1 <html><head><title>N1548 Committee Draft -- December 2, 2010 ISO/IEC 9899:201x</title></head><body><pre>
2 N1548 Committee Draft -- December 2, 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 (N1256) 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 . . . . . . . . . . . . . . . . . . . . 120</a>
116 <a href="#6.7.4"> 6.7.4 Function specifiers . . . . . . . . . . . . . . . . . . 124</a>
117 <a href="#6.7.5"> 6.7.5 Alignment specifier . . . . . . . . . . . . . . . . . . 126</a>
118 <a href="#6.7.6"> 6.7.6 Declarators . . . . . . . . . . . . . . . . . . . . . 127</a>
119 <a href="#6.7.7"> 6.7.7 Type names . . . . . . . . . . . . . . . . . . . . . 135</a>
120 <a href="#6.7.8"> 6.7.8 Type definitions . . . . . . . . . . . . . . . . . . . 136</a>
121 <a href="#6.7.9"> 6.7.9 Initialization . . . . . . . . . . . . . . . . . . . . 138</a>
122 <a href="#6.7.10"> 6.7.10 Static assertions . . . . . . . . . . . . . . . . . . . 144</a>
123 <a href="#6.8"> 6.8 Statements and blocks . . . . . . . . . . . . . . . . . . . . 145</a>
124 <a href="#6.8.1"> 6.8.1 Labeled statements . . . . . . . . . . . . . . . . . . 145</a>
125 <a href="#6.8.2"> 6.8.2 Compound statement . . . . . . . . . . . . . . . . . 146</a>
126 <a href="#6.8.3"> 6.8.3 Expression and null statements . . . . . . . . . . . . . 146</a>
127 <a href="#6.8.4"> 6.8.4 Selection statements . . . . . . . . . . . . . . . . . 147</a>
128 <a href="#6.8.5"> 6.8.5 Iteration statements . . . . . . . . . . . . . . . . . . 149</a>
129 <a href="#6.8.6"> 6.8.6 Jump statements . . . . . . . . . . . . . . . . . . . 150</a>
130 <a href="#6.9"> 6.9 External definitions . . . . . . . . . . . . . . . . . . . . . 154</a>
131 <a href="#6.9.1"> 6.9.1 Function definitions . . . . . . . . . . . . . . . . . . 155</a>
132 <a href="#6.9.2"> 6.9.2 External object definitions . . . . . . . . . . . . . . . 157</a>
133 <a href="#6.10"> 6.10 Preprocessing directives . . . . . . . . . . . . . . . . . . . 159</a>
134 <a href="#6.10.1"> 6.10.1 Conditional inclusion . . . . . . . . . . . . . . . . . 161</a>
135 <a href="#6.10.2"> 6.10.2 Source file inclusion . . . . . . . . . . . . . . . . . 163</a>
136 <a href="#6.10.3"> 6.10.3 Macro replacement . . . . . . . . . . . . . . . . . . 165</a>
141 <a href="#6.10.4"> 6.10.4 Line control . . . . . . . . . . . . . . . . . . . . . 172</a>
142 <a href="#6.10.5"> 6.10.5 Error directive . . . . . . . . . . . . . . . . . . . . 173</a>
143 <a href="#6.10.6"> 6.10.6 Pragma directive . . . . . . . . . . . . . . . . . . . 173</a>
144 <a href="#6.10.7"> 6.10.7 Null directive . . . . . . . . . . . . . . . . . . . . 174</a>
145 <a href="#6.10.8"> 6.10.8 Predefined macro names . . . . . . . . . . . . . . . . 174</a>
146 <a href="#6.10.9"> 6.10.9 Pragma operator . . . . . . . . . . . . . . . . . . . 176</a>
147 <a href="#6.11"> 6.11 Future language directions . . . . . . . . . . . . . . . . . . 178</a>
148 <a href="#6.11.1"> 6.11.1 Floating types . . . . . . . . . . . . . . . . . . . . 178</a>
149 <a href="#6.11.2"> 6.11.2 Linkages of identifiers . . . . . . . . . . . . . . . . . 178</a>
150 <a href="#6.11.3"> 6.11.3 External names . . . . . . . . . . . . . . . . . . . 178</a>
151 <a href="#6.11.4"> 6.11.4 Character escape sequences . . . . . . . . . . . . . . 178</a>
152 <a href="#6.11.5"> 6.11.5 Storage-class specifiers . . . . . . . . . . . . . . . . 178</a>
153 <a href="#6.11.6"> 6.11.6 Function declarators . . . . . . . . . . . . . . . . . 178</a>
154 <a href="#6.11.7"> 6.11.7 Function definitions . . . . . . . . . . . . . . . . . . 178</a>
155 <a href="#6.11.8"> 6.11.8 Pragma directives . . . . . . . . . . . . . . . . . . 178</a>
156 <a href="#6.11.9"> 6.11.9 Predefined macro names . . . . . . . . . . . . . . . . 178</a>
157 <a href="#7">7. Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179</a>
158 <a href="#7.1"> 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 179</a>
159 <a href="#7.1.1"> 7.1.1 Definitions of terms . . . . . . . . . . . . . . . . . . 179</a>
160 <a href="#7.1.2"> 7.1.2 Standard headers . . . . . . . . . . . . . . . . . . . 180</a>
161 <a href="#7.1.3"> 7.1.3 Reserved identifiers . . . . . . . . . . . . . . . . . . 181</a>
162 <a href="#7.1.4"> 7.1.4 Use of library functions . . . . . . . . . . . . . . . . 182</a>
163 <a href="#7.2"> 7.2 Diagnostics <assert.h> . . . . . . . . . . . . . . . . . . 185</a>
164 <a href="#7.2.1"> 7.2.1 Program diagnostics . . . . . . . . . . . . . . . . . 185</a>
165 <a href="#7.3"> 7.3 Complex arithmetic <complex.h> . . . . . . . . . . . . . . 187</a>
166 <a href="#7.3.1"> 7.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . 187</a>
167 <a href="#7.3.2"> 7.3.2 Conventions . . . . . . . . . . . . . . . . . . . . . 188</a>
168 <a href="#7.3.3"> 7.3.3 Branch cuts . . . . . . . . . . . . . . . . . . . . . 188</a>
169 <a href="#7.3.4"> 7.3.4 The CX_LIMITED_RANGE pragma . . . . . . . . . . . 188</a>
170 <a href="#7.3.5"> 7.3.5 Trigonometric functions . . . . . . . . . . . . . . . . 189</a>
171 <a href="#7.3.6"> 7.3.6 Hyperbolic functions . . . . . . . . . . . . . . . . . 191</a>
172 <a href="#7.3.7"> 7.3.7 Exponential and logarithmic functions . . . . . . . . . . 193</a>
173 <a href="#7.3.8"> 7.3.8 Power and absolute-value functions . . . . . . . . . . . 194</a>
174 <a href="#7.3.9"> 7.3.9 Manipulation functions . . . . . . . . . . . . . . . . 195</a>
175 <a href="#7.4"> 7.4 Character handling <ctype.h> . . . . . . . . . . . . . . . . 199</a>
176 <a href="#7.4.1"> 7.4.1 Character classification functions . . . . . . . . . . . . 199</a>
177 <a href="#7.4.2"> 7.4.2 Character case mapping functions . . . . . . . . . . . . 202</a>
178 <a href="#7.5"> 7.5 Errors <errno.h> . . . . . . . . . . . . . . . . . . . . . 204</a>
179 <a href="#7.6"> 7.6 Floating-point environment <fenv.h> . . . . . . . . . . . . . 205</a>
180 <a href="#7.6.1"> 7.6.1 The FENV_ACCESS pragma . . . . . . . . . . . . . . 207</a>
181 <a href="#7.6.2"> 7.6.2 Floating-point exceptions . . . . . . . . . . . . . . . 208</a>
182 <a href="#7.6.3"> 7.6.3 Rounding . . . . . . . . . . . . . . . . . . . . . . 211</a>
183 <a href="#7.6.4"> 7.6.4 Environment . . . . . . . . . . . . . . . . . . . . 212</a>
184 <a href="#7.7"> 7.7 Characteristics of floating types <float.h> . . . . . . . . . . . 215</a>
188 <a href="#7.8"> 7.8 Format conversion of integer types <inttypes.h> . . . . . . . . 216</a>
189 <a href="#7.8.1"> 7.8.1 Macros for format specifiers . . . . . . . . . . . . . . 216</a>
190 <a href="#7.8.2"> 7.8.2 Functions for greatest-width integer types . . . . . . . . . 217</a>
191 <a href="#7.9"> 7.9 Alternative spellings <iso646.h> . . . . . . . . . . . . . . . 220</a>
192 <a href="#7.10"> 7.10 Sizes of integer types <limits.h> . . . . . . . . . . . . . . 221</a>
193 <a href="#7.11"> 7.11 Localization <locale.h> . . . . . . . . . . . . . . . . . . 222</a>
194 <a href="#7.11.1"> 7.11.1 Locale control . . . . . . . . . . . . . . . . . . . . 223</a>
195 <a href="#7.11.2"> 7.11.2 Numeric formatting convention inquiry . . . . . . . . . . 224</a>
196 <a href="#7.12"> 7.12 Mathematics <math.h> . . . . . . . . . . . . . . . . . . . 230</a>
197 <a href="#7.12.1"> 7.12.1 Treatment of error conditions . . . . . . . . . . . . . . 232</a>
198 <a href="#7.12.2"> 7.12.2 The FP_CONTRACT pragma . . . . . . . . . . . . . . 234</a>
199 <a href="#7.12.3"> 7.12.3 Classification macros . . . . . . . . . . . . . . . . . 234</a>
200 <a href="#7.12.4"> 7.12.4 Trigonometric functions . . . . . . . . . . . . . . . . 237</a>
201 <a href="#7.12.5"> 7.12.5 Hyperbolic functions . . . . . . . . . . . . . . . . . 239</a>
202 <a href="#7.12.6"> 7.12.6 Exponential and logarithmic functions . . . . . . . . . . 241</a>
203 <a href="#7.12.7"> 7.12.7 Power and absolute-value functions . . . . . . . . . . . 246</a>
204 <a href="#7.12.8"> 7.12.8 Error and gamma functions . . . . . . . . . . . . . . . 248</a>
205 <a href="#7.12.9"> 7.12.9 Nearest integer functions . . . . . . . . . . . . . . . . 250</a>
206 <a href="#7.12.10"> 7.12.10 Remainder functions . . . . . . . . . . . . . . . . . 253</a>
207 <a href="#7.12.11"> 7.12.11 Manipulation functions . . . . . . . . . . . . . . . . 254</a>
208 <a href="#7.12.12"> 7.12.12 Maximum, minimum, and positive difference functions . . . 256</a>
209 <a href="#7.12.13"> 7.12.13 Floating multiply-add . . . . . . . . . . . . . . . . . 257</a>
210 <a href="#7.12.14"> 7.12.14 Comparison macros . . . . . . . . . . . . . . . . . . 258</a>
211 <a href="#7.13"> 7.13 Nonlocal jumps <setjmp.h> . . . . . . . . . . . . . . . . 261</a>
212 <a href="#7.13.1"> 7.13.1 Save calling environment . . . . . . . . . . . . . . . 261</a>
213 <a href="#7.13.2"> 7.13.2 Restore calling environment . . . . . . . . . . . . . . 262</a>
214 <a href="#7.14"> 7.14 Signal handling <signal.h> . . . . . . . . . . . . . . . . . 264</a>
215 <a href="#7.14.1"> 7.14.1 Specify signal handling . . . . . . . . . . . . . . . . 265</a>
216 <a href="#7.14.2"> 7.14.2 Send signal . . . . . . . . . . . . . . . . . . . . . 266</a>
217 <a href="#7.15"> 7.15 Alignment <stdalign.h> . . . . . . . . . . . . . . . . . 267</a>
218 <a href="#7.16"> 7.16 Variable arguments <stdarg.h> . . . . . . . . . . . . . . . 268</a>
219 <a href="#7.16.1"> 7.16.1 Variable argument list access macros . . . . . . . . . . . 268</a>
220 <a href="#7.17"> 7.17 Atomics <stdatomic.h> . . . . . . . . . . . . . . . . . . 272</a>
221 <a href="#7.17.1"> 7.17.1 Introduction . . . . . . . . . . . . . . . . . . . . . 272</a>
222 <a href="#7.17.2"> 7.17.2 Initialization . . . . . . . . . . . . . . . . . . . . 273</a>
223 <a href="#7.17.3"> 7.17.3 Order and consistency . . . . . . . . . . . . . . . . . 274</a>
224 <a href="#7.17.4"> 7.17.4 Fences . . . . . . . . . . . . . . . . . . . . . . . 277</a>
225 <a href="#7.17.5"> 7.17.5 Lock-free property . . . . . . . . . . . . . . . . . . 278</a>
226 <a href="#7.17.6"> 7.17.6 Atomic integer and address types . . . . . . . . . . . . 279</a>
227 <a href="#7.17.7"> 7.17.7 Operations on atomic types . . . . . . . . . . . . . . . 281</a>
228 <a href="#7.17.8"> 7.17.8 Atomic flag type and operations . . . . . . . . . . . . . 284</a>
229 <a href="#7.18"> 7.18 Boolean type and values <stdbool.h> . . . . . . . . . . . . 286</a>
230 <a href="#7.19"> 7.19 Common definitions <stddef.h> . . . . . . . . . . . . . . . 287</a>
231 <a href="#7.20"> 7.20 Integer types <stdint.h> . . . . . . . . . . . . . . . . . . 289</a>
236 <a href="#7.20.1"> 7.20.1 Integer types . . . . . . . . . . . . . . . . . . . . 289</a>
237 <a href="#7.20.2"> 7.20.2 Limits of specified-width integer types . . . . . . . . . . 291</a>
238 <a href="#7.20.3"> 7.20.3 Limits of other integer types . . . . . . . . . . . . . . 293</a>
239 <a href="#7.20.4"> 7.20.4 Macros for integer constants . . . . . . . . . . . . . . 294</a>
240 <a href="#7.21"> 7.21 Input/output <stdio.h> . . . . . . . . . . . . . . . . . . 296</a>
241 <a href="#7.21.1"> 7.21.1 Introduction . . . . . . . . . . . . . . . . . . . . . 296</a>
242 <a href="#7.21.2"> 7.21.2 Streams . . . . . . . . . . . . . . . . . . . . . . 298</a>
243 <a href="#7.21.3"> 7.21.3 Files . . . . . . . . . . . . . . . . . . . . . . . . 300</a>
244 <a href="#7.21.4"> 7.21.4 Operations on files . . . . . . . . . . . . . . . . . . 302</a>
245 <a href="#7.21.5"> 7.21.5 File access functions . . . . . . . . . . . . . . . . . 304</a>
246 <a href="#7.21.6"> 7.21.6 Formatted input/output functions . . . . . . . . . . . . 309</a>
247 <a href="#7.21.7"> 7.21.7 Character input/output functions . . . . . . . . . . . . . 330</a>
248 <a href="#7.21.8"> 7.21.8 Direct input/output functions . . . . . . . . . . . . . . 334</a>
249 <a href="#7.21.9"> 7.21.9 File positioning functions . . . . . . . . . . . . . . . 335</a>
250 <a href="#7.21.10"> 7.21.10 Error-handling functions . . . . . . . . . . . . . . . . 338</a>
251 <a href="#7.22"> 7.22 General utilities <stdlib.h> . . . . . . . . . . . . . . . . 340</a>
252 <a href="#7.22.1"> 7.22.1 Numeric conversion functions . . . . . . . . . . . . . . 341</a>
253 <a href="#7.22.2"> 7.22.2 Pseudo-random sequence generation functions . . . . . . . 346</a>
254 <a href="#7.22.3"> 7.22.3 Memory management functions . . . . . . . . . . . . . 347</a>
255 <a href="#7.22.4"> 7.22.4 Communication with the environment . . . . . . . . . . 349</a>
256 <a href="#7.22.5"> 7.22.5 Searching and sorting utilities . . . . . . . . . . . . . . 353</a>
257 <a href="#7.22.6"> 7.22.6 Integer arithmetic functions . . . . . . . . . . . . . . 355</a>
258 <a href="#7.22.7"> 7.22.7 Multibyte/wide character conversion functions . . . . . . . 356</a>
259 <a href="#7.22.8"> 7.22.8 Multibyte/wide string conversion functions . . . . . . . . 358</a>
260 <a href="#7.23"> 7.23 String handling <string.h> . . . . . . . . . . . . . . . . . 360</a>
261 <a href="#7.23.1"> 7.23.1 String function conventions . . . . . . . . . . . . . . . 360</a>
262 <a href="#7.23.2"> 7.23.2 Copying functions . . . . . . . . . . . . . . . . . . 360</a>
263 <a href="#7.23.3"> 7.23.3 Concatenation functions . . . . . . . . . . . . . . . . 362</a>
264 <a href="#7.23.4"> 7.23.4 Comparison functions . . . . . . . . . . . . . . . . . 363</a>
265 <a href="#7.23.5"> 7.23.5 Search functions . . . . . . . . . . . . . . . . . . . 365</a>
266 <a href="#7.23.6"> 7.23.6 Miscellaneous functions . . . . . . . . . . . . . . . . 368</a>
267 <a href="#7.24"> 7.24 Type-generic math <tgmath.h> . . . . . . . . . . . . . . . 370</a>
268 <a href="#7.25"> 7.25 Threads <threads.h> . . . . . . . . . . . . . . . . . . . 373</a>
269 <a href="#7.25.1"> 7.25.1 Introduction . . . . . . . . . . . . . . . . . . . . . 373</a>
270 <a href="#7.25.2"> 7.25.2 Initialization functions . . . . . . . . . . . . . . . . . 375</a>
271 <a href="#7.25.3"> 7.25.3 Condition variable functions . . . . . . . . . . . . . . 375</a>
272 <a href="#7.25.4"> 7.25.4 Mutex functions . . . . . . . . . . . . . . . . . . . 377</a>
273 <a href="#7.25.5"> 7.25.5 Thread functions . . . . . . . . . . . . . . . . . . . 380</a>
274 <a href="#7.25.6"> 7.25.6 Thread-specific storage functions . . . . . . . . . . . . 382</a>
275 <a href="#7.25.7"> 7.25.7 Time functions . . . . . . . . . . . . . . . . . . . . 384</a>
276 <a href="#7.26"> 7.26 Date and time <time.h> . . . . . . . . . . . . . . . . . . 385</a>
277 <a href="#7.26.1"> 7.26.1 Components of time . . . . . . . . . . . . . . . . . 385</a>
278 <a href="#7.26.2"> 7.26.2 Time manipulation functions . . . . . . . . . . . . . . 386</a>
279 <a href="#7.26.3"> 7.26.3 Time conversion functions . . . . . . . . . . . . . . . 388</a>
284 <a href="#7.27"> 7.27 Unicode utilities <uchar.h> . . . . . . . . . . . . . . . . . 395</a>
285 <a href="#7.27.1"> 7.27.1 Restartable multibyte/wide character conversion functions . . 395</a>
286 <a href="#7.28"> 7.28 Extended multibyte and wide character utilities <wchar.h> . . . . . 399</a>
287 <a href="#7.28.1"> 7.28.1 Introduction . . . . . . . . . . . . . . . . . . . . . 399</a>
288 <a href="#7.28.2"> 7.28.2 Formatted wide character input/output functions . . . . . . 400</a>
289 <a href="#7.28.3"> 7.28.3 Wide character input/output functions . . . . . . . . . . 418</a>
290 <a href="#7.28.4"> 7.28.4 General wide string utilities . . . . . . . . . . . . . . 422</a>
291 <a href="#7.28.4.1"> 7.28.4.1 Wide string numeric conversion functions . . . . . 423</a>
292 <a href="#7.28.4.2"> 7.28.4.2 Wide string copying functions . . . . . . . . . . 427</a>
293 <a href="#7.28.4.3"> 7.28.4.3 Wide string concatenation functions . . . . . . . 429</a>
294 <a href="#7.28.4.4"> 7.28.4.4 Wide string comparison functions . . . . . . . . 430</a>
295 <a href="#7.28.4.5"> 7.28.4.5 Wide string search functions . . . . . . . . . . 432</a>
296 <a href="#7.28.4.6"> 7.28.4.6 Miscellaneous functions . . . . . . . . . . . . 436</a>
297 <a href="#7.28.5"> 7.28.5 Wide character time conversion functions . . . . . . . . . 436</a>
298 <a href="#7.28.6"> 7.28.6 Extended multibyte/wide character conversion utilities . . . . 437</a>
299 <a href="#7.28.6.1"> 7.28.6.1 Single-byte/wide character conversion functions . . . 438</a>
300 <a href="#7.28.6.2"> 7.28.6.2 Conversion state functions . . . . . . . . . . . 438</a>
301 <a href="#7.28.6.3"> 7.28.6.3 Restartable multibyte/wide character conversion
302 functions . . . . . . . . . . . . . . . . . . 439</a>
303 <a href="#7.28.6.4"> 7.28.6.4 Restartable multibyte/wide string conversion
304 functions . . . . . . . . . . . . . . . . . . 441</a>
305 <a href="#7.29"> 7.29 Wide character classification and mapping utilities <wctype.h> . . . 444</a>
306 <a href="#7.29.1"> 7.29.1 Introduction . . . . . . . . . . . . . . . . . . . . . 444</a>
307 <a href="#7.29.2"> 7.29.2 Wide character classification utilities . . . . . . . . . . . 445</a>
308 <a href="#7.29.2.1"> 7.29.2.1 Wide character classification functions . . . . . . 445</a>
309 <a href="#7.29.2.2"> 7.29.2.2 Extensible wide character classification
310 functions . . . . . . . . . . . . . . . . . . 448</a>
311 <a href="#7.29.3"> 7.29.3 Wide character case mapping utilities . . . . . . . . . . . 450</a>
312 <a href="#7.29.3.1"> 7.29.3.1 Wide character case mapping functions . . . . . . 450</a>
313 <a href="#7.29.3.2"> 7.29.3.2 Extensible wide character case mapping
314 functions . . . . . . . . . . . . . . . . . . 450</a>
315 <a href="#7.30"> 7.30 Future library directions . . . . . . . . . . . . . . . . . . . 452</a>
316 <a href="#7.30.1"> 7.30.1 Complex arithmetic <complex.h> . . . . . . . . . . . 452</a>
317 <a href="#7.30.2"> 7.30.2 Character handling <ctype.h> . . . . . . . . . . . . 452</a>
318 <a href="#7.30.3"> 7.30.3 Errors <errno.h> . . . . . . . . . . . . . . . . . 452</a>
319 <a href="#7.30.4"> 7.30.4 Format conversion of integer types <inttypes.h> . . . . 452</a>
320 <a href="#7.30.5"> 7.30.5 Localization <locale.h> . . . . . . . . . . . . . . 452</a>
321 <a href="#7.30.6"> 7.30.6 Signal handling <signal.h> . . . . . . . . . . . . . 452</a>
322 <a href="#7.30.7"> 7.30.7 Boolean type and values <stdbool.h> . . . . . . . . . 452</a>
323 <a href="#7.30.8"> 7.30.8 Integer types <stdint.h> . . . . . . . . . . . . . . 452</a>
324 <a href="#7.30.9"> 7.30.9 Input/output <stdio.h> . . . . . . . . . . . . . . . 453</a>
325 <a href="#7.30.10"> 7.30.10 General utilities <stdlib.h> . . . . . . . . . . . . . 453</a>
326 <a href="#7.30.11"> 7.30.11 String handling <string.h> . . . . . . . . . . . . . 453</a>
332 <a href="#7.30.12"> 7.30.12 Extended multibyte and wide character utilities
333 <wchar.h> . . . . . . . . . . . . . . . . . . . . 453</a>
334 <a href="#7.30.13"> 7.30.13 Wide character classification and mapping utilities
335 <wctype.h> . . . . . . . . . . . . . . . . . . . . 453</a>
336 <a href="#A">Annex A (informative) Language syntax summary . . . . . . . . . . . . 454</a>
337 <a href="#A.1"> A.1 Lexical grammar . . . . . . . . . . . . . . . . . . . . . . 454</a>
338 <a href="#A.2"> A.2 Phrase structure grammar . . . . . . . . . . . . . . . . . . . 461</a>
339 <a href="#A.3"> A.3 Preprocessing directives . . . . . . . . . . . . . . . . . . . 469</a>
340 <a href="#B">Annex B (informative) Library summary . . . . . . . . . . . . . . . . 471</a>
341 <a href="#B.1"> B.1 Diagnostics <assert.h> . . . . . . . . . . . . . . . . . . 471</a>
342 <a href="#B.2"> B.2 Complex <complex.h> . . . . . . . . . . . . . . . . . . . 471</a>
343 <a href="#B.3"> B.3 Character handling <ctype.h> . . . . . . . . . . . . . . . . 473</a>
344 <a href="#B.4"> B.4 Errors <errno.h> . . . . . . . . . . . . . . . . . . . . . 473</a>
345 <a href="#B.5"> B.5 Floating-point environment <fenv.h> . . . . . . . . . . . . . 473</a>
346 <a href="#B.6"> B.6 Characteristics of floating types <float.h> . . . . . . . . . . . 474</a>
347 <a href="#B.7"> B.7 Format conversion of integer types <inttypes.h> . . . . . . . . 474</a>
348 <a href="#B.8"> B.8 Alternative spellings <iso646.h> . . . . . . . . . . . . . . . 475</a>
349 <a href="#B.9"> B.9 Sizes of integer types <limits.h> . . . . . . . . . . . . . . 475</a>
350 <a href="#B.10"> B.10 Localization <locale.h> . . . . . . . . . . . . . . . . . . 475</a>
351 <a href="#B.11"> B.11 Mathematics <math.h> . . . . . . . . . . . . . . . . . . . 475</a>
352 <a href="#B.12"> B.12 Nonlocal jumps <setjmp.h> . . . . . . . . . . . . . . . . 480</a>
353 <a href="#B.13"> B.13 Signal handling <signal.h> . . . . . . . . . . . . . . . . . 480</a>
354 <a href="#B.14"> B.14 Alignment <stdalign.h> . . . . . . . . . . . . . . . . . 481</a>
355 <a href="#B.15"> B.15 Variable arguments <stdarg.h> . . . . . . . . . . . . . . . 481</a>
356 <a href="#B.16"> B.16 Atomics <stdatomic.h> . . . . . . . . . . . . . . . . . . 481</a>
357 <a href="#B.17"> B.17 Boolean type and values <stdbool.h> . . . . . . . . . . . . 483</a>
358 <a href="#B.18"> B.18 Common definitions <stddef.h> . . . . . . . . . . . . . . . 483</a>
359 <a href="#B.19"> B.19 Integer types <stdint.h> . . . . . . . . . . . . . . . . . . 483</a>
360 <a href="#B.20"> B.20 Input/output <stdio.h> . . . . . . . . . . . . . . . . . . 484</a>
361 <a href="#B.21"> B.21 General utilities <stdlib.h> . . . . . . . . . . . . . . . . 487</a>
362 <a href="#B.22"> B.22 String handling <string.h> . . . . . . . . . . . . . . . . . 489</a>
363 <a href="#B.23"> B.23 Type-generic math <tgmath.h> . . . . . . . . . . . . . . . 491</a>
364 <a href="#B.24"> B.24 Threads <threads.h> . . . . . . . . . . . . . . . . . . . 491</a>
365 <a href="#B.25"> B.25 Date and time <time.h> . . . . . . . . . . . . . . . . . . 492</a>
366 <a href="#B.26"> B.26 Unicode utilities <uchar.h> . . . . . . . . . . . . . . . . . 493</a>
367 <a href="#B.27"> B.27 Extended multibyte/wide character utilities <wchar.h> . . . . . . 493</a>
368 <a href="#B.28"> B.28 Wide character classification and mapping utilities <wctype.h> . . . 498</a>
369 <a href="#C">Annex C (informative) Sequence points . . . . . . . . . . . . . . . . . 499</a>
370 <a href="#D">Annex D (normative) Universal character names for identifiers . . . . . . . 500</a>
371 <a href="#D.1"> D.1 Ranges of characters allowed . . . . . . . . . . . . . . . . . 500</a>
372 <a href="#D.2"> D.2 Ranges of characters disallowed initially . . . . . . . . . . . . . 500</a>
373 <a href="#E">Annex E (informative) Implementation limits . . . . . . . . . . . . . . 501</a>
377 <a href="#F">Annex F (normative) IEC 60559 floating-point arithmetic . . . . . . . . . . 503</a>
378 <a href="#F.1"> F.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 503</a>
379 <a href="#F.2"> F.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 503</a>
380 <a href="#F.3"> F.3 Operators and functions . . . . . . . . . . . . . . . . . . . 504</a>
381 <a href="#F.4"> F.4 Floating to integer conversion . . . . . . . . . . . . . . . . . 506</a>
382 <a href="#F.5"> F.5 Binary-decimal conversion . . . . . . . . . . . . . . . . . . 506</a>
383 <a href="#F.6"> F.6 The return statement . . . . . . . . . . . . . . . . . . . . 507</a>
384 <a href="#F.7"> F.7 Contracted expressions . . . . . . . . . . . . . . . . . . . . 507</a>
385 <a href="#F.8"> F.8 Floating-point environment . . . . . . . . . . . . . . . . . . 507</a>
386 <a href="#F.9"> F.9 Optimization . . . . . . . . . . . . . . . . . . . . . . . . 510</a>
387 <a href="#F.10"> F.10 Mathematics <math.h> . . . . . . . . . . . . . . . . . . . 513</a>
388 <a href="#F.10.1"> F.10.1 Trigonometric functions . . . . . . . . . . . . . . . . 514</a>
389 <a href="#F.10.2"> F.10.2 Hyperbolic functions . . . . . . . . . . . . . . . . . 516</a>
390 <a href="#F.10.3"> F.10.3 Exponential and logarithmic functions . . . . . . . . . . 516</a>
391 <a href="#F.10.4"> F.10.4 Power and absolute value functions . . . . . . . . . . . 520</a>
392 <a href="#F.10.5"> F.10.5 Error and gamma functions . . . . . . . . . . . . . . . 521</a>
393 <a href="#F.10.6"> F.10.6 Nearest integer functions . . . . . . . . . . . . . . . . 522</a>
394 <a href="#F.10.7"> F.10.7 Remainder functions . . . . . . . . . . . . . . . . . 524</a>
395 <a href="#F.10.8"> F.10.8 Manipulation functions . . . . . . . . . . . . . . . . 525</a>
396 <a href="#F.10.9"> F.10.9 Maximum, minimum, and positive difference functions . . . 526</a>
397 <a href="#F.10.10"> F.10.10 Floating multiply-add . . . . . . . . . . . . . . . . . 526</a>
398 <a href="#F.10.11"> F.10.11 Comparison macros . . . . . . . . . . . . . . . . . . 527</a>
399 <a href="#G">Annex G (normative) IEC 60559-compatible complex arithmetic . . . . . . . 528</a>
400 <a href="#G.1"> G.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 528</a>
401 <a href="#G.2"> G.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 528</a>
402 <a href="#G.3"> G.3 Conventions . . . . . . . . . . . . . . . . . . . . . . . . 528</a>
403 <a href="#G.4"> G.4 Conversions . . . . . . . . . . . . . . . . . . . . . . . . 529</a>
404 <a href="#G.4.1"> G.4.1 Imaginary types . . . . . . . . . . . . . . . . . . . 529</a>
405 <a href="#G.4.2"> G.4.2 Real and imaginary . . . . . . . . . . . . . . . . . . 529</a>
406 <a href="#G.4.3"> G.4.3 Imaginary and complex . . . . . . . . . . . . . . . . 529</a>
407 <a href="#G.5"> G.5 Binary operators . . . . . . . . . . . . . . . . . . . . . . 529</a>
408 <a href="#G.5.1"> G.5.1 Multiplicative operators . . . . . . . . . . . . . . . . 530</a>
409 <a href="#G.5.2"> G.5.2 Additive operators . . . . . . . . . . . . . . . . . . 533</a>
410 <a href="#G.6"> G.6 Complex arithmetic <complex.h> . . . . . . . . . . . . . . 533</a>
411 <a href="#G.6.1"> G.6.1 Trigonometric functions . . . . . . . . . . . . . . . . 535</a>
412 <a href="#G.6.2"> G.6.2 Hyperbolic functions . . . . . . . . . . . . . . . . . 535</a>
413 <a href="#G.6.3"> G.6.3 Exponential and logarithmic functions . . . . . . . . . . 539</a>
414 <a href="#G.6.4"> G.6.4 Power and absolute-value functions . . . . . . . . . . . 540</a>
415 <a href="#G.7"> G.7 Type-generic math <tgmath.h> . . . . . . . . . . . . . . . 541</a>
416 <a href="#H">Annex H (informative) Language independent arithmetic . . . . . . . . . . 542</a>
417 <a href="#H.1"> H.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 542</a>
418 <a href="#H.2"> H.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 542</a>
419 <a href="#H.3"> H.3 Notification . . . . . . . . . . . . . . . . . . . . . . . . 546</a>
424 <a href="#I">Annex I (informative) Common warnings . . . . . . . . . . . . . . . . 548</a>
425 <a href="#J">Annex J (informative) Portability issues . . . . . . . . . . . . . . . . . 550</a>
426 <a href="#J.1"> J.1 Unspecified behavior . . . . . . . . . . . . . . . . . . . . . 550</a>
427 <a href="#J.2"> J.2 Undefined behavior . . . . . . . . . . . . . . . . . . . . . 553</a>
428 <a href="#J.3"> J.3 Implementation-defined behavior . . . . . . . . . . . . . . . . 566</a>
429 <a href="#J.4"> J.4 Locale-specific behavior . . . . . . . . . . . . . . . . . . . 574</a>
430 <a href="#J.5"> J.5 Common extensions . . . . . . . . . . . . . . . . . . . . . 575</a>
431 <a href="#K">Annex K (normative) Bounds-checking interfaces . . . . . . . . . . . . . 578</a>
432 <a href="#K.1"> K.1 Background . . . . . . . . . . . . . . . . . . . . . . . . 578</a>
433 <a href="#K.2"> K.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 579</a>
434 <a href="#K.3"> K.3 Library . . . . . . . . . . . . . . . . . . . . . . . . . . 579</a>
435 <a href="#K.3.1"> K.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . 579</a>
436 <a href="#K.3.1.1"> K.3.1.1 Standard headers . . . . . . . . . . . . . . . 579</a>
437 <a href="#K.3.1.2"> K.3.1.2 Reserved identifiers . . . . . . . . . . . . . . 580</a>
438 <a href="#K.3.1.3"> K.3.1.3 Use of errno . . . . . . . . . . . . . . . . . 580</a>
439 <a href="#K.3.1.4"> K.3.1.4 Runtime-constraint violations . . . . . . . . . . 580</a>
440 <a href="#K.3.2"> K.3.2 Errors <errno.h> . . . . . . . . . . . . . . . . . 581</a>
441 <a href="#K.3.3"> K.3.3 Common definitions <stddef.h> . . . . . . . . . . . 581</a>
442 <a href="#K.3.4"> K.3.4 Integer types <stdint.h> . . . . . . . . . . . . . . 581</a>
443 <a href="#K.3.5"> K.3.5 Input/output <stdio.h> . . . . . . . . . . . . . . . 582</a>
444 <a href="#K.3.5.1"> K.3.5.1 Operations on files . . . . . . . . . . . . . . 582</a>
445 <a href="#K.3.5.2"> K.3.5.2 File access functions . . . . . . . . . . . . . . 584</a>
446 <a href="#K.3.5.3"> K.3.5.3 Formatted input/output functions . . . . . . . . . 587</a>
447 <a href="#K.3.5.4"> K.3.5.4 Character input/output functions . . . . . . . . . 598</a>
448 <a href="#K.3.6"> K.3.6 General utilities <stdlib.h> . . . . . . . . . . . . . 600</a>
449 <a href="#K.3.6.1"> K.3.6.1 Runtime-constraint handling . . . . . . . . . . 600</a>
450 <a href="#K.3.6.2"> K.3.6.2 Communication with the environment . . . . . . . 602</a>
451 <a href="#K.3.6.3"> K.3.6.3 Searching and sorting utilities . . . . . . . . . . 603</a>
452 <a href="#K.3.6.4"> K.3.6.4 Multibyte/wide character conversion functions . . . 606</a>
453 <a href="#K.3.6.5"> K.3.6.5 Multibyte/wide string conversion functions . . . . . 607</a>
454 <a href="#K.3.7"> K.3.7 String handling <string.h> . . . . . . . . . . . . . 610</a>
455 <a href="#K.3.7.1"> K.3.7.1 Copying functions . . . . . . . . . . . . . . 610</a>
456 <a href="#K.3.7.2"> K.3.7.2 Concatenation functions . . . . . . . . . . . . 613</a>
457 <a href="#K.3.7.3"> K.3.7.3 Search functions . . . . . . . . . . . . . . . 616</a>
458 <a href="#K.3.7.4"> K.3.7.4 Miscellaneous functions . . . . . . . . . . . . 617</a>
459 <a href="#K.3.8"> K.3.8 Date and time <time.h> . . . . . . . . . . . . . . . 620</a>
460 <a href="#K.3.8.1"> K.3.8.1 Components of time . . . . . . . . . . . . . . 620</a>
461 <a href="#K.3.8.2"> K.3.8.2 Time conversion functions . . . . . . . . . . . 620</a>
462 <a href="#K.3.9"> K.3.9 Extended multibyte and wide character utilities
463 <wchar.h> . . . . . . . . . . . . . . . . . . . . 623</a>
464 <a href="#K.3.9.1"> K.3.9.1 Formatted wide character input/output functions . . . 624</a>
465 <a href="#K.3.9.2"> K.3.9.2 General wide string utilities . . . . . . . . . . . 635</a>
471 <a href="#K.3.9.3"> K.3.9.3 Extended multibyte/wide character conversion
472 utilities . . . . . . . . . . . . . . . . . . . 643</a>
473 <a href="#L">Annex L (normative) Analyzability . . . . . . . . . . . . . . . . . . 648</a>
474 <a href="#L.1"> L.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 648</a>
475 <a href="#L.2"> L.2 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 648</a>
476 <a href="#L.3"> L.3 Requirements . . . . . . . . . . . . . . . . . . . . . . . . 649</a>
477 <a href="#Bibliography">Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . 650</a>
478 <a href="#Index">Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 653</a>
483 [<a name="pxii" href="#pxii">page xii</a>] (<a href="#Contents">Contents</a>)
485 <a name="Foreword" href="#Foreword"><b> Foreword</b></a>
486 1 ISO (the International Organization for Standardization) and IEC (the International
487 Electrotechnical Commission) form the specialized system for worldwide
488 standardization. National bodies that are member of ISO or IEC participate in the
489 development of International Standards through technical committees established by the
490 respective organization to deal with particular fields of technical activity. ISO and IEC
491 technical committees collaborate in fields of mutual interest. Other international
492 organizations, governmental and non-governmental, in liaison with ISO and IEC, also
493 take part in the work.
494 2 International Standards are drafted in accordance with the rules given in the ISO/IEC
495 Directives, Part 2. This International Standard was drafted in accordance with the fifth
497 3 In the field of information technology, ISO and IEC have established a joint technical
498 committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
499 committee are circulated to national bodies for voting. Publication as an International
500 Standard requires approval by at least 75% of the national bodies casting a vote.
501 4 Attention is drawn to the possibility that some of the elements of this document may be
502 the subject of patent rights. ISO and IEC shall not be held responsible for identifying any
503 or all such patent rights.
504 5 This International Standard was prepared by Joint Technical Committee ISO/IEC JTC 1,
505 Information technology, Subcommittee SC 22, Programming languages, their
506 environments and system software interfaces. The Working Group responsible for this
507 standard (WG 14) maintains a site on the World Wide Web at http://www.open-
508 std.org/JTC1/SC22/WG14/ containing additional information relevant to this
509 standard such as a Rationale for many of the decisions made during its preparation and a
510 log of Defect Reports and Responses.
511 6 This third edition cancels and replaces the second edition, ISO/IEC 9899:1999, as
512 corrected by ISO/IEC 9899:1999/Cor 1:2001, ISO/IEC 9899:1999/Cor 2:2004, and
513 ISO/IEC 9899:1999/Cor 3:2007. Major changes from the previous edition include:
514 -- conditional (optional) features (including some that were previously mandatory)
515 -- support for multiple threads of execution including an improved memory sequencing
516 model, atomic objects, and thread-local storage (<a href="#7.17"><stdatomic.h></a> and
517 <a href="#7.25"><threads.h></a>)
518 -- additional floating-point characteristic macros (<a href="#7.7"><float.h></a>)
519 -- querying and specifying alignment of objects (<a href="#7.15"><stdalign.h></a>, <a href="#7.22"><stdlib.h></a>)
520 -- Unicode characters and strings (<a href="#7.27"><uchar.h></a>) (originally specified in
521 ISO/IEC TR 19769:2004)
522 -- type-generic expressions
525 [<a name="pxiii" href="#pxiii">page xiii</a>] (<a href="#Contents">Contents</a>)
528 -- anonymous structures and unions
529 -- no-return functions
530 -- macros to create complex numbers (<a href="#7.3"><complex.h></a>)
531 -- support for opening files for exclusive access
532 -- removed the gets function (<a href="#7.21"><stdio.h></a>)
533 -- added the aligned_alloc, at_quick_exit, and quick_exit functions
534 (<a href="#7.22"><stdlib.h></a>)
535 -- (conditional) support for bounds-checking interfaces (originally specified in
536 ISO/IEC TR 24731-1:2007)
537 -- (conditional) support for analyzability
538 7 Major changes in the second edition included:
539 -- restricted character set support via digraphs and <a href="#7.9"><iso646.h></a> (originally specified
541 -- wide character library support in <a href="#7.28"><wchar.h></a> and <a href="#7.29"><wctype.h></a> (originally
543 -- more precise aliasing rules via effective type
544 -- restricted pointers
545 -- variable length arrays
546 -- flexible array members
547 -- static and type qualifiers in parameter array declarators
548 -- complex (and imaginary) support in <a href="#7.3"><complex.h></a>
549 -- type-generic math macros in <a href="#7.24"><tgmath.h></a>
550 -- the long long int type and library functions
551 -- increased minimum translation limits
552 -- additional floating-point characteristics in <a href="#7.7"><float.h></a>
553 -- remove implicit int
554 -- reliable integer division
555 -- universal character names (\u and \U)
556 -- extended identifiers
557 -- hexadecimal floating-point constants and %a and %A printf/scanf conversion
562 [<a name="pxiv" href="#pxiv">page xiv</a>] (<a href="#Contents">Contents</a>)
565 -- designated initializers
567 -- extended integer types and library functions in <a href="#7.8"><inttypes.h></a> and <a href="#7.20"><stdint.h></a>
568 -- remove implicit function declaration
569 -- preprocessor arithmetic done in intmax_t/uintmax_t
570 -- mixed declarations and code
571 -- new block scopes for selection and iteration statements
572 -- integer constant type rules
573 -- integer promotion rules
574 -- macros with a variable number of arguments
575 -- the vscanf family of functions in <a href="#7.21"><stdio.h></a> and <a href="#7.28"><wchar.h></a>
576 -- additional math library functions in <a href="#7.12"><math.h></a>
577 -- treatment of error conditions by math library functions (math_errhandling)
578 -- floating-point environment access in <a href="#7.6"><fenv.h></a>
579 -- IEC 60559 (also known as IEC 559 or IEEE arithmetic) support
580 -- trailing comma allowed in enum declaration
581 -- %lf conversion specifier allowed in printf
583 -- the snprintf family of functions in <a href="#7.21"><stdio.h></a>
584 -- boolean type in <a href="#7.18"><stdbool.h></a>
585 -- idempotent type qualifiers
586 -- empty macro arguments
587 -- new structure type compatibility rules (tag compatibility)
588 -- additional predefined macro names
589 -- _Pragma preprocessing operator
591 -- __func__ predefined identifier
593 -- additional strftime conversion specifiers
594 -- LIA compatibility annex
597 [<a name="pxv" href="#pxv">page xv</a>] (<a href="#Contents">Contents</a>)
599 -- deprecate ungetc at the beginning of a binary file
600 -- remove deprecation of aliased array parameters
601 -- conversion of array to pointer not limited to lvalues
602 -- relaxed constraints on aggregate and union initialization
603 -- relaxed restrictions on portable header names
604 -- return without expression not permitted in function that returns a value (and vice
606 8 Annexes D, F, G, K, and L form a normative part of this standard; annexes A, B, C, E, H, *
607 I, J, the bibliography, and the index are for information only. In accordance with Part 2 of
608 the ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples
609 are also for information only.
614 [<a name="pxvi" href="#pxvi">page xvi</a>] (<a href="#Contents">Contents</a>)
616 <a name="Introduction" href="#Introduction"><b> Introduction</b></a>
617 1 With the introduction of new devices and extended character sets, new features may be
618 added to this International Standard. Subclauses in the language and library clauses warn
619 implementors and programmers of usages which, though valid in themselves, may
620 conflict with future additions.
621 2 Certain features are obsolescent, which means that they may be considered for
622 withdrawal in future revisions of this International Standard. They are retained because
623 of their widespread use, but their use in new implementations (for implementation
624 features) or new programs (for language [6.11] or library features [7.30]) is discouraged.
625 3 This International Standard is divided into four major subdivisions:
626 -- preliminary elements (clauses 1-4);
627 -- the characteristics of environments that translate and execute C programs (clause 5);
628 -- the language syntax, constraints, and semantics (clause 6);
629 -- the library facilities (clause 7).
630 4 Examples are provided to illustrate possible forms of the constructions described.
631 Footnotes are provided to emphasize consequences of the rules described in that
632 subclause or elsewhere in this International Standard. References are used to refer to
633 other related subclauses. Recommendations are provided to give advice or guidance to
634 implementors. Annexes provide additional information and summarize the information
635 contained in this International Standard. A bibliography lists documents that were
636 referred to during the preparation of the standard.
637 5 The language clause (clause 6) is derived from ''The C Reference Manual''.
638 6 The library clause (clause 7) is based on the 1984 /usr/group Standard.
643 [<a name="pxvii" href="#pxvii">page xvii</a>] (<a href="#Contents">Contents</a>)
647 [<a name="pxviii" href="#pxviii">page xviii</a>] (<a href="#Contents">Contents</a>)
651 Programming languages -- C
655 <a name="1" href="#1"><b> 1. Scope</b></a>
656 1 This International Standard specifies the form and establishes the interpretation of
657 programs written in the C programming language.<sup><a href="#note1"><b>1)</b></a></sup> It specifies
658 -- the representation of C programs;
659 -- the syntax and constraints of the C language;
660 -- the semantic rules for interpreting C programs;
661 -- the representation of input data to be processed by C programs;
662 -- the representation of output data produced by C programs;
663 -- the restrictions and limits imposed by a conforming implementation of C.
664 2 This International Standard does not specify
665 -- the mechanism by which C programs are transformed for use by a data-processing
667 -- the mechanism by which C programs are invoked for use by a data-processing
669 -- the mechanism by which input data are transformed for use by a C program;
670 -- the mechanism by which output data are transformed after being produced by a C
672 -- the size or complexity of a program and its data that will exceed the capacity of any
673 specific data-processing system or the capacity of a particular processor;
674 -- all minimal requirements of a data-processing system that is capable of supporting a
675 conforming implementation.
678 <sup><a name="note1" href="#note1"><b>1)</b></a></sup> This International Standard is designed to promote the portability of C programs among a variety of
679 data-processing systems. It is intended for use by implementors and programmers.
681 [<a name="p1" href="#p1">page 1</a>] (<a href="#Contents">Contents</a>)
684 <a name="2" href="#2"><b> 2. Normative references</b></a>
685 1 The following referenced documents are indispensable for the application of this
686 document. For dated references, only the edition cited applies. For undated references,
687 the latest edition of the referenced document (including any amendments) applies.
688 2 ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and symbols for
689 use in the physical sciences and technology.
690 3 ISO/IEC 646, Information technology -- ISO 7-bit coded character set for information
692 4 ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1: Fundamental
694 5 ISO 4217, Codes for the representation of currencies and funds.
695 6 ISO 8601, Data elements and interchange formats -- Information interchange --
696 Representation of dates and times.
697 7 ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded
699 8 IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems (previously
700 designated IEC 559:1989).
705 [<a name="p2" href="#p2">page 2</a>] (<a href="#Contents">Contents</a>)
708 <a name="3" href="#3"><b> 3. Terms, definitions, and symbols</b></a>
709 1 For the purposes of this International Standard, the following definitions apply. Other
710 terms are defined where they appear in italic type or on the left side of a syntax rule.
711 Terms explicitly defined in this International Standard are not to be presumed to refer
712 implicitly to similar terms defined elsewhere. Terms not defined in this International
713 Standard are to be interpreted according to ISO/IEC 2382-1. Mathematical symbols not
714 defined in this International Standard are to be interpreted according to ISO 31-11.
715 <a name="3.1" href="#3.1"><b> 3.1</b></a>
717 <execution-time action> to read or modify the value of an object
718 2 NOTE 1 Where only one of these two actions is meant, ''read'' or ''modify'' is used.
720 3 NOTE 2 ''Modify'' includes the case where the new value being stored is the same as the previous value.
722 4 NOTE 3 Expressions that are not evaluated do not access objects.
724 <a name="3.2" href="#3.2"><b> 3.2</b></a>
726 requirement that objects of a particular type be located on storage boundaries with
727 addresses that are particular multiples of a byte address
728 <a name="3.3" href="#3.3"><b> 3.3</b></a>
731 actual parameter (deprecated)
732 expression in the comma-separated list bounded by the parentheses in a function call
733 expression, or a sequence of preprocessing tokens in the comma-separated list bounded
734 by the parentheses in a function-like macro invocation
735 <a name="3.4" href="#3.4"><b> 3.4</b></a>
737 external appearance or action
738 <a name="3.4.1" href="#3.4.1"><b> 3.4.1</b></a>
739 1 implementation-defined behavior
740 unspecified behavior where each implementation documents how the choice is made
741 2 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
742 when a signed integer is shifted right.
744 <a name="3.4.2" href="#3.4.2"><b> 3.4.2</b></a>
745 1 locale-specific behavior
746 behavior that depends on local conventions of nationality, culture, and language that each
747 implementation documents
750 [<a name="p3" href="#p3">page 3</a>] (<a href="#Contents">Contents</a>)
752 2 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
753 characters other than the 26 lowercase Latin letters.
755 <a name="3.4.3" href="#3.4.3"><b> 3.4.3</b></a>
757 behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
758 for which this International Standard imposes no requirements
759 2 NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable
760 results, to behaving during translation or program execution in a documented manner characteristic of the
761 environment (with or without the issuance of a diagnostic message), to terminating a translation or
762 execution (with the issuance of a diagnostic message).
764 3 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
766 <a name="3.4.4" href="#3.4.4"><b> 3.4.4</b></a>
767 1 unspecified behavior
768 use of an unspecified value, or other behavior where this International Standard provides
769 two or more possibilities and imposes no further requirements on which is chosen in any
771 2 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
774 <a name="3.5" href="#3.5"><b> 3.5</b></a>
776 unit of data storage in the execution environment large enough to hold an object that may
777 have one of two values
778 2 NOTE It need not be possible to express the address of each individual bit of an object.
780 <a name="3.6" href="#3.6"><b> 3.6</b></a>
782 addressable unit of data storage large enough to hold any member of the basic character
783 set of the execution environment
784 2 NOTE 1 It is possible to express the address of each individual byte of an object uniquely.
786 3 NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
787 defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order
790 <a name="3.7" href="#3.7"><b> 3.7</b></a>
792 <abstract> member of a set of elements used for the organization, control, or
793 representation of data
794 <a name="3.7.1" href="#3.7.1"><b> 3.7.1</b></a>
796 single-byte character
797 <C> bit representation that fits in a byte
798 [<a name="p4" href="#p4">page 4</a>] (<a href="#Contents">Contents</a>)
800 <a name="3.7.2" href="#3.7.2"><b> 3.7.2</b></a>
801 1 multibyte character
802 sequence of one or more bytes representing a member of the extended character set of
803 either the source or the execution environment
804 2 NOTE The extended character set is a superset of the basic character set.
806 <a name="3.7.3" href="#3.7.3"><b> 3.7.3</b></a>
808 bit representation that fits in an object of type wchar_t, capable of representing any
809 character in the current locale
810 <a name="3.8" href="#3.8"><b> 3.8</b></a>
812 restriction, either syntactic or semantic, by which the exposition of language elements is
814 <a name="3.9" href="#3.9"><b> 3.9</b></a>
815 1 correctly rounded result
816 representation in the result format that is nearest in value, subject to the current rounding
817 mode, to what the result would be given unlimited range and precision
818 <a name="3.10" href="#3.10"><b> 3.10</b></a>
820 message belonging to an implementation-defined subset of the implementation's message
822 <a name="3.11" href="#3.11"><b> 3.11</b></a>
824 reference to a later subclause of this International Standard that contains additional
825 information relevant to this subclause
826 <a name="3.12" href="#3.12"><b> 3.12</b></a>
828 particular set of software, running in a particular translation environment under particular
829 control options, that performs translation of programs for, and supports execution of
830 functions in, a particular execution environment
831 <a name="3.13" href="#3.13"><b> 3.13</b></a>
832 1 implementation limit
833 restriction imposed upon programs by the implementation
834 <a name="3.14" href="#3.14"><b> 3.14</b></a>
836 either an object of scalar type, or a maximal sequence of adjacent bit-fields all having
839 [<a name="p5" href="#p5">page 5</a>] (<a href="#Contents">Contents</a>)
841 2 NOTE 1 Two threads of execution can update and access separate memory locations without interfering
844 3 NOTE 2 A bit-field and an adjacent non-bit-field member are in separate memory locations. The same
845 applies to two bit-fields, if one is declared inside a nested structure declaration and the other is not, or if the
846 two are separated by a zero-length bit-field declaration, or if they are separated by a non-bit-field member
847 declaration. It is not safe to concurrently update two non-atomic bit-fields in the same structure if all
848 members declared between them are also (non-zero-length) bit-fields, no matter what the sizes of those
849 intervening bit-fields happen to be.
851 4 EXAMPLE A structure declared as
854 int b:5, c:11, :0, d:8;
855 struct { int ee:8; } e;
857 contains four separate memory locations: The member a, and bit-fields d and e.ee are each separate
858 memory locations, and can be modified concurrently without interfering with each other. The bit-fields b
859 and c together constitute the fourth memory location. The bit-fields b and c cannot be concurrently
860 modified, but b and a, for example, can be.
862 <a name="3.15" href="#3.15"><b> 3.15</b></a>
864 region of data storage in the execution environment, the contents of which can represent
866 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>.
868 <a name="3.16" href="#3.16"><b> 3.16</b></a>
871 formal argument (deprecated)
872 object declared as part of a function declaration or definition that acquires a value on
873 entry to the function, or an identifier from the comma-separated list bounded by the
874 parentheses immediately following the macro name in a function-like macro definition
875 <a name="3.17" href="#3.17"><b> 3.17</b></a>
876 1 recommended practice
877 specification that is strongly recommended as being in keeping with the intent of the
878 standard, but that may be impractical for some implementations
879 <a name="3.18" href="#3.18"><b> 3.18</b></a>
881 requirement on a program when calling a library function
882 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
883 need not be diagnosed at translation time.
885 3 NOTE 2 Implementations that support the extensions in <a href="#K">annex K</a> are required to verify that the runtime-
886 constraints for a library function are not violated by the program; see <a href="#K.3.1.4">K.3.1.4</a>.
888 [<a name="p6" href="#p6">page 6</a>] (<a href="#Contents">Contents</a>)
890 <a name="3.19" href="#3.19"><b> 3.19</b></a>
892 precise meaning of the contents of an object when interpreted as having a specific type
893 <a name="3.19.1" href="#3.19.1"><b> 3.19.1</b></a>
894 1 implementation-defined value
895 unspecified value where each implementation documents how the choice is made
896 <a name="3.19.2" href="#3.19.2"><b> 3.19.2</b></a>
897 1 indeterminate value
898 either an unspecified value or a trap representation
899 <a name="3.19.3" href="#3.19.3"><b> 3.19.3</b></a>
901 valid value of the relevant type where this International Standard imposes no
902 requirements on which value is chosen in any instance
903 2 NOTE An unspecified value cannot be a trap representation.
905 <a name="3.19.4" href="#3.19.4"><b> 3.19.4</b></a>
906 1 trap representation
907 an object representation that need not represent a value of the object type
908 <a name="3.19.5" href="#3.19.5"><b> 3.19.5</b></a>
910 interrupt execution of the program such that no further operations are performed
911 2 NOTE In this International Standard, when the word ''trap'' is not immediately followed by
912 ''representation'', this is the intended usage.<sup><a href="#note2"><b>2)</b></a></sup>
914 <a name="3.20" href="#3.20"><b> 3.20</b></a>
916 ceiling of x: the least integer greater than or equal to x
917 2 EXAMPLE [^2.4^] is 3, [^-2.4^] is -2.
919 <a name="3.21" href="#3.21"><b> 3.21</b></a>
921 floor of x: the greatest integer less than or equal to x
922 2 EXAMPLE [_2.4_] is 2, [_-2.4_] is -3.
927 <sup><a name="note2" href="#note2"><b>2)</b></a></sup> For example, ''Trapping or stopping (if supported) is disabled...'' (<a href="#F.8.2">F.8.2</a>). Note that fetching a trap
928 representation might perform a trap but is not required to (see <a href="#6.2.6.1">6.2.6.1</a>).
930 [<a name="p7" href="#p7">page 7</a>] (<a href="#Contents">Contents</a>)
933 <a name="4" href="#4"><b> 4. Conformance</b></a>
934 1 In this International Standard, ''shall'' is to be interpreted as a requirement on an
935 implementation or on a program; conversely, ''shall not'' is to be interpreted as a
937 2 If a ''shall'' or ''shall not'' requirement that appears outside of a constraint or runtime-
938 constraint is violated, the behavior is undefined. Undefined behavior is otherwise
939 indicated in this International Standard by the words ''undefined behavior'' or by the
940 omission of any explicit definition of behavior. There is no difference in emphasis among
941 these three; they all describe ''behavior that is undefined''.
942 3 A program that is correct in all other aspects, operating on correct data, containing
943 unspecified behavior shall be a correct program and act in accordance with <a href="#5.1.2.3">5.1.2.3</a>.
944 4 The implementation shall not successfully translate a preprocessing translation unit
945 containing a #error preprocessing directive unless it is part of a group skipped by
946 conditional inclusion.
947 5 A strictly conforming program shall use only those features of the language and library
948 specified in this International Standard.<sup><a href="#note3"><b>3)</b></a></sup> It shall not produce output dependent on any
949 unspecified, undefined, or implementation-defined behavior, and shall not exceed any
950 minimum implementation limit.
951 6 The two forms of conforming implementation are hosted and freestanding. A conforming
952 hosted implementation shall accept any strictly conforming program. A conforming
953 freestanding implementation shall accept any strictly conforming program that does not
954 use complex types and in which the use of the features specified in the library clause
955 (clause 7) is confined to the contents of the standard headers <a href="#7.7"><float.h></a>,
956 <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>,
957 <a href="#7.19"><stddef.h></a>, and <a href="#7.20"><stdint.h></a>. A conforming implementation may have extensions
958 (including additional library functions), provided they do not alter the behavior of any
959 strictly conforming program.<sup><a href="#note4"><b>4)</b></a></sup>
963 <sup><a name="note3" href="#note3"><b>3)</b></a></sup> 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
964 by an appropriate conditional inclusion preprocessing directive using the related macro. For example:
965 #ifdef __STDC_IEC_559__ /* FE_UPWARD defined */
967 fesetround(FE_UPWARD);
971 <sup><a name="note4" href="#note4"><b>4)</b></a></sup> This implies that a conforming implementation reserves no identifiers other than those explicitly
972 reserved in this International Standard.
974 [<a name="p8" href="#p8">page 8</a>] (<a href="#Contents">Contents</a>)
976 7 A conforming program is one that is acceptable to a conforming implementation.<sup><a href="#note5"><b>5)</b></a></sup>
977 8 An implementation shall be accompanied by a document that defines all implementation-
978 defined and locale-specific characteristics and all extensions.
979 Forward references: conditional inclusion (<a href="#6.10.1">6.10.1</a>), error directive (<a href="#6.10.5">6.10.5</a>),
980 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>
981 (<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>),
982 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>
983 (<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>).
988 <sup><a name="note5" href="#note5"><b>5)</b></a></sup> Strictly conforming programs are intended to be maximally portable among conforming
989 implementations. Conforming programs may depend upon nonportable features of a conforming
992 [<a name="p9" href="#p9">page 9</a>] (<a href="#Contents">Contents</a>)
995 <a name="5" href="#5"><b> 5. Environment</b></a>
996 1 An implementation translates C source files and executes C programs in two data-
997 processing-system environments, which will be called the translation environment and
998 the execution environment in this International Standard. Their characteristics define and
999 constrain the results of executing conforming C programs constructed according to the
1000 syntactic and semantic rules for conforming implementations.
1001 Forward references: In this clause, only a few of many possible forward references
1003 <a name="5.1" href="#5.1"><b> 5.1 Conceptual models</b></a>
1004 <a name="5.1.1" href="#5.1.1"><b> 5.1.1 Translation environment</b></a>
1005 <a name="5.1.1.1" href="#5.1.1.1"><b> 5.1.1.1 Program structure</b></a>
1006 1 A C program need not all be translated at the same time. The text of the program is kept
1007 in units called source files, (or preprocessing files) in this International Standard. A
1008 source file together with all the headers and source files included via the preprocessing
1009 directive #include is known as a preprocessing translation unit. After preprocessing, a
1010 preprocessing translation unit is called a translation unit. Previously translated translation
1011 units may be preserved individually or in libraries. The separate translation units of a
1012 program communicate by (for example) calls to functions whose identifiers have external
1013 linkage, manipulation of objects whose identifiers have external linkage, or manipulation
1014 of data files. Translation units may be separately translated and then later linked to
1015 produce an executable program.
1016 Forward references: linkages of identifiers (<a href="#6.2.2">6.2.2</a>), external definitions (<a href="#6.9">6.9</a>),
1017 preprocessing directives (<a href="#6.10">6.10</a>).
1018 <a name="5.1.1.2" href="#5.1.1.2"><b> 5.1.1.2 Translation phases</b></a>
1019 1 The precedence among the syntax rules of translation is specified by the following
1020 phases.<sup><a href="#note6"><b>6)</b></a></sup>
1021 1. Physical source file multibyte characters are mapped, in an implementation-
1022 defined manner, to the source character set (introducing new-line characters for
1023 end-of-line indicators) if necessary. Trigraph sequences are replaced by
1024 corresponding single-character internal representations.
1028 <sup><a name="note6" href="#note6"><b>6)</b></a></sup> Implementations shall behave as if these separate phases occur, even though many are typically folded
1029 together in practice. Source files, translation units, and translated translation units need not
1030 necessarily be stored as files, nor need there be any one-to-one correspondence between these entities
1031 and any external representation. The description is conceptual only, and does not specify any
1032 particular implementation.
1034 [<a name="p10" href="#p10">page 10</a>] (<a href="#Contents">Contents</a>)
1036 2. Each instance of a backslash character (\) immediately followed by a new-line
1037 character is deleted, splicing physical source lines to form logical source lines.
1038 Only the last backslash on any physical source line shall be eligible for being part
1039 of such a splice. A source file that is not empty shall end in a new-line character,
1040 which shall not be immediately preceded by a backslash character before any such
1041 splicing takes place.
1042 3. The source file is decomposed into preprocessing tokens<sup><a href="#note7"><b>7)</b></a></sup> and sequences of
1043 white-space characters (including comments). A source file shall not end in a
1044 partial preprocessing token or in a partial comment. Each comment is replaced by
1045 one space character. New-line characters are retained. Whether each nonempty
1046 sequence of white-space characters other than new-line is retained or replaced by
1047 one space character is implementation-defined.
1048 4. Preprocessing directives are executed, macro invocations are expanded, and
1049 _Pragma unary operator expressions are executed. If a character sequence that
1050 matches the syntax of a universal character name is produced by token
1051 concatenation (<a href="#6.10.3.3">6.10.3.3</a>), the behavior is undefined. A #include preprocessing
1052 directive causes the named header or source file to be processed from phase 1
1053 through phase 4, recursively. All preprocessing directives are then deleted.
1054 5. Each source character set member and escape sequence in character constants and
1055 string literals is converted to the corresponding member of the execution character
1056 set; if there is no corresponding member, it is converted to an implementation-
1057 defined member other than the null (wide) character.<sup><a href="#note8"><b>8)</b></a></sup>
1058 6. Adjacent string literal tokens are concatenated.
1059 7. White-space characters separating tokens are no longer significant. Each
1060 preprocessing token is converted into a token. The resulting tokens are
1061 syntactically and semantically analyzed and translated as a translation unit.
1062 8. All external object and function references are resolved. Library components are
1063 linked to satisfy external references to functions and objects not defined in the
1064 current translation. All such translator output is collected into a program image
1065 which contains information needed for execution in its execution environment.
1066 Forward references: universal character names (<a href="#6.4.3">6.4.3</a>), lexical elements (<a href="#6.4">6.4</a>),
1067 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>).
1071 <sup><a name="note7" href="#note7"><b>7)</b></a></sup> As described in <a href="#6.4">6.4</a>, the process of dividing a source file's characters into preprocessing tokens is
1072 context-dependent. For example, see the handling of < within a #include preprocessing directive.
1073 <sup><a name="note8" href="#note8"><b>8)</b></a></sup> An implementation need not convert all non-corresponding source characters to the same execution
1076 [<a name="p11" href="#p11">page 11</a>] (<a href="#Contents">Contents</a>)
1078 <a name="5.1.1.3" href="#5.1.1.3"><b> 5.1.1.3 Diagnostics</b></a>
1079 1 A conforming implementation shall produce at least one diagnostic message (identified in
1080 an implementation-defined manner) if a preprocessing translation unit or translation unit
1081 contains a violation of any syntax rule or constraint, even if the behavior is also explicitly
1082 specified as undefined or implementation-defined. Diagnostic messages need not be
1083 produced in other circumstances.<sup><a href="#note9"><b>9)</b></a></sup>
1084 2 EXAMPLE An implementation shall issue a diagnostic for the translation unit:
1087 because in those cases where wording in this International Standard describes the behavior for a construct
1088 as being both a constraint error and resulting in undefined behavior, the constraint error shall be diagnosed.
1090 <a name="5.1.2" href="#5.1.2"><b> 5.1.2 Execution environments</b></a>
1091 1 Two execution environments are defined: freestanding and hosted. In both cases,
1092 program startup occurs when a designated C function is called by the execution
1093 environment. All objects with static storage duration shall be initialized (set to their
1094 initial values) before program startup. The manner and timing of such initialization are
1095 otherwise unspecified. Program termination returns control to the execution
1097 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>).
1098 <a name="5.1.2.1" href="#5.1.2.1"><b> 5.1.2.1 Freestanding environment</b></a>
1099 1 In a freestanding environment (in which C program execution may take place without any
1100 benefit of an operating system), the name and type of the function called at program
1101 startup are implementation-defined. Any library facilities available to a freestanding
1102 program, other than the minimal set required by clause 4, are implementation-defined.
1103 2 The effect of program termination in a freestanding environment is implementation-
1105 <a name="5.1.2.2" href="#5.1.2.2"><b> 5.1.2.2 Hosted environment</b></a>
1106 1 A hosted environment need not be provided, but shall conform to the following
1107 specifications if present.
1112 <sup><a name="note9" href="#note9"><b>9)</b></a></sup> The intent is that an implementation should identify the nature of, and where possible localize, each
1113 violation. Of course, an implementation is free to produce any number of diagnostics as long as a
1114 valid program is still correctly translated. It may also successfully translate an invalid program.
1116 [<a name="p12" href="#p12">page 12</a>] (<a href="#Contents">Contents</a>)
1118 <a name="5.1.2.2.1" href="#5.1.2.2.1"><b> 5.1.2.2.1 Program startup</b></a>
1119 1 The function called at program startup is named main. The implementation declares no
1120 prototype for this function. It shall be defined with a return type of int and with no
1122 int main(void) { /* ... */ }
1123 or with two parameters (referred to here as argc and argv, though any names may be
1124 used, as they are local to the function in which they are declared):
1125 int main(int argc, char *argv[]) { /* ... */ }
1126 or equivalent;<sup><a href="#note10"><b>10)</b></a></sup> or in some other implementation-defined manner.
1127 2 If they are declared, the parameters to the main function shall obey the following
1129 -- The value of argc shall be nonnegative.
1130 -- argv[argc] shall be a null pointer.
1131 -- If the value of argc is greater than zero, the array members argv[0] through
1132 argv[argc-1] inclusive shall contain pointers to strings, which are given
1133 implementation-defined values by the host environment prior to program startup. The
1134 intent is to supply to the program information determined prior to program startup
1135 from elsewhere in the hosted environment. If the host environment is not capable of
1136 supplying strings with letters in both uppercase and lowercase, the implementation
1137 shall ensure that the strings are received in lowercase.
1138 -- If the value of argc is greater than zero, the string pointed to by argv[0]
1139 represents the program name; argv[0][0] shall be the null character if the
1140 program name is not available from the host environment. If the value of argc is
1141 greater than one, the strings pointed to by argv[1] through argv[argc-1]
1142 represent the program parameters.
1143 -- The parameters argc and argv and the strings pointed to by the argv array shall
1144 be modifiable by the program, and retain their last-stored values between program
1145 startup and program termination.
1146 <a name="5.1.2.2.2" href="#5.1.2.2.2"><b> 5.1.2.2.2 Program execution</b></a>
1147 1 In a hosted environment, a program may use all the functions, macros, type definitions,
1148 and objects described in the library clause (clause 7).
1153 <sup><a name="note10" href="#note10"><b>10)</b></a></sup> Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as
1154 char ** argv, and so on.
1156 [<a name="p13" href="#p13">page 13</a>] (<a href="#Contents">Contents</a>)
1158 <a name="5.1.2.2.3" href="#5.1.2.2.3"><b> 5.1.2.2.3 Program termination</b></a>
1159 1 If the return type of the main function is a type compatible with int, a return from the
1160 initial call to the main function is equivalent to calling the exit function with the value
1161 returned by the main function as its argument;<sup><a href="#note11"><b>11)</b></a></sup> reaching the } that terminates the
1162 main function returns a value of 0. If the return type is not compatible with int, the
1163 termination status returned to the host environment is unspecified.
1164 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>).
1165 <a name="5.1.2.3" href="#5.1.2.3"><b> 5.1.2.3 Program execution</b></a>
1166 1 The semantic descriptions in this International Standard describe the behavior of an
1167 abstract machine in which issues of optimization are irrelevant.
1168 2 Accessing a volatile object, modifying an object, modifying a file, or calling a function
1169 that does any of those operations are all side effects,<sup><a href="#note12"><b>12)</b></a></sup> which are changes in the state of
1170 the execution environment. Evaluation of an expression in general includes both value
1171 computations and initiation of side effects. Value computation for an lvalue expression
1172 includes determining the identity of the designated object.
1173 3 Sequenced before is an asymmetric, transitive, pair-wise relation between evaluations
1174 executed by a single thread, which induces a partial order among those evaluations.
1175 Given any two evaluations A and B, if A is sequenced before B, then the execution of A
1176 shall precede the execution of B. (Conversely, if A is sequenced before B, then B is
1177 sequenced after A.) If A is not sequenced before or after B, then A and B are
1178 unsequenced. Evaluations A and B are indeterminately sequenced when A is sequenced
1179 either before or after B, but it is unspecified which.<sup><a href="#note13"><b>13)</b></a></sup> The presence of a sequence point
1180 between the evaluation of expressions A and B implies that every value computation and
1181 side effect associated with A is sequenced before every value computation and side effect
1182 associated with B. (A summary of the sequence points is given in <a href="#C">annex C</a>.)
1183 4 In the abstract machine, all expressions are evaluated as specified by the semantics. An
1184 actual implementation need not evaluate part of an expression if it can deduce that its
1185 value is not used and that no needed side effects are produced (including any caused by
1187 <sup><a name="note11" href="#note11"><b>11)</b></a></sup> In accordance with <a href="#6.2.4">6.2.4</a>, the lifetimes of objects with automatic storage duration declared in main
1188 will have ended in the former case, even where they would not have in the latter.
1189 <sup><a name="note12" href="#note12"><b>12)</b></a></sup> The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status
1190 flags and control modes. Floating-point operations implicitly set the status flags; modes affect result
1191 values of floating-point operations. Implementations that support such floating-point state are
1192 required to regard changes to it as side effects -- see <a href="#F">annex F</a> for details. The floating-point
1193 environment library <a href="#7.6"><fenv.h></a> provides a programming facility for indicating when these side
1194 effects matter, freeing the implementations in other cases.
1195 <sup><a name="note13" href="#note13"><b>13)</b></a></sup> The executions of unsequenced evaluations can interleave. Indeterminately sequenced evaluations
1196 cannot interleave, but can be executed in any order.
1198 [<a name="p14" href="#p14">page 14</a>] (<a href="#Contents">Contents</a>)
1200 calling a function or accessing a volatile object).
1201 5 When the processing of the abstract machine is interrupted by receipt of a signal, the
1202 values of objects that are neither lock-free atomic objects nor of type volatile
1203 sig_atomic_t are unspecified, and the value of any object that is modified by the
1204 handler that is neither a lock-free atomic object nor of type volatile
1205 sig_atomic_t becomes undefined.
1206 6 The least requirements on a conforming implementation are:
1207 -- Accesses to volatile objects are evaluated strictly according to the rules of the abstract
1209 -- At program termination, all data written into files shall be identical to the result that
1210 execution of the program according to the abstract semantics would have produced.
1211 -- The input and output dynamics of interactive devices shall take place as specified in
1212 <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>
1213 appear as soon as possible, to ensure that prompting messages actually appear prior to
1214 a program waiting for input.
1215 This is the observable behavior of the program.
1216 7 What constitutes an interactive device is implementation-defined.
1217 8 More stringent correspondences between abstract and actual semantics may be defined by
1218 each implementation.
1219 9 EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual
1220 semantics: at every sequence point, the values of the actual objects would agree with those specified by the
1221 abstract semantics. The keyword volatile would then be redundant.
1222 10 Alternatively, an implementation might perform various optimizations within each translation unit, such
1223 that the actual semantics would agree with the abstract semantics only when making function calls across
1224 translation unit boundaries. In such an implementation, at the time of each function entry and function
1225 return where the calling function and the called function are in different translation units, the values of all
1226 externally linked objects and of all objects accessible via pointers therein would agree with the abstract
1227 semantics. Furthermore, at the time of each such function entry the values of the parameters of the called
1228 function and of all objects accessible via pointers therein would agree with the abstract semantics. In this
1229 type of implementation, objects referred to by interrupt service routines activated by the signal function
1230 would require explicit specification of volatile storage, as well as other implementation-defined
1233 11 EXAMPLE 2 In executing the fragment
1237 the ''integer promotions'' require that the abstract machine promote the value of each variable to int size
1238 and then add the two ints and truncate the sum. Provided the addition of two chars can be done without
1239 overflow, or with overflow wrapping silently to produce the correct result, the actual execution need only
1240 produce the same result, possibly omitting the promotions.
1242 [<a name="p15" href="#p15">page 15</a>] (<a href="#Contents">Contents</a>)
1244 12 EXAMPLE 3 Similarly, in the fragment
1249 the multiplication may be executed using single-precision arithmetic if the implementation can ascertain
1250 that the result would be the same as if it were executed using double-precision arithmetic (for example, if d
1251 were replaced by the constant 2.0, which has type double).
1253 13 EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate
1254 semantics. Values are independent of whether they are represented in a register or in memory. For
1255 example, an implicit spilling of a register is not permitted to alter the value. Also, an explicit store and load
1256 is required to round to the precision of the storage type. In particular, casts and assignments are required to
1257 perform their specified conversion. For the fragment
1260 d1 = f = expression;
1261 d2 = (float) expression;
1262 the values assigned to d1 and d2 are required to have been converted to float.
1264 14 EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in
1265 precision as well as range. The implementation cannot generally apply the mathematical associative rules
1266 for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of
1267 overflow and underflow. Likewise, implementations cannot generally replace decimal constants in order to
1268 rearrange expressions. In the following fragment, rearrangements suggested by mathematical rules for real
1269 numbers are often not valid (see <a href="#F.9">F.9</a>).
1272 x = (x * y) * z; // not equivalent to x *= y * z;
1273 z = (x - y) + y ; // not equivalent to z = x;
1274 z = x + x * y; // not equivalent to z = x * (1.0 + y);
1275 y = x / 5.0; // not equivalent to y = x * 0.2;
1277 15 EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
1280 a = a + 32760 + b + 5;
1281 the expression statement behaves exactly the same as
1282 a = (((a + 32760) + b) + 5);
1283 due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is
1284 next added to b, and that result is then added to 5 which results in the value assigned to a. On a machine in
1285 which overflows produce an explicit trap and in which the range of values representable by an int is
1286 [-32768, +32767], the implementation cannot rewrite this expression as
1287 a = ((a + b) + 32765);
1288 since if the values for a and b were, respectively, -32754 and -15, the sum a + b would produce a trap
1289 while the original expression would not; nor can the expression be rewritten either as
1292 [<a name="p16" href="#p16">page 16</a>] (<a href="#Contents">Contents</a>)
1294 a = ((a + 32765) + b);
1296 a = (a + (b + 32765));
1297 since the values for a and b might have been, respectively, 4 and -8 or -17 and 12. However, on a machine
1298 in which overflow silently generates some value and where positive and negative overflows cancel, the
1299 above expression statement can be rewritten by the implementation in any of the above ways because the
1300 same result will occur.
1302 16 EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the
1304 #include <a href="#7.21"><stdio.h></a>
1308 sum = sum * 10 - '0' + (*p++ = getchar());
1309 the expression statement is grouped as if it were written as
1310 sum = (((sum * 10) - '0') + ((*(p++)) = (getchar())));
1311 but the actual increment of p can occur at any time between the previous sequence point and the next
1312 sequence point (the ;), and the call to getchar can occur at any point prior to the need of its returned
1315 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
1316 signal function (<a href="#7.14">7.14</a>), files (<a href="#7.21.3">7.21.3</a>).
1317 <a name="5.1.2.4" href="#5.1.2.4"><b> 5.1.2.4 Multi-threaded executions and data races</b></a>
1318 1 Under a hosted implementation, a program can have more than one thread of execution
1319 (or thread) running concurrently. The execution of each thread proceeds as defined by
1320 the remainder of this standard. The execution of the entire program consists of an
1321 execution of all of its threads.<sup><a href="#note14"><b>14)</b></a></sup> Under a freestanding implementation, it is
1322 implementation-defined whether a program can have more than one thread of execution.
1323 2 The value of an object visible to a thread T at a particular point is the initial value of the
1324 object, a value stored in the object by T , or a value stored in the object by another thread,
1325 according to the rules below.
1326 3 NOTE 1 In some cases, there may instead be undefined behavior. Much of this section is motivated by
1327 the desire to support atomic operations with explicit and detailed visibility constraints. However, it also
1328 implicitly supports a simpler view for more restricted programs.
1330 4 Two expression evaluations conflict if one of them modifies a memory location and the
1331 other one reads or modifies the same memory location.
1336 <sup><a name="note14" href="#note14"><b>14)</b></a></sup> The execution can usually be viewed as an interleaving of all of the threads. However, some kinds of
1337 atomic operations, for example, allow executions inconsistent with a simple interleaving as described
1340 [<a name="p17" href="#p17">page 17</a>] (<a href="#Contents">Contents</a>)
1342 5 The library defines a number of atomic operations (<a href="#7.17">7.17</a>) and operations on mutexes
1343 (<a href="#7.25.4">7.25.4</a>) that are specially identified as synchronization operations. These operations play
1344 a special role in making assignments in one thread visible to another. A synchronization
1345 operation on one or more memory locations is either an acquire operation, a release
1346 operation, both an acquire and release operation, or a consume operation. A
1347 synchronization operation without an associated memory location is a fence and can be
1348 either an acquire fence, a release fence, or both an acquire and release fence. In addition,
1349 there are relaxed atomic operations, which are not synchronization operations, and
1350 atomic read-modify-write operations, which have special characteristics.
1351 6 NOTE 2 For example, a call that acquires a mutex will perform an acquire operation on the locations
1352 composing the mutex. Correspondingly, a call that releases the same mutex will perform a release
1353 operation on those same locations. Informally, performing a release operation on A forces prior side effects
1354 on other memory locations to become visible to other threads that later perform an acquire or consume
1355 operation on A. We do not include relaxed atomic operations as synchronization operations although, like
1356 synchronization operations, they cannot contribute to data races.
1358 7 All modifications to a particular atomic object M occur in some particular total order,
1359 called the modification order of M. If A and B are modifications of an atomic object M,
1360 and A happens before B, then A shall precede B in the modification order of M, which is
1362 8 NOTE 3 This states that the modification orders must respect the ''happens before'' relation.
1364 9 NOTE 4 There is a separate order for each atomic object. There is no requirement that these can be
1365 combined into a single total order for all objects. In general this will be impossible since different threads
1366 may observe modifications to different variables in inconsistent orders.
1368 10 A release sequence on an atomic object M is a maximal contiguous sub-sequence of side
1369 effects in the modification order of M, where the first operation is a release and every
1370 subsequent operation either is performed by the same thread that performed the release or
1371 is an atomic read-modify-write operation.
1372 11 Certain library calls synchronize with other library calls performed by another thread. In
1373 particular, an atomic operation A that performs a release operation on an object M
1374 synchronizes with an atomic operation B that performs an acquire operation on M and
1375 reads a value written by any side effect in the release sequence headed by A.
1376 12 NOTE 5 Except in the specified cases, reading a later value does not necessarily ensure visibility as
1377 described below. Such a requirement would sometimes interfere with efficient implementation.
1379 13 NOTE 6 The specifications of the synchronization operations define when one reads the value written by
1380 another. For atomic variables, the definition is clear. All operations on a given mutex occur in a single total
1381 order. Each mutex acquisition ''reads the value written'' by the last mutex release.
1383 14 An evaluation A carries a dependency <sup><a href="#note15"><b>15)</b></a></sup> to an evaluation B if:
1386 <sup><a name="note15" href="#note15"><b>15)</b></a></sup> The ''carries a dependency'' relation is a subset of the ''sequenced before'' relation, and is similarly
1387 strictly intra-thread.
1389 [<a name="p18" href="#p18">page 18</a>] (<a href="#Contents">Contents</a>)
1391 -- the value of A is used as an operand of B, unless:
1392 o B is an invocation of the kill_dependency macro,
1394 o A is the left operand of a && or || operator,
1396 o A is the left operand of a ? : operator, or
1398 o A is the left operand of a , operator;
1400 -- A writes a scalar object or bit-field M, B reads from M the value written by A, and A
1401 is sequenced before B, or
1402 -- for some evaluation X, A carries a dependency to X and X carries a dependency to B.
1403 15 An evaluation A is dependency-ordered before<sup><a href="#note16"><b>16)</b></a></sup> an evaluation B if:
1404 -- A performs a release operation on an atomic object M, and B performs a consume
1405 operation on M and reads a value written by any side effect in the release sequence
1407 -- for some evaluation X, A is dependency-ordered before X and X carries a
1409 16 An evaluation A inter-thread happens before an evaluation B if A synchronizes with B, A
1410 is dependency-ordered before B, or, for some evaluation X:
1411 -- A synchronizes with X and X is sequenced before B,
1412 -- A is sequenced before X and X inter-thread happens before B, or
1413 -- A inter-thread happens before X and X inter-thread happens before B.
1414 17 NOTE 7 The ''inter-thread happens before'' relation describes arbitrary concatenations of ''sequenced
1415 before'', ''synchronizes with'', and ''dependency-ordered before'' relationships, with two exceptions. The
1416 first exception is that a concatenation is not permitted to end with ''dependency-ordered before'' followed
1417 by ''sequenced before''. The reason for this limitation is that a consume operation participating in a
1418 ''dependency-ordered before'' relationship provides ordering only with respect to operations to which this
1419 consume operation actually carries a dependency. The reason that this limitation applies only to the end of
1420 such a concatenation is that any subsequent release operation will provide the required ordering for a prior
1421 consume operation. The second exception is that a concatenation is not permitted to consist entirely of
1422 ''sequenced before''. The reasons for this limitation are (1) to permit ''inter-thread happens before'' to be
1423 transitively closed and (2) the ''happens before'' relation, defined below, provides for relationships
1424 consisting entirely of ''sequenced before''.
1426 18 An evaluation A happens before an evaluation B if A is sequenced before B or A inter-
1427 thread happens before B.
1431 <sup><a name="note16" href="#note16"><b>16)</b></a></sup> The ''dependency-ordered before'' relation is analogous to the ''synchronizes with'' relation, but uses
1432 release/consume in place of release/acquire.
1434 [<a name="p19" href="#p19">page 19</a>] (<a href="#Contents">Contents</a>)
1436 19 A visible side effect A on an object M with respect to a value computation B of M
1437 satisfies the conditions:
1438 -- A happens before B, and
1439 -- there is no other side effect X to M such that A happens before X and X happens
1441 The value of a non-atomic scalar object M, as determined by evaluation B, shall be the
1442 value stored by the visible side effect A.
1443 20 NOTE 8 If there is ambiguity about which side effect to a non-atomic object is visible, then there is a data
1444 race and the behavior is undefined.
1446 21 NOTE 9 This states that operations on ordinary variables are not visibly reordered. This is not actually
1447 detectable without data races, but it is necessary to ensure that data races, as defined here, and with suitable
1448 restrictions on the use of atomics, correspond to data races in a simple interleaved (sequentially consistent)
1451 22 The visible sequence of side effects on an atomic object M, with respect to a value
1452 computation B of M, is a maximal contiguous sub-sequence of side effects in the
1453 modification order of M, where the first side effect is visible with respect to B, and for
1454 every subsequent side effect, it is not the case that B happens before it. The value of an
1455 atomic object M, as determined by evaluation B, shall be the value stored by some
1456 operation in the visible sequence of M with respect to B. Furthermore, if a value
1457 computation A of an atomic object M happens before a value computation B of M, and
1458 the value computed by A corresponds to the value stored by side effect X, then the value
1459 computed by B shall either equal the value computed by A, or be the value stored by side
1460 effect Y , where Y follows X in the modification order of M.
1461 23 NOTE 10 This effectively disallows compiler reordering of atomic operations to a single object, even if
1462 both operations are ''relaxed'' loads. By doing so, we effectively make the ''cache coherence'' guarantee
1463 provided by most hardware available to C atomic operations.
1465 24 NOTE 11 The visible sequence depends on the ''happens before'' relation, which in turn depends on the
1466 values observed by loads of atomics, which we are restricting here. The intended reading is that there must
1467 exist an association of atomic loads with modifications they observe that, together with suitably chosen
1468 modification orders and the ''happens before'' relation derived as described above, satisfy the resulting
1469 constraints as imposed here.
1471 25 The execution of a program contains a data race if it contains two conflicting actions in
1472 different threads, at least one of which is not atomic, and neither happens before the
1473 other. Any such data race results in undefined behavior.
1474 26 NOTE 12 It can be shown that programs that correctly use simple mutexes and
1475 memory_order_seq_cst operations to prevent all data races, and use no other synchronization
1476 operations, behave as though the operations executed by their constituent threads were simply interleaved,
1477 with each value computation of an object being the last value stored in that interleaving. This is normally
1478 referred to as ''sequential consistency''. However, this applies only to data-race-free programs, and data-
1479 race-free programs cannot observe most program transformations that do not change single-threaded
1480 program semantics. In fact, most single-threaded program transformations continue to be allowed, since
1481 any program that behaves differently as a result must contain undefined behavior.
1483 [<a name="p20" href="#p20">page 20</a>] (<a href="#Contents">Contents</a>)
1485 27 NOTE 13 Compiler transformations that introduce assignments to a potentially shared memory location
1486 that would not be modified by the abstract machine are generally precluded by this standard, since such an
1487 assignment might overwrite another assignment by a different thread in cases in which an abstract machine
1488 execution would not have encountered a data race. This includes implementations of data member
1489 assignment that overwrite adjacent members in separate memory locations. We also generally preclude
1490 reordering of atomic loads in cases in which the atomics in question may alias, since this may violate the
1491 "visible sequence" rules.
1493 28 NOTE 14 Transformations that introduce a speculative read of a potentially shared memory location may
1494 not preserve the semantics of the program as defined in this standard, since they potentially introduce a data
1495 race. However, they are typically valid in the context of an optimizing compiler that targets a specific
1496 machine with well-defined semantics for data races. They would be invalid for a hypothetical machine that
1497 is not tolerant of races or provides hardware race detection.
1502 [<a name="p21" href="#p21">page 21</a>] (<a href="#Contents">Contents</a>)
1504 <a name="5.2" href="#5.2"><b> 5.2 Environmental considerations</b></a>
1505 <a name="5.2.1" href="#5.2.1"><b> 5.2.1 Character sets</b></a>
1506 1 Two sets of characters and their associated collating sequences shall be defined: the set in
1507 which source files are written (the source character set), and the set interpreted in the
1508 execution environment (the execution character set). Each set is further divided into a
1509 basic character set, whose contents are given by this subclause, and a set of zero or more
1510 locale-specific members (which are not members of the basic character set) called
1511 extended characters. The combined set is also called the extended character set. The
1512 values of the members of the execution character set are implementation-defined.
1513 2 In a character constant or string literal, members of the execution character set shall be
1514 represented by corresponding members of the source character set or by escape
1515 sequences consisting of the backslash \ followed by one or more characters. A byte with
1516 all bits set to 0, called the null character, shall exist in the basic execution character set; it
1517 is used to terminate a character string.
1518 3 Both the basic source and basic execution character sets shall have the following
1519 members: the 26 uppercase 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 26 lowercase letters of the Latin alphabet
1523 a b c d e f g h i j k l m
1524 n o p q r s t u v w x y z
1525 the 10 decimal digits
1527 the following 29 graphic characters
1528 ! " # % & ' ( ) * + , - . / :
1529 ; < = > ? [ \ ] ^ _ { | } ~
1530 the space character, and control characters representing horizontal tab, vertical tab, and
1531 form feed. The representation of each member of the source and execution basic
1532 character sets shall fit in a byte. In both the source and execution basic character sets, the
1533 value of each character after 0 in the above list of decimal digits shall be one greater than
1534 the value of the previous. In source files, there shall be some way of indicating the end of
1535 each line of text; this International Standard treats such an end-of-line indicator as if it
1536 were a single new-line character. In the basic execution character set, there shall be
1537 control characters representing alert, backspace, carriage return, and new line. If any
1538 other characters are encountered in a source file (except in an identifier, a character
1539 constant, a string literal, a header name, a comment, or a preprocessing token that is never
1541 [<a name="p22" href="#p22">page 22</a>] (<a href="#Contents">Contents</a>)
1543 converted to a token), the behavior is undefined.
1544 4 A letter is an uppercase letter or a lowercase letter as defined above; in this International
1545 Standard the term does not include other characters that are letters in other alphabets.
1546 5 The universal character name construct provides a way to name other characters.
1547 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>),
1548 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>).
1549 <a name="5.2.1.1" href="#5.2.1.1"><b> 5.2.1.1 Trigraph sequences</b></a>
1550 1 Before any other processing takes place, each occurrence of one of the following
1551 sequences of three characters (called trigraph sequences<sup><a href="#note17"><b>17)</b></a></sup>) is replaced with the
1552 corresponding single character.
1554 ??( [ ??' ^ ??> }
1555 ??/ \ ??< { ??- ~
1556 No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
1557 above is not changed.
1559 ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)
1561 #define arraycheck(a, b) a[b] || b[a]
1563 3 EXAMPLE 2 The following source line
1565 becomes (after replacement of the trigraph sequence ??/)
1568 <a name="5.2.1.2" href="#5.2.1.2"><b> 5.2.1.2 Multibyte characters</b></a>
1569 1 The source character set may contain multibyte characters, used to represent members of
1570 the extended character set. The execution character set may also contain multibyte
1571 characters, which need not have the same encoding as for the source character set. For
1572 both character sets, the following shall hold:
1573 -- The basic character set shall be present and each character shall be encoded as a
1575 -- The presence, meaning, and representation of any additional members is locale-
1578 <sup><a name="note17" href="#note17"><b>17)</b></a></sup> The trigraph sequences enable the input of characters that are not defined in the Invariant Code Set as
1579 described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
1581 [<a name="p23" href="#p23">page 23</a>] (<a href="#Contents">Contents</a>)
1583 -- A multibyte character set may have a state-dependent encoding, wherein each
1584 sequence of multibyte characters begins in an initial shift state and enters other
1585 locale-specific shift states when specific multibyte characters are encountered in the
1586 sequence. While in the initial shift state, all single-byte characters retain their usual
1587 interpretation and do not alter the shift state. The interpretation for subsequent bytes
1588 in the sequence is a function of the current shift state.
1589 -- A byte with all bits zero shall be interpreted as a null character independent of shift
1590 state. Such a byte shall not occur as part of any other multibyte character.
1591 2 For source files, the following shall hold:
1592 -- An identifier, comment, string literal, character constant, or header name shall begin
1593 and end in the initial shift state.
1594 -- An identifier, comment, string literal, character constant, or header name shall consist
1595 of a sequence of valid multibyte characters.
1596 <a name="5.2.2" href="#5.2.2"><b> 5.2.2 Character display semantics</b></a>
1597 1 The active position is that location on a display device where the next character output by
1598 the fputc function would appear. The intent of writing a printing character (as defined
1599 by the isprint function) to a display device is to display a graphic representation of
1600 that character at the active position and then advance the active position to the next
1601 position on the current line. The direction of writing is locale-specific. If the active
1602 position is at the final position of a line (if there is one), the behavior of the display device
1604 2 Alphabetic escape sequences representing nongraphic characters in the execution
1605 character set are intended to produce actions on display devices as follows:
1606 \a (alert) Produces an audible or visible alert without changing the active position.
1607 \b (backspace) Moves the active position to the previous position on the current line. If
1608 the active position is at the initial position of a line, the behavior of the display
1609 device is unspecified.
1610 \f ( form feed) Moves the active position to the initial position at the start of the next
1612 \n (new line) Moves the active position to the initial position of the next line.
1613 \r (carriage return) Moves the active position to the initial position of the current line.
1614 \t (horizontal tab) Moves the active position to the next horizontal tabulation position
1615 on the current line. If the active position is at or past the last defined horizontal
1616 tabulation position, the behavior of the display device is unspecified.
1617 \v (vertical tab) Moves the active position to the initial position of the next vertical
1618 tabulation position. If the active position is at or past the last defined vertical
1619 [<a name="p24" href="#p24">page 24</a>] (<a href="#Contents">Contents</a>)
1621 tabulation position, the behavior of the display device is unspecified.
1622 3 Each of these escape sequences shall produce a unique implementation-defined value
1623 which can be stored in a single char object. The external representations in a text file
1624 need not be identical to the internal representations, and are outside the scope of this
1625 International Standard.
1626 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>).
1627 <a name="5.2.3" href="#5.2.3"><b> 5.2.3 Signals and interrupts</b></a>
1628 1 Functions shall be implemented such that they may be interrupted at any time by a signal,
1629 or may be called by a signal handler, or both, with no alteration to earlier, but still active,
1630 invocations' control flow (after the interruption), function return values, or objects with
1631 automatic storage duration. All such objects shall be maintained outside the function
1632 image (the instructions that compose the executable representation of a function) on a
1633 per-invocation basis.
1634 <a name="5.2.4" href="#5.2.4"><b> 5.2.4 Environmental limits</b></a>
1635 1 Both the translation and execution environments constrain the implementation of
1636 language translators and libraries. The following summarizes the language-related
1637 environmental limits on a conforming implementation; the library-related limits are
1638 discussed in clause 7.
1639 <a name="5.2.4.1" href="#5.2.4.1"><b> 5.2.4.1 Translation limits</b></a>
1640 1 The implementation shall be able to translate and execute at least one program that
1641 contains at least one instance of every one of the following limits:<sup><a href="#note18"><b>18)</b></a></sup>
1642 -- 127 nesting levels of blocks
1643 -- 63 nesting levels of conditional inclusion
1644 -- 12 pointer, array, and function declarators (in any combinations) modifying an
1645 arithmetic, structure, union, or void type in a declaration
1646 -- 63 nesting levels of parenthesized declarators within a full declarator
1647 -- 63 nesting levels of parenthesized expressions within a full expression
1648 -- 63 significant initial characters in an internal identifier or a macro name (each
1649 universal character name or extended source character is considered a single
1651 -- 31 significant initial characters in an external identifier (each universal character name
1652 specifying a short identifier of 0000FFFF or less is considered 6 characters, each
1655 <sup><a name="note18" href="#note18"><b>18)</b></a></sup> Implementations should avoid imposing fixed translation limits whenever possible.
1657 [<a name="p25" href="#p25">page 25</a>] (<a href="#Contents">Contents</a>)
1659 universal character name specifying a short identifier of 00010000 or more is
1660 considered 10 characters, and each extended source character is considered the same
1661 number of characters as the corresponding universal character name, if any)<sup><a href="#note19"><b>19)</b></a></sup>
1662 -- 4095 external identifiers in one translation unit
1663 -- 511 identifiers with block scope declared in one block
1664 -- 4095 macro identifiers simultaneously defined in one preprocessing translation unit
1665 -- 127 parameters in one function definition
1666 -- 127 arguments in one function call
1667 -- 127 parameters in one macro definition
1668 -- 127 arguments in one macro invocation
1669 -- 4095 characters in a logical source line
1670 -- 4095 characters in a string literal (after concatenation)
1671 -- 65535 bytes in an object (in a hosted environment only)
1672 -- 15 nesting levels for #included files
1673 -- 1023 case labels for a switch statement (excluding those for any nested switch
1675 -- 1023 members in a single structure or union
1676 -- 1023 enumeration constants in a single enumeration
1677 -- 63 levels of nested structure or union definitions in a single struct-declaration-list
1678 <a name="5.2.4.2" href="#5.2.4.2"><b> 5.2.4.2 Numerical limits</b></a>
1679 1 An implementation is required to document all the limits specified in this subclause,
1680 which are specified in the headers <a href="#7.10"><limits.h></a> and <a href="#7.7"><float.h></a>. Additional limits are
1681 specified in <a href="#7.20"><stdint.h></a>.
1682 Forward references: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>).
1683 <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>
1684 1 The values given below shall be replaced by constant expressions suitable for use in #if
1685 preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the
1686 following shall be replaced by expressions that have the same type as would an
1687 expression that is an object of the corresponding type converted according to the integer
1688 promotions. Their implementation-defined values shall be equal or greater in magnitude
1691 <sup><a name="note19" href="#note19"><b>19)</b></a></sup> See ''future language directions'' (<a href="#6.11.3">6.11.3</a>).
1693 [<a name="p26" href="#p26">page 26</a>] (<a href="#Contents">Contents</a>)
1695 (absolute value) to those shown, with the same sign.
1696 -- number of bits for smallest object that is not a bit-field (byte)
1698 -- minimum value for an object of type signed char
1699 SCHAR_MIN -127 // -(27 - 1)
1700 -- maximum value for an object of type signed char
1701 SCHAR_MAX +127 // 27 - 1
1702 -- maximum value for an object of type unsigned char
1703 UCHAR_MAX 255 // 28 - 1
1704 -- minimum value for an object of type char
1706 -- maximum value for an object of type char
1708 -- maximum number of bytes in a multibyte character, for any supported locale
1710 -- minimum value for an object of type short int
1711 SHRT_MIN -32767 // -(215 - 1)
1712 -- maximum value for an object of type short int
1713 SHRT_MAX +32767 // 215 - 1
1714 -- maximum value for an object of type unsigned short int
1715 USHRT_MAX 65535 // 216 - 1
1716 -- minimum value for an object of type int
1717 INT_MIN -32767 // -(215 - 1)
1718 -- maximum value for an object of type int
1719 INT_MAX +32767 // 215 - 1
1720 -- maximum value for an object of type unsigned int
1721 UINT_MAX 65535 // 216 - 1
1722 -- minimum value for an object of type long int
1723 LONG_MIN -2147483647 // -(231 - 1)
1724 -- maximum value for an object of type long int
1725 LONG_MAX +2147483647 // 231 - 1
1726 -- maximum value for an object of type unsigned long int
1727 ULONG_MAX 4294967295 // 232 - 1
1730 [<a name="p27" href="#p27">page 27</a>] (<a href="#Contents">Contents</a>)
1732 -- minimum value for an object of type long long int
1733 LLONG_MIN -9223372036854775807 // -(263 - 1)
1734 -- maximum value for an object of type long long int
1735 LLONG_MAX +9223372036854775807 // 263 - 1
1736 -- maximum value for an object of type unsigned long long int
1737 ULLONG_MAX 18446744073709551615 // 264 - 1
1738 2 If the value of an object of type char is treated as a signed integer when used in an
1739 expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the
1740 value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of
1741 CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of
1742 UCHAR_MAX.<sup><a href="#note20"><b>20)</b></a></sup> The value UCHAR_MAX shall equal 2CHAR_BIT - 1.
1743 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>).
1744 <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>
1745 1 The characteristics of floating types are defined in terms of a model that describes a
1746 representation of floating-point numbers and values that provide information about an
1747 implementation's floating-point arithmetic.<sup><a href="#note21"><b>21)</b></a></sup> The following parameters are used to
1748 define the model for each floating-point type:
1750 b base or radix of exponent representation (an integer > 1)
1751 e exponent (an integer between a minimum emin and a maximum emax )
1752 p precision (the number of base-b digits in the significand)
1753 fk nonnegative integers less than b (the significand digits)
1754 2 A floating-point number (x) is defined by the following model:
1756 x = sb e (Sum) f k b-k ,
1758 emin <= e <= emax
1760 3 In addition to normalized floating-point numbers ( f 1 > 0 if x != 0), floating types may be
1761 able to contain other kinds of floating-point numbers, such as subnormal floating-point
1762 numbers (x != 0, e = emin , f 1 = 0) and unnormalized floating-point numbers (x != 0,
1763 e > emin , f 1 = 0), and values that are not floating-point numbers, such as infinities and
1764 NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates
1765 through almost every arithmetic operation without raising a floating-point exception; a
1766 signaling NaN generally raises a floating-point exception when occurring as an
1769 <sup><a name="note20" href="#note20"><b>20)</b></a></sup> See <a href="#6.2.5">6.2.5</a>.
1770 <sup><a name="note21" href="#note21"><b>21)</b></a></sup> The floating-point model is intended to clarify the description of each floating-point characteristic and
1771 does not require the floating-point arithmetic of the implementation to be identical.
1773 [<a name="p28" href="#p28">page 28</a>] (<a href="#Contents">Contents</a>)
1775 arithmetic operand.<sup><a href="#note22"><b>22)</b></a></sup>
1776 4 An implementation may give zero and values that are not floating-point numbers (such as
1777 infinities and NaNs) a sign or may leave them unsigned. Wherever such values are
1778 unsigned, any requirement in this International Standard to retrieve the sign shall produce
1779 an unspecified sign, and any requirement to set the sign shall be ignored.
1780 5 The minimum range of representable values for a floating type is the most negative finite
1781 floating-point number representable in that type through the most positive finite floating-
1782 point number representable in that type. In addition, if negative infinity is representable
1783 in a type, the range of that type is extended to all negative real numbers; likewise, if
1784 positive infinity is representable in a type, the range of that type is extended to all positive
1786 6 The accuracy of the floating-point operations (+, -, *, /) and of the library functions in
1787 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results is implementation-
1788 defined, as is the accuracy of the conversion between floating-point internal
1789 representations and string representations performed by the library functions in
1790 <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
1791 accuracy is unknown.
1792 7 All integer values in the <a href="#7.7"><float.h></a> header, except FLT_ROUNDS, shall be constant
1793 expressions suitable for use in #if preprocessing directives; all floating values shall be
1794 constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
1795 and FLT_ROUNDS have separate names for all three floating-point types. The floating-
1796 point model representation is provided for all values except FLT_EVAL_METHOD and
1798 8 The rounding mode for floating-point addition is characterized by the implementation-
1799 defined value of FLT_ROUNDS:<sup><a href="#note23"><b>23)</b></a></sup>
1803 2 toward positive infinity
1804 3 toward negative infinity
1805 All other values for FLT_ROUNDS characterize implementation-defined rounding
1809 <sup><a name="note22" href="#note22"><b>22)</b></a></sup> IEC 60559:1989 specifies quiet and signaling NaNs. For implementations that do not support
1810 IEC 60559:1989, the terms quiet NaN and signaling NaN are intended to apply to encodings with
1812 <sup><a name="note23" href="#note23"><b>23)</b></a></sup> Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
1813 the function fesetround in <a href="#7.6"><fenv.h></a>.
1815 [<a name="p29" href="#p29">page 29</a>] (<a href="#Contents">Contents</a>)
1817 9 Except for assignment and cast (which remove all extra range and precision), the values
1818 yielded by operators with floating operands and values subject to the usual arithmetic
1819 conversions and of floating constants are evaluated to a format whose range and precision
1820 may be greater than required by the type. The use of evaluation formats is characterized
1821 by the implementation-defined value of FLT_EVAL_METHOD:<sup><a href="#note24"><b>24)</b></a></sup>
1823 0 evaluate all operations and constants just to the range and precision of the
1825 1 evaluate operations and constants of type float and double to the
1826 range and precision of the double type, evaluate long double
1827 operations and constants to the range and precision of the long double
1829 2 evaluate all operations and constants to the range and precision of the
1831 All other negative values for FLT_EVAL_METHOD characterize implementation-defined
1833 10 The presence or absence of subnormal numbers is characterized by the implementation-
1834 defined values of FLT_HAS_SUBNORM, DBL_HAS_SUBNORM, and
1836 -1 indeterminable<sup><a href="#note25"><b>25)</b></a></sup>
1837 0 absent<sup><a href="#note26"><b>26)</b></a></sup> (type does not support subnormal numbers)
1838 1 present (type does support subnormal numbers)
1839 11 The values given in the following list shall be replaced by constant expressions with
1840 implementation-defined values that are greater or equal in magnitude (absolute value) to
1841 those shown, with the same sign:
1842 -- radix of exponent representation, b
1848 <sup><a name="note24" href="#note24"><b>24)</b></a></sup> The evaluation method determines evaluation formats of expressions involving all floating types, not
1849 just real types. For example, if FLT_EVAL_METHOD is 1, then the product of two float
1850 _Complex operands is represented in the double _Complex format, and its parts are evaluated to
1852 <sup><a name="note25" href="#note25"><b>25)</b></a></sup> Characterization as indeterminable is intended if floating-point operations do not consistently interpret
1853 subnormal representations as zero, nor as nonzero.
1854 <sup><a name="note26" href="#note26"><b>26)</b></a></sup> Characterization as absent is intended if no floating-point operations produce subnormal results from
1855 non-subnormal inputs, even if the type format includes representations of subnormal numbers.
1857 [<a name="p30" href="#p30">page 30</a>] (<a href="#Contents">Contents</a>)
1859 -- number of base-FLT_RADIX digits in the floating-point significand, p
1863 -- number of decimal digits, n, such that any floating-point number with p radix b digits
1864 can be rounded to a floating-point number with n decimal digits and back again
1865 without change to the value,
1866 { p log10 b if b is a power of 10
1868 { [^1 + p log10 b^] otherwise
1872 -- number of decimal digits, n, such that any floating-point number in the widest
1873 supported floating type with pmax radix b digits can be rounded to a floating-point
1874 number with n decimal digits and back again without change to the value,
1875 { pmax log10 b if b is a power of 10
1877 { [^1 + pmax log10 b^] otherwise
1879 -- number of decimal digits, q, such that any floating-point number with q decimal digits
1880 can be rounded into a floating-point number with p radix b digits and back again
1881 without change to the q decimal digits,
1882 { p log10 b if b is a power of 10
1884 { [_( p - 1) log10 b_] otherwise
1888 -- minimum negative integer such that FLT_RADIX raised to one less than that power is
1889 a normalized floating-point number, emin
1897 [<a name="p31" href="#p31">page 31</a>] (<a href="#Contents">Contents</a>)
1899 -- minimum negative integer such that 10 raised to that power is in the range of
1900 normalized floating-point numbers, [^log10 b emin -1 ^]
1905 -- maximum integer such that FLT_RADIX raised to one less than that power is a
1906 representable finite floating-point number, emax
1910 -- maximum integer such that 10 raised to that power is in the range of representable
1911 finite floating-point numbers, [_log10 ((1 - b- p )b emax )_]
1915 12 The values given in the following list shall be replaced by constant expressions with
1916 implementation-defined values that are greater than or equal to those shown:
1917 -- maximum representable finite floating-point number, (1 - b- p )b emax
1921 13 The values given in the following list shall be replaced by constant expressions with
1922 implementation-defined (positive) values that are less than or equal to those shown:
1923 -- the difference between 1 and the least value greater than 1 that is representable in the
1924 given floating point type, b1- p
1928 -- minimum normalized positive floating-point number, b emin -1
1936 [<a name="p32" href="#p32">page 32</a>] (<a href="#Contents">Contents</a>)
1938 -- minimum positive floating-point number<sup><a href="#note27"><b>27)</b></a></sup>
1942 Recommended practice
1943 14 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
1944 should be the identity function.
1945 15 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
1946 requirements of this International Standard, and the appropriate values in a <a href="#7.7"><float.h></a> header for type
1949 x = s16e (Sum) f k 16-k ,
1951 -31 <= e <= +32
1955 FLT_EPSILON 9.53674316E-07F
1959 FLT_MIN 2.93873588E-39F
1962 FLT_MAX 3.40282347E+38F
1965 16 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
1966 single-precision and double-precision numbers in IEC 60559,<sup><a href="#note28"><b>28)</b></a></sup> and the appropriate values in a
1967 <a href="#7.7"><float.h></a> header for types float and double:
1969 x f = s2e (Sum) f k 2-k ,
1971 -125 <= e <= +128
1974 x d = s2e (Sum) f k 2-k ,
1976 -1021 <= e <= +1024
1981 FLT_EPSILON 1.19209290E-07F // decimal constant
1982 FLT_EPSILON 0X1P-23F // hex constant
1986 <sup><a name="note27" href="#note27"><b>27)</b></a></sup> If the presence or absence of subnormal numbers is indeterminable, then the value is intended to be a
1987 positive number no greater than the minimum normalized positive number for the type.
1988 <sup><a name="note28" href="#note28"><b>28)</b></a></sup> The floating-point model in that standard sums powers of b from zero, so the values of the exponent
1989 limits are one less than shown here.
1991 [<a name="p33" href="#p33">page 33</a>] (<a href="#Contents">Contents</a>)
1995 FLT_MIN 1.17549435E-38F // decimal constant
1996 FLT_MIN 0X1P-126F // hex constant
1997 FLT_TRUE_MIN 1.40129846E-45F // decimal constant
1998 FLT_TRUE_MIN 0X1P-149F // hex constant
2002 FLT_MAX 3.40282347E+38F // decimal constant
2003 FLT_MAX 0X1.fffffeP127F // hex constant
2006 DBL_EPSILON 2.2204460492503131E-16 // decimal constant
2007 DBL_EPSILON 0X1P-52 // hex constant
2011 DBL_MIN 2.2250738585072014E-308 // decimal constant
2012 DBL_MIN 0X1P-1022 // hex constant
2013 DBL_TRUE_MIN 4.9406564584124654E-324 // decimal constant
2014 DBL_TRUE_MIN 0X1P-1074 // hex constant
2018 DBL_MAX 1.7976931348623157E+308 // decimal constant
2019 DBL_MAX 0X1.fffffffffffffP1023 // hex constant
2021 If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
2022 example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
2023 precision), then DECIMAL_DIG would be 21.
2025 Forward references: conditional inclusion (<a href="#6.10.1">6.10.1</a>), complex arithmetic
2026 <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>
2027 (<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>
2028 (<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>).
2033 [<a name="p34" href="#p34">page 34</a>] (<a href="#Contents">Contents</a>)
2036 <a name="6" href="#6"><b> 6. Language</b></a>
2037 <a name="6.1" href="#6.1"><b> 6.1 Notation</b></a>
2038 1 In the syntax notation used in this clause, syntactic categories (nonterminals) are
2039 indicated by italic type, and literal words and character set members (terminals) by bold
2040 type. A colon (:) following a nonterminal introduces its definition. Alternative
2041 definitions are listed on separate lines, except when prefaced by the words ''one of''. An
2042 optional symbol is indicated by the subscript ''opt'', so that
2044 indicates an optional expression enclosed in braces.
2045 2 When syntactic categories are referred to in the main text, they are not italicized and
2046 words are separated by spaces instead of hyphens.
2047 3 A summary of the language syntax is given in <a href="#A">annex A</a>.
2048 <a name="6.2" href="#6.2"><b> 6.2 Concepts</b></a>
2049 <a name="6.2.1" href="#6.2.1"><b> 6.2.1 Scopes of identifiers</b></a>
2050 1 An identifier can denote an object; a function; a tag or a member of a structure, union, or
2051 enumeration; a typedef name; a label name; a macro name; or a macro parameter. The
2052 same identifier can denote different entities at different points in the program. A member
2053 of an enumeration is called an enumeration constant. Macro names and macro
2054 parameters are not considered further here, because prior to the semantic phase of
2055 program translation any occurrences of macro names in the source file are replaced by the
2056 preprocessing token sequences that constitute their macro definitions.
2057 2 For each different entity that an identifier designates, the identifier is visible (i.e., can be
2058 used) only within a region of program text called its scope. Different entities designated
2059 by the same identifier either have different scopes, or are in different name spaces. There
2060 are four kinds of scopes: function, file, block, and function prototype. (A function
2061 prototype is a declaration of a function that declares the types of its parameters.)
2062 3 A label name is the only kind of identifier that has function scope. It can be used (in a
2063 goto statement) anywhere in the function in which it appears, and is declared implicitly
2064 by its syntactic appearance (followed by a : and a statement).
2065 4 Every other identifier has scope determined by the placement of its declaration (in a
2066 declarator or type specifier). If the declarator or type specifier that declares the identifier
2067 appears outside of any block or list of parameters, the identifier has file scope, which
2068 terminates at the end of the translation unit. If the declarator or type specifier that
2069 declares the identifier appears inside a block or within the list of parameter declarations in
2070 a function definition, the identifier has block scope, which terminates at the end of the
2071 associated block. If the declarator or type specifier that declares the identifier appears
2073 [<a name="p35" href="#p35">page 35</a>] (<a href="#Contents">Contents</a>)
2075 within the list of parameter declarations in a function prototype (not part of a function
2076 definition), the identifier has function prototype scope, which terminates at the end of the
2077 function declarator. If an identifier designates two different entities in the same name
2078 space, the scopes might overlap. If so, the scope of one entity (the inner scope) will end
2079 strictly before the scope of the other entity (the outer scope). Within the inner scope, the
2080 identifier designates the entity declared in the inner scope; the entity declared in the outer
2081 scope is hidden (and not visible) within the inner scope.
2082 5 Unless explicitly stated otherwise, where this International Standard uses the term
2083 ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the
2084 entity in the relevant name space whose declaration is visible at the point the identifier
2086 6 Two identifiers have the same scope if and only if their scopes terminate at the same
2088 7 Structure, union, and enumeration tags have scope that begins just after the appearance of
2089 the tag in a type specifier that declares the tag. Each enumeration constant has scope that
2090 begins just after the appearance of its defining enumerator in an enumerator list. Any
2091 other identifier has scope that begins just after the completion of its declarator.
2092 8 As a special case, a type name (which is not a declaration of an identifier) is considered to
2093 have a scope that begins just after the place within the type name where the omitted
2094 identifier would appear were it not omitted.
2095 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
2096 (<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>),
2097 source file inclusion (<a href="#6.10.2">6.10.2</a>), statements (<a href="#6.8">6.8</a>).
2098 <a name="6.2.2" href="#6.2.2"><b> 6.2.2 Linkages of identifiers</b></a>
2099 1 An identifier declared in different scopes or in the same scope more than once can be
2100 made to refer to the same object or function by a process called linkage.<sup><a href="#note29"><b>29)</b></a></sup> There are
2101 three kinds of linkage: external, internal, and none.
2102 2 In the set of translation units and libraries that constitutes an entire program, each
2103 declaration of a particular identifier with external linkage denotes the same object or
2104 function. Within one translation unit, each declaration of an identifier with internal
2105 linkage denotes the same object or function. Each declaration of an identifier with no
2106 linkage denotes a unique entity.
2107 3 If the declaration of a file scope identifier for an object or a function contains the storage-
2108 class specifier static, the identifier has internal linkage.<sup><a href="#note30"><b>30)</b></a></sup>
2112 <sup><a name="note29" href="#note29"><b>29)</b></a></sup> There is no linkage between different identifiers.
2114 [<a name="p36" href="#p36">page 36</a>] (<a href="#Contents">Contents</a>)
2116 4 For an identifier declared with the storage-class specifier extern in a scope in which a
2117 prior declaration of that identifier is visible,<sup><a href="#note31"><b>31)</b></a></sup> if the prior declaration specifies internal or
2118 external linkage, the linkage of the identifier at the later declaration is the same as the
2119 linkage specified at the prior declaration. If no prior declaration is visible, or if the prior
2120 declaration specifies no linkage, then the identifier has external linkage.
2121 5 If the declaration of an identifier for a function has no storage-class specifier, its linkage
2122 is determined exactly as if it were declared with the storage-class specifier extern. If
2123 the declaration of an identifier for an object has file scope and no storage-class specifier,
2124 its linkage is external.
2125 6 The following identifiers have no linkage: an identifier declared to be anything other than
2126 an object or a function; an identifier declared to be a function parameter; a block scope
2127 identifier for an object declared without the storage-class specifier extern.
2128 7 If, within a translation unit, the same identifier appears with both internal and external
2129 linkage, the behavior is undefined.
2130 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>),
2131 statements (<a href="#6.8">6.8</a>).
2132 <a name="6.2.3" href="#6.2.3"><b> 6.2.3 Name spaces of identifiers</b></a>
2133 1 If more than one declaration of a particular identifier is visible at any point in a
2134 translation unit, the syntactic context disambiguates uses that refer to different entities.
2135 Thus, there are separate name spaces for various categories of identifiers, as follows:
2136 -- label names (disambiguated by the syntax of the label declaration and use);
2137 -- the tags of structures, unions, and enumerations (disambiguated by following any<sup><a href="#note32"><b>32)</b></a></sup>
2138 of the keywords struct, union, or enum);
2139 -- the members of structures or unions; each structure or union has a separate name
2140 space for its members (disambiguated by the type of the expression used to access the
2141 member via the . or -> operator);
2142 -- all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
2143 enumeration constants).
2144 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>),
2145 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
2146 (<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>).
2148 <sup><a name="note30" href="#note30"><b>30)</b></a></sup> A function declaration can contain the storage-class specifier static only if it is at file scope; see
2149 <a href="#6.7.1">6.7.1</a>.
2150 <sup><a name="note31" href="#note31"><b>31)</b></a></sup> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
2151 <sup><a name="note32" href="#note32"><b>32)</b></a></sup> There is only one name space for tags even though three are possible.
2153 [<a name="p37" href="#p37">page 37</a>] (<a href="#Contents">Contents</a>)
2155 <a name="6.2.4" href="#6.2.4"><b> 6.2.4 Storage durations of objects</b></a>
2156 1 An object has a storage duration that determines its lifetime. There are four storage
2157 durations: static, thread, automatic, and allocated. Allocated storage is described in
2158 <a href="#7.22.3">7.22.3</a>.
2159 2 The lifetime of an object is the portion of program execution during which storage is
2160 guaranteed to be reserved for it. An object exists, has a constant address,<sup><a href="#note33"><b>33)</b></a></sup> and retains
2161 its last-stored value throughout its lifetime.<sup><a href="#note34"><b>34)</b></a></sup> If an object is referred to outside of its
2162 lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
2163 the object it points to (or just past) reaches the end of its lifetime.
2164 3 An object whose identifier is declared without the storage-class specifier
2165 _Thread_local, and either with external or internal linkage or with the storage-class
2166 specifier static, has static storage duration. Its lifetime is the entire execution of the
2167 program and its stored value is initialized only once, prior to program startup.
2168 4 An object whose identifier is declared with the storage-class specifier _Thread_local
2169 has thread storage duration. Its lifetime is the entire execution of the thread for which it
2170 is created, and its stored value is initialized when the thread is started. There is a distinct
2171 object per thread, and use of the declared name in an expression refers to the object
2172 associated with the thread evaluating the expression. The result of attempting to
2173 indirectly access an object with thread storage duration from a thread other than the one
2174 with which the object is associated is implementation-defined.
2175 5 An object whose identifier is declared with no linkage and without the storage-class
2176 specifier static has automatic storage duration, as do some compound literals. The
2177 result of attempting to indirectly access an object with automatic storage duration from a
2178 thread other than the one with which the object is associated is implementation-defined.
2179 6 For such an object that does not have a variable length array type, its lifetime extends
2180 from entry into the block with which it is associated until execution of that block ends in
2181 any way. (Entering an enclosed block or calling a function suspends, but does not end,
2182 execution of the current block.) If the block is entered recursively, a new instance of the
2183 object is created each time. The initial value of the object is indeterminate. If an
2184 initialization is specified for the object, it is performed each time the declaration or
2185 compound literal is reached in the execution of the block; otherwise, the value becomes
2186 indeterminate each time the declaration is reached.
2190 <sup><a name="note33" href="#note33"><b>33)</b></a></sup> The term ''constant address'' means that two pointers to the object constructed at possibly different
2191 times will compare equal. The address may be different during two different executions of the same
2193 <sup><a name="note34" href="#note34"><b>34)</b></a></sup> In the case of a volatile object, the last store need not be explicit in the program.
2195 [<a name="p38" href="#p38">page 38</a>] (<a href="#Contents">Contents</a>)
2197 7 For such an object that does have a variable length array type, its lifetime extends from
2198 the declaration of the object until execution of the program leaves the scope of the
2199 declaration.<sup><a href="#note35"><b>35)</b></a></sup> If the scope is entered recursively, a new instance of the object is created
2200 each time. The initial value of the object is indeterminate.
2201 8 A non-lvalue expression with structure or union type, where the structure or union
2202 contains a member with array type (including, recursively, members of all contained
2203 structures and unions) refers to an object with automatic storage duration and temporary
2204 lifetime.<sup><a href="#note36"><b>36)</b></a></sup> Its lifetime begins when the expression is evaluated and its initial value is the
2205 value of the expression. Its lifetime ends when the evaluation of the containing full
2206 expression or full declarator ends. Any attempt to modify an object with temporary
2207 lifetime results in undefined behavior.
2208 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
2209 (<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>).
2210 <a name="6.2.5" href="#6.2.5"><b> 6.2.5 Types</b></a>
2211 1 The meaning of a value stored in an object or returned by a function is determined by the
2212 type of the expression used to access it. (An identifier declared to be an object is the
2213 simplest such expression; the type is specified in the declaration of the identifier.) Types
2214 are partitioned into object types (types that describe objects) and function types (types
2215 that describe functions). At various points within a translation unit an object type may be
2216 incomplete (lacking sufficient information to determine the size of objects of that type) or
2217 complete (having sufficient information).<sup><a href="#note37"><b>37)</b></a></sup>
2218 2 An object declared as type _Bool is large enough to store the values 0 and 1.
2219 3 An object declared as type char is large enough to store any member of the basic
2220 execution character set. If a member of the basic execution character set is stored in a
2221 char object, its value is guaranteed to be nonnegative. If any other character is stored in
2222 a char object, the resulting value is implementation-defined but shall be within the range
2223 of values that can be represented in that type.
2224 4 There are five standard signed integer types, designated as signed char, short
2225 int, int, long int, and long long int. (These and other types may be
2226 designated in several additional ways, as described in <a href="#6.7.2">6.7.2</a>.) There may also be
2227 implementation-defined extended signed integer types.<sup><a href="#note38"><b>38)</b></a></sup> The standard and extended
2228 signed integer types are collectively called signed integer types.<sup><a href="#note39"><b>39)</b></a></sup>
2230 <sup><a name="note35" href="#note35"><b>35)</b></a></sup> Leaving the innermost block containing the declaration, or jumping to a point in that block or an
2231 embedded block prior to the declaration, leaves the scope of the declaration.
2232 <sup><a name="note36" href="#note36"><b>36)</b></a></sup> The address of such an object is taken implicitly when an array member is accessed.
2233 <sup><a name="note37" href="#note37"><b>37)</b></a></sup> A type may be incomplete or complete throughout an entire translation unit, or it may change states at
2234 different points within a translation unit.
2236 [<a name="p39" href="#p39">page 39</a>] (<a href="#Contents">Contents</a>)
2238 5 An object declared as type signed char occupies the same amount of storage as a
2239 ''plain'' char object. A ''plain'' int object has the natural size suggested by the
2240 architecture of the execution environment (large enough to contain any value in the range
2241 INT_MIN to INT_MAX as defined in the header <a href="#7.10"><limits.h></a>).
2242 6 For each of the signed integer types, there is a corresponding (but different) unsigned
2243 integer type (designated with the keyword unsigned) that uses the same amount of
2244 storage (including sign information) and has the same alignment requirements. The type
2245 _Bool and the unsigned integer types that correspond to the standard signed integer
2246 types are the standard unsigned integer types. The unsigned integer types that
2247 correspond to the extended signed integer types are the extended unsigned integer types.
2248 The standard and extended unsigned integer types are collectively called unsigned integer
2249 types.<sup><a href="#note40"><b>40)</b></a></sup>
2250 7 The standard signed integer types and standard unsigned integer types are collectively
2251 called the standard integer types, the extended signed integer types and extended
2252 unsigned integer types are collectively called the extended integer types.
2253 8 For any two integer types with the same signedness and different integer conversion rank
2254 (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
2255 subrange of the values of the other type.
2256 9 The range of nonnegative values of a signed integer type is a subrange of the
2257 corresponding unsigned integer type, and the representation of the same value in each
2258 type is the same.<sup><a href="#note41"><b>41)</b></a></sup> A computation involving unsigned operands can never overflow,
2259 because a result that cannot be represented by the resulting unsigned integer type is
2260 reduced modulo the number that is one greater than the largest value that can be
2261 represented by the resulting type.
2262 10 There are three real floating types, designated as float, double, and long
2263 double.<sup><a href="#note42"><b>42)</b></a></sup> The set of values of the type float is a subset of the set of values of the
2264 type double; the set of values of the type double is a subset of the set of values of the
2268 <sup><a name="note38" href="#note38"><b>38)</b></a></sup> Implementation-defined keywords shall have the form of an identifier reserved for any use as
2269 described in <a href="#7.1.3">7.1.3</a>.
2270 <sup><a name="note39" href="#note39"><b>39)</b></a></sup> Therefore, any statement in this Standard about signed integer types also applies to the extended
2271 signed integer types.
2272 <sup><a name="note40" href="#note40"><b>40)</b></a></sup> Therefore, any statement in this Standard about unsigned integer types also applies to the extended
2273 unsigned integer types.
2274 <sup><a name="note41" href="#note41"><b>41)</b></a></sup> The same representation and alignment requirements are meant to imply interchangeability as
2275 arguments to functions, return values from functions, and members of unions.
2276 <sup><a name="note42" href="#note42"><b>42)</b></a></sup> See ''future language directions'' (<a href="#6.11.1">6.11.1</a>).
2278 [<a name="p40" href="#p40">page 40</a>] (<a href="#Contents">Contents</a>)
2280 11 There are three complex types, designated as float _Complex, double
2281 _Complex, and long double _Complex.<sup><a href="#note43"><b>43)</b></a></sup> (Complex types are a conditional
2282 feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.) The real floating and
2283 complex types are collectively called the floating types.
2284 12 For each floating type there is a corresponding real type, which is always a real floating
2285 type. For real floating types, it is the same type. For complex types, it is the type given
2286 by deleting the keyword _Complex from the type name.
2287 13 Each complex type has the same representation and alignment requirements as an array
2288 type containing exactly two elements of the corresponding real type; the first element is
2289 equal to the real part, and the second element to the imaginary part, of the complex
2291 14 The type char, the signed and unsigned integer types, and the floating types are
2292 collectively called the basic types. The basic types are complete object types. Even if the
2293 implementation defines two or more basic types to have the same representation, they are
2294 nevertheless different types.<sup><a href="#note44"><b>44)</b></a></sup>
2295 15 The three types char, signed char, and unsigned char are collectively called
2296 the character types. The implementation shall define char to have the same range,
2297 representation, and behavior as either signed char or unsigned char.<sup><a href="#note45"><b>45)</b></a></sup>
2298 16 An enumeration comprises a set of named integer constant values. Each distinct
2299 enumeration constitutes a different enumerated type.
2300 17 The type char, the signed and unsigned integer types, and the enumerated types are
2301 collectively called integer types. The integer and real floating types are collectively called
2303 18 Integer and floating types are collectively called arithmetic types. Each arithmetic type
2304 belongs to one type domain: the real type domain comprises the real types, the complex
2305 type domain comprises the complex types.
2306 19 The void type comprises an empty set of values; it is an incomplete object type that
2307 cannot be completed.
2311 <sup><a name="note43" href="#note43"><b>43)</b></a></sup> A specification for imaginary types is in <a href="#G">annex G</a>.
2312 <sup><a name="note44" href="#note44"><b>44)</b></a></sup> An implementation may define new keywords that provide alternative ways to designate a basic (or
2313 any other) type; this does not violate the requirement that all basic types be different.
2314 Implementation-defined keywords shall have the form of an identifier reserved for any use as
2315 described in <a href="#7.1.3">7.1.3</a>.
2316 <sup><a name="note45" href="#note45"><b>45)</b></a></sup> 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
2317 used to distinguish the two options. Irrespective of the choice made, char is a separate type from the
2318 other two and is not compatible with either.
2320 [<a name="p41" href="#p41">page 41</a>] (<a href="#Contents">Contents</a>)
2322 20 Any number of derived types can be constructed from the object and function types, as
2324 -- An array type describes a contiguously allocated nonempty set of objects with a
2325 particular member object type, called the element type. The element type shall be
2326 complete whenever the array type is specified. Array types are characterized by their
2327 element type and by the number of elements in the array. An array type is said to be
2328 derived from its element type, and if its element type is T , the array type is sometimes
2329 called ''array of T ''. The construction of an array type from an element type is called
2330 ''array type derivation''.
2331 -- A structure type describes a sequentially allocated nonempty set of member objects
2332 (and, in certain circumstances, an incomplete array), each of which has an optionally
2333 specified name and possibly distinct type.
2334 -- A union type describes an overlapping nonempty set of member objects, each of
2335 which has an optionally specified name and possibly distinct type.
2336 -- A function type describes a function with specified return type. A function type is
2337 characterized by its return type and the number and types of its parameters. A
2338 function type is said to be derived from its return type, and if its return type is T , the
2339 function type is sometimes called ''function returning T ''. The construction of a
2340 function type from a return type is called ''function type derivation''.
2341 -- A pointer type may be derived from a function type or an object type, called the
2342 referenced type. A pointer type describes an object whose value provides a reference
2343 to an entity of the referenced type. A pointer type derived from the referenced type T
2344 is sometimes called ''pointer to T ''. The construction of a pointer type from a
2345 referenced type is called ''pointer type derivation''. A pointer type is a complete
2347 -- An atomic type describes the type designated by the construct _Atomic ( type-
2348 name ). (Atomic types are a conditional feature that implementations need not
2349 support; see <a href="#6.10.8.3">6.10.8.3</a>.)
2350 These methods of constructing derived types can be applied recursively.
2351 21 Arithmetic types and pointer types are collectively called scalar types. Array and
2352 structure types are collectively called aggregate types.<sup><a href="#note46"><b>46)</b></a></sup>
2353 22 An array type of unknown size is an incomplete type. It is completed, for an identifier of
2354 that type, by specifying the size in a later declaration (with internal or external linkage).
2355 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
2358 <sup><a name="note46" href="#note46"><b>46)</b></a></sup> Note that aggregate type does not include union type because an object with union type can only
2359 contain one member at a time.
2361 [<a name="p42" href="#p42">page 42</a>] (<a href="#Contents">Contents</a>)
2363 type. It is completed, for all declarations of that type, by declaring the same structure or
2364 union tag with its defining content later in the same scope.
2365 23 A type has known constant size if the type is not incomplete and is not a variable length
2367 24 Array, function, and pointer types are collectively called derived declarator types. A
2368 declarator type derivation from a type T is the construction of a derived declarator type
2369 from T by the application of an array-type, a function-type, or a pointer-type derivation to
2371 25 A type is characterized by its type category, which is either the outermost derivation of a
2372 derived type (as noted above in the construction of derived types), or the type itself if the
2373 type consists of no derived types.
2374 26 Any type so far mentioned is an unqualified type. Each unqualified type has several
2375 qualified versions of its type,<sup><a href="#note47"><b>47)</b></a></sup> corresponding to the combinations of one, two, or all
2376 three of the const, volatile, and restrict qualifiers. The qualified or unqualified
2377 versions of a type are distinct types that belong to the same type category and have the
2378 same representation and alignment requirements.<sup><a href="#note48"><b>48)</b></a></sup> A derived type is not qualified by the
2379 qualifiers (if any) of the type from which it is derived.
2380 27 Further, there is the _Atomic qualifier. The presence of the _Atomic qualifier
2381 designates an atomic type. The size, representation, and alignment of an atomic type
2382 need not be the same as those of the corresponding unqualified type. Therefore, this
2383 Standard explicitly uses the phrase ''atomic, qualified or unqualified type'' whenever the
2384 atomic version of a type is permitted along with the other qualified versions of a type.
2385 The phrase ''qualified or unqualified type'', without specific mention of atomic, does not
2386 include the atomic types.
2387 28 A pointer to void shall have the same representation and alignment requirements as a
2388 pointer to a character type.48) Similarly, pointers to qualified or unqualified versions of
2389 compatible types shall have the same representation and alignment requirements. All
2390 pointers to structure types shall have the same representation and alignment requirements
2391 as each other. All pointers to union types shall have the same representation and
2392 alignment requirements as each other. Pointers to other types need not have the same
2393 representation or alignment requirements.
2394 29 EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is
2395 pointer, not a floating type. The const-qualified version of this type is designated as ''float * const''
2396 whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const-
2399 <sup><a name="note47" href="#note47"><b>47)</b></a></sup> See <a href="#6.7.3">6.7.3</a> regarding qualified array and function types.
2400 <sup><a name="note48" href="#note48"><b>48)</b></a></sup> The same representation and alignment requirements are meant to imply interchangeability as
2401 arguments to functions, return values from functions, and members of unions.
2403 [<a name="p43" href="#p43">page 43</a>] (<a href="#Contents">Contents</a>)
2405 qualified float'' and is a pointer to a qualified type.
2407 30 EXAMPLE 2 The type designated as ''struct tag (*[5])(float)'' has type ''array of pointer to
2408 function returning struct tag''. The array has length five and the function has a single parameter of type
2409 float. Its type category is array.
2411 Forward references: compatible type and composite type (<a href="#6.2.7">6.2.7</a>), declarations (<a href="#6.7">6.7</a>).
2412 <a name="6.2.6" href="#6.2.6"><b> 6.2.6 Representations of types</b></a>
2413 <a name="6.2.6.1" href="#6.2.6.1"><b> 6.2.6.1 General</b></a>
2414 1 The representations of all types are unspecified except as stated in this subclause.
2415 2 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes,
2416 the number, order, and encoding of which are either explicitly specified or
2417 implementation-defined.
2418 3 Values stored in unsigned bit-fields and objects of type unsigned char shall be
2419 represented using a pure binary notation.<sup><a href="#note49"><b>49)</b></a></sup>
2420 4 Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT
2421 bits, where n is the size of an object of that type, in bytes. The value may be copied into
2422 an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is
2423 called the object representation of the value. Values stored in bit-fields consist of m bits,
2424 where m is the size specified for the bit-field. The object representation is the set of m
2425 bits the bit-field comprises in the addressable storage unit holding it. Two values (other
2426 than NaNs) with the same object representation compare equal, but values that compare
2427 equal may have different object representations.
2428 5 Certain object representations need not represent a value of the object type. If the stored
2429 value of an object has such a representation and is read by an lvalue expression that does
2430 not have character type, the behavior is undefined. If such a representation is produced
2431 by a side effect that modifies all or any part of the object by an lvalue expression that
2432 does not have character type, the behavior is undefined.<sup><a href="#note50"><b>50)</b></a></sup> Such a representation is called
2433 a trap representation.
2434 6 When a value is stored in an object of structure or union type, including in a member
2435 object, the bytes of the object representation that correspond to any padding bytes take
2436 unspecified values.<sup><a href="#note51"><b>51)</b></a></sup> The value of a structure or union object is never a trap
2439 <sup><a name="note49" href="#note49"><b>49)</b></a></sup> A positional representation for integers that uses the binary digits 0 and 1, in which the values
2440 represented by successive bits are additive, begin with 1, and are multiplied by successive integral
2441 powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
2442 Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
2443 type unsigned char range from 0 to 2
2446 <sup><a name="note50" href="#note50"><b>50)</b></a></sup> Thus, an automatic variable can be initialized to a trap representation without causing undefined
2447 behavior, but the value of the variable cannot be used until a proper value is stored in it.
2449 [<a name="p44" href="#p44">page 44</a>] (<a href="#Contents">Contents</a>)
2451 representation, even though the value of a member of the structure or union object may be
2452 a trap representation.
2453 7 When a value is stored in a member of an object of union type, the bytes of the object
2454 representation that do not correspond to that member but do correspond to other members
2455 take unspecified values.
2456 8 Where an operator is applied to a value that has more than one object representation,
2457 which object representation is used shall not affect the value of the result.<sup><a href="#note52"><b>52)</b></a></sup> Where a
2458 value is stored in an object using a type that has more than one object representation for
2459 that value, it is unspecified which representation is used, but a trap representation shall
2461 9 Loads and stores of objects with atomic types are done with
2462 memory_order_seq_cst semantics.
2463 Forward references: declarations (<a href="#6.7">6.7</a>), expressions (<a href="#6.5">6.5</a>), lvalues, arrays, and function
2464 designators (<a href="#6.3.2.1">6.3.2.1</a>), order and consistency (<a href="#7.17.3">7.17.3</a>).
2465 <a name="6.2.6.2" href="#6.2.6.2"><b> 6.2.6.2 Integer types</b></a>
2466 1 For unsigned integer types other than unsigned char, the bits of the object
2467 representation shall be divided into two groups: value bits and padding bits (there need
2468 not be any of the latter). If there are N value bits, each bit shall represent a different
2469 power of 2 between 1 and 2 N -1 , so that objects of that type shall be capable of
2470 representing values from 0 to 2 N - 1 using a pure binary representation; this shall be
2471 known as the value representation. The values of any padding bits are unspecified.<sup><a href="#note53"><b>53)</b></a></sup>
2472 2 For signed integer types, the bits of the object representation shall be divided into three
2473 groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
2474 signed char shall not have any padding bits. There shall be exactly one sign bit.
2475 Each bit that is a value bit shall have the same value as the same bit in the object
2476 representation of the corresponding unsigned type (if there are M value bits in the signed
2477 type and N in the unsigned type, then M <= N ). If the sign bit is zero, it shall not affect
2479 <sup><a name="note51" href="#note51"><b>51)</b></a></sup> Thus, for example, structure assignment need not copy any padding bits.
2480 <sup><a name="note52" href="#note52"><b>52)</b></a></sup> It is possible for objects x and y with the same effective type T to have the same value when they are
2481 accessed as objects of type T, but to have different values in other contexts. In particular, if == is
2482 defined for type T, then x == y does not imply that memcmp(&x, &y, sizeof (T)) == 0.
2483 Furthermore, x == y does not necessarily imply that x and y have the same value; other operations
2484 on values of type T may distinguish between them.
2485 <sup><a name="note53" href="#note53"><b>53)</b></a></sup> Some combinations of padding bits might generate trap representations, for example, if one padding
2486 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2487 representation other than as part of an exceptional condition such as an overflow, and this cannot occur
2488 with unsigned types. All other combinations of padding bits are alternative object representations of
2489 the value specified by the value bits.
2491 [<a name="p45" href="#p45">page 45</a>] (<a href="#Contents">Contents</a>)
2493 the resulting value. If the sign bit is one, the value shall be modified in one of the
2495 -- the corresponding value with sign bit 0 is negated (sign and magnitude);
2496 -- the sign bit has the value -(2 M ) (two's complement);
2497 -- the sign bit has the value -(2 M - 1) (ones' complement).
2498 Which of these applies is implementation-defined, as is whether the value with sign bit 1
2499 and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones'
2500 complement), is a trap representation or a normal value. In the case of sign and
2501 magnitude and ones' complement, if this representation is a normal value it is called a
2503 3 If the implementation supports negative zeros, they shall be generated only by:
2504 -- the &, |, ^, ~, <<, and >> operators with operands that produce such a value;
2505 -- the +, -, *, /, and % operators where one operand is a negative zero and the result is
2507 -- compound assignment operators based on the above cases.
2508 It is unspecified whether these cases actually generate a negative zero or a normal zero,
2509 and whether a negative zero becomes a normal zero when stored in an object.
2510 4 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
2511 and >> operators with operands that would produce such a value is undefined.
2512 5 The values of any padding bits are unspecified.<sup><a href="#note54"><b>54)</b></a></sup> A valid (non-trap) object representation
2513 of a signed integer type where the sign bit is zero is a valid object representation of the
2514 corresponding unsigned type, and shall represent the same value. For any integer type,
2515 the object representation where all the bits are zero shall be a representation of the value
2517 6 The precision of an integer type is the number of bits it uses to represent values,
2518 excluding any sign and padding bits. The width of an integer type is the same but
2519 including any sign bit; thus for unsigned integer types the two values are the same, while
2520 for signed integer types the width is one greater than the precision.
2525 <sup><a name="note54" href="#note54"><b>54)</b></a></sup> Some combinations of padding bits might generate trap representations, for example, if one padding
2526 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2527 representation other than as part of an exceptional condition such as an overflow. All other
2528 combinations of padding bits are alternative object representations of the value specified by the value
2531 [<a name="p46" href="#p46">page 46</a>] (<a href="#Contents">Contents</a>)
2533 <a name="6.2.7" href="#6.2.7"><b> 6.2.7 Compatible type and composite type</b></a>
2534 1 Two types have compatible type if their types are the same. Additional rules for
2535 determining whether two types are compatible are described in <a href="#6.7.2">6.7.2</a> for type specifiers,
2536 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.<sup><a href="#note55"><b>55)</b></a></sup> Moreover, two structure,
2537 union, or enumerated types declared in separate translation units are compatible if their
2538 tags and members satisfy the following requirements: If one is declared with a tag, the
2539 other shall be declared with the same tag. If both are completed anywhere within their
2540 respective translation units, then the following additional requirements apply: there shall
2541 be a one-to-one correspondence between their members such that each pair of
2542 corresponding members are declared with compatible types; if one member of the pair is
2543 declared with an alignment specifier, the other is declared with an equivalent alignment
2544 specifier; and if one member of the pair is declared with a name, the other is declared
2545 with the same name. For two structures, corresponding members shall be declared in the
2546 same order. For two structures or unions, corresponding bit-fields shall have the same
2547 widths. For two enumerations, corresponding members shall have the same values.
2548 2 All declarations that refer to the same object or function shall have compatible type;
2549 otherwise, the behavior is undefined.
2550 3 A composite type can be constructed from two types that are compatible; it is a type that
2551 is compatible with both of the two types and satisfies the following conditions:
2552 -- If both types are array types, the following rules are applied:
2553 o If one type is an array of known constant size, the composite type is an array of
2555 o Otherwise, if one type is a variable length array whose size is specified by an
2556 expression that is not evaluated, the behavior is undefined.
2557 o Otherwise, if one type is a variable length array whose size is specified, the
2558 composite type is a variable length array of that size.
2559 o Otherwise, if one type is a variable length array of unspecified size, the composite
2560 type is a variable length array of unspecified size.
2561 o Otherwise, both types are arrays of unknown size and the composite type is an
2562 array of unknown size.
2563 The element type of the composite type is the composite type of the two element
2565 -- If only one type is a function type with a parameter type list (a function prototype),
2566 the composite type is a function prototype with the parameter type list.
2569 <sup><a name="note55" href="#note55"><b>55)</b></a></sup> Two types need not be identical to be compatible.
2571 [<a name="p47" href="#p47">page 47</a>] (<a href="#Contents">Contents</a>)
2573 -- If both types are function types with parameter type lists, the type of each parameter
2574 in the composite parameter type list is the composite type of the corresponding
2576 These rules apply recursively to the types from which the two types are derived.
2577 4 For an identifier with internal or external linkage declared in a scope in which a prior
2578 declaration of that identifier is visible,<sup><a href="#note56"><b>56)</b></a></sup> if the prior declaration specifies internal or
2579 external linkage, the type of the identifier at the later declaration becomes the composite
2581 Forward references: array declarators (<a href="#6.7.6.2">6.7.6.2</a>).
2582 5 EXAMPLE Given the following two file scope declarations:
2583 int f(int (*)(), double (*)[3]);
2584 int f(int (*)(char *), double (*)[]);
2585 The resulting composite type for the function is:
2586 int f(int (*)(char *), double (*)[3]);
2588 <a name="6.2.8" href="#6.2.8"><b> 6.2.8 Alignment of objects</b></a>
2589 1 Complete object types have alignment requirements which place restrictions on the
2590 addresses at which objects of that type may be allocated. An alignment is an
2591 implementation-defined integer value representing the number of bytes between
2592 successive addresses at which a given object can be allocated. An object type imposes an
2593 alignment requirement on every object of that type: stricter alignment can be requested
2594 using the _Alignas keyword.
2595 2 A fundamental alignment is represented by an alignment less than or equal to the greatest
2596 alignment supported by the implementation in all contexts, which is equal to
2597 alignof(max_align_t).
2598 3 An extended alignment is represented by an alignment greater than
2599 alignof(max_align_t). It is implementation-defined whether any extended
2600 alignments are supported and the contexts in which they are supported. A type having an
2601 extended alignment requirement is an over-aligned type.<sup><a href="#note57"><b>57)</b></a></sup>
2602 4 Alignments are represented as values of the type size_t. Valid alignments include only
2603 those values returned by an alignof expression for fundamental types, plus an
2604 additional implementation-defined set of values, which may be empty. Every valid
2605 alignment value shall be a nonnegative integral power of two.
2608 <sup><a name="note56" href="#note56"><b>56)</b></a></sup> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
2609 <sup><a name="note57" href="#note57"><b>57)</b></a></sup> Every over-aligned type is, or contains, a structure or union type with a member to which an extended
2610 alignment has been applied.
2612 [<a name="p48" href="#p48">page 48</a>] (<a href="#Contents">Contents</a>)
2614 5 Alignments have an order from weaker to stronger or stricter alignments. Stricter
2615 alignments have larger alignment values. An address that satisfies an alignment
2616 requirement also satisfies any weaker valid alignment requirement.
2617 6 The alignment requirement of a complete type can be queried using an alignof
2618 expression. The types char, signed char, and unsigned char shall have the
2619 weakest alignment requirement.
2620 7 Comparing alignments is meaningful and provides the obvious results:
2621 -- Two alignments are equal when their numeric values are equal.
2622 -- Two alignments are different when their numeric values are not equal.
2623 -- When an alignment is larger than another it represents a stricter alignment.
2628 [<a name="p49" href="#p49">page 49</a>] (<a href="#Contents">Contents</a>)
2630 <a name="6.3" href="#6.3"><b> 6.3 Conversions</b></a>
2631 1 Several operators convert operand values from one type to another automatically. This
2632 subclause specifies the result required from such an implicit conversion, as well as those
2633 that result from a cast operation (an explicit conversion). The list in <a href="#6.3.1.8">6.3.1.8</a> summarizes
2634 the conversions performed by most ordinary operators; it is supplemented as required by
2635 the discussion of each operator in <a href="#6.5">6.5</a>.
2636 2 Conversion of an operand value to a compatible type causes no change to the value or the
2638 Forward references: cast operators (<a href="#6.5.4">6.5.4</a>).
2639 <a name="6.3.1" href="#6.3.1"><b> 6.3.1 Arithmetic operands</b></a>
2640 <a name="6.3.1.1" href="#6.3.1.1"><b> 6.3.1.1 Boolean, characters, and integers</b></a>
2641 1 Every integer type has an integer conversion rank defined as follows:
2642 -- No two signed integer types shall have the same rank, even if they have the same
2644 -- The rank of a signed integer type shall be greater than the rank of any signed integer
2645 type with less precision.
2646 -- The rank of long long int shall be greater than the rank of long int, which
2647 shall be greater than the rank of int, which shall be greater than the rank of short
2648 int, which shall be greater than the rank of signed char.
2649 -- The rank of any unsigned integer type shall equal the rank of the corresponding
2650 signed integer type, if any.
2651 -- The rank of any standard integer type shall be greater than the rank of any extended
2652 integer type with the same width.
2653 -- The rank of char shall equal the rank of signed char and unsigned char.
2654 -- The rank of _Bool shall be less than the rank of all other standard integer types.
2655 -- The rank of any enumerated type shall equal the rank of the compatible integer type
2656 (see <a href="#6.7.2.2">6.7.2.2</a>).
2657 -- The rank of any extended signed integer type relative to another extended signed
2658 integer type with the same precision is implementation-defined, but still subject to the
2659 other rules for determining the integer conversion rank.
2660 -- For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has
2661 greater rank than T3, then T1 has greater rank than T3.
2662 2 The following may be used in an expression wherever an int or unsigned int may
2665 [<a name="p50" href="#p50">page 50</a>] (<a href="#Contents">Contents</a>)
2667 -- An object or expression with an integer type (other than int or unsigned int)
2668 whose integer conversion rank is less than or equal to the rank of int and
2670 -- A bit-field of type _Bool, int, signed int, or unsigned int.
2671 If an int can represent all values of the original type (as restricted by the width, for a
2672 bit-field), the value is converted to an int; otherwise, it is converted to an unsigned
2673 int. These are called the integer promotions.<sup><a href="#note58"><b>58)</b></a></sup> All other types are unchanged by the
2675 3 The integer promotions preserve value including sign. As discussed earlier, whether a
2676 ''plain'' char is treated as signed is implementation-defined.
2677 Forward references: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
2678 (<a href="#6.7.2.1">6.7.2.1</a>).
2679 <a name="6.3.1.2" href="#6.3.1.2"><b> 6.3.1.2 Boolean type</b></a>
2680 1 When any scalar value is converted to _Bool, the result is 0 if the value compares equal
2681 to 0; otherwise, the result is 1.<sup><a href="#note59"><b>59)</b></a></sup>
2682 <a name="6.3.1.3" href="#6.3.1.3"><b> 6.3.1.3 Signed and unsigned integers</b></a>
2683 1 When a value with integer type is converted to another integer type other than _Bool, if
2684 the value can be represented by the new type, it is unchanged.
2685 2 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or
2686 subtracting one more than the maximum value that can be represented in the new type
2687 until the value is in the range of the new type.<sup><a href="#note60"><b>60)</b></a></sup>
2688 3 Otherwise, the new type is signed and the value cannot be represented in it; either the
2689 result is implementation-defined or an implementation-defined signal is raised.
2690 <a name="6.3.1.4" href="#6.3.1.4"><b> 6.3.1.4 Real floating and integer</b></a>
2691 1 When a finite value of real floating type is converted to an integer type other than _Bool,
2692 the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
2693 the integral part cannot be represented by the integer type, the behavior is undefined.<sup><a href="#note61"><b>61)</b></a></sup>
2696 <sup><a name="note58" href="#note58"><b>58)</b></a></sup> The integer promotions are applied only: as part of the usual arithmetic conversions, to certain
2697 argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the
2698 shift operators, as specified by their respective subclauses.
2699 <sup><a name="note59" href="#note59"><b>59)</b></a></sup> NaNs do not compare equal to 0 and thus convert to 1.
2700 <sup><a name="note60" href="#note60"><b>60)</b></a></sup> The rules describe arithmetic on the mathematical value, not the value of a given type of expression.
2701 <sup><a name="note61" href="#note61"><b>61)</b></a></sup> The remaindering operation performed when a value of integer type is converted to unsigned type
2702 need not be performed when a value of real floating type is converted to unsigned type. Thus, the
2703 range of portable real floating values is (-1, Utype_MAX+1).
2705 [<a name="p51" href="#p51">page 51</a>] (<a href="#Contents">Contents</a>)
2707 2 When a value of integer type is converted to a real floating type, if the value being
2708 converted can be represented exactly in the new type, it is unchanged. If the value being
2709 converted is in the range of values that can be represented but cannot be represented
2710 exactly, the result is either the nearest higher or nearest lower representable value, chosen
2711 in an implementation-defined manner. If the value being converted is outside the range of
2712 values that can be represented, the behavior is undefined. Results of some implicit
2713 conversions (<a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a>) may be represented in greater precision and range than that
2714 required by the new type.
2715 <a name="6.3.1.5" href="#6.3.1.5"><b> 6.3.1.5 Real floating types</b></a>
2716 1 When a value of real floating type is converted to a real floating type, if the value being
2717 converted can be represented exactly in the new type, it is unchanged. If the value being
2718 converted is in the range of values that can be represented but cannot be represented
2719 exactly, the result is either the nearest higher or nearest lower representable value, chosen
2720 in an implementation-defined manner. If the value being converted is outside the range of
2721 values that can be represented, the behavior is undefined. Results of some implicit
2722 conversions (<a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a>) may be represented in greater precision and range than that
2723 required by the new type.
2724 <a name="6.3.1.6" href="#6.3.1.6"><b> 6.3.1.6 Complex types</b></a>
2725 1 When a value of complex type is converted to another complex type, both the real and
2726 imaginary parts follow the conversion rules for the corresponding real types.
2727 <a name="6.3.1.7" href="#6.3.1.7"><b> 6.3.1.7 Real and complex</b></a>
2728 1 When a value of real type is converted to a complex type, the real part of the complex
2729 result value is determined by the rules of conversion to the corresponding real type and
2730 the imaginary part of the complex result value is a positive zero or an unsigned zero.
2731 2 When a value of complex type is converted to a real type, the imaginary part of the
2732 complex value is discarded and the value of the real part is converted according to the
2733 conversion rules for the corresponding real type.
2734 <a name="6.3.1.8" href="#6.3.1.8"><b> 6.3.1.8 Usual arithmetic conversions</b></a>
2735 1 Many operators that expect operands of arithmetic type cause conversions and yield result
2736 types in a similar way. The purpose is to determine a common real type for the operands
2737 and result. For the specified operands, each operand is converted, without change of type
2738 domain, to a type whose corresponding real type is the common real type. Unless
2739 explicitly stated otherwise, the common real type is also the corresponding real type of
2740 the result, whose type domain is the type domain of the operands if they are the same,
2741 and complex otherwise. This pattern is called the usual arithmetic conversions:
2742 First, if the corresponding real type of either operand is long double, the other
2743 operand is converted, without change of type domain, to a type whose
2745 [<a name="p52" href="#p52">page 52</a>] (<a href="#Contents">Contents</a>)
2747 corresponding real type is long double.
2748 Otherwise, if the corresponding real type of either operand is double, the other
2749 operand is converted, without change of type domain, to a type whose
2750 corresponding real type is double.
2751 Otherwise, if the corresponding real type of either operand is float, the other
2752 operand is converted, without change of type domain, to a type whose
2753 corresponding real type is float.<sup><a href="#note62"><b>62)</b></a></sup>
2754 Otherwise, the integer promotions are performed on both operands. Then the
2755 following rules are applied to the promoted operands:
2756 If both operands have the same type, then no further conversion is needed.
2757 Otherwise, if both operands have signed integer types or both have unsigned
2758 integer types, the operand with the type of lesser integer conversion rank is
2759 converted to the type of the operand with greater rank.
2760 Otherwise, if the operand that has unsigned integer type has rank greater or
2761 equal to the rank of the type of the other operand, then the operand with
2762 signed integer type is converted to the type of the operand with unsigned
2764 Otherwise, if the type of the operand with signed integer type can represent
2765 all of the values of the type of the operand with unsigned integer type, then
2766 the operand with unsigned integer type is converted to the type of the
2767 operand with signed integer type.
2768 Otherwise, both operands are converted to the unsigned integer type
2769 corresponding to the type of the operand with signed integer type.
2770 2 The values of floating operands and of the results of floating expressions may be
2771 represented in greater precision and range than that required by the type; the types are not
2772 changed thereby.<sup><a href="#note63"><b>63)</b></a></sup>
2777 <sup><a name="note62" href="#note62"><b>62)</b></a></sup> For example, addition of a double _Complex and a float entails just the conversion of the
2778 float operand to double (and yields a double _Complex result).
2779 <sup><a name="note63" href="#note63"><b>63)</b></a></sup> The cast and assignment operators are still required to remove extra range and precision.
2781 [<a name="p53" href="#p53">page 53</a>] (<a href="#Contents">Contents</a>)
2783 <a name="6.3.2" href="#6.3.2"><b> 6.3.2 Other operands</b></a>
2784 <a name="6.3.2.1" href="#6.3.2.1"><b> 6.3.2.1 Lvalues, arrays, and function designators</b></a>
2785 1 An lvalue is an expression (with an object type other than void) that potentially
2786 designates an object;<sup><a href="#note64"><b>64)</b></a></sup> if an lvalue does not designate an object when it is evaluated, the
2787 behavior is undefined. When an object is said to have a particular type, the type is
2788 specified by the lvalue used to designate the object. A modifiable lvalue is an lvalue that
2789 does not have array type, does not have an incomplete type, does not have a const-
2790 qualified type, and if it is a structure or union, does not have any member (including,
2791 recursively, any member or element of all contained aggregates or unions) with a const-
2793 2 Except when it is the operand of the sizeof operator, the unary & operator, the ++
2794 operator, the -- operator, or the left operand of the . operator or an assignment operator,
2795 an lvalue that does not have array type is converted to the value stored in the designated
2796 object (and is no longer an lvalue); this is called lvalue conversion. If the lvalue has
2797 qualified type, the value has the unqualified version of the type of the lvalue; additionally,
2798 if the lvalue has atomic type, the value has the non-atomic version of the type of the
2799 lvalue; otherwise, the value has the type of the lvalue. If the lvalue has an incomplete
2800 type and does not have array type, the behavior is undefined. If the lvalue designates an
2801 object of automatic storage duration that could have been declared with the register
2802 storage class (never had its address taken), and that object is uninitialized (not declared
2803 with an initializer and no assignment to it has been performed prior to use), the behavior
2805 3 Except when it is the operand of the sizeof operator or the unary & operator, or is a
2806 string literal used to initialize an array, an expression that has type ''array of type'' is
2807 converted to an expression with type ''pointer to type'' that points to the initial element of
2808 the array object and is not an lvalue. If the array object has register storage class, the
2809 behavior is undefined.
2810 4 A function designator is an expression that has function type. Except when it is the
2811 operand of the sizeof operator<sup><a href="#note65"><b>65)</b></a></sup> or the unary & operator, a function designator with
2812 type ''function returning type'' is converted to an expression that has type ''pointer to
2815 <sup><a name="note64" href="#note64"><b>64)</b></a></sup> The name ''lvalue'' comes originally from the assignment expression E1 = E2, in which the left
2816 operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
2817 object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described
2818 as the ''value of an expression''.
2819 An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
2820 expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.
2821 <sup><a name="note65" href="#note65"><b>65)</b></a></sup> Because this conversion does not occur, the operand of the sizeof operator remains a function
2822 designator and violates the constraint in <a href="#6.5.3.4">6.5.3.4</a>.
2824 [<a name="p54" href="#p54">page 54</a>] (<a href="#Contents">Contents</a>)
2826 function returning type''.
2827 Forward references: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), assignment operators
2828 (<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
2829 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2830 (<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>).
2831 <a href="#6.3.2.2">6.3.2.2</a> void
2832 1 The (nonexistent) value of a void expression (an expression that has type void) shall not
2833 be used in any way, and implicit or explicit conversions (except to void) shall not be
2834 applied to such an expression. If an expression of any other type is evaluated as a void
2835 expression, its value or designator is discarded. (A void expression is evaluated for its
2837 <a name="6.3.2.3" href="#6.3.2.3"><b> 6.3.2.3 Pointers</b></a>
2838 1 A pointer to void may be converted to or from a pointer to any object type. A pointer to
2839 any object type may be converted to a pointer to void and back again; the result shall
2840 compare equal to the original pointer.
2841 2 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to
2842 the q-qualified version of the type; the values stored in the original and converted pointers
2843 shall compare equal.
2844 3 An integer constant expression with the value 0, or such an expression cast to type
2845 void *, is called a null pointer constant.<sup><a href="#note66"><b>66)</b></a></sup> If a null pointer constant is converted to a
2846 pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal
2847 to a pointer to any object or function.
2848 4 Conversion of a null pointer to another pointer type yields a null pointer of that type.
2849 Any two null pointers shall compare equal.
2850 5 An integer may be converted to any pointer type. Except as previously specified, the
2851 result is implementation-defined, might not be correctly aligned, might not point to an
2852 entity of the referenced type, and might be a trap representation.<sup><a href="#note67"><b>67)</b></a></sup>
2853 6 Any pointer type may be converted to an integer type. Except as previously specified, the
2854 result is implementation-defined. If the result cannot be represented in the integer type,
2855 the behavior is undefined. The result need not be in the range of values of any integer
2861 <sup><a name="note66" href="#note66"><b>66)</b></a></sup> 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>.
2862 <sup><a name="note67" href="#note67"><b>67)</b></a></sup> The mapping functions for converting a pointer to an integer or an integer to a pointer are intended to
2863 be consistent with the addressing structure of the execution environment.
2865 [<a name="p55" href="#p55">page 55</a>] (<a href="#Contents">Contents</a>)
2867 7 A pointer to an object type may be converted to a pointer to a different object type. If the
2868 resulting pointer is not correctly aligned<sup><a href="#note68"><b>68)</b></a></sup> for the referenced type, the behavior is
2869 undefined. Otherwise, when converted back again, the result shall compare equal to the
2870 original pointer. When a pointer to an object is converted to a pointer to a character type,
2871 the result points to the lowest addressed byte of the object. Successive increments of the
2872 result, up to the size of the object, yield pointers to the remaining bytes of the object.
2873 8 A pointer to a function of one type may be converted to a pointer to a function of another
2874 type and back again; the result shall compare equal to the original pointer. If a converted
2875 pointer is used to call a function whose type is not compatible with the referenced type,
2876 the behavior is undefined.
2877 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
2878 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>).
2883 <sup><a name="note68" href="#note68"><b>68)</b></a></sup> In general, the concept ''correctly aligned'' is transitive: if a pointer to type A is correctly aligned for a
2884 pointer to type B, which in turn is correctly aligned for a pointer to type C, then a pointer to type A is
2885 correctly aligned for a pointer to type C.
2887 [<a name="p56" href="#p56">page 56</a>] (<a href="#Contents">Contents</a>)
2889 <a name="6.4" href="#6.4"><b> 6.4 Lexical elements</b></a>
2897 preprocessing-token:
2904 each non-white-space character that cannot be one of the above
2906 2 Each preprocessing token that is converted to a token shall have the lexical form of a
2907 keyword, an identifier, a constant, a string literal, or a punctuator.
2909 3 A token is the minimal lexical element of the language in translation phases 7 and 8. The
2910 categories of tokens are: keywords, identifiers, constants, string literals, and punctuators.
2911 A preprocessing token is the minimal lexical element of the language in translation
2912 phases 3 through 6. The categories of preprocessing tokens are: header names,
2913 identifiers, preprocessing numbers, character constants, string literals, punctuators, and
2914 single non-white-space characters that do not lexically match the other preprocessing
2915 token categories.<sup><a href="#note69"><b>69)</b></a></sup> If a ' or a " character matches the last category, the behavior is
2916 undefined. Preprocessing tokens can be separated by white space; this consists of
2917 comments (described later), or white-space characters (space, horizontal tab, new-line,
2918 vertical tab, and form-feed), or both. As described in <a href="#6.10">6.10</a>, in certain circumstances
2919 during translation phase 4, white space (or the absence thereof) serves as more than
2920 preprocessing token separation. White space may appear within a preprocessing token
2921 only as part of a header name or between the quotation characters in a character constant
2926 <sup><a name="note69" href="#note69"><b>69)</b></a></sup> 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
2927 occur in source files.
2929 [<a name="p57" href="#p57">page 57</a>] (<a href="#Contents">Contents</a>)
2931 4 If the input stream has been parsed into preprocessing tokens up to a given character, the
2932 next preprocessing token is the longest sequence of characters that could constitute a
2933 preprocessing token. There is one exception to this rule: header name preprocessing
2934 tokens are recognized only within #include preprocessing directives and in
2935 implementation-defined locations within #pragma directives. In such contexts, a
2936 sequence of characters that could be either a header name or a string literal is recognized
2938 5 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a
2939 valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex
2940 might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program
2941 fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or
2942 not E is a macro name.
2944 6 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
2945 increment operators, even though the parse x ++ + ++ y might yield a correct expression.
2947 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>),
2948 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
2949 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2950 (<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
2951 (<a href="#6.4.5">6.4.5</a>).
2952 <a name="6.4.1" href="#6.4.1"><b> 6.4.1 Keywords</b></a>
2960 const register _Alignas
2961 continue restrict _Atomic
2962 default return _Bool
2964 double signed _Generic
2965 else sizeof _Imaginary
2966 enum static _Noreturn
2967 extern struct _Static_assert
2968 float switch _Thread_local
2971 2 The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as
2972 keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
2973 [<a name="p58" href="#p58">page 58</a>] (<a href="#Contents">Contents</a>)
2975 specifying imaginary types.<sup><a href="#note70"><b>70)</b></a></sup>
2976 <a name="6.4.2" href="#6.4.2"><b> 6.4.2 Identifiers</b></a>
2977 <a name="6.4.2.1" href="#6.4.2.1"><b> 6.4.2.1 General</b></a>
2981 identifier identifier-nondigit
2983 identifier-nondigit:
2985 universal-character-name
2986 other implementation-defined characters
2988 _ a b c d e f g h i j k l m
2989 n o p q r s t u v w x y z
2990 A B C D E F G H I J K L M
2991 N O P Q R S T U V W X Y Z
2995 2 An identifier is a sequence of nondigit characters (including the underscore _, the
2996 lowercase and uppercase Latin letters, and other characters) and digits, which designates
2997 one or more entities as described in <a href="#6.2.1">6.2.1</a>. Lowercase and uppercase letters are distinct.
2998 There is no specific limit on the maximum length of an identifier.
2999 3 Each universal character name in an identifier shall designate a character whose encoding
3000 in ISO/IEC 10646 falls into one of the ranges specified in D.1.<sup><a href="#note71"><b>71)</b></a></sup> The initial character
3001 shall not be a universal character name designating a character whose encoding falls into
3002 one of the ranges specified in <a href="#D.2">D.2</a>. An implementation may allow multibyte characters
3003 that are not part of the basic source character set to appear in identifiers; which characters
3004 and their correspondence to universal character names is implementation-defined.
3008 <sup><a name="note70" href="#note70"><b>70)</b></a></sup> One possible specification for imaginary types appears in <a href="#G">annex G</a>.
3009 <sup><a name="note71" href="#note71"><b>71)</b></a></sup> On systems in which linkers cannot accept extended characters, an encoding of the universal character
3010 name may be used in forming valid external identifiers. For example, some otherwise unused
3011 character or sequence of characters may be used to encode the \u in a universal character name.
3012 Extended characters may produce a long external identifier.
3014 [<a name="p59" href="#p59">page 59</a>] (<a href="#Contents">Contents</a>)
3016 4 When preprocessing tokens are converted to tokens during translation phase 7, if a
3017 preprocessing token could be converted to either a keyword or an identifier, it is converted
3019 Implementation limits
3020 5 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of significant initial
3021 characters in an identifier; the limit for an external name (an identifier that has external
3022 linkage) may be more restrictive than that for an internal name (a macro name or an
3023 identifier that does not have external linkage). The number of significant characters in an
3024 identifier is implementation-defined.
3025 6 Any identifiers that differ in a significant character are different identifiers. If two
3026 identifiers differ only in nonsignificant characters, the behavior is undefined.
3027 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>).
3028 <a name="6.4.2.2" href="#6.4.2.2"><b> 6.4.2.2 Predefined identifiers</b></a>
3030 1 The identifier __func__ shall be implicitly declared by the translator as if,
3031 immediately following the opening brace of each function definition, the declaration
3032 static const char __func__[] = "function-name";
3033 appeared, where function-name is the name of the lexically-enclosing function.<sup><a href="#note72"><b>72)</b></a></sup>
3034 2 This name is encoded as if the implicit declaration had been written in the source
3035 character set and then translated into the execution character set as indicated in translation
3037 3 EXAMPLE Consider the code fragment:
3038 #include <a href="#7.21"><stdio.h></a>
3041 printf("%s\n", __func__);
3044 Each time the function is called, it will print to the standard output stream:
3047 Forward references: function definitions (<a href="#6.9.1">6.9.1</a>).
3052 <sup><a name="note72" href="#note72"><b>72)</b></a></sup> Since the name __func__ is reserved for any use by the implementation (<a href="#7.1.3">7.1.3</a>), if any other
3053 identifier is explicitly declared using the name __func__, the behavior is undefined.
3055 [<a name="p60" href="#p60">page 60</a>] (<a href="#Contents">Contents</a>)
3057 <a name="6.4.3" href="#6.4.3"><b> 6.4.3 Universal character names</b></a>
3059 1 universal-character-name:
3061 \U hex-quad hex-quad
3063 hexadecimal-digit hexadecimal-digit
3064 hexadecimal-digit hexadecimal-digit
3066 2 A universal character name shall not specify a character whose short identifier is less than
3067 00A0 other than 0024 ($), 0040 (@), or 0060 ('), nor one in the range D800 through
3068 DFFF inclusive.<sup><a href="#note73"><b>73)</b></a></sup>
3070 3 Universal character names may be used in identifiers, character constants, and string
3071 literals to designate characters that are not in the basic character set.
3073 4 The universal character name \Unnnnnnnn designates the character whose eight-digit
3074 short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.<sup><a href="#note74"><b>74)</b></a></sup> Similarly, the universal
3075 character name \unnnn designates the character whose four-digit short identifier is nnnn
3076 (and whose eight-digit short identifier is 0000nnnn).
3081 <sup><a name="note73" href="#note73"><b>73)</b></a></sup> The disallowed characters are the characters in the basic character set and the code positions reserved
3082 by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by
3085 <sup><a name="note74" href="#note74"><b>74)</b></a></sup> Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
3087 [<a name="p61" href="#p61">page 61</a>] (<a href="#Contents">Contents</a>)
3089 <a name="6.4.4" href="#6.4.4"><b> 6.4.4 Constants</b></a>
3094 enumeration-constant
3097 2 Each constant shall have a type and the value of a constant shall be in the range of
3098 representable values for its type.
3100 3 Each constant has a type, determined by its form and value, as detailed later.
3101 <a name="6.4.4.1" href="#6.4.4.1"><b> 6.4.4.1 Integer constants</b></a>
3104 decimal-constant integer-suffixopt
3105 octal-constant integer-suffixopt
3106 hexadecimal-constant integer-suffixopt
3109 decimal-constant digit
3112 octal-constant octal-digit
3113 hexadecimal-constant:
3114 hexadecimal-prefix hexadecimal-digit
3115 hexadecimal-constant hexadecimal-digit
3116 hexadecimal-prefix: one of
3118 nonzero-digit: one of
3126 [<a name="p62" href="#p62">page 62</a>] (<a href="#Contents">Contents</a>)
3128 hexadecimal-digit: one of
3133 unsigned-suffix long-suffixopt
3134 unsigned-suffix long-long-suffix
3135 long-suffix unsigned-suffixopt
3136 long-long-suffix unsigned-suffixopt
3137 unsigned-suffix: one of
3141 long-long-suffix: one of
3144 2 An integer constant begins with a digit, but has no period or exponent part. It may have a
3145 prefix that specifies its base and a suffix that specifies its type.
3146 3 A decimal constant begins with a nonzero digit and consists of a sequence of decimal
3147 digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
3148 digits 0 through 7 only. A hexadecimal constant consists of the prefix 0x or 0X followed
3149 by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
3150 10 through 15 respectively.
3152 4 The value of a decimal constant is computed base 10; that of an octal constant, base 8;
3153 that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
3154 5 The type of an integer constant is the first of the corresponding list in which its value can
3160 [<a name="p63" href="#p63">page 63</a>] (<a href="#Contents">Contents</a>)
3162 Octal or Hexadecimal
3163 Suffix Decimal Constant Constant
3166 long int unsigned int
3167 long long int long int
3170 unsigned long long int
3172 u or U unsigned int unsigned int
3173 unsigned long int unsigned long int
3174 unsigned long long int unsigned long long int
3176 l or L long int long int
3177 long long int unsigned long int
3179 unsigned long long int
3181 Both u or U unsigned long int unsigned long int
3182 and l or L unsigned long long int unsigned long long int
3184 ll or LL long long int long long int
3185 unsigned long long int
3187 Both u or U unsigned long long int unsigned long long int
3189 6 If an integer constant cannot be represented by any type in its list, it may have an
3190 extended integer type, if the extended integer type can represent its value. If all of the
3191 types in the list for the constant are signed, the extended integer type shall be signed. If
3192 all of the types in the list for the constant are unsigned, the extended integer type shall be
3193 unsigned. If the list contains both signed and unsigned types, the extended integer type
3194 may be signed or unsigned. If an integer constant cannot be represented by any type in
3195 its list and has no extended integer type, then the integer constant has no type.
3200 [<a name="p64" href="#p64">page 64</a>] (<a href="#Contents">Contents</a>)
3202 <a name="6.4.4.2" href="#6.4.4.2"><b> 6.4.4.2 Floating constants</b></a>
3204 1 floating-constant:
3205 decimal-floating-constant
3206 hexadecimal-floating-constant
3207 decimal-floating-constant:
3208 fractional-constant exponent-partopt floating-suffixopt
3209 digit-sequence exponent-part floating-suffixopt
3210 hexadecimal-floating-constant:
3211 hexadecimal-prefix hexadecimal-fractional-constant
3212 binary-exponent-part floating-suffixopt
3213 hexadecimal-prefix hexadecimal-digit-sequence
3214 binary-exponent-part floating-suffixopt
3215 fractional-constant:
3216 digit-sequenceopt . digit-sequence
3219 e signopt digit-sequence
3220 E signopt digit-sequence
3225 digit-sequence digit
3226 hexadecimal-fractional-constant:
3227 hexadecimal-digit-sequenceopt .
3228 hexadecimal-digit-sequence
3229 hexadecimal-digit-sequence .
3230 binary-exponent-part:
3231 p signopt digit-sequence
3232 P signopt digit-sequence
3233 hexadecimal-digit-sequence:
3235 hexadecimal-digit-sequence hexadecimal-digit
3236 floating-suffix: one of
3239 [<a name="p65" href="#p65">page 65</a>] (<a href="#Contents">Contents</a>)
3242 2 A floating constant has a significand part that may be followed by an exponent part and a
3243 suffix that specifies its type. The components of the significand part may include a digit
3244 sequence representing the whole-number part, followed by a period (.), followed by a
3245 digit sequence representing the fraction part. The components of the exponent part are an
3246 e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
3247 Either the whole-number part or the fraction part has to be present; for decimal floating
3248 constants, either the period or the exponent part has to be present.
3250 3 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
3251 digit sequence in the exponent part is interpreted as a decimal integer. For decimal
3252 floating constants, the exponent indicates the power of 10 by which the significand part is
3253 to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
3254 by which the significand part is to be scaled. For decimal floating constants, and also for
3255 hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
3256 the nearest representable value, or the larger or smaller representable value immediately
3257 adjacent to the nearest representable value, chosen in an implementation-defined manner.
3258 For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
3260 4 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
3261 type float. If suffixed by the letter l or L, it has type long double.
3262 5 Floating constants are converted to internal format as if at translation-time. The
3263 conversion of a floating constant shall not raise an exceptional condition or a floating-
3264 point exception at execution time. All floating constants of the same source form<sup><a href="#note75"><b>75)</b></a></sup> shall
3265 convert to the same internal format with the same value.
3266 Recommended practice
3267 6 The implementation should produce a diagnostic message if a hexadecimal constant
3268 cannot be represented exactly in its evaluation format; the implementation should then
3269 proceed with the translation of the program.
3270 7 The translation-time conversion of floating constants should match the execution-time
3271 conversion of character strings by library functions, such as strtod, given matching
3272 inputs suitable for both conversions, the same result format, and default execution-time
3273 rounding.<sup><a href="#note76"><b>76)</b></a></sup>
3275 <sup><a name="note75" href="#note75"><b>75)</b></a></sup> <a href="#1.23">1.23</a>, 1.230, 123e-2, 123e-02, and 1.23L are all different source forms and thus need not
3276 convert to the same internal format and value.
3277 <sup><a name="note76" href="#note76"><b>76)</b></a></sup> The specification for the library functions recommends more accurate conversion than required for
3278 floating constants (see <a href="#7.22.1.3">7.22.1.3</a>).
3280 [<a name="p66" href="#p66">page 66</a>] (<a href="#Contents">Contents</a>)
3282 <a name="6.4.4.3" href="#6.4.4.3"><b> 6.4.4.3 Enumeration constants</b></a>
3284 1 enumeration-constant:
3287 2 An identifier declared as an enumeration constant has type int.
3288 Forward references: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>).
3289 <a name="6.4.4.4" href="#6.4.4.4"><b> 6.4.4.4 Character constants</b></a>
3291 1 character-constant:
3293 L' c-char-sequence '
3294 u' c-char-sequence '
3295 U' c-char-sequence '
3298 c-char-sequence c-char
3300 any member of the source character set except
3301 the single-quote ', backslash \, or new-line character
3304 simple-escape-sequence
3305 octal-escape-sequence
3306 hexadecimal-escape-sequence
3307 universal-character-name
3308 simple-escape-sequence: one of
3310 \a \b \f \n \r \t \v
3311 octal-escape-sequence:
3313 \ octal-digit octal-digit
3314 \ octal-digit octal-digit octal-digit
3319 [<a name="p67" href="#p67">page 67</a>] (<a href="#Contents">Contents</a>)
3321 hexadecimal-escape-sequence:
3322 \x hexadecimal-digit
3323 hexadecimal-escape-sequence hexadecimal-digit
3325 2 An integer character constant is a sequence of one or more multibyte characters enclosed
3326 in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
3327 letter L, u, or U. With a few exceptions detailed later, the elements of the sequence are
3328 any members of the source character set; they are mapped in an implementation-defined
3329 manner to members of the execution character set.
3330 3 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
3331 arbitrary integer values are representable according to the following table of escape
3337 octal character \octal digits
3338 hexadecimal character \x hexadecimal digits
3339 4 The double-quote " and question-mark ? are representable either by themselves or by the
3340 escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
3341 shall be represented, respectively, by the escape sequences \' and \\.
3342 5 The octal digits that follow the backslash in an octal escape sequence are taken to be part
3343 of the construction of a single character for an integer character constant or of a single
3344 wide character for a wide character constant. The numerical value of the octal integer so
3345 formed specifies the value of the desired character or wide character.
3346 6 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
3347 sequence are taken to be part of the construction of a single character for an integer
3348 character constant or of a single wide character for a wide character constant. The
3349 numerical value of the hexadecimal integer so formed specifies the value of the desired
3350 character or wide character.
3351 7 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
3352 constitute the escape sequence.
3353 8 In addition, characters not in the basic character set are representable by universal
3354 character names and certain nongraphic characters are representable by escape sequences
3355 consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
3356 and \v.<sup><a href="#note77"><b>77)</b></a></sup>
3360 [<a name="p68" href="#p68">page 68</a>] (<a href="#Contents">Contents</a>)
3363 9 The value of an octal or hexadecimal escape sequence shall be in the range of
3364 representable values for the corresponding type:
3365 Prefix Corresponding Type
3367 L the unsigned type corresponding to wchar_t
3371 10 An integer character constant has type int. The value of an integer character constant
3372 containing a single character that maps to a single-byte execution character is the
3373 numerical value of the representation of the mapped character interpreted as an integer.
3374 The value of an integer character constant containing more than one character (e.g.,
3375 'ab'), or containing a character or escape sequence that does not map to a single-byte
3376 execution character, is implementation-defined. If an integer character constant contains
3377 a single character or escape sequence, its value is the one that results when an object with
3378 type char whose value is that of the single character or escape sequence is converted to
3380 11 A wide character constant prefixed by the letter L has type wchar_t, an integer type
3381 defined in the <a href="#7.19"><stddef.h></a> header; a wide character constant prefixed by the letter u or
3382 U has type char16_t or char32_t, respectively, unsigned integer types defined in the
3383 <a href="#7.27"><uchar.h></a> header. The value of a wide character constant containing a single
3384 multibyte character that maps to a single member of the extended execution character set
3385 is the wide character corresponding to that multibyte character, as defined by the
3386 mbtowc, mbrtoc16, or mbrtoc32 function as appropriate for its type, with an
3387 implementation-defined current locale. The value of a wide character constant containing
3388 more than one multibyte character or a single multibyte character that maps to multiple
3389 members of the extended execution character set, or containing a multibyte character or
3390 escape sequence not represented in the extended execution character set, is
3391 implementation-defined.
3392 12 EXAMPLE 1 The construction '\0' is commonly used to represent the null character.
3394 13 EXAMPLE 2 Consider implementations that use two's complement representation for integers and eight
3395 bits for objects that have type char. In an implementation in which type char has the same range of
3396 values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
3397 same range of values as unsigned char, the character constant '\xFF' has the value +255.
3402 <sup><a name="note77" href="#note77"><b>77)</b></a></sup> The semantics of these characters were discussed in <a href="#5.2.2">5.2.2</a>. If any other character follows a backslash,
3403 the result is not a token and a diagnostic is required. See ''future language directions'' (<a href="#6.11.4">6.11.4</a>).
3405 [<a name="p69" href="#p69">page 69</a>] (<a href="#Contents">Contents</a>)
3407 14 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
3408 specifies an integer character constant containing only one character, since a hexadecimal escape sequence
3409 is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
3410 two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
3411 escape sequence is terminated after three octal digits. (The value of this two-character integer character
3412 constant is implementation-defined.)
3414 15 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
3415 L'\1234' specifies the implementation-defined value that results from the combination of the values
3418 Forward references: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbtowc function
3419 (<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>).
3420 <a name="6.4.5" href="#6.4.5"><b> 6.4.5 String literals</b></a>
3423 encoding-prefixopt " s-char-sequenceopt "
3431 s-char-sequence s-char
3433 any member of the source character set except
3434 the double-quote ", backslash \, or new-line character
3437 2 A sequence of adjacent string literal tokens shall not include both a wide string literal and
3438 a UTF-8 string literal.
3440 3 A character string literal is a sequence of zero or more multibyte characters enclosed in
3441 double-quotes, as in "xyz". A UTF-8 string literal is the same, except prefixed by u8.
3442 A wide string literal is the same, except prefixed by the letter L, u, or U.
3443 4 The same considerations apply to each element of the sequence in a string literal as if it
3444 were in an integer character constant (for a character or UTF-8 string literal) or a wide
3445 character constant (for a wide string literal), except that the single-quote ' is
3446 representable either by itself or by the escape sequence \', but the double-quote " shall
3447 [<a name="p70" href="#p70">page 70</a>] (<a href="#Contents">Contents</a>)
3449 be represented by the escape sequence \".
3451 5 In translation phase 6, the multibyte character sequences specified by any sequence of
3452 adjacent character and identically-prefixed string literal tokens are concatenated into a
3453 single multibyte character sequence. If any of the tokens has an encoding prefix, the
3454 resulting multibyte character sequence is treated as having the same prefix; otherwise, it
3455 is treated as a character string literal. Whether differently-prefixed wide string literal
3456 tokens can be concatenated and, if so, the treatment of the resulting multibyte character
3457 sequence are implementation-defined.
3458 6 In translation phase 7, a byte or code of value zero is appended to each multibyte
3459 character sequence that results from a string literal or literals.<sup><a href="#note78"><b>78)</b></a></sup> The multibyte character
3460 sequence is then used to initialize an array of static storage duration and length just
3461 sufficient to contain the sequence. For character string literals, the array elements have
3462 type char, and are initialized with the individual bytes of the multibyte character
3463 sequence. For UTF-8 string literals, the array elements have type char, and are
3464 initialized with the characters of the multibyte character sequence, as encoded in UTF-8.
3465 For wide string literals prefixed by the letter L, the array elements have type wchar_t
3466 and are initialized with the sequence of wide characters corresponding to the multibyte
3467 character sequence, as defined by the mbstowcs function with an implementation-
3468 defined current locale. For wide string literals prefixed by the letter u or U, the array
3469 elements have type char16_t or char32_t, respectively, and are initialized with the
3470 sequence of wide characters corresponding to the multibyte character sequence, as
3471 defined by successive calls to the mbrtoc16, or mbrtoc32 function as appropriate for
3472 its type, with an implementation-defined current locale. The value of a string literal
3473 containing a multibyte character or escape sequence not represented in the execution
3474 character set is implementation-defined.
3475 7 It is unspecified whether these arrays are distinct provided their elements have the
3476 appropriate values. If the program attempts to modify such an array, the behavior is
3478 8 EXAMPLE 1 This pair of adjacent character string literals
3480 produces a single character string literal containing the two characters whose values are '\x12' and '3',
3481 because escape sequences are converted into single members of the execution character set just prior to
3482 adjacent string literal concatenation.
3484 9 EXAMPLE 2 Each of the sequences of adjacent string literal tokens
3488 <sup><a name="note78" href="#note78"><b>78)</b></a></sup> 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
3491 [<a name="p71" href="#p71">page 71</a>] (<a href="#Contents">Contents</a>)
3497 is equivalent to the string literal
3499 Likewise, each of the sequences
3507 Forward references: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbstowcs
3508 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>).
3509 <a name="6.4.6" href="#6.4.6"><b> 6.4.6 Punctuators</b></a>
3511 1 punctuator: one of
3513 ++ -- & * + - ~ !
3514 / % << >> < > <= >= == != ^ | && ||
3516 = *= /= %= += -= <<= >>= &= ^= |=
3518 <: :> <% %> %: %:%:
3520 2 A punctuator is a symbol that has independent syntactic and semantic significance.
3521 Depending on context, it may specify an operation to be performed (which in turn may
3522 yield a value or a function designator, produce a side effect, or some combination thereof)
3523 in which case it is known as an operator (other forms of operator also exist in some
3524 contexts). An operand is an entity on which an operator acts.
3529 [<a name="p72" href="#p72">page 72</a>] (<a href="#Contents">Contents</a>)
3531 3 In all aspects of the language, the six tokens<sup><a href="#note79"><b>79)</b></a></sup>
3532 <: :> <% %> %: %:%:
3533 behave, respectively, the same as the six tokens
3535 except for their spelling.<sup><a href="#note80"><b>80)</b></a></sup>
3536 Forward references: expressions (<a href="#6.5">6.5</a>), declarations (<a href="#6.7">6.7</a>), preprocessing directives
3537 (<a href="#6.10">6.10</a>), statements (<a href="#6.8">6.8</a>).
3538 <a name="6.4.7" href="#6.4.7"><b> 6.4.7 Header names</b></a>
3541 < h-char-sequence >
3545 h-char-sequence h-char
3547 any member of the source character set except
3548 the new-line character and >
3551 q-char-sequence q-char
3553 any member of the source character set except
3554 the new-line character and "
3556 2 The sequences in both forms of header names are mapped in an implementation-defined
3557 manner to headers or external source file names as specified in <a href="#6.10.2">6.10.2</a>.
3558 3 If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters,
3559 the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the
3564 <sup><a name="note79" href="#note79"><b>79)</b></a></sup> These tokens are sometimes called ''digraphs''.
3565 <sup><a name="note80" href="#note80"><b>80)</b></a></sup> Thus [ and <: behave differently when ''stringized'' (see <a href="#6.10.3.2">6.10.3.2</a>), but can otherwise be freely
3568 [<a name="p73" href="#p73">page 73</a>] (<a href="#Contents">Contents</a>)
3570 sequence between the " delimiters, the behavior is undefined.<sup><a href="#note81"><b>81)</b></a></sup> Header name
3571 preprocessing tokens are recognized only within #include preprocessing directives and
3572 in implementation-defined locations within #pragma directives.<sup><a href="#note82"><b>82)</b></a></sup>
3573 4 EXAMPLE The following sequence of characters:
3575 #include <1/a.h>
3576 #define const.member@$
3577 forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
3578 by a { on the left and a } on the right).
3579 {0x3}{<}{1}{/}{a}{.}{h}{>}{1e2}
3580 {#}{include} {<1/a.h>}
3581 {#}{define} {const}{.}{member}{@}{$}
3583 Forward references: source file inclusion (<a href="#6.10.2">6.10.2</a>).
3584 <a name="6.4.8" href="#6.4.8"><b> 6.4.8 Preprocessing numbers</b></a>
3590 pp-number identifier-nondigit
3597 2 A preprocessing number begins with a digit optionally preceded by a period (.) and may
3598 be followed by valid identifier characters and the character sequences e+, e-, E+, E-,
3600 3 Preprocessing number tokens lexically include all floating and integer constant tokens.
3602 4 A preprocessing number does not have type or a value; it acquires both after a successful
3603 conversion (as part of translation phase 7) to a floating constant token or an integer
3607 <sup><a name="note81" href="#note81"><b>81)</b></a></sup> Thus, sequences of characters that resemble escape sequences cause undefined behavior.
3608 <sup><a name="note82" href="#note82"><b>82)</b></a></sup> For an example of a header name preprocessing token used in a #pragma directive, see <a href="#6.10.9">6.10.9</a>.
3610 [<a name="p74" href="#p74">page 74</a>] (<a href="#Contents">Contents</a>)
3612 <a name="6.4.9" href="#6.4.9"><b> 6.4.9 Comments</b></a>
3613 1 Except within a character constant, a string literal, or a comment, the characters /*
3614 introduce a comment. The contents of such a comment are examined only to identify
3615 multibyte characters and to find the characters */ that terminate it.<sup><a href="#note83"><b>83)</b></a></sup>
3616 2 Except within a character constant, a string literal, or a comment, the characters //
3617 introduce a comment that includes all multibyte characters up to, but not including, the
3618 next new-line character. The contents of such a comment are examined only to identify
3619 multibyte characters and to find the terminating new-line character.
3621 "a//b" // four-character string literal
3622 #include "//e" // undefined behavior
3623 // */ // comment, not syntax error
3624 f = g/**//h; // equivalent to f = g / h;
3626 i(); // part of a two-line comment
3628 / j(); // part of a two-line comment
3629 #define glue(x,y) x##y
3630 glue(/,/) k(); // syntax error, not comment
3631 /*//*/ l(); // equivalent to l();
3633 + p; // equivalent to m = n + p;
3638 <sup><a name="note83" href="#note83"><b>83)</b></a></sup> Thus, /* ... */ comments do not nest.
3640 [<a name="p75" href="#p75">page 75</a>] (<a href="#Contents">Contents</a>)
3642 <a name="6.5" href="#6.5"><b> 6.5 Expressions</b></a>
3643 1 An expression is a sequence of operators and operands that specifies computation of a
3644 value, or that designates an object or a function, or that generates side effects, or that
3645 performs a combination thereof. The value computations of the operands of an operator
3646 are sequenced before the value computation of the result of the operator.
3647 2 If a side effect on a scalar object is unsequenced relative to either a different side effect
3648 on the same scalar object or a value computation using the value of the same scalar
3649 object, the behavior is undefined. If there are multiple allowable orderings of the
3650 subexpressions of an expression, the behavior is undefined if such an unsequenced side
3651 effect occurs in any of the orderings.<sup><a href="#note84"><b>84)</b></a></sup>
3652 3 The grouping of operators and operands is indicated by the syntax.<sup><a href="#note85"><b>85)</b></a></sup> Except as specified
3653 later, side effects and value computations of subexpressions are unsequenced.<sup><a href="#note86"><b>86)</b></a></sup> *
3654 4 Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |,
3655 collectively described as bitwise operators) are required to have operands that have
3656 integer type. These operators yield values that depend on the internal representations of
3657 integers, and have implementation-defined and undefined aspects for signed types.
3658 5 If an exceptional condition occurs during the evaluation of an expression (that is, if the
3659 result is not mathematically defined or not in the range of representable values for its
3660 type), the behavior is undefined.
3664 <sup><a name="note84" href="#note84"><b>84)</b></a></sup> This paragraph renders undefined statement expressions such as
3671 <sup><a name="note85" href="#note85"><b>85)</b></a></sup> The syntax specifies the precedence of operators in the evaluation of an expression, which is the same
3672 as the order of the major subclauses of this subclause, highest precedence first. Thus, for example, the
3673 expressions allowed as the operands of the binary + operator (<a href="#6.5.6">6.5.6</a>) are those expressions defined in
3674 <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
3675 (<a href="#6.5.3">6.5.3</a>), and an operand contained between any of the following pairs of operators: grouping
3676 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
3677 the conditional operator ? : (<a href="#6.5.15">6.5.15</a>).
3678 Within each major subclause, the operators have the same precedence. Left- or right-associativity is
3679 indicated in each subclause by the syntax for the expressions discussed therein.
3680 <sup><a name="note86" href="#note86"><b>86)</b></a></sup> In an expression that is evaluated more than once during the execution of a program, unsequenced and
3681 indeterminately sequenced evaluations of its subexpressions need not be performed consistently in
3682 different evaluations.
3684 [<a name="p76" href="#p76">page 76</a>] (<a href="#Contents">Contents</a>)
3686 6 The effective type of an object for an access to its stored value is the declared type of the
3687 object, if any.<sup><a href="#note87"><b>87)</b></a></sup> If a value is stored into an object having no declared type through an
3688 lvalue having a type that is not a character type, then the type of the lvalue becomes the
3689 effective type of the object for that access and for subsequent accesses that do not modify
3690 the stored value. If a value is copied into an object having no declared type using
3691 memcpy or memmove, or is copied as an array of character type, then the effective type
3692 of the modified object for that access and for subsequent accesses that do not modify the
3693 value is the effective type of the object from which the value is copied, if it has one. For
3694 all other accesses to an object having no declared type, the effective type of the object is
3695 simply the type of the lvalue used for the access.
3696 7 An object shall have its stored value accessed only by an lvalue expression that has one of
3697 the following types:<sup><a href="#note88"><b>88)</b></a></sup>
3698 -- a type compatible with the effective type of the object,
3699 -- a qualified version of a type compatible with the effective type of the object,
3700 -- a type that is the signed or unsigned type corresponding to the effective type of the
3702 -- a type that is the signed or unsigned type corresponding to a qualified version of the
3703 effective type of the object,
3704 -- an aggregate or union type that includes one of the aforementioned types among its
3705 members (including, recursively, a member of a subaggregate or contained union), or
3706 -- a character type.
3707 8 A floating expression may be contracted, that is, evaluated as though it were a single
3708 operation, thereby omitting rounding errors implied by the source code and the
3709 expression evaluation method.<sup><a href="#note89"><b>89)</b></a></sup> The FP_CONTRACT pragma in <a href="#7.12"><math.h></a> provides a
3710 way to disallow contracted expressions. Otherwise, whether and how expressions are
3711 contracted is implementation-defined.<sup><a href="#note90"><b>90)</b></a></sup>
3712 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>).
3715 <sup><a name="note87" href="#note87"><b>87)</b></a></sup> Allocated objects have no declared type.
3716 <sup><a name="note88" href="#note88"><b>88)</b></a></sup> The intent of this list is to specify those circumstances in which an object may or may not be aliased.
3717 <sup><a name="note89" href="#note89"><b>89)</b></a></sup> The intermediate operations in the contracted expression are evaluated as if to infinite precision and
3718 range, while the final operation is rounded to the format determined by the expression evaluation
3719 method. A contracted expression might also omit the raising of floating-point exceptions.
3720 <sup><a name="note90" href="#note90"><b>90)</b></a></sup> This license is specifically intended to allow implementations to exploit fast machine instructions that
3721 combine multiple C operators. As contractions potentially undermine predictability, and can even
3722 decrease accuracy for containing expressions, their use needs to be well-defined and clearly
3725 [<a name="p77" href="#p77">page 77</a>] (<a href="#Contents">Contents</a>)
3727 <a name="6.5.1" href="#6.5.1"><b> 6.5.1 Primary expressions</b></a>
3729 1 primary-expression:
3736 2 An identifier is a primary expression, provided it has been declared as designating an
3737 object (in which case it is an lvalue) or a function (in which case it is a function
3738 designator).<sup><a href="#note91"><b>91)</b></a></sup>
3739 3 A constant is a primary expression. Its type depends on its form and value, as detailed in
3740 <a href="#6.4.4">6.4.4</a>.
3741 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>.
3742 5 A parenthesized expression is a primary expression. Its type and value are identical to
3743 those of the unparenthesized expression. It is an lvalue, a function designator, or a void
3744 expression if the unparenthesized expression is, respectively, an lvalue, a function
3745 designator, or a void expression.
3746 Forward references: declarations (<a href="#6.7">6.7</a>).
3747 <a name="6.5.1.1" href="#6.5.1.1"><b> 6.5.1.1 Generic selection</b></a>
3749 1 generic-selection:
3750 _Generic ( assignment-expression , generic-assoc-list )
3753 generic-assoc-list , generic-association
3754 generic-association:
3755 type-name : assignment-expression
3756 default : assignment-expression
3758 2 A generic selection shall have no more than one default generic association. The type
3759 name in a generic association shall specify a complete object type other than a variably
3761 <sup><a name="note91" href="#note91"><b>91)</b></a></sup> Thus, an undeclared identifier is a violation of the syntax.
3763 [<a name="p78" href="#p78">page 78</a>] (<a href="#Contents">Contents</a>)
3765 modified type. No two generic associations in the same generic selection shall specify
3766 compatible types. The controlling expression of a generic selection shall have type
3767 compatible with at most one of the types named in its generic association list. If a
3768 generic selection has no default generic association, its controlling expression shall
3769 have type compatible with exactly one of the types named in its generic association list.
3771 3 The controlling expression of a generic selection is not evaluated. If a generic selection
3772 has a generic association with a type name that is compatible with the type of the
3773 controlling expression, then the result expression of the generic selection is the
3774 expression in that generic association. Otherwise, the result expression of the generic
3775 selection is the expression in the default generic association. None of the expressions
3776 from any other generic association of the generic selection is evaluated.
3777 4 The type and value of a generic selection are identical to those of its result expression. It
3778 is an lvalue, a function designator, or a void expression if its result expression is,
3779 respectively, an lvalue, a function designator, or a void expression.
3780 5 EXAMPLE The cbrt type-generic macro could be implemented as follows:
3781 #define cbrt(X) _Generic((X), \
3782 long double: cbrtl, \
3787 <a name="6.5.2" href="#6.5.2"><b> 6.5.2 Postfix operators</b></a>
3789 1 postfix-expression:
3791 postfix-expression [ expression ]
3792 postfix-expression ( argument-expression-listopt )
3793 postfix-expression . identifier
3794 postfix-expression -> identifier
3795 postfix-expression ++
3796 postfix-expression --
3797 ( type-name ) { initializer-list }
3798 ( type-name ) { initializer-list , }
3799 argument-expression-list:
3800 assignment-expression
3801 argument-expression-list , assignment-expression
3806 [<a name="p79" href="#p79">page 79</a>] (<a href="#Contents">Contents</a>)
3808 <a name="6.5.2.1" href="#6.5.2.1"><b> 6.5.2.1 Array subscripting</b></a>
3810 1 One of the expressions shall have type ''pointer to complete object type'', the other
3811 expression shall have integer type, and the result has type ''type''.
3813 2 A postfix expression followed by an expression in square brackets [] is a subscripted
3814 designation of an element of an array object. The definition of the subscript operator []
3815 is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that
3816 apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the
3817 initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th
3818 element of E1 (counting from zero).
3819 3 Successive subscript operators designate an element of a multidimensional array object.
3820 If E is an n-dimensional array (n >= 2) with dimensions i x j x . . . x k, then E (used as
3821 other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with
3822 dimensions j x . . . x k. If the unary * operator is applied to this pointer explicitly, or
3823 implicitly as a result of subscripting, the result is the referenced (n - 1)-dimensional
3824 array, which itself is converted into a pointer if used as other than an lvalue. It follows
3825 from this that arrays are stored in row-major order (last subscript varies fastest).
3826 4 EXAMPLE Consider the array object defined by the declaration
3828 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
3829 array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
3830 a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually
3831 entails multiplying i by the size of the object to which the pointer points, namely an array of five int
3832 objects. The results are added and indirection is applied to yield an array of five ints. When used in the
3833 expression x[i][j], that array is in turn converted to a pointer to the first of the ints, so x[i][j]
3836 Forward references: additive operators (<a href="#6.5.6">6.5.6</a>), address and indirection operators
3837 (<a href="#6.5.3.2">6.5.3.2</a>), array declarators (<a href="#6.7.6.2">6.7.6.2</a>).
3838 <a name="6.5.2.2" href="#6.5.2.2"><b> 6.5.2.2 Function calls</b></a>
3840 1 The expression that denotes the called function<sup><a href="#note92"><b>92)</b></a></sup> shall have type pointer to function
3841 returning void or returning a complete object type other than an array type.
3842 2 If the expression that denotes the called function has a type that includes a prototype, the
3843 number of arguments shall agree with the number of parameters. Each argument shall
3846 <sup><a name="note92" href="#note92"><b>92)</b></a></sup> Most often, this is the result of converting an identifier that is a function designator.
3848 [<a name="p80" href="#p80">page 80</a>] (<a href="#Contents">Contents</a>)
3850 have a type such that its value may be assigned to an object with the unqualified version
3851 of the type of its corresponding parameter.
3853 3 A postfix expression followed by parentheses () containing a possibly empty, comma-
3854 separated list of expressions is a function call. The postfix expression denotes the called
3855 function. The list of expressions specifies the arguments to the function.
3856 4 An argument may be an expression of any complete object type. In preparing for the call
3857 to a function, the arguments are evaluated, and each parameter is assigned the value of the
3858 corresponding argument.<sup><a href="#note93"><b>93)</b></a></sup>
3859 5 If the expression that denotes the called function has type pointer to function returning an
3860 object type, the function call expression has the same type as that object type, and has the
3861 value determined as specified in <a href="#6.8.6.4">6.8.6.4</a>. Otherwise, the function call has type void. *
3862 6 If the expression that denotes the called function has a type that does not include a
3863 prototype, the integer promotions are performed on each argument, and arguments that
3864 have type float are promoted to double. These are called the default argument
3865 promotions. If the number of arguments does not equal the number of parameters, the
3866 behavior is undefined. If the function is defined with a type that includes a prototype, and
3867 either the prototype ends with an ellipsis (, ...) or the types of the arguments after
3868 promotion are not compatible with the types of the parameters, the behavior is undefined.
3869 If the function is defined with a type that does not include a prototype, and the types of
3870 the arguments after promotion are not compatible with those of the parameters after
3871 promotion, the behavior is undefined, except for the following cases:
3872 -- one promoted type is a signed integer type, the other promoted type is the
3873 corresponding unsigned integer type, and the value is representable in both types;
3874 -- both types are pointers to qualified or unqualified versions of a character type or
3876 7 If the expression that denotes the called function has a type that does include a prototype,
3877 the arguments are implicitly converted, as if by assignment, to the types of the
3878 corresponding parameters, taking the type of each parameter to be the unqualified version
3879 of its declared type. The ellipsis notation in a function prototype declarator causes
3880 argument type conversion to stop after the last declared parameter. The default argument
3881 promotions are performed on trailing arguments.
3885 <sup><a name="note93" href="#note93"><b>93)</b></a></sup> A function may change the values of its parameters, but these changes cannot affect the values of the
3886 arguments. On the other hand, it is possible to pass a pointer to an object, and the function may
3887 change the value of the object pointed to. A parameter declared to have array or function type is
3888 adjusted to have a pointer type as described in <a href="#6.9.1">6.9.1</a>.
3890 [<a name="p81" href="#p81">page 81</a>] (<a href="#Contents">Contents</a>)
3892 8 No other conversions are performed implicitly; in particular, the number and types of
3893 arguments are not compared with those of the parameters in a function definition that
3894 does not include a function prototype declarator.
3895 9 If the function is defined with a type that is not compatible with the type (of the
3896 expression) pointed to by the expression that denotes the called function, the behavior is
3898 10 There is a sequence point after the evaluations of the function designator and the actual
3899 arguments but before the actual call. Every evaluation in the calling function (including
3900 other function calls) that is not otherwise specifically sequenced before or after the
3901 execution of the body of the called function is indeterminately sequenced with respect to
3902 the execution of the called function.<sup><a href="#note94"><b>94)</b></a></sup>
3903 11 Recursive function calls shall be permitted, both directly and indirectly through any chain
3905 12 EXAMPLE In the function call
3906 (*pf[f1()]) (f2(), f3() + f4())
3907 the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before
3908 the function pointed to by pf[f1()] is called.
3910 Forward references: function declarators (including prototypes) (<a href="#6.7.6.3">6.7.6.3</a>), function
3911 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>).
3912 <a name="6.5.2.3" href="#6.5.2.3"><b> 6.5.2.3 Structure and union members</b></a>
3914 1 The first operand of the . operator shall have an atomic, qualified, or unqualified
3915 structure or union type, and the second operand shall name a member of that type.
3916 2 The first operand of the -> operator shall have type ''pointer to atomic, qualified, or
3917 unqualified structure'' or ''pointer to atomic, qualified, or unqualified union'', and the
3918 second operand shall name a member of the type pointed to.
3920 3 A postfix expression followed by the . operator and an identifier designates a member of
3921 a structure or union object. The value is that of the named member,<sup><a href="#note95"><b>95)</b></a></sup> and is an lvalue if
3922 the first expression is an lvalue. If the first expression has qualified type, the result has
3923 the so-qualified version of the type of the designated member.
3925 <sup><a name="note94" href="#note94"><b>94)</b></a></sup> In other words, function executions do not ''interleave'' with each other.
3926 <sup><a name="note95" href="#note95"><b>95)</b></a></sup> If the member used to read the contents of a union object is not the same as the member last used to
3927 store a value in the object, the appropriate part of the object representation of the value is reinterpreted
3928 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
3929 punning''). This might be a trap representation.
3931 [<a name="p82" href="#p82">page 82</a>] (<a href="#Contents">Contents</a>)
3933 4 A postfix expression followed by the -> operator and an identifier designates a member
3934 of a structure or union object. The value is that of the named member of the object to
3935 which the first expression points, and is an lvalue.<sup><a href="#note96"><b>96)</b></a></sup> If the first expression is a pointer to
3936 a qualified type, the result has the so-qualified version of the type of the designated
3938 5 Accessing a member of an atomic structure or union object results in undefined
3939 behavior.<sup><a href="#note97"><b>97)</b></a></sup>
3940 6 One special guarantee is made in order to simplify the use of unions: if a union contains
3941 several structures that share a common initial sequence (see below), and if the union
3942 object currently contains one of these structures, it is permitted to inspect the common
3943 initial part of any of them anywhere that a declaration of the completed type of the union
3944 is visible. Two structures share a common initial sequence if corresponding members
3945 have compatible types (and, for bit-fields, the same widths) for a sequence of one or more
3947 7 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or
3948 union, f().x is a valid postfix expression but is not an lvalue.
3951 struct s { int i; const int ci; };
3954 volatile struct s vs;
3955 the various members have the types:
3961 vs.ci volatile const int
3966 <sup><a name="note96" href="#note96"><b>96)</b></a></sup> If &E is a valid pointer expression (where & is the ''address-of '' operator, which generates a pointer to
3967 its operand), the expression (&E)->MOS is the same as E.MOS.
3968 <sup><a name="note97" href="#note97"><b>97)</b></a></sup> For example, a data race would occur if access to the entire structure or union in one thread conflicts
3969 with access to a member from another thread, where at least one access is a modification. Members
3970 can be safely accessed using a non-atomic object which is assigned to or from the atomic object.
3972 [<a name="p83" href="#p83">page 83</a>] (<a href="#Contents">Contents</a>)
3974 9 EXAMPLE 3 The following is a valid fragment:
3989 u.nf.doublenode = <a href="#3.14">3.14</a>;
3991 if (u.n.alltypes == 1)
3992 if (sin(u.nf.doublenode) == 0.0)
3994 The following is not a valid fragment (because the union type is not visible within function f):
3995 struct t1 { int m; };
3996 struct t2 { int m; };
3997 int f(struct t1 *p1, struct t2 *p2)
3999 if (p1->m < 0)
4000 p2->m = -p2->m;
4010 return f(&u.s1, &u.s2);
4013 Forward references: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), structure and union
4014 specifiers (<a href="#6.7.2.1">6.7.2.1</a>).
4019 [<a name="p84" href="#p84">page 84</a>] (<a href="#Contents">Contents</a>)
4021 <a name="6.5.2.4" href="#6.5.2.4"><b> 6.5.2.4 Postfix increment and decrement operators</b></a>
4023 1 The operand of the postfix increment or decrement operator shall have atomic, qualified,
4024 or unqualified real or pointer type, and shall be a modifiable lvalue.
4026 2 The result of the postfix ++ operator is the value of the operand. As a side effect, the
4027 value of the operand object is incremented (that is, the value 1 of the appropriate type is
4028 added to it). See the discussions of additive operators and compound assignment for
4029 information on constraints, types, and conversions and the effects of operations on
4030 pointers. The value computation of the result is sequenced before the side effect of
4031 updating the stored value of the operand. With respect to an indeterminately-sequenced
4032 function call, the operation of postfix ++ is a single evaluation. Postfix ++ on an object
4033 with atomic type is a read-modify-write operation with memory_order_seq_cst
4034 memory order semantics.<sup><a href="#note98"><b>98)</b></a></sup>
4035 3 The postfix -- operator is analogous to the postfix ++ operator, except that the value of
4036 the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
4038 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>).
4039 <a name="6.5.2.5" href="#6.5.2.5"><b> 6.5.2.5 Compound literals</b></a>
4041 1 The type name shall specify a complete object type or an array of unknown size, but not a
4042 variable length array type.
4043 2 All the constraints for initializer lists in <a href="#6.7.9">6.7.9</a> also apply to compound literals.
4045 3 A postfix expression that consists of a parenthesized type name followed by a brace-
4046 enclosed list of initializers is a compound literal. It provides an unnamed object whose
4047 value is given by the initializer list.<sup><a href="#note99"><b>99)</b></a></sup>
4050 <sup><a name="note98" href="#note98"><b>98)</b></a></sup> Where a pointer to an atomic object can be formed, this is equivalent to the following code sequence
4051 where T is the type of E:
4056 } while (!atomic_compare_exchange_strong(&E, &result, tmp));
4057 with result being the result of the operation.
4059 [<a name="p85" href="#p85">page 85</a>] (<a href="#Contents">Contents</a>)
4061 4 If the type name specifies an array of unknown size, the size is determined by the
4062 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
4063 completed array type. Otherwise (when the type name specifies an object type), the type
4064 of the compound literal is that specified by the type name. In either case, the result is an
4066 5 The value of the compound literal is that of an unnamed object initialized by the
4067 initializer list. If the compound literal occurs outside the body of a function, the object
4068 has static storage duration; otherwise, it has automatic storage duration associated with
4069 the enclosing block.
4070 6 All the semantic rules for initializer lists in <a href="#6.7.9">6.7.9</a> also apply to compound literals.<sup><a href="#note100"><b>100)</b></a></sup>
4071 7 String literals, and compound literals with const-qualified types, need not designate
4072 distinct objects.<sup><a href="#note101"><b>101)</b></a></sup>
4073 8 EXAMPLE 1 The file scope definition
4074 int *p = (int []){2, 4};
4075 initializes p to point to the first element of an array of two ints, the first having the value two and the
4076 second, four. The expressions in this compound literal are required to be constant. The unnamed object
4077 has static storage duration.
4079 9 EXAMPLE 2 In contrast, in
4087 p is assigned the address of the first element of an array of two ints, the first having the value previously
4088 pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
4089 unnamed object has automatic storage duration.
4091 10 EXAMPLE 3 Initializers with designations can be combined with compound literals. Structure objects
4092 created using compound literals can be passed to functions without depending on member order:
4093 drawline((struct point){.x=1, .y=1},
4094 (struct point){.x=3, .y=4});
4095 Or, if drawline instead expected pointers to struct point:
4099 <sup><a name="note99" href="#note99"><b>99)</b></a></sup> Note that this differs from a cast expression. For example, a cast specifies a conversion to scalar types
4100 or void only, and the result of a cast expression is not an lvalue.
4101 <sup><a name="note100" href="#note100"><b>100)</b></a></sup> For example, subobjects without explicit initializers are initialized to zero.
4102 <sup><a name="note101" href="#note101"><b>101)</b></a></sup> This allows implementations to share storage for string literals and constant compound literals with
4103 the same or overlapping representations.
4105 [<a name="p86" href="#p86">page 86</a>] (<a href="#Contents">Contents</a>)
4107 drawline(&(struct point){.x=1, .y=1},
4108 &(struct point){.x=3, .y=4});
4110 11 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
4111 (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}
4113 12 EXAMPLE 5 The following three expressions have different meanings:
4115 (char []){"/tmp/fileXXXXXX"}
4116 (const char []){"/tmp/fileXXXXXX"}
4117 The first always has static storage duration and has type array of char, but need not be modifiable; the last
4118 two have automatic storage duration when they occur within the body of a function, and the first of these
4121 13 EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory
4122 and can even be shared. For example,
4123 (const char []){"abc"} == "abc"
4124 might yield 1 if the literals' storage is shared.
4126 14 EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly
4127 linked object. For example, there is no way to write a self-referential compound literal that could be used
4128 as the function argument in place of the named object endless_zeros below:
4129 struct int_list { int car; struct int_list *cdr; };
4130 struct int_list endless_zeros = {0, &endless_zeros};
4131 eval(endless_zeros);
4133 15 EXAMPLE 8 Each compound literal creates only a single object in a given scope:
4134 struct s { int i; };
4137 struct s *p = 0, *q;
4140 q = p, p = &((struct s){ j++ });
4141 if (j < 2) goto again;
4142 return p == q && q->i == 1;
4144 The function f() always returns the value 1.
4145 16 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
4146 lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
4147 have an indeterminate value, which would result in undefined behavior.
4149 Forward references: type names (<a href="#6.7.7">6.7.7</a>), initialization (<a href="#6.7.9">6.7.9</a>).
4154 [<a name="p87" href="#p87">page 87</a>] (<a href="#Contents">Contents</a>)
4156 <a name="6.5.3" href="#6.5.3"><b> 6.5.3 Unary operators</b></a>
4162 unary-operator cast-expression
4163 sizeof unary-expression
4164 sizeof ( type-name )
4165 alignof ( type-name )
4166 unary-operator: one of
4168 <a name="6.5.3.1" href="#6.5.3.1"><b> 6.5.3.1 Prefix increment and decrement operators</b></a>
4170 1 The operand of the prefix increment or decrement operator shall have atomic, qualified,
4171 or unqualified real or pointer type, and shall be a modifiable lvalue.
4173 2 The value of the operand of the prefix ++ operator is incremented. The result is the new
4174 value of the operand after incrementation. The expression ++E is equivalent to (E+=1).
4175 See the discussions of additive operators and compound assignment for information on
4176 constraints, types, side effects, and conversions and the effects of operations on pointers.
4177 3 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
4178 operand is decremented.
4179 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>).
4180 <a name="6.5.3.2" href="#6.5.3.2"><b> 6.5.3.2 Address and indirection operators</b></a>
4182 1 The operand of the unary & operator shall be either a function designator, the result of a
4183 [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is
4184 not declared with the register storage-class specifier.
4185 2 The operand of the unary * operator shall have pointer type.
4187 3 The unary & operator yields the address of its operand. If the operand has type ''type'',
4188 the result has type ''pointer to type''. If the operand is the result of a unary * operator,
4189 neither that operator nor the & operator is evaluated and the result is as if both were
4190 omitted, except that the constraints on the operators still apply and the result is not an
4192 [<a name="p88" href="#p88">page 88</a>] (<a href="#Contents">Contents</a>)
4194 lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor
4195 the unary * that is implied by the [] is evaluated and the result is as if the & operator
4196 were removed and the [] operator were changed to a + operator. Otherwise, the result is
4197 a pointer to the object or function designated by its operand.
4198 4 The unary * operator denotes indirection. If the operand points to a function, the result is
4199 a function designator; if it points to an object, the result is an lvalue designating the
4200 object. If the operand has type ''pointer to type'', the result has type ''type''. If an
4201 invalid value has been assigned to the pointer, the behavior of the unary * operator is
4202 undefined.<sup><a href="#note102"><b>102)</b></a></sup>
4203 Forward references: storage-class specifiers (<a href="#6.7.1">6.7.1</a>), structure and union specifiers
4204 (<a href="#6.7.2.1">6.7.2.1</a>).
4205 <a name="6.5.3.3" href="#6.5.3.3"><b> 6.5.3.3 Unary arithmetic operators</b></a>
4207 1 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
4208 integer type; of the ! operator, scalar type.
4210 2 The result of the unary + operator is the value of its (promoted) operand. The integer
4211 promotions are performed on the operand, and the result has the promoted type.
4212 3 The result of the unary - operator is the negative of its (promoted) operand. The integer
4213 promotions are performed on the operand, and the result has the promoted type.
4214 4 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is,
4215 each bit in the result is set if and only if the corresponding bit in the converted operand is
4216 not set). The integer promotions are performed on the operand, and the result has the
4217 promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent
4218 to the maximum value representable in that type minus E.
4219 5 The result of the logical negation operator ! is 0 if the value of its operand compares
4220 unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int.
4221 The expression !E is equivalent to (0==E).
4225 <sup><a name="note102" href="#note102"><b>102)</b></a></sup> Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). It is
4226 always true that if E is a function designator or an lvalue that is a valid operand of the unary &
4227 operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of
4228 an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points.
4229 Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an
4230 address inappropriately aligned for the type of object pointed to, and the address of an object after the
4231 end of its lifetime.
4233 [<a name="p89" href="#p89">page 89</a>] (<a href="#Contents">Contents</a>)
4235 <a name="6.5.3.4" href="#6.5.3.4"><b> 6.5.3.4 The sizeof and alignof operators</b></a>
4237 1 The sizeof operator shall not be applied to an expression that has function type or an
4238 incomplete type, to the parenthesized name of such a type, or to an expression that
4239 designates a bit-field member. The alignof operator shall not be applied to a function
4240 type or an incomplete type.
4242 2 The sizeof operator yields the size (in bytes) of its operand, which may be an
4243 expression or the parenthesized name of a type. The size is determined from the type of
4244 the operand. The result is an integer. If the type of the operand is a variable length array
4245 type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an
4247 3 The alignof operator yields the alignment requirement of its operand type. The result
4248 is an integer constant. When applied to an array type, the result is the alignment
4249 requirement of the element type.
4250 4 When sizeof is applied to an operand that has type char, unsigned char, or
4251 signed char, (or a qualified version thereof) the result is 1. When applied to an
4252 operand that has array type, the result is the total number of bytes in the array.<sup><a href="#note103"><b>103)</b></a></sup> When
4253 applied to an operand that has structure or union type, the result is the total number of
4254 bytes in such an object, including internal and trailing padding.
4255 5 The value of the result of both operators is implementation-defined, and its type (an
4256 unsigned integer type) is size_t, defined in <a href="#7.19"><stddef.h></a> (and other headers).
4257 6 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage
4258 allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to
4259 allocate and return a pointer to void. For example:
4260 extern void *alloc(size_t);
4261 double *dp = alloc(sizeof *dp);
4262 The implementation of the alloc function should ensure that its return value is aligned suitably for
4263 conversion to a pointer to double.
4265 7 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
4266 sizeof array / sizeof array[0]
4268 8 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a
4270 #include <a href="#7.19"><stddef.h></a>
4274 <sup><a name="note103" href="#note103"><b>103)</b></a></sup> When applied to a parameter declared to have array or function type, the sizeof operator yields the
4275 size of the adjusted (pointer) type (see <a href="#6.9.1">6.9.1</a>).
4277 [<a name="p90" href="#p90">page 90</a>] (<a href="#Contents">Contents</a>)
4279 size_t fsize3(int n)
4281 char b[n+3]; // variable length array
4282 return sizeof b; // execution time sizeof
4287 size = fsize3(10); // fsize3 returns 13
4291 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>),
4292 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>).
4293 <a name="6.5.4" href="#6.5.4"><b> 6.5.4 Cast operators</b></a>
4297 ( type-name ) cast-expression
4299 2 Unless the type name specifies a void type, the type name shall specify atomic, qualified,
4300 or unqualified scalar type, and the operand shall have scalar type.
4301 3 Conversions that involve pointers, other than where permitted by the constraints of
4302 <a href="#6.5.16.1">6.5.16.1</a>, shall be specified by means of an explicit cast.
4303 4 A pointer type shall not be converted to any floating type. A floating type shall not be
4304 converted to any pointer type.
4306 5 Preceding an expression by a parenthesized type name converts the value of the
4307 expression to the named type. This construction is called a cast.<sup><a href="#note104"><b>104)</b></a></sup> A cast that specifies
4308 no conversion has no effect on the type or value of an expression.
4309 6 If the value of the expression is represented with greater precision or range than required
4310 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
4311 type of the expression is the same as the named type and removes any extra range and
4313 Forward references: equality operators (<a href="#6.5.9">6.5.9</a>), function declarators (including
4314 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>).
4316 <sup><a name="note104" href="#note104"><b>104)</b></a></sup> A cast does not yield an lvalue. Thus, a cast to a qualified type has the same effect as a cast to the
4317 unqualified version of the type.
4319 [<a name="p91" href="#p91">page 91</a>] (<a href="#Contents">Contents</a>)
4321 <a name="6.5.5" href="#6.5.5"><b> 6.5.5 Multiplicative operators</b></a>
4323 1 multiplicative-expression:
4325 multiplicative-expression * cast-expression
4326 multiplicative-expression / cast-expression
4327 multiplicative-expression % cast-expression
4329 2 Each of the operands shall have arithmetic type. The operands of the % operator shall
4332 3 The usual arithmetic conversions are performed on the operands.
4333 4 The result of the binary * operator is the product of the operands.
4334 5 The result of the / operator is the quotient from the division of the first operand by the
4335 second; the result of the % operator is the remainder. In both operations, if the value of
4336 the second operand is zero, the behavior is undefined.
4337 6 When integers are divided, the result of the / operator is the algebraic quotient with any
4338 fractional part discarded.<sup><a href="#note105"><b>105)</b></a></sup> If the quotient a/b is representable, the expression
4339 (a/b)*b + a%b shall equal a; otherwise, the behavior of both a/b and a%b is
4341 <a name="6.5.6" href="#6.5.6"><b> 6.5.6 Additive operators</b></a>
4343 1 additive-expression:
4344 multiplicative-expression
4345 additive-expression + multiplicative-expression
4346 additive-expression - multiplicative-expression
4348 2 For addition, either both operands shall have arithmetic type, or one operand shall be a
4349 pointer to a complete object type and the other shall have integer type. (Incrementing is
4350 equivalent to adding 1.)
4351 3 For subtraction, one of the following shall hold:
4356 <sup><a name="note105" href="#note105"><b>105)</b></a></sup> This is often called ''truncation toward zero''.
4358 [<a name="p92" href="#p92">page 92</a>] (<a href="#Contents">Contents</a>)
4360 -- both operands have arithmetic type;
4361 -- both operands are pointers to qualified or unqualified versions of compatible complete
4363 -- the left operand is a pointer to a complete object type and the right operand has
4365 (Decrementing is equivalent to subtracting 1.)
4367 4 If both operands have arithmetic type, the usual arithmetic conversions are performed on
4369 5 The result of the binary + operator is the sum of the operands.
4370 6 The result of the binary - operator is the difference resulting from the subtraction of the
4371 second operand from the first.
4372 7 For the purposes of these operators, a pointer to an object that is not an element of an
4373 array behaves the same as a pointer to the first element of an array of length one with the
4374 type of the object as its element type.
4375 8 When an expression that has integer type is added to or subtracted from a pointer, the
4376 result has the type of the pointer operand. If the pointer operand points to an element of
4377 an array object, and the array is large enough, the result points to an element offset from
4378 the original element such that the difference of the subscripts of the resulting and original
4379 array elements equals the integer expression. In other words, if the expression P points to
4380 the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
4381 (P)-N (where N has the value n) point to, respectively, the i+n-th and i-n-th elements of
4382 the array object, provided they exist. Moreover, if the expression P points to the last
4383 element of an array object, the expression (P)+1 points one past the last element of the
4384 array object, and if the expression Q points one past the last element of an array object,
4385 the expression (Q)-1 points to the last element of the array object. If both the pointer
4386 operand and the result point to elements of the same array object, or one past the last
4387 element of the array object, the evaluation shall not produce an overflow; otherwise, the
4388 behavior is undefined. If the result points one past the last element of the array object, it
4389 shall not be used as the operand of a unary * operator that is evaluated.
4390 9 When two pointers are subtracted, both shall point to elements of the same array object,
4391 or one past the last element of the array object; the result is the difference of the
4392 subscripts of the two array elements. The size of the result is implementation-defined,
4393 and its type (a signed integer type) is ptrdiff_t defined in the <a href="#7.19"><stddef.h></a> header.
4394 If the result is not representable in an object of that type, the behavior is undefined. In
4395 other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of
4396 an array object, the expression (P)-(Q) has the value i-j provided the value fits in an
4398 [<a name="p93" href="#p93">page 93</a>] (<a href="#Contents">Contents</a>)
4400 object of type ptrdiff_t. Moreover, if the expression P points either to an element of
4401 an array object or one past the last element of an array object, and the expression Q points
4402 to the last element of the same array object, the expression ((Q)+1)-(P) has the same
4403 value as ((Q)-(P))+1 and as -((P)-((Q)+1)), and has the value zero if the
4404 expression P points one past the last element of the array object, even though the
4405 expression (Q)+1 does not point to an element of the array object.<sup><a href="#note106"><b>106)</b></a></sup>
4406 10 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
4410 int (*p)[m] = a; // p == &a[0]
4411 p += 1; // p == &a[1]
4412 (*p)[2] = 99; // a[1][2] == 99
4413 n = p - a; // n == 1
4415 11 If array a in the above example were declared to be an array of known constant size, and pointer p were
4416 declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
4419 Forward references: array declarators (<a href="#6.7.6.2">6.7.6.2</a>), common definitions <a href="#7.19"><stddef.h></a>
4420 (<a href="#7.19">7.19</a>).
4421 <a name="6.5.7" href="#6.5.7"><b> 6.5.7 Bitwise shift operators</b></a>
4425 shift-expression << additive-expression
4426 shift-expression >> additive-expression
4428 2 Each of the operands shall have integer type.
4430 3 The integer promotions are performed on each of the operands. The type of the result is
4431 that of the promoted left operand. If the value of the right operand is negative or is
4433 <sup><a name="note106" href="#note106"><b>106)</b></a></sup> Another way to approach pointer arithmetic is first to convert the pointer(s) to character pointer(s): In
4434 this scheme the integer expression added to or subtracted from the converted pointer is first multiplied
4435 by the size of the object originally pointed to, and the resulting pointer is converted back to the
4436 original type. For pointer subtraction, the result of the difference between the character pointers is
4437 similarly divided by the size of the object originally pointed to.
4438 When viewed in this way, an implementation need only provide one extra byte (which may overlap
4439 another object in the program) just after the end of the object in order to satisfy the ''one past the last
4440 element'' requirements.
4442 [<a name="p94" href="#p94">page 94</a>] (<a href="#Contents">Contents</a>)
4444 greater than or equal to the width of the promoted left operand, the behavior is undefined.
4445 4 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with
4446 zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo
4447 one more than the maximum value representable in the result type. If E1 has a signed
4448 type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is
4449 the resulting value; otherwise, the behavior is undefined.
4450 5 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
4451 or if E1 has a signed type and a nonnegative value, the value of the result is the integral
4452 part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
4453 resulting value is implementation-defined.
4454 <a name="6.5.8" href="#6.5.8"><b> 6.5.8 Relational operators</b></a>
4456 1 relational-expression:
4458 relational-expression < shift-expression
4459 relational-expression > shift-expression
4460 relational-expression <= shift-expression
4461 relational-expression >= shift-expression
4463 2 One of the following shall hold:
4464 -- both operands have real type; or *
4465 -- both operands are pointers to qualified or unqualified versions of compatible object
4468 3 If both of the operands have arithmetic type, the usual arithmetic conversions are
4470 4 For the purposes of these operators, a pointer to an object that is not an element of an
4471 array behaves the same as a pointer to the first element of an array of length one with the
4472 type of the object as its element type.
4473 5 When two pointers are compared, the result depends on the relative locations in the
4474 address space of the objects pointed to. If two pointers to object types both point to the
4475 same object, or both point one past the last element of the same array object, they
4476 compare equal. If the objects pointed to are members of the same aggregate object,
4477 pointers to structure members declared later compare greater than pointers to members
4478 declared earlier in the structure, and pointers to array elements with larger subscript
4479 values compare greater than pointers to elements of the same array with lower subscript
4481 [<a name="p95" href="#p95">page 95</a>] (<a href="#Contents">Contents</a>)
4483 values. All pointers to members of the same union object compare equal. If the
4484 expression P points to an element of an array object and the expression Q points to the
4485 last element of the same array object, the pointer expression Q+1 compares greater than
4486 P. In all other cases, the behavior is undefined.
4487 6 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
4488 (greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is
4489 false.<sup><a href="#note107"><b>107)</b></a></sup> The result has type int.
4490 <a name="6.5.9" href="#6.5.9"><b> 6.5.9 Equality operators</b></a>
4492 1 equality-expression:
4493 relational-expression
4494 equality-expression == relational-expression
4495 equality-expression != relational-expression
4497 2 One of the following shall hold:
4498 -- both operands have arithmetic type;
4499 -- both operands are pointers to qualified or unqualified versions of compatible types;
4500 -- one operand is a pointer to an object type and the other is a pointer to a qualified or
4501 unqualified version of void; or
4502 -- one operand is a pointer and the other is a null pointer constant.
4504 3 The == (equal to) and != (not equal to) operators are analogous to the relational
4505 operators except for their lower precedence.<sup><a href="#note108"><b>108)</b></a></sup> Each of the operators yields 1 if the
4506 specified relation is true and 0 if it is false. The result has type int. For any pair of
4507 operands, exactly one of the relations is true.
4508 4 If both of the operands have arithmetic type, the usual arithmetic conversions are
4509 performed. Values of complex types are equal if and only if both their real parts are equal
4510 and also their imaginary parts are equal. Any two values of arithmetic types from
4511 different type domains are equal if and only if the results of their conversions to the
4512 (complex) result type determined by the usual arithmetic conversions are equal.
4516 <sup><a name="note107" href="#note107"><b>107)</b></a></sup> The expression a<b<c is not interpreted as in ordinary mathematics. As the syntax indicates, it
4517 means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
4518 <sup><a name="note108" href="#note108"><b>108)</b></a></sup> Because of the precedences, a<b == c<d is 1 whenever a<b and c<d have the same truth-value.
4520 [<a name="p96" href="#p96">page 96</a>] (<a href="#Contents">Contents</a>)
4522 5 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a
4523 null pointer constant, the null pointer constant is converted to the type of the pointer. If
4524 one operand is a pointer to an object type and the other is a pointer to a qualified or
4525 unqualified version of void, the former is converted to the type of the latter.
4526 6 Two pointers compare equal if and only if both are null pointers, both are pointers to the
4527 same object (including a pointer to an object and a subobject at its beginning) or function,
4528 both are pointers to one past the last element of the same array object, or one is a pointer
4529 to one past the end of one array object and the other is a pointer to the start of a different
4530 array object that happens to immediately follow the first array object in the address
4531 space.<sup><a href="#note109"><b>109)</b></a></sup>
4532 7 For the purposes of these operators, a pointer to an object that is not an element of an
4533 array behaves the same as a pointer to the first element of an array of length one with the
4534 type of the object as its element type.
4535 <a name="6.5.10" href="#6.5.10"><b> 6.5.10 Bitwise AND operator</b></a>
4539 AND-expression & equality-expression
4541 2 Each of the operands shall have integer type.
4543 3 The usual arithmetic conversions are performed on the operands.
4544 4 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
4545 the result is set if and only if each of the corresponding bits in the converted operands is
4551 <sup><a name="note109" href="#note109"><b>109)</b></a></sup> Two objects may be adjacent in memory because they are adjacent elements of a larger array or
4552 adjacent members of a structure with no padding between them, or because the implementation chose
4553 to place them so, even though they are unrelated. If prior invalid pointer operations (such as accesses
4554 outside array bounds) produced undefined behavior, subsequent comparisons also produce undefined
4557 [<a name="p97" href="#p97">page 97</a>] (<a href="#Contents">Contents</a>)
4559 <a name="6.5.11" href="#6.5.11"><b> 6.5.11 Bitwise exclusive OR operator</b></a>
4561 1 exclusive-OR-expression:
4563 exclusive-OR-expression ^ AND-expression
4565 2 Each of the operands shall have integer type.
4567 3 The usual arithmetic conversions are performed on the operands.
4568 4 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
4569 in the result is set if and only if exactly one of the corresponding bits in the converted
4571 <a name="6.5.12" href="#6.5.12"><b> 6.5.12 Bitwise inclusive OR operator</b></a>
4573 1 inclusive-OR-expression:
4574 exclusive-OR-expression
4575 inclusive-OR-expression | exclusive-OR-expression
4577 2 Each of the operands shall have integer type.
4579 3 The usual arithmetic conversions are performed on the operands.
4580 4 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
4581 the result is set if and only if at least one of the corresponding bits in the converted
4587 [<a name="p98" href="#p98">page 98</a>] (<a href="#Contents">Contents</a>)
4589 <a name="6.5.13" href="#6.5.13"><b> 6.5.13 Logical AND operator</b></a>
4591 1 logical-AND-expression:
4592 inclusive-OR-expression
4593 logical-AND-expression && inclusive-OR-expression
4595 2 Each of the operands shall have scalar type.
4597 3 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
4598 yields 0. The result has type int.
4599 4 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
4600 if the second operand is evaluated, there is a sequence point between the evaluations of
4601 the first and second operands. If the first operand compares equal to 0, the second
4602 operand is not evaluated.
4603 <a name="6.5.14" href="#6.5.14"><b> 6.5.14 Logical OR operator</b></a>
4605 1 logical-OR-expression:
4606 logical-AND-expression
4607 logical-OR-expression || logical-AND-expression
4609 2 Each of the operands shall have scalar type.
4611 3 The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it
4612 yields 0. The result has type int.
4613 4 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; if the
4614 second operand is evaluated, there is a sequence point between the evaluations of the first
4615 and second operands. If the first operand compares unequal to 0, the second operand is
4621 [<a name="p99" href="#p99">page 99</a>] (<a href="#Contents">Contents</a>)
4623 <a name="6.5.15" href="#6.5.15"><b> 6.5.15 Conditional operator</b></a>
4625 1 conditional-expression:
4626 logical-OR-expression
4627 logical-OR-expression ? expression : conditional-expression
4629 2 The first operand shall have scalar type.
4630 3 One of the following shall hold for the second and third operands:
4631 -- both operands have arithmetic type;
4632 -- both operands have the same structure or union type;
4633 -- both operands have void type;
4634 -- both operands are pointers to qualified or unqualified versions of compatible types;
4635 -- one operand is a pointer and the other is a null pointer constant; or
4636 -- one operand is a pointer to an object type and the other is a pointer to a qualified or
4637 unqualified version of void.
4639 4 The first operand is evaluated; there is a sequence point between its evaluation and the
4640 evaluation of the second or third operand (whichever is evaluated). The second operand
4641 is evaluated only if the first compares unequal to 0; the third operand is evaluated only if
4642 the first compares equal to 0; the result is the value of the second or third operand
4643 (whichever is evaluated), converted to the type described below.<sup><a href="#note110"><b>110)</b></a></sup> *
4644 5 If both the second and third operands have arithmetic type, the result type that would be
4645 determined by the usual arithmetic conversions, were they applied to those two operands,
4646 is the type of the result. If both the operands have structure or union type, the result has
4647 that type. If both operands have void type, the result has void type.
4648 6 If both the second and third operands are pointers or one is a null pointer constant and the
4649 other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
4650 of the types referenced by both operands. Furthermore, if both operands are pointers to
4651 compatible types or to differently qualified versions of compatible types, the result type is
4652 a pointer to an appropriately qualified version of the composite type; if one operand is a
4653 null pointer constant, the result has the type of the other operand; otherwise, one operand
4654 is a pointer to void or a qualified version of void, in which case the result type is a
4655 pointer to an appropriately qualified version of void.
4657 <sup><a name="note110" href="#note110"><b>110)</b></a></sup> A conditional expression does not yield an lvalue.
4659 [<a name="p100" href="#p100">page 100</a>] (<a href="#Contents">Contents</a>)
4661 7 EXAMPLE The common type that results when the second and third operands are pointers is determined
4662 in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two
4663 pointers have compatible types.
4664 8 Given the declarations
4671 the third column in the following table is the common type that is the result of a conditional expression in
4672 which the first two columns are the second and third operands (in either order):
4673 c_vp c_ip const void *
4674 v_ip 0 volatile int *
4675 c_ip v_ip const volatile int *
4676 vp c_cp const void *
4680 <a name="6.5.16" href="#6.5.16"><b> 6.5.16 Assignment operators</b></a>
4682 1 assignment-expression:
4683 conditional-expression
4684 unary-expression assignment-operator assignment-expression
4685 assignment-operator: one of
4686 = *= /= %= += -= <<= >>= &= ^= |=
4688 2 An assignment operator shall have a modifiable lvalue as its left operand.
4690 3 An assignment operator stores a value in the object designated by the left operand. An
4691 assignment expression has the value of the left operand after the assignment,<sup><a href="#note111"><b>111)</b></a></sup> but is not
4692 an lvalue. The type of an assignment expression is the type the left operand would have
4693 after lvalue conversion. The side effect of updating the stored value of the left operand is
4694 sequenced after the value computations of the left and right operands. The evaluations of
4695 the operands are unsequenced.
4700 <sup><a name="note111" href="#note111"><b>111)</b></a></sup> The implementation is permitted to read the object to determine the value but is not required to, even
4701 when the object has volatile-qualified type.
4703 [<a name="p101" href="#p101">page 101</a>] (<a href="#Contents">Contents</a>)
4705 <a name="6.5.16.1" href="#6.5.16.1"><b> 6.5.16.1 Simple assignment</b></a>
4707 1 One of the following shall hold:<sup><a href="#note112"><b>112)</b></a></sup>
4708 -- the left operand has atomic, qualified, or unqualified arithmetic type, and the right has
4710 -- the left operand has an atomic, qualified, or unqualified version of a structure or union
4711 type compatible with the type of the right;
4712 -- the left operand has atomic, qualified, or unqualified pointer type, and (considering
4713 the type the left operand would have after lvalue conversion) both operands are
4714 pointers to qualified or unqualified versions of compatible types, and the type pointed
4715 to by the left has all the qualifiers of the type pointed to by the right;
4716 -- the left operand has atomic, qualified, or unqualified pointer type, and (considering
4717 the type the left operand would have after lvalue conversion) one operand is a pointer
4718 to an object type, and the other is a pointer to a qualified or unqualified version of
4719 void, and the type pointed to by the left has all the qualifiers of the type pointed to
4721 -- the left operand is an atomic, qualified, or unqualified pointer, and the right is a null
4722 pointer constant; or
4723 -- the left operand has type atomic, qualified, or unqualified _Bool, and the right is a
4726 2 In simple assignment (=), the value of the right operand is converted to the type of the
4727 assignment expression and replaces the value stored in the object designated by the left
4729 3 If the value being stored in an object is read from another object that overlaps in any way
4730 the storage of the first object, then the overlap shall be exact and the two objects shall
4731 have qualified or unqualified versions of a compatible type; otherwise, the behavior is
4733 4 EXAMPLE 1 In the program fragment
4738 <sup><a name="note112" href="#note112"><b>112)</b></a></sup> The asymmetric appearance of these constraints with respect to type qualifiers is due to the conversion
4739 (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
4740 qualifiers that were applied to the type category of the expression (for example, it removes const but
4741 not volatile from the type int volatile * const).
4743 [<a name="p102" href="#p102">page 102</a>] (<a href="#Contents">Contents</a>)
4748 if ((c = f()) == -1)
4750 the int value returned by the function may be truncated when stored in the char, and then converted back
4751 to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
4752 values as unsigned char (and char is narrower than int), the result of the conversion cannot be
4753 negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
4754 variable c should be declared as int.
4756 5 EXAMPLE 2 In the fragment:
4761 the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
4762 of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
4763 that is, long int type.
4765 6 EXAMPLE 3 Consider the fragment:
4769 cpp = &p; // constraint violation
4770 *cpp = &c; // valid
4772 The first assignment is unsafe because it would allow the following valid code to attempt to change the
4773 value of the const object c.
4775 <a name="6.5.16.2" href="#6.5.16.2"><b> 6.5.16.2 Compound assignment</b></a>
4777 1 For the operators += and -= only, either the left operand shall be an atomic, qualified, or
4778 unqualified pointer to a complete object type, and the right shall have integer type; or the
4779 left operand shall have atomic, qualified, or unqualified arithmetic type, and the right
4780 shall have arithmetic type.
4781 2 For the other operators, the left operand shall have atomic, qualified, or unqualified
4782 arithmetic type, and (considering the type the left operand would have after lvalue
4783 conversion) each operand shall have arithmetic type consistent with those allowed by the
4784 corresponding binary operator.
4786 3 A compound assignment of the form E1 op = E2 is equivalent to the simple assignment
4787 expression E1 = E1 op (E2), except that the lvalue E1 is evaluated only once, and with
4788 respect to an indeterminately-sequenced function call, the operation of a compound
4789 [<a name="p103" href="#p103">page 103</a>] (<a href="#Contents">Contents</a>)
4791 assignment is a single evaluation. If E1 has an atomic type, compound assignment is a
4792 read-modify-write operation with memory_order_seq_cst memory order
4793 semantics.<sup><a href="#note113"><b>113)</b></a></sup>
4794 <a name="6.5.17" href="#6.5.17"><b> 6.5.17 Comma operator</b></a>
4797 assignment-expression
4798 expression , assignment-expression
4800 2 The left operand of a comma operator is evaluated as a void expression; there is a
4801 sequence point between its evaluation and that of the right operand. Then the right
4802 operand is evaluated; the result has its type and value.<sup><a href="#note114"><b>114)</b></a></sup> *
4803 3 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot
4804 appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists
4805 of initializers). On the other hand, it can be used within a parenthesized expression or within the second
4806 expression of a conditional operator in such contexts. In the function call
4808 the function has three arguments, the second of which has the value 5.
4810 Forward references: initialization (<a href="#6.7.9">6.7.9</a>).
4815 <sup><a name="note113" href="#note113"><b>113)</b></a></sup> Where a pointer to an atomic object can be formed, this is equivalent to the following code sequence
4816 where T is the type of E1:
4820 result = tmp op (E2);
4821 } while (!atomic_compare_exchange_strong(&E1, &tmp, result));
4822 with result being the result of the operation.
4823 <sup><a name="note114" href="#note114"><b>114)</b></a></sup> A comma operator does not yield an lvalue.
4825 [<a name="p104" href="#p104">page 104</a>] (<a href="#Contents">Contents</a>)
4827 <a name="6.6" href="#6.6"><b> 6.6 Constant expressions</b></a>
4829 1 constant-expression:
4830 conditional-expression
4832 2 A constant expression can be evaluated during translation rather than runtime, and
4833 accordingly may be used in any place that a constant may be.
4835 3 Constant expressions shall not contain assignment, increment, decrement, function-call,
4836 or comma operators, except when they are contained within a subexpression that is not
4837 evaluated.<sup><a href="#note115"><b>115)</b></a></sup>
4838 4 Each constant expression shall evaluate to a constant that is in the range of representable
4839 values for its type.
4841 5 An expression that evaluates to a constant is required in several contexts. If a floating
4842 expression is evaluated in the translation environment, the arithmetic precision and range
4843 shall be at least as great as if the expression were being evaluated in the execution
4844 environment.<sup><a href="#note116"><b>116)</b></a></sup>
4845 6 An integer constant expression<sup><a href="#note117"><b>117)</b></a></sup> shall have integer type and shall only have operands
4846 that are integer constants, enumeration constants, character constants, sizeof
4847 expressions whose results are integer constants, and floating constants that are the
4848 immediate operands of casts. Cast operators in an integer constant expression shall only
4849 convert arithmetic types to integer types, except as part of an operand to the sizeof
4851 7 More latitude is permitted for constant expressions in initializers. Such a constant
4852 expression shall be, or evaluate to, one of the following:
4853 -- an arithmetic constant expression,
4857 <sup><a name="note115" href="#note115"><b>115)</b></a></sup> The operand of a sizeof operator is usually not evaluated (<a href="#6.5.3.4">6.5.3.4</a>).
4858 <sup><a name="note116" href="#note116"><b>116)</b></a></sup> The use of evaluation formats as characterized by FLT_EVAL_METHOD also applies to evaluation in
4859 the translation environment.
4860 <sup><a name="note117" href="#note117"><b>117)</b></a></sup> An integer constant expression is required in a number of contexts such as the size of a bit-field
4861 member of a structure, the value of an enumeration constant, and the size of a non-variable length
4862 array. Further constraints that apply to the integer constant expressions used in conditional-inclusion
4863 preprocessing directives are discussed in <a href="#6.10.1">6.10.1</a>.
4865 [<a name="p105" href="#p105">page 105</a>] (<a href="#Contents">Contents</a>)
4867 -- a null pointer constant,
4868 -- an address constant, or
4869 -- an address constant for a complete object type plus or minus an integer constant
4871 8 An arithmetic constant expression shall have arithmetic type and shall only have
4872 operands that are integer constants, floating constants, enumeration constants, character
4873 constants, and sizeof expressions. Cast operators in an arithmetic constant expression
4874 shall only convert arithmetic types to arithmetic types, except as part of an operand to a
4875 sizeof operator whose result is an integer constant.
4876 9 An address constant is a null pointer, a pointer to an lvalue designating an object of static
4877 storage duration, or a pointer to a function designator; it shall be created explicitly using
4878 the unary & operator or an integer constant cast to pointer type, or implicitly by the use of
4879 an expression of array or function type. The array-subscript [] and member-access .
4880 and -> operators, the address & and indirection * unary operators, and pointer casts may
4881 be used in the creation of an address constant, but the value of an object shall not be
4882 accessed by use of these operators.
4883 10 An implementation may accept other forms of constant expressions.
4884 11 The semantic rules for the evaluation of a constant expression are the same as for
4885 nonconstant expressions.<sup><a href="#note118"><b>118)</b></a></sup>
4886 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>).
4891 <sup><a name="note118" href="#note118"><b>118)</b></a></sup> Thus, in the following initialization,
4892 static int i = 2 || 1 / 0;
4893 the expression is a valid integer constant expression with value one.
4895 [<a name="p106" href="#p106">page 106</a>] (<a href="#Contents">Contents</a>)
4897 <a name="6.7" href="#6.7"><b> 6.7 Declarations</b></a>
4900 declaration-specifiers init-declarator-listopt ;
4901 static_assert-declaration
4902 declaration-specifiers:
4903 storage-class-specifier declaration-specifiersopt
4904 type-specifier declaration-specifiersopt
4905 type-qualifier declaration-specifiersopt
4906 function-specifier declaration-specifiersopt
4907 alignment-specifier declaration-specifiersopt
4908 init-declarator-list:
4910 init-declarator-list , init-declarator
4913 declarator = initializer
4915 2 A declaration other than a static_assert declaration shall declare at least a declarator
4916 (other than the parameters of a function or the members of a structure or union), a tag, or
4917 the members of an enumeration.
4918 3 If an identifier has no linkage, there shall be no more than one declaration of the identifier
4919 (in a declarator or type specifier) with the same scope and in the same name space, except
4920 that a typedef name can be redefined to denote the same type as it currently does and tags
4921 may be redeclared as specified in <a href="#6.7.2.3">6.7.2.3</a>.
4922 4 All declarations in the same scope that refer to the same object or function shall specify
4925 5 A declaration specifies the interpretation and attributes of a set of identifiers. A definition
4926 of an identifier is a declaration for that identifier that:
4927 -- for an object, causes storage to be reserved for that object;
4928 -- for a function, includes the function body;<sup><a href="#note119"><b>119)</b></a></sup>
4932 <sup><a name="note119" href="#note119"><b>119)</b></a></sup> Function definitions have a different syntax, described in <a href="#6.9.1">6.9.1</a>.
4934 [<a name="p107" href="#p107">page 107</a>] (<a href="#Contents">Contents</a>)
4936 -- for an enumeration constant or typedef name, is the (only) declaration of the
4938 6 The declaration specifiers consist of a sequence of specifiers that indicate the linkage,
4939 storage duration, and part of the type of the entities that the declarators denote. The init-
4940 declarator-list is a comma-separated sequence of declarators, each of which may have
4941 additional type information, or an initializer, or both. The declarators contain the
4942 identifiers (if any) being declared.
4943 7 If an identifier for an object is declared with no linkage, the type for the object shall be
4944 complete by the end of its declarator, or by the end of its init-declarator if it has an
4945 initializer; in the case of function parameters (including in prototypes), it is the adjusted
4946 type (see <a href="#6.7.6.3">6.7.6.3</a>) that is required to be complete.
4947 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
4948 (<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>).
4949 <a name="6.7.1" href="#6.7.1"><b> 6.7.1 Storage-class specifiers</b></a>
4951 1 storage-class-specifier:
4959 2 At most, one storage-class specifier may be given in the declaration specifiers in a
4960 declaration, except that _Thread_local may appear with static or extern.<sup><a href="#note120"><b>120)</b></a></sup>
4961 3 In the declaration of an object with block scope, if the declaration specifiers include
4962 _Thread_local, they shall also include either static or extern. If
4963 _Thread_local appears in any declaration of an object, it shall be present in every
4964 declaration of that object.
4966 4 The typedef specifier is called a ''storage-class specifier'' for syntactic convenience
4967 only; it is discussed in <a href="#6.7.8">6.7.8</a>. The meanings of the various linkages and storage durations
4968 were discussed in <a href="#6.2.2">6.2.2</a> and <a href="#6.2.4">6.2.4</a>.
4972 <sup><a name="note120" href="#note120"><b>120)</b></a></sup> See ''future language directions'' (<a href="#6.11.5">6.11.5</a>).
4974 [<a name="p108" href="#p108">page 108</a>] (<a href="#Contents">Contents</a>)
4976 5 A declaration of an identifier for an object with storage-class specifier register
4977 suggests that access to the object be as fast as possible. The extent to which such
4978 suggestions are effective is implementation-defined.<sup><a href="#note121"><b>121)</b></a></sup>
4979 6 The declaration of an identifier for a function that has block scope shall have no explicit
4980 storage-class specifier other than extern.
4981 7 If an aggregate or union object is declared with a storage-class specifier other than
4982 typedef, the properties resulting from the storage-class specifier, except with respect to
4983 linkage, also apply to the members of the object, and so on recursively for any aggregate
4984 or union member objects.
4985 Forward references: type definitions (<a href="#6.7.8">6.7.8</a>).
4986 <a name="6.7.2" href="#6.7.2"><b> 6.7.2 Type specifiers</b></a>
5000 atomic-type-specifier
5001 struct-or-union-specifier
5005 2 At least one type specifier shall be given in the declaration specifiers in each declaration,
5006 and in the specifier-qualifier list in each struct declaration and type name. Each list of
5009 <sup><a name="note121" href="#note121"><b>121)</b></a></sup> The implementation may treat any register declaration simply as an auto declaration. However,
5010 whether or not addressable storage is actually used, the address of any part of an object declared with
5011 storage-class specifier register cannot be computed, either explicitly (by use of the unary &
5012 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
5013 <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
5016 [<a name="p109" href="#p109">page 109</a>] (<a href="#Contents">Contents</a>)
5018 type specifiers shall be one of the following multisets (delimited by commas, when there
5019 is more than one multiset per item); the type specifiers may occur in any order, possibly
5020 intermixed with the other declaration specifiers.
5025 -- short, signed short, short int, or signed short int
5026 -- unsigned short, or unsigned short int
5027 -- int, signed, or signed int
5028 -- unsigned, or unsigned int
5029 -- long, signed long, long int, or signed long int
5030 -- unsigned long, or unsigned long int
5031 -- long long, signed long long, long long int, or
5032 signed long long int
5033 -- unsigned long long, or unsigned long long int
5040 -- long double _Complex
5041 -- atomic type specifier
5042 -- struct or union specifier
5045 3 The type specifier _Complex shall not be used if the implementation does not support
5046 complex types (see <a href="#6.10.8.3">6.10.8.3</a>).
5051 [<a name="p110" href="#p110">page 110</a>] (<a href="#Contents">Contents</a>)
5054 4 Specifiers for structures, unions, enumerations, and atomic types are discussed in <a href="#6.7.2.1">6.7.2.1</a>
5055 through <a href="#6.7.2.4">6.7.2.4</a>. Declarations of typedef names are discussed in <a href="#6.7.8">6.7.8</a>. The
5056 characteristics of the other types are discussed in <a href="#6.2.5">6.2.5</a>.
5057 5 Each of the comma-separated multisets designates the same type, except that for bit-
5058 fields, it is implementation-defined whether the specifier int designates the same type as
5059 signed int or the same type as unsigned int.
5060 Forward references: atomic type specifiers (<a href="#6.7.2.4">6.7.2.4</a>), enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>),
5061 structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), tags (<a href="#6.7.2.3">6.7.2.3</a>), type definitions (<a href="#6.7.8">6.7.8</a>).
5062 <a name="6.7.2.1" href="#6.7.2.1"><b> 6.7.2.1 Structure and union specifiers</b></a>
5064 1 struct-or-union-specifier:
5065 struct-or-union identifieropt { struct-declaration-list }
5066 struct-or-union identifier
5070 struct-declaration-list:
5072 struct-declaration-list struct-declaration
5074 specifier-qualifier-list struct-declarator-listopt ;
5075 static_assert-declaration
5076 specifier-qualifier-list:
5077 type-specifier specifier-qualifier-listopt
5078 type-qualifier specifier-qualifier-listopt
5079 struct-declarator-list:
5081 struct-declarator-list , struct-declarator
5084 declaratoropt : constant-expression
5086 2 A struct-declaration that does not declare an anonymous structure or anonymous union
5087 shall contain a struct-declarator-list.
5090 [<a name="p111" href="#p111">page 111</a>] (<a href="#Contents">Contents</a>)
5092 3 A structure or union shall not contain a member with incomplete or function type (hence,
5093 a structure shall not contain an instance of itself, but may contain a pointer to an instance
5094 of itself), except that the last member of a structure with more than one named member
5095 may have incomplete array type; such a structure (and any union containing, possibly
5096 recursively, a member that is such a structure) shall not be a member of a structure or an
5097 element of an array.
5098 4 The expression that specifies the width of a bit-field shall be an integer constant
5099 expression with a nonnegative value that does not exceed the width of an object of the
5100 type that would be specified were the colon and expression omitted.<sup><a href="#note122"><b>122)</b></a></sup> If the value is
5101 zero, the declaration shall have no declarator.
5102 5 A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed
5103 int, unsigned int, or some other implementation-defined type. It is
5104 implementation-defined whether atomic types are permitted.
5106 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
5107 storage is allocated in an ordered sequence, and a union is a type consisting of a sequence
5108 of members whose storage overlap.
5109 7 Structure and union specifiers have the same form. The keywords struct and union
5110 indicate that the type being specified is, respectively, a structure type or a union type.
5111 8 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
5112 within a translation unit. The struct-declaration-list is a sequence of declarations for the
5113 members of the structure or union. If the struct-declaration-list contains no named
5114 members, no anonymous structures, and no anonymous unions, the behavior is undefined.
5115 The type is incomplete until immediately after the } that terminates the list, and complete
5117 9 A member of a structure or union may have any complete object type other than a
5118 variably modified type.<sup><a href="#note123"><b>123)</b></a></sup> In addition, a member may be declared to consist of a
5119 specified number of bits (including a sign bit, if any). Such a member is called a
5120 bit-field;<sup><a href="#note124"><b>124)</b></a></sup> its width is preceded by a colon.
5121 10 A bit-field is interpreted as having a signed or unsigned integer type consisting of the
5122 specified number of bits.<sup><a href="#note125"><b>125)</b></a></sup> If the value 0 or 1 is stored into a nonzero-width bit-field of
5124 <sup><a name="note122" href="#note122"><b>122)</b></a></sup> While the number of bits in a _Bool object is at least CHAR_BIT, the width (number of sign and
5125 value bits) of a _Bool may be just 1 bit.
5126 <sup><a name="note123" href="#note123"><b>123)</b></a></sup> A structure or union cannot contain a member with a variably modified type because member names
5127 are not ordinary identifiers as defined in <a href="#6.2.3">6.2.3</a>.
5128 <sup><a name="note124" href="#note124"><b>124)</b></a></sup> The unary & (address-of) operator cannot be applied to a bit-field object; thus, there are no pointers to
5129 or arrays of bit-field objects.
5131 [<a name="p112" href="#p112">page 112</a>] (<a href="#Contents">Contents</a>)
5133 type _Bool, the value of the bit-field shall compare equal to the value stored; a _Bool
5134 bit-field has the semantics of a _Bool.
5135 11 An implementation may allocate any addressable storage unit large enough to hold a bit-
5136 field. If enough space remains, a bit-field that immediately follows another bit-field in a
5137 structure shall be packed into adjacent bits of the same unit. If insufficient space remains,
5138 whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is
5139 implementation-defined. The order of allocation of bit-fields within a unit (high-order to
5140 low-order or low-order to high-order) is implementation-defined. The alignment of the
5141 addressable storage unit is unspecified.
5142 12 A bit-field declaration with no declarator, but only a colon and a width, indicates an
5143 unnamed bit-field.<sup><a href="#note126"><b>126)</b></a></sup> As a special case, a bit-field structure member with a width of 0
5144 indicates that no further bit-field is to be packed into the unit in which the previous bit-
5145 field, if any, was placed.
5146 13 An unnamed member of structure type with no tag is called an anonymous structure; an
5147 unnamed member of union type with no tag is called an anonymous union. The members
5148 of an anonymous structure or union are considered to be members of the containing
5149 structure or union. This applies recursively if the containing structure or union is also
5151 14 Each non-bit-field member of a structure or union object is aligned in an implementation-
5152 defined manner appropriate to its type.
5153 15 Within a structure object, the non-bit-field members and the units in which bit-fields
5154 reside have addresses that increase in the order in which they are declared. A pointer to a
5155 structure object, suitably converted, points to its initial member (or if that member is a
5156 bit-field, then to the unit in which it resides), and vice versa. There may be unnamed
5157 padding within a structure object, but not at its beginning.
5158 16 The size of a union is sufficient to contain the largest of its members. The value of at
5159 most one of the members can be stored in a union object at any time. A pointer to a
5160 union object, suitably converted, points to each of its members (or if a member is a bit-
5161 field, then to the unit in which it resides), and vice versa.
5162 17 There may be unnamed padding at the end of a structure or union.
5163 18 As a special case, the last element of a structure with more than one named member may
5164 have an incomplete array type; this is called a flexible array member. In most situations,
5167 <sup><a name="note125" href="#note125"><b>125)</b></a></sup> 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,
5168 then it is implementation-defined whether the bit-field is signed or unsigned.
5169 <sup><a name="note126" href="#note126"><b>126)</b></a></sup> An unnamed bit-field structure member is useful for padding to conform to externally imposed
5172 [<a name="p113" href="#p113">page 113</a>] (<a href="#Contents">Contents</a>)
5174 the flexible array member is ignored. In particular, the size of the structure is as if the
5175 flexible array member were omitted except that it may have more trailing padding than
5176 the omission would imply. However, when a . (or ->) operator has a left operand that is
5177 (a pointer to) a structure with a flexible array member and the right operand names that
5178 member, it behaves as if that member were replaced with the longest array (with the same
5179 element type) that would not make the structure larger than the object being accessed; the
5180 offset of the array shall remain that of the flexible array member, even if this would differ
5181 from that of the replacement array. If this array would have no elements, it behaves as if
5182 it had one element but the behavior is undefined if any attempt is made to access that
5183 element or to generate a pointer one past it.
5184 19 EXAMPLE 1 The following illustrates anonymous structures and unions:
5186 union { // anonymous union
5187 struct { int i, j; }; // anonymous structure
5188 struct { long k, l; } w;
5193 v1.k = 3; // invalid: inner structure is not anonymous
5194 v1.w.k = 5; // valid
5196 20 EXAMPLE 2 After the declaration:
5197 struct s { int n; double d[]; };
5198 the structure struct s has a flexible array member d. A typical way to use this is:
5199 int m = /* some value */;
5200 struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));
5201 and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
5202 p had been declared as:
5203 struct { int n; double d[m]; } *p;
5204 (there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
5206 21 Following the above declaration:
5207 struct s t1 = { 0 }; // valid
5208 struct s t2 = { 1, { <a href="#4.2">4.2</a> }}; // invalid
5210 t1.d[0] = <a href="#4.2">4.2</a>; // might be undefined behavior
5211 The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
5212 contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
5213 sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)
5214 in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming
5217 [<a name="p114" href="#p114">page 114</a>] (<a href="#Contents">Contents</a>)
5219 22 After the further declaration:
5220 struct ss { int n; };
5222 sizeof (struct s) >= sizeof (struct ss)
5223 sizeof (struct s) >= offsetof(struct s, d)
5224 are always equal to 1.
5225 23 If sizeof (double) is 8, then after the following code is executed:
5228 s1 = malloc(sizeof (struct s) + 64);
5229 s2 = malloc(sizeof (struct s) + 46);
5230 and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
5231 purposes, as if the identifiers had been declared as:
5232 struct { int n; double d[8]; } *s1;
5233 struct { int n; double d[5]; } *s2;
5234 24 Following the further successful assignments:
5235 s1 = malloc(sizeof (struct s) + 10);
5236 s2 = malloc(sizeof (struct s) + 6);
5237 they then behave as if the declarations were:
5238 struct { int n; double d[1]; } *s1, *s2;
5241 dp = &(s1->d[0]); // valid
5243 dp = &(s2->d[0]); // valid
5244 *dp = 42; // undefined behavior
5247 only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes
5248 of the structure, they might be copied or simply overwritten with indeterminate values.
5250 Forward references: declarators (<a href="#6.7.6">6.7.6</a>), tags (<a href="#6.7.2.3">6.7.2.3</a>).
5255 [<a name="p115" href="#p115">page 115</a>] (<a href="#Contents">Contents</a>)
5257 <a name="6.7.2.2" href="#6.7.2.2"><b> 6.7.2.2 Enumeration specifiers</b></a>
5260 enum identifieropt { enumerator-list }
5261 enum identifieropt { enumerator-list , }
5265 enumerator-list , enumerator
5267 enumeration-constant
5268 enumeration-constant = constant-expression
5270 2 The expression that defines the value of an enumeration constant shall be an integer
5271 constant expression that has a value representable as an int.
5273 3 The identifiers in an enumerator list are declared as constants that have type int and
5274 may appear wherever such are permitted.<sup><a href="#note127"><b>127)</b></a></sup> An enumerator with = defines its
5275 enumeration constant as the value of the constant expression. If the first enumerator has
5276 no =, the value of its enumeration constant is 0. Each subsequent enumerator with no =
5277 defines its enumeration constant as the value of the constant expression obtained by
5278 adding 1 to the value of the previous enumeration constant. (The use of enumerators with
5279 = may produce enumeration constants with values that duplicate other values in the same
5280 enumeration.) The enumerators of an enumeration are also known as its members.
5281 4 Each enumerated type shall be compatible with char, a signed integer type, or an
5282 unsigned integer type. The choice of type is implementation-defined,<sup><a href="#note128"><b>128)</b></a></sup> but shall be
5283 capable of representing the values of all the members of the enumeration. The
5284 enumerated type is incomplete until immediately after the } that terminates the list of
5285 enumerator declarations, and complete thereafter.
5290 <sup><a name="note127" href="#note127"><b>127)</b></a></sup> Thus, the identifiers of enumeration constants declared in the same scope shall all be distinct from
5291 each other and from other identifiers declared in ordinary declarators.
5292 <sup><a name="note128" href="#note128"><b>128)</b></a></sup> An implementation may delay the choice of which integer type until all enumeration constants have
5295 [<a name="p116" href="#p116">page 116</a>] (<a href="#Contents">Contents</a>)
5297 5 EXAMPLE The following fragment:
5298 enum hue { chartreuse, burgundy, claret=20, winedark };
5302 if (*cp != burgundy)
5304 makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
5305 pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
5307 Forward references: tags (<a href="#6.7.2.3">6.7.2.3</a>).
5308 <a name="6.7.2.3" href="#6.7.2.3"><b> 6.7.2.3 Tags</b></a>
5310 1 A specific type shall have its content defined at most once.
5311 2 Where two declarations that use the same tag declare the same type, they shall both use
5312 the same choice of struct, union, or enum.
5313 3 A type specifier of the form
5315 without an enumerator list shall only appear after the type it specifies is complete.
5317 4 All declarations of structure, union, or enumerated types that have the same scope and
5318 use the same tag declare the same type. Irrespective of whether there is a tag or what
5319 other declarations of the type are in the same translation unit, the type is incomplete<sup><a href="#note129"><b>129)</b></a></sup>
5320 until immediately after the closing brace of the list defining the content, and complete
5322 5 Two declarations of structure, union, or enumerated types which are in different scopes or
5323 use different tags declare distinct types. Each declaration of a structure, union, or
5324 enumerated type which does not include a tag declares a distinct type.
5325 6 A type specifier of the form
5330 <sup><a name="note129" href="#note129"><b>129)</b></a></sup> An incomplete type may only by used when the size of an object of that type is not needed. It is not
5331 needed, for example, when a typedef name is declared to be a specifier for a structure or union, or
5332 when a pointer to or a function returning a structure or union is being declared. (See incomplete types
5333 in <a href="#6.2.5">6.2.5</a>.) The specification has to be complete before such a function is called or defined.
5335 [<a name="p117" href="#p117">page 117</a>] (<a href="#Contents">Contents</a>)
5337 struct-or-union identifieropt { struct-declaration-list }
5339 enum identifieropt { enumerator-list }
5341 enum identifieropt { enumerator-list , }
5342 declares a structure, union, or enumerated type. The list defines the structure content,
5343 union content, or enumeration content. If an identifier is provided,<sup><a href="#note130"><b>130)</b></a></sup> the type specifier
5344 also declares the identifier to be the tag of that type.
5345 7 A declaration of the form
5346 struct-or-union identifier ;
5347 specifies a structure or union type and declares the identifier as a tag of that type.<sup><a href="#note131"><b>131)</b></a></sup>
5348 8 If a type specifier of the form
5349 struct-or-union identifier
5350 occurs other than as part of one of the above forms, and no other declaration of the
5351 identifier as a tag is visible, then it declares an incomplete structure or union type, and
5352 declares the identifier as the tag of that type.131)
5353 9 If a type specifier of the form
5354 struct-or-union identifier
5357 occurs other than as part of one of the above forms, and a declaration of the identifier as a
5358 tag is visible, then it specifies the same type as that other declaration, and does not
5360 10 EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
5363 struct tnode *left, *right;
5365 specifies a structure that contains an integer and two pointers to objects of the same type. Once this
5366 declaration has been given, the declaration
5371 <sup><a name="note130" href="#note130"><b>130)</b></a></sup> If there is no identifier, the type can, within the translation unit, only be referred to by the declaration
5372 of which it is a part. Of course, when the declaration is of a typedef name, subsequent declarations
5373 can make use of that typedef name to declare objects having the specified structure, union, or
5375 <sup><a name="note131" href="#note131"><b>131)</b></a></sup> A similar construction with enum does not exist.
5377 [<a name="p118" href="#p118">page 118</a>] (<a href="#Contents">Contents</a>)
5379 struct tnode s, *sp;
5380 declares s to be an object of the given type and sp to be a pointer to an object of the given type. With
5381 these declarations, the expression sp->left refers to the left struct tnode pointer of the object to
5382 which sp points; the expression s.right->count designates the count member of the right struct
5383 tnode pointed to from s.
5384 11 The following alternative formulation uses the typedef mechanism:
5385 typedef struct tnode TNODE;
5388 TNODE *left, *right;
5392 12 EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential
5393 structures, the declarations
5394 struct s1 { struct s2 *s2p; /* ... */ }; // D1
5395 struct s2 { struct s1 *s1p; /* ... */ }; // D2
5396 specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
5397 declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
5398 D2. To eliminate this context sensitivity, the declaration
5400 may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then
5401 completes the specification of the new type.
5403 Forward references: declarators (<a href="#6.7.6">6.7.6</a>), type definitions (<a href="#6.7.8">6.7.8</a>).
5404 <a name="6.7.2.4" href="#6.7.2.4"><b> 6.7.2.4 Atomic type specifiers</b></a>
5406 1 atomic-type-specifier:
5407 _Atomic ( type-name )
5409 2 Atomic type specifiers shall not be used if the implementation does not support atomic
5410 types (see <a href="#6.10.8.3">6.10.8.3</a>).
5411 3 The type name in an atomic type specifier shall not refer to an array type, a function type,
5412 an atomic type, or a qualified type.
5414 4 The properties associated with atomic types are meaningful only for expressions that are
5415 lvalues. If the _Atomic keyword is immediately followed by a left parenthesis, it is
5416 interpreted as a type specifier (with a type name), not as a type qualifier.
5421 [<a name="p119" href="#p119">page 119</a>] (<a href="#Contents">Contents</a>)
5423 <a name="6.7.3" href="#6.7.3"><b> 6.7.3 Type qualifiers</b></a>
5431 2 Types other than pointer types whose referenced type is an object type shall not be
5433 3 The type modified by the _Atomic qualifier shall not be an array type or a function
5436 4 The properties associated with qualified types are meaningful only for expressions that
5437 are lvalues.<sup><a href="#note132"><b>132)</b></a></sup>
5438 5 If the same qualifier appears more than once in the same specifier-qualifier-list, either
5439 directly or via one or more typedefs, the behavior is the same as if it appeared only
5440 once. If other qualifiers appear along with the _Atomic qualifier in a specifier-qualifier-
5441 list, the resulting type is the so-qualified atomic type.
5442 6 If an attempt is made to modify an object defined with a const-qualified type through use
5443 of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is
5444 made to refer to an object defined with a volatile-qualified type through use of an lvalue
5445 with non-volatile-qualified type, the behavior is undefined.<sup><a href="#note133"><b>133)</b></a></sup>
5446 7 An object that has volatile-qualified type may be modified in ways unknown to the
5447 implementation or have other unknown side effects. Therefore any expression referring
5448 to such an object shall be evaluated strictly according to the rules of the abstract machine,
5449 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
5450 object shall agree with that prescribed by the abstract machine, except as modified by the
5455 <sup><a name="note132" href="#note132"><b>132)</b></a></sup> The implementation may place a const object that is not volatile in a read-only region of
5456 storage. Moreover, the implementation need not allocate storage for such an object if its address is
5458 <sup><a name="note133" href="#note133"><b>133)</b></a></sup> This applies to those objects that behave as if they were defined with qualified types, even if they are
5459 never actually defined as objects in the program (such as an object at a memory-mapped input/output
5462 [<a name="p120" href="#p120">page 120</a>] (<a href="#Contents">Contents</a>)
5464 unknown factors mentioned previously.<sup><a href="#note134"><b>134)</b></a></sup> What constitutes an access to an object that
5465 has volatile-qualified type is implementation-defined.
5466 8 An object that is accessed through a restrict-qualified pointer has a special association
5467 with that pointer. This association, defined in <a href="#6.7.3.1">6.7.3.1</a> below, requires that all accesses to
5468 that object use, directly or indirectly, the value of that particular pointer.<sup><a href="#note135"><b>135)</b></a></sup> The intended
5469 use of the restrict qualifier (like the register storage class) is to promote
5470 optimization, and deleting all instances of the qualifier from all preprocessing translation
5471 units composing a conforming program does not change its meaning (i.e., observable
5473 9 If the specification of an array type includes any type qualifiers, the element type is so-
5474 qualified, not the array type. If the specification of a function type includes any type
5475 qualifiers, the behavior is undefined.<sup><a href="#note136"><b>136)</b></a></sup>
5476 10 For two qualified types to be compatible, both shall have the identically qualified version
5477 of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers
5478 does not affect the specified type.
5479 11 EXAMPLE 1 An object declared
5480 extern const volatile int real_time_clock;
5481 may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
5483 12 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers
5484 modify an aggregate type:
5485 const struct s { int mem; } cs = { 1 };
5486 struct s ncs; // the object ncs is modifiable
5487 typedef int A[2][3];
5488 const A a = {{4, 5, 6}, {7, 8, 9}}; // array of array of const int
5492 cs = ncs; // violates modifiable lvalue constraint for =
5493 pi = &ncs.mem; // valid
5494 pi = &cs.mem; // violates type constraints for =
5495 pci = &cs.mem; // valid
5496 pi = a[0]; // invalid: a[0] has type ''const int *''
5500 <sup><a name="note134" href="#note134"><b>134)</b></a></sup> A volatile declaration may be used to describe an object corresponding to a memory-mapped
5501 input/output port or an object accessed by an asynchronously interrupting function. Actions on
5502 objects so declared shall not be ''optimized out'' by an implementation or reordered except as
5503 permitted by the rules for evaluating expressions.
5504 <sup><a name="note135" href="#note135"><b>135)</b></a></sup> For example, a statement that assigns a value returned by malloc to a single pointer establishes this
5505 association between the allocated object and the pointer.
5506 <sup><a name="note136" href="#note136"><b>136)</b></a></sup> Both of these can occur through the use of typedefs.
5508 [<a name="p121" href="#p121">page 121</a>] (<a href="#Contents">Contents</a>)
5510 13 EXAMPLE 3 The declaration
5511 _Atomic volatile int *p;
5512 specifies that p has the type ''pointer to volatile atomic int'', a pointer to a volatile-qualified atomic type.
5514 <a name="6.7.3.1" href="#6.7.3.1"><b> 6.7.3.1 Formal definition of restrict</b></a>
5515 1 Let D be a declaration of an ordinary identifier that provides a means of designating an
5516 object P as a restrict-qualified pointer to type T.
5517 2 If D appears inside a block and does not have storage class extern, let B denote the
5518 block. If D appears in the list of parameter declarations of a function definition, let B
5519 denote the associated block. Otherwise, let B denote the block of main (or the block of
5520 whatever function is called at program startup in a freestanding environment).
5521 3 In what follows, a pointer expression E is said to be based on object P if (at some
5522 sequence point in the execution of B prior to the evaluation of E) modifying P to point to
5523 a copy of the array object into which it formerly pointed would change the value of E.<sup><a href="#note137"><b>137)</b></a></sup>
5524 Note that ''based'' is defined only for expressions with pointer types.
5525 4 During each execution of B, let L be any lvalue that has &L based on P. If L is used to
5526 access the value of the object X that it designates, and X is also modified (by any means),
5527 then the following requirements apply: T shall not be const-qualified. Every other lvalue
5528 used to access the value of X shall also have its address based on P. Every access that
5529 modifies X shall be considered also to modify P, for the purposes of this subclause. If P
5530 is assigned the value of a pointer expression E that is based on another restricted pointer
5531 object P2, associated with block B2, then either the execution of B2 shall begin before
5532 the execution of B, or the execution of B2 shall end prior to the assignment. If these
5533 requirements are not met, then the behavior is undefined.
5534 5 Here an execution of B means that portion of the execution of the program that would
5535 correspond to the lifetime of an object with scalar type and automatic storage duration
5537 6 A translator is free to ignore any or all aliasing implications of uses of restrict.
5538 7 EXAMPLE 1 The file scope declarations
5542 assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
5543 program, then it is never accessed using either of the other two.
5546 <sup><a name="note137" href="#note137"><b>137)</b></a></sup> In other words, E depends on the value of P itself rather than on the value of an object referenced
5547 indirectly through P. For example, if identifier p has type (int **restrict), then the pointer
5548 expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer
5549 expressions *p and p[1] are not.
5551 [<a name="p122" href="#p122">page 122</a>] (<a href="#Contents">Contents</a>)
5553 8 EXAMPLE 2 The function parameter declarations in the following example
5554 void f(int n, int * restrict p, int * restrict q)
5559 assert that, during each execution of the function, if an object is accessed through one of the pointer
5560 parameters, then it is not also accessed through the other.
5561 9 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence
5562 analysis of function f without examining any of the calls of f in the program. The cost is that the
5563 programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the
5564 second call of f in g has undefined behavior because each of d[1] through d[49] is accessed through
5569 f(50, d + 50, d); // valid
5570 f(50, d + 1, d); // undefined behavior
5573 10 EXAMPLE 3 The function parameter declarations
5574 void h(int n, int * restrict p, int * restrict q, int * restrict r)
5577 for (i = 0; i < n; i++)
5580 illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
5581 are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
5582 modified within function h.
5584 11 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a
5585 function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments
5586 between restricted pointers declared in nested blocks have defined behavior.
5590 p1 = q1; // undefined behavior
5592 int * restrict p2 = p1; // valid
5593 int * restrict q2 = q1; // valid
5594 p1 = q2; // undefined behavior
5595 p2 = q2; // undefined behavior
5602 [<a name="p123" href="#p123">page 123</a>] (<a href="#Contents">Contents</a>)
5604 12 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more
5605 precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For
5606 example, this permits new_vector to return a vector.
5607 typedef struct { int n; float * restrict v; } vector;
5608 vector new_vector(int n)
5612 t.v = malloc(n * sizeof (float));
5616 <a name="6.7.4" href="#6.7.4"><b> 6.7.4 Function specifiers</b></a>
5618 1 function-specifier:
5622 2 Function specifiers shall be used only in the declaration of an identifier for a function.
5623 3 An inline definition of a function with external linkage shall not contain a definition of a
5624 modifiable object with static or thread storage duration, and shall not contain a reference
5625 to an identifier with internal linkage.
5626 4 In a hosted environment, no function specifier(s) shall appear in a declaration of main.
5628 5 A function specifier may appear more than once; the behavior is the same as if it
5630 6 A function declared with an inline function specifier is an inline function. Making a *
5631 function an inline function suggests that calls to the function be as fast as possible.<sup><a href="#note138"><b>138)</b></a></sup>
5632 The extent to which such suggestions are effective is implementation-defined.<sup><a href="#note139"><b>139)</b></a></sup>
5637 <sup><a name="note138" href="#note138"><b>138)</b></a></sup> By using, for example, an alternative to the usual function call mechanism, such as ''inline
5638 substitution''. Inline substitution is not textual substitution, nor does it create a new function.
5639 Therefore, for example, the expansion of a macro used within the body of the function uses the
5640 definition it had at the point the function body appears, and not where the function is called; and
5641 identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a
5642 single address, regardless of the number of inline definitions that occur in addition to the external
5644 <sup><a name="note139" href="#note139"><b>139)</b></a></sup> For example, an implementation might never perform inline substitution, or might only perform inline
5645 substitutions to calls in the scope of an inline declaration.
5647 [<a name="p124" href="#p124">page 124</a>] (<a href="#Contents">Contents</a>)
5649 7 Any function with internal linkage can be an inline function. For a function with external
5650 linkage, the following restrictions apply: If a function is declared with an inline
5651 function specifier, then it shall also be defined in the same translation unit. If all of the
5652 file scope declarations for a function in a translation unit include the inline function
5653 specifier without extern, then the definition in that translation unit is an inline
5654 definition. An inline definition does not provide an external definition for the function,
5655 and does not forbid an external definition in another translation unit. An inline definition
5656 provides an alternative to an external definition, which a translator may use to implement
5657 any call to the function in the same translation unit. It is unspecified whether a call to the
5658 function uses the inline definition or the external definition.<sup><a href="#note140"><b>140)</b></a></sup>
5659 8 A function declared with a _Noreturn function specifier shall not return to its caller.
5660 Recommended practice
5661 9 The implementation should produce a diagnostic message for a function declared with a
5662 _Noreturn function specifier that appears to be capable of returning to its caller.
5663 10 EXAMPLE 1 The declaration of an inline function with external linkage can result in either an external
5664 definition, or a definition available for use only within the translation unit. A file scope declaration with
5665 extern creates an external definition. The following example shows an entire translation unit.
5666 inline double fahr(double t)
5668 return (9.0 * t) / 5.0 + 32.0;
5670 inline double cels(double t)
5672 return (5.0 * (t - 32.0)) / 9.0;
5674 extern double fahr(double); // creates an external definition
5675 double convert(int is_fahr, double temp)
5677 /* A translator may perform inline substitutions */
5678 return is_fahr ? cels(temp) : fahr(temp);
5680 11 Note that the definition of fahr is an external definition because fahr is also declared with extern, but
5681 the definition of cels is an inline definition. Because cels has external linkage and is referenced, an
5682 external definition has to appear in another translation unit (see <a href="#6.9">6.9</a>); the inline definition and the external
5683 definition are distinct and either may be used for the call.
5690 <sup><a name="note140" href="#note140"><b>140)</b></a></sup> Since an inline definition is distinct from the corresponding external definition and from any other
5691 corresponding inline definitions in other translation units, all corresponding objects with static storage
5692 duration are also distinct in each of the definitions.
5694 [<a name="p125" href="#p125">page 125</a>] (<a href="#Contents">Contents</a>)
5696 _Noreturn void f () {
5699 _Noreturn void g (int i) { // causes undefined behavior if i <= 0
5700 if (i > 0) abort();
5703 Forward references: function definitions (<a href="#6.9.1">6.9.1</a>).
5704 <a name="6.7.5" href="#6.7.5"><b> 6.7.5 Alignment specifier</b></a>
5706 1 alignment-specifier:
5707 _Alignas ( type-name )
5708 _Alignas ( constant-expression )
5710 2 An alignment attribute shall not be specified in a declaration of a typedef, or a bit-field, or
5711 a function, or a parameter, or an object declared with the register storage-class
5713 3 The constant expression shall be an integer constant expression. It shall evaluate to a
5714 valid fundamental alignment, or to a valid extended alignment supported by the
5715 implementation in the context in which it appears, or to zero.
5716 4 The combined effect of all alignment attributes in a declaration shall not specify an
5717 alignment that is less strict than the alignment that would otherwise be required for the
5718 type of the object or member being declared.
5720 5 The first form is equivalent to _Alignas(alignof(type-name)).
5721 6 The alignment requirement of the declared object or member is taken to be the specified
5722 alignment. An alignment specification of zero has no effect.<sup><a href="#note141"><b>141)</b></a></sup> When multiple
5723 alignment specifiers occur in a declaration, the effective alignment requirement is the
5724 strictest specified alignment.
5725 7 If the definition of an object has an alignment specifier, any other declaration of that
5726 object shall either specify equivalent alignment or have no alignment specifier. If the
5727 definition of an object does not have an alignment specifier, any other declaration of that
5728 object shall also have no alignment specifier. If declarations of an object in different
5729 translation units have different alignment specifiers, the behavior is undefined.
5733 <sup><a name="note141" href="#note141"><b>141)</b></a></sup> An alignment specification of zero also does not affect other alignment specifications in the same
5736 [<a name="p126" href="#p126">page 126</a>] (<a href="#Contents">Contents</a>)
5738 <a name="6.7.6" href="#6.7.6"><b> 6.7.6 Declarators</b></a>
5741 pointeropt direct-declarator
5745 direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
5746 direct-declarator [ static type-qualifier-listopt assignment-expression ]
5747 direct-declarator [ type-qualifier-list static assignment-expression ]
5748 direct-declarator [ type-qualifier-listopt * ]
5749 direct-declarator ( parameter-type-list )
5750 direct-declarator ( identifier-listopt )
5752 * type-qualifier-listopt
5753 * type-qualifier-listopt pointer
5754 type-qualifier-list:
5756 type-qualifier-list type-qualifier
5757 parameter-type-list:
5759 parameter-list , ...
5761 parameter-declaration
5762 parameter-list , parameter-declaration
5763 parameter-declaration:
5764 declaration-specifiers declarator
5765 declaration-specifiers abstract-declaratoropt
5768 identifier-list , identifier
5770 2 Each declarator declares one identifier, and asserts that when an operand of the same
5771 form as the declarator appears in an expression, it designates a function or object with the
5772 scope, storage duration, and type indicated by the declaration specifiers.
5773 3 A full declarator is a declarator that is not part of another declarator. The end of a full
5774 declarator is a sequence point. If, in the nested sequence of declarators in a full
5775 [<a name="p127" href="#p127">page 127</a>] (<a href="#Contents">Contents</a>)
5777 declarator, there is a declarator specifying a variable length array type, the type specified
5778 by the full declarator is said to be variably modified. Furthermore, any type derived by
5779 declarator type derivation from a variably modified type is itself variably modified.
5780 4 In the following subclauses, consider a declaration
5782 where T contains the declaration specifiers that specify a type T (such as int) and D1 is
5783 a declarator that contains an identifier ident. The type specified for the identifier ident in
5784 the various forms of declarator is described inductively using this notation.
5785 5 If, in the declaration ''T D1'', D1 has the form
5787 then the type specified for ident is T .
5788 6 If, in the declaration ''T D1'', D1 has the form
5790 then ident has the type specified by the declaration ''T D''. Thus, a declarator in
5791 parentheses is identical to the unparenthesized declarator, but the binding of complicated
5792 declarators may be altered by parentheses.
5793 Implementation limits
5794 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
5795 function declarators that modify an arithmetic, structure, union, or void type, either
5796 directly or via one or more typedefs.
5797 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>).
5798 <a name="6.7.6.1" href="#6.7.6.1"><b> 6.7.6.1 Pointer declarators</b></a>
5800 1 If, in the declaration ''T D1'', D1 has the form
5801 * type-qualifier-listopt D
5802 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5803 T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list
5804 pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer.
5805 2 For two pointer types to be compatible, both shall be identically qualified and both shall
5806 be pointers to compatible types.
5807 3 EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer
5808 to a constant value'' and a ''constant pointer to a variable value''.
5813 [<a name="p128" href="#p128">page 128</a>] (<a href="#Contents">Contents</a>)
5815 const int *ptr_to_constant;
5816 int *const constant_ptr;
5817 The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
5818 but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
5819 int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
5821 4 The declaration of the constant pointer constant_ptr may be clarified by including a definition for the
5822 type ''pointer to int''.
5823 typedef int *int_ptr;
5824 const int_ptr constant_ptr;
5825 declares constant_ptr as an object that has type ''const-qualified pointer to int''.
5827 <a name="6.7.6.2" href="#6.7.6.2"><b> 6.7.6.2 Array declarators</b></a>
5829 1 In addition to optional type qualifiers and the keyword static, the [ and ] may delimit
5830 an expression or *. If they delimit an expression (which specifies the size of an array), the
5831 expression shall have an integer type. If the expression is a constant expression, it shall
5832 have a value greater than zero. The element type shall not be an incomplete or function
5833 type. The optional type qualifiers and the keyword static shall appear only in a
5834 declaration of a function parameter with an array type, and then only in the outermost
5835 array type derivation.
5836 2 If an identifier is declared as having a variably modified type, it shall be an ordinary
5837 identifier (as defined in <a href="#6.2.3">6.2.3</a>), have no linkage, and have either block scope or function
5838 prototype scope. If an identifier is declared to be an object with static or thread storage
5839 duration, it shall not have a variable length array type.
5841 3 If, in the declaration ''T D1'', D1 has one of the forms:
5842 D[ type-qualifier-listopt assignment-expressionopt ]
5843 D[ static type-qualifier-listopt assignment-expression ]
5844 D[ type-qualifier-list static assignment-expression ]
5845 D[ type-qualifier-listopt * ]
5846 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5847 T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.<sup><a href="#note142"><b>142)</b></a></sup>
5848 (See <a href="#6.7.6.3">6.7.6.3</a> for the meaning of the optional type qualifiers and the keyword static.)
5849 4 If the size is not present, the array type is an incomplete type. If the size is * instead of
5850 being an expression, the array type is a variable length array type of unspecified size,
5851 which can only be used in declarations or type names with function prototype scope;<sup><a href="#note143"><b>143)</b></a></sup>
5853 <sup><a name="note142" href="#note142"><b>142)</b></a></sup> When several ''array of'' specifications are adjacent, a multidimensional array is declared.
5855 [<a name="p129" href="#p129">page 129</a>] (<a href="#Contents">Contents</a>)
5857 such arrays are nonetheless complete types. If the size is an integer constant expression
5858 and the element type has a known constant size, the array type is not a variable length
5859 array type; otherwise, the array type is a variable length array type. (Variable length
5860 arrays are a conditional feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.)
5861 5 If the size is an expression that is not an integer constant expression: if it occurs in a
5862 declaration at function prototype scope, it is treated as if it were replaced by *; otherwise,
5863 each time it is evaluated it shall have a value greater than zero. The size of each instance
5864 of a variable length array type does not change during its lifetime. Where a size
5865 expression is part of the operand of a sizeof operator and changing the value of the
5866 size expression would not affect the result of the operator, it is unspecified whether or not
5867 the size expression is evaluated.
5868 6 For two array types to be compatible, both shall have compatible element types, and if
5869 both size specifiers are present, and are integer constant expressions, then both size
5870 specifiers shall have the same constant value. If the two array types are used in a context
5871 which requires them to be compatible, it is undefined behavior if the two size specifiers
5872 evaluate to unequal values.
5874 float fa[11], *afp[17];
5875 declares an array of float numbers and an array of pointers to float numbers.
5877 8 EXAMPLE 2 Note the distinction between the declarations
5880 The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
5881 (an incomplete type), the storage for which is defined elsewhere.
5883 9 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
5891 int (*r)[n][n][n+1];
5892 p = a; // invalid: not compatible because 4 != 6
5893 r = c; // compatible, but defined behavior only if
5894 // n == 6 and m == n+1
5900 <sup><a name="note143" href="#note143"><b>143)</b></a></sup> Thus, * can be used only in function declarations that are not definitions (see <a href="#6.7.6.3">6.7.6.3</a>).
5902 [<a name="p130" href="#p130">page 130</a>] (<a href="#Contents">Contents</a>)
5904 10 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or
5905 function prototype scope. Array objects declared with the _Thread_local, static, or extern
5906 storage-class specifier cannot have a variable length array (VLA) type. However, an object declared with
5907 the static storage-class specifier can have a VM type (that is, a pointer to a VLA type). Finally, all
5908 identifiers declared with a VM type have to be ordinary identifiers and cannot, therefore, be members of
5909 structures or unions.
5911 int A[n]; // invalid: file scope VLA
5912 extern int (*p2)[n]; // invalid: file scope VM
5913 int B[100]; // valid: file scope but not VM
5914 void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
5915 void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
5917 typedef int VLA[m][m]; // valid: block scope typedef VLA
5919 int (*y)[n]; // invalid: y not ordinary identifier
5920 int z[n]; // invalid: z not ordinary identifier
5922 int D[m]; // valid: auto VLA
5923 static int E[m]; // invalid: static block scope VLA
5924 extern int F[m]; // invalid: F has linkage and is VLA
5925 int (*s)[m]; // valid: auto pointer to VLA
5926 extern int (*r)[m]; // invalid: r has linkage and points to VLA
5927 static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
5930 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>),
5931 initialization (<a href="#6.7.9">6.7.9</a>).
5932 <a name="6.7.6.3" href="#6.7.6.3"><b> 6.7.6.3 Function declarators (including prototypes)</b></a>
5934 1 A function declarator shall not specify a return type that is a function type or an array
5936 2 The only storage-class specifier that shall occur in a parameter declaration is register.
5937 3 An identifier list in a function declarator that is not part of a definition of that function
5939 4 After adjustment, the parameters in a parameter type list in a function declarator that is
5940 part of a definition of that function shall not have incomplete type.
5942 5 If, in the declaration ''T D1'', D1 has the form
5947 [<a name="p131" href="#p131">page 131</a>] (<a href="#Contents">Contents</a>)
5949 D( parameter-type-list )
5951 D( identifier-listopt )
5952 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5953 T '', then the type specified for ident is ''derived-declarator-type-list function returning
5955 6 A parameter type list specifies the types of, and may declare identifiers for, the
5956 parameters of the function.
5957 7 A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to
5958 type'', where the type qualifiers (if any) are those specified within the [ and ] of the
5959 array type derivation. If the keyword static also appears within the [ and ] of the
5960 array type derivation, then for each call to the function, the value of the corresponding
5961 actual argument shall provide access to the first element of an array with at least as many
5962 elements as specified by the size expression.
5963 8 A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to
5964 function returning type'', as in <a href="#6.3.2.1">6.3.2.1</a>.
5965 9 If the list terminates with an ellipsis (, ...), no information about the number or types
5966 of the parameters after the comma is supplied.<sup><a href="#note144"><b>144)</b></a></sup>
5967 10 The special case of an unnamed parameter of type void as the only item in the list
5968 specifies that the function has no parameters.
5969 11 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a
5970 parameter name, it shall be taken as a typedef name.
5971 12 If the function declarator is not part of a definition of that function, parameters may have
5972 incomplete type and may use the [*] notation in their sequences of declarator specifiers
5973 to specify variable length array types.
5974 13 The storage-class specifier in the declaration specifiers for a parameter declaration, if
5975 present, is ignored unless the declared parameter is one of the members of the parameter
5976 type list for a function definition.
5977 14 An identifier list declares only the identifiers of the parameters of the function. An empty
5978 list in a function declarator that is part of a definition of that function specifies that the
5979 function has no parameters. The empty list in a function declarator that is not part of a
5980 definition of that function specifies that no information about the number or types of the
5981 parameters is supplied.<sup><a href="#note145"><b>145)</b></a></sup>
5985 <sup><a name="note144" href="#note144"><b>144)</b></a></sup> 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
5986 correspond to the ellipsis.
5988 [<a name="p132" href="#p132">page 132</a>] (<a href="#Contents">Contents</a>)
5990 15 For two function types to be compatible, both shall specify compatible return types.<sup><a href="#note146"><b>146)</b></a></sup>
5991 Moreover, the parameter type lists, if both are present, shall agree in the number of
5992 parameters and in use of the ellipsis terminator; corresponding parameters shall have
5993 compatible types. If one type has a parameter type list and the other type is specified by a
5994 function declarator that is not part of a function definition and that contains an empty
5995 identifier list, the parameter list shall not have an ellipsis terminator and the type of each
5996 parameter shall be compatible with the type that results from the application of the
5997 default argument promotions. If one type has a parameter type list and the other type is
5998 specified by a function definition that contains a (possibly empty) identifier list, both shall
5999 agree in the number of parameters, and the type of each prototype parameter shall be
6000 compatible with the type that results from the application of the default argument
6001 promotions to the type of the corresponding identifier. (In the determination of type
6002 compatibility and of a composite type, each parameter declared with function or array
6003 type is taken as having the adjusted type and each parameter declared with qualified type
6004 is taken as having the unqualified version of its declared type.)
6005 16 EXAMPLE 1 The declaration
6006 int f(void), *fip(), (*pfi)();
6007 declares a function f with no parameters returning an int, a function fip with no parameter specification
6008 returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an
6009 int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the
6010 declaration suggests, and the same construction in an expression requires, the calling of a function fip,
6011 and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the
6012 extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function
6013 designator, which is then used to call the function; it returns an int.
6014 17 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the
6015 declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either
6016 internal or external linkage (depending on what file scope declarations for these identifiers are visible), and
6017 the identifier of the pointer pfi has block scope and no linkage.
6019 18 EXAMPLE 2 The declaration
6020 int (*apfi[3])(int *x, int *y);
6021 declares an array apfi of three pointers to functions returning int. Each of these functions has two
6022 parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and
6023 go out of scope at the end of the declaration of apfi.
6025 19 EXAMPLE 3 The declaration
6026 int (*fpfi(int (*)(long), int))(int, ...);
6027 declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two
6028 parameters: a pointer to a function returning an int (with one parameter of type long int), and an int.
6029 The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more
6032 <sup><a name="note145" href="#note145"><b>145)</b></a></sup> See ''future language directions'' (<a href="#6.11.6">6.11.6</a>).
6033 <sup><a name="note146" href="#note146"><b>146)</b></a></sup> If both function types are ''old style'', parameter types are not compared.
6035 [<a name="p133" href="#p133">page 133</a>] (<a href="#Contents">Contents</a>)
6037 additional arguments of any type.
6039 20 EXAMPLE 4 The following prototype has a variably modified parameter.
6040 void addscalar(int n, int m,
6041 double a[n][n*m+300], double x);
6045 addscalar(4, 2, b, <a href="#2.17">2.17</a>);
6048 void addscalar(int n, int m,
6049 double a[n][n*m+300], double x)
6051 for (int i = 0; i < n; i++)
6052 for (int j = 0, k = n*m+300; j < k; j++)
6053 // a is a pointer to a VLA with n*m+300 elements
6057 21 EXAMPLE 5 The following are all compatible function prototype declarators.
6058 double maximum(int n, int m, double a[n][m]);
6059 double maximum(int n, int m, double a[*][*]);
6060 double maximum(int n, int m, double a[ ][*]);
6061 double maximum(int n, int m, double a[ ][m]);
6063 void f(double (* restrict a)[5]);
6064 void f(double a[restrict][5]);
6065 void f(double a[restrict 3][5]);
6066 void f(double a[restrict static 3][5]);
6067 (Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
6068 non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
6070 Forward references: function definitions (<a href="#6.9.1">6.9.1</a>), type names (<a href="#6.7.7">6.7.7</a>).
6075 [<a name="p134" href="#p134">page 134</a>] (<a href="#Contents">Contents</a>)
6077 <a name="6.7.7" href="#6.7.7"><b> 6.7.7 Type names</b></a>
6080 specifier-qualifier-list abstract-declaratoropt
6081 abstract-declarator:
6083 pointeropt direct-abstract-declarator
6084 direct-abstract-declarator:
6085 ( abstract-declarator )
6086 direct-abstract-declaratoropt [ type-qualifier-listopt
6087 assignment-expressionopt ]
6088 direct-abstract-declaratoropt [ static type-qualifier-listopt
6089 assignment-expression ]
6090 direct-abstract-declaratoropt [ type-qualifier-list static
6091 assignment-expression ]
6092 direct-abstract-declaratoropt [ * ]
6093 direct-abstract-declaratoropt ( parameter-type-listopt )
6095 2 In several contexts, it is necessary to specify a type. This is accomplished using a type
6096 name, which is syntactically a declaration for a function or an object of that type that
6097 omits the identifier.<sup><a href="#note147"><b>147)</b></a></sup>
6098 3 EXAMPLE The constructions
6106 (h) int (*const [])(unsigned int, ...)
6107 name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
6108 array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
6109 with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
6110 returning an int, and (h) array of an unspecified number of constant pointers to functions, each with one
6111 parameter that has type unsigned int and an unspecified number of other parameters, returning an
6117 <sup><a name="note147" href="#note147"><b>147)</b></a></sup> As indicated by the syntax, empty parentheses in a type name are interpreted as ''function with no
6118 parameter specification'', rather than redundant parentheses around the omitted identifier.
6120 [<a name="p135" href="#p135">page 135</a>] (<a href="#Contents">Contents</a>)
6122 <a name="6.7.8" href="#6.7.8"><b> 6.7.8 Type definitions</b></a>
6127 2 If a typedef name specifies a variably modified type then it shall have block scope.
6129 3 In a declaration whose storage-class specifier is typedef, each declarator defines an
6130 identifier to be a typedef name that denotes the type specified for the identifier in the way
6131 described in <a href="#6.7.6">6.7.6</a>. Any array size expressions associated with variable length array
6132 declarators are evaluated each time the declaration of the typedef name is reached in the
6133 order of execution. A typedef declaration does not introduce a new type, only a
6134 synonym for the type so specified. That is, in the following declarations:
6135 typedef T type_ident;
6137 type_ident is defined as a typedef name with the type specified by the declaration
6138 specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
6139 type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
6140 typedef name shares the same name space as other identifiers declared in ordinary
6143 typedef int MILES, KLICKSP();
6144 typedef struct { double hi, lo; } range;
6147 extern KLICKSP *metricp;
6150 are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
6151 parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
6152 such a structure. The object distance has a type compatible with any other int object.
6154 5 EXAMPLE 2 After the declarations
6155 typedef struct s1 { int x; } t1, *tp1;
6156 typedef struct s2 { int x; } t2, *tp2;
6157 type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
6158 s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
6163 [<a name="p136" href="#p136">page 136</a>] (<a href="#Contents">Contents</a>)
6165 6 EXAMPLE 3 The following obscure constructions
6166 typedef signed int t;
6173 declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
6174 with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
6175 qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
6176 [-16, +15], and one named r that contains values in one of the ranges [0, 31], [-15, +15], or [-16, +15].
6177 (The choice of range is implementation-defined.) The first two bit-field declarations differ in that
6178 unsigned is a type specifier (which forces t to be the name of a structure member), while const is a
6179 type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed
6180 in an inner scope by
6183 then a function f is declared with type ''function returning signed int with one unnamed parameter
6184 with type pointer to function returning signed int with one unnamed parameter with type signed
6185 int'', and an identifier t with type long int.
6187 7 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the
6188 following declarations of the signal function specify exactly the same type, the first without making use
6189 of any typedef names.
6190 typedef void fv(int), (*pfv)(int);
6191 void (*signal(int, void (*)(int)))(int);
6192 fv *signal(int, fv *);
6193 pfv signal(int, pfv);
6195 8 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the
6196 time the typedef name is defined, not each time it is used:
6199 typedef int B[n]; // B is n ints, n evaluated now
6201 B a; // a is n ints, n without += 1
6202 int b[n]; // a and b are different sizes
6203 for (int i = 1; i < n; i++)
6210 [<a name="p137" href="#p137">page 137</a>] (<a href="#Contents">Contents</a>)
6212 <a name="6.7.9" href="#6.7.9"><b> 6.7.9 Initialization</b></a>
6215 assignment-expression
6216 { initializer-list }
6217 { initializer-list , }
6219 designationopt initializer
6220 initializer-list , designationopt initializer
6225 designator-list designator
6227 [ constant-expression ]
6230 2 No initializer shall attempt to provide a value for an object not contained within the entity
6232 3 The type of the entity to be initialized shall be an array of unknown size or a complete
6233 object type that is not a variable length array type.
6234 4 All the expressions in an initializer for an object that has static or thread storage duration
6235 shall be constant expressions or string literals.
6236 5 If the declaration of an identifier has block scope, and the identifier has external or
6237 internal linkage, the declaration shall have no initializer for the identifier.
6238 6 If a designator has the form
6239 [ constant-expression ]
6240 then the current object (defined below) shall have array type and the expression shall be
6241 an integer constant expression. If the array is of unknown size, any nonnegative value is
6243 7 If a designator has the form
6245 then the current object (defined below) shall have structure or union type and the
6246 identifier shall be the name of a member of that type.
6247 [<a name="p138" href="#p138">page 138</a>] (<a href="#Contents">Contents</a>)
6250 8 An initializer specifies the initial value stored in an object.
6251 9 Except where explicitly stated otherwise, for the purposes of this subclause unnamed
6252 members of objects of structure and union type do not participate in initialization.
6253 Unnamed members of structure objects have indeterminate value even after initialization.
6254 10 If an object that has automatic storage duration is not initialized explicitly, its value is
6255 indeterminate. If an object that has static or thread storage duration is not initialized
6257 -- if it has pointer type, it is initialized to a null pointer;
6258 -- if it has arithmetic type, it is initialized to (positive or unsigned) zero;
6259 -- if it is an aggregate, every member is initialized (recursively) according to these rules,
6260 and any padding is initialized to zero bits;
6261 -- if it is a union, the first named member is initialized (recursively) according to these
6262 rules, and any padding is initialized to zero bits;
6263 11 The initializer for a scalar shall be a single expression, optionally enclosed in braces. The
6264 initial value of the object is that of the expression (after conversion); the same type
6265 constraints and conversions as for simple assignment apply, taking the type of the scalar
6266 to be the unqualified version of its declared type.
6267 12 The rest of this subclause deals with initializers for objects that have aggregate or union
6269 13 The initializer for a structure or union object that has automatic storage duration shall be
6270 either an initializer list as described below, or a single expression that has compatible
6271 structure or union type. In the latter case, the initial value of the object, including
6272 unnamed members, is that of the expression.
6273 14 An array of character type may be initialized by a character string literal or UTF-8 string
6274 literal, optionally enclosed in braces. Successive bytes of the string literal (including the
6275 terminating null character if there is room or if the array is of unknown size) initialize the
6276 elements of the array.
6277 15 An array with element type compatible with a qualified or unqualified version of
6278 wchar_t may be initialized by a wide string literal, optionally enclosed in braces.
6279 Successive wide characters of the wide string literal (including the terminating null wide
6280 character if there is room or if the array is of unknown size) initialize the elements of the
6282 16 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-
6283 enclosed list of initializers for the elements or named members.
6286 [<a name="p139" href="#p139">page 139</a>] (<a href="#Contents">Contents</a>)
6288 17 Each brace-enclosed initializer list has an associated current object. When no
6289 designations are present, subobjects of the current object are initialized in order according
6290 to the type of the current object: array elements in increasing subscript order, structure
6291 members in declaration order, and the first named member of a union.<sup><a href="#note148"><b>148)</b></a></sup> In contrast, a
6292 designation causes the following initializer to begin initialization of the subobject
6293 described by the designator. Initialization then continues forward in order, beginning
6294 with the next subobject after that described by the designator.<sup><a href="#note149"><b>149)</b></a></sup>
6295 18 Each designator list begins its description with the current object associated with the
6296 closest surrounding brace pair. Each item in the designator list (in order) specifies a
6297 particular member of its current object and changes the current object for the next
6298 designator (if any) to be that member.<sup><a href="#note150"><b>150)</b></a></sup> The current object that results at the end of the
6299 designator list is the subobject to be initialized by the following initializer.
6300 19 The initialization shall occur in initializer list order, each initializer provided for a
6301 particular subobject overriding any previously listed initializer for the same subobject;<sup><a href="#note151"><b>151)</b></a></sup>
6302 all subobjects that are not initialized explicitly shall be initialized implicitly the same as
6303 objects that have static storage duration.
6304 20 If the aggregate or union contains elements or members that are aggregates or unions,
6305 these rules apply recursively to the subaggregates or contained unions. If the initializer of
6306 a subaggregate or contained union begins with a left brace, the initializers enclosed by
6307 that brace and its matching right brace initialize the elements or members of the
6308 subaggregate or the contained union. Otherwise, only enough initializers from the list are
6309 taken to account for the elements or members of the subaggregate or the first member of
6310 the contained union; any remaining initializers are left to initialize the next element or
6311 member of the aggregate of which the current subaggregate or contained union is a part.
6312 21 If there are fewer initializers in a brace-enclosed list than there are elements or members
6313 of an aggregate, or fewer characters in a string literal used to initialize an array of known
6314 size than there are elements in the array, the remainder of the aggregate shall be
6315 initialized implicitly the same as objects that have static storage duration.
6319 <sup><a name="note148" href="#note148"><b>148)</b></a></sup> If the initializer list for a subaggregate or contained union does not begin with a left brace, its
6320 subobjects are initialized as usual, but the subaggregate or contained union does not become the
6321 current object: current objects are associated only with brace-enclosed initializer lists.
6322 <sup><a name="note149" href="#note149"><b>149)</b></a></sup> After a union member is initialized, the next object is not the next member of the union; instead, it is
6323 the next subobject of an object containing the union.
6324 <sup><a name="note150" href="#note150"><b>150)</b></a></sup> Thus, a designator can only specify a strict subobject of the aggregate or union that is associated with
6325 the surrounding brace pair. Note, too, that each separate designator list is independent.
6326 <sup><a name="note151" href="#note151"><b>151)</b></a></sup> Any initializer for the subobject which is overridden and so not used to initialize that subobject might
6327 not be evaluated at all.
6329 [<a name="p140" href="#p140">page 140</a>] (<a href="#Contents">Contents</a>)
6331 22 If an array of unknown size is initialized, its size is determined by the largest indexed
6332 element with an explicit initializer. The array type is completed at the end of its
6334 23 The evaluations of the initialization list expressions are indeterminately sequenced with
6335 respect to one another and thus the order in which any side effects occur is
6336 unspecified.<sup><a href="#note152"><b>152)</b></a></sup>
6337 24 EXAMPLE 1 Provided that <a href="#7.3"><complex.h></a> has been #included, the declarations
6338 int i = <a href="#3.5">3.5</a>;
6339 double complex c = 5 + 3 * I;
6340 define and initialize i with the value 3 and c with the value 5.0 + i3.0.
6342 25 EXAMPLE 2 The declaration
6343 int x[] = { 1, 3, 5 };
6344 defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
6345 and there are three initializers.
6347 26 EXAMPLE 3 The declaration
6353 is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
6354 y[0]), namely y[0][0], y[0][1], and y[0][2]. Likewise the next two lines initialize y[1] and
6355 y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
6358 1, 3, 5, 2, 4, 6, 3, 5, 7
6360 The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
6361 next three are taken successively for y[1] and y[2].
6363 27 EXAMPLE 4 The declaration
6365 { 1 }, { 2 }, { 3 }, { 4 }
6367 initializes the first column of z as specified and initializes the rest with zeros.
6369 28 EXAMPLE 5 The declaration
6370 struct { int a[3], b; } w[] = { { 1 }, 2 };
6371 is a definition with an inconsistently bracketed initialization. It defines an array with two element
6375 <sup><a name="note152" href="#note152"><b>152)</b></a></sup> In particular, the evaluation order need not be the same as the order of subobject initialization.
6377 [<a name="p141" href="#p141">page 141</a>] (<a href="#Contents">Contents</a>)
6379 structures: w[0].a[0] is 1 and w[1].a[0] is 2; all the other elements are zero.
6381 29 EXAMPLE 6 The declaration
6382 short q[4][3][2] = {
6387 contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
6388 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
6389 q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
6390 q[0][0] does not begin with a left brace, so up to six items from the current list may be used. There is
6391 only one, so the values for the remaining five elements are initialized with zero. Likewise, the initializers
6392 for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their
6393 respective two-dimensional subaggregates. If there had been more than six items in any of the lists, a
6394 diagnostic message would have been issued. The same initialization result could have been achieved by:
6395 short q[4][3][2] = {
6401 short q[4][3][2] = {
6413 in a fully bracketed form.
6414 30 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
6417 31 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the
6419 typedef int A[]; // OK - declared with block scope
6421 A a = { 1, 2 }, b = { 3, 4, 5 };
6423 int a[] = { 1, 2 }, b[] = { 3, 4, 5 };
6424 due to the rules for incomplete types.
6426 [<a name="p142" href="#p142">page 142</a>] (<a href="#Contents">Contents</a>)
6428 32 EXAMPLE 8 The declaration
6429 char s[] = "abc", t[3] = "abc";
6430 defines ''plain'' char array objects s and t whose elements are initialized with character string literals.
6431 This declaration is identical to
6432 char s[] = { 'a', 'b', 'c', '\0' },
6433 t[] = { 'a', 'b', 'c' };
6434 The contents of the arrays are modifiable. On the other hand, the declaration
6436 defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char''
6437 with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to
6438 modify the contents of the array, the behavior is undefined.
6440 33 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using
6442 enum { member_one, member_two };
6443 const char *nm[] = {
6444 [member_two] = "member two",
6445 [member_one] = "member one",
6448 34 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
6449 div_t answer = { .quot = 2, .rem = -1 };
6451 35 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
6452 might be misunderstood:
6453 struct { int a[3], b; } w[] =
6454 { [0].a = {1}, [1].a[0] = 2 };
6456 36 EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator:
6458 1, 3, 5, 7, 9, [MAX-5] = 8, 6, 4, 2, 0
6460 37 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less
6461 than ten, some of the values provided by the first five initializers will be overridden by the second five.
6463 38 EXAMPLE 13 Any member of a union can be initialized:
6464 union { /* ... */ } u = { .any_member = 42 };
6466 Forward references: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>).
6471 [<a name="p143" href="#p143">page 143</a>] (<a href="#Contents">Contents</a>)
6473 <a name="6.7.10" href="#6.7.10"><b> 6.7.10 Static assertions</b></a>
6475 1 static_assert-declaration:
6476 _Static_assert ( constant-expression , string-literal ) ;
6478 2 The constant expression shall compare unequal to 0.
6480 3 The constant expression shall be an integer constant expression. If the value of the
6481 constant expression compares unequal to 0, the declaration has no effect. Otherwise, the
6482 constraint is violated and the implementation shall produce a diagnostic message that
6483 includes the text of the string literal, except that characters not in the basic source
6484 character set are not required to appear in the message.
6485 Forward references: diagnostics (<a href="#7.2">7.2</a>).
6490 [<a name="p144" href="#p144">page 144</a>] (<a href="#Contents">Contents</a>)
6492 <a name="6.8" href="#6.8"><b> 6.8 Statements and blocks</b></a>
6497 expression-statement
6502 2 A statement specifies an action to be performed. Except as indicated, statements are
6503 executed in sequence.
6504 3 A block allows a set of declarations and statements to be grouped into one syntactic unit.
6505 The initializers of objects that have automatic storage duration, and the variable length
6506 array declarators of ordinary identifiers with block scope, are evaluated and the values are
6507 stored in the objects (including storing an indeterminate value in objects without an
6508 initializer) each time the declaration is reached in the order of execution, as if it were a
6509 statement, and within each declaration in the order that declarators appear.
6510 4 A full expression is an expression that is not part of another expression or of a declarator.
6511 Each of the following is a full expression: an initializer that is not part of a compound
6512 literal; the expression in an expression statement; the controlling expression of a selection
6513 statement (if or switch); the controlling expression of a while or do statement; each
6514 of the (optional) expressions of a for statement; the (optional) expression in a return
6515 statement. There is a sequence point between the evaluation of a full expression and the
6516 evaluation of the next full expression to be evaluated.
6517 Forward references: expression and null statements (<a href="#6.8.3">6.8.3</a>), selection statements
6518 (<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>).
6519 <a name="6.8.1" href="#6.8.1"><b> 6.8.1 Labeled statements</b></a>
6521 1 labeled-statement:
6522 identifier : statement
6523 case constant-expression : statement
6526 2 A case or default label shall appear only in a switch statement. Further
6527 constraints on such labels are discussed under the switch statement.
6529 [<a name="p145" href="#p145">page 145</a>] (<a href="#Contents">Contents</a>)
6531 3 Label names shall be unique within a function.
6533 4 Any statement may be preceded by a prefix that declares an identifier as a label name.
6534 Labels in themselves do not alter the flow of control, which continues unimpeded across
6536 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>).
6537 <a name="6.8.2" href="#6.8.2"><b> 6.8.2 Compound statement</b></a>
6539 1 compound-statement:
6540 { block-item-listopt }
6543 block-item-list block-item
6548 2 A compound statement is a block.
6549 <a name="6.8.3" href="#6.8.3"><b> 6.8.3 Expression and null statements</b></a>
6551 1 expression-statement:
6554 2 The expression in an expression statement is evaluated as a void expression for its side
6555 effects.<sup><a href="#note153"><b>153)</b></a></sup>
6556 3 A null statement (consisting of just a semicolon) performs no operations.
6557 4 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the
6558 discarding of its value may be made explicit by converting the expression to a void expression by means of
6566 <sup><a name="note153" href="#note153"><b>153)</b></a></sup> Such as assignments, and function calls which have side effects.
6568 [<a name="p146" href="#p146">page 146</a>] (<a href="#Contents">Contents</a>)
6570 5 EXAMPLE 2 In the program fragment
6573 while (*s++ != '\0')
6575 a null statement is used to supply an empty loop body to the iteration statement.
6577 6 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
6591 Forward references: iteration statements (<a href="#6.8.5">6.8.5</a>).
6592 <a name="6.8.4" href="#6.8.4"><b> 6.8.4 Selection statements</b></a>
6594 1 selection-statement:
6595 if ( expression ) statement
6596 if ( expression ) statement else statement
6597 switch ( expression ) statement
6599 2 A selection statement selects among a set of statements depending on the value of a
6600 controlling expression.
6601 3 A selection statement is a block whose scope is a strict subset of the scope of its
6602 enclosing block. Each associated substatement is also a block whose scope is a strict
6603 subset of the scope of the selection statement.
6604 <a name="6.8.4.1" href="#6.8.4.1"><b> 6.8.4.1 The if statement</b></a>
6606 1 The controlling expression of an if statement shall have scalar type.
6608 2 In both forms, the first substatement is executed if the expression compares unequal to 0.
6609 In the else form, the second substatement is executed if the expression compares equal
6612 [<a name="p147" href="#p147">page 147</a>] (<a href="#Contents">Contents</a>)
6614 to 0. If the first substatement is reached via a label, the second substatement is not
6616 3 An else is associated with the lexically nearest preceding if that is allowed by the
6618 <a name="6.8.4.2" href="#6.8.4.2"><b> 6.8.4.2 The switch statement</b></a>
6620 1 The controlling expression of a switch statement shall have integer type.
6621 2 If a switch statement has an associated case or default label within the scope of an
6622 identifier with a variably modified type, the entire switch statement shall be within the
6623 scope of that identifier.<sup><a href="#note154"><b>154)</b></a></sup>
6624 3 The expression of each case label shall be an integer constant expression and no two of
6625 the case constant expressions in the same switch statement shall have the same value
6626 after conversion. There may be at most one default label in a switch statement.
6627 (Any enclosed switch statement may have a default label or case constant
6628 expressions with values that duplicate case constant expressions in the enclosing
6631 4 A switch statement causes control to jump to, into, or past the statement that is the
6632 switch body, depending on the value of a controlling expression, and on the presence of a
6633 default label and the values of any case labels on or in the switch body. A case or
6634 default label is accessible only within the closest enclosing switch statement.
6635 5 The integer promotions are performed on the controlling expression. The constant
6636 expression in each case label is converted to the promoted type of the controlling
6637 expression. If a converted value matches that of the promoted controlling expression,
6638 control jumps to the statement following the matched case label. Otherwise, if there is
6639 a default label, control jumps to the labeled statement. If no converted case constant
6640 expression matches and there is no default label, no part of the switch body is
6642 Implementation limits
6643 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
6649 <sup><a name="note154" href="#note154"><b>154)</b></a></sup> That is, the declaration either precedes the switch statement, or it follows the last case or
6650 default label associated with the switch that is in the block containing the declaration.
6652 [<a name="p148" href="#p148">page 148</a>] (<a href="#Contents">Contents</a>)
6654 7 EXAMPLE In the artificial program fragment
6661 /* falls through into default code */
6665 the object whose identifier is i exists with automatic storage duration (within the block) but is never
6666 initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
6667 access an indeterminate value. Similarly, the call to the function f cannot be reached.
6669 <a name="6.8.5" href="#6.8.5"><b> 6.8.5 Iteration statements</b></a>
6671 1 iteration-statement:
6672 while ( expression ) statement
6673 do statement while ( expression ) ;
6674 for ( expressionopt ; expressionopt ; expressionopt ) statement
6675 for ( declaration expressionopt ; expressionopt ) statement
6677 2 The controlling expression of an iteration statement shall have scalar type.
6678 3 The declaration part of a for statement shall only declare identifiers for objects having
6679 storage class auto or register.
6681 4 An iteration statement causes a statement called the loop body to be executed repeatedly
6682 until the controlling expression compares equal to 0. The repetition occurs regardless of
6683 whether the loop body is entered from the iteration statement or by a jump.<sup><a href="#note155"><b>155)</b></a></sup>
6684 5 An iteration statement is a block whose scope is a strict subset of the scope of its
6685 enclosing block. The loop body is also a block whose scope is a strict subset of the scope
6686 of the iteration statement.
6687 6 An iteration statement whose controlling expression is not a constant expression,<sup><a href="#note156"><b>156)</b></a></sup> that
6688 performs no input/output operations, does not access volatile objects, and performs no
6689 synchronization or atomic operations in its body, controlling expression, or (in the case of
6691 <sup><a name="note155" href="#note155"><b>155)</b></a></sup> Code jumped over is not executed. In particular, the controlling expression of a for or while
6692 statement is not evaluated before entering the loop body, nor is clause-1 of a for statement.
6693 <sup><a name="note156" href="#note156"><b>156)</b></a></sup> An omitted controlling expression is replaced by a nonzero constant, which is a constant expression.
6695 [<a name="p149" href="#p149">page 149</a>] (<a href="#Contents">Contents</a>)
6697 a for statement) its expression-3, may be assumed by the implementation to
6698 terminate.<sup><a href="#note157"><b>157)</b></a></sup>
6699 <a name="6.8.5.1" href="#6.8.5.1"><b> 6.8.5.1 The while statement</b></a>
6700 1 The evaluation of the controlling expression takes place before each execution of the loop
6702 <a name="6.8.5.2" href="#6.8.5.2"><b> 6.8.5.2 The do statement</b></a>
6703 1 The evaluation of the controlling expression takes place after each execution of the loop
6705 <a name="6.8.5.3" href="#6.8.5.3"><b> 6.8.5.3 The for statement</b></a>
6707 for ( clause-1 ; expression-2 ; expression-3 ) statement
6708 behaves as follows: The expression expression-2 is the controlling expression that is
6709 evaluated before each execution of the loop body. The expression expression-3 is
6710 evaluated as a void expression after each execution of the loop body. If clause-1 is a
6711 declaration, the scope of any identifiers it declares is the remainder of the declaration and
6712 the entire loop, including the other two expressions; it is reached in the order of execution
6713 before the first evaluation of the controlling expression. If clause-1 is an expression, it is
6714 evaluated as a void expression before the first evaluation of the controlling expression.<sup><a href="#note158"><b>158)</b></a></sup>
6715 2 Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a
6717 <a name="6.8.6" href="#6.8.6"><b> 6.8.6 Jump statements</b></a>
6723 return expressionopt ;
6728 <sup><a name="note157" href="#note157"><b>157)</b></a></sup> This is intended to allow compiler transformations such as removal of empty loops even when
6729 termination cannot be proven.
6730 <sup><a name="note158" href="#note158"><b>158)</b></a></sup> Thus, clause-1 specifies initialization for the loop, possibly declaring one or more variables for use in
6731 the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration,
6732 such that execution of the loop continues until the expression compares equal to 0; and expression-3
6733 specifies an operation (such as incrementing) that is performed after each iteration.
6735 [<a name="p150" href="#p150">page 150</a>] (<a href="#Contents">Contents</a>)
6738 2 A jump statement causes an unconditional jump to another place.
6739 <a name="6.8.6.1" href="#6.8.6.1"><b> 6.8.6.1 The goto statement</b></a>
6741 1 The identifier in a goto statement shall name a label located somewhere in the enclosing
6742 function. A goto statement shall not jump from outside the scope of an identifier having
6743 a variably modified type to inside the scope of that identifier.
6745 2 A goto statement causes an unconditional jump to the statement prefixed by the named
6746 label in the enclosing function.
6747 3 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The
6748 following outline presents one possible approach to a problem based on these three assumptions:
6749 1. The general initialization code accesses objects only visible to the current function.
6750 2. The general initialization code is too large to warrant duplication.
6751 3. The code to determine the next operation is at the head of the loop. (To allow it to be reached by
6752 continue statements, for example.)
6756 // determine next operation
6758 if (need to reinitialize) {
6759 // reinitialize-only code
6762 // general initialization code
6766 // handle other operations
6773 [<a name="p151" href="#p151">page 151</a>] (<a href="#Contents">Contents</a>)
6775 4 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably
6776 modified types. A jump within the scope, however, is permitted.
6777 goto lab3; // invalid: going INTO scope of VLA.
6780 a[j] = <a href="#4.4">4.4</a>;
6782 a[j] = <a href="#3.3">3.3</a>;
6783 goto lab4; // valid: going WITHIN scope of VLA.
6784 a[j] = <a href="#5.5">5.5</a>;
6786 a[j] = <a href="#6.6">6.6</a>;
6788 goto lab4; // invalid: going INTO scope of VLA.
6790 <a name="6.8.6.2" href="#6.8.6.2"><b> 6.8.6.2 The continue statement</b></a>
6792 1 A continue statement shall appear only in or as a loop body.
6794 2 A continue statement causes a jump to the loop-continuation portion of the smallest
6795 enclosing iteration statement; that is, to the end of the loop body. More precisely, in each
6797 while (/* ... */) { do { for (/* ... */) {
6798 /* ... */ /* ... */ /* ... */
6799 continue; continue; continue;
6800 /* ... */ /* ... */ /* ... */
6801 contin: ; contin: ; contin: ;
6802 } } while (/* ... */); }
6803 unless the continue statement shown is in an enclosed iteration statement (in which
6804 case it is interpreted within that statement), it is equivalent to goto contin;.<sup><a href="#note159"><b>159)</b></a></sup>
6805 <a name="6.8.6.3" href="#6.8.6.3"><b> 6.8.6.3 The break statement</b></a>
6807 1 A break statement shall appear only in or as a switch body or loop body.
6809 2 A break statement terminates execution of the smallest enclosing switch or iteration
6814 <sup><a name="note159" href="#note159"><b>159)</b></a></sup> Following the contin: label is a null statement.
6816 [<a name="p152" href="#p152">page 152</a>] (<a href="#Contents">Contents</a>)
6818 <a name="6.8.6.4" href="#6.8.6.4"><b> 6.8.6.4 The return statement</b></a>
6820 1 A return statement with an expression shall not appear in a function whose return type
6821 is void. A return statement without an expression shall only appear in a function
6822 whose return type is void.
6824 2 A return statement terminates execution of the current function and returns control to
6825 its caller. A function may have any number of return statements.
6826 3 If a return statement with an expression is executed, the value of the expression is
6827 returned to the caller as the value of the function call expression. If the expression has a
6828 type different from the return type of the function in which it appears, the value is
6829 converted as if by assignment to an object having the return type of the function.<sup><a href="#note160"><b>160)</b></a></sup>
6831 struct s { double i; } f(void);
6848 there is no undefined behavior, although there would be if the assignment were done directly (without using
6849 a function call to fetch the value).
6854 <sup><a name="note160" href="#note160"><b>160)</b></a></sup> 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
6855 apply to the case of function return. The representation of floating-point values may have wider range
6856 or precision than implied by the type; a cast may be used to remove this extra range and precision.
6858 [<a name="p153" href="#p153">page 153</a>] (<a href="#Contents">Contents</a>)
6860 <a name="6.9" href="#6.9"><b> 6.9 External definitions</b></a>
6863 external-declaration
6864 translation-unit external-declaration
6865 external-declaration:
6869 2 The storage-class specifiers auto and register shall not appear in the declaration
6870 specifiers in an external declaration.
6871 3 There shall be no more than one external definition for each identifier declared with
6872 internal linkage in a translation unit. Moreover, if an identifier declared with internal
6873 linkage is used in an expression (other than as a part of the operand of a sizeof
6874 operator whose result is an integer constant), there shall be exactly one external definition
6875 for the identifier in the translation unit.
6877 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,
6878 which consists of a sequence of external declarations. These are described as ''external''
6879 because they appear outside any function (and hence have file scope). As discussed in
6880 <a href="#6.7">6.7</a>, a declaration that also causes storage to be reserved for an object or a function named
6881 by the identifier is a definition.
6882 5 An external definition is an external declaration that is also a definition of a function
6883 (other than an inline definition) or an object. If an identifier declared with external
6884 linkage is used in an expression (other than as part of the operand of a sizeof operator
6885 whose result is an integer constant), somewhere in the entire program there shall be
6886 exactly one external definition for the identifier; otherwise, there shall be no more than
6887 one.<sup><a href="#note161"><b>161)</b></a></sup>
6892 <sup><a name="note161" href="#note161"><b>161)</b></a></sup> Thus, if an identifier declared with external linkage is not used in an expression, there need be no
6893 external definition for it.
6895 [<a name="p154" href="#p154">page 154</a>] (<a href="#Contents">Contents</a>)
6897 <a name="6.9.1" href="#6.9.1"><b> 6.9.1 Function definitions</b></a>
6899 1 function-definition:
6900 declaration-specifiers declarator declaration-listopt compound-statement
6903 declaration-list declaration
6905 2 The identifier declared in a function definition (which is the name of the function) shall
6906 have a function type, as specified by the declarator portion of the function definition.<sup><a href="#note162"><b>162)</b></a></sup>
6907 3 The return type of a function shall be void or a complete object type other than array
6909 4 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
6911 5 If the declarator includes a parameter type list, the declaration of each parameter shall
6912 include an identifier, except for the special case of a parameter list consisting of a single
6913 parameter of type void, in which case there shall not be an identifier. No declaration list
6915 6 If the declarator includes an identifier list, each declaration in the declaration list shall
6916 have at least one declarator, those declarators shall declare only identifiers from the
6917 identifier list, and every identifier in the identifier list shall be declared. An identifier
6918 declared as a typedef name shall not be redeclared as a parameter. The declarations in the
6919 declaration list shall contain no storage-class specifier other than register and no
6924 <sup><a name="note162" href="#note162"><b>162)</b></a></sup> The intent is that the type category in a function definition cannot be inherited from a typedef:
6925 typedef int F(void); // type F is ''function with no parameters
6927 F f, g; // f and g both have type compatible with F
6928 F f { /* ... */ } // WRONG: syntax/constraint error
6929 F g() { /* ... */ } // WRONG: declares that g returns a function
6930 int f(void) { /* ... */ } // RIGHT: f has type compatible with F
6931 int g() { /* ... */ } // RIGHT: g has type compatible with F
6932 F *e(void) { /* ... */ } // e returns a pointer to a function
6933 F *((e))(void) { /* ... */ } // same: parentheses irrelevant
6934 int (*fp)(void); // fp points to a function that has type F
6935 F *Fp; // Fp points to a function that has type F
6938 [<a name="p155" href="#p155">page 155</a>] (<a href="#Contents">Contents</a>)
6941 7 The declarator in a function definition specifies the name of the function being defined
6942 and the identifiers of its parameters. If the declarator includes a parameter type list, the
6943 list also specifies the types of all the parameters; such a declarator also serves as a
6944 function prototype for later calls to the same function in the same translation unit. If the
6945 declarator includes an identifier list,<sup><a href="#note163"><b>163)</b></a></sup> the types of the parameters shall be declared in a
6946 following declaration list. In either case, the type of each parameter is adjusted as
6947 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
6949 8 If a function that accepts a variable number of arguments is defined without a parameter
6950 type list that ends with the ellipsis notation, the behavior is undefined.
6951 9 Each parameter has automatic storage duration; its identifier is an lvalue.<sup><a href="#note164"><b>164)</b></a></sup> The layout
6952 of the storage for parameters is unspecified.
6953 10 On entry to the function, the size expressions of each variably modified parameter are
6954 evaluated and the value of each argument expression is converted to the type of the
6955 corresponding parameter as if by assignment. (Array expressions and function
6956 designators as arguments were converted to pointers before the call.)
6957 11 After all parameters have been assigned, the compound statement that constitutes the
6958 body of the function definition is executed.
6959 12 If the } that terminates a function is reached, and the value of the function call is used by
6960 the caller, the behavior is undefined.
6961 13 EXAMPLE 1 In the following:
6962 extern int max(int a, int b)
6964 return a > b ? a : b;
6966 extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
6967 function declarator; and
6968 { return a > b ? a : b; }
6969 is the function body. The following similar definition uses the identifier-list form for the parameter
6975 <sup><a name="note163" href="#note163"><b>163)</b></a></sup> See ''future language directions'' (<a href="#6.11.7">6.11.7</a>).
6976 <sup><a name="note164" href="#note164"><b>164)</b></a></sup> A parameter identifier cannot be redeclared in the function body except in an enclosed block.
6978 [<a name="p156" href="#p156">page 156</a>] (<a href="#Contents">Contents</a>)
6980 extern int max(a, b)
6983 return a > b ? a : b;
6985 Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
6986 that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
6987 to the function, whereas the second form does not.
6989 14 EXAMPLE 2 To pass one function to another, one might say
6993 Then the definition of g might read
6994 void g(int (*funcp)(void))
6997 (*funcp)(); /* or funcp(); ... */
7000 void g(int func(void))
7003 func(); /* or (*func)(); ... */
7006 <a name="6.9.2" href="#6.9.2"><b> 6.9.2 External object definitions</b></a>
7008 1 If the declaration of an identifier for an object has file scope and an initializer, the
7009 declaration is an external definition for the identifier.
7010 2 A declaration of an identifier for an object that has file scope without an initializer, and
7011 without a storage-class specifier or with the storage-class specifier static, constitutes a
7012 tentative definition. If a translation unit contains one or more tentative definitions for an
7013 identifier, and the translation unit contains no external definition for that identifier, then
7014 the behavior is exactly as if the translation unit contains a file scope declaration of that
7015 identifier, with the composite type as of the end of the translation unit, with an initializer
7017 3 If the declaration of an identifier for an object is a tentative definition and has internal
7018 linkage, the declared type shall not be an incomplete type.
7023 [<a name="p157" href="#p157">page 157</a>] (<a href="#Contents">Contents</a>)
7026 int i1 = 1; // definition, external linkage
7027 static int i2 = 2; // definition, internal linkage
7028 extern int i3 = 3; // definition, external linkage
7029 int i4; // tentative definition, external linkage
7030 static int i5; // tentative definition, internal linkage
7031 int i1; // valid tentative definition, refers to previous
7032 int i2; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
7033 int i3; // valid tentative definition, refers to previous
7034 int i4; // valid tentative definition, refers to previous
7035 int i5; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
7036 extern int i1; // refers to previous, whose linkage is external
7037 extern int i2; // refers to previous, whose linkage is internal
7038 extern int i3; // refers to previous, whose linkage is external
7039 extern int i4; // refers to previous, whose linkage is external
7040 extern int i5; // refers to previous, whose linkage is internal
7042 5 EXAMPLE 2 If at the end of the translation unit containing
7044 the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to
7045 zero on program startup.
7050 [<a name="p158" href="#p158">page 158</a>] (<a href="#Contents">Contents</a>)
7052 <a name="6.10" href="#6.10"><b> 6.10 Preprocessing directives</b></a>
7054 1 preprocessing-file:
7065 if-group elif-groupsopt else-groupopt endif-line
7067 # if constant-expression new-line groupopt
7068 # ifdef identifier new-line groupopt
7069 # ifndef identifier new-line groupopt
7072 elif-groups elif-group
7074 # elif constant-expression new-line groupopt
7076 # else new-line groupopt
7083 [<a name="p159" href="#p159">page 159</a>] (<a href="#Contents">Contents</a>)
7086 # include pp-tokens new-line
7087 # define identifier replacement-list new-line
7088 # define identifier lparen identifier-listopt )
7089 replacement-list new-line
7090 # define identifier lparen ... ) replacement-list new-line
7091 # define identifier lparen identifier-list , ... )
7092 replacement-list new-line
7093 # undef identifier new-line
7094 # line pp-tokens new-line
7095 # error pp-tokensopt new-line
7096 # pragma pp-tokensopt new-line
7099 pp-tokensopt new-line
7103 a ( character not immediately preceded by white-space
7108 pp-tokens preprocessing-token
7110 the new-line character
7112 2 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the
7113 following constraints: The first token in the sequence is a # preprocessing token that (at
7114 the start of translation phase 4) is either the first character in the source file (optionally
7115 after white space containing no new-line characters) or that follows white space
7116 containing at least one new-line character. The last token in the sequence is the first new-
7117 line character that follows the first token in the sequence.<sup><a href="#note165"><b>165)</b></a></sup> A new-line character ends
7118 the preprocessing directive even if it occurs within what would otherwise be an
7120 <sup><a name="note165" href="#note165"><b>165)</b></a></sup> Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic
7121 significance, as all white space is equivalent except in certain situations during preprocessing (see the
7122 # character string literal creation operator in <a href="#6.10.3.2">6.10.3.2</a>, for example).
7124 [<a name="p160" href="#p160">page 160</a>] (<a href="#Contents">Contents</a>)
7126 invocation of a function-like macro.
7127 3 A text line shall not begin with a # preprocessing token. A non-directive shall not begin
7128 with any of the directive names appearing in the syntax.
7129 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
7130 sequence of preprocessing tokens to occur between the directive name and the following
7133 5 The only white-space characters that shall appear between preprocessing tokens within a
7134 preprocessing directive (from just after the introducing # preprocessing token through
7135 just before the terminating new-line character) are space and horizontal-tab (including
7136 spaces that have replaced comments or possibly other white-space characters in
7137 translation phase 3).
7139 6 The implementation can process and skip sections of source files conditionally, include
7140 other source files, and replace macros. These capabilities are called preprocessing,
7141 because conceptually they occur before translation of the resulting translation unit.
7142 7 The preprocessing tokens within a preprocessing directive are not subject to macro
7143 expansion unless otherwise stated.
7146 EMPTY # include <file.h>
7147 the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
7148 begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
7151 <a name="6.10.1" href="#6.10.1"><b> 6.10.1 Conditional inclusion</b></a>
7153 1 The expression that controls conditional inclusion shall be an integer constant expression
7154 except that: identifiers (including those lexically identical to keywords) are interpreted as *
7155 described below;<sup><a href="#note166"><b>166)</b></a></sup> and it may contain unary operator expressions of the form
7158 defined ( identifier )
7159 which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is
7162 <sup><a name="note166" href="#note166"><b>166)</b></a></sup> Because the controlling constant expression is evaluated during translation phase 4, all identifiers
7163 either are or are not macro names -- there simply are no keywords, enumeration constants, etc.
7165 [<a name="p161" href="#p161">page 161</a>] (<a href="#Contents">Contents</a>)
7167 predefined or if it has been the subject of a #define preprocessing directive without an
7168 intervening #undef directive with the same subject identifier), 0 if it is not.
7169 2 Each preprocessing token that remains (in the list of preprocessing tokens that will
7170 become the controlling expression) after all macro replacements have occurred shall be in
7171 the lexical form of a token (<a href="#6.4">6.4</a>).
7173 3 Preprocessing directives of the forms
7174 # if constant-expression new-line groupopt
7175 # elif constant-expression new-line groupopt
7176 check whether the controlling constant expression evaluates to nonzero.
7177 4 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
7178 the controlling constant expression are replaced (except for those macro names modified
7179 by the defined unary operator), just as in normal text. If the token defined is
7180 generated as a result of this replacement process or use of the defined unary operator
7181 does not match one of the two specified forms prior to macro replacement, the behavior is
7182 undefined. After all replacements due to macro expansion and the defined unary
7183 operator have been performed, all remaining identifiers (including those lexically
7184 identical to keywords) are replaced with the pp-number 0, and then each preprocessing
7185 token is converted into a token. The resulting tokens compose the controlling constant
7186 expression which is evaluated according to the rules of <a href="#6.6">6.6</a>. For the purposes of this
7187 token conversion and evaluation, all signed integer types and all unsigned integer types
7188 act as if they have the same representation as, respectively, the types intmax_t and
7189 uintmax_t defined in the header <a href="#7.20"><stdint.h></a>.<sup><a href="#note167"><b>167)</b></a></sup> This includes interpreting
7190 character constants, which may involve converting escape sequences into execution
7191 character set members. Whether the numeric value for these character constants matches
7192 the value obtained when an identical character constant occurs in an expression (other
7193 than within a #if or #elif directive) is implementation-defined.<sup><a href="#note168"><b>168)</b></a></sup> Also, whether a
7194 single-character character constant may have a negative value is implementation-defined.
7199 <sup><a name="note167" href="#note167"><b>167)</b></a></sup> Thus, on an implementation where INT_MAX is 0x7FFF and UINT_MAX is 0xFFFF, the constant
7200 0x8000 is signed and positive within a #if expression even though it would be unsigned in
7201 translation phase 7.
7202 <sup><a name="note168" href="#note168"><b>168)</b></a></sup> Thus, the constant expression in the following #if directive and if statement is not guaranteed to
7203 evaluate to the same value in these two contexts.
7205 if ('z' - 'a' == 25)
7208 [<a name="p162" href="#p162">page 162</a>] (<a href="#Contents">Contents</a>)
7210 5 Preprocessing directives of the forms
7211 # ifdef identifier new-line groupopt
7212 # ifndef identifier new-line groupopt
7213 check whether the identifier is or is not currently defined as a macro name. Their
7214 conditions are equivalent to #if defined identifier and #if !defined identifier
7216 6 Each directive's condition is checked in order. If it evaluates to false (zero), the group
7217 that it controls is skipped: directives are processed only through the name that determines
7218 the directive in order to keep track of the level of nested conditionals; the rest of the
7219 directives' preprocessing tokens are ignored, as are the other preprocessing tokens in the
7220 group. Only the first group whose control condition evaluates to true (nonzero) is
7221 processed. If none of the conditions evaluates to true, and there is a #else directive, the
7222 group controlled by the #else is processed; lacking a #else directive, all the groups
7223 until the #endif are skipped.<sup><a href="#note169"><b>169)</b></a></sup>
7224 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
7225 integer types (<a href="#7.20.1.5">7.20.1.5</a>).
7226 <a name="6.10.2" href="#6.10.2"><b> 6.10.2 Source file inclusion</b></a>
7228 1 A #include directive shall identify a header or source file that can be processed by the
7231 2 A preprocessing directive of the form
7232 # include <h-char-sequence> new-line
7233 searches a sequence of implementation-defined places for a header identified uniquely by
7234 the specified sequence between the < and > delimiters, and causes the replacement of that
7235 directive by the entire contents of the header. How the places are specified or the header
7236 identified is implementation-defined.
7237 3 A preprocessing directive of the form
7238 # include "q-char-sequence" new-line
7239 causes the replacement of that directive by the entire contents of the source file identified
7240 by the specified sequence between the " delimiters. The named source file is searched
7243 <sup><a name="note169" href="#note169"><b>169)</b></a></sup> As indicated by the syntax, a preprocessing token shall not follow a #else or #endif directive
7244 before the terminating new-line character. However, comments may appear anywhere in a source file,
7245 including within a preprocessing directive.
7247 [<a name="p163" href="#p163">page 163</a>] (<a href="#Contents">Contents</a>)
7249 for in an implementation-defined manner. If this search is not supported, or if the search
7250 fails, the directive is reprocessed as if it read
7251 # include <h-char-sequence> new-line
7252 with the identical contained sequence (including > characters, if any) from the original
7254 4 A preprocessing directive of the form
7255 # include pp-tokens new-line
7256 (that does not match one of the two previous forms) is permitted. The preprocessing
7257 tokens after include in the directive are processed just as in normal text. (Each
7258 identifier currently defined as a macro name is replaced by its replacement list of
7259 preprocessing tokens.) The directive resulting after all replacements shall match one of
7260 the two previous forms.<sup><a href="#note170"><b>170)</b></a></sup> The method by which a sequence of preprocessing tokens
7261 between a < and a > preprocessing token pair or a pair of " characters is combined into a
7262 single header name preprocessing token is implementation-defined.
7263 5 The implementation shall provide unique mappings for sequences consisting of one or
7264 more nondigits or digits (<a href="#6.4.2.1">6.4.2.1</a>) followed by a period (.) and a single nondigit. The
7265 first character shall not be a digit. The implementation may ignore distinctions of
7266 alphabetical case and restrict the mapping to eight significant characters before the
7268 6 A #include preprocessing directive may appear in a source file that has been read
7269 because of a #include directive in another file, up to an implementation-defined
7270 nesting limit (see <a href="#5.2.4.1">5.2.4.1</a>).
7271 7 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
7272 #include <a href="#7.21"><stdio.h></a>
7278 <sup><a name="note170" href="#note170"><b>170)</b></a></sup> Note that adjacent string literals are not concatenated into a single string literal (see the translation
7279 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.
7281 [<a name="p164" href="#p164">page 164</a>] (<a href="#Contents">Contents</a>)
7283 8 EXAMPLE 2 This illustrates macro-replaced #include directives:
7285 #define INCFILE "vers1.h"
7287 #define INCFILE "vers2.h" // and so on
7289 #define INCFILE "versN.h"
7293 Forward references: macro replacement (<a href="#6.10.3">6.10.3</a>).
7294 <a name="6.10.3" href="#6.10.3"><b> 6.10.3 Macro replacement</b></a>
7296 1 Two replacement lists are identical if and only if the preprocessing tokens in both have
7297 the same number, ordering, spelling, and white-space separation, where all white-space
7298 separations are considered identical.
7299 2 An identifier currently defined as an object-like macro shall not be redefined by another
7300 #define preprocessing directive unless the second definition is an object-like macro
7301 definition and the two replacement lists are identical. Likewise, an identifier currently
7302 defined as a function-like macro shall not be redefined by another #define
7303 preprocessing directive unless the second definition is a function-like macro definition
7304 that has the same number and spelling of parameters, and the two replacement lists are
7306 3 There shall be white-space between the identifier and the replacement list in the definition
7307 of an object-like macro.
7308 4 If the identifier-list in the macro definition does not end with an ellipsis, the number of
7309 arguments (including those arguments consisting of no preprocessing tokens) in an
7310 invocation of a function-like macro shall equal the number of parameters in the macro
7311 definition. Otherwise, there shall be more arguments in the invocation than there are
7312 parameters in the macro definition (excluding the ...). There shall exist a )
7313 preprocessing token that terminates the invocation.
7314 5 The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like
7315 macro that uses the ellipsis notation in the parameters.
7316 6 A parameter identifier in a function-like macro shall be uniquely declared within its
7319 7 The identifier immediately following the define is called the macro name. There is one
7320 name space for macro names. Any white-space characters preceding or following the
7321 replacement list of preprocessing tokens are not considered part of the replacement list
7323 [<a name="p165" href="#p165">page 165</a>] (<a href="#Contents">Contents</a>)
7325 for either form of macro.
7326 8 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
7327 a preprocessing directive could begin, the identifier is not subject to macro replacement.
7328 9 A preprocessing directive of the form
7329 # define identifier replacement-list new-line
7330 defines an object-like macro that causes each subsequent instance of the macro name<sup><a href="#note171"><b>171)</b></a></sup>
7331 to be replaced by the replacement list of preprocessing tokens that constitute the
7332 remainder of the directive. The replacement list is then rescanned for more macro names
7334 10 A preprocessing directive of the form
7335 # define identifier lparen identifier-listopt ) replacement-list new-line
7336 # define identifier lparen ... ) replacement-list new-line
7337 # define identifier lparen identifier-list , ... ) replacement-list new-line
7338 defines a function-like macro with parameters, whose use is similar syntactically to a
7339 function call. The parameters are specified by the optional list of identifiers, whose scope
7340 extends from their declaration in the identifier list until the new-line character that
7341 terminates the #define preprocessing directive. Each subsequent instance of the
7342 function-like macro name followed by a ( as the next preprocessing token introduces the
7343 sequence of preprocessing tokens that is replaced by the replacement list in the definition
7344 (an invocation of the macro). The replaced sequence of preprocessing tokens is
7345 terminated by the matching ) preprocessing token, skipping intervening matched pairs of
7346 left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
7347 tokens making up an invocation of a function-like macro, new-line is considered a normal
7348 white-space character.
7349 11 The sequence of preprocessing tokens bounded by the outside-most matching parentheses
7350 forms the list of arguments for the function-like macro. The individual arguments within
7351 the list are separated by comma preprocessing tokens, but comma preprocessing tokens
7352 between matching inner parentheses do not separate arguments. If there are sequences of
7353 preprocessing tokens within the list of arguments that would otherwise act as
7354 preprocessing directives,<sup><a href="#note172"><b>172)</b></a></sup> the behavior is undefined.
7355 12 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
7356 including any separating comma preprocessing tokens, are merged to form a single item:
7359 <sup><a name="note171" href="#note171"><b>171)</b></a></sup> Since, by macro-replacement time, all character constants and string literals are preprocessing tokens,
7360 not sequences possibly containing identifier-like subsequences (see <a href="#5.1.1.2">5.1.1.2</a>, translation phases), they
7361 are never scanned for macro names or parameters.
7362 <sup><a name="note172" href="#note172"><b>172)</b></a></sup> Despite the name, a non-directive is a preprocessing directive.
7364 [<a name="p166" href="#p166">page 166</a>] (<a href="#Contents">Contents</a>)
7366 the variable arguments. The number of arguments so combined is such that, following
7367 merger, the number of arguments is one more than the number of parameters in the macro
7368 definition (excluding the ...).
7369 <a name="6.10.3.1" href="#6.10.3.1"><b> 6.10.3.1 Argument substitution</b></a>
7370 1 After the arguments for the invocation of a function-like macro have been identified,
7371 argument substitution takes place. A parameter in the replacement list, unless preceded
7372 by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
7373 replaced by the corresponding argument after all macros contained therein have been
7374 expanded. Before being substituted, each argument's preprocessing tokens are
7375 completely macro replaced as if they formed the rest of the preprocessing file; no other
7376 preprocessing tokens are available.
7377 2 An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
7378 were a parameter, and the variable arguments shall form the preprocessing tokens used to
7380 <a name="6.10.3.2" href="#6.10.3.2"><b> 6.10.3.2 The # operator</b></a>
7382 1 Each # preprocessing token in the replacement list for a function-like macro shall be
7383 followed by a parameter as the next preprocessing token in the replacement list.
7385 2 If, in the replacement list, a parameter is immediately preceded by a # preprocessing
7386 token, both are replaced by a single character string literal preprocessing token that
7387 contains the spelling of the preprocessing token sequence for the corresponding
7388 argument. Each occurrence of white space between the argument's preprocessing tokens
7389 becomes a single space character in the character string literal. White space before the
7390 first preprocessing token and after the last preprocessing token composing the argument
7391 is deleted. Otherwise, the original spelling of each preprocessing token in the argument
7392 is retained in the character string literal, except for special handling for producing the
7393 spelling of string literals and character constants: a \ character is inserted before each "
7394 and \ character of a character constant or string literal (including the delimiting "
7395 characters), except that it is implementation-defined whether a \ character is inserted
7396 before the \ character beginning a universal character name. If the replacement that
7397 results is not a valid character string literal, the behavior is undefined. The character
7398 string literal corresponding to an empty argument is "". The order of evaluation of # and
7399 ## operators is unspecified.
7404 [<a name="p167" href="#p167">page 167</a>] (<a href="#Contents">Contents</a>)
7406 <a name="6.10.3.3" href="#6.10.3.3"><b> 6.10.3.3 The ## operator</b></a>
7408 1 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
7409 list for either form of macro definition.
7411 2 If, in the replacement list of a function-like macro, a parameter is immediately preceded
7412 or followed by a ## preprocessing token, the parameter is replaced by the corresponding
7413 argument's preprocessing token sequence; however, if an argument consists of no
7414 preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
7415 instead.<sup><a href="#note173"><b>173)</b></a></sup>
7416 3 For both object-like and function-like macro invocations, before the replacement list is
7417 reexamined for more macro names to replace, each instance of a ## preprocessing token
7418 in the replacement list (not from an argument) is deleted and the preceding preprocessing
7419 token is concatenated with the following preprocessing token. Placemarker
7420 preprocessing tokens are handled specially: concatenation of two placemarkers results in
7421 a single placemarker preprocessing token, and concatenation of a placemarker with a
7422 non-placemarker preprocessing token results in the non-placemarker preprocessing token.
7423 If the result is not a valid preprocessing token, the behavior is undefined. The resulting
7424 token is available for further macro replacement. The order of evaluation of ## operators
7426 4 EXAMPLE In the following fragment:
7427 #define hash_hash # ## #
7428 #define mkstr(a) # a
7429 #define in_between(a) mkstr(a)
7430 #define join(c, d) in_between(c hash_hash d)
7431 char p[] = join(x, y); // equivalent to
7432 // char p[] = "x ## y";
7433 The expansion produces, at various stages:
7435 in_between(x hash_hash y)
7439 In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
7440 this new token is not the ## operator.
7443 <sup><a name="note173" href="#note173"><b>173)</b></a></sup> Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
7444 exist only within translation phase 4.
7446 [<a name="p168" href="#p168">page 168</a>] (<a href="#Contents">Contents</a>)
7448 <a name="6.10.3.4" href="#6.10.3.4"><b> 6.10.3.4 Rescanning and further replacement</b></a>
7449 1 After all parameters in the replacement list have been substituted and # and ##
7450 processing has taken place, all placemarker preprocessing tokens are removed. The
7451 resulting preprocessing token sequence is then rescanned, along with all subsequent
7452 preprocessing tokens of the source file, for more macro names to replace.
7453 2 If the name of the macro being replaced is found during this scan of the replacement list
7454 (not including the rest of the source file's preprocessing tokens), it is not replaced.
7455 Furthermore, if any nested replacements encounter the name of the macro being replaced,
7456 it is not replaced. These nonreplaced macro name preprocessing tokens are no longer
7457 available for further replacement even if they are later (re)examined in contexts in which
7458 that macro name preprocessing token would otherwise have been replaced.
7459 3 The resulting completely macro-replaced preprocessing token sequence is not processed
7460 as a preprocessing directive even if it resembles one, but all pragma unary operator
7461 expressions within it are then processed as specified in <a href="#6.10.9">6.10.9</a> below.
7462 <a name="6.10.3.5" href="#6.10.3.5"><b> 6.10.3.5 Scope of macro definitions</b></a>
7463 1 A macro definition lasts (independent of block structure) until a corresponding #undef
7464 directive is encountered or (if none is encountered) until the end of the preprocessing
7465 translation unit. Macro definitions have no significance after translation phase 4.
7466 2 A preprocessing directive of the form
7467 # undef identifier new-line
7468 causes the specified identifier no longer to be defined as a macro name. It is ignored if
7469 the specified identifier is not currently defined as a macro name.
7470 3 EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
7474 4 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments.
7475 It has the advantages of working for any compatible types of the arguments and of generating in-line code
7476 without the overhead of function calling. It has the disadvantages of evaluating one or the other of its
7477 arguments a second time (including side effects) and generating more code than a function if invoked
7478 several times. It also cannot have its address taken, as it has none.
7479 #define max(a, b) ((a) > (b) ? (a) : (b))
7480 The parentheses ensure that the arguments and the resulting expression are bound properly.
7485 [<a name="p169" href="#p169">page 169</a>] (<a href="#Contents">Contents</a>)
7487 5 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
7489 #define f(a) f(x * (a))
7500 #define r(x,y) x ## y
7502 f(y+1) + f(f(z)) % t(t(g)(0) + t)(1);
7503 g(x+(3,4)-w) | h 5) & m
7505 p() i[q()] = { q(1), r(2,3), r(4,), r(,5), r(,) };
7506 char c[2][6] = { str(hello), str() };
7508 f(2 * (y+1)) + f(2 * (f(2 * (z[0])))) % f(2 * (0)) + t(1);
7509 f(2 * (2+(3,4)-0,1)) | f(2 * (~ 5)) & f(2 * (0,1))^m(0,1);
7510 int i[] = { 1, 23, 4, 5, };
7511 char c[2][6] = { "hello", "" };
7513 6 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the
7516 #define xstr(s) str(s)
7517 #define debug(s, t) printf("x" # s "= %d, x" # t "= %s", \
7519 #define INCFILE(n) vers ## n
7520 #define glue(a, b) a ## b
7521 #define xglue(a, b) glue(a, b)
7522 #define HIGHLOW "hello"
7523 #define LOW LOW ", world"
7525 fputs(str(strncmp("abc\0d", "abc", '\4') // this goes away
7526 == 0) str(: @\n), s);
7527 #include xstr(INCFILE(2).h)
7535 [<a name="p170" href="#p170">page 170</a>] (<a href="#Contents">Contents</a>)
7537 printf("x" "1" "= %d, x" "2" "= %s", x1, x2);
7539 "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0" ": @\n",
7541 #include "vers2.h" (after macro replacement, before file access)
7544 or, after concatenation of the character string literals,
7545 printf("x1= %d, x2= %s", x1, x2);
7547 "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0: @\n",
7549 #include "vers2.h" (after macro replacement, before file access)
7552 Space around the # and ## tokens in the macro definition is optional.
7554 7 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
7555 #define t(x,y,z) x ## y ## z
7556 int j[] = { t(1,2,3), t(,4,5), t(6,,7), t(8,9,),
7557 t(10,,), t(,11,), t(,,12), t(,,) };
7559 int j[] = { 123, 45, 67, 89,
7562 8 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
7563 #define OBJ_LIKE (1-1)
7564 #define OBJ_LIKE /* white space */ (1-1) /* other */
7565 #define FUNC_LIKE(a) ( a )
7566 #define FUNC_LIKE( a )( /* note the white space */ \
7567 a /* other stuff on this line
7569 But the following redefinitions are invalid:
7570 #define OBJ_LIKE (0) // different token sequence
7571 #define OBJ_LIKE (1 - 1) // different white space
7572 #define FUNC_LIKE(b) ( a ) // different parameter usage
7573 #define FUNC_LIKE(b) ( b ) // different parameter spelling
7575 9 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
7576 #define debug(...) fprintf(stderr, __VA_ARGS__)
7577 #define showlist(...) puts(#__VA_ARGS__)
7578 #define report(test, ...) ((test)?puts(#test):\
7579 printf(__VA_ARGS__))
7581 debug("X = %d\n", x);
7582 showlist(The first, second, and third items.);
7583 report(x>y, "x is %d but y is %d", x, y);
7586 [<a name="p171" href="#p171">page 171</a>] (<a href="#Contents">Contents</a>)
7589 fprintf(stderr, "Flag" );
7590 fprintf(stderr, "X = %d\n", x );
7591 puts( "The first, second, and third items." );
7592 ((x>y)?puts("x>y"):
7593 printf("x is %d but y is %d", x, y));
7595 <a name="6.10.4" href="#6.10.4"><b> 6.10.4 Line control</b></a>
7597 1 The string literal of a #line directive, if present, shall be a character string literal.
7599 2 The line number of the current source line is one greater than the number of new-line
7600 characters read or introduced in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>) while processing the source
7601 file to the current token.
7602 3 A preprocessing directive of the form
7603 # line digit-sequence new-line
7604 causes the implementation to behave as if the following sequence of source lines begins
7605 with a source line that has a line number as specified by the digit sequence (interpreted as
7606 a decimal integer). The digit sequence shall not specify zero, nor a number greater than
7608 4 A preprocessing directive of the form
7609 # line digit-sequence "s-char-sequenceopt" new-line
7610 sets the presumed line number similarly and changes the presumed name of the source
7611 file to be the contents of the character string literal.
7612 5 A preprocessing directive of the form
7613 # line pp-tokens new-line
7614 (that does not match one of the two previous forms) is permitted. The preprocessing
7615 tokens after line on the directive are processed just as in normal text (each identifier
7616 currently defined as a macro name is replaced by its replacement list of preprocessing
7617 tokens). The directive resulting after all replacements shall match one of the two
7618 previous forms and is then processed as appropriate.
7623 [<a name="p172" href="#p172">page 172</a>] (<a href="#Contents">Contents</a>)
7625 <a name="6.10.5" href="#6.10.5"><b> 6.10.5 Error directive</b></a>
7627 1 A preprocessing directive of the form
7628 # error pp-tokensopt new-line
7629 causes the implementation to produce a diagnostic message that includes the specified
7630 sequence of preprocessing tokens.
7631 <a name="6.10.6" href="#6.10.6"><b> 6.10.6 Pragma directive</b></a>
7633 1 A preprocessing directive of the form
7634 # pragma pp-tokensopt new-line
7635 where the preprocessing token STDC does not immediately follow pragma in the
7636 directive (prior to any macro replacement)<sup><a href="#note174"><b>174)</b></a></sup> causes the implementation to behave in an
7637 implementation-defined manner. The behavior might cause translation to fail or cause the
7638 translator or the resulting program to behave in a non-conforming manner. Any such
7639 pragma that is not recognized by the implementation is ignored.
7640 2 If the preprocessing token STDC does immediately follow pragma in the directive (prior
7641 to any macro replacement), then no macro replacement is performed on the directive, and
7642 the directive shall have one of the following forms<sup><a href="#note175"><b>175)</b></a></sup> whose meanings are described
7644 #pragma STDC FP_CONTRACT on-off-switch
7645 #pragma STDC FENV_ACCESS on-off-switch
7646 #pragma STDC CX_LIMITED_RANGE on-off-switch
7647 on-off-switch: one of
7649 Forward references: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), the FENV_ACCESS pragma
7650 (<a href="#7.6.1">7.6.1</a>), the CX_LIMITED_RANGE pragma (<a href="#7.3.4">7.3.4</a>).
7655 <sup><a name="note174" href="#note174"><b>174)</b></a></sup> An implementation is not required to perform macro replacement in pragmas, but it is permitted
7656 except for in standard pragmas (where STDC immediately follows pragma). If the result of macro
7657 replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still
7658 implementation-defined; an implementation is permitted to behave as if it were the standard pragma,
7659 but is not required to.
7660 <sup><a name="note175" href="#note175"><b>175)</b></a></sup> See ''future language directions'' (<a href="#6.11.8">6.11.8</a>).
7662 [<a name="p173" href="#p173">page 173</a>] (<a href="#Contents">Contents</a>)
7664 <a name="6.10.7" href="#6.10.7"><b> 6.10.7 Null directive</b></a>
7666 1 A preprocessing directive of the form
7669 <a name="6.10.8" href="#6.10.8"><b> 6.10.8 Predefined macro names</b></a>
7670 1 The values of the predefined macros listed in the following subclauses<sup><a href="#note176"><b>176)</b></a></sup> (except for
7671 __FILE__ and __LINE__) remain constant throughout the translation unit.
7672 2 None of these macro names, nor the identifier defined, shall be the subject of a
7673 #define or a #undef preprocessing directive. Any other predefined macro names
7674 shall begin with a leading underscore followed by an uppercase letter or a second
7676 3 The implementation shall not predefine the macro __cplusplus, nor shall it define it
7677 in any standard header.
7678 Forward references: standard headers (<a href="#7.1.2">7.1.2</a>).
7679 <a name="6.10.8.1" href="#6.10.8.1"><b> 6.10.8.1 Mandatory macros</b></a>
7680 1 The following macro names shall be defined by the implementation:
7681 __DATE__ The date of translation of the preprocessing translation unit: a character
7682 string literal of the form "Mmm dd yyyy", where the names of the
7683 months are the same as those generated by the asctime function, and the
7684 first character of dd is a space character if the value is less than 10. If the
7685 date of translation is not available, an implementation-defined valid date
7687 __FILE__ The presumed name of the current source file (a character string literal).<sup><a href="#note177"><b>177)</b></a></sup>
7688 __LINE__ The presumed line number (within the current source file) of the current
7689 source line (an integer constant).177)
7690 __STDC__ The integer constant 1, intended to indicate a conforming implementation.
7691 __STDC_HOSTED__ The integer constant 1 if the implementation is a hosted
7692 implementation or the integer constant 0 if it is not.
7697 <sup><a name="note176" href="#note176"><b>176)</b></a></sup> See ''future language directions'' (<a href="#6.11.9">6.11.9</a>).
7698 <sup><a name="note177" href="#note177"><b>177)</b></a></sup> The presumed source file name and line number can be changed by the #line directive.
7700 [<a name="p174" href="#p174">page 174</a>] (<a href="#Contents">Contents</a>)
7702 __STDC_VERSION__ The integer constant 201ymmL.<sup><a href="#note178"><b>178)</b></a></sup>
7703 __TIME__ The time of translation of the preprocessing translation unit: a character
7704 string literal of the form "hh:mm:ss" as in the time generated by the
7705 asctime function. If the time of translation is not available, an
7706 implementation-defined valid time shall be supplied.
7707 Forward references: the asctime function (<a href="#7.26.3.1">7.26.3.1</a>).
7708 <a name="6.10.8.2" href="#6.10.8.2"><b> 6.10.8.2 Environment macros</b></a>
7709 1 The following macro names are conditionally defined by the implementation:
7710 __STDC_ISO_10646__ An integer constant of the form yyyymmL (for example,
7711 199712L). If this symbol is defined, then every character in the Unicode
7712 required set, when stored in an object of type wchar_t, has the same
7713 value as the short identifier of that character. The Unicode required set
7714 consists of all the characters that are defined by ISO/IEC 10646, along with
7715 all amendments and technical corrigenda, as of the specified year and
7716 month. If some other encoding is used, the macro shall not be defined and
7717 the actual encoding used is implementation-defined.
7718 __STDC_MB_MIGHT_NEQ_WC__ The integer constant 1, intended to indicate that, in
7719 the encoding for wchar_t, a member of the basic character set need not
7720 have a code value equal to its value when used as the lone character in an
7721 integer character constant.
7722 __STDC_UTF_16__ The integer constant 1, intended to indicate that values of type
7723 char16_t are UTF-16 encoded. If some other encoding is used, the
7724 macro shall not be defined and the actual encoding used is implementation-
7726 __STDC_UTF_32__ The integer constant 1, intended to indicate that values of type
7727 char32_t are UTF-32 encoded. If some other encoding is used, the
7728 macro shall not be defined and the actual encoding used is implementation-
7730 Forward references: common definitions (<a href="#7.19">7.19</a>), unicode utilities (<a href="#7.27">7.27</a>).
7735 <sup><a name="note178" href="#note178"><b>178)</b></a></sup> This macro was not specified in ISO/IEC 9899:1990 and was specified as 199409L in
7736 ISO/IEC 9899/AMD1:1995 and as 199901L in ISO/IEC 9899:1999. The intention is that this will
7737 remain an integer constant of type long int that is increased with each revision of this International
7740 [<a name="p175" href="#p175">page 175</a>] (<a href="#Contents">Contents</a>)
7742 <a name="6.10.8.3" href="#6.10.8.3"><b> 6.10.8.3 Conditional feature macros</b></a>
7743 1 The following macro names are conditionally defined by the implementation:
7744 __STDC_ANALYZABLE__ The integer constant 1, intended to indicate conformance to
7745 the specifications in <a href="#L">annex L</a> (Analyzability).
7746 __STDC_IEC_559__ The integer constant 1, intended to indicate conformance to the
7747 specifications in <a href="#F">annex F</a> (IEC 60559 floating-point arithmetic).
7748 __STDC_IEC_559_COMPLEX__ The integer constant 1, intended to indicate
7749 adherence to the specifications in <a href="#G">annex G</a> (IEC 60559 compatible complex
7751 __STDC_LIB_EXT1__ The integer constant 201ymmL, intended to indicate support
7752 for the extensions defined in <a href="#K">annex K</a> (Bounds-checking interfaces).<sup><a href="#note179"><b>179)</b></a></sup>
7753 __STDC_NO_COMPLEX__ The integer constant 1, intended to indicate that the
7754 implementation does not support complex types or the <a href="#7.3"><complex.h></a>
7756 __STDC_NO_THREADS__ The integer constant 1, intended to indicate that the
7757 implementation does not support atomic types (including the _Atomic
7758 type qualifier and the <a href="#7.17"><stdatomic.h></a> header) or the <a href="#7.25"><threads.h></a>
7760 __STDC_NO_VLA__ The integer constant 1, intended to indicate that the
7761 implementation does not support variable length arrays or variably
7763 2 An implementation that defines __STDC_NO_COMPLEX__ shall not define
7764 __STDC_IEC_559_COMPLEX__.
7765 <a name="6.10.9" href="#6.10.9"><b> 6.10.9 Pragma operator</b></a>
7767 1 A unary operator expression of the form:
7768 _Pragma ( string-literal )
7769 is processed as follows: The string literal is destringized by deleting the L prefix, if
7770 present, deleting the leading and trailing double-quotes, replacing each escape sequence
7771 \" by a double-quote, and replacing each escape sequence \\ by a single backslash. The
7772 resulting sequence of characters is processed through translation phase 3 to produce
7773 preprocessing tokens that are executed as if they were the pp-tokens in a pragma
7776 <sup><a name="note179" href="#note179"><b>179)</b></a></sup> The intention is that this will remain an integer constant of type long int that is increased with
7777 each revision of this International Standard.
7779 [<a name="p176" href="#p176">page 176</a>] (<a href="#Contents">Contents</a>)
7781 directive. The original four preprocessing tokens in the unary operator expression are
7783 2 EXAMPLE A directive of the form:
7784 #pragma listing on "..\listing.dir"
7785 can also be expressed as:
7786 _Pragma ( "listing on \"..\\listing.dir\"" )
7787 The latter form is processed in the same way whether it appears literally as shown, or results from macro
7789 #define LISTING(x) PRAGMA(listing on #x)
7790 #define PRAGMA(x) _Pragma(#x)
7791 LISTING ( ..\listing.dir )
7796 [<a name="p177" href="#p177">page 177</a>] (<a href="#Contents">Contents</a>)
7798 <a name="6.11" href="#6.11"><b> 6.11 Future language directions</b></a>
7799 <a name="6.11.1" href="#6.11.1"><b> 6.11.1 Floating types</b></a>
7800 1 Future standardization may include additional floating-point types, including those with
7801 greater range, precision, or both than long double.
7802 <a name="6.11.2" href="#6.11.2"><b> 6.11.2 Linkages of identifiers</b></a>
7803 1 Declaring an identifier with internal linkage at file scope without the static storage-
7804 class specifier is an obsolescent feature.
7805 <a name="6.11.3" href="#6.11.3"><b> 6.11.3 External names</b></a>
7806 1 Restriction of the significance of an external name to fewer than 255 characters
7807 (considering each universal character name or extended source character as a single
7808 character) is an obsolescent feature that is a concession to existing implementations.
7809 <a name="6.11.4" href="#6.11.4"><b> 6.11.4 Character escape sequences</b></a>
7810 1 Lowercase letters as escape sequences are reserved for future standardization. Other
7811 characters may be used in extensions.
7812 <a name="6.11.5" href="#6.11.5"><b> 6.11.5 Storage-class specifiers</b></a>
7813 1 The placement of a storage-class specifier other than at the beginning of the declaration
7814 specifiers in a declaration is an obsolescent feature.
7815 <a name="6.11.6" href="#6.11.6"><b> 6.11.6 Function declarators</b></a>
7816 1 The use of function declarators with empty parentheses (not prototype-format parameter
7817 type declarators) is an obsolescent feature.
7818 <a name="6.11.7" href="#6.11.7"><b> 6.11.7 Function definitions</b></a>
7819 1 The use of function definitions with separate parameter identifier and declaration lists
7820 (not prototype-format parameter type and identifier declarators) is an obsolescent feature.
7821 <a name="6.11.8" href="#6.11.8"><b> 6.11.8 Pragma directives</b></a>
7822 1 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
7823 <a name="6.11.9" href="#6.11.9"><b> 6.11.9 Predefined macro names</b></a>
7824 1 Macro names beginning with __STDC_ are reserved for future standardization.
7829 [<a name="p178" href="#p178">page 178</a>] (<a href="#Contents">Contents</a>)
7832 <a name="7" href="#7"><b> 7. Library</b></a>
7833 <a name="7.1" href="#7.1"><b> 7.1 Introduction</b></a>
7834 <a name="7.1.1" href="#7.1.1"><b> 7.1.1 Definitions of terms</b></a>
7835 1 A string is a contiguous sequence of characters terminated by and including the first null
7836 character. The term multibyte string is sometimes used instead to emphasize special
7837 processing given to multibyte characters contained in the string or to avoid confusion
7838 with a wide string. A pointer to a string is a pointer to its initial (lowest addressed)
7839 character. The length of a string is the number of bytes preceding the null character and
7840 the value of a string is the sequence of the values of the contained characters, in order.
7841 2 The decimal-point character is the character used by functions that convert floating-point
7842 numbers to or from character sequences to denote the beginning of the fractional part of
7843 such character sequences.<sup><a href="#note180"><b>180)</b></a></sup> It is represented in the text and examples by a period, but
7844 may be changed by the setlocale function.
7845 3 A null wide character is a wide character with code value zero.
7846 4 A wide string is a contiguous sequence of wide characters terminated by and including
7847 the first null wide character. A pointer to a wide string is a pointer to its initial (lowest
7848 addressed) wide character. The length of a wide string is the number of wide characters
7849 preceding the null wide character and the value of a wide string is the sequence of code
7850 values of the contained wide characters, in order.
7851 5 A shift sequence is a contiguous sequence of bytes within a multibyte string that
7852 (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
7853 corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
7854 character.<sup><a href="#note181"><b>181)</b></a></sup>
7855 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>).
7860 <sup><a name="note180" href="#note180"><b>180)</b></a></sup> The functions that make use of the decimal-point character are the numeric conversion functions
7861 (<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>).
7862 <sup><a name="note181" href="#note181"><b>181)</b></a></sup> For state-dependent encodings, the values for MB_CUR_MAX and MB_LEN_MAX shall thus be large
7863 enough to count all the bytes in any complete multibyte character plus at least one adjacent shift
7864 sequence of maximum length. Whether these counts provide for more than one shift sequence is the
7865 implementation's choice.
7867 [<a name="p179" href="#p179">page 179</a>] (<a href="#Contents">Contents</a>)
7869 <a name="7.1.2" href="#7.1.2"><b> 7.1.2 Standard headers</b></a>
7870 1 Each library function is declared, with a type that includes a prototype, in a header,<sup><a href="#note182"><b>182)</b></a></sup>
7871 whose contents are made available by the #include preprocessing directive. The
7872 header declares a set of related functions, plus any necessary types and additional macros
7873 needed to facilitate their use. Declarations of types described in this clause shall not
7874 include type qualifiers, unless explicitly stated otherwise.
7875 2 The standard headers are<sup><a href="#note183"><b>183)</b></a></sup>
7876 <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>
7877 <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>
7878 <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>
7879 <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>
7880 <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>
7881 <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>
7882 <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>
7883 3 If a file with the same name as one of the above < and > delimited sequences, not
7884 provided as part of the implementation, is placed in any of the standard places that are
7885 searched for included source files, the behavior is undefined.
7886 4 Standard headers may be included in any order; each may be included more than once in
7887 a given scope, with no effect different from being included only once, except that the
7888 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
7889 used, a header shall be included outside of any external declaration or definition, and it
7890 shall first be included before the first reference to any of the functions or objects it
7891 declares, or to any of the types or macros it defines. However, if an identifier is declared
7892 or defined in more than one header, the second and subsequent associated headers may be
7893 included after the initial reference to the identifier. The program shall not have any
7894 macros with names lexically identical to keywords currently defined prior to the
7896 5 Any definition of an object-like macro described in this clause shall expand to code that is
7897 fully protected by parentheses where necessary, so that it groups in an arbitrary
7898 expression as if it were a single identifier.
7899 6 Any declaration of a library function shall have external linkage.
7904 <sup><a name="note182" href="#note182"><b>182)</b></a></sup> A header is not necessarily a source file, nor are the < and > delimited sequences in header names
7905 necessarily valid source file names.
7906 <sup><a name="note183" href="#note183"><b>183)</b></a></sup> 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
7907 implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.
7909 [<a name="p180" href="#p180">page 180</a>] (<a href="#Contents">Contents</a>)
7911 7 A summary of the contents of the standard headers is given in <a href="#B">annex B</a>.
7912 Forward references: diagnostics (<a href="#7.2">7.2</a>).
7913 <a name="7.1.3" href="#7.1.3"><b> 7.1.3 Reserved identifiers</b></a>
7914 1 Each header declares or defines all identifiers listed in its associated subclause, and
7915 optionally declares or defines identifiers listed in its associated future library directions
7916 subclause and identifiers which are always reserved either for any use or for use as file
7918 -- All identifiers that begin with an underscore and either an uppercase letter or another
7919 underscore are always reserved for any use.
7920 -- All identifiers that begin with an underscore are always reserved for use as identifiers
7921 with file scope in both the ordinary and tag name spaces.
7922 -- Each macro name in any of the following subclauses (including the future library
7923 directions) is reserved for use as specified if any of its associated headers is included;
7924 unless explicitly stated otherwise (see <a href="#7.1.4">7.1.4</a>).
7925 -- All identifiers with external linkage in any of the following subclauses (including the
7926 future library directions) and errno are always reserved for use as identifiers with
7927 external linkage.<sup><a href="#note184"><b>184)</b></a></sup>
7928 -- Each identifier with file scope listed in any of the following subclauses (including the
7929 future library directions) is reserved for use as a macro name and as an identifier with
7930 file scope in the same name space if any of its associated headers is included.
7931 2 No other identifiers are reserved. If the program declares or defines an identifier in a
7932 context in which it is reserved (other than as allowed by <a href="#7.1.4">7.1.4</a>), or defines a reserved
7933 identifier as a macro name, the behavior is undefined.
7934 3 If the program removes (with #undef) any macro definition of an identifier in the first
7935 group listed above, the behavior is undefined.
7940 <sup><a name="note184" href="#note184"><b>184)</b></a></sup> The list of reserved identifiers with external linkage includes math_errhandling, setjmp,
7941 va_copy, and va_end.
7943 [<a name="p181" href="#p181">page 181</a>] (<a href="#Contents">Contents</a>)
7945 <a name="7.1.4" href="#7.1.4"><b> 7.1.4 Use of library functions</b></a>
7946 1 Each of the following statements applies unless explicitly stated otherwise in the detailed
7947 descriptions that follow: If an argument to a function has an invalid value (such as a value
7948 outside the domain of the function, or a pointer outside the address space of the program,
7949 or a null pointer, or a pointer to non-modifiable storage when the corresponding
7950 parameter is not const-qualified) or a type (after promotion) not expected by a function
7951 with variable number of arguments, the behavior is undefined. If a function argument is
7952 described as being an array, the pointer actually passed to the function shall have a value
7953 such that all address computations and accesses to objects (that would be valid if the
7954 pointer did point to the first element of such an array) are in fact valid. Any function
7955 declared in a header may be additionally implemented as a function-like macro defined in
7956 the header, so if a library function is declared explicitly when its header is included, one
7957 of the techniques shown below can be used to ensure the declaration is not affected by
7958 such a macro. Any macro definition of a function can be suppressed locally by enclosing
7959 the name of the function in parentheses, because the name is then not followed by the left
7960 parenthesis that indicates expansion of a macro function name. For the same syntactic
7961 reason, it is permitted to take the address of a library function even if it is also defined as
7962 a macro.<sup><a href="#note185"><b>185)</b></a></sup> The use of #undef to remove any macro definition will also ensure that an
7963 actual function is referred to. Any invocation of a library function that is implemented as
7964 a macro shall expand to code that evaluates each of its arguments exactly once, fully
7965 protected by parentheses where necessary, so it is generally safe to use arbitrary
7966 expressions as arguments.<sup><a href="#note186"><b>186)</b></a></sup> Likewise, those function-like macros described in the
7967 following subclauses may be invoked in an expression anywhere a function with a
7968 compatible return type could be called.<sup><a href="#note187"><b>187)</b></a></sup> All object-like macros listed as expanding to
7971 <sup><a name="note185" href="#note185"><b>185)</b></a></sup> This means that an implementation shall provide an actual function for each library function, even if it
7972 also provides a macro for that function.
7973 <sup><a name="note186" href="#note186"><b>186)</b></a></sup> Such macros might not contain the sequence points that the corresponding function calls do.
7974 <sup><a name="note187" href="#note187"><b>187)</b></a></sup> Because external identifiers and some macro names beginning with an underscore are reserved,
7975 implementations may provide special semantics for such names. For example, the identifier
7976 _BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
7977 appropriate header could specify
7978 #define abs(x) _BUILTIN_abs(x)
7979 for a compiler whose code generator will accept it.
7980 In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
7983 whether the implementation's header provides a macro implementation of abs or a built-in
7984 implementation. The prototype for the function, which precedes and is hidden by any macro
7985 definition, is thereby revealed also.
7987 [<a name="p182" href="#p182">page 182</a>] (<a href="#Contents">Contents</a>)
7989 integer constant expressions shall additionally be suitable for use in #if preprocessing
7991 2 Provided that a library function can be declared without reference to any type defined in a
7992 header, it is also permissible to declare the function and use it without including its
7994 3 There is a sequence point immediately before a library function returns.
7995 4 The functions in the standard library are not guaranteed to be reentrant and may modify
7996 objects with static or thread storage duration.<sup><a href="#note188"><b>188)</b></a></sup>
7997 5 Unless explicitly stated otherwise in the detailed descriptions that follow, library
7998 functions shall prevent data races as follows: A library function shall not directly or
7999 indirectly access objects accessible by threads other than the current thread unless the
8000 objects are accessed directly or indirectly via the function's arguments. A library
8001 function shall not directly or indirectly modify objects accessible by threads other than
8002 the current thread unless the objects are accessed directly or indirectly via the function's
8003 non-const arguments.<sup><a href="#note189"><b>189)</b></a></sup> Implementations may share their own internal objects between
8004 threads if the objects are not visible to users and are protected against data races.
8005 6 Unless otherwise specified, library functions shall perform all operations solely within the
8006 current thread if those operations have effects that are visible to users.<sup><a href="#note190"><b>190)</b></a></sup>
8007 7 EXAMPLE The function atoi may be used in any of several ways:
8008 -- by use of its associated header (possibly generating a macro expansion)
8009 #include <a href="#7.22"><stdlib.h></a>
8013 -- by use of its associated header (assuredly generating a true function reference)
8018 <sup><a name="note188" href="#note188"><b>188)</b></a></sup> Thus, a signal handler cannot, in general, call standard library functions.
8019 <sup><a name="note189" href="#note189"><b>189)</b></a></sup> This means, for example, that an implementation is not permitted to use a static object for internal
8020 purposes without synchronization because it could cause a data race even in programs that do not
8021 explicitly share objects between threads.
8022 <sup><a name="note190" href="#note190"><b>190)</b></a></sup> This allows implementations to parallelize operations if there are no visible side effects.
8024 [<a name="p183" href="#p183">page 183</a>] (<a href="#Contents">Contents</a>)
8026 #include <a href="#7.22"><stdlib.h></a>
8032 #include <a href="#7.22"><stdlib.h></a>
8036 -- by explicit declaration
8037 extern int atoi(const char *);
8045 [<a name="p184" href="#p184">page 184</a>] (<a href="#Contents">Contents</a>)
8047 <a name="7.2" href="#7.2"><b> 7.2 Diagnostics <assert.h></b></a>
8048 1 The header <a href="#7.2"><assert.h></a> defines the assert and static_assert macros and
8049 refers to another macro,
8051 which is not defined by <a href="#7.2"><assert.h></a>. If NDEBUG is defined as a macro name at the
8052 point in the source file where <a href="#7.2"><assert.h></a> is included, the assert macro is defined
8054 #define assert(ignore) ((void)0)
8055 The assert macro is redefined according to the current state of NDEBUG each time that
8056 <a href="#7.2"><assert.h></a> is included.
8057 2 The assert macro shall be implemented as a macro, not as an actual function. If the
8058 macro definition is suppressed in order to access an actual function, the behavior is
8062 expands to _Static_assert.
8063 <a name="7.2.1" href="#7.2.1"><b> 7.2.1 Program diagnostics</b></a>
8064 <a name="7.2.1.1" href="#7.2.1.1"><b> 7.2.1.1 The assert macro</b></a>
8066 1 #include <a href="#7.2"><assert.h></a>
8067 void assert(scalar expression);
8069 2 The assert macro puts diagnostic tests into programs; it expands to a void expression.
8070 When it is executed, if expression (which shall have a scalar type) is false (that is,
8071 compares equal to 0), the assert macro writes information about the particular call that
8072 failed (including the text of the argument, the name of the source file, the source line
8073 number, and the name of the enclosing function -- the latter are respectively the values of
8074 the preprocessing macros __FILE__ and __LINE__ and of the identifier
8075 __func__) on the standard error stream in an implementation-defined format.<sup><a href="#note191"><b>191)</b></a></sup> It
8076 then calls the abort function.
8080 <sup><a name="note191" href="#note191"><b>191)</b></a></sup> The message written might be of the form:
8081 Assertion failed: expression, function abc, file xyz, line nnn.
8084 [<a name="p185" href="#p185">page 185</a>] (<a href="#Contents">Contents</a>)
8087 3 The assert macro returns no value.
8088 Forward references: the abort function (<a href="#7.22.4.1">7.22.4.1</a>).
8093 [<a name="p186" href="#p186">page 186</a>] (<a href="#Contents">Contents</a>)
8095 <a name="7.3" href="#7.3"><b> 7.3 Complex arithmetic <complex.h></b></a>
8096 <a name="7.3.1" href="#7.3.1"><b> 7.3.1 Introduction</b></a>
8097 1 The header <a href="#7.3"><complex.h></a> defines macros and declares functions that support complex
8098 arithmetic.<sup><a href="#note192"><b>192)</b></a></sup>
8099 2 Implementations that define the macro __STDC_NO_COMPLEX__ need not provide
8100 this header nor support any of its facilities.
8101 3 Each synopsis specifies a family of functions consisting of a principal function with one
8102 or more double complex parameters and a double complex or double return
8103 value; and other functions with the same name but with f and l suffixes which are
8104 corresponding functions with float and long double parameters and return values.
8107 expands to _Complex; the macro
8109 expands to a constant expression of type const float _Complex, with the value of
8110 the imaginary unit.<sup><a href="#note193"><b>193)</b></a></sup>
8115 are defined if and only if the implementation supports imaginary types;<sup><a href="#note194"><b>194)</b></a></sup> if defined,
8116 they expand to _Imaginary and a constant expression of type const float
8117 _Imaginary with the value of the imaginary unit.
8120 expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
8121 defined, I shall expand to _Complex_I.
8122 7 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
8123 redefine the macros complex, imaginary, and I.
8125 <sup><a name="note192" href="#note192"><b>192)</b></a></sup> See ''future library directions'' (<a href="#7.30.1">7.30.1</a>).
8126 <sup><a name="note193" href="#note193"><b>193)</b></a></sup> The imaginary unit is a number i such that i 2 = -1.
8127 <sup><a name="note194" href="#note194"><b>194)</b></a></sup> A specification for imaginary types is in informative <a href="#G">annex G</a>.
8129 [<a name="p187" href="#p187">page 187</a>] (<a href="#Contents">Contents</a>)
8131 Forward references: IEC 60559-compatible complex arithmetic (<a href="#G">annex G</a>).
8132 <a name="7.3.2" href="#7.3.2"><b> 7.3.2 Conventions</b></a>
8133 1 Values are interpreted as radians, not degrees. An implementation may set errno but is
8135 <a name="7.3.3" href="#7.3.3"><b> 7.3.3 Branch cuts</b></a>
8136 1 Some of the functions below have branch cuts, across which the function is
8137 discontinuous. For implementations with a signed zero (including all IEC 60559
8138 implementations) that follow the specifications of <a href="#G">annex G</a>, the sign of zero distinguishes
8139 one side of a cut from another so the function is continuous (except for format
8140 limitations) as the cut is approached from either side. For example, for the square root
8141 function, which has a branch cut along the negative real axis, the top of the cut, with
8142 imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with
8143 imaginary part -0, maps to the negative imaginary axis.
8144 2 Implementations that do not support a signed zero (see <a href="#F">annex F</a>) cannot distinguish the
8145 sides of branch cuts. These implementations shall map a cut so the function is continuous
8146 as the cut is approached coming around the finite endpoint of the cut in a counter
8147 clockwise direction. (Branch cuts for the functions specified here have just one finite
8148 endpoint.) For example, for the square root function, coming counter clockwise around
8149 the finite endpoint of the cut along the negative real axis approaches the cut from above,
8150 so the cut maps to the positive imaginary axis.
8151 <a name="7.3.4" href="#7.3.4"><b> 7.3.4 The CX_LIMITED_RANGE pragma</b></a>
8153 1 #include <a href="#7.3"><complex.h></a>
8154 #pragma STDC CX_LIMITED_RANGE on-off-switch
8156 2 The usual mathematical formulas for complex multiply, divide, and absolute value are
8157 problematic because of their treatment of infinities and because of undue overflow and
8158 underflow. The CX_LIMITED_RANGE pragma can be used to inform the
8159 implementation that (where the state is ''on'') the usual mathematical formulas are
8160 acceptable.<sup><a href="#note195"><b>195)</b></a></sup> The pragma can occur either outside external declarations or preceding all
8161 explicit declarations and statements inside a compound statement. When outside external
8162 declarations, the pragma takes effect from its occurrence until another
8163 CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit.
8164 When inside a compound statement, the pragma takes effect from its occurrence until
8165 another CX_LIMITED_RANGE pragma is encountered (including within a nested
8166 compound statement), or until the end of the compound statement; at the end of a
8167 compound statement the state for the pragma is restored to its condition just before the
8169 [<a name="p188" href="#p188">page 188</a>] (<a href="#Contents">Contents</a>)
8171 compound statement. If this pragma is used in any other context, the behavior is
8172 undefined. The default state for the pragma is ''off''.
8173 <a name="7.3.5" href="#7.3.5"><b> 7.3.5 Trigonometric functions</b></a>
8174 <a name="7.3.5.1" href="#7.3.5.1"><b> 7.3.5.1 The cacos functions</b></a>
8176 1 #include <a href="#7.3"><complex.h></a>
8177 double complex cacos(double complex z);
8178 float complex cacosf(float complex z);
8179 long double complex cacosl(long double complex z);
8181 2 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
8182 interval [-1, +1] along the real axis.
8184 3 The cacos functions return the complex arc cosine value, in the range of a strip
8185 mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
8187 <a name="7.3.5.2" href="#7.3.5.2"><b> 7.3.5.2 The casin functions</b></a>
8189 1 #include <a href="#7.3"><complex.h></a>
8190 double complex casin(double complex z);
8191 float complex casinf(float complex z);
8192 long double complex casinl(long double complex z);
8194 2 The casin functions compute the complex arc sine of z, with branch cuts outside the
8195 interval [-1, +1] along the real axis.
8197 3 The casin functions return the complex arc sine value, in the range of a strip
8198 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
8200 <sup><a name="note195" href="#note195"><b>195)</b></a></sup> The purpose of the pragma is to allow the implementation to use the formulas:
8201 (x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
8202 (x + iy) / (u + iv) = [(xu + yv) + i(yu - xv)]/(u2 + v 2 )
8203 | x + iy | = sqrt: x 2 + y 2
8205 where the programmer can determine they are safe.
8207 [<a name="p189" href="#p189">page 189</a>] (<a href="#Contents">Contents</a>)
8209 along the real axis.
8210 <a name="7.3.5.3" href="#7.3.5.3"><b> 7.3.5.3 The catan functions</b></a>
8212 1 #include <a href="#7.3"><complex.h></a>
8213 double complex catan(double complex z);
8214 float complex catanf(float complex z);
8215 long double complex catanl(long double complex z);
8217 2 The catan functions compute the complex arc tangent of z, with branch cuts outside the
8218 interval [-i, +i] along the imaginary axis.
8220 3 The catan functions return the complex arc tangent value, in the range of a strip
8221 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
8222 along the real axis.
8223 <a name="7.3.5.4" href="#7.3.5.4"><b> 7.3.5.4 The ccos functions</b></a>
8225 1 #include <a href="#7.3"><complex.h></a>
8226 double complex ccos(double complex z);
8227 float complex ccosf(float complex z);
8228 long double complex ccosl(long double complex z);
8230 2 The ccos functions compute the complex cosine of z.
8232 3 The ccos functions return the complex cosine value.
8233 <a name="7.3.5.5" href="#7.3.5.5"><b> 7.3.5.5 The csin functions</b></a>
8235 1 #include <a href="#7.3"><complex.h></a>
8236 double complex csin(double complex z);
8237 float complex csinf(float complex z);
8238 long double complex csinl(long double complex z);
8240 2 The csin functions compute the complex sine of z.
8244 [<a name="p190" href="#p190">page 190</a>] (<a href="#Contents">Contents</a>)
8247 3 The csin functions return the complex sine value.
8248 <a name="7.3.5.6" href="#7.3.5.6"><b> 7.3.5.6 The ctan functions</b></a>
8250 1 #include <a href="#7.3"><complex.h></a>
8251 double complex ctan(double complex z);
8252 float complex ctanf(float complex z);
8253 long double complex ctanl(long double complex z);
8255 2 The ctan functions compute the complex tangent of z.
8257 3 The ctan functions return the complex tangent value.
8258 <a name="7.3.6" href="#7.3.6"><b> 7.3.6 Hyperbolic functions</b></a>
8259 <a name="7.3.6.1" href="#7.3.6.1"><b> 7.3.6.1 The cacosh functions</b></a>
8261 1 #include <a href="#7.3"><complex.h></a>
8262 double complex cacosh(double complex z);
8263 float complex cacoshf(float complex z);
8264 long double complex cacoshl(long double complex z);
8266 2 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch
8267 cut at values less than 1 along the real axis.
8269 3 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
8270 half-strip of nonnegative values along the real axis and in the interval [-ipi , +ipi ] along the
8272 <a name="7.3.6.2" href="#7.3.6.2"><b> 7.3.6.2 The casinh functions</b></a>
8274 1 #include <a href="#7.3"><complex.h></a>
8275 double complex casinh(double complex z);
8276 float complex casinhf(float complex z);
8277 long double complex casinhl(long double complex z);
8281 [<a name="p191" href="#p191">page 191</a>] (<a href="#Contents">Contents</a>)
8284 2 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts
8285 outside the interval [-i, +i] along the imaginary axis.
8287 3 The casinh functions return the complex arc hyperbolic sine value, in the range of a
8288 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
8289 along the imaginary axis.
8290 <a name="7.3.6.3" href="#7.3.6.3"><b> 7.3.6.3 The catanh functions</b></a>
8292 1 #include <a href="#7.3"><complex.h></a>
8293 double complex catanh(double complex z);
8294 float complex catanhf(float complex z);
8295 long double complex catanhl(long double complex z);
8297 2 The catanh functions compute the complex arc hyperbolic tangent of z, with branch
8298 cuts outside the interval [-1, +1] along the real axis.
8300 3 The catanh functions return the complex arc hyperbolic tangent value, in the range of a
8301 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
8302 along the imaginary axis.
8303 <a name="7.3.6.4" href="#7.3.6.4"><b> 7.3.6.4 The ccosh functions</b></a>
8305 1 #include <a href="#7.3"><complex.h></a>
8306 double complex ccosh(double complex z);
8307 float complex ccoshf(float complex z);
8308 long double complex ccoshl(long double complex z);
8310 2 The ccosh functions compute the complex hyperbolic cosine of z.
8312 3 The ccosh functions return the complex hyperbolic cosine value.
8317 [<a name="p192" href="#p192">page 192</a>] (<a href="#Contents">Contents</a>)
8319 <a name="7.3.6.5" href="#7.3.6.5"><b> 7.3.6.5 The csinh functions</b></a>
8321 1 #include <a href="#7.3"><complex.h></a>
8322 double complex csinh(double complex z);
8323 float complex csinhf(float complex z);
8324 long double complex csinhl(long double complex z);
8326 2 The csinh functions compute the complex hyperbolic sine of z.
8328 3 The csinh functions return the complex hyperbolic sine value.
8329 <a name="7.3.6.6" href="#7.3.6.6"><b> 7.3.6.6 The ctanh functions</b></a>
8331 1 #include <a href="#7.3"><complex.h></a>
8332 double complex ctanh(double complex z);
8333 float complex ctanhf(float complex z);
8334 long double complex ctanhl(long double complex z);
8336 2 The ctanh functions compute the complex hyperbolic tangent of z.
8338 3 The ctanh functions return the complex hyperbolic tangent value.
8339 <a name="7.3.7" href="#7.3.7"><b> 7.3.7 Exponential and logarithmic functions</b></a>
8340 <a name="7.3.7.1" href="#7.3.7.1"><b> 7.3.7.1 The cexp functions</b></a>
8342 1 #include <a href="#7.3"><complex.h></a>
8343 double complex cexp(double complex z);
8344 float complex cexpf(float complex z);
8345 long double complex cexpl(long double complex z);
8347 2 The cexp functions compute the complex base-e exponential of z.
8349 3 The cexp functions return the complex base-e exponential value.
8353 [<a name="p193" href="#p193">page 193</a>] (<a href="#Contents">Contents</a>)
8355 <a name="7.3.7.2" href="#7.3.7.2"><b> 7.3.7.2 The clog functions</b></a>
8357 1 #include <a href="#7.3"><complex.h></a>
8358 double complex clog(double complex z);
8359 float complex clogf(float complex z);
8360 long double complex clogl(long double complex z);
8362 2 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
8363 cut along the negative real axis.
8365 3 The clog functions return the complex natural logarithm value, in the range of a strip
8366 mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
8368 <a name="7.3.8" href="#7.3.8"><b> 7.3.8 Power and absolute-value functions</b></a>
8369 <a name="7.3.8.1" href="#7.3.8.1"><b> 7.3.8.1 The cabs functions</b></a>
8371 1 #include <a href="#7.3"><complex.h></a>
8372 double cabs(double complex z);
8373 float cabsf(float complex z);
8374 long double cabsl(long double complex z);
8376 2 The cabs functions compute the complex absolute value (also called norm, modulus, or
8379 3 The cabs functions return the complex absolute value.
8380 <a name="7.3.8.2" href="#7.3.8.2"><b> 7.3.8.2 The cpow functions</b></a>
8382 1 #include <a href="#7.3"><complex.h></a>
8383 double complex cpow(double complex x, double complex y);
8384 float complex cpowf(float complex x, float complex y);
8385 long double complex cpowl(long double complex x,
8386 long double complex y);
8391 [<a name="p194" href="#p194">page 194</a>] (<a href="#Contents">Contents</a>)
8394 2 The cpow functions compute the complex power function xy , with a branch cut for the
8395 first parameter along the negative real axis.
8397 3 The cpow functions return the complex power function value.
8398 <a name="7.3.8.3" href="#7.3.8.3"><b> 7.3.8.3 The csqrt functions</b></a>
8400 1 #include <a href="#7.3"><complex.h></a>
8401 double complex csqrt(double complex z);
8402 float complex csqrtf(float complex z);
8403 long double complex csqrtl(long double complex z);
8405 2 The csqrt functions compute the complex square root of z, with a branch cut along the
8408 3 The csqrt functions return the complex square root value, in the range of the right half-
8409 plane (including the imaginary axis).
8410 <a name="7.3.9" href="#7.3.9"><b> 7.3.9 Manipulation functions</b></a>
8411 <a name="7.3.9.1" href="#7.3.9.1"><b> 7.3.9.1 The carg functions</b></a>
8413 1 #include <a href="#7.3"><complex.h></a>
8414 double carg(double complex z);
8415 float cargf(float complex z);
8416 long double cargl(long double complex z);
8418 2 The carg functions compute the argument (also called phase angle) of z, with a branch
8419 cut along the negative real axis.
8421 3 The carg functions return the value of the argument in the interval [-pi , +pi ].
8426 [<a name="p195" href="#p195">page 195</a>] (<a href="#Contents">Contents</a>)
8428 <a name="7.3.9.2" href="#7.3.9.2"><b> 7.3.9.2 The cimag functions</b></a>
8430 1 #include <a href="#7.3"><complex.h></a>
8431 double cimag(double complex z);
8432 float cimagf(float complex z);
8433 long double cimagl(long double complex z);
8435 2 The cimag functions compute the imaginary part of z.<sup><a href="#note196"><b>196)</b></a></sup>
8437 3 The cimag functions return the imaginary part value (as a real).
8438 <a name="7.3.9.3" href="#7.3.9.3"><b> 7.3.9.3 The CMPLX macros</b></a>
8440 1 #include <a href="#7.3"><complex.h></a>
8441 double complex CMPLX(double x, double y);
8442 float complex CMPLXF(float x, float y);
8443 long double complex CMPLXL(long double x, long double y);
8445 2 The CMPLX macros expand to an expression of the specified complex type, with the real
8446 part having the (converted) value of x and the imaginary part having the (converted)
8448 Recommended practice
8449 3 The resulting expression should be suitable for use as an initializer for an object with
8450 static or thread storage duration, provided both arguments are likewise suitable.
8452 4 The CMPLX macros return the complex value x + i y.
8453 5 NOTE These macros act as if the implementation supported imaginary types and the definitions were:
8454 #define CMPLX(x, y) ((double complex)((double)(x) + \
8455 _Imaginary_I * (double)(y)))
8456 #define CMPLXF(x, y) ((float complex)((float)(x) + \
8457 _Imaginary_I * (float)(y)))
8458 #define CMPLXL(x, y) ((long double complex)((long double)(x) + \
8459 _Imaginary_I * (long double)(y)))
8464 <sup><a name="note196" href="#note196"><b>196)</b></a></sup> For a variable z of complex type, z == creal(z) + cimag(z)*I.
8466 [<a name="p196" href="#p196">page 196</a>] (<a href="#Contents">Contents</a>)
8468 <a name="7.3.9.4" href="#7.3.9.4"><b> 7.3.9.4 The conj functions</b></a>
8470 1 #include <a href="#7.3"><complex.h></a>
8471 double complex conj(double complex z);
8472 float complex conjf(float complex z);
8473 long double complex conjl(long double complex z);
8475 2 The conj functions compute the complex conjugate of z, by reversing the sign of its
8478 3 The conj functions return the complex conjugate value.
8479 <a name="7.3.9.5" href="#7.3.9.5"><b> 7.3.9.5 The cproj functions</b></a>
8481 1 #include <a href="#7.3"><complex.h></a>
8482 double complex cproj(double complex z);
8483 float complex cprojf(float complex z);
8484 long double complex cprojl(long double complex z);
8486 2 The cproj functions compute a projection of z onto the Riemann sphere: z projects to
8487 z except that all complex infinities (even those with one infinite part and one NaN part)
8488 project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is
8490 INFINITY + I * copysign(0.0, cimag(z))
8492 3 The cproj functions return the value of the projection onto the Riemann sphere.
8493 <a name="7.3.9.6" href="#7.3.9.6"><b> 7.3.9.6 The creal functions</b></a>
8495 1 #include <a href="#7.3"><complex.h></a>
8496 double creal(double complex z);
8497 float crealf(float complex z);
8498 long double creall(long double complex z);
8500 2 The creal functions compute the real part of z.<sup><a href="#note197"><b>197)</b></a></sup>
8503 [<a name="p197" href="#p197">page 197</a>] (<a href="#Contents">Contents</a>)
8506 3 The creal functions return the real part value.
8511 <sup><a name="note197" href="#note197"><b>197)</b></a></sup> For a variable z of complex type, z == creal(z) + cimag(z)*I.
8513 [<a name="p198" href="#p198">page 198</a>] (<a href="#Contents">Contents</a>)
8515 <a name="7.4" href="#7.4"><b> 7.4 Character handling <ctype.h></b></a>
8516 1 The header <a href="#7.4"><ctype.h></a> declares several functions useful for classifying and mapping
8517 characters.<sup><a href="#note198"><b>198)</b></a></sup> In all cases the argument is an int, the value of which shall be
8518 representable as an unsigned char or shall equal the value of the macro EOF. If the
8519 argument has any other value, the behavior is undefined.
8520 2 The behavior of these functions is affected by the current locale. Those functions that
8521 have locale-specific aspects only when not in the "C" locale are noted below.
8522 3 The term printing character refers to a member of a locale-specific set of characters, each
8523 of which occupies one printing position on a display device; the term control character
8524 refers to a member of a locale-specific set of characters that are not printing
8525 characters.<sup><a href="#note199"><b>199)</b></a></sup> All letters and digits are printing characters.
8526 Forward references: EOF (<a href="#7.21.1">7.21.1</a>), localization (<a href="#7.11">7.11</a>).
8527 <a name="7.4.1" href="#7.4.1"><b> 7.4.1 Character classification functions</b></a>
8528 1 The functions in this subclause return nonzero (true) if and only if the value of the
8529 argument c conforms to that in the description of the function.
8530 <a name="7.4.1.1" href="#7.4.1.1"><b> 7.4.1.1 The isalnum function</b></a>
8532 1 #include <a href="#7.4"><ctype.h></a>
8535 2 The isalnum function tests for any character for which isalpha or isdigit is true.
8536 <a name="7.4.1.2" href="#7.4.1.2"><b> 7.4.1.2 The isalpha function</b></a>
8538 1 #include <a href="#7.4"><ctype.h></a>
8541 2 The isalpha function tests for any character for which isupper or islower is true,
8542 or any character that is one of a locale-specific set of alphabetic characters for which
8546 <sup><a name="note198" href="#note198"><b>198)</b></a></sup> See ''future library directions'' (<a href="#7.30.2">7.30.2</a>).
8547 <sup><a name="note199" href="#note199"><b>199)</b></a></sup> In an implementation that uses the seven-bit US ASCII character set, the printing characters are those
8548 whose values lie from 0x20 (space) through 0x7E (tilde); the control characters are those whose
8549 values lie from 0 (NUL) through 0x1F (US), and the character 0x7F (DEL).
8551 [<a name="p199" href="#p199">page 199</a>] (<a href="#Contents">Contents</a>)
8553 none of iscntrl, isdigit, ispunct, or isspace is true.<sup><a href="#note200"><b>200)</b></a></sup> In the "C" locale,
8554 isalpha returns true only for the characters for which isupper or islower is true.
8555 <a name="7.4.1.3" href="#7.4.1.3"><b> 7.4.1.3 The isblank function</b></a>
8557 1 #include <a href="#7.4"><ctype.h></a>
8560 2 The isblank function tests for any character that is a standard blank character or is one
8561 of a locale-specific set of characters for which isspace is true and that is used to
8562 separate words within a line of text. The standard blank characters are the following:
8563 space (' '), and horizontal tab ('\t'). In the "C" locale, isblank returns true only
8564 for the standard blank characters.
8565 <a name="7.4.1.4" href="#7.4.1.4"><b> 7.4.1.4 The iscntrl function</b></a>
8567 1 #include <a href="#7.4"><ctype.h></a>
8570 2 The iscntrl function tests for any control character.
8571 <a name="7.4.1.5" href="#7.4.1.5"><b> 7.4.1.5 The isdigit function</b></a>
8573 1 #include <a href="#7.4"><ctype.h></a>
8576 2 The isdigit function tests for any decimal-digit character (as defined in <a href="#5.2.1">5.2.1</a>).
8577 <a name="7.4.1.6" href="#7.4.1.6"><b> 7.4.1.6 The isgraph function</b></a>
8579 1 #include <a href="#7.4"><ctype.h></a>
8585 <sup><a name="note200" href="#note200"><b>200)</b></a></sup> The functions islower and isupper test true or false separately for each of these additional
8586 characters; all four combinations are possible.
8588 [<a name="p200" href="#p200">page 200</a>] (<a href="#Contents">Contents</a>)
8591 2 The isgraph function tests for any printing character except space (' ').
8592 <a name="7.4.1.7" href="#7.4.1.7"><b> 7.4.1.7 The islower function</b></a>
8594 1 #include <a href="#7.4"><ctype.h></a>
8597 2 The islower function tests for any character that is a lowercase letter or is one of a
8598 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
8599 isspace is true. In the "C" locale, islower returns true only for the lowercase
8600 letters (as defined in <a href="#5.2.1">5.2.1</a>).
8601 <a name="7.4.1.8" href="#7.4.1.8"><b> 7.4.1.8 The isprint function</b></a>
8603 1 #include <a href="#7.4"><ctype.h></a>
8606 2 The isprint function tests for any printing character including space (' ').
8607 <a name="7.4.1.9" href="#7.4.1.9"><b> 7.4.1.9 The ispunct function</b></a>
8609 1 #include <a href="#7.4"><ctype.h></a>
8612 2 The ispunct function tests for any printing character that is one of a locale-specific set
8613 of punctuation characters for which neither isspace nor isalnum is true. In the "C"
8614 locale, ispunct returns true for every printing character for which neither isspace
8615 nor isalnum is true.
8616 <a name="7.4.1.10" href="#7.4.1.10"><b> 7.4.1.10 The isspace function</b></a>
8618 1 #include <a href="#7.4"><ctype.h></a>
8621 2 The isspace function tests for any character that is a standard white-space character or
8622 is one of a locale-specific set of characters for which isalnum is false. The standard
8624 [<a name="p201" href="#p201">page 201</a>] (<a href="#Contents">Contents</a>)
8626 white-space characters are the following: space (' '), form feed ('\f'), new-line
8627 ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
8628 "C" locale, isspace returns true only for the standard white-space characters.
8629 <a name="7.4.1.11" href="#7.4.1.11"><b> 7.4.1.11 The isupper function</b></a>
8631 1 #include <a href="#7.4"><ctype.h></a>
8634 2 The isupper function tests for any character that is an uppercase letter or is one of a
8635 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
8636 isspace is true. In the "C" locale, isupper returns true only for the uppercase
8637 letters (as defined in <a href="#5.2.1">5.2.1</a>).
8638 <a name="7.4.1.12" href="#7.4.1.12"><b> 7.4.1.12 The isxdigit function</b></a>
8640 1 #include <a href="#7.4"><ctype.h></a>
8641 int isxdigit(int c);
8643 2 The isxdigit function tests for any hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
8644 <a name="7.4.2" href="#7.4.2"><b> 7.4.2 Character case mapping functions</b></a>
8645 <a name="7.4.2.1" href="#7.4.2.1"><b> 7.4.2.1 The tolower function</b></a>
8647 1 #include <a href="#7.4"><ctype.h></a>
8650 2 The tolower function converts an uppercase letter to a corresponding lowercase letter.
8652 3 If the argument is a character for which isupper is true and there are one or more
8653 corresponding characters, as specified by the current locale, for which islower is true,
8654 the tolower function returns one of the corresponding characters (always the same one
8655 for any given locale); otherwise, the argument is returned unchanged.
8660 [<a name="p202" href="#p202">page 202</a>] (<a href="#Contents">Contents</a>)
8662 <a name="7.4.2.2" href="#7.4.2.2"><b> 7.4.2.2 The toupper function</b></a>
8664 1 #include <a href="#7.4"><ctype.h></a>
8667 2 The toupper function converts a lowercase letter to a corresponding uppercase letter.
8669 3 If the argument is a character for which islower is true and there are one or more
8670 corresponding characters, as specified by the current locale, for which isupper is true,
8671 the toupper function returns one of the corresponding characters (always the same one
8672 for any given locale); otherwise, the argument is returned unchanged.
8677 [<a name="p203" href="#p203">page 203</a>] (<a href="#Contents">Contents</a>)
8679 <a name="7.5" href="#7.5"><b> 7.5 Errors <errno.h></b></a>
8680 1 The header <a href="#7.5"><errno.h></a> defines several macros, all relating to the reporting of error
8686 which expand to integer constant expressions with type int, distinct positive values, and
8687 which are suitable for use in #if preprocessing directives; and
8689 which expands to a modifiable lvalue<sup><a href="#note201"><b>201)</b></a></sup> that has type int and thread local storage
8690 duration, the value of which is set to a positive error number by several library functions.
8691 If a macro definition is suppressed in order to access an actual object, or a program
8692 defines an identifier with the name errno, the behavior is undefined.
8693 3 The value of errno in the initial thread is zero at program startup (the initial value of
8694 errno in other threads is an indeterminate value), but is never set to zero by any library
8695 function.<sup><a href="#note202"><b>202)</b></a></sup> The value of errno may be set to nonzero by a library function call
8696 whether or not there is an error, provided the use of errno is not documented in the
8697 description of the function in this International Standard.
8698 4 Additional macro definitions, beginning with E and a digit or E and an uppercase
8699 letter,<sup><a href="#note203"><b>203)</b></a></sup> may also be specified by the implementation.
8704 <sup><a name="note201" href="#note201"><b>201)</b></a></sup> The macro errno need not be the identifier of an object. It might expand to a modifiable lvalue
8705 resulting from a function call (for example, *errno()).
8706 <sup><a name="note202" href="#note202"><b>202)</b></a></sup> Thus, a program that uses errno for error checking should set it to zero before a library function call,
8707 then inspect it before a subsequent library function call. Of course, a library function can save the
8708 value of errno on entry and then set it to zero, as long as the original value is restored if errno's
8709 value is still zero just before the return.
8710 <sup><a name="note203" href="#note203"><b>203)</b></a></sup> See ''future library directions'' (<a href="#7.30.3">7.30.3</a>).
8712 [<a name="p204" href="#p204">page 204</a>] (<a href="#Contents">Contents</a>)
8714 <a name="7.6" href="#7.6"><b> 7.6 Floating-point environment <fenv.h></b></a>
8715 1 The header <a href="#7.6"><fenv.h></a> defines several macros, and declares types and functions that
8716 provide access to the floating-point environment. The floating-point environment refers
8717 collectively to any floating-point status flags and control modes supported by the
8718 implementation.<sup><a href="#note204"><b>204)</b></a></sup> A floating-point status flag is a system variable whose value is set
8719 (but never cleared) when a floating-point exception is raised, which occurs as a side effect
8720 of exceptional floating-point arithmetic to provide auxiliary information.<sup><a href="#note205"><b>205)</b></a></sup> A floating-
8721 point control mode is a system variable whose value may be set by the user to affect the
8722 subsequent behavior of floating-point arithmetic.
8723 2 The floating-point environment has thread storage duration. The initial state for a
8724 thread's floating-point environment is the current state of the floating-point environment
8725 of the thread that creates it at the time of creation.
8726 3 Certain programming conventions support the intended model of use for the floating-
8727 point environment:<sup><a href="#note206"><b>206)</b></a></sup>
8728 -- a function call does not alter its caller's floating-point control modes, clear its caller's
8729 floating-point status flags, nor depend on the state of its caller's floating-point status
8730 flags unless the function is so documented;
8731 -- a function call is assumed to require default floating-point control modes, unless its
8732 documentation promises otherwise;
8733 -- a function call is assumed to have the potential for raising floating-point exceptions,
8734 unless its documentation promises otherwise.
8737 represents the entire floating-point environment.
8740 represents the floating-point status flags collectively, including any status the
8741 implementation associates with the flags.
8744 <sup><a name="note204" href="#note204"><b>204)</b></a></sup> This header is designed to support the floating-point exception status flags and directed-rounding
8745 control modes required by IEC 60559, and other similar floating-point state information. It is also
8746 designed to facilitate code portability among all systems.
8747 <sup><a name="note205" href="#note205"><b>205)</b></a></sup> A floating-point status flag is not an object and can be set more than once within an expression.
8748 <sup><a name="note206" href="#note206"><b>206)</b></a></sup> With these conventions, a programmer can safely assume default floating-point control modes (or be
8749 unaware of them). The responsibilities associated with accessing the floating-point environment fall
8750 on the programmer or program that does so explicitly.
8752 [<a name="p205" href="#p205">page 205</a>] (<a href="#Contents">Contents</a>)
8754 6 Each of the macros
8760 is defined if and only if the implementation supports the floating-point exception by
8761 means of the functions in 7.6.2.<sup><a href="#note207"><b>207)</b></a></sup> Additional implementation-defined floating-point
8762 exceptions, with macro definitions beginning with FE_ and an uppercase letter, may also
8763 be specified by the implementation. The defined macros expand to integer constant
8764 expressions with values such that bitwise ORs of all combinations of the macros result in
8765 distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
8766 zero.<sup><a href="#note208"><b>208)</b></a></sup>
8769 is simply the bitwise OR of all floating-point exception macros defined by the
8770 implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
8771 8 Each of the macros
8776 is defined if and only if the implementation supports getting and setting the represented
8777 rounding direction by means of the fegetround and fesetround functions.
8778 Additional implementation-defined rounding directions, with macro definitions beginning
8779 with FE_ and an uppercase letter, may also be specified by the implementation. The
8780 defined macros expand to integer constant expressions whose values are distinct
8781 nonnegative values.<sup><a href="#note209"><b>209)</b></a></sup>
8786 <sup><a name="note207" href="#note207"><b>207)</b></a></sup> The implementation supports a floating-point exception if there are circumstances where a call to at
8787 least one of the functions in <a href="#7.6.2">7.6.2</a>, using the macro as the appropriate argument, will succeed. It is not
8788 necessary for all the functions to succeed all the time.
8789 <sup><a name="note208" href="#note208"><b>208)</b></a></sup> The macros should be distinct powers of two.
8790 <sup><a name="note209" href="#note209"><b>209)</b></a></sup> Even though the rounding direction macros may expand to constants corresponding to the values of
8791 FLT_ROUNDS, they are not required to do so.
8793 [<a name="p206" href="#p206">page 206</a>] (<a href="#Contents">Contents</a>)
8796 represents the default floating-point environment -- the one installed at program startup
8797 -- and has type ''pointer to const-qualified fenv_t''. It can be used as an argument to
8798 <a href="#7.6"><fenv.h></a> functions that manage the floating-point environment.
8799 10 Additional implementation-defined environments, with macro definitions beginning with
8800 FE_ and an uppercase letter, and having type ''pointer to const-qualified fenv_t'', may
8801 also be specified by the implementation.
8802 <a name="7.6.1" href="#7.6.1"><b> 7.6.1 The FENV_ACCESS pragma</b></a>
8804 1 #include <a href="#7.6"><fenv.h></a>
8805 #pragma STDC FENV_ACCESS on-off-switch
8807 2 The FENV_ACCESS pragma provides a means to inform the implementation when a
8808 program might access the floating-point environment to test floating-point status flags or
8809 run under non-default floating-point control modes.<sup><a href="#note210"><b>210)</b></a></sup> The pragma shall occur either
8810 outside external declarations or preceding all explicit declarations and statements inside a
8811 compound statement. When outside external declarations, the pragma takes effect from
8812 its occurrence until another FENV_ACCESS pragma is encountered, or until the end of
8813 the translation unit. When inside a compound statement, the pragma takes effect from its
8814 occurrence until another FENV_ACCESS pragma is encountered (including within a
8815 nested compound statement), or until the end of the compound statement; at the end of a
8816 compound statement the state for the pragma is restored to its condition just before the
8817 compound statement. If this pragma is used in any other context, the behavior is
8818 undefined. If part of a program tests floating-point status flags, sets floating-point control
8819 modes, or runs under non-default mode settings, but was translated with the state for the
8820 FENV_ACCESS pragma ''off'', the behavior is undefined. The default state (''on'' or
8821 ''off'') for the pragma is implementation-defined. (When execution passes from a part of
8822 the program translated with FENV_ACCESS ''off'' to a part translated with
8823 FENV_ACCESS ''on'', the state of the floating-point status flags is unspecified and the
8824 floating-point control modes have their default settings.)
8829 <sup><a name="note210" href="#note210"><b>210)</b></a></sup> The purpose of the FENV_ACCESS pragma is to allow certain optimizations that could subvert flag
8830 tests and mode changes (e.g., global common subexpression elimination, code motion, and constant
8831 folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default
8832 modes are in effect and the flags are not tested.
8834 [<a name="p207" href="#p207">page 207</a>] (<a href="#Contents">Contents</a>)
8837 #include <a href="#7.6"><fenv.h></a>
8840 #pragma STDC FENV_ACCESS ON
8848 4 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
8849 x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
8850 contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.<sup><a href="#note211"><b>211)</b></a></sup>
8852 <a name="7.6.2" href="#7.6.2"><b> 7.6.2 Floating-point exceptions</b></a>
8853 1 The following functions provide access to the floating-point status flags.<sup><a href="#note212"><b>212)</b></a></sup> The int
8854 input argument for the functions represents a subset of floating-point exceptions, and can
8855 be zero or the bitwise OR of one or more floating-point exception macros, for example
8856 FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
8857 functions is undefined.
8858 <a name="7.6.2.1" href="#7.6.2.1"><b> 7.6.2.1 The feclearexcept function</b></a>
8860 1 #include <a href="#7.6"><fenv.h></a>
8861 int feclearexcept(int excepts);
8863 2 The feclearexcept function attempts to clear the supported floating-point exceptions
8864 represented by its argument.
8866 3 The feclearexcept function returns zero if the excepts argument is zero or if all
8867 the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
8870 <sup><a name="note211" href="#note211"><b>211)</b></a></sup> The side effects impose a temporal ordering that requires two evaluations of x + 1. On the other
8871 hand, without the #pragma STDC FENV_ACCESS ON pragma, and assuming the default state is
8872 ''off'', just one evaluation of x + 1 would suffice.
8873 <sup><a name="note212" href="#note212"><b>212)</b></a></sup> The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
8874 abstraction of flags that are either set or clear. An implementation may endow floating-point status
8875 flags with more information -- for example, the address of the code which first raised the floating-
8876 point exception; the functions fegetexceptflag and fesetexceptflag deal with the full
8879 [<a name="p208" href="#p208">page 208</a>] (<a href="#Contents">Contents</a>)
8881 <a name="7.6.2.2" href="#7.6.2.2"><b> 7.6.2.2 The fegetexceptflag function</b></a>
8883 1 #include <a href="#7.6"><fenv.h></a>
8884 int fegetexceptflag(fexcept_t *flagp,
8887 2 The fegetexceptflag function attempts to store an implementation-defined
8888 representation of the states of the floating-point status flags indicated by the argument
8889 excepts in the object pointed to by the argument flagp.
8891 3 The fegetexceptflag function returns zero if the representation was successfully
8892 stored. Otherwise, it returns a nonzero value.
8893 <a name="7.6.2.3" href="#7.6.2.3"><b> 7.6.2.3 The feraiseexcept function</b></a>
8895 1 #include <a href="#7.6"><fenv.h></a>
8896 int feraiseexcept(int excepts);
8898 2 The feraiseexcept function attempts to raise the supported floating-point exceptions
8899 represented by its argument.<sup><a href="#note213"><b>213)</b></a></sup> The order in which these floating-point exceptions are
8900 raised is unspecified, except as stated in <a href="#F.8.6">F.8.6</a>. Whether the feraiseexcept function
8901 additionally raises the ''inexact'' floating-point exception whenever it raises the
8902 ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
8904 3 The feraiseexcept function returns zero if the excepts argument is zero or if all
8905 the specified exceptions were successfully raised. Otherwise, it returns a nonzero value.
8910 <sup><a name="note213" href="#note213"><b>213)</b></a></sup> The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations.
8911 Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
8912 in <a href="#F.8.6">F.8.6</a> is in the same spirit.
8914 [<a name="p209" href="#p209">page 209</a>] (<a href="#Contents">Contents</a>)
8916 <a name="7.6.2.4" href="#7.6.2.4"><b> 7.6.2.4 The fesetexceptflag function</b></a>
8918 1 #include <a href="#7.6"><fenv.h></a>
8919 int fesetexceptflag(const fexcept_t *flagp,
8922 2 The fesetexceptflag function attempts to set the floating-point status flags
8923 indicated by the argument excepts to the states stored in the object pointed to by
8924 flagp. The value of *flagp shall have been set by a previous call to
8925 fegetexceptflag whose second argument represented at least those floating-point
8926 exceptions represented by the argument excepts. This function does not raise floating-
8927 point exceptions, but only sets the state of the flags.
8929 3 The fesetexceptflag function returns zero if the excepts argument is zero or if
8930 all the specified flags were successfully set to the appropriate state. Otherwise, it returns
8932 <a name="7.6.2.5" href="#7.6.2.5"><b> 7.6.2.5 The fetestexcept function</b></a>
8934 1 #include <a href="#7.6"><fenv.h></a>
8935 int fetestexcept(int excepts);
8937 2 The fetestexcept function determines which of a specified subset of the floating-
8938 point exception flags are currently set. The excepts argument specifies the floating-
8939 point status flags to be queried.<sup><a href="#note214"><b>214)</b></a></sup>
8941 3 The fetestexcept function returns the value of the bitwise OR of the floating-point
8942 exception macros corresponding to the currently set floating-point exceptions included in
8944 4 EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set:
8949 <sup><a name="note214" href="#note214"><b>214)</b></a></sup> This mechanism allows testing several floating-point exceptions with just one function call.
8951 [<a name="p210" href="#p210">page 210</a>] (<a href="#Contents">Contents</a>)
8953 #include <a href="#7.6"><fenv.h></a>
8956 #pragma STDC FENV_ACCESS ON
8958 feclearexcept(FE_INVALID | FE_OVERFLOW);
8959 // maybe raise exceptions
8960 set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
8961 if (set_excepts & FE_INVALID) f();
8962 if (set_excepts & FE_OVERFLOW) g();
8966 <a name="7.6.3" href="#7.6.3"><b> 7.6.3 Rounding</b></a>
8967 1 The fegetround and fesetround functions provide control of rounding direction
8969 <a name="7.6.3.1" href="#7.6.3.1"><b> 7.6.3.1 The fegetround function</b></a>
8971 1 #include <a href="#7.6"><fenv.h></a>
8972 int fegetround(void);
8974 2 The fegetround function gets the current rounding direction.
8976 3 The fegetround function returns the value of the rounding direction macro
8977 representing the current rounding direction or a negative value if there is no such
8978 rounding direction macro or the current rounding direction is not determinable.
8979 <a name="7.6.3.2" href="#7.6.3.2"><b> 7.6.3.2 The fesetround function</b></a>
8981 1 #include <a href="#7.6"><fenv.h></a>
8982 int fesetround(int round);
8984 2 The fesetround function establishes the rounding direction represented by its
8985 argument round. If the argument is not equal to the value of a rounding direction macro,
8986 the rounding direction is not changed.
8988 3 The fesetround function returns zero if and only if the requested rounding direction
8992 [<a name="p211" href="#p211">page 211</a>] (<a href="#Contents">Contents</a>)
8994 4 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the
8995 rounding direction fails.
8996 #include <a href="#7.6"><fenv.h></a>
8997 #include <a href="#7.2"><assert.h></a>
8998 void f(int round_dir)
9000 #pragma STDC FENV_ACCESS ON
9003 save_round = fegetround();
9004 setround_ok = fesetround(round_dir);
9005 assert(setround_ok == 0);
9007 fesetround(save_round);
9011 <a name="7.6.4" href="#7.6.4"><b> 7.6.4 Environment</b></a>
9012 1 The functions in this section manage the floating-point environment -- status flags and
9013 control modes -- as one entity.
9014 <a name="7.6.4.1" href="#7.6.4.1"><b> 7.6.4.1 The fegetenv function</b></a>
9016 1 #include <a href="#7.6"><fenv.h></a>
9017 int fegetenv(fenv_t *envp);
9019 2 The fegetenv function attempts to store the current floating-point environment in the
9020 object pointed to by envp.
9022 3 The fegetenv function returns zero if the environment was successfully stored.
9023 Otherwise, it returns a nonzero value.
9024 <a name="7.6.4.2" href="#7.6.4.2"><b> 7.6.4.2 The feholdexcept function</b></a>
9026 1 #include <a href="#7.6"><fenv.h></a>
9027 int feholdexcept(fenv_t *envp);
9029 2 The feholdexcept function saves the current floating-point environment in the object
9030 pointed to by envp, clears the floating-point status flags, and then installs a non-stop
9031 (continue on floating-point exceptions) mode, if available, for all floating-point
9032 exceptions.<sup><a href="#note215"><b>215)</b></a></sup>
9034 [<a name="p212" href="#p212">page 212</a>] (<a href="#Contents">Contents</a>)
9037 3 The feholdexcept function returns zero if and only if non-stop floating-point
9038 exception handling was successfully installed.
9039 <a name="7.6.4.3" href="#7.6.4.3"><b> 7.6.4.3 The fesetenv function</b></a>
9041 1 #include <a href="#7.6"><fenv.h></a>
9042 int fesetenv(const fenv_t *envp);
9044 2 The fesetenv function attempts to establish the floating-point environment represented
9045 by the object pointed to by envp. The argument envp shall point to an object set by a
9046 call to fegetenv or feholdexcept, or equal a floating-point environment macro.
9047 Note that fesetenv merely installs the state of the floating-point status flags
9048 represented through its argument, and does not raise these floating-point exceptions.
9050 3 The fesetenv function returns zero if the environment was successfully established.
9051 Otherwise, it returns a nonzero value.
9052 <a name="7.6.4.4" href="#7.6.4.4"><b> 7.6.4.4 The feupdateenv function</b></a>
9054 1 #include <a href="#7.6"><fenv.h></a>
9055 int feupdateenv(const fenv_t *envp);
9057 2 The feupdateenv function attempts to save the currently raised floating-point
9058 exceptions in its automatic storage, install the floating-point environment represented by
9059 the object pointed to by envp, and then raise the saved floating-point exceptions. The
9060 argument envp shall point to an object set by a call to feholdexcept or fegetenv,
9061 or equal a floating-point environment macro.
9063 3 The feupdateenv function returns zero if all the actions were successfully carried out.
9064 Otherwise, it returns a nonzero value.
9069 <sup><a name="note215" href="#note215"><b>215)</b></a></sup> IEC 60559 systems have a default non-stop mode, and typically at least one other mode for trap
9070 handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For
9071 such systems, the feholdexcept function can be used in conjunction with the feupdateenv
9072 function to write routines that hide spurious floating-point exceptions from their callers.
9074 [<a name="p213" href="#p213">page 213</a>] (<a href="#Contents">Contents</a>)
9076 4 EXAMPLE Hide spurious underflow floating-point exceptions:
9077 #include <a href="#7.6"><fenv.h></a>
9080 #pragma STDC FENV_ACCESS ON
9083 if (feholdexcept(&save_env))
9084 return /* indication of an environmental problem */;
9086 if (/* test spurious underflow */)
9087 if (feclearexcept(FE_UNDERFLOW))
9088 return /* indication of an environmental problem */;
9089 if (feupdateenv(&save_env))
9090 return /* indication of an environmental problem */;
9097 [<a name="p214" href="#p214">page 214</a>] (<a href="#Contents">Contents</a>)
9099 <a name="7.7" href="#7.7"><b> 7.7 Characteristics of floating types <float.h></b></a>
9100 1 The header <a href="#7.7"><float.h></a> defines several macros that expand to various limits and
9101 parameters of the standard floating-point types.
9102 2 The macros, their meanings, and the constraints (or restrictions) on their values are listed
9103 in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
9108 [<a name="p215" href="#p215">page 215</a>] (<a href="#Contents">Contents</a>)
9110 <a name="7.8" href="#7.8"><b> 7.8 Format conversion of integer types <inttypes.h></b></a>
9111 1 The header <a href="#7.8"><inttypes.h></a> includes the header <a href="#7.20"><stdint.h></a> and extends it with
9112 additional facilities provided by hosted implementations.
9113 2 It declares functions for manipulating greatest-width integers and converting numeric
9114 character strings to greatest-width integers, and it declares the type
9116 which is a structure type that is the type of the value returned by the imaxdiv function.
9117 For each type declared in <a href="#7.20"><stdint.h></a>, it defines corresponding macros for conversion
9118 specifiers for use with the formatted input/output functions.<sup><a href="#note216"><b>216)</b></a></sup>
9119 Forward references: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>), formatted input/output
9120 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>).
9121 <a name="7.8.1" href="#7.8.1"><b> 7.8.1 Macros for format specifiers</b></a>
9122 1 Each of the following object-like macros expands to a character string literal containing a *
9123 conversion specifier, possibly modified by a length modifier, suitable for use within the
9124 format argument of a formatted input/output function when converting the corresponding
9125 integer type. These macro names have the general form of PRI (character string literals
9126 for the fprintf and fwprintf family) or SCN (character string literals for the
9127 fscanf and fwscanf family),<sup><a href="#note217"><b>217)</b></a></sup> followed by the conversion specifier, followed by a
9128 name corresponding to a similar type name in <a href="#7.20.1">7.20.1</a>. In these names, N represents the
9129 width of the type as described in <a href="#7.20.1">7.20.1</a>. For example, PRIdFAST32 can be used in a
9130 format string to print the value of an integer of type int_fast32_t.
9131 2 The fprintf macros for signed integers are:
9132 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
9133 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
9134 3 The fprintf macros for unsigned integers are:
9135 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
9136 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
9137 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
9138 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
9139 4 The fscanf macros for signed integers are:
9143 <sup><a name="note216" href="#note216"><b>216)</b></a></sup> See ''future library directions'' (<a href="#7.30.4">7.30.4</a>).
9144 <sup><a name="note217" href="#note217"><b>217)</b></a></sup> Separate macros are given for use with fprintf and fscanf functions because, in the general case,
9145 different format specifiers may be required for fprintf and fscanf, even when the type is the
9148 [<a name="p216" href="#p216">page 216</a>] (<a href="#Contents">Contents</a>)
9150 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
9151 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
9152 5 The fscanf macros for unsigned integers are:
9153 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
9154 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
9155 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
9156 6 For each type that the implementation provides in <a href="#7.20"><stdint.h></a>, the corresponding
9157 fprintf macros shall be defined and the corresponding fscanf macros shall be
9158 defined unless the implementation does not have a suitable fscanf length modifier for
9161 #include <a href="#7.8"><inttypes.h></a>
9162 #include <a href="#7.28"><wchar.h></a>
9165 uintmax_t i = UINTMAX_MAX; // this type always exists
9166 wprintf(L"The largest integer value is %020"
9171 <a name="7.8.2" href="#7.8.2"><b> 7.8.2 Functions for greatest-width integer types</b></a>
9172 <a name="7.8.2.1" href="#7.8.2.1"><b> 7.8.2.1 The imaxabs function</b></a>
9174 1 #include <a href="#7.8"><inttypes.h></a>
9175 intmax_t imaxabs(intmax_t j);
9177 2 The imaxabs function computes the absolute value of an integer j. If the result cannot
9178 be represented, the behavior is undefined.<sup><a href="#note218"><b>218)</b></a></sup>
9180 3 The imaxabs function returns the absolute value.
9185 <sup><a name="note218" href="#note218"><b>218)</b></a></sup> The absolute value of the most negative number cannot be represented in two's complement.
9187 [<a name="p217" href="#p217">page 217</a>] (<a href="#Contents">Contents</a>)
9189 <a name="7.8.2.2" href="#7.8.2.2"><b> 7.8.2.2 The imaxdiv function</b></a>
9191 1 #include <a href="#7.8"><inttypes.h></a>
9192 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
9194 2 The imaxdiv function computes numer / denom and numer % denom in a single
9197 3 The imaxdiv function returns a structure of type imaxdiv_t comprising both the
9198 quotient and the remainder. The structure shall contain (in either order) the members
9199 quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
9200 either part of the result cannot be represented, the behavior is undefined.
9201 <a name="7.8.2.3" href="#7.8.2.3"><b> 7.8.2.3 The strtoimax and strtoumax functions</b></a>
9203 1 #include <a href="#7.8"><inttypes.h></a>
9204 intmax_t strtoimax(const char * restrict nptr,
9205 char ** restrict endptr, int base);
9206 uintmax_t strtoumax(const char * restrict nptr,
9207 char ** restrict endptr, int base);
9209 2 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll,
9210 strtoul, and strtoull functions, except that the initial portion of the string is
9211 converted to intmax_t and uintmax_t representation, respectively.
9213 3 The strtoimax and strtoumax functions return the converted value, if any. If no
9214 conversion could be performed, zero is returned. If the correct value is outside the range
9215 of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned
9216 (according to the return type and sign of the value, if any), and the value of the macro
9217 ERANGE is stored in errno.
9218 Forward references: the strtol, strtoll, strtoul, and strtoull functions
9219 (<a href="#7.22.1.4">7.22.1.4</a>).
9224 [<a name="p218" href="#p218">page 218</a>] (<a href="#Contents">Contents</a>)
9226 <a name="7.8.2.4" href="#7.8.2.4"><b> 7.8.2.4 The wcstoimax and wcstoumax functions</b></a>
9228 1 #include <a href="#7.19"><stddef.h></a> // for wchar_t
9229 #include <a href="#7.8"><inttypes.h></a>
9230 intmax_t wcstoimax(const wchar_t * restrict nptr,
9231 wchar_t ** restrict endptr, int base);
9232 uintmax_t wcstoumax(const wchar_t * restrict nptr,
9233 wchar_t ** restrict endptr, int base);
9235 2 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll,
9236 wcstoul, and wcstoull functions except that the initial portion of the wide string is
9237 converted to intmax_t and uintmax_t representation, respectively.
9239 3 The wcstoimax function returns the converted value, if any. If no conversion could be
9240 performed, zero is returned. If the correct value is outside the range of representable
9241 values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the
9242 return type and sign of the value, if any), and the value of the macro ERANGE is stored in
9244 Forward references: the wcstol, wcstoll, wcstoul, and wcstoull functions
9245 (<a href="#7.28.4.1.2">7.28.4.1.2</a>).
9250 [<a name="p219" href="#p219">page 219</a>] (<a href="#Contents">Contents</a>)
9252 <a name="7.9" href="#7.9"><b> 7.9 Alternative spellings <iso646.h></b></a>
9253 1 The header <a href="#7.9"><iso646.h></a> defines the following eleven macros (on the left) that expand
9254 to the corresponding tokens (on the right):
9270 [<a name="p220" href="#p220">page 220</a>] (<a href="#Contents">Contents</a>)
9272 <a name="7.10" href="#7.10"><b> 7.10 Sizes of integer types <limits.h></b></a>
9273 1 The header <a href="#7.10"><limits.h></a> defines several macros that expand to various limits and
9274 parameters of the standard integer types.
9275 2 The macros, their meanings, and the constraints (or restrictions) on their values are listed
9276 in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
9281 [<a name="p221" href="#p221">page 221</a>] (<a href="#Contents">Contents</a>)
9283 <a name="7.11" href="#7.11"><b> 7.11 Localization <locale.h></b></a>
9284 1 The header <a href="#7.11"><locale.h></a> declares two functions, one type, and defines several macros.
9287 which contains members related to the formatting of numeric values. The structure shall
9288 contain at least the following members, in any order. The semantics of the members and
9289 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
9290 the values specified in the comments.
9291 char *decimal_point; // "."
9292 char *thousands_sep; // ""
9293 char *grouping; // ""
9294 char *mon_decimal_point; // ""
9295 char *mon_thousands_sep; // ""
9296 char *mon_grouping; // ""
9297 char *positive_sign; // ""
9298 char *negative_sign; // ""
9299 char *currency_symbol; // ""
9300 char frac_digits; // CHAR_MAX
9301 char p_cs_precedes; // CHAR_MAX
9302 char n_cs_precedes; // CHAR_MAX
9303 char p_sep_by_space; // CHAR_MAX
9304 char n_sep_by_space; // CHAR_MAX
9305 char p_sign_posn; // CHAR_MAX
9306 char n_sign_posn; // CHAR_MAX
9307 char *int_curr_symbol; // ""
9308 char int_frac_digits; // CHAR_MAX
9309 char int_p_cs_precedes; // CHAR_MAX
9310 char int_n_cs_precedes; // CHAR_MAX
9311 char int_p_sep_by_space; // CHAR_MAX
9312 char int_n_sep_by_space; // CHAR_MAX
9313 char int_p_sign_posn; // CHAR_MAX
9314 char int_n_sign_posn; // CHAR_MAX
9319 [<a name="p222" href="#p222">page 222</a>] (<a href="#Contents">Contents</a>)
9321 3 The macros defined are NULL (described in <a href="#7.19">7.19</a>); and
9328 which expand to integer constant expressions with distinct values, suitable for use as the
9329 first argument to the setlocale function.<sup><a href="#note219"><b>219)</b></a></sup> Additional macro definitions, beginning
9330 with the characters LC_ and an uppercase letter,<sup><a href="#note220"><b>220)</b></a></sup> may also be specified by the
9332 <a name="7.11.1" href="#7.11.1"><b> 7.11.1 Locale control</b></a>
9333 <a name="7.11.1.1" href="#7.11.1.1"><b> 7.11.1.1 The setlocale function</b></a>
9335 1 #include <a href="#7.11"><locale.h></a>
9336 char *setlocale(int category, const char *locale);
9338 2 The setlocale function selects the appropriate portion of the program's locale as
9339 specified by the category and locale arguments. The setlocale function may be
9340 used to change or query the program's entire current locale or portions thereof. The value
9341 LC_ALL for category names the program's entire locale; the other values for
9342 category name only a portion of the program's locale. LC_COLLATE affects the
9343 behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of
9344 the character handling functions<sup><a href="#note221"><b>221)</b></a></sup> and the multibyte and wide character functions.
9345 LC_MONETARY affects the monetary formatting information returned by the
9346 localeconv function. LC_NUMERIC affects the decimal-point character for the
9347 formatted input/output functions and the string conversion functions, as well as the
9348 nonmonetary formatting information returned by the localeconv function. LC_TIME
9349 affects the behavior of the strftime and wcsftime functions.
9350 3 A value of "C" for locale specifies the minimal environment for C translation; a value
9351 of "" for locale specifies the locale-specific native environment. Other
9352 implementation-defined strings may be passed as the second argument to setlocale.
9354 <sup><a name="note219" href="#note219"><b>219)</b></a></sup> ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.
9355 <sup><a name="note220" href="#note220"><b>220)</b></a></sup> See ''future library directions'' (<a href="#7.30.5">7.30.5</a>).
9356 <sup><a name="note221" href="#note221"><b>221)</b></a></sup> The only functions in <a href="#7.4">7.4</a> whose behavior is not affected by the current locale are isdigit and
9359 [<a name="p223" href="#p223">page 223</a>] (<a href="#Contents">Contents</a>)
9361 4 At program startup, the equivalent of
9362 setlocale(LC_ALL, "C");
9364 5 A call to the setlocale function may introduce a data race with other calls to the
9365 setlocale function or with calls to functions that are affected by the current locale.
9366 The implementation shall behave as if no library function calls the setlocale function.
9368 6 If a pointer to a string is given for locale and the selection can be honored, the
9369 setlocale function returns a pointer to the string associated with the specified
9370 category for the new locale. If the selection cannot be honored, the setlocale
9371 function returns a null pointer and the program's locale is not changed.
9372 7 A null pointer for locale causes the setlocale function to return a pointer to the
9373 string associated with the category for the program's current locale; the program's
9374 locale is not changed.<sup><a href="#note222"><b>222)</b></a></sup>
9375 8 The pointer to string returned by the setlocale function is such that a subsequent call
9376 with that string value and its associated category will restore that part of the program's
9377 locale. The string pointed to shall not be modified by the program, but may be
9378 overwritten by a subsequent call to the setlocale function.
9379 Forward references: formatted input/output functions (<a href="#7.21.6">7.21.6</a>), multibyte/wide
9380 character conversion functions (<a href="#7.22.7">7.22.7</a>), multibyte/wide string conversion functions
9381 (<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
9382 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>).
9383 <a name="7.11.2" href="#7.11.2"><b> 7.11.2 Numeric formatting convention inquiry</b></a>
9384 <a name="7.11.2.1" href="#7.11.2.1"><b> 7.11.2.1 The localeconv function</b></a>
9386 1 #include <a href="#7.11"><locale.h></a>
9387 struct lconv *localeconv(void);
9389 2 The localeconv function sets the components of an object with type struct lconv
9390 with values appropriate for the formatting of numeric quantities (monetary and otherwise)
9391 according to the rules of the current locale.
9395 <sup><a name="note222" href="#note222"><b>222)</b></a></sup> The implementation shall arrange to encode in a string the various categories due to a heterogeneous
9396 locale when category has the value LC_ALL.
9398 [<a name="p224" href="#p224">page 224</a>] (<a href="#Contents">Contents</a>)
9400 3 The members of the structure with type char * are pointers to strings, any of which
9401 (except decimal_point) can point to "", to indicate that the value is not available in
9402 the current locale or is of zero length. Apart from grouping and mon_grouping, the
9403 strings shall start and end in the initial shift state. The members with type char are
9404 nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not
9405 available in the current locale. The members include the following:
9407 The decimal-point character used to format nonmonetary quantities.
9409 The character used to separate groups of digits before the decimal-point
9410 character in formatted nonmonetary quantities.
9412 A string whose elements indicate the size of each group of digits in
9413 formatted nonmonetary quantities.
9414 char *mon_decimal_point
9415 The decimal-point used to format monetary quantities.
9416 char *mon_thousands_sep
9417 The separator for groups of digits before the decimal-point in formatted
9418 monetary quantities.
9420 A string whose elements indicate the size of each group of digits in
9421 formatted monetary quantities.
9423 The string used to indicate a nonnegative-valued formatted monetary
9426 The string used to indicate a negative-valued formatted monetary quantity.
9427 char *currency_symbol
9428 The local currency symbol applicable to the current locale.
9430 The number of fractional digits (those after the decimal-point) to be
9431 displayed in a locally formatted monetary quantity.
9433 Set to 1 or 0 if the currency_symbol respectively precedes or
9434 succeeds the value for a nonnegative locally formatted monetary quantity.
9438 [<a name="p225" href="#p225">page 225</a>] (<a href="#Contents">Contents</a>)
9441 Set to 1 or 0 if the currency_symbol respectively precedes or
9442 succeeds the value for a negative locally formatted monetary quantity.
9444 Set to a value indicating the separation of the currency_symbol, the
9445 sign string, and the value for a nonnegative locally formatted monetary
9448 Set to a value indicating the separation of the currency_symbol, the
9449 sign string, and the value for a negative locally formatted monetary
9452 Set to a value indicating the positioning of the positive_sign for a
9453 nonnegative locally formatted monetary quantity.
9455 Set to a value indicating the positioning of the negative_sign for a
9456 negative locally formatted monetary quantity.
9457 char *int_curr_symbol
9458 The international currency symbol applicable to the current locale. The
9459 first three characters contain the alphabetic international currency symbol
9460 in accordance with those specified in ISO 4217. The fourth character
9461 (immediately preceding the null character) is the character used to separate
9462 the international currency symbol from the monetary quantity.
9463 char int_frac_digits
9464 The number of fractional digits (those after the decimal-point) to be
9465 displayed in an internationally formatted monetary quantity.
9466 char int_p_cs_precedes
9467 Set to 1 or 0 if the int_curr_symbol respectively precedes or
9468 succeeds the value for a nonnegative internationally formatted monetary
9470 char int_n_cs_precedes
9471 Set to 1 or 0 if the int_curr_symbol respectively precedes or
9472 succeeds the value for a negative internationally formatted monetary
9474 char int_p_sep_by_space
9475 Set to a value indicating the separation of the int_curr_symbol, the
9476 sign string, and the value for a nonnegative internationally formatted
9478 [<a name="p226" href="#p226">page 226</a>] (<a href="#Contents">Contents</a>)
9480 char int_n_sep_by_space
9481 Set to a value indicating the separation of the int_curr_symbol, the
9482 sign string, and the value for a negative internationally formatted monetary
9484 char int_p_sign_posn
9485 Set to a value indicating the positioning of the positive_sign for a
9486 nonnegative internationally formatted monetary quantity.
9487 char int_n_sign_posn
9488 Set to a value indicating the positioning of the negative_sign for a
9489 negative internationally formatted monetary quantity.
9490 4 The elements of grouping and mon_grouping are interpreted according to the
9492 CHAR_MAX No further grouping is to be performed.
9493 0 The previous element is to be repeatedly used for the remainder of the
9495 other The integer value is the number of digits that compose the current group.
9496 The next element is examined to determine the size of the next group of
9497 digits before the current group.
9498 5 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space,
9499 and int_n_sep_by_space are interpreted according to the following:
9500 0 No space separates the currency symbol and value.
9501 1 If the currency symbol and sign string are adjacent, a space separates them from the
9502 value; otherwise, a space separates the currency symbol from the value.
9503 2 If the currency symbol and sign string are adjacent, a space separates them;
9504 otherwise, a space separates the sign string from the value.
9505 For int_p_sep_by_space and int_n_sep_by_space, the fourth character of
9506 int_curr_symbol is used instead of a space.
9507 6 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and
9508 int_n_sign_posn are interpreted according to the following:
9509 0 Parentheses surround the quantity and currency symbol.
9510 1 The sign string precedes the quantity and currency symbol.
9511 2 The sign string succeeds the quantity and currency symbol.
9512 3 The sign string immediately precedes the currency symbol.
9513 4 The sign string immediately succeeds the currency symbol.
9516 [<a name="p227" href="#p227">page 227</a>] (<a href="#Contents">Contents</a>)
9518 7 The implementation shall behave as if no library function calls the localeconv
9521 8 The localeconv function returns a pointer to the filled-in object. The structure
9522 pointed to by the return value shall not be modified by the program, but may be
9523 overwritten by a subsequent call to the localeconv function. In addition, calls to the
9524 setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may
9525 overwrite the contents of the structure.
9526 9 EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format
9527 monetary quantities.
9528 Local format International format
9530 Country Positive Negative Positive Negative
9532 Country1 1.234,56 mk -1.234,56 mk FIM 1.234,56 FIM -1.234,56
9533 Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234
9534 Country3 fl. 1.234,56 fl. -1.234,56 NLG 1.234,56 NLG -1.234,56
9535 Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C
9536 10 For these four countries, the respective values for the monetary members of the structure returned by
9537 localeconv could be:
9538 Country1 Country2 Country3 Country4
9540 mon_decimal_point "," "" "," "."
9541 mon_thousands_sep "." "." "." ","
9542 mon_grouping "\3" "\3" "\3" "\3"
9543 positive_sign "" "" "" ""
9544 negative_sign "-" "-" "-" "C"
9545 currency_symbol "mk" "L." "\u0192" "SFrs."
9547 p_cs_precedes 0 1 1 1
9548 n_cs_precedes 0 1 1 1
9549 p_sep_by_space 1 0 1 0
9550 n_sep_by_space 1 0 2 0
9553 int_curr_symbol "FIM " "ITL " "NLG " "CHF "
9554 int_frac_digits 2 0 2 2
9555 int_p_cs_precedes 1 1 1 1
9556 int_n_cs_precedes 1 1 1 1
9557 int_p_sep_by_space 1 1 1 1
9558 int_n_sep_by_space 2 1 2 1
9559 int_p_sign_posn 1 1 1 1
9560 int_n_sign_posn 4 1 4 2
9565 [<a name="p228" href="#p228">page 228</a>] (<a href="#Contents">Contents</a>)
9567 11 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
9568 affect the formatted value.
9571 p_cs_precedes p_sign_posn 0 1 2
9573 0 0 (<a href="#1.25">1.25</a>$) (<a href="#1.25">1.25</a> $) (<a href="#1.25">1.25</a>$)
9574 1 +1.25$ +1.25 $ + <a href="#1.25">1.25</a>$
9575 2 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +
9576 3 <a href="#1.25">1.25</a>+$ <a href="#1.25">1.25</a> +$ <a href="#1.25">1.25</a>+ $
9577 4 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +
9579 1 0 ($1.25) ($ <a href="#1.25">1.25</a>) ($1.25)
9580 1 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
9581 2 $1.25+ $ <a href="#1.25">1.25</a>+ $1.25 +
9582 3 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
9583 4 $+1.25 $+ <a href="#1.25">1.25</a> $ +1.25
9588 [<a name="p229" href="#p229">page 229</a>] (<a href="#Contents">Contents</a>)
9590 <a name="7.12" href="#7.12"><b> 7.12 Mathematics <math.h></b></a>
9591 1 The header <a href="#7.12"><math.h></a> declares two types and many mathematical functions and defines
9592 several macros. Most synopses specify a family of functions consisting of a principal
9593 function with one or more double parameters, a double return value, or both; and
9594 other functions with the same name but with f and l suffixes, which are corresponding
9595 functions with float and long double parameters, return values, or both.<sup><a href="#note223"><b>223)</b></a></sup>
9596 Integer arithmetic functions and conversion functions are discussed later.
9600 are floating types at least as wide as float and double, respectively, and such that
9601 double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
9602 float_t and double_t are float and double, respectively; if
9603 FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
9604 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
9605 otherwise implementation-defined.<sup><a href="#note224"><b>224)</b></a></sup>
9608 expands to a positive double constant expression, not necessarily representable as a
9612 are respectively float and long double analogs of HUGE_VAL.<sup><a href="#note225"><b>225)</b></a></sup>
9615 expands to a constant expression of type float representing positive or unsigned
9616 infinity, if available; else to a positive constant of type float that overflows at
9620 <sup><a name="note223" href="#note223"><b>223)</b></a></sup> Particularly on systems with wide expression evaluation, a <a href="#7.12"><math.h></a> function might pass arguments
9621 and return values in wider format than the synopsis prototype indicates.
9622 <sup><a name="note224" href="#note224"><b>224)</b></a></sup> The types float_t and double_t are intended to be the implementation's most efficient types at
9623 least as wide as float and double, respectively. For FLT_EVAL_METHOD equal 0, 1, or 2, the
9624 type float_t is the narrowest type used by the implementation to evaluate floating expressions.
9625 <sup><a name="note225" href="#note225"><b>225)</b></a></sup> HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
9626 supports infinities.
9628 [<a name="p230" href="#p230">page 230</a>] (<a href="#Contents">Contents</a>)
9630 translation time.<sup><a href="#note226"><b>226)</b></a></sup>
9633 is defined if and only if the implementation supports quiet NaNs for the float type. It
9634 expands to a constant expression of type float representing a quiet NaN.
9635 6 The number classification macros
9641 represent the mutually exclusive kinds of floating-point values. They expand to integer
9642 constant expressions with distinct values. Additional implementation-defined floating-
9643 point classifications, with macro definitions beginning with FP_ and an uppercase letter,
9644 may also be specified by the implementation.
9647 is optionally defined. If defined, it indicates that the fma function generally executes
9648 about as fast as, or faster than, a multiply and an add of double operands.<sup><a href="#note227"><b>227)</b></a></sup> The
9652 are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
9653 these macros expand to the integer constant 1.
9657 expand to integer constant expressions whose values are returned by ilogb(x) if x is
9658 zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
9659 -INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
9662 <sup><a name="note226" href="#note226"><b>226)</b></a></sup> In this case, using INFINITY will violate the constraint in <a href="#6.4.4">6.4.4</a> and thus require a diagnostic.
9663 <sup><a name="note227" href="#note227"><b>227)</b></a></sup> Typically, the FP_FAST_FMA macro is defined if and only if the fma function is implemented
9664 directly with a hardware multiply-add instruction. Software implementations are expected to be
9665 substantially slower.
9667 [<a name="p231" href="#p231">page 231</a>] (<a href="#Contents">Contents</a>)
9672 expand to the integer constants 1 and 2, respectively; the macro
9674 expands to an expression that has type int and the value MATH_ERRNO,
9675 MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is
9676 constant for the duration of the program. It is unspecified whether
9677 math_errhandling is a macro or an identifier with external linkage. If a macro
9678 definition is suppressed or a program defines an identifier with the name
9679 math_errhandling, the behavior is undefined. If the expression
9680 math_errhandling & MATH_ERREXCEPT can be nonzero, the implementation
9681 shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in
9682 <a href="#7.6"><fenv.h></a>.
9683 <a name="7.12.1" href="#7.12.1"><b> 7.12.1 Treatment of error conditions</b></a>
9684 1 The behavior of each of the functions in <a href="#7.12"><math.h></a> is specified for all representable
9685 values of its input arguments, except where stated otherwise. Each function shall execute
9686 as if it were a single operation without raising SIGFPE and without generating any of the
9687 floating-point exceptions ''invalid'', ''divide-by-zero'', or ''overflow'' except to reflect
9688 the result of the function.
9689 2 For all functions, a domain error occurs if an input argument is outside the domain over
9690 which the mathematical function is defined. The description of each function lists any
9691 required domain errors; an implementation may define additional domain errors, provided
9692 that such errors are consistent with the mathematical definition of the function.<sup><a href="#note228"><b>228)</b></a></sup> On a
9693 domain error, the function returns an implementation-defined value; if the integer
9694 expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
9695 errno acquires the value EDOM; if the integer expression math_errhandling &
9696 MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised.
9697 3 Similarly, a pole error (also known as a singularity or infinitary) occurs if the
9698 mathematical function has an exact infinite result as the finite input argument(s) are
9699 approached in the limit (for example, log(0.0)). The description of each function lists
9700 any required pole errors; an implementation may define additional pole errors, provided
9701 that such errors are consistent with the mathematical definition of the function. On a pole
9702 error, the function returns an implementation-defined value; if the integer expression
9705 <sup><a name="note228" href="#note228"><b>228)</b></a></sup> In an implementation that supports infinities, this allows an infinity as an argument to be a domain
9706 error if the mathematical domain of the function does not include the infinity.
9708 [<a name="p232" href="#p232">page 232</a>] (<a href="#Contents">Contents</a>)
9710 math_errhandling & MATH_ERRNO is nonzero, the integer expression errno
9711 acquires the value ERANGE; if the integer expression math_errhandling &
9712 MATH_ERREXCEPT is nonzero, the ''divide-by-zero'' floating-point exception is raised.
9713 4 Likewise, a range error occurs if the mathematical result of the function cannot be
9714 represented in an object of the specified type, due to extreme magnitude.
9715 5 A floating result overflows if the magnitude of the mathematical result is finite but so
9716 large that the mathematical result cannot be represented without extraordinary roundoff
9717 error in an object of the specified type. If a floating result overflows and default rounding
9718 is in effect, then the function returns the value of the macro HUGE_VAL, HUGE_VALF, or *
9719 HUGE_VALL according to the return type, with the same sign as the correct value of the
9720 function; if the integer expression math_errhandling & MATH_ERRNO is nonzero,
9721 the integer expression errno acquires the value ERANGE; if the integer expression
9722 math_errhandling & MATH_ERREXCEPT is nonzero, the ''overflow'' floating-
9723 point exception is raised.
9724 6 The result underflows if the magnitude of the mathematical result is so small that the
9725 mathematical result cannot be represented, without extraordinary roundoff error, in an
9726 object of the specified type.<sup><a href="#note229"><b>229)</b></a></sup> If the result underflows, the function returns an
9727 implementation-defined value whose magnitude is no greater than the smallest
9728 normalized positive number in the specified type; if the integer expression
9729 math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the
9730 value ERANGE is implementation-defined; if the integer expression
9731 math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow''
9732 floating-point exception is raised is implementation-defined.
9733 7 If a domain, pole, or range error occurs and the integer expression
9734 math_errhandling & MATH_ERRNO is zero,<sup><a href="#note230"><b>230)</b></a></sup> then errno shall either be set to
9735 the value corresponding to the error or left unmodified. If no such error occurs, errno
9736 shall be left unmodified regardless of the setting of math_errhandling.
9741 <sup><a name="note229" href="#note229"><b>229)</b></a></sup> The term underflow here is intended to encompass both ''gradual underflow'' as in IEC 60559 and
9742 also ''flush-to-zero'' underflow.
9743 <sup><a name="note230" href="#note230"><b>230)</b></a></sup> Math errors are being indicated by the floating-point exception flags rather than by errno.
9745 [<a name="p233" href="#p233">page 233</a>] (<a href="#Contents">Contents</a>)
9747 <a name="7.12.2" href="#7.12.2"><b> 7.12.2 The FP_CONTRACT pragma</b></a>
9749 1 #include <a href="#7.12"><math.h></a>
9750 #pragma STDC FP_CONTRACT on-off-switch
9752 2 The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
9753 state is ''off'') the implementation to contract expressions (<a href="#6.5">6.5</a>). Each pragma can occur
9754 either outside external declarations or preceding all explicit declarations and statements
9755 inside a compound statement. When outside external declarations, the pragma takes
9756 effect from its occurrence until another FP_CONTRACT pragma is encountered, or until
9757 the end of the translation unit. When inside a compound statement, the pragma takes
9758 effect from its occurrence until another FP_CONTRACT pragma is encountered
9759 (including within a nested compound statement), or until the end of the compound
9760 statement; at the end of a compound statement the state for the pragma is restored to its
9761 condition just before the compound statement. If this pragma is used in any other
9762 context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
9763 implementation-defined.
9764 <a name="7.12.3" href="#7.12.3"><b> 7.12.3 Classification macros</b></a>
9765 1 In the synopses in this subclause, real-floating indicates that the argument shall be an
9766 expression of real floating type.
9767 <a name="7.12.3.1" href="#7.12.3.1"><b> 7.12.3.1 The fpclassify macro</b></a>
9769 1 #include <a href="#7.12"><math.h></a>
9770 int fpclassify(real-floating x);
9772 2 The fpclassify macro classifies its argument value as NaN, infinite, normal,
9773 subnormal, zero, or into another implementation-defined category. First, an argument
9774 represented in a format wider than its semantic type is converted to its semantic type.
9775 Then classification is based on the type of the argument.<sup><a href="#note231"><b>231)</b></a></sup>
9777 3 The fpclassify macro returns the value of the number classification macro
9778 appropriate to the value of its argument. *
9781 <sup><a name="note231" href="#note231"><b>231)</b></a></sup> Since an expression can be evaluated with more range and precision than its type has, it is important to
9782 know the type that classification is based on. For example, a normal long double value might
9783 become subnormal when converted to double, and zero when converted to float.
9785 [<a name="p234" href="#p234">page 234</a>] (<a href="#Contents">Contents</a>)
9787 <a name="7.12.3.2" href="#7.12.3.2"><b> 7.12.3.2 The isfinite macro</b></a>
9789 1 #include <a href="#7.12"><math.h></a>
9790 int isfinite(real-floating x);
9792 2 The isfinite macro determines whether its argument has a finite value (zero,
9793 subnormal, or normal, and not infinite or NaN). First, an argument represented in a
9794 format wider than its semantic type is converted to its semantic type. Then determination
9795 is based on the type of the argument.
9797 3 The isfinite macro returns a nonzero value if and only if its argument has a finite
9799 <a name="7.12.3.3" href="#7.12.3.3"><b> 7.12.3.3 The isinf macro</b></a>
9801 1 #include <a href="#7.12"><math.h></a>
9802 int isinf(real-floating x);
9804 2 The isinf macro determines whether its argument value is an infinity (positive or
9805 negative). First, an argument represented in a format wider than its semantic type is
9806 converted to its semantic type. Then determination is based on the type of the argument.
9808 3 The isinf macro returns a nonzero value if and only if its argument has an infinite
9810 <a name="7.12.3.4" href="#7.12.3.4"><b> 7.12.3.4 The isnan macro</b></a>
9812 1 #include <a href="#7.12"><math.h></a>
9813 int isnan(real-floating x);
9815 2 The isnan macro determines whether its argument value is a NaN. First, an argument
9816 represented in a format wider than its semantic type is converted to its semantic type.
9817 Then determination is based on the type of the argument.<sup><a href="#note232"><b>232)</b></a></sup>
9820 <sup><a name="note232" href="#note232"><b>232)</b></a></sup> For the isnan macro, the type for determination does not matter unless the implementation supports
9821 NaNs in the evaluation type but not in the semantic type.
9823 [<a name="p235" href="#p235">page 235</a>] (<a href="#Contents">Contents</a>)
9826 3 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
9827 <a name="7.12.3.5" href="#7.12.3.5"><b> 7.12.3.5 The isnormal macro</b></a>
9829 1 #include <a href="#7.12"><math.h></a>
9830 int isnormal(real-floating x);
9832 2 The isnormal macro determines whether its argument value is normal (neither zero,
9833 subnormal, infinite, nor NaN). First, an argument represented in a format wider than its
9834 semantic type is converted to its semantic type. Then determination is based on the type
9837 3 The isnormal macro returns a nonzero value if and only if its argument has a normal
9839 <a name="7.12.3.6" href="#7.12.3.6"><b> 7.12.3.6 The signbit macro</b></a>
9841 1 #include <a href="#7.12"><math.h></a>
9842 int signbit(real-floating x);
9844 2 The signbit macro determines whether the sign of its argument value is negative.<sup><a href="#note233"><b>233)</b></a></sup>
9846 3 The signbit macro returns a nonzero value if and only if the sign of its argument value
9852 <sup><a name="note233" href="#note233"><b>233)</b></a></sup> The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is
9853 unsigned, it is treated as positive.
9855 [<a name="p236" href="#p236">page 236</a>] (<a href="#Contents">Contents</a>)
9857 <a name="7.12.4" href="#7.12.4"><b> 7.12.4 Trigonometric functions</b></a>
9858 <a name="7.12.4.1" href="#7.12.4.1"><b> 7.12.4.1 The acos functions</b></a>
9860 1 #include <a href="#7.12"><math.h></a>
9861 double acos(double x);
9862 float acosf(float x);
9863 long double acosl(long double x);
9865 2 The acos functions compute the principal value of the arc cosine of x. A domain error
9866 occurs for arguments not in the interval [-1, +1].
9868 3 The acos functions return arccos x in the interval [0, pi ] radians.
9869 <a name="7.12.4.2" href="#7.12.4.2"><b> 7.12.4.2 The asin functions</b></a>
9871 1 #include <a href="#7.12"><math.h></a>
9872 double asin(double x);
9873 float asinf(float x);
9874 long double asinl(long double x);
9876 2 The asin functions compute the principal value of the arc sine of x. A domain error
9877 occurs for arguments not in the interval [-1, +1].
9879 3 The asin functions return arcsin x in the interval [-pi /2, +pi /2] radians.
9880 <a name="7.12.4.3" href="#7.12.4.3"><b> 7.12.4.3 The atan functions</b></a>
9882 1 #include <a href="#7.12"><math.h></a>
9883 double atan(double x);
9884 float atanf(float x);
9885 long double atanl(long double x);
9887 2 The atan functions compute the principal value of the arc tangent of x.
9892 [<a name="p237" href="#p237">page 237</a>] (<a href="#Contents">Contents</a>)
9895 3 The atan functions return arctan x in the interval [-pi /2, +pi /2] radians.
9896 <a name="7.12.4.4" href="#7.12.4.4"><b> 7.12.4.4 The atan2 functions</b></a>
9898 1 #include <a href="#7.12"><math.h></a>
9899 double atan2(double y, double x);
9900 float atan2f(float y, float x);
9901 long double atan2l(long double y, long double x);
9903 2 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
9904 arguments to determine the quadrant of the return value. A domain error may occur if
9905 both arguments are zero.
9907 3 The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
9908 <a name="7.12.4.5" href="#7.12.4.5"><b> 7.12.4.5 The cos functions</b></a>
9910 1 #include <a href="#7.12"><math.h></a>
9911 double cos(double x);
9912 float cosf(float x);
9913 long double cosl(long double x);
9915 2 The cos functions compute the cosine of x (measured in radians).
9917 3 The cos functions return cos x.
9918 <a name="7.12.4.6" href="#7.12.4.6"><b> 7.12.4.6 The sin functions</b></a>
9920 1 #include <a href="#7.12"><math.h></a>
9921 double sin(double x);
9922 float sinf(float x);
9923 long double sinl(long double x);
9925 2 The sin functions compute the sine of x (measured in radians).
9929 [<a name="p238" href="#p238">page 238</a>] (<a href="#Contents">Contents</a>)
9932 3 The sin functions return sin x.
9933 <a name="7.12.4.7" href="#7.12.4.7"><b> 7.12.4.7 The tan functions</b></a>
9935 1 #include <a href="#7.12"><math.h></a>
9936 double tan(double x);
9937 float tanf(float x);
9938 long double tanl(long double x);
9940 2 The tan functions return the tangent of x (measured in radians).
9942 3 The tan functions return tan x.
9943 <a name="7.12.5" href="#7.12.5"><b> 7.12.5 Hyperbolic functions</b></a>
9944 <a name="7.12.5.1" href="#7.12.5.1"><b> 7.12.5.1 The acosh functions</b></a>
9946 1 #include <a href="#7.12"><math.h></a>
9947 double acosh(double x);
9948 float acoshf(float x);
9949 long double acoshl(long double x);
9951 2 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
9952 error occurs for arguments less than 1.
9954 3 The acosh functions return arcosh x in the interval [0, +(inf)].
9955 <a name="7.12.5.2" href="#7.12.5.2"><b> 7.12.5.2 The asinh functions</b></a>
9957 1 #include <a href="#7.12"><math.h></a>
9958 double asinh(double x);
9959 float asinhf(float x);
9960 long double asinhl(long double x);
9962 2 The asinh functions compute the arc hyperbolic sine of x.
9965 [<a name="p239" href="#p239">page 239</a>] (<a href="#Contents">Contents</a>)
9968 3 The asinh functions return arsinh x.
9969 <a name="7.12.5.3" href="#7.12.5.3"><b> 7.12.5.3 The atanh functions</b></a>
9971 1 #include <a href="#7.12"><math.h></a>
9972 double atanh(double x);
9973 float atanhf(float x);
9974 long double atanhl(long double x);
9976 2 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
9977 for arguments not in the interval [-1, +1]. A pole error may occur if the argument equals
9980 3 The atanh functions return artanh x.
9981 <a name="7.12.5.4" href="#7.12.5.4"><b> 7.12.5.4 The cosh functions</b></a>
9983 1 #include <a href="#7.12"><math.h></a>
9984 double cosh(double x);
9985 float coshf(float x);
9986 long double coshl(long double x);
9988 2 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
9989 magnitude of x is too large.
9991 3 The cosh functions return cosh x.
9992 <a name="7.12.5.5" href="#7.12.5.5"><b> 7.12.5.5 The sinh functions</b></a>
9994 1 #include <a href="#7.12"><math.h></a>
9995 double sinh(double x);
9996 float sinhf(float x);
9997 long double sinhl(long double x);
9999 2 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
10000 magnitude of x is too large.
10001 [<a name="p240" href="#p240">page 240</a>] (<a href="#Contents">Contents</a>)
10004 3 The sinh functions return sinh x.
10005 <a name="7.12.5.6" href="#7.12.5.6"><b> 7.12.5.6 The tanh functions</b></a>
10007 1 #include <a href="#7.12"><math.h></a>
10008 double tanh(double x);
10009 float tanhf(float x);
10010 long double tanhl(long double x);
10011 <b> Description</b>
10012 2 The tanh functions compute the hyperbolic tangent of x.
10014 3 The tanh functions return tanh x.
10015 <a name="7.12.6" href="#7.12.6"><b> 7.12.6 Exponential and logarithmic functions</b></a>
10016 <a name="7.12.6.1" href="#7.12.6.1"><b> 7.12.6.1 The exp functions</b></a>
10018 1 #include <a href="#7.12"><math.h></a>
10019 double exp(double x);
10020 float expf(float x);
10021 long double expl(long double x);
10022 <b> Description</b>
10023 2 The exp functions compute the base-e exponential of x. A range error occurs if the
10024 magnitude of x is too large.
10026 3 The exp functions return ex .
10027 <a name="7.12.6.2" href="#7.12.6.2"><b> 7.12.6.2 The exp2 functions</b></a>
10029 1 #include <a href="#7.12"><math.h></a>
10030 double exp2(double x);
10031 float exp2f(float x);
10032 long double exp2l(long double x);
10033 <b> Description</b>
10034 2 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
10035 magnitude of x is too large.
10037 [<a name="p241" href="#p241">page 241</a>] (<a href="#Contents">Contents</a>)
10040 3 The exp2 functions return 2x .
10041 <a name="7.12.6.3" href="#7.12.6.3"><b> 7.12.6.3 The expm1 functions</b></a>
10043 1 #include <a href="#7.12"><math.h></a>
10044 double expm1(double x);
10045 float expm1f(float x);
10046 long double expm1l(long double x);
10047 <b> Description</b>
10048 2 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
10049 error occurs if x is too large.<sup><a href="#note234"><b>234)</b></a></sup>
10051 3 The expm1 functions return ex - 1.
10052 <a name="7.12.6.4" href="#7.12.6.4"><b> 7.12.6.4 The frexp functions</b></a>
10054 1 #include <a href="#7.12"><math.h></a>
10055 double frexp(double value, int *exp);
10056 float frexpf(float value, int *exp);
10057 long double frexpl(long double value, int *exp);
10058 <b> Description</b>
10059 2 The frexp functions break a floating-point number into a normalized fraction and an
10060 integral power of 2. They store the integer in the int object pointed to by exp.
10062 3 If value is not a floating-point number or if the integral power of 2 is outside the range
10063 of int, the results are unspecified. Otherwise, the frexp functions return the value x,
10064 such that x has a magnitude in the interval [1/2, 1) or zero, and value equals x x 2*exp .
10065 If value is zero, both parts of the result are zero.
10070 <sup><a name="note234" href="#note234"><b>234)</b></a></sup> For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1.
10072 [<a name="p242" href="#p242">page 242</a>] (<a href="#Contents">Contents</a>)
10074 <a name="7.12.6.5" href="#7.12.6.5"><b> 7.12.6.5 The ilogb functions</b></a>
10076 1 #include <a href="#7.12"><math.h></a>
10077 int ilogb(double x);
10078 int ilogbf(float x);
10079 int ilogbl(long double x);
10080 <b> Description</b>
10081 2 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
10082 compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
10083 a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
10084 the corresponding logb function and casting the returned value to type int. A domain
10085 error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
10086 the range of the return type, the numeric result is unspecified.
10088 3 The ilogb functions return the exponent of x as a signed int value.
10089 Forward references: the logb functions (<a href="#7.12.6.11">7.12.6.11</a>).
10090 <a name="7.12.6.6" href="#7.12.6.6"><b> 7.12.6.6 The ldexp functions</b></a>
10092 1 #include <a href="#7.12"><math.h></a>
10093 double ldexp(double x, int exp);
10094 float ldexpf(float x, int exp);
10095 long double ldexpl(long double x, int exp);
10096 <b> Description</b>
10097 2 The ldexp functions multiply a floating-point number by an integral power of 2. A
10098 range error may occur.
10100 3 The ldexp functions return x x 2exp .
10101 <a name="7.12.6.7" href="#7.12.6.7"><b> 7.12.6.7 The log functions</b></a>
10103 1 #include <a href="#7.12"><math.h></a>
10104 double log(double x);
10105 float logf(float x);
10106 long double logl(long double x);
10110 [<a name="p243" href="#p243">page 243</a>] (<a href="#Contents">Contents</a>)
10112 <b> Description</b>
10113 2 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
10114 the argument is negative. A pole error may occur if the argument is zero.
10116 3 The log functions return loge x.
10117 <a name="7.12.6.8" href="#7.12.6.8"><b> 7.12.6.8 The log10 functions</b></a>
10119 1 #include <a href="#7.12"><math.h></a>
10120 double log10(double x);
10121 float log10f(float x);
10122 long double log10l(long double x);
10123 <b> Description</b>
10124 2 The log10 functions compute the base-10 (common) logarithm of x. A domain error
10125 occurs if the argument is negative. A pole error may occur if the argument is zero.
10127 3 The log10 functions return log10 x.
10128 <a name="7.12.6.9" href="#7.12.6.9"><b> 7.12.6.9 The log1p functions</b></a>
10130 1 #include <a href="#7.12"><math.h></a>
10131 double log1p(double x);
10132 float log1pf(float x);
10133 long double log1pl(long double x);
10134 <b> Description</b>
10135 2 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.<sup><a href="#note235"><b>235)</b></a></sup>
10136 A domain error occurs if the argument is less than -1. A pole error may occur if the
10137 argument equals -1.
10139 3 The log1p functions return loge (1 + x).
10144 <sup><a name="note235" href="#note235"><b>235)</b></a></sup> For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x).
10146 [<a name="p244" href="#p244">page 244</a>] (<a href="#Contents">Contents</a>)
10148 <a name="7.12.6.10" href="#7.12.6.10"><b> 7.12.6.10 The log2 functions</b></a>
10150 1 #include <a href="#7.12"><math.h></a>
10151 double log2(double x);
10152 float log2f(float x);
10153 long double log2l(long double x);
10154 <b> Description</b>
10155 2 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
10156 argument is less than zero. A pole error may occur if the argument is zero.
10158 3 The log2 functions return log2 x.
10159 <a name="7.12.6.11" href="#7.12.6.11"><b> 7.12.6.11 The logb functions</b></a>
10161 1 #include <a href="#7.12"><math.h></a>
10162 double logb(double x);
10163 float logbf(float x);
10164 long double logbl(long double x);
10165 <b> Description</b>
10166 2 The logb functions extract the exponent of x, as a signed integer value in floating-point
10167 format. If x is subnormal it is treated as though it were normalized; thus, for positive
10169 1 <= x x FLT_RADIX-logb(x) < FLT_RADIX
10170 A domain error or pole error may occur if the argument is zero.
10172 3 The logb functions return the signed exponent of x.
10173 <a name="7.12.6.12" href="#7.12.6.12"><b> 7.12.6.12 The modf functions</b></a>
10175 1 #include <a href="#7.12"><math.h></a>
10176 double modf(double value, double *iptr);
10177 float modff(float value, float *iptr);
10178 long double modfl(long double value, long double *iptr);
10179 <b> Description</b>
10180 2 The modf functions break the argument value into integral and fractional parts, each of
10181 which has the same type and sign as the argument. They store the integral part (in
10182 [<a name="p245" href="#p245">page 245</a>] (<a href="#Contents">Contents</a>)
10184 floating-point format) in the object pointed to by iptr.
10186 3 The modf functions return the signed fractional part of value.
10187 <a name="7.12.6.13" href="#7.12.6.13"><b> 7.12.6.13 The scalbn and scalbln functions</b></a>
10189 1 #include <a href="#7.12"><math.h></a>
10190 double scalbn(double x, int n);
10191 float scalbnf(float x, int n);
10192 long double scalbnl(long double x, int n);
10193 double scalbln(double x, long int n);
10194 float scalblnf(float x, long int n);
10195 long double scalblnl(long double x, long int n);
10196 <b> Description</b>
10197 2 The scalbn and scalbln functions compute x x FLT_RADIXn efficiently, not
10198 normally by computing FLT_RADIXn explicitly. A range error may occur.
10200 3 The scalbn and scalbln functions return x x FLT_RADIXn .
10201 <a name="7.12.7" href="#7.12.7"><b> 7.12.7 Power and absolute-value functions</b></a>
10202 <a name="7.12.7.1" href="#7.12.7.1"><b> 7.12.7.1 The cbrt functions</b></a>
10204 1 #include <a href="#7.12"><math.h></a>
10205 double cbrt(double x);
10206 float cbrtf(float x);
10207 long double cbrtl(long double x);
10208 <b> Description</b>
10209 2 The cbrt functions compute the real cube root of x.
10211 3 The cbrt functions return x1/3 .
10216 [<a name="p246" href="#p246">page 246</a>] (<a href="#Contents">Contents</a>)
10218 <a name="7.12.7.2" href="#7.12.7.2"><b> 7.12.7.2 The fabs functions</b></a>
10220 1 #include <a href="#7.12"><math.h></a>
10221 double fabs(double x);
10222 float fabsf(float x);
10223 long double fabsl(long double x);
10224 <b> Description</b>
10225 2 The fabs functions compute the absolute value of a floating-point number x.
10227 3 The fabs functions return | x |.
10228 <a name="7.12.7.3" href="#7.12.7.3"><b> 7.12.7.3 The hypot functions</b></a>
10230 1 #include <a href="#7.12"><math.h></a>
10231 double hypot(double x, double y);
10232 float hypotf(float x, float y);
10233 long double hypotl(long double x, long double y);
10234 <b> Description</b>
10235 2 The hypot functions compute the square root of the sum of the squares of x and y,
10236 without undue overflow or underflow. A range error may occur.
10238 4 The hypot functions return sqrt:x2 + y2 .
10241 <a name="7.12.7.4" href="#7.12.7.4"><b> 7.12.7.4 The pow functions</b></a>
10243 1 #include <a href="#7.12"><math.h></a>
10244 double pow(double x, double y);
10245 float powf(float x, float y);
10246 long double powl(long double x, long double y);
10247 <b> Description</b>
10248 2 The pow functions compute x raised to the power y. A domain error occurs if x is finite
10249 and negative and y is finite and not an integer value. A range error may occur. A domain
10250 error may occur if x is zero and y is zero. A domain error or pole error may occur if x is
10251 zero and y is less than zero.
10256 [<a name="p247" href="#p247">page 247</a>] (<a href="#Contents">Contents</a>)
10259 3 The pow functions return xy .
10260 <a name="7.12.7.5" href="#7.12.7.5"><b> 7.12.7.5 The sqrt functions</b></a>
10262 1 #include <a href="#7.12"><math.h></a>
10263 double sqrt(double x);
10264 float sqrtf(float x);
10265 long double sqrtl(long double x);
10266 <b> Description</b>
10267 2 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
10268 the argument is less than zero.
10270 3 The sqrt functions return sqrt:x.
10273 <a name="7.12.8" href="#7.12.8"><b> 7.12.8 Error and gamma functions</b></a>
10274 <a name="7.12.8.1" href="#7.12.8.1"><b> 7.12.8.1 The erf functions</b></a>
10276 1 #include <a href="#7.12"><math.h></a>
10277 double erf(double x);
10278 float erff(float x);
10279 long double erfl(long double x);
10280 <b> Description</b>
10281 2 The erf functions compute the error function of x.
10286 The erf functions return erf x =
10291 <a name="7.12.8.2" href="#7.12.8.2"><b> 7.12.8.2 The erfc functions</b></a>
10293 1 #include <a href="#7.12"><math.h></a>
10294 double erfc(double x);
10295 float erfcf(float x);
10296 long double erfcl(long double x);
10297 <b> Description</b>
10298 2 The erfc functions compute the complementary error function of x. A range error
10299 occurs if x is too large.
10300 [<a name="p248" href="#p248">page 248</a>] (<a href="#Contents">Contents</a>)
10306 The erfc functions return erfc x = 1 - erf x =
10311 <a name="7.12.8.3" href="#7.12.8.3"><b> 7.12.8.3 The lgamma functions</b></a>
10313 1 #include <a href="#7.12"><math.h></a>
10314 double lgamma(double x);
10315 float lgammaf(float x);
10316 long double lgammal(long double x);
10317 <b> Description</b>
10318 2 The lgamma functions compute the natural logarithm of the absolute value of gamma of
10319 x. A range error occurs if x is too large. A pole error may occur if x is a negative integer
10322 3 The lgamma functions return loge | (Gamma)(x) |.
10323 <a name="7.12.8.4" href="#7.12.8.4"><b> 7.12.8.4 The tgamma functions</b></a>
10325 1 #include <a href="#7.12"><math.h></a>
10326 double tgamma(double x);
10327 float tgammaf(float x);
10328 long double tgammal(long double x);
10329 <b> Description</b>
10330 2 The tgamma functions compute the gamma function of x. A domain error or pole error
10331 may occur if x is a negative integer or zero. A range error occurs if the magnitude of x is
10332 too large and may occur if the magnitude of x is too small.
10334 3 The tgamma functions return (Gamma)(x).
10339 [<a name="p249" href="#p249">page 249</a>] (<a href="#Contents">Contents</a>)
10341 <a name="7.12.9" href="#7.12.9"><b> 7.12.9 Nearest integer functions</b></a>
10342 <a name="7.12.9.1" href="#7.12.9.1"><b> 7.12.9.1 The ceil functions</b></a>
10344 1 #include <a href="#7.12"><math.h></a>
10345 double ceil(double x);
10346 float ceilf(float x);
10347 long double ceill(long double x);
10348 <b> Description</b>
10349 2 The ceil functions compute the smallest integer value not less than x.
10351 3 The ceil functions return [^x^], expressed as a floating-point number.
10352 <a name="7.12.9.2" href="#7.12.9.2"><b> 7.12.9.2 The floor functions</b></a>
10354 1 #include <a href="#7.12"><math.h></a>
10355 double floor(double x);
10356 float floorf(float x);
10357 long double floorl(long double x);
10358 <b> Description</b>
10359 2 The floor functions compute the largest integer value not greater than x.
10361 3 The floor functions return [_x_], expressed as a floating-point number.
10362 <a name="7.12.9.3" href="#7.12.9.3"><b> 7.12.9.3 The nearbyint functions</b></a>
10364 1 #include <a href="#7.12"><math.h></a>
10365 double nearbyint(double x);
10366 float nearbyintf(float x);
10367 long double nearbyintl(long double x);
10368 <b> Description</b>
10369 2 The nearbyint functions round their argument to an integer value in floating-point
10370 format, using the current rounding direction and without raising the ''inexact'' floating-
10376 [<a name="p250" href="#p250">page 250</a>] (<a href="#Contents">Contents</a>)
10379 3 The nearbyint functions return the rounded integer value.
10380 <a name="7.12.9.4" href="#7.12.9.4"><b> 7.12.9.4 The rint functions</b></a>
10382 1 #include <a href="#7.12"><math.h></a>
10383 double rint(double x);
10384 float rintf(float x);
10385 long double rintl(long double x);
10386 <b> Description</b>
10387 2 The rint functions differ from the nearbyint functions (<a href="#7.12.9.3">7.12.9.3</a>) only in that the
10388 rint functions may raise the ''inexact'' floating-point exception if the result differs in
10389 value from the argument.
10391 3 The rint functions return the rounded integer value.
10392 <a name="7.12.9.5" href="#7.12.9.5"><b> 7.12.9.5 The lrint and llrint functions</b></a>
10394 1 #include <a href="#7.12"><math.h></a>
10395 long int lrint(double x);
10396 long int lrintf(float x);
10397 long int lrintl(long double x);
10398 long long int llrint(double x);
10399 long long int llrintf(float x);
10400 long long int llrintl(long double x);
10401 <b> Description</b>
10402 2 The lrint and llrint functions round their argument to the nearest integer value,
10403 rounding according to the current rounding direction. If the rounded value is outside the
10404 range of the return type, the numeric result is unspecified and a domain error or range
10407 3 The lrint and llrint functions return the rounded integer value.
10412 [<a name="p251" href="#p251">page 251</a>] (<a href="#Contents">Contents</a>)
10414 <a name="7.12.9.6" href="#7.12.9.6"><b> 7.12.9.6 The round functions</b></a>
10416 1 #include <a href="#7.12"><math.h></a>
10417 double round(double x);
10418 float roundf(float x);
10419 long double roundl(long double x);
10420 <b> Description</b>
10421 2 The round functions round their argument to the nearest integer value in floating-point
10422 format, rounding halfway cases away from zero, regardless of the current rounding
10425 3 The round functions return the rounded integer value.
10426 <a name="7.12.9.7" href="#7.12.9.7"><b> 7.12.9.7 The lround and llround functions</b></a>
10428 1 #include <a href="#7.12"><math.h></a>
10429 long int lround(double x);
10430 long int lroundf(float x);
10431 long int lroundl(long double x);
10432 long long int llround(double x);
10433 long long int llroundf(float x);
10434 long long int llroundl(long double x);
10435 <b> Description</b>
10436 2 The lround and llround functions round their argument to the nearest integer value,
10437 rounding halfway cases away from zero, regardless of the current rounding direction. If
10438 the rounded value is outside the range of the return type, the numeric result is unspecified
10439 and a domain error or range error may occur.
10441 3 The lround and llround functions return the rounded integer value.
10442 <a name="7.12.9.8" href="#7.12.9.8"><b> 7.12.9.8 The trunc functions</b></a>
10444 1 #include <a href="#7.12"><math.h></a>
10445 double trunc(double x);
10446 float truncf(float x);
10447 long double truncl(long double x);
10450 [<a name="p252" href="#p252">page 252</a>] (<a href="#Contents">Contents</a>)
10452 <b> Description</b>
10453 2 The trunc functions round their argument to the integer value, in floating format,
10454 nearest to but no larger in magnitude than the argument.
10456 3 The trunc functions return the truncated integer value.
10457 <a name="7.12.10" href="#7.12.10"><b> 7.12.10 Remainder functions</b></a>
10458 <a name="7.12.10.1" href="#7.12.10.1"><b> 7.12.10.1 The fmod functions</b></a>
10460 1 #include <a href="#7.12"><math.h></a>
10461 double fmod(double x, double y);
10462 float fmodf(float x, float y);
10463 long double fmodl(long double x, long double y);
10464 <b> Description</b>
10465 2 The fmod functions compute the floating-point remainder of x/y.
10467 3 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
10468 the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
10469 whether a domain error occurs or the fmod functions return zero is implementation-
10471 <a name="7.12.10.2" href="#7.12.10.2"><b> 7.12.10.2 The remainder functions</b></a>
10473 1 #include <a href="#7.12"><math.h></a>
10474 double remainder(double x, double y);
10475 float remainderf(float x, float y);
10476 long double remainderl(long double x, long double y);
10477 <b> Description</b>
10478 2 The remainder functions compute the remainder x REM y required by IEC 60559.<sup><a href="#note236"><b>236)</b></a></sup>
10483 <sup><a name="note236" href="#note236"><b>236)</b></a></sup> ''When y != 0, the remainder r = x REM y is defined regardless of the rounding mode by the
10484 mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever
10485 | n - x/y | = 1/2, then n is even. If r = 0, its sign shall be that of x.'' This definition is applicable for *
10486 all implementations.
10488 [<a name="p253" href="#p253">page 253</a>] (<a href="#Contents">Contents</a>)
10491 3 The remainder functions return x REM y. If y is zero, whether a domain error occurs
10492 or the functions return zero is implementation defined.
10493 <a name="7.12.10.3" href="#7.12.10.3"><b> 7.12.10.3 The remquo functions</b></a>
10495 1 #include <a href="#7.12"><math.h></a>
10496 double remquo(double x, double y, int *quo);
10497 float remquof(float x, float y, int *quo);
10498 long double remquol(long double x, long double y,
10500 <b> Description</b>
10501 2 The remquo functions compute the same remainder as the remainder functions. In
10502 the object pointed to by quo they store a value whose sign is the sign of x/y and whose
10503 magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where
10504 n is an implementation-defined integer greater than or equal to 3.
10506 3 The remquo functions return x REM y. If y is zero, the value stored in the object
10507 pointed to by quo is unspecified and whether a domain error occurs or the functions
10508 return zero is implementation defined.
10509 <a name="7.12.11" href="#7.12.11"><b> 7.12.11 Manipulation functions</b></a>
10510 <a name="7.12.11.1" href="#7.12.11.1"><b> 7.12.11.1 The copysign functions</b></a>
10512 1 #include <a href="#7.12"><math.h></a>
10513 double copysign(double x, double y);
10514 float copysignf(float x, float y);
10515 long double copysignl(long double x, long double y);
10516 <b> Description</b>
10517 2 The copysign functions produce a value with the magnitude of x and the sign of y.
10518 They produce a NaN (with the sign of y) if x is a NaN. On implementations that
10519 represent a signed zero but do not treat negative zero consistently in arithmetic
10520 operations, the copysign functions regard the sign of zero as positive.
10522 3 The copysign functions return a value with the magnitude of x and the sign of y.
10526 [<a name="p254" href="#p254">page 254</a>] (<a href="#Contents">Contents</a>)
10528 <a name="7.12.11.2" href="#7.12.11.2"><b> 7.12.11.2 The nan functions</b></a>
10530 1 #include <a href="#7.12"><math.h></a>
10531 double nan(const char *tagp);
10532 float nanf(const char *tagp);
10533 long double nanl(const char *tagp);
10534 <b> Description</b>
10535 2 The call nan("n-char-sequence") is equivalent to strtod("NAN(n-char-
10536 sequence)", (char**) NULL); the call nan("") is equivalent to
10537 strtod("NAN()", (char**) NULL). If tagp does not point to an n-char
10538 sequence or an empty string, the call is equivalent to strtod("NAN", (char**)
10539 NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof
10542 3 The nan functions return a quiet NaN, if available, with content indicated through tagp.
10543 If the implementation does not support quiet NaNs, the functions return zero.
10544 Forward references: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
10545 <a name="7.12.11.3" href="#7.12.11.3"><b> 7.12.11.3 The nextafter functions</b></a>
10547 1 #include <a href="#7.12"><math.h></a>
10548 double nextafter(double x, double y);
10549 float nextafterf(float x, float y);
10550 long double nextafterl(long double x, long double y);
10551 <b> Description</b>
10552 2 The nextafter functions determine the next representable value, in the type of the
10553 function, after x in the direction of y, where x and y are first converted to the type of the
10554 function.<sup><a href="#note237"><b>237)</b></a></sup> The nextafter functions return y if x equals y. A range error may occur
10555 if the magnitude of x is the largest finite value representable in the type and the result is
10556 infinite or not representable in the type.
10558 3 The nextafter functions return the next representable value in the specified format
10559 after x in the direction of y.
10562 <sup><a name="note237" href="#note237"><b>237)</b></a></sup> The argument values are converted to the type of the function, even by a macro implementation of the
10565 [<a name="p255" href="#p255">page 255</a>] (<a href="#Contents">Contents</a>)
10567 <a name="7.12.11.4" href="#7.12.11.4"><b> 7.12.11.4 The nexttoward functions</b></a>
10569 1 #include <a href="#7.12"><math.h></a>
10570 double nexttoward(double x, long double y);
10571 float nexttowardf(float x, long double y);
10572 long double nexttowardl(long double x, long double y);
10573 <b> Description</b>
10574 2 The nexttoward functions are equivalent to the nextafter functions except that the
10575 second parameter has type long double and the functions return y converted to the
10576 type of the function if x equals y.<sup><a href="#note238"><b>238)</b></a></sup>
10577 <a name="7.12.12" href="#7.12.12"><b> 7.12.12 Maximum, minimum, and positive difference functions</b></a>
10578 <a name="7.12.12.1" href="#7.12.12.1"><b> 7.12.12.1 The fdim functions</b></a>
10580 1 #include <a href="#7.12"><math.h></a>
10581 double fdim(double x, double y);
10582 float fdimf(float x, float y);
10583 long double fdiml(long double x, long double y);
10584 <b> Description</b>
10585 2 The fdim functions determine the positive difference between their arguments:
10589 A range error may occur.
10591 3 The fdim functions return the positive difference value.
10592 <a name="7.12.12.2" href="#7.12.12.2"><b> 7.12.12.2 The fmax functions</b></a>
10594 1 #include <a href="#7.12"><math.h></a>
10595 double fmax(double x, double y);
10596 float fmaxf(float x, float y);
10597 long double fmaxl(long double x, long double y);
10601 <sup><a name="note238" href="#note238"><b>238)</b></a></sup> The result of the nexttoward functions is determined in the type of the function, without loss of
10602 range or precision in a floating second argument.
10604 [<a name="p256" href="#p256">page 256</a>] (<a href="#Contents">Contents</a>)
10606 <b> Description</b>
10607 2 The fmax functions determine the maximum numeric value of their arguments.<sup><a href="#note239"><b>239)</b></a></sup>
10609 3 The fmax functions return the maximum numeric value of their arguments.
10610 <a name="7.12.12.3" href="#7.12.12.3"><b> 7.12.12.3 The fmin functions</b></a>
10612 1 #include <a href="#7.12"><math.h></a>
10613 double fmin(double x, double y);
10614 float fminf(float x, float y);
10615 long double fminl(long double x, long double y);
10616 <b> Description</b>
10617 2 The fmin functions determine the minimum numeric value of their arguments.<sup><a href="#note240"><b>240)</b></a></sup>
10619 3 The fmin functions return the minimum numeric value of their arguments.
10620 <a name="7.12.13" href="#7.12.13"><b> 7.12.13 Floating multiply-add</b></a>
10621 <a name="7.12.13.1" href="#7.12.13.1"><b> 7.12.13.1 The fma functions</b></a>
10623 1 #include <a href="#7.12"><math.h></a>
10624 double fma(double x, double y, double z);
10625 float fmaf(float x, float y, float z);
10626 long double fmal(long double x, long double y,
10628 <b> Description</b>
10629 2 The fma functions compute (x x y) + z, rounded as one ternary operation: they compute
10630 the value (as if) to infinite precision and round once to the result format, according to the
10631 current rounding mode. A range error may occur.
10633 3 The fma functions return (x x y) + z, rounded as one ternary operation.
10638 <sup><a name="note239" href="#note239"><b>239)</b></a></sup> NaN arguments are treated as missing data: if one argument is a NaN and the other numeric, then the
10639 fmax functions choose the numeric value. See <a href="#F.10.9.2">F.10.9.2</a>.
10640 <sup><a name="note240" href="#note240"><b>240)</b></a></sup> The fmin functions are analogous to the fmax functions in their treatment of NaNs.
10642 [<a name="p257" href="#p257">page 257</a>] (<a href="#Contents">Contents</a>)
10644 <a name="7.12.14" href="#7.12.14"><b> 7.12.14 Comparison macros</b></a>
10645 1 The relational and equality operators support the usual mathematical relationships
10646 between numeric values. For any ordered pair of numeric values exactly one of the
10647 relationships -- less, greater, and equal -- is true. Relational operators may raise the
10648 ''invalid'' floating-point exception when argument values are NaNs. For a NaN and a
10649 numeric value, or for two NaNs, just the unordered relationship is true.<sup><a href="#note241"><b>241)</b></a></sup> The following
10650 subclauses provide macros that are quiet (non floating-point exception raising) versions
10651 of the relational operators, and other comparison macros that facilitate writing efficient
10652 code that accounts for NaNs without suffering the ''invalid'' floating-point exception. In
10653 the synopses in this subclause, real-floating indicates that the argument shall be an
10654 expression of real floating type<sup><a href="#note242"><b>242)</b></a></sup> (both arguments need not have the same type).<sup><a href="#note243"><b>243)</b></a></sup>
10655 <a name="7.12.14.1" href="#7.12.14.1"><b> 7.12.14.1 The isgreater macro</b></a>
10657 1 #include <a href="#7.12"><math.h></a>
10658 int isgreater(real-floating x, real-floating y);
10659 <b> Description</b>
10660 2 The isgreater macro determines whether its first argument is greater than its second
10661 argument. The value of isgreater(x, y) is always equal to (x) > (y); however,
10662 unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point
10663 exception when x and y are unordered.
10665 3 The isgreater macro returns the value of (x) > (y).
10666 <a name="7.12.14.2" href="#7.12.14.2"><b> 7.12.14.2 The isgreaterequal macro</b></a>
10668 1 #include <a href="#7.12"><math.h></a>
10669 int isgreaterequal(real-floating x, real-floating y);
10674 <sup><a name="note241" href="#note241"><b>241)</b></a></sup> IEC 60559 requires that the built-in relational operators raise the ''invalid'' floating-point exception if
10675 the operands compare unordered, as an error indicator for programs written without consideration of
10676 NaNs; the result in these cases is false.
10677 <sup><a name="note242" href="#note242"><b>242)</b></a></sup> If any argument is of integer type, or any other type that is not a real floating type, the behavior is
10679 <sup><a name="note243" href="#note243"><b>243)</b></a></sup> Whether an argument represented in a format wider than its semantic type is converted to the semantic
10680 type is unspecified.
10682 [<a name="p258" href="#p258">page 258</a>] (<a href="#Contents">Contents</a>)
10684 <b> Description</b>
10685 2 The isgreaterequal macro determines whether its first argument is greater than or
10686 equal to its second argument. The value of isgreaterequal(x, y) is always equal
10687 to (x) >= (y); however, unlike (x) >= (y), isgreaterequal(x, y) does
10688 not raise the ''invalid'' floating-point exception when x and y are unordered.
10690 3 The isgreaterequal macro returns the value of (x) >= (y).
10691 <a name="7.12.14.3" href="#7.12.14.3"><b> 7.12.14.3 The isless macro</b></a>
10693 1 #include <a href="#7.12"><math.h></a>
10694 int isless(real-floating x, real-floating y);
10695 <b> Description</b>
10696 2 The isless macro determines whether its first argument is less than its second
10697 argument. The value of isless(x, y) is always equal to (x) < (y); however,
10698 unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point
10699 exception when x and y are unordered.
10701 3 The isless macro returns the value of (x) < (y).
10702 <a name="7.12.14.4" href="#7.12.14.4"><b> 7.12.14.4 The islessequal macro</b></a>
10704 1 #include <a href="#7.12"><math.h></a>
10705 int islessequal(real-floating x, real-floating y);
10706 <b> Description</b>
10707 2 The islessequal macro determines whether its first argument is less than or equal to
10708 its second argument. The value of islessequal(x, y) is always equal to
10709 (x) <= (y); however, unlike (x) <= (y), islessequal(x, y) does not raise
10710 the ''invalid'' floating-point exception when x and y are unordered.
10712 3 The islessequal macro returns the value of (x) <= (y).
10717 [<a name="p259" href="#p259">page 259</a>] (<a href="#Contents">Contents</a>)
10719 <a name="7.12.14.5" href="#7.12.14.5"><b> 7.12.14.5 The islessgreater macro</b></a>
10721 1 #include <a href="#7.12"><math.h></a>
10722 int islessgreater(real-floating x, real-floating y);
10723 <b> Description</b>
10724 2 The islessgreater macro determines whether its first argument is less than or
10725 greater than its second argument. The islessgreater(x, y) macro is similar to
10726 (x) < (y) || (x) > (y); however, islessgreater(x, y) does not raise
10727 the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x
10730 3 The islessgreater macro returns the value of (x) < (y) || (x) > (y).
10731 <a name="7.12.14.6" href="#7.12.14.6"><b> 7.12.14.6 The isunordered macro</b></a>
10733 1 #include <a href="#7.12"><math.h></a>
10734 int isunordered(real-floating x, real-floating y);
10735 <b> Description</b>
10736 2 The isunordered macro determines whether its arguments are unordered.
10738 3 The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
10743 [<a name="p260" href="#p260">page 260</a>] (<a href="#Contents">Contents</a>)
10745 <a name="7.13" href="#7.13"><b> 7.13 Nonlocal jumps <setjmp.h></b></a>
10746 1 The header <a href="#7.13"><setjmp.h></a> defines the macro setjmp, and declares one function and
10747 one type, for bypassing the normal function call and return discipline.<sup><a href="#note244"><b>244)</b></a></sup>
10748 2 The type declared is
10750 which is an array type suitable for holding the information needed to restore a calling
10751 environment. The environment of a call to the setjmp macro consists of information
10752 sufficient for a call to the longjmp function to return execution to the correct block and
10753 invocation of that block, were it called recursively. It does not include the state of the
10754 floating-point status flags, of open files, or of any other component of the abstract
10756 3 It is unspecified whether setjmp is a macro or an identifier declared with external
10757 linkage. If a macro definition is suppressed in order to access an actual function, or a
10758 program defines an external identifier with the name setjmp, the behavior is undefined.
10759 <a name="7.13.1" href="#7.13.1"><b> 7.13.1 Save calling environment</b></a>
10760 <a name="7.13.1.1" href="#7.13.1.1"><b> 7.13.1.1 The setjmp macro</b></a>
10762 1 #include <a href="#7.13"><setjmp.h></a>
10763 int setjmp(jmp_buf env);
10764 <b> Description</b>
10765 2 The setjmp macro saves its calling environment in its jmp_buf argument for later use
10766 by the longjmp function.
10768 3 If the return is from a direct invocation, the setjmp macro returns the value zero. If the
10769 return is from a call to the longjmp function, the setjmp macro returns a nonzero
10771 Environmental limits
10772 4 An invocation of the setjmp macro shall appear only in one of the following contexts:
10773 -- the entire controlling expression of a selection or iteration statement;
10774 -- one operand of a relational or equality operator with the other operand an integer
10775 constant expression, with the resulting expression being the entire controlling
10778 <sup><a name="note244" href="#note244"><b>244)</b></a></sup> These functions are useful for dealing with unusual conditions encountered in a low-level function of
10781 [<a name="p261" href="#p261">page 261</a>] (<a href="#Contents">Contents</a>)
10783 expression of a selection or iteration statement;
10784 -- the operand of a unary ! operator with the resulting expression being the entire
10785 controlling expression of a selection or iteration statement; or
10786 -- the entire expression of an expression statement (possibly cast to void).
10787 5 If the invocation appears in any other context, the behavior is undefined.
10788 <a name="7.13.2" href="#7.13.2"><b> 7.13.2 Restore calling environment</b></a>
10789 <a name="7.13.2.1" href="#7.13.2.1"><b> 7.13.2.1 The longjmp function</b></a>
10791 1 #include <a href="#7.13"><setjmp.h></a>
10792 _Noreturn void longjmp(jmp_buf env, int val);
10793 <b> Description</b>
10794 2 The longjmp function restores the environment saved by the most recent invocation of
10795 the setjmp macro in the same invocation of the program with the corresponding
10796 jmp_buf argument. If there has been no such invocation, or if the function containing
10797 the invocation of the setjmp macro has terminated execution<sup><a href="#note245"><b>245)</b></a></sup> in the interim, or if the
10798 invocation of the setjmp macro was within the scope of an identifier with variably
10799 modified type and execution has left that scope in the interim, the behavior is undefined.
10800 3 All accessible objects have values, and all other components of the abstract machine<sup><a href="#note246"><b>246)</b></a></sup>
10801 have state, as of the time the longjmp function was called, except that the values of
10802 objects of automatic storage duration that are local to the function containing the
10803 invocation of the corresponding setjmp macro that do not have volatile-qualified type
10804 and have been changed between the setjmp invocation and longjmp call are
10807 4 After longjmp is completed, program execution continues as if the corresponding
10808 invocation of the setjmp macro had just returned the value specified by val. The
10809 longjmp function cannot cause the setjmp macro to return the value 0; if val is 0,
10810 the setjmp macro returns the value 1.
10811 5 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation
10812 might cause memory associated with a variable length array object to be squandered.
10817 <sup><a name="note245" href="#note245"><b>245)</b></a></sup> For example, by executing a return statement or because another longjmp call has caused a
10818 transfer to a setjmp invocation in a function earlier in the set of nested calls.
10819 <sup><a name="note246" href="#note246"><b>246)</b></a></sup> This includes, but is not limited to, the floating-point status flags and the state of open files.
10821 [<a name="p262" href="#p262">page 262</a>] (<a href="#Contents">Contents</a>)
10823 #include <a href="#7.13"><setjmp.h></a>
10830 int x[n]; // valid: f is not terminated
10836 int a[n]; // a may remain allocated
10841 int b[n]; // b may remain allocated
10842 longjmp(buf, 2); // might cause memory loss
10848 [<a name="p263" href="#p263">page 263</a>] (<a href="#Contents">Contents</a>)
10850 <a name="7.14" href="#7.14"><b> 7.14 Signal handling <signal.h></b></a>
10851 1 The header <a href="#7.14"><signal.h></a> declares a type and two functions and defines several macros,
10852 for handling various signals (conditions that may be reported during program execution).
10853 2 The type defined is
10855 which is the (possibly volatile-qualified) integer type of an object that can be accessed as
10856 an atomic entity, even in the presence of asynchronous interrupts.
10857 3 The macros defined are
10861 which expand to constant expressions with distinct values that have type compatible with
10862 the second argument to, and the return value of, the signal function, and whose values
10863 compare unequal to the address of any declarable function; and the following, which
10864 expand to positive integer constant expressions with type int and distinct values that are
10865 the signal numbers, each corresponding to the specified condition:
10866 SIGABRT abnormal termination, such as is initiated by the abort function
10867 SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
10868 resulting in overflow
10869 SIGILL detection of an invalid function image, such as an invalid instruction
10870 SIGINT receipt of an interactive attention signal
10871 SIGSEGV an invalid access to storage
10872 SIGTERM a termination request sent to the program
10873 4 An implementation need not generate any of these signals, except as a result of explicit
10874 calls to the raise function. Additional signals and pointers to undeclarable functions,
10875 with macro definitions beginning, respectively, with the letters SIG and an uppercase
10876 letter or with SIG_ and an uppercase letter,<sup><a href="#note247"><b>247)</b></a></sup> may also be specified by the
10877 implementation. The complete set of signals, their semantics, and their default handling
10878 is implementation-defined; all signal numbers shall be positive.
10883 <sup><a name="note247" href="#note247"><b>247)</b></a></sup> See ''future library directions'' (<a href="#7.30.6">7.30.6</a>). The names of the signal numbers reflect the following terms
10884 (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
10887 [<a name="p264" href="#p264">page 264</a>] (<a href="#Contents">Contents</a>)
10889 <a name="7.14.1" href="#7.14.1"><b> 7.14.1 Specify signal handling</b></a>
10890 <a name="7.14.1.1" href="#7.14.1.1"><b> 7.14.1.1 The signal function</b></a>
10892 1 #include <a href="#7.14"><signal.h></a>
10893 void (*signal(int sig, void (*func)(int)))(int);
10894 <b> Description</b>
10895 2 The signal function chooses one of three ways in which receipt of the signal number
10896 sig is to be subsequently handled. If the value of func is SIG_DFL, default handling
10897 for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored.
10898 Otherwise, func shall point to a function to be called when that signal occurs. An
10899 invocation of such a function because of a signal, or (recursively) of any further functions
10900 called by that invocation (other than functions in the standard library),<sup><a href="#note248"><b>248)</b></a></sup> is called a
10902 3 When a signal occurs and func points to a function, it is implementation-defined
10903 whether the equivalent of signal(sig, SIG_DFL); is executed or the
10904 implementation prevents some implementation-defined set of signals (at least including
10905 sig) from occurring until the current signal handling has completed; in the case of
10906 SIGILL, the implementation may alternatively define that no action is taken. Then the
10907 equivalent of (*func)(sig); is executed. If and when the function returns, if the
10908 value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined
10909 value corresponding to a computational exception, the behavior is undefined; otherwise
10910 the program will resume execution at the point it was interrupted.
10911 4 If the signal occurs as the result of calling the abort or raise function, the signal
10912 handler shall not call the raise function.
10913 5 If the signal occurs other than as the result of calling the abort or raise function, the
10914 behavior is undefined if the signal handler refers to any object with static or thread
10915 storage duration that is not a lock-free atomic object other than by assigning a value to an
10916 object declared as volatile sig_atomic_t, or the signal handler calls any function
10917 in the standard library other than the abort function, the _Exit function, the
10918 quick_exit function, or the signal function with the first argument equal to the
10919 signal number corresponding to the signal that caused the invocation of the handler.
10920 Furthermore, if such a call to the signal function results in a SIG_ERR return, the
10921 value of errno is indeterminate.<sup><a href="#note249"><b>249)</b></a></sup>
10924 <sup><a name="note248" href="#note248"><b>248)</b></a></sup> This includes functions called indirectly via standard library functions (e.g., a SIGABRT handler
10925 called via the abort function).
10926 <sup><a name="note249" href="#note249"><b>249)</b></a></sup> If any signal is generated by an asynchronous signal handler, the behavior is undefined.
10928 [<a name="p265" href="#p265">page 265</a>] (<a href="#Contents">Contents</a>)
10930 6 At program startup, the equivalent of
10931 signal(sig, SIG_IGN);
10932 may be executed for some signals selected in an implementation-defined manner; the
10934 signal(sig, SIG_DFL);
10935 is executed for all other signals defined by the implementation.
10936 7 The implementation shall behave as if no library function calls the signal function.
10938 8 If the request can be honored, the signal function returns the value of func for the
10939 most recent successful call to signal for the specified signal sig. Otherwise, a value of
10940 SIG_ERR is returned and a positive value is stored in errno.
10941 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
10942 _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>).
10943 <a name="7.14.2" href="#7.14.2"><b> 7.14.2 Send signal</b></a>
10944 <a name="7.14.2.1" href="#7.14.2.1"><b> 7.14.2.1 The raise function</b></a>
10946 1 #include <a href="#7.14"><signal.h></a>
10947 int raise(int sig);
10948 <b> Description</b>
10949 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
10950 signal handler is called, the raise function shall not return until after the signal handler
10953 3 The raise function returns zero if successful, nonzero if unsuccessful.
10958 [<a name="p266" href="#p266">page 266</a>] (<a href="#Contents">Contents</a>)
10960 <a name="7.15" href="#7.15"><b> 7.15 Alignment <stdalign.h></b></a>
10961 1 The header <a href="#7.15"><stdalign.h></a> defines two macros.
10964 expands to _Alignas.
10965 3 The remaining macro is suitable for use in #if preprocessing directives. It is
10966 __alignas_is_defined
10967 which expands to the integer constant 1.
10972 [<a name="p267" href="#p267">page 267</a>] (<a href="#Contents">Contents</a>)
10974 <a name="7.16" href="#7.16"><b> 7.16 Variable arguments <stdarg.h></b></a>
10975 1 The header <a href="#7.16"><stdarg.h></a> declares a type and defines four macros, for advancing
10976 through a list of arguments whose number and types are not known to the called function
10977 when it is translated.
10978 2 A function may be called with a variable number of arguments of varying types. As
10979 described in <a href="#6.9.1">6.9.1</a>, its parameter list contains one or more parameters. The rightmost
10980 parameter plays a special role in the access mechanism, and will be designated parmN in
10982 3 The type declared is
10984 which is a complete object type suitable for holding information needed by the macros
10985 va_start, va_arg, va_end, and va_copy. If access to the varying arguments is
10986 desired, the called function shall declare an object (generally referred to as ap in this
10987 subclause) having type va_list. The object ap may be passed as an argument to
10988 another function; if that function invokes the va_arg macro with parameter ap, the
10989 value of ap in the calling function is indeterminate and shall be passed to the va_end
10990 macro prior to any further reference to ap.<sup><a href="#note250"><b>250)</b></a></sup>
10991 <a name="7.16.1" href="#7.16.1"><b> 7.16.1 Variable argument list access macros</b></a>
10992 1 The va_start and va_arg macros described in this subclause shall be implemented
10993 as macros, not functions. It is unspecified whether va_copy and va_end are macros or
10994 identifiers declared with external linkage. If a macro definition is suppressed in order to
10995 access an actual function, or a program defines an external identifier with the same name,
10996 the behavior is undefined. Each invocation of the va_start and va_copy macros
10997 shall be matched by a corresponding invocation of the va_end macro in the same
10999 <a name="7.16.1.1" href="#7.16.1.1"><b> 7.16.1.1 The va_arg macro</b></a>
11001 1 #include <a href="#7.16"><stdarg.h></a>
11002 type va_arg(va_list ap, type);
11003 <b> Description</b>
11004 2 The va_arg macro expands to an expression that has the specified type and the value of
11005 the next argument in the call. The parameter ap shall have been initialized by the
11006 va_start or va_copy macro (without an intervening invocation of the va_end
11008 <sup><a name="note250" href="#note250"><b>250)</b></a></sup> It is permitted to create a pointer to a va_list and pass that pointer to another function, in which
11009 case the original function may make further use of the original list after the other function returns.
11011 [<a name="p268" href="#p268">page 268</a>] (<a href="#Contents">Contents</a>)
11013 macro for the same ap). Each invocation of the va_arg macro modifies ap so that the
11014 values of successive arguments are returned in turn. The parameter type shall be a type
11015 name specified such that the type of a pointer to an object that has the specified type can
11016 be obtained simply by postfixing a * to type. If there is no actual next argument, or if
11017 type is not compatible with the type of the actual next argument (as promoted according
11018 to the default argument promotions), the behavior is undefined, except for the following
11020 -- one type is a signed integer type, the other type is the corresponding unsigned integer
11021 type, and the value is representable in both types;
11022 -- one type is pointer to void and the other is a pointer to a character type.
11024 3 The first invocation of the va_arg macro after that of the va_start macro returns the
11025 value of the argument after that specified by parmN . Successive invocations return the
11026 values of the remaining arguments in succession.
11027 <a name="7.16.1.2" href="#7.16.1.2"><b> 7.16.1.2 The va_copy macro</b></a>
11029 1 #include <a href="#7.16"><stdarg.h></a>
11030 void va_copy(va_list dest, va_list src);
11031 <b> Description</b>
11032 2 The va_copy macro initializes dest as a copy of src, as if the va_start macro had
11033 been applied to dest followed by the same sequence of uses of the va_arg macro as
11034 had previously been used to reach the present state of src. Neither the va_copy nor
11035 va_start macro shall be invoked to reinitialize dest without an intervening
11036 invocation of the va_end macro for the same dest.
11038 3 The va_copy macro returns no value.
11039 <a name="7.16.1.3" href="#7.16.1.3"><b> 7.16.1.3 The va_end macro</b></a>
11041 1 #include <a href="#7.16"><stdarg.h></a>
11042 void va_end(va_list ap);
11043 <b> Description</b>
11044 2 The va_end macro facilitates a normal return from the function whose variable
11045 argument list was referred to by the expansion of the va_start macro, or the function
11046 containing the expansion of the va_copy macro, that initialized the va_list ap. The
11047 va_end macro may modify ap so that it is no longer usable (without being reinitialized
11049 [<a name="p269" href="#p269">page 269</a>] (<a href="#Contents">Contents</a>)
11051 by the va_start or va_copy macro). If there is no corresponding invocation of the
11052 va_start or va_copy macro, or if the va_end macro is not invoked before the
11053 return, the behavior is undefined.
11055 3 The va_end macro returns no value.
11056 <a name="7.16.1.4" href="#7.16.1.4"><b> 7.16.1.4 The va_start macro</b></a>
11058 1 #include <a href="#7.16"><stdarg.h></a>
11059 void va_start(va_list ap, parmN);
11060 <b> Description</b>
11061 2 The va_start macro shall be invoked before any access to the unnamed arguments.
11062 3 The va_start macro initializes ap for subsequent use by the va_arg and va_end
11063 macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap
11064 without an intervening invocation of the va_end macro for the same ap.
11065 4 The parameter parmN is the identifier of the rightmost parameter in the variable
11066 parameter list in the function definition (the one just before the , ...). If the parameter
11067 parmN is declared with the register storage class, with a function or array type, or
11068 with a type that is not compatible with the type that results after application of the default
11069 argument promotions, the behavior is undefined.
11071 5 The va_start macro returns no value.
11072 6 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not
11073 more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of
11074 pointers is specified by the first argument to f1.
11075 #include <a href="#7.16"><stdarg.h></a>
11077 void f1(int n_ptrs, ...)
11080 char *array[MAXARGS];
11086 [<a name="p270" href="#p270">page 270</a>] (<a href="#Contents">Contents</a>)
11088 if (n_ptrs > MAXARGS)
11090 va_start(ap, n_ptrs);
11091 while (ptr_no < n_ptrs)
11092 array[ptr_no++] = va_arg(ap, char *);
11096 Each call to f1 is required to have visible the definition of the function or a declaration such as
11099 7 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the
11100 indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list
11101 is gathered again and passed to function f4.
11102 #include <a href="#7.16"><stdarg.h></a>
11104 void f3(int n_ptrs, int f4_after, ...)
11106 va_list ap, ap_save;
11107 char *array[MAXARGS];
11109 if (n_ptrs > MAXARGS)
11111 va_start(ap, f4_after);
11112 while (ptr_no < n_ptrs) {
11113 array[ptr_no++] = va_arg(ap, char *);
11114 if (ptr_no == f4_after)
11115 va_copy(ap_save, ap);
11119 // Now process the saved copy.
11120 n_ptrs -= f4_after;
11122 while (ptr_no < n_ptrs)
11123 array[ptr_no++] = va_arg(ap_save, char *);
11131 [<a name="p271" href="#p271">page 271</a>] (<a href="#Contents">Contents</a>)
11133 <a name="7.17" href="#7.17"><b> 7.17 Atomics <stdatomic.h></b></a>
11134 <a name="7.17.1" href="#7.17.1"><b> 7.17.1 Introduction</b></a>
11135 1 The header <a href="#7.17"><stdatomic.h></a> defines several macros and declares several types and
11136 functions for performing atomic operations on data shared between threads.
11137 2 Implementations that define the macro __STDC_NO_THREADS__ need not provide
11138 this header nor support any of its facilities.
11139 3 The macros defined are the atomic lock-free macros
11140 ATOMIC_CHAR_LOCK_FREE
11141 ATOMIC_CHAR16_T_LOCK_FREE
11142 ATOMIC_CHAR32_T_LOCK_FREE
11143 ATOMIC_WCHAR_T_LOCK_FREE
11144 ATOMIC_SHORT_LOCK_FREE
11145 ATOMIC_INT_LOCK_FREE
11146 ATOMIC_LONG_LOCK_FREE
11147 ATOMIC_LLONG_LOCK_FREE
11148 ATOMIC_ADDRESS_LOCK_FREE
11149 which indicate the lock-free property of the corresponding atomic types (both signed and
11152 which expands to an initializer for an object of type atomic_flag.
11153 4 The types include
11155 which is an enumerated type whose enumerators identify memory ordering constraints;
11157 which is a structure type representing a lock-free, primitive atomic flag;
11159 which is a structure type representing the atomic analog of the type _Bool;
11161 which is a structure type representing the atomic analog of a pointer type; and several
11162 atomic analogs of integer types.
11163 5 In the following operation definitions:
11164 -- An A refers to one of the atomic types.
11167 [<a name="p272" href="#p272">page 272</a>] (<a href="#Contents">Contents</a>)
11169 -- A C refers to its corresponding non-atomic type. The atomic_address atomic
11170 type corresponds to the void * non-atomic type.
11171 -- An M refers to the type of the other argument for arithmetic operations. For atomic
11172 integer types, M is C. For atomic address types, M is ptrdiff_t.
11173 -- The functions not ending in _explicit have the same semantics as the
11174 corresponding _explicit function with memory_order_seq_cst for the
11175 memory_order argument.
11176 6 NOTE Many operations are volatile-qualified. The ''volatile as device register'' semantics have not
11177 changed in the standard. This qualification means that volatility is preserved when applying these
11178 operations to volatile objects.
11180 <a name="7.17.2" href="#7.17.2"><b> 7.17.2 Initialization</b></a>
11181 <a name="7.17.2.1" href="#7.17.2.1"><b> 7.17.2.1 The ATOMIC_VAR_INIT macro</b></a>
11183 1 #include <a href="#7.17"><stdatomic.h></a>
11184 #define ATOMIC_VAR_INIT(C value)
11185 <b> Description</b>
11186 2 The ATOMIC_VAR_INIT macro expands to a token sequence suitable for initializing an
11187 atomic object of a type that is initialization-compatible with value. An atomic object
11188 with automatic storage duration that is not explicitly initialized using
11189 ATOMIC_VAR_INIT is initially in an indeterminate state; however, the default (zero)
11190 initialization for objects with static or thread-local storage duration is guaranteed to
11191 produce a valid state.
11192 3 Concurrent access to the variable being initialized, even via an atomic operation,
11193 constitutes a data race.
11195 atomic_int guide = ATOMIC_VAR_INIT(42);
11197 <a name="7.17.2.2" href="#7.17.2.2"><b> 7.17.2.2 The atomic_init generic function</b></a>
11199 1 #include <a href="#7.17"><stdatomic.h></a>
11200 void atomic_init(volatile A *obj, C value);
11201 <b> Description</b>
11202 2 The atomic_init generic function initializes the atomic object pointed to by obj to
11203 the value value, while also initializing any additional state that the implementation
11204 might need to carry for the atomic object.
11208 [<a name="p273" href="#p273">page 273</a>] (<a href="#Contents">Contents</a>)
11210 3 Although this function initializes an atomic object, it does not avoid data races;
11211 concurrent access to the variable being initialized, even via an atomic operation,
11212 constitutes a data race.
11214 4 The atomic_init generic function returns no value.
11217 atomic_init(&guide, 42);
11219 <a name="7.17.3" href="#7.17.3"><b> 7.17.3 Order and consistency</b></a>
11220 1 The enumerated type memory_order specifies the detailed regular (non-atomic)
11221 memory synchronization operations as defined in <a href="#5.1.2.4">5.1.2.4</a> and may provide for operation
11222 ordering. Its enumeration constants are as follows:
11223 memory_order_relaxed
11224 memory_order_consume
11225 memory_order_acquire
11226 memory_order_release
11227 memory_order_acq_rel
11228 memory_order_seq_cst
11229 2 For memory_order_relaxed, no operation orders memory.
11230 3 For memory_order_release, memory_order_acq_rel, and
11231 memory_order_seq_cst, a store operation performs a release operation on the
11232 affected memory location.
11233 4 For memory_order_acquire, memory_order_acq_rel, and
11234 memory_order_seq_cst, a load operation performs an acquire operation on the
11235 affected memory location.
11236 5 For memory_order_consume, a load operation performs a consume operation on the
11237 affected memory location.
11238 6 For memory_order_seq_cst, there shall be a single total order S on all operations,
11239 consistent with the ''happens before'' order and modification orders for all affected
11240 locations, such that each memory_order_seq_cst operation that loads a value
11241 observes either the last preceding modification according to this order S, or the result of
11242 an operation that is not memory_order_seq_cst.
11243 7 NOTE 1 Although it is not explicitly required that S include lock operations, it can always be extended to
11244 an order that does include lock and unlock operations, since the ordering between those is already included
11245 in the ''happens before'' ordering.
11247 8 NOTE 2 Atomic operations specifying memory_order_relaxed are relaxed only with respect to
11248 memory ordering. Implementations must still guarantee that any given atomic access to a particular atomic
11250 [<a name="p274" href="#p274">page 274</a>] (<a href="#Contents">Contents</a>)
11252 object be indivisible with respect to all other atomic accesses to that object.
11254 9 For an atomic operation B that reads the value of an atomic object M, if there is a
11255 memory_order_seq_cst fence X sequenced before B, then B observes either the
11256 last memory_order_seq_cst modification of M preceding X in the total order S or
11257 a later modification of M in its modification order.
11258 10 For atomic operations A and B on an atomic object M, where A modifies M and B takes
11259 its value, if there is a memory_order_seq_cst fence X such that A is sequenced
11260 before X and B follows X in S, then B observes either the effects of A or a later
11261 modification of M in its modification order.
11262 11 For atomic operations A and B on an atomic object M, where A modifies M and B takes
11263 its value, if there are memory_order_seq_cst fences X and Y such that A is
11264 sequenced before X, Y is sequenced before B, and X precedes Y in S, then B observes
11265 either the effects of A or a later modification of M in its modification order.
11266 12 Atomic read-modify-write operations shall always read the last value (in the modification
11267 order) stored before the write associated with the read-modify-write operation.
11268 13 An atomic store shall only store a value that has been computed from constants and
11269 program input values by a finite sequence of program evaluations, such that each
11270 evaluation observes the values of variables as computed by the last prior assignment in
11271 the sequence.<sup><a href="#note251"><b>251)</b></a></sup> The ordering of evaluations in this sequence shall be such that
11272 -- If an evaluation B observes a value computed by A in a different thread, then B does
11273 not happen before A.
11274 -- If an evaluation A is included in the sequence, then all evaluations that assign to the
11275 same variable and happen before A are also included.
11276 14 NOTE 3 The second requirement disallows ''out-of-thin-air'', or ''speculative'' stores of atomics when
11277 relaxed atomics are used. Since unordered operations are involved, evaluations may appear in this
11278 sequence out of thread order. For example, with x and y initially zero,
11280 r1 = atomic_load_explicit(&y, memory_order_relaxed);
11281 atomic_store_explicit(&x, r1, memory_order_relaxed);
11284 r2 = atomic_load_explicit(&x, memory_order_relaxed);
11285 atomic_store_explicit(&y, 42, memory_order_relaxed);
11286 is allowed to produce r1 == 42 && r2 == 42. The sequence of evaluations justifying this consists of:
11291 <sup><a name="note251" href="#note251"><b>251)</b></a></sup> Among other implications, atomic variables shall not decay.
11293 [<a name="p275" href="#p275">page 275</a>] (<a href="#Contents">Contents</a>)
11295 atomic_store_explicit(&y, 42, memory_order_relaxed);
11296 r1 = atomic_load_explicit(&y, memory_order_relaxed);
11297 atomic_store_explicit(&x, r1, memory_order_relaxed);
11298 r2 = atomic_load_explicit(&x, memory_order_relaxed);
11301 r1 = atomic_load_explicit(&y, memory_order_relaxed);
11302 atomic_store_explicit(&x, r1, memory_order_relaxed);
11305 r2 = atomic_load_explicit(&x, memory_order_relaxed);
11306 atomic_store_explicit(&y, r2, memory_order_relaxed);
11307 is not allowed to produce r1 == 42 && r2 = 42, since there is no sequence of evaluations that results
11308 in the computation of 42. In the absence of ''relaxed'' operations and read-modify-write operations with
11309 weaker than memory_order_acq_rel ordering, the second requirement has no impact.
11311 Recommended practice
11312 15 The requirements do not forbid r1 == 42 && r2 == 42 in the following example,
11313 with x and y initially zero:
11315 r1 = atomic_load_explicit(&x, memory_order_relaxed);
11317 atomic_store_explicit(&y, r1, memory_order_relaxed);
11320 r2 = atomic_load_explicit(&y, memory_order_relaxed);
11322 atomic_store_explicit(&x, 42, memory_order_relaxed);
11323 However, this is not useful behavior, and implementations should not allow it.
11324 16 Implementations should make atomic stores visible to atomic loads within a reasonable
11326 <a name="7.17.3.1" href="#7.17.3.1"><b> 7.17.3.1 The kill_dependency macro</b></a>
11328 1 #include <a href="#7.17"><stdatomic.h></a>
11329 type kill_dependency(type y);
11330 <b> Description</b>
11331 2 The kill_dependency macro terminates a dependency chain; the argument does not
11332 carry a dependency to the return value.
11336 [<a name="p276" href="#p276">page 276</a>] (<a href="#Contents">Contents</a>)
11339 3 The kill_dependency macro returns the value of y.
11340 <a name="7.17.4" href="#7.17.4"><b> 7.17.4 Fences</b></a>
11341 1 This subclause introduces synchronization primitives called fences. Fences can have
11342 acquire semantics, release semantics, or both. A fence with acquire semantics is called
11343 an acquire fence; a fence with release semantics is called a release fence.
11344 2 A release fence A synchronizes with an acquire fence B if there exist atomic operations
11345 X and Y , both operating on some atomic object M, such that A is sequenced before X, X
11346 modifies M, Y is sequenced before B, and Y reads the value written by X or a value
11347 written by any side effect in the hypothetical release sequence X would head if it were a
11349 3 A release fence A synchronizes with an atomic operation B that performs an acquire
11350 operation on an atomic object M if there exists an atomic operation X such that A is
11351 sequenced before X, X modifies M, and B reads the value written by X or a value written
11352 by any side effect in the hypothetical release sequence X would head if it were a release
11354 4 An atomic operation A that is a release operation on an atomic object M synchronizes
11355 with an acquire fence B if there exists some atomic operation X on M such that X is
11356 sequenced before B and reads the value written by A or a value written by any side effect
11357 in the release sequence headed by A.
11358 <a name="7.17.4.1" href="#7.17.4.1"><b> 7.17.4.1 The atomic_thread_fence function</b></a>
11360 1 #include <a href="#7.17"><stdatomic.h></a>
11361 void atomic_thread_fence(memory_order order);
11362 <b> Description</b>
11363 2 Depending on the value of order, this operation:
11364 -- has no effects, if order == memory_order_relaxed;
11365 -- is an acquire fence, if order == memory_order_acquire or order ==
11366 memory_order_consume;
11367 -- is a release fence, if order == memory_order_release;
11368 -- is both an acquire fence and a release fence, if order ==
11369 memory_order_acq_rel;
11370 -- is a sequentially consistent acquire and release fence, if order ==
11371 memory_order_seq_cst.
11374 [<a name="p277" href="#p277">page 277</a>] (<a href="#Contents">Contents</a>)
11377 3 The atomic_thread_fence function returns no value.
11378 <a name="7.17.4.2" href="#7.17.4.2"><b> 7.17.4.2 The atomic_signal_fence function</b></a>
11380 1 #include <a href="#7.17"><stdatomic.h></a>
11381 void atomic_signal_fence(memory_order order);
11382 <b> Description</b>
11383 2 Equivalent to atomic_thread_fence(order), except that ''synchronizes with''
11384 relationships are established only between a thread and a signal handler executed in the
11386 3 NOTE 1 The atomic_signal_fence function can be used to specify the order in which actions
11387 performed by the thread become visible to the signal handler.
11389 4 NOTE 2 Compiler optimizations and reorderings of loads and stores are inhibited in the same way as with
11390 atomic_thread_fence, but the hardware fence instructions that atomic_thread_fence would
11391 have inserted are not emitted.
11394 5 The atomic_signal_fence function returns no value.
11395 <a name="7.17.5" href="#7.17.5"><b> 7.17.5 Lock-free property</b></a>
11396 1 The atomic lock-free macros indicate the lock-free property of integer and address atomic
11397 types. A value of 0 indicates that the type is never lock-free; a value of 1 indicates that
11398 the type is sometimes lock-free; a value of 2 indicates that the type is always lock-free.
11399 2 NOTE Operations that are lock-free should also be address-free. That is, atomic operations on the same
11400 memory location via two different addresses will communicate atomically. The implementation should not
11401 depend on any per-process state. This restriction enables communication via memory mapped into a
11402 process more than once and memory shared between two processes.
11404 <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>
11406 1 #include <a href="#7.17"><stdatomic.h></a>
11407 _Bool atomic_is_lock_free(atomic_type const volatile *obj);
11408 <b> Description</b>
11409 2 The atomic_is_lock_free generic function indicates whether or not the object
11410 pointed to by obj is lock-free. atomic_type can be any atomic type.
11412 3 The atomic_is_lock_free generic function returns nonzero (true) if and only if the
11413 object's operations are lock-free. The result of a lock-free query on one object cannot be
11415 [<a name="p278" href="#p278">page 278</a>] (<a href="#Contents">Contents</a>)
11417 inferred from the result of a lock-free query on another object.
11418 <a name="7.17.6" href="#7.17.6"><b> 7.17.6 Atomic integer and address types</b></a>
11419 1 For each line in the following table, the atomic type name is declared as the
11420 corresponding direct type.
11425 [<a name="p279" href="#p279">page 279</a>] (<a href="#Contents">Contents</a>)
11427 Atomic type name Direct type
11428 atomic_char _Atomic char
11429 atomic_schar _Atomic signed char
11430 atomic_uchar _Atomic unsigned char
11431 atomic_short _Atomic short
11432 atomic_ushort _Atomic unsigned short
11433 atomic_int _Atomic int
11434 atomic_uint _Atomic unsigned int
11435 atomic_long _Atomic long
11436 atomic_ulong _Atomic unsigned long
11437 atomic_llong _Atomic long long
11438 atomic_ullong _Atomic unsigned long long
11439 atomic_char16_t _Atomic char16_t
11440 atomic_char32_t _Atomic char32_t
11441 atomic_wchar_t _Atomic wchar_t
11442 atomic_int_least8_t _Atomic int_least8_t
11443 atomic_uint_least8_t _Atomic uint_least8_t
11444 atomic_int_least16_t _Atomic int_least16_t
11445 atomic_uint_least16_t _Atomic uint_least16_t
11446 atomic_int_least32_t _Atomic int_least32_t
11447 atomic_uint_least32_t _Atomic uint_least32_t
11448 atomic_int_least64_t _Atomic int_least64_t
11449 atomic_uint_least64_t _Atomic uint_least64_t
11450 atomic_int_fast8_t _Atomic int_fast8_t
11451 atomic_uint_fast8_t _Atomic uint_fast8_t
11452 atomic_int_fast16_t _Atomic int_fast16_t
11453 atomic_uint_fast16_t _Atomic uint_fast16_t
11454 atomic_int_fast32_t _Atomic int_fast32_t
11455 atomic_uint_fast32_t _Atomic uint_fast32_t
11456 atomic_int_fast64_t _Atomic int_fast64_t
11457 atomic_uint_fast64_t _Atomic uint_fast64_t
11458 atomic_intptr_t _Atomic intptr_t
11459 atomic_uintptr_t _Atomic uintptr_t
11460 atomic_size_t _Atomic size_t
11461 atomic_ptrdiff_t _Atomic ptrdiff_t
11462 atomic_intmax_t _Atomic intmax_t
11463 atomic_uintmax_t _Atomic uintmax_t
11464 2 The semantics of the operations on these types are defined in <a href="#7.17.7">7.17.7</a>.
11465 3 The atomic_bool type provides an atomic boolean.
11468 [<a name="p280" href="#p280">page 280</a>] (<a href="#Contents">Contents</a>)
11470 4 The atomic_address type provides atomic void * operations. The unit of
11471 addition/subtraction shall be one byte.
11472 5 NOTE The representation of atomic integer and address types need not have the same size as their
11473 corresponding regular types. They should have the same size whenever possible, as it eases effort required
11474 to port existing code.
11476 <a name="7.17.7" href="#7.17.7"><b> 7.17.7 Operations on atomic types</b></a>
11477 1 There are only a few kinds of operations on atomic types, though there are many
11478 instances of those kinds. This subclause specifies each general kind.
11479 <a name="7.17.7.1" href="#7.17.7.1"><b> 7.17.7.1 The atomic_store generic functions</b></a>
11481 1 #include <a href="#7.17"><stdatomic.h></a>
11482 void atomic_store(volatile A *object, C desired);
11483 void atomic_store_explicit(volatile A *object,
11484 C desired, memory_order order);
11485 <b> Description</b>
11486 2 The order argument shall not be memory_order_acquire,
11487 memory_order_consume, nor memory_order_acq_rel. Atomically replace the
11488 value pointed to by object with the value of desired. Memory is affected according
11489 to the value of order.
11491 3 The atomic_store generic functions return no value.
11492 <a name="7.17.7.2" href="#7.17.7.2"><b> 7.17.7.2 The atomic_load generic functions</b></a>
11494 1 #include <a href="#7.17"><stdatomic.h></a>
11495 C atomic_load(volatile A *object);
11496 C atomic_load_explicit(volatile A *object,
11497 memory_order order);
11498 <b> Description</b>
11499 2 The order argument shall not be memory_order_release nor
11500 memory_order_acq_rel. Memory is affected according to the value of order.
11502 Atomically returns the value pointed to by object.
11507 [<a name="p281" href="#p281">page 281</a>] (<a href="#Contents">Contents</a>)
11509 <a name="7.17.7.3" href="#7.17.7.3"><b> 7.17.7.3 The atomic_exchange generic functions</b></a>
11511 1 #include <a href="#7.17"><stdatomic.h></a>
11512 C atomic_exchange(volatile A *object, C desired);
11513 C atomic_exchange_explicit(volatile A *object,
11514 C desired, memory_order order);
11515 <b> Description</b>
11516 2 Atomically replace the value pointed to by object with desired. Memory is affected
11517 according to the value of order. These operations are read-modify-write operations
11518 (<a href="#5.1.2.4">5.1.2.4</a>).
11520 3 Atomically returns the value pointed to by object immediately before the effects.
11521 <a name="7.17.7.4" href="#7.17.7.4"><b> 7.17.7.4 The atomic_compare_exchange generic functions</b></a>
11523 1 #include <a href="#7.17"><stdatomic.h></a>
11524 _Bool atomic_compare_exchange_strong(volatile A *object,
11525 C *expected, C desired);
11526 _Bool atomic_compare_exchange_strong_explicit(
11527 volatile A *object, C *expected, C desired,
11528 memory_order success, memory_order failure);
11529 _Bool atomic_compare_exchange_weak(volatile A *object,
11530 C *expected, C desired);
11531 _Bool atomic_compare_exchange_weak_explicit(
11532 volatile A *object, C *expected, C desired,
11533 memory_order success, memory_order failure);
11534 <b> Description</b>
11535 2 The failure argument shall not be memory_order_release nor
11536 memory_order_acq_rel. The failure argument shall be no stronger than the
11537 success argument. Atomically, compares the value pointed to by object for equality
11538 with that in expected, and if true, replaces the value pointed to by object with
11539 desired, and if false, updates the value in expected with the value pointed to by
11540 object. Further, if the comparison is true, memory is affected according to the value of
11541 success, and if the comparison is false, memory is affected according to the value of
11542 failure. These operations are atomic read-modify-write operations (<a href="#5.1.2.4">5.1.2.4</a>).
11543 3 NOTE 1 The effect of the compare-and-exchange operations is
11548 [<a name="p282" href="#p282">page 282</a>] (<a href="#Contents">Contents</a>)
11550 if (*object == *expected)
11553 *expected = *object;
11555 4 The weak compare-and-exchange operations may fail spuriously, that is, return zero
11556 while leaving the value pointed to by expected unchanged.
11557 5 NOTE 2 This spurious failure enables implementation of compare-and-exchange on a broader class of
11558 machines, e.g. load-locked store-conditional machines.
11560 6 EXAMPLE A consequence of spurious failure is that nearly all uses of weak compare-and-exchange will
11562 exp = atomic_load(&cur);
11564 des = function(exp);
11565 } while (!atomic_compare_exchange_weak(&cur, &exp, des));
11566 When a compare-and-exchange is in a loop, the weak version will yield better performance on some
11567 platforms. When a weak compare-and-exchange would require a loop and a strong one would not, the
11568 strong one is preferable.
11571 7 The result of the comparison.
11572 <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>
11573 1 The following operations perform arithmetic and bitwise computations. All of these
11574 operations are applicable to an object of any atomic integer type. Only addition and
11575 subtraction are applicable to atomic_address. None of these operations is applicable
11576 to atomic_bool. The key, operator, and computation correspondence is:
11580 or | bitwise inclusive or
11581 xor ^ bitwise exclusive or
11582 and & bitwise and
11584 2 #include <a href="#7.17"><stdatomic.h></a>
11585 C atomic_fetch_key(volatile A *object, M operand);
11586 C atomic_fetch_key_explicit(volatile A *object,
11587 M operand, memory_order order);
11588 <b> Description</b>
11589 3 Atomically replaces the value pointed to by object with the result of the computation
11590 applied to the value pointed to by object and the given operand. Memory is affected
11591 according to the value of order. These operations are atomic read-modify-write
11592 [<a name="p283" href="#p283">page 283</a>] (<a href="#Contents">Contents</a>)
11594 operations (<a href="#5.1.2.4">5.1.2.4</a>). For signed integer types, arithmetic is defined to use two's
11595 complement representation with silent wrap-around on overflow; there are no undefined
11596 results. For address types, the result may be an undefined address, but the operations
11597 otherwise have no undefined behavior.
11599 4 Atomically, the value pointed to by object immediately before the effects.
11600 5 NOTE The operation of the atomic_fetch and modify generic functions are nearly equivalent to the
11601 operation of the corresponding op= compound assignment operators. The only differences are that the
11602 compound assignment operators are not guaranteed to operate atomically, and the value yielded by a
11603 compound assignment operator is the updated value of the object, whereas the value returned by the
11604 atomic_fetch and modify generic functions is the previous value of the atomic object.
11606 <a name="7.17.8" href="#7.17.8"><b> 7.17.8 Atomic flag type and operations</b></a>
11607 1 The atomic_flag type provides the classic test-and-set functionality. It has two
11608 states, set and clear.
11609 2 Operations on an object of type atomic_flag shall be lock free.
11610 3 NOTE Hence the operations should also be address-free. No other type requires lock-free operations, so
11611 the atomic_flag type is the minimum hardware-implemented type needed to conform to this
11612 International standard. The remaining types can be emulated with atomic_flag, though with less than
11615 4 The macro ATOMIC_FLAG_INIT may be used to initialize an atomic_flag to the
11616 clear state. An atomic_flag that is not explicitly initialized with
11617 ATOMIC_FLAG_INIT is initially in an indeterminate state.
11619 atomic_flag guard = ATOMIC_FLAG_INIT;
11621 <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>
11623 1 #include <a href="#7.17"><stdatomic.h></a>
11624 bool atomic_flag_test_and_set(
11625 volatile atomic_flag *object);
11626 bool atomic_flag_test_and_set_explicit(
11627 volatile atomic_flag *object, memory_order order);
11628 <b> Description</b>
11629 2 Atomically sets the value pointed to by object to true. Memory is affected according
11630 to the value of order. These operations are atomic read-modify-write operations
11631 (<a href="#5.1.2.4">5.1.2.4</a>).
11636 [<a name="p284" href="#p284">page 284</a>] (<a href="#Contents">Contents</a>)
11639 3 Atomically, the value of the object immediately before the effects.
11640 <a name="7.17.8.2" href="#7.17.8.2"><b> 7.17.8.2 The atomic_flag_clear functions</b></a>
11642 1 #include <a href="#7.17"><stdatomic.h></a>
11643 void atomic_flag_clear(volatile atomic_flag *object);
11644 void atomic_flag_clear_explicit(
11645 volatile atomic_flag *object, memory_order order);
11646 <b> Description</b>
11647 2 The order argument shall not be memory_order_acquire nor
11648 memory_order_acq_rel. Atomically sets the value pointed to by object to false.
11649 Memory is affected according to the value of order.
11651 3 The atomic_flag_clear functions return no value.
11656 [<a name="p285" href="#p285">page 285</a>] (<a href="#Contents">Contents</a>)
11658 <a name="7.18" href="#7.18"><b> 7.18 Boolean type and values <stdbool.h></b></a>
11659 1 The header <a href="#7.18"><stdbool.h></a> defines four macros.
11663 3 The remaining three macros are suitable for use in #if preprocessing directives. They
11666 which expands to the integer constant 1,
11668 which expands to the integer constant 0, and
11669 __bool_true_false_are_defined
11670 which expands to the integer constant 1.
11671 4 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
11672 redefine the macros bool, true, and false.<sup><a href="#note252"><b>252)</b></a></sup>
11677 <sup><a name="note252" href="#note252"><b>252)</b></a></sup> See ''future library directions'' (<a href="#7.30.7">7.30.7</a>).
11679 [<a name="p286" href="#p286">page 286</a>] (<a href="#Contents">Contents</a>)
11681 <a name="7.19" href="#7.19"><b> 7.19 Common definitions <stddef.h></b></a>
11682 1 The header <a href="#7.19"><stddef.h></a> defines the following macros and declares the following types.
11683 Some are also defined in other headers, as noted in their respective subclauses.
11686 which is the signed integer type of the result of subtracting two pointers;
11688 which is the unsigned integer type of the result of the sizeof operator;
11690 which is an object type whose alignment is as great as is supported by the implementation
11691 in all contexts; and
11693 which is an integer type whose range of values can represent distinct codes for all
11694 members of the largest extended character set specified among the supported locales; the
11695 null character shall have the code value zero. Each member of the basic character set
11696 shall have a code value equal to its value when used as the lone character in an integer
11697 character constant if an implementation does not define
11698 __STDC_MB_MIGHT_NEQ_WC__.
11701 which expands to an implementation-defined null pointer constant; and
11702 offsetof(type, member-designator)
11703 which expands to an integer constant expression that has type size_t, the value of
11704 which is the offset in bytes, to the structure member (designated by member-designator),
11705 from the beginning of its structure (designated by type). The type and member designator
11706 shall be such that given
11708 then the expression &(t.member-designator) evaluates to an address constant. (If the
11709 specified member is a bit-field, the behavior is undefined.)
11710 Recommended practice
11711 4 The types used for size_t and ptrdiff_t should not have an integer conversion rank
11712 greater than that of signed long int unless the implementation supports objects
11713 large enough to make this necessary.
11715 [<a name="p287" href="#p287">page 287</a>] (<a href="#Contents">Contents</a>)
11717 Forward references: localization (<a href="#7.11">7.11</a>).
11722 [<a name="p288" href="#p288">page 288</a>] (<a href="#Contents">Contents</a>)
11724 <a name="7.20" href="#7.20"><b> 7.20 Integer types <stdint.h></b></a>
11725 1 The header <a href="#7.20"><stdint.h></a> declares sets of integer types having specified widths, and
11726 defines corresponding sets of macros.<sup><a href="#note253"><b>253)</b></a></sup> It also defines macros that specify limits of
11727 integer types corresponding to types defined in other standard headers.
11728 2 Types are defined in the following categories:
11729 -- integer types having certain exact widths;
11730 -- integer types having at least certain specified widths;
11731 -- fastest integer types having at least certain specified widths;
11732 -- integer types wide enough to hold pointers to objects;
11733 -- integer types having greatest width.
11734 (Some of these types may denote the same type.)
11735 3 Corresponding macros specify limits of the declared types and construct suitable
11737 4 For each type described herein that the implementation provides,<sup><a href="#note254"><b>254)</b></a></sup> <a href="#7.20"><stdint.h></a> shall
11738 declare that typedef name and define the associated macros. Conversely, for each type
11739 described herein that the implementation does not provide, <a href="#7.20"><stdint.h></a> shall not
11740 declare that typedef name nor shall it define the associated macros. An implementation
11741 shall provide those types described as ''required'', but need not provide any of the others
11742 (described as ''optional'').
11743 <a name="7.20.1" href="#7.20.1"><b> 7.20.1 Integer types</b></a>
11744 1 When typedef names differing only in the absence or presence of the initial u are defined,
11745 they shall denote corresponding signed and unsigned types as described in <a href="#6.2.5">6.2.5</a>; an
11746 implementation providing one of these corresponding types shall also provide the other.
11747 2 In the following descriptions, the symbol N represents an unsigned decimal integer with
11748 no leading zeros (e.g., 8 or 24, but not 04 or 048).
11753 <sup><a name="note253" href="#note253"><b>253)</b></a></sup> See ''future library directions'' (<a href="#7.30.8">7.30.8</a>).
11754 <sup><a name="note254" href="#note254"><b>254)</b></a></sup> Some of these types may denote implementation-defined extended integer types.
11756 [<a name="p289" href="#p289">page 289</a>] (<a href="#Contents">Contents</a>)
11758 <a name="7.20.1.1" href="#7.20.1.1"><b> 7.20.1.1 Exact-width integer types</b></a>
11759 1 The typedef name intN_t designates a signed integer type with width N , no padding
11760 bits, and a two's complement representation. Thus, int8_t denotes such a signed
11761 integer type with a width of exactly 8 bits.
11762 2 The typedef name uintN_t designates an unsigned integer type with width N and no
11763 padding bits. Thus, uint24_t denotes such an unsigned integer type with a width of
11765 3 These types are optional. However, if an implementation provides integer types with
11766 widths of 8, 16, 32, or 64 bits, no padding bits, and (for the signed types) that have a
11767 two's complement representation, it shall define the corresponding typedef names.
11768 <a name="7.20.1.2" href="#7.20.1.2"><b> 7.20.1.2 Minimum-width integer types</b></a>
11769 1 The typedef name int_leastN_t designates a signed integer type with a width of at
11770 least N , such that no signed integer type with lesser size has at least the specified width.
11771 Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits.
11772 2 The typedef name uint_leastN_t designates an unsigned integer type with a width
11773 of at least N , such that no unsigned integer type with lesser size has at least the specified
11774 width. Thus, uint_least16_t denotes an unsigned integer type with a width of at
11776 3 The following types are required:
11777 int_least8_t uint_least8_t
11778 int_least16_t uint_least16_t
11779 int_least32_t uint_least32_t
11780 int_least64_t uint_least64_t
11781 All other types of this form are optional.
11782 <a name="7.20.1.3" href="#7.20.1.3"><b> 7.20.1.3 Fastest minimum-width integer types</b></a>
11783 1 Each of the following types designates an integer type that is usually fastest<sup><a href="#note255"><b>255)</b></a></sup> to operate
11784 with among all integer types that have at least the specified width.
11785 2 The typedef name int_fastN_t designates the fastest signed integer type with a width
11786 of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer
11787 type with a width of at least N .
11792 <sup><a name="note255" href="#note255"><b>255)</b></a></sup> The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear
11793 grounds for choosing one type over another, it will simply pick some integer type satisfying the
11794 signedness and width requirements.
11796 [<a name="p290" href="#p290">page 290</a>] (<a href="#Contents">Contents</a>)
11798 3 The following types are required:
11799 int_fast8_t uint_fast8_t
11800 int_fast16_t uint_fast16_t
11801 int_fast32_t uint_fast32_t
11802 int_fast64_t uint_fast64_t
11803 All other types of this form are optional.
11804 <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>
11805 1 The following type designates a signed integer type with the property that any valid
11806 pointer to void can be converted to this type, then converted back to pointer to void,
11807 and the result will compare equal to the original pointer:
11809 The following type designates an unsigned integer type with the property that any valid
11810 pointer to void can be converted to this type, then converted back to pointer to void,
11811 and the result will compare equal to the original pointer:
11813 These types are optional.
11814 <a name="7.20.1.5" href="#7.20.1.5"><b> 7.20.1.5 Greatest-width integer types</b></a>
11815 1 The following type designates a signed integer type capable of representing any value of
11816 any signed integer type:
11818 The following type designates an unsigned integer type capable of representing any value
11819 of any unsigned integer type:
11821 These types are required.
11822 <a name="7.20.2" href="#7.20.2"><b> 7.20.2 Limits of specified-width integer types</b></a>
11823 1 The following object-like macros specify the minimum and maximum limits of the types *
11824 declared in <a href="#7.20"><stdint.h></a>. Each macro name corresponds to a similar type name in
11825 <a href="#7.20.1">7.20.1</a>.
11826 2 Each instance of any defined macro shall be replaced by a constant expression suitable
11827 for use in #if preprocessing directives, and this expression shall have the same type as
11828 would an expression that is an object of the corresponding type converted according to
11829 the integer promotions. Its implementation-defined value shall be equal to or greater in
11830 magnitude (absolute value) than the corresponding value given below, with the same sign,
11831 except where stated to be exactly the given value.
11833 [<a name="p291" href="#p291">page 291</a>] (<a href="#Contents">Contents</a>)
11835 <a name="7.20.2.1" href="#7.20.2.1"><b> 7.20.2.1 Limits of exact-width integer types</b></a>
11836 1 -- minimum values of exact-width signed integer types
11837 INTN_MIN exactly -(2 N -1 )
11838 -- maximum values of exact-width signed integer types
11839 INTN_MAX exactly 2 N -1 - 1
11840 -- maximum values of exact-width unsigned integer types
11841 UINTN_MAX exactly 2 N - 1
11842 <a name="7.20.2.2" href="#7.20.2.2"><b> 7.20.2.2 Limits of minimum-width integer types</b></a>
11843 1 -- minimum values of minimum-width signed integer types
11844 INT_LEASTN_MIN -(2 N -1 - 1)
11845 -- maximum values of minimum-width signed integer types
11846 INT_LEASTN_MAX 2 N -1 - 1
11847 -- maximum values of minimum-width unsigned integer types
11848 UINT_LEASTN_MAX 2N - 1
11849 <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>
11850 1 -- minimum values of fastest minimum-width signed integer types
11851 INT_FASTN_MIN -(2 N -1 - 1)
11852 -- maximum values of fastest minimum-width signed integer types
11853 INT_FASTN_MAX 2 N -1 - 1
11854 -- maximum values of fastest minimum-width unsigned integer types
11855 UINT_FASTN_MAX 2N - 1
11856 <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>
11857 1 -- minimum value of pointer-holding signed integer type
11858 INTPTR_MIN -(215 - 1)
11859 -- maximum value of pointer-holding signed integer type
11861 -- maximum value of pointer-holding unsigned integer type
11862 UINTPTR_MAX 216 - 1
11866 [<a name="p292" href="#p292">page 292</a>] (<a href="#Contents">Contents</a>)
11868 <a name="7.20.2.5" href="#7.20.2.5"><b> 7.20.2.5 Limits of greatest-width integer types</b></a>
11869 1 -- minimum value of greatest-width signed integer type
11870 INTMAX_MIN -(263 - 1)
11871 -- maximum value of greatest-width signed integer type
11873 -- maximum value of greatest-width unsigned integer type
11874 UINTMAX_MAX 264 - 1
11875 <a name="7.20.3" href="#7.20.3"><b> 7.20.3 Limits of other integer types</b></a>
11876 1 The following object-like macros specify the minimum and maximum limits of integer *
11877 types corresponding to types defined in other standard headers.
11878 2 Each instance of these macros shall be replaced by a constant expression suitable for use
11879 in #if preprocessing directives, and this expression shall have the same type as would an
11880 expression that is an object of the corresponding type converted according to the integer
11881 promotions. Its implementation-defined value shall be equal to or greater in magnitude
11882 (absolute value) than the corresponding value given below, with the same sign. An
11883 implementation shall define only the macros corresponding to those typedef names it
11884 actually provides.<sup><a href="#note256"><b>256)</b></a></sup>
11885 -- limits of ptrdiff_t
11888 -- limits of sig_atomic_t
11889 SIG_ATOMIC_MIN see below
11890 SIG_ATOMIC_MAX see below
11893 -- limits of wchar_t
11894 WCHAR_MIN see below
11895 WCHAR_MAX see below
11896 -- limits of wint_t
11901 <sup><a name="note256" href="#note256"><b>256)</b></a></sup> A freestanding implementation need not provide all of these types.
11903 [<a name="p293" href="#p293">page 293</a>] (<a href="#Contents">Contents</a>)
11907 3 If sig_atomic_t (see <a href="#7.14">7.14</a>) is defined as a signed integer type, the value of
11908 SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX
11909 shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
11910 type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
11911 SIG_ATOMIC_MAX shall be no less than 255.
11912 4 If wchar_t (see <a href="#7.19">7.19</a>) is defined as a signed integer type, the value of WCHAR_MIN
11913 shall be no greater than -127 and the value of WCHAR_MAX shall be no less than 127;
11914 otherwise, wchar_t is defined as an unsigned integer type, and the value of
11915 WCHAR_MIN shall be 0 and the value of WCHAR_MAX shall be no less than 255.<sup><a href="#note257"><b>257)</b></a></sup>
11916 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
11917 be no greater than -32767 and the value of WINT_MAX shall be no less than 32767;
11918 otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
11919 shall be 0 and the value of WINT_MAX shall be no less than 65535.
11920 <a name="7.20.4" href="#7.20.4"><b> 7.20.4 Macros for integer constants</b></a>
11921 1 The following function-like macros expand to integer constants suitable for initializing *
11922 objects that have integer types corresponding to types defined in <a href="#7.20"><stdint.h></a>. Each
11923 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>.
11924 2 The argument in any instance of these macros shall be an unsuffixed integer constant (as
11925 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.
11926 3 Each invocation of one of these macros shall expand to an integer constant expression
11927 suitable for use in #if preprocessing directives. The type of the expression shall have
11928 the same type as would an expression of the corresponding type converted according to
11929 the integer promotions. The value of the expression shall be that of the argument.
11930 <a name="7.20.4.1" href="#7.20.4.1"><b> 7.20.4.1 Macros for minimum-width integer constants</b></a>
11931 1 The macro INTN_C(value) shall expand to an integer constant expression
11932 corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
11933 to an integer constant expression corresponding to the type uint_leastN_t. For
11934 example, if uint_least64_t is a name for the type unsigned long long int,
11935 then UINT64_C(0x123) might expand to the integer constant 0x123ULL.
11940 <sup><a name="note257" href="#note257"><b>257)</b></a></sup> The values WCHAR_MIN and WCHAR_MAX do not necessarily correspond to members of the extended
11943 [<a name="p294" href="#p294">page 294</a>] (<a href="#Contents">Contents</a>)
11945 <a name="7.20.4.2" href="#7.20.4.2"><b> 7.20.4.2 Macros for greatest-width integer constants</b></a>
11946 1 The following macro expands to an integer constant expression having the value specified
11947 by its argument and the type intmax_t:
11949 The following macro expands to an integer constant expression having the value specified
11950 by its argument and the type uintmax_t:
11956 [<a name="p295" href="#p295">page 295</a>] (<a href="#Contents">Contents</a>)
11958 <a name="7.21" href="#7.21"><b> 7.21 Input/output <stdio.h></b></a>
11959 <a name="7.21.1" href="#7.21.1"><b> 7.21.1 Introduction</b></a>
11960 1 The header <a href="#7.21"><stdio.h></a> defines several macros, and declares three types and many
11961 functions for performing input and output.
11962 2 The types declared are size_t (described in <a href="#7.19">7.19</a>);
11964 which is an object type capable of recording all the information needed to control a
11965 stream, including its file position indicator, a pointer to its associated buffer (if any), an
11966 error indicator that records whether a read/write error has occurred, and an end-of-file
11967 indicator that records whether the end of the file has been reached; and
11969 which is a complete object type other than an array type capable of recording all the
11970 information needed to specify uniquely every position within a file.
11971 3 The macros are NULL (described in <a href="#7.19">7.19</a>);
11975 which expand to integer constant expressions with distinct values, suitable for use as the
11976 third argument to the setvbuf function;
11978 which expands to an integer constant expression that is the size of the buffer used by the
11981 which expands to an integer constant expression, with type int and a negative value, that
11982 is returned by several functions to indicate end-of-file, that is, no more input from a
11985 which expands to an integer constant expression that is the minimum number of files that
11986 the implementation guarantees can be open simultaneously;
11988 which expands to an integer constant expression that is the size needed for an array of
11989 char large enough to hold the longest file name string that the implementation
11993 [<a name="p296" href="#p296">page 296</a>] (<a href="#Contents">Contents</a>)
11995 guarantees can be opened;<sup><a href="#note258"><b>258)</b></a></sup>
11997 which expands to an integer constant expression that is the size needed for an array of
11998 char large enough to hold a temporary file name string generated by the tmpnam
12003 which expand to integer constant expressions with distinct values, suitable for use as the
12004 third argument to the fseek function;
12006 which expands to an integer constant expression that is the minimum number of unique
12007 file names that can be generated by the tmpnam function;
12011 which are expressions of type ''pointer to FILE'' that point to the FILE objects
12012 associated, respectively, with the standard error, input, and output streams.
12013 4 The header <a href="#7.28"><wchar.h></a> declares a number of functions useful for wide character input
12014 and output. The wide character input/output functions described in that subclause
12015 provide operations analogous to most of those described here, except that the
12016 fundamental units internal to the program are wide characters. The external
12017 representation (in the file) is a sequence of ''generalized'' multibyte characters, as
12018 described further in <a href="#7.21.3">7.21.3</a>.
12019 5 The input/output functions are given the following collective terms:
12020 -- The wide character input functions -- those functions described in <a href="#7.28">7.28</a> that perform
12021 input into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar,
12022 fwscanf, wscanf, vfwscanf, and vwscanf.
12023 -- The wide character output functions -- those functions described in <a href="#7.28">7.28</a> that perform
12024 output from wide characters and wide strings: fputwc, fputws, putwc,
12025 putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
12028 <sup><a name="note258" href="#note258"><b>258)</b></a></sup> If the implementation imposes no practical limit on the length of file name strings, the value of
12029 FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
12030 string. Of course, file name string contents are subject to other system-specific constraints; therefore
12031 all possible strings of length FILENAME_MAX cannot be expected to be opened successfully.
12033 [<a name="p297" href="#p297">page 297</a>] (<a href="#Contents">Contents</a>)
12035 -- The wide character input/output functions -- the union of the ungetwc function, the
12036 wide character input functions, and the wide character output functions.
12037 -- The byte input/output functions -- those functions described in this subclause that
12038 perform input/output: fgetc, fgets, fprintf, fputc, fputs, fread,
12039 fscanf, fwrite, getc, getchar, printf, putc, putchar, puts, scanf, *
12040 ungetc, vfprintf, vfscanf, vprintf, and vscanf.
12041 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
12042 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>).
12043 <a name="7.21.2" href="#7.21.2"><b> 7.21.2 Streams</b></a>
12044 1 Input and output, whether to or from physical devices such as terminals and tape drives,
12045 or whether to or from files supported on structured storage devices, are mapped into
12046 logical data streams, whose properties are more uniform than their various inputs and
12047 outputs. Two forms of mapping are supported, for text streams and for binary
12048 streams.<sup><a href="#note259"><b>259)</b></a></sup>
12049 2 A text stream is an ordered sequence of characters composed into lines, each line
12050 consisting of zero or more characters plus a terminating new-line character. Whether the
12051 last line requires a terminating new-line character is implementation-defined. Characters
12052 may have to be added, altered, or deleted on input and output to conform to differing
12053 conventions for representing text in the host environment. Thus, there need not be a one-
12054 to-one correspondence between the characters in a stream and those in the external
12055 representation. Data read in from a text stream will necessarily compare equal to the data
12056 that were earlier written out to that stream only if: the data consist only of printing
12057 characters and the control characters horizontal tab and new-line; no new-line character is
12058 immediately preceded by space characters; and the last character is a new-line character.
12059 Whether space characters that are written out immediately before a new-line character
12060 appear when read in is implementation-defined.
12061 3 A binary stream is an ordered sequence of characters that can transparently record
12062 internal data. Data read in from a binary stream shall compare equal to the data that were
12063 earlier written out to that stream, under the same implementation. Such a stream may,
12064 however, have an implementation-defined number of null characters appended to the end
12066 4 Each stream has an orientation. After a stream is associated with an external file, but
12067 before any operations are performed on it, the stream is without orientation. Once a wide
12068 character input/output function has been applied to a stream without orientation, the
12071 <sup><a name="note259" href="#note259"><b>259)</b></a></sup> An implementation need not distinguish between text streams and binary streams. In such an
12072 implementation, there need be no new-line characters in a text stream nor any limit to the length of a
12075 [<a name="p298" href="#p298">page 298</a>] (<a href="#Contents">Contents</a>)
12077 stream becomes a wide-oriented stream. Similarly, once a byte input/output function has
12078 been applied to a stream without orientation, the stream becomes a byte-oriented stream.
12079 Only a call to the freopen function or the fwide function can otherwise alter the
12080 orientation of a stream. (A successful call to freopen removes any orientation.)<sup><a href="#note260"><b>260)</b></a></sup>
12081 5 Byte input/output functions shall not be applied to a wide-oriented stream and wide
12082 character input/output functions shall not be applied to a byte-oriented stream. The
12083 remaining stream operations do not affect, and are not affected by, a stream's orientation,
12084 except for the following additional restrictions:
12085 -- Binary wide-oriented streams have the file-positioning restrictions ascribed to both
12086 text and binary streams.
12087 -- For wide-oriented streams, after a successful call to a file-positioning function that
12088 leaves the file position indicator prior to the end-of-file, a wide character output
12089 function can overwrite a partial multibyte character; any file contents beyond the
12090 byte(s) written are henceforth indeterminate.
12091 6 Each wide-oriented stream has an associated mbstate_t object that stores the current
12092 parse state of the stream. A successful call to fgetpos stores a representation of the
12093 value of this mbstate_t object as part of the value of the fpos_t object. A later
12094 successful call to fsetpos using the same stored fpos_t value restores the value of
12095 the associated mbstate_t object as well as the position within the controlled stream.
12096 Environmental limits
12097 7 An implementation shall support text files with lines containing at least 254 characters,
12098 including the terminating new-line character. The value of the macro BUFSIZ shall be at
12100 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>),
12101 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
12102 (<a href="#7.21.9.3">7.21.9.3</a>).
12107 <sup><a name="note260" href="#note260"><b>260)</b></a></sup> The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
12109 [<a name="p299" href="#p299">page 299</a>] (<a href="#Contents">Contents</a>)
12111 <a name="7.21.3" href="#7.21.3"><b> 7.21.3 Files</b></a>
12112 1 A stream is associated with an external file (which may be a physical device) by opening
12113 a file, which may involve creating a new file. Creating an existing file causes its former
12114 contents to be discarded, if necessary. If a file can support positioning requests (such as a
12115 disk file, as opposed to a terminal), then a file position indicator associated with the
12116 stream is positioned at the start (character number zero) of the file, unless the file is
12117 opened with append mode in which case it is implementation-defined whether the file
12118 position indicator is initially positioned at the beginning or the end of the file. The file
12119 position indicator is maintained by subsequent reads, writes, and positioning requests, to
12120 facilitate an orderly progression through the file.
12121 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
12122 stream causes the associated file to be truncated beyond that point is implementation-
12124 3 When a stream is unbuffered, characters are intended to appear from the source or at the
12125 destination as soon as possible. Otherwise characters may be accumulated and
12126 transmitted to or from the host environment as a block. When a stream is fully buffered,
12127 characters are intended to be transmitted to or from the host environment as a block when
12128 a buffer is filled. When a stream is line buffered, characters are intended to be
12129 transmitted to or from the host environment as a block when a new-line character is
12130 encountered. Furthermore, characters are intended to be transmitted as a block to the host
12131 environment when a buffer is filled, when input is requested on an unbuffered stream, or
12132 when input is requested on a line buffered stream that requires the transmission of
12133 characters from the host environment. Support for these characteristics is
12134 implementation-defined, and may be affected via the setbuf and setvbuf functions.
12135 4 A file may be disassociated from a controlling stream by closing the file. Output streams
12136 are flushed (any unwritten buffer contents are transmitted to the host environment) before
12137 the stream is disassociated from the file. The value of a pointer to a FILE object is
12138 indeterminate after the associated file is closed (including the standard text streams).
12139 Whether a file of zero length (on which no characters have been written by an output
12140 stream) actually exists is implementation-defined.
12141 5 The file may be subsequently reopened, by the same or another program execution, and
12142 its contents reclaimed or modified (if it can be repositioned at its start). If the main
12143 function returns to its original caller, or if the exit function is called, all open files are
12144 closed (hence all output streams are flushed) before program termination. Other paths to
12145 program termination, such as calling the abort function, need not close all files
12147 6 The address of the FILE object used to control a stream may be significant; a copy of a
12148 FILE object need not serve in place of the original.
12150 [<a name="p300" href="#p300">page 300</a>] (<a href="#Contents">Contents</a>)
12152 7 At program startup, three text streams are predefined and need not be opened explicitly
12153 -- standard input (for reading conventional input), standard output (for writing
12154 conventional output), and standard error (for writing diagnostic output). As initially
12155 opened, the standard error stream is not fully buffered; the standard input and standard
12156 output streams are fully buffered if and only if the stream can be determined not to refer
12157 to an interactive device.
12158 8 Functions that open additional (nontemporary) files require a file name, which is a string.
12159 The rules for composing valid file names are implementation-defined. Whether the same
12160 file can be simultaneously open multiple times is also implementation-defined.
12161 9 Although both text and binary wide-oriented streams are conceptually sequences of wide
12162 characters, the external file associated with a wide-oriented stream is a sequence of
12163 multibyte characters, generalized as follows:
12164 -- Multibyte encodings within files may contain embedded null bytes (unlike multibyte
12165 encodings valid for use internal to the program).
12166 -- A file need not begin nor end in the initial shift state.<sup><a href="#note261"><b>261)</b></a></sup>
12167 10 Moreover, the encodings used for multibyte characters may differ among files. Both the
12168 nature and choice of such encodings are implementation-defined.
12169 11 The wide character input functions read multibyte characters from the stream and convert
12170 them to wide characters as if they were read by successive calls to the fgetwc function.
12171 Each conversion occurs as if by a call to the mbrtowc function, with the conversion state
12172 described by the stream's own mbstate_t object. The byte input functions read
12173 characters from the stream as if by successive calls to the fgetc function.
12174 12 The wide character output functions convert wide characters to multibyte characters and
12175 write them to the stream as if they were written by successive calls to the fputwc
12176 function. Each conversion occurs as if by a call to the wcrtomb function, with the
12177 conversion state described by the stream's own mbstate_t object. The byte output
12178 functions write characters to the stream as if by successive calls to the fputc function.
12179 13 In some cases, some of the byte input/output functions also perform conversions between
12180 multibyte characters and wide characters. These conversions also occur as if by calls to
12181 the mbrtowc and wcrtomb functions.
12182 14 An encoding error occurs if the character sequence presented to the underlying
12183 mbrtowc function does not form a valid (generalized) multibyte character, or if the code
12184 value passed to the underlying wcrtomb does not correspond to a valid (generalized)
12187 <sup><a name="note261" href="#note261"><b>261)</b></a></sup> Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END), has
12188 undefined behavior for a binary stream (because of possible trailing null characters) or for any stream
12189 with state-dependent encoding that does not assuredly end in the initial shift state.
12191 [<a name="p301" href="#p301">page 301</a>] (<a href="#Contents">Contents</a>)
12193 multibyte character. The wide character input/output functions and the byte input/output
12194 functions store the value of the macro EILSEQ in errno if and only if an encoding error
12196 Environmental limits
12197 15 The value of FOPEN_MAX shall be at least eight, including the three standard text
12199 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
12200 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
12201 (<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
12202 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
12203 (<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>).
12204 <a name="7.21.4" href="#7.21.4"><b> 7.21.4 Operations on files</b></a>
12205 <a name="7.21.4.1" href="#7.21.4.1"><b> 7.21.4.1 The remove function</b></a>
12207 1 #include <a href="#7.21"><stdio.h></a>
12208 int remove(const char *filename);
12209 <b> Description</b>
12210 2 The remove function causes the file whose name is the string pointed to by filename
12211 to be no longer accessible by that name. A subsequent attempt to open that file using that
12212 name will fail, unless it is created anew. If the file is open, the behavior of the remove
12213 function is implementation-defined.
12215 3 The remove function returns zero if the operation succeeds, nonzero if it fails.
12216 <a name="7.21.4.2" href="#7.21.4.2"><b> 7.21.4.2 The rename function</b></a>
12218 1 #include <a href="#7.21"><stdio.h></a>
12219 int rename(const char *old, const char *new);
12220 <b> Description</b>
12221 2 The rename function causes the file whose name is the string pointed to by old to be
12222 henceforth known by the name given by the string pointed to by new. The file named
12223 old is no longer accessible by that name. If a file named by the string pointed to by new
12224 exists prior to the call to the rename function, the behavior is implementation-defined.
12229 [<a name="p302" href="#p302">page 302</a>] (<a href="#Contents">Contents</a>)
12232 3 The rename function returns zero if the operation succeeds, nonzero if it fails,<sup><a href="#note262"><b>262)</b></a></sup> in
12233 which case if the file existed previously it is still known by its original name.
12234 <a name="7.21.4.3" href="#7.21.4.3"><b> 7.21.4.3 The tmpfile function</b></a>
12236 1 #include <a href="#7.21"><stdio.h></a>
12237 FILE *tmpfile(void);
12238 <b> Description</b>
12239 2 The tmpfile function creates a temporary binary file that is different from any other
12240 existing file and that will automatically be removed when it is closed or at program
12241 termination. If the program terminates abnormally, whether an open temporary file is
12242 removed is implementation-defined. The file is opened for update with "wb+" mode.
12243 Recommended practice
12244 3 It should be possible to open at least TMP_MAX temporary files during the lifetime of the
12245 program (this limit may be shared with tmpnam) and there should be no limit on the
12246 number simultaneously open other than this limit and any limit on the number of open
12249 4 The tmpfile function returns a pointer to the stream of the file that it created. If the file
12250 cannot be created, the tmpfile function returns a null pointer.
12251 Forward references: the fopen function (<a href="#7.21.5.3">7.21.5.3</a>).
12252 <a name="7.21.4.4" href="#7.21.4.4"><b> 7.21.4.4 The tmpnam function</b></a>
12254 1 #include <a href="#7.21"><stdio.h></a>
12255 char *tmpnam(char *s);
12256 <b> Description</b>
12257 2 The tmpnam function generates a string that is a valid file name and that is not the same
12258 as the name of an existing file.<sup><a href="#note263"><b>263)</b></a></sup> The function is potentially capable of generating at
12261 <sup><a name="note262" href="#note262"><b>262)</b></a></sup> Among the reasons the implementation may cause the rename function to fail are that the file is open
12262 or that it is necessary to copy its contents to effectuate its renaming.
12263 <sup><a name="note263" href="#note263"><b>263)</b></a></sup> Files created using strings generated by the tmpnam function are temporary only in the sense that
12264 their names should not collide with those generated by conventional naming rules for the
12265 implementation. It is still necessary to use the remove function to remove such files when their use
12266 is ended, and before program termination.
12268 [<a name="p303" href="#p303">page 303</a>] (<a href="#Contents">Contents</a>)
12270 least TMP_MAX different strings, but any or all of them may already be in use by existing
12271 files and thus not be suitable return values.
12272 3 The tmpnam function generates a different string each time it is called.
12273 4 Calls to the tmpnam function with a null pointer argument may introduce data races with
12274 each other. The implementation shall behave as if no library function calls the tmpnam
12277 5 If no suitable string can be generated, the tmpnam function returns a null pointer.
12278 Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an
12279 internal static object and returns a pointer to that object (subsequent calls to the tmpnam
12280 function may modify the same object). If the argument is not a null pointer, it is assumed
12281 to point to an array of at least L_tmpnam chars; the tmpnam function writes its result
12282 in that array and returns the argument as its value.
12283 Environmental limits
12284 6 The value of the macro TMP_MAX shall be at least 25.
12285 <a name="7.21.5" href="#7.21.5"><b> 7.21.5 File access functions</b></a>
12286 <a name="7.21.5.1" href="#7.21.5.1"><b> 7.21.5.1 The fclose function</b></a>
12288 1 #include <a href="#7.21"><stdio.h></a>
12289 int fclose(FILE *stream);
12290 <b> Description</b>
12291 2 A successful call to the fclose function causes the stream pointed to by stream to be
12292 flushed and the associated file to be closed. Any unwritten buffered data for the stream
12293 are delivered to the host environment to be written to the file; any unread buffered data
12294 are discarded. Whether or not the call succeeds, the stream is disassociated from the file
12295 and any buffer set by the setbuf or setvbuf function is disassociated from the stream
12296 (and deallocated if it was automatically allocated).
12298 3 The fclose function returns zero if the stream was successfully closed, or EOF if any
12299 errors were detected.
12304 [<a name="p304" href="#p304">page 304</a>] (<a href="#Contents">Contents</a>)
12306 <a name="7.21.5.2" href="#7.21.5.2"><b> 7.21.5.2 The fflush function</b></a>
12308 1 #include <a href="#7.21"><stdio.h></a>
12309 int fflush(FILE *stream);
12310 <b> Description</b>
12311 2 If stream points to an output stream or an update stream in which the most recent
12312 operation was not input, the fflush function causes any unwritten data for that stream
12313 to be delivered to the host environment to be written to the file; otherwise, the behavior is
12315 3 If stream is a null pointer, the fflush function performs this flushing action on all
12316 streams for which the behavior is defined above.
12318 4 The fflush function sets the error indicator for the stream and returns EOF if a write
12319 error occurs, otherwise it returns zero.
12320 Forward references: the fopen function (<a href="#7.21.5.3">7.21.5.3</a>).
12321 <a name="7.21.5.3" href="#7.21.5.3"><b> 7.21.5.3 The fopen function</b></a>
12323 1 #include <a href="#7.21"><stdio.h></a>
12324 FILE *fopen(const char * restrict filename,
12325 const char * restrict mode);
12326 <b> Description</b>
12327 2 The fopen function opens the file whose name is the string pointed to by filename,
12328 and associates a stream with it.
12329 3 The argument mode points to a string. If the string is one of the following, the file is
12330 open in the indicated mode. Otherwise, the behavior is undefined.<sup><a href="#note264"><b>264)</b></a></sup>
12331 r open text file for reading
12332 w truncate to zero length or create text file for writing
12333 wx create text file for writing
12334 a append; open or create text file for writing at end-of-file
12335 rb open binary file for reading
12336 wb truncate to zero length or create binary file for writing
12339 <sup><a name="note264" href="#note264"><b>264)</b></a></sup> If the string begins with one of the above sequences, the implementation might choose to ignore the
12340 remaining characters, or it might use them to select different kinds of a file (some of which might not
12341 conform to the properties in <a href="#7.21.2">7.21.2</a>).
12343 [<a name="p305" href="#p305">page 305</a>] (<a href="#Contents">Contents</a>)
12345 wbx create binary file for writing
12346 ab append; open or create binary file for writing at end-of-file
12347 r+ open text file for update (reading and writing)
12348 w+ truncate to zero length or create text file for update
12349 w+x create text file for update
12350 a+ append; open or create text file for update, writing at end-of-file
12351 r+b or rb+ open binary file for update (reading and writing)
12352 w+b or wb+ truncate to zero length or create binary file for update
12353 w+bx or wb+x create binary file for update
12354 a+b or ab+ append; open or create binary file for update, writing at end-of-file
12355 4 Opening a file with read mode ('r' as the first character in the mode argument) fails if
12356 the file does not exist or cannot be read.
12357 5 Opening a file with exclusive mode ('x' as the last character in the mode argument)
12358 fails if the file already exists or cannot be created. Otherwise, the file is created with
12359 exclusive (also known as non-shared) access to the extent that the underlying system
12360 supports exclusive access.
12361 6 Opening a file with append mode ('a' as the first character in the mode argument)
12362 causes all subsequent writes to the file to be forced to the then current end-of-file,
12363 regardless of intervening calls to the fseek function. In some implementations, opening
12364 a binary file with append mode ('b' as the second or third character in the above list of
12365 mode argument values) may initially position the file position indicator for the stream
12366 beyond the last data written, because of null character padding.
12367 7 When a file is opened with update mode ('+' as the second or third character in the
12368 above list of mode argument values), both input and output may be performed on the
12369 associated stream. However, output shall not be directly followed by input without an
12370 intervening call to the fflush function or to a file positioning function (fseek,
12371 fsetpos, or rewind), and input shall not be directly followed by output without an
12372 intervening call to a file positioning function, unless the input operation encounters end-
12373 of-file. Opening (or creating) a text file with update mode may instead open (or create) a
12374 binary stream in some implementations.
12375 8 When opened, a stream is fully buffered if and only if it can be determined not to refer to
12376 an interactive device. The error and end-of-file indicators for the stream are cleared.
12378 9 The fopen function returns a pointer to the object controlling the stream. If the open
12379 operation fails, fopen returns a null pointer.
12380 Forward references: file positioning functions (<a href="#7.21.9">7.21.9</a>).
12384 [<a name="p306" href="#p306">page 306</a>] (<a href="#Contents">Contents</a>)
12386 <a name="7.21.5.4" href="#7.21.5.4"><b> 7.21.5.4 The freopen function</b></a>
12388 1 #include <a href="#7.21"><stdio.h></a>
12389 FILE *freopen(const char * restrict filename,
12390 const char * restrict mode,
12391 FILE * restrict stream);
12392 <b> Description</b>
12393 2 The freopen function opens the file whose name is the string pointed to by filename
12394 and associates the stream pointed to by stream with it. The mode argument is used just
12395 as in the fopen function.<sup><a href="#note265"><b>265)</b></a></sup>
12396 3 If filename is a null pointer, the freopen function attempts to change the mode of
12397 the stream to that specified by mode, as if the name of the file currently associated with
12398 the stream had been used. It is implementation-defined which changes of mode are
12399 permitted (if any), and under what circumstances.
12400 4 The freopen function first attempts to close any file that is associated with the specified
12401 stream. Failure to close the file is ignored. The error and end-of-file indicators for the
12402 stream are cleared.
12404 5 The freopen function returns a null pointer if the open operation fails. Otherwise,
12405 freopen returns the value of stream.
12406 <a name="7.21.5.5" href="#7.21.5.5"><b> 7.21.5.5 The setbuf function</b></a>
12408 1 #include <a href="#7.21"><stdio.h></a>
12409 void setbuf(FILE * restrict stream,
12410 char * restrict buf);
12411 <b> Description</b>
12412 2 Except that it returns no value, the setbuf function is equivalent to the setvbuf
12413 function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
12414 is a null pointer), with the value _IONBF for mode.
12419 <sup><a name="note265" href="#note265"><b>265)</b></a></sup> The primary use of the freopen function is to change the file associated with a standard text stream
12420 (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value
12421 returned by the fopen function may be assigned.
12423 [<a name="p307" href="#p307">page 307</a>] (<a href="#Contents">Contents</a>)
12426 3 The setbuf function returns no value.
12427 Forward references: the setvbuf function (<a href="#7.21.5.6">7.21.5.6</a>).
12428 <a name="7.21.5.6" href="#7.21.5.6"><b> 7.21.5.6 The setvbuf function</b></a>
12430 1 #include <a href="#7.21"><stdio.h></a>
12431 int setvbuf(FILE * restrict stream,
12432 char * restrict buf,
12433 int mode, size_t size);
12434 <b> Description</b>
12435 2 The setvbuf function may be used only after the stream pointed to by stream has
12436 been associated with an open file and before any other operation (other than an
12437 unsuccessful call to setvbuf) is performed on the stream. The argument mode
12438 determines how stream will be buffered, as follows: _IOFBF causes input/output to be
12439 fully buffered; _IOLBF causes input/output to be line buffered; _IONBF causes
12440 input/output to be unbuffered. If buf is not a null pointer, the array it points to may be
12441 used instead of a buffer allocated by the setvbuf function<sup><a href="#note266"><b>266)</b></a></sup> and the argument size
12442 specifies the size of the array; otherwise, size may determine the size of a buffer
12443 allocated by the setvbuf function. The contents of the array at any time are
12446 3 The setvbuf function returns zero on success, or nonzero if an invalid value is given
12447 for mode or if the request cannot be honored.
12452 <sup><a name="note266" href="#note266"><b>266)</b></a></sup> The buffer has to have a lifetime at least as great as the open stream, so the stream should be closed
12453 before a buffer that has automatic storage duration is deallocated upon block exit.
12455 [<a name="p308" href="#p308">page 308</a>] (<a href="#Contents">Contents</a>)
12457 <a name="7.21.6" href="#7.21.6"><b> 7.21.6 Formatted input/output functions</b></a>
12458 1 The formatted input/output functions shall behave as if there is a sequence point after the
12459 actions associated with each specifier.<sup><a href="#note267"><b>267)</b></a></sup>
12460 <a name="7.21.6.1" href="#7.21.6.1"><b> 7.21.6.1 The fprintf function</b></a>
12462 1 #include <a href="#7.21"><stdio.h></a>
12463 int fprintf(FILE * restrict stream,
12464 const char * restrict format, ...);
12465 <b> Description</b>
12466 2 The fprintf function writes output to the stream pointed to by stream, under control
12467 of the string pointed to by format that specifies how subsequent arguments are
12468 converted for output. If there are insufficient arguments for the format, the behavior is
12469 undefined. If the format is exhausted while arguments remain, the excess arguments are
12470 evaluated (as always) but are otherwise ignored. The fprintf function returns when
12471 the end of the format string is encountered.
12472 3 The format shall be a multibyte character sequence, beginning and ending in its initial
12473 shift state. The format is composed of zero or more directives: ordinary multibyte
12474 characters (not %), which are copied unchanged to the output stream; and conversion
12475 specifications, each of which results in fetching zero or more subsequent arguments,
12476 converting them, if applicable, according to the corresponding conversion specifier, and
12477 then writing the result to the output stream.
12478 4 Each conversion specification is introduced by the character %. After the %, the following
12479 appear in sequence:
12480 -- Zero or more flags (in any order) that modify the meaning of the conversion
12482 -- An optional minimum field width. If the converted value has fewer characters than the
12483 field width, it is padded with spaces (by default) on the left (or right, if the left
12484 adjustment flag, described later, has been given) to the field width. The field width
12485 takes the form of an asterisk * (described later) or a nonnegative decimal integer.<sup><a href="#note268"><b>268)</b></a></sup>
12486 -- An optional precision that gives the minimum number of digits to appear for the d, i,
12487 o, u, x, and X conversions, the number of digits to appear after the decimal-point
12488 character for a, A, e, E, f, and F conversions, the maximum number of significant
12489 digits for the g and G conversions, or the maximum number of bytes to be written for
12492 <sup><a name="note267" href="#note267"><b>267)</b></a></sup> The fprintf functions perform writes to memory for the %n specifier.
12493 <sup><a name="note268" href="#note268"><b>268)</b></a></sup> Note that 0 is taken as a flag, not as the beginning of a field width.
12495 [<a name="p309" href="#p309">page 309</a>] (<a href="#Contents">Contents</a>)
12497 s conversions. The precision takes the form of a period (.) followed either by an
12498 asterisk * (described later) or by an optional decimal integer; if only the period is
12499 specified, the precision is taken as zero. If a precision appears with any other
12500 conversion specifier, the behavior is undefined.
12501 -- An optional length modifier that specifies the size of the argument.
12502 -- A conversion specifier character that specifies the type of conversion to be applied.
12503 5 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
12504 this case, an int argument supplies the field width or precision. The arguments
12505 specifying field width, or precision, or both, shall appear (in that order) before the
12506 argument (if any) to be converted. A negative field width argument is taken as a - flag
12507 followed by a positive field width. A negative precision argument is taken as if the
12508 precision were omitted.
12509 6 The flag characters and their meanings are:
12510 - The result of the conversion is left-justified within the field. (It is right-justified if
12511 this flag is not specified.)
12512 + The result of a signed conversion always begins with a plus or minus sign. (It
12513 begins with a sign only when a negative value is converted if this flag is not
12514 specified.)<sup><a href="#note269"><b>269)</b></a></sup>
12515 space If the first character of a signed conversion is not a sign, or if a signed conversion
12516 results in no characters, a space is prefixed to the result. If the space and + flags
12517 both appear, the space flag is ignored.
12518 # The result is converted to an ''alternative form''. For o conversion, it increases
12519 the precision, if and only if necessary, to force the first digit of the result to be a
12520 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
12521 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
12522 and G conversions, the result of converting a floating-point number always
12523 contains a decimal-point character, even if no digits follow it. (Normally, a
12524 decimal-point character appears in the result of these conversions only if a digit
12525 follows it.) For g and G conversions, trailing zeros are not removed from the
12526 result. For other conversions, the behavior is undefined.
12527 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
12528 (following any indication of sign or base) are used to pad to the field width rather
12529 than performing space padding, except when converting an infinity or NaN. If the
12530 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
12533 <sup><a name="note269" href="#note269"><b>269)</b></a></sup> The results of all floating conversions of a negative zero, and of negative values that round to zero,
12534 include a minus sign.
12536 [<a name="p310" href="#p310">page 310</a>] (<a href="#Contents">Contents</a>)
12538 conversions, if a precision is specified, the 0 flag is ignored. For other
12539 conversions, the behavior is undefined.
12540 7 The length modifiers and their meanings are:
12541 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12542 signed char or unsigned char argument (the argument will have
12543 been promoted according to the integer promotions, but its value shall be
12544 converted to signed char or unsigned char before printing); or that
12545 a following n conversion specifier applies to a pointer to a signed char
12547 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12548 short int or unsigned short int argument (the argument will
12549 have been promoted according to the integer promotions, but its value shall
12550 be converted to short int or unsigned short int before printing);
12551 or that a following n conversion specifier applies to a pointer to a short
12553 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12554 long int or unsigned long int argument; that a following n
12555 conversion specifier applies to a pointer to a long int argument; that a
12556 following c conversion specifier applies to a wint_t argument; that a
12557 following s conversion specifier applies to a pointer to a wchar_t
12558 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
12560 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12561 long long int or unsigned long long int argument; or that a
12562 following n conversion specifier applies to a pointer to a long long int
12564 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
12565 an intmax_t or uintmax_t argument; or that a following n conversion
12566 specifier applies to a pointer to an intmax_t argument.
12567 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12568 size_t or the corresponding signed integer type argument; or that a
12569 following n conversion specifier applies to a pointer to a signed integer type
12570 corresponding to size_t argument.
12571 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12572 ptrdiff_t or the corresponding unsigned integer type argument; or that a
12573 following n conversion specifier applies to a pointer to a ptrdiff_t
12577 [<a name="p311" href="#p311">page 311</a>] (<a href="#Contents">Contents</a>)
12579 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
12580 applies to a long double argument.
12581 If a length modifier appears with any conversion specifier other than as specified above,
12582 the behavior is undefined.
12583 8 The conversion specifiers and their meanings are:
12584 d,i The int argument is converted to signed decimal in the style [-]dddd. The
12585 precision specifies the minimum number of digits to appear; if the value
12586 being converted can be represented in fewer digits, it is expanded with
12587 leading zeros. The default precision is 1. The result of converting a zero
12588 value with a precision of zero is no characters.
12589 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
12590 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
12591 letters abcdef are used for x conversion and the letters ABCDEF for X
12592 conversion. The precision specifies the minimum number of digits to appear;
12593 if the value being converted can be represented in fewer digits, it is expanded
12594 with leading zeros. The default precision is 1. The result of converting a
12595 zero value with a precision of zero is no characters.
12596 f,F A double argument representing a floating-point number is converted to
12597 decimal notation in the style [-]ddd.ddd, where the number of digits after
12598 the decimal-point character is equal to the precision specification. If the
12599 precision is missing, it is taken as 6; if the precision is zero and the # flag is
12600 not specified, no decimal-point character appears. If a decimal-point
12601 character appears, at least one digit appears before it. The value is rounded to
12602 the appropriate number of digits.
12603 A double argument representing an infinity is converted in one of the styles
12604 [-]inf or [-]infinity -- which style is implementation-defined. A
12605 double argument representing a NaN is converted in one of the styles
12606 [-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
12607 any n-char-sequence, is implementation-defined. The F conversion specifier
12608 produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
12609 respectively.<sup><a href="#note270"><b>270)</b></a></sup>
12610 e,E A double argument representing a floating-point number is converted in the
12611 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
12612 argument is nonzero) before the decimal-point character and the number of
12613 digits after it is equal to the precision; if the precision is missing, it is taken as
12616 <sup><a name="note270" href="#note270"><b>270)</b></a></sup> When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning;
12617 the # and 0 flag characters have no effect.
12619 [<a name="p312" href="#p312">page 312</a>] (<a href="#Contents">Contents</a>)
12621 6; if the precision is zero and the # flag is not specified, no decimal-point
12622 character appears. The value is rounded to the appropriate number of digits.
12623 The E conversion specifier produces a number with E instead of e
12624 introducing the exponent. The exponent always contains at least two digits,
12625 and only as many more digits as necessary to represent the exponent. If the
12626 value is zero, the exponent is zero.
12627 A double argument representing an infinity or NaN is converted in the style
12628 of an f or F conversion specifier.
12629 g,G A double argument representing a floating-point number is converted in
12630 style f or e (or in style F or E in the case of a G conversion specifier),
12631 depending on the value converted and the precision. Let P equal the
12632 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
12633 Then, if a conversion with style E would have an exponent of X:
12634 -- if P > X >= -4, the conversion is with style f (or F) and precision
12636 -- otherwise, the conversion is with style e (or E) and precision P - 1.
12637 Finally, unless the # flag is used, any trailing zeros are removed from the
12638 fractional portion of the result and the decimal-point character is removed if
12639 there is no fractional portion remaining.
12640 A double argument representing an infinity or NaN is converted in the style
12641 of an f or F conversion specifier.
12642 a,A A double argument representing a floating-point number is converted in the
12643 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
12644 nonzero if the argument is a normalized floating-point number and is
12645 otherwise unspecified) before the decimal-point character<sup><a href="#note271"><b>271)</b></a></sup> and the number
12646 of hexadecimal digits after it is equal to the precision; if the precision is
12647 missing and FLT_RADIX is a power of 2, then the precision is sufficient for
12648 an exact representation of the value; if the precision is missing and
12649 FLT_RADIX is not a power of 2, then the precision is sufficient to
12654 <sup><a name="note271" href="#note271"><b>271)</b></a></sup> Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so
12655 that subsequent digits align to nibble (4-bit) boundaries.
12657 [<a name="p313" href="#p313">page 313</a>] (<a href="#Contents">Contents</a>)
12659 distinguish<sup><a href="#note272"><b>272)</b></a></sup> values of type double, except that trailing zeros may be
12660 omitted; if the precision is zero and the # flag is not specified, no decimal-
12661 point character appears. The letters abcdef are used for a conversion and
12662 the letters ABCDEF for A conversion. The A conversion specifier produces a
12663 number with X and P instead of x and p. The exponent always contains at
12664 least one digit, and only as many more digits as necessary to represent the
12665 decimal exponent of 2. If the value is zero, the exponent is zero.
12666 A double argument representing an infinity or NaN is converted in the style
12667 of an f or F conversion specifier.
12668 c If no l length modifier is present, the int argument is converted to an
12669 unsigned char, and the resulting character is written.
12670 If an l length modifier is present, the wint_t argument is converted as if by
12671 an ls conversion specification with no precision and an argument that points
12672 to the initial element of a two-element array of wchar_t, the first element
12673 containing the wint_t argument to the lc conversion specification and the
12674 second a null wide character.
12675 s If no l length modifier is present, the argument shall be a pointer to the initial
12676 element of an array of character type.<sup><a href="#note273"><b>273)</b></a></sup> Characters from the array are
12677 written up to (but not including) the terminating null character. If the
12678 precision is specified, no more than that many bytes are written. If the
12679 precision is not specified or is greater than the size of the array, the array shall
12680 contain a null character.
12681 If an l length modifier is present, the argument shall be a pointer to the initial
12682 element of an array of wchar_t type. Wide characters from the array are
12683 converted to multibyte characters (each as if by a call to the wcrtomb
12684 function, with the conversion state described by an mbstate_t object
12685 initialized to zero before the first wide character is converted) up to and
12686 including a terminating null wide character. The resulting multibyte
12687 characters are written up to (but not including) the terminating null character
12688 (byte). If no precision is specified, the array shall contain a null wide
12689 character. If a precision is specified, no more than that many bytes are
12690 written (including shift sequences, if any), and the array shall contain a null
12691 wide character if, to equal the multibyte character sequence length given by
12693 <sup><a name="note272" href="#note272"><b>272)</b></a></sup> The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
12694 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
12695 might suffice depending on the implementation's scheme for determining the digit to the left of the
12696 decimal-point character.
12697 <sup><a name="note273" href="#note273"><b>273)</b></a></sup> No special provisions are made for multibyte characters.
12699 [<a name="p314" href="#p314">page 314</a>] (<a href="#Contents">Contents</a>)
12701 the precision, the function would need to access a wide character one past the
12702 end of the array. In no case is a partial multibyte character written.<sup><a href="#note274"><b>274)</b></a></sup>
12703 p The argument shall be a pointer to void. The value of the pointer is
12704 converted to a sequence of printing characters, in an implementation-defined
12706 n The argument shall be a pointer to signed integer into which is written the
12707 number of characters written to the output stream so far by this call to
12708 fprintf. No argument is converted, but one is consumed. If the conversion
12709 specification includes any flags, a field width, or a precision, the behavior is
12711 % A % character is written. No argument is converted. The complete
12712 conversion specification shall be %%.
12713 9 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note275"><b>275)</b></a></sup> If any argument is
12714 not the correct type for the corresponding conversion specification, the behavior is
12716 10 In no case does a nonexistent or small field width cause truncation of a field; if the result
12717 of a conversion is wider than the field width, the field is expanded to contain the
12719 11 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
12720 to a hexadecimal floating number with the given precision.
12721 Recommended practice
12722 12 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
12723 representable in the given precision, the result should be one of the two adjacent numbers
12724 in hexadecimal floating style with the given precision, with the extra stipulation that the
12725 error should have a correct sign for the current rounding direction.
12726 13 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
12727 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note276"><b>276)</b></a></sup> If the number of
12728 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
12729 representable with DECIMAL_DIG digits, then the result should be an exact
12730 representation with trailing zeros. Otherwise, the source value is bounded by two
12731 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
12734 <sup><a name="note274" href="#note274"><b>274)</b></a></sup> Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
12735 <sup><a name="note275" href="#note275"><b>275)</b></a></sup> See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
12736 <sup><a name="note276" href="#note276"><b>276)</b></a></sup> For binary-to-decimal conversion, the result format's values are the numbers representable with the
12737 given format specifier. The number of significant digits is determined by the format specifier, and in
12738 the case of fixed-point conversion by the source value as well.
12740 [<a name="p315" href="#p315">page 315</a>] (<a href="#Contents">Contents</a>)
12742 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
12743 the error should have a correct sign for the current rounding direction.
12745 14 The fprintf function returns the number of characters transmitted, or a negative value
12746 if an output or encoding error occurred.
12747 Environmental limits
12748 15 The number of characters that can be produced by any single conversion shall be at least
12750 16 EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
12752 #include <a href="#7.12"><math.h></a>
12753 #include <a href="#7.21"><stdio.h></a>
12755 char *weekday, *month; // pointers to strings
12756 int day, hour, min;
12757 fprintf(stdout, "%s, %s %d, %.2d:%.2d\n",
12758 weekday, month, day, hour, min);
12759 fprintf(stdout, "pi = %.5f\n", 4 * atan(1.0));
12761 17 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the
12762 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
12763 the first of which is denoted here by a and the second by an uppercase letter.
12764 18 Given the following wide string with length seven,
12765 static wchar_t wstr[] = L" X Yabc Z W";
12767 fprintf(stdout, "|1234567890123|\n");
12768 fprintf(stdout, "|%13ls|\n", wstr);
12769 fprintf(stdout, "|%-13.9ls|\n", wstr);
12770 fprintf(stdout, "|%13.10ls|\n", wstr);
12771 fprintf(stdout, "|%13.11ls|\n", wstr);
12772 fprintf(stdout, "|%13.15ls|\n", &wstr[2]);
12773 fprintf(stdout, "|%13lc|\n", (wint_t) wstr[5]);
12774 will print the following seven lines:
12783 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>).
12787 [<a name="p316" href="#p316">page 316</a>] (<a href="#Contents">Contents</a>)
12789 <a name="7.21.6.2" href="#7.21.6.2"><b> 7.21.6.2 The fscanf function</b></a>
12791 1 #include <a href="#7.21"><stdio.h></a>
12792 int fscanf(FILE * restrict stream,
12793 const char * restrict format, ...);
12794 <b> Description</b>
12795 2 The fscanf function reads input from the stream pointed to by stream, under control
12796 of the string pointed to by format that specifies the admissible input sequences and how
12797 they are to be converted for assignment, using subsequent arguments as pointers to the
12798 objects to receive the converted input. If there are insufficient arguments for the format,
12799 the behavior is undefined. If the format is exhausted while arguments remain, the excess
12800 arguments are evaluated (as always) but are otherwise ignored.
12801 3 The format shall be a multibyte character sequence, beginning and ending in its initial
12802 shift state. The format is composed of zero or more directives: one or more white-space
12803 characters, an ordinary multibyte character (neither % nor a white-space character), or a
12804 conversion specification. Each conversion specification is introduced by the character %.
12805 After the %, the following appear in sequence:
12806 -- An optional assignment-suppressing character *.
12807 -- An optional decimal integer greater than zero that specifies the maximum field width
12809 -- An optional length modifier that specifies the size of the receiving object.
12810 -- A conversion specifier character that specifies the type of conversion to be applied.
12811 4 The fscanf function executes each directive of the format in turn. When all directives
12812 have been executed, or if a directive fails (as detailed below), the function returns.
12813 Failures are described as input failures (due to the occurrence of an encoding error or the
12814 unavailability of input characters), or matching failures (due to inappropriate input).
12815 5 A directive composed of white-space character(s) is executed by reading input up to the
12816 first non-white-space character (which remains unread), or until no more characters can
12818 6 A directive that is an ordinary multibyte character is executed by reading the next
12819 characters of the stream. If any of those characters differ from the ones composing the
12820 directive, the directive fails and the differing and subsequent characters remain unread.
12821 Similarly, if end-of-file, an encoding error, or a read error prevents a character from being
12822 read, the directive fails.
12823 7 A directive that is a conversion specification defines a set of matching input sequences, as
12824 described below for each specifier. A conversion specification is executed in the
12826 [<a name="p317" href="#p317">page 317</a>] (<a href="#Contents">Contents</a>)
12829 8 Input white-space characters (as specified by the isspace function) are skipped, unless
12830 the specification includes a [, c, or n specifier.<sup><a href="#note277"><b>277)</b></a></sup>
12831 9 An input item is read from the stream, unless the specification includes an n specifier. An
12832 input item is defined as the longest sequence of input characters which does not exceed
12833 any specified field width and which is, or is a prefix of, a matching input sequence.<sup><a href="#note278"><b>278)</b></a></sup>
12834 The first character, if any, after the input item remains unread. If the length of the input
12835 item is zero, the execution of the directive fails; this condition is a matching failure unless
12836 end-of-file, an encoding error, or a read error prevented input from the stream, in which
12837 case it is an input failure.
12838 10 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
12839 count of input characters) is converted to a type appropriate to the conversion specifier. If
12840 the input item is not a matching sequence, the execution of the directive fails: this
12841 condition is a matching failure. Unless assignment suppression was indicated by a *, the
12842 result of the conversion is placed in the object pointed to by the first argument following
12843 the format argument that has not already received a conversion result. If this object
12844 does not have an appropriate type, or if the result of the conversion cannot be represented
12845 in the object, the behavior is undefined.
12846 11 The length modifiers and their meanings are:
12847 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12848 to an argument with type pointer to signed char or unsigned char.
12849 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12850 to an argument with type pointer to short int or unsigned short
12852 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12853 to an argument with type pointer to long int or unsigned long
12854 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
12855 an argument with type pointer to double; or that a following c, s, or [
12856 conversion specifier applies to an argument with type pointer to wchar_t.
12857 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12858 to an argument with type pointer to long long int or unsigned
12863 <sup><a name="note277" href="#note277"><b>277)</b></a></sup> These white-space characters are not counted against a specified field width.
12864 <sup><a name="note278" href="#note278"><b>278)</b></a></sup> fscanf pushes back at most one input character onto the input stream. Therefore, some sequences
12865 that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.
12867 [<a name="p318" href="#p318">page 318</a>] (<a href="#Contents">Contents</a>)
12869 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12870 to an argument with type pointer to intmax_t or uintmax_t.
12871 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12872 to an argument with type pointer to size_t or the corresponding signed
12874 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12875 to an argument with type pointer to ptrdiff_t or the corresponding
12876 unsigned integer type.
12877 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
12878 applies to an argument with type pointer to long double.
12879 If a length modifier appears with any conversion specifier other than as specified above,
12880 the behavior is undefined.
12881 12 The conversion specifiers and their meanings are:
12882 d Matches an optionally signed decimal integer, whose format is the same as
12883 expected for the subject sequence of the strtol function with the value 10
12884 for the base argument. The corresponding argument shall be a pointer to
12886 i Matches an optionally signed integer, whose format is the same as expected
12887 for the subject sequence of the strtol function with the value 0 for the
12888 base argument. The corresponding argument shall be a pointer to signed
12890 o Matches an optionally signed octal integer, whose format is the same as
12891 expected for the subject sequence of the strtoul function with the value 8
12892 for the base argument. The corresponding argument shall be a pointer to
12894 u Matches an optionally signed decimal integer, whose format is the same as
12895 expected for the subject sequence of the strtoul function with the value 10
12896 for the base argument. The corresponding argument shall be a pointer to
12898 x Matches an optionally signed hexadecimal integer, whose format is the same
12899 as expected for the subject sequence of the strtoul function with the value
12900 16 for the base argument. The corresponding argument shall be a pointer to
12902 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
12903 format is the same as expected for the subject sequence of the strtod
12904 function. The corresponding argument shall be a pointer to floating.
12907 [<a name="p319" href="#p319">page 319</a>] (<a href="#Contents">Contents</a>)
12909 c Matches a sequence of characters of exactly the number specified by the field
12910 width (1 if no field width is present in the directive).<sup><a href="#note279"><b>279)</b></a></sup>
12911 If no l length modifier is present, the corresponding argument shall be a
12912 pointer to the initial element of a character array large enough to accept the
12913 sequence. No null character is added.
12914 If an l length modifier is present, the input shall be a sequence of multibyte
12915 characters that begins in the initial shift state. Each multibyte character in the
12916 sequence is converted to a wide character as if by a call to the mbrtowc
12917 function, with the conversion state described by an mbstate_t object
12918 initialized to zero before the first multibyte character is converted. The
12919 corresponding argument shall be a pointer to the initial element of an array of
12920 wchar_t large enough to accept the resulting sequence of wide characters.
12921 No null wide character is added.
12922 s Matches a sequence of non-white-space characters.279)
12923 If no l length modifier is present, the corresponding argument shall be a
12924 pointer to the initial element of a character array large enough to accept the
12925 sequence and a terminating null character, which will be added automatically.
12926 If an l length modifier is present, the input shall be a sequence of multibyte
12927 characters that begins in the initial shift state. Each multibyte character is
12928 converted to a wide character as if by a call to the mbrtowc function, with
12929 the conversion state described by an mbstate_t object initialized to zero
12930 before the first multibyte character is converted. The corresponding argument
12931 shall be a pointer to the initial element of an array of wchar_t large enough
12932 to accept the sequence and the terminating null wide character, which will be
12933 added automatically.
12934 [ Matches a nonempty sequence of characters from a set of expected characters
12936 If no l length modifier is present, the corresponding argument shall be a
12937 pointer to the initial element of a character array large enough to accept the
12938 sequence and a terminating null character, which will be added automatically.
12939 If an l length modifier is present, the input shall be a sequence of multibyte
12940 characters that begins in the initial shift state. Each multibyte character is
12941 converted to a wide character as if by a call to the mbrtowc function, with
12942 the conversion state described by an mbstate_t object initialized to zero
12944 <sup><a name="note279" href="#note279"><b>279)</b></a></sup> No special provisions are made for multibyte characters in the matching rules used by the c, s, and [
12945 conversion specifiers -- the extent of the input field is determined on a byte-by-byte basis. The
12946 resulting field is nevertheless a sequence of multibyte characters that begins in the initial shift state.
12948 [<a name="p320" href="#p320">page 320</a>] (<a href="#Contents">Contents</a>)
12950 before the first multibyte character is converted. The corresponding argument
12951 shall be a pointer to the initial element of an array of wchar_t large enough
12952 to accept the sequence and the terminating null wide character, which will be
12953 added automatically.
12954 The conversion specifier includes all subsequent characters in the format
12955 string, up to and including the matching right bracket (]). The characters
12956 between the brackets (the scanlist) compose the scanset, unless the character
12957 after the left bracket is a circumflex (^), in which case the scanset contains all
12958 characters that do not appear in the scanlist between the circumflex and the
12959 right bracket. If the conversion specifier begins with [] or [^], the right
12960 bracket character is in the scanlist and the next following right bracket
12961 character is the matching right bracket that ends the specification; otherwise
12962 the first following right bracket character is the one that ends the
12963 specification. If a - character is in the scanlist and is not the first, nor the
12964 second where the first character is a ^, nor the last character, the behavior is
12965 implementation-defined.
12966 p Matches an implementation-defined set of sequences, which should be the
12967 same as the set of sequences that may be produced by the %p conversion of
12968 the fprintf function. The corresponding argument shall be a pointer to a
12969 pointer to void. The input item is converted to a pointer value in an
12970 implementation-defined manner. If the input item is a value converted earlier
12971 during the same program execution, the pointer that results shall compare
12972 equal to that value; otherwise the behavior of the %p conversion is undefined.
12973 n No input is consumed. The corresponding argument shall be a pointer to
12974 signed integer into which is to be written the number of characters read from
12975 the input stream so far by this call to the fscanf function. Execution of a
12976 %n directive does not increment the assignment count returned at the
12977 completion of execution of the fscanf function. No argument is converted,
12978 but one is consumed. If the conversion specification includes an assignment-
12979 suppressing character or a field width, the behavior is undefined.
12980 % Matches a single % character; no conversion or assignment occurs. The
12981 complete conversion specification shall be %%.
12982 13 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note280"><b>280)</b></a></sup>
12983 14 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
12984 respectively, a, e, f, g, and x.
12988 <sup><a name="note280" href="#note280"><b>280)</b></a></sup> See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
12990 [<a name="p321" href="#p321">page 321</a>] (<a href="#Contents">Contents</a>)
12992 15 Trailing white space (including new-line characters) is left unread unless matched by a
12993 directive. The success of literal matches and suppressed assignments is not directly
12994 determinable other than via the %n directive.
12996 16 The fscanf function returns the value of the macro EOF if an input failure occurs
12997 before the first conversion (if any) has completed. Otherwise, the function returns the
12998 number of input items assigned, which can be fewer than provided for, or even zero, in
12999 the event of an early matching failure.
13000 17 EXAMPLE 1 The call:
13001 #include <a href="#7.21"><stdio.h></a>
13003 int n, i; float x; char name[50];
13004 n = fscanf(stdin, "%d%f%s", &i, &x, name);
13005 with the input line:
13006 25 54.32E-1 thompson
13007 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
13010 18 EXAMPLE 2 The call:
13011 #include <a href="#7.21"><stdio.h></a>
13013 int i; float x; char name[50];
13014 fscanf(stdin, "%2d%f%*d %[0123456789]", &i, &x, name);
13017 will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the
13018 sequence 56\0. The next character read from the input stream will be a.
13020 19 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
13021 #include <a href="#7.21"><stdio.h></a>
13023 int count; float quant; char units[21], item[21];
13025 count = fscanf(stdin, "%f%20s of %20s", &quant, units, item);
13026 fscanf(stdin,"%*[^\n]");
13027 } while (!feof(stdin) && !ferror(stdin));
13028 20 If the stdin stream contains the following lines:
13030 -12.8degrees Celsius
13036 [<a name="p322" href="#p322">page 322</a>] (<a href="#Contents">Contents</a>)
13038 the execution of the above example will be analogous to the following assignments:
13039 quant = 2; strcpy(units, "quarts"); strcpy(item, "oil");
13041 quant = -12.8; strcpy(units, "degrees");
13042 count = 2; // "C" fails to match "o"
13043 count = 0; // "l" fails to match "%f"
13044 quant = 10.0; strcpy(units, "LBS"); strcpy(item, "dirt");
13046 count = 0; // "100e" fails to match "%f"
13050 #include <a href="#7.21"><stdio.h></a>
13052 int d1, d2, n1, n2, i;
13053 i = sscanf("123", "%d%n%n%d", &d1, &n1, &n2, &d2);
13054 the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure the value
13055 of 3 is also assigned to n2. The value of d2 is not affected. The value 1 is assigned to i.
13057 22 EXAMPLE 5 In these examples, multibyte characters do have a state-dependent encoding, and the
13058 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
13059 the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as
13060 such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes
13061 entry into the alternate shift state.
13063 #include <a href="#7.21"><stdio.h></a>
13066 fscanf(stdin, "a%s", str);
13067 with the input line:
13068 a(uparrow) X Y(downarrow) bc
13069 str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte
13070 characters, in the more general case) appears to be a single-byte white-space character.
13071 24 In contrast, after the call:
13072 #include <a href="#7.21"><stdio.h></a>
13073 #include <a href="#7.19"><stddef.h></a>
13076 fscanf(stdin, "a%ls", wstr);
13077 with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
13078 terminating null wide character.
13079 25 However, the call:
13084 [<a name="p323" href="#p323">page 323</a>] (<a href="#Contents">Contents</a>)
13086 #include <a href="#7.21"><stdio.h></a>
13087 #include <a href="#7.19"><stddef.h></a>
13090 fscanf(stdin, "a(uparrow) X(downarrow)%ls", wstr);
13091 with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
13093 26 Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte
13094 character Y, after the call:
13095 #include <a href="#7.21"><stdio.h></a>
13096 #include <a href="#7.19"><stddef.h></a>
13099 fscanf(stdin, "a(uparrow) Y(downarrow)%ls", wstr);
13100 with the same input line, zero will again be returned, but stdin will be left with a partially consumed
13101 multibyte character.
13103 Forward references: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>), the
13104 strtol, strtoll, strtoul, and strtoull functions (<a href="#7.22.1.4">7.22.1.4</a>), conversion state
13105 (<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>).
13106 <a name="7.21.6.3" href="#7.21.6.3"><b> 7.21.6.3 The printf function</b></a>
13108 1 #include <a href="#7.21"><stdio.h></a>
13109 int printf(const char * restrict format, ...);
13110 <b> Description</b>
13111 2 The printf function is equivalent to fprintf with the argument stdout interposed
13112 before the arguments to printf.
13114 3 The printf function returns the number of characters transmitted, or a negative value if
13115 an output or encoding error occurred.
13116 <a name="7.21.6.4" href="#7.21.6.4"><b> 7.21.6.4 The scanf function</b></a>
13118 1 #include <a href="#7.21"><stdio.h></a>
13119 int scanf(const char * restrict format, ...);
13120 <b> Description</b>
13121 2 The scanf function is equivalent to fscanf with the argument stdin interposed
13122 before the arguments to scanf.
13126 [<a name="p324" href="#p324">page 324</a>] (<a href="#Contents">Contents</a>)
13129 3 The scanf function returns the value of the macro EOF if an input failure occurs before
13130 the first conversion (if any) has completed. Otherwise, the scanf function returns the
13131 number of input items assigned, which can be fewer than provided for, or even zero, in
13132 the event of an early matching failure.
13133 <a name="7.21.6.5" href="#7.21.6.5"><b> 7.21.6.5 The snprintf function</b></a>
13135 1 #include <a href="#7.21"><stdio.h></a>
13136 int snprintf(char * restrict s, size_t n,
13137 const char * restrict format, ...);
13138 <b> Description</b>
13139 2 The snprintf function is equivalent to fprintf, except that the output is written into
13140 an array (specified by argument s) rather than to a stream. If n is zero, nothing is written,
13141 and s may be a null pointer. Otherwise, output characters beyond the n-1st are
13142 discarded rather than being written to the array, and a null character is written at the end
13143 of the characters actually written into the array. If copying takes place between objects
13144 that overlap, the behavior is undefined.
13146 3 The snprintf function returns the number of characters that would have been written
13147 had n been sufficiently large, not counting the terminating null character, or a negative
13148 value if an encoding error occurred. Thus, the null-terminated output has been
13149 completely written if and only if the returned value is nonnegative and less than n.
13150 <a name="7.21.6.6" href="#7.21.6.6"><b> 7.21.6.6 The sprintf function</b></a>
13152 1 #include <a href="#7.21"><stdio.h></a>
13153 int sprintf(char * restrict s,
13154 const char * restrict format, ...);
13155 <b> Description</b>
13156 2 The sprintf function is equivalent to fprintf, except that the output is written into
13157 an array (specified by the argument s) rather than to a stream. A null character is written
13158 at the end of the characters written; it is not counted as part of the returned value. If
13159 copying takes place between objects that overlap, the behavior is undefined.
13161 3 The sprintf function returns the number of characters written in the array, not
13162 counting the terminating null character, or a negative value if an encoding error occurred.
13164 [<a name="p325" href="#p325">page 325</a>] (<a href="#Contents">Contents</a>)
13166 <a name="7.21.6.7" href="#7.21.6.7"><b> 7.21.6.7 The sscanf function</b></a>
13168 1 #include <a href="#7.21"><stdio.h></a>
13169 int sscanf(const char * restrict s,
13170 const char * restrict format, ...);
13171 <b> Description</b>
13172 2 The sscanf function is equivalent to fscanf, except that input is obtained from a
13173 string (specified by the argument s) rather than from a stream. Reaching the end of the
13174 string is equivalent to encountering end-of-file for the fscanf function. If copying
13175 takes place between objects that overlap, the behavior is undefined.
13177 3 The sscanf function returns the value of the macro EOF if an input failure occurs
13178 before the first conversion (if any) has completed. Otherwise, the sscanf 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="7.21.6.8" href="#7.21.6.8"><b> 7.21.6.8 The vfprintf function</b></a>
13183 1 #include <a href="#7.16"><stdarg.h></a>
13184 #include <a href="#7.21"><stdio.h></a>
13185 int vfprintf(FILE * restrict stream,
13186 const char * restrict format,
13188 <b> Description</b>
13189 2 The vfprintf function is equivalent to fprintf, with the variable argument list
13190 replaced by arg, which shall have been initialized by the va_start macro (and
13191 possibly subsequent va_arg calls). The vfprintf function does not invoke the
13192 va_end macro.<sup><a href="#note281"><b>281)</b></a></sup>
13194 3 The vfprintf function returns the number of characters transmitted, or a negative
13195 value if an output or encoding error occurred.
13196 4 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
13201 <sup><a name="note281" href="#note281"><b>281)</b></a></sup> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
13202 vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
13204 [<a name="p326" href="#p326">page 326</a>] (<a href="#Contents">Contents</a>)
13206 #include <a href="#7.16"><stdarg.h></a>
13207 #include <a href="#7.21"><stdio.h></a>
13208 void error(char *function_name, char *format, ...)
13211 va_start(args, format);
13212 // print out name of function causing error
13213 fprintf(stderr, "ERROR in %s: ", function_name);
13214 // print out remainder of message
13215 vfprintf(stderr, format, args);
13219 <a name="7.21.6.9" href="#7.21.6.9"><b> 7.21.6.9 The vfscanf function</b></a>
13221 1 #include <a href="#7.16"><stdarg.h></a>
13222 #include <a href="#7.21"><stdio.h></a>
13223 int vfscanf(FILE * restrict stream,
13224 const char * restrict format,
13226 <b> Description</b>
13227 2 The vfscanf function is equivalent to fscanf, with the variable argument list
13228 replaced by arg, which shall have been initialized by the va_start macro (and
13229 possibly subsequent va_arg calls). The vfscanf function does not invoke the
13232 3 The vfscanf function returns the value of the macro EOF if an input failure occurs
13233 before the first conversion (if any) has completed. Otherwise, the vfscanf function
13234 returns the number of input items assigned, which can be fewer than provided for, or even
13235 zero, in the event of an early matching failure.
13236 <a name="7.21.6.10" href="#7.21.6.10"><b> 7.21.6.10 The vprintf function</b></a>
13238 1 #include <a href="#7.16"><stdarg.h></a>
13239 #include <a href="#7.21"><stdio.h></a>
13240 int vprintf(const char * restrict format,
13242 <b> Description</b>
13243 2 The vprintf function is equivalent to printf, with the variable argument list
13244 replaced by arg, which shall have been initialized by the va_start macro (and
13246 [<a name="p327" href="#p327">page 327</a>] (<a href="#Contents">Contents</a>)
13248 possibly subsequent va_arg calls). The vprintf function does not invoke the
13251 3 The vprintf function returns the number of characters transmitted, or a negative value
13252 if an output or encoding error occurred.
13253 <a name="7.21.6.11" href="#7.21.6.11"><b> 7.21.6.11 The vscanf function</b></a>
13255 1 #include <a href="#7.16"><stdarg.h></a>
13256 #include <a href="#7.21"><stdio.h></a>
13257 int vscanf(const char * restrict format,
13259 <b> Description</b>
13260 2 The vscanf function is equivalent to scanf, with the variable argument list replaced
13261 by arg, which shall have been initialized by the va_start macro (and possibly
13262 subsequent va_arg calls). The vscanf function does not invoke the va_end
13265 3 The vscanf function returns the value of the macro EOF if an input failure occurs
13266 before the first conversion (if any) has completed. Otherwise, the vscanf function
13267 returns the number of input items assigned, which can be fewer than provided for, or even
13268 zero, in the event of an early matching failure.
13269 <a name="7.21.6.12" href="#7.21.6.12"><b> 7.21.6.12 The vsnprintf function</b></a>
13271 1 #include <a href="#7.16"><stdarg.h></a>
13272 #include <a href="#7.21"><stdio.h></a>
13273 int vsnprintf(char * restrict s, size_t n,
13274 const char * restrict format,
13276 <b> Description</b>
13277 2 The vsnprintf function is equivalent to snprintf, with the variable argument list
13278 replaced by arg, which shall have been initialized by the va_start macro (and
13279 possibly subsequent va_arg calls). The vsnprintf function does not invoke the
13280 va_end macro.281) If copying takes place between objects that overlap, the behavior is
13285 [<a name="p328" href="#p328">page 328</a>] (<a href="#Contents">Contents</a>)
13288 3 The vsnprintf function returns the number of characters that would have been written
13289 had n been sufficiently large, not counting the terminating null character, or a negative
13290 value if an encoding error occurred. Thus, the null-terminated output has been
13291 completely written if and only if the returned value is nonnegative and less than n.
13292 <a name="7.21.6.13" href="#7.21.6.13"><b> 7.21.6.13 The vsprintf function</b></a>
13294 1 #include <a href="#7.16"><stdarg.h></a>
13295 #include <a href="#7.21"><stdio.h></a>
13296 int vsprintf(char * restrict s,
13297 const char * restrict format,
13299 <b> Description</b>
13300 2 The vsprintf function is equivalent to sprintf, with the variable argument list
13301 replaced by arg, which shall have been initialized by the va_start macro (and
13302 possibly subsequent va_arg calls). The vsprintf function does not invoke the
13303 va_end macro.281) If copying takes place between objects that overlap, the behavior is
13306 3 The vsprintf function returns the number of characters written in the array, not
13307 counting the terminating null character, or a negative value if an encoding error occurred.
13308 <a name="7.21.6.14" href="#7.21.6.14"><b> 7.21.6.14 The vsscanf function</b></a>
13310 1 #include <a href="#7.16"><stdarg.h></a>
13311 #include <a href="#7.21"><stdio.h></a>
13312 int vsscanf(const char * restrict s,
13313 const char * restrict format,
13315 <b> Description</b>
13316 2 The vsscanf function is equivalent to sscanf, with the variable argument list
13317 replaced by arg, which shall have been initialized by the va_start macro (and
13318 possibly subsequent va_arg calls). The vsscanf function does not invoke the
13321 3 The vsscanf function returns the value of the macro EOF if an input failure occurs
13322 before the first conversion (if any) has completed. Otherwise, the vsscanf function
13323 [<a name="p329" href="#p329">page 329</a>] (<a href="#Contents">Contents</a>)
13325 returns the number of input items assigned, which can be fewer than provided for, or even
13326 zero, in the event of an early matching failure.
13327 <a name="7.21.7" href="#7.21.7"><b> 7.21.7 Character input/output functions</b></a>
13328 <a name="7.21.7.1" href="#7.21.7.1"><b> 7.21.7.1 The fgetc function</b></a>
13330 1 #include <a href="#7.21"><stdio.h></a>
13331 int fgetc(FILE *stream);
13332 <b> Description</b>
13333 2 If the end-of-file indicator for the input stream pointed to by stream is not set and a
13334 next character is present, the fgetc function obtains that character as an unsigned
13335 char converted to an int and advances the associated file position indicator for the
13336 stream (if defined).
13338 3 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
13339 of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the
13340 fgetc function returns the next character from the input stream pointed to by stream.
13341 If a read error occurs, the error indicator for the stream is set and the fgetc function
13342 returns EOF.<sup><a href="#note282"><b>282)</b></a></sup>
13343 <a name="7.21.7.2" href="#7.21.7.2"><b> 7.21.7.2 The fgets function</b></a>
13345 1 #include <a href="#7.21"><stdio.h></a>
13346 char *fgets(char * restrict s, int n,
13347 FILE * restrict stream);
13348 <b> Description</b>
13349 2 The fgets function reads at most one less than the number of characters specified by n
13350 from the stream pointed to by stream into the array pointed to by s. No additional
13351 characters are read after a new-line character (which is retained) or after end-of-file. A
13352 null character is written immediately after the last character read into the array.
13354 3 The fgets function returns s if successful. If end-of-file is encountered and no
13355 characters have been read into the array, the contents of the array remain unchanged and a
13356 null pointer is returned. If a read error occurs during the operation, the array contents are
13357 indeterminate and a null pointer is returned.
13359 <sup><a name="note282" href="#note282"><b>282)</b></a></sup> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
13361 [<a name="p330" href="#p330">page 330</a>] (<a href="#Contents">Contents</a>)
13363 <a name="7.21.7.3" href="#7.21.7.3"><b> 7.21.7.3 The fputc function</b></a>
13365 1 #include <a href="#7.21"><stdio.h></a>
13366 int fputc(int c, FILE *stream);
13367 <b> Description</b>
13368 2 The fputc function writes the character specified by c (converted to an unsigned
13369 char) to the output stream pointed to by stream, at the position indicated by the
13370 associated file position indicator for the stream (if defined), and advances the indicator
13371 appropriately. If the file cannot support positioning requests, or if the stream was opened
13372 with append mode, the character is appended to the output stream.
13374 3 The fputc function returns the character written. If a write error occurs, the error
13375 indicator for the stream is set and fputc returns EOF.
13376 <a name="7.21.7.4" href="#7.21.7.4"><b> 7.21.7.4 The fputs function</b></a>
13378 1 #include <a href="#7.21"><stdio.h></a>
13379 int fputs(const char * restrict s,
13380 FILE * restrict stream);
13381 <b> Description</b>
13382 2 The fputs function writes the string pointed to by s to the stream pointed to by
13383 stream. The terminating null character is not written.
13385 3 The fputs function returns EOF if a write error occurs; otherwise it returns a
13387 <a name="7.21.7.5" href="#7.21.7.5"><b> 7.21.7.5 The getc function</b></a>
13389 1 #include <a href="#7.21"><stdio.h></a>
13390 int getc(FILE *stream);
13391 <b> Description</b>
13392 2 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it
13393 may evaluate stream more than once, so the argument should never be an expression
13399 [<a name="p331" href="#p331">page 331</a>] (<a href="#Contents">Contents</a>)
13402 3 The getc function returns the next character from the input stream pointed to by
13403 stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
13404 getc returns EOF. If a read error occurs, the error indicator for the stream is set and
13406 <a name="7.21.7.6" href="#7.21.7.6"><b> 7.21.7.6 The getchar function</b></a>
13408 1 #include <a href="#7.21"><stdio.h></a>
13410 <b> Description</b>
13411 2 The getchar function is equivalent to getc with the argument stdin.
13413 3 The getchar function returns the next character from the input stream pointed to by
13414 stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
13415 getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
13416 getchar returns EOF. *
13417 <a name="7.21.7.7" href="#7.21.7.7"><b> 7.21.7.7 The putc function</b></a>
13419 1 #include <a href="#7.21"><stdio.h></a>
13420 int putc(int c, FILE *stream);
13421 <b> Description</b>
13422 2 The putc function is equivalent to fputc, except that if it is implemented as a macro, it
13423 may evaluate stream more than once, so that argument should never be an expression
13426 3 The putc function returns the character written. If a write error occurs, the error
13427 indicator for the stream is set and putc returns EOF.
13428 <a name="7.21.7.8" href="#7.21.7.8"><b> 7.21.7.8 The putchar function</b></a>
13430 1 #include <a href="#7.21"><stdio.h></a>
13431 int putchar(int c);
13432 <b> Description</b>
13433 2 The putchar function is equivalent to putc with the second argument stdout.
13436 [<a name="p332" href="#p332">page 332</a>] (<a href="#Contents">Contents</a>)
13439 3 The putchar function returns the character written. If a write error occurs, the error
13440 indicator for the stream is set and putchar returns EOF.
13441 <a name="7.21.7.9" href="#7.21.7.9"><b> 7.21.7.9 The puts function</b></a>
13443 1 #include <a href="#7.21"><stdio.h></a>
13444 int puts(const char *s);
13445 <b> Description</b>
13446 2 The puts function writes the string pointed to by s to the stream pointed to by stdout,
13447 and appends a new-line character to the output. The terminating null character is not
13450 3 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
13452 <a name="7.21.7.10" href="#7.21.7.10"><b> 7.21.7.10 The ungetc function</b></a>
13454 1 #include <a href="#7.21"><stdio.h></a>
13455 int ungetc(int c, FILE *stream);
13456 <b> Description</b>
13457 2 The ungetc function pushes the character specified by c (converted to an unsigned
13458 char) back onto the input stream pointed to by stream. Pushed-back characters will be
13459 returned by subsequent reads on that stream in the reverse order of their pushing. A
13460 successful intervening call (with the stream pointed to by stream) to a file positioning
13461 function (fseek, fsetpos, or rewind) discards any pushed-back characters for the
13462 stream. The external storage corresponding to the stream is unchanged.
13463 3 One character of pushback is guaranteed. If the ungetc function is called too many
13464 times on the same stream without an intervening read or file positioning operation on that
13465 stream, the operation may fail.
13466 4 If the value of c equals that of the macro EOF, the operation fails and the input stream is
13468 5 A successful call to the ungetc function clears the end-of-file indicator for the stream.
13469 The value of the file position indicator for the stream after reading or discarding all
13470 pushed-back characters shall be the same as it was before the characters were pushed
13471 back. For a text stream, the value of its file position indicator after a successful call to the
13472 ungetc function is unspecified until all pushed-back characters are read or discarded.
13474 [<a name="p333" href="#p333">page 333</a>] (<a href="#Contents">Contents</a>)
13476 For a binary stream, its file position indicator is decremented by each successful call to
13477 the ungetc function; if its value was zero before a call, it is indeterminate after the
13478 call.<sup><a href="#note283"><b>283)</b></a></sup>
13480 6 The ungetc function returns the character pushed back after conversion, or EOF if the
13482 Forward references: file positioning functions (<a href="#7.21.9">7.21.9</a>).
13483 <a name="7.21.8" href="#7.21.8"><b> 7.21.8 Direct input/output functions</b></a>
13484 <a name="7.21.8.1" href="#7.21.8.1"><b> 7.21.8.1 The fread function</b></a>
13486 1 #include <a href="#7.21"><stdio.h></a>
13487 size_t fread(void * restrict ptr,
13488 size_t size, size_t nmemb,
13489 FILE * restrict stream);
13490 <b> Description</b>
13491 2 The fread function reads, into the array pointed to by ptr, up to nmemb elements
13492 whose size is specified by size, from the stream pointed to by stream. For each
13493 object, size calls are made to the fgetc function and the results stored, in the order
13494 read, in an array of unsigned char exactly overlaying the object. The file position
13495 indicator for the stream (if defined) is advanced by the number of characters successfully
13496 read. If an error occurs, the resulting value of the file position indicator for the stream is
13497 indeterminate. If a partial element is read, its value is indeterminate.
13499 3 The fread function returns the number of elements successfully read, which may be
13500 less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
13501 fread returns zero and the contents of the array and the state of the stream remain
13507 <sup><a name="note283" href="#note283"><b>283)</b></a></sup> See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
13509 [<a name="p334" href="#p334">page 334</a>] (<a href="#Contents">Contents</a>)
13511 <a name="7.21.8.2" href="#7.21.8.2"><b> 7.21.8.2 The fwrite function</b></a>
13513 1 #include <a href="#7.21"><stdio.h></a>
13514 size_t fwrite(const void * restrict ptr,
13515 size_t size, size_t nmemb,
13516 FILE * restrict stream);
13517 <b> Description</b>
13518 2 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements
13519 whose size is specified by size, to the stream pointed to by stream. For each object,
13520 size calls are made to the fputc function, taking the values (in order) from an array of
13521 unsigned char exactly overlaying the object. The file position indicator for the
13522 stream (if defined) is advanced by the number of characters successfully written. If an
13523 error occurs, the resulting value of the file position indicator for the stream is
13526 3 The fwrite function returns the number of elements successfully written, which will be
13527 less than nmemb only if a write error is encountered. If size or nmemb is zero,
13528 fwrite returns zero and the state of the stream remains unchanged.
13529 <a name="7.21.9" href="#7.21.9"><b> 7.21.9 File positioning functions</b></a>
13530 <a name="7.21.9.1" href="#7.21.9.1"><b> 7.21.9.1 The fgetpos function</b></a>
13532 1 #include <a href="#7.21"><stdio.h></a>
13533 int fgetpos(FILE * restrict stream,
13534 fpos_t * restrict pos);
13535 <b> Description</b>
13536 2 The fgetpos function stores the current values of the parse state (if any) and file
13537 position indicator for the stream pointed to by stream in the object pointed to by pos.
13538 The values stored contain unspecified information usable by the fsetpos function for
13539 repositioning the stream to its position at the time of the call to the fgetpos function.
13541 3 If successful, the fgetpos function returns zero; on failure, the fgetpos function
13542 returns nonzero and stores an implementation-defined positive value in errno.
13543 Forward references: the fsetpos function (<a href="#7.21.9.3">7.21.9.3</a>).
13548 [<a name="p335" href="#p335">page 335</a>] (<a href="#Contents">Contents</a>)
13550 <a name="7.21.9.2" href="#7.21.9.2"><b> 7.21.9.2 The fseek function</b></a>
13552 1 #include <a href="#7.21"><stdio.h></a>
13553 int fseek(FILE *stream, long int offset, int whence);
13554 <b> Description</b>
13555 2 The fseek function sets the file position indicator for the stream pointed to by stream.
13556 If a read or write error occurs, the error indicator for the stream is set and fseek fails.
13557 3 For a binary stream, the new position, measured in characters from the beginning of the
13558 file, is obtained by adding offset to the position specified by whence. The specified
13559 position is the beginning of the file if whence is SEEK_SET, the current value of the file
13560 position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
13561 meaningfully support fseek calls with a whence value of SEEK_END.
13562 4 For a text stream, either offset shall be zero, or offset shall be a value returned by
13563 an earlier successful call to the ftell function on a stream associated with the same file
13564 and whence shall be SEEK_SET.
13565 5 After determining the new position, a successful call to the fseek function undoes any
13566 effects of the ungetc function on the stream, clears the end-of-file indicator for the
13567 stream, and then establishes the new position. After a successful fseek call, the next
13568 operation on an update stream may be either input or output.
13570 6 The fseek function returns nonzero only for a request that cannot be satisfied.
13571 Forward references: the ftell function (<a href="#7.21.9.4">7.21.9.4</a>).
13572 <a name="7.21.9.3" href="#7.21.9.3"><b> 7.21.9.3 The fsetpos function</b></a>
13574 1 #include <a href="#7.21"><stdio.h></a>
13575 int fsetpos(FILE *stream, const fpos_t *pos);
13576 <b> Description</b>
13577 2 The fsetpos function sets the mbstate_t object (if any) and file position indicator
13578 for the stream pointed to by stream according to the value of the object pointed to by
13579 pos, which shall be a value obtained from an earlier successful call to the fgetpos
13580 function on a stream associated with the same file. If a read or write error occurs, the
13581 error indicator for the stream is set and fsetpos fails.
13582 3 A successful call to the fsetpos function undoes any effects of the ungetc function
13583 on the stream, clears the end-of-file indicator for the stream, and then establishes the new
13584 parse state and position. After a successful fsetpos call, the next operation on an
13586 [<a name="p336" href="#p336">page 336</a>] (<a href="#Contents">Contents</a>)
13588 update stream may be either input or output.
13590 4 If successful, the fsetpos function returns zero; on failure, the fsetpos function
13591 returns nonzero and stores an implementation-defined positive value in errno.
13592 <a name="7.21.9.4" href="#7.21.9.4"><b> 7.21.9.4 The ftell function</b></a>
13594 1 #include <a href="#7.21"><stdio.h></a>
13595 long int ftell(FILE *stream);
13596 <b> Description</b>
13597 2 The ftell function obtains the current value of the file position indicator for the stream
13598 pointed to by stream. For a binary stream, the value is the number of characters from
13599 the beginning of the file. For a text stream, its file position indicator contains unspecified
13600 information, usable by the fseek function for returning the file position indicator for the
13601 stream to its position at the time of the ftell call; the difference between two such
13602 return values is not necessarily a meaningful measure of the number of characters written
13605 3 If successful, the ftell function returns the current value of the file position indicator
13606 for the stream. On failure, the ftell function returns -1L and stores an
13607 implementation-defined positive value in errno.
13608 <a name="7.21.9.5" href="#7.21.9.5"><b> 7.21.9.5 The rewind function</b></a>
13610 1 #include <a href="#7.21"><stdio.h></a>
13611 void rewind(FILE *stream);
13612 <b> Description</b>
13613 2 The rewind function sets the file position indicator for the stream pointed to by
13614 stream to the beginning of the file. It is equivalent to
13615 (void)fseek(stream, 0L, SEEK_SET)
13616 except that the error indicator for the stream is also cleared.
13618 3 The rewind function returns no value.
13623 [<a name="p337" href="#p337">page 337</a>] (<a href="#Contents">Contents</a>)
13625 <a name="7.21.10" href="#7.21.10"><b> 7.21.10 Error-handling functions</b></a>
13626 <a name="7.21.10.1" href="#7.21.10.1"><b> 7.21.10.1 The clearerr function</b></a>
13628 1 #include <a href="#7.21"><stdio.h></a>
13629 void clearerr(FILE *stream);
13630 <b> Description</b>
13631 2 The clearerr function clears the end-of-file and error indicators for the stream pointed
13634 3 The clearerr function returns no value.
13635 <a name="7.21.10.2" href="#7.21.10.2"><b> 7.21.10.2 The feof function</b></a>
13637 1 #include <a href="#7.21"><stdio.h></a>
13638 int feof(FILE *stream);
13639 <b> Description</b>
13640 2 The feof function tests the end-of-file indicator for the stream pointed to by stream.
13642 3 The feof function returns nonzero if and only if the end-of-file indicator is set for
13644 <a name="7.21.10.3" href="#7.21.10.3"><b> 7.21.10.3 The ferror function</b></a>
13646 1 #include <a href="#7.21"><stdio.h></a>
13647 int ferror(FILE *stream);
13648 <b> Description</b>
13649 2 The ferror function tests the error indicator for the stream pointed to by stream.
13651 3 The ferror function returns nonzero if and only if the error indicator is set for
13657 [<a name="p338" href="#p338">page 338</a>] (<a href="#Contents">Contents</a>)
13659 <a name="7.21.10.4" href="#7.21.10.4"><b> 7.21.10.4 The perror function</b></a>
13661 1 #include <a href="#7.21"><stdio.h></a>
13662 void perror(const char *s);
13663 <b> Description</b>
13664 2 The perror function maps the error number in the integer expression errno to an
13665 error message. It writes a sequence of characters to the standard error stream thus: first
13666 (if s is not a null pointer and the character pointed to by s is not the null character), the
13667 string pointed to by s followed by a colon (:) and a space; then an appropriate error
13668 message string followed by a new-line character. The contents of the error message
13669 strings are the same as those returned by the strerror function with argument errno.
13671 3 The perror function returns no value.
13672 Forward references: the strerror function (<a href="#7.23.6.2">7.23.6.2</a>).
13677 [<a name="p339" href="#p339">page 339</a>] (<a href="#Contents">Contents</a>)
13679 <a name="7.22" href="#7.22"><b> 7.22 General utilities <stdlib.h></b></a>
13680 1 The header <a href="#7.22"><stdlib.h></a> declares five types and several functions of general utility, and
13681 defines several macros.<sup><a href="#note284"><b>284)</b></a></sup>
13682 2 The types declared are size_t and wchar_t (both described in <a href="#7.19">7.19</a>),
13684 which is a structure type that is the type of the value returned by the div function,
13686 which is a structure type that is the type of the value returned by the ldiv function, and
13688 which is a structure type that is the type of the value returned by the lldiv function.
13689 3 The macros defined are NULL (described in <a href="#7.19">7.19</a>);
13693 which expand to integer constant expressions that can be used as the argument to the
13694 exit function to return unsuccessful or successful termination status, respectively, to the
13697 which expands to an integer constant expression that is the maximum value returned by
13698 the rand function; and
13700 which expands to a positive integer expression with type size_t that is the maximum
13701 number of bytes in a multibyte character for the extended character set specified by the
13702 current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX.
13707 <sup><a name="note284" href="#note284"><b>284)</b></a></sup> See ''future library directions'' (<a href="#7.30.10">7.30.10</a>).
13709 [<a name="p340" href="#p340">page 340</a>] (<a href="#Contents">Contents</a>)
13711 <a name="7.22.1" href="#7.22.1"><b> 7.22.1 Numeric conversion functions</b></a>
13712 1 The functions atof, atoi, atol, and atoll need not affect the value of the integer
13713 expression errno on an error. If the value of the result cannot be represented, the
13714 behavior is undefined.
13715 <a name="7.22.1.1" href="#7.22.1.1"><b> 7.22.1.1 The atof function</b></a>
13717 1 #include <a href="#7.22"><stdlib.h></a>
13718 double atof(const char *nptr);
13719 <b> Description</b>
13720 2 The atof function converts the initial portion of the string pointed to by nptr to
13721 double representation. Except for the behavior on error, it is equivalent to
13722 strtod(nptr, (char **)NULL)
13724 3 The atof function returns the converted value.
13725 Forward references: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
13726 <a name="7.22.1.2" href="#7.22.1.2"><b> 7.22.1.2 The atoi, atol, and atoll functions</b></a>
13728 1 #include <a href="#7.22"><stdlib.h></a>
13729 int atoi(const char *nptr);
13730 long int atol(const char *nptr);
13731 long long int atoll(const char *nptr);
13732 <b> Description</b>
13733 2 The atoi, atol, and atoll functions convert the initial portion of the string pointed
13734 to by nptr to int, long int, and long long int representation, respectively.
13735 Except for the behavior on error, they are equivalent to
13736 atoi: (int)strtol(nptr, (char **)NULL, 10)
13737 atol: strtol(nptr, (char **)NULL, 10)
13738 atoll: strtoll(nptr, (char **)NULL, 10)
13740 3 The atoi, atol, and atoll functions return the converted value.
13741 Forward references: the strtol, strtoll, strtoul, and strtoull functions
13742 (<a href="#7.22.1.4">7.22.1.4</a>).
13746 [<a name="p341" href="#p341">page 341</a>] (<a href="#Contents">Contents</a>)
13748 <a name="7.22.1.3" href="#7.22.1.3"><b> 7.22.1.3 The strtod, strtof, and strtold functions</b></a>
13750 1 #include <a href="#7.22"><stdlib.h></a>
13751 double strtod(const char * restrict nptr,
13752 char ** restrict endptr);
13753 float strtof(const char * restrict nptr,
13754 char ** restrict endptr);
13755 long double strtold(const char * restrict nptr,
13756 char ** restrict endptr);
13757 <b> Description</b>
13758 2 The strtod, strtof, and strtold functions convert the initial portion of the string
13759 pointed to by nptr to double, float, and long double representation,
13760 respectively. First, they decompose the input string into three parts: an initial, possibly
13761 empty, sequence of white-space characters (as specified by the isspace function), a
13762 subject sequence resembling a floating-point constant or representing an infinity or NaN;
13763 and a final string of one or more unrecognized characters, including the terminating null
13764 character of the input string. Then, they attempt to convert the subject sequence to a
13765 floating-point number, and return the result.
13766 3 The expected form of the subject sequence is an optional plus or minus sign, then one of
13768 -- a nonempty sequence of decimal digits optionally containing a decimal-point
13769 character, then an optional exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
13770 -- a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
13771 decimal-point character, then an optional binary exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
13772 -- INF or INFINITY, ignoring case
13773 -- NAN or NAN(n-char-sequenceopt), ignoring case in the NAN part, where:
13777 n-char-sequence digit
13778 n-char-sequence nondigit
13779 The subject sequence is defined as the longest initial subsequence of the input string,
13780 starting with the first non-white-space character, that is of the expected form. The subject
13781 sequence contains no characters if the input string is not of the expected form.
13782 4 If the subject sequence has the expected form for a floating-point number, the sequence of
13783 characters starting with the first digit or the decimal-point character (whichever occurs
13784 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
13785 [<a name="p342" href="#p342">page 342</a>] (<a href="#Contents">Contents</a>)
13787 decimal-point character is used in place of a period, and that if neither an exponent part
13788 nor a decimal-point character appears in a decimal floating point number, or if a binary
13789 exponent part does not appear in a hexadecimal floating point number, an exponent part
13790 of the appropriate type with value zero is assumed to follow the last digit in the string. If
13791 the subject sequence begins with a minus sign, the sequence is interpreted as negated.<sup><a href="#note285"><b>285)</b></a></sup>
13792 A character sequence INF or INFINITY is interpreted as an infinity, if representable in
13793 the return type, else like a floating constant that is too large for the range of the return
13794 type. A character sequence NAN or NAN(n-char-sequenceopt), is interpreted as a quiet
13795 NaN, if supported in the return type, else like a subject sequence part that does not have
13796 the expected form; the meaning of the n-char sequences is implementation-defined.<sup><a href="#note286"><b>286)</b></a></sup> A
13797 pointer to the final string is stored in the object pointed to by endptr, provided that
13798 endptr is not a null pointer.
13799 5 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
13800 value resulting from the conversion is correctly rounded.
13801 6 In other than the "C" locale, additional locale-specific subject sequence forms may be
13803 7 If the subject sequence is empty or does not have the expected form, no conversion is
13804 performed; the value of nptr is stored in the object pointed to by endptr, provided
13805 that endptr is not a null pointer.
13806 Recommended practice
13807 8 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
13808 the result is not exactly representable, the result should be one of the two numbers in the
13809 appropriate internal format that are adjacent to the hexadecimal floating source value,
13810 with the extra stipulation that the error should have a correct sign for the current rounding
13812 9 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
13813 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
13814 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
13815 consider the two bounding, adjacent decimal strings L and U, both having
13816 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
13817 The result should be one of the (equal or adjacent) values that would be obtained by
13818 correctly rounding L and U according to the current rounding direction, with the extra
13820 <sup><a name="note285" href="#note285"><b>285)</b></a></sup> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
13821 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
13822 methods may yield different results if rounding is toward positive or negative infinity. In either case,
13823 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
13824 <sup><a name="note286" href="#note286"><b>286)</b></a></sup> An implementation may use the n-char sequence to determine extra information to be represented in
13825 the NaN's significand.
13827 [<a name="p343" href="#p343">page 343</a>] (<a href="#Contents">Contents</a>)
13829 stipulation that the error with respect to D should have a correct sign for the current
13830 rounding direction.<sup><a href="#note287"><b>287)</b></a></sup>
13832 10 The functions return the converted value, if any. If no conversion could be performed,
13833 zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
13834 plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
13835 return type and sign of the value), and the value of the macro ERANGE is stored in
13836 errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
13837 no greater than the smallest normalized positive number in the return type; whether
13838 errno acquires the value ERANGE is implementation-defined.
13839 <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>
13841 1 #include <a href="#7.22"><stdlib.h></a>
13843 const char * restrict nptr,
13844 char ** restrict endptr,
13846 long long int strtoll(
13847 const char * restrict nptr,
13848 char ** restrict endptr,
13850 unsigned long int strtoul(
13851 const char * restrict nptr,
13852 char ** restrict endptr,
13854 unsigned long long int strtoull(
13855 const char * restrict nptr,
13856 char ** restrict endptr,
13858 <b> Description</b>
13859 2 The strtol, strtoll, strtoul, and strtoull functions convert the initial
13860 portion of the string pointed to by nptr to long int, long long int, unsigned
13861 long int, and unsigned long long int representation, respectively. First,
13862 they decompose the input string into three parts: an initial, possibly empty, sequence of
13863 white-space characters (as specified by the isspace function), a subject sequence
13866 <sup><a name="note287" href="#note287"><b>287)</b></a></sup> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
13867 to the same internal floating value, but if not will round to adjacent values.
13869 [<a name="p344" href="#p344">page 344</a>] (<a href="#Contents">Contents</a>)
13871 resembling an integer represented in some radix determined by the value of base, and a
13872 final string of one or more unrecognized characters, including the terminating null
13873 character of the input string. Then, they attempt to convert the subject sequence to an
13874 integer, and return the result.
13875 3 If the value of base is zero, the expected form of the subject sequence is that of an
13876 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
13877 not including an integer suffix. If the value of base is between 2 and 36 (inclusive), the
13878 expected form of the subject sequence is a sequence of letters and digits representing an
13879 integer with the radix specified by base, optionally preceded by a plus or minus sign,
13880 but not including an integer suffix. The letters from a (or A) through z (or Z) are
13881 ascribed the values 10 through 35; only letters and digits whose ascribed values are less
13882 than that of base are permitted. If the value of base is 16, the characters 0x or 0X may
13883 optionally precede the sequence of letters and digits, following the sign if present.
13884 4 The subject sequence is defined as the longest initial subsequence of the input string,
13885 starting with the first non-white-space character, that is of the expected form. The subject
13886 sequence contains no characters if the input string is empty or consists entirely of white
13887 space, or if the first non-white-space character is other than a sign or a permissible letter
13889 5 If the subject sequence has the expected form and the value of base is zero, the sequence
13890 of characters starting with the first digit is interpreted as an integer constant according to
13891 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
13892 is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
13893 as given above. If the subject sequence begins with a minus sign, the value resulting from
13894 the conversion is negated (in the return type). A pointer to the final string is stored in the
13895 object pointed to by endptr, provided that endptr is not a null pointer.
13896 6 In other than the "C" locale, additional locale-specific subject sequence forms may be
13898 7 If the subject sequence is empty or does not have the expected form, no conversion is
13899 performed; the value of nptr is stored in the object pointed to by endptr, provided
13900 that endptr is not a null pointer.
13902 8 The strtol, strtoll, strtoul, and strtoull functions return the converted
13903 value, if any. If no conversion could be performed, zero is returned. If the correct value
13904 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
13905 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
13906 and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
13911 [<a name="p345" href="#p345">page 345</a>] (<a href="#Contents">Contents</a>)
13913 <a name="7.22.2" href="#7.22.2"><b> 7.22.2 Pseudo-random sequence generation functions</b></a>
13914 <a name="7.22.2.1" href="#7.22.2.1"><b> 7.22.2.1 The rand function</b></a>
13916 1 #include <a href="#7.22"><stdlib.h></a>
13918 <b> Description</b>
13919 2 The rand function computes a sequence of pseudo-random integers in the range 0 to
13920 RAND_MAX.<sup><a href="#note288"><b>288)</b></a></sup>
13921 3 The rand function is not required to avoid data races. The implementation shall behave
13922 as if no library function calls the rand function.
13924 4 The rand function returns a pseudo-random integer.
13925 Environmental limits
13926 5 The value of the RAND_MAX macro shall be at least 32767.
13927 <a name="7.22.2.2" href="#7.22.2.2"><b> 7.22.2.2 The srand function</b></a>
13929 1 #include <a href="#7.22"><stdlib.h></a>
13930 void srand(unsigned int seed);
13931 <b> Description</b>
13932 2 The srand function uses the argument as a seed for a new sequence of pseudo-random
13933 numbers to be returned by subsequent calls to rand. If srand is then called with the
13934 same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
13935 called before any calls to srand have been made, the same sequence shall be generated
13936 as when srand is first called with a seed value of 1.
13937 3 The implementation shall behave as if no library function calls the srand function.
13939 4 The srand function returns no value.
13944 <sup><a name="note288" href="#note288"><b>288)</b></a></sup> There are no guarantees as to the quality of the random sequence produced and some implementations
13945 are known to produce sequences with distressingly non-random low-order bits. Applications with
13946 particular requirements should use a generator that is known to be sufficient for their needs.
13948 [<a name="p346" href="#p346">page 346</a>] (<a href="#Contents">Contents</a>)
13950 5 EXAMPLE The following functions define a portable implementation of rand and srand.
13951 static unsigned long int next = 1;
13952 int rand(void) // RAND_MAX assumed to be 32767
13954 next = next * 1103515245 + 12345;
13955 return (unsigned int)(next/65536) % 32768;
13957 void srand(unsigned int seed)
13962 <a name="7.22.3" href="#7.22.3"><b> 7.22.3 Memory management functions</b></a>
13963 1 The order and contiguity of storage allocated by successive calls to the
13964 aligned_alloc, calloc, malloc, and realloc functions is unspecified. The
13965 pointer returned if the allocation succeeds is suitably aligned so that it may be assigned to
13966 a pointer to any type of object with a fundamental alignment requirement and then used
13967 to access such an object or an array of such objects in the space allocated (until the space
13968 is explicitly deallocated). The lifetime of an allocated object extends from the allocation
13969 until the deallocation. Each such allocation shall yield a pointer to an object disjoint from
13970 any other object. The pointer returned points to the start (lowest byte address) of the
13971 allocated space. If the space cannot be allocated, a null pointer is returned. If the size of
13972 the space requested is zero, the behavior is implementation-defined: either a null pointer
13973 is returned, or the behavior is as if the size were some nonzero value, except that the
13974 returned pointer shall not be used to access an object.
13975 <a name="7.22.3.1" href="#7.22.3.1"><b> 7.22.3.1 The aligned_alloc function</b></a>
13977 1 #include <a href="#7.22"><stdlib.h></a>
13978 void *aligned_alloc(size_t alignment, size_t size);
13979 <b> Description</b>
13980 2 The aligned_alloc function allocates space for an object whose alignment is
13981 specified by alignment, whose size is specified by size, and whose value is
13982 indeterminate. The value of alignment shall be a valid alignment supported by the
13983 implementation and the value of size shall be an integral multiple of alignment.
13985 3 The aligned_alloc function returns either a null pointer or a pointer to the allocated
13991 [<a name="p347" href="#p347">page 347</a>] (<a href="#Contents">Contents</a>)
13993 <a name="7.22.3.2" href="#7.22.3.2"><b> 7.22.3.2 The calloc function</b></a>
13995 1 #include <a href="#7.22"><stdlib.h></a>
13996 void *calloc(size_t nmemb, size_t size);
13997 <b> Description</b>
13998 2 The calloc function allocates space for an array of nmemb objects, each of whose size
13999 is size. The space is initialized to all bits zero.<sup><a href="#note289"><b>289)</b></a></sup>
14001 3 The calloc function returns either a null pointer or a pointer to the allocated space.
14002 <a name="7.22.3.3" href="#7.22.3.3"><b> 7.22.3.3 The free function</b></a>
14004 1 #include <a href="#7.22"><stdlib.h></a>
14005 void free(void *ptr);
14006 <b> Description</b>
14007 2 The free function causes the space pointed to by ptr to be deallocated, that is, made
14008 available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
14009 the argument does not match a pointer earlier returned by a memory management
14010 function, or if the space has been deallocated by a call to free or realloc, the
14011 behavior is undefined.
14013 3 The free function returns no value.
14014 <a name="7.22.3.4" href="#7.22.3.4"><b> 7.22.3.4 The malloc function</b></a>
14016 1 #include <a href="#7.22"><stdlib.h></a>
14017 void *malloc(size_t size);
14018 <b> Description</b>
14019 2 The malloc function allocates space for an object whose size is specified by size and
14020 whose value is indeterminate.
14025 <sup><a name="note289" href="#note289"><b>289)</b></a></sup> Note that this need not be the same as the representation of floating-point zero or a null pointer
14028 [<a name="p348" href="#p348">page 348</a>] (<a href="#Contents">Contents</a>)
14031 3 The malloc function returns either a null pointer or a pointer to the allocated space.
14032 <a name="7.22.3.5" href="#7.22.3.5"><b> 7.22.3.5 The realloc function</b></a>
14034 1 #include <a href="#7.22"><stdlib.h></a>
14035 void *realloc(void *ptr, size_t size);
14036 <b> Description</b>
14037 2 The realloc function deallocates the old object pointed to by ptr and returns a
14038 pointer to a new object that has the size specified by size. The contents of the new
14039 object shall be the same as that of the old object prior to deallocation, up to the lesser of
14040 the new and old sizes. Any bytes in the new object beyond the size of the old object have
14041 indeterminate values.
14042 3 If ptr is a null pointer, the realloc function behaves like the malloc function for the
14043 specified size. Otherwise, if ptr does not match a pointer earlier returned by a memory
14044 management function, or if the space has been deallocated by a call to the free or
14045 realloc function, the behavior is undefined. If memory for the new object cannot be
14046 allocated, the old object is not deallocated and its value is unchanged.
14048 4 The realloc function returns a pointer to the new object (which may have the same
14049 value as a pointer to the old object), or a null pointer if the new object could not be
14051 <a name="7.22.4" href="#7.22.4"><b> 7.22.4 Communication with the environment</b></a>
14052 <a name="7.22.4.1" href="#7.22.4.1"><b> 7.22.4.1 The abort function</b></a>
14054 1 #include <a href="#7.22"><stdlib.h></a>
14055 _Noreturn void abort(void);
14056 <b> Description</b>
14057 2 The abort function causes abnormal program termination to occur, unless the signal
14058 SIGABRT is being caught and the signal handler does not return. Whether open streams
14059 with unwritten buffered data are flushed, open streams are closed, or temporary files are
14060 removed is implementation-defined. An implementation-defined form of the status
14061 unsuccessful termination is returned to the host environment by means of the function
14062 call raise(SIGABRT).
14067 [<a name="p349" href="#p349">page 349</a>] (<a href="#Contents">Contents</a>)
14070 3 The abort function does not return to its caller.
14071 <a name="7.22.4.2" href="#7.22.4.2"><b> 7.22.4.2 The atexit function</b></a>
14073 1 #include <a href="#7.22"><stdlib.h></a>
14074 int atexit(void (*func)(void));
14075 <b> Description</b>
14076 2 The atexit function registers the function pointed to by func, to be called without
14077 arguments at normal program termination.<sup><a href="#note290"><b>290)</b></a></sup>
14078 Environmental limits
14079 3 The implementation shall support the registration of at least 32 functions.
14081 4 The atexit function returns zero if the registration succeeds, nonzero if it fails.
14082 Forward references: the at_quick_exit function (<a href="#7.22.4.3">7.22.4.3</a>), the exit function
14083 (<a href="#7.22.4.4">7.22.4.4</a>).
14084 <a name="7.22.4.3" href="#7.22.4.3"><b> 7.22.4.3 The at_quick_exit function</b></a>
14086 1 #include <a href="#7.22"><stdlib.h></a>
14087 int at_quick_exit(void (*func)(void));
14088 <b> Description</b>
14089 2 The at_quick_exit function registers the function pointed to by func, to be called
14090 without arguments should quick_exit be called.<sup><a href="#note291"><b>291)</b></a></sup>
14091 Environmental limits
14092 3 The implementation shall support the registration of at least 32 functions.
14094 4 The at_quick_exit function returns zero if the registration succeeds, nonzero if it
14096 Forward references: the quick_exit function (<a href="#7.22.4.7">7.22.4.7</a>).
14099 <sup><a name="note290" href="#note290"><b>290)</b></a></sup> The atexit function registrations are distinct from the at_quick_exit registrations, so
14100 applications may need to call both registration functions with the same argument.
14101 <sup><a name="note291" href="#note291"><b>291)</b></a></sup> The at_quick_exit function registrations are distinct from the atexit registrations, so
14102 applications may need to call both registration functions with the same argument.
14104 [<a name="p350" href="#p350">page 350</a>] (<a href="#Contents">Contents</a>)
14106 <a name="7.22.4.4" href="#7.22.4.4"><b> 7.22.4.4 The exit function</b></a>
14108 1 #include <a href="#7.22"><stdlib.h></a>
14109 _Noreturn void exit(int status);
14110 <b> Description</b>
14111 2 The exit function causes normal program termination to occur. No functions registered
14112 by the at_quick_exit function are called. If a program calls the exit function
14113 more than once, or calls the quick_exit function in addition to the exit function, the
14114 behavior is undefined.
14115 3 First, all functions registered by the atexit function are called, in the reverse order of
14116 their registration,<sup><a href="#note292"><b>292)</b></a></sup> except that a function is called after any previously registered
14117 functions that had already been called at the time it was registered. If, during the call to
14118 any such function, a call to the longjmp function is made that would terminate the call
14119 to the registered function, the behavior is undefined.
14120 4 Next, all open streams with unwritten buffered data are flushed, all open streams are
14121 closed, and all files created by the tmpfile function are removed.
14122 5 Finally, control is returned to the host environment. If the value of status is zero or
14123 EXIT_SUCCESS, an implementation-defined form of the status successful termination is
14124 returned. If the value of status is EXIT_FAILURE, an implementation-defined form
14125 of the status unsuccessful termination is returned. Otherwise the status returned is
14126 implementation-defined.
14128 6 The exit function cannot return to its caller.
14129 <a name="7.22.4.5" href="#7.22.4.5"><b> 7.22.4.5 The _Exit function</b></a>
14131 1 #include <a href="#7.22"><stdlib.h></a>
14132 _Noreturn void _Exit(int status);
14133 <b> Description</b>
14134 2 The _Exit function causes normal program termination to occur and control to be
14135 returned to the host environment. No functions registered by the atexit function, the
14136 at_quick_exit function, or signal handlers registered by the signal function are
14137 called. The status returned to the host environment is determined in the same way as for
14140 <sup><a name="note292" href="#note292"><b>292)</b></a></sup> Each function is called as many times as it was registered, and in the correct order with respect to
14141 other registered functions.
14143 [<a name="p351" href="#p351">page 351</a>] (<a href="#Contents">Contents</a>)
14145 the exit function (<a href="#7.22.4.4">7.22.4.4</a>). Whether open streams with unwritten buffered data are
14146 flushed, open streams are closed, or temporary files are removed is implementation-
14149 3 The _Exit function cannot return to its caller.
14150 <a name="7.22.4.6" href="#7.22.4.6"><b> 7.22.4.6 The getenv function</b></a>
14152 1 #include <a href="#7.22"><stdlib.h></a>
14153 char *getenv(const char *name);
14154 <b> Description</b>
14155 2 The getenv function searches an environment list, provided by the host environment,
14156 for a string that matches the string pointed to by name. The set of environment names
14157 and the method for altering the environment list are implementation-defined. The
14158 getenv function need not avoid data races with other threads of execution that modify
14159 the environment list.<sup><a href="#note293"><b>293)</b></a></sup>
14160 3 The implementation shall behave as if no library function calls the getenv function.
14162 4 The getenv function returns a pointer to a string associated with the matched list
14163 member. The string pointed to shall not be modified by the program, but may be
14164 overwritten by a subsequent call to the getenv function. If the specified name cannot
14165 be found, a null pointer is returned.
14166 <a name="7.22.4.7" href="#7.22.4.7"><b> 7.22.4.7 The quick_exit function</b></a>
14168 1 #include <a href="#7.22"><stdlib.h></a>
14169 _Noreturn void quick_exit(int status);
14170 <b> Description</b>
14171 2 The quick_exit function causes normal program termination to occur. No functions
14172 registered by the atexit function or signal handlers registered by the signal function
14173 are called. If a program calls the quick_exit function more than once, or calls the
14174 exit function in addition to the quick_exit function, the behavior is undefined.
14175 3 The quick_exit function first calls all functions registered by the at_quick_exit
14176 function, in the reverse order of their registration,<sup><a href="#note294"><b>294)</b></a></sup> except that a function is called after
14179 <sup><a name="note293" href="#note293"><b>293)</b></a></sup> Many implementations provide non-standard functions that modify the environment list.
14181 [<a name="p352" href="#p352">page 352</a>] (<a href="#Contents">Contents</a>)
14183 any previously registered functions that had already been called at the time it was
14184 registered. If, during the call to any such function, a call to the longjmp function is
14185 made that would terminate the call to the registered function, the behavior is undefined.
14186 4 Then control is returned to the host environment by means of the function call
14189 5 The quick_exit function cannot return to its caller.
14190 <a name="7.22.4.8" href="#7.22.4.8"><b> 7.22.4.8 The system function</b></a>
14192 1 #include <a href="#7.22"><stdlib.h></a>
14193 int system(const char *string);
14194 <b> Description</b>
14195 2 If string is a null pointer, the system function determines whether the host
14196 environment has a command processor. If string is not a null pointer, the system
14197 function passes the string pointed to by string to that command processor to be
14198 executed in a manner which the implementation shall document; this might then cause the
14199 program calling system to behave in a non-conforming manner or to terminate.
14201 3 If the argument is a null pointer, the system function returns nonzero only if a
14202 command processor is available. If the argument is not a null pointer, and the system
14203 function does return, it returns an implementation-defined value.
14204 <a name="7.22.5" href="#7.22.5"><b> 7.22.5 Searching and sorting utilities</b></a>
14205 1 These utilities make use of a comparison function to search or sort arrays of unspecified
14206 type. Where an argument declared as size_t nmemb specifies the length of the array
14207 for a function, nmemb can have the value zero on a call to that function; the comparison
14208 function is not called, a search finds no matching element, and sorting performs no
14209 rearrangement. Pointer arguments on such a call shall still have valid values, as described
14210 in <a href="#7.1.4">7.1.4</a>.
14211 2 The implementation shall ensure that the second argument of the comparison function
14212 (when called from bsearch), or both arguments (when called from qsort), are
14213 pointers to elements of the array.<sup><a href="#note295"><b>295)</b></a></sup> The first argument when called from bsearch
14218 <sup><a name="note294" href="#note294"><b>294)</b></a></sup> Each function is called as many times as it was registered, and in the correct order with respect to
14219 other registered functions.
14221 [<a name="p353" href="#p353">page 353</a>] (<a href="#Contents">Contents</a>)
14223 3 The comparison function shall not alter the contents of the array. The implementation
14224 may reorder elements of the array between calls to the comparison function, but shall not
14225 alter the contents of any individual element.
14226 4 When the same objects (consisting of size bytes, irrespective of their current positions
14227 in the array) are passed more than once to the comparison function, the results shall be
14228 consistent with one another. That is, for qsort they shall define a total ordering on the
14229 array, and for bsearch the same object shall always compare the same way with the
14231 5 A sequence point occurs immediately before and immediately after each call to the
14232 comparison function, and also between any call to the comparison function and any
14233 movement of the objects passed as arguments to that call.
14234 <a name="7.22.5.1" href="#7.22.5.1"><b> 7.22.5.1 The bsearch function</b></a>
14236 1 #include <a href="#7.22"><stdlib.h></a>
14237 void *bsearch(const void *key, const void *base,
14238 size_t nmemb, size_t size,
14239 int (*compar)(const void *, const void *));
14240 <b> Description</b>
14241 2 The bsearch function searches an array of nmemb objects, the initial element of which
14242 is pointed to by base, for an element that matches the object pointed to by key. The
14243 size of each element of the array is specified by size.
14244 3 The comparison function pointed to by compar is called with two arguments that point
14245 to the key object and to an array element, in that order. The function shall return an
14246 integer less than, equal to, or greater than zero if the key object is considered,
14247 respectively, to be less than, to match, or to be greater than the array element. The array
14248 shall consist of: all the elements that compare less than, all the elements that compare
14249 equal to, and all the elements that compare greater than the key object, in that order.<sup><a href="#note296"><b>296)</b></a></sup>
14251 4 The bsearch function returns a pointer to a matching element of the array, or a null
14252 pointer if no match is found. If two elements compare as equal, which element is
14255 <sup><a name="note295" href="#note295"><b>295)</b></a></sup> That is, if the value passed is p, then the following expressions are always nonzero:
14256 ((char *)p - (char *)base) % size == 0
14257 (char *)p >= (char *)base
14258 (char *)p < (char *)base + nmemb * size
14260 <sup><a name="note296" href="#note296"><b>296)</b></a></sup> In practice, the entire array is sorted according to the comparison function.
14262 [<a name="p354" href="#p354">page 354</a>] (<a href="#Contents">Contents</a>)
14264 matched is unspecified.
14265 <a name="7.22.5.2" href="#7.22.5.2"><b> 7.22.5.2 The qsort function</b></a>
14267 1 #include <a href="#7.22"><stdlib.h></a>
14268 void qsort(void *base, size_t nmemb, size_t size,
14269 int (*compar)(const void *, const void *));
14270 <b> Description</b>
14271 2 The qsort function sorts an array of nmemb objects, the initial element of which is
14272 pointed to by base. The size of each object is specified by size.
14273 3 The contents of the array are sorted into ascending order according to a comparison
14274 function pointed to by compar, which is called with two arguments that point to the
14275 objects being compared. The function shall return an integer less than, equal to, or
14276 greater than zero if the first argument is considered to be respectively less than, equal to,
14277 or greater than the second.
14278 4 If two elements compare as equal, their order in the resulting sorted array is unspecified.
14280 5 The qsort function returns no value.
14281 <a name="7.22.6" href="#7.22.6"><b> 7.22.6 Integer arithmetic functions</b></a>
14282 <a name="7.22.6.1" href="#7.22.6.1"><b> 7.22.6.1 The abs, labs and llabs functions</b></a>
14284 1 #include <a href="#7.22"><stdlib.h></a>
14286 long int labs(long int j);
14287 long long int llabs(long long int j);
14288 <b> Description</b>
14289 2 The abs, labs, and llabs functions compute the absolute value of an integer j. If the
14290 result cannot be represented, the behavior is undefined.<sup><a href="#note297"><b>297)</b></a></sup>
14292 3 The abs, labs, and llabs, functions return the absolute value.
14297 <sup><a name="note297" href="#note297"><b>297)</b></a></sup> The absolute value of the most negative number cannot be represented in two's complement.
14299 [<a name="p355" href="#p355">page 355</a>] (<a href="#Contents">Contents</a>)
14301 <a name="7.22.6.2" href="#7.22.6.2"><b> 7.22.6.2 The div, ldiv, and lldiv functions</b></a>
14303 1 #include <a href="#7.22"><stdlib.h></a>
14304 div_t div(int numer, int denom);
14305 ldiv_t ldiv(long int numer, long int denom);
14306 lldiv_t lldiv(long long int numer, long long int denom);
14307 <b> Description</b>
14308 2 The div, ldiv, and lldiv, functions compute numer / denom and numer %
14309 denom in a single operation.
14311 3 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
14312 lldiv_t, respectively, comprising both the quotient and the remainder. The structures
14313 shall contain (in either order) the members quot (the quotient) and rem (the remainder),
14314 each of which has the same type as the arguments numer and denom. If either part of
14315 the result cannot be represented, the behavior is undefined.
14316 <a name="7.22.7" href="#7.22.7"><b> 7.22.7 Multibyte/wide character conversion functions</b></a>
14317 1 The behavior of the multibyte character functions is affected by the LC_CTYPE category
14318 of the current locale. For a state-dependent encoding, each function is placed into its
14319 initial conversion state at program startup and can be returned to that state by a call for
14320 which its character pointer argument, s, is a null pointer. Subsequent calls with s as
14321 other than a null pointer cause the internal conversion state of the function to be altered as
14322 necessary. A call with s as a null pointer causes these functions to return a nonzero value
14323 if encodings have state dependency, and zero otherwise.<sup><a href="#note298"><b>298)</b></a></sup> Changing the LC_CTYPE
14324 category causes the conversion state of these functions to be indeterminate.
14325 <a name="7.22.7.1" href="#7.22.7.1"><b> 7.22.7.1 The mblen function</b></a>
14327 1 #include <a href="#7.22"><stdlib.h></a>
14328 int mblen(const char *s, size_t n);
14329 <b> Description</b>
14330 2 If s is not a null pointer, the mblen function determines the number of bytes contained
14331 in the multibyte character pointed to by s. Except that the conversion state of the
14332 mbtowc function is not affected, it is equivalent to
14336 <sup><a name="note298" href="#note298"><b>298)</b></a></sup> If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
14337 character codes, but are grouped with an adjacent multibyte character.
14339 [<a name="p356" href="#p356">page 356</a>] (<a href="#Contents">Contents</a>)
14341 mbtowc((wchar_t *)0, (const char *)0, 0);
14342 mbtowc((wchar_t *)0, s, n);
14343 3 The implementation shall behave as if no library function calls the mblen function.
14345 4 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte
14346 character encodings, respectively, do or do not have state-dependent encodings. If s is
14347 not a null pointer, the mblen function either returns 0 (if s points to the null character),
14348 or returns the number of bytes that are contained in the multibyte character (if the next n
14349 or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid
14350 multibyte character).
14351 Forward references: the mbtowc function (<a href="#7.22.7.2">7.22.7.2</a>).
14352 <a name="7.22.7.2" href="#7.22.7.2"><b> 7.22.7.2 The mbtowc function</b></a>
14354 1 #include <a href="#7.22"><stdlib.h></a>
14355 int mbtowc(wchar_t * restrict pwc,
14356 const char * restrict s,
14358 <b> Description</b>
14359 2 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with
14360 the byte pointed to by s to determine the number of bytes needed to complete the next
14361 multibyte character (including any shift sequences). If the function determines that the
14362 next multibyte character is complete and valid, it determines the value of the
14363 corresponding wide character and then, if pwc is not a null pointer, stores that value in
14364 the object pointed to by pwc. If the corresponding wide character is the null wide
14365 character, the function is left in the initial conversion state.
14366 3 The implementation shall behave as if no library function calls the mbtowc function.
14368 4 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte
14369 character encodings, respectively, do or do not have state-dependent encodings. If s is
14370 not a null pointer, the mbtowc function either returns 0 (if s points to the null character),
14371 or returns the number of bytes that are contained in the converted multibyte character (if
14372 the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not
14373 form a valid multibyte character).
14374 5 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
14378 [<a name="p357" href="#p357">page 357</a>] (<a href="#Contents">Contents</a>)
14380 <a name="7.22.7.3" href="#7.22.7.3"><b> 7.22.7.3 The wctomb function</b></a>
14382 1 #include <a href="#7.22"><stdlib.h></a>
14383 int wctomb(char *s, wchar_t wc);
14384 <b> Description</b>
14385 2 The wctomb function determines the number of bytes needed to represent the multibyte
14386 character corresponding to the wide character given by wc (including any shift
14387 sequences), and stores the multibyte character representation in the array whose first
14388 element is pointed to by s (if s is not a null pointer). At most MB_CUR_MAX characters
14389 are stored. If wc is a null wide character, a null byte is stored, preceded by any shift
14390 sequence needed to restore the initial shift state, and the function is left in the initial
14392 3 The implementation shall behave as if no library function calls the wctomb function.
14394 4 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte
14395 character encodings, respectively, do or do not have state-dependent encodings. If s is
14396 not a null pointer, the wctomb function returns -1 if the value of wc does not correspond
14397 to a valid multibyte character, or returns the number of bytes that are contained in the
14398 multibyte character corresponding to the value of wc.
14399 5 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
14400 <a name="7.22.8" href="#7.22.8"><b> 7.22.8 Multibyte/wide string conversion functions</b></a>
14401 1 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
14402 the current locale.
14403 <a name="7.22.8.1" href="#7.22.8.1"><b> 7.22.8.1 The mbstowcs function</b></a>
14405 1 #include <a href="#7.22"><stdlib.h></a>
14406 size_t mbstowcs(wchar_t * restrict pwcs,
14407 const char * restrict s,
14409 <b> Description</b>
14410 2 The mbstowcs function converts a sequence of multibyte characters that begins in the
14411 initial shift state from the array pointed to by s into a sequence of corresponding wide
14412 characters and stores not more than n wide characters into the array pointed to by pwcs.
14413 No multibyte characters that follow a null character (which is converted into a null wide
14414 character) will be examined or converted. Each multibyte character is converted as if by
14415 a call to the mbtowc function, except that the conversion state of the mbtowc function is
14416 [<a name="p358" href="#p358">page 358</a>] (<a href="#Contents">Contents</a>)
14419 3 No more than n elements will be modified in the array pointed to by pwcs. If copying
14420 takes place between objects that overlap, the behavior is undefined.
14422 4 If an invalid multibyte character is encountered, the mbstowcs function returns
14423 (size_t)(-1). Otherwise, the mbstowcs function returns the number of array
14424 elements modified, not including a terminating null wide character, if any.<sup><a href="#note299"><b>299)</b></a></sup>
14425 <a name="7.22.8.2" href="#7.22.8.2"><b> 7.22.8.2 The wcstombs function</b></a>
14427 1 #include <a href="#7.22"><stdlib.h></a>
14428 size_t wcstombs(char * restrict s,
14429 const wchar_t * restrict pwcs,
14431 <b> Description</b>
14432 2 The wcstombs function converts a sequence of wide characters from the array pointed
14433 to by pwcs into a sequence of corresponding multibyte characters that begins in the
14434 initial shift state, and stores these multibyte characters into the array pointed to by s,
14435 stopping if a multibyte character would exceed the limit of n total bytes or if a null
14436 character is stored. Each wide character is converted as if by a call to the wctomb
14437 function, except that the conversion state of the wctomb function is not affected.
14438 3 No more than n bytes will be modified in the array pointed to by s. If copying takes place
14439 between objects that overlap, the behavior is undefined.
14441 4 If a wide character is encountered that does not correspond to a valid multibyte character,
14442 the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
14443 returns the number of bytes modified, not including a terminating null character, if
14449 <sup><a name="note299" href="#note299"><b>299)</b></a></sup> The array will not be null-terminated if the value returned is n.
14451 [<a name="p359" href="#p359">page 359</a>] (<a href="#Contents">Contents</a>)
14453 <a name="7.23" href="#7.23"><b> 7.23 String handling <string.h></b></a>
14454 <a name="7.23.1" href="#7.23.1"><b> 7.23.1 String function conventions</b></a>
14455 1 The header <a href="#7.23"><string.h></a> declares one type and several functions, and defines one
14456 macro useful for manipulating arrays of character type and other objects treated as arrays
14457 of character type.<sup><a href="#note300"><b>300)</b></a></sup> The type is size_t and the macro is NULL (both described in
14458 <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>
14459 a char * or void * argument points to the initial (lowest addressed) character of the
14460 array. If an array is accessed beyond the end of an object, the behavior is undefined.
14461 2 Where an argument declared as size_t n specifies the length of the array for a
14462 function, n can have the value zero on a call to that function. Unless explicitly stated
14463 otherwise in the description of a particular function in this subclause, pointer arguments
14464 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
14465 function that locates a character finds no occurrence, a function that compares two
14466 character sequences returns zero, and a function that copies characters copies zero
14468 3 For all functions in this subclause, each character shall be interpreted as if it had the type
14469 unsigned char (and therefore every possible object representation is valid and has a
14471 <a name="7.23.2" href="#7.23.2"><b> 7.23.2 Copying functions</b></a>
14472 <a name="7.23.2.1" href="#7.23.2.1"><b> 7.23.2.1 The memcpy function</b></a>
14474 1 #include <a href="#7.23"><string.h></a>
14475 void *memcpy(void * restrict s1,
14476 const void * restrict s2,
14478 <b> Description</b>
14479 2 The memcpy function copies n characters from the object pointed to by s2 into the
14480 object pointed to by s1. If copying takes place between objects that overlap, the behavior
14483 3 The memcpy function returns the value of s1.
14488 <sup><a name="note300" href="#note300"><b>300)</b></a></sup> See ''future library directions'' (<a href="#7.30.11">7.30.11</a>).
14490 [<a name="p360" href="#p360">page 360</a>] (<a href="#Contents">Contents</a>)
14492 <a name="7.23.2.2" href="#7.23.2.2"><b> 7.23.2.2 The memmove function</b></a>
14494 1 #include <a href="#7.23"><string.h></a>
14495 void *memmove(void *s1, const void *s2, size_t n);
14496 <b> Description</b>
14497 2 The memmove function copies n characters from the object pointed to by s2 into the
14498 object pointed to by s1. Copying takes place as if the n characters from the object
14499 pointed to by s2 are first copied into a temporary array of n characters that does not
14500 overlap the objects pointed to by s1 and s2, and then the n characters from the
14501 temporary array are copied into the object pointed to by s1.
14503 3 The memmove function returns the value of s1.
14504 <a name="7.23.2.3" href="#7.23.2.3"><b> 7.23.2.3 The strcpy function</b></a>
14506 1 #include <a href="#7.23"><string.h></a>
14507 char *strcpy(char * restrict s1,
14508 const char * restrict s2);
14509 <b> Description</b>
14510 2 The strcpy function copies the string pointed to by s2 (including the terminating null
14511 character) into the array pointed to by s1. If copying takes place between objects that
14512 overlap, the behavior is undefined.
14514 3 The strcpy function returns the value of s1.
14515 <a name="7.23.2.4" href="#7.23.2.4"><b> 7.23.2.4 The strncpy function</b></a>
14517 1 #include <a href="#7.23"><string.h></a>
14518 char *strncpy(char * restrict s1,
14519 const char * restrict s2,
14521 <b> Description</b>
14522 2 The strncpy function copies not more than n characters (characters that follow a null
14523 character are not copied) from the array pointed to by s2 to the array pointed to by
14528 [<a name="p361" href="#p361">page 361</a>] (<a href="#Contents">Contents</a>)
14530 s1.<sup><a href="#note301"><b>301)</b></a></sup> If copying takes place between objects that overlap, the behavior is undefined.
14531 3 If the array pointed to by s2 is a string that is shorter than n characters, null characters
14532 are appended to the copy in the array pointed to by s1, until n characters in all have been
14535 4 The strncpy function returns the value of s1.
14536 <a name="7.23.3" href="#7.23.3"><b> 7.23.3 Concatenation functions</b></a>
14537 <a name="7.23.3.1" href="#7.23.3.1"><b> 7.23.3.1 The strcat function</b></a>
14539 1 #include <a href="#7.23"><string.h></a>
14540 char *strcat(char * restrict s1,
14541 const char * restrict s2);
14542 <b> Description</b>
14543 2 The strcat function appends a copy of the string pointed to by s2 (including the
14544 terminating null character) to the end of the string pointed to by s1. The initial character
14545 of s2 overwrites the null character at the end of s1. If copying takes place between
14546 objects that overlap, the behavior is undefined.
14548 3 The strcat function returns the value of s1.
14549 <a name="7.23.3.2" href="#7.23.3.2"><b> 7.23.3.2 The strncat function</b></a>
14551 1 #include <a href="#7.23"><string.h></a>
14552 char *strncat(char * restrict s1,
14553 const char * restrict s2,
14555 <b> Description</b>
14556 2 The strncat function appends not more than n characters (a null character and
14557 characters that follow it are not appended) from the array pointed to by s2 to the end of
14558 the string pointed to by s1. The initial character of s2 overwrites the null character at the
14559 end of s1. A terminating null character is always appended to the result.<sup><a href="#note302"><b>302)</b></a></sup> If copying
14561 <sup><a name="note301" href="#note301"><b>301)</b></a></sup> Thus, if there is no null character in the first n characters of the array pointed to by s2, the result will
14562 not be null-terminated.
14563 <sup><a name="note302" href="#note302"><b>302)</b></a></sup> Thus, the maximum number of characters that can end up in the array pointed to by s1 is
14566 [<a name="p362" href="#p362">page 362</a>] (<a href="#Contents">Contents</a>)
14568 takes place between objects that overlap, the behavior is undefined.
14570 3 The strncat function returns the value of s1.
14571 Forward references: the strlen function (<a href="#7.23.6.3">7.23.6.3</a>).
14572 <a name="7.23.4" href="#7.23.4"><b> 7.23.4 Comparison functions</b></a>
14573 1 The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
14574 and strncmp is determined by the sign of the difference between the values of the first
14575 pair of characters (both interpreted as unsigned char) that differ in the objects being
14577 <a name="7.23.4.1" href="#7.23.4.1"><b> 7.23.4.1 The memcmp function</b></a>
14579 1 #include <a href="#7.23"><string.h></a>
14580 int memcmp(const void *s1, const void *s2, size_t n);
14581 <b> Description</b>
14582 2 The memcmp function compares the first n characters of the object pointed to by s1 to
14583 the first n characters of the object pointed to by s2.<sup><a href="#note303"><b>303)</b></a></sup>
14585 3 The memcmp function returns an integer greater than, equal to, or less than zero,
14586 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
14588 <a name="7.23.4.2" href="#7.23.4.2"><b> 7.23.4.2 The strcmp function</b></a>
14590 1 #include <a href="#7.23"><string.h></a>
14591 int strcmp(const char *s1, const char *s2);
14592 <b> Description</b>
14593 2 The strcmp function compares the string pointed to by s1 to the string pointed to by
14596 3 The strcmp function returns an integer greater than, equal to, or less than zero,
14597 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
14599 <sup><a name="note303" href="#note303"><b>303)</b></a></sup> The contents of ''holes'' used as padding for purposes of alignment within structure objects are
14600 indeterminate. Strings shorter than their allocated space and unions may also cause problems in
14603 [<a name="p363" href="#p363">page 363</a>] (<a href="#Contents">Contents</a>)
14606 <a name="7.23.4.3" href="#7.23.4.3"><b> 7.23.4.3 The strcoll function</b></a>
14608 1 #include <a href="#7.23"><string.h></a>
14609 int strcoll(const char *s1, const char *s2);
14610 <b> Description</b>
14611 2 The strcoll function compares the string pointed to by s1 to the string pointed to by
14612 s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
14614 3 The strcoll function returns an integer greater than, equal to, or less than zero,
14615 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
14616 pointed to by s2 when both are interpreted as appropriate to the current locale.
14617 <a name="7.23.4.4" href="#7.23.4.4"><b> 7.23.4.4 The strncmp function</b></a>
14619 1 #include <a href="#7.23"><string.h></a>
14620 int strncmp(const char *s1, const char *s2, size_t n);
14621 <b> Description</b>
14622 2 The strncmp function compares not more than n characters (characters that follow a
14623 null character are not compared) from the array pointed to by s1 to the array pointed to
14626 3 The strncmp function returns an integer greater than, equal to, or less than zero,
14627 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
14628 to, or less than the possibly null-terminated array pointed to by s2.
14629 <a name="7.23.4.5" href="#7.23.4.5"><b> 7.23.4.5 The strxfrm function</b></a>
14631 1 #include <a href="#7.23"><string.h></a>
14632 size_t strxfrm(char * restrict s1,
14633 const char * restrict s2,
14635 <b> Description</b>
14636 2 The strxfrm function transforms the string pointed to by s2 and places the resulting
14637 string into the array pointed to by s1. The transformation is such that if the strcmp
14638 function is applied to two transformed strings, it returns a value greater than, equal to, or
14640 [<a name="p364" href="#p364">page 364</a>] (<a href="#Contents">Contents</a>)
14642 less than zero, corresponding to the result of the strcoll function applied to the same
14643 two original strings. No more than n characters are placed into the resulting array
14644 pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
14645 be a null pointer. If copying takes place between objects that overlap, the behavior is
14648 3 The strxfrm function returns the length of the transformed string (not including the
14649 terminating null character). If the value returned is n or more, the contents of the array
14650 pointed to by s1 are indeterminate.
14651 4 EXAMPLE The value of the following expression is the size of the array needed to hold the
14652 transformation of the string pointed to by s.
14653 1 + strxfrm(NULL, s, 0)
14655 <a name="7.23.5" href="#7.23.5"><b> 7.23.5 Search functions</b></a>
14656 <a name="7.23.5.1" href="#7.23.5.1"><b> 7.23.5.1 The memchr function</b></a>
14658 1 #include <a href="#7.23"><string.h></a>
14659 void *memchr(const void *s, int c, size_t n);
14660 <b> Description</b>
14661 2 The memchr function locates the first occurrence of c (converted to an unsigned
14662 char) in the initial n characters (each interpreted as unsigned char) of the object
14663 pointed to by s. The implementation shall behave as if it reads the characters sequentially
14664 and stops as soon as a matching character is found.
14666 3 The memchr function returns a pointer to the located character, or a null pointer if the
14667 character does not occur in the object.
14668 <a name="7.23.5.2" href="#7.23.5.2"><b> 7.23.5.2 The strchr function</b></a>
14670 1 #include <a href="#7.23"><string.h></a>
14671 char *strchr(const char *s, int c);
14672 <b> Description</b>
14673 2 The strchr function locates the first occurrence of c (converted to a char) in the
14674 string pointed to by s. The terminating null character is considered to be part of the
14679 [<a name="p365" href="#p365">page 365</a>] (<a href="#Contents">Contents</a>)
14682 3 The strchr function returns a pointer to the located character, or a null pointer if the
14683 character does not occur in the string.
14684 <a name="7.23.5.3" href="#7.23.5.3"><b> 7.23.5.3 The strcspn function</b></a>
14686 1 #include <a href="#7.23"><string.h></a>
14687 size_t strcspn(const char *s1, const char *s2);
14688 <b> Description</b>
14689 2 The strcspn function computes the length of the maximum initial segment of the string
14690 pointed to by s1 which consists entirely of characters not from the string pointed to by
14693 3 The strcspn function returns the length of the segment.
14694 <a name="7.23.5.4" href="#7.23.5.4"><b> 7.23.5.4 The strpbrk function</b></a>
14696 1 #include <a href="#7.23"><string.h></a>
14697 char *strpbrk(const char *s1, const char *s2);
14698 <b> Description</b>
14699 2 The strpbrk function locates the first occurrence in the string pointed to by s1 of any
14700 character from the string pointed to by s2.
14702 3 The strpbrk function returns a pointer to the character, or a null pointer if no character
14703 from s2 occurs in s1.
14704 <a name="7.23.5.5" href="#7.23.5.5"><b> 7.23.5.5 The strrchr function</b></a>
14706 1 #include <a href="#7.23"><string.h></a>
14707 char *strrchr(const char *s, int c);
14708 <b> Description</b>
14709 2 The strrchr function locates the last occurrence of c (converted to a char) in the
14710 string pointed to by s. The terminating null character is considered to be part of the
14716 [<a name="p366" href="#p366">page 366</a>] (<a href="#Contents">Contents</a>)
14719 3 The strrchr function returns a pointer to the character, or a null pointer if c does not
14720 occur in the string.
14721 <a name="7.23.5.6" href="#7.23.5.6"><b> 7.23.5.6 The strspn function</b></a>
14723 1 #include <a href="#7.23"><string.h></a>
14724 size_t strspn(const char *s1, const char *s2);
14725 <b> Description</b>
14726 2 The strspn function computes the length of the maximum initial segment of the string
14727 pointed to by s1 which consists entirely of characters from the string pointed to by s2.
14729 3 The strspn function returns the length of the segment.
14730 <a name="7.23.5.7" href="#7.23.5.7"><b> 7.23.5.7 The strstr function</b></a>
14732 1 #include <a href="#7.23"><string.h></a>
14733 char *strstr(const char *s1, const char *s2);
14734 <b> Description</b>
14735 2 The strstr function locates the first occurrence in the string pointed to by s1 of the
14736 sequence of characters (excluding the terminating null character) in the string pointed to
14739 3 The strstr function returns a pointer to the located string, or a null pointer if the string
14740 is not found. If s2 points to a string with zero length, the function returns s1.
14741 <a name="7.23.5.8" href="#7.23.5.8"><b> 7.23.5.8 The strtok function</b></a>
14743 1 #include <a href="#7.23"><string.h></a>
14744 char *strtok(char * restrict s1,
14745 const char * restrict s2);
14746 <b> Description</b>
14747 2 A sequence of calls to the strtok function breaks the string pointed to by s1 into a
14748 sequence of tokens, each of which is delimited by a character from the string pointed to
14749 by s2. The first call in the sequence has a non-null first argument; subsequent calls in the
14750 sequence have a null first argument. The separator string pointed to by s2 may be
14751 different from call to call.
14752 [<a name="p367" href="#p367">page 367</a>] (<a href="#Contents">Contents</a>)
14754 3 The first call in the sequence searches the string pointed to by s1 for the first character
14755 that is not contained in the current separator string pointed to by s2. If no such character
14756 is found, then there are no tokens in the string pointed to by s1 and the strtok function
14757 returns a null pointer. If such a character is found, it is the start of the first token.
14758 4 The strtok function then searches from there for a character that is contained in the
14759 current separator string. If no such character is found, the current token extends to the
14760 end of the string pointed to by s1, and subsequent searches for a token will return a null
14761 pointer. If such a character is found, it is overwritten by a null character, which
14762 terminates the current token. The strtok function saves a pointer to the following
14763 character, from which the next search for a token will start.
14764 5 Each subsequent call, with a null pointer as the value of the first argument, starts
14765 searching from the saved pointer and behaves as described above.
14766 6 The strtok function is not required to avoid data races. The implementation shall
14767 behave as if no library function calls the strtok function.
14769 7 The strtok function returns a pointer to the first character of a token, or a null pointer
14770 if there is no token.
14772 #include <a href="#7.23"><string.h></a>
14773 static char str[] = "?a???b,,,#c";
14775 t = strtok(str, "?"); // t points to the token "a"
14776 t = strtok(NULL, ","); // t points to the token "??b"
14777 t = strtok(NULL, "#,"); // t points to the token "c"
14778 t = strtok(NULL, "?"); // t is a null pointer
14780 <a name="7.23.6" href="#7.23.6"><b> 7.23.6 Miscellaneous functions</b></a>
14781 <a name="7.23.6.1" href="#7.23.6.1"><b> 7.23.6.1 The memset function</b></a>
14783 1 #include <a href="#7.23"><string.h></a>
14784 void *memset(void *s, int c, size_t n);
14785 <b> Description</b>
14786 2 The memset function copies the value of c (converted to an unsigned char) into
14787 each of the first n characters of the object pointed to by s.
14789 3 The memset function returns the value of s.
14793 [<a name="p368" href="#p368">page 368</a>] (<a href="#Contents">Contents</a>)
14795 <a name="7.23.6.2" href="#7.23.6.2"><b> 7.23.6.2 The strerror function</b></a>
14797 1 #include <a href="#7.23"><string.h></a>
14798 char *strerror(int errnum);
14799 <b> Description</b>
14800 2 The strerror function maps the number in errnum to a message string. Typically,
14801 the values for errnum come from errno, but strerror shall map any value of type
14803 3 The strerror function is not required to avoid data races. The implementation shall
14804 behave as if no library function calls the strerror function.
14806 4 The strerror function returns a pointer to the string, the contents of which are locale-
14807 specific. The array pointed to shall not be modified by the program, but may be
14808 overwritten by a subsequent call to the strerror function.
14809 <a name="7.23.6.3" href="#7.23.6.3"><b> 7.23.6.3 The strlen function</b></a>
14811 1 #include <a href="#7.23"><string.h></a>
14812 size_t strlen(const char *s);
14813 <b> Description</b>
14814 2 The strlen function computes the length of the string pointed to by s.
14816 3 The strlen function returns the number of characters that precede the terminating null
14822 [<a name="p369" href="#p369">page 369</a>] (<a href="#Contents">Contents</a>)
14824 <a name="7.24" href="#7.24"><b> 7.24 Type-generic math <tgmath.h></b></a>
14825 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
14826 defines several type-generic macros.
14827 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
14828 double) suffix, several have one or more parameters whose corresponding real type is
14829 double. For each such function, except modf, there is a corresponding type-generic
14830 macro.<sup><a href="#note304"><b>304)</b></a></sup> The parameters whose corresponding real type is double in the function
14831 synopsis are generic parameters. Use of the macro invokes a function whose
14832 corresponding real type and type domain are determined by the arguments for the generic
14833 parameters.<sup><a href="#note305"><b>305)</b></a></sup>
14834 3 Use of the macro invokes a function whose generic parameters have the corresponding
14835 real type determined as follows:
14836 -- First, if any argument for generic parameters has type long double, the type
14837 determined is long double.
14838 -- Otherwise, if any argument for generic parameters has type double or is of integer
14839 type, the type determined is double.
14840 -- Otherwise, the type determined is float.
14841 4 For each unsuffixed function in <a href="#7.12"><math.h></a> for which there is a function in
14842 <a href="#7.3"><complex.h></a> with the same name except for a c prefix, the corresponding type-
14843 generic macro (for both functions) has the same name as the function in <a href="#7.12"><math.h></a>. The
14844 corresponding type-generic macro for fabs and cabs is fabs.
14849 <sup><a name="note304" href="#note304"><b>304)</b></a></sup> Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to
14850 make available the corresponding ordinary function.
14851 <sup><a name="note305" href="#note305"><b>305)</b></a></sup> If the type of the argument is not compatible with the type of the parameter for the selected function,
14852 the behavior is undefined.
14854 [<a name="p370" href="#p370">page 370</a>] (<a href="#Contents">Contents</a>)
14856 <a href="#7.12"><math.h></a> <a href="#7.3"><complex.h></a> type-generic
14857 function function macro
14875 If at least one argument for a generic parameter is complex, then use of the macro invokes
14876 a complex function; otherwise, use of the macro invokes a real function.
14877 5 For each unsuffixed function in <a href="#7.12"><math.h></a> without a c-prefixed counterpart in
14878 <a href="#7.3"><complex.h></a> (except modf), the corresponding type-generic macro has the same
14879 name as the function. These type-generic macros are:
14880 atan2 fma llround remainder
14881 cbrt fmax log10 remquo
14882 ceil fmin log1p rint
14883 copysign fmod log2 round
14884 erf frexp logb scalbn
14885 erfc hypot lrint scalbln
14886 exp2 ilogb lround tgamma
14887 expm1 ldexp nearbyint trunc
14888 fdim lgamma nextafter
14889 floor llrint nexttoward
14890 If all arguments for generic parameters are real, then use of the macro invokes a real
14891 function; otherwise, use of the macro results in undefined behavior.
14896 [<a name="p371" href="#p371">page 371</a>] (<a href="#Contents">Contents</a>)
14898 6 For each unsuffixed function in <a href="#7.3"><complex.h></a> that is not a c-prefixed counterpart to a
14899 function in <a href="#7.12"><math.h></a>, the corresponding type-generic macro has the same name as the
14900 function. These type-generic macros are:
14903 Use of the macro with any real or complex argument invokes a complex function.
14904 7 EXAMPLE With the declarations
14905 #include <a href="#7.24"><tgmath.h></a>
14912 long double complex ldc;
14913 functions invoked by use of type-generic macros are shown in the following table:
14915 exp(n) exp(n), the function
14917 sin(d) sin(d), the function
14921 pow(ldc, f) cpowl(ldc, f)
14922 remainder(n, n) remainder(n, n), the function
14923 nextafter(d, f) nextafter(d, f), the function
14924 nexttoward(f, ld) nexttowardf(f, ld)
14925 copysign(n, ld) copysignl(n, ld)
14926 ceil(fc) undefined behavior
14927 rint(dc) undefined behavior
14928 fmax(ldc, ld) undefined behavior
14929 carg(n) carg(n), the function
14931 creal(d) creal(d), the function
14932 cimag(ld) cimagl(ld)
14934 carg(dc) carg(dc), the function
14935 cproj(ldc) cprojl(ldc)
14940 [<a name="p372" href="#p372">page 372</a>] (<a href="#Contents">Contents</a>)
14942 <a name="7.25" href="#7.25"><b> 7.25 Threads <threads.h></b></a>
14943 <a name="7.25.1" href="#7.25.1"><b> 7.25.1 Introduction</b></a>
14944 1 The header <a href="#7.25"><threads.h></a> defines macros, and declares types, enumeration constants,
14945 and functions that support multiple threads of execution.
14946 2 Implementations that define the macro __STDC_NO_THREADS__ need not provide
14947 this header nor support any of its facilities.
14950 which expands to a value that can be used to initialize an object of type once_flag;
14952 TSS_DTOR_ITERATIONS
14953 which expands to an integer constant expression representing the maximum number of
14954 times that destructors will be called when a thread terminates.
14957 which is a complete object type that holds an identifier for a condition variable;
14959 which is a complete object type that holds an identifier for a thread;
14961 which is a complete object type that holds an identifier for a thread-specific storage
14964 which is a complete object type that holds an identifier for a mutex;
14966 which is the function pointer type void (*)(void*), used for a destructor for a
14967 thread-specific storage pointer;
14969 which is the function pointer type int (*)(void*) that is passed to thrd_create
14970 to create a new thread;
14972 which is a complete object type that holds a flag for use by call_once; and
14975 [<a name="p373" href="#p373">page 373</a>] (<a href="#Contents">Contents</a>)
14978 which is a structure type that holds a time specified in seconds and nanoseconds. The
14979 structure shall contain at least the following members, in any order.
14982 5 The enumeration constants are
14984 which is passed to mtx_init to create a mutex object that supports neither timeout nor
14987 which is passed to mtx_init to create a mutex object that supports recursive locking;
14989 which is passed to mtx_init to create a mutex object that supports timeout;
14991 which is passed to mtx_init to create a mutex object that supports test and return;
14993 which is returned by a timed wait function to indicate that the time specified in the call
14994 was reached without acquiring the requested resource;
14996 which is returned by a function to indicate that the requested operation succeeded;
14998 which is returned by a function to indicate that the requested operation failed because a
14999 resource requested by a test and return function is already in use;
15001 which is returned by a function to indicate that the requested operation failed; and
15003 which is returned by a function to indicate that the requested operation failed because it
15004 was unable to allocate memory.
15009 [<a name="p374" href="#p374">page 374</a>] (<a href="#Contents">Contents</a>)
15011 <a name="7.25.2" href="#7.25.2"><b> 7.25.2 Initialization functions</b></a>
15012 <a name="7.25.2.1" href="#7.25.2.1"><b> 7.25.2.1 The call_once function</b></a>
15014 1 #include <a href="#7.25"><threads.h></a>
15015 void call_once(once_flag *flag, void (*func)(void));
15016 <b> Description</b>
15017 2 The call_once function uses the once_flag pointed to by flag to ensure that
15018 func is called exactly once, the first time the call_once function is called with that
15019 value of flag. Completion of an effective call to the call_once function synchronizes
15020 with all subsequent calls to the call_once function with the same value of flag.
15022 3 The call_once function returns no value.
15023 <a name="7.25.3" href="#7.25.3"><b> 7.25.3 Condition variable functions</b></a>
15024 <a name="7.25.3.1" href="#7.25.3.1"><b> 7.25.3.1 The cnd_broadcast function</b></a>
15026 1 #include <a href="#7.25"><threads.h></a>
15027 int cnd_broadcast(cnd_t *cond);
15028 <b> Description</b>
15029 2 The cnd_broadcast function unblocks all of the threads that are blocked on the
15030 condition variable pointed to by cond at the time of the call. If no threads are blocked
15031 on the condition variable pointed to by cond at the time of the call, the function does
15034 3 The cnd_broadcast function returns thrd_success on success, or thrd_error
15035 if the request could not be honored.
15036 <a name="7.25.3.2" href="#7.25.3.2"><b> 7.25.3.2 The cnd_destroy function</b></a>
15038 1 #include <a href="#7.25"><threads.h></a>
15039 void cnd_destroy(cnd_t *cond);
15040 <b> Description</b>
15041 2 The cnd_destroy function releases all resources used by the condition variable
15042 pointed to by cond. The cnd_destroy function requires that no threads be blocked
15043 waiting for the condition variable pointed to by cond.
15045 [<a name="p375" href="#p375">page 375</a>] (<a href="#Contents">Contents</a>)
15048 3 The cnd_destroy function returns no value.
15049 <a name="7.25.3.3" href="#7.25.3.3"><b> 7.25.3.3 The cnd_init function</b></a>
15051 1 #include <a href="#7.25"><threads.h></a>
15052 int cnd_init(cnd_t *cond);
15053 <b> Description</b>
15054 2 The cnd_init function creates a condition variable. If it succeeds it sets the variable
15055 pointed to by cond to a value that uniquely identifies the newly created condition
15056 variable. A thread that calls cnd_wait on a newly created condition variable will
15059 3 The cnd_init function returns thrd_success on success, or thrd_nomem if no
15060 memory could be allocated for the newly created condition, or thrd_error if the
15061 request could not be honored.
15062 <a name="7.25.3.4" href="#7.25.3.4"><b> 7.25.3.4 The cnd_signal function</b></a>
15064 1 #include <a href="#7.25"><threads.h></a>
15065 int cnd_signal(cnd_t *cond);
15066 <b> Description</b>
15067 2 The cnd_signal function unblocks one of the threads that are blocked on the
15068 condition variable pointed to by cond at the time of the call. If no threads are blocked
15069 on the condition variable at the time of the call, the function does nothing and return
15072 3 The cnd_signal function returns thrd_success on success or thrd_error if
15073 the request could not be honored.
15074 <a name="7.25.3.5" href="#7.25.3.5"><b> 7.25.3.5 The cnd_timedwait function</b></a>
15076 1 #include <a href="#7.25"><threads.h></a>
15077 int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
15083 [<a name="p376" href="#p376">page 376</a>] (<a href="#Contents">Contents</a>)
15085 <b> Description</b>
15086 2 The cnd_timedwait function atomically unlocks the mutex pointed to by mtx and
15087 endeavors to block until the condition variable pointed to by cond is signaled by a call to
15088 cnd_signal or to cnd_broadcast, or until after the time specified by the xtime
15089 object pointed to by xt. When the calling thread becomes unblocked it locks the variable
15090 pointed to by mtx before it returns. The cnd_timedwait function requires that the
15091 mutex pointed to by mtx be locked by the calling thread.
15093 3 The cnd_timedwait function returns thrd_success upon success, or
15094 thrd_timeout if the time specified in the call was reached without acquiring the
15095 requested resource, or thrd_error if the request could not be honored.
15096 <a name="7.25.3.6" href="#7.25.3.6"><b> 7.25.3.6 The cnd_wait function</b></a>
15098 1 #include <a href="#7.25"><threads.h></a>
15099 int cnd_wait(cnd_t *cond, mtx_t *mtx);
15100 <b> Description</b>
15101 2 The cnd_wait function atomically unlocks the mutex pointed to by mtx and endeavors
15102 to block until the condition variable pointed to by cond is signaled by a call to
15103 cnd_signal or to cnd_broadcast. When the calling thread becomes unblocked it
15104 locks the mutex pointed to by mtx before it returns. If the mutex pointed to by mtx is
15105 not locked by the calling thread, the cnd_wait function will act as if the abort
15106 function is called.
15108 3 The cnd_wait function returns thrd_success on success or thrd_error if the
15109 request could not be honored.
15110 <a name="7.25.4" href="#7.25.4"><b> 7.25.4 Mutex functions</b></a>
15111 <a name="7.25.4.1" href="#7.25.4.1"><b> 7.25.4.1 The mtx_destroy function</b></a>
15113 1 #include <a href="#7.25"><threads.h></a>
15114 void mtx_destroy(mtx_t *mtx);
15115 <b> Description</b>
15116 2 The mtx_destroy function releases any resources used by the mutex pointed to by
15117 mtx. No threads can be blocked waiting for the mutex pointed to by mtx.
15121 [<a name="p377" href="#p377">page 377</a>] (<a href="#Contents">Contents</a>)
15124 3 The mtx_destroy function returns no value.
15125 <a name="7.25.4.2" href="#7.25.4.2"><b> 7.25.4.2 The mtx_init function</b></a>
15127 1 #include <a href="#7.25"><threads.h></a>
15128 int mtx_init(mtx_t *mtx, int type);
15129 <b> Description</b>
15130 2 The mtx_init function creates a mutex object with properties indicated by type,
15131 which must have one of the six values:
15132 mtx_plain for a simple non-recursive mutex,
15133 mtx_timed for a non-recursive mutex that supports timeout,
15134 mtx_try for a non-recursive mutex that supports test and return,
15135 mtx_plain | mtx_recursive for a simple recursive mutex,
15136 mtx_timed | mtx_recursive for a recursive mutex that supports timeout, or
15137 mtx_try | mtx_recursive for a recursive mutex that supports test and return.
15138 3 If the mtx_init function succeeds, it sets the mutex pointed to by mtx to a value that
15139 uniquely identifies the newly created mutex.
15141 4 The mtx_init function returns thrd_success on success, or thrd_error if the
15142 request could not be honored.
15143 <a name="7.25.4.3" href="#7.25.4.3"><b> 7.25.4.3 The mtx_lock function</b></a>
15145 1 #include <a href="#7.25"><threads.h></a>
15146 int mtx_lock(mtx_t *mtx);
15147 <b> Description</b>
15148 2 The mtx_lock function blocks until it locks the mutex pointed to by mtx. If the mutex
15149 is non-recursive, it shall not be locked by the calling thread. Prior calls to mtx_unlock
15150 on the same mutex shall synchronize with this operation.
15152 3 The mtx_lock function returns thrd_success on success, or thrd_busy if the
15153 resource requested is already in use, or thrd_error if the request could not be
15159 [<a name="p378" href="#p378">page 378</a>] (<a href="#Contents">Contents</a>)
15161 <a name="7.25.4.4" href="#7.25.4.4"><b> 7.25.4.4 The mtx_timedlock function</b></a>
15163 1 #include <a href="#7.25"><threads.h></a>
15164 int mtx_timedlock(mtx_t *mtx, const xtime *xt);
15165 <b> Description</b>
15166 2 The mtx_timedlock function endeavors to block until it locks the mutex pointed to by
15167 mtx or until the time specified by the xtime object xt has passed. The specified mutex
15168 shall support timeout. If the operation succeeds, prior calls to mtx_unlock on the same
15169 mutex shall synchronize with this operation.
15171 3 The mtx_timedlock function returns thrd_success on success, or thrd_busy
15172 if the resource requested is already in use, or thrd_timeout if the time specified was
15173 reached without acquiring the requested resource, or thrd_error if the request could
15175 <a name="7.25.4.5" href="#7.25.4.5"><b> 7.25.4.5 The mtx_trylock function</b></a>
15177 1 #include <a href="#7.25"><threads.h></a>
15178 int mtx_trylock(mtx_t *mtx);
15179 <b> Description</b>
15180 2 The mtx_trylock function endeavors to lock the mutex pointed to by mtx. The
15181 specified mutex shall support either test and return or timeout. If the mutex is already
15182 locked, the function returns without blocking. If the operation succeeds, prior calls to
15183 mtx_unlock on the same mutex shall synchronize with this operation.
15185 3 The mtx_trylock function returns thrd_success on success, or thrd_busy if
15186 the resource requested is already in use, or thrd_error if the request could not be
15188 <a name="7.25.4.6" href="#7.25.4.6"><b> 7.25.4.6 The mtx_unlock function</b></a>
15190 1 #include <a href="#7.25"><threads.h></a>
15191 int mtx_unlock(mtx_t *mtx);
15192 <b> Description</b>
15193 2 The mtx_unlock function unlocks the mutex pointed to by mtx. The mutex pointed to
15194 by mtx shall be locked by the calling thread.
15196 [<a name="p379" href="#p379">page 379</a>] (<a href="#Contents">Contents</a>)
15199 3 The mtx_unlock function returns thrd_success on success or thrd_error if
15200 the request could not be honored.
15201 <a name="7.25.5" href="#7.25.5"><b> 7.25.5 Thread functions</b></a>
15202 <a name="7.25.5.1" href="#7.25.5.1"><b> 7.25.5.1 The thrd_create function</b></a>
15204 1 #include <a href="#7.25"><threads.h></a>
15205 int thrd_create(thrd_t *thr, thrd_start_t func,
15207 <b> Description</b>
15208 2 The thrd_create function creates a new thread executing func(arg). If the
15209 thrd_create function succeeds, it sets the object pointed to by thr to the identifier of
15210 the newly created thread. (A thread's identifier may be reused for a different thread once
15211 the original thread has exited and either been detached or joined to another thread.) The
15212 completion of the thrd_create function synchronizes with the beginning of the
15213 execution of the new thread.
15215 3 The thrd_create function returns thrd_success on success, or thrd_nomem if
15216 no memory could be allocated for the thread requested, or thrd_error if the request
15217 could not be honored.
15218 <a name="7.25.5.2" href="#7.25.5.2"><b> 7.25.5.2 The thrd_current function</b></a>
15220 1 #include <a href="#7.25"><threads.h></a>
15221 thrd_t thrd_current(void);
15222 <b> Description</b>
15223 2 The thrd_current function identifies the thread that called it.
15225 3 The thrd_current function returns the identifier of the thread that called it.
15226 <a name="7.25.5.3" href="#7.25.5.3"><b> 7.25.5.3 The thrd_detach function</b></a>
15228 1 #include <a href="#7.25"><threads.h></a>
15229 int thrd_detach(thrd_t thr);
15233 [<a name="p380" href="#p380">page 380</a>] (<a href="#Contents">Contents</a>)
15235 <b> Description</b>
15236 2 The thrd_detach function tells the operating system to dispose of any resources
15237 allocated to the thread identified by thr when that thread terminates. The thread
15238 identified by thr shall not have been previously detached or joined with another thread.
15240 3 The thrd_detach function returns thrd_success on success or thrd_error if
15241 the request could not be honored.
15242 <a name="7.25.5.4" href="#7.25.5.4"><b> 7.25.5.4 The thrd_equal function</b></a>
15244 1 #include <a href="#7.25"><threads.h></a>
15245 int thrd_equal(thrd_t thr0, thrd_t thr1);
15246 <b> Description</b>
15247 2 The thrd_equal function will determine whether the thread identified by thr0 refers
15248 to the thread identified by thr1.
15250 3 The thrd_equal function returns zero if the thread thr0 and the thread thr1 refer to
15251 different threads. Otherwise the thrd_equal function returns a nonzero value.
15252 <a name="7.25.5.5" href="#7.25.5.5"><b> 7.25.5.5 The thrd_exit function</b></a>
15254 1 #include <a href="#7.25"><threads.h></a>
15255 void thrd_exit(int res);
15256 <b> Description</b>
15257 2 The thrd_exit function terminates execution of the calling thread and sets its result
15260 3 The thrd_exit function returns no value.
15261 <a name="7.25.5.6" href="#7.25.5.6"><b> 7.25.5.6 The thrd_join function</b></a>
15263 1 #include <a href="#7.25"><threads.h></a>
15264 int thrd_join(thrd_t thr, int *res);
15265 <b> Description</b>
15266 2 The thrd_join function joins the thread identified by thr with the current thread by
15267 blocking until the other thread has terminated. If the parameter res is not a null pointer,
15269 [<a name="p381" href="#p381">page 381</a>] (<a href="#Contents">Contents</a>)
15271 it stores the thread's result code in the integer pointed to by res. The termination of the
15272 other thread synchronizes with the completion of the thrd_join function. The thread
15273 identified by thr shall not have been previously detached or joined with another thread.
15275 3 The thrd_join function returns thrd_success on success or thrd_error if the
15276 request could not be honored.
15277 <a name="7.25.5.7" href="#7.25.5.7"><b> 7.25.5.7 The thrd_sleep function</b></a>
15279 1 #include <a href="#7.25"><threads.h></a>
15280 void thrd_sleep(const xtime *xt);
15281 <b> Description</b>
15282 2 The thrd_sleep function suspends execution of the calling thread until after the time
15283 specified by the xtime object pointed to by xt.
15285 3 The thrd_sleep function returns no value.
15286 <a name="7.25.5.8" href="#7.25.5.8"><b> 7.25.5.8 The thrd_yield function</b></a>
15288 1 #include <a href="#7.25"><threads.h></a>
15289 void thrd_yield(void);
15290 <b> Description</b>
15291 2 The thrd_yield function endeavors to permit other threads to run, even if the current
15292 thread would ordinarily continue to run.
15294 3 The thrd_yield function returns no value.
15295 <a name="7.25.6" href="#7.25.6"><b> 7.25.6 Thread-specific storage functions</b></a>
15296 <a name="7.25.6.1" href="#7.25.6.1"><b> 7.25.6.1 The tss_create function</b></a>
15298 1 #include <a href="#7.25"><threads.h></a>
15299 int tss_create(tss_t *key, tss_dtor_t dtor);
15300 <b> Description</b>
15301 2 The tss_create function creates a thread-specific storage pointer with destructor
15302 dtor, which may be null.
15305 [<a name="p382" href="#p382">page 382</a>] (<a href="#Contents">Contents</a>)
15308 3 If the tss_create function is successful, it sets the thread-specific storage pointed to
15309 by key to a value that uniquely identifies the newly created pointer and returns
15310 thrd_success; otherwise, thrd_error is returned and the thread-specific storage
15311 pointed to by key is set to an undefined value.
15312 <a name="7.25.6.2" href="#7.25.6.2"><b> 7.25.6.2 The tss_delete function</b></a>
15314 1 #include <a href="#7.25"><threads.h></a>
15315 void tss_delete(tss_t key);
15316 <b> Description</b>
15317 2 The tss_delete function releases any resources used by the thread-specific storage
15320 3 The tss_delete function returns no value.
15321 <a name="7.25.6.3" href="#7.25.6.3"><b> 7.25.6.3 The tss_get function</b></a>
15323 1 #include <a href="#7.25"><threads.h></a>
15324 void *tss_get(tss_t key);
15325 <b> Description</b>
15326 2 The tss_get function returns the value for the current thread held in the thread-specific
15327 storage identified by key.
15329 3 The tss_get function returns the value for the current thread if successful, or zero if
15331 <a name="7.25.6.4" href="#7.25.6.4"><b> 7.25.6.4 The tss_set function</b></a>
15333 1 #include <a href="#7.25"><threads.h></a>
15334 int tss_set(tss_t key, void *val);
15335 <b> Description</b>
15336 2 The tss_set function sets the value for the current thread held in the thread-specific
15337 storage identified by key to val.
15342 [<a name="p383" href="#p383">page 383</a>] (<a href="#Contents">Contents</a>)
15345 3 The tss_set function returns thrd_success on success or thrd_error if the
15346 request could not be honored.
15347 <a name="7.25.7" href="#7.25.7"><b> 7.25.7 Time functions</b></a>
15348 <a name="7.25.7.1" href="#7.25.7.1"><b> 7.25.7.1 The xtime_get function</b></a>
15350 1 #include <a href="#7.25"><threads.h></a>
15351 int xtime_get(xtime *xt, int base);
15352 <b> Description</b>
15353 2 The xtime_get function sets the xtime object pointed to by xt to hold the current
15354 time based on the time base base.
15356 3 If the xtime_get function is successful it returns the nonzero value base, which must
15357 be TIME_UTC; otherwise, it returns zero.<sup><a href="#note306"><b>306)</b></a></sup>
15362 <sup><a name="note306" href="#note306"><b>306)</b></a></sup> Although an xtime object describes times with nanosecond resolution, the actual resolution in an
15363 xtime object is system dependent.
15365 [<a name="p384" href="#p384">page 384</a>] (<a href="#Contents">Contents</a>)
15367 <a name="7.26" href="#7.26"><b> 7.26 Date and time <time.h></b></a>
15368 <a name="7.26.1" href="#7.26.1"><b> 7.26.1 Components of time</b></a>
15369 1 The header <a href="#7.26"><time.h></a> defines two macros, and declares several types and functions for
15370 manipulating time. Many functions deal with a calendar time that represents the current
15371 date (according to the Gregorian calendar) and time. Some functions deal with local
15372 time, which is the calendar time expressed for some specific time zone, and with Daylight
15373 Saving Time, which is a temporary change in the algorithm for determining local time.
15374 The local time zone and Daylight Saving Time are implementation-defined.
15375 2 The macros defined are NULL (described in <a href="#7.19">7.19</a>); and
15377 which expands to an expression with type clock_t (described below) that is the
15378 number per second of the value returned by the clock function.
15379 3 The types declared are size_t (described in <a href="#7.19">7.19</a>);
15383 which are arithmetic types capable of representing times; and
15385 which holds the components of a calendar time, called the broken-down time.
15386 4 The range and precision of times representable in clock_t and time_t are
15387 implementation-defined. The tm structure shall contain at least the following members,
15388 in any order. The semantics of the members and their normal ranges are expressed in the
15389 comments.<sup><a href="#note307"><b>307)</b></a></sup>
15390 int tm_sec; // seconds after the minute -- [0, 60]
15391 int tm_min; // minutes after the hour -- [0, 59]
15392 int tm_hour; // hours since midnight -- [0, 23]
15393 int tm_mday; // day of the month -- [1, 31]
15394 int tm_mon; // months since January -- [0, 11]
15395 int tm_year; // years since 1900
15396 int tm_wday; // days since Sunday -- [0, 6]
15397 int tm_yday; // days since January 1 -- [0, 365]
15398 int tm_isdst; // Daylight Saving Time flag
15402 <sup><a name="note307" href="#note307"><b>307)</b></a></sup> The range [0, 60] for tm_sec allows for a positive leap second.
15404 [<a name="p385" href="#p385">page 385</a>] (<a href="#Contents">Contents</a>)
15406 The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight
15407 Saving Time is not in effect, and negative if the information is not available.
15408 <a name="7.26.2" href="#7.26.2"><b> 7.26.2 Time manipulation functions</b></a>
15409 <a name="7.26.2.1" href="#7.26.2.1"><b> 7.26.2.1 The clock function</b></a>
15411 1 #include <a href="#7.26"><time.h></a>
15412 clock_t clock(void);
15413 <b> Description</b>
15414 2 The clock function determines the processor time used.
15416 3 The clock function returns the implementation's best approximation to the processor
15417 time used by the program since the beginning of an implementation-defined era related
15418 only to the program invocation. To determine the time in seconds, the value returned by
15419 the clock function should be divided by the value of the macro CLOCKS_PER_SEC. If
15420 the processor time used is not available or its value cannot be represented, the function
15421 returns the value (clock_t)(-1).<sup><a href="#note308"><b>308)</b></a></sup>
15422 <a name="7.26.2.2" href="#7.26.2.2"><b> 7.26.2.2 The difftime function</b></a>
15424 1 #include <a href="#7.26"><time.h></a>
15425 double difftime(time_t time1, time_t time0);
15426 <b> Description</b>
15427 2 The difftime function computes the difference between two calendar times: time1 -
15430 3 The difftime function returns the difference expressed in seconds as a double.
15435 <sup><a name="note308" href="#note308"><b>308)</b></a></sup> In order to measure the time spent in a program, the clock function should be called at the start of
15436 the program and its return value subtracted from the value returned by subsequent calls.
15438 [<a name="p386" href="#p386">page 386</a>] (<a href="#Contents">Contents</a>)
15440 <a name="7.26.2.3" href="#7.26.2.3"><b> 7.26.2.3 The mktime function</b></a>
15442 1 #include <a href="#7.26"><time.h></a>
15443 time_t mktime(struct tm *timeptr);
15444 <b> Description</b>
15445 2 The mktime function converts the broken-down time, expressed as local time, in the
15446 structure pointed to by timeptr into a calendar time value with the same encoding as
15447 that of the values returned by the time function. The original values of the tm_wday
15448 and tm_yday components of the structure are ignored, and the original values of the
15449 other components are not restricted to the ranges indicated above.<sup><a href="#note309"><b>309)</b></a></sup> On successful
15450 completion, the values of the tm_wday and tm_yday components of the structure are
15451 set appropriately, and the other components are set to represent the specified calendar
15452 time, but with their values forced to the ranges indicated above; the final value of
15453 tm_mday is not set until tm_mon and tm_year are determined.
15455 3 The mktime function returns the specified calendar time encoded as a value of type
15456 time_t. If the calendar time cannot be represented, the function returns the value
15458 4 EXAMPLE What day of the week is July 4, 2001?
15459 #include <a href="#7.21"><stdio.h></a>
15460 #include <a href="#7.26"><time.h></a>
15461 static const char *const wday[] = {
15462 "Sunday", "Monday", "Tuesday", "Wednesday",
15463 "Thursday", "Friday", "Saturday", "-unknown-"
15465 struct tm time_str;
15471 <sup><a name="note309" href="#note309"><b>309)</b></a></sup> Thus, a positive or zero value for tm_isdst causes the mktime function to presume initially that
15472 Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value
15473 causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time.
15475 [<a name="p387" href="#p387">page 387</a>] (<a href="#Contents">Contents</a>)
15477 time_str.tm_year = 2001 - 1900;
15478 time_str.tm_mon = 7 - 1;
15479 time_str.tm_mday = 4;
15480 time_str.tm_hour = 0;
15481 time_str.tm_min = 0;
15482 time_str.tm_sec = 1;
15483 time_str.tm_isdst = -1;
15484 if (mktime(&time_str) == (time_t)(-1))
15485 time_str.tm_wday = 7;
15486 printf("%s\n", wday[time_str.tm_wday]);
15488 <a name="7.26.2.4" href="#7.26.2.4"><b> 7.26.2.4 The time function</b></a>
15490 1 #include <a href="#7.26"><time.h></a>
15491 time_t time(time_t *timer);
15492 <b> Description</b>
15493 2 The time function determines the current calendar time. The encoding of the value is
15496 3 The time function returns the implementation's best approximation to the current
15497 calendar time. The value (time_t)(-1) is returned if the calendar time is not
15498 available. If timer is not a null pointer, the return value is also assigned to the object it
15500 <a name="7.26.3" href="#7.26.3"><b> 7.26.3 Time conversion functions</b></a>
15501 1 Except for the strftime function, these functions each return a pointer to one of two
15502 types of static objects: a broken-down time structure or an array of char. Execution of
15503 any of the functions that return a pointer to one of these object types may overwrite the
15504 information in any object of the same type pointed to by the value returned from any
15505 previous call to any of them and the functions are not required to avoid data races. The
15506 implementation shall behave as if no other library functions call these functions.
15507 <a name="7.26.3.1" href="#7.26.3.1"><b> 7.26.3.1 The asctime function</b></a>
15509 1 #include <a href="#7.26"><time.h></a>
15510 char *asctime(const struct tm *timeptr);
15511 <b> Description</b>
15512 2 The asctime function converts the broken-down time in the structure pointed to by
15513 timeptr into a string in the form
15514 Sun Sep 16 01:03:52 1973\n\0
15516 [<a name="p388" href="#p388">page 388</a>] (<a href="#Contents">Contents</a>)
15518 using the equivalent of the following algorithm.
15519 char *asctime(const struct tm *timeptr)
15521 static const char wday_name[7][3] = {
15522 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
15524 static const char mon_name[12][3] = {
15525 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
15526 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
15528 static char result[26];
15529 sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
15530 wday_name[timeptr->tm_wday],
15531 mon_name[timeptr->tm_mon],
15532 timeptr->tm_mday, timeptr->tm_hour,
15533 timeptr->tm_min, timeptr->tm_sec,
15534 1900 + timeptr->tm_year);
15537 3 If any of the fields of the broken-down time contain values that are outside their normal
15538 ranges,<sup><a href="#note310"><b>310)</b></a></sup> the behavior of the asctime function is undefined. Likewise, if the
15539 calculated year exceeds four digits or is less than the year 1000, the behavior is
15542 4 The asctime function returns a pointer to the string.
15543 <a name="7.26.3.2" href="#7.26.3.2"><b> 7.26.3.2 The ctime function</b></a>
15545 1 #include <a href="#7.26"><time.h></a>
15546 char *ctime(const time_t *timer);
15547 <b> Description</b>
15548 2 The ctime function converts the calendar time pointed to by timer to local time in the
15549 form of a string. It is equivalent to
15550 asctime(localtime(timer))
15554 <sup><a name="note310" href="#note310"><b>310)</b></a></sup> See <a href="#7.26.1">7.26.1</a>.
15556 [<a name="p389" href="#p389">page 389</a>] (<a href="#Contents">Contents</a>)
15559 3 The ctime function returns the pointer returned by the asctime function with that
15560 broken-down time as argument.
15561 Forward references: the localtime function (<a href="#7.26.3.4">7.26.3.4</a>).
15562 <a name="7.26.3.3" href="#7.26.3.3"><b> 7.26.3.3 The gmtime function</b></a>
15564 1 #include <a href="#7.26"><time.h></a>
15565 struct tm *gmtime(const time_t *timer);
15566 <b> Description</b>
15567 2 The gmtime function converts the calendar time pointed to by timer into a broken-
15568 down time, expressed as UTC.
15570 3 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
15571 specified time cannot be converted to UTC.
15572 <a name="7.26.3.4" href="#7.26.3.4"><b> 7.26.3.4 The localtime function</b></a>
15574 1 #include <a href="#7.26"><time.h></a>
15575 struct tm *localtime(const time_t *timer);
15576 <b> Description</b>
15577 2 The localtime function converts the calendar time pointed to by timer into a
15578 broken-down time, expressed as local time.
15580 3 The localtime function returns a pointer to the broken-down time, or a null pointer if
15581 the specified time cannot be converted to local time.
15582 <a name="7.26.3.5" href="#7.26.3.5"><b> 7.26.3.5 The strftime function</b></a>
15584 1 #include <a href="#7.26"><time.h></a>
15585 size_t strftime(char * restrict s,
15587 const char * restrict format,
15588 const struct tm * restrict timeptr);
15593 [<a name="p390" href="#p390">page 390</a>] (<a href="#Contents">Contents</a>)
15595 <b> Description</b>
15596 2 The strftime function places characters into the array pointed to by s as controlled by
15597 the string pointed to by format. The format shall be a multibyte character sequence,
15598 beginning and ending in its initial shift state. The format string consists of zero or
15599 more conversion specifiers and ordinary multibyte characters. A conversion specifier
15600 consists of a % character, possibly followed by an E or O modifier character (described
15601 below), followed by a character that determines the behavior of the conversion specifier.
15602 All ordinary multibyte characters (including the terminating null character) are copied
15603 unchanged into the array. If copying takes place between objects that overlap, the
15604 behavior is undefined. No more than maxsize characters are placed into the array.
15605 3 Each conversion specifier is replaced by appropriate characters as described in the
15606 following list. The appropriate characters are determined using the LC_TIME category
15607 of the current locale and by the values of zero or more members of the broken-down time
15608 structure pointed to by timeptr, as specified in brackets in the description. If any of
15609 the specified values is outside the normal range, the characters stored are unspecified.
15610 %a is replaced by the locale's abbreviated weekday name. [tm_wday]
15611 %A is replaced by the locale's full weekday name. [tm_wday]
15612 %b is replaced by the locale's abbreviated month name. [tm_mon]
15613 %B is replaced by the locale's full month name. [tm_mon]
15614 %c is replaced by the locale's appropriate date and time representation. [all specified
15615 in <a href="#7.26.1">7.26.1</a>]
15616 %C is replaced by the year divided by 100 and truncated to an integer, as a decimal
15617 number (00-99). [tm_year]
15618 %d is replaced by the day of the month as a decimal number (01-31). [tm_mday]
15619 %D is equivalent to ''%m/%d/%y''. [tm_mon, tm_mday, tm_year]
15620 %e is replaced by the day of the month as a decimal number (1-31); a single digit is
15621 preceded by a space. [tm_mday]
15622 %F is equivalent to ''%Y-%m-%d'' (the ISO 8601 date format). [tm_year, tm_mon,
15624 %g is replaced by the last 2 digits of the week-based year (see below) as a decimal
15625 number (00-99). [tm_year, tm_wday, tm_yday]
15626 %G is replaced by the week-based year (see below) as a decimal number (e.g., 1997).
15627 [tm_year, tm_wday, tm_yday]
15628 %h is equivalent to ''%b''. [tm_mon]
15629 %H is replaced by the hour (24-hour clock) as a decimal number (00-23). [tm_hour]
15630 %I is replaced by the hour (12-hour clock) as a decimal number (01-12). [tm_hour]
15631 %j is replaced by the day of the year as a decimal number (001-366). [tm_yday]
15632 %m is replaced by the month as a decimal number (01-12). [tm_mon]
15633 %M is replaced by the minute as a decimal number (00-59). [tm_min]
15634 %n is replaced by a new-line character.
15636 [<a name="p391" href="#p391">page 391</a>] (<a href="#Contents">Contents</a>)
15638 %p is replaced by the locale's equivalent of the AM/PM designations associated with a
15639 12-hour clock. [tm_hour]
15640 %r is replaced by the locale's 12-hour clock time. [tm_hour, tm_min, tm_sec]
15641 %R is equivalent to ''%H:%M''. [tm_hour, tm_min]
15642 %S is replaced by the second as a decimal number (00-60). [tm_sec]
15643 %t is replaced by a horizontal-tab character.
15644 %T is equivalent to ''%H:%M:%S'' (the ISO 8601 time format). [tm_hour, tm_min,
15646 %u is replaced by the ISO 8601 weekday as a decimal number (1-7), where Monday
15648 %U is replaced by the week number of the year (the first Sunday as the first day of week
15649 <sup><a name="note1" href="#note1"><b>1)</b></a></sup> as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
15650 %V is replaced by the ISO 8601 week number (see below) as a decimal number
15651 (01-53). [tm_year, tm_wday, tm_yday]
15652 %w is replaced by the weekday as a decimal number (0-6), where Sunday is 0.
15654 %W is replaced by the week number of the year (the first Monday as the first day of
15655 week 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
15656 %x is replaced by the locale's appropriate date representation. [all specified in <a href="#7.26.1">7.26.1</a>]
15657 %X is replaced by the locale's appropriate time representation. [all specified in <a href="#7.26.1">7.26.1</a>]
15658 %y is replaced by the last 2 digits of the year as a decimal number (00-99).
15660 %Y is replaced by the year as a decimal number (e.g., 1997). [tm_year]
15661 %z is replaced by the offset from UTC in the ISO 8601 format ''-0430'' (meaning 4
15662 hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
15663 zone is determinable. [tm_isdst]
15664 %Z is replaced by the locale's time zone name or abbreviation, or by no characters if no
15665 time zone is determinable. [tm_isdst]
15666 %% is replaced by %.
15667 4 Some conversion specifiers can be modified by the inclusion of an E or O modifier
15668 character to indicate an alternative format or specification. If the alternative format or
15669 specification does not exist for the current locale, the modifier is ignored.
15670 %Ec is replaced by the locale's alternative date and time representation.
15671 %EC is replaced by the name of the base year (period) in the locale's alternative
15673 %Ex is replaced by the locale's alternative date representation.
15674 %EX is replaced by the locale's alternative time representation.
15675 %Ey is replaced by the offset from %EC (year only) in the locale's alternative
15677 %EY is replaced by the locale's full alternative year representation.
15679 [<a name="p392" href="#p392">page 392</a>] (<a href="#Contents">Contents</a>)
15681 %Od is replaced by the day of the month, using the locale's alternative numeric symbols
15682 (filled as needed with leading zeros, or with leading spaces if there is no alternative
15684 %Oe is replaced by the day of the month, using the locale's alternative numeric symbols
15685 (filled as needed with leading spaces).
15686 %OH is replaced by the hour (24-hour clock), using the locale's alternative numeric
15688 %OI is replaced by the hour (12-hour clock), using the locale's alternative numeric
15690 %Om is replaced by the month, using the locale's alternative numeric symbols.
15691 %OM is replaced by the minutes, using the locale's alternative numeric symbols.
15692 %OS is replaced by the seconds, using the locale's alternative numeric symbols.
15693 %Ou is replaced by the ISO 8601 weekday as a number in the locale's alternative
15694 representation, where Monday is 1.
15695 %OU is replaced by the week number, using the locale's alternative numeric symbols.
15696 %OV is replaced by the ISO 8601 week number, using the locale's alternative numeric
15698 %Ow is replaced by the weekday as a number, using the locale's alternative numeric
15700 %OW is replaced by the week number of the year, using the locale's alternative numeric
15702 %Oy is replaced by the last 2 digits of the year, using the locale's alternative numeric
15704 5 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system,
15705 weeks begin on a Monday and week 1 of the year is the week that includes January 4th,
15706 which is also the week that includes the first Thursday of the year, and is also the first
15707 week that contains at least four days in the year. If the first Monday of January is the
15708 2nd, 3rd, or 4th, the preceding days are part of the last week of the preceding year; thus,
15709 for Saturday 2nd January 1999, %G is replaced by 1998 and %V is replaced by 53. If
15710 December 29th, 30th, or 31st is a Monday, it and any following days are part of week 1 of
15711 the following year. Thus, for Tuesday 30th December 1997, %G is replaced by 1998 and
15712 %V is replaced by 01.
15713 6 If a conversion specifier is not one of the above, the behavior is undefined.
15714 7 In the "C" locale, the E and O modifiers are ignored and the replacement strings for the
15715 following specifiers are:
15716 %a the first three characters of %A.
15717 %A one of ''Sunday'', ''Monday'', ... , ''Saturday''.
15718 %b the first three characters of %B.
15719 %B one of ''January'', ''February'', ... , ''December''.
15720 %c equivalent to ''%a %b %e %T %Y''.
15721 [<a name="p393" href="#p393">page 393</a>] (<a href="#Contents">Contents</a>)
15723 %p one of ''AM'' or ''PM''.
15724 %r equivalent to ''%I:%M:%S %p''.
15725 %x equivalent to ''%m/%d/%y''.
15726 %X equivalent to %T.
15727 %Z implementation-defined.
15729 8 If the total number of resulting characters including the terminating null character is not
15730 more than maxsize, the strftime function returns the number of characters placed
15731 into the array pointed to by s not including the terminating null character. Otherwise,
15732 zero is returned and the contents of the array are indeterminate.
15737 [<a name="p394" href="#p394">page 394</a>] (<a href="#Contents">Contents</a>)
15739 <a name="7.27" href="#7.27"><b> 7.27 Unicode utilities <uchar.h></b></a>
15740 1 The header <a href="#7.27"><uchar.h></a> declares types and functions for manipulating Unicode
15742 2 The types declared are mbstate_t (described in <a href="#7.29.1">7.29.1</a>) and size_t (described in
15743 <a name="7.19);" href="#7.19);"><b> 7.19);</b></a>
15745 which is an unsigned integer type used for 16-bit characters and is the same type as
15746 uint_least16_t (described in <a href="#7.20.1.2">7.20.1.2</a>); and
15748 which is an unsigned integer type used for 32-bit characters and is the same type as
15749 uint_least32_t (also described in <a href="#7.20.1.2">7.20.1.2</a>).
15750 <a name="7.27.1" href="#7.27.1"><b> 7.27.1 Restartable multibyte/wide character conversion functions</b></a>
15751 1 These functions have a parameter, ps, of type pointer to mbstate_t that points to an
15752 object that can completely describe the current conversion state of the associated
15753 multibyte character sequence, which the functions alter as necessary. If ps is a null
15754 pointer, each function uses its own internal mbstate_t object instead, which is
15755 initialized at program startup to the initial conversion state; the functions are not required
15756 to avoid data races in this case. The implementation behaves as if no library function
15757 calls these functions with a null pointer for ps.
15758 <a name="7.27.1.1" href="#7.27.1.1"><b> 7.27.1.1 The mbrtoc16 function</b></a>
15760 1 #include <a href="#7.27"><uchar.h></a>
15761 size_t mbrtoc16(char16_t * restrict pc16,
15762 const char * restrict s, size_t n,
15763 mbstate_t * restrict ps);
15764 <b> Description</b>
15765 2 If s is a null pointer, the mbrtoc16 function is equivalent to the call:
15766 mbrtoc16(NULL, "", 1, ps)
15767 In this case, the values of the parameters pc16 and n are ignored.
15768 3 If s is not a null pointer, the mbrtoc16 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 pc16 is not a null pointer, stores the value of
15773 the first (or only) such character in the object pointed to by pc16. Subsequent calls will
15774 [<a name="p395" href="#p395">page 395</a>] (<a href="#Contents">Contents</a>)
15776 store successive wide characters without consuming any additional input until all the
15777 characters have been stored. If the corresponding wide character is the null wide
15778 character, the resulting state described is the initial conversion state.
15780 4 The mbrtoc16 function returns the first of the following that applies (given the current
15782 0 if the next n or fewer bytes complete the multibyte character that
15783 corresponds to the null wide character (which is the value stored).
15784 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
15785 character (which is the value stored); the value returned is the number
15786 of bytes that complete the multibyte character.
15787 (size_t)(-3) if the next character resulting from a previous call has been stored (no
15788 bytes from the input have been consumed by this call).
15789 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
15790 multibyte character, and all n bytes have been processed (no value is
15791 stored).<sup><a href="#note311"><b>311)</b></a></sup>
15792 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
15793 do not contribute to a complete and valid multibyte character (no
15794 value is stored); the value of the macro EILSEQ is stored in errno,
15795 and the conversion state is unspecified.
15796 <a name="7.27.1.2" href="#7.27.1.2"><b> 7.27.1.2 The c16rtomb function</b></a>
15798 1 #include <a href="#7.27"><uchar.h></a>
15799 size_t c16rtomb(char * restrict s, char16_t c16,
15800 mbstate_t * restrict ps);
15801 <b> Description</b>
15802 2 If s is a null pointer, the c16rtomb function is equivalent to the call
15803 c16rtomb(buf, L'\0', ps)
15804 where buf is an internal buffer.
15805 3 If s is not a null pointer, the c16rtomb function determines the number of bytes needed
15806 to represent the multibyte character that corresponds to the wide character given by c16
15807 (including any shift sequences), and stores the multibyte character representation in the
15810 <sup><a name="note311" href="#note311"><b>311)</b></a></sup> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
15811 sequence of redundant shift sequences (for implementations with state-dependent encodings).
15813 [<a name="p396" href="#p396">page 396</a>] (<a href="#Contents">Contents</a>)
15815 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
15816 c16 is a null wide character, a null byte is stored, preceded by any shift sequence needed
15817 to restore the initial shift state; the resulting state described is the initial conversion state.
15819 4 The c16rtomb function returns the number of bytes stored in the array object (including
15820 any shift sequences). When c16 is not a valid wide character, an encoding error occurs:
15821 the function stores the value of the macro EILSEQ in errno and returns
15822 (size_t)(-1); the conversion state is unspecified.
15823 <a name="7.27.1.3" href="#7.27.1.3"><b> 7.27.1.3 The mbrtoc32 function</b></a>
15825 1 #include <a href="#7.27"><uchar.h></a>
15826 size_t mbrtoc32(char32_t * restrict pc32,
15827 const char * restrict s, size_t n,
15828 mbstate_t * restrict ps);
15829 <b> Description</b>
15830 2 If s is a null pointer, the mbrtoc32 function is equivalent to the call:
15831 mbrtoc32(NULL, "", 1, ps)
15832 In this case, the values of the parameters pc32 and n are ignored.
15833 3 If s is not a null pointer, the mbrtoc32 function inspects at most n bytes beginning with
15834 the byte pointed to by s to determine the number of bytes needed to complete the next
15835 multibyte character (including any shift sequences). If the function determines that the
15836 next multibyte character is complete and valid, it determines the values of the
15837 corresponding wide characters and then, if pc32 is not a null pointer, stores the value of
15838 the first (or only) such character in the object pointed to by pc32. Subsequent calls will
15839 store successive wide characters without consuming any additional input until all the
15840 characters have been stored. If the corresponding wide character is the null wide
15841 character, the resulting state described is the initial conversion state.
15843 4 The mbrtoc32 function returns the first of the following that applies (given the current
15845 0 if the next n or fewer bytes complete the multibyte character that
15846 corresponds to the null wide character (which is the value stored).
15847 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
15848 character (which is the value stored); the value returned is the number
15849 of bytes that complete the multibyte character.
15852 [<a name="p397" href="#p397">page 397</a>] (<a href="#Contents">Contents</a>)
15854 (size_t)(-3) if the next character resulting from a previous call has been stored (no
15855 bytes from the input have been consumed by this call).
15856 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
15857 multibyte character, and all n bytes have been processed (no value is
15858 stored).<sup><a href="#note312"><b>312)</b></a></sup>
15859 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
15860 do not contribute to a complete and valid multibyte character (no
15861 value is stored); the value of the macro EILSEQ is stored in errno,
15862 and the conversion state is unspecified.
15863 <a name="7.27.1.4" href="#7.27.1.4"><b> 7.27.1.4 The c32rtomb function</b></a>
15865 1 #include <a href="#7.27"><uchar.h></a>
15866 size_t c32rtomb(char * restrict s, char32_t c32,
15867 mbstate_t * restrict ps);
15868 <b> Description</b>
15869 2 If s is a null pointer, the c32rtomb function is equivalent to the call
15870 c32rtomb(buf, L'\0', ps)
15871 where buf is an internal buffer.
15872 3 If s is not a null pointer, the c32rtomb function determines the number of bytes needed
15873 to represent the multibyte character that corresponds to the wide character given by c32
15874 (including any shift sequences), and stores the multibyte character representation in the
15875 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
15876 c32 is a null wide character, a null byte is stored, preceded by any shift sequence needed
15877 to restore the initial shift state; the resulting state described is the initial conversion state.
15879 4 The c32rtomb function returns the number of bytes stored in the array object (including
15880 any shift sequences). When c32 is not a valid wide character, an encoding error occurs:
15881 the function stores the value of the macro EILSEQ in errno and returns
15882 (size_t)(-1); the conversion state is unspecified.
15887 <sup><a name="note312" href="#note312"><b>312)</b></a></sup> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
15888 sequence of redundant shift sequences (for implementations with state-dependent encodings).
15890 [<a name="p398" href="#p398">page 398</a>] (<a href="#Contents">Contents</a>)
15892 <a name="7.28" href="#7.28"><b> 7.28 Extended multibyte and wide character utilities <wchar.h></b></a>
15893 <a name="7.28.1" href="#7.28.1"><b> 7.28.1 Introduction</b></a>
15894 1 The header <a href="#7.28"><wchar.h></a> defines four macros, and declares four data types, one tag, and
15895 many functions.<sup><a href="#note313"><b>313)</b></a></sup>
15896 2 The types declared are wchar_t and size_t (both described in <a href="#7.19">7.19</a>);
15898 which is a complete object type other than an array type that can hold the conversion state
15899 information necessary to convert between sequences of multibyte characters and wide
15902 which is an integer type unchanged by default argument promotions that can hold any
15903 value corresponding to members of the extended character set, as well as at least one
15904 value that does not correspond to any member of the extended character set (see WEOF
15905 below);<sup><a href="#note314"><b>314)</b></a></sup> and
15907 which is declared as an incomplete structure type (the contents are described in <a href="#7.26.1">7.26.1</a>).
15908 3 The macros defined are NULL (described in <a href="#7.19">7.19</a>); WCHAR_MIN and WCHAR_MAX
15909 (described in <a href="#7.20.3">7.20.3</a>); and
15911 which expands to a constant expression of type wint_t whose value does not
15912 correspond to any member of the extended character set.<sup><a href="#note315"><b>315)</b></a></sup> It is accepted (and returned)
15913 by several functions in this subclause to indicate end-of-file, that is, no more input from a
15914 stream. It is also used as a wide character value that does not correspond to any member
15915 of the extended character set.
15916 4 The functions declared are grouped as follows:
15917 -- Functions that perform input and output of wide characters, or multibyte characters,
15919 -- Functions that provide wide string numeric conversion;
15920 -- Functions that perform general wide string manipulation;
15923 <sup><a name="note313" href="#note313"><b>313)</b></a></sup> See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
15924 <sup><a name="note314" href="#note314"><b>314)</b></a></sup> wchar_t and wint_t can be the same integer type.
15925 <sup><a name="note315" href="#note315"><b>315)</b></a></sup> The value of the macro WEOF may differ from that of EOF and need not be negative.
15927 [<a name="p399" href="#p399">page 399</a>] (<a href="#Contents">Contents</a>)
15929 -- Functions for wide string date and time conversion; and
15930 -- Functions that provide extended capabilities for conversion between multibyte and
15931 wide character sequences.
15932 5 Unless explicitly stated otherwise, if the execution of a function described in this
15933 subclause causes copying to take place between objects that overlap, the behavior is
15935 <a name="7.28.2" href="#7.28.2"><b> 7.28.2 Formatted wide character input/output functions</b></a>
15936 1 The formatted wide character input/output functions shall behave as if there is a sequence
15937 point after the actions associated with each specifier.<sup><a href="#note316"><b>316)</b></a></sup>
15938 <a name="7.28.2.1" href="#7.28.2.1"><b> 7.28.2.1 The fwprintf function</b></a>
15940 1 #include <a href="#7.21"><stdio.h></a>
15941 #include <a href="#7.28"><wchar.h></a>
15942 int fwprintf(FILE * restrict stream,
15943 const wchar_t * restrict format, ...);
15944 <b> Description</b>
15945 2 The fwprintf function writes output to the stream pointed to by stream, under
15946 control of the wide string pointed to by format that specifies how subsequent arguments
15947 are converted for output. If there are insufficient arguments for the format, the behavior
15948 is undefined. If the format is exhausted while arguments remain, the excess arguments
15949 are evaluated (as always) but are otherwise ignored. The fwprintf function returns
15950 when the end of the format string is encountered.
15951 3 The format is composed of zero or more directives: ordinary wide characters (not %),
15952 which are copied unchanged to the output stream; and conversion specifications, each of
15953 which results in fetching zero or more subsequent arguments, converting them, if
15954 applicable, according to the corresponding conversion specifier, and then writing the
15955 result to the output stream.
15956 4 Each conversion specification is introduced by the wide character %. After the %, the
15957 following appear in sequence:
15958 -- Zero or more flags (in any order) that modify the meaning of the conversion
15960 -- An optional minimum field width. If the converted value has fewer wide characters
15961 than the field width, it is padded with spaces (by default) on the left (or right, if the
15964 <sup><a name="note316" href="#note316"><b>316)</b></a></sup> The fwprintf functions perform writes to memory for the %n specifier.
15966 [<a name="p400" href="#p400">page 400</a>] (<a href="#Contents">Contents</a>)
15968 left adjustment flag, described later, has been given) to the field width. The field
15969 width takes the form of an asterisk * (described later) or a nonnegative decimal
15970 integer.<sup><a href="#note317"><b>317)</b></a></sup>
15971 -- An optional precision that gives the minimum number of digits to appear for the d, i,
15972 o, u, x, and X conversions, the number of digits to appear after the decimal-point
15973 wide character for a, A, e, E, f, and F conversions, the maximum number of
15974 significant digits for the g and G conversions, or the maximum number of wide
15975 characters to be written for s conversions. The precision takes the form of a period
15976 (.) followed either by an asterisk * (described later) or by an optional decimal
15977 integer; if only the period is specified, the precision is taken as zero. If a precision
15978 appears with any other conversion specifier, the behavior is undefined.
15979 -- An optional length modifier that specifies the size of the argument.
15980 -- A conversion specifier wide character that specifies the type of conversion to be
15982 5 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
15983 this case, an int argument supplies the field width or precision. The arguments
15984 specifying field width, or precision, or both, shall appear (in that order) before the
15985 argument (if any) to be converted. A negative field width argument is taken as a - flag
15986 followed by a positive field width. A negative precision argument is taken as if the
15987 precision were omitted.
15988 6 The flag wide characters and their meanings are:
15989 - The result of the conversion is left-justified within the field. (It is right-justified if
15990 this flag is not specified.)
15991 + The result of a signed conversion always begins with a plus or minus sign. (It
15992 begins with a sign only when a negative value is converted if this flag is not
15993 specified.)<sup><a href="#note318"><b>318)</b></a></sup>
15994 space If the first wide character of a signed conversion is not a sign, or if a signed
15995 conversion results in no wide characters, a space is prefixed to the result. If the
15996 space and + flags both appear, the space flag is ignored.
15997 # The result is converted to an ''alternative form''. For o conversion, it increases
15998 the precision, if and only if necessary, to force the first digit of the result to be a
15999 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
16000 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
16003 <sup><a name="note317" href="#note317"><b>317)</b></a></sup> Note that 0 is taken as a flag, not as the beginning of a field width.
16004 <sup><a name="note318" href="#note318"><b>318)</b></a></sup> The results of all floating conversions of a negative zero, and of negative values that round to zero,
16005 include a minus sign.
16007 [<a name="p401" href="#p401">page 401</a>] (<a href="#Contents">Contents</a>)
16009 and G conversions, the result of converting a floating-point number always
16010 contains a decimal-point wide character, even if no digits follow it. (Normally, a
16011 decimal-point wide character appears in the result of these conversions only if a
16012 digit follows it.) For g and G conversions, trailing zeros are not removed from the
16013 result. For other conversions, the behavior is undefined.
16014 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
16015 (following any indication of sign or base) are used to pad to the field width rather
16016 than performing space padding, except when converting an infinity or NaN. If the
16017 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
16018 conversions, if a precision is specified, the 0 flag is ignored. For other
16019 conversions, the behavior is undefined.
16020 7 The length modifiers and their meanings are:
16021 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16022 signed char or unsigned char argument (the argument will have
16023 been promoted according to the integer promotions, but its value shall be
16024 converted to signed char or unsigned char before printing); or that
16025 a following n conversion specifier applies to a pointer to a signed char
16027 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16028 short int or unsigned short int argument (the argument will
16029 have been promoted according to the integer promotions, but its value shall
16030 be converted to short int or unsigned short int before printing);
16031 or that a following n conversion specifier applies to a pointer to a short
16033 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16034 long int or unsigned long int argument; that a following n
16035 conversion specifier applies to a pointer to a long int argument; that a
16036 following c conversion specifier applies to a wint_t argument; that a
16037 following s conversion specifier applies to a pointer to a wchar_t
16038 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
16040 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16041 long long int or unsigned long long int argument; or that a
16042 following n conversion specifier applies to a pointer to a long long int
16044 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
16045 an intmax_t or uintmax_t argument; or that a following n conversion
16046 specifier applies to a pointer to an intmax_t argument.
16048 [<a name="p402" href="#p402">page 402</a>] (<a href="#Contents">Contents</a>)
16050 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16051 size_t or the corresponding signed integer type argument; or that a
16052 following n conversion specifier applies to a pointer to a signed integer type
16053 corresponding to size_t argument.
16054 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16055 ptrdiff_t or the corresponding unsigned integer type argument; or that a
16056 following n conversion specifier applies to a pointer to a ptrdiff_t
16058 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
16059 applies to a long double argument.
16060 If a length modifier appears with any conversion specifier other than as specified above,
16061 the behavior is undefined.
16062 8 The conversion specifiers and their meanings are:
16063 d,i The int argument is converted to signed decimal in the style [-]dddd. The
16064 precision specifies the minimum number of digits to appear; if the value
16065 being converted can be represented in fewer digits, it is expanded with
16066 leading zeros. The default precision is 1. The result of converting a zero
16067 value with a precision of zero is no wide characters.
16068 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
16069 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
16070 letters abcdef are used for x conversion and the letters ABCDEF for X
16071 conversion. The precision specifies the minimum number of digits to appear;
16072 if the value being converted can be represented in fewer digits, it is expanded
16073 with leading zeros. The default precision is 1. The result of converting a
16074 zero value with a precision of zero is no wide characters.
16075 f,F A double argument representing a floating-point number is converted to
16076 decimal notation in the style [-]ddd.ddd, where the number of digits after
16077 the decimal-point wide character is equal to the precision specification. If the
16078 precision is missing, it is taken as 6; if the precision is zero and the # flag is
16079 not specified, no decimal-point wide character appears. If a decimal-point
16080 wide character appears, at least one digit appears before it. The value is
16081 rounded to the appropriate number of digits.
16082 A double argument representing an infinity is converted in one of the styles
16083 [-]inf or [-]infinity -- which style is implementation-defined. A
16084 double argument representing a NaN is converted in one of the styles
16085 [-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
16086 any n-wchar-sequence, is implementation-defined. The F conversion
16087 specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
16089 [<a name="p403" href="#p403">page 403</a>] (<a href="#Contents">Contents</a>)
16091 nan, respectively.<sup><a href="#note319"><b>319)</b></a></sup>
16092 e,E A double argument representing a floating-point number is converted in the
16093 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
16094 argument is nonzero) before the decimal-point wide character and the number
16095 of digits after it is equal to the precision; if the precision is missing, it is taken
16096 as 6; if the precision is zero and the # flag is not specified, no decimal-point
16097 wide character appears. The value is rounded to the appropriate number of
16098 digits. The E conversion specifier produces a number with E instead of e
16099 introducing the exponent. The exponent always contains at least two digits,
16100 and only as many more digits as necessary to represent the exponent. If the
16101 value is zero, the exponent is zero.
16102 A double argument representing an infinity or NaN is converted in the style
16103 of an f or F conversion specifier.
16104 g,G A double argument representing a floating-point number is converted in
16105 style f or e (or in style F or E in the case of a G conversion specifier),
16106 depending on the value converted and the precision. Let P equal the
16107 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
16108 Then, if a conversion with style E would have an exponent of X:
16109 -- if P > X >= -4, the conversion is with style f (or F) and precision
16111 -- otherwise, the conversion is with style e (or E) and precision P - 1.
16112 Finally, unless the # flag is used, any trailing zeros are removed from the
16113 fractional portion of the result and the decimal-point wide character is
16114 removed if there is no fractional portion remaining.
16115 A double argument representing an infinity or NaN is converted in the style
16116 of an f or F conversion specifier.
16117 a,A A double argument representing a floating-point number is converted in the
16118 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
16119 nonzero if the argument is a normalized floating-point number and is
16120 otherwise unspecified) before the decimal-point wide character<sup><a href="#note320"><b>320)</b></a></sup> and the
16121 number of hexadecimal digits after it is equal to the precision; if the precision
16122 is missing and FLT_RADIX is a power of 2, then the precision is sufficient
16125 <sup><a name="note319" href="#note319"><b>319)</b></a></sup> When applied to infinite and NaN values, the -, +, and space flag wide characters have their usual
16126 meaning; the # and 0 flag wide characters have no effect.
16127 <sup><a name="note320" href="#note320"><b>320)</b></a></sup> Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide
16128 character so that subsequent digits align to nibble (4-bit) boundaries.
16130 [<a name="p404" href="#p404">page 404</a>] (<a href="#Contents">Contents</a>)
16132 for an exact representation of the value; if the precision is missing and
16133 FLT_RADIX is not a power of 2, then the precision is sufficient to
16134 distinguish<sup><a href="#note321"><b>321)</b></a></sup> values of type double, except that trailing zeros may be
16135 omitted; if the precision is zero and the # flag is not specified, no decimal-
16136 point wide character appears. The letters abcdef are used for a conversion
16137 and the letters ABCDEF for A conversion. The A conversion specifier
16138 produces a number with X and P instead of x and p. The exponent always
16139 contains at least one digit, and only as many more digits as necessary to
16140 represent the decimal exponent of 2. If the value is zero, the exponent is
16142 A double argument representing an infinity or NaN is converted in the style
16143 of an f or F conversion specifier.
16144 c If no l length modifier is present, the int argument is converted to a wide
16145 character as if by calling btowc and the resulting wide character is written.
16146 If an l length modifier is present, the wint_t argument is converted to
16147 wchar_t and written.
16148 s If no l length modifier is present, the argument shall be a pointer to the initial
16149 element of a character array containing a multibyte character sequence
16150 beginning in the initial shift state. Characters from the array are converted as
16151 if by repeated calls to the mbrtowc function, with the conversion state
16152 described by an mbstate_t object initialized to zero before the first
16153 multibyte character is converted, and written up to (but not including) the
16154 terminating null wide character. If the precision is specified, no more than
16155 that many wide characters are written. If the precision is not specified or is
16156 greater than the size of the converted array, the converted array shall contain a
16157 null wide character.
16158 If an l length modifier is present, the argument shall be a pointer to the initial
16159 element of an array of wchar_t type. Wide characters from the array are
16160 written up to (but not including) a terminating null wide character. If the
16161 precision is specified, no more than that many wide characters are written. If
16162 the precision is not specified or is greater than the size of the array, the array
16163 shall contain a null wide character.
16164 p The argument shall be a pointer to void. The value of the pointer is
16165 converted to a sequence of printing wide characters, in an implementation-
16167 <sup><a name="note321" href="#note321"><b>321)</b></a></sup> The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
16168 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
16169 might suffice depending on the implementation's scheme for determining the digit to the left of the
16170 decimal-point wide character.
16172 [<a name="p405" href="#p405">page 405</a>] (<a href="#Contents">Contents</a>)
16175 n The argument shall be a pointer to signed integer into which is written the
16176 number of wide characters written to the output stream so far by this call to
16177 fwprintf. No argument is converted, but one is consumed. If the
16178 conversion specification includes any flags, a field width, or a precision, the
16179 behavior is undefined.
16180 % A % wide character is written. No argument is converted. The complete
16181 conversion specification shall be %%.
16182 9 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note322"><b>322)</b></a></sup> If any argument is
16183 not the correct type for the corresponding conversion specification, the behavior is
16185 10 In no case does a nonexistent or small field width cause truncation of a field; if the result
16186 of a conversion is wider than the field width, the field is expanded to contain the
16188 11 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
16189 to a hexadecimal floating number with the given precision.
16190 Recommended practice
16191 12 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
16192 representable in the given precision, the result should be one of the two adjacent numbers
16193 in hexadecimal floating style with the given precision, with the extra stipulation that the
16194 error should have a correct sign for the current rounding direction.
16195 13 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
16196 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note323"><b>323)</b></a></sup> If the number of
16197 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
16198 representable with DECIMAL_DIG digits, then the result should be an exact
16199 representation with trailing zeros. Otherwise, the source value is bounded by two
16200 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
16201 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
16202 the error should have a correct sign for the current rounding direction.
16204 14 The fwprintf function returns the number of wide characters transmitted, or a negative
16205 value if an output or encoding error occurred.
16207 <sup><a name="note322" href="#note322"><b>322)</b></a></sup> See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
16208 <sup><a name="note323" href="#note323"><b>323)</b></a></sup> For binary-to-decimal conversion, the result format's values are the numbers representable with the
16209 given format specifier. The number of significant digits is determined by the format specifier, and in
16210 the case of fixed-point conversion by the source value as well.
16212 [<a name="p406" href="#p406">page 406</a>] (<a href="#Contents">Contents</a>)
16214 Environmental limits
16215 15 The number of wide characters that can be produced by any single conversion shall be at
16217 16 EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
16219 #include <a href="#7.12"><math.h></a>
16220 #include <a href="#7.21"><stdio.h></a>
16221 #include <a href="#7.28"><wchar.h></a>
16223 wchar_t *weekday, *month; // pointers to wide strings
16224 int day, hour, min;
16225 fwprintf(stdout, L"%ls, %ls %d, %.2d:%.2d\n",
16226 weekday, month, day, hour, min);
16227 fwprintf(stdout, L"pi = %.5f\n", 4 * atan(1.0));
16229 Forward references: the btowc function (<a href="#7.28.6.1.1">7.28.6.1.1</a>), the mbrtowc function
16230 (<a href="#7.28.6.3.2">7.28.6.3.2</a>).
16231 <a name="7.28.2.2" href="#7.28.2.2"><b> 7.28.2.2 The fwscanf function</b></a>
16233 1 #include <a href="#7.21"><stdio.h></a>
16234 #include <a href="#7.28"><wchar.h></a>
16235 int fwscanf(FILE * restrict stream,
16236 const wchar_t * restrict format, ...);
16237 <b> Description</b>
16238 2 The fwscanf function reads input from the stream pointed to by stream, under
16239 control of the wide string pointed to by format that specifies the admissible input
16240 sequences and how they are to be converted for assignment, using subsequent arguments
16241 as pointers to the objects to receive the converted input. If there are insufficient
16242 arguments for the format, the behavior is undefined. If the format is exhausted while
16243 arguments remain, the excess arguments are evaluated (as always) but are otherwise
16245 3 The format is composed of zero or more directives: one or more white-space wide
16246 characters, an ordinary wide character (neither % nor a white-space wide character), or a
16247 conversion specification. Each conversion specification is introduced by the wide
16248 character %. After the %, the following appear in sequence:
16249 -- An optional assignment-suppressing wide character *.
16250 -- An optional decimal integer greater than zero that specifies the maximum field width
16251 (in wide characters).
16255 [<a name="p407" href="#p407">page 407</a>] (<a href="#Contents">Contents</a>)
16257 -- An optional length modifier that specifies the size of the receiving object.
16258 -- A conversion specifier wide character that specifies the type of conversion to be
16260 4 The fwscanf function executes each directive of the format in turn. When all directives
16261 have been executed, or if a directive fails (as detailed below), the function returns.
16262 Failures are described as input failures (due to the occurrence of an encoding error or the
16263 unavailability of input characters), or matching failures (due to inappropriate input).
16264 5 A directive composed of white-space wide character(s) is executed by reading input up to
16265 the first non-white-space wide character (which remains unread), or until no more wide
16266 characters can be read.
16267 6 A directive that is an ordinary wide character is executed by reading the next wide
16268 character of the stream. If that wide character differs from the directive, the directive
16269 fails and the differing and subsequent wide characters remain unread. Similarly, if end-
16270 of-file, an encoding error, or a read error prevents a wide character from being read, the
16272 7 A directive that is a conversion specification defines a set of matching input sequences, as
16273 described below for each specifier. A conversion specification is executed in the
16275 8 Input white-space wide characters (as specified by the iswspace function) are skipped,
16276 unless the specification includes a [, c, or n specifier.<sup><a href="#note324"><b>324)</b></a></sup>
16277 9 An input item is read from the stream, unless the specification includes an n specifier. An
16278 input item is defined as the longest sequence of input wide characters which does not
16279 exceed any specified field width and which is, or is a prefix of, a matching input
16280 sequence.<sup><a href="#note325"><b>325)</b></a></sup> The first wide character, if any, after the input item remains unread. If the
16281 length of the input item is zero, the execution of the directive fails; this condition is a
16282 matching failure unless end-of-file, an encoding error, or a read error prevented input
16283 from the stream, in which case it is an input failure.
16284 10 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
16285 count of input wide characters) is converted to a type appropriate to the conversion
16286 specifier. If the input item is not a matching sequence, the execution of the directive fails:
16287 this condition is a matching failure. Unless assignment suppression was indicated by a *,
16288 the result of the conversion is placed in the object pointed to by the first argument
16289 following the format argument that has not already received a conversion result. If this
16292 <sup><a name="note324" href="#note324"><b>324)</b></a></sup> These white-space wide characters are not counted against a specified field width.
16293 <sup><a name="note325" href="#note325"><b>325)</b></a></sup> fwscanf pushes back at most one input wide character onto the input stream. Therefore, some
16294 sequences that are acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
16296 [<a name="p408" href="#p408">page 408</a>] (<a href="#Contents">Contents</a>)
16298 object does not have an appropriate type, or if the result of the conversion cannot be
16299 represented in the object, the behavior is undefined.
16300 11 The length modifiers and their meanings are:
16301 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16302 to an argument with type pointer to signed char or unsigned char.
16303 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16304 to an argument with type pointer to short int or unsigned short
16306 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16307 to an argument with type pointer to long int or unsigned long
16308 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
16309 an argument with type pointer to double; or that a following c, s, or [
16310 conversion specifier applies to an argument with type pointer to wchar_t.
16311 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16312 to an argument with type pointer to long long int or unsigned
16314 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16315 to an argument with type pointer to intmax_t or uintmax_t.
16316 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16317 to an argument with type pointer to size_t or the corresponding signed
16319 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
16320 to an argument with type pointer to ptrdiff_t or the corresponding
16321 unsigned integer type.
16322 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
16323 applies to an argument with type pointer to long double.
16324 If a length modifier appears with any conversion specifier other than as specified above,
16325 the behavior is undefined.
16326 12 The conversion specifiers and their meanings are:
16327 d Matches an optionally signed decimal integer, whose format is the same as
16328 expected for the subject sequence of the wcstol function with the value 10
16329 for the base argument. The corresponding argument shall be a pointer to
16331 i Matches an optionally signed integer, whose format is the same as expected
16332 for the subject sequence of the wcstol function with the value 0 for the
16333 base argument. The corresponding argument shall be a pointer to signed
16335 [<a name="p409" href="#p409">page 409</a>] (<a href="#Contents">Contents</a>)
16338 o Matches an optionally signed octal integer, whose format is the same as
16339 expected for the subject sequence of the wcstoul function with the value 8
16340 for the base argument. The corresponding argument shall be a pointer to
16342 u Matches an optionally signed decimal integer, whose format is the same as
16343 expected for the subject sequence of the wcstoul function with the value 10
16344 for the base argument. The corresponding argument shall be a pointer to
16346 x Matches an optionally signed hexadecimal integer, whose format is the same
16347 as expected for the subject sequence of the wcstoul function with the value
16348 16 for the base argument. The corresponding argument shall be a pointer to
16350 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
16351 format is the same as expected for the subject sequence of the wcstod
16352 function. The corresponding argument shall be a pointer to floating.
16353 c Matches a sequence of wide characters of exactly the number specified by the
16354 field width (1 if no field width is present in the directive).
16355 If no l length modifier is present, characters from the input field are
16356 converted as if by repeated calls to the wcrtomb function, with the
16357 conversion state described by an mbstate_t object initialized to zero
16358 before the first wide character is converted. The corresponding argument
16359 shall be a pointer to the initial element of a character array large enough to
16360 accept the sequence. No null character is added.
16361 If an l length modifier is present, the corresponding argument shall be a
16362 pointer to the initial element of an array of wchar_t large enough to accept
16363 the sequence. No null wide character is added.
16364 s Matches a sequence of non-white-space wide characters.
16365 If no l length modifier is present, characters from the input field are
16366 converted as if by repeated calls to the wcrtomb function, with the
16367 conversion state described by an mbstate_t object initialized to zero
16368 before the first wide character is converted. The corresponding argument
16369 shall be a pointer to the initial element of a character array large enough to
16370 accept the sequence and a terminating null character, which will be added
16372 If an l length modifier is present, the corresponding argument shall be a
16373 pointer to the initial element of an array of wchar_t large enough to accept
16375 [<a name="p410" href="#p410">page 410</a>] (<a href="#Contents">Contents</a>)
16377 the sequence and the terminating null wide character, which will be added
16379 [ Matches a nonempty sequence of wide characters from a set of expected
16380 characters (the scanset).
16381 If no l length modifier is present, characters from the input field are
16382 converted as if by repeated calls to the wcrtomb function, with the
16383 conversion state described by an mbstate_t object initialized to zero
16384 before the first wide character is converted. The corresponding argument
16385 shall be a pointer to the initial element of a character array large enough to
16386 accept the sequence and a terminating null character, which will be added
16388 If an l length modifier is present, the corresponding argument shall be a
16389 pointer to the initial element of an array of wchar_t large enough to accept
16390 the sequence and the terminating null wide character, which will be added
16392 The conversion specifier includes all subsequent wide characters in the
16393 format string, up to and including the matching right bracket (]). The wide
16394 characters between the brackets (the scanlist) compose the scanset, unless the
16395 wide character after the left bracket is a circumflex (^), in which case the
16396 scanset contains all wide characters that do not appear in the scanlist between
16397 the circumflex and the right bracket. If the conversion specifier begins with
16398 [] or [^], the right bracket wide character is in the scanlist and the next
16399 following right bracket wide character is the matching right bracket that ends
16400 the specification; otherwise the first following right bracket wide character is
16401 the one that ends the specification. If a - wide character is in the scanlist and
16402 is not the first, nor the second where the first wide character is a ^, nor the
16403 last character, the behavior is implementation-defined.
16404 p Matches an implementation-defined set of sequences, which should be the
16405 same as the set of sequences that may be produced by the %p conversion of
16406 the fwprintf function. The corresponding argument shall be a pointer to a
16407 pointer to void. The input item is converted to a pointer value in an
16408 implementation-defined manner. If the input item is a value converted earlier
16409 during the same program execution, the pointer that results shall compare
16410 equal to that value; otherwise the behavior of the %p conversion is undefined.
16411 n No input is consumed. The corresponding argument shall be a pointer to
16412 signed integer into which is to be written the number of wide characters read
16413 from the input stream so far by this call to the fwscanf function. Execution
16414 of a %n directive does not increment the assignment count returned at the
16415 completion of execution of the fwscanf function. No argument is
16416 [<a name="p411" href="#p411">page 411</a>] (<a href="#Contents">Contents</a>)
16418 converted, but one is consumed. If the conversion specification includes an
16419 assignment-suppressing wide character or a field width, the behavior is
16421 % Matches a single % wide character; no conversion or assignment occurs. The
16422 complete conversion specification shall be %%.
16423 13 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note326"><b>326)</b></a></sup>
16424 14 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
16425 respectively, a, e, f, g, and x.
16426 15 Trailing white space (including new-line wide characters) is left unread unless matched
16427 by a directive. The success of literal matches and suppressed assignments is not directly
16428 determinable other than via the %n directive.
16430 16 The fwscanf function returns the value of the macro EOF if an input failure occurs
16431 before the first conversion (if any) has completed. Otherwise, the function returns the
16432 number of input items assigned, which can be fewer than provided for, or even zero, in
16433 the event of an early matching failure.
16434 17 EXAMPLE 1 The call:
16435 #include <a href="#7.21"><stdio.h></a>
16436 #include <a href="#7.28"><wchar.h></a>
16438 int n, i; float x; wchar_t name[50];
16439 n = fwscanf(stdin, L"%d%f%ls", &i, &x, name);
16440 with the input line:
16441 25 54.32E-1 thompson
16442 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
16445 18 EXAMPLE 2 The call:
16446 #include <a href="#7.21"><stdio.h></a>
16447 #include <a href="#7.28"><wchar.h></a>
16449 int i; float x; double y;
16450 fwscanf(stdin, L"%2d%f%*d %lf", &i, &x, &y);
16453 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
16454 56.0. The next wide character read from the input stream will be a.
16457 <sup><a name="note326" href="#note326"><b>326)</b></a></sup> See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
16459 [<a name="p412" href="#p412">page 412</a>] (<a href="#Contents">Contents</a>)
16461 Forward references: the wcstod, wcstof, and wcstold functions (<a href="#7.28.4.1.1">7.28.4.1.1</a>), the
16462 wcstol, wcstoll, wcstoul, and wcstoull functions (<a href="#7.28.4.1.2">7.28.4.1.2</a>), the wcrtomb
16463 function (<a href="#7.28.6.3.3">7.28.6.3.3</a>).
16464 <a name="7.28.2.3" href="#7.28.2.3"><b> 7.28.2.3 The swprintf function</b></a>
16466 1 #include <a href="#7.28"><wchar.h></a>
16467 int swprintf(wchar_t * restrict s,
16469 const wchar_t * restrict format, ...);
16470 <b> Description</b>
16471 2 The swprintf function is equivalent to fwprintf, except that the argument s
16472 specifies an array of wide characters into which the generated output is to be written,
16473 rather than written to a stream. No more than n wide characters are written, including a
16474 terminating null wide character, which is always added (unless n is zero).
16476 3 The swprintf function returns the number of wide characters written in the array, not
16477 counting the terminating null wide character, or a negative value if an encoding error
16478 occurred or if n or more wide characters were requested to be written.
16479 <a name="7.28.2.4" href="#7.28.2.4"><b> 7.28.2.4 The swscanf function</b></a>
16481 1 #include <a href="#7.28"><wchar.h></a>
16482 int swscanf(const wchar_t * restrict s,
16483 const wchar_t * restrict format, ...);
16484 <b> Description</b>
16485 2 The swscanf function is equivalent to fwscanf, except that the argument s specifies a
16486 wide string from which the input is to be obtained, rather than from a stream. Reaching
16487 the end of the wide string is equivalent to encountering end-of-file for the fwscanf
16490 3 The swscanf function returns the value of the macro EOF if an input failure occurs
16491 before the first conversion (if any) has completed. Otherwise, the swscanf function
16492 returns the number of input items assigned, which can be fewer than provided for, or even
16493 zero, in the event of an early matching failure.
16498 [<a name="p413" href="#p413">page 413</a>] (<a href="#Contents">Contents</a>)
16500 <a name="7.28.2.5" href="#7.28.2.5"><b> 7.28.2.5 The vfwprintf function</b></a>
16502 1 #include <a href="#7.16"><stdarg.h></a>
16503 #include <a href="#7.21"><stdio.h></a>
16504 #include <a href="#7.28"><wchar.h></a>
16505 int vfwprintf(FILE * restrict stream,
16506 const wchar_t * restrict format,
16508 <b> Description</b>
16509 2 The vfwprintf function is equivalent to fwprintf, with the variable argument list
16510 replaced by arg, which shall have been initialized by the va_start macro (and
16511 possibly subsequent va_arg calls). The vfwprintf function does not invoke the
16512 va_end macro.<sup><a href="#note327"><b>327)</b></a></sup>
16514 3 The vfwprintf function returns the number of wide characters transmitted, or a
16515 negative value if an output or encoding error occurred.
16516 4 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting
16518 #include <a href="#7.16"><stdarg.h></a>
16519 #include <a href="#7.21"><stdio.h></a>
16520 #include <a href="#7.28"><wchar.h></a>
16521 void error(char *function_name, wchar_t *format, ...)
16524 va_start(args, format);
16525 // print out name of function causing error
16526 fwprintf(stderr, L"ERROR in %s: ", function_name);
16527 // print out remainder of message
16528 vfwprintf(stderr, format, args);
16535 <sup><a name="note327" href="#note327"><b>327)</b></a></sup> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
16536 invoke the va_arg macro, the value of arg after the return is indeterminate.
16538 [<a name="p414" href="#p414">page 414</a>] (<a href="#Contents">Contents</a>)
16540 <a name="7.28.2.6" href="#7.28.2.6"><b> 7.28.2.6 The vfwscanf function</b></a>
16542 1 #include <a href="#7.16"><stdarg.h></a>
16543 #include <a href="#7.21"><stdio.h></a>
16544 #include <a href="#7.28"><wchar.h></a>
16545 int vfwscanf(FILE * restrict stream,
16546 const wchar_t * restrict format,
16548 <b> Description</b>
16549 2 The vfwscanf function is equivalent to fwscanf, with the variable argument list
16550 replaced by arg, which shall have been initialized by the va_start macro (and
16551 possibly subsequent va_arg calls). The vfwscanf function does not invoke the
16554 3 The vfwscanf function returns the value of the macro EOF if an input failure occurs
16555 before the first conversion (if any) has completed. Otherwise, the vfwscanf function
16556 returns the number of input items assigned, which can be fewer than provided for, or even
16557 zero, in the event of an early matching failure.
16558 <a name="7.28.2.7" href="#7.28.2.7"><b> 7.28.2.7 The vswprintf function</b></a>
16560 1 #include <a href="#7.16"><stdarg.h></a>
16561 #include <a href="#7.28"><wchar.h></a>
16562 int vswprintf(wchar_t * restrict s,
16564 const wchar_t * restrict format,
16566 <b> Description</b>
16567 2 The vswprintf function is equivalent to swprintf, with the variable argument list
16568 replaced by arg, which shall have been initialized by the va_start macro (and
16569 possibly subsequent va_arg calls). The vswprintf function does not invoke the
16572 3 The vswprintf function returns the number of wide characters written in the array, not
16573 counting the terminating null wide character, or a negative value if an encoding error
16574 occurred or if n or more wide characters were requested to be generated.
16577 [<a name="p415" href="#p415">page 415</a>] (<a href="#Contents">Contents</a>)
16579 <a name="7.28.2.8" href="#7.28.2.8"><b> 7.28.2.8 The vswscanf function</b></a>
16581 1 #include <a href="#7.16"><stdarg.h></a>
16582 #include <a href="#7.28"><wchar.h></a>
16583 int vswscanf(const wchar_t * restrict s,
16584 const wchar_t * restrict format,
16586 <b> Description</b>
16587 2 The vswscanf function is equivalent to swscanf, with the variable argument list
16588 replaced by arg, which shall have been initialized by the va_start macro (and
16589 possibly subsequent va_arg calls). The vswscanf function does not invoke the
16592 3 The vswscanf function returns the value of the macro EOF if an input failure occurs
16593 before the first conversion (if any) has completed. Otherwise, the vswscanf function
16594 returns the number of input items assigned, which can be fewer than provided for, or even
16595 zero, in the event of an early matching failure.
16596 <a name="7.28.2.9" href="#7.28.2.9"><b> 7.28.2.9 The vwprintf function</b></a>
16598 1 #include <a href="#7.16"><stdarg.h></a>
16599 #include <a href="#7.28"><wchar.h></a>
16600 int vwprintf(const wchar_t * restrict format,
16602 <b> Description</b>
16603 2 The vwprintf function is equivalent to wprintf, with the variable argument list
16604 replaced by arg, which shall have been initialized by the va_start macro (and
16605 possibly subsequent va_arg calls). The vwprintf function does not invoke the
16608 3 The vwprintf function returns the number of wide characters transmitted, or a negative
16609 value if an output or encoding error occurred.
16614 [<a name="p416" href="#p416">page 416</a>] (<a href="#Contents">Contents</a>)
16616 <a name="7.28.2.10" href="#7.28.2.10"><b> 7.28.2.10 The vwscanf function</b></a>
16618 1 #include <a href="#7.16"><stdarg.h></a>
16619 #include <a href="#7.28"><wchar.h></a>
16620 int vwscanf(const wchar_t * restrict format,
16622 <b> Description</b>
16623 2 The vwscanf function is equivalent to wscanf, with the variable argument list
16624 replaced by arg, which shall have been initialized by the va_start macro (and
16625 possibly subsequent va_arg calls). The vwscanf function does not invoke the
16628 3 The vwscanf function returns the value of the macro EOF if an input failure occurs
16629 before the first conversion (if any) has completed. Otherwise, the vwscanf function
16630 returns the number of input items assigned, which can be fewer than provided for, or even
16631 zero, in the event of an early matching failure.
16632 <a name="7.28.2.11" href="#7.28.2.11"><b> 7.28.2.11 The wprintf function</b></a>
16634 1 #include <a href="#7.28"><wchar.h></a>
16635 int wprintf(const wchar_t * restrict format, ...);
16636 <b> Description</b>
16637 2 The wprintf function is equivalent to fwprintf with the argument stdout
16638 interposed before the arguments to wprintf.
16640 3 The wprintf function returns the number of wide characters transmitted, or a negative
16641 value if an output or encoding error occurred.
16642 <a name="7.28.2.12" href="#7.28.2.12"><b> 7.28.2.12 The wscanf function</b></a>
16644 1 #include <a href="#7.28"><wchar.h></a>
16645 int wscanf(const wchar_t * restrict format, ...);
16646 <b> Description</b>
16647 2 The wscanf function is equivalent to fwscanf with the argument stdin interposed
16648 before the arguments to wscanf.
16651 [<a name="p417" href="#p417">page 417</a>] (<a href="#Contents">Contents</a>)
16654 3 The wscanf function returns the value of the macro EOF if an input failure occurs
16655 before the first conversion (if any) has completed. Otherwise, the wscanf function
16656 returns the number of input items assigned, which can be fewer than provided for, or even
16657 zero, in the event of an early matching failure.
16658 <a name="7.28.3" href="#7.28.3"><b> 7.28.3 Wide character input/output functions</b></a>
16659 <a name="7.28.3.1" href="#7.28.3.1"><b> 7.28.3.1 The fgetwc function</b></a>
16661 1 #include <a href="#7.21"><stdio.h></a>
16662 #include <a href="#7.28"><wchar.h></a>
16663 wint_t fgetwc(FILE *stream);
16664 <b> Description</b>
16665 2 If the end-of-file indicator for the input stream pointed to by stream is not set and a
16666 next wide character is present, the fgetwc function obtains that wide character as a
16667 wchar_t converted to a wint_t and advances the associated file position indicator for
16668 the stream (if defined).
16670 3 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
16671 of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
16672 the fgetwc function returns the next wide character from the input stream pointed to by
16673 stream. If a read error occurs, the error indicator for the stream is set and the fgetwc
16674 function returns WEOF. If an encoding error occurs (including too few bytes), the value of
16675 the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.<sup><a href="#note328"><b>328)</b></a></sup>
16676 <a name="7.28.3.2" href="#7.28.3.2"><b> 7.28.3.2 The fgetws function</b></a>
16678 1 #include <a href="#7.21"><stdio.h></a>
16679 #include <a href="#7.28"><wchar.h></a>
16680 wchar_t *fgetws(wchar_t * restrict s,
16681 int n, FILE * restrict stream);
16682 <b> Description</b>
16683 2 The fgetws function reads at most one less than the number of wide characters
16684 specified by n from the stream pointed to by stream into the array pointed to by s. No
16687 <sup><a name="note328" href="#note328"><b>328)</b></a></sup> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
16688 Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
16690 [<a name="p418" href="#p418">page 418</a>] (<a href="#Contents">Contents</a>)
16692 additional wide characters are read after a new-line wide character (which is retained) or
16693 after end-of-file. A null wide character is written immediately after the last wide
16694 character read into the array.
16696 3 The fgetws function returns s if successful. If end-of-file is encountered and no
16697 characters have been read into the array, the contents of the array remain unchanged and a
16698 null pointer is returned. If a read or encoding error occurs during the operation, the array
16699 contents are indeterminate and a null pointer is returned.
16700 <a name="7.28.3.3" href="#7.28.3.3"><b> 7.28.3.3 The fputwc function</b></a>
16702 1 #include <a href="#7.21"><stdio.h></a>
16703 #include <a href="#7.28"><wchar.h></a>
16704 wint_t fputwc(wchar_t c, FILE *stream);
16705 <b> Description</b>
16706 2 The fputwc function writes the wide character specified by c to the output stream
16707 pointed to by stream, at the position indicated by the associated file position indicator
16708 for the stream (if defined), and advances the indicator appropriately. If the file cannot
16709 support positioning requests, or if the stream was opened with append mode, the
16710 character is appended to the output stream.
16712 3 The fputwc function returns the wide character written. If a write error occurs, the
16713 error indicator for the stream is set and fputwc returns WEOF. If an encoding error
16714 occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
16715 <a name="7.28.3.4" href="#7.28.3.4"><b> 7.28.3.4 The fputws function</b></a>
16717 1 #include <a href="#7.21"><stdio.h></a>
16718 #include <a href="#7.28"><wchar.h></a>
16719 int fputws(const wchar_t * restrict s,
16720 FILE * restrict stream);
16721 <b> Description</b>
16722 2 The fputws function writes the wide string pointed to by s to the stream pointed to by
16723 stream. The terminating null wide character is not written.
16725 3 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
16726 returns a nonnegative value.
16728 [<a name="p419" href="#p419">page 419</a>] (<a href="#Contents">Contents</a>)
16730 <a name="7.28.3.5" href="#7.28.3.5"><b> 7.28.3.5 The fwide function</b></a>
16732 1 #include <a href="#7.21"><stdio.h></a>
16733 #include <a href="#7.28"><wchar.h></a>
16734 int fwide(FILE *stream, int mode);
16735 <b> Description</b>
16736 2 The fwide function determines the orientation of the stream pointed to by stream. If
16737 mode is greater than zero, the function first attempts to make the stream wide oriented. If
16738 mode is less than zero, the function first attempts to make the stream byte oriented.<sup><a href="#note329"><b>329)</b></a></sup>
16739 Otherwise, mode is zero and the function does not alter the orientation of the stream.
16741 3 The fwide function returns a value greater than zero if, after the call, the stream has
16742 wide orientation, a value less than zero if the stream has byte orientation, or zero if the
16743 stream has no orientation.
16744 <a name="7.28.3.6" href="#7.28.3.6"><b> 7.28.3.6 The getwc function</b></a>
16746 1 #include <a href="#7.21"><stdio.h></a>
16747 #include <a href="#7.28"><wchar.h></a>
16748 wint_t getwc(FILE *stream);
16749 <b> Description</b>
16750 2 The getwc function is equivalent to fgetwc, except that if it is implemented as a
16751 macro, it may evaluate stream more than once, so the argument should never be an
16752 expression with side effects.
16754 3 The getwc function returns the next wide character from the input stream pointed to by
16756 <a name="7.28.3.7" href="#7.28.3.7"><b> 7.28.3.7 The getwchar function</b></a>
16758 1 #include <a href="#7.28"><wchar.h></a>
16759 wint_t getwchar(void);
16764 <sup><a name="note329" href="#note329"><b>329)</b></a></sup> If the orientation of the stream has already been determined, fwide does not change it.
16766 [<a name="p420" href="#p420">page 420</a>] (<a href="#Contents">Contents</a>)
16768 <b> Description</b>
16769 2 The getwchar function is equivalent to getwc with the argument stdin.
16771 3 The getwchar function returns the next wide character from the input stream pointed to
16773 <a name="7.28.3.8" href="#7.28.3.8"><b> 7.28.3.8 The putwc function</b></a>
16775 1 #include <a href="#7.21"><stdio.h></a>
16776 #include <a href="#7.28"><wchar.h></a>
16777 wint_t putwc(wchar_t c, FILE *stream);
16778 <b> Description</b>
16779 2 The putwc function is equivalent to fputwc, except that if it is implemented as a
16780 macro, it may evaluate stream more than once, so that argument should never be an
16781 expression with side effects.
16783 3 The putwc function returns the wide character written, or WEOF.
16784 <a name="7.28.3.9" href="#7.28.3.9"><b> 7.28.3.9 The putwchar function</b></a>
16786 1 #include <a href="#7.28"><wchar.h></a>
16787 wint_t putwchar(wchar_t c);
16788 <b> Description</b>
16789 2 The putwchar function is equivalent to putwc with the second argument stdout.
16791 3 The putwchar function returns the character written, or WEOF.
16792 <a name="7.28.3.10" href="#7.28.3.10"><b> 7.28.3.10 The ungetwc function</b></a>
16794 1 #include <a href="#7.21"><stdio.h></a>
16795 #include <a href="#7.28"><wchar.h></a>
16796 wint_t ungetwc(wint_t c, FILE *stream);
16797 <b> Description</b>
16798 2 The ungetwc function pushes the wide character specified by c back onto the input
16799 stream pointed to by stream. Pushed-back wide characters will be returned by
16800 subsequent reads on that stream in the reverse order of their pushing. A successful
16802 [<a name="p421" href="#p421">page 421</a>] (<a href="#Contents">Contents</a>)
16804 intervening call (with the stream pointed to by stream) to a file positioning function
16805 (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the
16806 stream. The external storage corresponding to the stream is unchanged.
16807 3 One wide character of pushback is guaranteed, even if the call to the ungetwc function
16808 follows just after a call to a formatted wide character input function fwscanf,
16809 vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times
16810 on the same stream without an intervening read or file positioning operation on that
16811 stream, the operation may fail.
16812 4 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
16814 5 A successful call to the ungetwc function clears the end-of-file indicator for the stream.
16815 The value of the file position indicator for the stream after reading or discarding all
16816 pushed-back wide characters is the same as it was before the wide characters were pushed
16817 back. For a text or binary stream, the value of its file position indicator after a successful
16818 call to the ungetwc function is unspecified until all pushed-back wide characters are
16821 6 The ungetwc function returns the wide character pushed back, or WEOF if the operation
16823 <a name="7.28.4" href="#7.28.4"><b> 7.28.4 General wide string utilities</b></a>
16824 1 The header <a href="#7.28"><wchar.h></a> declares a number of functions useful for wide string
16825 manipulation. Various methods are used for determining the lengths of the arrays, but in
16826 all cases a wchar_t * argument points to the initial (lowest addressed) element of the
16827 array. If an array is accessed beyond the end of an object, the behavior is undefined.
16828 2 Where an argument declared as size_t n determines the length of the array for a
16829 function, n can have the value zero on a call to that function. Unless explicitly stated
16830 otherwise in the description of a particular function in this subclause, pointer arguments
16831 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
16832 function that locates a wide character finds no occurrence, a function that compares two
16833 wide character sequences returns zero, and a function that copies wide characters copies
16834 zero wide characters.
16839 [<a name="p422" href="#p422">page 422</a>] (<a href="#Contents">Contents</a>)
16841 <a name="7.28.4.1" href="#7.28.4.1"><b> 7.28.4.1 Wide string numeric conversion functions</b></a>
16842 <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>
16844 1 #include <a href="#7.28"><wchar.h></a>
16845 double wcstod(const wchar_t * restrict nptr,
16846 wchar_t ** restrict endptr);
16847 float wcstof(const wchar_t * restrict nptr,
16848 wchar_t ** restrict endptr);
16849 long double wcstold(const wchar_t * restrict nptr,
16850 wchar_t ** restrict endptr);
16851 <b> Description</b>
16852 2 The wcstod, wcstof, and wcstold functions convert the initial portion of the wide
16853 string pointed to by nptr to double, float, and long double representation,
16854 respectively. First, they decompose the input string into three parts: an initial, possibly
16855 empty, sequence of white-space wide characters (as specified by the iswspace
16856 function), a subject sequence resembling a floating-point constant or representing an
16857 infinity or NaN; and a final wide string of one or more unrecognized wide characters,
16858 including the terminating null wide character of the input wide string. Then, they attempt
16859 to convert the subject sequence to a floating-point number, and return the result.
16860 3 The expected form of the subject sequence is an optional plus or minus sign, then one of
16862 -- a nonempty sequence of decimal digits optionally containing a decimal-point wide
16863 character, then an optional exponent part as defined for the corresponding single-byte
16864 characters in <a href="#6.4.4.2">6.4.4.2</a>;
16865 -- a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
16866 decimal-point wide character, then an optional binary exponent part as defined in
16867 <a href="#6.4.4.2">6.4.4.2</a>;
16868 -- INF or INFINITY, or any other wide string equivalent except for case
16869 -- NAN or NAN(n-wchar-sequenceopt), or any other wide string equivalent except for
16870 case in the NAN part, where:
16874 n-wchar-sequence digit
16875 n-wchar-sequence nondigit
16876 The subject sequence is defined as the longest initial subsequence of the input wide
16877 string, starting with the first non-white-space wide character, that is of the expected form.
16878 [<a name="p423" href="#p423">page 423</a>] (<a href="#Contents">Contents</a>)
16880 The subject sequence contains no wide characters if the input wide string is not of the
16882 4 If the subject sequence has the expected form for a floating-point number, the sequence of
16883 wide characters starting with the first digit or the decimal-point wide character
16884 (whichever occurs first) is interpreted as a floating constant according to the rules of
16885 <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
16886 if neither an exponent part nor a decimal-point wide character appears in a decimal
16887 floating point number, or if a binary exponent part does not appear in a hexadecimal
16888 floating point number, an exponent part of the appropriate type with value zero is
16889 assumed to follow the last digit in the string. If the subject sequence begins with a minus
16890 sign, the sequence is interpreted as negated.<sup><a href="#note330"><b>330)</b></a></sup> A wide character sequence INF or
16891 INFINITY is interpreted as an infinity, if representable in the return type, else like a
16892 floating constant that is too large for the range of the return type. A wide character
16893 sequence NAN or NAN(n-wchar-sequenceopt) is interpreted as a quiet NaN, if supported
16894 in the return type, else like a subject sequence part that does not have the expected form;
16895 the meaning of the n-wchar sequences is implementation-defined.<sup><a href="#note331"><b>331)</b></a></sup> A pointer to the
16896 final wide string is stored in the object pointed to by endptr, provided that endptr is
16897 not a null pointer.
16898 5 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
16899 value resulting from the conversion is correctly rounded.
16900 6 In other than the "C" locale, additional locale-specific subject sequence forms may be
16902 7 If the subject sequence is empty or does not have the expected form, no conversion is
16903 performed; the value of nptr is stored in the object pointed to by endptr, provided
16904 that endptr is not a null pointer.
16905 Recommended practice
16906 8 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
16907 the result is not exactly representable, the result should be one of the two numbers in the
16908 appropriate internal format that are adjacent to the hexadecimal floating source value,
16909 with the extra stipulation that the error should have a correct sign for the current rounding
16914 <sup><a name="note330" href="#note330"><b>330)</b></a></sup> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
16915 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
16916 methods may yield different results if rounding is toward positive or negative infinity. In either case,
16917 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
16918 <sup><a name="note331" href="#note331"><b>331)</b></a></sup> An implementation may use the n-wchar sequence to determine extra information to be represented in
16919 the NaN's significand.
16921 [<a name="p424" href="#p424">page 424</a>] (<a href="#Contents">Contents</a>)
16923 9 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
16924 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
16925 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
16926 consider the two bounding, adjacent decimal strings L and U, both having
16927 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
16928 The result should be one of the (equal or adjacent) values that would be obtained by
16929 correctly rounding L and U according to the current rounding direction, with the extra
16930 stipulation that the error with respect to D should have a correct sign for the current
16931 rounding direction.<sup><a href="#note332"><b>332)</b></a></sup>
16933 10 The functions return the converted value, if any. If no conversion could be performed,
16934 zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
16935 plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
16936 return type and sign of the value), and the value of the macro ERANGE is stored in
16937 errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
16938 no greater than the smallest normalized positive number in the return type; whether
16939 errno acquires the value ERANGE is implementation-defined.
16944 <sup><a name="note332" href="#note332"><b>332)</b></a></sup> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
16945 to the same internal floating value, but if not will round to adjacent values.
16947 [<a name="p425" href="#p425">page 425</a>] (<a href="#Contents">Contents</a>)
16949 <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>
16951 1 #include <a href="#7.28"><wchar.h></a>
16953 const wchar_t * restrict nptr,
16954 wchar_t ** restrict endptr,
16956 long long int wcstoll(
16957 const wchar_t * restrict nptr,
16958 wchar_t ** restrict endptr,
16960 unsigned long int wcstoul(
16961 const wchar_t * restrict nptr,
16962 wchar_t ** restrict endptr,
16964 unsigned long long int wcstoull(
16965 const wchar_t * restrict nptr,
16966 wchar_t ** restrict endptr,
16968 <b> Description</b>
16969 2 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial
16970 portion of the wide string pointed to by nptr to long int, long long int,
16971 unsigned long int, and unsigned long long int representation,
16972 respectively. First, they decompose the input string into three parts: an initial, possibly
16973 empty, sequence of white-space wide characters (as specified by the iswspace
16974 function), a subject sequence resembling an integer represented in some radix determined
16975 by the value of base, and a final wide string of one or more unrecognized wide
16976 characters, including the terminating null wide character of the input wide string. Then,
16977 they attempt to convert the subject sequence to an integer, and return the result.
16978 3 If the value of base is zero, the expected form of the subject sequence is that of an
16979 integer constant as described for the corresponding single-byte characters in <a href="#6.4.4.1">6.4.4.1</a>,
16980 optionally preceded by a plus or minus sign, but not including an integer suffix. If the
16981 value of base is between 2 and 36 (inclusive), the expected form of the subject sequence
16982 is a sequence of letters and digits representing an integer with the radix specified by
16983 base, optionally preceded by a plus or minus sign, but not including an integer suffix.
16984 The letters from a (or A) through z (or Z) are ascribed the values 10 through 35; only
16985 letters and digits whose ascribed values are less than that of base are permitted. If the
16986 value of base is 16, the wide characters 0x or 0X may optionally precede the sequence
16987 of letters and digits, following the sign if present.
16989 [<a name="p426" href="#p426">page 426</a>] (<a href="#Contents">Contents</a>)
16991 4 The subject sequence is defined as the longest initial subsequence of the input wide
16992 string, starting with the first non-white-space wide character, that is of the expected form.
16993 The subject sequence contains no wide characters if the input wide string is empty or
16994 consists entirely of white space, or if the first non-white-space wide character is other
16995 than a sign or a permissible letter or digit.
16996 5 If the subject sequence has the expected form and the value of base is zero, the sequence
16997 of wide characters starting with the first digit is interpreted as an integer constant
16998 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
16999 value of base is between 2 and 36, it is used as the base for conversion, ascribing to each
17000 letter its value as given above. If the subject sequence begins with a minus sign, the value
17001 resulting from the conversion is negated (in the return type). A pointer to the final wide
17002 string is stored in the object pointed to by endptr, provided that endptr is not a null
17004 6 In other than the "C" locale, additional locale-specific subject sequence forms may be
17006 7 If the subject sequence is empty or does not have the expected form, no conversion is
17007 performed; the value of nptr is stored in the object pointed to by endptr, provided
17008 that endptr is not a null pointer.
17010 8 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
17011 value, if any. If no conversion could be performed, zero is returned. If the correct value
17012 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
17013 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
17014 sign of the value, if any), and the value of the macro ERANGE is stored in errno.
17015 <a name="7.28.4.2" href="#7.28.4.2"><b> 7.28.4.2 Wide string copying functions</b></a>
17016 <a name="7.28.4.2.1" href="#7.28.4.2.1"><b> 7.28.4.2.1 The wcscpy function</b></a>
17018 1 #include <a href="#7.28"><wchar.h></a>
17019 wchar_t *wcscpy(wchar_t * restrict s1,
17020 const wchar_t * restrict s2);
17021 <b> Description</b>
17022 2 The wcscpy function copies the wide string pointed to by s2 (including the terminating
17023 null wide character) into the array pointed to by s1.
17025 3 The wcscpy function returns the value of s1.
17028 [<a name="p427" href="#p427">page 427</a>] (<a href="#Contents">Contents</a>)
17030 <a name="7.28.4.2.2" href="#7.28.4.2.2"><b> 7.28.4.2.2 The wcsncpy function</b></a>
17032 1 #include <a href="#7.28"><wchar.h></a>
17033 wchar_t *wcsncpy(wchar_t * restrict s1,
17034 const wchar_t * restrict s2,
17036 <b> Description</b>
17037 2 The wcsncpy function copies not more than n wide characters (those that follow a null
17038 wide character are not copied) from the array pointed to by s2 to the array pointed to by
17039 s1.<sup><a href="#note333"><b>333)</b></a></sup>
17040 3 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null
17041 wide characters are appended to the copy in the array pointed to by s1, until n wide
17042 characters in all have been written.
17044 4 The wcsncpy function returns the value of s1.
17045 <a name="7.28.4.2.3" href="#7.28.4.2.3"><b> 7.28.4.2.3 The wmemcpy function</b></a>
17047 1 #include <a href="#7.28"><wchar.h></a>
17048 wchar_t *wmemcpy(wchar_t * restrict s1,
17049 const wchar_t * restrict s2,
17051 <b> Description</b>
17052 2 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
17053 object pointed to by s1.
17055 3 The wmemcpy function returns the value of s1.
17060 <sup><a name="note333" href="#note333"><b>333)</b></a></sup> Thus, if there is no null wide character in the first n wide characters of the array pointed to by s2, the
17061 result will not be null-terminated.
17063 [<a name="p428" href="#p428">page 428</a>] (<a href="#Contents">Contents</a>)
17065 <a name="7.28.4.2.4" href="#7.28.4.2.4"><b> 7.28.4.2.4 The wmemmove function</b></a>
17067 1 #include <a href="#7.28"><wchar.h></a>
17068 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
17070 <b> Description</b>
17071 2 The wmemmove function copies n wide characters from the object pointed to by s2 to
17072 the object pointed to by s1. Copying takes place as if the n wide characters from the
17073 object pointed to by s2 are first copied into a temporary array of n wide characters that
17074 does not overlap the objects pointed to by s1 or s2, and then the n wide characters from
17075 the temporary array are copied into the object pointed to by s1.
17077 3 The wmemmove function returns the value of s1.
17078 <a name="7.28.4.3" href="#7.28.4.3"><b> 7.28.4.3 Wide string concatenation functions</b></a>
17079 <a name="7.28.4.3.1" href="#7.28.4.3.1"><b> 7.28.4.3.1 The wcscat function</b></a>
17081 1 #include <a href="#7.28"><wchar.h></a>
17082 wchar_t *wcscat(wchar_t * restrict s1,
17083 const wchar_t * restrict s2);
17084 <b> Description</b>
17085 2 The wcscat function appends a copy of the wide string pointed to by s2 (including the
17086 terminating null wide character) to the end of the wide string pointed to by s1. The initial
17087 wide character of s2 overwrites the null wide character at the end of s1.
17089 3 The wcscat function returns the value of s1.
17090 <a name="7.28.4.3.2" href="#7.28.4.3.2"><b> 7.28.4.3.2 The wcsncat function</b></a>
17092 1 #include <a href="#7.28"><wchar.h></a>
17093 wchar_t *wcsncat(wchar_t * restrict s1,
17094 const wchar_t * restrict s2,
17096 <b> Description</b>
17097 2 The wcsncat function appends not more than n wide characters (a null wide character
17098 and those that follow it are not appended) from the array pointed to by s2 to the end of
17100 [<a name="p429" href="#p429">page 429</a>] (<a href="#Contents">Contents</a>)
17102 the wide string pointed to by s1. The initial wide character of s2 overwrites the null
17103 wide character at the end of s1. A terminating null wide character is always appended to
17104 the result.<sup><a href="#note334"><b>334)</b></a></sup>
17106 3 The wcsncat function returns the value of s1.
17107 <a name="7.28.4.4" href="#7.28.4.4"><b> 7.28.4.4 Wide string comparison functions</b></a>
17108 1 Unless explicitly stated otherwise, the functions described in this subclause order two
17109 wide characters the same way as two integers of the underlying integer type designated
17111 <a name="7.28.4.4.1" href="#7.28.4.4.1"><b> 7.28.4.4.1 The wcscmp function</b></a>
17113 1 #include <a href="#7.28"><wchar.h></a>
17114 int wcscmp(const wchar_t *s1, const wchar_t *s2);
17115 <b> Description</b>
17116 2 The wcscmp function compares the wide string pointed to by s1 to the wide string
17119 3 The wcscmp function returns an integer greater than, equal to, or less than zero,
17120 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
17121 wide string pointed to by s2.
17122 <a name="7.28.4.4.2" href="#7.28.4.4.2"><b> 7.28.4.4.2 The wcscoll function</b></a>
17124 1 #include <a href="#7.28"><wchar.h></a>
17125 int wcscoll(const wchar_t *s1, const wchar_t *s2);
17126 <b> Description</b>
17127 2 The wcscoll function compares the wide string pointed to by s1 to the wide string
17128 pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the
17131 3 The wcscoll function returns an integer greater than, equal to, or less than zero,
17132 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
17135 <sup><a name="note334" href="#note334"><b>334)</b></a></sup> Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is
17138 [<a name="p430" href="#p430">page 430</a>] (<a href="#Contents">Contents</a>)
17140 wide string pointed to by s2 when both are interpreted as appropriate to the current
17142 <a name="7.28.4.4.3" href="#7.28.4.4.3"><b> 7.28.4.4.3 The wcsncmp function</b></a>
17144 1 #include <a href="#7.28"><wchar.h></a>
17145 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
17147 <b> Description</b>
17148 2 The wcsncmp function compares not more than n wide characters (those that follow a
17149 null wide character are not compared) from the array pointed to by s1 to the array
17152 3 The wcsncmp function returns an integer greater than, equal to, or less than zero,
17153 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
17154 to, or less than the possibly null-terminated array pointed to by s2.
17155 <a name="7.28.4.4.4" href="#7.28.4.4.4"><b> 7.28.4.4.4 The wcsxfrm function</b></a>
17157 1 #include <a href="#7.28"><wchar.h></a>
17158 size_t wcsxfrm(wchar_t * restrict s1,
17159 const wchar_t * restrict s2,
17161 <b> Description</b>
17162 2 The wcsxfrm function transforms the wide string pointed to by s2 and places the
17163 resulting wide string into the array pointed to by s1. The transformation is such that if
17164 the wcscmp function is applied to two transformed wide strings, it returns a value greater
17165 than, equal to, or less than zero, corresponding to the result of the wcscoll function
17166 applied to the same two original wide strings. No more than n wide characters are placed
17167 into the resulting array pointed to by s1, including the terminating null wide character. If
17168 n is zero, s1 is permitted to be a null pointer.
17170 3 The wcsxfrm function returns the length of the transformed wide string (not including
17171 the terminating null wide character). If the value returned is n or greater, the contents of
17172 the array pointed to by s1 are indeterminate.
17173 4 EXAMPLE The value of the following expression is the length of the array needed to hold the
17174 transformation of the wide string pointed to by s:
17177 [<a name="p431" href="#p431">page 431</a>] (<a href="#Contents">Contents</a>)
17179 1 + wcsxfrm(NULL, s, 0)
17181 <a name="7.28.4.4.5" href="#7.28.4.4.5"><b> 7.28.4.4.5 The wmemcmp function</b></a>
17183 1 #include <a href="#7.28"><wchar.h></a>
17184 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
17186 <b> Description</b>
17187 2 The wmemcmp function compares the first n wide characters of the object pointed to by
17188 s1 to the first n wide characters of the object pointed to by s2.
17190 3 The wmemcmp function returns an integer greater than, equal to, or less than zero,
17191 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
17193 <a name="7.28.4.5" href="#7.28.4.5"><b> 7.28.4.5 Wide string search functions</b></a>
17194 <a name="7.28.4.5.1" href="#7.28.4.5.1"><b> 7.28.4.5.1 The wcschr function</b></a>
17196 1 #include <a href="#7.28"><wchar.h></a>
17197 wchar_t *wcschr(const wchar_t *s, wchar_t c);
17198 <b> Description</b>
17199 2 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
17200 The terminating null wide character is considered to be part of the wide string.
17202 3 The wcschr function returns a pointer to the located wide character, or a null pointer if
17203 the wide character does not occur in the wide string.
17204 <a name="7.28.4.5.2" href="#7.28.4.5.2"><b> 7.28.4.5.2 The wcscspn function</b></a>
17206 1 #include <a href="#7.28"><wchar.h></a>
17207 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
17208 <b> Description</b>
17209 2 The wcscspn function computes the length of the maximum initial segment of the wide
17210 string pointed to by s1 which consists entirely of wide characters not from the wide
17211 string pointed to by s2.
17215 [<a name="p432" href="#p432">page 432</a>] (<a href="#Contents">Contents</a>)
17218 3 The wcscspn function returns the length of the segment.
17219 <a name="7.28.4.5.3" href="#7.28.4.5.3"><b> 7.28.4.5.3 The wcspbrk function</b></a>
17221 1 #include <a href="#7.28"><wchar.h></a>
17222 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
17223 <b> Description</b>
17224 2 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
17225 any wide character from the wide string pointed to by s2.
17227 3 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
17228 no wide character from s2 occurs in s1.
17229 <a name="7.28.4.5.4" href="#7.28.4.5.4"><b> 7.28.4.5.4 The wcsrchr function</b></a>
17231 1 #include <a href="#7.28"><wchar.h></a>
17232 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
17233 <b> Description</b>
17234 2 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
17235 s. The terminating null wide character is considered to be part of the wide string.
17237 3 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
17238 not occur in the wide string.
17239 <a name="7.28.4.5.5" href="#7.28.4.5.5"><b> 7.28.4.5.5 The wcsspn function</b></a>
17241 1 #include <a href="#7.28"><wchar.h></a>
17242 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
17243 <b> Description</b>
17244 2 The wcsspn function computes the length of the maximum initial segment of the wide
17245 string pointed to by s1 which consists entirely of wide characters from the wide string
17248 3 The wcsspn function returns the length of the segment.
17251 [<a name="p433" href="#p433">page 433</a>] (<a href="#Contents">Contents</a>)
17253 <a name="7.28.4.5.6" href="#7.28.4.5.6"><b> 7.28.4.5.6 The wcsstr function</b></a>
17255 1 #include <a href="#7.28"><wchar.h></a>
17256 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
17257 <b> Description</b>
17258 2 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
17259 the sequence of wide characters (excluding the terminating null wide character) in the
17260 wide string pointed to by s2.
17262 3 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
17263 wide string is not found. If s2 points to a wide string with zero length, the function
17265 <a name="7.28.4.5.7" href="#7.28.4.5.7"><b> 7.28.4.5.7 The wcstok function</b></a>
17267 1 #include <a href="#7.28"><wchar.h></a>
17268 wchar_t *wcstok(wchar_t * restrict s1,
17269 const wchar_t * restrict s2,
17270 wchar_t ** restrict ptr);
17271 <b> Description</b>
17272 2 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
17273 a sequence of tokens, each of which is delimited by a wide character from the wide string
17274 pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
17275 which the wcstok function stores information necessary for it to continue scanning the
17277 3 The first call in a sequence has a non-null first argument and stores an initial value in the
17278 object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
17279 the object pointed to by ptr is required to have the value stored by the previous call in
17280 the sequence, which is then updated. The separator wide string pointed to by s2 may be
17281 different from call to call.
17282 4 The first call in the sequence searches the wide string pointed to by s1 for the first wide
17283 character that is not contained in the current separator wide string pointed to by s2. If no
17284 such wide character is found, then there are no tokens in the wide string pointed to by s1
17285 and the wcstok function returns a null pointer. If such a wide character is found, it is
17286 the start of the first token.
17287 5 The wcstok function then searches from there for a wide character that is contained in
17288 the current separator wide string. If no such wide character is found, the current token
17289 [<a name="p434" href="#p434">page 434</a>] (<a href="#Contents">Contents</a>)
17291 extends to the end of the wide string pointed to by s1, and subsequent searches in the
17292 same wide string for a token return a null pointer. If such a wide character is found, it is
17293 overwritten by a null wide character, which terminates the current token.
17294 6 In all cases, the wcstok function stores sufficient information in the pointer pointed to
17295 by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
17296 value for ptr, shall start searching just past the element overwritten by a null wide
17297 character (if any).
17299 7 The wcstok function returns a pointer to the first wide character of a token, or a null
17300 pointer if there is no token.
17302 #include <a href="#7.28"><wchar.h></a>
17303 static wchar_t str1[] = L"?a???b,,,#c";
17304 static wchar_t str2[] = L"\t \t";
17305 wchar_t *t, *ptr1, *ptr2;
17306 t = wcstok(str1, L"?", &ptr1); // t points to the token L"a"
17307 t = wcstok(NULL, L",", &ptr1); // t points to the token L"??b"
17308 t = wcstok(str2, L" \t", &ptr2); // t is a null pointer
17309 t = wcstok(NULL, L"#,", &ptr1); // t points to the token L"c"
17310 t = wcstok(NULL, L"?", &ptr1); // t is a null pointer
17312 <a name="7.28.4.5.8" href="#7.28.4.5.8"><b> 7.28.4.5.8 The wmemchr function</b></a>
17314 1 #include <a href="#7.28"><wchar.h></a>
17315 wchar_t *wmemchr(const wchar_t *s, wchar_t c,
17317 <b> Description</b>
17318 2 The wmemchr function locates the first occurrence of c in the initial n wide characters of
17319 the object pointed to by s.
17321 3 The wmemchr function returns a pointer to the located wide character, or a null pointer if
17322 the wide character does not occur in the object.
17327 [<a name="p435" href="#p435">page 435</a>] (<a href="#Contents">Contents</a>)
17329 <a name="7.28.4.6" href="#7.28.4.6"><b> 7.28.4.6 Miscellaneous functions</b></a>
17330 <a name="7.28.4.6.1" href="#7.28.4.6.1"><b> 7.28.4.6.1 The wcslen function</b></a>
17332 1 #include <a href="#7.28"><wchar.h></a>
17333 size_t wcslen(const wchar_t *s);
17334 <b> Description</b>
17335 2 The wcslen function computes the length of the wide string pointed to by s.
17337 3 The wcslen function returns the number of wide characters that precede the terminating
17338 null wide character.
17339 <a name="7.28.4.6.2" href="#7.28.4.6.2"><b> 7.28.4.6.2 The wmemset function</b></a>
17341 1 #include <a href="#7.28"><wchar.h></a>
17342 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
17343 <b> Description</b>
17344 2 The wmemset function copies the value of c into each of the first n wide characters of
17345 the object pointed to by s.
17347 3 The wmemset function returns the value of s.
17348 <a name="7.28.5" href="#7.28.5"><b> 7.28.5 Wide character time conversion functions</b></a>
17349 <a name="7.28.5.1" href="#7.28.5.1"><b> 7.28.5.1 The wcsftime function</b></a>
17351 1 #include <a href="#7.26"><time.h></a>
17352 #include <a href="#7.28"><wchar.h></a>
17353 size_t wcsftime(wchar_t * restrict s,
17355 const wchar_t * restrict format,
17356 const struct tm * restrict timeptr);
17357 <b> Description</b>
17358 2 The wcsftime function is equivalent to the strftime function, except that:
17359 -- The argument s points to the initial element of an array of wide characters into which
17360 the generated output is to be placed.
17363 [<a name="p436" href="#p436">page 436</a>] (<a href="#Contents">Contents</a>)
17365 -- The argument maxsize indicates the limiting number of wide characters.
17366 -- The argument format is a wide string and the conversion specifiers are replaced by
17367 corresponding sequences of wide characters.
17368 -- The return value indicates the number of wide characters.
17370 3 If the total number of resulting wide characters including the terminating null wide
17371 character is not more than maxsize, the wcsftime function returns the number of
17372 wide characters placed into the array pointed to by s not including the terminating null
17373 wide character. Otherwise, zero is returned and the contents of the array are
17375 <a name="7.28.6" href="#7.28.6"><b> 7.28.6 Extended multibyte/wide character conversion utilities</b></a>
17376 1 The header <a href="#7.28"><wchar.h></a> declares an extended set of functions useful for conversion
17377 between multibyte characters and wide characters.
17378 2 Most of the following functions -- those that are listed as ''restartable'', <a href="#7.28.6.3">7.28.6.3</a> and
17379 <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
17380 to describe the current conversion state from a particular multibyte character sequence to
17381 a wide character sequence (or the reverse) under the rules of a particular setting for the
17382 LC_CTYPE category of the current locale.
17383 3 The initial conversion state corresponds, for a conversion in either direction, to the
17384 beginning of a new multibyte character in the initial shift state. A zero-valued
17385 mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
17386 valued mbstate_t object can be used to initiate conversion involving any multibyte
17387 character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
17388 been altered by any of the functions described in this subclause, and is then used with a
17389 different multibyte character sequence, or in the other conversion direction, or with a
17390 different LC_CTYPE category setting than on earlier function calls, the behavior is
17391 undefined.<sup><a href="#note335"><b>335)</b></a></sup>
17392 4 On entry, each function takes the described conversion state (either internal or pointed to
17393 by an argument) as current. The conversion state described by the referenced object is
17394 altered as needed to track the shift state, and the position within a multibyte character, for
17395 the associated multibyte character sequence.
17400 <sup><a name="note335" href="#note335"><b>335)</b></a></sup> Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and
17401 mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
17404 [<a name="p437" href="#p437">page 437</a>] (<a href="#Contents">Contents</a>)
17406 <a name="7.28.6.1" href="#7.28.6.1"><b> 7.28.6.1 Single-byte/wide character conversion functions</b></a>
17407 <a name="7.28.6.1.1" href="#7.28.6.1.1"><b> 7.28.6.1.1 The btowc function</b></a>
17409 1 #include <a href="#7.28"><wchar.h></a> *
17410 wint_t btowc(int c);
17411 <b> Description</b>
17412 2 The btowc function determines whether c constitutes a valid single-byte character in the
17413 initial shift state.
17415 3 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
17416 does not constitute a valid single-byte character in the initial shift state. Otherwise, it
17417 returns the wide character representation of that character.
17418 <a name="7.28.6.1.2" href="#7.28.6.1.2"><b> 7.28.6.1.2 The wctob function</b></a>
17420 1 #include <a href="#7.28"><wchar.h></a> *
17421 int wctob(wint_t c);
17422 <b> Description</b>
17423 2 The wctob function determines whether c corresponds to a member of the extended
17424 character set whose multibyte character representation is a single byte when in the initial
17427 3 The wctob function returns EOF if c does not correspond to a multibyte character with
17428 length one in the initial shift state. Otherwise, it returns the single-byte representation of
17429 that character as an unsigned char converted to an int.
17430 <a name="7.28.6.2" href="#7.28.6.2"><b> 7.28.6.2 Conversion state functions</b></a>
17431 <a name="7.28.6.2.1" href="#7.28.6.2.1"><b> 7.28.6.2.1 The mbsinit function</b></a>
17433 1 #include <a href="#7.28"><wchar.h></a>
17434 int mbsinit(const mbstate_t *ps);
17435 <b> Description</b>
17436 2 If ps is not a null pointer, the mbsinit function determines whether the referenced
17437 mbstate_t object describes an initial conversion state.
17441 [<a name="p438" href="#p438">page 438</a>] (<a href="#Contents">Contents</a>)
17444 3 The mbsinit function returns nonzero if ps is a null pointer or if the referenced object
17445 describes an initial conversion state; otherwise, it returns zero.
17446 <a name="7.28.6.3" href="#7.28.6.3"><b> 7.28.6.3 Restartable multibyte/wide character conversion functions</b></a>
17447 1 These functions differ from the corresponding multibyte character functions of <a href="#7.22.7">7.22.7</a>
17448 (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type
17449 pointer to mbstate_t that points to an object that can completely describe the current
17450 conversion state of the associated multibyte character sequence. If ps is a null pointer,
17451 each function uses its own internal mbstate_t object instead, which is initialized at
17452 program startup to the initial conversion state; the functions are not required to avoid data
17453 races in this case. The implementation behaves as if no library function calls these
17454 functions with a null pointer for ps.
17455 2 Also unlike their corresponding functions, the return value does not represent whether the
17456 encoding is state-dependent.
17457 <a name="7.28.6.3.1" href="#7.28.6.3.1"><b> 7.28.6.3.1 The mbrlen function</b></a>
17459 1 #include <a href="#7.28"><wchar.h></a>
17460 size_t mbrlen(const char * restrict s,
17462 mbstate_t * restrict ps);
17463 <b> Description</b>
17464 2 The mbrlen function is equivalent to the call:
17465 mbrtowc(NULL, s, n, ps != NULL ? ps : &internal)
17466 where internal is the mbstate_t object for the mbrlen function, except that the
17467 expression designated by ps is evaluated only once.
17469 3 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
17471 Forward references: the mbrtowc function (<a href="#7.28.6.3.2">7.28.6.3.2</a>).
17476 [<a name="p439" href="#p439">page 439</a>] (<a href="#Contents">Contents</a>)
17478 <a name="7.28.6.3.2" href="#7.28.6.3.2"><b> 7.28.6.3.2 The mbrtowc function</b></a>
17480 1 #include <a href="#7.28"><wchar.h></a>
17481 size_t mbrtowc(wchar_t * restrict pwc,
17482 const char * restrict s,
17484 mbstate_t * restrict ps);
17485 <b> Description</b>
17486 2 If s is a null pointer, the mbrtowc function is equivalent to the call:
17487 mbrtowc(NULL, "", 1, ps)
17488 In this case, the values of the parameters pwc and n are ignored.
17489 3 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with
17490 the byte pointed to by s to determine the number of bytes needed to complete the next
17491 multibyte character (including any shift sequences). If the function determines that the
17492 next multibyte character is complete and valid, it determines the value of the
17493 corresponding wide character and then, if pwc is not a null pointer, stores that value in
17494 the object pointed to by pwc. If the corresponding wide character is the null wide
17495 character, the resulting state described is the initial conversion state.
17497 4 The mbrtowc function returns the first of the following that applies (given the current
17499 0 if the next n or fewer bytes complete the multibyte character that
17500 corresponds to the null wide character (which is the value stored).
17501 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
17502 character (which is the value stored); the value returned is the number
17503 of bytes that complete the multibyte character.
17504 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
17505 multibyte character, and all n bytes have been processed (no value is
17506 stored).<sup><a href="#note336"><b>336)</b></a></sup>
17507 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
17508 do not contribute to a complete and valid multibyte character (no
17509 value is stored); the value of the macro EILSEQ is stored in errno,
17510 and the conversion state is unspecified.
17512 <sup><a name="note336" href="#note336"><b>336)</b></a></sup> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
17513 sequence of redundant shift sequences (for implementations with state-dependent encodings).
17515 [<a name="p440" href="#p440">page 440</a>] (<a href="#Contents">Contents</a>)
17517 <a name="7.28.6.3.3" href="#7.28.6.3.3"><b> 7.28.6.3.3 The wcrtomb function</b></a>
17519 1 #include <a href="#7.28"><wchar.h></a>
17520 size_t wcrtomb(char * restrict s,
17522 mbstate_t * restrict ps);
17523 <b> Description</b>
17524 2 If s is a null pointer, the wcrtomb function is equivalent to the call
17525 wcrtomb(buf, L'\0', ps)
17526 where buf is an internal buffer.
17527 3 If s is not a null pointer, the wcrtomb function determines the number of bytes needed
17528 to represent the multibyte character that corresponds to the wide character given by wc
17529 (including any shift sequences), and stores the multibyte character representation in the
17530 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
17531 wc is a null wide character, a null byte is stored, preceded by any shift sequence needed
17532 to restore the initial shift state; the resulting state described is the initial conversion state.
17534 4 The wcrtomb function returns the number of bytes stored in the array object (including
17535 any shift sequences). When wc is not a valid wide character, an encoding error occurs:
17536 the function stores the value of the macro EILSEQ in errno and returns
17537 (size_t)(-1); the conversion state is unspecified.
17538 <a name="7.28.6.4" href="#7.28.6.4"><b> 7.28.6.4 Restartable multibyte/wide string conversion functions</b></a>
17539 1 These functions differ from the corresponding multibyte string functions of <a href="#7.22.8">7.22.8</a>
17540 (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to
17541 mbstate_t that points to an object that can completely describe the current conversion
17542 state of the associated multibyte character sequence. If ps is a null pointer, each function
17543 uses its own internal mbstate_t object instead, which is initialized at program startup
17544 to the initial conversion state; the functions are not required to avoid data races in this
17545 case. The implementation behaves as if no library function calls these functions with a
17546 null pointer for ps.
17547 2 Also unlike their corresponding functions, the conversion source parameter, src, has a
17548 pointer-to-pointer type. When the function is storing the results of conversions (that is,
17549 when dst is not a null pointer), the pointer object pointed to by this parameter is updated
17550 to reflect the amount of the source processed by that invocation.
17555 [<a name="p441" href="#p441">page 441</a>] (<a href="#Contents">Contents</a>)
17557 <a name="7.28.6.4.1" href="#7.28.6.4.1"><b> 7.28.6.4.1 The mbsrtowcs function</b></a>
17559 1 #include <a href="#7.28"><wchar.h></a>
17560 size_t mbsrtowcs(wchar_t * restrict dst,
17561 const char ** restrict src,
17563 mbstate_t * restrict ps);
17564 <b> Description</b>
17565 2 The mbsrtowcs function converts a sequence of multibyte characters that begins in the
17566 conversion state described by the object pointed to by ps, from the array indirectly
17567 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
17568 pointer, the converted characters are stored into the array pointed to by dst. Conversion
17569 continues up to and including a terminating null character, which is also stored.
17570 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
17571 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
17572 characters have been stored into the array pointed to by dst.<sup><a href="#note337"><b>337)</b></a></sup> Each conversion takes
17573 place as if by a call to the mbrtowc function.
17574 3 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
17575 pointer (if conversion stopped due to reaching a terminating null character) or the address
17576 just past the last multibyte character converted (if any). If conversion stopped due to
17577 reaching a terminating null character and if dst is not a null pointer, the resulting state
17578 described is the initial conversion state.
17580 4 If the input conversion encounters a sequence of bytes that do not form a valid multibyte
17581 character, an encoding error occurs: the mbsrtowcs function stores the value of the
17582 macro EILSEQ in errno and returns (size_t)(-1); the conversion state is
17583 unspecified. Otherwise, it returns the number of multibyte characters successfully
17584 converted, not including the terminating null character (if any).
17589 <sup><a name="note337" href="#note337"><b>337)</b></a></sup> Thus, the value of len is ignored if dst is a null pointer.
17591 [<a name="p442" href="#p442">page 442</a>] (<a href="#Contents">Contents</a>)
17593 <a name="7.28.6.4.2" href="#7.28.6.4.2"><b> 7.28.6.4.2 The wcsrtombs function</b></a>
17595 1 #include <a href="#7.28"><wchar.h></a>
17596 size_t wcsrtombs(char * restrict dst,
17597 const wchar_t ** restrict src,
17599 mbstate_t * restrict ps);
17600 <b> Description</b>
17601 2 The wcsrtombs function converts a sequence of wide characters from the array
17602 indirectly pointed to by src into a sequence of corresponding multibyte characters that
17603 begins in the conversion state described by the object pointed to by ps. If dst is not a
17604 null pointer, the converted characters are then stored into the array pointed to by dst.
17605 Conversion continues up to and including a terminating null wide character, which is also
17606 stored. Conversion stops earlier in two cases: when a wide character is reached that does
17607 not correspond to a valid multibyte character, or (if dst is not a null pointer) when the
17608 next multibyte character would exceed the limit of len total bytes to be stored into the
17609 array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb
17610 function.<sup><a href="#note338"><b>338)</b></a></sup>
17611 3 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
17612 pointer (if conversion stopped due to reaching a terminating null wide character) or the
17613 address just past the last wide character converted (if any). If conversion stopped due to
17614 reaching a terminating null wide character, the resulting state described is the initial
17617 4 If conversion stops because a wide character is reached that does not correspond to a
17618 valid multibyte character, an encoding error occurs: the wcsrtombs function stores the
17619 value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion
17620 state is unspecified. Otherwise, it returns the number of bytes in the resulting multibyte
17621 character sequence, not including the terminating null character (if any).
17626 <sup><a name="note338" href="#note338"><b>338)</b></a></sup> If conversion stops because a terminating null wide character has been reached, the bytes stored
17627 include those necessary to reach the initial shift state immediately before the null byte.
17629 [<a name="p443" href="#p443">page 443</a>] (<a href="#Contents">Contents</a>)
17631 <a name="7.29" href="#7.29"><b> 7.29 Wide character classification and mapping utilities <wctype.h></b></a>
17632 <a name="7.29.1" href="#7.29.1"><b> 7.29.1 Introduction</b></a>
17633 1 The header <a href="#7.29"><wctype.h></a> defines one macro, and declares three data types and many
17634 functions.<sup><a href="#note339"><b>339)</b></a></sup>
17635 2 The types declared are
17637 described in <a href="#7.28.1">7.28.1</a>;
17639 which is a scalar type that can hold values which represent locale-specific character
17642 which is a scalar type that can hold values which represent locale-specific character
17644 3 The macro defined is WEOF (described in <a href="#7.28.1">7.28.1</a>).
17645 4 The functions declared are grouped as follows:
17646 -- Functions that provide wide character classification;
17647 -- Extensible functions that provide wide character classification;
17648 -- Functions that provide wide character case mapping;
17649 -- Extensible functions that provide wide character mapping.
17650 5 For all functions described in this subclause that accept an argument of type wint_t, the
17651 value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If
17652 this argument has any other value, the behavior is undefined.
17653 6 The behavior of these functions is affected by the LC_CTYPE category of the current
17659 <sup><a name="note339" href="#note339"><b>339)</b></a></sup> See ''future library directions'' (<a href="#7.30.13">7.30.13</a>).
17661 [<a name="p444" href="#p444">page 444</a>] (<a href="#Contents">Contents</a>)
17663 <a name="7.29.2" href="#7.29.2"><b> 7.29.2 Wide character classification utilities</b></a>
17664 1 The header <a href="#7.29"><wctype.h></a> declares several functions useful for classifying wide
17666 2 The term printing wide character refers to a member of a locale-specific set of wide
17667 characters, each of which occupies at least one printing position on a display device. The
17668 term control wide character refers to a member of a locale-specific set of wide characters
17669 that are not printing wide characters.
17670 <a name="7.29.2.1" href="#7.29.2.1"><b> 7.29.2.1 Wide character classification functions</b></a>
17671 1 The functions in this subclause return nonzero (true) if and only if the value of the
17672 argument wc conforms to that in the description of the function.
17673 2 Each of the following functions returns true for each wide character that corresponds (as
17674 if by a call to the wctob function) to a single-byte character for which the corresponding
17675 character classification function from <a href="#7.4.1">7.4.1</a> returns true, except that the iswgraph and
17676 iswpunct functions may differ with respect to wide characters other than L' ' that are
17677 both printing and white-space wide characters.<sup><a href="#note340"><b>340)</b></a></sup>
17678 Forward references: the wctob function (<a href="#7.28.6.1.2">7.28.6.1.2</a>).
17679 <a name="7.29.2.1.1" href="#7.29.2.1.1"><b> 7.29.2.1.1 The iswalnum function</b></a>
17681 1 #include <a href="#7.29"><wctype.h></a>
17682 int iswalnum(wint_t wc);
17683 <b> Description</b>
17684 2 The iswalnum function tests for any wide character for which iswalpha or
17686 <a name="7.29.2.1.2" href="#7.29.2.1.2"><b> 7.29.2.1.2 The iswalpha function</b></a>
17688 1 #include <a href="#7.29"><wctype.h></a>
17689 int iswalpha(wint_t wc);
17690 <b> Description</b>
17691 2 The iswalpha function tests for any wide character for which iswupper or
17692 iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
17694 <sup><a name="note340" href="#note340"><b>340)</b></a></sup> For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call
17695 iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true
17696 (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc)
17697 && iswspace(wc) is true, but not both.
17699 [<a name="p445" href="#p445">page 445</a>] (<a href="#Contents">Contents</a>)
17701 wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
17702 is true.<sup><a href="#note341"><b>341)</b></a></sup>
17703 <a name="7.29.2.1.3" href="#7.29.2.1.3"><b> 7.29.2.1.3 The iswblank function</b></a>
17705 1 #include <a href="#7.29"><wctype.h></a>
17706 int iswblank(wint_t wc);
17707 <b> Description</b>
17708 2 The iswblank function tests for any wide character that is a standard blank wide
17709 character or is one of a locale-specific set of wide characters for which iswspace is true
17710 and that is used to separate words within a line of text. The standard blank wide
17711 characters are the following: space (L' '), and horizontal tab (L'\t'). In the "C"
17712 locale, iswblank returns true only for the standard blank characters.
17713 <a name="7.29.2.1.4" href="#7.29.2.1.4"><b> 7.29.2.1.4 The iswcntrl function</b></a>
17715 1 #include <a href="#7.29"><wctype.h></a>
17716 int iswcntrl(wint_t wc);
17717 <b> Description</b>
17718 2 The iswcntrl function tests for any control wide character.
17719 <a name="7.29.2.1.5" href="#7.29.2.1.5"><b> 7.29.2.1.5 The iswdigit function</b></a>
17721 1 #include <a href="#7.29"><wctype.h></a>
17722 int iswdigit(wint_t wc);
17723 <b> Description</b>
17724 2 The iswdigit function tests for any wide character that corresponds to a decimal-digit
17725 character (as defined in <a href="#5.2.1">5.2.1</a>).
17726 <a name="7.29.2.1.6" href="#7.29.2.1.6"><b> 7.29.2.1.6 The iswgraph function</b></a>
17728 1 #include <a href="#7.29"><wctype.h></a>
17729 int iswgraph(wint_t wc);
17734 <sup><a name="note341" href="#note341"><b>341)</b></a></sup> The functions iswlower and iswupper test true or false separately for each of these additional
17735 wide characters; all four combinations are possible.
17737 [<a name="p446" href="#p446">page 446</a>] (<a href="#Contents">Contents</a>)
17739 <b> Description</b>
17740 2 The iswgraph function tests for any wide character for which iswprint is true and
17741 iswspace is false.<sup><a href="#note342"><b>342)</b></a></sup>
17742 <a name="7.29.2.1.7" href="#7.29.2.1.7"><b> 7.29.2.1.7 The iswlower function</b></a>
17744 1 #include <a href="#7.29"><wctype.h></a>
17745 int iswlower(wint_t wc);
17746 <b> Description</b>
17747 2 The iswlower function tests for any wide character that corresponds to a lowercase
17748 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
17749 iswdigit, iswpunct, or iswspace is true.
17750 <a name="7.29.2.1.8" href="#7.29.2.1.8"><b> 7.29.2.1.8 The iswprint function</b></a>
17752 1 #include <a href="#7.29"><wctype.h></a>
17753 int iswprint(wint_t wc);
17754 <b> Description</b>
17755 2 The iswprint function tests for any printing wide character.
17756 <a name="7.29.2.1.9" href="#7.29.2.1.9"><b> 7.29.2.1.9 The iswpunct function</b></a>
17758 1 #include <a href="#7.29"><wctype.h></a>
17759 int iswpunct(wint_t wc);
17760 <b> Description</b>
17761 2 The iswpunct function tests for any printing wide character that is one of a locale-
17762 specific set of punctuation wide characters for which neither iswspace nor iswalnum
17764 <a name="7.29.2.1.10" href="#7.29.2.1.10"><b> 7.29.2.1.10 The iswspace function</b></a>
17766 1 #include <a href="#7.29"><wctype.h></a>
17767 int iswspace(wint_t wc);
17771 <sup><a name="note342" href="#note342"><b>342)</b></a></sup> Note that the behavior of the iswgraph and iswpunct functions may differ from their
17772 corresponding functions in <a href="#7.4.1">7.4.1</a> with respect to printing, white-space, single-byte execution
17773 characters other than ' '.
17775 [<a name="p447" href="#p447">page 447</a>] (<a href="#Contents">Contents</a>)
17777 <b> Description</b>
17778 2 The iswspace function tests for any wide character that corresponds to a locale-specific
17779 set of white-space wide characters for which none of iswalnum, iswgraph, or
17781 <a name="7.29.2.1.11" href="#7.29.2.1.11"><b> 7.29.2.1.11 The iswupper function</b></a>
17783 1 #include <a href="#7.29"><wctype.h></a>
17784 int iswupper(wint_t wc);
17785 <b> Description</b>
17786 2 The iswupper function tests for any wide character that corresponds to an uppercase
17787 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
17788 iswdigit, iswpunct, or iswspace is true.
17789 <a name="7.29.2.1.12" href="#7.29.2.1.12"><b> 7.29.2.1.12 The iswxdigit function</b></a>
17791 1 #include <a href="#7.29"><wctype.h></a>
17792 int iswxdigit(wint_t wc);
17793 <b> Description</b>
17794 2 The iswxdigit function tests for any wide character that corresponds to a
17795 hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
17796 <a name="7.29.2.2" href="#7.29.2.2"><b> 7.29.2.2 Extensible wide character classification functions</b></a>
17797 1 The functions wctype and iswctype provide extensible wide character classification
17798 as well as testing equivalent to that performed by the functions described in the previous
17799 subclause (<a href="#7.29.2.1">7.29.2.1</a>).
17800 <a name="7.29.2.2.1" href="#7.29.2.2.1"><b> 7.29.2.2.1 The iswctype function</b></a>
17802 1 #include <a href="#7.29"><wctype.h></a>
17803 int iswctype(wint_t wc, wctype_t desc);
17804 <b> Description</b>
17805 2 The iswctype function determines whether the wide character wc has the property
17806 described by desc. The current setting of the LC_CTYPE category shall be the same as
17807 during the call to wctype that returned the value desc.
17808 3 Each of the following expressions has a truth-value equivalent to the call to the wide
17809 character classification function (<a href="#7.29.2.1">7.29.2.1</a>) in the comment that follows the expression:
17812 [<a name="p448" href="#p448">page 448</a>] (<a href="#Contents">Contents</a>)
17814 iswctype(wc, wctype("alnum")) // iswalnum(wc)
17815 iswctype(wc, wctype("alpha")) // iswalpha(wc)
17816 iswctype(wc, wctype("blank")) // iswblank(wc)
17817 iswctype(wc, wctype("cntrl")) // iswcntrl(wc)
17818 iswctype(wc, wctype("digit")) // iswdigit(wc)
17819 iswctype(wc, wctype("graph")) // iswgraph(wc)
17820 iswctype(wc, wctype("lower")) // iswlower(wc)
17821 iswctype(wc, wctype("print")) // iswprint(wc)
17822 iswctype(wc, wctype("punct")) // iswpunct(wc)
17823 iswctype(wc, wctype("space")) // iswspace(wc)
17824 iswctype(wc, wctype("upper")) // iswupper(wc)
17825 iswctype(wc, wctype("xdigit")) // iswxdigit(wc)
17827 4 The iswctype function returns nonzero (true) if and only if the value of the wide
17828 character wc has the property described by desc. If desc is zero, the iswctype
17829 function returns zero (false).
17830 Forward references: the wctype function (<a href="#7.29.2.2.2">7.29.2.2.2</a>).
17831 <a name="7.29.2.2.2" href="#7.29.2.2.2"><b> 7.29.2.2.2 The wctype function</b></a>
17833 1 #include <a href="#7.29"><wctype.h></a>
17834 wctype_t wctype(const char *property);
17835 <b> Description</b>
17836 2 The wctype function constructs a value with type wctype_t that describes a class of
17837 wide characters identified by the string argument property.
17838 3 The strings listed in the description of the iswctype function shall be valid in all
17839 locales as property arguments to the wctype function.
17841 4 If property identifies a valid class of wide characters according to the LC_CTYPE
17842 category of the current locale, the wctype function returns a nonzero value that is valid
17843 as the second argument to the iswctype function; otherwise, it returns zero.
17848 [<a name="p449" href="#p449">page 449</a>] (<a href="#Contents">Contents</a>)
17850 <a name="7.29.3" href="#7.29.3"><b> 7.29.3 Wide character case mapping utilities</b></a>
17851 1 The header <a href="#7.29"><wctype.h></a> declares several functions useful for mapping wide characters.
17852 <a name="7.29.3.1" href="#7.29.3.1"><b> 7.29.3.1 Wide character case mapping functions</b></a>
17853 <a name="7.29.3.1.1" href="#7.29.3.1.1"><b> 7.29.3.1.1 The towlower function</b></a>
17855 1 #include <a href="#7.29"><wctype.h></a>
17856 wint_t towlower(wint_t wc);
17857 <b> Description</b>
17858 2 The towlower function converts an uppercase letter to a corresponding lowercase letter.
17860 3 If the argument is a wide character for which iswupper is true and there are one or
17861 more corresponding wide characters, as specified by the current locale, for which
17862 iswlower is true, the towlower function returns one of the corresponding wide
17863 characters (always the same one for any given locale); otherwise, the argument is
17864 returned unchanged.
17865 <a name="7.29.3.1.2" href="#7.29.3.1.2"><b> 7.29.3.1.2 The towupper function</b></a>
17867 1 #include <a href="#7.29"><wctype.h></a>
17868 wint_t towupper(wint_t wc);
17869 <b> Description</b>
17870 2 The towupper function converts a lowercase letter to a corresponding uppercase letter.
17872 3 If the argument is a wide character for which iswlower is true and there are one or
17873 more corresponding wide characters, as specified by the current locale, for which
17874 iswupper is true, the towupper function returns one of the corresponding wide
17875 characters (always the same one for any given locale); otherwise, the argument is
17876 returned unchanged.
17877 <a name="7.29.3.2" href="#7.29.3.2"><b> 7.29.3.2 Extensible wide character case mapping functions</b></a>
17878 1 The functions wctrans and towctrans provide extensible wide character mapping as
17879 well as case mapping equivalent to that performed by the functions described in the
17880 previous subclause (<a href="#7.29.3.1">7.29.3.1</a>).
17885 [<a name="p450" href="#p450">page 450</a>] (<a href="#Contents">Contents</a>)
17887 <a name="7.29.3.2.1" href="#7.29.3.2.1"><b> 7.29.3.2.1 The towctrans function</b></a>
17889 1 #include <a href="#7.29"><wctype.h></a>
17890 wint_t towctrans(wint_t wc, wctrans_t desc);
17891 <b> Description</b>
17892 2 The towctrans function maps the wide character wc using the mapping described by
17893 desc. The current setting of the LC_CTYPE category shall be the same as during the call
17894 to wctrans that returned the value desc.
17895 3 Each of the following expressions behaves the same as the call to the wide character case
17896 mapping function (<a href="#7.29.3.1">7.29.3.1</a>) in the comment that follows the expression:
17897 towctrans(wc, wctrans("tolower")) // towlower(wc)
17898 towctrans(wc, wctrans("toupper")) // towupper(wc)
17900 4 The towctrans function returns the mapped value of wc using the mapping described
17901 by desc. If desc is zero, the towctrans function returns the value of wc.
17902 <a name="7.29.3.2.2" href="#7.29.3.2.2"><b> 7.29.3.2.2 The wctrans function</b></a>
17904 1 #include <a href="#7.29"><wctype.h></a>
17905 wctrans_t wctrans(const char *property);
17906 <b> Description</b>
17907 2 The wctrans function constructs a value with type wctrans_t that describes a
17908 mapping between wide characters identified by the string argument property.
17909 3 The strings listed in the description of the towctrans function shall be valid in all
17910 locales as property arguments to the wctrans function.
17912 4 If property identifies a valid mapping of wide characters according to the LC_CTYPE
17913 category of the current locale, the wctrans function returns a nonzero value that is valid
17914 as the second argument to the towctrans function; otherwise, it returns zero.
17919 [<a name="p451" href="#p451">page 451</a>] (<a href="#Contents">Contents</a>)
17921 <a name="7.30" href="#7.30"><b> 7.30 Future library directions</b></a>
17922 1 The following names are grouped under individual headers for convenience. All external
17923 names described below are reserved no matter what headers are included by the program.
17924 <a name="7.30.1" href="#7.30.1"><b> 7.30.1 Complex arithmetic <complex.h></b></a>
17925 1 The function names
17927 cerfc clog10 clgamma
17928 cexp2 clog1p ctgamma
17929 and the same names suffixed with f or l may be added to the declarations in the
17930 <a href="#7.3"><complex.h></a> header.
17931 <a name="7.30.2" href="#7.30.2"><b> 7.30.2 Character handling <ctype.h></b></a>
17932 1 Function names that begin with either is or to, and a lowercase letter may be added to
17933 the declarations in the <a href="#7.4"><ctype.h></a> header.
17934 <a name="7.30.3" href="#7.30.3"><b> 7.30.3 Errors <errno.h></b></a>
17935 1 Macros that begin with E and a digit or E and an uppercase letter may be added to the
17936 declarations in the <a href="#7.5"><errno.h></a> header.
17937 <a name="7.30.4" href="#7.30.4"><b> 7.30.4 Format conversion of integer types <inttypes.h></b></a>
17938 1 Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
17939 added to the macros defined in the <a href="#7.8"><inttypes.h></a> header.
17940 <a name="7.30.5" href="#7.30.5"><b> 7.30.5 Localization <locale.h></b></a>
17941 1 Macros that begin with LC_ and an uppercase letter may be added to the definitions in
17942 the <a href="#7.11"><locale.h></a> header.
17943 <a name="7.30.6" href="#7.30.6"><b> 7.30.6 Signal handling <signal.h></b></a>
17944 1 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
17945 letter may be added to the definitions in the <a href="#7.14"><signal.h></a> header.
17946 <a name="7.30.7" href="#7.30.7"><b> 7.30.7 Boolean type and values <stdbool.h></b></a>
17947 1 The ability to undefine and perhaps then redefine the macros bool, true, and false is
17948 an obsolescent feature.
17949 <a name="7.30.8" href="#7.30.8"><b> 7.30.8 Integer types <stdint.h></b></a>
17950 1 Typedef names beginning with int or uint and ending with _t may be added to the
17951 types defined in the <a href="#7.20"><stdint.h></a> header. Macro names beginning with INT or UINT
17952 and ending with _MAX, _MIN, or _C may be added to the macros defined in the
17953 <a href="#7.20"><stdint.h></a> header.
17955 [<a name="p452" href="#p452">page 452</a>] (<a href="#Contents">Contents</a>)
17957 <a name="7.30.9" href="#7.30.9"><b> 7.30.9 Input/output <stdio.h></b></a>
17958 1 Lowercase letters may be added to the conversion specifiers and length modifiers in
17959 fprintf and fscanf. Other characters may be used in extensions.
17960 2 The use of ungetc on a binary stream where the file position indicator is zero prior to *
17961 the call is an obsolescent feature.
17962 <a name="7.30.10" href="#7.30.10"><b> 7.30.10 General utilities <stdlib.h></b></a>
17963 1 Function names that begin with str and a lowercase letter may be added to the
17964 declarations in the <a href="#7.22"><stdlib.h></a> header.
17965 <a name="7.30.11" href="#7.30.11"><b> 7.30.11 String handling <string.h></b></a>
17966 1 Function names that begin with str, mem, or wcs and a lowercase letter may be added
17967 to the declarations in the <a href="#7.23"><string.h></a> header.
17968 <a name="7.30.12" href="#7.30.12"><b> 7.30.12 Extended multibyte and wide character utilities <wchar.h></b></a>
17969 1 Function names that begin with wcs and a lowercase letter may be added to the
17970 declarations in the <a href="#7.28"><wchar.h></a> header.
17971 2 Lowercase letters may be added to the conversion specifiers and length modifiers in
17972 fwprintf and fwscanf. Other characters may be used in extensions.
17973 <a name="7.30.13" href="#7.30.13"><b> 7.30.13 Wide character classification and mapping utilities</b></a>
17974 <a href="#7.29"><wctype.h></a>
17975 1 Function names that begin with is or to and a lowercase letter may be added to the
17976 declarations in the <a href="#7.29"><wctype.h></a> header.
17981 [<a name="p453" href="#p453">page 453</a>] (<a href="#Contents">Contents</a>)
17983 <a name="A" href="#A"><b> Annex A</b></a>
17985 Language syntax summary
17986 1 NOTE The notation is described in <a href="#6.1">6.1</a>.
17988 <a name="A.1" href="#A.1"><b> A.1 Lexical grammar</b></a>
17989 <a name="A.1.1" href="#A.1.1"><b> A.1.1 Lexical elements</b></a>
17990 (<a href="#6.4">6.4</a>) token:
17996 (<a href="#6.4">6.4</a>) preprocessing-token:
18003 each non-white-space character that cannot be one of the above
18008 [<a name="p454" href="#p454">page 454</a>] (<a href="#Contents">Contents</a>)
18010 <a name="A.1.2" href="#A.1.2"><b>A.1.2 Keywords</b></a>
18011 (<a href="#6.4.1">6.4.1</a>) keyword: one of
18017 const register _Alignas
18018 continue restrict _Atomic
18019 default return _Bool
18021 double signed _Generic
18022 else sizeof _Imaginary
18023 enum static _Noreturn
18024 extern struct _Static_assert
18025 float switch _Thread_local
18027 <a name="A.1.3" href="#A.1.3"><b>A.1.3 Identifiers</b></a>
18028 (<a href="#6.4.2.1">6.4.2.1</a>) identifier:
18029 identifier-nondigit
18030 identifier identifier-nondigit
18032 (<a href="#6.4.2.1">6.4.2.1</a>) identifier-nondigit:
18034 universal-character-name
18035 other implementation-defined characters
18036 (<a href="#6.4.2.1">6.4.2.1</a>) nondigit: one of
18037 _ a b c d e f g h i j k l m
18038 n o p q r s t u v w x y z
18039 A B C D E F G H I J K L M
18040 N O P Q R S T U V W X Y Z
18041 (<a href="#6.4.2.1">6.4.2.1</a>) digit: one of
18042 0 1 2 3 4 5 6 7 8 9
18047 [<a name="p455" href="#p455">page 455</a>] (<a href="#Contents">Contents</a>)
18049 <a name="A.1.4" href="#A.1.4"><b>A.1.4 Universal character names</b></a>
18050 (<a href="#6.4.3">6.4.3</a>) universal-character-name:
18052 \U hex-quad hex-quad
18053 (<a href="#6.4.3">6.4.3</a>) hex-quad:
18054 hexadecimal-digit hexadecimal-digit
18055 hexadecimal-digit hexadecimal-digit
18056 <a name="A.1.5" href="#A.1.5"><b>A.1.5 Constants</b></a>
18057 (<a href="#6.4.4">6.4.4</a>) constant:
18060 enumeration-constant
18062 (<a href="#6.4.4.1">6.4.4.1</a>) integer-constant:
18063 decimal-constant integer-suffixopt
18064 octal-constant integer-suffixopt
18065 hexadecimal-constant integer-suffixopt
18066 (<a href="#6.4.4.1">6.4.4.1</a>) decimal-constant:
18068 decimal-constant digit
18069 (<a href="#6.4.4.1">6.4.4.1</a>) octal-constant:
18071 octal-constant octal-digit
18072 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-constant:
18073 hexadecimal-prefix hexadecimal-digit
18074 hexadecimal-constant hexadecimal-digit
18075 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-prefix: one of
18077 (<a href="#6.4.4.1">6.4.4.1</a>) nonzero-digit: one of
18079 (<a href="#6.4.4.1">6.4.4.1</a>) octal-digit: one of
18085 [<a name="p456" href="#p456">page 456</a>] (<a href="#Contents">Contents</a>)
18087 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-digit: one of
18088 0 1 2 3 4 5 6 7 8 9
18091 (<a href="#6.4.4.1">6.4.4.1</a>) integer-suffix:
18092 unsigned-suffix long-suffixopt
18093 unsigned-suffix long-long-suffix
18094 long-suffix unsigned-suffixopt
18095 long-long-suffix unsigned-suffixopt
18096 (<a href="#6.4.4.1">6.4.4.1</a>) unsigned-suffix: one of
18098 (<a href="#6.4.4.1">6.4.4.1</a>) long-suffix: one of
18100 (<a href="#6.4.4.1">6.4.4.1</a>) long-long-suffix: one of
18102 (<a href="#6.4.4.2">6.4.4.2</a>) floating-constant:
18103 decimal-floating-constant
18104 hexadecimal-floating-constant
18105 (<a href="#6.4.4.2">6.4.4.2</a>) decimal-floating-constant:
18106 fractional-constant exponent-partopt floating-suffixopt
18107 digit-sequence exponent-part floating-suffixopt
18108 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-floating-constant:
18109 hexadecimal-prefix hexadecimal-fractional-constant
18110 binary-exponent-part floating-suffixopt
18111 hexadecimal-prefix hexadecimal-digit-sequence
18112 binary-exponent-part floating-suffixopt
18113 (<a href="#6.4.4.2">6.4.4.2</a>) fractional-constant:
18114 digit-sequenceopt . digit-sequence
18116 (<a href="#6.4.4.2">6.4.4.2</a>) exponent-part:
18117 e signopt digit-sequence
18118 E signopt digit-sequence
18119 (<a href="#6.4.4.2">6.4.4.2</a>) sign: one of
18124 [<a name="p457" href="#p457">page 457</a>] (<a href="#Contents">Contents</a>)
18126 (<a href="#6.4.4.2">6.4.4.2</a>) digit-sequence:
18128 digit-sequence digit
18129 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-fractional-constant:
18130 hexadecimal-digit-sequenceopt .
18131 hexadecimal-digit-sequence
18132 hexadecimal-digit-sequence .
18133 (<a href="#6.4.4.2">6.4.4.2</a>) binary-exponent-part:
18134 p signopt digit-sequence
18135 P signopt digit-sequence
18136 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-digit-sequence:
18138 hexadecimal-digit-sequence hexadecimal-digit
18139 (<a href="#6.4.4.2">6.4.4.2</a>) floating-suffix: one of
18141 (<a href="#6.4.4.3">6.4.4.3</a>) enumeration-constant:
18143 (<a href="#6.4.4.4">6.4.4.4</a>) character-constant:
18144 ' c-char-sequence '
18145 L' c-char-sequence '
18146 u' c-char-sequence '
18147 U' c-char-sequence '
18148 (<a href="#6.4.4.4">6.4.4.4</a>) c-char-sequence:
18150 c-char-sequence c-char
18151 (<a href="#6.4.4.4">6.4.4.4</a>) c-char:
18152 any member of the source character set except
18153 the single-quote ', backslash \, or new-line character
18155 (<a href="#6.4.4.4">6.4.4.4</a>) escape-sequence:
18156 simple-escape-sequence
18157 octal-escape-sequence
18158 hexadecimal-escape-sequence
18159 universal-character-name
18164 [<a name="p458" href="#p458">page 458</a>] (<a href="#Contents">Contents</a>)
18166 (<a href="#6.4.4.4">6.4.4.4</a>) simple-escape-sequence: one of
18168 \a \b \f \n \r \t \v
18169 (<a href="#6.4.4.4">6.4.4.4</a>) octal-escape-sequence:
18171 \ octal-digit octal-digit
18172 \ octal-digit octal-digit octal-digit
18173 (<a href="#6.4.4.4">6.4.4.4</a>) hexadecimal-escape-sequence:
18174 \x hexadecimal-digit
18175 hexadecimal-escape-sequence hexadecimal-digit
18176 <a name="A.1.6" href="#A.1.6"><b>A.1.6 String literals</b></a>
18177 (<a href="#6.4.5">6.4.5</a>) string-literal:
18178 encoding-prefixopt " s-char-sequenceopt "
18179 (<a href="#6.4.5">6.4.5</a>) encoding-prefix:
18184 (<a href="#6.4.5">6.4.5</a>) s-char-sequence:
18186 s-char-sequence s-char
18187 (<a href="#6.4.5">6.4.5</a>) s-char:
18188 any member of the source character set except
18189 the double-quote ", backslash \, or new-line character
18191 <a name="A.1.7" href="#A.1.7"><b>A.1.7 Punctuators</b></a>
18192 (<a href="#6.4.6">6.4.6</a>) punctuator: one of
18193 [ ] ( ) { } . ->
18194 ++ -- & * + - ~ !
18195 / % << >> < > <= >= == != ^ | && ||
18197 = *= /= %= += -= <<= >>= &= ^= |=
18199 <: :> <% %> %: %:%:
18204 [<a name="p459" href="#p459">page 459</a>] (<a href="#Contents">Contents</a>)
18206 <a name="A.1.8" href="#A.1.8"><b>A.1.8 Header names</b></a>
18207 (<a href="#6.4.7">6.4.7</a>) header-name:
18208 < h-char-sequence >
18209 " q-char-sequence "
18210 (<a href="#6.4.7">6.4.7</a>) h-char-sequence:
18212 h-char-sequence h-char
18213 (<a href="#6.4.7">6.4.7</a>) h-char:
18214 any member of the source character set except
18215 the new-line character and >
18216 (<a href="#6.4.7">6.4.7</a>) q-char-sequence:
18218 q-char-sequence q-char
18219 (<a href="#6.4.7">6.4.7</a>) q-char:
18220 any member of the source character set except
18221 the new-line character and "
18222 <a name="A.1.9" href="#A.1.9"><b>A.1.9 Preprocessing numbers</b></a>
18223 (<a href="#6.4.8">6.4.8</a>) pp-number:
18227 pp-number identifier-nondigit
18237 [<a name="p460" href="#p460">page 460</a>] (<a href="#Contents">Contents</a>)
18239 <a name="A.2" href="#A.2"><b>A.2 Phrase structure grammar</b></a>
18240 <a name="A.2.1" href="#A.2.1"><b>A.2.1 Expressions</b></a>
18241 (<a href="#6.5.1">6.5.1</a>) primary-expression:
18247 (<a href="#6.5.1.1">6.5.1.1</a>) generic-selection:
18248 _Generic ( assignment-expression , generic-assoc-list )
18249 (<a href="#6.5.1.1">6.5.1.1</a>) generic-assoc-list:
18250 generic-association
18251 generic-assoc-list , generic-association
18252 (<a href="#6.5.1.1">6.5.1.1</a>) generic-association:
18253 type-name : assignment-expression
18254 default : assignment-expression
18255 (<a href="#6.5.2">6.5.2</a>) postfix-expression:
18257 postfix-expression [ expression ]
18258 postfix-expression ( argument-expression-listopt )
18259 postfix-expression . identifier
18260 postfix-expression -> identifier
18261 postfix-expression ++
18262 postfix-expression --
18263 ( type-name ) { initializer-list }
18264 ( type-name ) { initializer-list , }
18265 (<a href="#6.5.2">6.5.2</a>) argument-expression-list:
18266 assignment-expression
18267 argument-expression-list , assignment-expression
18268 (<a href="#6.5.3">6.5.3</a>) unary-expression:
18270 ++ unary-expression
18271 -- unary-expression
18272 unary-operator cast-expression
18273 sizeof unary-expression
18274 sizeof ( type-name )
18275 alignof ( type-name )
18277 [<a name="p461" href="#p461">page 461</a>] (<a href="#Contents">Contents</a>)
18279 (<a href="#6.5.3">6.5.3</a>) unary-operator: one of
18281 (<a href="#6.5.4">6.5.4</a>) cast-expression:
18283 ( type-name ) cast-expression
18284 (<a href="#6.5.5">6.5.5</a>) multiplicative-expression:
18286 multiplicative-expression * cast-expression
18287 multiplicative-expression / cast-expression
18288 multiplicative-expression % cast-expression
18289 (<a href="#6.5.6">6.5.6</a>) additive-expression:
18290 multiplicative-expression
18291 additive-expression + multiplicative-expression
18292 additive-expression - multiplicative-expression
18293 (<a href="#6.5.7">6.5.7</a>) shift-expression:
18294 additive-expression
18295 shift-expression << additive-expression
18296 shift-expression >> additive-expression
18297 (<a href="#6.5.8">6.5.8</a>) relational-expression:
18299 relational-expression < shift-expression
18300 relational-expression > shift-expression
18301 relational-expression <= shift-expression
18302 relational-expression >= shift-expression
18303 (<a href="#6.5.9">6.5.9</a>) equality-expression:
18304 relational-expression
18305 equality-expression == relational-expression
18306 equality-expression != relational-expression
18307 (<a href="#6.5.10">6.5.10</a>) AND-expression:
18308 equality-expression
18309 AND-expression & equality-expression
18310 (<a href="#6.5.11">6.5.11</a>) exclusive-OR-expression:
18312 exclusive-OR-expression ^ AND-expression
18317 [<a name="p462" href="#p462">page 462</a>] (<a href="#Contents">Contents</a>)
18319 (<a href="#6.5.12">6.5.12</a>) inclusive-OR-expression:
18320 exclusive-OR-expression
18321 inclusive-OR-expression | exclusive-OR-expression
18322 (<a href="#6.5.13">6.5.13</a>) logical-AND-expression:
18323 inclusive-OR-expression
18324 logical-AND-expression && inclusive-OR-expression
18325 (<a href="#6.5.14">6.5.14</a>) logical-OR-expression:
18326 logical-AND-expression
18327 logical-OR-expression || logical-AND-expression
18328 (<a href="#6.5.15">6.5.15</a>) conditional-expression:
18329 logical-OR-expression
18330 logical-OR-expression ? expression : conditional-expression
18331 (<a href="#6.5.16">6.5.16</a>) assignment-expression:
18332 conditional-expression
18333 unary-expression assignment-operator assignment-expression
18334 (<a href="#6.5.16">6.5.16</a>) assignment-operator: one of
18335 = *= /= %= += -= <<= >>= &= ^= |=
18336 (<a href="#6.5.17">6.5.17</a>) expression:
18337 assignment-expression
18338 expression , assignment-expression
18339 (<a href="#6.6">6.6</a>) constant-expression:
18340 conditional-expression
18341 <a name="A.2.2" href="#A.2.2"><b>A.2.2 Declarations</b></a>
18342 (<a href="#6.7">6.7</a>) declaration:
18343 declaration-specifiers init-declarator-listopt ;
18344 static_assert-declaration
18345 (<a href="#6.7">6.7</a>) declaration-specifiers:
18346 storage-class-specifier declaration-specifiersopt
18347 type-specifier declaration-specifiersopt
18348 type-qualifier declaration-specifiersopt
18349 function-specifier declaration-specifiersopt
18350 alignment-specifier declaration-specifiersopt
18351 (<a href="#6.7">6.7</a>) init-declarator-list:
18353 init-declarator-list , init-declarator
18356 [<a name="p463" href="#p463">page 463</a>] (<a href="#Contents">Contents</a>)
18358 (<a href="#6.7">6.7</a>) init-declarator:
18360 declarator = initializer
18361 (<a href="#6.7.1">6.7.1</a>) storage-class-specifier:
18368 (<a href="#6.7.2">6.7.2</a>) type-specifier:
18380 atomic-type-specifier
18381 struct-or-union-specifier
18384 (<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union-specifier:
18385 struct-or-union identifieropt { struct-declaration-list }
18386 struct-or-union identifier
18387 (<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union:
18390 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration-list:
18392 struct-declaration-list struct-declaration
18393 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration:
18394 specifier-qualifier-list struct-declarator-listopt ;
18395 static_assert-declaration
18397 [<a name="p464" href="#p464">page 464</a>] (<a href="#Contents">Contents</a>)
18399 (<a href="#6.7.2.1">6.7.2.1</a>) specifier-qualifier-list:
18400 type-specifier specifier-qualifier-listopt
18401 type-qualifier specifier-qualifier-listopt
18402 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator-list:
18404 struct-declarator-list , struct-declarator
18405 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator:
18407 declaratoropt : constant-expression
18408 (<a href="#6.7.2.2">6.7.2.2</a>) enum-specifier:
18409 enum identifieropt { enumerator-list }
18410 enum identifieropt { enumerator-list , }
18412 (<a href="#6.7.2.2">6.7.2.2</a>) enumerator-list:
18414 enumerator-list , enumerator
18415 (<a href="#6.7.2.2">6.7.2.2</a>) enumerator:
18416 enumeration-constant
18417 enumeration-constant = constant-expression
18418 (<a href="#6.7.2.4">6.7.2.4</a>) atomic-type-specifier:
18419 _Atomic ( type-name )
18420 (<a href="#6.7.3">6.7.3</a>) type-qualifier:
18425 (<a href="#6.7.4">6.7.4</a>) function-specifier:
18428 (<a href="#6.7.5">6.7.5</a>) alignment-specifier:
18429 _Alignas ( type-name )
18430 _Alignas ( constant-expression )
18431 (<a href="#6.7.6">6.7.6</a>) declarator:
18432 pointeropt direct-declarator
18436 [<a name="p465" href="#p465">page 465</a>] (<a href="#Contents">Contents</a>)
18438 (<a href="#6.7.6">6.7.6</a>) direct-declarator:
18441 direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
18442 direct-declarator [ static type-qualifier-listopt assignment-expression ]
18443 direct-declarator [ type-qualifier-list static assignment-expression ]
18444 direct-declarator [ type-qualifier-listopt * ]
18445 direct-declarator ( parameter-type-list )
18446 direct-declarator ( identifier-listopt )
18447 (<a href="#6.7.6">6.7.6</a>) pointer:
18448 * type-qualifier-listopt
18449 * type-qualifier-listopt pointer
18450 (<a href="#6.7.6">6.7.6</a>) type-qualifier-list:
18452 type-qualifier-list type-qualifier
18453 (<a href="#6.7.6">6.7.6</a>) parameter-type-list:
18455 parameter-list , ...
18456 (<a href="#6.7.6">6.7.6</a>) parameter-list:
18457 parameter-declaration
18458 parameter-list , parameter-declaration
18459 (<a href="#6.7.6">6.7.6</a>) parameter-declaration:
18460 declaration-specifiers declarator
18461 declaration-specifiers abstract-declaratoropt
18462 (<a href="#6.7.6">6.7.6</a>) identifier-list:
18464 identifier-list , identifier
18465 (<a href="#6.7.7">6.7.7</a>) type-name:
18466 specifier-qualifier-list abstract-declaratoropt
18467 (<a href="#6.7.7">6.7.7</a>) abstract-declarator:
18469 pointeropt direct-abstract-declarator
18474 [<a name="p466" href="#p466">page 466</a>] (<a href="#Contents">Contents</a>)
18476 (<a href="#6.7.7">6.7.7</a>) direct-abstract-declarator:
18477 ( abstract-declarator )
18478 direct-abstract-declaratoropt [ type-qualifier-listopt
18479 assignment-expressionopt ]
18480 direct-abstract-declaratoropt [ static type-qualifier-listopt
18481 assignment-expression ]
18482 direct-abstract-declaratoropt [ type-qualifier-list static
18483 assignment-expression ]
18484 direct-abstract-declaratoropt [ * ]
18485 direct-abstract-declaratoropt ( parameter-type-listopt )
18486 (<a href="#6.7.8">6.7.8</a>) typedef-name:
18488 (<a href="#6.7.9">6.7.9</a>) initializer:
18489 assignment-expression
18490 { initializer-list }
18491 { initializer-list , }
18492 (<a href="#6.7.9">6.7.9</a>) initializer-list:
18493 designationopt initializer
18494 initializer-list , designationopt initializer
18495 (<a href="#6.7.9">6.7.9</a>) designation:
18497 (<a href="#6.7.9">6.7.9</a>) designator-list:
18499 designator-list designator
18500 (<a href="#6.7.9">6.7.9</a>) designator:
18501 [ constant-expression ]
18503 (<a href="#6.7.10">6.7.10</a>) static_assert-declaration:
18504 _Static_assert ( constant-expression , string-literal ) ;
18509 [<a name="p467" href="#p467">page 467</a>] (<a href="#Contents">Contents</a>)
18511 <a name="A.2.3" href="#A.2.3"><b>A.2.3 Statements</b></a>
18512 (<a href="#6.8">6.8</a>) statement:
18515 expression-statement
18516 selection-statement
18517 iteration-statement
18519 (<a href="#6.8.1">6.8.1</a>) labeled-statement:
18520 identifier : statement
18521 case constant-expression : statement
18522 default : statement
18523 (<a href="#6.8.2">6.8.2</a>) compound-statement:
18524 { block-item-listopt }
18525 (<a href="#6.8.2">6.8.2</a>) block-item-list:
18527 block-item-list block-item
18528 (<a href="#6.8.2">6.8.2</a>) block-item:
18531 (<a href="#6.8.3">6.8.3</a>) expression-statement:
18533 (<a href="#6.8.4">6.8.4</a>) selection-statement:
18534 if ( expression ) statement
18535 if ( expression ) statement else statement
18536 switch ( expression ) statement
18537 (<a href="#6.8.5">6.8.5</a>) iteration-statement:
18538 while ( expression ) statement
18539 do statement while ( expression ) ;
18540 for ( expressionopt ; expressionopt ; expressionopt ) statement
18541 for ( declaration expressionopt ; expressionopt ) statement
18542 (<a href="#6.8.6">6.8.6</a>) jump-statement:
18546 return expressionopt ;
18548 [<a name="p468" href="#p468">page 468</a>] (<a href="#Contents">Contents</a>)
18550 <a name="A.2.4" href="#A.2.4"><b>A.2.4 External definitions</b></a>
18551 (<a href="#6.9">6.9</a>) translation-unit:
18552 external-declaration
18553 translation-unit external-declaration
18554 (<a href="#6.9">6.9</a>) external-declaration:
18555 function-definition
18557 (<a href="#6.9.1">6.9.1</a>) function-definition:
18558 declaration-specifiers declarator declaration-listopt compound-statement
18559 (<a href="#6.9.1">6.9.1</a>) declaration-list:
18561 declaration-list declaration
18562 <a name="A.3" href="#A.3"><b>A.3 Preprocessing directives</b></a>
18563 (<a href="#6.10">6.10</a>) preprocessing-file:
18565 (<a href="#6.10">6.10</a>) group:
18568 (<a href="#6.10">6.10</a>) group-part:
18573 (<a href="#6.10">6.10</a>) if-section:
18574 if-group elif-groupsopt else-groupopt endif-line
18575 (<a href="#6.10">6.10</a>) if-group:
18576 # if constant-expression new-line groupopt
18577 # ifdef identifier new-line groupopt
18578 # ifndef identifier new-line groupopt
18579 (<a href="#6.10">6.10</a>) elif-groups:
18581 elif-groups elif-group
18582 (<a href="#6.10">6.10</a>) elif-group:
18583 # elif constant-expression new-line groupopt
18586 [<a name="p469" href="#p469">page 469</a>] (<a href="#Contents">Contents</a>)
18588 (<a href="#6.10">6.10</a>) else-group:
18589 # else new-line groupopt
18590 (<a href="#6.10">6.10</a>) endif-line:
18592 (<a href="#6.10">6.10</a>) control-line:
18593 # include pp-tokens new-line
18594 # define identifier replacement-list new-line
18595 # define identifier lparen identifier-listopt )
18596 replacement-list new-line
18597 # define identifier lparen ... ) replacement-list new-line
18598 # define identifier lparen identifier-list , ... )
18599 replacement-list new-line
18600 # undef identifier new-line
18601 # line pp-tokens new-line
18602 # error pp-tokensopt new-line
18603 # pragma pp-tokensopt new-line
18605 (<a href="#6.10">6.10</a>) text-line:
18606 pp-tokensopt new-line
18607 (<a href="#6.10">6.10</a>) non-directive:
18609 (<a href="#6.10">6.10</a>) lparen:
18610 a ( character not immediately preceded by white-space
18611 (<a href="#6.10">6.10</a>) replacement-list:
18613 (<a href="#6.10">6.10</a>) pp-tokens:
18614 preprocessing-token
18615 pp-tokens preprocessing-token
18616 (<a href="#6.10">6.10</a>) new-line:
18617 the new-line character
18622 [<a name="p470" href="#p470">page 470</a>] (<a href="#Contents">Contents</a>)
18624 <a name="B" href="#B"><b> Annex B</b></a>
18627 <a name="B.1" href="#B.1"><b>B.1 Diagnostics <assert.h></b></a>
18630 void assert(scalar expression);
18631 <a name="B.2" href="#B.2"><b>B.2 Complex <complex.h></b></a>
18632 __STDC_NO_COMPLEX__ imaginary
18633 complex _Imaginary_I
18635 #pragma STDC CX_LIMITED_RANGE on-off-switch
18636 double complex cacos(double complex z);
18637 float complex cacosf(float complex z);
18638 long double complex cacosl(long double complex z);
18639 double complex casin(double complex z);
18640 float complex casinf(float complex z);
18641 long double complex casinl(long double complex z);
18642 double complex catan(double complex z);
18643 float complex catanf(float complex z);
18644 long double complex catanl(long double complex z);
18645 double complex ccos(double complex z);
18646 float complex ccosf(float complex z);
18647 long double complex ccosl(long double complex z);
18648 double complex csin(double complex z);
18649 float complex csinf(float complex z);
18650 long double complex csinl(long double complex z);
18651 double complex ctan(double complex z);
18652 float complex ctanf(float complex z);
18653 long double complex ctanl(long double complex z);
18654 double complex cacosh(double complex z);
18655 float complex cacoshf(float complex z);
18656 long double complex cacoshl(long double complex z);
18657 double complex casinh(double complex z);
18658 float complex casinhf(float complex z);
18659 long double complex casinhl(long double complex z);
18661 [<a name="p471" href="#p471">page 471</a>] (<a href="#Contents">Contents</a>)
18663 double complex catanh(double complex z);
18664 float complex catanhf(float complex z);
18665 long double complex catanhl(long double complex z);
18666 double complex ccosh(double complex z);
18667 float complex ccoshf(float complex z);
18668 long double complex ccoshl(long double complex z);
18669 double complex csinh(double complex z);
18670 float complex csinhf(float complex z);
18671 long double complex csinhl(long double complex z);
18672 double complex ctanh(double complex z);
18673 float complex ctanhf(float complex z);
18674 long double complex ctanhl(long double complex z);
18675 double complex cexp(double complex z);
18676 float complex cexpf(float complex z);
18677 long double complex cexpl(long double complex z);
18678 double complex clog(double complex z);
18679 float complex clogf(float complex z);
18680 long double complex clogl(long double complex z);
18681 double cabs(double complex z);
18682 float cabsf(float complex z);
18683 long double cabsl(long double complex z);
18684 double complex cpow(double complex x, double complex y);
18685 float complex cpowf(float complex x, float complex y);
18686 long double complex cpowl(long double complex x,
18687 long double complex y);
18688 double complex csqrt(double complex z);
18689 float complex csqrtf(float complex z);
18690 long double complex csqrtl(long double complex z);
18691 double carg(double complex z);
18692 float cargf(float complex z);
18693 long double cargl(long double complex z);
18694 double cimag(double complex z);
18695 float cimagf(float complex z);
18696 long double cimagl(long double complex z);
18697 double complex CMPLX(double x, double y);
18698 float complex CMPLXF(float x, float y);
18699 long double complex CMPLXL(long double x, long double y);
18700 double complex conj(double complex z);
18701 float complex conjf(float complex z);
18702 long double complex conjl(long double complex z);
18703 double complex cproj(double complex z);
18705 [<a name="p472" href="#p472">page 472</a>] (<a href="#Contents">Contents</a>)
18707 float complex cprojf(float complex z);
18708 long double complex cprojl(long double complex z);
18709 double creal(double complex z);
18710 float crealf(float complex z);
18711 long double creall(long double complex z);
18712 <a name="B.3" href="#B.3"><b>B.3 Character handling <ctype.h></b></a>
18713 int isalnum(int c);
18714 int isalpha(int c);
18715 int isblank(int c);
18716 int iscntrl(int c);
18717 int isdigit(int c);
18718 int isgraph(int c);
18719 int islower(int c);
18720 int isprint(int c);
18721 int ispunct(int c);
18722 int isspace(int c);
18723 int isupper(int c);
18724 int isxdigit(int c);
18725 int tolower(int c);
18726 int toupper(int c);
18727 <a name="B.4" href="#B.4"><b>B.4 Errors <errno.h></b></a>
18728 EDOM EILSEQ ERANGE errno
18729 __STDC_WANT_LIB_EXT1__
18731 <a name="B.5" href="#B.5"><b>B.5 Floating-point environment <fenv.h></b></a>
18732 fenv_t FE_OVERFLOW FE_TOWARDZERO
18733 fexcept_t FE_UNDERFLOW FE_UPWARD
18734 FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
18735 FE_INEXACT FE_DOWNWARD
18736 FE_INVALID FE_TONEAREST
18737 #pragma STDC FENV_ACCESS on-off-switch
18738 int feclearexcept(int excepts);
18739 int fegetexceptflag(fexcept_t *flagp, int excepts);
18740 int feraiseexcept(int excepts);
18741 int fesetexceptflag(const fexcept_t *flagp,
18743 int fetestexcept(int excepts);
18745 [<a name="p473" href="#p473">page 473</a>] (<a href="#Contents">Contents</a>)
18747 int fegetround(void);
18748 int fesetround(int round);
18749 int fegetenv(fenv_t *envp);
18750 int feholdexcept(fenv_t *envp);
18751 int fesetenv(const fenv_t *envp);
18752 int feupdateenv(const fenv_t *envp);
18753 <a name="B.6" href="#B.6"><b>B.6 Characteristics of floating types <float.h></b></a>
18754 FLT_ROUNDS DBL_DIG FLT_MAX
18755 FLT_EVAL_METHOD LDBL_DIG DBL_MAX
18756 FLT_HAS_SUBNORM FLT_MIN_EXP LDBL_MAX
18757 DBL_HAS_SUBNORM DBL_MIN_EXP FLT_EPSILON
18758 LDBL_HAS_SUBNORM LDBL_MIN_EXP DBL_EPSILON
18759 FLT_RADIX FLT_MIN_10_EXP LDBL_EPSILON
18760 FLT_MANT_DIG DBL_MIN_10_EXP FLT_MIN
18761 DBL_MANT_DIG LDBL_MIN_10_EXP DBL_MIN
18762 LDBL_MANT_DIG FLT_MAX_EXP LDBL_MIN
18763 FLT_DECIMAL_DIG DBL_MAX_EXP FLT_TRUE_MIN
18764 DBL_DECIMAL_DIG LDBL_MAX_EXP DBL_TRUE_MIN
18765 LDBL_DECIMAL_DIG FLT_MAX_10_EXP LDBL_TRUE_MIN
18766 DECIMAL_DIG DBL_MAX_10_EXP
18767 FLT_DIG LDBL_MAX_10_EXP
18768 <a name="B.7" href="#B.7"><b>B.7 Format conversion of integer types <inttypes.h></b></a>
18770 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
18771 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
18772 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
18773 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
18774 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
18775 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
18776 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
18777 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
18778 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
18779 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
18780 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
18781 intmax_t imaxabs(intmax_t j);
18782 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
18783 intmax_t strtoimax(const char * restrict nptr,
18784 char ** restrict endptr, int base);
18786 [<a name="p474" href="#p474">page 474</a>] (<a href="#Contents">Contents</a>)
18788 uintmax_t strtoumax(const char * restrict nptr,
18789 char ** restrict endptr, int base);
18790 intmax_t wcstoimax(const wchar_t * restrict nptr,
18791 wchar_t ** restrict endptr, int base);
18792 uintmax_t wcstoumax(const wchar_t * restrict nptr,
18793 wchar_t ** restrict endptr, int base);
18794 <a name="B.8" href="#B.8"><b>B.8 Alternative spellings <iso646.h></b></a>
18795 and bitor not_eq xor
18796 and_eq compl or xor_eq
18798 <a name="B.9" href="#B.9"><b>B.9 Sizes of integer types <limits.h></b></a>
18799 CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
18800 SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
18801 SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
18802 UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
18803 CHAR_MIN USHRT_MAX LONG_MAX
18804 <a name="B.10" href="#B.10"><b>B.10 Localization <locale.h></b></a>
18805 struct lconv LC_ALL LC_CTYPE LC_NUMERIC
18806 NULL LC_COLLATE LC_MONETARY LC_TIME
18807 char *setlocale(int category, const char *locale);
18808 struct lconv *localeconv(void);
18809 <a name="B.11" href="#B.11"><b>B.11 Mathematics <math.h></b></a>
18810 float_t FP_INFINITE FP_FAST_FMAL
18811 double_t FP_NAN FP_ILOGB0
18812 HUGE_VAL FP_NORMAL FP_ILOGBNAN
18813 HUGE_VALF FP_SUBNORMAL MATH_ERRNO
18814 HUGE_VALL FP_ZERO MATH_ERREXCEPT
18815 INFINITY FP_FAST_FMA math_errhandling
18817 #pragma STDC FP_CONTRACT on-off-switch
18818 int fpclassify(real-floating x);
18819 int isfinite(real-floating x);
18820 int isinf(real-floating x);
18821 int isnan(real-floating x);
18822 int isnormal(real-floating x);
18823 int signbit(real-floating x);
18824 [<a name="p475" href="#p475">page 475</a>] (<a href="#Contents">Contents</a>)
18826 double acos(double x);
18827 float acosf(float x);
18828 long double acosl(long double x);
18829 double asin(double x);
18830 float asinf(float x);
18831 long double asinl(long double x);
18832 double atan(double x);
18833 float atanf(float x);
18834 long double atanl(long double x);
18835 double atan2(double y, double x);
18836 float atan2f(float y, float x);
18837 long double atan2l(long double y, long double x);
18838 double cos(double x);
18839 float cosf(float x);
18840 long double cosl(long double x);
18841 double sin(double x);
18842 float sinf(float x);
18843 long double sinl(long double x);
18844 double tan(double x);
18845 float tanf(float x);
18846 long double tanl(long double x);
18847 double acosh(double x);
18848 float acoshf(float x);
18849 long double acoshl(long double x);
18850 double asinh(double x);
18851 float asinhf(float x);
18852 long double asinhl(long double x);
18853 double atanh(double x);
18854 float atanhf(float x);
18855 long double atanhl(long double x);
18856 double cosh(double x);
18857 float coshf(float x);
18858 long double coshl(long double x);
18859 double sinh(double x);
18860 float sinhf(float x);
18861 long double sinhl(long double x);
18862 double tanh(double x);
18863 float tanhf(float x);
18864 long double tanhl(long double x);
18865 double exp(double x);
18866 float expf(float x);
18868 [<a name="p476" href="#p476">page 476</a>] (<a href="#Contents">Contents</a>)
18870 long double expl(long double x);
18871 double exp2(double x);
18872 float exp2f(float x);
18873 long double exp2l(long double x);
18874 double expm1(double x);
18875 float expm1f(float x);
18876 long double expm1l(long double x);
18877 double frexp(double value, int *exp);
18878 float frexpf(float value, int *exp);
18879 long double frexpl(long double value, int *exp);
18880 int ilogb(double x);
18881 int ilogbf(float x);
18882 int ilogbl(long double x);
18883 double ldexp(double x, int exp);
18884 float ldexpf(float x, int exp);
18885 long double ldexpl(long double x, int exp);
18886 double log(double x);
18887 float logf(float x);
18888 long double logl(long double x);
18889 double log10(double x);
18890 float log10f(float x);
18891 long double log10l(long double x);
18892 double log1p(double x);
18893 float log1pf(float x);
18894 long double log1pl(long double x);
18895 double log2(double x);
18896 float log2f(float x);
18897 long double log2l(long double x);
18898 double logb(double x);
18899 float logbf(float x);
18900 long double logbl(long double x);
18901 double modf(double value, double *iptr);
18902 float modff(float value, float *iptr);
18903 long double modfl(long double value, long double *iptr);
18904 double scalbn(double x, int n);
18905 float scalbnf(float x, int n);
18906 long double scalbnl(long double x, int n);
18907 double scalbln(double x, long int n);
18908 float scalblnf(float x, long int n);
18909 long double scalblnl(long double x, long int n);
18910 double cbrt(double x);
18912 [<a name="p477" href="#p477">page 477</a>] (<a href="#Contents">Contents</a>)
18914 float cbrtf(float x);
18915 long double cbrtl(long double x);
18916 double fabs(double x);
18917 float fabsf(float x);
18918 long double fabsl(long double x);
18919 double hypot(double x, double y);
18920 float hypotf(float x, float y);
18921 long double hypotl(long double x, long double y);
18922 double pow(double x, double y);
18923 float powf(float x, float y);
18924 long double powl(long double x, long double y);
18925 double sqrt(double x);
18926 float sqrtf(float x);
18927 long double sqrtl(long double x);
18928 double erf(double x);
18929 float erff(float x);
18930 long double erfl(long double x);
18931 double erfc(double x);
18932 float erfcf(float x);
18933 long double erfcl(long double x);
18934 double lgamma(double x);
18935 float lgammaf(float x);
18936 long double lgammal(long double x);
18937 double tgamma(double x);
18938 float tgammaf(float x);
18939 long double tgammal(long double x);
18940 double ceil(double x);
18941 float ceilf(float x);
18942 long double ceill(long double x);
18943 double floor(double x);
18944 float floorf(float x);
18945 long double floorl(long double x);
18946 double nearbyint(double x);
18947 float nearbyintf(float x);
18948 long double nearbyintl(long double x);
18949 double rint(double x);
18950 float rintf(float x);
18951 long double rintl(long double x);
18952 long int lrint(double x);
18953 long int lrintf(float x);
18954 long int lrintl(long double x);
18956 [<a name="p478" href="#p478">page 478</a>] (<a href="#Contents">Contents</a>)
18958 long long int llrint(double x);
18959 long long int llrintf(float x);
18960 long long int llrintl(long double x);
18961 double round(double x);
18962 float roundf(float x);
18963 long double roundl(long double x);
18964 long int lround(double x);
18965 long int lroundf(float x);
18966 long int lroundl(long double x);
18967 long long int llround(double x);
18968 long long int llroundf(float x);
18969 long long int llroundl(long double x);
18970 double trunc(double x);
18971 float truncf(float x);
18972 long double truncl(long double x);
18973 double fmod(double x, double y);
18974 float fmodf(float x, float y);
18975 long double fmodl(long double x, long double y);
18976 double remainder(double x, double y);
18977 float remainderf(float x, float y);
18978 long double remainderl(long double x, long double y);
18979 double remquo(double x, double y, int *quo);
18980 float remquof(float x, float y, int *quo);
18981 long double remquol(long double x, long double y,
18983 double copysign(double x, double y);
18984 float copysignf(float x, float y);
18985 long double copysignl(long double x, long double y);
18986 double nan(const char *tagp);
18987 float nanf(const char *tagp);
18988 long double nanl(const char *tagp);
18989 double nextafter(double x, double y);
18990 float nextafterf(float x, float y);
18991 long double nextafterl(long double x, long double y);
18992 double nexttoward(double x, long double y);
18993 float nexttowardf(float x, long double y);
18994 long double nexttowardl(long double x, long double y);
18995 double fdim(double x, double y);
18996 float fdimf(float x, float y);
18997 long double fdiml(long double x, long double y);
18998 double fmax(double x, double y);
19000 [<a name="p479" href="#p479">page 479</a>] (<a href="#Contents">Contents</a>)
19002 float fmaxf(float x, float y);
19003 long double fmaxl(long double x, long double y);
19004 double fmin(double x, double y);
19005 float fminf(float x, float y);
19006 long double fminl(long double x, long double y);
19007 double fma(double x, double y, double z);
19008 float fmaf(float x, float y, float z);
19009 long double fmal(long double x, long double y,
19011 int isgreater(real-floating x, real-floating y);
19012 int isgreaterequal(real-floating x, real-floating y);
19013 int isless(real-floating x, real-floating y);
19014 int islessequal(real-floating x, real-floating y);
19015 int islessgreater(real-floating x, real-floating y);
19016 int isunordered(real-floating x, real-floating y);
19017 <a name="B.12" href="#B.12"><b>B.12 Nonlocal jumps <setjmp.h></b></a>
19019 int setjmp(jmp_buf env);
19020 _Noreturn void longjmp(jmp_buf env, int val);
19021 <a name="B.13" href="#B.13"><b>B.13 Signal handling <signal.h></b></a>
19022 sig_atomic_t SIG_IGN SIGILL SIGTERM
19023 SIG_DFL SIGABRT SIGINT
19024 SIG_ERR SIGFPE SIGSEGV
19025 void (*signal(int sig, void (*func)(int)))(int);
19026 int raise(int sig);
19031 [<a name="p480" href="#p480">page 480</a>] (<a href="#Contents">Contents</a>)
19033 <a name="B.14" href="#B.14"><b>B.14 Alignment <stdalign.h></b></a>
19035 __alignas_is_defined
19036 <a name="B.15" href="#B.15"><b>B.15 Variable arguments <stdarg.h></b></a>
19038 type va_arg(va_list ap, type);
19039 void va_copy(va_list dest, va_list src);
19040 void va_end(va_list ap);
19041 void va_start(va_list ap, parmN);
19042 <a name="B.16" href="#B.16"><b>B.16 Atomics <stdatomic.h></b></a>
19043 ATOMIC_CHAR_LOCK_FREE atomic_uint
19044 ATOMIC_CHAR16_T_LOCK_FREE atomic_long
19045 ATOMIC_CHAR32_T_LOCK_FREE atomic_ulong
19046 ATOMIC_WCHAR_T_LOCK_FREE atomic_llong
19047 ATOMIC_SHORT_LOCK_FREE atomic_ullong
19048 ATOMIC_INT_LOCK_FREE atomic_char16_t
19049 ATOMIC_LONG_LOCK_FREE atomic_char32_t
19050 ATOMIC_LLONG_LOCK_FREE atomic_wchar_t
19051 ATOMIC_ADDRESS_LOCK_FREE atomic_int_least8_t
19052 ATOMIC_FLAG_INIT atomic_uint_least8_t
19053 memory_order atomic_int_least16_t
19054 atomic_flag atomic_uint_least16_t
19055 atomic_bool atomic_int_least32_t
19056 atomic_address atomic_uint_least32_t
19057 memory_order_relaxed atomic_int_least64_t
19058 memory_order_consume atomic_uint_least64_t
19059 memory_order_acquire atomic_int_fast8_t
19060 memory_order_release atomic_uint_fast8_t
19061 memory_order_acq_rel atomic_int_fast16_t
19062 memory_order_seq_cst atomic_uint_fast16_t
19063 atomic_char atomic_int_fast32_t
19064 atomic_schar atomic_uint_fast32_t
19065 atomic_uchar atomic_int_fast64_t
19066 atomic_short atomic_uint_fast64_t
19067 atomic_ushort atomic_intptr_t
19068 atomic_int atomic_uintptr_t
19072 [<a name="p481" href="#p481">page 481</a>] (<a href="#Contents">Contents</a>)
19074 atomic_size_t atomic_intmax_t
19075 atomic_ptrdiff_t atomic_uintmax_t
19076 #define ATOMIC_VAR_INIT(C value)
19077 void atomic_init(volatile A *obj, C value);
19078 type kill_dependency(type y);
19079 void atomic_thread_fence(memory_order order);
19080 void atomic_signal_fence(memory_order order);
19081 _Bool atomic_is_lock_free(atomic_type const volatile *obj);
19082 void atomic_store(volatile A *object, C desired);
19083 void atomic_store_explicit(volatile A *object,
19084 C desired, memory_order order);
19085 C atomic_load(volatile A *object);
19086 C atomic_load_explicit(volatile A *object,
19087 memory_order order);
19088 C atomic_exchange(volatile A *object, C desired);
19089 C atomic_exchange_explicit(volatile A *object,
19090 C desired, memory_order order);
19091 _Bool atomic_compare_exchange_strong(volatile A *object,
19092 C *expected, C desired);
19093 _Bool atomic_compare_exchange_strong_explicit(
19094 volatile A *object, C *expected, C desired,
19095 memory_order success, memory_order failure);
19096 _Bool atomic_compare_exchange_weak(volatile A *object,
19097 C *expected, C desired);
19098 _Bool atomic_compare_exchange_weak_explicit(
19099 volatile A *object, C *expected, C desired,
19100 memory_order success, memory_order failure);
19101 C atomic_fetch_key(volatile A *object, M operand);
19102 C atomic_fetch_key_explicit(volatile A *object,
19103 M operand, memory_order order);
19104 bool atomic_flag_test_and_set(
19105 volatile atomic_flag *object);
19106 bool atomic_flag_test_and_set_explicit(
19107 volatile atomic_flag *object, memory_order order);
19108 void atomic_flag_clear(volatile atomic_flag *object);
19109 void atomic_flag_clear_explicit(
19110 volatile atomic_flag *object, memory_order order);
19115 [<a name="p482" href="#p482">page 482</a>] (<a href="#Contents">Contents</a>)
19117 <a name="B.17" href="#B.17"><b>B.17 Boolean type and values <stdbool.h></b></a>
19121 __bool_true_false_are_defined
19122 <a name="B.18" href="#B.18"><b>B.18 Common definitions <stddef.h></b></a>
19123 ptrdiff_t max_align_t NULL
19125 offsetof(type, member-designator)
19126 __STDC_WANT_LIB_EXT1__
19128 <a name="B.19" href="#B.19"><b>B.19 Integer types <stdint.h></b></a>
19129 intN_t INT_LEASTN_MIN PTRDIFF_MAX
19130 uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
19131 int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
19132 uint_leastN_t INT_FASTN_MIN SIZE_MAX
19133 int_fastN_t INT_FASTN_MAX WCHAR_MIN
19134 uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
19135 intptr_t INTPTR_MIN WINT_MIN
19136 uintptr_t INTPTR_MAX WINT_MAX
19137 intmax_t UINTPTR_MAX INTN_C(value)
19138 uintmax_t INTMAX_MIN UINTN_C(value)
19139 INTN_MIN INTMAX_MAX INTMAX_C(value)
19140 INTN_MAX UINTMAX_MAX UINTMAX_C(value)
19141 UINTN_MAX PTRDIFF_MIN
19142 __STDC_WANT_LIB_EXT1__
19148 [<a name="p483" href="#p483">page 483</a>] (<a href="#Contents">Contents</a>)
19150 <a name="B.20" href="#B.20"><b>B.20 Input/output <stdio.h></b></a>
19151 size_t _IOLBF FILENAME_MAX TMP_MAX
19152 FILE _IONBF L_tmpnam stderr
19153 fpos_t BUFSIZ SEEK_CUR stdin
19154 NULL EOF SEEK_END stdout
19155 _IOFBF FOPEN_MAX SEEK_SET
19156 int remove(const char *filename);
19157 int rename(const char *old, const char *new);
19158 FILE *tmpfile(void);
19159 char *tmpnam(char *s);
19160 int fclose(FILE *stream);
19161 int fflush(FILE *stream);
19162 FILE *fopen(const char * restrict filename,
19163 const char * restrict mode);
19164 FILE *freopen(const char * restrict filename,
19165 const char * restrict mode,
19166 FILE * restrict stream);
19167 void setbuf(FILE * restrict stream,
19168 char * restrict buf);
19169 int setvbuf(FILE * restrict stream,
19170 char * restrict buf,
19171 int mode, size_t size);
19172 int fprintf(FILE * restrict stream,
19173 const char * restrict format, ...);
19174 int fscanf(FILE * restrict stream,
19175 const char * restrict format, ...);
19176 int printf(const char * restrict format, ...);
19177 int scanf(const char * restrict format, ...);
19178 int snprintf(char * restrict s, size_t n,
19179 const char * restrict format, ...);
19180 int sprintf(char * restrict s,
19181 const char * restrict format, ...);
19182 int sscanf(const char * restrict s,
19183 const char * restrict format, ...);
19184 int vfprintf(FILE * restrict stream,
19185 const char * restrict format, va_list arg);
19186 int vfscanf(FILE * restrict stream,
19187 const char * restrict format, va_list arg);
19188 int vprintf(const char * restrict format, va_list arg);
19189 int vscanf(const char * restrict format, va_list arg);
19191 [<a name="p484" href="#p484">page 484</a>] (<a href="#Contents">Contents</a>)
19193 int vsnprintf(char * restrict s, size_t n,
19194 const char * restrict format, va_list arg);
19195 int vsprintf(char * restrict s,
19196 const char * restrict format, va_list arg);
19197 int vsscanf(const char * restrict s,
19198 const char * restrict format, va_list arg);
19199 int fgetc(FILE *stream);
19200 char *fgets(char * restrict s, int n,
19201 FILE * restrict stream);
19202 int fputc(int c, FILE *stream);
19203 int fputs(const char * restrict s,
19204 FILE * restrict stream);
19205 int getc(FILE *stream);
19207 int putc(int c, FILE *stream); *
19208 int putchar(int c);
19209 int puts(const char *s);
19210 int ungetc(int c, FILE *stream);
19211 size_t fread(void * restrict ptr,
19212 size_t size, size_t nmemb,
19213 FILE * restrict stream);
19214 size_t fwrite(const void * restrict ptr,
19215 size_t size, size_t nmemb,
19216 FILE * restrict stream);
19217 int fgetpos(FILE * restrict stream,
19218 fpos_t * restrict pos);
19219 int fseek(FILE *stream, long int offset, int whence);
19220 int fsetpos(FILE *stream, const fpos_t *pos);
19221 long int ftell(FILE *stream);
19222 void rewind(FILE *stream);
19223 void clearerr(FILE *stream);
19224 int feof(FILE *stream);
19225 int ferror(FILE *stream);
19226 void perror(const char *s);
19227 __STDC_WANT_LIB_EXT1__
19228 L_tmpnam_s TMP_MAX_S errno_t rsize_t
19229 errno_t tmpfile_s(FILE * restrict * restrict streamptr);
19230 errno_t tmpnam_s(char *s, rsize_t maxsize);
19234 [<a name="p485" href="#p485">page 485</a>] (<a href="#Contents">Contents</a>)
19236 errno_t fopen_s(FILE * restrict * restrict streamptr,
19237 const char * restrict filename,
19238 const char * restrict mode);
19239 errno_t freopen_s(FILE * restrict * restrict newstreamptr,
19240 const char * restrict filename,
19241 const char * restrict mode,
19242 FILE * restrict stream);
19243 int fprintf_s(FILE * restrict stream,
19244 const char * restrict format, ...);
19245 int fscanf_s(FILE * restrict stream,
19246 const char * restrict format, ...);
19247 int printf_s(const char * restrict format, ...);
19248 int scanf_s(const char * restrict format, ...);
19249 int snprintf_s(char * restrict s, rsize_t n,
19250 const char * restrict format, ...);
19251 int sprintf_s(char * restrict s, rsize_t n,
19252 const char * restrict format, ...);
19253 int sscanf_s(const char * restrict s,
19254 const char * restrict format, ...);
19255 int vfprintf_s(FILE * restrict stream,
19256 const char * restrict format,
19258 int vfscanf_s(FILE * restrict stream,
19259 const char * restrict format,
19261 int vprintf_s(const char * restrict format,
19263 int vscanf_s(const char * restrict format,
19265 int vsnprintf_s(char * restrict s, rsize_t n,
19266 const char * restrict format,
19268 int vsprintf_s(char * restrict s, rsize_t n,
19269 const char * restrict format,
19271 int vsscanf_s(const char * restrict s,
19272 const char * restrict format,
19274 char *gets_s(char *s, rsize_t n);
19278 [<a name="p486" href="#p486">page 486</a>] (<a href="#Contents">Contents</a>)
19280 <a name="B.21" href="#B.21"><b>B.21 General utilities <stdlib.h></b></a>
19281 size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
19282 wchar_t lldiv_t EXIT_SUCCESS
19283 div_t NULL RAND_MAX
19284 double atof(const char *nptr);
19285 int atoi(const char *nptr);
19286 long int atol(const char *nptr);
19287 long long int atoll(const char *nptr);
19288 double strtod(const char * restrict nptr,
19289 char ** restrict endptr);
19290 float strtof(const char * restrict nptr,
19291 char ** restrict endptr);
19292 long double strtold(const char * restrict nptr,
19293 char ** restrict endptr);
19294 long int strtol(const char * restrict nptr,
19295 char ** restrict endptr, int base);
19296 long long int strtoll(const char * restrict nptr,
19297 char ** restrict endptr, int base);
19298 unsigned long int strtoul(
19299 const char * restrict nptr,
19300 char ** restrict endptr, int base);
19301 unsigned long long int strtoull(
19302 const char * restrict nptr,
19303 char ** restrict endptr, int base);
19305 void srand(unsigned int seed);
19306 void *aligned_alloc(size_t alignment, size_t size);
19307 void *calloc(size_t nmemb, size_t size);
19308 void free(void *ptr);
19309 void *malloc(size_t size);
19310 void *realloc(void *ptr, size_t size);
19311 _Noreturn void abort(void);
19312 int atexit(void (*func)(void));
19313 int at_quick_exit(void (*func)(void));
19314 _Noreturn void exit(int status);
19315 _Noreturn void _Exit(int status);
19316 char *getenv(const char *name);
19317 _Noreturn void quick_exit(int status);
19318 int system(const char *string);
19321 [<a name="p487" href="#p487">page 487</a>] (<a href="#Contents">Contents</a>)
19323 void *bsearch(const void *key, const void *base,
19324 size_t nmemb, size_t size,
19325 int (*compar)(const void *, const void *));
19326 void qsort(void *base, size_t nmemb, size_t size,
19327 int (*compar)(const void *, const void *));
19329 long int labs(long int j);
19330 long long int llabs(long long int j);
19331 div_t div(int numer, int denom);
19332 ldiv_t ldiv(long int numer, long int denom);
19333 lldiv_t lldiv(long long int numer,
19334 long long int denom);
19335 int mblen(const char *s, size_t n);
19336 int mbtowc(wchar_t * restrict pwc,
19337 const char * restrict s, size_t n);
19338 int wctomb(char *s, wchar_t wchar);
19339 size_t mbstowcs(wchar_t * restrict pwcs,
19340 const char * restrict s, size_t n);
19341 size_t wcstombs(char * restrict s,
19342 const wchar_t * restrict pwcs, size_t n);
19343 __STDC_WANT_LIB_EXT1__
19346 constraint_handler_t
19347 constraint_handler_t set_constraint_handler_s(
19348 constraint_handler_t handler);
19349 void abort_handler_s(
19350 const char * restrict msg,
19351 void * restrict ptr,
19353 void ignore_handler_s(
19354 const char * restrict msg,
19355 void * restrict ptr,
19357 errno_t getenv_s(size_t * restrict len,
19358 char * restrict value, rsize_t maxsize,
19359 const char * restrict name);
19364 [<a name="p488" href="#p488">page 488</a>] (<a href="#Contents">Contents</a>)
19366 void *bsearch_s(const void *key, const void *base,
19367 rsize_t nmemb, rsize_t size,
19368 int (*compar)(const void *k, const void *y,
19371 errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
19372 int (*compar)(const void *x, const void *y,
19375 errno_t wctomb_s(int * restrict status,
19379 errno_t mbstowcs_s(size_t * restrict retval,
19380 wchar_t * restrict dst, rsize_t dstmax,
19381 const char * restrict src, rsize_t len);
19382 errno_t wcstombs_s(size_t * restrict retval,
19383 char * restrict dst, rsize_t dstmax,
19384 const wchar_t * restrict src, rsize_t len);
19385 <a name="B.22" href="#B.22"><b>B.22 String handling <string.h></b></a>
19388 void *memcpy(void * restrict s1,
19389 const void * restrict s2, size_t n);
19390 void *memmove(void *s1, const void *s2, size_t n);
19391 char *strcpy(char * restrict s1,
19392 const char * restrict s2);
19393 char *strncpy(char * restrict s1,
19394 const char * restrict s2, size_t n);
19395 char *strcat(char * restrict s1,
19396 const char * restrict s2);
19397 char *strncat(char * restrict s1,
19398 const char * restrict s2, size_t n);
19399 int memcmp(const void *s1, const void *s2, size_t n);
19400 int strcmp(const char *s1, const char *s2);
19401 int strcoll(const char *s1, const char *s2);
19402 int strncmp(const char *s1, const char *s2, size_t n);
19403 size_t strxfrm(char * restrict s1,
19404 const char * restrict s2, size_t n);
19405 void *memchr(const void *s, int c, size_t n);
19406 [<a name="p489" href="#p489">page 489</a>] (<a href="#Contents">Contents</a>)
19408 char *strchr(const char *s, int c);
19409 size_t strcspn(const char *s1, const char *s2);
19410 char *strpbrk(const char *s1, const char *s2);
19411 char *strrchr(const char *s, int c);
19412 size_t strspn(const char *s1, const char *s2);
19413 char *strstr(const char *s1, const char *s2);
19414 char *strtok(char * restrict s1,
19415 const char * restrict s2);
19416 void *memset(void *s, int c, size_t n);
19417 char *strerror(int errnum);
19418 size_t strlen(const char *s);
19419 __STDC_WANT_LIB_EXT1__
19422 errno_t memcpy_s(void * restrict s1, rsize_t s1max,
19423 const void * restrict s2, rsize_t n);
19424 errno_t memmove_s(void *s1, rsize_t s1max,
19425 const void *s2, rsize_t n);
19426 errno_t strcpy_s(char * restrict s1,
19428 const char * restrict s2);
19429 errno_t strncpy_s(char * restrict s1,
19431 const char * restrict s2,
19433 errno_t strcat_s(char * restrict s1,
19435 const char * restrict s2);
19436 errno_t strncat_s(char * restrict s1,
19438 const char * restrict s2,
19440 char *strtok_s(char * restrict s1,
19441 rsize_t * restrict s1max,
19442 const char * restrict s2,
19443 char ** restrict ptr);
19444 errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
19445 errno_t strerror_s(char *s, rsize_t maxsize,
19447 size_t strerrorlen_s(errno_t errnum);
19449 [<a name="p490" href="#p490">page 490</a>] (<a href="#Contents">Contents</a>)
19451 size_t strnlen_s(const char *s, size_t maxsize);
19452 <a name="B.23" href="#B.23"><b>B.23 Type-generic math <tgmath.h></b></a>
19453 acos sqrt fmod nextafter
19454 asin fabs frexp nexttoward
19455 atan atan2 hypot remainder
19456 acosh cbrt ilogb remquo
19457 asinh ceil ldexp rint
19458 atanh copysign lgamma round
19459 cos erf llrint scalbn
19460 sin erfc llround scalbln
19461 tan exp2 log10 tgamma
19462 cosh expm1 log1p trunc
19463 sinh fdim log2 carg
19464 tanh floor logb cimag
19466 log fmax lround cproj
19467 pow fmin nearbyint creal
19468 <a name="B.24" href="#B.24"><b>B.24 Threads <threads.h></b></a>
19469 ONCE_FLAG_INIT mtx_plain
19470 TSS_DTOR_ITERATIONS mtx_recursive
19475 tss_dtor_t thrd_busy
19476 thrd_start_t thrd_error
19477 once_flag thrd_nomem
19479 void call_once(once_flag *flag, void (*func)(void));
19480 int cnd_broadcast(cnd_t *cond);
19481 void cnd_destroy(cnd_t *cond);
19482 int cnd_init(cnd_t *cond);
19483 int cnd_signal(cnd_t *cond);
19484 int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
19486 int cnd_wait(cnd_t *cond, mtx_t *mtx);
19487 void mtx_destroy(mtx_t *mtx);
19488 int mtx_init(mtx_t *mtx, int type);
19489 int mtx_lock(mtx_t *mtx);
19490 [<a name="p491" href="#p491">page 491</a>] (<a href="#Contents">Contents</a>)
19492 int mtx_timedlock(mtx_t *mtx, const xtime *xt);
19493 int mtx_trylock(mtx_t *mtx);
19494 int mtx_unlock(mtx_t *mtx);
19495 int thrd_create(thrd_t *thr, thrd_start_t func,
19497 thrd_t thrd_current(void);
19498 int thrd_detach(thrd_t thr);
19499 int thrd_equal(thrd_t thr0, thrd_t thr1);
19500 void thrd_exit(int res);
19501 int thrd_join(thrd_t thr, int *res);
19502 void thrd_sleep(const xtime *xt);
19503 void thrd_yield(void);
19504 int tss_create(tss_t *key, tss_dtor_t dtor);
19505 void tss_delete(tss_t key);
19506 void *tss_get(tss_t key);
19507 int tss_set(tss_t key, void *val);
19508 int xtime_get(xtime *xt, int base);
19509 <a name="B.25" href="#B.25"><b>B.25 Date and time <time.h></b></a>
19511 CLOCKS_PER_SEC clock_t struct tm
19512 clock_t clock(void);
19513 double difftime(time_t time1, time_t time0);
19514 time_t mktime(struct tm *timeptr);
19515 time_t time(time_t *timer);
19516 char *asctime(const struct tm *timeptr);
19517 char *ctime(const time_t *timer);
19518 struct tm *gmtime(const time_t *timer);
19519 struct tm *localtime(const time_t *timer);
19520 size_t strftime(char * restrict s,
19522 const char * restrict format,
19523 const struct tm * restrict timeptr);
19524 __STDC_WANT_LIB_EXT1__
19527 errno_t asctime_s(char *s, rsize_t maxsize,
19528 const struct tm *timeptr);
19532 [<a name="p492" href="#p492">page 492</a>] (<a href="#Contents">Contents</a>)
19534 errno_t ctime_s(char *s, rsize_t maxsize,
19535 const time_t *timer);
19536 struct tm *gmtime_s(const time_t * restrict timer,
19537 struct tm * restrict result);
19538 struct tm *localtime_s(const time_t * restrict timer,
19539 struct tm * restrict result);
19540 <a name="B.26" href="#B.26"><b>B.26 Unicode utilities <uchar.h></b></a>
19541 mbstate_t size_t char16_t char32_t
19542 size_t mbrtoc16(char16_t * restrict pc16,
19543 const char * restrict s, size_t n,
19544 mbstate_t * restrict ps);
19545 size_t c16rtomb(char * restrict s, char16_t c16,
19546 mbstate_t * restrict ps);
19547 size_t mbrtoc32(char32_t * restrict pc32,
19548 const char * restrict s, size_t n,
19549 mbstate_t * restrict ps);
19550 size_t c32rtomb(char * restrict s, char32_t c32,
19551 mbstate_t * restrict ps);
19552 <a name="B.27" href="#B.27"><b>B.27 Extended multibyte/wide character utilities <wchar.h></b></a>
19553 wchar_t wint_t WCHAR_MAX
19554 size_t struct tm WCHAR_MIN
19555 mbstate_t NULL WEOF
19556 int fwprintf(FILE * restrict stream,
19557 const wchar_t * restrict format, ...);
19558 int fwscanf(FILE * restrict stream,
19559 const wchar_t * restrict format, ...);
19560 int swprintf(wchar_t * restrict s, size_t n,
19561 const wchar_t * restrict format, ...);
19562 int swscanf(const wchar_t * restrict s,
19563 const wchar_t * restrict format, ...);
19564 int vfwprintf(FILE * restrict stream,
19565 const wchar_t * restrict format, va_list arg);
19566 int vfwscanf(FILE * restrict stream,
19567 const wchar_t * restrict format, va_list arg);
19568 int vswprintf(wchar_t * restrict s, size_t n,
19569 const wchar_t * restrict format, va_list arg);
19573 [<a name="p493" href="#p493">page 493</a>] (<a href="#Contents">Contents</a>)
19575 int vswscanf(const wchar_t * restrict s,
19576 const wchar_t * restrict format, va_list arg);
19577 int vwprintf(const wchar_t * restrict format,
19579 int vwscanf(const wchar_t * restrict format,
19581 int wprintf(const wchar_t * restrict format, ...);
19582 int wscanf(const wchar_t * restrict format, ...);
19583 wint_t fgetwc(FILE *stream);
19584 wchar_t *fgetws(wchar_t * restrict s, int n,
19585 FILE * restrict stream);
19586 wint_t fputwc(wchar_t c, FILE *stream);
19587 int fputws(const wchar_t * restrict s,
19588 FILE * restrict stream);
19589 int fwide(FILE *stream, int mode);
19590 wint_t getwc(FILE *stream);
19591 wint_t getwchar(void);
19592 wint_t putwc(wchar_t c, FILE *stream);
19593 wint_t putwchar(wchar_t c);
19594 wint_t ungetwc(wint_t c, FILE *stream);
19595 double wcstod(const wchar_t * restrict nptr,
19596 wchar_t ** restrict endptr);
19597 float wcstof(const wchar_t * restrict nptr,
19598 wchar_t ** restrict endptr);
19599 long double wcstold(const wchar_t * restrict nptr,
19600 wchar_t ** restrict endptr);
19601 long int wcstol(const wchar_t * restrict nptr,
19602 wchar_t ** restrict endptr, int base);
19603 long long int wcstoll(const wchar_t * restrict nptr,
19604 wchar_t ** restrict endptr, int base);
19605 unsigned long int wcstoul(const wchar_t * restrict nptr,
19606 wchar_t ** restrict endptr, int base);
19607 unsigned long long int wcstoull(
19608 const wchar_t * restrict nptr,
19609 wchar_t ** restrict endptr, int base);
19610 wchar_t *wcscpy(wchar_t * restrict s1,
19611 const wchar_t * restrict s2);
19612 wchar_t *wcsncpy(wchar_t * restrict s1,
19613 const wchar_t * restrict s2, size_t n);
19617 [<a name="p494" href="#p494">page 494</a>] (<a href="#Contents">Contents</a>)
19619 wchar_t *wmemcpy(wchar_t * restrict s1,
19620 const wchar_t * restrict s2, size_t n);
19621 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
19623 wchar_t *wcscat(wchar_t * restrict s1,
19624 const wchar_t * restrict s2);
19625 wchar_t *wcsncat(wchar_t * restrict s1,
19626 const wchar_t * restrict s2, size_t n);
19627 int wcscmp(const wchar_t *s1, const wchar_t *s2);
19628 int wcscoll(const wchar_t *s1, const wchar_t *s2);
19629 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
19631 size_t wcsxfrm(wchar_t * restrict s1,
19632 const wchar_t * restrict s2, size_t n);
19633 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
19635 wchar_t *wcschr(const wchar_t *s, wchar_t c);
19636 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
19637 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
19638 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
19639 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
19640 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
19641 wchar_t *wcstok(wchar_t * restrict s1,
19642 const wchar_t * restrict s2,
19643 wchar_t ** restrict ptr);
19644 wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
19645 size_t wcslen(const wchar_t *s);
19646 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
19647 size_t wcsftime(wchar_t * restrict s, size_t maxsize,
19648 const wchar_t * restrict format,
19649 const struct tm * restrict timeptr);
19650 wint_t btowc(int c);
19651 int wctob(wint_t c);
19652 int mbsinit(const mbstate_t *ps);
19653 size_t mbrlen(const char * restrict s, size_t n,
19654 mbstate_t * restrict ps);
19655 size_t mbrtowc(wchar_t * restrict pwc,
19656 const char * restrict s, size_t n,
19657 mbstate_t * restrict ps);
19661 [<a name="p495" href="#p495">page 495</a>] (<a href="#Contents">Contents</a>)
19663 size_t wcrtomb(char * restrict s, wchar_t wc,
19664 mbstate_t * restrict ps);
19665 size_t mbsrtowcs(wchar_t * restrict dst,
19666 const char ** restrict src, size_t len,
19667 mbstate_t * restrict ps);
19668 size_t wcsrtombs(char * restrict dst,
19669 const wchar_t ** restrict src, size_t len,
19670 mbstate_t * restrict ps);
19671 __STDC_WANT_LIB_EXT1__
19674 int fwprintf_s(FILE * restrict stream,
19675 const wchar_t * restrict format, ...);
19676 int fwscanf_s(FILE * restrict stream,
19677 const wchar_t * restrict format, ...);
19678 int snwprintf_s(wchar_t * restrict s,
19680 const wchar_t * restrict format, ...);
19681 int swprintf_s(wchar_t * restrict s, rsize_t n,
19682 const wchar_t * restrict format, ...);
19683 int swscanf_s(const wchar_t * restrict s,
19684 const wchar_t * restrict format, ...);
19685 int vfwprintf_s(FILE * restrict stream,
19686 const wchar_t * restrict format,
19688 int vfwscanf_s(FILE * restrict stream,
19689 const wchar_t * restrict format, va_list arg);
19690 int vsnwprintf_s(wchar_t * restrict s,
19692 const wchar_t * restrict format,
19694 int vswprintf_s(wchar_t * restrict s,
19696 const wchar_t * restrict format,
19698 int vswscanf_s(const wchar_t * restrict s,
19699 const wchar_t * restrict format,
19704 [<a name="p496" href="#p496">page 496</a>] (<a href="#Contents">Contents</a>)
19706 int vwprintf_s(const wchar_t * restrict format,
19708 int vwscanf_s(const wchar_t * restrict format,
19710 int wprintf_s(const wchar_t * restrict format, ...);
19711 int wscanf_s(const wchar_t * restrict format, ...);
19712 errno_t wcscpy_s(wchar_t * restrict s1,
19714 const wchar_t * restrict s2);
19715 errno_t wcsncpy_s(wchar_t * restrict s1,
19717 const wchar_t * restrict s2,
19719 errno_t wmemcpy_s(wchar_t * restrict s1,
19721 const wchar_t * restrict s2,
19723 errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
19724 const wchar_t *s2, rsize_t n);
19725 errno_t wcscat_s(wchar_t * restrict s1,
19727 const wchar_t * restrict s2);
19728 errno_t wcsncat_s(wchar_t * restrict s1,
19730 const wchar_t * restrict s2,
19732 wchar_t *wcstok_s(wchar_t * restrict s1,
19733 rsize_t * restrict s1max,
19734 const wchar_t * restrict s2,
19735 wchar_t ** restrict ptr);
19736 size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
19737 errno_t wcrtomb_s(size_t * restrict retval,
19738 char * restrict s, rsize_t smax,
19739 wchar_t wc, mbstate_t * restrict ps);
19740 errno_t mbsrtowcs_s(size_t * restrict retval,
19741 wchar_t * restrict dst, rsize_t dstmax,
19742 const char ** restrict src, rsize_t len,
19743 mbstate_t * restrict ps);
19748 [<a name="p497" href="#p497">page 497</a>] (<a href="#Contents">Contents</a>)
19750 errno_t wcsrtombs_s(size_t * restrict retval,
19751 char * restrict dst, rsize_t dstmax,
19752 const wchar_t ** restrict src, rsize_t len,
19753 mbstate_t * restrict ps);
19754 <a name="B.28" href="#B.28"><b>B.28 Wide character classification and mapping utilities <wctype.h></b></a>
19755 wint_t wctrans_t wctype_t WEOF
19756 int iswalnum(wint_t wc);
19757 int iswalpha(wint_t wc);
19758 int iswblank(wint_t wc);
19759 int iswcntrl(wint_t wc);
19760 int iswdigit(wint_t wc);
19761 int iswgraph(wint_t wc);
19762 int iswlower(wint_t wc);
19763 int iswprint(wint_t wc);
19764 int iswpunct(wint_t wc);
19765 int iswspace(wint_t wc);
19766 int iswupper(wint_t wc);
19767 int iswxdigit(wint_t wc);
19768 int iswctype(wint_t wc, wctype_t desc);
19769 wctype_t wctype(const char *property);
19770 wint_t towlower(wint_t wc);
19771 wint_t towupper(wint_t wc);
19772 wint_t towctrans(wint_t wc, wctrans_t desc);
19773 wctrans_t wctrans(const char *property);
19778 [<a name="p498" href="#p498">page 498</a>] (<a href="#Contents">Contents</a>)
19780 <a name="C" href="#C"><b> Annex C</b></a>
19783 1 The following are the sequence points described in <a href="#5.1.2.3">5.1.2.3</a>:
19784 -- Between the evaluations of the function designator and actual arguments in a function
19785 call and the actual call. (<a href="#6.5.2.2">6.5.2.2</a>).
19786 -- Between the evaluations of the first and second operands of the following operators:
19787 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>). *
19788 -- Between the evaluations of the first operand of the conditional ? : operator and
19789 whichever of the second and third operands is evaluated (<a href="#6.5.15">6.5.15</a>).
19790 -- The end of a full declarator: declarators (<a href="#6.7.6">6.7.6</a>);
19791 -- Between the evaluation of a full expression and the next full expression to be
19792 evaluated. The following are full expressions: an initializer that is not part of a
19793 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
19794 controlling expression of a selection statement (if or switch) (<a href="#6.8.4">6.8.4</a>); the
19795 controlling expression of a while or do statement (<a href="#6.8.5">6.8.5</a>); each of the (optional)
19796 expressions of a for statement (<a href="#6.8.5.3">6.8.5.3</a>); the (optional) expression in a return
19797 statement (<a href="#6.8.6.4">6.8.6.4</a>).
19798 -- Immediately before a library function returns (<a href="#7.1.4">7.1.4</a>).
19799 -- After the actions associated with each formatted input/output function conversion
19800 specifier (<a href="#7.21.6">7.21.6</a>, <a href="#7.28.2">7.28.2</a>).
19801 -- Immediately before and immediately after each call to a comparison function, and
19802 also between any call to a comparison function and any movement of the objects
19803 passed as arguments to that call (<a href="#7.22.5">7.22.5</a>).
19808 [<a name="p499" href="#p499">page 499</a>] (<a href="#Contents">Contents</a>)
19810 <a name="D" href="#D"><b> Annex D</b></a>
19812 Universal character names for identifiers
19813 1 This clause lists the hexadecimal code values that are valid in universal character names
19815 <a name="D.1" href="#D.1"><b> D.1 Ranges of characters allowed</b></a>
19816 1 00A8, 00AA, 00AD, 00AF, 00B2-00B5, 00B7-00BA, 00BC-00BE, 00C0-00D6,
19817 00D8-00F6, 00F8-00FF
19818 2 0100-167F, 1681-180D, 180F-1FFF
19819 3 200B-200D, 202A-202E, 203F-2040, 2054, 2060-206F
19820 4 2070-218F, 2460-24FF, 2776-2793, 2C00-2DFF, 2E80-2FFF
19821 5 3004-3007, 3021-302F, 3031-303F
19823 7 F900-FD3D, FD40-FDCF, FDF0-FE44, FE47-FFFD
19824 8 10000-1FFFD, 20000-2FFFD, 30000-3FFFD, 40000-4FFFD, 50000-5FFFD,
19825 60000-6FFFD, 70000-7FFFD, 80000-8FFFD, 90000-9FFFD, A0000-AFFFD,
19826 B0000-BFFFD, C0000-CFFFD, D0000-DFFFD, E0000-EFFFD
19827 <a name="D.2" href="#D.2"><b> D.2 Ranges of characters disallowed initially</b></a>
19828 1 0300-036F, 1DC0-1DFF, 20D0-20FF, FE20-FE2F
19833 [<a name="p500" href="#p500">page 500</a>] (<a href="#Contents">Contents</a>)
19835 <a name="E" href="#E"><b> Annex E</b></a>
19837 Implementation limits
19838 1 The contents of the header <a href="#7.10"><limits.h></a> are given below, in alphabetical order. The
19839 minimum magnitudes shown shall be replaced by implementation-defined magnitudes
19840 with the same sign. The values shall all be constant expressions suitable for use in #if
19841 preprocessing directives. The components are described further in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
19843 #define CHAR_MAX UCHAR_MAX or SCHAR_MAX
19844 #define CHAR_MIN 0 or SCHAR_MIN
19845 #define INT_MAX +32767
19846 #define INT_MIN -32767
19847 #define LONG_MAX +2147483647
19848 #define LONG_MIN -2147483647
19849 #define LLONG_MAX +9223372036854775807
19850 #define LLONG_MIN -9223372036854775807
19851 #define MB_LEN_MAX 1
19852 #define SCHAR_MAX +127
19853 #define SCHAR_MIN -127
19854 #define SHRT_MAX +32767
19855 #define SHRT_MIN -32767
19856 #define UCHAR_MAX 255
19857 #define USHRT_MAX 65535
19858 #define UINT_MAX 65535
19859 #define ULONG_MAX 4294967295
19860 #define ULLONG_MAX 18446744073709551615
19861 2 The contents of the header <a href="#7.7"><float.h></a> are given below. All integer values, except
19862 FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing
19863 directives; all floating values shall be constant expressions. The components are
19864 described further in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
19865 3 The values given in the following list shall be replaced by implementation-defined
19867 #define FLT_EVAL_METHOD
19869 4 The values given in the following list shall be replaced by implementation-defined
19870 constant expressions that are greater or equal in magnitude (absolute value) to those
19871 shown, with the same sign:
19872 [<a name="p501" href="#p501">page 501</a>] (<a href="#Contents">Contents</a>)
19874 #define DLB_DECIMAL_DIG 10
19876 #define DBL_MANT_DIG
19877 #define DBL_MAX_10_EXP +37
19878 #define DBL_MAX_EXP
19879 #define DBL_MIN_10_EXP -37
19880 #define DBL_MIN_EXP
19881 #define DECIMAL_DIG 10
19882 #define FLT_DECIMAL_DIG 6
19884 #define FLT_MANT_DIG
19885 #define FLT_MAX_10_EXP +37
19886 #define FLT_MAX_EXP
19887 #define FLT_MIN_10_EXP -37
19888 #define FLT_MIN_EXP
19889 #define FLT_RADIX 2
19890 #define LDLB_DECIMAL_DIG 10
19891 #define LDBL_DIG 10
19892 #define LDBL_MANT_DIG
19893 #define LDBL_MAX_10_EXP +37
19894 #define LDBL_MAX_EXP
19895 #define LDBL_MIN_10_EXP -37
19896 #define LDBL_MIN_EXP
19897 5 The values given in the following list shall be replaced by implementation-defined
19898 constant expressions with values that are greater than or equal to those shown:
19899 #define DBL_MAX 1E+37
19900 #define FLT_MAX 1E+37
19901 #define LDBL_MAX 1E+37
19902 6 The values given in the following list shall be replaced by implementation-defined
19903 constant expressions with (positive) values that are less than or equal to those shown:
19904 #define DBL_EPSILON 1E-9
19905 #define DBL_MIN 1E-37
19906 #define FLT_EPSILON 1E-5
19907 #define FLT_MIN 1E-37
19908 #define LDBL_EPSILON 1E-9
19909 #define LDBL_MIN 1E-37
19914 [<a name="p502" href="#p502">page 502</a>] (<a href="#Contents">Contents</a>)
19916 <a name="F" href="#F"><b> Annex F</b></a>
19918 IEC 60559 floating-point arithmetic
19919 <a name="F.1" href="#F.1"><b> F.1 Introduction</b></a>
19920 1 This annex specifies C language support for the IEC 60559 floating-point standard. The
19921 IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
19922 microprocessor systems, second edition (IEC 60559:1989), previously designated
19923 IEC 559:1989 and as IEEE Standard for Binary Floating-Point Arithmetic
19924 (ANSI/IEEE 754-1985). IEEE Standard for Radix-Independent Floating-Point
19925 Arithmetic (ANSI/IEEE 854-1987) generalizes the binary standard to remove
19926 dependencies on radix and word length. IEC 60559 generally refers to the floating-point
19927 standard, as in IEC 60559 operation, IEC 60559 format, etc. An implementation that
19928 defines __STDC_IEC_559__ shall conform to the specifications in this annex.<sup><a href="#note343"><b>343)</b></a></sup>
19929 Where a binding between the C language and IEC 60559 is indicated, the
19930 IEC 60559-specified behavior is adopted by reference, unless stated otherwise. Since
19931 negative and positive infinity are representable in IEC 60559 formats, all real numbers lie
19932 within the range of representable values.
19933 <a name="F.2" href="#F.2"><b> F.2 Types</b></a>
19934 1 The C floating types match the IEC 60559 formats as follows:
19935 -- The float type matches the IEC 60559 single format.
19936 -- The double type matches the IEC 60559 double format.
19937 -- The long double type matches an IEC 60559 extended format,<sup><a href="#note344"><b>344)</b></a></sup> else a
19938 non-IEC 60559 extended format, else the IEC 60559 double format.
19939 Any non-IEC 60559 extended format used for the long double type shall have more
19940 precision than IEC 60559 double and at least the range of IEC 60559 double.<sup><a href="#note345"><b>345)</b></a></sup>
19945 <sup><a name="note343" href="#note343"><b>343)</b></a></sup> Implementations that do not define __STDC_IEC_559__ are not required to conform to these
19947 <sup><a name="note344" href="#note344"><b>344)</b></a></sup> ''Extended'' is IEC 60559's double-extended data format. Extended refers to both the common 80-bit
19948 and quadruple 128-bit IEC 60559 formats.
19949 <sup><a name="note345" href="#note345"><b>345)</b></a></sup> A non-IEC 60559 long double type is required to provide infinity and NaNs, as its values include
19952 [<a name="p503" href="#p503">page 503</a>] (<a href="#Contents">Contents</a>)
19954 Recommended practice
19955 2 The long double type should match an IEC 60559 extended format.
19956 <a name="F.2.1" href="#F.2.1"><b> F.2.1 Infinities, signed zeros, and NaNs</b></a>
19957 1 This specification does not define the behavior of signaling NaNs.<sup><a href="#note346"><b>346)</b></a></sup> It generally uses
19958 the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
19959 functions in <a href="#7.12"><math.h></a> provide designations for IEC 60559 NaNs and infinities.
19960 <a name="F.3" href="#F.3"><b> F.3 Operators and functions</b></a>
19961 1 C operators and functions provide IEC 60559 required and recommended facilities as
19963 -- The +, -, *, and / operators provide the IEC 60559 add, subtract, multiply, and
19965 -- The sqrt functions in <a href="#7.12"><math.h></a> provide the IEC 60559 square root operation.
19966 -- The remainder functions in <a href="#7.12"><math.h></a> provide the IEC 60559 remainder
19967 operation. The remquo functions in <a href="#7.12"><math.h></a> provide the same operation but
19968 with additional information.
19969 -- The rint functions in <a href="#7.12"><math.h></a> provide the IEC 60559 operation that rounds a
19970 floating-point number to an integer value (in the same precision). The nearbyint
19971 functions in <a href="#7.12"><math.h></a> provide the nearbyinteger function recommended in the
19972 Appendix to ANSI/IEEE 854.
19973 -- The conversions for floating types provide the IEC 60559 conversions between
19974 floating-point precisions.
19975 -- The conversions from integer to floating types provide the IEC 60559 conversions
19976 from integer to floating point.
19977 -- The conversions from floating to integer types provide IEC 60559-like conversions
19978 but always round toward zero.
19979 -- The lrint and llrint functions in <a href="#7.12"><math.h></a> provide the IEC 60559
19980 conversions, which honor the directed rounding mode, from floating point to the
19981 long int and long long int integer formats. The lrint and llrint
19982 functions can be used to implement IEC 60559 conversions from floating to other
19984 -- The translation time conversion of floating constants and the strtod, strtof,
19985 strtold, fprintf, fscanf, and related library functions in <a href="#7.22"><stdlib.h></a>,
19988 <sup><a name="note346" href="#note346"><b>346)</b></a></sup> Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are
19989 sufficient for closure of the arithmetic.
19991 [<a name="p504" href="#p504">page 504</a>] (<a href="#Contents">Contents</a>)
19993 <a href="#7.21"><stdio.h></a>, and <a href="#7.28"><wchar.h></a> provide IEC 60559 binary-decimal conversions. The
19994 strtold function in <a href="#7.22"><stdlib.h></a> provides the conv function recommended in the
19995 Appendix to ANSI/IEEE 854.
19996 -- The relational and equality operators provide IEC 60559 comparisons. IEC 60559
19997 identifies a need for additional comparison predicates to facilitate writing code that
19998 accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
19999 isless, islessequal, islessgreater, and isunordered) in <a href="#7.12"><math.h></a>
20000 supplement the language operators to address this need. The islessgreater and
20001 isunordered macros provide respectively a quiet version of the <> predicate and
20002 the unordered predicate recommended in the Appendix to IEC 60559.
20003 -- The feclearexcept, feraiseexcept, and fetestexcept functions in
20004 <a href="#7.6"><fenv.h></a> provide the facility to test and alter the IEC 60559 floating-point
20005 exception status flags. The fegetexceptflag and fesetexceptflag
20006 functions in <a href="#7.6"><fenv.h></a> provide the facility to save and restore all five status flags at
20007 one time. These functions are used in conjunction with the type fexcept_t and the
20008 floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
20009 FE_UNDERFLOW, FE_OVERFLOW, FE_INVALID) also in <a href="#7.6"><fenv.h></a>.
20010 -- The fegetround and fesetround functions in <a href="#7.6"><fenv.h></a> provide the facility
20011 to select among the IEC 60559 directed rounding modes represented by the rounding
20012 direction macros in <a href="#7.6"><fenv.h></a> (FE_TONEAREST, FE_UPWARD, FE_DOWNWARD,
20013 FE_TOWARDZERO) and the values 0, 1, 2, and 3 of FLT_ROUNDS are the
20014 IEC 60559 directed rounding modes.
20015 -- The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
20016 <a href="#7.6"><fenv.h></a> provide a facility to manage the floating-point environment, comprising
20017 the IEC 60559 status flags and control modes.
20018 -- The copysign functions in <a href="#7.12"><math.h></a> provide the copysign function
20019 recommended in the Appendix to IEC 60559.
20020 -- The fabs functions in <a href="#7.12"><math.h></a> provide the abs function recommended in the
20021 Appendix to IEC 60559.
20022 -- The unary minus (-) operator provides the unary minus (-) operation recommended
20023 in the Appendix to IEC 60559.
20024 -- The scalbn and scalbln functions in <a href="#7.12"><math.h></a> provide the scalb function
20025 recommended in the Appendix to IEC 60559.
20026 -- The logb functions in <a href="#7.12"><math.h></a> provide the logb function recommended in the
20027 Appendix to IEC 60559, but following the newer specifications in ANSI/IEEE 854.
20028 -- The nextafter and nexttoward functions in <a href="#7.12"><math.h></a> provide the nextafter
20029 function recommended in the Appendix to IEC 60559 (but with a minor change to
20031 [<a name="p505" href="#p505">page 505</a>] (<a href="#Contents">Contents</a>)
20033 better handle signed zeros).
20034 -- The isfinite macro in <a href="#7.12"><math.h></a> provides the finite function recommended in
20035 the Appendix to IEC 60559.
20036 -- The isnan macro in <a href="#7.12"><math.h></a> provides the isnan function recommended in the
20037 Appendix to IEC 60559.
20038 -- The signbit macro and the fpclassify macro in <a href="#7.12"><math.h></a>, used in
20039 conjunction with the number classification macros (FP_NAN, FP_INFINITE,
20040 FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
20041 function recommended in the Appendix to IEC 60559 (except that the classification
20042 macros defined in <a href="#7.12.3">7.12.3</a> do not distinguish signaling from quiet NaNs).
20043 <a name="F.4" href="#F.4"><b> F.4 Floating to integer conversion</b></a>
20044 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
20045 (even for NaN). Otherwise, if the floating value is infinite or NaN or if the integral part
20046 of the floating value exceeds the range of the integer type, then the ''invalid'' floating-
20047 point exception is raised and the resulting value is unspecified. Otherwise, the resulting
20048 value is determined by <a href="#6.3.1.4">6.3.1.4</a>. Conversion of an integral floating value that does not
20049 exceed the range of the integer type raises no floating-point exceptions; whether
20050 conversion of a non-integral floating value raises the ''inexact'' floating-point exception is
20051 unspecified.<sup><a href="#note347"><b>347)</b></a></sup>
20052 <a name="F.5" href="#F.5"><b> F.5 Binary-decimal conversion</b></a>
20053 1 Conversion from the widest supported IEC 60559 format to decimal with
20054 DECIMAL_DIG digits and back is the identity function.<sup><a href="#note348"><b>348)</b></a></sup>
20055 2 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
20056 particular, conversion between any supported IEC 60559 format and decimal with
20057 DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
20058 rounding mode), which assures that conversion from the widest supported IEC 60559
20059 format to decimal with DECIMAL_DIG digits and back is the identity function.
20063 <sup><a name="note347" href="#note347"><b>347)</b></a></sup> ANSI/IEEE 854, but not IEC 60559 (ANSI/IEEE 754), directly specifies that floating-to-integer
20064 conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those
20065 cases where it matters, library functions can be used to effect such conversions with or without raising
20066 the ''inexact'' floating-point exception. See rint, lrint, llrint, and nearbyint in
20067 <a href="#7.12"><math.h></a>.
20068 <sup><a name="note348" href="#note348"><b>348)</b></a></sup> If the minimum-width IEC 60559 extended format (64 bits of precision) is supported,
20069 DECIMAL_DIG shall be at least 21. If IEC 60559 double (53 bits of precision) is the widest
20070 IEC 60559 format supported, then DECIMAL_DIG shall be at least 17. (By contrast, LDBL_DIG and
20071 DBL_DIG are 18 and 15, respectively, for these formats.)
20073 [<a name="p506" href="#p506">page 506</a>] (<a href="#Contents">Contents</a>)
20075 3 Functions such as strtod that convert character sequences to floating types honor the
20076 rounding direction. Hence, if the rounding direction might be upward or downward, the
20077 implementation cannot convert a minus-signed sequence by negating the converted
20079 <a name="F.6" href="#F.6"><b> F.6 The return statement</b></a>
20080 If the return expression is evaluated in a floating-point format different from the return
20081 type, the expression is converted as if by assignment<sup><a href="#note349"><b>349)</b></a></sup> to the return type of the function
20082 and the resulting value is returned to the caller.
20083 <a name="F.7" href="#F.7"><b> F.7 Contracted expressions</b></a>
20084 1 A contracted expression is correctly rounded (once) and treats infinities, NaNs, signed
20085 zeros, subnormals, and the rounding directions in a manner consistent with the basic
20086 arithmetic operations covered by IEC 60559.
20087 Recommended practice
20088 2 A contracted expression should raise floating-point exceptions in a manner generally
20089 consistent with the basic arithmetic operations. *
20090 <a name="F.8" href="#F.8"><b> F.8 Floating-point environment</b></a>
20091 1 The floating-point environment defined in <a href="#7.6"><fenv.h></a> includes the IEC 60559 floating-
20092 point exception status flags and directed-rounding control modes. It includes also
20093 IEC 60559 dynamic rounding precision and trap enablement modes, if the
20094 implementation supports them.<sup><a href="#note350"><b>350)</b></a></sup>
20095 <a name="F.8.1" href="#F.8.1"><b> F.8.1 Environment management</b></a>
20096 1 IEC 60559 requires that floating-point operations implicitly raise floating-point exception
20097 status flags, and that rounding control modes can be set explicitly to affect result values of
20098 floating-point operations. When the state for the FENV_ACCESS pragma (defined in
20099 <a href="#7.6"><fenv.h></a>) is ''on'', these changes to the floating-point state are treated as side effects
20100 which respect sequence points.<sup><a href="#note351"><b>351)</b></a></sup>
20105 <sup><a name="note349" href="#note349"><b>349)</b></a></sup> Assignment removes any extra range and precision.
20106 <sup><a name="note350" href="#note350"><b>350)</b></a></sup> This specification does not require dynamic rounding precision nor trap enablement modes.
20107 <sup><a name="note351" href="#note351"><b>351)</b></a></sup> If the state for the FENV_ACCESS pragma is ''off'', the implementation is free to assume the floating-
20108 point control modes will be the default ones and the floating-point status flags will not be tested,
20109 which allows certain optimizations (see <a href="#F.9">F.9</a>).
20111 [<a name="p507" href="#p507">page 507</a>] (<a href="#Contents">Contents</a>)
20113 <a name="F.8.2" href="#F.8.2"><b> F.8.2 Translation</b></a>
20114 1 During translation the IEC 60559 default modes are in effect:
20115 -- The rounding direction mode is rounding to nearest.
20116 -- The rounding precision mode (if supported) is set so that results are not shortened.
20117 -- Trapping or stopping (if supported) is disabled on all floating-point exceptions.
20118 Recommended practice
20119 2 The implementation should produce a diagnostic message for each translation-time
20120 floating-point exception, other than ''inexact'';<sup><a href="#note352"><b>352)</b></a></sup> the implementation should then
20121 proceed with the translation of the program.
20122 <a name="F.8.3" href="#F.8.3"><b> F.8.3 Execution</b></a>
20123 1 At program startup the floating-point environment is initialized as prescribed by
20125 -- All floating-point exception status flags are cleared.
20126 -- The rounding direction mode is rounding to nearest.
20127 -- The dynamic rounding precision mode (if supported) is set so that results are not
20129 -- Trapping or stopping (if supported) is disabled on all floating-point exceptions.
20130 <a name="F.8.4" href="#F.8.4"><b> F.8.4 Constant expressions</b></a>
20131 1 An arithmetic constant expression of floating type, other than one in an initializer for an
20132 object that has static or thread storage duration, is evaluated (as if) during execution; thus,
20133 it is affected by any operative floating-point control modes and raises floating-point
20134 exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma
20135 is ''on'').<sup><a href="#note353"><b>353)</b></a></sup>
20140 <sup><a name="note352" href="#note352"><b>352)</b></a></sup> As floating constants are converted to appropriate internal representations at translation time, their
20141 conversion is subject to default rounding modes and raises no execution-time floating-point exceptions
20142 (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example
20143 strtod, provide execution-time conversion of numeric strings.
20144 <sup><a name="note353" href="#note353"><b>353)</b></a></sup> Where the state for the FENV_ACCESS pragma is ''on'', results of inexact expressions like 1.0/3.0
20145 are affected by rounding modes set at execution time, and expressions such as 0.0/0.0 and
20146 1.0/0.0 generate execution-time floating-point exceptions. The programmer can achieve the
20147 efficiency of translation-time evaluation through static initialization, such as
20148 const static double one_third = 1.0/3.0;
20151 [<a name="p508" href="#p508">page 508</a>] (<a href="#Contents">Contents</a>)
20153 #include <a href="#7.6"><fenv.h></a>
20154 #pragma STDC FENV_ACCESS ON
20157 float w[] = { 0.0/0.0 }; // raises an exception
20158 static float x = 0.0/0.0; // does not raise an exception
20159 float y = 0.0/0.0; // raises an exception
20160 double z = 0.0/0.0; // raises an exception
20163 3 For the static initialization, the division is done at translation time, raising no (execution-time) floating-
20164 point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at
20167 <a name="F.8.5" href="#F.8.5"><b> F.8.5 Initialization</b></a>
20168 1 All computation for automatic initialization is done (as if) at execution time; thus, it is
20169 affected by any operative modes and raises floating-point exceptions as required by
20170 IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation
20171 for initialization of objects that have static or thread storage duration is done (as if) at
20174 #include <a href="#7.6"><fenv.h></a>
20175 #pragma STDC FENV_ACCESS ON
20178 float u[] = { 1.1e75 }; // raises exceptions
20179 static float v = 1.1e75; // does not raise exceptions
20180 float w = 1.1e75; // raises exceptions
20181 double x = 1.1e75; // may raise exceptions
20182 float y = 1.1e75f; // may raise exceptions
20183 long double z = 1.1e75; // does not raise exceptions
20186 3 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is
20187 done at translation time. The automatic initialization of u and w require an execution-time conversion to
20188 float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations
20189 of x and y entail execution-time conversion; however, in some expression evaluation methods, the
20190 conversions is not to a narrower format, in which case no floating-point exception is raised.<sup><a href="#note354"><b>354)</b></a></sup> The
20191 automatic initialization of z entails execution-time conversion, but not to a narrower format, so no floating-
20192 point exception is raised. Note that the conversions of the floating constants 1.1e75 and 1.1e75f to
20196 <sup><a name="note354" href="#note354"><b>354)</b></a></sup> Use of float_t and double_t variables increases the likelihood of translation-time computation.
20197 For example, the automatic initialization
20198 double_t x = 1.1e75;
20199 could be done at translation time, regardless of the expression evaluation method.
20201 [<a name="p509" href="#p509">page 509</a>] (<a href="#Contents">Contents</a>)
20203 their internal representations occur at translation time in all cases.
20205 <a name="F.8.6" href="#F.8.6"><b> F.8.6 Changing the environment</b></a>
20206 1 Operations defined in <a href="#6.5">6.5</a> and functions and macros defined for the standard libraries
20207 change floating-point status flags and control modes just as indicated by their
20208 specifications (including conformance to IEC 60559). They do not change flags or modes
20209 (so as to be detectable by the user) in any other cases.
20210 2 If the argument to the feraiseexcept function in <a href="#7.6"><fenv.h></a> represents IEC 60559
20211 valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
20212 ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
20213 before ''inexact''.
20214 <a name="F.9" href="#F.9"><b> F.9 Optimization</b></a>
20215 1 This section identifies code transformations that might subvert IEC 60559-specified
20216 behavior, and others that do not.
20217 <a name="F.9.1" href="#F.9.1"><b> F.9.1 Global transformations</b></a>
20218 1 Floating-point arithmetic operations and external function calls may entail side effects
20219 which optimization shall honor, at least where the state of the FENV_ACCESS pragma is
20220 ''on''. The flags and modes in the floating-point environment may be regarded as global
20221 variables; floating-point operations (+, *, etc.) implicitly read the modes and write the
20223 2 Concern about side effects may inhibit code motion and removal of seemingly useless
20224 code. For example, in
20225 #include <a href="#7.6"><fenv.h></a>
20226 #pragma STDC FENV_ACCESS ON
20230 for (i = 0; i < n; i++) x + 1;
20233 x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
20234 body might not execute (maybe 0 >= n), x + 1 cannot be moved out of the loop. (Of
20235 course these optimizations are valid if the implementation can rule out the nettlesome
20237 3 This specification does not require support for trap handlers that maintain information
20238 about the order or count of floating-point exceptions. Therefore, between function calls,
20239 floating-point exceptions need not be precise: the actual order and number of occurrences
20240 of floating-point exceptions (> 1) may vary from what the source code expresses. Thus,
20241 [<a name="p510" href="#p510">page 510</a>] (<a href="#Contents">Contents</a>)
20243 the preceding loop could be treated as
20244 if (0 < n) x + 1;
20245 <a name="F.9.2" href="#F.9.2"><b> F.9.2 Expression transformations</b></a>
20246 1 x/2 (<->) x x 0.5 Although similar transformations involving inexact constants
20247 generally do not yield numerically equivalent expressions, if the
20248 constants are exact then such transformations can be made on
20249 IEC 60559 machines and others that round perfectly.
20250 1 x x and x/1 (->) x The expressions 1 x x, x/1, and x are equivalent (on IEC 60559
20251 machines, among others).<sup><a href="#note355"><b>355)</b></a></sup>
20252 x/x (->) 1.0 The expressions x/x and 1.0 are not equivalent if x can be zero,
20254 x - y (<->) x + (-y) The expressions x - y, x + (-y), and (-y) + x are equivalent (on
20255 IEC 60559 machines, among others).
20256 x - y (<->) -(y - x) The expressions x - y and -(y - x) are not equivalent because 1 - 1
20257 is +0 but -(1 - 1) is -0 (in the default rounding direction).<sup><a href="#note356"><b>356)</b></a></sup>
20258 x - x (->) 0.0 The expressions x - x and 0.0 are not equivalent if x is a NaN or
20260 0 x x (->) 0.0 The expressions 0 x x and 0.0 are not equivalent if x is a NaN,
20262 x+0(->) x The expressions x + 0 and x are not equivalent if x is -0, because
20263 (-0) + (+0) yields +0 (in the default rounding direction), not -0.
20264 x-0(->) x (+0) - (+0) yields -0 when rounding is downward (toward -(inf)), but
20265 +0 otherwise, and (-0) - (+0) always yields -0; so, if the state of the
20266 FENV_ACCESS pragma is ''off'', promising default rounding, then
20267 the implementation can replace x - 0 by x, even if x might be zero.
20268 -x (<->) 0 - x The expressions -x and 0 - x are not equivalent if x is +0, because
20269 -(+0) yields -0, but 0 - (+0) yields +0 (unless rounding is
20272 <sup><a name="note355" href="#note355"><b>355)</b></a></sup> Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
20273 other transformations that remove arithmetic operators.
20274 <sup><a name="note356" href="#note356"><b>356)</b></a></sup> IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
20276 1/(1/ (+-) (inf)) is (+-) (inf)
20278 conj(csqrt(z)) is csqrt(conj(z)),
20281 [<a name="p511" href="#p511">page 511</a>] (<a href="#Contents">Contents</a>)
20283 <a name="F.9.3" href="#F.9.3"><b> F.9.3 Relational operators</b></a>
20284 1 x != x (->) false The expression x != x is true if x is a NaN.
20285 x = x (->) true The expression x = x is false if x is a NaN.
20286 x < y (->) isless(x,y) (and similarly for <=, >, >=) Though numerically equal, these
20287 expressions are not equivalent because of side effects when x or y is a
20288 NaN and the state of the FENV_ACCESS pragma is ''on''. This
20289 transformation, which would be desirable if extra code were required
20290 to cause the ''invalid'' floating-point exception for unordered cases,
20291 could be performed provided the state of the FENV_ACCESS pragma
20293 The sense of relational operators shall be maintained. This includes handling unordered
20294 cases as expressed by the source code.
20296 // calls g and raises ''invalid'' if a and b are unordered
20301 is not equivalent to
20302 // calls f and raises ''invalid'' if a and b are unordered
20308 // calls f without raising ''invalid'' if a and b are unordered
20309 if (isgreaterequal(a,b))
20313 nor, unless the state of the FENV_ACCESS pragma is ''off'', to
20314 // calls g without raising ''invalid'' if a and b are unordered
20319 but is equivalent to
20324 [<a name="p512" href="#p512">page 512</a>] (<a href="#Contents">Contents</a>)
20331 <a name="F.9.4" href="#F.9.4"><b> F.9.4 Constant arithmetic</b></a>
20332 1 The implementation shall honor floating-point exceptions raised by execution-time
20333 constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See <a href="#F.8.4">F.8.4</a>
20334 and <a href="#F.8.5">F.8.5</a>.) An operation on constants that raises no floating-point exception can be
20335 folded during translation, except, if the state of the FENV_ACCESS pragma is ''on'', a
20336 further check is required to assure that changing the rounding direction to downward does
20337 not alter the sign of the result,<sup><a href="#note357"><b>357)</b></a></sup> and implementations that support dynamic rounding
20338 precision modes shall assure further that the result of the operation raises no floating-
20339 point exception when converted to the semantic type of the operation.
20340 <a name="F.10" href="#F.10"><b> F.10 Mathematics <math.h></b></a>
20341 1 This subclause contains specifications of <a href="#7.12"><math.h></a> facilities that are particularly suited
20342 for IEC 60559 implementations.
20343 2 The Standard C macro HUGE_VAL and its float and long double analogs,
20344 HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive
20346 3 Special cases for functions in <a href="#7.12"><math.h></a> are covered directly or indirectly by
20347 IEC 60559. The functions that IEC 60559 specifies directly are identified in <a href="#F.3">F.3</a>. The
20348 other functions in <a href="#7.12"><math.h></a> treat infinities, NaNs, signed zeros, subnormals, and
20349 (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags
20350 in a manner consistent with the basic arithmetic operations covered by IEC 60559.
20351 4 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
20353 5 The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in
20354 subsequent subclauses of this annex.
20355 6 The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of
20356 rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value
20357 whose magnitude is too large.
20358 7 The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially
20359 subnormal or zero) and suffers loss of accuracy.<sup><a href="#note358"><b>358)</b></a></sup>
20362 <sup><a name="note357" href="#note357"><b>357)</b></a></sup> 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
20363 <sup><a name="note358" href="#note358"><b>358)</b></a></sup> IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on
20364 when the floating-point exception is raised.
20366 [<a name="p513" href="#p513">page 513</a>] (<a href="#Contents">Contents</a>)
20368 8 Whether or when library functions raise the ''inexact'' floating-point exception is
20369 unspecified, unless explicitly specified otherwise.
20370 9 Whether or when library functions raise an undeserved ''underflow'' floating-point
20371 exception is unspecified.<sup><a href="#note359"><b>359)</b></a></sup> Otherwise, as implied by <a href="#F.8.6">F.8.6</a>, the <a href="#7.12"><math.h></a> functions do
20372 not raise spurious floating-point exceptions (detectable by the user), other than the
20373 ''inexact'' floating-point exception.
20374 10 Whether the functions honor the rounding direction mode is implementation-defined,
20375 unless explicitly specified otherwise.
20376 11 Functions with a NaN argument return a NaN result and raise no floating-point exception,
20377 except where stated otherwise.
20378 12 The specifications in the following subclauses append to the definitions in <a href="#7.12"><math.h></a>.
20379 For families of functions, the specifications apply to all of the functions even though only
20380 the principal function is shown. Unless otherwise specified, where the symbol ''(+-)''
20381 occurs in both an argument and the result, the result has the same sign as the argument.
20382 Recommended practice
20383 13 If a function with one or more NaN arguments returns a NaN result, the result should be
20384 the same as one of the NaN arguments (after possible type conversion), except perhaps
20386 <a name="F.10.1" href="#F.10.1"><b> F.10.1 Trigonometric functions</b></a>
20387 <a name="F.10.1.1" href="#F.10.1.1"><b> F.10.1.1 The acos functions</b></a>
20388 1 -- acos(1) returns +0.
20389 -- acos(x) returns a NaN and raises the ''invalid'' floating-point exception for
20391 <a name="F.10.1.2" href="#F.10.1.2"><b> F.10.1.2 The asin functions</b></a>
20392 1 -- asin((+-)0) returns (+-)0.
20393 -- asin(x) returns a NaN and raises the ''invalid'' floating-point exception for
20399 <sup><a name="note359" href="#note359"><b>359)</b></a></sup> It is intended that undeserved ''underflow'' and ''inexact'' floating-point exceptions are raised only if
20400 avoiding them would be too costly.
20402 [<a name="p514" href="#p514">page 514</a>] (<a href="#Contents">Contents</a>)
20404 <a name="F.10.1.3" href="#F.10.1.3"><b> F.10.1.3 The atan functions</b></a>
20405 1 -- atan((+-)0) returns (+-)0.
20406 -- atan((+-)(inf)) returns (+-)pi /2.
20407 <a name="F.10.1.4" href="#F.10.1.4"><b> F.10.1.4 The atan2 functions</b></a>
20408 1 -- atan2((+-)0, -0) returns (+-)pi .<sup><a href="#note360"><b>360)</b></a></sup>
20409 -- atan2((+-)0, +0) returns (+-)0.
20410 -- atan2((+-)0, x) returns (+-)pi for x < 0.
20411 -- atan2((+-)0, x) returns (+-)0 for x > 0.
20412 -- atan2(y, (+-)0) returns -pi /2 for y < 0.
20413 -- atan2(y, (+-)0) returns pi /2 for y > 0.
20414 -- atan2((+-)y, -(inf)) returns (+-)pi for finite y > 0.
20415 -- atan2((+-)y, +(inf)) returns (+-)0 for finite y > 0.
20416 -- atan2((+-)(inf), x) returns (+-)pi /2 for finite x.
20417 -- atan2((+-)(inf), -(inf)) returns (+-)3pi /4.
20418 -- atan2((+-)(inf), +(inf)) returns (+-)pi /4.
20419 <a name="F.10.1.5" href="#F.10.1.5"><b> F.10.1.5 The cos functions</b></a>
20420 1 -- cos((+-)0) returns 1.
20421 -- cos((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
20422 <a name="F.10.1.6" href="#F.10.1.6"><b> F.10.1.6 The sin functions</b></a>
20423 1 -- sin((+-)0) returns (+-)0.
20424 -- sin((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
20425 <a name="F.10.1.7" href="#F.10.1.7"><b> F.10.1.7 The tan functions</b></a>
20426 1 -- tan((+-)0) returns (+-)0.
20427 -- tan((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
20432 <sup><a name="note360" href="#note360"><b>360)</b></a></sup> atan2(0, 0) does not raise the ''invalid'' floating-point exception, nor does atan2( y , 0) raise
20433 the ''divide-by-zero'' floating-point exception.
20435 [<a name="p515" href="#p515">page 515</a>] (<a href="#Contents">Contents</a>)
20437 <a name="F.10.2" href="#F.10.2"><b> F.10.2 Hyperbolic functions</b></a>
20438 <a name="F.10.2.1" href="#F.10.2.1"><b> F.10.2.1 The acosh functions</b></a>
20439 1 -- acosh(1) returns +0.
20440 -- acosh(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 1.
20441 -- acosh(+(inf)) returns +(inf).
20442 <a name="F.10.2.2" href="#F.10.2.2"><b> F.10.2.2 The asinh functions</b></a>
20443 1 -- asinh((+-)0) returns (+-)0.
20444 -- asinh((+-)(inf)) returns (+-)(inf).
20445 <a name="F.10.2.3" href="#F.10.2.3"><b> F.10.2.3 The atanh functions</b></a>
20446 1 -- atanh((+-)0) returns (+-)0.
20447 -- atanh((+-)1) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
20448 -- atanh(x) returns a NaN and raises the ''invalid'' floating-point exception for
20450 <a name="F.10.2.4" href="#F.10.2.4"><b> F.10.2.4 The cosh functions</b></a>
20451 1 -- cosh((+-)0) returns 1.
20452 -- cosh((+-)(inf)) returns +(inf).
20453 <a name="F.10.2.5" href="#F.10.2.5"><b> F.10.2.5 The sinh functions</b></a>
20454 1 -- sinh((+-)0) returns (+-)0.
20455 -- sinh((+-)(inf)) returns (+-)(inf).
20456 <a name="F.10.2.6" href="#F.10.2.6"><b> F.10.2.6 The tanh functions</b></a>
20457 1 -- tanh((+-)0) returns (+-)0.
20458 -- tanh((+-)(inf)) returns (+-)1.
20459 <a name="F.10.3" href="#F.10.3"><b> F.10.3 Exponential and logarithmic functions</b></a>
20460 <a name="F.10.3.1" href="#F.10.3.1"><b> F.10.3.1 The exp functions</b></a>
20461 1 -- exp((+-)0) returns 1.
20462 -- exp(-(inf)) returns +0.
20463 -- exp(+(inf)) returns +(inf).
20468 [<a name="p516" href="#p516">page 516</a>] (<a href="#Contents">Contents</a>)
20470 <a name="F.10.3.2" href="#F.10.3.2"><b> F.10.3.2 The exp2 functions</b></a>
20471 1 -- exp2((+-)0) returns 1.
20472 -- exp2(-(inf)) returns +0.
20473 -- exp2(+(inf)) returns +(inf).
20474 <a name="F.10.3.3" href="#F.10.3.3"><b> F.10.3.3 The expm1 functions</b></a>
20475 1 -- expm1((+-)0) returns (+-)0.
20476 -- expm1(-(inf)) returns -1.
20477 -- expm1(+(inf)) returns +(inf).
20478 <a name="F.10.3.4" href="#F.10.3.4"><b> F.10.3.4 The frexp functions</b></a>
20479 1 -- frexp((+-)0, exp) returns (+-)0, and stores 0 in the object pointed to by exp.
20480 -- frexp((+-)(inf), exp) returns (+-)(inf), and stores an unspecified value in the object
20482 -- frexp(NaN, exp) stores an unspecified value in the object pointed to by exp
20483 (and returns a NaN).
20484 2 frexp raises no floating-point exceptions.
20485 3 When the radix of the argument is a power of 2, the returned value is exact and is
20486 independent of the current rounding direction mode.
20487 4 On a binary system, the body of the frexp function might be
20489 *exp = (value == 0) ? 0 : (int)(1 + logb(value));
20490 return scalbn(value, -(*exp));
20492 <a name="F.10.3.5" href="#F.10.3.5"><b> F.10.3.5 The ilogb functions</b></a>
20493 1 When the correct result is representable in the range of the return type, the returned value
20494 is exact and is independent of the current rounding direction mode.
20495 2 If the correct result is outside the range of the return type, the numeric result is
20496 unspecified and the ''invalid'' floating-point exception is raised.
20501 [<a name="p517" href="#p517">page 517</a>] (<a href="#Contents">Contents</a>)
20503 <a name="F.10.3.6" href="#F.10.3.6"><b> F.10.3.6 The ldexp functions</b></a>
20504 1 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
20505 <a name="F.10.3.7" href="#F.10.3.7"><b> F.10.3.7 The log functions</b></a>
20506 1 -- log((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
20507 -- log(1) returns +0.
20508 -- log(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
20509 -- log(+(inf)) returns +(inf).
20510 <a name="F.10.3.8" href="#F.10.3.8"><b> F.10.3.8 The log10 functions</b></a>
20511 1 -- log10((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
20512 -- log10(1) returns +0.
20513 -- log10(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
20514 -- log10(+(inf)) returns +(inf).
20515 <a name="F.10.3.9" href="#F.10.3.9"><b> F.10.3.9 The log1p functions</b></a>
20516 1 -- log1p((+-)0) returns (+-)0.
20517 -- log1p(-1) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
20518 -- log1p(x) returns a NaN and raises the ''invalid'' floating-point exception for
20520 -- log1p(+(inf)) returns +(inf).
20521 <a name="F.10.3.10" href="#F.10.3.10"><b> F.10.3.10 The log2 functions</b></a>
20522 1 -- log2((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
20523 -- log2(1) returns +0.
20524 -- log2(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
20525 -- log2(+(inf)) returns +(inf).
20526 <a name="F.10.3.11" href="#F.10.3.11"><b> F.10.3.11 The logb functions</b></a>
20527 1 -- logb((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
20528 -- logb((+-)(inf)) returns +(inf).
20529 2 The returned value is exact and is independent of the current rounding direction mode.
20534 [<a name="p518" href="#p518">page 518</a>] (<a href="#Contents">Contents</a>)
20536 <a name="F.10.3.12" href="#F.10.3.12"><b> F.10.3.12 The modf functions</b></a>
20537 1 -- modf((+-)x, iptr) returns a result with the same sign as x.
20538 -- modf((+-)(inf), iptr) returns (+-)0 and stores (+-)(inf) in the object pointed to by iptr.
20539 -- modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
20541 2 The returned values are exact and are independent of the current rounding direction
20543 3 modf behaves as though implemented by
20544 #include <a href="#7.12"><math.h></a>
20545 #include <a href="#7.6"><fenv.h></a>
20546 #pragma STDC FENV_ACCESS ON
20547 double modf(double value, double *iptr)
20549 int save_round = fegetround();
20550 fesetround(FE_TOWARDZERO);
20551 *iptr = nearbyint(value);
20552 fesetround(save_round);
20554 isinf(value) ? 0.0 :
20555 value - (*iptr), value);
20557 <a name="F.10.3.13" href="#F.10.3.13"><b> F.10.3.13 The scalbn and scalbln functions</b></a>
20558 1 -- scalbn((+-)0, n) returns (+-)0.
20559 -- scalbn(x, 0) returns x.
20560 -- scalbn((+-)(inf), n) returns (+-)(inf).
20561 2 If the calculation does not overflow or underflow, the returned value is exact and
20562 independent of the current rounding direction mode.
20567 [<a name="p519" href="#p519">page 519</a>] (<a href="#Contents">Contents</a>)
20569 <a name="F.10.4" href="#F.10.4"><b> F.10.4 Power and absolute value functions</b></a>
20570 <a name="F.10.4.1" href="#F.10.4.1"><b> F.10.4.1 The cbrt functions</b></a>
20571 1 -- cbrt((+-)0) returns (+-)0.
20572 -- cbrt((+-)(inf)) returns (+-)(inf).
20573 <a name="F.10.4.2" href="#F.10.4.2"><b> F.10.4.2 The fabs functions</b></a>
20574 1 -- fabs((+-)0) returns +0.
20575 -- fabs((+-)(inf)) returns +(inf).
20576 2 The returned value is exact and is independent of the current rounding direction mode.
20577 <a name="F.10.4.3" href="#F.10.4.3"><b> F.10.4.3 The hypot functions</b></a>
20578 1 -- hypot(x, y), hypot(y, x), and hypot(x, -y) are equivalent.
20579 -- hypot(x, (+-)0) is equivalent to fabs(x).
20580 -- hypot((+-)(inf), y) returns +(inf), even if y is a NaN.
20581 <a name="F.10.4.4" href="#F.10.4.4"><b> F.10.4.4 The pow functions</b></a>
20582 1 -- pow((+-)0, y) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception
20583 for y an odd integer < 0.
20584 -- pow((+-)0, y) returns +(inf) and raises the ''divide-by-zero'' floating-point exception
20585 for y < 0, finite, and not an odd integer.
20586 -- pow((+-)0, -(inf)) returns +(inf) and may raise the ''divide-by-zero'' floating-point
20588 -- pow((+-)0, y) returns (+-)0 for y an odd integer > 0.
20589 -- pow((+-)0, y) returns +0 for y > 0 and not an odd integer.
20590 -- pow(-1, (+-)(inf)) returns 1.
20591 -- pow(+1, y) returns 1 for any y, even a NaN.
20592 -- pow(x, (+-)0) returns 1 for any x, even a NaN.
20593 -- pow(x, y) returns a NaN and raises the ''invalid'' floating-point exception for
20594 finite x < 0 and finite non-integer y.
20595 -- pow(x, -(inf)) returns +(inf) for | x | < 1.
20596 -- pow(x, -(inf)) returns +0 for | x | > 1.
20597 -- pow(x, +(inf)) returns +0 for | x | < 1.
20598 -- pow(x, +(inf)) returns +(inf) for | x | > 1.
20601 [<a name="p520" href="#p520">page 520</a>] (<a href="#Contents">Contents</a>)
20603 -- pow(-(inf), y) returns -0 for y an odd integer < 0.
20604 -- pow(-(inf), y) returns +0 for y < 0 and not an odd integer.
20605 -- pow(-(inf), y) returns -(inf) for y an odd integer > 0.
20606 -- pow(-(inf), y) returns +(inf) for y > 0 and not an odd integer.
20607 -- pow(+(inf), y) returns +0 for y < 0.
20608 -- pow(+(inf), y) returns +(inf) for y > 0.
20609 <a name="F.10.4.5" href="#F.10.4.5"><b> F.10.4.5 The sqrt functions</b></a>
20610 1 sqrt is fully specified as a basic arithmetic operation in IEC 60559. The returned value
20611 is dependent on the current rounding direction mode.
20612 <a name="F.10.5" href="#F.10.5"><b> F.10.5 Error and gamma functions</b></a>
20613 <a name="F.10.5.1" href="#F.10.5.1"><b> F.10.5.1 The erf functions</b></a>
20614 1 -- erf((+-)0) returns (+-)0.
20615 -- erf((+-)(inf)) returns (+-)1.
20616 <a name="F.10.5.2" href="#F.10.5.2"><b> F.10.5.2 The erfc functions</b></a>
20617 1 -- erfc(-(inf)) returns 2.
20618 -- erfc(+(inf)) returns +0.
20619 <a name="F.10.5.3" href="#F.10.5.3"><b> F.10.5.3 The lgamma functions</b></a>
20620 1 -- lgamma(1) returns +0.
20621 -- lgamma(2) returns +0.
20622 -- lgamma(x) returns +(inf) and raises the ''divide-by-zero'' floating-point exception for
20623 x a negative integer or zero.
20624 -- lgamma(-(inf)) returns +(inf).
20625 -- lgamma(+(inf)) returns +(inf).
20626 <a name="F.10.5.4" href="#F.10.5.4"><b> F.10.5.4 The tgamma functions</b></a>
20627 1 -- tgamma((+-)0) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
20628 -- tgamma(x) returns a NaN and raises the ''invalid'' floating-point exception for x a
20630 -- tgamma(-(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
20631 -- tgamma(+(inf)) returns +(inf).
20635 [<a name="p521" href="#p521">page 521</a>] (<a href="#Contents">Contents</a>)
20637 <a name="F.10.6" href="#F.10.6"><b> F.10.6 Nearest integer functions</b></a>
20638 <a name="F.10.6.1" href="#F.10.6.1"><b> F.10.6.1 The ceil functions</b></a>
20639 1 -- ceil((+-)0) returns (+-)0.
20640 -- ceil((+-)(inf)) returns (+-)(inf).
20641 2 The returned value is independent of the current rounding direction mode.
20642 3 The double version of ceil behaves as though implemented by
20643 #include <a href="#7.12"><math.h></a>
20644 #include <a href="#7.6"><fenv.h></a>
20645 #pragma STDC FENV_ACCESS ON
20646 double ceil(double x)
20649 int save_round = fegetround();
20650 fesetround(FE_UPWARD);
20651 result = rint(x); // or nearbyint instead of rint
20652 fesetround(save_round);
20655 4 The ceil functions may, but are not required to, raise the ''inexact'' floating-point
20656 exception for finite non-integer arguments, as this implementation does.
20657 <a name="F.10.6.2" href="#F.10.6.2"><b> F.10.6.2 The floor functions</b></a>
20658 1 -- floor((+-)0) returns (+-)0.
20659 -- floor((+-)(inf)) returns (+-)(inf).
20660 2 The returned value and is independent of the current rounding direction mode.
20661 3 See the sample implementation for ceil in <a href="#F.10.6.1">F.10.6.1</a>. The floor functions may, but are
20662 not required to, raise the ''inexact'' floating-point exception for finite non-integer
20663 arguments, as that implementation does.
20664 <a name="F.10.6.3" href="#F.10.6.3"><b> F.10.6.3 The nearbyint functions</b></a>
20665 1 The nearbyint functions use IEC 60559 rounding according to the current rounding
20666 direction. They do not raise the ''inexact'' floating-point exception if the result differs in
20667 value from the argument.
20668 -- nearbyint((+-)0) returns (+-)0 (for all rounding directions).
20669 -- nearbyint((+-)(inf)) returns (+-)(inf) (for all rounding directions).
20673 [<a name="p522" href="#p522">page 522</a>] (<a href="#Contents">Contents</a>)
20675 <a name="F.10.6.4" href="#F.10.6.4"><b> F.10.6.4 The rint functions</b></a>
20676 1 The rint functions differ from the nearbyint functions only in that they do raise the
20677 ''inexact'' floating-point exception if the result differs in value from the argument.
20678 <a name="F.10.6.5" href="#F.10.6.5"><b> F.10.6.5 The lrint and llrint functions</b></a>
20679 1 The lrint and llrint functions provide floating-to-integer conversion as prescribed
20680 by IEC 60559. They round according to the current rounding direction. If the rounded
20681 value is outside the range of the return type, the numeric result is unspecified and the
20682 ''invalid'' floating-point exception is raised. When they raise no other floating-point
20683 exception and the result differs from the argument, they raise the ''inexact'' floating-point
20685 <a name="F.10.6.6" href="#F.10.6.6"><b> F.10.6.6 The round functions</b></a>
20686 1 -- round((+-)0) returns (+-)0.
20687 -- round((+-)(inf)) returns (+-)(inf).
20688 2 The returned value is independent of the current rounding direction mode.
20689 3 The double version of round behaves as though implemented by
20690 #include <a href="#7.12"><math.h></a>
20691 #include <a href="#7.6"><fenv.h></a>
20692 #pragma STDC FENV_ACCESS ON
20693 double round(double x)
20697 feholdexcept(&save_env);
20699 if (fetestexcept(FE_INEXACT)) {
20700 fesetround(FE_TOWARDZERO);
20701 result = rint(copysign(0.5 + fabs(x), x));
20703 feupdateenv(&save_env);
20706 The round functions may, but are not required to, raise the ''inexact'' floating-point
20707 exception for finite non-integer numeric arguments, as this implementation does.
20712 [<a name="p523" href="#p523">page 523</a>] (<a href="#Contents">Contents</a>)
20714 <a name="F.10.6.7" href="#F.10.6.7"><b> F.10.6.7 The lround and llround functions</b></a>
20715 1 The lround and llround functions differ from the lrint and llrint functions
20716 with the default rounding direction just in that the lround and llround functions
20717 round halfway cases away from zero and need not raise the ''inexact'' floating-point
20718 exception for non-integer arguments that round to within the range of the return type.
20719 <a name="F.10.6.8" href="#F.10.6.8"><b> F.10.6.8 The trunc functions</b></a>
20720 1 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
20721 rounding direction). The returned value is exact.
20722 -- trunc((+-)0) returns (+-)0.
20723 -- trunc((+-)(inf)) returns (+-)(inf).
20724 2 The returned value is independent of the current rounding direction mode. The trunc
20725 functions may, but are not required to, raise the ''inexact'' floating-point exception for
20726 finite non-integer arguments.
20727 <a name="F.10.7" href="#F.10.7"><b> F.10.7 Remainder functions</b></a>
20728 <a name="F.10.7.1" href="#F.10.7.1"><b> F.10.7.1 The fmod functions</b></a>
20729 1 -- fmod((+-)0, y) returns (+-)0 for y not zero.
20730 -- fmod(x, y) returns a NaN and raises the ''invalid'' floating-point exception for x
20731 infinite or y zero (and neither is a NaN).
20732 -- fmod(x, (+-)(inf)) returns x for x not infinite.
20733 2 When subnormal results are supported, the returned value is exact and is independent of
20734 the current rounding direction mode.
20735 3 The double version of fmod behaves as though implemented by
20736 #include <a href="#7.12"><math.h></a>
20737 #include <a href="#7.6"><fenv.h></a>
20738 #pragma STDC FENV_ACCESS ON
20739 double fmod(double x, double y)
20742 result = remainder(fabs(x), (y = fabs(y)));
20743 if (signbit(result)) result += y;
20744 return copysign(result, x);
20750 [<a name="p524" href="#p524">page 524</a>] (<a href="#Contents">Contents</a>)
20752 <a name="F.10.7.2" href="#F.10.7.2"><b> F.10.7.2 The remainder functions</b></a>
20753 1 The remainder functions are fully specified as a basic arithmetic operation in
20755 2 When subnormal results are supported, the returned value is exact and is independent of
20756 the current rounding direction mode.
20757 <a name="F.10.7.3" href="#F.10.7.3"><b> F.10.7.3 The remquo functions</b></a>
20758 1 The remquo functions follow the specifications for the remainder functions. They
20759 have no further specifications special to IEC 60559 implementations.
20760 2 When subnormal results are supported, the returned value is exact and is independent of
20761 the current rounding direction mode.
20762 <a name="F.10.8" href="#F.10.8"><b> F.10.8 Manipulation functions</b></a>
20763 <a name="F.10.8.1" href="#F.10.8.1"><b> F.10.8.1 The copysign functions</b></a>
20764 1 copysign is specified in the Appendix to IEC 60559.
20765 2 The returned value is exact and is independent of the current rounding direction mode.
20766 <a name="F.10.8.2" href="#F.10.8.2"><b> F.10.8.2 The nan functions</b></a>
20767 1 All IEC 60559 implementations support quiet NaNs, in all floating formats.
20768 2 The returned value is exact and is independent of the current rounding direction mode.
20769 <a name="F.10.8.3" href="#F.10.8.3"><b> F.10.8.3 The nextafter functions</b></a>
20770 1 -- nextafter(x, y) raises the ''overflow'' and ''inexact'' floating-point exceptions
20771 for x finite and the function value infinite.
20772 -- nextafter(x, y) raises the ''underflow'' and ''inexact'' floating-point
20773 exceptions for the function value subnormal or zero and x != y.
20774 2 Even though underflow or overflow can occur, the returned value is independent of the
20775 current rounding direction mode.
20776 <a name="F.10.8.4" href="#F.10.8.4"><b> F.10.8.4 The nexttoward functions</b></a>
20777 1 No additional requirements beyond those on nextafter.
20778 2 Even though underflow or overflow can occur, the returned value is independent of the
20779 current rounding direction mode.
20784 [<a name="p525" href="#p525">page 525</a>] (<a href="#Contents">Contents</a>)
20786 <a name="F.10.9" href="#F.10.9"><b> F.10.9 Maximum, minimum, and positive difference functions</b></a>
20787 <a name="F.10.9.1" href="#F.10.9.1"><b> F.10.9.1 The fdim functions</b></a>
20788 1 No additional requirements.
20789 <a name="F.10.9.2" href="#F.10.9.2"><b> F.10.9.2 The fmax functions</b></a>
20790 1 If just one argument is a NaN, the fmax functions return the other argument (if both
20791 arguments are NaNs, the functions return a NaN).
20792 2 The returned value is exact and is independent of the current rounding direction mode.
20793 3 The body of the fmax function might be<sup><a href="#note361"><b>361)</b></a></sup>
20794 { return (isgreaterequal(x, y) ||
20795 isnan(y)) ? x : y; }
20796 <a name="F.10.9.3" href="#F.10.9.3"><b> F.10.9.3 The fmin functions</b></a>
20797 1 The fmin functions are analogous to the fmax functions (see <a href="#F.10.9.2">F.10.9.2</a>).
20798 2 The returned value is exact and is independent of the current rounding direction mode.
20799 <a name="F.10.10" href="#F.10.10"><b> F.10.10 Floating multiply-add</b></a>
20800 <a name="F.10.10.1" href="#F.10.10.1"><b> F.10.10.1 The fma functions</b></a>
20801 1 -- fma(x, y, z) computes xy + z, correctly rounded once.
20802 -- fma(x, y, z) returns a NaN and optionally raises the ''invalid'' floating-point
20803 exception if one of x and y is infinite, the other is zero, and z is a NaN.
20804 -- fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if
20805 one of x and y is infinite, the other is zero, and z is not a NaN.
20806 -- fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if x
20807 times y is an exact infinity and z is also an infinity but with the opposite sign.
20812 <sup><a name="note361" href="#note361"><b>361)</b></a></sup> Ideally, fmax would be sensitive to the sign of zero, for example fmax(-0.0, +0.0) would
20813 return +0; however, implementation in software might be impractical.
20815 [<a name="p526" href="#p526">page 526</a>] (<a href="#Contents">Contents</a>)
20817 <a name="F.10.11" href="#F.10.11"><b> F.10.11 Comparison macros</b></a>
20818 1 Relational operators and their corresponding comparison macros (<a href="#7.12.14">7.12.14</a>) produce
20819 equivalent result values, even if argument values are represented in wider formats. Thus,
20820 comparison macro arguments represented in formats wider than their semantic types are
20821 not converted to the semantic types, unless the wide evaluation method converts operands
20822 of relational operators to their semantic types. The standard wide evaluation methods
20823 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
20824 operands of relational operators to their semantic types.
20829 [<a name="p527" href="#p527">page 527</a>] (<a href="#Contents">Contents</a>)
20831 <a name="G" href="#G"><b> Annex G</b></a>
20833 IEC 60559-compatible complex arithmetic
20834 <a name="G.1" href="#G.1"><b> G.1 Introduction</b></a>
20835 1 This annex supplements <a href="#F">annex F</a> to specify complex arithmetic for compatibility with
20836 IEC 60559 real floating-point arithmetic. An implementation that defines *
20837 __STDC_IEC_559_COMPLEX__ shall conform to the specifications in this annex.<sup><a href="#note362"><b>362)</b></a></sup>
20838 <a name="G.2" href="#G.2"><b> G.2 Types</b></a>
20839 1 There is a new keyword _Imaginary, which is used to specify imaginary types. It is
20840 used as a type specifier within declaration specifiers in the same way as _Complex is
20841 (thus, _Imaginary float is a valid type name).
20842 2 There are three imaginary types, designated as float _Imaginary, double
20843 _Imaginary, and long double _Imaginary. The imaginary types (along with
20844 the real floating and complex types) are floating types.
20845 3 For imaginary types, the corresponding real type is given by deleting the keyword
20846 _Imaginary from the type name.
20847 4 Each imaginary type has the same representation and alignment requirements as the
20848 corresponding real type. The value of an object of imaginary type is the value of the real
20849 representation times the imaginary unit.
20850 5 The imaginary type domain comprises the imaginary types.
20851 <a name="G.3" href="#G.3"><b> G.3 Conventions</b></a>
20852 1 A complex or imaginary value with at least one infinite part is regarded as an infinity
20853 (even if its other part is a NaN). A complex or imaginary value is a finite number if each
20854 of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
20855 a zero if each of its parts is a zero.
20860 <sup><a name="note362" href="#note362"><b>362)</b></a></sup> Implementations that do not define __STDC_IEC_559_COMPLEX__ are not required to conform
20861 to these specifications.
20863 [<a name="p528" href="#p528">page 528</a>] (<a href="#Contents">Contents</a>)
20865 <a name="G.4" href="#G.4"><b> G.4 Conversions</b></a>
20866 <a name="G.4.1" href="#G.4.1"><b> G.4.1 Imaginary types</b></a>
20867 1 Conversions among imaginary types follow rules analogous to those for real floating
20869 <a name="G.4.2" href="#G.4.2"><b> G.4.2 Real and imaginary</b></a>
20870 1 When a value of imaginary type is converted to a real type other than _Bool,<sup><a href="#note363"><b>363)</b></a></sup> the
20871 result is a positive zero.
20872 2 When a value of real type is converted to an imaginary type, the result is a positive
20874 <a name="G.4.3" href="#G.4.3"><b> G.4.3 Imaginary and complex</b></a>
20875 1 When a value of imaginary type is converted to a complex type, the real part of the
20876 complex result value is a positive zero and the imaginary part of the complex result value
20877 is determined by the conversion rules for the corresponding real types.
20878 2 When a value of complex type is converted to an imaginary type, the real part of the
20879 complex value is discarded and the value of the imaginary part is converted according to
20880 the conversion rules for the corresponding real types.
20881 <a name="G.5" href="#G.5"><b> G.5 Binary operators</b></a>
20882 1 The following subclauses supplement <a href="#6.5">6.5</a> in order to specify the type of the result for an
20883 operation with an imaginary operand.
20884 2 For most operand types, the value of the result of a binary operator with an imaginary or
20885 complex operand is completely determined, with reference to real arithmetic, by the usual
20886 mathematical formula. For some operand types, the usual mathematical formula is
20887 problematic because of its treatment of infinities and because of undue overflow or
20888 underflow; in these cases the result satisfies certain properties (specified in <a href="#G.5.1">G.5.1</a>), but is
20889 not completely determined.
20894 <sup><a name="note363" href="#note363"><b>363)</b></a></sup> See <a href="#6.3.1.2">6.3.1.2</a>.
20896 [<a name="p529" href="#p529">page 529</a>] (<a href="#Contents">Contents</a>)
20898 <a name="G.5.1" href="#G.5.1"><b> G.5.1 Multiplicative operators</b></a>
20900 1 If one operand has real type and the other operand has imaginary type, then the result has
20901 imaginary type. If both operands have imaginary type, then the result has real type. (If
20902 either operand has complex type, then the result has complex type.)
20903 2 If the operands are not both complex, then the result and floating-point exception
20904 behavior of the * operator is defined by the usual mathematical formula:
20907 x xu i(xv) (xu) + i(xv)
20909 iy i(yu) -yv (-yv) + i(yu)
20911 x + iy (xu) + i(yu) (-yv) + i(xv)
20912 3 If the second operand is not complex, then the result and floating-point exception
20913 behavior of the / operator is defined by the usual mathematical formula:
20920 x + iy (x/u) + i(y/u) (y/v) + i(-x/v)
20921 4 The * and / operators satisfy the following infinity properties for all real, imaginary, and
20922 complex operands:<sup><a href="#note364"><b>364)</b></a></sup>
20923 -- if one operand is an infinity and the other operand is a nonzero finite number or an
20924 infinity, then the result of the * operator is an infinity;
20925 -- if the first operand is an infinity and the second operand is a finite number, then the
20926 result of the / operator is an infinity;
20927 -- if the first operand is a finite number and the second operand is an infinity, then the
20928 result of the / operator is a zero;
20933 <sup><a name="note364" href="#note364"><b>364)</b></a></sup> These properties are already implied for those cases covered in the tables, but are required for all cases
20934 (at least where the state for CX_LIMITED_RANGE is ''off'').
20936 [<a name="p530" href="#p530">page 530</a>] (<a href="#Contents">Contents</a>)
20938 -- if the first operand is a nonzero finite number or an infinity and the second operand is
20939 a zero, then the result of the / operator is an infinity.
20940 5 If both operands of the * operator are complex or if the second operand of the / operator
20941 is complex, the operator raises floating-point exceptions if appropriate for the calculation
20942 of the parts of the result, and may raise spurious floating-point exceptions.
20943 6 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
20944 that the imaginary unit I has imaginary type (see <a href="#G.6">G.6</a>).
20945 #include <a href="#7.12"><math.h></a>
20946 #include <a href="#7.3"><complex.h></a>
20947 /* Multiply z * w ... */
20948 double complex _Cmultd(double complex z, double complex w)
20950 #pragma STDC FP_CONTRACT OFF
20951 double a, b, c, d, ac, bd, ad, bc, x, y;
20952 a = creal(z); b = cimag(z);
20953 c = creal(w); d = cimag(w);
20954 ac = a * c; bd = b * d;
20955 ad = a * d; bc = b * c;
20956 x = ac - bd; y = ad + bc;
20957 if (isnan(x) && isnan(y)) {
20958 /* Recover infinities that computed as NaN+iNaN ... */
20960 if ( isinf(a) || isinf(b) ) { // z is infinite
20961 /* "Box" the infinity and change NaNs in the other factor to 0 */
20962 a = copysign(isinf(a) ? 1.0 : 0.0, a);
20963 b = copysign(isinf(b) ? 1.0 : 0.0, b);
20964 if (isnan(c)) c = copysign(0.0, c);
20965 if (isnan(d)) d = copysign(0.0, d);
20968 if ( isinf(c) || isinf(d) ) { // w is infinite
20969 /* "Box" the infinity and change NaNs in the other factor to 0 */
20970 c = copysign(isinf(c) ? 1.0 : 0.0, c);
20971 d = copysign(isinf(d) ? 1.0 : 0.0, d);
20972 if (isnan(a)) a = copysign(0.0, a);
20973 if (isnan(b)) b = copysign(0.0, b);
20976 if (!recalc && (isinf(ac) || isinf(bd) ||
20977 isinf(ad) || isinf(bc))) {
20978 /* Recover infinities from overflow by changing NaNs to 0 ... */
20979 if (isnan(a)) a = copysign(0.0, a);
20980 if (isnan(b)) b = copysign(0.0, b);
20981 if (isnan(c)) c = copysign(0.0, c);
20982 if (isnan(d)) d = copysign(0.0, d);
20987 [<a name="p531" href="#p531">page 531</a>] (<a href="#Contents">Contents</a>)
20989 x = INFINITY * ( a * c - b * d );
20990 y = INFINITY * ( a * d + b * c );
20995 7 This implementation achieves the required treatment of infinities at the cost of only one isnan test in
20996 ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur.
20998 8 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
20999 #include <a href="#7.12"><math.h></a>
21000 #include <a href="#7.3"><complex.h></a>
21001 /* Divide z / w ... */
21002 double complex _Cdivd(double complex z, double complex w)
21004 #pragma STDC FP_CONTRACT OFF
21005 double a, b, c, d, logbw, denom, x, y;
21007 a = creal(z); b = cimag(z);
21008 c = creal(w); d = cimag(w);
21009 logbw = logb(fmax(fabs(c), fabs(d)));
21010 if (logbw == INFINITY) {
21011 ilogbw = (int)logbw;
21012 c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
21014 denom = c * c + d * d;
21015 x = scalbn((a * c + b * d) / denom, -ilogbw);
21016 y = scalbn((b * c - a * d) / denom, -ilogbw);
21017 /* Recover infinities and zeros that computed as NaN+iNaN; */
21018 /* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
21019 if (isnan(x) && isnan(y)) {
21020 if ((denom == 0.0) &&
21021 (!isnan(a) || !isnan(b))) {
21022 x = copysign(INFINITY, c) * a;
21023 y = copysign(INFINITY, c) * b;
21025 else if ((isinf(a) || isinf(b)) &&
21026 isfinite(c) && isfinite(d)) {
21027 a = copysign(isinf(a) ? 1.0 : 0.0, a);
21028 b = copysign(isinf(b) ? 1.0 : 0.0, b);
21029 x = INFINITY * ( a * c + b * d );
21030 y = INFINITY * ( b * c - a * d );
21032 else if (isinf(logbw) &&
21033 isfinite(a) && isfinite(b)) {
21034 c = copysign(isinf(c) ? 1.0 : 0.0, c);
21035 d = copysign(isinf(d) ? 1.0 : 0.0, d);
21036 x = 0.0 * ( a * c + b * d );
21037 y = 0.0 * ( b * c - a * d );
21039 [<a name="p532" href="#p532">page 532</a>] (<a href="#Contents">Contents</a>)
21045 9 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
21046 for multiplication. In the spirit of the multiplication example above, this code does not defend against
21047 overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
21048 with division, provides better roundoff characteristics.
21050 <a name="G.5.2" href="#G.5.2"><b> G.5.2 Additive operators</b></a>
21052 1 If both operands have imaginary type, then the result has imaginary type. (If one operand
21053 has real type and the other operand has imaginary type, or if either operand has complex
21054 type, then the result has complex type.)
21055 2 In all cases the result and floating-point exception behavior of a + or - operator is defined
21056 by the usual mathematical formula:
21059 x x(+-)u x (+-) iv (x (+-) u) (+-) iv
21061 iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)
21063 x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)
21064 <a name="G.6" href="#G.6"><b> G.6 Complex arithmetic <complex.h></b></a>
21069 are defined, respectively, as _Imaginary and a constant expression of type const
21070 float _Imaginary with the value of the imaginary unit. The macro
21072 is defined to be _Imaginary_I (not _Complex_I as stated in <a href="#7.3">7.3</a>). Notwithstanding
21073 the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and then perhaps redefine the macro
21075 2 This subclause contains specifications for the <a href="#7.3"><complex.h></a> functions that are
21076 particularly suited to IEC 60559 implementations. For families of functions, the
21077 specifications apply to all of the functions even though only the principal function is
21079 [<a name="p533" href="#p533">page 533</a>] (<a href="#Contents">Contents</a>)
21081 shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument
21082 and the result, the result has the same sign as the argument.
21083 3 The functions are continuous onto both sides of their branch cuts, taking into account the
21084 sign of zero. For example, csqrt(-2 (+-) i0) = (+-)isqrt:2. -
21085 4 Since complex and imaginary values are composed of real values, each function may be
21086 regarded as computing real values from real values. Except as noted, the functions treat
21087 real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
21088 manner consistent with the specifications for real functions in F.10.<sup><a href="#note365"><b>365)</b></a></sup>
21089 5 The functions cimag, conj, cproj, and creal are fully specified for all
21090 implementations, including IEC 60559 ones, in <a href="#7.3.9">7.3.9</a>. These functions raise no floating-
21092 6 Each of the functions cabs and carg is specified by a formula in terms of a real
21093 function (whose special cases are covered in <a href="#F">annex F</a>):
21094 cabs(x + iy) = hypot(x, y)
21095 carg(x + iy) = atan2(y, x)
21096 7 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
21097 a formula in terms of other complex functions (whose special cases are specified below):
21098 casin(z) = -i casinh(iz)
21099 catan(z) = -i catanh(iz)
21100 ccos(z) = ccosh(iz)
21101 csin(z) = -i csinh(iz)
21102 ctan(z) = -i ctanh(iz)
21103 8 For the other functions, the following subclauses specify behavior for special cases,
21104 including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For
21105 families of functions, the specifications apply to all of the functions even though only the
21106 principal function is shown. For a function f satisfying f (conj(z)) = conj( f (z)), the
21107 specifications for the upper half-plane imply the specifications for the lower half-plane; if
21108 the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the
21109 specifications for the first quadrant imply the specifications for the other three quadrants.
21110 9 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
21115 <sup><a name="note365" href="#note365"><b>365)</b></a></sup> 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
21116 other part is a NaN.
21118 [<a name="p534" href="#p534">page 534</a>] (<a href="#Contents">Contents</a>)
21120 <a name="G.6.1" href="#G.6.1"><b> G.6.1 Trigonometric functions</b></a>
21121 <a name="G.6.1.1" href="#G.6.1.1"><b> G.6.1.1 The cacos functions</b></a>
21122 1 -- cacos(conj(z)) = conj(cacos(z)).
21123 -- cacos((+-)0 + i0) returns pi /2 - i0.
21124 -- cacos((+-)0 + iNaN) returns pi /2 + iNaN.
21125 -- cacos(x + i (inf)) returns pi /2 - i (inf), for finite x.
21126 -- cacos(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21127 point exception, for nonzero finite x.
21128 -- cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.
21129 -- cacos(+(inf) + iy) returns +0 - i (inf), for positive-signed finite y.
21130 -- cacos(-(inf) + i (inf)) returns 3pi /4 - i (inf).
21131 -- cacos(+(inf) + i (inf)) returns pi /4 - i (inf).
21132 -- cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
21133 result is unspecified).
21134 -- cacos(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21135 point exception, for finite y.
21136 -- cacos(NaN + i (inf)) returns NaN - i (inf).
21137 -- cacos(NaN + iNaN) returns NaN + iNaN.
21138 <a name="G.6.2" href="#G.6.2"><b> G.6.2 Hyperbolic functions</b></a>
21139 <a name="G.6.2.1" href="#G.6.2.1"><b> G.6.2.1 The cacosh functions</b></a>
21140 1 -- cacosh(conj(z)) = conj(cacosh(z)).
21141 -- cacosh((+-)0 + i0) returns +0 + ipi /2.
21142 -- cacosh(x + i (inf)) returns +(inf) + ipi /2, for finite x.
21143 -- cacosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
21144 floating-point exception, for finite x.
21145 -- cacosh(-(inf) + iy) returns +(inf) + ipi , for positive-signed finite y.
21146 -- cacosh(+(inf) + iy) returns +(inf) + i0, for positive-signed finite y.
21147 -- cacosh(-(inf) + i (inf)) returns +(inf) + i3pi /4.
21148 -- cacosh(+(inf) + i (inf)) returns +(inf) + ipi /4.
21149 -- cacosh((+-)(inf) + iNaN) returns +(inf) + iNaN.
21152 [<a name="p535" href="#p535">page 535</a>] (<a href="#Contents">Contents</a>)
21154 -- cacosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
21155 floating-point exception, for finite y.
21156 -- cacosh(NaN + i (inf)) returns +(inf) + iNaN.
21157 -- cacosh(NaN + iNaN) returns NaN + iNaN.
21158 <a name="G.6.2.2" href="#G.6.2.2"><b> G.6.2.2 The casinh functions</b></a>
21159 1 -- casinh(conj(z)) = conj(casinh(z)) and casinh is odd.
21160 -- casinh(+0 + i0) returns 0 + i0.
21161 -- casinh(x + i (inf)) returns +(inf) + ipi /2 for positive-signed finite x.
21162 -- casinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
21163 floating-point exception, for finite x.
21164 -- casinh(+(inf) + iy) returns +(inf) + i0 for positive-signed finite y.
21165 -- casinh(+(inf) + i (inf)) returns +(inf) + ipi /4.
21166 -- casinh(+(inf) + iNaN) returns +(inf) + iNaN.
21167 -- casinh(NaN + i0) returns NaN + i0.
21168 -- casinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
21169 floating-point exception, for finite nonzero y.
21170 -- casinh(NaN + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result
21172 -- casinh(NaN + iNaN) returns NaN + iNaN.
21173 <a name="G.6.2.3" href="#G.6.2.3"><b> G.6.2.3 The catanh functions</b></a>
21174 1 -- catanh(conj(z)) = conj(catanh(z)) and catanh is odd.
21175 -- catanh(+0 + i0) returns +0 + i0.
21176 -- catanh(+0 + iNaN) returns +0 + iNaN.
21177 -- catanh(+1 + i0) returns +(inf) + i0 and raises the ''divide-by-zero'' floating-point
21179 -- catanh(x + i (inf)) returns +0 + ipi /2, for finite positive-signed x.
21180 -- catanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
21181 floating-point exception, for nonzero finite x.
21182 -- catanh(+(inf) + iy) returns +0 + ipi /2, for finite positive-signed y.
21183 -- catanh(+(inf) + i (inf)) returns +0 + ipi /2.
21184 -- catanh(+(inf) + iNaN) returns +0 + iNaN.
21186 [<a name="p536" href="#p536">page 536</a>] (<a href="#Contents">Contents</a>)
21188 -- catanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
21189 floating-point exception, for finite y.
21190 -- catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is
21192 -- catanh(NaN + iNaN) returns NaN + iNaN.
21193 <a name="G.6.2.4" href="#G.6.2.4"><b> G.6.2.4 The ccosh functions</b></a>
21194 1 -- ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
21195 -- ccosh(+0 + i0) returns 1 + i0.
21196 -- ccosh(+0 + i (inf)) returns NaN (+-) i0 (where the sign of the imaginary part of the
21197 result is unspecified) and raises the ''invalid'' floating-point exception.
21198 -- ccosh(+0 + iNaN) returns NaN (+-) i0 (where the sign of the imaginary part of the
21199 result is unspecified).
21200 -- ccosh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
21201 exception, for finite nonzero x.
21202 -- ccosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21203 point exception, for finite nonzero x.
21204 -- ccosh(+(inf) + i0) returns +(inf) + i0.
21205 -- ccosh(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
21206 -- ccosh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
21207 unspecified) and raises the ''invalid'' floating-point exception.
21208 -- ccosh(+(inf) + iNaN) returns +(inf) + iNaN.
21209 -- ccosh(NaN + i0) returns NaN (+-) i0 (where the sign of the imaginary part of the
21210 result is unspecified).
21211 -- ccosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21212 point exception, for all nonzero numbers y.
21213 -- ccosh(NaN + iNaN) returns NaN + iNaN.
21214 <a name="G.6.2.5" href="#G.6.2.5"><b> G.6.2.5 The csinh functions</b></a>
21215 1 -- csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
21216 -- csinh(+0 + i0) returns +0 + i0.
21217 -- csinh(+0 + i (inf)) returns (+-)0 + iNaN (where the sign of the real part of the result is
21218 unspecified) and raises the ''invalid'' floating-point exception.
21219 -- csinh(+0 + iNaN) returns (+-)0 + iNaN (where the sign of the real part of the result is
21221 [<a name="p537" href="#p537">page 537</a>] (<a href="#Contents">Contents</a>)
21223 -- csinh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
21224 exception, for positive finite x.
21225 -- csinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21226 point exception, for finite nonzero x.
21227 -- csinh(+(inf) + i0) returns +(inf) + i0.
21228 -- csinh(+(inf) + iy) returns +(inf) cis(y), for positive finite y.
21229 -- csinh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
21230 unspecified) and raises the ''invalid'' floating-point exception.
21231 -- csinh(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
21233 -- csinh(NaN + i0) returns NaN + i0.
21234 -- csinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21235 point exception, for all nonzero numbers y.
21236 -- csinh(NaN + iNaN) returns NaN + iNaN.
21237 <a name="G.6.2.6" href="#G.6.2.6"><b> G.6.2.6 The ctanh functions</b></a>
21238 1 -- ctanh(conj(z)) = conj(ctanh(z))and ctanh is odd.
21239 -- ctanh(+0 + i0) returns +0 + i0.
21240 -- ctanh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
21241 exception, for finite x.
21242 -- ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21243 point exception, for finite x.
21244 -- ctanh(+(inf) + iy) returns 1 + i0 sin(2y), for positive-signed finite y.
21245 -- ctanh(+(inf) + i (inf)) returns 1 (+-) i0 (where the sign of the imaginary part of the result
21247 -- ctanh(+(inf) + iNaN) returns 1 (+-) i0 (where the sign of the imaginary part of the
21248 result is unspecified).
21249 -- ctanh(NaN + i0) returns NaN + i0.
21250 -- ctanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21251 point exception, for all nonzero numbers y.
21252 -- ctanh(NaN + iNaN) returns NaN + iNaN.
21257 [<a name="p538" href="#p538">page 538</a>] (<a href="#Contents">Contents</a>)
21259 <a name="G.6.3" href="#G.6.3"><b> G.6.3 Exponential and logarithmic functions</b></a>
21260 <a name="G.6.3.1" href="#G.6.3.1"><b> G.6.3.1 The cexp functions</b></a>
21261 1 -- cexp(conj(z)) = conj(cexp(z)).
21262 -- cexp((+-)0 + i0) returns 1 + i0.
21263 -- cexp(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
21264 exception, for finite x.
21265 -- cexp(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21266 point exception, for finite x.
21267 -- cexp(+(inf) + i0) returns +(inf) + i0.
21268 -- cexp(-(inf) + iy) returns +0 cis(y), for finite y.
21269 -- cexp(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
21270 -- cexp(-(inf) + i (inf)) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts of
21271 the result are unspecified).
21272 -- cexp(+(inf) + i (inf)) returns (+-)(inf) + iNaN and raises the ''invalid'' floating-point
21273 exception (where the sign of the real part of the result is unspecified).
21274 -- cexp(-(inf) + iNaN) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts
21275 of the result are unspecified).
21276 -- cexp(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
21278 -- cexp(NaN + i0) returns NaN + i0.
21279 -- cexp(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21280 point exception, for all nonzero numbers y.
21281 -- cexp(NaN + iNaN) returns NaN + iNaN.
21282 <a name="G.6.3.2" href="#G.6.3.2"><b> G.6.3.2 The clog functions</b></a>
21283 1 -- clog(conj(z)) = conj(clog(z)).
21284 -- clog(-0 + i0) returns -(inf) + ipi and raises the ''divide-by-zero'' floating-point
21286 -- clog(+0 + i0) returns -(inf) + i0 and raises the ''divide-by-zero'' floating-point
21288 -- clog(x + i (inf)) returns +(inf) + ipi /2, for finite x.
21289 -- clog(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21290 point exception, for finite x.
21292 [<a name="p539" href="#p539">page 539</a>] (<a href="#Contents">Contents</a>)
21294 -- clog(-(inf) + iy) returns +(inf) + ipi , for finite positive-signed y.
21295 -- clog(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
21296 -- clog(-(inf) + i (inf)) returns +(inf) + i3pi /4.
21297 -- clog(+(inf) + i (inf)) returns +(inf) + ipi /4.
21298 -- clog((+-)(inf) + iNaN) returns +(inf) + iNaN.
21299 -- clog(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21300 point exception, for finite y.
21301 -- clog(NaN + i (inf)) returns +(inf) + iNaN.
21302 -- clog(NaN + iNaN) returns NaN + iNaN.
21303 <a name="G.6.4" href="#G.6.4"><b> G.6.4 Power and absolute-value functions</b></a>
21304 <a name="G.6.4.1" href="#G.6.4.1"><b> G.6.4.1 The cpow functions</b></a>
21305 1 The cpow functions raise floating-point exceptions if appropriate for the calculation of
21306 the parts of the result, and may also raise spurious floating-point exceptions.<sup><a href="#note366"><b>366)</b></a></sup>
21307 <a name="G.6.4.2" href="#G.6.4.2"><b> G.6.4.2 The csqrt functions</b></a>
21308 1 -- csqrt(conj(z)) = conj(csqrt(z)).
21309 -- csqrt((+-)0 + i0) returns +0 + i0.
21310 -- csqrt(x + i (inf)) returns +(inf) + i (inf), for all x (including NaN).
21311 -- csqrt(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21312 point exception, for finite x.
21313 -- csqrt(-(inf) + iy) returns +0 + i (inf), for finite positive-signed y.
21314 -- csqrt(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
21315 -- csqrt(-(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
21316 result is unspecified).
21317 -- csqrt(+(inf) + iNaN) returns +(inf) + iNaN.
21318 -- csqrt(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
21319 point exception, for finite y.
21320 -- csqrt(NaN + iNaN) returns NaN + iNaN.
21325 <sup><a name="note366" href="#note366"><b>366)</b></a></sup> This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding
21326 implementations that treat special cases more carefully.
21328 [<a name="p540" href="#p540">page 540</a>] (<a href="#Contents">Contents</a>)
21330 <a name="G.7" href="#G.7"><b> G.7 Type-generic math <tgmath.h></b></a>
21331 1 Type-generic macros that accept complex arguments also accept imaginary arguments. If
21332 an argument is imaginary, the macro expands to an expression whose type is real,
21333 imaginary, or complex, as appropriate for the particular function: if the argument is
21334 imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the
21335 types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and
21336 the types of the others are complex.
21337 2 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh,
21338 sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real
21341 sin(iy) = i sinh(y)
21342 tan(iy) = i tanh(y)
21344 sinh(iy) = i sin(y)
21345 tanh(iy) = i tan(y)
21346 asin(iy) = i asinh(y)
21347 atan(iy) = i atanh(y)
21348 asinh(iy) = i asin(y)
21349 atanh(iy) = i atan(y)
21354 [<a name="p541" href="#p541">page 541</a>] (<a href="#Contents">Contents</a>)
21356 <a name="H" href="#H"><b> Annex H</b></a>
21358 Language independent arithmetic
21359 <a name="H.1" href="#H.1"><b> H.1 Introduction</b></a>
21360 1 This annex documents the extent to which the C language supports the ISO/IEC 10967-1
21361 standard for language-independent arithmetic (LIA-1). LIA-1 is more general than
21362 IEC 60559 (<a href="#F">annex F</a>) in that it covers integer and diverse floating-point arithmetics.
21363 <a name="H.2" href="#H.2"><b> H.2 Types</b></a>
21364 1 The relevant C arithmetic types meet the requirements of LIA-1 types if an
21365 implementation adds notification of exceptional arithmetic operations and meets the 1
21366 unit in the last place (ULP) accuracy requirement (LIA-1 subclause <a href="#5.2.8">5.2.8</a>).
21367 <a name="H.2.1" href="#H.2.1"><b> H.2.1 Boolean type</b></a>
21368 1 The LIA-1 data type Boolean is implemented by the C data type bool with values of
21369 true and false, all from <a href="#7.18"><stdbool.h></a>.
21370 <a name="H.2.2" href="#H.2.2"><b> H.2.2 Integer types</b></a>
21371 1 The signed C integer types int, long int, long long int, and the corresponding
21372 unsigned types are compatible with LIA-1. If an implementation adds support for the
21373 LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are
21374 LIA-1 conformant types. C's unsigned integer types are ''modulo'' in the LIA-1 sense
21375 in that overflows or out-of-bounds results silently wrap. An implementation that defines
21376 signed integer types as also being modulo need not detect integer overflow, in which case,
21377 only integer divide-by-zero need be detected.
21378 2 The parameters for the integer data types can be accessed by the following:
21379 maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
21381 minint INT_MIN, LONG_MIN, LLONG_MIN
21382 3 The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
21383 is always 0 for the unsigned types, and is not provided for those types.
21388 [<a name="p542" href="#p542">page 542</a>] (<a href="#Contents">Contents</a>)
21390 <a name="H.2.2.1" href="#H.2.2.1"><b> H.2.2.1 Integer operations</b></a>
21391 1 The integer operations on integer types are the following:
21398 absI abs(x), labs(x), llabs(x)
21405 where x and y are expressions of the same integer type.
21406 <a name="H.2.3" href="#H.2.3"><b> H.2.3 Floating-point types</b></a>
21407 1 The C floating-point types float, double, and long double are compatible with
21408 LIA-1. If an implementation adds support for the LIA-1 exceptional values
21409 ''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
21410 with LIA-1. An implementation that uses IEC 60559 floating-point formats and
21411 operations (see <a href="#F">annex F</a>) along with IEC 60559 status flags and traps has LIA-1
21413 <a name="H.2.3.1" href="#H.2.3.1"><b> H.2.3.1 Floating-point parameters</b></a>
21414 1 The parameters for a floating point data type can be accessed by the following:
21416 p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
21417 emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
21418 emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
21419 2 The derived constants for the floating point types are accessed by the following:
21422 [<a name="p543" href="#p543">page 543</a>] (<a href="#Contents">Contents</a>)
21424 fmax FLT_MAX, DBL_MAX, LDBL_MAX
21425 fminN FLT_MIN, DBL_MIN, LDBL_MIN
21426 epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
21427 rnd_style FLT_ROUNDS
21428 <a name="H.2.3.2" href="#H.2.3.2"><b> H.2.3.2 Floating-point operations</b></a>
21429 1 The floating-point operations on floating-point types are the following:
21435 absF fabsf(x), fabs(x), fabsl(x)
21436 exponentF 1.f+logbf(x), 1.0+logb(x), 1.L+logbl(x)
21437 scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
21438 scalblnf(x, li), scalbln(x, li), scalblnl(x, li)
21439 intpartF modff(x, &y), modf(x, &y), modfl(x, &y)
21440 fractpartF modff(x, &y), modf(x, &y), modfl(x, &y)
21447 where x and y are expressions of the same floating point type, n is of type int, and li
21448 is of type long int.
21449 <a name="H.2.3.3" href="#H.2.3.3"><b> H.2.3.3 Rounding styles</b></a>
21450 1 The C Standard requires all floating types to use the same radix and rounding style, so
21451 that only one identifier for each is provided to map to LIA-1.
21452 2 The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
21453 truncate FLT_ROUNDS == 0
21456 [<a name="p544" href="#p544">page 544</a>] (<a href="#Contents">Contents</a>)
21458 nearest FLT_ROUNDS == 1
21459 other FLT_ROUNDS != 0 && FLT_ROUNDS != 1
21460 provided that an implementation extends FLT_ROUNDS to cover the rounding style used
21461 in all relevant LIA-1 operations, not just addition as in C.
21462 <a name="H.2.4" href="#H.2.4"><b> H.2.4 Type conversions</b></a>
21463 1 The LIA-1 type conversions are the following type casts:
21464 cvtI' (->) I (int)i, (long int)i, (long long int)i,
21465 (unsigned int)i, (unsigned long int)i,
21466 (unsigned long long int)i
21467 cvtF (->) I (int)x, (long int)x, (long long int)x,
21468 (unsigned int)x, (unsigned long int)x,
21469 (unsigned long long int)x
21470 cvtI (->) F (float)i, (double)i, (long double)i
21471 cvtF' (->) F (float)x, (double)x, (long double)x
21472 2 In the above conversions from floating to integer, the use of (cast)x can be replaced with
21473 (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
21474 (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer
21475 conversion functions, lrint(), llrint(), lround(), and llround(), can be
21476 used. They all meet LIA-1's requirements on floating to integer rounding for in-range
21477 values. For out-of-range values, the conversions shall silently wrap for the modulo types.
21478 3 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
21479 fmod( fabs(rint(x)), 65536.0 ) or (0.0 <= (y = fmod( rint(x),
21480 65536.0 )) ? y : 65536.0 + y) will compute an integer value in the range 0.0
21481 to 65535.0 which can then be cast to unsigned short int. But, the
21482 remainder() function is not useful for doing silent wrapping to signed integer types,
21483 e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
21484 range -32767.0 to +32768.0 which is not, in general, in the range of signed short
21486 4 C's conversions (casts) from floating-point to floating-point can meet LIA-1
21487 requirements if an implementation uses round-to-nearest (IEC 60559 default).
21488 5 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
21489 implementation uses round-to-nearest.
21494 [<a name="p545" href="#p545">page 545</a>] (<a href="#Contents">Contents</a>)
21496 <a name="H.3" href="#H.3"><b> H.3 Notification</b></a>
21497 1 Notification is the process by which a user or program is informed that an exceptional
21498 arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
21499 allows an implementation to cause a notification to occur when any arithmetic operation
21500 returns an exceptional value as defined in LIA-1 clause 5.
21501 <a name="H.3.1" href="#H.3.1"><b> H.3.1 Notification alternatives</b></a>
21502 1 LIA-1 requires at least the following two alternatives for handling of notifications:
21503 setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and-
21505 2 An implementation need only support a given notification alternative for the entire
21506 program. An implementation may support the ability to switch between notification
21507 alternatives during execution, but is not required to do so. An implementation can
21508 provide separate selection for each kind of notification, but this is not required.
21509 3 C allows an implementation to provide notification. C's SIGFPE (for traps) and
21510 FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
21511 can provide LIA-1 notification.
21512 4 C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
21513 provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
21514 math library function calls. User-provided signal handlers for SIGFPE allow for trap-
21515 and-resume behavior with the same constraint.
21516 <a name="H.3.1.1" href="#H.3.1.1"><b> H.3.1.1 Indicators</b></a>
21517 1 C's <a href="#7.6"><fenv.h></a> status flags are compatible with the LIA-1 indicators.
21518 2 The following mapping is for floating-point types:
21519 undefined FE_INVALID, FE_DIVBYZERO
21520 floating_overflow FE_OVERFLOW
21521 underflow FE_UNDERFLOW
21522 3 The floating-point indicator interrogation and manipulation operations are:
21523 set_indicators feraiseexcept(i)
21524 clear_indicators feclearexcept(i)
21525 test_indicators fetestexcept(i)
21526 current_indicators fetestexcept(FE_ALL_EXCEPT)
21527 where i is an expression of type int representing a subset of the LIA-1 indicators.
21528 4 C allows an implementation to provide the following LIA-1 required behavior: at
21529 program termination if any indicator is set the implementation shall send an unambiguous
21530 [<a name="p546" href="#p546">page 546</a>] (<a href="#Contents">Contents</a>)
21532 and ''hard to ignore'' message (see LIA-1 subclause <a href="#6.1.2">6.1.2</a>)
21533 5 LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
21534 This documentation makes that distinction because <a href="#7.6"><fenv.h></a> covers only the floating-
21536 <a name="H.3.1.2" href="#H.3.1.2"><b> H.3.1.2 Traps</b></a>
21537 1 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
21538 math library functions (which are not permitted to invoke a user's signal handler for
21539 SIGFPE). An implementation can provide an alternative of notification through
21540 termination with a ''hard-to-ignore'' message (see LIA-1 subclause <a href="#6.1.3">6.1.3</a>).
21541 2 LIA-1 does not require that traps be precise.
21542 3 C does require that SIGFPE be the signal corresponding to LIA-1 arithmetic exceptions,
21543 if there is any signal raised for them.
21544 4 C supports signal handlers for SIGFPE and allows trapping of LIA-1 arithmetic
21545 exceptions. When LIA-1 arithmetic exceptions do trap, C's signal-handler mechanism
21546 allows trap-and-terminate (either default implementation behavior or user replacement for
21547 it) or trap-and-resume, at the programmer's option.
21552 [<a name="p547" href="#p547">page 547</a>] (<a href="#Contents">Contents</a>)
21554 <a name="I" href="#I"><b> Annex I</b></a>
21557 1 An implementation may generate warnings in many situations, none of which are
21558 specified as part of this International Standard. The following are a few of the more
21560 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>).
21561 -- A block with initialization of an object that has automatic storage duration is jumped
21562 into (<a href="#6.2.4">6.2.4</a>).
21563 -- An implicit narrowing conversion is encountered, such as the assignment of a long
21564 int or a double to an int, or a pointer to void to a pointer to any type other than
21565 a character type (<a href="#6.3">6.3</a>).
21566 -- A hexadecimal floating constant cannot be represented exactly in its evaluation format
21567 (<a href="#6.4.4.2">6.4.4.2</a>).
21568 -- An integer character constant includes more than one character or a wide character
21569 constant includes more than one multibyte character (<a href="#6.4.4.4">6.4.4.4</a>).
21570 -- The characters /* are found in a comment (<a href="#6.4.7">6.4.7</a>).
21571 -- An ''unordered'' binary operator (not comma, &&, or ||) contains a side effect to an
21572 lvalue in one operand, and a side effect to, or an access to the value of, the identical
21573 lvalue in the other operand (<a href="#6.5">6.5</a>).
21574 -- A function is called but no prototype has been supplied (<a href="#6.5.2.2">6.5.2.2</a>).
21575 -- The arguments in a function call do not agree in number and type with those of the
21576 parameters in a function definition that is not a prototype (<a href="#6.5.2.2">6.5.2.2</a>).
21577 -- An object is defined but not used (<a href="#6.7">6.7</a>).
21578 -- A value is given to an object of an enumerated type other than by assignment of an
21579 enumeration constant that is a member of that type, or an enumeration object that has
21580 the same type, or the value of a function that returns the same enumerated type
21581 (<a href="#6.7.2.2">6.7.2.2</a>).
21582 -- An aggregate has a partly bracketed initialization (<a href="#6.7.8">6.7.8</a>).
21583 -- A statement cannot be reached (<a href="#6.8">6.8</a>).
21584 -- A statement with no apparent effect is encountered (<a href="#6.8">6.8</a>).
21585 -- A constant expression is used as the controlling expression of a selection statement
21586 (<a href="#6.8.4">6.8.4</a>).
21587 [<a name="p548" href="#p548">page 548</a>] (<a href="#Contents">Contents</a>)
21589 -- An incorrectly formed preprocessing group is encountered while skipping a
21590 preprocessing group (<a href="#6.10.1">6.10.1</a>).
21591 -- An unrecognized #pragma directive is encountered (<a href="#6.10.6">6.10.6</a>).
21596 [<a name="p549" href="#p549">page 549</a>] (<a href="#Contents">Contents</a>)
21598 <a name="J" href="#J"><b> Annex J</b></a>
21601 1 This annex collects some information about portability that appears in this International
21603 <a name="J.1" href="#J.1"><b> J.1 Unspecified behavior</b></a>
21604 1 The following are unspecified:
21605 -- The manner and timing of static initialization (<a href="#5.1.2">5.1.2</a>).
21606 -- The termination status returned to the hosted environment if the return type of main
21607 is not compatible with int (<a href="#5.1.2.2.3">5.1.2.2.3</a>).
21608 -- The behavior of the display device if a printing character is written when the active
21609 position is at the final position of a line (<a href="#5.2.2">5.2.2</a>).
21610 -- The behavior of the display device if a backspace character is written when the active
21611 position is at the initial position of a line (<a href="#5.2.2">5.2.2</a>).
21612 -- The behavior of the display device if a horizontal tab character is written when the
21613 active position is at or past the last defined horizontal tabulation position (<a href="#5.2.2">5.2.2</a>).
21614 -- The behavior of the display device if a vertical tab character is written when the active
21615 position is at or past the last defined vertical tabulation position (<a href="#5.2.2">5.2.2</a>).
21616 -- How an extended source character that does not correspond to a universal character
21617 name counts toward the significant initial characters in an external identifier (<a href="#5.2.4.1">5.2.4.1</a>).
21618 -- Many aspects of the representations of types (<a href="#6.2.6">6.2.6</a>).
21619 -- The value of padding bytes when storing values in structures or unions (<a href="#6.2.6.1">6.2.6.1</a>).
21620 -- The values of bytes that correspond to union members other than the one last stored
21621 into (<a href="#6.2.6.1">6.2.6.1</a>).
21622 -- The representation used when storing a value in an object that has more than one
21623 object representation for that value (<a href="#6.2.6.1">6.2.6.1</a>).
21624 -- The values of any padding bits in integer representations (<a href="#6.2.6.2">6.2.6.2</a>).
21625 -- Whether certain operators can generate negative zeros and whether a negative zero
21626 becomes a normal zero when stored in an object (<a href="#6.2.6.2">6.2.6.2</a>).
21627 -- Whether two string literals result in distinct arrays (<a href="#6.4.5">6.4.5</a>).
21628 -- The order in which subexpressions are evaluated and the order in which side effects
21629 take place, except as specified for the function-call (), &&, ||, ? :, and comma
21630 [<a name="p550" href="#p550">page 550</a>] (<a href="#Contents">Contents</a>)
21632 operators (<a href="#6.5">6.5</a>).
21633 -- The order in which the function designator, arguments, and subexpressions within the
21634 arguments are evaluated in a function call (<a href="#6.5.2.2">6.5.2.2</a>).
21635 -- The order of side effects among compound literal initialization list expressions
21636 (<a href="#6.5.2.5">6.5.2.5</a>).
21637 -- The order in which the operands of an assignment operator are evaluated (<a href="#6.5.16">6.5.16</a>).
21638 -- The alignment of the addressable storage unit allocated to hold a bit-field (<a href="#6.7.2.1">6.7.2.1</a>).
21639 -- Whether a call to an inline function uses the inline definition or the external definition
21640 of the function (<a href="#6.7.4">6.7.4</a>).
21641 -- Whether or not a size expression is evaluated when it is part of the operand of a
21642 sizeof operator and changing the value of the size expression would not affect the
21643 result of the operator (<a href="#6.7.6.2">6.7.6.2</a>).
21644 -- The order in which any side effects occur among the initialization list expressions in
21645 an initializer (<a href="#6.7.9">6.7.9</a>).
21646 -- The layout of storage for function parameters (<a href="#6.9.1">6.9.1</a>).
21647 -- When a fully expanded macro replacement list contains a function-like macro name
21648 as its last preprocessing token and the next preprocessing token from the source file is
21649 a (, and the fully expanded replacement of that macro ends with the name of the first
21650 macro and the next preprocessing token from the source file is again a (, whether that
21651 is considered a nested replacement (<a href="#6.10.3">6.10.3</a>).
21652 -- The order in which # and ## operations are evaluated during macro substitution
21653 (<a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>).
21654 -- The state of the floating-point status flags when execution passes from a part of the *
21655 program translated with FENV_ACCESS ''off'' to a part translated with
21656 FENV_ACCESS ''on'' (<a href="#7.6.1">7.6.1</a>).
21657 -- The order in which feraiseexcept raises floating-point exceptions, except as
21658 stated in <a href="#F.8.6">F.8.6</a> (<a href="#7.6.2.3">7.6.2.3</a>).
21659 -- Whether math_errhandling is a macro or an identifier with external linkage
21660 (<a href="#7.12">7.12</a>).
21661 -- The results of the frexp functions when the specified value is not a floating-point
21662 number (<a href="#7.12.6.4">7.12.6.4</a>).
21663 -- The numeric result of the ilogb functions when the correct value is outside the
21664 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>).
21665 -- 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>).
21668 [<a name="p551" href="#p551">page 551</a>] (<a href="#Contents">Contents</a>)
21670 -- The value stored by the remquo functions in the object pointed to by quo when y is
21671 zero (<a href="#7.12.10.3">7.12.10.3</a>).
21672 -- Whether a comparison macro argument that is represented in a format wider than its
21673 semantic type is converted to the semantic type (<a href="#7.12.14">7.12.14</a>).
21674 -- Whether setjmp is a macro or an identifier with external linkage (<a href="#7.13">7.13</a>).
21675 -- Whether va_copy and va_end are macros or identifiers with external linkage
21676 (<a href="#7.16.1">7.16.1</a>).
21677 -- The hexadecimal digit before the decimal point when a non-normalized floating-point
21678 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>).
21679 -- The value of the file position indicator after a successful call to the ungetc function
21680 for a text stream, or the ungetwc function for any stream, until all pushed-back
21681 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>).
21682 -- The details of the value stored by the fgetpos function (<a href="#7.21.9.1">7.21.9.1</a>).
21683 -- 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>).
21684 -- Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold
21685 functions convert a minus-signed sequence to a negative number directly or by
21686 negating the value resulting from converting the corresponding unsigned sequence
21687 (<a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.28.4.1.1">7.28.4.1.1</a>).
21688 -- The order and contiguity of storage allocated by successive calls to the calloc,
21689 malloc, and realloc functions (<a href="#7.22.3">7.22.3</a>).
21690 -- The amount of storage allocated by a successful call to the calloc, malloc, or
21691 realloc function when 0 bytes was requested (<a href="#7.22.3">7.22.3</a>).
21692 -- Which of two elements that compare as equal is matched by the bsearch function
21693 (<a href="#7.22.5.1">7.22.5.1</a>).
21694 -- The order of two elements that compare as equal in an array sorted by the qsort
21695 function (<a href="#7.22.5.2">7.22.5.2</a>).
21696 -- The encoding of the calendar time returned by the time function (<a href="#7.26.2.4">7.26.2.4</a>).
21697 -- The characters stored by the strftime or wcsftime function if any of the time
21698 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>).
21699 -- 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>,
21700 <a href="#7.28.6.4.2">7.28.6.4.2</a>,
21701 -- The resulting value when the ''invalid'' floating-point exception is raised during
21702 IEC 60559 floating to integer conversion (<a href="#F.4">F.4</a>).
21706 [<a name="p552" href="#p552">page 552</a>] (<a href="#Contents">Contents</a>)
21708 -- Whether conversion of non-integer IEC 60559 floating values to integer raises the
21709 ''inexact'' floating-point exception (<a href="#F.4">F.4</a>).
21710 -- Whether or when library functions in <a href="#7.12"><math.h></a> raise the ''inexact'' floating-point
21711 exception in an IEC 60559 conformant implementation (<a href="#F.10">F.10</a>).
21712 -- Whether or when library functions in <a href="#7.12"><math.h></a> raise an undeserved ''underflow''
21713 floating-point exception in an IEC 60559 conformant implementation (<a href="#F.10">F.10</a>).
21714 -- The exponent value stored by frexp for a NaN or infinity (<a href="#F.10.3.4">F.10.3.4</a>).
21715 -- The numeric result returned by the lrint, llrint, lround, and llround
21716 functions if the rounded value is outside the range of the return type (<a href="#F.10.6.5">F.10.6.5</a>,
21717 <a href="#F.10.6.7">F.10.6.7</a>).
21718 -- The sign of one part of the complex result of several math functions for certain
21719 special cases in IEC 60559 compatible implementations (<a href="#G.6.1.1">G.6.1.1</a>, <a href="#G.6.2.2">G.6.2.2</a>, <a href="#G.6.2.3">G.6.2.3</a>,
21720 <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>).
21721 <a name="J.2" href="#J.2"><b> J.2 Undefined behavior</b></a>
21722 1 The behavior is undefined in the following circumstances:
21723 -- A ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated
21725 -- A nonempty source file does not end in a new-line character which is not immediately
21726 preceded by a backslash character or ends in a partial preprocessing token or
21727 comment (<a href="#5.1.1.2">5.1.1.2</a>).
21728 -- Token concatenation produces a character sequence matching the syntax of a
21729 universal character name (<a href="#5.1.1.2">5.1.1.2</a>).
21730 -- A program in a hosted environment does not define a function named main using one
21731 of the specified forms (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
21732 -- The execution of a program contains a data race (<a href="#5.1.2.4">5.1.2.4</a>).
21733 -- A character not in the basic source character set is encountered in a source file, except
21734 in an identifier, a character constant, a string literal, a header name, a comment, or a
21735 preprocessing token that is never converted to a token (<a href="#5.2.1">5.2.1</a>).
21736 -- An identifier, comment, string literal, character constant, or header name contains an
21737 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>).
21738 -- The same identifier has both internal and external linkage in the same translation unit
21739 (<a href="#6.2.2">6.2.2</a>).
21740 -- An object is referred to outside of its lifetime (<a href="#6.2.4">6.2.4</a>).
21744 [<a name="p553" href="#p553">page 553</a>] (<a href="#Contents">Contents</a>)
21746 -- The value of a pointer to an object whose lifetime has ended is used (<a href="#6.2.4">6.2.4</a>).
21747 -- The value of an object with automatic storage duration is used while it is
21748 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>).
21749 -- A trap representation is read by an lvalue expression that does not have character type
21750 (<a href="#6.2.6.1">6.2.6.1</a>).
21751 -- A trap representation is produced by a side effect that modifies any part of the object
21752 using an lvalue expression that does not have character type (<a href="#6.2.6.1">6.2.6.1</a>).
21753 -- The operands to certain operators are such that they could produce a negative zero
21754 result, but the implementation does not support negative zeros (<a href="#6.2.6.2">6.2.6.2</a>).
21755 -- Two declarations of the same object or function specify types that are not compatible
21756 (<a href="#6.2.7">6.2.7</a>).
21757 -- A program requires the formation of a composite type from a variable length array
21758 type whose size is specified by an expression that is not evaluated (<a href="#6.2.7">6.2.7</a>).
21759 -- Conversion to or from an integer type produces a value outside the range that can be
21760 represented (<a href="#6.3.1.4">6.3.1.4</a>).
21761 -- Demotion of one real floating type to another produces a value outside the range that
21762 can be represented (<a href="#6.3.1.5">6.3.1.5</a>).
21763 -- An lvalue does not designate an object when evaluated (<a href="#6.3.2.1">6.3.2.1</a>).
21764 -- A non-array lvalue with an incomplete type is used in a context that requires the value
21765 of the designated object (<a href="#6.3.2.1">6.3.2.1</a>).
21766 -- An lvalue designating an object of automatic storage duration that could have been
21767 declared with the register storage class is used in a context that requires the value
21768 of the designated object, but the object is uninitialized. (<a href="#6.3.2.1">6.3.2.1</a>).
21769 -- An lvalue having array type is converted to a pointer to the initial element of the
21770 array, and the array object has register storage class (<a href="#6.3.2.1">6.3.2.1</a>).
21771 -- An attempt is made to use the value of a void expression, or an implicit or explicit
21772 conversion (except to void) is applied to a void expression (<a href="#6.3.2.2">6.3.2.2</a>).
21773 -- Conversion of a pointer to an integer type produces a value outside the range that can
21774 be represented (<a href="#6.3.2.3">6.3.2.3</a>).
21775 -- Conversion between two pointer types produces a result that is incorrectly aligned
21776 (<a href="#6.3.2.3">6.3.2.3</a>).
21777 -- A pointer is used to call a function whose type is not compatible with the referenced
21778 type (<a href="#6.3.2.3">6.3.2.3</a>).
21782 [<a name="p554" href="#p554">page 554</a>] (<a href="#Contents">Contents</a>)
21784 -- An unmatched ' or " character is encountered on a logical source line during
21785 tokenization (<a href="#6.4">6.4</a>).
21786 -- A reserved keyword token is used in translation phase 7 or 8 for some purpose other
21787 than as a keyword (<a href="#6.4.1">6.4.1</a>).
21788 -- A universal character name in an identifier does not designate a character whose
21789 encoding falls into one of the specified ranges (<a href="#6.4.2.1">6.4.2.1</a>).
21790 -- The initial character of an identifier is a universal character name designating a digit
21791 (<a href="#6.4.2.1">6.4.2.1</a>).
21792 -- Two identifiers differ only in nonsignificant characters (<a href="#6.4.2.1">6.4.2.1</a>).
21793 -- The identifier __func__ is explicitly declared (<a href="#6.4.2.2">6.4.2.2</a>).
21794 -- The program attempts to modify a string literal (<a href="#6.4.5">6.4.5</a>).
21795 -- The characters ', \, ", //, or /* occur in the sequence between the < and >
21796 delimiters, or the characters ', \, //, or /* occur in the sequence between the "
21797 delimiters, in a header name preprocessing token (<a href="#6.4.7">6.4.7</a>).
21798 -- A side effect on a scalar object is unsequenced relative to either a different side effect
21799 on the same scalar object or a value computation using the value of the same scalar
21800 object (<a href="#6.5">6.5</a>).
21801 -- An exceptional condition occurs during the evaluation of an expression (<a href="#6.5">6.5</a>).
21802 -- An object has its stored value accessed other than by an lvalue of an allowable type
21803 (<a href="#6.5">6.5</a>).
21804 -- For a call to a function without a function prototype in scope, the number of *
21805 arguments does not equal the number of parameters (<a href="#6.5.2.2">6.5.2.2</a>).
21806 -- For call to a function without a function prototype in scope where the function is
21807 defined with a function prototype, either the prototype ends with an ellipsis or the
21808 types of the arguments after promotion are not compatible with the types of the
21809 parameters (<a href="#6.5.2.2">6.5.2.2</a>).
21810 -- For a call to a function without a function prototype in scope where the function is not
21811 defined with a function prototype, the types of the arguments after promotion are not
21812 compatible with those of the parameters after promotion (with certain exceptions)
21813 (<a href="#6.5.2.2">6.5.2.2</a>).
21814 -- A function is defined with a type that is not compatible with the type (of the
21815 expression) pointed to by the expression that denotes the called function (<a href="#6.5.2.2">6.5.2.2</a>).
21816 -- A member of an atomic structure or union is accessed (<a href="#6.5.2.3">6.5.2.3</a>).
21817 -- The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
21820 [<a name="p555" href="#p555">page 555</a>] (<a href="#Contents">Contents</a>)
21822 -- A pointer is converted to other than an integer or pointer type (<a href="#6.5.4">6.5.4</a>).
21823 -- The value of the second operand of the / or % operator is zero (<a href="#6.5.5">6.5.5</a>).
21824 -- Addition or subtraction of a pointer into, or just beyond, an array object and an
21825 integer type produces a result that does not point into, or just beyond, the same array
21826 object (<a href="#6.5.6">6.5.6</a>).
21827 -- Addition or subtraction of a pointer into, or just beyond, an array object and an
21828 integer type produces a result that points just beyond the array object and is used as
21829 the operand of a unary * operator that is evaluated (<a href="#6.5.6">6.5.6</a>).
21830 -- Pointers that do not point into, or just beyond, the same array object are subtracted
21831 (<a href="#6.5.6">6.5.6</a>).
21832 -- An array subscript is out of range, even if an object is apparently accessible with the
21833 given subscript (as in the lvalue expression a[1][7] given the declaration int
21834 a[4][5]) (<a href="#6.5.6">6.5.6</a>).
21835 -- The result of subtracting two pointers is not representable in an object of type
21836 ptrdiff_t (<a href="#6.5.6">6.5.6</a>).
21837 -- An expression is shifted by a negative number or by an amount greater than or equal
21838 to the width of the promoted expression (<a href="#6.5.7">6.5.7</a>).
21839 -- An expression having signed promoted type is left-shifted and either the value of the
21840 expression is negative or the result of shifting would be not be representable in the
21841 promoted type (<a href="#6.5.7">6.5.7</a>).
21842 -- Pointers that do not point to the same aggregate or union (nor just beyond the same
21843 array object) are compared using relational operators (<a href="#6.5.8">6.5.8</a>).
21844 -- An object is assigned to an inexactly overlapping object or to an exactly overlapping
21845 object with incompatible type (<a href="#6.5.16.1">6.5.16.1</a>).
21846 -- An expression that is required to be an integer constant expression does not have an
21847 integer type; has operands that are not integer constants, enumeration constants,
21848 character constants, sizeof expressions whose results are integer constants, or
21849 immediately-cast floating constants; or contains casts (outside operands to sizeof
21850 operators) other than conversions of arithmetic types to integer types (<a href="#6.6">6.6</a>).
21851 -- A constant expression in an initializer is not, or does not evaluate to, one of the
21852 following: an arithmetic constant expression, a null pointer constant, an address
21853 constant, or an address constant for a complete object type plus or minus an integer
21854 constant expression (<a href="#6.6">6.6</a>).
21855 -- An arithmetic constant expression does not have arithmetic type; has operands that
21856 are not integer constants, floating constants, enumeration constants, character
21857 constants, or sizeof expressions; or contains casts (outside operands to sizeof
21859 [<a name="p556" href="#p556">page 556</a>] (<a href="#Contents">Contents</a>)
21861 operators) other than conversions of arithmetic types to arithmetic types (<a href="#6.6">6.6</a>).
21862 -- The value of an object is accessed by an array-subscript [], member-access . or ->,
21863 address &, or indirection * operator or a pointer cast in creating an address constant
21864 (<a href="#6.6">6.6</a>).
21865 -- An identifier for an object is declared with no linkage and the type of the object is
21866 incomplete after its declarator, or after its init-declarator if it has an initializer (<a href="#6.7">6.7</a>).
21867 -- A function is declared at block scope with an explicit storage-class specifier other
21868 than extern (<a href="#6.7.1">6.7.1</a>).
21869 -- A structure or union is defined as containing no named members, no anonymous
21870 structures, and no anonymous unions (<a href="#6.7.2.1">6.7.2.1</a>).
21871 -- An attempt is made to access, or generate a pointer to just past, a flexible array
21872 member of a structure when the referenced object provides no elements for that array
21873 (<a href="#6.7.2.1">6.7.2.1</a>).
21874 -- When the complete type is needed, an incomplete structure or union type is not
21875 completed in the same scope by another declaration of the tag that defines the content
21876 (<a href="#6.7.2.3">6.7.2.3</a>).
21877 -- An attempt is made to modify an object defined with a const-qualified type through
21878 use of an lvalue with non-const-qualified type (<a href="#6.7.3">6.7.3</a>).
21879 -- An attempt is made to refer to an object defined with a volatile-qualified type through
21880 use of an lvalue with non-volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
21881 -- The specification of a function type includes any type qualifiers (<a href="#6.7.3">6.7.3</a>). *
21882 -- Two qualified types that are required to be compatible do not have the identically
21883 qualified version of a compatible type (<a href="#6.7.3">6.7.3</a>).
21884 -- An object which has been modified is accessed through a restrict-qualified pointer to
21885 a const-qualified type, or through a restrict-qualified pointer and another pointer that
21886 are not both based on the same object (<a href="#6.7.3.1">6.7.3.1</a>).
21887 -- A restrict-qualified pointer is assigned a value based on another restricted pointer
21888 whose associated block neither began execution before the block associated with this
21889 pointer, nor ended before the assignment (<a href="#6.7.3.1">6.7.3.1</a>).
21890 -- A function with external linkage is declared with an inline function specifier, but is
21891 not also defined in the same translation unit (<a href="#6.7.4">6.7.4</a>).
21892 -- A function declared with a _Noreturn function specifier returns to its caller (<a href="#6.7.4">6.7.4</a>).
21893 -- The definition of an object has an alignment specifier and another declaration of that
21894 object has a different alignment specifier (<a href="#6.7.5">6.7.5</a>).
21897 [<a name="p557" href="#p557">page 557</a>] (<a href="#Contents">Contents</a>)
21899 -- Declarations of an object in different translation units have different alignment
21900 specifiers (<a href="#6.7.5">6.7.5</a>).
21901 -- Two pointer types that are required to be compatible are not identically qualified, or
21902 are not pointers to compatible types (<a href="#6.7.6.1">6.7.6.1</a>).
21903 -- The size expression in an array declaration is not a constant expression and evaluates
21904 at program execution time to a nonpositive value (<a href="#6.7.6.2">6.7.6.2</a>).
21905 -- In a context requiring two array types to be compatible, they do not have compatible
21906 element types, or their size specifiers evaluate to unequal values (<a href="#6.7.6.2">6.7.6.2</a>).
21907 -- A declaration of an array parameter includes the keyword static within the [ and
21908 ] and the corresponding argument does not provide access to the first element of an
21909 array with at least the specified number of elements (<a href="#6.7.6.3">6.7.6.3</a>).
21910 -- A storage-class specifier or type qualifier modifies the keyword void as a function
21911 parameter type list (<a href="#6.7.6.3">6.7.6.3</a>).
21912 -- In a context requiring two function types to be compatible, they do not have
21913 compatible return types, or their parameters disagree in use of the ellipsis terminator
21914 or the number and type of parameters (after default argument promotion, when there
21915 is no parameter type list or when one type is specified by a function definition with an
21916 identifier list) (<a href="#6.7.6.3">6.7.6.3</a>).
21917 -- The value of an unnamed member of a structure or union is used (<a href="#6.7.9">6.7.9</a>).
21918 -- The initializer for a scalar is neither a single expression nor a single expression
21919 enclosed in braces (<a href="#6.7.9">6.7.9</a>).
21920 -- The initializer for a structure or union object that has automatic storage duration is
21921 neither an initializer list nor a single expression that has compatible structure or union
21922 type (<a href="#6.7.9">6.7.9</a>).
21923 -- The initializer for an aggregate or union, other than an array initialized by a string
21924 literal, is not a brace-enclosed list of initializers for its elements or members (<a href="#6.7.9">6.7.9</a>).
21925 -- An identifier with external linkage is used, but in the program there does not exist
21926 exactly one external definition for the identifier, or the identifier is not used and there
21927 exist multiple external definitions for the identifier (<a href="#6.9">6.9</a>).
21928 -- A function definition includes an identifier list, but the types of the parameters are not
21929 declared in a following declaration list (<a href="#6.9.1">6.9.1</a>).
21930 -- An adjusted parameter type in a function definition is not a complete object type
21931 (<a href="#6.9.1">6.9.1</a>).
21932 -- A function that accepts a variable number of arguments is defined without a
21933 parameter type list that ends with the ellipsis notation (<a href="#6.9.1">6.9.1</a>).
21935 [<a name="p558" href="#p558">page 558</a>] (<a href="#Contents">Contents</a>)
21937 -- The } that terminates a function is reached, and the value of the function call is used
21938 by the caller (<a href="#6.9.1">6.9.1</a>).
21939 -- An identifier for an object with internal linkage and an incomplete type is declared
21940 with a tentative definition (<a href="#6.9.2">6.9.2</a>).
21941 -- The token defined is generated during the expansion of a #if or #elif
21942 preprocessing directive, or the use of the defined unary operator does not match
21943 one of the two specified forms prior to macro replacement (<a href="#6.10.1">6.10.1</a>).
21944 -- The #include preprocessing directive that results after expansion does not match
21945 one of the two header name forms (<a href="#6.10.2">6.10.2</a>).
21946 -- The character sequence in an #include preprocessing directive does not start with a
21947 letter (<a href="#6.10.2">6.10.2</a>).
21948 -- There are sequences of preprocessing tokens within the list of macro arguments that
21949 would otherwise act as preprocessing directives (<a href="#6.10.3">6.10.3</a>).
21950 -- The result of the preprocessing operator # is not a valid character string literal
21951 (<a href="#6.10.3.2">6.10.3.2</a>).
21952 -- The result of the preprocessing operator ## is not a valid preprocessing token
21953 (<a href="#6.10.3.3">6.10.3.3</a>).
21954 -- The #line preprocessing directive that results after expansion does not match one of
21955 the two well-defined forms, or its digit sequence specifies zero or a number greater
21956 than 2147483647 (<a href="#6.10.4">6.10.4</a>).
21957 -- A non-STDC #pragma preprocessing directive that is documented as causing
21958 translation failure or some other form of undefined behavior is encountered (<a href="#6.10.6">6.10.6</a>).
21959 -- A #pragma STDC preprocessing directive does not match one of the well-defined
21960 forms (<a href="#6.10.6">6.10.6</a>).
21961 -- The name of a predefined macro, or the identifier defined, is the subject of a
21962 #define or #undef preprocessing directive (<a href="#6.10.8">6.10.8</a>).
21963 -- An attempt is made to copy an object to an overlapping object by use of a library
21964 function, other than as explicitly allowed (e.g., memmove) (clause 7).
21965 -- A file with the same name as one of the standard headers, not provided as part of the
21966 implementation, is placed in any of the standard places that are searched for included
21967 source files (<a href="#7.1.2">7.1.2</a>).
21968 -- A header is included within an external declaration or definition (<a href="#7.1.2">7.1.2</a>).
21969 -- A function, object, type, or macro that is specified as being declared or defined by
21970 some standard header is used before any header that declares or defines it is included
21971 (<a href="#7.1.2">7.1.2</a>).
21973 [<a name="p559" href="#p559">page 559</a>] (<a href="#Contents">Contents</a>)
21975 -- A standard header is included while a macro is defined with the same name as a
21976 keyword (<a href="#7.1.2">7.1.2</a>).
21977 -- The program attempts to declare a library function itself, rather than via a standard
21978 header, but the declaration does not have external linkage (<a href="#7.1.2">7.1.2</a>).
21979 -- The program declares or defines a reserved identifier, other than as allowed by <a href="#7.1.4">7.1.4</a>
21980 (<a href="#7.1.3">7.1.3</a>).
21981 -- The program removes the definition of a macro whose name begins with an
21982 underscore and either an uppercase letter or another underscore (<a href="#7.1.3">7.1.3</a>).
21983 -- An argument to a library function has an invalid value or a type not expected by a
21984 function with variable number of arguments (<a href="#7.1.4">7.1.4</a>).
21985 -- The pointer passed to a library function array parameter does not have a value such
21986 that all address computations and object accesses are valid (<a href="#7.1.4">7.1.4</a>).
21987 -- The macro definition of assert is suppressed in order to access an actual function
21988 (<a href="#7.2">7.2</a>).
21989 -- The argument to the assert macro does not have a scalar type (<a href="#7.2">7.2</a>).
21990 -- The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in
21991 any context other than outside all external declarations or preceding all explicit
21992 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>).
21993 -- The value of an argument to a character handling function is neither equal to the value
21994 of EOF nor representable as an unsigned char (<a href="#7.4">7.4</a>).
21995 -- A macro definition of errno is suppressed in order to access an actual object, or the
21996 program defines an identifier with the name errno (<a href="#7.5">7.5</a>).
21997 -- Part of the program tests floating-point status flags, sets floating-point control modes,
21998 or runs under non-default mode settings, but was translated with the state for the
21999 FENV_ACCESS pragma ''off'' (<a href="#7.6.1">7.6.1</a>).
22000 -- The exception-mask argument for one of the functions that provide access to the
22001 floating-point status flags has a nonzero value not obtained by bitwise OR of the
22002 floating-point exception macros (<a href="#7.6.2">7.6.2</a>).
22003 -- The fesetexceptflag function is used to set floating-point status flags that were
22004 not specified in the call to the fegetexceptflag function that provided the value
22005 of the corresponding fexcept_t object (<a href="#7.6.2.4">7.6.2.4</a>).
22006 -- The argument to fesetenv or feupdateenv is neither an object set by a call to
22007 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>).
22008 -- The value of the result of an integer arithmetic or conversion function cannot be
22009 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>).
22011 [<a name="p560" href="#p560">page 560</a>] (<a href="#Contents">Contents</a>)
22013 -- The program modifies the string pointed to by the value returned by the setlocale
22014 function (<a href="#7.11.1.1">7.11.1.1</a>).
22015 -- The program modifies the structure pointed to by the value returned by the
22016 localeconv function (<a href="#7.11.2.1">7.11.2.1</a>).
22017 -- A macro definition of math_errhandling is suppressed or the program defines
22018 an identifier with the name math_errhandling (<a href="#7.12">7.12</a>).
22019 -- An argument to a floating-point classification or comparison macro is not of real
22020 floating type (<a href="#7.12.3">7.12.3</a>, <a href="#7.12.14">7.12.14</a>).
22021 -- A macro definition of setjmp is suppressed in order to access an actual function, or
22022 the program defines an external identifier with the name setjmp (<a href="#7.13">7.13</a>).
22023 -- An invocation of the setjmp macro occurs other than in an allowed context
22024 (<a href="#7.13.2.1">7.13.2.1</a>).
22025 -- The longjmp function is invoked to restore a nonexistent environment (<a href="#7.13.2.1">7.13.2.1</a>).
22026 -- After a longjmp, there is an attempt to access the value of an object of automatic
22027 storage duration that does not have volatile-qualified type, local to the function
22028 containing the invocation of the corresponding setjmp macro, that was changed
22029 between the setjmp invocation and longjmp call (<a href="#7.13.2.1">7.13.2.1</a>).
22030 -- The program specifies an invalid pointer to a signal handler function (<a href="#7.14.1.1">7.14.1.1</a>).
22031 -- A signal handler returns when the signal corresponded to a computational exception
22032 (<a href="#7.14.1.1">7.14.1.1</a>).
22033 -- A signal occurs as the result of calling the abort or raise function, and the signal
22034 handler calls the raise function (<a href="#7.14.1.1">7.14.1.1</a>).
22035 -- A signal occurs other than as the result of calling the abort or raise function, and
22036 the signal handler refers to an object with static or thread storage duration that is not a
22037 lock-free atomic object other than by assigning a value to an object declared as
22038 volatile sig_atomic_t, or calls any function in the standard library other
22039 than the abort function, the _Exit function, the quick_exit function, or the
22040 signal function (for the same signal number) (<a href="#7.14.1.1">7.14.1.1</a>).
22041 -- The value of errno is referred to after a signal occurred other than as the result of
22042 calling the abort or raise function and the corresponding signal handler obtained
22043 a SIG_ERR return from a call to the signal function (<a href="#7.14.1.1">7.14.1.1</a>).
22044 -- A signal is generated by an asynchronous signal handler (<a href="#7.14.1.1">7.14.1.1</a>).
22045 -- A function with a variable number of arguments attempts to access its varying
22046 arguments other than through a properly declared and initialized va_list object, or
22047 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>).
22049 [<a name="p561" href="#p561">page 561</a>] (<a href="#Contents">Contents</a>)
22051 -- The macro va_arg is invoked using the parameter ap that was passed to a function
22052 that invoked the macro va_arg with the same parameter (<a href="#7.16">7.16</a>).
22053 -- A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in
22054 order to access an actual function, or the program defines an external identifier with
22055 the name va_copy or va_end (<a href="#7.16.1">7.16.1</a>).
22056 -- The va_start or va_copy macro is invoked without a corresponding invocation
22057 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>,
22058 <a href="#7.16.1.4">7.16.1.4</a>).
22059 -- The type parameter to the va_arg macro is not such that a pointer to an object of
22060 that type can be obtained simply by postfixing a * (<a href="#7.16.1.1">7.16.1.1</a>).
22061 -- The va_arg macro is invoked when there is no actual next argument, or with a
22062 specified type that is not compatible with the promoted type of the actual next
22063 argument, with certain exceptions (<a href="#7.16.1.1">7.16.1.1</a>).
22064 -- The va_copy or va_start macro is called to initialize a va_list that was
22065 previously initialized by either macro without an intervening invocation of the
22066 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>).
22067 -- The parameter parmN of a va_start macro is declared with the register
22068 storage class, with a function or array type, or with a type that is not compatible with
22069 the type that results after application of the default argument promotions (<a href="#7.16.1.4">7.16.1.4</a>).
22070 -- The member designator parameter of an offsetof macro is an invalid right
22071 operand of the . operator for the type parameter, or designates a bit-field (<a href="#7.19">7.19</a>).
22072 -- The argument in an instance of one of the integer-constant macros is not a decimal,
22073 octal, or hexadecimal constant, or it has a value that exceeds the limits for the
22074 corresponding type (<a href="#7.20.4">7.20.4</a>).
22075 -- A byte input/output function is applied to a wide-oriented stream, or a wide character
22076 input/output function is applied to a byte-oriented stream (<a href="#7.21.2">7.21.2</a>).
22077 -- Use is made of any portion of a file beyond the most recent wide character written to
22078 a wide-oriented stream (<a href="#7.21.2">7.21.2</a>).
22079 -- The value of a pointer to a FILE object is used after the associated file is closed
22080 (<a href="#7.21.3">7.21.3</a>).
22081 -- The stream for the fflush function points to an input stream or to an update stream
22082 in which the most recent operation was input (<a href="#7.21.5.2">7.21.5.2</a>).
22083 -- The string pointed to by the mode argument in a call to the fopen function does not
22084 exactly match one of the specified character sequences (<a href="#7.21.5.3">7.21.5.3</a>).
22085 -- An output operation on an update stream is followed by an input operation without an
22086 intervening call to the fflush function or a file positioning function, or an input
22087 [<a name="p562" href="#p562">page 562</a>] (<a href="#Contents">Contents</a>)
22089 operation on an update stream is followed by an output operation with an intervening
22090 call to a file positioning function (<a href="#7.21.5.3">7.21.5.3</a>).
22091 -- An attempt is made to use the contents of the array that was supplied in a call to the
22092 setvbuf function (<a href="#7.21.5.6">7.21.5.6</a>).
22093 -- There are insufficient arguments for the format in a call to one of the formatted
22094 input/output functions, or an argument does not have an appropriate type (<a href="#7.21.6.1">7.21.6.1</a>,
22095 <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>).
22096 -- The format in a call to one of the formatted input/output functions or to the
22097 strftime or wcsftime function is not a valid multibyte character sequence that
22098 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>,
22099 <a href="#7.28.5.1">7.28.5.1</a>).
22100 -- In a call to one of the formatted output functions, a precision appears with a
22101 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>).
22102 -- A conversion specification for a formatted output function uses an asterisk to denote
22103 an argument-supplied field width or precision, but the corresponding argument is not
22104 provided (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>).
22105 -- A conversion specification for a formatted output function uses a # or 0 flag with a
22106 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>).
22107 -- A conversion specification for one of the formatted input/output functions uses a
22108 length modifier with a conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>,
22109 <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>).
22110 -- An s conversion specifier is encountered by one of the formatted output functions,
22111 and the argument is missing the null terminator (unless a precision is specified that
22112 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>).
22113 -- An n conversion specification for one of the formatted input/output functions includes
22114 any flags, an assignment-suppressing character, a field width, or a precision (<a href="#7.21.6.1">7.21.6.1</a>,
22115 <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>).
22116 -- A % conversion specifier is encountered by one of the formatted input/output
22117 functions, but the complete conversion specification is not exactly %% (<a href="#7.21.6.1">7.21.6.1</a>,
22118 <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>).
22119 -- An invalid conversion specification is found in the format for one of the formatted
22120 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>,
22121 <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>).
22122 -- The number of characters transmitted by a formatted output function is greater than
22123 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>).
22126 [<a name="p563" href="#p563">page 563</a>] (<a href="#Contents">Contents</a>)
22128 -- The result of a conversion by one of the formatted input functions cannot be
22129 represented in the corresponding object, or the receiving object does not have an
22130 appropriate type (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>).
22131 -- A c, s, or [ conversion specifier is encountered by one of the formatted input
22132 functions, and the array pointed to by the corresponding argument is not large enough
22133 to accept the input sequence (and a null terminator if the conversion specifier is s or
22134 [) (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>).
22135 -- A c, s, or [ conversion specifier with an l qualifier is encountered by one of the
22136 formatted input functions, but the input is not a valid multibyte character sequence
22137 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>).
22138 -- The input item for a %p conversion by one of the formatted input functions is not a
22139 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>).
22140 -- The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf,
22141 vsscanf, vfwprintf, vfwscanf, vswprintf, vswscanf, vwprintf, or
22142 vwscanf function is called with an improperly initialized va_list argument, or
22143 the argument is used (other than in an invocation of va_end) after the function
22144 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>,
22145 <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>).
22146 -- The contents of the array supplied in a call to the fgets or fgetws function are
22147 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>).
22148 -- The file position indicator for a binary stream is used after a call to the ungetc
22149 function where its value was zero before the call (<a href="#7.21.7.10">7.21.7.10</a>).
22150 -- The file position indicator for a stream is used after an error occurred during a call to
22151 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>).
22152 -- A partial element read by a call to the fread function is used (<a href="#7.21.8.1">7.21.8.1</a>).
22153 -- The fseek function is called for a text stream with a nonzero offset and either the
22154 offset was not returned by a previous successful call to the ftell function on a
22155 stream associated with the same file or whence is not SEEK_SET (<a href="#7.21.9.2">7.21.9.2</a>).
22156 -- The fsetpos function is called to set a position that was not returned by a previous
22157 successful call to the fgetpos function on a stream associated with the same file
22158 (<a href="#7.21.9.3">7.21.9.3</a>).
22159 -- A non-null pointer returned by a call to the calloc, malloc, or realloc function
22160 with a zero requested size is used to access an object (<a href="#7.22.3">7.22.3</a>).
22161 -- The value of a pointer that refers to space deallocated by a call to the free or
22162 realloc function is used (<a href="#7.22.3">7.22.3</a>).
22165 [<a name="p564" href="#p564">page 564</a>] (<a href="#Contents">Contents</a>)
22167 -- The alignment requested of the aligned_alloc function is not valid or not
22168 supported by the implementation, or the size requested is not an integral multiple of
22169 the alignment (<a href="#7.22.3.1">7.22.3.1</a>).
22170 -- The pointer argument to the free or realloc function does not match a pointer
22171 earlier returned by a memory management function, or the space has been deallocated
22172 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>).
22173 -- The value of the object allocated by the malloc function is used (<a href="#7.22.3.4">7.22.3.4</a>).
22174 -- The value of any bytes in a new object allocated by the realloc function beyond
22175 the size of the old object are used (<a href="#7.22.3.5">7.22.3.5</a>).
22176 -- The program calls the exit or quick_exit function more than once, or calls both
22177 functions (<a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.7">7.22.4.7</a>).
22178 -- During the call to a function registered with the atexit or at_quick_exit
22179 function, a call is made to the longjmp function that would terminate the call to the
22180 registered function (<a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.7">7.22.4.7</a>).
22181 -- The string set up by the getenv or strerror function is modified by the program
22182 (<a href="#7.22.4.6">7.22.4.6</a>, <a href="#7.23.6.2">7.23.6.2</a>).
22183 -- A command is executed through the system function in a way that is documented as
22184 causing termination or some other form of undefined behavior (<a href="#7.22.4.8">7.22.4.8</a>).
22185 -- A searching or sorting utility function is called with an invalid pointer argument, even
22186 if the number of elements is zero (<a href="#7.22.5">7.22.5</a>).
22187 -- The comparison function called by a searching or sorting utility function alters the
22188 contents of the array being searched or sorted, or returns ordering values
22189 inconsistently (<a href="#7.22.5">7.22.5</a>).
22190 -- The array being searched by the bsearch function does not have its elements in
22191 proper order (<a href="#7.22.5.1">7.22.5.1</a>).
22192 -- The current conversion state is used by a multibyte/wide character conversion
22193 function after changing the LC_CTYPE category (<a href="#7.22.7">7.22.7</a>).
22194 -- A string or wide string utility function is instructed to access an array beyond the end
22195 of an object (<a href="#7.23.1">7.23.1</a>, <a href="#7.28.4">7.28.4</a>).
22196 -- A string or wide string utility function is called with an invalid pointer argument, even
22197 if the length is zero (<a href="#7.23.1">7.23.1</a>, <a href="#7.28.4">7.28.4</a>).
22198 -- The contents of the destination array are used after a call to the strxfrm,
22199 strftime, wcsxfrm, or wcsftime function in which the specified length was
22200 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>,
22201 <a href="#7.28.5.1">7.28.5.1</a>).
22203 [<a name="p565" href="#p565">page 565</a>] (<a href="#Contents">Contents</a>)
22205 -- The first argument in the very first call to the strtok or wcstok is a null pointer
22206 (<a href="#7.23.5.8">7.23.5.8</a>, <a href="#7.28.4.5.7">7.28.4.5.7</a>).
22207 -- The type of an argument to a type-generic macro is not compatible with the type of
22208 the corresponding parameter of the selected function (<a href="#7.24">7.24</a>).
22209 -- A complex argument is supplied for a generic parameter of a type-generic macro that
22210 has no corresponding complex function (<a href="#7.24">7.24</a>).
22211 -- At least one field of the broken-down time passed to asctime contains a value
22212 outside its normal range, or the calculated year exceeds four digits or is less than the
22213 year 1000 (<a href="#7.26.3.1">7.26.3.1</a>).
22214 -- The argument corresponding to an s specifier without an l qualifier in a call to the
22215 fwprintf function does not point to a valid multibyte character sequence that
22216 begins in the initial shift state (<a href="#7.28.2.11">7.28.2.11</a>).
22217 -- In a call to the wcstok function, the object pointed to by ptr does not have the
22218 value stored by the previous call for the same wide string (<a href="#7.28.4.5.7">7.28.4.5.7</a>).
22219 -- An mbstate_t object is used inappropriately (<a href="#7.28.6">7.28.6</a>).
22220 -- The value of an argument of type wint_t to a wide character classification or case
22221 mapping function is neither equal to the value of WEOF nor representable as a
22222 wchar_t (<a href="#7.29.1">7.29.1</a>).
22223 -- The iswctype function is called using a different LC_CTYPE category from the
22224 one in effect for the call to the wctype function that returned the description
22225 (<a href="#7.29.2.2.1">7.29.2.2.1</a>).
22226 -- The towctrans function is called using a different LC_CTYPE category from the
22227 one in effect for the call to the wctrans function that returned the description
22228 (<a href="#7.29.3.2.1">7.29.3.2.1</a>).
22229 <a name="J.3" href="#J.3"><b> J.3 Implementation-defined behavior</b></a>
22230 1 A conforming implementation is required to document its choice of behavior in each of
22231 the areas listed in this subclause. The following are implementation-defined:
22236 [<a name="p566" href="#p566">page 566</a>] (<a href="#Contents">Contents</a>)
22238 <a name="J.3.1" href="#J.3.1"><b> J.3.1 Translation</b></a>
22239 1 -- How a diagnostic is identified (<a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a>).
22240 -- Whether each nonempty sequence of white-space characters other than new-line is
22241 retained or replaced by one space character in translation phase 3 (<a href="#5.1.1.2">5.1.1.2</a>).
22242 <a name="J.3.2" href="#J.3.2"><b> J.3.2 Environment</b></a>
22243 1 -- The mapping between physical source file multibyte characters and the source
22244 character set in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>).
22245 -- The name and type of the function called at program startup in a freestanding
22246 environment (<a href="#5.1.2.1">5.1.2.1</a>).
22247 -- The effect of program termination in a freestanding environment (<a href="#5.1.2.1">5.1.2.1</a>).
22248 -- An alternative manner in which the main function may be defined (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
22249 -- 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>).
22250 -- What constitutes an interactive device (<a href="#5.1.2.3">5.1.2.3</a>).
22251 -- Whether a program can have more than one thread of execution in a freestanding
22252 environment (<a href="#5.1.2.4">5.1.2.4</a>).
22253 -- The set of signals, their semantics, and their default handling (<a href="#7.14">7.14</a>).
22254 -- Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
22255 computational exception (<a href="#7.14.1.1">7.14.1.1</a>).
22256 -- Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
22257 program startup (<a href="#7.14.1.1">7.14.1.1</a>).
22258 -- The set of environment names and the method for altering the environment list used
22259 by the getenv function (<a href="#7.22.4.6">7.22.4.6</a>).
22260 -- The manner of execution of the string by the system function (<a href="#7.22.4.8">7.22.4.8</a>).
22261 <a name="J.3.3" href="#J.3.3"><b> J.3.3 Identifiers</b></a>
22262 1 -- Which additional multibyte characters may appear in identifiers and their
22263 correspondence to universal character names (<a href="#6.4.2">6.4.2</a>).
22264 -- 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>).
22269 [<a name="p567" href="#p567">page 567</a>] (<a href="#Contents">Contents</a>)
22271 <a name="J.3.4" href="#J.3.4"><b> J.3.4 Characters</b></a>
22272 1 -- The number of bits in a byte (<a href="#3.6">3.6</a>).
22273 -- The values of the members of the execution character set (<a href="#5.2.1">5.2.1</a>).
22274 -- The unique value of the member of the execution character set produced for each of
22275 the standard alphabetic escape sequences (<a href="#5.2.2">5.2.2</a>).
22276 -- The value of a char object into which has been stored any character other than a
22277 member of the basic execution character set (<a href="#6.2.5">6.2.5</a>).
22278 -- Which of signed char or unsigned char has the same range, representation,
22279 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>).
22280 -- The mapping of members of the source character set (in character constants and string
22281 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>).
22282 -- The value of an integer character constant containing more than one character or
22283 containing a character or escape sequence that does not map to a single-byte
22284 execution character (<a href="#6.4.4.4">6.4.4.4</a>).
22285 -- The value of a wide character constant containing more than one multibyte character
22286 or a single multibyte character that maps to multiple members of the extended
22287 execution character set, or containing a multibyte character or escape sequence not
22288 represented in the extended execution character set (<a href="#6.4.4.4">6.4.4.4</a>).
22289 -- The current locale used to convert a wide character constant consisting of a single
22290 multibyte character that maps to a member of the extended execution character set
22291 into a corresponding wide character code (<a href="#6.4.4.4">6.4.4.4</a>).
22292 -- Whether differently-prefixed wide string literal tokens can be concatenated and, if so,
22293 the treatment of the resulting multibyte character sequence (<a href="#6.4.5">6.4.5</a>).
22294 -- The current locale used to convert a wide string literal into corresponding wide
22295 character codes (<a href="#6.4.5">6.4.5</a>).
22296 -- The value of a string literal containing a multibyte character or escape sequence not
22297 represented in the execution character set (<a href="#6.4.5">6.4.5</a>).
22298 -- The encoding of any of wchar_t, char16_t, and char32_t where the
22299 corresponding standard encoding macro (__STDC_ISO_10646__,
22300 __STDC_UTF_16__, or __STDC_UTF_32__) is not defined (<a href="#6.10.8.2">6.10.8.2</a>).
22305 [<a name="p568" href="#p568">page 568</a>] (<a href="#Contents">Contents</a>)
22307 <a name="J.3.5" href="#J.3.5"><b> J.3.5 Integers</b></a>
22308 1 -- Any extended integer types that exist in the implementation (<a href="#6.2.5">6.2.5</a>).
22309 -- Whether signed integer types are represented using sign and magnitude, two's
22310 complement, or ones' complement, and whether the extraordinary value is a trap
22311 representation or an ordinary value (<a href="#6.2.6.2">6.2.6.2</a>).
22312 -- The rank of any extended integer type relative to another extended integer type with
22313 the same precision (<a href="#6.3.1.1">6.3.1.1</a>).
22314 -- The result of, or the signal raised by, converting an integer to a signed integer type
22315 when the value cannot be represented in an object of that type (<a href="#6.3.1.3">6.3.1.3</a>).
22316 -- The results of some bitwise operations on signed integers (<a href="#6.5">6.5</a>).
22317 <a name="J.3.6" href="#J.3.6"><b> J.3.6 Floating point</b></a>
22318 1 -- The accuracy of the floating-point operations and of the library functions in
22319 <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>).
22320 -- The accuracy of the conversions between floating-point internal representations and
22321 string representations performed by the library functions in <a href="#7.21"><stdio.h></a>,
22322 <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>).
22323 -- The rounding behaviors characterized by non-standard values of FLT_ROUNDS
22324 (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
22325 -- The evaluation methods characterized by non-standard negative values of
22326 FLT_EVAL_METHOD (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
22327 -- The direction of rounding when an integer is converted to a floating-point number that
22328 cannot exactly represent the original value (<a href="#6.3.1.4">6.3.1.4</a>).
22329 -- The direction of rounding when a floating-point number is converted to a narrower
22330 floating-point number (<a href="#6.3.1.5">6.3.1.5</a>).
22331 -- How the nearest representable value or the larger or smaller representable value
22332 immediately adjacent to the nearest representable value is chosen for certain floating
22333 constants (<a href="#6.4.4.2">6.4.4.2</a>).
22334 -- Whether and how floating expressions are contracted when not disallowed by the
22335 FP_CONTRACT pragma (<a href="#6.5">6.5</a>).
22336 -- The default state for the FENV_ACCESS pragma (<a href="#7.6.1">7.6.1</a>).
22337 -- Additional floating-point exceptions, rounding modes, environments, and
22338 classifications, and their macro names (<a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>).
22339 -- The default state for the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>).
22342 [<a name="p569" href="#p569">page 569</a>] (<a href="#Contents">Contents</a>)
22344 <a name="J.3.7" href="#J.3.7"><b> J.3.7 Arrays and pointers</b></a>
22345 1 -- The result of converting a pointer to an integer or vice versa (<a href="#6.3.2.3">6.3.2.3</a>).
22346 -- The size of the result of subtracting two pointers to elements of the same array
22347 (<a href="#6.5.6">6.5.6</a>).
22348 <a name="J.3.8" href="#J.3.8"><b> J.3.8 Hints</b></a>
22349 1 -- The extent to which suggestions made by using the register storage-class
22350 specifier are effective (<a href="#6.7.1">6.7.1</a>).
22351 -- The extent to which suggestions made by using the inline function specifier are
22352 effective (<a href="#6.7.4">6.7.4</a>).
22353 <a name="J.3.9" href="#J.3.9"><b> J.3.9 Structures, unions, enumerations, and bit-fields</b></a>
22354 1 -- Whether a ''plain'' int bit-field is treated as a signed int bit-field or as an
22355 unsigned int bit-field (<a href="#6.7.2">6.7.2</a>, <a href="#6.7.2.1">6.7.2.1</a>).
22356 -- Allowable bit-field types other than _Bool, signed int, and unsigned int
22357 (<a href="#6.7.2.1">6.7.2.1</a>).
22358 -- Whether atomic types are permitted for bit-fields (<a href="#6.7.2.1">6.7.2.1</a>).
22359 -- Whether a bit-field can straddle a storage-unit boundary (<a href="#6.7.2.1">6.7.2.1</a>).
22360 -- The order of allocation of bit-fields within a unit (<a href="#6.7.2.1">6.7.2.1</a>).
22361 -- The alignment of non-bit-field members of structures (<a href="#6.7.2.1">6.7.2.1</a>). This should present
22362 no problem unless binary data written by one implementation is read by another.
22363 -- The integer type compatible with each enumerated type (<a href="#6.7.2.2">6.7.2.2</a>).
22364 <a name="J.3.10" href="#J.3.10"><b> J.3.10 Qualifiers</b></a>
22365 1 -- What constitutes an access to an object that has volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
22366 <a name="J.3.11" href="#J.3.11"><b> J.3.11 Preprocessing directives</b></a>
22367 1 -- The locations within #pragma directives where header name preprocessing tokens
22368 are recognized (<a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>).
22369 -- How sequences in both forms of header names are mapped to headers or external
22370 source file names (<a href="#6.4.7">6.4.7</a>).
22371 -- Whether the value of a character constant in a constant expression that controls
22372 conditional inclusion matches the value of the same character constant in the
22373 execution character set (<a href="#6.10.1">6.10.1</a>).
22374 -- Whether the value of a single-character character constant in a constant expression
22375 that controls conditional inclusion may have a negative value (<a href="#6.10.1">6.10.1</a>).
22378 [<a name="p570" href="#p570">page 570</a>] (<a href="#Contents">Contents</a>)
22380 -- The places that are searched for an included < > delimited header, and how the places
22381 are specified or the header is identified (<a href="#6.10.2">6.10.2</a>).
22382 -- How the named source file is searched for in an included " " delimited header
22383 (<a href="#6.10.2">6.10.2</a>).
22384 -- The method by which preprocessing tokens (possibly resulting from macro
22385 expansion) in a #include directive are combined into a header name (<a href="#6.10.2">6.10.2</a>).
22386 -- The nesting limit for #include processing (<a href="#6.10.2">6.10.2</a>).
22387 -- Whether the # operator inserts a \ character before the \ character that begins a
22388 universal character name in a character constant or string literal (<a href="#6.10.3.2">6.10.3.2</a>).
22389 -- The behavior on each recognized non-STDC #pragma directive (<a href="#6.10.6">6.10.6</a>).
22390 -- The definitions for __DATE__ and __TIME__ when respectively, the date and
22391 time of translation are not available (<a href="#6.10.8.1">6.10.8.1</a>).
22392 <a name="J.3.12" href="#J.3.12"><b> J.3.12 Library functions</b></a>
22393 1 -- Any library facilities available to a freestanding program, other than the minimal set
22394 required by clause 4 (<a href="#5.1.2.1">5.1.2.1</a>).
22395 -- The format of the diagnostic printed by the assert macro (<a href="#7.2.1.1">7.2.1.1</a>).
22396 -- The representation of the floating-point status flags stored by the
22397 fegetexceptflag function (<a href="#7.6.2.2">7.6.2.2</a>).
22398 -- Whether the feraiseexcept function raises the ''inexact'' floating-point
22399 exception in addition to the ''overflow'' or ''underflow'' floating-point exception
22400 (<a href="#7.6.2.3">7.6.2.3</a>).
22401 -- Strings other than "C" and "" that may be passed as the second argument to the
22402 setlocale function (<a href="#7.11.1.1">7.11.1.1</a>).
22403 -- The types defined for float_t and double_t when the value of the
22404 FLT_EVAL_METHOD macro is less than 0 (<a href="#7.12">7.12</a>).
22405 -- Domain errors for the mathematics functions, other than those required by this
22406 International Standard (<a href="#7.12.1">7.12.1</a>).
22407 -- The values returned by the mathematics functions on domain errors or pole errors
22408 (<a href="#7.12.1">7.12.1</a>).
22409 -- The values returned by the mathematics functions on underflow range errors, whether
22410 errno is set to the value of the macro ERANGE when the integer expression
22411 math_errhandling & MATH_ERRNO is nonzero, and whether the ''underflow''
22412 floating-point exception is raised when the integer expression math_errhandling
22413 & MATH_ERREXCEPT is nonzero. (<a href="#7.12.1">7.12.1</a>).
22415 [<a name="p571" href="#p571">page 571</a>] (<a href="#Contents">Contents</a>)
22417 -- Whether a domain error occurs or zero is returned when an fmod function has a
22418 second argument of zero (<a href="#7.12.10.1">7.12.10.1</a>).
22419 -- Whether a domain error occurs or zero is returned when a remainder function has
22420 a second argument of zero (<a href="#7.12.10.2">7.12.10.2</a>).
22421 -- The base-2 logarithm of the modulus used by the remquo functions in reducing the
22422 quotient (<a href="#7.12.10.3">7.12.10.3</a>).
22423 -- Whether a domain error occurs or zero is returned when a remquo function has a
22424 second argument of zero (<a href="#7.12.10.3">7.12.10.3</a>).
22425 -- Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call
22426 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>).
22427 -- The null pointer constant to which the macro NULL expands (<a href="#7.19">7.19</a>).
22428 -- Whether the last line of a text stream requires a terminating new-line character
22429 (<a href="#7.21.2">7.21.2</a>).
22430 -- Whether space characters that are written out to a text stream immediately before a
22431 new-line character appear when read in (<a href="#7.21.2">7.21.2</a>).
22432 -- The number of null characters that may be appended to data written to a binary
22433 stream (<a href="#7.21.2">7.21.2</a>).
22434 -- Whether the file position indicator of an append-mode stream is initially positioned at
22435 the beginning or end of the file (<a href="#7.21.3">7.21.3</a>).
22436 -- Whether a write on a text stream causes the associated file to be truncated beyond that
22437 point (<a href="#7.21.3">7.21.3</a>).
22438 -- The characteristics of file buffering (<a href="#7.21.3">7.21.3</a>).
22439 -- Whether a zero-length file actually exists (<a href="#7.21.3">7.21.3</a>).
22440 -- The rules for composing valid file names (<a href="#7.21.3">7.21.3</a>).
22441 -- Whether the same file can be simultaneously open multiple times (<a href="#7.21.3">7.21.3</a>).
22442 -- The nature and choice of encodings used for multibyte characters in files (<a href="#7.21.3">7.21.3</a>).
22443 -- The effect of the remove function on an open file (<a href="#7.21.4.1">7.21.4.1</a>).
22444 -- The effect if a file with the new name exists prior to a call to the rename function
22445 (<a href="#7.21.4.2">7.21.4.2</a>).
22446 -- Whether an open temporary file is removed upon abnormal program termination
22447 (<a href="#7.21.4.3">7.21.4.3</a>).
22448 -- Which changes of mode are permitted (if any), and under what circumstances
22449 (<a href="#7.21.5.4">7.21.5.4</a>).
22451 [<a name="p572" href="#p572">page 572</a>] (<a href="#Contents">Contents</a>)
22453 -- The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
22454 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>).
22455 -- The output for %p conversion in the fprintf or fwprintf function (<a href="#7.21.6.1">7.21.6.1</a>,
22456 <a href="#7.28.2.1">7.28.2.1</a>).
22457 -- The interpretation of a - character that is neither the first nor the last character, nor
22458 the second where a ^ character is the first, in the scanlist for %[ conversion in the
22459 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>).
22460 -- The set of sequences matched by a %p conversion and the interpretation of the
22461 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>).
22462 -- The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
22463 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>).
22464 -- The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
22465 converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold
22466 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>).
22467 -- Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
22468 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>).
22469 -- Whether the calloc, malloc, and realloc functions return a null pointer or a
22470 pointer to an allocated object when the size requested is zero (<a href="#7.22.3">7.22.3</a>).
22471 -- Whether open streams with unwritten buffered data are flushed, open streams are
22472 closed, or temporary files are removed when the abort or _Exit function is called
22473 (<a href="#7.22.4.1">7.22.4.1</a>, <a href="#7.22.4.5">7.22.4.5</a>).
22474 -- The termination status returned to the host environment by the abort, exit,
22475 _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>).
22476 -- The value returned by the system function when its argument is not a null pointer
22477 (<a href="#7.22.4.8">7.22.4.8</a>).
22478 -- The local time zone and Daylight Saving Time (<a href="#7.26.1">7.26.1</a>).
22479 -- The range and precision of times representable in clock_t and time_t (<a href="#7.26">7.26</a>).
22480 -- The era for the clock function (<a href="#7.26.2.1">7.26.2.1</a>).
22481 -- The replacement string for the %Z specifier to the strftime, and wcsftime
22482 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>).
22483 -- Whether the functions in <a href="#7.12"><math.h></a> honor the rounding direction mode in an
22484 IEC 60559 conformant implementation, unless explicitly specified otherwise (<a href="#F.10">F.10</a>).
22489 [<a name="p573" href="#p573">page 573</a>] (<a href="#Contents">Contents</a>)
22491 <a name="J.3.13" href="#J.3.13"><b> J.3.13 Architecture</b></a>
22492 1 -- The values or expressions assigned to the macros specified in the headers
22493 <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>).
22494 -- The result of attempting to indirectly access an object with automatic or thread
22495 storage duration from a thread other than the one with which it is associated (<a href="#6.2.4">6.2.4</a>).
22496 -- The number, order, and encoding of bytes in any object (when not explicitly specified
22497 in this International Standard) (<a href="#6.2.6.1">6.2.6.1</a>).
22498 -- Whether any extended alignments are supported and the contexts in which they are
22499 supported (<a href="#6.2.8">6.2.8</a>).
22500 -- Valid alignment values other than those returned by an alignof expression for
22501 fundamental types, if any (<a href="#6.2.8">6.2.8</a>).
22502 -- The value of the result of the sizeof and alignof operators (<a href="#6.5.3.4">6.5.3.4</a>).
22503 <a name="J.4" href="#J.4"><b> J.4 Locale-specific behavior</b></a>
22504 1 The following characteristics of a hosted environment are locale-specific and are required
22505 to be documented by the implementation:
22506 -- Additional members of the source and execution character sets beyond the basic
22507 character set (<a href="#5.2.1">5.2.1</a>).
22508 -- The presence, meaning, and representation of additional multibyte characters in the
22509 execution character set beyond the basic character set (<a href="#5.2.1.2">5.2.1.2</a>).
22510 -- The shift states used for the encoding of multibyte characters (<a href="#5.2.1.2">5.2.1.2</a>).
22511 -- The direction of writing of successive printing characters (<a href="#5.2.2">5.2.2</a>).
22512 -- The decimal-point character (<a href="#7.1.1">7.1.1</a>).
22513 -- The set of printing characters (<a href="#7.4">7.4</a>, <a href="#7.29.2">7.29.2</a>).
22514 -- The set of control characters (<a href="#7.4">7.4</a>, <a href="#7.29.2">7.29.2</a>).
22515 -- The sets of characters tested for by the isalpha, isblank, islower, ispunct,
22516 isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
22517 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>,
22518 <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>).
22519 -- The native environment (<a href="#7.11.1.1">7.11.1.1</a>).
22520 -- Additional subject sequences accepted by the numeric conversion functions (<a href="#7.22.1">7.22.1</a>,
22521 <a href="#7.28.4.1">7.28.4.1</a>).
22522 -- 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>).
22525 [<a name="p574" href="#p574">page 574</a>] (<a href="#Contents">Contents</a>)
22527 -- The contents of the error message strings set up by the strerror function
22528 (<a href="#7.23.6.2">7.23.6.2</a>).
22529 -- 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>).
22530 -- Character mappings that are supported by the towctrans function (<a href="#7.29.1">7.29.1</a>).
22531 -- Character classifications that are supported by the iswctype function (<a href="#7.29.1">7.29.1</a>).
22532 <a name="J.5" href="#J.5"><b> J.5 Common extensions</b></a>
22533 1 The following extensions are widely used in many systems, but are not portable to all
22534 implementations. The inclusion of any extension that may cause a strictly conforming
22535 program to become invalid renders an implementation nonconforming. Examples of such
22536 extensions are new keywords, extra library functions declared in standard headers, or
22537 predefined macros with names that do not begin with an underscore.
22538 <a name="J.5.1" href="#J.5.1"><b> J.5.1 Environment arguments</b></a>
22539 1 In a hosted environment, the main function receives a third argument, char *envp[],
22540 that points to a null-terminated array of pointers to char, each of which points to a string
22541 that provides information about the environment for this execution of the program
22542 (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
22543 <a name="J.5.2" href="#J.5.2"><b> J.5.2 Specialized identifiers</b></a>
22544 1 Characters other than the underscore _, letters, and digits, that are not part of the basic
22545 source character set (such as the dollar sign $, or characters in national character sets)
22546 may appear in an identifier (<a href="#6.4.2">6.4.2</a>).
22547 <a name="J.5.3" href="#J.5.3"><b> J.5.3 Lengths and cases of identifiers</b></a>
22548 1 All characters in identifiers (with or without external linkage) are significant (<a href="#6.4.2">6.4.2</a>).
22549 <a name="J.5.4" href="#J.5.4"><b> J.5.4 Scopes of identifiers</b></a>
22550 1 A function identifier, or the identifier of an object the declaration of which contains the
22551 keyword extern, has file scope (<a href="#6.2.1">6.2.1</a>).
22552 <a name="J.5.5" href="#J.5.5"><b> J.5.5 Writable string literals</b></a>
22553 1 String literals are modifiable (in which case, identical string literals should denote distinct
22554 objects) (<a href="#6.4.5">6.4.5</a>).
22559 [<a name="p575" href="#p575">page 575</a>] (<a href="#Contents">Contents</a>)
22561 <a name="J.5.6" href="#J.5.6"><b> J.5.6 Other arithmetic types</b></a>
22562 1 Additional arithmetic types, such as __int128 or double double, and their
22563 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
22564 more range or precision than long double, may be used for evaluating expressions of
22565 other floating types, and may be used to define float_t or double_t.
22566 <a name="J.5.7" href="#J.5.7"><b> J.5.7 Function pointer casts</b></a>
22567 1 A pointer to an object or to void may be cast to a pointer to a function, allowing data to
22568 be invoked as a function (<a href="#6.5.4">6.5.4</a>).
22569 2 A pointer to a function may be cast to a pointer to an object or to void, allowing a
22570 function to be inspected or modified (for example, by a debugger) (<a href="#6.5.4">6.5.4</a>).
22571 <a name="J.5.8" href="#J.5.8"><b> J.5.8 Extended bit-field types</b></a>
22572 1 A bit-field may be declared with a type other than _Bool, unsigned int, or
22573 signed int, with an appropriate maximum width (<a href="#6.7.2.1">6.7.2.1</a>).
22574 <a name="J.5.9" href="#J.5.9"><b> J.5.9 The fortran keyword</b></a>
22575 1 The fortran function specifier may be used in a function declaration to indicate that
22576 calls suitable for FORTRAN should be generated, or that a different representation for the
22577 external name is to be generated (<a href="#6.7.4">6.7.4</a>).
22578 <a name="J.5.10" href="#J.5.10"><b> J.5.10 The asm keyword</b></a>
22579 1 The asm keyword may be used to insert assembly language directly into the translator
22580 output (<a href="#6.8">6.8</a>). The most common implementation is via a statement of the form:
22581 asm ( character-string-literal );
22582 <a name="J.5.11" href="#J.5.11"><b> J.5.11 Multiple external definitions</b></a>
22583 1 There may be more than one external definition for the identifier of an object, with or
22584 without the explicit use of the keyword extern; if the definitions disagree, or more than
22585 one is initialized, the behavior is undefined (<a href="#6.9.2">6.9.2</a>).
22586 <a name="J.5.12" href="#J.5.12"><b> J.5.12 Predefined macro names</b></a>
22587 1 Macro names that do not begin with an underscore, describing the translation and
22588 execution environments, are defined by the implementation before translation begins
22589 (<a href="#6.10.8">6.10.8</a>).
22594 [<a name="p576" href="#p576">page 576</a>] (<a href="#Contents">Contents</a>)
22596 <a name="J.5.13" href="#J.5.13"><b> J.5.13 Floating-point status flags</b></a>
22597 1 If any floating-point status flags are set on normal termination after all calls to functions
22598 registered by the atexit function have been made (see <a href="#7.22.4.4">7.22.4.4</a>), the implementation
22599 writes some diagnostics indicating the fact to the stderr stream, if it is still open,
22600 <a name="J.5.14" href="#J.5.14"><b> J.5.14 Extra arguments for signal handlers</b></a>
22601 1 Handlers for specific signals are called with extra arguments in addition to the signal
22602 number (<a href="#7.14.1.1">7.14.1.1</a>).
22603 <a name="J.5.15" href="#J.5.15"><b> J.5.15 Additional stream types and file-opening modes</b></a>
22604 1 Additional mappings from files to streams are supported (<a href="#7.21.2">7.21.2</a>).
22605 2 Additional file-opening modes may be specified by characters appended to the mode
22606 argument of the fopen function (<a href="#7.21.5.3">7.21.5.3</a>).
22607 <a name="J.5.16" href="#J.5.16"><b> J.5.16 Defined file position indicator</b></a>
22608 1 The file position indicator is decremented by each successful call to the ungetc or
22609 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>,
22610 <a name="7.28.3.10)" href="#7.28.3.10)"><b> 7.28.3.10).</b></a>
22611 <a name="J.5.17" href="#J.5.17"><b> J.5.17 Math error reporting</b></a>
22612 1 Functions declared in <a href="#7.3"><complex.h></a> and <a href="#7.12"><math.h></a> raise SIGFPE to report errors
22613 instead of, or in addition to, setting errno or raising floating-point exceptions (<a href="#7.3">7.3</a>,
22614 <a name="7.12)" href="#7.12)"><b> 7.12).</b></a>
22619 [<a name="p577" href="#p577">page 577</a>] (<a href="#Contents">Contents</a>)
22621 <a name="K" href="#K"><b> Annex K</b></a>
22623 Bounds-checking interfaces
22624 <a name="K.1" href="#K.1"><b> K.1 Background</b></a>
22625 1 Traditionally, the C Library has contained many functions that trust the programmer to
22626 provide output character arrays big enough to hold the result being produced. Not only
22627 do these functions not check that the arrays are big enough, they frequently lack the
22628 information needed to perform such checks. While it is possible to write safe, robust, and
22629 error-free code using the existing library, the library tends to promote programming styles
22630 that lead to mysterious failures if a result is too big for the provided array.
22631 2 A common programming style is to declare character arrays large enough to handle most
22632 practical cases. However, if these arrays are not large enough to handle the resulting
22633 strings, data can be written past the end of the array overwriting other data and program
22634 structures. The program never gets any indication that a problem exists, and so never has
22635 a chance to recover or to fail gracefully.
22636 3 Worse, this style of programming has compromised the security of computers and
22637 networks. Buffer overflows can often be exploited to run arbitrary code with the
22638 permissions of the vulnerable (defective) program.
22639 4 If the programmer writes runtime checks to verify lengths before calling library
22640 functions, then those runtime checks frequently duplicate work done inside the library
22641 functions, which discover string lengths as a side effect of doing their job.
22642 5 This annex provides alternative library functions that promote safer, more secure
22643 programming. The alternative functions verify that output buffers are large enough for
22644 the intended result and return a failure indicator if they are not. Data is never written past
22645 the end of an array. All string results are null terminated.
22646 6 This annex also addresses another problem that complicates writing robust code:
22647 functions that are not reentrant because they return pointers to static objects owned by the
22648 function. Such functions can be troublesome since a previously returned result can
22649 change if the function is called again, perhaps by another thread.
22654 [<a name="p578" href="#p578">page 578</a>] (<a href="#Contents">Contents</a>)
22656 <a name="K.2" href="#K.2"><b> K.2 Scope</b></a>
22657 1 This annex specifies a series of optional extensions that can be useful in the mitigation of
22658 security vulnerabilities in programs, and comprise new functions, macros, and types
22659 declared or defined in existing standard headers.
22660 2 An implementation that defines __STDC_LIB_EXT1__ shall conform to the
22661 specifications in this annex.<sup><a href="#note367"><b>367)</b></a></sup>
22662 3 Subclause <a href="#K.3">K.3</a> should be read as if it were merged into the parallel structure of named
22663 subclauses of clause 7.
22664 <a name="K.3" href="#K.3"><b> K.3 Library</b></a>
22665 <a name="K.3.1" href="#K.3.1"><b> K.3.1 Introduction</b></a>
22666 <a name="K.3.1.1" href="#K.3.1.1"><b> K.3.1.1 Standard headers</b></a>
22667 1 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are not
22668 declared or defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
22669 defined as a macro which expands to the integer constant 0 at the point in the source file
22670 where the appropriate header is first included.
22671 2 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are
22672 declared and defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
22673 defined as a macro which expands to the integer constant 1 at the point in the source file
22674 where the appropriate header is first included.<sup><a href="#note368"><b>368)</b></a></sup>
22675 3 It is implementation-defined whether the functions, macros, and types declared or defined
22676 in <a href="#K.3">K.3</a> and its subclauses are declared or defined by their respective headers if
22677 __STDC_WANT_LIB_EXT1__ is not defined as a macro at the point in the source file
22678 where the appropriate header is first included.<sup><a href="#note369"><b>369)</b></a></sup>
22679 4 Within a preprocessing translation unit, __STDC_WANT_LIB_EXT1__ shall be
22680 defined identically for all inclusions of any headers from subclause <a href="#K.3">K.3</a>. If
22681 __STDC_WANT_LIB_EXT1__ is defined differently for any such inclusion, the
22682 implementation shall issue a diagnostic as if a preprocessor error directive were used.
22685 <sup><a name="note367" href="#note367"><b>367)</b></a></sup> Implementations that do not define __STDC_LIB_EXT1__ are not required to conform to these
22687 <sup><a name="note368" href="#note368"><b>368)</b></a></sup> Future revisions of this International Standard may define meanings for other values of
22688 __STDC_WANT_LIB_EXT1__.
22689 <sup><a name="note369" href="#note369"><b>369)</b></a></sup> Subclause <a href="#7.1.3">7.1.3</a> reserves certain names and patterns of names that an implementation may use in
22690 headers. All other names are not reserved, and a conforming implementation is not permitted to use
22691 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
22692 unreserved name is defined in a header when __STDC_WANT_LIB_EXT1__ is defined as 0, the
22693 implementation is not conforming.
22695 [<a name="p579" href="#p579">page 579</a>] (<a href="#Contents">Contents</a>)
22697 <a name="K.3.1.2" href="#K.3.1.2"><b> K.3.1.2 Reserved identifiers</b></a>
22698 1 Each macro name in any of the following subclauses is reserved for use as specified if it
22699 is defined by any of its associated headers when included; unless explicitly stated
22700 otherwise (see <a href="#7.1.4">7.1.4</a>).
22701 2 All identifiers with external linkage in any of the following subclauses are reserved for
22702 use as identifiers with external linkage if any of them are used by the program. None of
22703 them are reserved if none of them are used.
22704 3 Each identifier with file scope listed in any of the following subclauses is reserved for use
22705 as a macro name and as an identifier with file scope in the same name space if it is
22706 defined by any of its associated headers when included.
22707 <a name="K.3.1.3" href="#K.3.1.3"><b> K.3.1.3 Use of errno</b></a>
22708 1 An implementation may set errno for the functions defined in this annex, but is not
22710 <a name="K.3.1.4" href="#K.3.1.4"><b> K.3.1.4 Runtime-constraint violations</b></a>
22711 1 Most functions in this annex include as part of their specification a list of runtime-
22712 constraints. These runtime-constraints are requirements on the program using the
22713 library.<sup><a href="#note370"><b>370)</b></a></sup>
22714 2 Implementations shall verify that the runtime-constraints for a function are not violated
22715 by the program. If a runtime-constraint is violated, the implementation shall call the
22716 currently registered runtime-constraint handler (see set_constraint_handler_s
22717 in <a href="#7.22"><stdlib.h></a>). Multiple runtime-constraint violations in the same call to a library
22718 function result in only one call to the runtime-constraint handler. It is unspecified which
22719 one of the multiple runtime-constraint violations cause the handler to be called.
22720 3 If the runtime-constraints section for a function states an action to be performed when a
22721 runtime-constraint violation occurs, the function shall perform the action before calling
22722 the runtime-constraint handler. If the runtime-constraints section lists actions that are
22723 prohibited when a runtime-constraint violation occurs, then such actions are prohibited to
22724 the function both before calling the handler and after the handler returns.
22725 4 The runtime-constraint handler might not return. If the handler does return, the library
22726 function whose runtime-constraint was violated shall return some indication of failure as
22727 given by the returns section in the function's specification.
22731 <sup><a name="note370" href="#note370"><b>370)</b></a></sup> Although runtime-constraints replace many cases of undefined behavior, undefined behavior still
22732 exists in this annex. Implementations are free to detect any case of undefined behavior and treat it as a
22733 runtime-constraint violation by calling the runtime-constraint handler. This license comes directly
22734 from the definition of undefined behavior.
22736 [<a name="p580" href="#p580">page 580</a>] (<a href="#Contents">Contents</a>)
22738 <a name="K.3.2" href="#K.3.2"><b> K.3.2 Errors <errno.h></b></a>
22739 1 The header <a href="#7.5"><errno.h></a> defines a type.
22742 which is type int.<sup><a href="#note371"><b>371)</b></a></sup>
22743 <a name="K.3.3" href="#K.3.3"><b> K.3.3 Common definitions <stddef.h></b></a>
22744 1 The header <a href="#7.19"><stddef.h></a> defines a type.
22747 which is the type size_t.<sup><a href="#note372"><b>372)</b></a></sup>
22748 <a name="K.3.4" href="#K.3.4"><b> K.3.4 Integer types <stdint.h></b></a>
22749 1 The header <a href="#7.20"><stdint.h></a> defines a macro.
22752 which expands to a value<sup><a href="#note373"><b>373)</b></a></sup> of type size_t. Functions that have parameters of type
22753 rsize_t consider it a runtime-constraint violation if the values of those parameters are
22754 greater than RSIZE_MAX.
22755 Recommended practice
22756 3 Extremely large object sizes are frequently a sign that an object's size was calculated
22757 incorrectly. For example, negative numbers appear as very large positive numbers when
22758 converted to an unsigned type like size_t. Also, some implementations do not support
22759 objects as large as the maximum value that can be represented by type size_t.
22760 4 For those reasons, it is sometimes beneficial to restrict the range of object sizes to detect
22761 programming errors. For implementations targeting machines with large address spaces,
22762 it is recommended that RSIZE_MAX be defined as the smaller of the size of the largest
22763 object supported or (SIZE_MAX >> 1), even if this limit is smaller than the size of
22764 some legitimate, but very large, objects. Implementations targeting machines with small
22765 address spaces may wish to define RSIZE_MAX as SIZE_MAX, which means that there
22767 <sup><a name="note371" href="#note371"><b>371)</b></a></sup> As a matter of programming style, errno_t may be used as the type of something that deals only
22768 with the values that might be found in errno. For example, a function which returns the value of
22769 errno might be declared as having the return type errno_t.
22770 <sup><a name="note372" href="#note372"><b>372)</b></a></sup> See the description of the RSIZE_MAX macro in <a href="#7.20"><stdint.h></a>.
22771 <sup><a name="note373" href="#note373"><b>373)</b></a></sup> The macro RSIZE_MAX need not expand to a constant expression.
22773 [<a name="p581" href="#p581">page 581</a>] (<a href="#Contents">Contents</a>)
22775 is no object size that is considered a runtime-constraint violation.
22776 <a name="K.3.5" href="#K.3.5"><b> K.3.5 Input/output <stdio.h></b></a>
22777 1 The header <a href="#7.21"><stdio.h></a> defines several macros and two types.
22780 which expands to an integer constant expression that is the size needed for an array of
22781 char large enough to hold a temporary file name string generated by the tmpnam_s
22784 which expands to an integer constant expression that is the maximum number of unique
22785 file names that can be generated by the tmpnam_s function.
22788 which is type int; and
22790 which is the type size_t.
22791 <a name="K.3.5.1" href="#K.3.5.1"><b> K.3.5.1 Operations on files</b></a>
22792 <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>
22794 1 #define __STDC_WANT_LIB_EXT1__ 1
22795 #include <a href="#7.21"><stdio.h></a>
22796 errno_t tmpfile_s(FILE * restrict * restrict streamptr);
22797 Runtime-constraints
22798 2 streamptr shall not be a null pointer.
22799 3 If there is a runtime-constraint violation, tmpfile_s does not attempt to create a file.
22800 <b> Description</b>
22801 4 The tmpfile_s function creates a temporary binary file that is different from any other
22802 existing file and that will automatically be removed when it is closed or at program
22803 termination. If the program terminates abnormally, whether an open temporary file is
22804 removed is implementation-defined. The file is opened for update with "wb+" mode
22805 with the meaning that mode has in the fopen_s function (including the mode's effect
22806 on exclusive access and file permissions).
22809 [<a name="p582" href="#p582">page 582</a>] (<a href="#Contents">Contents</a>)
22811 5 If the file was created successfully, then the pointer to FILE pointed to by streamptr
22812 will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
22813 to FILE pointed to by streamptr will be set to a null pointer.
22814 Recommended practice
22815 It should be possible to open at least TMP_MAX_S temporary files during the lifetime of
22816 the program (this limit may be shared with tmpnam_s) and there should be no limit on
22817 the number simultaneously open other than this limit and any limit on the number of open
22820 6 The tmpfile_s function returns zero if it created the file. If it did not create the file or
22821 there was a runtime-constraint violation, tmpfile_s returns a nonzero value.
22822 <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>
22824 1 #define __STDC_WANT_LIB_EXT1__ 1
22825 #include <a href="#7.21"><stdio.h></a>
22826 errno_t tmpnam_s(char *s, rsize_t maxsize);
22827 Runtime-constraints
22828 2 s shall not be a null pointer. maxsize shall be less than or equal to RSIZE_MAX.
22829 maxsize shall be greater than the length of the generated file name string.
22830 <b> Description</b>
22831 3 The tmpnam_s function generates a string that is a valid file name and that is not the
22832 same as the name of an existing file.<sup><a href="#note374"><b>374)</b></a></sup> The function is potentially capable of generating
22833 TMP_MAX_S different strings, but any or all of them may already be in use by existing
22834 files and thus not be suitable return values. The lengths of these strings shall be less than
22835 the value of the L_tmpnam_s macro.
22836 4 The tmpnam_s function generates a different string each time it is called.
22837 5 It is assumed that s points to an array of at least maxsize characters. This array will be
22838 set to generated string, as specified below.
22842 <sup><a name="note374" href="#note374"><b>374)</b></a></sup> Files created using strings generated by the tmpnam_s function are temporary only in the sense that
22843 their names should not collide with those generated by conventional naming rules for the
22844 implementation. It is still necessary to use the remove function to remove such files when their use
22845 is ended, and before program termination. Implementations should take care in choosing the patterns
22846 used for names returned by tmpnam_s. For example, making a thread id part of the names avoids the
22847 race condition and possible conflict when multiple programs run simultaneously by the same user
22848 generate the same temporary file names.
22850 [<a name="p583" href="#p583">page 583</a>] (<a href="#Contents">Contents</a>)
22852 6 The implementation shall behave as if no library function except tmpnam calls the
22853 tmpnam_s function.<sup><a href="#note375"><b>375)</b></a></sup>
22854 Recommended practice
22855 7 After a program obtains a file name using the tmpnam_s function and before the
22856 program creates a file with that name, the possibility exists that someone else may create
22857 a file with that same name. To avoid this race condition, the tmpfile_s function
22858 should be used instead of tmpnam_s when possible. One situation that requires the use
22859 of the tmpnam_s function is when the program needs to create a temporary directory
22860 rather than a temporary file.
22862 8 If no suitable string can be generated, or if there is a runtime-constraint violation, the
22863 tmpnam_s function writes a null character to s[0] (only if s is not null and maxsize
22864 is greater than zero) and returns a nonzero value.
22865 9 Otherwise, the tmpnam_s function writes the string in the array pointed to by s and
22867 Environmental limits
22868 10 The value of the macro TMP_MAX_S shall be at least 25.
22869 <a name="K.3.5.2" href="#K.3.5.2"><b> K.3.5.2 File access functions</b></a>
22870 <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>
22872 1 #define __STDC_WANT_LIB_EXT1__ 1
22873 #include <a href="#7.21"><stdio.h></a>
22874 errno_t fopen_s(FILE * restrict * restrict streamptr,
22875 const char * restrict filename,
22876 const char * restrict mode);
22877 Runtime-constraints
22878 2 None of streamptr, filename, or mode shall be a null pointer.
22879 3 If there is a runtime-constraint violation, fopen_s does not attempt to open a file.
22880 Furthermore, if streamptr is not a null pointer, fopen_s sets *streamptr to the
22886 <sup><a name="note375" href="#note375"><b>375)</b></a></sup> An implementation may have tmpnam call tmpnam_s (perhaps so there is only one naming
22887 convention for temporary files), but this is not required.
22889 [<a name="p584" href="#p584">page 584</a>] (<a href="#Contents">Contents</a>)
22891 <b> Description</b>
22892 4 The fopen_s function opens the file whose name is the string pointed to by
22893 filename, and associates a stream with it.
22894 5 The mode string shall be as described for fopen, with the addition that modes starting
22895 with the character 'w' or 'a' may be preceded by the character 'u', see below:
22896 uw truncate to zero length or create text file for writing, default
22898 uwx create text file for writing, default permissions
22899 ua append; open or create text file for writing at end-of-file, default
22901 uwb truncate to zero length or create binary file for writing, default
22903 uwbx create binary file for writing, default permissions
22904 uab append; open or create binary file for writing at end-of-file, default
22906 uw+ truncate to zero length or create text file for update, default
22908 uw+x create text file for update, default permissions
22909 ua+ append; open or create text file for update, writing at end-of-file,
22910 default permissions
22911 uw+b or uwb+ truncate to zero length or create binary file for update, default
22913 uw+bx or uwb+x create binary file for update, default permissions
22914 ua+b or uab+ append; open or create binary file for update, writing at end-of-file,
22915 default permissions
22916 6 Opening a file with exclusive mode ('x' as the last character in the mode argument)
22917 fails if the file already exists or cannot be created.
22918 7 To the extent that the underlying system supports the concepts, files opened for writing
22919 shall be opened with exclusive (also known as non-shared) access. If the file is being
22920 created, and the first character of the mode string is not 'u', to the extent that the
22921 underlying system supports it, the file shall have a file permission that prevents other
22922 users on the system from accessing the file. If the file is being created and first character
22923 of the mode string is 'u', then by the time the file has been closed, it shall have the
22924 system default file access permissions.<sup><a href="#note376"><b>376)</b></a></sup>
22925 8 If the file was opened successfully, then the pointer to FILE pointed to by streamptr
22926 will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
22929 <sup><a name="note376" href="#note376"><b>376)</b></a></sup> These are the same permissions that the file would have been created with by fopen.
22931 [<a name="p585" href="#p585">page 585</a>] (<a href="#Contents">Contents</a>)
22933 to FILE pointed to by streamptr will be set to a null pointer.
22935 9 The fopen_s function returns zero if it opened the file. If it did not open the file or if
22936 there was a runtime-constraint violation, fopen_s returns a nonzero value.
22937 <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>
22939 1 #define __STDC_WANT_LIB_EXT1__ 1
22940 #include <a href="#7.21"><stdio.h></a>
22941 errno_t freopen_s(FILE * restrict * restrict newstreamptr,
22942 const char * restrict filename,
22943 const char * restrict mode,
22944 FILE * restrict stream);
22945 Runtime-constraints
22946 2 None of newstreamptr, mode, and stream shall be a null pointer.
22947 3 If there is a runtime-constraint violation, freopen_s neither attempts to close any file
22948 associated with stream nor attempts to open a file. Furthermore, if newstreamptr is
22949 not a null pointer, fopen_s sets *newstreamptr to the null pointer.
22950 <b> Description</b>
22951 4 The freopen_s function opens the file whose name is the string pointed to by
22952 filename and associates the stream pointed to by stream with it. The mode
22953 argument has the same meaning as in the fopen_s function (including the mode's effect
22954 on exclusive access and file permissions).
22955 5 If filename is a null pointer, the freopen_s function attempts to change the mode of
22956 the stream to that specified by mode, as if the name of the file currently associated with
22957 the stream had been used. It is implementation-defined which changes of mode are
22958 permitted (if any), and under what circumstances.
22959 6 The freopen_s function first attempts to close any file that is associated with stream.
22960 Failure to close the file is ignored. The error and end-of-file indicators for the stream are
22962 7 If the file was opened successfully, then the pointer to FILE pointed to by
22963 newstreamptr will be set to the value of stream. Otherwise, the pointer to FILE
22964 pointed to by newstreamptr will be set to a null pointer.
22966 8 The freopen_s function returns zero if it opened the file. If it did not open the file or
22967 there was a runtime-constraint violation, freopen_s returns a nonzero value.
22969 [<a name="p586" href="#p586">page 586</a>] (<a href="#Contents">Contents</a>)
22971 <a name="K.3.5.3" href="#K.3.5.3"><b> K.3.5.3 Formatted input/output functions</b></a>
22972 1 Unless explicitly stated otherwise, if the execution of a function described in this
22973 subclause causes copying to take place between objects that overlap, the objects take on
22974 unspecified values.
22975 <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>
22977 1 #define __STDC_WANT_LIB_EXT1__ 1
22978 #include <a href="#7.21"><stdio.h></a>
22979 int fprintf_s(FILE * restrict stream,
22980 const char * restrict format, ...);
22981 Runtime-constraints
22982 2 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note377"><b>377)</b></a></sup> (modified or
22983 not by flags, field width, or precision) shall not appear in the string pointed to by
22984 format. Any argument to fprintf_s corresponding to a %s specifier shall not be a
22986 3 If there is a runtime-constraint violation,<sup><a href="#note378"><b>378)</b></a></sup> the fprintf_s function does not attempt
22987 to produce further output, and it is unspecified to what extent fprintf_s produced
22988 output before discovering the runtime-constraint violation.
22989 <b> Description</b>
22990 4 The fprintf_s function is equivalent to the fprintf function except for the explicit
22991 runtime-constraints listed above.
22993 5 The fprintf_s function returns the number of characters transmitted, or a negative
22994 value if an output error, encoding error, or runtime-constraint violation occurred.
22999 <sup><a name="note377" href="#note377"><b>377)</b></a></sup> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
23000 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
23001 format string was %%n.
23002 <sup><a name="note378" href="#note378"><b>378)</b></a></sup> Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
23003 implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
23004 constraint violation.
23006 [<a name="p587" href="#p587">page 587</a>] (<a href="#Contents">Contents</a>)
23008 <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>
23010 1 #define __STDC_WANT_LIB_EXT1__ 1
23011 #include <a href="#7.21"><stdio.h></a>
23012 int fscanf_s(FILE * restrict stream,
23013 const char * restrict format, ...);
23014 Runtime-constraints
23015 2 Neither stream nor format shall be a null pointer. Any argument indirected though in
23016 order to store converted input shall not be a null pointer.
23017 3 If there is a runtime-constraint violation,<sup><a href="#note379"><b>379)</b></a></sup> the fscanf_s function does not attempt to
23018 perform further input, and it is unspecified to what extent fscanf_s performed input
23019 before discovering the runtime-constraint violation.
23020 <b> Description</b>
23021 4 The fscanf_s function is equivalent to fscanf except that the c, s, and [ conversion
23022 specifiers apply to a pair of arguments (unless assignment suppression is indicated by a
23023 *). The first of these arguments is the same as for fscanf. That argument is
23024 immediately followed in the argument list by the second argument, which has type
23025 rsize_t and gives the number of elements in the array pointed to by the first argument
23026 of the pair. If the first argument points to a scalar object, it is considered to be an array of
23027 one element.<sup><a href="#note380"><b>380)</b></a></sup>
23028 5 A matching failure occurs if the number of elements in a receiving object is insufficient to
23029 hold the converted input (including any trailing null character).
23031 6 The fscanf_s function returns the value of the macro EOF if an input failure occurs
23032 before any conversion or if there is a runtime-constraint violation. Otherwise, the
23034 <sup><a name="note379" href="#note379"><b>379)</b></a></sup> Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
23035 implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
23036 constraint violation.
23037 <sup><a name="note380" href="#note380"><b>380)</b></a></sup> If the format is known at translation time, an implementation may issue a diagnostic for any argument
23038 used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
23039 argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
23040 the format is not known at translation time. For example, an implementation may issue a diagnostic
23041 for each argument after format that has of type pointer to one of char, signed char,
23042 unsigned char, or void that is not followed by an argument of a type compatible with
23043 rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
23044 using the hh length modifier, a length argument must follow the pointer argument. Another useful
23045 diagnostic could flag any non-pointer argument following format that did not have a type
23046 compatible with rsize_t.
23048 [<a name="p588" href="#p588">page 588</a>] (<a href="#Contents">Contents</a>)
23050 fscanf_s function returns the number of input items assigned, which can be fewer than
23051 provided for, or even zero, in the event of an early matching failure.
23052 7 EXAMPLE 1 The call:
23053 #define __STDC_WANT_LIB_EXT1__ 1
23054 #include <a href="#7.21"><stdio.h></a>
23056 int n, i; float x; char name[50];
23057 n = fscanf_s(stdin, "%d%f%s", &i, &x, name, (rsize_t) 50);
23058 with the input line:
23059 25 54.32E-1 thompson
23060 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
23063 8 EXAMPLE 2 The call:
23064 #define __STDC_WANT_LIB_EXT1__ 1
23065 #include <a href="#7.21"><stdio.h></a>
23068 n = fscanf_s(stdin, "%s", s, sizeof s);
23069 with the input line:
23071 will assign to n the value 0 since a matching failure occurred because the sequence hello\0 requires an
23072 array of six characters to store it.
23074 <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>
23076 1 #define __STDC_WANT_LIB_EXT1__ 1
23077 #include <a href="#7.21"><stdio.h></a>
23078 int printf_s(const char * restrict format, ...);
23079 Runtime-constraints
23080 2 format shall not be a null pointer. The %n specifier<sup><a href="#note381"><b>381)</b></a></sup> (modified or not by flags, field
23081 width, or precision) shall not appear in the string pointed to by format. Any argument
23082 to printf_s corresponding to a %s specifier shall not be a null pointer.
23083 3 If there is a runtime-constraint violation, the printf_s function does not attempt to
23084 produce further output, and it is unspecified to what extent printf_s produced output
23085 before discovering the runtime-constraint violation.
23088 <sup><a name="note381" href="#note381"><b>381)</b></a></sup> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
23089 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
23090 format string was %%n.
23092 [<a name="p589" href="#p589">page 589</a>] (<a href="#Contents">Contents</a>)
23094 <b> Description</b>
23095 4 The printf_s function is equivalent to the printf function except for the explicit
23096 runtime-constraints listed above.
23098 5 The printf_s function returns the number of characters transmitted, or a negative
23099 value if an output error, encoding error, or runtime-constraint violation occurred.
23100 <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>
23102 1 #define __STDC_WANT_LIB_EXT1__ 1
23103 #include <a href="#7.21"><stdio.h></a>
23104 int scanf_s(const char * restrict format, ...);
23105 Runtime-constraints
23106 2 format shall not be a null pointer. Any argument indirected though in order to store
23107 converted input shall not be a null pointer.
23108 3 If there is a runtime-constraint violation, the scanf_s function does not attempt to
23109 perform further input, and it is unspecified to what extent scanf_s performed input
23110 before discovering the runtime-constraint violation.
23111 <b> Description</b>
23112 4 The scanf_s function is equivalent to fscanf_s with the argument stdin
23113 interposed before the arguments to scanf_s.
23115 5 The scanf_s function returns the value of the macro EOF if an input failure occurs
23116 before any conversion or if there is a runtime-constraint violation. Otherwise, the
23117 scanf_s function returns the number of input items assigned, which can be fewer than
23118 provided for, or even zero, in the event of an early matching failure.
23119 <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>
23121 1 #define __STDC_WANT_LIB_EXT1__ 1
23122 #include <a href="#7.21"><stdio.h></a>
23123 int snprintf_s(char * restrict s, rsize_t n,
23124 const char * restrict format, ...);
23125 Runtime-constraints
23126 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
23127 than RSIZE_MAX. The %n specifier<sup><a href="#note382"><b>382)</b></a></sup> (modified or not by flags, field width, or
23128 precision) shall not appear in the string pointed to by format. Any argument to
23129 [<a name="p590" href="#p590">page 590</a>] (<a href="#Contents">Contents</a>)
23131 snprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
23133 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
23134 than zero and less than RSIZE_MAX, then the snprintf_s function sets s[0] to the
23136 <b> Description</b>
23137 4 The snprintf_s function is equivalent to the snprintf function except for the
23138 explicit runtime-constraints listed above.
23139 5 The snprintf_s function, unlike sprintf_s, will truncate the result to fit within the
23140 array pointed to by s.
23142 6 The snprintf_s function returns the number of characters that would have been
23143 written had n been sufficiently large, not counting the terminating null character, or a
23144 negative value if a runtime-constraint violation occurred. Thus, the null-terminated
23145 output has been completely written if and only if the returned value is nonnegative and
23147 <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>
23149 1 #define __STDC_WANT_LIB_EXT1__ 1
23150 #include <a href="#7.21"><stdio.h></a>
23151 int sprintf_s(char * restrict s, rsize_t n,
23152 const char * restrict format, ...);
23153 Runtime-constraints
23154 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
23155 than RSIZE_MAX. The number of characters (including the trailing null) required for the
23156 result to be written to the array pointed to by s shall not be greater than n. The %n
23157 specifier<sup><a href="#note383"><b>383)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
23158 string pointed to by format. Any argument to sprintf_s corresponding to a %s
23159 specifier shall not be a null pointer. No encoding error shall occur.
23163 <sup><a name="note382" href="#note382"><b>382)</b></a></sup> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
23164 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
23165 format string was %%n.
23166 <sup><a name="note383" href="#note383"><b>383)</b></a></sup> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
23167 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
23168 format string was %%n.
23170 [<a name="p591" href="#p591">page 591</a>] (<a href="#Contents">Contents</a>)
23172 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
23173 than zero and less than RSIZE_MAX, then the sprintf_s function sets s[0] to the
23175 <b> Description</b>
23176 4 The sprintf_s function is equivalent to the sprintf function except for the
23177 parameter n and the explicit runtime-constraints listed above.
23178 5 The sprintf_s function, unlike snprintf_s, treats a result too big for the array
23179 pointed to by s as a runtime-constraint violation.
23181 6 If no runtime-constraint violation occurred, the sprintf_s function returns the number
23182 of characters written in the array, not counting the terminating null character. If an
23183 encoding error occurred, sprintf_s returns a negative value. If any other runtime-
23184 constraint violation occurred, sprintf_s returns zero.
23185 <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>
23187 1 #define __STDC_WANT_LIB_EXT1__ 1
23188 #include <a href="#7.21"><stdio.h></a>
23189 int sscanf_s(const char * restrict s,
23190 const char * restrict format, ...);
23191 Runtime-constraints
23192 2 Neither s nor format shall be a null pointer. Any argument indirected though in order
23193 to store converted input shall not be a null pointer.
23194 3 If there is a runtime-constraint violation, the sscanf_s function does not attempt to
23195 perform further input, and it is unspecified to what extent sscanf_s performed input
23196 before discovering the runtime-constraint violation.
23197 <b> Description</b>
23198 4 The sscanf_s function is equivalent to fscanf_s, except that input is obtained from
23199 a string (specified by the argument s) rather than from a stream. Reaching the end of the
23200 string is equivalent to encountering end-of-file for the fscanf_s function. If copying
23201 takes place between objects that overlap, the objects take on unspecified values.
23203 5 The sscanf_s function returns the value of the macro EOF if an input failure occurs
23204 before any conversion or if there is a runtime-constraint violation. Otherwise, the
23205 sscanf_s function returns the number of input items assigned, which can be fewer than
23206 provided for, or even zero, in the event of an early matching failure.
23208 [<a name="p592" href="#p592">page 592</a>] (<a href="#Contents">Contents</a>)
23210 <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>
23212 1 #define __STDC_WANT_LIB_EXT1__ 1
23213 #include <a href="#7.16"><stdarg.h></a>
23214 #include <a href="#7.21"><stdio.h></a>
23215 int vfprintf_s(FILE * restrict stream,
23216 const char * restrict format,
23218 Runtime-constraints
23219 2 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note384"><b>384)</b></a></sup> (modified or
23220 not by flags, field width, or precision) shall not appear in the string pointed to by
23221 format. Any argument to vfprintf_s corresponding to a %s specifier shall not be a
23223 3 If there is a runtime-constraint violation, the vfprintf_s function does not attempt to
23224 produce further output, and it is unspecified to what extent vfprintf_s produced
23225 output before discovering the runtime-constraint violation.
23226 <b> Description</b>
23227 4 The vfprintf_s function is equivalent to the vfprintf function except for the
23228 explicit runtime-constraints listed above.
23230 5 The vfprintf_s function returns the number of characters transmitted, or a negative
23231 value if an output error, encoding error, or runtime-constraint violation occurred.
23232 <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>
23234 1 #define __STDC_WANT_LIB_EXT1__ 1
23235 #include <a href="#7.16"><stdarg.h></a>
23236 #include <a href="#7.21"><stdio.h></a>
23237 int vfscanf_s(FILE * restrict stream,
23238 const char * restrict format,
23244 <sup><a name="note384" href="#note384"><b>384)</b></a></sup> 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>)
23250 Runtime-constraints
23251 2 Neither stream nor format shall be a null pointer. Any argument indirected though in
23252 order to store converted input shall not be a null pointer.
23253 3 If there is a runtime-constraint violation, the vfscanf_s function does not attempt to
23254 perform further input, and it is unspecified to what extent vfscanf_s performed input
23255 before discovering the runtime-constraint violation.
23256 <b> Description</b>
23257 4 The vfscanf_s function is equivalent to fscanf_s, with the variable argument list
23258 replaced by arg, which shall have been initialized by the va_start macro (and
23259 possibly subsequent va_arg calls). The vfscanf_s function does not invoke the
23260 va_end macro.<sup><a href="#note385"><b>385)</b></a></sup>
23262 5 The vfscanf_s function returns the value of the macro EOF if an input failure occurs
23263 before any conversion or if there is a runtime-constraint violation. Otherwise, the
23264 vfscanf_s function returns the number of input items assigned, which can be fewer
23265 than provided for, or even zero, in the event of an early matching failure.
23266 <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>
23268 1 #define __STDC_WANT_LIB_EXT1__ 1
23269 #include <a href="#7.16"><stdarg.h></a>
23270 #include <a href="#7.21"><stdio.h></a>
23271 int vprintf_s(const char * restrict format,
23273 Runtime-constraints
23274 2 format shall not be a null pointer. The %n specifier<sup><a href="#note386"><b>386)</b></a></sup> (modified or not by flags, field
23275 width, or precision) shall not appear in the string pointed to by format. Any argument
23276 to vprintf_s corresponding to a %s specifier shall not be a null pointer.
23277 3 If there is a runtime-constraint violation, the vprintf_s function does not attempt to
23278 produce further output, and it is unspecified to what extent vprintf_s produced output
23279 before discovering the runtime-constraint violation.
23281 <sup><a name="note385" href="#note385"><b>385)</b></a></sup> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
23282 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
23284 <sup><a name="note386" href="#note386"><b>386)</b></a></sup> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
23285 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
23286 format string was %%n.
23288 [<a name="p594" href="#p594">page 594</a>] (<a href="#Contents">Contents</a>)
23290 <b> Description</b>
23291 4 The vprintf_s function is equivalent to the vprintf function except for the explicit
23292 runtime-constraints listed above.
23294 5 The vprintf_s function returns the number of characters transmitted, or a negative
23295 value if an output error, encoding error, or runtime-constraint violation occurred.
23296 <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>
23298 1 #define __STDC_WANT_LIB_EXT1__ 1
23299 #include <a href="#7.16"><stdarg.h></a>
23300 #include <a href="#7.21"><stdio.h></a>
23301 int vscanf_s(const char * restrict format,
23303 Runtime-constraints
23304 2 format shall not be a null pointer. Any argument indirected though in order to store
23305 converted input shall not be a null pointer.
23306 3 If there is a runtime-constraint violation, the vscanf_s function does not attempt to
23307 perform further input, and it is unspecified to what extent vscanf_s performed input
23308 before discovering the runtime-constraint violation.
23309 <b> Description</b>
23310 4 The vscanf_s function is equivalent to scanf_s, with the variable argument list
23311 replaced by arg, which shall have been initialized by the va_start macro (and
23312 possibly subsequent va_arg calls). The vscanf_s function does not invoke the
23313 va_end macro.<sup><a href="#note387"><b>387)</b></a></sup>
23315 5 The vscanf_s function returns the value of the macro EOF if an input failure occurs
23316 before any conversion or if there is a runtime-constraint violation. Otherwise, the
23317 vscanf_s function returns the number of input items assigned, which can be fewer than
23318 provided for, or even zero, in the event of an early matching failure.
23323 <sup><a name="note387" href="#note387"><b>387)</b></a></sup> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
23324 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
23327 [<a name="p595" href="#p595">page 595</a>] (<a href="#Contents">Contents</a>)
23329 <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>
23331 1 #define __STDC_WANT_LIB_EXT1__ 1
23332 #include <a href="#7.16"><stdarg.h></a>
23333 #include <a href="#7.21"><stdio.h></a>
23334 int vsnprintf_s(char * restrict s, rsize_t n,
23335 const char * restrict format,
23337 Runtime-constraints
23338 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
23339 than RSIZE_MAX. The %n specifier<sup><a href="#note388"><b>388)</b></a></sup> (modified or not by flags, field width, or
23340 precision) shall not appear in the string pointed to by format. Any argument to
23341 vsnprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
23343 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
23344 than zero and less than RSIZE_MAX, then the vsnprintf_s function sets s[0] to the
23346 <b> Description</b>
23347 4 The vsnprintf_s function is equivalent to the vsnprintf function except for the
23348 explicit runtime-constraints listed above.
23349 5 The vsnprintf_s function, unlike vsprintf_s, will truncate the result to fit within
23350 the array pointed to by s.
23352 6 The vsnprintf_s function returns the number of characters that would have been
23353 written had n been sufficiently large, not counting the terminating null character, or a
23354 negative value if a runtime-constraint violation occurred. Thus, the null-terminated
23355 output has been completely written if and only if the returned value is nonnegative and
23361 <sup><a name="note388" href="#note388"><b>388)</b></a></sup> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
23362 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
23363 format string was %%n.
23365 [<a name="p596" href="#p596">page 596</a>] (<a href="#Contents">Contents</a>)
23367 <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>
23369 1 #define __STDC_WANT_LIB_EXT1__ 1
23370 #include <a href="#7.16"><stdarg.h></a>
23371 #include <a href="#7.21"><stdio.h></a>
23372 int vsprintf_s(char * restrict s, rsize_t n,
23373 const char * restrict format,
23375 Runtime-constraints
23376 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
23377 than RSIZE_MAX. The number of characters (including the trailing null) required for the
23378 result to be written to the array pointed to by s shall not be greater than n. The %n
23379 specifier<sup><a href="#note389"><b>389)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
23380 string pointed to by format. Any argument to vsprintf_s corresponding to a %s
23381 specifier shall not be a null pointer. No encoding error shall occur.
23382 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
23383 than zero and less than RSIZE_MAX, then the vsprintf_s function sets s[0] to the
23385 <b> Description</b>
23386 4 The vsprintf_s function is equivalent to the vsprintf function except for the
23387 parameter n and the explicit runtime-constraints listed above.
23388 5 The vsprintf_s function, unlike vsnprintf_s, treats a result too big for the array
23389 pointed to by s as a runtime-constraint violation.
23391 6 If no runtime-constraint violation occurred, the vsprintf_s function returns the
23392 number of characters written in the array, not counting the terminating null character. If
23393 an encoding error occurred, vsprintf_s returns a negative value. If any other
23394 runtime-constraint violation occurred, vsprintf_s returns zero.
23399 <sup><a name="note389" href="#note389"><b>389)</b></a></sup> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
23400 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
23401 format string was %%n.
23403 [<a name="p597" href="#p597">page 597</a>] (<a href="#Contents">Contents</a>)
23405 <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>
23407 1 #define __STDC_WANT_LIB_EXT1__ 1
23408 #include <a href="#7.16"><stdarg.h></a>
23409 #include <a href="#7.21"><stdio.h></a>
23410 int vsscanf_s(const char * restrict s,
23411 const char * restrict format,
23413 Runtime-constraints
23414 2 Neither s nor format shall be a null pointer. Any argument indirected though in order
23415 to store converted input shall not be a null pointer.
23416 3 If there is a runtime-constraint violation, the vsscanf_s function does not attempt to
23417 perform further input, and it is unspecified to what extent vsscanf_s performed input
23418 before discovering the runtime-constraint violation.
23419 <b> Description</b>
23420 4 The vsscanf_s function is equivalent to sscanf_s, with the variable argument list
23421 replaced by arg, which shall have been initialized by the va_start macro (and
23422 possibly subsequent va_arg calls). The vsscanf_s function does not invoke the
23423 va_end macro.<sup><a href="#note390"><b>390)</b></a></sup>
23425 5 The vsscanf_s function returns the value of the macro EOF if an input failure occurs
23426 before any conversion or if there is a runtime-constraint violation. Otherwise, the
23427 vscanf_s function returns the number of input items assigned, which can be fewer than
23428 provided for, or even zero, in the event of an early matching failure.
23429 <a name="K.3.5.4" href="#K.3.5.4"><b> K.3.5.4 Character input/output functions</b></a>
23430 <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>
23432 1 #define __STDC_WANT_LIB_EXT1__ 1
23433 #include <a href="#7.21"><stdio.h></a>
23434 char *gets_s(char *s, rsize_t n);
23439 <sup><a name="note390" href="#note390"><b>390)</b></a></sup> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
23440 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
23443 [<a name="p598" href="#p598">page 598</a>] (<a href="#Contents">Contents</a>)
23445 Runtime-constraints
23446 2 s shall not be a null pointer. n shall neither be equal to zero nor be greater than
23447 RSIZE_MAX. A new-line character, end-of-file, or read error shall occur within reading
23448 n-1 characters from stdin.<sup><a href="#note391"><b>391)</b></a></sup>
23449 3 If there is a runtime-constraint violation, s[0] is set to the null character, and characters
23450 are read and discarded from stdin until a new-line character is read, or end-of-file or a
23452 <b> Description</b>
23453 4 The gets_s function reads at most one less than the number of characters specified by n
23454 from the stream pointed to by stdin, into the array pointed to by s. No additional
23455 characters are read after a new-line character (which is discarded) or after end-of-file.
23456 The discarded new-line character does not count towards number of characters read. A
23457 null character is written immediately after the last character read into the array.
23458 5 If end-of-file is encountered and no characters have been read into the array, or if a read
23459 error occurs during the operation, then s[0] is set to the null character, and the other
23460 elements of s take unspecified values.
23461 Recommended practice
23462 6 The fgets function allows properly-written programs to safely process input lines too
23463 long to store in the result array. In general this requires that callers of fgets pay
23464 attention to the presence or absence of a new-line character in the result array. Consider
23465 using fgets (along with any needed processing based on new-line characters) instead of
23468 7 The gets_s function returns s if successful. If there was a runtime-constraint violation,
23469 or if end-of-file is encountered and no characters have been read into the array, or if a
23470 read error occurs during the operation, then a null pointer is returned.
23475 <sup><a name="note391" href="#note391"><b>391)</b></a></sup> The gets_s function, unlike the historical gets function, makes it a runtime-constraint violation for
23476 a line of input to overflow the buffer to store it. Unlike the fgets function, gets_s maintains a
23477 one-to-one relationship between input lines and successful calls to gets_s. Programs that use gets
23478 expect such a relationship.
23480 [<a name="p599" href="#p599">page 599</a>] (<a href="#Contents">Contents</a>)
23482 <a name="K.3.6" href="#K.3.6"><b> K.3.6 General utilities <stdlib.h></b></a>
23483 1 The header <a href="#7.22"><stdlib.h></a> defines three types.
23486 which is type int; and
23488 which is the type size_t; and
23489 constraint_handler_t
23490 which has the following definition
23491 typedef void (*constraint_handler_t)(
23492 const char * restrict msg,
23493 void * restrict ptr,
23495 <a name="K.3.6.1" href="#K.3.6.1"><b> K.3.6.1 Runtime-constraint handling</b></a>
23496 <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>
23498 1 #define __STDC_WANT_LIB_EXT1__ 1
23499 #include <a href="#7.22"><stdlib.h></a>
23500 constraint_handler_t set_constraint_handler_s(
23501 constraint_handler_t handler);
23502 <b> Description</b>
23503 2 The set_constraint_handler_s function sets the runtime-constraint handler to
23504 be handler. The runtime-constraint handler is the function to be called when a library
23505 function detects a runtime-constraint violation. Only the most recent handler registered
23506 with set_constraint_handler_s is called when a runtime-constraint violation
23508 3 When the handler is called, it is passed the following arguments in the following order:
23509 1. A pointer to a character string describing the runtime-constraint violation.
23510 2. A null pointer or a pointer to an implementation defined object.
23511 3. If the function calling the handler has a return type declared as errno_t, the
23512 return value of the function is passed. Otherwise, a positive value of type
23517 [<a name="p600" href="#p600">page 600</a>] (<a href="#Contents">Contents</a>)
23519 4 The implementation has a default constraint handler that is used if no calls to the
23520 set_constraint_handler_s function have been made. The behavior of the
23521 default handler is implementation-defined, and it may cause the program to exit or abort.
23522 5 If the handler argument to set_constraint_handler_s is a null pointer, the
23523 implementation default handler becomes the current constraint handler.
23525 6 The set_constraint_handler_s function returns a pointer to the previously
23526 registered handler.<sup><a href="#note392"><b>392)</b></a></sup>
23527 <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>
23529 1 #define __STDC_WANT_LIB_EXT1__ 1
23530 #include <a href="#7.22"><stdlib.h></a>
23531 void abort_handler_s(
23532 const char * restrict msg,
23533 void * restrict ptr,
23535 <b> Description</b>
23536 2 A pointer to the abort_handler_s function shall be a suitable argument to the
23537 set_constraint_handler_s function.
23538 3 The abort_handler_s function writes a message on the standard error stream in an
23539 implementation-defined format. The message shall include the string pointed to by msg.
23540 The abort_handler_s function then calls the abort function.<sup><a href="#note393"><b>393)</b></a></sup>
23542 4 The abort_handler_s function does not return to its caller.
23547 <sup><a name="note392" href="#note392"><b>392)</b></a></sup> If the previous handler was registered by calling set_constraint_handler_s with a null
23548 pointer argument, a pointer to the implementation default handler is returned (not NULL).
23549 <sup><a name="note393" href="#note393"><b>393)</b></a></sup> Many implementations invoke a debugger when the abort function is called.
23551 [<a name="p601" href="#p601">page 601</a>] (<a href="#Contents">Contents</a>)
23553 <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>
23555 1 #define __STDC_WANT_LIB_EXT1__ 1
23556 #include <a href="#7.22"><stdlib.h></a>
23557 void ignore_handler_s(
23558 const char * restrict msg,
23559 void * restrict ptr,
23561 <b> Description</b>
23562 2 A pointer to the ignore_handler_s function shall be a suitable argument to the
23563 set_constraint_handler_s function.
23564 3 The ignore_handler_s function simply returns to its caller.<sup><a href="#note394"><b>394)</b></a></sup>
23566 4 The ignore_handler_s function returns no value.
23567 <a name="K.3.6.2" href="#K.3.6.2"><b> K.3.6.2 Communication with the environment</b></a>
23568 <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>
23570 1 #define __STDC_WANT_LIB_EXT1__ 1
23571 #include <a href="#7.22"><stdlib.h></a>
23572 errno_t getenv_s(size_t * restrict len,
23573 char * restrict value, rsize_t maxsize,
23574 const char * restrict name);
23575 Runtime-constraints
23576 2 name shall not be a null pointer. maxsize shall neither equal zero nor be greater than
23577 RSIZE_MAX. If maxsize is not equal to zero, then value shall not be a null pointer.
23578 3 If there is a runtime-constraint violation, the integer pointed to by len is set to 0 (if len
23579 is not null), and the environment list is not searched.
23580 <b> Description</b>
23581 4 The getenv_s function searches an environment list, provided by the host environment,
23582 for a string that matches the string pointed to by name.
23585 <sup><a name="note394" href="#note394"><b>394)</b></a></sup> If the runtime-constraint handler is set to the ignore_handler_s function, any library function in
23586 which a runtime-constraint violation occurs will return to its caller. The caller can determine whether
23587 a runtime-constraint violation occurred based on the library function's specification (usually, the
23588 library function returns a nonzero errno_t).
23590 [<a name="p602" href="#p602">page 602</a>] (<a href="#Contents">Contents</a>)
23592 5 If that name is found then getenv_s performs the following actions. If len is not a
23593 null pointer, the length of the string associated with the matched list member is stored in
23594 the integer pointed to by len. If the length of the associated string is less than maxsize,
23595 then the associated string is copied to the array pointed to by value.
23596 6 If that name is not found then getenv_s performs the following actions. If len is not
23597 a null pointer, zero is stored in the integer pointed to by len. If maxsize is greater than
23598 zero, then value[0] is set to the null character.
23599 7 The set of environment names and the method for altering the environment list are
23600 implementation-defined.
23602 8 The getenv_s function returns zero if the specified name is found and the associated
23603 string was successfully stored in value. Otherwise, a nonzero value is returned.
23604 <a name="K.3.6.3" href="#K.3.6.3"><b> K.3.6.3 Searching and sorting utilities</b></a>
23605 1 These utilities make use of a comparison function to search or sort arrays of unspecified
23606 type. Where an argument declared as size_t nmemb specifies the length of the array
23607 for a function, if nmemb has the value zero on a call to that function, then the comparison
23608 function is not called, a search finds no matching element, sorting performs no
23609 rearrangement, and the pointer to the array may be null.
23610 2 The implementation shall ensure that the second argument of the comparison function
23611 (when called from bsearch_s), or both arguments (when called from qsort_s), are
23612 pointers to elements of the array.<sup><a href="#note395"><b>395)</b></a></sup> The first argument when called from bsearch_s
23614 3 The comparison function shall not alter the contents of either the array or search key. The
23615 implementation may reorder elements of the array between calls to the comparison
23616 function, but shall not otherwise alter the contents of any individual element.
23617 4 When the same objects (consisting of size bytes, irrespective of their current positions
23618 in the array) are passed more than once to the comparison function, the results shall be
23619 consistent with one another. That is, for qsort_s they shall define a total ordering on
23620 the array, and for bsearch_s the same object shall always compare the same way with
23626 <sup><a name="note395" href="#note395"><b>395)</b></a></sup> That is, if the value passed is p, then the following expressions are always valid and nonzero:
23627 ((char *)p - (char *)base) % size == 0
23628 (char *)p >= (char *)base
23629 (char *)p < (char *)base + nmemb * size
23632 [<a name="p603" href="#p603">page 603</a>] (<a href="#Contents">Contents</a>)
23634 5 A sequence point occurs immediately before and immediately after each call to the
23635 comparison function, and also between any call to the comparison function and any
23636 movement of the objects passed as arguments to that call.
23637 <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>
23639 1 #define __STDC_WANT_LIB_EXT1__ 1
23640 #include <a href="#7.22"><stdlib.h></a>
23641 void *bsearch_s(const void *key, const void *base,
23642 rsize_t nmemb, rsize_t size,
23643 int (*compar)(const void *k, 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 none of key, base, or compar shall be a null pointer.
23649 3 If there is a runtime-constraint violation, the bsearch_s function does not search the
23651 <b> Description</b>
23652 4 The bsearch_s function searches an array of nmemb objects, the initial element of
23653 which is pointed to by base, for an element that matches the object pointed to by key.
23654 The size of each element of the array is specified by size.
23655 5 The comparison function pointed to by compar is called with three arguments. The first
23656 two point to the key object and to an array element, in that order. The function shall
23657 return an integer less than, equal to, or greater than zero if the key object is considered,
23658 respectively, to be less than, to match, or to be greater than the array element. The array
23659 shall consist of: all the elements that compare less than, all the elements that compare
23660 equal to, and all the elements that compare greater than the key object, in that order.<sup><a href="#note396"><b>396)</b></a></sup>
23661 The third argument to the comparison function is the context argument passed to
23662 bsearch_s. The sole use of context by bsearch_s is to pass it to the comparison
23663 function.<sup><a href="#note397"><b>397)</b></a></sup>
23668 <sup><a name="note396" href="#note396"><b>396)</b></a></sup> In practice, this means that the entire array has been sorted according to the comparison function.
23669 <sup><a name="note397" href="#note397"><b>397)</b></a></sup> 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>)
23675 6 The bsearch_s function returns a pointer to a matching element of the array, or a null
23676 pointer if no match is found or there is a runtime-constraint violation. If two elements
23677 compare as equal, which element is matched is unspecified.
23678 <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>
23680 1 #define __STDC_WANT_LIB_EXT1__ 1
23681 #include <a href="#7.22"><stdlib.h></a>
23682 errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
23683 int (*compar)(const void *x, const void *y,
23686 Runtime-constraints
23687 2 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
23688 zero, then neither base nor compar shall be a null pointer.
23689 3 If there is a runtime-constraint violation, the qsort_s function does not sort the array.
23690 <b> Description</b>
23691 4 The qsort_s function sorts an array of nmemb objects, the initial element of which is
23692 pointed to by base. The size of each object is specified by size.
23693 5 The contents of the array are sorted into ascending order according to a comparison
23694 function pointed to by compar, which is called with three arguments. The first two
23695 point to the objects being compared. The function shall return an integer less than, equal
23696 to, or greater than zero if the first argument is considered to be respectively less than,
23697 equal to, or greater than the second. The third argument to the comparison function is the
23698 context argument passed to qsort_s. The sole use of context by qsort_s is to
23699 pass it to the comparison function.<sup><a href="#note398"><b>398)</b></a></sup>
23700 6 If two elements compare as equal, their relative order in the resulting sorted array is
23703 7 The qsort_s function returns zero if there was no runtime-constraint violation.
23704 Otherwise, a nonzero value is returned.
23709 <sup><a name="note398" href="#note398"><b>398)</b></a></sup> The context argument is for the use of the comparison function in performing its duties. For
23710 example, it might specify a collating sequence used by the comparison function.
23712 [<a name="p605" href="#p605">page 605</a>] (<a href="#Contents">Contents</a>)
23714 <a name="K.3.6.4" href="#K.3.6.4"><b> K.3.6.4 Multibyte/wide character conversion functions</b></a>
23715 1 The behavior of the multibyte character functions is affected by the LC_CTYPE category
23716 of the current locale. For a state-dependent encoding, each function is placed into its
23717 initial conversion state by a call for which its character pointer argument, s, is a null
23718 pointer. Subsequent calls with s as other than a null pointer cause the internal conversion
23719 state of the function to be altered as necessary. A call with s as a null pointer causes
23720 these functions to set the int pointed to by their status argument to a nonzero value if
23721 encodings have state dependency, and zero otherwise.<sup><a href="#note399"><b>399)</b></a></sup> Changing the LC_CTYPE
23722 category causes the conversion state of these functions to be indeterminate.
23723 <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>
23725 1 #define __STDC_WANT_LIB_EXT1__ 1
23726 #include <a href="#7.22"><stdlib.h></a>
23727 errno_t wctomb_s(int * restrict status,
23731 Runtime-constraints
23732 2 Let n denote the number of bytes needed to represent the multibyte character
23733 corresponding to the wide character given by wc (including any shift sequences).
23734 3 If s is not a null pointer, then smax shall not be less than n, and smax shall not be
23735 greater than RSIZE_MAX. If s is a null pointer, then smax shall equal zero.
23736 4 If there is a runtime-constraint violation, wctomb_s does not modify the int pointed to
23737 by status, and if s is not a null pointer, no more than smax elements in the array
23738 pointed to by s will be accessed.
23739 <b> Description</b>
23740 5 The wctomb_s function determines n and stores the multibyte character representation
23741 of wc in the array whose first element is pointed to by s (if s is not a null pointer). The
23742 number of characters stored never exceeds MB_CUR_MAX or smax. If wc is a null wide
23743 character, a null byte is stored, preceded by any shift sequence needed to restore the
23744 initial shift state, and the function is left in the initial conversion state.
23745 6 The implementation shall behave as if no library function calls the wctomb_s function.
23750 <sup><a name="note399" href="#note399"><b>399)</b></a></sup> If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
23751 character codes, but are grouped with an adjacent multibyte character.
23753 [<a name="p606" href="#p606">page 606</a>] (<a href="#Contents">Contents</a>)
23755 7 If s is a null pointer, the wctomb_s function stores into the int pointed to by status a
23756 nonzero or zero value, if multibyte character encodings, respectively, do or do not have
23757 state-dependent encodings.
23758 8 If s is not a null pointer, the wctomb_s function stores into the int pointed to by
23759 status either n or -1 if wc, respectively, does or does not correspond to a valid
23760 multibyte character.
23761 9 In no case will the int pointed to by status be set to a value greater than the
23764 10 The wctomb_s function returns zero if successful, and a nonzero value if there was a
23765 runtime-constraint violation or wc did not correspond to a valid multibyte character.
23766 <a name="K.3.6.5" href="#K.3.6.5"><b> K.3.6.5 Multibyte/wide string conversion functions</b></a>
23767 1 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
23768 the current locale.
23769 <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>
23771 1 #include <a href="#7.22"><stdlib.h></a>
23772 errno_t mbstowcs_s(size_t * restrict retval,
23773 wchar_t * restrict dst, rsize_t dstmax,
23774 const char * restrict src, rsize_t len);
23775 Runtime-constraints
23776 2 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
23777 neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
23778 then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
23779 zero. If dst is not a null pointer and len is not less than dstmax, then a null character
23780 shall occur within the first dstmax multibyte characters of the array pointed to by src.
23781 3 If there is a runtime-constraint violation, then mbstowcs_s does the following. If
23782 retval is not a null pointer, then mbstowcs_s sets *retval to (size_t)(-1). If
23783 dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
23784 then mbstowcs_s sets dst[0] to the null wide character.
23785 <b> Description</b>
23786 4 The mbstowcs_s function converts a sequence of multibyte characters that begins in
23787 the initial shift state from the array pointed to by src into a sequence of corresponding
23788 wide characters. If dst is not a null pointer, the converted characters are stored into the
23789 array pointed to by dst. Conversion continues up to and including a terminating null
23790 character, which is also stored. Conversion stops earlier in two cases: when a sequence of
23791 [<a name="p607" href="#p607">page 607</a>] (<a href="#Contents">Contents</a>)
23793 bytes is encountered that does not form a valid multibyte character, or (if dst is not a
23794 null pointer) when len wide characters have been stored into the array pointed to by
23795 dst.<sup><a href="#note400"><b>400)</b></a></sup> If dst is not a null pointer and no null wide character was stored into the array
23796 pointed to by dst, then dst[len] is set to the null wide character. Each conversion
23797 takes place as if by a call to the mbrtowc function.
23798 5 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
23799 sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
23800 the mbstowcs_s function stores the value (size_t)(-1) into *retval.
23801 Otherwise, the mbstowcs_s function stores into *retval the number of multibyte
23802 characters successfully converted, not including the terminating null character (if any).
23803 6 All elements following the terminating null wide character (if any) written by
23804 mbstowcs_s in the array of dstmax wide characters pointed to by dst take
23805 unspecified values when mbstowcs_s returns.<sup><a href="#note401"><b>401)</b></a></sup>
23806 7 If copying takes place between objects that overlap, the objects take on unspecified
23809 8 The mbstowcs_s function returns zero if no runtime-constraint violation and no
23810 encoding error occurred. Otherwise, a nonzero value is returned.
23811 <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>
23813 1 #include <a href="#7.22"><stdlib.h></a>
23814 errno_t wcstombs_s(size_t * restrict retval,
23815 char * restrict dst, rsize_t dstmax,
23816 const wchar_t * restrict src, rsize_t len);
23817 Runtime-constraints
23818 2 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
23819 neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
23820 then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
23821 zero. If dst is not a null pointer and len is not less than dstmax, then the conversion
23822 shall have been stopped (see below) because a terminating null wide character was
23823 reached or because an encoding error occurred.
23828 <sup><a name="note400" href="#note400"><b>400)</b></a></sup> Thus, the value of len is ignored if dst is a null pointer.
23829 <sup><a name="note401" href="#note401"><b>401)</b></a></sup> This allows an implementation to attempt converting the multibyte string before discovering a
23830 terminating null character did not occur where required.
23832 [<a name="p608" href="#p608">page 608</a>] (<a href="#Contents">Contents</a>)
23834 3 If there is a runtime-constraint violation, then wcstombs_s does the following. If
23835 retval is not a null pointer, then wcstombs_s sets *retval to (size_t)(-1). If
23836 dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
23837 then wcstombs_s sets dst[0] to the null character.
23838 <b> Description</b>
23839 4 The wcstombs_s function converts a sequence of wide characters from the array
23840 pointed to by src into a sequence of corresponding multibyte characters that begins in
23841 the initial shift state. If dst is not a null pointer, the converted characters are then stored
23842 into the array pointed to by dst. Conversion continues up to and including a terminating
23843 null wide character, which is also stored. Conversion stops earlier in two cases:
23844 -- when a wide character is reached that does not correspond to a valid multibyte
23846 -- (if dst is not a null pointer) when the next multibyte character would exceed the
23847 limit of n total bytes to be stored into the array pointed to by dst. If the wide
23848 character being converted is the null wide character, then n is the lesser of len or
23849 dstmax. Otherwise, n is the lesser of len or dstmax-1.
23850 If the conversion stops without converting a null wide character and dst is not a null
23851 pointer, then a null character is stored into the array pointed to by dst immediately
23852 following any multibyte characters already stored. Each conversion takes place as if by a
23853 call to the wcrtomb function.<sup><a href="#note402"><b>402)</b></a></sup>
23854 5 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
23855 wide character that does not correspond to a valid multibyte character, an encoding error
23856 occurs: the wcstombs_s function stores the value (size_t)(-1) into *retval.
23857 Otherwise, the wcstombs_s function stores into *retval the number of bytes in the
23858 resulting multibyte character sequence, not including the terminating null character (if
23860 6 All elements following the terminating null character (if any) written by wcstombs_s
23861 in the array of dstmax elements pointed to by dst take unspecified values when
23862 wcstombs_s returns.<sup><a href="#note403"><b>403)</b></a></sup>
23863 7 If copying takes place between objects that overlap, the objects take on unspecified
23867 <sup><a name="note402" href="#note402"><b>402)</b></a></sup> If conversion stops because a terminating null wide character has been reached, the bytes stored
23868 include those necessary to reach the initial shift state immediately before the null byte. However, if
23869 the conversion stops before a terminating null wide character has been reached, the result will be null
23870 terminated, but might not end in the initial shift state.
23871 <sup><a name="note403" href="#note403"><b>403)</b></a></sup> When len is not less than dstmax, the implementation might fill the array before discovering a
23872 runtime-constraint violation.
23874 [<a name="p609" href="#p609">page 609</a>] (<a href="#Contents">Contents</a>)
23877 8 The wcstombs_s function returns zero if no runtime-constraint violation and no
23878 encoding error occurred. Otherwise, a nonzero value is returned.
23879 <a name="K.3.7" href="#K.3.7"><b> K.3.7 String handling <string.h></b></a>
23880 1 The header <a href="#7.23"><string.h></a> defines two types.
23883 which is type int; and
23885 which is the type size_t.
23886 <a name="K.3.7.1" href="#K.3.7.1"><b> K.3.7.1 Copying functions</b></a>
23887 <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>
23889 1 #define __STDC_WANT_LIB_EXT1__ 1
23890 #include <a href="#7.23"><string.h></a>
23891 errno_t memcpy_s(void * restrict s1, rsize_t s1max,
23892 const void * restrict s2, rsize_t n);
23893 Runtime-constraints
23894 2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
23895 RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
23896 objects that overlap.
23897 3 If there is a runtime-constraint violation, the memcpy_s function stores zeros in the first
23898 s1max characters of the object pointed to by s1 if s1 is not a null pointer and s1max is
23899 not greater than RSIZE_MAX.
23900 <b> Description</b>
23901 4 The memcpy_s function copies n characters from the object pointed to by s2 into the
23902 object pointed to by s1.
23904 5 The memcpy_s function returns zero if there was no runtime-constraint violation.
23905 Otherwise, a nonzero value is returned.
23910 [<a name="p610" href="#p610">page 610</a>] (<a href="#Contents">Contents</a>)
23912 <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>
23914 1 #define __STDC_WANT_LIB_EXT1__ 1
23915 #include <a href="#7.23"><string.h></a>
23916 errno_t memmove_s(void *s1, rsize_t s1max,
23917 const void *s2, rsize_t n);
23918 Runtime-constraints
23919 2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
23920 RSIZE_MAX. n shall not be greater than s1max.
23921 3 If there is a runtime-constraint violation, the memmove_s function stores zeros in the
23922 first s1max characters of the object pointed to by s1 if s1 is not a null pointer and
23923 s1max is not greater than RSIZE_MAX.
23924 <b> Description</b>
23925 4 The memmove_s function copies n characters from the object pointed to by s2 into the
23926 object pointed to by s1. This copying takes place as if the n characters from the object
23927 pointed to by s2 are first copied into a temporary array of n characters that does not
23928 overlap the objects pointed to by s1 or s2, and then the n characters from the temporary
23929 array are copied into the object pointed to by s1.
23931 5 The memmove_s function returns zero if there was no runtime-constraint violation.
23932 Otherwise, a nonzero value is returned.
23933 <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>
23935 1 #define __STDC_WANT_LIB_EXT1__ 1
23936 #include <a href="#7.23"><string.h></a>
23937 errno_t strcpy_s(char * restrict s1,
23939 const char * restrict s2);
23940 Runtime-constraints
23941 2 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
23942 s1max shall not equal zero. s1max shall be greater than strnlen_s(s2, s1max).
23943 Copying shall not take place between objects that overlap.
23944 3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
23945 greater than zero and not greater than RSIZE_MAX, then strcpy_s sets s1[0] to the
23948 [<a name="p611" href="#p611">page 611</a>] (<a href="#Contents">Contents</a>)
23950 <b> Description</b>
23951 4 The strcpy_s function copies the string pointed to by s2 (including the terminating
23952 null character) into the array pointed to by s1.
23953 5 All elements following the terminating null character (if any) written by strcpy_s in
23954 the array of s1max characters pointed to by s1 take unspecified values when
23955 strcpy_s returns.<sup><a href="#note404"><b>404)</b></a></sup>
23957 6 The strcpy_s function returns zero<sup><a href="#note405"><b>405)</b></a></sup> if there was no runtime-constraint violation.
23958 Otherwise, a nonzero value is returned.
23959 <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>
23961 1 #define __STDC_WANT_LIB_EXT1__ 1
23962 #include <a href="#7.23"><string.h></a>
23963 errno_t strncpy_s(char * restrict s1,
23965 const char * restrict s2,
23967 Runtime-constraints
23968 2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
23969 RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
23970 shall be greater than strnlen_s(s2, s1max). Copying shall not take place between
23971 objects that overlap.
23972 3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
23973 greater than zero and not greater than RSIZE_MAX, then strncpy_s sets s1[0] to the
23975 <b> Description</b>
23976 4 The strncpy_s function copies not more than n successive characters (characters that
23977 follow a null character are not copied) from the array pointed to by s2 to the array
23978 pointed to by s1. If no null character was copied from s2, then s1[n] is set to a null
23982 <sup><a name="note404" href="#note404"><b>404)</b></a></sup> This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
23983 any of those characters are null. Such an approach might write a character to every element of s1
23984 before discovering that the first element should be set to the null character.
23985 <sup><a name="note405" href="#note405"><b>405)</b></a></sup> A zero return value implies that all of the requested characters from the string pointed to by s2 fit
23986 within the array pointed to by s1 and that the result in s1 is null terminated.
23988 [<a name="p612" href="#p612">page 612</a>] (<a href="#Contents">Contents</a>)
23990 5 All elements following the terminating null character (if any) written by strncpy_s in
23991 the array of s1max characters pointed to by s1 take unspecified values when
23992 strncpy_s returns.<sup><a href="#note406"><b>406)</b></a></sup>
23994 6 The strncpy_s function returns zero<sup><a href="#note407"><b>407)</b></a></sup> if there was no runtime-constraint violation.
23995 Otherwise, a nonzero value is returned.
23996 7 EXAMPLE 1 The strncpy_s function can be used to copy a string without the danger that the result
23997 will not be null terminated or that characters will be written past the end of the destination array.
23998 #define __STDC_WANT_LIB_EXT1__ 1
23999 #include <a href="#7.23"><string.h></a>
24001 char src1[100] = "hello";
24002 char src2[7] = {'g', 'o', 'o', 'd', 'b', 'y', 'e'};
24003 char dst1[6], dst2[5], dst3[5];
24005 r1 = strncpy_s(dst1, 6, src1, 100);
24006 r2 = strncpy_s(dst2, 5, src2, 7);
24007 r3 = strncpy_s(dst3, 5, src2, 4);
24008 The first call will assign to r1 the value zero and to dst1 the sequence hello\0.
24009 The second call will assign to r2 a nonzero value and to dst2 the sequence \0.
24010 The third call will assign to r3 the value zero and to dst3 the sequence good\0.
24012 <a name="K.3.7.2" href="#K.3.7.2"><b> K.3.7.2 Concatenation functions</b></a>
24013 <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>
24015 1 #define __STDC_WANT_LIB_EXT1__ 1
24016 #include <a href="#7.23"><string.h></a>
24017 errno_t strcat_s(char * restrict s1,
24019 const char * restrict s2);
24020 Runtime-constraints
24021 2 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
24027 <sup><a name="note406" href="#note406"><b>406)</b></a></sup> This allows an implementation to copy characters from s2 to s1 while simultaneously checking if
24028 any of those characters are null. Such an approach might write a character to every element of s1
24029 before discovering that the first element should be set to the null character.
24030 <sup><a name="note407" href="#note407"><b>407)</b></a></sup> A zero return value implies that all of the requested characters from the string pointed to by s2 fit
24031 within the array pointed to by s1 and that the result in s1 is null terminated.
24033 [<a name="p613" href="#p613">page 613</a>] (<a href="#Contents">Contents</a>)
24035 3 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
24036 s1max shall not equal zero. m shall not equal zero.<sup><a href="#note408"><b>408)</b></a></sup> m shall be greater than
24037 strnlen_s(s2, m). Copying shall not take place between objects that overlap.
24038 4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
24039 greater than zero and not greater than RSIZE_MAX, then strcat_s sets s1[0] to the
24041 <b> Description</b>
24042 5 The strcat_s function appends a copy of the string pointed to by s2 (including the
24043 terminating null character) to the end of the string pointed to by s1. The initial character
24044 from s2 overwrites the null character at the end of s1.
24045 6 All elements following the terminating null character (if any) written by strcat_s in
24046 the array of s1max characters pointed to by s1 take unspecified values when
24047 strcat_s returns.<sup><a href="#note409"><b>409)</b></a></sup>
24049 7 The strcat_s function returns zero<sup><a href="#note410"><b>410)</b></a></sup> if there was no runtime-constraint violation.
24050 Otherwise, a nonzero value is returned.
24051 <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>
24053 1 #define __STDC_WANT_LIB_EXT1__ 1
24054 #include <a href="#7.23"><string.h></a>
24055 errno_t strncat_s(char * restrict s1,
24057 const char * restrict s2,
24059 Runtime-constraints
24060 2 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
24062 3 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
24063 RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.<sup><a href="#note411"><b>411)</b></a></sup> If n is not less
24066 <sup><a name="note408" href="#note408"><b>408)</b></a></sup> Zero means that s1 was not null terminated upon entry to strcat_s.
24067 <sup><a name="note409" href="#note409"><b>409)</b></a></sup> This allows an implementation to append characters from s2 to s1 while simultaneously checking if
24068 any of those characters are null. Such an approach might write a character to every element of s1
24069 before discovering that the first element should be set to the null character.
24070 <sup><a name="note410" href="#note410"><b>410)</b></a></sup> A zero return value implies that all of the requested characters from the string pointed to by s2 were
24071 appended to the string pointed to by s1 and that the result in s1 is null terminated.
24073 [<a name="p614" href="#p614">page 614</a>] (<a href="#Contents">Contents</a>)
24075 than m, then m shall be greater than strnlen_s(s2, m). Copying shall not take
24076 place between objects that overlap.
24077 4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
24078 greater than zero and not greater than RSIZE_MAX, then strncat_s sets s1[0] to the
24080 <b> Description</b>
24081 5 The strncat_s function appends not more than n successive characters (characters
24082 that follow a null character are not copied) from the array pointed to by s2 to the end of
24083 the string pointed to by s1. The initial character from s2 overwrites the null character at
24084 the end of s1. If no null character was copied from s2, then s1[s1max-m+n] is set to
24086 6 All elements following the terminating null character (if any) written by strncat_s in
24087 the array of s1max characters pointed to by s1 take unspecified values when
24088 strncat_s returns.<sup><a href="#note412"><b>412)</b></a></sup>
24090 7 The strncat_s function returns zero<sup><a href="#note413"><b>413)</b></a></sup> if there was no runtime-constraint violation.
24091 Otherwise, a nonzero value is returned.
24092 8 EXAMPLE 1 The strncat_s function can be used to copy a string without the danger that the result
24093 will not be null terminated or that characters will be written past the end of the destination array.
24094 #define __STDC_WANT_LIB_EXT1__ 1
24095 #include <a href="#7.23"><string.h></a>
24097 char s1[100] = "good";
24098 char s2[6] = "hello";
24099 char s3[6] = "hello";
24100 char s4[7] = "abc";
24101 char s5[1000] = "bye";
24102 int r1, r2, r3, r4;
24103 r1 = strncat_s(s1, 100, s5, 1000);
24104 r2 = strncat_s(s2, 6, "", 1);
24105 r3 = strncat_s(s3, 6, "X", 2);
24106 r4 = strncat_s(s4, 7, "defghijklmn", 3);
24107 After the first call r1 will have the value zero and s1 will contain the sequence goodbye\0.
24111 <sup><a name="note411" href="#note411"><b>411)</b></a></sup> Zero means that s1 was not null terminated upon entry to strncat_s.
24112 <sup><a name="note412" href="#note412"><b>412)</b></a></sup> This allows an implementation to append characters from s2 to s1 while simultaneously checking if
24113 any of those characters are null. Such an approach might write a character to every element of s1
24114 before discovering that the first element should be set to the null character.
24115 <sup><a name="note413" href="#note413"><b>413)</b></a></sup> A zero return value implies that all of the requested characters from the string pointed to by s2 were
24116 appended to the string pointed to by s1 and that the result in s1 is null terminated.
24118 [<a name="p615" href="#p615">page 615</a>] (<a href="#Contents">Contents</a>)
24120 After the second call r2 will have the value zero and s2 will contain the sequence hello\0.
24121 After the third call r3 will have a nonzero value and s3 will contain the sequence \0.
24122 After the fourth call r4 will have the value zero and s4 will contain the sequence abcdef\0.
24124 <a name="K.3.7.3" href="#K.3.7.3"><b> K.3.7.3 Search functions</b></a>
24125 <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>
24127 1 #define __STDC_WANT_LIB_EXT1__ 1
24128 #include <a href="#7.23"><string.h></a>
24129 char *strtok_s(char * restrict s1,
24130 rsize_t * restrict s1max,
24131 const char * restrict s2,
24132 char ** restrict ptr);
24133 Runtime-constraints
24134 2 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
24135 shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
24136 The end of the token found shall occur within the first *s1max characters of s1 for the
24137 first call, and shall occur within the first *s1max characters of where searching resumes
24138 on subsequent calls.
24139 3 If there is a runtime-constraint violation, the strtok_s function does not indirect
24140 through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
24141 <b> Description</b>
24142 4 A sequence of calls to the strtok_s function breaks the string pointed to by s1 into a
24143 sequence of tokens, each of which is delimited by a character from the string pointed to
24144 by s2. The fourth argument points to a caller-provided char pointer into which the
24145 strtok_s function stores information necessary for it to continue scanning the same
24147 5 The first call in a sequence has a non-null first argument and s1max points to an object
24148 whose value is the number of elements in the character array pointed to by the first
24149 argument. The first call stores an initial value in the object pointed to by ptr and
24150 updates the value pointed to by s1max to reflect the number of elements that remain in
24151 relation to ptr. Subsequent calls in the sequence have a null first argument and the
24152 objects pointed to by s1max and ptr are required to have the values stored by the
24153 previous call in the sequence, which are then updated. The separator string pointed to by
24154 s2 may be different from call to call.
24155 6 The first call in the sequence searches the string pointed to by s1 for the first character
24156 that is not contained in the current separator string pointed to by s2. If no such character
24157 is found, then there are no tokens in the string pointed to by s1 and the strtok_s
24158 function returns a null pointer. If such a character is found, it is the start of the first token.
24159 [<a name="p616" href="#p616">page 616</a>] (<a href="#Contents">Contents</a>)
24161 7 The strtok_s function then searches from there for the first character in s1 that is
24162 contained in the current separator string. If no such character is found, the current token
24163 extends to the end of the string pointed to by s1, and subsequent searches in the same
24164 string for a token return a null pointer. If such a character is found, it is overwritten by a
24165 null character, which terminates the current token.
24166 8 In all cases, the strtok_s function stores sufficient information in the pointer pointed
24167 to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
24168 value for ptr, shall start searching just past the element overwritten by a null character
24171 9 The strtok_s function returns a pointer to the first character of a token, or a null
24172 pointer if there is no token or there is a runtime-constraint violation.
24174 #define __STDC_WANT_LIB_EXT1__ 1
24175 #include <a href="#7.23"><string.h></a>
24176 static char str1[] = "?a???b,,,#c";
24177 static char str2[] = "\t \t";
24178 char *t, *ptr1, *ptr2;
24179 rsize_t max1 = sizeof(str1);
24180 rsize_t max2 = sizeof(str2);
24181 t = strtok_s(str1, &max1, "?", &ptr1); // t points to the token "a"
24182 t = strtok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
24183 t = strtok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
24184 t = strtok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
24185 t = strtok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
24187 <a name="K.3.7.4" href="#K.3.7.4"><b> K.3.7.4 Miscellaneous functions</b></a>
24188 <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>
24190 1 #define __STDC_WANT_LIB_EXT1__ 1
24191 #include <a href="#7.23"><string.h></a>
24192 errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
24193 Runtime-constraints
24194 2 s shall not be a null pointer. Neither smax nor n shall be greater than RSIZE_MAX. n
24195 shall not be greater than smax.
24196 3 If there is a runtime-constraint violation, then if s is not a null pointer and smax is not
24197 greater than RSIZE_MAX, the memset_s function stores the value of c (converted to an
24198 unsigned char) into each of the first smax characters of the object pointed to by s.
24202 [<a name="p617" href="#p617">page 617</a>] (<a href="#Contents">Contents</a>)
24204 <b> Description</b>
24205 4 The memset_s function copies the value of c (converted to an unsigned char) into
24206 each of the first n characters of the object pointed to by s. Unlike memset, any call to
24207 the memset_s function shall be evaluated strictly according to the rules of the abstract
24208 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
24209 assume that the memory indicated by s and n may be accessible in the future and thus
24210 must contain the values indicated by c.
24212 5 The memset_s function returns zero if there was no runtime-constraint violation.
24213 Otherwise, a nonzero value is returned.
24214 <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>
24216 1 #define __STDC_WANT_LIB_EXT1__ 1
24217 #include <a href="#7.23"><string.h></a>
24218 errno_t strerror_s(char *s, rsize_t maxsize,
24220 Runtime-constraints
24221 2 s shall not be a null pointer. maxsize shall not be greater than RSIZE_MAX.
24222 maxsize shall not equal zero.
24223 3 If there is a runtime-constraint violation, then the array (if any) pointed to by s is not
24225 <b> Description</b>
24226 4 The strerror_s function maps the number in errnum to a locale-specific message
24227 string. Typically, the values for errnum come from errno, but strerror_s shall
24228 map any value of type int to a message.
24229 5 If the length of the desired string is less than maxsize, then the string is copied to the
24230 array pointed to by s.
24231 6 Otherwise, if maxsize is greater than zero, then maxsize-1 characters are copied
24232 from the string to the array pointed to by s and then s[maxsize-1] is set to the null
24233 character. Then, if maxsize is greater than 3, then s[maxsize-2],
24234 s[maxsize-3], and s[maxsize-4] are set to the character period (.).
24236 7 The strerror_s function returns zero if the length of the desired string was less than
24237 maxsize and there was no runtime-constraint violation. Otherwise, the strerror_s
24238 function returns a nonzero value.
24240 [<a name="p618" href="#p618">page 618</a>] (<a href="#Contents">Contents</a>)
24242 <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>
24244 1 #define __STDC_WANT_LIB_EXT1__ 1
24245 #include <a href="#7.23"><string.h></a>
24246 size_t strerrorlen_s(errno_t errnum);
24247 <b> Description</b>
24248 2 The strerrorlen_s function calculates the length of the (untruncated) locale-specific
24249 message string that the strerror_s function maps to errnum.
24251 3 The strerrorlen_s function returns the number of characters (not including the null
24252 character) in the full message string.
24253 <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>
24255 1 #define __STDC_WANT_LIB_EXT1__ 1
24256 #include <a href="#7.23"><string.h></a>
24257 size_t strnlen_s(const char *s, size_t maxsize);
24258 <b> Description</b>
24259 2 The strnlen_s function computes the length of the string pointed to by s.
24261 3 If s is a null pointer,<sup><a href="#note414"><b>414)</b></a></sup> then the strnlen_s function returns zero.
24262 4 Otherwise, the strnlen_s function returns the number of characters that precede the
24263 terminating null character. If there is no null character in the first maxsize characters of
24264 s then strnlen_s returns maxsize. At most the first maxsize characters of s shall
24265 be accessed by strnlen_s.
24270 <sup><a name="note414" href="#note414"><b>414)</b></a></sup> Note that the strnlen_s function has no runtime-constraints. This lack of runtime-constraints
24271 along with the values returned for a null pointer or an unterminated string argument make
24272 strnlen_s useful in algorithms that gracefully handle such exceptional data.
24274 [<a name="p619" href="#p619">page 619</a>] (<a href="#Contents">Contents</a>)
24276 <a name="K.3.8" href="#K.3.8"><b> K.3.8 Date and time <time.h></b></a>
24277 1 The header <a href="#7.26"><time.h></a> defines two types.
24280 which is type int; and
24282 which is the type size_t.
24283 <a name="K.3.8.1" href="#K.3.8.1"><b> K.3.8.1 Components of time</b></a>
24284 1 A broken-down time is normalized if the values of the members of the tm structure are in
24285 their normal rages.<sup><a href="#note415"><b>415)</b></a></sup>
24286 <a name="K.3.8.2" href="#K.3.8.2"><b> K.3.8.2 Time conversion functions</b></a>
24287 1 Like the strftime function, the asctime_s and ctime_s functions do not return a
24288 pointer to a static object, and other library functions are permitted to call them.
24289 <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>
24291 1 #define __STDC_WANT_LIB_EXT1__ 1
24292 #include <a href="#7.26"><time.h></a>
24293 errno_t asctime_s(char *s, rsize_t maxsize,
24294 const struct tm *timeptr);
24295 Runtime-constraints
24296 2 Neither s nor timeptr shall be a null pointer. maxsize shall not be less than 26 and
24297 shall not be greater than RSIZE_MAX. The broken-down time pointed to by timeptr
24298 shall be normalized. The calendar year represented by the broken-down time pointed to
24299 by timeptr shall not be less than calendar year 0 and shall not be greater than calendar
24301 3 If there is a runtime-constraint violation, there is no attempt to convert the time, and
24302 s[0] is set to a null character if s is not a null pointer and maxsize is not zero and is
24303 not greater than RSIZE_MAX.
24304 <b> Description</b>
24305 4 The asctime_s function converts the normalized broken-down time in the structure
24306 pointed to by timeptr into a 26 character (including the null character) string in the
24309 <sup><a name="note415" href="#note415"><b>415)</b></a></sup> The normal ranges are defined in <a href="#7.26.1">7.26.1</a>.
24311 [<a name="p620" href="#p620">page 620</a>] (<a href="#Contents">Contents</a>)
24314 Sun Sep 16 01:03:52 1973\n\0
24315 The fields making up this string are (in order):
24316 1. The name of the day of the week represented by timeptr->tm_wday using the
24317 following three character weekday names: Sun, Mon, Tue, Wed, Thu, Fri, and Sat.
24318 2. The character space.
24319 3. The name of the month represented by timeptr->tm_mon using the following
24320 three character month names: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct,
24322 4. The character space.
24323 5. The value of timeptr->tm_mday as if printed using the fprintf format
24325 6. The character space.
24326 7. The value of timeptr->tm_hour as if printed using the fprintf format
24328 8. The character colon.
24329 9. The value of timeptr->tm_min as if printed using the fprintf format
24331 10. The character colon.
24332 11. The value of timeptr->tm_sec as if printed using the fprintf format
24334 12. The character space.
24335 13. The value of timeptr->tm_year + 1900 as if printed using the fprintf
24337 14. The character new line.
24338 15. The null character.
24339 Recommended practice
24340 The strftime function allows more flexible formatting and supports locale-specific
24341 behavior. If you do not require the exact form of the result string produced by the
24342 asctime_s function, consider using the strftime function instead.
24344 5 The asctime_s function returns zero if the time was successfully converted and stored
24345 into the array pointed to by s. Otherwise, it returns a nonzero value.
24346 [<a name="p621" href="#p621">page 621</a>] (<a href="#Contents">Contents</a>)
24348 <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>
24350 1 #define __STDC_WANT_LIB_EXT1__ 1
24351 #include <a href="#7.26"><time.h></a>
24352 errno_t ctime_s(char *s, rsize_t maxsize,
24353 const time_t *timer);
24354 Runtime-constraints
24355 2 Neither s nor timer shall be a null pointer. maxsize shall not be less than 26 and
24356 shall not be greater than RSIZE_MAX.
24357 3 If there is a runtime-constraint violation, s[0] is set to a null character if s is not a null
24358 pointer and maxsize is not equal zero and is not greater than RSIZE_MAX.
24359 <b> Description</b>
24360 4 The ctime_s function converts the calendar time pointed to by timer to local time in
24361 the form of a string. It is equivalent to
24362 asctime_s(s, maxsize, localtime_s(timer))
24363 Recommended practice
24364 The strftime function allows more flexible formatting and supports locale-specific
24365 behavior. If you do not require the exact form of the result string produced by the
24366 ctime_s function, consider using the strftime function instead.
24368 5 The ctime_s function returns zero if the time was successfully converted and stored
24369 into the array pointed to by s. Otherwise, it returns a nonzero value.
24370 <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>
24372 1 #define __STDC_WANT_LIB_EXT1__ 1
24373 #include <a href="#7.26"><time.h></a>
24374 struct tm *gmtime_s(const time_t * restrict timer,
24375 struct tm * restrict result);
24376 Runtime-constraints
24377 2 Neither timer nor result shall be a null pointer.
24378 3 If there is a runtime-constraint violation, there is no attempt to convert the time.
24379 <b> Description</b>
24380 4 The gmtime_s function converts the calendar time pointed to by timer into a broken-
24381 down time, expressed as UTC. The broken-down time is stored in the structure pointed
24382 [<a name="p622" href="#p622">page 622</a>] (<a href="#Contents">Contents</a>)
24386 5 The gmtime_s function returns result, or a null pointer if the specified time cannot
24387 be converted to UTC or there is a runtime-constraint violation.
24388 <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>
24390 1 #define __STDC_WANT_LIB_EXT1__ 1
24391 #include <a href="#7.26"><time.h></a>
24392 struct tm *localtime_s(const time_t * restrict timer,
24393 struct tm * restrict result);
24394 Runtime-constraints
24395 2 Neither timer nor result shall be a null pointer.
24396 3 If there is a runtime-constraint violation, there is no attempt to convert the time.
24397 <b> Description</b>
24398 4 The localtime_s function converts the calendar time pointed to by timer into a
24399 broken-down time, expressed as local time. The broken-down time is stored in the
24400 structure pointed to by result.
24402 5 The localtime_s function returns result, or a null pointer if the specified time
24403 cannot be converted to local time or there is a runtime-constraint violation.
24404 <a name="K.3.9" href="#K.3.9"><b> K.3.9 Extended multibyte and wide character utilities <wchar.h></b></a>
24405 1 The header <a href="#7.28"><wchar.h></a> defines two types.
24408 which is type int; and
24410 which is the type size_t.
24411 3 Unless explicitly stated otherwise, if the execution of a function described in this
24412 subclause causes copying to take place between objects that overlap, the objects take on
24413 unspecified values.
24418 [<a name="p623" href="#p623">page 623</a>] (<a href="#Contents">Contents</a>)
24420 <a name="K.3.9.1" href="#K.3.9.1"><b> K.3.9.1 Formatted wide character input/output functions</b></a>
24421 <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>
24423 1 #define __STDC_WANT_LIB_EXT1__ 1
24424 #include <a href="#7.28"><wchar.h></a>
24425 int fwprintf_s(FILE * restrict stream,
24426 const wchar_t * restrict format, ...);
24427 Runtime-constraints
24428 2 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note416"><b>416)</b></a></sup> (modified or
24429 not by flags, field width, or precision) shall not appear in the wide string pointed to by
24430 format. Any argument to fwprintf_s corresponding to a %s specifier shall not be a
24432 3 If there is a runtime-constraint violation, the fwprintf_s function does not attempt to
24433 produce further output, and it is unspecified to what extent fwprintf_s produced
24434 output before discovering the runtime-constraint violation.
24435 <b> Description</b>
24436 4 The fwprintf_s function is equivalent to the fwprintf function except for the
24437 explicit runtime-constraints listed above.
24439 5 The fwprintf_s function returns the number of wide characters transmitted, or a
24440 negative value if an output error, encoding error, or runtime-constraint violation occurred.
24441 <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>
24443 1 #define __STDC_WANT_LIB_EXT1__ 1
24444 #include <a href="#7.21"><stdio.h></a>
24445 #include <a href="#7.28"><wchar.h></a>
24446 int fwscanf_s(FILE * restrict stream,
24447 const wchar_t * restrict format, ...);
24448 Runtime-constraints
24449 2 Neither stream nor format shall be a null pointer. Any argument indirected though in
24450 order to store converted input shall not be a null pointer.
24453 <sup><a name="note416" href="#note416"><b>416)</b></a></sup> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24454 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24455 example, if the entire format string was L"%%n".
24457 [<a name="p624" href="#p624">page 624</a>] (<a href="#Contents">Contents</a>)
24459 3 If there is a runtime-constraint violation, the fwscanf_s function does not attempt to
24460 perform further input, and it is unspecified to what extent fwscanf_s performed input
24461 before discovering the runtime-constraint violation.
24462 <b> Description</b>
24463 4 The fwscanf_s function is equivalent to fwscanf except that the c, s, and [
24464 conversion specifiers apply to a pair of arguments (unless assignment suppression is
24465 indicated by a *). The first of these arguments is the same as for fwscanf. That
24466 argument is immediately followed in the argument list by the second argument, which has
24467 type size_t and gives the number of elements in the array pointed to by the first
24468 argument of the pair. If the first argument points to a scalar object, it is considered to be
24469 an array of one element.<sup><a href="#note417"><b>417)</b></a></sup>
24470 5 A matching failure occurs if the number of elements in a receiving object is insufficient to
24471 hold the converted input (including any trailing null character).
24473 6 The fwscanf_s function returns the value of the macro EOF if an input failure occurs
24474 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24475 fwscanf_s function returns the number of input items assigned, which can be fewer
24476 than provided for, or even zero, in the event of an early matching failure.
24477 <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>
24479 1 #define __STDC_WANT_LIB_EXT1__ 1
24480 #include <a href="#7.28"><wchar.h></a>
24481 int snwprintf_s(wchar_t * restrict s,
24483 const wchar_t * restrict format, ...);
24484 Runtime-constraints
24485 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
24486 than RSIZE_MAX. The %n specifier<sup><a href="#note418"><b>418)</b></a></sup> (modified or not by flags, field width, or
24488 <sup><a name="note417" href="#note417"><b>417)</b></a></sup> If the format is known at translation time, an implementation may issue a diagnostic for any argument
24489 used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
24490 argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
24491 the format is not known at translation time. For example, an implementation may issue a diagnostic
24492 for each argument after format that has of type pointer to one of char, signed char,
24493 unsigned char, or void that is not followed by an argument of a type compatible with
24494 rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
24495 using the hh length modifier, a length argument must follow the pointer argument. Another useful
24496 diagnostic could flag any non-pointer argument following format that did not have a type
24497 compatible with rsize_t.
24499 [<a name="p625" href="#p625">page 625</a>] (<a href="#Contents">Contents</a>)
24501 precision) shall not appear in the wide string pointed to by format. Any argument to
24502 snwprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
24504 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
24505 than zero and less than RSIZE_MAX, then the snwprintf_s function sets s[0] to the
24506 null wide character.
24507 <b> Description</b>
24508 4 The snwprintf_s function is equivalent to the swprintf function except for the
24509 explicit runtime-constraints listed above.
24510 5 The snwprintf_s function, unlike swprintf_s, will truncate the result to fit within
24511 the array pointed to by s.
24513 6 The snwprintf_s function returns the number of wide characters that would have
24514 been written had n been sufficiently large, not counting the terminating wide null
24515 character, or a negative value if a runtime-constraint violation occurred. Thus, the null-
24516 terminated output has been completely written if and only if the returned value is
24517 nonnegative and less than n.
24518 <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>
24520 1 #define __STDC_WANT_LIB_EXT1__ 1
24521 #include <a href="#7.28"><wchar.h></a>
24522 int swprintf_s(wchar_t * restrict s, rsize_t n,
24523 const wchar_t * restrict format, ...);
24524 Runtime-constraints
24525 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
24526 than RSIZE_MAX. The number of wide characters (including the trailing null) required
24527 for the result to be written to the array pointed to by s shall not be greater than n. The %n
24528 specifier<sup><a href="#note419"><b>419)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
24529 wide string pointed to by format. Any argument to swprintf_s corresponding to a
24530 %s specifier shall not be a null pointer. No encoding error shall occur.
24533 <sup><a name="note418" href="#note418"><b>418)</b></a></sup> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24534 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24535 example, if the entire format string was L"%%n".
24536 <sup><a name="note419" href="#note419"><b>419)</b></a></sup> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24537 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24538 example, if the entire format string was L"%%n".
24540 [<a name="p626" href="#p626">page 626</a>] (<a href="#Contents">Contents</a>)
24542 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
24543 than zero and less than RSIZE_MAX, then the swprintf_s function sets s[0] to the
24544 null wide character.
24545 <b> Description</b>
24546 4 The swprintf_s function is equivalent to the swprintf function except for the
24547 explicit runtime-constraints listed above.
24548 5 The swprintf_s function, unlike snwprintf_s, treats a result too big for the array
24549 pointed to by s as a runtime-constraint violation.
24551 6 If no runtime-constraint violation occurred, the swprintf_s function returns the
24552 number of wide characters written in the array, not counting the terminating null wide
24553 character. If an encoding error occurred or if n or more wide characters are requested to
24554 be written, swprintf_s returns a negative value. If any other runtime-constraint
24555 violation occurred, swprintf_s returns zero.
24556 <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>
24558 1 #define __STDC_WANT_LIB_EXT1__ 1
24559 #include <a href="#7.28"><wchar.h></a>
24560 int swscanf_s(const wchar_t * restrict s,
24561 const wchar_t * restrict format, ...);
24562 Runtime-constraints
24563 2 Neither s nor format shall be a null pointer. Any argument indirected though in order
24564 to store converted input shall not be a null pointer.
24565 3 If there is a runtime-constraint violation, the swscanf_s function does not attempt to
24566 perform further input, and it is unspecified to what extent swscanf_s performed input
24567 before discovering the runtime-constraint violation.
24568 <b> Description</b>
24569 4 The swscanf_s function is equivalent to fwscanf_s, except that the argument s
24570 specifies a wide string from which the input is to be obtained, rather than from a stream.
24571 Reaching the end of the wide string is equivalent to encountering end-of-file for the
24572 fwscanf_s function.
24574 5 The swscanf_s function returns the value of the macro EOF if an input failure occurs
24575 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24576 swscanf_s function returns the number of input items assigned, which can be fewer
24577 than provided for, or even zero, in the event of an early matching failure.
24578 [<a name="p627" href="#p627">page 627</a>] (<a href="#Contents">Contents</a>)
24580 <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>
24582 1 #define __STDC_WANT_LIB_EXT1__ 1
24583 #include <a href="#7.16"><stdarg.h></a>
24584 #include <a href="#7.21"><stdio.h></a>
24585 #include <a href="#7.28"><wchar.h></a>
24586 int vfwprintf_s(FILE * restrict stream,
24587 const wchar_t * restrict format,
24589 Runtime-constraints
24590 2 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note420"><b>420)</b></a></sup> (modified or
24591 not by flags, field width, or precision) shall not appear in the wide string pointed to by
24592 format. Any argument to vfwprintf_s corresponding to a %s specifier shall not be
24594 3 If there is a runtime-constraint violation, the vfwprintf_s function does not attempt
24595 to produce further output, and it is unspecified to what extent vfwprintf_s produced
24596 output before discovering the runtime-constraint violation.
24597 <b> Description</b>
24598 4 The vfwprintf_s function is equivalent to the vfwprintf function except for the
24599 explicit runtime-constraints listed above.
24601 5 The vfwprintf_s function returns the number of wide characters transmitted, or a
24602 negative value if an output error, encoding error, or runtime-constraint violation occurred.
24603 <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>
24605 1 #define __STDC_WANT_LIB_EXT1__ 1
24606 #include <a href="#7.16"><stdarg.h></a>
24607 #include <a href="#7.21"><stdio.h></a>
24608 #include <a href="#7.28"><wchar.h></a>
24609 int vfwscanf_s(FILE * restrict stream,
24610 const wchar_t * restrict format, va_list arg);
24614 <sup><a name="note420" href="#note420"><b>420)</b></a></sup> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24615 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24616 example, if the entire format string was L"%%n".
24618 [<a name="p628" href="#p628">page 628</a>] (<a href="#Contents">Contents</a>)
24620 Runtime-constraints
24621 2 Neither stream nor format shall be a null pointer. Any argument indirected though in
24622 order to store converted input shall not be a null pointer.
24623 3 If there is a runtime-constraint violation, the vfwscanf_s function does not attempt to
24624 perform further input, and it is unspecified to what extent vfwscanf_s performed input
24625 before discovering the runtime-constraint violation.
24626 <b> Description</b>
24627 4 The vfwscanf_s function is equivalent to fwscanf_s, with the variable argument
24628 list replaced by arg, which shall have been initialized by the va_start macro (and
24629 possibly subsequent va_arg calls). The vfwscanf_s function does not invoke the
24630 va_end macro.<sup><a href="#note421"><b>421)</b></a></sup>
24632 5 The vfwscanf_s function returns the value of the macro EOF if an input failure occurs
24633 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24634 vfwscanf_s function returns the number of input items assigned, which can be fewer
24635 than provided for, or even zero, in the event of an early matching failure.
24636 <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>
24638 1 #define __STDC_WANT_LIB_EXT1__ 1
24639 #include <a href="#7.16"><stdarg.h></a>
24640 #include <a href="#7.28"><wchar.h></a>
24641 int vsnwprintf_s(wchar_t * restrict s,
24643 const wchar_t * restrict format,
24645 Runtime-constraints
24646 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
24647 than RSIZE_MAX. The %n specifier<sup><a href="#note422"><b>422)</b></a></sup> (modified or not by flags, field width, or
24648 precision) shall not appear in the wide string pointed to by format. Any argument to
24649 vsnwprintf_s corresponding to a %s specifier shall not be a null pointer. No
24650 encoding error shall occur.
24652 <sup><a name="note421" href="#note421"><b>421)</b></a></sup> As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
24653 value of arg after the return is indeterminate.
24654 <sup><a name="note422" href="#note422"><b>422)</b></a></sup> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24655 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24656 example, if the entire format string was L"%%n".
24658 [<a name="p629" href="#p629">page 629</a>] (<a href="#Contents">Contents</a>)
24660 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
24661 than zero and less than RSIZE_MAX, then the vsnwprintf_s function sets s[0] to
24662 the null wide character.
24663 <b> Description</b>
24664 4 The vsnwprintf_s function is equivalent to the vswprintf function except for the
24665 explicit runtime-constraints listed above.
24666 5 The vsnwprintf_s function, unlike vswprintf_s, will truncate the result to fit
24667 within the array pointed to by s.
24669 6 The vsnwprintf_s function returns the number of wide characters that would have
24670 been written had n been sufficiently large, not counting the terminating null character, or
24671 a negative value if a runtime-constraint violation occurred. Thus, the null-terminated
24672 output has been completely written if and only if the returned value is nonnegative and
24674 <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>
24676 1 #define __STDC_WANT_LIB_EXT1__ 1
24677 #include <a href="#7.16"><stdarg.h></a>
24678 #include <a href="#7.28"><wchar.h></a>
24679 int vswprintf_s(wchar_t * restrict s,
24681 const wchar_t * restrict format,
24683 Runtime-constraints
24684 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
24685 than RSIZE_MAX. The number of wide characters (including the trailing null) required
24686 for the result to be written to the array pointed to by s shall not be greater than n. The %n
24687 specifier<sup><a href="#note423"><b>423)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
24688 wide string pointed to by format. Any argument to vswprintf_s corresponding to a
24689 %s specifier shall not be a null pointer. No encoding error shall occur.
24690 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
24691 than zero and less than RSIZE_MAX, then the vswprintf_s function sets s[0] to the
24692 null wide character.
24694 <sup><a name="note423" href="#note423"><b>423)</b></a></sup> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24695 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24696 example, if the entire format string was L"%%n".
24698 [<a name="p630" href="#p630">page 630</a>] (<a href="#Contents">Contents</a>)
24700 <b> Description</b>
24701 4 The vswprintf_s function is equivalent to the vswprintf function except for the
24702 explicit runtime-constraints listed above.
24703 5 The vswprintf_s function, unlike vsnwprintf_s, treats a result too big for the
24704 array pointed to by s as a runtime-constraint violation.
24706 6 If no runtime-constraint violation occurred, the vswprintf_s function returns the
24707 number of wide characters written in the array, not counting the terminating null wide
24708 character. If an encoding error occurred or if n or more wide characters are requested to
24709 be written, vswprintf_s returns a negative value. If any other runtime-constraint
24710 violation occurred, vswprintf_s returns zero.
24711 <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>
24713 1 #define __STDC_WANT_LIB_EXT1__ 1
24714 #include <a href="#7.16"><stdarg.h></a>
24715 #include <a href="#7.28"><wchar.h></a>
24716 int vswscanf_s(const wchar_t * restrict s,
24717 const wchar_t * restrict format,
24719 Runtime-constraints
24720 2 Neither s nor format shall be a null pointer. Any argument indirected though in order
24721 to store converted input shall not be a null pointer.
24722 3 If there is a runtime-constraint violation, the vswscanf_s function does not attempt to
24723 perform further input, and it is unspecified to what extent vswscanf_s performed input
24724 before discovering the runtime-constraint violation.
24725 <b> Description</b>
24726 4 The vswscanf_s function is equivalent to swscanf_s, with the variable argument
24727 list replaced by arg, which shall have been initialized by the va_start macro (and
24728 possibly subsequent va_arg calls). The vswscanf_s function does not invoke the
24729 va_end macro.<sup><a href="#note424"><b>424)</b></a></sup>
24734 <sup><a name="note424" href="#note424"><b>424)</b></a></sup> As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
24735 value of arg after the return is indeterminate.
24737 [<a name="p631" href="#p631">page 631</a>] (<a href="#Contents">Contents</a>)
24740 5 The vswscanf_s function returns the value of the macro EOF if an input failure occurs
24741 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24742 vswscanf_s function returns the number of input items assigned, which can be fewer
24743 than provided for, or even zero, in the event of an early matching failure.
24744 <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>
24746 1 #define __STDC_WANT_LIB_EXT1__ 1
24747 #include <a href="#7.16"><stdarg.h></a>
24748 #include <a href="#7.28"><wchar.h></a>
24749 int vwprintf_s(const wchar_t * restrict format,
24751 Runtime-constraints
24752 2 format shall not be a null pointer. The %n specifier<sup><a href="#note425"><b>425)</b></a></sup> (modified or not by flags, field
24753 width, or precision) shall not appear in the wide string pointed to by format. Any
24754 argument to vwprintf_s corresponding to a %s specifier shall not be a null pointer.
24755 3 If there is a runtime-constraint violation, the vwprintf_s function does not attempt to
24756 produce further output, and it is unspecified to what extent vwprintf_s produced
24757 output before discovering the runtime-constraint violation.
24758 <b> Description</b>
24759 4 The vwprintf_s function is equivalent to the vwprintf function except for the
24760 explicit runtime-constraints listed above.
24762 5 The vwprintf_s function returns the number of wide characters transmitted, or a
24763 negative value if an output error, encoding error, or runtime-constraint violation occurred.
24768 <sup><a name="note425" href="#note425"><b>425)</b></a></sup> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24769 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24770 example, if the entire format string was L"%%n".
24772 [<a name="p632" href="#p632">page 632</a>] (<a href="#Contents">Contents</a>)
24774 <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>
24776 1 #define __STDC_WANT_LIB_EXT1__ 1
24777 #include <a href="#7.16"><stdarg.h></a>
24778 #include <a href="#7.28"><wchar.h></a>
24779 int vwscanf_s(const wchar_t * restrict format,
24781 Runtime-constraints
24782 2 format shall not be a null pointer. Any argument indirected though in order to store
24783 converted input shall not be a null pointer.
24784 3 If there is a runtime-constraint violation, the vwscanf_s function does not attempt to
24785 perform further input, and it is unspecified to what extent vwscanf_s performed input
24786 before discovering the runtime-constraint violation.
24787 <b> Description</b>
24788 4 The vwscanf_s function is equivalent to wscanf_s, with the variable argument list
24789 replaced by arg, which shall have been initialized by the va_start macro (and
24790 possibly subsequent va_arg calls). The vwscanf_s function does not invoke the
24791 va_end macro.<sup><a href="#note426"><b>426)</b></a></sup>
24793 5 The vwscanf_s function returns the value of the macro EOF if an input failure occurs
24794 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24795 vwscanf_s function returns the number of input items assigned, which can be fewer
24796 than provided for, or even zero, in the event of an early matching failure.
24797 <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>
24799 1 #define __STDC_WANT_LIB_EXT1__ 1
24800 #include <a href="#7.28"><wchar.h></a>
24801 int wprintf_s(const wchar_t * restrict format, ...);
24802 Runtime-constraints
24803 2 format shall not be a null pointer. The %n specifier<sup><a href="#note427"><b>427)</b></a></sup> (modified or not by flags, field
24805 <sup><a name="note426" href="#note426"><b>426)</b></a></sup> As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
24806 value of arg after the return is indeterminate.
24807 <sup><a name="note427" href="#note427"><b>427)</b></a></sup> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
24808 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24809 example, if the entire format string was L"%%n".
24811 [<a name="p633" href="#p633">page 633</a>] (<a href="#Contents">Contents</a>)
24813 width, or precision) shall not appear in the wide string pointed to by format. Any
24814 argument to wprintf_s corresponding to a %s specifier shall not be a null pointer.
24815 3 If there is a runtime-constraint violation, the wprintf_s function does not attempt to
24816 produce further output, and it is unspecified to what extent wprintf_s produced output
24817 before discovering the runtime-constraint violation.
24818 <b> Description</b>
24819 4 The wprintf_s function is equivalent to the wprintf function except for the explicit
24820 runtime-constraints listed above.
24822 5 The wprintf_s function returns the number of wide characters transmitted, or a
24823 negative value if an output error, encoding error, or runtime-constraint violation occurred.
24824 <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>
24826 1 #define __STDC_WANT_LIB_EXT1__ 1
24827 #include <a href="#7.28"><wchar.h></a>
24828 int wscanf_s(const wchar_t * restrict format, ...);
24829 Runtime-constraints
24830 2 format shall not be a null pointer. Any argument indirected though in order to store
24831 converted input shall not be a null pointer.
24832 3 If there is a runtime-constraint violation, the wscanf_s function does not attempt to
24833 perform further input, and it is unspecified to what extent wscanf_s performed input
24834 before discovering the runtime-constraint violation.
24835 <b> Description</b>
24836 4 The wscanf_s function is equivalent to fwscanf_s with the argument stdin
24837 interposed before the arguments to wscanf_s.
24839 5 The wscanf_s function returns the value of the macro EOF if an input failure occurs
24840 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24841 wscanf_s function returns the number of input items assigned, which can be fewer than
24842 provided for, or even zero, in the event of an early matching failure.
24847 [<a name="p634" href="#p634">page 634</a>] (<a href="#Contents">Contents</a>)
24849 <a name="K.3.9.2" href="#K.3.9.2"><b> K.3.9.2 General wide string utilities</b></a>
24850 <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>
24851 <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>
24853 1 #define __STDC_WANT_LIB_EXT1__ 1
24854 #include <a href="#7.28"><wchar.h></a>
24855 errno_t wcscpy_s(wchar_t * restrict s1,
24857 const wchar_t * restrict s2);
24858 Runtime-constraints
24859 2 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
24860 s1max shall not equal zero. s1max shall be greater than wcsnlen_s(s2, s1max).
24861 Copying shall not take place between objects that overlap.
24862 3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
24863 greater than zero and not greater than RSIZE_MAX, then wcscpy_s sets s1[0] to the
24864 null wide character.
24865 <b> Description</b>
24866 4 The wcscpy_s function copies the wide string pointed to by s2 (including the
24867 terminating null wide character) into the array pointed to by s1.
24868 5 All elements following the terminating null wide character (if any) written by
24869 wcscpy_s in the array of s1max wide characters pointed to by s1 take unspecified
24870 values when wcscpy_s returns.<sup><a href="#note428"><b>428)</b></a></sup>
24872 6 The wcscpy_s function returns zero<sup><a href="#note429"><b>429)</b></a></sup> if there was no runtime-constraint violation.
24873 Otherwise, a nonzero value is returned.
24878 <sup><a name="note428" href="#note428"><b>428)</b></a></sup> This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
24879 if any of those wide characters are null. Such an approach might write a wide character to every
24880 element of s1 before discovering that the first element should be set to the null wide character.
24881 <sup><a name="note429" href="#note429"><b>429)</b></a></sup> A zero return value implies that all of the requested wide characters from the string pointed to by s2
24882 fit within the array pointed to by s1 and that the result in s1 is null terminated.
24884 [<a name="p635" href="#p635">page 635</a>] (<a href="#Contents">Contents</a>)
24886 <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>
24888 7 #define __STDC_WANT_LIB_EXT1__ 1
24889 #include <a href="#7.28"><wchar.h></a>
24890 errno_t wcsncpy_s(wchar_t * restrict s1,
24892 const wchar_t * restrict s2,
24894 Runtime-constraints
24895 8 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
24896 RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
24897 shall be greater than wcsnlen_s(s2, s1max). Copying shall not take place between
24898 objects that overlap.
24899 9 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
24900 greater than zero and not greater than RSIZE_MAX, then wcsncpy_s sets s1[0] to the
24901 null wide character.
24902 <b> Description</b>
24903 10 The wcsncpy_s function copies not more than n successive wide characters (wide
24904 characters that follow a null wide character are not copied) from the array pointed to by
24905 s2 to the array pointed to by s1. If no null wide character was copied from s2, then
24906 s1[n] is set to a null wide character.
24907 11 All elements following the terminating null wide character (if any) written by
24908 wcsncpy_s in the array of s1max wide characters pointed to by s1 take unspecified
24909 values when wcsncpy_s returns.<sup><a href="#note430"><b>430)</b></a></sup>
24911 12 The wcsncpy_s function returns zero<sup><a href="#note431"><b>431)</b></a></sup> if there was no runtime-constraint violation.
24912 Otherwise, a nonzero value is returned.
24913 13 EXAMPLE 1 The wcsncpy_s function can be used to copy a wide string without the danger that the
24914 result will not be null terminated or that wide characters will be written past the end of the destination
24920 <sup><a name="note430" href="#note430"><b>430)</b></a></sup> This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
24921 if any of those wide characters are null. Such an approach might write a wide character to every
24922 element of s1 before discovering that the first element should be set to the null wide character.
24923 <sup><a name="note431" href="#note431"><b>431)</b></a></sup> A zero return value implies that all of the requested wide characters from the string pointed to by s2
24924 fit within the array pointed to by s1 and that the result in s1 is null terminated.
24926 [<a name="p636" href="#p636">page 636</a>] (<a href="#Contents">Contents</a>)
24928 #define __STDC_WANT_LIB_EXT1__ 1
24929 #include <a href="#7.28"><wchar.h></a>
24931 wchar_t src1[100] = L"hello";
24932 wchar_t src2[7] = {L'g', L'o', L'o', L'd', L'b', L'y', L'e'};
24933 wchar_t dst1[6], dst2[5], dst3[5];
24935 r1 = wcsncpy_s(dst1, 6, src1, 100);
24936 r2 = wcsncpy_s(dst2, 5, src2, 7);
24937 r3 = wcsncpy_s(dst3, 5, src2, 4);
24938 The first call will assign to r1 the value zero and to dst1 the sequence of wide characters hello\0.
24939 The second call will assign to r2 a nonzero value and to dst2 the sequence of wide characters \0.
24940 The third call will assign to r3 the value zero and to dst3 the sequence of wide characters good\0.
24942 <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>
24944 14 #define __STDC_WANT_LIB_EXT1__ 1
24945 #include <a href="#7.28"><wchar.h></a>
24946 errno_t wmemcpy_s(wchar_t * restrict s1,
24948 const wchar_t * restrict s2,
24950 Runtime-constraints
24951 15 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
24952 RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
24953 objects that overlap.
24954 16 If there is a runtime-constraint violation, the wmemcpy_s function stores zeros in the
24955 first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
24956 s1max is not greater than RSIZE_MAX.
24957 <b> Description</b>
24958 17 The wmemcpy_s function copies n successive wide characters from the object pointed
24959 to by s2 into the object pointed to by s1.
24961 18 The wmemcpy_s function returns zero if there was no runtime-constraint violation.
24962 Otherwise, a nonzero value is returned.
24967 [<a name="p637" href="#p637">page 637</a>] (<a href="#Contents">Contents</a>)
24969 <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>
24971 19 #define __STDC_WANT_LIB_EXT1__ 1
24972 #include <a href="#7.28"><wchar.h></a>
24973 errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
24974 const wchar_t *s2, rsize_t n);
24975 Runtime-constraints
24976 20 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
24977 RSIZE_MAX. n shall not be greater than s1max.
24978 21 If there is a runtime-constraint violation, the wmemmove_s function stores zeros in the
24979 first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
24980 s1max is not greater than RSIZE_MAX.
24981 <b> Description</b>
24982 22 The wmemmove_s function copies n successive wide characters from the object pointed
24983 to by s2 into the object pointed to by s1. This copying takes place as if the n wide
24984 characters from the object pointed to by s2 are first copied into a temporary array of n
24985 wide characters that does not overlap the objects pointed to by s1 or s2, and then the n
24986 wide characters from the temporary array are copied into the object pointed to by s1.
24988 23 The wmemmove_s function returns zero if there was no runtime-constraint violation.
24989 Otherwise, a nonzero value is returned.
24990 <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>
24991 <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>
24993 1 #define __STDC_WANT_LIB_EXT1__ 1
24994 #include <a href="#7.28"><wchar.h></a>
24995 errno_t wcscat_s(wchar_t * restrict s1,
24997 const wchar_t * restrict s2);
24998 Runtime-constraints
24999 2 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
25001 3 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
25002 s1max shall not equal zero. m shall not equal zero.<sup><a href="#note432"><b>432)</b></a></sup> m shall be greater than
25003 wcsnlen_s(s2, m). Copying shall not take place between objects that overlap.
25005 [<a name="p638" href="#p638">page 638</a>] (<a href="#Contents">Contents</a>)
25007 4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
25008 greater than zero and not greater than RSIZE_MAX, then wcscat_s sets s1[0] to the
25009 null wide character.
25010 <b> Description</b>
25011 5 The wcscat_s function appends a copy of the wide string pointed to by s2 (including
25012 the terminating null wide character) to the end of the wide string pointed to by s1. The
25013 initial wide character from s2 overwrites the null wide character at the end of s1.
25014 6 All elements following the terminating null wide character (if any) written by
25015 wcscat_s in the array of s1max wide characters pointed to by s1 take unspecified
25016 values when wcscat_s returns.<sup><a href="#note433"><b>433)</b></a></sup>
25018 7 The wcscat_s function returns zero<sup><a href="#note434"><b>434)</b></a></sup> if there was no runtime-constraint violation.
25019 Otherwise, a nonzero value is returned.
25020 <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>
25022 8 #define __STDC_WANT_LIB_EXT1__ 1
25023 #include <a href="#7.28"><wchar.h></a>
25024 errno_t wcsncat_s(wchar_t * restrict s1,
25026 const wchar_t * restrict s2,
25028 Runtime-constraints
25029 9 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
25031 10 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
25032 RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.<sup><a href="#note435"><b>435)</b></a></sup> If n is not less
25033 than m, then m shall be greater than wcsnlen_s(s2, m). Copying shall not take
25034 place between objects that overlap.
25037 <sup><a name="note432" href="#note432"><b>432)</b></a></sup> Zero means that s1 was not null terminated upon entry to wcscat_s.
25038 <sup><a name="note433" href="#note433"><b>433)</b></a></sup> This allows an implementation to append wide characters from s2 to s1 while simultaneously
25039 checking if any of those wide characters are null. Such an approach might write a wide character to
25040 every element of s1 before discovering that the first element should be set to the null wide character.
25041 <sup><a name="note434" href="#note434"><b>434)</b></a></sup> A zero return value implies that all of the requested wide characters from the wide string pointed to by
25042 s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
25043 <sup><a name="note435" href="#note435"><b>435)</b></a></sup> Zero means that s1 was not null terminated upon entry to wcsncat_s.
25045 [<a name="p639" href="#p639">page 639</a>] (<a href="#Contents">Contents</a>)
25047 11 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
25048 greater than zero and not greater than RSIZE_MAX, then wcsncat_s sets s1[0] to the
25049 null wide character.
25050 <b> Description</b>
25051 12 The wcsncat_s function appends not more than n successive wide characters (wide
25052 characters that follow a null wide character are not copied) from the array pointed to by
25053 s2 to the end of the wide string pointed to by s1. The initial wide character from s2
25054 overwrites the null wide character at the end of s1. If no null wide character was copied
25055 from s2, then s1[s1max-m+n] is set to a null wide character.
25056 13 All elements following the terminating null wide character (if any) written by
25057 wcsncat_s in the array of s1max wide characters pointed to by s1 take unspecified
25058 values when wcsncat_s returns.<sup><a href="#note436"><b>436)</b></a></sup>
25060 14 The wcsncat_s function returns zero<sup><a href="#note437"><b>437)</b></a></sup> if there was no runtime-constraint violation.
25061 Otherwise, a nonzero value is returned.
25062 15 EXAMPLE 1 The wcsncat_s function can be used to copy a wide string without the danger that the
25063 result will not be null terminated or that wide characters will be written past the end of the destination
25065 #define __STDC_WANT_LIB_EXT1__ 1
25066 #include <a href="#7.28"><wchar.h></a>
25068 wchar_t s1[100] = L"good";
25069 wchar_t s2[6] = L"hello";
25070 wchar_t s3[6] = L"hello";
25071 wchar_t s4[7] = L"abc";
25072 wchar_t s5[1000] = L"bye";
25073 int r1, r2, r3, r4;
25074 r1 = wcsncat_s(s1, 100, s5, 1000);
25075 r2 = wcsncat_s(s2, 6, L"", 1);
25076 r3 = wcsncat_s(s3, 6, L"X", 2);
25077 r4 = wcsncat_s(s4, 7, L"defghijklmn", 3);
25078 After the first call r1 will have the value zero and s1 will be the wide character sequence goodbye\0.
25079 After the second call r2 will have the value zero and s2 will be the wide character sequence hello\0.
25080 After the third call r3 will have a nonzero value and s3 will be the wide character sequence \0.
25081 After the fourth call r4 will have the value zero and s4 will be the wide character sequence abcdef\0.
25086 <sup><a name="note436" href="#note436"><b>436)</b></a></sup> This allows an implementation to append wide characters from s2 to s1 while simultaneously
25087 checking if any of those wide characters are null. Such an approach might write a wide character to
25088 every element of s1 before discovering that the first element should be set to the null wide character.
25089 <sup><a name="note437" href="#note437"><b>437)</b></a></sup> A zero return value implies that all of the requested wide characters from the wide string pointed to by
25090 s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
25092 [<a name="p640" href="#p640">page 640</a>] (<a href="#Contents">Contents</a>)
25094 <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>
25095 <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>
25097 1 #define __STDC_WANT_LIB_EXT1__ 1
25098 #include <a href="#7.28"><wchar.h></a>
25099 wchar_t *wcstok_s(wchar_t * restrict s1,
25100 rsize_t * restrict s1max,
25101 const wchar_t * restrict s2,
25102 wchar_t ** restrict ptr);
25103 Runtime-constraints
25104 2 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
25105 shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
25106 The end of the token found shall occur within the first *s1max wide characters of s1 for
25107 the first call, and shall occur within the first *s1max wide characters of where searching
25108 resumes on subsequent calls.
25109 3 If there is a runtime-constraint violation, the wcstok_s function does not indirect
25110 through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
25111 <b> Description</b>
25112 4 A sequence of calls to the wcstok_s function breaks the wide string pointed to by s1
25113 into a sequence of tokens, each of which is delimited by a wide character from the wide
25114 string pointed to by s2. The fourth argument points to a caller-provided wchar_t
25115 pointer into which the wcstok_s function stores information necessary for it to
25116 continue scanning the same wide string.
25117 5 The first call in a sequence has a non-null first argument and s1max points to an object
25118 whose value is the number of elements in the wide character array pointed to by the first
25119 argument. The first call stores an initial value in the object pointed to by ptr and
25120 updates the value pointed to by s1max to reflect the number of elements that remain in
25121 relation to ptr. Subsequent calls in the sequence have a null first argument and the
25122 objects pointed to by s1max and ptr are required to have the values stored by the
25123 previous call in the sequence, which are then updated. The separator wide string pointed
25124 to by s2 may be different from call to call.
25125 6 The first call in the sequence searches the wide string pointed to by s1 for the first wide
25126 character that is not contained in the current separator wide string pointed to by s2. If no
25127 such wide character is found, then there are no tokens in the wide string pointed to by s1
25128 and the wcstok_s function returns a null pointer. If such a wide character is found, it is
25129 the start of the first token.
25132 [<a name="p641" href="#p641">page 641</a>] (<a href="#Contents">Contents</a>)
25134 7 The wcstok_s function then searches from there for the first wide character in s1 that
25135 is contained in the current separator wide string. If no such wide character is found, the
25136 current token extends to the end of the wide string pointed to by s1, and subsequent
25137 searches in the same wide string for a token return a null pointer. If such a wide character
25138 is found, it is overwritten by a null wide character, which terminates the current token.
25139 8 In all cases, the wcstok_s function stores sufficient information in the pointer pointed
25140 to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
25141 value for ptr, shall start searching just past the element overwritten by a null wide
25142 character (if any).
25144 9 The wcstok_s function returns a pointer to the first wide character of a token, or a null
25145 pointer if there is no token or there is a runtime-constraint violation.
25147 #define __STDC_WANT_LIB_EXT1__ 1
25148 #include <a href="#7.28"><wchar.h></a>
25149 static wchar_t str1[] = L"?a???b,,,#c";
25150 static wchar_t str2[] = L"\t \t";
25151 wchar_t *t, *ptr1, *ptr2;
25152 rsize_t max1 = wcslen(str1)+1;
25153 rsize_t max2 = wcslen(str2)+1;
25154 t = wcstok_s(str1, &max1, "?", &ptr1); // t points to the token "a"
25155 t = wcstok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
25156 t = wcstok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
25157 t = wcstok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
25158 t = wcstok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
25160 <a name="K.3.9.2.4" href="#K.3.9.2.4"><b> K.3.9.2.4 Miscellaneous functions</b></a>
25161 <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>
25163 1 #define __STDC_WANT_LIB_EXT1__ 1
25164 #include <a href="#7.28"><wchar.h></a>
25165 size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
25166 <b> Description</b>
25167 2 The wcsnlen_s function computes the length of the wide string pointed to by s.
25169 3 If s is a null pointer,<sup><a href="#note438"><b>438)</b></a></sup> then the wcsnlen_s function returns zero.
25170 4 Otherwise, the wcsnlen_s function returns the number of wide characters that precede
25171 the terminating null wide character. If there is no null wide character in the first
25172 maxsize wide characters of s then wcsnlen_s returns maxsize. At most the first
25174 [<a name="p642" href="#p642">page 642</a>] (<a href="#Contents">Contents</a>)
25176 maxsize wide characters of s shall be accessed by wcsnlen_s.
25177 <a name="K.3.9.3" href="#K.3.9.3"><b> K.3.9.3 Extended multibyte/wide character conversion utilities</b></a>
25178 <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>
25179 1 Unlike wcrtomb, wcrtomb_s does not permit the ps parameter (the pointer to the
25180 conversion state) to be a null pointer.
25181 <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>
25183 2 #include <a href="#7.28"><wchar.h></a>
25184 errno_t wcrtomb_s(size_t * restrict retval,
25185 char * restrict s, rsize_t smax,
25186 wchar_t wc, mbstate_t * restrict ps);
25187 Runtime-constraints
25188 3 Neither retval nor ps shall be a null pointer. If s is not a null pointer, then smax
25189 shall not equal zero and shall not be greater than RSIZE_MAX. If s is not a null pointer,
25190 then smax shall be not be less than the number of bytes to be stored in the array pointed
25191 to by s. If s is a null pointer, then smax shall equal zero.
25192 4 If there is a runtime-constraint violation, then wcrtomb_s does the following. If s is
25193 not a null pointer and smax is greater than zero and not greater than RSIZE_MAX, then
25194 wcrtomb_s sets s[0] to the null character. If retval is not a null pointer, then
25195 wcrtomb_s sets *retval to (size_t)(-1).
25196 <b> Description</b>
25197 5 If s is a null pointer, the wcrtomb_s function is equivalent to the call
25198 wcrtomb_s(&retval, buf, sizeof buf, L'\0', ps)
25199 where retval and buf are internal variables of the appropriate types, and the size of
25200 buf is greater than MB_CUR_MAX.
25201 6 If s is not a null pointer, the wcrtomb_s function determines the number of bytes
25202 needed to represent the multibyte character that corresponds to the wide character given
25203 by wc (including any shift sequences), and stores the multibyte character representation
25204 in the array whose first element is pointed to by s. At most MB_CUR_MAX bytes are
25205 stored. If wc is a null wide character, a null byte is stored, preceded by any shift
25206 sequence needed to restore the initial shift state; the resulting state described is the initial
25209 <sup><a name="note438" href="#note438"><b>438)</b></a></sup> Note that the wcsnlen_s function has no runtime-constraints. This lack of runtime-constraints
25210 along with the values returned for a null pointer or an unterminated wide string argument make
25211 wcsnlen_s useful in algorithms that gracefully handle such exceptional data.
25213 [<a name="p643" href="#p643">page 643</a>] (<a href="#Contents">Contents</a>)
25215 7 If wc does not correspond to a valid multibyte character, an encoding error occurs: the
25216 wcrtomb_s function stores the value (size_t)(-1) into *retval and the
25217 conversion state is unspecified. Otherwise, the wcrtomb_s function stores into
25218 *retval the number of bytes (including any shift sequences) stored in the array pointed
25221 8 The wcrtomb_s function returns zero if no runtime-constraint violation and no
25222 encoding error occurred. Otherwise, a nonzero value is returned.
25223 <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>
25224 1 Unlike mbsrtowcs and wcsrtombs, mbsrtowcs_s and wcsrtombs_s do not
25225 permit the ps parameter (the pointer to the conversion state) to be a null pointer.
25226 <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>
25228 2 #include <a href="#7.28"><wchar.h></a>
25229 errno_t mbsrtowcs_s(size_t * restrict retval,
25230 wchar_t * restrict dst, rsize_t dstmax,
25231 const char ** restrict src, rsize_t len,
25232 mbstate_t * restrict ps);
25233 Runtime-constraints
25234 3 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
25235 then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
25236 pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
25237 not equal zero. If dst is not a null pointer and len is not less than dstmax, then a null
25238 character shall occur within the first dstmax multibyte characters of the array pointed to
25240 4 If there is a runtime-constraint violation, then mbsrtowcs_s does the following. If
25241 retval is not a null pointer, then mbsrtowcs_s sets *retval to (size_t)(-1).
25242 If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
25243 then mbsrtowcs_s sets dst[0] to the null wide character.
25244 <b> Description</b>
25245 5 The mbsrtowcs_s function converts a sequence of multibyte characters that begins in
25246 the conversion state described by the object pointed to by ps, from the array indirectly
25247 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
25248 pointer, the converted characters are stored into the array pointed to by dst. Conversion
25249 continues up to and including a terminating null character, which is also stored.
25250 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
25251 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
25252 [<a name="p644" href="#p644">page 644</a>] (<a href="#Contents">Contents</a>)
25254 characters have been stored into the array pointed to by dst.<sup><a href="#note439"><b>439)</b></a></sup> If dst is not a null
25255 pointer and no null wide character was stored into the array pointed to by dst, then
25256 dst[len] is set to the null wide character. Each conversion takes place as if by a call
25257 to the mbrtowc function.
25258 6 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
25259 pointer (if conversion stopped due to reaching a terminating null character) or the address
25260 just past the last multibyte character converted (if any). If conversion stopped due to
25261 reaching a terminating null character and if dst is not a null pointer, the resulting state
25262 described is the initial conversion state.
25263 7 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
25264 sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
25265 the mbsrtowcs_s function stores the value (size_t)(-1) into *retval and the
25266 conversion state is unspecified. Otherwise, the mbsrtowcs_s function stores into
25267 *retval the number of multibyte characters successfully converted, not including the
25268 terminating null character (if any).
25269 8 All elements following the terminating null wide character (if any) written by
25270 mbsrtowcs_s in the array of dstmax wide characters pointed to by dst take
25271 unspecified values when mbsrtowcs_s returns.<sup><a href="#note440"><b>440)</b></a></sup>
25272 9 If copying takes place between objects that overlap, the objects take on unspecified
25275 10 The mbsrtowcs_s function returns zero if no runtime-constraint violation and no
25276 encoding error occurred. Otherwise, a nonzero value is returned.
25277 <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>
25279 11 #include <a href="#7.28"><wchar.h></a>
25280 errno_t wcsrtombs_s(size_t * restrict retval,
25281 char * restrict dst, rsize_t dstmax,
25282 const wchar_t ** restrict src, rsize_t len,
25283 mbstate_t * restrict ps);
25288 <sup><a name="note439" href="#note439"><b>439)</b></a></sup> Thus, the value of len is ignored if dst is a null pointer.
25289 <sup><a name="note440" href="#note440"><b>440)</b></a></sup> This allows an implementation to attempt converting the multibyte string before discovering a
25290 terminating null character did not occur where required.
25292 [<a name="p645" href="#p645">page 645</a>] (<a href="#Contents">Contents</a>)
25294 Runtime-constraints
25295 12 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
25296 then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
25297 pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
25298 not equal zero. If dst is not a null pointer and len is not less than dstmax, then the
25299 conversion shall have been stopped (see below) because a terminating null wide character
25300 was reached or because an encoding error occurred.
25301 13 If there is a runtime-constraint violation, then wcsrtombs_s does the following. If
25302 retval is not a null pointer, then wcsrtombs_s sets *retval to (size_t)(-1).
25303 If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
25304 then wcsrtombs_s sets dst[0] to the null character.
25305 <b> Description</b>
25306 14 The wcsrtombs_s function converts a sequence of wide characters from the array
25307 indirectly pointed to by src into a sequence of corresponding multibyte characters that
25308 begins in the conversion state described by the object pointed to by ps. If dst is not a
25309 null pointer, the converted characters are then stored into the array pointed to by dst.
25310 Conversion continues up to and including a terminating null wide character, which is also
25311 stored. Conversion stops earlier in two cases:
25312 -- when a wide character is reached that does not correspond to a valid multibyte
25314 -- (if dst is not a null pointer) when the next multibyte character would exceed the
25315 limit of n total bytes to be stored into the array pointed to by dst. If the wide
25316 character being converted is the null wide character, then n is the lesser of len or
25317 dstmax. Otherwise, n is the lesser of len or dstmax-1.
25318 If the conversion stops without converting a null wide character and dst is not a null
25319 pointer, then a null character is stored into the array pointed to by dst immediately
25320 following any multibyte characters already stored. Each conversion takes place as if by a
25321 call to the wcrtomb function.<sup><a href="#note441"><b>441)</b></a></sup>
25322 15 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
25323 pointer (if conversion stopped due to reaching a terminating null wide character) or the
25324 address just past the last wide character converted (if any). If conversion stopped due to
25325 reaching a terminating null wide character, the resulting state described is the initial
25329 <sup><a name="note441" href="#note441"><b>441)</b></a></sup> If conversion stops because a terminating null wide character has been reached, the bytes stored
25330 include those necessary to reach the initial shift state immediately before the null byte. However, if
25331 the conversion stops before a terminating null wide character has been reached, the result will be null
25332 terminated, but might not end in the initial shift state.
25334 [<a name="p646" href="#p646">page 646</a>] (<a href="#Contents">Contents</a>)
25336 16 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
25337 wide character that does not correspond to a valid multibyte character, an encoding error
25338 occurs: the wcsrtombs_s function stores the value (size_t)(-1) into *retval
25339 and the conversion state is unspecified. Otherwise, the wcsrtombs_s function stores
25340 into *retval the number of bytes in the resulting multibyte character sequence, not
25341 including the terminating null character (if any).
25342 17 All elements following the terminating null character (if any) written by wcsrtombs_s
25343 in the array of dstmax elements pointed to by dst take unspecified values when
25344 wcsrtombs_s returns.<sup><a href="#note442"><b>442)</b></a></sup>
25345 18 If copying takes place between objects that overlap, the objects take on unspecified
25348 19 The wcsrtombs_s function returns zero if no runtime-constraint violation and no
25349 encoding error occurred. Otherwise, a nonzero value is returned.
25354 <sup><a name="note442" href="#note442"><b>442)</b></a></sup> When len is not less than dstmax, the implementation might fill the array before discovering a
25355 runtime-constraint violation.
25357 [<a name="p647" href="#p647">page 647</a>] (<a href="#Contents">Contents</a>)
25359 <a name="L" href="#L"><b> Annex L</b></a>
25362 <a name="L.1" href="#L.1"><b> L.1 Scope</b></a>
25363 1 This annex specifies optional behavior that can aid in the analyzability of C programs.
25364 2 An implementation that defines __STDC_ANALYZABLE__ shall conform to the
25365 specifications in this annex.<sup><a href="#note443"><b>443)</b></a></sup>
25366 <a name="L.2" href="#L.2"><b> L.2 Definitions</b></a>
25367 <a name="L.2.1" href="#L.2.1"><b> L.2.1</b></a>
25368 1 out-of-bounds store
25369 an (attempted) access (<a href="#3.1">3.1</a>) that, at run time, for a given computational state, would
25370 modify (or, for an object declared volatile, fetch) one or more bytes that lie outside
25371 the bounds permitted by this Standard.
25372 <a name="L.2.2" href="#L.2.2"><b> L.2.2</b></a>
25373 1 bounded undefined behavior
25374 undefined behavior (<a href="#3.4.3">3.4.3</a>) that does not perform an out-of-bounds store.
25375 2 NOTE 1 The behavior might perform a trap.
25377 3 NOTE 2 Any values produced or stored might be indeterminate values.
25379 <a name="L.2.3" href="#L.2.3"><b> L.2.3</b></a>
25380 1 critical undefined behavior
25381 undefined behavior that is not bounded undefined behavior.
25382 2 NOTE The behavior might perform an out-of-bounds store or perform a trap.
25387 <sup><a name="note443" href="#note443"><b>443)</b></a></sup> Implementations that do not define __STDC_ANALYZABLE__ are not required to conform to these
25390 [<a name="p648" href="#p648">page 648</a>] (<a href="#Contents">Contents</a>)
25392 <a name="L.3" href="#L.3"><b> L.3 Requirements</b></a>
25393 1 If the program performs a trap (<a href="#3.19.5">3.19.5</a>), the implementation is permitted to invoke a
25394 runtime-constraint handler. Any such semantics are implementation-defined.
25395 2 All undefined behavior shall be limited to bounded undefined behavior, except for the
25396 following which are permitted to result in critical undefined behavior:
25397 -- An object is referred to outside of its lifetime (<a href="#6.2.4">6.2.4</a>).
25398 -- An lvalue does not designate an object when evaluated (<a href="#6.3.2.1">6.3.2.1</a>).
25399 -- A pointer is used to call a function whose type is not compatible with the referenced
25400 type (<a href="#6.3.2.3">6.3.2.3</a>).
25401 -- The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
25402 -- Addition or subtraction of a pointer into, or just beyond, an array object and an
25403 integer type produces a result that points just beyond the array object and is used as
25404 the operand of a unary * operator that is evaluated (<a href="#6.5.6">6.5.6</a>).
25405 -- An argument to a library function has an invalid value or a type not expected by a
25406 function with variable number of arguments (<a href="#7.1.4">7.1.4</a>).
25407 -- The value of a pointer that refers to space deallocated by a call to the free or realloc
25408 function is used (<a href="#7.22.3">7.22.3</a>).
25409 -- A string or wide string utility function is instructed to access an array beyond the end
25410 of an object (<a href="#7.23.1">7.23.1</a>, <a href="#7.28.4">7.28.4</a>).
25415 [<a name="p649" href="#p649">page 649</a>] (<a href="#Contents">Contents</a>)
25418 <a name="Bibliography" href="#Bibliography"><b> Bibliography</b></a>
25419 1. ''The C Reference Manual'' by Dennis M. Ritchie, a version of which was
25420 published in The C Programming Language by Brian W. Kernighan and Dennis
25421 M. Ritchie, Prentice-Hall, Inc., (1978). Copyright owned by AT&T.
25422 2. 1984 /usr/group Standard by the /usr/group Standards Committee, Santa Clara,
25423 California, USA, November 1984.
25424 3. ANSI X3/TR-1-82 (1982), American National Dictionary for Information
25425 Processing Systems, Information Processing Systems Technical Report.
25426 4. ANSI/IEEE 754-1985, American National Standard for Binary Floating-Point
25428 5. ANSI/IEEE 854-1988, American National Standard for Radix-Independent
25429 Floating-Point Arithmetic.
25430 6. IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems,
25431 second edition (previously designated IEC 559:1989).
25432 7. ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and
25433 symbols for use in the physical sciences and technology.
25434 8. ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for
25435 information interchange.
25436 9. ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1:
25438 10. ISO 4217:1995, Codes for the representation of currencies and funds.
25439 11. ISO 8601:1988, Data elements and interchange formats -- Information
25440 interchange -- Representation of dates and times.
25441 12. ISO/IEC 9899:1990, Programming languages -- C.
25442 13. ISO/IEC 9899/COR1:1994, Technical Corrigendum 1.
25443 14. ISO/IEC 9899/COR2:1996, Technical Corrigendum 2.
25444 15. ISO/IEC 9899/AMD1:1995, Amendment 1 to ISO/IEC 9899:1990 C Integrity.
25445 16. ISO/IEC 9899:1999, Programming languages -- C.
25446 17. ISO/IEC 9899:1999/Cor.1:2001, Technical Corrigendum 1.
25447 18. ISO/IEC 9899:1999/Cor.2:2004, Technical Corrigendum 2.
25448 19. ISO/IEC 9899:1999/Cor.3:2007, Technical Corrigendum 3.
25452 [<a name="p650" href="#p650">page 650</a>] (<a href="#Contents">Contents</a>)
25454 20. ISO/IEC 9945-2:1993, Information technology -- Portable Operating System
25455 Interface (POSIX) -- Part 2: Shell and Utilities.
25456 21. ISO/IEC TR 10176:1998, Information technology -- Guidelines for the
25457 preparation of programming language standards.
25458 22. ISO/IEC 10646-1:1993, Information technology -- Universal Multiple-Octet
25459 Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
25460 23. ISO/IEC 10646-1/COR1:1996, Technical Corrigendum 1 to
25461 ISO/IEC 10646-1:1993.
25462 24. ISO/IEC 10646-1/COR2:1998, Technical Corrigendum 2 to
25463 ISO/IEC 10646-1:1993.
25464 25. ISO/IEC 10646-1/AMD1:1996, Amendment 1 to ISO/IEC 10646-1:1993
25465 Transformation Format for 16 planes of group 00 (UTF-16).
25466 26. ISO/IEC 10646-1/AMD2:1996, Amendment 2 to ISO/IEC 10646-1:1993 UCS
25467 Transformation Format 8 (UTF-8).
25468 27. ISO/IEC 10646-1/AMD3:1996, Amendment 3 to ISO/IEC 10646-1:1993.
25469 28. ISO/IEC 10646-1/AMD4:1996, Amendment 4 to ISO/IEC 10646-1:1993.
25470 29. ISO/IEC 10646-1/AMD5:1998, Amendment 5 to ISO/IEC 10646-1:1993 Hangul
25472 30. ISO/IEC 10646-1/AMD6:1997, Amendment 6 to ISO/IEC 10646-1:1993
25474 31. ISO/IEC 10646-1/AMD7:1997, Amendment 7 to ISO/IEC 10646-1:1993 33
25475 additional characters.
25476 32. ISO/IEC 10646-1/AMD8:1997, Amendment 8 to ISO/IEC 10646-1:1993.
25477 33. ISO/IEC 10646-1/AMD9:1997, Amendment 9 to ISO/IEC 10646-1:1993
25478 Identifiers for characters.
25479 34. ISO/IEC 10646-1/AMD10:1998, Amendment 10 to ISO/IEC 10646-1:1993
25481 35. ISO/IEC 10646-1/AMD11:1998, Amendment 11 to ISO/IEC 10646-1:1993
25482 Unified Canadian Aboriginal Syllabics.
25483 36. ISO/IEC 10646-1/AMD12:1998, Amendment 12 to ISO/IEC 10646-1:1993
25485 37. ISO/IEC 10967-1:1994, Information technology -- Language independent
25486 arithmetic -- Part 1: Integer and floating point arithmetic.
25489 [<a name="p651" href="#p651">page 651</a>] (<a href="#Contents">Contents</a>)
25491 38. ISO/IEC TR 19769:2004, Information technology -- Programming languages,
25492 their environments and system software interfaces -- Extensions for the
25493 programming language C to support new character data types.
25494 39. ISO/IEC TR 24731-1:2007, Information technology -- Programming languages,
25495 their environments and system software interfaces -- Extensions to the C library
25496 -- Part 1: Bounds-checking interfaces.
25501 [<a name="p652" href="#p652">page 652</a>] (<a href="#Contents">Contents</a>)
25504 <a name="Index" href="#Index"><b>Index</b></a>
25505 [^ 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>
25506 , (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>,
25507 [_ 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>
25508 ! (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>
25509 != (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>
25510 # 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>
25511 # 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>
25512 # punctuator, <a href="#6.10">6.10</a> -= (subtraction assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
25513 ## 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>
25514 #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>,
25515 #elif preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#6.5.2.3">6.5.2.3</a>
25516 #else preprocessing directive, <a href="#6.10.1">6.10.1</a> . punctuator, <a href="#6.7.9">6.7.9</a>
25517 #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>
25518 #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>
25519 #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>
25520 <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>
25521 #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>
25522 #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>
25523 #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>
25524 <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>,
25525 #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>
25526 #pragma preprocessing directive, <a href="#6.10.6">6.10.6</a> < (less-than operator), <a href="#6.5.8">6.5.8</a>
25527 #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>
25528 <a href="#7.1.4">7.1.4</a> <: (alternative spelling of [), <a href="#6.4.6">6.4.6</a>
25529 % (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>
25530 %: (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>
25531 %:%: (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>
25532 %= (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>
25533 %> (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>,
25534 & (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>
25535 & (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>
25536 && (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>
25537 &= (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>,
25538 ' ' (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>
25539 <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>,
25540 ( ) (cast operator), <a href="#6.5.4">6.5.4</a> <a href="#7.28.4.1.1">7.28.4.1.1</a>
25541 ( ) (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>
25542 ( ) (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>
25543 ( ){ } (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>
25544 * (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>
25545 * (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>,
25546 * (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>
25547 <a href="#G.5.1">G.5.1</a> <a href="#7.13"><setjmp.h></a> header, <a href="#7.13">7.13</a>
25548 *= (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>
25549 + (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>
25550 <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>
25551 + (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>
25552 ++ (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>
25553 ++ (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>,
25554 += (addition assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
25555 [<a name="p653" href="#p653">page 653</a>] (<a href="#Contents">Contents</a>)
25557 <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
25558 <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>
25559 <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>
25560 <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),
25561 <a href="#K.3.5">K.3.5</a> <a href="#6.5.16.2">6.5.16.2</a>
25562 <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>
25563 <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
25564 <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>
25565 <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>
25566 <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>
25567 <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>
25568 <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>
25569 <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>
25570 <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>
25571 <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>
25572 = (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>
25573 = (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>
25574 == (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>
25575 > (greater-than operator), <a href="#6.5.8">6.5.8</a> __STDC_IEC_559_COMPLEX__ macro,
25576 >= (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>
25577 >> (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>
25578 >>= (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>
25579 ? : (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,
25580 ?? (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>
25581 [ ] (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>,
25582 [ ] (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>
25583 \ (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>,
25584 \ (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>
25585 \" (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>
25586 <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>
25587 \\ (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>
25588 \' (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>
25589 \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>
25590 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>
25591 \? (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>
25592 \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>
25593 \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="#6.7.3">6.7.3</a>
25594 \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>, _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>,
25595 <a href="#7.4.1.10">7.4.1.10</a> <a href="#F.4">F.4</a>
25596 \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 conversions, <a href="#6.3.1.2">6.3.1.2</a>
25597 <a href="#7.4.1.10">7.4.1.10</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>
25598 \octal digits (octal-character escape sequence), _Complex_I macro, <a href="#7.3.1">7.3.1</a>
25599 <a href="#6.4.4.4">6.4.4.4</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>
25600 \r (carriage-return escape sequence), <a href="#5.2.2">5.2.2</a>, _Imaginary keyword, <a href="#G.2">G.2</a>
25601 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a> _Imaginary types, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a>
25602 \t (horizontal-tab escape sequence), <a href="#5.2.2">5.2.2</a>, _Imaginary_I macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a>
25603 <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> _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>
25604 \U (universal character names), <a href="#6.4.3">6.4.3</a> _IOLBF macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.5.6">7.21.5.6</a>
25605 \u (universal character names), <a href="#6.4.3">6.4.3</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>
25606 \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>, _Noreturn, <a href="#6.7.4">6.7.4</a>
25607 <a href="#7.4.1.10">7.4.1.10</a> _Pragma operator, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a>
25609 [<a name="p654" href="#p654">page 654</a>] (<a href="#Contents">Contents</a>)
25611 _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>
25612 _Thread_local storage-class specifier, <a href="#6.2.4">6.2.4</a>, and macro, <a href="#7.9">7.9</a>
25613 <a href="#6.7.1">6.7.1</a> AND operators
25614 { } (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>
25615 <a href="#6.8.2">6.8.2</a> bitwise assignment (&=), <a href="#6.5.16.2">6.5.16.2</a>
25616 { } (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>
25617 | (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>
25618 |= (bitwise inclusive OR assignment operator), anonymous structure, <a href="#6.7.2.1">6.7.2.1</a>
25619 <a href="#6.5.16.2">6.5.16.2</a> anonymous union, <a href="#6.7.2.1">6.7.2.1</a>
25620 || (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>
25621 ~ (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>
25622 argc (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a>
25623 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>
25624 <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>
25625 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>
25626 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>
25627 absolute-value functions macro, substitution, <a href="#6.10.3.1">6.10.3.1</a>
25628 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>
25629 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>
25630 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>
25631 abstract declarator, <a href="#6.7.7">6.7.7</a> arithmetic conversions, usual, see usual arithmetic
25632 abstract machine, <a href="#5.1.2.3">5.1.2.3</a> conversions
25633 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
25634 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>
25635 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>
25636 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>
25637 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>
25638 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>
25639 acquire fence, <a href="#7.17.4">7.17.4</a> unary, <a href="#6.5.3.3">6.5.3.3</a>
25640 acquire operation, <a href="#5.1.2.4">5.1.2.4</a> arithmetic types, <a href="#6.2.5">6.2.5</a>
25641 active position, <a href="#5.2.2">5.2.2</a> arithmetic, pointer, <a href="#6.5.6">6.5.6</a>
25642 actual argument, <a href="#3.3">3.3</a> array
25643 actual parameter (deprecated), <a href="#3.3">3.3</a> argument, <a href="#6.9.1">6.9.1</a>
25644 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>
25645 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>
25646 <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>
25647 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>
25648 address constant, <a href="#6.6">6.6</a> storage order, <a href="#6.5.2.1">6.5.2.1</a>
25649 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>
25650 address-free, <a href="#7.17.5">7.17.5</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
25651 aggregate initialization, <a href="#6.7.9">6.7.9</a> type, <a href="#6.2.5">6.2.5</a>
25652 aggregate types, <a href="#6.2.5">6.2.5</a> type conversion, <a href="#6.3.2.1">6.3.2.1</a>
25653 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>
25654 aliasing, <a href="#6.5">6.5</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
25655 alignas macro, <a href="#7.15">7.15</a> as-if rule, <a href="#5.1.2.3">5.1.2.3</a>
25656 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>
25657 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>
25658 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>
25659 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>
25660 alignment specifier, <a href="#6.7.5">6.7.5</a> asin type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a>
25661 alignof operator, <a href="#6.5.3">6.5.3</a>, <a href="#6.5.3.4">6.5.3.4</a> asinh functions, <a href="#7.12.5.2">7.12.5.2</a>, <a href="#F.10.2.2">F.10.2.2</a>
25663 [<a name="p655" href="#p655">page 655</a>] (<a href="#Contents">Contents</a>)
25665 asinh type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> atomic_is_lock_free generic function,
25666 asm keyword, <a href="#J.5.10">J.5.10</a> <a href="#7.17.5.1">7.17.5.1</a>
25667 assert macro, <a href="#7.2.1.1">7.2.1.1</a> ATOMIC_LLONG_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
25668 assert.h header, <a href="#7.2">7.2</a> atomic_load generic functions, <a href="#7.17.7.2">7.17.7.2</a>
25669 assignment ATOMIC_LONG_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
25670 compound, <a href="#6.5.16.2">6.5.16.2</a> ATOMIC_SHORT_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
25671 conversion, <a href="#6.5.16.1">6.5.16.1</a> atomic_signal_fence function, <a href="#7.17.4.2">7.17.4.2</a>
25672 expression, <a href="#6.5.16">6.5.16</a> atomic_store generic functions, <a href="#7.17.7.1">7.17.7.1</a>
25673 operators, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.16">6.5.16</a> atomic_thread_fence function, <a href="#7.17.4.1">7.17.4.1</a>
25674 simple, <a href="#6.5.16.1">6.5.16.1</a> ATOMIC_VAR_INIT macro, <a href="#7.17.2.1">7.17.2.1</a>
25675 associativity of operators, <a href="#6.5">6.5</a> ATOMIC_WCHAR_T_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
25676 asterisk punctuator (*), <a href="#6.7.6.1">6.7.6.1</a>, <a href="#6.7.6.2">6.7.6.2</a> atomics header, <a href="#7.17">7.17</a>
25677 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>, auto storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a>
25678 <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> automatic storage duration, <a href="#5.2.3">5.2.3</a>, <a href="#6.2.4">6.2.4</a>
25679 atan functions, <a href="#7.12.4.3">7.12.4.3</a>, <a href="#F.10.1.3">F.10.1.3</a>
25680 atan type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.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>
25681 atan2 functions, <a href="#7.12.4.4">7.12.4.4</a>, <a href="#F.10.1.4">F.10.1.4</a> backslash escape sequence (\\), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a>
25682 atan2 type-generic macro, <a href="#7.24">7.24</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>
25683 atanh functions, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#F.10.2.3">F.10.2.3</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>
25684 atanh type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> basic types, <a href="#6.2.5">6.2.5</a>
25685 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>, behavior, <a href="#3.4">3.4</a>
25686 <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> 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>,
25687 atof function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.1">7.22.1.1</a> <a href="#7.21.9.4">7.21.9.4</a>
25688 atoi function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.2">7.22.1.2</a> bit, <a href="#3.5">3.5</a>
25689 atol function, <a href="#7.22.1">7.22.1</a>, <a href="#7.22.1.2">7.22.1.2</a> high order, <a href="#3.6">3.6</a>
25690 atoll 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>
25691 atomic lock-free macros, <a href="#7.17.1">7.17.1</a>, <a href="#7.17.5">7.17.5</a> bit-field, <a href="#6.7.2.1">6.7.2.1</a>
25692 atomic operations, <a href="#5.1.2.4">5.1.2.4</a> bitand macro, <a href="#7.9">7.9</a>
25693 atomic types, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.2.5">6.2.5</a>, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.3.2.1">6.3.2.1</a>, bitor macro, <a href="#7.9">7.9</a>
25694 <a href="#6.5.2.3">6.5.2.3</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="#6.7.2.4">6.7.2.4</a>, <a href="#6.10.8.3">6.10.8.3</a>, bitwise operators, <a href="#6.5">6.5</a>
25695 <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>
25696 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>
25697 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>
25698 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>
25699 ATOMIC_CHAR16_T_LOCK_FREE macro, exclusive OR assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
25700 <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>
25701 ATOMIC_CHAR32_T_LOCK_FREE macro, inclusive OR assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
25702 <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>
25703 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>
25704 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>
25705 functions, <a href="#7.17.7.4">7.17.7.4</a> block scope, <a href="#6.2.1">6.2.1</a>
25706 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>
25707 atomic_fetch and modify generic functions, bold type convention, <a href="#6.1">6.1</a>
25708 <a href="#7.17.7.5">7.17.7.5</a> bool macro, <a href="#7.18">7.18</a>
25709 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>
25710 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>
25711 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>
25712 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>,
25713 <a href="#7.17.8.1">7.17.8.1</a> <a href="#6.8.2">6.8.2</a>
25714 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>
25715 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>
25717 [<a name="p656" href="#p656">page 656</a>] (<a href="#Contents">Contents</a>)
25719 branch cuts, <a href="#7.3.3">7.3.3</a> type-generic macro for, <a href="#7.24">7.24</a>
25720 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>
25721 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>
25722 <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>
25723 <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>
25724 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>
25725 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>
25726 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>
25727 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>
25728 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>
25729 byte input/output functions, <a href="#7.21.1">7.21.1</a> cexpm1 function, <a href="#7.30.1">7.30.1</a>
25730 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>,
25731 <a href="#K.3.9.1.2">K.3.9.1.2</a>
25732 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>,
25733 c16rtomb function, <a href="#7.27.1.2">7.27.1.2</a> <a href="#6.3.1.8">6.3.1.8</a>
25734 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>
25735 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>
25736 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>
25737 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>
25738 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>
25739 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>
25740 type-generic macro for, <a href="#7.24">7.24</a> character array initialization, <a href="#6.7.9">6.7.9</a>
25741 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>
25742 <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>
25743 <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>
25744 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>
25745 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>
25746 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>
25747 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>
25748 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>
25749 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>
25750 <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>
25751 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>
25752 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>
25753 case mapping functions character string literal, see string literal
25754 character, <a href="#7.4.2">7.4.2</a> character type conversion, <a href="#6.3.1.1">6.3.1.1</a>
25755 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>
25756 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>
25757 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>
25758 type-generic macro for, <a href="#7.24">7.24</a> cis function, <a href="#G.6">G.6</a>
25759 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
25760 type-generic macro for, <a href="#7.24">7.24</a> character, <a href="#7.4.1">7.4.1</a>
25761 cast expression, <a href="#6.5.4">6.5.4</a> floating-point, <a href="#7.12.3">7.12.3</a>
25762 cast operator (( )), <a href="#6.5.4">6.5.4</a> wide character, <a href="#7.29.2.1">7.29.2.1</a>
25763 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>
25764 type-generic macro for, <a href="#7.24">7.24</a> clearerr function, <a href="#7.21.10.1">7.21.10.1</a>
25765 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>
25766 type-generic macro for, <a href="#7.24">7.24</a> clock function, <a href="#7.26.2.1">7.26.2.1</a>
25767 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>
25768 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>
25769 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>
25771 [<a name="p657" href="#p657">page 657</a>] (<a href="#Contents">Contents</a>)
25773 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>
25774 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>
25775 clog1p function, <a href="#7.30.1">7.30.1</a> concatenation, preprocessing, see preprocessing
25776 clog2 function, <a href="#7.30.1">7.30.1</a> concatenation
25777 CMPLX macros, <a href="#7.3.9.3">7.3.9.3</a> conceptual models, <a href="#5.1">5.1</a>
25778 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>,
25779 <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>
25780 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>
25781 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>
25782 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>
25783 <a href="#7.25.3.6">7.25.3.6</a> conformance, <a href="#4">4</a>
25784 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>
25785 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>
25786 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>
25787 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>
25788 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>
25789 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>
25790 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>
25791 <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>
25792 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>
25793 comment delimiters (/* */ and //), <a href="#6.4.9">6.4.9</a> floating, <a href="#6.4.4.2">6.4.4.2</a>
25794 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>
25795 common extensions, <a href="#J.5">J.5</a> integer, <a href="#6.4.4.1">6.4.4.1</a>
25796 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>
25797 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>
25798 common warnings, <a href="#I">I</a> constraint_handler_t type, <a href="#K.3.6">K.3.6</a>
25799 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>
25800 <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>
25801 string, <a href="#7.23.4">7.23.4</a> contiguity of allocated storage, <a href="#7.22.3">7.22.3</a>
25802 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>
25803 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>
25804 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>
25805 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>
25806 compl macro, <a href="#7.9">7.9</a> conversion, <a href="#6.3">6.3</a>
25807 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>
25808 complete type, <a href="#6.2.5">6.2.5</a> array argument, <a href="#6.9.1">6.9.1</a>
25809 complex macro, <a href="#7.3.1">7.3.1</a> array parameter, <a href="#6.9.1">6.9.1</a>
25810 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>
25811 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>
25812 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>
25813 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>
25814 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>
25815 <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>
25816 compliance, see conformance explicit, <a href="#6.3">6.3</a>
25817 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>
25818 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>
25819 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>
25820 compound literals, <a href="#6.5.2.5">6.5.2.5</a> function parameter, <a href="#6.9.1">6.9.1</a>
25821 compound statement, <a href="#6.8.2">6.8.2</a> imaginary, <a href="#G.4.1">G.4.1</a>
25822 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>
25823 concatenation functions implicit, <a href="#6.3">6.3</a>
25825 [<a name="p658" href="#p658">page 658</a>] (<a href="#Contents">Contents</a>)
25827 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>
25828 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>
25829 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>
25830 real and imaginary, <a href="#G.4.2">G.4.2</a> type-generic macro for, <a href="#7.24">7.24</a>
25831 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>
25832 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>
25833 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>
25834 usual arithmetic, see usual arithmetic type-generic macro for, <a href="#7.24">7.24</a>
25835 conversions ctgamma function, <a href="#7.30.1">7.30.1</a>
25836 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>
25837 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>
25838 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>
25839 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>
25840 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>
25841 multibyte/wide string, <a href="#7.22.8">7.22.8</a>, <a href="#K.3.6.5">K.3.6.5</a>
25842 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>,
25843 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>,
25844 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>
25845 single byte/wide character, <a href="#7.28.6.1">7.28.6.1</a> data stream, see streams
25846 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>
25847 wide character, <a href="#7.28.5">7.28.5</a> Daylight Saving Time, <a href="#7.26.1">7.26.1</a>
25848 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>
25849 <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>
25850 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>
25851 <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>
25852 <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>
25853 <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>
25854 <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>
25855 <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>
25856 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>
25857 copying functions DBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25858 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>
25859 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>
25860 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>
25861 <a href="#F.10.8.1">F.10.8.1</a> decimal digit, <a href="#5.2.1">5.2.1</a>
25862 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>
25863 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>,
25864 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>
25865 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>
25866 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>
25867 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>
25868 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>
25869 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>
25870 type-generic macro for, <a href="#7.24">7.24</a> typedef, <a href="#6.7.8">6.7.8</a>
25871 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>
25872 cproj type-generic macro, <a href="#7.24">7.24</a> abstract, <a href="#6.7.7">6.7.7</a>
25873 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>
25874 creal type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> decrement operators, see arithmetic operators,
25875 critical undefined behavior, <a href="#L.2.3">L.2.3</a> increment and decrement
25876 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>
25877 type-generic macro for, <a href="#7.24">7.24</a> default initialization, <a href="#6.7.9">6.7.9</a>
25879 [<a name="p659" href="#p659">page 659</a>] (<a href="#Contents">Contents</a>)
25881 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>
25882 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>
25883 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>
25884 definition, <a href="#6.7">6.7</a> else statement, <a href="#6.8.4.1">6.8.4.1</a>
25885 function, <a href="#6.9.1">6.9.1</a> empty statement, <a href="#6.8.3">6.8.3</a>
25886 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>,
25887 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>,
25888 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>,
25889 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>,
25890 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>
25891 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>
25892 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>,
25893 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>,
25894 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>,
25895 difftime function, <a href="#7.26.2.2">7.26.2.2</a> <a href="#7.28.3.10">7.28.3.10</a>
25896 digit, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> end-of-file macro, see EOF macro
25897 digraphs, <a href="#6.4.6">6.4.6</a> end-of-line indicator, <a href="#5.2.1">5.2.1</a>
25898 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>
25899 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>
25900 div function, <a href="#7.22.6.2">7.22.6.2</a> enumerated type, <a href="#6.2.5">6.2.5</a>
25901 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>
25902 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>
25903 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>
25904 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>
25905 documentation of implementation, <a href="#4">4</a> enumeration specifiers, <a href="#6.7.2.2">6.7.2.2</a>
25906 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>
25907 <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>
25908 <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>
25909 <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>
25910 <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>
25911 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> environmental considerations, <a href="#5.2">5.2</a>
25912 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>,
25913 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>,
25914 <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>
25915 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>,
25916 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>,
25917 <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>,
25918 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>,
25919 <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>,
25920 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>,
25921 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>,
25922 <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>,
25923 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>,
25924 <a href="#K.3.9.1.14">K.3.9.1.14</a>
25925 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>
25926 effective type, <a href="#6.5">6.5</a> equal-to operator, see equality operator
25927 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>
25928 <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>
25929 <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>,
25930 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
25931 element type, <a href="#6.2.5">6.2.5</a> also range error, pole error
25933 [<a name="p660" href="#p660">page 660</a>] (<a href="#Contents">Contents</a>)
25935 erf functions, <a href="#7.12.8.1">7.12.8.1</a>, <a href="#F.10.5.1">F.10.5.1</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>
25936 erf type-generic macro, <a href="#7.24">7.24</a> exp2 type-generic macro, <a href="#7.24">7.24</a>
25937 erfc functions, <a href="#7.12.8.2">7.12.8.2</a>, <a href="#F.10.5.2">F.10.5.2</a> explicit conversion, <a href="#6.3">6.3</a>
25938 erfc type-generic macro, <a href="#7.24">7.24</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>
25939 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 type-generic macro, <a href="#7.24">7.24</a>
25940 <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>, exponent part, <a href="#6.4.4.2">6.4.4.2</a>
25941 <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>, exponential functions
25942 <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>, complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a>
25943 <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>, real, <a href="#7.12.6">7.12.6</a>, <a href="#F.10.3">F.10.3</a>
25944 <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>, expression, <a href="#6.5">6.5</a>
25945 <a href="#K.3.1.3">K.3.1.3</a>, <a href="#K.3.7.4.2">K.3.7.4.2</a> assignment, <a href="#6.5.16">6.5.16</a>
25946 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> cast, <a href="#6.5.4">6.5.4</a>
25947 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>, constant, <a href="#6.6">6.6</a>
25948 <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> evaluation, <a href="#5.1.2.3">5.1.2.3</a>
25949 error full, <a href="#6.8">6.8</a>
25950 domain, see domain error order of evaluation, see order of evaluation
25951 encoding, see encoding error parenthesized, <a href="#6.5.1">6.5.1</a>
25952 pole, see pole error primary, <a href="#6.5.1">6.5.1</a>
25953 range, see range error unary, <a href="#6.5.3">6.5.3</a>
25954 error conditions, <a href="#7.12.1">7.12.1</a> expression statement, <a href="#6.8.3">6.8.3</a>
25955 error functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.10.5">F.10.5</a> extended alignment, <a href="#6.2.8">6.2.8</a>
25956 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 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>
25957 <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 characters, <a href="#5.2.1">5.2.1</a>
25958 <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 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>,
25959 <a href="#7.28.3.1">7.28.3.1</a>, <a href="#7.28.3.3">7.28.3.3</a> <a href="#7.20">7.20</a>
25960 error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> extended multibyte/wide character conversion
25961 error-handling functions, <a href="#7.21.10">7.21.10</a>, <a href="#7.23.6.2">7.23.6.2</a>, utilities, <a href="#7.28.6">7.28.6</a>, <a href="#K.3.9.3">K.3.9.3</a>
25962 <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> extensible wide character case mapping functions,
25963 escape character (\), <a href="#6.4.4.4">6.4.4.4</a> <a href="#7.29.3.2">7.29.3.2</a>
25964 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> extensible wide character classification functions,
25965 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> <a href="#7.29.2.2">7.29.2.2</a>
25966 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> extern storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.7.1">6.7.1</a>
25967 evaluation of expression, <a href="#5.1.2.3">5.1.2.3</a> external definition, <a href="#6.9">6.9</a>
25968 evaluation order, see order of evaluation external identifiers, underscore, <a href="#7.1.3">7.1.3</a>
25969 exceptional condition, <a href="#6.5">6.5</a> external linkage, <a href="#6.2.2">6.2.2</a>
25970 excess precision, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> external name, <a href="#6.4.2.1">6.4.2.1</a>
25971 excess range, <a href="#5.2.4.2.2">5.2.4.2.2</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>
25972 exclusive OR operators
25973 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>
25974 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>
25975 executable program, <a href="#5.1.1.1">5.1.1.1</a> false macro, <a href="#7.18">7.18</a>
25976 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>
25977 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>
25978 environmental limits fdim type-generic macro, <a href="#7.24">7.24</a>
25979 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>
25980 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>
25981 <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>
25982 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>
25983 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>
25984 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>
25985 exp type-generic macro, <a href="#7.24">7.24</a> FE_OVERFLOW macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
25987 [<a name="p661" href="#p661">page 661</a>] (<a href="#Contents">Contents</a>)
25989 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>,
25990 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>
25991 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>
25992 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>
25993 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>,
25994 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>
25995 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>,
25996 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>
25997 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>
25998 <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>
25999 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>
26000 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>,
26001 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>
26002 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>
26003 <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>,
26004 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
26005 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>
26006 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>
26007 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>
26008 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>
26009 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>
26010 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>
26011 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>
26012 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>
26013 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>
26014 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>
26015 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>
26016 <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>
26017 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>
26018 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>,
26019 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>
26020 <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>
26021 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>
26022 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>
26023 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>
26024 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>
26025 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>
26026 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>
26027 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>
26028 <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>,
26029 <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>
26030 <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>
26031 <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>
26032 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>
26033 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>
26034 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>
26035 FILENAME_MAX macro, <a href="#7.21.1">7.21.1</a> fmax type-generic macro, <a href="#7.24">7.24</a>
26036 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>
26037 status flag fmin type-generic macro, <a href="#7.24">7.24</a>
26038 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>
26039 float _Complex type, <a href="#6.2.5">6.2.5</a> fmod type-generic macro, <a href="#7.24">7.24</a>
26041 [<a name="p662" href="#p662">page 662</a>] (<a href="#Contents">Contents</a>)
26043 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>
26044 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>,
26045 <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>
26046 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>,
26047 <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>
26048 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>
26049 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>
26050 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>
26051 <a href="#7.4.1.10">7.4.1.10</a> fully buffered stream, <a href="#7.21.3">7.21.3</a>
26052 formal argument (deprecated), <a href="#3.16">3.16</a> function
26053 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>
26054 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>
26055 <a href="#K.3.5.3">K.3.5.3</a> call, <a href="#6.5.2.2">6.5.2.2</a>
26056 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>
26057 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>
26058 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>
26059 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>
26060 also contracted expression image, <a href="#5.2.3">5.2.3</a>
26061 FP_FAST_FMA macro, <a href="#7.12">7.12</a> inline, <a href="#6.7.4">6.7.4</a>
26062 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>
26063 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>
26064 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>
26065 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>
26066 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>,
26067 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>
26068 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>
26069 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>
26070 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>
26071 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>
26072 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>
26073 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>
26074 <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>
26075 <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>
26076 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>
26077 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>
26078 <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>
26079 fputs function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.4">7.21.7.4</a> future directions
26080 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>
26081 <a href="#7.28.3.8">7.28.3.8</a> library, <a href="#7.30">7.30</a>
26082 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>
26083 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>,
26084 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>,
26085 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>
26086 <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>
26087 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>
26088 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>,
26089 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>,
26090 frexp type-generic macro, <a href="#7.24">7.24</a> <a href="#K.3.9.1.2">K.3.9.1.2</a>
26091 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>,
26092 <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>
26093 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>,
26095 [<a name="p663" href="#p663">page 663</a>] (<a href="#Contents">Contents</a>)
26097 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>
26098 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>
26099 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>
26100 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>
26101 generic parameters, <a href="#7.24">7.24</a> identifier list, <a href="#6.7.6">6.7.6</a>
26102 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>
26103 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>
26104 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>,
26105 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>,
26106 getenv_s function, <a href="#K.3.6.2.1">K.3.6.2.1</a> <a href="#H.1">H.1</a>
26107 gets function, <a href="#K.3.5.4.1">K.3.5.4.1</a> IEEE 754, <a href="#F.1">F.1</a>
26108 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>
26109 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
26110 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,
26111 gmtime function, <a href="#7.26.3.3">7.26.3.3</a> ANSI/IEEE 854
26112 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>,
26113 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>
26114 graphic characters, <a href="#5.2.1">5.2.1</a> if statement, <a href="#6.8.4.1">6.8.4.1</a>
26115 greater-than operator (>), <a href="#6.5.8">6.5.8</a> ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a>
26116 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>
26117 ignore_handler_s function, <a href="#K.3.6.1.3">K.3.6.1.3</a>
26118 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>
26119 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>
26120 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>
26121 hexadecimal constant, <a href="#6.4.4.1">6.4.4.1</a> imaginary numbers, <a href="#G">G</a>
26122 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>
26123 hexadecimal prefix, <a href="#6.4.4.1">6.4.4.1</a> imaginary types, <a href="#G">G</a>
26124 hexadecimal-character escape sequence imaxabs function, <a href="#7.8.2.1">7.8.2.1</a>
26125 (\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>
26126 high-order bit, <a href="#3.6">3.6</a> imaxdiv_t type, <a href="#7.8">7.8</a>
26127 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>
26128 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>,
26129 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
26130 <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
26131 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>
26132 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>
26133 <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>
26134 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>
26135 <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>
26136 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
26137 <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>
26138 hyperbolic functions bitwise assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
26139 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>
26140 real, <a href="#7.12.5">7.12.5</a>, <a href="#F.10.2">F.10.2</a> increment operators, see arithmetic operators,
26141 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
26142 hypot type-generic macro, <a href="#7.24">7.24</a> indeterminate value, <a href="#3.19.2">3.19.2</a>
26143 indeterminately sequenced, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5.2.2">6.5.2.2</a>,
26144 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,
26145 identifier, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.5.1">6.5.1</a> unsequenced
26146 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>
26147 maximum length, <a href="#6.4.2.1">6.4.2.1</a> inequality operator (!=), <a href="#6.5.9">6.5.9</a>
26149 [<a name="p664" href="#p664">page 664</a>] (<a href="#Contents">Contents</a>)
26151 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>
26152 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>
26153 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>
26154 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>
26155 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>
26156 <a href="#F.8.5">F.8.5</a> interrupt, <a href="#5.2.3">5.2.3</a>
26157 in blocks, <a href="#6.8">6.8</a> INTMAX_C macro, <a href="#7.20.4.2">7.20.4.2</a>
26158 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>
26159 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>
26160 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>,
26161 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>
26162 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>
26163 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>
26164 <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>
26165 <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>
26166 <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>
26167 input/output functions INTPTR_MIN macro, <a href="#7.20.2.4">7.20.2.4</a>
26168 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>
26169 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>
26170 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>
26171 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>
26172 wide character, <a href="#7.28.3">7.28.3</a> isblank function, <a href="#7.4.1.3">7.4.1.3</a>
26173 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>,
26174 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>
26175 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>,
26176 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>
26177 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>
26178 <a href="#6.3.1.8">6.3.1.8</a> isgraph function, <a href="#7.4.1.6">7.4.1.6</a>
26179 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>
26180 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>
26181 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>
26182 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>
26183 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>
26184 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>
26185 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>,
26186 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>
26187 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>
26188 <a href="#7.22.6">7.22.6</a> isnormal macro, <a href="#7.12.3.5">7.12.3.5</a>
26189 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>
26190 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>
26191 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>
26192 <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>
26193 <a href="#7.1.4">7.1.4</a> ISO/IEC 10976-1, <a href="#H.1">H.1</a>
26194 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>
26195 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>
26196 <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>
26197 <a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a> iso646.h header, <a href="#4">4</a>, <a href="#7.9">7.9</a> *
26198 integer suffix, <a href="#6.4.4.1">6.4.4.1</a> isprint function, <a href="#5.2.2">5.2.2</a>, <a href="#7.4.1.8">7.4.1.8</a>
26199 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>, 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>,
26200 <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> <a href="#7.4.1.11">7.4.1.11</a>
26201 integer types, <a href="#6.2.5">6.2.5</a>, <a href="#7.20">7.20</a> isspace function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>,
26203 [<a name="p665" href="#p665">page 665</a>] (<a href="#Contents">Contents</a>)
26205 <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>
26206 <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>,
26207 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>
26208 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>,
26209 <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>,
26210 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>
26211 <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>
26212 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>
26213 <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>
26214 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>
26215 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>
26216 <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>
26217 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>
26218 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>
26219 <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>
26220 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>
26221 <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>
26222 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>
26223 <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>
26224 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>
26225 <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>
26226 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>
26227 <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>
26228 <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>
26229 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>
26230 <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>
26231 <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>
26232 <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>
26233 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>
26234 <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
26235 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>
26236 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>
26237 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>
26238 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>
26239 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>,
26240 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>
26241 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>,
26242 <a href="#7.28.2.2">7.28.2.2</a>
26243 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>
26244 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>
26245 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>
26246 lexical elements, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>
26247 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>
26248 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>
26249 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>
26250 labeled statement, <a href="#6.8.1">6.8.1</a> future directions, <a href="#7.30">7.30</a>
26251 labs function, <a href="#7.22.6.1">7.22.6.1</a> summary, <a href="#B">B</a>
26252 language, <a href="#6">6</a> terms, <a href="#7.1.1">7.1.1</a>
26253 future directions, <a href="#6.11">6.11</a> use of functions, <a href="#7.1.4">7.1.4</a>
26254 syntax summary, <a href="#A">A</a> lifetime, <a href="#6.2.4">6.2.4</a>
26255 Latin alphabet, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.2.1">6.4.2.1</a> limits
26257 [<a name="p666" href="#p666">page 666</a>] (<a href="#Contents">Contents</a>)
26259 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>
26260 implementation, see implementation limits long double _Imaginary type, <a href="#G.2">G.2</a>
26261 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>
26262 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>,
26263 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>
26264 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>,
26265 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>
26266 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>,
26267 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>
26268 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>,
26269 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>
26270 <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>
26271 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>,
26272 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>
26273 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>,
26274 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>
26275 <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>
26276 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>
26277 <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>
26278 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>,
26279 llrint type-generic macro, <a href="#7.24">7.24</a> <a href="#7.22.4.7">7.22.4.7</a>
26280 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>
26281 llround type-generic macro, <a href="#7.24">7.24</a> low-order bit, <a href="#3.6">3.6</a>
26282 local time, <a href="#7.26.1">7.26.1</a> lowercase letter, <a href="#5.2.1">5.2.1</a>
26283 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>
26284 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>
26285 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>
26286 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>
26287 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>,
26288 localtime function, <a href="#7.26.3.4">7.26.3.4</a> <a href="#6.7.2.4">6.7.2.4</a>
26289 localtime_s function, <a href="#K.3.8.2.4">K.3.8.2.4</a> lvalue conversion, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.16">6.5.16</a>, <a href="#6.5.16.1">6.5.16.1</a>,
26290 log functions, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#F.10.3.7">F.10.3.7</a> <a href="#6.5.16.2">6.5.16.2</a>
26291 log type-generic macro, <a href="#7.24">7.24</a>
26292 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 argument substitution, <a href="#6.10.3.1">6.10.3.1</a>
26293 log10 type-generic macro, <a href="#7.24">7.24</a> macro definition
26294 log1p functions, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#F.10.3.9">F.10.3.9</a> library function, <a href="#7.1.4">7.1.4</a>
26295 log1p type-generic macro, <a href="#7.24">7.24</a> macro invocation, <a href="#6.10.3">6.10.3</a>
26296 log2 functions, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#F.10.3.10">F.10.3.10</a> macro name, <a href="#6.10.3">6.10.3</a>
26297 log2 type-generic macro, <a href="#7.24">7.24</a> length, <a href="#5.2.4.1">5.2.4.1</a>
26298 logarithmic functions predefined, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a>
26299 complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a> redefinition, <a href="#6.10.3">6.10.3</a>
26300 real, <a href="#7.12.6">7.12.6</a>, <a href="#F.10.3">F.10.3</a> scope, <a href="#6.10.3.5">6.10.3.5</a>
26301 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> macro parameter, <a href="#6.10.3">6.10.3</a>
26302 logb type-generic macro, <a href="#7.24">7.24</a> macro preprocessor, <a href="#6.10">6.10</a>
26303 logical operators macro replacement, <a href="#6.10.3">6.10.3</a>
26304 AND (&&), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.13">6.5.13</a> magnitude, complex, <a href="#7.3.8.1">7.3.8.1</a>
26305 negation (!), <a href="#6.5.3.3">6.5.3.3</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>,
26306 OR (||), <a href="#5.1.2.4">5.1.2.4</a>, <a href="#6.5.14">6.5.14</a> <a href="#7.21.3">7.21.3</a>
26307 logical source lines, <a href="#5.1.1.2">5.1.1.2</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>
26308 long double _Complex type, <a href="#6.2.5">6.2.5</a> manipulation functions
26309 long double _Complex type conversion, complex, <a href="#7.3.9">7.3.9</a>
26311 [<a name="p667" href="#p667">page 667</a>] (<a href="#Contents">Contents</a>)
26313 real, <a href="#7.12.11">7.12.11</a>, <a href="#F.10.8">F.10.8</a> modf functions, <a href="#7.12.6.12">7.12.6.12</a>, <a href="#F.10.3.12">F.10.3.12</a>
26314 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>, modifiable lvalue, <a href="#6.3.2.1">6.3.2.1</a>
26315 <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>
26316 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>
26317 <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>
26318 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>
26319 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>
26320 MATH_ERRNO macro, <a href="#7.12">7.12</a> mtx_lock function, <a href="#7.25.4.3">7.25.4.3</a>
26321 max_align_t type, <a href="#7.19">7.19</a> mtx_t type, <a href="#7.25.1">7.25.1</a>
26322 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>
26323 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>
26324 <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>,
26325 <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>
26326 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>
26327 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
26328 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>
26329 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>
26330 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>
26331 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>
26332 <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>
26333 <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>
26334 mbsinit function, <a href="#7.28.6.2.1">7.28.6.2.1</a> multibyte/wide character conversion functions,
26335 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>
26336 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>
26337 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>
26338 <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,
26339 <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>
26340 <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>
26341 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>
26342 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>
26343 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>,
26344 <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>
26345 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>
26346 member alignment, <a href="#6.7.2.1">6.7.2.1</a>
26347 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>
26348 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>
26349 memcpy function, <a href="#7.23.2.1">7.23.2.1</a> name
26350 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>
26351 memmove function, <a href="#7.23.2.2">7.23.2.2</a> file, <a href="#7.21.3">7.21.3</a>
26352 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>
26353 memory location, <a href="#3.14">3.14</a> label, <a href="#6.2.3">6.2.3</a>
26354 memory management functions, <a href="#7.22.3">7.22.3</a> structure/union member, <a href="#6.2.3">6.2.3</a>
26355 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>
26356 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>
26357 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>
26358 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>
26359 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>
26360 miscellaneous functions NDEBUG macro, <a href="#7.2">7.2</a>
26361 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>,
26362 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>
26363 mktime function, <a href="#7.26.2.3">7.26.2.3</a> nearbyint type-generic macro, <a href="#7.24">7.24</a>
26365 [<a name="p668" href="#p668">page 668</a>] (<a href="#Contents">Contents</a>)
26367 nearest integer functions, <a href="#7.12.9">7.12.9</a>, <a href="#F.10.6">F.10.6</a> operating system, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#7.22.4.8">7.22.4.8</a>
26368 negation operator (!), <a href="#6.5.3.3">6.5.3.3</a> operations on files, <a href="#7.21.4">7.21.4</a>, <a href="#K.3.5.1">K.3.5.1</a>
26369 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>
26370 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>
26371 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>
26372 <a href="#7.4.1.10">7.4.1.10</a> alignof, <a href="#6.5.3.4">6.5.3.4</a>
26373 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>
26374 <a href="#F.10.8.3">F.10.8.3</a> associativity, <a href="#6.5">6.5</a>
26375 nextafter type-generic macro, <a href="#7.24">7.24</a> equality, <a href="#6.5.9">6.5.9</a>
26376 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>
26377 nexttoward type-generic macro, <a href="#7.24">7.24</a> postfix, <a href="#6.5.2">6.5.2</a>
26378 no linkage, <a href="#6.2.2">6.2.2</a> precedence, <a href="#6.5">6.5</a>
26379 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>
26380 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>
26381 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>
26382 nonlocal jumps header, <a href="#7.13">7.13</a> sizeof, <a href="#6.5.3.4">6.5.3.4</a>
26383 norm, complex, <a href="#7.3.8.1">7.3.8.1</a> unary, <a href="#6.5.3">6.5.3</a>
26384 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>
26385 not macro, <a href="#7.9">7.9</a> optional features, see conditional features
26386 not-equal-to operator, see inequality operator or macro, <a href="#7.9">7.9</a>
26387 not_eq macro, <a href="#7.9">7.9</a> OR operators
26388 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>
26389 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>
26390 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>
26391 <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>
26392 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>
26393 null pointer constant, <a href="#6.3.2.3">6.3.2.3</a> or_eq macro, <a href="#7.9">7.9</a>
26394 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>
26395 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>,
26396 null wide character, <a href="#7.1.1">7.1.1</a> see also sequence points
26397 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>
26398 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>
26399 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>
26400 numerical limits, <a href="#5.2.4.2">5.2.4.2</a> outer scope, <a href="#6.2.1">6.2.1</a>
26401 over-aligned, <a href="#6.2.8">6.2.8</a>
26402 object, <a href="#3.15">3.15</a>
26403 object representation, <a href="#6.2.6.1">6.2.6.1</a> padding
26404 object type, <a href="#6.2.5">6.2.5</a> binary stream, <a href="#7.21.2">7.21.2</a>
26405 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>
26406 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>
26407 obsolescence, <a href="#6.11">6.11</a>, <a href="#7.30">7.30</a> parameter, <a href="#3.16">3.16</a>
26408 octal constant, <a href="#6.4.4.1">6.4.4.1</a> array, <a href="#6.9.1">6.9.1</a>
26409 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>
26410 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>
26411 <a href="#6.4.4.4">6.4.4.4</a> macro, <a href="#6.10.3">6.10.3</a>
26412 offsetof macro, <a href="#7.19">7.19</a> main function, <a href="#5.1.2.2.1">5.1.2.2.1</a>
26413 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>
26414 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>
26415 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>
26416 ones' complement, <a href="#6.2.6.2">6.2.6.2</a> parenthesized expression, <a href="#6.5.1">6.5.1</a>
26417 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>
26419 [<a name="p669" href="#p669">page 669</a>] (<a href="#Contents">Contents</a>)
26421 perform a trap, <a href="#3.19.5">3.19.5</a> preprocessor, <a href="#6.10">6.10</a>
26422 permitted form of initializer, <a href="#6.6">6.6</a> PRIcFASTN macros, <a href="#7.8.1">7.8.1</a>
26423 perror function, <a href="#7.21.10.4">7.21.10.4</a> PRIcLEASTN macros, <a href="#7.8.1">7.8.1</a>
26424 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>
26425 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>
26426 placemarker, <a href="#6.10.3.3">6.10.3.3</a> PRIcPTR macros, <a href="#7.8.1">7.8.1</a>
26427 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>
26428 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>,
26429 pointer comparison, <a href="#6.5.8">6.5.8</a> <a href="#K.3.5.3.3">K.3.5.3.3</a>
26430 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>
26431 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>
26432 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>
26433 pointer type, <a href="#6.2.5">6.2.5</a> program diagnostics, <a href="#7.2.1">7.2.1</a>
26434 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>
26435 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>
26436 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>
26437 <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>
26438 <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>
26439 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>
26440 position indicator, file, see file position indicator program structure, <a href="#5.1.1.1">5.1.1.1</a>
26441 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>,
26442 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>
26443 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>
26444 postfix expressions, <a href="#6.5.2">6.5.2</a> program, strictly conforming, <a href="#4">4</a>
26445 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
26446 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>
26447 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>
26448 power functions prototype, see function prototype
26449 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>
26450 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>
26451 pp-number, <a href="#6.4.8">6.4.8</a> PTRDIFF_MIN macro, <a href="#7.20.3">7.20.3</a>
26452 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>,
26453 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>
26454 precedence of operators, <a href="#6.5">6.5</a> punctuators, <a href="#6.4.6">6.4.6</a>
26455 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>
26456 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>
26457 excess, <a href="#5.2.4.2.2">5.2.4.2.2</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>
26458 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>
26459 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>
26460 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>
26461 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>
26462 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>
26463 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>
26464 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>
26465 preprocessing operators question-mark escape sequence (\?), <a href="#6.4.4.4">6.4.4.4</a>
26466 #, <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>,
26467 ##, <a href="#6.10.3.3">6.10.3.3</a> <a href="#7.22.4.7">7.22.4.7</a>
26468 _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>
26469 defined, <a href="#6.10.1">6.10.1</a>
26470 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>
26471 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>
26473 [<a name="p670" href="#p670">page 670</a>] (<a href="#Contents">Contents</a>)
26475 RAND_MAX macro, <a href="#7.22">7.22</a>, <a href="#7.22.2.1">7.22.2.1</a> restrict-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a>
26476 range return statement, <a href="#6.8.6.4">6.8.6.4</a>, <a href="#F.6">F.6</a>
26477 excess, <a href="#5.2.4.2.2">5.2.4.2.2</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>,
26478 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>
26479 <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>
26480 <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>
26481 <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>
26482 <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>
26483 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>
26484 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>
26485 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>
26486 <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>,
26487 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>,
26488 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>,
26489 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>,
26490 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>,
26491 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>,
26492 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>,
26493 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>,
26494 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>,
26495 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>,
26496 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>
26497 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>,
26498 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>
26499 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>
26500 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>
26501 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>
26502 release fence, <a href="#7.17.4">7.17.4</a>
26503 release operation, <a href="#5.1.2.4">5.1.2.4</a> same scope, <a href="#6.2.1">6.2.1</a>
26504 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>
26505 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>
26506 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>
26507 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>
26508 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>
26509 <a href="#F.10.7.2">F.10.7.2</a> scalbn type-generic macro, <a href="#7.24">7.24</a>
26510 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>
26511 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>
26512 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>
26513 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>
26514 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>
26515 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>
26516 representations of types, <a href="#6.2.6">6.2.6</a> SCNcFASTN macros, <a href="#7.8.1">7.8.1</a>
26517 pointer, <a href="#6.2.5">6.2.5</a> SCNcLEASTN macros, <a href="#7.8.1">7.8.1</a>
26518 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>
26519 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>
26520 restartable multibyte/wide character conversion SCNcPTR macros, <a href="#7.8.1">7.8.1</a>
26521 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>
26522 restartable multibyte/wide string conversion search functions
26523 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>
26524 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>
26525 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>
26527 [<a name="p671" href="#p671">page 671</a>] (<a href="#Contents">Contents</a>)
26529 SEEK_CUR macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.9.2">7.21.9.2</a> sign and magnitude, <a href="#6.2.6.2">6.2.6.2</a>
26530 SEEK_END macro, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.9.2">7.21.9.2</a> sign bit, <a href="#6.2.6.2">6.2.6.2</a>
26531 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>
26532 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>
26533 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>
26534 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>
26535 <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>
26536 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>
26537 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>
26538 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>,
26539 <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>
26540 <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>
26541 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>
26542 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>,
26543 <a href="#6.5.16">6.5.16</a>, see also indeterminately sequenced, <a href="#6.3.1.8">6.3.1.8</a>
26544 unsequenced signed types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>
26545 sequencing of statements, <a href="#6.8">6.8</a> significand part, <a href="#6.4.4.2">6.4.4.2</a>
26546 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>
26547 <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>
26548 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>
26549 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>
26550 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>
26551 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>
26552 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,
26553 <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>
26554 shall, <a href="#4">4</a> single-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a>
26555 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>
26556 shift sequence, <a href="#7.1.1">7.1.1</a> singularity, <a href="#7.12.1">7.12.1</a>
26557 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>
26558 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>
26559 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>
26560 <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>,
26561 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>,
26562 <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>,
26563 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>
26564 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>
26565 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>,
26566 <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>
26567 <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>
26568 <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>
26569 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>
26570 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>
26571 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>
26572 <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>
26573 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>
26574 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>
26575 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>
26576 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>,
26577 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>
26578 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>
26579 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>
26581 [<a name="p672" href="#p672">page 672</a>] (<a href="#Contents">Contents</a>)
26583 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> do, <a href="#6.8.5.2">6.8.5.2</a>
26584 sqrt type-generic macro, <a href="#7.24">7.24</a> else, <a href="#6.8.4.1">6.8.4.1</a>
26585 srand function, <a href="#7.22.2.2">7.22.2.2</a> expression, <a href="#6.8.3">6.8.3</a>
26586 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>
26587 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>
26588 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>
26589 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>
26590 <a href="#7.2"><assert.h></a>, <a href="#7.2">7.2</a> jump, <a href="#6.8.6">6.8.6</a>
26591 <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>
26592 <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>
26593 <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>
26594 <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>
26595 <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>
26596 <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>
26597 <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>
26598 <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>
26599 <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>
26600 <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>
26601 <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>
26602 <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>
26603 <a href="#J.5.17">J.5.17</a> static_assert macro, <a href="#7.2">7.2</a>
26604 <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>
26605 <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>
26606 <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>
26607 <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>
26608 <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>
26609 <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>,
26610 <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>
26611 <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>
26612 <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>,
26613 <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>,
26614 <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>
26615 <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>,
26616 <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>
26617 <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>
26618 <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>,
26619 <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>
26620 <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>,
26621 <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>
26622 <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>
26623 <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>
26624 <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>
26625 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>
26626 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>
26627 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>
26628 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>
26629 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>
26630 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>
26631 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>
26632 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>
26633 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>
26635 [<a name="p673" href="#p673">page 673</a>] (<a href="#Contents">Contents</a>)
26637 streams, <a href="#7.21.2">7.21.2</a>, <a href="#7.22.4.4">7.22.4.4</a> <a href="#7.22.1.4">7.22.1.4</a>, <a href="#7.28.2.2">7.28.2.2</a>
26638 fully buffered, <a href="#7.21.3">7.21.3</a> strtoull function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1.2">7.22.1.2</a>, <a href="#7.22.1.4">7.22.1.4</a>
26639 line buffered, <a href="#7.21.3">7.21.3</a> strtoumax function, <a href="#7.8.2.3">7.8.2.3</a>
26640 orientation, <a href="#7.21.2">7.21.2</a> struct hack, see flexible array member
26641 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>
26642 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>
26643 standard output, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> structure
26644 unbuffered, <a href="#7.21.3">7.21.3</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
26645 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>
26646 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>
26647 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>
26648 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>
26649 <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>
26650 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>
26651 strictly conforming program, <a href="#4">4</a> pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a>
26652 string, <a href="#7.1.1">7.1.1</a> specifier, <a href="#6.7.2.1">6.7.2.1</a>
26653 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>
26654 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>
26655 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>
26656 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>
26657 library function conventions, <a href="#7.23.1">7.23.1</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
26658 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>
26659 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>
26660 numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a> suffix
26661 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>
26662 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>
26663 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>
26664 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>
26665 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>
26666 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>
26667 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>,
26668 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>
26669 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>
26670 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>
26671 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>
26672 stronger, <a href="#6.2.8">6.2.8</a> symbols, <a href="#3">3</a>
26673 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>
26674 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>
26675 strspn function, <a href="#7.23.5.6">7.23.5.6</a> syntactic categories, <a href="#6.1">6.1</a>
26676 strstr function, <a href="#7.23.5.7">7.23.5.7</a> syntax notation, <a href="#6.1">6.1</a>
26677 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>
26678 <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>
26679 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>
26680 strtoimax function, <a href="#7.8.2.3">7.8.2.3</a>
26681 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>
26682 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>
26683 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>
26684 <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>
26685 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>
26686 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>
26687 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>
26689 [<a name="p674" href="#p674">page 674</a>] (<a href="#Contents">Contents</a>)
26691 tanh type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> toupper function, <a href="#7.4.2.2">7.4.2.2</a>
26692 temporary lifetime, <a href="#6.2.4">6.2.4</a> towctrans function, <a href="#7.29.3.2.1">7.29.3.2.1</a>, <a href="#7.29.3.2.2">7.29.3.2.2</a>
26693 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>
26694 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>
26695 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>
26696 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>
26697 tgamma type-generic macro, <a href="#7.24">7.24</a> translation phases, <a href="#5.1.1.2">5.1.1.2</a>
26698 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>
26699 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
26700 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>,
26701 thrd_detach function, <a href="#7.25.5.3">7.25.5.3</a> <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.5.2.3">6.5.2.3</a>
26702 thrd_equal function, <a href="#7.25.5.4">7.25.5.4</a> trigonometric functions
26703 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>
26704 thrd_join function, <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>
26705 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>
26706 thrd_start_t type, <a href="#7.25.1">7.25.1</a> true macro, <a href="#7.18">7.18</a>
26707 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>
26708 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>
26709 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>
26710 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>
26711 threads header, <a href="#7.25">7.25</a> tss_create function, <a href="#7.25.6.1">7.25.6.1</a>
26712 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>
26713 time TSS_DTOR_ITERATIONS macro, <a href="#7.25.1">7.25.1</a>
26714 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>
26715 <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>
26716 <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>
26717 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>
26718 <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>
26719 <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>
26720 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>
26721 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>
26722 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>
26723 local, <a href="#7.26.1">7.26.1</a> type names, <a href="#6.7.7">6.7.7</a>
26724 manipulation functions, <a href="#7.26.2">7.26.2</a> type punning, <a href="#6.5.2.3">6.5.2.3</a>
26725 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>
26726 time function, <a href="#7.26.2.4">7.26.2.4</a> type specifiers, <a href="#6.7.2">6.7.2</a>
26727 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>
26728 time_t type, <a href="#7.26.1">7.26.1</a> typedef declaration, <a href="#6.7.8">6.7.8</a>
26729 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>
26730 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>
26731 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, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.2.5">6.2.5</a>, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a>,
26732 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="#6.7.2.4">6.7.2.4</a>, <a href="#6.10.8.3">6.10.8.3</a>, <a href="#7.17.6">7.17.6</a>
26733 tmpfile function, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.22.4.4">7.22.4.4</a> character, <a href="#6.7.9">6.7.9</a>
26734 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> 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>
26735 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>, complex, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a>
26736 <a href="#K.3.5.1.2">K.3.5.1.2</a> composite, <a href="#6.2.7">6.2.7</a>
26737 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> const qualified, <a href="#6.7.3">6.7.3</a>
26738 token, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, see also preprocessing tokens conversions, <a href="#6.3">6.3</a>
26739 token concatenation, <a href="#6.10.3.3">6.10.3.3</a> imaginary, <a href="#G">G</a>
26740 token pasting, <a href="#6.10.3.3">6.10.3.3</a> restrict qualified, <a href="#6.7.3">6.7.3</a>
26741 tolower function, <a href="#7.4.2.1">7.4.2.1</a> volatile qualified, <a href="#6.7.3">6.7.3</a>
26743 [<a name="p675" href="#p675">page 675</a>] (<a href="#Contents">Contents</a>)
26745 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>
26746 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>
26747 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>
26748 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>
26749 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
26750 uint_least32_t type, <a href="#7.27">7.27</a> indeterminately sequenced, sequenced
26751 UINT_LEASTN_MAX macros, <a href="#7.20.2.2">7.20.2.2</a> before
26752 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>
26753 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>
26754 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>
26755 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>,
26756 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>
26757 <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>,
26758 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>
26759 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>
26760 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>
26761 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>
26762 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>
26763 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>
26764 <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>,
26765 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>
26766 <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>
26767 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>
26768 unary expression, <a href="#6.5.3">6.5.3</a> UTF-8 string literal, see string literal
26769 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>
26770 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>
26771 unary plus operator (+), <a href="#6.5.3.3">6.5.3.3</a>
26772 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>,
26773 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>,
26774 <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>,
26775 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>,
26776 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>,
26777 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>
26778 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>,
26779 <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>
26780 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>,
26781 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>,
26782 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>,
26783 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>,
26784 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>,
26785 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>
26786 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>
26787 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>,
26788 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>,
26789 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>,
26790 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>,
26791 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>,
26792 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>,
26793 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>
26794 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>
26795 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>
26797 [<a name="p676" href="#p676">page 676</a>] (<a href="#Contents">Contents</a>)
26799 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>
26800 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>
26801 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>
26802 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>
26803 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>
26804 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>
26805 <a href="#7.4.1.10">7.4.1.10</a>
26806 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>
26807 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>,
26808 <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>
26809 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>
26810 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>
26811 <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>,
26812 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>,
26813 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>
26814 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>,
26815 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>,
26816 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>
26817 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>
26818 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>
26819 VLA, see variable length array wcscat_s function, <a href="#K.3.9.2.2.1">K.3.9.2.2.1</a>
26820 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>
26821 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>
26822 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>
26823 <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>
26824 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>
26825 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>
26826 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>
26827 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>
26828 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>
26829 <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>
26830 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>
26831 <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>
26832 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>
26833 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>
26834 <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>
26835 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>
26836 <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>
26837 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>
26838 <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>
26839 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>
26840 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>
26841 <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>
26842 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>
26843 <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>
26844 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>
26845 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>
26846 <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>,
26847 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>
26848 <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>
26849 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>
26851 [<a name="p677" href="#p677">page 677</a>] (<a href="#Contents">Contents</a>)
26853 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>
26854 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>
26855 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>
26856 <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>
26857 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>
26858 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>
26859 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>
26860 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>
26861 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>,
26862 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>
26863 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>
26864 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>,
26865 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>
26866 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>
26867 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>
26868 weaker, <a href="#6.2.8">6.2.8</a> xor macro, <a href="#7.9">7.9</a>
26869 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>
26870 <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>,
26871 <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>
26872 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>
26873 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>,
26874 <a href="#7.29.2.1.10">7.29.2.1.10</a>
26875 white-space characters, <a href="#6.4">6.4</a>
26876 wide character, <a href="#3.7.3">3.7.3</a>
26877 case mapping functions, <a href="#7.29.3.1">7.29.3.1</a>
26878 extensible, <a href="#7.29.3.2">7.29.3.2</a>
26879 classification functions, <a href="#7.29.2.1">7.29.2.1</a>
26880 extensible, <a href="#7.29.2.2">7.29.2.2</a>
26881 constant, <a href="#6.4.4.4">6.4.4.4</a>
26882 formatted input/output functions, <a href="#7.28.2">7.28.2</a>,
26883 <a href="#K.3.9.1">K.3.9.1</a>
26884 input functions, <a href="#7.21.1">7.21.1</a>
26885 input/output functions, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3">7.28.3</a>
26886 output functions, <a href="#7.21.1">7.21.1</a>
26887 single-byte conversion functions, <a href="#7.28.6.1">7.28.6.1</a>
26888 wide string, <a href="#7.1.1">7.1.1</a>
26889 wide string comparison functions, <a href="#7.28.4.4">7.28.4.4</a>
26890 wide string concatenation functions, <a href="#7.28.4.3">7.28.4.3</a>,
26891 <a href="#K.3.9.2.2">K.3.9.2.2</a>
26892 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>
26893 wide string literal, see string literal
26894 wide string miscellaneous functions, <a href="#7.28.4.6">7.28.4.6</a>,
26895 <a href="#K.3.9.2.4">K.3.9.2.4</a>
26896 wide string numeric conversion functions, <a href="#7.8.2.4">7.8.2.4</a>,
26897 <a href="#7.28.4.1">7.28.4.1</a>
26898 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>
26899 wide-oriented stream, <a href="#7.21.2">7.21.2</a>
26900 width, <a href="#6.2.6.2">6.2.6.2</a>
26901 WINT_MAX macro, <a href="#7.20.3">7.20.3</a>
26902 WINT_MIN macro, <a href="#7.20.3">7.20.3</a>
26903 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>,
26905 [<a name="p678" href="#p678">page 678</a>] (<a href="#Contents">Contents</a>)
26906 </pre></body></html>
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