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 '' ''.
45 <a name="Contents" href="#Contents">Contents</a>
46 <a href="#Foreword">Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii</a>
47 <a href="#Introduction">Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii</a>
48 <a href="#1">1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1</a>
49 <a href="#2">2. Normative references . . . . . . . . . . . . . . . . . . . . . . . 2</a>
50 <a href="#3">3. Terms, definitions, and symbols . . . . . . . . . . . . . . . . . . . 3</a>
51 <a href="#4">4. Conformance . . . . . . . . . . . . . . . . . . . . . . . . . . 8</a>
52 <a href="#5">5. Environment . . . . . . . . . . . . . . . . . . . . . . . . . . 10</a>
53 <a href="#5.1"> 5.1 Conceptual models . . . . . . . . . . . . . . . . . . . . . 10</a>
54 <a href="#5.1.1"> 5.1.1 Translation environment . . . . . . . . . . . . . . . . 10</a>
55 <a href="#5.1.2"> 5.1.2 Execution environments . . . . . . . . . . . . . . . . 12</a>
56 <a href="#5.2"> 5.2 Environmental considerations . . . . . . . . . . . . . . . . . 22</a>
57 <a href="#5.2.1"> 5.2.1 Character sets . . . . . . . . . . . . . . . . . . . . 22</a>
58 <a href="#5.2.2"> 5.2.2 Character display semantics . . . . . . . . . . . . . . 24</a>
59 <a href="#5.2.3"> 5.2.3 Signals and interrupts . . . . . . . . . . . . . . . . . 25</a>
60 <a href="#5.2.4"> 5.2.4 Environmental limits . . . . . . . . . . . . . . . . . 25</a>
61 <a href="#6">6. Language . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35</a>
62 <a href="#6.1"> 6.1 Notation . . . . . . . . . . . . . . . . . . . . . . . . . . 35</a>
63 <a href="#6.2"> 6.2 Concepts . . . . . . . . . . . . . . . . . . . . . . . . . 35</a>
64 <a href="#6.2.1"> 6.2.1 Scopes of identifiers . . . . . . . . . . . . . . . . . 35</a>
65 <a href="#6.2.2"> 6.2.2 Linkages of identifiers . . . . . . . . . . . . . . . . . 36</a>
66 <a href="#6.2.3"> 6.2.3 Name spaces of identifiers . . . . . . . . . . . . . . . 37</a>
67 <a href="#6.2.4"> 6.2.4 Storage durations of objects . . . . . . . . . . . . . . 38</a>
68 <a href="#6.2.5"> 6.2.5 Types . . . . . . . . . . . . . . . . . . . . . . . 39</a>
69 <a href="#6.2.6"> 6.2.6 Representations of types . . . . . . . . . . . . . . . . 44</a>
70 <a href="#6.2.7"> 6.2.7 Compatible type and composite type . . . . . . . . . . . 47</a>
71 <a href="#6.2.8"> 6.2.8 Alignment of objects . . . . . . . . . . . . . . . . . 48</a>
72 <a href="#6.3"> 6.3 Conversions . . . . . . . . . . . . . . . . . . . . . . . . 50</a>
73 <a href="#6.3.1"> 6.3.1 Arithmetic operands . . . . . . . . . . . . . . . . . 50</a>
74 <a href="#6.3.2"> 6.3.2 Other operands . . . . . . . . . . . . . . . . . . . 54</a>
75 <a href="#6.4"> 6.4 Lexical elements . . . . . . . . . . . . . . . . . . . . . . 57</a>
76 <a href="#6.4.1"> 6.4.1 Keywords . . . . . . . . . . . . . . . . . . . . . . 58</a>
77 <a href="#6.4.2"> 6.4.2 Identifiers . . . . . . . . . . . . . . . . . . . . . . 59</a>
78 <a href="#6.4.3"> 6.4.3 Universal character names . . . . . . . . . . . . . . . 61</a>
79 <a href="#6.4.4"> 6.4.4 Constants . . . . . . . . . . . . . . . . . . . . . . 62</a>
80 <a href="#6.4.5"> 6.4.5 String literals . . . . . . . . . . . . . . . . . . . . 70</a>
81 <a href="#6.4.6"> 6.4.6 Punctuators . . . . . . . . . . . . . . . . . . . . . 72</a>
82 <a href="#6.4.7"> 6.4.7 Header names . . . . . . . . . . . . . . . . . . . . 73</a>
83 <a href="#6.4.8"> 6.4.8 Preprocessing numbers . . . . . . . . . . . . . . . . 74</a>
84 <a href="#6.4.9"> 6.4.9 Comments . . . . . . . . . . . . . . . . . . . . . 75</a>
88 <a href="#6.5"> 6.5 Expressions . . . . . . . . . . . . . . . . . . . . . . . . 76</a>
89 <a href="#6.5.1"> 6.5.1 Primary expressions . . . . . . . . . . . . . . . . . 78</a>
90 <a href="#6.5.2"> 6.5.2 Postfix operators . . . . . . . . . . . . . . . . . . . 79</a>
91 <a href="#6.5.3"> 6.5.3 Unary operators . . . . . . . . . . . . . . . . . . . 88</a>
92 <a href="#6.5.4"> 6.5.4 Cast operators . . . . . . . . . . . . . . . . . . . . 91</a>
93 <a href="#6.5.5"> 6.5.5 Multiplicative operators . . . . . . . . . . . . . . . . 92</a>
94 <a href="#6.5.6"> 6.5.6 Additive operators . . . . . . . . . . . . . . . . . . 92</a>
95 <a href="#6.5.7"> 6.5.7 Bitwise shift operators . . . . . . . . . . . . . . . . . 94</a>
96 <a href="#6.5.8"> 6.5.8 Relational operators . . . . . . . . . . . . . . . . . . 95</a>
97 <a href="#6.5.9"> 6.5.9 Equality operators . . . . . . . . . . . . . . . . . . 96</a>
98 <a href="#6.5.10"> 6.5.10 Bitwise AND operator . . . . . . . . . . . . . . . . . 97</a>
99 <a href="#6.5.11"> 6.5.11 Bitwise exclusive OR operator . . . . . . . . . . . . . 98</a>
100 <a href="#6.5.12"> 6.5.12 Bitwise inclusive OR operator . . . . . . . . . . . . . . 98</a>
101 <a href="#6.5.13"> 6.5.13 Logical AND operator . . . . . . . . . . . . . . . . . 99</a>
102 <a href="#6.5.14"> 6.5.14 Logical OR operator . . . . . . . . . . . . . . . . . 99</a>
103 <a href="#6.5.15"> 6.5.15 Conditional operator . . . . . . . . . . . . . . . . . 100</a>
104 <a href="#6.5.16"> 6.5.16 Assignment operators . . . . . . . . . . . . . . . . . 101</a>
105 <a href="#6.5.17"> 6.5.17 Comma operator . . . . . . . . . . . . . . . . . . . 104</a>
106 <a href="#6.6"> 6.6 Constant expressions . . . . . . . . . . . . . . . . . . . . . 105</a>
107 <a href="#6.7"> 6.7 Declarations . . . . . . . . . . . . . . . . . . . . . . . . 107</a>
108 <a href="#6.7.1"> 6.7.1 Storage-class specifiers . . . . . . . . . . . . . . . . 108</a>
109 <a href="#6.7.2"> 6.7.2 Type specifiers . . . . . . . . . . . . . . . . . . . . 109</a>
110 <a href="#6.7.3"> 6.7.3 Type qualifiers . . . . . . . . . . . . . . . . . . . . 120</a>
111 <a href="#6.7.4"> 6.7.4 Function specifiers . . . . . . . . . . . . . . . . . . 124</a>
112 <a href="#6.7.5"> 6.7.5 Alignment specifier . . . . . . . . . . . . . . . . . . 126</a>
113 <a href="#6.7.6"> 6.7.6 Declarators . . . . . . . . . . . . . . . . . . . . . 127</a>
114 <a href="#6.7.7"> 6.7.7 Type names . . . . . . . . . . . . . . . . . . . . . 135</a>
115 <a href="#6.7.8"> 6.7.8 Type definitions . . . . . . . . . . . . . . . . . . . 136</a>
116 <a href="#6.7.9"> 6.7.9 Initialization . . . . . . . . . . . . . . . . . . . . 138</a>
117 <a href="#6.7.10"> 6.7.10 Static assertions . . . . . . . . . . . . . . . . . . . 144</a>
118 <a href="#6.8"> 6.8 Statements and blocks . . . . . . . . . . . . . . . . . . . . 145</a>
119 <a href="#6.8.1"> 6.8.1 Labeled statements . . . . . . . . . . . . . . . . . . 145</a>
120 <a href="#6.8.2"> 6.8.2 Compound statement . . . . . . . . . . . . . . . . . 146</a>
121 <a href="#6.8.3"> 6.8.3 Expression and null statements . . . . . . . . . . . . . 146</a>
122 <a href="#6.8.4"> 6.8.4 Selection statements . . . . . . . . . . . . . . . . . 147</a>
123 <a href="#6.8.5"> 6.8.5 Iteration statements . . . . . . . . . . . . . . . . . . 149</a>
124 <a href="#6.8.6"> 6.8.6 Jump statements . . . . . . . . . . . . . . . . . . . 150</a>
125 <a href="#6.9"> 6.9 External definitions . . . . . . . . . . . . . . . . . . . . . 154</a>
126 <a href="#6.9.1"> 6.9.1 Function definitions . . . . . . . . . . . . . . . . . . 155</a>
127 <a href="#6.9.2"> 6.9.2 External object definitions . . . . . . . . . . . . . . . 157</a>
128 <a href="#6.10"> 6.10 Preprocessing directives . . . . . . . . . . . . . . . . . . . 159</a>
129 <a href="#6.10.1"> 6.10.1 Conditional inclusion . . . . . . . . . . . . . . . . . 161</a>
130 <a href="#6.10.2"> 6.10.2 Source file inclusion . . . . . . . . . . . . . . . . . 163</a>
131 <a href="#6.10.3"> 6.10.3 Macro replacement . . . . . . . . . . . . . . . . . . 165</a>
135 <a href="#6.10.4"> 6.10.4 Line control . . . . . . . . . . . . . . . . . . . . . 172</a>
136 <a href="#6.10.5"> 6.10.5 Error directive . . . . . . . . . . . . . . . . . . . . 173</a>
137 <a href="#6.10.6"> 6.10.6 Pragma directive . . . . . . . . . . . . . . . . . . . 173</a>
138 <a href="#6.10.7"> 6.10.7 Null directive . . . . . . . . . . . . . . . . . . . . 174</a>
139 <a href="#6.10.8"> 6.10.8 Predefined macro names . . . . . . . . . . . . . . . . 174</a>
140 <a href="#6.10.9"> 6.10.9 Pragma operator . . . . . . . . . . . . . . . . . . . 176</a>
141 <a href="#6.11"> 6.11 Future language directions . . . . . . . . . . . . . . . . . . 178</a>
142 <a href="#6.11.1"> 6.11.1 Floating types . . . . . . . . . . . . . . . . . . . . 178</a>
143 <a href="#6.11.2"> 6.11.2 Linkages of identifiers . . . . . . . . . . . . . . . . . 178</a>
144 <a href="#6.11.3"> 6.11.3 External names . . . . . . . . . . . . . . . . . . . 178</a>
145 <a href="#6.11.4"> 6.11.4 Character escape sequences . . . . . . . . . . . . . . 178</a>
146 <a href="#6.11.5"> 6.11.5 Storage-class specifiers . . . . . . . . . . . . . . . . 178</a>
147 <a href="#6.11.6"> 6.11.6 Function declarators . . . . . . . . . . . . . . . . . 178</a>
148 <a href="#6.11.7"> 6.11.7 Function definitions . . . . . . . . . . . . . . . . . . 178</a>
149 <a href="#6.11.8"> 6.11.8 Pragma directives . . . . . . . . . . . . . . . . . . 178</a>
150 <a href="#6.11.9"> 6.11.9 Predefined macro names . . . . . . . . . . . . . . . . 178</a>
151 <a href="#7">7. Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179</a>
152 <a href="#7.1"> 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 179</a>
153 <a href="#7.1.1"> 7.1.1 Definitions of terms . . . . . . . . . . . . . . . . . . 179</a>
154 <a href="#7.1.2"> 7.1.2 Standard headers . . . . . . . . . . . . . . . . . . . 180</a>
155 <a href="#7.1.3"> 7.1.3 Reserved identifiers . . . . . . . . . . . . . . . . . . 181</a>
156 <a href="#7.1.4"> 7.1.4 Use of library functions . . . . . . . . . . . . . . . . 182</a>
157 <a href="#7.2"> 7.2 Diagnostics <assert.h> . . . . . . . . . . . . . . . . . . 185</a>
158 <a href="#7.2.1"> 7.2.1 Program diagnostics . . . . . . . . . . . . . . . . . 185</a>
159 <a href="#7.3"> 7.3 Complex arithmetic <complex.h> . . . . . . . . . . . . . . 187</a>
160 <a href="#7.3.1"> 7.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . 187</a>
161 <a href="#7.3.2"> 7.3.2 Conventions . . . . . . . . . . . . . . . . . . . . . 188</a>
162 <a href="#7.3.3"> 7.3.3 Branch cuts . . . . . . . . . . . . . . . . . . . . . 188</a>
163 <a href="#7.3.4"> 7.3.4 The CX_LIMITED_RANGE pragma . . . . . . . . . . . 188</a>
164 <a href="#7.3.5"> 7.3.5 Trigonometric functions . . . . . . . . . . . . . . . . 189</a>
165 <a href="#7.3.6"> 7.3.6 Hyperbolic functions . . . . . . . . . . . . . . . . . 191</a>
166 <a href="#7.3.7"> 7.3.7 Exponential and logarithmic functions . . . . . . . . . . 193</a>
167 <a href="#7.3.8"> 7.3.8 Power and absolute-value functions . . . . . . . . . . . 194</a>
168 <a href="#7.3.9"> 7.3.9 Manipulation functions . . . . . . . . . . . . . . . . 195</a>
169 <a href="#7.4"> 7.4 Character handling <ctype.h> . . . . . . . . . . . . . . . . 199</a>
170 <a href="#7.4.1"> 7.4.1 Character classification functions . . . . . . . . . . . . 199</a>
171 <a href="#7.4.2"> 7.4.2 Character case mapping functions . . . . . . . . . . . . 202</a>
172 <a href="#7.5"> 7.5 Errors <errno.h> . . . . . . . . . . . . . . . . . . . . . 204</a>
173 <a href="#7.6"> 7.6 Floating-point environment <fenv.h> . . . . . . . . . . . . . 205</a>
174 <a href="#7.6.1"> 7.6.1 The FENV_ACCESS pragma . . . . . . . . . . . . . . 207</a>
175 <a href="#7.6.2"> 7.6.2 Floating-point exceptions . . . . . . . . . . . . . . . 208</a>
176 <a href="#7.6.3"> 7.6.3 Rounding . . . . . . . . . . . . . . . . . . . . . . 211</a>
177 <a href="#7.6.4"> 7.6.4 Environment . . . . . . . . . . . . . . . . . . . . 212</a>
178 <a href="#7.7"> 7.7 Characteristics of floating types <float.h> . . . . . . . . . . . 215</a>
182 <a href="#7.8"> 7.8 Format conversion of integer types <inttypes.h> . . . . . . . . 216</a>
183 <a href="#7.8.1"> 7.8.1 Macros for format specifiers . . . . . . . . . . . . . . 216</a>
184 <a href="#7.8.2"> 7.8.2 Functions for greatest-width integer types . . . . . . . . . 217</a>
185 <a href="#7.9"> 7.9 Alternative spellings <iso646.h> . . . . . . . . . . . . . . . 220</a>
186 <a href="#7.10"> 7.10 Sizes of integer types <limits.h> . . . . . . . . . . . . . . 221</a>
187 <a href="#7.11"> 7.11 Localization <locale.h> . . . . . . . . . . . . . . . . . . 222</a>
188 <a href="#7.11.1"> 7.11.1 Locale control . . . . . . . . . . . . . . . . . . . . 223</a>
189 <a href="#7.11.2"> 7.11.2 Numeric formatting convention inquiry . . . . . . . . . . 224</a>
190 <a href="#7.12"> 7.12 Mathematics <math.h> . . . . . . . . . . . . . . . . . . . 230</a>
191 <a href="#7.12.1"> 7.12.1 Treatment of error conditions . . . . . . . . . . . . . . 232</a>
192 <a href="#7.12.2"> 7.12.2 The FP_CONTRACT pragma . . . . . . . . . . . . . . 234</a>
193 <a href="#7.12.3"> 7.12.3 Classification macros . . . . . . . . . . . . . . . . . 234</a>
194 <a href="#7.12.4"> 7.12.4 Trigonometric functions . . . . . . . . . . . . . . . . 237</a>
195 <a href="#7.12.5"> 7.12.5 Hyperbolic functions . . . . . . . . . . . . . . . . . 239</a>
196 <a href="#7.12.6"> 7.12.6 Exponential and logarithmic functions . . . . . . . . . . 241</a>
197 <a href="#7.12.7"> 7.12.7 Power and absolute-value functions . . . . . . . . . . . 246</a>
198 <a href="#7.12.8"> 7.12.8 Error and gamma functions . . . . . . . . . . . . . . . 248</a>
199 <a href="#7.12.9"> 7.12.9 Nearest integer functions . . . . . . . . . . . . . . . . 250</a>
200 <a href="#7.12.10"> 7.12.10 Remainder functions . . . . . . . . . . . . . . . . . 253</a>
201 <a href="#7.12.11"> 7.12.11 Manipulation functions . . . . . . . . . . . . . . . . 254</a>
202 <a href="#7.12.12"> 7.12.12 Maximum, minimum, and positive difference functions . . . 256</a>
203 <a href="#7.12.13"> 7.12.13 Floating multiply-add . . . . . . . . . . . . . . . . . 257</a>
204 <a href="#7.12.14"> 7.12.14 Comparison macros . . . . . . . . . . . . . . . . . . 258</a>
205 <a href="#7.13"> 7.13 Nonlocal jumps <setjmp.h> . . . . . . . . . . . . . . . . 261</a>
206 <a href="#7.13.1"> 7.13.1 Save calling environment . . . . . . . . . . . . . . . 261</a>
207 <a href="#7.13.2"> 7.13.2 Restore calling environment . . . . . . . . . . . . . . 262</a>
208 <a href="#7.14"> 7.14 Signal handling <signal.h> . . . . . . . . . . . . . . . . . 264</a>
209 <a href="#7.14.1"> 7.14.1 Specify signal handling . . . . . . . . . . . . . . . . 265</a>
210 <a href="#7.14.2"> 7.14.2 Send signal . . . . . . . . . . . . . . . . . . . . . 266</a>
211 <a href="#7.15"> 7.15 Alignment <stdalign.h> . . . . . . . . . . . . . . . . . 267</a>
212 <a href="#7.16"> 7.16 Variable arguments <stdarg.h> . . . . . . . . . . . . . . . 268</a>
213 <a href="#7.16.1"> 7.16.1 Variable argument list access macros . . . . . . . . . . . 268</a>
214 <a href="#7.17"> 7.17 Atomics <stdatomic.h> . . . . . . . . . . . . . . . . . . 272</a>
215 <a href="#7.17.1"> 7.17.1 Introduction . . . . . . . . . . . . . . . . . . . . . 272</a>
216 <a href="#7.17.2"> 7.17.2 Initialization . . . . . . . . . . . . . . . . . . . . 273</a>
217 <a href="#7.17.3"> 7.17.3 Order and consistency . . . . . . . . . . . . . . . . . 274</a>
218 <a href="#7.17.4"> 7.17.4 Fences . . . . . . . . . . . . . . . . . . . . . . . 277</a>
219 <a href="#7.17.5"> 7.17.5 Lock-free property . . . . . . . . . . . . . . . . . . 278</a>
220 <a href="#7.17.6"> 7.17.6 Atomic integer and address types . . . . . . . . . . . . 279</a>
221 <a href="#7.17.7"> 7.17.7 Operations on atomic types . . . . . . . . . . . . . . . 281</a>
222 <a href="#7.17.8"> 7.17.8 Atomic flag type and operations . . . . . . . . . . . . . 284</a>
223 <a href="#7.18"> 7.18 Boolean type and values <stdbool.h> . . . . . . . . . . . . 286</a>
224 <a href="#7.19"> 7.19 Common definitions <stddef.h> . . . . . . . . . . . . . . . 287</a>
225 <a href="#7.20"> 7.20 Integer types <stdint.h> . . . . . . . . . . . . . . . . . . 289</a>
229 <a href="#7.20.1"> 7.20.1 Integer types . . . . . . . . . . . . . . . . . . . . 289</a>
230 <a href="#7.20.2"> 7.20.2 Limits of specified-width integer types . . . . . . . . . . 291</a>
231 <a href="#7.20.3"> 7.20.3 Limits of other integer types . . . . . . . . . . . . . . 293</a>
232 <a href="#7.20.4"> 7.20.4 Macros for integer constants . . . . . . . . . . . . . . 294</a>
233 <a href="#7.21"> 7.21 Input/output <stdio.h> . . . . . . . . . . . . . . . . . . 296</a>
234 <a href="#7.21.1"> 7.21.1 Introduction . . . . . . . . . . . . . . . . . . . . . 296</a>
235 <a href="#7.21.2"> 7.21.2 Streams . . . . . . . . . . . . . . . . . . . . . . 298</a>
236 <a href="#7.21.3"> 7.21.3 Files . . . . . . . . . . . . . . . . . . . . . . . . 300</a>
237 <a href="#7.21.4"> 7.21.4 Operations on files . . . . . . . . . . . . . . . . . . 302</a>
238 <a href="#7.21.5"> 7.21.5 File access functions . . . . . . . . . . . . . . . . . 304</a>
239 <a href="#7.21.6"> 7.21.6 Formatted input/output functions . . . . . . . . . . . . 309</a>
240 <a href="#7.21.7"> 7.21.7 Character input/output functions . . . . . . . . . . . . . 330</a>
241 <a href="#7.21.8"> 7.21.8 Direct input/output functions . . . . . . . . . . . . . . 334</a>
242 <a href="#7.21.9"> 7.21.9 File positioning functions . . . . . . . . . . . . . . . 335</a>
243 <a href="#7.21.10"> 7.21.10 Error-handling functions . . . . . . . . . . . . . . . . 338</a>
244 <a href="#7.22"> 7.22 General utilities <stdlib.h> . . . . . . . . . . . . . . . . 340</a>
245 <a href="#7.22.1"> 7.22.1 Numeric conversion functions . . . . . . . . . . . . . . 341</a>
246 <a href="#7.22.2"> 7.22.2 Pseudo-random sequence generation functions . . . . . . . 346</a>
247 <a href="#7.22.3"> 7.22.3 Memory management functions . . . . . . . . . . . . . 347</a>
248 <a href="#7.22.4"> 7.22.4 Communication with the environment . . . . . . . . . . 349</a>
249 <a href="#7.22.5"> 7.22.5 Searching and sorting utilities . . . . . . . . . . . . . . 353</a>
250 <a href="#7.22.6"> 7.22.6 Integer arithmetic functions . . . . . . . . . . . . . . 355</a>
251 <a href="#7.22.7"> 7.22.7 Multibyte/wide character conversion functions . . . . . . . 356</a>
252 <a href="#7.22.8"> 7.22.8 Multibyte/wide string conversion functions . . . . . . . . 358</a>
253 <a href="#7.23"> 7.23 String handling <string.h> . . . . . . . . . . . . . . . . . 360</a>
254 <a href="#7.23.1"> 7.23.1 String function conventions . . . . . . . . . . . . . . . 360</a>
255 <a href="#7.23.2"> 7.23.2 Copying functions . . . . . . . . . . . . . . . . . . 360</a>
256 <a href="#7.23.3"> 7.23.3 Concatenation functions . . . . . . . . . . . . . . . . 362</a>
257 <a href="#7.23.4"> 7.23.4 Comparison functions . . . . . . . . . . . . . . . . . 363</a>
258 <a href="#7.23.5"> 7.23.5 Search functions . . . . . . . . . . . . . . . . . . . 365</a>
259 <a href="#7.23.6"> 7.23.6 Miscellaneous functions . . . . . . . . . . . . . . . . 368</a>
260 <a href="#7.24"> 7.24 Type-generic math <tgmath.h> . . . . . . . . . . . . . . . 370</a>
261 <a href="#7.25"> 7.25 Threads <threads.h> . . . . . . . . . . . . . . . . . . . 373</a>
262 <a href="#7.25.1"> 7.25.1 Introduction . . . . . . . . . . . . . . . . . . . . . 373</a>
263 <a href="#7.25.2"> 7.25.2 Initialization functions . . . . . . . . . . . . . . . . . 375</a>
264 <a href="#7.25.3"> 7.25.3 Condition variable functions . . . . . . . . . . . . . . 375</a>
265 <a href="#7.25.4"> 7.25.4 Mutex functions . . . . . . . . . . . . . . . . . . . 377</a>
266 <a href="#7.25.5"> 7.25.5 Thread functions . . . . . . . . . . . . . . . . . . . 380</a>
267 <a href="#7.25.6"> 7.25.6 Thread-specific storage functions . . . . . . . . . . . . 382</a>
268 <a href="#7.25.7"> 7.25.7 Time functions . . . . . . . . . . . . . . . . . . . . 384</a>
269 <a href="#7.26"> 7.26 Date and time <time.h> . . . . . . . . . . . . . . . . . . 385</a>
270 <a href="#7.26.1"> 7.26.1 Components of time . . . . . . . . . . . . . . . . . 385</a>
271 <a href="#7.26.2"> 7.26.2 Time manipulation functions . . . . . . . . . . . . . . 386</a>
272 <a href="#7.26.3"> 7.26.3 Time conversion functions . . . . . . . . . . . . . . . 388</a>
276 <a href="#7.27"> 7.27 Unicode utilities <uchar.h> . . . . . . . . . . . . . . . . . 395</a>
277 <a href="#7.27.1"> 7.27.1 Restartable multibyte/wide character conversion functions . . 395</a>
278 <a href="#7.28"> 7.28 Extended multibyte and wide character utilities <wchar.h> . . . . . 399</a>
279 <a href="#7.28.1"> 7.28.1 Introduction . . . . . . . . . . . . . . . . . . . . . 399</a>
280 <a href="#7.28.2"> 7.28.2 Formatted wide character input/output functions . . . . . . 400</a>
281 <a href="#7.28.3"> 7.28.3 Wide character input/output functions . . . . . . . . . . 418</a>
282 <a href="#7.28.4"> 7.28.4 General wide string utilities . . . . . . . . . . . . . . 422</a>
283 <a href="#7.28.4.1"> 7.28.4.1 Wide string numeric conversion functions . . . . . 423</a>
284 <a href="#7.28.4.2"> 7.28.4.2 Wide string copying functions . . . . . . . . . . 427</a>
285 <a href="#7.28.4.3"> 7.28.4.3 Wide string concatenation functions . . . . . . . 429</a>
286 <a href="#7.28.4.4"> 7.28.4.4 Wide string comparison functions . . . . . . . . 430</a>
287 <a href="#7.28.4.5"> 7.28.4.5 Wide string search functions . . . . . . . . . . 432</a>
288 <a href="#7.28.4.6"> 7.28.4.6 Miscellaneous functions . . . . . . . . . . . . 436</a>
289 <a href="#7.28.5"> 7.28.5 Wide character time conversion functions . . . . . . . . . 436</a>
290 <a href="#7.28.6"> 7.28.6 Extended multibyte/wide character conversion utilities . . . . 437</a>
291 <a href="#7.28.6.1"> 7.28.6.1 Single-byte/wide character conversion functions . . . 438</a>
292 <a href="#7.28.6.2"> 7.28.6.2 Conversion state functions . . . . . . . . . . . 438</a>
293 <a href="#7.28.6.3"> 7.28.6.3 Restartable multibyte/wide character conversion
294 functions . . . . . . . . . . . . . . . . . . 439</a>
295 <a href="#7.28.6.4"> 7.28.6.4 Restartable multibyte/wide string conversion
296 functions . . . . . . . . . . . . . . . . . . 441</a>
297 <a href="#7.29"> 7.29 Wide character classification and mapping utilities <wctype.h> . . . 444</a>
298 <a href="#7.29.1"> 7.29.1 Introduction . . . . . . . . . . . . . . . . . . . . . 444</a>
299 <a href="#7.29.2"> 7.29.2 Wide character classification utilities . . . . . . . . . . . 445</a>
300 <a href="#7.29.2.1"> 7.29.2.1 Wide character classification functions . . . . . . 445</a>
301 <a href="#7.29.2.2"> 7.29.2.2 Extensible wide character classification
302 functions . . . . . . . . . . . . . . . . . . 448</a>
303 <a href="#7.29.3"> 7.29.3 Wide character case mapping utilities . . . . . . . . . . . 450</a>
304 <a href="#7.29.3.1"> 7.29.3.1 Wide character case mapping functions . . . . . . 450</a>
305 <a href="#7.29.3.2"> 7.29.3.2 Extensible wide character case mapping
306 functions . . . . . . . . . . . . . . . . . . 450</a>
307 <a href="#7.30"> 7.30 Future library directions . . . . . . . . . . . . . . . . . . . 452</a>
308 <a href="#7.30.1"> 7.30.1 Complex arithmetic <complex.h> . . . . . . . . . . . 452</a>
309 <a href="#7.30.2"> 7.30.2 Character handling <ctype.h> . . . . . . . . . . . . 452</a>
310 <a href="#7.30.3"> 7.30.3 Errors <errno.h> . . . . . . . . . . . . . . . . . 452</a>
311 <a href="#7.30.4"> 7.30.4 Format conversion of integer types <inttypes.h> . . . . 452</a>
312 <a href="#7.30.5"> 7.30.5 Localization <locale.h> . . . . . . . . . . . . . . 452</a>
313 <a href="#7.30.6"> 7.30.6 Signal handling <signal.h> . . . . . . . . . . . . . 452</a>
314 <a href="#7.30.7"> 7.30.7 Boolean type and values <stdbool.h> . . . . . . . . . 452</a>
315 <a href="#7.30.8"> 7.30.8 Integer types <stdint.h> . . . . . . . . . . . . . . 452</a>
316 <a href="#7.30.9"> 7.30.9 Input/output <stdio.h> . . . . . . . . . . . . . . . 453</a>
317 <a href="#7.30.10"> 7.30.10 General utilities <stdlib.h> . . . . . . . . . . . . . 453</a>
318 <a href="#7.30.11"> 7.30.11 String handling <string.h> . . . . . . . . . . . . . 453</a>
322 <a href="#7.30.12"> 7.30.12 Extended multibyte and wide character utilities
323 <wchar.h> . . . . . . . . . . . . . . . . . . . . 453</a>
324 <a href="#7.30.13"> 7.30.13 Wide character classification and mapping utilities
325 <wctype.h> . . . . . . . . . . . . . . . . . . . . 453</a>
326 <a href="#A">Annex A (informative) Language syntax summary . . . . . . . . . . . . 454</a>
327 <a href="#A.1"> A.1 Lexical grammar . . . . . . . . . . . . . . . . . . . . . . 454</a>
328 <a href="#A.2"> A.2 Phrase structure grammar . . . . . . . . . . . . . . . . . . . 461</a>
329 <a href="#A.3"> A.3 Preprocessing directives . . . . . . . . . . . . . . . . . . . 469</a>
330 <a href="#B">Annex B (informative) Library summary . . . . . . . . . . . . . . . . 471</a>
331 <a href="#B.1"> B.1 Diagnostics <assert.h> . . . . . . . . . . . . . . . . . . 471</a>
332 <a href="#B.2"> B.2 Complex <complex.h> . . . . . . . . . . . . . . . . . . . 471</a>
333 <a href="#B.3"> B.3 Character handling <ctype.h> . . . . . . . . . . . . . . . . 473</a>
334 <a href="#B.4"> B.4 Errors <errno.h> . . . . . . . . . . . . . . . . . . . . . 473</a>
335 <a href="#B.5"> B.5 Floating-point environment <fenv.h> . . . . . . . . . . . . . 473</a>
336 <a href="#B.6"> B.6 Characteristics of floating types <float.h> . . . . . . . . . . . 474</a>
337 <a href="#B.7"> B.7 Format conversion of integer types <inttypes.h> . . . . . . . . 474</a>
338 <a href="#B.8"> B.8 Alternative spellings <iso646.h> . . . . . . . . . . . . . . . 475</a>
339 <a href="#B.9"> B.9 Sizes of integer types <limits.h> . . . . . . . . . . . . . . 475</a>
340 <a href="#B.10"> B.10 Localization <locale.h> . . . . . . . . . . . . . . . . . . 475</a>
341 <a href="#B.11"> B.11 Mathematics <math.h> . . . . . . . . . . . . . . . . . . . 475</a>
342 <a href="#B.12"> B.12 Nonlocal jumps <setjmp.h> . . . . . . . . . . . . . . . . 480</a>
343 <a href="#B.13"> B.13 Signal handling <signal.h> . . . . . . . . . . . . . . . . . 480</a>
344 <a href="#B.14"> B.14 Alignment <stdalign.h> . . . . . . . . . . . . . . . . . 481</a>
345 <a href="#B.15"> B.15 Variable arguments <stdarg.h> . . . . . . . . . . . . . . . 481</a>
346 <a href="#B.16"> B.16 Atomics <stdatomic.h> . . . . . . . . . . . . . . . . . . 481</a>
347 <a href="#B.17"> B.17 Boolean type and values <stdbool.h> . . . . . . . . . . . . 483</a>
348 <a href="#B.18"> B.18 Common definitions <stddef.h> . . . . . . . . . . . . . . . 483</a>
349 <a href="#B.19"> B.19 Integer types <stdint.h> . . . . . . . . . . . . . . . . . . 483</a>
350 <a href="#B.20"> B.20 Input/output <stdio.h> . . . . . . . . . . . . . . . . . . 484</a>
351 <a href="#B.21"> B.21 General utilities <stdlib.h> . . . . . . . . . . . . . . . . 487</a>
352 <a href="#B.22"> B.22 String handling <string.h> . . . . . . . . . . . . . . . . . 489</a>
353 <a href="#B.23"> B.23 Type-generic math <tgmath.h> . . . . . . . . . . . . . . . 491</a>
354 <a href="#B.24"> B.24 Threads <threads.h> . . . . . . . . . . . . . . . . . . . 491</a>
355 <a href="#B.25"> B.25 Date and time <time.h> . . . . . . . . . . . . . . . . . . 492</a>
356 <a href="#B.26"> B.26 Unicode utilities <uchar.h> . . . . . . . . . . . . . . . . . 493</a>
357 <a href="#B.27"> B.27 Extended multibyte/wide character utilities <wchar.h> . . . . . . 493</a>
358 <a href="#B.28"> B.28 Wide character classification and mapping utilities <wctype.h> . . . 498</a>
359 <a href="#C">Annex C (informative) Sequence points . . . . . . . . . . . . . . . . . 499</a>
360 <a href="#D">Annex D (normative) Universal character names for identifiers . . . . . . . 500</a>
361 <a href="#D.1"> D.1 Ranges of characters allowed . . . . . . . . . . . . . . . . . 500</a>
362 <a href="#D.2"> D.2 Ranges of characters disallowed initially . . . . . . . . . . . . . 500</a>
363 <a href="#E">Annex E (informative) Implementation limits . . . . . . . . . . . . . . 501</a>
367 <a href="#F">Annex F (normative) IEC 60559 floating-point arithmetic . . . . . . . . . . 503</a>
368 <a href="#F.1"> F.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 503</a>
369 <a href="#F.2"> F.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 503</a>
370 <a href="#F.3"> F.3 Operators and functions . . . . . . . . . . . . . . . . . . . 504</a>
371 <a href="#F.4"> F.4 Floating to integer conversion . . . . . . . . . . . . . . . . . 506</a>
372 <a href="#F.5"> F.5 Binary-decimal conversion . . . . . . . . . . . . . . . . . . 506</a>
373 <a href="#F.6"> F.6 The return statement . . . . . . . . . . . . . . . . . . . . 507</a>
374 <a href="#F.7"> F.7 Contracted expressions . . . . . . . . . . . . . . . . . . . . 507</a>
375 <a href="#F.8"> F.8 Floating-point environment . . . . . . . . . . . . . . . . . . 507</a>
376 <a href="#F.9"> F.9 Optimization . . . . . . . . . . . . . . . . . . . . . . . . 510</a>
377 <a href="#F.10"> F.10 Mathematics <math.h> . . . . . . . . . . . . . . . . . . . 513</a>
378 <a href="#F.10.1"> F.10.1 Trigonometric functions . . . . . . . . . . . . . . . . 514</a>
379 <a href="#F.10.2"> F.10.2 Hyperbolic functions . . . . . . . . . . . . . . . . . 516</a>
380 <a href="#F.10.3"> F.10.3 Exponential and logarithmic functions . . . . . . . . . . 516</a>
381 <a href="#F.10.4"> F.10.4 Power and absolute value functions . . . . . . . . . . . 520</a>
382 <a href="#F.10.5"> F.10.5 Error and gamma functions . . . . . . . . . . . . . . . 521</a>
383 <a href="#F.10.6"> F.10.6 Nearest integer functions . . . . . . . . . . . . . . . . 522</a>
384 <a href="#F.10.7"> F.10.7 Remainder functions . . . . . . . . . . . . . . . . . 524</a>
385 <a href="#F.10.8"> F.10.8 Manipulation functions . . . . . . . . . . . . . . . . 525</a>
386 <a href="#F.10.9"> F.10.9 Maximum, minimum, and positive difference functions . . . 526</a>
387 <a href="#F.10.10"> F.10.10 Floating multiply-add . . . . . . . . . . . . . . . . . 526</a>
388 <a href="#F.10.11"> F.10.11 Comparison macros . . . . . . . . . . . . . . . . . . 527</a>
389 <a href="#G">Annex G (normative) IEC 60559-compatible complex arithmetic . . . . . . . 528</a>
390 <a href="#G.1"> G.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 528</a>
391 <a href="#G.2"> G.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 528</a>
392 <a href="#G.3"> G.3 Conventions . . . . . . . . . . . . . . . . . . . . . . . . 528</a>
393 <a href="#G.4"> G.4 Conversions . . . . . . . . . . . . . . . . . . . . . . . . 529</a>
394 <a href="#G.4.1"> G.4.1 Imaginary types . . . . . . . . . . . . . . . . . . . 529</a>
395 <a href="#G.4.2"> G.4.2 Real and imaginary . . . . . . . . . . . . . . . . . . 529</a>
396 <a href="#G.4.3"> G.4.3 Imaginary and complex . . . . . . . . . . . . . . . . 529</a>
397 <a href="#G.5"> G.5 Binary operators . . . . . . . . . . . . . . . . . . . . . . 529</a>
398 <a href="#G.5.1"> G.5.1 Multiplicative operators . . . . . . . . . . . . . . . . 530</a>
399 <a href="#G.5.2"> G.5.2 Additive operators . . . . . . . . . . . . . . . . . . 533</a>
400 <a href="#G.6"> G.6 Complex arithmetic <complex.h> . . . . . . . . . . . . . . 533</a>
401 <a href="#G.6.1"> G.6.1 Trigonometric functions . . . . . . . . . . . . . . . . 535</a>
402 <a href="#G.6.2"> G.6.2 Hyperbolic functions . . . . . . . . . . . . . . . . . 535</a>
403 <a href="#G.6.3"> G.6.3 Exponential and logarithmic functions . . . . . . . . . . 539</a>
404 <a href="#G.6.4"> G.6.4 Power and absolute-value functions . . . . . . . . . . . 540</a>
405 <a href="#G.7"> G.7 Type-generic math <tgmath.h> . . . . . . . . . . . . . . . 541</a>
406 <a href="#H">Annex H (informative) Language independent arithmetic . . . . . . . . . . 542</a>
407 <a href="#H.1"> H.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 542</a>
408 <a href="#H.2"> H.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 542</a>
409 <a href="#H.3"> H.3 Notification . . . . . . . . . . . . . . . . . . . . . . . . 546</a>
413 <a href="#I">Annex I (informative) Common warnings . . . . . . . . . . . . . . . . 548</a>
414 <a href="#J">Annex J (informative) Portability issues . . . . . . . . . . . . . . . . . 550</a>
415 <a href="#J.1"> J.1 Unspecified behavior . . . . . . . . . . . . . . . . . . . . . 550</a>
416 <a href="#J.2"> J.2 Undefined behavior . . . . . . . . . . . . . . . . . . . . . 553</a>
417 <a href="#J.3"> J.3 Implementation-defined behavior . . . . . . . . . . . . . . . . 566</a>
418 <a href="#J.4"> J.4 Locale-specific behavior . . . . . . . . . . . . . . . . . . . 574</a>
419 <a href="#J.5"> J.5 Common extensions . . . . . . . . . . . . . . . . . . . . . 575</a>
420 <a href="#K">Annex K (normative) Bounds-checking interfaces . . . . . . . . . . . . . 578</a>
421 <a href="#K.1"> K.1 Background . . . . . . . . . . . . . . . . . . . . . . . . 578</a>
422 <a href="#K.2"> K.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 579</a>
423 <a href="#K.3"> K.3 Library . . . . . . . . . . . . . . . . . . . . . . . . . . 579</a>
424 <a href="#K.3.1"> K.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . 579</a>
425 <a href="#K.3.1.1"> K.3.1.1 Standard headers . . . . . . . . . . . . . . . 579</a>
426 <a href="#K.3.1.2"> K.3.1.2 Reserved identifiers . . . . . . . . . . . . . . 580</a>
427 <a href="#K.3.1.3"> K.3.1.3 Use of errno . . . . . . . . . . . . . . . . . 580</a>
428 <a href="#K.3.1.4"> K.3.1.4 Runtime-constraint violations . . . . . . . . . . 580</a>
429 <a href="#K.3.2"> K.3.2 Errors <errno.h> . . . . . . . . . . . . . . . . . 581</a>
430 <a href="#K.3.3"> K.3.3 Common definitions <stddef.h> . . . . . . . . . . . 581</a>
431 <a href="#K.3.4"> K.3.4 Integer types <stdint.h> . . . . . . . . . . . . . . 581</a>
432 <a href="#K.3.5"> K.3.5 Input/output <stdio.h> . . . . . . . . . . . . . . . 582</a>
433 <a href="#K.3.5.1"> K.3.5.1 Operations on files . . . . . . . . . . . . . . 582</a>
434 <a href="#K.3.5.2"> K.3.5.2 File access functions . . . . . . . . . . . . . . 584</a>
435 <a href="#K.3.5.3"> K.3.5.3 Formatted input/output functions . . . . . . . . . 587</a>
436 <a href="#K.3.5.4"> K.3.5.4 Character input/output functions . . . . . . . . . 598</a>
437 <a href="#K.3.6"> K.3.6 General utilities <stdlib.h> . . . . . . . . . . . . . 600</a>
438 <a href="#K.3.6.1"> K.3.6.1 Runtime-constraint handling . . . . . . . . . . 600</a>
439 <a href="#K.3.6.2"> K.3.6.2 Communication with the environment . . . . . . . 602</a>
440 <a href="#K.3.6.3"> K.3.6.3 Searching and sorting utilities . . . . . . . . . . 603</a>
441 <a href="#K.3.6.4"> K.3.6.4 Multibyte/wide character conversion functions . . . 606</a>
442 <a href="#K.3.6.5"> K.3.6.5 Multibyte/wide string conversion functions . . . . . 607</a>
443 <a href="#K.3.7"> K.3.7 String handling <string.h> . . . . . . . . . . . . . 610</a>
444 <a href="#K.3.7.1"> K.3.7.1 Copying functions . . . . . . . . . . . . . . 610</a>
445 <a href="#K.3.7.2"> K.3.7.2 Concatenation functions . . . . . . . . . . . . 613</a>
446 <a href="#K.3.7.3"> K.3.7.3 Search functions . . . . . . . . . . . . . . . 616</a>
447 <a href="#K.3.7.4"> K.3.7.4 Miscellaneous functions . . . . . . . . . . . . 617</a>
448 <a href="#K.3.8"> K.3.8 Date and time <time.h> . . . . . . . . . . . . . . . 620</a>
449 <a href="#K.3.8.1"> K.3.8.1 Components of time . . . . . . . . . . . . . . 620</a>
450 <a href="#K.3.8.2"> K.3.8.2 Time conversion functions . . . . . . . . . . . 620</a>
451 <a href="#K.3.9"> K.3.9 Extended multibyte and wide character utilities
452 <wchar.h> . . . . . . . . . . . . . . . . . . . . 623</a>
453 <a href="#K.3.9.1"> K.3.9.1 Formatted wide character input/output functions . . . 624</a>
454 <a href="#K.3.9.2"> K.3.9.2 General wide string utilities . . . . . . . . . . . 635</a>
458 <a href="#K.3.9.3"> K.3.9.3 Extended multibyte/wide character conversion
459 utilities . . . . . . . . . . . . . . . . . . . 643</a>
460 <a href="#L">Annex L (normative) Analyzability . . . . . . . . . . . . . . . . . . 648</a>
461 <a href="#L.1"> L.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 648</a>
462 <a href="#L.2"> L.2 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 648</a>
463 <a href="#L.3"> L.3 Requirements . . . . . . . . . . . . . . . . . . . . . . . . 649</a>
464 <a href="#Bibliography">Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . 650</a>
465 <a href="#Index">Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 653</a>
467 [<a name="pxii" href="#pxii">page xii</a>] (<a href="#Contents">Contents</a>)
469 <a name="Foreword" href="#Foreword"><b> Foreword</b></a>
470 1 ISO (the International Organization for Standardization) and IEC (the International
471 Electrotechnical Commission) form the specialized system for worldwide
472 standardization. National bodies that are member of ISO or IEC participate in the
473 development of International Standards through technical committees established by the
474 respective organization to deal with particular fields of technical activity. ISO and IEC
475 technical committees collaborate in fields of mutual interest. Other international
476 organizations, governmental and non-governmental, in liaison with ISO and IEC, also
477 take part in the work.
478 2 International Standards are drafted in accordance with the rules given in the ISO/IEC
479 Directives, Part 2. This International Standard was drafted in accordance with the fifth
481 3 In the field of information technology, ISO and IEC have established a joint technical
482 committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
483 committee are circulated to national bodies for voting. Publication as an International
484 Standard requires approval by at least 75% of the national bodies casting a vote.
485 4 Attention is drawn to the possibility that some of the elements of this document may be
486 the subject of patent rights. ISO and IEC shall not be held responsible for identifying any
487 or all such patent rights.
488 5 This International Standard was prepared by Joint Technical Committee ISO/IEC JTC 1,
489 Information technology, Subcommittee SC 22, Programming languages, their
490 environments and system software interfaces. The Working Group responsible for this
491 standard (WG 14) maintains a site on the World Wide Web at http://www.open-
492 std.org/JTC1/SC22/WG14/ containing additional information relevant to this
493 standard such as a Rationale for many of the decisions made during its preparation and a
494 log of Defect Reports and Responses.
495 6 This third edition cancels and replaces the second edition, ISO/IEC 9899:1999, as
496 corrected by ISO/IEC 9899:1999/Cor 1:2001, ISO/IEC 9899:1999/Cor 2:2004, and
497 ISO/IEC 9899:1999/Cor 3:2007. Major changes from the previous edition include:
498 -- conditional (optional) features (including some that were previously mandatory)
499 -- support for multiple threads of execution including an improved memory sequencing
500 model, atomic objects, and thread-local storage (<a href="#7.17"><stdatomic.h></a> and
501 <a href="#7.25"><threads.h></a>)
502 -- additional floating-point characteristic macros (<a href="#7.7"><float.h></a>)
503 -- querying and specifying alignment of objects (<a href="#7.15"><stdalign.h></a>, <a href="#7.22"><stdlib.h></a>)
504 -- Unicode characters and strings (<a href="#7.27"><uchar.h></a>) (originally specified in
505 ISO/IEC TR 19769:2004)
506 -- type-generic expressions
508 [<a name="pxiii" href="#pxiii">page xiii</a>] (<a href="#Contents">Contents</a>)
511 -- anonymous structures and unions
512 -- no-return functions
513 -- macros to create complex numbers (<a href="#7.3"><complex.h></a>)
514 -- support for opening files for exclusive access
515 -- removed the gets function (<a href="#7.21"><stdio.h></a>)
516 -- added the aligned_alloc, at_quick_exit, and quick_exit functions
517 (<a href="#7.22"><stdlib.h></a>)
518 -- (conditional) support for bounds-checking interfaces (originally specified in
519 ISO/IEC TR 24731-1:2007)
520 -- (conditional) support for analyzability
521 7 Major changes in the second edition included:
522 -- restricted character set support via digraphs and <a href="#7.9"><iso646.h></a> (originally specified
524 -- wide character library support in <a href="#7.28"><wchar.h></a> and <a href="#7.29"><wctype.h></a> (originally
526 -- more precise aliasing rules via effective type
527 -- restricted pointers
528 -- variable length arrays
529 -- flexible array members
530 -- static and type qualifiers in parameter array declarators
531 -- complex (and imaginary) support in <a href="#7.3"><complex.h></a>
532 -- type-generic math macros in <a href="#7.24"><tgmath.h></a>
533 -- the long long int type and library functions
534 -- increased minimum translation limits
535 -- additional floating-point characteristics in <a href="#7.7"><float.h></a>
536 -- remove implicit int
537 -- reliable integer division
538 -- universal character names (\u and \U)
539 -- extended identifiers
540 -- hexadecimal floating-point constants and %a and %A printf/scanf conversion
543 [<a name="pxiv" href="#pxiv">page xiv</a>] (<a href="#Contents">Contents</a>)
546 -- designated initializers
548 -- extended integer types and library functions in <a href="#7.8"><inttypes.h></a> and <a href="#7.20"><stdint.h></a>
549 -- remove implicit function declaration
550 -- preprocessor arithmetic done in intmax_t/uintmax_t
551 -- mixed declarations and code
552 -- new block scopes for selection and iteration statements
553 -- integer constant type rules
554 -- integer promotion rules
555 -- macros with a variable number of arguments
556 -- the vscanf family of functions in <a href="#7.21"><stdio.h></a> and <a href="#7.28"><wchar.h></a>
557 -- additional math library functions in <a href="#7.12"><math.h></a>
558 -- treatment of error conditions by math library functions (math_errhandling)
559 -- floating-point environment access in <a href="#7.6"><fenv.h></a>
560 -- IEC 60559 (also known as IEC 559 or IEEE arithmetic) support
561 -- trailing comma allowed in enum declaration
562 -- %lf conversion specifier allowed in printf
564 -- the snprintf family of functions in <a href="#7.21"><stdio.h></a>
565 -- boolean type in <a href="#7.18"><stdbool.h></a>
566 -- idempotent type qualifiers
567 -- empty macro arguments
568 -- new structure type compatibility rules (tag compatibility)
569 -- additional predefined macro names
570 -- _Pragma preprocessing operator
572 -- __func__ predefined identifier
574 -- additional strftime conversion specifiers
575 -- LIA compatibility annex
577 [<a name="pxv" href="#pxv">page xv</a>] (<a href="#Contents">Contents</a>)
579 -- deprecate ungetc at the beginning of a binary file
580 -- remove deprecation of aliased array parameters
581 -- conversion of array to pointer not limited to lvalues
582 -- relaxed constraints on aggregate and union initialization
583 -- relaxed restrictions on portable header names
584 -- return without expression not permitted in function that returns a value (and vice
586 8 Annexes D, F, G, K, and L form a normative part of this standard; annexes A, B, C, E, H, *
587 I, J, the bibliography, and the index are for information only. In accordance with Part 2 of
588 the ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples
589 are also for information only.
591 [<a name="pxvi" href="#pxvi">page xvi</a>] (<a href="#Contents">Contents</a>)
593 <a name="Introduction" href="#Introduction"><b> Introduction</b></a>
594 1 With the introduction of new devices and extended character sets, new features may be
595 added to this International Standard. Subclauses in the language and library clauses warn
596 implementors and programmers of usages which, though valid in themselves, may
597 conflict with future additions.
598 2 Certain features are obsolescent, which means that they may be considered for
599 withdrawal in future revisions of this International Standard. They are retained because
600 of their widespread use, but their use in new implementations (for implementation
601 features) or new programs (for language [6.11] or library features [7.30]) is discouraged.
602 3 This International Standard is divided into four major subdivisions:
603 -- preliminary elements (clauses 1-4);
604 -- the characteristics of environments that translate and execute C programs (clause 5);
605 -- the language syntax, constraints, and semantics (clause 6);
606 -- the library facilities (clause 7).
607 4 Examples are provided to illustrate possible forms of the constructions described.
608 Footnotes are provided to emphasize consequences of the rules described in that
609 subclause or elsewhere in this International Standard. References are used to refer to
610 other related subclauses. Recommendations are provided to give advice or guidance to
611 implementors. Annexes provide additional information and summarize the information
612 contained in this International Standard. A bibliography lists documents that were
613 referred to during the preparation of the standard.
614 5 The language clause (clause 6) is derived from ''The C Reference Manual''.
615 6 The library clause (clause 7) is based on the 1984 /usr/group Standard.
617 [<a name="pxvii" href="#pxvii">page xvii</a>] (<a href="#Contents">Contents</a>)
620 [<a name="pxviii" href="#pxviii">page xviii</a>] (<a href="#Contents">Contents</a>)
624 Programming languages -- C
628 <a name="1" href="#1"><b> 1. Scope</b></a>
629 1 This International Standard specifies the form and establishes the interpretation of
630 programs written in the C programming language.<sup><a href="#note1"><b>1)</b></a></sup> It specifies
631 -- the representation of C programs;
632 -- the syntax and constraints of the C language;
633 -- the semantic rules for interpreting C programs;
634 -- the representation of input data to be processed by C programs;
635 -- the representation of output data produced by C programs;
636 -- the restrictions and limits imposed by a conforming implementation of C.
637 2 This International Standard does not specify
638 -- the mechanism by which C programs are transformed for use by a data-processing
640 -- the mechanism by which C programs are invoked for use by a data-processing
642 -- the mechanism by which input data are transformed for use by a C program;
643 -- the mechanism by which output data are transformed after being produced by a C
645 -- the size or complexity of a program and its data that will exceed the capacity of any
646 specific data-processing system or the capacity of a particular processor;
647 -- all minimal requirements of a data-processing system that is capable of supporting a
648 conforming implementation.
651 <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
652 data-processing systems. It is intended for use by implementors and programmers.
654 [<a name="p1" href="#p1">page 1</a>] (<a href="#Contents">Contents</a>)
657 <a name="2" href="#2"><b> 2. Normative references</b></a>
658 1 The following referenced documents are indispensable for the application of this
659 document. For dated references, only the edition cited applies. For undated references,
660 the latest edition of the referenced document (including any amendments) applies.
661 2 ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and symbols for
662 use in the physical sciences and technology.
663 3 ISO/IEC 646, Information technology -- ISO 7-bit coded character set for information
665 4 ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1: Fundamental
667 5 ISO 4217, Codes for the representation of currencies and funds.
668 6 ISO 8601, Data elements and interchange formats -- Information interchange --
669 Representation of dates and times.
670 7 ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded
672 8 IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems (previously
673 designated IEC 559:1989).
675 [<a name="p2" href="#p2">page 2</a>] (<a href="#Contents">Contents</a>)
678 <a name="3" href="#3"><b> 3. Terms, definitions, and symbols</b></a>
679 1 For the purposes of this International Standard, the following definitions apply. Other
680 terms are defined where they appear in italic type or on the left side of a syntax rule.
681 Terms explicitly defined in this International Standard are not to be presumed to refer
682 implicitly to similar terms defined elsewhere. Terms not defined in this International
683 Standard are to be interpreted according to ISO/IEC 2382-1. Mathematical symbols not
684 defined in this International Standard are to be interpreted according to ISO 31-11.
685 <a name="3.1" href="#3.1"><b> 3.1</b></a>
687 <execution-time action> to read or modify the value of an object
688 2 NOTE 1 Where only one of these two actions is meant, ''read'' or ''modify'' is used.
690 3 NOTE 2 ''Modify'' includes the case where the new value being stored is the same as the previous value.
692 4 NOTE 3 Expressions that are not evaluated do not access objects.
694 <a name="3.2" href="#3.2"><b> 3.2</b></a>
696 requirement that objects of a particular type be located on storage boundaries with
697 addresses that are particular multiples of a byte address
698 <a name="3.3" href="#3.3"><b> 3.3</b></a>
701 actual parameter (deprecated)
702 expression in the comma-separated list bounded by the parentheses in a function call
703 expression, or a sequence of preprocessing tokens in the comma-separated list bounded
704 by the parentheses in a function-like macro invocation
705 <a name="3.4" href="#3.4"><b> 3.4</b></a>
707 external appearance or action
708 <a name="3.4.1" href="#3.4.1"><b> 3.4.1</b></a>
709 1 implementation-defined behavior
710 unspecified behavior where each implementation documents how the choice is made
711 2 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
712 when a signed integer is shifted right.
714 <a name="3.4.2" href="#3.4.2"><b> 3.4.2</b></a>
715 1 locale-specific behavior
716 behavior that depends on local conventions of nationality, culture, and language that each
717 implementation documents
719 [<a name="p3" href="#p3">page 3</a>] (<a href="#Contents">Contents</a>)
721 2 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
722 characters other than the 26 lowercase Latin letters.
724 <a name="3.4.3" href="#3.4.3"><b> 3.4.3</b></a>
726 behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
727 for which this International Standard imposes no requirements
728 2 NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable
729 results, to behaving during translation or program execution in a documented manner characteristic of the
730 environment (with or without the issuance of a diagnostic message), to terminating a translation or
731 execution (with the issuance of a diagnostic message).
733 3 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
735 <a name="3.4.4" href="#3.4.4"><b> 3.4.4</b></a>
736 1 unspecified behavior
737 use of an unspecified value, or other behavior where this International Standard provides
738 two or more possibilities and imposes no further requirements on which is chosen in any
740 2 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
743 <a name="3.5" href="#3.5"><b> 3.5</b></a>
745 unit of data storage in the execution environment large enough to hold an object that may
746 have one of two values
747 2 NOTE It need not be possible to express the address of each individual bit of an object.
749 <a name="3.6" href="#3.6"><b> 3.6</b></a>
751 addressable unit of data storage large enough to hold any member of the basic character
752 set of the execution environment
753 2 NOTE 1 It is possible to express the address of each individual byte of an object uniquely.
755 3 NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
756 defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order
759 <a name="3.7" href="#3.7"><b> 3.7</b></a>
761 <abstract> member of a set of elements used for the organization, control, or
762 representation of data
763 <a name="3.7.1" href="#3.7.1"><b> 3.7.1</b></a>
765 single-byte character
766 <C> bit representation that fits in a byte
768 [<a name="p4" href="#p4">page 4</a>] (<a href="#Contents">Contents</a>)
770 <a name="3.7.2" href="#3.7.2"><b> 3.7.2</b></a>
771 1 multibyte character
772 sequence of one or more bytes representing a member of the extended character set of
773 either the source or the execution environment
774 2 NOTE The extended character set is a superset of the basic character set.
776 <a name="3.7.3" href="#3.7.3"><b> 3.7.3</b></a>
778 bit representation that fits in an object of type wchar_t, capable of representing any
779 character in the current locale
780 <a name="3.8" href="#3.8"><b> 3.8</b></a>
782 restriction, either syntactic or semantic, by which the exposition of language elements is
784 <a name="3.9" href="#3.9"><b> 3.9</b></a>
785 1 correctly rounded result
786 representation in the result format that is nearest in value, subject to the current rounding
787 mode, to what the result would be given unlimited range and precision
788 <a name="3.10" href="#3.10"><b> 3.10</b></a>
790 message belonging to an implementation-defined subset of the implementation's message
792 <a name="3.11" href="#3.11"><b> 3.11</b></a>
794 reference to a later subclause of this International Standard that contains additional
795 information relevant to this subclause
796 <a name="3.12" href="#3.12"><b> 3.12</b></a>
798 particular set of software, running in a particular translation environment under particular
799 control options, that performs translation of programs for, and supports execution of
800 functions in, a particular execution environment
801 <a name="3.13" href="#3.13"><b> 3.13</b></a>
802 1 implementation limit
803 restriction imposed upon programs by the implementation
804 <a name="3.14" href="#3.14"><b> 3.14</b></a>
806 either an object of scalar type, or a maximal sequence of adjacent bit-fields all having
809 [<a name="p5" href="#p5">page 5</a>] (<a href="#Contents">Contents</a>)
811 2 NOTE 1 Two threads of execution can update and access separate memory locations without interfering
814 3 NOTE 2 A bit-field and an adjacent non-bit-field member are in separate memory locations. The same
815 applies to two bit-fields, if one is declared inside a nested structure declaration and the other is not, or if the
816 two are separated by a zero-length bit-field declaration, or if they are separated by a non-bit-field member
817 declaration. It is not safe to concurrently update two non-atomic bit-fields in the same structure if all
818 members declared between them are also (non-zero-length) bit-fields, no matter what the sizes of those
819 intervening bit-fields happen to be.
821 4 EXAMPLE A structure declared as
824 int b:5, c:11, :0, d:8;
825 struct { int ee:8; } e;
827 contains four separate memory locations: The member a, and bit-fields d and e.ee are each separate
828 memory locations, and can be modified concurrently without interfering with each other. The bit-fields b
829 and c together constitute the fourth memory location. The bit-fields b and c cannot be concurrently
830 modified, but b and a, for example, can be.
832 <a name="3.15" href="#3.15"><b> 3.15</b></a>
834 region of data storage in the execution environment, the contents of which can represent
836 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>.
838 <a name="3.16" href="#3.16"><b> 3.16</b></a>
841 formal argument (deprecated)
842 object declared as part of a function declaration or definition that acquires a value on
843 entry to the function, or an identifier from the comma-separated list bounded by the
844 parentheses immediately following the macro name in a function-like macro definition
845 <a name="3.17" href="#3.17"><b> 3.17</b></a>
846 1 recommended practice
847 specification that is strongly recommended as being in keeping with the intent of the
848 standard, but that may be impractical for some implementations
849 <a name="3.18" href="#3.18"><b> 3.18</b></a>
851 requirement on a program when calling a library function
852 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
853 need not be diagnosed at translation time.
855 3 NOTE 2 Implementations that support the extensions in <a href="#K">annex K</a> are required to verify that the runtime-
856 constraints for a library function are not violated by the program; see <a href="#K.3.1.4">K.3.1.4</a>.
858 [<a name="p6" href="#p6">page 6</a>] (<a href="#Contents">Contents</a>)
860 <a name="3.19" href="#3.19"><b> 3.19</b></a>
862 precise meaning of the contents of an object when interpreted as having a specific type
863 <a name="3.19.1" href="#3.19.1"><b> 3.19.1</b></a>
864 1 implementation-defined value
865 unspecified value where each implementation documents how the choice is made
866 <a name="3.19.2" href="#3.19.2"><b> 3.19.2</b></a>
867 1 indeterminate value
868 either an unspecified value or a trap representation
869 <a name="3.19.3" href="#3.19.3"><b> 3.19.3</b></a>
871 valid value of the relevant type where this International Standard imposes no
872 requirements on which value is chosen in any instance
873 2 NOTE An unspecified value cannot be a trap representation.
875 <a name="3.19.4" href="#3.19.4"><b> 3.19.4</b></a>
876 1 trap representation
877 an object representation that need not represent a value of the object type
878 <a name="3.19.5" href="#3.19.5"><b> 3.19.5</b></a>
880 interrupt execution of the program such that no further operations are performed
881 2 NOTE In this International Standard, when the word ''trap'' is not immediately followed by
882 ''representation'', this is the intended usage.<sup><a href="#note2"><b>2)</b></a></sup>
884 <a name="3.20" href="#3.20"><b> 3.20</b></a>
886 ceiling of x: the least integer greater than or equal to x
887 2 EXAMPLE [^2.4^] is 3, [^-2.4^] is -2.
889 <a name="3.21" href="#3.21"><b> 3.21</b></a>
891 floor of x: the greatest integer less than or equal to x
892 2 EXAMPLE [_2.4_] is 2, [_-2.4_] is -3.
897 <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
898 representation might perform a trap but is not required to (see <a href="#6.2.6.1">6.2.6.1</a>).
900 [<a name="p7" href="#p7">page 7</a>] (<a href="#Contents">Contents</a>)
903 <a name="4" href="#4"><b> 4. Conformance</b></a>
904 1 In this International Standard, ''shall'' is to be interpreted as a requirement on an
905 implementation or on a program; conversely, ''shall not'' is to be interpreted as a
907 2 If a ''shall'' or ''shall not'' requirement that appears outside of a constraint or runtime-
908 constraint is violated, the behavior is undefined. Undefined behavior is otherwise
909 indicated in this International Standard by the words ''undefined behavior'' or by the
910 omission of any explicit definition of behavior. There is no difference in emphasis among
911 these three; they all describe ''behavior that is undefined''.
912 3 A program that is correct in all other aspects, operating on correct data, containing
913 unspecified behavior shall be a correct program and act in accordance with <a href="#5.1.2.3">5.1.2.3</a>.
914 4 The implementation shall not successfully translate a preprocessing translation unit
915 containing a #error preprocessing directive unless it is part of a group skipped by
916 conditional inclusion.
917 5 A strictly conforming program shall use only those features of the language and library
918 specified in this International Standard.<sup><a href="#note3"><b>3)</b></a></sup> It shall not produce output dependent on any
919 unspecified, undefined, or implementation-defined behavior, and shall not exceed any
920 minimum implementation limit.
921 6 The two forms of conforming implementation are hosted and freestanding. A conforming
922 hosted implementation shall accept any strictly conforming program. A conforming
923 freestanding implementation shall accept any strictly conforming program that does not
924 use complex types and in which the use of the features specified in the library clause
925 (clause 7) is confined to the contents of the standard headers <a href="#7.7"><float.h></a>,
926 <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>,
927 <a href="#7.19"><stddef.h></a>, and <a href="#7.20"><stdint.h></a>. A conforming implementation may have extensions
928 (including additional library functions), provided they do not alter the behavior of any
929 strictly conforming program.<sup><a href="#note4"><b>4)</b></a></sup>
933 <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
934 by an appropriate conditional inclusion preprocessing directive using the related macro. For example:
935 #ifdef __STDC_IEC_559__ /* FE_UPWARD defined */
937 fesetround(FE_UPWARD);
941 <sup><a name="note4" href="#note4"><b>4)</b></a></sup> This implies that a conforming implementation reserves no identifiers other than those explicitly
942 reserved in this International Standard.
944 [<a name="p8" href="#p8">page 8</a>] (<a href="#Contents">Contents</a>)
946 7 A conforming program is one that is acceptable to a conforming implementation.<sup><a href="#note5"><b>5)</b></a></sup>
947 8 An implementation shall be accompanied by a document that defines all implementation-
948 defined and locale-specific characteristics and all extensions.
949 Forward references: conditional inclusion (<a href="#6.10.1">6.10.1</a>), error directive (<a href="#6.10.5">6.10.5</a>),
950 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>
951 (<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>),
952 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>
953 (<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>).
958 <sup><a name="note5" href="#note5"><b>5)</b></a></sup> Strictly conforming programs are intended to be maximally portable among conforming
959 implementations. Conforming programs may depend upon nonportable features of a conforming
962 [<a name="p9" href="#p9">page 9</a>] (<a href="#Contents">Contents</a>)
965 <a name="5" href="#5"><b> 5. Environment</b></a>
966 1 An implementation translates C source files and executes C programs in two data-
967 processing-system environments, which will be called the translation environment and
968 the execution environment in this International Standard. Their characteristics define and
969 constrain the results of executing conforming C programs constructed according to the
970 syntactic and semantic rules for conforming implementations.
971 Forward references: In this clause, only a few of many possible forward references
973 <a name="5.1" href="#5.1"><b> 5.1 Conceptual models</b></a>
974 <a name="5.1.1" href="#5.1.1"><b> 5.1.1 Translation environment</b></a>
975 <a name="5.1.1.1" href="#5.1.1.1"><b> 5.1.1.1 Program structure</b></a>
976 1 A C program need not all be translated at the same time. The text of the program is kept
977 in units called source files, (or preprocessing files) in this International Standard. A
978 source file together with all the headers and source files included via the preprocessing
979 directive #include is known as a preprocessing translation unit. After preprocessing, a
980 preprocessing translation unit is called a translation unit. Previously translated translation
981 units may be preserved individually or in libraries. The separate translation units of a
982 program communicate by (for example) calls to functions whose identifiers have external
983 linkage, manipulation of objects whose identifiers have external linkage, or manipulation
984 of data files. Translation units may be separately translated and then later linked to
985 produce an executable program.
986 Forward references: linkages of identifiers (<a href="#6.2.2">6.2.2</a>), external definitions (<a href="#6.9">6.9</a>),
987 preprocessing directives (<a href="#6.10">6.10</a>).
988 <a name="5.1.1.2" href="#5.1.1.2"><b> 5.1.1.2 Translation phases</b></a>
989 1 The precedence among the syntax rules of translation is specified by the following
990 phases.<sup><a href="#note6"><b>6)</b></a></sup>
991 1. Physical source file multibyte characters are mapped, in an implementation-
992 defined manner, to the source character set (introducing new-line characters for
993 end-of-line indicators) if necessary. Trigraph sequences are replaced by
994 corresponding single-character internal representations.
998 <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
999 together in practice. Source files, translation units, and translated translation units need not
1000 necessarily be stored as files, nor need there be any one-to-one correspondence between these entities
1001 and any external representation. The description is conceptual only, and does not specify any
1002 particular implementation.
1004 [<a name="p10" href="#p10">page 10</a>] (<a href="#Contents">Contents</a>)
1006 2. Each instance of a backslash character (\) immediately followed by a new-line
1007 character is deleted, splicing physical source lines to form logical source lines.
1008 Only the last backslash on any physical source line shall be eligible for being part
1009 of such a splice. A source file that is not empty shall end in a new-line character,
1010 which shall not be immediately preceded by a backslash character before any such
1011 splicing takes place.
1012 3. The source file is decomposed into preprocessing tokens<sup><a href="#note7"><b>7)</b></a></sup> and sequences of
1013 white-space characters (including comments). A source file shall not end in a
1014 partial preprocessing token or in a partial comment. Each comment is replaced by
1015 one space character. New-line characters are retained. Whether each nonempty
1016 sequence of white-space characters other than new-line is retained or replaced by
1017 one space character is implementation-defined.
1018 4. Preprocessing directives are executed, macro invocations are expanded, and
1019 _Pragma unary operator expressions are executed. If a character sequence that
1020 matches the syntax of a universal character name is produced by token
1021 concatenation (<a href="#6.10.3.3">6.10.3.3</a>), the behavior is undefined. A #include preprocessing
1022 directive causes the named header or source file to be processed from phase 1
1023 through phase 4, recursively. All preprocessing directives are then deleted.
1024 5. Each source character set member and escape sequence in character constants and
1025 string literals is converted to the corresponding member of the execution character
1026 set; if there is no corresponding member, it is converted to an implementation-
1027 defined member other than the null (wide) character.<sup><a href="#note8"><b>8)</b></a></sup>
1028 6. Adjacent string literal tokens are concatenated.
1029 7. White-space characters separating tokens are no longer significant. Each
1030 preprocessing token is converted into a token. The resulting tokens are
1031 syntactically and semantically analyzed and translated as a translation unit.
1032 8. All external object and function references are resolved. Library components are
1033 linked to satisfy external references to functions and objects not defined in the
1034 current translation. All such translator output is collected into a program image
1035 which contains information needed for execution in its execution environment.
1036 Forward references: universal character names (<a href="#6.4.3">6.4.3</a>), lexical elements (<a href="#6.4">6.4</a>),
1037 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>).
1041 <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
1042 context-dependent. For example, see the handling of < within a #include preprocessing directive.
1043 <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
1046 [<a name="p11" href="#p11">page 11</a>] (<a href="#Contents">Contents</a>)
1048 <a name="5.1.1.3" href="#5.1.1.3"><b> 5.1.1.3 Diagnostics</b></a>
1049 1 A conforming implementation shall produce at least one diagnostic message (identified in
1050 an implementation-defined manner) if a preprocessing translation unit or translation unit
1051 contains a violation of any syntax rule or constraint, even if the behavior is also explicitly
1052 specified as undefined or implementation-defined. Diagnostic messages need not be
1053 produced in other circumstances.<sup><a href="#note9"><b>9)</b></a></sup>
1054 2 EXAMPLE An implementation shall issue a diagnostic for the translation unit:
1057 because in those cases where wording in this International Standard describes the behavior for a construct
1058 as being both a constraint error and resulting in undefined behavior, the constraint error shall be diagnosed.
1060 <a name="5.1.2" href="#5.1.2"><b> 5.1.2 Execution environments</b></a>
1061 1 Two execution environments are defined: freestanding and hosted. In both cases,
1062 program startup occurs when a designated C function is called by the execution
1063 environment. All objects with static storage duration shall be initialized (set to their
1064 initial values) before program startup. The manner and timing of such initialization are
1065 otherwise unspecified. Program termination returns control to the execution
1067 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>).
1068 <a name="5.1.2.1" href="#5.1.2.1"><b> 5.1.2.1 Freestanding environment</b></a>
1069 1 In a freestanding environment (in which C program execution may take place without any
1070 benefit of an operating system), the name and type of the function called at program
1071 startup are implementation-defined. Any library facilities available to a freestanding
1072 program, other than the minimal set required by clause 4, are implementation-defined.
1073 2 The effect of program termination in a freestanding environment is implementation-
1075 <a name="5.1.2.2" href="#5.1.2.2"><b> 5.1.2.2 Hosted environment</b></a>
1076 1 A hosted environment need not be provided, but shall conform to the following
1077 specifications if present.
1082 <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
1083 violation. Of course, an implementation is free to produce any number of diagnostics as long as a
1084 valid program is still correctly translated. It may also successfully translate an invalid program.
1086 [<a name="p12" href="#p12">page 12</a>] (<a href="#Contents">Contents</a>)
1088 <a name="5.1.2.2.1" href="#5.1.2.2.1"><b> 5.1.2.2.1 Program startup</b></a>
1089 1 The function called at program startup is named main. The implementation declares no
1090 prototype for this function. It shall be defined with a return type of int and with no
1092 int main(void) { /* ... */ }
1093 or with two parameters (referred to here as argc and argv, though any names may be
1094 used, as they are local to the function in which they are declared):
1095 int main(int argc, char *argv[]) { /* ... */ }
1096 or equivalent;<sup><a href="#note10"><b>10)</b></a></sup> or in some other implementation-defined manner.
1097 2 If they are declared, the parameters to the main function shall obey the following
1099 -- The value of argc shall be nonnegative.
1100 -- argv[argc] shall be a null pointer.
1101 -- If the value of argc is greater than zero, the array members argv[0] through
1102 argv[argc-1] inclusive shall contain pointers to strings, which are given
1103 implementation-defined values by the host environment prior to program startup. The
1104 intent is to supply to the program information determined prior to program startup
1105 from elsewhere in the hosted environment. If the host environment is not capable of
1106 supplying strings with letters in both uppercase and lowercase, the implementation
1107 shall ensure that the strings are received in lowercase.
1108 -- If the value of argc is greater than zero, the string pointed to by argv[0]
1109 represents the program name; argv[0][0] shall be the null character if the
1110 program name is not available from the host environment. If the value of argc is
1111 greater than one, the strings pointed to by argv[1] through argv[argc-1]
1112 represent the program parameters.
1113 -- The parameters argc and argv and the strings pointed to by the argv array shall
1114 be modifiable by the program, and retain their last-stored values between program
1115 startup and program termination.
1116 <a name="5.1.2.2.2" href="#5.1.2.2.2"><b> 5.1.2.2.2 Program execution</b></a>
1117 1 In a hosted environment, a program may use all the functions, macros, type definitions,
1118 and objects described in the library clause (clause 7).
1123 <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
1124 char ** argv, and so on.
1126 [<a name="p13" href="#p13">page 13</a>] (<a href="#Contents">Contents</a>)
1128 <a name="5.1.2.2.3" href="#5.1.2.2.3"><b> 5.1.2.2.3 Program termination</b></a>
1129 1 If the return type of the main function is a type compatible with int, a return from the
1130 initial call to the main function is equivalent to calling the exit function with the value
1131 returned by the main function as its argument;<sup><a href="#note11"><b>11)</b></a></sup> reaching the } that terminates the
1132 main function returns a value of 0. If the return type is not compatible with int, the
1133 termination status returned to the host environment is unspecified.
1134 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>).
1135 <a name="5.1.2.3" href="#5.1.2.3"><b> 5.1.2.3 Program execution</b></a>
1136 1 The semantic descriptions in this International Standard describe the behavior of an
1137 abstract machine in which issues of optimization are irrelevant.
1138 2 Accessing a volatile object, modifying an object, modifying a file, or calling a function
1139 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
1140 the execution environment. Evaluation of an expression in general includes both value
1141 computations and initiation of side effects. Value computation for an lvalue expression
1142 includes determining the identity of the designated object.
1143 3 Sequenced before is an asymmetric, transitive, pair-wise relation between evaluations
1144 executed by a single thread, which induces a partial order among those evaluations.
1145 Given any two evaluations A and B, if A is sequenced before B, then the execution of A
1146 shall precede the execution of B. (Conversely, if A is sequenced before B, then B is
1147 sequenced after A.) If A is not sequenced before or after B, then A and B are
1148 unsequenced. Evaluations A and B are indeterminately sequenced when A is sequenced
1149 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
1150 between the evaluation of expressions A and B implies that every value computation and
1151 side effect associated with A is sequenced before every value computation and side effect
1152 associated with B. (A summary of the sequence points is given in <a href="#C">annex C</a>.)
1153 4 In the abstract machine, all expressions are evaluated as specified by the semantics. An
1154 actual implementation need not evaluate part of an expression if it can deduce that its
1155 value is not used and that no needed side effects are produced (including any caused by
1157 <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
1158 will have ended in the former case, even where they would not have in the latter.
1159 <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
1160 flags and control modes. Floating-point operations implicitly set the status flags; modes affect result
1161 values of floating-point operations. Implementations that support such floating-point state are
1162 required to regard changes to it as side effects -- see <a href="#F">annex F</a> for details. The floating-point
1163 environment library <a href="#7.6"><fenv.h></a> provides a programming facility for indicating when these side
1164 effects matter, freeing the implementations in other cases.
1165 <sup><a name="note13" href="#note13"><b>13)</b></a></sup> The executions of unsequenced evaluations can interleave. Indeterminately sequenced evaluations
1166 cannot interleave, but can be executed in any order.
1168 [<a name="p14" href="#p14">page 14</a>] (<a href="#Contents">Contents</a>)
1170 calling a function or accessing a volatile object).
1171 5 When the processing of the abstract machine is interrupted by receipt of a signal, the
1172 values of objects that are neither lock-free atomic objects nor of type volatile
1173 sig_atomic_t are unspecified, and the value of any object that is modified by the
1174 handler that is neither a lock-free atomic object nor of type volatile
1175 sig_atomic_t becomes undefined.
1176 6 The least requirements on a conforming implementation are:
1177 -- Accesses to volatile objects are evaluated strictly according to the rules of the abstract
1179 -- At program termination, all data written into files shall be identical to the result that
1180 execution of the program according to the abstract semantics would have produced.
1181 -- The input and output dynamics of interactive devices shall take place as specified in
1182 <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>
1183 appear as soon as possible, to ensure that prompting messages actually appear prior to
1184 a program waiting for input.
1185 This is the observable behavior of the program.
1186 7 What constitutes an interactive device is implementation-defined.
1187 8 More stringent correspondences between abstract and actual semantics may be defined by
1188 each implementation.
1189 9 EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual
1190 semantics: at every sequence point, the values of the actual objects would agree with those specified by the
1191 abstract semantics. The keyword volatile would then be redundant.
1192 10 Alternatively, an implementation might perform various optimizations within each translation unit, such
1193 that the actual semantics would agree with the abstract semantics only when making function calls across
1194 translation unit boundaries. In such an implementation, at the time of each function entry and function
1195 return where the calling function and the called function are in different translation units, the values of all
1196 externally linked objects and of all objects accessible via pointers therein would agree with the abstract
1197 semantics. Furthermore, at the time of each such function entry the values of the parameters of the called
1198 function and of all objects accessible via pointers therein would agree with the abstract semantics. In this
1199 type of implementation, objects referred to by interrupt service routines activated by the signal function
1200 would require explicit specification of volatile storage, as well as other implementation-defined
1203 11 EXAMPLE 2 In executing the fragment
1207 the ''integer promotions'' require that the abstract machine promote the value of each variable to int size
1208 and then add the two ints and truncate the sum. Provided the addition of two chars can be done without
1209 overflow, or with overflow wrapping silently to produce the correct result, the actual execution need only
1210 produce the same result, possibly omitting the promotions.
1212 [<a name="p15" href="#p15">page 15</a>] (<a href="#Contents">Contents</a>)
1214 12 EXAMPLE 3 Similarly, in the fragment
1219 the multiplication may be executed using single-precision arithmetic if the implementation can ascertain
1220 that the result would be the same as if it were executed using double-precision arithmetic (for example, if d
1221 were replaced by the constant 2.0, which has type double).
1223 13 EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate
1224 semantics. Values are independent of whether they are represented in a register or in memory. For
1225 example, an implicit spilling of a register is not permitted to alter the value. Also, an explicit store and load
1226 is required to round to the precision of the storage type. In particular, casts and assignments are required to
1227 perform their specified conversion. For the fragment
1230 d1 = f = expression;
1231 d2 = (float) expression;
1232 the values assigned to d1 and d2 are required to have been converted to float.
1234 14 EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in
1235 precision as well as range. The implementation cannot generally apply the mathematical associative rules
1236 for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of
1237 overflow and underflow. Likewise, implementations cannot generally replace decimal constants in order to
1238 rearrange expressions. In the following fragment, rearrangements suggested by mathematical rules for real
1239 numbers are often not valid (see <a href="#F.9">F.9</a>).
1242 x = (x * y) * z; // not equivalent to x *= y * z;
1243 z = (x - y) + y ; // not equivalent to z = x;
1244 z = x + x * y; // not equivalent to z = x * (1.0 + y);
1245 y = x / 5.0; // not equivalent to y = x * 0.2;
1247 15 EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
1250 a = a + 32760 + b + 5;
1251 the expression statement behaves exactly the same as
1252 a = (((a + 32760) + b) + 5);
1253 due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is
1254 next added to b, and that result is then added to 5 which results in the value assigned to a. On a machine in
1255 which overflows produce an explicit trap and in which the range of values representable by an int is
1256 [-32768, +32767], the implementation cannot rewrite this expression as
1257 a = ((a + b) + 32765);
1258 since if the values for a and b were, respectively, -32754 and -15, the sum a + b would produce a trap
1259 while the original expression would not; nor can the expression be rewritten either as
1261 [<a name="p16" href="#p16">page 16</a>] (<a href="#Contents">Contents</a>)
1263 a = ((a + 32765) + b);
1265 a = (a + (b + 32765));
1266 since the values for a and b might have been, respectively, 4 and -8 or -17 and 12. However, on a machine
1267 in which overflow silently generates some value and where positive and negative overflows cancel, the
1268 above expression statement can be rewritten by the implementation in any of the above ways because the
1269 same result will occur.
1271 16 EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the
1273 #include <a href="#7.21"><stdio.h></a>
1277 sum = sum * 10 - '0' + (*p++ = getchar());
1278 the expression statement is grouped as if it were written as
1279 sum = (((sum * 10) - '0') + ((*(p++)) = (getchar())));
1280 but the actual increment of p can occur at any time between the previous sequence point and the next
1281 sequence point (the ;), and the call to getchar can occur at any point prior to the need of its returned
1284 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
1285 signal function (<a href="#7.14">7.14</a>), files (<a href="#7.21.3">7.21.3</a>).
1286 <a name="5.1.2.4" href="#5.1.2.4"><b> 5.1.2.4 Multi-threaded executions and data races</b></a>
1287 1 Under a hosted implementation, a program can have more than one thread of execution
1288 (or thread) running concurrently. The execution of each thread proceeds as defined by
1289 the remainder of this standard. The execution of the entire program consists of an
1290 execution of all of its threads.<sup><a href="#note14"><b>14)</b></a></sup> Under a freestanding implementation, it is
1291 implementation-defined whether a program can have more than one thread of execution.
1292 2 The value of an object visible to a thread T at a particular point is the initial value of the
1293 object, a value stored in the object by T , or a value stored in the object by another thread,
1294 according to the rules below.
1295 3 NOTE 1 In some cases, there may instead be undefined behavior. Much of this section is motivated by
1296 the desire to support atomic operations with explicit and detailed visibility constraints. However, it also
1297 implicitly supports a simpler view for more restricted programs.
1299 4 Two expression evaluations conflict if one of them modifies a memory location and the
1300 other one reads or modifies the same memory location.
1305 <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
1306 atomic operations, for example, allow executions inconsistent with a simple interleaving as described
1309 [<a name="p17" href="#p17">page 17</a>] (<a href="#Contents">Contents</a>)
1311 5 The library defines a number of atomic operations (<a href="#7.17">7.17</a>) and operations on mutexes
1312 (<a href="#7.25.4">7.25.4</a>) that are specially identified as synchronization operations. These operations play
1313 a special role in making assignments in one thread visible to another. A synchronization
1314 operation on one or more memory locations is either an acquire operation, a release
1315 operation, both an acquire and release operation, or a consume operation. A
1316 synchronization operation without an associated memory location is a fence and can be
1317 either an acquire fence, a release fence, or both an acquire and release fence. In addition,
1318 there are relaxed atomic operations, which are not synchronization operations, and
1319 atomic read-modify-write operations, which have special characteristics.
1320 6 NOTE 2 For example, a call that acquires a mutex will perform an acquire operation on the locations
1321 composing the mutex. Correspondingly, a call that releases the same mutex will perform a release
1322 operation on those same locations. Informally, performing a release operation on A forces prior side effects
1323 on other memory locations to become visible to other threads that later perform an acquire or consume
1324 operation on A. We do not include relaxed atomic operations as synchronization operations although, like
1325 synchronization operations, they cannot contribute to data races.
1327 7 All modifications to a particular atomic object M occur in some particular total order,
1328 called the modification order of M. If A and B are modifications of an atomic object M,
1329 and A happens before B, then A shall precede B in the modification order of M, which is
1331 8 NOTE 3 This states that the modification orders must respect the ''happens before'' relation.
1333 9 NOTE 4 There is a separate order for each atomic object. There is no requirement that these can be
1334 combined into a single total order for all objects. In general this will be impossible since different threads
1335 may observe modifications to different variables in inconsistent orders.
1337 10 A release sequence on an atomic object M is a maximal contiguous sub-sequence of side
1338 effects in the modification order of M, where the first operation is a release and every
1339 subsequent operation either is performed by the same thread that performed the release or
1340 is an atomic read-modify-write operation.
1341 11 Certain library calls synchronize with other library calls performed by another thread. In
1342 particular, an atomic operation A that performs a release operation on an object M
1343 synchronizes with an atomic operation B that performs an acquire operation on M and
1344 reads a value written by any side effect in the release sequence headed by A.
1345 12 NOTE 5 Except in the specified cases, reading a later value does not necessarily ensure visibility as
1346 described below. Such a requirement would sometimes interfere with efficient implementation.
1348 13 NOTE 6 The specifications of the synchronization operations define when one reads the value written by
1349 another. For atomic variables, the definition is clear. All operations on a given mutex occur in a single total
1350 order. Each mutex acquisition ''reads the value written'' by the last mutex release.
1352 14 An evaluation A carries a dependency <sup><a href="#note15"><b>15)</b></a></sup> to an evaluation B if:
1355 <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
1356 strictly intra-thread.
1358 [<a name="p18" href="#p18">page 18</a>] (<a href="#Contents">Contents</a>)
1360 -- the value of A is used as an operand of B, unless:
1361 o B is an invocation of the kill_dependency macro,
1363 o A is the left operand of a && or || operator,
1365 o A is the left operand of a ? : operator, or
1367 o A is the left operand of a , operator;
1369 -- A writes a scalar object or bit-field M, B reads from M the value written by A, and A
1370 is sequenced before B, or
1371 -- for some evaluation X, A carries a dependency to X and X carries a dependency to B.
1372 15 An evaluation A is dependency-ordered before<sup><a href="#note16"><b>16)</b></a></sup> an evaluation B if:
1373 -- A performs a release operation on an atomic object M, and B performs a consume
1374 operation on M and reads a value written by any side effect in the release sequence
1376 -- for some evaluation X, A is dependency-ordered before X and X carries a
1378 16 An evaluation A inter-thread happens before an evaluation B if A synchronizes with B, A
1379 is dependency-ordered before B, or, for some evaluation X:
1380 -- A synchronizes with X and X is sequenced before B,
1381 -- A is sequenced before X and X inter-thread happens before B, or
1382 -- A inter-thread happens before X and X inter-thread happens before B.
1383 17 NOTE 7 The ''inter-thread happens before'' relation describes arbitrary concatenations of ''sequenced
1384 before'', ''synchronizes with'', and ''dependency-ordered before'' relationships, with two exceptions. The
1385 first exception is that a concatenation is not permitted to end with ''dependency-ordered before'' followed
1386 by ''sequenced before''. The reason for this limitation is that a consume operation participating in a
1387 ''dependency-ordered before'' relationship provides ordering only with respect to operations to which this
1388 consume operation actually carries a dependency. The reason that this limitation applies only to the end of
1389 such a concatenation is that any subsequent release operation will provide the required ordering for a prior
1390 consume operation. The second exception is that a concatenation is not permitted to consist entirely of
1391 ''sequenced before''. The reasons for this limitation are (1) to permit ''inter-thread happens before'' to be
1392 transitively closed and (2) the ''happens before'' relation, defined below, provides for relationships
1393 consisting entirely of ''sequenced before''.
1395 18 An evaluation A happens before an evaluation B if A is sequenced before B or A inter-
1396 thread happens before B.
1400 <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
1401 release/consume in place of release/acquire.
1403 [<a name="p19" href="#p19">page 19</a>] (<a href="#Contents">Contents</a>)
1405 19 A visible side effect A on an object M with respect to a value computation B of M
1406 satisfies the conditions:
1407 -- A happens before B, and
1408 -- there is no other side effect X to M such that A happens before X and X happens
1410 The value of a non-atomic scalar object M, as determined by evaluation B, shall be the
1411 value stored by the visible side effect A.
1412 20 NOTE 8 If there is ambiguity about which side effect to a non-atomic object is visible, then there is a data
1413 race and the behavior is undefined.
1415 21 NOTE 9 This states that operations on ordinary variables are not visibly reordered. This is not actually
1416 detectable without data races, but it is necessary to ensure that data races, as defined here, and with suitable
1417 restrictions on the use of atomics, correspond to data races in a simple interleaved (sequentially consistent)
1420 22 The visible sequence of side effects on an atomic object M, with respect to a value
1421 computation B of M, is a maximal contiguous sub-sequence of side effects in the
1422 modification order of M, where the first side effect is visible with respect to B, and for
1423 every subsequent side effect, it is not the case that B happens before it. The value of an
1424 atomic object M, as determined by evaluation B, shall be the value stored by some
1425 operation in the visible sequence of M with respect to B. Furthermore, if a value
1426 computation A of an atomic object M happens before a value computation B of M, and
1427 the value computed by A corresponds to the value stored by side effect X, then the value
1428 computed by B shall either equal the value computed by A, or be the value stored by side
1429 effect Y , where Y follows X in the modification order of M.
1430 23 NOTE 10 This effectively disallows compiler reordering of atomic operations to a single object, even if
1431 both operations are ''relaxed'' loads. By doing so, we effectively make the ''cache coherence'' guarantee
1432 provided by most hardware available to C atomic operations.
1434 24 NOTE 11 The visible sequence depends on the ''happens before'' relation, which in turn depends on the
1435 values observed by loads of atomics, which we are restricting here. The intended reading is that there must
1436 exist an association of atomic loads with modifications they observe that, together with suitably chosen
1437 modification orders and the ''happens before'' relation derived as described above, satisfy the resulting
1438 constraints as imposed here.
1440 25 The execution of a program contains a data race if it contains two conflicting actions in
1441 different threads, at least one of which is not atomic, and neither happens before the
1442 other. Any such data race results in undefined behavior.
1443 26 NOTE 12 It can be shown that programs that correctly use simple mutexes and
1444 memory_order_seq_cst operations to prevent all data races, and use no other synchronization
1445 operations, behave as though the operations executed by their constituent threads were simply interleaved,
1446 with each value computation of an object being the last value stored in that interleaving. This is normally
1447 referred to as ''sequential consistency''. However, this applies only to data-race-free programs, and data-
1448 race-free programs cannot observe most program transformations that do not change single-threaded
1449 program semantics. In fact, most single-threaded program transformations continue to be allowed, since
1450 any program that behaves differently as a result must contain undefined behavior.
1452 [<a name="p20" href="#p20">page 20</a>] (<a href="#Contents">Contents</a>)
1454 27 NOTE 13 Compiler transformations that introduce assignments to a potentially shared memory location
1455 that would not be modified by the abstract machine are generally precluded by this standard, since such an
1456 assignment might overwrite another assignment by a different thread in cases in which an abstract machine
1457 execution would not have encountered a data race. This includes implementations of data member
1458 assignment that overwrite adjacent members in separate memory locations. We also generally preclude
1459 reordering of atomic loads in cases in which the atomics in question may alias, since this may violate the
1460 "visible sequence" rules.
1462 28 NOTE 14 Transformations that introduce a speculative read of a potentially shared memory location may
1463 not preserve the semantics of the program as defined in this standard, since they potentially introduce a data
1464 race. However, they are typically valid in the context of an optimizing compiler that targets a specific
1465 machine with well-defined semantics for data races. They would be invalid for a hypothetical machine that
1466 is not tolerant of races or provides hardware race detection.
1468 [<a name="p21" href="#p21">page 21</a>] (<a href="#Contents">Contents</a>)
1470 <a name="5.2" href="#5.2"><b> 5.2 Environmental considerations</b></a>
1471 <a name="5.2.1" href="#5.2.1"><b> 5.2.1 Character sets</b></a>
1472 1 Two sets of characters and their associated collating sequences shall be defined: the set in
1473 which source files are written (the source character set), and the set interpreted in the
1474 execution environment (the execution character set). Each set is further divided into a
1475 basic character set, whose contents are given by this subclause, and a set of zero or more
1476 locale-specific members (which are not members of the basic character set) called
1477 extended characters. The combined set is also called the extended character set. The
1478 values of the members of the execution character set are implementation-defined.
1479 2 In a character constant or string literal, members of the execution character set shall be
1480 represented by corresponding members of the source character set or by escape
1481 sequences consisting of the backslash \ followed by one or more characters. A byte with
1482 all bits set to 0, called the null character, shall exist in the basic execution character set; it
1483 is used to terminate a character string.
1484 3 Both the basic source and basic execution character sets shall have the following
1485 members: the 26 uppercase letters of the Latin alphabet
1486 A B C D E F G H I J K L M
1487 N O P Q R S T U V W X Y Z
1488 the 26 lowercase letters of the Latin alphabet
1489 a b c d e f g h i j k l m
1490 n o p q r s t u v w x y z
1491 the 10 decimal digits
1493 the following 29 graphic characters
1494 ! " # % & ' ( ) * + , - . / :
1495 ; < = > ? [ \ ] ^ _ { | } ~
1496 the space character, and control characters representing horizontal tab, vertical tab, and
1497 form feed. The representation of each member of the source and execution basic
1498 character sets shall fit in a byte. In both the source and execution basic character sets, the
1499 value of each character after 0 in the above list of decimal digits shall be one greater than
1500 the value of the previous. In source files, there shall be some way of indicating the end of
1501 each line of text; this International Standard treats such an end-of-line indicator as if it
1502 were a single new-line character. In the basic execution character set, there shall be
1503 control characters representing alert, backspace, carriage return, and new line. If any
1504 other characters are encountered in a source file (except in an identifier, a character
1505 constant, a string literal, a header name, a comment, or a preprocessing token that is never
1507 [<a name="p22" href="#p22">page 22</a>] (<a href="#Contents">Contents</a>)
1509 converted to a token), the behavior is undefined.
1510 4 A letter is an uppercase letter or a lowercase letter as defined above; in this International
1511 Standard the term does not include other characters that are letters in other alphabets.
1512 5 The universal character name construct provides a way to name other characters.
1513 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>),
1514 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>).
1515 <a name="5.2.1.1" href="#5.2.1.1"><b> 5.2.1.1 Trigraph sequences</b></a>
1516 1 Before any other processing takes place, each occurrence of one of the following
1517 sequences of three characters (called trigraph sequences<sup><a href="#note17"><b>17)</b></a></sup>) is replaced with the
1518 corresponding single character.
1520 ??( [ ??' ^ ??> }
1521 ??/ \ ??< { ??- ~
1522 No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
1523 above is not changed.
1525 ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)
1527 #define arraycheck(a, b) a[b] || b[a]
1529 3 EXAMPLE 2 The following source line
1531 becomes (after replacement of the trigraph sequence ??/)
1534 <a name="5.2.1.2" href="#5.2.1.2"><b> 5.2.1.2 Multibyte characters</b></a>
1535 1 The source character set may contain multibyte characters, used to represent members of
1536 the extended character set. The execution character set may also contain multibyte
1537 characters, which need not have the same encoding as for the source character set. For
1538 both character sets, the following shall hold:
1539 -- The basic character set shall be present and each character shall be encoded as a
1541 -- The presence, meaning, and representation of any additional members is locale-
1544 <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
1545 described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
1547 [<a name="p23" href="#p23">page 23</a>] (<a href="#Contents">Contents</a>)
1549 -- A multibyte character set may have a state-dependent encoding, wherein each
1550 sequence of multibyte characters begins in an initial shift state and enters other
1551 locale-specific shift states when specific multibyte characters are encountered in the
1552 sequence. While in the initial shift state, all single-byte characters retain their usual
1553 interpretation and do not alter the shift state. The interpretation for subsequent bytes
1554 in the sequence is a function of the current shift state.
1555 -- A byte with all bits zero shall be interpreted as a null character independent of shift
1556 state. Such a byte shall not occur as part of any other multibyte character.
1557 2 For source files, the following shall hold:
1558 -- An identifier, comment, string literal, character constant, or header name shall begin
1559 and end in the initial shift state.
1560 -- An identifier, comment, string literal, character constant, or header name shall consist
1561 of a sequence of valid multibyte characters.
1562 <a name="5.2.2" href="#5.2.2"><b> 5.2.2 Character display semantics</b></a>
1563 1 The active position is that location on a display device where the next character output by
1564 the fputc function would appear. The intent of writing a printing character (as defined
1565 by the isprint function) to a display device is to display a graphic representation of
1566 that character at the active position and then advance the active position to the next
1567 position on the current line. The direction of writing is locale-specific. If the active
1568 position is at the final position of a line (if there is one), the behavior of the display device
1570 2 Alphabetic escape sequences representing nongraphic characters in the execution
1571 character set are intended to produce actions on display devices as follows:
1572 \a (alert) Produces an audible or visible alert without changing the active position.
1573 \b (backspace) Moves the active position to the previous position on the current line. If
1574 the active position is at the initial position of a line, the behavior of the display
1575 device is unspecified.
1576 \f ( form feed) Moves the active position to the initial position at the start of the next
1578 \n (new line) Moves the active position to the initial position of the next line.
1579 \r (carriage return) Moves the active position to the initial position of the current line.
1580 \t (horizontal tab) Moves the active position to the next horizontal tabulation position
1581 on the current line. If the active position is at or past the last defined horizontal
1582 tabulation position, the behavior of the display device is unspecified.
1583 \v (vertical tab) Moves the active position to the initial position of the next vertical
1584 tabulation position. If the active position is at or past the last defined vertical
1586 [<a name="p24" href="#p24">page 24</a>] (<a href="#Contents">Contents</a>)
1588 tabulation position, the behavior of the display device is unspecified.
1589 3 Each of these escape sequences shall produce a unique implementation-defined value
1590 which can be stored in a single char object. The external representations in a text file
1591 need not be identical to the internal representations, and are outside the scope of this
1592 International Standard.
1593 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>).
1594 <a name="5.2.3" href="#5.2.3"><b> 5.2.3 Signals and interrupts</b></a>
1595 1 Functions shall be implemented such that they may be interrupted at any time by a signal,
1596 or may be called by a signal handler, or both, with no alteration to earlier, but still active,
1597 invocations' control flow (after the interruption), function return values, or objects with
1598 automatic storage duration. All such objects shall be maintained outside the function
1599 image (the instructions that compose the executable representation of a function) on a
1600 per-invocation basis.
1601 <a name="5.2.4" href="#5.2.4"><b> 5.2.4 Environmental limits</b></a>
1602 1 Both the translation and execution environments constrain the implementation of
1603 language translators and libraries. The following summarizes the language-related
1604 environmental limits on a conforming implementation; the library-related limits are
1605 discussed in clause 7.
1606 <a name="5.2.4.1" href="#5.2.4.1"><b> 5.2.4.1 Translation limits</b></a>
1607 1 The implementation shall be able to translate and execute at least one program that
1608 contains at least one instance of every one of the following limits:<sup><a href="#note18"><b>18)</b></a></sup>
1609 -- 127 nesting levels of blocks
1610 -- 63 nesting levels of conditional inclusion
1611 -- 12 pointer, array, and function declarators (in any combinations) modifying an
1612 arithmetic, structure, union, or void type in a declaration
1613 -- 63 nesting levels of parenthesized declarators within a full declarator
1614 -- 63 nesting levels of parenthesized expressions within a full expression
1615 -- 63 significant initial characters in an internal identifier or a macro name (each
1616 universal character name or extended source character is considered a single
1618 -- 31 significant initial characters in an external identifier (each universal character name
1619 specifying a short identifier of 0000FFFF or less is considered 6 characters, each
1622 <sup><a name="note18" href="#note18"><b>18)</b></a></sup> Implementations should avoid imposing fixed translation limits whenever possible.
1624 [<a name="p25" href="#p25">page 25</a>] (<a href="#Contents">Contents</a>)
1626 universal character name specifying a short identifier of 00010000 or more is
1627 considered 10 characters, and each extended source character is considered the same
1628 number of characters as the corresponding universal character name, if any)<sup><a href="#note19"><b>19)</b></a></sup>
1629 -- 4095 external identifiers in one translation unit
1630 -- 511 identifiers with block scope declared in one block
1631 -- 4095 macro identifiers simultaneously defined in one preprocessing translation unit
1632 -- 127 parameters in one function definition
1633 -- 127 arguments in one function call
1634 -- 127 parameters in one macro definition
1635 -- 127 arguments in one macro invocation
1636 -- 4095 characters in a logical source line
1637 -- 4095 characters in a string literal (after concatenation)
1638 -- 65535 bytes in an object (in a hosted environment only)
1639 -- 15 nesting levels for #included files
1640 -- 1023 case labels for a switch statement (excluding those for any nested switch
1642 -- 1023 members in a single structure or union
1643 -- 1023 enumeration constants in a single enumeration
1644 -- 63 levels of nested structure or union definitions in a single struct-declaration-list
1645 <a name="5.2.4.2" href="#5.2.4.2"><b> 5.2.4.2 Numerical limits</b></a>
1646 1 An implementation is required to document all the limits specified in this subclause,
1647 which are specified in the headers <a href="#7.10"><limits.h></a> and <a href="#7.7"><float.h></a>. Additional limits are
1648 specified in <a href="#7.20"><stdint.h></a>.
1649 Forward references: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>).
1650 <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>
1651 1 The values given below shall be replaced by constant expressions suitable for use in #if
1652 preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the
1653 following shall be replaced by expressions that have the same type as would an
1654 expression that is an object of the corresponding type converted according to the integer
1655 promotions. Their implementation-defined values shall be equal or greater in magnitude
1658 <sup><a name="note19" href="#note19"><b>19)</b></a></sup> See ''future language directions'' (<a href="#6.11.3">6.11.3</a>).
1660 [<a name="p26" href="#p26">page 26</a>] (<a href="#Contents">Contents</a>)
1662 (absolute value) to those shown, with the same sign.
1663 -- number of bits for smallest object that is not a bit-field (byte)
1665 -- minimum value for an object of type signed char
1666 SCHAR_MIN -127 // -(27 - 1)
1667 -- maximum value for an object of type signed char
1668 SCHAR_MAX +127 // 27 - 1
1669 -- maximum value for an object of type unsigned char
1670 UCHAR_MAX 255 // 28 - 1
1671 -- minimum value for an object of type char
1673 -- maximum value for an object of type char
1675 -- maximum number of bytes in a multibyte character, for any supported locale
1677 -- minimum value for an object of type short int
1678 SHRT_MIN -32767 // -(215 - 1)
1679 -- maximum value for an object of type short int
1680 SHRT_MAX +32767 // 215 - 1
1681 -- maximum value for an object of type unsigned short int
1682 USHRT_MAX 65535 // 216 - 1
1683 -- minimum value for an object of type int
1684 INT_MIN -32767 // -(215 - 1)
1685 -- maximum value for an object of type int
1686 INT_MAX +32767 // 215 - 1
1687 -- maximum value for an object of type unsigned int
1688 UINT_MAX 65535 // 216 - 1
1689 -- minimum value for an object of type long int
1690 LONG_MIN -2147483647 // -(231 - 1)
1691 -- maximum value for an object of type long int
1692 LONG_MAX +2147483647 // 231 - 1
1693 -- maximum value for an object of type unsigned long int
1694 ULONG_MAX 4294967295 // 232 - 1
1696 [<a name="p27" href="#p27">page 27</a>] (<a href="#Contents">Contents</a>)
1698 -- minimum value for an object of type long long int
1699 LLONG_MIN -9223372036854775807 // -(263 - 1)
1700 -- maximum value for an object of type long long int
1701 LLONG_MAX +9223372036854775807 // 263 - 1
1702 -- maximum value for an object of type unsigned long long int
1703 ULLONG_MAX 18446744073709551615 // 264 - 1
1704 2 If the value of an object of type char is treated as a signed integer when used in an
1705 expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the
1706 value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of
1707 CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of
1708 UCHAR_MAX.<sup><a href="#note20"><b>20)</b></a></sup> The value UCHAR_MAX shall equal 2CHAR_BIT - 1.
1709 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>).
1710 <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>
1711 1 The characteristics of floating types are defined in terms of a model that describes a
1712 representation of floating-point numbers and values that provide information about an
1713 implementation's floating-point arithmetic.<sup><a href="#note21"><b>21)</b></a></sup> The following parameters are used to
1714 define the model for each floating-point type:
1716 b base or radix of exponent representation (an integer > 1)
1717 e exponent (an integer between a minimum emin and a maximum emax )
1718 p precision (the number of base-b digits in the significand)
1719 fk nonnegative integers less than b (the significand digits)
1720 2 A floating-point number (x) is defined by the following model:
1722 x = sb e (Sum) f k b-k ,
1724 emin <= e <= emax
1726 3 In addition to normalized floating-point numbers ( f 1 > 0 if x != 0), floating types may be
1727 able to contain other kinds of floating-point numbers, such as subnormal floating-point
1728 numbers (x != 0, e = emin , f 1 = 0) and unnormalized floating-point numbers (x != 0,
1729 e > emin , f 1 = 0), and values that are not floating-point numbers, such as infinities and
1730 NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates
1731 through almost every arithmetic operation without raising a floating-point exception; a
1732 signaling NaN generally raises a floating-point exception when occurring as an
1735 <sup><a name="note20" href="#note20"><b>20)</b></a></sup> See <a href="#6.2.5">6.2.5</a>.
1736 <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
1737 does not require the floating-point arithmetic of the implementation to be identical.
1739 [<a name="p28" href="#p28">page 28</a>] (<a href="#Contents">Contents</a>)
1741 arithmetic operand.<sup><a href="#note22"><b>22)</b></a></sup>
1742 4 An implementation may give zero and values that are not floating-point numbers (such as
1743 infinities and NaNs) a sign or may leave them unsigned. Wherever such values are
1744 unsigned, any requirement in this International Standard to retrieve the sign shall produce
1745 an unspecified sign, and any requirement to set the sign shall be ignored.
1746 5 The minimum range of representable values for a floating type is the most negative finite
1747 floating-point number representable in that type through the most positive finite floating-
1748 point number representable in that type. In addition, if negative infinity is representable
1749 in a type, the range of that type is extended to all negative real numbers; likewise, if
1750 positive infinity is representable in a type, the range of that type is extended to all positive
1752 6 The accuracy of the floating-point operations (+, -, *, /) and of the library functions in
1753 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results is implementation-
1754 defined, as is the accuracy of the conversion between floating-point internal
1755 representations and string representations performed by the library functions in
1756 <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
1757 accuracy is unknown.
1758 7 All integer values in the <a href="#7.7"><float.h></a> header, except FLT_ROUNDS, shall be constant
1759 expressions suitable for use in #if preprocessing directives; all floating values shall be
1760 constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
1761 and FLT_ROUNDS have separate names for all three floating-point types. The floating-
1762 point model representation is provided for all values except FLT_EVAL_METHOD and
1764 8 The rounding mode for floating-point addition is characterized by the implementation-
1765 defined value of FLT_ROUNDS:<sup><a href="#note23"><b>23)</b></a></sup>
1769 2 toward positive infinity
1770 3 toward negative infinity
1771 All other values for FLT_ROUNDS characterize implementation-defined rounding
1775 <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
1776 IEC 60559:1989, the terms quiet NaN and signaling NaN are intended to apply to encodings with
1778 <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
1779 the function fesetround in <a href="#7.6"><fenv.h></a>.
1781 [<a name="p29" href="#p29">page 29</a>] (<a href="#Contents">Contents</a>)
1783 9 Except for assignment and cast (which remove all extra range and precision), the values
1784 yielded by operators with floating operands and values subject to the usual arithmetic
1785 conversions and of floating constants are evaluated to a format whose range and precision
1786 may be greater than required by the type. The use of evaluation formats is characterized
1787 by the implementation-defined value of FLT_EVAL_METHOD:<sup><a href="#note24"><b>24)</b></a></sup>
1789 0 evaluate all operations and constants just to the range and precision of the
1791 1 evaluate operations and constants of type float and double to the
1792 range and precision of the double type, evaluate long double
1793 operations and constants to the range and precision of the long double
1795 2 evaluate all operations and constants to the range and precision of the
1797 All other negative values for FLT_EVAL_METHOD characterize implementation-defined
1799 10 The presence or absence of subnormal numbers is characterized by the implementation-
1800 defined values of FLT_HAS_SUBNORM, DBL_HAS_SUBNORM, and
1802 -1 indeterminable<sup><a href="#note25"><b>25)</b></a></sup>
1803 0 absent<sup><a href="#note26"><b>26)</b></a></sup> (type does not support subnormal numbers)
1804 1 present (type does support subnormal numbers)
1805 11 The values given in the following list shall be replaced by constant expressions with
1806 implementation-defined values that are greater or equal in magnitude (absolute value) to
1807 those shown, with the same sign:
1808 -- radix of exponent representation, b
1814 <sup><a name="note24" href="#note24"><b>24)</b></a></sup> The evaluation method determines evaluation formats of expressions involving all floating types, not
1815 just real types. For example, if FLT_EVAL_METHOD is 1, then the product of two float
1816 _Complex operands is represented in the double _Complex format, and its parts are evaluated to
1818 <sup><a name="note25" href="#note25"><b>25)</b></a></sup> Characterization as indeterminable is intended if floating-point operations do not consistently interpret
1819 subnormal representations as zero, nor as nonzero.
1820 <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
1821 non-subnormal inputs, even if the type format includes representations of subnormal numbers.
1823 [<a name="p30" href="#p30">page 30</a>] (<a href="#Contents">Contents</a>)
1825 -- number of base-FLT_RADIX digits in the floating-point significand, p
1829 -- number of decimal digits, n, such that any floating-point number with p radix b digits
1830 can be rounded to a floating-point number with n decimal digits and back again
1831 without change to the value,
1832 { p log10 b if b is a power of 10
1834 { [^1 + p log10 b^] otherwise
1838 -- number of decimal digits, n, such that any floating-point number in the widest
1839 supported floating type with pmax radix b digits can be rounded to a floating-point
1840 number with n decimal digits and back again without change to the value,
1841 { pmax log10 b if b is a power of 10
1843 { [^1 + pmax log10 b^] otherwise
1845 -- number of decimal digits, q, such that any floating-point number with q decimal digits
1846 can be rounded into a floating-point number with p radix b digits and back again
1847 without change to the q decimal digits,
1848 { p log10 b if b is a power of 10
1850 { [_( p - 1) log10 b_] otherwise
1854 -- minimum negative integer such that FLT_RADIX raised to one less than that power is
1855 a normalized floating-point number, emin
1860 [<a name="p31" href="#p31">page 31</a>] (<a href="#Contents">Contents</a>)
1862 -- minimum negative integer such that 10 raised to that power is in the range of
1863 normalized floating-point numbers, [^log10 b emin -1 ^]
1868 -- maximum integer such that FLT_RADIX raised to one less than that power is a
1869 representable finite floating-point number, emax
1873 -- maximum integer such that 10 raised to that power is in the range of representable
1874 finite floating-point numbers, [_log10 ((1 - b- p )b emax )_]
1878 12 The values given in the following list shall be replaced by constant expressions with
1879 implementation-defined values that are greater than or equal to those shown:
1880 -- maximum representable finite floating-point number, (1 - b- p )b emax
1884 13 The values given in the following list shall be replaced by constant expressions with
1885 implementation-defined (positive) values that are less than or equal to those shown:
1886 -- the difference between 1 and the least value greater than 1 that is representable in the
1887 given floating point type, b1- p
1891 -- minimum normalized positive floating-point number, b emin -1
1896 [<a name="p32" href="#p32">page 32</a>] (<a href="#Contents">Contents</a>)
1898 -- minimum positive floating-point number<sup><a href="#note27"><b>27)</b></a></sup>
1902 Recommended practice
1903 14 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
1904 should be the identity function.
1905 15 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
1906 requirements of this International Standard, and the appropriate values in a <a href="#7.7"><float.h></a> header for type
1909 x = s16e (Sum) f k 16-k ,
1911 -31 <= e <= +32
1915 FLT_EPSILON 9.53674316E-07F
1919 FLT_MIN 2.93873588E-39F
1922 FLT_MAX 3.40282347E+38F
1925 16 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
1926 single-precision and double-precision numbers in IEC 60559,<sup><a href="#note28"><b>28)</b></a></sup> and the appropriate values in a
1927 <a href="#7.7"><float.h></a> header for types float and double:
1929 x f = s2e (Sum) f k 2-k ,
1931 -125 <= e <= +128
1934 x d = s2e (Sum) f k 2-k ,
1936 -1021 <= e <= +1024
1941 FLT_EPSILON 1.19209290E-07F // decimal constant
1942 FLT_EPSILON 0X1P-23F // hex constant
1946 <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
1947 positive number no greater than the minimum normalized positive number for the type.
1948 <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
1949 limits are one less than shown here.
1951 [<a name="p33" href="#p33">page 33</a>] (<a href="#Contents">Contents</a>)
1955 FLT_MIN 1.17549435E-38F // decimal constant
1956 FLT_MIN 0X1P-126F // hex constant
1957 FLT_TRUE_MIN 1.40129846E-45F // decimal constant
1958 FLT_TRUE_MIN 0X1P-149F // hex constant
1962 FLT_MAX 3.40282347E+38F // decimal constant
1963 FLT_MAX 0X1.fffffeP127F // hex constant
1966 DBL_EPSILON 2.2204460492503131E-16 // decimal constant
1967 DBL_EPSILON 0X1P-52 // hex constant
1971 DBL_MIN 2.2250738585072014E-308 // decimal constant
1972 DBL_MIN 0X1P-1022 // hex constant
1973 DBL_TRUE_MIN 4.9406564584124654E-324 // decimal constant
1974 DBL_TRUE_MIN 0X1P-1074 // hex constant
1978 DBL_MAX 1.7976931348623157E+308 // decimal constant
1979 DBL_MAX 0X1.fffffffffffffP1023 // hex constant
1981 If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
1982 example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
1983 precision), then DECIMAL_DIG would be 21.
1985 Forward references: conditional inclusion (<a href="#6.10.1">6.10.1</a>), complex arithmetic
1986 <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>
1987 (<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>
1988 (<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>).
1990 [<a name="p34" href="#p34">page 34</a>] (<a href="#Contents">Contents</a>)
1993 <a name="6" href="#6"><b> 6. Language</b></a>
1994 <a name="6.1" href="#6.1"><b> 6.1 Notation</b></a>
1995 1 In the syntax notation used in this clause, syntactic categories (nonterminals) are
1996 indicated by italic type, and literal words and character set members (terminals) by bold
1997 type. A colon (:) following a nonterminal introduces its definition. Alternative
1998 definitions are listed on separate lines, except when prefaced by the words ''one of''. An
1999 optional symbol is indicated by the subscript ''opt'', so that
2001 indicates an optional expression enclosed in braces.
2002 2 When syntactic categories are referred to in the main text, they are not italicized and
2003 words are separated by spaces instead of hyphens.
2004 3 A summary of the language syntax is given in <a href="#A">annex A</a>.
2005 <a name="6.2" href="#6.2"><b> 6.2 Concepts</b></a>
2006 <a name="6.2.1" href="#6.2.1"><b> 6.2.1 Scopes of identifiers</b></a>
2007 1 An identifier can denote an object; a function; a tag or a member of a structure, union, or
2008 enumeration; a typedef name; a label name; a macro name; or a macro parameter. The
2009 same identifier can denote different entities at different points in the program. A member
2010 of an enumeration is called an enumeration constant. Macro names and macro
2011 parameters are not considered further here, because prior to the semantic phase of
2012 program translation any occurrences of macro names in the source file are replaced by the
2013 preprocessing token sequences that constitute their macro definitions.
2014 2 For each different entity that an identifier designates, the identifier is visible (i.e., can be
2015 used) only within a region of program text called its scope. Different entities designated
2016 by the same identifier either have different scopes, or are in different name spaces. There
2017 are four kinds of scopes: function, file, block, and function prototype. (A function
2018 prototype is a declaration of a function that declares the types of its parameters.)
2019 3 A label name is the only kind of identifier that has function scope. It can be used (in a
2020 goto statement) anywhere in the function in which it appears, and is declared implicitly
2021 by its syntactic appearance (followed by a : and a statement).
2022 4 Every other identifier has scope determined by the placement of its declaration (in a
2023 declarator or type specifier). If the declarator or type specifier that declares the identifier
2024 appears outside of any block or list of parameters, the identifier has file scope, which
2025 terminates at the end of the translation unit. If the declarator or type specifier that
2026 declares the identifier appears inside a block or within the list of parameter declarations in
2027 a function definition, the identifier has block scope, which terminates at the end of the
2028 associated block. If the declarator or type specifier that declares the identifier appears
2030 [<a name="p35" href="#p35">page 35</a>] (<a href="#Contents">Contents</a>)
2032 within the list of parameter declarations in a function prototype (not part of a function
2033 definition), the identifier has function prototype scope, which terminates at the end of the
2034 function declarator. If an identifier designates two different entities in the same name
2035 space, the scopes might overlap. If so, the scope of one entity (the inner scope) will end
2036 strictly before the scope of the other entity (the outer scope). Within the inner scope, the
2037 identifier designates the entity declared in the inner scope; the entity declared in the outer
2038 scope is hidden (and not visible) within the inner scope.
2039 5 Unless explicitly stated otherwise, where this International Standard uses the term
2040 ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the
2041 entity in the relevant name space whose declaration is visible at the point the identifier
2043 6 Two identifiers have the same scope if and only if their scopes terminate at the same
2045 7 Structure, union, and enumeration tags have scope that begins just after the appearance of
2046 the tag in a type specifier that declares the tag. Each enumeration constant has scope that
2047 begins just after the appearance of its defining enumerator in an enumerator list. Any
2048 other identifier has scope that begins just after the completion of its declarator.
2049 8 As a special case, a type name (which is not a declaration of an identifier) is considered to
2050 have a scope that begins just after the place within the type name where the omitted
2051 identifier would appear were it not omitted.
2052 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
2053 (<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>),
2054 source file inclusion (<a href="#6.10.2">6.10.2</a>), statements (<a href="#6.8">6.8</a>).
2055 <a name="6.2.2" href="#6.2.2"><b> 6.2.2 Linkages of identifiers</b></a>
2056 1 An identifier declared in different scopes or in the same scope more than once can be
2057 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
2058 three kinds of linkage: external, internal, and none.
2059 2 In the set of translation units and libraries that constitutes an entire program, each
2060 declaration of a particular identifier with external linkage denotes the same object or
2061 function. Within one translation unit, each declaration of an identifier with internal
2062 linkage denotes the same object or function. Each declaration of an identifier with no
2063 linkage denotes a unique entity.
2064 3 If the declaration of a file scope identifier for an object or a function contains the storage-
2065 class specifier static, the identifier has internal linkage.<sup><a href="#note30"><b>30)</b></a></sup>
2069 <sup><a name="note29" href="#note29"><b>29)</b></a></sup> There is no linkage between different identifiers.
2071 [<a name="p36" href="#p36">page 36</a>] (<a href="#Contents">Contents</a>)
2073 4 For an identifier declared with the storage-class specifier extern in a scope in which a
2074 prior declaration of that identifier is visible,<sup><a href="#note31"><b>31)</b></a></sup> if the prior declaration specifies internal or
2075 external linkage, the linkage of the identifier at the later declaration is the same as the
2076 linkage specified at the prior declaration. If no prior declaration is visible, or if the prior
2077 declaration specifies no linkage, then the identifier has external linkage.
2078 5 If the declaration of an identifier for a function has no storage-class specifier, its linkage
2079 is determined exactly as if it were declared with the storage-class specifier extern. If
2080 the declaration of an identifier for an object has file scope and no storage-class specifier,
2081 its linkage is external.
2082 6 The following identifiers have no linkage: an identifier declared to be anything other than
2083 an object or a function; an identifier declared to be a function parameter; a block scope
2084 identifier for an object declared without the storage-class specifier extern.
2085 7 If, within a translation unit, the same identifier appears with both internal and external
2086 linkage, the behavior is undefined.
2087 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>),
2088 statements (<a href="#6.8">6.8</a>).
2089 <a name="6.2.3" href="#6.2.3"><b> 6.2.3 Name spaces of identifiers</b></a>
2090 1 If more than one declaration of a particular identifier is visible at any point in a
2091 translation unit, the syntactic context disambiguates uses that refer to different entities.
2092 Thus, there are separate name spaces for various categories of identifiers, as follows:
2093 -- label names (disambiguated by the syntax of the label declaration and use);
2094 -- the tags of structures, unions, and enumerations (disambiguated by following any<sup><a href="#note32"><b>32)</b></a></sup>
2095 of the keywords struct, union, or enum);
2096 -- the members of structures or unions; each structure or union has a separate name
2097 space for its members (disambiguated by the type of the expression used to access the
2098 member via the . or -> operator);
2099 -- all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
2100 enumeration constants).
2101 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>),
2102 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
2103 (<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>).
2105 <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
2106 <a href="#6.7.1">6.7.1</a>.
2107 <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.
2108 <sup><a name="note32" href="#note32"><b>32)</b></a></sup> There is only one name space for tags even though three are possible.
2110 [<a name="p37" href="#p37">page 37</a>] (<a href="#Contents">Contents</a>)
2112 <a name="6.2.4" href="#6.2.4"><b> 6.2.4 Storage durations of objects</b></a>
2113 1 An object has a storage duration that determines its lifetime. There are four storage
2114 durations: static, thread, automatic, and allocated. Allocated storage is described in
2115 <a href="#7.22.3">7.22.3</a>.
2116 2 The lifetime of an object is the portion of program execution during which storage is
2117 guaranteed to be reserved for it. An object exists, has a constant address,<sup><a href="#note33"><b>33)</b></a></sup> and retains
2118 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
2119 lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
2120 the object it points to (or just past) reaches the end of its lifetime.
2121 3 An object whose identifier is declared without the storage-class specifier
2122 _Thread_local, and either with external or internal linkage or with the storage-class
2123 specifier static, has static storage duration. Its lifetime is the entire execution of the
2124 program and its stored value is initialized only once, prior to program startup.
2125 4 An object whose identifier is declared with the storage-class specifier _Thread_local
2126 has thread storage duration. Its lifetime is the entire execution of the thread for which it
2127 is created, and its stored value is initialized when the thread is started. There is a distinct
2128 object per thread, and use of the declared name in an expression refers to the object
2129 associated with the thread evaluating the expression. The result of attempting to
2130 indirectly access an object with thread storage duration from a thread other than the one
2131 with which the object is associated is implementation-defined.
2132 5 An object whose identifier is declared with no linkage and without the storage-class
2133 specifier static has automatic storage duration, as do some compound literals. The
2134 result of attempting to indirectly access an object with automatic storage duration from a
2135 thread other than the one with which the object is associated is implementation-defined.
2136 6 For such an object that does not have a variable length array type, its lifetime extends
2137 from entry into the block with which it is associated until execution of that block ends in
2138 any way. (Entering an enclosed block or calling a function suspends, but does not end,
2139 execution of the current block.) If the block is entered recursively, a new instance of the
2140 object is created each time. The initial value of the object is indeterminate. If an
2141 initialization is specified for the object, it is performed each time the declaration or
2142 compound literal is reached in the execution of the block; otherwise, the value becomes
2143 indeterminate each time the declaration is reached.
2147 <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
2148 times will compare equal. The address may be different during two different executions of the same
2150 <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.
2152 [<a name="p38" href="#p38">page 38</a>] (<a href="#Contents">Contents</a>)
2154 7 For such an object that does have a variable length array type, its lifetime extends from
2155 the declaration of the object until execution of the program leaves the scope of the
2156 declaration.<sup><a href="#note35"><b>35)</b></a></sup> If the scope is entered recursively, a new instance of the object is created
2157 each time. The initial value of the object is indeterminate.
2158 8 A non-lvalue expression with structure or union type, where the structure or union
2159 contains a member with array type (including, recursively, members of all contained
2160 structures and unions) refers to an object with automatic storage duration and temporary
2161 lifetime.<sup><a href="#note36"><b>36)</b></a></sup> Its lifetime begins when the expression is evaluated and its initial value is the
2162 value of the expression. Its lifetime ends when the evaluation of the containing full
2163 expression or full declarator ends. Any attempt to modify an object with temporary
2164 lifetime results in undefined behavior.
2165 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
2166 (<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>).
2167 <a name="6.2.5" href="#6.2.5"><b> 6.2.5 Types</b></a>
2168 1 The meaning of a value stored in an object or returned by a function is determined by the
2169 type of the expression used to access it. (An identifier declared to be an object is the
2170 simplest such expression; the type is specified in the declaration of the identifier.) Types
2171 are partitioned into object types (types that describe objects) and function types (types
2172 that describe functions). At various points within a translation unit an object type may be
2173 incomplete (lacking sufficient information to determine the size of objects of that type) or
2174 complete (having sufficient information).<sup><a href="#note37"><b>37)</b></a></sup>
2175 2 An object declared as type _Bool is large enough to store the values 0 and 1.
2176 3 An object declared as type char is large enough to store any member of the basic
2177 execution character set. If a member of the basic execution character set is stored in a
2178 char object, its value is guaranteed to be nonnegative. If any other character is stored in
2179 a char object, the resulting value is implementation-defined but shall be within the range
2180 of values that can be represented in that type.
2181 4 There are five standard signed integer types, designated as signed char, short
2182 int, int, long int, and long long int. (These and other types may be
2183 designated in several additional ways, as described in <a href="#6.7.2">6.7.2</a>.) There may also be
2184 implementation-defined extended signed integer types.<sup><a href="#note38"><b>38)</b></a></sup> The standard and extended
2185 signed integer types are collectively called signed integer types.<sup><a href="#note39"><b>39)</b></a></sup>
2187 <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
2188 embedded block prior to the declaration, leaves the scope of the declaration.
2189 <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.
2190 <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
2191 different points within a translation unit.
2193 [<a name="p39" href="#p39">page 39</a>] (<a href="#Contents">Contents</a>)
2195 5 An object declared as type signed char occupies the same amount of storage as a
2196 ''plain'' char object. A ''plain'' int object has the natural size suggested by the
2197 architecture of the execution environment (large enough to contain any value in the range
2198 INT_MIN to INT_MAX as defined in the header <a href="#7.10"><limits.h></a>).
2199 6 For each of the signed integer types, there is a corresponding (but different) unsigned
2200 integer type (designated with the keyword unsigned) that uses the same amount of
2201 storage (including sign information) and has the same alignment requirements. The type
2202 _Bool and the unsigned integer types that correspond to the standard signed integer
2203 types are the standard unsigned integer types. The unsigned integer types that
2204 correspond to the extended signed integer types are the extended unsigned integer types.
2205 The standard and extended unsigned integer types are collectively called unsigned integer
2206 types.<sup><a href="#note40"><b>40)</b></a></sup>
2207 7 The standard signed integer types and standard unsigned integer types are collectively
2208 called the standard integer types, the extended signed integer types and extended
2209 unsigned integer types are collectively called the extended integer types.
2210 8 For any two integer types with the same signedness and different integer conversion rank
2211 (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
2212 subrange of the values of the other type.
2213 9 The range of nonnegative values of a signed integer type is a subrange of the
2214 corresponding unsigned integer type, and the representation of the same value in each
2215 type is the same.<sup><a href="#note41"><b>41)</b></a></sup> A computation involving unsigned operands can never overflow,
2216 because a result that cannot be represented by the resulting unsigned integer type is
2217 reduced modulo the number that is one greater than the largest value that can be
2218 represented by the resulting type.
2219 10 There are three real floating types, designated as float, double, and long
2220 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
2221 type double; the set of values of the type double is a subset of the set of values of the
2225 <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
2226 described in <a href="#7.1.3">7.1.3</a>.
2227 <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
2228 signed integer types.
2229 <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
2230 unsigned integer types.
2231 <sup><a name="note41" href="#note41"><b>41)</b></a></sup> The same representation and alignment requirements are meant to imply interchangeability as
2232 arguments to functions, return values from functions, and members of unions.
2233 <sup><a name="note42" href="#note42"><b>42)</b></a></sup> See ''future language directions'' (<a href="#6.11.1">6.11.1</a>).
2235 [<a name="p40" href="#p40">page 40</a>] (<a href="#Contents">Contents</a>)
2237 11 There are three complex types, designated as float _Complex, double
2238 _Complex, and long double _Complex.<sup><a href="#note43"><b>43)</b></a></sup> (Complex types are a conditional
2239 feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.) The real floating and
2240 complex types are collectively called the floating types.
2241 12 For each floating type there is a corresponding real type, which is always a real floating
2242 type. For real floating types, it is the same type. For complex types, it is the type given
2243 by deleting the keyword _Complex from the type name.
2244 13 Each complex type has the same representation and alignment requirements as an array
2245 type containing exactly two elements of the corresponding real type; the first element is
2246 equal to the real part, and the second element to the imaginary part, of the complex
2248 14 The type char, the signed and unsigned integer types, and the floating types are
2249 collectively called the basic types. The basic types are complete object types. Even if the
2250 implementation defines two or more basic types to have the same representation, they are
2251 nevertheless different types.<sup><a href="#note44"><b>44)</b></a></sup>
2252 15 The three types char, signed char, and unsigned char are collectively called
2253 the character types. The implementation shall define char to have the same range,
2254 representation, and behavior as either signed char or unsigned char.<sup><a href="#note45"><b>45)</b></a></sup>
2255 16 An enumeration comprises a set of named integer constant values. Each distinct
2256 enumeration constitutes a different enumerated type.
2257 17 The type char, the signed and unsigned integer types, and the enumerated types are
2258 collectively called integer types. The integer and real floating types are collectively called
2260 18 Integer and floating types are collectively called arithmetic types. Each arithmetic type
2261 belongs to one type domain: the real type domain comprises the real types, the complex
2262 type domain comprises the complex types.
2263 19 The void type comprises an empty set of values; it is an incomplete object type that
2264 cannot be completed.
2268 <sup><a name="note43" href="#note43"><b>43)</b></a></sup> A specification for imaginary types is in <a href="#G">annex G</a>.
2269 <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
2270 any other) type; this does not violate the requirement that all basic types be different.
2271 Implementation-defined keywords shall have the form of an identifier reserved for any use as
2272 described in <a href="#7.1.3">7.1.3</a>.
2273 <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
2274 used to distinguish the two options. Irrespective of the choice made, char is a separate type from the
2275 other two and is not compatible with either.
2277 [<a name="p41" href="#p41">page 41</a>] (<a href="#Contents">Contents</a>)
2279 20 Any number of derived types can be constructed from the object and function types, as
2281 -- An array type describes a contiguously allocated nonempty set of objects with a
2282 particular member object type, called the element type. The element type shall be
2283 complete whenever the array type is specified. Array types are characterized by their
2284 element type and by the number of elements in the array. An array type is said to be
2285 derived from its element type, and if its element type is T , the array type is sometimes
2286 called ''array of T ''. The construction of an array type from an element type is called
2287 ''array type derivation''.
2288 -- A structure type describes a sequentially allocated nonempty set of member objects
2289 (and, in certain circumstances, an incomplete array), each of which has an optionally
2290 specified name and possibly distinct type.
2291 -- A union type describes an overlapping nonempty set of member objects, each of
2292 which has an optionally specified name and possibly distinct type.
2293 -- A function type describes a function with specified return type. A function type is
2294 characterized by its return type and the number and types of its parameters. A
2295 function type is said to be derived from its return type, and if its return type is T , the
2296 function type is sometimes called ''function returning T ''. The construction of a
2297 function type from a return type is called ''function type derivation''.
2298 -- A pointer type may be derived from a function type or an object type, called the
2299 referenced type. A pointer type describes an object whose value provides a reference
2300 to an entity of the referenced type. A pointer type derived from the referenced type T
2301 is sometimes called ''pointer to T ''. The construction of a pointer type from a
2302 referenced type is called ''pointer type derivation''. A pointer type is a complete
2304 -- An atomic type describes the type designated by the construct _Atomic ( type-
2305 name ). (Atomic types are a conditional feature that implementations need not
2306 support; see <a href="#6.10.8.3">6.10.8.3</a>.)
2307 These methods of constructing derived types can be applied recursively.
2308 21 Arithmetic types and pointer types are collectively called scalar types. Array and
2309 structure types are collectively called aggregate types.<sup><a href="#note46"><b>46)</b></a></sup>
2310 22 An array type of unknown size is an incomplete type. It is completed, for an identifier of
2311 that type, by specifying the size in a later declaration (with internal or external linkage).
2312 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
2315 <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
2316 contain one member at a time.
2318 [<a name="p42" href="#p42">page 42</a>] (<a href="#Contents">Contents</a>)
2320 type. It is completed, for all declarations of that type, by declaring the same structure or
2321 union tag with its defining content later in the same scope.
2322 23 A type has known constant size if the type is not incomplete and is not a variable length
2324 24 Array, function, and pointer types are collectively called derived declarator types. A
2325 declarator type derivation from a type T is the construction of a derived declarator type
2326 from T by the application of an array-type, a function-type, or a pointer-type derivation to
2328 25 A type is characterized by its type category, which is either the outermost derivation of a
2329 derived type (as noted above in the construction of derived types), or the type itself if the
2330 type consists of no derived types.
2331 26 Any type so far mentioned is an unqualified type. Each unqualified type has several
2332 qualified versions of its type,<sup><a href="#note47"><b>47)</b></a></sup> corresponding to the combinations of one, two, or all
2333 three of the const, volatile, and restrict qualifiers. The qualified or unqualified
2334 versions of a type are distinct types that belong to the same type category and have the
2335 same representation and alignment requirements.<sup><a href="#note48"><b>48)</b></a></sup> A derived type is not qualified by the
2336 qualifiers (if any) of the type from which it is derived.
2337 27 Further, there is the _Atomic qualifier. The presence of the _Atomic qualifier
2338 designates an atomic type. The size, representation, and alignment of an atomic type
2339 need not be the same as those of the corresponding unqualified type. Therefore, this
2340 Standard explicitly uses the phrase ''atomic, qualified or unqualified type'' whenever the
2341 atomic version of a type is permitted along with the other qualified versions of a type.
2342 The phrase ''qualified or unqualified type'', without specific mention of atomic, does not
2343 include the atomic types.
2344 28 A pointer to void shall have the same representation and alignment requirements as a
2345 pointer to a character type.48) Similarly, pointers to qualified or unqualified versions of
2346 compatible types shall have the same representation and alignment requirements. All
2347 pointers to structure types shall have the same representation and alignment requirements
2348 as each other. All pointers to union types shall have the same representation and
2349 alignment requirements as each other. Pointers to other types need not have the same
2350 representation or alignment requirements.
2351 29 EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is
2352 pointer, not a floating type. The const-qualified version of this type is designated as ''float * const''
2353 whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const-
2356 <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.
2357 <sup><a name="note48" href="#note48"><b>48)</b></a></sup> The same representation and alignment requirements are meant to imply interchangeability as
2358 arguments to functions, return values from functions, and members of unions.
2360 [<a name="p43" href="#p43">page 43</a>] (<a href="#Contents">Contents</a>)
2362 qualified float'' and is a pointer to a qualified type.
2364 30 EXAMPLE 2 The type designated as ''struct tag (*[5])(float)'' has type ''array of pointer to
2365 function returning struct tag''. The array has length five and the function has a single parameter of type
2366 float. Its type category is array.
2368 Forward references: compatible type and composite type (<a href="#6.2.7">6.2.7</a>), declarations (<a href="#6.7">6.7</a>).
2369 <a name="6.2.6" href="#6.2.6"><b> 6.2.6 Representations of types</b></a>
2370 <a name="6.2.6.1" href="#6.2.6.1"><b> 6.2.6.1 General</b></a>
2371 1 The representations of all types are unspecified except as stated in this subclause.
2372 2 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes,
2373 the number, order, and encoding of which are either explicitly specified or
2374 implementation-defined.
2375 3 Values stored in unsigned bit-fields and objects of type unsigned char shall be
2376 represented using a pure binary notation.<sup><a href="#note49"><b>49)</b></a></sup>
2377 4 Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT
2378 bits, where n is the size of an object of that type, in bytes. The value may be copied into
2379 an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is
2380 called the object representation of the value. Values stored in bit-fields consist of m bits,
2381 where m is the size specified for the bit-field. The object representation is the set of m
2382 bits the bit-field comprises in the addressable storage unit holding it. Two values (other
2383 than NaNs) with the same object representation compare equal, but values that compare
2384 equal may have different object representations.
2385 5 Certain object representations need not represent a value of the object type. If the stored
2386 value of an object has such a representation and is read by an lvalue expression that does
2387 not have character type, the behavior is undefined. If such a representation is produced
2388 by a side effect that modifies all or any part of the object by an lvalue expression that
2389 does not have character type, the behavior is undefined.<sup><a href="#note50"><b>50)</b></a></sup> Such a representation is called
2390 a trap representation.
2391 6 When a value is stored in an object of structure or union type, including in a member
2392 object, the bytes of the object representation that correspond to any padding bytes take
2393 unspecified values.<sup><a href="#note51"><b>51)</b></a></sup> The value of a structure or union object is never a trap
2396 <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
2397 represented by successive bits are additive, begin with 1, and are multiplied by successive integral
2398 powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
2399 Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
2400 type unsigned char range from 0 to 2
2403 <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
2404 behavior, but the value of the variable cannot be used until a proper value is stored in it.
2406 [<a name="p44" href="#p44">page 44</a>] (<a href="#Contents">Contents</a>)
2408 representation, even though the value of a member of the structure or union object may be
2409 a trap representation.
2410 7 When a value is stored in a member of an object of union type, the bytes of the object
2411 representation that do not correspond to that member but do correspond to other members
2412 take unspecified values.
2413 8 Where an operator is applied to a value that has more than one object representation,
2414 which object representation is used shall not affect the value of the result.<sup><a href="#note52"><b>52)</b></a></sup> Where a
2415 value is stored in an object using a type that has more than one object representation for
2416 that value, it is unspecified which representation is used, but a trap representation shall
2418 9 Loads and stores of objects with atomic types are done with
2419 memory_order_seq_cst semantics.
2420 Forward references: declarations (<a href="#6.7">6.7</a>), expressions (<a href="#6.5">6.5</a>), lvalues, arrays, and function
2421 designators (<a href="#6.3.2.1">6.3.2.1</a>), order and consistency (<a href="#7.17.3">7.17.3</a>).
2422 <a name="6.2.6.2" href="#6.2.6.2"><b> 6.2.6.2 Integer types</b></a>
2423 1 For unsigned integer types other than unsigned char, the bits of the object
2424 representation shall be divided into two groups: value bits and padding bits (there need
2425 not be any of the latter). If there are N value bits, each bit shall represent a different
2426 power of 2 between 1 and 2 N -1 , so that objects of that type shall be capable of
2427 representing values from 0 to 2 N - 1 using a pure binary representation; this shall be
2428 known as the value representation. The values of any padding bits are unspecified.<sup><a href="#note53"><b>53)</b></a></sup>
2429 2 For signed integer types, the bits of the object representation shall be divided into three
2430 groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
2431 signed char shall not have any padding bits. There shall be exactly one sign bit.
2432 Each bit that is a value bit shall have the same value as the same bit in the object
2433 representation of the corresponding unsigned type (if there are M value bits in the signed
2434 type and N in the unsigned type, then M <= N ). If the sign bit is zero, it shall not affect
2436 <sup><a name="note51" href="#note51"><b>51)</b></a></sup> Thus, for example, structure assignment need not copy any padding bits.
2437 <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
2438 accessed as objects of type T, but to have different values in other contexts. In particular, if == is
2439 defined for type T, then x == y does not imply that memcmp(&x, &y, sizeof (T)) == 0.
2440 Furthermore, x == y does not necessarily imply that x and y have the same value; other operations
2441 on values of type T may distinguish between them.
2442 <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
2443 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2444 representation other than as part of an exceptional condition such as an overflow, and this cannot occur
2445 with unsigned types. All other combinations of padding bits are alternative object representations of
2446 the value specified by the value bits.
2448 [<a name="p45" href="#p45">page 45</a>] (<a href="#Contents">Contents</a>)
2450 the resulting value. If the sign bit is one, the value shall be modified in one of the
2452 -- the corresponding value with sign bit 0 is negated (sign and magnitude);
2453 -- the sign bit has the value -(2 M ) (two's complement);
2454 -- the sign bit has the value -(2 M - 1) (ones' complement).
2455 Which of these applies is implementation-defined, as is whether the value with sign bit 1
2456 and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones'
2457 complement), is a trap representation or a normal value. In the case of sign and
2458 magnitude and ones' complement, if this representation is a normal value it is called a
2460 3 If the implementation supports negative zeros, they shall be generated only by:
2461 -- the &, |, ^, ~, <<, and >> operators with operands that produce such a value;
2462 -- the +, -, *, /, and % operators where one operand is a negative zero and the result is
2464 -- compound assignment operators based on the above cases.
2465 It is unspecified whether these cases actually generate a negative zero or a normal zero,
2466 and whether a negative zero becomes a normal zero when stored in an object.
2467 4 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
2468 and >> operators with operands that would produce such a value is undefined.
2469 5 The values of any padding bits are unspecified.<sup><a href="#note54"><b>54)</b></a></sup> A valid (non-trap) object representation
2470 of a signed integer type where the sign bit is zero is a valid object representation of the
2471 corresponding unsigned type, and shall represent the same value. For any integer type,
2472 the object representation where all the bits are zero shall be a representation of the value
2474 6 The precision of an integer type is the number of bits it uses to represent values,
2475 excluding any sign and padding bits. The width of an integer type is the same but
2476 including any sign bit; thus for unsigned integer types the two values are the same, while
2477 for signed integer types the width is one greater than the precision.
2482 <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
2483 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2484 representation other than as part of an exceptional condition such as an overflow. All other
2485 combinations of padding bits are alternative object representations of the value specified by the value
2488 [<a name="p46" href="#p46">page 46</a>] (<a href="#Contents">Contents</a>)
2490 <a name="6.2.7" href="#6.2.7"><b> 6.2.7 Compatible type and composite type</b></a>
2491 1 Two types have compatible type if their types are the same. Additional rules for
2492 determining whether two types are compatible are described in <a href="#6.7.2">6.7.2</a> for type specifiers,
2493 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,
2494 union, or enumerated types declared in separate translation units are compatible if their
2495 tags and members satisfy the following requirements: If one is declared with a tag, the
2496 other shall be declared with the same tag. If both are completed anywhere within their
2497 respective translation units, then the following additional requirements apply: there shall
2498 be a one-to-one correspondence between their members such that each pair of
2499 corresponding members are declared with compatible types; if one member of the pair is
2500 declared with an alignment specifier, the other is declared with an equivalent alignment
2501 specifier; and if one member of the pair is declared with a name, the other is declared
2502 with the same name. For two structures, corresponding members shall be declared in the
2503 same order. For two structures or unions, corresponding bit-fields shall have the same
2504 widths. For two enumerations, corresponding members shall have the same values.
2505 2 All declarations that refer to the same object or function shall have compatible type;
2506 otherwise, the behavior is undefined.
2507 3 A composite type can be constructed from two types that are compatible; it is a type that
2508 is compatible with both of the two types and satisfies the following conditions:
2509 -- If both types are array types, the following rules are applied:
2510 o If one type is an array of known constant size, the composite type is an array of
2512 o Otherwise, if one type is a variable length array whose size is specified by an
2513 expression that is not evaluated, the behavior is undefined.
2514 o Otherwise, if one type is a variable length array whose size is specified, the
2515 composite type is a variable length array of that size.
2516 o Otherwise, if one type is a variable length array of unspecified size, the composite
2517 type is a variable length array of unspecified size.
2518 o Otherwise, both types are arrays of unknown size and the composite type is an
2519 array of unknown size.
2520 The element type of the composite type is the composite type of the two element
2522 -- If only one type is a function type with a parameter type list (a function prototype),
2523 the composite type is a function prototype with the parameter type list.
2526 <sup><a name="note55" href="#note55"><b>55)</b></a></sup> Two types need not be identical to be compatible.
2528 [<a name="p47" href="#p47">page 47</a>] (<a href="#Contents">Contents</a>)
2530 -- If both types are function types with parameter type lists, the type of each parameter
2531 in the composite parameter type list is the composite type of the corresponding
2533 These rules apply recursively to the types from which the two types are derived.
2534 4 For an identifier with internal or external linkage declared in a scope in which a prior
2535 declaration of that identifier is visible,<sup><a href="#note56"><b>56)</b></a></sup> if the prior declaration specifies internal or
2536 external linkage, the type of the identifier at the later declaration becomes the composite
2538 Forward references: array declarators (<a href="#6.7.6.2">6.7.6.2</a>).
2539 5 EXAMPLE Given the following two file scope declarations:
2540 int f(int (*)(), double (*)[3]);
2541 int f(int (*)(char *), double (*)[]);
2542 The resulting composite type for the function is:
2543 int f(int (*)(char *), double (*)[3]);
2545 <a name="6.2.8" href="#6.2.8"><b> 6.2.8 Alignment of objects</b></a>
2546 1 Complete object types have alignment requirements which place restrictions on the
2547 addresses at which objects of that type may be allocated. An alignment is an
2548 implementation-defined integer value representing the number of bytes between
2549 successive addresses at which a given object can be allocated. An object type imposes an
2550 alignment requirement on every object of that type: stricter alignment can be requested
2551 using the _Alignas keyword.
2552 2 A fundamental alignment is represented by an alignment less than or equal to the greatest
2553 alignment supported by the implementation in all contexts, which is equal to
2554 alignof(max_align_t).
2555 3 An extended alignment is represented by an alignment greater than
2556 alignof(max_align_t). It is implementation-defined whether any extended
2557 alignments are supported and the contexts in which they are supported. A type having an
2558 extended alignment requirement is an over-aligned type.<sup><a href="#note57"><b>57)</b></a></sup>
2559 4 Alignments are represented as values of the type size_t. Valid alignments include only
2560 those values returned by an alignof expression for fundamental types, plus an
2561 additional implementation-defined set of values, which may be empty. Every valid
2562 alignment value shall be a nonnegative integral power of two.
2565 <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.
2566 <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
2567 alignment has been applied.
2569 [<a name="p48" href="#p48">page 48</a>] (<a href="#Contents">Contents</a>)
2571 5 Alignments have an order from weaker to stronger or stricter alignments. Stricter
2572 alignments have larger alignment values. An address that satisfies an alignment
2573 requirement also satisfies any weaker valid alignment requirement.
2574 6 The alignment requirement of a complete type can be queried using an alignof
2575 expression. The types char, signed char, and unsigned char shall have the
2576 weakest alignment requirement.
2577 7 Comparing alignments is meaningful and provides the obvious results:
2578 -- Two alignments are equal when their numeric values are equal.
2579 -- Two alignments are different when their numeric values are not equal.
2580 -- When an alignment is larger than another it represents a stricter alignment.
2582 [<a name="p49" href="#p49">page 49</a>] (<a href="#Contents">Contents</a>)
2584 <a name="6.3" href="#6.3"><b> 6.3 Conversions</b></a>
2585 1 Several operators convert operand values from one type to another automatically. This
2586 subclause specifies the result required from such an implicit conversion, as well as those
2587 that result from a cast operation (an explicit conversion). The list in <a href="#6.3.1.8">6.3.1.8</a> summarizes
2588 the conversions performed by most ordinary operators; it is supplemented as required by
2589 the discussion of each operator in <a href="#6.5">6.5</a>.
2590 2 Conversion of an operand value to a compatible type causes no change to the value or the
2592 Forward references: cast operators (<a href="#6.5.4">6.5.4</a>).
2593 <a name="6.3.1" href="#6.3.1"><b> 6.3.1 Arithmetic operands</b></a>
2594 <a name="6.3.1.1" href="#6.3.1.1"><b> 6.3.1.1 Boolean, characters, and integers</b></a>
2595 1 Every integer type has an integer conversion rank defined as follows:
2596 -- No two signed integer types shall have the same rank, even if they have the same
2598 -- The rank of a signed integer type shall be greater than the rank of any signed integer
2599 type with less precision.
2600 -- The rank of long long int shall be greater than the rank of long int, which
2601 shall be greater than the rank of int, which shall be greater than the rank of short
2602 int, which shall be greater than the rank of signed char.
2603 -- The rank of any unsigned integer type shall equal the rank of the corresponding
2604 signed integer type, if any.
2605 -- The rank of any standard integer type shall be greater than the rank of any extended
2606 integer type with the same width.
2607 -- The rank of char shall equal the rank of signed char and unsigned char.
2608 -- The rank of _Bool shall be less than the rank of all other standard integer types.
2609 -- The rank of any enumerated type shall equal the rank of the compatible integer type
2610 (see <a href="#6.7.2.2">6.7.2.2</a>).
2611 -- The rank of any extended signed integer type relative to another extended signed
2612 integer type with the same precision is implementation-defined, but still subject to the
2613 other rules for determining the integer conversion rank.
2614 -- For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has
2615 greater rank than T3, then T1 has greater rank than T3.
2616 2 The following may be used in an expression wherever an int or unsigned int may
2619 [<a name="p50" href="#p50">page 50</a>] (<a href="#Contents">Contents</a>)
2621 -- An object or expression with an integer type (other than int or unsigned int)
2622 whose integer conversion rank is less than or equal to the rank of int and
2624 -- A bit-field of type _Bool, int, signed int, or unsigned int.
2625 If an int can represent all values of the original type (as restricted by the width, for a
2626 bit-field), the value is converted to an int; otherwise, it is converted to an unsigned
2627 int. These are called the integer promotions.<sup><a href="#note58"><b>58)</b></a></sup> All other types are unchanged by the
2629 3 The integer promotions preserve value including sign. As discussed earlier, whether a
2630 ''plain'' char is treated as signed is implementation-defined.
2631 Forward references: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
2632 (<a href="#6.7.2.1">6.7.2.1</a>).
2633 <a name="6.3.1.2" href="#6.3.1.2"><b> 6.3.1.2 Boolean type</b></a>
2634 1 When any scalar value is converted to _Bool, the result is 0 if the value compares equal
2635 to 0; otherwise, the result is 1.<sup><a href="#note59"><b>59)</b></a></sup>
2636 <a name="6.3.1.3" href="#6.3.1.3"><b> 6.3.1.3 Signed and unsigned integers</b></a>
2637 1 When a value with integer type is converted to another integer type other than _Bool, if
2638 the value can be represented by the new type, it is unchanged.
2639 2 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or
2640 subtracting one more than the maximum value that can be represented in the new type
2641 until the value is in the range of the new type.<sup><a href="#note60"><b>60)</b></a></sup>
2642 3 Otherwise, the new type is signed and the value cannot be represented in it; either the
2643 result is implementation-defined or an implementation-defined signal is raised.
2644 <a name="6.3.1.4" href="#6.3.1.4"><b> 6.3.1.4 Real floating and integer</b></a>
2645 1 When a finite value of real floating type is converted to an integer type other than _Bool,
2646 the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
2647 the integral part cannot be represented by the integer type, the behavior is undefined.<sup><a href="#note61"><b>61)</b></a></sup>
2650 <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
2651 argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the
2652 shift operators, as specified by their respective subclauses.
2653 <sup><a name="note59" href="#note59"><b>59)</b></a></sup> NaNs do not compare equal to 0 and thus convert to 1.
2654 <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.
2655 <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
2656 need not be performed when a value of real floating type is converted to unsigned type. Thus, the
2657 range of portable real floating values is (-1, Utype_MAX+1).
2659 [<a name="p51" href="#p51">page 51</a>] (<a href="#Contents">Contents</a>)
2661 2 When a value of integer type is converted to a real floating type, if the value being
2662 converted can be represented exactly in the new type, it is unchanged. If the value being
2663 converted is in the range of values that can be represented but cannot be represented
2664 exactly, the result is either the nearest higher or nearest lower representable value, chosen
2665 in an implementation-defined manner. If the value being converted is outside the range of
2666 values that can be represented, the behavior is undefined. Results of some implicit
2667 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
2668 required by the new type.
2669 <a name="6.3.1.5" href="#6.3.1.5"><b> 6.3.1.5 Real floating types</b></a>
2670 1 When a value of real floating type is converted to a real floating type, if the value being
2671 converted can be represented exactly in the new type, it is unchanged. If the value being
2672 converted is in the range of values that can be represented but cannot be represented
2673 exactly, the result is either the nearest higher or nearest lower representable value, chosen
2674 in an implementation-defined manner. If the value being converted is outside the range of
2675 values that can be represented, the behavior is undefined. Results of some implicit
2676 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
2677 required by the new type.
2678 <a name="6.3.1.6" href="#6.3.1.6"><b> 6.3.1.6 Complex types</b></a>
2679 1 When a value of complex type is converted to another complex type, both the real and
2680 imaginary parts follow the conversion rules for the corresponding real types.
2681 <a name="6.3.1.7" href="#6.3.1.7"><b> 6.3.1.7 Real and complex</b></a>
2682 1 When a value of real type is converted to a complex type, the real part of the complex
2683 result value is determined by the rules of conversion to the corresponding real type and
2684 the imaginary part of the complex result value is a positive zero or an unsigned zero.
2685 2 When a value of complex type is converted to a real type, the imaginary part of the
2686 complex value is discarded and the value of the real part is converted according to the
2687 conversion rules for the corresponding real type.
2688 <a name="6.3.1.8" href="#6.3.1.8"><b> 6.3.1.8 Usual arithmetic conversions</b></a>
2689 1 Many operators that expect operands of arithmetic type cause conversions and yield result
2690 types in a similar way. The purpose is to determine a common real type for the operands
2691 and result. For the specified operands, each operand is converted, without change of type
2692 domain, to a type whose corresponding real type is the common real type. Unless
2693 explicitly stated otherwise, the common real type is also the corresponding real type of
2694 the result, whose type domain is the type domain of the operands if they are the same,
2695 and complex otherwise. This pattern is called the usual arithmetic conversions:
2696 First, if the corresponding real type of either operand is long double, the other
2697 operand is converted, without change of type domain, to a type whose
2699 [<a name="p52" href="#p52">page 52</a>] (<a href="#Contents">Contents</a>)
2701 corresponding real type is long double.
2702 Otherwise, if the corresponding real type of either operand is double, the other
2703 operand is converted, without change of type domain, to a type whose
2704 corresponding real type is double.
2705 Otherwise, if the corresponding real type of either operand is float, the other
2706 operand is converted, without change of type domain, to a type whose
2707 corresponding real type is float.<sup><a href="#note62"><b>62)</b></a></sup>
2708 Otherwise, the integer promotions are performed on both operands. Then the
2709 following rules are applied to the promoted operands:
2710 If both operands have the same type, then no further conversion is needed.
2711 Otherwise, if both operands have signed integer types or both have unsigned
2712 integer types, the operand with the type of lesser integer conversion rank is
2713 converted to the type of the operand with greater rank.
2714 Otherwise, if the operand that has unsigned integer type has rank greater or
2715 equal to the rank of the type of the other operand, then the operand with
2716 signed integer type is converted to the type of the operand with unsigned
2718 Otherwise, if the type of the operand with signed integer type can represent
2719 all of the values of the type of the operand with unsigned integer type, then
2720 the operand with unsigned integer type is converted to the type of the
2721 operand with signed integer type.
2722 Otherwise, both operands are converted to the unsigned integer type
2723 corresponding to the type of the operand with signed integer type.
2724 2 The values of floating operands and of the results of floating expressions may be
2725 represented in greater precision and range than that required by the type; the types are not
2726 changed thereby.<sup><a href="#note63"><b>63)</b></a></sup>
2731 <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
2732 float operand to double (and yields a double _Complex result).
2733 <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.
2735 [<a name="p53" href="#p53">page 53</a>] (<a href="#Contents">Contents</a>)
2737 <a name="6.3.2" href="#6.3.2"><b> 6.3.2 Other operands</b></a>
2738 <a name="6.3.2.1" href="#6.3.2.1"><b> 6.3.2.1 Lvalues, arrays, and function designators</b></a>
2739 1 An lvalue is an expression (with an object type other than void) that potentially
2740 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
2741 behavior is undefined. When an object is said to have a particular type, the type is
2742 specified by the lvalue used to designate the object. A modifiable lvalue is an lvalue that
2743 does not have array type, does not have an incomplete type, does not have a const-
2744 qualified type, and if it is a structure or union, does not have any member (including,
2745 recursively, any member or element of all contained aggregates or unions) with a const-
2747 2 Except when it is the operand of the sizeof operator, the unary & operator, the ++
2748 operator, the -- operator, or the left operand of the . operator or an assignment operator,
2749 an lvalue that does not have array type is converted to the value stored in the designated
2750 object (and is no longer an lvalue); this is called lvalue conversion. If the lvalue has
2751 qualified type, the value has the unqualified version of the type of the lvalue; additionally,
2752 if the lvalue has atomic type, the value has the non-atomic version of the type of the
2753 lvalue; otherwise, the value has the type of the lvalue. If the lvalue has an incomplete
2754 type and does not have array type, the behavior is undefined. If the lvalue designates an
2755 object of automatic storage duration that could have been declared with the register
2756 storage class (never had its address taken), and that object is uninitialized (not declared
2757 with an initializer and no assignment to it has been performed prior to use), the behavior
2759 3 Except when it is the operand of the sizeof operator or the unary & operator, or is a
2760 string literal used to initialize an array, an expression that has type ''array of type'' is
2761 converted to an expression with type ''pointer to type'' that points to the initial element of
2762 the array object and is not an lvalue. If the array object has register storage class, the
2763 behavior is undefined.
2764 4 A function designator is an expression that has function type. Except when it is the
2765 operand of the sizeof operator<sup><a href="#note65"><b>65)</b></a></sup> or the unary & operator, a function designator with
2766 type ''function returning type'' is converted to an expression that has type ''pointer to
2769 <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
2770 operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
2771 object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described
2772 as the ''value of an expression''.
2773 An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
2774 expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.
2775 <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
2776 designator and violates the constraint in <a href="#6.5.3.4">6.5.3.4</a>.
2778 [<a name="p54" href="#p54">page 54</a>] (<a href="#Contents">Contents</a>)
2780 function returning type''.
2781 Forward references: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), assignment operators
2782 (<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
2783 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2784 (<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>).
2785 <a href="#6.3.2.2">6.3.2.2</a> void
2786 1 The (nonexistent) value of a void expression (an expression that has type void) shall not
2787 be used in any way, and implicit or explicit conversions (except to void) shall not be
2788 applied to such an expression. If an expression of any other type is evaluated as a void
2789 expression, its value or designator is discarded. (A void expression is evaluated for its
2791 <a name="6.3.2.3" href="#6.3.2.3"><b> 6.3.2.3 Pointers</b></a>
2792 1 A pointer to void may be converted to or from a pointer to any object type. A pointer to
2793 any object type may be converted to a pointer to void and back again; the result shall
2794 compare equal to the original pointer.
2795 2 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to
2796 the q-qualified version of the type; the values stored in the original and converted pointers
2797 shall compare equal.
2798 3 An integer constant expression with the value 0, or such an expression cast to type
2799 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
2800 pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal
2801 to a pointer to any object or function.
2802 4 Conversion of a null pointer to another pointer type yields a null pointer of that type.
2803 Any two null pointers shall compare equal.
2804 5 An integer may be converted to any pointer type. Except as previously specified, the
2805 result is implementation-defined, might not be correctly aligned, might not point to an
2806 entity of the referenced type, and might be a trap representation.<sup><a href="#note67"><b>67)</b></a></sup>
2807 6 Any pointer type may be converted to an integer type. Except as previously specified, the
2808 result is implementation-defined. If the result cannot be represented in the integer type,
2809 the behavior is undefined. The result need not be in the range of values of any integer
2815 <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>.
2816 <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
2817 be consistent with the addressing structure of the execution environment.
2819 [<a name="p55" href="#p55">page 55</a>] (<a href="#Contents">Contents</a>)
2821 7 A pointer to an object type may be converted to a pointer to a different object type. If the
2822 resulting pointer is not correctly aligned<sup><a href="#note68"><b>68)</b></a></sup> for the referenced type, the behavior is
2823 undefined. Otherwise, when converted back again, the result shall compare equal to the
2824 original pointer. When a pointer to an object is converted to a pointer to a character type,
2825 the result points to the lowest addressed byte of the object. Successive increments of the
2826 result, up to the size of the object, yield pointers to the remaining bytes of the object.
2827 8 A pointer to a function of one type may be converted to a pointer to a function of another
2828 type and back again; the result shall compare equal to the original pointer. If a converted
2829 pointer is used to call a function whose type is not compatible with the referenced type,
2830 the behavior is undefined.
2831 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
2832 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>).
2837 <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
2838 pointer to type B, which in turn is correctly aligned for a pointer to type C, then a pointer to type A is
2839 correctly aligned for a pointer to type C.
2841 [<a name="p56" href="#p56">page 56</a>] (<a href="#Contents">Contents</a>)
2843 <a name="6.4" href="#6.4"><b> 6.4 Lexical elements</b></a>
2851 preprocessing-token:
2858 each non-white-space character that cannot be one of the above
2860 2 Each preprocessing token that is converted to a token shall have the lexical form of a
2861 keyword, an identifier, a constant, a string literal, or a punctuator.
2863 3 A token is the minimal lexical element of the language in translation phases 7 and 8. The
2864 categories of tokens are: keywords, identifiers, constants, string literals, and punctuators.
2865 A preprocessing token is the minimal lexical element of the language in translation
2866 phases 3 through 6. The categories of preprocessing tokens are: header names,
2867 identifiers, preprocessing numbers, character constants, string literals, punctuators, and
2868 single non-white-space characters that do not lexically match the other preprocessing
2869 token categories.<sup><a href="#note69"><b>69)</b></a></sup> If a ' or a " character matches the last category, the behavior is
2870 undefined. Preprocessing tokens can be separated by white space; this consists of
2871 comments (described later), or white-space characters (space, horizontal tab, new-line,
2872 vertical tab, and form-feed), or both. As described in <a href="#6.10">6.10</a>, in certain circumstances
2873 during translation phase 4, white space (or the absence thereof) serves as more than
2874 preprocessing token separation. White space may appear within a preprocessing token
2875 only as part of a header name or between the quotation characters in a character constant
2880 <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
2881 occur in source files.
2883 [<a name="p57" href="#p57">page 57</a>] (<a href="#Contents">Contents</a>)
2885 4 If the input stream has been parsed into preprocessing tokens up to a given character, the
2886 next preprocessing token is the longest sequence of characters that could constitute a
2887 preprocessing token. There is one exception to this rule: header name preprocessing
2888 tokens are recognized only within #include preprocessing directives and in
2889 implementation-defined locations within #pragma directives. In such contexts, a
2890 sequence of characters that could be either a header name or a string literal is recognized
2892 5 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a
2893 valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex
2894 might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program
2895 fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or
2896 not E is a macro name.
2898 6 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
2899 increment operators, even though the parse x ++ + ++ y might yield a correct expression.
2901 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>),
2902 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
2903 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2904 (<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
2905 (<a href="#6.4.5">6.4.5</a>).
2906 <a name="6.4.1" href="#6.4.1"><b> 6.4.1 Keywords</b></a>
2914 const register _Alignas
2915 continue restrict _Atomic
2916 default return _Bool
2918 double signed _Generic
2919 else sizeof _Imaginary
2920 enum static _Noreturn
2921 extern struct _Static_assert
2922 float switch _Thread_local
2925 2 The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as
2926 keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
2928 [<a name="p58" href="#p58">page 58</a>] (<a href="#Contents">Contents</a>)
2930 specifying imaginary types.<sup><a href="#note70"><b>70)</b></a></sup>
2931 <a name="6.4.2" href="#6.4.2"><b> 6.4.2 Identifiers</b></a>
2932 <a name="6.4.2.1" href="#6.4.2.1"><b> 6.4.2.1 General</b></a>
2936 identifier identifier-nondigit
2938 identifier-nondigit:
2940 universal-character-name
2941 other implementation-defined characters
2943 _ a b c d e f g h i j k l m
2944 n o p q r s t u v w x y z
2945 A B C D E F G H I J K L M
2946 N O P Q R S T U V W X Y Z
2950 2 An identifier is a sequence of nondigit characters (including the underscore _, the
2951 lowercase and uppercase Latin letters, and other characters) and digits, which designates
2952 one or more entities as described in <a href="#6.2.1">6.2.1</a>. Lowercase and uppercase letters are distinct.
2953 There is no specific limit on the maximum length of an identifier.
2954 3 Each universal character name in an identifier shall designate a character whose encoding
2955 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
2956 shall not be a universal character name designating a character whose encoding falls into
2957 one of the ranges specified in <a href="#D.2">D.2</a>. An implementation may allow multibyte characters
2958 that are not part of the basic source character set to appear in identifiers; which characters
2959 and their correspondence to universal character names is implementation-defined.
2963 <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>.
2964 <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
2965 name may be used in forming valid external identifiers. For example, some otherwise unused
2966 character or sequence of characters may be used to encode the \u in a universal character name.
2967 Extended characters may produce a long external identifier.
2969 [<a name="p59" href="#p59">page 59</a>] (<a href="#Contents">Contents</a>)
2971 4 When preprocessing tokens are converted to tokens during translation phase 7, if a
2972 preprocessing token could be converted to either a keyword or an identifier, it is converted
2974 Implementation limits
2975 5 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of significant initial
2976 characters in an identifier; the limit for an external name (an identifier that has external
2977 linkage) may be more restrictive than that for an internal name (a macro name or an
2978 identifier that does not have external linkage). The number of significant characters in an
2979 identifier is implementation-defined.
2980 6 Any identifiers that differ in a significant character are different identifiers. If two
2981 identifiers differ only in nonsignificant characters, the behavior is undefined.
2982 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>).
2983 <a name="6.4.2.2" href="#6.4.2.2"><b> 6.4.2.2 Predefined identifiers</b></a>
2985 1 The identifier __func__ shall be implicitly declared by the translator as if,
2986 immediately following the opening brace of each function definition, the declaration
2987 static const char __func__[] = "function-name";
2988 appeared, where function-name is the name of the lexically-enclosing function.<sup><a href="#note72"><b>72)</b></a></sup>
2989 2 This name is encoded as if the implicit declaration had been written in the source
2990 character set and then translated into the execution character set as indicated in translation
2992 3 EXAMPLE Consider the code fragment:
2993 #include <a href="#7.21"><stdio.h></a>
2996 printf("%s\n", __func__);
2999 Each time the function is called, it will print to the standard output stream:
3002 Forward references: function definitions (<a href="#6.9.1">6.9.1</a>).
3007 <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
3008 identifier is explicitly declared using the name __func__, the behavior is undefined.
3010 [<a name="p60" href="#p60">page 60</a>] (<a href="#Contents">Contents</a>)
3012 <a name="6.4.3" href="#6.4.3"><b> 6.4.3 Universal character names</b></a>
3014 1 universal-character-name:
3016 \U hex-quad hex-quad
3018 hexadecimal-digit hexadecimal-digit
3019 hexadecimal-digit hexadecimal-digit
3021 2 A universal character name shall not specify a character whose short identifier is less than
3022 00A0 other than 0024 ($), 0040 (@), or 0060 ('), nor one in the range D800 through
3023 DFFF inclusive.<sup><a href="#note73"><b>73)</b></a></sup>
3025 3 Universal character names may be used in identifiers, character constants, and string
3026 literals to designate characters that are not in the basic character set.
3028 4 The universal character name \Unnnnnnnn designates the character whose eight-digit
3029 short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.<sup><a href="#note74"><b>74)</b></a></sup> Similarly, the universal
3030 character name \unnnn designates the character whose four-digit short identifier is nnnn
3031 (and whose eight-digit short identifier is 0000nnnn).
3036 <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
3037 by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by
3040 <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.
3042 [<a name="p61" href="#p61">page 61</a>] (<a href="#Contents">Contents</a>)
3044 <a name="6.4.4" href="#6.4.4"><b> 6.4.4 Constants</b></a>
3049 enumeration-constant
3052 2 Each constant shall have a type and the value of a constant shall be in the range of
3053 representable values for its type.
3055 3 Each constant has a type, determined by its form and value, as detailed later.
3056 <a name="6.4.4.1" href="#6.4.4.1"><b> 6.4.4.1 Integer constants</b></a>
3059 decimal-constant integer-suffixopt
3060 octal-constant integer-suffixopt
3061 hexadecimal-constant integer-suffixopt
3064 decimal-constant digit
3067 octal-constant octal-digit
3068 hexadecimal-constant:
3069 hexadecimal-prefix hexadecimal-digit
3070 hexadecimal-constant hexadecimal-digit
3071 hexadecimal-prefix: one of
3073 nonzero-digit: one of
3078 [<a name="p62" href="#p62">page 62</a>] (<a href="#Contents">Contents</a>)
3080 hexadecimal-digit: one of
3085 unsigned-suffix long-suffixopt
3086 unsigned-suffix long-long-suffix
3087 long-suffix unsigned-suffixopt
3088 long-long-suffix unsigned-suffixopt
3089 unsigned-suffix: one of
3093 long-long-suffix: one of
3096 2 An integer constant begins with a digit, but has no period or exponent part. It may have a
3097 prefix that specifies its base and a suffix that specifies its type.
3098 3 A decimal constant begins with a nonzero digit and consists of a sequence of decimal
3099 digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
3100 digits 0 through 7 only. A hexadecimal constant consists of the prefix 0x or 0X followed
3101 by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
3102 10 through 15 respectively.
3104 4 The value of a decimal constant is computed base 10; that of an octal constant, base 8;
3105 that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
3106 5 The type of an integer constant is the first of the corresponding list in which its value can
3109 [<a name="p63" href="#p63">page 63</a>] (<a href="#Contents">Contents</a>)
3111 Octal or Hexadecimal
3112 Suffix Decimal Constant Constant
3115 long int unsigned int
3116 long long int long int
3119 unsigned long long int
3121 u or U unsigned int unsigned int
3122 unsigned long int unsigned long int
3123 unsigned long long int unsigned long long int
3125 l or L long int long int
3126 long long int unsigned long int
3128 unsigned long long int
3130 Both u or U unsigned long int unsigned long int
3131 and l or L unsigned long long int unsigned long long int
3133 ll or LL long long int long long int
3134 unsigned long long int
3136 Both u or U unsigned long long int unsigned long long int
3138 6 If an integer constant cannot be represented by any type in its list, it may have an
3139 extended integer type, if the extended integer type can represent its value. If all of the
3140 types in the list for the constant are signed, the extended integer type shall be signed. If
3141 all of the types in the list for the constant are unsigned, the extended integer type shall be
3142 unsigned. If the list contains both signed and unsigned types, the extended integer type
3143 may be signed or unsigned. If an integer constant cannot be represented by any type in
3144 its list and has no extended integer type, then the integer constant has no type.
3146 [<a name="p64" href="#p64">page 64</a>] (<a href="#Contents">Contents</a>)
3148 <a name="6.4.4.2" href="#6.4.4.2"><b> 6.4.4.2 Floating constants</b></a>
3150 1 floating-constant:
3151 decimal-floating-constant
3152 hexadecimal-floating-constant
3153 decimal-floating-constant:
3154 fractional-constant exponent-partopt floating-suffixopt
3155 digit-sequence exponent-part floating-suffixopt
3156 hexadecimal-floating-constant:
3157 hexadecimal-prefix hexadecimal-fractional-constant
3158 binary-exponent-part floating-suffixopt
3159 hexadecimal-prefix hexadecimal-digit-sequence
3160 binary-exponent-part floating-suffixopt
3161 fractional-constant:
3162 digit-sequenceopt . digit-sequence
3165 e signopt digit-sequence
3166 E signopt digit-sequence
3171 digit-sequence digit
3172 hexadecimal-fractional-constant:
3173 hexadecimal-digit-sequenceopt .
3174 hexadecimal-digit-sequence
3175 hexadecimal-digit-sequence .
3176 binary-exponent-part:
3177 p signopt digit-sequence
3178 P signopt digit-sequence
3179 hexadecimal-digit-sequence:
3181 hexadecimal-digit-sequence hexadecimal-digit
3182 floating-suffix: one of
3185 [<a name="p65" href="#p65">page 65</a>] (<a href="#Contents">Contents</a>)
3188 2 A floating constant has a significand part that may be followed by an exponent part and a
3189 suffix that specifies its type. The components of the significand part may include a digit
3190 sequence representing the whole-number part, followed by a period (.), followed by a
3191 digit sequence representing the fraction part. The components of the exponent part are an
3192 e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
3193 Either the whole-number part or the fraction part has to be present; for decimal floating
3194 constants, either the period or the exponent part has to be present.
3196 3 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
3197 digit sequence in the exponent part is interpreted as a decimal integer. For decimal
3198 floating constants, the exponent indicates the power of 10 by which the significand part is
3199 to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
3200 by which the significand part is to be scaled. For decimal floating constants, and also for
3201 hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
3202 the nearest representable value, or the larger or smaller representable value immediately
3203 adjacent to the nearest representable value, chosen in an implementation-defined manner.
3204 For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
3206 4 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
3207 type float. If suffixed by the letter l or L, it has type long double.
3208 5 Floating constants are converted to internal format as if at translation-time. The
3209 conversion of a floating constant shall not raise an exceptional condition or a floating-
3210 point exception at execution time. All floating constants of the same source form<sup><a href="#note75"><b>75)</b></a></sup> shall
3211 convert to the same internal format with the same value.
3212 Recommended practice
3213 6 The implementation should produce a diagnostic message if a hexadecimal constant
3214 cannot be represented exactly in its evaluation format; the implementation should then
3215 proceed with the translation of the program.
3216 7 The translation-time conversion of floating constants should match the execution-time
3217 conversion of character strings by library functions, such as strtod, given matching
3218 inputs suitable for both conversions, the same result format, and default execution-time
3219 rounding.<sup><a href="#note76"><b>76)</b></a></sup>
3221 <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
3222 convert to the same internal format and value.
3223 <sup><a name="note76" href="#note76"><b>76)</b></a></sup> The specification for the library functions recommends more accurate conversion than required for
3224 floating constants (see <a href="#7.22.1.3">7.22.1.3</a>).
3226 [<a name="p66" href="#p66">page 66</a>] (<a href="#Contents">Contents</a>)
3228 <a name="6.4.4.3" href="#6.4.4.3"><b> 6.4.4.3 Enumeration constants</b></a>
3230 1 enumeration-constant:
3233 2 An identifier declared as an enumeration constant has type int.
3234 Forward references: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>).
3235 <a name="6.4.4.4" href="#6.4.4.4"><b> 6.4.4.4 Character constants</b></a>
3237 1 character-constant:
3239 L' c-char-sequence '
3240 u' c-char-sequence '
3241 U' c-char-sequence '
3244 c-char-sequence c-char
3246 any member of the source character set except
3247 the single-quote ', backslash \, or new-line character
3250 simple-escape-sequence
3251 octal-escape-sequence
3252 hexadecimal-escape-sequence
3253 universal-character-name
3254 simple-escape-sequence: one of
3256 \a \b \f \n \r \t \v
3257 octal-escape-sequence:
3259 \ octal-digit octal-digit
3260 \ octal-digit octal-digit octal-digit
3262 [<a name="p67" href="#p67">page 67</a>] (<a href="#Contents">Contents</a>)
3264 hexadecimal-escape-sequence:
3265 \x hexadecimal-digit
3266 hexadecimal-escape-sequence hexadecimal-digit
3268 2 An integer character constant is a sequence of one or more multibyte characters enclosed
3269 in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
3270 letter L, u, or U. With a few exceptions detailed later, the elements of the sequence are
3271 any members of the source character set; they are mapped in an implementation-defined
3272 manner to members of the execution character set.
3273 3 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
3274 arbitrary integer values are representable according to the following table of escape
3280 octal character \octal digits
3281 hexadecimal character \x hexadecimal digits
3282 4 The double-quote " and question-mark ? are representable either by themselves or by the
3283 escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
3284 shall be represented, respectively, by the escape sequences \' and \\.
3285 5 The octal digits that follow the backslash in an octal escape sequence are taken to be part
3286 of the construction of a single character for an integer character constant or of a single
3287 wide character for a wide character constant. The numerical value of the octal integer so
3288 formed specifies the value of the desired character or wide character.
3289 6 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
3290 sequence are taken to be part of the construction of a single character for an integer
3291 character constant or of a single wide character for a wide character constant. The
3292 numerical value of the hexadecimal integer so formed specifies the value of the desired
3293 character or wide character.
3294 7 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
3295 constitute the escape sequence.
3296 8 In addition, characters not in the basic character set are representable by universal
3297 character names and certain nongraphic characters are representable by escape sequences
3298 consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
3299 and \v.<sup><a href="#note77"><b>77)</b></a></sup>
3301 [<a name="p68" href="#p68">page 68</a>] (<a href="#Contents">Contents</a>)
3304 9 The value of an octal or hexadecimal escape sequence shall be in the range of
3305 representable values for the corresponding type:
3306 Prefix Corresponding Type
3308 L the unsigned type corresponding to wchar_t
3312 10 An integer character constant has type int. The value of an integer character constant
3313 containing a single character that maps to a single-byte execution character is the
3314 numerical value of the representation of the mapped character interpreted as an integer.
3315 The value of an integer character constant containing more than one character (e.g.,
3316 'ab'), or containing a character or escape sequence that does not map to a single-byte
3317 execution character, is implementation-defined. If an integer character constant contains
3318 a single character or escape sequence, its value is the one that results when an object with
3319 type char whose value is that of the single character or escape sequence is converted to
3321 11 A wide character constant prefixed by the letter L has type wchar_t, an integer type
3322 defined in the <a href="#7.19"><stddef.h></a> header; a wide character constant prefixed by the letter u or
3323 U has type char16_t or char32_t, respectively, unsigned integer types defined in the
3324 <a href="#7.27"><uchar.h></a> header. The value of a wide character constant containing a single
3325 multibyte character that maps to a single member of the extended execution character set
3326 is the wide character corresponding to that multibyte character, as defined by the
3327 mbtowc, mbrtoc16, or mbrtoc32 function as appropriate for its type, with an
3328 implementation-defined current locale. The value of a wide character constant containing
3329 more than one multibyte character or a single multibyte character that maps to multiple
3330 members of the extended execution character set, or containing a multibyte character or
3331 escape sequence not represented in the extended execution character set, is
3332 implementation-defined.
3333 12 EXAMPLE 1 The construction '\0' is commonly used to represent the null character.
3335 13 EXAMPLE 2 Consider implementations that use two's complement representation for integers and eight
3336 bits for objects that have type char. In an implementation in which type char has the same range of
3337 values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
3338 same range of values as unsigned char, the character constant '\xFF' has the value +255.
3343 <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,
3344 the result is not a token and a diagnostic is required. See ''future language directions'' (<a href="#6.11.4">6.11.4</a>).
3346 [<a name="p69" href="#p69">page 69</a>] (<a href="#Contents">Contents</a>)
3348 14 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
3349 specifies an integer character constant containing only one character, since a hexadecimal escape sequence
3350 is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
3351 two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
3352 escape sequence is terminated after three octal digits. (The value of this two-character integer character
3353 constant is implementation-defined.)
3355 15 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
3356 L'\1234' specifies the implementation-defined value that results from the combination of the values
3359 Forward references: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbtowc function
3360 (<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>).
3361 <a name="6.4.5" href="#6.4.5"><b> 6.4.5 String literals</b></a>
3364 encoding-prefixopt " s-char-sequenceopt "
3372 s-char-sequence s-char
3374 any member of the source character set except
3375 the double-quote ", backslash \, or new-line character
3378 2 A sequence of adjacent string literal tokens shall not include both a wide string literal and
3379 a UTF-8 string literal.
3381 3 A character string literal is a sequence of zero or more multibyte characters enclosed in
3382 double-quotes, as in "xyz". A UTF-8 string literal is the same, except prefixed by u8.
3383 A wide string literal is the same, except prefixed by the letter L, u, or U.
3384 4 The same considerations apply to each element of the sequence in a string literal as if it
3385 were in an integer character constant (for a character or UTF-8 string literal) or a wide
3386 character constant (for a wide string literal), except that the single-quote ' is
3387 representable either by itself or by the escape sequence \', but the double-quote " shall
3389 [<a name="p70" href="#p70">page 70</a>] (<a href="#Contents">Contents</a>)
3391 be represented by the escape sequence \".
3393 5 In translation phase 6, the multibyte character sequences specified by any sequence of
3394 adjacent character and identically-prefixed string literal tokens are concatenated into a
3395 single multibyte character sequence. If any of the tokens has an encoding prefix, the
3396 resulting multibyte character sequence is treated as having the same prefix; otherwise, it
3397 is treated as a character string literal. Whether differently-prefixed wide string literal
3398 tokens can be concatenated and, if so, the treatment of the resulting multibyte character
3399 sequence are implementation-defined.
3400 6 In translation phase 7, a byte or code of value zero is appended to each multibyte
3401 character sequence that results from a string literal or literals.<sup><a href="#note78"><b>78)</b></a></sup> The multibyte character
3402 sequence is then used to initialize an array of static storage duration and length just
3403 sufficient to contain the sequence. For character string literals, the array elements have
3404 type char, and are initialized with the individual bytes of the multibyte character
3405 sequence. For UTF-8 string literals, the array elements have type char, and are
3406 initialized with the characters of the multibyte character sequence, as encoded in UTF-8.
3407 For wide string literals prefixed by the letter L, the array elements have type wchar_t
3408 and are initialized with the sequence of wide characters corresponding to the multibyte
3409 character sequence, as defined by the mbstowcs function with an implementation-
3410 defined current locale. For wide string literals prefixed by the letter u or U, the array
3411 elements have type char16_t or char32_t, respectively, and are initialized with the
3412 sequence of wide characters corresponding to the multibyte character sequence, as
3413 defined by successive calls to the mbrtoc16, or mbrtoc32 function as appropriate for
3414 its type, with an implementation-defined current locale. The value of a string literal
3415 containing a multibyte character or escape sequence not represented in the execution
3416 character set is implementation-defined.
3417 7 It is unspecified whether these arrays are distinct provided their elements have the
3418 appropriate values. If the program attempts to modify such an array, the behavior is
3420 8 EXAMPLE 1 This pair of adjacent character string literals
3422 produces a single character string literal containing the two characters whose values are '\x12' and '3',
3423 because escape sequences are converted into single members of the execution character set just prior to
3424 adjacent string literal concatenation.
3426 9 EXAMPLE 2 Each of the sequences of adjacent string literal tokens
3430 <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
3433 [<a name="p71" href="#p71">page 71</a>] (<a href="#Contents">Contents</a>)
3439 is equivalent to the string literal
3441 Likewise, each of the sequences
3449 Forward references: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>), the mbstowcs
3450 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>).
3451 <a name="6.4.6" href="#6.4.6"><b> 6.4.6 Punctuators</b></a>
3453 1 punctuator: one of
3455 ++ -- & * + - ~ !
3456 / % << >> < > <= >= == != ^ | && ||
3458 = *= /= %= += -= <<= >>= &= ^= |=
3460 <: :> <% %> %: %:%:
3462 2 A punctuator is a symbol that has independent syntactic and semantic significance.
3463 Depending on context, it may specify an operation to be performed (which in turn may
3464 yield a value or a function designator, produce a side effect, or some combination thereof)
3465 in which case it is known as an operator (other forms of operator also exist in some
3466 contexts). An operand is an entity on which an operator acts.
3468 [<a name="p72" href="#p72">page 72</a>] (<a href="#Contents">Contents</a>)
3470 3 In all aspects of the language, the six tokens<sup><a href="#note79"><b>79)</b></a></sup>
3471 <: :> <% %> %: %:%:
3472 behave, respectively, the same as the six tokens
3474 except for their spelling.<sup><a href="#note80"><b>80)</b></a></sup>
3475 Forward references: expressions (<a href="#6.5">6.5</a>), declarations (<a href="#6.7">6.7</a>), preprocessing directives
3476 (<a href="#6.10">6.10</a>), statements (<a href="#6.8">6.8</a>).
3477 <a name="6.4.7" href="#6.4.7"><b> 6.4.7 Header names</b></a>
3480 < h-char-sequence >
3484 h-char-sequence h-char
3486 any member of the source character set except
3487 the new-line character and >
3490 q-char-sequence q-char
3492 any member of the source character set except
3493 the new-line character and "
3495 2 The sequences in both forms of header names are mapped in an implementation-defined
3496 manner to headers or external source file names as specified in <a href="#6.10.2">6.10.2</a>.
3497 3 If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters,
3498 the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the
3503 <sup><a name="note79" href="#note79"><b>79)</b></a></sup> These tokens are sometimes called ''digraphs''.
3504 <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
3507 [<a name="p73" href="#p73">page 73</a>] (<a href="#Contents">Contents</a>)
3509 sequence between the " delimiters, the behavior is undefined.<sup><a href="#note81"><b>81)</b></a></sup> Header name
3510 preprocessing tokens are recognized only within #include preprocessing directives and
3511 in implementation-defined locations within #pragma directives.<sup><a href="#note82"><b>82)</b></a></sup>
3512 4 EXAMPLE The following sequence of characters:
3514 #include <1/a.h>
3515 #define const.member@$
3516 forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
3517 by a { on the left and a } on the right).
3518 {0x3}{<}{1}{/}{a}{.}{h}{>}{1e2}
3519 {#}{include} {<1/a.h>}
3520 {#}{define} {const}{.}{member}{@}{$}
3522 Forward references: source file inclusion (<a href="#6.10.2">6.10.2</a>).
3523 <a name="6.4.8" href="#6.4.8"><b> 6.4.8 Preprocessing numbers</b></a>
3529 pp-number identifier-nondigit
3536 2 A preprocessing number begins with a digit optionally preceded by a period (.) and may
3537 be followed by valid identifier characters and the character sequences e+, e-, E+, E-,
3539 3 Preprocessing number tokens lexically include all floating and integer constant tokens.
3541 4 A preprocessing number does not have type or a value; it acquires both after a successful
3542 conversion (as part of translation phase 7) to a floating constant token or an integer
3546 <sup><a name="note81" href="#note81"><b>81)</b></a></sup> Thus, sequences of characters that resemble escape sequences cause undefined behavior.
3547 <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>.
3549 [<a name="p74" href="#p74">page 74</a>] (<a href="#Contents">Contents</a>)
3551 <a name="6.4.9" href="#6.4.9"><b> 6.4.9 Comments</b></a>
3552 1 Except within a character constant, a string literal, or a comment, the characters /*
3553 introduce a comment. The contents of such a comment are examined only to identify
3554 multibyte characters and to find the characters */ that terminate it.<sup><a href="#note83"><b>83)</b></a></sup>
3555 2 Except within a character constant, a string literal, or a comment, the characters //
3556 introduce a comment that includes all multibyte characters up to, but not including, the
3557 next new-line character. The contents of such a comment are examined only to identify
3558 multibyte characters and to find the terminating new-line character.
3560 "a//b" // four-character string literal
3561 #include "//e" // undefined behavior
3562 // */ // comment, not syntax error
3563 f = g/**//h; // equivalent to f = g / h;
3565 i(); // part of a two-line comment
3567 / j(); // part of a two-line comment
3568 #define glue(x,y) x##y
3569 glue(/,/) k(); // syntax error, not comment
3570 /*//*/ l(); // equivalent to l();
3572 + p; // equivalent to m = n + p;
3577 <sup><a name="note83" href="#note83"><b>83)</b></a></sup> Thus, /* ... */ comments do not nest.
3579 [<a name="p75" href="#p75">page 75</a>] (<a href="#Contents">Contents</a>)
3581 <a name="6.5" href="#6.5"><b> 6.5 Expressions</b></a>
3582 1 An expression is a sequence of operators and operands that specifies computation of a
3583 value, or that designates an object or a function, or that generates side effects, or that
3584 performs a combination thereof. The value computations of the operands of an operator
3585 are sequenced before the value computation of the result of the operator.
3586 2 If a side effect on a scalar object is unsequenced relative to either a different side effect
3587 on the same scalar object or a value computation using the value of the same scalar
3588 object, the behavior is undefined. If there are multiple allowable orderings of the
3589 subexpressions of an expression, the behavior is undefined if such an unsequenced side
3590 effect occurs in any of the orderings.<sup><a href="#note84"><b>84)</b></a></sup>
3591 3 The grouping of operators and operands is indicated by the syntax.<sup><a href="#note85"><b>85)</b></a></sup> Except as specified
3592 later, side effects and value computations of subexpressions are unsequenced.<sup><a href="#note86"><b>86)</b></a></sup> *
3593 4 Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |,
3594 collectively described as bitwise operators) are required to have operands that have
3595 integer type. These operators yield values that depend on the internal representations of
3596 integers, and have implementation-defined and undefined aspects for signed types.
3597 5 If an exceptional condition occurs during the evaluation of an expression (that is, if the
3598 result is not mathematically defined or not in the range of representable values for its
3599 type), the behavior is undefined.
3603 <sup><a name="note84" href="#note84"><b>84)</b></a></sup> This paragraph renders undefined statement expressions such as
3610 <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
3611 as the order of the major subclauses of this subclause, highest precedence first. Thus, for example, the
3612 expressions allowed as the operands of the binary + operator (<a href="#6.5.6">6.5.6</a>) are those expressions defined in
3613 <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
3614 (<a href="#6.5.3">6.5.3</a>), and an operand contained between any of the following pairs of operators: grouping
3615 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
3616 the conditional operator ? : (<a href="#6.5.15">6.5.15</a>).
3617 Within each major subclause, the operators have the same precedence. Left- or right-associativity is
3618 indicated in each subclause by the syntax for the expressions discussed therein.
3619 <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
3620 indeterminately sequenced evaluations of its subexpressions need not be performed consistently in
3621 different evaluations.
3623 [<a name="p76" href="#p76">page 76</a>] (<a href="#Contents">Contents</a>)
3625 6 The effective type of an object for an access to its stored value is the declared type of the
3626 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
3627 lvalue having a type that is not a character type, then the type of the lvalue becomes the
3628 effective type of the object for that access and for subsequent accesses that do not modify
3629 the stored value. If a value is copied into an object having no declared type using
3630 memcpy or memmove, or is copied as an array of character type, then the effective type
3631 of the modified object for that access and for subsequent accesses that do not modify the
3632 value is the effective type of the object from which the value is copied, if it has one. For
3633 all other accesses to an object having no declared type, the effective type of the object is
3634 simply the type of the lvalue used for the access.
3635 7 An object shall have its stored value accessed only by an lvalue expression that has one of
3636 the following types:<sup><a href="#note88"><b>88)</b></a></sup>
3637 -- a type compatible with the effective type of the object,
3638 -- a qualified version of a type compatible with the effective type of the object,
3639 -- a type that is the signed or unsigned type corresponding to the effective type of the
3641 -- a type that is the signed or unsigned type corresponding to a qualified version of the
3642 effective type of the object,
3643 -- an aggregate or union type that includes one of the aforementioned types among its
3644 members (including, recursively, a member of a subaggregate or contained union), or
3645 -- a character type.
3646 8 A floating expression may be contracted, that is, evaluated as though it were a single
3647 operation, thereby omitting rounding errors implied by the source code and the
3648 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
3649 way to disallow contracted expressions. Otherwise, whether and how expressions are
3650 contracted is implementation-defined.<sup><a href="#note90"><b>90)</b></a></sup>
3651 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>).
3654 <sup><a name="note87" href="#note87"><b>87)</b></a></sup> Allocated objects have no declared type.
3655 <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.
3656 <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
3657 range, while the final operation is rounded to the format determined by the expression evaluation
3658 method. A contracted expression might also omit the raising of floating-point exceptions.
3659 <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
3660 combine multiple C operators. As contractions potentially undermine predictability, and can even
3661 decrease accuracy for containing expressions, their use needs to be well-defined and clearly
3664 [<a name="p77" href="#p77">page 77</a>] (<a href="#Contents">Contents</a>)
3666 <a name="6.5.1" href="#6.5.1"><b> 6.5.1 Primary expressions</b></a>
3668 1 primary-expression:
3675 2 An identifier is a primary expression, provided it has been declared as designating an
3676 object (in which case it is an lvalue) or a function (in which case it is a function
3677 designator).<sup><a href="#note91"><b>91)</b></a></sup>
3678 3 A constant is a primary expression. Its type depends on its form and value, as detailed in
3679 <a href="#6.4.4">6.4.4</a>.
3680 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>.
3681 5 A parenthesized expression is a primary expression. Its type and value are identical to
3682 those of the unparenthesized expression. It is an lvalue, a function designator, or a void
3683 expression if the unparenthesized expression is, respectively, an lvalue, a function
3684 designator, or a void expression.
3685 Forward references: declarations (<a href="#6.7">6.7</a>).
3686 <a name="6.5.1.1" href="#6.5.1.1"><b> 6.5.1.1 Generic selection</b></a>
3688 1 generic-selection:
3689 _Generic ( assignment-expression , generic-assoc-list )
3692 generic-assoc-list , generic-association
3693 generic-association:
3694 type-name : assignment-expression
3695 default : assignment-expression
3697 2 A generic selection shall have no more than one default generic association. The type
3698 name in a generic association shall specify a complete object type other than a variably
3700 <sup><a name="note91" href="#note91"><b>91)</b></a></sup> Thus, an undeclared identifier is a violation of the syntax.
3702 [<a name="p78" href="#p78">page 78</a>] (<a href="#Contents">Contents</a>)
3704 modified type. No two generic associations in the same generic selection shall specify
3705 compatible types. The controlling expression of a generic selection shall have type
3706 compatible with at most one of the types named in its generic association list. If a
3707 generic selection has no default generic association, its controlling expression shall
3708 have type compatible with exactly one of the types named in its generic association list.
3710 3 The controlling expression of a generic selection is not evaluated. If a generic selection
3711 has a generic association with a type name that is compatible with the type of the
3712 controlling expression, then the result expression of the generic selection is the
3713 expression in that generic association. Otherwise, the result expression of the generic
3714 selection is the expression in the default generic association. None of the expressions
3715 from any other generic association of the generic selection is evaluated.
3716 4 The type and value of a generic selection are identical to those of its result expression. It
3717 is an lvalue, a function designator, or a void expression if its result expression is,
3718 respectively, an lvalue, a function designator, or a void expression.
3719 5 EXAMPLE The cbrt type-generic macro could be implemented as follows:
3720 #define cbrt(X) _Generic((X), \
3721 long double: cbrtl, \
3726 <a name="6.5.2" href="#6.5.2"><b> 6.5.2 Postfix operators</b></a>
3728 1 postfix-expression:
3730 postfix-expression [ expression ]
3731 postfix-expression ( argument-expression-listopt )
3732 postfix-expression . identifier
3733 postfix-expression -> identifier
3734 postfix-expression ++
3735 postfix-expression --
3736 ( type-name ) { initializer-list }
3737 ( type-name ) { initializer-list , }
3738 argument-expression-list:
3739 assignment-expression
3740 argument-expression-list , assignment-expression
3742 [<a name="p79" href="#p79">page 79</a>] (<a href="#Contents">Contents</a>)
3744 <a name="6.5.2.1" href="#6.5.2.1"><b> 6.5.2.1 Array subscripting</b></a>
3746 1 One of the expressions shall have type ''pointer to complete object type'', the other
3747 expression shall have integer type, and the result has type ''type''.
3749 2 A postfix expression followed by an expression in square brackets [] is a subscripted
3750 designation of an element of an array object. The definition of the subscript operator []
3751 is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that
3752 apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the
3753 initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th
3754 element of E1 (counting from zero).
3755 3 Successive subscript operators designate an element of a multidimensional array object.
3756 If E is an n-dimensional array (n >= 2) with dimensions i x j x . . . x k, then E (used as
3757 other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with
3758 dimensions j x . . . x k. If the unary * operator is applied to this pointer explicitly, or
3759 implicitly as a result of subscripting, the result is the referenced (n - 1)-dimensional
3760 array, which itself is converted into a pointer if used as other than an lvalue. It follows
3761 from this that arrays are stored in row-major order (last subscript varies fastest).
3762 4 EXAMPLE Consider the array object defined by the declaration
3764 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
3765 array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
3766 a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually
3767 entails multiplying i by the size of the object to which the pointer points, namely an array of five int
3768 objects. The results are added and indirection is applied to yield an array of five ints. When used in the
3769 expression x[i][j], that array is in turn converted to a pointer to the first of the ints, so x[i][j]
3772 Forward references: additive operators (<a href="#6.5.6">6.5.6</a>), address and indirection operators
3773 (<a href="#6.5.3.2">6.5.3.2</a>), array declarators (<a href="#6.7.6.2">6.7.6.2</a>).
3774 <a name="6.5.2.2" href="#6.5.2.2"><b> 6.5.2.2 Function calls</b></a>
3776 1 The expression that denotes the called function<sup><a href="#note92"><b>92)</b></a></sup> shall have type pointer to function
3777 returning void or returning a complete object type other than an array type.
3778 2 If the expression that denotes the called function has a type that includes a prototype, the
3779 number of arguments shall agree with the number of parameters. Each argument shall
3782 <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.
3784 [<a name="p80" href="#p80">page 80</a>] (<a href="#Contents">Contents</a>)
3786 have a type such that its value may be assigned to an object with the unqualified version
3787 of the type of its corresponding parameter.
3789 3 A postfix expression followed by parentheses () containing a possibly empty, comma-
3790 separated list of expressions is a function call. The postfix expression denotes the called
3791 function. The list of expressions specifies the arguments to the function.
3792 4 An argument may be an expression of any complete object type. In preparing for the call
3793 to a function, the arguments are evaluated, and each parameter is assigned the value of the
3794 corresponding argument.<sup><a href="#note93"><b>93)</b></a></sup>
3795 5 If the expression that denotes the called function has type pointer to function returning an
3796 object type, the function call expression has the same type as that object type, and has the
3797 value determined as specified in <a href="#6.8.6.4">6.8.6.4</a>. Otherwise, the function call has type void. *
3798 6 If the expression that denotes the called function has a type that does not include a
3799 prototype, the integer promotions are performed on each argument, and arguments that
3800 have type float are promoted to double. These are called the default argument
3801 promotions. If the number of arguments does not equal the number of parameters, the
3802 behavior is undefined. If the function is defined with a type that includes a prototype, and
3803 either the prototype ends with an ellipsis (, ...) or the types of the arguments after
3804 promotion are not compatible with the types of the parameters, the behavior is undefined.
3805 If the function is defined with a type that does not include a prototype, and the types of
3806 the arguments after promotion are not compatible with those of the parameters after
3807 promotion, the behavior is undefined, except for the following cases:
3808 -- one promoted type is a signed integer type, the other promoted type is the
3809 corresponding unsigned integer type, and the value is representable in both types;
3810 -- both types are pointers to qualified or unqualified versions of a character type or
3812 7 If the expression that denotes the called function has a type that does include a prototype,
3813 the arguments are implicitly converted, as if by assignment, to the types of the
3814 corresponding parameters, taking the type of each parameter to be the unqualified version
3815 of its declared type. The ellipsis notation in a function prototype declarator causes
3816 argument type conversion to stop after the last declared parameter. The default argument
3817 promotions are performed on trailing arguments.
3821 <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
3822 arguments. On the other hand, it is possible to pass a pointer to an object, and the function may
3823 change the value of the object pointed to. A parameter declared to have array or function type is
3824 adjusted to have a pointer type as described in <a href="#6.9.1">6.9.1</a>.
3826 [<a name="p81" href="#p81">page 81</a>] (<a href="#Contents">Contents</a>)
3828 8 No other conversions are performed implicitly; in particular, the number and types of
3829 arguments are not compared with those of the parameters in a function definition that
3830 does not include a function prototype declarator.
3831 9 If the function is defined with a type that is not compatible with the type (of the
3832 expression) pointed to by the expression that denotes the called function, the behavior is
3834 10 There is a sequence point after the evaluations of the function designator and the actual
3835 arguments but before the actual call. Every evaluation in the calling function (including
3836 other function calls) that is not otherwise specifically sequenced before or after the
3837 execution of the body of the called function is indeterminately sequenced with respect to
3838 the execution of the called function.<sup><a href="#note94"><b>94)</b></a></sup>
3839 11 Recursive function calls shall be permitted, both directly and indirectly through any chain
3841 12 EXAMPLE In the function call
3842 (*pf[f1()]) (f2(), f3() + f4())
3843 the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before
3844 the function pointed to by pf[f1()] is called.
3846 Forward references: function declarators (including prototypes) (<a href="#6.7.6.3">6.7.6.3</a>), function
3847 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>).
3848 <a name="6.5.2.3" href="#6.5.2.3"><b> 6.5.2.3 Structure and union members</b></a>
3850 1 The first operand of the . operator shall have an atomic, qualified, or unqualified
3851 structure or union type, and the second operand shall name a member of that type.
3852 2 The first operand of the -> operator shall have type ''pointer to atomic, qualified, or
3853 unqualified structure'' or ''pointer to atomic, qualified, or unqualified union'', and the
3854 second operand shall name a member of the type pointed to.
3856 3 A postfix expression followed by the . operator and an identifier designates a member of
3857 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
3858 the first expression is an lvalue. If the first expression has qualified type, the result has
3859 the so-qualified version of the type of the designated member.
3861 <sup><a name="note94" href="#note94"><b>94)</b></a></sup> In other words, function executions do not ''interleave'' with each other.
3862 <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
3863 store a value in the object, the appropriate part of the object representation of the value is reinterpreted
3864 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
3865 punning''). This might be a trap representation.
3867 [<a name="p82" href="#p82">page 82</a>] (<a href="#Contents">Contents</a>)
3869 4 A postfix expression followed by the -> operator and an identifier designates a member
3870 of a structure or union object. The value is that of the named member of the object to
3871 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
3872 a qualified type, the result has the so-qualified version of the type of the designated
3874 5 Accessing a member of an atomic structure or union object results in undefined
3875 behavior.<sup><a href="#note97"><b>97)</b></a></sup>
3876 6 One special guarantee is made in order to simplify the use of unions: if a union contains
3877 several structures that share a common initial sequence (see below), and if the union
3878 object currently contains one of these structures, it is permitted to inspect the common
3879 initial part of any of them anywhere that a declaration of the completed type of the union
3880 is visible. Two structures share a common initial sequence if corresponding members
3881 have compatible types (and, for bit-fields, the same widths) for a sequence of one or more
3883 7 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or
3884 union, f().x is a valid postfix expression but is not an lvalue.
3887 struct s { int i; const int ci; };
3890 volatile struct s vs;
3891 the various members have the types:
3897 vs.ci volatile const int
3902 <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
3903 its operand), the expression (&E)->MOS is the same as E.MOS.
3904 <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
3905 with access to a member from another thread, where at least one access is a modification. Members
3906 can be safely accessed using a non-atomic object which is assigned to or from the atomic object.
3908 [<a name="p83" href="#p83">page 83</a>] (<a href="#Contents">Contents</a>)
3910 9 EXAMPLE 3 The following is a valid fragment:
3925 u.nf.doublenode = <a href="#3.14">3.14</a>;
3927 if (u.n.alltypes == 1)
3928 if (sin(u.nf.doublenode) == 0.0)
3930 The following is not a valid fragment (because the union type is not visible within function f):
3931 struct t1 { int m; };
3932 struct t2 { int m; };
3933 int f(struct t1 *p1, struct t2 *p2)
3935 if (p1->m < 0)
3936 p2->m = -p2->m;
3946 return f(&u.s1, &u.s2);
3949 Forward references: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), structure and union
3950 specifiers (<a href="#6.7.2.1">6.7.2.1</a>).
3952 [<a name="p84" href="#p84">page 84</a>] (<a href="#Contents">Contents</a>)
3954 <a name="6.5.2.4" href="#6.5.2.4"><b> 6.5.2.4 Postfix increment and decrement operators</b></a>
3956 1 The operand of the postfix increment or decrement operator shall have atomic, qualified,
3957 or unqualified real or pointer type, and shall be a modifiable lvalue.
3959 2 The result of the postfix ++ operator is the value of the operand. As a side effect, the
3960 value of the operand object is incremented (that is, the value 1 of the appropriate type is
3961 added to it). See the discussions of additive operators and compound assignment for
3962 information on constraints, types, and conversions and the effects of operations on
3963 pointers. The value computation of the result is sequenced before the side effect of
3964 updating the stored value of the operand. With respect to an indeterminately-sequenced
3965 function call, the operation of postfix ++ is a single evaluation. Postfix ++ on an object
3966 with atomic type is a read-modify-write operation with memory_order_seq_cst
3967 memory order semantics.<sup><a href="#note98"><b>98)</b></a></sup>
3968 3 The postfix -- operator is analogous to the postfix ++ operator, except that the value of
3969 the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
3971 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>).
3972 <a name="6.5.2.5" href="#6.5.2.5"><b> 6.5.2.5 Compound literals</b></a>
3974 1 The type name shall specify a complete object type or an array of unknown size, but not a
3975 variable length array type.
3976 2 All the constraints for initializer lists in <a href="#6.7.9">6.7.9</a> also apply to compound literals.
3978 3 A postfix expression that consists of a parenthesized type name followed by a brace-
3979 enclosed list of initializers is a compound literal. It provides an unnamed object whose
3980 value is given by the initializer list.<sup><a href="#note99"><b>99)</b></a></sup>
3983 <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
3984 where T is the type of E:
3989 } while (!atomic_compare_exchange_strong(&E, &result, tmp));
3990 with result being the result of the operation.
3992 [<a name="p85" href="#p85">page 85</a>] (<a href="#Contents">Contents</a>)
3994 4 If the type name specifies an array of unknown size, the size is determined by the
3995 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
3996 completed array type. Otherwise (when the type name specifies an object type), the type
3997 of the compound literal is that specified by the type name. In either case, the result is an
3999 5 The value of the compound literal is that of an unnamed object initialized by the
4000 initializer list. If the compound literal occurs outside the body of a function, the object
4001 has static storage duration; otherwise, it has automatic storage duration associated with
4002 the enclosing block.
4003 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>
4004 7 String literals, and compound literals with const-qualified types, need not designate
4005 distinct objects.<sup><a href="#note101"><b>101)</b></a></sup>
4006 8 EXAMPLE 1 The file scope definition
4007 int *p = (int []){2, 4};
4008 initializes p to point to the first element of an array of two ints, the first having the value two and the
4009 second, four. The expressions in this compound literal are required to be constant. The unnamed object
4010 has static storage duration.
4012 9 EXAMPLE 2 In contrast, in
4020 p is assigned the address of the first element of an array of two ints, the first having the value previously
4021 pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
4022 unnamed object has automatic storage duration.
4024 10 EXAMPLE 3 Initializers with designations can be combined with compound literals. Structure objects
4025 created using compound literals can be passed to functions without depending on member order:
4026 drawline((struct point){.x=1, .y=1},
4027 (struct point){.x=3, .y=4});
4028 Or, if drawline instead expected pointers to struct point:
4032 <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
4033 or void only, and the result of a cast expression is not an lvalue.
4034 <sup><a name="note100" href="#note100"><b>100)</b></a></sup> For example, subobjects without explicit initializers are initialized to zero.
4035 <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
4036 the same or overlapping representations.
4038 [<a name="p86" href="#p86">page 86</a>] (<a href="#Contents">Contents</a>)
4040 drawline(&(struct point){.x=1, .y=1},
4041 &(struct point){.x=3, .y=4});
4043 11 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
4044 (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}
4046 12 EXAMPLE 5 The following three expressions have different meanings:
4048 (char []){"/tmp/fileXXXXXX"}
4049 (const char []){"/tmp/fileXXXXXX"}
4050 The first always has static storage duration and has type array of char, but need not be modifiable; the last
4051 two have automatic storage duration when they occur within the body of a function, and the first of these
4054 13 EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory
4055 and can even be shared. For example,
4056 (const char []){"abc"} == "abc"
4057 might yield 1 if the literals' storage is shared.
4059 14 EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly
4060 linked object. For example, there is no way to write a self-referential compound literal that could be used
4061 as the function argument in place of the named object endless_zeros below:
4062 struct int_list { int car; struct int_list *cdr; };
4063 struct int_list endless_zeros = {0, &endless_zeros};
4064 eval(endless_zeros);
4066 15 EXAMPLE 8 Each compound literal creates only a single object in a given scope:
4067 struct s { int i; };
4070 struct s *p = 0, *q;
4073 q = p, p = &((struct s){ j++ });
4074 if (j < 2) goto again;
4075 return p == q && q->i == 1;
4077 The function f() always returns the value 1.
4078 16 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
4079 lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
4080 have an indeterminate value, which would result in undefined behavior.
4082 Forward references: type names (<a href="#6.7.7">6.7.7</a>), initialization (<a href="#6.7.9">6.7.9</a>).
4084 [<a name="p87" href="#p87">page 87</a>] (<a href="#Contents">Contents</a>)
4086 <a name="6.5.3" href="#6.5.3"><b> 6.5.3 Unary operators</b></a>
4092 unary-operator cast-expression
4093 sizeof unary-expression
4094 sizeof ( type-name )
4095 alignof ( type-name )
4096 unary-operator: one of
4098 <a name="6.5.3.1" href="#6.5.3.1"><b> 6.5.3.1 Prefix increment and decrement operators</b></a>
4100 1 The operand of the prefix increment or decrement operator shall have atomic, qualified,
4101 or unqualified real or pointer type, and shall be a modifiable lvalue.
4103 2 The value of the operand of the prefix ++ operator is incremented. The result is the new
4104 value of the operand after incrementation. The expression ++E is equivalent to (E+=1).
4105 See the discussions of additive operators and compound assignment for information on
4106 constraints, types, side effects, and conversions and the effects of operations on pointers.
4107 3 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
4108 operand is decremented.
4109 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>).
4110 <a name="6.5.3.2" href="#6.5.3.2"><b> 6.5.3.2 Address and indirection operators</b></a>
4112 1 The operand of the unary & operator shall be either a function designator, the result of a
4113 [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is
4114 not declared with the register storage-class specifier.
4115 2 The operand of the unary * operator shall have pointer type.
4117 3 The unary & operator yields the address of its operand. If the operand has type ''type'',
4118 the result has type ''pointer to type''. If the operand is the result of a unary * operator,
4119 neither that operator nor the & operator is evaluated and the result is as if both were
4120 omitted, except that the constraints on the operators still apply and the result is not an
4122 [<a name="p88" href="#p88">page 88</a>] (<a href="#Contents">Contents</a>)
4124 lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor
4125 the unary * that is implied by the [] is evaluated and the result is as if the & operator
4126 were removed and the [] operator were changed to a + operator. Otherwise, the result is
4127 a pointer to the object or function designated by its operand.
4128 4 The unary * operator denotes indirection. If the operand points to a function, the result is
4129 a function designator; if it points to an object, the result is an lvalue designating the
4130 object. If the operand has type ''pointer to type'', the result has type ''type''. If an
4131 invalid value has been assigned to the pointer, the behavior of the unary * operator is
4132 undefined.<sup><a href="#note102"><b>102)</b></a></sup>
4133 Forward references: storage-class specifiers (<a href="#6.7.1">6.7.1</a>), structure and union specifiers
4134 (<a href="#6.7.2.1">6.7.2.1</a>).
4135 <a name="6.5.3.3" href="#6.5.3.3"><b> 6.5.3.3 Unary arithmetic operators</b></a>
4137 1 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
4138 integer type; of the ! operator, scalar type.
4140 2 The result of the unary + operator is the value of its (promoted) operand. The integer
4141 promotions are performed on the operand, and the result has the promoted type.
4142 3 The result of the unary - operator is the negative of its (promoted) operand. The integer
4143 promotions are performed on the operand, and the result has the promoted type.
4144 4 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is,
4145 each bit in the result is set if and only if the corresponding bit in the converted operand is
4146 not set). The integer promotions are performed on the operand, and the result has the
4147 promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent
4148 to the maximum value representable in that type minus E.
4149 5 The result of the logical negation operator ! is 0 if the value of its operand compares
4150 unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int.
4151 The expression !E is equivalent to (0==E).
4155 <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
4156 always true that if E is a function designator or an lvalue that is a valid operand of the unary &
4157 operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of
4158 an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points.
4159 Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an
4160 address inappropriately aligned for the type of object pointed to, and the address of an object after the
4161 end of its lifetime.
4163 [<a name="p89" href="#p89">page 89</a>] (<a href="#Contents">Contents</a>)
4165 <a name="6.5.3.4" href="#6.5.3.4"><b> 6.5.3.4 The sizeof and alignof operators</b></a>
4167 1 The sizeof operator shall not be applied to an expression that has function type or an
4168 incomplete type, to the parenthesized name of such a type, or to an expression that
4169 designates a bit-field member. The alignof operator shall not be applied to a function
4170 type or an incomplete type.
4172 2 The sizeof operator yields the size (in bytes) of its operand, which may be an
4173 expression or the parenthesized name of a type. The size is determined from the type of
4174 the operand. The result is an integer. If the type of the operand is a variable length array
4175 type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an
4177 3 The alignof operator yields the alignment requirement of its operand type. The result
4178 is an integer constant. When applied to an array type, the result is the alignment
4179 requirement of the element type.
4180 4 When sizeof is applied to an operand that has type char, unsigned char, or
4181 signed char, (or a qualified version thereof) the result is 1. When applied to an
4182 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
4183 applied to an operand that has structure or union type, the result is the total number of
4184 bytes in such an object, including internal and trailing padding.
4185 5 The value of the result of both operators is implementation-defined, and its type (an
4186 unsigned integer type) is size_t, defined in <a href="#7.19"><stddef.h></a> (and other headers).
4187 6 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage
4188 allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to
4189 allocate and return a pointer to void. For example:
4190 extern void *alloc(size_t);
4191 double *dp = alloc(sizeof *dp);
4192 The implementation of the alloc function should ensure that its return value is aligned suitably for
4193 conversion to a pointer to double.
4195 7 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
4196 sizeof array / sizeof array[0]
4198 8 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a
4200 #include <a href="#7.19"><stddef.h></a>
4204 <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
4205 size of the adjusted (pointer) type (see <a href="#6.9.1">6.9.1</a>).
4207 [<a name="p90" href="#p90">page 90</a>] (<a href="#Contents">Contents</a>)
4209 size_t fsize3(int n)
4211 char b[n+3]; // variable length array
4212 return sizeof b; // execution time sizeof
4217 size = fsize3(10); // fsize3 returns 13
4221 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>),
4222 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>).
4223 <a name="6.5.4" href="#6.5.4"><b> 6.5.4 Cast operators</b></a>
4227 ( type-name ) cast-expression
4229 2 Unless the type name specifies a void type, the type name shall specify atomic, qualified,
4230 or unqualified scalar type, and the operand shall have scalar type.
4231 3 Conversions that involve pointers, other than where permitted by the constraints of
4232 <a href="#6.5.16.1">6.5.16.1</a>, shall be specified by means of an explicit cast.
4233 4 A pointer type shall not be converted to any floating type. A floating type shall not be
4234 converted to any pointer type.
4236 5 Preceding an expression by a parenthesized type name converts the value of the
4237 expression to the named type. This construction is called a cast.<sup><a href="#note104"><b>104)</b></a></sup> A cast that specifies
4238 no conversion has no effect on the type or value of an expression.
4239 6 If the value of the expression is represented with greater precision or range than required
4240 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
4241 type of the expression is the same as the named type and removes any extra range and
4243 Forward references: equality operators (<a href="#6.5.9">6.5.9</a>), function declarators (including
4244 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>).
4246 <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
4247 unqualified version of the type.
4249 [<a name="p91" href="#p91">page 91</a>] (<a href="#Contents">Contents</a>)
4251 <a name="6.5.5" href="#6.5.5"><b> 6.5.5 Multiplicative operators</b></a>
4253 1 multiplicative-expression:
4255 multiplicative-expression * cast-expression
4256 multiplicative-expression / cast-expression
4257 multiplicative-expression % cast-expression
4259 2 Each of the operands shall have arithmetic type. The operands of the % operator shall
4262 3 The usual arithmetic conversions are performed on the operands.
4263 4 The result of the binary * operator is the product of the operands.
4264 5 The result of the / operator is the quotient from the division of the first operand by the
4265 second; the result of the % operator is the remainder. In both operations, if the value of
4266 the second operand is zero, the behavior is undefined.
4267 6 When integers are divided, the result of the / operator is the algebraic quotient with any
4268 fractional part discarded.<sup><a href="#note105"><b>105)</b></a></sup> If the quotient a/b is representable, the expression
4269 (a/b)*b + a%b shall equal a; otherwise, the behavior of both a/b and a%b is
4271 <a name="6.5.6" href="#6.5.6"><b> 6.5.6 Additive operators</b></a>
4273 1 additive-expression:
4274 multiplicative-expression
4275 additive-expression + multiplicative-expression
4276 additive-expression - multiplicative-expression
4278 2 For addition, either both operands shall have arithmetic type, or one operand shall be a
4279 pointer to a complete object type and the other shall have integer type. (Incrementing is
4280 equivalent to adding 1.)
4281 3 For subtraction, one of the following shall hold:
4286 <sup><a name="note105" href="#note105"><b>105)</b></a></sup> This is often called ''truncation toward zero''.
4288 [<a name="p92" href="#p92">page 92</a>] (<a href="#Contents">Contents</a>)
4290 -- both operands have arithmetic type;
4291 -- both operands are pointers to qualified or unqualified versions of compatible complete
4293 -- the left operand is a pointer to a complete object type and the right operand has
4295 (Decrementing is equivalent to subtracting 1.)
4297 4 If both operands have arithmetic type, the usual arithmetic conversions are performed on
4299 5 The result of the binary + operator is the sum of the operands.
4300 6 The result of the binary - operator is the difference resulting from the subtraction of the
4301 second operand from the first.
4302 7 For the purposes of these operators, a pointer to an object that is not an element of an
4303 array behaves the same as a pointer to the first element of an array of length one with the
4304 type of the object as its element type.
4305 8 When an expression that has integer type is added to or subtracted from a pointer, the
4306 result has the type of the pointer operand. If the pointer operand points to an element of
4307 an array object, and the array is large enough, the result points to an element offset from
4308 the original element such that the difference of the subscripts of the resulting and original
4309 array elements equals the integer expression. In other words, if the expression P points to
4310 the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
4311 (P)-N (where N has the value n) point to, respectively, the i+n-th and i-n-th elements of
4312 the array object, provided they exist. Moreover, if the expression P points to the last
4313 element of an array object, the expression (P)+1 points one past the last element of the
4314 array object, and if the expression Q points one past the last element of an array object,
4315 the expression (Q)-1 points to the last element of the array object. If both the pointer
4316 operand and the result point to elements of the same array object, or one past the last
4317 element of the array object, the evaluation shall not produce an overflow; otherwise, the
4318 behavior is undefined. If the result points one past the last element of the array object, it
4319 shall not be used as the operand of a unary * operator that is evaluated.
4320 9 When two pointers are subtracted, both shall point to elements of the same array object,
4321 or one past the last element of the array object; the result is the difference of the
4322 subscripts of the two array elements. The size of the result is implementation-defined,
4323 and its type (a signed integer type) is ptrdiff_t defined in the <a href="#7.19"><stddef.h></a> header.
4324 If the result is not representable in an object of that type, the behavior is undefined. In
4325 other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of
4326 an array object, the expression (P)-(Q) has the value i-j provided the value fits in an
4328 [<a name="p93" href="#p93">page 93</a>] (<a href="#Contents">Contents</a>)
4330 object of type ptrdiff_t. Moreover, if the expression P points either to an element of
4331 an array object or one past the last element of an array object, and the expression Q points
4332 to the last element of the same array object, the expression ((Q)+1)-(P) has the same
4333 value as ((Q)-(P))+1 and as -((P)-((Q)+1)), and has the value zero if the
4334 expression P points one past the last element of the array object, even though the
4335 expression (Q)+1 does not point to an element of the array object.<sup><a href="#note106"><b>106)</b></a></sup>
4336 10 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
4340 int (*p)[m] = a; // p == &a[0]
4341 p += 1; // p == &a[1]
4342 (*p)[2] = 99; // a[1][2] == 99
4343 n = p - a; // n == 1
4345 11 If array a in the above example were declared to be an array of known constant size, and pointer p were
4346 declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
4349 Forward references: array declarators (<a href="#6.7.6.2">6.7.6.2</a>), common definitions <a href="#7.19"><stddef.h></a>
4350 (<a href="#7.19">7.19</a>).
4351 <a name="6.5.7" href="#6.5.7"><b> 6.5.7 Bitwise shift operators</b></a>
4355 shift-expression << additive-expression
4356 shift-expression >> additive-expression
4358 2 Each of the operands shall have integer type.
4360 3 The integer promotions are performed on each of the operands. The type of the result is
4361 that of the promoted left operand. If the value of the right operand is negative or is
4363 <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
4364 this scheme the integer expression added to or subtracted from the converted pointer is first multiplied
4365 by the size of the object originally pointed to, and the resulting pointer is converted back to the
4366 original type. For pointer subtraction, the result of the difference between the character pointers is
4367 similarly divided by the size of the object originally pointed to.
4368 When viewed in this way, an implementation need only provide one extra byte (which may overlap
4369 another object in the program) just after the end of the object in order to satisfy the ''one past the last
4370 element'' requirements.
4372 [<a name="p94" href="#p94">page 94</a>] (<a href="#Contents">Contents</a>)
4374 greater than or equal to the width of the promoted left operand, the behavior is undefined.
4375 4 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with
4376 zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo
4377 one more than the maximum value representable in the result type. If E1 has a signed
4378 type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is
4379 the resulting value; otherwise, the behavior is undefined.
4380 5 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
4381 or if E1 has a signed type and a nonnegative value, the value of the result is the integral
4382 part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
4383 resulting value is implementation-defined.
4384 <a name="6.5.8" href="#6.5.8"><b> 6.5.8 Relational operators</b></a>
4386 1 relational-expression:
4388 relational-expression < shift-expression
4389 relational-expression > shift-expression
4390 relational-expression <= shift-expression
4391 relational-expression >= shift-expression
4393 2 One of the following shall hold:
4394 -- both operands have real type; or *
4395 -- both operands are pointers to qualified or unqualified versions of compatible object
4398 3 If both of the operands have arithmetic type, the usual arithmetic conversions are
4400 4 For the purposes of these operators, a pointer to an object that is not an element of an
4401 array behaves the same as a pointer to the first element of an array of length one with the
4402 type of the object as its element type.
4403 5 When two pointers are compared, the result depends on the relative locations in the
4404 address space of the objects pointed to. If two pointers to object types both point to the
4405 same object, or both point one past the last element of the same array object, they
4406 compare equal. If the objects pointed to are members of the same aggregate object,
4407 pointers to structure members declared later compare greater than pointers to members
4408 declared earlier in the structure, and pointers to array elements with larger subscript
4409 values compare greater than pointers to elements of the same array with lower subscript
4411 [<a name="p95" href="#p95">page 95</a>] (<a href="#Contents">Contents</a>)
4413 values. All pointers to members of the same union object compare equal. If the
4414 expression P points to an element of an array object and the expression Q points to the
4415 last element of the same array object, the pointer expression Q+1 compares greater than
4416 P. In all other cases, the behavior is undefined.
4417 6 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
4418 (greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is
4419 false.<sup><a href="#note107"><b>107)</b></a></sup> The result has type int.
4420 <a name="6.5.9" href="#6.5.9"><b> 6.5.9 Equality operators</b></a>
4422 1 equality-expression:
4423 relational-expression
4424 equality-expression == relational-expression
4425 equality-expression != relational-expression
4427 2 One of the following shall hold:
4428 -- both operands have arithmetic type;
4429 -- both operands are pointers to qualified or unqualified versions of compatible types;
4430 -- one operand is a pointer to an object type and the other is a pointer to a qualified or
4431 unqualified version of void; or
4432 -- one operand is a pointer and the other is a null pointer constant.
4434 3 The == (equal to) and != (not equal to) operators are analogous to the relational
4435 operators except for their lower precedence.<sup><a href="#note108"><b>108)</b></a></sup> Each of the operators yields 1 if the
4436 specified relation is true and 0 if it is false. The result has type int. For any pair of
4437 operands, exactly one of the relations is true.
4438 4 If both of the operands have arithmetic type, the usual arithmetic conversions are
4439 performed. Values of complex types are equal if and only if both their real parts are equal
4440 and also their imaginary parts are equal. Any two values of arithmetic types from
4441 different type domains are equal if and only if the results of their conversions to the
4442 (complex) result type determined by the usual arithmetic conversions are equal.
4446 <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
4447 means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
4448 <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.
4450 [<a name="p96" href="#p96">page 96</a>] (<a href="#Contents">Contents</a>)
4452 5 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a
4453 null pointer constant, the null pointer constant is converted to the type of the pointer. If
4454 one operand is a pointer to an object type and the other is a pointer to a qualified or
4455 unqualified version of void, the former is converted to the type of the latter.
4456 6 Two pointers compare equal if and only if both are null pointers, both are pointers to the
4457 same object (including a pointer to an object and a subobject at its beginning) or function,
4458 both are pointers to one past the last element of the same array object, or one is a pointer
4459 to one past the end of one array object and the other is a pointer to the start of a different
4460 array object that happens to immediately follow the first array object in the address
4461 space.<sup><a href="#note109"><b>109)</b></a></sup>
4462 7 For the purposes of these operators, a pointer to an object that is not an element of an
4463 array behaves the same as a pointer to the first element of an array of length one with the
4464 type of the object as its element type.
4465 <a name="6.5.10" href="#6.5.10"><b> 6.5.10 Bitwise AND operator</b></a>
4469 AND-expression & equality-expression
4471 2 Each of the operands shall have integer type.
4473 3 The usual arithmetic conversions are performed on the operands.
4474 4 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
4475 the result is set if and only if each of the corresponding bits in the converted operands is
4481 <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
4482 adjacent members of a structure with no padding between them, or because the implementation chose
4483 to place them so, even though they are unrelated. If prior invalid pointer operations (such as accesses
4484 outside array bounds) produced undefined behavior, subsequent comparisons also produce undefined
4487 [<a name="p97" href="#p97">page 97</a>] (<a href="#Contents">Contents</a>)
4489 <a name="6.5.11" href="#6.5.11"><b> 6.5.11 Bitwise exclusive OR operator</b></a>
4491 1 exclusive-OR-expression:
4493 exclusive-OR-expression ^ AND-expression
4495 2 Each of the operands shall have integer type.
4497 3 The usual arithmetic conversions are performed on the operands.
4498 4 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
4499 in the result is set if and only if exactly one of the corresponding bits in the converted
4501 <a name="6.5.12" href="#6.5.12"><b> 6.5.12 Bitwise inclusive OR operator</b></a>
4503 1 inclusive-OR-expression:
4504 exclusive-OR-expression
4505 inclusive-OR-expression | exclusive-OR-expression
4507 2 Each of the operands shall have integer type.
4509 3 The usual arithmetic conversions are performed on the operands.
4510 4 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
4511 the result is set if and only if at least one of the corresponding bits in the converted
4514 [<a name="p98" href="#p98">page 98</a>] (<a href="#Contents">Contents</a>)
4516 <a name="6.5.13" href="#6.5.13"><b> 6.5.13 Logical AND operator</b></a>
4518 1 logical-AND-expression:
4519 inclusive-OR-expression
4520 logical-AND-expression && inclusive-OR-expression
4522 2 Each of the operands shall have scalar type.
4524 3 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
4525 yields 0. The result has type int.
4526 4 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
4527 if the second operand is evaluated, there is a sequence point between the evaluations of
4528 the first and second operands. If the first operand compares equal to 0, the second
4529 operand is not evaluated.
4530 <a name="6.5.14" href="#6.5.14"><b> 6.5.14 Logical OR operator</b></a>
4532 1 logical-OR-expression:
4533 logical-AND-expression
4534 logical-OR-expression || logical-AND-expression
4536 2 Each of the operands shall have scalar type.
4538 3 The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it
4539 yields 0. The result has type int.
4540 4 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; if the
4541 second operand is evaluated, there is a sequence point between the evaluations of the first
4542 and second operands. If the first operand compares unequal to 0, the second operand is
4545 [<a name="p99" href="#p99">page 99</a>] (<a href="#Contents">Contents</a>)
4547 <a name="6.5.15" href="#6.5.15"><b> 6.5.15 Conditional operator</b></a>
4549 1 conditional-expression:
4550 logical-OR-expression
4551 logical-OR-expression ? expression : conditional-expression
4553 2 The first operand shall have scalar type.
4554 3 One of the following shall hold for the second and third operands:
4555 -- both operands have arithmetic type;
4556 -- both operands have the same structure or union type;
4557 -- both operands have void type;
4558 -- both operands are pointers to qualified or unqualified versions of compatible types;
4559 -- one operand is a pointer and the other is a null pointer constant; or
4560 -- one operand is a pointer to an object type and the other is a pointer to a qualified or
4561 unqualified version of void.
4563 4 The first operand is evaluated; there is a sequence point between its evaluation and the
4564 evaluation of the second or third operand (whichever is evaluated). The second operand
4565 is evaluated only if the first compares unequal to 0; the third operand is evaluated only if
4566 the first compares equal to 0; the result is the value of the second or third operand
4567 (whichever is evaluated), converted to the type described below.<sup><a href="#note110"><b>110)</b></a></sup> *
4568 5 If both the second and third operands have arithmetic type, the result type that would be
4569 determined by the usual arithmetic conversions, were they applied to those two operands,
4570 is the type of the result. If both the operands have structure or union type, the result has
4571 that type. If both operands have void type, the result has void type.
4572 6 If both the second and third operands are pointers or one is a null pointer constant and the
4573 other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
4574 of the types referenced by both operands. Furthermore, if both operands are pointers to
4575 compatible types or to differently qualified versions of compatible types, the result type is
4576 a pointer to an appropriately qualified version of the composite type; if one operand is a
4577 null pointer constant, the result has the type of the other operand; otherwise, one operand
4578 is a pointer to void or a qualified version of void, in which case the result type is a
4579 pointer to an appropriately qualified version of void.
4581 <sup><a name="note110" href="#note110"><b>110)</b></a></sup> A conditional expression does not yield an lvalue.
4583 [<a name="p100" href="#p100">page 100</a>] (<a href="#Contents">Contents</a>)
4585 7 EXAMPLE The common type that results when the second and third operands are pointers is determined
4586 in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two
4587 pointers have compatible types.
4588 8 Given the declarations
4595 the third column in the following table is the common type that is the result of a conditional expression in
4596 which the first two columns are the second and third operands (in either order):
4597 c_vp c_ip const void *
4598 v_ip 0 volatile int *
4599 c_ip v_ip const volatile int *
4600 vp c_cp const void *
4604 <a name="6.5.16" href="#6.5.16"><b> 6.5.16 Assignment operators</b></a>
4606 1 assignment-expression:
4607 conditional-expression
4608 unary-expression assignment-operator assignment-expression
4609 assignment-operator: one of
4610 = *= /= %= += -= <<= >>= &= ^= |=
4612 2 An assignment operator shall have a modifiable lvalue as its left operand.
4614 3 An assignment operator stores a value in the object designated by the left operand. An
4615 assignment expression has the value of the left operand after the assignment,<sup><a href="#note111"><b>111)</b></a></sup> but is not
4616 an lvalue. The type of an assignment expression is the type the left operand would have
4617 after lvalue conversion. The side effect of updating the stored value of the left operand is
4618 sequenced after the value computations of the left and right operands. The evaluations of
4619 the operands are unsequenced.
4624 <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
4625 when the object has volatile-qualified type.
4627 [<a name="p101" href="#p101">page 101</a>] (<a href="#Contents">Contents</a>)
4629 <a name="6.5.16.1" href="#6.5.16.1"><b> 6.5.16.1 Simple assignment</b></a>
4631 1 One of the following shall hold:<sup><a href="#note112"><b>112)</b></a></sup>
4632 -- the left operand has atomic, qualified, or unqualified arithmetic type, and the right has
4634 -- the left operand has an atomic, qualified, or unqualified version of a structure or union
4635 type compatible with the type of the right;
4636 -- the left operand has atomic, qualified, or unqualified pointer type, and (considering
4637 the type the left operand would have after lvalue conversion) both operands are
4638 pointers to qualified or unqualified versions of compatible types, and the type pointed
4639 to by the left has all the qualifiers of the type pointed to by the right;
4640 -- the left operand has atomic, qualified, or unqualified pointer type, and (considering
4641 the type the left operand would have after lvalue conversion) one operand is a pointer
4642 to an object type, and the other is a pointer to a qualified or unqualified version of
4643 void, and the type pointed to by the left has all the qualifiers of the type pointed to
4645 -- the left operand is an atomic, qualified, or unqualified pointer, and the right is a null
4646 pointer constant; or
4647 -- the left operand has type atomic, qualified, or unqualified _Bool, and the right is a
4650 2 In simple assignment (=), the value of the right operand is converted to the type of the
4651 assignment expression and replaces the value stored in the object designated by the left
4653 3 If the value being stored in an object is read from another object that overlaps in any way
4654 the storage of the first object, then the overlap shall be exact and the two objects shall
4655 have qualified or unqualified versions of a compatible type; otherwise, the behavior is
4657 4 EXAMPLE 1 In the program fragment
4662 <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
4663 (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
4664 qualifiers that were applied to the type category of the expression (for example, it removes const but
4665 not volatile from the type int volatile * const).
4667 [<a name="p102" href="#p102">page 102</a>] (<a href="#Contents">Contents</a>)
4672 if ((c = f()) == -1)
4674 the int value returned by the function may be truncated when stored in the char, and then converted back
4675 to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
4676 values as unsigned char (and char is narrower than int), the result of the conversion cannot be
4677 negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
4678 variable c should be declared as int.
4680 5 EXAMPLE 2 In the fragment:
4685 the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
4686 of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
4687 that is, long int type.
4689 6 EXAMPLE 3 Consider the fragment:
4693 cpp = &p; // constraint violation
4694 *cpp = &c; // valid
4696 The first assignment is unsafe because it would allow the following valid code to attempt to change the
4697 value of the const object c.
4699 <a name="6.5.16.2" href="#6.5.16.2"><b> 6.5.16.2 Compound assignment</b></a>
4701 1 For the operators += and -= only, either the left operand shall be an atomic, qualified, or
4702 unqualified pointer to a complete object type, and the right shall have integer type; or the
4703 left operand shall have atomic, qualified, or unqualified arithmetic type, and the right
4704 shall have arithmetic type.
4705 2 For the other operators, the left operand shall have atomic, qualified, or unqualified
4706 arithmetic type, and (considering the type the left operand would have after lvalue
4707 conversion) each operand shall have arithmetic type consistent with those allowed by the
4708 corresponding binary operator.
4710 3 A compound assignment of the form E1 op = E2 is equivalent to the simple assignment
4711 expression E1 = E1 op (E2), except that the lvalue E1 is evaluated only once, and with
4712 respect to an indeterminately-sequenced function call, the operation of a compound
4714 [<a name="p103" href="#p103">page 103</a>] (<a href="#Contents">Contents</a>)
4716 assignment is a single evaluation. If E1 has an atomic type, compound assignment is a
4717 read-modify-write operation with memory_order_seq_cst memory order
4718 semantics.<sup><a href="#note113"><b>113)</b></a></sup>
4719 <a name="6.5.17" href="#6.5.17"><b> 6.5.17 Comma operator</b></a>
4722 assignment-expression
4723 expression , assignment-expression
4725 2 The left operand of a comma operator is evaluated as a void expression; there is a
4726 sequence point between its evaluation and that of the right operand. Then the right
4727 operand is evaluated; the result has its type and value.<sup><a href="#note114"><b>114)</b></a></sup> *
4728 3 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot
4729 appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists
4730 of initializers). On the other hand, it can be used within a parenthesized expression or within the second
4731 expression of a conditional operator in such contexts. In the function call
4733 the function has three arguments, the second of which has the value 5.
4735 Forward references: initialization (<a href="#6.7.9">6.7.9</a>).
4740 <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
4741 where T is the type of E1:
4745 result = tmp op (E2);
4746 } while (!atomic_compare_exchange_strong(&E1, &tmp, result));
4747 with result being the result of the operation.
4748 <sup><a name="note114" href="#note114"><b>114)</b></a></sup> A comma operator does not yield an lvalue.
4750 [<a name="p104" href="#p104">page 104</a>] (<a href="#Contents">Contents</a>)
4752 <a name="6.6" href="#6.6"><b> 6.6 Constant expressions</b></a>
4754 1 constant-expression:
4755 conditional-expression
4757 2 A constant expression can be evaluated during translation rather than runtime, and
4758 accordingly may be used in any place that a constant may be.
4760 3 Constant expressions shall not contain assignment, increment, decrement, function-call,
4761 or comma operators, except when they are contained within a subexpression that is not
4762 evaluated.<sup><a href="#note115"><b>115)</b></a></sup>
4763 4 Each constant expression shall evaluate to a constant that is in the range of representable
4764 values for its type.
4766 5 An expression that evaluates to a constant is required in several contexts. If a floating
4767 expression is evaluated in the translation environment, the arithmetic precision and range
4768 shall be at least as great as if the expression were being evaluated in the execution
4769 environment.<sup><a href="#note116"><b>116)</b></a></sup>
4770 6 An integer constant expression<sup><a href="#note117"><b>117)</b></a></sup> shall have integer type and shall only have operands
4771 that are integer constants, enumeration constants, character constants, sizeof
4772 expressions whose results are integer constants, and floating constants that are the
4773 immediate operands of casts. Cast operators in an integer constant expression shall only
4774 convert arithmetic types to integer types, except as part of an operand to the sizeof
4776 7 More latitude is permitted for constant expressions in initializers. Such a constant
4777 expression shall be, or evaluate to, one of the following:
4778 -- an arithmetic constant expression,
4782 <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>).
4783 <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
4784 the translation environment.
4785 <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
4786 member of a structure, the value of an enumeration constant, and the size of a non-variable length
4787 array. Further constraints that apply to the integer constant expressions used in conditional-inclusion
4788 preprocessing directives are discussed in <a href="#6.10.1">6.10.1</a>.
4790 [<a name="p105" href="#p105">page 105</a>] (<a href="#Contents">Contents</a>)
4792 -- a null pointer constant,
4793 -- an address constant, or
4794 -- an address constant for a complete object type plus or minus an integer constant
4796 8 An arithmetic constant expression shall have arithmetic type and shall only have
4797 operands that are integer constants, floating constants, enumeration constants, character
4798 constants, and sizeof expressions. Cast operators in an arithmetic constant expression
4799 shall only convert arithmetic types to arithmetic types, except as part of an operand to a
4800 sizeof operator whose result is an integer constant.
4801 9 An address constant is a null pointer, a pointer to an lvalue designating an object of static
4802 storage duration, or a pointer to a function designator; it shall be created explicitly using
4803 the unary & operator or an integer constant cast to pointer type, or implicitly by the use of
4804 an expression of array or function type. The array-subscript [] and member-access .
4805 and -> operators, the address & and indirection * unary operators, and pointer casts may
4806 be used in the creation of an address constant, but the value of an object shall not be
4807 accessed by use of these operators.
4808 10 An implementation may accept other forms of constant expressions.
4809 11 The semantic rules for the evaluation of a constant expression are the same as for
4810 nonconstant expressions.<sup><a href="#note118"><b>118)</b></a></sup>
4811 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>).
4816 <sup><a name="note118" href="#note118"><b>118)</b></a></sup> Thus, in the following initialization,
4817 static int i = 2 || 1 / 0;
4818 the expression is a valid integer constant expression with value one.
4820 [<a name="p106" href="#p106">page 106</a>] (<a href="#Contents">Contents</a>)
4822 <a name="6.7" href="#6.7"><b> 6.7 Declarations</b></a>
4825 declaration-specifiers init-declarator-listopt ;
4826 static_assert-declaration
4827 declaration-specifiers:
4828 storage-class-specifier declaration-specifiersopt
4829 type-specifier declaration-specifiersopt
4830 type-qualifier declaration-specifiersopt
4831 function-specifier declaration-specifiersopt
4832 alignment-specifier declaration-specifiersopt
4833 init-declarator-list:
4835 init-declarator-list , init-declarator
4838 declarator = initializer
4840 2 A declaration other than a static_assert declaration shall declare at least a declarator
4841 (other than the parameters of a function or the members of a structure or union), a tag, or
4842 the members of an enumeration.
4843 3 If an identifier has no linkage, there shall be no more than one declaration of the identifier
4844 (in a declarator or type specifier) with the same scope and in the same name space, except
4845 that a typedef name can be redefined to denote the same type as it currently does and tags
4846 may be redeclared as specified in <a href="#6.7.2.3">6.7.2.3</a>.
4847 4 All declarations in the same scope that refer to the same object or function shall specify
4850 5 A declaration specifies the interpretation and attributes of a set of identifiers. A definition
4851 of an identifier is a declaration for that identifier that:
4852 -- for an object, causes storage to be reserved for that object;
4853 -- for a function, includes the function body;<sup><a href="#note119"><b>119)</b></a></sup>
4857 <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>.
4859 [<a name="p107" href="#p107">page 107</a>] (<a href="#Contents">Contents</a>)
4861 -- for an enumeration constant or typedef name, is the (only) declaration of the
4863 6 The declaration specifiers consist of a sequence of specifiers that indicate the linkage,
4864 storage duration, and part of the type of the entities that the declarators denote. The init-
4865 declarator-list is a comma-separated sequence of declarators, each of which may have
4866 additional type information, or an initializer, or both. The declarators contain the
4867 identifiers (if any) being declared.
4868 7 If an identifier for an object is declared with no linkage, the type for the object shall be
4869 complete by the end of its declarator, or by the end of its init-declarator if it has an
4870 initializer; in the case of function parameters (including in prototypes), it is the adjusted
4871 type (see <a href="#6.7.6.3">6.7.6.3</a>) that is required to be complete.
4872 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
4873 (<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>).
4874 <a name="6.7.1" href="#6.7.1"><b> 6.7.1 Storage-class specifiers</b></a>
4876 1 storage-class-specifier:
4884 2 At most, one storage-class specifier may be given in the declaration specifiers in a
4885 declaration, except that _Thread_local may appear with static or extern.<sup><a href="#note120"><b>120)</b></a></sup>
4886 3 In the declaration of an object with block scope, if the declaration specifiers include
4887 _Thread_local, they shall also include either static or extern. If
4888 _Thread_local appears in any declaration of an object, it shall be present in every
4889 declaration of that object.
4891 4 The typedef specifier is called a ''storage-class specifier'' for syntactic convenience
4892 only; it is discussed in <a href="#6.7.8">6.7.8</a>. The meanings of the various linkages and storage durations
4893 were discussed in <a href="#6.2.2">6.2.2</a> and <a href="#6.2.4">6.2.4</a>.
4897 <sup><a name="note120" href="#note120"><b>120)</b></a></sup> See ''future language directions'' (<a href="#6.11.5">6.11.5</a>).
4899 [<a name="p108" href="#p108">page 108</a>] (<a href="#Contents">Contents</a>)
4901 5 A declaration of an identifier for an object with storage-class specifier register
4902 suggests that access to the object be as fast as possible. The extent to which such
4903 suggestions are effective is implementation-defined.<sup><a href="#note121"><b>121)</b></a></sup>
4904 6 The declaration of an identifier for a function that has block scope shall have no explicit
4905 storage-class specifier other than extern.
4906 7 If an aggregate or union object is declared with a storage-class specifier other than
4907 typedef, the properties resulting from the storage-class specifier, except with respect to
4908 linkage, also apply to the members of the object, and so on recursively for any aggregate
4909 or union member objects.
4910 Forward references: type definitions (<a href="#6.7.8">6.7.8</a>).
4911 <a name="6.7.2" href="#6.7.2"><b> 6.7.2 Type specifiers</b></a>
4925 atomic-type-specifier
4926 struct-or-union-specifier
4930 2 At least one type specifier shall be given in the declaration specifiers in each declaration,
4931 and in the specifier-qualifier list in each struct declaration and type name. Each list of
4934 <sup><a name="note121" href="#note121"><b>121)</b></a></sup> The implementation may treat any register declaration simply as an auto declaration. However,
4935 whether or not addressable storage is actually used, the address of any part of an object declared with
4936 storage-class specifier register cannot be computed, either explicitly (by use of the unary &
4937 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
4938 <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
4941 [<a name="p109" href="#p109">page 109</a>] (<a href="#Contents">Contents</a>)
4943 type specifiers shall be one of the following multisets (delimited by commas, when there
4944 is more than one multiset per item); the type specifiers may occur in any order, possibly
4945 intermixed with the other declaration specifiers.
4950 -- short, signed short, short int, or signed short int
4951 -- unsigned short, or unsigned short int
4952 -- int, signed, or signed int
4953 -- unsigned, or unsigned int
4954 -- long, signed long, long int, or signed long int
4955 -- unsigned long, or unsigned long int
4956 -- long long, signed long long, long long int, or
4957 signed long long int
4958 -- unsigned long long, or unsigned long long int
4965 -- long double _Complex
4966 -- atomic type specifier
4967 -- struct or union specifier
4970 3 The type specifier _Complex shall not be used if the implementation does not support
4971 complex types (see <a href="#6.10.8.3">6.10.8.3</a>).
4973 [<a name="p110" href="#p110">page 110</a>] (<a href="#Contents">Contents</a>)
4976 4 Specifiers for structures, unions, enumerations, and atomic types are discussed in <a href="#6.7.2.1">6.7.2.1</a>
4977 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
4978 characteristics of the other types are discussed in <a href="#6.2.5">6.2.5</a>.
4979 5 Each of the comma-separated multisets designates the same type, except that for bit-
4980 fields, it is implementation-defined whether the specifier int designates the same type as
4981 signed int or the same type as unsigned int.
4982 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>),
4983 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>).
4984 <a name="6.7.2.1" href="#6.7.2.1"><b> 6.7.2.1 Structure and union specifiers</b></a>
4986 1 struct-or-union-specifier:
4987 struct-or-union identifieropt { struct-declaration-list }
4988 struct-or-union identifier
4992 struct-declaration-list:
4994 struct-declaration-list struct-declaration
4996 specifier-qualifier-list struct-declarator-listopt ;
4997 static_assert-declaration
4998 specifier-qualifier-list:
4999 type-specifier specifier-qualifier-listopt
5000 type-qualifier specifier-qualifier-listopt
5001 struct-declarator-list:
5003 struct-declarator-list , struct-declarator
5006 declaratoropt : constant-expression
5008 2 A struct-declaration that does not declare an anonymous structure or anonymous union
5009 shall contain a struct-declarator-list.
5011 [<a name="p111" href="#p111">page 111</a>] (<a href="#Contents">Contents</a>)
5013 3 A structure or union shall not contain a member with incomplete or function type (hence,
5014 a structure shall not contain an instance of itself, but may contain a pointer to an instance
5015 of itself), except that the last member of a structure with more than one named member
5016 may have incomplete array type; such a structure (and any union containing, possibly
5017 recursively, a member that is such a structure) shall not be a member of a structure or an
5018 element of an array.
5019 4 The expression that specifies the width of a bit-field shall be an integer constant
5020 expression with a nonnegative value that does not exceed the width of an object of the
5021 type that would be specified were the colon and expression omitted.<sup><a href="#note122"><b>122)</b></a></sup> If the value is
5022 zero, the declaration shall have no declarator.
5023 5 A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed
5024 int, unsigned int, or some other implementation-defined type. It is
5025 implementation-defined whether atomic types are permitted.
5027 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
5028 storage is allocated in an ordered sequence, and a union is a type consisting of a sequence
5029 of members whose storage overlap.
5030 7 Structure and union specifiers have the same form. The keywords struct and union
5031 indicate that the type being specified is, respectively, a structure type or a union type.
5032 8 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
5033 within a translation unit. The struct-declaration-list is a sequence of declarations for the
5034 members of the structure or union. If the struct-declaration-list contains no named
5035 members, no anonymous structures, and no anonymous unions, the behavior is undefined.
5036 The type is incomplete until immediately after the } that terminates the list, and complete
5038 9 A member of a structure or union may have any complete object type other than a
5039 variably modified type.<sup><a href="#note123"><b>123)</b></a></sup> In addition, a member may be declared to consist of a
5040 specified number of bits (including a sign bit, if any). Such a member is called a
5041 bit-field;<sup><a href="#note124"><b>124)</b></a></sup> its width is preceded by a colon.
5042 10 A bit-field is interpreted as having a signed or unsigned integer type consisting of the
5043 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
5045 <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
5046 value bits) of a _Bool may be just 1 bit.
5047 <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
5048 are not ordinary identifiers as defined in <a href="#6.2.3">6.2.3</a>.
5049 <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
5050 or arrays of bit-field objects.
5052 [<a name="p112" href="#p112">page 112</a>] (<a href="#Contents">Contents</a>)
5054 type _Bool, the value of the bit-field shall compare equal to the value stored; a _Bool
5055 bit-field has the semantics of a _Bool.
5056 11 An implementation may allocate any addressable storage unit large enough to hold a bit-
5057 field. If enough space remains, a bit-field that immediately follows another bit-field in a
5058 structure shall be packed into adjacent bits of the same unit. If insufficient space remains,
5059 whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is
5060 implementation-defined. The order of allocation of bit-fields within a unit (high-order to
5061 low-order or low-order to high-order) is implementation-defined. The alignment of the
5062 addressable storage unit is unspecified.
5063 12 A bit-field declaration with no declarator, but only a colon and a width, indicates an
5064 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
5065 indicates that no further bit-field is to be packed into the unit in which the previous bit-
5066 field, if any, was placed.
5067 13 An unnamed member of structure type with no tag is called an anonymous structure; an
5068 unnamed member of union type with no tag is called an anonymous union. The members
5069 of an anonymous structure or union are considered to be members of the containing
5070 structure or union. This applies recursively if the containing structure or union is also
5072 14 Each non-bit-field member of a structure or union object is aligned in an implementation-
5073 defined manner appropriate to its type.
5074 15 Within a structure object, the non-bit-field members and the units in which bit-fields
5075 reside have addresses that increase in the order in which they are declared. A pointer to a
5076 structure object, suitably converted, points to its initial member (or if that member is a
5077 bit-field, then to the unit in which it resides), and vice versa. There may be unnamed
5078 padding within a structure object, but not at its beginning.
5079 16 The size of a union is sufficient to contain the largest of its members. The value of at
5080 most one of the members can be stored in a union object at any time. A pointer to a
5081 union object, suitably converted, points to each of its members (or if a member is a bit-
5082 field, then to the unit in which it resides), and vice versa.
5083 17 There may be unnamed padding at the end of a structure or union.
5084 18 As a special case, the last element of a structure with more than one named member may
5085 have an incomplete array type; this is called a flexible array member. In most situations,
5088 <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,
5089 then it is implementation-defined whether the bit-field is signed or unsigned.
5090 <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
5093 [<a name="p113" href="#p113">page 113</a>] (<a href="#Contents">Contents</a>)
5095 the flexible array member is ignored. In particular, the size of the structure is as if the
5096 flexible array member were omitted except that it may have more trailing padding than
5097 the omission would imply. However, when a . (or ->) operator has a left operand that is
5098 (a pointer to) a structure with a flexible array member and the right operand names that
5099 member, it behaves as if that member were replaced with the longest array (with the same
5100 element type) that would not make the structure larger than the object being accessed; the
5101 offset of the array shall remain that of the flexible array member, even if this would differ
5102 from that of the replacement array. If this array would have no elements, it behaves as if
5103 it had one element but the behavior is undefined if any attempt is made to access that
5104 element or to generate a pointer one past it.
5105 19 EXAMPLE 1 The following illustrates anonymous structures and unions:
5107 union { // anonymous union
5108 struct { int i, j; }; // anonymous structure
5109 struct { long k, l; } w;
5114 v1.k = 3; // invalid: inner structure is not anonymous
5115 v1.w.k = 5; // valid
5117 20 EXAMPLE 2 After the declaration:
5118 struct s { int n; double d[]; };
5119 the structure struct s has a flexible array member d. A typical way to use this is:
5120 int m = /* some value */;
5121 struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));
5122 and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
5123 p had been declared as:
5124 struct { int n; double d[m]; } *p;
5125 (there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
5127 21 Following the above declaration:
5128 struct s t1 = { 0 }; // valid
5129 struct s t2 = { 1, { <a href="#4.2">4.2</a> }}; // invalid
5131 t1.d[0] = <a href="#4.2">4.2</a>; // might be undefined behavior
5132 The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
5133 contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
5134 sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)
5135 in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming
5138 [<a name="p114" href="#p114">page 114</a>] (<a href="#Contents">Contents</a>)
5140 22 After the further declaration:
5141 struct ss { int n; };
5143 sizeof (struct s) >= sizeof (struct ss)
5144 sizeof (struct s) >= offsetof(struct s, d)
5145 are always equal to 1.
5146 23 If sizeof (double) is 8, then after the following code is executed:
5149 s1 = malloc(sizeof (struct s) + 64);
5150 s2 = malloc(sizeof (struct s) + 46);
5151 and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
5152 purposes, as if the identifiers had been declared as:
5153 struct { int n; double d[8]; } *s1;
5154 struct { int n; double d[5]; } *s2;
5155 24 Following the further successful assignments:
5156 s1 = malloc(sizeof (struct s) + 10);
5157 s2 = malloc(sizeof (struct s) + 6);
5158 they then behave as if the declarations were:
5159 struct { int n; double d[1]; } *s1, *s2;
5162 dp = &(s1->d[0]); // valid
5164 dp = &(s2->d[0]); // valid
5165 *dp = 42; // undefined behavior
5168 only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes
5169 of the structure, they might be copied or simply overwritten with indeterminate values.
5171 Forward references: declarators (<a href="#6.7.6">6.7.6</a>), tags (<a href="#6.7.2.3">6.7.2.3</a>).
5173 [<a name="p115" href="#p115">page 115</a>] (<a href="#Contents">Contents</a>)
5175 <a name="6.7.2.2" href="#6.7.2.2"><b> 6.7.2.2 Enumeration specifiers</b></a>
5178 enum identifieropt { enumerator-list }
5179 enum identifieropt { enumerator-list , }
5183 enumerator-list , enumerator
5185 enumeration-constant
5186 enumeration-constant = constant-expression
5188 2 The expression that defines the value of an enumeration constant shall be an integer
5189 constant expression that has a value representable as an int.
5191 3 The identifiers in an enumerator list are declared as constants that have type int and
5192 may appear wherever such are permitted.<sup><a href="#note127"><b>127)</b></a></sup> An enumerator with = defines its
5193 enumeration constant as the value of the constant expression. If the first enumerator has
5194 no =, the value of its enumeration constant is 0. Each subsequent enumerator with no =
5195 defines its enumeration constant as the value of the constant expression obtained by
5196 adding 1 to the value of the previous enumeration constant. (The use of enumerators with
5197 = may produce enumeration constants with values that duplicate other values in the same
5198 enumeration.) The enumerators of an enumeration are also known as its members.
5199 4 Each enumerated type shall be compatible with char, a signed integer type, or an
5200 unsigned integer type. The choice of type is implementation-defined,<sup><a href="#note128"><b>128)</b></a></sup> but shall be
5201 capable of representing the values of all the members of the enumeration. The
5202 enumerated type is incomplete until immediately after the } that terminates the list of
5203 enumerator declarations, and complete thereafter.
5208 <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
5209 each other and from other identifiers declared in ordinary declarators.
5210 <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
5213 [<a name="p116" href="#p116">page 116</a>] (<a href="#Contents">Contents</a>)
5215 5 EXAMPLE The following fragment:
5216 enum hue { chartreuse, burgundy, claret=20, winedark };
5220 if (*cp != burgundy)
5222 makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
5223 pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
5225 Forward references: tags (<a href="#6.7.2.3">6.7.2.3</a>).
5226 <a name="6.7.2.3" href="#6.7.2.3"><b> 6.7.2.3 Tags</b></a>
5228 1 A specific type shall have its content defined at most once.
5229 2 Where two declarations that use the same tag declare the same type, they shall both use
5230 the same choice of struct, union, or enum.
5231 3 A type specifier of the form
5233 without an enumerator list shall only appear after the type it specifies is complete.
5235 4 All declarations of structure, union, or enumerated types that have the same scope and
5236 use the same tag declare the same type. Irrespective of whether there is a tag or what
5237 other declarations of the type are in the same translation unit, the type is incomplete<sup><a href="#note129"><b>129)</b></a></sup>
5238 until immediately after the closing brace of the list defining the content, and complete
5240 5 Two declarations of structure, union, or enumerated types which are in different scopes or
5241 use different tags declare distinct types. Each declaration of a structure, union, or
5242 enumerated type which does not include a tag declares a distinct type.
5243 6 A type specifier of the form
5248 <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
5249 needed, for example, when a typedef name is declared to be a specifier for a structure or union, or
5250 when a pointer to or a function returning a structure or union is being declared. (See incomplete types
5251 in <a href="#6.2.5">6.2.5</a>.) The specification has to be complete before such a function is called or defined.
5253 [<a name="p117" href="#p117">page 117</a>] (<a href="#Contents">Contents</a>)
5255 struct-or-union identifieropt { struct-declaration-list }
5257 enum identifieropt { enumerator-list }
5259 enum identifieropt { enumerator-list , }
5260 declares a structure, union, or enumerated type. The list defines the structure content,
5261 union content, or enumeration content. If an identifier is provided,<sup><a href="#note130"><b>130)</b></a></sup> the type specifier
5262 also declares the identifier to be the tag of that type.
5263 7 A declaration of the form
5264 struct-or-union identifier ;
5265 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>
5266 8 If a type specifier of the form
5267 struct-or-union identifier
5268 occurs other than as part of one of the above forms, and no other declaration of the
5269 identifier as a tag is visible, then it declares an incomplete structure or union type, and
5270 declares the identifier as the tag of that type.131)
5271 9 If a type specifier of the form
5272 struct-or-union identifier
5275 occurs other than as part of one of the above forms, and a declaration of the identifier as a
5276 tag is visible, then it specifies the same type as that other declaration, and does not
5278 10 EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
5281 struct tnode *left, *right;
5283 specifies a structure that contains an integer and two pointers to objects of the same type. Once this
5284 declaration has been given, the declaration
5289 <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
5290 of which it is a part. Of course, when the declaration is of a typedef name, subsequent declarations
5291 can make use of that typedef name to declare objects having the specified structure, union, or
5293 <sup><a name="note131" href="#note131"><b>131)</b></a></sup> A similar construction with enum does not exist.
5295 [<a name="p118" href="#p118">page 118</a>] (<a href="#Contents">Contents</a>)
5297 struct tnode s, *sp;
5298 declares s to be an object of the given type and sp to be a pointer to an object of the given type. With
5299 these declarations, the expression sp->left refers to the left struct tnode pointer of the object to
5300 which sp points; the expression s.right->count designates the count member of the right struct
5301 tnode pointed to from s.
5302 11 The following alternative formulation uses the typedef mechanism:
5303 typedef struct tnode TNODE;
5306 TNODE *left, *right;
5310 12 EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential
5311 structures, the declarations
5312 struct s1 { struct s2 *s2p; /* ... */ }; // D1
5313 struct s2 { struct s1 *s1p; /* ... */ }; // D2
5314 specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
5315 declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
5316 D2. To eliminate this context sensitivity, the declaration
5318 may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then
5319 completes the specification of the new type.
5321 Forward references: declarators (<a href="#6.7.6">6.7.6</a>), type definitions (<a href="#6.7.8">6.7.8</a>).
5322 <a name="6.7.2.4" href="#6.7.2.4"><b> 6.7.2.4 Atomic type specifiers</b></a>
5324 1 atomic-type-specifier:
5325 _Atomic ( type-name )
5327 2 Atomic type specifiers shall not be used if the implementation does not support atomic
5328 types (see <a href="#6.10.8.3">6.10.8.3</a>).
5329 3 The type name in an atomic type specifier shall not refer to an array type, a function type,
5330 an atomic type, or a qualified type.
5332 4 The properties associated with atomic types are meaningful only for expressions that are
5333 lvalues. If the _Atomic keyword is immediately followed by a left parenthesis, it is
5334 interpreted as a type specifier (with a type name), not as a type qualifier.
5336 [<a name="p119" href="#p119">page 119</a>] (<a href="#Contents">Contents</a>)
5338 <a name="6.7.3" href="#6.7.3"><b> 6.7.3 Type qualifiers</b></a>
5346 2 Types other than pointer types whose referenced type is an object type shall not be
5348 3 The type modified by the _Atomic qualifier shall not be an array type or a function
5351 4 The properties associated with qualified types are meaningful only for expressions that
5352 are lvalues.<sup><a href="#note132"><b>132)</b></a></sup>
5353 5 If the same qualifier appears more than once in the same specifier-qualifier-list, either
5354 directly or via one or more typedefs, the behavior is the same as if it appeared only
5355 once. If other qualifiers appear along with the _Atomic qualifier in a specifier-qualifier-
5356 list, the resulting type is the so-qualified atomic type.
5357 6 If an attempt is made to modify an object defined with a const-qualified type through use
5358 of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is
5359 made to refer to an object defined with a volatile-qualified type through use of an lvalue
5360 with non-volatile-qualified type, the behavior is undefined.<sup><a href="#note133"><b>133)</b></a></sup>
5361 7 An object that has volatile-qualified type may be modified in ways unknown to the
5362 implementation or have other unknown side effects. Therefore any expression referring
5363 to such an object shall be evaluated strictly according to the rules of the abstract machine,
5364 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
5365 object shall agree with that prescribed by the abstract machine, except as modified by the
5370 <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
5371 storage. Moreover, the implementation need not allocate storage for such an object if its address is
5373 <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
5374 never actually defined as objects in the program (such as an object at a memory-mapped input/output
5377 [<a name="p120" href="#p120">page 120</a>] (<a href="#Contents">Contents</a>)
5379 unknown factors mentioned previously.<sup><a href="#note134"><b>134)</b></a></sup> What constitutes an access to an object that
5380 has volatile-qualified type is implementation-defined.
5381 8 An object that is accessed through a restrict-qualified pointer has a special association
5382 with that pointer. This association, defined in <a href="#6.7.3.1">6.7.3.1</a> below, requires that all accesses to
5383 that object use, directly or indirectly, the value of that particular pointer.<sup><a href="#note135"><b>135)</b></a></sup> The intended
5384 use of the restrict qualifier (like the register storage class) is to promote
5385 optimization, and deleting all instances of the qualifier from all preprocessing translation
5386 units composing a conforming program does not change its meaning (i.e., observable
5388 9 If the specification of an array type includes any type qualifiers, the element type is so-
5389 qualified, not the array type. If the specification of a function type includes any type
5390 qualifiers, the behavior is undefined.<sup><a href="#note136"><b>136)</b></a></sup>
5391 10 For two qualified types to be compatible, both shall have the identically qualified version
5392 of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers
5393 does not affect the specified type.
5394 11 EXAMPLE 1 An object declared
5395 extern const volatile int real_time_clock;
5396 may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
5398 12 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers
5399 modify an aggregate type:
5400 const struct s { int mem; } cs = { 1 };
5401 struct s ncs; // the object ncs is modifiable
5402 typedef int A[2][3];
5403 const A a = {{4, 5, 6}, {7, 8, 9}}; // array of array of const int
5407 cs = ncs; // violates modifiable lvalue constraint for =
5408 pi = &ncs.mem; // valid
5409 pi = &cs.mem; // violates type constraints for =
5410 pci = &cs.mem; // valid
5411 pi = a[0]; // invalid: a[0] has type ''const int *''
5415 <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
5416 input/output port or an object accessed by an asynchronously interrupting function. Actions on
5417 objects so declared shall not be ''optimized out'' by an implementation or reordered except as
5418 permitted by the rules for evaluating expressions.
5419 <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
5420 association between the allocated object and the pointer.
5421 <sup><a name="note136" href="#note136"><b>136)</b></a></sup> Both of these can occur through the use of typedefs.
5423 [<a name="p121" href="#p121">page 121</a>] (<a href="#Contents">Contents</a>)
5425 13 EXAMPLE 3 The declaration
5426 _Atomic volatile int *p;
5427 specifies that p has the type ''pointer to volatile atomic int'', a pointer to a volatile-qualified atomic type.
5429 <a name="6.7.3.1" href="#6.7.3.1"><b> 6.7.3.1 Formal definition of restrict</b></a>
5430 1 Let D be a declaration of an ordinary identifier that provides a means of designating an
5431 object P as a restrict-qualified pointer to type T.
5432 2 If D appears inside a block and does not have storage class extern, let B denote the
5433 block. If D appears in the list of parameter declarations of a function definition, let B
5434 denote the associated block. Otherwise, let B denote the block of main (or the block of
5435 whatever function is called at program startup in a freestanding environment).
5436 3 In what follows, a pointer expression E is said to be based on object P if (at some
5437 sequence point in the execution of B prior to the evaluation of E) modifying P to point to
5438 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>
5439 Note that ''based'' is defined only for expressions with pointer types.
5440 4 During each execution of B, let L be any lvalue that has &L based on P. If L is used to
5441 access the value of the object X that it designates, and X is also modified (by any means),
5442 then the following requirements apply: T shall not be const-qualified. Every other lvalue
5443 used to access the value of X shall also have its address based on P. Every access that
5444 modifies X shall be considered also to modify P, for the purposes of this subclause. If P
5445 is assigned the value of a pointer expression E that is based on another restricted pointer
5446 object P2, associated with block B2, then either the execution of B2 shall begin before
5447 the execution of B, or the execution of B2 shall end prior to the assignment. If these
5448 requirements are not met, then the behavior is undefined.
5449 5 Here an execution of B means that portion of the execution of the program that would
5450 correspond to the lifetime of an object with scalar type and automatic storage duration
5452 6 A translator is free to ignore any or all aliasing implications of uses of restrict.
5453 7 EXAMPLE 1 The file scope declarations
5457 assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
5458 program, then it is never accessed using either of the other two.
5461 <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
5462 indirectly through P. For example, if identifier p has type (int **restrict), then the pointer
5463 expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer
5464 expressions *p and p[1] are not.
5466 [<a name="p122" href="#p122">page 122</a>] (<a href="#Contents">Contents</a>)
5468 8 EXAMPLE 2 The function parameter declarations in the following example
5469 void f(int n, int * restrict p, int * restrict q)
5474 assert that, during each execution of the function, if an object is accessed through one of the pointer
5475 parameters, then it is not also accessed through the other.
5476 9 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence
5477 analysis of function f without examining any of the calls of f in the program. The cost is that the
5478 programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the
5479 second call of f in g has undefined behavior because each of d[1] through d[49] is accessed through
5484 f(50, d + 50, d); // valid
5485 f(50, d + 1, d); // undefined behavior
5488 10 EXAMPLE 3 The function parameter declarations
5489 void h(int n, int * restrict p, int * restrict q, int * restrict r)
5492 for (i = 0; i < n; i++)
5495 illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
5496 are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
5497 modified within function h.
5499 11 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a
5500 function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments
5501 between restricted pointers declared in nested blocks have defined behavior.
5505 p1 = q1; // undefined behavior
5507 int * restrict p2 = p1; // valid
5508 int * restrict q2 = q1; // valid
5509 p1 = q2; // undefined behavior
5510 p2 = q2; // undefined behavior
5514 [<a name="p123" href="#p123">page 123</a>] (<a href="#Contents">Contents</a>)
5516 12 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more
5517 precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For
5518 example, this permits new_vector to return a vector.
5519 typedef struct { int n; float * restrict v; } vector;
5520 vector new_vector(int n)
5524 t.v = malloc(n * sizeof (float));
5528 <a name="6.7.4" href="#6.7.4"><b> 6.7.4 Function specifiers</b></a>
5530 1 function-specifier:
5534 2 Function specifiers shall be used only in the declaration of an identifier for a function.
5535 3 An inline definition of a function with external linkage shall not contain a definition of a
5536 modifiable object with static or thread storage duration, and shall not contain a reference
5537 to an identifier with internal linkage.
5538 4 In a hosted environment, no function specifier(s) shall appear in a declaration of main.
5540 5 A function specifier may appear more than once; the behavior is the same as if it
5542 6 A function declared with an inline function specifier is an inline function. Making a *
5543 function an inline function suggests that calls to the function be as fast as possible.<sup><a href="#note138"><b>138)</b></a></sup>
5544 The extent to which such suggestions are effective is implementation-defined.<sup><a href="#note139"><b>139)</b></a></sup>
5549 <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
5550 substitution''. Inline substitution is not textual substitution, nor does it create a new function.
5551 Therefore, for example, the expansion of a macro used within the body of the function uses the
5552 definition it had at the point the function body appears, and not where the function is called; and
5553 identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a
5554 single address, regardless of the number of inline definitions that occur in addition to the external
5556 <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
5557 substitutions to calls in the scope of an inline declaration.
5559 [<a name="p124" href="#p124">page 124</a>] (<a href="#Contents">Contents</a>)
5561 7 Any function with internal linkage can be an inline function. For a function with external
5562 linkage, the following restrictions apply: If a function is declared with an inline
5563 function specifier, then it shall also be defined in the same translation unit. If all of the
5564 file scope declarations for a function in a translation unit include the inline function
5565 specifier without extern, then the definition in that translation unit is an inline
5566 definition. An inline definition does not provide an external definition for the function,
5567 and does not forbid an external definition in another translation unit. An inline definition
5568 provides an alternative to an external definition, which a translator may use to implement
5569 any call to the function in the same translation unit. It is unspecified whether a call to the
5570 function uses the inline definition or the external definition.<sup><a href="#note140"><b>140)</b></a></sup>
5571 8 A function declared with a _Noreturn function specifier shall not return to its caller.
5572 Recommended practice
5573 9 The implementation should produce a diagnostic message for a function declared with a
5574 _Noreturn function specifier that appears to be capable of returning to its caller.
5575 10 EXAMPLE 1 The declaration of an inline function with external linkage can result in either an external
5576 definition, or a definition available for use only within the translation unit. A file scope declaration with
5577 extern creates an external definition. The following example shows an entire translation unit.
5578 inline double fahr(double t)
5580 return (9.0 * t) / 5.0 + 32.0;
5582 inline double cels(double t)
5584 return (5.0 * (t - 32.0)) / 9.0;
5586 extern double fahr(double); // creates an external definition
5587 double convert(int is_fahr, double temp)
5589 /* A translator may perform inline substitutions */
5590 return is_fahr ? cels(temp) : fahr(temp);
5592 11 Note that the definition of fahr is an external definition because fahr is also declared with extern, but
5593 the definition of cels is an inline definition. Because cels has external linkage and is referenced, an
5594 external definition has to appear in another translation unit (see <a href="#6.9">6.9</a>); the inline definition and the external
5595 definition are distinct and either may be used for the call.
5602 <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
5603 corresponding inline definitions in other translation units, all corresponding objects with static storage
5604 duration are also distinct in each of the definitions.
5606 [<a name="p125" href="#p125">page 125</a>] (<a href="#Contents">Contents</a>)
5608 _Noreturn void f () {
5611 _Noreturn void g (int i) { // causes undefined behavior if i <= 0
5612 if (i > 0) abort();
5615 Forward references: function definitions (<a href="#6.9.1">6.9.1</a>).
5616 <a name="6.7.5" href="#6.7.5"><b> 6.7.5 Alignment specifier</b></a>
5618 1 alignment-specifier:
5619 _Alignas ( type-name )
5620 _Alignas ( constant-expression )
5622 2 An alignment attribute shall not be specified in a declaration of a typedef, or a bit-field, or
5623 a function, or a parameter, or an object declared with the register storage-class
5625 3 The constant expression shall be an integer constant expression. It shall evaluate to a
5626 valid fundamental alignment, or to a valid extended alignment supported by the
5627 implementation in the context in which it appears, or to zero.
5628 4 The combined effect of all alignment attributes in a declaration shall not specify an
5629 alignment that is less strict than the alignment that would otherwise be required for the
5630 type of the object or member being declared.
5632 5 The first form is equivalent to _Alignas(alignof(type-name)).
5633 6 The alignment requirement of the declared object or member is taken to be the specified
5634 alignment. An alignment specification of zero has no effect.<sup><a href="#note141"><b>141)</b></a></sup> When multiple
5635 alignment specifiers occur in a declaration, the effective alignment requirement is the
5636 strictest specified alignment.
5637 7 If the definition of an object has an alignment specifier, any other declaration of that
5638 object shall either specify equivalent alignment or have no alignment specifier. If the
5639 definition of an object does not have an alignment specifier, any other declaration of that
5640 object shall also have no alignment specifier. If declarations of an object in different
5641 translation units have different alignment specifiers, the behavior is undefined.
5645 <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
5648 [<a name="p126" href="#p126">page 126</a>] (<a href="#Contents">Contents</a>)
5650 <a name="6.7.6" href="#6.7.6"><b> 6.7.6 Declarators</b></a>
5653 pointeropt direct-declarator
5657 direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
5658 direct-declarator [ static type-qualifier-listopt assignment-expression ]
5659 direct-declarator [ type-qualifier-list static assignment-expression ]
5660 direct-declarator [ type-qualifier-listopt * ]
5661 direct-declarator ( parameter-type-list )
5662 direct-declarator ( identifier-listopt )
5664 * type-qualifier-listopt
5665 * type-qualifier-listopt pointer
5666 type-qualifier-list:
5668 type-qualifier-list type-qualifier
5669 parameter-type-list:
5671 parameter-list , ...
5673 parameter-declaration
5674 parameter-list , parameter-declaration
5675 parameter-declaration:
5676 declaration-specifiers declarator
5677 declaration-specifiers abstract-declaratoropt
5680 identifier-list , identifier
5682 2 Each declarator declares one identifier, and asserts that when an operand of the same
5683 form as the declarator appears in an expression, it designates a function or object with the
5684 scope, storage duration, and type indicated by the declaration specifiers.
5685 3 A full declarator is a declarator that is not part of another declarator. The end of a full
5686 declarator is a sequence point. If, in the nested sequence of declarators in a full
5688 [<a name="p127" href="#p127">page 127</a>] (<a href="#Contents">Contents</a>)
5690 declarator, there is a declarator specifying a variable length array type, the type specified
5691 by the full declarator is said to be variably modified. Furthermore, any type derived by
5692 declarator type derivation from a variably modified type is itself variably modified.
5693 4 In the following subclauses, consider a declaration
5695 where T contains the declaration specifiers that specify a type T (such as int) and D1 is
5696 a declarator that contains an identifier ident. The type specified for the identifier ident in
5697 the various forms of declarator is described inductively using this notation.
5698 5 If, in the declaration ''T D1'', D1 has the form
5700 then the type specified for ident is T .
5701 6 If, in the declaration ''T D1'', D1 has the form
5703 then ident has the type specified by the declaration ''T D''. Thus, a declarator in
5704 parentheses is identical to the unparenthesized declarator, but the binding of complicated
5705 declarators may be altered by parentheses.
5706 Implementation limits
5707 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
5708 function declarators that modify an arithmetic, structure, union, or void type, either
5709 directly or via one or more typedefs.
5710 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>).
5711 <a name="6.7.6.1" href="#6.7.6.1"><b> 6.7.6.1 Pointer declarators</b></a>
5713 1 If, in the declaration ''T D1'', D1 has the form
5714 * type-qualifier-listopt D
5715 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5716 T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list
5717 pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer.
5718 2 For two pointer types to be compatible, both shall be identically qualified and both shall
5719 be pointers to compatible types.
5720 3 EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer
5721 to a constant value'' and a ''constant pointer to a variable value''.
5723 [<a name="p128" href="#p128">page 128</a>] (<a href="#Contents">Contents</a>)
5725 const int *ptr_to_constant;
5726 int *const constant_ptr;
5727 The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
5728 but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
5729 int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
5731 4 The declaration of the constant pointer constant_ptr may be clarified by including a definition for the
5732 type ''pointer to int''.
5733 typedef int *int_ptr;
5734 const int_ptr constant_ptr;
5735 declares constant_ptr as an object that has type ''const-qualified pointer to int''.
5737 <a name="6.7.6.2" href="#6.7.6.2"><b> 6.7.6.2 Array declarators</b></a>
5739 1 In addition to optional type qualifiers and the keyword static, the [ and ] may delimit
5740 an expression or *. If they delimit an expression (which specifies the size of an array), the
5741 expression shall have an integer type. If the expression is a constant expression, it shall
5742 have a value greater than zero. The element type shall not be an incomplete or function
5743 type. The optional type qualifiers and the keyword static shall appear only in a
5744 declaration of a function parameter with an array type, and then only in the outermost
5745 array type derivation.
5746 2 If an identifier is declared as having a variably modified type, it shall be an ordinary
5747 identifier (as defined in <a href="#6.2.3">6.2.3</a>), have no linkage, and have either block scope or function
5748 prototype scope. If an identifier is declared to be an object with static or thread storage
5749 duration, it shall not have a variable length array type.
5751 3 If, in the declaration ''T D1'', D1 has one of the forms:
5752 D[ type-qualifier-listopt assignment-expressionopt ]
5753 D[ static type-qualifier-listopt assignment-expression ]
5754 D[ type-qualifier-list static assignment-expression ]
5755 D[ type-qualifier-listopt * ]
5756 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5757 T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.<sup><a href="#note142"><b>142)</b></a></sup>
5758 (See <a href="#6.7.6.3">6.7.6.3</a> for the meaning of the optional type qualifiers and the keyword static.)
5759 4 If the size is not present, the array type is an incomplete type. If the size is * instead of
5760 being an expression, the array type is a variable length array type of unspecified size,
5761 which can only be used in declarations or type names with function prototype scope;<sup><a href="#note143"><b>143)</b></a></sup>
5763 <sup><a name="note142" href="#note142"><b>142)</b></a></sup> When several ''array of'' specifications are adjacent, a multidimensional array is declared.
5765 [<a name="p129" href="#p129">page 129</a>] (<a href="#Contents">Contents</a>)
5767 such arrays are nonetheless complete types. If the size is an integer constant expression
5768 and the element type has a known constant size, the array type is not a variable length
5769 array type; otherwise, the array type is a variable length array type. (Variable length
5770 arrays are a conditional feature that implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.)
5771 5 If the size is an expression that is not an integer constant expression: if it occurs in a
5772 declaration at function prototype scope, it is treated as if it were replaced by *; otherwise,
5773 each time it is evaluated it shall have a value greater than zero. The size of each instance
5774 of a variable length array type does not change during its lifetime. Where a size
5775 expression is part of the operand of a sizeof operator and changing the value of the
5776 size expression would not affect the result of the operator, it is unspecified whether or not
5777 the size expression is evaluated.
5778 6 For two array types to be compatible, both shall have compatible element types, and if
5779 both size specifiers are present, and are integer constant expressions, then both size
5780 specifiers shall have the same constant value. If the two array types are used in a context
5781 which requires them to be compatible, it is undefined behavior if the two size specifiers
5782 evaluate to unequal values.
5784 float fa[11], *afp[17];
5785 declares an array of float numbers and an array of pointers to float numbers.
5787 8 EXAMPLE 2 Note the distinction between the declarations
5790 The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
5791 (an incomplete type), the storage for which is defined elsewhere.
5793 9 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
5801 int (*r)[n][n][n+1];
5802 p = a; // invalid: not compatible because 4 != 6
5803 r = c; // compatible, but defined behavior only if
5804 // n == 6 and m == n+1
5810 <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>).
5812 [<a name="p130" href="#p130">page 130</a>] (<a href="#Contents">Contents</a>)
5814 10 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or
5815 function prototype scope. Array objects declared with the _Thread_local, static, or extern
5816 storage-class specifier cannot have a variable length array (VLA) type. However, an object declared with
5817 the static storage-class specifier can have a VM type (that is, a pointer to a VLA type). Finally, all
5818 identifiers declared with a VM type have to be ordinary identifiers and cannot, therefore, be members of
5819 structures or unions.
5821 int A[n]; // invalid: file scope VLA
5822 extern int (*p2)[n]; // invalid: file scope VM
5823 int B[100]; // valid: file scope but not VM
5824 void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
5825 void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
5827 typedef int VLA[m][m]; // valid: block scope typedef VLA
5829 int (*y)[n]; // invalid: y not ordinary identifier
5830 int z[n]; // invalid: z not ordinary identifier
5832 int D[m]; // valid: auto VLA
5833 static int E[m]; // invalid: static block scope VLA
5834 extern int F[m]; // invalid: F has linkage and is VLA
5835 int (*s)[m]; // valid: auto pointer to VLA
5836 extern int (*r)[m]; // invalid: r has linkage and points to VLA
5837 static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
5840 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>),
5841 initialization (<a href="#6.7.9">6.7.9</a>).
5842 <a name="6.7.6.3" href="#6.7.6.3"><b> 6.7.6.3 Function declarators (including prototypes)</b></a>
5844 1 A function declarator shall not specify a return type that is a function type or an array
5846 2 The only storage-class specifier that shall occur in a parameter declaration is register.
5847 3 An identifier list in a function declarator that is not part of a definition of that function
5849 4 After adjustment, the parameters in a parameter type list in a function declarator that is
5850 part of a definition of that function shall not have incomplete type.
5852 5 If, in the declaration ''T D1'', D1 has the form
5854 [<a name="p131" href="#p131">page 131</a>] (<a href="#Contents">Contents</a>)
5856 D( parameter-type-list )
5858 D( identifier-listopt )
5859 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5860 T '', then the type specified for ident is ''derived-declarator-type-list function returning
5862 6 A parameter type list specifies the types of, and may declare identifiers for, the
5863 parameters of the function.
5864 7 A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to
5865 type'', where the type qualifiers (if any) are those specified within the [ and ] of the
5866 array type derivation. If the keyword static also appears within the [ and ] of the
5867 array type derivation, then for each call to the function, the value of the corresponding
5868 actual argument shall provide access to the first element of an array with at least as many
5869 elements as specified by the size expression.
5870 8 A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to
5871 function returning type'', as in <a href="#6.3.2.1">6.3.2.1</a>.
5872 9 If the list terminates with an ellipsis (, ...), no information about the number or types
5873 of the parameters after the comma is supplied.<sup><a href="#note144"><b>144)</b></a></sup>
5874 10 The special case of an unnamed parameter of type void as the only item in the list
5875 specifies that the function has no parameters.
5876 11 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a
5877 parameter name, it shall be taken as a typedef name.
5878 12 If the function declarator is not part of a definition of that function, parameters may have
5879 incomplete type and may use the [*] notation in their sequences of declarator specifiers
5880 to specify variable length array types.
5881 13 The storage-class specifier in the declaration specifiers for a parameter declaration, if
5882 present, is ignored unless the declared parameter is one of the members of the parameter
5883 type list for a function definition.
5884 14 An identifier list declares only the identifiers of the parameters of the function. An empty
5885 list in a function declarator that is part of a definition of that function specifies that the
5886 function has no parameters. The empty list in a function declarator that is not part of a
5887 definition of that function specifies that no information about the number or types of the
5888 parameters is supplied.<sup><a href="#note145"><b>145)</b></a></sup>
5892 <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
5893 correspond to the ellipsis.
5895 [<a name="p132" href="#p132">page 132</a>] (<a href="#Contents">Contents</a>)
5897 15 For two function types to be compatible, both shall specify compatible return types.<sup><a href="#note146"><b>146)</b></a></sup>
5898 Moreover, the parameter type lists, if both are present, shall agree in the number of
5899 parameters and in use of the ellipsis terminator; corresponding parameters shall have
5900 compatible types. If one type has a parameter type list and the other type is specified by a
5901 function declarator that is not part of a function definition and that contains an empty
5902 identifier list, the parameter list shall not have an ellipsis terminator and the type of each
5903 parameter shall be compatible with the type that results from the application of the
5904 default argument promotions. If one type has a parameter type list and the other type is
5905 specified by a function definition that contains a (possibly empty) identifier list, both shall
5906 agree in the number of parameters, and the type of each prototype parameter shall be
5907 compatible with the type that results from the application of the default argument
5908 promotions to the type of the corresponding identifier. (In the determination of type
5909 compatibility and of a composite type, each parameter declared with function or array
5910 type is taken as having the adjusted type and each parameter declared with qualified type
5911 is taken as having the unqualified version of its declared type.)
5912 16 EXAMPLE 1 The declaration
5913 int f(void), *fip(), (*pfi)();
5914 declares a function f with no parameters returning an int, a function fip with no parameter specification
5915 returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an
5916 int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the
5917 declaration suggests, and the same construction in an expression requires, the calling of a function fip,
5918 and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the
5919 extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function
5920 designator, which is then used to call the function; it returns an int.
5921 17 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the
5922 declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either
5923 internal or external linkage (depending on what file scope declarations for these identifiers are visible), and
5924 the identifier of the pointer pfi has block scope and no linkage.
5926 18 EXAMPLE 2 The declaration
5927 int (*apfi[3])(int *x, int *y);
5928 declares an array apfi of three pointers to functions returning int. Each of these functions has two
5929 parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and
5930 go out of scope at the end of the declaration of apfi.
5932 19 EXAMPLE 3 The declaration
5933 int (*fpfi(int (*)(long), int))(int, ...);
5934 declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two
5935 parameters: a pointer to a function returning an int (with one parameter of type long int), and an int.
5936 The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more
5939 <sup><a name="note145" href="#note145"><b>145)</b></a></sup> See ''future language directions'' (<a href="#6.11.6">6.11.6</a>).
5940 <sup><a name="note146" href="#note146"><b>146)</b></a></sup> If both function types are ''old style'', parameter types are not compared.
5942 [<a name="p133" href="#p133">page 133</a>] (<a href="#Contents">Contents</a>)
5944 additional arguments of any type.
5946 20 EXAMPLE 4 The following prototype has a variably modified parameter.
5947 void addscalar(int n, int m,
5948 double a[n][n*m+300], double x);
5952 addscalar(4, 2, b, <a href="#2.17">2.17</a>);
5955 void addscalar(int n, int m,
5956 double a[n][n*m+300], double x)
5958 for (int i = 0; i < n; i++)
5959 for (int j = 0, k = n*m+300; j < k; j++)
5960 // a is a pointer to a VLA with n*m+300 elements
5964 21 EXAMPLE 5 The following are all compatible function prototype declarators.
5965 double maximum(int n, int m, double a[n][m]);
5966 double maximum(int n, int m, double a[*][*]);
5967 double maximum(int n, int m, double a[ ][*]);
5968 double maximum(int n, int m, double a[ ][m]);
5970 void f(double (* restrict a)[5]);
5971 void f(double a[restrict][5]);
5972 void f(double a[restrict 3][5]);
5973 void f(double a[restrict static 3][5]);
5974 (Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
5975 non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
5977 Forward references: function definitions (<a href="#6.9.1">6.9.1</a>), type names (<a href="#6.7.7">6.7.7</a>).
5979 [<a name="p134" href="#p134">page 134</a>] (<a href="#Contents">Contents</a>)
5981 <a name="6.7.7" href="#6.7.7"><b> 6.7.7 Type names</b></a>
5984 specifier-qualifier-list abstract-declaratoropt
5985 abstract-declarator:
5987 pointeropt direct-abstract-declarator
5988 direct-abstract-declarator:
5989 ( abstract-declarator )
5990 direct-abstract-declaratoropt [ type-qualifier-listopt
5991 assignment-expressionopt ]
5992 direct-abstract-declaratoropt [ static type-qualifier-listopt
5993 assignment-expression ]
5994 direct-abstract-declaratoropt [ type-qualifier-list static
5995 assignment-expression ]
5996 direct-abstract-declaratoropt [ * ]
5997 direct-abstract-declaratoropt ( parameter-type-listopt )
5999 2 In several contexts, it is necessary to specify a type. This is accomplished using a type
6000 name, which is syntactically a declaration for a function or an object of that type that
6001 omits the identifier.<sup><a href="#note147"><b>147)</b></a></sup>
6002 3 EXAMPLE The constructions
6010 (h) int (*const [])(unsigned int, ...)
6011 name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
6012 array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
6013 with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
6014 returning an int, and (h) array of an unspecified number of constant pointers to functions, each with one
6015 parameter that has type unsigned int and an unspecified number of other parameters, returning an
6021 <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
6022 parameter specification'', rather than redundant parentheses around the omitted identifier.
6024 [<a name="p135" href="#p135">page 135</a>] (<a href="#Contents">Contents</a>)
6026 <a name="6.7.8" href="#6.7.8"><b> 6.7.8 Type definitions</b></a>
6031 2 If a typedef name specifies a variably modified type then it shall have block scope.
6033 3 In a declaration whose storage-class specifier is typedef, each declarator defines an
6034 identifier to be a typedef name that denotes the type specified for the identifier in the way
6035 described in <a href="#6.7.6">6.7.6</a>. Any array size expressions associated with variable length array
6036 declarators are evaluated each time the declaration of the typedef name is reached in the
6037 order of execution. A typedef declaration does not introduce a new type, only a
6038 synonym for the type so specified. That is, in the following declarations:
6039 typedef T type_ident;
6041 type_ident is defined as a typedef name with the type specified by the declaration
6042 specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
6043 type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
6044 typedef name shares the same name space as other identifiers declared in ordinary
6047 typedef int MILES, KLICKSP();
6048 typedef struct { double hi, lo; } range;
6051 extern KLICKSP *metricp;
6054 are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
6055 parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
6056 such a structure. The object distance has a type compatible with any other int object.
6058 5 EXAMPLE 2 After the declarations
6059 typedef struct s1 { int x; } t1, *tp1;
6060 typedef struct s2 { int x; } t2, *tp2;
6061 type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
6062 s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
6064 [<a name="p136" href="#p136">page 136</a>] (<a href="#Contents">Contents</a>)
6066 6 EXAMPLE 3 The following obscure constructions
6067 typedef signed int t;
6074 declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
6075 with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
6076 qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
6077 [-16, +15], and one named r that contains values in one of the ranges [0, 31], [-15, +15], or [-16, +15].
6078 (The choice of range is implementation-defined.) The first two bit-field declarations differ in that
6079 unsigned is a type specifier (which forces t to be the name of a structure member), while const is a
6080 type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed
6081 in an inner scope by
6084 then a function f is declared with type ''function returning signed int with one unnamed parameter
6085 with type pointer to function returning signed int with one unnamed parameter with type signed
6086 int'', and an identifier t with type long int.
6088 7 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the
6089 following declarations of the signal function specify exactly the same type, the first without making use
6090 of any typedef names.
6091 typedef void fv(int), (*pfv)(int);
6092 void (*signal(int, void (*)(int)))(int);
6093 fv *signal(int, fv *);
6094 pfv signal(int, pfv);
6096 8 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the
6097 time the typedef name is defined, not each time it is used:
6100 typedef int B[n]; // B is n ints, n evaluated now
6102 B a; // a is n ints, n without += 1
6103 int b[n]; // a and b are different sizes
6104 for (int i = 1; i < n; i++)
6108 [<a name="p137" href="#p137">page 137</a>] (<a href="#Contents">Contents</a>)
6110 <a name="6.7.9" href="#6.7.9"><b> 6.7.9 Initialization</b></a>
6113 assignment-expression
6114 { initializer-list }
6115 { initializer-list , }
6117 designationopt initializer
6118 initializer-list , designationopt initializer
6123 designator-list designator
6125 [ constant-expression ]
6128 2 No initializer shall attempt to provide a value for an object not contained within the entity
6130 3 The type of the entity to be initialized shall be an array of unknown size or a complete
6131 object type that is not a variable length array type.
6132 4 All the expressions in an initializer for an object that has static or thread storage duration
6133 shall be constant expressions or string literals.
6134 5 If the declaration of an identifier has block scope, and the identifier has external or
6135 internal linkage, the declaration shall have no initializer for the identifier.
6136 6 If a designator has the form
6137 [ constant-expression ]
6138 then the current object (defined below) shall have array type and the expression shall be
6139 an integer constant expression. If the array is of unknown size, any nonnegative value is
6141 7 If a designator has the form
6143 then the current object (defined below) shall have structure or union type and the
6144 identifier shall be the name of a member of that type.
6146 [<a name="p138" href="#p138">page 138</a>] (<a href="#Contents">Contents</a>)
6149 8 An initializer specifies the initial value stored in an object.
6150 9 Except where explicitly stated otherwise, for the purposes of this subclause unnamed
6151 members of objects of structure and union type do not participate in initialization.
6152 Unnamed members of structure objects have indeterminate value even after initialization.
6153 10 If an object that has automatic storage duration is not initialized explicitly, its value is
6154 indeterminate. If an object that has static or thread storage duration is not initialized
6156 -- if it has pointer type, it is initialized to a null pointer;
6157 -- if it has arithmetic type, it is initialized to (positive or unsigned) zero;
6158 -- if it is an aggregate, every member is initialized (recursively) according to these rules,
6159 and any padding is initialized to zero bits;
6160 -- if it is a union, the first named member is initialized (recursively) according to these
6161 rules, and any padding is initialized to zero bits;
6162 11 The initializer for a scalar shall be a single expression, optionally enclosed in braces. The
6163 initial value of the object is that of the expression (after conversion); the same type
6164 constraints and conversions as for simple assignment apply, taking the type of the scalar
6165 to be the unqualified version of its declared type.
6166 12 The rest of this subclause deals with initializers for objects that have aggregate or union
6168 13 The initializer for a structure or union object that has automatic storage duration shall be
6169 either an initializer list as described below, or a single expression that has compatible
6170 structure or union type. In the latter case, the initial value of the object, including
6171 unnamed members, is that of the expression.
6172 14 An array of character type may be initialized by a character string literal or UTF-8 string
6173 literal, optionally enclosed in braces. Successive bytes of the string literal (including the
6174 terminating null character if there is room or if the array is of unknown size) initialize the
6175 elements of the array.
6176 15 An array with element type compatible with a qualified or unqualified version of
6177 wchar_t may be initialized by a wide string literal, optionally enclosed in braces.
6178 Successive wide characters of the wide string literal (including the terminating null wide
6179 character if there is room or if the array is of unknown size) initialize the elements of the
6181 16 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-
6182 enclosed list of initializers for the elements or named members.
6184 [<a name="p139" href="#p139">page 139</a>] (<a href="#Contents">Contents</a>)
6186 17 Each brace-enclosed initializer list has an associated current object. When no
6187 designations are present, subobjects of the current object are initialized in order according
6188 to the type of the current object: array elements in increasing subscript order, structure
6189 members in declaration order, and the first named member of a union.<sup><a href="#note148"><b>148)</b></a></sup> In contrast, a
6190 designation causes the following initializer to begin initialization of the subobject
6191 described by the designator. Initialization then continues forward in order, beginning
6192 with the next subobject after that described by the designator.<sup><a href="#note149"><b>149)</b></a></sup>
6193 18 Each designator list begins its description with the current object associated with the
6194 closest surrounding brace pair. Each item in the designator list (in order) specifies a
6195 particular member of its current object and changes the current object for the next
6196 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
6197 designator list is the subobject to be initialized by the following initializer.
6198 19 The initialization shall occur in initializer list order, each initializer provided for a
6199 particular subobject overriding any previously listed initializer for the same subobject;<sup><a href="#note151"><b>151)</b></a></sup>
6200 all subobjects that are not initialized explicitly shall be initialized implicitly the same as
6201 objects that have static storage duration.
6202 20 If the aggregate or union contains elements or members that are aggregates or unions,
6203 these rules apply recursively to the subaggregates or contained unions. If the initializer of
6204 a subaggregate or contained union begins with a left brace, the initializers enclosed by
6205 that brace and its matching right brace initialize the elements or members of the
6206 subaggregate or the contained union. Otherwise, only enough initializers from the list are
6207 taken to account for the elements or members of the subaggregate or the first member of
6208 the contained union; any remaining initializers are left to initialize the next element or
6209 member of the aggregate of which the current subaggregate or contained union is a part.
6210 21 If there are fewer initializers in a brace-enclosed list than there are elements or members
6211 of an aggregate, or fewer characters in a string literal used to initialize an array of known
6212 size than there are elements in the array, the remainder of the aggregate shall be
6213 initialized implicitly the same as objects that have static storage duration.
6217 <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
6218 subobjects are initialized as usual, but the subaggregate or contained union does not become the
6219 current object: current objects are associated only with brace-enclosed initializer lists.
6220 <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
6221 the next subobject of an object containing the union.
6222 <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
6223 the surrounding brace pair. Note, too, that each separate designator list is independent.
6224 <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
6225 not be evaluated at all.
6227 [<a name="p140" href="#p140">page 140</a>] (<a href="#Contents">Contents</a>)
6229 22 If an array of unknown size is initialized, its size is determined by the largest indexed
6230 element with an explicit initializer. The array type is completed at the end of its
6232 23 The evaluations of the initialization list expressions are indeterminately sequenced with
6233 respect to one another and thus the order in which any side effects occur is
6234 unspecified.<sup><a href="#note152"><b>152)</b></a></sup>
6235 24 EXAMPLE 1 Provided that <a href="#7.3"><complex.h></a> has been #included, the declarations
6236 int i = <a href="#3.5">3.5</a>;
6237 double complex c = 5 + 3 * I;
6238 define and initialize i with the value 3 and c with the value 5.0 + i3.0.
6240 25 EXAMPLE 2 The declaration
6241 int x[] = { 1, 3, 5 };
6242 defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
6243 and there are three initializers.
6245 26 EXAMPLE 3 The declaration
6251 is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
6252 y[0]), namely y[0][0], y[0][1], and y[0][2]. Likewise the next two lines initialize y[1] and
6253 y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
6256 1, 3, 5, 2, 4, 6, 3, 5, 7
6258 The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
6259 next three are taken successively for y[1] and y[2].
6261 27 EXAMPLE 4 The declaration
6263 { 1 }, { 2 }, { 3 }, { 4 }
6265 initializes the first column of z as specified and initializes the rest with zeros.
6267 28 EXAMPLE 5 The declaration
6268 struct { int a[3], b; } w[] = { { 1 }, 2 };
6269 is a definition with an inconsistently bracketed initialization. It defines an array with two element
6273 <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.
6275 [<a name="p141" href="#p141">page 141</a>] (<a href="#Contents">Contents</a>)
6277 structures: w[0].a[0] is 1 and w[1].a[0] is 2; all the other elements are zero.
6279 29 EXAMPLE 6 The declaration
6280 short q[4][3][2] = {
6285 contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
6286 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
6287 q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
6288 q[0][0] does not begin with a left brace, so up to six items from the current list may be used. There is
6289 only one, so the values for the remaining five elements are initialized with zero. Likewise, the initializers
6290 for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their
6291 respective two-dimensional subaggregates. If there had been more than six items in any of the lists, a
6292 diagnostic message would have been issued. The same initialization result could have been achieved by:
6293 short q[4][3][2] = {
6299 short q[4][3][2] = {
6311 in a fully bracketed form.
6312 30 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
6315 31 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the
6317 typedef int A[]; // OK - declared with block scope
6319 A a = { 1, 2 }, b = { 3, 4, 5 };
6321 int a[] = { 1, 2 }, b[] = { 3, 4, 5 };
6322 due to the rules for incomplete types.
6324 [<a name="p142" href="#p142">page 142</a>] (<a href="#Contents">Contents</a>)
6326 32 EXAMPLE 8 The declaration
6327 char s[] = "abc", t[3] = "abc";
6328 defines ''plain'' char array objects s and t whose elements are initialized with character string literals.
6329 This declaration is identical to
6330 char s[] = { 'a', 'b', 'c', '\0' },
6331 t[] = { 'a', 'b', 'c' };
6332 The contents of the arrays are modifiable. On the other hand, the declaration
6334 defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char''
6335 with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to
6336 modify the contents of the array, the behavior is undefined.
6338 33 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using
6340 enum { member_one, member_two };
6341 const char *nm[] = {
6342 [member_two] = "member two",
6343 [member_one] = "member one",
6346 34 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
6347 div_t answer = { .quot = 2, .rem = -1 };
6349 35 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
6350 might be misunderstood:
6351 struct { int a[3], b; } w[] =
6352 { [0].a = {1}, [1].a[0] = 2 };
6354 36 EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator:
6356 1, 3, 5, 7, 9, [MAX-5] = 8, 6, 4, 2, 0
6358 37 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less
6359 than ten, some of the values provided by the first five initializers will be overridden by the second five.
6361 38 EXAMPLE 13 Any member of a union can be initialized:
6362 union { /* ... */ } u = { .any_member = 42 };
6364 Forward references: common definitions <a href="#7.19"><stddef.h></a> (<a href="#7.19">7.19</a>).
6366 [<a name="p143" href="#p143">page 143</a>] (<a href="#Contents">Contents</a>)
6368 <a name="6.7.10" href="#6.7.10"><b> 6.7.10 Static assertions</b></a>
6370 1 static_assert-declaration:
6371 _Static_assert ( constant-expression , string-literal ) ;
6373 2 The constant expression shall compare unequal to 0.
6375 3 The constant expression shall be an integer constant expression. If the value of the
6376 constant expression compares unequal to 0, the declaration has no effect. Otherwise, the
6377 constraint is violated and the implementation shall produce a diagnostic message that
6378 includes the text of the string literal, except that characters not in the basic source
6379 character set are not required to appear in the message.
6380 Forward references: diagnostics (<a href="#7.2">7.2</a>).
6382 [<a name="p144" href="#p144">page 144</a>] (<a href="#Contents">Contents</a>)
6384 <a name="6.8" href="#6.8"><b> 6.8 Statements and blocks</b></a>
6389 expression-statement
6394 2 A statement specifies an action to be performed. Except as indicated, statements are
6395 executed in sequence.
6396 3 A block allows a set of declarations and statements to be grouped into one syntactic unit.
6397 The initializers of objects that have automatic storage duration, and the variable length
6398 array declarators of ordinary identifiers with block scope, are evaluated and the values are
6399 stored in the objects (including storing an indeterminate value in objects without an
6400 initializer) each time the declaration is reached in the order of execution, as if it were a
6401 statement, and within each declaration in the order that declarators appear.
6402 4 A full expression is an expression that is not part of another expression or of a declarator.
6403 Each of the following is a full expression: an initializer that is not part of a compound
6404 literal; the expression in an expression statement; the controlling expression of a selection
6405 statement (if or switch); the controlling expression of a while or do statement; each
6406 of the (optional) expressions of a for statement; the (optional) expression in a return
6407 statement. There is a sequence point between the evaluation of a full expression and the
6408 evaluation of the next full expression to be evaluated.
6409 Forward references: expression and null statements (<a href="#6.8.3">6.8.3</a>), selection statements
6410 (<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>).
6411 <a name="6.8.1" href="#6.8.1"><b> 6.8.1 Labeled statements</b></a>
6413 1 labeled-statement:
6414 identifier : statement
6415 case constant-expression : statement
6418 2 A case or default label shall appear only in a switch statement. Further
6419 constraints on such labels are discussed under the switch statement.
6421 [<a name="p145" href="#p145">page 145</a>] (<a href="#Contents">Contents</a>)
6423 3 Label names shall be unique within a function.
6425 4 Any statement may be preceded by a prefix that declares an identifier as a label name.
6426 Labels in themselves do not alter the flow of control, which continues unimpeded across
6428 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>).
6429 <a name="6.8.2" href="#6.8.2"><b> 6.8.2 Compound statement</b></a>
6431 1 compound-statement:
6432 { block-item-listopt }
6435 block-item-list block-item
6440 2 A compound statement is a block.
6441 <a name="6.8.3" href="#6.8.3"><b> 6.8.3 Expression and null statements</b></a>
6443 1 expression-statement:
6446 2 The expression in an expression statement is evaluated as a void expression for its side
6447 effects.<sup><a href="#note153"><b>153)</b></a></sup>
6448 3 A null statement (consisting of just a semicolon) performs no operations.
6449 4 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the
6450 discarding of its value may be made explicit by converting the expression to a void expression by means of
6458 <sup><a name="note153" href="#note153"><b>153)</b></a></sup> Such as assignments, and function calls which have side effects.
6460 [<a name="p146" href="#p146">page 146</a>] (<a href="#Contents">Contents</a>)
6462 5 EXAMPLE 2 In the program fragment
6465 while (*s++ != '\0')
6467 a null statement is used to supply an empty loop body to the iteration statement.
6469 6 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
6483 Forward references: iteration statements (<a href="#6.8.5">6.8.5</a>).
6484 <a name="6.8.4" href="#6.8.4"><b> 6.8.4 Selection statements</b></a>
6486 1 selection-statement:
6487 if ( expression ) statement
6488 if ( expression ) statement else statement
6489 switch ( expression ) statement
6491 2 A selection statement selects among a set of statements depending on the value of a
6492 controlling expression.
6493 3 A selection statement is a block whose scope is a strict subset of the scope of its
6494 enclosing block. Each associated substatement is also a block whose scope is a strict
6495 subset of the scope of the selection statement.
6496 <a name="6.8.4.1" href="#6.8.4.1"><b> 6.8.4.1 The if statement</b></a>
6498 1 The controlling expression of an if statement shall have scalar type.
6500 2 In both forms, the first substatement is executed if the expression compares unequal to 0.
6501 In the else form, the second substatement is executed if the expression compares equal
6503 [<a name="p147" href="#p147">page 147</a>] (<a href="#Contents">Contents</a>)
6505 to 0. If the first substatement is reached via a label, the second substatement is not
6507 3 An else is associated with the lexically nearest preceding if that is allowed by the
6509 <a name="6.8.4.2" href="#6.8.4.2"><b> 6.8.4.2 The switch statement</b></a>
6511 1 The controlling expression of a switch statement shall have integer type.
6512 2 If a switch statement has an associated case or default label within the scope of an
6513 identifier with a variably modified type, the entire switch statement shall be within the
6514 scope of that identifier.<sup><a href="#note154"><b>154)</b></a></sup>
6515 3 The expression of each case label shall be an integer constant expression and no two of
6516 the case constant expressions in the same switch statement shall have the same value
6517 after conversion. There may be at most one default label in a switch statement.
6518 (Any enclosed switch statement may have a default label or case constant
6519 expressions with values that duplicate case constant expressions in the enclosing
6522 4 A switch statement causes control to jump to, into, or past the statement that is the
6523 switch body, depending on the value of a controlling expression, and on the presence of a
6524 default label and the values of any case labels on or in the switch body. A case or
6525 default label is accessible only within the closest enclosing switch statement.
6526 5 The integer promotions are performed on the controlling expression. The constant
6527 expression in each case label is converted to the promoted type of the controlling
6528 expression. If a converted value matches that of the promoted controlling expression,
6529 control jumps to the statement following the matched case label. Otherwise, if there is
6530 a default label, control jumps to the labeled statement. If no converted case constant
6531 expression matches and there is no default label, no part of the switch body is
6533 Implementation limits
6534 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
6540 <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
6541 default label associated with the switch that is in the block containing the declaration.
6543 [<a name="p148" href="#p148">page 148</a>] (<a href="#Contents">Contents</a>)
6545 7 EXAMPLE In the artificial program fragment
6552 /* falls through into default code */
6556 the object whose identifier is i exists with automatic storage duration (within the block) but is never
6557 initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
6558 access an indeterminate value. Similarly, the call to the function f cannot be reached.
6560 <a name="6.8.5" href="#6.8.5"><b> 6.8.5 Iteration statements</b></a>
6562 1 iteration-statement:
6563 while ( expression ) statement
6564 do statement while ( expression ) ;
6565 for ( expressionopt ; expressionopt ; expressionopt ) statement
6566 for ( declaration expressionopt ; expressionopt ) statement
6568 2 The controlling expression of an iteration statement shall have scalar type.
6569 3 The declaration part of a for statement shall only declare identifiers for objects having
6570 storage class auto or register.
6572 4 An iteration statement causes a statement called the loop body to be executed repeatedly
6573 until the controlling expression compares equal to 0. The repetition occurs regardless of
6574 whether the loop body is entered from the iteration statement or by a jump.<sup><a href="#note155"><b>155)</b></a></sup>
6575 5 An iteration statement is a block whose scope is a strict subset of the scope of its
6576 enclosing block. The loop body is also a block whose scope is a strict subset of the scope
6577 of the iteration statement.
6578 6 An iteration statement whose controlling expression is not a constant expression,<sup><a href="#note156"><b>156)</b></a></sup> that
6579 performs no input/output operations, does not access volatile objects, and performs no
6580 synchronization or atomic operations in its body, controlling expression, or (in the case of
6582 <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
6583 statement is not evaluated before entering the loop body, nor is clause-1 of a for statement.
6584 <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.
6586 [<a name="p149" href="#p149">page 149</a>] (<a href="#Contents">Contents</a>)
6588 a for statement) its expression-3, may be assumed by the implementation to
6589 terminate.<sup><a href="#note157"><b>157)</b></a></sup>
6590 <a name="6.8.5.1" href="#6.8.5.1"><b> 6.8.5.1 The while statement</b></a>
6591 1 The evaluation of the controlling expression takes place before each execution of the loop
6593 <a name="6.8.5.2" href="#6.8.5.2"><b> 6.8.5.2 The do statement</b></a>
6594 1 The evaluation of the controlling expression takes place after each execution of the loop
6596 <a name="6.8.5.3" href="#6.8.5.3"><b> 6.8.5.3 The for statement</b></a>
6598 for ( clause-1 ; expression-2 ; expression-3 ) statement
6599 behaves as follows: The expression expression-2 is the controlling expression that is
6600 evaluated before each execution of the loop body. The expression expression-3 is
6601 evaluated as a void expression after each execution of the loop body. If clause-1 is a
6602 declaration, the scope of any identifiers it declares is the remainder of the declaration and
6603 the entire loop, including the other two expressions; it is reached in the order of execution
6604 before the first evaluation of the controlling expression. If clause-1 is an expression, it is
6605 evaluated as a void expression before the first evaluation of the controlling expression.<sup><a href="#note158"><b>158)</b></a></sup>
6606 2 Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a
6608 <a name="6.8.6" href="#6.8.6"><b> 6.8.6 Jump statements</b></a>
6614 return expressionopt ;
6619 <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
6620 termination cannot be proven.
6621 <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
6622 the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration,
6623 such that execution of the loop continues until the expression compares equal to 0; and expression-3
6624 specifies an operation (such as incrementing) that is performed after each iteration.
6626 [<a name="p150" href="#p150">page 150</a>] (<a href="#Contents">Contents</a>)
6629 2 A jump statement causes an unconditional jump to another place.
6630 <a name="6.8.6.1" href="#6.8.6.1"><b> 6.8.6.1 The goto statement</b></a>
6632 1 The identifier in a goto statement shall name a label located somewhere in the enclosing
6633 function. A goto statement shall not jump from outside the scope of an identifier having
6634 a variably modified type to inside the scope of that identifier.
6636 2 A goto statement causes an unconditional jump to the statement prefixed by the named
6637 label in the enclosing function.
6638 3 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The
6639 following outline presents one possible approach to a problem based on these three assumptions:
6640 1. The general initialization code accesses objects only visible to the current function.
6641 2. The general initialization code is too large to warrant duplication.
6642 3. The code to determine the next operation is at the head of the loop. (To allow it to be reached by
6643 continue statements, for example.)
6647 // determine next operation
6649 if (need to reinitialize) {
6650 // reinitialize-only code
6653 // general initialization code
6657 // handle other operations
6661 [<a name="p151" href="#p151">page 151</a>] (<a href="#Contents">Contents</a>)
6663 4 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably
6664 modified types. A jump within the scope, however, is permitted.
6665 goto lab3; // invalid: going INTO scope of VLA.
6668 a[j] = <a href="#4.4">4.4</a>;
6670 a[j] = <a href="#3.3">3.3</a>;
6671 goto lab4; // valid: going WITHIN scope of VLA.
6672 a[j] = <a href="#5.5">5.5</a>;
6674 a[j] = <a href="#6.6">6.6</a>;
6676 goto lab4; // invalid: going INTO scope of VLA.
6678 <a name="6.8.6.2" href="#6.8.6.2"><b> 6.8.6.2 The continue statement</b></a>
6680 1 A continue statement shall appear only in or as a loop body.
6682 2 A continue statement causes a jump to the loop-continuation portion of the smallest
6683 enclosing iteration statement; that is, to the end of the loop body. More precisely, in each
6685 while (/* ... */) { do { for (/* ... */) {
6686 /* ... */ /* ... */ /* ... */
6687 continue; continue; continue;
6688 /* ... */ /* ... */ /* ... */
6689 contin: ; contin: ; contin: ;
6690 } } while (/* ... */); }
6691 unless the continue statement shown is in an enclosed iteration statement (in which
6692 case it is interpreted within that statement), it is equivalent to goto contin;.<sup><a href="#note159"><b>159)</b></a></sup>
6693 <a name="6.8.6.3" href="#6.8.6.3"><b> 6.8.6.3 The break statement</b></a>
6695 1 A break statement shall appear only in or as a switch body or loop body.
6697 2 A break statement terminates execution of the smallest enclosing switch or iteration
6702 <sup><a name="note159" href="#note159"><b>159)</b></a></sup> Following the contin: label is a null statement.
6704 [<a name="p152" href="#p152">page 152</a>] (<a href="#Contents">Contents</a>)
6706 <a name="6.8.6.4" href="#6.8.6.4"><b> 6.8.6.4 The return statement</b></a>
6708 1 A return statement with an expression shall not appear in a function whose return type
6709 is void. A return statement without an expression shall only appear in a function
6710 whose return type is void.
6712 2 A return statement terminates execution of the current function and returns control to
6713 its caller. A function may have any number of return statements.
6714 3 If a return statement with an expression is executed, the value of the expression is
6715 returned to the caller as the value of the function call expression. If the expression has a
6716 type different from the return type of the function in which it appears, the value is
6717 converted as if by assignment to an object having the return type of the function.<sup><a href="#note160"><b>160)</b></a></sup>
6719 struct s { double i; } f(void);
6736 there is no undefined behavior, although there would be if the assignment were done directly (without using
6737 a function call to fetch the value).
6742 <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
6743 apply to the case of function return. The representation of floating-point values may have wider range
6744 or precision than implied by the type; a cast may be used to remove this extra range and precision.
6746 [<a name="p153" href="#p153">page 153</a>] (<a href="#Contents">Contents</a>)
6748 <a name="6.9" href="#6.9"><b> 6.9 External definitions</b></a>
6751 external-declaration
6752 translation-unit external-declaration
6753 external-declaration:
6757 2 The storage-class specifiers auto and register shall not appear in the declaration
6758 specifiers in an external declaration.
6759 3 There shall be no more than one external definition for each identifier declared with
6760 internal linkage in a translation unit. Moreover, if an identifier declared with internal
6761 linkage is used in an expression (other than as a part of the operand of a sizeof
6762 operator whose result is an integer constant), there shall be exactly one external definition
6763 for the identifier in the translation unit.
6765 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,
6766 which consists of a sequence of external declarations. These are described as ''external''
6767 because they appear outside any function (and hence have file scope). As discussed in
6768 <a href="#6.7">6.7</a>, a declaration that also causes storage to be reserved for an object or a function named
6769 by the identifier is a definition.
6770 5 An external definition is an external declaration that is also a definition of a function
6771 (other than an inline definition) or an object. If an identifier declared with external
6772 linkage is used in an expression (other than as part of the operand of a sizeof operator
6773 whose result is an integer constant), somewhere in the entire program there shall be
6774 exactly one external definition for the identifier; otherwise, there shall be no more than
6775 one.<sup><a href="#note161"><b>161)</b></a></sup>
6780 <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
6781 external definition for it.
6783 [<a name="p154" href="#p154">page 154</a>] (<a href="#Contents">Contents</a>)
6785 <a name="6.9.1" href="#6.9.1"><b> 6.9.1 Function definitions</b></a>
6787 1 function-definition:
6788 declaration-specifiers declarator declaration-listopt compound-statement
6791 declaration-list declaration
6793 2 The identifier declared in a function definition (which is the name of the function) shall
6794 have a function type, as specified by the declarator portion of the function definition.<sup><a href="#note162"><b>162)</b></a></sup>
6795 3 The return type of a function shall be void or a complete object type other than array
6797 4 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
6799 5 If the declarator includes a parameter type list, the declaration of each parameter shall
6800 include an identifier, except for the special case of a parameter list consisting of a single
6801 parameter of type void, in which case there shall not be an identifier. No declaration list
6803 6 If the declarator includes an identifier list, each declaration in the declaration list shall
6804 have at least one declarator, those declarators shall declare only identifiers from the
6805 identifier list, and every identifier in the identifier list shall be declared. An identifier
6806 declared as a typedef name shall not be redeclared as a parameter. The declarations in the
6807 declaration list shall contain no storage-class specifier other than register and no
6812 <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:
6813 typedef int F(void); // type F is ''function with no parameters
6815 F f, g; // f and g both have type compatible with F
6816 F f { /* ... */ } // WRONG: syntax/constraint error
6817 F g() { /* ... */ } // WRONG: declares that g returns a function
6818 int f(void) { /* ... */ } // RIGHT: f has type compatible with F
6819 int g() { /* ... */ } // RIGHT: g has type compatible with F
6820 F *e(void) { /* ... */ } // e returns a pointer to a function
6821 F *((e))(void) { /* ... */ } // same: parentheses irrelevant
6822 int (*fp)(void); // fp points to a function that has type F
6823 F *Fp; // Fp points to a function that has type F
6825 [<a name="p155" href="#p155">page 155</a>] (<a href="#Contents">Contents</a>)
6828 7 The declarator in a function definition specifies the name of the function being defined
6829 and the identifiers of its parameters. If the declarator includes a parameter type list, the
6830 list also specifies the types of all the parameters; such a declarator also serves as a
6831 function prototype for later calls to the same function in the same translation unit. If the
6832 declarator includes an identifier list,<sup><a href="#note163"><b>163)</b></a></sup> the types of the parameters shall be declared in a
6833 following declaration list. In either case, the type of each parameter is adjusted as
6834 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
6836 8 If a function that accepts a variable number of arguments is defined without a parameter
6837 type list that ends with the ellipsis notation, the behavior is undefined.
6838 9 Each parameter has automatic storage duration; its identifier is an lvalue.<sup><a href="#note164"><b>164)</b></a></sup> The layout
6839 of the storage for parameters is unspecified.
6840 10 On entry to the function, the size expressions of each variably modified parameter are
6841 evaluated and the value of each argument expression is converted to the type of the
6842 corresponding parameter as if by assignment. (Array expressions and function
6843 designators as arguments were converted to pointers before the call.)
6844 11 After all parameters have been assigned, the compound statement that constitutes the
6845 body of the function definition is executed.
6846 12 If the } that terminates a function is reached, and the value of the function call is used by
6847 the caller, the behavior is undefined.
6848 13 EXAMPLE 1 In the following:
6849 extern int max(int a, int b)
6851 return a > b ? a : b;
6853 extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
6854 function declarator; and
6855 { return a > b ? a : b; }
6856 is the function body. The following similar definition uses the identifier-list form for the parameter
6862 <sup><a name="note163" href="#note163"><b>163)</b></a></sup> See ''future language directions'' (<a href="#6.11.7">6.11.7</a>).
6863 <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.
6865 [<a name="p156" href="#p156">page 156</a>] (<a href="#Contents">Contents</a>)
6867 extern int max(a, b)
6870 return a > b ? a : b;
6872 Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
6873 that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
6874 to the function, whereas the second form does not.
6876 14 EXAMPLE 2 To pass one function to another, one might say
6880 Then the definition of g might read
6881 void g(int (*funcp)(void))
6884 (*funcp)(); /* or funcp(); ... */
6887 void g(int func(void))
6890 func(); /* or (*func)(); ... */
6893 <a name="6.9.2" href="#6.9.2"><b> 6.9.2 External object definitions</b></a>
6895 1 If the declaration of an identifier for an object has file scope and an initializer, the
6896 declaration is an external definition for the identifier.
6897 2 A declaration of an identifier for an object that has file scope without an initializer, and
6898 without a storage-class specifier or with the storage-class specifier static, constitutes a
6899 tentative definition. If a translation unit contains one or more tentative definitions for an
6900 identifier, and the translation unit contains no external definition for that identifier, then
6901 the behavior is exactly as if the translation unit contains a file scope declaration of that
6902 identifier, with the composite type as of the end of the translation unit, with an initializer
6904 3 If the declaration of an identifier for an object is a tentative definition and has internal
6905 linkage, the declared type shall not be an incomplete type.
6907 [<a name="p157" href="#p157">page 157</a>] (<a href="#Contents">Contents</a>)
6910 int i1 = 1; // definition, external linkage
6911 static int i2 = 2; // definition, internal linkage
6912 extern int i3 = 3; // definition, external linkage
6913 int i4; // tentative definition, external linkage
6914 static int i5; // tentative definition, internal linkage
6915 int i1; // valid tentative definition, refers to previous
6916 int i2; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
6917 int i3; // valid tentative definition, refers to previous
6918 int i4; // valid tentative definition, refers to previous
6919 int i5; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
6920 extern int i1; // refers to previous, whose linkage is external
6921 extern int i2; // refers to previous, whose linkage is internal
6922 extern int i3; // refers to previous, whose linkage is external
6923 extern int i4; // refers to previous, whose linkage is external
6924 extern int i5; // refers to previous, whose linkage is internal
6926 5 EXAMPLE 2 If at the end of the translation unit containing
6928 the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to
6929 zero on program startup.
6931 [<a name="p158" href="#p158">page 158</a>] (<a href="#Contents">Contents</a>)
6933 <a name="6.10" href="#6.10"><b> 6.10 Preprocessing directives</b></a>
6935 1 preprocessing-file:
6946 if-group elif-groupsopt else-groupopt endif-line
6948 # if constant-expression new-line groupopt
6949 # ifdef identifier new-line groupopt
6950 # ifndef identifier new-line groupopt
6953 elif-groups elif-group
6955 # elif constant-expression new-line groupopt
6957 # else new-line groupopt
6961 [<a name="p159" href="#p159">page 159</a>] (<a href="#Contents">Contents</a>)
6964 # include pp-tokens new-line
6965 # define identifier replacement-list new-line
6966 # define identifier lparen identifier-listopt )
6967 replacement-list new-line
6968 # define identifier lparen ... ) replacement-list new-line
6969 # define identifier lparen identifier-list , ... )
6970 replacement-list new-line
6971 # undef identifier new-line
6972 # line pp-tokens new-line
6973 # error pp-tokensopt new-line
6974 # pragma pp-tokensopt new-line
6977 pp-tokensopt new-line
6981 a ( character not immediately preceded by white-space
6986 pp-tokens preprocessing-token
6988 the new-line character
6990 2 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the
6991 following constraints: The first token in the sequence is a # preprocessing token that (at
6992 the start of translation phase 4) is either the first character in the source file (optionally
6993 after white space containing no new-line characters) or that follows white space
6994 containing at least one new-line character. The last token in the sequence is the first new-
6995 line character that follows the first token in the sequence.<sup><a href="#note165"><b>165)</b></a></sup> A new-line character ends
6996 the preprocessing directive even if it occurs within what would otherwise be an
6998 <sup><a name="note165" href="#note165"><b>165)</b></a></sup> Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic
6999 significance, as all white space is equivalent except in certain situations during preprocessing (see the
7000 # character string literal creation operator in <a href="#6.10.3.2">6.10.3.2</a>, for example).
7002 [<a name="p160" href="#p160">page 160</a>] (<a href="#Contents">Contents</a>)
7004 invocation of a function-like macro.
7005 3 A text line shall not begin with a # preprocessing token. A non-directive shall not begin
7006 with any of the directive names appearing in the syntax.
7007 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
7008 sequence of preprocessing tokens to occur between the directive name and the following
7011 5 The only white-space characters that shall appear between preprocessing tokens within a
7012 preprocessing directive (from just after the introducing # preprocessing token through
7013 just before the terminating new-line character) are space and horizontal-tab (including
7014 spaces that have replaced comments or possibly other white-space characters in
7015 translation phase 3).
7017 6 The implementation can process and skip sections of source files conditionally, include
7018 other source files, and replace macros. These capabilities are called preprocessing,
7019 because conceptually they occur before translation of the resulting translation unit.
7020 7 The preprocessing tokens within a preprocessing directive are not subject to macro
7021 expansion unless otherwise stated.
7024 EMPTY # include <file.h>
7025 the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
7026 begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
7029 <a name="6.10.1" href="#6.10.1"><b> 6.10.1 Conditional inclusion</b></a>
7031 1 The expression that controls conditional inclusion shall be an integer constant expression
7032 except that: identifiers (including those lexically identical to keywords) are interpreted as *
7033 described below;<sup><a href="#note166"><b>166)</b></a></sup> and it may contain unary operator expressions of the form
7036 defined ( identifier )
7037 which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is
7040 <sup><a name="note166" href="#note166"><b>166)</b></a></sup> Because the controlling constant expression is evaluated during translation phase 4, all identifiers
7041 either are or are not macro names -- there simply are no keywords, enumeration constants, etc.
7043 [<a name="p161" href="#p161">page 161</a>] (<a href="#Contents">Contents</a>)
7045 predefined or if it has been the subject of a #define preprocessing directive without an
7046 intervening #undef directive with the same subject identifier), 0 if it is not.
7047 2 Each preprocessing token that remains (in the list of preprocessing tokens that will
7048 become the controlling expression) after all macro replacements have occurred shall be in
7049 the lexical form of a token (<a href="#6.4">6.4</a>).
7051 3 Preprocessing directives of the forms
7052 # if constant-expression new-line groupopt
7053 # elif constant-expression new-line groupopt
7054 check whether the controlling constant expression evaluates to nonzero.
7055 4 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
7056 the controlling constant expression are replaced (except for those macro names modified
7057 by the defined unary operator), just as in normal text. If the token defined is
7058 generated as a result of this replacement process or use of the defined unary operator
7059 does not match one of the two specified forms prior to macro replacement, the behavior is
7060 undefined. After all replacements due to macro expansion and the defined unary
7061 operator have been performed, all remaining identifiers (including those lexically
7062 identical to keywords) are replaced with the pp-number 0, and then each preprocessing
7063 token is converted into a token. The resulting tokens compose the controlling constant
7064 expression which is evaluated according to the rules of <a href="#6.6">6.6</a>. For the purposes of this
7065 token conversion and evaluation, all signed integer types and all unsigned integer types
7066 act as if they have the same representation as, respectively, the types intmax_t and
7067 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
7068 character constants, which may involve converting escape sequences into execution
7069 character set members. Whether the numeric value for these character constants matches
7070 the value obtained when an identical character constant occurs in an expression (other
7071 than within a #if or #elif directive) is implementation-defined.<sup><a href="#note168"><b>168)</b></a></sup> Also, whether a
7072 single-character character constant may have a negative value is implementation-defined.
7077 <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
7078 0x8000 is signed and positive within a #if expression even though it would be unsigned in
7079 translation phase 7.
7080 <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
7081 evaluate to the same value in these two contexts.
7083 if ('z' - 'a' == 25)
7085 [<a name="p162" href="#p162">page 162</a>] (<a href="#Contents">Contents</a>)
7087 5 Preprocessing directives of the forms
7088 # ifdef identifier new-line groupopt
7089 # ifndef identifier new-line groupopt
7090 check whether the identifier is or is not currently defined as a macro name. Their
7091 conditions are equivalent to #if defined identifier and #if !defined identifier
7093 6 Each directive's condition is checked in order. If it evaluates to false (zero), the group
7094 that it controls is skipped: directives are processed only through the name that determines
7095 the directive in order to keep track of the level of nested conditionals; the rest of the
7096 directives' preprocessing tokens are ignored, as are the other preprocessing tokens in the
7097 group. Only the first group whose control condition evaluates to true (nonzero) is
7098 processed. If none of the conditions evaluates to true, and there is a #else directive, the
7099 group controlled by the #else is processed; lacking a #else directive, all the groups
7100 until the #endif are skipped.<sup><a href="#note169"><b>169)</b></a></sup>
7101 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
7102 integer types (<a href="#7.20.1.5">7.20.1.5</a>).
7103 <a name="6.10.2" href="#6.10.2"><b> 6.10.2 Source file inclusion</b></a>
7105 1 A #include directive shall identify a header or source file that can be processed by the
7108 2 A preprocessing directive of the form
7109 # include <h-char-sequence> new-line
7110 searches a sequence of implementation-defined places for a header identified uniquely by
7111 the specified sequence between the < and > delimiters, and causes the replacement of that
7112 directive by the entire contents of the header. How the places are specified or the header
7113 identified is implementation-defined.
7114 3 A preprocessing directive of the form
7115 # include "q-char-sequence" new-line
7116 causes the replacement of that directive by the entire contents of the source file identified
7117 by the specified sequence between the " delimiters. The named source file is searched
7120 <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
7121 before the terminating new-line character. However, comments may appear anywhere in a source file,
7122 including within a preprocessing directive.
7124 [<a name="p163" href="#p163">page 163</a>] (<a href="#Contents">Contents</a>)
7126 for in an implementation-defined manner. If this search is not supported, or if the search
7127 fails, the directive is reprocessed as if it read
7128 # include <h-char-sequence> new-line
7129 with the identical contained sequence (including > characters, if any) from the original
7131 4 A preprocessing directive of the form
7132 # include pp-tokens new-line
7133 (that does not match one of the two previous forms) is permitted. The preprocessing
7134 tokens after include in the directive are processed just as in normal text. (Each
7135 identifier currently defined as a macro name is replaced by its replacement list of
7136 preprocessing tokens.) The directive resulting after all replacements shall match one of
7137 the two previous forms.<sup><a href="#note170"><b>170)</b></a></sup> The method by which a sequence of preprocessing tokens
7138 between a < and a > preprocessing token pair or a pair of " characters is combined into a
7139 single header name preprocessing token is implementation-defined.
7140 5 The implementation shall provide unique mappings for sequences consisting of one or
7141 more nondigits or digits (<a href="#6.4.2.1">6.4.2.1</a>) followed by a period (.) and a single nondigit. The
7142 first character shall not be a digit. The implementation may ignore distinctions of
7143 alphabetical case and restrict the mapping to eight significant characters before the
7145 6 A #include preprocessing directive may appear in a source file that has been read
7146 because of a #include directive in another file, up to an implementation-defined
7147 nesting limit (see <a href="#5.2.4.1">5.2.4.1</a>).
7148 7 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
7149 #include <a href="#7.21"><stdio.h></a>
7155 <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
7156 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.
7158 [<a name="p164" href="#p164">page 164</a>] (<a href="#Contents">Contents</a>)
7160 8 EXAMPLE 2 This illustrates macro-replaced #include directives:
7162 #define INCFILE "vers1.h"
7164 #define INCFILE "vers2.h" // and so on
7166 #define INCFILE "versN.h"
7170 Forward references: macro replacement (<a href="#6.10.3">6.10.3</a>).
7171 <a name="6.10.3" href="#6.10.3"><b> 6.10.3 Macro replacement</b></a>
7173 1 Two replacement lists are identical if and only if the preprocessing tokens in both have
7174 the same number, ordering, spelling, and white-space separation, where all white-space
7175 separations are considered identical.
7176 2 An identifier currently defined as an object-like macro shall not be redefined by another
7177 #define preprocessing directive unless the second definition is an object-like macro
7178 definition and the two replacement lists are identical. Likewise, an identifier currently
7179 defined as a function-like macro shall not be redefined by another #define
7180 preprocessing directive unless the second definition is a function-like macro definition
7181 that has the same number and spelling of parameters, and the two replacement lists are
7183 3 There shall be white-space between the identifier and the replacement list in the definition
7184 of an object-like macro.
7185 4 If the identifier-list in the macro definition does not end with an ellipsis, the number of
7186 arguments (including those arguments consisting of no preprocessing tokens) in an
7187 invocation of a function-like macro shall equal the number of parameters in the macro
7188 definition. Otherwise, there shall be more arguments in the invocation than there are
7189 parameters in the macro definition (excluding the ...). There shall exist a )
7190 preprocessing token that terminates the invocation.
7191 5 The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like
7192 macro that uses the ellipsis notation in the parameters.
7193 6 A parameter identifier in a function-like macro shall be uniquely declared within its
7196 7 The identifier immediately following the define is called the macro name. There is one
7197 name space for macro names. Any white-space characters preceding or following the
7198 replacement list of preprocessing tokens are not considered part of the replacement list
7200 [<a name="p165" href="#p165">page 165</a>] (<a href="#Contents">Contents</a>)
7202 for either form of macro.
7203 8 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
7204 a preprocessing directive could begin, the identifier is not subject to macro replacement.
7205 9 A preprocessing directive of the form
7206 # define identifier replacement-list new-line
7207 defines an object-like macro that causes each subsequent instance of the macro name<sup><a href="#note171"><b>171)</b></a></sup>
7208 to be replaced by the replacement list of preprocessing tokens that constitute the
7209 remainder of the directive. The replacement list is then rescanned for more macro names
7211 10 A preprocessing directive of the form
7212 # define identifier lparen identifier-listopt ) replacement-list new-line
7213 # define identifier lparen ... ) replacement-list new-line
7214 # define identifier lparen identifier-list , ... ) replacement-list new-line
7215 defines a function-like macro with parameters, whose use is similar syntactically to a
7216 function call. The parameters are specified by the optional list of identifiers, whose scope
7217 extends from their declaration in the identifier list until the new-line character that
7218 terminates the #define preprocessing directive. Each subsequent instance of the
7219 function-like macro name followed by a ( as the next preprocessing token introduces the
7220 sequence of preprocessing tokens that is replaced by the replacement list in the definition
7221 (an invocation of the macro). The replaced sequence of preprocessing tokens is
7222 terminated by the matching ) preprocessing token, skipping intervening matched pairs of
7223 left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
7224 tokens making up an invocation of a function-like macro, new-line is considered a normal
7225 white-space character.
7226 11 The sequence of preprocessing tokens bounded by the outside-most matching parentheses
7227 forms the list of arguments for the function-like macro. The individual arguments within
7228 the list are separated by comma preprocessing tokens, but comma preprocessing tokens
7229 between matching inner parentheses do not separate arguments. If there are sequences of
7230 preprocessing tokens within the list of arguments that would otherwise act as
7231 preprocessing directives,<sup><a href="#note172"><b>172)</b></a></sup> the behavior is undefined.
7232 12 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
7233 including any separating comma preprocessing tokens, are merged to form a single item:
7236 <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,
7237 not sequences possibly containing identifier-like subsequences (see <a href="#5.1.1.2">5.1.1.2</a>, translation phases), they
7238 are never scanned for macro names or parameters.
7239 <sup><a name="note172" href="#note172"><b>172)</b></a></sup> Despite the name, a non-directive is a preprocessing directive.
7241 [<a name="p166" href="#p166">page 166</a>] (<a href="#Contents">Contents</a>)
7243 the variable arguments. The number of arguments so combined is such that, following
7244 merger, the number of arguments is one more than the number of parameters in the macro
7245 definition (excluding the ...).
7246 <a name="6.10.3.1" href="#6.10.3.1"><b> 6.10.3.1 Argument substitution</b></a>
7247 1 After the arguments for the invocation of a function-like macro have been identified,
7248 argument substitution takes place. A parameter in the replacement list, unless preceded
7249 by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
7250 replaced by the corresponding argument after all macros contained therein have been
7251 expanded. Before being substituted, each argument's preprocessing tokens are
7252 completely macro replaced as if they formed the rest of the preprocessing file; no other
7253 preprocessing tokens are available.
7254 2 An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
7255 were a parameter, and the variable arguments shall form the preprocessing tokens used to
7257 <a name="6.10.3.2" href="#6.10.3.2"><b> 6.10.3.2 The # operator</b></a>
7259 1 Each # preprocessing token in the replacement list for a function-like macro shall be
7260 followed by a parameter as the next preprocessing token in the replacement list.
7262 2 If, in the replacement list, a parameter is immediately preceded by a # preprocessing
7263 token, both are replaced by a single character string literal preprocessing token that
7264 contains the spelling of the preprocessing token sequence for the corresponding
7265 argument. Each occurrence of white space between the argument's preprocessing tokens
7266 becomes a single space character in the character string literal. White space before the
7267 first preprocessing token and after the last preprocessing token composing the argument
7268 is deleted. Otherwise, the original spelling of each preprocessing token in the argument
7269 is retained in the character string literal, except for special handling for producing the
7270 spelling of string literals and character constants: a \ character is inserted before each "
7271 and \ character of a character constant or string literal (including the delimiting "
7272 characters), except that it is implementation-defined whether a \ character is inserted
7273 before the \ character beginning a universal character name. If the replacement that
7274 results is not a valid character string literal, the behavior is undefined. The character
7275 string literal corresponding to an empty argument is "". The order of evaluation of # and
7276 ## operators is unspecified.
7278 [<a name="p167" href="#p167">page 167</a>] (<a href="#Contents">Contents</a>)
7280 <a name="6.10.3.3" href="#6.10.3.3"><b> 6.10.3.3 The ## operator</b></a>
7282 1 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
7283 list for either form of macro definition.
7285 2 If, in the replacement list of a function-like macro, a parameter is immediately preceded
7286 or followed by a ## preprocessing token, the parameter is replaced by the corresponding
7287 argument's preprocessing token sequence; however, if an argument consists of no
7288 preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
7289 instead.<sup><a href="#note173"><b>173)</b></a></sup>
7290 3 For both object-like and function-like macro invocations, before the replacement list is
7291 reexamined for more macro names to replace, each instance of a ## preprocessing token
7292 in the replacement list (not from an argument) is deleted and the preceding preprocessing
7293 token is concatenated with the following preprocessing token. Placemarker
7294 preprocessing tokens are handled specially: concatenation of two placemarkers results in
7295 a single placemarker preprocessing token, and concatenation of a placemarker with a
7296 non-placemarker preprocessing token results in the non-placemarker preprocessing token.
7297 If the result is not a valid preprocessing token, the behavior is undefined. The resulting
7298 token is available for further macro replacement. The order of evaluation of ## operators
7300 4 EXAMPLE In the following fragment:
7301 #define hash_hash # ## #
7302 #define mkstr(a) # a
7303 #define in_between(a) mkstr(a)
7304 #define join(c, d) in_between(c hash_hash d)
7305 char p[] = join(x, y); // equivalent to
7306 // char p[] = "x ## y";
7307 The expansion produces, at various stages:
7309 in_between(x hash_hash y)
7313 In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
7314 this new token is not the ## operator.
7317 <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
7318 exist only within translation phase 4.
7320 [<a name="p168" href="#p168">page 168</a>] (<a href="#Contents">Contents</a>)
7322 <a name="6.10.3.4" href="#6.10.3.4"><b> 6.10.3.4 Rescanning and further replacement</b></a>
7323 1 After all parameters in the replacement list have been substituted and # and ##
7324 processing has taken place, all placemarker preprocessing tokens are removed. The
7325 resulting preprocessing token sequence is then rescanned, along with all subsequent
7326 preprocessing tokens of the source file, for more macro names to replace.
7327 2 If the name of the macro being replaced is found during this scan of the replacement list
7328 (not including the rest of the source file's preprocessing tokens), it is not replaced.
7329 Furthermore, if any nested replacements encounter the name of the macro being replaced,
7330 it is not replaced. These nonreplaced macro name preprocessing tokens are no longer
7331 available for further replacement even if they are later (re)examined in contexts in which
7332 that macro name preprocessing token would otherwise have been replaced.
7333 3 The resulting completely macro-replaced preprocessing token sequence is not processed
7334 as a preprocessing directive even if it resembles one, but all pragma unary operator
7335 expressions within it are then processed as specified in <a href="#6.10.9">6.10.9</a> below.
7336 <a name="6.10.3.5" href="#6.10.3.5"><b> 6.10.3.5 Scope of macro definitions</b></a>
7337 1 A macro definition lasts (independent of block structure) until a corresponding #undef
7338 directive is encountered or (if none is encountered) until the end of the preprocessing
7339 translation unit. Macro definitions have no significance after translation phase 4.
7340 2 A preprocessing directive of the form
7341 # undef identifier new-line
7342 causes the specified identifier no longer to be defined as a macro name. It is ignored if
7343 the specified identifier is not currently defined as a macro name.
7344 3 EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
7348 4 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments.
7349 It has the advantages of working for any compatible types of the arguments and of generating in-line code
7350 without the overhead of function calling. It has the disadvantages of evaluating one or the other of its
7351 arguments a second time (including side effects) and generating more code than a function if invoked
7352 several times. It also cannot have its address taken, as it has none.
7353 #define max(a, b) ((a) > (b) ? (a) : (b))
7354 The parentheses ensure that the arguments and the resulting expression are bound properly.
7356 [<a name="p169" href="#p169">page 169</a>] (<a href="#Contents">Contents</a>)
7358 5 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
7360 #define f(a) f(x * (a))
7371 #define r(x,y) x ## y
7373 f(y+1) + f(f(z)) % t(t(g)(0) + t)(1);
7374 g(x+(3,4)-w) | h 5) & m
7376 p() i[q()] = { q(1), r(2,3), r(4,), r(,5), r(,) };
7377 char c[2][6] = { str(hello), str() };
7379 f(2 * (y+1)) + f(2 * (f(2 * (z[0])))) % f(2 * (0)) + t(1);
7380 f(2 * (2+(3,4)-0,1)) | f(2 * (~ 5)) & f(2 * (0,1))^m(0,1);
7381 int i[] = { 1, 23, 4, 5, };
7382 char c[2][6] = { "hello", "" };
7384 6 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the
7387 #define xstr(s) str(s)
7388 #define debug(s, t) printf("x" # s "= %d, x" # t "= %s", \
7390 #define INCFILE(n) vers ## n
7391 #define glue(a, b) a ## b
7392 #define xglue(a, b) glue(a, b)
7393 #define HIGHLOW "hello"
7394 #define LOW LOW ", world"
7396 fputs(str(strncmp("abc\0d", "abc", '\4') // this goes away
7397 == 0) str(: @\n), s);
7398 #include xstr(INCFILE(2).h)
7403 [<a name="p170" href="#p170">page 170</a>] (<a href="#Contents">Contents</a>)
7405 printf("x" "1" "= %d, x" "2" "= %s", x1, x2);
7407 "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0" ": @\n",
7409 #include "vers2.h" (after macro replacement, before file access)
7412 or, after concatenation of the character string literals,
7413 printf("x1= %d, x2= %s", x1, x2);
7415 "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0: @\n",
7417 #include "vers2.h" (after macro replacement, before file access)
7420 Space around the # and ## tokens in the macro definition is optional.
7422 7 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
7423 #define t(x,y,z) x ## y ## z
7424 int j[] = { t(1,2,3), t(,4,5), t(6,,7), t(8,9,),
7425 t(10,,), t(,11,), t(,,12), t(,,) };
7427 int j[] = { 123, 45, 67, 89,
7430 8 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
7431 #define OBJ_LIKE (1-1)
7432 #define OBJ_LIKE /* white space */ (1-1) /* other */
7433 #define FUNC_LIKE(a) ( a )
7434 #define FUNC_LIKE( a )( /* note the white space */ \
7435 a /* other stuff on this line
7437 But the following redefinitions are invalid:
7438 #define OBJ_LIKE (0) // different token sequence
7439 #define OBJ_LIKE (1 - 1) // different white space
7440 #define FUNC_LIKE(b) ( a ) // different parameter usage
7441 #define FUNC_LIKE(b) ( b ) // different parameter spelling
7443 9 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
7444 #define debug(...) fprintf(stderr, __VA_ARGS__)
7445 #define showlist(...) puts(#__VA_ARGS__)
7446 #define report(test, ...) ((test)?puts(#test):\
7447 printf(__VA_ARGS__))
7449 debug("X = %d\n", x);
7450 showlist(The first, second, and third items.);
7451 report(x>y, "x is %d but y is %d", x, y);
7453 [<a name="p171" href="#p171">page 171</a>] (<a href="#Contents">Contents</a>)
7456 fprintf(stderr, "Flag" );
7457 fprintf(stderr, "X = %d\n", x );
7458 puts( "The first, second, and third items." );
7459 ((x>y)?puts("x>y"):
7460 printf("x is %d but y is %d", x, y));
7462 <a name="6.10.4" href="#6.10.4"><b> 6.10.4 Line control</b></a>
7464 1 The string literal of a #line directive, if present, shall be a character string literal.
7466 2 The line number of the current source line is one greater than the number of new-line
7467 characters read or introduced in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>) while processing the source
7468 file to the current token.
7469 3 A preprocessing directive of the form
7470 # line digit-sequence new-line
7471 causes the implementation to behave as if the following sequence of source lines begins
7472 with a source line that has a line number as specified by the digit sequence (interpreted as
7473 a decimal integer). The digit sequence shall not specify zero, nor a number greater than
7475 4 A preprocessing directive of the form
7476 # line digit-sequence "s-char-sequenceopt" new-line
7477 sets the presumed line number similarly and changes the presumed name of the source
7478 file to be the contents of the character string literal.
7479 5 A preprocessing directive of the form
7480 # line pp-tokens new-line
7481 (that does not match one of the two previous forms) is permitted. The preprocessing
7482 tokens after line on the directive are processed just as in normal text (each identifier
7483 currently defined as a macro name is replaced by its replacement list of preprocessing
7484 tokens). The directive resulting after all replacements shall match one of the two
7485 previous forms and is then processed as appropriate.
7487 [<a name="p172" href="#p172">page 172</a>] (<a href="#Contents">Contents</a>)
7489 <a name="6.10.5" href="#6.10.5"><b> 6.10.5 Error directive</b></a>
7491 1 A preprocessing directive of the form
7492 # error pp-tokensopt new-line
7493 causes the implementation to produce a diagnostic message that includes the specified
7494 sequence of preprocessing tokens.
7495 <a name="6.10.6" href="#6.10.6"><b> 6.10.6 Pragma directive</b></a>
7497 1 A preprocessing directive of the form
7498 # pragma pp-tokensopt new-line
7499 where the preprocessing token STDC does not immediately follow pragma in the
7500 directive (prior to any macro replacement)<sup><a href="#note174"><b>174)</b></a></sup> causes the implementation to behave in an
7501 implementation-defined manner. The behavior might cause translation to fail or cause the
7502 translator or the resulting program to behave in a non-conforming manner. Any such
7503 pragma that is not recognized by the implementation is ignored.
7504 2 If the preprocessing token STDC does immediately follow pragma in the directive (prior
7505 to any macro replacement), then no macro replacement is performed on the directive, and
7506 the directive shall have one of the following forms<sup><a href="#note175"><b>175)</b></a></sup> whose meanings are described
7508 #pragma STDC FP_CONTRACT on-off-switch
7509 #pragma STDC FENV_ACCESS on-off-switch
7510 #pragma STDC CX_LIMITED_RANGE on-off-switch
7511 on-off-switch: one of
7513 Forward references: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), the FENV_ACCESS pragma
7514 (<a href="#7.6.1">7.6.1</a>), the CX_LIMITED_RANGE pragma (<a href="#7.3.4">7.3.4</a>).
7519 <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
7520 except for in standard pragmas (where STDC immediately follows pragma). If the result of macro
7521 replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still
7522 implementation-defined; an implementation is permitted to behave as if it were the standard pragma,
7523 but is not required to.
7524 <sup><a name="note175" href="#note175"><b>175)</b></a></sup> See ''future language directions'' (<a href="#6.11.8">6.11.8</a>).
7526 [<a name="p173" href="#p173">page 173</a>] (<a href="#Contents">Contents</a>)
7528 <a name="6.10.7" href="#6.10.7"><b> 6.10.7 Null directive</b></a>
7530 1 A preprocessing directive of the form
7533 <a name="6.10.8" href="#6.10.8"><b> 6.10.8 Predefined macro names</b></a>
7534 1 The values of the predefined macros listed in the following subclauses<sup><a href="#note176"><b>176)</b></a></sup> (except for
7535 __FILE__ and __LINE__) remain constant throughout the translation unit.
7536 2 None of these macro names, nor the identifier defined, shall be the subject of a
7537 #define or a #undef preprocessing directive. Any other predefined macro names
7538 shall begin with a leading underscore followed by an uppercase letter or a second
7540 3 The implementation shall not predefine the macro __cplusplus, nor shall it define it
7541 in any standard header.
7542 Forward references: standard headers (<a href="#7.1.2">7.1.2</a>).
7543 <a name="6.10.8.1" href="#6.10.8.1"><b> 6.10.8.1 Mandatory macros</b></a>
7544 1 The following macro names shall be defined by the implementation:
7545 __DATE__ The date of translation of the preprocessing translation unit: a character
7546 string literal of the form "Mmm dd yyyy", where the names of the
7547 months are the same as those generated by the asctime function, and the
7548 first character of dd is a space character if the value is less than 10. If the
7549 date of translation is not available, an implementation-defined valid date
7551 __FILE__ The presumed name of the current source file (a character string literal).<sup><a href="#note177"><b>177)</b></a></sup>
7552 __LINE__ The presumed line number (within the current source file) of the current
7553 source line (an integer constant).177)
7554 __STDC__ The integer constant 1, intended to indicate a conforming implementation.
7555 __STDC_HOSTED__ The integer constant 1 if the implementation is a hosted
7556 implementation or the integer constant 0 if it is not.
7561 <sup><a name="note176" href="#note176"><b>176)</b></a></sup> See ''future language directions'' (<a href="#6.11.9">6.11.9</a>).
7562 <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.
7564 [<a name="p174" href="#p174">page 174</a>] (<a href="#Contents">Contents</a>)
7566 __STDC_VERSION__ The integer constant 201ymmL.<sup><a href="#note178"><b>178)</b></a></sup>
7567 __TIME__ The time of translation of the preprocessing translation unit: a character
7568 string literal of the form "hh:mm:ss" as in the time generated by the
7569 asctime function. If the time of translation is not available, an
7570 implementation-defined valid time shall be supplied.
7571 Forward references: the asctime function (<a href="#7.26.3.1">7.26.3.1</a>).
7572 <a name="6.10.8.2" href="#6.10.8.2"><b> 6.10.8.2 Environment macros</b></a>
7573 1 The following macro names are conditionally defined by the implementation:
7574 __STDC_ISO_10646__ An integer constant of the form yyyymmL (for example,
7575 199712L). If this symbol is defined, then every character in the Unicode
7576 required set, when stored in an object of type wchar_t, has the same
7577 value as the short identifier of that character. The Unicode required set
7578 consists of all the characters that are defined by ISO/IEC 10646, along with
7579 all amendments and technical corrigenda, as of the specified year and
7580 month. If some other encoding is used, the macro shall not be defined and
7581 the actual encoding used is implementation-defined.
7582 __STDC_MB_MIGHT_NEQ_WC__ The integer constant 1, intended to indicate that, in
7583 the encoding for wchar_t, a member of the basic character set need not
7584 have a code value equal to its value when used as the lone character in an
7585 integer character constant.
7586 __STDC_UTF_16__ The integer constant 1, intended to indicate that values of type
7587 char16_t are UTF-16 encoded. If some other encoding is used, the
7588 macro shall not be defined and the actual encoding used is implementation-
7590 __STDC_UTF_32__ The integer constant 1, intended to indicate that values of type
7591 char32_t are UTF-32 encoded. If some other encoding is used, the
7592 macro shall not be defined and the actual encoding used is implementation-
7594 Forward references: common definitions (<a href="#7.19">7.19</a>), unicode utilities (<a href="#7.27">7.27</a>).
7599 <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
7600 ISO/IEC 9899/AMD1:1995 and as 199901L in ISO/IEC 9899:1999. The intention is that this will
7601 remain an integer constant of type long int that is increased with each revision of this International
7604 [<a name="p175" href="#p175">page 175</a>] (<a href="#Contents">Contents</a>)
7606 <a name="6.10.8.3" href="#6.10.8.3"><b> 6.10.8.3 Conditional feature macros</b></a>
7607 1 The following macro names are conditionally defined by the implementation:
7608 __STDC_ANALYZABLE__ The integer constant 1, intended to indicate conformance to
7609 the specifications in <a href="#L">annex L</a> (Analyzability).
7610 __STDC_IEC_559__ The integer constant 1, intended to indicate conformance to the
7611 specifications in <a href="#F">annex F</a> (IEC 60559 floating-point arithmetic).
7612 __STDC_IEC_559_COMPLEX__ The integer constant 1, intended to indicate
7613 adherence to the specifications in <a href="#G">annex G</a> (IEC 60559 compatible complex
7615 __STDC_LIB_EXT1__ The integer constant 201ymmL, intended to indicate support
7616 for the extensions defined in <a href="#K">annex K</a> (Bounds-checking interfaces).<sup><a href="#note179"><b>179)</b></a></sup>
7617 __STDC_NO_COMPLEX__ The integer constant 1, intended to indicate that the
7618 implementation does not support complex types or the <a href="#7.3"><complex.h></a>
7620 __STDC_NO_THREADS__ The integer constant 1, intended to indicate that the
7621 implementation does not support atomic types (including the _Atomic
7622 type qualifier and the <a href="#7.17"><stdatomic.h></a> header) or the <a href="#7.25"><threads.h></a>
7624 __STDC_NO_VLA__ The integer constant 1, intended to indicate that the
7625 implementation does not support variable length arrays or variably
7627 2 An implementation that defines __STDC_NO_COMPLEX__ shall not define
7628 __STDC_IEC_559_COMPLEX__.
7629 <a name="6.10.9" href="#6.10.9"><b> 6.10.9 Pragma operator</b></a>
7631 1 A unary operator expression of the form:
7632 _Pragma ( string-literal )
7633 is processed as follows: The string literal is destringized by deleting the L prefix, if
7634 present, deleting the leading and trailing double-quotes, replacing each escape sequence
7635 \" by a double-quote, and replacing each escape sequence \\ by a single backslash. The
7636 resulting sequence of characters is processed through translation phase 3 to produce
7637 preprocessing tokens that are executed as if they were the pp-tokens in a pragma
7640 <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
7641 each revision of this International Standard.
7643 [<a name="p176" href="#p176">page 176</a>] (<a href="#Contents">Contents</a>)
7645 directive. The original four preprocessing tokens in the unary operator expression are
7647 2 EXAMPLE A directive of the form:
7648 #pragma listing on "..\listing.dir"
7649 can also be expressed as:
7650 _Pragma ( "listing on \"..\\listing.dir\"" )
7651 The latter form is processed in the same way whether it appears literally as shown, or results from macro
7653 #define LISTING(x) PRAGMA(listing on #x)
7654 #define PRAGMA(x) _Pragma(#x)
7655 LISTING ( ..\listing.dir )
7657 [<a name="p177" href="#p177">page 177</a>] (<a href="#Contents">Contents</a>)
7659 <a name="6.11" href="#6.11"><b> 6.11 Future language directions</b></a>
7660 <a name="6.11.1" href="#6.11.1"><b> 6.11.1 Floating types</b></a>
7661 1 Future standardization may include additional floating-point types, including those with
7662 greater range, precision, or both than long double.
7663 <a name="6.11.2" href="#6.11.2"><b> 6.11.2 Linkages of identifiers</b></a>
7664 1 Declaring an identifier with internal linkage at file scope without the static storage-
7665 class specifier is an obsolescent feature.
7666 <a name="6.11.3" href="#6.11.3"><b> 6.11.3 External names</b></a>
7667 1 Restriction of the significance of an external name to fewer than 255 characters
7668 (considering each universal character name or extended source character as a single
7669 character) is an obsolescent feature that is a concession to existing implementations.
7670 <a name="6.11.4" href="#6.11.4"><b> 6.11.4 Character escape sequences</b></a>
7671 1 Lowercase letters as escape sequences are reserved for future standardization. Other
7672 characters may be used in extensions.
7673 <a name="6.11.5" href="#6.11.5"><b> 6.11.5 Storage-class specifiers</b></a>
7674 1 The placement of a storage-class specifier other than at the beginning of the declaration
7675 specifiers in a declaration is an obsolescent feature.
7676 <a name="6.11.6" href="#6.11.6"><b> 6.11.6 Function declarators</b></a>
7677 1 The use of function declarators with empty parentheses (not prototype-format parameter
7678 type declarators) is an obsolescent feature.
7679 <a name="6.11.7" href="#6.11.7"><b> 6.11.7 Function definitions</b></a>
7680 1 The use of function definitions with separate parameter identifier and declaration lists
7681 (not prototype-format parameter type and identifier declarators) is an obsolescent feature.
7682 <a name="6.11.8" href="#6.11.8"><b> 6.11.8 Pragma directives</b></a>
7683 1 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
7684 <a name="6.11.9" href="#6.11.9"><b> 6.11.9 Predefined macro names</b></a>
7685 1 Macro names beginning with __STDC_ are reserved for future standardization.
7687 [<a name="p178" href="#p178">page 178</a>] (<a href="#Contents">Contents</a>)
7690 <a name="7" href="#7"><b> 7. Library</b></a>
7691 <a name="7.1" href="#7.1"><b> 7.1 Introduction</b></a>
7692 <a name="7.1.1" href="#7.1.1"><b> 7.1.1 Definitions of terms</b></a>
7693 1 A string is a contiguous sequence of characters terminated by and including the first null
7694 character. The term multibyte string is sometimes used instead to emphasize special
7695 processing given to multibyte characters contained in the string or to avoid confusion
7696 with a wide string. A pointer to a string is a pointer to its initial (lowest addressed)
7697 character. The length of a string is the number of bytes preceding the null character and
7698 the value of a string is the sequence of the values of the contained characters, in order.
7699 2 The decimal-point character is the character used by functions that convert floating-point
7700 numbers to or from character sequences to denote the beginning of the fractional part of
7701 such character sequences.<sup><a href="#note180"><b>180)</b></a></sup> It is represented in the text and examples by a period, but
7702 may be changed by the setlocale function.
7703 3 A null wide character is a wide character with code value zero.
7704 4 A wide string is a contiguous sequence of wide characters terminated by and including
7705 the first null wide character. A pointer to a wide string is a pointer to its initial (lowest
7706 addressed) wide character. The length of a wide string is the number of wide characters
7707 preceding the null wide character and the value of a wide string is the sequence of code
7708 values of the contained wide characters, in order.
7709 5 A shift sequence is a contiguous sequence of bytes within a multibyte string that
7710 (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
7711 corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
7712 character.<sup><a href="#note181"><b>181)</b></a></sup>
7713 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>).
7718 <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
7719 (<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>).
7720 <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
7721 enough to count all the bytes in any complete multibyte character plus at least one adjacent shift
7722 sequence of maximum length. Whether these counts provide for more than one shift sequence is the
7723 implementation's choice.
7725 [<a name="p179" href="#p179">page 179</a>] (<a href="#Contents">Contents</a>)
7727 <a name="7.1.2" href="#7.1.2"><b> 7.1.2 Standard headers</b></a>
7728 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>
7729 whose contents are made available by the #include preprocessing directive. The
7730 header declares a set of related functions, plus any necessary types and additional macros
7731 needed to facilitate their use. Declarations of types described in this clause shall not
7732 include type qualifiers, unless explicitly stated otherwise.
7733 2 The standard headers are<sup><a href="#note183"><b>183)</b></a></sup>
7734 <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>
7735 <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>
7736 <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>
7737 <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>
7738 <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>
7739 <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>
7740 <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>
7741 3 If a file with the same name as one of the above < and > delimited sequences, not
7742 provided as part of the implementation, is placed in any of the standard places that are
7743 searched for included source files, the behavior is undefined.
7744 4 Standard headers may be included in any order; each may be included more than once in
7745 a given scope, with no effect different from being included only once, except that the
7746 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
7747 used, a header shall be included outside of any external declaration or definition, and it
7748 shall first be included before the first reference to any of the functions or objects it
7749 declares, or to any of the types or macros it defines. However, if an identifier is declared
7750 or defined in more than one header, the second and subsequent associated headers may be
7751 included after the initial reference to the identifier. The program shall not have any
7752 macros with names lexically identical to keywords currently defined prior to the
7754 5 Any definition of an object-like macro described in this clause shall expand to code that is
7755 fully protected by parentheses where necessary, so that it groups in an arbitrary
7756 expression as if it were a single identifier.
7757 6 Any declaration of a library function shall have external linkage.
7762 <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
7763 necessarily valid source file names.
7764 <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
7765 implementations need not support; see <a href="#6.10.8.3">6.10.8.3</a>.
7767 [<a name="p180" href="#p180">page 180</a>] (<a href="#Contents">Contents</a>)
7769 7 A summary of the contents of the standard headers is given in <a href="#B">annex B</a>.
7770 Forward references: diagnostics (<a href="#7.2">7.2</a>).
7771 <a name="7.1.3" href="#7.1.3"><b> 7.1.3 Reserved identifiers</b></a>
7772 1 Each header declares or defines all identifiers listed in its associated subclause, and
7773 optionally declares or defines identifiers listed in its associated future library directions
7774 subclause and identifiers which are always reserved either for any use or for use as file
7776 -- All identifiers that begin with an underscore and either an uppercase letter or another
7777 underscore are always reserved for any use.
7778 -- All identifiers that begin with an underscore are always reserved for use as identifiers
7779 with file scope in both the ordinary and tag name spaces.
7780 -- Each macro name in any of the following subclauses (including the future library
7781 directions) is reserved for use as specified if any of its associated headers is included;
7782 unless explicitly stated otherwise (see <a href="#7.1.4">7.1.4</a>).
7783 -- All identifiers with external linkage in any of the following subclauses (including the
7784 future library directions) and errno are always reserved for use as identifiers with
7785 external linkage.<sup><a href="#note184"><b>184)</b></a></sup>
7786 -- Each identifier with file scope listed in any of the following subclauses (including the
7787 future library directions) is reserved for use as a macro name and as an identifier with
7788 file scope in the same name space if any of its associated headers is included.
7789 2 No other identifiers are reserved. If the program declares or defines an identifier in a
7790 context in which it is reserved (other than as allowed by <a href="#7.1.4">7.1.4</a>), or defines a reserved
7791 identifier as a macro name, the behavior is undefined.
7792 3 If the program removes (with #undef) any macro definition of an identifier in the first
7793 group listed above, the behavior is undefined.
7798 <sup><a name="note184" href="#note184"><b>184)</b></a></sup> The list of reserved identifiers with external linkage includes math_errhandling, setjmp,
7799 va_copy, and va_end.
7801 [<a name="p181" href="#p181">page 181</a>] (<a href="#Contents">Contents</a>)
7803 <a name="7.1.4" href="#7.1.4"><b> 7.1.4 Use of library functions</b></a>
7804 1 Each of the following statements applies unless explicitly stated otherwise in the detailed
7805 descriptions that follow: If an argument to a function has an invalid value (such as a value
7806 outside the domain of the function, or a pointer outside the address space of the program,
7807 or a null pointer, or a pointer to non-modifiable storage when the corresponding
7808 parameter is not const-qualified) or a type (after promotion) not expected by a function
7809 with variable number of arguments, the behavior is undefined. If a function argument is
7810 described as being an array, the pointer actually passed to the function shall have a value
7811 such that all address computations and accesses to objects (that would be valid if the
7812 pointer did point to the first element of such an array) are in fact valid. Any function
7813 declared in a header may be additionally implemented as a function-like macro defined in
7814 the header, so if a library function is declared explicitly when its header is included, one
7815 of the techniques shown below can be used to ensure the declaration is not affected by
7816 such a macro. Any macro definition of a function can be suppressed locally by enclosing
7817 the name of the function in parentheses, because the name is then not followed by the left
7818 parenthesis that indicates expansion of a macro function name. For the same syntactic
7819 reason, it is permitted to take the address of a library function even if it is also defined as
7820 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
7821 actual function is referred to. Any invocation of a library function that is implemented as
7822 a macro shall expand to code that evaluates each of its arguments exactly once, fully
7823 protected by parentheses where necessary, so it is generally safe to use arbitrary
7824 expressions as arguments.<sup><a href="#note186"><b>186)</b></a></sup> Likewise, those function-like macros described in the
7825 following subclauses may be invoked in an expression anywhere a function with a
7826 compatible return type could be called.<sup><a href="#note187"><b>187)</b></a></sup> All object-like macros listed as expanding to
7829 <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
7830 also provides a macro for that function.
7831 <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.
7832 <sup><a name="note187" href="#note187"><b>187)</b></a></sup> Because external identifiers and some macro names beginning with an underscore are reserved,
7833 implementations may provide special semantics for such names. For example, the identifier
7834 _BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
7835 appropriate header could specify
7836 #define abs(x) _BUILTIN_abs(x)
7837 for a compiler whose code generator will accept it.
7838 In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
7841 whether the implementation's header provides a macro implementation of abs or a built-in
7842 implementation. The prototype for the function, which precedes and is hidden by any macro
7843 definition, is thereby revealed also.
7845 [<a name="p182" href="#p182">page 182</a>] (<a href="#Contents">Contents</a>)
7847 integer constant expressions shall additionally be suitable for use in #if preprocessing
7849 2 Provided that a library function can be declared without reference to any type defined in a
7850 header, it is also permissible to declare the function and use it without including its
7852 3 There is a sequence point immediately before a library function returns.
7853 4 The functions in the standard library are not guaranteed to be reentrant and may modify
7854 objects with static or thread storage duration.<sup><a href="#note188"><b>188)</b></a></sup>
7855 5 Unless explicitly stated otherwise in the detailed descriptions that follow, library
7856 functions shall prevent data races as follows: A library function shall not directly or
7857 indirectly access objects accessible by threads other than the current thread unless the
7858 objects are accessed directly or indirectly via the function's arguments. A library
7859 function shall not directly or indirectly modify objects accessible by threads other than
7860 the current thread unless the objects are accessed directly or indirectly via the function's
7861 non-const arguments.<sup><a href="#note189"><b>189)</b></a></sup> Implementations may share their own internal objects between
7862 threads if the objects are not visible to users and are protected against data races.
7863 6 Unless otherwise specified, library functions shall perform all operations solely within the
7864 current thread if those operations have effects that are visible to users.<sup><a href="#note190"><b>190)</b></a></sup>
7865 7 EXAMPLE The function atoi may be used in any of several ways:
7866 -- by use of its associated header (possibly generating a macro expansion)
7867 #include <a href="#7.22"><stdlib.h></a>
7871 -- by use of its associated header (assuredly generating a true function reference)
7876 <sup><a name="note188" href="#note188"><b>188)</b></a></sup> Thus, a signal handler cannot, in general, call standard library functions.
7877 <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
7878 purposes without synchronization because it could cause a data race even in programs that do not
7879 explicitly share objects between threads.
7880 <sup><a name="note190" href="#note190"><b>190)</b></a></sup> This allows implementations to parallelize operations if there are no visible side effects.
7882 [<a name="p183" href="#p183">page 183</a>] (<a href="#Contents">Contents</a>)
7884 #include <a href="#7.22"><stdlib.h></a>
7890 #include <a href="#7.22"><stdlib.h></a>
7894 -- by explicit declaration
7895 extern int atoi(const char *);
7900 [<a name="p184" href="#p184">page 184</a>] (<a href="#Contents">Contents</a>)
7902 <a name="7.2" href="#7.2"><b> 7.2 Diagnostics <assert.h></b></a>
7903 1 The header <a href="#7.2"><assert.h></a> defines the assert and static_assert macros and
7904 refers to another macro,
7906 which is not defined by <a href="#7.2"><assert.h></a>. If NDEBUG is defined as a macro name at the
7907 point in the source file where <a href="#7.2"><assert.h></a> is included, the assert macro is defined
7909 #define assert(ignore) ((void)0)
7910 The assert macro is redefined according to the current state of NDEBUG each time that
7911 <a href="#7.2"><assert.h></a> is included.
7912 2 The assert macro shall be implemented as a macro, not as an actual function. If the
7913 macro definition is suppressed in order to access an actual function, the behavior is
7917 expands to _Static_assert.
7918 <a name="7.2.1" href="#7.2.1"><b> 7.2.1 Program diagnostics</b></a>
7919 <a name="7.2.1.1" href="#7.2.1.1"><b> 7.2.1.1 The assert macro</b></a>
7921 1 #include <a href="#7.2"><assert.h></a>
7922 void assert(scalar expression);
7924 2 The assert macro puts diagnostic tests into programs; it expands to a void expression.
7925 When it is executed, if expression (which shall have a scalar type) is false (that is,
7926 compares equal to 0), the assert macro writes information about the particular call that
7927 failed (including the text of the argument, the name of the source file, the source line
7928 number, and the name of the enclosing function -- the latter are respectively the values of
7929 the preprocessing macros __FILE__ and __LINE__ and of the identifier
7930 __func__) on the standard error stream in an implementation-defined format.<sup><a href="#note191"><b>191)</b></a></sup> It
7931 then calls the abort function.
7935 <sup><a name="note191" href="#note191"><b>191)</b></a></sup> The message written might be of the form:
7936 Assertion failed: expression, function abc, file xyz, line nnn.
7938 [<a name="p185" href="#p185">page 185</a>] (<a href="#Contents">Contents</a>)
7941 3 The assert macro returns no value.
7942 Forward references: the abort function (<a href="#7.22.4.1">7.22.4.1</a>).
7944 [<a name="p186" href="#p186">page 186</a>] (<a href="#Contents">Contents</a>)
7946 <a name="7.3" href="#7.3"><b> 7.3 Complex arithmetic <complex.h></b></a>
7947 <a name="7.3.1" href="#7.3.1"><b> 7.3.1 Introduction</b></a>
7948 1 The header <a href="#7.3"><complex.h></a> defines macros and declares functions that support complex
7949 arithmetic.<sup><a href="#note192"><b>192)</b></a></sup>
7950 2 Implementations that define the macro __STDC_NO_COMPLEX__ need not provide
7951 this header nor support any of its facilities.
7952 3 Each synopsis specifies a family of functions consisting of a principal function with one
7953 or more double complex parameters and a double complex or double return
7954 value; and other functions with the same name but with f and l suffixes which are
7955 corresponding functions with float and long double parameters and return values.
7958 expands to _Complex; the macro
7960 expands to a constant expression of type const float _Complex, with the value of
7961 the imaginary unit.<sup><a href="#note193"><b>193)</b></a></sup>
7966 are defined if and only if the implementation supports imaginary types;<sup><a href="#note194"><b>194)</b></a></sup> if defined,
7967 they expand to _Imaginary and a constant expression of type const float
7968 _Imaginary with the value of the imaginary unit.
7971 expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
7972 defined, I shall expand to _Complex_I.
7973 7 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
7974 redefine the macros complex, imaginary, and I.
7976 <sup><a name="note192" href="#note192"><b>192)</b></a></sup> See ''future library directions'' (<a href="#7.30.1">7.30.1</a>).
7977 <sup><a name="note193" href="#note193"><b>193)</b></a></sup> The imaginary unit is a number i such that i 2 = -1.
7978 <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>.
7980 [<a name="p187" href="#p187">page 187</a>] (<a href="#Contents">Contents</a>)
7982 Forward references: IEC 60559-compatible complex arithmetic (<a href="#G">annex G</a>).
7983 <a name="7.3.2" href="#7.3.2"><b> 7.3.2 Conventions</b></a>
7984 1 Values are interpreted as radians, not degrees. An implementation may set errno but is
7986 <a name="7.3.3" href="#7.3.3"><b> 7.3.3 Branch cuts</b></a>
7987 1 Some of the functions below have branch cuts, across which the function is
7988 discontinuous. For implementations with a signed zero (including all IEC 60559
7989 implementations) that follow the specifications of <a href="#G">annex G</a>, the sign of zero distinguishes
7990 one side of a cut from another so the function is continuous (except for format
7991 limitations) as the cut is approached from either side. For example, for the square root
7992 function, which has a branch cut along the negative real axis, the top of the cut, with
7993 imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with
7994 imaginary part -0, maps to the negative imaginary axis.
7995 2 Implementations that do not support a signed zero (see <a href="#F">annex F</a>) cannot distinguish the
7996 sides of branch cuts. These implementations shall map a cut so the function is continuous
7997 as the cut is approached coming around the finite endpoint of the cut in a counter
7998 clockwise direction. (Branch cuts for the functions specified here have just one finite
7999 endpoint.) For example, for the square root function, coming counter clockwise around
8000 the finite endpoint of the cut along the negative real axis approaches the cut from above,
8001 so the cut maps to the positive imaginary axis.
8002 <a name="7.3.4" href="#7.3.4"><b> 7.3.4 The CX_LIMITED_RANGE pragma</b></a>
8004 1 #include <a href="#7.3"><complex.h></a>
8005 #pragma STDC CX_LIMITED_RANGE on-off-switch
8007 2 The usual mathematical formulas for complex multiply, divide, and absolute value are
8008 problematic because of their treatment of infinities and because of undue overflow and
8009 underflow. The CX_LIMITED_RANGE pragma can be used to inform the
8010 implementation that (where the state is ''on'') the usual mathematical formulas are
8011 acceptable.<sup><a href="#note195"><b>195)</b></a></sup> The pragma can occur either outside external declarations or preceding all
8012 explicit declarations and statements inside a compound statement. When outside external
8013 declarations, the pragma takes effect from its occurrence until another
8014 CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit.
8015 When inside a compound statement, the pragma takes effect from its occurrence until
8016 another CX_LIMITED_RANGE pragma is encountered (including within a nested
8017 compound statement), or until the end of the compound statement; at the end of a
8018 compound statement the state for the pragma is restored to its condition just before the
8020 [<a name="p188" href="#p188">page 188</a>] (<a href="#Contents">Contents</a>)
8022 compound statement. If this pragma is used in any other context, the behavior is
8023 undefined. The default state for the pragma is ''off''.
8024 <a name="7.3.5" href="#7.3.5"><b> 7.3.5 Trigonometric functions</b></a>
8025 <a name="7.3.5.1" href="#7.3.5.1"><b> 7.3.5.1 The cacos functions</b></a>
8027 1 #include <a href="#7.3"><complex.h></a>
8028 double complex cacos(double complex z);
8029 float complex cacosf(float complex z);
8030 long double complex cacosl(long double complex z);
8032 2 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
8033 interval [-1, +1] along the real axis.
8035 3 The cacos functions return the complex arc cosine value, in the range of a strip
8036 mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
8038 <a name="7.3.5.2" href="#7.3.5.2"><b> 7.3.5.2 The casin functions</b></a>
8040 1 #include <a href="#7.3"><complex.h></a>
8041 double complex casin(double complex z);
8042 float complex casinf(float complex z);
8043 long double complex casinl(long double complex z);
8045 2 The casin functions compute the complex arc sine of z, with branch cuts outside the
8046 interval [-1, +1] along the real axis.
8048 3 The casin functions return the complex arc sine value, in the range of a strip
8049 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
8051 <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:
8052 (x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
8053 (x + iy) / (u + iv) = [(xu + yv) + i(yu - xv)]/(u2 + v 2 )
8054 | x + iy | = (sqrt) x 2 + y 2
8056 where the programmer can determine they are safe.
8058 [<a name="p189" href="#p189">page 189</a>] (<a href="#Contents">Contents</a>)
8060 along the real axis.
8061 <a name="7.3.5.3" href="#7.3.5.3"><b> 7.3.5.3 The catan functions</b></a>
8063 1 #include <a href="#7.3"><complex.h></a>
8064 double complex catan(double complex z);
8065 float complex catanf(float complex z);
8066 long double complex catanl(long double complex z);
8068 2 The catan functions compute the complex arc tangent of z, with branch cuts outside the
8069 interval [-i, +i] along the imaginary axis.
8071 3 The catan functions return the complex arc tangent value, in the range of a strip
8072 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
8073 along the real axis.
8074 <a name="7.3.5.4" href="#7.3.5.4"><b> 7.3.5.4 The ccos functions</b></a>
8076 1 #include <a href="#7.3"><complex.h></a>
8077 double complex ccos(double complex z);
8078 float complex ccosf(float complex z);
8079 long double complex ccosl(long double complex z);
8081 2 The ccos functions compute the complex cosine of z.
8083 3 The ccos functions return the complex cosine value.
8084 <a name="7.3.5.5" href="#7.3.5.5"><b> 7.3.5.5 The csin functions</b></a>
8086 1 #include <a href="#7.3"><complex.h></a>
8087 double complex csin(double complex z);
8088 float complex csinf(float complex z);
8089 long double complex csinl(long double complex z);
8091 2 The csin functions compute the complex sine of z.
8093 [<a name="p190" href="#p190">page 190</a>] (<a href="#Contents">Contents</a>)
8096 3 The csin functions return the complex sine value.
8097 <a name="7.3.5.6" href="#7.3.5.6"><b> 7.3.5.6 The ctan functions</b></a>
8099 1 #include <a href="#7.3"><complex.h></a>
8100 double complex ctan(double complex z);
8101 float complex ctanf(float complex z);
8102 long double complex ctanl(long double complex z);
8104 2 The ctan functions compute the complex tangent of z.
8106 3 The ctan functions return the complex tangent value.
8107 <a name="7.3.6" href="#7.3.6"><b> 7.3.6 Hyperbolic functions</b></a>
8108 <a name="7.3.6.1" href="#7.3.6.1"><b> 7.3.6.1 The cacosh functions</b></a>
8110 1 #include <a href="#7.3"><complex.h></a>
8111 double complex cacosh(double complex z);
8112 float complex cacoshf(float complex z);
8113 long double complex cacoshl(long double complex z);
8115 2 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch
8116 cut at values less than 1 along the real axis.
8118 3 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
8119 half-strip of nonnegative values along the real axis and in the interval [-ipi , +ipi ] along the
8121 <a name="7.3.6.2" href="#7.3.6.2"><b> 7.3.6.2 The casinh functions</b></a>
8123 1 #include <a href="#7.3"><complex.h></a>
8124 double complex casinh(double complex z);
8125 float complex casinhf(float complex z);
8126 long double complex casinhl(long double complex z);
8128 [<a name="p191" href="#p191">page 191</a>] (<a href="#Contents">Contents</a>)
8131 2 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts
8132 outside the interval [-i, +i] along the imaginary axis.
8134 3 The casinh functions return the complex arc hyperbolic sine value, in the range of a
8135 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
8136 along the imaginary axis.
8137 <a name="7.3.6.3" href="#7.3.6.3"><b> 7.3.6.3 The catanh functions</b></a>
8139 1 #include <a href="#7.3"><complex.h></a>
8140 double complex catanh(double complex z);
8141 float complex catanhf(float complex z);
8142 long double complex catanhl(long double complex z);
8144 2 The catanh functions compute the complex arc hyperbolic tangent of z, with branch
8145 cuts outside the interval [-1, +1] along the real axis.
8147 3 The catanh functions return the complex arc hyperbolic tangent value, in the range of a
8148 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
8149 along the imaginary axis.
8150 <a name="7.3.6.4" href="#7.3.6.4"><b> 7.3.6.4 The ccosh functions</b></a>
8152 1 #include <a href="#7.3"><complex.h></a>
8153 double complex ccosh(double complex z);
8154 float complex ccoshf(float complex z);
8155 long double complex ccoshl(long double complex z);
8157 2 The ccosh functions compute the complex hyperbolic cosine of z.
8159 3 The ccosh functions return the complex hyperbolic cosine value.
8161 [<a name="p192" href="#p192">page 192</a>] (<a href="#Contents">Contents</a>)
8163 <a name="7.3.6.5" href="#7.3.6.5"><b> 7.3.6.5 The csinh functions</b></a>
8165 1 #include <a href="#7.3"><complex.h></a>
8166 double complex csinh(double complex z);
8167 float complex csinhf(float complex z);
8168 long double complex csinhl(long double complex z);
8170 2 The csinh functions compute the complex hyperbolic sine of z.
8172 3 The csinh functions return the complex hyperbolic sine value.
8173 <a name="7.3.6.6" href="#7.3.6.6"><b> 7.3.6.6 The ctanh functions</b></a>
8175 1 #include <a href="#7.3"><complex.h></a>
8176 double complex ctanh(double complex z);
8177 float complex ctanhf(float complex z);
8178 long double complex ctanhl(long double complex z);
8180 2 The ctanh functions compute the complex hyperbolic tangent of z.
8182 3 The ctanh functions return the complex hyperbolic tangent value.
8183 <a name="7.3.7" href="#7.3.7"><b> 7.3.7 Exponential and logarithmic functions</b></a>
8184 <a name="7.3.7.1" href="#7.3.7.1"><b> 7.3.7.1 The cexp functions</b></a>
8186 1 #include <a href="#7.3"><complex.h></a>
8187 double complex cexp(double complex z);
8188 float complex cexpf(float complex z);
8189 long double complex cexpl(long double complex z);
8191 2 The cexp functions compute the complex base-e exponential of z.
8193 3 The cexp functions return the complex base-e exponential value.
8195 [<a name="p193" href="#p193">page 193</a>] (<a href="#Contents">Contents</a>)
8197 <a name="7.3.7.2" href="#7.3.7.2"><b> 7.3.7.2 The clog functions</b></a>
8199 1 #include <a href="#7.3"><complex.h></a>
8200 double complex clog(double complex z);
8201 float complex clogf(float complex z);
8202 long double complex clogl(long double complex z);
8204 2 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
8205 cut along the negative real axis.
8207 3 The clog functions return the complex natural logarithm value, in the range of a strip
8208 mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
8210 <a name="7.3.8" href="#7.3.8"><b> 7.3.8 Power and absolute-value functions</b></a>
8211 <a name="7.3.8.1" href="#7.3.8.1"><b> 7.3.8.1 The cabs functions</b></a>
8213 1 #include <a href="#7.3"><complex.h></a>
8214 double cabs(double complex z);
8215 float cabsf(float complex z);
8216 long double cabsl(long double complex z);
8218 2 The cabs functions compute the complex absolute value (also called norm, modulus, or
8221 3 The cabs functions return the complex absolute value.
8222 <a name="7.3.8.2" href="#7.3.8.2"><b> 7.3.8.2 The cpow functions</b></a>
8224 1 #include <a href="#7.3"><complex.h></a>
8225 double complex cpow(double complex x, double complex y);
8226 float complex cpowf(float complex x, float complex y);
8227 long double complex cpowl(long double complex x,
8228 long double complex y);
8230 [<a name="p194" href="#p194">page 194</a>] (<a href="#Contents">Contents</a>)
8233 2 The cpow functions compute the complex power function xy , with a branch cut for the
8234 first parameter along the negative real axis.
8236 3 The cpow functions return the complex power function value.
8237 <a name="7.3.8.3" href="#7.3.8.3"><b> 7.3.8.3 The csqrt functions</b></a>
8239 1 #include <a href="#7.3"><complex.h></a>
8240 double complex csqrt(double complex z);
8241 float complex csqrtf(float complex z);
8242 long double complex csqrtl(long double complex z);
8244 2 The csqrt functions compute the complex square root of z, with a branch cut along the
8247 3 The csqrt functions return the complex square root value, in the range of the right half-
8248 plane (including the imaginary axis).
8249 <a name="7.3.9" href="#7.3.9"><b> 7.3.9 Manipulation functions</b></a>
8250 <a name="7.3.9.1" href="#7.3.9.1"><b> 7.3.9.1 The carg functions</b></a>
8252 1 #include <a href="#7.3"><complex.h></a>
8253 double carg(double complex z);
8254 float cargf(float complex z);
8255 long double cargl(long double complex z);
8257 2 The carg functions compute the argument (also called phase angle) of z, with a branch
8258 cut along the negative real axis.
8260 3 The carg functions return the value of the argument in the interval [-pi , +pi ].
8262 [<a name="p195" href="#p195">page 195</a>] (<a href="#Contents">Contents</a>)
8264 <a name="7.3.9.2" href="#7.3.9.2"><b> 7.3.9.2 The cimag functions</b></a>
8266 1 #include <a href="#7.3"><complex.h></a>
8267 double cimag(double complex z);
8268 float cimagf(float complex z);
8269 long double cimagl(long double complex z);
8271 2 The cimag functions compute the imaginary part of z.<sup><a href="#note196"><b>196)</b></a></sup>
8273 3 The cimag functions return the imaginary part value (as a real).
8274 <a name="7.3.9.3" href="#7.3.9.3"><b> 7.3.9.3 The CMPLX macros</b></a>
8276 1 #include <a href="#7.3"><complex.h></a>
8277 double complex CMPLX(double x, double y);
8278 float complex CMPLXF(float x, float y);
8279 long double complex CMPLXL(long double x, long double y);
8281 2 The CMPLX macros expand to an expression of the specified complex type, with the real
8282 part having the (converted) value of x and the imaginary part having the (converted)
8284 Recommended practice
8285 3 The resulting expression should be suitable for use as an initializer for an object with
8286 static or thread storage duration, provided both arguments are likewise suitable.
8288 4 The CMPLX macros return the complex value x + i y.
8289 5 NOTE These macros act as if the implementation supported imaginary types and the definitions were:
8290 #define CMPLX(x, y) ((double complex)((double)(x) + \
8291 _Imaginary_I * (double)(y)))
8292 #define CMPLXF(x, y) ((float complex)((float)(x) + \
8293 _Imaginary_I * (float)(y)))
8294 #define CMPLXL(x, y) ((long double complex)((long double)(x) + \
8295 _Imaginary_I * (long double)(y)))
8300 <sup><a name="note196" href="#note196"><b>196)</b></a></sup> For a variable z of complex type, z == creal(z) + cimag(z)*I.
8302 [<a name="p196" href="#p196">page 196</a>] (<a href="#Contents">Contents</a>)
8304 <a name="7.3.9.4" href="#7.3.9.4"><b> 7.3.9.4 The conj functions</b></a>
8306 1 #include <a href="#7.3"><complex.h></a>
8307 double complex conj(double complex z);
8308 float complex conjf(float complex z);
8309 long double complex conjl(long double complex z);
8311 2 The conj functions compute the complex conjugate of z, by reversing the sign of its
8314 3 The conj functions return the complex conjugate value.
8315 <a name="7.3.9.5" href="#7.3.9.5"><b> 7.3.9.5 The cproj functions</b></a>
8317 1 #include <a href="#7.3"><complex.h></a>
8318 double complex cproj(double complex z);
8319 float complex cprojf(float complex z);
8320 long double complex cprojl(long double complex z);
8322 2 The cproj functions compute a projection of z onto the Riemann sphere: z projects to
8323 z except that all complex infinities (even those with one infinite part and one NaN part)
8324 project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is
8326 INFINITY + I * copysign(0.0, cimag(z))
8328 3 The cproj functions return the value of the projection onto the Riemann sphere.
8329 <a name="7.3.9.6" href="#7.3.9.6"><b> 7.3.9.6 The creal functions</b></a>
8331 1 #include <a href="#7.3"><complex.h></a>
8332 double creal(double complex z);
8333 float crealf(float complex z);
8334 long double creall(long double complex z);
8336 2 The creal functions compute the real part of z.<sup><a href="#note197"><b>197)</b></a></sup>
8338 [<a name="p197" href="#p197">page 197</a>] (<a href="#Contents">Contents</a>)
8341 3 The creal functions return the real part value.
8346 <sup><a name="note197" href="#note197"><b>197)</b></a></sup> For a variable z of complex type, z == creal(z) + cimag(z)*I.
8348 [<a name="p198" href="#p198">page 198</a>] (<a href="#Contents">Contents</a>)
8350 <a name="7.4" href="#7.4"><b> 7.4 Character handling <ctype.h></b></a>
8351 1 The header <a href="#7.4"><ctype.h></a> declares several functions useful for classifying and mapping
8352 characters.<sup><a href="#note198"><b>198)</b></a></sup> In all cases the argument is an int, the value of which shall be
8353 representable as an unsigned char or shall equal the value of the macro EOF. If the
8354 argument has any other value, the behavior is undefined.
8355 2 The behavior of these functions is affected by the current locale. Those functions that
8356 have locale-specific aspects only when not in the "C" locale are noted below.
8357 3 The term printing character refers to a member of a locale-specific set of characters, each
8358 of which occupies one printing position on a display device; the term control character
8359 refers to a member of a locale-specific set of characters that are not printing
8360 characters.<sup><a href="#note199"><b>199)</b></a></sup> All letters and digits are printing characters.
8361 Forward references: EOF (<a href="#7.21.1">7.21.1</a>), localization (<a href="#7.11">7.11</a>).
8362 <a name="7.4.1" href="#7.4.1"><b> 7.4.1 Character classification functions</b></a>
8363 1 The functions in this subclause return nonzero (true) if and only if the value of the
8364 argument c conforms to that in the description of the function.
8365 <a name="7.4.1.1" href="#7.4.1.1"><b> 7.4.1.1 The isalnum function</b></a>
8367 1 #include <a href="#7.4"><ctype.h></a>
8370 2 The isalnum function tests for any character for which isalpha or isdigit is true.
8371 <a name="7.4.1.2" href="#7.4.1.2"><b> 7.4.1.2 The isalpha function</b></a>
8373 1 #include <a href="#7.4"><ctype.h></a>
8376 2 The isalpha function tests for any character for which isupper or islower is true,
8377 or any character that is one of a locale-specific set of alphabetic characters for which
8381 <sup><a name="note198" href="#note198"><b>198)</b></a></sup> See ''future library directions'' (<a href="#7.30.2">7.30.2</a>).
8382 <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
8383 whose values lie from 0x20 (space) through 0x7E (tilde); the control characters are those whose
8384 values lie from 0 (NUL) through 0x1F (US), and the character 0x7F (DEL).
8386 [<a name="p199" href="#p199">page 199</a>] (<a href="#Contents">Contents</a>)
8388 none of iscntrl, isdigit, ispunct, or isspace is true.<sup><a href="#note200"><b>200)</b></a></sup> In the "C" locale,
8389 isalpha returns true only for the characters for which isupper or islower is true.
8390 <a name="7.4.1.3" href="#7.4.1.3"><b> 7.4.1.3 The isblank function</b></a>
8392 1 #include <a href="#7.4"><ctype.h></a>
8395 2 The isblank function tests for any character that is a standard blank character or is one
8396 of a locale-specific set of characters for which isspace is true and that is used to
8397 separate words within a line of text. The standard blank characters are the following:
8398 space (' '), and horizontal tab ('\t'). In the "C" locale, isblank returns true only
8399 for the standard blank characters.
8400 <a name="7.4.1.4" href="#7.4.1.4"><b> 7.4.1.4 The iscntrl function</b></a>
8402 1 #include <a href="#7.4"><ctype.h></a>
8405 2 The iscntrl function tests for any control character.
8406 <a name="7.4.1.5" href="#7.4.1.5"><b> 7.4.1.5 The isdigit function</b></a>
8408 1 #include <a href="#7.4"><ctype.h></a>
8411 2 The isdigit function tests for any decimal-digit character (as defined in <a href="#5.2.1">5.2.1</a>).
8412 <a name="7.4.1.6" href="#7.4.1.6"><b> 7.4.1.6 The isgraph function</b></a>
8414 1 #include <a href="#7.4"><ctype.h></a>
8420 <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
8421 characters; all four combinations are possible.
8423 [<a name="p200" href="#p200">page 200</a>] (<a href="#Contents">Contents</a>)
8426 2 The isgraph function tests for any printing character except space (' ').
8427 <a name="7.4.1.7" href="#7.4.1.7"><b> 7.4.1.7 The islower function</b></a>
8429 1 #include <a href="#7.4"><ctype.h></a>
8432 2 The islower function tests for any character that is a lowercase letter or is one of a
8433 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
8434 isspace is true. In the "C" locale, islower returns true only for the lowercase
8435 letters (as defined in <a href="#5.2.1">5.2.1</a>).
8436 <a name="7.4.1.8" href="#7.4.1.8"><b> 7.4.1.8 The isprint function</b></a>
8438 1 #include <a href="#7.4"><ctype.h></a>
8441 2 The isprint function tests for any printing character including space (' ').
8442 <a name="7.4.1.9" href="#7.4.1.9"><b> 7.4.1.9 The ispunct function</b></a>
8444 1 #include <a href="#7.4"><ctype.h></a>
8447 2 The ispunct function tests for any printing character that is one of a locale-specific set
8448 of punctuation characters for which neither isspace nor isalnum is true. In the "C"
8449 locale, ispunct returns true for every printing character for which neither isspace
8450 nor isalnum is true.
8451 <a name="7.4.1.10" href="#7.4.1.10"><b> 7.4.1.10 The isspace function</b></a>
8453 1 #include <a href="#7.4"><ctype.h></a>
8456 2 The isspace function tests for any character that is a standard white-space character or
8457 is one of a locale-specific set of characters for which isalnum is false. The standard
8459 [<a name="p201" href="#p201">page 201</a>] (<a href="#Contents">Contents</a>)
8461 white-space characters are the following: space (' '), form feed ('\f'), new-line
8462 ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
8463 "C" locale, isspace returns true only for the standard white-space characters.
8464 <a name="7.4.1.11" href="#7.4.1.11"><b> 7.4.1.11 The isupper function</b></a>
8466 1 #include <a href="#7.4"><ctype.h></a>
8469 2 The isupper function tests for any character that is an uppercase letter or is one of a
8470 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
8471 isspace is true. In the "C" locale, isupper returns true only for the uppercase
8472 letters (as defined in <a href="#5.2.1">5.2.1</a>).
8473 <a name="7.4.1.12" href="#7.4.1.12"><b> 7.4.1.12 The isxdigit function</b></a>
8475 1 #include <a href="#7.4"><ctype.h></a>
8476 int isxdigit(int c);
8478 2 The isxdigit function tests for any hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
8479 <a name="7.4.2" href="#7.4.2"><b> 7.4.2 Character case mapping functions</b></a>
8480 <a name="7.4.2.1" href="#7.4.2.1"><b> 7.4.2.1 The tolower function</b></a>
8482 1 #include <a href="#7.4"><ctype.h></a>
8485 2 The tolower function converts an uppercase letter to a corresponding lowercase letter.
8487 3 If the argument is a character for which isupper is true and there are one or more
8488 corresponding characters, as specified by the current locale, for which islower is true,
8489 the tolower function returns one of the corresponding characters (always the same one
8490 for any given locale); otherwise, the argument is returned unchanged.
8492 [<a name="p202" href="#p202">page 202</a>] (<a href="#Contents">Contents</a>)
8494 <a name="7.4.2.2" href="#7.4.2.2"><b> 7.4.2.2 The toupper function</b></a>
8496 1 #include <a href="#7.4"><ctype.h></a>
8499 2 The toupper function converts a lowercase letter to a corresponding uppercase letter.
8501 3 If the argument is a character for which islower is true and there are one or more
8502 corresponding characters, as specified by the current locale, for which isupper is true,
8503 the toupper function returns one of the corresponding characters (always the same one
8504 for any given locale); otherwise, the argument is returned unchanged.
8506 [<a name="p203" href="#p203">page 203</a>] (<a href="#Contents">Contents</a>)
8508 <a name="7.5" href="#7.5"><b> 7.5 Errors <errno.h></b></a>
8509 1 The header <a href="#7.5"><errno.h></a> defines several macros, all relating to the reporting of error
8515 which expand to integer constant expressions with type int, distinct positive values, and
8516 which are suitable for use in #if preprocessing directives; and
8518 which expands to a modifiable lvalue<sup><a href="#note201"><b>201)</b></a></sup> that has type int and thread local storage
8519 duration, the value of which is set to a positive error number by several library functions.
8520 If a macro definition is suppressed in order to access an actual object, or a program
8521 defines an identifier with the name errno, the behavior is undefined.
8522 3 The value of errno in the initial thread is zero at program startup (the initial value of
8523 errno in other threads is an indeterminate value), but is never set to zero by any library
8524 function.<sup><a href="#note202"><b>202)</b></a></sup> The value of errno may be set to nonzero by a library function call
8525 whether or not there is an error, provided the use of errno is not documented in the
8526 description of the function in this International Standard.
8527 4 Additional macro definitions, beginning with E and a digit or E and an uppercase
8528 letter,<sup><a href="#note203"><b>203)</b></a></sup> may also be specified by the implementation.
8533 <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
8534 resulting from a function call (for example, *errno()).
8535 <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,
8536 then inspect it before a subsequent library function call. Of course, a library function can save the
8537 value of errno on entry and then set it to zero, as long as the original value is restored if errno's
8538 value is still zero just before the return.
8539 <sup><a name="note203" href="#note203"><b>203)</b></a></sup> See ''future library directions'' (<a href="#7.30.3">7.30.3</a>).
8541 [<a name="p204" href="#p204">page 204</a>] (<a href="#Contents">Contents</a>)
8543 <a name="7.6" href="#7.6"><b> 7.6 Floating-point environment <fenv.h></b></a>
8544 1 The header <a href="#7.6"><fenv.h></a> defines several macros, and declares types and functions that
8545 provide access to the floating-point environment. The floating-point environment refers
8546 collectively to any floating-point status flags and control modes supported by the
8547 implementation.<sup><a href="#note204"><b>204)</b></a></sup> A floating-point status flag is a system variable whose value is set
8548 (but never cleared) when a floating-point exception is raised, which occurs as a side effect
8549 of exceptional floating-point arithmetic to provide auxiliary information.<sup><a href="#note205"><b>205)</b></a></sup> A floating-
8550 point control mode is a system variable whose value may be set by the user to affect the
8551 subsequent behavior of floating-point arithmetic.
8552 2 The floating-point environment has thread storage duration. The initial state for a
8553 thread's floating-point environment is the current state of the floating-point environment
8554 of the thread that creates it at the time of creation.
8555 3 Certain programming conventions support the intended model of use for the floating-
8556 point environment:<sup><a href="#note206"><b>206)</b></a></sup>
8557 -- a function call does not alter its caller's floating-point control modes, clear its caller's
8558 floating-point status flags, nor depend on the state of its caller's floating-point status
8559 flags unless the function is so documented;
8560 -- a function call is assumed to require default floating-point control modes, unless its
8561 documentation promises otherwise;
8562 -- a function call is assumed to have the potential for raising floating-point exceptions,
8563 unless its documentation promises otherwise.
8566 represents the entire floating-point environment.
8569 represents the floating-point status flags collectively, including any status the
8570 implementation associates with the flags.
8573 <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
8574 control modes required by IEC 60559, and other similar floating-point state information. It is also
8575 designed to facilitate code portability among all systems.
8576 <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.
8577 <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
8578 unaware of them). The responsibilities associated with accessing the floating-point environment fall
8579 on the programmer or program that does so explicitly.
8581 [<a name="p205" href="#p205">page 205</a>] (<a href="#Contents">Contents</a>)
8583 6 Each of the macros
8589 is defined if and only if the implementation supports the floating-point exception by
8590 means of the functions in 7.6.2.<sup><a href="#note207"><b>207)</b></a></sup> Additional implementation-defined floating-point
8591 exceptions, with macro definitions beginning with FE_ and an uppercase letter, may also
8592 be specified by the implementation. The defined macros expand to integer constant
8593 expressions with values such that bitwise ORs of all combinations of the macros result in
8594 distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
8595 zero.<sup><a href="#note208"><b>208)</b></a></sup>
8598 is simply the bitwise OR of all floating-point exception macros defined by the
8599 implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
8600 8 Each of the macros
8605 is defined if and only if the implementation supports getting and setting the represented
8606 rounding direction by means of the fegetround and fesetround functions.
8607 Additional implementation-defined rounding directions, with macro definitions beginning
8608 with FE_ and an uppercase letter, may also be specified by the implementation. The
8609 defined macros expand to integer constant expressions whose values are distinct
8610 nonnegative values.<sup><a href="#note209"><b>209)</b></a></sup>
8615 <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
8616 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
8617 necessary for all the functions to succeed all the time.
8618 <sup><a name="note208" href="#note208"><b>208)</b></a></sup> The macros should be distinct powers of two.
8619 <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
8620 FLT_ROUNDS, they are not required to do so.
8622 [<a name="p206" href="#p206">page 206</a>] (<a href="#Contents">Contents</a>)
8625 represents the default floating-point environment -- the one installed at program startup
8626 -- and has type ''pointer to const-qualified fenv_t''. It can be used as an argument to
8627 <a href="#7.6"><fenv.h></a> functions that manage the floating-point environment.
8628 10 Additional implementation-defined environments, with macro definitions beginning with
8629 FE_ and an uppercase letter, and having type ''pointer to const-qualified fenv_t'', may
8630 also be specified by the implementation.
8631 <a name="7.6.1" href="#7.6.1"><b> 7.6.1 The FENV_ACCESS pragma</b></a>
8633 1 #include <a href="#7.6"><fenv.h></a>
8634 #pragma STDC FENV_ACCESS on-off-switch
8636 2 The FENV_ACCESS pragma provides a means to inform the implementation when a
8637 program might access the floating-point environment to test floating-point status flags or
8638 run under non-default floating-point control modes.<sup><a href="#note210"><b>210)</b></a></sup> The pragma shall occur either
8639 outside external declarations or preceding all explicit declarations and statements inside a
8640 compound statement. When outside external declarations, the pragma takes effect from
8641 its occurrence until another FENV_ACCESS pragma is encountered, or until the end of
8642 the translation unit. When inside a compound statement, the pragma takes effect from its
8643 occurrence until another FENV_ACCESS pragma is encountered (including within a
8644 nested compound statement), or until the end of the compound statement; at the end of a
8645 compound statement the state for the pragma is restored to its condition just before the
8646 compound statement. If this pragma is used in any other context, the behavior is
8647 undefined. If part of a program tests floating-point status flags, sets floating-point control
8648 modes, or runs under non-default mode settings, but was translated with the state for the
8649 FENV_ACCESS pragma ''off'', the behavior is undefined. The default state (''on'' or
8650 ''off'') for the pragma is implementation-defined. (When execution passes from a part of
8651 the program translated with FENV_ACCESS ''off'' to a part translated with
8652 FENV_ACCESS ''on'', the state of the floating-point status flags is unspecified and the
8653 floating-point control modes have their default settings.)
8658 <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
8659 tests and mode changes (e.g., global common subexpression elimination, code motion, and constant
8660 folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default
8661 modes are in effect and the flags are not tested.
8663 [<a name="p207" href="#p207">page 207</a>] (<a href="#Contents">Contents</a>)
8666 #include <a href="#7.6"><fenv.h></a>
8669 #pragma STDC FENV_ACCESS ON
8677 4 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
8678 x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
8679 contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.<sup><a href="#note211"><b>211)</b></a></sup>
8681 <a name="7.6.2" href="#7.6.2"><b> 7.6.2 Floating-point exceptions</b></a>
8682 1 The following functions provide access to the floating-point status flags.<sup><a href="#note212"><b>212)</b></a></sup> The int
8683 input argument for the functions represents a subset of floating-point exceptions, and can
8684 be zero or the bitwise OR of one or more floating-point exception macros, for example
8685 FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
8686 functions is undefined.
8687 <a name="7.6.2.1" href="#7.6.2.1"><b> 7.6.2.1 The feclearexcept function</b></a>
8689 1 #include <a href="#7.6"><fenv.h></a>
8690 int feclearexcept(int excepts);
8692 2 The feclearexcept function attempts to clear the supported floating-point exceptions
8693 represented by its argument.
8695 3 The feclearexcept function returns zero if the excepts argument is zero or if all
8696 the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
8699 <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
8700 hand, without the #pragma STDC FENV_ACCESS ON pragma, and assuming the default state is
8701 ''off'', just one evaluation of x + 1 would suffice.
8702 <sup><a name="note212" href="#note212"><b>212)</b></a></sup> The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
8703 abstraction of flags that are either set or clear. An implementation may endow floating-point status
8704 flags with more information -- for example, the address of the code which first raised the floating-
8705 point exception; the functions fegetexceptflag and fesetexceptflag deal with the full
8708 [<a name="p208" href="#p208">page 208</a>] (<a href="#Contents">Contents</a>)
8710 <a name="7.6.2.2" href="#7.6.2.2"><b> 7.6.2.2 The fegetexceptflag function</b></a>
8712 1 #include <a href="#7.6"><fenv.h></a>
8713 int fegetexceptflag(fexcept_t *flagp,
8716 2 The fegetexceptflag function attempts to store an implementation-defined
8717 representation of the states of the floating-point status flags indicated by the argument
8718 excepts in the object pointed to by the argument flagp.
8720 3 The fegetexceptflag function returns zero if the representation was successfully
8721 stored. Otherwise, it returns a nonzero value.
8722 <a name="7.6.2.3" href="#7.6.2.3"><b> 7.6.2.3 The feraiseexcept function</b></a>
8724 1 #include <a href="#7.6"><fenv.h></a>
8725 int feraiseexcept(int excepts);
8727 2 The feraiseexcept function attempts to raise the supported floating-point exceptions
8728 represented by its argument.<sup><a href="#note213"><b>213)</b></a></sup> The order in which these floating-point exceptions are
8729 raised is unspecified, except as stated in <a href="#F.8.6">F.8.6</a>. Whether the feraiseexcept function
8730 additionally raises the ''inexact'' floating-point exception whenever it raises the
8731 ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
8733 3 The feraiseexcept function returns zero if the excepts argument is zero or if all
8734 the specified exceptions were successfully raised. Otherwise, it returns a nonzero value.
8739 <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.
8740 Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
8741 in <a href="#F.8.6">F.8.6</a> is in the same spirit.
8743 [<a name="p209" href="#p209">page 209</a>] (<a href="#Contents">Contents</a>)
8745 <a name="7.6.2.4" href="#7.6.2.4"><b> 7.6.2.4 The fesetexceptflag function</b></a>
8747 1 #include <a href="#7.6"><fenv.h></a>
8748 int fesetexceptflag(const fexcept_t *flagp,
8751 2 The fesetexceptflag function attempts to set the floating-point status flags
8752 indicated by the argument excepts to the states stored in the object pointed to by
8753 flagp. The value of *flagp shall have been set by a previous call to
8754 fegetexceptflag whose second argument represented at least those floating-point
8755 exceptions represented by the argument excepts. This function does not raise floating-
8756 point exceptions, but only sets the state of the flags.
8758 3 The fesetexceptflag function returns zero if the excepts argument is zero or if
8759 all the specified flags were successfully set to the appropriate state. Otherwise, it returns
8761 <a name="7.6.2.5" href="#7.6.2.5"><b> 7.6.2.5 The fetestexcept function</b></a>
8763 1 #include <a href="#7.6"><fenv.h></a>
8764 int fetestexcept(int excepts);
8766 2 The fetestexcept function determines which of a specified subset of the floating-
8767 point exception flags are currently set. The excepts argument specifies the floating-
8768 point status flags to be queried.<sup><a href="#note214"><b>214)</b></a></sup>
8770 3 The fetestexcept function returns the value of the bitwise OR of the floating-point
8771 exception macros corresponding to the currently set floating-point exceptions included in
8773 4 EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set:
8778 <sup><a name="note214" href="#note214"><b>214)</b></a></sup> This mechanism allows testing several floating-point exceptions with just one function call.
8780 [<a name="p210" href="#p210">page 210</a>] (<a href="#Contents">Contents</a>)
8782 #include <a href="#7.6"><fenv.h></a>
8785 #pragma STDC FENV_ACCESS ON
8787 feclearexcept(FE_INVALID | FE_OVERFLOW);
8788 // maybe raise exceptions
8789 set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
8790 if (set_excepts & FE_INVALID) f();
8791 if (set_excepts & FE_OVERFLOW) g();
8795 <a name="7.6.3" href="#7.6.3"><b> 7.6.3 Rounding</b></a>
8796 1 The fegetround and fesetround functions provide control of rounding direction
8798 <a name="7.6.3.1" href="#7.6.3.1"><b> 7.6.3.1 The fegetround function</b></a>
8800 1 #include <a href="#7.6"><fenv.h></a>
8801 int fegetround(void);
8803 2 The fegetround function gets the current rounding direction.
8805 3 The fegetround function returns the value of the rounding direction macro
8806 representing the current rounding direction or a negative value if there is no such
8807 rounding direction macro or the current rounding direction is not determinable.
8808 <a name="7.6.3.2" href="#7.6.3.2"><b> 7.6.3.2 The fesetround function</b></a>
8810 1 #include <a href="#7.6"><fenv.h></a>
8811 int fesetround(int round);
8813 2 The fesetround function establishes the rounding direction represented by its
8814 argument round. If the argument is not equal to the value of a rounding direction macro,
8815 the rounding direction is not changed.
8817 3 The fesetround function returns zero if and only if the requested rounding direction
8820 [<a name="p211" href="#p211">page 211</a>] (<a href="#Contents">Contents</a>)
8822 4 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the
8823 rounding direction fails.
8824 #include <a href="#7.6"><fenv.h></a>
8825 #include <a href="#7.2"><assert.h></a>
8826 void f(int round_dir)
8828 #pragma STDC FENV_ACCESS ON
8831 save_round = fegetround();
8832 setround_ok = fesetround(round_dir);
8833 assert(setround_ok == 0);
8835 fesetround(save_round);
8839 <a name="7.6.4" href="#7.6.4"><b> 7.6.4 Environment</b></a>
8840 1 The functions in this section manage the floating-point environment -- status flags and
8841 control modes -- as one entity.
8842 <a name="7.6.4.1" href="#7.6.4.1"><b> 7.6.4.1 The fegetenv function</b></a>
8844 1 #include <a href="#7.6"><fenv.h></a>
8845 int fegetenv(fenv_t *envp);
8847 2 The fegetenv function attempts to store the current floating-point environment in the
8848 object pointed to by envp.
8850 3 The fegetenv function returns zero if the environment was successfully stored.
8851 Otherwise, it returns a nonzero value.
8852 <a name="7.6.4.2" href="#7.6.4.2"><b> 7.6.4.2 The feholdexcept function</b></a>
8854 1 #include <a href="#7.6"><fenv.h></a>
8855 int feholdexcept(fenv_t *envp);
8857 2 The feholdexcept function saves the current floating-point environment in the object
8858 pointed to by envp, clears the floating-point status flags, and then installs a non-stop
8859 (continue on floating-point exceptions) mode, if available, for all floating-point
8860 exceptions.<sup><a href="#note215"><b>215)</b></a></sup>
8862 [<a name="p212" href="#p212">page 212</a>] (<a href="#Contents">Contents</a>)
8865 3 The feholdexcept function returns zero if and only if non-stop floating-point
8866 exception handling was successfully installed.
8867 <a name="7.6.4.3" href="#7.6.4.3"><b> 7.6.4.3 The fesetenv function</b></a>
8869 1 #include <a href="#7.6"><fenv.h></a>
8870 int fesetenv(const fenv_t *envp);
8872 2 The fesetenv function attempts to establish the floating-point environment represented
8873 by the object pointed to by envp. The argument envp shall point to an object set by a
8874 call to fegetenv or feholdexcept, or equal a floating-point environment macro.
8875 Note that fesetenv merely installs the state of the floating-point status flags
8876 represented through its argument, and does not raise these floating-point exceptions.
8878 3 The fesetenv function returns zero if the environment was successfully established.
8879 Otherwise, it returns a nonzero value.
8880 <a name="7.6.4.4" href="#7.6.4.4"><b> 7.6.4.4 The feupdateenv function</b></a>
8882 1 #include <a href="#7.6"><fenv.h></a>
8883 int feupdateenv(const fenv_t *envp);
8885 2 The feupdateenv function attempts to save the currently raised floating-point
8886 exceptions in its automatic storage, install the floating-point environment represented by
8887 the object pointed to by envp, and then raise the saved floating-point exceptions. The
8888 argument envp shall point to an object set by a call to feholdexcept or fegetenv,
8889 or equal a floating-point environment macro.
8891 3 The feupdateenv function returns zero if all the actions were successfully carried out.
8892 Otherwise, it returns a nonzero value.
8897 <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
8898 handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For
8899 such systems, the feholdexcept function can be used in conjunction with the feupdateenv
8900 function to write routines that hide spurious floating-point exceptions from their callers.
8902 [<a name="p213" href="#p213">page 213</a>] (<a href="#Contents">Contents</a>)
8904 4 EXAMPLE Hide spurious underflow floating-point exceptions:
8905 #include <a href="#7.6"><fenv.h></a>
8908 #pragma STDC FENV_ACCESS ON
8911 if (feholdexcept(&save_env))
8912 return /* indication of an environmental problem */;
8914 if (/* test spurious underflow */)
8915 if (feclearexcept(FE_UNDERFLOW))
8916 return /* indication of an environmental problem */;
8917 if (feupdateenv(&save_env))
8918 return /* indication of an environmental problem */;
8922 [<a name="p214" href="#p214">page 214</a>] (<a href="#Contents">Contents</a>)
8924 <a name="7.7" href="#7.7"><b> 7.7 Characteristics of floating types <float.h></b></a>
8925 1 The header <a href="#7.7"><float.h></a> defines several macros that expand to various limits and
8926 parameters of the standard floating-point types.
8927 2 The macros, their meanings, and the constraints (or restrictions) on their values are listed
8928 in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
8930 [<a name="p215" href="#p215">page 215</a>] (<a href="#Contents">Contents</a>)
8932 <a name="7.8" href="#7.8"><b> 7.8 Format conversion of integer types <inttypes.h></b></a>
8933 1 The header <a href="#7.8"><inttypes.h></a> includes the header <a href="#7.20"><stdint.h></a> and extends it with
8934 additional facilities provided by hosted implementations.
8935 2 It declares functions for manipulating greatest-width integers and converting numeric
8936 character strings to greatest-width integers, and it declares the type
8938 which is a structure type that is the type of the value returned by the imaxdiv function.
8939 For each type declared in <a href="#7.20"><stdint.h></a>, it defines corresponding macros for conversion
8940 specifiers for use with the formatted input/output functions.<sup><a href="#note216"><b>216)</b></a></sup>
8941 Forward references: integer types <a href="#7.20"><stdint.h></a> (<a href="#7.20">7.20</a>), formatted input/output
8942 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>).
8943 <a name="7.8.1" href="#7.8.1"><b> 7.8.1 Macros for format specifiers</b></a>
8944 1 Each of the following object-like macros expands to a character string literal containing a *
8945 conversion specifier, possibly modified by a length modifier, suitable for use within the
8946 format argument of a formatted input/output function when converting the corresponding
8947 integer type. These macro names have the general form of PRI (character string literals
8948 for the fprintf and fwprintf family) or SCN (character string literals for the
8949 fscanf and fwscanf family),<sup><a href="#note217"><b>217)</b></a></sup> followed by the conversion specifier, followed by a
8950 name corresponding to a similar type name in <a href="#7.20.1">7.20.1</a>. In these names, N represents the
8951 width of the type as described in <a href="#7.20.1">7.20.1</a>. For example, PRIdFAST32 can be used in a
8952 format string to print the value of an integer of type int_fast32_t.
8953 2 The fprintf macros for signed integers are:
8954 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
8955 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
8956 3 The fprintf macros for unsigned integers are:
8957 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
8958 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
8959 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
8960 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
8961 4 The fscanf macros for signed integers are:
8965 <sup><a name="note216" href="#note216"><b>216)</b></a></sup> See ''future library directions'' (<a href="#7.30.4">7.30.4</a>).
8966 <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,
8967 different format specifiers may be required for fprintf and fscanf, even when the type is the
8970 [<a name="p216" href="#p216">page 216</a>] (<a href="#Contents">Contents</a>)
8972 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
8973 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
8974 5 The fscanf macros for unsigned integers are:
8975 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
8976 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
8977 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
8978 6 For each type that the implementation provides in <a href="#7.20"><stdint.h></a>, the corresponding
8979 fprintf macros shall be defined and the corresponding fscanf macros shall be
8980 defined unless the implementation does not have a suitable fscanf length modifier for
8983 #include <a href="#7.8"><inttypes.h></a>
8984 #include <a href="#7.28"><wchar.h></a>
8987 uintmax_t i = UINTMAX_MAX; // this type always exists
8988 wprintf(L"The largest integer value is %020"
8993 <a name="7.8.2" href="#7.8.2"><b> 7.8.2 Functions for greatest-width integer types</b></a>
8994 <a name="7.8.2.1" href="#7.8.2.1"><b> 7.8.2.1 The imaxabs function</b></a>
8996 1 #include <a href="#7.8"><inttypes.h></a>
8997 intmax_t imaxabs(intmax_t j);
8999 2 The imaxabs function computes the absolute value of an integer j. If the result cannot
9000 be represented, the behavior is undefined.<sup><a href="#note218"><b>218)</b></a></sup>
9002 3 The imaxabs function returns the absolute value.
9007 <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.
9009 [<a name="p217" href="#p217">page 217</a>] (<a href="#Contents">Contents</a>)
9011 <a name="7.8.2.2" href="#7.8.2.2"><b> 7.8.2.2 The imaxdiv function</b></a>
9013 1 #include <a href="#7.8"><inttypes.h></a>
9014 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
9016 2 The imaxdiv function computes numer / denom and numer % denom in a single
9019 3 The imaxdiv function returns a structure of type imaxdiv_t comprising both the
9020 quotient and the remainder. The structure shall contain (in either order) the members
9021 quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
9022 either part of the result cannot be represented, the behavior is undefined.
9023 <a name="7.8.2.3" href="#7.8.2.3"><b> 7.8.2.3 The strtoimax and strtoumax functions</b></a>
9025 1 #include <a href="#7.8"><inttypes.h></a>
9026 intmax_t strtoimax(const char * restrict nptr,
9027 char ** restrict endptr, int base);
9028 uintmax_t strtoumax(const char * restrict nptr,
9029 char ** restrict endptr, int base);
9031 2 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll,
9032 strtoul, and strtoull functions, except that the initial portion of the string is
9033 converted to intmax_t and uintmax_t representation, respectively.
9035 3 The strtoimax and strtoumax functions return the converted value, if any. If no
9036 conversion could be performed, zero is returned. If the correct value is outside the range
9037 of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned
9038 (according to the return type and sign of the value, if any), and the value of the macro
9039 ERANGE is stored in errno.
9040 Forward references: the strtol, strtoll, strtoul, and strtoull functions
9041 (<a href="#7.22.1.4">7.22.1.4</a>).
9043 [<a name="p218" href="#p218">page 218</a>] (<a href="#Contents">Contents</a>)
9045 <a name="7.8.2.4" href="#7.8.2.4"><b> 7.8.2.4 The wcstoimax and wcstoumax functions</b></a>
9047 1 #include <a href="#7.19"><stddef.h></a> // for wchar_t
9048 #include <a href="#7.8"><inttypes.h></a>
9049 intmax_t wcstoimax(const wchar_t * restrict nptr,
9050 wchar_t ** restrict endptr, int base);
9051 uintmax_t wcstoumax(const wchar_t * restrict nptr,
9052 wchar_t ** restrict endptr, int base);
9054 2 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll,
9055 wcstoul, and wcstoull functions except that the initial portion of the wide string is
9056 converted to intmax_t and uintmax_t representation, respectively.
9058 3 The wcstoimax function returns the converted value, if any. If no conversion could be
9059 performed, zero is returned. If the correct value is outside the range of representable
9060 values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the
9061 return type and sign of the value, if any), and the value of the macro ERANGE is stored in
9063 Forward references: the wcstol, wcstoll, wcstoul, and wcstoull functions
9064 (<a href="#7.28.4.1.2">7.28.4.1.2</a>).
9066 [<a name="p219" href="#p219">page 219</a>] (<a href="#Contents">Contents</a>)
9068 <a name="7.9" href="#7.9"><b> 7.9 Alternative spellings <iso646.h></b></a>
9069 1 The header <a href="#7.9"><iso646.h></a> defines the following eleven macros (on the left) that expand
9070 to the corresponding tokens (on the right):
9083 [<a name="p220" href="#p220">page 220</a>] (<a href="#Contents">Contents</a>)
9085 <a name="7.10" href="#7.10"><b> 7.10 Sizes of integer types <limits.h></b></a>
9086 1 The header <a href="#7.10"><limits.h></a> defines several macros that expand to various limits and
9087 parameters of the standard integer types.
9088 2 The macros, their meanings, and the constraints (or restrictions) on their values are listed
9089 in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
9091 [<a name="p221" href="#p221">page 221</a>] (<a href="#Contents">Contents</a>)
9093 <a name="7.11" href="#7.11"><b> 7.11 Localization <locale.h></b></a>
9094 1 The header <a href="#7.11"><locale.h></a> declares two functions, one type, and defines several macros.
9097 which contains members related to the formatting of numeric values. The structure shall
9098 contain at least the following members, in any order. The semantics of the members and
9099 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
9100 the values specified in the comments.
9101 char *decimal_point; // "."
9102 char *thousands_sep; // ""
9103 char *grouping; // ""
9104 char *mon_decimal_point; // ""
9105 char *mon_thousands_sep; // ""
9106 char *mon_grouping; // ""
9107 char *positive_sign; // ""
9108 char *negative_sign; // ""
9109 char *currency_symbol; // ""
9110 char frac_digits; // CHAR_MAX
9111 char p_cs_precedes; // CHAR_MAX
9112 char n_cs_precedes; // CHAR_MAX
9113 char p_sep_by_space; // CHAR_MAX
9114 char n_sep_by_space; // CHAR_MAX
9115 char p_sign_posn; // CHAR_MAX
9116 char n_sign_posn; // CHAR_MAX
9117 char *int_curr_symbol; // ""
9118 char int_frac_digits; // CHAR_MAX
9119 char int_p_cs_precedes; // CHAR_MAX
9120 char int_n_cs_precedes; // CHAR_MAX
9121 char int_p_sep_by_space; // CHAR_MAX
9122 char int_n_sep_by_space; // CHAR_MAX
9123 char int_p_sign_posn; // CHAR_MAX
9124 char int_n_sign_posn; // CHAR_MAX
9126 [<a name="p222" href="#p222">page 222</a>] (<a href="#Contents">Contents</a>)
9128 3 The macros defined are NULL (described in <a href="#7.19">7.19</a>); and
9135 which expand to integer constant expressions with distinct values, suitable for use as the
9136 first argument to the setlocale function.<sup><a href="#note219"><b>219)</b></a></sup> Additional macro definitions, beginning
9137 with the characters LC_ and an uppercase letter,<sup><a href="#note220"><b>220)</b></a></sup> may also be specified by the
9139 <a name="7.11.1" href="#7.11.1"><b> 7.11.1 Locale control</b></a>
9140 <a name="7.11.1.1" href="#7.11.1.1"><b> 7.11.1.1 The setlocale function</b></a>
9142 1 #include <a href="#7.11"><locale.h></a>
9143 char *setlocale(int category, const char *locale);
9145 2 The setlocale function selects the appropriate portion of the program's locale as
9146 specified by the category and locale arguments. The setlocale function may be
9147 used to change or query the program's entire current locale or portions thereof. The value
9148 LC_ALL for category names the program's entire locale; the other values for
9149 category name only a portion of the program's locale. LC_COLLATE affects the
9150 behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of
9151 the character handling functions<sup><a href="#note221"><b>221)</b></a></sup> and the multibyte and wide character functions.
9152 LC_MONETARY affects the monetary formatting information returned by the
9153 localeconv function. LC_NUMERIC affects the decimal-point character for the
9154 formatted input/output functions and the string conversion functions, as well as the
9155 nonmonetary formatting information returned by the localeconv function. LC_TIME
9156 affects the behavior of the strftime and wcsftime functions.
9157 3 A value of "C" for locale specifies the minimal environment for C translation; a value
9158 of "" for locale specifies the locale-specific native environment. Other
9159 implementation-defined strings may be passed as the second argument to setlocale.
9161 <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.
9162 <sup><a name="note220" href="#note220"><b>220)</b></a></sup> See ''future library directions'' (<a href="#7.30.5">7.30.5</a>).
9163 <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
9166 [<a name="p223" href="#p223">page 223</a>] (<a href="#Contents">Contents</a>)
9168 4 At program startup, the equivalent of
9169 setlocale(LC_ALL, "C");
9171 5 A call to the setlocale function may introduce a data race with other calls to the
9172 setlocale function or with calls to functions that are affected by the current locale.
9173 The implementation shall behave as if no library function calls the setlocale function.
9175 6 If a pointer to a string is given for locale and the selection can be honored, the
9176 setlocale function returns a pointer to the string associated with the specified
9177 category for the new locale. If the selection cannot be honored, the setlocale
9178 function returns a null pointer and the program's locale is not changed.
9179 7 A null pointer for locale causes the setlocale function to return a pointer to the
9180 string associated with the category for the program's current locale; the program's
9181 locale is not changed.<sup><a href="#note222"><b>222)</b></a></sup>
9182 8 The pointer to string returned by the setlocale function is such that a subsequent call
9183 with that string value and its associated category will restore that part of the program's
9184 locale. The string pointed to shall not be modified by the program, but may be
9185 overwritten by a subsequent call to the setlocale function.
9186 Forward references: formatted input/output functions (<a href="#7.21.6">7.21.6</a>), multibyte/wide
9187 character conversion functions (<a href="#7.22.7">7.22.7</a>), multibyte/wide string conversion functions
9188 (<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
9189 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>).
9190 <a name="7.11.2" href="#7.11.2"><b> 7.11.2 Numeric formatting convention inquiry</b></a>
9191 <a name="7.11.2.1" href="#7.11.2.1"><b> 7.11.2.1 The localeconv function</b></a>
9193 1 #include <a href="#7.11"><locale.h></a>
9194 struct lconv *localeconv(void);
9196 2 The localeconv function sets the components of an object with type struct lconv
9197 with values appropriate for the formatting of numeric quantities (monetary and otherwise)
9198 according to the rules of the current locale.
9202 <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
9203 locale when category has the value LC_ALL.
9205 [<a name="p224" href="#p224">page 224</a>] (<a href="#Contents">Contents</a>)
9207 3 The members of the structure with type char * are pointers to strings, any of which
9208 (except decimal_point) can point to "", to indicate that the value is not available in
9209 the current locale or is of zero length. Apart from grouping and mon_grouping, the
9210 strings shall start and end in the initial shift state. The members with type char are
9211 nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not
9212 available in the current locale. The members include the following:
9214 The decimal-point character used to format nonmonetary quantities.
9216 The character used to separate groups of digits before the decimal-point
9217 character in formatted nonmonetary quantities.
9219 A string whose elements indicate the size of each group of digits in
9220 formatted nonmonetary quantities.
9221 char *mon_decimal_point
9222 The decimal-point used to format monetary quantities.
9223 char *mon_thousands_sep
9224 The separator for groups of digits before the decimal-point in formatted
9225 monetary quantities.
9227 A string whose elements indicate the size of each group of digits in
9228 formatted monetary quantities.
9230 The string used to indicate a nonnegative-valued formatted monetary
9233 The string used to indicate a negative-valued formatted monetary quantity.
9234 char *currency_symbol
9235 The local currency symbol applicable to the current locale.
9237 The number of fractional digits (those after the decimal-point) to be
9238 displayed in a locally formatted monetary quantity.
9240 Set to 1 or 0 if the currency_symbol respectively precedes or
9241 succeeds the value for a nonnegative locally formatted monetary quantity.
9243 [<a name="p225" href="#p225">page 225</a>] (<a href="#Contents">Contents</a>)
9246 Set to 1 or 0 if the currency_symbol respectively precedes or
9247 succeeds the value for a negative locally formatted monetary quantity.
9249 Set to a value indicating the separation of the currency_symbol, the
9250 sign string, and the value for a nonnegative locally formatted monetary
9253 Set to a value indicating the separation of the currency_symbol, the
9254 sign string, and the value for a negative locally formatted monetary
9257 Set to a value indicating the positioning of the positive_sign for a
9258 nonnegative locally formatted monetary quantity.
9260 Set to a value indicating the positioning of the negative_sign for a
9261 negative locally formatted monetary quantity.
9262 char *int_curr_symbol
9263 The international currency symbol applicable to the current locale. The
9264 first three characters contain the alphabetic international currency symbol
9265 in accordance with those specified in ISO 4217. The fourth character
9266 (immediately preceding the null character) is the character used to separate
9267 the international currency symbol from the monetary quantity.
9268 char int_frac_digits
9269 The number of fractional digits (those after the decimal-point) to be
9270 displayed in an internationally formatted monetary quantity.
9271 char int_p_cs_precedes
9272 Set to 1 or 0 if the int_curr_symbol respectively precedes or
9273 succeeds the value for a nonnegative internationally formatted monetary
9275 char int_n_cs_precedes
9276 Set to 1 or 0 if the int_curr_symbol respectively precedes or
9277 succeeds the value for a negative internationally formatted monetary
9279 char int_p_sep_by_space
9280 Set to a value indicating the separation of the int_curr_symbol, the
9281 sign string, and the value for a nonnegative internationally formatted
9284 [<a name="p226" href="#p226">page 226</a>] (<a href="#Contents">Contents</a>)
9286 char int_n_sep_by_space
9287 Set to a value indicating the separation of the int_curr_symbol, the
9288 sign string, and the value for a negative internationally formatted monetary
9290 char int_p_sign_posn
9291 Set to a value indicating the positioning of the positive_sign for a
9292 nonnegative internationally formatted monetary quantity.
9293 char int_n_sign_posn
9294 Set to a value indicating the positioning of the negative_sign for a
9295 negative internationally formatted monetary quantity.
9296 4 The elements of grouping and mon_grouping are interpreted according to the
9298 CHAR_MAX No further grouping is to be performed.
9299 0 The previous element is to be repeatedly used for the remainder of the
9301 other The integer value is the number of digits that compose the current group.
9302 The next element is examined to determine the size of the next group of
9303 digits before the current group.
9304 5 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space,
9305 and int_n_sep_by_space are interpreted according to the following:
9306 0 No space separates the currency symbol and value.
9307 1 If the currency symbol and sign string are adjacent, a space separates them from the
9308 value; otherwise, a space separates the currency symbol from the value.
9309 2 If the currency symbol and sign string are adjacent, a space separates them;
9310 otherwise, a space separates the sign string from the value.
9311 For int_p_sep_by_space and int_n_sep_by_space, the fourth character of
9312 int_curr_symbol is used instead of a space.
9313 6 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and
9314 int_n_sign_posn are interpreted according to the following:
9315 0 Parentheses surround the quantity and currency symbol.
9316 1 The sign string precedes the quantity and currency symbol.
9317 2 The sign string succeeds the quantity and currency symbol.
9318 3 The sign string immediately precedes the currency symbol.
9319 4 The sign string immediately succeeds the currency symbol.
9321 [<a name="p227" href="#p227">page 227</a>] (<a href="#Contents">Contents</a>)
9323 7 The implementation shall behave as if no library function calls the localeconv
9326 8 The localeconv function returns a pointer to the filled-in object. The structure
9327 pointed to by the return value shall not be modified by the program, but may be
9328 overwritten by a subsequent call to the localeconv function. In addition, calls to the
9329 setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may
9330 overwrite the contents of the structure.
9331 9 EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format
9332 monetary quantities.
9333 Local format International format
9335 Country Positive Negative Positive Negative
9337 Country1 1.234,56 mk -1.234,56 mk FIM 1.234,56 FIM -1.234,56
9338 Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234
9339 Country3 fl. 1.234,56 fl. -1.234,56 NLG 1.234,56 NLG -1.234,56
9340 Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C
9341 10 For these four countries, the respective values for the monetary members of the structure returned by
9342 localeconv could be:
9343 Country1 Country2 Country3 Country4
9345 mon_decimal_point "," "" "," "."
9346 mon_thousands_sep "." "." "." ","
9347 mon_grouping "\3" "\3" "\3" "\3"
9348 positive_sign "" "" "" ""
9349 negative_sign "-" "-" "-" "C"
9350 currency_symbol "mk" "L." "\u0192" "SFrs."
9352 p_cs_precedes 0 1 1 1
9353 n_cs_precedes 0 1 1 1
9354 p_sep_by_space 1 0 1 0
9355 n_sep_by_space 1 0 2 0
9358 int_curr_symbol "FIM " "ITL " "NLG " "CHF "
9359 int_frac_digits 2 0 2 2
9360 int_p_cs_precedes 1 1 1 1
9361 int_n_cs_precedes 1 1 1 1
9362 int_p_sep_by_space 1 1 1 1
9363 int_n_sep_by_space 2 1 2 1
9364 int_p_sign_posn 1 1 1 1
9365 int_n_sign_posn 4 1 4 2
9367 [<a name="p228" href="#p228">page 228</a>] (<a href="#Contents">Contents</a>)
9369 11 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
9370 affect the formatted value.
9373 p_cs_precedes p_sign_posn 0 1 2
9375 0 0 (<a href="#1.25">1.25</a>$) (<a href="#1.25">1.25</a> $) (<a href="#1.25">1.25</a>$)
9376 1 +1.25$ +1.25 $ + <a href="#1.25">1.25</a>$
9377 2 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +
9378 3 <a href="#1.25">1.25</a>+$ <a href="#1.25">1.25</a> +$ <a href="#1.25">1.25</a>+ $
9379 4 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +
9381 1 0 ($1.25) ($ <a href="#1.25">1.25</a>) ($1.25)
9382 1 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
9383 2 $1.25+ $ <a href="#1.25">1.25</a>+ $1.25 +
9384 3 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
9385 4 $+1.25 $+ <a href="#1.25">1.25</a> $ +1.25
9387 [<a name="p229" href="#p229">page 229</a>] (<a href="#Contents">Contents</a>)
9389 <a name="7.12" href="#7.12"><b> 7.12 Mathematics <math.h></b></a>
9390 1 The header <a href="#7.12"><math.h></a> declares two types and many mathematical functions and defines
9391 several macros. Most synopses specify a family of functions consisting of a principal
9392 function with one or more double parameters, a double return value, or both; and
9393 other functions with the same name but with f and l suffixes, which are corresponding
9394 functions with float and long double parameters, return values, or both.<sup><a href="#note223"><b>223)</b></a></sup>
9395 Integer arithmetic functions and conversion functions are discussed later.
9399 are floating types at least as wide as float and double, respectively, and such that
9400 double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
9401 float_t and double_t are float and double, respectively; if
9402 FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
9403 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
9404 otherwise implementation-defined.<sup><a href="#note224"><b>224)</b></a></sup>
9407 expands to a positive double constant expression, not necessarily representable as a
9411 are respectively float and long double analogs of HUGE_VAL.<sup><a href="#note225"><b>225)</b></a></sup>
9414 expands to a constant expression of type float representing positive or unsigned
9415 infinity, if available; else to a positive constant of type float that overflows at
9419 <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
9420 and return values in wider format than the synopsis prototype indicates.
9421 <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
9422 least as wide as float and double, respectively. For FLT_EVAL_METHOD equal 0, 1, or 2, the
9423 type float_t is the narrowest type used by the implementation to evaluate floating expressions.
9424 <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
9425 supports infinities.
9427 [<a name="p230" href="#p230">page 230</a>] (<a href="#Contents">Contents</a>)
9429 translation time.<sup><a href="#note226"><b>226)</b></a></sup>
9432 is defined if and only if the implementation supports quiet NaNs for the float type. It
9433 expands to a constant expression of type float representing a quiet NaN.
9434 6 The number classification macros
9440 represent the mutually exclusive kinds of floating-point values. They expand to integer
9441 constant expressions with distinct values. Additional implementation-defined floating-
9442 point classifications, with macro definitions beginning with FP_ and an uppercase letter,
9443 may also be specified by the implementation.
9446 is optionally defined. If defined, it indicates that the fma function generally executes
9447 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
9451 are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
9452 these macros expand to the integer constant 1.
9456 expand to integer constant expressions whose values are returned by ilogb(x) if x is
9457 zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
9458 -INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
9461 <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.
9462 <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
9463 directly with a hardware multiply-add instruction. Software implementations are expected to be
9464 substantially slower.
9466 [<a name="p231" href="#p231">page 231</a>] (<a href="#Contents">Contents</a>)
9471 expand to the integer constants 1 and 2, respectively; the macro
9473 expands to an expression that has type int and the value MATH_ERRNO,
9474 MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is
9475 constant for the duration of the program. It is unspecified whether
9476 math_errhandling is a macro or an identifier with external linkage. If a macro
9477 definition is suppressed or a program defines an identifier with the name
9478 math_errhandling, the behavior is undefined. If the expression
9479 math_errhandling & MATH_ERREXCEPT can be nonzero, the implementation
9480 shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in
9481 <a href="#7.6"><fenv.h></a>.
9482 <a name="7.12.1" href="#7.12.1"><b> 7.12.1 Treatment of error conditions</b></a>
9483 1 The behavior of each of the functions in <a href="#7.12"><math.h></a> is specified for all representable
9484 values of its input arguments, except where stated otherwise. Each function shall execute
9485 as if it were a single operation without raising SIGFPE and without generating any of the
9486 floating-point exceptions ''invalid'', ''divide-by-zero'', or ''overflow'' except to reflect
9487 the result of the function.
9488 2 For all functions, a domain error occurs if an input argument is outside the domain over
9489 which the mathematical function is defined. The description of each function lists any
9490 required domain errors; an implementation may define additional domain errors, provided
9491 that such errors are consistent with the mathematical definition of the function.<sup><a href="#note228"><b>228)</b></a></sup> On a
9492 domain error, the function returns an implementation-defined value; if the integer
9493 expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
9494 errno acquires the value EDOM; if the integer expression math_errhandling &
9495 MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised.
9496 3 Similarly, a pole error (also known as a singularity or infinitary) occurs if the
9497 mathematical function has an exact infinite result as the finite input argument(s) are
9498 approached in the limit (for example, log(0.0)). The description of each function lists
9499 any required pole errors; an implementation may define additional pole errors, provided
9500 that such errors are consistent with the mathematical definition of the function. On a pole
9501 error, the function returns an implementation-defined value; if the integer expression
9504 <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
9505 error if the mathematical domain of the function does not include the infinity.
9507 [<a name="p232" href="#p232">page 232</a>] (<a href="#Contents">Contents</a>)
9509 math_errhandling & MATH_ERRNO is nonzero, the integer expression errno
9510 acquires the value ERANGE; if the integer expression math_errhandling &
9511 MATH_ERREXCEPT is nonzero, the ''divide-by-zero'' floating-point exception is raised.
9512 4 Likewise, a range error occurs if the mathematical result of the function cannot be
9513 represented in an object of the specified type, due to extreme magnitude.
9514 5 A floating result overflows if the magnitude of the mathematical result is finite but so
9515 large that the mathematical result cannot be represented without extraordinary roundoff
9516 error in an object of the specified type. If a floating result overflows and default rounding
9517 is in effect, then the function returns the value of the macro HUGE_VAL, HUGE_VALF, or *
9518 HUGE_VALL according to the return type, with the same sign as the correct value of the
9519 function; if the integer expression math_errhandling & MATH_ERRNO is nonzero,
9520 the integer expression errno acquires the value ERANGE; if the integer expression
9521 math_errhandling & MATH_ERREXCEPT is nonzero, the ''overflow'' floating-
9522 point exception is raised.
9523 6 The result underflows if the magnitude of the mathematical result is so small that the
9524 mathematical result cannot be represented, without extraordinary roundoff error, in an
9525 object of the specified type.<sup><a href="#note229"><b>229)</b></a></sup> If the result underflows, the function returns an
9526 implementation-defined value whose magnitude is no greater than the smallest
9527 normalized positive number in the specified type; if the integer expression
9528 math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the
9529 value ERANGE is implementation-defined; if the integer expression
9530 math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow''
9531 floating-point exception is raised is implementation-defined.
9532 7 If a domain, pole, or range error occurs and the integer expression
9533 math_errhandling & MATH_ERRNO is zero,<sup><a href="#note230"><b>230)</b></a></sup> then errno shall either be set to
9534 the value corresponding to the error or left unmodified. If no such error occurs, errno
9535 shall be left unmodified regardless of the setting of math_errhandling.
9540 <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
9541 also ''flush-to-zero'' underflow.
9542 <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.
9544 [<a name="p233" href="#p233">page 233</a>] (<a href="#Contents">Contents</a>)
9546 <a name="7.12.2" href="#7.12.2"><b> 7.12.2 The FP_CONTRACT pragma</b></a>
9548 1 #include <a href="#7.12"><math.h></a>
9549 #pragma STDC FP_CONTRACT on-off-switch
9551 2 The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
9552 state is ''off'') the implementation to contract expressions (<a href="#6.5">6.5</a>). Each pragma can occur
9553 either outside external declarations or preceding all explicit declarations and statements
9554 inside a compound statement. When outside external declarations, the pragma takes
9555 effect from its occurrence until another FP_CONTRACT pragma is encountered, or until
9556 the end of the translation unit. When inside a compound statement, the pragma takes
9557 effect from its occurrence until another FP_CONTRACT pragma is encountered
9558 (including within a nested compound statement), or until the end of the compound
9559 statement; at the end of a compound statement the state for the pragma is restored to its
9560 condition just before the compound statement. If this pragma is used in any other
9561 context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
9562 implementation-defined.
9563 <a name="7.12.3" href="#7.12.3"><b> 7.12.3 Classification macros</b></a>
9564 1 In the synopses in this subclause, real-floating indicates that the argument shall be an
9565 expression of real floating type.
9566 <a name="7.12.3.1" href="#7.12.3.1"><b> 7.12.3.1 The fpclassify macro</b></a>
9568 1 #include <a href="#7.12"><math.h></a>
9569 int fpclassify(real-floating x);
9571 2 The fpclassify macro classifies its argument value as NaN, infinite, normal,
9572 subnormal, zero, or into another implementation-defined category. First, an argument
9573 represented in a format wider than its semantic type is converted to its semantic type.
9574 Then classification is based on the type of the argument.<sup><a href="#note231"><b>231)</b></a></sup>
9576 3 The fpclassify macro returns the value of the number classification macro
9577 appropriate to the value of its argument. *
9580 <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
9581 know the type that classification is based on. For example, a normal long double value might
9582 become subnormal when converted to double, and zero when converted to float.
9584 [<a name="p234" href="#p234">page 234</a>] (<a href="#Contents">Contents</a>)
9586 <a name="7.12.3.2" href="#7.12.3.2"><b> 7.12.3.2 The isfinite macro</b></a>
9588 1 #include <a href="#7.12"><math.h></a>
9589 int isfinite(real-floating x);
9591 2 The isfinite macro determines whether its argument has a finite value (zero,
9592 subnormal, or normal, and not infinite or NaN). First, an argument represented in a
9593 format wider than its semantic type is converted to its semantic type. Then determination
9594 is based on the type of the argument.
9596 3 The isfinite macro returns a nonzero value if and only if its argument has a finite
9598 <a name="7.12.3.3" href="#7.12.3.3"><b> 7.12.3.3 The isinf macro</b></a>
9600 1 #include <a href="#7.12"><math.h></a>
9601 int isinf(real-floating x);
9603 2 The isinf macro determines whether its argument value is an infinity (positive or
9604 negative). First, an argument represented in a format wider than its semantic type is
9605 converted to its semantic type. Then determination is based on the type of the argument.
9607 3 The isinf macro returns a nonzero value if and only if its argument has an infinite
9609 <a name="7.12.3.4" href="#7.12.3.4"><b> 7.12.3.4 The isnan macro</b></a>
9611 1 #include <a href="#7.12"><math.h></a>
9612 int isnan(real-floating x);
9614 2 The isnan macro determines whether its argument value is a NaN. First, an argument
9615 represented in a format wider than its semantic type is converted to its semantic type.
9616 Then determination is based on the type of the argument.<sup><a href="#note232"><b>232)</b></a></sup>
9619 <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
9620 NaNs in the evaluation type but not in the semantic type.
9622 [<a name="p235" href="#p235">page 235</a>] (<a href="#Contents">Contents</a>)
9625 3 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
9626 <a name="7.12.3.5" href="#7.12.3.5"><b> 7.12.3.5 The isnormal macro</b></a>
9628 1 #include <a href="#7.12"><math.h></a>
9629 int isnormal(real-floating x);
9631 2 The isnormal macro determines whether its argument value is normal (neither zero,
9632 subnormal, infinite, nor NaN). First, an argument represented in a format wider than its
9633 semantic type is converted to its semantic type. Then determination is based on the type
9636 3 The isnormal macro returns a nonzero value if and only if its argument has a normal
9638 <a name="7.12.3.6" href="#7.12.3.6"><b> 7.12.3.6 The signbit macro</b></a>
9640 1 #include <a href="#7.12"><math.h></a>
9641 int signbit(real-floating x);
9643 2 The signbit macro determines whether the sign of its argument value is negative.<sup><a href="#note233"><b>233)</b></a></sup>
9645 3 The signbit macro returns a nonzero value if and only if the sign of its argument value
9651 <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
9652 unsigned, it is treated as positive.
9654 [<a name="p236" href="#p236">page 236</a>] (<a href="#Contents">Contents</a>)
9656 <a name="7.12.4" href="#7.12.4"><b> 7.12.4 Trigonometric functions</b></a>
9657 <a name="7.12.4.1" href="#7.12.4.1"><b> 7.12.4.1 The acos functions</b></a>
9659 1 #include <a href="#7.12"><math.h></a>
9660 double acos(double x);
9661 float acosf(float x);
9662 long double acosl(long double x);
9664 2 The acos functions compute the principal value of the arc cosine of x. A domain error
9665 occurs for arguments not in the interval [-1, +1].
9667 3 The acos functions return arccos x in the interval [0, pi ] radians.
9668 <a name="7.12.4.2" href="#7.12.4.2"><b> 7.12.4.2 The asin functions</b></a>
9670 1 #include <a href="#7.12"><math.h></a>
9671 double asin(double x);
9672 float asinf(float x);
9673 long double asinl(long double x);
9675 2 The asin functions compute the principal value of the arc sine of x. A domain error
9676 occurs for arguments not in the interval [-1, +1].
9678 3 The asin functions return arcsin x in the interval [-pi /2, +pi /2] radians.
9679 <a name="7.12.4.3" href="#7.12.4.3"><b> 7.12.4.3 The atan functions</b></a>
9681 1 #include <a href="#7.12"><math.h></a>
9682 double atan(double x);
9683 float atanf(float x);
9684 long double atanl(long double x);
9686 2 The atan functions compute the principal value of the arc tangent of x.
9688 [<a name="p237" href="#p237">page 237</a>] (<a href="#Contents">Contents</a>)
9691 3 The atan functions return arctan x in the interval [-pi /2, +pi /2] radians.
9692 <a name="7.12.4.4" href="#7.12.4.4"><b> 7.12.4.4 The atan2 functions</b></a>
9694 1 #include <a href="#7.12"><math.h></a>
9695 double atan2(double y, double x);
9696 float atan2f(float y, float x);
9697 long double atan2l(long double y, long double x);
9699 2 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
9700 arguments to determine the quadrant of the return value. A domain error may occur if
9701 both arguments are zero.
9703 3 The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
9704 <a name="7.12.4.5" href="#7.12.4.5"><b> 7.12.4.5 The cos functions</b></a>
9706 1 #include <a href="#7.12"><math.h></a>
9707 double cos(double x);
9708 float cosf(float x);
9709 long double cosl(long double x);
9711 2 The cos functions compute the cosine of x (measured in radians).
9713 3 The cos functions return cos x.
9714 <a name="7.12.4.6" href="#7.12.4.6"><b> 7.12.4.6 The sin functions</b></a>
9716 1 #include <a href="#7.12"><math.h></a>
9717 double sin(double x);
9718 float sinf(float x);
9719 long double sinl(long double x);
9721 2 The sin functions compute the sine of x (measured in radians).
9723 [<a name="p238" href="#p238">page 238</a>] (<a href="#Contents">Contents</a>)
9726 3 The sin functions return sin x.
9727 <a name="7.12.4.7" href="#7.12.4.7"><b> 7.12.4.7 The tan functions</b></a>
9729 1 #include <a href="#7.12"><math.h></a>
9730 double tan(double x);
9731 float tanf(float x);
9732 long double tanl(long double x);
9734 2 The tan functions return the tangent of x (measured in radians).
9736 3 The tan functions return tan x.
9737 <a name="7.12.5" href="#7.12.5"><b> 7.12.5 Hyperbolic functions</b></a>
9738 <a name="7.12.5.1" href="#7.12.5.1"><b> 7.12.5.1 The acosh functions</b></a>
9740 1 #include <a href="#7.12"><math.h></a>
9741 double acosh(double x);
9742 float acoshf(float x);
9743 long double acoshl(long double x);
9745 2 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
9746 error occurs for arguments less than 1.
9748 3 The acosh functions return arcosh x in the interval [0, +(inf)].
9749 <a name="7.12.5.2" href="#7.12.5.2"><b> 7.12.5.2 The asinh functions</b></a>
9751 1 #include <a href="#7.12"><math.h></a>
9752 double asinh(double x);
9753 float asinhf(float x);
9754 long double asinhl(long double x);
9756 2 The asinh functions compute the arc hyperbolic sine of x.
9758 [<a name="p239" href="#p239">page 239</a>] (<a href="#Contents">Contents</a>)
9761 3 The asinh functions return arsinh x.
9762 <a name="7.12.5.3" href="#7.12.5.3"><b> 7.12.5.3 The atanh functions</b></a>
9764 1 #include <a href="#7.12"><math.h></a>
9765 double atanh(double x);
9766 float atanhf(float x);
9767 long double atanhl(long double x);
9769 2 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
9770 for arguments not in the interval [-1, +1]. A pole error may occur if the argument equals
9773 3 The atanh functions return artanh x.
9774 <a name="7.12.5.4" href="#7.12.5.4"><b> 7.12.5.4 The cosh functions</b></a>
9776 1 #include <a href="#7.12"><math.h></a>
9777 double cosh(double x);
9778 float coshf(float x);
9779 long double coshl(long double x);
9781 2 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
9782 magnitude of x is too large.
9784 3 The cosh functions return cosh x.
9785 <a name="7.12.5.5" href="#7.12.5.5"><b> 7.12.5.5 The sinh functions</b></a>
9787 1 #include <a href="#7.12"><math.h></a>
9788 double sinh(double x);
9789 float sinhf(float x);
9790 long double sinhl(long double x);
9792 2 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
9793 magnitude of x is too large.
9795 [<a name="p240" href="#p240">page 240</a>] (<a href="#Contents">Contents</a>)
9798 3 The sinh functions return sinh x.
9799 <a name="7.12.5.6" href="#7.12.5.6"><b> 7.12.5.6 The tanh functions</b></a>
9801 1 #include <a href="#7.12"><math.h></a>
9802 double tanh(double x);
9803 float tanhf(float x);
9804 long double tanhl(long double x);
9806 2 The tanh functions compute the hyperbolic tangent of x.
9808 3 The tanh functions return tanh x.
9809 <a name="7.12.6" href="#7.12.6"><b> 7.12.6 Exponential and logarithmic functions</b></a>
9810 <a name="7.12.6.1" href="#7.12.6.1"><b> 7.12.6.1 The exp functions</b></a>
9812 1 #include <a href="#7.12"><math.h></a>
9813 double exp(double x);
9814 float expf(float x);
9815 long double expl(long double x);
9817 2 The exp functions compute the base-e exponential of x. A range error occurs if the
9818 magnitude of x is too large.
9820 3 The exp functions return ex .
9821 <a name="7.12.6.2" href="#7.12.6.2"><b> 7.12.6.2 The exp2 functions</b></a>
9823 1 #include <a href="#7.12"><math.h></a>
9824 double exp2(double x);
9825 float exp2f(float x);
9826 long double exp2l(long double x);
9828 2 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
9829 magnitude of x is too large.
9831 [<a name="p241" href="#p241">page 241</a>] (<a href="#Contents">Contents</a>)
9834 3 The exp2 functions return 2x .
9835 <a name="7.12.6.3" href="#7.12.6.3"><b> 7.12.6.3 The expm1 functions</b></a>
9837 1 #include <a href="#7.12"><math.h></a>
9838 double expm1(double x);
9839 float expm1f(float x);
9840 long double expm1l(long double x);
9842 2 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
9843 error occurs if x is too large.<sup><a href="#note234"><b>234)</b></a></sup>
9845 3 The expm1 functions return ex - 1.
9846 <a name="7.12.6.4" href="#7.12.6.4"><b> 7.12.6.4 The frexp functions</b></a>
9848 1 #include <a href="#7.12"><math.h></a>
9849 double frexp(double value, int *exp);
9850 float frexpf(float value, int *exp);
9851 long double frexpl(long double value, int *exp);
9853 2 The frexp functions break a floating-point number into a normalized fraction and an
9854 integral power of 2. They store the integer in the int object pointed to by exp.
9856 3 If value is not a floating-point number or if the integral power of 2 is outside the range
9857 of int, the results are unspecified. Otherwise, the frexp functions return the value x,
9858 such that x has a magnitude in the interval [1/2, 1) or zero, and value equals x x 2*exp .
9859 If value is zero, both parts of the result are zero.
9864 <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.
9866 [<a name="p242" href="#p242">page 242</a>] (<a href="#Contents">Contents</a>)
9868 <a name="7.12.6.5" href="#7.12.6.5"><b> 7.12.6.5 The ilogb functions</b></a>
9870 1 #include <a href="#7.12"><math.h></a>
9871 int ilogb(double x);
9872 int ilogbf(float x);
9873 int ilogbl(long double x);
9875 2 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
9876 compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
9877 a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
9878 the corresponding logb function and casting the returned value to type int. A domain
9879 error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
9880 the range of the return type, the numeric result is unspecified.
9882 3 The ilogb functions return the exponent of x as a signed int value.
9883 Forward references: the logb functions (<a href="#7.12.6.11">7.12.6.11</a>).
9884 <a name="7.12.6.6" href="#7.12.6.6"><b> 7.12.6.6 The ldexp functions</b></a>
9886 1 #include <a href="#7.12"><math.h></a>
9887 double ldexp(double x, int exp);
9888 float ldexpf(float x, int exp);
9889 long double ldexpl(long double x, int exp);
9891 2 The ldexp functions multiply a floating-point number by an integral power of 2. A
9892 range error may occur.
9894 3 The ldexp functions return x x 2exp .
9895 <a name="7.12.6.7" href="#7.12.6.7"><b> 7.12.6.7 The log functions</b></a>
9897 1 #include <a href="#7.12"><math.h></a>
9898 double log(double x);
9899 float logf(float x);
9900 long double logl(long double x);
9902 [<a name="p243" href="#p243">page 243</a>] (<a href="#Contents">Contents</a>)
9905 2 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
9906 the argument is negative. A pole error may occur if the argument is zero.
9908 3 The log functions return loge x.
9909 <a name="7.12.6.8" href="#7.12.6.8"><b> 7.12.6.8 The log10 functions</b></a>
9911 1 #include <a href="#7.12"><math.h></a>
9912 double log10(double x);
9913 float log10f(float x);
9914 long double log10l(long double x);
9916 2 The log10 functions compute the base-10 (common) logarithm of x. A domain error
9917 occurs if the argument is negative. A pole error may occur if the argument is zero.
9919 3 The log10 functions return log10 x.
9920 <a name="7.12.6.9" href="#7.12.6.9"><b> 7.12.6.9 The log1p functions</b></a>
9922 1 #include <a href="#7.12"><math.h></a>
9923 double log1p(double x);
9924 float log1pf(float x);
9925 long double log1pl(long double x);
9927 2 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.<sup><a href="#note235"><b>235)</b></a></sup>
9928 A domain error occurs if the argument is less than -1. A pole error may occur if the
9931 3 The log1p functions return loge (1 + x).
9936 <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).
9938 [<a name="p244" href="#p244">page 244</a>] (<a href="#Contents">Contents</a>)
9940 <a name="7.12.6.10" href="#7.12.6.10"><b> 7.12.6.10 The log2 functions</b></a>
9942 1 #include <a href="#7.12"><math.h></a>
9943 double log2(double x);
9944 float log2f(float x);
9945 long double log2l(long double x);
9947 2 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
9948 argument is less than zero. A pole error may occur if the argument is zero.
9950 3 The log2 functions return log2 x.
9951 <a name="7.12.6.11" href="#7.12.6.11"><b> 7.12.6.11 The logb functions</b></a>
9953 1 #include <a href="#7.12"><math.h></a>
9954 double logb(double x);
9955 float logbf(float x);
9956 long double logbl(long double x);
9958 2 The logb functions extract the exponent of x, as a signed integer value in floating-point
9959 format. If x is subnormal it is treated as though it were normalized; thus, for positive
9961 1 <= x x FLT_RADIX-logb(x) < FLT_RADIX
9962 A domain error or pole error may occur if the argument is zero.
9964 3 The logb functions return the signed exponent of x.
9965 <a name="7.12.6.12" href="#7.12.6.12"><b> 7.12.6.12 The modf functions</b></a>
9967 1 #include <a href="#7.12"><math.h></a>
9968 double modf(double value, double *iptr);
9969 float modff(float value, float *iptr);
9970 long double modfl(long double value, long double *iptr);
9972 2 The modf functions break the argument value into integral and fractional parts, each of
9973 which has the same type and sign as the argument. They store the integral part (in
9975 [<a name="p245" href="#p245">page 245</a>] (<a href="#Contents">Contents</a>)
9977 floating-point format) in the object pointed to by iptr.
9979 3 The modf functions return the signed fractional part of value.
9980 <a name="7.12.6.13" href="#7.12.6.13"><b> 7.12.6.13 The scalbn and scalbln functions</b></a>
9982 1 #include <a href="#7.12"><math.h></a>
9983 double scalbn(double x, int n);
9984 float scalbnf(float x, int n);
9985 long double scalbnl(long double x, int n);
9986 double scalbln(double x, long int n);
9987 float scalblnf(float x, long int n);
9988 long double scalblnl(long double x, long int n);
9990 2 The scalbn and scalbln functions compute x x FLT_RADIXn efficiently, not
9991 normally by computing FLT_RADIXn explicitly. A range error may occur.
9993 3 The scalbn and scalbln functions return x x FLT_RADIXn .
9994 <a name="7.12.7" href="#7.12.7"><b> 7.12.7 Power and absolute-value functions</b></a>
9995 <a name="7.12.7.1" href="#7.12.7.1"><b> 7.12.7.1 The cbrt functions</b></a>
9997 1 #include <a href="#7.12"><math.h></a>
9998 double cbrt(double x);
9999 float cbrtf(float x);
10000 long double cbrtl(long double x);
10001 <b> Description</b>
10002 2 The cbrt functions compute the real cube root of x.
10004 3 The cbrt functions return x1/3 .
10006 [<a name="p246" href="#p246">page 246</a>] (<a href="#Contents">Contents</a>)
10008 <a name="7.12.7.2" href="#7.12.7.2"><b> 7.12.7.2 The fabs functions</b></a>
10010 1 #include <a href="#7.12"><math.h></a>
10011 double fabs(double x);
10012 float fabsf(float x);
10013 long double fabsl(long double x);
10014 <b> Description</b>
10015 2 The fabs functions compute the absolute value of a floating-point number x.
10017 3 The fabs functions return | x |.
10018 <a name="7.12.7.3" href="#7.12.7.3"><b> 7.12.7.3 The hypot functions</b></a>
10020 1 #include <a href="#7.12"><math.h></a>
10021 double hypot(double x, double y);
10022 float hypotf(float x, float y);
10023 long double hypotl(long double x, long double y);
10024 <b> Description</b>
10025 2 The hypot functions compute the square root of the sum of the squares of x and y,
10026 without undue overflow or underflow. A range error may occur.
10028 4 The hypot functions return (sqrt)x2 + y2 .
10031 <a name="7.12.7.4" href="#7.12.7.4"><b> 7.12.7.4 The pow functions</b></a>
10033 1 #include <a href="#7.12"><math.h></a>
10034 double pow(double x, double y);
10035 float powf(float x, float y);
10036 long double powl(long double x, long double y);
10037 <b> Description</b>
10038 2 The pow functions compute x raised to the power y. A domain error occurs if x is finite
10039 and negative and y is finite and not an integer value. A range error may occur. A domain
10040 error may occur if x is zero and y is zero. A domain error or pole error may occur if x is
10041 zero and y is less than zero.
10043 [<a name="p247" href="#p247">page 247</a>] (<a href="#Contents">Contents</a>)
10046 3 The pow functions return xy .
10047 <a name="7.12.7.5" href="#7.12.7.5"><b> 7.12.7.5 The sqrt functions</b></a>
10049 1 #include <a href="#7.12"><math.h></a>
10050 double sqrt(double x);
10051 float sqrtf(float x);
10052 long double sqrtl(long double x);
10053 <b> Description</b>
10054 2 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
10055 the argument is less than zero.
10057 3 The sqrt functions return (sqrt)x.
10060 <a name="7.12.8" href="#7.12.8"><b> 7.12.8 Error and gamma functions</b></a>
10061 <a name="7.12.8.1" href="#7.12.8.1"><b> 7.12.8.1 The erf functions</b></a>
10063 1 #include <a href="#7.12"><math.h></a>
10064 double erf(double x);
10065 float erff(float x);
10066 long double erfl(long double x);
10067 <b> Description</b>
10068 2 The erf functions compute the error function of x.
10073 The erf functions return erf x =
10078 <a name="7.12.8.2" href="#7.12.8.2"><b> 7.12.8.2 The erfc functions</b></a>
10080 1 #include <a href="#7.12"><math.h></a>
10081 double erfc(double x);
10082 float erfcf(float x);
10083 long double erfcl(long double x);
10084 <b> Description</b>
10085 2 The erfc functions compute the complementary error function of x. A range error
10086 occurs if x is too large.
10088 [<a name="p248" href="#p248">page 248</a>] (<a href="#Contents">Contents</a>)
10094 The erfc functions return erfc x = 1 - erf x =
10099 <a name="7.12.8.3" href="#7.12.8.3"><b> 7.12.8.3 The lgamma functions</b></a>
10101 1 #include <a href="#7.12"><math.h></a>
10102 double lgamma(double x);
10103 float lgammaf(float x);
10104 long double lgammal(long double x);
10105 <b> Description</b>
10106 2 The lgamma functions compute the natural logarithm of the absolute value of gamma of
10107 x. A range error occurs if x is too large. A pole error may occur if x is a negative integer
10110 3 The lgamma functions return loge | (Gamma)(x) |.
10111 <a name="7.12.8.4" href="#7.12.8.4"><b> 7.12.8.4 The tgamma functions</b></a>
10113 1 #include <a href="#7.12"><math.h></a>
10114 double tgamma(double x);
10115 float tgammaf(float x);
10116 long double tgammal(long double x);
10117 <b> Description</b>
10118 2 The tgamma functions compute the gamma function of x. A domain error or pole error
10119 may occur if x is a negative integer or zero. A range error occurs if the magnitude of x is
10120 too large and may occur if the magnitude of x is too small.
10122 3 The tgamma functions return (Gamma)(x).
10124 [<a name="p249" href="#p249">page 249</a>] (<a href="#Contents">Contents</a>)
10126 <a name="7.12.9" href="#7.12.9"><b> 7.12.9 Nearest integer functions</b></a>
10127 <a name="7.12.9.1" href="#7.12.9.1"><b> 7.12.9.1 The ceil functions</b></a>
10129 1 #include <a href="#7.12"><math.h></a>
10130 double ceil(double x);
10131 float ceilf(float x);
10132 long double ceill(long double x);
10133 <b> Description</b>
10134 2 The ceil functions compute the smallest integer value not less than x.
10136 3 The ceil functions return [^x^], expressed as a floating-point number.
10137 <a name="7.12.9.2" href="#7.12.9.2"><b> 7.12.9.2 The floor functions</b></a>
10139 1 #include <a href="#7.12"><math.h></a>
10140 double floor(double x);
10141 float floorf(float x);
10142 long double floorl(long double x);
10143 <b> Description</b>
10144 2 The floor functions compute the largest integer value not greater than x.
10146 3 The floor functions return [_x_], expressed as a floating-point number.
10147 <a name="7.12.9.3" href="#7.12.9.3"><b> 7.12.9.3 The nearbyint functions</b></a>
10149 1 #include <a href="#7.12"><math.h></a>
10150 double nearbyint(double x);
10151 float nearbyintf(float x);
10152 long double nearbyintl(long double x);
10153 <b> Description</b>
10154 2 The nearbyint functions round their argument to an integer value in floating-point
10155 format, using the current rounding direction and without raising the ''inexact'' floating-
10158 [<a name="p250" href="#p250">page 250</a>] (<a href="#Contents">Contents</a>)
10161 3 The nearbyint functions return the rounded integer value.
10162 <a name="7.12.9.4" href="#7.12.9.4"><b> 7.12.9.4 The rint functions</b></a>
10164 1 #include <a href="#7.12"><math.h></a>
10165 double rint(double x);
10166 float rintf(float x);
10167 long double rintl(long double x);
10168 <b> Description</b>
10169 2 The rint functions differ from the nearbyint functions (<a href="#7.12.9.3">7.12.9.3</a>) only in that the
10170 rint functions may raise the ''inexact'' floating-point exception if the result differs in
10171 value from the argument.
10173 3 The rint functions return the rounded integer value.
10174 <a name="7.12.9.5" href="#7.12.9.5"><b> 7.12.9.5 The lrint and llrint functions</b></a>
10176 1 #include <a href="#7.12"><math.h></a>
10177 long int lrint(double x);
10178 long int lrintf(float x);
10179 long int lrintl(long double x);
10180 long long int llrint(double x);
10181 long long int llrintf(float x);
10182 long long int llrintl(long double x);
10183 <b> Description</b>
10184 2 The lrint and llrint functions round their argument to the nearest integer value,
10185 rounding according to the current rounding direction. If the rounded value is outside the
10186 range of the return type, the numeric result is unspecified and a domain error or range
10189 3 The lrint and llrint functions return the rounded integer value.
10191 [<a name="p251" href="#p251">page 251</a>] (<a href="#Contents">Contents</a>)
10193 <a name="7.12.9.6" href="#7.12.9.6"><b> 7.12.9.6 The round functions</b></a>
10195 1 #include <a href="#7.12"><math.h></a>
10196 double round(double x);
10197 float roundf(float x);
10198 long double roundl(long double x);
10199 <b> Description</b>
10200 2 The round functions round their argument to the nearest integer value in floating-point
10201 format, rounding halfway cases away from zero, regardless of the current rounding
10204 3 The round functions return the rounded integer value.
10205 <a name="7.12.9.7" href="#7.12.9.7"><b> 7.12.9.7 The lround and llround functions</b></a>
10207 1 #include <a href="#7.12"><math.h></a>
10208 long int lround(double x);
10209 long int lroundf(float x);
10210 long int lroundl(long double x);
10211 long long int llround(double x);
10212 long long int llroundf(float x);
10213 long long int llroundl(long double x);
10214 <b> Description</b>
10215 2 The lround and llround functions round their argument to the nearest integer value,
10216 rounding halfway cases away from zero, regardless of the current rounding direction. If
10217 the rounded value is outside the range of the return type, the numeric result is unspecified
10218 and a domain error or range error may occur.
10220 3 The lround and llround functions return the rounded integer value.
10221 <a name="7.12.9.8" href="#7.12.9.8"><b> 7.12.9.8 The trunc functions</b></a>
10223 1 #include <a href="#7.12"><math.h></a>
10224 double trunc(double x);
10225 float truncf(float x);
10226 long double truncl(long double x);
10228 [<a name="p252" href="#p252">page 252</a>] (<a href="#Contents">Contents</a>)
10230 <b> Description</b>
10231 2 The trunc functions round their argument to the integer value, in floating format,
10232 nearest to but no larger in magnitude than the argument.
10234 3 The trunc functions return the truncated integer value.
10235 <a name="7.12.10" href="#7.12.10"><b> 7.12.10 Remainder functions</b></a>
10236 <a name="7.12.10.1" href="#7.12.10.1"><b> 7.12.10.1 The fmod functions</b></a>
10238 1 #include <a href="#7.12"><math.h></a>
10239 double fmod(double x, double y);
10240 float fmodf(float x, float y);
10241 long double fmodl(long double x, long double y);
10242 <b> Description</b>
10243 2 The fmod functions compute the floating-point remainder of x/y.
10245 3 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
10246 the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
10247 whether a domain error occurs or the fmod functions return zero is implementation-
10249 <a name="7.12.10.2" href="#7.12.10.2"><b> 7.12.10.2 The remainder functions</b></a>
10251 1 #include <a href="#7.12"><math.h></a>
10252 double remainder(double x, double y);
10253 float remainderf(float x, float y);
10254 long double remainderl(long double x, long double y);
10255 <b> Description</b>
10256 2 The remainder functions compute the remainder x REM y required by IEC 60559.<sup><a href="#note236"><b>236)</b></a></sup>
10261 <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
10262 mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever
10263 | n - x/y | = 1/2, then n is even. If r = 0, its sign shall be that of x.'' This definition is applicable for *
10264 all implementations.
10266 [<a name="p253" href="#p253">page 253</a>] (<a href="#Contents">Contents</a>)
10269 3 The remainder functions return x REM y. If y is zero, whether a domain error occurs
10270 or the functions return zero is implementation defined.
10271 <a name="7.12.10.3" href="#7.12.10.3"><b> 7.12.10.3 The remquo functions</b></a>
10273 1 #include <a href="#7.12"><math.h></a>
10274 double remquo(double x, double y, int *quo);
10275 float remquof(float x, float y, int *quo);
10276 long double remquol(long double x, long double y,
10278 <b> Description</b>
10279 2 The remquo functions compute the same remainder as the remainder functions. In
10280 the object pointed to by quo they store a value whose sign is the sign of x/y and whose
10281 magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where
10282 n is an implementation-defined integer greater than or equal to 3.
10284 3 The remquo functions return x REM y. If y is zero, the value stored in the object
10285 pointed to by quo is unspecified and whether a domain error occurs or the functions
10286 return zero is implementation defined.
10287 <a name="7.12.11" href="#7.12.11"><b> 7.12.11 Manipulation functions</b></a>
10288 <a name="7.12.11.1" href="#7.12.11.1"><b> 7.12.11.1 The copysign functions</b></a>
10290 1 #include <a href="#7.12"><math.h></a>
10291 double copysign(double x, double y);
10292 float copysignf(float x, float y);
10293 long double copysignl(long double x, long double y);
10294 <b> Description</b>
10295 2 The copysign functions produce a value with the magnitude of x and the sign of y.
10296 They produce a NaN (with the sign of y) if x is a NaN. On implementations that
10297 represent a signed zero but do not treat negative zero consistently in arithmetic
10298 operations, the copysign functions regard the sign of zero as positive.
10300 3 The copysign functions return a value with the magnitude of x and the sign of y.
10302 [<a name="p254" href="#p254">page 254</a>] (<a href="#Contents">Contents</a>)
10304 <a name="7.12.11.2" href="#7.12.11.2"><b> 7.12.11.2 The nan functions</b></a>
10306 1 #include <a href="#7.12"><math.h></a>
10307 double nan(const char *tagp);
10308 float nanf(const char *tagp);
10309 long double nanl(const char *tagp);
10310 <b> Description</b>
10311 2 The call nan("n-char-sequence") is equivalent to strtod("NAN(n-char-
10312 sequence)", (char**) NULL); the call nan("") is equivalent to
10313 strtod("NAN()", (char**) NULL). If tagp does not point to an n-char
10314 sequence or an empty string, the call is equivalent to strtod("NAN", (char**)
10315 NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof
10318 3 The nan functions return a quiet NaN, if available, with content indicated through tagp.
10319 If the implementation does not support quiet NaNs, the functions return zero.
10320 Forward references: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
10321 <a name="7.12.11.3" href="#7.12.11.3"><b> 7.12.11.3 The nextafter functions</b></a>
10323 1 #include <a href="#7.12"><math.h></a>
10324 double nextafter(double x, double y);
10325 float nextafterf(float x, float y);
10326 long double nextafterl(long double x, long double y);
10327 <b> Description</b>
10328 2 The nextafter functions determine the next representable value, in the type of the
10329 function, after x in the direction of y, where x and y are first converted to the type of the
10330 function.<sup><a href="#note237"><b>237)</b></a></sup> The nextafter functions return y if x equals y. A range error may occur
10331 if the magnitude of x is the largest finite value representable in the type and the result is
10332 infinite or not representable in the type.
10334 3 The nextafter functions return the next representable value in the specified format
10335 after x in the direction of y.
10338 <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
10341 [<a name="p255" href="#p255">page 255</a>] (<a href="#Contents">Contents</a>)
10343 <a name="7.12.11.4" href="#7.12.11.4"><b> 7.12.11.4 The nexttoward functions</b></a>
10345 1 #include <a href="#7.12"><math.h></a>
10346 double nexttoward(double x, long double y);
10347 float nexttowardf(float x, long double y);
10348 long double nexttowardl(long double x, long double y);
10349 <b> Description</b>
10350 2 The nexttoward functions are equivalent to the nextafter functions except that the
10351 second parameter has type long double and the functions return y converted to the
10352 type of the function if x equals y.<sup><a href="#note238"><b>238)</b></a></sup>
10353 <a name="7.12.12" href="#7.12.12"><b> 7.12.12 Maximum, minimum, and positive difference functions</b></a>
10354 <a name="7.12.12.1" href="#7.12.12.1"><b> 7.12.12.1 The fdim functions</b></a>
10356 1 #include <a href="#7.12"><math.h></a>
10357 double fdim(double x, double y);
10358 float fdimf(float x, float y);
10359 long double fdiml(long double x, long double y);
10360 <b> Description</b>
10361 2 The fdim functions determine the positive difference between their arguments:
10365 A range error may occur.
10367 3 The fdim functions return the positive difference value.
10368 <a name="7.12.12.2" href="#7.12.12.2"><b> 7.12.12.2 The fmax functions</b></a>
10370 1 #include <a href="#7.12"><math.h></a>
10371 double fmax(double x, double y);
10372 float fmaxf(float x, float y);
10373 long double fmaxl(long double x, long double y);
10377 <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
10378 range or precision in a floating second argument.
10380 [<a name="p256" href="#p256">page 256</a>] (<a href="#Contents">Contents</a>)
10382 <b> Description</b>
10383 2 The fmax functions determine the maximum numeric value of their arguments.<sup><a href="#note239"><b>239)</b></a></sup>
10385 3 The fmax functions return the maximum numeric value of their arguments.
10386 <a name="7.12.12.3" href="#7.12.12.3"><b> 7.12.12.3 The fmin functions</b></a>
10388 1 #include <a href="#7.12"><math.h></a>
10389 double fmin(double x, double y);
10390 float fminf(float x, float y);
10391 long double fminl(long double x, long double y);
10392 <b> Description</b>
10393 2 The fmin functions determine the minimum numeric value of their arguments.<sup><a href="#note240"><b>240)</b></a></sup>
10395 3 The fmin functions return the minimum numeric value of their arguments.
10396 <a name="7.12.13" href="#7.12.13"><b> 7.12.13 Floating multiply-add</b></a>
10397 <a name="7.12.13.1" href="#7.12.13.1"><b> 7.12.13.1 The fma functions</b></a>
10399 1 #include <a href="#7.12"><math.h></a>
10400 double fma(double x, double y, double z);
10401 float fmaf(float x, float y, float z);
10402 long double fmal(long double x, long double y,
10404 <b> Description</b>
10405 2 The fma functions compute (x x y) + z, rounded as one ternary operation: they compute
10406 the value (as if) to infinite precision and round once to the result format, according to the
10407 current rounding mode. A range error may occur.
10409 3 The fma functions return (x x y) + z, rounded as one ternary operation.
10414 <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
10415 fmax functions choose the numeric value. See <a href="#F.10.9.2">F.10.9.2</a>.
10416 <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.
10418 [<a name="p257" href="#p257">page 257</a>] (<a href="#Contents">Contents</a>)
10420 <a name="7.12.14" href="#7.12.14"><b> 7.12.14 Comparison macros</b></a>
10421 1 The relational and equality operators support the usual mathematical relationships
10422 between numeric values. For any ordered pair of numeric values exactly one of the
10423 relationships -- less, greater, and equal -- is true. Relational operators may raise the
10424 ''invalid'' floating-point exception when argument values are NaNs. For a NaN and a
10425 numeric value, or for two NaNs, just the unordered relationship is true.<sup><a href="#note241"><b>241)</b></a></sup> The following
10426 subclauses provide macros that are quiet (non floating-point exception raising) versions
10427 of the relational operators, and other comparison macros that facilitate writing efficient
10428 code that accounts for NaNs without suffering the ''invalid'' floating-point exception. In
10429 the synopses in this subclause, real-floating indicates that the argument shall be an
10430 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>
10431 <a name="7.12.14.1" href="#7.12.14.1"><b> 7.12.14.1 The isgreater macro</b></a>
10433 1 #include <a href="#7.12"><math.h></a>
10434 int isgreater(real-floating x, real-floating y);
10435 <b> Description</b>
10436 2 The isgreater macro determines whether its first argument is greater than its second
10437 argument. The value of isgreater(x, y) is always equal to (x) > (y); however,
10438 unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point
10439 exception when x and y are unordered.
10441 3 The isgreater macro returns the value of (x) > (y).
10442 <a name="7.12.14.2" href="#7.12.14.2"><b> 7.12.14.2 The isgreaterequal macro</b></a>
10444 1 #include <a href="#7.12"><math.h></a>
10445 int isgreaterequal(real-floating x, real-floating y);
10450 <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
10451 the operands compare unordered, as an error indicator for programs written without consideration of
10452 NaNs; the result in these cases is false.
10453 <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
10455 <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
10456 type is unspecified.
10458 [<a name="p258" href="#p258">page 258</a>] (<a href="#Contents">Contents</a>)
10460 <b> Description</b>
10461 2 The isgreaterequal macro determines whether its first argument is greater than or
10462 equal to its second argument. The value of isgreaterequal(x, y) is always equal
10463 to (x) >= (y); however, unlike (x) >= (y), isgreaterequal(x, y) does
10464 not raise the ''invalid'' floating-point exception when x and y are unordered.
10466 3 The isgreaterequal macro returns the value of (x) >= (y).
10467 <a name="7.12.14.3" href="#7.12.14.3"><b> 7.12.14.3 The isless macro</b></a>
10469 1 #include <a href="#7.12"><math.h></a>
10470 int isless(real-floating x, real-floating y);
10471 <b> Description</b>
10472 2 The isless macro determines whether its first argument is less than its second
10473 argument. The value of isless(x, y) is always equal to (x) < (y); however,
10474 unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point
10475 exception when x and y are unordered.
10477 3 The isless macro returns the value of (x) < (y).
10478 <a name="7.12.14.4" href="#7.12.14.4"><b> 7.12.14.4 The islessequal macro</b></a>
10480 1 #include <a href="#7.12"><math.h></a>
10481 int islessequal(real-floating x, real-floating y);
10482 <b> Description</b>
10483 2 The islessequal macro determines whether its first argument is less than or equal to
10484 its second argument. The value of islessequal(x, y) is always equal to
10485 (x) <= (y); however, unlike (x) <= (y), islessequal(x, y) does not raise
10486 the ''invalid'' floating-point exception when x and y are unordered.
10488 3 The islessequal macro returns the value of (x) <= (y).
10490 [<a name="p259" href="#p259">page 259</a>] (<a href="#Contents">Contents</a>)
10492 <a name="7.12.14.5" href="#7.12.14.5"><b> 7.12.14.5 The islessgreater macro</b></a>
10494 1 #include <a href="#7.12"><math.h></a>
10495 int islessgreater(real-floating x, real-floating y);
10496 <b> Description</b>
10497 2 The islessgreater macro determines whether its first argument is less than or
10498 greater than its second argument. The islessgreater(x, y) macro is similar to
10499 (x) < (y) || (x) > (y); however, islessgreater(x, y) does not raise
10500 the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x
10503 3 The islessgreater macro returns the value of (x) < (y) || (x) > (y).
10504 <a name="7.12.14.6" href="#7.12.14.6"><b> 7.12.14.6 The isunordered macro</b></a>
10506 1 #include <a href="#7.12"><math.h></a>
10507 int isunordered(real-floating x, real-floating y);
10508 <b> Description</b>
10509 2 The isunordered macro determines whether its arguments are unordered.
10511 3 The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
10513 [<a name="p260" href="#p260">page 260</a>] (<a href="#Contents">Contents</a>)
10515 <a name="7.13" href="#7.13"><b> 7.13 Nonlocal jumps <setjmp.h></b></a>
10516 1 The header <a href="#7.13"><setjmp.h></a> defines the macro setjmp, and declares one function and
10517 one type, for bypassing the normal function call and return discipline.<sup><a href="#note244"><b>244)</b></a></sup>
10518 2 The type declared is
10520 which is an array type suitable for holding the information needed to restore a calling
10521 environment. The environment of a call to the setjmp macro consists of information
10522 sufficient for a call to the longjmp function to return execution to the correct block and
10523 invocation of that block, were it called recursively. It does not include the state of the
10524 floating-point status flags, of open files, or of any other component of the abstract
10526 3 It is unspecified whether setjmp is a macro or an identifier declared with external
10527 linkage. If a macro definition is suppressed in order to access an actual function, or a
10528 program defines an external identifier with the name setjmp, the behavior is undefined.
10529 <a name="7.13.1" href="#7.13.1"><b> 7.13.1 Save calling environment</b></a>
10530 <a name="7.13.1.1" href="#7.13.1.1"><b> 7.13.1.1 The setjmp macro</b></a>
10532 1 #include <a href="#7.13"><setjmp.h></a>
10533 int setjmp(jmp_buf env);
10534 <b> Description</b>
10535 2 The setjmp macro saves its calling environment in its jmp_buf argument for later use
10536 by the longjmp function.
10538 3 If the return is from a direct invocation, the setjmp macro returns the value zero. If the
10539 return is from a call to the longjmp function, the setjmp macro returns a nonzero
10541 Environmental limits
10542 4 An invocation of the setjmp macro shall appear only in one of the following contexts:
10543 -- the entire controlling expression of a selection or iteration statement;
10544 -- one operand of a relational or equality operator with the other operand an integer
10545 constant expression, with the resulting expression being the entire controlling
10548 <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
10551 [<a name="p261" href="#p261">page 261</a>] (<a href="#Contents">Contents</a>)
10553 expression of a selection or iteration statement;
10554 -- the operand of a unary ! operator with the resulting expression being the entire
10555 controlling expression of a selection or iteration statement; or
10556 -- the entire expression of an expression statement (possibly cast to void).
10557 5 If the invocation appears in any other context, the behavior is undefined.
10558 <a name="7.13.2" href="#7.13.2"><b> 7.13.2 Restore calling environment</b></a>
10559 <a name="7.13.2.1" href="#7.13.2.1"><b> 7.13.2.1 The longjmp function</b></a>
10561 1 #include <a href="#7.13"><setjmp.h></a>
10562 _Noreturn void longjmp(jmp_buf env, int val);
10563 <b> Description</b>
10564 2 The longjmp function restores the environment saved by the most recent invocation of
10565 the setjmp macro in the same invocation of the program with the corresponding
10566 jmp_buf argument. If there has been no such invocation, or if the function containing
10567 the invocation of the setjmp macro has terminated execution<sup><a href="#note245"><b>245)</b></a></sup> in the interim, or if the
10568 invocation of the setjmp macro was within the scope of an identifier with variably
10569 modified type and execution has left that scope in the interim, the behavior is undefined.
10570 3 All accessible objects have values, and all other components of the abstract machine<sup><a href="#note246"><b>246)</b></a></sup>
10571 have state, as of the time the longjmp function was called, except that the values of
10572 objects of automatic storage duration that are local to the function containing the
10573 invocation of the corresponding setjmp macro that do not have volatile-qualified type
10574 and have been changed between the setjmp invocation and longjmp call are
10577 4 After longjmp is completed, program execution continues as if the corresponding
10578 invocation of the setjmp macro had just returned the value specified by val. The
10579 longjmp function cannot cause the setjmp macro to return the value 0; if val is 0,
10580 the setjmp macro returns the value 1.
10581 5 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation
10582 might cause memory associated with a variable length array object to be squandered.
10587 <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
10588 transfer to a setjmp invocation in a function earlier in the set of nested calls.
10589 <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.
10591 [<a name="p262" href="#p262">page 262</a>] (<a href="#Contents">Contents</a>)
10593 #include <a href="#7.13"><setjmp.h></a>
10600 int x[n]; // valid: f is not terminated
10606 int a[n]; // a may remain allocated
10611 int b[n]; // b may remain allocated
10612 longjmp(buf, 2); // might cause memory loss
10615 [<a name="p263" href="#p263">page 263</a>] (<a href="#Contents">Contents</a>)
10617 <a name="7.14" href="#7.14"><b> 7.14 Signal handling <signal.h></b></a>
10618 1 The header <a href="#7.14"><signal.h></a> declares a type and two functions and defines several macros,
10619 for handling various signals (conditions that may be reported during program execution).
10620 2 The type defined is
10622 which is the (possibly volatile-qualified) integer type of an object that can be accessed as
10623 an atomic entity, even in the presence of asynchronous interrupts.
10624 3 The macros defined are
10628 which expand to constant expressions with distinct values that have type compatible with
10629 the second argument to, and the return value of, the signal function, and whose values
10630 compare unequal to the address of any declarable function; and the following, which
10631 expand to positive integer constant expressions with type int and distinct values that are
10632 the signal numbers, each corresponding to the specified condition:
10633 SIGABRT abnormal termination, such as is initiated by the abort function
10634 SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
10635 resulting in overflow
10636 SIGILL detection of an invalid function image, such as an invalid instruction
10637 SIGINT receipt of an interactive attention signal
10638 SIGSEGV an invalid access to storage
10639 SIGTERM a termination request sent to the program
10640 4 An implementation need not generate any of these signals, except as a result of explicit
10641 calls to the raise function. Additional signals and pointers to undeclarable functions,
10642 with macro definitions beginning, respectively, with the letters SIG and an uppercase
10643 letter or with SIG_ and an uppercase letter,<sup><a href="#note247"><b>247)</b></a></sup> may also be specified by the
10644 implementation. The complete set of signals, their semantics, and their default handling
10645 is implementation-defined; all signal numbers shall be positive.
10650 <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
10651 (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
10654 [<a name="p264" href="#p264">page 264</a>] (<a href="#Contents">Contents</a>)
10656 <a name="7.14.1" href="#7.14.1"><b> 7.14.1 Specify signal handling</b></a>
10657 <a name="7.14.1.1" href="#7.14.1.1"><b> 7.14.1.1 The signal function</b></a>
10659 1 #include <a href="#7.14"><signal.h></a>
10660 void (*signal(int sig, void (*func)(int)))(int);
10661 <b> Description</b>
10662 2 The signal function chooses one of three ways in which receipt of the signal number
10663 sig is to be subsequently handled. If the value of func is SIG_DFL, default handling
10664 for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored.
10665 Otherwise, func shall point to a function to be called when that signal occurs. An
10666 invocation of such a function because of a signal, or (recursively) of any further functions
10667 called by that invocation (other than functions in the standard library),<sup><a href="#note248"><b>248)</b></a></sup> is called a
10669 3 When a signal occurs and func points to a function, it is implementation-defined
10670 whether the equivalent of signal(sig, SIG_DFL); is executed or the
10671 implementation prevents some implementation-defined set of signals (at least including
10672 sig) from occurring until the current signal handling has completed; in the case of
10673 SIGILL, the implementation may alternatively define that no action is taken. Then the
10674 equivalent of (*func)(sig); is executed. If and when the function returns, if the
10675 value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined
10676 value corresponding to a computational exception, the behavior is undefined; otherwise
10677 the program will resume execution at the point it was interrupted.
10678 4 If the signal occurs as the result of calling the abort or raise function, the signal
10679 handler shall not call the raise function.
10680 5 If the signal occurs other than as the result of calling the abort or raise function, the
10681 behavior is undefined if the signal handler refers to any object with static or thread
10682 storage duration that is not a lock-free atomic object other than by assigning a value to an
10683 object declared as volatile sig_atomic_t, or the signal handler calls any function
10684 in the standard library other than the abort function, the _Exit function, the
10685 quick_exit function, or the signal function with the first argument equal to the
10686 signal number corresponding to the signal that caused the invocation of the handler.
10687 Furthermore, if such a call to the signal function results in a SIG_ERR return, the
10688 value of errno is indeterminate.<sup><a href="#note249"><b>249)</b></a></sup>
10691 <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
10692 called via the abort function).
10693 <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.
10695 [<a name="p265" href="#p265">page 265</a>] (<a href="#Contents">Contents</a>)
10697 6 At program startup, the equivalent of
10698 signal(sig, SIG_IGN);
10699 may be executed for some signals selected in an implementation-defined manner; the
10701 signal(sig, SIG_DFL);
10702 is executed for all other signals defined by the implementation.
10703 7 The implementation shall behave as if no library function calls the signal function.
10705 8 If the request can be honored, the signal function returns the value of func for the
10706 most recent successful call to signal for the specified signal sig. Otherwise, a value of
10707 SIG_ERR is returned and a positive value is stored in errno.
10708 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
10709 _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>).
10710 <a name="7.14.2" href="#7.14.2"><b> 7.14.2 Send signal</b></a>
10711 <a name="7.14.2.1" href="#7.14.2.1"><b> 7.14.2.1 The raise function</b></a>
10713 1 #include <a href="#7.14"><signal.h></a>
10714 int raise(int sig);
10715 <b> Description</b>
10716 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
10717 signal handler is called, the raise function shall not return until after the signal handler
10720 3 The raise function returns zero if successful, nonzero if unsuccessful.
10722 [<a name="p266" href="#p266">page 266</a>] (<a href="#Contents">Contents</a>)
10724 <a name="7.15" href="#7.15"><b> 7.15 Alignment <stdalign.h></b></a>
10725 1 The header <a href="#7.15"><stdalign.h></a> defines two macros.
10728 expands to _Alignas.
10729 3 The remaining macro is suitable for use in #if preprocessing directives. It is
10730 __alignas_is_defined
10731 which expands to the integer constant 1.
10733 [<a name="p267" href="#p267">page 267</a>] (<a href="#Contents">Contents</a>)
10735 <a name="7.16" href="#7.16"><b> 7.16 Variable arguments <stdarg.h></b></a>
10736 1 The header <a href="#7.16"><stdarg.h></a> declares a type and defines four macros, for advancing
10737 through a list of arguments whose number and types are not known to the called function
10738 when it is translated.
10739 2 A function may be called with a variable number of arguments of varying types. As
10740 described in <a href="#6.9.1">6.9.1</a>, its parameter list contains one or more parameters. The rightmost
10741 parameter plays a special role in the access mechanism, and will be designated parmN in
10743 3 The type declared is
10745 which is a complete object type suitable for holding information needed by the macros
10746 va_start, va_arg, va_end, and va_copy. If access to the varying arguments is
10747 desired, the called function shall declare an object (generally referred to as ap in this
10748 subclause) having type va_list. The object ap may be passed as an argument to
10749 another function; if that function invokes the va_arg macro with parameter ap, the
10750 value of ap in the calling function is indeterminate and shall be passed to the va_end
10751 macro prior to any further reference to ap.<sup><a href="#note250"><b>250)</b></a></sup>
10752 <a name="7.16.1" href="#7.16.1"><b> 7.16.1 Variable argument list access macros</b></a>
10753 1 The va_start and va_arg macros described in this subclause shall be implemented
10754 as macros, not functions. It is unspecified whether va_copy and va_end are macros or
10755 identifiers declared with external linkage. If a macro definition is suppressed in order to
10756 access an actual function, or a program defines an external identifier with the same name,
10757 the behavior is undefined. Each invocation of the va_start and va_copy macros
10758 shall be matched by a corresponding invocation of the va_end macro in the same
10760 <a name="7.16.1.1" href="#7.16.1.1"><b> 7.16.1.1 The va_arg macro</b></a>
10762 1 #include <a href="#7.16"><stdarg.h></a>
10763 type va_arg(va_list ap, type);
10764 <b> Description</b>
10765 2 The va_arg macro expands to an expression that has the specified type and the value of
10766 the next argument in the call. The parameter ap shall have been initialized by the
10767 va_start or va_copy macro (without an intervening invocation of the va_end
10769 <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
10770 case the original function may make further use of the original list after the other function returns.
10772 [<a name="p268" href="#p268">page 268</a>] (<a href="#Contents">Contents</a>)
10774 macro for the same ap). Each invocation of the va_arg macro modifies ap so that the
10775 values of successive arguments are returned in turn. The parameter type shall be a type
10776 name specified such that the type of a pointer to an object that has the specified type can
10777 be obtained simply by postfixing a * to type. If there is no actual next argument, or if
10778 type is not compatible with the type of the actual next argument (as promoted according
10779 to the default argument promotions), the behavior is undefined, except for the following
10781 -- one type is a signed integer type, the other type is the corresponding unsigned integer
10782 type, and the value is representable in both types;
10783 -- one type is pointer to void and the other is a pointer to a character type.
10785 3 The first invocation of the va_arg macro after that of the va_start macro returns the
10786 value of the argument after that specified by parmN . Successive invocations return the
10787 values of the remaining arguments in succession.
10788 <a name="7.16.1.2" href="#7.16.1.2"><b> 7.16.1.2 The va_copy macro</b></a>
10790 1 #include <a href="#7.16"><stdarg.h></a>
10791 void va_copy(va_list dest, va_list src);
10792 <b> Description</b>
10793 2 The va_copy macro initializes dest as a copy of src, as if the va_start macro had
10794 been applied to dest followed by the same sequence of uses of the va_arg macro as
10795 had previously been used to reach the present state of src. Neither the va_copy nor
10796 va_start macro shall be invoked to reinitialize dest without an intervening
10797 invocation of the va_end macro for the same dest.
10799 3 The va_copy macro returns no value.
10800 <a name="7.16.1.3" href="#7.16.1.3"><b> 7.16.1.3 The va_end macro</b></a>
10802 1 #include <a href="#7.16"><stdarg.h></a>
10803 void va_end(va_list ap);
10804 <b> Description</b>
10805 2 The va_end macro facilitates a normal return from the function whose variable
10806 argument list was referred to by the expansion of the va_start macro, or the function
10807 containing the expansion of the va_copy macro, that initialized the va_list ap. The
10808 va_end macro may modify ap so that it is no longer usable (without being reinitialized
10810 [<a name="p269" href="#p269">page 269</a>] (<a href="#Contents">Contents</a>)
10812 by the va_start or va_copy macro). If there is no corresponding invocation of the
10813 va_start or va_copy macro, or if the va_end macro is not invoked before the
10814 return, the behavior is undefined.
10816 3 The va_end macro returns no value.
10817 <a name="7.16.1.4" href="#7.16.1.4"><b> 7.16.1.4 The va_start macro</b></a>
10819 1 #include <a href="#7.16"><stdarg.h></a>
10820 void va_start(va_list ap, parmN);
10821 <b> Description</b>
10822 2 The va_start macro shall be invoked before any access to the unnamed arguments.
10823 3 The va_start macro initializes ap for subsequent use by the va_arg and va_end
10824 macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap
10825 without an intervening invocation of the va_end macro for the same ap.
10826 4 The parameter parmN is the identifier of the rightmost parameter in the variable
10827 parameter list in the function definition (the one just before the , ...). If the parameter
10828 parmN is declared with the register storage class, with a function or array type, or
10829 with a type that is not compatible with the type that results after application of the default
10830 argument promotions, the behavior is undefined.
10832 5 The va_start macro returns no value.
10833 6 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not
10834 more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of
10835 pointers is specified by the first argument to f1.
10836 #include <a href="#7.16"><stdarg.h></a>
10838 void f1(int n_ptrs, ...)
10841 char *array[MAXARGS];
10844 [<a name="p270" href="#p270">page 270</a>] (<a href="#Contents">Contents</a>)
10846 if (n_ptrs > MAXARGS)
10848 va_start(ap, n_ptrs);
10849 while (ptr_no < n_ptrs)
10850 array[ptr_no++] = va_arg(ap, char *);
10854 Each call to f1 is required to have visible the definition of the function or a declaration such as
10857 7 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the
10858 indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list
10859 is gathered again and passed to function f4.
10860 #include <a href="#7.16"><stdarg.h></a>
10862 void f3(int n_ptrs, int f4_after, ...)
10864 va_list ap, ap_save;
10865 char *array[MAXARGS];
10867 if (n_ptrs > MAXARGS)
10869 va_start(ap, f4_after);
10870 while (ptr_no < n_ptrs) {
10871 array[ptr_no++] = va_arg(ap, char *);
10872 if (ptr_no == f4_after)
10873 va_copy(ap_save, ap);
10877 // Now process the saved copy.
10878 n_ptrs -= f4_after;
10880 while (ptr_no < n_ptrs)
10881 array[ptr_no++] = va_arg(ap_save, char *);
10886 [<a name="p271" href="#p271">page 271</a>] (<a href="#Contents">Contents</a>)
10888 <a name="7.17" href="#7.17"><b> 7.17 Atomics <stdatomic.h></b></a>
10889 <a name="7.17.1" href="#7.17.1"><b> 7.17.1 Introduction</b></a>
10890 1 The header <a href="#7.17"><stdatomic.h></a> defines several macros and declares several types and
10891 functions for performing atomic operations on data shared between threads.
10892 2 Implementations that define the macro __STDC_NO_THREADS__ need not provide
10893 this header nor support any of its facilities.
10894 3 The macros defined are the atomic lock-free macros
10895 ATOMIC_CHAR_LOCK_FREE
10896 ATOMIC_CHAR16_T_LOCK_FREE
10897 ATOMIC_CHAR32_T_LOCK_FREE
10898 ATOMIC_WCHAR_T_LOCK_FREE
10899 ATOMIC_SHORT_LOCK_FREE
10900 ATOMIC_INT_LOCK_FREE
10901 ATOMIC_LONG_LOCK_FREE
10902 ATOMIC_LLONG_LOCK_FREE
10903 ATOMIC_ADDRESS_LOCK_FREE
10904 which indicate the lock-free property of the corresponding atomic types (both signed and
10907 which expands to an initializer for an object of type atomic_flag.
10908 4 The types include
10910 which is an enumerated type whose enumerators identify memory ordering constraints;
10912 which is a structure type representing a lock-free, primitive atomic flag;
10914 which is a structure type representing the atomic analog of the type _Bool;
10916 which is a structure type representing the atomic analog of a pointer type; and several
10917 atomic analogs of integer types.
10918 5 In the following operation definitions:
10919 -- An A refers to one of the atomic types.
10921 [<a name="p272" href="#p272">page 272</a>] (<a href="#Contents">Contents</a>)
10923 -- A C refers to its corresponding non-atomic type. The atomic_address atomic
10924 type corresponds to the void * non-atomic type.
10925 -- An M refers to the type of the other argument for arithmetic operations. For atomic
10926 integer types, M is C. For atomic address types, M is ptrdiff_t.
10927 -- The functions not ending in _explicit have the same semantics as the
10928 corresponding _explicit function with memory_order_seq_cst for the
10929 memory_order argument.
10930 6 NOTE Many operations are volatile-qualified. The ''volatile as device register'' semantics have not
10931 changed in the standard. This qualification means that volatility is preserved when applying these
10932 operations to volatile objects.
10934 <a name="7.17.2" href="#7.17.2"><b> 7.17.2 Initialization</b></a>
10935 <a name="7.17.2.1" href="#7.17.2.1"><b> 7.17.2.1 The ATOMIC_VAR_INIT macro</b></a>
10937 1 #include <a href="#7.17"><stdatomic.h></a>
10938 #define ATOMIC_VAR_INIT(C value)
10939 <b> Description</b>
10940 2 The ATOMIC_VAR_INIT macro expands to a token sequence suitable for initializing an
10941 atomic object of a type that is initialization-compatible with value. An atomic object
10942 with automatic storage duration that is not explicitly initialized using
10943 ATOMIC_VAR_INIT is initially in an indeterminate state; however, the default (zero)
10944 initialization for objects with static or thread-local storage duration is guaranteed to
10945 produce a valid state.
10946 3 Concurrent access to the variable being initialized, even via an atomic operation,
10947 constitutes a data race.
10949 atomic_int guide = ATOMIC_VAR_INIT(42);
10951 <a name="7.17.2.2" href="#7.17.2.2"><b> 7.17.2.2 The atomic_init generic function</b></a>
10953 1 #include <a href="#7.17"><stdatomic.h></a>
10954 void atomic_init(volatile A *obj, C value);
10955 <b> Description</b>
10956 2 The atomic_init generic function initializes the atomic object pointed to by obj to
10957 the value value, while also initializing any additional state that the implementation
10958 might need to carry for the atomic object.
10960 [<a name="p273" href="#p273">page 273</a>] (<a href="#Contents">Contents</a>)
10962 3 Although this function initializes an atomic object, it does not avoid data races;
10963 concurrent access to the variable being initialized, even via an atomic operation,
10964 constitutes a data race.
10966 4 The atomic_init generic function returns no value.
10969 atomic_init(&guide, 42);
10971 <a name="7.17.3" href="#7.17.3"><b> 7.17.3 Order and consistency</b></a>
10972 1 The enumerated type memory_order specifies the detailed regular (non-atomic)
10973 memory synchronization operations as defined in <a href="#5.1.2.4">5.1.2.4</a> and may provide for operation
10974 ordering. Its enumeration constants are as follows:
10975 memory_order_relaxed
10976 memory_order_consume
10977 memory_order_acquire
10978 memory_order_release
10979 memory_order_acq_rel
10980 memory_order_seq_cst
10981 2 For memory_order_relaxed, no operation orders memory.
10982 3 For memory_order_release, memory_order_acq_rel, and
10983 memory_order_seq_cst, a store operation performs a release operation on the
10984 affected memory location.
10985 4 For memory_order_acquire, memory_order_acq_rel, and
10986 memory_order_seq_cst, a load operation performs an acquire operation on the
10987 affected memory location.
10988 5 For memory_order_consume, a load operation performs a consume operation on the
10989 affected memory location.
10990 6 For memory_order_seq_cst, there shall be a single total order S on all operations,
10991 consistent with the ''happens before'' order and modification orders for all affected
10992 locations, such that each memory_order_seq_cst operation that loads a value
10993 observes either the last preceding modification according to this order S, or the result of
10994 an operation that is not memory_order_seq_cst.
10995 7 NOTE 1 Although it is not explicitly required that S include lock operations, it can always be extended to
10996 an order that does include lock and unlock operations, since the ordering between those is already included
10997 in the ''happens before'' ordering.
10999 8 NOTE 2 Atomic operations specifying memory_order_relaxed are relaxed only with respect to
11000 memory ordering. Implementations must still guarantee that any given atomic access to a particular atomic
11002 [<a name="p274" href="#p274">page 274</a>] (<a href="#Contents">Contents</a>)
11004 object be indivisible with respect to all other atomic accesses to that object.
11006 9 For an atomic operation B that reads the value of an atomic object M, if there is a
11007 memory_order_seq_cst fence X sequenced before B, then B observes either the
11008 last memory_order_seq_cst modification of M preceding X in the total order S or
11009 a later modification of M in its modification order.
11010 10 For atomic operations A and B on an atomic object M, where A modifies M and B takes
11011 its value, if there is a memory_order_seq_cst fence X such that A is sequenced
11012 before X and B follows X in S, then B observes either the effects of A or a later
11013 modification of M in its modification order.
11014 11 For atomic operations A and B on an atomic object M, where A modifies M and B takes
11015 its value, if there are memory_order_seq_cst fences X and Y such that A is
11016 sequenced before X, Y is sequenced before B, and X precedes Y in S, then B observes
11017 either the effects of A or a later modification of M in its modification order.
11018 12 Atomic read-modify-write operations shall always read the last value (in the modification
11019 order) stored before the write associated with the read-modify-write operation.
11020 13 An atomic store shall only store a value that has been computed from constants and
11021 program input values by a finite sequence of program evaluations, such that each
11022 evaluation observes the values of variables as computed by the last prior assignment in
11023 the sequence.<sup><a href="#note251"><b>251)</b></a></sup> The ordering of evaluations in this sequence shall be such that
11024 -- If an evaluation B observes a value computed by A in a different thread, then B does
11025 not happen before A.
11026 -- If an evaluation A is included in the sequence, then all evaluations that assign to the
11027 same variable and happen before A are also included.
11028 14 NOTE 3 The second requirement disallows ''out-of-thin-air'', or ''speculative'' stores of atomics when
11029 relaxed atomics are used. Since unordered operations are involved, evaluations may appear in this
11030 sequence out of thread order. For example, with x and y initially zero,
11032 r1 = atomic_load_explicit(&y, memory_order_relaxed);
11033 atomic_store_explicit(&x, r1, memory_order_relaxed);
11036 r2 = atomic_load_explicit(&x, memory_order_relaxed);
11037 atomic_store_explicit(&y, 42, memory_order_relaxed);
11038 is allowed to produce r1 == 42 && r2 == 42. The sequence of evaluations justifying this consists of:
11043 <sup><a name="note251" href="#note251"><b>251)</b></a></sup> Among other implications, atomic variables shall not decay.
11045 [<a name="p275" href="#p275">page 275</a>] (<a href="#Contents">Contents</a>)
11047 atomic_store_explicit(&y, 42, memory_order_relaxed);
11048 r1 = atomic_load_explicit(&y, memory_order_relaxed);
11049 atomic_store_explicit(&x, r1, memory_order_relaxed);
11050 r2 = atomic_load_explicit(&x, memory_order_relaxed);
11053 r1 = atomic_load_explicit(&y, memory_order_relaxed);
11054 atomic_store_explicit(&x, r1, memory_order_relaxed);
11057 r2 = atomic_load_explicit(&x, memory_order_relaxed);
11058 atomic_store_explicit(&y, r2, memory_order_relaxed);
11059 is not allowed to produce r1 == 42 && r2 = 42, since there is no sequence of evaluations that results
11060 in the computation of 42. In the absence of ''relaxed'' operations and read-modify-write operations with
11061 weaker than memory_order_acq_rel ordering, the second requirement has no impact.
11063 Recommended practice
11064 15 The requirements do not forbid r1 == 42 && r2 == 42 in the following example,
11065 with x and y initially zero:
11067 r1 = atomic_load_explicit(&x, memory_order_relaxed);
11069 atomic_store_explicit(&y, r1, memory_order_relaxed);
11072 r2 = atomic_load_explicit(&y, memory_order_relaxed);
11074 atomic_store_explicit(&x, 42, memory_order_relaxed);
11075 However, this is not useful behavior, and implementations should not allow it.
11076 16 Implementations should make atomic stores visible to atomic loads within a reasonable
11078 <a name="7.17.3.1" href="#7.17.3.1"><b> 7.17.3.1 The kill_dependency macro</b></a>
11080 1 #include <a href="#7.17"><stdatomic.h></a>
11081 type kill_dependency(type y);
11082 <b> Description</b>
11083 2 The kill_dependency macro terminates a dependency chain; the argument does not
11084 carry a dependency to the return value.
11086 [<a name="p276" href="#p276">page 276</a>] (<a href="#Contents">Contents</a>)
11089 3 The kill_dependency macro returns the value of y.
11090 <a name="7.17.4" href="#7.17.4"><b> 7.17.4 Fences</b></a>
11091 1 This subclause introduces synchronization primitives called fences. Fences can have
11092 acquire semantics, release semantics, or both. A fence with acquire semantics is called
11093 an acquire fence; a fence with release semantics is called a release fence.
11094 2 A release fence A synchronizes with an acquire fence B if there exist atomic operations
11095 X and Y , both operating on some atomic object M, such that A is sequenced before X, X
11096 modifies M, Y is sequenced before B, and Y reads the value written by X or a value
11097 written by any side effect in the hypothetical release sequence X would head if it were a
11099 3 A release fence A synchronizes with an atomic operation B that performs an acquire
11100 operation on an atomic object M if there exists an atomic operation X such that A is
11101 sequenced before X, X modifies M, and B reads the value written by X or a value written
11102 by any side effect in the hypothetical release sequence X would head if it were a release
11104 4 An atomic operation A that is a release operation on an atomic object M synchronizes
11105 with an acquire fence B if there exists some atomic operation X on M such that X is
11106 sequenced before B and reads the value written by A or a value written by any side effect
11107 in the release sequence headed by A.
11108 <a name="7.17.4.1" href="#7.17.4.1"><b> 7.17.4.1 The atomic_thread_fence function</b></a>
11110 1 #include <a href="#7.17"><stdatomic.h></a>
11111 void atomic_thread_fence(memory_order order);
11112 <b> Description</b>
11113 2 Depending on the value of order, this operation:
11114 -- has no effects, if order == memory_order_relaxed;
11115 -- is an acquire fence, if order == memory_order_acquire or order ==
11116 memory_order_consume;
11117 -- is a release fence, if order == memory_order_release;
11118 -- is both an acquire fence and a release fence, if order ==
11119 memory_order_acq_rel;
11120 -- is a sequentially consistent acquire and release fence, if order ==
11121 memory_order_seq_cst.
11123 [<a name="p277" href="#p277">page 277</a>] (<a href="#Contents">Contents</a>)
11126 3 The atomic_thread_fence function returns no value.
11127 <a name="7.17.4.2" href="#7.17.4.2"><b> 7.17.4.2 The atomic_signal_fence function</b></a>
11129 1 #include <a href="#7.17"><stdatomic.h></a>
11130 void atomic_signal_fence(memory_order order);
11131 <b> Description</b>
11132 2 Equivalent to atomic_thread_fence(order), except that ''synchronizes with''
11133 relationships are established only between a thread and a signal handler executed in the
11135 3 NOTE 1 The atomic_signal_fence function can be used to specify the order in which actions
11136 performed by the thread become visible to the signal handler.
11138 4 NOTE 2 Compiler optimizations and reorderings of loads and stores are inhibited in the same way as with
11139 atomic_thread_fence, but the hardware fence instructions that atomic_thread_fence would
11140 have inserted are not emitted.
11143 5 The atomic_signal_fence function returns no value.
11144 <a name="7.17.5" href="#7.17.5"><b> 7.17.5 Lock-free property</b></a>
11145 1 The atomic lock-free macros indicate the lock-free property of integer and address atomic
11146 types. A value of 0 indicates that the type is never lock-free; a value of 1 indicates that
11147 the type is sometimes lock-free; a value of 2 indicates that the type is always lock-free.
11148 2 NOTE Operations that are lock-free should also be address-free. That is, atomic operations on the same
11149 memory location via two different addresses will communicate atomically. The implementation should not
11150 depend on any per-process state. This restriction enables communication via memory mapped into a
11151 process more than once and memory shared between two processes.
11153 <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>
11155 1 #include <a href="#7.17"><stdatomic.h></a>
11156 _Bool atomic_is_lock_free(atomic_type const volatile *obj);
11157 <b> Description</b>
11158 2 The atomic_is_lock_free generic function indicates whether or not the object
11159 pointed to by obj is lock-free. atomic_type can be any atomic type.
11161 3 The atomic_is_lock_free generic function returns nonzero (true) if and only if the
11162 object's operations are lock-free. The result of a lock-free query on one object cannot be
11164 [<a name="p278" href="#p278">page 278</a>] (<a href="#Contents">Contents</a>)
11166 inferred from the result of a lock-free query on another object.
11167 <a name="7.17.6" href="#7.17.6"><b> 7.17.6 Atomic integer and address types</b></a>
11168 1 For each line in the following table, the atomic type name is declared as the
11169 corresponding direct type.
11171 [<a name="p279" href="#p279">page 279</a>] (<a href="#Contents">Contents</a>)
11173 Atomic type name Direct type
11174 atomic_char _Atomic char
11175 atomic_schar _Atomic signed char
11176 atomic_uchar _Atomic unsigned char
11177 atomic_short _Atomic short
11178 atomic_ushort _Atomic unsigned short
11179 atomic_int _Atomic int
11180 atomic_uint _Atomic unsigned int
11181 atomic_long _Atomic long
11182 atomic_ulong _Atomic unsigned long
11183 atomic_llong _Atomic long long
11184 atomic_ullong _Atomic unsigned long long
11185 atomic_char16_t _Atomic char16_t
11186 atomic_char32_t _Atomic char32_t
11187 atomic_wchar_t _Atomic wchar_t
11188 atomic_int_least8_t _Atomic int_least8_t
11189 atomic_uint_least8_t _Atomic uint_least8_t
11190 atomic_int_least16_t _Atomic int_least16_t
11191 atomic_uint_least16_t _Atomic uint_least16_t
11192 atomic_int_least32_t _Atomic int_least32_t
11193 atomic_uint_least32_t _Atomic uint_least32_t
11194 atomic_int_least64_t _Atomic int_least64_t
11195 atomic_uint_least64_t _Atomic uint_least64_t
11196 atomic_int_fast8_t _Atomic int_fast8_t
11197 atomic_uint_fast8_t _Atomic uint_fast8_t
11198 atomic_int_fast16_t _Atomic int_fast16_t
11199 atomic_uint_fast16_t _Atomic uint_fast16_t
11200 atomic_int_fast32_t _Atomic int_fast32_t
11201 atomic_uint_fast32_t _Atomic uint_fast32_t
11202 atomic_int_fast64_t _Atomic int_fast64_t
11203 atomic_uint_fast64_t _Atomic uint_fast64_t
11204 atomic_intptr_t _Atomic intptr_t
11205 atomic_uintptr_t _Atomic uintptr_t
11206 atomic_size_t _Atomic size_t
11207 atomic_ptrdiff_t _Atomic ptrdiff_t
11208 atomic_intmax_t _Atomic intmax_t
11209 atomic_uintmax_t _Atomic uintmax_t
11210 2 The semantics of the operations on these types are defined in <a href="#7.17.7">7.17.7</a>.
11211 3 The atomic_bool type provides an atomic boolean.
11213 [<a name="p280" href="#p280">page 280</a>] (<a href="#Contents">Contents</a>)
11215 4 The atomic_address type provides atomic void * operations. The unit of
11216 addition/subtraction shall be one byte.
11217 5 NOTE The representation of atomic integer and address types need not have the same size as their
11218 corresponding regular types. They should have the same size whenever possible, as it eases effort required
11219 to port existing code.
11221 <a name="7.17.7" href="#7.17.7"><b> 7.17.7 Operations on atomic types</b></a>
11222 1 There are only a few kinds of operations on atomic types, though there are many
11223 instances of those kinds. This subclause specifies each general kind.
11224 <a name="7.17.7.1" href="#7.17.7.1"><b> 7.17.7.1 The atomic_store generic functions</b></a>
11226 1 #include <a href="#7.17"><stdatomic.h></a>
11227 void atomic_store(volatile A *object, C desired);
11228 void atomic_store_explicit(volatile A *object,
11229 C desired, memory_order order);
11230 <b> Description</b>
11231 2 The order argument shall not be memory_order_acquire,
11232 memory_order_consume, nor memory_order_acq_rel. Atomically replace the
11233 value pointed to by object with the value of desired. Memory is affected according
11234 to the value of order.
11236 3 The atomic_store generic functions return no value.
11237 <a name="7.17.7.2" href="#7.17.7.2"><b> 7.17.7.2 The atomic_load generic functions</b></a>
11239 1 #include <a href="#7.17"><stdatomic.h></a>
11240 C atomic_load(volatile A *object);
11241 C atomic_load_explicit(volatile A *object,
11242 memory_order order);
11243 <b> Description</b>
11244 2 The order argument shall not be memory_order_release nor
11245 memory_order_acq_rel. Memory is affected according to the value of order.
11247 Atomically returns the value pointed to by object.
11249 [<a name="p281" href="#p281">page 281</a>] (<a href="#Contents">Contents</a>)
11251 <a name="7.17.7.3" href="#7.17.7.3"><b> 7.17.7.3 The atomic_exchange generic functions</b></a>
11253 1 #include <a href="#7.17"><stdatomic.h></a>
11254 C atomic_exchange(volatile A *object, C desired);
11255 C atomic_exchange_explicit(volatile A *object,
11256 C desired, memory_order order);
11257 <b> Description</b>
11258 2 Atomically replace the value pointed to by object with desired. Memory is affected
11259 according to the value of order. These operations are read-modify-write operations
11260 (<a href="#5.1.2.4">5.1.2.4</a>).
11262 3 Atomically returns the value pointed to by object immediately before the effects.
11263 <a name="7.17.7.4" href="#7.17.7.4"><b> 7.17.7.4 The atomic_compare_exchange generic functions</b></a>
11265 1 #include <a href="#7.17"><stdatomic.h></a>
11266 _Bool atomic_compare_exchange_strong(volatile A *object,
11267 C *expected, C desired);
11268 _Bool atomic_compare_exchange_strong_explicit(
11269 volatile A *object, C *expected, C desired,
11270 memory_order success, memory_order failure);
11271 _Bool atomic_compare_exchange_weak(volatile A *object,
11272 C *expected, C desired);
11273 _Bool atomic_compare_exchange_weak_explicit(
11274 volatile A *object, C *expected, C desired,
11275 memory_order success, memory_order failure);
11276 <b> Description</b>
11277 2 The failure argument shall not be memory_order_release nor
11278 memory_order_acq_rel. The failure argument shall be no stronger than the
11279 success argument. Atomically, compares the value pointed to by object for equality
11280 with that in expected, and if true, replaces the value pointed to by object with
11281 desired, and if false, updates the value in expected with the value pointed to by
11282 object. Further, if the comparison is true, memory is affected according to the value of
11283 success, and if the comparison is false, memory is affected according to the value of
11284 failure. These operations are atomic read-modify-write operations (<a href="#5.1.2.4">5.1.2.4</a>).
11285 3 NOTE 1 The effect of the compare-and-exchange operations is
11287 [<a name="p282" href="#p282">page 282</a>] (<a href="#Contents">Contents</a>)
11289 if (*object == *expected)
11292 *expected = *object;
11294 4 The weak compare-and-exchange operations may fail spuriously, that is, return zero
11295 while leaving the value pointed to by expected unchanged.
11296 5 NOTE 2 This spurious failure enables implementation of compare-and-exchange on a broader class of
11297 machines, e.g. load-locked store-conditional machines.
11299 6 EXAMPLE A consequence of spurious failure is that nearly all uses of weak compare-and-exchange will
11301 exp = atomic_load(&cur);
11303 des = function(exp);
11304 } while (!atomic_compare_exchange_weak(&cur, &exp, des));
11305 When a compare-and-exchange is in a loop, the weak version will yield better performance on some
11306 platforms. When a weak compare-and-exchange would require a loop and a strong one would not, the
11307 strong one is preferable.
11310 7 The result of the comparison.
11311 <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>
11312 1 The following operations perform arithmetic and bitwise computations. All of these
11313 operations are applicable to an object of any atomic integer type. Only addition and
11314 subtraction are applicable to atomic_address. None of these operations is applicable
11315 to atomic_bool. The key, operator, and computation correspondence is:
11319 or | bitwise inclusive or
11320 xor ^ bitwise exclusive or
11321 and & bitwise and
11323 2 #include <a href="#7.17"><stdatomic.h></a>
11324 C atomic_fetch_key(volatile A *object, M operand);
11325 C atomic_fetch_key_explicit(volatile A *object,
11326 M operand, memory_order order);
11327 <b> Description</b>
11328 3 Atomically replaces the value pointed to by object with the result of the computation
11329 applied to the value pointed to by object and the given operand. Memory is affected
11330 according to the value of order. These operations are atomic read-modify-write
11332 [<a name="p283" href="#p283">page 283</a>] (<a href="#Contents">Contents</a>)
11334 operations (<a href="#5.1.2.4">5.1.2.4</a>). For signed integer types, arithmetic is defined to use two's
11335 complement representation with silent wrap-around on overflow; there are no undefined
11336 results. For address types, the result may be an undefined address, but the operations
11337 otherwise have no undefined behavior.
11339 4 Atomically, the value pointed to by object immediately before the effects.
11340 5 NOTE The operation of the atomic_fetch and modify generic functions are nearly equivalent to the
11341 operation of the corresponding op= compound assignment operators. The only differences are that the
11342 compound assignment operators are not guaranteed to operate atomically, and the value yielded by a
11343 compound assignment operator is the updated value of the object, whereas the value returned by the
11344 atomic_fetch and modify generic functions is the previous value of the atomic object.
11346 <a name="7.17.8" href="#7.17.8"><b> 7.17.8 Atomic flag type and operations</b></a>
11347 1 The atomic_flag type provides the classic test-and-set functionality. It has two
11348 states, set and clear.
11349 2 Operations on an object of type atomic_flag shall be lock free.
11350 3 NOTE Hence the operations should also be address-free. No other type requires lock-free operations, so
11351 the atomic_flag type is the minimum hardware-implemented type needed to conform to this
11352 International standard. The remaining types can be emulated with atomic_flag, though with less than
11355 4 The macro ATOMIC_FLAG_INIT may be used to initialize an atomic_flag to the
11356 clear state. An atomic_flag that is not explicitly initialized with
11357 ATOMIC_FLAG_INIT is initially in an indeterminate state.
11359 atomic_flag guard = ATOMIC_FLAG_INIT;
11361 <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>
11363 1 #include <a href="#7.17"><stdatomic.h></a>
11364 bool atomic_flag_test_and_set(
11365 volatile atomic_flag *object);
11366 bool atomic_flag_test_and_set_explicit(
11367 volatile atomic_flag *object, memory_order order);
11368 <b> Description</b>
11369 2 Atomically sets the value pointed to by object to true. Memory is affected according
11370 to the value of order. These operations are atomic read-modify-write operations
11371 (<a href="#5.1.2.4">5.1.2.4</a>).
11373 [<a name="p284" href="#p284">page 284</a>] (<a href="#Contents">Contents</a>)
11376 3 Atomically, the value of the object immediately before the effects.
11377 <a name="7.17.8.2" href="#7.17.8.2"><b> 7.17.8.2 The atomic_flag_clear functions</b></a>
11379 1 #include <a href="#7.17"><stdatomic.h></a>
11380 void atomic_flag_clear(volatile atomic_flag *object);
11381 void atomic_flag_clear_explicit(
11382 volatile atomic_flag *object, memory_order order);
11383 <b> Description</b>
11384 2 The order argument shall not be memory_order_acquire nor
11385 memory_order_acq_rel. Atomically sets the value pointed to by object to false.
11386 Memory is affected according to the value of order.
11388 3 The atomic_flag_clear functions return no value.
11390 [<a name="p285" href="#p285">page 285</a>] (<a href="#Contents">Contents</a>)
11392 <a name="7.18" href="#7.18"><b> 7.18 Boolean type and values <stdbool.h></b></a>
11393 1 The header <a href="#7.18"><stdbool.h></a> defines four macros.
11397 3 The remaining three macros are suitable for use in #if preprocessing directives. They
11400 which expands to the integer constant 1,
11402 which expands to the integer constant 0, and
11403 __bool_true_false_are_defined
11404 which expands to the integer constant 1.
11405 4 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
11406 redefine the macros bool, true, and false.<sup><a href="#note252"><b>252)</b></a></sup>
11411 <sup><a name="note252" href="#note252"><b>252)</b></a></sup> See ''future library directions'' (<a href="#7.30.7">7.30.7</a>).
11413 [<a name="p286" href="#p286">page 286</a>] (<a href="#Contents">Contents</a>)
11415 <a name="7.19" href="#7.19"><b> 7.19 Common definitions <stddef.h></b></a>
11416 1 The header <a href="#7.19"><stddef.h></a> defines the following macros and declares the following types.
11417 Some are also defined in other headers, as noted in their respective subclauses.
11420 which is the signed integer type of the result of subtracting two pointers;
11422 which is the unsigned integer type of the result of the sizeof operator;
11424 which is an object type whose alignment is as great as is supported by the implementation
11425 in all contexts; and
11427 which is an integer type whose range of values can represent distinct codes for all
11428 members of the largest extended character set specified among the supported locales; the
11429 null character shall have the code value zero. Each member of the basic character set
11430 shall have a code value equal to its value when used as the lone character in an integer
11431 character constant if an implementation does not define
11432 __STDC_MB_MIGHT_NEQ_WC__.
11435 which expands to an implementation-defined null pointer constant; and
11436 offsetof(type, member-designator)
11437 which expands to an integer constant expression that has type size_t, the value of
11438 which is the offset in bytes, to the structure member (designated by member-designator),
11439 from the beginning of its structure (designated by type). The type and member designator
11440 shall be such that given
11442 then the expression &(t.member-designator) evaluates to an address constant. (If the
11443 specified member is a bit-field, the behavior is undefined.)
11444 Recommended practice
11445 4 The types used for size_t and ptrdiff_t should not have an integer conversion rank
11446 greater than that of signed long int unless the implementation supports objects
11447 large enough to make this necessary.
11449 [<a name="p287" href="#p287">page 287</a>] (<a href="#Contents">Contents</a>)
11451 Forward references: localization (<a href="#7.11">7.11</a>).
11453 [<a name="p288" href="#p288">page 288</a>] (<a href="#Contents">Contents</a>)
11455 <a name="7.20" href="#7.20"><b> 7.20 Integer types <stdint.h></b></a>
11456 1 The header <a href="#7.20"><stdint.h></a> declares sets of integer types having specified widths, and
11457 defines corresponding sets of macros.<sup><a href="#note253"><b>253)</b></a></sup> It also defines macros that specify limits of
11458 integer types corresponding to types defined in other standard headers.
11459 2 Types are defined in the following categories:
11460 -- integer types having certain exact widths;
11461 -- integer types having at least certain specified widths;
11462 -- fastest integer types having at least certain specified widths;
11463 -- integer types wide enough to hold pointers to objects;
11464 -- integer types having greatest width.
11465 (Some of these types may denote the same type.)
11466 3 Corresponding macros specify limits of the declared types and construct suitable
11468 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
11469 declare that typedef name and define the associated macros. Conversely, for each type
11470 described herein that the implementation does not provide, <a href="#7.20"><stdint.h></a> shall not
11471 declare that typedef name nor shall it define the associated macros. An implementation
11472 shall provide those types described as ''required'', but need not provide any of the others
11473 (described as ''optional'').
11474 <a name="7.20.1" href="#7.20.1"><b> 7.20.1 Integer types</b></a>
11475 1 When typedef names differing only in the absence or presence of the initial u are defined,
11476 they shall denote corresponding signed and unsigned types as described in <a href="#6.2.5">6.2.5</a>; an
11477 implementation providing one of these corresponding types shall also provide the other.
11478 2 In the following descriptions, the symbol N represents an unsigned decimal integer with
11479 no leading zeros (e.g., 8 or 24, but not 04 or 048).
11484 <sup><a name="note253" href="#note253"><b>253)</b></a></sup> See ''future library directions'' (<a href="#7.30.8">7.30.8</a>).
11485 <sup><a name="note254" href="#note254"><b>254)</b></a></sup> Some of these types may denote implementation-defined extended integer types.
11487 [<a name="p289" href="#p289">page 289</a>] (<a href="#Contents">Contents</a>)
11489 <a name="7.20.1.1" href="#7.20.1.1"><b> 7.20.1.1 Exact-width integer types</b></a>
11490 1 The typedef name intN_t designates a signed integer type with width N , no padding
11491 bits, and a two's complement representation. Thus, int8_t denotes such a signed
11492 integer type with a width of exactly 8 bits.
11493 2 The typedef name uintN_t designates an unsigned integer type with width N and no
11494 padding bits. Thus, uint24_t denotes such an unsigned integer type with a width of
11496 3 These types are optional. However, if an implementation provides integer types with
11497 widths of 8, 16, 32, or 64 bits, no padding bits, and (for the signed types) that have a
11498 two's complement representation, it shall define the corresponding typedef names.
11499 <a name="7.20.1.2" href="#7.20.1.2"><b> 7.20.1.2 Minimum-width integer types</b></a>
11500 1 The typedef name int_leastN_t designates a signed integer type with a width of at
11501 least N , such that no signed integer type with lesser size has at least the specified width.
11502 Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits.
11503 2 The typedef name uint_leastN_t designates an unsigned integer type with a width
11504 of at least N , such that no unsigned integer type with lesser size has at least the specified
11505 width. Thus, uint_least16_t denotes an unsigned integer type with a width of at
11507 3 The following types are required:
11508 int_least8_t uint_least8_t
11509 int_least16_t uint_least16_t
11510 int_least32_t uint_least32_t
11511 int_least64_t uint_least64_t
11512 All other types of this form are optional.
11513 <a name="7.20.1.3" href="#7.20.1.3"><b> 7.20.1.3 Fastest minimum-width integer types</b></a>
11514 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
11515 with among all integer types that have at least the specified width.
11516 2 The typedef name int_fastN_t designates the fastest signed integer type with a width
11517 of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer
11518 type with a width of at least N .
11523 <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
11524 grounds for choosing one type over another, it will simply pick some integer type satisfying the
11525 signedness and width requirements.
11527 [<a name="p290" href="#p290">page 290</a>] (<a href="#Contents">Contents</a>)
11529 3 The following types are required:
11530 int_fast8_t uint_fast8_t
11531 int_fast16_t uint_fast16_t
11532 int_fast32_t uint_fast32_t
11533 int_fast64_t uint_fast64_t
11534 All other types of this form are optional.
11535 <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>
11536 1 The following type designates a signed integer type with the property that any valid
11537 pointer to void can be converted to this type, then converted back to pointer to void,
11538 and the result will compare equal to the original pointer:
11540 The following type designates an unsigned integer type with the property that any valid
11541 pointer to void can be converted to this type, then converted back to pointer to void,
11542 and the result will compare equal to the original pointer:
11544 These types are optional.
11545 <a name="7.20.1.5" href="#7.20.1.5"><b> 7.20.1.5 Greatest-width integer types</b></a>
11546 1 The following type designates a signed integer type capable of representing any value of
11547 any signed integer type:
11549 The following type designates an unsigned integer type capable of representing any value
11550 of any unsigned integer type:
11552 These types are required.
11553 <a name="7.20.2" href="#7.20.2"><b> 7.20.2 Limits of specified-width integer types</b></a>
11554 1 The following object-like macros specify the minimum and maximum limits of the types *
11555 declared in <a href="#7.20"><stdint.h></a>. Each macro name corresponds to a similar type name in
11556 <a href="#7.20.1">7.20.1</a>.
11557 2 Each instance of any defined macro shall be replaced by a constant expression suitable
11558 for use in #if preprocessing directives, and this expression shall have the same type as
11559 would an expression that is an object of the corresponding type converted according to
11560 the integer promotions. Its implementation-defined value shall be equal to or greater in
11561 magnitude (absolute value) than the corresponding value given below, with the same sign,
11562 except where stated to be exactly the given value.
11564 [<a name="p291" href="#p291">page 291</a>] (<a href="#Contents">Contents</a>)
11566 <a name="7.20.2.1" href="#7.20.2.1"><b> 7.20.2.1 Limits of exact-width integer types</b></a>
11567 1 -- minimum values of exact-width signed integer types
11568 INTN_MIN exactly -(2 N -1 )
11569 -- maximum values of exact-width signed integer types
11570 INTN_MAX exactly 2 N -1 - 1
11571 -- maximum values of exact-width unsigned integer types
11572 UINTN_MAX exactly 2 N - 1
11573 <a name="7.20.2.2" href="#7.20.2.2"><b> 7.20.2.2 Limits of minimum-width integer types</b></a>
11574 1 -- minimum values of minimum-width signed integer types
11575 INT_LEASTN_MIN -(2 N -1 - 1)
11576 -- maximum values of minimum-width signed integer types
11577 INT_LEASTN_MAX 2 N -1 - 1
11578 -- maximum values of minimum-width unsigned integer types
11579 UINT_LEASTN_MAX 2N - 1
11580 <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>
11581 1 -- minimum values of fastest minimum-width signed integer types
11582 INT_FASTN_MIN -(2 N -1 - 1)
11583 -- maximum values of fastest minimum-width signed integer types
11584 INT_FASTN_MAX 2 N -1 - 1
11585 -- maximum values of fastest minimum-width unsigned integer types
11586 UINT_FASTN_MAX 2N - 1
11587 <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>
11588 1 -- minimum value of pointer-holding signed integer type
11589 INTPTR_MIN -(215 - 1)
11590 -- maximum value of pointer-holding signed integer type
11592 -- maximum value of pointer-holding unsigned integer type
11593 UINTPTR_MAX 216 - 1
11595 [<a name="p292" href="#p292">page 292</a>] (<a href="#Contents">Contents</a>)
11597 <a name="7.20.2.5" href="#7.20.2.5"><b> 7.20.2.5 Limits of greatest-width integer types</b></a>
11598 1 -- minimum value of greatest-width signed integer type
11599 INTMAX_MIN -(263 - 1)
11600 -- maximum value of greatest-width signed integer type
11602 -- maximum value of greatest-width unsigned integer type
11603 UINTMAX_MAX 264 - 1
11604 <a name="7.20.3" href="#7.20.3"><b> 7.20.3 Limits of other integer types</b></a>
11605 1 The following object-like macros specify the minimum and maximum limits of integer *
11606 types corresponding to types defined in other standard headers.
11607 2 Each instance of these macros shall be replaced by a constant expression suitable for use
11608 in #if preprocessing directives, and this expression shall have the same type as would an
11609 expression that is an object of the corresponding type converted according to the integer
11610 promotions. Its implementation-defined value shall be equal to or greater in magnitude
11611 (absolute value) than the corresponding value given below, with the same sign. An
11612 implementation shall define only the macros corresponding to those typedef names it
11613 actually provides.<sup><a href="#note256"><b>256)</b></a></sup>
11614 -- limits of ptrdiff_t
11617 -- limits of sig_atomic_t
11618 SIG_ATOMIC_MIN see below
11619 SIG_ATOMIC_MAX see below
11622 -- limits of wchar_t
11623 WCHAR_MIN see below
11624 WCHAR_MAX see below
11625 -- limits of wint_t
11630 <sup><a name="note256" href="#note256"><b>256)</b></a></sup> A freestanding implementation need not provide all of these types.
11632 [<a name="p293" href="#p293">page 293</a>] (<a href="#Contents">Contents</a>)
11636 3 If sig_atomic_t (see <a href="#7.14">7.14</a>) is defined as a signed integer type, the value of
11637 SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX
11638 shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
11639 type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
11640 SIG_ATOMIC_MAX shall be no less than 255.
11641 4 If wchar_t (see <a href="#7.19">7.19</a>) is defined as a signed integer type, the value of WCHAR_MIN
11642 shall be no greater than -127 and the value of WCHAR_MAX shall be no less than 127;
11643 otherwise, wchar_t is defined as an unsigned integer type, and the value of
11644 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>
11645 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
11646 be no greater than -32767 and the value of WINT_MAX shall be no less than 32767;
11647 otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
11648 shall be 0 and the value of WINT_MAX shall be no less than 65535.
11649 <a name="7.20.4" href="#7.20.4"><b> 7.20.4 Macros for integer constants</b></a>
11650 1 The following function-like macros expand to integer constants suitable for initializing *
11651 objects that have integer types corresponding to types defined in <a href="#7.20"><stdint.h></a>. Each
11652 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>.
11653 2 The argument in any instance of these macros shall be an unsuffixed integer constant (as
11654 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.
11655 3 Each invocation of one of these macros shall expand to an integer constant expression
11656 suitable for use in #if preprocessing directives. The type of the expression shall have
11657 the same type as would an expression of the corresponding type converted according to
11658 the integer promotions. The value of the expression shall be that of the argument.
11659 <a name="7.20.4.1" href="#7.20.4.1"><b> 7.20.4.1 Macros for minimum-width integer constants</b></a>
11660 1 The macro INTN_C(value) shall expand to an integer constant expression
11661 corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
11662 to an integer constant expression corresponding to the type uint_leastN_t. For
11663 example, if uint_least64_t is a name for the type unsigned long long int,
11664 then UINT64_C(0x123) might expand to the integer constant 0x123ULL.
11669 <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
11672 [<a name="p294" href="#p294">page 294</a>] (<a href="#Contents">Contents</a>)
11674 <a name="7.20.4.2" href="#7.20.4.2"><b> 7.20.4.2 Macros for greatest-width integer constants</b></a>
11675 1 The following macro expands to an integer constant expression having the value specified
11676 by its argument and the type intmax_t:
11678 The following macro expands to an integer constant expression having the value specified
11679 by its argument and the type uintmax_t:
11682 [<a name="p295" href="#p295">page 295</a>] (<a href="#Contents">Contents</a>)
11684 <a name="7.21" href="#7.21"><b> 7.21 Input/output <stdio.h></b></a>
11685 <a name="7.21.1" href="#7.21.1"><b> 7.21.1 Introduction</b></a>
11686 1 The header <a href="#7.21"><stdio.h></a> defines several macros, and declares three types and many
11687 functions for performing input and output.
11688 2 The types declared are size_t (described in <a href="#7.19">7.19</a>);
11690 which is an object type capable of recording all the information needed to control a
11691 stream, including its file position indicator, a pointer to its associated buffer (if any), an
11692 error indicator that records whether a read/write error has occurred, and an end-of-file
11693 indicator that records whether the end of the file has been reached; and
11695 which is a complete object type other than an array type capable of recording all the
11696 information needed to specify uniquely every position within a file.
11697 3 The macros are NULL (described in <a href="#7.19">7.19</a>);
11701 which expand to integer constant expressions with distinct values, suitable for use as the
11702 third argument to the setvbuf function;
11704 which expands to an integer constant expression that is the size of the buffer used by the
11707 which expands to an integer constant expression, with type int and a negative value, that
11708 is returned by several functions to indicate end-of-file, that is, no more input from a
11711 which expands to an integer constant expression that is the minimum number of files that
11712 the implementation guarantees can be open simultaneously;
11714 which expands to an integer constant expression that is the size needed for an array of
11715 char large enough to hold the longest file name string that the implementation
11717 [<a name="p296" href="#p296">page 296</a>] (<a href="#Contents">Contents</a>)
11719 guarantees can be opened;<sup><a href="#note258"><b>258)</b></a></sup>
11721 which expands to an integer constant expression that is the size needed for an array of
11722 char large enough to hold a temporary file name string generated by the tmpnam
11727 which expand to integer constant expressions with distinct values, suitable for use as the
11728 third argument to the fseek function;
11730 which expands to an integer constant expression that is the minimum number of unique
11731 file names that can be generated by the tmpnam function;
11735 which are expressions of type ''pointer to FILE'' that point to the FILE objects
11736 associated, respectively, with the standard error, input, and output streams.
11737 4 The header <a href="#7.28"><wchar.h></a> declares a number of functions useful for wide character input
11738 and output. The wide character input/output functions described in that subclause
11739 provide operations analogous to most of those described here, except that the
11740 fundamental units internal to the program are wide characters. The external
11741 representation (in the file) is a sequence of ''generalized'' multibyte characters, as
11742 described further in <a href="#7.21.3">7.21.3</a>.
11743 5 The input/output functions are given the following collective terms:
11744 -- The wide character input functions -- those functions described in <a href="#7.28">7.28</a> that perform
11745 input into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar,
11746 fwscanf, wscanf, vfwscanf, and vwscanf.
11747 -- The wide character output functions -- those functions described in <a href="#7.28">7.28</a> that perform
11748 output from wide characters and wide strings: fputwc, fputws, putwc,
11749 putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
11752 <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
11753 FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
11754 string. Of course, file name string contents are subject to other system-specific constraints; therefore
11755 all possible strings of length FILENAME_MAX cannot be expected to be opened successfully.
11757 [<a name="p297" href="#p297">page 297</a>] (<a href="#Contents">Contents</a>)
11759 -- The wide character input/output functions -- the union of the ungetwc function, the
11760 wide character input functions, and the wide character output functions.
11761 -- The byte input/output functions -- those functions described in this subclause that
11762 perform input/output: fgetc, fgets, fprintf, fputc, fputs, fread,
11763 fscanf, fwrite, getc, getchar, printf, putc, putchar, puts, scanf, *
11764 ungetc, vfprintf, vfscanf, vprintf, and vscanf.
11765 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
11766 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>).
11767 <a name="7.21.2" href="#7.21.2"><b> 7.21.2 Streams</b></a>
11768 1 Input and output, whether to or from physical devices such as terminals and tape drives,
11769 or whether to or from files supported on structured storage devices, are mapped into
11770 logical data streams, whose properties are more uniform than their various inputs and
11771 outputs. Two forms of mapping are supported, for text streams and for binary
11772 streams.<sup><a href="#note259"><b>259)</b></a></sup>
11773 2 A text stream is an ordered sequence of characters composed into lines, each line
11774 consisting of zero or more characters plus a terminating new-line character. Whether the
11775 last line requires a terminating new-line character is implementation-defined. Characters
11776 may have to be added, altered, or deleted on input and output to conform to differing
11777 conventions for representing text in the host environment. Thus, there need not be a one-
11778 to-one correspondence between the characters in a stream and those in the external
11779 representation. Data read in from a text stream will necessarily compare equal to the data
11780 that were earlier written out to that stream only if: the data consist only of printing
11781 characters and the control characters horizontal tab and new-line; no new-line character is
11782 immediately preceded by space characters; and the last character is a new-line character.
11783 Whether space characters that are written out immediately before a new-line character
11784 appear when read in is implementation-defined.
11785 3 A binary stream is an ordered sequence of characters that can transparently record
11786 internal data. Data read in from a binary stream shall compare equal to the data that were
11787 earlier written out to that stream, under the same implementation. Such a stream may,
11788 however, have an implementation-defined number of null characters appended to the end
11790 4 Each stream has an orientation. After a stream is associated with an external file, but
11791 before any operations are performed on it, the stream is without orientation. Once a wide
11792 character input/output function has been applied to a stream without orientation, the
11795 <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
11796 implementation, there need be no new-line characters in a text stream nor any limit to the length of a
11799 [<a name="p298" href="#p298">page 298</a>] (<a href="#Contents">Contents</a>)
11801 stream becomes a wide-oriented stream. Similarly, once a byte input/output function has
11802 been applied to a stream without orientation, the stream becomes a byte-oriented stream.
11803 Only a call to the freopen function or the fwide function can otherwise alter the
11804 orientation of a stream. (A successful call to freopen removes any orientation.)<sup><a href="#note260"><b>260)</b></a></sup>
11805 5 Byte input/output functions shall not be applied to a wide-oriented stream and wide
11806 character input/output functions shall not be applied to a byte-oriented stream. The
11807 remaining stream operations do not affect, and are not affected by, a stream's orientation,
11808 except for the following additional restrictions:
11809 -- Binary wide-oriented streams have the file-positioning restrictions ascribed to both
11810 text and binary streams.
11811 -- For wide-oriented streams, after a successful call to a file-positioning function that
11812 leaves the file position indicator prior to the end-of-file, a wide character output
11813 function can overwrite a partial multibyte character; any file contents beyond the
11814 byte(s) written are henceforth indeterminate.
11815 6 Each wide-oriented stream has an associated mbstate_t object that stores the current
11816 parse state of the stream. A successful call to fgetpos stores a representation of the
11817 value of this mbstate_t object as part of the value of the fpos_t object. A later
11818 successful call to fsetpos using the same stored fpos_t value restores the value of
11819 the associated mbstate_t object as well as the position within the controlled stream.
11820 Environmental limits
11821 7 An implementation shall support text files with lines containing at least 254 characters,
11822 including the terminating new-line character. The value of the macro BUFSIZ shall be at
11824 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>),
11825 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
11826 (<a href="#7.21.9.3">7.21.9.3</a>).
11831 <sup><a name="note260" href="#note260"><b>260)</b></a></sup> The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
11833 [<a name="p299" href="#p299">page 299</a>] (<a href="#Contents">Contents</a>)
11835 <a name="7.21.3" href="#7.21.3"><b> 7.21.3 Files</b></a>
11836 1 A stream is associated with an external file (which may be a physical device) by opening
11837 a file, which may involve creating a new file. Creating an existing file causes its former
11838 contents to be discarded, if necessary. If a file can support positioning requests (such as a
11839 disk file, as opposed to a terminal), then a file position indicator associated with the
11840 stream is positioned at the start (character number zero) of the file, unless the file is
11841 opened with append mode in which case it is implementation-defined whether the file
11842 position indicator is initially positioned at the beginning or the end of the file. The file
11843 position indicator is maintained by subsequent reads, writes, and positioning requests, to
11844 facilitate an orderly progression through the file.
11845 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
11846 stream causes the associated file to be truncated beyond that point is implementation-
11848 3 When a stream is unbuffered, characters are intended to appear from the source or at the
11849 destination as soon as possible. Otherwise characters may be accumulated and
11850 transmitted to or from the host environment as a block. When a stream is fully buffered,
11851 characters are intended to be transmitted to or from the host environment as a block when
11852 a buffer is filled. When a stream is line buffered, characters are intended to be
11853 transmitted to or from the host environment as a block when a new-line character is
11854 encountered. Furthermore, characters are intended to be transmitted as a block to the host
11855 environment when a buffer is filled, when input is requested on an unbuffered stream, or
11856 when input is requested on a line buffered stream that requires the transmission of
11857 characters from the host environment. Support for these characteristics is
11858 implementation-defined, and may be affected via the setbuf and setvbuf functions.
11859 4 A file may be disassociated from a controlling stream by closing the file. Output streams
11860 are flushed (any unwritten buffer contents are transmitted to the host environment) before
11861 the stream is disassociated from the file. The value of a pointer to a FILE object is
11862 indeterminate after the associated file is closed (including the standard text streams).
11863 Whether a file of zero length (on which no characters have been written by an output
11864 stream) actually exists is implementation-defined.
11865 5 The file may be subsequently reopened, by the same or another program execution, and
11866 its contents reclaimed or modified (if it can be repositioned at its start). If the main
11867 function returns to its original caller, or if the exit function is called, all open files are
11868 closed (hence all output streams are flushed) before program termination. Other paths to
11869 program termination, such as calling the abort function, need not close all files
11871 6 The address of the FILE object used to control a stream may be significant; a copy of a
11872 FILE object need not serve in place of the original.
11874 [<a name="p300" href="#p300">page 300</a>] (<a href="#Contents">Contents</a>)
11876 7 At program startup, three text streams are predefined and need not be opened explicitly
11877 -- standard input (for reading conventional input), standard output (for writing
11878 conventional output), and standard error (for writing diagnostic output). As initially
11879 opened, the standard error stream is not fully buffered; the standard input and standard
11880 output streams are fully buffered if and only if the stream can be determined not to refer
11881 to an interactive device.
11882 8 Functions that open additional (nontemporary) files require a file name, which is a string.
11883 The rules for composing valid file names are implementation-defined. Whether the same
11884 file can be simultaneously open multiple times is also implementation-defined.
11885 9 Although both text and binary wide-oriented streams are conceptually sequences of wide
11886 characters, the external file associated with a wide-oriented stream is a sequence of
11887 multibyte characters, generalized as follows:
11888 -- Multibyte encodings within files may contain embedded null bytes (unlike multibyte
11889 encodings valid for use internal to the program).
11890 -- A file need not begin nor end in the initial shift state.<sup><a href="#note261"><b>261)</b></a></sup>
11891 10 Moreover, the encodings used for multibyte characters may differ among files. Both the
11892 nature and choice of such encodings are implementation-defined.
11893 11 The wide character input functions read multibyte characters from the stream and convert
11894 them to wide characters as if they were read by successive calls to the fgetwc function.
11895 Each conversion occurs as if by a call to the mbrtowc function, with the conversion state
11896 described by the stream's own mbstate_t object. The byte input functions read
11897 characters from the stream as if by successive calls to the fgetc function.
11898 12 The wide character output functions convert wide characters to multibyte characters and
11899 write them to the stream as if they were written by successive calls to the fputwc
11900 function. Each conversion occurs as if by a call to the wcrtomb function, with the
11901 conversion state described by the stream's own mbstate_t object. The byte output
11902 functions write characters to the stream as if by successive calls to the fputc function.
11903 13 In some cases, some of the byte input/output functions also perform conversions between
11904 multibyte characters and wide characters. These conversions also occur as if by calls to
11905 the mbrtowc and wcrtomb functions.
11906 14 An encoding error occurs if the character sequence presented to the underlying
11907 mbrtowc function does not form a valid (generalized) multibyte character, or if the code
11908 value passed to the underlying wcrtomb does not correspond to a valid (generalized)
11911 <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
11912 undefined behavior for a binary stream (because of possible trailing null characters) or for any stream
11913 with state-dependent encoding that does not assuredly end in the initial shift state.
11915 [<a name="p301" href="#p301">page 301</a>] (<a href="#Contents">Contents</a>)
11917 multibyte character. The wide character input/output functions and the byte input/output
11918 functions store the value of the macro EILSEQ in errno if and only if an encoding error
11920 Environmental limits
11921 15 The value of FOPEN_MAX shall be at least eight, including the three standard text
11923 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
11924 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
11925 (<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
11926 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
11927 (<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>).
11928 <a name="7.21.4" href="#7.21.4"><b> 7.21.4 Operations on files</b></a>
11929 <a name="7.21.4.1" href="#7.21.4.1"><b> 7.21.4.1 The remove function</b></a>
11931 1 #include <a href="#7.21"><stdio.h></a>
11932 int remove(const char *filename);
11933 <b> Description</b>
11934 2 The remove function causes the file whose name is the string pointed to by filename
11935 to be no longer accessible by that name. A subsequent attempt to open that file using that
11936 name will fail, unless it is created anew. If the file is open, the behavior of the remove
11937 function is implementation-defined.
11939 3 The remove function returns zero if the operation succeeds, nonzero if it fails.
11940 <a name="7.21.4.2" href="#7.21.4.2"><b> 7.21.4.2 The rename function</b></a>
11942 1 #include <a href="#7.21"><stdio.h></a>
11943 int rename(const char *old, const char *new);
11944 <b> Description</b>
11945 2 The rename function causes the file whose name is the string pointed to by old to be
11946 henceforth known by the name given by the string pointed to by new. The file named
11947 old is no longer accessible by that name. If a file named by the string pointed to by new
11948 exists prior to the call to the rename function, the behavior is implementation-defined.
11950 [<a name="p302" href="#p302">page 302</a>] (<a href="#Contents">Contents</a>)
11953 3 The rename function returns zero if the operation succeeds, nonzero if it fails,<sup><a href="#note262"><b>262)</b></a></sup> in
11954 which case if the file existed previously it is still known by its original name.
11955 <a name="7.21.4.3" href="#7.21.4.3"><b> 7.21.4.3 The tmpfile function</b></a>
11957 1 #include <a href="#7.21"><stdio.h></a>
11958 FILE *tmpfile(void);
11959 <b> Description</b>
11960 2 The tmpfile function creates a temporary binary file that is different from any other
11961 existing file and that will automatically be removed when it is closed or at program
11962 termination. If the program terminates abnormally, whether an open temporary file is
11963 removed is implementation-defined. The file is opened for update with "wb+" mode.
11964 Recommended practice
11965 3 It should be possible to open at least TMP_MAX temporary files during the lifetime of the
11966 program (this limit may be shared with tmpnam) and there should be no limit on the
11967 number simultaneously open other than this limit and any limit on the number of open
11970 4 The tmpfile function returns a pointer to the stream of the file that it created. If the file
11971 cannot be created, the tmpfile function returns a null pointer.
11972 Forward references: the fopen function (<a href="#7.21.5.3">7.21.5.3</a>).
11973 <a name="7.21.4.4" href="#7.21.4.4"><b> 7.21.4.4 The tmpnam function</b></a>
11975 1 #include <a href="#7.21"><stdio.h></a>
11976 char *tmpnam(char *s);
11977 <b> Description</b>
11978 2 The tmpnam function generates a string that is a valid file name and that is not the same
11979 as the name of an existing file.<sup><a href="#note263"><b>263)</b></a></sup> The function is potentially capable of generating at
11982 <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
11983 or that it is necessary to copy its contents to effectuate its renaming.
11984 <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
11985 their names should not collide with those generated by conventional naming rules for the
11986 implementation. It is still necessary to use the remove function to remove such files when their use
11987 is ended, and before program termination.
11989 [<a name="p303" href="#p303">page 303</a>] (<a href="#Contents">Contents</a>)
11991 least TMP_MAX different strings, but any or all of them may already be in use by existing
11992 files and thus not be suitable return values.
11993 3 The tmpnam function generates a different string each time it is called.
11994 4 Calls to the tmpnam function with a null pointer argument may introduce data races with
11995 each other. The implementation shall behave as if no library function calls the tmpnam
11998 5 If no suitable string can be generated, the tmpnam function returns a null pointer.
11999 Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an
12000 internal static object and returns a pointer to that object (subsequent calls to the tmpnam
12001 function may modify the same object). If the argument is not a null pointer, it is assumed
12002 to point to an array of at least L_tmpnam chars; the tmpnam function writes its result
12003 in that array and returns the argument as its value.
12004 Environmental limits
12005 6 The value of the macro TMP_MAX shall be at least 25.
12006 <a name="7.21.5" href="#7.21.5"><b> 7.21.5 File access functions</b></a>
12007 <a name="7.21.5.1" href="#7.21.5.1"><b> 7.21.5.1 The fclose function</b></a>
12009 1 #include <a href="#7.21"><stdio.h></a>
12010 int fclose(FILE *stream);
12011 <b> Description</b>
12012 2 A successful call to the fclose function causes the stream pointed to by stream to be
12013 flushed and the associated file to be closed. Any unwritten buffered data for the stream
12014 are delivered to the host environment to be written to the file; any unread buffered data
12015 are discarded. Whether or not the call succeeds, the stream is disassociated from the file
12016 and any buffer set by the setbuf or setvbuf function is disassociated from the stream
12017 (and deallocated if it was automatically allocated).
12019 3 The fclose function returns zero if the stream was successfully closed, or EOF if any
12020 errors were detected.
12022 [<a name="p304" href="#p304">page 304</a>] (<a href="#Contents">Contents</a>)
12024 <a name="7.21.5.2" href="#7.21.5.2"><b> 7.21.5.2 The fflush function</b></a>
12026 1 #include <a href="#7.21"><stdio.h></a>
12027 int fflush(FILE *stream);
12028 <b> Description</b>
12029 2 If stream points to an output stream or an update stream in which the most recent
12030 operation was not input, the fflush function causes any unwritten data for that stream
12031 to be delivered to the host environment to be written to the file; otherwise, the behavior is
12033 3 If stream is a null pointer, the fflush function performs this flushing action on all
12034 streams for which the behavior is defined above.
12036 4 The fflush function sets the error indicator for the stream and returns EOF if a write
12037 error occurs, otherwise it returns zero.
12038 Forward references: the fopen function (<a href="#7.21.5.3">7.21.5.3</a>).
12039 <a name="7.21.5.3" href="#7.21.5.3"><b> 7.21.5.3 The fopen function</b></a>
12041 1 #include <a href="#7.21"><stdio.h></a>
12042 FILE *fopen(const char * restrict filename,
12043 const char * restrict mode);
12044 <b> Description</b>
12045 2 The fopen function opens the file whose name is the string pointed to by filename,
12046 and associates a stream with it.
12047 3 The argument mode points to a string. If the string is one of the following, the file is
12048 open in the indicated mode. Otherwise, the behavior is undefined.<sup><a href="#note264"><b>264)</b></a></sup>
12049 r open text file for reading
12050 w truncate to zero length or create text file for writing
12051 wx create text file for writing
12052 a append; open or create text file for writing at end-of-file
12053 rb open binary file for reading
12054 wb truncate to zero length or create binary file for writing
12057 <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
12058 remaining characters, or it might use them to select different kinds of a file (some of which might not
12059 conform to the properties in <a href="#7.21.2">7.21.2</a>).
12061 [<a name="p305" href="#p305">page 305</a>] (<a href="#Contents">Contents</a>)
12063 wbx create binary file for writing
12064 ab append; open or create binary file for writing at end-of-file
12065 r+ open text file for update (reading and writing)
12066 w+ truncate to zero length or create text file for update
12067 w+x create text file for update
12068 a+ append; open or create text file for update, writing at end-of-file
12069 r+b or rb+ open binary file for update (reading and writing)
12070 w+b or wb+ truncate to zero length or create binary file for update
12071 w+bx or wb+x create binary file for update
12072 a+b or ab+ append; open or create binary file for update, writing at end-of-file
12073 4 Opening a file with read mode ('r' as the first character in the mode argument) fails if
12074 the file does not exist or cannot be read.
12075 5 Opening a file with exclusive mode ('x' as the last character in the mode argument)
12076 fails if the file already exists or cannot be created. Otherwise, the file is created with
12077 exclusive (also known as non-shared) access to the extent that the underlying system
12078 supports exclusive access.
12079 6 Opening a file with append mode ('a' as the first character in the mode argument)
12080 causes all subsequent writes to the file to be forced to the then current end-of-file,
12081 regardless of intervening calls to the fseek function. In some implementations, opening
12082 a binary file with append mode ('b' as the second or third character in the above list of
12083 mode argument values) may initially position the file position indicator for the stream
12084 beyond the last data written, because of null character padding.
12085 7 When a file is opened with update mode ('+' as the second or third character in the
12086 above list of mode argument values), both input and output may be performed on the
12087 associated stream. However, output shall not be directly followed by input without an
12088 intervening call to the fflush function or to a file positioning function (fseek,
12089 fsetpos, or rewind), and input shall not be directly followed by output without an
12090 intervening call to a file positioning function, unless the input operation encounters end-
12091 of-file. Opening (or creating) a text file with update mode may instead open (or create) a
12092 binary stream in some implementations.
12093 8 When opened, a stream is fully buffered if and only if it can be determined not to refer to
12094 an interactive device. The error and end-of-file indicators for the stream are cleared.
12096 9 The fopen function returns a pointer to the object controlling the stream. If the open
12097 operation fails, fopen returns a null pointer.
12098 Forward references: file positioning functions (<a href="#7.21.9">7.21.9</a>).
12100 [<a name="p306" href="#p306">page 306</a>] (<a href="#Contents">Contents</a>)
12102 <a name="7.21.5.4" href="#7.21.5.4"><b> 7.21.5.4 The freopen function</b></a>
12104 1 #include <a href="#7.21"><stdio.h></a>
12105 FILE *freopen(const char * restrict filename,
12106 const char * restrict mode,
12107 FILE * restrict stream);
12108 <b> Description</b>
12109 2 The freopen function opens the file whose name is the string pointed to by filename
12110 and associates the stream pointed to by stream with it. The mode argument is used just
12111 as in the fopen function.<sup><a href="#note265"><b>265)</b></a></sup>
12112 3 If filename is a null pointer, the freopen function attempts to change the mode of
12113 the stream to that specified by mode, as if the name of the file currently associated with
12114 the stream had been used. It is implementation-defined which changes of mode are
12115 permitted (if any), and under what circumstances.
12116 4 The freopen function first attempts to close any file that is associated with the specified
12117 stream. Failure to close the file is ignored. The error and end-of-file indicators for the
12118 stream are cleared.
12120 5 The freopen function returns a null pointer if the open operation fails. Otherwise,
12121 freopen returns the value of stream.
12122 <a name="7.21.5.5" href="#7.21.5.5"><b> 7.21.5.5 The setbuf function</b></a>
12124 1 #include <a href="#7.21"><stdio.h></a>
12125 void setbuf(FILE * restrict stream,
12126 char * restrict buf);
12127 <b> Description</b>
12128 2 Except that it returns no value, the setbuf function is equivalent to the setvbuf
12129 function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
12130 is a null pointer), with the value _IONBF for mode.
12135 <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
12136 (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value
12137 returned by the fopen function may be assigned.
12139 [<a name="p307" href="#p307">page 307</a>] (<a href="#Contents">Contents</a>)
12142 3 The setbuf function returns no value.
12143 Forward references: the setvbuf function (<a href="#7.21.5.6">7.21.5.6</a>).
12144 <a name="7.21.5.6" href="#7.21.5.6"><b> 7.21.5.6 The setvbuf function</b></a>
12146 1 #include <a href="#7.21"><stdio.h></a>
12147 int setvbuf(FILE * restrict stream,
12148 char * restrict buf,
12149 int mode, size_t size);
12150 <b> Description</b>
12151 2 The setvbuf function may be used only after the stream pointed to by stream has
12152 been associated with an open file and before any other operation (other than an
12153 unsuccessful call to setvbuf) is performed on the stream. The argument mode
12154 determines how stream will be buffered, as follows: _IOFBF causes input/output to be
12155 fully buffered; _IOLBF causes input/output to be line buffered; _IONBF causes
12156 input/output to be unbuffered. If buf is not a null pointer, the array it points to may be
12157 used instead of a buffer allocated by the setvbuf function<sup><a href="#note266"><b>266)</b></a></sup> and the argument size
12158 specifies the size of the array; otherwise, size may determine the size of a buffer
12159 allocated by the setvbuf function. The contents of the array at any time are
12162 3 The setvbuf function returns zero on success, or nonzero if an invalid value is given
12163 for mode or if the request cannot be honored.
12168 <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
12169 before a buffer that has automatic storage duration is deallocated upon block exit.
12171 [<a name="p308" href="#p308">page 308</a>] (<a href="#Contents">Contents</a>)
12173 <a name="7.21.6" href="#7.21.6"><b> 7.21.6 Formatted input/output functions</b></a>
12174 1 The formatted input/output functions shall behave as if there is a sequence point after the
12175 actions associated with each specifier.<sup><a href="#note267"><b>267)</b></a></sup>
12176 <a name="7.21.6.1" href="#7.21.6.1"><b> 7.21.6.1 The fprintf function</b></a>
12178 1 #include <a href="#7.21"><stdio.h></a>
12179 int fprintf(FILE * restrict stream,
12180 const char * restrict format, ...);
12181 <b> Description</b>
12182 2 The fprintf function writes output to the stream pointed to by stream, under control
12183 of the string pointed to by format that specifies how subsequent arguments are
12184 converted for output. If there are insufficient arguments for the format, the behavior is
12185 undefined. If the format is exhausted while arguments remain, the excess arguments are
12186 evaluated (as always) but are otherwise ignored. The fprintf function returns when
12187 the end of the format string is encountered.
12188 3 The format shall be a multibyte character sequence, beginning and ending in its initial
12189 shift state. The format is composed of zero or more directives: ordinary multibyte
12190 characters (not %), which are copied unchanged to the output stream; and conversion
12191 specifications, each of which results in fetching zero or more subsequent arguments,
12192 converting them, if applicable, according to the corresponding conversion specifier, and
12193 then writing the result to the output stream.
12194 4 Each conversion specification is introduced by the character %. After the %, the following
12195 appear in sequence:
12196 -- Zero or more flags (in any order) that modify the meaning of the conversion
12198 -- An optional minimum field width. If the converted value has fewer characters than the
12199 field width, it is padded with spaces (by default) on the left (or right, if the left
12200 adjustment flag, described later, has been given) to the field width. The field width
12201 takes the form of an asterisk * (described later) or a nonnegative decimal integer.<sup><a href="#note268"><b>268)</b></a></sup>
12202 -- An optional precision that gives the minimum number of digits to appear for the d, i,
12203 o, u, x, and X conversions, the number of digits to appear after the decimal-point
12204 character for a, A, e, E, f, and F conversions, the maximum number of significant
12205 digits for the g and G conversions, or the maximum number of bytes to be written for
12208 <sup><a name="note267" href="#note267"><b>267)</b></a></sup> The fprintf functions perform writes to memory for the %n specifier.
12209 <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.
12211 [<a name="p309" href="#p309">page 309</a>] (<a href="#Contents">Contents</a>)
12213 s conversions. The precision takes the form of a period (.) followed either by an
12214 asterisk * (described later) or by an optional decimal integer; if only the period is
12215 specified, the precision is taken as zero. If a precision appears with any other
12216 conversion specifier, the behavior is undefined.
12217 -- An optional length modifier that specifies the size of the argument.
12218 -- A conversion specifier character that specifies the type of conversion to be applied.
12219 5 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
12220 this case, an int argument supplies the field width or precision. The arguments
12221 specifying field width, or precision, or both, shall appear (in that order) before the
12222 argument (if any) to be converted. A negative field width argument is taken as a - flag
12223 followed by a positive field width. A negative precision argument is taken as if the
12224 precision were omitted.
12225 6 The flag characters and their meanings are:
12226 - The result of the conversion is left-justified within the field. (It is right-justified if
12227 this flag is not specified.)
12228 + The result of a signed conversion always begins with a plus or minus sign. (It
12229 begins with a sign only when a negative value is converted if this flag is not
12230 specified.)<sup><a href="#note269"><b>269)</b></a></sup>
12231 space If the first character of a signed conversion is not a sign, or if a signed conversion
12232 results in no characters, a space is prefixed to the result. If the space and + flags
12233 both appear, the space flag is ignored.
12234 # The result is converted to an ''alternative form''. For o conversion, it increases
12235 the precision, if and only if necessary, to force the first digit of the result to be a
12236 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
12237 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
12238 and G conversions, the result of converting a floating-point number always
12239 contains a decimal-point character, even if no digits follow it. (Normally, a
12240 decimal-point character appears in the result of these conversions only if a digit
12241 follows it.) For g and G conversions, trailing zeros are not removed from the
12242 result. For other conversions, the behavior is undefined.
12243 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
12244 (following any indication of sign or base) are used to pad to the field width rather
12245 than performing space padding, except when converting an infinity or NaN. If the
12246 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
12249 <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,
12250 include a minus sign.
12252 [<a name="p310" href="#p310">page 310</a>] (<a href="#Contents">Contents</a>)
12254 conversions, if a precision is specified, the 0 flag is ignored. For other
12255 conversions, the behavior is undefined.
12256 7 The length modifiers and their meanings are:
12257 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12258 signed char or unsigned char argument (the argument will have
12259 been promoted according to the integer promotions, but its value shall be
12260 converted to signed char or unsigned char before printing); or that
12261 a following n conversion specifier applies to a pointer to a signed char
12263 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12264 short int or unsigned short int argument (the argument will
12265 have been promoted according to the integer promotions, but its value shall
12266 be converted to short int or unsigned short int before printing);
12267 or that a following n conversion specifier applies to a pointer to a short
12269 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12270 long int or unsigned long int argument; that a following n
12271 conversion specifier applies to a pointer to a long int argument; that a
12272 following c conversion specifier applies to a wint_t argument; that a
12273 following s conversion specifier applies to a pointer to a wchar_t
12274 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
12276 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12277 long long int or unsigned long long int argument; or that a
12278 following n conversion specifier applies to a pointer to a long long int
12280 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
12281 an intmax_t or uintmax_t argument; or that a following n conversion
12282 specifier applies to a pointer to an intmax_t argument.
12283 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12284 size_t or the corresponding signed integer type argument; or that a
12285 following n conversion specifier applies to a pointer to a signed integer type
12286 corresponding to size_t argument.
12287 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
12288 ptrdiff_t or the corresponding unsigned integer type argument; or that a
12289 following n conversion specifier applies to a pointer to a ptrdiff_t
12292 [<a name="p311" href="#p311">page 311</a>] (<a href="#Contents">Contents</a>)
12294 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
12295 applies to a long double argument.
12296 If a length modifier appears with any conversion specifier other than as specified above,
12297 the behavior is undefined.
12298 8 The conversion specifiers and their meanings are:
12299 d,i The int argument is converted to signed decimal in the style [-]dddd. The
12300 precision specifies the minimum number of digits to appear; if the value
12301 being converted can be represented in fewer digits, it is expanded with
12302 leading zeros. The default precision is 1. The result of converting a zero
12303 value with a precision of zero is no characters.
12304 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
12305 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
12306 letters abcdef are used for x conversion and the letters ABCDEF for X
12307 conversion. The precision specifies the minimum number of digits to appear;
12308 if the value being converted can be represented in fewer digits, it is expanded
12309 with leading zeros. The default precision is 1. The result of converting a
12310 zero value with a precision of zero is no characters.
12311 f,F A double argument representing a floating-point number is converted to
12312 decimal notation in the style [-]ddd.ddd, where the number of digits after
12313 the decimal-point character is equal to the precision specification. If the
12314 precision is missing, it is taken as 6; if the precision is zero and the # flag is
12315 not specified, no decimal-point character appears. If a decimal-point
12316 character appears, at least one digit appears before it. The value is rounded to
12317 the appropriate number of digits.
12318 A double argument representing an infinity is converted in one of the styles
12319 [-]inf or [-]infinity -- which style is implementation-defined. A
12320 double argument representing a NaN is converted in one of the styles
12321 [-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
12322 any n-char-sequence, is implementation-defined. The F conversion specifier
12323 produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
12324 respectively.<sup><a href="#note270"><b>270)</b></a></sup>
12325 e,E A double argument representing a floating-point number is converted in the
12326 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
12327 argument is nonzero) before the decimal-point character and the number of
12328 digits after it is equal to the precision; if the precision is missing, it is taken as
12331 <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;
12332 the # and 0 flag characters have no effect.
12334 [<a name="p312" href="#p312">page 312</a>] (<a href="#Contents">Contents</a>)
12336 6; if the precision is zero and the # flag is not specified, no decimal-point
12337 character appears. The value is rounded to the appropriate number of digits.
12338 The E conversion specifier produces a number with E instead of e
12339 introducing the exponent. The exponent always contains at least two digits,
12340 and only as many more digits as necessary to represent the exponent. If the
12341 value is zero, the exponent is zero.
12342 A double argument representing an infinity or NaN is converted in the style
12343 of an f or F conversion specifier.
12344 g,G A double argument representing a floating-point number is converted in
12345 style f or e (or in style F or E in the case of a G conversion specifier),
12346 depending on the value converted and the precision. Let P equal the
12347 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
12348 Then, if a conversion with style E would have an exponent of X:
12349 -- if P > X >= -4, the conversion is with style f (or F) and precision
12351 -- otherwise, the conversion is with style e (or E) and precision P - 1.
12352 Finally, unless the # flag is used, any trailing zeros are removed from the
12353 fractional portion of the result and the decimal-point character is removed if
12354 there is no fractional portion remaining.
12355 A double argument representing an infinity or NaN is converted in the style
12356 of an f or F conversion specifier.
12357 a,A A double argument representing a floating-point number is converted in the
12358 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
12359 nonzero if the argument is a normalized floating-point number and is
12360 otherwise unspecified) before the decimal-point character<sup><a href="#note271"><b>271)</b></a></sup> and the number
12361 of hexadecimal digits after it is equal to the precision; if the precision is
12362 missing and FLT_RADIX is a power of 2, then the precision is sufficient for
12363 an exact representation of the value; if the precision is missing and
12364 FLT_RADIX is not a power of 2, then the precision is sufficient to
12369 <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
12370 that subsequent digits align to nibble (4-bit) boundaries.
12372 [<a name="p313" href="#p313">page 313</a>] (<a href="#Contents">Contents</a>)
12374 distinguish<sup><a href="#note272"><b>272)</b></a></sup> values of type double, except that trailing zeros may be
12375 omitted; if the precision is zero and the # flag is not specified, no decimal-
12376 point character appears. The letters abcdef are used for a conversion and
12377 the letters ABCDEF for A conversion. The A conversion specifier produces a
12378 number with X and P instead of x and p. The exponent always contains at
12379 least one digit, and only as many more digits as necessary to represent the
12380 decimal exponent of 2. If the value is zero, the exponent is zero.
12381 A double argument representing an infinity or NaN is converted in the style
12382 of an f or F conversion specifier.
12383 c If no l length modifier is present, the int argument is converted to an
12384 unsigned char, and the resulting character is written.
12385 If an l length modifier is present, the wint_t argument is converted as if by
12386 an ls conversion specification with no precision and an argument that points
12387 to the initial element of a two-element array of wchar_t, the first element
12388 containing the wint_t argument to the lc conversion specification and the
12389 second a null wide character.
12390 s If no l length modifier is present, the argument shall be a pointer to the initial
12391 element of an array of character type.<sup><a href="#note273"><b>273)</b></a></sup> Characters from the array are
12392 written up to (but not including) the terminating null character. If the
12393 precision is specified, no more than that many bytes are written. If the
12394 precision is not specified or is greater than the size of the array, the array shall
12395 contain a null character.
12396 If an l length modifier is present, the argument shall be a pointer to the initial
12397 element of an array of wchar_t type. Wide characters from the array are
12398 converted to multibyte characters (each as if by a call to the wcrtomb
12399 function, with the conversion state described by an mbstate_t object
12400 initialized to zero before the first wide character is converted) up to and
12401 including a terminating null wide character. The resulting multibyte
12402 characters are written up to (but not including) the terminating null character
12403 (byte). If no precision is specified, the array shall contain a null wide
12404 character. If a precision is specified, no more than that many bytes are
12405 written (including shift sequences, if any), and the array shall contain a null
12406 wide character if, to equal the multibyte character sequence length given by
12408 <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
12409 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
12410 might suffice depending on the implementation's scheme for determining the digit to the left of the
12411 decimal-point character.
12412 <sup><a name="note273" href="#note273"><b>273)</b></a></sup> No special provisions are made for multibyte characters.
12414 [<a name="p314" href="#p314">page 314</a>] (<a href="#Contents">Contents</a>)
12416 the precision, the function would need to access a wide character one past the
12417 end of the array. In no case is a partial multibyte character written.<sup><a href="#note274"><b>274)</b></a></sup>
12418 p The argument shall be a pointer to void. The value of the pointer is
12419 converted to a sequence of printing characters, in an implementation-defined
12421 n The argument shall be a pointer to signed integer into which is written the
12422 number of characters written to the output stream so far by this call to
12423 fprintf. No argument is converted, but one is consumed. If the conversion
12424 specification includes any flags, a field width, or a precision, the behavior is
12426 % A % character is written. No argument is converted. The complete
12427 conversion specification shall be %%.
12428 9 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note275"><b>275)</b></a></sup> If any argument is
12429 not the correct type for the corresponding conversion specification, the behavior is
12431 10 In no case does a nonexistent or small field width cause truncation of a field; if the result
12432 of a conversion is wider than the field width, the field is expanded to contain the
12434 11 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
12435 to a hexadecimal floating number with the given precision.
12436 Recommended practice
12437 12 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
12438 representable in the given precision, the result should be one of the two adjacent numbers
12439 in hexadecimal floating style with the given precision, with the extra stipulation that the
12440 error should have a correct sign for the current rounding direction.
12441 13 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
12442 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note276"><b>276)</b></a></sup> If the number of
12443 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
12444 representable with DECIMAL_DIG digits, then the result should be an exact
12445 representation with trailing zeros. Otherwise, the source value is bounded by two
12446 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
12449 <sup><a name="note274" href="#note274"><b>274)</b></a></sup> Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
12450 <sup><a name="note275" href="#note275"><b>275)</b></a></sup> See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
12451 <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
12452 given format specifier. The number of significant digits is determined by the format specifier, and in
12453 the case of fixed-point conversion by the source value as well.
12455 [<a name="p315" href="#p315">page 315</a>] (<a href="#Contents">Contents</a>)
12457 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
12458 the error should have a correct sign for the current rounding direction.
12460 14 The fprintf function returns the number of characters transmitted, or a negative value
12461 if an output or encoding error occurred.
12462 Environmental limits
12463 15 The number of characters that can be produced by any single conversion shall be at least
12465 16 EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
12467 #include <a href="#7.12"><math.h></a>
12468 #include <a href="#7.21"><stdio.h></a>
12470 char *weekday, *month; // pointers to strings
12471 int day, hour, min;
12472 fprintf(stdout, "%s, %s %d, %.2d:%.2d\n",
12473 weekday, month, day, hour, min);
12474 fprintf(stdout, "pi = %.5f\n", 4 * atan(1.0));
12476 17 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the
12477 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
12478 the first of which is denoted here by a and the second by an uppercase letter.
12479 18 Given the following wide string with length seven,
12480 static wchar_t wstr[] = L" X Yabc Z W";
12482 fprintf(stdout, "|1234567890123|\n");
12483 fprintf(stdout, "|%13ls|\n", wstr);
12484 fprintf(stdout, "|%-13.9ls|\n", wstr);
12485 fprintf(stdout, "|%13.10ls|\n", wstr);
12486 fprintf(stdout, "|%13.11ls|\n", wstr);
12487 fprintf(stdout, "|%13.15ls|\n", &wstr[2]);
12488 fprintf(stdout, "|%13lc|\n", (wint_t) wstr[5]);
12489 will print the following seven lines:
12498 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>).
12500 [<a name="p316" href="#p316">page 316</a>] (<a href="#Contents">Contents</a>)
12502 <a name="7.21.6.2" href="#7.21.6.2"><b> 7.21.6.2 The fscanf function</b></a>
12504 1 #include <a href="#7.21"><stdio.h></a>
12505 int fscanf(FILE * restrict stream,
12506 const char * restrict format, ...);
12507 <b> Description</b>
12508 2 The fscanf function reads input from the stream pointed to by stream, under control
12509 of the string pointed to by format that specifies the admissible input sequences and how
12510 they are to be converted for assignment, using subsequent arguments as pointers to the
12511 objects to receive the converted input. If there are insufficient arguments for the format,
12512 the behavior is undefined. If the format is exhausted while arguments remain, the excess
12513 arguments are evaluated (as always) but are otherwise ignored.
12514 3 The format shall be a multibyte character sequence, beginning and ending in its initial
12515 shift state. The format is composed of zero or more directives: one or more white-space
12516 characters, an ordinary multibyte character (neither % nor a white-space character), or a
12517 conversion specification. Each conversion specification is introduced by the character %.
12518 After the %, the following appear in sequence:
12519 -- An optional assignment-suppressing character *.
12520 -- An optional decimal integer greater than zero that specifies the maximum field width
12522 -- An optional length modifier that specifies the size of the receiving object.
12523 -- A conversion specifier character that specifies the type of conversion to be applied.
12524 4 The fscanf function executes each directive of the format in turn. When all directives
12525 have been executed, or if a directive fails (as detailed below), the function returns.
12526 Failures are described as input failures (due to the occurrence of an encoding error or the
12527 unavailability of input characters), or matching failures (due to inappropriate input).
12528 5 A directive composed of white-space character(s) is executed by reading input up to the
12529 first non-white-space character (which remains unread), or until no more characters can
12531 6 A directive that is an ordinary multibyte character is executed by reading the next
12532 characters of the stream. If any of those characters differ from the ones composing the
12533 directive, the directive fails and the differing and subsequent characters remain unread.
12534 Similarly, if end-of-file, an encoding error, or a read error prevents a character from being
12535 read, the directive fails.
12536 7 A directive that is a conversion specification defines a set of matching input sequences, as
12537 described below for each specifier. A conversion specification is executed in the
12539 [<a name="p317" href="#p317">page 317</a>] (<a href="#Contents">Contents</a>)
12542 8 Input white-space characters (as specified by the isspace function) are skipped, unless
12543 the specification includes a [, c, or n specifier.<sup><a href="#note277"><b>277)</b></a></sup>
12544 9 An input item is read from the stream, unless the specification includes an n specifier. An
12545 input item is defined as the longest sequence of input characters which does not exceed
12546 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>
12547 The first character, if any, after the input item remains unread. If the length of the input
12548 item is zero, the execution of the directive fails; this condition is a matching failure unless
12549 end-of-file, an encoding error, or a read error prevented input from the stream, in which
12550 case it is an input failure.
12551 10 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
12552 count of input characters) is converted to a type appropriate to the conversion specifier. If
12553 the input item is not a matching sequence, the execution of the directive fails: this
12554 condition is a matching failure. Unless assignment suppression was indicated by a *, the
12555 result of the conversion is placed in the object pointed to by the first argument following
12556 the format argument that has not already received a conversion result. If this object
12557 does not have an appropriate type, or if the result of the conversion cannot be represented
12558 in the object, the behavior is undefined.
12559 11 The length modifiers and their meanings are:
12560 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12561 to an argument with type pointer to signed char or unsigned char.
12562 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12563 to an argument with type pointer to short int or unsigned short
12565 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12566 to an argument with type pointer to long int or unsigned long
12567 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
12568 an argument with type pointer to double; or that a following c, s, or [
12569 conversion specifier applies to an argument with type pointer to wchar_t.
12570 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12571 to an argument with type pointer to long long int or unsigned
12576 <sup><a name="note277" href="#note277"><b>277)</b></a></sup> These white-space characters are not counted against a specified field width.
12577 <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
12578 that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.
12580 [<a name="p318" href="#p318">page 318</a>] (<a href="#Contents">Contents</a>)
12582 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12583 to an argument with type pointer to intmax_t or uintmax_t.
12584 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12585 to an argument with type pointer to size_t or the corresponding signed
12587 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
12588 to an argument with type pointer to ptrdiff_t or the corresponding
12589 unsigned integer type.
12590 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
12591 applies to an argument with type pointer to long double.
12592 If a length modifier appears with any conversion specifier other than as specified above,
12593 the behavior is undefined.
12594 12 The conversion specifiers and their meanings are:
12595 d Matches an optionally signed decimal integer, whose format is the same as
12596 expected for the subject sequence of the strtol function with the value 10
12597 for the base argument. The corresponding argument shall be a pointer to
12599 i Matches an optionally signed integer, whose format is the same as expected
12600 for the subject sequence of the strtol function with the value 0 for the
12601 base argument. The corresponding argument shall be a pointer to signed
12603 o Matches an optionally signed octal integer, whose format is the same as
12604 expected for the subject sequence of the strtoul function with the value 8
12605 for the base argument. The corresponding argument shall be a pointer to
12607 u Matches an optionally signed decimal integer, whose format is the same as
12608 expected for the subject sequence of the strtoul function with the value 10
12609 for the base argument. The corresponding argument shall be a pointer to
12611 x Matches an optionally signed hexadecimal integer, whose format is the same
12612 as expected for the subject sequence of the strtoul function with the value
12613 16 for the base argument. The corresponding argument shall be a pointer to
12615 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
12616 format is the same as expected for the subject sequence of the strtod
12617 function. The corresponding argument shall be a pointer to floating.
12619 [<a name="p319" href="#p319">page 319</a>] (<a href="#Contents">Contents</a>)
12621 c Matches a sequence of characters of exactly the number specified by the field
12622 width (1 if no field width is present in the directive).<sup><a href="#note279"><b>279)</b></a></sup>
12623 If no l length modifier is present, the corresponding argument shall be a
12624 pointer to the initial element of a character array large enough to accept the
12625 sequence. No null character is added.
12626 If an l length modifier is present, the input shall be a sequence of multibyte
12627 characters that begins in the initial shift state. Each multibyte character in the
12628 sequence is converted to a wide character as if by a call to the mbrtowc
12629 function, with the conversion state described by an mbstate_t object
12630 initialized to zero before the first multibyte character is converted. The
12631 corresponding argument shall be a pointer to the initial element of an array of
12632 wchar_t large enough to accept the resulting sequence of wide characters.
12633 No null wide character is added.
12634 s Matches a sequence of non-white-space characters.279)
12635 If no l length modifier is present, the corresponding argument shall be a
12636 pointer to the initial element of a character array large enough to accept the
12637 sequence and a terminating null character, which will be added automatically.
12638 If an l length modifier is present, the input shall be a sequence of multibyte
12639 characters that begins in the initial shift state. Each multibyte character is
12640 converted to a wide character as if by a call to the mbrtowc function, with
12641 the conversion state described by an mbstate_t object initialized to zero
12642 before the first multibyte character is converted. The corresponding argument
12643 shall be a pointer to the initial element of an array of wchar_t large enough
12644 to accept the sequence and the terminating null wide character, which will be
12645 added automatically.
12646 [ Matches a nonempty sequence of characters from a set of expected characters
12648 If no l length modifier is present, the corresponding argument shall be a
12649 pointer to the initial element of a character array large enough to accept the
12650 sequence and a terminating null character, which will be added automatically.
12651 If an l length modifier is present, the input shall be a sequence of multibyte
12652 characters that begins in the initial shift state. Each multibyte character is
12653 converted to a wide character as if by a call to the mbrtowc function, with
12654 the conversion state described by an mbstate_t object initialized to zero
12656 <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 [
12657 conversion specifiers -- the extent of the input field is determined on a byte-by-byte basis. The
12658 resulting field is nevertheless a sequence of multibyte characters that begins in the initial shift state.
12660 [<a name="p320" href="#p320">page 320</a>] (<a href="#Contents">Contents</a>)
12662 before the first multibyte character is converted. The corresponding argument
12663 shall be a pointer to the initial element of an array of wchar_t large enough
12664 to accept the sequence and the terminating null wide character, which will be
12665 added automatically.
12666 The conversion specifier includes all subsequent characters in the format
12667 string, up to and including the matching right bracket (]). The characters
12668 between the brackets (the scanlist) compose the scanset, unless the character
12669 after the left bracket is a circumflex (^), in which case the scanset contains all
12670 characters that do not appear in the scanlist between the circumflex and the
12671 right bracket. If the conversion specifier begins with [] or [^], the right
12672 bracket character is in the scanlist and the next following right bracket
12673 character is the matching right bracket that ends the specification; otherwise
12674 the first following right bracket character is the one that ends the
12675 specification. If a - character is in the scanlist and is not the first, nor the
12676 second where the first character is a ^, nor the last character, the behavior is
12677 implementation-defined.
12678 p Matches an implementation-defined set of sequences, which should be the
12679 same as the set of sequences that may be produced by the %p conversion of
12680 the fprintf function. The corresponding argument shall be a pointer to a
12681 pointer to void. The input item is converted to a pointer value in an
12682 implementation-defined manner. If the input item is a value converted earlier
12683 during the same program execution, the pointer that results shall compare
12684 equal to that value; otherwise the behavior of the %p conversion is undefined.
12685 n No input is consumed. The corresponding argument shall be a pointer to
12686 signed integer into which is to be written the number of characters read from
12687 the input stream so far by this call to the fscanf function. Execution of a
12688 %n directive does not increment the assignment count returned at the
12689 completion of execution of the fscanf function. No argument is converted,
12690 but one is consumed. If the conversion specification includes an assignment-
12691 suppressing character or a field width, the behavior is undefined.
12692 % Matches a single % character; no conversion or assignment occurs. The
12693 complete conversion specification shall be %%.
12694 13 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note280"><b>280)</b></a></sup>
12695 14 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
12696 respectively, a, e, f, g, and x.
12700 <sup><a name="note280" href="#note280"><b>280)</b></a></sup> See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
12702 [<a name="p321" href="#p321">page 321</a>] (<a href="#Contents">Contents</a>)
12704 15 Trailing white space (including new-line characters) is left unread unless matched by a
12705 directive. The success of literal matches and suppressed assignments is not directly
12706 determinable other than via the %n directive.
12708 16 The fscanf function returns the value of the macro EOF if an input failure occurs
12709 before the first conversion (if any) has completed. Otherwise, the function returns the
12710 number of input items assigned, which can be fewer than provided for, or even zero, in
12711 the event of an early matching failure.
12712 17 EXAMPLE 1 The call:
12713 #include <a href="#7.21"><stdio.h></a>
12715 int n, i; float x; char name[50];
12716 n = fscanf(stdin, "%d%f%s", &i, &x, name);
12717 with the input line:
12718 25 54.32E-1 thompson
12719 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
12722 18 EXAMPLE 2 The call:
12723 #include <a href="#7.21"><stdio.h></a>
12725 int i; float x; char name[50];
12726 fscanf(stdin, "%2d%f%*d %[0123456789]", &i, &x, name);
12729 will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the
12730 sequence 56\0. The next character read from the input stream will be a.
12732 19 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
12733 #include <a href="#7.21"><stdio.h></a>
12735 int count; float quant; char units[21], item[21];
12737 count = fscanf(stdin, "%f%20s of %20s", &quant, units, item);
12738 fscanf(stdin,"%*[^\n]");
12739 } while (!feof(stdin) && !ferror(stdin));
12740 20 If the stdin stream contains the following lines:
12742 -12.8degrees Celsius
12748 [<a name="p322" href="#p322">page 322</a>] (<a href="#Contents">Contents</a>)
12750 the execution of the above example will be analogous to the following assignments:
12751 quant = 2; strcpy(units, "quarts"); strcpy(item, "oil");
12753 quant = -12.8; strcpy(units, "degrees");
12754 count = 2; // "C" fails to match "o"
12755 count = 0; // "l" fails to match "%f"
12756 quant = 10.0; strcpy(units, "LBS"); strcpy(item, "dirt");
12758 count = 0; // "100e" fails to match "%f"
12762 #include <a href="#7.21"><stdio.h></a>
12764 int d1, d2, n1, n2, i;
12765 i = sscanf("123", "%d%n%n%d", &d1, &n1, &n2, &d2);
12766 the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure the value
12767 of 3 is also assigned to n2. The value of d2 is not affected. The value 1 is assigned to i.
12769 22 EXAMPLE 5 In these examples, multibyte characters do have a state-dependent encoding, and the
12770 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
12771 the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as
12772 such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes
12773 entry into the alternate shift state.
12775 #include <a href="#7.21"><stdio.h></a>
12778 fscanf(stdin, "a%s", str);
12779 with the input line:
12780 a(uparrow) X Y(downarrow) bc
12781 str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte
12782 characters, in the more general case) appears to be a single-byte white-space character.
12783 24 In contrast, after the call:
12784 #include <a href="#7.21"><stdio.h></a>
12785 #include <a href="#7.19"><stddef.h></a>
12788 fscanf(stdin, "a%ls", wstr);
12789 with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
12790 terminating null wide character.
12791 25 However, the call:
12793 [<a name="p323" href="#p323">page 323</a>] (<a href="#Contents">Contents</a>)
12795 #include <a href="#7.21"><stdio.h></a>
12796 #include <a href="#7.19"><stddef.h></a>
12799 fscanf(stdin, "a(uparrow) X(downarrow)%ls", wstr);
12800 with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
12802 26 Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte
12803 character Y, after the call:
12804 #include <a href="#7.21"><stdio.h></a>
12805 #include <a href="#7.19"><stddef.h></a>
12808 fscanf(stdin, "a(uparrow) Y(downarrow)%ls", wstr);
12809 with the same input line, zero will again be returned, but stdin will be left with a partially consumed
12810 multibyte character.
12812 Forward references: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>), the
12813 strtol, strtoll, strtoul, and strtoull functions (<a href="#7.22.1.4">7.22.1.4</a>), conversion state
12814 (<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>).
12815 <a name="7.21.6.3" href="#7.21.6.3"><b> 7.21.6.3 The printf function</b></a>
12817 1 #include <a href="#7.21"><stdio.h></a>
12818 int printf(const char * restrict format, ...);
12819 <b> Description</b>
12820 2 The printf function is equivalent to fprintf with the argument stdout interposed
12821 before the arguments to printf.
12823 3 The printf function returns the number of characters transmitted, or a negative value if
12824 an output or encoding error occurred.
12825 <a name="7.21.6.4" href="#7.21.6.4"><b> 7.21.6.4 The scanf function</b></a>
12827 1 #include <a href="#7.21"><stdio.h></a>
12828 int scanf(const char * restrict format, ...);
12829 <b> Description</b>
12830 2 The scanf function is equivalent to fscanf with the argument stdin interposed
12831 before the arguments to scanf.
12833 [<a name="p324" href="#p324">page 324</a>] (<a href="#Contents">Contents</a>)
12836 3 The scanf function returns the value of the macro EOF if an input failure occurs before
12837 the first conversion (if any) has completed. Otherwise, the scanf function returns the
12838 number of input items assigned, which can be fewer than provided for, or even zero, in
12839 the event of an early matching failure.
12840 <a name="7.21.6.5" href="#7.21.6.5"><b> 7.21.6.5 The snprintf function</b></a>
12842 1 #include <a href="#7.21"><stdio.h></a>
12843 int snprintf(char * restrict s, size_t n,
12844 const char * restrict format, ...);
12845 <b> Description</b>
12846 2 The snprintf function is equivalent to fprintf, except that the output is written into
12847 an array (specified by argument s) rather than to a stream. If n is zero, nothing is written,
12848 and s may be a null pointer. Otherwise, output characters beyond the n-1st are
12849 discarded rather than being written to the array, and a null character is written at the end
12850 of the characters actually written into the array. If copying takes place between objects
12851 that overlap, the behavior is undefined.
12853 3 The snprintf function returns the number of characters that would have been written
12854 had n been sufficiently large, not counting the terminating null character, or a negative
12855 value if an encoding error occurred. Thus, the null-terminated output has been
12856 completely written if and only if the returned value is nonnegative and less than n.
12857 <a name="7.21.6.6" href="#7.21.6.6"><b> 7.21.6.6 The sprintf function</b></a>
12859 1 #include <a href="#7.21"><stdio.h></a>
12860 int sprintf(char * restrict s,
12861 const char * restrict format, ...);
12862 <b> Description</b>
12863 2 The sprintf function is equivalent to fprintf, except that the output is written into
12864 an array (specified by the argument s) rather than to a stream. A null character is written
12865 at the end of the characters written; it is not counted as part of the returned value. If
12866 copying takes place between objects that overlap, the behavior is undefined.
12868 3 The sprintf function returns the number of characters written in the array, not
12869 counting the terminating null character, or a negative value if an encoding error occurred.
12871 [<a name="p325" href="#p325">page 325</a>] (<a href="#Contents">Contents</a>)
12873 <a name="7.21.6.7" href="#7.21.6.7"><b> 7.21.6.7 The sscanf function</b></a>
12875 1 #include <a href="#7.21"><stdio.h></a>
12876 int sscanf(const char * restrict s,
12877 const char * restrict format, ...);
12878 <b> Description</b>
12879 2 The sscanf function is equivalent to fscanf, except that input is obtained from a
12880 string (specified by the argument s) rather than from a stream. Reaching the end of the
12881 string is equivalent to encountering end-of-file for the fscanf function. If copying
12882 takes place between objects that overlap, the behavior is undefined.
12884 3 The sscanf function returns the value of the macro EOF if an input failure occurs
12885 before the first conversion (if any) has completed. Otherwise, the sscanf function
12886 returns the number of input items assigned, which can be fewer than provided for, or even
12887 zero, in the event of an early matching failure.
12888 <a name="7.21.6.8" href="#7.21.6.8"><b> 7.21.6.8 The vfprintf function</b></a>
12890 1 #include <a href="#7.16"><stdarg.h></a>
12891 #include <a href="#7.21"><stdio.h></a>
12892 int vfprintf(FILE * restrict stream,
12893 const char * restrict format,
12895 <b> Description</b>
12896 2 The vfprintf function is equivalent to fprintf, with the variable argument list
12897 replaced by arg, which shall have been initialized by the va_start macro (and
12898 possibly subsequent va_arg calls). The vfprintf function does not invoke the
12899 va_end macro.<sup><a href="#note281"><b>281)</b></a></sup>
12901 3 The vfprintf function returns the number of characters transmitted, or a negative
12902 value if an output or encoding error occurred.
12903 4 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
12908 <sup><a name="note281" href="#note281"><b>281)</b></a></sup> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
12909 vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
12911 [<a name="p326" href="#p326">page 326</a>] (<a href="#Contents">Contents</a>)
12913 #include <a href="#7.16"><stdarg.h></a>
12914 #include <a href="#7.21"><stdio.h></a>
12915 void error(char *function_name, char *format, ...)
12918 va_start(args, format);
12919 // print out name of function causing error
12920 fprintf(stderr, "ERROR in %s: ", function_name);
12921 // print out remainder of message
12922 vfprintf(stderr, format, args);
12926 <a name="7.21.6.9" href="#7.21.6.9"><b> 7.21.6.9 The vfscanf function</b></a>
12928 1 #include <a href="#7.16"><stdarg.h></a>
12929 #include <a href="#7.21"><stdio.h></a>
12930 int vfscanf(FILE * restrict stream,
12931 const char * restrict format,
12933 <b> Description</b>
12934 2 The vfscanf function is equivalent to fscanf, with the variable argument list
12935 replaced by arg, which shall have been initialized by the va_start macro (and
12936 possibly subsequent va_arg calls). The vfscanf function does not invoke the
12939 3 The vfscanf function returns the value of the macro EOF if an input failure occurs
12940 before the first conversion (if any) has completed. Otherwise, the vfscanf function
12941 returns the number of input items assigned, which can be fewer than provided for, or even
12942 zero, in the event of an early matching failure.
12943 <a name="7.21.6.10" href="#7.21.6.10"><b> 7.21.6.10 The vprintf function</b></a>
12945 1 #include <a href="#7.16"><stdarg.h></a>
12946 #include <a href="#7.21"><stdio.h></a>
12947 int vprintf(const char * restrict format,
12949 <b> Description</b>
12950 2 The vprintf function is equivalent to printf, with the variable argument list
12951 replaced by arg, which shall have been initialized by the va_start macro (and
12953 [<a name="p327" href="#p327">page 327</a>] (<a href="#Contents">Contents</a>)
12955 possibly subsequent va_arg calls). The vprintf function does not invoke the
12958 3 The vprintf function returns the number of characters transmitted, or a negative value
12959 if an output or encoding error occurred.
12960 <a name="7.21.6.11" href="#7.21.6.11"><b> 7.21.6.11 The vscanf function</b></a>
12962 1 #include <a href="#7.16"><stdarg.h></a>
12963 #include <a href="#7.21"><stdio.h></a>
12964 int vscanf(const char * restrict format,
12966 <b> Description</b>
12967 2 The vscanf function is equivalent to scanf, with the variable argument list replaced
12968 by arg, which shall have been initialized by the va_start macro (and possibly
12969 subsequent va_arg calls). The vscanf function does not invoke the va_end
12972 3 The vscanf function returns the value of the macro EOF if an input failure occurs
12973 before the first conversion (if any) has completed. Otherwise, the vscanf function
12974 returns the number of input items assigned, which can be fewer than provided for, or even
12975 zero, in the event of an early matching failure.
12976 <a name="7.21.6.12" href="#7.21.6.12"><b> 7.21.6.12 The vsnprintf function</b></a>
12978 1 #include <a href="#7.16"><stdarg.h></a>
12979 #include <a href="#7.21"><stdio.h></a>
12980 int vsnprintf(char * restrict s, size_t n,
12981 const char * restrict format,
12983 <b> Description</b>
12984 2 The vsnprintf function is equivalent to snprintf, with the variable argument list
12985 replaced by arg, which shall have been initialized by the va_start macro (and
12986 possibly subsequent va_arg calls). The vsnprintf function does not invoke the
12987 va_end macro.281) If copying takes place between objects that overlap, the behavior is
12990 [<a name="p328" href="#p328">page 328</a>] (<a href="#Contents">Contents</a>)
12993 3 The vsnprintf function returns the number of characters that would have been written
12994 had n been sufficiently large, not counting the terminating null character, or a negative
12995 value if an encoding error occurred. Thus, the null-terminated output has been
12996 completely written if and only if the returned value is nonnegative and less than n.
12997 <a name="7.21.6.13" href="#7.21.6.13"><b> 7.21.6.13 The vsprintf function</b></a>
12999 1 #include <a href="#7.16"><stdarg.h></a>
13000 #include <a href="#7.21"><stdio.h></a>
13001 int vsprintf(char * restrict s,
13002 const char * restrict format,
13004 <b> Description</b>
13005 2 The vsprintf function is equivalent to sprintf, with the variable argument list
13006 replaced by arg, which shall have been initialized by the va_start macro (and
13007 possibly subsequent va_arg calls). The vsprintf function does not invoke the
13008 va_end macro.281) If copying takes place between objects that overlap, the behavior is
13011 3 The vsprintf function returns the number of characters written in the array, not
13012 counting the terminating null character, or a negative value if an encoding error occurred.
13013 <a name="7.21.6.14" href="#7.21.6.14"><b> 7.21.6.14 The vsscanf function</b></a>
13015 1 #include <a href="#7.16"><stdarg.h></a>
13016 #include <a href="#7.21"><stdio.h></a>
13017 int vsscanf(const char * restrict s,
13018 const char * restrict format,
13020 <b> Description</b>
13021 2 The vsscanf function is equivalent to sscanf, with the variable argument list
13022 replaced by arg, which shall have been initialized by the va_start macro (and
13023 possibly subsequent va_arg calls). The vsscanf function does not invoke the
13026 3 The vsscanf function returns the value of the macro EOF if an input failure occurs
13027 before the first conversion (if any) has completed. Otherwise, the vsscanf function
13029 [<a name="p329" href="#p329">page 329</a>] (<a href="#Contents">Contents</a>)
13031 returns the number of input items assigned, which can be fewer than provided for, or even
13032 zero, in the event of an early matching failure.
13033 <a name="7.21.7" href="#7.21.7"><b> 7.21.7 Character input/output functions</b></a>
13034 <a name="7.21.7.1" href="#7.21.7.1"><b> 7.21.7.1 The fgetc function</b></a>
13036 1 #include <a href="#7.21"><stdio.h></a>
13037 int fgetc(FILE *stream);
13038 <b> Description</b>
13039 2 If the end-of-file indicator for the input stream pointed to by stream is not set and a
13040 next character is present, the fgetc function obtains that character as an unsigned
13041 char converted to an int and advances the associated file position indicator for the
13042 stream (if defined).
13044 3 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
13045 of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the
13046 fgetc function returns the next character from the input stream pointed to by stream.
13047 If a read error occurs, the error indicator for the stream is set and the fgetc function
13048 returns EOF.<sup><a href="#note282"><b>282)</b></a></sup>
13049 <a name="7.21.7.2" href="#7.21.7.2"><b> 7.21.7.2 The fgets function</b></a>
13051 1 #include <a href="#7.21"><stdio.h></a>
13052 char *fgets(char * restrict s, int n,
13053 FILE * restrict stream);
13054 <b> Description</b>
13055 2 The fgets function reads at most one less than the number of characters specified by n
13056 from the stream pointed to by stream into the array pointed to by s. No additional
13057 characters are read after a new-line character (which is retained) or after end-of-file. A
13058 null character is written immediately after the last character read into the array.
13060 3 The fgets function returns s if successful. If end-of-file is encountered and no
13061 characters have been read into the array, the contents of the array remain unchanged and a
13062 null pointer is returned. If a read error occurs during the operation, the array contents are
13063 indeterminate and a null pointer is returned.
13065 <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.
13067 [<a name="p330" href="#p330">page 330</a>] (<a href="#Contents">Contents</a>)
13069 <a name="7.21.7.3" href="#7.21.7.3"><b> 7.21.7.3 The fputc function</b></a>
13071 1 #include <a href="#7.21"><stdio.h></a>
13072 int fputc(int c, FILE *stream);
13073 <b> Description</b>
13074 2 The fputc function writes the character specified by c (converted to an unsigned
13075 char) to the output stream pointed to by stream, at the position indicated by the
13076 associated file position indicator for the stream (if defined), and advances the indicator
13077 appropriately. If the file cannot support positioning requests, or if the stream was opened
13078 with append mode, the character is appended to the output stream.
13080 3 The fputc function returns the character written. If a write error occurs, the error
13081 indicator for the stream is set and fputc returns EOF.
13082 <a name="7.21.7.4" href="#7.21.7.4"><b> 7.21.7.4 The fputs function</b></a>
13084 1 #include <a href="#7.21"><stdio.h></a>
13085 int fputs(const char * restrict s,
13086 FILE * restrict stream);
13087 <b> Description</b>
13088 2 The fputs function writes the string pointed to by s to the stream pointed to by
13089 stream. The terminating null character is not written.
13091 3 The fputs function returns EOF if a write error occurs; otherwise it returns a
13093 <a name="7.21.7.5" href="#7.21.7.5"><b> 7.21.7.5 The getc function</b></a>
13095 1 #include <a href="#7.21"><stdio.h></a>
13096 int getc(FILE *stream);
13097 <b> Description</b>
13098 2 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it
13099 may evaluate stream more than once, so the argument should never be an expression
13102 [<a name="p331" href="#p331">page 331</a>] (<a href="#Contents">Contents</a>)
13105 3 The getc function returns the next character from the input stream pointed to by
13106 stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
13107 getc returns EOF. If a read error occurs, the error indicator for the stream is set and
13109 <a name="7.21.7.6" href="#7.21.7.6"><b> 7.21.7.6 The getchar function</b></a>
13111 1 #include <a href="#7.21"><stdio.h></a>
13113 <b> Description</b>
13114 2 The getchar function is equivalent to getc with the argument stdin.
13116 3 The getchar function returns the next character from the input stream pointed to by
13117 stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
13118 getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
13119 getchar returns EOF. *
13120 <a name="7.21.7.7" href="#7.21.7.7"><b> 7.21.7.7 The putc function</b></a>
13122 1 #include <a href="#7.21"><stdio.h></a>
13123 int putc(int c, FILE *stream);
13124 <b> Description</b>
13125 2 The putc function is equivalent to fputc, except that if it is implemented as a macro, it
13126 may evaluate stream more than once, so that argument should never be an expression
13129 3 The putc function returns the character written. If a write error occurs, the error
13130 indicator for the stream is set and putc returns EOF.
13131 <a name="7.21.7.8" href="#7.21.7.8"><b> 7.21.7.8 The putchar function</b></a>
13133 1 #include <a href="#7.21"><stdio.h></a>
13134 int putchar(int c);
13135 <b> Description</b>
13136 2 The putchar function is equivalent to putc with the second argument stdout.
13138 [<a name="p332" href="#p332">page 332</a>] (<a href="#Contents">Contents</a>)
13141 3 The putchar function returns the character written. If a write error occurs, the error
13142 indicator for the stream is set and putchar returns EOF.
13143 <a name="7.21.7.9" href="#7.21.7.9"><b> 7.21.7.9 The puts function</b></a>
13145 1 #include <a href="#7.21"><stdio.h></a>
13146 int puts(const char *s);
13147 <b> Description</b>
13148 2 The puts function writes the string pointed to by s to the stream pointed to by stdout,
13149 and appends a new-line character to the output. The terminating null character is not
13152 3 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
13154 <a name="7.21.7.10" href="#7.21.7.10"><b> 7.21.7.10 The ungetc function</b></a>
13156 1 #include <a href="#7.21"><stdio.h></a>
13157 int ungetc(int c, FILE *stream);
13158 <b> Description</b>
13159 2 The ungetc function pushes the character specified by c (converted to an unsigned
13160 char) back onto the input stream pointed to by stream. Pushed-back characters will be
13161 returned by subsequent reads on that stream in the reverse order of their pushing. A
13162 successful intervening call (with the stream pointed to by stream) to a file positioning
13163 function (fseek, fsetpos, or rewind) discards any pushed-back characters for the
13164 stream. The external storage corresponding to the stream is unchanged.
13165 3 One character of pushback is guaranteed. If the ungetc function is called too many
13166 times on the same stream without an intervening read or file positioning operation on that
13167 stream, the operation may fail.
13168 4 If the value of c equals that of the macro EOF, the operation fails and the input stream is
13170 5 A successful call to the ungetc function clears the end-of-file indicator for the stream.
13171 The value of the file position indicator for the stream after reading or discarding all
13172 pushed-back characters shall be the same as it was before the characters were pushed
13173 back. For a text stream, the value of its file position indicator after a successful call to the
13174 ungetc function is unspecified until all pushed-back characters are read or discarded.
13176 [<a name="p333" href="#p333">page 333</a>] (<a href="#Contents">Contents</a>)
13178 For a binary stream, its file position indicator is decremented by each successful call to
13179 the ungetc function; if its value was zero before a call, it is indeterminate after the
13180 call.<sup><a href="#note283"><b>283)</b></a></sup>
13182 6 The ungetc function returns the character pushed back after conversion, or EOF if the
13184 Forward references: file positioning functions (<a href="#7.21.9">7.21.9</a>).
13185 <a name="7.21.8" href="#7.21.8"><b> 7.21.8 Direct input/output functions</b></a>
13186 <a name="7.21.8.1" href="#7.21.8.1"><b> 7.21.8.1 The fread function</b></a>
13188 1 #include <a href="#7.21"><stdio.h></a>
13189 size_t fread(void * restrict ptr,
13190 size_t size, size_t nmemb,
13191 FILE * restrict stream);
13192 <b> Description</b>
13193 2 The fread function reads, into the array pointed to by ptr, up to nmemb elements
13194 whose size is specified by size, from the stream pointed to by stream. For each
13195 object, size calls are made to the fgetc function and the results stored, in the order
13196 read, in an array of unsigned char exactly overlaying the object. The file position
13197 indicator for the stream (if defined) is advanced by the number of characters successfully
13198 read. If an error occurs, the resulting value of the file position indicator for the stream is
13199 indeterminate. If a partial element is read, its value is indeterminate.
13201 3 The fread function returns the number of elements successfully read, which may be
13202 less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
13203 fread returns zero and the contents of the array and the state of the stream remain
13209 <sup><a name="note283" href="#note283"><b>283)</b></a></sup> See ''future library directions'' (<a href="#7.30.9">7.30.9</a>).
13211 [<a name="p334" href="#p334">page 334</a>] (<a href="#Contents">Contents</a>)
13213 <a name="7.21.8.2" href="#7.21.8.2"><b> 7.21.8.2 The fwrite function</b></a>
13215 1 #include <a href="#7.21"><stdio.h></a>
13216 size_t fwrite(const void * restrict ptr,
13217 size_t size, size_t nmemb,
13218 FILE * restrict stream);
13219 <b> Description</b>
13220 2 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements
13221 whose size is specified by size, to the stream pointed to by stream. For each object,
13222 size calls are made to the fputc function, taking the values (in order) from an array of
13223 unsigned char exactly overlaying the object. The file position indicator for the
13224 stream (if defined) is advanced by the number of characters successfully written. If an
13225 error occurs, the resulting value of the file position indicator for the stream is
13228 3 The fwrite function returns the number of elements successfully written, which will be
13229 less than nmemb only if a write error is encountered. If size or nmemb is zero,
13230 fwrite returns zero and the state of the stream remains unchanged.
13231 <a name="7.21.9" href="#7.21.9"><b> 7.21.9 File positioning functions</b></a>
13232 <a name="7.21.9.1" href="#7.21.9.1"><b> 7.21.9.1 The fgetpos function</b></a>
13234 1 #include <a href="#7.21"><stdio.h></a>
13235 int fgetpos(FILE * restrict stream,
13236 fpos_t * restrict pos);
13237 <b> Description</b>
13238 2 The fgetpos function stores the current values of the parse state (if any) and file
13239 position indicator for the stream pointed to by stream in the object pointed to by pos.
13240 The values stored contain unspecified information usable by the fsetpos function for
13241 repositioning the stream to its position at the time of the call to the fgetpos function.
13243 3 If successful, the fgetpos function returns zero; on failure, the fgetpos function
13244 returns nonzero and stores an implementation-defined positive value in errno.
13245 Forward references: the fsetpos function (<a href="#7.21.9.3">7.21.9.3</a>).
13247 [<a name="p335" href="#p335">page 335</a>] (<a href="#Contents">Contents</a>)
13249 <a name="7.21.9.2" href="#7.21.9.2"><b> 7.21.9.2 The fseek function</b></a>
13251 1 #include <a href="#7.21"><stdio.h></a>
13252 int fseek(FILE *stream, long int offset, int whence);
13253 <b> Description</b>
13254 2 The fseek function sets the file position indicator for the stream pointed to by stream.
13255 If a read or write error occurs, the error indicator for the stream is set and fseek fails.
13256 3 For a binary stream, the new position, measured in characters from the beginning of the
13257 file, is obtained by adding offset to the position specified by whence. The specified
13258 position is the beginning of the file if whence is SEEK_SET, the current value of the file
13259 position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
13260 meaningfully support fseek calls with a whence value of SEEK_END.
13261 4 For a text stream, either offset shall be zero, or offset shall be a value returned by
13262 an earlier successful call to the ftell function on a stream associated with the same file
13263 and whence shall be SEEK_SET.
13264 5 After determining the new position, a successful call to the fseek function undoes any
13265 effects of the ungetc function on the stream, clears the end-of-file indicator for the
13266 stream, and then establishes the new position. After a successful fseek call, the next
13267 operation on an update stream may be either input or output.
13269 6 The fseek function returns nonzero only for a request that cannot be satisfied.
13270 Forward references: the ftell function (<a href="#7.21.9.4">7.21.9.4</a>).
13271 <a name="7.21.9.3" href="#7.21.9.3"><b> 7.21.9.3 The fsetpos function</b></a>
13273 1 #include <a href="#7.21"><stdio.h></a>
13274 int fsetpos(FILE *stream, const fpos_t *pos);
13275 <b> Description</b>
13276 2 The fsetpos function sets the mbstate_t object (if any) and file position indicator
13277 for the stream pointed to by stream according to the value of the object pointed to by
13278 pos, which shall be a value obtained from an earlier successful call to the fgetpos
13279 function on a stream associated with the same file. If a read or write error occurs, the
13280 error indicator for the stream is set and fsetpos fails.
13281 3 A successful call to the fsetpos function undoes any effects of the ungetc function
13282 on the stream, clears the end-of-file indicator for the stream, and then establishes the new
13283 parse state and position. After a successful fsetpos call, the next operation on an
13285 [<a name="p336" href="#p336">page 336</a>] (<a href="#Contents">Contents</a>)
13287 update stream may be either input or output.
13289 4 If successful, the fsetpos function returns zero; on failure, the fsetpos function
13290 returns nonzero and stores an implementation-defined positive value in errno.
13291 <a name="7.21.9.4" href="#7.21.9.4"><b> 7.21.9.4 The ftell function</b></a>
13293 1 #include <a href="#7.21"><stdio.h></a>
13294 long int ftell(FILE *stream);
13295 <b> Description</b>
13296 2 The ftell function obtains the current value of the file position indicator for the stream
13297 pointed to by stream. For a binary stream, the value is the number of characters from
13298 the beginning of the file. For a text stream, its file position indicator contains unspecified
13299 information, usable by the fseek function for returning the file position indicator for the
13300 stream to its position at the time of the ftell call; the difference between two such
13301 return values is not necessarily a meaningful measure of the number of characters written
13304 3 If successful, the ftell function returns the current value of the file position indicator
13305 for the stream. On failure, the ftell function returns -1L and stores an
13306 implementation-defined positive value in errno.
13307 <a name="7.21.9.5" href="#7.21.9.5"><b> 7.21.9.5 The rewind function</b></a>
13309 1 #include <a href="#7.21"><stdio.h></a>
13310 void rewind(FILE *stream);
13311 <b> Description</b>
13312 2 The rewind function sets the file position indicator for the stream pointed to by
13313 stream to the beginning of the file. It is equivalent to
13314 (void)fseek(stream, 0L, SEEK_SET)
13315 except that the error indicator for the stream is also cleared.
13317 3 The rewind function returns no value.
13319 [<a name="p337" href="#p337">page 337</a>] (<a href="#Contents">Contents</a>)
13321 <a name="7.21.10" href="#7.21.10"><b> 7.21.10 Error-handling functions</b></a>
13322 <a name="7.21.10.1" href="#7.21.10.1"><b> 7.21.10.1 The clearerr function</b></a>
13324 1 #include <a href="#7.21"><stdio.h></a>
13325 void clearerr(FILE *stream);
13326 <b> Description</b>
13327 2 The clearerr function clears the end-of-file and error indicators for the stream pointed
13330 3 The clearerr function returns no value.
13331 <a name="7.21.10.2" href="#7.21.10.2"><b> 7.21.10.2 The feof function</b></a>
13333 1 #include <a href="#7.21"><stdio.h></a>
13334 int feof(FILE *stream);
13335 <b> Description</b>
13336 2 The feof function tests the end-of-file indicator for the stream pointed to by stream.
13338 3 The feof function returns nonzero if and only if the end-of-file indicator is set for
13340 <a name="7.21.10.3" href="#7.21.10.3"><b> 7.21.10.3 The ferror function</b></a>
13342 1 #include <a href="#7.21"><stdio.h></a>
13343 int ferror(FILE *stream);
13344 <b> Description</b>
13345 2 The ferror function tests the error indicator for the stream pointed to by stream.
13347 3 The ferror function returns nonzero if and only if the error indicator is set for
13350 [<a name="p338" href="#p338">page 338</a>] (<a href="#Contents">Contents</a>)
13352 <a name="7.21.10.4" href="#7.21.10.4"><b> 7.21.10.4 The perror function</b></a>
13354 1 #include <a href="#7.21"><stdio.h></a>
13355 void perror(const char *s);
13356 <b> Description</b>
13357 2 The perror function maps the error number in the integer expression errno to an
13358 error message. It writes a sequence of characters to the standard error stream thus: first
13359 (if s is not a null pointer and the character pointed to by s is not the null character), the
13360 string pointed to by s followed by a colon (:) and a space; then an appropriate error
13361 message string followed by a new-line character. The contents of the error message
13362 strings are the same as those returned by the strerror function with argument errno.
13364 3 The perror function returns no value.
13365 Forward references: the strerror function (<a href="#7.23.6.2">7.23.6.2</a>).
13367 [<a name="p339" href="#p339">page 339</a>] (<a href="#Contents">Contents</a>)
13369 <a name="7.22" href="#7.22"><b> 7.22 General utilities <stdlib.h></b></a>
13370 1 The header <a href="#7.22"><stdlib.h></a> declares five types and several functions of general utility, and
13371 defines several macros.<sup><a href="#note284"><b>284)</b></a></sup>
13372 2 The types declared are size_t and wchar_t (both described in <a href="#7.19">7.19</a>),
13374 which is a structure type that is the type of the value returned by the div function,
13376 which is a structure type that is the type of the value returned by the ldiv function, and
13378 which is a structure type that is the type of the value returned by the lldiv function.
13379 3 The macros defined are NULL (described in <a href="#7.19">7.19</a>);
13383 which expand to integer constant expressions that can be used as the argument to the
13384 exit function to return unsuccessful or successful termination status, respectively, to the
13387 which expands to an integer constant expression that is the maximum value returned by
13388 the rand function; and
13390 which expands to a positive integer expression with type size_t that is the maximum
13391 number of bytes in a multibyte character for the extended character set specified by the
13392 current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX.
13397 <sup><a name="note284" href="#note284"><b>284)</b></a></sup> See ''future library directions'' (<a href="#7.30.10">7.30.10</a>).
13399 [<a name="p340" href="#p340">page 340</a>] (<a href="#Contents">Contents</a>)
13401 <a name="7.22.1" href="#7.22.1"><b> 7.22.1 Numeric conversion functions</b></a>
13402 1 The functions atof, atoi, atol, and atoll need not affect the value of the integer
13403 expression errno on an error. If the value of the result cannot be represented, the
13404 behavior is undefined.
13405 <a name="7.22.1.1" href="#7.22.1.1"><b> 7.22.1.1 The atof function</b></a>
13407 1 #include <a href="#7.22"><stdlib.h></a>
13408 double atof(const char *nptr);
13409 <b> Description</b>
13410 2 The atof function converts the initial portion of the string pointed to by nptr to
13411 double representation. Except for the behavior on error, it is equivalent to
13412 strtod(nptr, (char **)NULL)
13414 3 The atof function returns the converted value.
13415 Forward references: the strtod, strtof, and strtold functions (<a href="#7.22.1.3">7.22.1.3</a>).
13416 <a name="7.22.1.2" href="#7.22.1.2"><b> 7.22.1.2 The atoi, atol, and atoll functions</b></a>
13418 1 #include <a href="#7.22"><stdlib.h></a>
13419 int atoi(const char *nptr);
13420 long int atol(const char *nptr);
13421 long long int atoll(const char *nptr);
13422 <b> Description</b>
13423 2 The atoi, atol, and atoll functions convert the initial portion of the string pointed
13424 to by nptr to int, long int, and long long int representation, respectively.
13425 Except for the behavior on error, they are equivalent to
13426 atoi: (int)strtol(nptr, (char **)NULL, 10)
13427 atol: strtol(nptr, (char **)NULL, 10)
13428 atoll: strtoll(nptr, (char **)NULL, 10)
13430 3 The atoi, atol, and atoll functions return the converted value.
13431 Forward references: the strtol, strtoll, strtoul, and strtoull functions
13432 (<a href="#7.22.1.4">7.22.1.4</a>).
13434 [<a name="p341" href="#p341">page 341</a>] (<a href="#Contents">Contents</a>)
13436 <a name="7.22.1.3" href="#7.22.1.3"><b> 7.22.1.3 The strtod, strtof, and strtold functions</b></a>
13438 1 #include <a href="#7.22"><stdlib.h></a>
13439 double strtod(const char * restrict nptr,
13440 char ** restrict endptr);
13441 float strtof(const char * restrict nptr,
13442 char ** restrict endptr);
13443 long double strtold(const char * restrict nptr,
13444 char ** restrict endptr);
13445 <b> Description</b>
13446 2 The strtod, strtof, and strtold functions convert the initial portion of the string
13447 pointed to by nptr to double, float, and long double representation,
13448 respectively. First, they decompose the input string into three parts: an initial, possibly
13449 empty, sequence of white-space characters (as specified by the isspace function), a
13450 subject sequence resembling a floating-point constant or representing an infinity or NaN;
13451 and a final string of one or more unrecognized characters, including the terminating null
13452 character of the input string. Then, they attempt to convert the subject sequence to a
13453 floating-point number, and return the result.
13454 3 The expected form of the subject sequence is an optional plus or minus sign, then one of
13456 -- a nonempty sequence of decimal digits optionally containing a decimal-point
13457 character, then an optional exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
13458 -- a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
13459 decimal-point character, then an optional binary exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
13460 -- INF or INFINITY, ignoring case
13461 -- NAN or NAN(n-char-sequenceopt), ignoring case in the NAN part, where:
13465 n-char-sequence digit
13466 n-char-sequence nondigit
13467 The subject sequence is defined as the longest initial subsequence of the input string,
13468 starting with the first non-white-space character, that is of the expected form. The subject
13469 sequence contains no characters if the input string is not of the expected form.
13470 4 If the subject sequence has the expected form for a floating-point number, the sequence of
13471 characters starting with the first digit or the decimal-point character (whichever occurs
13472 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
13474 [<a name="p342" href="#p342">page 342</a>] (<a href="#Contents">Contents</a>)
13476 decimal-point character is used in place of a period, and that if neither an exponent part
13477 nor a decimal-point character appears in a decimal floating point number, or if a binary
13478 exponent part does not appear in a hexadecimal floating point number, an exponent part
13479 of the appropriate type with value zero is assumed to follow the last digit in the string. If
13480 the subject sequence begins with a minus sign, the sequence is interpreted as negated.<sup><a href="#note285"><b>285)</b></a></sup>
13481 A character sequence INF or INFINITY is interpreted as an infinity, if representable in
13482 the return type, else like a floating constant that is too large for the range of the return
13483 type. A character sequence NAN or NAN(n-char-sequenceopt), is interpreted as a quiet
13484 NaN, if supported in the return type, else like a subject sequence part that does not have
13485 the expected form; the meaning of the n-char sequences is implementation-defined.<sup><a href="#note286"><b>286)</b></a></sup> A
13486 pointer to the final string is stored in the object pointed to by endptr, provided that
13487 endptr is not a null pointer.
13488 5 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
13489 value resulting from the conversion is correctly rounded.
13490 6 In other than the "C" locale, additional locale-specific subject sequence forms may be
13492 7 If the subject sequence is empty or does not have the expected form, no conversion is
13493 performed; the value of nptr is stored in the object pointed to by endptr, provided
13494 that endptr is not a null pointer.
13495 Recommended practice
13496 8 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
13497 the result is not exactly representable, the result should be one of the two numbers in the
13498 appropriate internal format that are adjacent to the hexadecimal floating source value,
13499 with the extra stipulation that the error should have a correct sign for the current rounding
13501 9 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
13502 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
13503 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
13504 consider the two bounding, adjacent decimal strings L and U, both having
13505 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
13506 The result should be one of the (equal or adjacent) values that would be obtained by
13507 correctly rounding L and U according to the current rounding direction, with the extra
13509 <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
13510 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
13511 methods may yield different results if rounding is toward positive or negative infinity. In either case,
13512 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
13513 <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
13514 the NaN's significand.
13516 [<a name="p343" href="#p343">page 343</a>] (<a href="#Contents">Contents</a>)
13518 stipulation that the error with respect to D should have a correct sign for the current
13519 rounding direction.<sup><a href="#note287"><b>287)</b></a></sup>
13521 10 The functions return the converted value, if any. If no conversion could be performed,
13522 zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
13523 plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
13524 return type and sign of the value), and the value of the macro ERANGE is stored in
13525 errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
13526 no greater than the smallest normalized positive number in the return type; whether
13527 errno acquires the value ERANGE is implementation-defined.
13528 <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>
13530 1 #include <a href="#7.22"><stdlib.h></a>
13532 const char * restrict nptr,
13533 char ** restrict endptr,
13535 long long int strtoll(
13536 const char * restrict nptr,
13537 char ** restrict endptr,
13539 unsigned long int strtoul(
13540 const char * restrict nptr,
13541 char ** restrict endptr,
13543 unsigned long long int strtoull(
13544 const char * restrict nptr,
13545 char ** restrict endptr,
13547 <b> Description</b>
13548 2 The strtol, strtoll, strtoul, and strtoull functions convert the initial
13549 portion of the string pointed to by nptr to long int, long long int, unsigned
13550 long int, and unsigned long long int representation, respectively. First,
13551 they decompose the input string into three parts: an initial, possibly empty, sequence of
13552 white-space characters (as specified by the isspace function), a subject sequence
13555 <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
13556 to the same internal floating value, but if not will round to adjacent values.
13558 [<a name="p344" href="#p344">page 344</a>] (<a href="#Contents">Contents</a>)
13560 resembling an integer represented in some radix determined by the value of base, and a
13561 final string of one or more unrecognized characters, including the terminating null
13562 character of the input string. Then, they attempt to convert the subject sequence to an
13563 integer, and return the result.
13564 3 If the value of base is zero, the expected form of the subject sequence is that of an
13565 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
13566 not including an integer suffix. If the value of base is between 2 and 36 (inclusive), the
13567 expected form of the subject sequence is a sequence of letters and digits representing an
13568 integer with the radix specified by base, optionally preceded by a plus or minus sign,
13569 but not including an integer suffix. The letters from a (or A) through z (or Z) are
13570 ascribed the values 10 through 35; only letters and digits whose ascribed values are less
13571 than that of base are permitted. If the value of base is 16, the characters 0x or 0X may
13572 optionally precede the sequence of letters and digits, following the sign if present.
13573 4 The subject sequence is defined as the longest initial subsequence of the input string,
13574 starting with the first non-white-space character, that is of the expected form. The subject
13575 sequence contains no characters if the input string is empty or consists entirely of white
13576 space, or if the first non-white-space character is other than a sign or a permissible letter
13578 5 If the subject sequence has the expected form and the value of base is zero, the sequence
13579 of characters starting with the first digit is interpreted as an integer constant according to
13580 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
13581 is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
13582 as given above. If the subject sequence begins with a minus sign, the value resulting from
13583 the conversion is negated (in the return type). A pointer to the final string is stored in the
13584 object pointed to by endptr, provided that endptr is not a null pointer.
13585 6 In other than the "C" locale, additional locale-specific subject sequence forms may be
13587 7 If the subject sequence is empty or does not have the expected form, no conversion is
13588 performed; the value of nptr is stored in the object pointed to by endptr, provided
13589 that endptr is not a null pointer.
13591 8 The strtol, strtoll, strtoul, and strtoull functions return the converted
13592 value, if any. If no conversion could be performed, zero is returned. If the correct value
13593 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
13594 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
13595 and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
13597 [<a name="p345" href="#p345">page 345</a>] (<a href="#Contents">Contents</a>)
13599 <a name="7.22.2" href="#7.22.2"><b> 7.22.2 Pseudo-random sequence generation functions</b></a>
13600 <a name="7.22.2.1" href="#7.22.2.1"><b> 7.22.2.1 The rand function</b></a>
13602 1 #include <a href="#7.22"><stdlib.h></a>
13604 <b> Description</b>
13605 2 The rand function computes a sequence of pseudo-random integers in the range 0 to
13606 RAND_MAX.<sup><a href="#note288"><b>288)</b></a></sup>
13607 3 The rand function is not required to avoid data races. The implementation shall behave
13608 as if no library function calls the rand function.
13610 4 The rand function returns a pseudo-random integer.
13611 Environmental limits
13612 5 The value of the RAND_MAX macro shall be at least 32767.
13613 <a name="7.22.2.2" href="#7.22.2.2"><b> 7.22.2.2 The srand function</b></a>
13615 1 #include <a href="#7.22"><stdlib.h></a>
13616 void srand(unsigned int seed);
13617 <b> Description</b>
13618 2 The srand function uses the argument as a seed for a new sequence of pseudo-random
13619 numbers to be returned by subsequent calls to rand. If srand is then called with the
13620 same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
13621 called before any calls to srand have been made, the same sequence shall be generated
13622 as when srand is first called with a seed value of 1.
13623 3 The implementation shall behave as if no library function calls the srand function.
13625 4 The srand function returns no value.
13630 <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
13631 are known to produce sequences with distressingly non-random low-order bits. Applications with
13632 particular requirements should use a generator that is known to be sufficient for their needs.
13634 [<a name="p346" href="#p346">page 346</a>] (<a href="#Contents">Contents</a>)
13636 5 EXAMPLE The following functions define a portable implementation of rand and srand.
13637 static unsigned long int next = 1;
13638 int rand(void) // RAND_MAX assumed to be 32767
13640 next = next * 1103515245 + 12345;
13641 return (unsigned int)(next/65536) % 32768;
13643 void srand(unsigned int seed)
13648 <a name="7.22.3" href="#7.22.3"><b> 7.22.3 Memory management functions</b></a>
13649 1 The order and contiguity of storage allocated by successive calls to the
13650 aligned_alloc, calloc, malloc, and realloc functions is unspecified. The
13651 pointer returned if the allocation succeeds is suitably aligned so that it may be assigned to
13652 a pointer to any type of object with a fundamental alignment requirement and then used
13653 to access such an object or an array of such objects in the space allocated (until the space
13654 is explicitly deallocated). The lifetime of an allocated object extends from the allocation
13655 until the deallocation. Each such allocation shall yield a pointer to an object disjoint from
13656 any other object. The pointer returned points to the start (lowest byte address) of the
13657 allocated space. If the space cannot be allocated, a null pointer is returned. If the size of
13658 the space requested is zero, the behavior is implementation-defined: either a null pointer
13659 is returned, or the behavior is as if the size were some nonzero value, except that the
13660 returned pointer shall not be used to access an object.
13661 <a name="7.22.3.1" href="#7.22.3.1"><b> 7.22.3.1 The aligned_alloc function</b></a>
13663 1 #include <a href="#7.22"><stdlib.h></a>
13664 void *aligned_alloc(size_t alignment, size_t size);
13665 <b> Description</b>
13666 2 The aligned_alloc function allocates space for an object whose alignment is
13667 specified by alignment, whose size is specified by size, and whose value is
13668 indeterminate. The value of alignment shall be a valid alignment supported by the
13669 implementation and the value of size shall be an integral multiple of alignment.
13671 3 The aligned_alloc function returns either a null pointer or a pointer to the allocated
13674 [<a name="p347" href="#p347">page 347</a>] (<a href="#Contents">Contents</a>)
13676 <a name="7.22.3.2" href="#7.22.3.2"><b> 7.22.3.2 The calloc function</b></a>
13678 1 #include <a href="#7.22"><stdlib.h></a>
13679 void *calloc(size_t nmemb, size_t size);
13680 <b> Description</b>
13681 2 The calloc function allocates space for an array of nmemb objects, each of whose size
13682 is size. The space is initialized to all bits zero.<sup><a href="#note289"><b>289)</b></a></sup>
13684 3 The calloc function returns either a null pointer or a pointer to the allocated space.
13685 <a name="7.22.3.3" href="#7.22.3.3"><b> 7.22.3.3 The free function</b></a>
13687 1 #include <a href="#7.22"><stdlib.h></a>
13688 void free(void *ptr);
13689 <b> Description</b>
13690 2 The free function causes the space pointed to by ptr to be deallocated, that is, made
13691 available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
13692 the argument does not match a pointer earlier returned by a memory management
13693 function, or if the space has been deallocated by a call to free or realloc, the
13694 behavior is undefined.
13696 3 The free function returns no value.
13697 <a name="7.22.3.4" href="#7.22.3.4"><b> 7.22.3.4 The malloc function</b></a>
13699 1 #include <a href="#7.22"><stdlib.h></a>
13700 void *malloc(size_t size);
13701 <b> Description</b>
13702 2 The malloc function allocates space for an object whose size is specified by size and
13703 whose value is indeterminate.
13708 <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
13711 [<a name="p348" href="#p348">page 348</a>] (<a href="#Contents">Contents</a>)
13714 3 The malloc function returns either a null pointer or a pointer to the allocated space.
13715 <a name="7.22.3.5" href="#7.22.3.5"><b> 7.22.3.5 The realloc function</b></a>
13717 1 #include <a href="#7.22"><stdlib.h></a>
13718 void *realloc(void *ptr, size_t size);
13719 <b> Description</b>
13720 2 The realloc function deallocates the old object pointed to by ptr and returns a
13721 pointer to a new object that has the size specified by size. The contents of the new
13722 object shall be the same as that of the old object prior to deallocation, up to the lesser of
13723 the new and old sizes. Any bytes in the new object beyond the size of the old object have
13724 indeterminate values.
13725 3 If ptr is a null pointer, the realloc function behaves like the malloc function for the
13726 specified size. Otherwise, if ptr does not match a pointer earlier returned by a memory
13727 management function, or if the space has been deallocated by a call to the free or
13728 realloc function, the behavior is undefined. If memory for the new object cannot be
13729 allocated, the old object is not deallocated and its value is unchanged.
13731 4 The realloc function returns a pointer to the new object (which may have the same
13732 value as a pointer to the old object), or a null pointer if the new object could not be
13734 <a name="7.22.4" href="#7.22.4"><b> 7.22.4 Communication with the environment</b></a>
13735 <a name="7.22.4.1" href="#7.22.4.1"><b> 7.22.4.1 The abort function</b></a>
13737 1 #include <a href="#7.22"><stdlib.h></a>
13738 _Noreturn void abort(void);
13739 <b> Description</b>
13740 2 The abort function causes abnormal program termination to occur, unless the signal
13741 SIGABRT is being caught and the signal handler does not return. Whether open streams
13742 with unwritten buffered data are flushed, open streams are closed, or temporary files are
13743 removed is implementation-defined. An implementation-defined form of the status
13744 unsuccessful termination is returned to the host environment by means of the function
13745 call raise(SIGABRT).
13747 [<a name="p349" href="#p349">page 349</a>] (<a href="#Contents">Contents</a>)
13750 3 The abort function does not return to its caller.
13751 <a name="7.22.4.2" href="#7.22.4.2"><b> 7.22.4.2 The atexit function</b></a>
13753 1 #include <a href="#7.22"><stdlib.h></a>
13754 int atexit(void (*func)(void));
13755 <b> Description</b>
13756 2 The atexit function registers the function pointed to by func, to be called without
13757 arguments at normal program termination.<sup><a href="#note290"><b>290)</b></a></sup>
13758 Environmental limits
13759 3 The implementation shall support the registration of at least 32 functions.
13761 4 The atexit function returns zero if the registration succeeds, nonzero if it fails.
13762 Forward references: the at_quick_exit function (<a href="#7.22.4.3">7.22.4.3</a>), the exit function
13763 (<a href="#7.22.4.4">7.22.4.4</a>).
13764 <a name="7.22.4.3" href="#7.22.4.3"><b> 7.22.4.3 The at_quick_exit function</b></a>
13766 1 #include <a href="#7.22"><stdlib.h></a>
13767 int at_quick_exit(void (*func)(void));
13768 <b> Description</b>
13769 2 The at_quick_exit function registers the function pointed to by func, to be called
13770 without arguments should quick_exit be called.<sup><a href="#note291"><b>291)</b></a></sup>
13771 Environmental limits
13772 3 The implementation shall support the registration of at least 32 functions.
13774 4 The at_quick_exit function returns zero if the registration succeeds, nonzero if it
13776 Forward references: the quick_exit function (<a href="#7.22.4.7">7.22.4.7</a>).
13779 <sup><a name="note290" href="#note290"><b>290)</b></a></sup> The atexit function registrations are distinct from the at_quick_exit registrations, so
13780 applications may need to call both registration functions with the same argument.
13781 <sup><a name="note291" href="#note291"><b>291)</b></a></sup> The at_quick_exit function registrations are distinct from the atexit registrations, so
13782 applications may need to call both registration functions with the same argument.
13784 [<a name="p350" href="#p350">page 350</a>] (<a href="#Contents">Contents</a>)
13786 <a name="7.22.4.4" href="#7.22.4.4"><b> 7.22.4.4 The exit function</b></a>
13788 1 #include <a href="#7.22"><stdlib.h></a>
13789 _Noreturn void exit(int status);
13790 <b> Description</b>
13791 2 The exit function causes normal program termination to occur. No functions registered
13792 by the at_quick_exit function are called. If a program calls the exit function
13793 more than once, or calls the quick_exit function in addition to the exit function, the
13794 behavior is undefined.
13795 3 First, all functions registered by the atexit function are called, in the reverse order of
13796 their registration,<sup><a href="#note292"><b>292)</b></a></sup> except that a function is called after any previously registered
13797 functions that had already been called at the time it was registered. If, during the call to
13798 any such function, a call to the longjmp function is made that would terminate the call
13799 to the registered function, the behavior is undefined.
13800 4 Next, all open streams with unwritten buffered data are flushed, all open streams are
13801 closed, and all files created by the tmpfile function are removed.
13802 5 Finally, control is returned to the host environment. If the value of status is zero or
13803 EXIT_SUCCESS, an implementation-defined form of the status successful termination is
13804 returned. If the value of status is EXIT_FAILURE, an implementation-defined form
13805 of the status unsuccessful termination is returned. Otherwise the status returned is
13806 implementation-defined.
13808 6 The exit function cannot return to its caller.
13809 <a name="7.22.4.5" href="#7.22.4.5"><b> 7.22.4.5 The _Exit function</b></a>
13811 1 #include <a href="#7.22"><stdlib.h></a>
13812 _Noreturn void _Exit(int status);
13813 <b> Description</b>
13814 2 The _Exit function causes normal program termination to occur and control to be
13815 returned to the host environment. No functions registered by the atexit function, the
13816 at_quick_exit function, or signal handlers registered by the signal function are
13817 called. The status returned to the host environment is determined in the same way as for
13820 <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
13821 other registered functions.
13823 [<a name="p351" href="#p351">page 351</a>] (<a href="#Contents">Contents</a>)
13825 the exit function (<a href="#7.22.4.4">7.22.4.4</a>). Whether open streams with unwritten buffered data are
13826 flushed, open streams are closed, or temporary files are removed is implementation-
13829 3 The _Exit function cannot return to its caller.
13830 <a name="7.22.4.6" href="#7.22.4.6"><b> 7.22.4.6 The getenv function</b></a>
13832 1 #include <a href="#7.22"><stdlib.h></a>
13833 char *getenv(const char *name);
13834 <b> Description</b>
13835 2 The getenv function searches an environment list, provided by the host environment,
13836 for a string that matches the string pointed to by name. The set of environment names
13837 and the method for altering the environment list are implementation-defined. The
13838 getenv function need not avoid data races with other threads of execution that modify
13839 the environment list.<sup><a href="#note293"><b>293)</b></a></sup>
13840 3 The implementation shall behave as if no library function calls the getenv function.
13842 4 The getenv function returns a pointer to a string associated with the matched list
13843 member. The string pointed to shall not be modified by the program, but may be
13844 overwritten by a subsequent call to the getenv function. If the specified name cannot
13845 be found, a null pointer is returned.
13846 <a name="7.22.4.7" href="#7.22.4.7"><b> 7.22.4.7 The quick_exit function</b></a>
13848 1 #include <a href="#7.22"><stdlib.h></a>
13849 _Noreturn void quick_exit(int status);
13850 <b> Description</b>
13851 2 The quick_exit function causes normal program termination to occur. No functions
13852 registered by the atexit function or signal handlers registered by the signal function
13853 are called. If a program calls the quick_exit function more than once, or calls the
13854 exit function in addition to the quick_exit function, the behavior is undefined.
13855 3 The quick_exit function first calls all functions registered by the at_quick_exit
13856 function, in the reverse order of their registration,<sup><a href="#note294"><b>294)</b></a></sup> except that a function is called after
13859 <sup><a name="note293" href="#note293"><b>293)</b></a></sup> Many implementations provide non-standard functions that modify the environment list.
13861 [<a name="p352" href="#p352">page 352</a>] (<a href="#Contents">Contents</a>)
13863 any previously registered functions that had already been called at the time it was
13864 registered. If, during the call to any such function, a call to the longjmp function is
13865 made that would terminate the call to the registered function, the behavior is undefined.
13866 4 Then control is returned to the host environment by means of the function call
13869 5 The quick_exit function cannot return to its caller.
13870 <a name="7.22.4.8" href="#7.22.4.8"><b> 7.22.4.8 The system function</b></a>
13872 1 #include <a href="#7.22"><stdlib.h></a>
13873 int system(const char *string);
13874 <b> Description</b>
13875 2 If string is a null pointer, the system function determines whether the host
13876 environment has a command processor. If string is not a null pointer, the system
13877 function passes the string pointed to by string to that command processor to be
13878 executed in a manner which the implementation shall document; this might then cause the
13879 program calling system to behave in a non-conforming manner or to terminate.
13881 3 If the argument is a null pointer, the system function returns nonzero only if a
13882 command processor is available. If the argument is not a null pointer, and the system
13883 function does return, it returns an implementation-defined value.
13884 <a name="7.22.5" href="#7.22.5"><b> 7.22.5 Searching and sorting utilities</b></a>
13885 1 These utilities make use of a comparison function to search or sort arrays of unspecified
13886 type. Where an argument declared as size_t nmemb specifies the length of the array
13887 for a function, nmemb can have the value zero on a call to that function; the comparison
13888 function is not called, a search finds no matching element, and sorting performs no
13889 rearrangement. Pointer arguments on such a call shall still have valid values, as described
13890 in <a href="#7.1.4">7.1.4</a>.
13891 2 The implementation shall ensure that the second argument of the comparison function
13892 (when called from bsearch), or both arguments (when called from qsort), are
13893 pointers to elements of the array.<sup><a href="#note295"><b>295)</b></a></sup> The first argument when called from bsearch
13898 <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
13899 other registered functions.
13901 [<a name="p353" href="#p353">page 353</a>] (<a href="#Contents">Contents</a>)
13903 3 The comparison function shall not alter the contents of the array. The implementation
13904 may reorder elements of the array between calls to the comparison function, but shall not
13905 alter the contents of any individual element.
13906 4 When the same objects (consisting of size bytes, irrespective of their current positions
13907 in the array) are passed more than once to the comparison function, the results shall be
13908 consistent with one another. That is, for qsort they shall define a total ordering on the
13909 array, and for bsearch the same object shall always compare the same way with the
13911 5 A sequence point occurs immediately before and immediately after each call to the
13912 comparison function, and also between any call to the comparison function and any
13913 movement of the objects passed as arguments to that call.
13914 <a name="7.22.5.1" href="#7.22.5.1"><b> 7.22.5.1 The bsearch function</b></a>
13916 1 #include <a href="#7.22"><stdlib.h></a>
13917 void *bsearch(const void *key, const void *base,
13918 size_t nmemb, size_t size,
13919 int (*compar)(const void *, const void *));
13920 <b> Description</b>
13921 2 The bsearch function searches an array of nmemb objects, the initial element of which
13922 is pointed to by base, for an element that matches the object pointed to by key. The
13923 size of each element of the array is specified by size.
13924 3 The comparison function pointed to by compar is called with two arguments that point
13925 to the key object and to an array element, in that order. The function shall return an
13926 integer less than, equal to, or greater than zero if the key object is considered,
13927 respectively, to be less than, to match, or to be greater than the array element. The array
13928 shall consist of: all the elements that compare less than, all the elements that compare
13929 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>
13931 4 The bsearch function returns a pointer to a matching element of the array, or a null
13932 pointer if no match is found. If two elements compare as equal, which element is
13935 <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:
13936 ((char *)p - (char *)base) % size == 0
13937 (char *)p >= (char *)base
13938 (char *)p < (char *)base + nmemb * size
13940 <sup><a name="note296" href="#note296"><b>296)</b></a></sup> In practice, the entire array is sorted according to the comparison function.
13942 [<a name="p354" href="#p354">page 354</a>] (<a href="#Contents">Contents</a>)
13944 matched is unspecified.
13945 <a name="7.22.5.2" href="#7.22.5.2"><b> 7.22.5.2 The qsort function</b></a>
13947 1 #include <a href="#7.22"><stdlib.h></a>
13948 void qsort(void *base, size_t nmemb, size_t size,
13949 int (*compar)(const void *, const void *));
13950 <b> Description</b>
13951 2 The qsort function sorts an array of nmemb objects, the initial element of which is
13952 pointed to by base. The size of each object is specified by size.
13953 3 The contents of the array are sorted into ascending order according to a comparison
13954 function pointed to by compar, which is called with two arguments that point to the
13955 objects being compared. The function shall return an integer less than, equal to, or
13956 greater than zero if the first argument is considered to be respectively less than, equal to,
13957 or greater than the second.
13958 4 If two elements compare as equal, their order in the resulting sorted array is unspecified.
13960 5 The qsort function returns no value.
13961 <a name="7.22.6" href="#7.22.6"><b> 7.22.6 Integer arithmetic functions</b></a>
13962 <a name="7.22.6.1" href="#7.22.6.1"><b> 7.22.6.1 The abs, labs and llabs functions</b></a>
13964 1 #include <a href="#7.22"><stdlib.h></a>
13966 long int labs(long int j);
13967 long long int llabs(long long int j);
13968 <b> Description</b>
13969 2 The abs, labs, and llabs functions compute the absolute value of an integer j. If the
13970 result cannot be represented, the behavior is undefined.<sup><a href="#note297"><b>297)</b></a></sup>
13972 3 The abs, labs, and llabs, functions return the absolute value.
13977 <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.
13979 [<a name="p355" href="#p355">page 355</a>] (<a href="#Contents">Contents</a>)
13981 <a name="7.22.6.2" href="#7.22.6.2"><b> 7.22.6.2 The div, ldiv, and lldiv functions</b></a>
13983 1 #include <a href="#7.22"><stdlib.h></a>
13984 div_t div(int numer, int denom);
13985 ldiv_t ldiv(long int numer, long int denom);
13986 lldiv_t lldiv(long long int numer, long long int denom);
13987 <b> Description</b>
13988 2 The div, ldiv, and lldiv, functions compute numer / denom and numer %
13989 denom in a single operation.
13991 3 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
13992 lldiv_t, respectively, comprising both the quotient and the remainder. The structures
13993 shall contain (in either order) the members quot (the quotient) and rem (the remainder),
13994 each of which has the same type as the arguments numer and denom. If either part of
13995 the result cannot be represented, the behavior is undefined.
13996 <a name="7.22.7" href="#7.22.7"><b> 7.22.7 Multibyte/wide character conversion functions</b></a>
13997 1 The behavior of the multibyte character functions is affected by the LC_CTYPE category
13998 of the current locale. For a state-dependent encoding, each function is placed into its
13999 initial conversion state at program startup and can be returned to that state by a call for
14000 which its character pointer argument, s, is a null pointer. Subsequent calls with s as
14001 other than a null pointer cause the internal conversion state of the function to be altered as
14002 necessary. A call with s as a null pointer causes these functions to return a nonzero value
14003 if encodings have state dependency, and zero otherwise.<sup><a href="#note298"><b>298)</b></a></sup> Changing the LC_CTYPE
14004 category causes the conversion state of these functions to be indeterminate.
14005 <a name="7.22.7.1" href="#7.22.7.1"><b> 7.22.7.1 The mblen function</b></a>
14007 1 #include <a href="#7.22"><stdlib.h></a>
14008 int mblen(const char *s, size_t n);
14009 <b> Description</b>
14010 2 If s is not a null pointer, the mblen function determines the number of bytes contained
14011 in the multibyte character pointed to by s. Except that the conversion state of the
14012 mbtowc function is not affected, it is equivalent to
14016 <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
14017 character codes, but are grouped with an adjacent multibyte character.
14019 [<a name="p356" href="#p356">page 356</a>] (<a href="#Contents">Contents</a>)
14021 mbtowc((wchar_t *)0, (const char *)0, 0);
14022 mbtowc((wchar_t *)0, s, n);
14023 3 The implementation shall behave as if no library function calls the mblen function.
14025 4 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte
14026 character encodings, respectively, do or do not have state-dependent encodings. If s is
14027 not a null pointer, the mblen function either returns 0 (if s points to the null character),
14028 or returns the number of bytes that are contained in the multibyte character (if the next n
14029 or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid
14030 multibyte character).
14031 Forward references: the mbtowc function (<a href="#7.22.7.2">7.22.7.2</a>).
14032 <a name="7.22.7.2" href="#7.22.7.2"><b> 7.22.7.2 The mbtowc function</b></a>
14034 1 #include <a href="#7.22"><stdlib.h></a>
14035 int mbtowc(wchar_t * restrict pwc,
14036 const char * restrict s,
14038 <b> Description</b>
14039 2 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with
14040 the byte pointed to by s to determine the number of bytes needed to complete the next
14041 multibyte character (including any shift sequences). If the function determines that the
14042 next multibyte character is complete and valid, it determines the value of the
14043 corresponding wide character and then, if pwc is not a null pointer, stores that value in
14044 the object pointed to by pwc. If the corresponding wide character is the null wide
14045 character, the function is left in the initial conversion state.
14046 3 The implementation shall behave as if no library function calls the mbtowc function.
14048 4 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte
14049 character encodings, respectively, do or do not have state-dependent encodings. If s is
14050 not a null pointer, the mbtowc function either returns 0 (if s points to the null character),
14051 or returns the number of bytes that are contained in the converted multibyte character (if
14052 the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not
14053 form a valid multibyte character).
14054 5 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
14057 [<a name="p357" href="#p357">page 357</a>] (<a href="#Contents">Contents</a>)
14059 <a name="7.22.7.3" href="#7.22.7.3"><b> 7.22.7.3 The wctomb function</b></a>
14061 1 #include <a href="#7.22"><stdlib.h></a>
14062 int wctomb(char *s, wchar_t wc);
14063 <b> Description</b>
14064 2 The wctomb function determines the number of bytes needed to represent the multibyte
14065 character corresponding to the wide character given by wc (including any shift
14066 sequences), and stores the multibyte character representation in the array whose first
14067 element is pointed to by s (if s is not a null pointer). At most MB_CUR_MAX characters
14068 are stored. If wc is a null wide character, a null byte is stored, preceded by any shift
14069 sequence needed to restore the initial shift state, and the function is left in the initial
14071 3 The implementation shall behave as if no library function calls the wctomb function.
14073 4 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte
14074 character encodings, respectively, do or do not have state-dependent encodings. If s is
14075 not a null pointer, the wctomb function returns -1 if the value of wc does not correspond
14076 to a valid multibyte character, or returns the number of bytes that are contained in the
14077 multibyte character corresponding to the value of wc.
14078 5 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
14079 <a name="7.22.8" href="#7.22.8"><b> 7.22.8 Multibyte/wide string conversion functions</b></a>
14080 1 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
14081 the current locale.
14082 <a name="7.22.8.1" href="#7.22.8.1"><b> 7.22.8.1 The mbstowcs function</b></a>
14084 1 #include <a href="#7.22"><stdlib.h></a>
14085 size_t mbstowcs(wchar_t * restrict pwcs,
14086 const char * restrict s,
14088 <b> Description</b>
14089 2 The mbstowcs function converts a sequence of multibyte characters that begins in the
14090 initial shift state from the array pointed to by s into a sequence of corresponding wide
14091 characters and stores not more than n wide characters into the array pointed to by pwcs.
14092 No multibyte characters that follow a null character (which is converted into a null wide
14093 character) will be examined or converted. Each multibyte character is converted as if by
14094 a call to the mbtowc function, except that the conversion state of the mbtowc function is
14096 [<a name="p358" href="#p358">page 358</a>] (<a href="#Contents">Contents</a>)
14099 3 No more than n elements will be modified in the array pointed to by pwcs. If copying
14100 takes place between objects that overlap, the behavior is undefined.
14102 4 If an invalid multibyte character is encountered, the mbstowcs function returns
14103 (size_t)(-1). Otherwise, the mbstowcs function returns the number of array
14104 elements modified, not including a terminating null wide character, if any.<sup><a href="#note299"><b>299)</b></a></sup>
14105 <a name="7.22.8.2" href="#7.22.8.2"><b> 7.22.8.2 The wcstombs function</b></a>
14107 1 #include <a href="#7.22"><stdlib.h></a>
14108 size_t wcstombs(char * restrict s,
14109 const wchar_t * restrict pwcs,
14111 <b> Description</b>
14112 2 The wcstombs function converts a sequence of wide characters from the array pointed
14113 to by pwcs into a sequence of corresponding multibyte characters that begins in the
14114 initial shift state, and stores these multibyte characters into the array pointed to by s,
14115 stopping if a multibyte character would exceed the limit of n total bytes or if a null
14116 character is stored. Each wide character is converted as if by a call to the wctomb
14117 function, except that the conversion state of the wctomb function is not affected.
14118 3 No more than n bytes will be modified in the array pointed to by s. If copying takes place
14119 between objects that overlap, the behavior is undefined.
14121 4 If a wide character is encountered that does not correspond to a valid multibyte character,
14122 the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
14123 returns the number of bytes modified, not including a terminating null character, if
14129 <sup><a name="note299" href="#note299"><b>299)</b></a></sup> The array will not be null-terminated if the value returned is n.
14131 [<a name="p359" href="#p359">page 359</a>] (<a href="#Contents">Contents</a>)
14133 <a name="7.23" href="#7.23"><b> 7.23 String handling <string.h></b></a>
14134 <a name="7.23.1" href="#7.23.1"><b> 7.23.1 String function conventions</b></a>
14135 1 The header <a href="#7.23"><string.h></a> declares one type and several functions, and defines one
14136 macro useful for manipulating arrays of character type and other objects treated as arrays
14137 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
14138 <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>
14139 a char * or void * argument points to the initial (lowest addressed) character of the
14140 array. If an array is accessed beyond the end of an object, the behavior is undefined.
14141 2 Where an argument declared as size_t n specifies the length of the array for a
14142 function, n can have the value zero on a call to that function. Unless explicitly stated
14143 otherwise in the description of a particular function in this subclause, pointer arguments
14144 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
14145 function that locates a character finds no occurrence, a function that compares two
14146 character sequences returns zero, and a function that copies characters copies zero
14148 3 For all functions in this subclause, each character shall be interpreted as if it had the type
14149 unsigned char (and therefore every possible object representation is valid and has a
14151 <a name="7.23.2" href="#7.23.2"><b> 7.23.2 Copying functions</b></a>
14152 <a name="7.23.2.1" href="#7.23.2.1"><b> 7.23.2.1 The memcpy function</b></a>
14154 1 #include <a href="#7.23"><string.h></a>
14155 void *memcpy(void * restrict s1,
14156 const void * restrict s2,
14158 <b> Description</b>
14159 2 The memcpy function copies n characters from the object pointed to by s2 into the
14160 object pointed to by s1. If copying takes place between objects that overlap, the behavior
14163 3 The memcpy function returns the value of s1.
14168 <sup><a name="note300" href="#note300"><b>300)</b></a></sup> See ''future library directions'' (<a href="#7.30.11">7.30.11</a>).
14170 [<a name="p360" href="#p360">page 360</a>] (<a href="#Contents">Contents</a>)
14172 <a name="7.23.2.2" href="#7.23.2.2"><b> 7.23.2.2 The memmove function</b></a>
14174 1 #include <a href="#7.23"><string.h></a>
14175 void *memmove(void *s1, const void *s2, size_t n);
14176 <b> Description</b>
14177 2 The memmove function copies n characters from the object pointed to by s2 into the
14178 object pointed to by s1. Copying takes place as if the n characters from the object
14179 pointed to by s2 are first copied into a temporary array of n characters that does not
14180 overlap the objects pointed to by s1 and s2, and then the n characters from the
14181 temporary array are copied into the object pointed to by s1.
14183 3 The memmove function returns the value of s1.
14184 <a name="7.23.2.3" href="#7.23.2.3"><b> 7.23.2.3 The strcpy function</b></a>
14186 1 #include <a href="#7.23"><string.h></a>
14187 char *strcpy(char * restrict s1,
14188 const char * restrict s2);
14189 <b> Description</b>
14190 2 The strcpy function copies the string pointed to by s2 (including the terminating null
14191 character) into the array pointed to by s1. If copying takes place between objects that
14192 overlap, the behavior is undefined.
14194 3 The strcpy function returns the value of s1.
14195 <a name="7.23.2.4" href="#7.23.2.4"><b> 7.23.2.4 The strncpy function</b></a>
14197 1 #include <a href="#7.23"><string.h></a>
14198 char *strncpy(char * restrict s1,
14199 const char * restrict s2,
14201 <b> Description</b>
14202 2 The strncpy function copies not more than n characters (characters that follow a null
14203 character are not copied) from the array pointed to by s2 to the array pointed to by
14205 [<a name="p361" href="#p361">page 361</a>] (<a href="#Contents">Contents</a>)
14207 s1.<sup><a href="#note301"><b>301)</b></a></sup> If copying takes place between objects that overlap, the behavior is undefined.
14208 3 If the array pointed to by s2 is a string that is shorter than n characters, null characters
14209 are appended to the copy in the array pointed to by s1, until n characters in all have been
14212 4 The strncpy function returns the value of s1.
14213 <a name="7.23.3" href="#7.23.3"><b> 7.23.3 Concatenation functions</b></a>
14214 <a name="7.23.3.1" href="#7.23.3.1"><b> 7.23.3.1 The strcat function</b></a>
14216 1 #include <a href="#7.23"><string.h></a>
14217 char *strcat(char * restrict s1,
14218 const char * restrict s2);
14219 <b> Description</b>
14220 2 The strcat function appends a copy of the string pointed to by s2 (including the
14221 terminating null character) to the end of the string pointed to by s1. The initial character
14222 of s2 overwrites the null character at the end of s1. If copying takes place between
14223 objects that overlap, the behavior is undefined.
14225 3 The strcat function returns the value of s1.
14226 <a name="7.23.3.2" href="#7.23.3.2"><b> 7.23.3.2 The strncat function</b></a>
14228 1 #include <a href="#7.23"><string.h></a>
14229 char *strncat(char * restrict s1,
14230 const char * restrict s2,
14232 <b> Description</b>
14233 2 The strncat function appends not more than n characters (a null character and
14234 characters that follow it are not appended) from the array pointed to by s2 to the end of
14235 the string pointed to by s1. The initial character of s2 overwrites the null character at the
14236 end of s1. A terminating null character is always appended to the result.<sup><a href="#note302"><b>302)</b></a></sup> If copying
14238 <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
14239 not be null-terminated.
14240 <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
14243 [<a name="p362" href="#p362">page 362</a>] (<a href="#Contents">Contents</a>)
14245 takes place between objects that overlap, the behavior is undefined.
14247 3 The strncat function returns the value of s1.
14248 Forward references: the strlen function (<a href="#7.23.6.3">7.23.6.3</a>).
14249 <a name="7.23.4" href="#7.23.4"><b> 7.23.4 Comparison functions</b></a>
14250 1 The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
14251 and strncmp is determined by the sign of the difference between the values of the first
14252 pair of characters (both interpreted as unsigned char) that differ in the objects being
14254 <a name="7.23.4.1" href="#7.23.4.1"><b> 7.23.4.1 The memcmp function</b></a>
14256 1 #include <a href="#7.23"><string.h></a>
14257 int memcmp(const void *s1, const void *s2, size_t n);
14258 <b> Description</b>
14259 2 The memcmp function compares the first n characters of the object pointed to by s1 to
14260 the first n characters of the object pointed to by s2.<sup><a href="#note303"><b>303)</b></a></sup>
14262 3 The memcmp function returns an integer greater than, equal to, or less than zero,
14263 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
14265 <a name="7.23.4.2" href="#7.23.4.2"><b> 7.23.4.2 The strcmp function</b></a>
14267 1 #include <a href="#7.23"><string.h></a>
14268 int strcmp(const char *s1, const char *s2);
14269 <b> Description</b>
14270 2 The strcmp function compares the string pointed to by s1 to the string pointed to by
14273 3 The strcmp function returns an integer greater than, equal to, or less than zero,
14274 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
14276 <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
14277 indeterminate. Strings shorter than their allocated space and unions may also cause problems in
14280 [<a name="p363" href="#p363">page 363</a>] (<a href="#Contents">Contents</a>)
14283 <a name="7.23.4.3" href="#7.23.4.3"><b> 7.23.4.3 The strcoll function</b></a>
14285 1 #include <a href="#7.23"><string.h></a>
14286 int strcoll(const char *s1, const char *s2);
14287 <b> Description</b>
14288 2 The strcoll function compares the string pointed to by s1 to the string pointed to by
14289 s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
14291 3 The strcoll function returns an integer greater than, equal to, or less than zero,
14292 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
14293 pointed to by s2 when both are interpreted as appropriate to the current locale.
14294 <a name="7.23.4.4" href="#7.23.4.4"><b> 7.23.4.4 The strncmp function</b></a>
14296 1 #include <a href="#7.23"><string.h></a>
14297 int strncmp(const char *s1, const char *s2, size_t n);
14298 <b> Description</b>
14299 2 The strncmp function compares not more than n characters (characters that follow a
14300 null character are not compared) from the array pointed to by s1 to the array pointed to
14303 3 The strncmp function returns an integer greater than, equal to, or less than zero,
14304 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
14305 to, or less than the possibly null-terminated array pointed to by s2.
14306 <a name="7.23.4.5" href="#7.23.4.5"><b> 7.23.4.5 The strxfrm function</b></a>
14308 1 #include <a href="#7.23"><string.h></a>
14309 size_t strxfrm(char * restrict s1,
14310 const char * restrict s2,
14312 <b> Description</b>
14313 2 The strxfrm function transforms the string pointed to by s2 and places the resulting
14314 string into the array pointed to by s1. The transformation is such that if the strcmp
14315 function is applied to two transformed strings, it returns a value greater than, equal to, or
14317 [<a name="p364" href="#p364">page 364</a>] (<a href="#Contents">Contents</a>)
14319 less than zero, corresponding to the result of the strcoll function applied to the same
14320 two original strings. No more than n characters are placed into the resulting array
14321 pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
14322 be a null pointer. If copying takes place between objects that overlap, the behavior is
14325 3 The strxfrm function returns the length of the transformed string (not including the
14326 terminating null character). If the value returned is n or more, the contents of the array
14327 pointed to by s1 are indeterminate.
14328 4 EXAMPLE The value of the following expression is the size of the array needed to hold the
14329 transformation of the string pointed to by s.
14330 1 + strxfrm(NULL, s, 0)
14332 <a name="7.23.5" href="#7.23.5"><b> 7.23.5 Search functions</b></a>
14333 <a name="7.23.5.1" href="#7.23.5.1"><b> 7.23.5.1 The memchr function</b></a>
14335 1 #include <a href="#7.23"><string.h></a>
14336 void *memchr(const void *s, int c, size_t n);
14337 <b> Description</b>
14338 2 The memchr function locates the first occurrence of c (converted to an unsigned
14339 char) in the initial n characters (each interpreted as unsigned char) of the object
14340 pointed to by s. The implementation shall behave as if it reads the characters sequentially
14341 and stops as soon as a matching character is found.
14343 3 The memchr function returns a pointer to the located character, or a null pointer if the
14344 character does not occur in the object.
14345 <a name="7.23.5.2" href="#7.23.5.2"><b> 7.23.5.2 The strchr function</b></a>
14347 1 #include <a href="#7.23"><string.h></a>
14348 char *strchr(const char *s, int c);
14349 <b> Description</b>
14350 2 The strchr function locates the first occurrence of c (converted to a char) in the
14351 string pointed to by s. The terminating null character is considered to be part of the
14354 [<a name="p365" href="#p365">page 365</a>] (<a href="#Contents">Contents</a>)
14357 3 The strchr function returns a pointer to the located character, or a null pointer if the
14358 character does not occur in the string.
14359 <a name="7.23.5.3" href="#7.23.5.3"><b> 7.23.5.3 The strcspn function</b></a>
14361 1 #include <a href="#7.23"><string.h></a>
14362 size_t strcspn(const char *s1, const char *s2);
14363 <b> Description</b>
14364 2 The strcspn function computes the length of the maximum initial segment of the string
14365 pointed to by s1 which consists entirely of characters not from the string pointed to by
14368 3 The strcspn function returns the length of the segment.
14369 <a name="7.23.5.4" href="#7.23.5.4"><b> 7.23.5.4 The strpbrk function</b></a>
14371 1 #include <a href="#7.23"><string.h></a>
14372 char *strpbrk(const char *s1, const char *s2);
14373 <b> Description</b>
14374 2 The strpbrk function locates the first occurrence in the string pointed to by s1 of any
14375 character from the string pointed to by s2.
14377 3 The strpbrk function returns a pointer to the character, or a null pointer if no character
14378 from s2 occurs in s1.
14379 <a name="7.23.5.5" href="#7.23.5.5"><b> 7.23.5.5 The strrchr function</b></a>
14381 1 #include <a href="#7.23"><string.h></a>
14382 char *strrchr(const char *s, int c);
14383 <b> Description</b>
14384 2 The strrchr function locates the last occurrence of c (converted to a char) in the
14385 string pointed to by s. The terminating null character is considered to be part of the
14388 [<a name="p366" href="#p366">page 366</a>] (<a href="#Contents">Contents</a>)
14391 3 The strrchr function returns a pointer to the character, or a null pointer if c does not
14392 occur in the string.
14393 <a name="7.23.5.6" href="#7.23.5.6"><b> 7.23.5.6 The strspn function</b></a>
14395 1 #include <a href="#7.23"><string.h></a>
14396 size_t strspn(const char *s1, const char *s2);
14397 <b> Description</b>
14398 2 The strspn function computes the length of the maximum initial segment of the string
14399 pointed to by s1 which consists entirely of characters from the string pointed to by s2.
14401 3 The strspn function returns the length of the segment.
14402 <a name="7.23.5.7" href="#7.23.5.7"><b> 7.23.5.7 The strstr function</b></a>
14404 1 #include <a href="#7.23"><string.h></a>
14405 char *strstr(const char *s1, const char *s2);
14406 <b> Description</b>
14407 2 The strstr function locates the first occurrence in the string pointed to by s1 of the
14408 sequence of characters (excluding the terminating null character) in the string pointed to
14411 3 The strstr function returns a pointer to the located string, or a null pointer if the string
14412 is not found. If s2 points to a string with zero length, the function returns s1.
14413 <a name="7.23.5.8" href="#7.23.5.8"><b> 7.23.5.8 The strtok function</b></a>
14415 1 #include <a href="#7.23"><string.h></a>
14416 char *strtok(char * restrict s1,
14417 const char * restrict s2);
14418 <b> Description</b>
14419 2 A sequence of calls to the strtok function breaks the string pointed to by s1 into a
14420 sequence of tokens, each of which is delimited by a character from the string pointed to
14421 by s2. The first call in the sequence has a non-null first argument; subsequent calls in the
14422 sequence have a null first argument. The separator string pointed to by s2 may be
14423 different from call to call.
14425 [<a name="p367" href="#p367">page 367</a>] (<a href="#Contents">Contents</a>)
14427 3 The first call in the sequence searches the string pointed to by s1 for the first character
14428 that is not contained in the current separator string pointed to by s2. If no such character
14429 is found, then there are no tokens in the string pointed to by s1 and the strtok function
14430 returns a null pointer. If such a character is found, it is the start of the first token.
14431 4 The strtok function then searches from there for a character that is contained in the
14432 current separator string. If no such character is found, the current token extends to the
14433 end of the string pointed to by s1, and subsequent searches for a token will return a null
14434 pointer. If such a character is found, it is overwritten by a null character, which
14435 terminates the current token. The strtok function saves a pointer to the following
14436 character, from which the next search for a token will start.
14437 5 Each subsequent call, with a null pointer as the value of the first argument, starts
14438 searching from the saved pointer and behaves as described above.
14439 6 The strtok function is not required to avoid data races. The implementation shall
14440 behave as if no library function calls the strtok function.
14442 7 The strtok function returns a pointer to the first character of a token, or a null pointer
14443 if there is no token.
14445 #include <a href="#7.23"><string.h></a>
14446 static char str[] = "?a???b,,,#c";
14448 t = strtok(str, "?"); // t points to the token "a"
14449 t = strtok(NULL, ","); // t points to the token "??b"
14450 t = strtok(NULL, "#,"); // t points to the token "c"
14451 t = strtok(NULL, "?"); // t is a null pointer
14453 <a name="7.23.6" href="#7.23.6"><b> 7.23.6 Miscellaneous functions</b></a>
14454 <a name="7.23.6.1" href="#7.23.6.1"><b> 7.23.6.1 The memset function</b></a>
14456 1 #include <a href="#7.23"><string.h></a>
14457 void *memset(void *s, int c, size_t n);
14458 <b> Description</b>
14459 2 The memset function copies the value of c (converted to an unsigned char) into
14460 each of the first n characters of the object pointed to by s.
14462 3 The memset function returns the value of s.
14464 [<a name="p368" href="#p368">page 368</a>] (<a href="#Contents">Contents</a>)
14466 <a name="7.23.6.2" href="#7.23.6.2"><b> 7.23.6.2 The strerror function</b></a>
14468 1 #include <a href="#7.23"><string.h></a>
14469 char *strerror(int errnum);
14470 <b> Description</b>
14471 2 The strerror function maps the number in errnum to a message string. Typically,
14472 the values for errnum come from errno, but strerror shall map any value of type
14474 3 The strerror function is not required to avoid data races. The implementation shall
14475 behave as if no library function calls the strerror function.
14477 4 The strerror function returns a pointer to the string, the contents of which are locale-
14478 specific. The array pointed to shall not be modified by the program, but may be
14479 overwritten by a subsequent call to the strerror function.
14480 <a name="7.23.6.3" href="#7.23.6.3"><b> 7.23.6.3 The strlen function</b></a>
14482 1 #include <a href="#7.23"><string.h></a>
14483 size_t strlen(const char *s);
14484 <b> Description</b>
14485 2 The strlen function computes the length of the string pointed to by s.
14487 3 The strlen function returns the number of characters that precede the terminating null
14490 [<a name="p369" href="#p369">page 369</a>] (<a href="#Contents">Contents</a>)
14492 <a name="7.24" href="#7.24"><b> 7.24 Type-generic math <tgmath.h></b></a>
14493 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
14494 defines several type-generic macros.
14495 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
14496 double) suffix, several have one or more parameters whose corresponding real type is
14497 double. For each such function, except modf, there is a corresponding type-generic
14498 macro.<sup><a href="#note304"><b>304)</b></a></sup> The parameters whose corresponding real type is double in the function
14499 synopsis are generic parameters. Use of the macro invokes a function whose
14500 corresponding real type and type domain are determined by the arguments for the generic
14501 parameters.<sup><a href="#note305"><b>305)</b></a></sup>
14502 3 Use of the macro invokes a function whose generic parameters have the corresponding
14503 real type determined as follows:
14504 -- First, if any argument for generic parameters has type long double, the type
14505 determined is long double.
14506 -- Otherwise, if any argument for generic parameters has type double or is of integer
14507 type, the type determined is double.
14508 -- Otherwise, the type determined is float.
14509 4 For each unsuffixed function in <a href="#7.12"><math.h></a> for which there is a function in
14510 <a href="#7.3"><complex.h></a> with the same name except for a c prefix, the corresponding type-
14511 generic macro (for both functions) has the same name as the function in <a href="#7.12"><math.h></a>. The
14512 corresponding type-generic macro for fabs and cabs is fabs.
14517 <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
14518 make available the corresponding ordinary function.
14519 <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,
14520 the behavior is undefined.
14522 [<a name="p370" href="#p370">page 370</a>] (<a href="#Contents">Contents</a>)
14524 <a href="#7.12"><math.h></a> <a href="#7.3"><complex.h></a> type-generic
14525 function function macro
14543 If at least one argument for a generic parameter is complex, then use of the macro invokes
14544 a complex function; otherwise, use of the macro invokes a real function.
14545 5 For each unsuffixed function in <a href="#7.12"><math.h></a> without a c-prefixed counterpart in
14546 <a href="#7.3"><complex.h></a> (except modf), the corresponding type-generic macro has the same
14547 name as the function. These type-generic macros are:
14548 atan2 fma llround remainder
14549 cbrt fmax log10 remquo
14550 ceil fmin log1p rint
14551 copysign fmod log2 round
14552 erf frexp logb scalbn
14553 erfc hypot lrint scalbln
14554 exp2 ilogb lround tgamma
14555 expm1 ldexp nearbyint trunc
14556 fdim lgamma nextafter
14557 floor llrint nexttoward
14558 If all arguments for generic parameters are real, then use of the macro invokes a real
14559 function; otherwise, use of the macro results in undefined behavior.
14561 [<a name="p371" href="#p371">page 371</a>] (<a href="#Contents">Contents</a>)
14563 6 For each unsuffixed function in <a href="#7.3"><complex.h></a> that is not a c-prefixed counterpart to a
14564 function in <a href="#7.12"><math.h></a>, the corresponding type-generic macro has the same name as the
14565 function. These type-generic macros are:
14568 Use of the macro with any real or complex argument invokes a complex function.
14569 7 EXAMPLE With the declarations
14570 #include <a href="#7.24"><tgmath.h></a>
14577 long double complex ldc;
14578 functions invoked by use of type-generic macros are shown in the following table:
14580 exp(n) exp(n), the function
14582 sin(d) sin(d), the function
14586 pow(ldc, f) cpowl(ldc, f)
14587 remainder(n, n) remainder(n, n), the function
14588 nextafter(d, f) nextafter(d, f), the function
14589 nexttoward(f, ld) nexttowardf(f, ld)
14590 copysign(n, ld) copysignl(n, ld)
14591 ceil(fc) undefined behavior
14592 rint(dc) undefined behavior
14593 fmax(ldc, ld) undefined behavior
14594 carg(n) carg(n), the function
14596 creal(d) creal(d), the function
14597 cimag(ld) cimagl(ld)
14599 carg(dc) carg(dc), the function
14600 cproj(ldc) cprojl(ldc)
14602 [<a name="p372" href="#p372">page 372</a>] (<a href="#Contents">Contents</a>)
14604 <a name="7.25" href="#7.25"><b> 7.25 Threads <threads.h></b></a>
14605 <a name="7.25.1" href="#7.25.1"><b> 7.25.1 Introduction</b></a>
14606 1 The header <a href="#7.25"><threads.h></a> defines macros, and declares types, enumeration constants,
14607 and functions that support multiple threads of execution.
14608 2 Implementations that define the macro __STDC_NO_THREADS__ need not provide
14609 this header nor support any of its facilities.
14612 which expands to a value that can be used to initialize an object of type once_flag;
14614 TSS_DTOR_ITERATIONS
14615 which expands to an integer constant expression representing the maximum number of
14616 times that destructors will be called when a thread terminates.
14619 which is a complete object type that holds an identifier for a condition variable;
14621 which is a complete object type that holds an identifier for a thread;
14623 which is a complete object type that holds an identifier for a thread-specific storage
14626 which is a complete object type that holds an identifier for a mutex;
14628 which is the function pointer type void (*)(void*), used for a destructor for a
14629 thread-specific storage pointer;
14631 which is the function pointer type int (*)(void*) that is passed to thrd_create
14632 to create a new thread;
14634 which is a complete object type that holds a flag for use by call_once; and
14636 [<a name="p373" href="#p373">page 373</a>] (<a href="#Contents">Contents</a>)
14639 which is a structure type that holds a time specified in seconds and nanoseconds. The
14640 structure shall contain at least the following members, in any order.
14643 5 The enumeration constants are
14645 which is passed to mtx_init to create a mutex object that supports neither timeout nor
14648 which is passed to mtx_init to create a mutex object that supports recursive locking;
14650 which is passed to mtx_init to create a mutex object that supports timeout;
14652 which is passed to mtx_init to create a mutex object that supports test and return;
14654 which is returned by a timed wait function to indicate that the time specified in the call
14655 was reached without acquiring the requested resource;
14657 which is returned by a function to indicate that the requested operation succeeded;
14659 which is returned by a function to indicate that the requested operation failed because a
14660 resource requested by a test and return function is already in use;
14662 which is returned by a function to indicate that the requested operation failed; and
14664 which is returned by a function to indicate that the requested operation failed because it
14665 was unable to allocate memory.
14667 [<a name="p374" href="#p374">page 374</a>] (<a href="#Contents">Contents</a>)
14669 <a name="7.25.2" href="#7.25.2"><b> 7.25.2 Initialization functions</b></a>
14670 <a name="7.25.2.1" href="#7.25.2.1"><b> 7.25.2.1 The call_once function</b></a>
14672 1 #include <a href="#7.25"><threads.h></a>
14673 void call_once(once_flag *flag, void (*func)(void));
14674 <b> Description</b>
14675 2 The call_once function uses the once_flag pointed to by flag to ensure that
14676 func is called exactly once, the first time the call_once function is called with that
14677 value of flag. Completion of an effective call to the call_once function synchronizes
14678 with all subsequent calls to the call_once function with the same value of flag.
14680 3 The call_once function returns no value.
14681 <a name="7.25.3" href="#7.25.3"><b> 7.25.3 Condition variable functions</b></a>
14682 <a name="7.25.3.1" href="#7.25.3.1"><b> 7.25.3.1 The cnd_broadcast function</b></a>
14684 1 #include <a href="#7.25"><threads.h></a>
14685 int cnd_broadcast(cnd_t *cond);
14686 <b> Description</b>
14687 2 The cnd_broadcast function unblocks all of the threads that are blocked on the
14688 condition variable pointed to by cond at the time of the call. If no threads are blocked
14689 on the condition variable pointed to by cond at the time of the call, the function does
14692 3 The cnd_broadcast function returns thrd_success on success, or thrd_error
14693 if the request could not be honored.
14694 <a name="7.25.3.2" href="#7.25.3.2"><b> 7.25.3.2 The cnd_destroy function</b></a>
14696 1 #include <a href="#7.25"><threads.h></a>
14697 void cnd_destroy(cnd_t *cond);
14698 <b> Description</b>
14699 2 The cnd_destroy function releases all resources used by the condition variable
14700 pointed to by cond. The cnd_destroy function requires that no threads be blocked
14701 waiting for the condition variable pointed to by cond.
14703 [<a name="p375" href="#p375">page 375</a>] (<a href="#Contents">Contents</a>)
14706 3 The cnd_destroy function returns no value.
14707 <a name="7.25.3.3" href="#7.25.3.3"><b> 7.25.3.3 The cnd_init function</b></a>
14709 1 #include <a href="#7.25"><threads.h></a>
14710 int cnd_init(cnd_t *cond);
14711 <b> Description</b>
14712 2 The cnd_init function creates a condition variable. If it succeeds it sets the variable
14713 pointed to by cond to a value that uniquely identifies the newly created condition
14714 variable. A thread that calls cnd_wait on a newly created condition variable will
14717 3 The cnd_init function returns thrd_success on success, or thrd_nomem if no
14718 memory could be allocated for the newly created condition, or thrd_error if the
14719 request could not be honored.
14720 <a name="7.25.3.4" href="#7.25.3.4"><b> 7.25.3.4 The cnd_signal function</b></a>
14722 1 #include <a href="#7.25"><threads.h></a>
14723 int cnd_signal(cnd_t *cond);
14724 <b> Description</b>
14725 2 The cnd_signal function unblocks one of the threads that are blocked on the
14726 condition variable pointed to by cond at the time of the call. If no threads are blocked
14727 on the condition variable at the time of the call, the function does nothing and return
14730 3 The cnd_signal function returns thrd_success on success or thrd_error if
14731 the request could not be honored.
14732 <a name="7.25.3.5" href="#7.25.3.5"><b> 7.25.3.5 The cnd_timedwait function</b></a>
14734 1 #include <a href="#7.25"><threads.h></a>
14735 int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
14738 [<a name="p376" href="#p376">page 376</a>] (<a href="#Contents">Contents</a>)
14740 <b> Description</b>
14741 2 The cnd_timedwait function atomically unlocks the mutex pointed to by mtx and
14742 endeavors to block until the condition variable pointed to by cond is signaled by a call to
14743 cnd_signal or to cnd_broadcast, or until after the time specified by the xtime
14744 object pointed to by xt. When the calling thread becomes unblocked it locks the variable
14745 pointed to by mtx before it returns. The cnd_timedwait function requires that the
14746 mutex pointed to by mtx be locked by the calling thread.
14748 3 The cnd_timedwait function returns thrd_success upon success, or
14749 thrd_timeout if the time specified in the call was reached without acquiring the
14750 requested resource, or thrd_error if the request could not be honored.
14751 <a name="7.25.3.6" href="#7.25.3.6"><b> 7.25.3.6 The cnd_wait function</b></a>
14753 1 #include <a href="#7.25"><threads.h></a>
14754 int cnd_wait(cnd_t *cond, mtx_t *mtx);
14755 <b> Description</b>
14756 2 The cnd_wait function atomically unlocks the mutex pointed to by mtx and endeavors
14757 to block until the condition variable pointed to by cond is signaled by a call to
14758 cnd_signal or to cnd_broadcast. When the calling thread becomes unblocked it
14759 locks the mutex pointed to by mtx before it returns. If the mutex pointed to by mtx is
14760 not locked by the calling thread, the cnd_wait function will act as if the abort
14761 function is called.
14763 3 The cnd_wait function returns thrd_success on success or thrd_error if the
14764 request could not be honored.
14765 <a name="7.25.4" href="#7.25.4"><b> 7.25.4 Mutex functions</b></a>
14766 <a name="7.25.4.1" href="#7.25.4.1"><b> 7.25.4.1 The mtx_destroy function</b></a>
14768 1 #include <a href="#7.25"><threads.h></a>
14769 void mtx_destroy(mtx_t *mtx);
14770 <b> Description</b>
14771 2 The mtx_destroy function releases any resources used by the mutex pointed to by
14772 mtx. No threads can be blocked waiting for the mutex pointed to by mtx.
14774 [<a name="p377" href="#p377">page 377</a>] (<a href="#Contents">Contents</a>)
14777 3 The mtx_destroy function returns no value.
14778 <a name="7.25.4.2" href="#7.25.4.2"><b> 7.25.4.2 The mtx_init function</b></a>
14780 1 #include <a href="#7.25"><threads.h></a>
14781 int mtx_init(mtx_t *mtx, int type);
14782 <b> Description</b>
14783 2 The mtx_init function creates a mutex object with properties indicated by type,
14784 which must have one of the six values:
14785 mtx_plain for a simple non-recursive mutex,
14786 mtx_timed for a non-recursive mutex that supports timeout,
14787 mtx_try for a non-recursive mutex that supports test and return,
14788 mtx_plain | mtx_recursive for a simple recursive mutex,
14789 mtx_timed | mtx_recursive for a recursive mutex that supports timeout, or
14790 mtx_try | mtx_recursive for a recursive mutex that supports test and return.
14791 3 If the mtx_init function succeeds, it sets the mutex pointed to by mtx to a value that
14792 uniquely identifies the newly created mutex.
14794 4 The mtx_init function returns thrd_success on success, or thrd_error if the
14795 request could not be honored.
14796 <a name="7.25.4.3" href="#7.25.4.3"><b> 7.25.4.3 The mtx_lock function</b></a>
14798 1 #include <a href="#7.25"><threads.h></a>
14799 int mtx_lock(mtx_t *mtx);
14800 <b> Description</b>
14801 2 The mtx_lock function blocks until it locks the mutex pointed to by mtx. If the mutex
14802 is non-recursive, it shall not be locked by the calling thread. Prior calls to mtx_unlock
14803 on the same mutex shall synchronize with this operation.
14805 3 The mtx_lock function returns thrd_success on success, or thrd_busy if the
14806 resource requested is already in use, or thrd_error if the request could not be
14809 [<a name="p378" href="#p378">page 378</a>] (<a href="#Contents">Contents</a>)
14811 <a name="7.25.4.4" href="#7.25.4.4"><b> 7.25.4.4 The mtx_timedlock function</b></a>
14813 1 #include <a href="#7.25"><threads.h></a>
14814 int mtx_timedlock(mtx_t *mtx, const xtime *xt);
14815 <b> Description</b>
14816 2 The mtx_timedlock function endeavors to block until it locks the mutex pointed to by
14817 mtx or until the time specified by the xtime object xt has passed. The specified mutex
14818 shall support timeout. If the operation succeeds, prior calls to mtx_unlock on the same
14819 mutex shall synchronize with this operation.
14821 3 The mtx_timedlock function returns thrd_success on success, or thrd_busy
14822 if the resource requested is already in use, or thrd_timeout if the time specified was
14823 reached without acquiring the requested resource, or thrd_error if the request could
14825 <a name="7.25.4.5" href="#7.25.4.5"><b> 7.25.4.5 The mtx_trylock function</b></a>
14827 1 #include <a href="#7.25"><threads.h></a>
14828 int mtx_trylock(mtx_t *mtx);
14829 <b> Description</b>
14830 2 The mtx_trylock function endeavors to lock the mutex pointed to by mtx. The
14831 specified mutex shall support either test and return or timeout. If the mutex is already
14832 locked, the function returns without blocking. If the operation succeeds, prior calls to
14833 mtx_unlock on the same mutex shall synchronize with this operation.
14835 3 The mtx_trylock function returns thrd_success on success, or thrd_busy if
14836 the resource requested is already in use, or thrd_error if the request could not be
14838 <a name="7.25.4.6" href="#7.25.4.6"><b> 7.25.4.6 The mtx_unlock function</b></a>
14840 1 #include <a href="#7.25"><threads.h></a>
14841 int mtx_unlock(mtx_t *mtx);
14842 <b> Description</b>
14843 2 The mtx_unlock function unlocks the mutex pointed to by mtx. The mutex pointed to
14844 by mtx shall be locked by the calling thread.
14846 [<a name="p379" href="#p379">page 379</a>] (<a href="#Contents">Contents</a>)
14849 3 The mtx_unlock function returns thrd_success on success or thrd_error if
14850 the request could not be honored.
14851 <a name="7.25.5" href="#7.25.5"><b> 7.25.5 Thread functions</b></a>
14852 <a name="7.25.5.1" href="#7.25.5.1"><b> 7.25.5.1 The thrd_create function</b></a>
14854 1 #include <a href="#7.25"><threads.h></a>
14855 int thrd_create(thrd_t *thr, thrd_start_t func,
14857 <b> Description</b>
14858 2 The thrd_create function creates a new thread executing func(arg). If the
14859 thrd_create function succeeds, it sets the object pointed to by thr to the identifier of
14860 the newly created thread. (A thread's identifier may be reused for a different thread once
14861 the original thread has exited and either been detached or joined to another thread.) The
14862 completion of the thrd_create function synchronizes with the beginning of the
14863 execution of the new thread.
14865 3 The thrd_create function returns thrd_success on success, or thrd_nomem if
14866 no memory could be allocated for the thread requested, or thrd_error if the request
14867 could not be honored.
14868 <a name="7.25.5.2" href="#7.25.5.2"><b> 7.25.5.2 The thrd_current function</b></a>
14870 1 #include <a href="#7.25"><threads.h></a>
14871 thrd_t thrd_current(void);
14872 <b> Description</b>
14873 2 The thrd_current function identifies the thread that called it.
14875 3 The thrd_current function returns the identifier of the thread that called it.
14876 <a name="7.25.5.3" href="#7.25.5.3"><b> 7.25.5.3 The thrd_detach function</b></a>
14878 1 #include <a href="#7.25"><threads.h></a>
14879 int thrd_detach(thrd_t thr);
14881 [<a name="p380" href="#p380">page 380</a>] (<a href="#Contents">Contents</a>)
14883 <b> Description</b>
14884 2 The thrd_detach function tells the operating system to dispose of any resources
14885 allocated to the thread identified by thr when that thread terminates. The thread
14886 identified by thr shall not have been previously detached or joined with another thread.
14888 3 The thrd_detach function returns thrd_success on success or thrd_error if
14889 the request could not be honored.
14890 <a name="7.25.5.4" href="#7.25.5.4"><b> 7.25.5.4 The thrd_equal function</b></a>
14892 1 #include <a href="#7.25"><threads.h></a>
14893 int thrd_equal(thrd_t thr0, thrd_t thr1);
14894 <b> Description</b>
14895 2 The thrd_equal function will determine whether the thread identified by thr0 refers
14896 to the thread identified by thr1.
14898 3 The thrd_equal function returns zero if the thread thr0 and the thread thr1 refer to
14899 different threads. Otherwise the thrd_equal function returns a nonzero value.
14900 <a name="7.25.5.5" href="#7.25.5.5"><b> 7.25.5.5 The thrd_exit function</b></a>
14902 1 #include <a href="#7.25"><threads.h></a>
14903 void thrd_exit(int res);
14904 <b> Description</b>
14905 2 The thrd_exit function terminates execution of the calling thread and sets its result
14908 3 The thrd_exit function returns no value.
14909 <a name="7.25.5.6" href="#7.25.5.6"><b> 7.25.5.6 The thrd_join function</b></a>
14911 1 #include <a href="#7.25"><threads.h></a>
14912 int thrd_join(thrd_t thr, int *res);
14913 <b> Description</b>
14914 2 The thrd_join function joins the thread identified by thr with the current thread by
14915 blocking until the other thread has terminated. If the parameter res is not a null pointer,
14917 [<a name="p381" href="#p381">page 381</a>] (<a href="#Contents">Contents</a>)
14919 it stores the thread's result code in the integer pointed to by res. The termination of the
14920 other thread synchronizes with the completion of the thrd_join function. The thread
14921 identified by thr shall not have been previously detached or joined with another thread.
14923 3 The thrd_join function returns thrd_success on success or thrd_error if the
14924 request could not be honored.
14925 <a name="7.25.5.7" href="#7.25.5.7"><b> 7.25.5.7 The thrd_sleep function</b></a>
14927 1 #include <a href="#7.25"><threads.h></a>
14928 void thrd_sleep(const xtime *xt);
14929 <b> Description</b>
14930 2 The thrd_sleep function suspends execution of the calling thread until after the time
14931 specified by the xtime object pointed to by xt.
14933 3 The thrd_sleep function returns no value.
14934 <a name="7.25.5.8" href="#7.25.5.8"><b> 7.25.5.8 The thrd_yield function</b></a>
14936 1 #include <a href="#7.25"><threads.h></a>
14937 void thrd_yield(void);
14938 <b> Description</b>
14939 2 The thrd_yield function endeavors to permit other threads to run, even if the current
14940 thread would ordinarily continue to run.
14942 3 The thrd_yield function returns no value.
14943 <a name="7.25.6" href="#7.25.6"><b> 7.25.6 Thread-specific storage functions</b></a>
14944 <a name="7.25.6.1" href="#7.25.6.1"><b> 7.25.6.1 The tss_create function</b></a>
14946 1 #include <a href="#7.25"><threads.h></a>
14947 int tss_create(tss_t *key, tss_dtor_t dtor);
14948 <b> Description</b>
14949 2 The tss_create function creates a thread-specific storage pointer with destructor
14950 dtor, which may be null.
14952 [<a name="p382" href="#p382">page 382</a>] (<a href="#Contents">Contents</a>)
14955 3 If the tss_create function is successful, it sets the thread-specific storage pointed to
14956 by key to a value that uniquely identifies the newly created pointer and returns
14957 thrd_success; otherwise, thrd_error is returned and the thread-specific storage
14958 pointed to by key is set to an undefined value.
14959 <a name="7.25.6.2" href="#7.25.6.2"><b> 7.25.6.2 The tss_delete function</b></a>
14961 1 #include <a href="#7.25"><threads.h></a>
14962 void tss_delete(tss_t key);
14963 <b> Description</b>
14964 2 The tss_delete function releases any resources used by the thread-specific storage
14967 3 The tss_delete function returns no value.
14968 <a name="7.25.6.3" href="#7.25.6.3"><b> 7.25.6.3 The tss_get function</b></a>
14970 1 #include <a href="#7.25"><threads.h></a>
14971 void *tss_get(tss_t key);
14972 <b> Description</b>
14973 2 The tss_get function returns the value for the current thread held in the thread-specific
14974 storage identified by key.
14976 3 The tss_get function returns the value for the current thread if successful, or zero if
14978 <a name="7.25.6.4" href="#7.25.6.4"><b> 7.25.6.4 The tss_set function</b></a>
14980 1 #include <a href="#7.25"><threads.h></a>
14981 int tss_set(tss_t key, void *val);
14982 <b> Description</b>
14983 2 The tss_set function sets the value for the current thread held in the thread-specific
14984 storage identified by key to val.
14986 [<a name="p383" href="#p383">page 383</a>] (<a href="#Contents">Contents</a>)
14989 3 The tss_set function returns thrd_success on success or thrd_error if the
14990 request could not be honored.
14991 <a name="7.25.7" href="#7.25.7"><b> 7.25.7 Time functions</b></a>
14992 <a name="7.25.7.1" href="#7.25.7.1"><b> 7.25.7.1 The xtime_get function</b></a>
14994 1 #include <a href="#7.25"><threads.h></a>
14995 int xtime_get(xtime *xt, int base);
14996 <b> Description</b>
14997 2 The xtime_get function sets the xtime object pointed to by xt to hold the current
14998 time based on the time base base.
15000 3 If the xtime_get function is successful it returns the nonzero value base, which must
15001 be TIME_UTC; otherwise, it returns zero.<sup><a href="#note306"><b>306)</b></a></sup>
15006 <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
15007 xtime object is system dependent.
15009 [<a name="p384" href="#p384">page 384</a>] (<a href="#Contents">Contents</a>)
15011 <a name="7.26" href="#7.26"><b> 7.26 Date and time <time.h></b></a>
15012 <a name="7.26.1" href="#7.26.1"><b> 7.26.1 Components of time</b></a>
15013 1 The header <a href="#7.26"><time.h></a> defines two macros, and declares several types and functions for
15014 manipulating time. Many functions deal with a calendar time that represents the current
15015 date (according to the Gregorian calendar) and time. Some functions deal with local
15016 time, which is the calendar time expressed for some specific time zone, and with Daylight
15017 Saving Time, which is a temporary change in the algorithm for determining local time.
15018 The local time zone and Daylight Saving Time are implementation-defined.
15019 2 The macros defined are NULL (described in <a href="#7.19">7.19</a>); and
15021 which expands to an expression with type clock_t (described below) that is the
15022 number per second of the value returned by the clock function.
15023 3 The types declared are size_t (described in <a href="#7.19">7.19</a>);
15027 which are arithmetic types capable of representing times; and
15029 which holds the components of a calendar time, called the broken-down time.
15030 4 The range and precision of times representable in clock_t and time_t are
15031 implementation-defined. The tm structure shall contain at least the following members,
15032 in any order. The semantics of the members and their normal ranges are expressed in the
15033 comments.<sup><a href="#note307"><b>307)</b></a></sup>
15034 int tm_sec; // seconds after the minute -- [0, 60]
15035 int tm_min; // minutes after the hour -- [0, 59]
15036 int tm_hour; // hours since midnight -- [0, 23]
15037 int tm_mday; // day of the month -- [1, 31]
15038 int tm_mon; // months since January -- [0, 11]
15039 int tm_year; // years since 1900
15040 int tm_wday; // days since Sunday -- [0, 6]
15041 int tm_yday; // days since January 1 -- [0, 365]
15042 int tm_isdst; // Daylight Saving Time flag
15046 <sup><a name="note307" href="#note307"><b>307)</b></a></sup> The range [0, 60] for tm_sec allows for a positive leap second.
15048 [<a name="p385" href="#p385">page 385</a>] (<a href="#Contents">Contents</a>)
15050 The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight
15051 Saving Time is not in effect, and negative if the information is not available.
15052 <a name="7.26.2" href="#7.26.2"><b> 7.26.2 Time manipulation functions</b></a>
15053 <a name="7.26.2.1" href="#7.26.2.1"><b> 7.26.2.1 The clock function</b></a>
15055 1 #include <a href="#7.26"><time.h></a>
15056 clock_t clock(void);
15057 <b> Description</b>
15058 2 The clock function determines the processor time used.
15060 3 The clock function returns the implementation's best approximation to the processor
15061 time used by the program since the beginning of an implementation-defined era related
15062 only to the program invocation. To determine the time in seconds, the value returned by
15063 the clock function should be divided by the value of the macro CLOCKS_PER_SEC. If
15064 the processor time used is not available or its value cannot be represented, the function
15065 returns the value (clock_t)(-1).<sup><a href="#note308"><b>308)</b></a></sup>
15066 <a name="7.26.2.2" href="#7.26.2.2"><b> 7.26.2.2 The difftime function</b></a>
15068 1 #include <a href="#7.26"><time.h></a>
15069 double difftime(time_t time1, time_t time0);
15070 <b> Description</b>
15071 2 The difftime function computes the difference between two calendar times: time1 -
15074 3 The difftime function returns the difference expressed in seconds as a double.
15079 <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
15080 the program and its return value subtracted from the value returned by subsequent calls.
15082 [<a name="p386" href="#p386">page 386</a>] (<a href="#Contents">Contents</a>)
15084 <a name="7.26.2.3" href="#7.26.2.3"><b> 7.26.2.3 The mktime function</b></a>
15086 1 #include <a href="#7.26"><time.h></a>
15087 time_t mktime(struct tm *timeptr);
15088 <b> Description</b>
15089 2 The mktime function converts the broken-down time, expressed as local time, in the
15090 structure pointed to by timeptr into a calendar time value with the same encoding as
15091 that of the values returned by the time function. The original values of the tm_wday
15092 and tm_yday components of the structure are ignored, and the original values of the
15093 other components are not restricted to the ranges indicated above.<sup><a href="#note309"><b>309)</b></a></sup> On successful
15094 completion, the values of the tm_wday and tm_yday components of the structure are
15095 set appropriately, and the other components are set to represent the specified calendar
15096 time, but with their values forced to the ranges indicated above; the final value of
15097 tm_mday is not set until tm_mon and tm_year are determined.
15099 3 The mktime function returns the specified calendar time encoded as a value of type
15100 time_t. If the calendar time cannot be represented, the function returns the value
15102 4 EXAMPLE What day of the week is July 4, 2001?
15103 #include <a href="#7.21"><stdio.h></a>
15104 #include <a href="#7.26"><time.h></a>
15105 static const char *const wday[] = {
15106 "Sunday", "Monday", "Tuesday", "Wednesday",
15107 "Thursday", "Friday", "Saturday", "-unknown-"
15109 struct tm time_str;
15115 <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
15116 Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value
15117 causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time.
15119 [<a name="p387" href="#p387">page 387</a>] (<a href="#Contents">Contents</a>)
15121 time_str.tm_year = 2001 - 1900;
15122 time_str.tm_mon = 7 - 1;
15123 time_str.tm_mday = 4;
15124 time_str.tm_hour = 0;
15125 time_str.tm_min = 0;
15126 time_str.tm_sec = 1;
15127 time_str.tm_isdst = -1;
15128 if (mktime(&time_str) == (time_t)(-1))
15129 time_str.tm_wday = 7;
15130 printf("%s\n", wday[time_str.tm_wday]);
15132 <a name="7.26.2.4" href="#7.26.2.4"><b> 7.26.2.4 The time function</b></a>
15134 1 #include <a href="#7.26"><time.h></a>
15135 time_t time(time_t *timer);
15136 <b> Description</b>
15137 2 The time function determines the current calendar time. The encoding of the value is
15140 3 The time function returns the implementation's best approximation to the current
15141 calendar time. The value (time_t)(-1) is returned if the calendar time is not
15142 available. If timer is not a null pointer, the return value is also assigned to the object it
15144 <a name="7.26.3" href="#7.26.3"><b> 7.26.3 Time conversion functions</b></a>
15145 1 Except for the strftime function, these functions each return a pointer to one of two
15146 types of static objects: a broken-down time structure or an array of char. Execution of
15147 any of the functions that return a pointer to one of these object types may overwrite the
15148 information in any object of the same type pointed to by the value returned from any
15149 previous call to any of them and the functions are not required to avoid data races. The
15150 implementation shall behave as if no other library functions call these functions.
15151 <a name="7.26.3.1" href="#7.26.3.1"><b> 7.26.3.1 The asctime function</b></a>
15153 1 #include <a href="#7.26"><time.h></a>
15154 char *asctime(const struct tm *timeptr);
15155 <b> Description</b>
15156 2 The asctime function converts the broken-down time in the structure pointed to by
15157 timeptr into a string in the form
15158 Sun Sep 16 01:03:52 1973\n\0
15160 [<a name="p388" href="#p388">page 388</a>] (<a href="#Contents">Contents</a>)
15162 using the equivalent of the following algorithm.
15163 char *asctime(const struct tm *timeptr)
15165 static const char wday_name[7][3] = {
15166 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
15168 static const char mon_name[12][3] = {
15169 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
15170 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
15172 static char result[26];
15173 sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
15174 wday_name[timeptr->tm_wday],
15175 mon_name[timeptr->tm_mon],
15176 timeptr->tm_mday, timeptr->tm_hour,
15177 timeptr->tm_min, timeptr->tm_sec,
15178 1900 + timeptr->tm_year);
15181 3 If any of the fields of the broken-down time contain values that are outside their normal
15182 ranges,<sup><a href="#note310"><b>310)</b></a></sup> the behavior of the asctime function is undefined. Likewise, if the
15183 calculated year exceeds four digits or is less than the year 1000, the behavior is
15186 4 The asctime function returns a pointer to the string.
15187 <a name="7.26.3.2" href="#7.26.3.2"><b> 7.26.3.2 The ctime function</b></a>
15189 1 #include <a href="#7.26"><time.h></a>
15190 char *ctime(const time_t *timer);
15191 <b> Description</b>
15192 2 The ctime function converts the calendar time pointed to by timer to local time in the
15193 form of a string. It is equivalent to
15194 asctime(localtime(timer))
15198 <sup><a name="note310" href="#note310"><b>310)</b></a></sup> See <a href="#7.26.1">7.26.1</a>.
15200 [<a name="p389" href="#p389">page 389</a>] (<a href="#Contents">Contents</a>)
15203 3 The ctime function returns the pointer returned by the asctime function with that
15204 broken-down time as argument.
15205 Forward references: the localtime function (<a href="#7.26.3.4">7.26.3.4</a>).
15206 <a name="7.26.3.3" href="#7.26.3.3"><b> 7.26.3.3 The gmtime function</b></a>
15208 1 #include <a href="#7.26"><time.h></a>
15209 struct tm *gmtime(const time_t *timer);
15210 <b> Description</b>
15211 2 The gmtime function converts the calendar time pointed to by timer into a broken-
15212 down time, expressed as UTC.
15214 3 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
15215 specified time cannot be converted to UTC.
15216 <a name="7.26.3.4" href="#7.26.3.4"><b> 7.26.3.4 The localtime function</b></a>
15218 1 #include <a href="#7.26"><time.h></a>
15219 struct tm *localtime(const time_t *timer);
15220 <b> Description</b>
15221 2 The localtime function converts the calendar time pointed to by timer into a
15222 broken-down time, expressed as local time.
15224 3 The localtime function returns a pointer to the broken-down time, or a null pointer if
15225 the specified time cannot be converted to local time.
15226 <a name="7.26.3.5" href="#7.26.3.5"><b> 7.26.3.5 The strftime function</b></a>
15228 1 #include <a href="#7.26"><time.h></a>
15229 size_t strftime(char * restrict s,
15231 const char * restrict format,
15232 const struct tm * restrict timeptr);
15234 [<a name="p390" href="#p390">page 390</a>] (<a href="#Contents">Contents</a>)
15236 <b> Description</b>
15237 2 The strftime function places characters into the array pointed to by s as controlled by
15238 the string pointed to by format. The format shall be a multibyte character sequence,
15239 beginning and ending in its initial shift state. The format string consists of zero or
15240 more conversion specifiers and ordinary multibyte characters. A conversion specifier
15241 consists of a % character, possibly followed by an E or O modifier character (described
15242 below), followed by a character that determines the behavior of the conversion specifier.
15243 All ordinary multibyte characters (including the terminating null character) are copied
15244 unchanged into the array. If copying takes place between objects that overlap, the
15245 behavior is undefined. No more than maxsize characters are placed into the array.
15246 3 Each conversion specifier is replaced by appropriate characters as described in the
15247 following list. The appropriate characters are determined using the LC_TIME category
15248 of the current locale and by the values of zero or more members of the broken-down time
15249 structure pointed to by timeptr, as specified in brackets in the description. If any of
15250 the specified values is outside the normal range, the characters stored are unspecified.
15251 %a is replaced by the locale's abbreviated weekday name. [tm_wday]
15252 %A is replaced by the locale's full weekday name. [tm_wday]
15253 %b is replaced by the locale's abbreviated month name. [tm_mon]
15254 %B is replaced by the locale's full month name. [tm_mon]
15255 %c is replaced by the locale's appropriate date and time representation. [all specified
15256 in <a href="#7.26.1">7.26.1</a>]
15257 %C is replaced by the year divided by 100 and truncated to an integer, as a decimal
15258 number (00-99). [tm_year]
15259 %d is replaced by the day of the month as a decimal number (01-31). [tm_mday]
15260 %D is equivalent to ''%m/%d/%y''. [tm_mon, tm_mday, tm_year]
15261 %e is replaced by the day of the month as a decimal number (1-31); a single digit is
15262 preceded by a space. [tm_mday]
15263 %F is equivalent to ''%Y-%m-%d'' (the ISO 8601 date format). [tm_year, tm_mon,
15265 %g is replaced by the last 2 digits of the week-based year (see below) as a decimal
15266 number (00-99). [tm_year, tm_wday, tm_yday]
15267 %G is replaced by the week-based year (see below) as a decimal number (e.g., 1997).
15268 [tm_year, tm_wday, tm_yday]
15269 %h is equivalent to ''%b''. [tm_mon]
15270 %H is replaced by the hour (24-hour clock) as a decimal number (00-23). [tm_hour]
15271 %I is replaced by the hour (12-hour clock) as a decimal number (01-12). [tm_hour]
15272 %j is replaced by the day of the year as a decimal number (001-366). [tm_yday]
15273 %m is replaced by the month as a decimal number (01-12). [tm_mon]
15274 %M is replaced by the minute as a decimal number (00-59). [tm_min]
15275 %n is replaced by a new-line character.
15277 [<a name="p391" href="#p391">page 391</a>] (<a href="#Contents">Contents</a>)
15279 %p is replaced by the locale's equivalent of the AM/PM designations associated with a
15280 12-hour clock. [tm_hour]
15281 %r is replaced by the locale's 12-hour clock time. [tm_hour, tm_min, tm_sec]
15282 %R is equivalent to ''%H:%M''. [tm_hour, tm_min]
15283 %S is replaced by the second as a decimal number (00-60). [tm_sec]
15284 %t is replaced by a horizontal-tab character.
15285 %T is equivalent to ''%H:%M:%S'' (the ISO 8601 time format). [tm_hour, tm_min,
15287 %u is replaced by the ISO 8601 weekday as a decimal number (1-7), where Monday
15289 %U is replaced by the week number of the year (the first Sunday as the first day of week
15290 <sup><a name="note1" href="#note1"><b>1)</b></a></sup> as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
15291 %V is replaced by the ISO 8601 week number (see below) as a decimal number
15292 (01-53). [tm_year, tm_wday, tm_yday]
15293 %w is replaced by the weekday as a decimal number (0-6), where Sunday is 0.
15295 %W is replaced by the week number of the year (the first Monday as the first day of
15296 week 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]
15297 %x is replaced by the locale's appropriate date representation. [all specified in <a href="#7.26.1">7.26.1</a>]
15298 %X is replaced by the locale's appropriate time representation. [all specified in <a href="#7.26.1">7.26.1</a>]
15299 %y is replaced by the last 2 digits of the year as a decimal number (00-99).
15301 %Y is replaced by the year as a decimal number (e.g., 1997). [tm_year]
15302 %z is replaced by the offset from UTC in the ISO 8601 format ''-0430'' (meaning 4
15303 hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
15304 zone is determinable. [tm_isdst]
15305 %Z is replaced by the locale's time zone name or abbreviation, or by no characters if no
15306 time zone is determinable. [tm_isdst]
15307 %% is replaced by %.
15308 4 Some conversion specifiers can be modified by the inclusion of an E or O modifier
15309 character to indicate an alternative format or specification. If the alternative format or
15310 specification does not exist for the current locale, the modifier is ignored.
15311 %Ec is replaced by the locale's alternative date and time representation.
15312 %EC is replaced by the name of the base year (period) in the locale's alternative
15314 %Ex is replaced by the locale's alternative date representation.
15315 %EX is replaced by the locale's alternative time representation.
15316 %Ey is replaced by the offset from %EC (year only) in the locale's alternative
15318 %EY is replaced by the locale's full alternative year representation.
15320 [<a name="p392" href="#p392">page 392</a>] (<a href="#Contents">Contents</a>)
15322 %Od is replaced by the day of the month, using the locale's alternative numeric symbols
15323 (filled as needed with leading zeros, or with leading spaces if there is no alternative
15325 %Oe is replaced by the day of the month, using the locale's alternative numeric symbols
15326 (filled as needed with leading spaces).
15327 %OH is replaced by the hour (24-hour clock), using the locale's alternative numeric
15329 %OI is replaced by the hour (12-hour clock), using the locale's alternative numeric
15331 %Om is replaced by the month, using the locale's alternative numeric symbols.
15332 %OM is replaced by the minutes, using the locale's alternative numeric symbols.
15333 %OS is replaced by the seconds, using the locale's alternative numeric symbols.
15334 %Ou is replaced by the ISO 8601 weekday as a number in the locale's alternative
15335 representation, where Monday is 1.
15336 %OU is replaced by the week number, using the locale's alternative numeric symbols.
15337 %OV is replaced by the ISO 8601 week number, using the locale's alternative numeric
15339 %Ow is replaced by the weekday as a number, using the locale's alternative numeric
15341 %OW is replaced by the week number of the year, using the locale's alternative numeric
15343 %Oy is replaced by the last 2 digits of the year, using the locale's alternative numeric
15345 5 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system,
15346 weeks begin on a Monday and week 1 of the year is the week that includes January 4th,
15347 which is also the week that includes the first Thursday of the year, and is also the first
15348 week that contains at least four days in the year. If the first Monday of January is the
15349 2nd, 3rd, or 4th, the preceding days are part of the last week of the preceding year; thus,
15350 for Saturday 2nd January 1999, %G is replaced by 1998 and %V is replaced by 53. If
15351 December 29th, 30th, or 31st is a Monday, it and any following days are part of week 1 of
15352 the following year. Thus, for Tuesday 30th December 1997, %G is replaced by 1998 and
15353 %V is replaced by 01.
15354 6 If a conversion specifier is not one of the above, the behavior is undefined.
15355 7 In the "C" locale, the E and O modifiers are ignored and the replacement strings for the
15356 following specifiers are:
15357 %a the first three characters of %A.
15358 %A one of ''Sunday'', ''Monday'', ... , ''Saturday''.
15359 %b the first three characters of %B.
15360 %B one of ''January'', ''February'', ... , ''December''.
15361 %c equivalent to ''%a %b %e %T %Y''.
15363 [<a name="p393" href="#p393">page 393</a>] (<a href="#Contents">Contents</a>)
15365 %p one of ''AM'' or ''PM''.
15366 %r equivalent to ''%I:%M:%S %p''.
15367 %x equivalent to ''%m/%d/%y''.
15368 %X equivalent to %T.
15369 %Z implementation-defined.
15371 8 If the total number of resulting characters including the terminating null character is not
15372 more than maxsize, the strftime function returns the number of characters placed
15373 into the array pointed to by s not including the terminating null character. Otherwise,
15374 zero is returned and the contents of the array are indeterminate.
15376 [<a name="p394" href="#p394">page 394</a>] (<a href="#Contents">Contents</a>)
15378 <a name="7.27" href="#7.27"><b> 7.27 Unicode utilities <uchar.h></b></a>
15379 1 The header <a href="#7.27"><uchar.h></a> declares types and functions for manipulating Unicode
15381 2 The types declared are mbstate_t (described in <a href="#7.29.1">7.29.1</a>) and size_t (described in
15382 <a name="7.19);" href="#7.19);"><b> 7.19);</b></a>
15384 which is an unsigned integer type used for 16-bit characters and is the same type as
15385 uint_least16_t (described in <a href="#7.20.1.2">7.20.1.2</a>); and
15387 which is an unsigned integer type used for 32-bit characters and is the same type as
15388 uint_least32_t (also described in <a href="#7.20.1.2">7.20.1.2</a>).
15389 <a name="7.27.1" href="#7.27.1"><b> 7.27.1 Restartable multibyte/wide character conversion functions</b></a>
15390 1 These functions have a parameter, ps, of type pointer to mbstate_t that points to an
15391 object that can completely describe the current conversion state of the associated
15392 multibyte character sequence, which the functions alter as necessary. If ps is a null
15393 pointer, each function uses its own internal mbstate_t object instead, which is
15394 initialized at program startup to the initial conversion state; the functions are not required
15395 to avoid data races in this case. The implementation behaves as if no library function
15396 calls these functions with a null pointer for ps.
15397 <a name="7.27.1.1" href="#7.27.1.1"><b> 7.27.1.1 The mbrtoc16 function</b></a>
15399 1 #include <a href="#7.27"><uchar.h></a>
15400 size_t mbrtoc16(char16_t * restrict pc16,
15401 const char * restrict s, size_t n,
15402 mbstate_t * restrict ps);
15403 <b> Description</b>
15404 2 If s is a null pointer, the mbrtoc16 function is equivalent to the call:
15405 mbrtoc16(NULL, "", 1, ps)
15406 In this case, the values of the parameters pc16 and n are ignored.
15407 3 If s is not a null pointer, the mbrtoc16 function inspects at most n bytes beginning with
15408 the byte pointed to by s to determine the number of bytes needed to complete the next
15409 multibyte character (including any shift sequences). If the function determines that the
15410 next multibyte character is complete and valid, it determines the values of the
15411 corresponding wide characters and then, if pc16 is not a null pointer, stores the value of
15412 the first (or only) such character in the object pointed to by pc16. Subsequent calls will
15414 [<a name="p395" href="#p395">page 395</a>] (<a href="#Contents">Contents</a>)
15416 store successive wide characters without consuming any additional input until all the
15417 characters have been stored. If the corresponding wide character is the null wide
15418 character, the resulting state described is the initial conversion state.
15420 4 The mbrtoc16 function returns the first of the following that applies (given the current
15422 0 if the next n or fewer bytes complete the multibyte character that
15423 corresponds to the null wide character (which is the value stored).
15424 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
15425 character (which is the value stored); the value returned is the number
15426 of bytes that complete the multibyte character.
15427 (size_t)(-3) if the next character resulting from a previous call has been stored (no
15428 bytes from the input have been consumed by this call).
15429 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
15430 multibyte character, and all n bytes have been processed (no value is
15431 stored).<sup><a href="#note311"><b>311)</b></a></sup>
15432 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
15433 do not contribute to a complete and valid multibyte character (no
15434 value is stored); the value of the macro EILSEQ is stored in errno,
15435 and the conversion state is unspecified.
15436 <a name="7.27.1.2" href="#7.27.1.2"><b> 7.27.1.2 The c16rtomb function</b></a>
15438 1 #include <a href="#7.27"><uchar.h></a>
15439 size_t c16rtomb(char * restrict s, char16_t c16,
15440 mbstate_t * restrict ps);
15441 <b> Description</b>
15442 2 If s is a null pointer, the c16rtomb function is equivalent to the call
15443 c16rtomb(buf, L'\0', ps)
15444 where buf is an internal buffer.
15445 3 If s is not a null pointer, the c16rtomb function determines the number of bytes needed
15446 to represent the multibyte character that corresponds to the wide character given by c16
15447 (including any shift sequences), and stores the multibyte character representation in the
15450 <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
15451 sequence of redundant shift sequences (for implementations with state-dependent encodings).
15453 [<a name="p396" href="#p396">page 396</a>] (<a href="#Contents">Contents</a>)
15455 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
15456 c16 is a null wide character, a null byte is stored, preceded by any shift sequence needed
15457 to restore the initial shift state; the resulting state described is the initial conversion state.
15459 4 The c16rtomb function returns the number of bytes stored in the array object (including
15460 any shift sequences). When c16 is not a valid wide character, an encoding error occurs:
15461 the function stores the value of the macro EILSEQ in errno and returns
15462 (size_t)(-1); the conversion state is unspecified.
15463 <a name="7.27.1.3" href="#7.27.1.3"><b> 7.27.1.3 The mbrtoc32 function</b></a>
15465 1 #include <a href="#7.27"><uchar.h></a>
15466 size_t mbrtoc32(char32_t * restrict pc32,
15467 const char * restrict s, size_t n,
15468 mbstate_t * restrict ps);
15469 <b> Description</b>
15470 2 If s is a null pointer, the mbrtoc32 function is equivalent to the call:
15471 mbrtoc32(NULL, "", 1, ps)
15472 In this case, the values of the parameters pc32 and n are ignored.
15473 3 If s is not a null pointer, the mbrtoc32 function inspects at most n bytes beginning with
15474 the byte pointed to by s to determine the number of bytes needed to complete the next
15475 multibyte character (including any shift sequences). If the function determines that the
15476 next multibyte character is complete and valid, it determines the values of the
15477 corresponding wide characters and then, if pc32 is not a null pointer, stores the value of
15478 the first (or only) such character in the object pointed to by pc32. Subsequent calls will
15479 store successive wide characters without consuming any additional input until all the
15480 characters have been stored. If the corresponding wide character is the null wide
15481 character, the resulting state described is the initial conversion state.
15483 4 The mbrtoc32 function returns the first of the following that applies (given the current
15485 0 if the next n or fewer bytes complete the multibyte character that
15486 corresponds to the null wide character (which is the value stored).
15487 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
15488 character (which is the value stored); the value returned is the number
15489 of bytes that complete the multibyte character.
15491 [<a name="p397" href="#p397">page 397</a>] (<a href="#Contents">Contents</a>)
15493 (size_t)(-3) if the next character resulting from a previous call has been stored (no
15494 bytes from the input have been consumed by this call).
15495 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
15496 multibyte character, and all n bytes have been processed (no value is
15497 stored).<sup><a href="#note312"><b>312)</b></a></sup>
15498 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
15499 do not contribute to a complete and valid multibyte character (no
15500 value is stored); the value of the macro EILSEQ is stored in errno,
15501 and the conversion state is unspecified.
15502 <a name="7.27.1.4" href="#7.27.1.4"><b> 7.27.1.4 The c32rtomb function</b></a>
15504 1 #include <a href="#7.27"><uchar.h></a>
15505 size_t c32rtomb(char * restrict s, char32_t c32,
15506 mbstate_t * restrict ps);
15507 <b> Description</b>
15508 2 If s is a null pointer, the c32rtomb function is equivalent to the call
15509 c32rtomb(buf, L'\0', ps)
15510 where buf is an internal buffer.
15511 3 If s is not a null pointer, the c32rtomb function determines the number of bytes needed
15512 to represent the multibyte character that corresponds to the wide character given by c32
15513 (including any shift sequences), and stores the multibyte character representation in the
15514 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
15515 c32 is a null wide character, a null byte is stored, preceded by any shift sequence needed
15516 to restore the initial shift state; the resulting state described is the initial conversion state.
15518 4 The c32rtomb function returns the number of bytes stored in the array object (including
15519 any shift sequences). When c32 is not a valid wide character, an encoding error occurs:
15520 the function stores the value of the macro EILSEQ in errno and returns
15521 (size_t)(-1); the conversion state is unspecified.
15526 <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
15527 sequence of redundant shift sequences (for implementations with state-dependent encodings).
15529 [<a name="p398" href="#p398">page 398</a>] (<a href="#Contents">Contents</a>)
15531 <a name="7.28" href="#7.28"><b> 7.28 Extended multibyte and wide character utilities <wchar.h></b></a>
15532 <a name="7.28.1" href="#7.28.1"><b> 7.28.1 Introduction</b></a>
15533 1 The header <a href="#7.28"><wchar.h></a> defines four macros, and declares four data types, one tag, and
15534 many functions.<sup><a href="#note313"><b>313)</b></a></sup>
15535 2 The types declared are wchar_t and size_t (both described in <a href="#7.19">7.19</a>);
15537 which is a complete object type other than an array type that can hold the conversion state
15538 information necessary to convert between sequences of multibyte characters and wide
15541 which is an integer type unchanged by default argument promotions that can hold any
15542 value corresponding to members of the extended character set, as well as at least one
15543 value that does not correspond to any member of the extended character set (see WEOF
15544 below);<sup><a href="#note314"><b>314)</b></a></sup> and
15546 which is declared as an incomplete structure type (the contents are described in <a href="#7.26.1">7.26.1</a>).
15547 3 The macros defined are NULL (described in <a href="#7.19">7.19</a>); WCHAR_MIN and WCHAR_MAX
15548 (described in <a href="#7.20.3">7.20.3</a>); and
15550 which expands to a constant expression of type wint_t whose value does not
15551 correspond to any member of the extended character set.<sup><a href="#note315"><b>315)</b></a></sup> It is accepted (and returned)
15552 by several functions in this subclause to indicate end-of-file, that is, no more input from a
15553 stream. It is also used as a wide character value that does not correspond to any member
15554 of the extended character set.
15555 4 The functions declared are grouped as follows:
15556 -- Functions that perform input and output of wide characters, or multibyte characters,
15558 -- Functions that provide wide string numeric conversion;
15559 -- Functions that perform general wide string manipulation;
15562 <sup><a name="note313" href="#note313"><b>313)</b></a></sup> See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
15563 <sup><a name="note314" href="#note314"><b>314)</b></a></sup> wchar_t and wint_t can be the same integer type.
15564 <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.
15566 [<a name="p399" href="#p399">page 399</a>] (<a href="#Contents">Contents</a>)
15568 -- Functions for wide string date and time conversion; and
15569 -- Functions that provide extended capabilities for conversion between multibyte and
15570 wide character sequences.
15571 5 Unless explicitly stated otherwise, if the execution of a function described in this
15572 subclause causes copying to take place between objects that overlap, the behavior is
15574 <a name="7.28.2" href="#7.28.2"><b> 7.28.2 Formatted wide character input/output functions</b></a>
15575 1 The formatted wide character input/output functions shall behave as if there is a sequence
15576 point after the actions associated with each specifier.<sup><a href="#note316"><b>316)</b></a></sup>
15577 <a name="7.28.2.1" href="#7.28.2.1"><b> 7.28.2.1 The fwprintf function</b></a>
15579 1 #include <a href="#7.21"><stdio.h></a>
15580 #include <a href="#7.28"><wchar.h></a>
15581 int fwprintf(FILE * restrict stream,
15582 const wchar_t * restrict format, ...);
15583 <b> Description</b>
15584 2 The fwprintf function writes output to the stream pointed to by stream, under
15585 control of the wide string pointed to by format that specifies how subsequent arguments
15586 are converted for output. If there are insufficient arguments for the format, the behavior
15587 is undefined. If the format is exhausted while arguments remain, the excess arguments
15588 are evaluated (as always) but are otherwise ignored. The fwprintf function returns
15589 when the end of the format string is encountered.
15590 3 The format is composed of zero or more directives: ordinary wide characters (not %),
15591 which are copied unchanged to the output stream; and conversion specifications, each of
15592 which results in fetching zero or more subsequent arguments, converting them, if
15593 applicable, according to the corresponding conversion specifier, and then writing the
15594 result to the output stream.
15595 4 Each conversion specification is introduced by the wide character %. After the %, the
15596 following appear in sequence:
15597 -- Zero or more flags (in any order) that modify the meaning of the conversion
15599 -- An optional minimum field width. If the converted value has fewer wide characters
15600 than the field width, it is padded with spaces (by default) on the left (or right, if the
15603 <sup><a name="note316" href="#note316"><b>316)</b></a></sup> The fwprintf functions perform writes to memory for the %n specifier.
15605 [<a name="p400" href="#p400">page 400</a>] (<a href="#Contents">Contents</a>)
15607 left adjustment flag, described later, has been given) to the field width. The field
15608 width takes the form of an asterisk * (described later) or a nonnegative decimal
15609 integer.<sup><a href="#note317"><b>317)</b></a></sup>
15610 -- An optional precision that gives the minimum number of digits to appear for the d, i,
15611 o, u, x, and X conversions, the number of digits to appear after the decimal-point
15612 wide character for a, A, e, E, f, and F conversions, the maximum number of
15613 significant digits for the g and G conversions, or the maximum number of wide
15614 characters to be written for s conversions. The precision takes the form of a period
15615 (.) followed either by an asterisk * (described later) or by an optional decimal
15616 integer; if only the period is specified, the precision is taken as zero. If a precision
15617 appears with any other conversion specifier, the behavior is undefined.
15618 -- An optional length modifier that specifies the size of the argument.
15619 -- A conversion specifier wide character that specifies the type of conversion to be
15621 5 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
15622 this case, an int argument supplies the field width or precision. The arguments
15623 specifying field width, or precision, or both, shall appear (in that order) before the
15624 argument (if any) to be converted. A negative field width argument is taken as a - flag
15625 followed by a positive field width. A negative precision argument is taken as if the
15626 precision were omitted.
15627 6 The flag wide characters and their meanings are:
15628 - The result of the conversion is left-justified within the field. (It is right-justified if
15629 this flag is not specified.)
15630 + The result of a signed conversion always begins with a plus or minus sign. (It
15631 begins with a sign only when a negative value is converted if this flag is not
15632 specified.)<sup><a href="#note318"><b>318)</b></a></sup>
15633 space If the first wide character of a signed conversion is not a sign, or if a signed
15634 conversion results in no wide characters, a space is prefixed to the result. If the
15635 space and + flags both appear, the space flag is ignored.
15636 # The result is converted to an ''alternative form''. For o conversion, it increases
15637 the precision, if and only if necessary, to force the first digit of the result to be a
15638 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
15639 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
15642 <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.
15643 <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,
15644 include a minus sign.
15646 [<a name="p401" href="#p401">page 401</a>] (<a href="#Contents">Contents</a>)
15648 and G conversions, the result of converting a floating-point number always
15649 contains a decimal-point wide character, even if no digits follow it. (Normally, a
15650 decimal-point wide character appears in the result of these conversions only if a
15651 digit follows it.) For g and G conversions, trailing zeros are not removed from the
15652 result. For other conversions, the behavior is undefined.
15653 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
15654 (following any indication of sign or base) are used to pad to the field width rather
15655 than performing space padding, except when converting an infinity or NaN. If the
15656 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
15657 conversions, if a precision is specified, the 0 flag is ignored. For other
15658 conversions, the behavior is undefined.
15659 7 The length modifiers and their meanings are:
15660 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15661 signed char or unsigned char argument (the argument will have
15662 been promoted according to the integer promotions, but its value shall be
15663 converted to signed char or unsigned char before printing); or that
15664 a following n conversion specifier applies to a pointer to a signed char
15666 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15667 short int or unsigned short int argument (the argument will
15668 have been promoted according to the integer promotions, but its value shall
15669 be converted to short int or unsigned short int before printing);
15670 or that a following n conversion specifier applies to a pointer to a short
15672 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15673 long int or unsigned long int argument; that a following n
15674 conversion specifier applies to a pointer to a long int argument; that a
15675 following c conversion specifier applies to a wint_t argument; that a
15676 following s conversion specifier applies to a pointer to a wchar_t
15677 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
15679 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15680 long long int or unsigned long long int argument; or that a
15681 following n conversion specifier applies to a pointer to a long long int
15683 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
15684 an intmax_t or uintmax_t argument; or that a following n conversion
15685 specifier applies to a pointer to an intmax_t argument.
15687 [<a name="p402" href="#p402">page 402</a>] (<a href="#Contents">Contents</a>)
15689 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15690 size_t or the corresponding signed integer type argument; or that a
15691 following n conversion specifier applies to a pointer to a signed integer type
15692 corresponding to size_t argument.
15693 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
15694 ptrdiff_t or the corresponding unsigned integer type argument; or that a
15695 following n conversion specifier applies to a pointer to a ptrdiff_t
15697 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
15698 applies to a long double argument.
15699 If a length modifier appears with any conversion specifier other than as specified above,
15700 the behavior is undefined.
15701 8 The conversion specifiers and their meanings are:
15702 d,i The int argument is converted to signed decimal in the style [-]dddd. The
15703 precision specifies the minimum number of digits to appear; if the value
15704 being converted can be represented in fewer digits, it is expanded with
15705 leading zeros. The default precision is 1. The result of converting a zero
15706 value with a precision of zero is no wide characters.
15707 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
15708 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
15709 letters abcdef are used for x conversion and the letters ABCDEF for X
15710 conversion. The precision specifies the minimum number of digits to appear;
15711 if the value being converted can be represented in fewer digits, it is expanded
15712 with leading zeros. The default precision is 1. The result of converting a
15713 zero value with a precision of zero is no wide characters.
15714 f,F A double argument representing a floating-point number is converted to
15715 decimal notation in the style [-]ddd.ddd, where the number of digits after
15716 the decimal-point wide character is equal to the precision specification. If the
15717 precision is missing, it is taken as 6; if the precision is zero and the # flag is
15718 not specified, no decimal-point wide character appears. If a decimal-point
15719 wide character appears, at least one digit appears before it. The value is
15720 rounded to the appropriate number of digits.
15721 A double argument representing an infinity is converted in one of the styles
15722 [-]inf or [-]infinity -- which style is implementation-defined. A
15723 double argument representing a NaN is converted in one of the styles
15724 [-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
15725 any n-wchar-sequence, is implementation-defined. The F conversion
15726 specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
15728 [<a name="p403" href="#p403">page 403</a>] (<a href="#Contents">Contents</a>)
15730 nan, respectively.<sup><a href="#note319"><b>319)</b></a></sup>
15731 e,E A double argument representing a floating-point number is converted in the
15732 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
15733 argument is nonzero) before the decimal-point wide character and the number
15734 of digits after it is equal to the precision; if the precision is missing, it is taken
15735 as 6; if the precision is zero and the # flag is not specified, no decimal-point
15736 wide character appears. The value is rounded to the appropriate number of
15737 digits. The E conversion specifier produces a number with E instead of e
15738 introducing the exponent. The exponent always contains at least two digits,
15739 and only as many more digits as necessary to represent the exponent. If the
15740 value is zero, the exponent is zero.
15741 A double argument representing an infinity or NaN is converted in the style
15742 of an f or F conversion specifier.
15743 g,G A double argument representing a floating-point number is converted in
15744 style f or e (or in style F or E in the case of a G conversion specifier),
15745 depending on the value converted and the precision. Let P equal the
15746 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
15747 Then, if a conversion with style E would have an exponent of X:
15748 -- if P > X >= -4, the conversion is with style f (or F) and precision
15750 -- otherwise, the conversion is with style e (or E) and precision P - 1.
15751 Finally, unless the # flag is used, any trailing zeros are removed from the
15752 fractional portion of the result and the decimal-point wide character is
15753 removed if there is no fractional portion remaining.
15754 A double argument representing an infinity or NaN is converted in the style
15755 of an f or F conversion specifier.
15756 a,A A double argument representing a floating-point number is converted in the
15757 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
15758 nonzero if the argument is a normalized floating-point number and is
15759 otherwise unspecified) before the decimal-point wide character<sup><a href="#note320"><b>320)</b></a></sup> and the
15760 number of hexadecimal digits after it is equal to the precision; if the precision
15761 is missing and FLT_RADIX is a power of 2, then the precision is sufficient
15764 <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
15765 meaning; the # and 0 flag wide characters have no effect.
15766 <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
15767 character so that subsequent digits align to nibble (4-bit) boundaries.
15769 [<a name="p404" href="#p404">page 404</a>] (<a href="#Contents">Contents</a>)
15771 for an exact representation of the value; if the precision is missing and
15772 FLT_RADIX is not a power of 2, then the precision is sufficient to
15773 distinguish<sup><a href="#note321"><b>321)</b></a></sup> values of type double, except that trailing zeros may be
15774 omitted; if the precision is zero and the # flag is not specified, no decimal-
15775 point wide character appears. The letters abcdef are used for a conversion
15776 and the letters ABCDEF for A conversion. The A conversion specifier
15777 produces a number with X and P instead of x and p. The exponent always
15778 contains at least one digit, and only as many more digits as necessary to
15779 represent the decimal exponent of 2. If the value is zero, the exponent is
15781 A double argument representing an infinity or NaN is converted in the style
15782 of an f or F conversion specifier.
15783 c If no l length modifier is present, the int argument is converted to a wide
15784 character as if by calling btowc and the resulting wide character is written.
15785 If an l length modifier is present, the wint_t argument is converted to
15786 wchar_t and written.
15787 s If no l length modifier is present, the argument shall be a pointer to the initial
15788 element of a character array containing a multibyte character sequence
15789 beginning in the initial shift state. Characters from the array are converted as
15790 if by repeated calls to the mbrtowc function, with the conversion state
15791 described by an mbstate_t object initialized to zero before the first
15792 multibyte character is converted, and written up to (but not including) the
15793 terminating null wide character. If the precision is specified, no more than
15794 that many wide characters are written. If the precision is not specified or is
15795 greater than the size of the converted array, the converted array shall contain a
15796 null wide character.
15797 If an l length modifier is present, the argument shall be a pointer to the initial
15798 element of an array of wchar_t type. Wide characters from the array are
15799 written up to (but not including) a terminating null wide character. If the
15800 precision is specified, no more than that many wide characters are written. If
15801 the precision is not specified or is greater than the size of the array, the array
15802 shall contain a null wide character.
15803 p The argument shall be a pointer to void. The value of the pointer is
15804 converted to a sequence of printing wide characters, in an implementation-
15806 <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
15807 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
15808 might suffice depending on the implementation's scheme for determining the digit to the left of the
15809 decimal-point wide character.
15811 [<a name="p405" href="#p405">page 405</a>] (<a href="#Contents">Contents</a>)
15814 n The argument shall be a pointer to signed integer into which is written the
15815 number of wide characters written to the output stream so far by this call to
15816 fwprintf. No argument is converted, but one is consumed. If the
15817 conversion specification includes any flags, a field width, or a precision, the
15818 behavior is undefined.
15819 % A % wide character is written. No argument is converted. The complete
15820 conversion specification shall be %%.
15821 9 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note322"><b>322)</b></a></sup> If any argument is
15822 not the correct type for the corresponding conversion specification, the behavior is
15824 10 In no case does a nonexistent or small field width cause truncation of a field; if the result
15825 of a conversion is wider than the field width, the field is expanded to contain the
15827 11 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
15828 to a hexadecimal floating number with the given precision.
15829 Recommended practice
15830 12 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
15831 representable in the given precision, the result should be one of the two adjacent numbers
15832 in hexadecimal floating style with the given precision, with the extra stipulation that the
15833 error should have a correct sign for the current rounding direction.
15834 13 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
15835 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note323"><b>323)</b></a></sup> If the number of
15836 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
15837 representable with DECIMAL_DIG digits, then the result should be an exact
15838 representation with trailing zeros. Otherwise, the source value is bounded by two
15839 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
15840 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
15841 the error should have a correct sign for the current rounding direction.
15843 14 The fwprintf function returns the number of wide characters transmitted, or a negative
15844 value if an output or encoding error occurred.
15846 <sup><a name="note322" href="#note322"><b>322)</b></a></sup> See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
15847 <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
15848 given format specifier. The number of significant digits is determined by the format specifier, and in
15849 the case of fixed-point conversion by the source value as well.
15851 [<a name="p406" href="#p406">page 406</a>] (<a href="#Contents">Contents</a>)
15853 Environmental limits
15854 15 The number of wide characters that can be produced by any single conversion shall be at
15856 16 EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
15858 #include <a href="#7.12"><math.h></a>
15859 #include <a href="#7.21"><stdio.h></a>
15860 #include <a href="#7.28"><wchar.h></a>
15862 wchar_t *weekday, *month; // pointers to wide strings
15863 int day, hour, min;
15864 fwprintf(stdout, L"%ls, %ls %d, %.2d:%.2d\n",
15865 weekday, month, day, hour, min);
15866 fwprintf(stdout, L"pi = %.5f\n", 4 * atan(1.0));
15868 Forward references: the btowc function (<a href="#7.28.6.1.1">7.28.6.1.1</a>), the mbrtowc function
15869 (<a href="#7.28.6.3.2">7.28.6.3.2</a>).
15870 <a name="7.28.2.2" href="#7.28.2.2"><b> 7.28.2.2 The fwscanf function</b></a>
15872 1 #include <a href="#7.21"><stdio.h></a>
15873 #include <a href="#7.28"><wchar.h></a>
15874 int fwscanf(FILE * restrict stream,
15875 const wchar_t * restrict format, ...);
15876 <b> Description</b>
15877 2 The fwscanf function reads input from the stream pointed to by stream, under
15878 control of the wide string pointed to by format that specifies the admissible input
15879 sequences and how they are to be converted for assignment, using subsequent arguments
15880 as pointers to the objects to receive the converted input. If there are insufficient
15881 arguments for the format, the behavior is undefined. If the format is exhausted while
15882 arguments remain, the excess arguments are evaluated (as always) but are otherwise
15884 3 The format is composed of zero or more directives: one or more white-space wide
15885 characters, an ordinary wide character (neither % nor a white-space wide character), or a
15886 conversion specification. Each conversion specification is introduced by the wide
15887 character %. After the %, the following appear in sequence:
15888 -- An optional assignment-suppressing wide character *.
15889 -- An optional decimal integer greater than zero that specifies the maximum field width
15890 (in wide characters).
15892 [<a name="p407" href="#p407">page 407</a>] (<a href="#Contents">Contents</a>)
15894 -- An optional length modifier that specifies the size of the receiving object.
15895 -- A conversion specifier wide character that specifies the type of conversion to be
15897 4 The fwscanf function executes each directive of the format in turn. When all directives
15898 have been executed, or if a directive fails (as detailed below), the function returns.
15899 Failures are described as input failures (due to the occurrence of an encoding error or the
15900 unavailability of input characters), or matching failures (due to inappropriate input).
15901 5 A directive composed of white-space wide character(s) is executed by reading input up to
15902 the first non-white-space wide character (which remains unread), or until no more wide
15903 characters can be read.
15904 6 A directive that is an ordinary wide character is executed by reading the next wide
15905 character of the stream. If that wide character differs from the directive, the directive
15906 fails and the differing and subsequent wide characters remain unread. Similarly, if end-
15907 of-file, an encoding error, or a read error prevents a wide character from being read, the
15909 7 A directive that is a conversion specification defines a set of matching input sequences, as
15910 described below for each specifier. A conversion specification is executed in the
15912 8 Input white-space wide characters (as specified by the iswspace function) are skipped,
15913 unless the specification includes a [, c, or n specifier.<sup><a href="#note324"><b>324)</b></a></sup>
15914 9 An input item is read from the stream, unless the specification includes an n specifier. An
15915 input item is defined as the longest sequence of input wide characters which does not
15916 exceed any specified field width and which is, or is a prefix of, a matching input
15917 sequence.<sup><a href="#note325"><b>325)</b></a></sup> The first wide character, if any, after the input item remains unread. If the
15918 length of the input item is zero, the execution of the directive fails; this condition is a
15919 matching failure unless end-of-file, an encoding error, or a read error prevented input
15920 from the stream, in which case it is an input failure.
15921 10 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
15922 count of input wide characters) is converted to a type appropriate to the conversion
15923 specifier. If the input item is not a matching sequence, the execution of the directive fails:
15924 this condition is a matching failure. Unless assignment suppression was indicated by a *,
15925 the result of the conversion is placed in the object pointed to by the first argument
15926 following the format argument that has not already received a conversion result. If this
15929 <sup><a name="note324" href="#note324"><b>324)</b></a></sup> These white-space wide characters are not counted against a specified field width.
15930 <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
15931 sequences that are acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
15933 [<a name="p408" href="#p408">page 408</a>] (<a href="#Contents">Contents</a>)
15935 object does not have an appropriate type, or if the result of the conversion cannot be
15936 represented in the object, the behavior is undefined.
15937 11 The length modifiers and their meanings are:
15938 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
15939 to an argument with type pointer to signed char or unsigned char.
15940 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
15941 to an argument with type pointer to short int or unsigned short
15943 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
15944 to an argument with type pointer to long int or unsigned long
15945 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
15946 an argument with type pointer to double; or that a following c, s, or [
15947 conversion specifier applies to an argument with type pointer to wchar_t.
15948 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
15949 to an argument with type pointer to long long int or unsigned
15951 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
15952 to an argument with type pointer to intmax_t or uintmax_t.
15953 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
15954 to an argument with type pointer to size_t or the corresponding signed
15956 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
15957 to an argument with type pointer to ptrdiff_t or the corresponding
15958 unsigned integer type.
15959 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
15960 applies to an argument with type pointer to long double.
15961 If a length modifier appears with any conversion specifier other than as specified above,
15962 the behavior is undefined.
15963 12 The conversion specifiers and their meanings are:
15964 d Matches an optionally signed decimal integer, whose format is the same as
15965 expected for the subject sequence of the wcstol function with the value 10
15966 for the base argument. The corresponding argument shall be a pointer to
15968 i Matches an optionally signed integer, whose format is the same as expected
15969 for the subject sequence of the wcstol function with the value 0 for the
15970 base argument. The corresponding argument shall be a pointer to signed
15972 [<a name="p409" href="#p409">page 409</a>] (<a href="#Contents">Contents</a>)
15975 o Matches an optionally signed octal integer, whose format is the same as
15976 expected for the subject sequence of the wcstoul function with the value 8
15977 for the base argument. The corresponding argument shall be a pointer to
15979 u Matches an optionally signed decimal integer, whose format is the same as
15980 expected for the subject sequence of the wcstoul function with the value 10
15981 for the base argument. The corresponding argument shall be a pointer to
15983 x Matches an optionally signed hexadecimal integer, whose format is the same
15984 as expected for the subject sequence of the wcstoul function with the value
15985 16 for the base argument. The corresponding argument shall be a pointer to
15987 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
15988 format is the same as expected for the subject sequence of the wcstod
15989 function. The corresponding argument shall be a pointer to floating.
15990 c Matches a sequence of wide characters of exactly the number specified by the
15991 field width (1 if no field width is present in the directive).
15992 If no l length modifier is present, characters from the input field are
15993 converted as if by repeated calls to the wcrtomb function, with the
15994 conversion state described by an mbstate_t object initialized to zero
15995 before the first wide character is converted. The corresponding argument
15996 shall be a pointer to the initial element of a character array large enough to
15997 accept the sequence. No null character is added.
15998 If an l length modifier is present, the corresponding argument shall be a
15999 pointer to the initial element of an array of wchar_t large enough to accept
16000 the sequence. No null wide character is added.
16001 s Matches a sequence of non-white-space wide characters.
16002 If no l length modifier is present, characters from the input field are
16003 converted as if by repeated calls to the wcrtomb function, with the
16004 conversion state described by an mbstate_t object initialized to zero
16005 before the first wide character is converted. The corresponding argument
16006 shall be a pointer to the initial element of a character array large enough to
16007 accept the sequence and a terminating null character, which will be added
16009 If an l length modifier is present, the corresponding argument shall be a
16010 pointer to the initial element of an array of wchar_t large enough to accept
16012 [<a name="p410" href="#p410">page 410</a>] (<a href="#Contents">Contents</a>)
16014 the sequence and the terminating null wide character, which will be added
16016 [ Matches a nonempty sequence of wide characters from a set of expected
16017 characters (the scanset).
16018 If no l length modifier is present, characters from the input field are
16019 converted as if by repeated calls to the wcrtomb function, with the
16020 conversion state described by an mbstate_t object initialized to zero
16021 before the first wide character is converted. The corresponding argument
16022 shall be a pointer to the initial element of a character array large enough to
16023 accept the sequence and a terminating null character, which will be added
16025 If an l length modifier is present, the corresponding argument shall be a
16026 pointer to the initial element of an array of wchar_t large enough to accept
16027 the sequence and the terminating null wide character, which will be added
16029 The conversion specifier includes all subsequent wide characters in the
16030 format string, up to and including the matching right bracket (]). The wide
16031 characters between the brackets (the scanlist) compose the scanset, unless the
16032 wide character after the left bracket is a circumflex (^), in which case the
16033 scanset contains all wide characters that do not appear in the scanlist between
16034 the circumflex and the right bracket. If the conversion specifier begins with
16035 [] or [^], the right bracket wide character is in the scanlist and the next
16036 following right bracket wide character is the matching right bracket that ends
16037 the specification; otherwise the first following right bracket wide character is
16038 the one that ends the specification. If a - wide character is in the scanlist and
16039 is not the first, nor the second where the first wide character is a ^, nor the
16040 last character, the behavior is implementation-defined.
16041 p Matches an implementation-defined set of sequences, which should be the
16042 same as the set of sequences that may be produced by the %p conversion of
16043 the fwprintf function. The corresponding argument shall be a pointer to a
16044 pointer to void. The input item is converted to a pointer value in an
16045 implementation-defined manner. If the input item is a value converted earlier
16046 during the same program execution, the pointer that results shall compare
16047 equal to that value; otherwise the behavior of the %p conversion is undefined.
16048 n No input is consumed. The corresponding argument shall be a pointer to
16049 signed integer into which is to be written the number of wide characters read
16050 from the input stream so far by this call to the fwscanf function. Execution
16051 of a %n directive does not increment the assignment count returned at the
16052 completion of execution of the fwscanf function. No argument is
16054 [<a name="p411" href="#p411">page 411</a>] (<a href="#Contents">Contents</a>)
16056 converted, but one is consumed. If the conversion specification includes an
16057 assignment-suppressing wide character or a field width, the behavior is
16059 % Matches a single % wide character; no conversion or assignment occurs. The
16060 complete conversion specification shall be %%.
16061 13 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note326"><b>326)</b></a></sup>
16062 14 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
16063 respectively, a, e, f, g, and x.
16064 15 Trailing white space (including new-line wide characters) is left unread unless matched
16065 by a directive. The success of literal matches and suppressed assignments is not directly
16066 determinable other than via the %n directive.
16068 16 The fwscanf function returns the value of the macro EOF if an input failure occurs
16069 before the first conversion (if any) has completed. Otherwise, the function returns the
16070 number of input items assigned, which can be fewer than provided for, or even zero, in
16071 the event of an early matching failure.
16072 17 EXAMPLE 1 The call:
16073 #include <a href="#7.21"><stdio.h></a>
16074 #include <a href="#7.28"><wchar.h></a>
16076 int n, i; float x; wchar_t name[50];
16077 n = fwscanf(stdin, L"%d%f%ls", &i, &x, name);
16078 with the input line:
16079 25 54.32E-1 thompson
16080 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
16083 18 EXAMPLE 2 The call:
16084 #include <a href="#7.21"><stdio.h></a>
16085 #include <a href="#7.28"><wchar.h></a>
16087 int i; float x; double y;
16088 fwscanf(stdin, L"%2d%f%*d %lf", &i, &x, &y);
16091 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
16092 56.0. The next wide character read from the input stream will be a.
16095 <sup><a name="note326" href="#note326"><b>326)</b></a></sup> See ''future library directions'' (<a href="#7.30.12">7.30.12</a>).
16097 [<a name="p412" href="#p412">page 412</a>] (<a href="#Contents">Contents</a>)
16099 Forward references: the wcstod, wcstof, and wcstold functions (<a href="#7.28.4.1.1">7.28.4.1.1</a>), the
16100 wcstol, wcstoll, wcstoul, and wcstoull functions (<a href="#7.28.4.1.2">7.28.4.1.2</a>), the wcrtomb
16101 function (<a href="#7.28.6.3.3">7.28.6.3.3</a>).
16102 <a name="7.28.2.3" href="#7.28.2.3"><b> 7.28.2.3 The swprintf function</b></a>
16104 1 #include <a href="#7.28"><wchar.h></a>
16105 int swprintf(wchar_t * restrict s,
16107 const wchar_t * restrict format, ...);
16108 <b> Description</b>
16109 2 The swprintf function is equivalent to fwprintf, except that the argument s
16110 specifies an array of wide characters into which the generated output is to be written,
16111 rather than written to a stream. No more than n wide characters are written, including a
16112 terminating null wide character, which is always added (unless n is zero).
16114 3 The swprintf function returns the number of wide characters written in the array, not
16115 counting the terminating null wide character, or a negative value if an encoding error
16116 occurred or if n or more wide characters were requested to be written.
16117 <a name="7.28.2.4" href="#7.28.2.4"><b> 7.28.2.4 The swscanf function</b></a>
16119 1 #include <a href="#7.28"><wchar.h></a>
16120 int swscanf(const wchar_t * restrict s,
16121 const wchar_t * restrict format, ...);
16122 <b> Description</b>
16123 2 The swscanf function is equivalent to fwscanf, except that the argument s specifies a
16124 wide string from which the input is to be obtained, rather than from a stream. Reaching
16125 the end of the wide string is equivalent to encountering end-of-file for the fwscanf
16128 3 The swscanf function returns the value of the macro EOF if an input failure occurs
16129 before the first conversion (if any) has completed. Otherwise, the swscanf function
16130 returns the number of input items assigned, which can be fewer than provided for, or even
16131 zero, in the event of an early matching failure.
16133 [<a name="p413" href="#p413">page 413</a>] (<a href="#Contents">Contents</a>)
16135 <a name="7.28.2.5" href="#7.28.2.5"><b> 7.28.2.5 The vfwprintf function</b></a>
16137 1 #include <a href="#7.16"><stdarg.h></a>
16138 #include <a href="#7.21"><stdio.h></a>
16139 #include <a href="#7.28"><wchar.h></a>
16140 int vfwprintf(FILE * restrict stream,
16141 const wchar_t * restrict format,
16143 <b> Description</b>
16144 2 The vfwprintf function is equivalent to fwprintf, with the variable argument list
16145 replaced by arg, which shall have been initialized by the va_start macro (and
16146 possibly subsequent va_arg calls). The vfwprintf function does not invoke the
16147 va_end macro.<sup><a href="#note327"><b>327)</b></a></sup>
16149 3 The vfwprintf function returns the number of wide characters transmitted, or a
16150 negative value if an output or encoding error occurred.
16151 4 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting
16153 #include <a href="#7.16"><stdarg.h></a>
16154 #include <a href="#7.21"><stdio.h></a>
16155 #include <a href="#7.28"><wchar.h></a>
16156 void error(char *function_name, wchar_t *format, ...)
16159 va_start(args, format);
16160 // print out name of function causing error
16161 fwprintf(stderr, L"ERROR in %s: ", function_name);
16162 // print out remainder of message
16163 vfwprintf(stderr, format, args);
16170 <sup><a name="note327" href="#note327"><b>327)</b></a></sup> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
16171 invoke the va_arg macro, the value of arg after the return is indeterminate.
16173 [<a name="p414" href="#p414">page 414</a>] (<a href="#Contents">Contents</a>)
16175 <a name="7.28.2.6" href="#7.28.2.6"><b> 7.28.2.6 The vfwscanf function</b></a>
16177 1 #include <a href="#7.16"><stdarg.h></a>
16178 #include <a href="#7.21"><stdio.h></a>
16179 #include <a href="#7.28"><wchar.h></a>
16180 int vfwscanf(FILE * restrict stream,
16181 const wchar_t * restrict format,
16183 <b> Description</b>
16184 2 The vfwscanf function is equivalent to fwscanf, with the variable argument list
16185 replaced by arg, which shall have been initialized by the va_start macro (and
16186 possibly subsequent va_arg calls). The vfwscanf function does not invoke the
16189 3 The vfwscanf function returns the value of the macro EOF if an input failure occurs
16190 before the first conversion (if any) has completed. Otherwise, the vfwscanf function
16191 returns the number of input items assigned, which can be fewer than provided for, or even
16192 zero, in the event of an early matching failure.
16193 <a name="7.28.2.7" href="#7.28.2.7"><b> 7.28.2.7 The vswprintf function</b></a>
16195 1 #include <a href="#7.16"><stdarg.h></a>
16196 #include <a href="#7.28"><wchar.h></a>
16197 int vswprintf(wchar_t * restrict s,
16199 const wchar_t * restrict format,
16201 <b> Description</b>
16202 2 The vswprintf function is equivalent to swprintf, with the variable argument list
16203 replaced by arg, which shall have been initialized by the va_start macro (and
16204 possibly subsequent va_arg calls). The vswprintf function does not invoke the
16207 3 The vswprintf function returns the number of wide characters written in the array, not
16208 counting the terminating null wide character, or a negative value if an encoding error
16209 occurred or if n or more wide characters were requested to be generated.
16211 [<a name="p415" href="#p415">page 415</a>] (<a href="#Contents">Contents</a>)
16213 <a name="7.28.2.8" href="#7.28.2.8"><b> 7.28.2.8 The vswscanf function</b></a>
16215 1 #include <a href="#7.16"><stdarg.h></a>
16216 #include <a href="#7.28"><wchar.h></a>
16217 int vswscanf(const wchar_t * restrict s,
16218 const wchar_t * restrict format,
16220 <b> Description</b>
16221 2 The vswscanf function is equivalent to swscanf, with the variable argument list
16222 replaced by arg, which shall have been initialized by the va_start macro (and
16223 possibly subsequent va_arg calls). The vswscanf function does not invoke the
16226 3 The vswscanf function returns the value of the macro EOF if an input failure occurs
16227 before the first conversion (if any) has completed. Otherwise, the vswscanf function
16228 returns the number of input items assigned, which can be fewer than provided for, or even
16229 zero, in the event of an early matching failure.
16230 <a name="7.28.2.9" href="#7.28.2.9"><b> 7.28.2.9 The vwprintf function</b></a>
16232 1 #include <a href="#7.16"><stdarg.h></a>
16233 #include <a href="#7.28"><wchar.h></a>
16234 int vwprintf(const wchar_t * restrict format,
16236 <b> Description</b>
16237 2 The vwprintf function is equivalent to wprintf, with the variable argument list
16238 replaced by arg, which shall have been initialized by the va_start macro (and
16239 possibly subsequent va_arg calls). The vwprintf function does not invoke the
16242 3 The vwprintf function returns the number of wide characters transmitted, or a negative
16243 value if an output or encoding error occurred.
16245 [<a name="p416" href="#p416">page 416</a>] (<a href="#Contents">Contents</a>)
16247 <a name="7.28.2.10" href="#7.28.2.10"><b> 7.28.2.10 The vwscanf function</b></a>
16249 1 #include <a href="#7.16"><stdarg.h></a>
16250 #include <a href="#7.28"><wchar.h></a>
16251 int vwscanf(const wchar_t * restrict format,
16253 <b> Description</b>
16254 2 The vwscanf function is equivalent to wscanf, with the variable argument list
16255 replaced by arg, which shall have been initialized by the va_start macro (and
16256 possibly subsequent va_arg calls). The vwscanf function does not invoke the
16259 3 The vwscanf function returns the value of the macro EOF if an input failure occurs
16260 before the first conversion (if any) has completed. Otherwise, the vwscanf function
16261 returns the number of input items assigned, which can be fewer than provided for, or even
16262 zero, in the event of an early matching failure.
16263 <a name="7.28.2.11" href="#7.28.2.11"><b> 7.28.2.11 The wprintf function</b></a>
16265 1 #include <a href="#7.28"><wchar.h></a>
16266 int wprintf(const wchar_t * restrict format, ...);
16267 <b> Description</b>
16268 2 The wprintf function is equivalent to fwprintf with the argument stdout
16269 interposed before the arguments to wprintf.
16271 3 The wprintf function returns the number of wide characters transmitted, or a negative
16272 value if an output or encoding error occurred.
16273 <a name="7.28.2.12" href="#7.28.2.12"><b> 7.28.2.12 The wscanf function</b></a>
16275 1 #include <a href="#7.28"><wchar.h></a>
16276 int wscanf(const wchar_t * restrict format, ...);
16277 <b> Description</b>
16278 2 The wscanf function is equivalent to fwscanf with the argument stdin interposed
16279 before the arguments to wscanf.
16281 [<a name="p417" href="#p417">page 417</a>] (<a href="#Contents">Contents</a>)
16284 3 The wscanf function returns the value of the macro EOF if an input failure occurs
16285 before the first conversion (if any) has completed. Otherwise, the wscanf function
16286 returns the number of input items assigned, which can be fewer than provided for, or even
16287 zero, in the event of an early matching failure.
16288 <a name="7.28.3" href="#7.28.3"><b> 7.28.3 Wide character input/output functions</b></a>
16289 <a name="7.28.3.1" href="#7.28.3.1"><b> 7.28.3.1 The fgetwc function</b></a>
16291 1 #include <a href="#7.21"><stdio.h></a>
16292 #include <a href="#7.28"><wchar.h></a>
16293 wint_t fgetwc(FILE *stream);
16294 <b> Description</b>
16295 2 If the end-of-file indicator for the input stream pointed to by stream is not set and a
16296 next wide character is present, the fgetwc function obtains that wide character as a
16297 wchar_t converted to a wint_t and advances the associated file position indicator for
16298 the stream (if defined).
16300 3 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
16301 of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
16302 the fgetwc function returns the next wide character from the input stream pointed to by
16303 stream. If a read error occurs, the error indicator for the stream is set and the fgetwc
16304 function returns WEOF. If an encoding error occurs (including too few bytes), the value of
16305 the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.<sup><a href="#note328"><b>328)</b></a></sup>
16306 <a name="7.28.3.2" href="#7.28.3.2"><b> 7.28.3.2 The fgetws function</b></a>
16308 1 #include <a href="#7.21"><stdio.h></a>
16309 #include <a href="#7.28"><wchar.h></a>
16310 wchar_t *fgetws(wchar_t * restrict s,
16311 int n, FILE * restrict stream);
16312 <b> Description</b>
16313 2 The fgetws function reads at most one less than the number of wide characters
16314 specified by n from the stream pointed to by stream into the array pointed to by s. No
16317 <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.
16318 Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
16320 [<a name="p418" href="#p418">page 418</a>] (<a href="#Contents">Contents</a>)
16322 additional wide characters are read after a new-line wide character (which is retained) or
16323 after end-of-file. A null wide character is written immediately after the last wide
16324 character read into the array.
16326 3 The fgetws function returns s if successful. If end-of-file is encountered and no
16327 characters have been read into the array, the contents of the array remain unchanged and a
16328 null pointer is returned. If a read or encoding error occurs during the operation, the array
16329 contents are indeterminate and a null pointer is returned.
16330 <a name="7.28.3.3" href="#7.28.3.3"><b> 7.28.3.3 The fputwc function</b></a>
16332 1 #include <a href="#7.21"><stdio.h></a>
16333 #include <a href="#7.28"><wchar.h></a>
16334 wint_t fputwc(wchar_t c, FILE *stream);
16335 <b> Description</b>
16336 2 The fputwc function writes the wide character specified by c to the output stream
16337 pointed to by stream, at the position indicated by the associated file position indicator
16338 for the stream (if defined), and advances the indicator appropriately. If the file cannot
16339 support positioning requests, or if the stream was opened with append mode, the
16340 character is appended to the output stream.
16342 3 The fputwc function returns the wide character written. If a write error occurs, the
16343 error indicator for the stream is set and fputwc returns WEOF. If an encoding error
16344 occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
16345 <a name="7.28.3.4" href="#7.28.3.4"><b> 7.28.3.4 The fputws function</b></a>
16347 1 #include <a href="#7.21"><stdio.h></a>
16348 #include <a href="#7.28"><wchar.h></a>
16349 int fputws(const wchar_t * restrict s,
16350 FILE * restrict stream);
16351 <b> Description</b>
16352 2 The fputws function writes the wide string pointed to by s to the stream pointed to by
16353 stream. The terminating null wide character is not written.
16355 3 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
16356 returns a nonnegative value.
16358 [<a name="p419" href="#p419">page 419</a>] (<a href="#Contents">Contents</a>)
16360 <a name="7.28.3.5" href="#7.28.3.5"><b> 7.28.3.5 The fwide function</b></a>
16362 1 #include <a href="#7.21"><stdio.h></a>
16363 #include <a href="#7.28"><wchar.h></a>
16364 int fwide(FILE *stream, int mode);
16365 <b> Description</b>
16366 2 The fwide function determines the orientation of the stream pointed to by stream. If
16367 mode is greater than zero, the function first attempts to make the stream wide oriented. If
16368 mode is less than zero, the function first attempts to make the stream byte oriented.<sup><a href="#note329"><b>329)</b></a></sup>
16369 Otherwise, mode is zero and the function does not alter the orientation of the stream.
16371 3 The fwide function returns a value greater than zero if, after the call, the stream has
16372 wide orientation, a value less than zero if the stream has byte orientation, or zero if the
16373 stream has no orientation.
16374 <a name="7.28.3.6" href="#7.28.3.6"><b> 7.28.3.6 The getwc function</b></a>
16376 1 #include <a href="#7.21"><stdio.h></a>
16377 #include <a href="#7.28"><wchar.h></a>
16378 wint_t getwc(FILE *stream);
16379 <b> Description</b>
16380 2 The getwc function is equivalent to fgetwc, except that if it is implemented as a
16381 macro, it may evaluate stream more than once, so the argument should never be an
16382 expression with side effects.
16384 3 The getwc function returns the next wide character from the input stream pointed to by
16386 <a name="7.28.3.7" href="#7.28.3.7"><b> 7.28.3.7 The getwchar function</b></a>
16388 1 #include <a href="#7.28"><wchar.h></a>
16389 wint_t getwchar(void);
16394 <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.
16396 [<a name="p420" href="#p420">page 420</a>] (<a href="#Contents">Contents</a>)
16398 <b> Description</b>
16399 2 The getwchar function is equivalent to getwc with the argument stdin.
16401 3 The getwchar function returns the next wide character from the input stream pointed to
16403 <a name="7.28.3.8" href="#7.28.3.8"><b> 7.28.3.8 The putwc function</b></a>
16405 1 #include <a href="#7.21"><stdio.h></a>
16406 #include <a href="#7.28"><wchar.h></a>
16407 wint_t putwc(wchar_t c, FILE *stream);
16408 <b> Description</b>
16409 2 The putwc function is equivalent to fputwc, except that if it is implemented as a
16410 macro, it may evaluate stream more than once, so that argument should never be an
16411 expression with side effects.
16413 3 The putwc function returns the wide character written, or WEOF.
16414 <a name="7.28.3.9" href="#7.28.3.9"><b> 7.28.3.9 The putwchar function</b></a>
16416 1 #include <a href="#7.28"><wchar.h></a>
16417 wint_t putwchar(wchar_t c);
16418 <b> Description</b>
16419 2 The putwchar function is equivalent to putwc with the second argument stdout.
16421 3 The putwchar function returns the character written, or WEOF.
16422 <a name="7.28.3.10" href="#7.28.3.10"><b> 7.28.3.10 The ungetwc function</b></a>
16424 1 #include <a href="#7.21"><stdio.h></a>
16425 #include <a href="#7.28"><wchar.h></a>
16426 wint_t ungetwc(wint_t c, FILE *stream);
16427 <b> Description</b>
16428 2 The ungetwc function pushes the wide character specified by c back onto the input
16429 stream pointed to by stream. Pushed-back wide characters will be returned by
16430 subsequent reads on that stream in the reverse order of their pushing. A successful
16432 [<a name="p421" href="#p421">page 421</a>] (<a href="#Contents">Contents</a>)
16434 intervening call (with the stream pointed to by stream) to a file positioning function
16435 (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the
16436 stream. The external storage corresponding to the stream is unchanged.
16437 3 One wide character of pushback is guaranteed, even if the call to the ungetwc function
16438 follows just after a call to a formatted wide character input function fwscanf,
16439 vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times
16440 on the same stream without an intervening read or file positioning operation on that
16441 stream, the operation may fail.
16442 4 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
16444 5 A successful call to the ungetwc function clears the end-of-file indicator for the stream.
16445 The value of the file position indicator for the stream after reading or discarding all
16446 pushed-back wide characters is the same as it was before the wide characters were pushed
16447 back. For a text or binary stream, the value of its file position indicator after a successful
16448 call to the ungetwc function is unspecified until all pushed-back wide characters are
16451 6 The ungetwc function returns the wide character pushed back, or WEOF if the operation
16453 <a name="7.28.4" href="#7.28.4"><b> 7.28.4 General wide string utilities</b></a>
16454 1 The header <a href="#7.28"><wchar.h></a> declares a number of functions useful for wide string
16455 manipulation. Various methods are used for determining the lengths of the arrays, but in
16456 all cases a wchar_t * argument points to the initial (lowest addressed) element of the
16457 array. If an array is accessed beyond the end of an object, the behavior is undefined.
16458 2 Where an argument declared as size_t n determines the length of the array for a
16459 function, n can have the value zero on a call to that function. Unless explicitly stated
16460 otherwise in the description of a particular function in this subclause, pointer arguments
16461 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
16462 function that locates a wide character finds no occurrence, a function that compares two
16463 wide character sequences returns zero, and a function that copies wide characters copies
16464 zero wide characters.
16466 [<a name="p422" href="#p422">page 422</a>] (<a href="#Contents">Contents</a>)
16468 <a name="7.28.4.1" href="#7.28.4.1"><b> 7.28.4.1 Wide string numeric conversion functions</b></a>
16469 <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>
16471 1 #include <a href="#7.28"><wchar.h></a>
16472 double wcstod(const wchar_t * restrict nptr,
16473 wchar_t ** restrict endptr);
16474 float wcstof(const wchar_t * restrict nptr,
16475 wchar_t ** restrict endptr);
16476 long double wcstold(const wchar_t * restrict nptr,
16477 wchar_t ** restrict endptr);
16478 <b> Description</b>
16479 2 The wcstod, wcstof, and wcstold functions convert the initial portion of the wide
16480 string pointed to by nptr to double, float, and long double representation,
16481 respectively. First, they decompose the input string into three parts: an initial, possibly
16482 empty, sequence of white-space wide characters (as specified by the iswspace
16483 function), a subject sequence resembling a floating-point constant or representing an
16484 infinity or NaN; and a final wide string of one or more unrecognized wide characters,
16485 including the terminating null wide character of the input wide string. Then, they attempt
16486 to convert the subject sequence to a floating-point number, and return the result.
16487 3 The expected form of the subject sequence is an optional plus or minus sign, then one of
16489 -- a nonempty sequence of decimal digits optionally containing a decimal-point wide
16490 character, then an optional exponent part as defined for the corresponding single-byte
16491 characters in <a href="#6.4.4.2">6.4.4.2</a>;
16492 -- a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
16493 decimal-point wide character, then an optional binary exponent part as defined in
16494 <a href="#6.4.4.2">6.4.4.2</a>;
16495 -- INF or INFINITY, or any other wide string equivalent except for case
16496 -- NAN or NAN(n-wchar-sequenceopt), or any other wide string equivalent except for
16497 case in the NAN part, where:
16501 n-wchar-sequence digit
16502 n-wchar-sequence nondigit
16503 The subject sequence is defined as the longest initial subsequence of the input wide
16504 string, starting with the first non-white-space wide character, that is of the expected form.
16506 [<a name="p423" href="#p423">page 423</a>] (<a href="#Contents">Contents</a>)
16508 The subject sequence contains no wide characters if the input wide string is not of the
16510 4 If the subject sequence has the expected form for a floating-point number, the sequence of
16511 wide characters starting with the first digit or the decimal-point wide character
16512 (whichever occurs first) is interpreted as a floating constant according to the rules of
16513 <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
16514 if neither an exponent part nor a decimal-point wide character appears in a decimal
16515 floating point number, or if a binary exponent part does not appear in a hexadecimal
16516 floating point number, an exponent part of the appropriate type with value zero is
16517 assumed to follow the last digit in the string. If the subject sequence begins with a minus
16518 sign, the sequence is interpreted as negated.<sup><a href="#note330"><b>330)</b></a></sup> A wide character sequence INF or
16519 INFINITY is interpreted as an infinity, if representable in the return type, else like a
16520 floating constant that is too large for the range of the return type. A wide character
16521 sequence NAN or NAN(n-wchar-sequenceopt) is interpreted as a quiet NaN, if supported
16522 in the return type, else like a subject sequence part that does not have the expected form;
16523 the meaning of the n-wchar sequences is implementation-defined.<sup><a href="#note331"><b>331)</b></a></sup> A pointer to the
16524 final wide string is stored in the object pointed to by endptr, provided that endptr is
16525 not a null pointer.
16526 5 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
16527 value resulting from the conversion is correctly rounded.
16528 6 In other than the "C" locale, additional locale-specific subject sequence forms may be
16530 7 If the subject sequence is empty or does not have the expected form, no conversion is
16531 performed; the value of nptr is stored in the object pointed to by endptr, provided
16532 that endptr is not a null pointer.
16533 Recommended practice
16534 8 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
16535 the result is not exactly representable, the result should be one of the two numbers in the
16536 appropriate internal format that are adjacent to the hexadecimal floating source value,
16537 with the extra stipulation that the error should have a correct sign for the current rounding
16542 <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
16543 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
16544 methods may yield different results if rounding is toward positive or negative infinity. In either case,
16545 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
16546 <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
16547 the NaN's significand.
16549 [<a name="p424" href="#p424">page 424</a>] (<a href="#Contents">Contents</a>)
16551 9 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
16552 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
16553 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
16554 consider the two bounding, adjacent decimal strings L and U, both having
16555 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
16556 The result should be one of the (equal or adjacent) values that would be obtained by
16557 correctly rounding L and U according to the current rounding direction, with the extra
16558 stipulation that the error with respect to D should have a correct sign for the current
16559 rounding direction.<sup><a href="#note332"><b>332)</b></a></sup>
16561 10 The functions return the converted value, if any. If no conversion could be performed,
16562 zero is returned. If the correct value overflows and default rounding is in effect (<a href="#7.12.1">7.12.1</a>),
16563 plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
16564 return type and sign of the value), and the value of the macro ERANGE is stored in
16565 errno. If the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is
16566 no greater than the smallest normalized positive number in the return type; whether
16567 errno acquires the value ERANGE is implementation-defined.
16572 <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
16573 to the same internal floating value, but if not will round to adjacent values.
16575 [<a name="p425" href="#p425">page 425</a>] (<a href="#Contents">Contents</a>)
16577 <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>
16579 1 #include <a href="#7.28"><wchar.h></a>
16581 const wchar_t * restrict nptr,
16582 wchar_t ** restrict endptr,
16584 long long int wcstoll(
16585 const wchar_t * restrict nptr,
16586 wchar_t ** restrict endptr,
16588 unsigned long int wcstoul(
16589 const wchar_t * restrict nptr,
16590 wchar_t ** restrict endptr,
16592 unsigned long long int wcstoull(
16593 const wchar_t * restrict nptr,
16594 wchar_t ** restrict endptr,
16596 <b> Description</b>
16597 2 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial
16598 portion of the wide string pointed to by nptr to long int, long long int,
16599 unsigned long int, and unsigned long long int representation,
16600 respectively. First, they decompose the input string into three parts: an initial, possibly
16601 empty, sequence of white-space wide characters (as specified by the iswspace
16602 function), a subject sequence resembling an integer represented in some radix determined
16603 by the value of base, and a final wide string of one or more unrecognized wide
16604 characters, including the terminating null wide character of the input wide string. Then,
16605 they attempt to convert the subject sequence to an integer, and return the result.
16606 3 If the value of base is zero, the expected form of the subject sequence is that of an
16607 integer constant as described for the corresponding single-byte characters in <a href="#6.4.4.1">6.4.4.1</a>,
16608 optionally preceded by a plus or minus sign, but not including an integer suffix. If the
16609 value of base is between 2 and 36 (inclusive), the expected form of the subject sequence
16610 is a sequence of letters and digits representing an integer with the radix specified by
16611 base, optionally preceded by a plus or minus sign, but not including an integer suffix.
16612 The letters from a (or A) through z (or Z) are ascribed the values 10 through 35; only
16613 letters and digits whose ascribed values are less than that of base are permitted. If the
16614 value of base is 16, the wide characters 0x or 0X may optionally precede the sequence
16615 of letters and digits, following the sign if present.
16617 [<a name="p426" href="#p426">page 426</a>] (<a href="#Contents">Contents</a>)
16619 4 The subject sequence is defined as the longest initial subsequence of the input wide
16620 string, starting with the first non-white-space wide character, that is of the expected form.
16621 The subject sequence contains no wide characters if the input wide string is empty or
16622 consists entirely of white space, or if the first non-white-space wide character is other
16623 than a sign or a permissible letter or digit.
16624 5 If the subject sequence has the expected form and the value of base is zero, the sequence
16625 of wide characters starting with the first digit is interpreted as an integer constant
16626 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
16627 value of base is between 2 and 36, it is used as the base for conversion, ascribing to each
16628 letter its value as given above. If the subject sequence begins with a minus sign, the value
16629 resulting from the conversion is negated (in the return type). A pointer to the final wide
16630 string is stored in the object pointed to by endptr, provided that endptr is not a null
16632 6 In other than the "C" locale, additional locale-specific subject sequence forms may be
16634 7 If the subject sequence is empty or does not have the expected form, no conversion is
16635 performed; the value of nptr is stored in the object pointed to by endptr, provided
16636 that endptr is not a null pointer.
16638 8 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
16639 value, if any. If no conversion could be performed, zero is returned. If the correct value
16640 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
16641 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
16642 sign of the value, if any), and the value of the macro ERANGE is stored in errno.
16643 <a name="7.28.4.2" href="#7.28.4.2"><b> 7.28.4.2 Wide string copying functions</b></a>
16644 <a name="7.28.4.2.1" href="#7.28.4.2.1"><b> 7.28.4.2.1 The wcscpy function</b></a>
16646 1 #include <a href="#7.28"><wchar.h></a>
16647 wchar_t *wcscpy(wchar_t * restrict s1,
16648 const wchar_t * restrict s2);
16649 <b> Description</b>
16650 2 The wcscpy function copies the wide string pointed to by s2 (including the terminating
16651 null wide character) into the array pointed to by s1.
16653 3 The wcscpy function returns the value of s1.
16655 [<a name="p427" href="#p427">page 427</a>] (<a href="#Contents">Contents</a>)
16657 <a name="7.28.4.2.2" href="#7.28.4.2.2"><b> 7.28.4.2.2 The wcsncpy function</b></a>
16659 1 #include <a href="#7.28"><wchar.h></a>
16660 wchar_t *wcsncpy(wchar_t * restrict s1,
16661 const wchar_t * restrict s2,
16663 <b> Description</b>
16664 2 The wcsncpy function copies not more than n wide characters (those that follow a null
16665 wide character are not copied) from the array pointed to by s2 to the array pointed to by
16666 s1.<sup><a href="#note333"><b>333)</b></a></sup>
16667 3 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null
16668 wide characters are appended to the copy in the array pointed to by s1, until n wide
16669 characters in all have been written.
16671 4 The wcsncpy function returns the value of s1.
16672 <a name="7.28.4.2.3" href="#7.28.4.2.3"><b> 7.28.4.2.3 The wmemcpy function</b></a>
16674 1 #include <a href="#7.28"><wchar.h></a>
16675 wchar_t *wmemcpy(wchar_t * restrict s1,
16676 const wchar_t * restrict s2,
16678 <b> Description</b>
16679 2 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
16680 object pointed to by s1.
16682 3 The wmemcpy function returns the value of s1.
16687 <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
16688 result will not be null-terminated.
16690 [<a name="p428" href="#p428">page 428</a>] (<a href="#Contents">Contents</a>)
16692 <a name="7.28.4.2.4" href="#7.28.4.2.4"><b> 7.28.4.2.4 The wmemmove function</b></a>
16694 1 #include <a href="#7.28"><wchar.h></a>
16695 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
16697 <b> Description</b>
16698 2 The wmemmove function copies n wide characters from the object pointed to by s2 to
16699 the object pointed to by s1. Copying takes place as if the n wide characters from the
16700 object pointed to by s2 are first copied into a temporary array of n wide characters that
16701 does not overlap the objects pointed to by s1 or s2, and then the n wide characters from
16702 the temporary array are copied into the object pointed to by s1.
16704 3 The wmemmove function returns the value of s1.
16705 <a name="7.28.4.3" href="#7.28.4.3"><b> 7.28.4.3 Wide string concatenation functions</b></a>
16706 <a name="7.28.4.3.1" href="#7.28.4.3.1"><b> 7.28.4.3.1 The wcscat function</b></a>
16708 1 #include <a href="#7.28"><wchar.h></a>
16709 wchar_t *wcscat(wchar_t * restrict s1,
16710 const wchar_t * restrict s2);
16711 <b> Description</b>
16712 2 The wcscat function appends a copy of the wide string pointed to by s2 (including the
16713 terminating null wide character) to the end of the wide string pointed to by s1. The initial
16714 wide character of s2 overwrites the null wide character at the end of s1.
16716 3 The wcscat function returns the value of s1.
16717 <a name="7.28.4.3.2" href="#7.28.4.3.2"><b> 7.28.4.3.2 The wcsncat function</b></a>
16719 1 #include <a href="#7.28"><wchar.h></a>
16720 wchar_t *wcsncat(wchar_t * restrict s1,
16721 const wchar_t * restrict s2,
16723 <b> Description</b>
16724 2 The wcsncat function appends not more than n wide characters (a null wide character
16725 and those that follow it are not appended) from the array pointed to by s2 to the end of
16727 [<a name="p429" href="#p429">page 429</a>] (<a href="#Contents">Contents</a>)
16729 the wide string pointed to by s1. The initial wide character of s2 overwrites the null
16730 wide character at the end of s1. A terminating null wide character is always appended to
16731 the result.<sup><a href="#note334"><b>334)</b></a></sup>
16733 3 The wcsncat function returns the value of s1.
16734 <a name="7.28.4.4" href="#7.28.4.4"><b> 7.28.4.4 Wide string comparison functions</b></a>
16735 1 Unless explicitly stated otherwise, the functions described in this subclause order two
16736 wide characters the same way as two integers of the underlying integer type designated
16738 <a name="7.28.4.4.1" href="#7.28.4.4.1"><b> 7.28.4.4.1 The wcscmp function</b></a>
16740 1 #include <a href="#7.28"><wchar.h></a>
16741 int wcscmp(const wchar_t *s1, const wchar_t *s2);
16742 <b> Description</b>
16743 2 The wcscmp function compares the wide string pointed to by s1 to the wide string
16746 3 The wcscmp function returns an integer greater than, equal to, or less than zero,
16747 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
16748 wide string pointed to by s2.
16749 <a name="7.28.4.4.2" href="#7.28.4.4.2"><b> 7.28.4.4.2 The wcscoll function</b></a>
16751 1 #include <a href="#7.28"><wchar.h></a>
16752 int wcscoll(const wchar_t *s1, const wchar_t *s2);
16753 <b> Description</b>
16754 2 The wcscoll function compares the wide string pointed to by s1 to the wide string
16755 pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the
16758 3 The wcscoll function returns an integer greater than, equal to, or less than zero,
16759 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
16762 <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
16765 [<a name="p430" href="#p430">page 430</a>] (<a href="#Contents">Contents</a>)
16767 wide string pointed to by s2 when both are interpreted as appropriate to the current
16769 <a name="7.28.4.4.3" href="#7.28.4.4.3"><b> 7.28.4.4.3 The wcsncmp function</b></a>
16771 1 #include <a href="#7.28"><wchar.h></a>
16772 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
16774 <b> Description</b>
16775 2 The wcsncmp function compares not more than n wide characters (those that follow a
16776 null wide character are not compared) from the array pointed to by s1 to the array
16779 3 The wcsncmp function returns an integer greater than, equal to, or less than zero,
16780 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
16781 to, or less than the possibly null-terminated array pointed to by s2.
16782 <a name="7.28.4.4.4" href="#7.28.4.4.4"><b> 7.28.4.4.4 The wcsxfrm function</b></a>
16784 1 #include <a href="#7.28"><wchar.h></a>
16785 size_t wcsxfrm(wchar_t * restrict s1,
16786 const wchar_t * restrict s2,
16788 <b> Description</b>
16789 2 The wcsxfrm function transforms the wide string pointed to by s2 and places the
16790 resulting wide string into the array pointed to by s1. The transformation is such that if
16791 the wcscmp function is applied to two transformed wide strings, it returns a value greater
16792 than, equal to, or less than zero, corresponding to the result of the wcscoll function
16793 applied to the same two original wide strings. No more than n wide characters are placed
16794 into the resulting array pointed to by s1, including the terminating null wide character. If
16795 n is zero, s1 is permitted to be a null pointer.
16797 3 The wcsxfrm function returns the length of the transformed wide string (not including
16798 the terminating null wide character). If the value returned is n or greater, the contents of
16799 the array pointed to by s1 are indeterminate.
16800 4 EXAMPLE The value of the following expression is the length of the array needed to hold the
16801 transformation of the wide string pointed to by s:
16803 [<a name="p431" href="#p431">page 431</a>] (<a href="#Contents">Contents</a>)
16805 1 + wcsxfrm(NULL, s, 0)
16807 <a name="7.28.4.4.5" href="#7.28.4.4.5"><b> 7.28.4.4.5 The wmemcmp function</b></a>
16809 1 #include <a href="#7.28"><wchar.h></a>
16810 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
16812 <b> Description</b>
16813 2 The wmemcmp function compares the first n wide characters of the object pointed to by
16814 s1 to the first n wide characters of the object pointed to by s2.
16816 3 The wmemcmp function returns an integer greater than, equal to, or less than zero,
16817 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
16819 <a name="7.28.4.5" href="#7.28.4.5"><b> 7.28.4.5 Wide string search functions</b></a>
16820 <a name="7.28.4.5.1" href="#7.28.4.5.1"><b> 7.28.4.5.1 The wcschr function</b></a>
16822 1 #include <a href="#7.28"><wchar.h></a>
16823 wchar_t *wcschr(const wchar_t *s, wchar_t c);
16824 <b> Description</b>
16825 2 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
16826 The terminating null wide character is considered to be part of the wide string.
16828 3 The wcschr function returns a pointer to the located wide character, or a null pointer if
16829 the wide character does not occur in the wide string.
16830 <a name="7.28.4.5.2" href="#7.28.4.5.2"><b> 7.28.4.5.2 The wcscspn function</b></a>
16832 1 #include <a href="#7.28"><wchar.h></a>
16833 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
16834 <b> Description</b>
16835 2 The wcscspn function computes the length of the maximum initial segment of the wide
16836 string pointed to by s1 which consists entirely of wide characters not from the wide
16837 string pointed to by s2.
16839 [<a name="p432" href="#p432">page 432</a>] (<a href="#Contents">Contents</a>)
16842 3 The wcscspn function returns the length of the segment.
16843 <a name="7.28.4.5.3" href="#7.28.4.5.3"><b> 7.28.4.5.3 The wcspbrk function</b></a>
16845 1 #include <a href="#7.28"><wchar.h></a>
16846 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
16847 <b> Description</b>
16848 2 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
16849 any wide character from the wide string pointed to by s2.
16851 3 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
16852 no wide character from s2 occurs in s1.
16853 <a name="7.28.4.5.4" href="#7.28.4.5.4"><b> 7.28.4.5.4 The wcsrchr function</b></a>
16855 1 #include <a href="#7.28"><wchar.h></a>
16856 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
16857 <b> Description</b>
16858 2 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
16859 s. The terminating null wide character is considered to be part of the wide string.
16861 3 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
16862 not occur in the wide string.
16863 <a name="7.28.4.5.5" href="#7.28.4.5.5"><b> 7.28.4.5.5 The wcsspn function</b></a>
16865 1 #include <a href="#7.28"><wchar.h></a>
16866 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
16867 <b> Description</b>
16868 2 The wcsspn function computes the length of the maximum initial segment of the wide
16869 string pointed to by s1 which consists entirely of wide characters from the wide string
16872 3 The wcsspn function returns the length of the segment.
16874 [<a name="p433" href="#p433">page 433</a>] (<a href="#Contents">Contents</a>)
16876 <a name="7.28.4.5.6" href="#7.28.4.5.6"><b> 7.28.4.5.6 The wcsstr function</b></a>
16878 1 #include <a href="#7.28"><wchar.h></a>
16879 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
16880 <b> Description</b>
16881 2 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
16882 the sequence of wide characters (excluding the terminating null wide character) in the
16883 wide string pointed to by s2.
16885 3 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
16886 wide string is not found. If s2 points to a wide string with zero length, the function
16888 <a name="7.28.4.5.7" href="#7.28.4.5.7"><b> 7.28.4.5.7 The wcstok function</b></a>
16890 1 #include <a href="#7.28"><wchar.h></a>
16891 wchar_t *wcstok(wchar_t * restrict s1,
16892 const wchar_t * restrict s2,
16893 wchar_t ** restrict ptr);
16894 <b> Description</b>
16895 2 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
16896 a sequence of tokens, each of which is delimited by a wide character from the wide string
16897 pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
16898 which the wcstok function stores information necessary for it to continue scanning the
16900 3 The first call in a sequence has a non-null first argument and stores an initial value in the
16901 object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
16902 the object pointed to by ptr is required to have the value stored by the previous call in
16903 the sequence, which is then updated. The separator wide string pointed to by s2 may be
16904 different from call to call.
16905 4 The first call in the sequence searches the wide string pointed to by s1 for the first wide
16906 character that is not contained in the current separator wide string pointed to by s2. If no
16907 such wide character is found, then there are no tokens in the wide string pointed to by s1
16908 and the wcstok function returns a null pointer. If such a wide character is found, it is
16909 the start of the first token.
16910 5 The wcstok function then searches from there for a wide character that is contained in
16911 the current separator wide string. If no such wide character is found, the current token
16913 [<a name="p434" href="#p434">page 434</a>] (<a href="#Contents">Contents</a>)
16915 extends to the end of the wide string pointed to by s1, and subsequent searches in the
16916 same wide string for a token return a null pointer. If such a wide character is found, it is
16917 overwritten by a null wide character, which terminates the current token.
16918 6 In all cases, the wcstok function stores sufficient information in the pointer pointed to
16919 by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
16920 value for ptr, shall start searching just past the element overwritten by a null wide
16921 character (if any).
16923 7 The wcstok function returns a pointer to the first wide character of a token, or a null
16924 pointer if there is no token.
16926 #include <a href="#7.28"><wchar.h></a>
16927 static wchar_t str1[] = L"?a???b,,,#c";
16928 static wchar_t str2[] = L"\t \t";
16929 wchar_t *t, *ptr1, *ptr2;
16930 t = wcstok(str1, L"?", &ptr1); // t points to the token L"a"
16931 t = wcstok(NULL, L",", &ptr1); // t points to the token L"??b"
16932 t = wcstok(str2, L" \t", &ptr2); // t is a null pointer
16933 t = wcstok(NULL, L"#,", &ptr1); // t points to the token L"c"
16934 t = wcstok(NULL, L"?", &ptr1); // t is a null pointer
16936 <a name="7.28.4.5.8" href="#7.28.4.5.8"><b> 7.28.4.5.8 The wmemchr function</b></a>
16938 1 #include <a href="#7.28"><wchar.h></a>
16939 wchar_t *wmemchr(const wchar_t *s, wchar_t c,
16941 <b> Description</b>
16942 2 The wmemchr function locates the first occurrence of c in the initial n wide characters of
16943 the object pointed to by s.
16945 3 The wmemchr function returns a pointer to the located wide character, or a null pointer if
16946 the wide character does not occur in the object.
16948 [<a name="p435" href="#p435">page 435</a>] (<a href="#Contents">Contents</a>)
16950 <a name="7.28.4.6" href="#7.28.4.6"><b> 7.28.4.6 Miscellaneous functions</b></a>
16951 <a name="7.28.4.6.1" href="#7.28.4.6.1"><b> 7.28.4.6.1 The wcslen function</b></a>
16953 1 #include <a href="#7.28"><wchar.h></a>
16954 size_t wcslen(const wchar_t *s);
16955 <b> Description</b>
16956 2 The wcslen function computes the length of the wide string pointed to by s.
16958 3 The wcslen function returns the number of wide characters that precede the terminating
16959 null wide character.
16960 <a name="7.28.4.6.2" href="#7.28.4.6.2"><b> 7.28.4.6.2 The wmemset function</b></a>
16962 1 #include <a href="#7.28"><wchar.h></a>
16963 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
16964 <b> Description</b>
16965 2 The wmemset function copies the value of c into each of the first n wide characters of
16966 the object pointed to by s.
16968 3 The wmemset function returns the value of s.
16969 <a name="7.28.5" href="#7.28.5"><b> 7.28.5 Wide character time conversion functions</b></a>
16970 <a name="7.28.5.1" href="#7.28.5.1"><b> 7.28.5.1 The wcsftime function</b></a>
16972 1 #include <a href="#7.26"><time.h></a>
16973 #include <a href="#7.28"><wchar.h></a>
16974 size_t wcsftime(wchar_t * restrict s,
16976 const wchar_t * restrict format,
16977 const struct tm * restrict timeptr);
16978 <b> Description</b>
16979 2 The wcsftime function is equivalent to the strftime function, except that:
16980 -- The argument s points to the initial element of an array of wide characters into which
16981 the generated output is to be placed.
16983 [<a name="p436" href="#p436">page 436</a>] (<a href="#Contents">Contents</a>)
16985 -- The argument maxsize indicates the limiting number of wide characters.
16986 -- The argument format is a wide string and the conversion specifiers are replaced by
16987 corresponding sequences of wide characters.
16988 -- The return value indicates the number of wide characters.
16990 3 If the total number of resulting wide characters including the terminating null wide
16991 character is not more than maxsize, the wcsftime function returns the number of
16992 wide characters placed into the array pointed to by s not including the terminating null
16993 wide character. Otherwise, zero is returned and the contents of the array are
16995 <a name="7.28.6" href="#7.28.6"><b> 7.28.6 Extended multibyte/wide character conversion utilities</b></a>
16996 1 The header <a href="#7.28"><wchar.h></a> declares an extended set of functions useful for conversion
16997 between multibyte characters and wide characters.
16998 2 Most of the following functions -- those that are listed as ''restartable'', <a href="#7.28.6.3">7.28.6.3</a> and
16999 <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
17000 to describe the current conversion state from a particular multibyte character sequence to
17001 a wide character sequence (or the reverse) under the rules of a particular setting for the
17002 LC_CTYPE category of the current locale.
17003 3 The initial conversion state corresponds, for a conversion in either direction, to the
17004 beginning of a new multibyte character in the initial shift state. A zero-valued
17005 mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
17006 valued mbstate_t object can be used to initiate conversion involving any multibyte
17007 character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
17008 been altered by any of the functions described in this subclause, and is then used with a
17009 different multibyte character sequence, or in the other conversion direction, or with a
17010 different LC_CTYPE category setting than on earlier function calls, the behavior is
17011 undefined.<sup><a href="#note335"><b>335)</b></a></sup>
17012 4 On entry, each function takes the described conversion state (either internal or pointed to
17013 by an argument) as current. The conversion state described by the referenced object is
17014 altered as needed to track the shift state, and the position within a multibyte character, for
17015 the associated multibyte character sequence.
17020 <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
17021 mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
17024 [<a name="p437" href="#p437">page 437</a>] (<a href="#Contents">Contents</a>)
17026 <a name="7.28.6.1" href="#7.28.6.1"><b> 7.28.6.1 Single-byte/wide character conversion functions</b></a>
17027 <a name="7.28.6.1.1" href="#7.28.6.1.1"><b> 7.28.6.1.1 The btowc function</b></a>
17029 1 #include <a href="#7.28"><wchar.h></a> *
17030 wint_t btowc(int c);
17031 <b> Description</b>
17032 2 The btowc function determines whether c constitutes a valid single-byte character in the
17033 initial shift state.
17035 3 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
17036 does not constitute a valid single-byte character in the initial shift state. Otherwise, it
17037 returns the wide character representation of that character.
17038 <a name="7.28.6.1.2" href="#7.28.6.1.2"><b> 7.28.6.1.2 The wctob function</b></a>
17040 1 #include <a href="#7.28"><wchar.h></a> *
17041 int wctob(wint_t c);
17042 <b> Description</b>
17043 2 The wctob function determines whether c corresponds to a member of the extended
17044 character set whose multibyte character representation is a single byte when in the initial
17047 3 The wctob function returns EOF if c does not correspond to a multibyte character with
17048 length one in the initial shift state. Otherwise, it returns the single-byte representation of
17049 that character as an unsigned char converted to an int.
17050 <a name="7.28.6.2" href="#7.28.6.2"><b> 7.28.6.2 Conversion state functions</b></a>
17051 <a name="7.28.6.2.1" href="#7.28.6.2.1"><b> 7.28.6.2.1 The mbsinit function</b></a>
17053 1 #include <a href="#7.28"><wchar.h></a>
17054 int mbsinit(const mbstate_t *ps);
17055 <b> Description</b>
17056 2 If ps is not a null pointer, the mbsinit function determines whether the referenced
17057 mbstate_t object describes an initial conversion state.
17059 [<a name="p438" href="#p438">page 438</a>] (<a href="#Contents">Contents</a>)
17062 3 The mbsinit function returns nonzero if ps is a null pointer or if the referenced object
17063 describes an initial conversion state; otherwise, it returns zero.
17064 <a name="7.28.6.3" href="#7.28.6.3"><b> 7.28.6.3 Restartable multibyte/wide character conversion functions</b></a>
17065 1 These functions differ from the corresponding multibyte character functions of <a href="#7.22.7">7.22.7</a>
17066 (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type
17067 pointer to mbstate_t that points to an object that can completely describe the current
17068 conversion state of the associated multibyte character sequence. If ps is a null pointer,
17069 each function uses its own internal mbstate_t object instead, which is initialized at
17070 program startup to the initial conversion state; the functions are not required to avoid data
17071 races in this case. The implementation behaves as if no library function calls these
17072 functions with a null pointer for ps.
17073 2 Also unlike their corresponding functions, the return value does not represent whether the
17074 encoding is state-dependent.
17075 <a name="7.28.6.3.1" href="#7.28.6.3.1"><b> 7.28.6.3.1 The mbrlen function</b></a>
17077 1 #include <a href="#7.28"><wchar.h></a>
17078 size_t mbrlen(const char * restrict s,
17080 mbstate_t * restrict ps);
17081 <b> Description</b>
17082 2 The mbrlen function is equivalent to the call:
17083 mbrtowc(NULL, s, n, ps != NULL ? ps : &internal)
17084 where internal is the mbstate_t object for the mbrlen function, except that the
17085 expression designated by ps is evaluated only once.
17087 3 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
17089 Forward references: the mbrtowc function (<a href="#7.28.6.3.2">7.28.6.3.2</a>).
17091 [<a name="p439" href="#p439">page 439</a>] (<a href="#Contents">Contents</a>)
17093 <a name="7.28.6.3.2" href="#7.28.6.3.2"><b> 7.28.6.3.2 The mbrtowc function</b></a>
17095 1 #include <a href="#7.28"><wchar.h></a>
17096 size_t mbrtowc(wchar_t * restrict pwc,
17097 const char * restrict s,
17099 mbstate_t * restrict ps);
17100 <b> Description</b>
17101 2 If s is a null pointer, the mbrtowc function is equivalent to the call:
17102 mbrtowc(NULL, "", 1, ps)
17103 In this case, the values of the parameters pwc and n are ignored.
17104 3 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with
17105 the byte pointed to by s to determine the number of bytes needed to complete the next
17106 multibyte character (including any shift sequences). If the function determines that the
17107 next multibyte character is complete and valid, it determines the value of the
17108 corresponding wide character and then, if pwc is not a null pointer, stores that value in
17109 the object pointed to by pwc. If the corresponding wide character is the null wide
17110 character, the resulting state described is the initial conversion state.
17112 4 The mbrtowc function returns the first of the following that applies (given the current
17114 0 if the next n or fewer bytes complete the multibyte character that
17115 corresponds to the null wide character (which is the value stored).
17116 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
17117 character (which is the value stored); the value returned is the number
17118 of bytes that complete the multibyte character.
17119 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
17120 multibyte character, and all n bytes have been processed (no value is
17121 stored).<sup><a href="#note336"><b>336)</b></a></sup>
17122 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
17123 do not contribute to a complete and valid multibyte character (no
17124 value is stored); the value of the macro EILSEQ is stored in errno,
17125 and the conversion state is unspecified.
17127 <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
17128 sequence of redundant shift sequences (for implementations with state-dependent encodings).
17130 [<a name="p440" href="#p440">page 440</a>] (<a href="#Contents">Contents</a>)
17132 <a name="7.28.6.3.3" href="#7.28.6.3.3"><b> 7.28.6.3.3 The wcrtomb function</b></a>
17134 1 #include <a href="#7.28"><wchar.h></a>
17135 size_t wcrtomb(char * restrict s,
17137 mbstate_t * restrict ps);
17138 <b> Description</b>
17139 2 If s is a null pointer, the wcrtomb function is equivalent to the call
17140 wcrtomb(buf, L'\0', ps)
17141 where buf is an internal buffer.
17142 3 If s is not a null pointer, the wcrtomb function determines the number of bytes needed
17143 to represent the multibyte character that corresponds to the wide character given by wc
17144 (including any shift sequences), and stores the multibyte character representation in the
17145 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
17146 wc is a null wide character, a null byte is stored, preceded by any shift sequence needed
17147 to restore the initial shift state; the resulting state described is the initial conversion state.
17149 4 The wcrtomb function returns the number of bytes stored in the array object (including
17150 any shift sequences). When wc is not a valid wide character, an encoding error occurs:
17151 the function stores the value of the macro EILSEQ in errno and returns
17152 (size_t)(-1); the conversion state is unspecified.
17153 <a name="7.28.6.4" href="#7.28.6.4"><b> 7.28.6.4 Restartable multibyte/wide string conversion functions</b></a>
17154 1 These functions differ from the corresponding multibyte string functions of <a href="#7.22.8">7.22.8</a>
17155 (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to
17156 mbstate_t that points to an object that can completely describe the current conversion
17157 state of the associated multibyte character sequence. If ps is a null pointer, each function
17158 uses its own internal mbstate_t object instead, which is initialized at program startup
17159 to the initial conversion state; the functions are not required to avoid data races in this
17160 case. The implementation behaves as if no library function calls these functions with a
17161 null pointer for ps.
17162 2 Also unlike their corresponding functions, the conversion source parameter, src, has a
17163 pointer-to-pointer type. When the function is storing the results of conversions (that is,
17164 when dst is not a null pointer), the pointer object pointed to by this parameter is updated
17165 to reflect the amount of the source processed by that invocation.
17167 [<a name="p441" href="#p441">page 441</a>] (<a href="#Contents">Contents</a>)
17169 <a name="7.28.6.4.1" href="#7.28.6.4.1"><b> 7.28.6.4.1 The mbsrtowcs function</b></a>
17171 1 #include <a href="#7.28"><wchar.h></a>
17172 size_t mbsrtowcs(wchar_t * restrict dst,
17173 const char ** restrict src,
17175 mbstate_t * restrict ps);
17176 <b> Description</b>
17177 2 The mbsrtowcs function converts a sequence of multibyte characters that begins in the
17178 conversion state described by the object pointed to by ps, from the array indirectly
17179 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
17180 pointer, the converted characters are stored into the array pointed to by dst. Conversion
17181 continues up to and including a terminating null character, which is also stored.
17182 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
17183 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
17184 characters have been stored into the array pointed to by dst.<sup><a href="#note337"><b>337)</b></a></sup> Each conversion takes
17185 place as if by a call to the mbrtowc function.
17186 3 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
17187 pointer (if conversion stopped due to reaching a terminating null character) or the address
17188 just past the last multibyte character converted (if any). If conversion stopped due to
17189 reaching a terminating null character and if dst is not a null pointer, the resulting state
17190 described is the initial conversion state.
17192 4 If the input conversion encounters a sequence of bytes that do not form a valid multibyte
17193 character, an encoding error occurs: the mbsrtowcs function stores the value of the
17194 macro EILSEQ in errno and returns (size_t)(-1); the conversion state is
17195 unspecified. Otherwise, it returns the number of multibyte characters successfully
17196 converted, not including the terminating null character (if any).
17201 <sup><a name="note337" href="#note337"><b>337)</b></a></sup> Thus, the value of len is ignored if dst is a null pointer.
17203 [<a name="p442" href="#p442">page 442</a>] (<a href="#Contents">Contents</a>)
17205 <a name="7.28.6.4.2" href="#7.28.6.4.2"><b> 7.28.6.4.2 The wcsrtombs function</b></a>
17207 1 #include <a href="#7.28"><wchar.h></a>
17208 size_t wcsrtombs(char * restrict dst,
17209 const wchar_t ** restrict src,
17211 mbstate_t * restrict ps);
17212 <b> Description</b>
17213 2 The wcsrtombs function converts a sequence of wide characters from the array
17214 indirectly pointed to by src into a sequence of corresponding multibyte characters that
17215 begins in the conversion state described by the object pointed to by ps. If dst is not a
17216 null pointer, the converted characters are then stored into the array pointed to by dst.
17217 Conversion continues up to and including a terminating null wide character, which is also
17218 stored. Conversion stops earlier in two cases: when a wide character is reached that does
17219 not correspond to a valid multibyte character, or (if dst is not a null pointer) when the
17220 next multibyte character would exceed the limit of len total bytes to be stored into the
17221 array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb
17222 function.<sup><a href="#note338"><b>338)</b></a></sup>
17223 3 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
17224 pointer (if conversion stopped due to reaching a terminating null wide character) or the
17225 address just past the last wide character converted (if any). If conversion stopped due to
17226 reaching a terminating null wide character, the resulting state described is the initial
17229 4 If conversion stops because a wide character is reached that does not correspond to a
17230 valid multibyte character, an encoding error occurs: the wcsrtombs function stores the
17231 value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion
17232 state is unspecified. Otherwise, it returns the number of bytes in the resulting multibyte
17233 character sequence, not including the terminating null character (if any).
17238 <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
17239 include those necessary to reach the initial shift state immediately before the null byte.
17241 [<a name="p443" href="#p443">page 443</a>] (<a href="#Contents">Contents</a>)
17243 <a name="7.29" href="#7.29"><b> 7.29 Wide character classification and mapping utilities <wctype.h></b></a>
17244 <a name="7.29.1" href="#7.29.1"><b> 7.29.1 Introduction</b></a>
17245 1 The header <a href="#7.29"><wctype.h></a> defines one macro, and declares three data types and many
17246 functions.<sup><a href="#note339"><b>339)</b></a></sup>
17247 2 The types declared are
17249 described in <a href="#7.28.1">7.28.1</a>;
17251 which is a scalar type that can hold values which represent locale-specific character
17254 which is a scalar type that can hold values which represent locale-specific character
17256 3 The macro defined is WEOF (described in <a href="#7.28.1">7.28.1</a>).
17257 4 The functions declared are grouped as follows:
17258 -- Functions that provide wide character classification;
17259 -- Extensible functions that provide wide character classification;
17260 -- Functions that provide wide character case mapping;
17261 -- Extensible functions that provide wide character mapping.
17262 5 For all functions described in this subclause that accept an argument of type wint_t, the
17263 value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If
17264 this argument has any other value, the behavior is undefined.
17265 6 The behavior of these functions is affected by the LC_CTYPE category of the current
17271 <sup><a name="note339" href="#note339"><b>339)</b></a></sup> See ''future library directions'' (<a href="#7.30.13">7.30.13</a>).
17273 [<a name="p444" href="#p444">page 444</a>] (<a href="#Contents">Contents</a>)
17275 <a name="7.29.2" href="#7.29.2"><b> 7.29.2 Wide character classification utilities</b></a>
17276 1 The header <a href="#7.29"><wctype.h></a> declares several functions useful for classifying wide
17278 2 The term printing wide character refers to a member of a locale-specific set of wide
17279 characters, each of which occupies at least one printing position on a display device. The
17280 term control wide character refers to a member of a locale-specific set of wide characters
17281 that are not printing wide characters.
17282 <a name="7.29.2.1" href="#7.29.2.1"><b> 7.29.2.1 Wide character classification functions</b></a>
17283 1 The functions in this subclause return nonzero (true) if and only if the value of the
17284 argument wc conforms to that in the description of the function.
17285 2 Each of the following functions returns true for each wide character that corresponds (as
17286 if by a call to the wctob function) to a single-byte character for which the corresponding
17287 character classification function from <a href="#7.4.1">7.4.1</a> returns true, except that the iswgraph and
17288 iswpunct functions may differ with respect to wide characters other than L' ' that are
17289 both printing and white-space wide characters.<sup><a href="#note340"><b>340)</b></a></sup>
17290 Forward references: the wctob function (<a href="#7.28.6.1.2">7.28.6.1.2</a>).
17291 <a name="7.29.2.1.1" href="#7.29.2.1.1"><b> 7.29.2.1.1 The iswalnum function</b></a>
17293 1 #include <a href="#7.29"><wctype.h></a>
17294 int iswalnum(wint_t wc);
17295 <b> Description</b>
17296 2 The iswalnum function tests for any wide character for which iswalpha or
17298 <a name="7.29.2.1.2" href="#7.29.2.1.2"><b> 7.29.2.1.2 The iswalpha function</b></a>
17300 1 #include <a href="#7.29"><wctype.h></a>
17301 int iswalpha(wint_t wc);
17302 <b> Description</b>
17303 2 The iswalpha function tests for any wide character for which iswupper or
17304 iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
17306 <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
17307 iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true
17308 (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc)
17309 && iswspace(wc) is true, but not both.
17311 [<a name="p445" href="#p445">page 445</a>] (<a href="#Contents">Contents</a>)
17313 wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
17314 is true.<sup><a href="#note341"><b>341)</b></a></sup>
17315 <a name="7.29.2.1.3" href="#7.29.2.1.3"><b> 7.29.2.1.3 The iswblank function</b></a>
17317 1 #include <a href="#7.29"><wctype.h></a>
17318 int iswblank(wint_t wc);
17319 <b> Description</b>
17320 2 The iswblank function tests for any wide character that is a standard blank wide
17321 character or is one of a locale-specific set of wide characters for which iswspace is true
17322 and that is used to separate words within a line of text. The standard blank wide
17323 characters are the following: space (L' '), and horizontal tab (L'\t'). In the "C"
17324 locale, iswblank returns true only for the standard blank characters.
17325 <a name="7.29.2.1.4" href="#7.29.2.1.4"><b> 7.29.2.1.4 The iswcntrl function</b></a>
17327 1 #include <a href="#7.29"><wctype.h></a>
17328 int iswcntrl(wint_t wc);
17329 <b> Description</b>
17330 2 The iswcntrl function tests for any control wide character.
17331 <a name="7.29.2.1.5" href="#7.29.2.1.5"><b> 7.29.2.1.5 The iswdigit function</b></a>
17333 1 #include <a href="#7.29"><wctype.h></a>
17334 int iswdigit(wint_t wc);
17335 <b> Description</b>
17336 2 The iswdigit function tests for any wide character that corresponds to a decimal-digit
17337 character (as defined in <a href="#5.2.1">5.2.1</a>).
17338 <a name="7.29.2.1.6" href="#7.29.2.1.6"><b> 7.29.2.1.6 The iswgraph function</b></a>
17340 1 #include <a href="#7.29"><wctype.h></a>
17341 int iswgraph(wint_t wc);
17346 <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
17347 wide characters; all four combinations are possible.
17349 [<a name="p446" href="#p446">page 446</a>] (<a href="#Contents">Contents</a>)
17351 <b> Description</b>
17352 2 The iswgraph function tests for any wide character for which iswprint is true and
17353 iswspace is false.<sup><a href="#note342"><b>342)</b></a></sup>
17354 <a name="7.29.2.1.7" href="#7.29.2.1.7"><b> 7.29.2.1.7 The iswlower function</b></a>
17356 1 #include <a href="#7.29"><wctype.h></a>
17357 int iswlower(wint_t wc);
17358 <b> Description</b>
17359 2 The iswlower function tests for any wide character that corresponds to a lowercase
17360 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
17361 iswdigit, iswpunct, or iswspace is true.
17362 <a name="7.29.2.1.8" href="#7.29.2.1.8"><b> 7.29.2.1.8 The iswprint function</b></a>
17364 1 #include <a href="#7.29"><wctype.h></a>
17365 int iswprint(wint_t wc);
17366 <b> Description</b>
17367 2 The iswprint function tests for any printing wide character.
17368 <a name="7.29.2.1.9" href="#7.29.2.1.9"><b> 7.29.2.1.9 The iswpunct function</b></a>
17370 1 #include <a href="#7.29"><wctype.h></a>
17371 int iswpunct(wint_t wc);
17372 <b> Description</b>
17373 2 The iswpunct function tests for any printing wide character that is one of a locale-
17374 specific set of punctuation wide characters for which neither iswspace nor iswalnum
17376 <a name="7.29.2.1.10" href="#7.29.2.1.10"><b> 7.29.2.1.10 The iswspace function</b></a>
17378 1 #include <a href="#7.29"><wctype.h></a>
17379 int iswspace(wint_t wc);
17383 <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
17384 corresponding functions in <a href="#7.4.1">7.4.1</a> with respect to printing, white-space, single-byte execution
17385 characters other than ' '.
17387 [<a name="p447" href="#p447">page 447</a>] (<a href="#Contents">Contents</a>)
17389 <b> Description</b>
17390 2 The iswspace function tests for any wide character that corresponds to a locale-specific
17391 set of white-space wide characters for which none of iswalnum, iswgraph, or
17393 <a name="7.29.2.1.11" href="#7.29.2.1.11"><b> 7.29.2.1.11 The iswupper function</b></a>
17395 1 #include <a href="#7.29"><wctype.h></a>
17396 int iswupper(wint_t wc);
17397 <b> Description</b>
17398 2 The iswupper function tests for any wide character that corresponds to an uppercase
17399 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
17400 iswdigit, iswpunct, or iswspace is true.
17401 <a name="7.29.2.1.12" href="#7.29.2.1.12"><b> 7.29.2.1.12 The iswxdigit function</b></a>
17403 1 #include <a href="#7.29"><wctype.h></a>
17404 int iswxdigit(wint_t wc);
17405 <b> Description</b>
17406 2 The iswxdigit function tests for any wide character that corresponds to a
17407 hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
17408 <a name="7.29.2.2" href="#7.29.2.2"><b> 7.29.2.2 Extensible wide character classification functions</b></a>
17409 1 The functions wctype and iswctype provide extensible wide character classification
17410 as well as testing equivalent to that performed by the functions described in the previous
17411 subclause (<a href="#7.29.2.1">7.29.2.1</a>).
17412 <a name="7.29.2.2.1" href="#7.29.2.2.1"><b> 7.29.2.2.1 The iswctype function</b></a>
17414 1 #include <a href="#7.29"><wctype.h></a>
17415 int iswctype(wint_t wc, wctype_t desc);
17416 <b> Description</b>
17417 2 The iswctype function determines whether the wide character wc has the property
17418 described by desc. The current setting of the LC_CTYPE category shall be the same as
17419 during the call to wctype that returned the value desc.
17420 3 Each of the following expressions has a truth-value equivalent to the call to the wide
17421 character classification function (<a href="#7.29.2.1">7.29.2.1</a>) in the comment that follows the expression:
17423 [<a name="p448" href="#p448">page 448</a>] (<a href="#Contents">Contents</a>)
17425 iswctype(wc, wctype("alnum")) // iswalnum(wc)
17426 iswctype(wc, wctype("alpha")) // iswalpha(wc)
17427 iswctype(wc, wctype("blank")) // iswblank(wc)
17428 iswctype(wc, wctype("cntrl")) // iswcntrl(wc)
17429 iswctype(wc, wctype("digit")) // iswdigit(wc)
17430 iswctype(wc, wctype("graph")) // iswgraph(wc)
17431 iswctype(wc, wctype("lower")) // iswlower(wc)
17432 iswctype(wc, wctype("print")) // iswprint(wc)
17433 iswctype(wc, wctype("punct")) // iswpunct(wc)
17434 iswctype(wc, wctype("space")) // iswspace(wc)
17435 iswctype(wc, wctype("upper")) // iswupper(wc)
17436 iswctype(wc, wctype("xdigit")) // iswxdigit(wc)
17438 4 The iswctype function returns nonzero (true) if and only if the value of the wide
17439 character wc has the property described by desc. If desc is zero, the iswctype
17440 function returns zero (false).
17441 Forward references: the wctype function (<a href="#7.29.2.2.2">7.29.2.2.2</a>).
17442 <a name="7.29.2.2.2" href="#7.29.2.2.2"><b> 7.29.2.2.2 The wctype function</b></a>
17444 1 #include <a href="#7.29"><wctype.h></a>
17445 wctype_t wctype(const char *property);
17446 <b> Description</b>
17447 2 The wctype function constructs a value with type wctype_t that describes a class of
17448 wide characters identified by the string argument property.
17449 3 The strings listed in the description of the iswctype function shall be valid in all
17450 locales as property arguments to the wctype function.
17452 4 If property identifies a valid class of wide characters according to the LC_CTYPE
17453 category of the current locale, the wctype function returns a nonzero value that is valid
17454 as the second argument to the iswctype function; otherwise, it returns zero.
17456 [<a name="p449" href="#p449">page 449</a>] (<a href="#Contents">Contents</a>)
17458 <a name="7.29.3" href="#7.29.3"><b> 7.29.3 Wide character case mapping utilities</b></a>
17459 1 The header <a href="#7.29"><wctype.h></a> declares several functions useful for mapping wide characters.
17460 <a name="7.29.3.1" href="#7.29.3.1"><b> 7.29.3.1 Wide character case mapping functions</b></a>
17461 <a name="7.29.3.1.1" href="#7.29.3.1.1"><b> 7.29.3.1.1 The towlower function</b></a>
17463 1 #include <a href="#7.29"><wctype.h></a>
17464 wint_t towlower(wint_t wc);
17465 <b> Description</b>
17466 2 The towlower function converts an uppercase letter to a corresponding lowercase letter.
17468 3 If the argument is a wide character for which iswupper is true and there are one or
17469 more corresponding wide characters, as specified by the current locale, for which
17470 iswlower is true, the towlower function returns one of the corresponding wide
17471 characters (always the same one for any given locale); otherwise, the argument is
17472 returned unchanged.
17473 <a name="7.29.3.1.2" href="#7.29.3.1.2"><b> 7.29.3.1.2 The towupper function</b></a>
17475 1 #include <a href="#7.29"><wctype.h></a>
17476 wint_t towupper(wint_t wc);
17477 <b> Description</b>
17478 2 The towupper function converts a lowercase letter to a corresponding uppercase letter.
17480 3 If the argument is a wide character for which iswlower is true and there are one or
17481 more corresponding wide characters, as specified by the current locale, for which
17482 iswupper is true, the towupper function returns one of the corresponding wide
17483 characters (always the same one for any given locale); otherwise, the argument is
17484 returned unchanged.
17485 <a name="7.29.3.2" href="#7.29.3.2"><b> 7.29.3.2 Extensible wide character case mapping functions</b></a>
17486 1 The functions wctrans and towctrans provide extensible wide character mapping as
17487 well as case mapping equivalent to that performed by the functions described in the
17488 previous subclause (<a href="#7.29.3.1">7.29.3.1</a>).
17490 [<a name="p450" href="#p450">page 450</a>] (<a href="#Contents">Contents</a>)
17492 <a name="7.29.3.2.1" href="#7.29.3.2.1"><b> 7.29.3.2.1 The towctrans function</b></a>
17494 1 #include <a href="#7.29"><wctype.h></a>
17495 wint_t towctrans(wint_t wc, wctrans_t desc);
17496 <b> Description</b>
17497 2 The towctrans function maps the wide character wc using the mapping described by
17498 desc. The current setting of the LC_CTYPE category shall be the same as during the call
17499 to wctrans that returned the value desc.
17500 3 Each of the following expressions behaves the same as the call to the wide character case
17501 mapping function (<a href="#7.29.3.1">7.29.3.1</a>) in the comment that follows the expression:
17502 towctrans(wc, wctrans("tolower")) // towlower(wc)
17503 towctrans(wc, wctrans("toupper")) // towupper(wc)
17505 4 The towctrans function returns the mapped value of wc using the mapping described
17506 by desc. If desc is zero, the towctrans function returns the value of wc.
17507 <a name="7.29.3.2.2" href="#7.29.3.2.2"><b> 7.29.3.2.2 The wctrans function</b></a>
17509 1 #include <a href="#7.29"><wctype.h></a>
17510 wctrans_t wctrans(const char *property);
17511 <b> Description</b>
17512 2 The wctrans function constructs a value with type wctrans_t that describes a
17513 mapping between wide characters identified by the string argument property.
17514 3 The strings listed in the description of the towctrans function shall be valid in all
17515 locales as property arguments to the wctrans function.
17517 4 If property identifies a valid mapping of wide characters according to the LC_CTYPE
17518 category of the current locale, the wctrans function returns a nonzero value that is valid
17519 as the second argument to the towctrans function; otherwise, it returns zero.
17521 [<a name="p451" href="#p451">page 451</a>] (<a href="#Contents">Contents</a>)
17523 <a name="7.30" href="#7.30"><b> 7.30 Future library directions</b></a>
17524 1 The following names are grouped under individual headers for convenience. All external
17525 names described below are reserved no matter what headers are included by the program.
17526 <a name="7.30.1" href="#7.30.1"><b> 7.30.1 Complex arithmetic <complex.h></b></a>
17527 1 The function names
17529 cerfc clog10 clgamma
17530 cexp2 clog1p ctgamma
17531 and the same names suffixed with f or l may be added to the declarations in the
17532 <a href="#7.3"><complex.h></a> header.
17533 <a name="7.30.2" href="#7.30.2"><b> 7.30.2 Character handling <ctype.h></b></a>
17534 1 Function names that begin with either is or to, and a lowercase letter may be added to
17535 the declarations in the <a href="#7.4"><ctype.h></a> header.
17536 <a name="7.30.3" href="#7.30.3"><b> 7.30.3 Errors <errno.h></b></a>
17537 1 Macros that begin with E and a digit or E and an uppercase letter may be added to the
17538 declarations in the <a href="#7.5"><errno.h></a> header.
17539 <a name="7.30.4" href="#7.30.4"><b> 7.30.4 Format conversion of integer types <inttypes.h></b></a>
17540 1 Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
17541 added to the macros defined in the <a href="#7.8"><inttypes.h></a> header.
17542 <a name="7.30.5" href="#7.30.5"><b> 7.30.5 Localization <locale.h></b></a>
17543 1 Macros that begin with LC_ and an uppercase letter may be added to the definitions in
17544 the <a href="#7.11"><locale.h></a> header.
17545 <a name="7.30.6" href="#7.30.6"><b> 7.30.6 Signal handling <signal.h></b></a>
17546 1 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
17547 letter may be added to the definitions in the <a href="#7.14"><signal.h></a> header.
17548 <a name="7.30.7" href="#7.30.7"><b> 7.30.7 Boolean type and values <stdbool.h></b></a>
17549 1 The ability to undefine and perhaps then redefine the macros bool, true, and false is
17550 an obsolescent feature.
17551 <a name="7.30.8" href="#7.30.8"><b> 7.30.8 Integer types <stdint.h></b></a>
17552 1 Typedef names beginning with int or uint and ending with _t may be added to the
17553 types defined in the <a href="#7.20"><stdint.h></a> header. Macro names beginning with INT or UINT
17554 and ending with _MAX, _MIN, or _C may be added to the macros defined in the
17555 <a href="#7.20"><stdint.h></a> header.
17557 [<a name="p452" href="#p452">page 452</a>] (<a href="#Contents">Contents</a>)
17559 <a name="7.30.9" href="#7.30.9"><b> 7.30.9 Input/output <stdio.h></b></a>
17560 1 Lowercase letters may be added to the conversion specifiers and length modifiers in
17561 fprintf and fscanf. Other characters may be used in extensions.
17562 2 The use of ungetc on a binary stream where the file position indicator is zero prior to *
17563 the call is an obsolescent feature.
17564 <a name="7.30.10" href="#7.30.10"><b> 7.30.10 General utilities <stdlib.h></b></a>
17565 1 Function names that begin with str and a lowercase letter may be added to the
17566 declarations in the <a href="#7.22"><stdlib.h></a> header.
17567 <a name="7.30.11" href="#7.30.11"><b> 7.30.11 String handling <string.h></b></a>
17568 1 Function names that begin with str, mem, or wcs and a lowercase letter may be added
17569 to the declarations in the <a href="#7.23"><string.h></a> header.
17570 <a name="7.30.12" href="#7.30.12"><b> 7.30.12 Extended multibyte and wide character utilities <wchar.h></b></a>
17571 1 Function names that begin with wcs and a lowercase letter may be added to the
17572 declarations in the <a href="#7.28"><wchar.h></a> header.
17573 2 Lowercase letters may be added to the conversion specifiers and length modifiers in
17574 fwprintf and fwscanf. Other characters may be used in extensions.
17575 <a name="7.30.13" href="#7.30.13"><b> 7.30.13 Wide character classification and mapping utilities</b></a>
17576 <a href="#7.29"><wctype.h></a>
17577 1 Function names that begin with is or to and a lowercase letter may be added to the
17578 declarations in the <a href="#7.29"><wctype.h></a> header.
17580 [<a name="p453" href="#p453">page 453</a>] (<a href="#Contents">Contents</a>)
17582 <a name="A" href="#A"><b> Annex A</b></a>
17584 Language syntax summary
17585 1 NOTE The notation is described in <a href="#6.1">6.1</a>.
17587 <a name="A.1" href="#A.1"><b> A.1 Lexical grammar</b></a>
17588 <a name="A.1.1" href="#A.1.1"><b> A.1.1 Lexical elements</b></a>
17589 (<a href="#6.4">6.4</a>) token:
17595 (<a href="#6.4">6.4</a>) preprocessing-token:
17602 each non-white-space character that cannot be one of the above
17604 [<a name="p454" href="#p454">page 454</a>] (<a href="#Contents">Contents</a>)
17606 <a name="A.1.2" href="#A.1.2"><b>A.1.2 Keywords</b></a>
17607 (<a href="#6.4.1">6.4.1</a>) keyword: one of
17613 const register _Alignas
17614 continue restrict _Atomic
17615 default return _Bool
17617 double signed _Generic
17618 else sizeof _Imaginary
17619 enum static _Noreturn
17620 extern struct _Static_assert
17621 float switch _Thread_local
17623 <a name="A.1.3" href="#A.1.3"><b>A.1.3 Identifiers</b></a>
17624 (<a href="#6.4.2.1">6.4.2.1</a>) identifier:
17625 identifier-nondigit
17626 identifier identifier-nondigit
17628 (<a href="#6.4.2.1">6.4.2.1</a>) identifier-nondigit:
17630 universal-character-name
17631 other implementation-defined characters
17632 (<a href="#6.4.2.1">6.4.2.1</a>) nondigit: one of
17633 _ a b c d e f g h i j k l m
17634 n o p q r s t u v w x y z
17635 A B C D E F G H I J K L M
17636 N O P Q R S T U V W X Y Z
17637 (<a href="#6.4.2.1">6.4.2.1</a>) digit: one of
17638 0 1 2 3 4 5 6 7 8 9
17640 [<a name="p455" href="#p455">page 455</a>] (<a href="#Contents">Contents</a>)
17642 <a name="A.1.4" href="#A.1.4"><b>A.1.4 Universal character names</b></a>
17643 (<a href="#6.4.3">6.4.3</a>) universal-character-name:
17645 \U hex-quad hex-quad
17646 (<a href="#6.4.3">6.4.3</a>) hex-quad:
17647 hexadecimal-digit hexadecimal-digit
17648 hexadecimal-digit hexadecimal-digit
17649 <a name="A.1.5" href="#A.1.5"><b>A.1.5 Constants</b></a>
17650 (<a href="#6.4.4">6.4.4</a>) constant:
17653 enumeration-constant
17655 (<a href="#6.4.4.1">6.4.4.1</a>) integer-constant:
17656 decimal-constant integer-suffixopt
17657 octal-constant integer-suffixopt
17658 hexadecimal-constant integer-suffixopt
17659 (<a href="#6.4.4.1">6.4.4.1</a>) decimal-constant:
17661 decimal-constant digit
17662 (<a href="#6.4.4.1">6.4.4.1</a>) octal-constant:
17664 octal-constant octal-digit
17665 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-constant:
17666 hexadecimal-prefix hexadecimal-digit
17667 hexadecimal-constant hexadecimal-digit
17668 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-prefix: one of
17670 (<a href="#6.4.4.1">6.4.4.1</a>) nonzero-digit: one of
17672 (<a href="#6.4.4.1">6.4.4.1</a>) octal-digit: one of
17675 [<a name="p456" href="#p456">page 456</a>] (<a href="#Contents">Contents</a>)
17677 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-digit: one of
17678 0 1 2 3 4 5 6 7 8 9
17681 (<a href="#6.4.4.1">6.4.4.1</a>) integer-suffix:
17682 unsigned-suffix long-suffixopt
17683 unsigned-suffix long-long-suffix
17684 long-suffix unsigned-suffixopt
17685 long-long-suffix unsigned-suffixopt
17686 (<a href="#6.4.4.1">6.4.4.1</a>) unsigned-suffix: one of
17688 (<a href="#6.4.4.1">6.4.4.1</a>) long-suffix: one of
17690 (<a href="#6.4.4.1">6.4.4.1</a>) long-long-suffix: one of
17692 (<a href="#6.4.4.2">6.4.4.2</a>) floating-constant:
17693 decimal-floating-constant
17694 hexadecimal-floating-constant
17695 (<a href="#6.4.4.2">6.4.4.2</a>) decimal-floating-constant:
17696 fractional-constant exponent-partopt floating-suffixopt
17697 digit-sequence exponent-part floating-suffixopt
17698 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-floating-constant:
17699 hexadecimal-prefix hexadecimal-fractional-constant
17700 binary-exponent-part floating-suffixopt
17701 hexadecimal-prefix hexadecimal-digit-sequence
17702 binary-exponent-part floating-suffixopt
17703 (<a href="#6.4.4.2">6.4.4.2</a>) fractional-constant:
17704 digit-sequenceopt . digit-sequence
17706 (<a href="#6.4.4.2">6.4.4.2</a>) exponent-part:
17707 e signopt digit-sequence
17708 E signopt digit-sequence
17709 (<a href="#6.4.4.2">6.4.4.2</a>) sign: one of
17712 [<a name="p457" href="#p457">page 457</a>] (<a href="#Contents">Contents</a>)
17714 (<a href="#6.4.4.2">6.4.4.2</a>) digit-sequence:
17716 digit-sequence digit
17717 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-fractional-constant:
17718 hexadecimal-digit-sequenceopt .
17719 hexadecimal-digit-sequence
17720 hexadecimal-digit-sequence .
17721 (<a href="#6.4.4.2">6.4.4.2</a>) binary-exponent-part:
17722 p signopt digit-sequence
17723 P signopt digit-sequence
17724 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-digit-sequence:
17726 hexadecimal-digit-sequence hexadecimal-digit
17727 (<a href="#6.4.4.2">6.4.4.2</a>) floating-suffix: one of
17729 (<a href="#6.4.4.3">6.4.4.3</a>) enumeration-constant:
17731 (<a href="#6.4.4.4">6.4.4.4</a>) character-constant:
17732 ' c-char-sequence '
17733 L' c-char-sequence '
17734 u' c-char-sequence '
17735 U' c-char-sequence '
17736 (<a href="#6.4.4.4">6.4.4.4</a>) c-char-sequence:
17738 c-char-sequence c-char
17739 (<a href="#6.4.4.4">6.4.4.4</a>) c-char:
17740 any member of the source character set except
17741 the single-quote ', backslash \, or new-line character
17743 (<a href="#6.4.4.4">6.4.4.4</a>) escape-sequence:
17744 simple-escape-sequence
17745 octal-escape-sequence
17746 hexadecimal-escape-sequence
17747 universal-character-name
17749 [<a name="p458" href="#p458">page 458</a>] (<a href="#Contents">Contents</a>)
17751 (<a href="#6.4.4.4">6.4.4.4</a>) simple-escape-sequence: one of
17753 \a \b \f \n \r \t \v
17754 (<a href="#6.4.4.4">6.4.4.4</a>) octal-escape-sequence:
17756 \ octal-digit octal-digit
17757 \ octal-digit octal-digit octal-digit
17758 (<a href="#6.4.4.4">6.4.4.4</a>) hexadecimal-escape-sequence:
17759 \x hexadecimal-digit
17760 hexadecimal-escape-sequence hexadecimal-digit
17761 <a name="A.1.6" href="#A.1.6"><b>A.1.6 String literals</b></a>
17762 (<a href="#6.4.5">6.4.5</a>) string-literal:
17763 encoding-prefixopt " s-char-sequenceopt "
17764 (<a href="#6.4.5">6.4.5</a>) encoding-prefix:
17769 (<a href="#6.4.5">6.4.5</a>) s-char-sequence:
17771 s-char-sequence s-char
17772 (<a href="#6.4.5">6.4.5</a>) s-char:
17773 any member of the source character set except
17774 the double-quote ", backslash \, or new-line character
17776 <a name="A.1.7" href="#A.1.7"><b>A.1.7 Punctuators</b></a>
17777 (<a href="#6.4.6">6.4.6</a>) punctuator: one of
17778 [ ] ( ) { } . ->
17779 ++ -- & * + - ~ !
17780 / % << >> < > <= >= == != ^ | && ||
17782 = *= /= %= += -= <<= >>= &= ^= |=
17784 <: :> <% %> %: %:%:
17786 [<a name="p459" href="#p459">page 459</a>] (<a href="#Contents">Contents</a>)
17788 <a name="A.1.8" href="#A.1.8"><b>A.1.8 Header names</b></a>
17789 (<a href="#6.4.7">6.4.7</a>) header-name:
17790 < h-char-sequence >
17791 " q-char-sequence "
17792 (<a href="#6.4.7">6.4.7</a>) h-char-sequence:
17794 h-char-sequence h-char
17795 (<a href="#6.4.7">6.4.7</a>) h-char:
17796 any member of the source character set except
17797 the new-line character and >
17798 (<a href="#6.4.7">6.4.7</a>) q-char-sequence:
17800 q-char-sequence q-char
17801 (<a href="#6.4.7">6.4.7</a>) q-char:
17802 any member of the source character set except
17803 the new-line character and "
17804 <a name="A.1.9" href="#A.1.9"><b>A.1.9 Preprocessing numbers</b></a>
17805 (<a href="#6.4.8">6.4.8</a>) pp-number:
17809 pp-number identifier-nondigit
17816 [<a name="p460" href="#p460">page 460</a>] (<a href="#Contents">Contents</a>)
17818 <a name="A.2" href="#A.2"><b>A.2 Phrase structure grammar</b></a>
17819 <a name="A.2.1" href="#A.2.1"><b>A.2.1 Expressions</b></a>
17820 (<a href="#6.5.1">6.5.1</a>) primary-expression:
17826 (<a href="#6.5.1.1">6.5.1.1</a>) generic-selection:
17827 _Generic ( assignment-expression , generic-assoc-list )
17828 (<a href="#6.5.1.1">6.5.1.1</a>) generic-assoc-list:
17829 generic-association
17830 generic-assoc-list , generic-association
17831 (<a href="#6.5.1.1">6.5.1.1</a>) generic-association:
17832 type-name : assignment-expression
17833 default : assignment-expression
17834 (<a href="#6.5.2">6.5.2</a>) postfix-expression:
17836 postfix-expression [ expression ]
17837 postfix-expression ( argument-expression-listopt )
17838 postfix-expression . identifier
17839 postfix-expression -> identifier
17840 postfix-expression ++
17841 postfix-expression --
17842 ( type-name ) { initializer-list }
17843 ( type-name ) { initializer-list , }
17844 (<a href="#6.5.2">6.5.2</a>) argument-expression-list:
17845 assignment-expression
17846 argument-expression-list , assignment-expression
17847 (<a href="#6.5.3">6.5.3</a>) unary-expression:
17849 ++ unary-expression
17850 -- unary-expression
17851 unary-operator cast-expression
17852 sizeof unary-expression
17853 sizeof ( type-name )
17854 alignof ( type-name )
17856 [<a name="p461" href="#p461">page 461</a>] (<a href="#Contents">Contents</a>)
17858 (<a href="#6.5.3">6.5.3</a>) unary-operator: one of
17860 (<a href="#6.5.4">6.5.4</a>) cast-expression:
17862 ( type-name ) cast-expression
17863 (<a href="#6.5.5">6.5.5</a>) multiplicative-expression:
17865 multiplicative-expression * cast-expression
17866 multiplicative-expression / cast-expression
17867 multiplicative-expression % cast-expression
17868 (<a href="#6.5.6">6.5.6</a>) additive-expression:
17869 multiplicative-expression
17870 additive-expression + multiplicative-expression
17871 additive-expression - multiplicative-expression
17872 (<a href="#6.5.7">6.5.7</a>) shift-expression:
17873 additive-expression
17874 shift-expression << additive-expression
17875 shift-expression >> additive-expression
17876 (<a href="#6.5.8">6.5.8</a>) relational-expression:
17878 relational-expression < shift-expression
17879 relational-expression > shift-expression
17880 relational-expression <= shift-expression
17881 relational-expression >= shift-expression
17882 (<a href="#6.5.9">6.5.9</a>) equality-expression:
17883 relational-expression
17884 equality-expression == relational-expression
17885 equality-expression != relational-expression
17886 (<a href="#6.5.10">6.5.10</a>) AND-expression:
17887 equality-expression
17888 AND-expression & equality-expression
17889 (<a href="#6.5.11">6.5.11</a>) exclusive-OR-expression:
17891 exclusive-OR-expression ^ AND-expression
17893 [<a name="p462" href="#p462">page 462</a>] (<a href="#Contents">Contents</a>)
17895 (<a href="#6.5.12">6.5.12</a>) inclusive-OR-expression:
17896 exclusive-OR-expression
17897 inclusive-OR-expression | exclusive-OR-expression
17898 (<a href="#6.5.13">6.5.13</a>) logical-AND-expression:
17899 inclusive-OR-expression
17900 logical-AND-expression && inclusive-OR-expression
17901 (<a href="#6.5.14">6.5.14</a>) logical-OR-expression:
17902 logical-AND-expression
17903 logical-OR-expression || logical-AND-expression
17904 (<a href="#6.5.15">6.5.15</a>) conditional-expression:
17905 logical-OR-expression
17906 logical-OR-expression ? expression : conditional-expression
17907 (<a href="#6.5.16">6.5.16</a>) assignment-expression:
17908 conditional-expression
17909 unary-expression assignment-operator assignment-expression
17910 (<a href="#6.5.16">6.5.16</a>) assignment-operator: one of
17911 = *= /= %= += -= <<= >>= &= ^= |=
17912 (<a href="#6.5.17">6.5.17</a>) expression:
17913 assignment-expression
17914 expression , assignment-expression
17915 (<a href="#6.6">6.6</a>) constant-expression:
17916 conditional-expression
17917 <a name="A.2.2" href="#A.2.2"><b>A.2.2 Declarations</b></a>
17918 (<a href="#6.7">6.7</a>) declaration:
17919 declaration-specifiers init-declarator-listopt ;
17920 static_assert-declaration
17921 (<a href="#6.7">6.7</a>) declaration-specifiers:
17922 storage-class-specifier declaration-specifiersopt
17923 type-specifier declaration-specifiersopt
17924 type-qualifier declaration-specifiersopt
17925 function-specifier declaration-specifiersopt
17926 alignment-specifier declaration-specifiersopt
17927 (<a href="#6.7">6.7</a>) init-declarator-list:
17929 init-declarator-list , init-declarator
17931 [<a name="p463" href="#p463">page 463</a>] (<a href="#Contents">Contents</a>)
17933 (<a href="#6.7">6.7</a>) init-declarator:
17935 declarator = initializer
17936 (<a href="#6.7.1">6.7.1</a>) storage-class-specifier:
17943 (<a href="#6.7.2">6.7.2</a>) type-specifier:
17955 atomic-type-specifier
17956 struct-or-union-specifier
17959 (<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union-specifier:
17960 struct-or-union identifieropt { struct-declaration-list }
17961 struct-or-union identifier
17962 (<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union:
17965 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration-list:
17967 struct-declaration-list struct-declaration
17968 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration:
17969 specifier-qualifier-list struct-declarator-listopt ;
17970 static_assert-declaration
17972 [<a name="p464" href="#p464">page 464</a>] (<a href="#Contents">Contents</a>)
17974 (<a href="#6.7.2.1">6.7.2.1</a>) specifier-qualifier-list:
17975 type-specifier specifier-qualifier-listopt
17976 type-qualifier specifier-qualifier-listopt
17977 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator-list:
17979 struct-declarator-list , struct-declarator
17980 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator:
17982 declaratoropt : constant-expression
17983 (<a href="#6.7.2.2">6.7.2.2</a>) enum-specifier:
17984 enum identifieropt { enumerator-list }
17985 enum identifieropt { enumerator-list , }
17987 (<a href="#6.7.2.2">6.7.2.2</a>) enumerator-list:
17989 enumerator-list , enumerator
17990 (<a href="#6.7.2.2">6.7.2.2</a>) enumerator:
17991 enumeration-constant
17992 enumeration-constant = constant-expression
17993 (<a href="#6.7.2.4">6.7.2.4</a>) atomic-type-specifier:
17994 _Atomic ( type-name )
17995 (<a href="#6.7.3">6.7.3</a>) type-qualifier:
18000 (<a href="#6.7.4">6.7.4</a>) function-specifier:
18003 (<a href="#6.7.5">6.7.5</a>) alignment-specifier:
18004 _Alignas ( type-name )
18005 _Alignas ( constant-expression )
18006 (<a href="#6.7.6">6.7.6</a>) declarator:
18007 pointeropt direct-declarator
18009 [<a name="p465" href="#p465">page 465</a>] (<a href="#Contents">Contents</a>)
18011 (<a href="#6.7.6">6.7.6</a>) direct-declarator:
18014 direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
18015 direct-declarator [ static type-qualifier-listopt assignment-expression ]
18016 direct-declarator [ type-qualifier-list static assignment-expression ]
18017 direct-declarator [ type-qualifier-listopt * ]
18018 direct-declarator ( parameter-type-list )
18019 direct-declarator ( identifier-listopt )
18020 (<a href="#6.7.6">6.7.6</a>) pointer:
18021 * type-qualifier-listopt
18022 * type-qualifier-listopt pointer
18023 (<a href="#6.7.6">6.7.6</a>) type-qualifier-list:
18025 type-qualifier-list type-qualifier
18026 (<a href="#6.7.6">6.7.6</a>) parameter-type-list:
18028 parameter-list , ...
18029 (<a href="#6.7.6">6.7.6</a>) parameter-list:
18030 parameter-declaration
18031 parameter-list , parameter-declaration
18032 (<a href="#6.7.6">6.7.6</a>) parameter-declaration:
18033 declaration-specifiers declarator
18034 declaration-specifiers abstract-declaratoropt
18035 (<a href="#6.7.6">6.7.6</a>) identifier-list:
18037 identifier-list , identifier
18038 (<a href="#6.7.7">6.7.7</a>) type-name:
18039 specifier-qualifier-list abstract-declaratoropt
18040 (<a href="#6.7.7">6.7.7</a>) abstract-declarator:
18042 pointeropt direct-abstract-declarator
18044 [<a name="p466" href="#p466">page 466</a>] (<a href="#Contents">Contents</a>)
18046 (<a href="#6.7.7">6.7.7</a>) direct-abstract-declarator:
18047 ( abstract-declarator )
18048 direct-abstract-declaratoropt [ type-qualifier-listopt
18049 assignment-expressionopt ]
18050 direct-abstract-declaratoropt [ static type-qualifier-listopt
18051 assignment-expression ]
18052 direct-abstract-declaratoropt [ type-qualifier-list static
18053 assignment-expression ]
18054 direct-abstract-declaratoropt [ * ]
18055 direct-abstract-declaratoropt ( parameter-type-listopt )
18056 (<a href="#6.7.8">6.7.8</a>) typedef-name:
18058 (<a href="#6.7.9">6.7.9</a>) initializer:
18059 assignment-expression
18060 { initializer-list }
18061 { initializer-list , }
18062 (<a href="#6.7.9">6.7.9</a>) initializer-list:
18063 designationopt initializer
18064 initializer-list , designationopt initializer
18065 (<a href="#6.7.9">6.7.9</a>) designation:
18067 (<a href="#6.7.9">6.7.9</a>) designator-list:
18069 designator-list designator
18070 (<a href="#6.7.9">6.7.9</a>) designator:
18071 [ constant-expression ]
18073 (<a href="#6.7.10">6.7.10</a>) static_assert-declaration:
18074 _Static_assert ( constant-expression , string-literal ) ;
18076 [<a name="p467" href="#p467">page 467</a>] (<a href="#Contents">Contents</a>)
18078 <a name="A.2.3" href="#A.2.3"><b>A.2.3 Statements</b></a>
18079 (<a href="#6.8">6.8</a>) statement:
18082 expression-statement
18083 selection-statement
18084 iteration-statement
18086 (<a href="#6.8.1">6.8.1</a>) labeled-statement:
18087 identifier : statement
18088 case constant-expression : statement
18089 default : statement
18090 (<a href="#6.8.2">6.8.2</a>) compound-statement:
18091 { block-item-listopt }
18092 (<a href="#6.8.2">6.8.2</a>) block-item-list:
18094 block-item-list block-item
18095 (<a href="#6.8.2">6.8.2</a>) block-item:
18098 (<a href="#6.8.3">6.8.3</a>) expression-statement:
18100 (<a href="#6.8.4">6.8.4</a>) selection-statement:
18101 if ( expression ) statement
18102 if ( expression ) statement else statement
18103 switch ( expression ) statement
18104 (<a href="#6.8.5">6.8.5</a>) iteration-statement:
18105 while ( expression ) statement
18106 do statement while ( expression ) ;
18107 for ( expressionopt ; expressionopt ; expressionopt ) statement
18108 for ( declaration expressionopt ; expressionopt ) statement
18109 (<a href="#6.8.6">6.8.6</a>) jump-statement:
18113 return expressionopt ;
18115 [<a name="p468" href="#p468">page 468</a>] (<a href="#Contents">Contents</a>)
18117 <a name="A.2.4" href="#A.2.4"><b>A.2.4 External definitions</b></a>
18118 (<a href="#6.9">6.9</a>) translation-unit:
18119 external-declaration
18120 translation-unit external-declaration
18121 (<a href="#6.9">6.9</a>) external-declaration:
18122 function-definition
18124 (<a href="#6.9.1">6.9.1</a>) function-definition:
18125 declaration-specifiers declarator declaration-listopt compound-statement
18126 (<a href="#6.9.1">6.9.1</a>) declaration-list:
18128 declaration-list declaration
18129 <a name="A.3" href="#A.3"><b>A.3 Preprocessing directives</b></a>
18130 (<a href="#6.10">6.10</a>) preprocessing-file:
18132 (<a href="#6.10">6.10</a>) group:
18135 (<a href="#6.10">6.10</a>) group-part:
18140 (<a href="#6.10">6.10</a>) if-section:
18141 if-group elif-groupsopt else-groupopt endif-line
18142 (<a href="#6.10">6.10</a>) if-group:
18143 # if constant-expression new-line groupopt
18144 # ifdef identifier new-line groupopt
18145 # ifndef identifier new-line groupopt
18146 (<a href="#6.10">6.10</a>) elif-groups:
18148 elif-groups elif-group
18149 (<a href="#6.10">6.10</a>) elif-group:
18150 # elif constant-expression new-line groupopt
18152 [<a name="p469" href="#p469">page 469</a>] (<a href="#Contents">Contents</a>)
18154 (<a href="#6.10">6.10</a>) else-group:
18155 # else new-line groupopt
18156 (<a href="#6.10">6.10</a>) endif-line:
18158 (<a href="#6.10">6.10</a>) control-line:
18159 # include pp-tokens new-line
18160 # define identifier replacement-list new-line
18161 # define identifier lparen identifier-listopt )
18162 replacement-list new-line
18163 # define identifier lparen ... ) replacement-list new-line
18164 # define identifier lparen identifier-list , ... )
18165 replacement-list new-line
18166 # undef identifier new-line
18167 # line pp-tokens new-line
18168 # error pp-tokensopt new-line
18169 # pragma pp-tokensopt new-line
18171 (<a href="#6.10">6.10</a>) text-line:
18172 pp-tokensopt new-line
18173 (<a href="#6.10">6.10</a>) non-directive:
18175 (<a href="#6.10">6.10</a>) lparen:
18176 a ( character not immediately preceded by white-space
18177 (<a href="#6.10">6.10</a>) replacement-list:
18179 (<a href="#6.10">6.10</a>) pp-tokens:
18180 preprocessing-token
18181 pp-tokens preprocessing-token
18182 (<a href="#6.10">6.10</a>) new-line:
18183 the new-line character
18185 [<a name="p470" href="#p470">page 470</a>] (<a href="#Contents">Contents</a>)
18187 <a name="B" href="#B"><b> Annex B</b></a>
18190 <a name="B.1" href="#B.1"><b>B.1 Diagnostics <assert.h></b></a>
18193 void assert(scalar expression);
18194 <a name="B.2" href="#B.2"><b>B.2 Complex <complex.h></b></a>
18195 __STDC_NO_COMPLEX__ imaginary
18196 complex _Imaginary_I
18198 #pragma STDC CX_LIMITED_RANGE on-off-switch
18199 double complex cacos(double complex z);
18200 float complex cacosf(float complex z);
18201 long double complex cacosl(long double complex z);
18202 double complex casin(double complex z);
18203 float complex casinf(float complex z);
18204 long double complex casinl(long double complex z);
18205 double complex catan(double complex z);
18206 float complex catanf(float complex z);
18207 long double complex catanl(long double complex z);
18208 double complex ccos(double complex z);
18209 float complex ccosf(float complex z);
18210 long double complex ccosl(long double complex z);
18211 double complex csin(double complex z);
18212 float complex csinf(float complex z);
18213 long double complex csinl(long double complex z);
18214 double complex ctan(double complex z);
18215 float complex ctanf(float complex z);
18216 long double complex ctanl(long double complex z);
18217 double complex cacosh(double complex z);
18218 float complex cacoshf(float complex z);
18219 long double complex cacoshl(long double complex z);
18220 double complex casinh(double complex z);
18221 float complex casinhf(float complex z);
18222 long double complex casinhl(long double complex z);
18224 [<a name="p471" href="#p471">page 471</a>] (<a href="#Contents">Contents</a>)
18226 double complex catanh(double complex z);
18227 float complex catanhf(float complex z);
18228 long double complex catanhl(long double complex z);
18229 double complex ccosh(double complex z);
18230 float complex ccoshf(float complex z);
18231 long double complex ccoshl(long double complex z);
18232 double complex csinh(double complex z);
18233 float complex csinhf(float complex z);
18234 long double complex csinhl(long double complex z);
18235 double complex ctanh(double complex z);
18236 float complex ctanhf(float complex z);
18237 long double complex ctanhl(long double complex z);
18238 double complex cexp(double complex z);
18239 float complex cexpf(float complex z);
18240 long double complex cexpl(long double complex z);
18241 double complex clog(double complex z);
18242 float complex clogf(float complex z);
18243 long double complex clogl(long double complex z);
18244 double cabs(double complex z);
18245 float cabsf(float complex z);
18246 long double cabsl(long double complex z);
18247 double complex cpow(double complex x, double complex y);
18248 float complex cpowf(float complex x, float complex y);
18249 long double complex cpowl(long double complex x,
18250 long double complex y);
18251 double complex csqrt(double complex z);
18252 float complex csqrtf(float complex z);
18253 long double complex csqrtl(long double complex z);
18254 double carg(double complex z);
18255 float cargf(float complex z);
18256 long double cargl(long double complex z);
18257 double cimag(double complex z);
18258 float cimagf(float complex z);
18259 long double cimagl(long double complex z);
18260 double complex CMPLX(double x, double y);
18261 float complex CMPLXF(float x, float y);
18262 long double complex CMPLXL(long double x, long double y);
18263 double complex conj(double complex z);
18264 float complex conjf(float complex z);
18265 long double complex conjl(long double complex z);
18266 double complex cproj(double complex z);
18268 [<a name="p472" href="#p472">page 472</a>] (<a href="#Contents">Contents</a>)
18270 float complex cprojf(float complex z);
18271 long double complex cprojl(long double complex z);
18272 double creal(double complex z);
18273 float crealf(float complex z);
18274 long double creall(long double complex z);
18275 <a name="B.3" href="#B.3"><b>B.3 Character handling <ctype.h></b></a>
18276 int isalnum(int c);
18277 int isalpha(int c);
18278 int isblank(int c);
18279 int iscntrl(int c);
18280 int isdigit(int c);
18281 int isgraph(int c);
18282 int islower(int c);
18283 int isprint(int c);
18284 int ispunct(int c);
18285 int isspace(int c);
18286 int isupper(int c);
18287 int isxdigit(int c);
18288 int tolower(int c);
18289 int toupper(int c);
18290 <a name="B.4" href="#B.4"><b>B.4 Errors <errno.h></b></a>
18291 EDOM EILSEQ ERANGE errno
18292 __STDC_WANT_LIB_EXT1__
18294 <a name="B.5" href="#B.5"><b>B.5 Floating-point environment <fenv.h></b></a>
18295 fenv_t FE_OVERFLOW FE_TOWARDZERO
18296 fexcept_t FE_UNDERFLOW FE_UPWARD
18297 FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
18298 FE_INEXACT FE_DOWNWARD
18299 FE_INVALID FE_TONEAREST
18300 #pragma STDC FENV_ACCESS on-off-switch
18301 int feclearexcept(int excepts);
18302 int fegetexceptflag(fexcept_t *flagp, int excepts);
18303 int feraiseexcept(int excepts);
18304 int fesetexceptflag(const fexcept_t *flagp,
18306 int fetestexcept(int excepts);
18308 [<a name="p473" href="#p473">page 473</a>] (<a href="#Contents">Contents</a>)
18310 int fegetround(void);
18311 int fesetround(int round);
18312 int fegetenv(fenv_t *envp);
18313 int feholdexcept(fenv_t *envp);
18314 int fesetenv(const fenv_t *envp);
18315 int feupdateenv(const fenv_t *envp);
18316 <a name="B.6" href="#B.6"><b>B.6 Characteristics of floating types <float.h></b></a>
18317 FLT_ROUNDS DBL_DIG FLT_MAX
18318 FLT_EVAL_METHOD LDBL_DIG DBL_MAX
18319 FLT_HAS_SUBNORM FLT_MIN_EXP LDBL_MAX
18320 DBL_HAS_SUBNORM DBL_MIN_EXP FLT_EPSILON
18321 LDBL_HAS_SUBNORM LDBL_MIN_EXP DBL_EPSILON
18322 FLT_RADIX FLT_MIN_10_EXP LDBL_EPSILON
18323 FLT_MANT_DIG DBL_MIN_10_EXP FLT_MIN
18324 DBL_MANT_DIG LDBL_MIN_10_EXP DBL_MIN
18325 LDBL_MANT_DIG FLT_MAX_EXP LDBL_MIN
18326 FLT_DECIMAL_DIG DBL_MAX_EXP FLT_TRUE_MIN
18327 DBL_DECIMAL_DIG LDBL_MAX_EXP DBL_TRUE_MIN
18328 LDBL_DECIMAL_DIG FLT_MAX_10_EXP LDBL_TRUE_MIN
18329 DECIMAL_DIG DBL_MAX_10_EXP
18330 FLT_DIG LDBL_MAX_10_EXP
18331 <a name="B.7" href="#B.7"><b>B.7 Format conversion of integer types <inttypes.h></b></a>
18333 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
18334 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
18335 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
18336 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
18337 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
18338 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
18339 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
18340 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
18341 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
18342 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
18343 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
18344 intmax_t imaxabs(intmax_t j);
18345 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
18346 intmax_t strtoimax(const char * restrict nptr,
18347 char ** restrict endptr, int base);
18349 [<a name="p474" href="#p474">page 474</a>] (<a href="#Contents">Contents</a>)
18351 uintmax_t strtoumax(const char * restrict nptr,
18352 char ** restrict endptr, int base);
18353 intmax_t wcstoimax(const wchar_t * restrict nptr,
18354 wchar_t ** restrict endptr, int base);
18355 uintmax_t wcstoumax(const wchar_t * restrict nptr,
18356 wchar_t ** restrict endptr, int base);
18357 <a name="B.8" href="#B.8"><b>B.8 Alternative spellings <iso646.h></b></a>
18358 and bitor not_eq xor
18359 and_eq compl or xor_eq
18361 <a name="B.9" href="#B.9"><b>B.9 Sizes of integer types <limits.h></b></a>
18362 CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
18363 SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
18364 SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
18365 UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
18366 CHAR_MIN USHRT_MAX LONG_MAX
18367 <a name="B.10" href="#B.10"><b>B.10 Localization <locale.h></b></a>
18368 struct lconv LC_ALL LC_CTYPE LC_NUMERIC
18369 NULL LC_COLLATE LC_MONETARY LC_TIME
18370 char *setlocale(int category, const char *locale);
18371 struct lconv *localeconv(void);
18372 <a name="B.11" href="#B.11"><b>B.11 Mathematics <math.h></b></a>
18373 float_t FP_INFINITE FP_FAST_FMAL
18374 double_t FP_NAN FP_ILOGB0
18375 HUGE_VAL FP_NORMAL FP_ILOGBNAN
18376 HUGE_VALF FP_SUBNORMAL MATH_ERRNO
18377 HUGE_VALL FP_ZERO MATH_ERREXCEPT
18378 INFINITY FP_FAST_FMA math_errhandling
18380 #pragma STDC FP_CONTRACT on-off-switch
18381 int fpclassify(real-floating x);
18382 int isfinite(real-floating x);
18383 int isinf(real-floating x);
18384 int isnan(real-floating x);
18385 int isnormal(real-floating x);
18386 int signbit(real-floating x);
18388 [<a name="p475" href="#p475">page 475</a>] (<a href="#Contents">Contents</a>)
18390 double acos(double x);
18391 float acosf(float x);
18392 long double acosl(long double x);
18393 double asin(double x);
18394 float asinf(float x);
18395 long double asinl(long double x);
18396 double atan(double x);
18397 float atanf(float x);
18398 long double atanl(long double x);
18399 double atan2(double y, double x);
18400 float atan2f(float y, float x);
18401 long double atan2l(long double y, long double x);
18402 double cos(double x);
18403 float cosf(float x);
18404 long double cosl(long double x);
18405 double sin(double x);
18406 float sinf(float x);
18407 long double sinl(long double x);
18408 double tan(double x);
18409 float tanf(float x);
18410 long double tanl(long double x);
18411 double acosh(double x);
18412 float acoshf(float x);
18413 long double acoshl(long double x);
18414 double asinh(double x);
18415 float asinhf(float x);
18416 long double asinhl(long double x);
18417 double atanh(double x);
18418 float atanhf(float x);
18419 long double atanhl(long double x);
18420 double cosh(double x);
18421 float coshf(float x);
18422 long double coshl(long double x);
18423 double sinh(double x);
18424 float sinhf(float x);
18425 long double sinhl(long double x);
18426 double tanh(double x);
18427 float tanhf(float x);
18428 long double tanhl(long double x);
18429 double exp(double x);
18430 float expf(float x);
18432 [<a name="p476" href="#p476">page 476</a>] (<a href="#Contents">Contents</a>)
18434 long double expl(long double x);
18435 double exp2(double x);
18436 float exp2f(float x);
18437 long double exp2l(long double x);
18438 double expm1(double x);
18439 float expm1f(float x);
18440 long double expm1l(long double x);
18441 double frexp(double value, int *exp);
18442 float frexpf(float value, int *exp);
18443 long double frexpl(long double value, int *exp);
18444 int ilogb(double x);
18445 int ilogbf(float x);
18446 int ilogbl(long double x);
18447 double ldexp(double x, int exp);
18448 float ldexpf(float x, int exp);
18449 long double ldexpl(long double x, int exp);
18450 double log(double x);
18451 float logf(float x);
18452 long double logl(long double x);
18453 double log10(double x);
18454 float log10f(float x);
18455 long double log10l(long double x);
18456 double log1p(double x);
18457 float log1pf(float x);
18458 long double log1pl(long double x);
18459 double log2(double x);
18460 float log2f(float x);
18461 long double log2l(long double x);
18462 double logb(double x);
18463 float logbf(float x);
18464 long double logbl(long double x);
18465 double modf(double value, double *iptr);
18466 float modff(float value, float *iptr);
18467 long double modfl(long double value, long double *iptr);
18468 double scalbn(double x, int n);
18469 float scalbnf(float x, int n);
18470 long double scalbnl(long double x, int n);
18471 double scalbln(double x, long int n);
18472 float scalblnf(float x, long int n);
18473 long double scalblnl(long double x, long int n);
18474 double cbrt(double x);
18476 [<a name="p477" href="#p477">page 477</a>] (<a href="#Contents">Contents</a>)
18478 float cbrtf(float x);
18479 long double cbrtl(long double x);
18480 double fabs(double x);
18481 float fabsf(float x);
18482 long double fabsl(long double x);
18483 double hypot(double x, double y);
18484 float hypotf(float x, float y);
18485 long double hypotl(long double x, long double y);
18486 double pow(double x, double y);
18487 float powf(float x, float y);
18488 long double powl(long double x, long double y);
18489 double sqrt(double x);
18490 float sqrtf(float x);
18491 long double sqrtl(long double x);
18492 double erf(double x);
18493 float erff(float x);
18494 long double erfl(long double x);
18495 double erfc(double x);
18496 float erfcf(float x);
18497 long double erfcl(long double x);
18498 double lgamma(double x);
18499 float lgammaf(float x);
18500 long double lgammal(long double x);
18501 double tgamma(double x);
18502 float tgammaf(float x);
18503 long double tgammal(long double x);
18504 double ceil(double x);
18505 float ceilf(float x);
18506 long double ceill(long double x);
18507 double floor(double x);
18508 float floorf(float x);
18509 long double floorl(long double x);
18510 double nearbyint(double x);
18511 float nearbyintf(float x);
18512 long double nearbyintl(long double x);
18513 double rint(double x);
18514 float rintf(float x);
18515 long double rintl(long double x);
18516 long int lrint(double x);
18517 long int lrintf(float x);
18518 long int lrintl(long double x);
18520 [<a name="p478" href="#p478">page 478</a>] (<a href="#Contents">Contents</a>)
18522 long long int llrint(double x);
18523 long long int llrintf(float x);
18524 long long int llrintl(long double x);
18525 double round(double x);
18526 float roundf(float x);
18527 long double roundl(long double x);
18528 long int lround(double x);
18529 long int lroundf(float x);
18530 long int lroundl(long double x);
18531 long long int llround(double x);
18532 long long int llroundf(float x);
18533 long long int llroundl(long double x);
18534 double trunc(double x);
18535 float truncf(float x);
18536 long double truncl(long double x);
18537 double fmod(double x, double y);
18538 float fmodf(float x, float y);
18539 long double fmodl(long double x, long double y);
18540 double remainder(double x, double y);
18541 float remainderf(float x, float y);
18542 long double remainderl(long double x, long double y);
18543 double remquo(double x, double y, int *quo);
18544 float remquof(float x, float y, int *quo);
18545 long double remquol(long double x, long double y,
18547 double copysign(double x, double y);
18548 float copysignf(float x, float y);
18549 long double copysignl(long double x, long double y);
18550 double nan(const char *tagp);
18551 float nanf(const char *tagp);
18552 long double nanl(const char *tagp);
18553 double nextafter(double x, double y);
18554 float nextafterf(float x, float y);
18555 long double nextafterl(long double x, long double y);
18556 double nexttoward(double x, long double y);
18557 float nexttowardf(float x, long double y);
18558 long double nexttowardl(long double x, long double y);
18559 double fdim(double x, double y);
18560 float fdimf(float x, float y);
18561 long double fdiml(long double x, long double y);
18562 double fmax(double x, double y);
18564 [<a name="p479" href="#p479">page 479</a>] (<a href="#Contents">Contents</a>)
18566 float fmaxf(float x, float y);
18567 long double fmaxl(long double x, long double y);
18568 double fmin(double x, double y);
18569 float fminf(float x, float y);
18570 long double fminl(long double x, long double y);
18571 double fma(double x, double y, double z);
18572 float fmaf(float x, float y, float z);
18573 long double fmal(long double x, long double y,
18575 int isgreater(real-floating x, real-floating y);
18576 int isgreaterequal(real-floating x, real-floating y);
18577 int isless(real-floating x, real-floating y);
18578 int islessequal(real-floating x, real-floating y);
18579 int islessgreater(real-floating x, real-floating y);
18580 int isunordered(real-floating x, real-floating y);
18581 <a name="B.12" href="#B.12"><b>B.12 Nonlocal jumps <setjmp.h></b></a>
18583 int setjmp(jmp_buf env);
18584 _Noreturn void longjmp(jmp_buf env, int val);
18585 <a name="B.13" href="#B.13"><b>B.13 Signal handling <signal.h></b></a>
18586 sig_atomic_t SIG_IGN SIGILL SIGTERM
18587 SIG_DFL SIGABRT SIGINT
18588 SIG_ERR SIGFPE SIGSEGV
18589 void (*signal(int sig, void (*func)(int)))(int);
18590 int raise(int sig);
18592 [<a name="p480" href="#p480">page 480</a>] (<a href="#Contents">Contents</a>)
18594 <a name="B.14" href="#B.14"><b>B.14 Alignment <stdalign.h></b></a>
18596 __alignas_is_defined
18597 <a name="B.15" href="#B.15"><b>B.15 Variable arguments <stdarg.h></b></a>
18599 type va_arg(va_list ap, type);
18600 void va_copy(va_list dest, va_list src);
18601 void va_end(va_list ap);
18602 void va_start(va_list ap, parmN);
18603 <a name="B.16" href="#B.16"><b>B.16 Atomics <stdatomic.h></b></a>
18604 ATOMIC_CHAR_LOCK_FREE atomic_uint
18605 ATOMIC_CHAR16_T_LOCK_FREE atomic_long
18606 ATOMIC_CHAR32_T_LOCK_FREE atomic_ulong
18607 ATOMIC_WCHAR_T_LOCK_FREE atomic_llong
18608 ATOMIC_SHORT_LOCK_FREE atomic_ullong
18609 ATOMIC_INT_LOCK_FREE atomic_char16_t
18610 ATOMIC_LONG_LOCK_FREE atomic_char32_t
18611 ATOMIC_LLONG_LOCK_FREE atomic_wchar_t
18612 ATOMIC_ADDRESS_LOCK_FREE atomic_int_least8_t
18613 ATOMIC_FLAG_INIT atomic_uint_least8_t
18614 memory_order atomic_int_least16_t
18615 atomic_flag atomic_uint_least16_t
18616 atomic_bool atomic_int_least32_t
18617 atomic_address atomic_uint_least32_t
18618 memory_order_relaxed atomic_int_least64_t
18619 memory_order_consume atomic_uint_least64_t
18620 memory_order_acquire atomic_int_fast8_t
18621 memory_order_release atomic_uint_fast8_t
18622 memory_order_acq_rel atomic_int_fast16_t
18623 memory_order_seq_cst atomic_uint_fast16_t
18624 atomic_char atomic_int_fast32_t
18625 atomic_schar atomic_uint_fast32_t
18626 atomic_uchar atomic_int_fast64_t
18627 atomic_short atomic_uint_fast64_t
18628 atomic_ushort atomic_intptr_t
18629 atomic_int atomic_uintptr_t
18631 [<a name="p481" href="#p481">page 481</a>] (<a href="#Contents">Contents</a>)
18633 atomic_size_t atomic_intmax_t
18634 atomic_ptrdiff_t atomic_uintmax_t
18635 #define ATOMIC_VAR_INIT(C value)
18636 void atomic_init(volatile A *obj, C value);
18637 type kill_dependency(type y);
18638 void atomic_thread_fence(memory_order order);
18639 void atomic_signal_fence(memory_order order);
18640 _Bool atomic_is_lock_free(atomic_type const volatile *obj);
18641 void atomic_store(volatile A *object, C desired);
18642 void atomic_store_explicit(volatile A *object,
18643 C desired, memory_order order);
18644 C atomic_load(volatile A *object);
18645 C atomic_load_explicit(volatile A *object,
18646 memory_order order);
18647 C atomic_exchange(volatile A *object, C desired);
18648 C atomic_exchange_explicit(volatile A *object,
18649 C desired, memory_order order);
18650 _Bool atomic_compare_exchange_strong(volatile A *object,
18651 C *expected, C desired);
18652 _Bool atomic_compare_exchange_strong_explicit(
18653 volatile A *object, C *expected, C desired,
18654 memory_order success, memory_order failure);
18655 _Bool atomic_compare_exchange_weak(volatile A *object,
18656 C *expected, C desired);
18657 _Bool atomic_compare_exchange_weak_explicit(
18658 volatile A *object, C *expected, C desired,
18659 memory_order success, memory_order failure);
18660 C atomic_fetch_key(volatile A *object, M operand);
18661 C atomic_fetch_key_explicit(volatile A *object,
18662 M operand, memory_order order);
18663 bool atomic_flag_test_and_set(
18664 volatile atomic_flag *object);
18665 bool atomic_flag_test_and_set_explicit(
18666 volatile atomic_flag *object, memory_order order);
18667 void atomic_flag_clear(volatile atomic_flag *object);
18668 void atomic_flag_clear_explicit(
18669 volatile atomic_flag *object, memory_order order);
18671 [<a name="p482" href="#p482">page 482</a>] (<a href="#Contents">Contents</a>)
18673 <a name="B.17" href="#B.17"><b>B.17 Boolean type and values <stdbool.h></b></a>
18677 __bool_true_false_are_defined
18678 <a name="B.18" href="#B.18"><b>B.18 Common definitions <stddef.h></b></a>
18679 ptrdiff_t max_align_t NULL
18681 offsetof(type, member-designator)
18682 __STDC_WANT_LIB_EXT1__
18684 <a name="B.19" href="#B.19"><b>B.19 Integer types <stdint.h></b></a>
18685 intN_t INT_LEASTN_MIN PTRDIFF_MAX
18686 uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
18687 int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
18688 uint_leastN_t INT_FASTN_MIN SIZE_MAX
18689 int_fastN_t INT_FASTN_MAX WCHAR_MIN
18690 uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
18691 intptr_t INTPTR_MIN WINT_MIN
18692 uintptr_t INTPTR_MAX WINT_MAX
18693 intmax_t UINTPTR_MAX INTN_C(value)
18694 uintmax_t INTMAX_MIN UINTN_C(value)
18695 INTN_MIN INTMAX_MAX INTMAX_C(value)
18696 INTN_MAX UINTMAX_MAX UINTMAX_C(value)
18697 UINTN_MAX PTRDIFF_MIN
18698 __STDC_WANT_LIB_EXT1__
18701 [<a name="p483" href="#p483">page 483</a>] (<a href="#Contents">Contents</a>)
18703 <a name="B.20" href="#B.20"><b>B.20 Input/output <stdio.h></b></a>
18704 size_t _IOLBF FILENAME_MAX TMP_MAX
18705 FILE _IONBF L_tmpnam stderr
18706 fpos_t BUFSIZ SEEK_CUR stdin
18707 NULL EOF SEEK_END stdout
18708 _IOFBF FOPEN_MAX SEEK_SET
18709 int remove(const char *filename);
18710 int rename(const char *old, const char *new);
18711 FILE *tmpfile(void);
18712 char *tmpnam(char *s);
18713 int fclose(FILE *stream);
18714 int fflush(FILE *stream);
18715 FILE *fopen(const char * restrict filename,
18716 const char * restrict mode);
18717 FILE *freopen(const char * restrict filename,
18718 const char * restrict mode,
18719 FILE * restrict stream);
18720 void setbuf(FILE * restrict stream,
18721 char * restrict buf);
18722 int setvbuf(FILE * restrict stream,
18723 char * restrict buf,
18724 int mode, size_t size);
18725 int fprintf(FILE * restrict stream,
18726 const char * restrict format, ...);
18727 int fscanf(FILE * restrict stream,
18728 const char * restrict format, ...);
18729 int printf(const char * restrict format, ...);
18730 int scanf(const char * restrict format, ...);
18731 int snprintf(char * restrict s, size_t n,
18732 const char * restrict format, ...);
18733 int sprintf(char * restrict s,
18734 const char * restrict format, ...);
18735 int sscanf(const char * restrict s,
18736 const char * restrict format, ...);
18737 int vfprintf(FILE * restrict stream,
18738 const char * restrict format, va_list arg);
18739 int vfscanf(FILE * restrict stream,
18740 const char * restrict format, va_list arg);
18741 int vprintf(const char * restrict format, va_list arg);
18742 int vscanf(const char * restrict format, va_list arg);
18744 [<a name="p484" href="#p484">page 484</a>] (<a href="#Contents">Contents</a>)
18746 int vsnprintf(char * restrict s, size_t n,
18747 const char * restrict format, va_list arg);
18748 int vsprintf(char * restrict s,
18749 const char * restrict format, va_list arg);
18750 int vsscanf(const char * restrict s,
18751 const char * restrict format, va_list arg);
18752 int fgetc(FILE *stream);
18753 char *fgets(char * restrict s, int n,
18754 FILE * restrict stream);
18755 int fputc(int c, FILE *stream);
18756 int fputs(const char * restrict s,
18757 FILE * restrict stream);
18758 int getc(FILE *stream);
18760 int putc(int c, FILE *stream); *
18761 int putchar(int c);
18762 int puts(const char *s);
18763 int ungetc(int c, FILE *stream);
18764 size_t fread(void * restrict ptr,
18765 size_t size, size_t nmemb,
18766 FILE * restrict stream);
18767 size_t fwrite(const void * restrict ptr,
18768 size_t size, size_t nmemb,
18769 FILE * restrict stream);
18770 int fgetpos(FILE * restrict stream,
18771 fpos_t * restrict pos);
18772 int fseek(FILE *stream, long int offset, int whence);
18773 int fsetpos(FILE *stream, const fpos_t *pos);
18774 long int ftell(FILE *stream);
18775 void rewind(FILE *stream);
18776 void clearerr(FILE *stream);
18777 int feof(FILE *stream);
18778 int ferror(FILE *stream);
18779 void perror(const char *s);
18780 __STDC_WANT_LIB_EXT1__
18781 L_tmpnam_s TMP_MAX_S errno_t rsize_t
18782 errno_t tmpfile_s(FILE * restrict * restrict streamptr);
18783 errno_t tmpnam_s(char *s, rsize_t maxsize);
18785 [<a name="p485" href="#p485">page 485</a>] (<a href="#Contents">Contents</a>)
18787 errno_t fopen_s(FILE * restrict * restrict streamptr,
18788 const char * restrict filename,
18789 const char * restrict mode);
18790 errno_t freopen_s(FILE * restrict * restrict newstreamptr,
18791 const char * restrict filename,
18792 const char * restrict mode,
18793 FILE * restrict stream);
18794 int fprintf_s(FILE * restrict stream,
18795 const char * restrict format, ...);
18796 int fscanf_s(FILE * restrict stream,
18797 const char * restrict format, ...);
18798 int printf_s(const char * restrict format, ...);
18799 int scanf_s(const char * restrict format, ...);
18800 int snprintf_s(char * restrict s, rsize_t n,
18801 const char * restrict format, ...);
18802 int sprintf_s(char * restrict s, rsize_t n,
18803 const char * restrict format, ...);
18804 int sscanf_s(const char * restrict s,
18805 const char * restrict format, ...);
18806 int vfprintf_s(FILE * restrict stream,
18807 const char * restrict format,
18809 int vfscanf_s(FILE * restrict stream,
18810 const char * restrict format,
18812 int vprintf_s(const char * restrict format,
18814 int vscanf_s(const char * restrict format,
18816 int vsnprintf_s(char * restrict s, rsize_t n,
18817 const char * restrict format,
18819 int vsprintf_s(char * restrict s, rsize_t n,
18820 const char * restrict format,
18822 int vsscanf_s(const char * restrict s,
18823 const char * restrict format,
18825 char *gets_s(char *s, rsize_t n);
18827 [<a name="p486" href="#p486">page 486</a>] (<a href="#Contents">Contents</a>)
18829 <a name="B.21" href="#B.21"><b>B.21 General utilities <stdlib.h></b></a>
18830 size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
18831 wchar_t lldiv_t EXIT_SUCCESS
18832 div_t NULL RAND_MAX
18833 double atof(const char *nptr);
18834 int atoi(const char *nptr);
18835 long int atol(const char *nptr);
18836 long long int atoll(const char *nptr);
18837 double strtod(const char * restrict nptr,
18838 char ** restrict endptr);
18839 float strtof(const char * restrict nptr,
18840 char ** restrict endptr);
18841 long double strtold(const char * restrict nptr,
18842 char ** restrict endptr);
18843 long int strtol(const char * restrict nptr,
18844 char ** restrict endptr, int base);
18845 long long int strtoll(const char * restrict nptr,
18846 char ** restrict endptr, int base);
18847 unsigned long int strtoul(
18848 const char * restrict nptr,
18849 char ** restrict endptr, int base);
18850 unsigned long long int strtoull(
18851 const char * restrict nptr,
18852 char ** restrict endptr, int base);
18854 void srand(unsigned int seed);
18855 void *aligned_alloc(size_t alignment, size_t size);
18856 void *calloc(size_t nmemb, size_t size);
18857 void free(void *ptr);
18858 void *malloc(size_t size);
18859 void *realloc(void *ptr, size_t size);
18860 _Noreturn void abort(void);
18861 int atexit(void (*func)(void));
18862 int at_quick_exit(void (*func)(void));
18863 _Noreturn void exit(int status);
18864 _Noreturn void _Exit(int status);
18865 char *getenv(const char *name);
18866 _Noreturn void quick_exit(int status);
18867 int system(const char *string);
18869 [<a name="p487" href="#p487">page 487</a>] (<a href="#Contents">Contents</a>)
18871 void *bsearch(const void *key, const void *base,
18872 size_t nmemb, size_t size,
18873 int (*compar)(const void *, const void *));
18874 void qsort(void *base, size_t nmemb, size_t size,
18875 int (*compar)(const void *, const void *));
18877 long int labs(long int j);
18878 long long int llabs(long long int j);
18879 div_t div(int numer, int denom);
18880 ldiv_t ldiv(long int numer, long int denom);
18881 lldiv_t lldiv(long long int numer,
18882 long long int denom);
18883 int mblen(const char *s, size_t n);
18884 int mbtowc(wchar_t * restrict pwc,
18885 const char * restrict s, size_t n);
18886 int wctomb(char *s, wchar_t wchar);
18887 size_t mbstowcs(wchar_t * restrict pwcs,
18888 const char * restrict s, size_t n);
18889 size_t wcstombs(char * restrict s,
18890 const wchar_t * restrict pwcs, size_t n);
18891 __STDC_WANT_LIB_EXT1__
18894 constraint_handler_t
18895 constraint_handler_t set_constraint_handler_s(
18896 constraint_handler_t handler);
18897 void abort_handler_s(
18898 const char * restrict msg,
18899 void * restrict ptr,
18901 void ignore_handler_s(
18902 const char * restrict msg,
18903 void * restrict ptr,
18905 errno_t getenv_s(size_t * restrict len,
18906 char * restrict value, rsize_t maxsize,
18907 const char * restrict name);
18909 [<a name="p488" href="#p488">page 488</a>] (<a href="#Contents">Contents</a>)
18911 void *bsearch_s(const void *key, const void *base,
18912 rsize_t nmemb, rsize_t size,
18913 int (*compar)(const void *k, const void *y,
18916 errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
18917 int (*compar)(const void *x, const void *y,
18920 errno_t wctomb_s(int * restrict status,
18924 errno_t mbstowcs_s(size_t * restrict retval,
18925 wchar_t * restrict dst, rsize_t dstmax,
18926 const char * restrict src, rsize_t len);
18927 errno_t wcstombs_s(size_t * restrict retval,
18928 char * restrict dst, rsize_t dstmax,
18929 const wchar_t * restrict src, rsize_t len);
18930 <a name="B.22" href="#B.22"><b>B.22 String handling <string.h></b></a>
18933 void *memcpy(void * restrict s1,
18934 const void * restrict s2, size_t n);
18935 void *memmove(void *s1, const void *s2, size_t n);
18936 char *strcpy(char * restrict s1,
18937 const char * restrict s2);
18938 char *strncpy(char * restrict s1,
18939 const char * restrict s2, size_t n);
18940 char *strcat(char * restrict s1,
18941 const char * restrict s2);
18942 char *strncat(char * restrict s1,
18943 const char * restrict s2, size_t n);
18944 int memcmp(const void *s1, const void *s2, size_t n);
18945 int strcmp(const char *s1, const char *s2);
18946 int strcoll(const char *s1, const char *s2);
18947 int strncmp(const char *s1, const char *s2, size_t n);
18948 size_t strxfrm(char * restrict s1,
18949 const char * restrict s2, size_t n);
18950 void *memchr(const void *s, int c, size_t n);
18952 [<a name="p489" href="#p489">page 489</a>] (<a href="#Contents">Contents</a>)
18954 char *strchr(const char *s, int c);
18955 size_t strcspn(const char *s1, const char *s2);
18956 char *strpbrk(const char *s1, const char *s2);
18957 char *strrchr(const char *s, int c);
18958 size_t strspn(const char *s1, const char *s2);
18959 char *strstr(const char *s1, const char *s2);
18960 char *strtok(char * restrict s1,
18961 const char * restrict s2);
18962 void *memset(void *s, int c, size_t n);
18963 char *strerror(int errnum);
18964 size_t strlen(const char *s);
18965 __STDC_WANT_LIB_EXT1__
18968 errno_t memcpy_s(void * restrict s1, rsize_t s1max,
18969 const void * restrict s2, rsize_t n);
18970 errno_t memmove_s(void *s1, rsize_t s1max,
18971 const void *s2, rsize_t n);
18972 errno_t strcpy_s(char * restrict s1,
18974 const char * restrict s2);
18975 errno_t strncpy_s(char * restrict s1,
18977 const char * restrict s2,
18979 errno_t strcat_s(char * restrict s1,
18981 const char * restrict s2);
18982 errno_t strncat_s(char * restrict s1,
18984 const char * restrict s2,
18986 char *strtok_s(char * restrict s1,
18987 rsize_t * restrict s1max,
18988 const char * restrict s2,
18989 char ** restrict ptr);
18990 errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
18991 errno_t strerror_s(char *s, rsize_t maxsize,
18993 size_t strerrorlen_s(errno_t errnum);
18995 [<a name="p490" href="#p490">page 490</a>] (<a href="#Contents">Contents</a>)
18997 size_t strnlen_s(const char *s, size_t maxsize);
18998 <a name="B.23" href="#B.23"><b>B.23 Type-generic math <tgmath.h></b></a>
18999 acos sqrt fmod nextafter
19000 asin fabs frexp nexttoward
19001 atan atan2 hypot remainder
19002 acosh cbrt ilogb remquo
19003 asinh ceil ldexp rint
19004 atanh copysign lgamma round
19005 cos erf llrint scalbn
19006 sin erfc llround scalbln
19007 tan exp2 log10 tgamma
19008 cosh expm1 log1p trunc
19009 sinh fdim log2 carg
19010 tanh floor logb cimag
19012 log fmax lround cproj
19013 pow fmin nearbyint creal
19014 <a name="B.24" href="#B.24"><b>B.24 Threads <threads.h></b></a>
19015 ONCE_FLAG_INIT mtx_plain
19016 TSS_DTOR_ITERATIONS mtx_recursive
19021 tss_dtor_t thrd_busy
19022 thrd_start_t thrd_error
19023 once_flag thrd_nomem
19025 void call_once(once_flag *flag, void (*func)(void));
19026 int cnd_broadcast(cnd_t *cond);
19027 void cnd_destroy(cnd_t *cond);
19028 int cnd_init(cnd_t *cond);
19029 int cnd_signal(cnd_t *cond);
19030 int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
19032 int cnd_wait(cnd_t *cond, mtx_t *mtx);
19033 void mtx_destroy(mtx_t *mtx);
19034 int mtx_init(mtx_t *mtx, int type);
19035 int mtx_lock(mtx_t *mtx);
19037 [<a name="p491" href="#p491">page 491</a>] (<a href="#Contents">Contents</a>)
19039 int mtx_timedlock(mtx_t *mtx, const xtime *xt);
19040 int mtx_trylock(mtx_t *mtx);
19041 int mtx_unlock(mtx_t *mtx);
19042 int thrd_create(thrd_t *thr, thrd_start_t func,
19044 thrd_t thrd_current(void);
19045 int thrd_detach(thrd_t thr);
19046 int thrd_equal(thrd_t thr0, thrd_t thr1);
19047 void thrd_exit(int res);
19048 int thrd_join(thrd_t thr, int *res);
19049 void thrd_sleep(const xtime *xt);
19050 void thrd_yield(void);
19051 int tss_create(tss_t *key, tss_dtor_t dtor);
19052 void tss_delete(tss_t key);
19053 void *tss_get(tss_t key);
19054 int tss_set(tss_t key, void *val);
19055 int xtime_get(xtime *xt, int base);
19056 <a name="B.25" href="#B.25"><b>B.25 Date and time <time.h></b></a>
19058 CLOCKS_PER_SEC clock_t struct tm
19059 clock_t clock(void);
19060 double difftime(time_t time1, time_t time0);
19061 time_t mktime(struct tm *timeptr);
19062 time_t time(time_t *timer);
19063 char *asctime(const struct tm *timeptr);
19064 char *ctime(const time_t *timer);
19065 struct tm *gmtime(const time_t *timer);
19066 struct tm *localtime(const time_t *timer);
19067 size_t strftime(char * restrict s,
19069 const char * restrict format,
19070 const struct tm * restrict timeptr);
19071 __STDC_WANT_LIB_EXT1__
19074 errno_t asctime_s(char *s, rsize_t maxsize,
19075 const struct tm *timeptr);
19077 [<a name="p492" href="#p492">page 492</a>] (<a href="#Contents">Contents</a>)
19079 errno_t ctime_s(char *s, rsize_t maxsize,
19080 const time_t *timer);
19081 struct tm *gmtime_s(const time_t * restrict timer,
19082 struct tm * restrict result);
19083 struct tm *localtime_s(const time_t * restrict timer,
19084 struct tm * restrict result);
19085 <a name="B.26" href="#B.26"><b>B.26 Unicode utilities <uchar.h></b></a>
19086 mbstate_t size_t char16_t char32_t
19087 size_t mbrtoc16(char16_t * restrict pc16,
19088 const char * restrict s, size_t n,
19089 mbstate_t * restrict ps);
19090 size_t c16rtomb(char * restrict s, char16_t c16,
19091 mbstate_t * restrict ps);
19092 size_t mbrtoc32(char32_t * restrict pc32,
19093 const char * restrict s, size_t n,
19094 mbstate_t * restrict ps);
19095 size_t c32rtomb(char * restrict s, char32_t c32,
19096 mbstate_t * restrict ps);
19097 <a name="B.27" href="#B.27"><b>B.27 Extended multibyte/wide character utilities <wchar.h></b></a>
19098 wchar_t wint_t WCHAR_MAX
19099 size_t struct tm WCHAR_MIN
19100 mbstate_t NULL WEOF
19101 int fwprintf(FILE * restrict stream,
19102 const wchar_t * restrict format, ...);
19103 int fwscanf(FILE * restrict stream,
19104 const wchar_t * restrict format, ...);
19105 int swprintf(wchar_t * restrict s, size_t n,
19106 const wchar_t * restrict format, ...);
19107 int swscanf(const wchar_t * restrict s,
19108 const wchar_t * restrict format, ...);
19109 int vfwprintf(FILE * restrict stream,
19110 const wchar_t * restrict format, va_list arg);
19111 int vfwscanf(FILE * restrict stream,
19112 const wchar_t * restrict format, va_list arg);
19113 int vswprintf(wchar_t * restrict s, size_t n,
19114 const wchar_t * restrict format, va_list arg);
19116 [<a name="p493" href="#p493">page 493</a>] (<a href="#Contents">Contents</a>)
19118 int vswscanf(const wchar_t * restrict s,
19119 const wchar_t * restrict format, va_list arg);
19120 int vwprintf(const wchar_t * restrict format,
19122 int vwscanf(const wchar_t * restrict format,
19124 int wprintf(const wchar_t * restrict format, ...);
19125 int wscanf(const wchar_t * restrict format, ...);
19126 wint_t fgetwc(FILE *stream);
19127 wchar_t *fgetws(wchar_t * restrict s, int n,
19128 FILE * restrict stream);
19129 wint_t fputwc(wchar_t c, FILE *stream);
19130 int fputws(const wchar_t * restrict s,
19131 FILE * restrict stream);
19132 int fwide(FILE *stream, int mode);
19133 wint_t getwc(FILE *stream);
19134 wint_t getwchar(void);
19135 wint_t putwc(wchar_t c, FILE *stream);
19136 wint_t putwchar(wchar_t c);
19137 wint_t ungetwc(wint_t c, FILE *stream);
19138 double wcstod(const wchar_t * restrict nptr,
19139 wchar_t ** restrict endptr);
19140 float wcstof(const wchar_t * restrict nptr,
19141 wchar_t ** restrict endptr);
19142 long double wcstold(const wchar_t * restrict nptr,
19143 wchar_t ** restrict endptr);
19144 long int wcstol(const wchar_t * restrict nptr,
19145 wchar_t ** restrict endptr, int base);
19146 long long int wcstoll(const wchar_t * restrict nptr,
19147 wchar_t ** restrict endptr, int base);
19148 unsigned long int wcstoul(const wchar_t * restrict nptr,
19149 wchar_t ** restrict endptr, int base);
19150 unsigned long long int wcstoull(
19151 const wchar_t * restrict nptr,
19152 wchar_t ** restrict endptr, int base);
19153 wchar_t *wcscpy(wchar_t * restrict s1,
19154 const wchar_t * restrict s2);
19155 wchar_t *wcsncpy(wchar_t * restrict s1,
19156 const wchar_t * restrict s2, size_t n);
19158 [<a name="p494" href="#p494">page 494</a>] (<a href="#Contents">Contents</a>)
19160 wchar_t *wmemcpy(wchar_t * restrict s1,
19161 const wchar_t * restrict s2, size_t n);
19162 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
19164 wchar_t *wcscat(wchar_t * restrict s1,
19165 const wchar_t * restrict s2);
19166 wchar_t *wcsncat(wchar_t * restrict s1,
19167 const wchar_t * restrict s2, size_t n);
19168 int wcscmp(const wchar_t *s1, const wchar_t *s2);
19169 int wcscoll(const wchar_t *s1, const wchar_t *s2);
19170 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
19172 size_t wcsxfrm(wchar_t * restrict s1,
19173 const wchar_t * restrict s2, size_t n);
19174 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
19176 wchar_t *wcschr(const wchar_t *s, wchar_t c);
19177 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
19178 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
19179 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
19180 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
19181 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
19182 wchar_t *wcstok(wchar_t * restrict s1,
19183 const wchar_t * restrict s2,
19184 wchar_t ** restrict ptr);
19185 wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
19186 size_t wcslen(const wchar_t *s);
19187 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
19188 size_t wcsftime(wchar_t * restrict s, size_t maxsize,
19189 const wchar_t * restrict format,
19190 const struct tm * restrict timeptr);
19191 wint_t btowc(int c);
19192 int wctob(wint_t c);
19193 int mbsinit(const mbstate_t *ps);
19194 size_t mbrlen(const char * restrict s, size_t n,
19195 mbstate_t * restrict ps);
19196 size_t mbrtowc(wchar_t * restrict pwc,
19197 const char * restrict s, size_t n,
19198 mbstate_t * restrict ps);
19200 [<a name="p495" href="#p495">page 495</a>] (<a href="#Contents">Contents</a>)
19202 size_t wcrtomb(char * restrict s, wchar_t wc,
19203 mbstate_t * restrict ps);
19204 size_t mbsrtowcs(wchar_t * restrict dst,
19205 const char ** restrict src, size_t len,
19206 mbstate_t * restrict ps);
19207 size_t wcsrtombs(char * restrict dst,
19208 const wchar_t ** restrict src, size_t len,
19209 mbstate_t * restrict ps);
19210 __STDC_WANT_LIB_EXT1__
19213 int fwprintf_s(FILE * restrict stream,
19214 const wchar_t * restrict format, ...);
19215 int fwscanf_s(FILE * restrict stream,
19216 const wchar_t * restrict format, ...);
19217 int snwprintf_s(wchar_t * restrict s,
19219 const wchar_t * restrict format, ...);
19220 int swprintf_s(wchar_t * restrict s, rsize_t n,
19221 const wchar_t * restrict format, ...);
19222 int swscanf_s(const wchar_t * restrict s,
19223 const wchar_t * restrict format, ...);
19224 int vfwprintf_s(FILE * restrict stream,
19225 const wchar_t * restrict format,
19227 int vfwscanf_s(FILE * restrict stream,
19228 const wchar_t * restrict format, va_list arg);
19229 int vsnwprintf_s(wchar_t * restrict s,
19231 const wchar_t * restrict format,
19233 int vswprintf_s(wchar_t * restrict s,
19235 const wchar_t * restrict format,
19237 int vswscanf_s(const wchar_t * restrict s,
19238 const wchar_t * restrict format,
19241 [<a name="p496" href="#p496">page 496</a>] (<a href="#Contents">Contents</a>)
19243 int vwprintf_s(const wchar_t * restrict format,
19245 int vwscanf_s(const wchar_t * restrict format,
19247 int wprintf_s(const wchar_t * restrict format, ...);
19248 int wscanf_s(const wchar_t * restrict format, ...);
19249 errno_t wcscpy_s(wchar_t * restrict s1,
19251 const wchar_t * restrict s2);
19252 errno_t wcsncpy_s(wchar_t * restrict s1,
19254 const wchar_t * restrict s2,
19256 errno_t wmemcpy_s(wchar_t * restrict s1,
19258 const wchar_t * restrict s2,
19260 errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
19261 const wchar_t *s2, rsize_t n);
19262 errno_t wcscat_s(wchar_t * restrict s1,
19264 const wchar_t * restrict s2);
19265 errno_t wcsncat_s(wchar_t * restrict s1,
19267 const wchar_t * restrict s2,
19269 wchar_t *wcstok_s(wchar_t * restrict s1,
19270 rsize_t * restrict s1max,
19271 const wchar_t * restrict s2,
19272 wchar_t ** restrict ptr);
19273 size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
19274 errno_t wcrtomb_s(size_t * restrict retval,
19275 char * restrict s, rsize_t smax,
19276 wchar_t wc, mbstate_t * restrict ps);
19277 errno_t mbsrtowcs_s(size_t * restrict retval,
19278 wchar_t * restrict dst, rsize_t dstmax,
19279 const char ** restrict src, rsize_t len,
19280 mbstate_t * restrict ps);
19282 [<a name="p497" href="#p497">page 497</a>] (<a href="#Contents">Contents</a>)
19284 errno_t wcsrtombs_s(size_t * restrict retval,
19285 char * restrict dst, rsize_t dstmax,
19286 const wchar_t ** restrict src, rsize_t len,
19287 mbstate_t * restrict ps);
19288 <a name="B.28" href="#B.28"><b>B.28 Wide character classification and mapping utilities <wctype.h></b></a>
19289 wint_t wctrans_t wctype_t WEOF
19290 int iswalnum(wint_t wc);
19291 int iswalpha(wint_t wc);
19292 int iswblank(wint_t wc);
19293 int iswcntrl(wint_t wc);
19294 int iswdigit(wint_t wc);
19295 int iswgraph(wint_t wc);
19296 int iswlower(wint_t wc);
19297 int iswprint(wint_t wc);
19298 int iswpunct(wint_t wc);
19299 int iswspace(wint_t wc);
19300 int iswupper(wint_t wc);
19301 int iswxdigit(wint_t wc);
19302 int iswctype(wint_t wc, wctype_t desc);
19303 wctype_t wctype(const char *property);
19304 wint_t towlower(wint_t wc);
19305 wint_t towupper(wint_t wc);
19306 wint_t towctrans(wint_t wc, wctrans_t desc);
19307 wctrans_t wctrans(const char *property);
19309 [<a name="p498" href="#p498">page 498</a>] (<a href="#Contents">Contents</a>)
19311 <a name="C" href="#C"><b> Annex C</b></a>
19314 1 The following are the sequence points described in <a href="#5.1.2.3">5.1.2.3</a>:
19315 -- Between the evaluations of the function designator and actual arguments in a function
19316 call and the actual call. (<a href="#6.5.2.2">6.5.2.2</a>).
19317 -- Between the evaluations of the first and second operands of the following operators:
19318 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>). *
19319 -- Between the evaluations of the first operand of the conditional ? : operator and
19320 whichever of the second and third operands is evaluated (<a href="#6.5.15">6.5.15</a>).
19321 -- The end of a full declarator: declarators (<a href="#6.7.6">6.7.6</a>);
19322 -- Between the evaluation of a full expression and the next full expression to be
19323 evaluated. The following are full expressions: an initializer that is not part of a
19324 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
19325 controlling expression of a selection statement (if or switch) (<a href="#6.8.4">6.8.4</a>); the
19326 controlling expression of a while or do statement (<a href="#6.8.5">6.8.5</a>); each of the (optional)
19327 expressions of a for statement (<a href="#6.8.5.3">6.8.5.3</a>); the (optional) expression in a return
19328 statement (<a href="#6.8.6.4">6.8.6.4</a>).
19329 -- Immediately before a library function returns (<a href="#7.1.4">7.1.4</a>).
19330 -- After the actions associated with each formatted input/output function conversion
19331 specifier (<a href="#7.21.6">7.21.6</a>, <a href="#7.28.2">7.28.2</a>).
19332 -- Immediately before and immediately after each call to a comparison function, and
19333 also between any call to a comparison function and any movement of the objects
19334 passed as arguments to that call (<a href="#7.22.5">7.22.5</a>).
19336 [<a name="p499" href="#p499">page 499</a>] (<a href="#Contents">Contents</a>)
19338 <a name="D" href="#D"><b> Annex D</b></a>
19340 Universal character names for identifiers
19341 1 This clause lists the hexadecimal code values that are valid in universal character names
19343 <a name="D.1" href="#D.1"><b> D.1 Ranges of characters allowed</b></a>
19344 1 00A8, 00AA, 00AD, 00AF, 00B2-00B5, 00B7-00BA, 00BC-00BE, 00C0-00D6,
19345 00D8-00F6, 00F8-00FF
19346 2 0100-167F, 1681-180D, 180F-1FFF
19347 3 200B-200D, 202A-202E, 203F-2040, 2054, 2060-206F
19348 4 2070-218F, 2460-24FF, 2776-2793, 2C00-2DFF, 2E80-2FFF
19349 5 3004-3007, 3021-302F, 3031-303F
19351 7 F900-FD3D, FD40-FDCF, FDF0-FE44, FE47-FFFD
19352 8 10000-1FFFD, 20000-2FFFD, 30000-3FFFD, 40000-4FFFD, 50000-5FFFD,
19353 60000-6FFFD, 70000-7FFFD, 80000-8FFFD, 90000-9FFFD, A0000-AFFFD,
19354 B0000-BFFFD, C0000-CFFFD, D0000-DFFFD, E0000-EFFFD
19355 <a name="D.2" href="#D.2"><b> D.2 Ranges of characters disallowed initially</b></a>
19356 1 0300-036F, 1DC0-1DFF, 20D0-20FF, FE20-FE2F
19358 [<a name="p500" href="#p500">page 500</a>] (<a href="#Contents">Contents</a>)
19360 <a name="E" href="#E"><b> Annex E</b></a>
19362 Implementation limits
19363 1 The contents of the header <a href="#7.10"><limits.h></a> are given below, in alphabetical order. The
19364 minimum magnitudes shown shall be replaced by implementation-defined magnitudes
19365 with the same sign. The values shall all be constant expressions suitable for use in #if
19366 preprocessing directives. The components are described further in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
19368 #define CHAR_MAX UCHAR_MAX or SCHAR_MAX
19369 #define CHAR_MIN 0 or SCHAR_MIN
19370 #define INT_MAX +32767
19371 #define INT_MIN -32767
19372 #define LONG_MAX +2147483647
19373 #define LONG_MIN -2147483647
19374 #define LLONG_MAX +9223372036854775807
19375 #define LLONG_MIN -9223372036854775807
19376 #define MB_LEN_MAX 1
19377 #define SCHAR_MAX +127
19378 #define SCHAR_MIN -127
19379 #define SHRT_MAX +32767
19380 #define SHRT_MIN -32767
19381 #define UCHAR_MAX 255
19382 #define USHRT_MAX 65535
19383 #define UINT_MAX 65535
19384 #define ULONG_MAX 4294967295
19385 #define ULLONG_MAX 18446744073709551615
19386 2 The contents of the header <a href="#7.7"><float.h></a> are given below. All integer values, except
19387 FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing
19388 directives; all floating values shall be constant expressions. The components are
19389 described further in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
19390 3 The values given in the following list shall be replaced by implementation-defined
19392 #define FLT_EVAL_METHOD
19394 4 The values given in the following list shall be replaced by implementation-defined
19395 constant expressions that are greater or equal in magnitude (absolute value) to those
19396 shown, with the same sign:
19398 [<a name="p501" href="#p501">page 501</a>] (<a href="#Contents">Contents</a>)
19400 #define DLB_DECIMAL_DIG 10
19402 #define DBL_MANT_DIG
19403 #define DBL_MAX_10_EXP +37
19404 #define DBL_MAX_EXP
19405 #define DBL_MIN_10_EXP -37
19406 #define DBL_MIN_EXP
19407 #define DECIMAL_DIG 10
19408 #define FLT_DECIMAL_DIG 6
19410 #define FLT_MANT_DIG
19411 #define FLT_MAX_10_EXP +37
19412 #define FLT_MAX_EXP
19413 #define FLT_MIN_10_EXP -37
19414 #define FLT_MIN_EXP
19415 #define FLT_RADIX 2
19416 #define LDLB_DECIMAL_DIG 10
19417 #define LDBL_DIG 10
19418 #define LDBL_MANT_DIG
19419 #define LDBL_MAX_10_EXP +37
19420 #define LDBL_MAX_EXP
19421 #define LDBL_MIN_10_EXP -37
19422 #define LDBL_MIN_EXP
19423 5 The values given in the following list shall be replaced by implementation-defined
19424 constant expressions with values that are greater than or equal to those shown:
19425 #define DBL_MAX 1E+37
19426 #define FLT_MAX 1E+37
19427 #define LDBL_MAX 1E+37
19428 6 The values given in the following list shall be replaced by implementation-defined
19429 constant expressions with (positive) values that are less than or equal to those shown:
19430 #define DBL_EPSILON 1E-9
19431 #define DBL_MIN 1E-37
19432 #define FLT_EPSILON 1E-5
19433 #define FLT_MIN 1E-37
19434 #define LDBL_EPSILON 1E-9
19435 #define LDBL_MIN 1E-37
19437 [<a name="p502" href="#p502">page 502</a>] (<a href="#Contents">Contents</a>)
19439 <a name="F" href="#F"><b> Annex F</b></a>
19441 IEC 60559 floating-point arithmetic
19442 <a name="F.1" href="#F.1"><b> F.1 Introduction</b></a>
19443 1 This annex specifies C language support for the IEC 60559 floating-point standard. The
19444 IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
19445 microprocessor systems, second edition (IEC 60559:1989), previously designated
19446 IEC 559:1989 and as IEEE Standard for Binary Floating-Point Arithmetic
19447 (ANSI/IEEE 754-1985). IEEE Standard for Radix-Independent Floating-Point
19448 Arithmetic (ANSI/IEEE 854-1987) generalizes the binary standard to remove
19449 dependencies on radix and word length. IEC 60559 generally refers to the floating-point
19450 standard, as in IEC 60559 operation, IEC 60559 format, etc. An implementation that
19451 defines __STDC_IEC_559__ shall conform to the specifications in this annex.<sup><a href="#note343"><b>343)</b></a></sup>
19452 Where a binding between the C language and IEC 60559 is indicated, the
19453 IEC 60559-specified behavior is adopted by reference, unless stated otherwise. Since
19454 negative and positive infinity are representable in IEC 60559 formats, all real numbers lie
19455 within the range of representable values.
19456 <a name="F.2" href="#F.2"><b> F.2 Types</b></a>
19457 1 The C floating types match the IEC 60559 formats as follows:
19458 -- The float type matches the IEC 60559 single format.
19459 -- The double type matches the IEC 60559 double format.
19460 -- The long double type matches an IEC 60559 extended format,<sup><a href="#note344"><b>344)</b></a></sup> else a
19461 non-IEC 60559 extended format, else the IEC 60559 double format.
19462 Any non-IEC 60559 extended format used for the long double type shall have more
19463 precision than IEC 60559 double and at least the range of IEC 60559 double.<sup><a href="#note345"><b>345)</b></a></sup>
19468 <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
19470 <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
19471 and quadruple 128-bit IEC 60559 formats.
19472 <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
19475 [<a name="p503" href="#p503">page 503</a>] (<a href="#Contents">Contents</a>)
19477 Recommended practice
19478 2 The long double type should match an IEC 60559 extended format.
19479 <a name="F.2.1" href="#F.2.1"><b> F.2.1 Infinities, signed zeros, and NaNs</b></a>
19480 1 This specification does not define the behavior of signaling NaNs.<sup><a href="#note346"><b>346)</b></a></sup> It generally uses
19481 the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
19482 functions in <a href="#7.12"><math.h></a> provide designations for IEC 60559 NaNs and infinities.
19483 <a name="F.3" href="#F.3"><b> F.3 Operators and functions</b></a>
19484 1 C operators and functions provide IEC 60559 required and recommended facilities as
19486 -- The +, -, *, and / operators provide the IEC 60559 add, subtract, multiply, and
19488 -- The sqrt functions in <a href="#7.12"><math.h></a> provide the IEC 60559 square root operation.
19489 -- The remainder functions in <a href="#7.12"><math.h></a> provide the IEC 60559 remainder
19490 operation. The remquo functions in <a href="#7.12"><math.h></a> provide the same operation but
19491 with additional information.
19492 -- The rint functions in <a href="#7.12"><math.h></a> provide the IEC 60559 operation that rounds a
19493 floating-point number to an integer value (in the same precision). The nearbyint
19494 functions in <a href="#7.12"><math.h></a> provide the nearbyinteger function recommended in the
19495 Appendix to ANSI/IEEE 854.
19496 -- The conversions for floating types provide the IEC 60559 conversions between
19497 floating-point precisions.
19498 -- The conversions from integer to floating types provide the IEC 60559 conversions
19499 from integer to floating point.
19500 -- The conversions from floating to integer types provide IEC 60559-like conversions
19501 but always round toward zero.
19502 -- The lrint and llrint functions in <a href="#7.12"><math.h></a> provide the IEC 60559
19503 conversions, which honor the directed rounding mode, from floating point to the
19504 long int and long long int integer formats. The lrint and llrint
19505 functions can be used to implement IEC 60559 conversions from floating to other
19507 -- The translation time conversion of floating constants and the strtod, strtof,
19508 strtold, fprintf, fscanf, and related library functions in <a href="#7.22"><stdlib.h></a>,
19511 <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
19512 sufficient for closure of the arithmetic.
19514 [<a name="p504" href="#p504">page 504</a>] (<a href="#Contents">Contents</a>)
19516 <a href="#7.21"><stdio.h></a>, and <a href="#7.28"><wchar.h></a> provide IEC 60559 binary-decimal conversions. The
19517 strtold function in <a href="#7.22"><stdlib.h></a> provides the conv function recommended in the
19518 Appendix to ANSI/IEEE 854.
19519 -- The relational and equality operators provide IEC 60559 comparisons. IEC 60559
19520 identifies a need for additional comparison predicates to facilitate writing code that
19521 accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
19522 isless, islessequal, islessgreater, and isunordered) in <a href="#7.12"><math.h></a>
19523 supplement the language operators to address this need. The islessgreater and
19524 isunordered macros provide respectively a quiet version of the <> predicate and
19525 the unordered predicate recommended in the Appendix to IEC 60559.
19526 -- The feclearexcept, feraiseexcept, and fetestexcept functions in
19527 <a href="#7.6"><fenv.h></a> provide the facility to test and alter the IEC 60559 floating-point
19528 exception status flags. The fegetexceptflag and fesetexceptflag
19529 functions in <a href="#7.6"><fenv.h></a> provide the facility to save and restore all five status flags at
19530 one time. These functions are used in conjunction with the type fexcept_t and the
19531 floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
19532 FE_UNDERFLOW, FE_OVERFLOW, FE_INVALID) also in <a href="#7.6"><fenv.h></a>.
19533 -- The fegetround and fesetround functions in <a href="#7.6"><fenv.h></a> provide the facility
19534 to select among the IEC 60559 directed rounding modes represented by the rounding
19535 direction macros in <a href="#7.6"><fenv.h></a> (FE_TONEAREST, FE_UPWARD, FE_DOWNWARD,
19536 FE_TOWARDZERO) and the values 0, 1, 2, and 3 of FLT_ROUNDS are the
19537 IEC 60559 directed rounding modes.
19538 -- The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
19539 <a href="#7.6"><fenv.h></a> provide a facility to manage the floating-point environment, comprising
19540 the IEC 60559 status flags and control modes.
19541 -- The copysign functions in <a href="#7.12"><math.h></a> provide the copysign function
19542 recommended in the Appendix to IEC 60559.
19543 -- The fabs functions in <a href="#7.12"><math.h></a> provide the abs function recommended in the
19544 Appendix to IEC 60559.
19545 -- The unary minus (-) operator provides the unary minus (-) operation recommended
19546 in the Appendix to IEC 60559.
19547 -- The scalbn and scalbln functions in <a href="#7.12"><math.h></a> provide the scalb function
19548 recommended in the Appendix to IEC 60559.
19549 -- The logb functions in <a href="#7.12"><math.h></a> provide the logb function recommended in the
19550 Appendix to IEC 60559, but following the newer specifications in ANSI/IEEE 854.
19551 -- The nextafter and nexttoward functions in <a href="#7.12"><math.h></a> provide the nextafter
19552 function recommended in the Appendix to IEC 60559 (but with a minor change to
19554 [<a name="p505" href="#p505">page 505</a>] (<a href="#Contents">Contents</a>)
19556 better handle signed zeros).
19557 -- The isfinite macro in <a href="#7.12"><math.h></a> provides the finite function recommended in
19558 the Appendix to IEC 60559.
19559 -- The isnan macro in <a href="#7.12"><math.h></a> provides the isnan function recommended in the
19560 Appendix to IEC 60559.
19561 -- The signbit macro and the fpclassify macro in <a href="#7.12"><math.h></a>, used in
19562 conjunction with the number classification macros (FP_NAN, FP_INFINITE,
19563 FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
19564 function recommended in the Appendix to IEC 60559 (except that the classification
19565 macros defined in <a href="#7.12.3">7.12.3</a> do not distinguish signaling from quiet NaNs).
19566 <a name="F.4" href="#F.4"><b> F.4 Floating to integer conversion</b></a>
19567 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
19568 (even for NaN). Otherwise, if the floating value is infinite or NaN or if the integral part
19569 of the floating value exceeds the range of the integer type, then the ''invalid'' floating-
19570 point exception is raised and the resulting value is unspecified. Otherwise, the resulting
19571 value is determined by <a href="#6.3.1.4">6.3.1.4</a>. Conversion of an integral floating value that does not
19572 exceed the range of the integer type raises no floating-point exceptions; whether
19573 conversion of a non-integral floating value raises the ''inexact'' floating-point exception is
19574 unspecified.<sup><a href="#note347"><b>347)</b></a></sup>
19575 <a name="F.5" href="#F.5"><b> F.5 Binary-decimal conversion</b></a>
19576 1 Conversion from the widest supported IEC 60559 format to decimal with
19577 DECIMAL_DIG digits and back is the identity function.<sup><a href="#note348"><b>348)</b></a></sup>
19578 2 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
19579 particular, conversion between any supported IEC 60559 format and decimal with
19580 DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
19581 rounding mode), which assures that conversion from the widest supported IEC 60559
19582 format to decimal with DECIMAL_DIG digits and back is the identity function.
19586 <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
19587 conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those
19588 cases where it matters, library functions can be used to effect such conversions with or without raising
19589 the ''inexact'' floating-point exception. See rint, lrint, llrint, and nearbyint in
19590 <a href="#7.12"><math.h></a>.
19591 <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,
19592 DECIMAL_DIG shall be at least 21. If IEC 60559 double (53 bits of precision) is the widest
19593 IEC 60559 format supported, then DECIMAL_DIG shall be at least 17. (By contrast, LDBL_DIG and
19594 DBL_DIG are 18 and 15, respectively, for these formats.)
19596 [<a name="p506" href="#p506">page 506</a>] (<a href="#Contents">Contents</a>)
19598 3 Functions such as strtod that convert character sequences to floating types honor the
19599 rounding direction. Hence, if the rounding direction might be upward or downward, the
19600 implementation cannot convert a minus-signed sequence by negating the converted
19602 <a name="F.6" href="#F.6"><b> F.6 The return statement</b></a>
19603 If the return expression is evaluated in a floating-point format different from the return
19604 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
19605 and the resulting value is returned to the caller.
19606 <a name="F.7" href="#F.7"><b> F.7 Contracted expressions</b></a>
19607 1 A contracted expression is correctly rounded (once) and treats infinities, NaNs, signed
19608 zeros, subnormals, and the rounding directions in a manner consistent with the basic
19609 arithmetic operations covered by IEC 60559.
19610 Recommended practice
19611 2 A contracted expression should raise floating-point exceptions in a manner generally
19612 consistent with the basic arithmetic operations. *
19613 <a name="F.8" href="#F.8"><b> F.8 Floating-point environment</b></a>
19614 1 The floating-point environment defined in <a href="#7.6"><fenv.h></a> includes the IEC 60559 floating-
19615 point exception status flags and directed-rounding control modes. It includes also
19616 IEC 60559 dynamic rounding precision and trap enablement modes, if the
19617 implementation supports them.<sup><a href="#note350"><b>350)</b></a></sup>
19618 <a name="F.8.1" href="#F.8.1"><b> F.8.1 Environment management</b></a>
19619 1 IEC 60559 requires that floating-point operations implicitly raise floating-point exception
19620 status flags, and that rounding control modes can be set explicitly to affect result values of
19621 floating-point operations. When the state for the FENV_ACCESS pragma (defined in
19622 <a href="#7.6"><fenv.h></a>) is ''on'', these changes to the floating-point state are treated as side effects
19623 which respect sequence points.<sup><a href="#note351"><b>351)</b></a></sup>
19628 <sup><a name="note349" href="#note349"><b>349)</b></a></sup> Assignment removes any extra range and precision.
19629 <sup><a name="note350" href="#note350"><b>350)</b></a></sup> This specification does not require dynamic rounding precision nor trap enablement modes.
19630 <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-
19631 point control modes will be the default ones and the floating-point status flags will not be tested,
19632 which allows certain optimizations (see <a href="#F.9">F.9</a>).
19634 [<a name="p507" href="#p507">page 507</a>] (<a href="#Contents">Contents</a>)
19636 <a name="F.8.2" href="#F.8.2"><b> F.8.2 Translation</b></a>
19637 1 During translation the IEC 60559 default modes are in effect:
19638 -- The rounding direction mode is rounding to nearest.
19639 -- The rounding precision mode (if supported) is set so that results are not shortened.
19640 -- Trapping or stopping (if supported) is disabled on all floating-point exceptions.
19641 Recommended practice
19642 2 The implementation should produce a diagnostic message for each translation-time
19643 floating-point exception, other than ''inexact'';<sup><a href="#note352"><b>352)</b></a></sup> the implementation should then
19644 proceed with the translation of the program.
19645 <a name="F.8.3" href="#F.8.3"><b> F.8.3 Execution</b></a>
19646 1 At program startup the floating-point environment is initialized as prescribed by
19648 -- All floating-point exception status flags are cleared.
19649 -- The rounding direction mode is rounding to nearest.
19650 -- The dynamic rounding precision mode (if supported) is set so that results are not
19652 -- Trapping or stopping (if supported) is disabled on all floating-point exceptions.
19653 <a name="F.8.4" href="#F.8.4"><b> F.8.4 Constant expressions</b></a>
19654 1 An arithmetic constant expression of floating type, other than one in an initializer for an
19655 object that has static or thread storage duration, is evaluated (as if) during execution; thus,
19656 it is affected by any operative floating-point control modes and raises floating-point
19657 exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma
19658 is ''on'').<sup><a href="#note353"><b>353)</b></a></sup>
19663 <sup><a name="note352" href="#note352"><b>352)</b></a></sup> As floating constants are converted to appropriate internal representations at translation time, their
19664 conversion is subject to default rounding modes and raises no execution-time floating-point exceptions
19665 (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example
19666 strtod, provide execution-time conversion of numeric strings.
19667 <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
19668 are affected by rounding modes set at execution time, and expressions such as 0.0/0.0 and
19669 1.0/0.0 generate execution-time floating-point exceptions. The programmer can achieve the
19670 efficiency of translation-time evaluation through static initialization, such as
19671 const static double one_third = 1.0/3.0;
19673 [<a name="p508" href="#p508">page 508</a>] (<a href="#Contents">Contents</a>)
19675 #include <a href="#7.6"><fenv.h></a>
19676 #pragma STDC FENV_ACCESS ON
19679 float w[] = { 0.0/0.0 }; // raises an exception
19680 static float x = 0.0/0.0; // does not raise an exception
19681 float y = 0.0/0.0; // raises an exception
19682 double z = 0.0/0.0; // raises an exception
19685 3 For the static initialization, the division is done at translation time, raising no (execution-time) floating-
19686 point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at
19689 <a name="F.8.5" href="#F.8.5"><b> F.8.5 Initialization</b></a>
19690 1 All computation for automatic initialization is done (as if) at execution time; thus, it is
19691 affected by any operative modes and raises floating-point exceptions as required by
19692 IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation
19693 for initialization of objects that have static or thread storage duration is done (as if) at
19696 #include <a href="#7.6"><fenv.h></a>
19697 #pragma STDC FENV_ACCESS ON
19700 float u[] = { 1.1e75 }; // raises exceptions
19701 static float v = 1.1e75; // does not raise exceptions
19702 float w = 1.1e75; // raises exceptions
19703 double x = 1.1e75; // may raise exceptions
19704 float y = 1.1e75f; // may raise exceptions
19705 long double z = 1.1e75; // does not raise exceptions
19708 3 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is
19709 done at translation time. The automatic initialization of u and w require an execution-time conversion to
19710 float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations
19711 of x and y entail execution-time conversion; however, in some expression evaluation methods, the
19712 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
19713 automatic initialization of z entails execution-time conversion, but not to a narrower format, so no floating-
19714 point exception is raised. Note that the conversions of the floating constants 1.1e75 and 1.1e75f to
19718 <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.
19719 For example, the automatic initialization
19720 double_t x = 1.1e75;
19721 could be done at translation time, regardless of the expression evaluation method.
19723 [<a name="p509" href="#p509">page 509</a>] (<a href="#Contents">Contents</a>)
19725 their internal representations occur at translation time in all cases.
19727 <a name="F.8.6" href="#F.8.6"><b> F.8.6 Changing the environment</b></a>
19728 1 Operations defined in <a href="#6.5">6.5</a> and functions and macros defined for the standard libraries
19729 change floating-point status flags and control modes just as indicated by their
19730 specifications (including conformance to IEC 60559). They do not change flags or modes
19731 (so as to be detectable by the user) in any other cases.
19732 2 If the argument to the feraiseexcept function in <a href="#7.6"><fenv.h></a> represents IEC 60559
19733 valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
19734 ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
19735 before ''inexact''.
19736 <a name="F.9" href="#F.9"><b> F.9 Optimization</b></a>
19737 1 This section identifies code transformations that might subvert IEC 60559-specified
19738 behavior, and others that do not.
19739 <a name="F.9.1" href="#F.9.1"><b> F.9.1 Global transformations</b></a>
19740 1 Floating-point arithmetic operations and external function calls may entail side effects
19741 which optimization shall honor, at least where the state of the FENV_ACCESS pragma is
19742 ''on''. The flags and modes in the floating-point environment may be regarded as global
19743 variables; floating-point operations (+, *, etc.) implicitly read the modes and write the
19745 2 Concern about side effects may inhibit code motion and removal of seemingly useless
19746 code. For example, in
19747 #include <a href="#7.6"><fenv.h></a>
19748 #pragma STDC FENV_ACCESS ON
19752 for (i = 0; i < n; i++) x + 1;
19755 x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
19756 body might not execute (maybe 0 >= n), x + 1 cannot be moved out of the loop. (Of
19757 course these optimizations are valid if the implementation can rule out the nettlesome
19759 3 This specification does not require support for trap handlers that maintain information
19760 about the order or count of floating-point exceptions. Therefore, between function calls,
19761 floating-point exceptions need not be precise: the actual order and number of occurrences
19762 of floating-point exceptions (> 1) may vary from what the source code expresses. Thus,
19764 [<a name="p510" href="#p510">page 510</a>] (<a href="#Contents">Contents</a>)
19766 the preceding loop could be treated as
19767 if (0 < n) x + 1;
19768 <a name="F.9.2" href="#F.9.2"><b> F.9.2 Expression transformations</b></a>
19769 1 x/2 <-> x x 0.5 Although similar transformations involving inexact constants
19770 generally do not yield numerically equivalent expressions, if the
19771 constants are exact then such transformations can be made on
19772 IEC 60559 machines and others that round perfectly.
19773 1 x x and x/1 -> x The expressions 1 x x, x/1, and x are equivalent (on IEC 60559
19774 machines, among others).<sup><a href="#note355"><b>355)</b></a></sup>
19775 x/x -> 1.0 The expressions x/x and 1.0 are not equivalent if x can be zero,
19777 x - y <-> x + (-y) The expressions x - y, x + (-y), and (-y) + x are equivalent (on
19778 IEC 60559 machines, among others).
19779 x - y <-> -(y - x) The expressions x - y and -(y - x) are not equivalent because 1 - 1
19780 is +0 but -(1 - 1) is -0 (in the default rounding direction).<sup><a href="#note356"><b>356)</b></a></sup>
19781 x - x -> 0.0 The expressions x - x and 0.0 are not equivalent if x is a NaN or
19783 0 x x -> 0.0 The expressions 0 x x and 0.0 are not equivalent if x is a NaN,
19785 x+0-> x The expressions x + 0 and x are not equivalent if x is -0, because
19786 (-0) + (+0) yields +0 (in the default rounding direction), not -0.
19787 x-0-> x (+0) - (+0) yields -0 when rounding is downward (toward -(inf)), but
19788 +0 otherwise, and (-0) - (+0) always yields -0; so, if the state of the
19789 FENV_ACCESS pragma is ''off'', promising default rounding, then
19790 the implementation can replace x - 0 by x, even if x might be zero.
19791 -x <-> 0 - x The expressions -x and 0 - x are not equivalent if x is +0, because
19792 -(+0) yields -0, but 0 - (+0) yields +0 (unless rounding is
19795 <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
19796 other transformations that remove arithmetic operators.
19797 <sup><a name="note356" href="#note356"><b>356)</b></a></sup> IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
19799 1/(1/ (+-) (inf)) is (+-) (inf)
19801 conj(csqrt(z)) is csqrt(conj(z)),
19804 [<a name="p511" href="#p511">page 511</a>] (<a href="#Contents">Contents</a>)
19806 <a name="F.9.3" href="#F.9.3"><b> F.9.3 Relational operators</b></a>
19807 1 x != x -> false The expression x != x is true if x is a NaN.
19808 x = x -> true The expression x = x is false if x is a NaN.
19809 x < y -> isless(x,y) (and similarly for <=, >, >=) Though numerically equal, these
19810 expressions are not equivalent because of side effects when x or y is a
19811 NaN and the state of the FENV_ACCESS pragma is ''on''. This
19812 transformation, which would be desirable if extra code were required
19813 to cause the ''invalid'' floating-point exception for unordered cases,
19814 could be performed provided the state of the FENV_ACCESS pragma
19816 The sense of relational operators shall be maintained. This includes handling unordered
19817 cases as expressed by the source code.
19819 // calls g and raises ''invalid'' if a and b are unordered
19824 is not equivalent to
19825 // calls f and raises ''invalid'' if a and b are unordered
19831 // calls f without raising ''invalid'' if a and b are unordered
19832 if (isgreaterequal(a,b))
19836 nor, unless the state of the FENV_ACCESS pragma is ''off'', to
19837 // calls g without raising ''invalid'' if a and b are unordered
19842 but is equivalent to
19844 [<a name="p512" href="#p512">page 512</a>] (<a href="#Contents">Contents</a>)
19851 <a name="F.9.4" href="#F.9.4"><b> F.9.4 Constant arithmetic</b></a>
19852 1 The implementation shall honor floating-point exceptions raised by execution-time
19853 constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See <a href="#F.8.4">F.8.4</a>
19854 and <a href="#F.8.5">F.8.5</a>.) An operation on constants that raises no floating-point exception can be
19855 folded during translation, except, if the state of the FENV_ACCESS pragma is ''on'', a
19856 further check is required to assure that changing the rounding direction to downward does
19857 not alter the sign of the result,<sup><a href="#note357"><b>357)</b></a></sup> and implementations that support dynamic rounding
19858 precision modes shall assure further that the result of the operation raises no floating-
19859 point exception when converted to the semantic type of the operation.
19860 <a name="F.10" href="#F.10"><b> F.10 Mathematics <math.h></b></a>
19861 1 This subclause contains specifications of <a href="#7.12"><math.h></a> facilities that are particularly suited
19862 for IEC 60559 implementations.
19863 2 The Standard C macro HUGE_VAL and its float and long double analogs,
19864 HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive
19866 3 Special cases for functions in <a href="#7.12"><math.h></a> are covered directly or indirectly by
19867 IEC 60559. The functions that IEC 60559 specifies directly are identified in <a href="#F.3">F.3</a>. The
19868 other functions in <a href="#7.12"><math.h></a> treat infinities, NaNs, signed zeros, subnormals, and
19869 (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags
19870 in a manner consistent with the basic arithmetic operations covered by IEC 60559.
19871 4 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
19873 5 The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in
19874 subsequent subclauses of this annex.
19875 6 The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of
19876 rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value
19877 whose magnitude is too large.
19878 7 The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially
19879 subnormal or zero) and suffers loss of accuracy.<sup><a href="#note358"><b>358)</b></a></sup>
19882 <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.
19883 <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
19884 when the floating-point exception is raised.
19886 [<a name="p513" href="#p513">page 513</a>] (<a href="#Contents">Contents</a>)
19888 8 Whether or when library functions raise the ''inexact'' floating-point exception is
19889 unspecified, unless explicitly specified otherwise.
19890 9 Whether or when library functions raise an undeserved ''underflow'' floating-point
19891 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
19892 not raise spurious floating-point exceptions (detectable by the user), other than the
19893 ''inexact'' floating-point exception.
19894 10 Whether the functions honor the rounding direction mode is implementation-defined,
19895 unless explicitly specified otherwise.
19896 11 Functions with a NaN argument return a NaN result and raise no floating-point exception,
19897 except where stated otherwise.
19898 12 The specifications in the following subclauses append to the definitions in <a href="#7.12"><math.h></a>.
19899 For families of functions, the specifications apply to all of the functions even though only
19900 the principal function is shown. Unless otherwise specified, where the symbol ''(+-)''
19901 occurs in both an argument and the result, the result has the same sign as the argument.
19902 Recommended practice
19903 13 If a function with one or more NaN arguments returns a NaN result, the result should be
19904 the same as one of the NaN arguments (after possible type conversion), except perhaps
19906 <a name="F.10.1" href="#F.10.1"><b> F.10.1 Trigonometric functions</b></a>
19907 <a name="F.10.1.1" href="#F.10.1.1"><b> F.10.1.1 The acos functions</b></a>
19908 1 -- acos(1) returns +0.
19909 -- acos(x) returns a NaN and raises the ''invalid'' floating-point exception for
19911 <a name="F.10.1.2" href="#F.10.1.2"><b> F.10.1.2 The asin functions</b></a>
19912 1 -- asin((+-)0) returns (+-)0.
19913 -- asin(x) returns a NaN and raises the ''invalid'' floating-point exception for
19919 <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
19920 avoiding them would be too costly.
19922 [<a name="p514" href="#p514">page 514</a>] (<a href="#Contents">Contents</a>)
19924 <a name="F.10.1.3" href="#F.10.1.3"><b> F.10.1.3 The atan functions</b></a>
19925 1 -- atan((+-)0) returns (+-)0.
19926 -- atan((+-)(inf)) returns (+-)pi /2.
19927 <a name="F.10.1.4" href="#F.10.1.4"><b> F.10.1.4 The atan2 functions</b></a>
19928 1 -- atan2((+-)0, -0) returns (+-)pi .<sup><a href="#note360"><b>360)</b></a></sup>
19929 -- atan2((+-)0, +0) returns (+-)0.
19930 -- atan2((+-)0, x) returns (+-)pi for x < 0.
19931 -- atan2((+-)0, x) returns (+-)0 for x > 0.
19932 -- atan2(y, (+-)0) returns -pi /2 for y < 0.
19933 -- atan2(y, (+-)0) returns pi /2 for y > 0.
19934 -- atan2((+-)y, -(inf)) returns (+-)pi for finite y > 0.
19935 -- atan2((+-)y, +(inf)) returns (+-)0 for finite y > 0.
19936 -- atan2((+-)(inf), x) returns (+-)pi /2 for finite x.
19937 -- atan2((+-)(inf), -(inf)) returns (+-)3pi /4.
19938 -- atan2((+-)(inf), +(inf)) returns (+-)pi /4.
19939 <a name="F.10.1.5" href="#F.10.1.5"><b> F.10.1.5 The cos functions</b></a>
19940 1 -- cos((+-)0) returns 1.
19941 -- cos((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
19942 <a name="F.10.1.6" href="#F.10.1.6"><b> F.10.1.6 The sin functions</b></a>
19943 1 -- sin((+-)0) returns (+-)0.
19944 -- sin((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
19945 <a name="F.10.1.7" href="#F.10.1.7"><b> F.10.1.7 The tan functions</b></a>
19946 1 -- tan((+-)0) returns (+-)0.
19947 -- tan((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
19952 <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
19953 the ''divide-by-zero'' floating-point exception.
19955 [<a name="p515" href="#p515">page 515</a>] (<a href="#Contents">Contents</a>)
19957 <a name="F.10.2" href="#F.10.2"><b> F.10.2 Hyperbolic functions</b></a>
19958 <a name="F.10.2.1" href="#F.10.2.1"><b> F.10.2.1 The acosh functions</b></a>
19959 1 -- acosh(1) returns +0.
19960 -- acosh(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 1.
19961 -- acosh(+(inf)) returns +(inf).
19962 <a name="F.10.2.2" href="#F.10.2.2"><b> F.10.2.2 The asinh functions</b></a>
19963 1 -- asinh((+-)0) returns (+-)0.
19964 -- asinh((+-)(inf)) returns (+-)(inf).
19965 <a name="F.10.2.3" href="#F.10.2.3"><b> F.10.2.3 The atanh functions</b></a>
19966 1 -- atanh((+-)0) returns (+-)0.
19967 -- atanh((+-)1) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
19968 -- atanh(x) returns a NaN and raises the ''invalid'' floating-point exception for
19970 <a name="F.10.2.4" href="#F.10.2.4"><b> F.10.2.4 The cosh functions</b></a>
19971 1 -- cosh((+-)0) returns 1.
19972 -- cosh((+-)(inf)) returns +(inf).
19973 <a name="F.10.2.5" href="#F.10.2.5"><b> F.10.2.5 The sinh functions</b></a>
19974 1 -- sinh((+-)0) returns (+-)0.
19975 -- sinh((+-)(inf)) returns (+-)(inf).
19976 <a name="F.10.2.6" href="#F.10.2.6"><b> F.10.2.6 The tanh functions</b></a>
19977 1 -- tanh((+-)0) returns (+-)0.
19978 -- tanh((+-)(inf)) returns (+-)1.
19979 <a name="F.10.3" href="#F.10.3"><b> F.10.3 Exponential and logarithmic functions</b></a>
19980 <a name="F.10.3.1" href="#F.10.3.1"><b> F.10.3.1 The exp functions</b></a>
19981 1 -- exp((+-)0) returns 1.
19982 -- exp(-(inf)) returns +0.
19983 -- exp(+(inf)) returns +(inf).
19985 [<a name="p516" href="#p516">page 516</a>] (<a href="#Contents">Contents</a>)
19987 <a name="F.10.3.2" href="#F.10.3.2"><b> F.10.3.2 The exp2 functions</b></a>
19988 1 -- exp2((+-)0) returns 1.
19989 -- exp2(-(inf)) returns +0.
19990 -- exp2(+(inf)) returns +(inf).
19991 <a name="F.10.3.3" href="#F.10.3.3"><b> F.10.3.3 The expm1 functions</b></a>
19992 1 -- expm1((+-)0) returns (+-)0.
19993 -- expm1(-(inf)) returns -1.
19994 -- expm1(+(inf)) returns +(inf).
19995 <a name="F.10.3.4" href="#F.10.3.4"><b> F.10.3.4 The frexp functions</b></a>
19996 1 -- frexp((+-)0, exp) returns (+-)0, and stores 0 in the object pointed to by exp.
19997 -- frexp((+-)(inf), exp) returns (+-)(inf), and stores an unspecified value in the object
19999 -- frexp(NaN, exp) stores an unspecified value in the object pointed to by exp
20000 (and returns a NaN).
20001 2 frexp raises no floating-point exceptions.
20002 3 When the radix of the argument is a power of 2, the returned value is exact and is
20003 independent of the current rounding direction mode.
20004 4 On a binary system, the body of the frexp function might be
20006 *exp = (value == 0) ? 0 : (int)(1 + logb(value));
20007 return scalbn(value, -(*exp));
20009 <a name="F.10.3.5" href="#F.10.3.5"><b> F.10.3.5 The ilogb functions</b></a>
20010 1 When the correct result is representable in the range of the return type, the returned value
20011 is exact and is independent of the current rounding direction mode.
20012 2 If the correct result is outside the range of the return type, the numeric result is
20013 unspecified and the ''invalid'' floating-point exception is raised.
20015 [<a name="p517" href="#p517">page 517</a>] (<a href="#Contents">Contents</a>)
20017 <a name="F.10.3.6" href="#F.10.3.6"><b> F.10.3.6 The ldexp functions</b></a>
20018 1 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
20019 <a name="F.10.3.7" href="#F.10.3.7"><b> F.10.3.7 The log functions</b></a>
20020 1 -- log((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
20021 -- log(1) returns +0.
20022 -- log(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
20023 -- log(+(inf)) returns +(inf).
20024 <a name="F.10.3.8" href="#F.10.3.8"><b> F.10.3.8 The log10 functions</b></a>
20025 1 -- log10((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
20026 -- log10(1) returns +0.
20027 -- log10(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
20028 -- log10(+(inf)) returns +(inf).
20029 <a name="F.10.3.9" href="#F.10.3.9"><b> F.10.3.9 The log1p functions</b></a>
20030 1 -- log1p((+-)0) returns (+-)0.
20031 -- log1p(-1) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
20032 -- log1p(x) returns a NaN and raises the ''invalid'' floating-point exception for
20034 -- log1p(+(inf)) returns +(inf).
20035 <a name="F.10.3.10" href="#F.10.3.10"><b> F.10.3.10 The log2 functions</b></a>
20036 1 -- log2((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
20037 -- log2(1) returns +0.
20038 -- log2(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
20039 -- log2(+(inf)) returns +(inf).
20040 <a name="F.10.3.11" href="#F.10.3.11"><b> F.10.3.11 The logb functions</b></a>
20041 1 -- logb((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
20042 -- logb((+-)(inf)) returns +(inf).
20043 2 The returned value is exact and is independent of the current rounding direction mode.
20045 [<a name="p518" href="#p518">page 518</a>] (<a href="#Contents">Contents</a>)
20047 <a name="F.10.3.12" href="#F.10.3.12"><b> F.10.3.12 The modf functions</b></a>
20048 1 -- modf((+-)x, iptr) returns a result with the same sign as x.
20049 -- modf((+-)(inf), iptr) returns (+-)0 and stores (+-)(inf) in the object pointed to by iptr.
20050 -- modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
20052 2 The returned values are exact and are independent of the current rounding direction
20054 3 modf behaves as though implemented by
20055 #include <a href="#7.12"><math.h></a>
20056 #include <a href="#7.6"><fenv.h></a>
20057 #pragma STDC FENV_ACCESS ON
20058 double modf(double value, double *iptr)
20060 int save_round = fegetround();
20061 fesetround(FE_TOWARDZERO);
20062 *iptr = nearbyint(value);
20063 fesetround(save_round);
20065 isinf(value) ? 0.0 :
20066 value - (*iptr), value);
20068 <a name="F.10.3.13" href="#F.10.3.13"><b> F.10.3.13 The scalbn and scalbln functions</b></a>
20069 1 -- scalbn((+-)0, n) returns (+-)0.
20070 -- scalbn(x, 0) returns x.
20071 -- scalbn((+-)(inf), n) returns (+-)(inf).
20072 2 If the calculation does not overflow or underflow, the returned value is exact and
20073 independent of the current rounding direction mode.
20075 [<a name="p519" href="#p519">page 519</a>] (<a href="#Contents">Contents</a>)
20077 <a name="F.10.4" href="#F.10.4"><b> F.10.4 Power and absolute value functions</b></a>
20078 <a name="F.10.4.1" href="#F.10.4.1"><b> F.10.4.1 The cbrt functions</b></a>
20079 1 -- cbrt((+-)0) returns (+-)0.
20080 -- cbrt((+-)(inf)) returns (+-)(inf).
20081 <a name="F.10.4.2" href="#F.10.4.2"><b> F.10.4.2 The fabs functions</b></a>
20082 1 -- fabs((+-)0) returns +0.
20083 -- fabs((+-)(inf)) returns +(inf).
20084 2 The returned value is exact and is independent of the current rounding direction mode.
20085 <a name="F.10.4.3" href="#F.10.4.3"><b> F.10.4.3 The hypot functions</b></a>
20086 1 -- hypot(x, y), hypot(y, x), and hypot(x, -y) are equivalent.
20087 -- hypot(x, (+-)0) is equivalent to fabs(x).
20088 -- hypot((+-)(inf), y) returns +(inf), even if y is a NaN.
20089 <a name="F.10.4.4" href="#F.10.4.4"><b> F.10.4.4 The pow functions</b></a>
20090 1 -- pow((+-)0, y) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception
20091 for y an odd integer < 0.
20092 -- pow((+-)0, y) returns +(inf) and raises the ''divide-by-zero'' floating-point exception
20093 for y < 0, finite, and not an odd integer.
20094 -- pow((+-)0, -(inf)) returns +(inf) and may raise the ''divide-by-zero'' floating-point
20096 -- pow((+-)0, y) returns (+-)0 for y an odd integer > 0.
20097 -- pow((+-)0, y) returns +0 for y > 0 and not an odd integer.
20098 -- pow(-1, (+-)(inf)) returns 1.
20099 -- pow(+1, y) returns 1 for any y, even a NaN.
20100 -- pow(x, (+-)0) returns 1 for any x, even a NaN.
20101 -- pow(x, y) returns a NaN and raises the ''invalid'' floating-point exception for
20102 finite x < 0 and finite non-integer y.
20103 -- pow(x, -(inf)) returns +(inf) for | x | < 1.
20104 -- pow(x, -(inf)) returns +0 for | x | > 1.
20105 -- pow(x, +(inf)) returns +0 for | x | < 1.
20106 -- pow(x, +(inf)) returns +(inf) for | x | > 1.
20108 [<a name="p520" href="#p520">page 520</a>] (<a href="#Contents">Contents</a>)
20110 -- pow(-(inf), y) returns -0 for y an odd integer < 0.
20111 -- pow(-(inf), y) returns +0 for y < 0 and not an odd integer.
20112 -- pow(-(inf), y) returns -(inf) for y an odd integer > 0.
20113 -- pow(-(inf), y) returns +(inf) for y > 0 and not an odd integer.
20114 -- pow(+(inf), y) returns +0 for y < 0.
20115 -- pow(+(inf), y) returns +(inf) for y > 0.
20116 <a name="F.10.4.5" href="#F.10.4.5"><b> F.10.4.5 The sqrt functions</b></a>
20117 1 sqrt is fully specified as a basic arithmetic operation in IEC 60559. The returned value
20118 is dependent on the current rounding direction mode.
20119 <a name="F.10.5" href="#F.10.5"><b> F.10.5 Error and gamma functions</b></a>
20120 <a name="F.10.5.1" href="#F.10.5.1"><b> F.10.5.1 The erf functions</b></a>
20121 1 -- erf((+-)0) returns (+-)0.
20122 -- erf((+-)(inf)) returns (+-)1.
20123 <a name="F.10.5.2" href="#F.10.5.2"><b> F.10.5.2 The erfc functions</b></a>
20124 1 -- erfc(-(inf)) returns 2.
20125 -- erfc(+(inf)) returns +0.
20126 <a name="F.10.5.3" href="#F.10.5.3"><b> F.10.5.3 The lgamma functions</b></a>
20127 1 -- lgamma(1) returns +0.
20128 -- lgamma(2) returns +0.
20129 -- lgamma(x) returns +(inf) and raises the ''divide-by-zero'' floating-point exception for
20130 x a negative integer or zero.
20131 -- lgamma(-(inf)) returns +(inf).
20132 -- lgamma(+(inf)) returns +(inf).
20133 <a name="F.10.5.4" href="#F.10.5.4"><b> F.10.5.4 The tgamma functions</b></a>
20134 1 -- tgamma((+-)0) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
20135 -- tgamma(x) returns a NaN and raises the ''invalid'' floating-point exception for x a
20137 -- tgamma(-(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
20138 -- tgamma(+(inf)) returns +(inf).
20140 [<a name="p521" href="#p521">page 521</a>] (<a href="#Contents">Contents</a>)
20142 <a name="F.10.6" href="#F.10.6"><b> F.10.6 Nearest integer functions</b></a>
20143 <a name="F.10.6.1" href="#F.10.6.1"><b> F.10.6.1 The ceil functions</b></a>
20144 1 -- ceil((+-)0) returns (+-)0.
20145 -- ceil((+-)(inf)) returns (+-)(inf).
20146 2 The returned value is independent of the current rounding direction mode.
20147 3 The double version of ceil behaves as though implemented by
20148 #include <a href="#7.12"><math.h></a>
20149 #include <a href="#7.6"><fenv.h></a>
20150 #pragma STDC FENV_ACCESS ON
20151 double ceil(double x)
20154 int save_round = fegetround();
20155 fesetround(FE_UPWARD);
20156 result = rint(x); // or nearbyint instead of rint
20157 fesetround(save_round);
20160 4 The ceil functions may, but are not required to, raise the ''inexact'' floating-point
20161 exception for finite non-integer arguments, as this implementation does.
20162 <a name="F.10.6.2" href="#F.10.6.2"><b> F.10.6.2 The floor functions</b></a>
20163 1 -- floor((+-)0) returns (+-)0.
20164 -- floor((+-)(inf)) returns (+-)(inf).
20165 2 The returned value and is independent of the current rounding direction mode.
20166 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
20167 not required to, raise the ''inexact'' floating-point exception for finite non-integer
20168 arguments, as that implementation does.
20169 <a name="F.10.6.3" href="#F.10.6.3"><b> F.10.6.3 The nearbyint functions</b></a>
20170 1 The nearbyint functions use IEC 60559 rounding according to the current rounding
20171 direction. They do not raise the ''inexact'' floating-point exception if the result differs in
20172 value from the argument.
20173 -- nearbyint((+-)0) returns (+-)0 (for all rounding directions).
20174 -- nearbyint((+-)(inf)) returns (+-)(inf) (for all rounding directions).
20176 [<a name="p522" href="#p522">page 522</a>] (<a href="#Contents">Contents</a>)
20178 <a name="F.10.6.4" href="#F.10.6.4"><b> F.10.6.4 The rint functions</b></a>
20179 1 The rint functions differ from the nearbyint functions only in that they do raise the
20180 ''inexact'' floating-point exception if the result differs in value from the argument.
20181 <a name="F.10.6.5" href="#F.10.6.5"><b> F.10.6.5 The lrint and llrint functions</b></a>
20182 1 The lrint and llrint functions provide floating-to-integer conversion as prescribed
20183 by IEC 60559. They round according to the current rounding direction. If the rounded
20184 value is outside the range of the return type, the numeric result is unspecified and the
20185 ''invalid'' floating-point exception is raised. When they raise no other floating-point
20186 exception and the result differs from the argument, they raise the ''inexact'' floating-point
20188 <a name="F.10.6.6" href="#F.10.6.6"><b> F.10.6.6 The round functions</b></a>
20189 1 -- round((+-)0) returns (+-)0.
20190 -- round((+-)(inf)) returns (+-)(inf).
20191 2 The returned value is independent of the current rounding direction mode.
20192 3 The double version of round behaves as though implemented by
20193 #include <a href="#7.12"><math.h></a>
20194 #include <a href="#7.6"><fenv.h></a>
20195 #pragma STDC FENV_ACCESS ON
20196 double round(double x)
20200 feholdexcept(&save_env);
20202 if (fetestexcept(FE_INEXACT)) {
20203 fesetround(FE_TOWARDZERO);
20204 result = rint(copysign(0.5 + fabs(x), x));
20206 feupdateenv(&save_env);
20209 The round functions may, but are not required to, raise the ''inexact'' floating-point
20210 exception for finite non-integer numeric arguments, as this implementation does.
20212 [<a name="p523" href="#p523">page 523</a>] (<a href="#Contents">Contents</a>)
20214 <a name="F.10.6.7" href="#F.10.6.7"><b> F.10.6.7 The lround and llround functions</b></a>
20215 1 The lround and llround functions differ from the lrint and llrint functions
20216 with the default rounding direction just in that the lround and llround functions
20217 round halfway cases away from zero and need not raise the ''inexact'' floating-point
20218 exception for non-integer arguments that round to within the range of the return type.
20219 <a name="F.10.6.8" href="#F.10.6.8"><b> F.10.6.8 The trunc functions</b></a>
20220 1 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
20221 rounding direction). The returned value is exact.
20222 -- trunc((+-)0) returns (+-)0.
20223 -- trunc((+-)(inf)) returns (+-)(inf).
20224 2 The returned value is independent of the current rounding direction mode. The trunc
20225 functions may, but are not required to, raise the ''inexact'' floating-point exception for
20226 finite non-integer arguments.
20227 <a name="F.10.7" href="#F.10.7"><b> F.10.7 Remainder functions</b></a>
20228 <a name="F.10.7.1" href="#F.10.7.1"><b> F.10.7.1 The fmod functions</b></a>
20229 1 -- fmod((+-)0, y) returns (+-)0 for y not zero.
20230 -- fmod(x, y) returns a NaN and raises the ''invalid'' floating-point exception for x
20231 infinite or y zero (and neither is a NaN).
20232 -- fmod(x, (+-)(inf)) returns x for x not infinite.
20233 2 When subnormal results are supported, the returned value is exact and is independent of
20234 the current rounding direction mode.
20235 3 The double version of fmod behaves as though implemented by
20236 #include <a href="#7.12"><math.h></a>
20237 #include <a href="#7.6"><fenv.h></a>
20238 #pragma STDC FENV_ACCESS ON
20239 double fmod(double x, double y)
20242 result = remainder(fabs(x), (y = fabs(y)));
20243 if (signbit(result)) result += y;
20244 return copysign(result, x);
20247 [<a name="p524" href="#p524">page 524</a>] (<a href="#Contents">Contents</a>)
20249 <a name="F.10.7.2" href="#F.10.7.2"><b> F.10.7.2 The remainder functions</b></a>
20250 1 The remainder functions are fully specified as a basic arithmetic operation in
20252 2 When subnormal results are supported, the returned value is exact and is independent of
20253 the current rounding direction mode.
20254 <a name="F.10.7.3" href="#F.10.7.3"><b> F.10.7.3 The remquo functions</b></a>
20255 1 The remquo functions follow the specifications for the remainder functions. They
20256 have no further specifications special to IEC 60559 implementations.
20257 2 When subnormal results are supported, the returned value is exact and is independent of
20258 the current rounding direction mode.
20259 <a name="F.10.8" href="#F.10.8"><b> F.10.8 Manipulation functions</b></a>
20260 <a name="F.10.8.1" href="#F.10.8.1"><b> F.10.8.1 The copysign functions</b></a>
20261 1 copysign is specified in the Appendix to IEC 60559.
20262 2 The returned value is exact and is independent of the current rounding direction mode.
20263 <a name="F.10.8.2" href="#F.10.8.2"><b> F.10.8.2 The nan functions</b></a>
20264 1 All IEC 60559 implementations support quiet NaNs, in all floating formats.
20265 2 The returned value is exact and is independent of the current rounding direction mode.
20266 <a name="F.10.8.3" href="#F.10.8.3"><b> F.10.8.3 The nextafter functions</b></a>
20267 1 -- nextafter(x, y) raises the ''overflow'' and ''inexact'' floating-point exceptions
20268 for x finite and the function value infinite.
20269 -- nextafter(x, y) raises the ''underflow'' and ''inexact'' floating-point
20270 exceptions for the function value subnormal or zero and x != y.
20271 2 Even though underflow or overflow can occur, the returned value is independent of the
20272 current rounding direction mode.
20273 <a name="F.10.8.4" href="#F.10.8.4"><b> F.10.8.4 The nexttoward functions</b></a>
20274 1 No additional requirements beyond those on nextafter.
20275 2 Even though underflow or overflow can occur, the returned value is independent of the
20276 current rounding direction mode.
20278 [<a name="p525" href="#p525">page 525</a>] (<a href="#Contents">Contents</a>)
20280 <a name="F.10.9" href="#F.10.9"><b> F.10.9 Maximum, minimum, and positive difference functions</b></a>
20281 <a name="F.10.9.1" href="#F.10.9.1"><b> F.10.9.1 The fdim functions</b></a>
20282 1 No additional requirements.
20283 <a name="F.10.9.2" href="#F.10.9.2"><b> F.10.9.2 The fmax functions</b></a>
20284 1 If just one argument is a NaN, the fmax functions return the other argument (if both
20285 arguments are NaNs, the functions return a NaN).
20286 2 The returned value is exact and is independent of the current rounding direction mode.
20287 3 The body of the fmax function might be<sup><a href="#note361"><b>361)</b></a></sup>
20288 { return (isgreaterequal(x, y) ||
20289 isnan(y)) ? x : y; }
20290 <a name="F.10.9.3" href="#F.10.9.3"><b> F.10.9.3 The fmin functions</b></a>
20291 1 The fmin functions are analogous to the fmax functions (see <a href="#F.10.9.2">F.10.9.2</a>).
20292 2 The returned value is exact and is independent of the current rounding direction mode.
20293 <a name="F.10.10" href="#F.10.10"><b> F.10.10 Floating multiply-add</b></a>
20294 <a name="F.10.10.1" href="#F.10.10.1"><b> F.10.10.1 The fma functions</b></a>
20295 1 -- fma(x, y, z) computes xy + z, correctly rounded once.
20296 -- fma(x, y, z) returns a NaN and optionally raises the ''invalid'' floating-point
20297 exception if one of x and y is infinite, the other is zero, and z is a NaN.
20298 -- fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if
20299 one of x and y is infinite, the other is zero, and z is not a NaN.
20300 -- fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if x
20301 times y is an exact infinity and z is also an infinity but with the opposite sign.
20306 <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
20307 return +0; however, implementation in software might be impractical.
20309 [<a name="p526" href="#p526">page 526</a>] (<a href="#Contents">Contents</a>)
20311 <a name="F.10.11" href="#F.10.11"><b> F.10.11 Comparison macros</b></a>
20312 1 Relational operators and their corresponding comparison macros (<a href="#7.12.14">7.12.14</a>) produce
20313 equivalent result values, even if argument values are represented in wider formats. Thus,
20314 comparison macro arguments represented in formats wider than their semantic types are
20315 not converted to the semantic types, unless the wide evaluation method converts operands
20316 of relational operators to their semantic types. The standard wide evaluation methods
20317 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
20318 operands of relational operators to their semantic types.
20320 [<a name="p527" href="#p527">page 527</a>] (<a href="#Contents">Contents</a>)
20322 <a name="G" href="#G"><b> Annex G</b></a>
20324 IEC 60559-compatible complex arithmetic
20325 <a name="G.1" href="#G.1"><b> G.1 Introduction</b></a>
20326 1 This annex supplements <a href="#F">annex F</a> to specify complex arithmetic for compatibility with
20327 IEC 60559 real floating-point arithmetic. An implementation that defines *
20328 __STDC_IEC_559_COMPLEX__ shall conform to the specifications in this annex.<sup><a href="#note362"><b>362)</b></a></sup>
20329 <a name="G.2" href="#G.2"><b> G.2 Types</b></a>
20330 1 There is a new keyword _Imaginary, which is used to specify imaginary types. It is
20331 used as a type specifier within declaration specifiers in the same way as _Complex is
20332 (thus, _Imaginary float is a valid type name).
20333 2 There are three imaginary types, designated as float _Imaginary, double
20334 _Imaginary, and long double _Imaginary. The imaginary types (along with
20335 the real floating and complex types) are floating types.
20336 3 For imaginary types, the corresponding real type is given by deleting the keyword
20337 _Imaginary from the type name.
20338 4 Each imaginary type has the same representation and alignment requirements as the
20339 corresponding real type. The value of an object of imaginary type is the value of the real
20340 representation times the imaginary unit.
20341 5 The imaginary type domain comprises the imaginary types.
20342 <a name="G.3" href="#G.3"><b> G.3 Conventions</b></a>
20343 1 A complex or imaginary value with at least one infinite part is regarded as an infinity
20344 (even if its other part is a NaN). A complex or imaginary value is a finite number if each
20345 of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
20346 a zero if each of its parts is a zero.
20351 <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
20352 to these specifications.
20354 [<a name="p528" href="#p528">page 528</a>] (<a href="#Contents">Contents</a>)
20356 <a name="G.4" href="#G.4"><b> G.4 Conversions</b></a>
20357 <a name="G.4.1" href="#G.4.1"><b> G.4.1 Imaginary types</b></a>
20358 1 Conversions among imaginary types follow rules analogous to those for real floating
20360 <a name="G.4.2" href="#G.4.2"><b> G.4.2 Real and imaginary</b></a>
20361 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
20362 result is a positive zero.
20363 2 When a value of real type is converted to an imaginary type, the result is a positive
20365 <a name="G.4.3" href="#G.4.3"><b> G.4.3 Imaginary and complex</b></a>
20366 1 When a value of imaginary type is converted to a complex type, the real part of the
20367 complex result value is a positive zero and the imaginary part of the complex result value
20368 is determined by the conversion rules for the corresponding real types.
20369 2 When a value of complex type is converted to an imaginary type, the real part of the
20370 complex value is discarded and the value of the imaginary part is converted according to
20371 the conversion rules for the corresponding real types.
20372 <a name="G.5" href="#G.5"><b> G.5 Binary operators</b></a>
20373 1 The following subclauses supplement <a href="#6.5">6.5</a> in order to specify the type of the result for an
20374 operation with an imaginary operand.
20375 2 For most operand types, the value of the result of a binary operator with an imaginary or
20376 complex operand is completely determined, with reference to real arithmetic, by the usual
20377 mathematical formula. For some operand types, the usual mathematical formula is
20378 problematic because of its treatment of infinities and because of undue overflow or
20379 underflow; in these cases the result satisfies certain properties (specified in <a href="#G.5.1">G.5.1</a>), but is
20380 not completely determined.
20385 <sup><a name="note363" href="#note363"><b>363)</b></a></sup> See <a href="#6.3.1.2">6.3.1.2</a>.
20387 [<a name="p529" href="#p529">page 529</a>] (<a href="#Contents">Contents</a>)
20389 <a name="G.5.1" href="#G.5.1"><b> G.5.1 Multiplicative operators</b></a>
20391 1 If one operand has real type and the other operand has imaginary type, then the result has
20392 imaginary type. If both operands have imaginary type, then the result has real type. (If
20393 either operand has complex type, then the result has complex type.)
20394 2 If the operands are not both complex, then the result and floating-point exception
20395 behavior of the * operator is defined by the usual mathematical formula:
20398 x xu i(xv) (xu) + i(xv)
20400 iy i(yu) -yv (-yv) + i(yu)
20402 x + iy (xu) + i(yu) (-yv) + i(xv)
20403 3 If the second operand is not complex, then the result and floating-point exception
20404 behavior of the / operator is defined by the usual mathematical formula:
20411 x + iy (x/u) + i(y/u) (y/v) + i(-x/v)
20412 4 The * and / operators satisfy the following infinity properties for all real, imaginary, and
20413 complex operands:<sup><a href="#note364"><b>364)</b></a></sup>
20414 -- if one operand is an infinity and the other operand is a nonzero finite number or an
20415 infinity, then the result of the * operator is an infinity;
20416 -- if the first operand is an infinity and the second operand is a finite number, then the
20417 result of the / operator is an infinity;
20418 -- if the first operand is a finite number and the second operand is an infinity, then the
20419 result of the / operator is a zero;
20424 <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
20425 (at least where the state for CX_LIMITED_RANGE is ''off'').
20427 [<a name="p530" href="#p530">page 530</a>] (<a href="#Contents">Contents</a>)
20429 -- if the first operand is a nonzero finite number or an infinity and the second operand is
20430 a zero, then the result of the / operator is an infinity.
20431 5 If both operands of the * operator are complex or if the second operand of the / operator
20432 is complex, the operator raises floating-point exceptions if appropriate for the calculation
20433 of the parts of the result, and may raise spurious floating-point exceptions.
20434 6 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
20435 that the imaginary unit I has imaginary type (see <a href="#G.6">G.6</a>).
20436 #include <a href="#7.12"><math.h></a>
20437 #include <a href="#7.3"><complex.h></a>
20438 /* Multiply z * w ... */
20439 double complex _Cmultd(double complex z, double complex w)
20441 #pragma STDC FP_CONTRACT OFF
20442 double a, b, c, d, ac, bd, ad, bc, x, y;
20443 a = creal(z); b = cimag(z);
20444 c = creal(w); d = cimag(w);
20445 ac = a * c; bd = b * d;
20446 ad = a * d; bc = b * c;
20447 x = ac - bd; y = ad + bc;
20448 if (isnan(x) && isnan(y)) {
20449 /* Recover infinities that computed as NaN+iNaN ... */
20451 if ( isinf(a) || isinf(b) ) { // z is infinite
20452 /* "Box" the infinity and change NaNs in the other factor to 0 */
20453 a = copysign(isinf(a) ? 1.0 : 0.0, a);
20454 b = copysign(isinf(b) ? 1.0 : 0.0, b);
20455 if (isnan(c)) c = copysign(0.0, c);
20456 if (isnan(d)) d = copysign(0.0, d);
20459 if ( isinf(c) || isinf(d) ) { // w is infinite
20460 /* "Box" the infinity and change NaNs in the other factor to 0 */
20461 c = copysign(isinf(c) ? 1.0 : 0.0, c);
20462 d = copysign(isinf(d) ? 1.0 : 0.0, d);
20463 if (isnan(a)) a = copysign(0.0, a);
20464 if (isnan(b)) b = copysign(0.0, b);
20467 if (!recalc && (isinf(ac) || isinf(bd) ||
20468 isinf(ad) || isinf(bc))) {
20469 /* Recover infinities from overflow by changing NaNs to 0 ... */
20470 if (isnan(a)) a = copysign(0.0, a);
20471 if (isnan(b)) b = copysign(0.0, b);
20472 if (isnan(c)) c = copysign(0.0, c);
20473 if (isnan(d)) d = copysign(0.0, d);
20478 [<a name="p531" href="#p531">page 531</a>] (<a href="#Contents">Contents</a>)
20480 x = INFINITY * ( a * c - b * d );
20481 y = INFINITY * ( a * d + b * c );
20486 7 This implementation achieves the required treatment of infinities at the cost of only one isnan test in
20487 ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur.
20489 8 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
20490 #include <a href="#7.12"><math.h></a>
20491 #include <a href="#7.3"><complex.h></a>
20492 /* Divide z / w ... */
20493 double complex _Cdivd(double complex z, double complex w)
20495 #pragma STDC FP_CONTRACT OFF
20496 double a, b, c, d, logbw, denom, x, y;
20498 a = creal(z); b = cimag(z);
20499 c = creal(w); d = cimag(w);
20500 logbw = logb(fmax(fabs(c), fabs(d)));
20501 if (logbw == INFINITY) {
20502 ilogbw = (int)logbw;
20503 c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
20505 denom = c * c + d * d;
20506 x = scalbn((a * c + b * d) / denom, -ilogbw);
20507 y = scalbn((b * c - a * d) / denom, -ilogbw);
20508 /* Recover infinities and zeros that computed as NaN+iNaN; */
20509 /* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
20510 if (isnan(x) && isnan(y)) {
20511 if ((denom == 0.0) &&
20512 (!isnan(a) || !isnan(b))) {
20513 x = copysign(INFINITY, c) * a;
20514 y = copysign(INFINITY, c) * b;
20516 else if ((isinf(a) || isinf(b)) &&
20517 isfinite(c) && isfinite(d)) {
20518 a = copysign(isinf(a) ? 1.0 : 0.0, a);
20519 b = copysign(isinf(b) ? 1.0 : 0.0, b);
20520 x = INFINITY * ( a * c + b * d );
20521 y = INFINITY * ( b * c - a * d );
20523 else if (isinf(logbw) &&
20524 isfinite(a) && isfinite(b)) {
20525 c = copysign(isinf(c) ? 1.0 : 0.0, c);
20526 d = copysign(isinf(d) ? 1.0 : 0.0, d);
20527 x = 0.0 * ( a * c + b * d );
20528 y = 0.0 * ( b * c - a * d );
20530 [<a name="p532" href="#p532">page 532</a>] (<a href="#Contents">Contents</a>)
20536 9 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
20537 for multiplication. In the spirit of the multiplication example above, this code does not defend against
20538 overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
20539 with division, provides better roundoff characteristics.
20541 <a name="G.5.2" href="#G.5.2"><b> G.5.2 Additive operators</b></a>
20543 1 If both operands have imaginary type, then the result has imaginary type. (If one operand
20544 has real type and the other operand has imaginary type, or if either operand has complex
20545 type, then the result has complex type.)
20546 2 In all cases the result and floating-point exception behavior of a + or - operator is defined
20547 by the usual mathematical formula:
20550 x x(+-)u x (+-) iv (x (+-) u) (+-) iv
20552 iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)
20554 x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)
20555 <a name="G.6" href="#G.6"><b> G.6 Complex arithmetic <complex.h></b></a>
20560 are defined, respectively, as _Imaginary and a constant expression of type const
20561 float _Imaginary with the value of the imaginary unit. The macro
20563 is defined to be _Imaginary_I (not _Complex_I as stated in <a href="#7.3">7.3</a>). Notwithstanding
20564 the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and then perhaps redefine the macro
20566 2 This subclause contains specifications for the <a href="#7.3"><complex.h></a> functions that are
20567 particularly suited to IEC 60559 implementations. For families of functions, the
20568 specifications apply to all of the functions even though only the principal function is
20570 [<a name="p533" href="#p533">page 533</a>] (<a href="#Contents">Contents</a>)
20572 shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument
20573 and the result, the result has the same sign as the argument.
20574 3 The functions are continuous onto both sides of their branch cuts, taking into account the
20575 sign of zero. For example, csqrt(-2 (+-) i0) = (+-)i(sqrt)2. -
20576 4 Since complex and imaginary values are composed of real values, each function may be
20577 regarded as computing real values from real values. Except as noted, the functions treat
20578 real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
20579 manner consistent with the specifications for real functions in F.10.<sup><a href="#note365"><b>365)</b></a></sup>
20580 5 The functions cimag, conj, cproj, and creal are fully specified for all
20581 implementations, including IEC 60559 ones, in <a href="#7.3.9">7.3.9</a>. These functions raise no floating-
20583 6 Each of the functions cabs and carg is specified by a formula in terms of a real
20584 function (whose special cases are covered in <a href="#F">annex F</a>):
20585 cabs(x + iy) = hypot(x, y)
20586 carg(x + iy) = atan2(y, x)
20587 7 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
20588 a formula in terms of other complex functions (whose special cases are specified below):
20589 casin(z) = -i casinh(iz)
20590 catan(z) = -i catanh(iz)
20591 ccos(z) = ccosh(iz)
20592 csin(z) = -i csinh(iz)
20593 ctan(z) = -i ctanh(iz)
20594 8 For the other functions, the following subclauses specify behavior for special cases,
20595 including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For
20596 families of functions, the specifications apply to all of the functions even though only the
20597 principal function is shown. For a function f satisfying f (conj(z)) = conj( f (z)), the
20598 specifications for the upper half-plane imply the specifications for the lower half-plane; if
20599 the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the
20600 specifications for the first quadrant imply the specifications for the other three quadrants.
20601 9 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
20606 <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
20607 other part is a NaN.
20609 [<a name="p534" href="#p534">page 534</a>] (<a href="#Contents">Contents</a>)
20611 <a name="G.6.1" href="#G.6.1"><b> G.6.1 Trigonometric functions</b></a>
20612 <a name="G.6.1.1" href="#G.6.1.1"><b> G.6.1.1 The cacos functions</b></a>
20613 1 -- cacos(conj(z)) = conj(cacos(z)).
20614 -- cacos((+-)0 + i0) returns pi /2 - i0.
20615 -- cacos((+-)0 + iNaN) returns pi /2 + iNaN.
20616 -- cacos(x + i (inf)) returns pi /2 - i (inf), for finite x.
20617 -- cacos(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
20618 point exception, for nonzero finite x.
20619 -- cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.
20620 -- cacos(+(inf) + iy) returns +0 - i (inf), for positive-signed finite y.
20621 -- cacos(-(inf) + i (inf)) returns 3pi /4 - i (inf).
20622 -- cacos(+(inf) + i (inf)) returns pi /4 - i (inf).
20623 -- cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
20624 result is unspecified).
20625 -- cacos(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
20626 point exception, for finite y.
20627 -- cacos(NaN + i (inf)) returns NaN - i (inf).
20628 -- cacos(NaN + iNaN) returns NaN + iNaN.
20629 <a name="G.6.2" href="#G.6.2"><b> G.6.2 Hyperbolic functions</b></a>
20630 <a name="G.6.2.1" href="#G.6.2.1"><b> G.6.2.1 The cacosh functions</b></a>
20631 1 -- cacosh(conj(z)) = conj(cacosh(z)).
20632 -- cacosh((+-)0 + i0) returns +0 + ipi /2.
20633 -- cacosh(x + i (inf)) returns +(inf) + ipi /2, for finite x.
20634 -- cacosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
20635 floating-point exception, for finite x.
20636 -- cacosh(-(inf) + iy) returns +(inf) + ipi , for positive-signed finite y.
20637 -- cacosh(+(inf) + iy) returns +(inf) + i0, for positive-signed finite y.
20638 -- cacosh(-(inf) + i (inf)) returns +(inf) + i3pi /4.
20639 -- cacosh(+(inf) + i (inf)) returns +(inf) + ipi /4.
20640 -- cacosh((+-)(inf) + iNaN) returns +(inf) + iNaN.
20642 [<a name="p535" href="#p535">page 535</a>] (<a href="#Contents">Contents</a>)
20644 -- cacosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
20645 floating-point exception, for finite y.
20646 -- cacosh(NaN + i (inf)) returns +(inf) + iNaN.
20647 -- cacosh(NaN + iNaN) returns NaN + iNaN.
20648 <a name="G.6.2.2" href="#G.6.2.2"><b> G.6.2.2 The casinh functions</b></a>
20649 1 -- casinh(conj(z)) = conj(casinh(z)) and casinh is odd.
20650 -- casinh(+0 + i0) returns 0 + i0.
20651 -- casinh(x + i (inf)) returns +(inf) + ipi /2 for positive-signed finite x.
20652 -- casinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
20653 floating-point exception, for finite x.
20654 -- casinh(+(inf) + iy) returns +(inf) + i0 for positive-signed finite y.
20655 -- casinh(+(inf) + i (inf)) returns +(inf) + ipi /4.
20656 -- casinh(+(inf) + iNaN) returns +(inf) + iNaN.
20657 -- casinh(NaN + i0) returns NaN + i0.
20658 -- casinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
20659 floating-point exception, for finite nonzero y.
20660 -- casinh(NaN + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result
20662 -- casinh(NaN + iNaN) returns NaN + iNaN.
20663 <a name="G.6.2.3" href="#G.6.2.3"><b> G.6.2.3 The catanh functions</b></a>
20664 1 -- catanh(conj(z)) = conj(catanh(z)) and catanh is odd.
20665 -- catanh(+0 + i0) returns +0 + i0.
20666 -- catanh(+0 + iNaN) returns +0 + iNaN.
20667 -- catanh(+1 + i0) returns +(inf) + i0 and raises the ''divide-by-zero'' floating-point
20669 -- catanh(x + i (inf)) returns +0 + ipi /2, for finite positive-signed x.
20670 -- catanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
20671 floating-point exception, for nonzero finite x.
20672 -- catanh(+(inf) + iy) returns +0 + ipi /2, for finite positive-signed y.
20673 -- catanh(+(inf) + i (inf)) returns +0 + ipi /2.
20674 -- catanh(+(inf) + iNaN) returns +0 + iNaN.
20676 [<a name="p536" href="#p536">page 536</a>] (<a href="#Contents">Contents</a>)
20678 -- catanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
20679 floating-point exception, for finite y.
20680 -- catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is
20682 -- catanh(NaN + iNaN) returns NaN + iNaN.
20683 <a name="G.6.2.4" href="#G.6.2.4"><b> G.6.2.4 The ccosh functions</b></a>
20684 1 -- ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
20685 -- ccosh(+0 + i0) returns 1 + i0.
20686 -- ccosh(+0 + i (inf)) returns NaN (+-) i0 (where the sign of the imaginary part of the
20687 result is unspecified) and raises the ''invalid'' floating-point exception.
20688 -- ccosh(+0 + iNaN) returns NaN (+-) i0 (where the sign of the imaginary part of the
20689 result is unspecified).
20690 -- ccosh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
20691 exception, for finite nonzero x.
20692 -- ccosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
20693 point exception, for finite nonzero x.
20694 -- ccosh(+(inf) + i0) returns +(inf) + i0.
20695 -- ccosh(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
20696 -- ccosh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
20697 unspecified) and raises the ''invalid'' floating-point exception.
20698 -- ccosh(+(inf) + iNaN) returns +(inf) + iNaN.
20699 -- ccosh(NaN + i0) returns NaN (+-) i0 (where the sign of the imaginary part of the
20700 result is unspecified).
20701 -- ccosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
20702 point exception, for all nonzero numbers y.
20703 -- ccosh(NaN + iNaN) returns NaN + iNaN.
20704 <a name="G.6.2.5" href="#G.6.2.5"><b> G.6.2.5 The csinh functions</b></a>
20705 1 -- csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
20706 -- csinh(+0 + i0) returns +0 + i0.
20707 -- csinh(+0 + i (inf)) returns (+-)0 + iNaN (where the sign of the real part of the result is
20708 unspecified) and raises the ''invalid'' floating-point exception.
20709 -- csinh(+0 + iNaN) returns (+-)0 + iNaN (where the sign of the real part of the result is
20712 [<a name="p537" href="#p537">page 537</a>] (<a href="#Contents">Contents</a>)
20714 -- csinh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
20715 exception, for positive finite x.
20716 -- csinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
20717 point exception, for finite nonzero x.
20718 -- csinh(+(inf) + i0) returns +(inf) + i0.
20719 -- csinh(+(inf) + iy) returns +(inf) cis(y), for positive finite y.
20720 -- csinh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
20721 unspecified) and raises the ''invalid'' floating-point exception.
20722 -- csinh(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
20724 -- csinh(NaN + i0) returns NaN + i0.
20725 -- csinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
20726 point exception, for all nonzero numbers y.
20727 -- csinh(NaN + iNaN) returns NaN + iNaN.
20728 <a name="G.6.2.6" href="#G.6.2.6"><b> G.6.2.6 The ctanh functions</b></a>
20729 1 -- ctanh(conj(z)) = conj(ctanh(z))and ctanh is odd.
20730 -- ctanh(+0 + i0) returns +0 + i0.
20731 -- ctanh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
20732 exception, for finite x.
20733 -- ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
20734 point exception, for finite x.
20735 -- ctanh(+(inf) + iy) returns 1 + i0 sin(2y), for positive-signed finite y.
20736 -- ctanh(+(inf) + i (inf)) returns 1 (+-) i0 (where the sign of the imaginary part of the result
20738 -- ctanh(+(inf) + iNaN) returns 1 (+-) i0 (where the sign of the imaginary part of the
20739 result is unspecified).
20740 -- ctanh(NaN + i0) returns NaN + i0.
20741 -- ctanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
20742 point exception, for all nonzero numbers y.
20743 -- ctanh(NaN + iNaN) returns NaN + iNaN.
20745 [<a name="p538" href="#p538">page 538</a>] (<a href="#Contents">Contents</a>)
20747 <a name="G.6.3" href="#G.6.3"><b> G.6.3 Exponential and logarithmic functions</b></a>
20748 <a name="G.6.3.1" href="#G.6.3.1"><b> G.6.3.1 The cexp functions</b></a>
20749 1 -- cexp(conj(z)) = conj(cexp(z)).
20750 -- cexp((+-)0 + i0) returns 1 + i0.
20751 -- cexp(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
20752 exception, for finite x.
20753 -- cexp(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
20754 point exception, for finite x.
20755 -- cexp(+(inf) + i0) returns +(inf) + i0.
20756 -- cexp(-(inf) + iy) returns +0 cis(y), for finite y.
20757 -- cexp(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
20758 -- cexp(-(inf) + i (inf)) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts of
20759 the result are unspecified).
20760 -- cexp(+(inf) + i (inf)) returns (+-)(inf) + iNaN and raises the ''invalid'' floating-point
20761 exception (where the sign of the real part of the result is unspecified).
20762 -- cexp(-(inf) + iNaN) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts
20763 of the result are unspecified).
20764 -- cexp(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
20766 -- cexp(NaN + i0) returns NaN + i0.
20767 -- cexp(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
20768 point exception, for all nonzero numbers y.
20769 -- cexp(NaN + iNaN) returns NaN + iNaN.
20770 <a name="G.6.3.2" href="#G.6.3.2"><b> G.6.3.2 The clog functions</b></a>
20771 1 -- clog(conj(z)) = conj(clog(z)).
20772 -- clog(-0 + i0) returns -(inf) + ipi and raises the ''divide-by-zero'' floating-point
20774 -- clog(+0 + i0) returns -(inf) + i0 and raises the ''divide-by-zero'' floating-point
20776 -- clog(x + i (inf)) returns +(inf) + ipi /2, for finite x.
20777 -- clog(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
20778 point exception, for finite x.
20780 [<a name="p539" href="#p539">page 539</a>] (<a href="#Contents">Contents</a>)
20782 -- clog(-(inf) + iy) returns +(inf) + ipi , for finite positive-signed y.
20783 -- clog(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
20784 -- clog(-(inf) + i (inf)) returns +(inf) + i3pi /4.
20785 -- clog(+(inf) + i (inf)) returns +(inf) + ipi /4.
20786 -- clog((+-)(inf) + iNaN) returns +(inf) + iNaN.
20787 -- clog(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
20788 point exception, for finite y.
20789 -- clog(NaN + i (inf)) returns +(inf) + iNaN.
20790 -- clog(NaN + iNaN) returns NaN + iNaN.
20791 <a name="G.6.4" href="#G.6.4"><b> G.6.4 Power and absolute-value functions</b></a>
20792 <a name="G.6.4.1" href="#G.6.4.1"><b> G.6.4.1 The cpow functions</b></a>
20793 1 The cpow functions raise floating-point exceptions if appropriate for the calculation of
20794 the parts of the result, and may also raise spurious floating-point exceptions.<sup><a href="#note366"><b>366)</b></a></sup>
20795 <a name="G.6.4.2" href="#G.6.4.2"><b> G.6.4.2 The csqrt functions</b></a>
20796 1 -- csqrt(conj(z)) = conj(csqrt(z)).
20797 -- csqrt((+-)0 + i0) returns +0 + i0.
20798 -- csqrt(x + i (inf)) returns +(inf) + i (inf), for all x (including NaN).
20799 -- csqrt(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
20800 point exception, for finite x.
20801 -- csqrt(-(inf) + iy) returns +0 + i (inf), for finite positive-signed y.
20802 -- csqrt(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
20803 -- csqrt(-(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
20804 result is unspecified).
20805 -- csqrt(+(inf) + iNaN) returns +(inf) + iNaN.
20806 -- csqrt(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
20807 point exception, for finite y.
20808 -- csqrt(NaN + iNaN) returns NaN + iNaN.
20813 <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
20814 implementations that treat special cases more carefully.
20816 [<a name="p540" href="#p540">page 540</a>] (<a href="#Contents">Contents</a>)
20818 <a name="G.7" href="#G.7"><b> G.7 Type-generic math <tgmath.h></b></a>
20819 1 Type-generic macros that accept complex arguments also accept imaginary arguments. If
20820 an argument is imaginary, the macro expands to an expression whose type is real,
20821 imaginary, or complex, as appropriate for the particular function: if the argument is
20822 imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the
20823 types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and
20824 the types of the others are complex.
20825 2 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh,
20826 sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real
20829 sin(iy) = i sinh(y)
20830 tan(iy) = i tanh(y)
20832 sinh(iy) = i sin(y)
20833 tanh(iy) = i tan(y)
20834 asin(iy) = i asinh(y)
20835 atan(iy) = i atanh(y)
20836 asinh(iy) = i asin(y)
20837 atanh(iy) = i atan(y)
20839 [<a name="p541" href="#p541">page 541</a>] (<a href="#Contents">Contents</a>)
20841 <a name="H" href="#H"><b> Annex H</b></a>
20843 Language independent arithmetic
20844 <a name="H.1" href="#H.1"><b> H.1 Introduction</b></a>
20845 1 This annex documents the extent to which the C language supports the ISO/IEC 10967-1
20846 standard for language-independent arithmetic (LIA-1). LIA-1 is more general than
20847 IEC 60559 (<a href="#F">annex F</a>) in that it covers integer and diverse floating-point arithmetics.
20848 <a name="H.2" href="#H.2"><b> H.2 Types</b></a>
20849 1 The relevant C arithmetic types meet the requirements of LIA-1 types if an
20850 implementation adds notification of exceptional arithmetic operations and meets the 1
20851 unit in the last place (ULP) accuracy requirement (LIA-1 subclause <a href="#5.2.8">5.2.8</a>).
20852 <a name="H.2.1" href="#H.2.1"><b> H.2.1 Boolean type</b></a>
20853 1 The LIA-1 data type Boolean is implemented by the C data type bool with values of
20854 true and false, all from <a href="#7.18"><stdbool.h></a>.
20855 <a name="H.2.2" href="#H.2.2"><b> H.2.2 Integer types</b></a>
20856 1 The signed C integer types int, long int, long long int, and the corresponding
20857 unsigned types are compatible with LIA-1. If an implementation adds support for the
20858 LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are
20859 LIA-1 conformant types. C's unsigned integer types are ''modulo'' in the LIA-1 sense
20860 in that overflows or out-of-bounds results silently wrap. An implementation that defines
20861 signed integer types as also being modulo need not detect integer overflow, in which case,
20862 only integer divide-by-zero need be detected.
20863 2 The parameters for the integer data types can be accessed by the following:
20864 maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
20866 minint INT_MIN, LONG_MIN, LLONG_MIN
20867 3 The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
20868 is always 0 for the unsigned types, and is not provided for those types.
20870 [<a name="p542" href="#p542">page 542</a>] (<a href="#Contents">Contents</a>)
20872 <a name="H.2.2.1" href="#H.2.2.1"><b> H.2.2.1 Integer operations</b></a>
20873 1 The integer operations on integer types are the following:
20880 absI abs(x), labs(x), llabs(x)
20887 where x and y are expressions of the same integer type.
20888 <a name="H.2.3" href="#H.2.3"><b> H.2.3 Floating-point types</b></a>
20889 1 The C floating-point types float, double, and long double are compatible with
20890 LIA-1. If an implementation adds support for the LIA-1 exceptional values
20891 ''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
20892 with LIA-1. An implementation that uses IEC 60559 floating-point formats and
20893 operations (see <a href="#F">annex F</a>) along with IEC 60559 status flags and traps has LIA-1
20895 <a name="H.2.3.1" href="#H.2.3.1"><b> H.2.3.1 Floating-point parameters</b></a>
20896 1 The parameters for a floating point data type can be accessed by the following:
20898 p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
20899 emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
20900 emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
20901 2 The derived constants for the floating point types are accessed by the following:
20903 [<a name="p543" href="#p543">page 543</a>] (<a href="#Contents">Contents</a>)
20905 fmax FLT_MAX, DBL_MAX, LDBL_MAX
20906 fminN FLT_MIN, DBL_MIN, LDBL_MIN
20907 epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
20908 rnd_style FLT_ROUNDS
20909 <a name="H.2.3.2" href="#H.2.3.2"><b> H.2.3.2 Floating-point operations</b></a>
20910 1 The floating-point operations on floating-point types are the following:
20916 absF fabsf(x), fabs(x), fabsl(x)
20917 exponentF 1.f+logbf(x), 1.0+logb(x), 1.L+logbl(x)
20918 scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
20919 scalblnf(x, li), scalbln(x, li), scalblnl(x, li)
20920 intpartF modff(x, &y), modf(x, &y), modfl(x, &y)
20921 fractpartF modff(x, &y), modf(x, &y), modfl(x, &y)
20928 where x and y are expressions of the same floating point type, n is of type int, and li
20929 is of type long int.
20930 <a name="H.2.3.3" href="#H.2.3.3"><b> H.2.3.3 Rounding styles</b></a>
20931 1 The C Standard requires all floating types to use the same radix and rounding style, so
20932 that only one identifier for each is provided to map to LIA-1.
20933 2 The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
20934 truncate FLT_ROUNDS == 0
20936 [<a name="p544" href="#p544">page 544</a>] (<a href="#Contents">Contents</a>)
20938 nearest FLT_ROUNDS == 1
20939 other FLT_ROUNDS != 0 && FLT_ROUNDS != 1
20940 provided that an implementation extends FLT_ROUNDS to cover the rounding style used
20941 in all relevant LIA-1 operations, not just addition as in C.
20942 <a name="H.2.4" href="#H.2.4"><b> H.2.4 Type conversions</b></a>
20943 1 The LIA-1 type conversions are the following type casts:
20944 cvtI' -> I (int)i, (long int)i, (long long int)i,
20945 (unsigned int)i, (unsigned long int)i,
20946 (unsigned long long int)i
20947 cvtF -> I (int)x, (long int)x, (long long int)x,
20948 (unsigned int)x, (unsigned long int)x,
20949 (unsigned long long int)x
20950 cvtI -> F (float)i, (double)i, (long double)i
20951 cvtF' -> F (float)x, (double)x, (long double)x
20952 2 In the above conversions from floating to integer, the use of (cast)x can be replaced with
20953 (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
20954 (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer
20955 conversion functions, lrint(), llrint(), lround(), and llround(), can be
20956 used. They all meet LIA-1's requirements on floating to integer rounding for in-range
20957 values. For out-of-range values, the conversions shall silently wrap for the modulo types.
20958 3 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
20959 fmod( fabs(rint(x)), 65536.0 ) or (0.0 <= (y = fmod( rint(x),
20960 65536.0 )) ? y : 65536.0 + y) will compute an integer value in the range 0.0
20961 to 65535.0 which can then be cast to unsigned short int. But, the
20962 remainder() function is not useful for doing silent wrapping to signed integer types,
20963 e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
20964 range -32767.0 to +32768.0 which is not, in general, in the range of signed short
20966 4 C's conversions (casts) from floating-point to floating-point can meet LIA-1
20967 requirements if an implementation uses round-to-nearest (IEC 60559 default).
20968 5 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
20969 implementation uses round-to-nearest.
20971 [<a name="p545" href="#p545">page 545</a>] (<a href="#Contents">Contents</a>)
20973 <a name="H.3" href="#H.3"><b> H.3 Notification</b></a>
20974 1 Notification is the process by which a user or program is informed that an exceptional
20975 arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
20976 allows an implementation to cause a notification to occur when any arithmetic operation
20977 returns an exceptional value as defined in LIA-1 clause 5.
20978 <a name="H.3.1" href="#H.3.1"><b> H.3.1 Notification alternatives</b></a>
20979 1 LIA-1 requires at least the following two alternatives for handling of notifications:
20980 setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and-
20982 2 An implementation need only support a given notification alternative for the entire
20983 program. An implementation may support the ability to switch between notification
20984 alternatives during execution, but is not required to do so. An implementation can
20985 provide separate selection for each kind of notification, but this is not required.
20986 3 C allows an implementation to provide notification. C's SIGFPE (for traps) and
20987 FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
20988 can provide LIA-1 notification.
20989 4 C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
20990 provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
20991 math library function calls. User-provided signal handlers for SIGFPE allow for trap-
20992 and-resume behavior with the same constraint.
20993 <a name="H.3.1.1" href="#H.3.1.1"><b> H.3.1.1 Indicators</b></a>
20994 1 C's <a href="#7.6"><fenv.h></a> status flags are compatible with the LIA-1 indicators.
20995 2 The following mapping is for floating-point types:
20996 undefined FE_INVALID, FE_DIVBYZERO
20997 floating_overflow FE_OVERFLOW
20998 underflow FE_UNDERFLOW
20999 3 The floating-point indicator interrogation and manipulation operations are:
21000 set_indicators feraiseexcept(i)
21001 clear_indicators feclearexcept(i)
21002 test_indicators fetestexcept(i)
21003 current_indicators fetestexcept(FE_ALL_EXCEPT)
21004 where i is an expression of type int representing a subset of the LIA-1 indicators.
21005 4 C allows an implementation to provide the following LIA-1 required behavior: at
21006 program termination if any indicator is set the implementation shall send an unambiguous
21008 [<a name="p546" href="#p546">page 546</a>] (<a href="#Contents">Contents</a>)
21010 and ''hard to ignore'' message (see LIA-1 subclause <a href="#6.1.2">6.1.2</a>)
21011 5 LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
21012 This documentation makes that distinction because <a href="#7.6"><fenv.h></a> covers only the floating-
21014 <a name="H.3.1.2" href="#H.3.1.2"><b> H.3.1.2 Traps</b></a>
21015 1 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
21016 math library functions (which are not permitted to invoke a user's signal handler for
21017 SIGFPE). An implementation can provide an alternative of notification through
21018 termination with a ''hard-to-ignore'' message (see LIA-1 subclause <a href="#6.1.3">6.1.3</a>).
21019 2 LIA-1 does not require that traps be precise.
21020 3 C does require that SIGFPE be the signal corresponding to LIA-1 arithmetic exceptions,
21021 if there is any signal raised for them.
21022 4 C supports signal handlers for SIGFPE and allows trapping of LIA-1 arithmetic
21023 exceptions. When LIA-1 arithmetic exceptions do trap, C's signal-handler mechanism
21024 allows trap-and-terminate (either default implementation behavior or user replacement for
21025 it) or trap-and-resume, at the programmer's option.
21027 [<a name="p547" href="#p547">page 547</a>] (<a href="#Contents">Contents</a>)
21029 <a name="I" href="#I"><b> Annex I</b></a>
21032 1 An implementation may generate warnings in many situations, none of which are
21033 specified as part of this International Standard. The following are a few of the more
21035 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>).
21036 -- A block with initialization of an object that has automatic storage duration is jumped
21037 into (<a href="#6.2.4">6.2.4</a>).
21038 -- An implicit narrowing conversion is encountered, such as the assignment of a long
21039 int or a double to an int, or a pointer to void to a pointer to any type other than
21040 a character type (<a href="#6.3">6.3</a>).
21041 -- A hexadecimal floating constant cannot be represented exactly in its evaluation format
21042 (<a href="#6.4.4.2">6.4.4.2</a>).
21043 -- An integer character constant includes more than one character or a wide character
21044 constant includes more than one multibyte character (<a href="#6.4.4.4">6.4.4.4</a>).
21045 -- The characters /* are found in a comment (<a href="#6.4.7">6.4.7</a>).
21046 -- An ''unordered'' binary operator (not comma, &&, or ||) contains a side effect to an
21047 lvalue in one operand, and a side effect to, or an access to the value of, the identical
21048 lvalue in the other operand (<a href="#6.5">6.5</a>).
21049 -- A function is called but no prototype has been supplied (<a href="#6.5.2.2">6.5.2.2</a>).
21050 -- The arguments in a function call do not agree in number and type with those of the
21051 parameters in a function definition that is not a prototype (<a href="#6.5.2.2">6.5.2.2</a>).
21052 -- An object is defined but not used (<a href="#6.7">6.7</a>).
21053 -- A value is given to an object of an enumerated type other than by assignment of an
21054 enumeration constant that is a member of that type, or an enumeration object that has
21055 the same type, or the value of a function that returns the same enumerated type
21056 (<a href="#6.7.2.2">6.7.2.2</a>).
21057 -- An aggregate has a partly bracketed initialization (<a href="#6.7.8">6.7.8</a>).
21058 -- A statement cannot be reached (<a href="#6.8">6.8</a>).
21059 -- A statement with no apparent effect is encountered (<a href="#6.8">6.8</a>).
21060 -- A constant expression is used as the controlling expression of a selection statement
21061 (<a href="#6.8.4">6.8.4</a>).
21063 [<a name="p548" href="#p548">page 548</a>] (<a href="#Contents">Contents</a>)
21065 -- An incorrectly formed preprocessing group is encountered while skipping a
21066 preprocessing group (<a href="#6.10.1">6.10.1</a>).
21067 -- An unrecognized #pragma directive is encountered (<a href="#6.10.6">6.10.6</a>).
21069 [<a name="p549" href="#p549">page 549</a>] (<a href="#Contents">Contents</a>)
21071 <a name="J" href="#J"><b> Annex J</b></a>
21074 1 This annex collects some information about portability that appears in this International
21076 <a name="J.1" href="#J.1"><b> J.1 Unspecified behavior</b></a>
21077 1 The following are unspecified:
21078 -- The manner and timing of static initialization (<a href="#5.1.2">5.1.2</a>).
21079 -- The termination status returned to the hosted environment if the return type of main
21080 is not compatible with int (<a href="#5.1.2.2.3">5.1.2.2.3</a>).
21081 -- The behavior of the display device if a printing character is written when the active
21082 position is at the final position of a line (<a href="#5.2.2">5.2.2</a>).
21083 -- The behavior of the display device if a backspace character is written when the active
21084 position is at the initial position of a line (<a href="#5.2.2">5.2.2</a>).
21085 -- The behavior of the display device if a horizontal tab character is written when the
21086 active position is at or past the last defined horizontal tabulation position (<a href="#5.2.2">5.2.2</a>).
21087 -- The behavior of the display device if a vertical tab character is written when the active
21088 position is at or past the last defined vertical tabulation position (<a href="#5.2.2">5.2.2</a>).
21089 -- How an extended source character that does not correspond to a universal character
21090 name counts toward the significant initial characters in an external identifier (<a href="#5.2.4.1">5.2.4.1</a>).
21091 -- Many aspects of the representations of types (<a href="#6.2.6">6.2.6</a>).
21092 -- The value of padding bytes when storing values in structures or unions (<a href="#6.2.6.1">6.2.6.1</a>).
21093 -- The values of bytes that correspond to union members other than the one last stored
21094 into (<a href="#6.2.6.1">6.2.6.1</a>).
21095 -- The representation used when storing a value in an object that has more than one
21096 object representation for that value (<a href="#6.2.6.1">6.2.6.1</a>).
21097 -- The values of any padding bits in integer representations (<a href="#6.2.6.2">6.2.6.2</a>).
21098 -- Whether certain operators can generate negative zeros and whether a negative zero
21099 becomes a normal zero when stored in an object (<a href="#6.2.6.2">6.2.6.2</a>).
21100 -- Whether two string literals result in distinct arrays (<a href="#6.4.5">6.4.5</a>).
21101 -- The order in which subexpressions are evaluated and the order in which side effects
21102 take place, except as specified for the function-call (), &&, ||, ? :, and comma
21104 [<a name="p550" href="#p550">page 550</a>] (<a href="#Contents">Contents</a>)
21106 operators (<a href="#6.5">6.5</a>).
21107 -- The order in which the function designator, arguments, and subexpressions within the
21108 arguments are evaluated in a function call (<a href="#6.5.2.2">6.5.2.2</a>).
21109 -- The order of side effects among compound literal initialization list expressions
21110 (<a href="#6.5.2.5">6.5.2.5</a>).
21111 -- The order in which the operands of an assignment operator are evaluated (<a href="#6.5.16">6.5.16</a>).
21112 -- The alignment of the addressable storage unit allocated to hold a bit-field (<a href="#6.7.2.1">6.7.2.1</a>).
21113 -- Whether a call to an inline function uses the inline definition or the external definition
21114 of the function (<a href="#6.7.4">6.7.4</a>).
21115 -- Whether or not a size expression is evaluated when it is part of the operand of a
21116 sizeof operator and changing the value of the size expression would not affect the
21117 result of the operator (<a href="#6.7.6.2">6.7.6.2</a>).
21118 -- The order in which any side effects occur among the initialization list expressions in
21119 an initializer (<a href="#6.7.9">6.7.9</a>).
21120 -- The layout of storage for function parameters (<a href="#6.9.1">6.9.1</a>).
21121 -- When a fully expanded macro replacement list contains a function-like macro name
21122 as its last preprocessing token and the next preprocessing token from the source file is
21123 a (, and the fully expanded replacement of that macro ends with the name of the first
21124 macro and the next preprocessing token from the source file is again a (, whether that
21125 is considered a nested replacement (<a href="#6.10.3">6.10.3</a>).
21126 -- The order in which # and ## operations are evaluated during macro substitution
21127 (<a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>).
21128 -- The state of the floating-point status flags when execution passes from a part of the *
21129 program translated with FENV_ACCESS ''off'' to a part translated with
21130 FENV_ACCESS ''on'' (<a href="#7.6.1">7.6.1</a>).
21131 -- The order in which feraiseexcept raises floating-point exceptions, except as
21132 stated in <a href="#F.8.6">F.8.6</a> (<a href="#7.6.2.3">7.6.2.3</a>).
21133 -- Whether math_errhandling is a macro or an identifier with external linkage
21134 (<a href="#7.12">7.12</a>).
21135 -- The results of the frexp functions when the specified value is not a floating-point
21136 number (<a href="#7.12.6.4">7.12.6.4</a>).
21137 -- The numeric result of the ilogb functions when the correct value is outside the
21138 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>).
21139 -- 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>).
21141 [<a name="p551" href="#p551">page 551</a>] (<a href="#Contents">Contents</a>)
21143 -- The value stored by the remquo functions in the object pointed to by quo when y is
21144 zero (<a href="#7.12.10.3">7.12.10.3</a>).
21145 -- Whether a comparison macro argument that is represented in a format wider than its
21146 semantic type is converted to the semantic type (<a href="#7.12.14">7.12.14</a>).
21147 -- Whether setjmp is a macro or an identifier with external linkage (<a href="#7.13">7.13</a>).
21148 -- Whether va_copy and va_end are macros or identifiers with external linkage
21149 (<a href="#7.16.1">7.16.1</a>).
21150 -- The hexadecimal digit before the decimal point when a non-normalized floating-point
21151 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>).
21152 -- The value of the file position indicator after a successful call to the ungetc function
21153 for a text stream, or the ungetwc function for any stream, until all pushed-back
21154 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>).
21155 -- The details of the value stored by the fgetpos function (<a href="#7.21.9.1">7.21.9.1</a>).
21156 -- 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>).
21157 -- Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold
21158 functions convert a minus-signed sequence to a negative number directly or by
21159 negating the value resulting from converting the corresponding unsigned sequence
21160 (<a href="#7.22.1.3">7.22.1.3</a>, <a href="#7.28.4.1.1">7.28.4.1.1</a>).
21161 -- The order and contiguity of storage allocated by successive calls to the calloc,
21162 malloc, and realloc functions (<a href="#7.22.3">7.22.3</a>).
21163 -- The amount of storage allocated by a successful call to the calloc, malloc, or
21164 realloc function when 0 bytes was requested (<a href="#7.22.3">7.22.3</a>).
21165 -- Which of two elements that compare as equal is matched by the bsearch function
21166 (<a href="#7.22.5.1">7.22.5.1</a>).
21167 -- The order of two elements that compare as equal in an array sorted by the qsort
21168 function (<a href="#7.22.5.2">7.22.5.2</a>).
21169 -- The encoding of the calendar time returned by the time function (<a href="#7.26.2.4">7.26.2.4</a>).
21170 -- The characters stored by the strftime or wcsftime function if any of the time
21171 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>).
21172 -- 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>,
21173 <a href="#7.28.6.4.2">7.28.6.4.2</a>,
21174 -- The resulting value when the ''invalid'' floating-point exception is raised during
21175 IEC 60559 floating to integer conversion (<a href="#F.4">F.4</a>).
21177 [<a name="p552" href="#p552">page 552</a>] (<a href="#Contents">Contents</a>)
21179 -- Whether conversion of non-integer IEC 60559 floating values to integer raises the
21180 ''inexact'' floating-point exception (<a href="#F.4">F.4</a>).
21181 -- Whether or when library functions in <a href="#7.12"><math.h></a> raise the ''inexact'' floating-point
21182 exception in an IEC 60559 conformant implementation (<a href="#F.10">F.10</a>).
21183 -- Whether or when library functions in <a href="#7.12"><math.h></a> raise an undeserved ''underflow''
21184 floating-point exception in an IEC 60559 conformant implementation (<a href="#F.10">F.10</a>).
21185 -- The exponent value stored by frexp for a NaN or infinity (<a href="#F.10.3.4">F.10.3.4</a>).
21186 -- The numeric result returned by the lrint, llrint, lround, and llround
21187 functions if the rounded value is outside the range of the return type (<a href="#F.10.6.5">F.10.6.5</a>,
21188 <a href="#F.10.6.7">F.10.6.7</a>).
21189 -- The sign of one part of the complex result of several math functions for certain
21190 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>,
21191 <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>).
21192 <a name="J.2" href="#J.2"><b> J.2 Undefined behavior</b></a>
21193 1 The behavior is undefined in the following circumstances:
21194 -- A ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated
21196 -- A nonempty source file does not end in a new-line character which is not immediately
21197 preceded by a backslash character or ends in a partial preprocessing token or
21198 comment (<a href="#5.1.1.2">5.1.1.2</a>).
21199 -- Token concatenation produces a character sequence matching the syntax of a
21200 universal character name (<a href="#5.1.1.2">5.1.1.2</a>).
21201 -- A program in a hosted environment does not define a function named main using one
21202 of the specified forms (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
21203 -- The execution of a program contains a data race (<a href="#5.1.2.4">5.1.2.4</a>).
21204 -- A character not in the basic source character set is encountered in a source file, except
21205 in an identifier, a character constant, a string literal, a header name, a comment, or a
21206 preprocessing token that is never converted to a token (<a href="#5.2.1">5.2.1</a>).
21207 -- An identifier, comment, string literal, character constant, or header name contains an
21208 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>).
21209 -- The same identifier has both internal and external linkage in the same translation unit
21210 (<a href="#6.2.2">6.2.2</a>).
21211 -- An object is referred to outside of its lifetime (<a href="#6.2.4">6.2.4</a>).
21213 [<a name="p553" href="#p553">page 553</a>] (<a href="#Contents">Contents</a>)
21215 -- The value of a pointer to an object whose lifetime has ended is used (<a href="#6.2.4">6.2.4</a>).
21216 -- The value of an object with automatic storage duration is used while it is
21217 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>).
21218 -- A trap representation is read by an lvalue expression that does not have character type
21219 (<a href="#6.2.6.1">6.2.6.1</a>).
21220 -- A trap representation is produced by a side effect that modifies any part of the object
21221 using an lvalue expression that does not have character type (<a href="#6.2.6.1">6.2.6.1</a>).
21222 -- The operands to certain operators are such that they could produce a negative zero
21223 result, but the implementation does not support negative zeros (<a href="#6.2.6.2">6.2.6.2</a>).
21224 -- Two declarations of the same object or function specify types that are not compatible
21225 (<a href="#6.2.7">6.2.7</a>).
21226 -- A program requires the formation of a composite type from a variable length array
21227 type whose size is specified by an expression that is not evaluated (<a href="#6.2.7">6.2.7</a>).
21228 -- Conversion to or from an integer type produces a value outside the range that can be
21229 represented (<a href="#6.3.1.4">6.3.1.4</a>).
21230 -- Demotion of one real floating type to another produces a value outside the range that
21231 can be represented (<a href="#6.3.1.5">6.3.1.5</a>).
21232 -- An lvalue does not designate an object when evaluated (<a href="#6.3.2.1">6.3.2.1</a>).
21233 -- A non-array lvalue with an incomplete type is used in a context that requires the value
21234 of the designated object (<a href="#6.3.2.1">6.3.2.1</a>).
21235 -- An lvalue designating an object of automatic storage duration that could have been
21236 declared with the register storage class is used in a context that requires the value
21237 of the designated object, but the object is uninitialized. (<a href="#6.3.2.1">6.3.2.1</a>).
21238 -- An lvalue having array type is converted to a pointer to the initial element of the
21239 array, and the array object has register storage class (<a href="#6.3.2.1">6.3.2.1</a>).
21240 -- An attempt is made to use the value of a void expression, or an implicit or explicit
21241 conversion (except to void) is applied to a void expression (<a href="#6.3.2.2">6.3.2.2</a>).
21242 -- Conversion of a pointer to an integer type produces a value outside the range that can
21243 be represented (<a href="#6.3.2.3">6.3.2.3</a>).
21244 -- Conversion between two pointer types produces a result that is incorrectly aligned
21245 (<a href="#6.3.2.3">6.3.2.3</a>).
21246 -- A pointer is used to call a function whose type is not compatible with the referenced
21247 type (<a href="#6.3.2.3">6.3.2.3</a>).
21249 [<a name="p554" href="#p554">page 554</a>] (<a href="#Contents">Contents</a>)
21251 -- An unmatched ' or " character is encountered on a logical source line during
21252 tokenization (<a href="#6.4">6.4</a>).
21253 -- A reserved keyword token is used in translation phase 7 or 8 for some purpose other
21254 than as a keyword (<a href="#6.4.1">6.4.1</a>).
21255 -- A universal character name in an identifier does not designate a character whose
21256 encoding falls into one of the specified ranges (<a href="#6.4.2.1">6.4.2.1</a>).
21257 -- The initial character of an identifier is a universal character name designating a digit
21258 (<a href="#6.4.2.1">6.4.2.1</a>).
21259 -- Two identifiers differ only in nonsignificant characters (<a href="#6.4.2.1">6.4.2.1</a>).
21260 -- The identifier __func__ is explicitly declared (<a href="#6.4.2.2">6.4.2.2</a>).
21261 -- The program attempts to modify a string literal (<a href="#6.4.5">6.4.5</a>).
21262 -- The characters ', \, ", //, or /* occur in the sequence between the < and >
21263 delimiters, or the characters ', \, //, or /* occur in the sequence between the "
21264 delimiters, in a header name preprocessing token (<a href="#6.4.7">6.4.7</a>).
21265 -- A side effect on a scalar object is unsequenced relative to either a different side effect
21266 on the same scalar object or a value computation using the value of the same scalar
21267 object (<a href="#6.5">6.5</a>).
21268 -- An exceptional condition occurs during the evaluation of an expression (<a href="#6.5">6.5</a>).
21269 -- An object has its stored value accessed other than by an lvalue of an allowable type
21270 (<a href="#6.5">6.5</a>).
21271 -- For a call to a function without a function prototype in scope, the number of *
21272 arguments does not equal the number of parameters (<a href="#6.5.2.2">6.5.2.2</a>).
21273 -- For call to a function without a function prototype in scope where the function is
21274 defined with a function prototype, either the prototype ends with an ellipsis or the
21275 types of the arguments after promotion are not compatible with the types of the
21276 parameters (<a href="#6.5.2.2">6.5.2.2</a>).
21277 -- For a call to a function without a function prototype in scope where the function is not
21278 defined with a function prototype, the types of the arguments after promotion are not
21279 compatible with those of the parameters after promotion (with certain exceptions)
21280 (<a href="#6.5.2.2">6.5.2.2</a>).
21281 -- A function is defined with a type that is not compatible with the type (of the
21282 expression) pointed to by the expression that denotes the called function (<a href="#6.5.2.2">6.5.2.2</a>).
21283 -- A member of an atomic structure or union is accessed (<a href="#6.5.2.3">6.5.2.3</a>).
21284 -- The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
21286 [<a name="p555" href="#p555">page 555</a>] (<a href="#Contents">Contents</a>)
21288 -- A pointer is converted to other than an integer or pointer type (<a href="#6.5.4">6.5.4</a>).
21289 -- The value of the second operand of the / or % operator is zero (<a href="#6.5.5">6.5.5</a>).
21290 -- Addition or subtraction of a pointer into, or just beyond, an array object and an
21291 integer type produces a result that does not point into, or just beyond, the same array
21292 object (<a href="#6.5.6">6.5.6</a>).
21293 -- Addition or subtraction of a pointer into, or just beyond, an array object and an
21294 integer type produces a result that points just beyond the array object and is used as
21295 the operand of a unary * operator that is evaluated (<a href="#6.5.6">6.5.6</a>).
21296 -- Pointers that do not point into, or just beyond, the same array object are subtracted
21297 (<a href="#6.5.6">6.5.6</a>).
21298 -- An array subscript is out of range, even if an object is apparently accessible with the
21299 given subscript (as in the lvalue expression a[1][7] given the declaration int
21300 a[4][5]) (<a href="#6.5.6">6.5.6</a>).
21301 -- The result of subtracting two pointers is not representable in an object of type
21302 ptrdiff_t (<a href="#6.5.6">6.5.6</a>).
21303 -- An expression is shifted by a negative number or by an amount greater than or equal
21304 to the width of the promoted expression (<a href="#6.5.7">6.5.7</a>).
21305 -- An expression having signed promoted type is left-shifted and either the value of the
21306 expression is negative or the result of shifting would be not be representable in the
21307 promoted type (<a href="#6.5.7">6.5.7</a>).
21308 -- Pointers that do not point to the same aggregate or union (nor just beyond the same
21309 array object) are compared using relational operators (<a href="#6.5.8">6.5.8</a>).
21310 -- An object is assigned to an inexactly overlapping object or to an exactly overlapping
21311 object with incompatible type (<a href="#6.5.16.1">6.5.16.1</a>).
21312 -- An expression that is required to be an integer constant expression does not have an
21313 integer type; has operands that are not integer constants, enumeration constants,
21314 character constants, sizeof expressions whose results are integer constants, or
21315 immediately-cast floating constants; or contains casts (outside operands to sizeof
21316 operators) other than conversions of arithmetic types to integer types (<a href="#6.6">6.6</a>).
21317 -- A constant expression in an initializer is not, or does not evaluate to, one of the
21318 following: an arithmetic constant expression, a null pointer constant, an address
21319 constant, or an address constant for a complete object type plus or minus an integer
21320 constant expression (<a href="#6.6">6.6</a>).
21321 -- An arithmetic constant expression does not have arithmetic type; has operands that
21322 are not integer constants, floating constants, enumeration constants, character
21323 constants, or sizeof expressions; or contains casts (outside operands to sizeof
21325 [<a name="p556" href="#p556">page 556</a>] (<a href="#Contents">Contents</a>)
21327 operators) other than conversions of arithmetic types to arithmetic types (<a href="#6.6">6.6</a>).
21328 -- The value of an object is accessed by an array-subscript [], member-access . or ->,
21329 address &, or indirection * operator or a pointer cast in creating an address constant
21330 (<a href="#6.6">6.6</a>).
21331 -- An identifier for an object is declared with no linkage and the type of the object is
21332 incomplete after its declarator, or after its init-declarator if it has an initializer (<a href="#6.7">6.7</a>).
21333 -- A function is declared at block scope with an explicit storage-class specifier other
21334 than extern (<a href="#6.7.1">6.7.1</a>).
21335 -- A structure or union is defined as containing no named members, no anonymous
21336 structures, and no anonymous unions (<a href="#6.7.2.1">6.7.2.1</a>).
21337 -- An attempt is made to access, or generate a pointer to just past, a flexible array
21338 member of a structure when the referenced object provides no elements for that array
21339 (<a href="#6.7.2.1">6.7.2.1</a>).
21340 -- When the complete type is needed, an incomplete structure or union type is not
21341 completed in the same scope by another declaration of the tag that defines the content
21342 (<a href="#6.7.2.3">6.7.2.3</a>).
21343 -- An attempt is made to modify an object defined with a const-qualified type through
21344 use of an lvalue with non-const-qualified type (<a href="#6.7.3">6.7.3</a>).
21345 -- An attempt is made to refer to an object defined with a volatile-qualified type through
21346 use of an lvalue with non-volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
21347 -- The specification of a function type includes any type qualifiers (<a href="#6.7.3">6.7.3</a>). *
21348 -- Two qualified types that are required to be compatible do not have the identically
21349 qualified version of a compatible type (<a href="#6.7.3">6.7.3</a>).
21350 -- An object which has been modified is accessed through a restrict-qualified pointer to
21351 a const-qualified type, or through a restrict-qualified pointer and another pointer that
21352 are not both based on the same object (<a href="#6.7.3.1">6.7.3.1</a>).
21353 -- A restrict-qualified pointer is assigned a value based on another restricted pointer
21354 whose associated block neither began execution before the block associated with this
21355 pointer, nor ended before the assignment (<a href="#6.7.3.1">6.7.3.1</a>).
21356 -- A function with external linkage is declared with an inline function specifier, but is
21357 not also defined in the same translation unit (<a href="#6.7.4">6.7.4</a>).
21358 -- A function declared with a _Noreturn function specifier returns to its caller (<a href="#6.7.4">6.7.4</a>).
21359 -- The definition of an object has an alignment specifier and another declaration of that
21360 object has a different alignment specifier (<a href="#6.7.5">6.7.5</a>).
21362 [<a name="p557" href="#p557">page 557</a>] (<a href="#Contents">Contents</a>)
21364 -- Declarations of an object in different translation units have different alignment
21365 specifiers (<a href="#6.7.5">6.7.5</a>).
21366 -- Two pointer types that are required to be compatible are not identically qualified, or
21367 are not pointers to compatible types (<a href="#6.7.6.1">6.7.6.1</a>).
21368 -- The size expression in an array declaration is not a constant expression and evaluates
21369 at program execution time to a nonpositive value (<a href="#6.7.6.2">6.7.6.2</a>).
21370 -- In a context requiring two array types to be compatible, they do not have compatible
21371 element types, or their size specifiers evaluate to unequal values (<a href="#6.7.6.2">6.7.6.2</a>).
21372 -- A declaration of an array parameter includes the keyword static within the [ and
21373 ] and the corresponding argument does not provide access to the first element of an
21374 array with at least the specified number of elements (<a href="#6.7.6.3">6.7.6.3</a>).
21375 -- A storage-class specifier or type qualifier modifies the keyword void as a function
21376 parameter type list (<a href="#6.7.6.3">6.7.6.3</a>).
21377 -- In a context requiring two function types to be compatible, they do not have
21378 compatible return types, or their parameters disagree in use of the ellipsis terminator
21379 or the number and type of parameters (after default argument promotion, when there
21380 is no parameter type list or when one type is specified by a function definition with an
21381 identifier list) (<a href="#6.7.6.3">6.7.6.3</a>).
21382 -- The value of an unnamed member of a structure or union is used (<a href="#6.7.9">6.7.9</a>).
21383 -- The initializer for a scalar is neither a single expression nor a single expression
21384 enclosed in braces (<a href="#6.7.9">6.7.9</a>).
21385 -- The initializer for a structure or union object that has automatic storage duration is
21386 neither an initializer list nor a single expression that has compatible structure or union
21387 type (<a href="#6.7.9">6.7.9</a>).
21388 -- The initializer for an aggregate or union, other than an array initialized by a string
21389 literal, is not a brace-enclosed list of initializers for its elements or members (<a href="#6.7.9">6.7.9</a>).
21390 -- An identifier with external linkage is used, but in the program there does not exist
21391 exactly one external definition for the identifier, or the identifier is not used and there
21392 exist multiple external definitions for the identifier (<a href="#6.9">6.9</a>).
21393 -- A function definition includes an identifier list, but the types of the parameters are not
21394 declared in a following declaration list (<a href="#6.9.1">6.9.1</a>).
21395 -- An adjusted parameter type in a function definition is not a complete object type
21396 (<a href="#6.9.1">6.9.1</a>).
21397 -- A function that accepts a variable number of arguments is defined without a
21398 parameter type list that ends with the ellipsis notation (<a href="#6.9.1">6.9.1</a>).
21400 [<a name="p558" href="#p558">page 558</a>] (<a href="#Contents">Contents</a>)
21402 -- The } that terminates a function is reached, and the value of the function call is used
21403 by the caller (<a href="#6.9.1">6.9.1</a>).
21404 -- An identifier for an object with internal linkage and an incomplete type is declared
21405 with a tentative definition (<a href="#6.9.2">6.9.2</a>).
21406 -- The token defined is generated during the expansion of a #if or #elif
21407 preprocessing directive, or the use of the defined unary operator does not match
21408 one of the two specified forms prior to macro replacement (<a href="#6.10.1">6.10.1</a>).
21409 -- The #include preprocessing directive that results after expansion does not match
21410 one of the two header name forms (<a href="#6.10.2">6.10.2</a>).
21411 -- The character sequence in an #include preprocessing directive does not start with a
21412 letter (<a href="#6.10.2">6.10.2</a>).
21413 -- There are sequences of preprocessing tokens within the list of macro arguments that
21414 would otherwise act as preprocessing directives (<a href="#6.10.3">6.10.3</a>).
21415 -- The result of the preprocessing operator # is not a valid character string literal
21416 (<a href="#6.10.3.2">6.10.3.2</a>).
21417 -- The result of the preprocessing operator ## is not a valid preprocessing token
21418 (<a href="#6.10.3.3">6.10.3.3</a>).
21419 -- The #line preprocessing directive that results after expansion does not match one of
21420 the two well-defined forms, or its digit sequence specifies zero or a number greater
21421 than 2147483647 (<a href="#6.10.4">6.10.4</a>).
21422 -- A non-STDC #pragma preprocessing directive that is documented as causing
21423 translation failure or some other form of undefined behavior is encountered (<a href="#6.10.6">6.10.6</a>).
21424 -- A #pragma STDC preprocessing directive does not match one of the well-defined
21425 forms (<a href="#6.10.6">6.10.6</a>).
21426 -- The name of a predefined macro, or the identifier defined, is the subject of a
21427 #define or #undef preprocessing directive (<a href="#6.10.8">6.10.8</a>).
21428 -- An attempt is made to copy an object to an overlapping object by use of a library
21429 function, other than as explicitly allowed (e.g., memmove) (clause 7).
21430 -- A file with the same name as one of the standard headers, not provided as part of the
21431 implementation, is placed in any of the standard places that are searched for included
21432 source files (<a href="#7.1.2">7.1.2</a>).
21433 -- A header is included within an external declaration or definition (<a href="#7.1.2">7.1.2</a>).
21434 -- A function, object, type, or macro that is specified as being declared or defined by
21435 some standard header is used before any header that declares or defines it is included
21436 (<a href="#7.1.2">7.1.2</a>).
21438 [<a name="p559" href="#p559">page 559</a>] (<a href="#Contents">Contents</a>)
21440 -- A standard header is included while a macro is defined with the same name as a
21441 keyword (<a href="#7.1.2">7.1.2</a>).
21442 -- The program attempts to declare a library function itself, rather than via a standard
21443 header, but the declaration does not have external linkage (<a href="#7.1.2">7.1.2</a>).
21444 -- The program declares or defines a reserved identifier, other than as allowed by <a href="#7.1.4">7.1.4</a>
21445 (<a href="#7.1.3">7.1.3</a>).
21446 -- The program removes the definition of a macro whose name begins with an
21447 underscore and either an uppercase letter or another underscore (<a href="#7.1.3">7.1.3</a>).
21448 -- An argument to a library function has an invalid value or a type not expected by a
21449 function with variable number of arguments (<a href="#7.1.4">7.1.4</a>).
21450 -- The pointer passed to a library function array parameter does not have a value such
21451 that all address computations and object accesses are valid (<a href="#7.1.4">7.1.4</a>).
21452 -- The macro definition of assert is suppressed in order to access an actual function
21453 (<a href="#7.2">7.2</a>).
21454 -- The argument to the assert macro does not have a scalar type (<a href="#7.2">7.2</a>).
21455 -- The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in
21456 any context other than outside all external declarations or preceding all explicit
21457 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>).
21458 -- The value of an argument to a character handling function is neither equal to the value
21459 of EOF nor representable as an unsigned char (<a href="#7.4">7.4</a>).
21460 -- A macro definition of errno is suppressed in order to access an actual object, or the
21461 program defines an identifier with the name errno (<a href="#7.5">7.5</a>).
21462 -- Part of the program tests floating-point status flags, sets floating-point control modes,
21463 or runs under non-default mode settings, but was translated with the state for the
21464 FENV_ACCESS pragma ''off'' (<a href="#7.6.1">7.6.1</a>).
21465 -- The exception-mask argument for one of the functions that provide access to the
21466 floating-point status flags has a nonzero value not obtained by bitwise OR of the
21467 floating-point exception macros (<a href="#7.6.2">7.6.2</a>).
21468 -- The fesetexceptflag function is used to set floating-point status flags that were
21469 not specified in the call to the fegetexceptflag function that provided the value
21470 of the corresponding fexcept_t object (<a href="#7.6.2.4">7.6.2.4</a>).
21471 -- The argument to fesetenv or feupdateenv is neither an object set by a call to
21472 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>).
21473 -- The value of the result of an integer arithmetic or conversion function cannot be
21474 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>).
21476 [<a name="p560" href="#p560">page 560</a>] (<a href="#Contents">Contents</a>)
21478 -- The program modifies the string pointed to by the value returned by the setlocale
21479 function (<a href="#7.11.1.1">7.11.1.1</a>).
21480 -- The program modifies the structure pointed to by the value returned by the
21481 localeconv function (<a href="#7.11.2.1">7.11.2.1</a>).
21482 -- A macro definition of math_errhandling is suppressed or the program defines
21483 an identifier with the name math_errhandling (<a href="#7.12">7.12</a>).
21484 -- An argument to a floating-point classification or comparison macro is not of real
21485 floating type (<a href="#7.12.3">7.12.3</a>, <a href="#7.12.14">7.12.14</a>).
21486 -- A macro definition of setjmp is suppressed in order to access an actual function, or
21487 the program defines an external identifier with the name setjmp (<a href="#7.13">7.13</a>).
21488 -- An invocation of the setjmp macro occurs other than in an allowed context
21489 (<a href="#7.13.2.1">7.13.2.1</a>).
21490 -- The longjmp function is invoked to restore a nonexistent environment (<a href="#7.13.2.1">7.13.2.1</a>).
21491 -- After a longjmp, there is an attempt to access the value of an object of automatic
21492 storage duration that does not have volatile-qualified type, local to the function
21493 containing the invocation of the corresponding setjmp macro, that was changed
21494 between the setjmp invocation and longjmp call (<a href="#7.13.2.1">7.13.2.1</a>).
21495 -- The program specifies an invalid pointer to a signal handler function (<a href="#7.14.1.1">7.14.1.1</a>).
21496 -- A signal handler returns when the signal corresponded to a computational exception
21497 (<a href="#7.14.1.1">7.14.1.1</a>).
21498 -- A signal occurs as the result of calling the abort or raise function, and the signal
21499 handler calls the raise function (<a href="#7.14.1.1">7.14.1.1</a>).
21500 -- A signal occurs other than as the result of calling the abort or raise function, and
21501 the signal handler refers to an object with static or thread storage duration that is not a
21502 lock-free atomic object other than by assigning a value to an object declared as
21503 volatile sig_atomic_t, or calls any function in the standard library other
21504 than the abort function, the _Exit function, the quick_exit function, or the
21505 signal function (for the same signal number) (<a href="#7.14.1.1">7.14.1.1</a>).
21506 -- The value of errno is referred to after a signal occurred other than as the result of
21507 calling the abort or raise function and the corresponding signal handler obtained
21508 a SIG_ERR return from a call to the signal function (<a href="#7.14.1.1">7.14.1.1</a>).
21509 -- A signal is generated by an asynchronous signal handler (<a href="#7.14.1.1">7.14.1.1</a>).
21510 -- A function with a variable number of arguments attempts to access its varying
21511 arguments other than through a properly declared and initialized va_list object, or
21512 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>).
21514 [<a name="p561" href="#p561">page 561</a>] (<a href="#Contents">Contents</a>)
21516 -- The macro va_arg is invoked using the parameter ap that was passed to a function
21517 that invoked the macro va_arg with the same parameter (<a href="#7.16">7.16</a>).
21518 -- A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in
21519 order to access an actual function, or the program defines an external identifier with
21520 the name va_copy or va_end (<a href="#7.16.1">7.16.1</a>).
21521 -- The va_start or va_copy macro is invoked without a corresponding invocation
21522 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>,
21523 <a href="#7.16.1.4">7.16.1.4</a>).
21524 -- The type parameter to the va_arg macro is not such that a pointer to an object of
21525 that type can be obtained simply by postfixing a * (<a href="#7.16.1.1">7.16.1.1</a>).
21526 -- The va_arg macro is invoked when there is no actual next argument, or with a
21527 specified type that is not compatible with the promoted type of the actual next
21528 argument, with certain exceptions (<a href="#7.16.1.1">7.16.1.1</a>).
21529 -- The va_copy or va_start macro is called to initialize a va_list that was
21530 previously initialized by either macro without an intervening invocation of the
21531 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>).
21532 -- The parameter parmN of a va_start macro is declared with the register
21533 storage class, with a function or array type, or with a type that is not compatible with
21534 the type that results after application of the default argument promotions (<a href="#7.16.1.4">7.16.1.4</a>).
21535 -- The member designator parameter of an offsetof macro is an invalid right
21536 operand of the . operator for the type parameter, or designates a bit-field (<a href="#7.19">7.19</a>).
21537 -- The argument in an instance of one of the integer-constant macros is not a decimal,
21538 octal, or hexadecimal constant, or it has a value that exceeds the limits for the
21539 corresponding type (<a href="#7.20.4">7.20.4</a>).
21540 -- A byte input/output function is applied to a wide-oriented stream, or a wide character
21541 input/output function is applied to a byte-oriented stream (<a href="#7.21.2">7.21.2</a>).
21542 -- Use is made of any portion of a file beyond the most recent wide character written to
21543 a wide-oriented stream (<a href="#7.21.2">7.21.2</a>).
21544 -- The value of a pointer to a FILE object is used after the associated file is closed
21545 (<a href="#7.21.3">7.21.3</a>).
21546 -- The stream for the fflush function points to an input stream or to an update stream
21547 in which the most recent operation was input (<a href="#7.21.5.2">7.21.5.2</a>).
21548 -- The string pointed to by the mode argument in a call to the fopen function does not
21549 exactly match one of the specified character sequences (<a href="#7.21.5.3">7.21.5.3</a>).
21550 -- An output operation on an update stream is followed by an input operation without an
21551 intervening call to the fflush function or a file positioning function, or an input
21553 [<a name="p562" href="#p562">page 562</a>] (<a href="#Contents">Contents</a>)
21555 operation on an update stream is followed by an output operation with an intervening
21556 call to a file positioning function (<a href="#7.21.5.3">7.21.5.3</a>).
21557 -- An attempt is made to use the contents of the array that was supplied in a call to the
21558 setvbuf function (<a href="#7.21.5.6">7.21.5.6</a>).
21559 -- There are insufficient arguments for the format in a call to one of the formatted
21560 input/output functions, or an argument does not have an appropriate type (<a href="#7.21.6.1">7.21.6.1</a>,
21561 <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>).
21562 -- The format in a call to one of the formatted input/output functions or to the
21563 strftime or wcsftime function is not a valid multibyte character sequence that
21564 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>,
21565 <a href="#7.28.5.1">7.28.5.1</a>).
21566 -- In a call to one of the formatted output functions, a precision appears with a
21567 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>).
21568 -- A conversion specification for a formatted output function uses an asterisk to denote
21569 an argument-supplied field width or precision, but the corresponding argument is not
21570 provided (<a href="#7.21.6.1">7.21.6.1</a>, <a href="#7.28.2.1">7.28.2.1</a>).
21571 -- A conversion specification for a formatted output function uses a # or 0 flag with a
21572 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>).
21573 -- A conversion specification for one of the formatted input/output functions uses a
21574 length modifier with a conversion specifier other than those described (<a href="#7.21.6.1">7.21.6.1</a>,
21575 <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>).
21576 -- An s conversion specifier is encountered by one of the formatted output functions,
21577 and the argument is missing the null terminator (unless a precision is specified that
21578 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>).
21579 -- An n conversion specification for one of the formatted input/output functions includes
21580 any flags, an assignment-suppressing character, a field width, or a precision (<a href="#7.21.6.1">7.21.6.1</a>,
21581 <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>).
21582 -- A % conversion specifier is encountered by one of the formatted input/output
21583 functions, but the complete conversion specification is not exactly %% (<a href="#7.21.6.1">7.21.6.1</a>,
21584 <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>).
21585 -- An invalid conversion specification is found in the format for one of the formatted
21586 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>,
21587 <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>).
21588 -- The number of characters transmitted by a formatted output function is greater than
21589 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>).
21591 [<a name="p563" href="#p563">page 563</a>] (<a href="#Contents">Contents</a>)
21593 -- The result of a conversion by one of the formatted input functions cannot be
21594 represented in the corresponding object, or the receiving object does not have an
21595 appropriate type (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>).
21596 -- A c, s, or [ conversion specifier is encountered by one of the formatted input
21597 functions, and the array pointed to by the corresponding argument is not large enough
21598 to accept the input sequence (and a null terminator if the conversion specifier is s or
21599 [) (<a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.28.2.2">7.28.2.2</a>).
21600 -- A c, s, or [ conversion specifier with an l qualifier is encountered by one of the
21601 formatted input functions, but the input is not a valid multibyte character sequence
21602 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>).
21603 -- The input item for a %p conversion by one of the formatted input functions is not a
21604 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>).
21605 -- The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf,
21606 vsscanf, vfwprintf, vfwscanf, vswprintf, vswscanf, vwprintf, or
21607 vwscanf function is called with an improperly initialized va_list argument, or
21608 the argument is used (other than in an invocation of va_end) after the function
21609 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>,
21610 <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>).
21611 -- The contents of the array supplied in a call to the fgets or fgetws function are
21612 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>).
21613 -- The file position indicator for a binary stream is used after a call to the ungetc
21614 function where its value was zero before the call (<a href="#7.21.7.10">7.21.7.10</a>).
21615 -- The file position indicator for a stream is used after an error occurred during a call to
21616 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>).
21617 -- A partial element read by a call to the fread function is used (<a href="#7.21.8.1">7.21.8.1</a>).
21618 -- The fseek function is called for a text stream with a nonzero offset and either the
21619 offset was not returned by a previous successful call to the ftell function on a
21620 stream associated with the same file or whence is not SEEK_SET (<a href="#7.21.9.2">7.21.9.2</a>).
21621 -- The fsetpos function is called to set a position that was not returned by a previous
21622 successful call to the fgetpos function on a stream associated with the same file
21623 (<a href="#7.21.9.3">7.21.9.3</a>).
21624 -- A non-null pointer returned by a call to the calloc, malloc, or realloc function
21625 with a zero requested size is used to access an object (<a href="#7.22.3">7.22.3</a>).
21626 -- The value of a pointer that refers to space deallocated by a call to the free or
21627 realloc function is used (<a href="#7.22.3">7.22.3</a>).
21629 [<a name="p564" href="#p564">page 564</a>] (<a href="#Contents">Contents</a>)
21631 -- The alignment requested of the aligned_alloc function is not valid or not
21632 supported by the implementation, or the size requested is not an integral multiple of
21633 the alignment (<a href="#7.22.3.1">7.22.3.1</a>).
21634 -- The pointer argument to the free or realloc function does not match a pointer
21635 earlier returned by a memory management function, or the space has been deallocated
21636 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>).
21637 -- The value of the object allocated by the malloc function is used (<a href="#7.22.3.4">7.22.3.4</a>).
21638 -- The value of any bytes in a new object allocated by the realloc function beyond
21639 the size of the old object are used (<a href="#7.22.3.5">7.22.3.5</a>).
21640 -- The program calls the exit or quick_exit function more than once, or calls both
21641 functions (<a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.7">7.22.4.7</a>).
21642 -- During the call to a function registered with the atexit or at_quick_exit
21643 function, a call is made to the longjmp function that would terminate the call to the
21644 registered function (<a href="#7.22.4.4">7.22.4.4</a>, <a href="#7.22.4.7">7.22.4.7</a>).
21645 -- The string set up by the getenv or strerror function is modified by the program
21646 (<a href="#7.22.4.6">7.22.4.6</a>, <a href="#7.23.6.2">7.23.6.2</a>).
21647 -- A command is executed through the system function in a way that is documented as
21648 causing termination or some other form of undefined behavior (<a href="#7.22.4.8">7.22.4.8</a>).
21649 -- A searching or sorting utility function is called with an invalid pointer argument, even
21650 if the number of elements is zero (<a href="#7.22.5">7.22.5</a>).
21651 -- The comparison function called by a searching or sorting utility function alters the
21652 contents of the array being searched or sorted, or returns ordering values
21653 inconsistently (<a href="#7.22.5">7.22.5</a>).
21654 -- The array being searched by the bsearch function does not have its elements in
21655 proper order (<a href="#7.22.5.1">7.22.5.1</a>).
21656 -- The current conversion state is used by a multibyte/wide character conversion
21657 function after changing the LC_CTYPE category (<a href="#7.22.7">7.22.7</a>).
21658 -- A string or wide string utility function is instructed to access an array beyond the end
21659 of an object (<a href="#7.23.1">7.23.1</a>, <a href="#7.28.4">7.28.4</a>).
21660 -- A string or wide string utility function is called with an invalid pointer argument, even
21661 if the length is zero (<a href="#7.23.1">7.23.1</a>, <a href="#7.28.4">7.28.4</a>).
21662 -- The contents of the destination array are used after a call to the strxfrm,
21663 strftime, wcsxfrm, or wcsftime function in which the specified length was
21664 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>,
21665 <a href="#7.28.5.1">7.28.5.1</a>).
21667 [<a name="p565" href="#p565">page 565</a>] (<a href="#Contents">Contents</a>)
21669 -- The first argument in the very first call to the strtok or wcstok is a null pointer
21670 (<a href="#7.23.5.8">7.23.5.8</a>, <a href="#7.28.4.5.7">7.28.4.5.7</a>).
21671 -- The type of an argument to a type-generic macro is not compatible with the type of
21672 the corresponding parameter of the selected function (<a href="#7.24">7.24</a>).
21673 -- A complex argument is supplied for a generic parameter of a type-generic macro that
21674 has no corresponding complex function (<a href="#7.24">7.24</a>).
21675 -- At least one field of the broken-down time passed to asctime contains a value
21676 outside its normal range, or the calculated year exceeds four digits or is less than the
21677 year 1000 (<a href="#7.26.3.1">7.26.3.1</a>).
21678 -- The argument corresponding to an s specifier without an l qualifier in a call to the
21679 fwprintf function does not point to a valid multibyte character sequence that
21680 begins in the initial shift state (<a href="#7.28.2.11">7.28.2.11</a>).
21681 -- In a call to the wcstok function, the object pointed to by ptr does not have the
21682 value stored by the previous call for the same wide string (<a href="#7.28.4.5.7">7.28.4.5.7</a>).
21683 -- An mbstate_t object is used inappropriately (<a href="#7.28.6">7.28.6</a>).
21684 -- The value of an argument of type wint_t to a wide character classification or case
21685 mapping function is neither equal to the value of WEOF nor representable as a
21686 wchar_t (<a href="#7.29.1">7.29.1</a>).
21687 -- The iswctype function is called using a different LC_CTYPE category from the
21688 one in effect for the call to the wctype function that returned the description
21689 (<a href="#7.29.2.2.1">7.29.2.2.1</a>).
21690 -- The towctrans function is called using a different LC_CTYPE category from the
21691 one in effect for the call to the wctrans function that returned the description
21692 (<a href="#7.29.3.2.1">7.29.3.2.1</a>).
21693 <a name="J.3" href="#J.3"><b> J.3 Implementation-defined behavior</b></a>
21694 1 A conforming implementation is required to document its choice of behavior in each of
21695 the areas listed in this subclause. The following are implementation-defined:
21697 [<a name="p566" href="#p566">page 566</a>] (<a href="#Contents">Contents</a>)
21699 <a name="J.3.1" href="#J.3.1"><b> J.3.1 Translation</b></a>
21700 1 -- How a diagnostic is identified (<a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a>).
21701 -- Whether each nonempty sequence of white-space characters other than new-line is
21702 retained or replaced by one space character in translation phase 3 (<a href="#5.1.1.2">5.1.1.2</a>).
21703 <a name="J.3.2" href="#J.3.2"><b> J.3.2 Environment</b></a>
21704 1 -- The mapping between physical source file multibyte characters and the source
21705 character set in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>).
21706 -- The name and type of the function called at program startup in a freestanding
21707 environment (<a href="#5.1.2.1">5.1.2.1</a>).
21708 -- The effect of program termination in a freestanding environment (<a href="#5.1.2.1">5.1.2.1</a>).
21709 -- An alternative manner in which the main function may be defined (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
21710 -- 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>).
21711 -- What constitutes an interactive device (<a href="#5.1.2.3">5.1.2.3</a>).
21712 -- Whether a program can have more than one thread of execution in a freestanding
21713 environment (<a href="#5.1.2.4">5.1.2.4</a>).
21714 -- The set of signals, their semantics, and their default handling (<a href="#7.14">7.14</a>).
21715 -- Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
21716 computational exception (<a href="#7.14.1.1">7.14.1.1</a>).
21717 -- Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
21718 program startup (<a href="#7.14.1.1">7.14.1.1</a>).
21719 -- The set of environment names and the method for altering the environment list used
21720 by the getenv function (<a href="#7.22.4.6">7.22.4.6</a>).
21721 -- The manner of execution of the string by the system function (<a href="#7.22.4.8">7.22.4.8</a>).
21722 <a name="J.3.3" href="#J.3.3"><b> J.3.3 Identifiers</b></a>
21723 1 -- Which additional multibyte characters may appear in identifiers and their
21724 correspondence to universal character names (<a href="#6.4.2">6.4.2</a>).
21725 -- 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>).
21727 [<a name="p567" href="#p567">page 567</a>] (<a href="#Contents">Contents</a>)
21729 <a name="J.3.4" href="#J.3.4"><b> J.3.4 Characters</b></a>
21730 1 -- The number of bits in a byte (<a href="#3.6">3.6</a>).
21731 -- The values of the members of the execution character set (<a href="#5.2.1">5.2.1</a>).
21732 -- The unique value of the member of the execution character set produced for each of
21733 the standard alphabetic escape sequences (<a href="#5.2.2">5.2.2</a>).
21734 -- The value of a char object into which has been stored any character other than a
21735 member of the basic execution character set (<a href="#6.2.5">6.2.5</a>).
21736 -- Which of signed char or unsigned char has the same range, representation,
21737 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>).
21738 -- The mapping of members of the source character set (in character constants and string
21739 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>).
21740 -- The value of an integer character constant containing more than one character or
21741 containing a character or escape sequence that does not map to a single-byte
21742 execution character (<a href="#6.4.4.4">6.4.4.4</a>).
21743 -- The value of a wide character constant containing more than one multibyte character
21744 or a single multibyte character that maps to multiple members of the extended
21745 execution character set, or containing a multibyte character or escape sequence not
21746 represented in the extended execution character set (<a href="#6.4.4.4">6.4.4.4</a>).
21747 -- The current locale used to convert a wide character constant consisting of a single
21748 multibyte character that maps to a member of the extended execution character set
21749 into a corresponding wide character code (<a href="#6.4.4.4">6.4.4.4</a>).
21750 -- Whether differently-prefixed wide string literal tokens can be concatenated and, if so,
21751 the treatment of the resulting multibyte character sequence (<a href="#6.4.5">6.4.5</a>).
21752 -- The current locale used to convert a wide string literal into corresponding wide
21753 character codes (<a href="#6.4.5">6.4.5</a>).
21754 -- The value of a string literal containing a multibyte character or escape sequence not
21755 represented in the execution character set (<a href="#6.4.5">6.4.5</a>).
21756 -- The encoding of any of wchar_t, char16_t, and char32_t where the
21757 corresponding standard encoding macro (__STDC_ISO_10646__,
21758 __STDC_UTF_16__, or __STDC_UTF_32__) is not defined (<a href="#6.10.8.2">6.10.8.2</a>).
21760 [<a name="p568" href="#p568">page 568</a>] (<a href="#Contents">Contents</a>)
21762 <a name="J.3.5" href="#J.3.5"><b> J.3.5 Integers</b></a>
21763 1 -- Any extended integer types that exist in the implementation (<a href="#6.2.5">6.2.5</a>).
21764 -- Whether signed integer types are represented using sign and magnitude, two's
21765 complement, or ones' complement, and whether the extraordinary value is a trap
21766 representation or an ordinary value (<a href="#6.2.6.2">6.2.6.2</a>).
21767 -- The rank of any extended integer type relative to another extended integer type with
21768 the same precision (<a href="#6.3.1.1">6.3.1.1</a>).
21769 -- The result of, or the signal raised by, converting an integer to a signed integer type
21770 when the value cannot be represented in an object of that type (<a href="#6.3.1.3">6.3.1.3</a>).
21771 -- The results of some bitwise operations on signed integers (<a href="#6.5">6.5</a>).
21772 <a name="J.3.6" href="#J.3.6"><b> J.3.6 Floating point</b></a>
21773 1 -- The accuracy of the floating-point operations and of the library functions in
21774 <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>).
21775 -- The accuracy of the conversions between floating-point internal representations and
21776 string representations performed by the library functions in <a href="#7.21"><stdio.h></a>,
21777 <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>).
21778 -- The rounding behaviors characterized by non-standard values of FLT_ROUNDS
21779 (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
21780 -- The evaluation methods characterized by non-standard negative values of
21781 FLT_EVAL_METHOD (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
21782 -- The direction of rounding when an integer is converted to a floating-point number that
21783 cannot exactly represent the original value (<a href="#6.3.1.4">6.3.1.4</a>).
21784 -- The direction of rounding when a floating-point number is converted to a narrower
21785 floating-point number (<a href="#6.3.1.5">6.3.1.5</a>).
21786 -- How the nearest representable value or the larger or smaller representable value
21787 immediately adjacent to the nearest representable value is chosen for certain floating
21788 constants (<a href="#6.4.4.2">6.4.4.2</a>).
21789 -- Whether and how floating expressions are contracted when not disallowed by the
21790 FP_CONTRACT pragma (<a href="#6.5">6.5</a>).
21791 -- The default state for the FENV_ACCESS pragma (<a href="#7.6.1">7.6.1</a>).
21792 -- Additional floating-point exceptions, rounding modes, environments, and
21793 classifications, and their macro names (<a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>).
21794 -- The default state for the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>).
21796 [<a name="p569" href="#p569">page 569</a>] (<a href="#Contents">Contents</a>)
21798 <a name="J.3.7" href="#J.3.7"><b> J.3.7 Arrays and pointers</b></a>
21799 1 -- The result of converting a pointer to an integer or vice versa (<a href="#6.3.2.3">6.3.2.3</a>).
21800 -- The size of the result of subtracting two pointers to elements of the same array
21801 (<a href="#6.5.6">6.5.6</a>).
21802 <a name="J.3.8" href="#J.3.8"><b> J.3.8 Hints</b></a>
21803 1 -- The extent to which suggestions made by using the register storage-class
21804 specifier are effective (<a href="#6.7.1">6.7.1</a>).
21805 -- The extent to which suggestions made by using the inline function specifier are
21806 effective (<a href="#6.7.4">6.7.4</a>).
21807 <a name="J.3.9" href="#J.3.9"><b> J.3.9 Structures, unions, enumerations, and bit-fields</b></a>
21808 1 -- Whether a ''plain'' int bit-field is treated as a signed int bit-field or as an
21809 unsigned int bit-field (<a href="#6.7.2">6.7.2</a>, <a href="#6.7.2.1">6.7.2.1</a>).
21810 -- Allowable bit-field types other than _Bool, signed int, and unsigned int
21811 (<a href="#6.7.2.1">6.7.2.1</a>).
21812 -- Whether atomic types are permitted for bit-fields (<a href="#6.7.2.1">6.7.2.1</a>).
21813 -- Whether a bit-field can straddle a storage-unit boundary (<a href="#6.7.2.1">6.7.2.1</a>).
21814 -- The order of allocation of bit-fields within a unit (<a href="#6.7.2.1">6.7.2.1</a>).
21815 -- The alignment of non-bit-field members of structures (<a href="#6.7.2.1">6.7.2.1</a>). This should present
21816 no problem unless binary data written by one implementation is read by another.
21817 -- The integer type compatible with each enumerated type (<a href="#6.7.2.2">6.7.2.2</a>).
21818 <a name="J.3.10" href="#J.3.10"><b> J.3.10 Qualifiers</b></a>
21819 1 -- What constitutes an access to an object that has volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
21820 <a name="J.3.11" href="#J.3.11"><b> J.3.11 Preprocessing directives</b></a>
21821 1 -- The locations within #pragma directives where header name preprocessing tokens
21822 are recognized (<a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>).
21823 -- How sequences in both forms of header names are mapped to headers or external
21824 source file names (<a href="#6.4.7">6.4.7</a>).
21825 -- Whether the value of a character constant in a constant expression that controls
21826 conditional inclusion matches the value of the same character constant in the
21827 execution character set (<a href="#6.10.1">6.10.1</a>).
21828 -- Whether the value of a single-character character constant in a constant expression
21829 that controls conditional inclusion may have a negative value (<a href="#6.10.1">6.10.1</a>).
21831 [<a name="p570" href="#p570">page 570</a>] (<a href="#Contents">Contents</a>)
21833 -- The places that are searched for an included < > delimited header, and how the places
21834 are specified or the header is identified (<a href="#6.10.2">6.10.2</a>).
21835 -- How the named source file is searched for in an included " " delimited header
21836 (<a href="#6.10.2">6.10.2</a>).
21837 -- The method by which preprocessing tokens (possibly resulting from macro
21838 expansion) in a #include directive are combined into a header name (<a href="#6.10.2">6.10.2</a>).
21839 -- The nesting limit for #include processing (<a href="#6.10.2">6.10.2</a>).
21840 -- Whether the # operator inserts a \ character before the \ character that begins a
21841 universal character name in a character constant or string literal (<a href="#6.10.3.2">6.10.3.2</a>).
21842 -- The behavior on each recognized non-STDC #pragma directive (<a href="#6.10.6">6.10.6</a>).
21843 -- The definitions for __DATE__ and __TIME__ when respectively, the date and
21844 time of translation are not available (<a href="#6.10.8.1">6.10.8.1</a>).
21845 <a name="J.3.12" href="#J.3.12"><b> J.3.12 Library functions</b></a>
21846 1 -- Any library facilities available to a freestanding program, other than the minimal set
21847 required by clause 4 (<a href="#5.1.2.1">5.1.2.1</a>).
21848 -- The format of the diagnostic printed by the assert macro (<a href="#7.2.1.1">7.2.1.1</a>).
21849 -- The representation of the floating-point status flags stored by the
21850 fegetexceptflag function (<a href="#7.6.2.2">7.6.2.2</a>).
21851 -- Whether the feraiseexcept function raises the ''inexact'' floating-point
21852 exception in addition to the ''overflow'' or ''underflow'' floating-point exception
21853 (<a href="#7.6.2.3">7.6.2.3</a>).
21854 -- Strings other than "C" and "" that may be passed as the second argument to the
21855 setlocale function (<a href="#7.11.1.1">7.11.1.1</a>).
21856 -- The types defined for float_t and double_t when the value of the
21857 FLT_EVAL_METHOD macro is less than 0 (<a href="#7.12">7.12</a>).
21858 -- Domain errors for the mathematics functions, other than those required by this
21859 International Standard (<a href="#7.12.1">7.12.1</a>).
21860 -- The values returned by the mathematics functions on domain errors or pole errors
21861 (<a href="#7.12.1">7.12.1</a>).
21862 -- The values returned by the mathematics functions on underflow range errors, whether
21863 errno is set to the value of the macro ERANGE when the integer expression
21864 math_errhandling & MATH_ERRNO is nonzero, and whether the ''underflow''
21865 floating-point exception is raised when the integer expression math_errhandling
21866 & MATH_ERREXCEPT is nonzero. (<a href="#7.12.1">7.12.1</a>).
21868 [<a name="p571" href="#p571">page 571</a>] (<a href="#Contents">Contents</a>)
21870 -- Whether a domain error occurs or zero is returned when an fmod function has a
21871 second argument of zero (<a href="#7.12.10.1">7.12.10.1</a>).
21872 -- Whether a domain error occurs or zero is returned when a remainder function has
21873 a second argument of zero (<a href="#7.12.10.2">7.12.10.2</a>).
21874 -- The base-2 logarithm of the modulus used by the remquo functions in reducing the
21875 quotient (<a href="#7.12.10.3">7.12.10.3</a>).
21876 -- Whether a domain error occurs or zero is returned when a remquo function has a
21877 second argument of zero (<a href="#7.12.10.3">7.12.10.3</a>).
21878 -- Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call
21879 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>).
21880 -- The null pointer constant to which the macro NULL expands (<a href="#7.19">7.19</a>).
21881 -- Whether the last line of a text stream requires a terminating new-line character
21882 (<a href="#7.21.2">7.21.2</a>).
21883 -- Whether space characters that are written out to a text stream immediately before a
21884 new-line character appear when read in (<a href="#7.21.2">7.21.2</a>).
21885 -- The number of null characters that may be appended to data written to a binary
21886 stream (<a href="#7.21.2">7.21.2</a>).
21887 -- Whether the file position indicator of an append-mode stream is initially positioned at
21888 the beginning or end of the file (<a href="#7.21.3">7.21.3</a>).
21889 -- Whether a write on a text stream causes the associated file to be truncated beyond that
21890 point (<a href="#7.21.3">7.21.3</a>).
21891 -- The characteristics of file buffering (<a href="#7.21.3">7.21.3</a>).
21892 -- Whether a zero-length file actually exists (<a href="#7.21.3">7.21.3</a>).
21893 -- The rules for composing valid file names (<a href="#7.21.3">7.21.3</a>).
21894 -- Whether the same file can be simultaneously open multiple times (<a href="#7.21.3">7.21.3</a>).
21895 -- The nature and choice of encodings used for multibyte characters in files (<a href="#7.21.3">7.21.3</a>).
21896 -- The effect of the remove function on an open file (<a href="#7.21.4.1">7.21.4.1</a>).
21897 -- The effect if a file with the new name exists prior to a call to the rename function
21898 (<a href="#7.21.4.2">7.21.4.2</a>).
21899 -- Whether an open temporary file is removed upon abnormal program termination
21900 (<a href="#7.21.4.3">7.21.4.3</a>).
21901 -- Which changes of mode are permitted (if any), and under what circumstances
21902 (<a href="#7.21.5.4">7.21.5.4</a>).
21904 [<a name="p572" href="#p572">page 572</a>] (<a href="#Contents">Contents</a>)
21906 -- The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
21907 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>).
21908 -- The output for %p conversion in the fprintf or fwprintf function (<a href="#7.21.6.1">7.21.6.1</a>,
21909 <a href="#7.28.2.1">7.28.2.1</a>).
21910 -- The interpretation of a - character that is neither the first nor the last character, nor
21911 the second where a ^ character is the first, in the scanlist for %[ conversion in the
21912 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>).
21913 -- The set of sequences matched by a %p conversion and the interpretation of the
21914 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>).
21915 -- The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
21916 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>).
21917 -- The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
21918 converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold
21919 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>).
21920 -- Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
21921 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>).
21922 -- Whether the calloc, malloc, and realloc functions return a null pointer or a
21923 pointer to an allocated object when the size requested is zero (<a href="#7.22.3">7.22.3</a>).
21924 -- Whether open streams with unwritten buffered data are flushed, open streams are
21925 closed, or temporary files are removed when the abort or _Exit function is called
21926 (<a href="#7.22.4.1">7.22.4.1</a>, <a href="#7.22.4.5">7.22.4.5</a>).
21927 -- The termination status returned to the host environment by the abort, exit,
21928 _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>).
21929 -- The value returned by the system function when its argument is not a null pointer
21930 (<a href="#7.22.4.8">7.22.4.8</a>).
21931 -- The local time zone and Daylight Saving Time (<a href="#7.26.1">7.26.1</a>).
21932 -- The range and precision of times representable in clock_t and time_t (<a href="#7.26">7.26</a>).
21933 -- The era for the clock function (<a href="#7.26.2.1">7.26.2.1</a>).
21934 -- The replacement string for the %Z specifier to the strftime, and wcsftime
21935 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>).
21936 -- Whether the functions in <a href="#7.12"><math.h></a> honor the rounding direction mode in an
21937 IEC 60559 conformant implementation, unless explicitly specified otherwise (<a href="#F.10">F.10</a>).
21939 [<a name="p573" href="#p573">page 573</a>] (<a href="#Contents">Contents</a>)
21941 <a name="J.3.13" href="#J.3.13"><b> J.3.13 Architecture</b></a>
21942 1 -- The values or expressions assigned to the macros specified in the headers
21943 <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>).
21944 -- The result of attempting to indirectly access an object with automatic or thread
21945 storage duration from a thread other than the one with which it is associated (<a href="#6.2.4">6.2.4</a>).
21946 -- The number, order, and encoding of bytes in any object (when not explicitly specified
21947 in this International Standard) (<a href="#6.2.6.1">6.2.6.1</a>).
21948 -- Whether any extended alignments are supported and the contexts in which they are
21949 supported (<a href="#6.2.8">6.2.8</a>).
21950 -- Valid alignment values other than those returned by an alignof expression for
21951 fundamental types, if any (<a href="#6.2.8">6.2.8</a>).
21952 -- The value of the result of the sizeof and alignof operators (<a href="#6.5.3.4">6.5.3.4</a>).
21953 <a name="J.4" href="#J.4"><b> J.4 Locale-specific behavior</b></a>
21954 1 The following characteristics of a hosted environment are locale-specific and are required
21955 to be documented by the implementation:
21956 -- Additional members of the source and execution character sets beyond the basic
21957 character set (<a href="#5.2.1">5.2.1</a>).
21958 -- The presence, meaning, and representation of additional multibyte characters in the
21959 execution character set beyond the basic character set (<a href="#5.2.1.2">5.2.1.2</a>).
21960 -- The shift states used for the encoding of multibyte characters (<a href="#5.2.1.2">5.2.1.2</a>).
21961 -- The direction of writing of successive printing characters (<a href="#5.2.2">5.2.2</a>).
21962 -- The decimal-point character (<a href="#7.1.1">7.1.1</a>).
21963 -- The set of printing characters (<a href="#7.4">7.4</a>, <a href="#7.29.2">7.29.2</a>).
21964 -- The set of control characters (<a href="#7.4">7.4</a>, <a href="#7.29.2">7.29.2</a>).
21965 -- The sets of characters tested for by the isalpha, isblank, islower, ispunct,
21966 isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
21967 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>,
21968 <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>).
21969 -- The native environment (<a href="#7.11.1.1">7.11.1.1</a>).
21970 -- Additional subject sequences accepted by the numeric conversion functions (<a href="#7.22.1">7.22.1</a>,
21971 <a href="#7.28.4.1">7.28.4.1</a>).
21972 -- 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>).
21974 [<a name="p574" href="#p574">page 574</a>] (<a href="#Contents">Contents</a>)
21976 -- The contents of the error message strings set up by the strerror function
21977 (<a href="#7.23.6.2">7.23.6.2</a>).
21978 -- 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>).
21979 -- Character mappings that are supported by the towctrans function (<a href="#7.29.1">7.29.1</a>).
21980 -- Character classifications that are supported by the iswctype function (<a href="#7.29.1">7.29.1</a>).
21981 <a name="J.5" href="#J.5"><b> J.5 Common extensions</b></a>
21982 1 The following extensions are widely used in many systems, but are not portable to all
21983 implementations. The inclusion of any extension that may cause a strictly conforming
21984 program to become invalid renders an implementation nonconforming. Examples of such
21985 extensions are new keywords, extra library functions declared in standard headers, or
21986 predefined macros with names that do not begin with an underscore.
21987 <a name="J.5.1" href="#J.5.1"><b> J.5.1 Environment arguments</b></a>
21988 1 In a hosted environment, the main function receives a third argument, char *envp[],
21989 that points to a null-terminated array of pointers to char, each of which points to a string
21990 that provides information about the environment for this execution of the program
21991 (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
21992 <a name="J.5.2" href="#J.5.2"><b> J.5.2 Specialized identifiers</b></a>
21993 1 Characters other than the underscore _, letters, and digits, that are not part of the basic
21994 source character set (such as the dollar sign $, or characters in national character sets)
21995 may appear in an identifier (<a href="#6.4.2">6.4.2</a>).
21996 <a name="J.5.3" href="#J.5.3"><b> J.5.3 Lengths and cases of identifiers</b></a>
21997 1 All characters in identifiers (with or without external linkage) are significant (<a href="#6.4.2">6.4.2</a>).
21998 <a name="J.5.4" href="#J.5.4"><b> J.5.4 Scopes of identifiers</b></a>
21999 1 A function identifier, or the identifier of an object the declaration of which contains the
22000 keyword extern, has file scope (<a href="#6.2.1">6.2.1</a>).
22001 <a name="J.5.5" href="#J.5.5"><b> J.5.5 Writable string literals</b></a>
22002 1 String literals are modifiable (in which case, identical string literals should denote distinct
22003 objects) (<a href="#6.4.5">6.4.5</a>).
22005 [<a name="p575" href="#p575">page 575</a>] (<a href="#Contents">Contents</a>)
22007 <a name="J.5.6" href="#J.5.6"><b> J.5.6 Other arithmetic types</b></a>
22008 1 Additional arithmetic types, such as __int128 or double double, and their
22009 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
22010 more range or precision than long double, may be used for evaluating expressions of
22011 other floating types, and may be used to define float_t or double_t.
22012 <a name="J.5.7" href="#J.5.7"><b> J.5.7 Function pointer casts</b></a>
22013 1 A pointer to an object or to void may be cast to a pointer to a function, allowing data to
22014 be invoked as a function (<a href="#6.5.4">6.5.4</a>).
22015 2 A pointer to a function may be cast to a pointer to an object or to void, allowing a
22016 function to be inspected or modified (for example, by a debugger) (<a href="#6.5.4">6.5.4</a>).
22017 <a name="J.5.8" href="#J.5.8"><b> J.5.8 Extended bit-field types</b></a>
22018 1 A bit-field may be declared with a type other than _Bool, unsigned int, or
22019 signed int, with an appropriate maximum width (<a href="#6.7.2.1">6.7.2.1</a>).
22020 <a name="J.5.9" href="#J.5.9"><b> J.5.9 The fortran keyword</b></a>
22021 1 The fortran function specifier may be used in a function declaration to indicate that
22022 calls suitable for FORTRAN should be generated, or that a different representation for the
22023 external name is to be generated (<a href="#6.7.4">6.7.4</a>).
22024 <a name="J.5.10" href="#J.5.10"><b> J.5.10 The asm keyword</b></a>
22025 1 The asm keyword may be used to insert assembly language directly into the translator
22026 output (<a href="#6.8">6.8</a>). The most common implementation is via a statement of the form:
22027 asm ( character-string-literal );
22028 <a name="J.5.11" href="#J.5.11"><b> J.5.11 Multiple external definitions</b></a>
22029 1 There may be more than one external definition for the identifier of an object, with or
22030 without the explicit use of the keyword extern; if the definitions disagree, or more than
22031 one is initialized, the behavior is undefined (<a href="#6.9.2">6.9.2</a>).
22032 <a name="J.5.12" href="#J.5.12"><b> J.5.12 Predefined macro names</b></a>
22033 1 Macro names that do not begin with an underscore, describing the translation and
22034 execution environments, are defined by the implementation before translation begins
22035 (<a href="#6.10.8">6.10.8</a>).
22037 [<a name="p576" href="#p576">page 576</a>] (<a href="#Contents">Contents</a>)
22039 <a name="J.5.13" href="#J.5.13"><b> J.5.13 Floating-point status flags</b></a>
22040 1 If any floating-point status flags are set on normal termination after all calls to functions
22041 registered by the atexit function have been made (see <a href="#7.22.4.4">7.22.4.4</a>), the implementation
22042 writes some diagnostics indicating the fact to the stderr stream, if it is still open,
22043 <a name="J.5.14" href="#J.5.14"><b> J.5.14 Extra arguments for signal handlers</b></a>
22044 1 Handlers for specific signals are called with extra arguments in addition to the signal
22045 number (<a href="#7.14.1.1">7.14.1.1</a>).
22046 <a name="J.5.15" href="#J.5.15"><b> J.5.15 Additional stream types and file-opening modes</b></a>
22047 1 Additional mappings from files to streams are supported (<a href="#7.21.2">7.21.2</a>).
22048 2 Additional file-opening modes may be specified by characters appended to the mode
22049 argument of the fopen function (<a href="#7.21.5.3">7.21.5.3</a>).
22050 <a name="J.5.16" href="#J.5.16"><b> J.5.16 Defined file position indicator</b></a>
22051 1 The file position indicator is decremented by each successful call to the ungetc or
22052 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>,
22053 <a name="7.28.3.10)" href="#7.28.3.10)"><b> 7.28.3.10).</b></a>
22054 <a name="J.5.17" href="#J.5.17"><b> J.5.17 Math error reporting</b></a>
22055 1 Functions declared in <a href="#7.3"><complex.h></a> and <a href="#7.12"><math.h></a> raise SIGFPE to report errors
22056 instead of, or in addition to, setting errno or raising floating-point exceptions (<a href="#7.3">7.3</a>,
22057 <a name="7.12)" href="#7.12)"><b> 7.12).</b></a>
22059 [<a name="p577" href="#p577">page 577</a>] (<a href="#Contents">Contents</a>)
22061 <a name="K" href="#K"><b> Annex K</b></a>
22063 Bounds-checking interfaces
22064 <a name="K.1" href="#K.1"><b> K.1 Background</b></a>
22065 1 Traditionally, the C Library has contained many functions that trust the programmer to
22066 provide output character arrays big enough to hold the result being produced. Not only
22067 do these functions not check that the arrays are big enough, they frequently lack the
22068 information needed to perform such checks. While it is possible to write safe, robust, and
22069 error-free code using the existing library, the library tends to promote programming styles
22070 that lead to mysterious failures if a result is too big for the provided array.
22071 2 A common programming style is to declare character arrays large enough to handle most
22072 practical cases. However, if these arrays are not large enough to handle the resulting
22073 strings, data can be written past the end of the array overwriting other data and program
22074 structures. The program never gets any indication that a problem exists, and so never has
22075 a chance to recover or to fail gracefully.
22076 3 Worse, this style of programming has compromised the security of computers and
22077 networks. Buffer overflows can often be exploited to run arbitrary code with the
22078 permissions of the vulnerable (defective) program.
22079 4 If the programmer writes runtime checks to verify lengths before calling library
22080 functions, then those runtime checks frequently duplicate work done inside the library
22081 functions, which discover string lengths as a side effect of doing their job.
22082 5 This annex provides alternative library functions that promote safer, more secure
22083 programming. The alternative functions verify that output buffers are large enough for
22084 the intended result and return a failure indicator if they are not. Data is never written past
22085 the end of an array. All string results are null terminated.
22086 6 This annex also addresses another problem that complicates writing robust code:
22087 functions that are not reentrant because they return pointers to static objects owned by the
22088 function. Such functions can be troublesome since a previously returned result can
22089 change if the function is called again, perhaps by another thread.
22091 [<a name="p578" href="#p578">page 578</a>] (<a href="#Contents">Contents</a>)
22093 <a name="K.2" href="#K.2"><b> K.2 Scope</b></a>
22094 1 This annex specifies a series of optional extensions that can be useful in the mitigation of
22095 security vulnerabilities in programs, and comprise new functions, macros, and types
22096 declared or defined in existing standard headers.
22097 2 An implementation that defines __STDC_LIB_EXT1__ shall conform to the
22098 specifications in this annex.<sup><a href="#note367"><b>367)</b></a></sup>
22099 3 Subclause <a href="#K.3">K.3</a> should be read as if it were merged into the parallel structure of named
22100 subclauses of clause 7.
22101 <a name="K.3" href="#K.3"><b> K.3 Library</b></a>
22102 <a name="K.3.1" href="#K.3.1"><b> K.3.1 Introduction</b></a>
22103 <a name="K.3.1.1" href="#K.3.1.1"><b> K.3.1.1 Standard headers</b></a>
22104 1 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are not
22105 declared or defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
22106 defined as a macro which expands to the integer constant 0 at the point in the source file
22107 where the appropriate header is first included.
22108 2 The functions, macros, and types declared or defined in <a href="#K.3">K.3</a> and its subclauses are
22109 declared and defined by their respective headers if __STDC_WANT_LIB_EXT1__ is
22110 defined as a macro which expands to the integer constant 1 at the point in the source file
22111 where the appropriate header is first included.<sup><a href="#note368"><b>368)</b></a></sup>
22112 3 It is implementation-defined whether the functions, macros, and types declared or defined
22113 in <a href="#K.3">K.3</a> and its subclauses are declared or defined by their respective headers if
22114 __STDC_WANT_LIB_EXT1__ is not defined as a macro at the point in the source file
22115 where the appropriate header is first included.<sup><a href="#note369"><b>369)</b></a></sup>
22116 4 Within a preprocessing translation unit, __STDC_WANT_LIB_EXT1__ shall be
22117 defined identically for all inclusions of any headers from subclause <a href="#K.3">K.3</a>. If
22118 __STDC_WANT_LIB_EXT1__ is defined differently for any such inclusion, the
22119 implementation shall issue a diagnostic as if a preprocessor error directive were used.
22122 <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
22124 <sup><a name="note368" href="#note368"><b>368)</b></a></sup> Future revisions of this International Standard may define meanings for other values of
22125 __STDC_WANT_LIB_EXT1__.
22126 <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
22127 headers. All other names are not reserved, and a conforming implementation is not permitted to use
22128 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
22129 unreserved name is defined in a header when __STDC_WANT_LIB_EXT1__ is defined as 0, the
22130 implementation is not conforming.
22132 [<a name="p579" href="#p579">page 579</a>] (<a href="#Contents">Contents</a>)
22134 <a name="K.3.1.2" href="#K.3.1.2"><b> K.3.1.2 Reserved identifiers</b></a>
22135 1 Each macro name in any of the following subclauses is reserved for use as specified if it
22136 is defined by any of its associated headers when included; unless explicitly stated
22137 otherwise (see <a href="#7.1.4">7.1.4</a>).
22138 2 All identifiers with external linkage in any of the following subclauses are reserved for
22139 use as identifiers with external linkage if any of them are used by the program. None of
22140 them are reserved if none of them are used.
22141 3 Each identifier with file scope listed in any of the following subclauses is reserved for use
22142 as a macro name and as an identifier with file scope in the same name space if it is
22143 defined by any of its associated headers when included.
22144 <a name="K.3.1.3" href="#K.3.1.3"><b> K.3.1.3 Use of errno</b></a>
22145 1 An implementation may set errno for the functions defined in this annex, but is not
22147 <a name="K.3.1.4" href="#K.3.1.4"><b> K.3.1.4 Runtime-constraint violations</b></a>
22148 1 Most functions in this annex include as part of their specification a list of runtime-
22149 constraints. These runtime-constraints are requirements on the program using the
22150 library.<sup><a href="#note370"><b>370)</b></a></sup>
22151 2 Implementations shall verify that the runtime-constraints for a function are not violated
22152 by the program. If a runtime-constraint is violated, the implementation shall call the
22153 currently registered runtime-constraint handler (see set_constraint_handler_s
22154 in <a href="#7.22"><stdlib.h></a>). Multiple runtime-constraint violations in the same call to a library
22155 function result in only one call to the runtime-constraint handler. It is unspecified which
22156 one of the multiple runtime-constraint violations cause the handler to be called.
22157 3 If the runtime-constraints section for a function states an action to be performed when a
22158 runtime-constraint violation occurs, the function shall perform the action before calling
22159 the runtime-constraint handler. If the runtime-constraints section lists actions that are
22160 prohibited when a runtime-constraint violation occurs, then such actions are prohibited to
22161 the function both before calling the handler and after the handler returns.
22162 4 The runtime-constraint handler might not return. If the handler does return, the library
22163 function whose runtime-constraint was violated shall return some indication of failure as
22164 given by the returns section in the function's specification.
22168 <sup><a name="note370" href="#note370"><b>370)</b></a></sup> Although runtime-constraints replace many cases of undefined behavior, undefined behavior still
22169 exists in this annex. Implementations are free to detect any case of undefined behavior and treat it as a
22170 runtime-constraint violation by calling the runtime-constraint handler. This license comes directly
22171 from the definition of undefined behavior.
22173 [<a name="p580" href="#p580">page 580</a>] (<a href="#Contents">Contents</a>)
22175 <a name="K.3.2" href="#K.3.2"><b> K.3.2 Errors <errno.h></b></a>
22176 1 The header <a href="#7.5"><errno.h></a> defines a type.
22179 which is type int.<sup><a href="#note371"><b>371)</b></a></sup>
22180 <a name="K.3.3" href="#K.3.3"><b> K.3.3 Common definitions <stddef.h></b></a>
22181 1 The header <a href="#7.19"><stddef.h></a> defines a type.
22184 which is the type size_t.<sup><a href="#note372"><b>372)</b></a></sup>
22185 <a name="K.3.4" href="#K.3.4"><b> K.3.4 Integer types <stdint.h></b></a>
22186 1 The header <a href="#7.20"><stdint.h></a> defines a macro.
22189 which expands to a value<sup><a href="#note373"><b>373)</b></a></sup> of type size_t. Functions that have parameters of type
22190 rsize_t consider it a runtime-constraint violation if the values of those parameters are
22191 greater than RSIZE_MAX.
22192 Recommended practice
22193 3 Extremely large object sizes are frequently a sign that an object's size was calculated
22194 incorrectly. For example, negative numbers appear as very large positive numbers when
22195 converted to an unsigned type like size_t. Also, some implementations do not support
22196 objects as large as the maximum value that can be represented by type size_t.
22197 4 For those reasons, it is sometimes beneficial to restrict the range of object sizes to detect
22198 programming errors. For implementations targeting machines with large address spaces,
22199 it is recommended that RSIZE_MAX be defined as the smaller of the size of the largest
22200 object supported or (SIZE_MAX >> 1), even if this limit is smaller than the size of
22201 some legitimate, but very large, objects. Implementations targeting machines with small
22202 address spaces may wish to define RSIZE_MAX as SIZE_MAX, which means that there
22204 <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
22205 with the values that might be found in errno. For example, a function which returns the value of
22206 errno might be declared as having the return type errno_t.
22207 <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>.
22208 <sup><a name="note373" href="#note373"><b>373)</b></a></sup> The macro RSIZE_MAX need not expand to a constant expression.
22210 [<a name="p581" href="#p581">page 581</a>] (<a href="#Contents">Contents</a>)
22212 is no object size that is considered a runtime-constraint violation.
22213 <a name="K.3.5" href="#K.3.5"><b> K.3.5 Input/output <stdio.h></b></a>
22214 1 The header <a href="#7.21"><stdio.h></a> defines several macros and two types.
22217 which expands to an integer constant expression that is the size needed for an array of
22218 char large enough to hold a temporary file name string generated by the tmpnam_s
22221 which expands to an integer constant expression that is the maximum number of unique
22222 file names that can be generated by the tmpnam_s function.
22225 which is type int; and
22227 which is the type size_t.
22228 <a name="K.3.5.1" href="#K.3.5.1"><b> K.3.5.1 Operations on files</b></a>
22229 <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>
22231 1 #define __STDC_WANT_LIB_EXT1__ 1
22232 #include <a href="#7.21"><stdio.h></a>
22233 errno_t tmpfile_s(FILE * restrict * restrict streamptr);
22234 Runtime-constraints
22235 2 streamptr shall not be a null pointer.
22236 3 If there is a runtime-constraint violation, tmpfile_s does not attempt to create a file.
22237 <b> Description</b>
22238 4 The tmpfile_s function creates a temporary binary file that is different from any other
22239 existing file and that will automatically be removed when it is closed or at program
22240 termination. If the program terminates abnormally, whether an open temporary file is
22241 removed is implementation-defined. The file is opened for update with "wb+" mode
22242 with the meaning that mode has in the fopen_s function (including the mode's effect
22243 on exclusive access and file permissions).
22245 [<a name="p582" href="#p582">page 582</a>] (<a href="#Contents">Contents</a>)
22247 5 If the file was created successfully, then the pointer to FILE pointed to by streamptr
22248 will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
22249 to FILE pointed to by streamptr will be set to a null pointer.
22250 Recommended practice
22251 It should be possible to open at least TMP_MAX_S temporary files during the lifetime of
22252 the program (this limit may be shared with tmpnam_s) and there should be no limit on
22253 the number simultaneously open other than this limit and any limit on the number of open
22256 6 The tmpfile_s function returns zero if it created the file. If it did not create the file or
22257 there was a runtime-constraint violation, tmpfile_s returns a nonzero value.
22258 <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>
22260 1 #define __STDC_WANT_LIB_EXT1__ 1
22261 #include <a href="#7.21"><stdio.h></a>
22262 errno_t tmpnam_s(char *s, rsize_t maxsize);
22263 Runtime-constraints
22264 2 s shall not be a null pointer. maxsize shall be less than or equal to RSIZE_MAX.
22265 maxsize shall be greater than the length of the generated file name string.
22266 <b> Description</b>
22267 3 The tmpnam_s function generates a string that is a valid file name and that is not the
22268 same as the name of an existing file.<sup><a href="#note374"><b>374)</b></a></sup> The function is potentially capable of generating
22269 TMP_MAX_S different strings, but any or all of them may already be in use by existing
22270 files and thus not be suitable return values. The lengths of these strings shall be less than
22271 the value of the L_tmpnam_s macro.
22272 4 The tmpnam_s function generates a different string each time it is called.
22273 5 It is assumed that s points to an array of at least maxsize characters. This array will be
22274 set to generated string, as specified below.
22278 <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
22279 their names should not collide with those generated by conventional naming rules for the
22280 implementation. It is still necessary to use the remove function to remove such files when their use
22281 is ended, and before program termination. Implementations should take care in choosing the patterns
22282 used for names returned by tmpnam_s. For example, making a thread id part of the names avoids the
22283 race condition and possible conflict when multiple programs run simultaneously by the same user
22284 generate the same temporary file names.
22286 [<a name="p583" href="#p583">page 583</a>] (<a href="#Contents">Contents</a>)
22288 6 The implementation shall behave as if no library function except tmpnam calls the
22289 tmpnam_s function.<sup><a href="#note375"><b>375)</b></a></sup>
22290 Recommended practice
22291 7 After a program obtains a file name using the tmpnam_s function and before the
22292 program creates a file with that name, the possibility exists that someone else may create
22293 a file with that same name. To avoid this race condition, the tmpfile_s function
22294 should be used instead of tmpnam_s when possible. One situation that requires the use
22295 of the tmpnam_s function is when the program needs to create a temporary directory
22296 rather than a temporary file.
22298 8 If no suitable string can be generated, or if there is a runtime-constraint violation, the
22299 tmpnam_s function writes a null character to s[0] (only if s is not null and maxsize
22300 is greater than zero) and returns a nonzero value.
22301 9 Otherwise, the tmpnam_s function writes the string in the array pointed to by s and
22303 Environmental limits
22304 10 The value of the macro TMP_MAX_S shall be at least 25.
22305 <a name="K.3.5.2" href="#K.3.5.2"><b> K.3.5.2 File access functions</b></a>
22306 <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>
22308 1 #define __STDC_WANT_LIB_EXT1__ 1
22309 #include <a href="#7.21"><stdio.h></a>
22310 errno_t fopen_s(FILE * restrict * restrict streamptr,
22311 const char * restrict filename,
22312 const char * restrict mode);
22313 Runtime-constraints
22314 2 None of streamptr, filename, or mode shall be a null pointer.
22315 3 If there is a runtime-constraint violation, fopen_s does not attempt to open a file.
22316 Furthermore, if streamptr is not a null pointer, fopen_s sets *streamptr to the
22322 <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
22323 convention for temporary files), but this is not required.
22325 [<a name="p584" href="#p584">page 584</a>] (<a href="#Contents">Contents</a>)
22327 <b> Description</b>
22328 4 The fopen_s function opens the file whose name is the string pointed to by
22329 filename, and associates a stream with it.
22330 5 The mode string shall be as described for fopen, with the addition that modes starting
22331 with the character 'w' or 'a' may be preceded by the character 'u', see below:
22332 uw truncate to zero length or create text file for writing, default
22334 uwx create text file for writing, default permissions
22335 ua append; open or create text file for writing at end-of-file, default
22337 uwb truncate to zero length or create binary file for writing, default
22339 uwbx create binary file for writing, default permissions
22340 uab append; open or create binary file for writing at end-of-file, default
22342 uw+ truncate to zero length or create text file for update, default
22344 uw+x create text file for update, default permissions
22345 ua+ append; open or create text file for update, writing at end-of-file,
22346 default permissions
22347 uw+b or uwb+ truncate to zero length or create binary file for update, default
22349 uw+bx or uwb+x create binary file for update, default permissions
22350 ua+b or uab+ append; open or create binary file for update, writing at end-of-file,
22351 default permissions
22352 6 Opening a file with exclusive mode ('x' as the last character in the mode argument)
22353 fails if the file already exists or cannot be created.
22354 7 To the extent that the underlying system supports the concepts, files opened for writing
22355 shall be opened with exclusive (also known as non-shared) access. If the file is being
22356 created, and the first character of the mode string is not 'u', to the extent that the
22357 underlying system supports it, the file shall have a file permission that prevents other
22358 users on the system from accessing the file. If the file is being created and first character
22359 of the mode string is 'u', then by the time the file has been closed, it shall have the
22360 system default file access permissions.<sup><a href="#note376"><b>376)</b></a></sup>
22361 8 If the file was opened successfully, then the pointer to FILE pointed to by streamptr
22362 will be set to the pointer to the object controlling the opened file. Otherwise, the pointer
22365 <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.
22367 [<a name="p585" href="#p585">page 585</a>] (<a href="#Contents">Contents</a>)
22369 to FILE pointed to by streamptr will be set to a null pointer.
22371 9 The fopen_s function returns zero if it opened the file. If it did not open the file or if
22372 there was a runtime-constraint violation, fopen_s returns a nonzero value.
22373 <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>
22375 1 #define __STDC_WANT_LIB_EXT1__ 1
22376 #include <a href="#7.21"><stdio.h></a>
22377 errno_t freopen_s(FILE * restrict * restrict newstreamptr,
22378 const char * restrict filename,
22379 const char * restrict mode,
22380 FILE * restrict stream);
22381 Runtime-constraints
22382 2 None of newstreamptr, mode, and stream shall be a null pointer.
22383 3 If there is a runtime-constraint violation, freopen_s neither attempts to close any file
22384 associated with stream nor attempts to open a file. Furthermore, if newstreamptr is
22385 not a null pointer, fopen_s sets *newstreamptr to the null pointer.
22386 <b> Description</b>
22387 4 The freopen_s function opens the file whose name is the string pointed to by
22388 filename and associates the stream pointed to by stream with it. The mode
22389 argument has the same meaning as in the fopen_s function (including the mode's effect
22390 on exclusive access and file permissions).
22391 5 If filename is a null pointer, the freopen_s function attempts to change the mode of
22392 the stream to that specified by mode, as if the name of the file currently associated with
22393 the stream had been used. It is implementation-defined which changes of mode are
22394 permitted (if any), and under what circumstances.
22395 6 The freopen_s function first attempts to close any file that is associated with stream.
22396 Failure to close the file is ignored. The error and end-of-file indicators for the stream are
22398 7 If the file was opened successfully, then the pointer to FILE pointed to by
22399 newstreamptr will be set to the value of stream. Otherwise, the pointer to FILE
22400 pointed to by newstreamptr will be set to a null pointer.
22402 8 The freopen_s function returns zero if it opened the file. If it did not open the file or
22403 there was a runtime-constraint violation, freopen_s returns a nonzero value.
22405 [<a name="p586" href="#p586">page 586</a>] (<a href="#Contents">Contents</a>)
22407 <a name="K.3.5.3" href="#K.3.5.3"><b> K.3.5.3 Formatted input/output functions</b></a>
22408 1 Unless explicitly stated otherwise, if the execution of a function described in this
22409 subclause causes copying to take place between objects that overlap, the objects take on
22410 unspecified values.
22411 <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>
22413 1 #define __STDC_WANT_LIB_EXT1__ 1
22414 #include <a href="#7.21"><stdio.h></a>
22415 int fprintf_s(FILE * restrict stream,
22416 const char * restrict format, ...);
22417 Runtime-constraints
22418 2 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note377"><b>377)</b></a></sup> (modified or
22419 not by flags, field width, or precision) shall not appear in the string pointed to by
22420 format. Any argument to fprintf_s corresponding to a %s specifier shall not be a
22422 3 If there is a runtime-constraint violation,<sup><a href="#note378"><b>378)</b></a></sup> the fprintf_s function does not attempt
22423 to produce further output, and it is unspecified to what extent fprintf_s produced
22424 output before discovering the runtime-constraint violation.
22425 <b> Description</b>
22426 4 The fprintf_s function is equivalent to the fprintf function except for the explicit
22427 runtime-constraints listed above.
22429 5 The fprintf_s function returns the number of characters transmitted, or a negative
22430 value if an output error, encoding error, or runtime-constraint violation occurred.
22435 <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
22436 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
22437 format string was %%n.
22438 <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
22439 implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
22440 constraint violation.
22442 [<a name="p587" href="#p587">page 587</a>] (<a href="#Contents">Contents</a>)
22444 <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>
22446 1 #define __STDC_WANT_LIB_EXT1__ 1
22447 #include <a href="#7.21"><stdio.h></a>
22448 int fscanf_s(FILE * restrict stream,
22449 const char * restrict format, ...);
22450 Runtime-constraints
22451 2 Neither stream nor format shall be a null pointer. Any argument indirected though in
22452 order to store converted input shall not be a null pointer.
22453 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
22454 perform further input, and it is unspecified to what extent fscanf_s performed input
22455 before discovering the runtime-constraint violation.
22456 <b> Description</b>
22457 4 The fscanf_s function is equivalent to fscanf except that the c, s, and [ conversion
22458 specifiers apply to a pair of arguments (unless assignment suppression is indicated by a
22459 *). The first of these arguments is the same as for fscanf. That argument is
22460 immediately followed in the argument list by the second argument, which has type
22461 rsize_t and gives the number of elements in the array pointed to by the first argument
22462 of the pair. If the first argument points to a scalar object, it is considered to be an array of
22463 one element.<sup><a href="#note380"><b>380)</b></a></sup>
22464 5 A matching failure occurs if the number of elements in a receiving object is insufficient to
22465 hold the converted input (including any trailing null character).
22467 6 The fscanf_s function returns the value of the macro EOF if an input failure occurs
22468 before any conversion or if there is a runtime-constraint violation. Otherwise, the
22470 <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
22471 implementation may treat any unsupported specifiers in the string pointed to by format as a runtime-
22472 constraint violation.
22473 <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
22474 used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
22475 argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
22476 the format is not known at translation time. For example, an implementation may issue a diagnostic
22477 for each argument after format that has of type pointer to one of char, signed char,
22478 unsigned char, or void that is not followed by an argument of a type compatible with
22479 rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
22480 using the hh length modifier, a length argument must follow the pointer argument. Another useful
22481 diagnostic could flag any non-pointer argument following format that did not have a type
22482 compatible with rsize_t.
22484 [<a name="p588" href="#p588">page 588</a>] (<a href="#Contents">Contents</a>)
22486 fscanf_s function returns the number of input items assigned, which can be fewer than
22487 provided for, or even zero, in the event of an early matching failure.
22488 7 EXAMPLE 1 The call:
22489 #define __STDC_WANT_LIB_EXT1__ 1
22490 #include <a href="#7.21"><stdio.h></a>
22492 int n, i; float x; char name[50];
22493 n = fscanf_s(stdin, "%d%f%s", &i, &x, name, (rsize_t) 50);
22494 with the input line:
22495 25 54.32E-1 thompson
22496 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
22499 8 EXAMPLE 2 The call:
22500 #define __STDC_WANT_LIB_EXT1__ 1
22501 #include <a href="#7.21"><stdio.h></a>
22504 n = fscanf_s(stdin, "%s", s, sizeof s);
22505 with the input line:
22507 will assign to n the value 0 since a matching failure occurred because the sequence hello\0 requires an
22508 array of six characters to store it.
22510 <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>
22512 1 #define __STDC_WANT_LIB_EXT1__ 1
22513 #include <a href="#7.21"><stdio.h></a>
22514 int printf_s(const char * restrict format, ...);
22515 Runtime-constraints
22516 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
22517 width, or precision) shall not appear in the string pointed to by format. Any argument
22518 to printf_s corresponding to a %s specifier shall not be a null pointer.
22519 3 If there is a runtime-constraint violation, the printf_s function does not attempt to
22520 produce further output, and it is unspecified to what extent printf_s produced output
22521 before discovering the runtime-constraint violation.
22524 <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
22525 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
22526 format string was %%n.
22528 [<a name="p589" href="#p589">page 589</a>] (<a href="#Contents">Contents</a>)
22530 <b> Description</b>
22531 4 The printf_s function is equivalent to the printf function except for the explicit
22532 runtime-constraints listed above.
22534 5 The printf_s function returns the number of characters transmitted, or a negative
22535 value if an output error, encoding error, or runtime-constraint violation occurred.
22536 <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>
22538 1 #define __STDC_WANT_LIB_EXT1__ 1
22539 #include <a href="#7.21"><stdio.h></a>
22540 int scanf_s(const char * restrict format, ...);
22541 Runtime-constraints
22542 2 format shall not be a null pointer. Any argument indirected though in order to store
22543 converted input shall not be a null pointer.
22544 3 If there is a runtime-constraint violation, the scanf_s function does not attempt to
22545 perform further input, and it is unspecified to what extent scanf_s performed input
22546 before discovering the runtime-constraint violation.
22547 <b> Description</b>
22548 4 The scanf_s function is equivalent to fscanf_s with the argument stdin
22549 interposed before the arguments to scanf_s.
22551 5 The scanf_s function returns the value of the macro EOF if an input failure occurs
22552 before any conversion or if there is a runtime-constraint violation. Otherwise, the
22553 scanf_s function returns the number of input items assigned, which can be fewer than
22554 provided for, or even zero, in the event of an early matching failure.
22555 <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>
22557 1 #define __STDC_WANT_LIB_EXT1__ 1
22558 #include <a href="#7.21"><stdio.h></a>
22559 int snprintf_s(char * restrict s, rsize_t n,
22560 const char * restrict format, ...);
22561 Runtime-constraints
22562 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
22563 than RSIZE_MAX. The %n specifier<sup><a href="#note382"><b>382)</b></a></sup> (modified or not by flags, field width, or
22564 precision) shall not appear in the string pointed to by format. Any argument to
22566 [<a name="p590" href="#p590">page 590</a>] (<a href="#Contents">Contents</a>)
22568 snprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
22570 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
22571 than zero and less than RSIZE_MAX, then the snprintf_s function sets s[0] to the
22573 <b> Description</b>
22574 4 The snprintf_s function is equivalent to the snprintf function except for the
22575 explicit runtime-constraints listed above.
22576 5 The snprintf_s function, unlike sprintf_s, will truncate the result to fit within the
22577 array pointed to by s.
22579 6 The snprintf_s function returns the number of characters that would have been
22580 written had n been sufficiently large, not counting the terminating null character, or a
22581 negative value if a runtime-constraint violation occurred. Thus, the null-terminated
22582 output has been completely written if and only if the returned value is nonnegative and
22584 <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>
22586 1 #define __STDC_WANT_LIB_EXT1__ 1
22587 #include <a href="#7.21"><stdio.h></a>
22588 int sprintf_s(char * restrict s, rsize_t n,
22589 const char * restrict format, ...);
22590 Runtime-constraints
22591 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
22592 than RSIZE_MAX. The number of characters (including the trailing null) required for the
22593 result to be written to the array pointed to by s shall not be greater than n. The %n
22594 specifier<sup><a href="#note383"><b>383)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
22595 string pointed to by format. Any argument to sprintf_s corresponding to a %s
22596 specifier shall not be a null pointer. No encoding error shall occur.
22600 <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
22601 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
22602 format string was %%n.
22603 <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
22604 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
22605 format string was %%n.
22607 [<a name="p591" href="#p591">page 591</a>] (<a href="#Contents">Contents</a>)
22609 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
22610 than zero and less than RSIZE_MAX, then the sprintf_s function sets s[0] to the
22612 <b> Description</b>
22613 4 The sprintf_s function is equivalent to the sprintf function except for the
22614 parameter n and the explicit runtime-constraints listed above.
22615 5 The sprintf_s function, unlike snprintf_s, treats a result too big for the array
22616 pointed to by s as a runtime-constraint violation.
22618 6 If no runtime-constraint violation occurred, the sprintf_s function returns the number
22619 of characters written in the array, not counting the terminating null character. If an
22620 encoding error occurred, sprintf_s returns a negative value. If any other runtime-
22621 constraint violation occurred, sprintf_s returns zero.
22622 <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>
22624 1 #define __STDC_WANT_LIB_EXT1__ 1
22625 #include <a href="#7.21"><stdio.h></a>
22626 int sscanf_s(const char * restrict s,
22627 const char * restrict format, ...);
22628 Runtime-constraints
22629 2 Neither s nor format shall be a null pointer. Any argument indirected though in order
22630 to store converted input shall not be a null pointer.
22631 3 If there is a runtime-constraint violation, the sscanf_s function does not attempt to
22632 perform further input, and it is unspecified to what extent sscanf_s performed input
22633 before discovering the runtime-constraint violation.
22634 <b> Description</b>
22635 4 The sscanf_s function is equivalent to fscanf_s, except that input is obtained from
22636 a string (specified by the argument s) rather than from a stream. Reaching the end of the
22637 string is equivalent to encountering end-of-file for the fscanf_s function. If copying
22638 takes place between objects that overlap, the objects take on unspecified values.
22640 5 The sscanf_s function returns the value of the macro EOF if an input failure occurs
22641 before any conversion or if there is a runtime-constraint violation. Otherwise, the
22642 sscanf_s function returns the number of input items assigned, which can be fewer than
22643 provided for, or even zero, in the event of an early matching failure.
22645 [<a name="p592" href="#p592">page 592</a>] (<a href="#Contents">Contents</a>)
22647 <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>
22649 1 #define __STDC_WANT_LIB_EXT1__ 1
22650 #include <a href="#7.16"><stdarg.h></a>
22651 #include <a href="#7.21"><stdio.h></a>
22652 int vfprintf_s(FILE * restrict stream,
22653 const char * restrict format,
22655 Runtime-constraints
22656 2 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note384"><b>384)</b></a></sup> (modified or
22657 not by flags, field width, or precision) shall not appear in the string pointed to by
22658 format. Any argument to vfprintf_s corresponding to a %s specifier shall not be a
22660 3 If there is a runtime-constraint violation, the vfprintf_s function does not attempt to
22661 produce further output, and it is unspecified to what extent vfprintf_s produced
22662 output before discovering the runtime-constraint violation.
22663 <b> Description</b>
22664 4 The vfprintf_s function is equivalent to the vfprintf function except for the
22665 explicit runtime-constraints listed above.
22667 5 The vfprintf_s function returns the number of characters transmitted, or a negative
22668 value if an output error, encoding error, or runtime-constraint violation occurred.
22669 <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>
22671 1 #define __STDC_WANT_LIB_EXT1__ 1
22672 #include <a href="#7.16"><stdarg.h></a>
22673 #include <a href="#7.21"><stdio.h></a>
22674 int vfscanf_s(FILE * restrict stream,
22675 const char * restrict format,
22681 <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
22682 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
22683 format string was %%n.
22685 [<a name="p593" href="#p593">page 593</a>] (<a href="#Contents">Contents</a>)
22687 Runtime-constraints
22688 2 Neither stream nor format shall be a null pointer. Any argument indirected though in
22689 order to store converted input shall not be a null pointer.
22690 3 If there is a runtime-constraint violation, the vfscanf_s function does not attempt to
22691 perform further input, and it is unspecified to what extent vfscanf_s performed input
22692 before discovering the runtime-constraint violation.
22693 <b> Description</b>
22694 4 The vfscanf_s function is equivalent to fscanf_s, with the variable argument list
22695 replaced by arg, which shall have been initialized by the va_start macro (and
22696 possibly subsequent va_arg calls). The vfscanf_s function does not invoke the
22697 va_end macro.<sup><a href="#note385"><b>385)</b></a></sup>
22699 5 The vfscanf_s function returns the value of the macro EOF if an input failure occurs
22700 before any conversion or if there is a runtime-constraint violation. Otherwise, the
22701 vfscanf_s function returns the number of input items assigned, which can be fewer
22702 than provided for, or even zero, in the event of an early matching failure.
22703 <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>
22705 1 #define __STDC_WANT_LIB_EXT1__ 1
22706 #include <a href="#7.16"><stdarg.h></a>
22707 #include <a href="#7.21"><stdio.h></a>
22708 int vprintf_s(const char * restrict format,
22710 Runtime-constraints
22711 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
22712 width, or precision) shall not appear in the string pointed to by format. Any argument
22713 to vprintf_s corresponding to a %s specifier shall not be a null pointer.
22714 3 If there is a runtime-constraint violation, the vprintf_s function does not attempt to
22715 produce further output, and it is unspecified to what extent vprintf_s produced output
22716 before discovering the runtime-constraint violation.
22718 <sup><a name="note385" href="#note385"><b>385)</b></a></sup> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
22719 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
22721 <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
22722 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
22723 format string was %%n.
22725 [<a name="p594" href="#p594">page 594</a>] (<a href="#Contents">Contents</a>)
22727 <b> Description</b>
22728 4 The vprintf_s function is equivalent to the vprintf function except for the explicit
22729 runtime-constraints listed above.
22731 5 The vprintf_s function returns the number of characters transmitted, or a negative
22732 value if an output error, encoding error, or runtime-constraint violation occurred.
22733 <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>
22735 1 #define __STDC_WANT_LIB_EXT1__ 1
22736 #include <a href="#7.16"><stdarg.h></a>
22737 #include <a href="#7.21"><stdio.h></a>
22738 int vscanf_s(const char * restrict format,
22740 Runtime-constraints
22741 2 format shall not be a null pointer. Any argument indirected though in order to store
22742 converted input shall not be a null pointer.
22743 3 If there is a runtime-constraint violation, the vscanf_s function does not attempt to
22744 perform further input, and it is unspecified to what extent vscanf_s performed input
22745 before discovering the runtime-constraint violation.
22746 <b> Description</b>
22747 4 The vscanf_s function is equivalent to scanf_s, with the variable argument list
22748 replaced by arg, which shall have been initialized by the va_start macro (and
22749 possibly subsequent va_arg calls). The vscanf_s function does not invoke the
22750 va_end macro.<sup><a href="#note387"><b>387)</b></a></sup>
22752 5 The vscanf_s function returns the value of the macro EOF if an input failure occurs
22753 before any conversion or if there is a runtime-constraint violation. Otherwise, the
22754 vscanf_s function returns the number of input items assigned, which can be fewer than
22755 provided for, or even zero, in the event of an early matching failure.
22760 <sup><a name="note387" href="#note387"><b>387)</b></a></sup> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
22761 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
22764 [<a name="p595" href="#p595">page 595</a>] (<a href="#Contents">Contents</a>)
22766 <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>
22768 1 #define __STDC_WANT_LIB_EXT1__ 1
22769 #include <a href="#7.16"><stdarg.h></a>
22770 #include <a href="#7.21"><stdio.h></a>
22771 int vsnprintf_s(char * restrict s, rsize_t n,
22772 const char * restrict format,
22774 Runtime-constraints
22775 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
22776 than RSIZE_MAX. The %n specifier<sup><a href="#note388"><b>388)</b></a></sup> (modified or not by flags, field width, or
22777 precision) shall not appear in the string pointed to by format. Any argument to
22778 vsnprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
22780 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
22781 than zero and less than RSIZE_MAX, then the vsnprintf_s function sets s[0] to the
22783 <b> Description</b>
22784 4 The vsnprintf_s function is equivalent to the vsnprintf function except for the
22785 explicit runtime-constraints listed above.
22786 5 The vsnprintf_s function, unlike vsprintf_s, will truncate the result to fit within
22787 the array pointed to by s.
22789 6 The vsnprintf_s function returns the number of characters that would have been
22790 written had n been sufficiently large, not counting the terminating null character, or a
22791 negative value if a runtime-constraint violation occurred. Thus, the null-terminated
22792 output has been completely written if and only if the returned value is nonnegative and
22798 <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
22799 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
22800 format string was %%n.
22802 [<a name="p596" href="#p596">page 596</a>] (<a href="#Contents">Contents</a>)
22804 <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>
22806 1 #define __STDC_WANT_LIB_EXT1__ 1
22807 #include <a href="#7.16"><stdarg.h></a>
22808 #include <a href="#7.21"><stdio.h></a>
22809 int vsprintf_s(char * restrict s, rsize_t n,
22810 const char * restrict format,
22812 Runtime-constraints
22813 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
22814 than RSIZE_MAX. The number of characters (including the trailing null) required for the
22815 result to be written to the array pointed to by s shall not be greater than n. The %n
22816 specifier<sup><a href="#note389"><b>389)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
22817 string pointed to by format. Any argument to vsprintf_s corresponding to a %s
22818 specifier shall not be a null pointer. No encoding error shall occur.
22819 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
22820 than zero and less than RSIZE_MAX, then the vsprintf_s function sets s[0] to the
22822 <b> Description</b>
22823 4 The vsprintf_s function is equivalent to the vsprintf function except for the
22824 parameter n and the explicit runtime-constraints listed above.
22825 5 The vsprintf_s function, unlike vsnprintf_s, treats a result too big for the array
22826 pointed to by s as a runtime-constraint violation.
22828 6 If no runtime-constraint violation occurred, the vsprintf_s function returns the
22829 number of characters written in the array, not counting the terminating null character. If
22830 an encoding error occurred, vsprintf_s returns a negative value. If any other
22831 runtime-constraint violation occurred, vsprintf_s returns zero.
22836 <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
22837 at by format when those characters are not a interpreted as a %n specifier. For example, if the entire
22838 format string was %%n.
22840 [<a name="p597" href="#p597">page 597</a>] (<a href="#Contents">Contents</a>)
22842 <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>
22844 1 #define __STDC_WANT_LIB_EXT1__ 1
22845 #include <a href="#7.16"><stdarg.h></a>
22846 #include <a href="#7.21"><stdio.h></a>
22847 int vsscanf_s(const char * restrict s,
22848 const char * restrict format,
22850 Runtime-constraints
22851 2 Neither s nor format shall be a null pointer. Any argument indirected though in order
22852 to store converted input shall not be a null pointer.
22853 3 If there is a runtime-constraint violation, the vsscanf_s function does not attempt to
22854 perform further input, and it is unspecified to what extent vsscanf_s performed input
22855 before discovering the runtime-constraint violation.
22856 <b> Description</b>
22857 4 The vsscanf_s function is equivalent to sscanf_s, with the variable argument list
22858 replaced by arg, which shall have been initialized by the va_start macro (and
22859 possibly subsequent va_arg calls). The vsscanf_s function does not invoke the
22860 va_end macro.<sup><a href="#note390"><b>390)</b></a></sup>
22862 5 The vsscanf_s function returns the value of the macro EOF if an input failure occurs
22863 before any conversion or if there is a runtime-constraint violation. Otherwise, the
22864 vscanf_s function returns the number of input items assigned, which can be fewer than
22865 provided for, or even zero, in the event of an early matching failure.
22866 <a name="K.3.5.4" href="#K.3.5.4"><b> K.3.5.4 Character input/output functions</b></a>
22867 <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>
22869 1 #define __STDC_WANT_LIB_EXT1__ 1
22870 #include <a href="#7.21"><stdio.h></a>
22871 char *gets_s(char *s, rsize_t n);
22876 <sup><a name="note390" href="#note390"><b>390)</b></a></sup> As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
22877 vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is
22880 [<a name="p598" href="#p598">page 598</a>] (<a href="#Contents">Contents</a>)
22882 Runtime-constraints
22883 2 s shall not be a null pointer. n shall neither be equal to zero nor be greater than
22884 RSIZE_MAX. A new-line character, end-of-file, or read error shall occur within reading
22885 n-1 characters from stdin.<sup><a href="#note391"><b>391)</b></a></sup>
22886 3 If there is a runtime-constraint violation, s[0] is set to the null character, and characters
22887 are read and discarded from stdin until a new-line character is read, or end-of-file or a
22889 <b> Description</b>
22890 4 The gets_s function reads at most one less than the number of characters specified by n
22891 from the stream pointed to by stdin, into the array pointed to by s. No additional
22892 characters are read after a new-line character (which is discarded) or after end-of-file.
22893 The discarded new-line character does not count towards number of characters read. A
22894 null character is written immediately after the last character read into the array.
22895 5 If end-of-file is encountered and no characters have been read into the array, or if a read
22896 error occurs during the operation, then s[0] is set to the null character, and the other
22897 elements of s take unspecified values.
22898 Recommended practice
22899 6 The fgets function allows properly-written programs to safely process input lines too
22900 long to store in the result array. In general this requires that callers of fgets pay
22901 attention to the presence or absence of a new-line character in the result array. Consider
22902 using fgets (along with any needed processing based on new-line characters) instead of
22905 7 The gets_s function returns s if successful. If there was a runtime-constraint violation,
22906 or if end-of-file is encountered and no characters have been read into the array, or if a
22907 read error occurs during the operation, then a null pointer is returned.
22912 <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
22913 a line of input to overflow the buffer to store it. Unlike the fgets function, gets_s maintains a
22914 one-to-one relationship between input lines and successful calls to gets_s. Programs that use gets
22915 expect such a relationship.
22917 [<a name="p599" href="#p599">page 599</a>] (<a href="#Contents">Contents</a>)
22919 <a name="K.3.6" href="#K.3.6"><b> K.3.6 General utilities <stdlib.h></b></a>
22920 1 The header <a href="#7.22"><stdlib.h></a> defines three types.
22923 which is type int; and
22925 which is the type size_t; and
22926 constraint_handler_t
22927 which has the following definition
22928 typedef void (*constraint_handler_t)(
22929 const char * restrict msg,
22930 void * restrict ptr,
22932 <a name="K.3.6.1" href="#K.3.6.1"><b> K.3.6.1 Runtime-constraint handling</b></a>
22933 <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>
22935 1 #define __STDC_WANT_LIB_EXT1__ 1
22936 #include <a href="#7.22"><stdlib.h></a>
22937 constraint_handler_t set_constraint_handler_s(
22938 constraint_handler_t handler);
22939 <b> Description</b>
22940 2 The set_constraint_handler_s function sets the runtime-constraint handler to
22941 be handler. The runtime-constraint handler is the function to be called when a library
22942 function detects a runtime-constraint violation. Only the most recent handler registered
22943 with set_constraint_handler_s is called when a runtime-constraint violation
22945 3 When the handler is called, it is passed the following arguments in the following order:
22946 1. A pointer to a character string describing the runtime-constraint violation.
22947 2. A null pointer or a pointer to an implementation defined object.
22948 3. If the function calling the handler has a return type declared as errno_t, the
22949 return value of the function is passed. Otherwise, a positive value of type
22952 [<a name="p600" href="#p600">page 600</a>] (<a href="#Contents">Contents</a>)
22954 4 The implementation has a default constraint handler that is used if no calls to the
22955 set_constraint_handler_s function have been made. The behavior of the
22956 default handler is implementation-defined, and it may cause the program to exit or abort.
22957 5 If the handler argument to set_constraint_handler_s is a null pointer, the
22958 implementation default handler becomes the current constraint handler.
22960 6 The set_constraint_handler_s function returns a pointer to the previously
22961 registered handler.<sup><a href="#note392"><b>392)</b></a></sup>
22962 <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>
22964 1 #define __STDC_WANT_LIB_EXT1__ 1
22965 #include <a href="#7.22"><stdlib.h></a>
22966 void abort_handler_s(
22967 const char * restrict msg,
22968 void * restrict ptr,
22970 <b> Description</b>
22971 2 A pointer to the abort_handler_s function shall be a suitable argument to the
22972 set_constraint_handler_s function.
22973 3 The abort_handler_s function writes a message on the standard error stream in an
22974 implementation-defined format. The message shall include the string pointed to by msg.
22975 The abort_handler_s function then calls the abort function.<sup><a href="#note393"><b>393)</b></a></sup>
22977 4 The abort_handler_s function does not return to its caller.
22982 <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
22983 pointer argument, a pointer to the implementation default handler is returned (not NULL).
22984 <sup><a name="note393" href="#note393"><b>393)</b></a></sup> Many implementations invoke a debugger when the abort function is called.
22986 [<a name="p601" href="#p601">page 601</a>] (<a href="#Contents">Contents</a>)
22988 <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>
22990 1 #define __STDC_WANT_LIB_EXT1__ 1
22991 #include <a href="#7.22"><stdlib.h></a>
22992 void ignore_handler_s(
22993 const char * restrict msg,
22994 void * restrict ptr,
22996 <b> Description</b>
22997 2 A pointer to the ignore_handler_s function shall be a suitable argument to the
22998 set_constraint_handler_s function.
22999 3 The ignore_handler_s function simply returns to its caller.<sup><a href="#note394"><b>394)</b></a></sup>
23001 4 The ignore_handler_s function returns no value.
23002 <a name="K.3.6.2" href="#K.3.6.2"><b> K.3.6.2 Communication with the environment</b></a>
23003 <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>
23005 1 #define __STDC_WANT_LIB_EXT1__ 1
23006 #include <a href="#7.22"><stdlib.h></a>
23007 errno_t getenv_s(size_t * restrict len,
23008 char * restrict value, rsize_t maxsize,
23009 const char * restrict name);
23010 Runtime-constraints
23011 2 name shall not be a null pointer. maxsize shall neither equal zero nor be greater than
23012 RSIZE_MAX. If maxsize is not equal to zero, then value shall not be a null pointer.
23013 3 If there is a runtime-constraint violation, the integer pointed to by len is set to 0 (if len
23014 is not null), and the environment list is not searched.
23015 <b> Description</b>
23016 4 The getenv_s function searches an environment list, provided by the host environment,
23017 for a string that matches the string pointed to by name.
23020 <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
23021 which a runtime-constraint violation occurs will return to its caller. The caller can determine whether
23022 a runtime-constraint violation occurred based on the library function's specification (usually, the
23023 library function returns a nonzero errno_t).
23025 [<a name="p602" href="#p602">page 602</a>] (<a href="#Contents">Contents</a>)
23027 5 If that name is found then getenv_s performs the following actions. If len is not a
23028 null pointer, the length of the string associated with the matched list member is stored in
23029 the integer pointed to by len. If the length of the associated string is less than maxsize,
23030 then the associated string is copied to the array pointed to by value.
23031 6 If that name is not found then getenv_s performs the following actions. If len is not
23032 a null pointer, zero is stored in the integer pointed to by len. If maxsize is greater than
23033 zero, then value[0] is set to the null character.
23034 7 The set of environment names and the method for altering the environment list are
23035 implementation-defined.
23037 8 The getenv_s function returns zero if the specified name is found and the associated
23038 string was successfully stored in value. Otherwise, a nonzero value is returned.
23039 <a name="K.3.6.3" href="#K.3.6.3"><b> K.3.6.3 Searching and sorting utilities</b></a>
23040 1 These utilities make use of a comparison function to search or sort arrays of unspecified
23041 type. Where an argument declared as size_t nmemb specifies the length of the array
23042 for a function, if nmemb has the value zero on a call to that function, then the comparison
23043 function is not called, a search finds no matching element, sorting performs no
23044 rearrangement, and the pointer to the array may be null.
23045 2 The implementation shall ensure that the second argument of the comparison function
23046 (when called from bsearch_s), or both arguments (when called from qsort_s), are
23047 pointers to elements of the array.<sup><a href="#note395"><b>395)</b></a></sup> The first argument when called from bsearch_s
23049 3 The comparison function shall not alter the contents of either the array or search key. The
23050 implementation may reorder elements of the array between calls to the comparison
23051 function, but shall not otherwise alter the contents of any individual element.
23052 4 When the same objects (consisting of size bytes, irrespective of their current positions
23053 in the array) are passed more than once to the comparison function, the results shall be
23054 consistent with one another. That is, for qsort_s they shall define a total ordering on
23055 the array, and for bsearch_s the same object shall always compare the same way with
23061 <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:
23062 ((char *)p - (char *)base) % size == 0
23063 (char *)p >= (char *)base
23064 (char *)p < (char *)base + nmemb * size
23066 [<a name="p603" href="#p603">page 603</a>] (<a href="#Contents">Contents</a>)
23068 5 A sequence point occurs immediately before and immediately after each call to the
23069 comparison function, and also between any call to the comparison function and any
23070 movement of the objects passed as arguments to that call.
23071 <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>
23073 1 #define __STDC_WANT_LIB_EXT1__ 1
23074 #include <a href="#7.22"><stdlib.h></a>
23075 void *bsearch_s(const void *key, const void *base,
23076 rsize_t nmemb, rsize_t size,
23077 int (*compar)(const void *k, const void *y,
23080 Runtime-constraints
23081 2 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
23082 zero, then none of key, base, or compar shall be a null pointer.
23083 3 If there is a runtime-constraint violation, the bsearch_s function does not search the
23085 <b> Description</b>
23086 4 The bsearch_s function searches an array of nmemb objects, the initial element of
23087 which is pointed to by base, for an element that matches the object pointed to by key.
23088 The size of each element of the array is specified by size.
23089 5 The comparison function pointed to by compar is called with three arguments. The first
23090 two point to the key object and to an array element, in that order. The function shall
23091 return an integer less than, equal to, or greater than zero if the key object is considered,
23092 respectively, to be less than, to match, or to be greater than the array element. The array
23093 shall consist of: all the elements that compare less than, all the elements that compare
23094 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>
23095 The third argument to the comparison function is the context argument passed to
23096 bsearch_s. The sole use of context by bsearch_s is to pass it to the comparison
23097 function.<sup><a href="#note397"><b>397)</b></a></sup>
23102 <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.
23103 <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
23104 example, it might specify a collating sequence used by the comparison function.
23106 [<a name="p604" href="#p604">page 604</a>] (<a href="#Contents">Contents</a>)
23109 6 The bsearch_s function returns a pointer to a matching element of the array, or a null
23110 pointer if no match is found or there is a runtime-constraint violation. If two elements
23111 compare as equal, which element is matched is unspecified.
23112 <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>
23114 1 #define __STDC_WANT_LIB_EXT1__ 1
23115 #include <a href="#7.22"><stdlib.h></a>
23116 errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
23117 int (*compar)(const void *x, const void *y,
23120 Runtime-constraints
23121 2 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to
23122 zero, then neither base nor compar shall be a null pointer.
23123 3 If there is a runtime-constraint violation, the qsort_s function does not sort the array.
23124 <b> Description</b>
23125 4 The qsort_s function sorts an array of nmemb objects, the initial element of which is
23126 pointed to by base. The size of each object is specified by size.
23127 5 The contents of the array are sorted into ascending order according to a comparison
23128 function pointed to by compar, which is called with three arguments. The first two
23129 point to the objects being compared. The function shall return an integer less than, equal
23130 to, or greater than zero if the first argument is considered to be respectively less than,
23131 equal to, or greater than the second. The third argument to the comparison function is the
23132 context argument passed to qsort_s. The sole use of context by qsort_s is to
23133 pass it to the comparison function.<sup><a href="#note398"><b>398)</b></a></sup>
23134 6 If two elements compare as equal, their relative order in the resulting sorted array is
23137 7 The qsort_s function returns zero if there was no runtime-constraint violation.
23138 Otherwise, a nonzero value is returned.
23143 <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
23144 example, it might specify a collating sequence used by the comparison function.
23146 [<a name="p605" href="#p605">page 605</a>] (<a href="#Contents">Contents</a>)
23148 <a name="K.3.6.4" href="#K.3.6.4"><b> K.3.6.4 Multibyte/wide character conversion functions</b></a>
23149 1 The behavior of the multibyte character functions is affected by the LC_CTYPE category
23150 of the current locale. For a state-dependent encoding, each function is placed into its
23151 initial conversion state by a call for which its character pointer argument, s, is a null
23152 pointer. Subsequent calls with s as other than a null pointer cause the internal conversion
23153 state of the function to be altered as necessary. A call with s as a null pointer causes
23154 these functions to set the int pointed to by their status argument to a nonzero value if
23155 encodings have state dependency, and zero otherwise.<sup><a href="#note399"><b>399)</b></a></sup> Changing the LC_CTYPE
23156 category causes the conversion state of these functions to be indeterminate.
23157 <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>
23159 1 #define __STDC_WANT_LIB_EXT1__ 1
23160 #include <a href="#7.22"><stdlib.h></a>
23161 errno_t wctomb_s(int * restrict status,
23165 Runtime-constraints
23166 2 Let n denote the number of bytes needed to represent the multibyte character
23167 corresponding to the wide character given by wc (including any shift sequences).
23168 3 If s is not a null pointer, then smax shall not be less than n, and smax shall not be
23169 greater than RSIZE_MAX. If s is a null pointer, then smax shall equal zero.
23170 4 If there is a runtime-constraint violation, wctomb_s does not modify the int pointed to
23171 by status, and if s is not a null pointer, no more than smax elements in the array
23172 pointed to by s will be accessed.
23173 <b> Description</b>
23174 5 The wctomb_s function determines n and stores the multibyte character representation
23175 of wc in the array whose first element is pointed to by s (if s is not a null pointer). The
23176 number of characters stored never exceeds MB_CUR_MAX or smax. If wc is a null wide
23177 character, a null byte is stored, preceded by any shift sequence needed to restore the
23178 initial shift state, and the function is left in the initial conversion state.
23179 6 The implementation shall behave as if no library function calls the wctomb_s function.
23184 <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
23185 character codes, but are grouped with an adjacent multibyte character.
23187 [<a name="p606" href="#p606">page 606</a>] (<a href="#Contents">Contents</a>)
23189 7 If s is a null pointer, the wctomb_s function stores into the int pointed to by status a
23190 nonzero or zero value, if multibyte character encodings, respectively, do or do not have
23191 state-dependent encodings.
23192 8 If s is not a null pointer, the wctomb_s function stores into the int pointed to by
23193 status either n or -1 if wc, respectively, does or does not correspond to a valid
23194 multibyte character.
23195 9 In no case will the int pointed to by status be set to a value greater than the
23198 10 The wctomb_s function returns zero if successful, and a nonzero value if there was a
23199 runtime-constraint violation or wc did not correspond to a valid multibyte character.
23200 <a name="K.3.6.5" href="#K.3.6.5"><b> K.3.6.5 Multibyte/wide string conversion functions</b></a>
23201 1 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
23202 the current locale.
23203 <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>
23205 1 #include <a href="#7.22"><stdlib.h></a>
23206 errno_t mbstowcs_s(size_t * restrict retval,
23207 wchar_t * restrict dst, rsize_t dstmax,
23208 const char * restrict src, rsize_t len);
23209 Runtime-constraints
23210 2 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
23211 neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
23212 then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
23213 zero. If dst is not a null pointer and len is not less than dstmax, then a null character
23214 shall occur within the first dstmax multibyte characters of the array pointed to by src.
23215 3 If there is a runtime-constraint violation, then mbstowcs_s does the following. If
23216 retval is not a null pointer, then mbstowcs_s sets *retval to (size_t)(-1). If
23217 dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
23218 then mbstowcs_s sets dst[0] to the null wide character.
23219 <b> Description</b>
23220 4 The mbstowcs_s function converts a sequence of multibyte characters that begins in
23221 the initial shift state from the array pointed to by src into a sequence of corresponding
23222 wide characters. If dst is not a null pointer, the converted characters are stored into the
23223 array pointed to by dst. Conversion continues up to and including a terminating null
23224 character, which is also stored. Conversion stops earlier in two cases: when a sequence of
23226 [<a name="p607" href="#p607">page 607</a>] (<a href="#Contents">Contents</a>)
23228 bytes is encountered that does not form a valid multibyte character, or (if dst is not a
23229 null pointer) when len wide characters have been stored into the array pointed to by
23230 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
23231 pointed to by dst, then dst[len] is set to the null wide character. Each conversion
23232 takes place as if by a call to the mbrtowc function.
23233 5 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
23234 sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
23235 the mbstowcs_s function stores the value (size_t)(-1) into *retval.
23236 Otherwise, the mbstowcs_s function stores into *retval the number of multibyte
23237 characters successfully converted, not including the terminating null character (if any).
23238 6 All elements following the terminating null wide character (if any) written by
23239 mbstowcs_s in the array of dstmax wide characters pointed to by dst take
23240 unspecified values when mbstowcs_s returns.<sup><a href="#note401"><b>401)</b></a></sup>
23241 7 If copying takes place between objects that overlap, the objects take on unspecified
23244 8 The mbstowcs_s function returns zero if no runtime-constraint violation and no
23245 encoding error occurred. Otherwise, a nonzero value is returned.
23246 <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>
23248 1 #include <a href="#7.22"><stdlib.h></a>
23249 errno_t wcstombs_s(size_t * restrict retval,
23250 char * restrict dst, rsize_t dstmax,
23251 const wchar_t * restrict src, rsize_t len);
23252 Runtime-constraints
23253 2 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then
23254 neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer,
23255 then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal
23256 zero. If dst is not a null pointer and len is not less than dstmax, then the conversion
23257 shall have been stopped (see below) because a terminating null wide character was
23258 reached or because an encoding error occurred.
23263 <sup><a name="note400" href="#note400"><b>400)</b></a></sup> Thus, the value of len is ignored if dst is a null pointer.
23264 <sup><a name="note401" href="#note401"><b>401)</b></a></sup> This allows an implementation to attempt converting the multibyte string before discovering a
23265 terminating null character did not occur where required.
23267 [<a name="p608" href="#p608">page 608</a>] (<a href="#Contents">Contents</a>)
23269 3 If there is a runtime-constraint violation, then wcstombs_s does the following. If
23270 retval is not a null pointer, then wcstombs_s sets *retval to (size_t)(-1). If
23271 dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
23272 then wcstombs_s sets dst[0] to the null character.
23273 <b> Description</b>
23274 4 The wcstombs_s function converts a sequence of wide characters from the array
23275 pointed to by src into a sequence of corresponding multibyte characters that begins in
23276 the initial shift state. If dst is not a null pointer, the converted characters are then stored
23277 into the array pointed to by dst. Conversion continues up to and including a terminating
23278 null wide character, which is also stored. Conversion stops earlier in two cases:
23279 -- when a wide character is reached that does not correspond to a valid multibyte
23281 -- (if dst is not a null pointer) when the next multibyte character would exceed the
23282 limit of n total bytes to be stored into the array pointed to by dst. If the wide
23283 character being converted is the null wide character, then n is the lesser of len or
23284 dstmax. Otherwise, n is the lesser of len or dstmax-1.
23285 If the conversion stops without converting a null wide character and dst is not a null
23286 pointer, then a null character is stored into the array pointed to by dst immediately
23287 following any multibyte characters already stored. Each conversion takes place as if by a
23288 call to the wcrtomb function.<sup><a href="#note402"><b>402)</b></a></sup>
23289 5 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
23290 wide character that does not correspond to a valid multibyte character, an encoding error
23291 occurs: the wcstombs_s function stores the value (size_t)(-1) into *retval.
23292 Otherwise, the wcstombs_s function stores into *retval the number of bytes in the
23293 resulting multibyte character sequence, not including the terminating null character (if
23295 6 All elements following the terminating null character (if any) written by wcstombs_s
23296 in the array of dstmax elements pointed to by dst take unspecified values when
23297 wcstombs_s returns.<sup><a href="#note403"><b>403)</b></a></sup>
23298 7 If copying takes place between objects that overlap, the objects take on unspecified
23302 <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
23303 include those necessary to reach the initial shift state immediately before the null byte. However, if
23304 the conversion stops before a terminating null wide character has been reached, the result will be null
23305 terminated, but might not end in the initial shift state.
23306 <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
23307 runtime-constraint violation.
23309 [<a name="p609" href="#p609">page 609</a>] (<a href="#Contents">Contents</a>)
23312 8 The wcstombs_s function returns zero if no runtime-constraint violation and no
23313 encoding error occurred. Otherwise, a nonzero value is returned.
23314 <a name="K.3.7" href="#K.3.7"><b> K.3.7 String handling <string.h></b></a>
23315 1 The header <a href="#7.23"><string.h></a> defines two types.
23318 which is type int; and
23320 which is the type size_t.
23321 <a name="K.3.7.1" href="#K.3.7.1"><b> K.3.7.1 Copying functions</b></a>
23322 <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>
23324 1 #define __STDC_WANT_LIB_EXT1__ 1
23325 #include <a href="#7.23"><string.h></a>
23326 errno_t memcpy_s(void * restrict s1, rsize_t s1max,
23327 const void * restrict s2, rsize_t n);
23328 Runtime-constraints
23329 2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
23330 RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
23331 objects that overlap.
23332 3 If there is a runtime-constraint violation, the memcpy_s function stores zeros in the first
23333 s1max characters of the object pointed to by s1 if s1 is not a null pointer and s1max is
23334 not greater than RSIZE_MAX.
23335 <b> Description</b>
23336 4 The memcpy_s function copies n characters from the object pointed to by s2 into the
23337 object pointed to by s1.
23339 5 The memcpy_s function returns zero if there was no runtime-constraint violation.
23340 Otherwise, a nonzero value is returned.
23342 [<a name="p610" href="#p610">page 610</a>] (<a href="#Contents">Contents</a>)
23344 <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>
23346 1 #define __STDC_WANT_LIB_EXT1__ 1
23347 #include <a href="#7.23"><string.h></a>
23348 errno_t memmove_s(void *s1, rsize_t s1max,
23349 const void *s2, rsize_t n);
23350 Runtime-constraints
23351 2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
23352 RSIZE_MAX. n shall not be greater than s1max.
23353 3 If there is a runtime-constraint violation, the memmove_s function stores zeros in the
23354 first s1max characters of the object pointed to by s1 if s1 is not a null pointer and
23355 s1max is not greater than RSIZE_MAX.
23356 <b> Description</b>
23357 4 The memmove_s function copies n characters from the object pointed to by s2 into the
23358 object pointed to by s1. This copying takes place as if the n characters from the object
23359 pointed to by s2 are first copied into a temporary array of n characters that does not
23360 overlap the objects pointed to by s1 or s2, and then the n characters from the temporary
23361 array are copied into the object pointed to by s1.
23363 5 The memmove_s function returns zero if there was no runtime-constraint violation.
23364 Otherwise, a nonzero value is returned.
23365 <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>
23367 1 #define __STDC_WANT_LIB_EXT1__ 1
23368 #include <a href="#7.23"><string.h></a>
23369 errno_t strcpy_s(char * restrict s1,
23371 const char * restrict s2);
23372 Runtime-constraints
23373 2 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
23374 s1max shall not equal zero. s1max shall be greater than strnlen_s(s2, s1max).
23375 Copying shall not take place between objects that overlap.
23376 3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
23377 greater than zero and not greater than RSIZE_MAX, then strcpy_s sets s1[0] to the
23380 [<a name="p611" href="#p611">page 611</a>] (<a href="#Contents">Contents</a>)
23382 <b> Description</b>
23383 4 The strcpy_s function copies the string pointed to by s2 (including the terminating
23384 null character) into the array pointed to by s1.
23385 5 All elements following the terminating null character (if any) written by strcpy_s in
23386 the array of s1max characters pointed to by s1 take unspecified values when
23387 strcpy_s returns.<sup><a href="#note404"><b>404)</b></a></sup>
23389 6 The strcpy_s function returns zero<sup><a href="#note405"><b>405)</b></a></sup> if there was no runtime-constraint violation.
23390 Otherwise, a nonzero value is returned.
23391 <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>
23393 1 #define __STDC_WANT_LIB_EXT1__ 1
23394 #include <a href="#7.23"><string.h></a>
23395 errno_t strncpy_s(char * restrict s1,
23397 const char * restrict s2,
23399 Runtime-constraints
23400 2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
23401 RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
23402 shall be greater than strnlen_s(s2, s1max). Copying shall not take place between
23403 objects that overlap.
23404 3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
23405 greater than zero and not greater than RSIZE_MAX, then strncpy_s sets s1[0] to the
23407 <b> Description</b>
23408 4 The strncpy_s function copies not more than n successive characters (characters that
23409 follow a null character are not copied) from the array pointed to by s2 to the array
23410 pointed to by s1. If no null character was copied from s2, then s1[n] is set to a null
23414 <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
23415 any of those characters are null. Such an approach might write a character to every element of s1
23416 before discovering that the first element should be set to the null character.
23417 <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
23418 within the array pointed to by s1 and that the result in s1 is null terminated.
23420 [<a name="p612" href="#p612">page 612</a>] (<a href="#Contents">Contents</a>)
23422 5 All elements following the terminating null character (if any) written by strncpy_s in
23423 the array of s1max characters pointed to by s1 take unspecified values when
23424 strncpy_s returns.<sup><a href="#note406"><b>406)</b></a></sup>
23426 6 The strncpy_s function returns zero<sup><a href="#note407"><b>407)</b></a></sup> if there was no runtime-constraint violation.
23427 Otherwise, a nonzero value is returned.
23428 7 EXAMPLE 1 The strncpy_s function can be used to copy a string without the danger that the result
23429 will not be null terminated or that characters will be written past the end of the destination array.
23430 #define __STDC_WANT_LIB_EXT1__ 1
23431 #include <a href="#7.23"><string.h></a>
23433 char src1[100] = "hello";
23434 char src2[7] = {'g', 'o', 'o', 'd', 'b', 'y', 'e'};
23435 char dst1[6], dst2[5], dst3[5];
23437 r1 = strncpy_s(dst1, 6, src1, 100);
23438 r2 = strncpy_s(dst2, 5, src2, 7);
23439 r3 = strncpy_s(dst3, 5, src2, 4);
23440 The first call will assign to r1 the value zero and to dst1 the sequence hello\0.
23441 The second call will assign to r2 a nonzero value and to dst2 the sequence \0.
23442 The third call will assign to r3 the value zero and to dst3 the sequence good\0.
23444 <a name="K.3.7.2" href="#K.3.7.2"><b> K.3.7.2 Concatenation functions</b></a>
23445 <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>
23447 1 #define __STDC_WANT_LIB_EXT1__ 1
23448 #include <a href="#7.23"><string.h></a>
23449 errno_t strcat_s(char * restrict s1,
23451 const char * restrict s2);
23452 Runtime-constraints
23453 2 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
23459 <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
23460 any of those characters are null. Such an approach might write a character to every element of s1
23461 before discovering that the first element should be set to the null character.
23462 <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
23463 within the array pointed to by s1 and that the result in s1 is null terminated.
23465 [<a name="p613" href="#p613">page 613</a>] (<a href="#Contents">Contents</a>)
23467 3 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
23468 s1max shall not equal zero. m shall not equal zero.<sup><a href="#note408"><b>408)</b></a></sup> m shall be greater than
23469 strnlen_s(s2, m). Copying shall not take place between objects that overlap.
23470 4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
23471 greater than zero and not greater than RSIZE_MAX, then strcat_s sets s1[0] to the
23473 <b> Description</b>
23474 5 The strcat_s function appends a copy of the string pointed to by s2 (including the
23475 terminating null character) to the end of the string pointed to by s1. The initial character
23476 from s2 overwrites the null character at the end of s1.
23477 6 All elements following the terminating null character (if any) written by strcat_s in
23478 the array of s1max characters pointed to by s1 take unspecified values when
23479 strcat_s returns.<sup><a href="#note409"><b>409)</b></a></sup>
23481 7 The strcat_s function returns zero<sup><a href="#note410"><b>410)</b></a></sup> if there was no runtime-constraint violation.
23482 Otherwise, a nonzero value is returned.
23483 <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>
23485 1 #define __STDC_WANT_LIB_EXT1__ 1
23486 #include <a href="#7.23"><string.h></a>
23487 errno_t strncat_s(char * restrict s1,
23489 const char * restrict s2,
23491 Runtime-constraints
23492 2 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to
23494 3 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
23495 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
23498 <sup><a name="note408" href="#note408"><b>408)</b></a></sup> Zero means that s1 was not null terminated upon entry to strcat_s.
23499 <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
23500 any of those characters are null. Such an approach might write a character to every element of s1
23501 before discovering that the first element should be set to the null character.
23502 <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
23503 appended to the string pointed to by s1 and that the result in s1 is null terminated.
23505 [<a name="p614" href="#p614">page 614</a>] (<a href="#Contents">Contents</a>)
23507 than m, then m shall be greater than strnlen_s(s2, m). Copying shall not take
23508 place between objects that overlap.
23509 4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
23510 greater than zero and not greater than RSIZE_MAX, then strncat_s sets s1[0] to the
23512 <b> Description</b>
23513 5 The strncat_s function appends not more than n successive characters (characters
23514 that follow a null character are not copied) from the array pointed to by s2 to the end of
23515 the string pointed to by s1. The initial character from s2 overwrites the null character at
23516 the end of s1. If no null character was copied from s2, then s1[s1max-m+n] is set to
23518 6 All elements following the terminating null character (if any) written by strncat_s in
23519 the array of s1max characters pointed to by s1 take unspecified values when
23520 strncat_s returns.<sup><a href="#note412"><b>412)</b></a></sup>
23522 7 The strncat_s function returns zero<sup><a href="#note413"><b>413)</b></a></sup> if there was no runtime-constraint violation.
23523 Otherwise, a nonzero value is returned.
23524 8 EXAMPLE 1 The strncat_s function can be used to copy a string without the danger that the result
23525 will not be null terminated or that characters will be written past the end of the destination array.
23526 #define __STDC_WANT_LIB_EXT1__ 1
23527 #include <a href="#7.23"><string.h></a>
23529 char s1[100] = "good";
23530 char s2[6] = "hello";
23531 char s3[6] = "hello";
23532 char s4[7] = "abc";
23533 char s5[1000] = "bye";
23534 int r1, r2, r3, r4;
23535 r1 = strncat_s(s1, 100, s5, 1000);
23536 r2 = strncat_s(s2, 6, "", 1);
23537 r3 = strncat_s(s3, 6, "X", 2);
23538 r4 = strncat_s(s4, 7, "defghijklmn", 3);
23539 After the first call r1 will have the value zero and s1 will contain the sequence goodbye\0.
23543 <sup><a name="note411" href="#note411"><b>411)</b></a></sup> Zero means that s1 was not null terminated upon entry to strncat_s.
23544 <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
23545 any of those characters are null. Such an approach might write a character to every element of s1
23546 before discovering that the first element should be set to the null character.
23547 <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
23548 appended to the string pointed to by s1 and that the result in s1 is null terminated.
23550 [<a name="p615" href="#p615">page 615</a>] (<a href="#Contents">Contents</a>)
23552 After the second call r2 will have the value zero and s2 will contain the sequence hello\0.
23553 After the third call r3 will have a nonzero value and s3 will contain the sequence \0.
23554 After the fourth call r4 will have the value zero and s4 will contain the sequence abcdef\0.
23556 <a name="K.3.7.3" href="#K.3.7.3"><b> K.3.7.3 Search functions</b></a>
23557 <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>
23559 1 #define __STDC_WANT_LIB_EXT1__ 1
23560 #include <a href="#7.23"><string.h></a>
23561 char *strtok_s(char * restrict s1,
23562 rsize_t * restrict s1max,
23563 const char * restrict s2,
23564 char ** restrict ptr);
23565 Runtime-constraints
23566 2 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
23567 shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
23568 The end of the token found shall occur within the first *s1max characters of s1 for the
23569 first call, and shall occur within the first *s1max characters of where searching resumes
23570 on subsequent calls.
23571 3 If there is a runtime-constraint violation, the strtok_s function does not indirect
23572 through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
23573 <b> Description</b>
23574 4 A sequence of calls to the strtok_s function breaks the string pointed to by s1 into a
23575 sequence of tokens, each of which is delimited by a character from the string pointed to
23576 by s2. The fourth argument points to a caller-provided char pointer into which the
23577 strtok_s function stores information necessary for it to continue scanning the same
23579 5 The first call in a sequence has a non-null first argument and s1max points to an object
23580 whose value is the number of elements in the character array pointed to by the first
23581 argument. The first call stores an initial value in the object pointed to by ptr and
23582 updates the value pointed to by s1max to reflect the number of elements that remain in
23583 relation to ptr. Subsequent calls in the sequence have a null first argument and the
23584 objects pointed to by s1max and ptr are required to have the values stored by the
23585 previous call in the sequence, which are then updated. The separator string pointed to by
23586 s2 may be different from call to call.
23587 6 The first call in the sequence searches the string pointed to by s1 for the first character
23588 that is not contained in the current separator string pointed to by s2. If no such character
23589 is found, then there are no tokens in the string pointed to by s1 and the strtok_s
23590 function returns a null pointer. If such a character is found, it is the start of the first token.
23592 [<a name="p616" href="#p616">page 616</a>] (<a href="#Contents">Contents</a>)
23594 7 The strtok_s function then searches from there for the first character in s1 that is
23595 contained in the current separator string. If no such character is found, the current token
23596 extends to the end of the string pointed to by s1, and subsequent searches in the same
23597 string for a token return a null pointer. If such a character is found, it is overwritten by a
23598 null character, which terminates the current token.
23599 8 In all cases, the strtok_s function stores sufficient information in the pointer pointed
23600 to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
23601 value for ptr, shall start searching just past the element overwritten by a null character
23604 9 The strtok_s function returns a pointer to the first character of a token, or a null
23605 pointer if there is no token or there is a runtime-constraint violation.
23607 #define __STDC_WANT_LIB_EXT1__ 1
23608 #include <a href="#7.23"><string.h></a>
23609 static char str1[] = "?a???b,,,#c";
23610 static char str2[] = "\t \t";
23611 char *t, *ptr1, *ptr2;
23612 rsize_t max1 = sizeof(str1);
23613 rsize_t max2 = sizeof(str2);
23614 t = strtok_s(str1, &max1, "?", &ptr1); // t points to the token "a"
23615 t = strtok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
23616 t = strtok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
23617 t = strtok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
23618 t = strtok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
23620 <a name="K.3.7.4" href="#K.3.7.4"><b> K.3.7.4 Miscellaneous functions</b></a>
23621 <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>
23623 1 #define __STDC_WANT_LIB_EXT1__ 1
23624 #include <a href="#7.23"><string.h></a>
23625 errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
23626 Runtime-constraints
23627 2 s shall not be a null pointer. Neither smax nor n shall be greater than RSIZE_MAX. n
23628 shall not be greater than smax.
23629 3 If there is a runtime-constraint violation, then if s is not a null pointer and smax is not
23630 greater than RSIZE_MAX, the memset_s function stores the value of c (converted to an
23631 unsigned char) into each of the first smax characters of the object pointed to by s.
23633 [<a name="p617" href="#p617">page 617</a>] (<a href="#Contents">Contents</a>)
23635 <b> Description</b>
23636 4 The memset_s function copies the value of c (converted to an unsigned char) into
23637 each of the first n characters of the object pointed to by s. Unlike memset, any call to
23638 the memset_s function shall be evaluated strictly according to the rules of the abstract
23639 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
23640 assume that the memory indicated by s and n may be accessible in the future and thus
23641 must contain the values indicated by c.
23643 5 The memset_s function returns zero if there was no runtime-constraint violation.
23644 Otherwise, a nonzero value is returned.
23645 <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>
23647 1 #define __STDC_WANT_LIB_EXT1__ 1
23648 #include <a href="#7.23"><string.h></a>
23649 errno_t strerror_s(char *s, rsize_t maxsize,
23651 Runtime-constraints
23652 2 s shall not be a null pointer. maxsize shall not be greater than RSIZE_MAX.
23653 maxsize shall not equal zero.
23654 3 If there is a runtime-constraint violation, then the array (if any) pointed to by s is not
23656 <b> Description</b>
23657 4 The strerror_s function maps the number in errnum to a locale-specific message
23658 string. Typically, the values for errnum come from errno, but strerror_s shall
23659 map any value of type int to a message.
23660 5 If the length of the desired string is less than maxsize, then the string is copied to the
23661 array pointed to by s.
23662 6 Otherwise, if maxsize is greater than zero, then maxsize-1 characters are copied
23663 from the string to the array pointed to by s and then s[maxsize-1] is set to the null
23664 character. Then, if maxsize is greater than 3, then s[maxsize-2],
23665 s[maxsize-3], and s[maxsize-4] are set to the character period (.).
23667 7 The strerror_s function returns zero if the length of the desired string was less than
23668 maxsize and there was no runtime-constraint violation. Otherwise, the strerror_s
23669 function returns a nonzero value.
23671 [<a name="p618" href="#p618">page 618</a>] (<a href="#Contents">Contents</a>)
23673 <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>
23675 1 #define __STDC_WANT_LIB_EXT1__ 1
23676 #include <a href="#7.23"><string.h></a>
23677 size_t strerrorlen_s(errno_t errnum);
23678 <b> Description</b>
23679 2 The strerrorlen_s function calculates the length of the (untruncated) locale-specific
23680 message string that the strerror_s function maps to errnum.
23682 3 The strerrorlen_s function returns the number of characters (not including the null
23683 character) in the full message string.
23684 <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>
23686 1 #define __STDC_WANT_LIB_EXT1__ 1
23687 #include <a href="#7.23"><string.h></a>
23688 size_t strnlen_s(const char *s, size_t maxsize);
23689 <b> Description</b>
23690 2 The strnlen_s function computes the length of the string pointed to by s.
23692 3 If s is a null pointer,<sup><a href="#note414"><b>414)</b></a></sup> then the strnlen_s function returns zero.
23693 4 Otherwise, the strnlen_s function returns the number of characters that precede the
23694 terminating null character. If there is no null character in the first maxsize characters of
23695 s then strnlen_s returns maxsize. At most the first maxsize characters of s shall
23696 be accessed by strnlen_s.
23701 <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
23702 along with the values returned for a null pointer or an unterminated string argument make
23703 strnlen_s useful in algorithms that gracefully handle such exceptional data.
23705 [<a name="p619" href="#p619">page 619</a>] (<a href="#Contents">Contents</a>)
23707 <a name="K.3.8" href="#K.3.8"><b> K.3.8 Date and time <time.h></b></a>
23708 1 The header <a href="#7.26"><time.h></a> defines two types.
23711 which is type int; and
23713 which is the type size_t.
23714 <a name="K.3.8.1" href="#K.3.8.1"><b> K.3.8.1 Components of time</b></a>
23715 1 A broken-down time is normalized if the values of the members of the tm structure are in
23716 their normal rages.<sup><a href="#note415"><b>415)</b></a></sup>
23717 <a name="K.3.8.2" href="#K.3.8.2"><b> K.3.8.2 Time conversion functions</b></a>
23718 1 Like the strftime function, the asctime_s and ctime_s functions do not return a
23719 pointer to a static object, and other library functions are permitted to call them.
23720 <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>
23722 1 #define __STDC_WANT_LIB_EXT1__ 1
23723 #include <a href="#7.26"><time.h></a>
23724 errno_t asctime_s(char *s, rsize_t maxsize,
23725 const struct tm *timeptr);
23726 Runtime-constraints
23727 2 Neither s nor timeptr shall be a null pointer. maxsize shall not be less than 26 and
23728 shall not be greater than RSIZE_MAX. The broken-down time pointed to by timeptr
23729 shall be normalized. The calendar year represented by the broken-down time pointed to
23730 by timeptr shall not be less than calendar year 0 and shall not be greater than calendar
23732 3 If there is a runtime-constraint violation, there is no attempt to convert the time, and
23733 s[0] is set to a null character if s is not a null pointer and maxsize is not zero and is
23734 not greater than RSIZE_MAX.
23735 <b> Description</b>
23736 4 The asctime_s function converts the normalized broken-down time in the structure
23737 pointed to by timeptr into a 26 character (including the null character) string in the
23740 <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>.
23742 [<a name="p620" href="#p620">page 620</a>] (<a href="#Contents">Contents</a>)
23745 Sun Sep 16 01:03:52 1973\n\0
23746 The fields making up this string are (in order):
23747 1. The name of the day of the week represented by timeptr->tm_wday using the
23748 following three character weekday names: Sun, Mon, Tue, Wed, Thu, Fri, and Sat.
23749 2. The character space.
23750 3. The name of the month represented by timeptr->tm_mon using the following
23751 three character month names: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct,
23753 4. The character space.
23754 5. The value of timeptr->tm_mday as if printed using the fprintf format
23756 6. The character space.
23757 7. The value of timeptr->tm_hour as if printed using the fprintf format
23759 8. The character colon.
23760 9. The value of timeptr->tm_min as if printed using the fprintf format
23762 10. The character colon.
23763 11. The value of timeptr->tm_sec as if printed using the fprintf format
23765 12. The character space.
23766 13. The value of timeptr->tm_year + 1900 as if printed using the fprintf
23768 14. The character new line.
23769 15. The null character.
23770 Recommended practice
23771 The strftime function allows more flexible formatting and supports locale-specific
23772 behavior. If you do not require the exact form of the result string produced by the
23773 asctime_s function, consider using the strftime function instead.
23775 5 The asctime_s function returns zero if the time was successfully converted and stored
23776 into the array pointed to by s. Otherwise, it returns a nonzero value.
23778 [<a name="p621" href="#p621">page 621</a>] (<a href="#Contents">Contents</a>)
23780 <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>
23782 1 #define __STDC_WANT_LIB_EXT1__ 1
23783 #include <a href="#7.26"><time.h></a>
23784 errno_t ctime_s(char *s, rsize_t maxsize,
23785 const time_t *timer);
23786 Runtime-constraints
23787 2 Neither s nor timer shall be a null pointer. maxsize shall not be less than 26 and
23788 shall not be greater than RSIZE_MAX.
23789 3 If there is a runtime-constraint violation, s[0] is set to a null character if s is not a null
23790 pointer and maxsize is not equal zero and is not greater than RSIZE_MAX.
23791 <b> Description</b>
23792 4 The ctime_s function converts the calendar time pointed to by timer to local time in
23793 the form of a string. It is equivalent to
23794 asctime_s(s, maxsize, localtime_s(timer))
23795 Recommended practice
23796 The strftime function allows more flexible formatting and supports locale-specific
23797 behavior. If you do not require the exact form of the result string produced by the
23798 ctime_s function, consider using the strftime function instead.
23800 5 The ctime_s function returns zero if the time was successfully converted and stored
23801 into the array pointed to by s. Otherwise, it returns a nonzero value.
23802 <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>
23804 1 #define __STDC_WANT_LIB_EXT1__ 1
23805 #include <a href="#7.26"><time.h></a>
23806 struct tm *gmtime_s(const time_t * restrict timer,
23807 struct tm * restrict result);
23808 Runtime-constraints
23809 2 Neither timer nor result shall be a null pointer.
23810 3 If there is a runtime-constraint violation, there is no attempt to convert the time.
23811 <b> Description</b>
23812 4 The gmtime_s function converts the calendar time pointed to by timer into a broken-
23813 down time, expressed as UTC. The broken-down time is stored in the structure pointed
23815 [<a name="p622" href="#p622">page 622</a>] (<a href="#Contents">Contents</a>)
23819 5 The gmtime_s function returns result, or a null pointer if the specified time cannot
23820 be converted to UTC or there is a runtime-constraint violation.
23821 <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>
23823 1 #define __STDC_WANT_LIB_EXT1__ 1
23824 #include <a href="#7.26"><time.h></a>
23825 struct tm *localtime_s(const time_t * restrict timer,
23826 struct tm * restrict result);
23827 Runtime-constraints
23828 2 Neither timer nor result shall be a null pointer.
23829 3 If there is a runtime-constraint violation, there is no attempt to convert the time.
23830 <b> Description</b>
23831 4 The localtime_s function converts the calendar time pointed to by timer into a
23832 broken-down time, expressed as local time. The broken-down time is stored in the
23833 structure pointed to by result.
23835 5 The localtime_s function returns result, or a null pointer if the specified time
23836 cannot be converted to local time or there is a runtime-constraint violation.
23837 <a name="K.3.9" href="#K.3.9"><b> K.3.9 Extended multibyte and wide character utilities <wchar.h></b></a>
23838 1 The header <a href="#7.28"><wchar.h></a> defines two types.
23841 which is type int; and
23843 which is the type size_t.
23844 3 Unless explicitly stated otherwise, if the execution of a function described in this
23845 subclause causes copying to take place between objects that overlap, the objects take on
23846 unspecified values.
23848 [<a name="p623" href="#p623">page 623</a>] (<a href="#Contents">Contents</a>)
23850 <a name="K.3.9.1" href="#K.3.9.1"><b> K.3.9.1 Formatted wide character input/output functions</b></a>
23851 <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>
23853 1 #define __STDC_WANT_LIB_EXT1__ 1
23854 #include <a href="#7.28"><wchar.h></a>
23855 int fwprintf_s(FILE * restrict stream,
23856 const wchar_t * restrict format, ...);
23857 Runtime-constraints
23858 2 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note416"><b>416)</b></a></sup> (modified or
23859 not by flags, field width, or precision) shall not appear in the wide string pointed to by
23860 format. Any argument to fwprintf_s corresponding to a %s specifier shall not be a
23862 3 If there is a runtime-constraint violation, the fwprintf_s function does not attempt to
23863 produce further output, and it is unspecified to what extent fwprintf_s produced
23864 output before discovering the runtime-constraint violation.
23865 <b> Description</b>
23866 4 The fwprintf_s function is equivalent to the fwprintf function except for the
23867 explicit runtime-constraints listed above.
23869 5 The fwprintf_s function returns the number of wide characters transmitted, or a
23870 negative value if an output error, encoding error, or runtime-constraint violation occurred.
23871 <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>
23873 1 #define __STDC_WANT_LIB_EXT1__ 1
23874 #include <a href="#7.21"><stdio.h></a>
23875 #include <a href="#7.28"><wchar.h></a>
23876 int fwscanf_s(FILE * restrict stream,
23877 const wchar_t * restrict format, ...);
23878 Runtime-constraints
23879 2 Neither stream nor format shall be a null pointer. Any argument indirected though in
23880 order to store converted input shall not be a null pointer.
23883 <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
23884 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
23885 example, if the entire format string was L"%%n".
23887 [<a name="p624" href="#p624">page 624</a>] (<a href="#Contents">Contents</a>)
23889 3 If there is a runtime-constraint violation, the fwscanf_s function does not attempt to
23890 perform further input, and it is unspecified to what extent fwscanf_s performed input
23891 before discovering the runtime-constraint violation.
23892 <b> Description</b>
23893 4 The fwscanf_s function is equivalent to fwscanf except that the c, s, and [
23894 conversion specifiers apply to a pair of arguments (unless assignment suppression is
23895 indicated by a *). The first of these arguments is the same as for fwscanf. That
23896 argument is immediately followed in the argument list by the second argument, which has
23897 type size_t and gives the number of elements in the array pointed to by the first
23898 argument of the pair. If the first argument points to a scalar object, it is considered to be
23899 an array of one element.<sup><a href="#note417"><b>417)</b></a></sup>
23900 5 A matching failure occurs if the number of elements in a receiving object is insufficient to
23901 hold the converted input (including any trailing null character).
23903 6 The fwscanf_s function returns the value of the macro EOF if an input failure occurs
23904 before any conversion or if there is a runtime-constraint violation. Otherwise, the
23905 fwscanf_s function returns the number of input items assigned, which can be fewer
23906 than provided for, or even zero, in the event of an early matching failure.
23907 <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>
23909 1 #define __STDC_WANT_LIB_EXT1__ 1
23910 #include <a href="#7.28"><wchar.h></a>
23911 int snwprintf_s(wchar_t * restrict s,
23913 const wchar_t * restrict format, ...);
23914 Runtime-constraints
23915 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
23916 than RSIZE_MAX. The %n specifier<sup><a href="#note418"><b>418)</b></a></sup> (modified or not by flags, field width, or
23918 <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
23919 used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an
23920 argument of a type compatible with rsize_t. A limited amount of checking may be done if even if
23921 the format is not known at translation time. For example, an implementation may issue a diagnostic
23922 for each argument after format that has of type pointer to one of char, signed char,
23923 unsigned char, or void that is not followed by an argument of a type compatible with
23924 rsize_t. The diagnostic could warn that unless the pointer is being used with a conversion specifier
23925 using the hh length modifier, a length argument must follow the pointer argument. Another useful
23926 diagnostic could flag any non-pointer argument following format that did not have a type
23927 compatible with rsize_t.
23929 [<a name="p625" href="#p625">page 625</a>] (<a href="#Contents">Contents</a>)
23931 precision) shall not appear in the wide string pointed to by format. Any argument to
23932 snwprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
23934 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
23935 than zero and less than RSIZE_MAX, then the snwprintf_s function sets s[0] to the
23936 null wide character.
23937 <b> Description</b>
23938 4 The snwprintf_s function is equivalent to the swprintf function except for the
23939 explicit runtime-constraints listed above.
23940 5 The snwprintf_s function, unlike swprintf_s, will truncate the result to fit within
23941 the array pointed to by s.
23943 6 The snwprintf_s function returns the number of wide characters that would have
23944 been written had n been sufficiently large, not counting the terminating wide null
23945 character, or a negative value if a runtime-constraint violation occurred. Thus, the null-
23946 terminated output has been completely written if and only if the returned value is
23947 nonnegative and less than n.
23948 <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>
23950 1 #define __STDC_WANT_LIB_EXT1__ 1
23951 #include <a href="#7.28"><wchar.h></a>
23952 int swprintf_s(wchar_t * restrict s, rsize_t n,
23953 const wchar_t * restrict format, ...);
23954 Runtime-constraints
23955 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
23956 than RSIZE_MAX. The number of wide characters (including the trailing null) required
23957 for the result to be written to the array pointed to by s shall not be greater than n. The %n
23958 specifier<sup><a href="#note419"><b>419)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
23959 wide string pointed to by format. Any argument to swprintf_s corresponding to a
23960 %s specifier shall not be a null pointer. No encoding error shall occur.
23963 <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
23964 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
23965 example, if the entire format string was L"%%n".
23966 <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
23967 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
23968 example, if the entire format string was L"%%n".
23970 [<a name="p626" href="#p626">page 626</a>] (<a href="#Contents">Contents</a>)
23972 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
23973 than zero and less than RSIZE_MAX, then the swprintf_s function sets s[0] to the
23974 null wide character.
23975 <b> Description</b>
23976 4 The swprintf_s function is equivalent to the swprintf function except for the
23977 explicit runtime-constraints listed above.
23978 5 The swprintf_s function, unlike snwprintf_s, treats a result too big for the array
23979 pointed to by s as a runtime-constraint violation.
23981 6 If no runtime-constraint violation occurred, the swprintf_s function returns the
23982 number of wide characters written in the array, not counting the terminating null wide
23983 character. If an encoding error occurred or if n or more wide characters are requested to
23984 be written, swprintf_s returns a negative value. If any other runtime-constraint
23985 violation occurred, swprintf_s returns zero.
23986 <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>
23988 1 #define __STDC_WANT_LIB_EXT1__ 1
23989 #include <a href="#7.28"><wchar.h></a>
23990 int swscanf_s(const wchar_t * restrict s,
23991 const wchar_t * restrict format, ...);
23992 Runtime-constraints
23993 2 Neither s nor format shall be a null pointer. Any argument indirected though in order
23994 to store converted input shall not be a null pointer.
23995 3 If there is a runtime-constraint violation, the swscanf_s function does not attempt to
23996 perform further input, and it is unspecified to what extent swscanf_s performed input
23997 before discovering the runtime-constraint violation.
23998 <b> Description</b>
23999 4 The swscanf_s function is equivalent to fwscanf_s, except that the argument s
24000 specifies a wide string from which the input is to be obtained, rather than from a stream.
24001 Reaching the end of the wide string is equivalent to encountering end-of-file for the
24002 fwscanf_s function.
24004 5 The swscanf_s function returns the value of the macro EOF if an input failure occurs
24005 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24006 swscanf_s function returns the number of input items assigned, which can be fewer
24007 than provided for, or even zero, in the event of an early matching failure.
24009 [<a name="p627" href="#p627">page 627</a>] (<a href="#Contents">Contents</a>)
24011 <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>
24013 1 #define __STDC_WANT_LIB_EXT1__ 1
24014 #include <a href="#7.16"><stdarg.h></a>
24015 #include <a href="#7.21"><stdio.h></a>
24016 #include <a href="#7.28"><wchar.h></a>
24017 int vfwprintf_s(FILE * restrict stream,
24018 const wchar_t * restrict format,
24020 Runtime-constraints
24021 2 Neither stream nor format shall be a null pointer. The %n specifier<sup><a href="#note420"><b>420)</b></a></sup> (modified or
24022 not by flags, field width, or precision) shall not appear in the wide string pointed to by
24023 format. Any argument to vfwprintf_s corresponding to a %s specifier shall not be
24025 3 If there is a runtime-constraint violation, the vfwprintf_s function does not attempt
24026 to produce further output, and it is unspecified to what extent vfwprintf_s produced
24027 output before discovering the runtime-constraint violation.
24028 <b> Description</b>
24029 4 The vfwprintf_s function is equivalent to the vfwprintf function except for the
24030 explicit runtime-constraints listed above.
24032 5 The vfwprintf_s function returns the number of wide characters transmitted, or a
24033 negative value if an output error, encoding error, or runtime-constraint violation occurred.
24034 <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>
24036 1 #define __STDC_WANT_LIB_EXT1__ 1
24037 #include <a href="#7.16"><stdarg.h></a>
24038 #include <a href="#7.21"><stdio.h></a>
24039 #include <a href="#7.28"><wchar.h></a>
24040 int vfwscanf_s(FILE * restrict stream,
24041 const wchar_t * restrict format, va_list arg);
24045 <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
24046 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24047 example, if the entire format string was L"%%n".
24049 [<a name="p628" href="#p628">page 628</a>] (<a href="#Contents">Contents</a>)
24051 Runtime-constraints
24052 2 Neither stream nor format shall be a null pointer. Any argument indirected though in
24053 order to store converted input shall not be a null pointer.
24054 3 If there is a runtime-constraint violation, the vfwscanf_s function does not attempt to
24055 perform further input, and it is unspecified to what extent vfwscanf_s performed input
24056 before discovering the runtime-constraint violation.
24057 <b> Description</b>
24058 4 The vfwscanf_s function is equivalent to fwscanf_s, with the variable argument
24059 list replaced by arg, which shall have been initialized by the va_start macro (and
24060 possibly subsequent va_arg calls). The vfwscanf_s function does not invoke the
24061 va_end macro.<sup><a href="#note421"><b>421)</b></a></sup>
24063 5 The vfwscanf_s function returns the value of the macro EOF if an input failure occurs
24064 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24065 vfwscanf_s function returns the number of input items assigned, which can be fewer
24066 than provided for, or even zero, in the event of an early matching failure.
24067 <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>
24069 1 #define __STDC_WANT_LIB_EXT1__ 1
24070 #include <a href="#7.16"><stdarg.h></a>
24071 #include <a href="#7.28"><wchar.h></a>
24072 int vsnwprintf_s(wchar_t * restrict s,
24074 const wchar_t * restrict format,
24076 Runtime-constraints
24077 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
24078 than RSIZE_MAX. The %n specifier<sup><a href="#note422"><b>422)</b></a></sup> (modified or not by flags, field width, or
24079 precision) shall not appear in the wide string pointed to by format. Any argument to
24080 vsnwprintf_s corresponding to a %s specifier shall not be a null pointer. No
24081 encoding error shall occur.
24083 <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
24084 value of arg after the return is indeterminate.
24085 <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
24086 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24087 example, if the entire format string was L"%%n".
24089 [<a name="p629" href="#p629">page 629</a>] (<a href="#Contents">Contents</a>)
24091 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
24092 than zero and less than RSIZE_MAX, then the vsnwprintf_s function sets s[0] to
24093 the null wide character.
24094 <b> Description</b>
24095 4 The vsnwprintf_s function is equivalent to the vswprintf function except for the
24096 explicit runtime-constraints listed above.
24097 5 The vsnwprintf_s function, unlike vswprintf_s, will truncate the result to fit
24098 within the array pointed to by s.
24100 6 The vsnwprintf_s function returns the number of wide characters that would have
24101 been written had n been sufficiently large, not counting the terminating null character, or
24102 a negative value if a runtime-constraint violation occurred. Thus, the null-terminated
24103 output has been completely written if and only if the returned value is nonnegative and
24105 <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>
24107 1 #define __STDC_WANT_LIB_EXT1__ 1
24108 #include <a href="#7.16"><stdarg.h></a>
24109 #include <a href="#7.28"><wchar.h></a>
24110 int vswprintf_s(wchar_t * restrict s,
24112 const wchar_t * restrict format,
24114 Runtime-constraints
24115 2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater
24116 than RSIZE_MAX. The number of wide characters (including the trailing null) required
24117 for the result to be written to the array pointed to by s shall not be greater than n. The %n
24118 specifier<sup><a href="#note423"><b>423)</b></a></sup> (modified or not by flags, field width, or precision) shall not appear in the
24119 wide string pointed to by format. Any argument to vswprintf_s corresponding to a
24120 %s specifier shall not be a null pointer. No encoding error shall occur.
24121 3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater
24122 than zero and less than RSIZE_MAX, then the vswprintf_s function sets s[0] to the
24123 null wide character.
24125 <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
24126 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24127 example, if the entire format string was L"%%n".
24129 [<a name="p630" href="#p630">page 630</a>] (<a href="#Contents">Contents</a>)
24131 <b> Description</b>
24132 4 The vswprintf_s function is equivalent to the vswprintf function except for the
24133 explicit runtime-constraints listed above.
24134 5 The vswprintf_s function, unlike vsnwprintf_s, treats a result too big for the
24135 array pointed to by s as a runtime-constraint violation.
24137 6 If no runtime-constraint violation occurred, the vswprintf_s function returns the
24138 number of wide characters written in the array, not counting the terminating null wide
24139 character. If an encoding error occurred or if n or more wide characters are requested to
24140 be written, vswprintf_s returns a negative value. If any other runtime-constraint
24141 violation occurred, vswprintf_s returns zero.
24142 <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>
24144 1 #define __STDC_WANT_LIB_EXT1__ 1
24145 #include <a href="#7.16"><stdarg.h></a>
24146 #include <a href="#7.28"><wchar.h></a>
24147 int vswscanf_s(const wchar_t * restrict s,
24148 const wchar_t * restrict format,
24150 Runtime-constraints
24151 2 Neither s nor format shall be a null pointer. Any argument indirected though in order
24152 to store converted input shall not be a null pointer.
24153 3 If there is a runtime-constraint violation, the vswscanf_s function does not attempt to
24154 perform further input, and it is unspecified to what extent vswscanf_s performed input
24155 before discovering the runtime-constraint violation.
24156 <b> Description</b>
24157 4 The vswscanf_s function is equivalent to swscanf_s, with the variable argument
24158 list replaced by arg, which shall have been initialized by the va_start macro (and
24159 possibly subsequent va_arg calls). The vswscanf_s function does not invoke the
24160 va_end macro.<sup><a href="#note424"><b>424)</b></a></sup>
24165 <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
24166 value of arg after the return is indeterminate.
24168 [<a name="p631" href="#p631">page 631</a>] (<a href="#Contents">Contents</a>)
24171 5 The vswscanf_s function returns the value of the macro EOF if an input failure occurs
24172 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24173 vswscanf_s function returns the number of input items assigned, which can be fewer
24174 than provided for, or even zero, in the event of an early matching failure.
24175 <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>
24177 1 #define __STDC_WANT_LIB_EXT1__ 1
24178 #include <a href="#7.16"><stdarg.h></a>
24179 #include <a href="#7.28"><wchar.h></a>
24180 int vwprintf_s(const wchar_t * restrict format,
24182 Runtime-constraints
24183 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
24184 width, or precision) shall not appear in the wide string pointed to by format. Any
24185 argument to vwprintf_s corresponding to a %s specifier shall not be a null pointer.
24186 3 If there is a runtime-constraint violation, the vwprintf_s function does not attempt to
24187 produce further output, and it is unspecified to what extent vwprintf_s produced
24188 output before discovering the runtime-constraint violation.
24189 <b> Description</b>
24190 4 The vwprintf_s function is equivalent to the vwprintf function except for the
24191 explicit runtime-constraints listed above.
24193 5 The vwprintf_s function returns the number of wide characters transmitted, or a
24194 negative value if an output error, encoding error, or runtime-constraint violation occurred.
24199 <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
24200 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24201 example, if the entire format string was L"%%n".
24203 [<a name="p632" href="#p632">page 632</a>] (<a href="#Contents">Contents</a>)
24205 <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>
24207 1 #define __STDC_WANT_LIB_EXT1__ 1
24208 #include <a href="#7.16"><stdarg.h></a>
24209 #include <a href="#7.28"><wchar.h></a>
24210 int vwscanf_s(const wchar_t * restrict format,
24212 Runtime-constraints
24213 2 format shall not be a null pointer. Any argument indirected though in order to store
24214 converted input shall not be a null pointer.
24215 3 If there is a runtime-constraint violation, the vwscanf_s function does not attempt to
24216 perform further input, and it is unspecified to what extent vwscanf_s performed input
24217 before discovering the runtime-constraint violation.
24218 <b> Description</b>
24219 4 The vwscanf_s function is equivalent to wscanf_s, with the variable argument list
24220 replaced by arg, which shall have been initialized by the va_start macro (and
24221 possibly subsequent va_arg calls). The vwscanf_s function does not invoke the
24222 va_end macro.<sup><a href="#note426"><b>426)</b></a></sup>
24224 5 The vwscanf_s function returns the value of the macro EOF if an input failure occurs
24225 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24226 vwscanf_s function returns the number of input items assigned, which can be fewer
24227 than provided for, or even zero, in the event of an early matching failure.
24228 <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>
24230 1 #define __STDC_WANT_LIB_EXT1__ 1
24231 #include <a href="#7.28"><wchar.h></a>
24232 int wprintf_s(const wchar_t * restrict format, ...);
24233 Runtime-constraints
24234 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
24236 <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
24237 value of arg after the return is indeterminate.
24238 <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
24239 string pointed at by format when those wide characters are not a interpreted as a %n specifier. For
24240 example, if the entire format string was L"%%n".
24242 [<a name="p633" href="#p633">page 633</a>] (<a href="#Contents">Contents</a>)
24244 width, or precision) shall not appear in the wide string pointed to by format. Any
24245 argument to wprintf_s corresponding to a %s specifier shall not be a null pointer.
24246 3 If there is a runtime-constraint violation, the wprintf_s function does not attempt to
24247 produce further output, and it is unspecified to what extent wprintf_s produced output
24248 before discovering the runtime-constraint violation.
24249 <b> Description</b>
24250 4 The wprintf_s function is equivalent to the wprintf function except for the explicit
24251 runtime-constraints listed above.
24253 5 The wprintf_s function returns the number of wide characters transmitted, or a
24254 negative value if an output error, encoding error, or runtime-constraint violation occurred.
24255 <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>
24257 1 #define __STDC_WANT_LIB_EXT1__ 1
24258 #include <a href="#7.28"><wchar.h></a>
24259 int wscanf_s(const wchar_t * restrict format, ...);
24260 Runtime-constraints
24261 2 format shall not be a null pointer. Any argument indirected though in order to store
24262 converted input shall not be a null pointer.
24263 3 If there is a runtime-constraint violation, the wscanf_s function does not attempt to
24264 perform further input, and it is unspecified to what extent wscanf_s performed input
24265 before discovering the runtime-constraint violation.
24266 <b> Description</b>
24267 4 The wscanf_s function is equivalent to fwscanf_s with the argument stdin
24268 interposed before the arguments to wscanf_s.
24270 5 The wscanf_s function returns the value of the macro EOF if an input failure occurs
24271 before any conversion or if there is a runtime-constraint violation. Otherwise, the
24272 wscanf_s function returns the number of input items assigned, which can be fewer than
24273 provided for, or even zero, in the event of an early matching failure.
24275 [<a name="p634" href="#p634">page 634</a>] (<a href="#Contents">Contents</a>)
24277 <a name="K.3.9.2" href="#K.3.9.2"><b> K.3.9.2 General wide string utilities</b></a>
24278 <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>
24279 <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>
24281 1 #define __STDC_WANT_LIB_EXT1__ 1
24282 #include <a href="#7.28"><wchar.h></a>
24283 errno_t wcscpy_s(wchar_t * restrict s1,
24285 const wchar_t * restrict s2);
24286 Runtime-constraints
24287 2 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
24288 s1max shall not equal zero. s1max shall be greater than wcsnlen_s(s2, s1max).
24289 Copying shall not take place between objects that overlap.
24290 3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
24291 greater than zero and not greater than RSIZE_MAX, then wcscpy_s sets s1[0] to the
24292 null wide character.
24293 <b> Description</b>
24294 4 The wcscpy_s function copies the wide string pointed to by s2 (including the
24295 terminating null wide character) into the array pointed to by s1.
24296 5 All elements following the terminating null wide character (if any) written by
24297 wcscpy_s in the array of s1max wide characters pointed to by s1 take unspecified
24298 values when wcscpy_s returns.<sup><a href="#note428"><b>428)</b></a></sup>
24300 6 The wcscpy_s function returns zero<sup><a href="#note429"><b>429)</b></a></sup> if there was no runtime-constraint violation.
24301 Otherwise, a nonzero value is returned.
24306 <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
24307 if any of those wide characters are null. Such an approach might write a wide character to every
24308 element of s1 before discovering that the first element should be set to the null wide character.
24309 <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
24310 fit within the array pointed to by s1 and that the result in s1 is null terminated.
24312 [<a name="p635" href="#p635">page 635</a>] (<a href="#Contents">Contents</a>)
24314 <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>
24316 7 #define __STDC_WANT_LIB_EXT1__ 1
24317 #include <a href="#7.28"><wchar.h></a>
24318 errno_t wcsncpy_s(wchar_t * restrict s1,
24320 const wchar_t * restrict s2,
24322 Runtime-constraints
24323 8 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
24324 RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max
24325 shall be greater than wcsnlen_s(s2, s1max). Copying shall not take place between
24326 objects that overlap.
24327 9 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
24328 greater than zero and not greater than RSIZE_MAX, then wcsncpy_s sets s1[0] to the
24329 null wide character.
24330 <b> Description</b>
24331 10 The wcsncpy_s function copies not more than n successive wide characters (wide
24332 characters that follow a null wide character are not copied) from the array pointed to by
24333 s2 to the array pointed to by s1. If no null wide character was copied from s2, then
24334 s1[n] is set to a null wide character.
24335 11 All elements following the terminating null wide character (if any) written by
24336 wcsncpy_s in the array of s1max wide characters pointed to by s1 take unspecified
24337 values when wcsncpy_s returns.<sup><a href="#note430"><b>430)</b></a></sup>
24339 12 The wcsncpy_s function returns zero<sup><a href="#note431"><b>431)</b></a></sup> if there was no runtime-constraint violation.
24340 Otherwise, a nonzero value is returned.
24341 13 EXAMPLE 1 The wcsncpy_s function can be used to copy a wide string without the danger that the
24342 result will not be null terminated or that wide characters will be written past the end of the destination
24348 <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
24349 if any of those wide characters are null. Such an approach might write a wide character to every
24350 element of s1 before discovering that the first element should be set to the null wide character.
24351 <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
24352 fit within the array pointed to by s1 and that the result in s1 is null terminated.
24354 [<a name="p636" href="#p636">page 636</a>] (<a href="#Contents">Contents</a>)
24356 #define __STDC_WANT_LIB_EXT1__ 1
24357 #include <a href="#7.28"><wchar.h></a>
24359 wchar_t src1[100] = L"hello";
24360 wchar_t src2[7] = {L'g', L'o', L'o', L'd', L'b', L'y', L'e'};
24361 wchar_t dst1[6], dst2[5], dst3[5];
24363 r1 = wcsncpy_s(dst1, 6, src1, 100);
24364 r2 = wcsncpy_s(dst2, 5, src2, 7);
24365 r3 = wcsncpy_s(dst3, 5, src2, 4);
24366 The first call will assign to r1 the value zero and to dst1 the sequence of wide characters hello\0.
24367 The second call will assign to r2 a nonzero value and to dst2 the sequence of wide characters \0.
24368 The third call will assign to r3 the value zero and to dst3 the sequence of wide characters good\0.
24370 <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>
24372 14 #define __STDC_WANT_LIB_EXT1__ 1
24373 #include <a href="#7.28"><wchar.h></a>
24374 errno_t wmemcpy_s(wchar_t * restrict s1,
24376 const wchar_t * restrict s2,
24378 Runtime-constraints
24379 15 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
24380 RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between
24381 objects that overlap.
24382 16 If there is a runtime-constraint violation, the wmemcpy_s function stores zeros in the
24383 first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
24384 s1max is not greater than RSIZE_MAX.
24385 <b> Description</b>
24386 17 The wmemcpy_s function copies n successive wide characters from the object pointed
24387 to by s2 into the object pointed to by s1.
24389 18 The wmemcpy_s function returns zero if there was no runtime-constraint violation.
24390 Otherwise, a nonzero value is returned.
24392 [<a name="p637" href="#p637">page 637</a>] (<a href="#Contents">Contents</a>)
24394 <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>
24396 19 #define __STDC_WANT_LIB_EXT1__ 1
24397 #include <a href="#7.28"><wchar.h></a>
24398 errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
24399 const wchar_t *s2, rsize_t n);
24400 Runtime-constraints
24401 20 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
24402 RSIZE_MAX. n shall not be greater than s1max.
24403 21 If there is a runtime-constraint violation, the wmemmove_s function stores zeros in the
24404 first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and
24405 s1max is not greater than RSIZE_MAX.
24406 <b> Description</b>
24407 22 The wmemmove_s function copies n successive wide characters from the object pointed
24408 to by s2 into the object pointed to by s1. This copying takes place as if the n wide
24409 characters from the object pointed to by s2 are first copied into a temporary array of n
24410 wide characters that does not overlap the objects pointed to by s1 or s2, and then the n
24411 wide characters from the temporary array are copied into the object pointed to by s1.
24413 23 The wmemmove_s function returns zero if there was no runtime-constraint violation.
24414 Otherwise, a nonzero value is returned.
24415 <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>
24416 <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>
24418 1 #define __STDC_WANT_LIB_EXT1__ 1
24419 #include <a href="#7.28"><wchar.h></a>
24420 errno_t wcscat_s(wchar_t * restrict s1,
24422 const wchar_t * restrict s2);
24423 Runtime-constraints
24424 2 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
24426 3 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX.
24427 s1max shall not equal zero. m shall not equal zero.<sup><a href="#note432"><b>432)</b></a></sup> m shall be greater than
24428 wcsnlen_s(s2, m). Copying shall not take place between objects that overlap.
24430 [<a name="p638" href="#p638">page 638</a>] (<a href="#Contents">Contents</a>)
24432 4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
24433 greater than zero and not greater than RSIZE_MAX, then wcscat_s sets s1[0] to the
24434 null wide character.
24435 <b> Description</b>
24436 5 The wcscat_s function appends a copy of the wide string pointed to by s2 (including
24437 the terminating null wide character) to the end of the wide string pointed to by s1. The
24438 initial wide character from s2 overwrites the null wide character at the end of s1.
24439 6 All elements following the terminating null wide character (if any) written by
24440 wcscat_s in the array of s1max wide characters pointed to by s1 take unspecified
24441 values when wcscat_s returns.<sup><a href="#note433"><b>433)</b></a></sup>
24443 7 The wcscat_s function returns zero<sup><a href="#note434"><b>434)</b></a></sup> if there was no runtime-constraint violation.
24444 Otherwise, a nonzero value is returned.
24445 <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>
24447 8 #define __STDC_WANT_LIB_EXT1__ 1
24448 #include <a href="#7.28"><wchar.h></a>
24449 errno_t wcsncat_s(wchar_t * restrict s1,
24451 const wchar_t * restrict s2,
24453 Runtime-constraints
24454 9 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
24456 10 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
24457 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
24458 than m, then m shall be greater than wcsnlen_s(s2, m). Copying shall not take
24459 place between objects that overlap.
24462 <sup><a name="note432" href="#note432"><b>432)</b></a></sup> Zero means that s1 was not null terminated upon entry to wcscat_s.
24463 <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
24464 checking if any of those wide characters are null. Such an approach might write a wide character to
24465 every element of s1 before discovering that the first element should be set to the null wide character.
24466 <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
24467 s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
24468 <sup><a name="note435" href="#note435"><b>435)</b></a></sup> Zero means that s1 was not null terminated upon entry to wcsncat_s.
24470 [<a name="p639" href="#p639">page 639</a>] (<a href="#Contents">Contents</a>)
24472 11 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is
24473 greater than zero and not greater than RSIZE_MAX, then wcsncat_s sets s1[0] to the
24474 null wide character.
24475 <b> Description</b>
24476 12 The wcsncat_s function appends not more than n successive wide characters (wide
24477 characters that follow a null wide character are not copied) from the array pointed to by
24478 s2 to the end of the wide string pointed to by s1. The initial wide character from s2
24479 overwrites the null wide character at the end of s1. If no null wide character was copied
24480 from s2, then s1[s1max-m+n] is set to a null wide character.
24481 13 All elements following the terminating null wide character (if any) written by
24482 wcsncat_s in the array of s1max wide characters pointed to by s1 take unspecified
24483 values when wcsncat_s returns.<sup><a href="#note436"><b>436)</b></a></sup>
24485 14 The wcsncat_s function returns zero<sup><a href="#note437"><b>437)</b></a></sup> if there was no runtime-constraint violation.
24486 Otherwise, a nonzero value is returned.
24487 15 EXAMPLE 1 The wcsncat_s function can be used to copy a wide string without the danger that the
24488 result will not be null terminated or that wide characters will be written past the end of the destination
24490 #define __STDC_WANT_LIB_EXT1__ 1
24491 #include <a href="#7.28"><wchar.h></a>
24493 wchar_t s1[100] = L"good";
24494 wchar_t s2[6] = L"hello";
24495 wchar_t s3[6] = L"hello";
24496 wchar_t s4[7] = L"abc";
24497 wchar_t s5[1000] = L"bye";
24498 int r1, r2, r3, r4;
24499 r1 = wcsncat_s(s1, 100, s5, 1000);
24500 r2 = wcsncat_s(s2, 6, L"", 1);
24501 r3 = wcsncat_s(s3, 6, L"X", 2);
24502 r4 = wcsncat_s(s4, 7, L"defghijklmn", 3);
24503 After the first call r1 will have the value zero and s1 will be the wide character sequence goodbye\0.
24504 After the second call r2 will have the value zero and s2 will be the wide character sequence hello\0.
24505 After the third call r3 will have a nonzero value and s3 will be the wide character sequence \0.
24506 After the fourth call r4 will have the value zero and s4 will be the wide character sequence abcdef\0.
24511 <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
24512 checking if any of those wide characters are null. Such an approach might write a wide character to
24513 every element of s1 before discovering that the first element should be set to the null wide character.
24514 <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
24515 s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
24517 [<a name="p640" href="#p640">page 640</a>] (<a href="#Contents">Contents</a>)
24519 <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>
24520 <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>
24522 1 #define __STDC_WANT_LIB_EXT1__ 1
24523 #include <a href="#7.28"><wchar.h></a>
24524 wchar_t *wcstok_s(wchar_t * restrict s1,
24525 rsize_t * restrict s1max,
24526 const wchar_t * restrict s2,
24527 wchar_t ** restrict ptr);
24528 Runtime-constraints
24529 2 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr
24530 shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX.
24531 The end of the token found shall occur within the first *s1max wide characters of s1 for
24532 the first call, and shall occur within the first *s1max wide characters of where searching
24533 resumes on subsequent calls.
24534 3 If there is a runtime-constraint violation, the wcstok_s function does not indirect
24535 through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
24536 <b> Description</b>
24537 4 A sequence of calls to the wcstok_s function breaks the wide string pointed to by s1
24538 into a sequence of tokens, each of which is delimited by a wide character from the wide
24539 string pointed to by s2. The fourth argument points to a caller-provided wchar_t
24540 pointer into which the wcstok_s function stores information necessary for it to
24541 continue scanning the same wide string.
24542 5 The first call in a sequence has a non-null first argument and s1max points to an object
24543 whose value is the number of elements in the wide character array pointed to by the first
24544 argument. The first call stores an initial value in the object pointed to by ptr and
24545 updates the value pointed to by s1max to reflect the number of elements that remain in
24546 relation to ptr. Subsequent calls in the sequence have a null first argument and the
24547 objects pointed to by s1max and ptr are required to have the values stored by the
24548 previous call in the sequence, which are then updated. The separator wide string pointed
24549 to by s2 may be different from call to call.
24550 6 The first call in the sequence searches the wide string pointed to by s1 for the first wide
24551 character that is not contained in the current separator wide string pointed to by s2. If no
24552 such wide character is found, then there are no tokens in the wide string pointed to by s1
24553 and the wcstok_s function returns a null pointer. If such a wide character is found, it is
24554 the start of the first token.
24556 [<a name="p641" href="#p641">page 641</a>] (<a href="#Contents">Contents</a>)
24558 7 The wcstok_s function then searches from there for the first wide character in s1 that
24559 is contained in the current separator wide string. If no such wide character is found, the
24560 current token extends to the end of the wide string pointed to by s1, and subsequent
24561 searches in the same wide string for a token return a null pointer. If such a wide character
24562 is found, it is overwritten by a null wide character, which terminates the current token.
24563 8 In all cases, the wcstok_s function stores sufficient information in the pointer pointed
24564 to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
24565 value for ptr, shall start searching just past the element overwritten by a null wide
24566 character (if any).
24568 9 The wcstok_s function returns a pointer to the first wide character of a token, or a null
24569 pointer if there is no token or there is a runtime-constraint violation.
24571 #define __STDC_WANT_LIB_EXT1__ 1
24572 #include <a href="#7.28"><wchar.h></a>
24573 static wchar_t str1[] = L"?a???b,,,#c";
24574 static wchar_t str2[] = L"\t \t";
24575 wchar_t *t, *ptr1, *ptr2;
24576 rsize_t max1 = wcslen(str1)+1;
24577 rsize_t max2 = wcslen(str2)+1;
24578 t = wcstok_s(str1, &max1, "?", &ptr1); // t points to the token "a"
24579 t = wcstok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
24580 t = wcstok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
24581 t = wcstok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
24582 t = wcstok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
24584 <a name="K.3.9.2.4" href="#K.3.9.2.4"><b> K.3.9.2.4 Miscellaneous functions</b></a>
24585 <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>
24587 1 #define __STDC_WANT_LIB_EXT1__ 1
24588 #include <a href="#7.28"><wchar.h></a>
24589 size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
24590 <b> Description</b>
24591 2 The wcsnlen_s function computes the length of the wide string pointed to by s.
24593 3 If s is a null pointer,<sup><a href="#note438"><b>438)</b></a></sup> then the wcsnlen_s function returns zero.
24594 4 Otherwise, the wcsnlen_s function returns the number of wide characters that precede
24595 the terminating null wide character. If there is no null wide character in the first
24596 maxsize wide characters of s then wcsnlen_s returns maxsize. At most the first
24598 [<a name="p642" href="#p642">page 642</a>] (<a href="#Contents">Contents</a>)
24600 maxsize wide characters of s shall be accessed by wcsnlen_s.
24601 <a name="K.3.9.3" href="#K.3.9.3"><b> K.3.9.3 Extended multibyte/wide character conversion utilities</b></a>
24602 <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>
24603 1 Unlike wcrtomb, wcrtomb_s does not permit the ps parameter (the pointer to the
24604 conversion state) to be a null pointer.
24605 <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>
24607 2 #include <a href="#7.28"><wchar.h></a>
24608 errno_t wcrtomb_s(size_t * restrict retval,
24609 char * restrict s, rsize_t smax,
24610 wchar_t wc, mbstate_t * restrict ps);
24611 Runtime-constraints
24612 3 Neither retval nor ps shall be a null pointer. If s is not a null pointer, then smax
24613 shall not equal zero and shall not be greater than RSIZE_MAX. If s is not a null pointer,
24614 then smax shall be not be less than the number of bytes to be stored in the array pointed
24615 to by s. If s is a null pointer, then smax shall equal zero.
24616 4 If there is a runtime-constraint violation, then wcrtomb_s does the following. If s is
24617 not a null pointer and smax is greater than zero and not greater than RSIZE_MAX, then
24618 wcrtomb_s sets s[0] to the null character. If retval is not a null pointer, then
24619 wcrtomb_s sets *retval to (size_t)(-1).
24620 <b> Description</b>
24621 5 If s is a null pointer, the wcrtomb_s function is equivalent to the call
24622 wcrtomb_s(&retval, buf, sizeof buf, L'\0', ps)
24623 where retval and buf are internal variables of the appropriate types, and the size of
24624 buf is greater than MB_CUR_MAX.
24625 6 If s is not a null pointer, the wcrtomb_s function determines the number of bytes
24626 needed to represent the multibyte character that corresponds to the wide character given
24627 by wc (including any shift sequences), and stores the multibyte character representation
24628 in the array whose first element is pointed to by s. At most MB_CUR_MAX bytes are
24629 stored. If wc is a null wide character, a null byte is stored, preceded by any shift
24630 sequence needed to restore the initial shift state; the resulting state described is the initial
24633 <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
24634 along with the values returned for a null pointer or an unterminated wide string argument make
24635 wcsnlen_s useful in algorithms that gracefully handle such exceptional data.
24637 [<a name="p643" href="#p643">page 643</a>] (<a href="#Contents">Contents</a>)
24639 7 If wc does not correspond to a valid multibyte character, an encoding error occurs: the
24640 wcrtomb_s function stores the value (size_t)(-1) into *retval and the
24641 conversion state is unspecified. Otherwise, the wcrtomb_s function stores into
24642 *retval the number of bytes (including any shift sequences) stored in the array pointed
24645 8 The wcrtomb_s function returns zero if no runtime-constraint violation and no
24646 encoding error occurred. Otherwise, a nonzero value is returned.
24647 <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>
24648 1 Unlike mbsrtowcs and wcsrtombs, mbsrtowcs_s and wcsrtombs_s do not
24649 permit the ps parameter (the pointer to the conversion state) to be a null pointer.
24650 <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>
24652 2 #include <a href="#7.28"><wchar.h></a>
24653 errno_t mbsrtowcs_s(size_t * restrict retval,
24654 wchar_t * restrict dst, rsize_t dstmax,
24655 const char ** restrict src, rsize_t len,
24656 mbstate_t * restrict ps);
24657 Runtime-constraints
24658 3 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
24659 then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
24660 pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
24661 not equal zero. If dst is not a null pointer and len is not less than dstmax, then a null
24662 character shall occur within the first dstmax multibyte characters of the array pointed to
24664 4 If there is a runtime-constraint violation, then mbsrtowcs_s does the following. If
24665 retval is not a null pointer, then mbsrtowcs_s sets *retval to (size_t)(-1).
24666 If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
24667 then mbsrtowcs_s sets dst[0] to the null wide character.
24668 <b> Description</b>
24669 5 The mbsrtowcs_s function converts a sequence of multibyte characters that begins in
24670 the conversion state described by the object pointed to by ps, from the array indirectly
24671 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
24672 pointer, the converted characters are stored into the array pointed to by dst. Conversion
24673 continues up to and including a terminating null character, which is also stored.
24674 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
24675 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
24677 [<a name="p644" href="#p644">page 644</a>] (<a href="#Contents">Contents</a>)
24679 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
24680 pointer and no null wide character was stored into the array pointed to by dst, then
24681 dst[len] is set to the null wide character. Each conversion takes place as if by a call
24682 to the mbrtowc function.
24683 6 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
24684 pointer (if conversion stopped due to reaching a terminating null character) or the address
24685 just past the last multibyte character converted (if any). If conversion stopped due to
24686 reaching a terminating null character and if dst is not a null pointer, the resulting state
24687 described is the initial conversion state.
24688 7 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
24689 sequence of bytes that do not form a valid multibyte character, an encoding error occurs:
24690 the mbsrtowcs_s function stores the value (size_t)(-1) into *retval and the
24691 conversion state is unspecified. Otherwise, the mbsrtowcs_s function stores into
24692 *retval the number of multibyte characters successfully converted, not including the
24693 terminating null character (if any).
24694 8 All elements following the terminating null wide character (if any) written by
24695 mbsrtowcs_s in the array of dstmax wide characters pointed to by dst take
24696 unspecified values when mbsrtowcs_s returns.<sup><a href="#note440"><b>440)</b></a></sup>
24697 9 If copying takes place between objects that overlap, the objects take on unspecified
24700 10 The mbsrtowcs_s function returns zero if no runtime-constraint violation and no
24701 encoding error occurred. Otherwise, a nonzero value is returned.
24702 <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>
24704 11 #include <a href="#7.28"><wchar.h></a>
24705 errno_t wcsrtombs_s(size_t * restrict retval,
24706 char * restrict dst, rsize_t dstmax,
24707 const wchar_t ** restrict src, rsize_t len,
24708 mbstate_t * restrict ps);
24713 <sup><a name="note439" href="#note439"><b>439)</b></a></sup> Thus, the value of len is ignored if dst is a null pointer.
24714 <sup><a name="note440" href="#note440"><b>440)</b></a></sup> This allows an implementation to attempt converting the multibyte string before discovering a
24715 terminating null character did not occur where required.
24717 [<a name="p645" href="#p645">page 645</a>] (<a href="#Contents">Contents</a>)
24719 Runtime-constraints
24720 12 None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer,
24721 then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null
24722 pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall
24723 not equal zero. If dst is not a null pointer and len is not less than dstmax, then the
24724 conversion shall have been stopped (see below) because a terminating null wide character
24725 was reached or because an encoding error occurred.
24726 13 If there is a runtime-constraint violation, then wcsrtombs_s does the following. If
24727 retval is not a null pointer, then wcsrtombs_s sets *retval to (size_t)(-1).
24728 If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX,
24729 then wcsrtombs_s sets dst[0] to the null character.
24730 <b> Description</b>
24731 14 The wcsrtombs_s function converts a sequence of wide characters from the array
24732 indirectly pointed to by src into a sequence of corresponding multibyte characters that
24733 begins in the conversion state described by the object pointed to by ps. If dst is not a
24734 null pointer, the converted characters are then stored into the array pointed to by dst.
24735 Conversion continues up to and including a terminating null wide character, which is also
24736 stored. Conversion stops earlier in two cases:
24737 -- when a wide character is reached that does not correspond to a valid multibyte
24739 -- (if dst is not a null pointer) when the next multibyte character would exceed the
24740 limit of n total bytes to be stored into the array pointed to by dst. If the wide
24741 character being converted is the null wide character, then n is the lesser of len or
24742 dstmax. Otherwise, n is the lesser of len or dstmax-1.
24743 If the conversion stops without converting a null wide character and dst is not a null
24744 pointer, then a null character is stored into the array pointed to by dst immediately
24745 following any multibyte characters already stored. Each conversion takes place as if by a
24746 call to the wcrtomb function.<sup><a href="#note441"><b>441)</b></a></sup>
24747 15 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
24748 pointer (if conversion stopped due to reaching a terminating null wide character) or the
24749 address just past the last wide character converted (if any). If conversion stopped due to
24750 reaching a terminating null wide character, the resulting state described is the initial
24754 <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
24755 include those necessary to reach the initial shift state immediately before the null byte. However, if
24756 the conversion stops before a terminating null wide character has been reached, the result will be null
24757 terminated, but might not end in the initial shift state.
24759 [<a name="p646" href="#p646">page 646</a>] (<a href="#Contents">Contents</a>)
24761 16 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a
24762 wide character that does not correspond to a valid multibyte character, an encoding error
24763 occurs: the wcsrtombs_s function stores the value (size_t)(-1) into *retval
24764 and the conversion state is unspecified. Otherwise, the wcsrtombs_s function stores
24765 into *retval the number of bytes in the resulting multibyte character sequence, not
24766 including the terminating null character (if any).
24767 17 All elements following the terminating null character (if any) written by wcsrtombs_s
24768 in the array of dstmax elements pointed to by dst take unspecified values when
24769 wcsrtombs_s returns.<sup><a href="#note442"><b>442)</b></a></sup>
24770 18 If copying takes place between objects that overlap, the objects take on unspecified
24773 19 The wcsrtombs_s function returns zero if no runtime-constraint violation and no
24774 encoding error occurred. Otherwise, a nonzero value is returned.
24779 <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
24780 runtime-constraint violation.
24782 [<a name="p647" href="#p647">page 647</a>] (<a href="#Contents">Contents</a>)
24784 <a name="L" href="#L"><b> Annex L</b></a>
24787 <a name="L.1" href="#L.1"><b> L.1 Scope</b></a>
24788 1 This annex specifies optional behavior that can aid in the analyzability of C programs.
24789 2 An implementation that defines __STDC_ANALYZABLE__ shall conform to the
24790 specifications in this annex.<sup><a href="#note443"><b>443)</b></a></sup>
24791 <a name="L.2" href="#L.2"><b> L.2 Definitions</b></a>
24792 <a name="L.2.1" href="#L.2.1"><b> L.2.1</b></a>
24793 1 out-of-bounds store
24794 an (attempted) access (<a href="#3.1">3.1</a>) that, at run time, for a given computational state, would
24795 modify (or, for an object declared volatile, fetch) one or more bytes that lie outside
24796 the bounds permitted by this Standard.
24797 <a name="L.2.2" href="#L.2.2"><b> L.2.2</b></a>
24798 1 bounded undefined behavior
24799 undefined behavior (<a href="#3.4.3">3.4.3</a>) that does not perform an out-of-bounds store.
24800 2 NOTE 1 The behavior might perform a trap.
24802 3 NOTE 2 Any values produced or stored might be indeterminate values.
24804 <a name="L.2.3" href="#L.2.3"><b> L.2.3</b></a>
24805 1 critical undefined behavior
24806 undefined behavior that is not bounded undefined behavior.
24807 2 NOTE The behavior might perform an out-of-bounds store or perform a trap.
24812 <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
24815 [<a name="p648" href="#p648">page 648</a>] (<a href="#Contents">Contents</a>)
24817 <a name="L.3" href="#L.3"><b> L.3 Requirements</b></a>
24818 1 If the program performs a trap (<a href="#3.19.5">3.19.5</a>), the implementation is permitted to invoke a
24819 runtime-constraint handler. Any such semantics are implementation-defined.
24820 2 All undefined behavior shall be limited to bounded undefined behavior, except for the
24821 following which are permitted to result in critical undefined behavior:
24822 -- An object is referred to outside of its lifetime (<a href="#6.2.4">6.2.4</a>).
24823 -- An lvalue does not designate an object when evaluated (<a href="#6.3.2.1">6.3.2.1</a>).
24824 -- A pointer is used to call a function whose type is not compatible with the referenced
24825 type (<a href="#6.3.2.3">6.3.2.3</a>).
24826 -- The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
24827 -- Addition or subtraction of a pointer into, or just beyond, an array object and an
24828 integer type produces a result that points just beyond the array object and is used as
24829 the operand of a unary * operator that is evaluated (<a href="#6.5.6">6.5.6</a>).
24830 -- An argument to a library function has an invalid value or a type not expected by a
24831 function with variable number of arguments (<a href="#7.1.4">7.1.4</a>).
24832 -- The value of a pointer that refers to space deallocated by a call to the free or realloc
24833 function is used (<a href="#7.22.3">7.22.3</a>).
24834 -- A string or wide string utility function is instructed to access an array beyond the end
24835 of an object (<a href="#7.23.1">7.23.1</a>, <a href="#7.28.4">7.28.4</a>).
24837 [<a name="p649" href="#p649">page 649</a>] (<a href="#Contents">Contents</a>)
24840 <a name="Bibliography" href="#Bibliography"><b> Bibliography</b></a>
24841 1. ''The C Reference Manual'' by Dennis M. Ritchie, a version of which was
24842 published in The C Programming Language by Brian W. Kernighan and Dennis
24843 M. Ritchie, Prentice-Hall, Inc., (1978). Copyright owned by AT&T.
24844 2. 1984 /usr/group Standard by the /usr/group Standards Committee, Santa Clara,
24845 California, USA, November 1984.
24846 3. ANSI X3/TR-1-82 (1982), American National Dictionary for Information
24847 Processing Systems, Information Processing Systems Technical Report.
24848 4. ANSI/IEEE 754-1985, American National Standard for Binary Floating-Point
24850 5. ANSI/IEEE 854-1988, American National Standard for Radix-Independent
24851 Floating-Point Arithmetic.
24852 6. IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems,
24853 second edition (previously designated IEC 559:1989).
24854 7. ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and
24855 symbols for use in the physical sciences and technology.
24856 8. ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for
24857 information interchange.
24858 9. ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1:
24860 10. ISO 4217:1995, Codes for the representation of currencies and funds.
24861 11. ISO 8601:1988, Data elements and interchange formats -- Information
24862 interchange -- Representation of dates and times.
24863 12. ISO/IEC 9899:1990, Programming languages -- C.
24864 13. ISO/IEC 9899/COR1:1994, Technical Corrigendum 1.
24865 14. ISO/IEC 9899/COR2:1996, Technical Corrigendum 2.
24866 15. ISO/IEC 9899/AMD1:1995, Amendment 1 to ISO/IEC 9899:1990 C Integrity.
24867 16. ISO/IEC 9899:1999, Programming languages -- C.
24868 17. ISO/IEC 9899:1999/Cor.1:2001, Technical Corrigendum 1.
24869 18. ISO/IEC 9899:1999/Cor.2:2004, Technical Corrigendum 2.
24870 19. ISO/IEC 9899:1999/Cor.3:2007, Technical Corrigendum 3.
24872 [<a name="p650" href="#p650">page 650</a>] (<a href="#Contents">Contents</a>)
24874 20. ISO/IEC 9945-2:1993, Information technology -- Portable Operating System
24875 Interface (POSIX) -- Part 2: Shell and Utilities.
24876 21. ISO/IEC TR 10176:1998, Information technology -- Guidelines for the
24877 preparation of programming language standards.
24878 22. ISO/IEC 10646-1:1993, Information technology -- Universal Multiple-Octet
24879 Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
24880 23. ISO/IEC 10646-1/COR1:1996, Technical Corrigendum 1 to
24881 ISO/IEC 10646-1:1993.
24882 24. ISO/IEC 10646-1/COR2:1998, Technical Corrigendum 2 to
24883 ISO/IEC 10646-1:1993.
24884 25. ISO/IEC 10646-1/AMD1:1996, Amendment 1 to ISO/IEC 10646-1:1993
24885 Transformation Format for 16 planes of group 00 (UTF-16).
24886 26. ISO/IEC 10646-1/AMD2:1996, Amendment 2 to ISO/IEC 10646-1:1993 UCS
24887 Transformation Format 8 (UTF-8).
24888 27. ISO/IEC 10646-1/AMD3:1996, Amendment 3 to ISO/IEC 10646-1:1993.
24889 28. ISO/IEC 10646-1/AMD4:1996, Amendment 4 to ISO/IEC 10646-1:1993.
24890 29. ISO/IEC 10646-1/AMD5:1998, Amendment 5 to ISO/IEC 10646-1:1993 Hangul
24892 30. ISO/IEC 10646-1/AMD6:1997, Amendment 6 to ISO/IEC 10646-1:1993
24894 31. ISO/IEC 10646-1/AMD7:1997, Amendment 7 to ISO/IEC 10646-1:1993 33
24895 additional characters.
24896 32. ISO/IEC 10646-1/AMD8:1997, Amendment 8 to ISO/IEC 10646-1:1993.
24897 33. ISO/IEC 10646-1/AMD9:1997, Amendment 9 to ISO/IEC 10646-1:1993
24898 Identifiers for characters.
24899 34. ISO/IEC 10646-1/AMD10:1998, Amendment 10 to ISO/IEC 10646-1:1993
24901 35. ISO/IEC 10646-1/AMD11:1998, Amendment 11 to ISO/IEC 10646-1:1993
24902 Unified Canadian Aboriginal Syllabics.
24903 36. ISO/IEC 10646-1/AMD12:1998, Amendment 12 to ISO/IEC 10646-1:1993
24905 37. ISO/IEC 10967-1:1994, Information technology -- Language independent
24906 arithmetic -- Part 1: Integer and floating point arithmetic.
24908 [<a name="p651" href="#p651">page 651</a>] (<a href="#Contents">Contents</a>)
24910 38. ISO/IEC TR 19769:2004, Information technology -- Programming languages,
24911 their environments and system software interfaces -- Extensions for the
24912 programming language C to support new character data types.
24913 39. ISO/IEC TR 24731-1:2007, Information technology -- Programming languages,
24914 their environments and system software interfaces -- Extensions to the C library
24915 -- Part 1: Bounds-checking interfaces.
24917 [<a name="p652" href="#p652">page 652</a>] (<a href="#Contents">Contents</a>)
24920 <a name="Index" href="#Index"><b>Index</b></a>
24921 [^ 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>
24922 , (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>,
24923 [_ 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>
24924 ! (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>
24925 != (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>
24926 # 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>
24927 # 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>
24928 # punctuator, <a href="#6.10">6.10</a> -= (subtraction assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
24929 ## 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>
24930 #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>,
24931 #elif preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#6.5.2.3">6.5.2.3</a>
24932 #else preprocessing directive, <a href="#6.10.1">6.10.1</a> . punctuator, <a href="#6.7.9">6.7.9</a>
24933 #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>
24934 #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>
24935 #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>
24936 <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>
24937 #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>
24938 #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>
24939 #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>
24940 <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>,
24941 #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>
24942 #pragma preprocessing directive, <a href="#6.10.6">6.10.6</a> < (less-than operator), <a href="#6.5.8">6.5.8</a>
24943 #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>
24944 <a href="#7.1.4">7.1.4</a> <: (alternative spelling of [), <a href="#6.4.6">6.4.6</a>
24945 % (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>
24946 %: (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>
24947 %:%: (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>
24948 %= (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>
24949 %> (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>,
24950 & (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>
24951 & (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>
24952 && (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>
24953 &= (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>,
24954 ' ' (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>
24955 <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>,
24956 ( ) (cast operator), <a href="#6.5.4">6.5.4</a> <a href="#7.28.4.1.1">7.28.4.1.1</a>
24957 ( ) (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>
24958 ( ) (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>
24959 ( ){ } (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>
24960 * (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>
24961 * (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>,
24962 * (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>
24963 <a href="#G.5.1">G.5.1</a> <a href="#7.13"><setjmp.h></a> header, <a href="#7.13">7.13</a>
24964 *= (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>
24965 + (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>
24966 <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>
24967 + (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>
24968 ++ (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>
24969 ++ (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>,
24970 += (addition assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
24972 [<a name="p653" href="#p653">page 653</a>] (<a href="#Contents">Contents</a>)
24974 <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
24975 <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>
24976 <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>
24977 <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),
24978 <a href="#K.3.5">K.3.5</a> <a href="#6.5.16.2">6.5.16.2</a>
24979 <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>
24980 <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
24981 <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>
24982 <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>
24983 <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>
24984 <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>
24985 <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>
24986 <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>
24987 <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>
24988 <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>
24989 = (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>
24990 = (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>
24991 == (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>
24992 > (greater-than operator), <a href="#6.5.8">6.5.8</a> __STDC_IEC_559_COMPLEX__ macro,
24993 >= (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>
24994 >> (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>
24995 >>= (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>
24996 ? : (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,
24997 ?? (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>
24998 [ ] (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>,
24999 [ ] (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>
25000 \ (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>,
25001 \ (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>
25002 \" (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>
25003 <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>
25004 \\ (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>
25005 \' (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>
25006 \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>
25007 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>
25008 \? (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>
25009 \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>
25010 \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>
25011 \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>,
25012 <a href="#7.4.1.10">7.4.1.10</a> <a href="#F.4">F.4</a>
25013 \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>
25014 <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>
25015 \octal digits (octal-character escape sequence), _Complex_I macro, <a href="#7.3.1">7.3.1</a>
25016 <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>
25017 \r (carriage-return escape sequence), <a href="#5.2.2">5.2.2</a>, _Imaginary keyword, <a href="#G.2">G.2</a>
25018 <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>
25019 \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>
25020 <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>
25021 \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>
25022 \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>
25023 \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>
25024 <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>
25026 [<a name="p654" href="#p654">page 654</a>] (<a href="#Contents">Contents</a>)
25028 _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>
25029 _Thread_local storage-class specifier, <a href="#6.2.4">6.2.4</a>, and macro, <a href="#7.9">7.9</a>
25030 <a href="#6.7.1">6.7.1</a> AND operators
25031 { } (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>
25032 <a href="#6.8.2">6.8.2</a> bitwise assignment (&=), <a href="#6.5.16.2">6.5.16.2</a>
25033 { } (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>
25034 | (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>
25035 |= (bitwise inclusive OR assignment operator), anonymous structure, <a href="#6.7.2.1">6.7.2.1</a>
25036 <a href="#6.5.16.2">6.5.16.2</a> anonymous union, <a href="#6.7.2.1">6.7.2.1</a>
25037 || (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>
25038 ~ (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>
25039 argc (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a>
25040 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>
25041 <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>
25042 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>
25043 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>
25044 absolute-value functions macro, substitution, <a href="#6.10.3.1">6.10.3.1</a>
25045 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>
25046 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>
25047 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>
25048 abstract declarator, <a href="#6.7.7">6.7.7</a> arithmetic conversions, usual, see usual arithmetic
25049 abstract machine, <a href="#5.1.2.3">5.1.2.3</a> conversions
25050 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
25051 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>
25052 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>
25053 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>
25054 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>
25055 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>
25056 acquire fence, <a href="#7.17.4">7.17.4</a> unary, <a href="#6.5.3.3">6.5.3.3</a>
25057 acquire operation, <a href="#5.1.2.4">5.1.2.4</a> arithmetic types, <a href="#6.2.5">6.2.5</a>
25058 active position, <a href="#5.2.2">5.2.2</a> arithmetic, pointer, <a href="#6.5.6">6.5.6</a>
25059 actual argument, <a href="#3.3">3.3</a> array
25060 actual parameter (deprecated), <a href="#3.3">3.3</a> argument, <a href="#6.9.1">6.9.1</a>
25061 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>
25062 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>
25063 <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>
25064 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>
25065 address constant, <a href="#6.6">6.6</a> storage order, <a href="#6.5.2.1">6.5.2.1</a>
25066 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>
25067 address-free, <a href="#7.17.5">7.17.5</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
25068 aggregate initialization, <a href="#6.7.9">6.7.9</a> type, <a href="#6.2.5">6.2.5</a>
25069 aggregate types, <a href="#6.2.5">6.2.5</a> type conversion, <a href="#6.3.2.1">6.3.2.1</a>
25070 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>
25071 aliasing, <a href="#6.5">6.5</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
25072 alignas macro, <a href="#7.15">7.15</a> as-if rule, <a href="#5.1.2.3">5.1.2.3</a>
25073 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>
25074 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>
25075 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>
25076 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>
25077 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>
25078 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>
25080 [<a name="p655" href="#p655">page 655</a>] (<a href="#Contents">Contents</a>)
25082 asinh type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> atomic_is_lock_free generic function,
25083 asm keyword, <a href="#J.5.10">J.5.10</a> <a href="#7.17.5.1">7.17.5.1</a>
25084 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>
25085 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>
25086 assignment ATOMIC_LONG_LOCK_FREE macro, <a href="#7.17.1">7.17.1</a>
25087 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>
25088 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>
25089 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>
25090 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>
25091 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>
25092 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>
25093 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>
25094 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>
25095 <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>
25096 atan functions, <a href="#7.12.4.3">7.12.4.3</a>, <a href="#F.10.1.3">F.10.1.3</a>
25097 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>
25098 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>
25099 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>
25100 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>
25101 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>
25102 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>
25103 <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>,
25104 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>
25105 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>
25106 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>
25107 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>
25108 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>
25109 atomic operations, <a href="#5.1.2.4">5.1.2.4</a> bitand macro, <a href="#7.9">7.9</a>
25110 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>
25111 <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>
25112 <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>
25113 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>
25114 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>
25115 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>
25116 ATOMIC_CHAR16_T_LOCK_FREE macro, exclusive OR assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
25117 <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>
25118 ATOMIC_CHAR32_T_LOCK_FREE macro, inclusive OR assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
25119 <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>
25120 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>
25121 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>
25122 functions, <a href="#7.17.7.4">7.17.7.4</a> block scope, <a href="#6.2.1">6.2.1</a>
25123 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>
25124 atomic_fetch and modify generic functions, bold type convention, <a href="#6.1">6.1</a>
25125 <a href="#7.17.7.5">7.17.7.5</a> bool macro, <a href="#7.18">7.18</a>
25126 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>
25127 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>
25128 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>
25129 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>,
25130 <a href="#7.17.8.1">7.17.8.1</a> <a href="#6.8.2">6.8.2</a>
25131 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>
25132 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>
25134 [<a name="p656" href="#p656">page 656</a>] (<a href="#Contents">Contents</a>)
25136 branch cuts, <a href="#7.3.3">7.3.3</a> type-generic macro for, <a href="#7.24">7.24</a>
25137 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>
25138 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>
25139 <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>
25140 <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>
25141 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>
25142 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>
25143 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>
25144 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>
25145 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>
25146 byte input/output functions, <a href="#7.21.1">7.21.1</a> cexpm1 function, <a href="#7.30.1">7.30.1</a>
25147 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>,
25148 <a href="#K.3.9.1.2">K.3.9.1.2</a>
25149 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>,
25150 c16rtomb function, <a href="#7.27.1.2">7.27.1.2</a> <a href="#6.3.1.8">6.3.1.8</a>
25151 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>
25152 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>
25153 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>
25154 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>
25155 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>
25156 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>
25157 type-generic macro for, <a href="#7.24">7.24</a> character array initialization, <a href="#6.7.9">6.7.9</a>
25158 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>
25159 <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>
25160 <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>
25161 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>
25162 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>
25163 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>
25164 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>
25165 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>
25166 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>
25167 <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>
25168 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>
25169 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>
25170 case mapping functions character string literal, see string literal
25171 character, <a href="#7.4.2">7.4.2</a> character type conversion, <a href="#6.3.1.1">6.3.1.1</a>
25172 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>
25173 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>
25174 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>
25175 type-generic macro for, <a href="#7.24">7.24</a> cis function, <a href="#G.6">G.6</a>
25176 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
25177 type-generic macro for, <a href="#7.24">7.24</a> character, <a href="#7.4.1">7.4.1</a>
25178 cast expression, <a href="#6.5.4">6.5.4</a> floating-point, <a href="#7.12.3">7.12.3</a>
25179 cast operator (( )), <a href="#6.5.4">6.5.4</a> wide character, <a href="#7.29.2.1">7.29.2.1</a>
25180 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>
25181 type-generic macro for, <a href="#7.24">7.24</a> clearerr function, <a href="#7.21.10.1">7.21.10.1</a>
25182 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>
25183 type-generic macro for, <a href="#7.24">7.24</a> clock function, <a href="#7.26.2.1">7.26.2.1</a>
25184 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>
25185 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>
25186 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>
25188 [<a name="p657" href="#p657">page 657</a>] (<a href="#Contents">Contents</a>)
25190 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>
25191 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>
25192 clog1p function, <a href="#7.30.1">7.30.1</a> concatenation, preprocessing, see preprocessing
25193 clog2 function, <a href="#7.30.1">7.30.1</a> concatenation
25194 CMPLX macros, <a href="#7.3.9.3">7.3.9.3</a> conceptual models, <a href="#5.1">5.1</a>
25195 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>,
25196 <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>
25197 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>
25198 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>
25199 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>
25200 <a href="#7.25.3.6">7.25.3.6</a> conformance, <a href="#4">4</a>
25201 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>
25202 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>
25203 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>
25204 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>
25205 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>
25206 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>
25207 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>
25208 <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>
25209 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>
25210 comment delimiters (/* */ and //), <a href="#6.4.9">6.4.9</a> floating, <a href="#6.4.4.2">6.4.4.2</a>
25211 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>
25212 common extensions, <a href="#J.5">J.5</a> integer, <a href="#6.4.4.1">6.4.4.1</a>
25213 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>
25214 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>
25215 common warnings, <a href="#I">I</a> constraint_handler_t type, <a href="#K.3.6">K.3.6</a>
25216 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>
25217 <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>
25218 string, <a href="#7.23.4">7.23.4</a> contiguity of allocated storage, <a href="#7.22.3">7.22.3</a>
25219 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>
25220 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>
25221 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>
25222 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>
25223 compl macro, <a href="#7.9">7.9</a> conversion, <a href="#6.3">6.3</a>
25224 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>
25225 complete type, <a href="#6.2.5">6.2.5</a> array argument, <a href="#6.9.1">6.9.1</a>
25226 complex macro, <a href="#7.3.1">7.3.1</a> array parameter, <a href="#6.9.1">6.9.1</a>
25227 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>
25228 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>
25229 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>
25230 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>
25231 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>
25232 <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>
25233 compliance, see conformance explicit, <a href="#6.3">6.3</a>
25234 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>
25235 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>
25236 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>
25237 compound literals, <a href="#6.5.2.5">6.5.2.5</a> function parameter, <a href="#6.9.1">6.9.1</a>
25238 compound statement, <a href="#6.8.2">6.8.2</a> imaginary, <a href="#G.4.1">G.4.1</a>
25239 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>
25240 concatenation functions implicit, <a href="#6.3">6.3</a>
25242 [<a name="p658" href="#p658">page 658</a>] (<a href="#Contents">Contents</a>)
25244 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>
25245 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>
25246 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>
25247 real and imaginary, <a href="#G.4.2">G.4.2</a> type-generic macro for, <a href="#7.24">7.24</a>
25248 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>
25249 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>
25250 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>
25251 usual arithmetic, see usual arithmetic type-generic macro for, <a href="#7.24">7.24</a>
25252 conversions ctgamma function, <a href="#7.30.1">7.30.1</a>
25253 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>
25254 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>
25255 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>
25256 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>
25257 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>
25258 multibyte/wide string, <a href="#7.22.8">7.22.8</a>, <a href="#K.3.6.5">K.3.6.5</a>
25259 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>,
25260 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>,
25261 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>
25262 single byte/wide character, <a href="#7.28.6.1">7.28.6.1</a> data stream, see streams
25263 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>
25264 wide character, <a href="#7.28.5">7.28.5</a> Daylight Saving Time, <a href="#7.26.1">7.26.1</a>
25265 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>
25266 <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>
25267 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>
25268 <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>
25269 <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>
25270 <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>
25271 <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>
25272 <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>
25273 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>
25274 copying functions DBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
25275 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>
25276 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>
25277 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>
25278 <a href="#F.10.8.1">F.10.8.1</a> decimal digit, <a href="#5.2.1">5.2.1</a>
25279 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>
25280 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>,
25281 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>
25282 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>
25283 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>
25284 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>
25285 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>
25286 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>
25287 type-generic macro for, <a href="#7.24">7.24</a> typedef, <a href="#6.7.8">6.7.8</a>
25288 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>
25289 cproj type-generic macro, <a href="#7.24">7.24</a> abstract, <a href="#6.7.7">6.7.7</a>
25290 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>
25291 creal type-generic macro, <a href="#7.24">7.24</a>, <a href="#G.7">G.7</a> decrement operators, see arithmetic operators,
25292 critical undefined behavior, <a href="#L.2.3">L.2.3</a> increment and decrement
25293 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>
25294 type-generic macro for, <a href="#7.24">7.24</a> default initialization, <a href="#6.7.9">6.7.9</a>
25296 [<a name="p659" href="#p659">page 659</a>] (<a href="#Contents">Contents</a>)
25298 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>
25299 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>
25300 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>
25301 definition, <a href="#6.7">6.7</a> else statement, <a href="#6.8.4.1">6.8.4.1</a>
25302 function, <a href="#6.9.1">6.9.1</a> empty statement, <a href="#6.8.3">6.8.3</a>
25303 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>,
25304 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>,
25305 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>,
25306 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>,
25307 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>
25308 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>
25309 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>,
25310 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>,
25311 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>,
25312 difftime function, <a href="#7.26.2.2">7.26.2.2</a> <a href="#7.28.3.10">7.28.3.10</a>
25313 digit, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> end-of-file macro, see EOF macro
25314 digraphs, <a href="#6.4.6">6.4.6</a> end-of-line indicator, <a href="#5.2.1">5.2.1</a>
25315 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>
25316 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>
25317 div function, <a href="#7.22.6.2">7.22.6.2</a> enumerated type, <a href="#6.2.5">6.2.5</a>
25318 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>
25319 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>
25320 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>
25321 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>
25322 documentation of implementation, <a href="#4">4</a> enumeration specifiers, <a href="#6.7.2.2">6.7.2.2</a>
25323 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>
25324 <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>
25325 <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>
25326 <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>
25327 <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>
25328 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> environmental considerations, <a href="#5.2">5.2</a>
25329 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>,
25330 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>,
25331 <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>
25332 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>,
25333 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>,
25334 <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>,
25335 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>,
25336 <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>,
25337 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>,
25338 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>,
25339 <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>,
25340 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>,
25341 <a href="#K.3.9.1.14">K.3.9.1.14</a>
25342 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>
25343 effective type, <a href="#6.5">6.5</a> equal-to operator, see equality operator
25344 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>
25345 <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>
25346 <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>,
25347 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
25348 element type, <a href="#6.2.5">6.2.5</a> also range error, pole error
25350 [<a name="p660" href="#p660">page 660</a>] (<a href="#Contents">Contents</a>)
25352 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>
25353 erf type-generic macro, <a href="#7.24">7.24</a> exp2 type-generic macro, <a href="#7.24">7.24</a>
25354 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>
25355 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>
25356 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>
25357 <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>
25358 <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
25359 <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>
25360 <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>
25361 <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>
25362 <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>
25363 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>
25364 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>
25365 <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>
25366 error full, <a href="#6.8">6.8</a>
25367 domain, see domain error order of evaluation, see order of evaluation
25368 encoding, see encoding error parenthesized, <a href="#6.5.1">6.5.1</a>
25369 pole, see pole error primary, <a href="#6.5.1">6.5.1</a>
25370 range, see range error unary, <a href="#6.5.3">6.5.3</a>
25371 error conditions, <a href="#7.12.1">7.12.1</a> expression statement, <a href="#6.8.3">6.8.3</a>
25372 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>
25373 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>
25374 <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>
25375 <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>,
25376 <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>
25377 error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> extended multibyte/wide character conversion
25378 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>
25379 <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,
25380 escape character (\), <a href="#6.4.4.4">6.4.4.4</a> <a href="#7.29.3.2">7.29.3.2</a>
25381 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,
25382 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>
25383 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>
25384 evaluation of expression, <a href="#5.1.2.3">5.1.2.3</a> external definition, <a href="#6.9">6.9</a>
25385 evaluation order, see order of evaluation external identifiers, underscore, <a href="#7.1.3">7.1.3</a>
25386 exceptional condition, <a href="#6.5">6.5</a> external linkage, <a href="#6.2.2">6.2.2</a>
25387 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>
25388 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>
25389 exclusive OR operators
25390 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>
25391 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>
25392 executable program, <a href="#5.1.1.1">5.1.1.1</a> false macro, <a href="#7.18">7.18</a>
25393 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>
25394 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>
25395 environmental limits fdim type-generic macro, <a href="#7.24">7.24</a>
25396 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>
25397 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>
25398 <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>
25399 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>
25400 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>
25401 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>
25402 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>
25404 [<a name="p661" href="#p661">page 661</a>] (<a href="#Contents">Contents</a>)
25406 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>,
25407 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>
25408 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>
25409 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>
25410 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>,
25411 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>
25412 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>,
25413 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>
25414 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>
25415 <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>
25416 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>
25417 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>,
25418 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>
25419 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>
25420 <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>,
25421 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
25422 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>
25423 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>
25424 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>
25425 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>
25426 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>
25427 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>
25428 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>
25429 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>
25430 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>
25431 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>
25432 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>
25433 <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>
25434 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>
25435 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>,
25436 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>
25437 <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>
25438 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>
25439 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>
25440 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>
25441 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>
25442 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>
25443 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>
25444 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>
25445 <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>,
25446 <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>
25447 <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>
25448 <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>
25449 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>
25450 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>
25451 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>
25452 FILENAME_MAX macro, <a href="#7.21.1">7.21.1</a> fmax type-generic macro, <a href="#7.24">7.24</a>
25453 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>
25454 status flag fmin type-generic macro, <a href="#7.24">7.24</a>
25455 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>
25456 float _Complex type, <a href="#6.2.5">6.2.5</a> fmod type-generic macro, <a href="#7.24">7.24</a>
25458 [<a name="p662" href="#p662">page 662</a>] (<a href="#Contents">Contents</a>)
25460 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>
25461 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>,
25462 <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>
25463 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>,
25464 <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>
25465 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>
25466 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>
25467 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>
25468 <a href="#7.4.1.10">7.4.1.10</a> fully buffered stream, <a href="#7.21.3">7.21.3</a>
25469 formal argument (deprecated), <a href="#3.16">3.16</a> function
25470 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>
25471 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>
25472 <a href="#K.3.5.3">K.3.5.3</a> call, <a href="#6.5.2.2">6.5.2.2</a>
25473 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>
25474 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>
25475 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>
25476 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>
25477 also contracted expression image, <a href="#5.2.3">5.2.3</a>
25478 FP_FAST_FMA macro, <a href="#7.12">7.12</a> inline, <a href="#6.7.4">6.7.4</a>
25479 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>
25480 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>
25481 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>
25482 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>
25483 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>,
25484 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>
25485 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>
25486 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>
25487 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>
25488 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>
25489 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>
25490 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>
25491 <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>
25492 <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>
25493 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>
25494 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>
25495 <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>
25496 fputs function, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.7.4">7.21.7.4</a> future directions
25497 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>
25498 <a href="#7.28.3.8">7.28.3.8</a> library, <a href="#7.30">7.30</a>
25499 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>
25500 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>,
25501 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>,
25502 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>
25503 <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>
25504 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>
25505 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>,
25506 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>,
25507 frexp type-generic macro, <a href="#7.24">7.24</a> <a href="#K.3.9.1.2">K.3.9.1.2</a>
25508 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>,
25509 <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>
25510 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>,
25512 [<a name="p663" href="#p663">page 663</a>] (<a href="#Contents">Contents</a>)
25514 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>
25515 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>
25516 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>
25517 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>
25518 generic parameters, <a href="#7.24">7.24</a> identifier list, <a href="#6.7.6">6.7.6</a>
25519 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>
25520 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>
25521 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>,
25522 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>,
25523 getenv_s function, <a href="#K.3.6.2.1">K.3.6.2.1</a> <a href="#H.1">H.1</a>
25524 gets function, <a href="#K.3.5.4.1">K.3.5.4.1</a> IEEE 754, <a href="#F.1">F.1</a>
25525 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>
25526 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
25527 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,
25528 gmtime function, <a href="#7.26.3.3">7.26.3.3</a> ANSI/IEEE 854
25529 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>,
25530 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>
25531 graphic characters, <a href="#5.2.1">5.2.1</a> if statement, <a href="#6.8.4.1">6.8.4.1</a>
25532 greater-than operator (>), <a href="#6.5.8">6.5.8</a> ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a>
25533 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>
25534 ignore_handler_s function, <a href="#K.3.6.1.3">K.3.6.1.3</a>
25535 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>
25536 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>
25537 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>
25538 hexadecimal constant, <a href="#6.4.4.1">6.4.4.1</a> imaginary numbers, <a href="#G">G</a>
25539 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>
25540 hexadecimal prefix, <a href="#6.4.4.1">6.4.4.1</a> imaginary types, <a href="#G">G</a>
25541 hexadecimal-character escape sequence imaxabs function, <a href="#7.8.2.1">7.8.2.1</a>
25542 (\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>
25543 high-order bit, <a href="#3.6">3.6</a> imaxdiv_t type, <a href="#7.8">7.8</a>
25544 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>
25545 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>,
25546 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
25547 <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
25548 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>
25549 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>
25550 <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>
25551 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>
25552 <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>
25553 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
25554 <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>
25555 hyperbolic functions bitwise assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
25556 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>
25557 real, <a href="#7.12.5">7.12.5</a>, <a href="#F.10.2">F.10.2</a> increment operators, see arithmetic operators,
25558 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
25559 hypot type-generic macro, <a href="#7.24">7.24</a> indeterminate value, <a href="#3.19.2">3.19.2</a>
25560 indeterminately sequenced, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5.2.2">6.5.2.2</a>,
25561 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,
25562 identifier, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.5.1">6.5.1</a> unsequenced
25563 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>
25564 maximum length, <a href="#6.4.2.1">6.4.2.1</a> inequality operator (!=), <a href="#6.5.9">6.5.9</a>
25566 [<a name="p664" href="#p664">page 664</a>] (<a href="#Contents">Contents</a>)
25568 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>
25569 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>
25570 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>
25571 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>
25572 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>
25573 <a href="#F.8.5">F.8.5</a> interrupt, <a href="#5.2.3">5.2.3</a>
25574 in blocks, <a href="#6.8">6.8</a> INTMAX_C macro, <a href="#7.20.4.2">7.20.4.2</a>
25575 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>
25576 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>
25577 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>,
25578 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>
25579 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>
25580 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>
25581 <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>
25582 <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>
25583 <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>
25584 input/output functions INTPTR_MIN macro, <a href="#7.20.2.4">7.20.2.4</a>
25585 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>
25586 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>
25587 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>
25588 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>
25589 wide character, <a href="#7.28.3">7.28.3</a> isblank function, <a href="#7.4.1.3">7.4.1.3</a>
25590 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>,
25591 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>
25592 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>,
25593 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>
25594 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>
25595 <a href="#6.3.1.8">6.3.1.8</a> isgraph function, <a href="#7.4.1.6">7.4.1.6</a>
25596 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>
25597 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>
25598 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>
25599 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>
25600 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>
25601 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>
25602 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>,
25603 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>
25604 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>
25605 <a href="#7.22.6">7.22.6</a> isnormal macro, <a href="#7.12.3.5">7.12.3.5</a>
25606 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>
25607 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>
25608 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>
25609 <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>
25610 <a href="#7.1.4">7.1.4</a> ISO/IEC 10976-1, <a href="#H.1">H.1</a>
25611 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>
25612 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>
25613 <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>
25614 <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> *
25615 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>
25616 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>,
25617 <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>
25618 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>,
25620 [<a name="p665" href="#p665">page 665</a>] (<a href="#Contents">Contents</a>)
25622 <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>
25623 <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>,
25624 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>
25625 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>,
25626 <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>,
25627 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>
25628 <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>
25629 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>
25630 <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>
25631 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>
25632 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>
25633 <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>
25634 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>
25635 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>
25636 <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>
25637 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>
25638 <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>
25639 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>
25640 <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>
25641 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>
25642 <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>
25643 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>
25644 <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>
25645 <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>
25646 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>
25647 <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>
25648 <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>
25649 <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>
25650 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>
25651 <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
25652 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>
25653 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>
25654 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>
25655 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>
25656 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>,
25657 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>
25658 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>,
25659 <a href="#7.28.2.2">7.28.2.2</a>
25660 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>
25661 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>
25662 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>
25663 lexical elements, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>
25664 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>
25665 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>
25666 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>
25667 labeled statement, <a href="#6.8.1">6.8.1</a> future directions, <a href="#7.30">7.30</a>
25668 labs function, <a href="#7.22.6.1">7.22.6.1</a> summary, <a href="#B">B</a>
25669 language, <a href="#6">6</a> terms, <a href="#7.1.1">7.1.1</a>
25670 future directions, <a href="#6.11">6.11</a> use of functions, <a href="#7.1.4">7.1.4</a>
25671 syntax summary, <a href="#A">A</a> lifetime, <a href="#6.2.4">6.2.4</a>
25672 Latin alphabet, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.2.1">6.4.2.1</a> limits
25674 [<a name="p666" href="#p666">page 666</a>] (<a href="#Contents">Contents</a>)
25676 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>
25677 implementation, see implementation limits long double _Imaginary type, <a href="#G.2">G.2</a>
25678 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>
25679 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>,
25680 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>
25681 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>,
25682 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>
25683 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>,
25684 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>
25685 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>,
25686 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>
25687 <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>
25688 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>,
25689 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>
25690 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>,
25691 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>
25692 <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>
25693 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>
25694 <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>
25695 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>,
25696 llrint type-generic macro, <a href="#7.24">7.24</a> <a href="#7.22.4.7">7.22.4.7</a>
25697 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>
25698 llround type-generic macro, <a href="#7.24">7.24</a> low-order bit, <a href="#3.6">3.6</a>
25699 local time, <a href="#7.26.1">7.26.1</a> lowercase letter, <a href="#5.2.1">5.2.1</a>
25700 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>
25701 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>
25702 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>
25703 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>
25704 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>,
25705 localtime function, <a href="#7.26.3.4">7.26.3.4</a> <a href="#6.7.2.4">6.7.2.4</a>
25706 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>,
25707 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>
25708 log type-generic macro, <a href="#7.24">7.24</a>
25709 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>
25710 log10 type-generic macro, <a href="#7.24">7.24</a> macro definition
25711 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>
25712 log1p type-generic macro, <a href="#7.24">7.24</a> macro invocation, <a href="#6.10.3">6.10.3</a>
25713 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>
25714 log2 type-generic macro, <a href="#7.24">7.24</a> length, <a href="#5.2.4.1">5.2.4.1</a>
25715 logarithmic functions predefined, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a>
25716 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>
25717 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>
25718 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>
25719 logb type-generic macro, <a href="#7.24">7.24</a> macro preprocessor, <a href="#6.10">6.10</a>
25720 logical operators macro replacement, <a href="#6.10.3">6.10.3</a>
25721 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>
25722 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>,
25723 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>
25724 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>
25725 long double _Complex type, <a href="#6.2.5">6.2.5</a> manipulation functions
25726 long double _Complex type conversion, complex, <a href="#7.3.9">7.3.9</a>
25728 [<a name="p667" href="#p667">page 667</a>] (<a href="#Contents">Contents</a>)
25730 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>
25731 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>
25732 <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>
25733 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>
25734 <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>
25735 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>
25736 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>
25737 MATH_ERRNO macro, <a href="#7.12">7.12</a> mtx_lock function, <a href="#7.25.4.3">7.25.4.3</a>
25738 max_align_t type, <a href="#7.19">7.19</a> mtx_t type, <a href="#7.25.1">7.25.1</a>
25739 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>
25740 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>
25741 <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>,
25742 <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>
25743 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>
25744 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
25745 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>
25746 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>
25747 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>
25748 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>
25749 <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>
25750 <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>
25751 mbsinit function, <a href="#7.28.6.2.1">7.28.6.2.1</a> multibyte/wide character conversion functions,
25752 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>
25753 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>
25754 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>
25755 <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,
25756 <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>
25757 <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>
25758 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>
25759 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>
25760 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>,
25761 <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>
25762 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>
25763 member alignment, <a href="#6.7.2.1">6.7.2.1</a>
25764 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>
25765 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>
25766 memcpy function, <a href="#7.23.2.1">7.23.2.1</a> name
25767 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>
25768 memmove function, <a href="#7.23.2.2">7.23.2.2</a> file, <a href="#7.21.3">7.21.3</a>
25769 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>
25770 memory location, <a href="#3.14">3.14</a> label, <a href="#6.2.3">6.2.3</a>
25771 memory management functions, <a href="#7.22.3">7.22.3</a> structure/union member, <a href="#6.2.3">6.2.3</a>
25772 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>
25773 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>
25774 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>
25775 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>
25776 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>
25777 miscellaneous functions NDEBUG macro, <a href="#7.2">7.2</a>
25778 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>,
25779 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>
25780 mktime function, <a href="#7.26.2.3">7.26.2.3</a> nearbyint type-generic macro, <a href="#7.24">7.24</a>
25782 [<a name="p668" href="#p668">page 668</a>] (<a href="#Contents">Contents</a>)
25784 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>
25785 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>
25786 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>
25787 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>
25788 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>
25789 <a href="#7.4.1.10">7.4.1.10</a> alignof, <a href="#6.5.3.4">6.5.3.4</a>
25790 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>
25791 <a href="#F.10.8.3">F.10.8.3</a> associativity, <a href="#6.5">6.5</a>
25792 nextafter type-generic macro, <a href="#7.24">7.24</a> equality, <a href="#6.5.9">6.5.9</a>
25793 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>
25794 nexttoward type-generic macro, <a href="#7.24">7.24</a> postfix, <a href="#6.5.2">6.5.2</a>
25795 no linkage, <a href="#6.2.2">6.2.2</a> precedence, <a href="#6.5">6.5</a>
25796 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>
25797 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>
25798 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>
25799 nonlocal jumps header, <a href="#7.13">7.13</a> sizeof, <a href="#6.5.3.4">6.5.3.4</a>
25800 norm, complex, <a href="#7.3.8.1">7.3.8.1</a> unary, <a href="#6.5.3">6.5.3</a>
25801 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>
25802 not macro, <a href="#7.9">7.9</a> optional features, see conditional features
25803 not-equal-to operator, see inequality operator or macro, <a href="#7.9">7.9</a>
25804 not_eq macro, <a href="#7.9">7.9</a> OR operators
25805 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>
25806 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>
25807 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>
25808 <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>
25809 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>
25810 null pointer constant, <a href="#6.3.2.3">6.3.2.3</a> or_eq macro, <a href="#7.9">7.9</a>
25811 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>
25812 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>,
25813 null wide character, <a href="#7.1.1">7.1.1</a> see also sequence points
25814 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>
25815 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>
25816 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>
25817 numerical limits, <a href="#5.2.4.2">5.2.4.2</a> outer scope, <a href="#6.2.1">6.2.1</a>
25818 over-aligned, <a href="#6.2.8">6.2.8</a>
25819 object, <a href="#3.15">3.15</a>
25820 object representation, <a href="#6.2.6.1">6.2.6.1</a> padding
25821 object type, <a href="#6.2.5">6.2.5</a> binary stream, <a href="#7.21.2">7.21.2</a>
25822 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>
25823 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>
25824 obsolescence, <a href="#6.11">6.11</a>, <a href="#7.30">7.30</a> parameter, <a href="#3.16">3.16</a>
25825 octal constant, <a href="#6.4.4.1">6.4.4.1</a> array, <a href="#6.9.1">6.9.1</a>
25826 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>
25827 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>
25828 <a href="#6.4.4.4">6.4.4.4</a> macro, <a href="#6.10.3">6.10.3</a>
25829 offsetof macro, <a href="#7.19">7.19</a> main function, <a href="#5.1.2.2.1">5.1.2.2.1</a>
25830 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>
25831 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>
25832 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>
25833 ones' complement, <a href="#6.2.6.2">6.2.6.2</a> parenthesized expression, <a href="#6.5.1">6.5.1</a>
25834 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>
25836 [<a name="p669" href="#p669">page 669</a>] (<a href="#Contents">Contents</a>)
25838 perform a trap, <a href="#3.19.5">3.19.5</a> preprocessor, <a href="#6.10">6.10</a>
25839 permitted form of initializer, <a href="#6.6">6.6</a> PRIcFASTN macros, <a href="#7.8.1">7.8.1</a>
25840 perror function, <a href="#7.21.10.4">7.21.10.4</a> PRIcLEASTN macros, <a href="#7.8.1">7.8.1</a>
25841 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>
25842 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>
25843 placemarker, <a href="#6.10.3.3">6.10.3.3</a> PRIcPTR macros, <a href="#7.8.1">7.8.1</a>
25844 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>
25845 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>,
25846 pointer comparison, <a href="#6.5.8">6.5.8</a> <a href="#K.3.5.3.3">K.3.5.3.3</a>
25847 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>
25848 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>
25849 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>
25850 pointer type, <a href="#6.2.5">6.2.5</a> program diagnostics, <a href="#7.2.1">7.2.1</a>
25851 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>
25852 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>
25853 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>
25854 <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>
25855 <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>
25856 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>
25857 position indicator, file, see file position indicator program structure, <a href="#5.1.1.1">5.1.1.1</a>
25858 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>,
25859 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>
25860 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>
25861 postfix expressions, <a href="#6.5.2">6.5.2</a> program, strictly conforming, <a href="#4">4</a>
25862 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
25863 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>
25864 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>
25865 power functions prototype, see function prototype
25866 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>
25867 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>
25868 pp-number, <a href="#6.4.8">6.4.8</a> PTRDIFF_MIN macro, <a href="#7.20.3">7.20.3</a>
25869 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>,
25870 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>
25871 precedence of operators, <a href="#6.5">6.5</a> punctuators, <a href="#6.4.6">6.4.6</a>
25872 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>
25873 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>
25874 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>
25875 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>
25876 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>
25877 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>
25878 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>
25879 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>
25880 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>
25881 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>
25882 preprocessing operators question-mark escape sequence (\?), <a href="#6.4.4.4">6.4.4.4</a>
25883 #, <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>,
25884 ##, <a href="#6.10.3.3">6.10.3.3</a> <a href="#7.22.4.7">7.22.4.7</a>
25885 _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>
25886 defined, <a href="#6.10.1">6.10.1</a>
25887 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>
25888 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>
25890 [<a name="p670" href="#p670">page 670</a>] (<a href="#Contents">Contents</a>)
25892 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>
25893 range return statement, <a href="#6.8.6.4">6.8.6.4</a>, <a href="#F.6">F.6</a>
25894 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>,
25895 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>
25896 <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>
25897 <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>
25898 <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>
25899 <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>
25900 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>
25901 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>
25902 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>
25903 <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>,
25904 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>,
25905 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>,
25906 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>,
25907 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>,
25908 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>,
25909 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>,
25910 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>,
25911 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>,
25912 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>,
25913 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>
25914 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>,
25915 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>
25916 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>
25917 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>
25918 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>
25919 release fence, <a href="#7.17.4">7.17.4</a>
25920 release operation, <a href="#5.1.2.4">5.1.2.4</a> same scope, <a href="#6.2.1">6.2.1</a>
25921 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>
25922 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>
25923 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>
25924 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>
25925 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>
25926 <a href="#F.10.7.2">F.10.7.2</a> scalbn type-generic macro, <a href="#7.24">7.24</a>
25927 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>
25928 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>
25929 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>
25930 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>
25931 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>
25932 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>
25933 representations of types, <a href="#6.2.6">6.2.6</a> SCNcFASTN macros, <a href="#7.8.1">7.8.1</a>
25934 pointer, <a href="#6.2.5">6.2.5</a> SCNcLEASTN macros, <a href="#7.8.1">7.8.1</a>
25935 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>
25936 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>
25937 restartable multibyte/wide character conversion SCNcPTR macros, <a href="#7.8.1">7.8.1</a>
25938 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>
25939 restartable multibyte/wide string conversion search functions
25940 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>
25941 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>
25942 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>
25944 [<a name="p671" href="#p671">page 671</a>] (<a href="#Contents">Contents</a>)
25946 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>
25947 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>
25948 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>
25949 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>
25950 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>
25951 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>
25952 <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>
25953 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>
25954 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>
25955 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>,
25956 <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>
25957 <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>
25958 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>
25959 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>,
25960 <a href="#6.5.16">6.5.16</a>, see also indeterminately sequenced, <a href="#6.3.1.8">6.3.1.8</a>
25961 unsequenced signed types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>
25962 sequencing of statements, <a href="#6.8">6.8</a> significand part, <a href="#6.4.4.2">6.4.4.2</a>
25963 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>
25964 <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>
25965 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>
25966 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>
25967 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>
25968 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>
25969 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,
25970 <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>
25971 shall, <a href="#4">4</a> single-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a>
25972 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>
25973 shift sequence, <a href="#7.1.1">7.1.1</a> singularity, <a href="#7.12.1">7.12.1</a>
25974 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>
25975 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>
25976 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>
25977 <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>,
25978 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>,
25979 <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>,
25980 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>
25981 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>
25982 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>,
25983 <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>
25984 <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>
25985 <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>
25986 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>
25987 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>
25988 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>
25989 <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>
25990 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>
25991 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>
25992 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>
25993 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>,
25994 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>
25995 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>
25996 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>
25998 [<a name="p672" href="#p672">page 672</a>] (<a href="#Contents">Contents</a>)
26000 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>
26001 sqrt type-generic macro, <a href="#7.24">7.24</a> else, <a href="#6.8.4.1">6.8.4.1</a>
26002 srand function, <a href="#7.22.2.2">7.22.2.2</a> expression, <a href="#6.8.3">6.8.3</a>
26003 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>
26004 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>
26005 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>
26006 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>
26007 <a href="#7.2"><assert.h></a>, <a href="#7.2">7.2</a> jump, <a href="#6.8.6">6.8.6</a>
26008 <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>
26009 <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>
26010 <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>
26011 <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>
26012 <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>
26013 <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>
26014 <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>
26015 <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>
26016 <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>
26017 <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>
26018 <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>
26019 <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>
26020 <a href="#J.5.17">J.5.17</a> static_assert macro, <a href="#7.2">7.2</a>
26021 <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>
26022 <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>
26023 <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>
26024 <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>
26025 <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>
26026 <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>,
26027 <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>
26028 <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>
26029 <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>,
26030 <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>,
26031 <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>
26032 <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>,
26033 <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>
26034 <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>
26035 <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>,
26036 <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>
26037 <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>,
26038 <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>
26039 <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>
26040 <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>
26041 <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>
26042 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>
26043 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>
26044 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>
26045 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>
26046 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>
26047 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>
26048 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>
26049 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>
26050 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>
26052 [<a name="p673" href="#p673">page 673</a>] (<a href="#Contents">Contents</a>)
26054 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>
26055 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>
26056 line buffered, <a href="#7.21.3">7.21.3</a> strtoumax function, <a href="#7.8.2.3">7.8.2.3</a>
26057 orientation, <a href="#7.21.2">7.21.2</a> struct hack, see flexible array member
26058 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>
26059 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>
26060 standard output, <a href="#7.21.1">7.21.1</a>, <a href="#7.21.3">7.21.3</a> structure
26061 unbuffered, <a href="#7.21.3">7.21.3</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
26062 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>
26063 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>
26064 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>
26065 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>
26066 <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>
26067 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>
26068 strictly conforming program, <a href="#4">4</a> pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a>
26069 string, <a href="#7.1.1">7.1.1</a> specifier, <a href="#6.7.2.1">6.7.2.1</a>
26070 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>
26071 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>
26072 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>
26073 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>
26074 library function conventions, <a href="#7.23.1">7.23.1</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
26075 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>
26076 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>
26077 numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.22.1">7.22.1</a> suffix
26078 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>
26079 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>
26080 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>
26081 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>
26082 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>
26083 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>
26084 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>,
26085 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>
26086 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>
26087 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>
26088 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>
26089 stronger, <a href="#6.2.8">6.2.8</a> symbols, <a href="#3">3</a>
26090 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>
26091 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>
26092 strspn function, <a href="#7.23.5.6">7.23.5.6</a> syntactic categories, <a href="#6.1">6.1</a>
26093 strstr function, <a href="#7.23.5.7">7.23.5.7</a> syntax notation, <a href="#6.1">6.1</a>
26094 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>
26095 <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>
26096 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>
26097 strtoimax function, <a href="#7.8.2.3">7.8.2.3</a>
26098 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>
26099 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>
26100 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>
26101 <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>
26102 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>
26103 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>
26104 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>
26106 [<a name="p674" href="#p674">page 674</a>] (<a href="#Contents">Contents</a>)
26108 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>
26109 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>
26110 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>
26111 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>
26112 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>
26113 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>
26114 tgamma type-generic macro, <a href="#7.24">7.24</a> translation phases, <a href="#5.1.1.2">5.1.1.2</a>
26115 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>
26116 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
26117 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>,
26118 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>
26119 thrd_equal function, <a href="#7.25.5.4">7.25.5.4</a> trigonometric functions
26120 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>
26121 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>
26122 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>
26123 thrd_start_t type, <a href="#7.25.1">7.25.1</a> true macro, <a href="#7.18">7.18</a>
26124 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>
26125 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>
26126 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>
26127 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>
26128 threads header, <a href="#7.25">7.25</a> tss_create function, <a href="#7.25.6.1">7.25.6.1</a>
26129 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>
26130 time TSS_DTOR_ITERATIONS macro, <a href="#7.25.1">7.25.1</a>
26131 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>
26132 <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>
26133 <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>
26134 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>
26135 <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>
26136 <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>
26137 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>
26138 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>
26139 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>
26140 local, <a href="#7.26.1">7.26.1</a> type names, <a href="#6.7.7">6.7.7</a>
26141 manipulation functions, <a href="#7.26.2">7.26.2</a> type punning, <a href="#6.5.2.3">6.5.2.3</a>
26142 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>
26143 time function, <a href="#7.26.2.4">7.26.2.4</a> type specifiers, <a href="#6.7.2">6.7.2</a>
26144 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>
26145 time_t type, <a href="#7.26.1">7.26.1</a> typedef declaration, <a href="#6.7.8">6.7.8</a>
26146 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>
26147 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>
26148 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>,
26149 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>
26150 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>
26151 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>
26152 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>
26153 <a href="#K.3.5.1.2">K.3.5.1.2</a> composite, <a href="#6.2.7">6.2.7</a>
26154 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>
26155 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>
26156 token concatenation, <a href="#6.10.3.3">6.10.3.3</a> imaginary, <a href="#G">G</a>
26157 token pasting, <a href="#6.10.3.3">6.10.3.3</a> restrict qualified, <a href="#6.7.3">6.7.3</a>
26158 tolower function, <a href="#7.4.2.1">7.4.2.1</a> volatile qualified, <a href="#6.7.3">6.7.3</a>
26160 [<a name="p675" href="#p675">page 675</a>] (<a href="#Contents">Contents</a>)
26162 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>
26163 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>
26164 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>
26165 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>
26166 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
26167 uint_least32_t type, <a href="#7.27">7.27</a> indeterminately sequenced, sequenced
26168 UINT_LEASTN_MAX macros, <a href="#7.20.2.2">7.20.2.2</a> before
26169 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>
26170 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>
26171 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>
26172 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>,
26173 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>
26174 <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>,
26175 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>
26176 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>
26177 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>
26178 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>
26179 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>
26180 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>
26181 <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>,
26182 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>
26183 <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>
26184 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>
26185 unary expression, <a href="#6.5.3">6.5.3</a> UTF-8 string literal, see string literal
26186 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>
26187 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>
26188 unary plus operator (+), <a href="#6.5.3.3">6.5.3.3</a>
26189 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>,
26190 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>,
26191 <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>,
26192 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>,
26193 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>,
26194 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>
26195 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>,
26196 <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>
26197 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>,
26198 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>,
26199 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>,
26200 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>,
26201 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>,
26202 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>
26203 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>
26204 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>,
26205 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>,
26206 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>,
26207 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>,
26208 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>,
26209 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>,
26210 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>
26211 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>
26212 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>
26214 [<a name="p676" href="#p676">page 676</a>] (<a href="#Contents">Contents</a>)
26216 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>
26217 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>
26218 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>
26219 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>
26220 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>
26221 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>
26222 <a href="#7.4.1.10">7.4.1.10</a>
26223 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>
26224 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>,
26225 <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>
26226 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>
26227 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>
26228 <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>,
26229 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>,
26230 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>
26231 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>,
26232 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>,
26233 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>
26234 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>
26235 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>
26236 VLA, see variable length array wcscat_s function, <a href="#K.3.9.2.2.1">K.3.9.2.2.1</a>
26237 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>
26238 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>
26239 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>
26240 <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>
26241 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>
26242 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>
26243 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>
26244 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>
26245 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>
26246 <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>
26247 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>
26248 <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>
26249 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>
26250 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>
26251 <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>
26252 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>
26253 <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>
26254 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>
26255 <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>
26256 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>
26257 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>
26258 <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>
26259 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>
26260 <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>
26261 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>
26262 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>
26263 <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>,
26264 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>
26265 <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>
26266 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>
26268 [<a name="p677" href="#p677">page 677</a>] (<a href="#Contents">Contents</a>)
26270 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>
26271 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>
26272 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>
26273 <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>
26274 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>
26275 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>
26276 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>
26277 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>
26278 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>,
26279 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>
26280 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>
26281 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>,
26282 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>
26283 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>
26284 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>
26285 weaker, <a href="#6.2.8">6.2.8</a> xor macro, <a href="#7.9">7.9</a>
26286 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>
26287 <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>,
26288 <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>
26289 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>
26290 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>,
26291 <a href="#7.29.2.1.10">7.29.2.1.10</a>
26292 white-space characters, <a href="#6.4">6.4</a>
26293 wide character, <a href="#3.7.3">3.7.3</a>
26294 case mapping functions, <a href="#7.29.3.1">7.29.3.1</a>
26295 extensible, <a href="#7.29.3.2">7.29.3.2</a>
26296 classification functions, <a href="#7.29.2.1">7.29.2.1</a>
26297 extensible, <a href="#7.29.2.2">7.29.2.2</a>
26298 constant, <a href="#6.4.4.4">6.4.4.4</a>
26299 formatted input/output functions, <a href="#7.28.2">7.28.2</a>,
26300 <a href="#K.3.9.1">K.3.9.1</a>
26301 input functions, <a href="#7.21.1">7.21.1</a>
26302 input/output functions, <a href="#7.21.1">7.21.1</a>, <a href="#7.28.3">7.28.3</a>
26303 output functions, <a href="#7.21.1">7.21.1</a>
26304 single-byte conversion functions, <a href="#7.28.6.1">7.28.6.1</a>
26305 wide string, <a href="#7.1.1">7.1.1</a>
26306 wide string comparison functions, <a href="#7.28.4.4">7.28.4.4</a>
26307 wide string concatenation functions, <a href="#7.28.4.3">7.28.4.3</a>,
26308 <a href="#K.3.9.2.2">K.3.9.2.2</a>
26309 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>
26310 wide string literal, see string literal
26311 wide string miscellaneous functions, <a href="#7.28.4.6">7.28.4.6</a>,
26312 <a href="#K.3.9.2.4">K.3.9.2.4</a>
26313 wide string numeric conversion functions, <a href="#7.8.2.4">7.8.2.4</a>,
26314 <a href="#7.28.4.1">7.28.4.1</a>
26315 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>
26316 wide-oriented stream, <a href="#7.21.2">7.21.2</a>
26317 width, <a href="#6.2.6.2">6.2.6.2</a>
26318 WINT_MAX macro, <a href="#7.20.3">7.20.3</a>
26319 WINT_MIN macro, <a href="#7.20.3">7.20.3</a>
26320 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>,
26322 [<a name="p678" href="#p678">page 678</a>] (<a href="#Contents">Contents</a>)
26323 </pre></body></html>
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