 The functions wctrans and towctrans provide extensible wide character mapping as
17813 well as case mapping equivalent to that performed by the functions described in the
17814 previous subclause (<a href="#7.29.3.1">7.29.3.1</a>).
17819 [<a name="#p449" href="p449">page 449</a>] (<a href="#Contents">Contents</a>)
17821 <a name="7.29.3.2.1" href="#7.29.3.2.1"><b> 7.29.3.2.1 The towctrans function</b></a>
17823 1 #include <a href="#7.29"><wctype.h></a>
17824 wint_t towctrans(wint_t wc, wctrans_t desc);
17826 2 The towctrans function maps the wide character wc using the mapping described by
17827 desc. The current setting of the LC_CTYPE category shall be the same as during the call
17828 to wctrans that returned the value desc.
17829 3 Each of the following expressions behaves the same as the call to the wide character case
17830 mapping function (<a href="#7.29.3.1">7.29.3.1</a>) in the comment that follows the expression:
17831 towctrans(wc, wctrans("tolower")) // towlower(wc)
17832 towctrans(wc, wctrans("toupper")) // towupper(wc)
17834 4 The towctrans function returns the mapped value of wc using the mapping described
17836 <a name="7.29.3.2.2" href="#7.29.3.2.2"><b> 7.29.3.2.2 The wctrans function</b></a>
17838 1 #include <a href="#7.29"><wctype.h></a>
17839 wctrans_t wctrans(const char *property);
17841 2 The wctrans function constructs a value with type wctrans_t that describes a
17842 mapping between wide characters identified by the string argument property.
17843 3 The strings listed in the description of the towctrans function shall be valid in all
17844 locales as property arguments to the wctrans function.
17846 4 If property identifies a valid mapping of wide characters according to the LC_CTYPE
17847 category of the current locale, the wctrans function returns a nonzero value that is valid
17848 as the second argument to the towctrans function; otherwise, it returns zero.
17853 [<a name="#p450" href="p450">page 450</a>] (<a href="#Contents">Contents</a>)
17855 <a name="7.30" href="#7.30"><b> 7.30 Future library directions</b></a>
17856 1 The following names are grouped under individual headers for convenience. All external
17857 names described below are reserved no matter what headers are included by the program.
17858 <a name="7.30.1" href="#7.30.1"><b> 7.30.1 Complex arithmetic <complex.h></b></a>
17859 1 The function names
17861 cerfc clog10 clgamma
17862 cexp2 clog1p ctgamma
17863 and the same names suffixed with f or l may be added to the declarations in the
17864 <a href="#7.3"><complex.h></a> header.
17865 <a name="7.30.2" href="#7.30.2"><b> 7.30.2 Character handling <ctype.h></b></a>
17866 1 Function names that begin with either is or to, and a lowercase letter may be added to
17867 the declarations in the <a href="#7.4"><ctype.h></a> header.
17868 <a name="7.30.3" href="#7.30.3"><b> 7.30.3 Errors <errno.h></b></a>
17869 1 Macros that begin with E and a digit or E and an uppercase letter may be added to the
17870 declarations in the <a href="#7.5"><errno.h></a> header.
17871 <a name="7.30.4" href="#7.30.4"><b> 7.30.4 Format conversion of integer types <inttypes.h></b></a>
17872 1 Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
17873 added to the macros defined in the <a href="#7.8"><inttypes.h></a> header.
17874 <a name="7.30.5" href="#7.30.5"><b> 7.30.5 Localization <locale.h></b></a>
17875 1 Macros that begin with LC_ and an uppercase letter may be added to the definitions in
17876 the <a href="#7.11"><locale.h></a> header.
17877 <a name="7.30.6" href="#7.30.6"><b> 7.30.6 Signal handling <signal.h></b></a>
17878 1 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
17879 letter may be added to the definitions in the <a href="#7.14"><signal.h></a> header.
17880 <a name="7.30.7" href="#7.30.7"><b> 7.30.7 Boolean type and values <stdbool.h></b></a>
17881 1 The ability to undefine and perhaps then redefine the macros bool, true, and false is
17882 an obsolescent feature.
17883 <a name="7.30.8" href="#7.30.8"><b> 7.30.8 Integer types <stdint.h></b></a>
17884 1 Typedef names beginning with int or uint and ending with _t may be added to the
17885 types defined in the <a href="#7.20"><stdint.h></a> header. Macro names beginning with INT or UINT
17886 and ending with _MAX, _MIN, or _C may be added to the macros defined in the
17887 <a href="#7.20"><stdint.h></a> header.
17889 [<a name="#p451" href="p451">page 451</a>] (<a href="#Contents">Contents</a>)
17891 <a name="7.30.9" href="#7.30.9"><b> 7.30.9 Input/output <stdio.h></b></a>
17892 1 Lowercase letters may be added to the conversion specifiers and length modifiers in
17893 fprintf and fscanf. Other characters may be used in extensions.
17894 2 The use of ungetc on a binary stream where the file position indicator is zero prior to
17895 the call is an obsolescent feature.
17896 <a name="7.30.10" href="#7.30.10"><b> 7.30.10 General utilities <stdlib.h></b></a>
17897 1 Function names that begin with str and a lowercase letter may be added to the
17898 declarations in the <a href="#7.22"><stdlib.h></a> header.
17899 <a name="7.30.11" href="#7.30.11"><b> 7.30.11 String handling <string.h></b></a>
17900 1 Function names that begin with str, mem, or wcs and a lowercase letter may be added
17901 to the declarations in the <a href="#7.23"><string.h></a> header.
17902 <a name="7.30.12" href="#7.30.12"><b> 7.30.12 Extended multibyte and wide character utilities <wchar.h></b></a>
17903 1 Function names that begin with wcs and a lowercase letter may be added to the
17904 declarations in the <a href="#7.28"><wchar.h></a> header.
17905 2 Lowercase letters may be added to the conversion specifiers and length modifiers in
17906 fwprintf and fwscanf. Other characters may be used in extensions.
17907 <a name="7.30.13" href="#7.30.13"><b> 7.30.13 Wide character classification and mapping utilities</b></a>
17908 <a href="#7.29"><wctype.h></a>
17909 1 Function names that begin with is or to and a lowercase letter may be added to the
17910 declarations in the <a href="#7.29"><wctype.h></a> header.
17915 [<a name="#p452" href="p452">page 452</a>] (<a href="#Contents">Contents</a>)
17917 <a name="A" href="#A"><b> Annex A</b></a>
17919 Language syntax summary
17920 1 NOTE The notation is described in <a href="#6.1">6.1</a>.
17922 <a name="A.1" href="#A.1"><b> A.1 Lexical grammar</b></a>
17923 <a name="A.1.1" href="#A.1.1"><b> A.1.1 Lexical elements</b></a>
17924 (<a href="#6.4">6.4</a>) token:
17930 (<a href="#6.4">6.4</a>) preprocessing-token:
17937 each non-white-space character that cannot be one of the above
17942 [<a name="#p453" href="p453">page 453</a>] (<a href="#Contents">Contents</a>)
17944 <a name="A.1.2" href="#A.1.2"><b>A.1.2 Keywords</b></a>
17945 (<a href="#6.4.1">6.4.1</a>) keyword: one of
17951 const register _Alignas
17952 continue restrict _Atomic
17953 default return _Bool
17955 double signed _Generic
17956 else sizeof _Imaginary
17957 enum static _Noreturn
17958 extern struct _Static_assert
17959 float switch _Thread_local
17961 <a name="A.1.3" href="#A.1.3"><b>A.1.3 Identifiers</b></a>
17962 (<a href="#6.4.2.1">6.4.2.1</a>) identifier:
17963 identifier-nondigit
17964 identifier identifier-nondigit
17966 (<a href="#6.4.2.1">6.4.2.1</a>) identifier-nondigit:
17968 universal-character-name
17969 other implementation-defined characters
17970 (<a href="#6.4.2.1">6.4.2.1</a>) nondigit: one of
17971 _ a b c d e f g h i j k l m
17972 n o p q r s t u v w x y z
17973 A B C D E F G H I J K L M
17974 N O P Q R S T U V W X Y Z
17975 (<a href="#6.4.2.1">6.4.2.1</a>) digit: one of
17976 0 1 2 3 4 5 6 7 8 9
17981 [<a name="#p454" href="p454">page 454</a>] (<a href="#Contents">Contents</a>)
17983 <a name="A.1.4" href="#A.1.4"><b>A.1.4 Universal character names</b></a>
17984 (<a href="#6.4.3">6.4.3</a>) universal-character-name:
17986 \U hex-quad hex-quad
17987 (<a href="#6.4.3">6.4.3</a>) hex-quad:
17988 hexadecimal-digit hexadecimal-digit
17989 hexadecimal-digit hexadecimal-digit
17990 <a name="A.1.5" href="#A.1.5"><b>A.1.5 Constants</b></a>
17991 (<a href="#6.4.4">6.4.4</a>) constant:
17994 enumeration-constant
17996 (<a href="#6.4.4.1">6.4.4.1</a>) integer-constant:
17997 decimal-constant integer-suffixopt
17998 octal-constant integer-suffixopt
17999 hexadecimal-constant integer-suffixopt
18000 (<a href="#6.4.4.1">6.4.4.1</a>) decimal-constant:
18002 decimal-constant digit
18003 (<a href="#6.4.4.1">6.4.4.1</a>) octal-constant:
18005 octal-constant octal-digit
18006 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-constant:
18007 hexadecimal-prefix hexadecimal-digit
18008 hexadecimal-constant hexadecimal-digit
18009 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-prefix: one of
18011 (<a href="#6.4.4.1">6.4.4.1</a>) nonzero-digit: one of
18013 (<a href="#6.4.4.1">6.4.4.1</a>) octal-digit: one of
18019 [<a name="#p455" href="p455">page 455</a>] (<a href="#Contents">Contents</a>)
18021 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-digit: one of
18022 0 1 2 3 4 5 6 7 8 9
18025 (<a href="#6.4.4.1">6.4.4.1</a>) integer-suffix:
18026 unsigned-suffix long-suffixopt
18027 unsigned-suffix long-long-suffix
18028 long-suffix unsigned-suffixopt
18029 long-long-suffix unsigned-suffixopt
18030 (<a href="#6.4.4.1">6.4.4.1</a>) unsigned-suffix: one of
18032 (<a href="#6.4.4.1">6.4.4.1</a>) long-suffix: one of
18034 (<a href="#6.4.4.1">6.4.4.1</a>) long-long-suffix: one of
18036 (<a href="#6.4.4.2">6.4.4.2</a>) floating-constant:
18037 decimal-floating-constant
18038 hexadecimal-floating-constant
18039 (<a href="#6.4.4.2">6.4.4.2</a>) decimal-floating-constant:
18040 fractional-constant exponent-partopt floating-suffixopt
18041 digit-sequence exponent-part floating-suffixopt
18042 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-floating-constant:
18043 hexadecimal-prefix hexadecimal-fractional-constant
18044 binary-exponent-part floating-suffixopt
18045 hexadecimal-prefix hexadecimal-digit-sequence
18046 binary-exponent-part floating-suffixopt
18047 (<a href="#6.4.4.2">6.4.4.2</a>) fractional-constant:
18048 digit-sequenceopt . digit-sequence
18050 (<a href="#6.4.4.2">6.4.4.2</a>) exponent-part:
18051 e signopt digit-sequence
18052 E signopt digit-sequence
18053 (<a href="#6.4.4.2">6.4.4.2</a>) sign: one of
18058 [<a name="#p456" href="p456">page 456</a>] (<a href="#Contents">Contents</a>)
18060 (<a href="#6.4.4.2">6.4.4.2</a>) digit-sequence:
18062 digit-sequence digit
18063 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-fractional-constant:
18064 hexadecimal-digit-sequenceopt .
18065 hexadecimal-digit-sequence
18066 hexadecimal-digit-sequence .
18067 (<a href="#6.4.4.2">6.4.4.2</a>) binary-exponent-part:
18068 p signopt digit-sequence
18069 P signopt digit-sequence
18070 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-digit-sequence:
18072 hexadecimal-digit-sequence hexadecimal-digit
18073 (<a href="#6.4.4.2">6.4.4.2</a>) floating-suffix: one of
18075 (<a href="#6.4.4.3">6.4.4.3</a>) enumeration-constant:
18077 (<a href="#6.4.4.4">6.4.4.4</a>) character-constant:
18078 ' c-char-sequence '
18079 L' c-char-sequence '
18080 u' c-char-sequence '
18081 U' c-char-sequence '
18082 (<a href="#6.4.4.4">6.4.4.4</a>) c-char-sequence:
18084 c-char-sequence c-char
18085 (<a href="#6.4.4.4">6.4.4.4</a>) c-char:
18086 any member of the source character set except
18087 the single-quote ', backslash \, or new-line character
18089 (<a href="#6.4.4.4">6.4.4.4</a>) escape-sequence:
18090 simple-escape-sequence
18091 octal-escape-sequence
18092 hexadecimal-escape-sequence
18093 universal-character-name
18098 [<a name="#p457" href="p457">page 457</a>] (<a href="#Contents">Contents</a>)
18100 (<a href="#6.4.4.4">6.4.4.4</a>) simple-escape-sequence: one of
18102 \a \b \f \n \r \t \v
18103 (<a href="#6.4.4.4">6.4.4.4</a>) octal-escape-sequence:
18105 \ octal-digit octal-digit
18106 \ octal-digit octal-digit octal-digit
18107 (<a href="#6.4.4.4">6.4.4.4</a>) hexadecimal-escape-sequence:
18108 \x hexadecimal-digit
18109 hexadecimal-escape-sequence hexadecimal-digit
18110 <a name="A.1.6" href="#A.1.6"><b>A.1.6 String literals</b></a>
18111 (<a href="#6.4.5">6.4.5</a>) string-literal:
18112 encoding-prefixopt " s-char-sequenceopt "
18113 (<a href="#6.4.5">6.4.5</a>) encoding-prefix:
18118 (<a href="#6.4.5">6.4.5</a>) s-char-sequence:
18120 s-char-sequence s-char
18121 (<a href="#6.4.5">6.4.5</a>) s-char:
18122 any member of the source character set except
18123 the double-quote ", backslash \, or new-line character
18125 <a name="A.1.7" href="#A.1.7"><b>A.1.7 Punctuators</b></a>
18126 (<a href="#6.4.6">6.4.6</a>) punctuator: one of
18127 [ ] ( ) { } . ->
18128 ++ -- & * + - ~ !
18129 / % << >> < > <= >= == != ^ | && ||
18131 = *= /= %= += -= <<= >>= &= ^= |=
18133 <: :> <% %> %: %:%:
18138 [<a name="#p458" href="p458">page 458</a>] (<a href="#Contents">Contents</a>)
18140 <a name="A.1.8" href="#A.1.8"><b>A.1.8 Header names</b></a>
18141 (<a href="#6.4.7">6.4.7</a>) header-name:
18142 < h-char-sequence >
18143 " q-char-sequence "
18144 (<a href="#6.4.7">6.4.7</a>) h-char-sequence:
18146 h-char-sequence h-char
18147 (<a href="#6.4.7">6.4.7</a>) h-char:
18148 any member of the source character set except
18149 the new-line character and >
18150 (<a href="#6.4.7">6.4.7</a>) q-char-sequence:
18152 q-char-sequence q-char
18153 (<a href="#6.4.7">6.4.7</a>) q-char:
18154 any member of the source character set except
18155 the new-line character and "
18156 <a name="A.1.9" href="#A.1.9"><b>A.1.9 Preprocessing numbers</b></a>
18157 (<a href="#6.4.8">6.4.8</a>) pp-number:
18161 pp-number identifier-nondigit
18171 [<a name="#p459" href="p459">page 459</a>] (<a href="#Contents">Contents</a>)
18173 <a name="A.2" href="#A.2"><b>A.2 Phrase structure grammar</b></a>
18174 <a name="A.2.1" href="#A.2.1"><b>A.2.1 Expressions</b></a>
18175 (<a href="#6.5.1">6.5.1</a>) primary-expression:
18181 (<a href="#6.5.1.1">6.5.1.1</a>) generic-selection:
18182 _Generic ( assignment-expression , generic-assoc-list )
18183 (<a href="#6.5.1.1">6.5.1.1</a>) generic-assoc-list:
18184 generic-association
18185 generic-assoc-list , generic-association
18186 (<a href="#6.5.1.1">6.5.1.1</a>) generic-association:
18187 type-name : assignment-expression
18188 default : assignment-expression
18189 (<a href="#6.5.2">6.5.2</a>) postfix-expression:
18191 postfix-expression [ expression ]
18192 postfix-expression ( argument-expression-listopt )
18193 postfix-expression . identifier
18194 postfix-expression -> identifier
18195 postfix-expression ++
18196 postfix-expression --
18197 ( type-name ) { initializer-list }
18198 ( type-name ) { initializer-list , }
18199 (<a href="#6.5.2">6.5.2</a>) argument-expression-list:
18200 assignment-expression
18201 argument-expression-list , assignment-expression
18202 (<a href="#6.5.3">6.5.3</a>) unary-expression:
18204 ++ unary-expression
18205 -- unary-expression
18206 unary-operator cast-expression
18207 sizeof unary-expression
18208 sizeof ( type-name )
18209 alignof ( type-name )
18211 [<a name="#p460" href="p460">page 460</a>] (<a href="#Contents">Contents</a>)
18213 (<a href="#6.5.3">6.5.3</a>) unary-operator: one of
18215 (<a href="#6.5.4">6.5.4</a>) cast-expression:
18217 ( type-name ) cast-expression
18218 (<a href="#6.5.5">6.5.5</a>) multiplicative-expression:
18220 multiplicative-expression * cast-expression
18221 multiplicative-expression / cast-expression
18222 multiplicative-expression % cast-expression
18223 (<a href="#6.5.6">6.5.6</a>) additive-expression:
18224 multiplicative-expression
18225 additive-expression + multiplicative-expression
18226 additive-expression - multiplicative-expression
18227 (<a href="#6.5.7">6.5.7</a>) shift-expression:
18228 additive-expression
18229 shift-expression << additive-expression
18230 shift-expression >> additive-expression
18231 (<a href="#6.5.8">6.5.8</a>) relational-expression:
18233 relational-expression < shift-expression
18234 relational-expression > shift-expression
18235 relational-expression <= shift-expression
18236 relational-expression >= shift-expression
18237 (<a href="#6.5.9">6.5.9</a>) equality-expression:
18238 relational-expression
18239 equality-expression == relational-expression
18240 equality-expression != relational-expression
18241 (<a href="#6.5.10">6.5.10</a>) AND-expression:
18242 equality-expression
18243 AND-expression & equality-expression
18244 (<a href="#6.5.11">6.5.11</a>) exclusive-OR-expression:
18246 exclusive-OR-expression ^ AND-expression
18251 [<a name="#p461" href="p461">page 461</a>] (<a href="#Contents">Contents</a>)
18253 (<a href="#6.5.12">6.5.12</a>) inclusive-OR-expression:
18254 exclusive-OR-expression
18255 inclusive-OR-expression | exclusive-OR-expression
18256 (<a href="#6.5.13">6.5.13</a>) logical-AND-expression:
18257 inclusive-OR-expression
18258 logical-AND-expression && inclusive-OR-expression
18259 (<a href="#6.5.14">6.5.14</a>) logical-OR-expression:
18260 logical-AND-expression
18261 logical-OR-expression || logical-AND-expression
18262 (<a href="#6.5.15">6.5.15</a>) conditional-expression:
18263 logical-OR-expression
18264 logical-OR-expression ? expression : conditional-expression
18265 (<a href="#6.5.16">6.5.16</a>) assignment-expression:
18266 conditional-expression
18267 unary-expression assignment-operator assignment-expression
18268 (<a href="#6.5.16">6.5.16</a>) assignment-operator: one of
18269 = *= /= %= += -= <<= >>= &= ^= |=
18270 (<a href="#6.5.17">6.5.17</a>) expression:
18271 assignment-expression
18272 expression , assignment-expression
18273 (<a href="#6.6">6.6</a>) constant-expression:
18274 conditional-expression
18275 <a name="A.2.2" href="#A.2.2"><b>A.2.2 Declarations</b></a>
18276 (<a href="#6.7">6.7</a>) declaration:
18277 declaration-specifiers init-declarator-listopt ;
18278 static_assert-declaration *
18279 (<a href="#6.7">6.7</a>) declaration-specifiers:
18280 storage-class-specifier declaration-specifiersopt
18281 type-specifier declaration-specifiersopt
18282 type-qualifier declaration-specifiersopt
18283 function-specifier declaration-specifiersopt
18284 alignment-specifier declaration-specifiersopt
18285 (<a href="#6.7">6.7</a>) init-declarator-list:
18287 init-declarator-list , init-declarator
18290 [<a name="#p462" href="p462">page 462</a>] (<a href="#Contents">Contents</a>)
18292 (<a href="#6.7">6.7</a>) init-declarator:
18294 declarator = initializer
18295 (<a href="#6.7.1">6.7.1</a>) storage-class-specifier:
18302 (<a href="#6.7.2">6.7.2</a>) type-specifier:
18314 _Atomic ( type-name )
18315 struct-or-union-specifier
18318 (<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union-specifier:
18319 struct-or-union identifieropt { struct-declaration-list }
18320 struct-or-union identifier
18321 (<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union:
18324 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration-list:
18326 struct-declaration-list struct-declaration
18327 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration:
18328 specifier-qualifier-list struct-declarator-listopt ;
18329 static_assert-declaration
18331 [<a name="#p463" href="p463">page 463</a>] (<a href="#Contents">Contents</a>)
18333 (<a href="#6.7.2.1">6.7.2.1</a>) specifier-qualifier-list:
18334 type-specifier specifier-qualifier-listopt
18335 type-qualifier specifier-qualifier-listopt
18336 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator-list:
18338 struct-declarator-list , struct-declarator
18339 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator:
18341 declaratoropt : constant-expression
18342 (<a href="#6.7.2.2">6.7.2.2</a>) enum-specifier:
18343 enum identifieropt { enumerator-list }
18344 enum identifieropt { enumerator-list , }
18346 (<a href="#6.7.2.2">6.7.2.2</a>) enumerator-list:
18348 enumerator-list , enumerator
18349 (<a href="#6.7.2.2">6.7.2.2</a>) enumerator:
18350 enumeration-constant
18351 enumeration-constant = constant-expression
18352 (<a href="#6.7.3">6.7.3</a>) type-qualifier:
18357 (<a href="#6.7.4">6.7.4</a>) function-specifier:
18360 (<a href="#6.7.5">6.7.5</a>) alignment-specifier:
18361 _Alignas ( type-name )
18362 _Alignas ( constant-expression )
18363 (<a href="#6.7.6">6.7.6</a>) declarator:
18364 pointeropt direct-declarator
18369 [<a name="#p464" href="p464">page 464</a>] (<a href="#Contents">Contents</a>)
18371 (<a href="#6.7.6">6.7.6</a>) direct-declarator:
18374 direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
18375 direct-declarator [ static type-qualifier-listopt assignment-expression ]
18376 direct-declarator [ type-qualifier-list static assignment-expression ]
18377 direct-declarator [ type-qualifier-listopt * ]
18378 direct-declarator ( parameter-type-list )
18379 direct-declarator ( identifier-listopt )
18380 (<a href="#6.7.6">6.7.6</a>) pointer:
18381 * type-qualifier-listopt
18382 * type-qualifier-listopt pointer
18383 (<a href="#6.7.6">6.7.6</a>) type-qualifier-list:
18385 type-qualifier-list type-qualifier
18386 (<a href="#6.7.6">6.7.6</a>) parameter-type-list:
18388 parameter-list , ...
18389 (<a href="#6.7.6">6.7.6</a>) parameter-list:
18390 parameter-declaration
18391 parameter-list , parameter-declaration
18392 (<a href="#6.7.6">6.7.6</a>) parameter-declaration:
18393 declaration-specifiers declarator
18394 declaration-specifiers abstract-declaratoropt
18395 (<a href="#6.7.6">6.7.6</a>) identifier-list:
18397 identifier-list , identifier
18398 (<a href="#6.7.7">6.7.7</a>) type-name:
18399 specifier-qualifier-list abstract-declaratoropt
18400 (<a href="#6.7.7">6.7.7</a>) abstract-declarator:
18402 pointeropt direct-abstract-declarator
18407 [<a name="#p465" href="p465">page 465</a>] (<a href="#Contents">Contents</a>)
18409 (<a href="#6.7.7">6.7.7</a>) direct-abstract-declarator:
18410 ( abstract-declarator )
18411 direct-abstract-declaratoropt [ type-qualifier-listopt
18412 assignment-expressionopt ]
18413 direct-abstract-declaratoropt [ static type-qualifier-listopt
18414 assignment-expression ]
18415 direct-abstract-declaratoropt [ type-qualifier-list static
18416 assignment-expression ]
18417 direct-abstract-declaratoropt [ * ]
18418 direct-abstract-declaratoropt ( parameter-type-listopt )
18419 (<a href="#6.7.8">6.7.8</a>) typedef-name:
18421 (<a href="#6.7.9">6.7.9</a>) initializer:
18422 assignment-expression
18423 { initializer-list }
18424 { initializer-list , }
18425 (<a href="#6.7.9">6.7.9</a>) initializer-list:
18426 designationopt initializer
18427 initializer-list , designationopt initializer
18428 (<a href="#6.7.9">6.7.9</a>) designation:
18430 (<a href="#6.7.9">6.7.9</a>) designator-list:
18432 designator-list designator
18433 (<a href="#6.7.9">6.7.9</a>) designator:
18434 [ constant-expression ]
18436 (<a href="#6.7.10">6.7.10</a>) static_assert-declaration:
18437 _Static_assert ( constant-expression , string-literal ) ;
18442 [<a name="#p466" href="p466">page 466</a>] (<a href="#Contents">Contents</a>)
18444 <a name="A.2.3" href="#A.2.3"><b>A.2.3 Statements</b></a>
18445 (<a href="#6.8">6.8</a>) statement:
18448 expression-statement
18449 selection-statement
18450 iteration-statement
18452 (<a href="#6.8.1">6.8.1</a>) labeled-statement:
18453 identifier : statement
18454 case constant-expression : statement
18455 default : statement
18456 (<a href="#6.8.2">6.8.2</a>) compound-statement:
18457 { block-item-listopt }
18458 (<a href="#6.8.2">6.8.2</a>) block-item-list:
18460 block-item-list block-item
18461 (<a href="#6.8.2">6.8.2</a>) block-item:
18464 (<a href="#6.8.3">6.8.3</a>) expression-statement:
18466 (<a href="#6.8.4">6.8.4</a>) selection-statement:
18467 if ( expression ) statement
18468 if ( expression ) statement else statement
18469 switch ( expression ) statement
18470 (<a href="#6.8.5">6.8.5</a>) iteration-statement:
18471 while ( expression ) statement
18472 do statement while ( expression ) ;
18473 for ( expressionopt ; expressionopt ; expressionopt ) statement
18474 for ( declaration expressionopt ; expressionopt ) statement
18475 (<a href="#6.8.6">6.8.6</a>) jump-statement:
18479 return expressionopt ;
18481 [<a name="#p467" href="p467">page 467</a>] (<a href="#Contents">Contents</a>)
18483 <a name="A.2.4" href="#A.2.4"><b>A.2.4 External definitions</b></a>
18484 (<a href="#6.9">6.9</a>) translation-unit:
18485 external-declaration
18486 translation-unit external-declaration
18487 (<a href="#6.9">6.9</a>) external-declaration:
18488 function-definition
18490 (<a href="#6.9.1">6.9.1</a>) function-definition:
18491 declaration-specifiers declarator declaration-listopt compound-statement
18492 (<a href="#6.9.1">6.9.1</a>) declaration-list:
18494 declaration-list declaration
18495 <a name="A.3" href="#A.3"><b>A.3 Preprocessing directives</b></a>
18496 (<a href="#6.10">6.10</a>) preprocessing-file:
18498 (<a href="#6.10">6.10</a>) group:
18501 (<a href="#6.10">6.10</a>) group-part:
18506 (<a href="#6.10">6.10</a>) if-section:
18507 if-group elif-groupsopt else-groupopt endif-line
18508 (<a href="#6.10">6.10</a>) if-group:
18509 # if constant-expression new-line groupopt
18510 # ifdef identifier new-line groupopt
18511 # ifndef identifier new-line groupopt
18512 (<a href="#6.10">6.10</a>) elif-groups:
18514 elif-groups elif-group
18515 (<a href="#6.10">6.10</a>) elif-group:
18516 # elif constant-expression new-line groupopt
18519 [<a name="#p468" href="p468">page 468</a>] (<a href="#Contents">Contents</a>)
18521 (<a href="#6.10">6.10</a>) else-group:
18522 # else new-line groupopt
18523 (<a href="#6.10">6.10</a>) endif-line:
18525 (<a href="#6.10">6.10</a>) control-line:
18526 # include pp-tokens new-line
18527 # define identifier replacement-list new-line
18528 # define identifier lparen identifier-listopt )
18529 replacement-list new-line
18530 # define identifier lparen ... ) replacement-list new-line
18531 # define identifier lparen identifier-list , ... )
18532 replacement-list new-line
18533 # undef identifier new-line
18534 # line pp-tokens new-line
18535 # error pp-tokensopt new-line
18536 # pragma pp-tokensopt new-line
18538 (<a href="#6.10">6.10</a>) text-line:
18539 pp-tokensopt new-line
18540 (<a href="#6.10">6.10</a>) non-directive:
18542 (<a href="#6.10">6.10</a>) lparen:
18543 a ( character not immediately preceded by white-space
18544 (<a href="#6.10">6.10</a>) replacement-list:
18546 (<a href="#6.10">6.10</a>) pp-tokens:
18547 preprocessing-token
18548 pp-tokens preprocessing-token
18549 (<a href="#6.10">6.10</a>) new-line:
18550 the new-line character
18555 [<a name="#p469" href="p469">page 469</a>] (<a href="#Contents">Contents</a>)
18557 <a name="B" href="#B"><b> Annex B</b></a>
18560 <a name="B.1" href="#B.1"><b>B.1 Diagnostics <assert.h></b></a>
18563 void assert(scalar expression);
18564 <a name="B.2" href="#B.2"><b>B.2 Complex <complex.h></b></a>
18565 __STDC_NO_COMPLEX__ imaginary
18566 complex _Imaginary_I
18568 #pragma STDC CX_LIMITED_RANGE on-off-switch
18569 double complex cacos(double complex z);
18570 float complex cacosf(float complex z);
18571 long double complex cacosl(long double complex z);
18572 double complex casin(double complex z);
18573 float complex casinf(float complex z);
18574 long double complex casinl(long double complex z);
18575 double complex catan(double complex z);
18576 float complex catanf(float complex z);
18577 long double complex catanl(long double complex z);
18578 double complex ccos(double complex z);
18579 float complex ccosf(float complex z);
18580 long double complex ccosl(long double complex z);
18581 double complex csin(double complex z);
18582 float complex csinf(float complex z);
18583 long double complex csinl(long double complex z);
18584 double complex ctan(double complex z);
18585 float complex ctanf(float complex z);
18586 long double complex ctanl(long double complex z);
18587 double complex cacosh(double complex z);
18588 float complex cacoshf(float complex z);
18589 long double complex cacoshl(long double complex z);
18590 double complex casinh(double complex z);
18591 float complex casinhf(float complex z);
18592 long double complex casinhl(long double complex z);
18594 [<a name="#p470" href="p470">page 470</a>] (<a href="#Contents">Contents</a>)
18596 double complex catanh(double complex z);
18597 float complex catanhf(float complex z);
18598 long double complex catanhl(long double complex z);
18599 double complex ccosh(double complex z);
18600 float complex ccoshf(float complex z);
18601 long double complex ccoshl(long double complex z);
18602 double complex csinh(double complex z);
18603 float complex csinhf(float complex z);
18604 long double complex csinhl(long double complex z);
18605 double complex ctanh(double complex z);
18606 float complex ctanhf(float complex z);
18607 long double complex ctanhl(long double complex z);
18608 double complex cexp(double complex z);
18609 float complex cexpf(float complex z);
18610 long double complex cexpl(long double complex z);
18611 double complex clog(double complex z);
18612 float complex clogf(float complex z);
18613 long double complex clogl(long double complex z);
18614 double cabs(double complex z);
18615 float cabsf(float complex z);
18616 long double cabsl(long double complex z);
18617 double complex cpow(double complex x, double complex y);
18618 float complex cpowf(float complex x, float complex y);
18619 long double complex cpowl(long double complex x,
18620 long double complex y);
18621 double complex csqrt(double complex z);
18622 float complex csqrtf(float complex z);
18623 long double complex csqrtl(long double complex z);
18624 double carg(double complex z);
18625 float cargf(float complex z);
18626 long double cargl(long double complex z);
18627 double cimag(double complex z);
18628 float cimagf(float complex z);
18629 long double cimagl(long double complex z);
18630 double complex CMPLX(double x, double y);
18631 float complex CMPLXF(float x, float y);
18632 long double complex CMPLXL(long double x, long double y);
18633 double complex conj(double complex z);
18634 float complex conjf(float complex z);
18635 long double complex conjl(long double complex z);
18636 double complex cproj(double complex z);
18638 [<a name="#p471" href="p471">page 471</a>] (<a href="#Contents">Contents</a>)
18640 float complex cprojf(float complex z);
18641 long double complex cprojl(long double complex z);
18642 double creal(double complex z);
18643 float crealf(float complex z);
18644 long double creall(long double complex z);
18645 <a name="B.3" href="#B.3"><b>B.3 Character handling <ctype.h></b></a>
18646 int isalnum(int c);
18647 int isalpha(int c);
18648 int isblank(int c);
18649 int iscntrl(int c);
18650 int isdigit(int c);
18651 int isgraph(int c);
18652 int islower(int c);
18653 int isprint(int c);
18654 int ispunct(int c);
18655 int isspace(int c);
18656 int isupper(int c);
18657 int isxdigit(int c);
18658 int tolower(int c);
18659 int toupper(int c);
18660 <a name="B.4" href="#B.4"><b>B.4 Errors <errno.h></b></a>
18661 EDOM EILSEQ ERANGE errno
18662 __STDC_WANT_LIB_EXT1__
18664 <a name="B.5" href="#B.5"><b>B.5 Floating-point environment <fenv.h></b></a>
18665 fenv_t FE_OVERFLOW FE_TOWARDZERO
18666 fexcept_t FE_UNDERFLOW FE_UPWARD
18667 FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
18668 FE_INEXACT FE_DOWNWARD
18669 FE_INVALID FE_TONEAREST
18670 #pragma STDC FENV_ACCESS on-off-switch
18671 int feclearexcept(int excepts);
18672 int fegetexceptflag(fexcept_t *flagp, int excepts);
18673 int feraiseexcept(int excepts);
18674 int fesetexceptflag(const fexcept_t *flagp,
18676 int fetestexcept(int excepts);
18678 [<a name="#p472" href="p472">page 472</a>] (<a href="#Contents">Contents</a>)
18680 int fegetround(void);
18681 int fesetround(int round);
18682 int fegetenv(fenv_t *envp);
18683 int feholdexcept(fenv_t *envp);
18684 int fesetenv(const fenv_t *envp);
18685 int feupdateenv(const fenv_t *envp);
18686 <a name="B.6" href="#B.6"><b>B.6 Characteristics of floating types <float.h></b></a>
18687 FLT_ROUNDS DBL_DIG FLT_MAX
18688 FLT_EVAL_METHOD LDBL_DIG DBL_MAX
18689 FLT_HAS_SUBNORM FLT_MIN_EXP LDBL_MAX
18690 DBL_HAS_SUBNORM DBL_MIN_EXP FLT_EPSILON
18691 LDBL_HAS_SUBNORM LDBL_MIN_EXP DBL_EPSILON
18692 FLT_RADIX FLT_MIN_10_EXP LDBL_EPSILON
18693 FLT_MANT_DIG DBL_MIN_10_EXP FLT_MIN
18694 DBL_MANT_DIG LDBL_MIN_10_EXP DBL_MIN
18695 LDBL_MANT_DIG FLT_MAX_EXP LDBL_MIN
18696 FLT_DECIMAL_DIG DBL_MAX_EXP FLT_TRUE_MIN
18697 DBL_DECIMAL_DIG LDBL_MAX_EXP DBL_TRUE_MIN
18698 LDBL_DECIMAL_DIG FLT_MAX_10_EXP LDBL_TRUE_MIN
18699 DECIMAL_DIG DBL_MAX_10_EXP
18700 FLT_DIG LDBL_MAX_10_EXP
18701 <a name="B.7" href="#B.7"><b>B.7 Format conversion of integer types <inttypes.h></b></a>
18703 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
18704 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
18705 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
18706 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
18707 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
18708 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
18709 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
18710 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
18711 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
18712 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
18713 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
18714 intmax_t imaxabs(intmax_t j);
18715 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
18716 intmax_t strtoimax(const char * restrict nptr,
18717 char ** restrict endptr, int base);
18719 [<a name="#p473" href="p473">page 473</a>] (<a href="#Contents">Contents</a>)
18721 uintmax_t strtoumax(const char * restrict nptr,
18722 char ** restrict endptr, int base);
18723 intmax_t wcstoimax(const wchar_t * restrict nptr,
18724 wchar_t ** restrict endptr, int base);
18725 uintmax_t wcstoumax(const wchar_t * restrict nptr,
18726 wchar_t ** restrict endptr, int base);
18727 <a name="B.8" href="#B.8"><b>B.8 Alternative spellings <iso646.h></b></a>
18728 and bitor not_eq xor
18729 and_eq compl or xor_eq
18731 <a name="B.9" href="#B.9"><b>B.9 Sizes of integer types <limits.h></b></a>
18732 CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
18733 SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
18734 SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
18735 UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
18736 CHAR_MIN USHRT_MAX LONG_MAX
18737 <a name="B.10" href="#B.10"><b>B.10 Localization <locale.h></b></a>
18738 struct lconv LC_ALL LC_CTYPE LC_NUMERIC
18739 NULL LC_COLLATE LC_MONETARY LC_TIME
18740 char *setlocale(int category, const char *locale);
18741 struct lconv *localeconv(void);
18742 <a name="B.11" href="#B.11"><b>B.11 Mathematics <math.h></b></a>
18743 float_t FP_INFINITE FP_FAST_FMAL
18744 double_t FP_NAN FP_ILOGB0
18745 HUGE_VAL FP_NORMAL FP_ILOGBNAN
18746 HUGE_VALF FP_SUBNORMAL MATH_ERRNO
18747 HUGE_VALL FP_ZERO MATH_ERREXCEPT
18748 INFINITY FP_FAST_FMA math_errhandling
18750 #pragma STDC FP_CONTRACT on-off-switch
18751 int fpclassify(real-floating x);
18752 int isfinite(real-floating x);
18753 int isinf(real-floating x);
18754 int isnan(real-floating x);
18755 int isnormal(real-floating x);
18756 int signbit(real-floating x);
18757 [<a name="#p474" href="p474">page 474</a>] (<a href="#Contents">Contents</a>)
18759 double acos(double x);
18760 float acosf(float x);
18761 long double acosl(long double x);
18762 double asin(double x);
18763 float asinf(float x);
18764 long double asinl(long double x);
18765 double atan(double x);
18766 float atanf(float x);
18767 long double atanl(long double x);
18768 double atan2(double y, double x);
18769 float atan2f(float y, float x);
18770 long double atan2l(long double y, long double x);
18771 double cos(double x);
18772 float cosf(float x);
18773 long double cosl(long double x);
18774 double sin(double x);
18775 float sinf(float x);
18776 long double sinl(long double x);
18777 double tan(double x);
18778 float tanf(float x);
18779 long double tanl(long double x);
18780 double acosh(double x);
18781 float acoshf(float x);
18782 long double acoshl(long double x);
18783 double asinh(double x);
18784 float asinhf(float x);
18785 long double asinhl(long double x);
18786 double atanh(double x);
18787 float atanhf(float x);
18788 long double atanhl(long double x);
18789 double cosh(double x);
18790 float coshf(float x);
18791 long double coshl(long double x);
18792 double sinh(double x);
18793 float sinhf(float x);
18794 long double sinhl(long double x);
18795 double tanh(double x);
18796 float tanhf(float x);
18797 long double tanhl(long double x);
18798 double exp(double x);
18799 float expf(float x);
18801 [<a name="#p475" href="p475">page 475</a>] (<a href="#Contents">Contents</a>)
18803 long double expl(long double x);
18804 double exp2(double x);
18805 float exp2f(float x);
18806 long double exp2l(long double x);
18807 double expm1(double x);
18808 float expm1f(float x);
18809 long double expm1l(long double x);
18810 double frexp(double value, int *exp);
18811 float frexpf(float value, int *exp);
18812 long double frexpl(long double value, int *exp);
18813 int ilogb(double x);
18814 int ilogbf(float x);
18815 int ilogbl(long double x);
18816 double ldexp(double x, int exp);
18817 float ldexpf(float x, int exp);
18818 long double ldexpl(long double x, int exp);
18819 double log(double x);
18820 float logf(float x);
18821 long double logl(long double x);
18822 double log10(double x);
18823 float log10f(float x);
18824 long double log10l(long double x);
18825 double log1p(double x);
18826 float log1pf(float x);
18827 long double log1pl(long double x);
18828 double log2(double x);
18829 float log2f(float x);
18830 long double log2l(long double x);
18831 double logb(double x);
18832 float logbf(float x);
18833 long double logbl(long double x);
18834 double modf(double value, double *iptr);
18835 float modff(float value, float *iptr);
18836 long double modfl(long double value, long double *iptr);
18837 double scalbn(double x, int n);
18838 float scalbnf(float x, int n);
18839 long double scalbnl(long double x, int n);
18840 double scalbln(double x, long int n);
18841 float scalblnf(float x, long int n);
18842 long double scalblnl(long double x, long int n);
18843 double cbrt(double x);
18845 [<a name="#p476" href="p476">page 476</a>] (<a href="#Contents">Contents</a>)
18847 float cbrtf(float x);
18848 long double cbrtl(long double x);
18849 double fabs(double x);
18850 float fabsf(float x);
18851 long double fabsl(long double x);
18852 double hypot(double x, double y);
18853 float hypotf(float x, float y);
18854 long double hypotl(long double x, long double y);
18855 double pow(double x, double y);
18856 float powf(float x, float y);
18857 long double powl(long double x, long double y);
18858 double sqrt(double x);
18859 float sqrtf(float x);
18860 long double sqrtl(long double x);
18861 double erf(double x);
18862 float erff(float x);
18863 long double erfl(long double x);
18864 double erfc(double x);
18865 float erfcf(float x);
18866 long double erfcl(long double x);
18867 double lgamma(double x);
18868 float lgammaf(float x);
18869 long double lgammal(long double x);
18870 double tgamma(double x);
18871 float tgammaf(float x);
18872 long double tgammal(long double x);
18873 double ceil(double x);
18874 float ceilf(float x);
18875 long double ceill(long double x);
18876 double floor(double x);
18877 float floorf(float x);
18878 long double floorl(long double x);
18879 double nearbyint(double x);
18880 float nearbyintf(float x);
18881 long double nearbyintl(long double x);
18882 double rint(double x);
18883 float rintf(float x);
18884 long double rintl(long double x);
18885 long int lrint(double x);
18886 long int lrintf(float x);
18887 long int lrintl(long double x);
18889 [<a name="#p477" href="p477">page 477</a>] (<a href="#Contents">Contents</a>)
18891 long long int llrint(double x);
18892 long long int llrintf(float x);
18893 long long int llrintl(long double x);
18894 double round(double x);
18895 float roundf(float x);
18896 long double roundl(long double x);
18897 long int lround(double x);
18898 long int lroundf(float x);
18899 long int lroundl(long double x);
18900 long long int llround(double x);
18901 long long int llroundf(float x);
18902 long long int llroundl(long double x);
18903 double trunc(double x);
18904 float truncf(float x);
18905 long double truncl(long double x);
18906 double fmod(double x, double y);
18907 float fmodf(float x, float y);
18908 long double fmodl(long double x, long double y);
18909 double remainder(double x, double y);
18910 float remainderf(float x, float y);
18911 long double remainderl(long double x, long double y);
18912 double remquo(double x, double y, int *quo);
18913 float remquof(float x, float y, int *quo);
18914 long double remquol(long double x, long double y,
18916 double copysign(double x, double y);
18917 float copysignf(float x, float y);
18918 long double copysignl(long double x, long double y);
18919 double nan(const char *tagp);
18920 float nanf(const char *tagp);
18921 long double nanl(const char *tagp);
18922 double nextafter(double x, double y);
18923 float nextafterf(float x, float y);
18924 long double nextafterl(long double x, long double y);
18925 double nexttoward(double x, long double y);
18926 float nexttowardf(float x, long double y);
18927 long double nexttowardl(long double x, long double y);
18928 double fdim(double x, double y);
18929 float fdimf(float x, float y);
18930 long double fdiml(long double x, long double y);
18931 double fmax(double x, double y);
18933 [<a name="#p478" href="p478">page 478</a>] (<a href="#Contents">Contents</a>)
18935 float fmaxf(float x, float y);
18936 long double fmaxl(long double x, long double y);
18937 double fmin(double x, double y);
18938 float fminf(float x, float y);
18939 long double fminl(long double x, long double y);
18940 double fma(double x, double y, double z);
18941 float fmaf(float x, float y, float z);
18942 long double fmal(long double x, long double y,
18944 int isgreater(real-floating x, real-floating y);
18945 int isgreaterequal(real-floating x, real-floating y);
18946 int isless(real-floating x, real-floating y);
18947 int islessequal(real-floating x, real-floating y);
18948 int islessgreater(real-floating x, real-floating y);
18949 int isunordered(real-floating x, real-floating y);
18950 <a name="B.12" href="#B.12"><b>B.12 Nonlocal jumps <setjmp.h></b></a>
18952 int setjmp(jmp_buf env);
18953 _Noreturn void longjmp(jmp_buf env, int val);
18954 <a name="B.13" href="#B.13"><b>B.13 Signal handling <signal.h></b></a>
18955 sig_atomic_t SIG_IGN SIGILL SIGTERM
18956 SIG_DFL SIGABRT SIGINT
18957 SIG_ERR SIGFPE SIGSEGV
18958 void (*signal(int sig, void (*func)(int)))(int);
18959 int raise(int sig);
18964 [<a name="#p479" href="p479">page 479</a>] (<a href="#Contents">Contents</a>)
18966 <a name="B.14" href="#B.14"><b>B.14 Alignment <stdalign.h></b></a>
18968 __alignas_is_defined
18969 <a name="B.15" href="#B.15"><b>B.15 Variable arguments <stdarg.h></b></a>
18971 type va_arg(va_list ap, type);
18972 void va_copy(va_list dest, va_list src);
18973 void va_end(va_list ap);
18974 void va_start(va_list ap, parmN);
18975 <a name="B.16" href="#B.16"><b>B.16 Atomics <stdatomic.h></b></a>
18976 ATOMIC_CHAR_LOCK_FREE atomic_uint
18977 ATOMIC_CHAR16_T_LOCK_FREE atomic_long
18978 ATOMIC_CHAR32_T_LOCK_FREE atomic_ulong
18979 ATOMIC_WCHAR_T_LOCK_FREE atomic_llong
18980 ATOMIC_SHORT_LOCK_FREE atomic_ullong
18981 ATOMIC_INT_LOCK_FREE atomic_char16_t
18982 ATOMIC_LONG_LOCK_FREE atomic_char32_t
18983 ATOMIC_LLONG_LOCK_FREE atomic_wchar_t
18984 ATOMIC_ADDRESS_LOCK_FREE atomic_int_least8_t
18985 ATOMIC_FLAG_INIT atomic_uint_least8_t
18986 memory_order atomic_int_least16_t
18987 atomic_flag atomic_uint_least16_t
18988 atomic_bool atomic_int_least32_t
18989 atomic_address atomic_uint_least32_t
18990 memory_order_relaxed atomic_int_least64_t
18991 memory_order_consume atomic_uint_least64_t
18992 memory_order_acquire atomic_int_fast8_t
18993 memory_order_release atomic_uint_fast8_t
18994 memory_order_acq_rel atomic_int_fast16_t
18995 memory_order_seq_cst atomic_uint_fast16_t
18996 atomic_char atomic_int_fast32_t
18997 atomic_schar atomic_uint_fast32_t
18998 atomic_uchar atomic_int_fast64_t
18999 atomic_short atomic_uint_fast64_t
19000 atomic_ushort atomic_intptr_t
19001 atomic_int atomic_uintptr_t
19005 [<a name="#p480" href="p480">page 480</a>] (<a href="#Contents">Contents</a>)
19007 atomic_size_t atomic_intmax_t
19008 atomic_ptrdiff_t atomic_uintmax_t
19009 #define ATOMIC_VAR_INIT(C value)
19010 void atomic_init(volatile A *obj, C value);
19011 type kill_dependency(type y);
19012 void atomic_thread_fence(memory_order order);
19013 void atomic_signal_fence(memory_order order);
19014 _Bool atomic_is_lock_free(atomic_type const volatile *obj);
19015 void atomic_store(volatile A *object, C desired);
19016 void atomic_store_explicit(volatile A *object,
19017 C desired, memory_order order);
19018 C atomic_load(volatile A *object);
19019 C atomic_load_explicit(volatile A *object,
19020 memory_order order);
19021 C atomic_exchange(volatile A *object, C desired);
19022 C atomic_exchange_explicit(volatile A *object,
19023 C desired, memory_order order);
19024 _Bool atomic_compare_exchange_strong(volatile A *object,
19025 C *expected, C desired);
19026 _Bool atomic_compare_exchange_strong_explicit(
19027 volatile A *object, C *expected, C desired,
19028 memory_order success, memory_order failure);
19029 _Bool atomic_compare_exchange_weak(volatile A *object,
19030 C *expected, C desired);
19031 _Bool atomic_compare_exchange_weak_explicit(
19032 volatile A *object, C *expected, C desired,
19033 memory_order success, memory_order failure);
19034 C atomic_fetch_key(volatile A *object, M operand);
19035 C atomic_fetch_key_explicit(volatile A *object,
19036 M operand, memory_order order);
19037 bool atomic_flag_test_and_set(
19038 volatile atomic_flag *object);
19039 bool atomic_flag_test_and_set_explicit(
19040 volatile atomic_flag *object, memory_order order);
19041 void atomic_flag_clear(volatile atomic_flag *object);
19042 void atomic_flag_clear_explicit(
19043 volatile atomic_flag *object, memory_order order);
19048 [<a name="#p481" href="p481">page 481</a>] (<a href="#Contents">Contents</a>)
19050 <a name="B.17" href="#B.17"><b>B.17 Boolean type and values <stdbool.h></b></a>
19054 __bool_true_false_are_defined
19055 <a name="B.18" href="#B.18"><b>B.18 Common definitions <stddef.h></b></a>
19056 ptrdiff_t max_align_t NULL
19058 offsetof(type, member-designator)
19059 __STDC_WANT_LIB_EXT1__
19061 <a name="B.19" href="#B.19"><b>B.19 Integer types <stdint.h></b></a>
19062 intN_t INT_LEASTN_MIN PTRDIFF_MAX
19063 uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
19064 int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
19065 uint_leastN_t INT_FASTN_MIN SIZE_MAX
19066 int_fastN_t INT_FASTN_MAX WCHAR_MIN
19067 uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
19068 intptr_t INTPTR_MIN WINT_MIN
19069 uintptr_t INTPTR_MAX WINT_MAX
19070 intmax_t UINTPTR_MAX INTN_C(value)
19071 uintmax_t INTMAX_MIN UINTN_C(value)
19072 INTN_MIN INTMAX_MAX INTMAX_C(value)
19073 INTN_MAX UINTMAX_MAX UINTMAX_C(value)
19074 UINTN_MAX PTRDIFF_MIN
19075 __STDC_WANT_LIB_EXT1__
19081 [<a name="#p482" href="p482">page 482</a>] (<a href="#Contents">Contents</a>)
19083 <a name="B.20" href="#B.20"><b>B.20 Input/output <stdio.h></b></a>
19084 size_t _IOLBF FILENAME_MAX TMP_MAX
19085 FILE _IONBF L_tmpnam stderr
19086 fpos_t BUFSIZ SEEK_CUR stdin
19087 NULL EOF SEEK_END stdout
19088 _IOFBF FOPEN_MAX SEEK_SET
19089 int remove(const char *filename);
19090 int rename(const char *old, const char *new);
19091 FILE *tmpfile(void);
19092 char *tmpnam(char *s);
19093 int fclose(FILE *stream);
19094 int fflush(FILE *stream);
19095 FILE *fopen(const char * restrict filename,
19096 const char * restrict mode);
19097 FILE *freopen(const char * restrict filename,
19098 const char * restrict mode,
19099 FILE * restrict stream);
19100 void setbuf(FILE * restrict stream,
19101 char * restrict buf);
19102 int setvbuf(FILE * restrict stream,
19103 char * restrict buf,
19104 int mode, size_t size);
19105 int fprintf(FILE * restrict stream,
19106 const char * restrict format, ...);
19107 int fscanf(FILE * restrict stream,
19108 const char * restrict format, ...);
19109 int printf(const char * restrict format, ...);
19110 int scanf(const char * restrict format, ...);
19111 int snprintf(char * restrict s, size_t n,
19112 const char * restrict format, ...);
19113 int sprintf(char * restrict s,
19114 const char * restrict format, ...);
19115 int sscanf(const char * restrict s,
19116 const char * restrict format, ...);
19117 int vfprintf(FILE * restrict stream,
19118 const char * restrict format, va_list arg);
19119 int vfscanf(FILE * restrict stream,
19120 const char * restrict format, va_list arg);
19121 int vprintf(const char * restrict format, va_list arg);
19122 int vscanf(const char * restrict format, va_list arg);
19124 [<a name="#p483" href="p483">page 483</a>] (<a href="#Contents">Contents</a>)
19126 int vsnprintf(char * restrict s, size_t n,
19127 const char * restrict format, va_list arg);
19128 int vsprintf(char * restrict s,
19129 const char * restrict format, va_list arg);
19130 int vsscanf(const char * restrict s,
19131 const char * restrict format, va_list arg);
19132 int fgetc(FILE *stream);
19133 char *fgets(char * restrict s, int n,
19134 FILE * restrict stream);
19135 int fputc(int c, FILE *stream);
19136 int fputs(const char * restrict s,
19137 FILE * restrict stream);
19138 int getc(FILE *stream);
19140 int putc(int c, FILE *stream);
19141 int putchar(int c);
19142 int puts(const char *s);
19143 int ungetc(int c, FILE *stream);
19144 size_t fread(void * restrict ptr,
19145 size_t size, size_t nmemb,
19146 FILE * restrict stream);
19147 size_t fwrite(const void * restrict ptr,
19148 size_t size, size_t nmemb,
19149 FILE * restrict stream);
19150 int fgetpos(FILE * restrict stream,
19151 fpos_t * restrict pos);
19152 int fseek(FILE *stream, long int offset, int whence);
19153 int fsetpos(FILE *stream, const fpos_t *pos);
19154 long int ftell(FILE *stream);
19155 void rewind(FILE *stream);
19156 void clearerr(FILE *stream);
19157 int feof(FILE *stream);
19158 int ferror(FILE *stream);
19159 void perror(const char *s);
19160 __STDC_WANT_LIB_EXT1__
19161 L_tmpnam_s TMP_MAX_S errno_t rsize_t
19162 errno_t tmpfile_s(FILE * restrict * restrict streamptr);
19163 errno_t tmpnam_s(char *s, rsize_t maxsize);
19167 [<a name="#p484" href="p484">page 484</a>] (<a href="#Contents">Contents</a>)
19169 errno_t fopen_s(FILE * restrict * restrict streamptr,
19170 const char * restrict filename,
19171 const char * restrict mode);
19172 errno_t freopen_s(FILE * restrict * restrict newstreamptr,
19173 const char * restrict filename,
19174 const char * restrict mode,
19175 FILE * restrict stream);
19176 int fprintf_s(FILE * restrict stream,
19177 const char * restrict format, ...);
19178 int fscanf_s(FILE * restrict stream,
19179 const char * restrict format, ...);
19180 int printf_s(const char * restrict format, ...);
19181 int scanf_s(const char * restrict format, ...);
19182 int snprintf_s(char * restrict s, rsize_t n,
19183 const char * restrict format, ...);
19184 int sprintf_s(char * restrict s, rsize_t n,
19185 const char * restrict format, ...);
19186 int sscanf_s(const char * restrict s,
19187 const char * restrict format, ...);
19188 int vfprintf_s(FILE * restrict stream,
19189 const char * restrict format,
19191 int vfscanf_s(FILE * restrict stream,
19192 const char * restrict format,
19194 int vprintf_s(const char * restrict format,
19196 int vscanf_s(const char * restrict format,
19198 int vsnprintf_s(char * restrict s, rsize_t n,
19199 const char * restrict format,
19201 int vsprintf_s(char * restrict s, rsize_t n,
19202 const char * restrict format,
19204 int vsscanf_s(const char * restrict s,
19205 const char * restrict format,
19207 char *gets_s(char *s, rsize_t n);
19211 [<a name="#p485" href="p485">page 485</a>] (<a href="#Contents">Contents</a>)
19213 <a name="B.21" href="#B.21"><b>B.21 General utilities <stdlib.h></b></a>
19214 size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
19215 wchar_t lldiv_t EXIT_SUCCESS
19216 div_t NULL RAND_MAX
19217 double atof(const char *nptr);
19218 int atoi(const char *nptr);
19219 long int atol(const char *nptr);
19220 long long int atoll(const char *nptr);
19221 double strtod(const char * restrict nptr,
19222 char ** restrict endptr);
19223 float strtof(const char * restrict nptr,
19224 char ** restrict endptr);
19225 long double strtold(const char * restrict nptr,
19226 char ** restrict endptr);
19227 long int strtol(const char * restrict nptr,
19228 char ** restrict endptr, int base);
19229 long long int strtoll(const char * restrict nptr,
19230 char ** restrict endptr, int base);
19231 unsigned long int strtoul(
19232 const char * restrict nptr,
19233 char ** restrict endptr, int base);
19234 unsigned long long int strtoull(
19235 const char * restrict nptr,
19236 char ** restrict endptr, int base);
19238 void srand(unsigned int seed);
19239 void *aligned_alloc(size_t alignment, size_t size);
19240 void *calloc(size_t nmemb, size_t size);
19241 void free(void *ptr);
19242 void *malloc(size_t size);
19243 void *realloc(void *ptr, size_t size);
19244 _Noreturn void abort(void);
19245 int atexit(void (*func)(void));
19246 int at_quick_exit(void (*func)(void));
19247 _Noreturn void exit(int status);
19248 _Noreturn void _Exit(int status);
19249 char *getenv(const char *name);
19250 _Noreturn void quick_exit(int status);
19251 int system(const char *string);
19254 [<a name="#p486" href="p486">page 486</a>] (<a href="#Contents">Contents</a>)
19256 void *bsearch(const void *key, const void *base,
19257 size_t nmemb, size_t size,
19258 int (*compar)(const void *, const void *));
19259 void qsort(void *base, size_t nmemb, size_t size,
19260 int (*compar)(const void *, const void *));
19262 long int labs(long int j);
19263 long long int llabs(long long int j);
19264 div_t div(int numer, int denom);
19265 ldiv_t ldiv(long int numer, long int denom);
19266 lldiv_t lldiv(long long int numer,
19267 long long int denom);
19268 int mblen(const char *s, size_t n);
19269 int mbtowc(wchar_t * restrict pwc,
19270 const char * restrict s, size_t n);
19271 int wctomb(char *s, wchar_t wchar);
19272 size_t mbstowcs(wchar_t * restrict pwcs,
19273 const char * restrict s, size_t n);
19274 size_t wcstombs(char * restrict s,
19275 const wchar_t * restrict pwcs, size_t n);
19276 __STDC_WANT_LIB_EXT1__
19279 constraint_handler_t
19280 constraint_handler_t set_constraint_handler_s(
19281 constraint_handler_t handler);
19282 void abort_handler_s(
19283 const char * restrict msg,
19284 void * restrict ptr,
19286 void ignore_handler_s(
19287 const char * restrict msg,
19288 void * restrict ptr,
19290 errno_t getenv_s(size_t * restrict len,
19291 char * restrict value, rsize_t maxsize,
19292 const char * restrict name);
19297 [<a name="#p487" href="p487">page 487</a>] (<a href="#Contents">Contents</a>)
19299 void *bsearch_s(const void *key, const void *base,
19300 rsize_t nmemb, rsize_t size,
19301 int (*compar)(const void *k, const void *y,
19304 errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
19305 int (*compar)(const void *x, const void *y,
19308 errno_t wctomb_s(int * restrict status,
19312 errno_t mbstowcs_s(size_t * restrict retval,
19313 wchar_t * restrict dst, rsize_t dstmax,
19314 const char * restrict src, rsize_t len);
19315 errno_t wcstombs_s(size_t * restrict retval,
19316 char * restrict dst, rsize_t dstmax,
19317 const wchar_t * restrict src, rsize_t len);
19318 <a name="B.22" href="#B.22"><b>B.22 String handling <string.h></b></a>
19321 void *memcpy(void * restrict s1,
19322 const void * restrict s2, size_t n);
19323 void *memmove(void *s1, const void *s2, size_t n);
19324 char *strcpy(char * restrict s1,
19325 const char * restrict s2);
19326 char *strncpy(char * restrict s1,
19327 const char * restrict s2, size_t n);
19328 char *strcat(char * restrict s1,
19329 const char * restrict s2);
19330 char *strncat(char * restrict s1,
19331 const char * restrict s2, size_t n);
19332 int memcmp(const void *s1, const void *s2, size_t n);
19333 int strcmp(const char *s1, const char *s2);
19334 int strcoll(const char *s1, const char *s2);
19335 int strncmp(const char *s1, const char *s2, size_t n);
19336 size_t strxfrm(char * restrict s1,
19337 const char * restrict s2, size_t n);
19338 void *memchr(const void *s, int c, size_t n);
19339 [<a name="#p488" href="p488">page 488</a>] (<a href="#Contents">Contents</a>)
19341 char *strchr(const char *s, int c);
19342 size_t strcspn(const char *s1, const char *s2);
19343 char *strpbrk(const char *s1, const char *s2);
19344 char *strrchr(const char *s, int c);
19345 size_t strspn(const char *s1, const char *s2);
19346 char *strstr(const char *s1, const char *s2);
19347 char *strtok(char * restrict s1,
19348 const char * restrict s2);
19349 void *memset(void *s, int c, size_t n);
19350 char *strerror(int errnum);
19351 size_t strlen(const char *s);
19352 __STDC_WANT_LIB_EXT1__
19355 errno_t memcpy_s(void * restrict s1, rsize_t s1max,
19356 const void * restrict s2, rsize_t n);
19357 errno_t memmove_s(void *s1, rsize_t s1max,
19358 const void *s2, rsize_t n);
19359 errno_t strcpy_s(char * restrict s1,
19361 const char * restrict s2);
19362 errno_t strncpy_s(char * restrict s1,
19364 const char * restrict s2,
19366 errno_t strcat_s(char * restrict s1,
19368 const char * restrict s2);
19369 errno_t strncat_s(char * restrict s1,
19371 const char * restrict s2,
19373 char *strtok_s(char * restrict s1,
19374 rsize_t * restrict s1max,
19375 const char * restrict s2,
19376 char ** restrict ptr);
19377 errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
19378 errno_t strerror_s(char *s, rsize_t maxsize,
19380 size_t strerrorlen_s(errno_t errnum);
19382 [<a name="#p489" href="p489">page 489</a>] (<a href="#Contents">Contents</a>)
19384 size_t strnlen_s(const char *s, size_t maxsize);
19385 <a name="B.23" href="#B.23"><b>B.23 Type-generic math <tgmath.h></b></a>
19386 acos sqrt fmod nextafter
19387 asin fabs frexp nexttoward
19388 atan atan2 hypot remainder
19389 acosh cbrt ilogb remquo
19390 asinh ceil ldexp rint
19391 atanh copysign lgamma round
19392 cos erf llrint scalbn
19393 sin erfc llround scalbln
19394 tan exp2 log10 tgamma
19395 cosh expm1 log1p trunc
19396 sinh fdim log2 carg
19397 tanh floor logb cimag
19399 log fmax lround cproj
19400 pow fmin nearbyint creal
19401 <a name="B.24" href="#B.24"><b>B.24 Threads <threads.h></b></a>
19402 ONCE_FLAG_INIT mtx_plain
19403 TSS_DTOR_ITERATIONS mtx_recursive
19408 tss_dtor_t thrd_busy
19409 thrd_start_t thrd_error
19410 once_flag thrd_nomem
19412 void call_once(once_flag *flag, void (*func)(void));
19413 int cnd_broadcast(cnd_t *cond);
19414 void cnd_destroy(cnd_t *cond);
19415 int cnd_init(cnd_t *cond);
19416 int cnd_signal(cnd_t *cond);
19417 int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
19419 int cnd_wait(cnd_t *cond, mtx_t *mtx);
19420 void mtx_destroy(mtx_t *mtx);
19421 int mtx_init(mtx_t *mtx, int type);
19422 int mtx_lock(mtx_t *mtx);
19423 [<a name="#p490" href="p490">page 490</a>] (<a href="#Contents">Contents</a>)
19425 int mtx_timedlock(mtx_t *mtx, const xtime *xt);
19426 int mtx_trylock(mtx_t *mtx);
19427 int mtx_unlock(mtx_t *mtx);
19428 int thrd_create(thrd_t *thr, thrd_start_t func,
19430 thrd_t thrd_current(void);
19431 int thrd_detach(thrd_t thr);
19432 int thrd_equal(thrd_t thr0, thrd_t thr1);
19433 void thrd_exit(int res);
19434 int thrd_join(thrd_t thr, int *res);
19435 void thrd_sleep(const xtime *xt);
19436 void thrd_yield(void);
19437 int tss_create(tss_t *key, tss_dtor_t dtor);
19438 void tss_delete(tss_t key);
19439 void *tss_get(tss_t key);
19440 int tss_set(tss_t key, void *val);
19441 int xtime_get(xtime *xt, int base);
19442 <a name="B.25" href="#B.25"><b>B.25 Date and time <time.h></b></a>
19444 CLOCKS_PER_SEC clock_t struct tm
19445 clock_t clock(void);
19446 double difftime(time_t time1, time_t time0);
19447 time_t mktime(struct tm *timeptr);
19448 time_t time(time_t *timer);
19449 char *asctime(const struct tm *timeptr);
19450 char *ctime(const time_t *timer);
19451 struct tm *gmtime(const time_t *timer);
19452 struct tm *localtime(const time_t *timer);
19453 size_t strftime(char * restrict s,
19455 const char * restrict format,
19456 const struct tm * restrict timeptr);
19457 __STDC_WANT_LIB_EXT1__
19460 errno_t asctime_s(char *s, rsize_t maxsize,
19461 const struct tm *timeptr);
19465 [<a name="#p491" href="p491">page 491</a>] (<a href="#Contents">Contents</a>)
19467 errno_t ctime_s(char *s, rsize_t maxsize,
19468 const time_t *timer);
19469 struct tm *gmtime_s(const time_t * restrict timer,
19470 struct tm * restrict result);
19471 struct tm *localtime_s(const time_t * restrict timer,
19472 struct tm * restrict result);
19473 <a name="B.26" href="#B.26"><b>B.26 Unicode utilities <uchar.h></b></a>
19474 mbstate_t size_t char16_t char32_t
19475 size_t mbrtoc16(char16_t * restrict pc16,
19476 const char * restrict s, size_t n,
19477 mbstate_t * restrict ps);
19478 size_t c16rtomb(char * restrict s, char16_t c16,
19479 mbstate_t * restrict ps);
19480 size_t mbrtoc32(char32_t * restrict pc32,
19481 const char * restrict s, size_t n,
19482 mbstate_t * restrict ps);
19483 size_t c32rtomb(char * restrict s, char32_t c32,
19484 mbstate_t * restrict ps);
19485 <a name="B.27" href="#B.27"><b>B.27 Extended multibyte/wide character utilities <wchar.h></b></a>
19486 wchar_t wint_t WCHAR_MAX
19487 size_t struct tm WCHAR_MIN
19488 mbstate_t NULL WEOF
19489 int fwprintf(FILE * restrict stream,
19490 const wchar_t * restrict format, ...);
19491 int fwscanf(FILE * restrict stream,
19492 const wchar_t * restrict format, ...);
19493 int swprintf(wchar_t * restrict s, size_t n,
19494 const wchar_t * restrict format, ...);
19495 int swscanf(const wchar_t * restrict s,
19496 const wchar_t * restrict format, ...);
19497 int vfwprintf(FILE * restrict stream,
19498 const wchar_t * restrict format, va_list arg);
19499 int vfwscanf(FILE * restrict stream,
19500 const wchar_t * restrict format, va_list arg);
19501 int vswprintf(wchar_t * restrict s, size_t n,
19502 const wchar_t * restrict format, va_list arg);
19506 [<a name="#p492" href="p492">page 492</a>] (<a href="#Contents">Contents</a>)
19508 int vswscanf(const wchar_t * restrict s,
19509 const wchar_t * restrict format, va_list arg);
19510 int vwprintf(const wchar_t * restrict format,
19512 int vwscanf(const wchar_t * restrict format,
19514 int wprintf(const wchar_t * restrict format, ...);
19515 int wscanf(const wchar_t * restrict format, ...);
19516 wint_t fgetwc(FILE *stream);
19517 wchar_t *fgetws(wchar_t * restrict s, int n,
19518 FILE * restrict stream);
19519 wint_t fputwc(wchar_t c, FILE *stream);
19520 int fputws(const wchar_t * restrict s,
19521 FILE * restrict stream);
19522 int fwide(FILE *stream, int mode);
19523 wint_t getwc(FILE *stream);
19524 wint_t getwchar(void);
19525 wint_t putwc(wchar_t c, FILE *stream);
19526 wint_t putwchar(wchar_t c);
19527 wint_t ungetwc(wint_t c, FILE *stream);
19528 double wcstod(const wchar_t * restrict nptr,
19529 wchar_t ** restrict endptr);
19530 float wcstof(const wchar_t * restrict nptr,
19531 wchar_t ** restrict endptr);
19532 long double wcstold(const wchar_t * restrict nptr,
19533 wchar_t ** restrict endptr);
19534 long int wcstol(const wchar_t * restrict nptr,
19535 wchar_t ** restrict endptr, int base);
19536 long long int wcstoll(const wchar_t * restrict nptr,
19537 wchar_t ** restrict endptr, int base);
19538 unsigned long int wcstoul(const wchar_t * restrict nptr,
19539 wchar_t ** restrict endptr, int base);
19540 unsigned long long int wcstoull(
19541 const wchar_t * restrict nptr,
19542 wchar_t ** restrict endptr, int base);
19543 wchar_t *wcscpy(wchar_t * restrict s1,
19544 const wchar_t * restrict s2);
19545 wchar_t *wcsncpy(wchar_t * restrict s1,
19546 const wchar_t * restrict s2, size_t n);
19550 [<a name="#p493" href="p493">page 493</a>] (<a href="#Contents">Contents</a>)
19552 wchar_t *wmemcpy(wchar_t * restrict s1,
19553 const wchar_t * restrict s2, size_t n);
19554 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
19556 wchar_t *wcscat(wchar_t * restrict s1,
19557 const wchar_t * restrict s2);
19558 wchar_t *wcsncat(wchar_t * restrict s1,
19559 const wchar_t * restrict s2, size_t n);
19560 int wcscmp(const wchar_t *s1, const wchar_t *s2);
19561 int wcscoll(const wchar_t *s1, const wchar_t *s2);
19562 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
19564 size_t wcsxfrm(wchar_t * restrict s1,
19565 const wchar_t * restrict s2, size_t n);
19566 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
19568 wchar_t *wcschr(const wchar_t *s, wchar_t c);
19569 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
19570 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
19571 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
19572 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
19573 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
19574 wchar_t *wcstok(wchar_t * restrict s1,
19575 const wchar_t * restrict s2,
19576 wchar_t ** restrict ptr);
19577 wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
19578 size_t wcslen(const wchar_t *s);
19579 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
19580 size_t wcsftime(wchar_t * restrict s, size_t maxsize,
19581 const wchar_t * restrict format,
19582 const struct tm * restrict timeptr);
19583 wint_t btowc(int c);
19584 int wctob(wint_t c);
19585 int mbsinit(const mbstate_t *ps);
19586 size_t mbrlen(const char * restrict s, size_t n,
19587 mbstate_t * restrict ps);
19588 size_t mbrtowc(wchar_t * restrict pwc,
19589 const char * restrict s, size_t n,
19590 mbstate_t * restrict ps);
19594 [<a name="#p494" href="p494">page 494</a>] (<a href="#Contents">Contents</a>)
19596 size_t wcrtomb(char * restrict s, wchar_t wc,
19597 mbstate_t * restrict ps);
19598 size_t mbsrtowcs(wchar_t * restrict dst,
19599 const char ** restrict src, size_t len,
19600 mbstate_t * restrict ps);
19601 size_t wcsrtombs(char * restrict dst,
19602 const wchar_t ** restrict src, size_t len,
19603 mbstate_t * restrict ps);
19604 __STDC_WANT_LIB_EXT1__
19607 int fwprintf_s(FILE * restrict stream,
19608 const wchar_t * restrict format, ...);
19609 int fwscanf_s(FILE * restrict stream,
19610 const wchar_t * restrict format, ...);
19611 int snwprintf_s(wchar_t * restrict s,
19613 const wchar_t * restrict format, ...);
19614 int swprintf_s(wchar_t * restrict s, rsize_t n,
19615 const wchar_t * restrict format, ...);
19616 int swscanf_s(const wchar_t * restrict s,
19617 const wchar_t * restrict format, ...);
19618 int vfwprintf_s(FILE * restrict stream,
19619 const wchar_t * restrict format,
19621 int vfwscanf_s(FILE * restrict stream,
19622 const wchar_t * restrict format, va_list arg);
19623 int vsnwprintf_s(wchar_t * restrict s,
19625 const wchar_t * restrict format,
19627 int vswprintf_s(wchar_t * restrict s,
19629 const wchar_t * restrict format,
19631 int vswscanf_s(const wchar_t * restrict s,
19632 const wchar_t * restrict format,
19637 [<a name="#p495" href="p495">page 495</a>] (<a href="#Contents">Contents</a>)
19639 int vwprintf_s(const wchar_t * restrict format,
19641 int vwscanf_s(const wchar_t * restrict format,
19643 int wprintf_s(const wchar_t * restrict format, ...);
19644 int wscanf_s(const wchar_t * restrict format, ...);
19645 errno_t wcscpy_s(wchar_t * restrict s1,
19647 const wchar_t * restrict s2);
19648 errno_t wcsncpy_s(wchar_t * restrict s1,
19650 const wchar_t * restrict s2,
19652 errno_t wmemcpy_s(wchar_t * restrict s1,
19654 const wchar_t * restrict s2,
19656 errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
19657 const wchar_t *s2, rsize_t n);
19658 errno_t wcscat_s(wchar_t * restrict s1,
19660 const wchar_t * restrict s2);
19661 errno_t wcsncat_s(wchar_t * restrict s1,
19663 const wchar_t * restrict s2,
19665 wchar_t *wcstok_s(wchar_t * restrict s1,
19666 rsize_t * restrict s1max,
19667 const wchar_t * restrict s2,
19668 wchar_t ** restrict ptr);
19669 size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
19670 errno_t wcrtomb_s(size_t * restrict retval,
19671 char * restrict s, rsize_t smax,
19672 wchar_t wc, mbstate_t * restrict ps);
19673 errno_t mbsrtowcs_s(size_t * restrict retval,
19674 wchar_t * restrict dst, rsize_t dstmax,
19675 const char ** restrict src, rsize_t len,
19676 mbstate_t * restrict ps);
19681 [<a name="#p496" href="p496">page 496</a>] (<a href="#Contents">Contents</a>)
19683 errno_t wcsrtombs_s(size_t * restrict retval,
19684 char * restrict dst, rsize_t dstmax,
19685 const wchar_t ** restrict src, rsize_t len,
19686 mbstate_t * restrict ps);
19687 <a name="B.28" href="#B.28"><b>B.28 Wide character classification and mapping utilities <wctype.h></b></a>
19688 wint_t wctrans_t wctype_t WEOF
19689 int iswalnum(wint_t wc);
19690 int iswalpha(wint_t wc);
19691 int iswblank(wint_t wc);
19692 int iswcntrl(wint_t wc);
19693 int iswdigit(wint_t wc);
19694 int iswgraph(wint_t wc);
19695 int iswlower(wint_t wc);
19696 int iswprint(wint_t wc);
19697 int iswpunct(wint_t wc);
19698 int iswspace(wint_t wc);
19699 int iswupper(wint_t wc);
19700 int iswxdigit(wint_t wc);
19701 int iswctype(wint_t wc, wctype_t desc);
19702 wctype_t wctype(const char *property);
19703 wint_t towlower(wint_t wc);
19704 wint_t towupper(wint_t wc);
19705 wint_t towctrans(wint_t wc, wctrans_t desc);
19706 wctrans_t wctrans(const char *property);
19711 [<a name="#p497" href="p497">page 497</a>] (<a href="#Contents">Contents</a>)
19713 <a name="C" href="#C"><b> Annex C</b></a>
19716 1 The following are the sequence points described in <a href="#5.1.2.3">5.1.2.3</a>:
19717 -- Between the evaluations of the function designator and actual arguments in a function
19718 call and the actual call. (<a href="#6.5.2.2">6.5.2.2</a>).
19719 -- Between the evaluations of the first and second operands of the following operators:
19720 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>).
19721 -- Between the evaluations of the first operand of the conditional ? : operator and
19722 whichever of the second and third operands is evaluated (<a href="#6.5.15">6.5.15</a>).
19723 -- The end of a full declarator: declarators (<a href="#6.7.6">6.7.6</a>);
19724 -- Between the evaluation of a full expression and the next full expression to be
19725 evaluated. The following are full expressions: an initializer that is not part of a
19726 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
19727 controlling expression of a selection statement (if or switch) (<a href="#6.8.4">6.8.4</a>); the
19728 controlling expression of a while or do statement (<a href="#6.8.5">6.8.5</a>); each of the (optional)
19729 expressions of a for statement (<a href="#6.8.5.3">6.8.5.3</a>); the (optional) expression in a return
19730 statement (<a href="#6.8.6.4">6.8.6.4</a>).
19731 -- Immediately before a library function returns (<a href="#7.1.4">7.1.4</a>).
19732 -- After the actions associated with each formatted input/output function conversion
19733 specifier (<a href="#7.21.6">7.21.6</a>, <a href="#7.28.2">7.28.2</a>).
19734 -- Immediately before and immediately after each call to a comparison function, and
19735 also between any call to a comparison function and any movement of the objects
19736 passed as arguments to that call (<a href="#7.22.5">7.22.5</a>).
19741 [<a name="#p498" href="p498">page 498</a>] (<a href="#Contents">Contents</a>)
19743 <a name="D" href="#D"><b> Annex D</b></a>
19745 Universal character names for identifiers
19746 1 This clause lists the hexadecimal code values that are valid in universal character names
19748 2 This table is reproduced unchanged from ISO/IEC TR 10176:1998, produced by ISO/IEC
19749 JTC 1/SC 22/WG 20, except for the omission of ranges that are part of the basic character
19751 Latin: 00AA, 00BA, 00C0-00D6, 00D8-00F6, 00F8-01F5, 01FA-0217,
19752 0250-02A8, 1E00-1E9B, 1EA0-1EF9, 207F
19753 Greek: 0386, 0388-038A, 038C, 038E-03A1, 03A3-03CE, 03D0-03D6,
19754 03DA, 03DC, 03DE, 03E0, 03E2-03F3, 1F00-1F15, 1F18-1F1D,
19755 1F20-1F45, 1F48-1F4D, 1F50-1F57, 1F59, 1F5B, 1F5D,
19756 1F5F-1F7D, 1F80-1FB4, 1FB6-1FBC, 1FC2-1FC4, 1FC6-1FCC,
19757 1FD0-1FD3, 1FD6-1FDB, 1FE0-1FEC, 1FF2-1FF4, 1FF6-1FFC
19758 Cyrillic: 0401-040C, 040E-044F, 0451-045C, 045E-0481, 0490-04C4,
19759 04C7-04C8, 04CB-04CC, 04D0-04EB, 04EE-04F5, 04F8-04F9
19760 Armenian: 0531-0556, 0561-0587
19761 Hebrew: 05B0-05B9, 05BB-05BD, 05BF, 05C1-05C2, 05D0-05EA,
19763 Arabic: 0621-063A, 0640-0652, 0670-06B7, 06BA-06BE, 06C0-06CE,
19764 06D0-06DC, 06E5-06E8, 06EA-06ED
19765 Devanagari: 0901-0903, 0905-0939, 093E-094D, 0950-0952, 0958-0963
19766 Bengali: 0981-0983, 0985-098C, 098F-0990, 0993-09A8, 09AA-09B0,
19767 09B2, 09B6-09B9, 09BE-09C4, 09C7-09C8, 09CB-09CD,
19768 09DC-09DD, 09DF-09E3, 09F0-09F1
19769 Gurmukhi: 0A02, 0A05-0A0A, 0A0F-0A10, 0A13-0A28, 0A2A-0A30,
19770 0A32-0A33, 0A35-0A36, 0A38-0A39, 0A3E-0A42, 0A47-0A48,
19771 0A4B-0A4D, 0A59-0A5C, 0A5E, 0A74
19772 Gujarati: 0A81-0A83, 0A85-0A8B, 0A8D, 0A8F-0A91, 0A93-0AA8,
19773 0AAA-0AB0, 0AB2-0AB3, 0AB5-0AB9, 0ABD-0AC5,
19774 0AC7-0AC9, 0ACB-0ACD, 0AD0, 0AE0
19775 Oriya: 0B01-0B03, 0B05-0B0C, 0B0F-0B10, 0B13-0B28, 0B2A-0B30,
19776 0B32-0B33, 0B36-0B39, 0B3E-0B43, 0B47-0B48, 0B4B-0B4D,
19777 [<a name="#p499" href="p499">page 499</a>] (<a href="#Contents">Contents</a>)
19779 0B5C-0B5D, 0B5F-0B61
19780 Tamil: 0B82-0B83, 0B85-0B8A, 0B8E-0B90, 0B92-0B95, 0B99-0B9A,
19781 0B9C, 0B9E-0B9F, 0BA3-0BA4, 0BA8-0BAA, 0BAE-0BB5,
19782 0BB7-0BB9, 0BBE-0BC2, 0BC6-0BC8, 0BCA-0BCD
19783 Telugu: 0C01-0C03, 0C05-0C0C, 0C0E-0C10, 0C12-0C28, 0C2A-0C33,
19784 0C35-0C39, 0C3E-0C44, 0C46-0C48, 0C4A-0C4D, 0C60-0C61
19785 Kannada: 0C82-0C83, 0C85-0C8C, 0C8E-0C90, 0C92-0CA8, 0CAA-0CB3,
19786 0CB5-0CB9, 0CBE-0CC4, 0CC6-0CC8, 0CCA-0CCD, 0CDE,
19788 Malayalam: 0D02-0D03, 0D05-0D0C, 0D0E-0D10, 0D12-0D28, 0D2A-0D39,
19789 0D3E-0D43, 0D46-0D48, 0D4A-0D4D, 0D60-0D61
19790 Thai: 0E01-0E3A, 0E40-0E5B
19791 Lao: 0E81-0E82, 0E84, 0E87-0E88, 0E8A, 0E8D, 0E94-0E97,
19792 0E99-0E9F, 0EA1-0EA3, 0EA5, 0EA7, 0EAA-0EAB,
19793 0EAD-0EAE, 0EB0-0EB9, 0EBB-0EBD, 0EC0-0EC4, 0EC6,
19794 0EC8-0ECD, 0EDC-0EDD
19795 Tibetan: 0F00, 0F18-0F19, 0F35, 0F37, 0F39, 0F3E-0F47, 0F49-0F69,
19796 0F71-0F84, 0F86-0F8B, 0F90-0F95, 0F97, 0F99-0FAD,
19798 Georgian: 10A0-10C5, 10D0-10F6
19799 Hiragana: 3041-3093, 309B-309C
19800 Katakana: 30A1-30F6, 30FB-30FC
19801 Bopomofo: 3105-312C
19802 CJK Unified Ideographs: 4E00-9FA5
19804 Digits: 0660-0669, 06F0-06F9, 0966-096F, 09E6-09EF, 0A66-0A6F,
19805 0AE6-0AEF, 0B66-0B6F, 0BE7-0BEF, 0C66-0C6F, 0CE6-0CEF,
19806 0D66-0D6F, 0E50-0E59, 0ED0-0ED9, 0F20-0F33
19807 Special characters: 00B5, 00B7, 02B0-02B8, 02BB, 02BD-02C1, 02D0-02D1,
19808 02E0-02E4, 037A, 0559, 093D, 0B3D, 1FBE, 203F-2040, 2102,
19809 2107, 210A-2113, 2115, 2118-211D, 2124, 2126, 2128, 212A-2131,
19810 2133-2138, 2160-2182, 3005-3007, 3021-3029
19815 [<a name="#p500" href="p500">page 500</a>] (<a href="#Contents">Contents</a>)
19817 <a name="E" href="#E"><b> Annex E</b></a>
19819 Implementation limits
19820 1 The contents of the header <a href="#7.10"><limits.h></a> are given below, in alphabetical order. The
19821 minimum magnitudes shown shall be replaced by implementation-defined magnitudes
19822 with the same sign. The values shall all be constant expressions suitable for use in #if
19823 preprocessing directives. The components are described further in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
19825 #define CHAR_MAX UCHAR_MAX or SCHAR_MAX
19826 #define CHAR_MIN 0 or SCHAR_MIN
19827 #define INT_MAX +32767
19828 #define INT_MIN -32767
19829 #define LONG_MAX +2147483647
19830 #define LONG_MIN -2147483647
19831 #define LLONG_MAX +9223372036854775807
19832 #define LLONG_MIN -9223372036854775807
19833 #define MB_LEN_MAX 1
19834 #define SCHAR_MAX +127
19835 #define SCHAR_MIN -127
19836 #define SHRT_MAX +32767
19837 #define SHRT_MIN -32767
19838 #define UCHAR_MAX 255
19839 #define USHRT_MAX 65535
19840 #define UINT_MAX 65535
19841 #define ULONG_MAX 4294967295
19842 #define ULLONG_MAX 18446744073709551615
19843 2 The contents of the header <a href="#7.7"><float.h></a> are given below. All integer values, except
19844 FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing
19845 directives; all floating values shall be constant expressions. The components are
19846 described further in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
19847 3 The values given in the following list shall be replaced by implementation-defined
19849 #define FLT_EVAL_METHOD
19851 4 The values given in the following list shall be replaced by implementation-defined
19852 constant expressions that are greater or equal in magnitude (absolute value) to those
19853 shown, with the same sign:
19854 [<a name="#p501" href="p501">page 501</a>] (<a href="#Contents">Contents</a>)
19856 #define DLB_DECIMAL_DIG 10
19858 #define DBL_MANT_DIG
19859 #define DBL_MAX_10_EXP +37
19860 #define DBL_MAX_EXP
19861 #define DBL_MIN_10_EXP -37
19862 #define DBL_MIN_EXP
19863 #define DECIMAL_DIG 10
19864 #define FLT_DECIMAL_DIG 6
19866 #define FLT_MANT_DIG
19867 #define FLT_MAX_10_EXP +37
19868 #define FLT_MAX_EXP
19869 #define FLT_MIN_10_EXP -37
19870 #define FLT_MIN_EXP
19871 #define FLT_RADIX 2
19872 #define LDLB_DECIMAL_DIG 10
19873 #define LDBL_DIG 10
19874 #define LDBL_MANT_DIG
19875 #define LDBL_MAX_10_EXP +37
19876 #define LDBL_MAX_EXP
19877 #define LDBL_MIN_10_EXP -37
19878 #define LDBL_MIN_EXP
19879 5 The values given in the following list shall be replaced by implementation-defined
19880 constant expressions with values that are greater than or equal to those shown:
19881 #define DBL_MAX 1E+37
19882 #define FLT_MAX 1E+37
19883 #define LDBL_MAX 1E+37
19884 6 The values given in the following list shall be replaced by implementation-defined
19885 constant expressions with (positive) values that are less than or equal to those shown:
19886 #define DBL_EPSILON 1E-9
19887 #define DBL_MIN 1E-37
19888 #define FLT_EPSILON 1E-5
19889 #define FLT_MIN 1E-37
19890 #define LDBL_EPSILON 1E-9
19891 #define LDBL_MIN 1E-37
19896 [<a name="#p502" href="p502">page 502</a>] (<a href="#Contents">Contents</a>)
19898 <a name="F" href="#F"><b> Annex F</b></a>
19900 IEC 60559 floating-point arithmetic
19901 <a name="F.1" href="#F.1"><b> F.1 Introduction</b></a>
19902 1 This annex specifies C language support for the IEC 60559 floating-point standard. The
19903 IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
19904 microprocessor systems, second edition (IEC 60559:1989), previously designated
19905 IEC 559:1989 and as IEEE Standard for Binary Floating-Point Arithmetic
19906 (ANSI/IEEE 754-1985). IEEE Standard for Radix-Independent Floating-Point
19907 Arithmetic (ANSI/IEEE 854-1987) generalizes the binary standard to remove
19908 dependencies on radix and word length. IEC 60559 generally refers to the floating-point
19909 standard, as in IEC 60559 operation, IEC 60559 format, etc. An implementation that
19910 defines __STDC_IEC_559__ shall conform to the specifications in this annex.339)
19911 Where a binding between the C language and IEC 60559 is indicated, the
19912 IEC 60559-specified behavior is adopted by reference, unless stated otherwise. Since
19913 negative and positive infinity are representable in IEC 60559 formats, all real numbers lie
19914 within the range of representable values.
19915 <a name="F.2" href="#F.2"><b> F.2 Types</b></a>
19916 1 The C floating types match the IEC 60559 formats as follows:
19917 -- The float type matches the IEC 60559 single format.
19918 -- The double type matches the IEC 60559 double format.
19919 -- The long double type matches an IEC 60559 extended format,340) else a
19920 non-IEC 60559 extended format, else the IEC 60559 double format.
19921 Any non-IEC 60559 extended format used for the long double type shall have more
19922 precision than IEC 60559 double and at least the range of IEC 60559 double.341)
19927 339) Implementations that do not define __STDC_IEC_559__ are not required to conform to these
19929 340) ''Extended'' is IEC 60559's double-extended data format. Extended refers to both the common 80-bit
19930 and quadruple 128-bit IEC 60559 formats.
19931 341) A non-IEC 60559 long double type is required to provide infinity and NaNs, as its values include
19934 [<a name="#p503" href="p503">page 503</a>] (<a href="#Contents">Contents</a>)
19936 Recommended practice
19937 2 The long double type should match an IEC 60559 extended format.
19938 <a name="F.2.1" href="#F.2.1"><b> F.2.1 Infinities, signed zeros, and NaNs</b></a>
19939 1 This specification does not define the behavior of signaling NaNs.342) It generally uses
19940 the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
19941 functions in <a href="#7.12"><math.h></a> provide designations for IEC 60559 NaNs and infinities.
19942 <a name="F.3" href="#F.3"><b> F.3 Operators and functions</b></a>
19943 1 C operators and functions provide IEC 60559 required and recommended facilities as
19945 -- The +, -, *, and / operators provide the IEC 60559 add, subtract, multiply, and
19947 -- The sqrt functions in <a href="#7.12"><math.h></a> provide the IEC 60559 square root operation.
19948 -- The remainder functions in <a href="#7.12"><math.h></a> provide the IEC 60559 remainder
19949 operation. The remquo functions in <a href="#7.12"><math.h></a> provide the same operation but
19950 with additional information.
19951 -- The rint functions in <a href="#7.12"><math.h></a> provide the IEC 60559 operation that rounds a
19952 floating-point number to an integer value (in the same precision). The nearbyint
19953 functions in <a href="#7.12"><math.h></a> provide the nearbyinteger function recommended in the
19954 Appendix to ANSI/IEEE 854.
19955 -- The conversions for floating types provide the IEC 60559 conversions between
19956 floating-point precisions.
19957 -- The conversions from integer to floating types provide the IEC 60559 conversions
19958 from integer to floating point.
19959 -- The conversions from floating to integer types provide IEC 60559-like conversions
19960 but always round toward zero.
19961 -- The lrint and llrint functions in <a href="#7.12"><math.h></a> provide the IEC 60559
19962 conversions, which honor the directed rounding mode, from floating point to the
19963 long int and long long int integer formats. The lrint and llrint
19964 functions can be used to implement IEC 60559 conversions from floating to other
19966 -- The translation time conversion of floating constants and the strtod, strtof,
19967 strtold, fprintf, fscanf, and related library functions in <a href="#7.22"><stdlib.h></a>,
19970 342) Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are
19971 sufficient for closure of the arithmetic.
19973 [<a name="#p504" href="p504">page 504</a>] (<a href="#Contents">Contents</a>)
19975 <a href="#7.21"><stdio.h></a>, and <a href="#7.28"><wchar.h></a> provide IEC 60559 binary-decimal conversions. The
19976 strtold function in <a href="#7.22"><stdlib.h></a> provides the conv function recommended in the
19977 Appendix to ANSI/IEEE 854.
19978 -- The relational and equality operators provide IEC 60559 comparisons. IEC 60559
19979 identifies a need for additional comparison predicates to facilitate writing code that
19980 accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
19981 isless, islessequal, islessgreater, and isunordered) in <a href="#7.12"><math.h></a>
19982 supplement the language operators to address this need. The islessgreater and
19983 isunordered macros provide respectively a quiet version of the <> predicate and
19984 the unordered predicate recommended in the Appendix to IEC 60559.
19985 -- The feclearexcept, feraiseexcept, and fetestexcept functions in
19986 <a href="#7.6"><fenv.h></a> provide the facility to test and alter the IEC 60559 floating-point
19987 exception status flags. The fegetexceptflag and fesetexceptflag
19988 functions in <a href="#7.6"><fenv.h></a> provide the facility to save and restore all five status flags at
19989 one time. These functions are used in conjunction with the type fexcept_t and the
19990 floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
19991 FE_UNDERFLOW, FE_OVERFLOW, FE_INVALID) also in <a href="#7.6"><fenv.h></a>.
19992 -- The fegetround and fesetround functions in <a href="#7.6"><fenv.h></a> provide the facility
19993 to select among the IEC 60559 directed rounding modes represented by the rounding
19994 direction macros in <a href="#7.6"><fenv.h></a> (FE_TONEAREST, FE_UPWARD, FE_DOWNWARD,
19995 FE_TOWARDZERO) and the values 0, 1, 2, and 3 of FLT_ROUNDS are the
19996 IEC 60559 directed rounding modes.
19997 -- The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
19998 <a href="#7.6"><fenv.h></a> provide a facility to manage the floating-point environment, comprising
19999 the IEC 60559 status flags and control modes.
20000 -- The copysign functions in <a href="#7.12"><math.h></a> provide the copysign function
20001 recommended in the Appendix to IEC 60559.
20002 -- The fabs functions in <a href="#7.12"><math.h></a> provide the abs function recommended in the
20003 Appendix to IEC 60559.
20004 -- The unary minus (-) operator provides the unary minus (-) operation recommended
20005 in the Appendix to IEC 60559.
20006 -- The scalbn and scalbln functions in <a href="#7.12"><math.h></a> provide the scalb function
20007 recommended in the Appendix to IEC 60559.
20008 -- The logb functions in <a href="#7.12"><math.h></a> provide the logb function recommended in the
20009 Appendix to IEC 60559, but following the newer specifications in ANSI/IEEE 854.
20010 -- The nextafter and nexttoward functions in <a href="#7.12"><math.h></a> provide the nextafter
20011 function recommended in the Appendix to IEC 60559 (but with a minor change to
20013 [<a name="#p505" href="p505">page 505</a>] (<a href="#Contents">Contents</a>)
20015 better handle signed zeros).
20016 -- The isfinite macro in <a href="#7.12"><math.h></a> provides the finite function recommended in
20017 the Appendix to IEC 60559.
20018 -- The isnan macro in <a href="#7.12"><math.h></a> provides the isnan function recommended in the
20019 Appendix to IEC 60559.
20020 -- The signbit macro and the fpclassify macro in <a href="#7.12"><math.h></a>, used in
20021 conjunction with the number classification macros (FP_NAN, FP_INFINITE,
20022 FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
20023 function recommended in the Appendix to IEC 60559 (except that the classification
20024 macros defined in <a href="#7.12.3">7.12.3</a> do not distinguish signaling from quiet NaNs).
20025 <a name="F.4" href="#F.4"><b> F.4 Floating to integer conversion</b></a>
20026 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
20027 (even for NaN). Otherwise, if the floating value is infinite or NaN or if the integral part
20028 of the floating value exceeds the range of the integer type, then the ''invalid'' floating-
20029 point exception is raised and the resulting value is unspecified. Otherwise, the resulting
20030 value is determined by <a href="#6.3.1.4">6.3.1.4</a>. Conversion of an integral floating value that does not
20031 exceed the range of the integer type raises no floating-point exceptions; whether
20032 conversion of a non-integral floating value raises the ''inexact'' floating-point exception is
20034 <a name="F.5" href="#F.5"><b> F.5 Binary-decimal conversion</b></a>
20035 1 Conversion from the widest supported IEC 60559 format to decimal with
20036 DECIMAL_DIG digits and back is the identity function.344)
20037 2 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
20038 particular, conversion between any supported IEC 60559 format and decimal with
20039 DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
20040 rounding mode), which assures that conversion from the widest supported IEC 60559
20041 format to decimal with DECIMAL_DIG digits and back is the identity function.
20045 343) ANSI/IEEE 854, but not IEC 60559 (ANSI/IEEE 754), directly specifies that floating-to-integer
20046 conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those
20047 cases where it matters, library functions can be used to effect such conversions with or without raising
20048 the ''inexact'' floating-point exception. See rint, lrint, llrint, and nearbyint in
20049 <a href="#7.12"><math.h></a>.
20050 344) If the minimum-width IEC 60559 extended format (64 bits of precision) is supported,
20051 DECIMAL_DIG shall be at least 21. If IEC 60559 double (53 bits of precision) is the widest
20052 IEC 60559 format supported, then DECIMAL_DIG shall be at least 17. (By contrast, LDBL_DIG and
20053 DBL_DIG are 18 and 15, respectively, for these formats.)
20055 [<a name="#p506" href="p506">page 506</a>] (<a href="#Contents">Contents</a>)
20057 3 Functions such as strtod that convert character sequences to floating types honor the
20058 rounding direction. Hence, if the rounding direction might be upward or downward, the
20059 implementation cannot convert a minus-signed sequence by negating the converted
20061 <a name="F.6" href="#F.6"><b> F.6 The return statement</b></a>
20062 If the return expression is evaluated in a floating-point format different from the return
20063 type, the expression is converted to the return type of the function and the resulting value
20064 is returned to the caller.
20065 <a name="F.7" href="#F.7"><b> F.7 Contracted expressions</b></a>
20066 1 A contracted expression is correctly rounded (once) and treats infinities, NaNs, signed
20067 zeros, subnormals, and the rounding directions in a manner consistent with the basic
20068 arithmetic operations covered by IEC 60559.
20069 Recommended practice
20070 2 A contracted expression should raise floating-point exceptions in a manner generally
20071 consistent with the basic arithmetic operations.
20072 <a name="F.8" href="#F.8"><b> F.8 Floating-point environment</b></a>
20073 1 The floating-point environment defined in <a href="#7.6"><fenv.h></a> includes the IEC 60559 floating-
20074 point exception status flags and directed-rounding control modes. It includes also
20075 IEC 60559 dynamic rounding precision and trap enablement modes, if the
20076 implementation supports them.345)
20077 <a name="F.8.1" href="#F.8.1"><b> F.8.1 Environment management</b></a>
20078 1 IEC 60559 requires that floating-point operations implicitly raise floating-point exception
20079 status flags, and that rounding control modes can be set explicitly to affect result values of
20080 floating-point operations. When the state for the FENV_ACCESS pragma (defined in
20081 <a href="#7.6"><fenv.h></a>) is ''on'', these changes to the floating-point state are treated as side effects
20082 which respect sequence points.346)
20087 345) This specification does not require dynamic rounding precision nor trap enablement modes.
20088 346) If the state for the FENV_ACCESS pragma is ''off'', the implementation is free to assume the floating-
20089 point control modes will be the default ones and the floating-point status flags will not be tested,
20090 which allows certain optimizations (see <a href="#F.9">F.9</a>).
20092 [<a name="#p507" href="p507">page 507</a>] (<a href="#Contents">Contents</a>)
20094 <a name="F.8.2" href="#F.8.2"><b> F.8.2 Translation</b></a>
20095 1 During translation the IEC 60559 default modes are in effect:
20096 -- The rounding direction mode is rounding to nearest.
20097 -- The rounding precision mode (if supported) is set so that results are not shortened.
20098 -- Trapping or stopping (if supported) is disabled on all floating-point exceptions.
20099 Recommended practice
20100 2 The implementation should produce a diagnostic message for each translation-time
20101 floating-point exception, other than ''inexact'';347) the implementation should then
20102 proceed with the translation of the program.
20103 <a name="F.8.3" href="#F.8.3"><b> F.8.3 Execution</b></a>
20104 1 At program startup the floating-point environment is initialized as prescribed by
20106 -- All floating-point exception status flags are cleared.
20107 -- The rounding direction mode is rounding to nearest.
20108 -- The dynamic rounding precision mode (if supported) is set so that results are not
20110 -- Trapping or stopping (if supported) is disabled on all floating-point exceptions.
20111 <a name="F.8.4" href="#F.8.4"><b> F.8.4 Constant expressions</b></a>
20112 1 An arithmetic constant expression of floating type, other than one in an initializer for an
20113 object that has static or thread storage duration, is evaluated (as if) during execution; thus,
20114 it is affected by any operative floating-point control modes and raises floating-point
20115 exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma
20121 347) As floating constants are converted to appropriate internal representations at translation time, their
20122 conversion is subject to default rounding modes and raises no execution-time floating-point exceptions
20123 (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example
20124 strtod, provide execution-time conversion of numeric strings.
20125 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
20126 are affected by rounding modes set at execution time, and expressions such as 0.0/0.0 and
20127 <a href="#1.0">1.0</a>/0.0 generate execution-time floating-point exceptions. The programmer can achieve the
20128 efficiency of translation-time evaluation through static initialization, such as
20129 const static double one_third = <a href="#1.0">1.0</a>/3.0;
20132 [<a name="#p508" href="p508">page 508</a>] (<a href="#Contents">Contents</a>)
20134 #include <a href="#7.6"><fenv.h></a>
20135 #pragma STDC FENV_ACCESS ON
20138 float w[] = { 0.0/0.0 }; // raises an exception
20139 static float x = 0.0/0.0; // does not raise an exception
20140 float y = 0.0/0.0; // raises an exception
20141 double z = 0.0/0.0; // raises an exception
20144 3 For the static initialization, the division is done at translation time, raising no (execution-time) floating-
20145 point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at
20148 <a name="F.8.5" href="#F.8.5"><b> F.8.5 Initialization</b></a>
20149 1 All computation for automatic initialization is done (as if) at execution time; thus, it is
20150 affected by any operative modes and raises floating-point exceptions as required by
20151 IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation
20152 for initialization of objects that have static or thread storage duration is done (as if) at
20155 #include <a href="#7.6"><fenv.h></a>
20156 #pragma STDC FENV_ACCESS ON
20159 float u[] = { 1.1e75 }; // raises exceptions
20160 static float v = 1.1e75; // does not raise exceptions
20161 float w = 1.1e75; // raises exceptions
20162 double x = 1.1e75; // may raise exceptions
20163 float y = 1.1e75f; // may raise exceptions
20164 long double z = 1.1e75; // does not raise exceptions
20167 3 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is
20168 done at translation time. The automatic initialization of u and w require an execution-time conversion to
20169 float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations
20170 of x and y entail execution-time conversion; however, in some expression evaluation methods, the
20171 conversions is not to a narrower format, in which case no floating-point exception is raised.349) The
20172 automatic initialization of z entails execution-time conversion, but not to a narrower format, so no floating-
20173 point exception is raised. Note that the conversions of the floating constants 1.1e75 and 1.1e75f to
20177 349) Use of float_t and double_t variables increases the likelihood of translation-time computation.
20178 For example, the automatic initialization
20179 double_t x = 1.1e75;
20180 could be done at translation time, regardless of the expression evaluation method.
20182 [<a name="#p509" href="p509">page 509</a>] (<a href="#Contents">Contents</a>)
20184 their internal representations occur at translation time in all cases.
20186 <a name="F.8.6" href="#F.8.6"><b> F.8.6 Changing the environment</b></a>
20187 1 Operations defined in <a href="#6.5">6.5</a> and functions and macros defined for the standard libraries
20188 change floating-point status flags and control modes just as indicated by their
20189 specifications (including conformance to IEC 60559). They do not change flags or modes
20190 (so as to be detectable by the user) in any other cases.
20191 2 If the argument to the feraiseexcept function in <a href="#7.6"><fenv.h></a> represents IEC 60559
20192 valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
20193 ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
20194 before ''inexact''.
20195 <a name="F.9" href="#F.9"><b> F.9 Optimization</b></a>
20196 1 This section identifies code transformations that might subvert IEC 60559-specified
20197 behavior, and others that do not.
20198 <a name="F.9.1" href="#F.9.1"><b> F.9.1 Global transformations</b></a>
20199 1 Floating-point arithmetic operations and external function calls may entail side effects
20200 which optimization shall honor, at least where the state of the FENV_ACCESS pragma is
20201 ''on''. The flags and modes in the floating-point environment may be regarded as global
20202 variables; floating-point operations (+, *, etc.) implicitly read the modes and write the
20204 2 Concern about side effects may inhibit code motion and removal of seemingly useless
20205 code. For example, in
20206 #include <a href="#7.6"><fenv.h></a>
20207 #pragma STDC FENV_ACCESS ON
20211 for (i = 0; i < n; i++) x + 1;
20214 x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
20215 body might not execute (maybe 0 >= n), x + 1 cannot be moved out of the loop. (Of
20216 course these optimizations are valid if the implementation can rule out the nettlesome
20218 3 This specification does not require support for trap handlers that maintain information
20219 about the order or count of floating-point exceptions. Therefore, between function calls,
20220 floating-point exceptions need not be precise: the actual order and number of occurrences
20221 of floating-point exceptions (> 1) may vary from what the source code expresses. Thus,
20222 [<a name="#p510" href="p510">page 510</a>] (<a href="#Contents">Contents</a>)
20224 the preceding loop could be treated as
20225 if (0 < n) x + 1;
20226 <a name="F.9.2" href="#F.9.2"><b> F.9.2 Expression transformations</b></a>
20227 1 x/2 (<->) x x 0.5 Although similar transformations involving inexact constants
20228 generally do not yield numerically equivalent expressions, if the
20229 constants are exact then such transformations can be made on
20230 IEC 60559 machines and others that round perfectly.
20231 1 x x and x/1 (->) x The expressions 1 x x, x/1, and x are equivalent (on IEC 60559
20232 machines, among others).350)
20233 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,
20235 x - y (<->) x + (-y) The expressions x - y, x + (-y), and (-y) + x are equivalent (on
20236 IEC 60559 machines, among others).
20237 x - y (<->) -(y - x) The expressions x - y and -(y - x) are not equivalent because 1 - 1
20238 is +0 but -(1 - 1) is -0 (in the default rounding direction).351)
20239 x - x (->) 0.0 The expressions x - x and 0.0 are not equivalent if x is a NaN or
20241 0 x x (->) 0.0 The expressions 0 x x and 0.0 are not equivalent if x is a NaN,
20243 x+0(->) x The expressions x + 0 and x are not equivalent if x is -0, because
20244 (-0) + (+0) yields +0 (in the default rounding direction), not -0.
20245 x-0(->) x (+0) - (+0) yields -0 when rounding is downward (toward -(inf)), but
20246 +0 otherwise, and (-0) - (+0) always yields -0; so, if the state of the
20247 FENV_ACCESS pragma is ''off'', promising default rounding, then
20248 the implementation can replace x - 0 by x, even if x might be zero.
20249 -x (<->) 0 - x The expressions -x and 0 - x are not equivalent if x is +0, because
20250 -(+0) yields -0, but 0 - (+0) yields +0 (unless rounding is
20253 350) Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
20254 other transformations that remove arithmetic operators.
20255 351) IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
20257 1/(1/ (+-) (inf)) is (+-) (inf)
20259 conj(csqrt(z)) is csqrt(conj(z)),
20262 [<a name="#p511" href="p511">page 511</a>] (<a href="#Contents">Contents</a>)
20264 <a name="F.9.3" href="#F.9.3"><b> F.9.3 Relational operators</b></a>
20265 1 x != x (->) false The expression x != x is true if x is a NaN.
20266 x = x (->) true The expression x = x is false if x is a NaN.
20267 x < y (->) isless(x,y) (and similarly for <=, >, >=) Though numerically equal, these
20268 expressions are not equivalent because of side effects when x or y is a
20269 NaN and the state of the FENV_ACCESS pragma is ''on''. This
20270 transformation, which would be desirable if extra code were required
20271 to cause the ''invalid'' floating-point exception for unordered cases,
20272 could be performed provided the state of the FENV_ACCESS pragma
20274 The sense of relational operators shall be maintained. This includes handling unordered
20275 cases as expressed by the source code.
20277 // calls g and raises ''invalid'' if a and b are unordered
20282 is not equivalent to
20283 // calls f and raises ''invalid'' if a and b are unordered
20289 // calls f without raising ''invalid'' if a and b are unordered
20290 if (isgreaterequal(a,b))
20294 nor, unless the state of the FENV_ACCESS pragma is ''off'', to
20295 // calls g without raising ''invalid'' if a and b are unordered
20300 but is equivalent to
20305 [<a name="#p512" href="p512">page 512</a>] (<a href="#Contents">Contents</a>)
20312 <a name="F.9.4" href="#F.9.4"><b> F.9.4 Constant arithmetic</b></a>
20313 1 The implementation shall honor floating-point exceptions raised by execution-time
20314 constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See <a href="#F.8.4">F.8.4</a>
20315 and <a href="#F.8.5">F.8.5</a>.) An operation on constants that raises no floating-point exception can be
20316 folded during translation, except, if the state of the FENV_ACCESS pragma is ''on'', a
20317 further check is required to assure that changing the rounding direction to downward does
20318 not alter the sign of the result,352) and implementations that support dynamic rounding
20319 precision modes shall assure further that the result of the operation raises no floating-
20320 point exception when converted to the semantic type of the operation.
20321 <a name="F.10" href="#F.10"><b> F.10 Mathematics <math.h></b></a>
20322 1 This subclause contains specifications of <a href="#7.12"><math.h></a> facilities that are particularly suited
20323 for IEC 60559 implementations.
20324 2 The Standard C macro HUGE_VAL and its float and long double analogs,
20325 HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive
20327 3 Special cases for functions in <a href="#7.12"><math.h></a> are covered directly or indirectly by
20328 IEC 60559. The functions that IEC 60559 specifies directly are identified in <a href="#F.3">F.3</a>. The
20329 other functions in <a href="#7.12"><math.h></a> treat infinities, NaNs, signed zeros, subnormals, and
20330 (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags
20331 in a manner consistent with the basic arithmetic operations covered by IEC 60559.
20332 4 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
20334 5 The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in
20335 subsequent subclauses of this annex.
20336 6 The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of
20337 rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value
20338 whose magnitude is too large.
20339 7 The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially
20340 subnormal or zero) and suffers loss of accuracy.353)
20343 352) 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
20344 353) IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on
20345 when the floating-point exception is raised.
20347 [<a name="#p513" href="p513">page 513</a>] (<a href="#Contents">Contents</a>)
20349 8 Whether or when library functions raise the ''inexact'' floating-point exception is
20350 unspecified, unless explicitly specified otherwise.
20351 9 Whether or when library functions raise an undeserved ''underflow'' floating-point
20352 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
20353 not raise spurious floating-point exceptions (detectable by the user), other than the
20354 ''inexact'' floating-point exception.
20355 10 Whether the functions honor the rounding direction mode is implementation-defined,
20356 unless explicitly specified otherwise.
20357 11 Functions with a NaN argument return a NaN result and raise no floating-point exception,
20358 except where stated otherwise.
20359 12 The specifications in the following subclauses append to the definitions in <a href="#7.12"><math.h></a>.
20360 For families of functions, the specifications apply to all of the functions even though only
20361 the principal function is shown. Unless otherwise specified, where the symbol ''(+-)''
20362 occurs in both an argument and the result, the result has the same sign as the argument.
20363 Recommended practice
20364 13 If a function with one or more NaN arguments returns a NaN result, the result should be
20365 the same as one of the NaN arguments (after possible type conversion), except perhaps
20367 <a name="F.10.1" href="#F.10.1"><b> F.10.1 Trigonometric functions</b></a>
20368 <a name="F.10.1.1" href="#F.10.1.1"><b> F.10.1.1 The acos functions</b></a>
20369 1 -- acos(1) returns +0.
20370 -- acos(x) returns a NaN and raises the ''invalid'' floating-point exception for
20372 <a name="F.10.1.2" href="#F.10.1.2"><b> F.10.1.2 The asin functions</b></a>
20373 1 -- asin((+-)0) returns (+-)0.
20374 -- asin(x) returns a NaN and raises the ''invalid'' floating-point exception for
20380 354) It is intended that undeserved ''underflow'' and ''inexact'' floating-point exceptions are raised only if
20381 avoiding them would be too costly.
20383 [<a name="#p514" href="p514">page 514</a>] (<a href="#Contents">Contents</a>)
20385 <a name="F.10.1.3" href="#F.10.1.3"><b> F.10.1.3 The atan functions</b></a>
20386 1 -- atan((+-)0) returns (+-)0.
20387 -- atan((+-)(inf)) returns (+-)pi /2.
20388 <a name="F.10.1.4" href="#F.10.1.4"><b> F.10.1.4 The atan2 functions</b></a>
20389 1 -- atan2((+-)0, -0) returns (+-)pi .355)
20390 -- atan2((+-)0, +0) returns (+-)0.
20391 -- atan2((+-)0, x) returns (+-)pi for x < 0.
20392 -- atan2((+-)0, x) returns (+-)0 for x > 0.
20393 -- atan2(y, (+-)0) returns -pi /2 for y < 0.
20394 -- atan2(y, (+-)0) returns pi /2 for y > 0.
20395 -- atan2((+-)y, -(inf)) returns (+-)pi for finite y > 0.
20396 -- atan2((+-)y, +(inf)) returns (+-)0 for finite y > 0.
20397 -- atan2((+-)(inf), x) returns (+-)pi /2 for finite x.
20398 -- atan2((+-)(inf), -(inf)) returns (+-)3pi /4.
20399 -- atan2((+-)(inf), +(inf)) returns (+-)pi /4.
20400 <a name="F.10.1.5" href="#F.10.1.5"><b> F.10.1.5 The cos functions</b></a>
20401 1 -- cos((+-)0) returns 1.
20402 -- cos((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
20403 <a name="F.10.1.6" href="#F.10.1.6"><b> F.10.1.6 The sin functions</b></a>
20404 1 -- sin((+-)0) returns (+-)0.
20405 -- sin((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
20406 <a name="F.10.1.7" href="#F.10.1.7"><b> F.10.1.7 The tan functions</b></a>
20407 1 -- tan((+-)0) returns (+-)0.
20408 -- tan((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
20413 355) atan2(0, 0) does not raise the ''invalid'' floating-point exception, nor does atan2( y , 0) raise
20414 the ''divide-by-zero'' floating-point exception.
20416 [<a name="#p515" href="p515">page 515</a>] (<a href="#Contents">Contents</a>)
20418 <a name="F.10.2" href="#F.10.2"><b> F.10.2 Hyperbolic functions</b></a>
20419 <a name="F.10.2.1" href="#F.10.2.1"><b> F.10.2.1 The acosh functions</b></a>
20420 1 -- acosh(1) returns +0.
20421 -- acosh(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 1.
20422 -- acosh(+(inf)) returns +(inf).
20423 <a name="F.10.2.2" href="#F.10.2.2"><b> F.10.2.2 The asinh functions</b></a>
20424 1 -- asinh((+-)0) returns (+-)0.
20425 -- asinh((+-)(inf)) returns (+-)(inf).
20426 <a name="F.10.2.3" href="#F.10.2.3"><b> F.10.2.3 The atanh functions</b></a>
20427 1 -- atanh((+-)0) returns (+-)0.
20428 -- atanh((+-)1) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
20429 -- atanh(x) returns a NaN and raises the ''invalid'' floating-point exception for
20431 <a name="F.10.2.4" href="#F.10.2.4"><b> F.10.2.4 The cosh functions</b></a>
20432 1 -- cosh((+-)0) returns 1.
20433 -- cosh((+-)(inf)) returns +(inf).
20434 <a name="F.10.2.5" href="#F.10.2.5"><b> F.10.2.5 The sinh functions</b></a>
20435 1 -- sinh((+-)0) returns (+-)0.
20436 -- sinh((+-)(inf)) returns (+-)(inf).
20437 <a name="F.10.2.6" href="#F.10.2.6"><b> F.10.2.6 The tanh functions</b></a>
20438 1 -- tanh((+-)0) returns (+-)0.
20439 -- tanh((+-)(inf)) returns (+-)1.
20440 <a name="F.10.3" href="#F.10.3"><b> F.10.3 Exponential and logarithmic functions</b></a>
20441 <a name="F.10.3.1" href="#F.10.3.1"><b> F.10.3.1 The exp functions</b></a>
20442 1 -- exp((+-)0) returns 1.
20443 -- exp(-(inf)) returns +0.
20444 -- exp(+(inf)) returns +(inf).
20449 [<a name="#p516" href="p516">page 516</a>] (<a href="#Contents">Contents</a>)
20451 <a name="F.10.3.2" href="#F.10.3.2"><b> F.10.3.2 The exp2 functions</b></a>
20452 1 -- exp2((+-)0) returns 1.
20453 -- exp2(-(inf)) returns +0.
20454 -- exp2(+(inf)) returns +(inf).
20455 <a name="F.10.3.3" href="#F.10.3.3"><b> F.10.3.3 The expm1 functions</b></a>
20456 1 -- expm1((+-)0) returns (+-)0.
20457 -- expm1(-(inf)) returns -1.
20458 -- expm1(+(inf)) returns +(inf).
20459 <a name="F.10.3.4" href="#F.10.3.4"><b> F.10.3.4 The frexp functions</b></a>
20460 1 -- frexp((+-)0, exp) returns (+-)0, and stores 0 in the object pointed to by exp.
20461 -- frexp((+-)(inf), exp) returns (+-)(inf), and stores an unspecified value in the object
20463 -- frexp(NaN, exp) stores an unspecified value in the object pointed to by exp
20464 (and returns a NaN).
20465 2 frexp raises no floating-point exceptions.
20466 3 When the radix of the argument is a power of 2, the returned value is exact and is
20467 independent of the current rounding direction mode.
20468 4 On a binary system, the body of the frexp function might be
20470 *exp = (value == 0) ? 0 : (int)(1 + logb(value));
20471 return scalbn(value, -(*exp));
20473 <a name="F.10.3.5" href="#F.10.3.5"><b> F.10.3.5 The ilogb functions</b></a>
20474 1 When the correct result is representable in the range of the return type, the returned value
20475 is exact and is independent of the current rounding direction mode.
20476 2 If the correct result is outside the range of the return type, the numeric result is
20477 unspecified and the ''invalid'' floating-point exception is raised.
20482 [<a name="#p517" href="p517">page 517</a>] (<a href="#Contents">Contents</a>)
20484 <a name="F.10.3.6" href="#F.10.3.6"><b> F.10.3.6 The ldexp functions</b></a>
20485 1 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
20486 <a name="F.10.3.7" href="#F.10.3.7"><b> F.10.3.7 The log functions</b></a>
20487 1 -- log((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
20488 -- log(1) returns +0.
20489 -- log(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
20490 -- log(+(inf)) returns +(inf).
20491 <a name="F.10.3.8" href="#F.10.3.8"><b> F.10.3.8 The log10 functions</b></a>
20492 1 -- log10((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
20493 -- log10(1) returns +0.
20494 -- log10(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
20495 -- log10(+(inf)) returns +(inf).
20496 <a name="F.10.3.9" href="#F.10.3.9"><b> F.10.3.9 The log1p functions</b></a>
20497 1 -- log1p((+-)0) returns (+-)0.
20498 -- log1p(-1) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
20499 -- log1p(x) returns a NaN and raises the ''invalid'' floating-point exception for
20501 -- log1p(+(inf)) returns +(inf).
20502 <a name="F.10.3.10" href="#F.10.3.10"><b> F.10.3.10 The log2 functions</b></a>
20503 1 -- log2((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
20504 -- log2(1) returns +0.
20505 -- log2(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
20506 -- log2(+(inf)) returns +(inf).
20507 <a name="F.10.3.11" href="#F.10.3.11"><b> F.10.3.11 The logb functions</b></a>
20508 1 -- logb((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
20509 -- logb((+-)(inf)) returns +(inf).
20510 2 The returned value is exact and is independent of the current rounding direction mode.
20515 [<a name="#p518" href="p518">page 518</a>] (<a href="#Contents">Contents</a>)
20517 <a name="F.10.3.12" href="#F.10.3.12"><b> F.10.3.12 The modf functions</b></a>
20518 1 -- modf((+-)x, iptr) returns a result with the same sign as x.
20519 -- modf((+-)(inf), iptr) returns (+-)0 and stores (+-)(inf) in the object pointed to by iptr.
20520 -- modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
20522 2 The returned values are exact and are independent of the current rounding direction
20524 3 modf behaves as though implemented by
20525 #include <a href="#7.12"><math.h></a>
20526 #include <a href="#7.6"><fenv.h></a>
20527 #pragma STDC FENV_ACCESS ON
20528 double modf(double value, double *iptr)
20530 int save_round = fegetround();
20531 fesetround(FE_TOWARDZERO);
20532 *iptr = nearbyint(value);
20533 fesetround(save_round);
20535 isinf(value) ? 0.0 :
20536 value - (*iptr), value);
20538 <a name="F.10.3.13" href="#F.10.3.13"><b> F.10.3.13 The scalbn and scalbln functions</b></a>
20539 1 -- scalbn((+-)0, n) returns (+-)0.
20540 -- scalbn(x, 0) returns x.
20541 -- scalbn((+-)(inf), n) returns (+-)(inf).
20542 <a name="F.10.4" href="#F.10.4"><b> F.10.4 Power and absolute value functions</b></a>
20543 <a name="F.10.4.1" href="#F.10.4.1"><b> F.10.4.1 The cbrt functions</b></a>
20544 1 -- cbrt((+-)0) returns (+-)0.
20545 -- cbrt((+-)(inf)) returns (+-)(inf).
20550 [<a name="#p519" href="p519">page 519</a>] (<a href="#Contents">Contents</a>)
20552 <a name="F.10.4.2" href="#F.10.4.2"><b> F.10.4.2 The fabs functions</b></a>
20553 1 -- fabs((+-)0) returns +0.
20554 -- fabs((+-)(inf)) returns +(inf).
20555 2 The returned value is exact and is independent of the current rounding direction mode.
20556 <a name="F.10.4.3" href="#F.10.4.3"><b> F.10.4.3 The hypot functions</b></a>
20557 1 -- hypot(x, y), hypot(y, x), and hypot(x, -y) are equivalent.
20558 -- hypot(x, (+-)0) is equivalent to fabs(x).
20559 -- hypot((+-)(inf), y) returns +(inf), even if y is a NaN.
20560 <a name="F.10.4.4" href="#F.10.4.4"><b> F.10.4.4 The pow functions</b></a>
20561 1 -- pow((+-)0, y) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception
20562 for y an odd integer < 0.
20563 -- pow((+-)0, y) returns +(inf) and raises the ''divide-by-zero'' floating-point exception
20564 for y < 0 and not an odd integer.
20565 -- pow((+-)0, y) returns (+-)0 for y an odd integer > 0.
20566 -- pow((+-)0, y) returns +0 for y > 0 and not an odd integer.
20567 -- pow(-1, (+-)(inf)) returns 1.
20568 -- pow(+1, y) returns 1 for any y, even a NaN.
20569 -- pow(x, (+-)0) returns 1 for any x, even a NaN.
20570 -- pow(x, y) returns a NaN and raises the ''invalid'' floating-point exception for
20571 finite x < 0 and finite non-integer y.
20572 -- pow(x, -(inf)) returns +(inf) for | x | < 1.
20573 -- pow(x, -(inf)) returns +0 for | x | > 1.
20574 -- pow(x, +(inf)) returns +0 for | x | < 1.
20575 -- pow(x, +(inf)) returns +(inf) for | x | > 1.
20576 -- pow(-(inf), y) returns -0 for y an odd integer < 0.
20577 -- pow(-(inf), y) returns +0 for y < 0 and not an odd integer.
20578 -- pow(-(inf), y) returns -(inf) for y an odd integer > 0.
20579 -- pow(-(inf), y) returns +(inf) for y > 0 and not an odd integer.
20580 -- pow(+(inf), y) returns +0 for y < 0.
20581 -- pow(+(inf), y) returns +(inf) for y > 0.
20584 [<a name="#p520" href="p520">page 520</a>] (<a href="#Contents">Contents</a>)
20586 <a name="F.10.4.5" href="#F.10.4.5"><b> F.10.4.5 The sqrt functions</b></a>
20587 1 sqrt is fully specified as a basic arithmetic operation in IEC 60559. The returned value
20588 is dependent on the current rounding direction mode.
20589 <a name="F.10.5" href="#F.10.5"><b> F.10.5 Error and gamma functions</b></a>
20590 <a name="F.10.5.1" href="#F.10.5.1"><b> F.10.5.1 The erf functions</b></a>
20591 1 -- erf((+-)0) returns (+-)0.
20592 -- erf((+-)(inf)) returns (+-)1.
20593 <a name="F.10.5.2" href="#F.10.5.2"><b> F.10.5.2 The erfc functions</b></a>
20594 1 -- erfc(-(inf)) returns 2.
20595 -- erfc(+(inf)) returns +0.
20596 <a name="F.10.5.3" href="#F.10.5.3"><b> F.10.5.3 The lgamma functions</b></a>
20597 1 -- lgamma(1) returns +0.
20598 -- lgamma(2) returns +0.
20599 -- lgamma(x) returns +(inf) and raises the ''divide-by-zero'' floating-point exception for
20600 x a negative integer or zero.
20601 -- lgamma(-(inf)) returns +(inf).
20602 -- lgamma(+(inf)) returns +(inf).
20603 <a name="F.10.5.4" href="#F.10.5.4"><b> F.10.5.4 The tgamma functions</b></a>
20604 1 -- tgamma((+-)0) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
20605 -- tgamma(x) returns a NaN and raises the ''invalid'' floating-point exception for x a
20607 -- tgamma(-(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
20608 -- tgamma(+(inf)) returns +(inf).
20609 <a name="F.10.6" href="#F.10.6"><b> F.10.6 Nearest integer functions</b></a>
20610 <a name="F.10.6.1" href="#F.10.6.1"><b> F.10.6.1 The ceil functions</b></a>
20611 1 -- ceil((+-)0) returns (+-)0.
20612 -- ceil((+-)(inf)) returns (+-)(inf).
20613 2 The returned value is exact and is independent of the current rounding direction mode.
20614 3 The double version of ceil behaves as though implemented by
20618 [<a name="#p521" href="p521">page 521</a>] (<a href="#Contents">Contents</a>)
20620 #include <a href="#7.12"><math.h></a>
20621 #include <a href="#7.6"><fenv.h></a>
20622 #pragma STDC FENV_ACCESS ON
20623 double ceil(double x)
20626 int save_round = fegetround();
20627 fesetround(FE_UPWARD);
20628 result = rint(x); // or nearbyint instead of rint
20629 fesetround(save_round);
20632 <a name="F.10.6.2" href="#F.10.6.2"><b> F.10.6.2 The floor functions</b></a>
20633 1 -- floor((+-)0) returns (+-)0.
20634 -- floor((+-)(inf)) returns (+-)(inf).
20635 2 The returned value is exact and is independent of the current rounding direction mode.
20636 3 See the sample implementation for ceil in <a href="#F.10.6.1">F.10.6.1</a>.
20637 <a name="F.10.6.3" href="#F.10.6.3"><b> F.10.6.3 The nearbyint functions</b></a>
20638 1 The nearbyint functions use IEC 60559 rounding according to the current rounding
20639 direction. They do not raise the ''inexact'' floating-point exception if the result differs in
20640 value from the argument.
20641 -- nearbyint((+-)0) returns (+-)0 (for all rounding directions).
20642 -- nearbyint((+-)(inf)) returns (+-)(inf) (for all rounding directions).
20643 <a name="F.10.6.4" href="#F.10.6.4"><b> F.10.6.4 The rint functions</b></a>
20644 1 The rint functions differ from the nearbyint functions only in that they do raise the
20645 ''inexact'' floating-point exception if the result differs in value from the argument.
20646 <a name="F.10.6.5" href="#F.10.6.5"><b> F.10.6.5 The lrint and llrint functions</b></a>
20647 1 The lrint and llrint functions provide floating-to-integer conversion as prescribed
20648 by IEC 60559. They round according to the current rounding direction. If the rounded
20649 value is outside the range of the return type, the numeric result is unspecified and the
20650 ''invalid'' floating-point exception is raised. When they raise no other floating-point
20651 exception and the result differs from the argument, they raise the ''inexact'' floating-point
20657 [<a name="#p522" href="p522">page 522</a>] (<a href="#Contents">Contents</a>)
20659 <a name="F.10.6.6" href="#F.10.6.6"><b> F.10.6.6 The round functions</b></a>
20660 1 -- round((+-)0) returns (+-)0.
20661 -- round((+-)(inf)) returns (+-)(inf).
20662 2 The double version of round behaves as though implemented by
20663 #include <a href="#7.12"><math.h></a>
20664 #include <a href="#7.6"><fenv.h></a>
20665 #pragma STDC FENV_ACCESS ON
20666 double round(double x)
20670 feholdexcept(&save_env);
20672 if (fetestexcept(FE_INEXACT)) {
20673 fesetround(FE_TOWARDZERO);
20674 result = rint(copysign(0.5 + fabs(x), x));
20676 feupdateenv(&save_env);
20679 The round functions may, but are not required to, raise the ''inexact'' floating-point
20680 exception for non-integer numeric arguments, as this implementation does.
20681 <a name="F.10.6.7" href="#F.10.6.7"><b> F.10.6.7 The lround and llround functions</b></a>
20682 1 The lround and llround functions differ from the lrint and llrint functions
20683 with the default rounding direction just in that the lround and llround functions
20684 round halfway cases away from zero and need not raise the ''inexact'' floating-point
20685 exception for non-integer arguments that round to within the range of the return type.
20686 <a name="F.10.6.8" href="#F.10.6.8"><b> F.10.6.8 The trunc functions</b></a>
20687 1 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
20688 rounding direction). The returned value is exact.
20689 -- trunc((+-)0) returns (+-)0.
20690 -- trunc((+-)(inf)) returns (+-)(inf).
20695 [<a name="#p523" href="p523">page 523</a>] (<a href="#Contents">Contents</a>)
20697 <a name="F.10.7" href="#F.10.7"><b> F.10.7 Remainder functions</b></a>
20698 <a name="F.10.7.1" href="#F.10.7.1"><b> F.10.7.1 The fmod functions</b></a>
20699 1 -- fmod((+-)0, y) returns (+-)0 for y not zero.
20700 -- fmod(x, y) returns a NaN and raises the ''invalid'' floating-point exception for x
20701 infinite or y zero.
20702 -- fmod(x, (+-)(inf)) returns x for x not infinite.
20703 2 When subnormal results are supported, the returned value is exact and is independent of
20704 the current rounding direction mode.
20705 3 The double version of fmod behaves as though implemented by
20706 #include <a href="#7.12"><math.h></a>
20707 #include <a href="#7.6"><fenv.h></a>
20708 #pragma STDC FENV_ACCESS ON
20709 double fmod(double x, double y)
20712 result = remainder(fabs(x), (y = fabs(y)));
20713 if (signbit(result)) result += y;
20714 return copysign(result, x);
20716 <a name="F.10.7.2" href="#F.10.7.2"><b> F.10.7.2 The remainder functions</b></a>
20717 1 The remainder functions are fully specified as a basic arithmetic operation in
20719 2 When subnormal results are supported, the returned value is exact and is independent of
20720 the current rounding direction mode.
20721 <a name="F.10.7.3" href="#F.10.7.3"><b> F.10.7.3 The remquo functions</b></a>
20722 1 The remquo functions follow the specifications for the remainder functions. They
20723 have no further specifications special to IEC 60559 implementations.
20724 2 When subnormal results are supported, the returned value is exact and is independent of
20725 the current rounding direction mode.
20730 [<a name="#p524" href="p524">page 524</a>] (<a href="#Contents">Contents</a>)
20732 <a name="F.10.8" href="#F.10.8"><b> F.10.8 Manipulation functions</b></a>
20733 <a name="F.10.8.1" href="#F.10.8.1"><b> F.10.8.1 The copysign functions</b></a>
20734 1 copysign is specified in the Appendix to IEC 60559.
20735 2 The returned value is exact and is independent of the current rounding direction mode.
20736 <a name="F.10.8.2" href="#F.10.8.2"><b> F.10.8.2 The nan functions</b></a>
20737 1 All IEC 60559 implementations support quiet NaNs, in all floating formats.
20738 2 The returned value is exact and is independent of the current rounding direction mode.
20739 <a name="F.10.8.3" href="#F.10.8.3"><b> F.10.8.3 The nextafter functions</b></a>
20740 1 -- nextafter(x, y) raises the ''overflow'' and ''inexact'' floating-point exceptions
20741 for x finite and the function value infinite.
20742 -- nextafter(x, y) raises the ''underflow'' and ''inexact'' floating-point
20743 exceptions for the function value subnormal or zero and x != y.
20744 2 Even though underflow or overflow can occur, the returned value is independent of the
20745 current rounding direction mode.
20746 <a name="F.10.8.4" href="#F.10.8.4"><b> F.10.8.4 The nexttoward functions</b></a>
20747 1 No additional requirements beyond those on nextafter.
20748 2 Even though underflow or overflow can occur, the returned value is independent of the
20749 current rounding direction mode.
20750 <a name="F.10.9" href="#F.10.9"><b> F.10.9 Maximum, minimum, and positive difference functions</b></a>
20751 <a name="F.10.9.1" href="#F.10.9.1"><b> F.10.9.1 The fdim functions</b></a>
20752 1 No additional requirements.
20753 <a name="F.10.9.2" href="#F.10.9.2"><b> F.10.9.2 The fmax functions</b></a>
20754 1 If just one argument is a NaN, the fmax functions return the other argument (if both
20755 arguments are NaNs, the functions return a NaN).
20756 2 The returned value is exact and is independent of the current rounding direction mode.
20757 3 The body of the fmax function might be356)
20758 { return (isgreaterequal(x, y) ||
20759 isnan(y)) ? x : y; }
20763 356) Ideally, fmax would be sensitive to the sign of zero, for example fmax(-0.0, +0.0) would
20764 return +0; however, implementation in software might be impractical.
20766 [<a name="#p525" href="p525">page 525</a>] (<a href="#Contents">Contents</a>)
20768 <a name="F.10.9.3" href="#F.10.9.3"><b> F.10.9.3 The fmin functions</b></a>
20769 1 The fmin functions are analogous to the fmax functions (see <a href="#F.10.9.2">F.10.9.2</a>).
20770 2 The returned value is exact and is independent of the current rounding direction mode.
20771 <a name="F.10.10" href="#F.10.10"><b> F.10.10 Floating multiply-add</b></a>
20772 <a name="F.10.10.1" href="#F.10.10.1"><b> F.10.10.1 The fma functions</b></a>
20773 1 -- fma(x, y, z) computes xy + z, correctly rounded once.
20774 -- fma(x, y, z) returns a NaN and optionally raises the ''invalid'' floating-point
20775 exception if one of x and y is infinite, the other is zero, and z is a NaN.
20776 -- fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if
20777 one of x and y is infinite, the other is zero, and z is not a NaN.
20778 -- fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if x
20779 times y is an exact infinity and z is also an infinity but with the opposite sign.
20780 <a name="F.10.11" href="#F.10.11"><b> F.10.11 Comparison macros</b></a>
20781 1 Relational operators and their corresponding comparison macros (<a href="#7.12.14">7.12.14</a>) produce
20782 equivalent result values, even if argument values are represented in wider formats. Thus,
20783 comparison macro arguments represented in formats wider than their semantic types are
20784 not converted to the semantic types, unless the wide evaluation method converts operands
20785 of relational operators to their semantic types. The standard wide evaluation methods
20786 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
20787 operands of relational operators to their semantic types.
20792 [<a name="#p526" href="p526">page 526</a>] (<a href="#Contents">Contents</a>)
20794 <a name="G" href="#G"><b> Annex G</b></a>
20796 IEC 60559-compatible complex arithmetic
20797 <a name="G.1" href="#G.1"><b> G.1 Introduction</b></a>
20798 1 This annex supplements <a href="#F">annex F</a> to specify complex arithmetic for compatibility with
20799 IEC 60559 real floating-point arithmetic. Although these specifications have been
20800 carefully designed, there is little existing practice to validate the design decisions.
20801 Therefore, these specifications are not normative, but should be viewed more as
20802 recommended practice. An implementation that defines
20803 __STDC_IEC_559_COMPLEX__ should conform to the specifications in this annex.
20804 <a name="G.2" href="#G.2"><b> G.2 Types</b></a>
20805 1 There is a new keyword _Imaginary, which is used to specify imaginary types. It is
20806 used as a type specifier within declaration specifiers in the same way as _Complex is
20807 (thus, _Imaginary float is a valid type name).
20808 2 There are three imaginary types, designated as float _Imaginary, double
20809 _Imaginary, and long double _Imaginary. The imaginary types (along with
20810 the real floating and complex types) are floating types.
20811 3 For imaginary types, the corresponding real type is given by deleting the keyword
20812 _Imaginary from the type name.
20813 4 Each imaginary type has the same representation and alignment requirements as the
20814 corresponding real type. The value of an object of imaginary type is the value of the real
20815 representation times the imaginary unit.
20816 5 The imaginary type domain comprises the imaginary types.
20817 <a name="G.3" href="#G.3"><b> G.3 Conventions</b></a>
20818 1 A complex or imaginary value with at least one infinite part is regarded as an infinity
20819 (even if its other part is a NaN). A complex or imaginary value is a finite number if each
20820 of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
20821 a zero if each of its parts is a zero.
20826 [<a name="#p527" href="p527">page 527</a>] (<a href="#Contents">Contents</a>)
20828 <a name="G.4" href="#G.4"><b> G.4 Conversions</b></a>
20829 <a name="G.4.1" href="#G.4.1"><b> G.4.1 Imaginary types</b></a>
20830 1 Conversions among imaginary types follow rules analogous to those for real floating
20832 <a name="G.4.2" href="#G.4.2"><b> G.4.2 Real and imaginary</b></a>
20833 1 When a value of imaginary type is converted to a real type other than _Bool,357) the
20834 result is a positive zero.
20835 2 When a value of real type is converted to an imaginary type, the result is a positive
20837 <a name="G.4.3" href="#G.4.3"><b> G.4.3 Imaginary and complex</b></a>
20838 1 When a value of imaginary type is converted to a complex type, the real part of the
20839 complex result value is a positive zero and the imaginary part of the complex result value
20840 is determined by the conversion rules for the corresponding real types.
20841 2 When a value of complex type is converted to an imaginary type, the real part of the
20842 complex value is discarded and the value of the imaginary part is converted according to
20843 the conversion rules for the corresponding real types.
20844 <a name="G.5" href="#G.5"><b> G.5 Binary operators</b></a>
20845 1 The following subclauses supplement <a href="#6.5">6.5</a> in order to specify the type of the result for an
20846 operation with an imaginary operand.
20847 2 For most operand types, the value of the result of a binary operator with an imaginary or
20848 complex operand is completely determined, with reference to real arithmetic, by the usual
20849 mathematical formula. For some operand types, the usual mathematical formula is
20850 problematic because of its treatment of infinities and because of undue overflow or
20851 underflow; in these cases the result satisfies certain properties (specified in <a href="#G.5.1">G.5.1</a>), but is
20852 not completely determined.
20857 357) See <a href="#6.3.1.2">6.3.1.2</a>.
20859 [<a name="#p528" href="p528">page 528</a>] (<a href="#Contents">Contents</a>)
20861 <a name="G.5.1" href="#G.5.1"><b> G.5.1 Multiplicative operators</b></a>
20863 1 If one operand has real type and the other operand has imaginary type, then the result has
20864 imaginary type. If both operands have imaginary type, then the result has real type. (If
20865 either operand has complex type, then the result has complex type.)
20866 2 If the operands are not both complex, then the result and floating-point exception
20867 behavior of the * operator is defined by the usual mathematical formula:
20870 x xu i(xv) (xu) + i(xv)
20872 iy i(yu) -yv (-yv) + i(yu)
20874 x + iy (xu) + i(yu) (-yv) + i(xv)
20875 3 If the second operand is not complex, then the result and floating-point exception
20876 behavior of the / operator is defined by the usual mathematical formula:
20883 x + iy (x/u) + i(y/u) (y/v) + i(-x/v)
20884 4 The * and / operators satisfy the following infinity properties for all real, imaginary, and
20885 complex operands:358)
20886 -- if one operand is an infinity and the other operand is a nonzero finite number or an
20887 infinity, then the result of the * operator is an infinity;
20888 -- if the first operand is an infinity and the second operand is a finite number, then the
20889 result of the / operator is an infinity;
20890 -- if the first operand is a finite number and the second operand is an infinity, then the
20891 result of the / operator is a zero;
20896 358) These properties are already implied for those cases covered in the tables, but are required for all cases
20897 (at least where the state for CX_LIMITED_RANGE is ''off'').
20899 [<a name="#p529" href="p529">page 529</a>] (<a href="#Contents">Contents</a>)
20901 -- if the first operand is a nonzero finite number or an infinity and the second operand is
20902 a zero, then the result of the / operator is an infinity.
20903 5 If both operands of the * operator are complex or if the second operand of the / operator
20904 is complex, the operator raises floating-point exceptions if appropriate for the calculation
20905 of the parts of the result, and may raise spurious floating-point exceptions.
20906 6 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
20907 that the imaginary unit I has imaginary type (see <a href="#G.6">G.6</a>).
20908 #include <a href="#7.12"><math.h></a>
20909 #include <a href="#7.3"><complex.h></a>
20910 /* Multiply z * w ... */
20911 double complex _Cmultd(double complex z, double complex w)
20913 #pragma STDC FP_CONTRACT OFF
20914 double a, b, c, d, ac, bd, ad, bc, x, y;
20915 a = creal(z); b = cimag(z);
20916 c = creal(w); d = cimag(w);
20917 ac = a * c; bd = b * d;
20918 ad = a * d; bc = b * c;
20919 x = ac - bd; y = ad + bc;
20920 if (isnan(x) && isnan(y)) {
20921 /* Recover infinities that computed as NaN+iNaN ... */
20923 if ( isinf(a) || isinf(b) ) { // z is infinite
20924 /* "Box" the infinity and change NaNs in the other factor to 0 */
20925 a = copysign(isinf(a) ? <a href="#1.0">1.0</a> : 0.0, a);
20926 b = copysign(isinf(b) ? <a href="#1.0">1.0</a> : 0.0, b);
20927 if (isnan(c)) c = copysign(0.0, c);
20928 if (isnan(d)) d = copysign(0.0, d);
20931 if ( isinf(c) || isinf(d) ) { // w is infinite
20932 /* "Box" the infinity and change NaNs in the other factor to 0 */
20933 c = copysign(isinf(c) ? <a href="#1.0">1.0</a> : 0.0, c);
20934 d = copysign(isinf(d) ? <a href="#1.0">1.0</a> : 0.0, d);
20935 if (isnan(a)) a = copysign(0.0, a);
20936 if (isnan(b)) b = copysign(0.0, b);
20939 if (!recalc && (isinf(ac) || isinf(bd) ||
20940 isinf(ad) || isinf(bc))) {
20941 /* Recover infinities from overflow by changing NaNs to 0 ... */
20942 if (isnan(a)) a = copysign(0.0, a);
20943 if (isnan(b)) b = copysign(0.0, b);
20944 if (isnan(c)) c = copysign(0.0, c);
20945 if (isnan(d)) d = copysign(0.0, d);
20950 [<a name="#p530" href="p530">page 530</a>] (<a href="#Contents">Contents</a>)
20952 x = INFINITY * ( a * c - b * d );
20953 y = INFINITY * ( a * d + b * c );
20958 7 This implementation achieves the required treatment of infinities at the cost of only one isnan test in
20959 ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur.
20961 8 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
20962 #include <a href="#7.12"><math.h></a>
20963 #include <a href="#7.3"><complex.h></a>
20964 /* Divide z / w ... */
20965 double complex _Cdivd(double complex z, double complex w)
20967 #pragma STDC FP_CONTRACT OFF
20968 double a, b, c, d, logbw, denom, x, y;
20970 a = creal(z); b = cimag(z);
20971 c = creal(w); d = cimag(w);
20972 logbw = logb(fmax(fabs(c), fabs(d)));
20973 if (isfinite(logbw)) {
20974 ilogbw = (int)logbw;
20975 c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
20977 denom = c * c + d * d;
20978 x = scalbn((a * c + b * d) / denom, -ilogbw);
20979 y = scalbn((b * c - a * d) / denom, -ilogbw);
20980 /* Recover infinities and zeros that computed as NaN+iNaN; */
20981 /* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
20982 if (isnan(x) && isnan(y)) {
20983 if ((denom == 0.0) &&
20984 (!isnan(a) || !isnan(b))) {
20985 x = copysign(INFINITY, c) * a;
20986 y = copysign(INFINITY, c) * b;
20988 else if ((isinf(a) || isinf(b)) &&
20989 isfinite(c) && isfinite(d)) {
20990 a = copysign(isinf(a) ? <a href="#1.0">1.0</a> : 0.0, a);
20991 b = copysign(isinf(b) ? <a href="#1.0">1.0</a> : 0.0, b);
20992 x = INFINITY * ( a * c + b * d );
20993 y = INFINITY * ( b * c - a * d );
20995 else if (isinf(logbw) &&
20996 isfinite(a) && isfinite(b)) {
20997 c = copysign(isinf(c) ? <a href="#1.0">1.0</a> : 0.0, c);
20998 d = copysign(isinf(d) ? <a href="#1.0">1.0</a> : 0.0, d);
20999 x = 0.0 * ( a * c + b * d );
21000 y = 0.0 * ( b * c - a * d );
21002 [<a name="#p531" href="p531">page 531</a>] (<a href="#Contents">Contents</a>)
21008 9 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
21009 for multiplication. In the spirit of the multiplication example above, this code does not defend against
21010 overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
21011 with division, provides better roundoff characteristics.
21013 <a name="G.5.2" href="#G.5.2"><b> G.5.2 Additive operators</b></a>
21015 1 If both operands have imaginary type, then the result has imaginary type. (If one operand
21016 has real type and the other operand has imaginary type, or if either operand has complex
21017 type, then the result has complex type.)
21018 2 In all cases the result and floating-point exception behavior of a + or - operator is defined
21019 by the usual mathematical formula:
21022 x x(+-)u x (+-) iv (x (+-) u) (+-) iv
21024 iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)
21026 x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)
21027 <a name="G.6" href="#G.6"><b> G.6 Complex arithmetic <complex.h></b></a>
21032 are defined, respectively, as _Imaginary and a constant expression of type const
21033 float _Imaginary with the value of the imaginary unit. The macro
21035 is defined to be _Imaginary_I (not _Complex_I as stated in <a href="#7.3">7.3</a>). Notwithstanding
21036 the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and then perhaps redefine the macro
21038 2 This subclause contains specifications for the <a href="#7.3"><complex.h></a> functions that are
21039 particularly suited to IEC 60559 implementations. For families of functions, the
21040 specifications apply to all of the functions even though only the principal function is
21042 [<a name="#p532" href="p532">page 532</a>] (<a href="#Contents">Contents</a>)
21044 shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument
21045 and the result, the result has the same sign as the argument.
21046 3 The functions are continuous onto both sides of their branch cuts, taking into account the
21047 sign of zero. For example, csqrt(-2 (+-) i0) = (+-)isqrt:2. -
21048 4 Since complex and imaginary values are composed of real values, each function may be
21049 regarded as computing real values from real values. Except as noted, the functions treat
21050 real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
21051 manner consistent with the specifications for real functions in F.10.359)
21052 5 The functions cimag, conj, cproj, and creal are fully specified for all
21053 implementations, including IEC 60559 ones, in <a href="#7.3.9">7.3.9</a>. These functions raise no floating-
21055 6 Each of the functions cabs and carg is specified by a formula in terms of a real
21056 function (whose special cases are covered in <a href="#F">annex F</a>):
21057 cabs(x + iy) = hypot(x, y)
21058 carg(x + iy) = atan2(y, x)
21059 7 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
21060 a formula in terms of other complex functions (whose special cases are specified below):
21061 casin(z) = -i casinh(iz)
21062 catan(z) = -i catanh(iz)
21063 ccos(z) = ccosh(iz)
21064 csin(z) = -i csinh(iz)
21065 ctan(z) = -i ctanh(iz)
21066 8 For the other functions, the following subclauses specify behavior for special cases,
21067 including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For
21068 families of functions, the specifications apply to all of the functions even though only the
21069 principal function is shown. For a function f satisfying f (conj(z)) = conj( f (z)), the
21070 specifications for the upper half-plane imply the specifications for the lower half-plane; if
21071 the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the
21072 specifications for the first quadrant imply the specifications for the other three quadrants.
21073 9 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
21078 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
21079 other part is a NaN.
21081 [<a name="#p533" href="p533">page 533</a>] (<a href="#Contents">Contents</a>)
21083 <a name="G.6.1" href="#G.6.1"><b> G.6.1 Trigonometric functions</b></a>
21084 <a name="G.6.1.1" href="#G.6.1.1"><b> G.6.1.1 The cacos functions</b></a>
21085 1 -- cacos(conj(z)) = conj(cacos(z)).
21086 -- cacos((+-)0 + i0) returns pi /2 - i0.
21087 -- cacos((+-)0 + iNaN) returns pi /2 + iNaN.
21088 -- cacos(x + i (inf)) returns pi /2 - i (inf), for finite x.
21089 -- cacos(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21090 point exception, for nonzero finite x.
21091 -- cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.
21092 -- cacos(+(inf) + iy) returns +0 - i (inf), for positive-signed finite y.
21093 -- cacos(-(inf) + i (inf)) returns 3pi /4 - i (inf).
21094 -- cacos(+(inf) + i (inf)) returns pi /4 - i (inf).
21095 -- cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
21096 result is unspecified).
21097 -- cacos(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21098 point exception, for finite y.
21099 -- cacos(NaN + i (inf)) returns NaN - i (inf).
21100 -- cacos(NaN + iNaN) returns NaN + iNaN.
21101 <a name="G.6.2" href="#G.6.2"><b> G.6.2 Hyperbolic functions</b></a>
21102 <a name="G.6.2.1" href="#G.6.2.1"><b> G.6.2.1 The cacosh functions</b></a>
21103 1 -- cacosh(conj(z)) = conj(cacosh(z)).
21104 -- cacosh((+-)0 + i0) returns +0 + ipi /2.
21105 -- cacosh(x + i (inf)) returns +(inf) + ipi /2, for finite x.
21106 -- cacosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
21107 floating-point exception, for finite x.
21108 -- cacosh(-(inf) + iy) returns +(inf) + ipi , for positive-signed finite y.
21109 -- cacosh(+(inf) + iy) returns +(inf) + i0, for positive-signed finite y.
21110 -- cacosh(-(inf) + i (inf)) returns +(inf) + i3pi /4.
21111 -- cacosh(+(inf) + i (inf)) returns +(inf) + ipi /4.
21112 -- cacosh((+-)(inf) + iNaN) returns +(inf) + iNaN.
21115 [<a name="#p534" href="p534">page 534</a>] (<a href="#Contents">Contents</a>)
21117 -- cacosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
21118 floating-point exception, for finite y.
21119 -- cacosh(NaN + i (inf)) returns +(inf) + iNaN.
21120 -- cacosh(NaN + iNaN) returns NaN + iNaN.
21121 <a name="G.6.2.2" href="#G.6.2.2"><b> G.6.2.2 The casinh functions</b></a>
21122 1 -- casinh(conj(z)) = conj(casinh(z)) and casinh is odd.
21123 -- casinh(+0 + i0) returns 0 + i0.
21124 -- casinh(x + i (inf)) returns +(inf) + ipi /2 for positive-signed finite x.
21125 -- casinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
21126 floating-point exception, for finite x.
21127 -- casinh(+(inf) + iy) returns +(inf) + i0 for positive-signed finite y.
21128 -- casinh(+(inf) + i (inf)) returns +(inf) + ipi /4.
21129 -- casinh(+(inf) + iNaN) returns +(inf) + iNaN.
21130 -- casinh(NaN + i0) returns NaN + i0.
21131 -- casinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
21132 floating-point exception, for finite nonzero y.
21133 -- casinh(NaN + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result
21135 -- casinh(NaN + iNaN) returns NaN + iNaN.
21136 <a name="G.6.2.3" href="#G.6.2.3"><b> G.6.2.3 The catanh functions</b></a>
21137 1 -- catanh(conj(z)) = conj(catanh(z)) and catanh is odd.
21138 -- catanh(+0 + i0) returns +0 + i0.
21139 -- catanh(+0 + iNaN) returns +0 + iNaN.
21140 -- catanh(+1 + i0) returns +(inf) + i0 and raises the ''divide-by-zero'' floating-point
21142 -- catanh(x + i (inf)) returns +0 + ipi /2, for finite positive-signed x.
21143 -- catanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
21144 floating-point exception, for nonzero finite x.
21145 -- catanh(+(inf) + iy) returns +0 + ipi /2, for finite positive-signed y.
21146 -- catanh(+(inf) + i (inf)) returns +0 + ipi /2.
21147 -- catanh(+(inf) + iNaN) returns +0 + iNaN.
21149 [<a name="#p535" href="p535">page 535</a>] (<a href="#Contents">Contents</a>)
21151 -- catanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
21152 floating-point exception, for finite y.
21153 -- catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is
21155 -- catanh(NaN + iNaN) returns NaN + iNaN.
21156 <a name="G.6.2.4" href="#G.6.2.4"><b> G.6.2.4 The ccosh functions</b></a>
21157 1 -- ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
21158 -- ccosh(+0 + i0) returns 1 + i0.
21159 -- ccosh(+0 + i (inf)) returns NaN (+-) i0 (where the sign of the imaginary part of the
21160 result is unspecified) and raises the ''invalid'' floating-point exception.
21161 -- ccosh(+0 + iNaN) returns NaN (+-) i0 (where the sign of the imaginary part of the
21162 result is unspecified).
21163 -- ccosh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
21164 exception, for finite nonzero x.
21165 -- ccosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21166 point exception, for finite nonzero x.
21167 -- ccosh(+(inf) + i0) returns +(inf) + i0.
21168 -- ccosh(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
21169 -- ccosh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
21170 unspecified) and raises the ''invalid'' floating-point exception.
21171 -- ccosh(+(inf) + iNaN) returns +(inf) + iNaN.
21172 -- ccosh(NaN + i0) returns NaN (+-) i0 (where the sign of the imaginary part of the
21173 result is unspecified).
21174 -- ccosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21175 point exception, for all nonzero numbers y.
21176 -- ccosh(NaN + iNaN) returns NaN + iNaN.
21177 <a name="G.6.2.5" href="#G.6.2.5"><b> G.6.2.5 The csinh functions</b></a>
21178 1 -- csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
21179 -- csinh(+0 + i0) returns +0 + i0.
21180 -- csinh(+0 + i (inf)) returns (+-)0 + iNaN (where the sign of the real part of the result is
21181 unspecified) and raises the ''invalid'' floating-point exception.
21182 -- csinh(+0 + iNaN) returns (+-)0 + iNaN (where the sign of the real part of the result is
21184 [<a name="#p536" href="p536">page 536</a>] (<a href="#Contents">Contents</a>)
21186 -- csinh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
21187 exception, for positive finite x.
21188 -- csinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21189 point exception, for finite nonzero x.
21190 -- csinh(+(inf) + i0) returns +(inf) + i0.
21191 -- csinh(+(inf) + iy) returns +(inf) cis(y), for positive finite y.
21192 -- csinh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
21193 unspecified) and raises the ''invalid'' floating-point exception.
21194 -- csinh(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
21196 -- csinh(NaN + i0) returns NaN + i0.
21197 -- csinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21198 point exception, for all nonzero numbers y.
21199 -- csinh(NaN + iNaN) returns NaN + iNaN.
21200 <a name="G.6.2.6" href="#G.6.2.6"><b> G.6.2.6 The ctanh functions</b></a>
21201 1 -- ctanh(conj(z)) = conj(ctanh(z))and ctanh is odd.
21202 -- ctanh(+0 + i0) returns +0 + i0.
21203 -- ctanh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
21204 exception, for finite x.
21205 -- ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21206 point exception, for finite x.
21207 -- ctanh(+(inf) + iy) returns 1 + i0 sin(2y), for positive-signed finite y.
21208 -- ctanh(+(inf) + i (inf)) returns 1 (+-) i0 (where the sign of the imaginary part of the result
21210 -- ctanh(+(inf) + iNaN) returns 1 (+-) i0 (where the sign of the imaginary part of the
21211 result is unspecified).
21212 -- ctanh(NaN + i0) returns NaN + i0.
21213 -- ctanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21214 point exception, for all nonzero numbers y.
21215 -- ctanh(NaN + iNaN) returns NaN + iNaN.
21220 [<a name="#p537" href="p537">page 537</a>] (<a href="#Contents">Contents</a>)
21222 <a name="G.6.3" href="#G.6.3"><b> G.6.3 Exponential and logarithmic functions</b></a>
21223 <a name="G.6.3.1" href="#G.6.3.1"><b> G.6.3.1 The cexp functions</b></a>
21224 1 -- cexp(conj(z)) = conj(cexp(z)).
21225 -- cexp((+-)0 + i0) returns 1 + i0.
21226 -- cexp(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
21227 exception, for finite x.
21228 -- cexp(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21229 point exception, for finite x.
21230 -- cexp(+(inf) + i0) returns +(inf) + i0.
21231 -- cexp(-(inf) + iy) returns +0 cis(y), for finite y.
21232 -- cexp(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
21233 -- cexp(-(inf) + i (inf)) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts of
21234 the result are unspecified).
21235 -- cexp(+(inf) + i (inf)) returns (+-)(inf) + iNaN and raises the ''invalid'' floating-point
21236 exception (where the sign of the real part of the result is unspecified).
21237 -- cexp(-(inf) + iNaN) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts
21238 of the result are unspecified).
21239 -- cexp(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
21241 -- cexp(NaN + i0) returns NaN + i0.
21242 -- cexp(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21243 point exception, for all nonzero numbers y.
21244 -- cexp(NaN + iNaN) returns NaN + iNaN.
21245 <a name="G.6.3.2" href="#G.6.3.2"><b> G.6.3.2 The clog functions</b></a>
21246 1 -- clog(conj(z)) = conj(clog(z)).
21247 -- clog(-0 + i0) returns -(inf) + ipi and raises the ''divide-by-zero'' floating-point
21249 -- clog(+0 + i0) returns -(inf) + i0 and raises the ''divide-by-zero'' floating-point
21251 -- clog(x + i (inf)) returns +(inf) + ipi /2, for finite x.
21252 -- clog(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21253 point exception, for finite x.
21255 [<a name="#p538" href="p538">page 538</a>] (<a href="#Contents">Contents</a>)
21257 -- clog(-(inf) + iy) returns +(inf) + ipi , for finite positive-signed y.
21258 -- clog(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
21259 -- clog(-(inf) + i (inf)) returns +(inf) + i3pi /4.
21260 -- clog(+(inf) + i (inf)) returns +(inf) + ipi /4.
21261 -- clog((+-)(inf) + iNaN) returns +(inf) + iNaN.
21262 -- clog(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21263 point exception, for finite y.
21264 -- clog(NaN + i (inf)) returns +(inf) + iNaN.
21265 -- clog(NaN + iNaN) returns NaN + iNaN.
21266 <a name="G.6.4" href="#G.6.4"><b> G.6.4 Power and absolute-value functions</b></a>
21267 <a name="G.6.4.1" href="#G.6.4.1"><b> G.6.4.1 The cpow functions</b></a>
21268 1 The cpow functions raise floating-point exceptions if appropriate for the calculation of
21269 the parts of the result, and may raise spurious exceptions.360)
21270 <a name="G.6.4.2" href="#G.6.4.2"><b> G.6.4.2 The csqrt functions</b></a>
21271 1 -- csqrt(conj(z)) = conj(csqrt(z)).
21272 -- csqrt((+-)0 + i0) returns +0 + i0.
21273 -- csqrt(x + i (inf)) returns +(inf) + i (inf), for all x (including NaN).
21274 -- csqrt(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21275 point exception, for finite x.
21276 -- csqrt(-(inf) + iy) returns +0 + i (inf), for finite positive-signed y.
21277 -- csqrt(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
21278 -- csqrt(-(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
21279 result is unspecified).
21280 -- csqrt(+(inf) + iNaN) returns +(inf) + iNaN.
21281 -- csqrt(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21282 point exception, for finite y.
21283 -- csqrt(NaN + iNaN) returns NaN + iNaN.
21288 360) This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding
21289 implementations that treat special cases more carefully.
21291 [<a name="#p539" href="p539">page 539</a>] (<a href="#Contents">Contents</a>)
21293 <a name="G.7" href="#G.7"><b> G.7 Type-generic math <tgmath.h></b></a>
21294 1 Type-generic macros that accept complex arguments also accept imaginary arguments. If
21295 an argument is imaginary, the macro expands to an expression whose type is real,
21296 imaginary, or complex, as appropriate for the particular function: if the argument is
21297 imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the
21298 types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and
21299 the types of the others are complex.
21300 2 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh,
21301 sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real
21304 sin(iy) = i sinh(y)
21305 tan(iy) = i tanh(y)
21307 sinh(iy) = i sin(y)
21308 tanh(iy) = i tan(y)
21309 asin(iy) = i asinh(y)
21310 atan(iy) = i atanh(y)
21311 asinh(iy) = i asin(y)
21312 atanh(iy) = i atan(y)
21317 [<a name="#p540" href="p540">page 540</a>] (<a href="#Contents">Contents</a>)
21319 <a name="H" href="#H"><b> Annex H</b></a>
21321 Language independent arithmetic
21322 <a name="H.1" href="#H.1"><b> H.1 Introduction</b></a>
21323 1 This annex documents the extent to which the C language supports the ISO/IEC 10967-1
21324 standard for language-independent arithmetic (LIA-1). LIA-1 is more general than
21325 IEC 60559 (<a href="#F">annex F</a>) in that it covers integer and diverse floating-point arithmetics.
21326 <a name="H.2" href="#H.2"><b> H.2 Types</b></a>
21327 1 The relevant C arithmetic types meet the requirements of LIA-1 types if an
21328 implementation adds notification of exceptional arithmetic operations and meets the 1
21329 unit in the last place (ULP) accuracy requirement (LIA-1 subclause <a href="#5.2.8">5.2.8</a>).
21330 <a name="H.2.1" href="#H.2.1"><b> H.2.1 Boolean type</b></a>
21331 1 The LIA-1 data type Boolean is implemented by the C data type bool with values of
21332 true and false, all from <a href="#7.18"><stdbool.h></a>.
21333 <a name="H.2.2" href="#H.2.2"><b> H.2.2 Integer types</b></a>
21334 1 The signed C integer types int, long int, long long int, and the corresponding
21335 unsigned types are compatible with LIA-1. If an implementation adds support for the
21336 LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are
21337 LIA-1 conformant types. C's unsigned integer types are ''modulo'' in the LIA-1 sense
21338 in that overflows or out-of-bounds results silently wrap. An implementation that defines
21339 signed integer types as also being modulo need not detect integer overflow, in which case,
21340 only integer divide-by-zero need be detected.
21341 2 The parameters for the integer data types can be accessed by the following:
21342 maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
21344 minint INT_MIN, LONG_MIN, LLONG_MIN
21345 3 The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
21346 is always 0 for the unsigned types, and is not provided for those types.
21351 [<a name="#p541" href="p541">page 541</a>] (<a href="#Contents">Contents</a>)
21353 <a name="H.2.2.1" href="#H.2.2.1"><b> H.2.2.1 Integer operations</b></a>
21354 1 The integer operations on integer types are the following:
21361 absI abs(x), labs(x), llabs(x)
21368 where x and y are expressions of the same integer type.
21369 <a name="H.2.3" href="#H.2.3"><b> H.2.3 Floating-point types</b></a>
21370 1 The C floating-point types float, double, and long double are compatible with
21371 LIA-1. If an implementation adds support for the LIA-1 exceptional values
21372 ''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
21373 with LIA-1. An implementation that uses IEC 60559 floating-point formats and
21374 operations (see <a href="#F">annex F</a>) along with IEC 60559 status flags and traps has LIA-1
21376 <a name="H.2.3.1" href="#H.2.3.1"><b> H.2.3.1 Floating-point parameters</b></a>
21377 1 The parameters for a floating point data type can be accessed by the following:
21379 p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
21380 emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
21381 emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
21382 2 The derived constants for the floating point types are accessed by the following:
21385 [<a name="#p542" href="p542">page 542</a>] (<a href="#Contents">Contents</a>)
21387 fmax FLT_MAX, DBL_MAX, LDBL_MAX
21388 fminN FLT_MIN, DBL_MIN, LDBL_MIN
21389 epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
21390 rnd_style FLT_ROUNDS
21391 <a name="H.2.3.2" href="#H.2.3.2"><b> H.2.3.2 Floating-point operations</b></a>
21392 1 The floating-point operations on floating-point types are the following:
21398 absF fabsf(x), fabs(x), fabsl(x)
21399 exponentF 1.f+logbf(x), <a href="#1.0">1.0</a>+logb(x), 1.L+logbl(x)
21400 scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
21401 scalblnf(x, li), scalbln(x, li), scalblnl(x, li)
21402 intpartF modff(x, &y), modf(x, &y), modfl(x, &y)
21403 fractpartF modff(x, &y), modf(x, &y), modfl(x, &y)
21410 where x and y are expressions of the same floating point type, n is of type int, and li
21411 is of type long int.
21412 <a name="H.2.3.3" href="#H.2.3.3"><b> H.2.3.3 Rounding styles</b></a>
21413 1 The C Standard requires all floating types to use the same radix and rounding style, so
21414 that only one identifier for each is provided to map to LIA-1.
21415 2 The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
21416 truncate FLT_ROUNDS == 0
21419 [<a name="#p543" href="p543">page 543</a>] (<a href="#Contents">Contents</a>)
21421 nearest FLT_ROUNDS == 1
21422 other FLT_ROUNDS != 0 && FLT_ROUNDS != 1
21423 provided that an implementation extends FLT_ROUNDS to cover the rounding style used
21424 in all relevant LIA-1 operations, not just addition as in C.
21425 <a name="H.2.4" href="#H.2.4"><b> H.2.4 Type conversions</b></a>
21426 1 The LIA-1 type conversions are the following type casts:
21427 cvtI' (->) I (int)i, (long int)i, (long long int)i,
21428 (unsigned int)i, (unsigned long int)i,
21429 (unsigned long long int)i
21430 cvtF (->) I (int)x, (long int)x, (long long int)x,
21431 (unsigned int)x, (unsigned long int)x,
21432 (unsigned long long int)x
21433 cvtI (->) F (float)i, (double)i, (long double)i
21434 cvtF' (->) F (float)x, (double)x, (long double)x
21435 2 In the above conversions from floating to integer, the use of (cast)x can be replaced with
21436 (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
21437 (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer
21438 conversion functions, lrint(), llrint(), lround(), and llround(), can be
21439 used. They all meet LIA-1's requirements on floating to integer rounding for in-range
21440 values. For out-of-range values, the conversions shall silently wrap for the modulo types.
21441 3 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
21442 fmod( fabs(rint(x)), 65536.0 ) or (0.0 <= (y = fmod( rint(x),
21443 65536.0 )) ? y : 65536.0 + y) will compute an integer value in the range 0.0
21444 to 65535.0 which can then be cast to unsigned short int. But, the
21445 remainder() function is not useful for doing silent wrapping to signed integer types,
21446 e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
21447 range -32767.0 to +32768.0 which is not, in general, in the range of signed short
21449 4 C's conversions (casts) from floating-point to floating-point can meet LIA-1
21450 requirements if an implementation uses round-to-nearest (IEC 60559 default).
21451 5 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
21452 implementation uses round-to-nearest.
21457 [<a name="#p544" href="p544">page 544</a>] (<a href="#Contents">Contents</a>)
21459 <a name="H.3" href="#H.3"><b> H.3 Notification</b></a>
21460 1 Notification is the process by which a user or program is informed that an exceptional
21461 arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
21462 allows an implementation to cause a notification to occur when any arithmetic operation
21463 returns an exceptional value as defined in LIA-1 clause 5.
21464 <a name="H.3.1" href="#H.3.1"><b> H.3.1 Notification alternatives</b></a>
21465 1 LIA-1 requires at least the following two alternatives for handling of notifications:
21466 setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and-
21468 2 An implementation need only support a given notification alternative for the entire
21469 program. An implementation may support the ability to switch between notification
21470 alternatives during execution, but is not required to do so. An implementation can
21471 provide separate selection for each kind of notification, but this is not required.
21472 3 C allows an implementation to provide notification. C's SIGFPE (for traps) and
21473 FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
21474 can provide LIA-1 notification.
21475 4 C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
21476 provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
21477 math library function calls. User-provided signal handlers for SIGFPE allow for trap-
21478 and-resume behavior with the same constraint.
21479 <a name="H.3.1.1" href="#H.3.1.1"><b> H.3.1.1 Indicators</b></a>
21480 1 C's <a href="#7.6"><fenv.h></a> status flags are compatible with the LIA-1 indicators.
21481 2 The following mapping is for floating-point types:
21482 undefined FE_INVALID, FE_DIVBYZERO
21483 floating_overflow FE_OVERFLOW
21484 underflow FE_UNDERFLOW
21485 3 The floating-point indicator interrogation and manipulation operations are:
21486 set_indicators feraiseexcept(i)
21487 clear_indicators feclearexcept(i)
21488 test_indicators fetestexcept(i)
21489 current_indicators fetestexcept(FE_ALL_EXCEPT)
21490 where i is an expression of type int representing a subset of the LIA-1 indicators.
21491 4 C allows an implementation to provide the following LIA-1 required behavior: at
21492 program termination if any indicator is set the implementation shall send an unambiguous
21493 [<a name="#p545" href="p545">page 545</a>] (<a href="#Contents">Contents</a>)
21495 and ''hard to ignore'' message (see LIA-1 subclause <a href="#6.1.2">6.1.2</a>)
21496 5 LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
21497 This documentation makes that distinction because <a href="#7.6"><fenv.h></a> covers only the floating-
21499 <a name="H.3.1.2" href="#H.3.1.2"><b> H.3.1.2 Traps</b></a>
21500 1 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
21501 math library functions (which are not permitted to invoke a user's signal handler for
21502 SIGFPE). An implementation can provide an alternative of notification through
21503 termination with a ''hard-to-ignore'' message (see LIA-1 subclause <a href="#6.1.3">6.1.3</a>).
21504 2 LIA-1 does not require that traps be precise.
21505 3 C does require that SIGFPE be the signal corresponding to arithmetic exceptions, if there
21506 is any signal raised for them.
21507 4 C supports signal handlers for SIGFPE and allows trapping of arithmetic exceptions.
21508 When arithmetic exceptions do trap, C's signal-handler mechanism allows trap-and-
21509 terminate (either default implementation behavior or user replacement for it) or trap-and-
21510 resume, at the programmer's option.
21515 [<a name="#p546" href="p546">page 546</a>] (<a href="#Contents">Contents</a>)
21517 <a name="I" href="#I"><b> Annex I</b></a>
21520 1 An implementation may generate warnings in many situations, none of which are
21521 specified as part of this International Standard. The following are a few of the more
21523 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>).
21524 -- A block with initialization of an object that has automatic storage duration is jumped
21525 into (<a href="#6.2.4">6.2.4</a>).
21526 -- An implicit narrowing conversion is encountered, such as the assignment of a long
21527 int or a double to an int, or a pointer to void to a pointer to any type other than
21528 a character type (<a href="#6.3">6.3</a>).
21529 -- A hexadecimal floating constant cannot be represented exactly in its evaluation format
21530 (<a href="#6.4.4.2">6.4.4.2</a>).
21531 -- An integer character constant includes more than one character or a wide character
21532 constant includes more than one multibyte character (<a href="#6.4.4.4">6.4.4.4</a>).
21533 -- The characters /* are found in a comment (<a href="#6.4.7">6.4.7</a>).
21534 -- An ''unordered'' binary operator (not comma, &&, or ||) contains a side effect to an
21535 lvalue in one operand, and a side effect to, or an access to the value of, the identical
21536 lvalue in the other operand (<a href="#6.5">6.5</a>).
21537 -- A function is called but no prototype has been supplied (<a href="#6.5.2.2">6.5.2.2</a>).
21538 -- The arguments in a function call do not agree in number and type with those of the
21539 parameters in a function definition that is not a prototype (<a href="#6.5.2.2">6.5.2.2</a>).
21540 -- An object is defined but not used (<a href="#6.7">6.7</a>).
21541 -- A value is given to an object of an enumerated type other than by assignment of an
21542 enumeration constant that is a member of that type, or an enumeration object that has
21543 the same type, or the value of a function that returns the same enumerated type
21544 (<a href="#6.7.2.2">6.7.2.2</a>).
21545 -- An aggregate has a partly bracketed initialization (<a href="#6.7.8">6.7.8</a>).
21546 -- A statement cannot be reached (<a href="#6.8">6.8</a>).
21547 -- A statement with no apparent effect is encountered (<a href="#6.8">6.8</a>).
21548 -- A constant expression is used as the controlling expression of a selection statement
21549 (<a href="#6.8.4">6.8.4</a>).
21550 [<a name="#p547" href="p547">page 547</a>] (<a href="#Contents">Contents</a>)
21552 -- An incorrectly formed preprocessing group is encountered while skipping a
21553 preprocessing group (<a href="#6.10.1">6.10.1</a>).
21554 -- An unrecognized #pragma directive is encountered (<a href="#6.10.6">6.10.6</a>).
21559 [<a name="#p548" href="p548">page 548</a>] (<a href="#Contents">Contents</a>)
21561 <a name="J" href="#J"><b> Annex J</b></a>
21564 1 This annex collects some information about portability that appears in this International
21566 <a name="J.1" href="#J.1"><b> J.1 Unspecified behavior</b></a>
21567 1 The following are unspecified:
21568 -- The manner and timing of static initialization (<a href="#5.1.2">5.1.2</a>).
21569 -- The termination status returned to the hosted environment if the return type of main
21570 is not compatible with int (<a href="#5.1.2.2.3">5.1.2.2.3</a>).
21571 -- The behavior of the display device if a printing character is written when the active
21572 position is at the final position of a line (<a href="#5.2.2">5.2.2</a>).
21573 -- The behavior of the display device if a backspace character is written when the active
21574 position is at the initial position of a line (<a href="#5.2.2">5.2.2</a>).
21575 -- The behavior of the display device if a horizontal tab character is written when the
21576 active position is at or past the last defined horizontal tabulation position (<a href="#5.2.2">5.2.2</a>).
21577 -- The behavior of the display device if a vertical tab character is written when the active
21578 position is at or past the last defined vertical tabulation position (<a href="#5.2.2">5.2.2</a>).
21579 -- How an extended source character that does not correspond to a universal character
21580 name counts toward the significant initial characters in an external identifier (<a href="#5.2.4.1">5.2.4.1</a>).
21581 -- Many aspects of the representations of types (<a href="#6.2.6">6.2.6</a>).
21582 -- The value of padding bytes when storing values in structures or unions (<a href="#6.2.6.1">6.2.6.1</a>).
21583 -- The values of bytes that correspond to union members other than the one last stored
21584 into (<a href="#6.2.6.1">6.2.6.1</a>).
21585 -- The representation used when storing a value in an object that has more than one
21586 object representation for that value (<a href="#6.2.6.1">6.2.6.1</a>).
21587 -- The values of any padding bits in integer representations (<a href="#6.2.6.2">6.2.6.2</a>).
21588 -- Whether certain operators can generate negative zeros and whether a negative zero
21589 becomes a normal zero when stored in an object (<a href="#6.2.6.2">6.2.6.2</a>).
21590 -- Whether two string literals result in distinct arrays (<a href="#6.4.5">6.4.5</a>).
21591 -- The order in which subexpressions are evaluated and the order in which side effects
21592 take place, except as specified for the function-call (), &&, ||, ? :, and comma
21593 [<a name="#p549" href="p549">page 549</a>] (<a href="#Contents">Contents</a>)
21595 operators (<a href="#6.5">6.5</a>).
21596 -- The order in which the function designator, arguments, and subexpressions within the
21597 arguments are evaluated in a function call (<a href="#6.5.2.2">6.5.2.2</a>).
21598 -- The order of side effects among compound literal initialization list expressions
21599 (<a href="#6.5.2.5">6.5.2.5</a>).
21600 -- The order in which the operands of an assignment operator are evaluated (<a href="#6.5.16">6.5.16</a>).
21601 -- The alignment of the addressable storage unit allocated to hold a bit-field (<a href="#6.7.2.1">6.7.2.1</a>).
21602 -- Whether a call to an inline function uses the inline definition or the external definition
21603 of the function (<a href="#6.7.4">6.7.4</a>).
21604 -- Whether or not a size expression is evaluated when it is part of the operand of a
21605 sizeof operator and changing the value of the size expression would not affect the
21606 result of the operator (<a href="#6.7.6.2">6.7.6.2</a>).
21607 -- The order in which any side effects occur among the initialization list expressions in
21608 an initializer (<a href="#6.7.9">6.7.9</a>).
21609 -- The layout of storage for function parameters (<a href="#6.9.1">6.9.1</a>).
21610 -- When a fully expanded macro replacement list contains a function-like macro name
21611 as its last preprocessing token and the next preprocessing token from the source file is
21612 a (, and the fully expanded replacement of that macro ends with the name of the first
21613 macro and the next preprocessing token from the source file is again a (, whether that
21614 is considered a nested replacement (<a href="#6.10.3">6.10.3</a>).
21615 -- The order in which # and ## operations are evaluated during macro substitution
21616 (<a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>).
21617 -- The state of the floating-point status flags when execution passes from a part of the
21618 program translated with FENV_ACCESS ''off'' to a part translated with
21619 FENV_ACCESS ''on'' (<a href="#7.6.1">7.6.1</a>).
21620 -- The order in which feraiseexcept raises floating-point exceptions, except as
21621 stated in <a href="#F.8.6">F.8.6</a> (<a href="#7.6.2.3">7.6.2.3</a>).
21622 -- Whether math_errhandling is a macro or an identifier with external linkage
21623 (<a href="#7.12">7.12</a>).
21624 -- The results of the frexp functions when the specified value is not a floating-point
21625 number (<a href="#7.12.6.4">7.12.6.4</a>).
21626 -- The numeric result of the ilogb functions when the correct value is outside the
21627 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>).
21628 -- 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>).
21631 [<a name="#p550" href="p550">page 550</a>] (<a href="#Contents">Contents</a>)
21633 -- The value stored by the remquo functions in the object pointed to by quo when y is
21634 zero (<a href="#7.12.10.3">7.12.10.3</a>).
21635 -- Whether a comparison macro argument that is represented in a format wider than its
21636 semantic type is converted to the semantic type (<a href="#7.12.14">7.12.14</a>).
21637 -- Whether setjmp is a macro or an identifier with external linkage (<a href="#7.13">7.13</a>).
21638 -- Whether va_copy and va_end are macros or identifiers with external linkage
21639 (<a href="#7.16.1">7.16.1</a>).
21640 -- The hexadecimal digit before the decimal point when a non-normalized floating-point
21641 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>).
21642 -- The value of the file position indicator after a successful call to the ungetc function
21643 for a text stream, or the ungetwc function for any stream, until all pushed-back
21644 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>).
21645 -- The details of the value stored by the fgetpos function (<a href="#7.21.9.1">7.21.9.1</a>).
21646 -- 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>).
21647 -- Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold
21648 functions convert a minus-signed sequence to a negative number directly or by
21649 negating the value resulting from converting the corresponding unsigned sequence
21650 (<a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.28.4.1.1">7.28.4.1.1</a>).
21651 -- The order and contiguity of storage allocated by successive calls to the calloc,
21652 malloc, and realloc functions (<a href="#7.22.3">7.22.3</a>).
21653 -- The amount of storage allocated by a successful call to the calloc, malloc, or
21654 realloc function when 0 bytes was requested (<a href="#7.22.3">7.22.3</a>).
21655 -- Which of two elements that compare as equal is matched by the bsearch function
21656 (<a href="#7.22.5.1">7.22.5.1</a>).
21657 -- The order of two elements that compare as equal in an array sorted by the qsort
21658 function (<a href="#7.22.5.2">7.22.5.2</a>).
21659 -- The encoding of the calendar time returned by the time function (<a href="#7.26.2.4">7.26.2.4</a>).
21660 -- The characters stored by the strftime or wcsftime function if any of the time
21661 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>).
21662 -- 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>,
21663 <a href="#7.28.6.4.2">7.28.6.4.2</a>,
21664 -- The resulting value when the ''invalid'' floating-point exception is raised during
21665 IEC 60559 floating to integer conversion (<a href="#F.4">F.4</a>).
21669 [<a name="#p551" href="p551">page 551</a>] (<a href="#Contents">Contents</a>)
21671 -- Whether conversion of non-integer IEC 60559 floating values to integer raises the
21672 ''inexact'' floating-point exception (<a href="#F.4">F.4</a>).
21673 -- Whether or when library functions in <a href="#7.12"><math.h></a> raise the ''inexact'' floating-point
21674 exception in an IEC 60559 conformant implementation (<a href="#F.10">F.10</a>).
21675 -- Whether or when library functions in <a href="#7.12"><math.h></a> raise an undeserved ''underflow''
21676 floating-point exception in an IEC 60559 conformant implementation (<a href="#F.10">F.10</a>).
21677 -- The exponent value stored by frexp for a NaN or infinity (<a href="#F.10.3.4">F.10.3.4</a>).
21678 -- The numeric result returned by the lrint, llrint, lround, and llround
21679 functions if the rounded value is outside the range of the return type (<a href="#F.10.6.5">F.10.6.5</a>,
21680 <a href="#F.10.6.7">F.10.6.7</a>).
21681 -- The sign of one part of the complex result of several math functions for certain
21682 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>,
21683 <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>).
21684 <a name="J.2" href="#J.2"><b> J.2 Undefined behavior</b></a>
21685 1 The behavior is undefined in the following circumstances:
21686 -- A ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated
21688 -- A nonempty source file does not end in a new-line character which is not immediately
21689 preceded by a backslash character or ends in a partial preprocessing token or
21690 comment (<a href="#5.1.1.2">5.1.1.2</a>).
21691 -- Token concatenation produces a character sequence matching the syntax of a
21692 universal character name (<a href="#5.1.1.2">5.1.1.2</a>).
21693 -- A program in a hosted environment does not define a function named main using one
21694 of the specified forms (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
21695 -- The execution of a program contains a data race (<a href="#5.1.2.4">5.1.2.4</a>).
21696 -- A character not in the basic source character set is encountered in a source file, except
21697 in an identifier, a character constant, a string literal, a header name, a comment, or a
21698 preprocessing token that is never converted to a token (<a href="#5.2.1">5.2.1</a>).
21699 -- An identifier, comment, string literal, character constant, or header name contains an
21700 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>).
21701 -- The same identifier has both internal and external linkage in the same translation unit
21702 (<a href="#6.2.2">6.2.2</a>).
21703 -- An object is referred to outside of its lifetime (<a href="#6.2.4">6.2.4</a>).
21707 [<a name="#p552" href="p552">page 552</a>] (<a href="#Contents">Contents</a>)
21709 -- The value of a pointer to an object whose lifetime has ended is used (<a href="#6.2.4">6.2.4</a>).
21710 -- The value of an object with automatic storage duration is used while it is
21711 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>).
21712 -- A trap representation is read by an lvalue expression that does not have character type
21713 (<a href="#6.2.6.1">6.2.6.1</a>).
21714 -- A trap representation is produced by a side effect that modifies any part of the object
21715 using an lvalue expression that does not have character type (<a href="#6.2.6.1">6.2.6.1</a>).
21716 -- The operands to certain operators are such that they could produce a negative zero
21717 result, but the implementation does not support negative zeros (<a href="#6.2.6.2">6.2.6.2</a>).
21718 -- Two declarations of the same object or function specify types that are not compatible
21719 (<a href="#6.2.7">6.2.7</a>).
21720 -- A program requires the formation of a composite type from a variable length array
21721 type whose size is specified by an expression that is not evaluated (<a href="#6.2.7">6.2.7</a>).
21722 -- Conversion to or from an integer type produces a value outside the range that can be
21723 represented (<a href="#6.3.1.4">6.3.1.4</a>).
21724 -- Demotion of one real floating type to another produces a value outside the range that
21725 can be represented (<a href="#6.3.1.5">6.3.1.5</a>).
21726 -- An lvalue does not designate an object when evaluated (<a href="#6.3.2.1">6.3.2.1</a>).
21727 -- A non-array lvalue with an incomplete type is used in a context that requires the value
21728 of the designated object (<a href="#6.3.2.1">6.3.2.1</a>).
21729 -- An lvalue designating an object of automatic storage duration that could have been
21730 declared with the register storage class is used in a context that requires the value
21731 of the designated object, but the object is uninitialized. (<a href="#6.3.2.1">6.3.2.1</a>).
21732 -- An lvalue having array type is converted to a pointer to the initial element of the
21733 array, and the array object has register storage class (<a href="#6.3.2.1">6.3.2.1</a>).
21734 -- An attempt is made to use the value of a void expression, or an implicit or explicit
21735 conversion (except to void) is applied to a void expression (<a href="#6.3.2.2">6.3.2.2</a>).
21736 -- Conversion of a pointer to an integer type produces a value outside the range that can
21737 be represented (<a href="#6.3.2.3">6.3.2.3</a>).
21738 -- Conversion between two pointer types produces a result that is incorrectly aligned
21739 (<a href="#6.3.2.3">6.3.2.3</a>).
21740 -- A pointer is used to call a function whose type is not compatible with the referenced
21741 type (<a href="#6.3.2.3">6.3.2.3</a>).
21745 [<a name="#p553" href="p553">page 553</a>] (<a href="#Contents">Contents</a>)
21747 -- An unmatched ' or " character is encountered on a logical source line during
21748 tokenization (<a href="#6.4">6.4</a>).
21749 -- A reserved keyword token is used in translation phase 7 or 8 for some purpose other
21750 than as a keyword (<a href="#6.4.1">6.4.1</a>).
21751 -- A universal character name in an identifier does not designate a character whose
21752 encoding falls into one of the specified ranges (<a href="#6.4.2.1">6.4.2.1</a>).
21753 -- The initial character of an identifier is a universal character name designating a digit
21754 (<a href="#6.4.2.1">6.4.2.1</a>).
21755 -- Two identifiers differ only in nonsignificant characters (<a href="#6.4.2.1">6.4.2.1</a>).
21756 -- The identifier __func__ is explicitly declared (<a href="#6.4.2.2">6.4.2.2</a>).
21757 -- The program attempts to modify a string literal (<a href="#6.4.5">6.4.5</a>).
21758 -- The characters ', \, ", //, or /* occur in the sequence between the < and >
21759 delimiters, or the characters ', \, //, or /* occur in the sequence between the "
21760 delimiters, in a header name preprocessing token (<a href="#6.4.7">6.4.7</a>).
21761 -- A side effect on a scalar object is unsequenced relative to either a different side effect
21762 on the same scalar object or a value computation using the value of the same scalar
21763 object (<a href="#6.5">6.5</a>).
21764 -- An exceptional condition occurs during the evaluation of an expression (<a href="#6.5">6.5</a>).
21765 -- An object has its stored value accessed other than by an lvalue of an allowable type
21766 (<a href="#6.5">6.5</a>).
21767 -- For a call to a function without a function prototype in scope, the number of
21768 arguments does not equal the number of parameters (<a href="#6.5.2.2">6.5.2.2</a>).
21769 -- For call to a function without a function prototype in scope where the function is
21770 defined with a function prototype, either the prototype ends with an ellipsis or the
21771 types of the arguments after promotion are not compatible with the types of the
21772 parameters (<a href="#6.5.2.2">6.5.2.2</a>).
21773 -- For a call to a function without a function prototype in scope where the function is not
21774 defined with a function prototype, the types of the arguments after promotion are not
21775 compatible with those of the parameters after promotion (with certain exceptions)
21776 (<a href="#6.5.2.2">6.5.2.2</a>).
21777 -- A function is defined with a type that is not compatible with the type (of the
21778 expression) pointed to by the expression that denotes the called function (<a href="#6.5.2.2">6.5.2.2</a>).
21779 -- A member of an _Atomic-qualified structure or union is accessed (<a href="#6.5.2.3">6.5.2.3</a>).
21780 -- The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
21783 [<a name="#p554" href="p554">page 554</a>] (<a href="#Contents">Contents</a>)
21785 -- A pointer is converted to other than an integer or pointer type (<a href="#6.5.4">6.5.4</a>).
21786 -- The value of the second operand of the / or % operator is zero (<a href="#6.5.5">6.5.5</a>).
21787 -- Addition or subtraction of a pointer into, or just beyond, an array object and an
21788 integer type produces a result that does not point into, or just beyond, the same array
21789 object (<a href="#6.5.6">6.5.6</a>).
21790 -- Addition or subtraction of a pointer into, or just beyond, an array object and an
21791 integer type produces a result that points just beyond the array object and is used as
21792 the operand of a unary * operator that is evaluated (<a href="#6.5.6">6.5.6</a>).
21793 -- Pointers that do not point into, or just beyond, the same array object are subtracted
21794 (<a href="#6.5.6">6.5.6</a>).
21795 -- An array subscript is out of range, even if an object is apparently accessible with the
21796 given subscript (as in the lvalue expression a[1][7] given the declaration int
21797 a[4][5]) (<a href="#6.5.6">6.5.6</a>).
21798 -- The result of subtracting two pointers is not representable in an object of type
21799 ptrdiff_t (<a href="#6.5.6">6.5.6</a>).
21800 -- An expression is shifted by a negative number or by an amount greater than or equal
21801 to the width of the promoted expression (<a href="#6.5.7">6.5.7</a>).
21802 -- An expression having signed promoted type is left-shifted and either the value of the
21803 expression is negative or the result of shifting would be not be representable in the
21804 promoted type (<a href="#6.5.7">6.5.7</a>).
21805 -- Pointers that do not point to the same aggregate or union (nor just beyond the same
21806 array object) are compared using relational operators (<a href="#6.5.8">6.5.8</a>).
21807 -- An object is assigned to an inexactly overlapping object or to an exactly overlapping
21808 object with incompatible type (<a href="#6.5.16.1">6.5.16.1</a>).
21809 -- An expression that is required to be an integer constant expression does not have an
21810 integer type; has operands that are not integer constants, enumeration constants,
21811 character constants, sizeof expressions whose results are integer constants, or
21812 immediately-cast floating constants; or contains casts (outside operands to sizeof
21813 operators) other than conversions of arithmetic types to integer types (<a href="#6.6">6.6</a>).
21814 -- A constant expression in an initializer is not, or does not evaluate to, one of the
21815 following: an arithmetic constant expression, a null pointer constant, an address
21816 constant, or an address constant for a complete object type plus or minus an integer
21817 constant expression (<a href="#6.6">6.6</a>).
21818 -- An arithmetic constant expression does not have arithmetic type; has operands that
21819 are not integer constants, floating constants, enumeration constants, character
21820 constants, or sizeof expressions; or contains casts (outside operands to sizeof
21822 [<a name="#p555" href="p555">page 555</a>] (<a href="#Contents">Contents</a>)
21824 operators) other than conversions of arithmetic types to arithmetic types (<a href="#6.6">6.6</a>).
21825 -- The value of an object is accessed by an array-subscript [], member-access . or ->,
21826 address &, or indirection * operator or a pointer cast in creating an address constant
21827 (<a href="#6.6">6.6</a>).
21828 -- An identifier for an object is declared with no linkage and the type of the object is
21829 incomplete after its declarator, or after its init-declarator if it has an initializer (<a href="#6.7">6.7</a>).
21830 -- A function is declared at block scope with an explicit storage-class specifier other
21831 than extern (<a href="#6.7.1">6.7.1</a>).
21832 -- A structure or union is defined as containing no named members, no anonymous
21833 structures, and no anonymous unions (<a href="#6.7.2.1">6.7.2.1</a>).
21834 -- An attempt is made to access, or generate a pointer to just past, a flexible array
21835 member of a structure when the referenced object provides no elements for that array
21836 (<a href="#6.7.2.1">6.7.2.1</a>).
21837 -- When the complete type is needed, an incomplete structure or union type is not
21838 completed in the same scope by another declaration of the tag that defines the content
21839 (<a href="#6.7.2.3">6.7.2.3</a>).
21840 -- An attempt is made to modify an object defined with a const-qualified type through
21841 use of an lvalue with non-const-qualified type (<a href="#6.7.3">6.7.3</a>).
21842 -- An attempt is made to refer to an object defined with a volatile-qualified type through
21843 use of an lvalue with non-volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
21844 -- An attempt is made to refer to an object defined with an _Atomic-qualified type
21845 through use of an lvalue with non-_Atomic-qualified type (<a href="#6.7.3">6.7.3</a>).
21846 -- The specification of a function type includes any type qualifiers (<a href="#6.7.3">6.7.3</a>).
21847 -- Two qualified types that are required to be compatible do not have the identically
21848 qualified version of a compatible type (<a href="#6.7.3">6.7.3</a>).
21849 -- An object which has been modified is accessed through a restrict-qualified pointer to
21850 a const-qualified type, or through a restrict-qualified pointer and another pointer that
21851 are not both based on the same object (<a href="#6.7.3.1">6.7.3.1</a>).
21852 -- A restrict-qualified pointer is assigned a value based on another restricted pointer
21853 whose associated block neither began execution before the block associated with this
21854 pointer, nor ended before the assignment (<a href="#6.7.3.1">6.7.3.1</a>).
21855 -- A function with external linkage is declared with an inline function specifier, but is
21856 not also defined in the same translation unit (<a href="#6.7.4">6.7.4</a>).
21857 -- A function declared with a _Noreturn function specifier returns to its caller (<a href="#6.7.4">6.7.4</a>).
21860 [<a name="#p556" href="p556">page 556</a>] (<a href="#Contents">Contents</a>)
21862 -- The definition of an object has an alignment specifier and another declaration of that
21863 object has a different alignment specifier (<a href="#6.7.5">6.7.5</a>).
21864 -- Declarations of an object in different translation units have different alignment
21865 specifiers (<a href="#6.7.5">6.7.5</a>).
21866 -- Two pointer types that are required to be compatible are not identically qualified, or
21867 are not pointers to compatible types (<a href="#6.7.6.1">6.7.6.1</a>).
21868 -- The size expression in an array declaration is not a constant expression and evaluates
21869 at program execution time to a nonpositive value (<a href="#6.7.6.2">6.7.6.2</a>).
21870 -- In a context requiring two array types to be compatible, they do not have compatible
21871 element types, or their size specifiers evaluate to unequal values (<a href="#6.7.6.2">6.7.6.2</a>).
21872 -- A declaration of an array parameter includes the keyword static within the [ and
21873 ] and the corresponding argument does not provide access to the first element of an
21874 array with at least the specified number of elements (<a href="#6.7.6.3">6.7.6.3</a>).
21875 -- A storage-class specifier or type qualifier modifies the keyword void as a function
21876 parameter type list (<a href="#6.7.6.3">6.7.6.3</a>).
21877 -- In a context requiring two function types to be compatible, they do not have
21878 compatible return types, or their parameters disagree in use of the ellipsis terminator
21879 or the number and type of parameters (after default argument promotion, when there
21880 is no parameter type list or when one type is specified by a function definition with an
21881 identifier list) (<a href="#6.7.6.3">6.7.6.3</a>).
21882 -- The value of an unnamed member of a structure or union is used (<a href="#6.7.9">6.7.9</a>).
21883 -- The initializer for a scalar is neither a single expression nor a single expression
21884 enclosed in braces (<a href="#6.7.9">6.7.9</a>).
21885 -- The initializer for a structure or union object that has automatic storage duration is
21886 neither an initializer list nor a single expression that has compatible structure or union
21887 type (<a href="#6.7.9">6.7.9</a>).
21888 -- The initializer for an aggregate or union, other than an array initialized by a string
21889 literal, is not a brace-enclosed list of initializers for its elements or members (<a href="#6.7.9">6.7.9</a>).
21890 -- An identifier with external linkage is used, but in the program there does not exist
21891 exactly one external definition for the identifier, or the identifier is not used and there
21892 exist multiple external definitions for the identifier (<a href="#6.9">6.9</a>).
21893 -- A function definition includes an identifier list, but the types of the parameters are not
21894 declared in a following declaration list (<a href="#6.9.1">6.9.1</a>).
21895 -- An adjusted parameter type in a function definition is not a complete object type
21896 (<a href="#6.9.1">6.9.1</a>).
21898 [<a name="#p557" href="p557">page 557</a>] (<a href="#Contents">Contents</a>)
21900 -- A function that accepts a variable number of arguments is defined without a
21901 parameter type list that ends with the ellipsis notation (<a href="#6.9.1">6.9.1</a>).
21902 -- The } that terminates a function is reached, and the value of the function call is used
21903 by the caller (<a href="#6.9.1">6.9.1</a>).
21904 -- An identifier for an object with internal linkage and an incomplete type is declared
21905 with a tentative definition (<a href="#6.9.2">6.9.2</a>).
21906 -- The token defined is generated during the expansion of a #if or #elif
21907 preprocessing directive, or the use of the defined unary operator does not match
21908 one of the two specified forms prior to macro replacement (<a href="#6.10.1">6.10.1</a>).
21909 -- The #include preprocessing directive that results after expansion does not match
21910 one of the two header name forms (<a href="#6.10.2">6.10.2</a>).
21911 -- The character sequence in an #include preprocessing directive does not start with a
21912 letter (<a href="#6.10.2">6.10.2</a>).
21913 -- There are sequences of preprocessing tokens within the list of macro arguments that
21914 would otherwise act as preprocessing directives (<a href="#6.10.3">6.10.3</a>).
21915 -- The result of the preprocessing operator # is not a valid character string literal
21916 (<a href="#6.10.3.2">6.10.3.2</a>).
21917 -- The result of the preprocessing operator ## is not a valid preprocessing token
21918 (<a href="#6.10.3.3">6.10.3.3</a>).
21919 -- The #line preprocessing directive that results after expansion does not match one of
21920 the two well-defined forms, or its digit sequence specifies zero or a number greater
21921 than 2147483647 (<a href="#6.10.4">6.10.4</a>).
21922 -- A non-STDC #pragma preprocessing directive that is documented as causing
21923 translation failure or some other form of undefined behavior is encountered (<a href="#6.10.6">6.10.6</a>).
21924 -- A #pragma STDC preprocessing directive does not match one of the well-defined
21925 forms (<a href="#6.10.6">6.10.6</a>).
21926 -- The name of a predefined macro, or the identifier defined, is the subject of a
21927 #define or #undef preprocessing directive (<a href="#6.10.8">6.10.8</a>).
21928 -- An attempt is made to copy an object to an overlapping object by use of a library
21929 function, other than as explicitly allowed (e.g., memmove) (clause 7).
21930 -- A file with the same name as one of the standard headers, not provided as part of the
21931 implementation, is placed in any of the standard places that are searched for included
21932 source files (<a href="#7.1.2">7.1.2</a>).
21933 -- A header is included within an external declaration or definition (<a href="#7.1.2">7.1.2</a>).
21936 [<a name="#p558" href="p558">page 558</a>] (<a href="#Contents">Contents</a>)
21938 -- A function, object, type, or macro that is specified as being declared or defined by
21939 some standard header is used before any header that declares or defines it is included
21940 (<a href="#7.1.2">7.1.2</a>).
21941 -- A standard header is included while a macro is defined with the same name as a
21942 keyword (<a href="#7.1.2">7.1.2</a>).
21943 -- The program attempts to declare a library function itself, rather than via a standard
21944 header, but the declaration does not have external linkage (<a href="#7.1.2">7.1.2</a>).
21945 -- The program declares or defines a reserved identifier, other than as allowed by <a href="#7.1.4">7.1.4</a>
21946 (<a href="#7.1.3">7.1.3</a>).
21947 -- The program removes the definition of a macro whose name begins with an
21948 underscore and either an uppercase letter or another underscore (<a href="#7.1.3">7.1.3</a>).
21949 -- An argument to a library function has an invalid value or a type not expected by a
21950 function with variable number of arguments (<a href="#7.1.4">7.1.4</a>).
21951 -- The pointer passed to a library function array parameter does not have a value such
21952 that all address computations and object accesses are valid (<a href="#7.1.4">7.1.4</a>).
21953 -- The macro definition of assert is suppressed in order to access an actual function
21954 (<a href="#7.2">7.2</a>).
21955 -- The argument to the assert macro does not have a scalar type (<a href="#7.2">7.2</a>).
21956 -- The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in
21957 any context other than outside all external declarations or preceding all explicit
21958 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>).
21959 -- The value of an argument to a character handling function is neither equal to the value
21960 of EOF nor representable as an unsigned char (<a href="#7.4">7.4</a>).
21961 -- A macro definition of errno is suppressed in order to access an actual object, or the
21962 program defines an identifier with the name errno (<a href="#7.5">7.5</a>).
21963 -- Part of the program tests floating-point status flags, sets floating-point control modes,
21964 or runs under non-default mode settings, but was translated with the state for the
21965 FENV_ACCESS pragma ''off'' (<a href="#7.6.1">7.6.1</a>).
21966 -- The exception-mask argument for one of the functions that provide access to the
21967 floating-point status flags has a nonzero value not obtained by bitwise OR of the
21968 floating-point exception macros (<a href="#7.6.2">7.6.2</a>).
21969 -- The fesetexceptflag function is used to set floating-point status flags that were
21970 not specified in the call to the fegetexceptflag function that provided the value
21971 of the corresponding fexcept_t object (<a href="#7.6.2.4">7.6.2.4</a>).
21975 [<a name="#p559" href="p559">page 559</a>] (<a href="#Contents">Contents</a>)
21977 -- The argument to fesetenv or feupdateenv is neither an object set by a call to
21978 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>).
21979 -- The value of the result of an integer arithmetic or conversion function cannot be
21980 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>).
21981 -- The program modifies the string pointed to by the value returned by the setlocale
21982 function (<a href="#7.11.1.1">7.11.1.1</a>).
21983 -- The program modifies the structure pointed to by the value returned by the
21984 localeconv function (<a href="#7.11.2.1">7.11.2.1</a>).
21985 -- A macro definition of math_errhandling is suppressed or the program defines
21986 an identifier with the name math_errhandling (<a href="#7.12">7.12</a>).
21987 -- An argument to a floating-point classification or comparison macro is not of real
21988 floating type (<a href="#7.12.3">7.12.3</a>, <a href="#7.12.14">7.12.14</a>).
21989 -- A macro definition of setjmp is suppressed in order to access an actual function, or
21990 the program defines an external identifier with the name setjmp (<a href="#7.13">7.13</a>).
21991 -- An invocation of the setjmp macro occurs other than in an allowed context
21992 (<a href="#7.13.2.1">7.13.2.1</a>).
21993 -- The longjmp function is invoked to restore a nonexistent environment (<a href="#7.13.2.1">7.13.2.1</a>).
21994 -- After a longjmp, there is an attempt to access the value of an object of automatic
21995 storage duration that does not have volatile-qualified type, local to the function
21996 containing the invocation of the corresponding setjmp macro, that was changed
21997 between the setjmp invocation and longjmp call (<a href="#7.13.2.1">7.13.2.1</a>).
21998 -- The program specifies an invalid pointer to a signal handler function (<a href="#7.14.1.1">7.14.1.1</a>).
21999 -- A signal handler returns when the signal corresponded to a computational exception
22000 (<a href="#7.14.1.1">7.14.1.1</a>).
22001 -- A signal occurs as the result of calling the abort or raise function, and the signal
22002 handler calls the raise function (<a href="#7.14.1.1">7.14.1.1</a>).
22003 -- A signal occurs other than as the result of calling the abort or raise function, and
22004 the signal handler refers to an object with static storage duration other than by
22005 assigning a value to an object declared as volatile sig_atomic_t, or calls any
22006 function in the standard library other than the abort function, the _Exit function,
22007 the quick_exit function, or the signal function (for the same signal number)
22008 (<a href="#7.14.1.1">7.14.1.1</a>).
22009 -- The value of errno is referred to after a signal occurred other than as the result of
22010 calling the abort or raise function and the corresponding signal handler obtained
22011 a SIG_ERR return from a call to the signal function (<a href="#7.14.1.1">7.14.1.1</a>).
22013 [<a name="#p560" href="p560">page 560</a>] (<a href="#Contents">Contents</a>)
22015 -- A signal is generated by an asynchronous signal handler (<a href="#7.14.1.1">7.14.1.1</a>).
22016 -- A function with a variable number of arguments attempts to access its varying
22017 arguments other than through a properly declared and initialized va_list object, or
22018 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>).
22019 -- The macro va_arg is invoked using the parameter ap that was passed to a function
22020 that invoked the macro va_arg with the same parameter (<a href="#7.16">7.16</a>).
22021 -- A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in
22022 order to access an actual function, or the program defines an external identifier with
22023 the name va_copy or va_end (<a href="#7.16.1">7.16.1</a>).
22024 -- The va_start or va_copy macro is invoked without a corresponding invocation
22025 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>,
22026 <a href="#7.16.1.4">7.16.1.4</a>).
22027 -- The type parameter to the va_arg macro is not such that a pointer to an object of
22028 that type can be obtained simply by postfixing a * (<a href="#7.16.1.1">7.16.1.1</a>).
22029 -- The va_arg macro is invoked when there is no actual next argument, or with a
22030 specified type that is not compatible with the promoted type of the actual next
22031 argument, with certain exceptions (<a href="#7.16.1.1">7.16.1.1</a>).
22032 -- The va_copy or va_start macro is called to initialize a va_list that was
22033 previously initialized by either macro without an intervening invocation of the
22034 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>).
22035 -- The parameter parmN of a va_start macro is declared with the register
22036 storage class, with a function or array type, or with a type that is not compatible with
22037 the type that results after application of the default argument promotions (<a href="#7.16.1.4">7.16.1.4</a>).
22038 -- The member designator parameter of an offsetof macro is an invalid right
22039 operand of the . operator for the type parameter, or designates a bit-field (<a href="#7.19">7.19</a>).
22040 -- The argument in an instance of one of the integer-constant macros is not a decimal,
22041 octal, or hexadecimal constant, or it has a value that exceeds the limits for the
22042 corresponding type (<a href="#7.20.4">7.20.4</a>).
22043 -- A byte input/output function is applied to a wide-oriented stream, or a wide character
22044 input/output function is applied to a byte-oriented stream (<a href="#7.21.2">7.21.2</a>).
22045 -- Use is made of any portion of a file beyond the most recent wide character written to
22046 a wide-oriented stream (<a href="#7.21.2">7.21.2</a>).
22047 -- The value of a pointer to a FILE object is used after the associated file is closed
22048 (<a href="#7.21.3">7.21.3</a>).
22049 -- The stream for the fflush function points to an input stream or to an update stream
22050 in which the most recent operation was input (<a href="#7.21.5.2">7.21.5.2</a>).
22051 [<a name="#p561" href="p561">page 561</a>] (<a href="#Contents">Contents</a>)
22053 -- The string pointed to by the mode argument in a call to the fopen function does not
22054 exactly match one of the specified character sequences (<a href="#7.21.5.3">7.21.5.3</a>).
22055 -- An output operation on an update stream is followed by an input operation without an
22056 intervening call to the fflush function or a file positioning function, or an input
22057 operation on an update stream is followed by an output operation with an intervening
22058 call to a file positioning function (<a href="#7.21.5.3">7.21.5.3</a>).
22059 -- An attempt is made to use the contents of the array that was supplied in a call to the
22060 setvbuf function (<a href="#7.21.5.6">7.21.5.6</a>).
22061 -- There are insufficient arguments for the format in a call to one of the formatted
22062 input/output functions, or an argument does not have an appropriate type (<a href="#7.21.6.1">7.21.6.1</a>,
22063 <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>).
22064 -- The format in a call to one of the formatted input/output functions or to the
22065 strftime or wcsftime function is not a valid multibyte character sequence that
22066 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>,
22067 <a href="#7.28.5.1">7.28.5.1</a>).
22068 -- In a call to one of the formatted output functions, a precision appears with a
22069 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>).
22070 -- A conversion specification for a formatted output function uses an asterisk to denote
22071 an argument-supplied field width or precision, but the corresponding argument is not
22072 provided (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>).
22073 -- A conversion specification for a formatted output function uses a # or 0 flag with a
22074 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>).
22075 -- A conversion specification for one of the formatted input/output functions uses a
22076 length modifier with a conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>,
22077 <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>).
22078 -- An s conversion specifier is encountered by one of the formatted output functions,
22079 and the argument is missing the null terminator (unless a precision is specified that
22080 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>).
22081 -- An n conversion specification for one of the formatted input/output functions includes
22082 any flags, an assignment-suppressing character, a field width, or a precision (<a href="#7.21.6.1">7.21.6.1</a>,
22083 <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>).
22084 -- A % conversion specifier is encountered by one of the formatted input/output
22085 functions, but the complete conversion specification is not exactly %% (<a href="#7.21.6.1">7.21.6.1</a>,
22086 <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>).
22087 -- An invalid conversion specification is found in the format for one of the formatted
22088 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>,
22090 [<a name="#p562" href="p562">page 562</a>] (<a href="#Contents">Contents</a>)
22092 <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>).
22093 -- The number of characters transmitted by a formatted output function is greater than
22094 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>).
22095 -- The result of a conversion by one of the formatted input functions cannot be
22096 represented in the corresponding object, or the receiving object does not have an
22097 appropriate type (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>).
22098 -- A c, s, or [ conversion specifier is encountered by one of the formatted input
22099 functions, and the array pointed to by the corresponding argument is not large enough
22100 to accept the input sequence (and a null terminator if the conversion specifier is s or
22101 [) (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>).
22102 -- A c, s, or [ conversion specifier with an l qualifier is encountered by one of the
22103 formatted input functions, but the input is not a valid multibyte character sequence
22104 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>).
22105 -- The input item for a %p conversion by one of the formatted input functions is not a
22106 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>).
22107 -- The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf,
22108 vsscanf, vfwprintf, vfwscanf, vswprintf, vswscanf, vwprintf, or
22109 vwscanf function is called with an improperly initialized va_list argument, or
22110 the argument is used (other than in an invocation of va_end) after the function
22111 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>,
22112 <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>).
22113 -- The contents of the array supplied in a call to the fgets or fgetws function are
22114 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>).
22115 -- The file position indicator for a binary stream is used after a call to the ungetc
22116 function where its value was zero before the call (<a href="#7.21.7.10">7.21.7.10</a>).
22117 -- The file position indicator for a stream is used after an error occurred during a call to
22118 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>).
22119 -- A partial element read by a call to the fread function is used (<a href="#7.21.8.1">7.21.8.1</a>).
22120 -- The fseek function is called for a text stream with a nonzero offset and either the
22121 offset was not returned by a previous successful call to the ftell function on a
22122 stream associated with the same file or whence is not SEEK_SET (<a href="#7.21.9.2">7.21.9.2</a>).
22123 -- The fsetpos function is called to set a position that was not returned by a previous
22124 successful call to the fgetpos function on a stream associated with the same file
22125 (<a href="#7.21.9.3">7.21.9.3</a>).
22126 -- A non-null pointer returned by a call to the calloc, malloc, or realloc function
22127 with a zero requested size is used to access an object (<a href="#7.22.3">7.22.3</a>).
22129 [<a name="#p563" href="p563">page 563</a>] (<a href="#Contents">Contents</a>)
22131 -- The value of a pointer that refers to space deallocated by a call to the free or
22132 realloc function is used (<a href="#7.22.3">7.22.3</a>).
22133 -- The alignment requested of the aligned_alloc function is not valid or not
22134 supported by the implementation, or the size requested is not an integral multiple of
22135 the alignment (<a href="#7.22.3.1">7.22.3.1</a>).
22136 -- The pointer argument to the free or realloc function does not match a pointer
22137 earlier returned by a memory management function, or the space has been deallocated
22138 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>).
22139 -- The value of the object allocated by the malloc function is used (<a href="#7.22.3.4">7.22.3.4</a>).
22140 -- The value of any bytes in a new object allocated by the realloc function beyond
22141 the size of the old object are used (<a href="#7.22.3.5">7.22.3.5</a>).
22142 -- The program calls the exit or quick_exit function more than once, or calls both
22143 functions (<a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.7">7.22.4.7</a>).
22144 -- During the call to a function registered with the atexit or at_quick_exit
22145 function, a call is made to the longjmp function that would terminate the call to the
22146 registered function (<a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.7">7.22.4.7</a>).
22147 -- The string set up by the getenv or strerror function is modified by the program
22148 (<a href="#7.22.4.6">7.22.4.6</a>, <a href="#7.23.6.2">7.23.6.2</a>).
22149 -- A command is executed through the system function in a way that is documented as
22150 causing termination or some other form of undefined behavior (<a href="#7.22.4.8">7.22.4.8</a>).
22151 -- A searching or sorting utility function is called with an invalid pointer argument, even
22152 if the number of elements is zero (<a href="#7.22.5">7.22.5</a>).
22153 -- The comparison function called by a searching or sorting utility function alters the
22154 contents of the array being searched or sorted, or returns ordering values
22155 inconsistently (<a href="#7.22.5">7.22.5</a>).
22156 -- The array being searched by the bsearch function does not have its elements in
22157 proper order (<a href="#7.22.5.1">7.22.5.1</a>).
22158 -- The current conversion state is used by a multibyte/wide character conversion
22159 function after changing the LC_CTYPE category (<a href="#7.22.7">7.22.7</a>).
22160 -- A string or wide string utility function is instructed to access an array beyond the end
22161 of an object (<a href="#7.23.1">7.23.1</a>, <a href="#7.28.4">7.28.4</a>).
22162 -- A string or wide string utility function is called with an invalid pointer argument, even
22163 if the length is zero (<a href="#7.23.1">7.23.1</a>, <a href="#7.28.4">7.28.4</a>).
22164 -- The contents of the destination array are used after a call to the strxfrm,
22165 strftime, wcsxfrm, or wcsftime function in which the specified length was
22167 [<a name="#p564" href="p564">page 564</a>] (<a href="#Contents">Contents</a>)
22169 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>,
22170 <a href="#7.28.5.1">7.28.5.1</a>).
22171 -- The first argument in the very first call to the strtok or wcstok is a null pointer
22172 (<a href="#7.23.5.8">7.23.5.8</a>, <a href="#7.28.4.5.7">7.28.4.5.7</a>).
22173 -- The type of an argument to a type-generic macro is not compatible with the type of
22174 the corresponding parameter of the selected function (<a href="#7.24">7.24</a>).
22175 -- A complex argument is supplied for a generic parameter of a type-generic macro that
22176 has no corresponding complex function (<a href="#7.24">7.24</a>).
22177 -- At least one field of the broken-down time passed to asctime contains a value
22178 outside its normal range, or the calculated year exceeds four digits or is less than the
22179 year 1000 (<a href="#7.26.3.1">7.26.3.1</a>).
22180 -- The argument corresponding to an s specifier without an l qualifier in a call to the
22181 fwprintf function does not point to a valid multibyte character sequence that
22182 begins in the initial shift state (<a href="#7.28.2.11">7.28.2.11</a>).
22183 -- In a call to the wcstok function, the object pointed to by ptr does not have the
22184 value stored by the previous call for the same wide string (<a href="#7.28.4.5.7">7.28.4.5.7</a>).
22185 -- An mbstate_t object is used inappropriately (<a href="#7.28.6">7.28.6</a>).
22186 -- The value of an argument of type wint_t to a wide character classification or case
22187 mapping function is neither equal to the value of WEOF nor representable as a
22188 wchar_t (<a href="#7.29.1">7.29.1</a>).
22189 -- The iswctype function is called using a different LC_CTYPE category from the
22190 one in effect for the call to the wctype function that returned the description
22191 (<a href="#7.29.2.2.1">7.29.2.2.1</a>).
22192 -- The towctrans function is called using a different LC_CTYPE category from the
22193 one in effect for the call to the wctrans function that returned the description
22194 (<a href="#7.29.3.2.1">7.29.3.2.1</a>).
22199 [<a name="#p565" href="p565">page 565</a>] (<a href="#Contents">Contents</a>)
22201 <a name="J.3" href="#J.3"><b> J.3 Implementation-defined behavior</b></a>
22202 1 A conforming implementation is required to document its choice of behavior in each of
22203 the areas listed in this subclause. The following are implementation-defined:
22204 <a name="J.3.1" href="#J.3.1"><b> J.3.1 Translation</b></a>
22205 1 -- How a diagnostic is identified (<a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a>).
22206 -- Whether each nonempty sequence of white-space characters other than new-line is
22207 retained or replaced by one space character in translation phase 3 (<a href="#5.1.1.2">5.1.1.2</a>).
22208 <a name="J.3.2" href="#J.3.2"><b> J.3.2 Environment</b></a>
22209 1 -- The mapping between physical source file multibyte characters and the source
22210 character set in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>).
22211 -- The name and type of the function called at program startup in a freestanding
22212 environment (<a href="#5.1.2.1">5.1.2.1</a>).
22213 -- The effect of program termination in a freestanding environment (<a href="#5.1.2.1">5.1.2.1</a>).
22214 -- An alternative manner in which the main function may be defined (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
22215 -- 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>).
22216 -- What constitutes an interactive device (<a href="#5.1.2.3">5.1.2.3</a>).
22217 -- Whether a program can have more than one thread of execution in a freestanding
22218 environment (<a href="#5.1.2.4">5.1.2.4</a>).
22219 -- The set of signals, their semantics, and their default handling (<a href="#7.14">7.14</a>).
22220 -- Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
22221 computational exception (<a href="#7.14.1.1">7.14.1.1</a>).
22222 -- Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
22223 program startup (<a href="#7.14.1.1">7.14.1.1</a>).
22224 -- The set of environment names and the method for altering the environment list used
22225 by the getenv function (<a href="#7.22.4.6">7.22.4.6</a>).
22226 -- The manner of execution of the string by the system function (<a href="#7.22.4.8">7.22.4.8</a>).
22231 [<a name="#p566" href="p566">page 566</a>] (<a href="#Contents">Contents</a>)
22233 <a name="J.3.3" href="#J.3.3"><b> J.3.3 Identifiers</b></a>
22234 1 -- Which additional multibyte characters may appear in identifiers and their
22235 correspondence to universal character names (<a href="#6.4.2">6.4.2</a>).
22236 -- 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>).
22237 <a name="J.3.4" href="#J.3.4"><b> J.3.4 Characters</b></a>
22238 1 -- The number of bits in a byte (<a href="#3.6">3.6</a>).
22239 -- The values of the members of the execution character set (<a href="#5.2.1">5.2.1</a>).
22240 -- The unique value of the member of the execution character set produced for each of
22241 the standard alphabetic escape sequences (<a href="#5.2.2">5.2.2</a>).
22242 -- The value of a char object into which has been stored any character other than a
22243 member of the basic execution character set (<a href="#6.2.5">6.2.5</a>).
22244 -- Which of signed char or unsigned char has the same range, representation,
22245 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>).
22246 -- The mapping of members of the source character set (in character constants and string
22247 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>).
22248 -- The value of an integer character constant containing more than one character or
22249 containing a character or escape sequence that does not map to a single-byte
22250 execution character (<a href="#6.4.4.4">6.4.4.4</a>).
22251 -- The value of a wide character constant containing more than one multibyte character
22252 or a single multibyte character that maps to multiple members of the extended
22253 execution character set, or containing a multibyte character or escape sequence not
22254 represented in the extended execution character set (<a href="#6.4.4.4">6.4.4.4</a>).
22255 -- The current locale used to convert a wide character constant consisting of a single
22256 multibyte character that maps to a member of the extended execution character set
22257 into a corresponding wide character code (<a href="#6.4.4.4">6.4.4.4</a>).
22258 -- Whether differently-prefixed wide string literal tokens can be concatenated and, if so,
22259 the treatment of the resulting multibyte character sequence (<a href="#6.4.5">6.4.5</a>).
22260 -- The current locale used to convert a wide string literal into corresponding wide
22261 character codes (<a href="#6.4.5">6.4.5</a>).
22262 -- The value of a string literal containing a multibyte character or escape sequence not
22263 represented in the execution character set (<a href="#6.4.5">6.4.5</a>).
22264 -- The encoding of any of wchar_t, char16_t, and char32_t where the
22265 corresponding standard encoding macro (__STDC_ISO_10646__,
22266 __STDC_UTF_16__, or __STDC_UTF_32__) is not defined (<a href="#6.10.8.2">6.10.8.2</a>).
22268 [<a name="#p567" href="p567">page 567</a>] (<a href="#Contents">Contents</a>)
22270 <a name="J.3.5" href="#J.3.5"><b> J.3.5 Integers</b></a>
22271 1 -- Any extended integer types that exist in the implementation (<a href="#6.2.5">6.2.5</a>).
22272 -- Whether signed integer types are represented using sign and magnitude, two's
22273 complement, or ones' complement, and whether the extraordinary value is a trap
22274 representation or an ordinary value (<a href="#6.2.6.2">6.2.6.2</a>).
22275 -- The rank of any extended integer type relative to another extended integer type with
22276 the same precision (<a href="#6.3.1.1">6.3.1.1</a>).
22277 -- The result of, or the signal raised by, converting an integer to a signed integer type
22278 when the value cannot be represented in an object of that type (<a href="#6.3.1.3">6.3.1.3</a>).
22279 -- The results of some bitwise operations on signed integers (<a href="#6.5">6.5</a>).
22280 <a name="J.3.6" href="#J.3.6"><b> J.3.6 Floating point</b></a>
22281 1 -- The accuracy of the floating-point operations and of the library functions in
22282 <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>).
22283 -- The accuracy of the conversions between floating-point internal representations and
22284 string representations performed by the library functions in <a href="#7.21"><stdio.h></a>,
22285 <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>).
22286 -- The rounding behaviors characterized by non-standard values of FLT_ROUNDS
22287 (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
22288 -- The evaluation methods characterized by non-standard negative values of
22289 FLT_EVAL_METHOD (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
22290 -- The direction of rounding when an integer is converted to a floating-point number that
22291 cannot exactly represent the original value (<a href="#6.3.1.4">6.3.1.4</a>).
22292 -- The direction of rounding when a floating-point number is converted to a narrower
22293 floating-point number (<a href="#6.3.1.5">6.3.1.5</a>).
22294 -- How the nearest representable value or the larger or smaller representable value
22295 immediately adjacent to the nearest representable value is chosen for certain floating
22296 constants (<a href="#6.4.4.2">6.4.4.2</a>).
22297 -- Whether and how floating expressions are contracted when not disallowed by the
22298 FP_CONTRACT pragma (<a href="#6.5">6.5</a>).
22299 -- The default state for the FENV_ACCESS pragma (<a href="#7.6.1">7.6.1</a>).
22300 -- Additional floating-point exceptions, rounding modes, environments, and
22301 classifications, and their macro names (<a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>).
22302 -- The default state for the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>).
22305 [<a name="#p568" href="p568">page 568</a>] (<a href="#Contents">Contents</a>)
22307 <a name="J.3.7" href="#J.3.7"><b> J.3.7 Arrays and pointers</b></a>
22308 1 -- The result of converting a pointer to an integer or vice versa (<a href="#6.3.2.3">6.3.2.3</a>).
22309 -- The size of the result of subtracting two pointers to elements of the same array
22310 (<a href="#6.5.6">6.5.6</a>).
22311 <a name="J.3.8" href="#J.3.8"><b> J.3.8 Hints</b></a>
22312 1 -- The extent to which suggestions made by using the register storage-class
22313 specifier are effective (<a href="#6.7.1">6.7.1</a>).
22314 -- The extent to which suggestions made by using the inline function specifier are
22315 effective (<a href="#6.7.4">6.7.4</a>).
22316 <a name="J.3.9" href="#J.3.9"><b> J.3.9 Structures, unions, enumerations, and bit-fields</b></a>
22317 1 -- Whether a ''plain'' int bit-field is treated as a signed int bit-field or as an
22318 unsigned int bit-field (<a href="#6.7.2">6.7.2</a>, <a href="#6.7.2.1">6.7.2.1</a>).
22319 -- Allowable bit-field types other than _Bool, signed int, and unsigned int
22320 (<a href="#6.7.2.1">6.7.2.1</a>).
22321 -- Whether a bit-field can straddle a storage-unit boundary (<a href="#6.7.2.1">6.7.2.1</a>).
22322 -- The order of allocation of bit-fields within a unit (<a href="#6.7.2.1">6.7.2.1</a>).
22323 -- The alignment of non-bit-field members of structures (<a href="#6.7.2.1">6.7.2.1</a>). This should present
22324 no problem unless binary data written by one implementation is read by another.
22325 -- The integer type compatible with each enumerated type (<a href="#6.7.2.2">6.7.2.2</a>).
22326 <a name="J.3.10" href="#J.3.10"><b> J.3.10 Qualifiers</b></a>
22327 1 -- What constitutes an access to an object that has volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
22328 <a name="J.3.11" href="#J.3.11"><b> J.3.11 Preprocessing directives</b></a>
22329 1 -- The locations within #pragma directives where header name preprocessing tokens
22330 are recognized (<a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>).
22331 -- How sequences in both forms of header names are mapped to headers or external
22332 source file names (<a href="#6.4.7">6.4.7</a>).
22333 -- Whether the value of a character constant in a constant expression that controls
22334 conditional inclusion matches the value of the same character constant in the
22335 execution character set (<a href="#6.10.1">6.10.1</a>).
22336 -- Whether the value of a single-character character constant in a constant expression
22337 that controls conditional inclusion may have a negative value (<a href="#6.10.1">6.10.1</a>).
22338 -- The places that are searched for an included < > delimited header, and how the places
22339 are specified or the header is identified (<a href="#6.10.2">6.10.2</a>).
22340 [<a name="#p569" href="p569">page 569</a>] (<a href="#Contents">Contents</a>)
22342 -- How the named source file is searched for in an included " " delimited header
22343 (<a href="#6.10.2">6.10.2</a>).
22344 -- The method by which preprocessing tokens (possibly resulting from macro
22345 expansion) in a #include directive are combined into a header name (<a href="#6.10.2">6.10.2</a>).
22346 -- The nesting limit for #include processing (<a href="#6.10.2">6.10.2</a>).
22347 -- Whether the # operator inserts a \ character before the \ character that begins a
22348 universal character name in a character constant or string literal (<a href="#6.10.3.2">6.10.3.2</a>).
22349 -- The behavior on each recognized non-STDC #pragma directive (<a href="#6.10.6">6.10.6</a>).
22350 -- The definitions for __DATE__ and __TIME__ when respectively, the date and
22351 time of translation are not available (<a href="#6.10.8.1">6.10.8.1</a>).
22352 <a name="J.3.12" href="#J.3.12"><b> J.3.12 Library functions</b></a>
22353 1 -- Any library facilities available to a freestanding program, other than the minimal set
22354 required by clause 4 (<a href="#5.1.2.1">5.1.2.1</a>).
22355 -- The format of the diagnostic printed by the assert macro (<a href="#7.2.1.1">7.2.1.1</a>).
22356 -- The representation of the floating-point status flags stored by the
22357 fegetexceptflag function (<a href="#7.6.2.2">7.6.2.2</a>).
22358 -- Whether the feraiseexcept function raises the ''inexact'' floating-point
22359 exception in addition to the ''overflow'' or ''underflow'' floating-point exception
22360 (<a href="#7.6.2.3">7.6.2.3</a>).
22361 -- Strings other than "C" and "" that may be passed as the second argument to the
22362 setlocale function (<a href="#7.11.1.1">7.11.1.1</a>).
22363 -- The types defined for float_t and double_t when the value of the
22364 FLT_EVAL_METHOD macro is less than 0 (<a href="#7.12">7.12</a>).
22365 -- Domain errors for the mathematics functions, other than those required by this
22366 International Standard (<a href="#7.12.1">7.12.1</a>).
22367 -- The values returned by the mathematics functions on domain errors or pole errors
22368 (<a href="#7.12.1">7.12.1</a>).
22369 -- The values returned by the mathematics functions on underflow range errors, whether
22370 errno is set to the value of the macro ERANGE when the integer expression
22371 math_errhandling & MATH_ERRNO is nonzero, and whether the ''underflow''
22372 floating-point exception is raised when the integer expression math_errhandling
22373 & MATH_ERREXCEPT is nonzero. (<a href="#7.12.1">7.12.1</a>).
22374 -- Whether a domain error occurs or zero is returned when an fmod function has a
22375 second argument of zero (<a href="#7.12.10.1">7.12.10.1</a>).
22377 [<a name="#p570" href="p570">page 570</a>] (<a href="#Contents">Contents</a>)
22379 -- Whether a domain error occurs or zero is returned when a remainder function has
22380 a second argument of zero (<a href="#7.12.10.2">7.12.10.2</a>).
22381 -- The base-2 logarithm of the modulus used by the remquo functions in reducing the
22382 quotient (<a href="#7.12.10.3">7.12.10.3</a>).
22383 -- Whether a domain error occurs or zero is returned when a remquo function has a
22384 second argument of zero (<a href="#7.12.10.3">7.12.10.3</a>).
22385 -- Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call
22386 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>).
22387 -- The null pointer constant to which the macro NULL expands (<a href="#7.19">7.19</a>).
22388 -- Whether the last line of a text stream requires a terminating new-line character
22389 (<a href="#7.21.2">7.21.2</a>).
22390 -- Whether space characters that are written out to a text stream immediately before a
22391 new-line character appear when read in (<a href="#7.21.2">7.21.2</a>).
22392 -- The number of null characters that may be appended to data written to a binary
22393 stream (<a href="#7.21.2">7.21.2</a>).
22394 -- Whether the file position indicator of an append-mode stream is initially positioned at
22395 the beginning or end of the file (<a href="#7.21.3">7.21.3</a>).
22396 -- Whether a write on a text stream causes the associated file to be truncated beyond that
22397 point (<a href="#7.21.3">7.21.3</a>).
22398 -- The characteristics of file buffering (<a href="#7.21.3">7.21.3</a>).
22399 -- Whether a zero-length file actually exists (<a href="#7.21.3">7.21.3</a>).
22400 -- The rules for composing valid file names (<a href="#7.21.3">7.21.3</a>).
22401 -- Whether the same file can be simultaneously open multiple times (<a href="#7.21.3">7.21.3</a>).
22402 -- The nature and choice of encodings used for multibyte characters in files (<a href="#7.21.3">7.21.3</a>).
22403 -- The effect of the remove function on an open file (<a href="#7.21.4.1">7.21.4.1</a>).
22404 -- The effect if a file with the new name exists prior to a call to the rename function
22405 (<a href="#7.21.4.2">7.21.4.2</a>).
22406 -- Whether an open temporary file is removed upon abnormal program termination
22407 (<a href="#7.21.4.3">7.21.4.3</a>).
22408 -- Which changes of mode are permitted (if any), and under what circumstances
22409 (<a href="#7.21.5.4">7.21.5.4</a>).
22410 -- The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
22411 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>).
22413 [<a name="#p571" href="p571">page 571</a>] (<a href="#Contents">Contents</a>)
22415 -- The output for %p conversion in the fprintf or fwprintf function (<a href="#7.21.6.1">7.21.6.1</a>,
22416 <a href="#7.28.2.1">7.28.2.1</a>).
22417 -- The interpretation of a - character that is neither the first nor the last character, nor
22418 the second where a ^ character is the first, in the scanlist for %[ conversion in the
22419 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>).
22420 -- The set of sequences matched by a %p conversion and the interpretation of the
22421 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>).
22422 -- The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
22423 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>).
22424 -- The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
22425 converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold
22426 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>).
22427 -- Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
22428 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>).
22429 -- Whether the calloc, malloc, and realloc functions return a null pointer or a
22430 pointer to an allocated object when the size requested is zero (<a href="#7.22.3">7.22.3</a>).
22431 -- Whether open streams with unwritten buffered data are flushed, open streams are
22432 closed, or temporary files are removed when the abort or _Exit function is called
22433 (<a href="#7.22.4.1">7.22.4.1</a>, <a href="#7.22.4.5">7.22.4.5</a>).
22434 -- The termination status returned to the host environment by the abort, exit,
22435 _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>).
22436 -- The value returned by the system function when its argument is not a null pointer
22437 (<a href="#7.22.4.8">7.22.4.8</a>).
22438 -- The local time zone and Daylight Saving Time (<a href="#7.26.1">7.26.1</a>).
22439 -- The range and precision of times representable in clock_t and time_t (<a href="#7.26">7.26</a>).
22440 -- The era for the clock function (<a href="#7.26.2.1">7.26.2.1</a>).
22441 -- The replacement string for the %Z specifier to the strftime, and wcsftime
22442 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>).
22443 -- Whether the functions in <a href="#7.12"><math.h></a> honor the rounding direction mode in an
22444 IEC 60559 conformant implementation, unless explicitly specified otherwise (<a href="#F.10">F.10</a>).
22449 [<a name="#p572" href="p572">page 572</a>] (<a href="#Contents">Contents</a>)
22451 <a name="J.3.13" href="#J.3.13"><b> J.3.13 Architecture</b></a>
22452 1 -- The values or expressions assigned to the macros specified in the headers
22453 <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>).
22454 -- The result of attempting to indirectly access an object with automatic or thread
22455 storage duration from a thread other than the one with which it is associated (<a href="#6.2.4">6.2.4</a>).
22456 -- The number, order, and encoding of bytes in any object (when not explicitly specified
22457 in this International Standard) (<a href="#6.2.6.1">6.2.6.1</a>).
22458 -- Whether any extended alignments are supported and the contexts in which they are
22459 supported (<a href="#6.2.8">6.2.8</a>).
22460 -- Valid alignment values other than those returned by an alignof expression for
22461 fundamental types, if any (<a href="#6.2.8">6.2.8</a>).
22462 -- The value of the result of the sizeof and alignof operators (<a href="#6.5.3.4">6.5.3.4</a>).
22463 <a name="J.4" href="#J.4"><b> J.4 Locale-specific behavior</b></a>
22464 1 The following characteristics of a hosted environment are locale-specific and are required
22465 to be documented by the implementation:
22466 -- Additional members of the source and execution character sets beyond the basic
22467 character set (<a href="#5.2.1">5.2.1</a>).
22468 -- The presence, meaning, and representation of additional multibyte characters in the
22469 execution character set beyond the basic character set (<a href="#5.2.1.2">5.2.1.2</a>).
22470 -- The shift states used for the encoding of multibyte characters (<a href="#5.2.1.2">5.2.1.2</a>).
22471 -- The direction of writing of successive printing characters (<a href="#5.2.2">5.2.2</a>).
22472 -- The decimal-point character (<a href="#7.1.1">7.1.1</a>).
22473 -- The set of printing characters (<a href="#7.4">7.4</a>, <a href="#7.29.2">7.29.2</a>).
22474 -- The set of control characters (<a href="#7.4">7.4</a>, <a href="#7.29.2">7.29.2</a>).
22475 -- The sets of characters tested for by the isalpha, isblank, islower, ispunct,
22476 isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
22477 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>,
22478 <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>).
22479 -- The native environment (<a href="#7.11.1.1">7.11.1.1</a>).
22480 -- Additional subject sequences accepted by the numeric conversion functions (<a href="#7.22.1">7.22.1</a>,
22481 <a href="#7.28.4.1">7.28.4.1</a>).
22482 -- 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>).
22485 [<a name="#p573" href="p573">page 573</a>] (<a href="#Contents">Contents</a>)
22487 -- The contents of the error message strings set up by the strerror function
22488 (<a href="#7.23.6.2">7.23.6.2</a>).
22489 -- 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>).
22490 -- Character mappings that are supported by the towctrans function (<a href="#7.29.1">7.29.1</a>).
22491 -- Character classifications that are supported by the iswctype function (<a href="#7.29.1">7.29.1</a>).
22492 <a name="J.5" href="#J.5"><b> J.5 Common extensions</b></a>
22493 1 The following extensions are widely used in many systems, but are not portable to all
22494 implementations. The inclusion of any extension that may cause a strictly conforming
22495 program to become invalid renders an implementation nonconforming. Examples of such
22496 extensions are new keywords, extra library functions declared in standard headers, or
22497 predefined macros with names that do not begin with an underscore.
22498 <a name="J.5.1" href="#J.5.1"><b> J.5.1 Environment arguments</b></a>
22499 1 In a hosted environment, the main function receives a third argument, char *envp[],
22500 that points to a null-terminated array of pointers to char, each of which points to a string
22501 that provides information about the environment for this execution of the program
22502 (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
22503 <a name="J.5.2" href="#J.5.2"><b> J.5.2 Specialized identifiers</b></a>
22504 1 Characters other than the underscore _, letters, and digits, that are not part of the basic
22505 source character set (such as the dollar sign $, or characters in national character sets)
22506 may appear in an identifier (<a href="#6.4.2">6.4.2</a>).
22507 <a name="J.5.3" href="#J.5.3"><b> J.5.3 Lengths and cases of identifiers</b></a>
22508 1 All characters in identifiers (with or without external linkage) are significant (<a href="#6.4.2">6.4.2</a>).
22509 <a name="J.5.4" href="#J.5.4"><b> J.5.4 Scopes of identifiers</b></a>
22510 1 A function identifier, or the identifier of an object the declaration of which contains the
22511 keyword extern, has file scope (<a href="#6.2.1">6.2.1</a>).
22512 <a name="J.5.5" href="#J.5.5"><b> J.5.5 Writable string literals</b></a>
22513 1 String literals are modifiable (in which case, identical string literals should denote distinct
22514 objects) (<a href="#6.4.5">6.4.5</a>).
22519 [<a name="#p574" href="p574">page 574</a>] (<a href="#Contents">Contents</a>)
22521 <a name="J.5.6" href="#J.5.6"><b> J.5.6 Other arithmetic types</b></a>
22522 1 Additional arithmetic types, such as __int128 or double double, and their
22523 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
22524 more range or precision than long double, may be used for evaluating expressions of
22525 other floating types, and may be used to define float_t or double_t.
22526 <a name="J.5.7" href="#J.5.7"><b> J.5.7 Function pointer casts</b></a>
22527 1 A pointer to an object or to void may be cast to a pointer to a function, allowing data to
22528 be invoked as a function (<a href="#6.5.4">6.5.4</a>).
22529 2 A pointer to a function may be cast to a pointer to an object or to void, allowing a
22530 function to be inspected or modified (for example, by a debugger) (<a href="#6.5.4">6.5.4</a>).
22531 <a name="J.5.8" href="#J.5.8"><b> J.5.8 Extended bit-field types</b></a>
22532 1 A bit-field may be declared with a type other than _Bool, unsigned int, or
22533 signed int, with an appropriate maximum width (<a href="#6.7.2.1">6.7.2.1</a>).
22534 <a name="J.5.9" href="#J.5.9"><b> J.5.9 The fortran keyword</b></a>
22535 1 The fortran function specifier may be used in a function declaration to indicate that
22536 calls suitable for FORTRAN should be generated, or that a different representation for the
22537 external name is to be generated (<a href="#6.7.4">6.7.4</a>).
22538 <a name="J.5.10" href="#J.5.10"><b> J.5.10 The asm keyword</b></a>
22539 1 The asm keyword may be used to insert assembly language directly into the translator
22540 output (<a href="#6.8">6.8</a>). The most common implementation is via a statement of the form:
22541 asm ( character-string-literal );
22542 <a name="J.5.11" href="#J.5.11"><b> J.5.11 Multiple external definitions</b></a>
22543 1 There may be more than one external definition for the identifier of an object, with or
22544 without the explicit use of the keyword extern; if the definitions disagree, or more than
22545 one is initialized, the behavior is undefined (<a href="#6.9.2">6.9.2</a>).
22546 <a name="J.5.12" href="#J.5.12"><b> J.5.12 Predefined macro names</b></a>
22547 1 Macro names that do not begin with an underscore, describing the translation and
22548 execution environments, are defined by the implementation before translation begins
22549 (<a href="#6.10.8">6.10.8</a>).
22554 [<a name="#p575" href="p575">page 575</a>] (<a href="#Contents">Contents</a>)
22556 <a name="J.5.13" href="#J.5.13"><b> J.5.13 Floating-point status flags</b></a>
22557 1 If any floating-point status flags are set on normal termination after all calls to functions
22558 registered by the atexit function have been made (see <a href="#7.22.4.4">7.22.4.4</a>), the implementation
22559 writes some diagnostics indicating the fact to the stderr stream, if it is still open,
22560 <a name="J.5.14" href="#J.5.14"><b> J.5.14 Extra arguments for signal handlers</b></a>
22561 1 Handlers for specific signals are called with extra arguments in addition to the signal
22562 number (<a href="#7.14.1.1">7.14.1.1</a>).
22563 <a name="J.5.15" href="#J.5.15"><b> J.5.15 Additional stream types and file-opening modes</b></a>
22564 1 Additional mappings from files to streams are supported (<a href="#7.21.2">7.21.2</a>).
22565 2 Additional file-opening modes may be specified by characters appended to the mode
22566 argument of the fopen function (<a href="#7.21.5.3">7.21.5.3</a>).
22567 <a name="J.5.16" href="#J.5.16"><b> J.5.16 Defined file position indicator</b></a>
22568 1 The file position indicator is decremented by each successful call to the ungetc or
22569 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>,
22570 <a name="7.28.3.10)" href="#7.28.3.10)"><b> 7.28.3.10).</b></a>
22571 <a name="J.5.17" href="#J.5.17"><b> J.5.17 Math error reporting</b></a>
22572 1 Functions declared in <a href="#7.3"><complex.h></a> and <a href="#7.12"><math.h></a> raise SIGFPE to report errors
22573 instead of, or in addition to, setting errno or raising floating-point exceptions (<a href="#7.3">7.3</a>,
22574 <a name="7.12)" href="#7.12)"><b> 7.12).</b></a>
22579 [<a name="#p576" href="p576">page 576</a>] (<a href="#Contents">Contents</a>)
22581 <a name="K" href="#K"><b> Annex K</b></a>
22583 Bounds-checking interfaces
22584 <a name="K.1" href="#K.1"><b> K.1 Background</b></a>
22585 1 Traditionally, the C Library has contained many functions that trust the programmer to
22586 provide output character arrays big enough to hold the result being produced. Not only
22587 do these functions not check that the arrays are big enough, they frequently lack the
22588 information needed to perform such checks. While it is possible to write safe, robust, and
22589 error-free code using the existing library, the library tends to promote programming styles
22590 that lead to mysterious failures if a result is too big for the provided array.
22591 2 A common programming style is to declare character arrays large enough to handle most
22592 practical cases. However, if these arrays are not large enough to handle the resulting
22593 strings, data can be written past the end of the array overwriting other data and program
22594 structures. The program never gets any indication that a problem exists, and so never has
22595 a chance to recover or to fail gracefully.
22596 3 Worse, this style of programming has compromised the security of computers and
22597 networks. Buffer overflows can often be exploited to run arbitrary code with the
22598 permissions of the vulnerable (defective) program.
22599 4 If the programmer writes runtime checks to verify lengths before calling library
22600 functions, then those runtime checks frequently duplicate work done inside the library
22601 functions, which discover string lengths as a side effect of doing their job.
22602 5 This annex provides alternative library functions that promote safer, more secure
22603 programming. The alternative functions verify that output buffers are large enough for
22604 the intended result and return a failure indicator if they are not. Data is never written past
22605 the end of an array. All string results are null terminated.
22606 6 This annex also addresses another problem that complicates writing robust code:
22607 functions that are not reentrant because they return pointers to static objects owned by the
22608 function. Such functions can be troublesome since a previously returned result can
22609 change if the function is called again, perhaps by another thread.
22614 [<a name="#p577" href="p577">page 577</a>] (<a href="#Contents">Contents</a>)
22616 <a name="K.2" href="#K.2"><b> K.2 Scope</b></a>
22617 1 This annex specifies a series of optional extensions that can be useful in the mitigation of
22618 security vulnerabilities in programs, and comprise new functions, macros, and types
22619 declared or defined in existing standard headers.
22620 2 An implementation that defines __STDC_LIB_EXT1__ shall conform to the
22621 specifications in this annex.361)
22622 3 Subclause <a href="#K.3">K.3</a> should be read as if it were merged into the parallel structure of named
22623 subclauses of clause 7.
22624 <a name="K.3" href="#K.3"><b> K.3 Library</b></a>
22625 <a name="K.3.1" href="#K.3.1"><b> K.3.1 Introduction</b></a>
22626 <a name="K.3.1.1" href="#K.3.1.1"><b> K.3.1.1 Standard headers</b></a>
22627 1 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are not
22628 declared or defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
22629 defined as a macro which expands to the integer constant 0 at the point in the source file
22630 where the appropriate header is first included.
22631 2 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are
22632 declared and defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
22633 defined as a macro which expands to the integer constant 1 at the point in the source file
22634 where the appropriate header is first included.362)
22635 3 It is implementation-defined whether the functions, macros, and types declared or defined
22636 in <a href="#K.3">K.3</a> and its subclauses are declared or defined by their respective headers if
22637 __STDC_WANT_LIB_EXT1__ is not defined as a macro at the point in the source file
22638 where the appropriate header is first included.363)
22639 4 Within a preprocessing translation unit, __STDC_WANT_LIB_EXT1__ shall be
22640 defined identically for all inclusions of any headers from subclause <a href="#K.3">K.3</a>. If
22641 __STDC_WANT_LIB_EXT1__ is defined differently for any such inclusion, the
22642 implementation shall issue a diagnostic as if a preprocessor error directive were used.
22645 361) Implementations that do not define __STDC_LIB_EXT1__ are not required to conform to these
22647 362) Future revisions of this International Standard may define meanings for other values of
22648 __STDC_WANT_LIB_EXT1__.
22649 363) Subclause <a href="#7.1.3">7.1.3</a> reserves certain names and patterns of names that an implementation may use in
22650 headers. All other names are not reserved, and a conforming implementation is not permitted to use
22651 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
22652 unreserved name is defined in a header when __STDC_WANT_LIB_EXT1__ is defined as 0, the
22653 implementation is not conforming.
22655 [<a name="#p578" href="p578">page 578</a>] (<a href="#Contents">Contents</a>)
22657 <a name="K.3.1.2" href="#K.3.1.2"><b> K.3.1.2 Reserved identifiers</b></a>
22658 1 Each macro name in any of the following subclauses is reserved for use as specified if it
22659 is defined by any of its associated headers when included; unless explicitly stated
22660 otherwise (see <a href="#7.1.4">7.1.4</a>).
22661 2 All identifiers with external linkage in any of the following subclauses are reserved for
22662 use as identifiers with external linkage if any of them are used by the program. None of
22663 them are reserved if none of them are used.
22664 3 Each identifier with file scope listed in any of the following subclauses is reserved for use
22665 as a macro name and as an identifier with file scope in the same name space if it is
22666 defined by any of its associated headers when included.
22667 <a name="K.3.1.3" href="#K.3.1.3"><b> K.3.1.3 Use of errno</b></a>
22668 1 An implementation may set errno for the functions defined in this annex, but is not
22670 <a name="K.3.1.4" href="#K.3.1.4"><b> K.3.1.4 Runtime-constraint violations</b></a>
22671 1 Most functions in this annex include as part of their specification a list of runtime-
22672 constraints. These runtime-constraints are requirements on the program using the
22674 2 Implementations shall verify that the runtime-constraints for a function are not violated
22675 by the program. If a runtime-constraint is violated, the implementation shall call the
22676 currently registered runtime-constraint handler (see set_constraint_handler_s
22677 in <a href="#7.22"><stdlib.h></a>). Multiple runtime-constraint violations in the same call to a library
22678 function result in only one call to the runtime-constraint handler. It is unspecified which
22679 one of the multiple runtime-constraint violations cause the handler to be called.
22680 3 If the runtime-constraints section for a function states an action to be performed when a
22681 runtime-constraint violation occurs, the function shall perform the action before calling
22682 the runtime-constraint handler. If the runtime-constraints section lists actions that are
22683 prohibited when a runtime-constraint violation occurs, then such actions are prohibited to
22684 the function both before calling the handler and after the handler returns.
22685 4 The runtime-constraint handler might not return. If the handler does return, the library
22686 function whose runtime-constraint was violated shall return some indication of failure as
22687 given by the returns section in the function's specification.
22691 364) Although runtime-constraints replace many cases of undefined behavior, undefined behavior still
22692 exists in this annex. Implementations are free to detect any case of undefined behavior and treat it as a
22693 runtime-constraint violation by calling the runtime-constraint handler. This license comes directly
22694 from the definition of undefined behavior.
22696 [<a name="#p579" href="p579">page 579</a>] (<a href="#Contents">Contents</a>)
22698 <a name="K.3.2" href="#K.3.2"><b> K.3.2 Errors <errno.h></b></a>
22699 1 The header <a href="#7.5"><errno.h></a> defines a type.
22702 which is type int.365)
22703 <a name="K.3.3" href="#K.3.3"><b> K.3.3 Common definitions <stddef.h></b></a>
22704 1 The header <a href="#7.19"><stddef.h></a> defines a type.
22707 which is the type size_t.366)
22708 <a name="K.3.4" href="#K.3.4"><b> K.3.4 Integer types <stdint.h></b></a>
22709 1 The header <a href="#7.20"><stdint.h></a> defines a macro.
22712 which expands to a value367) of type size_t. Functions that have parameters of type
22713 rsize_t consider it a runtime-constraint violation if the values of those parameters are
22714 greater than RSIZE_MAX.
22715 Recommended practice
22716 3 Extremely large object sizes are frequently a sign that an object's size was calculated
22717 incorrectly. For example, negative numbers appear as very large positive numbers when
22718 converted to an unsigned type like size_t. Also, some implementations do not support
22719 objects as large as the maximum value that can be represented by type size_t.
22720 4 For those reasons, it is sometimes beneficial to restrict the range of object sizes to detect
22721 programming errors. For implementations targeting machines with large address spaces,
22722 it is recommended that RSIZE_MAX be defined as the smaller of the size of the largest
22723 object supported or (SIZE_MAX >> 1), even if this limit is smaller than the size of
22724 some legitimate, but very large, objects. Implementations targeting machines with small
22725 address spaces may wish to define RSIZE_MAX as SIZE_MAX, which means that there
22727 365) As a matter of programming style, errno_t may be used as the type of something that deals only
22728 with the values that might be found in errno. For example, a function which returns the value of
22729 errno might be declared as having the return type errno_t.
22730 366) See the description of the RSIZE_MAX macro in <a href="#7.20"><stdint.h></a>.
22731 367) The macro RSIZE_MAX need not expand to a constant expression.
22733 [<a name="#p580" href="p580">page 580</a>] (<a href="#Contents">Contents</a>)
22735 is no object size that is considered a runtime-constraint violation.
22736 <a name="K.3.5" href="#K.3.5"><b> K.3.5 Input/output <stdio.h></b></a>
22737 1 The header <a href="#7.21"><stdio.h></a> defines several macros and two types.
22740 which expands to an integer constant expression that is the size needed for an array of
22741 char large enough to hold a temporary file name string generated by the tmpnam_s
22744 which expands to an integer constant expression that is the maximum number of unique
22745 file names that can be generated by the tmpnam_s function.
22748 which is type int; and
22750 which is the type size_t.
22751 <a name="K.3.5.1" href="#K.3.5.1"><b> K.3.5.1 Operations on files</b></a>
22752 <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>
22754 1 #define __STDC_WANT_LIB_EXT1__ 1
22755 #include <a href="#7.21"><stdio.h></a>
22756 errno_t tmpfile_s(FILE * restrict * restrict streamptr);
22757 Runtime-constraints
22758 2 streamptr shall not be a null pointer.
22759 3 If there is a runtime-constraint violation, tmpfile_s does not attempt to create a file.
22761 4 The tmpfile_s function creates a temporary binary file that is different from any other
22762 existing file and that will automatically be removed when it is closed or at program
22763 termination. If the program terminates abnormally, whether an open temporary file is
22764 removed is implementation-defined. The file is opened for update with "wb+" mode
22765 with the meaning that mode has in the fopen_s function (including the mode's effect
22766 on exclusive access and file permissions).
22769 [<a name="#p581" href="p581">page 581</a>] (<a href="#Contents">Contents</a>)
22771 5 If the file was created successfully, then the pointer to FILE pointed to by streamptr
22772 will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
22773 to FILE pointed to by streamptr will be set to a null pointer.
22774 Recommended practice
22775 It should be possible to open at least TMP_MAX_S temporary files during the lifetime of
22776 the program (this limit may be shared with tmpnam_s) and there should be no limit on
22777 the number simultaneously open other than this limit and any limit on the number of open
22780 6 The tmpfile_s function returns zero if it created the file. If it did not create the file or
22781 there was a runtime-constraint violation, tmpfile_s returns a nonzero value.
22782 <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>
22784 1 #define __STDC_WANT_LIB_EXT1__ 1
22785 #include <a href="#7.21"><stdio.h></a>
22786 errno_t tmpnam_s(char *s, rsize_t maxsize);
22787 Runtime-constraints
22788 2 s shall not be a null pointer. maxsize shall be less than or equal to RSIZE_MAX.
22789 maxsize shall be greater than the length of the generated file name string.
22791 3 The tmpnam_s function generates a string that is a valid file name and that is not the
22792 same as the name of an existing file.368) The function is potentially capable of generating
22793 TMP_MAX_S different strings, but any or all of them may already be in use by existing
22794 files and thus not be suitable return values. The lengths of these strings shall be less than
22795 the value of the L_tmpnam_s macro.
22796 4 The tmpnam_s function generates a different string each time it is called.
22797 5 It is assumed that s points to an array of at least maxsize characters. This array will be
22798 set to generated string, as specified below.
22802 368) Files created using strings generated by the tmpnam_s function are temporary only in the sense that
22803 their names should not collide with those generated by conventional naming rules for the
22804 implementation. It is still necessary to use the remove function to remove such files when their use
22805 is ended, and before program termination. Implementations should take care in choosing the patterns
22806 used for names returned by tmpnam_s. For example, making a thread id part of the names avoids the
22807 race condition and possible conflict when multiple programs run simultaneously by the same user
22808 generate the same temporary file names.
22810 [<a name="#p582" href="p582">page 582</a>] (<a href="#Contents">Contents</a>)
22812 6 The implementation shall behave as if no library function except tmpnam calls the
22813 tmpnam_s function.369)
22814 Recommended practice
22815 7 After a program obtains a file name using the tmpnam_s function and before the
22816 program creates a file with that name, the possibility exists that someone else may create
22817 a file with that same name. To avoid this race condition, the tmpfile_s function
22818 should be used instead of tmpnam_s when possible. One situation that requires the use
22819 of the tmpnam_s function is when the program needs to create a temporary directory
22820 rather than a temporary file.
22822 8 If no suitable string can be generated, or if there is a runtime-constraint violation, the
22823 tmpnam_s function writes a null character to s[0] (only if s is not null and maxsize
22824 is greater than zero) and returns a nonzero value.
22825 9 Otherwise, the tmpnam_s function writes the string in the array pointed to by s and
22827 Environmental limits
22828 10 The value of the macro TMP_MAX_S shall be at least 25.
22829 <a name="K.3.5.2" href="#K.3.5.2"><b> K.3.5.2 File access functions</b></a>
22830 <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>
22832 1 #define __STDC_WANT_LIB_EXT1__ 1
22833 #include <a href="#7.21"><stdio.h></a>
22834 errno_t fopen_s(FILE * restrict * restrict streamptr,
22835 const char * restrict filename,
22836 const char * restrict mode);
22837 Runtime-constraints
22838 2 None of streamptr, filename, or mode shall be a null pointer.
22839 3 If there is a runtime-constraint violation, fopen_s does not attempt to open a file.
22840 Furthermore, if streamptr is not a null pointer, fopen_s sets *streamptr to the
22846 369) An implementation may have tmpnam call tmpnam_s (perhaps so there is only one naming
22847 convention for temporary files), but this is not required.
22849 [<a name="#p583" href="p583">page 583</a>] (<a href="#Contents">Contents</a>)
22852 4 The fopen_s function opens the file whose name is the string pointed to by
22853 filename, and associates a stream with it.
22854 5 The mode string shall be as described for fopen, with the addition that modes starting
22855 with the character 'w' or 'a' may be preceded by the character 'u', see below:
22856 uw truncate to zero length or create text file for writing, default
22858 uwx create text file for writing, default permissions
22859 ua append; open or create text file for writing at end-of-file, default
22861 uwb truncate to zero length or create binary file for writing, default
22863 uwbx create binary file for writing, default permissions
22864 uab append; open or create binary file for writing at end-of-file, default
22866 uw+ truncate to zero length or create text file for update, default
22868 uw+x create text file for update, default permissions
22869 ua+ append; open or create text file for update, writing at end-of-file,
22870 default permissions
22871 uw+b or uwb+ truncate to zero length or create binary file for update, default
22873 uw+bx or uwb+x create binary file for update, default permissions
22874 ua+b or uab+ append; open or create binary file for update, writing at end-of-file,
22875 default permissions
22876 6 Opening a file with exclusive mode ('x' as the last character in the mode argument)
22877 fails if the file already exists or cannot be created.
22878 7 To the extent that the underlying system supports the concepts, files opened for writing
22879 shall be opened with exclusive (also known as non-shared) access. If the file is being
22880 created, and the first character of the mode string is not 'u', to the extent that the
22881 underlying system supports it, the file shall have a file permission that prevents other
22882 users on the system from accessing the file. If the file is being created and first character
22883 of the mode string is 'u', then by the time the file has been closed, it shall have the
22884 system default file access permissions.370)
22885 8 If the file was opened successfully, then the pointer to FILE pointed to by streamptr
22886 will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
22889 370) These are the same permissions that the file would have been created with by fopen.
22891 [<a name="#p584" href="p584">page 584</a>] (<a href="#Contents">Contents</a>)
22893 to FILE pointed to by streamptr will be set to a null pointer.
22895 9 The fopen_s function returns zero if it opened the file. If it did not open the file or if
22896 there was a runtime-constraint violation, fopen_s returns a nonzero value.
22897 <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>
22899 1 #define __STDC_WANT_LIB_EXT1__ 1
22900 #include <a href="#7.21"><stdio.h></a>
22901 errno_t freopen_s(FILE * restrict * restrict newstreamptr,
22902 const char * restrict filename,
22903 const char * restrict mode,
22904 FILE * restrict stream);
22905 Runtime-constraints
22906 2 None of newstreamptr, mode, and stream shall be a null pointer.
22907 3 If there is a runtime-constraint violation, freopen_s neither attempts to close any file
22908 associated with stream nor attempts to open a file. Furthermore, if newstreamptr is
22909 not a null pointer, fopen_s sets *newstreamptr to the null pointer.
22911 4 The freopen_s function opens the file whose name is the string pointed to by
22912 filename and associates the stream pointed to by stream with it. The mode
22913 argument has the same meaning as in the fopen_s function (including the mode's effect
22914 on exclusive access and file permissions).
22915 5 If filename is a null pointer, the freopen_s function attempts to change the mode of
22916 the stream to that specified by mode, as if the name of the file currently associated with
22917 the stream had been used. It is implementation-defined which changes of mode are
22918 permitted (if any), and under what circumstances.
22919 6 The freopen_s function first attempts to close any file that is associated with stream.
22920 Failure to close the file is ignored. The error and end-of-file indicators for the stream are
22922 7 If the file was opened successfully, then the pointer to FILE pointed to by
22923 newstreamptr will be set to the value of stream. Otherwise, the pointer to FILE
22924 pointed to by newstreamptr will be set to a null pointer.
22926 8 The freopen_s function returns zero if it opened the file. If it did not open the file or
22927 there was a runtime-constraint violation, freopen_s returns a nonzero value.
22929 [<a name="#p585" href="p585">page 585</a>] (<a href="#Contents">Contents</a>)
22931 <a name="K.3.5.3" href="#K.3.5.3"><b> K.3.5.3 Formatted input/output functions</b></a>
22932 1 Unless explicitly stated otherwise, if the execution of a function described in this
22933 subclause causes copying to take place between objects that overlap, the objects take on
22934 unspecified values.
22935 <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>
22937 1 #define __STDC_WANT_LIB_EXT1__ 1
22938 #include <a href="#7.21"><stdio.h></a>
22939 int fprintf_s(FILE * restrict stream,
22940 const char * restrict format, ...);
22941 Runtime-constraints
22942 2 Neither stream nor format shall be a null pointer. The %n specifier371) (modified or
22943 not by flags, field width, or precision) shall not appear in the string pointed to by
22944 format. Any argument to fprintf_s corresponding to a %s specifier shall not be a
22946 3 If there is a runtime-constraint violation,372) the fprintf_s function does not attempt
22947 to produce further output, and it is unspecified to what extent fprintf_s produced
22948 output before discovering the runtime-constraint violation.
22950 4 The fprintf_s function is equivalent to the fprintf function except for the explicit
22951 runtime-constraints listed above.
22953 5 The fprintf_s function returns the number of characters transmitted, or a negative
22954 value if an output error, encoding error, or runtime-constraint violation occurred.
22959 371) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
22960 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
22961 format string was %%n.
22962 372) Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
22963 implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
22964 constraint violation.
22966 [<a name="#p586" href="p586">page 586</a>] (<a href="#Contents">Contents</a>)
22968 <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>
22970 1 #define __STDC_WANT_LIB_EXT1__ 1
22971 #include <a href="#7.21"><stdio.h></a>
22972 int fscanf_s(FILE * restrict stream,
22973 const char * restrict format, ...);
22974 Runtime-constraints
22975 2 Neither stream nor format shall be a null pointer. Any argument indirected though in
22976 order to store converted input shall not be a null pointer.
22977 3 If there is a runtime-constraint violation,373) the fscanf_s function does not attempt to
22978 perform further input, and it is unspecified to what extent fscanf_s performed input
22979 before discovering the runtime-constraint violation.
22981 4 The fscanf_s function is equivalent to fscanf except that the c, s, and [ conversion
22982 specifiers apply to a pair of arguments (unless assignment suppression is indicated by a
22983 *). The first of these arguments is the same as for fscanf. That argument is
22984 immediately followed in the argument list by the second argument, which has type
22985 rsize_t and gives the number of elements in the array pointed to by the first argument
22986 of the pair. If the first argument points to a scalar object, it is considered to be an array of
22988 5 A matching failure occurs if the number of elements in a receiving object is insufficient to
22989 hold the converted input (including any trailing null character).
22991 6 The fscanf_s function returns the value of the macro EOF if an input failure occurs
22992 before any conversion or if there is a runtime-constraint violation. Otherwise, the
22994 373) Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
22995 implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
22996 constraint violation.
22997 374) If the format is known at translation time, an implementation may issue a diagnostic for any argument
22998 used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
22999 argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
23000 the format is not known at translation time. For example, an implementation may issue a diagnostic
23001 for each argument after format that has of type pointer to one of char, signed char,
23002 unsigned char, or void that is not followed by an argument of a type compatible with
23003 rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
23004 using the hh length modifier, a length argument must follow the pointer argument. Another useful
23005 diagnostic could flag any non-pointer argument following format that did not have a type
23006 compatible with rsize_t.
23008 [<a name="#p587" href="p587">page 587</a>] (<a href="#Contents">Contents</a>)
23010 fscanf_s function returns the number of input items assigned, which can be fewer than
23011 provided for, or even zero, in the event of an early matching failure.
23012 7 EXAMPLE 1 The call:
23013 #define __STDC_WANT_LIB_EXT1__ 1
23014 #include <a href="#7.21"><stdio.h></a>
23016 int n, i; float x; char name[50];
23017 n = fscanf_s(stdin, "%d%f%s", &i, &x, name, (rsize_t) 50);
23018 with the input line:
23019 25 54.32E-1 thompson
23020 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
23023 8 EXAMPLE 2 The call:
23024 #define __STDC_WANT_LIB_EXT1__ 1
23025 #include <a href="#7.21"><stdio.h></a>
23028 n = fscanf_s(stdin, "%s", s, sizeof s);
23029 with the input line:
23031 will assign to n the value 0 since a matching failure occurred because the sequence hello\0 requires an
23032 array of six characters to store it.
23034 <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>
23036 1 #define __STDC_WANT_LIB_EXT1__ 1
23037 #include <a href="#7.21"><stdio.h></a>
23038 int printf_s(const char * restrict format, ...);
23039 Runtime-constraints
23040 2 format shall not be a null pointer. The %n specifier375) (modified or not by flags, field
23041 width, or precision) shall not appear in the string pointed to by format. Any argument
23042 to printf_s corresponding to a %s specifier shall not be a null pointer.
23043 3 If there is a runtime-constraint violation, the printf_s function does not attempt to
23044 produce further output, and it is unspecified to what extent printf_s produced output
23045 before discovering the runtime-constraint violation.
23048 375) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
23049 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
23050 format string was %%n.
23052 [<a name="#p588" href="p588">page 588</a>] (<a href="#Contents">Contents</a>)
23055 4 The printf_s function is equivalent to the printf function except for the explicit
23056 runtime-constraints listed above.
23058 5 The printf_s function returns the number of characters transmitted, or a negative
23059 value if an output error, encoding error, or runtime-constraint violation occurred.
23060 <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>
23062 1 #define __STDC_WANT_LIB_EXT1__ 1
23063 #include <a href="#7.21"><stdio.h></a>
23064 int scanf_s(const char * restrict format, ...);
23065 Runtime-constraints
23066 2 format shall not be a null pointer. Any argument indirected though in order to store
23067 converted input shall not be a null pointer.
23068 3 If there is a runtime-constraint violation, the scanf_s function does not attempt to
23069 perform further input, and it is unspecified to what extent scanf_s performed input
23070 before discovering the runtime-constraint violation.
23072 4 The scanf_s function is equivalent to fscanf_s with the argument stdin
23073 interposed before the arguments to scanf_s.
23075 5 The scanf_s function returns the value of the macro EOF if an input failure occurs
23076 before any conversion or if there is a runtime-constraint violation. Otherwise, the
23077 scanf_s function returns the number of input items assigned, which can be fewer than
23078 provided for, or even zero, in the event of an early matching failure.
23079 <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>
23081 1 #define __STDC_WANT_LIB_EXT1__ 1
23082 #include <a href="#7.21"><stdio.h></a>
23083 int snprintf_s(char * restrict s, rsize_t n,
23084 const char * restrict format, ...);
23085 Runtime-constraints
23086 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
23087 than RSIZE_MAX. The %n specifier376) (modified or not by flags, field width, or
23088 precision) shall not appear in the string pointed to by format. Any argument to
23089 [<a name="#p589" href="p589">page 589</a>] (<a href="#Contents">Contents</a>)
23091 snprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
23093 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
23094 than zero and less than RSIZE_MAX, then the snprintf_s function sets s[0] to the
23097 4 The snprintf_s function is equivalent to the snprintf function except for the
23098 explicit runtime-constraints listed above.
23099 5 The snprintf_s function, unlike sprintf_s, will truncate the result to fit within the
23100 array pointed to by s.
23102 6 The snprintf_s function returns the number of characters that would have been
23103 written had n been sufficiently large, not counting the terminating null character, or a
23104 negative value if a runtime-constraint violation occurred. Thus, the null-terminated
23105 output has been completely written if and only if the returned value is nonnegative and
23107 <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>
23109 1 #define __STDC_WANT_LIB_EXT1__ 1
23110 #include <a href="#7.21"><stdio.h></a>
23111 int sprintf_s(char * restrict s, rsize_t n,
23112 const char * restrict format, ...);
23113 Runtime-constraints
23114 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
23115 than RSIZE_MAX. The number of characters (including the trailing null) required for the
23116 result to be written to the array pointed to by s shall not be greater than n. The %n
23117 specifier377) (modified or not by flags, field width, or precision) shall not appear in the
23118 string pointed to by format. Any argument to sprintf_s corresponding to a %s
23119 specifier shall not be a null pointer. No encoding error shall occur.
23123 376) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
23124 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
23125 format string was %%n.
23126 377) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
23127 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
23128 format string was %%n.
23130 [<a name="#p590" href="p590">page 590</a>] (<a href="#Contents">Contents</a>)
23132 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
23133 than zero and less than RSIZE_MAX, then the sprintf_s function sets s[0] to the
23136 4 The sprintf_s function is equivalent to the sprintf function except for the
23137 parameter n and the explicit runtime-constraints listed above.
23138 5 The sprintf_s function, unlike snprintf_s, treats a result too big for the array
23139 pointed to by s as a runtime-constraint violation.
23141 6 If no runtime-constraint violation occurred, the sprintf_s function returns the number
23142 of characters written in the array, not counting the terminating null character. If an
23143 encoding error occurred, sprintf_s returns a negative value. If any other runtime-
23144 constraint violation occurred, sprintf_s returns zero.
23145 <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>
23147 1 #define __STDC_WANT_LIB_EXT1__ 1
23148 #include <a href="#7.21"><stdio.h></a>
23149 int sscanf_s(const char * restrict s,
23150 const char * restrict format, ...);
23151 Runtime-constraints
23152 2 Neither s nor format shall be a null pointer. Any argument indirected though in order
23153 to store converted input shall not be a null pointer.
23154 3 If there is a runtime-constraint violation, the sscanf_s function does not attempt to
23155 perform further input, and it is unspecified to what extent sscanf_s performed input
23156 before discovering the runtime-constraint violation.
23158 4 The sscanf_s function is equivalent to fscanf_s, except that input is obtained from
23159 a string (specified by the argument s) rather than from a stream. Reaching the end of the
23160 string is equivalent to encountering end-of-file for the fscanf_s function. If copying
23161 takes place between objects that overlap, the objects take on unspecified values.
23163 5 The sscanf_s function returns the value of the macro EOF if an input failure occurs
23164 before any conversion or if there is a runtime-constraint violation. Otherwise, the
23165 sscanf_s function returns the number of input items assigned, which can be fewer than
23166 provided for, or even zero, in the event of an early matching failure.
23168 [<a name="#p591" href="p591">page 591</a>] (<a href="#Contents">Contents</a>)
23170 <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>
23172 1 #define __STDC_WANT_LIB_EXT1__ 1
23173 #include <a href="#7.16"><stdarg.h></a>
23174 #include <a href="#7.21"><stdio.h></a>
23175 int vfprintf_s(FILE * restrict stream,
23176 const char * restrict format,
23178 Runtime-constraints
23179 2 Neither stream nor format shall be a null pointer. The %n specifier378) (modified or
23180 not by flags, field width, or precision) shall not appear in the string pointed to by
23181 format. Any argument to vfprintf_s corresponding to a %s specifier shall not be a
23183 3 If there is a runtime-constraint violation, the vfprintf_s function does not attempt to
23184 produce further output, and it is unspecified to what extent vfprintf_s produced
23185 output before discovering the runtime-constraint violation.
23187 4 The vfprintf_s function is equivalent to the vfprintf function except for the
23188 explicit runtime-constraints listed above.
23190 5 The vfprintf_s function returns the number of characters transmitted, or a negative
23191 value if an output error, encoding error, or runtime-constraint violation occurred.
23192 <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>
23194 1 #define __STDC_WANT_LIB_EXT1__ 1
23195 #include <a href="#7.16"><stdarg.h></a>
23196 #include <a href="#7.21"><stdio.h></a>
23197 int vfscanf_s(FILE * restrict stream,
23198 const char * restrict format,
23204 378) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
23205 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
23206 format string was %%n.
23208 [<a name="#p592" href="p592">page 592</a>] (<a href="#Contents">Contents</a>)
23210 Runtime-constraints
23211 2 Neither stream nor format shall be a null pointer. Any argument indirected though in
23212 order to store converted input shall not be a null pointer.
23213 3 If there is a runtime-constraint violation, the vfscanf_s function does not attempt to
23214 perform further input, and it is unspecified to what extent vfscanf_s performed input
23215 before discovering the runtime-constraint violation.
23217 4 The vfscanf_s function is equivalent to fscanf_s, with the variable argument list
23218 replaced by arg, which shall have been initialized by the va_start macro (and
23219 possibly subsequent va_arg calls). The vfscanf_s function does not invoke the
23222 5 The vfscanf_s function returns the value of the macro EOF if an input failure occurs
23223 before any conversion or if there is a runtime-constraint violation. Otherwise, the
23224 vfscanf_s function returns the number of input items assigned, which can be fewer
23225 than provided for, or even zero, in the event of an early matching failure.
23226 <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>
23228 1 #define __STDC_WANT_LIB_EXT1__ 1
23229 #include <a href="#7.16"><stdarg.h></a>
23230 #include <a href="#7.21"><stdio.h></a>
23231 int vprintf_s(const char * restrict format,
23233 Runtime-constraints
23234 2 format shall not be a null pointer. The %n specifier380) (modified or not by flags, field
23235 width, or precision) shall not appear in the string pointed to by format. Any argument
23236 to vprintf_s corresponding to a %s specifier shall not be a null pointer.
23237 3 If there is a runtime-constraint violation, the vprintf_s function does not attempt to
23238 produce further output, and it is unspecified to what extent vprintf_s produced output
23239 before discovering the runtime-constraint violation.
23241 379) As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
23242 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
23244 380) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
23245 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
23246 format string was %%n.
23248 [<a name="#p593" href="p593">page 593</a>] (<a href="#Contents">Contents</a>)
23251 4 The vprintf_s function is equivalent to the vprintf function except for the explicit
23252 runtime-constraints listed above.
23254 5 The vprintf_s function returns the number of characters transmitted, or a negative
23255 value if an output error, encoding error, or runtime-constraint violation occurred.
23256 <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>
23258 1 #define __STDC_WANT_LIB_EXT1__ 1
23259 #include <a href="#7.16"><stdarg.h></a>
23260 #include <a href="#7.21"><stdio.h></a>
23261 int vscanf_s(const char * restrict format,
23263 Runtime-constraints
23264 2 format shall not be a null pointer. Any argument indirected though in order to store
23265 converted input shall not be a null pointer.
23266 3 If there is a runtime-constraint violation, the vscanf_s function does not attempt to
23267 perform further input, and it is unspecified to what extent vscanf_s performed input
23268 before discovering the runtime-constraint violation.
23270 4 The vscanf_s function is equivalent to scanf_s, with the variable argument list
23271 replaced by arg, which shall have been initialized by the va_start macro (and
23272 possibly subsequent va_arg calls). The vscanf_s function does not invoke the
23275 5 The vscanf_s function returns the value of the macro EOF if an input failure occurs
23276 before any conversion or if there is a runtime-constraint violation. Otherwise, the
23277 vscanf_s function returns the number of input items assigned, which can be fewer than
23278 provided for, or even zero, in the event of an early matching failure.
23283 381) As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
23284 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
23287 [<a name="#p594" href="p594">page 594</a>] (<a href="#Contents">Contents</a>)
23289 <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>
23291 1 #define __STDC_WANT_LIB_EXT1__ 1
23292 #include <a href="#7.16"><stdarg.h></a>
23293 #include <a href="#7.21"><stdio.h></a>
23294 int vsnprintf_s(char * restrict s, rsize_t n,
23295 const char * restrict format,
23297 Runtime-constraints
23298 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
23299 than RSIZE_MAX. The %n specifier382) (modified or not by flags, field width, or
23300 precision) shall not appear in the string pointed to by format. Any argument to
23301 vsnprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
23303 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
23304 than zero and less than RSIZE_MAX, then the vsnprintf_s function sets s[0] to the
23307 4 The vsnprintf_s function is equivalent to the vsnprintf function except for the
23308 explicit runtime-constraints listed above.
23309 5 The vsnprintf_s function, unlike vsprintf_s, will truncate the result to fit within
23310 the array pointed to by s.
23312 6 The vsnprintf_s function returns the number of characters that would have been
23313 written had n been sufficiently large, not counting the terminating null character, or a
23314 negative value if a runtime-constraint violation occurred. Thus, the null-terminated
23315 output has been completely written if and only if the returned value is nonnegative and
23321 382) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
23322 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
23323 format string was %%n.
23325 [<a name="#p595" href="p595">page 595</a>] (<a href="#Contents">Contents</a>)
23327 <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>
23329 1 #define __STDC_WANT_LIB_EXT1__ 1
23330 #include <a href="#7.16"><stdarg.h></a>
23331 #include <a href="#7.21"><stdio.h></a>
23332 int vsprintf_s(char * restrict s, rsize_t n,
23333 const char * restrict format,
23335 Runtime-constraints
23336 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
23337 than RSIZE_MAX. The number of characters (including the trailing null) required for the
23338 result to be written to the array pointed to by s shall not be greater than n. The %n
23339 specifier383) (modified or not by flags, field width, or precision) shall not appear in the
23340 string pointed to by format. Any argument to vsprintf_s corresponding to a %s
23341 specifier shall not be a null pointer. No encoding error shall occur.
23342 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
23343 than zero and less than RSIZE_MAX, then the vsprintf_s function sets s[0] to the
23346 4 The vsprintf_s function is equivalent to the vsprintf function except for the
23347 parameter n and the explicit runtime-constraints listed above.
23348 5 The vsprintf_s function, unlike vsnprintf_s, treats a result too big for the array
23349 pointed to by s as a runtime-constraint violation.
23351 6 If no runtime-constraint violation occurred, the vsprintf_s function returns the
23352 number of characters written in the array, not counting the terminating null character. If
23353 an encoding error occurred, vsprintf_s returns a negative value. If any other
23354 runtime-constraint violation occurred, vsprintf_s returns zero.
23359 383) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
23360 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
23361 format string was %%n.
23363 [<a name="#p596" href="p596">page 596</a>] (<a href="#Contents">Contents</a>)
23365 <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>
23367 1 #define __STDC_WANT_LIB_EXT1__ 1
23368 #include <a href="#7.16"><stdarg.h></a>
23369 #include <a href="#7.21"><stdio.h></a>
23370 int vsscanf_s(const char * restrict s,
23371 const char * restrict format,
23373 Runtime-constraints
23374 2 Neither s nor format shall be a null pointer. Any argument indirected though in order
23375 to store converted input shall not be a null pointer.
23376 3 If there is a runtime-constraint violation, the vsscanf_s function does not attempt to
23377 perform further input, and it is unspecified to what extent vsscanf_s performed input
23378 before discovering the runtime-constraint violation.
23380 4 The vsscanf_s function is equivalent to sscanf_s, with the variable argument list
23381 replaced by arg, which shall have been initialized by the va_start macro (and
23382 possibly subsequent va_arg calls). The vsscanf_s function does not invoke the
23385 5 The vsscanf_s function returns the value of the macro EOF if an input failure occurs
23386 before any conversion or if there is a runtime-constraint violation. Otherwise, the
23387 vscanf_s function returns the number of input items assigned, which can be fewer than
23388 provided for, or even zero, in the event of an early matching failure.
23389 <a name="K.3.5.4" href="#K.3.5.4"><b> K.3.5.4 Character input/output functions</b></a>
23390 <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>
23392 1 #define __STDC_WANT_LIB_EXT1__ 1
23393 #include <a href="#7.21"><stdio.h></a>
23394 char *gets_s(char *s, rsize_t n);
23399 384) As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
23400 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
23403 [<a name="#p597" href="p597">page 597</a>] (<a href="#Contents">Contents</a>)
23405 Runtime-constraints
23406 2 s shall not be a null pointer. n shall neither be equal to zero nor be greater than
23407 RSIZE_MAX. A new-line character, end-of-file, or read error shall occur within reading
23408 n-1 characters from stdin.385)
23409 3 If there is a runtime-constraint violation, s[0] is set to the null character, and characters
23410 are read and discarded from stdin until a new-line character is read, or end-of-file or a
23413 4 The gets_s function reads at most one less than the number of characters specified by n
23414 from the stream pointed to by stdin, into the array pointed to by s. No additional
23415 characters are read after a new-line character (which is discarded) or after end-of-file.
23416 The discarded new-line character does not count towards number of characters read. A
23417 null character is written immediately after the last character read into the array.
23418 5 If end-of-file is encountered and no characters have been read into the array, or if a read
23419 error occurs during the operation, then s[0] is set to the null character, and the other
23420 elements of s take unspecified values.
23421 Recommended practice
23422 6 The fgets function allows properly-written programs to safely process input lines too
23423 long to store in the result array. In general this requires that callers of fgets pay
23424 attention to the presence or absence of a new-line character in the result array. Consider
23425 using fgets (along with any needed processing based on new-line characters) instead of
23428 7 The gets_s function returns s if successful. If there was a runtime-constraint violation,
23429 or if end-of-file is encountered and no characters have been read into the array, or if a
23430 read error occurs during the operation, then a null pointer is returned.
23435 385) The gets_s function, unlike the historical gets function, makes it a runtime-constraint violation for
23436 a line of input to overflow the buffer to store it. Unlike the fgets function, gets_s maintains a
23437 one-to-one relationship between input lines and successful calls to gets_s. Programs that use gets
23438 expect such a relationship.
23440 [<a name="#p598" href="p598">page 598</a>] (<a href="#Contents">Contents</a>)
23442 <a name="K.3.6" href="#K.3.6"><b> K.3.6 General utilities <stdlib.h></b></a>
23443 1 The header <a href="#7.22"><stdlib.h></a> defines three types.
23446 which is type int; and
23448 which is the type size_t; and
23449 constraint_handler_t
23450 which has the following definition
23451 typedef void (*constraint_handler_t)(
23452 const char * restrict msg,
23453 void * restrict ptr,
23455 <a name="K.3.6.1" href="#K.3.6.1"><b> K.3.6.1 Runtime-constraint handling</b></a>
23456 <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>
23458 1 #define __STDC_WANT_LIB_EXT1__ 1
23459 #include <a href="#7.22"><stdlib.h></a>
23460 constraint_handler_t set_constraint_handler_s(
23461 constraint_handler_t handler);
23463 2 The set_constraint_handler_s function sets the runtime-constraint handler to
23464 be handler. The runtime-constraint handler is the function to be called when a library
23465 function detects a runtime-constraint violation. Only the most recent handler registered
23466 with set_constraint_handler_s is called when a runtime-constraint violation
23468 3 When the handler is called, it is passed the following arguments in the following order:
23469 1. A pointer to a character string describing the runtime-constraint violation.
23470 2. A null pointer or a pointer to an implementation defined object.
23471 3. If the function calling the handler has a return type declared as errno_t, the
23472 return value of the function is passed. Otherwise, a positive value of type
23477 [<a name="#p599" href="p599">page 599</a>] (<a href="#Contents">Contents</a>)
23479 4 The implementation has a default constraint handler that is used if no calls to the
23480 set_constraint_handler_s function have been made. The behavior of the
23481 default handler is implementation-defined, and it may cause the program to exit or abort.
23482 5 If the handler argument to set_constraint_handler_s is a null pointer, the
23483 implementation default handler becomes the current constraint handler.
23485 6 The set_constraint_handler_s function returns a pointer to the previously
23486 registered handler.386)
23487 <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>
23489 1 #define __STDC_WANT_LIB_EXT1__ 1
23490 #include <a href="#7.22"><stdlib.h></a>
23491 void abort_handler_s(
23492 const char * restrict msg,
23493 void * restrict ptr,
23496 2 A pointer to the abort_handler_s function shall be a suitable argument to the
23497 set_constraint_handler_s function.
23498 3 The abort_handler_s function writes a message on the standard error stream in an
23499 implementation-defined format. The message shall include the string pointed to by msg.
23500 The abort_handler_s function then calls the abort function.387)
23502 4 The abort_handler_s function does not return to its caller.
23507 386) If the previous handler was registered by calling set_constraint_handler_s with a null
23508 pointer argument, a pointer to the implementation default handler is returned (not NULL).
23509 387) Many implementations invoke a debugger when the abort function is called.
23511 [<a name="#p600" href="p600">page 600</a>] (<a href="#Contents">Contents</a>)
23513 <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>
23515 1 #define __STDC_WANT_LIB_EXT1__ 1
23516 #include <a href="#7.22"><stdlib.h></a>
23517 void ignore_handler_s(
23518 const char * restrict msg,
23519 void * restrict ptr,
23522 2 A pointer to the ignore_handler_s function shall be a suitable argument to the
23523 set_constraint_handler_s function.
23524 3 The ignore_handler_s function simply returns to its caller.388)
23526 4 The ignore_handler_s function returns no value.
23527 <a name="K.3.6.2" href="#K.3.6.2"><b> K.3.6.2 Communication with the environment</b></a>
23528 <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>
23530 1 #define __STDC_WANT_LIB_EXT1__ 1
23531 #include <a href="#7.22"><stdlib.h></a>
23532 errno_t getenv_s(size_t * restrict len,
23533 char * restrict value, rsize_t maxsize,
23534 const char * restrict name);
23535 Runtime-constraints
23536 2 name shall not be a null pointer. maxsize shall neither equal zero nor be greater than
23537 RSIZE_MAX. If maxsize is not equal to zero, then value shall not be a null pointer.
23538 3 If there is a runtime-constraint violation, the integer pointed to by len is set to 0 (if len
23539 is not null), and the environment list is not searched.
23541 4 The getenv_s function searches an environment list, provided by the host environment,
23542 for a string that matches the string pointed to by name.
23545 388) If the runtime-constraint handler is set to the ignore_handler_s function, any library function in
23546 which a runtime-constraint violation occurs will return to its caller. The caller can determine whether
23547 a runtime-constraint violation occurred based on the library function's specification (usually, the
23548 library function returns a nonzero errno_t).
23550 [<a name="#p601" href="p601">page 601</a>] (<a href="#Contents">Contents</a>)
23552 5 If that name is found then getenv_s performs the following actions. If len is not a
23553 null pointer, the length of the string associated with the matched list member is stored in
23554 the integer pointed to by len. If the length of the associated string is less than maxsize,
23555 then the associated string is copied to the array pointed to by value.
23556 6 If that name is not found then getenv_s performs the following actions. If len is not
23557 a null pointer, zero is stored in the integer pointed to by len. If maxsize is greater than
23558 zero, then value[0] is set to the null character.
23559 7 The set of environment names and the method for altering the environment list are
23560 implementation-defined.
23562 8 The getenv_s function returns zero if the specified name is found and the associated
23563 string was successfully stored in value. Otherwise, a nonzero value is returned.
23564 <a name="K.3.6.3" href="#K.3.6.3"><b> K.3.6.3 Searching and sorting utilities</b></a>
23565 1 These utilities make use of a comparison function to search or sort arrays of unspecified
23566 type. Where an argument declared as size_t nmemb specifies the length of the array
23567 for a function, if nmemb has the value zero on a call to that function, then the comparison
23568 function is not called, a search finds no matching element, sorting performs no
23569 rearrangement, and the pointer to the array may be null.
23570 2 The implementation shall ensure that the second argument of the comparison function
23571 (when called from bsearch_s), or both arguments (when called from qsort_s), are
23572 pointers to elements of the array.389) The first argument when called from bsearch_s
23574 3 The comparison function shall not alter the contents of either the array or search key. The
23575 implementation may reorder elements of the array between calls to the comparison
23576 function, but shall not otherwise alter the contents of any individual element.
23577 4 When the same objects (consisting of size bytes, irrespective of their current positions
23578 in the array) are passed more than once to the comparison function, the results shall be
23579 consistent with one another. That is, for qsort_s they shall define a total ordering on
23580 the array, and for bsearch_s the same object shall always compare the same way with
23586 389) That is, if the value passed is p, then the following expressions are always valid and nonzero:
23587 ((char *)p - (char *)base) % size == 0
23588 (char *)p >= (char *)base
23589 (char *)p < (char *)base + nmemb * size
23592 [<a name="#p602" href="p602">page 602</a>] (<a href="#Contents">Contents</a>)
23594 5 A sequence point occurs immediately before and immediately after each call to the
23595 comparison function, and also between any call to the comparison function and any
23596 movement of the objects passed as arguments to that call.
23597 <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>
23599 1 #define __STDC_WANT_LIB_EXT1__ 1
23600 #include <a href="#7.22"><stdlib.h></a>
23601 void *bsearch_s(const void *key, const void *base,
23602 rsize_t nmemb, rsize_t size,
23603 int (*compar)(const void *k, const void *y,
23606 Runtime-constraints
23607 2 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
23608 zero, then none of key, base, or compar shall be a null pointer.
23609 3 If there is a runtime-constraint violation, the bsearch_s function does not search the
23612 4 The bsearch_s function searches an array of nmemb objects, the initial element of
23613 which is pointed to by base, for an element that matches the object pointed to by key.
23614 The size of each element of the array is specified by size.
23615 5 The comparison function pointed to by compar is called with three arguments. The first
23616 two point to the key object and to an array element, in that order. The function shall
23617 return an integer less than, equal to, or greater than zero if the key object is considered,
23618 respectively, to be less than, to match, or to be greater than the array element. The array
23619 shall consist of: all the elements that compare less than, all the elements that compare
23620 equal to, and all the elements that compare greater than the key object, in that order.390)
23621 The third argument to the comparison function is the context argument passed to
23622 bsearch_s. The sole use of context by bsearch_s is to pass it to the comparison
23628 390) In practice, this means that the entire array has been sorted according to the comparison function.
23629 391) The context argument is for the use of the comparison function in performing its duties. For
23630 example, it might specify a collating sequence used by the comparison function.
23632 [<a name="#p603" href="p603">page 603</a>] (<a href="#Contents">Contents</a>)
23635 6 The bsearch_s function returns a pointer to a matching element of the array, or a null
23636 pointer if no match is found or there is a runtime-constraint violation. If two elements
23637 compare as equal, which element is matched is unspecified.
23638 <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>
23640 1 #define __STDC_WANT_LIB_EXT1__ 1
23641 #include <a href="#7.22"><stdlib.h></a>
23642 errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
23643 int (*compar)(const void *x, const void *y,
23646 Runtime-constraints
23647 2 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
23648 zero, then neither base nor compar shall be a null pointer.
23649 3 If there is a runtime-constraint violation, the qsort_s function does not sort the array.
23651 4 The qsort_s function sorts an array of nmemb objects, the initial element of which is
23652 pointed to by base. The size of each object is specified by size.
23653 5 The contents of the array are sorted into ascending order according to a comparison
23654 function pointed to by compar, which is called with three arguments. The first two
23655 point to the objects being compared. The function shall return an integer less than, equal
23656 to, or greater than zero if the first argument is considered to be respectively less than,
23657 equal to, or greater than the second. The third argument to the comparison function is the
23658 context argument passed to qsort_s. The sole use of context by qsort_s is to
23659 pass it to the comparison function.392)
23660 6 If two elements compare as equal, their relative order in the resulting sorted array is
23663 7 The qsort_s function returns zero if there was no runtime-constraint violation.
23664 Otherwise, a nonzero value is returned.
23669 392) The context argument is for the use of the comparison function in performing its duties. For
23670 example, it might specify a collating sequence used by the comparison function.
23672 [<a name="#p604" href="p604">page 604</a>] (<a href="#Contents">Contents</a>)
23674 <a name="K.3.6.4" href="#K.3.6.4"><b> K.3.6.4 Multibyte/wide character conversion functions</b></a>
23675 1 The behavior of the multibyte character functions is affected by the LC_CTYPE category
23676 of the current locale. For a state-dependent encoding, each function is placed into its
23677 initial conversion state by a call for which its character pointer argument, s, is a null
23678 pointer. Subsequent calls with s as other than a null pointer cause the internal conversion
23679 state of the function to be altered as necessary. A call with s as a null pointer causes
23680 these functions to set the int pointed to by their status argument to a nonzero value if
23681 encodings have state dependency, and zero otherwise.393) Changing the LC_CTYPE
23682 category causes the conversion state of these functions to be indeterminate.
23683 <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>
23685 1 #define __STDC_WANT_LIB_EXT1__ 1
23686 #include <a href="#7.22"><stdlib.h></a>
23687 errno_t wctomb_s(int * restrict status,
23691 Runtime-constraints
23692 2 Let n denote the number of bytes needed to represent the multibyte character
23693 corresponding to the wide character given by wc (including any shift sequences).
23694 3 If s is not a null pointer, then smax shall not be less than n, and smax shall not be
23695 greater than RSIZE_MAX. If s is a null pointer, then smax shall equal zero.
23696 4 If there is a runtime-constraint violation, wctomb_s does not modify the int pointed to
23697 by status, and if s is not a null pointer, no more than smax elements in the array
23698 pointed to by s will be accessed.
23700 5 The wctomb_s function determines n and stores the multibyte character representation
23701 of wc in the array whose first element is pointed to by s (if s is not a null pointer). The
23702 number of characters stored never exceeds MB_CUR_MAX or smax. If wc is a null wide
23703 character, a null byte is stored, preceded by any shift sequence needed to restore the
23704 initial shift state, and the function is left in the initial conversion state.
23705 6 The implementation shall behave as if no library function calls the wctomb_s function.
23709 393) If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
23710 character codes, but are grouped with an adjacent multibyte character.
23712 [<a name="#p605" href="p605">page 605</a>] (<a href="#Contents">Contents</a>)
23714 7 If s is a null pointer, the wctomb_s function stores into the int pointed to by status a
23715 nonzero or zero value, if multibyte character encodings, respectively, do or do not have
23716 state-dependent encodings.
23717 8 If s is not a null pointer, the wctomb_s function stores into the int pointed to by
23718 status either n or -1 if wc, respectively, does or does not correspond to a valid
23719 multibyte character.
23720 9 In no case will the int pointed to by status be set to a value greater than the
23723 10 The wctomb_s function returns zero if successful, and a nonzero value if there was a
23724 runtime-constraint violation or wc did not correspond to a valid multibyte character.
23725 <a name="K.3.6.5" href="#K.3.6.5"><b> K.3.6.5 Multibyte/wide string conversion functions</b></a>
23726 1 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
23727 the current locale.
23728 <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>
23730 1 #include <a href="#7.22"><stdlib.h></a>
23731 errno_t mbstowcs_s(size_t * restrict retval,
23732 wchar_t * restrict dst, rsize_t dstmax,
23733 const char * restrict src, rsize_t len);
23734 Runtime-constraints
23735 2 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
23736 neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
23737 then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
23738 zero. If dst is not a null pointer and len is not less than dstmax, then a null character
23739 shall occur within the first dstmax multibyte characters of the array pointed to by src.
23740 3 If there is a runtime-constraint violation, then mbstowcs_s does the following. If
23741 retval is not a null pointer, then mbstowcs_s sets *retval to (size_t)(-1). If
23742 dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
23743 then mbstowcs_s sets dst[0] to the null wide character.
23745 4 The mbstowcs_s function converts a sequence of multibyte characters that begins in
23746 the initial shift state from the array pointed to by src into a sequence of corresponding
23747 wide characters. If dst is not a null pointer, the converted characters are stored into the
23748 array pointed to by dst. Conversion continues up to and including a terminating null
23749 character, which is also stored. Conversion stops earlier in two cases: when a sequence of
23750 [<a name="#p606" href="p606">page 606</a>] (<a href="#Contents">Contents</a>)
23752 bytes is encountered that does not form a valid multibyte character, or (if dst is not a
23753 null pointer) when len wide characters have been stored into the array pointed to by
23754 dst.394) If dst is not a null pointer and no null wide character was stored into the array
23755 pointed to by dst, then dst[len] is set to the null wide character. Each conversion
23756 takes place as if by a call to the mbrtowc function.
23757 5 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
23758 sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
23759 the mbstowcs_s function stores the value (size_t)(-1) into *retval.
23760 Otherwise, the mbstowcs_s function stores into *retval the number of multibyte
23761 characters successfully converted, not including the terminating null character (if any).
23762 6 All elements following the terminating null wide character (if any) written by
23763 mbstowcs_s in the array of dstmax wide characters pointed to by dst take
23764 unspecified values when mbstowcs_s returns.395)
23765 7 If copying takes place between objects that overlap, the objects take on unspecified
23768 8 The mbstowcs_s function returns zero if no runtime-constraint violation and no
23769 encoding error occurred. Otherwise, a nonzero value is returned.
23770 <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>
23772 1 #include <a href="#7.22"><stdlib.h></a>
23773 errno_t wcstombs_s(size_t * restrict retval,
23774 char * restrict dst, rsize_t dstmax,
23775 const wchar_t * restrict src, rsize_t len);
23776 Runtime-constraints
23777 2 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
23778 neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
23779 then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
23780 zero. If dst is not a null pointer and len is not less than dstmax, then the conversion
23781 shall have been stopped (see below) because a terminating null wide character was
23782 reached or because an encoding error occurred.
23787 394) Thus, the value of len is ignored if dst is a null pointer.
23788 395) This allows an implementation to attempt converting the multibyte string before discovering a
23789 terminating null character did not occur where required.
23791 [<a name="#p607" href="p607">page 607</a>] (<a href="#Contents">Contents</a>)
23793 3 If there is a runtime-constraint violation, then wcstombs_s does the following. If
23794 retval is not a null pointer, then wcstombs_s sets *retval to (size_t)(-1). If
23795 dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
23796 then wcstombs_s sets dst[0] to the null character.
23798 4 The wcstombs_s function converts a sequence of wide characters from the array
23799 pointed to by src into a sequence of corresponding multibyte characters that begins in
23800 the initial shift state. If dst is not a null pointer, the converted characters are then stored
23801 into the array pointed to by dst. Conversion continues up to and including a terminating
23802 null wide character, which is also stored. Conversion stops earlier in two cases:
23803 -- when a wide character is reached that does not correspond to a valid multibyte
23805 -- (if dst is not a null pointer) when the next multibyte character would exceed the
23806 limit of n total bytes to be stored into the array pointed to by dst. If the wide
23807 character being converted is the null wide character, then n is the lesser of len or
23808 dstmax. Otherwise, n is the lesser of len or dstmax-1.
23809 If the conversion stops without converting a null wide character and dst is not a null
23810 pointer, then a null character is stored into the array pointed to by dst immediately
23811 following any multibyte characters already stored. Each conversion takes place as if by a
23812 call to the wcrtomb function.396)
23813 5 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
23814 wide character that does not correspond to a valid multibyte character, an encoding error
23815 occurs: the wcstombs_s function stores the value (size_t)(-1) into *retval.
23816 Otherwise, the wcstombs_s function stores into *retval the number of bytes in the
23817 resulting multibyte character sequence, not including the terminating null character (if
23819 6 All elements following the terminating null character (if any) written by wcstombs_s
23820 in the array of dstmax elements pointed to by dst take unspecified values when
23821 wcstombs_s returns.397)
23822 7 If copying takes place between objects that overlap, the objects take on unspecified
23826 396) If conversion stops because a terminating null wide character has been reached, the bytes stored
23827 include those necessary to reach the initial shift state immediately before the null byte. However, if
23828 the conversion stops before a terminating null wide character has been reached, the result will be null
23829 terminated, but might not end in the initial shift state.
23830 397) When len is not less than dstmax, the implementation might fill the array before discovering a
23831 runtime-constraint violation.
23833 [<a name="#p608" href="p608">page 608</a>] (<a href="#Contents">Contents</a>)
23836 8 The wcstombs_s function returns zero if no runtime-constraint violation and no
23837 encoding error occurred. Otherwise, a nonzero value is returned.
23838 <a name="K.3.7" href="#K.3.7"><b> K.3.7 String handling <string.h></b></a>
23839 1 The header <a href="#7.23"><string.h></a> defines two types.
23842 which is type int; and
23844 which is the type size_t.
23845 <a name="K.3.7.1" href="#K.3.7.1"><b> K.3.7.1 Copying functions</b></a>
23846 <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>
23848 1 #define __STDC_WANT_LIB_EXT1__ 1
23849 #include <a href="#7.23"><string.h></a>
23850 errno_t memcpy_s(void * restrict s1, rsize_t s1max,
23851 const void * restrict s2, rsize_t n);
23852 Runtime-constraints
23853 2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
23854 RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
23855 objects that overlap.
23856 3 If there is a runtime-constraint violation, the memcpy_s function stores zeros in the first
23857 s1max characters of the object pointed to by s1 if s1 is not a null pointer and s1max is
23858 not greater than RSIZE_MAX.
23860 4 The memcpy_s function copies n characters from the object pointed to by s2 into the
23861 object pointed to by s1.
23863 5 The memcpy_s function returns zero if there was no runtime-constraint violation.
23864 Otherwise, a nonzero value is returned.
23869 [<a name="#p609" href="p609">page 609</a>] (<a href="#Contents">Contents</a>)
23871 <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>
23873 1 #define __STDC_WANT_LIB_EXT1__ 1
23874 #include <a href="#7.23"><string.h></a>
23875 errno_t memmove_s(void *s1, rsize_t s1max,
23876 const void *s2, rsize_t n);
23877 Runtime-constraints
23878 2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
23879 RSIZE_MAX. n shall not be greater than s1max.
23880 3 If there is a runtime-constraint violation, the memmove_s function stores zeros in the
23881 first s1max characters of the object pointed to by s1 if s1 is not a null pointer and
23882 s1max is not greater than RSIZE_MAX.
23884 4 The memmove_s function copies n characters from the object pointed to by s2 into the
23885 object pointed to by s1. This copying takes place as if the n characters from the object
23886 pointed to by s2 are first copied into a temporary array of n characters that does not
23887 overlap the objects pointed to by s1 or s2, and then the n characters from the temporary
23888 array are copied into the object pointed to by s1.
23890 5 The memmove_s function returns zero if there was no runtime-constraint violation.
23891 Otherwise, a nonzero value is returned.
23892 <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>
23894 1 #define __STDC_WANT_LIB_EXT1__ 1
23895 #include <a href="#7.23"><string.h></a>
23896 errno_t strcpy_s(char * restrict s1,
23898 const char * restrict s2);
23899 Runtime-constraints
23900 2 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
23901 s1max shall not equal zero. s1max shall be greater than strnlen_s(s2, s1max).
23902 Copying shall not take place between objects that overlap.
23903 3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
23904 greater than zero and not greater than RSIZE_MAX, then strcpy_s sets s1[0] to the
23907 [<a name="#p610" href="p610">page 610</a>] (<a href="#Contents">Contents</a>)
23910 4 The strcpy_s function copies the string pointed to by s2 (including the terminating
23911 null character) into the array pointed to by s1.
23912 5 All elements following the terminating null character (if any) written by strcpy_s in
23913 the array of s1max characters pointed to by s1 take unspecified values when
23914 strcpy_s returns.398)
23916 6 The strcpy_s function returns zero399) if there was no runtime-constraint violation.
23917 Otherwise, a nonzero value is returned.
23918 <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>
23920 1 #define __STDC_WANT_LIB_EXT1__ 1
23921 #include <a href="#7.23"><string.h></a>
23922 errno_t strncpy_s(char * restrict s1,
23924 const char * restrict s2,
23926 Runtime-constraints
23927 2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
23928 RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
23929 shall be greater than strnlen_s(s2, s1max). Copying shall not take place between
23930 objects that overlap.
23931 3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
23932 greater than zero and not greater than RSIZE_MAX, then strncpy_s sets s1[0] to the
23935 4 The strncpy_s function copies not more than n successive characters (characters that
23936 follow a null character are not copied) from the array pointed to by s2 to the array
23937 pointed to by s1. If no null character was copied from s2, then s1[n] is set to a null
23941 398) This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
23942 any of those characters are null. Such an approach might write a character to every element of s1
23943 before discovering that the first element should be set to the null character.
23944 399) A zero return value implies that all of the requested characters from the string pointed to by s2 fit
23945 within the array pointed to by s1 and that the result in s1 is null terminated.
23947 [<a name="#p611" href="p611">page 611</a>] (<a href="#Contents">Contents</a>)
23949 5 All elements following the terminating null character (if any) written by strncpy_s in
23950 the array of s1max characters pointed to by s1 take unspecified values when
23951 strncpy_s returns.400)
23953 6 The strncpy_s function returns zero401) if there was no runtime-constraint violation.
23954 Otherwise, a nonzero value is returned.
23955 7 EXAMPLE 1 The strncpy_s function can be used to copy a string without the danger that the result
23956 will not be null terminated or that characters will be written past the end of the destination array.
23957 #define __STDC_WANT_LIB_EXT1__ 1
23958 #include <a href="#7.23"><string.h></a>
23960 char src1[100] = "hello";
23961 char src2[7] = {'g', 'o', 'o', 'd', 'b', 'y', 'e'};
23962 char dst1[6], dst2[5], dst3[5];
23964 r1 = strncpy_s(dst1, 6, src1, 100);
23965 r2 = strncpy_s(dst2, 5, src2, 7);
23966 r3 = strncpy_s(dst3, 5, src2, 4);
23967 The first call will assign to r1 the value zero and to dst1 the sequence hello\0.
23968 The second call will assign to r2 a nonzero value and to dst2 the sequence \0.
23969 The third call will assign to r3 the value zero and to dst3 the sequence good\0.
23971 <a name="K.3.7.2" href="#K.3.7.2"><b> K.3.7.2 Concatenation functions</b></a>
23972 <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>
23974 1 #define __STDC_WANT_LIB_EXT1__ 1
23975 #include <a href="#7.23"><string.h></a>
23976 errno_t strcat_s(char * restrict s1,
23978 const char * restrict s2);
23979 Runtime-constraints
23980 2 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
23986 400) This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
23987 any of those characters are null. Such an approach might write a character to every element of s1
23988 before discovering that the first element should be set to the null character.
23989 401) A zero return value implies that all of the requested characters from the string pointed to by s2 fit
23990 within the array pointed to by s1 and that the result in s1 is null terminated.
23992 [<a name="#p612" href="p612">page 612</a>] (<a href="#Contents">Contents</a>)
23994 3 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
23995 s1max shall not equal zero. m shall not equal zero.402) m shall be greater than
23996 strnlen_s(s2, m). Copying shall not take place between objects that overlap.
23997 4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
23998 greater than zero and not greater than RSIZE_MAX, then strcat_s sets s1[0] to the
24001 5 The strcat_s function appends a copy of the string pointed to by s2 (including the
24002 terminating null character) to the end of the string pointed to by s1. The initial character
24003 from s2 overwrites the null character at the end of s1.
24004 6 All elements following the terminating null character (if any) written by strcat_s in
24005 the array of s1max characters pointed to by s1 take unspecified values when
24006 strcat_s returns.403)
24008 7 The strcat_s function returns zero404) if there was no runtime-constraint violation.
24009 Otherwise, a nonzero value is returned.
24010 <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>
24012 1 #define __STDC_WANT_LIB_EXT1__ 1
24013 #include <a href="#7.23"><string.h></a>
24014 errno_t strncat_s(char * restrict s1,
24016 const char * restrict s2,
24018 Runtime-constraints
24019 2 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
24021 3 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
24022 RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.405) If n is not less
24025 402) Zero means that s1 was not null terminated upon entry to strcat_s.
24026 403) This allows an implementation to append characters from s2 to s1 while simultaneously checking if
24027 any of those characters are null. Such an approach might write a character to every element of s1
24028 before discovering that the first element should be set to the null character.
24029 404) A zero return value implies that all of the requested characters from the string pointed to by s2 were
24030 appended to the string pointed to by s1 and that the result in s1 is null terminated.
24032 [<a name="#p613" href="p613">page 613</a>] (<a href="#Contents">Contents</a>)
24034 than m, then m shall be greater than strnlen_s(s2, m). Copying shall not take
24035 place between objects that overlap.
24036 4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
24037 greater than zero and not greater than RSIZE_MAX, then strncat_s sets s1[0] to the
24040 5 The strncat_s function appends not more than n successive characters (characters
24041 that follow a null character are not copied) from the array pointed to by s2 to the end of
24042 the string pointed to by s1. The initial character from s2 overwrites the null character at
24043 the end of s1. If no null character was copied from s2, then s1[s1max-m+n] is set to
24045 6 All elements following the terminating null character (if any) written by strncat_s in
24046 the array of s1max characters pointed to by s1 take unspecified values when
24047 strncat_s returns.406)
24049 7 The strncat_s function returns zero407) if there was no runtime-constraint violation.
24050 Otherwise, a nonzero value is returned.
24051 8 EXAMPLE 1 The strncat_s function can be used to copy a string without the danger that the result
24052 will not be null terminated or that characters will be written past the end of the destination array.
24053 #define __STDC_WANT_LIB_EXT1__ 1
24054 #include <a href="#7.23"><string.h></a>
24056 char s1[100] = "good";
24057 char s2[6] = "hello";
24058 char s3[6] = "hello";
24059 char s4[7] = "abc";
24060 char s5[1000] = "bye";
24061 int r1, r2, r3, r4;
24062 r1 = strncat_s(s1, 100, s5, 1000);
24063 r2 = strncat_s(s2, 6, "", 1);
24064 r3 = strncat_s(s3, 6, "X", 2);
24065 r4 = strncat_s(s4, 7, "defghijklmn", 3);
24066 After the first call r1 will have the value zero and s1 will contain the sequence goodbye\0.
24070 405) Zero means that s1 was not null terminated upon entry to strncat_s.
24071 406) This allows an implementation to append characters from s2 to s1 while simultaneously checking if
24072 any of those characters are null. Such an approach might write a character to every element of s1
24073 before discovering that the first element should be set to the null character.
24074 407) A zero return value implies that all of the requested characters from the string pointed to by s2 were
24075 appended to the string pointed to by s1 and that the result in s1 is null terminated.
24077 [<a name="#p614" href="p614">page 614</a>] (<a href="#Contents">Contents</a>)
24079 After the second call r2 will have the value zero and s2 will contain the sequence hello\0.
24080 After the third call r3 will have a nonzero value and s3 will contain the sequence \0.
24081 After the fourth call r4 will have the value zero and s4 will contain the sequence abcdef\0.
24083 <a name="K.3.7.3" href="#K.3.7.3"><b> K.3.7.3 Search functions</b></a>
24084 <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>
24086 1 #define __STDC_WANT_LIB_EXT1__ 1
24087 #include <a href="#7.23"><string.h></a>
24088 char *strtok_s(char * restrict s1,
24089 rsize_t * restrict s1max,
24090 const char * restrict s2,
24091 char ** restrict ptr);
24092 Runtime-constraints
24093 2 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
24094 shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
24095 The end of the token found shall occur within the first *s1max characters of s1 for the
24096 first call, and shall occur within the first *s1max characters of where searching resumes
24097 on subsequent calls.
24098 3 If there is a runtime-constraint violation, the strtok_s function does not indirect
24099 through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
24101 4 A sequence of calls to the strtok_s function breaks the string pointed to by s1 into a
24102 sequence of tokens, each of which is delimited by a character from the string pointed to
24103 by s2. The fourth argument points to a caller-provided char pointer into which the
24104 strtok_s function stores information necessary for it to continue scanning the same
24106 5 The first call in a sequence has a non-null first argument and s1max points to an object
24107 whose value is the number of elements in the character array pointed to by the first
24108 argument. The first call stores an initial value in the object pointed to by ptr and
24109 updates the value pointed to by s1max to reflect the number of elements that remain in
24110 relation to ptr. Subsequent calls in the sequence have a null first argument and the
24111 objects pointed to by s1max and ptr are required to have the values stored by the
24112 previous call in the sequence, which are then updated. The separator string pointed to by
24113 s2 may be different from call to call.
24114 6 The first call in the sequence searches the string pointed to by s1 for the first character
24115 that is not contained in the current separator string pointed to by s2. If no such character
24116 is found, then there are no tokens in the string pointed to by s1 and the strtok_s
24117 function returns a null pointer. If such a character is found, it is the start of the first token.
24118 [<a name="#p615" href="p615">page 615</a>] (<a href="#Contents">Contents</a>)
24120 7 The strtok_s function then searches from there for the first character in s1 that is
24121 contained in the current separator string. If no such character is found, the current token
24122 extends to the end of the string pointed to by s1, and subsequent searches in the same
24123 string for a token return a null pointer. If such a character is found, it is overwritten by a
24124 null character, which terminates the current token.
24125 8 In all cases, the strtok_s function stores sufficient information in the pointer pointed
24126 to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
24127 value for ptr, shall start searching just past the element overwritten by a null character
24130 9 The strtok_s function returns a pointer to the first character of a token, or a null
24131 pointer if there is no token or there is a runtime-constraint violation.
24133 #define __STDC_WANT_LIB_EXT1__ 1
24134 #include <a href="#7.23"><string.h></a>
24135 static char str1[] = "?a???b,,,#c";
24136 static char str2[] = "\t \t";
24137 char *t, *ptr1, *ptr2;
24138 rsize_t max1 = sizeof(str1);
24139 rsize_t max2 = sizeof(str2);
24140 t = strtok_s(str1, &max1, "?", &ptr1); // t points to the token "a"
24141 t = strtok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
24142 t = strtok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
24143 t = strtok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
24144 t = strtok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
24146 <a name="K.3.7.4" href="#K.3.7.4"><b> K.3.7.4 Miscellaneous functions</b></a>
24147 <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>
24149 1 #define __STDC_WANT_LIB_EXT1__ 1
24150 #include <a href="#7.23"><string.h></a>
24151 errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
24152 Runtime-constraints
24153 2 s shall not be a null pointer. Neither smax nor n shall be greater than RSIZE_MAX. n
24154 shall not be greater than smax.
24155 3 If there is a runtime-constraint violation, then if s is not a null pointer and smax is not
24156 greater than RSIZE_MAX, the memset_s function stores the value of c (converted to an
24157 unsigned char) into each of the first smax characters of the object pointed to by s.
24161 [<a name="#p616" href="p616">page 616</a>] (<a href="#Contents">Contents</a>)
24164 4 The memset_s function copies the value of c (converted to an unsigned char) into
24165 each of the first n characters of the object pointed to by s. Unlike memset, any call to
24166 the memset_s function shall be evaluated strictly according to the rules of the abstract
24167 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
24168 assume that the memory indicated by s and n may be accessible in the future and thus
24169 must contain the values indicated by c.
24171 5 The memset_s function returns zero if there was no runtime-constraint violation.
24172 Otherwise, a nonzero value is returned.
24173 <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>
24175 1 #define __STDC_WANT_LIB_EXT1__ 1
24176 #include <a href="#7.23"><string.h></a>
24177 errno_t strerror_s(char *s, rsize_t maxsize,
24179 Runtime-constraints
24180 2 s shall not be a null pointer. maxsize shall not be greater than RSIZE_MAX.
24181 maxsize shall not equal zero.
24182 3 If there is a runtime-constraint violation, then the array (if any) pointed to by s is not
24185 4 The strerror_s function maps the number in errnum to a locale-specific message
24186 string. Typically, the values for errnum come from errno, but strerror_s shall
24187 map any value of type int to a message.
24188 5 If the length of the desired string is less than maxsize, then the string is copied to the
24189 array pointed to by s.
24190 6 Otherwise, if maxsize is greater than zero, then maxsize-1 characters are copied
24191 from the string to the array pointed to by s and then s[maxsize-1] is set to the null
24192 character. Then, if maxsize is greater than 3, then s[maxsize-2],
24193 s[maxsize-3], and s[maxsize-4] are set to the character period (.).
24195 7 The strerror_s function returns zero if the length of the desired string was less than
24196 maxsize and there was no runtime-constraint violation. Otherwise, the strerror_s
24197 function returns a nonzero value.
24199 [<a name="#p617" href="p617">page 617</a>] (<a href="#Contents">Contents</a>)
24201 <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>
24203 1 #define __STDC_WANT_LIB_EXT1__ 1
24204 #include <a href="#7.23"><string.h></a>
24205 size_t strerrorlen_s(errno_t errnum);
24207 2 The strerrorlen_s function calculates the length of the (untruncated) locale-specific
24208 message string that the strerror_s function maps to errnum.
24210 3 The strerrorlen_s function returns the number of characters (not including the null
24211 character) in the full message string.
24212 <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>
24214 1 #define __STDC_WANT_LIB_EXT1__ 1
24215 #include <a href="#7.23"><string.h></a>
24216 size_t strnlen_s(const char *s, size_t maxsize);
24218 2 The strnlen_s function computes the length of the string pointed to by s.
24220 3 If s is a null pointer,408) then the strnlen_s function returns zero.
24221 4 Otherwise, the strnlen_s function returns the number of characters that precede the
24222 terminating null character. If there is no null character in the first maxsize characters of
24223 s then strnlen_s returns maxsize. At most the first maxsize characters of s shall
24224 be accessed by strnlen_s.
24229 408) Note that the strnlen_s function has no runtime-constraints. This lack of runtime-constraints
24230 along with the values returned for a null pointer or an unterminated string argument make
24231 strnlen_s useful in algorithms that gracefully handle such exceptional data.
24233 [<a name="#p618" href="p618">page 618</a>] (<a href="#Contents">Contents</a>)
24235 <a name="K.3.8" href="#K.3.8"><b> K.3.8 Date and time <time.h></b></a>
24236 1 The header <a href="#7.26"><time.h></a> defines two types.
24239 which is type int; and
24241 which is the type size_t.
24242 <a name="K.3.8.1" href="#K.3.8.1"><b> K.3.8.1 Components of time</b></a>
24243 1 A broken-down time is normalized if the values of the members of the tm structure are in
24244 their normal rages.409)
24245 <a name="K.3.8.2" href="#K.3.8.2"><b> K.3.8.2 Time conversion functions</b></a>
24246 1 Like the strftime function, the asctime_s and ctime_s functions do not return a
24247 pointer to a static object, and other library functions are permitted to call them.
24248 <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>
24250 1 #define __STDC_WANT_LIB_EXT1__ 1
24251 #include <a href="#7.26"><time.h></a>
24252 errno_t asctime_s(char *s, rsize_t maxsize,
24253 const struct tm *timeptr);
24254 Runtime-constraints
24255 2 Neither s nor timeptr shall be a null pointer. maxsize shall not be less than 26 and
24256 shall not be greater than RSIZE_MAX. The broken-down time pointed to by timeptr
24257 shall be normalized. The calendar year represented by the broken-down time pointed to
24258 by timeptr shall not be less than calendar year 0 and shall not be greater than calendar
24260 3 If there is a runtime-constraint violation, there is no attempt to convert the time, and
24261 s[0] is set to a null character if s is not a null pointer and maxsize is not zero and is
24262 not greater than RSIZE_MAX.
24264 4 The asctime_s function converts the normalized broken-down time in the structure
24265 pointed to by timeptr into a 26 character (including the null character) string in the
24268 409) The normal ranges are defined in <a href="#7.26.1">7.26.1</a>.
24270 [<a name="#p619" href="p619">page 619</a>] (<a href="#Contents">Contents</a>)
24273 Sun Sep 16 01:03:52 1973\n\0
24274 The fields making up this string are (in order):
24275 1. The name of the day of the week represented by timeptr->tm_wday using the
24276 following three character weekday names: Sun, Mon, Tue, Wed, Thu, Fri, and Sat.
24277 2. The character space.
24278 3. The name of the month represented by timeptr->tm_mon using the following
24279 three character month names: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct,
24281 4. The character space.
24282 5. The value of timeptr->tm_mday as if printed using the fprintf format
24284 6. The character space.
24285 7. The value of timeptr->tm_hour as if printed using the fprintf format
24287 8. The character colon.
24288 9. The value of timeptr->tm_min as if printed using the fprintf format
24290 10. The character colon.
24291 11. The value of timeptr->tm_sec as if printed using the fprintf format
24293 12. The character space.
24294 13. The value of timeptr->tm_year + 1900 as if printed using the fprintf
24296 14. The character new line.
24297 15. The null character.
24298 Recommended practice
24299 The strftime function allows more flexible formatting and supports locale-specific
24300 behavior. If you do not require the exact form of the result string produced by the
24301 asctime_s function, consider using the strftime function instead.
24303 5 The asctime_s function returns zero if the time was successfully converted and stored
24304 into the array pointed to by s. Otherwise, it returns a nonzero value.
24305 [<a name="#p620" href="p620">page 620</a>] (<a href="#Contents">Contents</a>)
24307 <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>
24309 1 #define __STDC_WANT_LIB_EXT1__ 1
24310 #include <a href="#7.26"><time.h></a>
24311 errno_t ctime_s(char *s, rsize_t maxsize,
24312 const time_t *timer);
24313 Runtime-constraints
24314 2 Neither s nor timer shall be a null pointer. maxsize shall not be less than 26 and
24315 shall not be greater than RSIZE_MAX.
24316 3 If there is a runtime-constraint violation, s[0] is set to a null character if s is not a null
24317 pointer and maxsize is not equal zero and is not greater than RSIZE_MAX.
24319 4 The ctime_s function converts the calendar time pointed to by timer to local time in
24320 the form of a string. It is equivalent to
24321 asctime_s(s, maxsize, localtime_s(timer))
24322 Recommended practice
24323 The strftime function allows more flexible formatting and supports locale-specific
24324 behavior. If you do not require the exact form of the result string produced by the
24325 ctime_s function, consider using the strftime function instead.
24327 5 The ctime_s function returns zero if the time was successfully converted and stored
24328 into the array pointed to by s. Otherwise, it returns a nonzero value.
24329 <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>
24331 1 #define __STDC_WANT_LIB_EXT1__ 1
24332 #include <a href="#7.26"><time.h></a>
24333 struct tm *gmtime_s(const time_t * restrict timer,
24334 struct tm * restrict result);
24335 Runtime-constraints
24336 2 Neither timer nor result shall be a null pointer.
24337 3 If there is a runtime-constraint violation, there is no attempt to convert the time.
24339 4 The gmtime_s function converts the calendar time pointed to by timer into a broken-
24340 down time, expressed as UTC. The broken-down time is stored in the structure pointed
24341 [<a name="#p621" href="p621">page 621</a>] (<a href="#Contents">Contents</a>)
24345 5 The gmtime_s function returns result, or a null pointer if the specified time cannot
24346 be converted to UTC or there is a runtime-constraint violation.
24347 <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>
24349 1 #define __STDC_WANT_LIB_EXT1__ 1
24350 #include <a href="#7.26"><time.h></a>
24351 struct tm *localtime_s(const time_t * restrict timer,
24352 struct tm * restrict result);
24353 Runtime-constraints
24354 2 Neither timer nor result shall be a null pointer.
24355 3 If there is a runtime-constraint violation, there is no attempt to convert the time.
24357 4 The localtime_s function converts the calendar time pointed to by timer into a
24358 broken-down time, expressed as local time. The broken-down time is stored in the
24359 structure pointed to by result.
24361 5 The localtime_s function returns result, or a null pointer if the specified time
24362 cannot be converted to local time or there is a runtime-constraint violation.
24363 <a name="K.3.9" href="#K.3.9"><b> K.3.9 Extended multibyte and wide character utilities <wchar.h></b></a>
24364 1 The header <a href="#7.28"><wchar.h></a> defines two types.
24367 which is type int; and
24369 which is the type size_t.
24370 3 Unless explicitly stated otherwise, if the execution of a function described in this
24371 subclause causes copying to take place between objects that overlap, the objects take on
24372 unspecified values.
24377 [<a name="#p622" href="p622">page 622</a>] (<a href="#Contents">Contents</a>)
24379 <a name="K.3.9.1" href="#K.3.9.1"><b> K.3.9.1 Formatted wide character input/output functions</b></a>
24380 <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>
24382 1 #define __STDC_WANT_LIB_EXT1__ 1
24383 #include <a href="#7.28"><wchar.h></a>
24384 int fwprintf_s(FILE * restrict stream,
24385 const wchar_t * restrict format, ...);
24386 Runtime-constraints
24387 2 Neither stream nor format shall be a null pointer. The %n specifier410) (modified or
24388 not by flags, field width, or precision) shall not appear in the wide string pointed to by
24389 format. Any argument to fwprintf_s corresponding to a %s specifier shall not be a
24391 3 If there is a runtime-constraint violation, the fwprintf_s function does not attempt to
24392 produce further output, and it is unspecified to what extent fwprintf_s produced
24393 output before discovering the runtime-constraint violation.
24395 4 The fwprintf_s function is equivalent to the fwprintf function except for the
24396 explicit runtime-constraints listed above.
24398 5 The fwprintf_s function returns the number of wide characters transmitted, or a
24399 negative value if an output error, encoding error, or runtime-constraint violation occurred.
24400 <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>
24402 1 #define __STDC_WANT_LIB_EXT1__ 1
24403 #include <a href="#7.21"><stdio.h></a>
24404 #include <a href="#7.28"><wchar.h></a>
24405 int fwscanf_s(FILE * restrict stream,
24406 const wchar_t * restrict format, ...);
24407 Runtime-constraints
24408 2 Neither stream nor format shall be a null pointer. Any argument indirected though in
24409 order to store converted input shall not be a null pointer.
24412 410) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24413 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24414 example, if the entire format string was L"%%n".
24416 [<a name="#p623" href="p623">page 623</a>] (<a href="#Contents">Contents</a>)
24418 3 If there is a runtime-constraint violation, the fwscanf_s function does not attempt to
24419 perform further input, and it is unspecified to what extent fwscanf_s performed input
24420 before discovering the runtime-constraint violation.
24422 4 The fwscanf_s function is equivalent to fwscanf except that the c, s, and [
24423 conversion specifiers apply to a pair of arguments (unless assignment suppression is
24424 indicated by a *). The first of these arguments is the same as for fwscanf. That
24425 argument is immediately followed in the argument list by the second argument, which has
24426 type size_t and gives the number of elements in the array pointed to by the first
24427 argument of the pair. If the first argument points to a scalar object, it is considered to be
24428 an array of one element.411)
24429 5 A matching failure occurs if the number of elements in a receiving object is insufficient to
24430 hold the converted input (including any trailing null character).
24432 6 The fwscanf_s function returns the value of the macro EOF if an input failure occurs
24433 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24434 fwscanf_s function returns the number of input items assigned, which can be fewer
24435 than provided for, or even zero, in the event of an early matching failure.
24436 <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>
24438 1 #define __STDC_WANT_LIB_EXT1__ 1
24439 #include <a href="#7.28"><wchar.h></a>
24440 int snwprintf_s(wchar_t * restrict s,
24442 const wchar_t * restrict format, ...);
24443 Runtime-constraints
24444 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
24445 than RSIZE_MAX. The %n specifier412) (modified or not by flags, field width, or
24447 411) If the format is known at translation time, an implementation may issue a diagnostic for any argument
24448 used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
24449 argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
24450 the format is not known at translation time. For example, an implementation may issue a diagnostic
24451 for each argument after format that has of type pointer to one of char, signed char,
24452 unsigned char, or void that is not followed by an argument of a type compatible with
24453 rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
24454 using the hh length modifier, a length argument must follow the pointer argument. Another useful
24455 diagnostic could flag any non-pointer argument following format that did not have a type
24456 compatible with rsize_t.
24458 [<a name="#p624" href="p624">page 624</a>] (<a href="#Contents">Contents</a>)
24460 precision) shall not appear in the wide string pointed to by format. Any argument to
24461 snwprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
24463 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
24464 than zero and less than RSIZE_MAX, then the snwprintf_s function sets s[0] to the
24465 null wide character.
24467 4 The snwprintf_s function is equivalent to the swprintf function except for the
24468 explicit runtime-constraints listed above.
24469 5 The snwprintf_s function, unlike swprintf_s, will truncate the result to fit within
24470 the array pointed to by s.
24472 6 The snwprintf_s function returns the number of wide characters that would have
24473 been written had n been sufficiently large, not counting the terminating wide null
24474 character, or a negative value if a runtime-constraint violation occurred. Thus, the null-
24475 terminated output has been completely written if and only if the returned value is
24476 nonnegative and less than n.
24477 <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>
24479 1 #define __STDC_WANT_LIB_EXT1__ 1
24480 #include <a href="#7.28"><wchar.h></a>
24481 int swprintf_s(wchar_t * restrict s, rsize_t n,
24482 const wchar_t * restrict format, ...);
24483 Runtime-constraints
24484 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
24485 than RSIZE_MAX. The number of wide characters (including the trailing null) required
24486 for the result to be written to the array pointed to by s shall not be greater than n. The %n
24487 specifier413) (modified or not by flags, field width, or precision) shall not appear in the
24488 wide string pointed to by format. Any argument to swprintf_s corresponding to a
24489 %s specifier shall not be a null pointer. No encoding error shall occur.
24492 412) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24493 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24494 example, if the entire format string was L"%%n".
24495 413) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24496 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24497 example, if the entire format string was L"%%n".
24499 [<a name="#p625" href="p625">page 625</a>] (<a href="#Contents">Contents</a>)
24501 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
24502 than zero and less than RSIZE_MAX, then the swprintf_s function sets s[0] to the
24503 null wide character.
24505 4 The swprintf_s function is equivalent to the swprintf function except for the
24506 explicit runtime-constraints listed above.
24507 5 The swprintf_s function, unlike snwprintf_s, treats a result too big for the array
24508 pointed to by s as a runtime-constraint violation.
24510 6 If no runtime-constraint violation occurred, the swprintf_s function returns the
24511 number of wide characters written in the array, not counting the terminating null wide
24512 character. If an encoding error occurred or if n or more wide characters are requested to
24513 be written, swprintf_s returns a negative value. If any other runtime-constraint
24514 violation occurred, swprintf_s returns zero.
24515 <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>
24517 1 #define __STDC_WANT_LIB_EXT1__ 1
24518 #include <a href="#7.28"><wchar.h></a>
24519 int swscanf_s(const wchar_t * restrict s,
24520 const wchar_t * restrict format, ...);
24521 Runtime-constraints
24522 2 Neither s nor format shall be a null pointer. Any argument indirected though in order
24523 to store converted input shall not be a null pointer.
24524 3 If there is a runtime-constraint violation, the swscanf_s function does not attempt to
24525 perform further input, and it is unspecified to what extent swscanf_s performed input
24526 before discovering the runtime-constraint violation.
24528 4 The swscanf_s function is equivalent to fwscanf_s, except that the argument s
24529 specifies a wide string from which the input is to be obtained, rather than from a stream.
24530 Reaching the end of the wide string is equivalent to encountering end-of-file for the
24531 fwscanf_s function.
24533 5 The swscanf_s function returns the value of the macro EOF if an input failure occurs
24534 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24535 swscanf_s function returns the number of input items assigned, which can be fewer
24536 than provided for, or even zero, in the event of an early matching failure.
24537 [<a name="#p626" href="p626">page 626</a>] (<a href="#Contents">Contents</a>)
24539 <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>
24541 1 #define __STDC_WANT_LIB_EXT1__ 1
24542 #include <a href="#7.16"><stdarg.h></a>
24543 #include <a href="#7.21"><stdio.h></a>
24544 #include <a href="#7.28"><wchar.h></a>
24545 int vfwprintf_s(FILE * restrict stream,
24546 const wchar_t * restrict format,
24548 Runtime-constraints
24549 2 Neither stream nor format shall be a null pointer. The %n specifier414) (modified or
24550 not by flags, field width, or precision) shall not appear in the wide string pointed to by
24551 format. Any argument to vfwprintf_s corresponding to a %s specifier shall not be
24553 3 If there is a runtime-constraint violation, the vfwprintf_s function does not attempt
24554 to produce further output, and it is unspecified to what extent vfwprintf_s produced
24555 output before discovering the runtime-constraint violation.
24557 4 The vfwprintf_s function is equivalent to the vfwprintf function except for the
24558 explicit runtime-constraints listed above.
24560 5 The vfwprintf_s function returns the number of wide characters transmitted, or a
24561 negative value if an output error, encoding error, or runtime-constraint violation occurred.
24562 <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>
24564 1 #define __STDC_WANT_LIB_EXT1__ 1
24565 #include <a href="#7.16"><stdarg.h></a>
24566 #include <a href="#7.21"><stdio.h></a>
24567 #include <a href="#7.28"><wchar.h></a>
24568 int vfwscanf_s(FILE * restrict stream,
24569 const wchar_t * restrict format, va_list arg);
24573 414) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24574 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24575 example, if the entire format string was L"%%n".
24577 [<a name="#p627" href="p627">page 627</a>] (<a href="#Contents">Contents</a>)
24579 Runtime-constraints
24580 2 Neither stream nor format shall be a null pointer. Any argument indirected though in
24581 order to store converted input shall not be a null pointer.
24582 3 If there is a runtime-constraint violation, the vfwscanf_s function does not attempt to
24583 perform further input, and it is unspecified to what extent vfwscanf_s performed input
24584 before discovering the runtime-constraint violation.
24586 4 The vfwscanf_s function is equivalent to fwscanf_s, with the variable argument
24587 list replaced by arg, which shall have been initialized by the va_start macro (and
24588 possibly subsequent va_arg calls). The vfwscanf_s function does not invoke the
24591 5 The vfwscanf_s function returns the value of the macro EOF if an input failure occurs
24592 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24593 vfwscanf_s function returns the number of input items assigned, which can be fewer
24594 than provided for, or even zero, in the event of an early matching failure.
24595 <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>
24597 1 #define __STDC_WANT_LIB_EXT1__ 1
24598 #include <a href="#7.16"><stdarg.h></a>
24599 #include <a href="#7.28"><wchar.h></a>
24600 int vsnwprintf_s(wchar_t * restrict s,
24602 const wchar_t * restrict format,
24604 Runtime-constraints
24605 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
24606 than RSIZE_MAX. The %n specifier416) (modified or not by flags, field width, or
24607 precision) shall not appear in the wide string pointed to by format. Any argument to
24608 vsnwprintf_s corresponding to a %s specifier shall not be a null pointer. No
24609 encoding error shall occur.
24611 415) As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
24612 value of arg after the return is indeterminate.
24613 416) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24614 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24615 example, if the entire format string was L"%%n".
24617 [<a name="#p628" href="p628">page 628</a>] (<a href="#Contents">Contents</a>)
24619 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
24620 than zero and less than RSIZE_MAX, then the vsnwprintf_s function sets s[0] to
24621 the null wide character.
24623 4 The vsnwprintf_s function is equivalent to the vswprintf function except for the
24624 explicit runtime-constraints listed above.
24625 5 The vsnwprintf_s function, unlike vswprintf_s, will truncate the result to fit
24626 within the array pointed to by s.
24628 6 The vsnwprintf_s function returns the number of wide characters that would have
24629 been written had n been sufficiently large, not counting the terminating null character, or
24630 a negative value if a runtime-constraint violation occurred. Thus, the null-terminated
24631 output has been completely written if and only if the returned value is nonnegative and
24633 <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>
24635 1 #define __STDC_WANT_LIB_EXT1__ 1
24636 #include <a href="#7.16"><stdarg.h></a>
24637 #include <a href="#7.28"><wchar.h></a>
24638 int vswprintf_s(wchar_t * restrict s,
24640 const wchar_t * restrict format,
24642 Runtime-constraints
24643 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
24644 than RSIZE_MAX. The number of wide characters (including the trailing null) required
24645 for the result to be written to the array pointed to by s shall not be greater than n. The %n
24646 specifier417) (modified or not by flags, field width, or precision) shall not appear in the
24647 wide string pointed to by format. Any argument to vswprintf_s corresponding to a
24648 %s specifier shall not be a null pointer. No encoding error shall occur.
24649 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
24650 than zero and less than RSIZE_MAX, then the vswprintf_s function sets s[0] to the
24651 null wide character.
24653 417) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24654 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24655 example, if the entire format string was L"%%n".
24657 [<a name="#p629" href="p629">page 629</a>] (<a href="#Contents">Contents</a>)
24660 4 The vswprintf_s function is equivalent to the vswprintf function except for the
24661 explicit runtime-constraints listed above.
24662 5 The vswprintf_s function, unlike vsnwprintf_s, treats a result too big for the
24663 array pointed to by s as a runtime-constraint violation.
24665 6 If no runtime-constraint violation occurred, the vswprintf_s function returns the
24666 number of wide characters written in the array, not counting the terminating null wide
24667 character. If an encoding error occurred or if n or more wide characters are requested to
24668 be written, vswprintf_s returns a negative value. If any other runtime-constraint
24669 violation occurred, vswprintf_s returns zero.
24670 <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>
24672 1 #define __STDC_WANT_LIB_EXT1__ 1
24673 #include <a href="#7.16"><stdarg.h></a>
24674 #include <a href="#7.28"><wchar.h></a>
24675 int vswscanf_s(const wchar_t * restrict s,
24676 const wchar_t * restrict format,
24678 Runtime-constraints
24679 2 Neither s nor format shall be a null pointer. Any argument indirected though in order
24680 to store converted input shall not be a null pointer.
24681 3 If there is a runtime-constraint violation, the vswscanf_s function does not attempt to
24682 perform further input, and it is unspecified to what extent vswscanf_s performed input
24683 before discovering the runtime-constraint violation.
24685 4 The vswscanf_s function is equivalent to swscanf_s, with the variable argument
24686 list replaced by arg, which shall have been initialized by the va_start macro (and
24687 possibly subsequent va_arg calls). The vswscanf_s function does not invoke the
24693 418) As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
24694 value of arg after the return is indeterminate.
24696 [<a name="#p630" href="p630">page 630</a>] (<a href="#Contents">Contents</a>)
24699 5 The vswscanf_s function returns the value of the macro EOF if an input failure occurs
24700 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24701 vswscanf_s function returns the number of input items assigned, which can be fewer
24702 than provided for, or even zero, in the event of an early matching failure.
24703 <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>
24705 1 #define __STDC_WANT_LIB_EXT1__ 1
24706 #include <a href="#7.16"><stdarg.h></a>
24707 #include <a href="#7.28"><wchar.h></a>
24708 int vwprintf_s(const wchar_t * restrict format,
24710 Runtime-constraints
24711 2 format shall not be a null pointer. The %n specifier419) (modified or not by flags, field
24712 width, or precision) shall not appear in the wide string pointed to by format. Any
24713 argument to vwprintf_s corresponding to a %s specifier shall not be a null pointer.
24714 3 If there is a runtime-constraint violation, the vwprintf_s function does not attempt to
24715 produce further output, and it is unspecified to what extent vwprintf_s produced
24716 output before discovering the runtime-constraint violation.
24718 4 The vwprintf_s function is equivalent to the vwprintf function except for the
24719 explicit runtime-constraints listed above.
24721 5 The vwprintf_s function returns the number of wide characters transmitted, or a
24722 negative value if an output error, encoding error, or runtime-constraint violation occurred.
24727 419) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24728 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24729 example, if the entire format string was L"%%n".
24731 [<a name="#p631" href="p631">page 631</a>] (<a href="#Contents">Contents</a>)
24733 <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>
24735 1 #define __STDC_WANT_LIB_EXT1__ 1
24736 #include <a href="#7.16"><stdarg.h></a>
24737 #include <a href="#7.28"><wchar.h></a>
24738 int vwscanf_s(const wchar_t * restrict format,
24740 Runtime-constraints
24741 2 format shall not be a null pointer. Any argument indirected though in order to store
24742 converted input shall not be a null pointer.
24743 3 If there is a runtime-constraint violation, the vwscanf_s function does not attempt to
24744 perform further input, and it is unspecified to what extent vwscanf_s performed input
24745 before discovering the runtime-constraint violation.
24747 4 The vwscanf_s function is equivalent to wscanf_s, with the variable argument list
24748 replaced by arg, which shall have been initialized by the va_start macro (and
24749 possibly subsequent va_arg calls). The vwscanf_s function does not invoke the
24752 5 The vwscanf_s function returns the value of the macro EOF if an input failure occurs
24753 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24754 vwscanf_s function returns the number of input items assigned, which can be fewer
24755 than provided for, or even zero, in the event of an early matching failure.
24756 <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>
24758 1 #define __STDC_WANT_LIB_EXT1__ 1
24759 #include <a href="#7.28"><wchar.h></a>
24760 int wprintf_s(const wchar_t * restrict format, ...);
24761 Runtime-constraints
24762 2 format shall not be a null pointer. The %n specifier421) (modified or not by flags, field
24764 420) As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
24765 value of arg after the return is indeterminate.
24766 421) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24767 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24768 example, if the entire format string was L"%%n".
24770 [<a name="#p632" href="p632">page 632</a>] (<a href="#Contents">Contents</a>)
24772 width, or precision) shall not appear in the wide string pointed to by format. Any
24773 argument to wprintf_s corresponding to a %s specifier shall not be a null pointer.
24774 3 If there is a runtime-constraint violation, the wprintf_s function does not attempt to
24775 produce further output, and it is unspecified to what extent wprintf_s produced output
24776 before discovering the runtime-constraint violation.
24778 4 The wprintf_s function is equivalent to the wprintf function except for the explicit
24779 runtime-constraints listed above.
24781 5 The wprintf_s function returns the number of wide characters transmitted, or a
24782 negative value if an output error, encoding error, or runtime-constraint violation occurred.
24783 <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>
24785 1 #define __STDC_WANT_LIB_EXT1__ 1
24786 #include <a href="#7.28"><wchar.h></a>
24787 int wscanf_s(const wchar_t * restrict format, ...);
24788 Runtime-constraints
24789 2 format shall not be a null pointer. Any argument indirected though in order to store
24790 converted input shall not be a null pointer.
24791 3 If there is a runtime-constraint violation, the wscanf_s function does not attempt to
24792 perform further input, and it is unspecified to what extent wscanf_s performed input
24793 before discovering the runtime-constraint violation.
24795 4 The wscanf_s function is equivalent to fwscanf_s with the argument stdin
24796 interposed before the arguments to wscanf_s.
24798 5 The wscanf_s function returns the value of the macro EOF if an input failure occurs
24799 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24800 wscanf_s function returns the number of input items assigned, which can be fewer than
24801 provided for, or even zero, in the event of an early matching failure.
24806 [<a name="#p633" href="p633">page 633</a>] (<a href="#Contents">Contents</a>)
24808 <a name="K.3.9.2" href="#K.3.9.2"><b> K.3.9.2 General wide string utilities</b></a>
24809 <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>
24810 <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>
24812 1 #define __STDC_WANT_LIB_EXT1__ 1
24813 #include <a href="#7.28"><wchar.h></a>
24814 errno_t wcscpy_s(wchar_t * restrict s1,
24816 const wchar_t * restrict s2);
24817 Runtime-constraints
24818 2 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
24819 s1max shall not equal zero. s1max shall be greater than wcsnlen_s(s2, s1max).
24820 Copying shall not take place between objects that overlap.
24821 3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
24822 greater than zero and not greater than RSIZE_MAX, then wcscpy_s sets s1[0] to the
24823 null wide character.
24825 4 The wcscpy_s function copies the wide string pointed to by s2 (including the
24826 terminating null wide character) into the array pointed to by s1.
24827 5 All elements following the terminating null wide character (if any) written by
24828 wcscpy_s in the array of s1max wide characters pointed to by s1 take unspecified
24829 values when wcscpy_s returns.422)
24831 6 The wcscpy_s function returns zero423) if there was no runtime-constraint violation.
24832 Otherwise, a nonzero value is returned.
24837 422) This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
24838 if any of those wide characters are null. Such an approach might write a wide character to every
24839 element of s1 before discovering that the first element should be set to the null wide character.
24840 423) A zero return value implies that all of the requested wide characters from the string pointed to by s2
24841 fit within the array pointed to by s1 and that the result in s1 is null terminated.
24843 [<a name="#p634" href="p634">page 634</a>] (<a href="#Contents">Contents</a>)
24845 <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>
24847 7 #define __STDC_WANT_LIB_EXT1__ 1
24848 #include <a href="#7.28"><wchar.h></a>
24849 errno_t wcsncpy_s(wchar_t * restrict s1,
24851 const wchar_t * restrict s2,
24853 Runtime-constraints
24854 8 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
24855 RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
24856 shall be greater than wcsnlen_s(s2, s1max). Copying shall not take place between
24857 objects that overlap.
24858 9 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
24859 greater than zero and not greater than RSIZE_MAX, then wcsncpy_s sets s1[0] to the
24860 null wide character.
24862 10 The wcsncpy_s function copies not more than n successive wide characters (wide
24863 characters that follow a null wide character are not copied) from the array pointed to by
24864 s2 to the array pointed to by s1. If no null wide character was copied from s2, then
24865 s1[n] is set to a null wide character.
24866 11 All elements following the terminating null wide character (if any) written by
24867 wcsncpy_s in the array of s1max wide characters pointed to by s1 take unspecified
24868 values when wcsncpy_s returns.424)
24870 12 The wcsncpy_s function returns zero425) if there was no runtime-constraint violation.
24871 Otherwise, a nonzero value is returned.
24872 13 EXAMPLE 1 The wcsncpy_s function can be used to copy a wide string without the danger that the
24873 result will not be null terminated or that wide characters will be written past the end of the destination
24879 424) This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
24880 if any of those wide characters are null. Such an approach might write a wide character to every
24881 element of s1 before discovering that the first element should be set to the null wide character.
24882 425) A zero return value implies that all of the requested wide characters from the string pointed to by s2
24883 fit within the array pointed to by s1 and that the result in s1 is null terminated.
24885 [<a name="#p635" href="p635">page 635</a>] (<a href="#Contents">Contents</a>)
24887 #define __STDC_WANT_LIB_EXT1__ 1
24888 #include <a href="#7.28"><wchar.h></a>
24890 wchar_t src1[100] = L"hello";
24891 wchar_t src2[7] = {L'g', L'o', L'o', L'd', L'b', L'y', L'e'};
24892 wchar_t dst1[6], dst2[5], dst3[5];
24894 r1 = wcsncpy_s(dst1, 6, src1, 100);
24895 r2 = wcsncpy_s(dst2, 5, src2, 7);
24896 r3 = wcsncpy_s(dst3, 5, src2, 4);
24897 The first call will assign to r1 the value zero and to dst1 the sequence of wide characters hello\0.
24898 The second call will assign to r2 a nonzero value and to dst2 the sequence of wide characters \0.
24899 The third call will assign to r3 the value zero and to dst3 the sequence of wide characters good\0.
24901 <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>
24903 14 #define __STDC_WANT_LIB_EXT1__ 1
24904 #include <a href="#7.28"><wchar.h></a>
24905 errno_t wmemcpy_s(wchar_t * restrict s1,
24907 const wchar_t * restrict s2,
24909 Runtime-constraints
24910 15 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
24911 RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
24912 objects that overlap.
24913 16 If there is a runtime-constraint violation, the wmemcpy_s function stores zeros in the
24914 first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
24915 s1max is not greater than RSIZE_MAX.
24917 17 The wmemcpy_s function copies n successive wide characters from the object pointed
24918 to by s2 into the object pointed to by s1.
24920 18 The wmemcpy_s function returns zero if there was no runtime-constraint violation.
24921 Otherwise, a nonzero value is returned.
24926 [<a name="#p636" href="p636">page 636</a>] (<a href="#Contents">Contents</a>)
24928 <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>
24930 19 #define __STDC_WANT_LIB_EXT1__ 1
24931 #include <a href="#7.28"><wchar.h></a>
24932 errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
24933 const wchar_t *s2, rsize_t n);
24934 Runtime-constraints
24935 20 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
24936 RSIZE_MAX. n shall not be greater than s1max.
24937 21 If there is a runtime-constraint violation, the wmemmove_s function stores zeros in the
24938 first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
24939 s1max is not greater than RSIZE_MAX.
24941 22 The wmemmove_s function copies n successive wide characters from the object pointed
24942 to by s2 into the object pointed to by s1. This copying takes place as if the n wide
24943 characters from the object pointed to by s2 are first copied into a temporary array of n
24944 wide characters that does not overlap the objects pointed to by s1 or s2, and then the n
24945 wide characters from the temporary array are copied into the object pointed to by s1.
24947 23 The wmemmove_s function returns zero if there was no runtime-constraint violation.
24948 Otherwise, a nonzero value is returned.
24949 <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>
24950 <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>
24952 1 #define __STDC_WANT_LIB_EXT1__ 1
24953 #include <a href="#7.28"><wchar.h></a>
24954 errno_t wcscat_s(wchar_t * restrict s1,
24956 const wchar_t * restrict s2);
24957 Runtime-constraints
24958 2 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
24960 3 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
24961 s1max shall not equal zero. m shall not equal zero.426) m shall be greater than
24962 wcsnlen_s(s2, m). Copying shall not take place between objects that overlap.
24964 [<a name="#p637" href="p637">page 637</a>] (<a href="#Contents">Contents</a>)
24966 4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
24967 greater than zero and not greater than RSIZE_MAX, then wcscat_s sets s1[0] to the
24968 null wide character.
24970 5 The wcscat_s function appends a copy of the wide string pointed to by s2 (including
24971 the terminating null wide character) to the end of the wide string pointed to by s1. The
24972 initial wide character from s2 overwrites the null wide character at the end of s1.
24973 6 All elements following the terminating null wide character (if any) written by
24974 wcscat_s in the array of s1max wide characters pointed to by s1 take unspecified
24975 values when wcscat_s returns.427)
24977 7 The wcscat_s function returns zero428) if there was no runtime-constraint violation.
24978 Otherwise, a nonzero value is returned.
24979 <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>
24981 8 #define __STDC_WANT_LIB_EXT1__ 1
24982 #include <a href="#7.28"><wchar.h></a>
24983 errno_t wcsncat_s(wchar_t * restrict s1,
24985 const wchar_t * restrict s2,
24987 Runtime-constraints
24988 9 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
24990 10 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
24991 RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.429) If n is not less
24992 than m, then m shall be greater than wcsnlen_s(s2, m). Copying shall not take
24993 place between objects that overlap.
24996 426) Zero means that s1 was not null terminated upon entry to wcscat_s.
24997 427) This allows an implementation to append wide characters from s2 to s1 while simultaneously
24998 checking if any of those wide characters are null. Such an approach might write a wide character to
24999 every element of s1 before discovering that the first element should be set to the null wide character.
25000 428) A zero return value implies that all of the requested wide characters from the wide string pointed to by
25001 s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
25002 429) Zero means that s1 was not null terminated upon entry to wcsncat_s.
25004 [<a name="#p638" href="p638">page 638</a>] (<a href="#Contents">Contents</a>)
25006 11 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
25007 greater than zero and not greater than RSIZE_MAX, then wcsncat_s sets s1[0] to the
25008 null wide character.
25010 12 The wcsncat_s function appends not more than n successive wide characters (wide
25011 characters that follow a null wide character are not copied) from the array pointed to by
25012 s2 to the end of the wide string pointed to by s1. The initial wide character from s2
25013 overwrites the null wide character at the end of s1. If no null wide character was copied
25014 from s2, then s1[s1max-m+n] is set to a null wide character.
25015 13 All elements following the terminating null wide character (if any) written by
25016 wcsncat_s in the array of s1max wide characters pointed to by s1 take unspecified
25017 values when wcsncat_s returns.430)
25019 14 The wcsncat_s function returns zero431) if there was no runtime-constraint violation.
25020 Otherwise, a nonzero value is returned.
25021 15 EXAMPLE 1 The wcsncat_s function can be used to copy a wide string without the danger that the
25022 result will not be null terminated or that wide characters will be written past the end of the destination
25024 #define __STDC_WANT_LIB_EXT1__ 1
25025 #include <a href="#7.28"><wchar.h></a>
25027 wchar_t s1[100] = L"good";
25028 wchar_t s2[6] = L"hello";
25029 wchar_t s3[6] = L"hello";
25030 wchar_t s4[7] = L"abc";
25031 wchar_t s5[1000] = L"bye";
25032 int r1, r2, r3, r4;
25033 r1 = wcsncat_s(s1, 100, s5, 1000);
25034 r2 = wcsncat_s(s2, 6, L"", 1);
25035 r3 = wcsncat_s(s3, 6, L"X", 2);
25036 r4 = wcsncat_s(s4, 7, L"defghijklmn", 3);
25037 After the first call r1 will have the value zero and s1 will be the wide character sequence goodbye\0.
25038 After the second call r2 will have the value zero and s2 will be the wide character sequence hello\0.
25039 After the third call r3 will have a nonzero value and s3 will be the wide character sequence \0.
25040 After the fourth call r4 will have the value zero and s4 will be the wide character sequence abcdef\0.
25045 430) This allows an implementation to append wide characters from s2 to s1 while simultaneously
25046 checking if any of those wide characters are null. Such an approach might write a wide character to
25047 every element of s1 before discovering that the first element should be set to the null wide character.
25048 431) A zero return value implies that all of the requested wide characters from the wide string pointed to by
25049 s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
25051 [<a name="#p639" href="p639">page 639</a>] (<a href="#Contents">Contents</a>)
25053 <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>
25054 <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>
25056 1 #define __STDC_WANT_LIB_EXT1__ 1
25057 #include <a href="#7.28"><wchar.h></a>
25058 wchar_t *wcstok_s(wchar_t * restrict s1,
25059 rsize_t * restrict s1max,
25060 const wchar_t * restrict s2,
25061 wchar_t ** restrict ptr);
25062 Runtime-constraints
25063 2 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
25064 shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
25065 The end of the token found shall occur within the first *s1max wide characters of s1 for
25066 the first call, and shall occur within the first *s1max wide characters of where searching
25067 resumes on subsequent calls.
25068 3 If there is a runtime-constraint violation, the wcstok_s function does not indirect
25069 through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
25071 4 A sequence of calls to the wcstok_s function breaks the wide string pointed to by s1
25072 into a sequence of tokens, each of which is delimited by a wide character from the wide
25073 string pointed to by s2. The fourth argument points to a caller-provided wchar_t
25074 pointer into which the wcstok_s function stores information necessary for it to
25075 continue scanning the same wide string.
25076 5 The first call in a sequence has a non-null first argument and s1max points to an object
25077 whose value is the number of elements in the wide character array pointed to by the first
25078 argument. The first call stores an initial value in the object pointed to by ptr and
25079 updates the value pointed to by s1max to reflect the number of elements that remain in
25080 relation to ptr. Subsequent calls in the sequence have a null first argument and the
25081 objects pointed to by s1max and ptr are required to have the values stored by the
25082 previous call in the sequence, which are then updated. The separator wide string pointed
25083 to by s2 may be different from call to call.
25084 6 The first call in the sequence searches the wide string pointed to by s1 for the first wide
25085 character that is not contained in the current separator wide string pointed to by s2. If no
25086 such wide character is found, then there are no tokens in the wide string pointed to by s1
25087 and the wcstok_s function returns a null pointer. If such a wide character is found, it is
25088 the start of the first token.
25091 [<a name="#p640" href="p640">page 640</a>] (<a href="#Contents">Contents</a>)
25093 7 The wcstok_s function then searches from there for the first wide character in s1 that
25094 is contained in the current separator wide string. If no such wide character is found, the
25095 current token extends to the end of the wide string pointed to by s1, and subsequent
25096 searches in the same wide string for a token return a null pointer. If such a wide character
25097 is found, it is overwritten by a null wide character, which terminates the current token.
25098 8 In all cases, the wcstok_s function stores sufficient information in the pointer pointed
25099 to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
25100 value for ptr, shall start searching just past the element overwritten by a null wide
25101 character (if any).
25103 9 The wcstok_s function returns a pointer to the first wide character of a token, or a null
25104 pointer if there is no token or there is a runtime-constraint violation.
25106 #define __STDC_WANT_LIB_EXT1__ 1
25107 #include <a href="#7.28"><wchar.h></a>
25108 static wchar_t str1[] = L"?a???b,,,#c";
25109 static wchar_t str2[] = L"\t \t";
25110 wchar_t *t, *ptr1, *ptr2;
25111 rsize_t max1 = wcslen(str1)+1;
25112 rsize_t max2 = wcslen(str2)+1;
25113 t = wcstok_s(str1, &max1, "?", &ptr1); // t points to the token "a"
25114 t = wcstok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
25115 t = wcstok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
25116 t = wcstok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
25117 t = wcstok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
25119 <a name="K.3.9.2.4" href="#K.3.9.2.4"><b> K.3.9.2.4 Miscellaneous functions</b></a>
25120 <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>
25122 1 #define __STDC_WANT_LIB_EXT1__ 1
25123 #include <a href="#7.28"><wchar.h></a>
25124 size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
25126 2 The wcsnlen_s function computes the length of the wide string pointed to by s.
25128 3 If s is a null pointer,432) then the wcsnlen_s function returns zero.
25129 4 Otherwise, the wcsnlen_s function returns the number of wide characters that precede
25130 the terminating null wide character. If there is no null wide character in the first
25131 maxsize wide characters of s then wcsnlen_s returns maxsize. At most the first
25133 [<a name="#p641" href="p641">page 641</a>] (<a href="#Contents">Contents</a>)
25135 maxsize wide characters of s shall be accessed by wcsnlen_s.
25136 <a name="K.3.9.3" href="#K.3.9.3"><b> K.3.9.3 Extended multibyte/wide character conversion utilities</b></a>
25137 <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>
25138 1 Unlike wcrtomb, wcrtomb_s does not permit the ps parameter (the pointer to the
25139 conversion state) to be a null pointer.
25140 <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>
25142 2 #include <a href="#7.28"><wchar.h></a>
25143 errno_t wcrtomb_s(size_t * restrict retval,
25144 char * restrict s, rsize_t smax,
25145 wchar_t wc, mbstate_t * restrict ps);
25146 Runtime-constraints
25147 3 Neither retval nor ps shall be a null pointer. If s is not a null pointer, then smax
25148 shall not equal zero and shall not be greater than RSIZE_MAX. If s is not a null pointer,
25149 then smax shall be not be less than the number of bytes to be stored in the array pointed
25150 to by s. If s is a null pointer, then smax shall equal zero.
25151 4 If there is a runtime-constraint violation, then wcrtomb_s does the following. If s is
25152 not a null pointer and smax is greater than zero and not greater than RSIZE_MAX, then
25153 wcrtomb_s sets s[0] to the null character. If retval is not a null pointer, then
25154 wcrtomb_s sets *retval to (size_t)(-1).
25156 5 If s is a null pointer, the wcrtomb_s function is equivalent to the call
25157 wcrtomb_s(&retval, buf, sizeof buf, L'\0', ps)
25158 where retval and buf are internal variables of the appropriate types, and the size of
25159 buf is greater than MB_CUR_MAX.
25160 6 If s is not a null pointer, the wcrtomb_s function determines the number of bytes
25161 needed to represent the multibyte character that corresponds to the wide character given
25162 by wc (including any shift sequences), and stores the multibyte character representation
25163 in the array whose first element is pointed to by s. At most MB_CUR_MAX bytes are
25164 stored. If wc is a null wide character, a null byte is stored, preceded by any shift
25165 sequence needed to restore the initial shift state; the resulting state described is the initial
25168 432) Note that the wcsnlen_s function has no runtime-constraints. This lack of runtime-constraints
25169 along with the values returned for a null pointer or an unterminated wide string argument make
25170 wcsnlen_s useful in algorithms that gracefully handle such exceptional data.
25172 [<a name="#p642" href="p642">page 642</a>] (<a href="#Contents">Contents</a>)
25174 7 If wc does not correspond to a valid multibyte character, an encoding error occurs: the
25175 wcrtomb_s function stores the value (size_t)(-1) into *retval and the
25176 conversion state is unspecified. Otherwise, the wcrtomb_s function stores into
25177 *retval the number of bytes (including any shift sequences) stored in the array pointed
25180 8 The wcrtomb_s function returns zero if no runtime-constraint violation and no
25181 encoding error occurred. Otherwise, a nonzero value is returned.
25182 <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>
25183 1 Unlike mbsrtowcs and wcsrtombs, mbsrtowcs_s and wcsrtombs_s do not
25184 permit the ps parameter (the pointer to the conversion state) to be a null pointer.
25185 <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>
25187 2 #include <a href="#7.28"><wchar.h></a>
25188 errno_t mbsrtowcs_s(size_t * restrict retval,
25189 wchar_t * restrict dst, rsize_t dstmax,
25190 const char ** restrict src, rsize_t len,
25191 mbstate_t * restrict ps);
25192 Runtime-constraints
25193 3 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
25194 then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
25195 pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
25196 not equal zero. If dst is not a null pointer and len is not less than dstmax, then a null
25197 character shall occur within the first dstmax multibyte characters of the array pointed to
25199 4 If there is a runtime-constraint violation, then mbsrtowcs_s does the following. If
25200 retval is not a null pointer, then mbsrtowcs_s sets *retval to (size_t)(-1).
25201 If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
25202 then mbsrtowcs_s sets dst[0] to the null wide character.
25204 5 The mbsrtowcs_s function converts a sequence of multibyte characters that begins in
25205 the conversion state described by the object pointed to by ps, from the array indirectly
25206 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
25207 pointer, the converted characters are stored into the array pointed to by dst. Conversion
25208 continues up to and including a terminating null character, which is also stored.
25209 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
25210 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
25211 [<a name="#p643" href="p643">page 643</a>] (<a href="#Contents">Contents</a>)
25213 characters have been stored into the array pointed to by dst.433) If dst is not a null
25214 pointer and no null wide character was stored into the array pointed to by dst, then
25215 dst[len] is set to the null wide character. Each conversion takes place as if by a call
25216 to the mbrtowc function.
25217 6 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
25218 pointer (if conversion stopped due to reaching a terminating null character) or the address
25219 just past the last multibyte character converted (if any). If conversion stopped due to
25220 reaching a terminating null character and if dst is not a null pointer, the resulting state
25221 described is the initial conversion state.
25222 7 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
25223 sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
25224 the mbsrtowcs_s function stores the value (size_t)(-1) into *retval and the
25225 conversion state is unspecified. Otherwise, the mbsrtowcs_s function stores into
25226 *retval the number of multibyte characters successfully converted, not including the
25227 terminating null character (if any).
25228 8 All elements following the terminating null wide character (if any) written by
25229 mbsrtowcs_s in the array of dstmax wide characters pointed to by dst take
25230 unspecified values when mbsrtowcs_s returns.434)
25231 9 If copying takes place between objects that overlap, the objects take on unspecified
25234 10 The mbsrtowcs_s function returns zero if no runtime-constraint violation and no
25235 encoding error occurred. Otherwise, a nonzero value is returned.
25236 <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>
25238 11 #include <a href="#7.28"><wchar.h></a>
25239 errno_t wcsrtombs_s(size_t * restrict retval,
25240 char * restrict dst, rsize_t dstmax,
25241 const wchar_t ** restrict src, rsize_t len,
25242 mbstate_t * restrict ps);
25247 433) Thus, the value of len is ignored if dst is a null pointer.
25248 434) This allows an implementation to attempt converting the multibyte string before discovering a
25249 terminating null character did not occur where required.
25251 [<a name="#p644" href="p644">page 644</a>] (<a href="#Contents">Contents</a>)
25253 Runtime-constraints
25254 12 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
25255 then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
25256 pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
25257 not equal zero. If dst is not a null pointer and len is not less than dstmax, then the
25258 conversion shall have been stopped (see below) because a terminating null wide character
25259 was reached or because an encoding error occurred.
25260 13 If there is a runtime-constraint violation, then wcsrtombs_s does the following. If
25261 retval is not a null pointer, then wcsrtombs_s sets *retval to (size_t)(-1).
25262 If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
25263 then wcsrtombs_s sets dst[0] to the null character.
25265 14 The wcsrtombs_s function converts a sequence of wide characters from the array
25266 indirectly pointed to by src into a sequence of corresponding multibyte characters that
25267 begins in the conversion state described by the object pointed to by ps. If dst is not a
25268 null pointer, the converted characters are then stored into the array pointed to by dst.
25269 Conversion continues up to and including a terminating null wide character, which is also
25270 stored. Conversion stops earlier in two cases:
25271 -- when a wide character is reached that does not correspond to a valid multibyte
25273 -- (if dst is not a null pointer) when the next multibyte character would exceed the
25274 limit of n total bytes to be stored into the array pointed to by dst. If the wide
25275 character being converted is the null wide character, then n is the lesser of len or
25276 dstmax. Otherwise, n is the lesser of len or dstmax-1.
25277 If the conversion stops without converting a null wide character and dst is not a null
25278 pointer, then a null character is stored into the array pointed to by dst immediately
25279 following any multibyte characters already stored. Each conversion takes place as if by a
25280 call to the wcrtomb function.435)
25281 15 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
25282 pointer (if conversion stopped due to reaching a terminating null wide character) or the
25283 address just past the last wide character converted (if any). If conversion stopped due to
25284 reaching a terminating null wide character, the resulting state described is the initial
25288 435) If conversion stops because a terminating null wide character has been reached, the bytes stored
25289 include those necessary to reach the initial shift state immediately before the null byte. However, if
25290 the conversion stops before a terminating null wide character has been reached, the result will be null
25291 terminated, but might not end in the initial shift state.
25293 [<a name="#p645" href="p645">page 645</a>] (<a href="#Contents">Contents</a>)
25295 16 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
25296 wide character that does not correspond to a valid multibyte character, an encoding error
25297 occurs: the wcsrtombs_s function stores the value (size_t)(-1) into *retval
25298 and the conversion state is unspecified. Otherwise, the wcsrtombs_s function stores
25299 into *retval the number of bytes in the resulting multibyte character sequence, not
25300 including the terminating null character (if any).
25301 17 All elements following the terminating null character (if any) written by wcsrtombs_s
25302 in the array of dstmax elements pointed to by dst take unspecified values when
25303 wcsrtombs_s returns.436)
25304 18 If copying takes place between objects that overlap, the objects take on unspecified
25307 19 The wcsrtombs_s function returns zero if no runtime-constraint violation and no
25308 encoding error occurred. Otherwise, a nonzero value is returned.
25313 436) When len is not less than dstmax, the implementation might fill the array before discovering a
25314 runtime-constraint violation.
25316 [<a name="#p646" href="p646">page 646</a>] (<a href="#Contents">Contents</a>)
25318 <a name="L" href="#L"><b> Annex L</b></a>
25321 <a name="L.1" href="#L.1"><b> L.1 Scope</b></a>
25322 1 This annex specifies optional behavior that can aid in the analyzability of C programs.
25323 2 An implementation that defines __STDC_ANALYZABLE__ shall conform to the
25324 specifications in this annex.437)
25325 <a name="L.2" href="#L.2"><b> L.2 Definitions</b></a>
25326 <a name="L.2.1" href="#L.2.1"><b> L.2.1</b></a>
25327 1 out-of-bounds store
25328 an (attempted) access (<a href="#3.1">3.1</a>) that, at run time, for a given computational state, would
25329 modify (or, for an object declared volatile, fetch) one or more bytes that lie outside
25330 the bounds permitted by this Standard.
25331 <a name="L.2.2" href="#L.2.2"><b> L.2.2</b></a>
25332 1 bounded undefined behavior
25333 undefined behavior (<a href="#3.4.3">3.4.3</a>) that does not perform an out-of-bounds store.
25334 2 NOTE 1 The behavior might perform a trap.
25336 3 NOTE 2 Any values produced or stored might be indeterminate values.
25338 <a name="L.2.3" href="#L.2.3"><b> L.2.3</b></a>
25339 1 critical undefined behavior
25340 undefined behavior that is not bounded undefined behavior.
25341 2 NOTE The behavior might perform an out-of-bounds store or perform a trap.
25346 437) Implementations that do not define __STDC_ANALYZABLE__ are not required to conform to these
25349 [<a name="#p647" href="p647">page 647</a>] (<a href="#Contents">Contents</a>)
25351 <a name="L.3" href="#L.3"><b> L.3 Requirements</b></a>
25352 1 If the program performs a trap (<a href="#3.19.5">3.19.5</a>), the implementation is permitted to invoke a
25353 runtime-constraint handler. Any such semantics are implementation-defined.
25354 2 All undefined behavior shall be limited to bounded undefined behavior, except for the
25355 following which are permitted to result in critical undefined behavior:
25356 -- An object is referred to outside of its lifetime (<a href="#6.2.4">6.2.4</a>).
25357 -- An lvalue does not designate an object when evaluated (<a href="#6.3.2.1">6.3.2.1</a>).
25358 -- A pointer is used to call a function whose type is not compatible with the referenced
25359 type (<a href="#6.3.2.3">6.3.2.3</a>).
25360 -- The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
25361 -- Addition or subtraction of a pointer into, or just beyond, an array object and an
25362 integer type produces a result that points just beyond the array object and is used as
25363 the operand of a unary * operator that is evaluated (<a href="#6.5.6">6.5.6</a>).
25364 -- An argument to a library function has an invalid value or a type not expected by a
25365 function with variable number of arguments (<a href="#7.1.4">7.1.4</a>).
25366 -- The value of a pointer that refers to space deallocated by a call to the free or realloc
25367 function is used (<a href="#7.22.3">7.22.3</a>).
25368 -- A string or wide string utility function is instructed to access an array beyond the end
25369 of an object (<a href="#7.23.1">7.23.1</a>, <a href="#7.28.4">7.28.4</a>).
25374 [<a name="#p648" href="p648">page 648</a>] (<a href="#Contents">Contents</a>)
25377 <a name="Bibliography" href="#Bibliography"><b> Bibliography</b></a>
25378 1. ''The C Reference Manual'' by Dennis M. Ritchie, a version of which was
25379 published in The C Programming Language by Brian W. Kernighan and Dennis
25380 M. Ritchie, Prentice-Hall, Inc., (1978). Copyright owned by AT&T.
25381 2. 1984 /usr/group Standard by the /usr/group Standards Committee, Santa Clara,
25382 California, USA, November 1984.
25383 3. ANSI X3/TR-1-82 (1982), American National Dictionary for Information
25384 Processing Systems, Information Processing Systems Technical Report.
25385 4. ANSI/IEEE 754-1985, American National Standard for Binary Floating-Point
25387 5. ANSI/IEEE 854-1988, American National Standard for Radix-Independent
25388 Floating-Point Arithmetic.
25389 6. IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems,
25390 second edition (previously designated IEC 559:1989).
25391 7. ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and
25392 symbols for use in the physical sciences and technology.
25393 8. ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for
25394 information interchange.
25395 9. ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1:
25397 10. ISO 4217:1995, Codes for the representation of currencies and funds.
25398 11. ISO 8601:1988, Data elements and interchange formats -- Information
25399 interchange -- Representation of dates and times.
25400 12. ISO/IEC 9899:1990, Programming languages -- C.
25401 13. ISO/IEC 9899/COR1:1994, Technical Corrigendum 1.
25402 14. ISO/IEC 9899/COR2:1996, Technical Corrigendum 2.
25403 15. ISO/IEC 9899/AMD1:1995, Amendment 1 to ISO/IEC 9899:1990 C Integrity.
25404 16. ISO/IEC 9899:1999, Programming languages -- C.
25405 17. ISO/IEC 9899:1999/Cor.1:2001, Technical Corrigendum 1.
25406 18. ISO/IEC 9899:1999/Cor.2:2004, Technical Corrigendum 2.
25407 19. ISO/IEC 9899:1999/Cor.3:2007, Technical Corrigendum 3.
25411 [<a name="#p649" href="p649">page 649</a>] (<a href="#Contents">Contents</a>)
25413 20. ISO/IEC 9945-2:1993, Information technology -- Portable Operating System
25414 Interface (POSIX) -- Part 2: Shell and Utilities.
25415 21. ISO/IEC TR 10176:1998, Information technology -- Guidelines for the
25416 preparation of programming language standards.
25417 22. ISO/IEC 10646-1:1993, Information technology -- Universal Multiple-Octet
25418 Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
25419 23. ISO/IEC 10646-1/COR1:1996, Technical Corrigendum 1 to
25420 ISO/IEC 10646-1:1993.
25421 24. ISO/IEC 10646-1/COR2:1998, Technical Corrigendum 2 to
25422 ISO/IEC 10646-1:1993.
25423 25. ISO/IEC 10646-1/AMD1:1996, Amendment 1 to ISO/IEC 10646-1:1993
25424 Transformation Format for 16 planes of group 00 (UTF-16).
25425 26. ISO/IEC 10646-1/AMD2:1996, Amendment 2 to ISO/IEC 10646-1:1993 UCS
25426 Transformation Format 8 (UTF-8).
25427 27. ISO/IEC 10646-1/AMD3:1996, Amendment 3 to ISO/IEC 10646-1:1993.
25428 28. ISO/IEC 10646-1/AMD4:1996, Amendment 4 to ISO/IEC 10646-1:1993.
25429 29. ISO/IEC 10646-1/AMD5:1998, Amendment 5 to ISO/IEC 10646-1:1993 Hangul
25431 30. ISO/IEC 10646-1/AMD6:1997, Amendment 6 to ISO/IEC 10646-1:1993
25433 31. ISO/IEC 10646-1/AMD7:1997, Amendment 7 to ISO/IEC 10646-1:1993 33
25434 additional characters.
25435 32. ISO/IEC 10646-1/AMD8:1997, Amendment 8 to ISO/IEC 10646-1:1993.
25436 33. ISO/IEC 10646-1/AMD9:1997, Amendment 9 to ISO/IEC 10646-1:1993
25437 Identifiers for characters.
25438 34. ISO/IEC 10646-1/AMD10:1998, Amendment 10 to ISO/IEC 10646-1:1993
25440 35. ISO/IEC 10646-1/AMD11:1998, Amendment 11 to ISO/IEC 10646-1:1993
25441 Unified Canadian Aboriginal Syllabics.
25442 36. ISO/IEC 10646-1/AMD12:1998, Amendment 12 to ISO/IEC 10646-1:1993
25444 37. ISO/IEC 10967-1:1994, Information technology -- Language independent
25445 arithmetic -- Part 1: Integer and floating point arithmetic.
25448 [<a name="#p650" href="p650">page 650</a>] (<a href="#Contents">Contents</a>)
25450 38. ISO/IEC TR 19769:2004, Information technology -- Programming languages,
25451 their environments and system software interfaces -- Extensions for the
25452 programming language C to support new character data types.
25453 39. ISO/IEC TR 24731-1:2007, Information technology -- Programming languages,
25454 their environments and system software interfaces -- Extensions to the C library
25455 -- Part 1: Bounds-checking interfaces.
25460 [<a name="#p651" href="p651">page 651</a>] (<a href="#Contents">Contents</a>)
25464 [<a name="#p652" href="p652">page 652</a>] (<a href="#Contents">Contents</a>)
25467 <a name="Index" href="#Index"><b>Index</b></a>
25468 [^ 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>
25469 , (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>,
25470 [_ 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>
25471 ! (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>
25472 != (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>
25473 # 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>
25474 # 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>
25475 # punctuator, <a href="#6.10">6.10</a> -= (subtraction assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
25476 ## 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>
25477 #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>,
25478 #elif preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#6.5.2.3">6.5.2.3</a>
25479 #else preprocessing directive, <a href="#6.10.1">6.10.1</a> . punctuator, <a href="#6.7.9">6.7.9</a>
25480 #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>
25481 #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>
25482 #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>
25483 <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>
25484 #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>
25485 #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>
25486 #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>
25487 <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>,
25488 #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>
25489 #pragma preprocessing directive, <a href="#6.10.6">6.10.6</a> < (less-than operator), <a href="#6.5.8">6.5.8</a>
25490 #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>
25491 <a href="#7.1.4">7.1.4</a> <: (alternative spelling of [), <a href="#6.4.6">6.4.6</a>
25492 % (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>
25493 %: (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>
25494 %:%: (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>
25495 %= (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>
25496 %> (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>,
25497 & (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>
25498 & (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>
25499 && (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>
25500 &= (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>,
25501 ' ' (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>
25502 <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>,
25503 ( ) (cast operator), <a href="#6.5.4">6.5.4</a> <a href="#7.28.4.1.1">7.28.4.1.1</a>
25504 ( ) (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>
25505 ( ) (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>
25506 ( ){ } (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>
25507 * (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>
25508 * (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>,
25509 * (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>
25510 <a href="#G.5.1">G.5.1</a> <a href="#7.13"><setjmp.h></a> header, <a href="#7.13">7.13</a>
25511 *= (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>
25512 + (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>
25513 <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>
25514 + (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>
25515 ++ (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>
25516 ++ (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>,
25517 += (addition assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
25518 [<a name="#p653" href="p653">page 653</a>] (<a href="#Contents">Contents</a>)
25520 <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
25521 <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>
25522 <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>
25523 <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),
25524 <a href="#K.3.5">K.3.5</a> <a href="#6.5.16.2">6.5.16.2</a>
25525 <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>
25526 <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
25527 <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>
25528 <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>
25529 <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>
25530 <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>
25531 <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>
25532 <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>
25533 <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>
25534 <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>
25535 = (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>
25536 = (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>
25537 == (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>
25538 > (greater-than operator), <a href="#6.5.8">6.5.8</a> __STDC_IEC_559_COMPLEX__ macro,
25539 >= (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>
25540 >> (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>
25541 >>= (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>
25542 ? : (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,
25543 ?? (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>
25544 [ ] (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>,
25545 [ ] (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>
25546 \ (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>,
25547 \ (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>
25548 \" (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>
25549 <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>
25550 \\ (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>
25551 \' (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>
25552 \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>
25553 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>
25554 \? (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>
25555 \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>
25556 \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>
25557 \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>,
25558 <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>
25559 \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>,
25560 <a href="#7.4.1.10">7.4.1.10</a> <a href="#F.4">F.4</a>
25561 \octal digits (octal-character escape sequence), _Bool type conversions, <a href="#6.3.1.2">6.3.1.2</a>
25562 <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>
25563 \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>
25564 <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>
25565 \t (horizontal-tab escape sequence), <a href="#5.2.2">5.2.2</a>, _Imaginary keyword, <a href="#G.2">G.2</a>
25566 <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>
25567 \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>
25568 \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>
25569 \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>
25570 <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>
25572 [<a name="#p654" href="p654">page 654</a>] (<a href="#Contents">Contents</a>)
25574 _Noreturn, <a href="#6.7.4">6.7.4</a> alignment specifier, <a href="#6.7.5">6.7.5</a>
25575 _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>
25576 _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>
25577 _Thread_local storage-class specifier, <a href="#6.2.4">6.2.4</a>, and macro, <a href="#7.9">7.9</a>
25578 <a href="#6.7.1">6.7.1</a> AND operators
25579 { } (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>
25580 <a href="#6.8.2">6.8.2</a> bitwise assignment (&=), <a href="#6.5.16.2">6.5.16.2</a>
25581 { } (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>
25582 | (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>
25583 |= (bitwise inclusive OR assignment operator), anonymous structure, <a href="#6.7.2.1">6.7.2.1</a>
25584 <a href="#6.5.16.2">6.5.16.2</a> anonymous union, <a href="#6.7.2.1">6.7.2.1</a>
25585 || (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>
25586 ~ (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>
25587 argc (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a>
25588 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>
25589 <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>
25590 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>
25591 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>
25592 absolute-value functions macro, substitution, <a href="#6.10.3.1">6.10.3.1</a>
25593 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>
25594 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>
25595 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>
25596 abstract declarator, <a href="#6.7.7">6.7.7</a> arithmetic conversions, usual, see usual arithmetic
25597 abstract machine, <a href="#5.1.2.3">5.1.2.3</a> conversions
25598 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
25599 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>
25600 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>
25601 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>
25602 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>
25603 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>
25604 acquire fence, <a href="#7.17.4">7.17.4</a> unary, <a href="#6.5.3.3">6.5.3.3</a>
25605 acquire operation, <a href="#5.1.2.4">5.1.2.4</a> arithmetic types, <a href="#6.2.5">6.2.5</a>
25606 active position, <a href="#5.2.2">5.2.2</a> arithmetic, pointer, <a href="#6.5.6">6.5.6</a>
25607 actual argument, <a href="#3.3">3.3</a> array
25608 actual parameter (deprecated), <a href="#3.3">3.3</a> argument, <a href="#6.9.1">6.9.1</a>
25609 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>
25610 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>
25611 <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>
25612 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>
25613 address constant, <a href="#6.6">6.6</a> storage order, <a href="#6.5.2.1">6.5.2.1</a>
25614 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>
25615 address-free, <a href="#7.17.5">7.17.5</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
25616 aggregate initialization, <a href="#6.7.9">6.7.9</a> type, <a href="#6.2.5">6.2.5</a>
25617 aggregate types, <a href="#6.2.5">6.2.5</a> type conversion, <a href="#6.3.2.1">6.3.2.1</a>
25618 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>
25619 aliasing, <a href="#6.5">6.5</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
25620 alignas macro, <a href="#7.15">7.15</a> as-if rule, <a href="#5.1.2.3">5.1.2.3</a>
25621 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>
25622 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>
25623 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>
25624 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>
25626 [<a name="#p655" href="p655">page 655</a>] (<a href="#Contents">Contents</a>)
25628 asin type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> atomic_is_lock_free generic function,
25629 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>
25630 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>
25631 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>
25632 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>
25633 assert.h header, <a href="#7.2">7.2</a> ATOMIC_SHORT_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
25634 assignment atomic_signal_fence function, <a href="#7.17.4.2">7.17.4.2</a>
25635 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>
25636 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>
25637 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>
25638 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>
25639 simple, <a href="#6.5.16.1">6.5.16.1</a> atomics header, <a href="#7.17">7.17</a>
25640 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>
25641 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>
25642 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>,
25643 <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>
25644 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>
25645 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>
25646 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>
25647 atan2 type-generic macro, <a href="#7.24">7.24</a> basic types, <a href="#6.2.5">6.2.5</a>
25648 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>
25649 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>,
25650 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>
25651 <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>
25652 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>
25653 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>
25654 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>
25655 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>
25656 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>
25657 atomic operations, <a href="#5.1.2.4">5.1.2.4</a> bitwise operators, <a href="#6.5">6.5</a>
25658 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>
25659 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>
25660 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>
25661 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>
25662 ATOMIC_CHAR16_T_LOCK_FREE macro, exclusive OR assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
25663 <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>
25664 ATOMIC_CHAR32_T_LOCK_FREE macro, inclusive OR assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
25665 <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>
25666 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>
25667 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>
25668 functions, <a href="#7.17.7.4">7.17.7.4</a> block scope, <a href="#6.2.1">6.2.1</a>
25669 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>
25670 atomic_fetch and modify generic functions, bold type convention, <a href="#6.1">6.1</a>
25671 <a href="#7.17.7.5">7.17.7.5</a> bool macro, <a href="#7.18">7.18</a>
25672 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>
25673 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>
25674 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>
25675 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>,
25676 <a href="#7.17.8.1">7.17.8.1</a> <a href="#6.8.2">6.8.2</a>
25677 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>
25678 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>
25680 [<a name="#p656" href="p656">page 656</a>] (<a href="#Contents">Contents</a>)
25682 branch cuts, <a href="#7.3.3">7.3.3</a> type-generic macro for, <a href="#7.24">7.24</a>
25683 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>
25684 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>
25685 <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>
25686 <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>
25687 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>
25688 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>
25689 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>
25690 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>
25691 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>
25692 byte input/output functions, <a href="#7.21.1">7.21.1</a> cexpm1 function, <a href="#7.30.1">7.30.1</a>
25693 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>,
25694 <a href="#K.3.9.1.2">K.3.9.1.2</a>
25695 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>,
25696 c16rtomb function, <a href="#7.27.1.2">7.27.1.2</a> <a href="#6.3.1.8">6.3.1.8</a>
25697 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>
25698 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>
25699 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>
25700 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>
25701 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>
25702 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>
25703 type-generic macro for, <a href="#7.24">7.24</a> character array initialization, <a href="#6.7.9">6.7.9</a>
25704 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>
25705 <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>
25706 <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>
25707 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>
25708 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>
25709 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>
25710 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>
25711 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>
25712 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>
25713 <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>
25714 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>
25715 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>
25716 case mapping functions character string literal, see string literal
25717 character, <a href="#7.4.2">7.4.2</a> character type conversion, <a href="#6.3.1.1">6.3.1.1</a>
25718 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>
25719 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>
25720 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>
25721 type-generic macro for, <a href="#7.24">7.24</a> cis function, <a href="#G.6">G.6</a>
25722 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
25723 type-generic macro for, <a href="#7.24">7.24</a> character, <a href="#7.4.1">7.4.1</a>
25724 cast expression, <a href="#6.5.4">6.5.4</a> floating-point, <a href="#7.12.3">7.12.3</a>
25725 cast operator (( )), <a href="#6.5.4">6.5.4</a> wide character, <a href="#7.29.2.1">7.29.2.1</a>
25726 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>
25727 type-generic macro for, <a href="#7.24">7.24</a> clearerr function, <a href="#7.21.10.1">7.21.10.1</a>
25728 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>
25729 type-generic macro for, <a href="#7.24">7.24</a> clock function, <a href="#7.26.2.1">7.26.2.1</a>
25730 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>
25731 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>
25732 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>
25734 [<a name="#p657" href="p657">page 657</a>] (<a href="#Contents">Contents</a>)
25736 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>
25737 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>
25738 clog1p function, <a href="#7.30.1">7.30.1</a> concatenation, preprocessing, see preprocessing
25739 clog2 function, <a href="#7.30.1">7.30.1</a> concatenation
25740 CMPLX macros, <a href="#7.3.9.3">7.3.9.3</a> conceptual models, <a href="#5.1">5.1</a>
25741 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>,
25742 <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>
25743 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>
25744 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>
25745 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>
25746 <a href="#7.25.3.6">7.25.3.6</a> conformance, <a href="#4">4</a>
25747 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>
25748 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>
25749 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>
25750 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>
25751 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>
25752 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>
25753 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>
25754 <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>
25755 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>
25756 comment delimiters (/* */ and //), <a href="#6.4.9">6.4.9</a> floating, <a href="#6.4.4.2">6.4.4.2</a>
25757 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>
25758 common extensions, <a href="#J.5">J.5</a> integer, <a href="#6.4.4.1">6.4.4.1</a>
25759 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>
25760 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>
25761 common warnings, <a href="#I">I</a> constraint_handler_t type, <a href="#K.3.6">K.3.6</a>
25762 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>
25763 <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>
25764 string, <a href="#7.23.4">7.23.4</a> contiguity of allocated storage, <a href="#7.22.3">7.22.3</a>
25765 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>
25766 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>
25767 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>
25768 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>
25769 compl macro, <a href="#7.9">7.9</a> conversion, <a href="#6.3">6.3</a>
25770 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>
25771 complete type, <a href="#6.2.5">6.2.5</a> array argument, <a href="#6.9.1">6.9.1</a>
25772 complex macro, <a href="#7.3.1">7.3.1</a> array parameter, <a href="#6.9.1">6.9.1</a>
25773 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>
25774 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>
25775 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>
25776 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>
25777 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>
25778 <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>
25779 compliance, see conformance explicit, <a href="#6.3">6.3</a>
25780 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>
25781 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>
25782 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>
25783 compound literals, <a href="#6.5.2.5">6.5.2.5</a> function parameter, <a href="#6.9.1">6.9.1</a>
25784 compound statement, <a href="#6.8.2">6.8.2</a> imaginary, <a href="#G.4.1">G.4.1</a>
25785 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>
25786 concatenation functions implicit, <a href="#6.3">6.3</a>
25788 [<a name="#p658" href="p658">page 658</a>] (<a href="#Contents">Contents</a>)
25790 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>
25791 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>
25792 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>
25793 real and imaginary, <a href="#G.4.2">G.4.2</a> type-generic macro for, <a href="#7.24">7.24</a>
25794 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>
25795 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>
25796 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>
25797 usual arithmetic, see usual arithmetic type-generic macro for, <a href="#7.24">7.24</a>
25798 conversions ctgamma function, <a href="#7.30.1">7.30.1</a>
25799 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>
25800 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>
25801 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>
25802 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>
25803 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>
25804 multibyte/wide string, <a href="#7.22.8">7.22.8</a>, <a href="#K.3.6.5">K.3.6.5</a>
25805 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>,
25806 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>,
25807 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>
25808 single byte/wide character, <a href="#7.28.6.1">7.28.6.1</a> data stream, see streams
25809 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>
25810 wide character, <a href="#7.28.5">7.28.5</a> Daylight Saving Time, <a href="#7.26.1">7.26.1</a>
25811 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>
25812 <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>
25813 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>
25814 <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>
25815 <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>
25816 <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>
25817 <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>
25818 <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>
25819 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>
25820 copying functions DBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25821 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>
25822 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>
25823 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>
25824 <a href="#F.10.8.1">F.10.8.1</a> decimal digit, <a href="#5.2.1">5.2.1</a>
25825 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>
25826 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>,
25827 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>
25828 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>
25829 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>
25830 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>
25831 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>
25832 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>
25833 type-generic macro for, <a href="#7.24">7.24</a> typedef, <a href="#6.7.8">6.7.8</a>
25834 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>
25835 cproj type-generic macro, <a href="#7.24">7.24</a> abstract, <a href="#6.7.7">6.7.7</a>
25836 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>
25837 creal type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> decrement operators, see arithmetic operators,
25838 critical undefined behavior, <a href="#L.2.3">L.2.3</a> increment and decrement
25839 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>
25840 type-generic macro for, <a href="#7.24">7.24</a> default initialization, <a href="#6.7.9">6.7.9</a>
25842 [<a name="#p659" href="p659">page 659</a>] (<a href="#Contents">Contents</a>)
25844 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>
25845 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>
25846 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>
25847 definition, <a href="#6.7">6.7</a> else statement, <a href="#6.8.4.1">6.8.4.1</a>
25848 function, <a href="#6.9.1">6.9.1</a> empty statement, <a href="#6.8.3">6.8.3</a>
25849 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>,
25850 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>,
25851 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>,
25852 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>,
25853 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>
25854 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>
25855 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>,
25856 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>,
25857 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>,
25858 difftime function, <a href="#7.26.2.2">7.26.2.2</a> <a href="#7.28.3.10">7.28.3.10</a>
25859 digit, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> end-of-file macro, see EOF macro
25860 digraphs, <a href="#6.4.6">6.4.6</a> end-of-line indicator, <a href="#5.2.1">5.2.1</a>
25861 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>
25862 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>
25863 div function, <a href="#7.22.6.2">7.22.6.2</a> enumerated type, <a href="#6.2.5">6.2.5</a>
25864 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>
25865 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>
25866 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>
25867 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>
25868 documentation of implementation, <a href="#4">4</a> enumeration specifiers, <a href="#6.7.2.2">6.7.2.2</a>
25869 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>
25870 <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>
25871 <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>
25872 <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>
25873 <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>
25874 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> environmental considerations, <a href="#5.2">5.2</a>
25875 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>,
25876 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>,
25877 <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>
25878 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>,
25879 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>,
25880 <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>,
25881 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>,
25882 <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>,
25883 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>,
25884 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>,
25885 <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>,
25886 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>,
25887 <a href="#K.3.9.1.14">K.3.9.1.14</a>
25888 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>
25889 effective type, <a href="#6.5">6.5</a> equal-to operator, see equality operator
25890 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>
25891 <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>
25892 <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>,
25893 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
25894 element type, <a href="#6.2.5">6.2.5</a> also range error, pole error
25896 [<a name="#p660" href="p660">page 660</a>] (<a href="#Contents">Contents</a>)
25898 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>
25899 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>
25900 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>
25901 erfc type-generic macro, <a href="#7.24">7.24</a> explicit conversion, <a href="#6.3">6.3</a>
25902 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>
25903 <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>
25904 <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>
25905 <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
25906 <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>
25907 <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>
25908 <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>
25909 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>
25910 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>
25911 <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>
25912 error evaluation, <a href="#5.1.2.3">5.1.2.3</a>
25913 domain, see domain error full, <a href="#6.8">6.8</a>
25914 encoding, see encoding error order of evaluation, see order of evaluation
25915 pole, see pole error parenthesized, <a href="#6.5.1">6.5.1</a>
25916 range, see range error primary, <a href="#6.5.1">6.5.1</a>
25917 error conditions, <a href="#7.12.1">7.12.1</a> unary, <a href="#6.5.3">6.5.3</a>
25918 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>
25919 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>
25920 <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>
25921 <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>
25922 <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>,
25923 error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> <a href="#7.20">7.20</a>
25924 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
25925 <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>
25926 escape character (\), <a href="#6.4.4.4">6.4.4.4</a> extensible wide character case mapping functions,
25927 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>
25928 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,
25929 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>
25930 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>
25931 evaluation order, see order of evaluation external definition, <a href="#6.9">6.9</a>
25932 exceptional condition, <a href="#6.5">6.5</a> external identifiers, underscore, <a href="#7.1.3">7.1.3</a>
25933 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>
25934 <a href="#6.8.6.4">6.8.6.4</a> external name, <a href="#6.4.2.1">6.4.2.1</a>
25935 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>
25936 exclusive OR operators
25937 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>
25938 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>
25939 executable program, <a href="#5.1.1.1">5.1.1.1</a> false macro, <a href="#7.18">7.18</a>
25940 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>
25941 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>
25942 environmental limits fdim type-generic macro, <a href="#7.24">7.24</a>
25943 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>
25944 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>
25945 <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>
25946 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>
25947 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>
25948 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>
25950 [<a name="#p661" href="p661">page 661</a>] (<a href="#Contents">Contents</a>)
25952 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>
25953 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>,
25954 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>
25955 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>
25956 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>
25957 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>,
25958 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>
25959 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>,
25960 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>
25961 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>
25962 <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>
25963 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>
25964 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>,
25965 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>
25966 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>
25967 <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>,
25968 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
25969 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>
25970 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>
25971 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>
25972 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>
25973 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>
25974 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>
25975 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>
25976 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>
25977 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>
25978 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>
25979 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>
25980 <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>
25981 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>
25982 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>,
25983 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>
25984 <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>
25985 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>
25986 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>
25987 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>
25988 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>
25989 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>
25990 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>
25991 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>
25992 <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>,
25993 <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>
25994 <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>
25995 <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>
25996 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>
25997 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>
25998 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>
25999 FILENAME_MAX macro, <a href="#7.21.1">7.21.1</a> fmax type-generic macro, <a href="#7.24">7.24</a>
26000 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>
26001 status flag fmin type-generic macro, <a href="#7.24">7.24</a>
26002 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>
26004 [<a name="#p662" href="p662">page 662</a>] (<a href="#Contents">Contents</a>)
26006 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>,
26007 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>
26008 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>,
26009 <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>
26010 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>,
26011 <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>
26012 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>
26013 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>
26014 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>
26015 <a href="#7.4.1.10">7.4.1.10</a> fully buffered stream, <a href="#7.21.3">7.21.3</a>
26016 formal argument (deprecated), <a href="#3.16">3.16</a> function
26017 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>
26018 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>
26019 <a href="#K.3.5.3">K.3.5.3</a> call, <a href="#6.5.2.2">6.5.2.2</a>
26020 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>
26021 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>
26022 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>
26023 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>
26024 also contracted expression image, <a href="#5.2.3">5.2.3</a>
26025 FP_FAST_FMA macro, <a href="#7.12">7.12</a> inline, <a href="#6.7.4">6.7.4</a>
26026 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>
26027 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>
26028 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>
26029 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>
26030 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>,
26031 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>
26032 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>
26033 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>
26034 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>
26035 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>
26036 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>
26037 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>
26038 <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>
26039 <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>
26040 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>
26041 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>
26042 <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>
26043 fputs function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.4">7.21.7.4</a> future directions
26044 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>
26045 <a href="#7.28.3.8">7.28.3.8</a> library, <a href="#7.30">7.30</a>
26046 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>
26047 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>,
26048 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>,
26049 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>
26050 <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>
26051 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>
26052 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>,
26053 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>,
26054 frexp type-generic macro, <a href="#7.24">7.24</a> <a href="#K.3.9.1.2">K.3.9.1.2</a>
26055 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>,
26056 <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>
26058 [<a name="#p663" href="p663">page 663</a>] (<a href="#Contents">Contents</a>)
26060 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>
26061 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>
26062 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>
26063 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>
26064 generic parameters, <a href="#7.24">7.24</a> identifier list, <a href="#6.7.6">6.7.6</a>
26065 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>
26066 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>
26067 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>,
26068 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>,
26069 getenv_s function, <a href="#K.3.6.2.1">K.3.6.2.1</a> <a href="#H.1">H.1</a>
26070 gets function, <a href="#K.3.5.4.1">K.3.5.4.1</a> IEEE 754, <a href="#F.1">F.1</a>
26071 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>
26072 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
26073 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,
26074 gmtime function, <a href="#7.26.3.3">7.26.3.3</a> ANSI/IEEE 854
26075 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>,
26076 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>
26077 graphic characters, <a href="#5.2.1">5.2.1</a> if statement, <a href="#6.8.4.1">6.8.4.1</a>
26078 greater-than operator (>), <a href="#6.5.8">6.5.8</a> ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a>
26079 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>
26080 ignore_handler_s function, <a href="#K.3.6.1.3">K.3.6.1.3</a>
26081 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>
26082 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>
26083 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>
26084 hexadecimal constant, <a href="#6.4.4.1">6.4.4.1</a> imaginary numbers, <a href="#G">G</a>
26085 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>
26086 hexadecimal prefix, <a href="#6.4.4.1">6.4.4.1</a> imaginary types, <a href="#G">G</a>
26087 hexadecimal-character escape sequence imaxabs function, <a href="#7.8.2.1">7.8.2.1</a>
26088 (\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>
26089 high-order bit, <a href="#3.6">3.6</a> imaxdiv_t type, <a href="#7.8">7.8</a>
26090 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>
26091 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>,
26092 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
26093 <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
26094 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>
26095 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>
26096 <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>
26097 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>
26098 <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>
26099 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
26100 <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>
26101 hyperbolic functions bitwise assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
26102 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>
26103 real, <a href="#7.12.5">7.12.5</a>, <a href="#F.10.2">F.10.2</a> increment operators, see arithmetic operators,
26104 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
26105 hypot type-generic macro, <a href="#7.24">7.24</a> indeterminate value, <a href="#3.19.2">3.19.2</a>
26106 indeterminately sequenced, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5.2.2">6.5.2.2</a>,
26107 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,
26108 identifier, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.5.1">6.5.1</a> unsequenced
26109 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>
26110 maximum length, <a href="#6.4.2.1">6.4.2.1</a> inequality operator (!=), <a href="#6.5.9">6.5.9</a>
26112 [<a name="#p664" href="p664">page 664</a>] (<a href="#Contents">Contents</a>)
26114 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>
26115 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>
26116 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>
26117 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>
26118 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>
26119 <a href="#F.8.5">F.8.5</a> interrupt, <a href="#5.2.3">5.2.3</a>
26120 in blocks, <a href="#6.8">6.8</a> INTMAX_C macro, <a href="#7.20.4.2">7.20.4.2</a>
26121 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>
26122 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>
26123 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>,
26124 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>
26125 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>
26126 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>
26127 <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>
26128 <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>
26129 <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>
26130 input/output functions INTPTR_MIN macro, <a href="#7.20.2.4">7.20.2.4</a>
26131 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>
26132 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>
26133 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>
26134 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>
26135 wide character, <a href="#7.28.3">7.28.3</a> isblank function, <a href="#7.4.1.3">7.4.1.3</a>
26136 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>,
26137 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>
26138 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>,
26139 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>
26140 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>
26141 <a href="#6.3.1.8">6.3.1.8</a> isgraph function, <a href="#7.4.1.6">7.4.1.6</a>
26142 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>
26143 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>
26144 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>
26145 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>
26146 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>
26147 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>
26148 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>,
26149 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>
26150 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>
26151 <a href="#7.22.6">7.22.6</a> isnormal macro, <a href="#7.12.3.5">7.12.3.5</a>
26152 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>
26153 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>
26154 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>
26155 <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>
26156 <a href="#7.1.4">7.1.4</a> ISO/IEC 10976-1, <a href="#H.1">H.1</a>
26157 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>
26158 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>
26159 <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>
26160 <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>
26161 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>
26162 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>
26163 <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>,
26164 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>
26166 [<a name="#p665" href="p665">page 665</a>] (<a href="#Contents">Contents</a>)
26168 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>
26169 <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>
26170 <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>,
26171 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>
26172 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>,
26173 <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>,
26174 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>
26175 <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>
26176 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>
26177 <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>
26178 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>
26179 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>
26180 <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>
26181 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>
26182 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>
26183 <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>
26184 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>
26185 <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>
26186 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>
26187 <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>
26188 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>
26189 <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>
26190 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>
26191 <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>
26192 <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>
26193 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>
26194 <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>
26195 <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>
26196 <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>
26197 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>
26198 <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
26199 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>
26200 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>
26201 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>
26202 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>
26203 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>,
26204 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>
26205 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>,
26206 <a href="#7.28.2.2">7.28.2.2</a>
26207 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>
26208 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>
26209 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>
26210 lexical elements, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>
26211 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>
26212 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>
26213 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>
26214 labeled statement, <a href="#6.8.1">6.8.1</a> future directions, <a href="#7.30">7.30</a>
26215 labs function, <a href="#7.22.6.1">7.22.6.1</a> summary, <a href="#B">B</a>
26216 language, <a href="#6">6</a> terms, <a href="#7.1.1">7.1.1</a>
26217 future directions, <a href="#6.11">6.11</a> use of functions, <a href="#7.1.4">7.1.4</a>
26218 syntax summary, <a href="#A">A</a> lifetime, <a href="#6.2.4">6.2.4</a>
26220 [<a name="#p666" href="p666">page 666</a>] (<a href="#Contents">Contents</a>)
26222 limits long double _Complex type conversion,
26223 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>
26224 implementation, see implementation limits long double _Imaginary type, <a href="#G.2">G.2</a>
26225 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>
26226 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>,
26227 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>
26228 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>,
26229 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>
26230 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>,
26231 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>
26232 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>,
26233 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>
26234 <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>
26235 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>,
26236 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>
26237 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>,
26238 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>
26239 <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>
26240 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>
26241 <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>
26242 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>,
26243 llrint type-generic macro, <a href="#7.24">7.24</a> <a href="#7.22.4.7">7.22.4.7</a>
26244 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>
26245 llround type-generic macro, <a href="#7.24">7.24</a> low-order bit, <a href="#3.6">3.6</a>
26246 local time, <a href="#7.26.1">7.26.1</a> lowercase letter, <a href="#5.2.1">5.2.1</a>
26247 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>
26248 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>
26249 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>
26250 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>
26251 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>
26252 localtime function, <a href="#7.26.3.4">7.26.3.4</a>
26253 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>
26254 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
26255 log type-generic macro, <a href="#7.24">7.24</a> library function, <a href="#7.1.4">7.1.4</a>
26256 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>
26257 log10 type-generic macro, <a href="#7.24">7.24</a> macro name, <a href="#6.10.3">6.10.3</a>
26258 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>
26259 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>
26260 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>
26261 log2 type-generic macro, <a href="#7.24">7.24</a> scope, <a href="#6.10.3.5">6.10.3.5</a>
26262 logarithmic functions macro parameter, <a href="#6.10.3">6.10.3</a>
26263 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>
26264 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>
26265 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>
26266 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>,
26267 logical operators <a href="#7.21.3">7.21.3</a>
26268 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>
26269 negation (!), <a href="#6.5.3.3">6.5.3.3</a> manipulation functions
26270 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>
26271 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>
26272 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>,
26274 [<a name="#p667" href="p667">page 667</a>] (<a href="#Contents">Contents</a>)
26276 <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>
26277 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>
26278 <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>
26279 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>
26280 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>
26281 MATH_ERRNO macro, <a href="#7.12">7.12</a> mtx_lock function, <a href="#7.25.4.3">7.25.4.3</a>
26282 max_align_t type, <a href="#7.19">7.19</a> mtx_t type, <a href="#7.25.1">7.25.1</a>
26283 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>
26284 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>
26285 <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>,
26286 <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>
26287 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>
26288 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
26289 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>
26290 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>
26291 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>
26292 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>
26293 <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>
26294 <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>
26295 mbsinit function, <a href="#7.28.6.2.1">7.28.6.2.1</a> multibyte/wide character conversion functions,
26296 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>
26297 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>
26298 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>
26299 <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,
26300 <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>
26301 <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>
26302 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>
26303 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>
26304 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>,
26305 <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>
26306 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>
26307 member alignment, <a href="#6.7.2.1">6.7.2.1</a>
26308 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>
26309 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>
26310 memcpy function, <a href="#7.23.2.1">7.23.2.1</a> name
26311 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>
26312 memmove function, <a href="#7.23.2.2">7.23.2.2</a> file, <a href="#7.21.3">7.21.3</a>
26313 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>
26314 memory location, <a href="#3.14">3.14</a> label, <a href="#6.2.3">6.2.3</a>
26315 memory management functions, <a href="#7.22.3">7.22.3</a> structure/union member, <a href="#6.2.3">6.2.3</a>
26316 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>
26317 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>
26318 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>
26319 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>
26320 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>
26321 miscellaneous functions NDEBUG macro, <a href="#7.2">7.2</a>
26322 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>,
26323 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>
26324 mktime function, <a href="#7.26.2.3">7.26.2.3</a> nearbyint type-generic macro, <a href="#7.24">7.24</a>
26325 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>
26326 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>
26328 [<a name="#p668" href="p668">page 668</a>] (<a href="#Contents">Contents</a>)
26330 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>
26331 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>
26332 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>
26333 <a href="#7.4.1.10">7.4.1.10</a> alignof, <a href="#6.5.3.4">6.5.3.4</a>
26334 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>
26335 <a href="#F.10.8.3">F.10.8.3</a> associativity, <a href="#6.5">6.5</a>
26336 nextafter type-generic macro, <a href="#7.24">7.24</a> equality, <a href="#6.5.9">6.5.9</a>
26337 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>
26338 nexttoward type-generic macro, <a href="#7.24">7.24</a> postfix, <a href="#6.5.2">6.5.2</a>
26339 no linkage, <a href="#6.2.2">6.2.2</a> precedence, <a href="#6.5">6.5</a>
26340 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>
26341 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>
26342 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>
26343 nonlocal jumps header, <a href="#7.13">7.13</a> sizeof, <a href="#6.5.3.4">6.5.3.4</a>
26344 norm, complex, <a href="#7.3.8.1">7.3.8.1</a> unary, <a href="#6.5.3">6.5.3</a>
26345 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>
26346 not macro, <a href="#7.9">7.9</a> optional features, see conditional features
26347 not-equal-to operator, see inequality operator or macro, <a href="#7.9">7.9</a>
26348 not_eq macro, <a href="#7.9">7.9</a> OR operators
26349 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>
26350 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>
26351 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>
26352 <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>
26353 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>
26354 null pointer constant, <a href="#6.3.2.3">6.3.2.3</a> or_eq macro, <a href="#7.9">7.9</a>
26355 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>
26356 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>,
26357 null wide character, <a href="#7.1.1">7.1.1</a> see also sequence points
26358 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>
26359 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>
26360 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>
26361 numerical limits, <a href="#5.2.4.2">5.2.4.2</a> outer scope, <a href="#6.2.1">6.2.1</a>
26362 over-aligned, <a href="#6.2.8">6.2.8</a>
26363 object, <a href="#3.15">3.15</a>
26364 object representation, <a href="#6.2.6.1">6.2.6.1</a> padding
26365 object type, <a href="#6.2.5">6.2.5</a> binary stream, <a href="#7.21.2">7.21.2</a>
26366 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>
26367 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>
26368 obsolescence, <a href="#6.11">6.11</a>, <a href="#7.30">7.30</a> parameter, <a href="#3.16">3.16</a>
26369 octal constant, <a href="#6.4.4.1">6.4.4.1</a> array, <a href="#6.9.1">6.9.1</a>
26370 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>
26371 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>
26372 <a href="#6.4.4.4">6.4.4.4</a> macro, <a href="#6.10.3">6.10.3</a>
26373 offsetof macro, <a href="#7.19">7.19</a> main function, <a href="#5.1.2.2.1">5.1.2.2.1</a>
26374 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>
26375 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>
26376 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>
26377 ones' complement, <a href="#6.2.6.2">6.2.6.2</a> parenthesized expression, <a href="#6.5.1">6.5.1</a>
26378 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>
26379 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>
26380 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>
26382 [<a name="#p669" href="p669">page 669</a>] (<a href="#Contents">Contents</a>)
26384 perror function, <a href="#7.21.10.4">7.21.10.4</a> PRIcLEASTN macros, <a href="#7.8.1">7.8.1</a>
26385 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>
26386 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>
26387 placemarker, <a href="#6.10.3.3">6.10.3.3</a> PRIcPTR macros, <a href="#7.8.1">7.8.1</a>
26388 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>
26389 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>,
26390 pointer comparison, <a href="#6.5.8">6.5.8</a> <a href="#K.3.5.3.3">K.3.5.3.3</a>
26391 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>
26392 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>
26393 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>
26394 pointer type, <a href="#6.2.5">6.2.5</a> program diagnostics, <a href="#7.2.1">7.2.1</a>
26395 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>
26396 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>
26397 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>
26398 <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>
26399 <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>
26400 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>
26401 position indicator, file, see file position indicator program structure, <a href="#5.1.1.1">5.1.1.1</a>
26402 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>,
26403 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>
26404 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>
26405 postfix expressions, <a href="#6.5.2">6.5.2</a> program, strictly conforming, <a href="#4">4</a>
26406 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
26407 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>
26408 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>
26409 power functions prototype, see function prototype
26410 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>
26411 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>
26412 pp-number, <a href="#6.4.8">6.4.8</a> PTRDIFF_MIN macro, <a href="#7.20.3">7.20.3</a>
26413 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>,
26414 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>
26415 precedence of operators, <a href="#6.5">6.5</a> punctuators, <a href="#6.4.6">6.4.6</a>
26416 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>
26417 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>
26418 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>
26419 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>
26420 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>
26421 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>
26422 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>
26423 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>
26424 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>
26425 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>
26426 preprocessing operators question-mark escape sequence (\?), <a href="#6.4.4.4">6.4.4.4</a>
26427 #, <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>,
26428 ##, <a href="#6.10.3.3">6.10.3.3</a> <a href="#7.22.4.7">7.22.4.7</a>
26429 _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>
26430 defined, <a href="#6.10.1">6.10.1</a>
26431 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>
26432 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>
26433 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>
26434 PRIcFASTN macros, <a href="#7.8.1">7.8.1</a> range
26436 [<a name="#p670" href="p670">page 670</a>] (<a href="#Contents">Contents</a>)
26438 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>,
26439 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>
26440 <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>
26441 <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>
26442 <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>
26443 <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>
26444 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>
26445 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>
26446 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>
26447 <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>,
26448 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>,
26449 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>,
26450 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>,
26451 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>,
26452 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>,
26453 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>,
26454 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>,
26455 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>,
26456 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>,
26457 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>
26458 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>,
26459 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>
26460 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>
26461 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>
26462 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>
26463 release fence, <a href="#7.17.4">7.17.4</a>
26464 release operation, <a href="#5.1.2.4">5.1.2.4</a> same scope, <a href="#6.2.1">6.2.1</a>
26465 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>
26466 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>
26467 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>
26468 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>
26469 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>
26470 <a href="#F.10.7.2">F.10.7.2</a> scalbn type-generic macro, <a href="#7.24">7.24</a>
26471 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>
26472 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>
26473 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>
26474 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>
26475 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>
26476 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>
26477 representations of types, <a href="#6.2.6">6.2.6</a> SCNcFASTN macros, <a href="#7.8.1">7.8.1</a>
26478 pointer, <a href="#6.2.5">6.2.5</a> SCNcLEASTN macros, <a href="#7.8.1">7.8.1</a>
26479 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>
26480 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>
26481 restartable multibyte/wide character conversion SCNcPTR macros, <a href="#7.8.1">7.8.1</a>
26482 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>
26483 restartable multibyte/wide string conversion search functions
26484 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>
26485 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>
26486 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>
26487 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>
26488 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>
26490 [<a name="#p671" href="p671">page 671</a>] (<a href="#Contents">Contents</a>)
26492 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>
26493 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>
26494 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>
26495 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>
26496 <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>
26497 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>
26498 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>
26499 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>,
26500 <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>
26501 <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>
26502 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>
26503 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>,
26504 <a href="#6.5.16">6.5.16</a>, see also indeterminately sequenced, <a href="#6.3.1.8">6.3.1.8</a>
26505 unsequenced signed types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>
26506 sequencing of statements, <a href="#6.8">6.8</a> significand part, <a href="#6.4.4.2">6.4.4.2</a>
26507 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>
26508 <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>
26509 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>
26510 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>
26511 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>
26512 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>
26513 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,
26514 <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>
26515 shall, <a href="#4">4</a> single-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a>
26516 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>
26517 shift sequence, <a href="#7.1.1">7.1.1</a> singularity, <a href="#7.12.1">7.12.1</a>
26518 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>
26519 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>
26520 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>
26521 <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>,
26522 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>,
26523 <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>,
26524 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>
26525 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>
26526 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>,
26527 <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>
26528 <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>
26529 <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>
26530 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>
26531 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>
26532 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>
26533 <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>
26534 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>
26535 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>
26536 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>
26537 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>,
26538 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>
26539 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>
26540 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>
26541 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>
26542 sign bit, <a href="#6.2.6.2">6.2.6.2</a> sqrt type-generic macro, <a href="#7.24">7.24</a>
26544 [<a name="#p672" href="p672">page 672</a>] (<a href="#Contents">Contents</a>)
26546 srand function, <a href="#7.22.2.2">7.22.2.2</a> expression, <a href="#6.8.3">6.8.3</a>
26547 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>
26548 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>
26549 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>
26550 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>
26551 <a href="#7.2"><assert.h></a>, <a href="#7.2">7.2</a> jump, <a href="#6.8.6">6.8.6</a>
26552 <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>
26553 <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>
26554 <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>
26555 <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>
26556 <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>
26557 <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>
26558 <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>
26559 <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>
26560 <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>
26561 <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>
26562 <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>
26563 <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>
26564 <a href="#J.5.17">J.5.17</a> static_assert macro, <a href="#7.2">7.2</a>
26565 <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>
26566 <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>
26567 <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>
26568 <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>
26569 <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>
26570 <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>,
26571 <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>
26572 <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>
26573 <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>,
26574 <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>,
26575 <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>
26576 <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>,
26577 <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>
26578 <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>
26579 <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>,
26580 <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>
26581 <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>,
26582 <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>
26583 <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>
26584 <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>
26585 <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>
26586 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>
26587 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>
26588 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>
26589 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>
26590 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>
26591 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>
26592 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>
26593 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>
26594 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>
26595 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>
26596 else, <a href="#6.8.4.1">6.8.4.1</a> fully buffered, <a href="#7.21.3">7.21.3</a>
26598 [<a name="#p673" href="p673">page 673</a>] (<a href="#Contents">Contents</a>)
26600 line buffered, <a href="#7.21.3">7.21.3</a> strtoumax function, <a href="#7.8.2.3">7.8.2.3</a>
26601 orientation, <a href="#7.21.2">7.21.2</a> struct hack, see flexible array member
26602 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>
26603 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>
26604 standard output, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> structure
26605 unbuffered, <a href="#7.21.3">7.21.3</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
26606 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>
26607 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>
26608 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>
26609 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>
26610 <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>
26611 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>
26612 strictly conforming program, <a href="#4">4</a> pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a>
26613 string, <a href="#7.1.1">7.1.1</a> specifier, <a href="#6.7.2.1">6.7.2.1</a>
26614 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>
26615 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>
26616 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>
26617 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>
26618 library function conventions, <a href="#7.23.1">7.23.1</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
26619 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>
26620 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>
26621 numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a> suffix
26622 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>
26623 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>
26624 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>
26625 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>
26626 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>
26627 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>
26628 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>,
26629 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>
26630 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>
26631 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>
26632 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>
26633 stronger, <a href="#6.2.8">6.2.8</a> symbols, <a href="#3">3</a>
26634 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>
26635 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>
26636 strspn function, <a href="#7.23.5.6">7.23.5.6</a> syntactic categories, <a href="#6.1">6.1</a>
26637 strstr function, <a href="#7.23.5.7">7.23.5.7</a> syntax notation, <a href="#6.1">6.1</a>
26638 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>
26639 <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>
26640 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>
26641 strtoimax function, <a href="#7.8.2.3">7.8.2.3</a>
26642 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>
26643 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>
26644 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>
26645 <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>
26646 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>
26647 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>
26648 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>
26649 <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>
26650 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>
26652 [<a name="#p674" href="p674">page 674</a>] (<a href="#Contents">Contents</a>)
26654 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>
26655 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>
26656 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>
26657 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>
26658 tgamma type-generic macro, <a href="#7.24">7.24</a> translation phases, <a href="#5.1.1.2">5.1.1.2</a>
26659 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>
26660 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
26661 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>,
26662 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>
26663 thrd_equal function, <a href="#7.25.5.4">7.25.5.4</a> trigonometric functions
26664 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>
26665 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>
26666 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>
26667 thrd_start_t type, <a href="#7.25.1">7.25.1</a> true macro, <a href="#7.18">7.18</a>
26668 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>
26669 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>
26670 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>
26671 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>
26672 threads header, <a href="#7.25">7.25</a> tss_create function, <a href="#7.25.6.1">7.25.6.1</a>
26673 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>
26674 time TSS_DTOR_ITERATIONS macro, <a href="#7.25.1">7.25.1</a>
26675 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>
26676 <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>
26677 <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>
26678 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>
26679 <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>
26680 <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>
26681 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>
26682 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>
26683 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>
26684 local, <a href="#7.26.1">7.26.1</a> type names, <a href="#6.7.7">6.7.7</a>
26685 manipulation functions, <a href="#7.26.2">7.26.2</a> type punning, <a href="#6.5.2.3">6.5.2.3</a>
26686 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>
26687 time function, <a href="#7.26.2.4">7.26.2.4</a> type specifiers, <a href="#6.7.2">6.7.2</a>
26688 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>
26689 time_t type, <a href="#7.26.1">7.26.1</a> typedef declaration, <a href="#6.7.8">6.7.8</a>
26690 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>
26691 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>
26692 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>,
26693 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>
26694 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>
26695 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>
26696 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>
26697 <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>
26698 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>
26699 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>
26700 token concatenation, <a href="#6.10.3.3">6.10.3.3</a> conversions, <a href="#6.3">6.3</a>
26701 token pasting, <a href="#6.10.3.3">6.10.3.3</a> imaginary, <a href="#G">G</a>
26702 tolower function, <a href="#7.4.2.1">7.4.2.1</a> restrict qualified, <a href="#6.7.3">6.7.3</a>
26703 toupper function, <a href="#7.4.2.2">7.4.2.2</a> volatile qualified, <a href="#6.7.3">6.7.3</a>
26704 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>
26706 [<a name="#p675" href="p675">page 675</a>] (<a href="#Contents">Contents</a>)
26708 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>
26709 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>
26710 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>
26711 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>
26712 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
26713 uint_least32_t type, <a href="#7.27">7.27</a> indeterminately sequenced, sequenced
26714 UINT_LEASTN_MAX macros, <a href="#7.20.2.2">7.20.2.2</a> before
26715 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>
26716 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>
26717 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>
26718 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>,
26719 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>
26720 <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>,
26721 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>
26722 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>
26723 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>
26724 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>
26725 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>
26726 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>
26727 <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>,
26728 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>
26729 <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>
26730 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>
26731 unary expression, <a href="#6.5.3">6.5.3</a> UTF-8 string literal, see string literal
26732 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>
26733 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>
26734 unary plus operator (+), <a href="#6.5.3.3">6.5.3.3</a>
26735 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>,
26736 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>,
26737 <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>,
26738 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>,
26739 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>,
26740 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>
26741 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>,
26742 <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>
26743 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>,
26744 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>,
26745 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>,
26746 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>,
26747 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>,
26748 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>
26749 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>
26750 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>,
26751 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>,
26752 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>,
26753 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>,
26754 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>,
26755 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>,
26756 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>
26757 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>
26758 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>
26760 [<a name="#p676" href="p676">page 676</a>] (<a href="#Contents">Contents</a>)
26762 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>
26763 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>
26764 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>
26765 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>
26766 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>
26767 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>
26768 <a href="#7.4.1.10">7.4.1.10</a>
26769 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>
26770 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>,
26771 <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>
26772 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>
26773 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>
26774 <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>,
26775 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>,
26776 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>
26777 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>,
26778 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>,
26779 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>
26780 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>
26781 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>
26782 VLA, see variable length array wcscat_s function, <a href="#K.3.9.2.2.1">K.3.9.2.2.1</a>
26783 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>
26784 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>
26785 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>
26786 <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>
26787 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>
26788 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>
26789 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>
26790 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>
26791 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>
26792 <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>
26793 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>
26794 <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>
26795 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>
26796 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>
26797 <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>
26798 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>
26799 <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>
26800 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>
26801 <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>
26802 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>
26803 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>
26804 <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>
26805 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>
26806 <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>
26807 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>
26808 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>
26809 <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>,
26810 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>
26811 <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>
26812 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>
26814 [<a name="#p677" href="p677">page 677</a>] (<a href="#Contents">Contents</a>)
26816 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>
26817 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>
26818 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>
26819 <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>
26820 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>
26821 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>
26822 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>
26823 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>
26824 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>,
26825 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>
26826 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>
26827 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>,
26828 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>
26829 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>
26830 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>
26831 weaker, <a href="#6.2.8">6.2.8</a> xor macro, <a href="#7.9">7.9</a>
26832 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>
26833 <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>,
26834 <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>
26835 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>
26836 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>,
26837 <a href="#7.29.2.1.10">7.29.2.1.10</a>
26838 white-space characters, <a href="#6.4">6.4</a>
26839 wide character, <a href="#3.7.3">3.7.3</a>
26840 case mapping functions, <a href="#7.29.3.1">7.29.3.1</a>
26841 extensible, <a href="#7.29.3.2">7.29.3.2</a>
26842 classification functions, <a href="#7.29.2.1">7.29.2.1</a>
26843 extensible, <a href="#7.29.2.2">7.29.2.2</a>
26844 constant, <a href="#6.4.4.4">6.4.4.4</a>
26845 formatted input/output functions, <a href="#7.28.2">7.28.2</a>,
26846 <a href="#K.3.9.1">K.3.9.1</a>
26847 input functions, <a href="#7.21.1">7.21.1</a>
26848 input/output functions, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3">7.28.3</a>
26849 output functions, <a href="#7.21.1">7.21.1</a>
26850 single-byte conversion functions, <a href="#7.28.6.1">7.28.6.1</a>
26851 wide string, <a href="#7.1.1">7.1.1</a>
26852 wide string comparison functions, <a href="#7.28.4.4">7.28.4.4</a>
26853 wide string concatenation functions, <a href="#7.28.4.3">7.28.4.3</a>,
26854 <a href="#K.3.9.2.2">K.3.9.2.2</a>
26855 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>
26856 wide string literal, see string literal
26857 wide string miscellaneous functions, <a href="#7.28.4.6">7.28.4.6</a>,
26858 <a href="#K.3.9.2.4">K.3.9.2.4</a>
26859 wide string numeric conversion functions, <a href="#7.8.2.4">7.8.2.4</a>,
26860 <a href="#7.28.4.1">7.28.4.1</a>
26861 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>
26862 wide-oriented stream, <a href="#7.21.2">7.21.2</a>
26863 width, <a href="#6.2.6.2">6.2.6.2</a>
26864 WINT_MAX macro, <a href="#7.20.3">7.20.3</a>
26865 WINT_MIN macro, <a href="#7.20.3">7.20.3</a>
26866 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>,
26868 [<a name="#p678" href="p678">page 678</a>] (<a href="#Contents">Contents</a>)
26869 </pre></body></html>
projects / c-standard / blob