1 <html><head><title>WG14/N1256 Septermber 7, 2007 ISO/IEC 9899:TC3</title></head><body>
3 WG14/N1256 Committee Draft -- Septermber 7, 2007 ISO/IEC 9899:TC3
8 <h2><a name="Contents" href="#Contents">Contents</a></h2>
10 <li><a href="#Foreword">Foreword</a>
11 <li><a href="#Introduction">Introduction</a>
12 <li><a href="#1">1. Scope</a>
13 <li><a href="#2">2. Normative references</a>
14 <li><a href="#3">3. Terms, definitions, and symbols</a>
15 <li><a href="#4">4. Conformance</a>
16 <li><a href="#5">5. Environment</a>
18 <li><a href="#5.1"> 5.1 Conceptual models</a>
20 <li><a href="#5.1.1"> 5.1.1 Translation environment</a>
21 <li><a href="#5.1.2"> 5.1.2 Execution environments</a>
23 <li><a href="#5.2"> 5.2 Environmental considerations</a>
25 <li><a href="#5.2.1"> 5.2.1 Character sets</a>
26 <li><a href="#5.2.2"> 5.2.2 Character display semantics</a>
27 <li><a href="#5.2.3"> 5.2.3 Signals and interrupts</a>
28 <li><a href="#5.2.4"> 5.2.4 Environmental limits</a>
31 <li><a href="#6">6. Language</a>
33 <li><a href="#6.1"> 6.1 Notation</a>
34 <li><a href="#6.2"> 6.2 Concepts</a>
36 <li><a href="#6.2.1"> 6.2.1 Scopes of identifiers</a>
37 <li><a href="#6.2.2"> 6.2.2 Linkages of identifiers</a>
38 <li><a href="#6.2.3"> 6.2.3 Name spaces of identifiers</a>
39 <li><a href="#6.2.4"> 6.2.4 Storage durations of objects</a>
40 <li><a href="#6.2.5"> 6.2.5 Types</a>
41 <li><a href="#6.2.6"> 6.2.6 Representations of types</a>
42 <li><a href="#6.2.7"> 6.2.7 Compatible type and composite type</a>
44 <li><a href="#6.3"> 6.3 Conversions</a>
46 <li><a href="#6.3.1"> 6.3.1 Arithmetic operands</a>
47 <li><a href="#6.3.2"> 6.3.2 Other operands</a>
49 <li><a href="#6.4"> 6.4 Lexical elements</a>
51 <li><a href="#6.4.1"> 6.4.1 Keywords</a>
52 <li><a href="#6.4.2"> 6.4.2 Identifiers</a>
53 <li><a href="#6.4.3"> 6.4.3 Universal character names</a>
54 <li><a href="#6.4.4"> 6.4.4 Constants</a>
55 <li><a href="#6.4.5"> 6.4.5 String literals</a>
56 <li><a href="#6.4.6"> 6.4.6 Punctuators</a>
57 <li><a href="#6.4.7"> 6.4.7 Header names</a>
58 <li><a href="#6.4.8"> 6.4.8 Preprocessing numbers</a>
59 <li><a href="#6.4.9"> 6.4.9 Comments</a>
61 <li><a href="#6.5"> 6.5 Expressions</a>
64 <li><a href="#6.5.1"> 6.5.1 Primary expressions</a>
65 <li><a href="#6.5.2"> 6.5.2 Postfix operators</a>
66 <li><a href="#6.5.3"> 6.5.3 Unary operators</a>
67 <li><a href="#6.5.4"> 6.5.4 Cast operators</a>
68 <li><a href="#6.5.5"> 6.5.5 Multiplicative operators</a>
69 <li><a href="#6.5.6"> 6.5.6 Additive operators</a>
70 <li><a href="#6.5.7"> 6.5.7 Bitwise shift operators</a>
71 <li><a href="#6.5.8"> 6.5.8 Relational operators</a>
72 <li><a href="#6.5.9"> 6.5.9 Equality operators</a>
73 <li><a href="#6.5.10"> 6.5.10 Bitwise AND operator</a>
74 <li><a href="#6.5.11"> 6.5.11 Bitwise exclusive OR operator</a>
75 <li><a href="#6.5.12"> 6.5.12 Bitwise inclusive OR operator</a>
76 <li><a href="#6.5.13"> 6.5.13 Logical AND operator</a>
77 <li><a href="#6.5.14"> 6.5.14 Logical OR operator</a>
78 <li><a href="#6.5.15"> 6.5.15 Conditional operator</a>
79 <li><a href="#6.5.16"> 6.5.16 Assignment operators</a>
80 <li><a href="#6.5.17"> 6.5.17 Comma operator</a>
82 <li><a href="#6.6"> 6.6 Constant expressions</a>
83 <li><a href="#6.7"> 6.7 Declarations</a>
85 <li><a href="#6.7.1"> 6.7.1 Storage-class specifiers</a>
86 <li><a href="#6.7.2"> 6.7.2 Type specifiers</a>
87 <li><a href="#6.7.3"> 6.7.3 Type qualifiers</a>
88 <li><a href="#6.7.4"> 6.7.4 Function specifiers</a>
89 <li><a href="#6.7.5"> 6.7.5 Declarators</a>
90 <li><a href="#6.7.6"> 6.7.6 Type names</a>
91 <li><a href="#6.7.7"> 6.7.7 Type definitions</a>
92 <li><a href="#6.7.8"> 6.7.8 Initialization</a>
94 <li><a href="#6.8"> 6.8 Statements and blocks</a>
96 <li><a href="#6.8.1"> 6.8.1 Labeled statements</a>
97 <li><a href="#6.8.2"> 6.8.2 Compound statement</a>
98 <li><a href="#6.8.3"> 6.8.3 Expression and null statements</a>
99 <li><a href="#6.8.4"> 6.8.4 Selection statements</a>
100 <li><a href="#6.8.5"> 6.8.5 Iteration statements</a>
101 <li><a href="#6.8.6"> 6.8.6 Jump statements</a>
103 <li><a href="#6.9"> 6.9 External definitions</a>
105 <li><a href="#6.9.1"> 6.9.1 Function definitions</a>
106 <li><a href="#6.9.2"> 6.9.2 External object definitions</a>
108 <li><a href="#6.10"> 6.10 Preprocessing directives</a>
110 <li><a href="#6.10.1"> 6.10.1 Conditional inclusion</a>
111 <li><a href="#6.10.2"> 6.10.2 Source file inclusion</a>
112 <li><a href="#6.10.3"> 6.10.3 Macro replacement</a>
113 <li><a href="#6.10.4"> 6.10.4 Line control</a>
114 <li><a href="#6.10.5"> 6.10.5 Error directive</a>
115 <li><a href="#6.10.6"> 6.10.6 Pragma directive</a>
117 <li><a href="#6.10.7"> 6.10.7 Null directive</a>
118 <li><a href="#6.10.8"> 6.10.8 Predefined macro names</a>
119 <li><a href="#6.10.9"> 6.10.9 Pragma operator</a>
121 <li><a href="#6.11"> 6.11 Future language directions</a>
123 <li><a href="#6.11.1"> 6.11.1 Floating types</a>
124 <li><a href="#6.11.2"> 6.11.2 Linkages of identifiers</a>
125 <li><a href="#6.11.3"> 6.11.3 External names</a>
126 <li><a href="#6.11.4"> 6.11.4 Character escape sequences</a>
127 <li><a href="#6.11.5"> 6.11.5 Storage-class specifiers</a>
128 <li><a href="#6.11.6"> 6.11.6 Function declarators</a>
129 <li><a href="#6.11.7"> 6.11.7 Function definitions</a>
130 <li><a href="#6.11.8"> 6.11.8 Pragma directives</a>
131 <li><a href="#6.11.9"> 6.11.9 Predefined macro names</a>
134 <li><a href="#7">7. Library</a>
136 <li><a href="#7.1"> 7.1 Introduction</a>
138 <li><a href="#7.1.1"> 7.1.1 Definitions of terms</a>
139 <li><a href="#7.1.2"> 7.1.2 Standard headers</a>
140 <li><a href="#7.1.3"> 7.1.3 Reserved identifiers</a>
141 <li><a href="#7.1.4"> 7.1.4 Use of library functions</a>
143 <li><a href="#7.2"> 7.2 Diagnostics <assert.h></a>
145 <li><a href="#7.2.1"> 7.2.1 Program diagnostics</a>
147 <li><a href="#7.3"> 7.3 Complex arithmetic <complex.h></a>
149 <li><a href="#7.3.1"> 7.3.1 Introduction</a>
150 <li><a href="#7.3.2"> 7.3.2 Conventions</a>
151 <li><a href="#7.3.3"> 7.3.3 Branch cuts</a>
152 <li><a href="#7.3.4"> 7.3.4 The CX_LIMITED_RANGE pragma</a>
153 <li><a href="#7.3.5"> 7.3.5 Trigonometric functions</a>
154 <li><a href="#7.3.6"> 7.3.6 Hyperbolic functions</a>
155 <li><a href="#7.3.7"> 7.3.7 Exponential and logarithmic functions</a>
156 <li><a href="#7.3.8"> 7.3.8 Power and absolute-value functions</a>
157 <li><a href="#7.3.9"> 7.3.9 Manipulation functions</a>
159 <li><a href="#7.4"> 7.4 Character handling <ctype.h></a>
161 <li><a href="#7.4.1"> 7.4.1 Character classification functions</a>
162 <li><a href="#7.4.2"> 7.4.2 Character case mapping functions</a>
164 <li><a href="#7.5"> 7.5 Errors <errno.h></a>
165 <li><a href="#7.6"> 7.6 Floating-point environment <fenv.h></a>
167 <li><a href="#7.6.1"> 7.6.1 The FENV_ACCESS pragma</a>
168 <li><a href="#7.6.2"> 7.6.2 Floating-point exceptions</a>
169 <li><a href="#7.6.3"> 7.6.3 Rounding</a>
170 <li><a href="#7.6.4"> 7.6.4 Environment</a>
172 <li><a href="#7.7"> 7.7 Characteristics of floating types <float.h></a>
173 <li><a href="#7.8"> 7.8 Format conversion of integer types <inttypes.h></a>
175 <li><a href="#7.8.1"> 7.8.1 Macros for format specifiers</a>
176 <li><a href="#7.8.2"> 7.8.2 Functions for greatest-width integer types</a>
179 <li><a href="#7.9"> 7.9 Alternative spellings <iso646.h></a>
180 <li><a href="#7.10"> 7.10 Sizes of integer types <limits.h></a>
181 <li><a href="#7.11"> 7.11 Localization <locale.h></a>
183 <li><a href="#7.11.1"> 7.11.1 Locale control</a>
184 <li><a href="#7.11.2"> 7.11.2 Numeric formatting convention inquiry</a>
186 <li><a href="#7.12"> 7.12 Mathematics <math.h></a>
188 <li><a href="#7.12.1"> 7.12.1 Treatment of error conditions</a>
189 <li><a href="#7.12.2"> 7.12.2 The FP_CONTRACT pragma</a>
190 <li><a href="#7.12.3"> 7.12.3 Classification macros</a>
191 <li><a href="#7.12.4"> 7.12.4 Trigonometric functions</a>
192 <li><a href="#7.12.5"> 7.12.5 Hyperbolic functions</a>
193 <li><a href="#7.12.6"> 7.12.6 Exponential and logarithmic functions</a>
194 <li><a href="#7.12.7"> 7.12.7 Power and absolute-value functions</a>
195 <li><a href="#7.12.8"> 7.12.8 Error and gamma functions</a>
196 <li><a href="#7.12.9"> 7.12.9 Nearest integer functions</a>
197 <li><a href="#7.12.10"> 7.12.10 Remainder functions</a>
198 <li><a href="#7.12.11"> 7.12.11 Manipulation functions</a>
199 <li><a href="#7.12.12"> 7.12.12 Maximum, minimum, and positive difference functions</a>
200 <li><a href="#7.12.13"> 7.12.13 Floating multiply-add</a>
201 <li><a href="#7.12.14"> 7.12.14 Comparison macros</a>
203 <li><a href="#7.13"> 7.13 Nonlocal jumps <setjmp.h></a>
205 <li><a href="#7.13.1"> 7.13.1 Save calling environment</a>
206 <li><a href="#7.13.2"> 7.13.2 Restore calling environment</a>
208 <li><a href="#7.14"> 7.14 Signal handling <signal.h></a>
210 <li><a href="#7.14.1"> 7.14.1 Specify signal handling</a>
211 <li><a href="#7.14.2"> 7.14.2 Send signal</a>
213 <li><a href="#7.15"> 7.15 Variable arguments <stdarg.h></a>
215 <li><a href="#7.15.1"> 7.15.1 Variable argument list access macros</a>
217 <li><a href="#7.16"> 7.16 Boolean type and values <stdbool.h></a>
218 <li><a href="#7.17"> 7.17 Common definitions <stddef.h></a>
219 <li><a href="#7.18"> 7.18 Integer types <stdint.h></a>
221 <li><a href="#7.18.1"> 7.18.1 Integer types</a>
222 <li><a href="#7.18.2"> 7.18.2 Limits of specified-width integer types</a>
223 <li><a href="#7.18.3"> 7.18.3 Limits of other integer types</a>
224 <li><a href="#7.18.4"> 7.18.4 Macros for integer constants</a>
226 <li><a href="#7.19"> 7.19 Input/output <stdio.h></a>
228 <li><a href="#7.19.1"> 7.19.1 Introduction</a>
229 <li><a href="#7.19.2"> 7.19.2 Streams</a>
230 <li><a href="#7.19.3"> 7.19.3 Files</a>
231 <li><a href="#7.19.4"> 7.19.4 Operations on files</a>
232 <li><a href="#7.19.5"> 7.19.5 File access functions</a>
233 <li><a href="#7.19.6"> 7.19.6 Formatted input/output functions</a>
234 <li><a href="#7.19.7"> 7.19.7 Character input/output functions</a>
235 <li><a href="#7.19.8"> 7.19.8 Direct input/output functions</a>
237 <li><a href="#7.19.9"> 7.19.9 File positioning functions</a>
238 <li><a href="#7.19.10"> 7.19.10 Error-handling functions</a>
240 <li><a href="#7.20"> 7.20 General utilities <stdlib.h></a>
242 <li><a href="#7.20.1"> 7.20.1 Numeric conversion functions</a>
243 <li><a href="#7.20.2"> 7.20.2 Pseudo-random sequence generation functions</a>
244 <li><a href="#7.20.3"> 7.20.3 Memory management functions</a>
245 <li><a href="#7.20.4"> 7.20.4 Communication with the environment</a>
246 <li><a href="#7.20.5"> 7.20.5 Searching and sorting utilities</a>
247 <li><a href="#7.20.6"> 7.20.6 Integer arithmetic functions</a>
248 <li><a href="#7.20.7"> 7.20.7 Multibyte/wide character conversion functions</a>
249 <li><a href="#7.20.8"> 7.20.8 Multibyte/wide string conversion functions</a>
251 <li><a href="#7.21"> 7.21 String handling <string.h></a>
253 <li><a href="#7.21.1"> 7.21.1 String function conventions</a>
254 <li><a href="#7.21.2"> 7.21.2 Copying functions</a>
255 <li><a href="#7.21.3"> 7.21.3 Concatenation functions</a>
256 <li><a href="#7.21.4"> 7.21.4 Comparison functions</a>
257 <li><a href="#7.21.5"> 7.21.5 Search functions</a>
258 <li><a href="#7.21.6"> 7.21.6 Miscellaneous functions</a>
260 <li><a href="#7.22"> 7.22 Type-generic math <tgmath.h></a>
261 <li><a href="#7.23"> 7.23 Date and time <time.h></a>
263 <li><a href="#7.23.1"> 7.23.1 Components of time</a>
264 <li><a href="#7.23.2"> 7.23.2 Time manipulation functions</a>
265 <li><a href="#7.23.3"> 7.23.3 Time conversion functions</a>
267 <li><a href="#7.24"> 7.24 Extended multibyte and wide character utilities <wchar.h></a>
269 <li><a href="#7.24.1"> 7.24.1 Introduction</a>
270 <li><a href="#7.24.2"> 7.24.2 Formatted wide character input/output functions</a>
271 <li><a href="#7.24.3"> 7.24.3 Wide character input/output functions</a>
272 <li><a href="#7.24.4"> 7.24.4 General wide string utilities</a>
273 <li><a href="#7.24.5"> 7.24.5 Wide character time conversion functions</a>
274 <li><a href="#7.24.6"> 7.24.6 Extended multibyte/wide character conversion utilities</a>
276 <li><a href="#7.25"> 7.25 Wide character classification and mapping utilities <wctype.h></a>
278 <li><a href="#7.25.1"> 7.25.1 Introduction</a>
279 <li><a href="#7.25.2"> 7.25.2 Wide character classification utilities</a>
280 <li><a href="#7.25.3"> 7.25.3 Wide character case mapping utilities</a>
282 <li><a href="#7.26"> 7.26 Future library directions</a>
284 <li><a href="#7.26.1"> 7.26.1 Complex arithmetic <complex.h></a>
285 <li><a href="#7.26.2"> 7.26.2 Character handling <ctype.h></a>
286 <li><a href="#7.26.3"> 7.26.3 Errors <errno.h></a>
287 <li><a href="#7.26.4"> 7.26.4 Format conversion of integer types <inttypes.h></a>
288 <li><a href="#7.26.5"> 7.26.5 Localization <locale.h></a>
289 <li><a href="#7.26.6"> 7.26.6 Signal handling <signal.h></a>
290 <li><a href="#7.26.7"> 7.26.7 Boolean type and values <stdbool.h></a>
291 <li><a href="#7.26.8"> 7.26.8 Integer types <stdint.h></a>
292 <li><a href="#7.26.9"> 7.26.9 Input/output <stdio.h></a>
294 <li><a href="#7.26.10"> 7.26.10 General utilities <stdlib.h></a>
295 <li><a href="#7.26.11"> 7.26.11 String handling <string.h></a>
296 <li><a href="#7.26.12"> 7.26.12 Extended multibyte and wide character utilities <wchar.h></a>
297 <li><a href="#7.26.13"> 7.26.13 Wide character classification and mapping utilities <wctype.h></a>
300 <li><a href="#A">Annex A (informative) Language syntax summary</a>
302 <li><a href="#A.1"> A.1 Lexical grammar</a>
303 <li><a href="#A.2"> A.2 Phrase structure grammar</a>
304 <li><a href="#A.3"> A.3 Preprocessing directives</a>
306 <li><a href="#B">Annex B (informative) Library summary</a>
308 <li><a href="#B.1"> B.1 Diagnostics <assert.h></a>
309 <li><a href="#B.2"> B.2 Complex <complex.h></a>
310 <li><a href="#B.3"> B.3 Character handling <ctype.h></a>
311 <li><a href="#B.4"> B.4 Errors <errno.h></a>
312 <li><a href="#B.5"> B.5 Floating-point environment <fenv.h></a>
313 <li><a href="#B.6"> B.6 Characteristics of floating types <float.h></a>
314 <li><a href="#B.7"> B.7 Format conversion of integer types <inttypes.h></a>
315 <li><a href="#B.8"> B.8 Alternative spellings <iso646.h></a>
316 <li><a href="#B.9"> B.9 Sizes of integer types <limits.h></a>
317 <li><a href="#B.10"> B.10 Localization <locale.h></a>
318 <li><a href="#B.11"> B.11 Mathematics <math.h></a>
319 <li><a href="#B.12"> B.12 Nonlocal jumps <setjmp.h></a>
320 <li><a href="#B.13"> B.13 Signal handling <signal.h></a>
321 <li><a href="#B.14"> B.14 Variable arguments <stdarg.h></a>
322 <li><a href="#B.15"> B.15 Boolean type and values <stdbool.h></a>
323 <li><a href="#B.16"> B.16 Common definitions <stddef.h></a>
324 <li><a href="#B.17"> B.17 Integer types <stdint.h></a>
325 <li><a href="#B.18"> B.18 Input/output <stdio.h></a>
326 <li><a href="#B.19"> B.19 General utilities <stdlib.h></a>
327 <li><a href="#B.20"> B.20 String handling <string.h></a>
328 <li><a href="#B.21"> B.21 Type-generic math <tgmath.h></a>
329 <li><a href="#B.22"> B.22 Date and time <time.h></a>
330 <li><a href="#B.23"> B.23 Extended multibyte/wide character utilities <wchar.h></a>
331 <li><a href="#B.24"> B.24 Wide character classification and mapping utilities <wctype.h></a>
333 <li><a href="#C">Annex C (informative) Sequence points</a>
334 <li><a href="#D">Annex D (normative) Universal character names for identifiers</a>
335 <li><a href="#E">Annex E (informative) Implementation limits</a>
336 <li><a href="#F">Annex F (normative) IEC 60559 floating-point arithmetic</a>
338 <li><a href="#F.1"> F.1 Introduction</a>
339 <li><a href="#F.2"> F.2 Types</a>
340 <li><a href="#F.3"> F.3 Operators and functions</a>
342 <li><a href="#F.4"> F.4 Floating to integer conversion</a>
343 <li><a href="#F.5"> F.5 Binary-decimal conversion</a>
344 <li><a href="#F.6"> F.6 Contracted expressions</a>
345 <li><a href="#F.7"> F.7 Floating-point environment</a>
346 <li><a href="#F.8"> F.8 Optimization</a>
347 <li><a href="#F.9"> F.9 Mathematics <math.h></a>
349 <li><a href="#G">Annex G (informative) IEC 60559-compatible complex arithmetic</a>
351 <li><a href="#G.1"> G.1 Introduction</a>
352 <li><a href="#G.2"> G.2 Types</a>
353 <li><a href="#G.3"> G.3 Conventions</a>
354 <li><a href="#G.4"> G.4 Conversions</a>
355 <li><a href="#G.5"> G.5 Binary operators</a>
356 <li><a href="#G.6"> G.6 Complex arithmetic <complex.h></a>
357 <li><a href="#G.7"> G.7 Type-generic math <tgmath.h></a>
359 <li><a href="#H">Annex H (informative) Language independent arithmetic</a>
361 <li><a href="#H.1"> H.1 Introduction</a>
362 <li><a href="#H.2"> H.2 Types</a>
363 <li><a href="#H.3"> H.3 Notification</a>
365 <li><a href="#I">Annex I (informative) Common warnings</a>
366 <li><a href="#J">Annex J (informative) Portability issues</a>
368 <li><a href="#J.1"> J.1 Unspecified behavior</a>
369 <li><a href="#J.2"> J.2 Undefined behavior</a>
370 <li><a href="#J.3"> J.3 Implementation-defined behavior</a>
371 <li><a href="#J.4"> J.4 Locale-specific behavior</a>
372 <li><a href="#J.5"> J.5 Common extensions</a>
374 <li><a href="#Bibliography">Bibliography</a>
375 <li><a href="#Index">Index</a>
380 <h2><a name="Foreword" href="#Foreword">Foreword</a></h2>
382 ISO (the International Organization for Standardization) and IEC (the International
383 Electrotechnical Commission) form the specialized system for worldwide
384 standardization. National bodies that are member of ISO or IEC participate in the
385 development of International Standards through technical committees established by the
386 respective organization to deal with particular fields of technical activity. ISO and IEC
387 technical committees collaborate in fields of mutual interest. Other international
388 organizations, governmental and non-governmental, in liaison with ISO and IEC, also
389 take part in the work.
391 International Standards are drafted in accordance with the rules given in the ISO/IEC
394 In the field of information technology, ISO and IEC have established a joint technical
395 committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
396 committee are circulated to national bodies for voting. Publication as an International
397 Standard requires approval by at least 75% of the national bodies casting a vote.
399 International Standard ISO/IEC 9899 was prepared by Joint Technical Committee
400 ISO/IEC JTC 1, Information technology, Subcommittee SC 22, Programming languages,
401 their environments and system software interfaces. The Working Group responsible for
402 this standard (WG 14) maintains a site on the World Wide Web at
403 http://www.open-std.org/JTC1/SC22/WG14/ containing additional
404 information relevant to this standard such as a Rationale for many of the decisions made
405 during its preparation and a log of Defect Reports and Responses.
407 This second edition cancels and replaces the first edition, ISO/IEC 9899:1990, as
408 amended and corrected by ISO/IEC 9899/COR1:1994, ISO/IEC 9899/AMD1:1995, and
409 ISO/IEC 9899/COR2:1996. Major changes from the previous edition include:
411 <li> restricted character set support via digraphs and <a href="#7.9"><iso646.h></a> (originally specified
413 <li> wide character library support in <a href="#7.24"><wchar.h></a> and <a href="#7.25"><wctype.h></a> (originally
415 <li> more precise aliasing rules via effective type
416 <li> restricted pointers
417 <li> variable length arrays
418 <li> flexible array members
419 <li> static and type qualifiers in parameter array declarators
420 <li> complex (and imaginary) support in <a href="#7.3"><complex.h></a>
421 <li> type-generic math macros in <a href="#7.22"><tgmath.h></a>
422 <li> the long long int type and library functions
424 <li> increased minimum translation limits
425 <li> additional floating-point characteristics in <a href="#7.7"><float.h></a>
426 <li> remove implicit int
427 <li> reliable integer division
428 <li> universal character names (\u and \U)
429 <li> extended identifiers
430 <li> hexadecimal floating-point constants and %a and %A printf/scanf conversion
432 <li> compound literals
433 <li> designated initializers
435 <li> extended integer types and library functions in <a href="#7.8"><inttypes.h></a> and <a href="#7.18"><stdint.h></a>
436 <li> remove implicit function declaration
437 <li> preprocessor arithmetic done in intmax_t/uintmax_t
438 <li> mixed declarations and code
439 <li> new block scopes for selection and iteration statements
440 <li> integer constant type rules
441 <li> integer promotion rules
442 <li> macros with a variable number of arguments
443 <li> the vscanf family of functions in <a href="#7.19"><stdio.h></a> and <a href="#7.24"><wchar.h></a>
444 <li> additional math library functions in <a href="#7.12"><math.h></a>
445 <li> treatment of error conditions by math library functions (math_errhandling)
446 <li> floating-point environment access in <a href="#7.6"><fenv.h></a>
447 <li> IEC 60559 (also known as IEC 559 or IEEE arithmetic) support
448 <li> trailing comma allowed in enum declaration
449 <li> %lf conversion specifier allowed in printf
450 <li> inline functions
451 <li> the snprintf family of functions in <a href="#7.19"><stdio.h></a>
452 <li> boolean type in <a href="#7.16"><stdbool.h></a>
453 <li> idempotent type qualifiers
454 <li> empty macro arguments
456 <li> new structure type compatibility rules (tag compatibility)
457 <li> additional predefined macro names
458 <li> _Pragma preprocessing operator
459 <li> standard pragmas
460 <li> __func__ predefined identifier
462 <li> additional strftime conversion specifiers
463 <li> LIA compatibility annex
464 <li> deprecate ungetc at the beginning of a binary file
465 <li> remove deprecation of aliased array parameters
466 <li> conversion of array to pointer not limited to lvalues
467 <li> relaxed constraints on aggregate and union initialization
468 <li> relaxed restrictions on portable header names
469 <li> return without expression not permitted in function that returns a value (and vice
473 Annexes D and F form a normative part of this standard; annexes A, B, C, E, G, H, I, J,
474 the bibliography, and the index are for information only. In accordance with Part 3 of the
475 ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples are
476 also for information only.
479 <h2><a name="Introduction" href="#Introduction">Introduction</a></h2>
481 With the introduction of new devices and extended character sets, new features may be
482 added to this International Standard. Subclauses in the language and library clauses warn
483 implementors and programmers of usages which, though valid in themselves, may
484 conflict with future additions.
486 Certain features are obsolescent, which means that they may be considered for
487 withdrawal in future revisions of this International Standard. They are retained because
488 of their widespread use, but their use in new implementations (for implementation
489 features) or new programs (for language [<a href="#6.11">6.11</a>] or library features [<a href="#7.26">7.26</a>]) is discouraged.
491 This International Standard is divided into four major subdivisions:
493 <li> preliminary elements (clauses 1-4);
494 <li> the characteristics of environments that translate and execute C programs (clause 5);
495 <li> the language syntax, constraints, and semantics (clause 6);
496 <li> the library facilities (clause 7).
499 Examples are provided to illustrate possible forms of the constructions described.
500 Footnotes are provided to emphasize consequences of the rules described in that
501 subclause or elsewhere in this International Standard. References are used to refer to
502 other related subclauses. Recommendations are provided to give advice or guidance to
503 implementors. Annexes provide additional information and summarize the information
504 contained in this International Standard. A bibliography lists documents that were
505 referred to during the preparation of the standard.
507 The language clause (clause 6) is derived from ''The C Reference Manual''.
509 The library clause (clause 7) is based on the 1984 /usr/group Standard.
512 <h1>Programming languages -- C</h1>
518 <h2><a name="1" href="#1">1. Scope</a></h2>
520 This International Standard specifies the form and establishes the interpretation of
521 programs written in the C programming language.<sup><a href="#note1"><b>1)</b></a></sup> It specifies
523 <li> the representation of C programs;
524 <li> the syntax and constraints of the C language;
525 <li> the semantic rules for interpreting C programs;
526 <li> the representation of input data to be processed by C programs;
527 <li> the representation of output data produced by C programs;
528 <li> the restrictions and limits imposed by a conforming implementation of C.
531 This International Standard does not specify
533 <li> the mechanism by which C programs are transformed for use by a data-processing
535 <li> the mechanism by which C programs are invoked for use by a data-processing
537 <li> the mechanism by which input data are transformed for use by a C program;
538 <li> the mechanism by which output data are transformed after being produced by a C
540 <li> the size or complexity of a program and its data that will exceed the capacity of any
541 specific data-processing system or the capacity of a particular processor;
545 <li> all minimal requirements of a data-processing system that is capable of supporting a
546 conforming implementation.
551 <p><small><a name="note1" href="#note1">1)</a> This International Standard is designed to promote the portability of C programs among a variety of
552 data-processing systems. It is intended for use by implementors and programmers.
555 <h2><a name="2" href="#2">2. Normative references</a></h2>
557 The following normative documents contain provisions which, through reference in this
558 text, constitute provisions of this International Standard. For dated references,
559 subsequent amendments to, or revisions of, any of these publications do not apply.
560 However, parties to agreements based on this International Standard are encouraged to
561 investigate the possibility of applying the most recent editions of the normative
562 documents indicated below. For undated references, the latest edition of the normative
563 document referred to applies. Members of ISO and IEC maintain registers of currently
564 valid International Standards.
566 ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and symbols for
567 use in the physical sciences and technology.
569 ISO/IEC 646, Information technology -- ISO 7-bit coded character set for information
572 ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1: Fundamental
575 ISO 4217, Codes for the representation of currencies and funds.
577 ISO 8601, Data elements and interchange formats -- Information interchange --
578 Representation of dates and times.
580 ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded
583 IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems (previously
584 designated IEC 559:1989).
587 <h2><a name="3" href="#3">3. Terms, definitions, and symbols</a></h2>
589 For the purposes of this International Standard, the following definitions apply. Other
590 terms are defined where they appear in italic type or on the left side of a syntax rule.
591 Terms explicitly defined in this International Standard are not to be presumed to refer
592 implicitly to similar terms defined elsewhere. Terms not defined in this International
593 Standard are to be interpreted according to ISO/IEC 2382-1. Mathematical symbols not
594 defined in this International Standard are to be interpreted according to ISO 31-11.
596 <h3><a name="3.1" href="#3.1">3.1</a></h3>
599 <execution-time action> to read or modify the value of an object
601 NOTE 1 Where only one of these two actions is meant, ''read'' or ''modify'' is used.
604 NOTE 2 "Modify'' includes the case where the new value being stored is the same as the previous value.
607 NOTE 3 Expressions that are not evaluated do not access objects.
610 <h3><a name="3.2" href="#3.2">3.2</a></h3>
612 <b> alignment</b><br>
613 requirement that objects of a particular type be located on storage boundaries with
614 addresses that are particular multiples of a byte address
616 <h3><a name="3.3" href="#3.3">3.3</a></h3>
620 actual parameter (deprecated)<br>
621 expression in the comma-separated list bounded by the parentheses in a function call
622 expression, or a sequence of preprocessing tokens in the comma-separated list bounded
623 by the parentheses in a function-like macro invocation
625 <h3><a name="3.4" href="#3.4">3.4</a></h3>
628 external appearance or action
630 <h4><a name="3.4.1" href="#3.4.1">3.4.1</a></h4>
632 <b> implementation-defined behavior</b><br>
633 unspecified behavior where each implementation documents how the choice is made
635 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
636 when a signed integer is shifted right.
639 <h4><a name="3.4.2" href="#3.4.2">3.4.2</a></h4>
641 <b> locale-specific behavior</b><br>
642 behavior that depends on local conventions of nationality, culture, and language that each
643 implementation documents
646 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
647 characters other than the 26 lowercase Latin letters.
650 <h4><a name="3.4.3" href="#3.4.3">3.4.3</a></h4>
652 <b> undefined behavior</b><br>
653 behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
654 for which this International Standard imposes no requirements
656 NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable
657 results, to behaving during translation or program execution in a documented manner characteristic of the
658 environment (with or without the issuance of a diagnostic message), to terminating a translation or
659 execution (with the issuance of a diagnostic message).
662 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
665 <h4><a name="3.4.4" href="#3.4.4">3.4.4</a></h4>
667 <b> unspecified behavior</b><br>
668 use of an unspecified value, or other behavior where this International Standard provides
669 two or more possibilities and imposes no further requirements on which is chosen in any
672 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
676 <h3><a name="3.5" href="#3.5">3.5</a></h3>
679 unit of data storage in the execution environment large enough to hold an object that may
680 have one of two values
682 NOTE It need not be possible to express the address of each individual bit of an object.
685 <h3><a name="3.6" href="#3.6">3.6</a></h3>
688 addressable unit of data storage large enough to hold any member of the basic character
689 set of the execution environment
691 NOTE 1 It is possible to express the address of each individual byte of an object uniquely.
694 NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
695 defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order
699 <h3><a name="3.7" href="#3.7">3.7</a></h3>
701 <b> character</b><br>
702 <abstract> member of a set of elements used for the organization, control, or
703 representation of data
705 <h4><a name="3.7.1" href="#3.7.1">3.7.1</a></h4>
707 <b> character</b><br>
708 single-byte character
709 <C> bit representation that fits in a byte
712 <h4><a name="3.7.2" href="#3.7.2">3.7.2</a></h4>
714 <b> multibyte character</b><br>
715 sequence of one or more bytes representing a member of the extended character set of
716 either the source or the execution environment
718 NOTE The extended character set is a superset of the basic character set.
721 <h4><a name="3.7.3" href="#3.7.3">3.7.3</a></h4>
723 <b> wide character</b><br>
724 bit representation that fits in an object of type wchar_t, capable of representing any
725 character in the current locale
727 <h3><a name="3.8" href="#3.8">3.8</a></h3>
729 <b> constraint</b><br>
730 restriction, either syntactic or semantic, by which the exposition of language elements is
733 <h3><a name="3.9" href="#3.9">3.9</a></h3>
735 <b> correctly rounded result</b><br>
736 representation in the result format that is nearest in value, subject to the current rounding
737 mode, to what the result would be given unlimited range and precision
739 <h3><a name="3.10" href="#3.10">3.10</a></h3>
741 <b> diagnostic message</b><br>
742 message belonging to an implementation-defined subset of the implementation's message
745 <h3><a name="3.11" href="#3.11">3.11</a></h3>
747 <b> forward reference</b><br>
748 reference to a later subclause of this International Standard that contains additional
749 information relevant to this subclause
751 <h3><a name="3.12" href="#3.12">3.12</a></h3>
753 <b> implementation</b><br>
754 particular set of software, running in a particular translation environment under particular
755 control options, that performs translation of programs for, and supports execution of
756 functions in, a particular execution environment
758 <h3><a name="3.13" href="#3.13">3.13</a></h3>
760 <b> implementation limit</b><br>
761 restriction imposed upon programs by the implementation
763 <h3><a name="3.14" href="#3.14">3.14</a></h3>
766 region of data storage in the execution environment, the contents of which can represent
770 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>.
773 <h3><a name="3.15" href="#3.15">3.15</a></h3>
775 <b> parameter</b><br>
777 formal argument (deprecated)
778 object declared as part of a function declaration or definition that acquires a value on
779 entry to the function, or an identifier from the comma-separated list bounded by the
780 parentheses immediately following the macro name in a function-like macro definition
782 <h3><a name="3.16" href="#3.16">3.16</a></h3>
784 <b> recommended practice</b><br>
785 specification that is strongly recommended as being in keeping with the intent of the
786 standard, but that may be impractical for some implementations
788 <h3><a name="3.17" href="#3.17">3.17</a></h3>
791 precise meaning of the contents of an object when interpreted as having a specific type
793 <h4><a name="3.17.1" href="#3.17.1">3.17.1</a></h4>
795 <b> implementation-defined value</b><br>
796 unspecified value where each implementation documents how the choice is made
798 <h4><a name="3.17.2" href="#3.17.2">3.17.2</a></h4>
800 <b> indeterminate value</b><br>
801 either an unspecified value or a trap representation
803 <h4><a name="3.17.3" href="#3.17.3">3.17.3</a></h4>
805 <b> unspecified value</b><br>
806 valid value of the relevant type where this International Standard imposes no
807 requirements on which value is chosen in any instance
809 NOTE An unspecified value cannot be a trap representation.
812 <h3><a name="3.18" href="#3.18">3.18</a></h3>
815 ceiling of x: the least integer greater than or equal to x
817 EXAMPLE ???2.4??? is 3, ???-2.4??? is -2.
820 <h3><a name="3.19" href="#3.19">3.19</a></h3>
823 floor of x: the greatest integer less than or equal to x
825 EXAMPLE ???2.4??? is 2, ???-2.4??? is -3.
828 <h2><a name="4" href="#4">4. Conformance</a></h2>
830 In this International Standard, ''shall'' is to be interpreted as a requirement on an
831 implementation or on a program; conversely, ''shall not'' is to be interpreted as a
834 If a ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated, the
835 behavior is undefined. Undefined behavior is otherwise indicated in this International
836 Standard by the words ''undefined behavior'' or by the omission of any explicit definition
837 of behavior. There is no difference in emphasis among these three; they all describe
838 ''behavior that is undefined''.
840 A program that is correct in all other aspects, operating on correct data, containing
841 unspecified behavior shall be a correct program and act in accordance with <a href="#5.1.2.3">5.1.2.3</a>.
843 The implementation shall not successfully translate a preprocessing translation unit
844 containing a #error preprocessing directive unless it is part of a group skipped by
845 conditional inclusion.
847 A strictly conforming program shall use only those features of the language and library
848 specified in this International Standard.<sup><a href="#note2"><b>2)</b></a></sup> It shall not produce output dependent on any
849 unspecified, undefined, or implementation-defined behavior, and shall not exceed any
850 minimum implementation limit.
852 The two forms of conforming implementation are hosted and freestanding. A conforming
853 hosted implementation shall accept any strictly conforming program. A conforming
854 freestanding implementation shall accept any strictly conforming program that does not
855 use complex types and in which the use of the features specified in the library clause
856 (clause 7) is confined to the contents of the standard headers <a href="#7.7"><float.h></a>,
857 <a href="#7.9"><iso646.h></a>, <a href="#7.10"><limits.h></a>, <a href="#7.15"><stdarg.h></a>, <a href="#7.16"><stdbool.h></a>, <a href="#7.17"><stddef.h></a>, and
858 <a href="#7.18"><stdint.h></a>. A conforming implementation may have extensions (including additional
859 library functions), provided they do not alter the behavior of any strictly conforming
860 program.<sup><a href="#note3"><b>3)</b></a></sup>
866 A conforming program is one that is acceptable to a conforming implementation.<sup><a href="#note4"><b>4)</b></a></sup>
868 An implementation shall be accompanied by a document that defines all implementation-
869 defined and locale-specific characteristics and all extensions.
870 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), error directive (<a href="#6.10.5">6.10.5</a>),
871 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>
872 (<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>), variable arguments <a href="#7.15"><stdarg.h></a>
873 (<a href="#7.15">7.15</a>), boolean type and values <a href="#7.16"><stdbool.h></a> (<a href="#7.16">7.16</a>), common definitions
874 <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>).
882 <p><small><a name="note2" href="#note2">2)</a> A strictly conforming program can use conditional features (such as those in <a href="#F">annex F</a>) provided the
883 use is guarded by a #ifdef directive with the appropriate macro. For example:
886 #ifdef __STDC_IEC_559__ /* FE_UPWARD defined */
888 fesetround(FE_UPWARD);
893 <p><small><a name="note3" href="#note3">3)</a> This implies that a conforming implementation reserves no identifiers other than those explicitly
894 reserved in this International Standard.
896 <p><small><a name="note4" href="#note4">4)</a> Strictly conforming programs are intended to be maximally portable among conforming
897 implementations. Conforming programs may depend upon nonportable features of a conforming
901 <h2><a name="5" href="#5">5. Environment</a></h2>
903 An implementation translates C source files and executes C programs in two data-
904 processing-system environments, which will be called the translation environment and
905 the execution environment in this International Standard. Their characteristics define and
906 constrain the results of executing conforming C programs constructed according to the
907 syntactic and semantic rules for conforming implementations.
908 <p><b> Forward references</b>: In this clause, only a few of many possible forward references
911 <h3><a name="5.1" href="#5.1">5.1 Conceptual models</a></h3>
913 <h4><a name="5.1.1" href="#5.1.1">5.1.1 Translation environment</a></h4>
915 <h5><a name="5.1.1.1" href="#5.1.1.1">5.1.1.1 Program structure</a></h5>
917 A C program need not all be translated at the same time. The text of the program is kept
918 in units called source files, (or preprocessing files) in this International Standard. A
919 source file together with all the headers and source files included via the preprocessing
920 directive #include is known as a preprocessing translation unit. After preprocessing, a
921 preprocessing translation unit is called a translation unit. Previously translated translation
922 units may be preserved individually or in libraries. The separate translation units of a
923 program communicate by (for example) calls to functions whose identifiers have external
924 linkage, manipulation of objects whose identifiers have external linkage, or manipulation
925 of data files. Translation units may be separately translated and then later linked to
926 produce an executable program.
927 <p><b> Forward references</b>: linkages of identifiers (<a href="#6.2.2">6.2.2</a>), external definitions (<a href="#6.9">6.9</a>),
928 preprocessing directives (<a href="#6.10">6.10</a>).
930 <h5><a name="5.1.1.2" href="#5.1.1.2">5.1.1.2 Translation phases</a></h5>
932 The precedence among the syntax rules of translation is specified by the following
933 phases.<sup><a href="#note5"><b>5)</b></a></sup>
935 <li> Physical source file multibyte characters are mapped, in an implementation-
936 defined manner, to the source character set (introducing new-line characters for
937 end-of-line indicators) if necessary. Trigraph sequences are replaced by
938 corresponding single-character internal representations.
943 <li> Each instance of a backslash character (\) immediately followed by a new-line
944 character is deleted, splicing physical source lines to form logical source lines.
945 Only the last backslash on any physical source line shall be eligible for being part
946 of such a splice. A source file that is not empty shall end in a new-line character,
947 which shall not be immediately preceded by a backslash character before any such
948 splicing takes place.
949 <li> The source file is decomposed into preprocessing tokens<sup><a href="#note6"><b>6)</b></a></sup> and sequences of
950 white-space characters (including comments). A source file shall not end in a
951 partial preprocessing token or in a partial comment. Each comment is replaced by
952 one space character. New-line characters are retained. Whether each nonempty
953 sequence of white-space characters other than new-line is retained or replaced by
954 one space character is implementation-defined.
955 <li> Preprocessing directives are executed, macro invocations are expanded, and
956 _Pragma unary operator expressions are executed. If a character sequence that
957 matches the syntax of a universal character name is produced by token
958 concatenation (<a href="#6.10.3.3">6.10.3.3</a>), the behavior is undefined. A #include preprocessing
959 directive causes the named header or source file to be processed from phase 1
960 through phase 4, recursively. All preprocessing directives are then deleted.
961 <li> Each source character set member and escape sequence in character constants and
962 string literals is converted to the corresponding member of the execution character
963 set; if there is no corresponding member, it is converted to an implementation-
964 defined member other than the null (wide) character.<sup><a href="#note7"><b>7)</b></a></sup>
965 <li> Adjacent string literal tokens are concatenated.
966 <li> White-space characters separating tokens are no longer significant. Each
967 preprocessing token is converted into a token. The resulting tokens are
968 syntactically and semantically analyzed and translated as a translation unit.
969 <li> All external object and function references are resolved. Library components are
970 linked to satisfy external references to functions and objects not defined in the
971 current translation. All such translator output is collected into a program image
972 which contains information needed for execution in its execution environment.
974 <p><b> Forward references</b>: universal character names (<a href="#6.4.3">6.4.3</a>), lexical elements (<a href="#6.4">6.4</a>),
975 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>).
982 <p><small><a name="note5" href="#note5">5)</a> Implementations shall behave as if these separate phases occur, even though many are typically folded
983 together in practice. Source files, translation units, and translated translation units need not
984 necessarily be stored as files, nor need there be any one-to-one correspondence between these entities
985 and any external representation. The description is conceptual only, and does not specify any
986 particular implementation.
988 <p><small><a name="note6" href="#note6">6)</a> As described in <a href="#6.4">6.4</a>, the process of dividing a source file's characters into preprocessing tokens is
989 context-dependent. For example, see the handling of < within a #include preprocessing directive.
991 <p><small><a name="note7" href="#note7">7)</a> An implementation need not convert all non-corresponding source characters to the same execution
995 <h5><a name="5.1.1.3" href="#5.1.1.3">5.1.1.3 Diagnostics</a></h5>
997 A conforming implementation shall produce at least one diagnostic message (identified in
998 an implementation-defined manner) if a preprocessing translation unit or translation unit
999 contains a violation of any syntax rule or constraint, even if the behavior is also explicitly
1000 specified as undefined or implementation-defined. Diagnostic messages need not be
1001 produced in other circumstances.<sup><a href="#note8"><b>8)</b></a></sup>
1003 EXAMPLE An implementation shall issue a diagnostic for the translation unit:
1007 because in those cases where wording in this International Standard describes the behavior for a construct
1008 as being both a constraint error and resulting in undefined behavior, the constraint error shall be diagnosed.
1012 <p><small><a name="note8" href="#note8">8)</a> The intent is that an implementation should identify the nature of, and where possible localize, each
1013 violation. Of course, an implementation is free to produce any number of diagnostics as long as a
1014 valid program is still correctly translated. It may also successfully translate an invalid program.
1017 <h4><a name="5.1.2" href="#5.1.2">5.1.2 Execution environments</a></h4>
1019 Two execution environments are defined: freestanding and hosted. In both cases,
1020 program startup occurs when a designated C function is called by the execution
1021 environment. All objects with static storage duration shall be initialized (set to their
1022 initial values) before program startup. The manner and timing of such initialization are
1023 otherwise unspecified. Program termination returns control to the execution
1025 <p><b> Forward references</b>: storage durations of objects (<a href="#6.2.4">6.2.4</a>), initialization (<a href="#6.7.8">6.7.8</a>).
1027 <h5><a name="5.1.2.1" href="#5.1.2.1">5.1.2.1 Freestanding environment</a></h5>
1029 In a freestanding environment (in which C program execution may take place without any
1030 benefit of an operating system), the name and type of the function called at program
1031 startup are implementation-defined. Any library facilities available to a freestanding
1032 program, other than the minimal set required by clause 4, are implementation-defined.
1034 The effect of program termination in a freestanding environment is implementation-
1037 <h5><a name="5.1.2.2" href="#5.1.2.2">5.1.2.2 Hosted environment</a></h5>
1039 A hosted environment need not be provided, but shall conform to the following
1040 specifications if present.
1047 <h5><a name="5.1.2.2.1" href="#5.1.2.2.1">5.1.2.2.1 Program startup</a></h5>
1049 The function called at program startup is named main. The implementation declares no
1050 prototype for this function. It shall be defined with a return type of int and with no
1053 int main(void) { /* ... */ }</pre>
1054 or with two parameters (referred to here as argc and argv, though any names may be
1055 used, as they are local to the function in which they are declared):
1057 int main(int argc, char *argv[]) { /* ... */ }</pre>
1058 or equivalent;<sup><a href="#note9"><b>9)</b></a></sup> or in some other implementation-defined manner.
1060 If they are declared, the parameters to the main function shall obey the following
1063 <li> The value of argc shall be nonnegative.
1064 <li> argv[argc] shall be a null pointer.
1065 <li> If the value of argc is greater than zero, the array members argv[0] through
1066 argv[argc-1] inclusive shall contain pointers to strings, which are given
1067 implementation-defined values by the host environment prior to program startup. The
1068 intent is to supply to the program information determined prior to program startup
1069 from elsewhere in the hosted environment. If the host environment is not capable of
1070 supplying strings with letters in both uppercase and lowercase, the implementation
1071 shall ensure that the strings are received in lowercase.
1072 <li> If the value of argc is greater than zero, the string pointed to by argv[0]
1073 represents the program name; argv[0][0] shall be the null character if the
1074 program name is not available from the host environment. If the value of argc is
1075 greater than one, the strings pointed to by argv[1] through argv[argc-1]
1076 represent the program parameters.
1077 <li> The parameters argc and argv and the strings pointed to by the argv array shall
1078 be modifiable by the program, and retain their last-stored values between program
1079 startup and program termination.
1083 <p><small><a name="note9" href="#note9">9)</a> Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as
1084 char ** argv, and so on.
1087 <h5><a name="5.1.2.2.2" href="#5.1.2.2.2">5.1.2.2.2 Program execution</a></h5>
1089 In a hosted environment, a program may use all the functions, macros, type definitions,
1090 and objects described in the library clause (clause 7).
1096 <h5><a name="5.1.2.2.3" href="#5.1.2.2.3">5.1.2.2.3 Program termination</a></h5>
1098 If the return type of the main function is a type compatible with int, a return from the
1099 initial call to the main function is equivalent to calling the exit function with the value
1100 returned by the main function as its argument;<sup><a href="#note10"><b>10)</b></a></sup> reaching the } that terminates the
1101 main function returns a value of 0. If the return type is not compatible with int, the
1102 termination status returned to the host environment is unspecified.
1103 <p><b> Forward references</b>: definition of terms (<a href="#7.1.1">7.1.1</a>), the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
1106 <p><small><a name="note10" href="#note10">10)</a> In accordance with <a href="#6.2.4">6.2.4</a>, the lifetimes of objects with automatic storage duration declared in main
1107 will have ended in the former case, even where they would not have in the latter.
1110 <h5><a name="5.1.2.3" href="#5.1.2.3">5.1.2.3 Program execution</a></h5>
1112 The semantic descriptions in this International Standard describe the behavior of an
1113 abstract machine in which issues of optimization are irrelevant.
1115 Accessing a volatile object, modifying an object, modifying a file, or calling a function
1116 that does any of those operations are all side effects,<sup><a href="#note11"><b>11)</b></a></sup> which are changes in the state of
1117 the execution environment. Evaluation of an expression may produce side effects. At
1118 certain specified points in the execution sequence called sequence points, all side effects
1119 of previous evaluations shall be complete and no side effects of subsequent evaluations
1120 shall have taken place. (A summary of the sequence points is given in <a href="#C">annex C</a>.)
1122 In the abstract machine, all expressions are evaluated as specified by the semantics. An
1123 actual implementation need not evaluate part of an expression if it can deduce that its
1124 value is not used and that no needed side effects are produced (including any caused by
1125 calling a function or accessing a volatile object).
1127 When the processing of the abstract machine is interrupted by receipt of a signal, only the
1128 values of objects as of the previous sequence point may be relied on. Objects that may be
1129 modified between the previous sequence point and the next sequence point need not have
1130 received their correct values yet.
1132 The least requirements on a conforming implementation are:
1134 <li> At sequence points, volatile objects are stable in the sense that previous accesses are
1135 complete and subsequent accesses have not yet occurred.
1141 <li> At program termination, all data written into files shall be identical to the result that
1142 execution of the program according to the abstract semantics would have produced.
1143 <li> The input and output dynamics of interactive devices shall take place as specified in
1144 <a href="#7.19.3">7.19.3</a>. The intent of these requirements is that unbuffered or line-buffered output
1145 appear as soon as possible, to ensure that prompting messages actually appear prior to
1146 a program waiting for input.
1149 What constitutes an interactive device is implementation-defined.
1151 More stringent correspondences between abstract and actual semantics may be defined by
1152 each implementation.
1154 EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual
1155 semantics: at every sequence point, the values of the actual objects would agree with those specified by the
1156 abstract semantics. The keyword volatile would then be redundant.
1158 Alternatively, an implementation might perform various optimizations within each translation unit, such
1159 that the actual semantics would agree with the abstract semantics only when making function calls across
1160 translation unit boundaries. In such an implementation, at the time of each function entry and function
1161 return where the calling function and the called function are in different translation units, the values of all
1162 externally linked objects and of all objects accessible via pointers therein would agree with the abstract
1163 semantics. Furthermore, at the time of each such function entry the values of the parameters of the called
1164 function and of all objects accessible via pointers therein would agree with the abstract semantics. In this
1165 type of implementation, objects referred to by interrupt service routines activated by the signal function
1166 would require explicit specification of volatile storage, as well as other implementation-defined
1170 EXAMPLE 2 In executing the fragment
1175 the ''integer promotions'' require that the abstract machine promote the value of each variable to int size
1176 and then add the two ints and truncate the sum. Provided the addition of two chars can be done without
1177 overflow, or with overflow wrapping silently to produce the correct result, the actual execution need only
1178 produce the same result, possibly omitting the promotions.
1181 EXAMPLE 3 Similarly, in the fragment
1187 the multiplication may be executed using single-precision arithmetic if the implementation can ascertain
1188 that the result would be the same as if it were executed using double-precision arithmetic (for example, if d
1189 were replaced by the constant 2.0, which has type double).
1192 EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate
1193 semantics. Values are independent of whether they are represented in a register or in memory. For
1194 example, an implicit spilling of a register is not permitted to alter the value. Also, an explicit store and load
1195 is required to round to the precision of the storage type. In particular, casts and assignments are required to
1196 perform their specified conversion. For the fragment
1200 d1 = f = expression;
1201 d2 = (float) expression;</pre>
1202 the values assigned to d1 and d2 are required to have been converted to float.
1205 EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in
1206 precision as well as range. The implementation cannot generally apply the mathematical associative rules
1207 for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of
1208 overflow and underflow. Likewise, implementations cannot generally replace decimal constants in order to
1209 rearrange expressions. In the following fragment, rearrangements suggested by mathematical rules for real
1210 numbers are often not valid (see <a href="#F.8">F.8</a>).
1214 x = (x * y) * z; // not equivalent to x *= y * z;
1215 z = (x - y) + y ; // not equivalent to z = x;
1216 z = x + x * y; // not equivalent to z = x * (1.0 + y);
1217 y = x / 5.0; // not equivalent to y = x * 0.2;</pre>
1220 EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
1224 a = a + 32760 + b + 5;</pre>
1225 the expression statement behaves exactly the same as
1227 a = (((a + 32760) + b) + 5);</pre>
1228 due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is
1229 next added to b, and that result is then added to 5 which results in the value assigned to a. On a machine in
1230 which overflows produce an explicit trap and in which the range of values representable by an int is
1231 [-32768, +32767], the implementation cannot rewrite this expression as
1233 a = ((a + b) + 32765);</pre>
1234 since if the values for a and b were, respectively, -32754 and -15, the sum a + b would produce a trap
1235 while the original expression would not; nor can the expression be rewritten either as
1237 a = ((a + 32765) + b);</pre>
1240 a = (a + (b + 32765));</pre>
1241 since the values for a and b might have been, respectively, 4 and -8 or -17 and 12. However, on a machine
1242 in which overflow silently generates some value and where positive and negative overflows cancel, the
1243 above expression statement can be rewritten by the implementation in any of the above ways because the
1244 same result will occur.
1247 EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the
1250 #include <a href="#7.19"><stdio.h></a>
1254 sum = sum * 10 - '0' + (*p++ = getchar());</pre>
1255 the expression statement is grouped as if it were written as
1257 sum = (((sum * 10) - '0') + ((*(p++)) = (getchar())));</pre>
1258 but the actual increment of p can occur at any time between the previous sequence point and the next
1259 sequence point (the ;), and the call to getchar can occur at any point prior to the need of its returned
1262 <p><b> Forward references</b>: 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
1263 signal function (<a href="#7.14">7.14</a>), files (<a href="#7.19.3">7.19.3</a>).
1267 <p><small><a name="note11" href="#note11">11)</a> The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status
1268 flags and control modes. Floating-point operations implicitly set the status flags; modes affect result
1269 values of floating-point operations. Implementations that support such floating-point state are
1270 required to regard changes to it as side effects -- see <a href="#F">annex F</a> for details. The floating-point
1271 environment library <a href="#7.6"><fenv.h></a> provides a programming facility for indicating when these side
1272 effects matter, freeing the implementations in other cases.
1275 <h3><a name="5.2" href="#5.2">5.2 Environmental considerations</a></h3>
1277 <h4><a name="5.2.1" href="#5.2.1">5.2.1 Character sets</a></h4>
1279 Two sets of characters and their associated collating sequences shall be defined: the set in
1280 which source files are written (the source character set), and the set interpreted in the
1281 execution environment (the execution character set). Each set is further divided into a
1282 basic character set, whose contents are given by this subclause, and a set of zero or more
1283 locale-specific members (which are not members of the basic character set) called
1284 extended characters. The combined set is also called the extended character set. The
1285 values of the members of the execution character set are implementation-defined.
1287 In a character constant or string literal, members of the execution character set shall be
1288 represented by corresponding members of the source character set or by escape
1289 sequences consisting of the backslash \ followed by one or more characters. A byte with
1290 all bits set to 0, called the null character, shall exist in the basic execution character set; it
1291 is used to terminate a character string.
1293 Both the basic source and basic execution character sets shall have the following
1294 members: the 26 uppercase letters of the Latin alphabet
1296 A B C D E F G H I J K L M
1297 N O P Q R S T U V W X Y Z</pre>
1298 the 26 lowercase letters of the Latin alphabet
1300 a b c d e f g h i j k l m
1301 n o p q r s t u v w x y z</pre>
1302 the 10 decimal digits
1304 0 1 2 3 4 5 6 7 8 9</pre>
1305 the following 29 graphic characters
1307 ! " # % & ' ( ) * + , - . / :
1308 ; < = > ? [ \ ] ^ _ { | } ~</pre>
1309 the space character, and control characters representing horizontal tab, vertical tab, and
1310 form feed. The representation of each member of the source and execution basic
1311 character sets shall fit in a byte. In both the source and execution basic character sets, the
1312 value of each character after 0 in the above list of decimal digits shall be one greater than
1313 the value of the previous. In source files, there shall be some way of indicating the end of
1314 each line of text; this International Standard treats such an end-of-line indicator as if it
1315 were a single new-line character. In the basic execution character set, there shall be
1316 control characters representing alert, backspace, carriage return, and new line. If any
1317 other characters are encountered in a source file (except in an identifier, a character
1318 constant, a string literal, a header name, a comment, or a preprocessing token that is never
1320 converted to a token), the behavior is undefined.
1322 A letter is an uppercase letter or a lowercase letter as defined above; in this International
1323 Standard the term does not include other characters that are letters in other alphabets.
1325 The universal character name construct provides a way to name other characters.
1326 <p><b> Forward references</b>: 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>),
1327 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>).
1329 <h5><a name="5.2.1.1" href="#5.2.1.1">5.2.1.1 Trigraph sequences</a></h5>
1331 Before any other processing takes place, each occurrence of one of the following
1332 sequences of three characters (called trigraph sequences<sup><a href="#note12"><b>12)</b></a></sup>) is replaced with the
1333 corresponding single character.
1336 ??( [ ??' ^ ??> }
1337 ??/ \ ??< { ??- ~</pre>
1338 No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
1339 above is not changed.
1343 ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)</pre>
1346 #define arraycheck(a, b) a[b] || b[a]</pre>
1349 EXAMPLE 2 The following source line
1351 printf("Eh???/n");</pre>
1352 becomes (after replacement of the trigraph sequence ??/)
1354 printf("Eh?\n");</pre>
1358 <p><small><a name="note12" href="#note12">12)</a> The trigraph sequences enable the input of characters that are not defined in the Invariant Code Set as
1359 described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
1362 <h5><a name="5.2.1.2" href="#5.2.1.2">5.2.1.2 Multibyte characters</a></h5>
1364 The source character set may contain multibyte characters, used to represent members of
1365 the extended character set. The execution character set may also contain multibyte
1366 characters, which need not have the same encoding as for the source character set. For
1367 both character sets, the following shall hold:
1369 <li> The basic character set shall be present and each character shall be encoded as a
1371 <li> The presence, meaning, and representation of any additional members is locale-
1375 <li> A multibyte character set may have a state-dependent encoding, wherein each
1376 sequence of multibyte characters begins in an initial shift state and enters other
1377 locale-specific shift states when specific multibyte characters are encountered in the
1378 sequence. While in the initial shift state, all single-byte characters retain their usual
1379 interpretation and do not alter the shift state. The interpretation for subsequent bytes
1380 in the sequence is a function of the current shift state.
1381 <li> A byte with all bits zero shall be interpreted as a null character independent of shift
1382 state. Such a byte shall not occur as part of any other multibyte character.
1385 For source files, the following shall hold:
1387 <li> An identifier, comment, string literal, character constant, or header name shall begin
1388 and end in the initial shift state.
1389 <li> An identifier, comment, string literal, character constant, or header name shall consist
1390 of a sequence of valid multibyte characters.
1393 <h4><a name="5.2.2" href="#5.2.2">5.2.2 Character display semantics</a></h4>
1395 The active position is that location on a display device where the next character output by
1396 the fputc function would appear. The intent of writing a printing character (as defined
1397 by the isprint function) to a display device is to display a graphic representation of
1398 that character at the active position and then advance the active position to the next
1399 position on the current line. The direction of writing is locale-specific. If the active
1400 position is at the final position of a line (if there is one), the behavior of the display device
1403 Alphabetic escape sequences representing nongraphic characters in the execution
1404 character set are intended to produce actions on display devices as follows:
1406 <dt> \a <dd>(alert) Produces an audible or visible alert without changing the active position.
1407 <dt> \b <dd>(backspace) Moves the active position to the previous position on the current line. If
1408 the active position is at the initial position of a line, the behavior of the display
1409 device is unspecified.
1410 <dt> \f <dd>( form feed) Moves the active position to the initial position at the start of the next
1412 <dt> \n <dd>(new line) Moves the active position to the initial position of the next line.
1413 <dt> \r <dd>(carriage return) Moves the active position to the initial position of the current line.
1414 <dt> \t <dd>(horizontal tab) Moves the active position to the next horizontal tabulation position
1415 on the current line. If the active position is at or past the last defined horizontal
1416 tabulation position, the behavior of the display device is unspecified.
1417 <dt> \v <dd>(vertical tab) Moves the active position to the initial position of the next vertical
1419 tabulation position. If the active position is at or past the last defined vertical
1420 tabulation position, the behavior of the display device is unspecified.
1423 Each of these escape sequences shall produce a unique implementation-defined value
1424 which can be stored in a single char object. The external representations in a text file
1425 need not be identical to the internal representations, and are outside the scope of this
1426 International Standard.
1427 <p><b> Forward references</b>: the isprint function (<a href="#7.4.1.8">7.4.1.8</a>), the fputc function (<a href="#7.19.7.3">7.19.7.3</a>).
1429 <h4><a name="5.2.3" href="#5.2.3">5.2.3 Signals and interrupts</a></h4>
1431 Functions shall be implemented such that they may be interrupted at any time by a signal,
1432 or may be called by a signal handler, or both, with no alteration to earlier, but still active,
1433 invocations' control flow (after the interruption), function return values, or objects with
1434 automatic storage duration. All such objects shall be maintained outside the function
1435 image (the instructions that compose the executable representation of a function) on a
1436 per-invocation basis.
1438 <h4><a name="5.2.4" href="#5.2.4">5.2.4 Environmental limits</a></h4>
1440 Both the translation and execution environments constrain the implementation of
1441 language translators and libraries. The following summarizes the language-related
1442 environmental limits on a conforming implementation; the library-related limits are
1443 discussed in clause 7.
1445 <h5><a name="5.2.4.1" href="#5.2.4.1">5.2.4.1 Translation limits</a></h5>
1447 The implementation shall be able to translate and execute at least one program that
1448 contains at least one instance of every one of the following limits:<sup><a href="#note13"><b>13)</b></a></sup>
1450 <li> 127 nesting levels of blocks
1451 <li> 63 nesting levels of conditional inclusion
1452 <li> 12 pointer, array, and function declarators (in any combinations) modifying an
1453 arithmetic, structure, union, or incomplete type in a declaration
1454 <li> 63 nesting levels of parenthesized declarators within a full declarator
1455 <li> 63 nesting levels of parenthesized expressions within a full expression
1456 <li> 63 significant initial characters in an internal identifier or a macro name (each
1457 universal character name or extended source character is considered a single
1459 <li> 31 significant initial characters in an external identifier (each universal character name
1460 specifying a short identifier of 0000FFFF or less is considered 6 characters, each
1464 universal character name specifying a short identifier of 00010000 or more is
1465 considered 10 characters, and each extended source character is considered the same
1466 number of characters as the corresponding universal character name, if any)<sup><a href="#note14"><b>14)</b></a></sup>
1467 <li> 4095 external identifiers in one translation unit
1468 <li> 511 identifiers with block scope declared in one block
1469 <li> 4095 macro identifiers simultaneously defined in one preprocessing translation unit
1470 <li> 127 parameters in one function definition
1471 <li> 127 arguments in one function call
1472 <li> 127 parameters in one macro definition
1473 <li> 127 arguments in one macro invocation
1474 <li> 4095 characters in a logical source line
1475 <li> 4095 characters in a character string literal or wide string literal (after concatenation)
1476 <li> 65535 bytes in an object (in a hosted environment only)
1477 <li> 15 nesting levels for #included files
1478 <li> 1023 case labels for a switch statement (excluding those for any nested switch
1480 <li> 1023 members in a single structure or union
1481 <li> 1023 enumeration constants in a single enumeration
1482 <li> 63 levels of nested structure or union definitions in a single struct-declaration-list
1486 <p><small><a name="note13" href="#note13">13)</a> Implementations should avoid imposing fixed translation limits whenever possible.
1488 <p><small><a name="note14" href="#note14">14)</a> See ''future language directions'' (<a href="#6.11.3">6.11.3</a>).
1491 <h5><a name="5.2.4.2" href="#5.2.4.2">5.2.4.2 Numerical limits</a></h5>
1493 An implementation is required to document all the limits specified in this subclause,
1494 which are specified in the headers <a href="#7.10"><limits.h></a> and <a href="#7.7"><float.h></a>. Additional limits are
1495 specified in <a href="#7.18"><stdint.h></a>.
1496 <p><b> Forward references</b>: integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>).
1498 <h5><a name="5.2.4.2.1" href="#5.2.4.2.1">5.2.4.2.1 Sizes of integer types <limits.h></a></h5>
1500 The values given below shall be replaced by constant expressions suitable for use in #if
1501 preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the
1502 following shall be replaced by expressions that have the same type as would an
1503 expression that is an object of the corresponding type converted according to the integer
1504 promotions. Their implementation-defined values shall be equal or greater in magnitude
1508 (absolute value) to those shown, with the same sign.
1510 <li> number of bits for smallest object that is not a bit-field (byte)
1511 <pre> CHAR_BIT 8</pre>
1512 <li> minimum value for an object of type signed char
1513 <pre> SCHAR_MIN -127 // -(2<sup>7</sup> - 1)</pre>
1514 <li> maximum value for an object of type signed char
1515 <pre> SCHAR_MAX +127 // 2<sup>7</sup> - 1</pre>
1516 <li> maximum value for an object of type unsigned char
1517 <pre> UCHAR_MAX 255 // 2<sup>8</sup> - 1</pre>
1518 <li> minimum value for an object of type char
1519 <pre> CHAR_MIN see below</pre>
1520 <li> maximum value for an object of type char
1521 <pre> CHAR_MAX see below</pre>
1522 <li> maximum number of bytes in a multibyte character, for any supported locale
1523 <pre> MB_LEN_MAX 1</pre>
1524 <li> minimum value for an object of type short int
1525 <pre> SHRT_MIN -32767 // -(2<sup>15</sup> - 1)</pre>
1526 <li> maximum value for an object of type short int
1527 <pre> SHRT_MAX +32767 // 2<sup>15</sup> - 1</pre>
1528 <li> maximum value for an object of type unsigned short int
1529 <pre> USHRT_MAX 65535 // 2<sup>16</sup> - 1</pre>
1530 <li> minimum value for an object of type int
1531 <pre> INT_MIN -32767 // -(2<sup>15</sup> - 1)</pre>
1532 <li> maximum value for an object of type int
1533 <pre> INT_MAX +32767 // 2<sup>15</sup> - 1</pre>
1534 <li> maximum value for an object of type unsigned int
1535 <pre> UINT_MAX 65535 // 2<sup>16</sup> - 1</pre>
1536 <li> minimum value for an object of type long int
1537 <pre> LONG_MIN -2147483647 // -(2<sup>31</sup> - 1)</pre>
1538 <li> maximum value for an object of type long int
1539 <pre> LONG_MAX +2147483647 // 2<sup>31</sup> - 1</pre>
1540 <li> maximum value for an object of type unsigned long int
1541 <pre> ULONG_MAX 4294967295 // 2<sup>32</sup> - 1</pre>
1543 <li> minimum value for an object of type long long int
1544 <pre> LLONG_MIN -9223372036854775807 // -(2<sup>63</sup> - 1)</pre>
1545 <li> maximum value for an object of type long long int
1546 <pre> LLONG_MAX +9223372036854775807 // 2<sup>63</sup> - 1</pre>
1547 <li> maximum value for an object of type unsigned long long int
1548 <pre> ULLONG_MAX 18446744073709551615 // 2<sup>64</sup> - 1</pre>
1551 If the value of an object of type char is treated as a signed integer when used in an
1552 expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the
1553 value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of
1554 CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of
1555 UCHAR_MAX.<sup><a href="#note15"><b>15)</b></a></sup> The value UCHAR_MAX shall equal 2<sup>CHAR_BIT</sup> - 1.
1556 <p><b> Forward references</b>: representations of types (<a href="#6.2.6">6.2.6</a>), conditional inclusion (<a href="#6.10.1">6.10.1</a>).
1559 <p><small><a name="note15" href="#note15">15)</a> See <a href="#6.2.5">6.2.5</a>.
1562 <h5><a name="5.2.4.2.2" href="#5.2.4.2.2">5.2.4.2.2 Characteristics of floating types <float.h></a></h5>
1564 The characteristics of floating types are defined in terms of a model that describes a
1565 representation of floating-point numbers and values that provide information about an
1566 implementation's floating-point arithmetic.<sup><a href="#note16"><b>16)</b></a></sup> The following parameters are used to
1567 define the model for each floating-point type:
1571 b base or radix of exponent representation (an integer > 1)
1572 e exponent (an integer between a minimum emin and a maximum emax )
1573 p precision (the number of base-b digits in the significand)
1574 fk nonnegative integers less than b (the significand digits)</pre>
1575 A floating-point number (x) is defined by the following model:
1578 x = sb e (Sum) f k b-k ,
1580 emin <= e <= emax</pre>
1583 In addition to normalized floating-point numbers ( f 1 > 0 if x != 0), floating types may be
1584 able to contain other kinds of floating-point numbers, such as subnormal floating-point
1585 numbers (x != 0, e = emin , f 1 = 0) and unnormalized floating-point numbers (x != 0,
1586 e > emin , f 1 = 0), and values that are not floating-point numbers, such as infinities and
1587 NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates
1588 through almost every arithmetic operation without raising a floating-point exception; a
1589 signaling NaN generally raises a floating-point exception when occurring as an
1593 arithmetic operand.<sup><a href="#note17"><b>17)</b></a></sup>
1595 An implementation may give zero and non-numeric values (such as infinities and NaNs) a
1596 sign or may leave them unsigned. Wherever such values are unsigned, any requirement
1597 in this International Standard to retrieve the sign shall produce an unspecified sign, and
1598 any requirement to set the sign shall be ignored.
1600 The accuracy of the floating-point operations (+, -, *, /) and of the library functions in
1601 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results is implementation-
1602 defined, as is the accuracy of the conversion between floating-point internal
1603 representations and string representations performed by the library functions in
1604 <a href="#7.19"><stdio.h></a>, <a href="#7.20"><stdlib.h></a>, and <a href="#7.24"><wchar.h></a>. The implementation may state that the
1605 accuracy is unknown.
1607 All integer values in the <a href="#7.7"><float.h></a> header, except FLT_ROUNDS, shall be constant
1608 expressions suitable for use in #if preprocessing directives; all floating values shall be
1609 constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
1610 and FLT_ROUNDS have separate names for all three floating-point types. The floating-
1611 point model representation is provided for all values except FLT_EVAL_METHOD and
1614 The rounding mode for floating-point addition is characterized by the implementation-
1615 defined value of FLT_ROUNDS:<sup><a href="#note18"><b>18)</b></a></sup>
1620 2 toward positive infinity
1621 3 toward negative infinity</pre>
1622 All other values for FLT_ROUNDS characterize implementation-defined rounding
1625 Except for assignment and cast (which remove all extra range and precision), the values
1626 of operations with floating operands and values subject to the usual arithmetic
1627 conversions and of floating constants are evaluated to a format whose range and precision
1628 may be greater than required by the type. The use of evaluation formats is characterized
1629 by the implementation-defined value of FLT_EVAL_METHOD:<sup><a href="#note19"><b>19)</b></a></sup>
1636 0 evaluate all operations and constants just to the range and precision of the
1638 1 evaluate operations and constants of type float and double to the
1639 range and precision of the double type, evaluate long double
1640 operations and constants to the range and precision of the long double
1642 2 evaluate all operations and constants to the range and precision of the
1643 long double type.</pre>
1644 All other negative values for FLT_EVAL_METHOD characterize implementation-defined
1647 The values given in the following list shall be replaced by constant expressions with
1648 implementation-defined values that are greater or equal in magnitude (absolute value) to
1649 those shown, with the same sign:
1651 <li> radix of exponent representation, b
1653 <li> number of base-FLT_RADIX digits in the floating-point significand, p
1657 <li> number of decimal digits, n, such that any floating-point number in the widest
1658 supported floating type with pmax radix b digits can be rounded to a floating-point
1659 number with n decimal digits and back again without change to the value,
1661 ??? pmax log10 b if b is a power of 10
1663 ??? ???1 + pmax log10 b??? otherwise</pre>
1665 <li> number of decimal digits, q, such that any floating-point number with q decimal digits
1666 can be rounded into a floating-point number with p radix b digits and back again
1667 without change to the q decimal digits,
1674 ??? p log10 b if b is a power of 10
1676 ??? ???( p - 1) log10 b??? otherwise</pre>
1680 <li> minimum negative integer such that FLT_RADIX raised to one less than that power is
1681 a normalized floating-point number, emin
1685 <li> minimum negative integer such that 10 raised to that power is in the range of
1686 normalized floating-point numbers, ???log10 b emin -1 ???
1692 <li> maximum integer such that FLT_RADIX raised to one less than that power is a
1693 representable finite floating-point number, emax
1697 <li> maximum integer such that 10 raised to that power is in the range of representable
1698 finite floating-point numbers, ???log10 ((1 - b- p )b emax )???
1704 The values given in the following list shall be replaced by constant expressions with
1705 implementation-defined values that are greater than or equal to those shown:
1707 <li> maximum representable finite floating-point number, (1 - b- p )b emax
1713 The values given in the following list shall be replaced by constant expressions with
1714 implementation-defined (positive) values that are less than or equal to those shown:
1716 <li> the difference between 1 and the least value greater than 1 that is representable in the
1717 given floating point type, b1- p
1722 <li> minimum normalized positive floating-point number, b emin -1
1727 Recommended practice
1729 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
1730 should be the identity function.
1732 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
1733 requirements of this International Standard, and the appropriate values in a <a href="#7.7"><float.h></a> header for type
1737 x = s16e (Sum) f k 16-k ,
1739 -31 <= e <= +32</pre>
1744 FLT_EPSILON 9.53674316E-07F
1747 FLT_MIN 2.93873588E-39F
1750 FLT_MAX 3.40282347E+38F
1751 FLT_MAX_10_EXP +38</pre>
1754 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
1755 single-precision and double-precision normalized numbers in IEC 60559,<sup><a href="#note20"><b>20)</b></a></sup> and the appropriate values in a
1756 <a href="#7.7"><float.h></a> header for types float and double:
1759 x f = s2e (Sum) f k 2-k ,
1761 -125 <= e <= +128</pre>
1765 x d = s2e (Sum) f k 2-k ,
1767 -1021 <= e <= +1024</pre>
1773 FLT_EPSILON 1.19209290E-07F // decimal constant
1774 FLT_EPSILON 0X1P-23F // hex constant</pre>
1781 FLT_MIN 1.17549435E-38F // decimal constant
1782 FLT_MIN 0X1P-126F // hex constant
1785 FLT_MAX 3.40282347E+38F // decimal constant
1786 FLT_MAX 0X1.fffffeP127F // hex constant
1789 DBL_EPSILON 2.2204460492503131E-16 // decimal constant
1790 DBL_EPSILON 0X1P-52 // hex constant
1793 DBL_MIN 2.2250738585072014E-308 // decimal constant
1794 DBL_MIN 0X1P-1022 // hex constant
1797 DBL_MAX 1.7976931348623157E+308 // decimal constant
1798 DBL_MAX 0X1.fffffffffffffP1023 // hex constant
1799 DBL_MAX_10_EXP +308</pre>
1800 If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
1801 example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
1802 precision), then DECIMAL_DIG would be 21.
1804 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), complex arithmetic
1805 <a href="#7.3"><complex.h></a> (<a href="#7.3">7.3</a>), extended multibyte and wide character utilities <a href="#7.24"><wchar.h></a>
1806 (<a href="#7.24">7.24</a>), floating-point environment <a href="#7.6"><fenv.h></a> (<a href="#7.6">7.6</a>), general utilities <a href="#7.20"><stdlib.h></a>
1807 (<a href="#7.20">7.20</a>), input/output <a href="#7.19"><stdio.h></a> (<a href="#7.19">7.19</a>), mathematics <a href="#7.12"><math.h></a> (<a href="#7.12">7.12</a>).
1811 <p><small><a name="note16" href="#note16">16)</a> The floating-point model is intended to clarify the description of each floating-point characteristic and
1812 does not require the floating-point arithmetic of the implementation to be identical.
1814 <p><small><a name="note17" href="#note17">17)</a> IEC 60559:1989 specifies quiet and signaling NaNs. For implementations that do not support
1815 IEC 60559:1989, the terms quiet NaN and signaling NaN are intended to apply to encodings with
1818 <p><small><a name="note18" href="#note18">18)</a> Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
1819 the function fesetround in <a href="#7.6"><fenv.h></a>.
1821 <p><small><a name="note19" href="#note19">19)</a> The evaluation method determines evaluation formats of expressions involving all floating types, not
1822 just real types. For example, if FLT_EVAL_METHOD is 1, then the product of two float
1823 _Complex operands is represented in the double _Complex format, and its parts are evaluated to
1826 <p><small><a name="note20" href="#note20">20)</a> The floating-point model in that standard sums powers of b from zero, so the values of the exponent
1827 limits are one less than shown here.
1830 <h2><a name="6" href="#6">6. Language</a></h2>
1832 <h3><a name="6.1" href="#6.1">6.1 Notation</a></h3>
1834 In the syntax notation used in this clause, syntactic categories (nonterminals) are
1835 indicated by italic type, and literal words and character set members (terminals) by bold
1836 type. A colon (:) following a nonterminal introduces its definition. Alternative
1837 definitions are listed on separate lines, except when prefaced by the words ''one of''. An
1838 optional symbol is indicated by the subscript ''opt'', so that
1840 { expressionopt }</pre>
1841 indicates an optional expression enclosed in braces.
1843 When syntactic categories are referred to in the main text, they are not italicized and
1844 words are separated by spaces instead of hyphens.
1846 A summary of the language syntax is given in <a href="#A">annex A</a>.
1848 <h3><a name="6.2" href="#6.2">6.2 Concepts</a></h3>
1850 <h4><a name="6.2.1" href="#6.2.1">6.2.1 Scopes of identifiers</a></h4>
1852 An identifier can denote an object; a function; a tag or a member of a structure, union, or
1853 enumeration; a typedef name; a label name; a macro name; or a macro parameter. The
1854 same identifier can denote different entities at different points in the program. A member
1855 of an enumeration is called an enumeration constant. Macro names and macro
1856 parameters are not considered further here, because prior to the semantic phase of
1857 program translation any occurrences of macro names in the source file are replaced by the
1858 preprocessing token sequences that constitute their macro definitions.
1860 For each different entity that an identifier designates, the identifier is visible (i.e., can be
1861 used) only within a region of program text called its scope. Different entities designated
1862 by the same identifier either have different scopes, or are in different name spaces. There
1863 are four kinds of scopes: function, file, block, and function prototype. (A function
1864 prototype is a declaration of a function that declares the types of its parameters.)
1866 A label name is the only kind of identifier that has function scope. It can be used (in a
1867 goto statement) anywhere in the function in which it appears, and is declared implicitly
1868 by its syntactic appearance (followed by a : and a statement).
1870 Every other identifier has scope determined by the placement of its declaration (in a
1871 declarator or type specifier). If the declarator or type specifier that declares the identifier
1872 appears outside of any block or list of parameters, the identifier has file scope, which
1873 terminates at the end of the translation unit. If the declarator or type specifier that
1874 declares the identifier appears inside a block or within the list of parameter declarations in
1875 a function definition, the identifier has block scope, which terminates at the end of the
1876 associated block. If the declarator or type specifier that declares the identifier appears
1878 within the list of parameter declarations in a function prototype (not part of a function
1879 definition), the identifier has function prototype scope, which terminates at the end of the
1880 function declarator. If an identifier designates two different entities in the same name
1881 space, the scopes might overlap. If so, the scope of one entity (the inner scope) will be a
1882 strict subset of the scope of the other entity (the outer scope). Within the inner scope, the
1883 identifier designates the entity declared in the inner scope; the entity declared in the outer
1884 scope is hidden (and not visible) within the inner scope.
1886 Unless explicitly stated otherwise, where this International Standard uses the term
1887 ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the
1888 entity in the relevant name space whose declaration is visible at the point the identifier
1891 Two identifiers have the same scope if and only if their scopes terminate at the same
1894 Structure, union, and enumeration tags have scope that begins just after the appearance of
1895 the tag in a type specifier that declares the tag. Each enumeration constant has scope that
1896 begins just after the appearance of its defining enumerator in an enumerator list. Any
1897 other identifier has scope that begins just after the completion of its declarator.
1898 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>), function calls (<a href="#6.5.2.2">6.5.2.2</a>), function definitions
1899 (<a href="#6.9.1">6.9.1</a>), identifiers (<a href="#6.4.2">6.4.2</a>), name spaces of identifiers (<a href="#6.2.3">6.2.3</a>), macro replacement (<a href="#6.10.3">6.10.3</a>),
1900 source file inclusion (<a href="#6.10.2">6.10.2</a>), statements (<a href="#6.8">6.8</a>).
1902 <h4><a name="6.2.2" href="#6.2.2">6.2.2 Linkages of identifiers</a></h4>
1904 An identifier declared in different scopes or in the same scope more than once can be
1905 made to refer to the same object or function by a process called linkage.<sup><a href="#note21"><b>21)</b></a></sup> There are
1906 three kinds of linkage: external, internal, and none.
1908 In the set of translation units and libraries that constitutes an entire program, each
1909 declaration of a particular identifier with external linkage denotes the same object or
1910 function. Within one translation unit, each declaration of an identifier with internal
1911 linkage denotes the same object or function. Each declaration of an identifier with no
1912 linkage denotes a unique entity.
1914 If the declaration of a file scope identifier for an object or a function contains the storage-
1915 class specifier static, the identifier has internal linkage.<sup><a href="#note22"><b>22)</b></a></sup>
1917 For an identifier declared with the storage-class specifier extern in a scope in which a
1922 prior declaration of that identifier is visible,<sup><a href="#note23"><b>23)</b></a></sup> if the prior declaration specifies internal or
1923 external linkage, the linkage of the identifier at the later declaration is the same as the
1924 linkage specified at the prior declaration. If no prior declaration is visible, or if the prior
1925 declaration specifies no linkage, then the identifier has external linkage.
1927 If the declaration of an identifier for a function has no storage-class specifier, its linkage
1928 is determined exactly as if it were declared with the storage-class specifier extern. If
1929 the declaration of an identifier for an object has file scope and no storage-class specifier,
1930 its linkage is external.
1932 The following identifiers have no linkage: an identifier declared to be anything other than
1933 an object or a function; an identifier declared to be a function parameter; a block scope
1934 identifier for an object declared without the storage-class specifier extern.
1936 If, within a translation unit, the same identifier appears with both internal and external
1937 linkage, the behavior is undefined.
1938 <p><b> Forward references</b>: 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>),
1939 statements (<a href="#6.8">6.8</a>).
1942 <p><small><a name="note21" href="#note21">21)</a> There is no linkage between different identifiers.
1944 <p><small><a name="note22" href="#note22">22)</a> A function declaration can contain the storage-class specifier static only if it is at file scope; see
1945 <a href="#6.7.1">6.7.1</a>.
1947 <p><small><a name="note23" href="#note23">23)</a> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
1950 <h4><a name="6.2.3" href="#6.2.3">6.2.3 Name spaces of identifiers</a></h4>
1952 If more than one declaration of a particular identifier is visible at any point in a
1953 translation unit, the syntactic context disambiguates uses that refer to different entities.
1954 Thus, there are separate name spaces for various categories of identifiers, as follows:
1956 <li> label names (disambiguated by the syntax of the label declaration and use);
1957 <li> the tags of structures, unions, and enumerations (disambiguated by following any<sup><a href="#note24"><b>24)</b></a></sup>
1958 of the keywords struct, union, or enum);
1959 <li> the members of structures or unions; each structure or union has a separate name
1960 space for its members (disambiguated by the type of the expression used to access the
1961 member via the . or -> operator);
1962 <li> all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
1963 enumeration constants).
1965 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), labeled statements (<a href="#6.8.1">6.8.1</a>),
1966 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
1967 (<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>).
1975 <p><small><a name="note24" href="#note24">24)</a> There is only one name space for tags even though three are possible.
1978 <h4><a name="6.2.4" href="#6.2.4">6.2.4 Storage durations of objects</a></h4>
1980 An object has a storage duration that determines its lifetime. There are three storage
1981 durations: static, automatic, and allocated. Allocated storage is described in <a href="#7.20.3">7.20.3</a>.
1983 The lifetime of an object is the portion of program execution during which storage is
1984 guaranteed to be reserved for it. An object exists, has a constant address,<sup><a href="#note25"><b>25)</b></a></sup> and retains
1985 its last-stored value throughout its lifetime.<sup><a href="#note26"><b>26)</b></a></sup> If an object is referred to outside of its
1986 lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
1987 the object it points to reaches the end of its lifetime.
1989 An object whose identifier is declared with external or internal linkage, or with the
1990 storage-class specifier static has static storage duration. Its lifetime is the entire
1991 execution of the program and its stored value is initialized only once, prior to program
1994 An object whose identifier is declared with no linkage and without the storage-class
1995 specifier static has automatic storage duration.
1997 For such an object that does not have a variable length array type, its lifetime extends
1998 from entry into the block with which it is associated until execution of that block ends in
1999 any way. (Entering an enclosed block or calling a function suspends, but does not end,
2000 execution of the current block.) If the block is entered recursively, a new instance of the
2001 object is created each time. The initial value of the object is indeterminate. If an
2002 initialization is specified for the object, it is performed each time the declaration is
2003 reached in the execution of the block; otherwise, the value becomes indeterminate each
2004 time the declaration is reached.
2006 For such an object that does have a variable length array type, its lifetime extends from
2007 the declaration of the object until execution of the program leaves the scope of the
2008 declaration.<sup><a href="#note27"><b>27)</b></a></sup> If the scope is entered recursively, a new instance of the object is created
2009 each time. The initial value of the object is indeterminate.
2010 <p><b> Forward references</b>: statements (<a href="#6.8">6.8</a>), function calls (<a href="#6.5.2.2">6.5.2.2</a>), declarators (<a href="#6.7.5">6.7.5</a>), array
2011 declarators (<a href="#6.7.5.2">6.7.5.2</a>), initialization (<a href="#6.7.8">6.7.8</a>).
2019 <p><small><a name="note25" href="#note25">25)</a> The term ''constant address'' means that two pointers to the object constructed at possibly different
2020 times will compare equal. The address may be different during two different executions of the same
2023 <p><small><a name="note26" href="#note26">26)</a> In the case of a volatile object, the last store need not be explicit in the program.
2025 <p><small><a name="note27" href="#note27">27)</a> Leaving the innermost block containing the declaration, or jumping to a point in that block or an
2026 embedded block prior to the declaration, leaves the scope of the declaration.
2029 <h4><a name="6.2.5" href="#6.2.5">6.2.5 Types</a></h4>
2031 The meaning of a value stored in an object or returned by a function is determined by the
2032 type of the expression used to access it. (An identifier declared to be an object is the
2033 simplest such expression; the type is specified in the declaration of the identifier.) Types
2034 are partitioned into object types (types that fully describe objects), function types (types
2035 that describe functions), and incomplete types (types that describe objects but lack
2036 information needed to determine their sizes).
2038 An object declared as type _Bool is large enough to store the values 0 and 1.
2040 An object declared as type char is large enough to store any member of the basic
2041 execution character set. If a member of the basic execution character set is stored in a
2042 char object, its value is guaranteed to be nonnegative. If any other character is stored in
2043 a char object, the resulting value is implementation-defined but shall be within the range
2044 of values that can be represented in that type.
2046 There are five standard signed integer types, designated as signed char, short
2047 int, int, long int, and long long int. (These and other types may be
2048 designated in several additional ways, as described in <a href="#6.7.2">6.7.2</a>.) There may also be
2049 implementation-defined extended signed integer types.<sup><a href="#note28"><b>28)</b></a></sup> The standard and extended
2050 signed integer types are collectively called signed integer types.<sup><a href="#note29"><b>29)</b></a></sup>
2052 An object declared as type signed char occupies the same amount of storage as a
2053 ''plain'' char object. A ''plain'' int object has the natural size suggested by the
2054 architecture of the execution environment (large enough to contain any value in the range
2055 INT_MIN to INT_MAX as defined in the header <a href="#7.10"><limits.h></a>).
2057 For each of the signed integer types, there is a corresponding (but different) unsigned
2058 integer type (designated with the keyword unsigned) that uses the same amount of
2059 storage (including sign information) and has the same alignment requirements. The type
2060 _Bool and the unsigned integer types that correspond to the standard signed integer
2061 types are the standard unsigned integer types. The unsigned integer types that
2062 correspond to the extended signed integer types are the extended unsigned integer types.
2063 The standard and extended unsigned integer types are collectively called unsigned integer
2064 types.<sup><a href="#note30"><b>30)</b></a></sup>
2070 The standard signed integer types and standard unsigned integer types are collectively
2071 called the standard integer types, the extended signed integer types and extended
2072 unsigned integer types are collectively called the extended integer types.
2074 For any two integer types with the same signedness and different integer conversion rank
2075 (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
2076 subrange of the values of the other type.
2078 The range of nonnegative values of a signed integer type is a subrange of the
2079 corresponding unsigned integer type, and the representation of the same value in each
2080 type is the same.<sup><a href="#note31"><b>31)</b></a></sup> A computation involving unsigned operands can never overflow,
2081 because a result that cannot be represented by the resulting unsigned integer type is
2082 reduced modulo the number that is one greater than the largest value that can be
2083 represented by the resulting type.
2085 There are three real floating types, designated as float, double, and long
2086 double.<sup><a href="#note32"><b>32)</b></a></sup> The set of values of the type float is a subset of the set of values of the
2087 type double; the set of values of the type double is a subset of the set of values of the
2090 There are three complex types, designated as float _Complex, double
2091 _Complex, and long double _Complex.<sup><a href="#note33"><b>33)</b></a></sup> The real floating and complex types
2092 are collectively called the floating types.
2094 For each floating type there is a corresponding real type, which is always a real floating
2095 type. For real floating types, it is the same type. For complex types, it is the type given
2096 by deleting the keyword _Complex from the type name.
2098 Each complex type has the same representation and alignment requirements as an array
2099 type containing exactly two elements of the corresponding real type; the first element is
2100 equal to the real part, and the second element to the imaginary part, of the complex
2103 The type char, the signed and unsigned integer types, and the floating types are
2104 collectively called the basic types. Even if the implementation defines two or more basic
2105 types to have the same representation, they are nevertheless different types.<sup><a href="#note34"><b>34)</b></a></sup>
2109 The three types char, signed char, and unsigned char are collectively called
2110 the character types. The implementation shall define char to have the same range,
2111 representation, and behavior as either signed char or unsigned char.<sup><a href="#note35"><b>35)</b></a></sup>
2113 An enumeration comprises a set of named integer constant values. Each distinct
2114 enumeration constitutes a different enumerated type.
2116 The type char, the signed and unsigned integer types, and the enumerated types are
2117 collectively called integer types. The integer and real floating types are collectively called
2120 Integer and floating types are collectively called arithmetic types. Each arithmetic type
2121 belongs to one type domain: the real type domain comprises the real types, the complex
2122 type domain comprises the complex types.
2124 The void type comprises an empty set of values; it is an incomplete type that cannot be
2127 Any number of derived types can be constructed from the object, function, and
2128 incomplete types, as follows:
2130 <li> An array type describes a contiguously allocated nonempty set of objects with a
2131 particular member object type, called the element type.<sup><a href="#note36"><b>36)</b></a></sup> Array types are
2132 characterized by their element type and by the number of elements in the array. An
2133 array type is said to be derived from its element type, and if its element type is T , the
2134 array type is sometimes called ''array of T ''. The construction of an array type from
2135 an element type is called ''array type derivation''.
2136 <li> A structure type describes a sequentially allocated nonempty set of member objects
2137 (and, in certain circumstances, an incomplete array), each of which has an optionally
2138 specified name and possibly distinct type.
2139 <li> A union type describes an overlapping nonempty set of member objects, each of
2140 which has an optionally specified name and possibly distinct type.
2141 <li> A function type describes a function with specified return type. A function type is
2142 characterized by its return type and the number and types of its parameters. A
2143 function type is said to be derived from its return type, and if its return type is T , the
2144 function type is sometimes called ''function returning T ''. The construction of a
2145 function type from a return type is called ''function type derivation''.
2150 <li> A pointer type may be derived from a function type, an object type, or an incomplete
2151 type, called the referenced type. A pointer type describes an object whose value
2152 provides a reference to an entity of the referenced type. A pointer type derived from
2153 the referenced type T is sometimes called ''pointer to T ''. The construction of a
2154 pointer type from a referenced type is called ''pointer type derivation''.
2156 These methods of constructing derived types can be applied recursively.
2158 Arithmetic types and pointer types are collectively called scalar types. Array and
2159 structure types are collectively called aggregate types.<sup><a href="#note37"><b>37)</b></a></sup>
2161 An array type of unknown size is an incomplete type. It is completed, for an identifier of
2162 that type, by specifying the size in a later declaration (with internal or external linkage).
2163 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
2164 type. It is completed, for all declarations of that type, by declaring the same structure or
2165 union tag with its defining content later in the same scope.
2167 A type has known constant size if the type is not incomplete and is not a variable length
2170 Array, function, and pointer types are collectively called derived declarator types. A
2171 declarator type derivation from a type T is the construction of a derived declarator type
2172 from T by the application of an array-type, a function-type, or a pointer-type derivation to
2175 A type is characterized by its type category, which is either the outermost derivation of a
2176 derived type (as noted above in the construction of derived types), or the type itself if the
2177 type consists of no derived types.
2179 Any type so far mentioned is an unqualified type. Each unqualified type has several
2180 qualified versions of its type,<sup><a href="#note38"><b>38)</b></a></sup> corresponding to the combinations of one, two, or all
2181 three of the const, volatile, and restrict qualifiers. The qualified or unqualified
2182 versions of a type are distinct types that belong to the same type category and have the
2183 same representation and alignment requirements.<sup><a href="#note39"><b>39)</b></a></sup> A derived type is not qualified by the
2184 qualifiers (if any) of the type from which it is derived.
2186 A pointer to void shall have the same representation and alignment requirements as a
2187 pointer to a character type.39) Similarly, pointers to qualified or unqualified versions of
2188 compatible types shall have the same representation and alignment requirements. All
2192 pointers to structure types shall have the same representation and alignment requirements
2193 as each other. All pointers to union types shall have the same representation and
2194 alignment requirements as each other. Pointers to other types need not have the same
2195 representation or alignment requirements.
2197 EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is
2198 pointer, not a floating type. The const-qualified version of this type is designated as ''float * const''
2199 whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const-
2200 qualified float'' and is a pointer to a qualified type.
2203 EXAMPLE 2 The type designated as ''struct tag (*[5])(float)'' has type ''array of pointer to
2204 function returning struct tag''. The array has length five and the function has a single parameter of type
2205 float. Its type category is array.
2207 <p><b> Forward references</b>: compatible type and composite type (<a href="#6.2.7">6.2.7</a>), declarations (<a href="#6.7">6.7</a>).
2210 <p><small><a name="note28" href="#note28">28)</a> Implementation-defined keywords shall have the form of an identifier reserved for any use as
2211 described in <a href="#7.1.3">7.1.3</a>.
2213 <p><small><a name="note29" href="#note29">29)</a> Therefore, any statement in this Standard about signed integer types also applies to the extended
2214 signed integer types.
2216 <p><small><a name="note30" href="#note30">30)</a> Therefore, any statement in this Standard about unsigned integer types also applies to the extended
2217 unsigned integer types.
2219 <p><small><a name="note31" href="#note31">31)</a> The same representation and alignment requirements are meant to imply interchangeability as
2220 arguments to functions, return values from functions, and members of unions.
2222 <p><small><a name="note32" href="#note32">32)</a> See ''future language directions'' (<a href="#6.11.1">6.11.1</a>).
2224 <p><small><a name="note33" href="#note33">33)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
2226 <p><small><a name="note34" href="#note34">34)</a> An implementation may define new keywords that provide alternative ways to designate a basic (or
2227 any other) type; this does not violate the requirement that all basic types be different.
2228 Implementation-defined keywords shall have the form of an identifier reserved for any use as
2229 described in <a href="#7.1.3">7.1.3</a>.
2231 <p><small><a name="note35" href="#note35">35)</a> 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
2232 used to distinguish the two options. Irrespective of the choice made, char is a separate type from the
2233 other two and is not compatible with either.
2235 <p><small><a name="note36" href="#note36">36)</a> Since object types do not include incomplete types, an array of incomplete type cannot be constructed.
2237 <p><small><a name="note37" href="#note37">37)</a> Note that aggregate type does not include union type because an object with union type can only
2238 contain one member at a time.
2240 <p><small><a name="note38" href="#note38">38)</a> See <a href="#6.7.3">6.7.3</a> regarding qualified array and function types.
2242 <p><small><a name="note39" href="#note39">39)</a> The same representation and alignment requirements are meant to imply interchangeability as
2243 arguments to functions, return values from functions, and members of unions.
2246 <h4><a name="6.2.6" href="#6.2.6">6.2.6 Representations of types</a></h4>
2248 <h5><a name="6.2.6.1" href="#6.2.6.1">6.2.6.1 General</a></h5>
2250 The representations of all types are unspecified except as stated in this subclause.
2252 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes,
2253 the number, order, and encoding of which are either explicitly specified or
2254 implementation-defined.
2256 Values stored in unsigned bit-fields and objects of type unsigned char shall be
2257 represented using a pure binary notation.<sup><a href="#note40"><b>40)</b></a></sup>
2259 Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT
2260 bits, where n is the size of an object of that type, in bytes. The value may be copied into
2261 an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is
2262 called the object representation of the value. Values stored in bit-fields consist of m bits,
2263 where m is the size specified for the bit-field. The object representation is the set of m
2264 bits the bit-field comprises in the addressable storage unit holding it. Two values (other
2265 than NaNs) with the same object representation compare equal, but values that compare
2266 equal may have different object representations.
2268 Certain object representations need not represent a value of the object type. If the stored
2269 value of an object has such a representation and is read by an lvalue expression that does
2270 not have character type, the behavior is undefined. If such a representation is produced
2271 by a side effect that modifies all or any part of the object by an lvalue expression that
2272 does not have character type, the behavior is undefined.<sup><a href="#note41"><b>41)</b></a></sup> Such a representation is called
2275 a trap representation.
2277 When a value is stored in an object of structure or union type, including in a member
2278 object, the bytes of the object representation that correspond to any padding bytes take
2279 unspecified values.<sup><a href="#note42"><b>42)</b></a></sup> The value of a structure or union object is never a trap
2280 representation, even though the value of a member of the structure or union object may be
2281 a trap representation.
2283 When a value is stored in a member of an object of union type, the bytes of the object
2284 representation that do not correspond to that member but do correspond to other members
2285 take unspecified values.
2287 Where an operator is applied to a value that has more than one object representation,
2288 which object representation is used shall not affect the value of the result.<sup><a href="#note43"><b>43)</b></a></sup> Where a
2289 value is stored in an object using a type that has more than one object representation for
2290 that value, it is unspecified which representation is used, but a trap representation shall
2292 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>), expressions (<a href="#6.5">6.5</a>), lvalues, arrays, and function
2293 designators (<a href="#6.3.2.1">6.3.2.1</a>).
2296 <p><small><a name="note40" href="#note40">40)</a> A positional representation for integers that uses the binary digits 0 and 1, in which the values
2297 represented by successive bits are additive, begin with 1, and are multiplied by successive integral
2298 powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
2299 Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
2300 type unsigned char range from 0 to 2
2306 <p><small><a name="note41" href="#note41">41)</a> Thus, an automatic variable can be initialized to a trap representation without causing undefined
2307 behavior, but the value of the variable cannot be used until a proper value is stored in it.
2309 <p><small><a name="note42" href="#note42">42)</a> Thus, for example, structure assignment need not copy any padding bits.
2311 <p><small><a name="note43" href="#note43">43)</a> It is possible for objects x and y with the same effective type T to have the same value when they are
2312 accessed as objects of type T, but to have different values in other contexts. In particular, if == is
2313 defined for type T, then x == y does not imply that memcmp(&x, &y, sizeof (T)) == 0.
2314 Furthermore, x == y does not necessarily imply that x and y have the same value; other operations
2315 on values of type T may distinguish between them.
2318 <h5><a name="6.2.6.2" href="#6.2.6.2">6.2.6.2 Integer types</a></h5>
2320 For unsigned integer types other than unsigned char, the bits of the object
2321 representation shall be divided into two groups: value bits and padding bits (there need
2322 not be any of the latter). If there are N value bits, each bit shall represent a different
2323 power of 2 between 1 and 2 N -1 , so that objects of that type shall be capable of
2324 representing values from 0 to 2 N - 1 using a pure binary representation; this shall be
2325 known as the value representation. The values of any padding bits are unspecified.<sup><a href="#note44"><b>44)</b></a></sup>
2327 For signed integer types, the bits of the object representation shall be divided into three
2328 groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
2331 there shall be exactly one sign bit. Each bit that is a value bit shall have the same value as
2332 the same bit in the object representation of the corresponding unsigned type (if there are
2333 M value bits in the signed type and N in the unsigned type, then M <= N ). If the sign bit
2334 is zero, it shall not affect the resulting value. If the sign bit is one, the value shall be
2335 modified in one of the following ways:
2337 <li> the corresponding value with sign bit 0 is negated (sign and magnitude);
2338 <li> the sign bit has the value -(2 N ) (two's complement);
2339 <li> the sign bit has the value -(2 N - 1) (ones' complement ).
2341 Which of these applies is implementation-defined, as is whether the value with sign bit 1
2342 and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones'
2343 complement), is a trap representation or a normal value. In the case of sign and
2344 magnitude and ones' complement, if this representation is a normal value it is called a
2347 If the implementation supports negative zeros, they shall be generated only by:
2349 <li> the &, |, ^, ~, <<, and >> operators with arguments that produce such a value;
2350 <li> the +, -, *, /, and % operators where one argument is a negative zero and the result is
2352 <li> compound assignment operators based on the above cases.
2354 It is unspecified whether these cases actually generate a negative zero or a normal zero,
2355 and whether a negative zero becomes a normal zero when stored in an object.
2357 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
2358 and >> operators with arguments that would produce such a value is undefined.
2360 The values of any padding bits are unspecified.<sup><a href="#note45"><b>45)</b></a></sup> A valid (non-trap) object representation
2361 of a signed integer type where the sign bit is zero is a valid object representation of the
2362 corresponding unsigned type, and shall represent the same value. For any integer type,
2363 the object representation where all the bits are zero shall be a representation of the value
2366 The precision of an integer type is the number of bits it uses to represent values,
2367 excluding any sign and padding bits. The width of an integer type is the same but
2368 including any sign bit; thus for unsigned integer types the two values are the same, while
2372 for signed integer types the width is one greater than the precision.
2375 <p><small><a name="note44" href="#note44">44)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
2376 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2377 representation other than as part of an exceptional condition such as an overflow, and this cannot occur
2378 with unsigned types. All other combinations of padding bits are alternative object representations of
2379 the value specified by the value bits.
2381 <p><small><a name="note45" href="#note45">45)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
2382 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2383 representation other than as part of an exceptional condition such as an overflow. All other
2384 combinations of padding bits are alternative object representations of the value specified by the value
2388 <h4><a name="6.2.7" href="#6.2.7">6.2.7 Compatible type and composite type</a></h4>
2390 Two types have compatible type if their types are the same. Additional rules for
2391 determining whether two types are compatible are described in <a href="#6.7.2">6.7.2</a> for type specifiers,
2392 in <a href="#6.7.3">6.7.3</a> for type qualifiers, and in <a href="#6.7.5">6.7.5</a> for declarators.<sup><a href="#note46"><b>46)</b></a></sup> Moreover, two structure,
2393 union, or enumerated types declared in separate translation units are compatible if their
2394 tags and members satisfy the following requirements: If one is declared with a tag, the
2395 other shall be declared with the same tag. If both are complete types, then the following
2396 additional requirements apply: there shall be a one-to-one correspondence between their
2397 members such that each pair of corresponding members are declared with compatible
2398 types, and such that if one member of a corresponding pair is declared with a name, the
2399 other member is declared with the same name. For two structures, corresponding
2400 members shall be declared in the same order. For two structures or unions, corresponding
2401 bit-fields shall have the same widths. For two enumerations, corresponding members
2402 shall have the same values.
2404 All declarations that refer to the same object or function shall have compatible type;
2405 otherwise, the behavior is undefined.
2407 A composite type can be constructed from two types that are compatible; it is a type that
2408 is compatible with both of the two types and satisfies the following conditions:
2410 <li> If one type is an array of known constant size, the composite type is an array of that
2411 size; otherwise, if one type is a variable length array, the composite type is that type.
2412 <li> If only one type is a function type with a parameter type list (a function prototype),
2413 the composite type is a function prototype with the parameter type list.
2414 <li> If both types are function types with parameter type lists, the type of each parameter
2415 in the composite parameter type list is the composite type of the corresponding
2418 These rules apply recursively to the types from which the two types are derived.
2420 For an identifier with internal or external linkage declared in a scope in which a prior
2421 declaration of that identifier is visible,<sup><a href="#note47"><b>47)</b></a></sup> if the prior declaration specifies internal or
2422 external linkage, the type of the identifier at the later declaration becomes the composite
2430 EXAMPLE Given the following two file scope declarations:
2432 int f(int (*)(), double (*)[3]);
2433 int f(int (*)(char *), double (*)[]);</pre>
2434 The resulting composite type for the function is:
2437 int f(int (*)(char *), double (*)[3]);</pre>
2440 <p><small><a name="note46" href="#note46">46)</a> Two types need not be identical to be compatible.
2442 <p><small><a name="note47" href="#note47">47)</a> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
2445 <h3><a name="6.3" href="#6.3">6.3 Conversions</a></h3>
2447 Several operators convert operand values from one type to another automatically. This
2448 subclause specifies the result required from such an implicit conversion, as well as those
2449 that result from a cast operation (an explicit conversion). The list in <a href="#6.3.1.8">6.3.1.8</a> summarizes
2450 the conversions performed by most ordinary operators; it is supplemented as required by
2451 the discussion of each operator in <a href="#6.5">6.5</a>.
2453 Conversion of an operand value to a compatible type causes no change to the value or the
2455 <p><b> Forward references</b>: cast operators (<a href="#6.5.4">6.5.4</a>).
2457 <h4><a name="6.3.1" href="#6.3.1">6.3.1 Arithmetic operands</a></h4>
2459 <h5><a name="6.3.1.1" href="#6.3.1.1">6.3.1.1 Boolean, characters, and integers</a></h5>
2461 Every integer type has an integer conversion rank defined as follows:
2463 <li> No two signed integer types shall have the same rank, even if they have the same
2465 <li> The rank of a signed integer type shall be greater than the rank of any signed integer
2466 type with less precision.
2467 <li> The rank of long long int shall be greater than the rank of long int, which
2468 shall be greater than the rank of int, which shall be greater than the rank of short
2469 int, which shall be greater than the rank of signed char.
2470 <li> The rank of any unsigned integer type shall equal the rank of the corresponding
2471 signed integer type, if any.
2472 <li> The rank of any standard integer type shall be greater than the rank of any extended
2473 integer type with the same width.
2474 <li> The rank of char shall equal the rank of signed char and unsigned char.
2475 <li> The rank of _Bool shall be less than the rank of all other standard integer types.
2476 <li> The rank of any enumerated type shall equal the rank of the compatible integer type
2477 (see <a href="#6.7.2.2">6.7.2.2</a>).
2478 <li> The rank of any extended signed integer type relative to another extended signed
2479 integer type with the same precision is implementation-defined, but still subject to the
2480 other rules for determining the integer conversion rank.
2481 <li> For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has
2482 greater rank than T3, then T1 has greater rank than T3.
2485 The following may be used in an expression wherever an int or unsigned int may
2489 <li> An object or expression with an integer type whose integer conversion rank is less
2490 than or equal to the rank of int and unsigned int.
2491 <li> A bit-field of type _Bool, int, signed int, or unsigned int.
2493 If an int can represent all values of the original type, the value is converted to an int;
2494 otherwise, it is converted to an unsigned int. These are called the integer
2495 promotions.<sup><a href="#note48"><b>48)</b></a></sup> All other types are unchanged by the integer promotions.
2497 The integer promotions preserve value including sign. As discussed earlier, whether a
2498 ''plain'' char is treated as signed is implementation-defined.
2499 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
2500 (<a href="#6.7.2.1">6.7.2.1</a>).
2503 <p><small><a name="note48" href="#note48">48)</a> The integer promotions are applied only: as part of the usual arithmetic conversions, to certain
2504 argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the
2505 shift operators, as specified by their respective subclauses.
2508 <h5><a name="6.3.1.2" href="#6.3.1.2">6.3.1.2 Boolean type</a></h5>
2510 When any scalar value is converted to _Bool, the result is 0 if the value compares equal
2511 to 0; otherwise, the result is 1.
2513 <h5><a name="6.3.1.3" href="#6.3.1.3">6.3.1.3 Signed and unsigned integers</a></h5>
2515 When a value with integer type is converted to another integer type other than _Bool, if
2516 the value can be represented by the new type, it is unchanged.
2518 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or
2519 subtracting one more than the maximum value that can be represented in the new type
2520 until the value is in the range of the new type.<sup><a href="#note49"><b>49)</b></a></sup>
2522 Otherwise, the new type is signed and the value cannot be represented in it; either the
2523 result is implementation-defined or an implementation-defined signal is raised.
2526 <p><small><a name="note49" href="#note49">49)</a> The rules describe arithmetic on the mathematical value, not the value of a given type of expression.
2529 <h5><a name="6.3.1.4" href="#6.3.1.4">6.3.1.4 Real floating and integer</a></h5>
2531 When a finite value of real floating type is converted to an integer type other than _Bool,
2532 the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
2533 the integral part cannot be represented by the integer type, the behavior is undefined.<sup><a href="#note50"><b>50)</b></a></sup>
2535 When a value of integer type is converted to a real floating type, if the value being
2536 converted can be represented exactly in the new type, it is unchanged. If the value being
2537 converted is in the range of values that can be represented but cannot be represented
2540 exactly, the result is either the nearest higher or nearest lower representable value, chosen
2541 in an implementation-defined manner. If the value being converted is outside the range of
2542 values that can be represented, the behavior is undefined.
2545 <p><small><a name="note50" href="#note50">50)</a> The remaindering operation performed when a value of integer type is converted to unsigned type
2546 need not be performed when a value of real floating type is converted to unsigned type. Thus, the
2547 range of portable real floating values is (-1, Utype_MAX+1).
2550 <h5><a name="6.3.1.5" href="#6.3.1.5">6.3.1.5 Real floating types</a></h5>
2552 When a float is promoted to double or long double, or a double is promoted
2553 to long double, its value is unchanged (if the source value is represented in the
2554 precision and range of its type).
2556 When a double is demoted to float, a long double is demoted to double or
2557 float, or a value being represented in greater precision and range than required by its
2558 semantic type (see <a href="#6.3.1.8">6.3.1.8</a>) is explicitly converted (including to its own type), if the value
2559 being converted can be represented exactly in the new type, it is unchanged. If the value
2560 being converted is in the range of values that can be represented but cannot be
2561 represented exactly, the result is either the nearest higher or nearest lower representable
2562 value, chosen in an implementation-defined manner. If the value being converted is
2563 outside the range of values that can be represented, the behavior is undefined.
2565 <h5><a name="6.3.1.6" href="#6.3.1.6">6.3.1.6 Complex types</a></h5>
2567 When a value of complex type is converted to another complex type, both the real and
2568 imaginary parts follow the conversion rules for the corresponding real types.
2570 <h5><a name="6.3.1.7" href="#6.3.1.7">6.3.1.7 Real and complex</a></h5>
2572 When a value of real type is converted to a complex type, the real part of the complex
2573 result value is determined by the rules of conversion to the corresponding real type and
2574 the imaginary part of the complex result value is a positive zero or an unsigned zero.
2576 When a value of complex type is converted to a real type, the imaginary part of the
2577 complex value is discarded and the value of the real part is converted according to the
2578 conversion rules for the corresponding real type.
2580 <h5><a name="6.3.1.8" href="#6.3.1.8">6.3.1.8 Usual arithmetic conversions</a></h5>
2582 Many operators that expect operands of arithmetic type cause conversions and yield result
2583 types in a similar way. The purpose is to determine a common real type for the operands
2584 and result. For the specified operands, each operand is converted, without change of type
2585 domain, to a type whose corresponding real type is the common real type. Unless
2586 explicitly stated otherwise, the common real type is also the corresponding real type of
2587 the result, whose type domain is the type domain of the operands if they are the same,
2588 and complex otherwise. This pattern is called the usual arithmetic conversions:
2592 First, if the corresponding real type of either operand is long double, the other
2593 operand is converted, without change of type domain, to a type whose
2594 corresponding real type is long double.
2595 Otherwise, if the corresponding real type of either operand is double, the other
2596 operand is converted, without change of type domain, to a type whose
2597 corresponding real type is double.
2598 Otherwise, if the corresponding real type of either operand is float, the other
2599 operand is converted, without change of type domain, to a type whose
2600 corresponding real type is float.<sup><a href="#note51"><b>51)</b></a></sup>
2601 Otherwise, the integer promotions are performed on both operands. Then the
2602 following rules are applied to the promoted operands:
2603 If both operands have the same type, then no further conversion is needed.
2604 Otherwise, if both operands have signed integer types or both have unsigned
2605 integer types, the operand with the type of lesser integer conversion rank is
2606 converted to the type of the operand with greater rank.
2607 Otherwise, if the operand that has unsigned integer type has rank greater or
2608 equal to the rank of the type of the other operand, then the operand with
2609 signed integer type is converted to the type of the operand with unsigned
2611 Otherwise, if the type of the operand with signed integer type can represent
2612 all of the values of the type of the operand with unsigned integer type, then
2613 the operand with unsigned integer type is converted to the type of the
2614 operand with signed integer type.
2615 Otherwise, both operands are converted to the unsigned integer type
2616 corresponding to the type of the operand with signed integer type.</pre>
2617 The values of floating operands and of the results of floating expressions may be
2618 represented in greater precision and range than that required by the type; the types are not
2619 changed thereby.<sup><a href="#note52"><b>52)</b></a></sup>
2627 <p><small><a name="note51" href="#note51">51)</a> For example, addition of a double _Complex and a float entails just the conversion of the
2628 float operand to double (and yields a double _Complex result).
2630 <p><small><a name="note52" href="#note52">52)</a> The cast and assignment operators are still required to perform their specified conversions as
2631 described in <a href="#6.3.1.4">6.3.1.4</a> and <a href="#6.3.1.5">6.3.1.5</a>.
2634 <h4><a name="6.3.2" href="#6.3.2">6.3.2 Other operands</a></h4>
2636 <h5><a name="6.3.2.1" href="#6.3.2.1">6.3.2.1 Lvalues, arrays, and function designators</a></h5>
2638 An lvalue is an expression with an object type or an incomplete type other than void;<sup><a href="#note53"><b>53)</b></a></sup>
2639 if an lvalue does not designate an object when it is evaluated, the behavior is undefined.
2640 When an object is said to have a particular type, the type is specified by the lvalue used to
2641 designate the object. A modifiable lvalue is an lvalue that does not have array type, does
2642 not have an incomplete type, does not have a const-qualified type, and if it is a structure
2643 or union, does not have any member (including, recursively, any member or element of
2644 all contained aggregates or unions) with a const-qualified type.
2646 Except when it is the operand of the sizeof operator, the unary & operator, the ++
2647 operator, the -- operator, or the left operand of the . operator or an assignment operator,
2648 an lvalue that does not have array type is converted to the value stored in the designated
2649 object (and is no longer an lvalue). If the lvalue has qualified type, the value has the
2650 unqualified version of the type of the lvalue; otherwise, the value has the type of the
2651 lvalue. If the lvalue has an incomplete type and does not have array type, the behavior is
2654 Except when it is the operand of the sizeof operator or the unary & operator, or is a
2655 string literal used to initialize an array, an expression that has type ''array of type'' is
2656 converted to an expression with type ''pointer to type'' that points to the initial element of
2657 the array object and is not an lvalue. If the array object has register storage class, the
2658 behavior is undefined.
2660 A function designator is an expression that has function type. Except when it is the
2661 operand of the sizeof operator<sup><a href="#note54"><b>54)</b></a></sup> or the unary & operator, a function designator with
2662 type ''function returning type'' is converted to an expression that has type ''pointer to
2663 function returning type''.
2664 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), assignment operators
2665 (<a href="#6.5.16">6.5.16</a>), common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), initialization (<a href="#6.7.8">6.7.8</a>), postfix
2666 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2667 (<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>).
2673 <p><small><a name="note53" href="#note53">53)</a> The name ''lvalue'' comes originally from the assignment expression E1 = E2, in which the left
2674 operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
2675 object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described
2676 as the ''value of an expression''.
2677 An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
2678 expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.
2680 <p><small><a name="note54" href="#note54">54)</a> Because this conversion does not occur, the operand of the sizeof operator remains a function
2681 designator and violates the constraint in <a href="#6.5.3.4">6.5.3.4</a>.
2684 <h5><a name="6.3.2.2" href="#6.3.2.2">6.3.2.2 void</a></h5>
2686 The (nonexistent) value of a void expression (an expression that has type void) shall not
2687 be used in any way, and implicit or explicit conversions (except to void) shall not be
2688 applied to such an expression. If an expression of any other type is evaluated as a void
2689 expression, its value or designator is discarded. (A void expression is evaluated for its
2692 <h5><a name="6.3.2.3" href="#6.3.2.3">6.3.2.3 Pointers</a></h5>
2694 A pointer to void may be converted to or from a pointer to any incomplete or object
2695 type. A pointer to any incomplete or object type may be converted to a pointer to void
2696 and back again; the result shall compare equal to the original pointer.
2698 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to
2699 the q-qualified version of the type; the values stored in the original and converted pointers
2700 shall compare equal.
2702 An integer constant expression with the value 0, or such an expression cast to type
2703 void *, is called a null pointer constant.<sup><a href="#note55"><b>55)</b></a></sup> If a null pointer constant is converted to a
2704 pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal
2705 to a pointer to any object or function.
2707 Conversion of a null pointer to another pointer type yields a null pointer of that type.
2708 Any two null pointers shall compare equal.
2710 An integer may be converted to any pointer type. Except as previously specified, the
2711 result is implementation-defined, might not be correctly aligned, might not point to an
2712 entity of the referenced type, and might be a trap representation.<sup><a href="#note56"><b>56)</b></a></sup>
2714 Any pointer type may be converted to an integer type. Except as previously specified, the
2715 result is implementation-defined. If the result cannot be represented in the integer type,
2716 the behavior is undefined. The result need not be in the range of values of any integer
2719 A pointer to an object or incomplete type may be converted to a pointer to a different
2720 object or incomplete type. If the resulting pointer is not correctly aligned<sup><a href="#note57"><b>57)</b></a></sup> for the
2721 pointed-to type, the behavior is undefined. Otherwise, when converted back again, the
2722 result shall compare equal to the original pointer. When a pointer to an object is
2726 converted to a pointer to a character type, the result points to the lowest addressed byte of
2727 the object. Successive increments of the result, up to the size of the object, yield pointers
2728 to the remaining bytes of the object.
2730 A pointer to a function of one type may be converted to a pointer to a function of another
2731 type and back again; the result shall compare equal to the original pointer. If a converted
2732 pointer is used to call a function whose type is not compatible with the pointed-to type,
2733 the behavior is undefined.
2734 <p><b> Forward references</b>: cast operators (<a href="#6.5.4">6.5.4</a>), equality operators (<a href="#6.5.9">6.5.9</a>), integer types
2735 capable of holding object pointers (<a href="#7.18.1.4">7.18.1.4</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>).
2739 <p><small><a name="note55" href="#note55">55)</a> The macro NULL is defined in <a href="#7.17"><stddef.h></a> (and other headers) as a null pointer constant; see <a href="#7.17">7.17</a>.
2741 <p><small><a name="note56" href="#note56">56)</a> The mapping functions for converting a pointer to an integer or an integer to a pointer are intended to
2742 be consistent with the addressing structure of the execution environment.
2744 <p><small><a name="note57" href="#note57">57)</a> In general, the concept ''correctly aligned'' is transitive: if a pointer to type A is correctly aligned for a
2745 pointer to type B, which in turn is correctly aligned for a pointer to type C, then a pointer to type A is
2746 correctly aligned for a pointer to type C.
2749 <h3><a name="6.4" href="#6.4">6.4 Lexical elements</a></h3>
2759 preprocessing-token:
2766 each non-white-space character that cannot be one of the above</pre>
2767 <h6>Constraints</h6>
2769 Each preprocessing token that is converted to a token shall have the lexical form of a
2770 keyword, an identifier, a constant, a string literal, or a punctuator.
2773 A token is the minimal lexical element of the language in translation phases 7 and 8. The
2774 categories of tokens are: keywords, identifiers, constants, string literals, and punctuators.
2775 A preprocessing token is the minimal lexical element of the language in translation
2776 phases 3 through 6. The categories of preprocessing tokens are: header names,
2777 identifiers, preprocessing numbers, character constants, string literals, punctuators, and
2778 single non-white-space characters that do not lexically match the other preprocessing
2779 token categories.<sup><a href="#note58"><b>58)</b></a></sup> If a ' or a " character matches the last category, the behavior is
2780 undefined. Preprocessing tokens can be separated by white space; this consists of
2781 comments (described later), or white-space characters (space, horizontal tab, new-line,
2782 vertical tab, and form-feed), or both. As described in <a href="#6.10">6.10</a>, in certain circumstances
2783 during translation phase 4, white space (or the absence thereof) serves as more than
2784 preprocessing token separation. White space may appear within a preprocessing token
2785 only as part of a header name or between the quotation characters in a character constant
2792 If the input stream has been parsed into preprocessing tokens up to a given character, the
2793 next preprocessing token is the longest sequence of characters that could constitute a
2794 preprocessing token. There is one exception to this rule: header name preprocessing
2795 tokens are recognized only within #include preprocessing directives and in
2796 implementation-defined locations within #pragma directives. In such contexts, a
2797 sequence of characters that could be either a header name or a string literal is recognized
2800 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a
2801 valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex
2802 might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program
2803 fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or
2804 not E is a macro name.
2807 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
2808 increment operators, even though the parse x ++ + ++ y might yield a correct expression.
2810 <p><b> Forward references</b>: 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>),
2811 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
2812 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2813 (<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
2814 (<a href="#6.4.5">6.4.5</a>).
2817 <p><small><a name="note58" href="#note58">58)</a> 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
2818 occur in source files.
2821 <h4><a name="6.4.1" href="#6.4.1">6.4.1 Keywords</a></h4>
2826 auto enum restrict unsigned
2827 break extern return void
2828 case float short volatile
2829 char for signed while
2830 const goto sizeof _Bool
2831 continue if static _Complex
2832 default inline struct _Imaginary
2835 else register union</pre>
2838 The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as
2839 keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
2840 specifying imaginary types.<sup><a href="#note59"><b>59)</b></a></sup>
2847 <p><small><a name="note59" href="#note59">59)</a> One possible specification for imaginary types appears in <a href="#G">annex G</a>.
2850 <h4><a name="6.4.2" href="#6.4.2">6.4.2 Identifiers</a></h4>
2852 <h5><a name="6.4.2.1" href="#6.4.2.1">6.4.2.1 General</a></h5>
2858 identifier identifier-nondigit
2860 identifier-nondigit:
2862 universal-character-name
2863 other implementation-defined characters
2865 _ a b c d e f g h i j k l m
2866 n o p q r s t u v w x y z
2867 A B C D E F G H I J K L M
2868 N O P Q R S T U V W X Y Z
2870 0 1 2 3 4 5 6 7 8 9</pre>
2873 An identifier is a sequence of nondigit characters (including the underscore _, the
2874 lowercase and uppercase Latin letters, and other characters) and digits, which designates
2875 one or more entities as described in <a href="#6.2.1">6.2.1</a>. Lowercase and uppercase letters are distinct.
2876 There is no specific limit on the maximum length of an identifier.
2878 Each universal character name in an identifier shall designate a character whose encoding
2879 in ISO/IEC 10646 falls into one of the ranges specified in <a href="#D">annex D</a>.<sup><a href="#note60"><b>60)</b></a></sup> The initial
2880 character shall not be a universal character name designating a digit. An implementation
2881 may allow multibyte characters that are not part of the basic source character set to
2882 appear in identifiers; which characters and their correspondence to universal character
2883 names is implementation-defined.
2885 When preprocessing tokens are converted to tokens during translation phase 7, if a
2886 preprocessing token could be converted to either a keyword or an identifier, it is converted
2891 Implementation limits
2893 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of significant initial
2894 characters in an identifier; the limit for an external name (an identifier that has external
2895 linkage) may be more restrictive than that for an internal name (a macro name or an
2896 identifier that does not have external linkage). The number of significant characters in an
2897 identifier is implementation-defined.
2899 Any identifiers that differ in a significant character are different identifiers. If two
2900 identifiers differ only in nonsignificant characters, the behavior is undefined.
2901 <p><b> Forward references</b>: universal character names (<a href="#6.4.3">6.4.3</a>), macro replacement (<a href="#6.10.3">6.10.3</a>).
2904 <p><small><a name="note60" href="#note60">60)</a> On systems in which linkers cannot accept extended characters, an encoding of the universal character
2905 name may be used in forming valid external identifiers. For example, some otherwise unused
2906 character or sequence of characters may be used to encode the \u in a universal character name.
2907 Extended characters may produce a long external identifier.
2910 <h5><a name="6.4.2.2" href="#6.4.2.2">6.4.2.2 Predefined identifiers</a></h5>
2913 The identifier __func__ shall be implicitly declared by the translator as if,
2914 immediately following the opening brace of each function definition, the declaration
2916 static const char __func__[] = "function-name";</pre>
2917 appeared, where function-name is the name of the lexically-enclosing function.<sup><a href="#note61"><b>61)</b></a></sup>
2919 This name is encoded as if the implicit declaration had been written in the source
2920 character set and then translated into the execution character set as indicated in translation
2923 EXAMPLE Consider the code fragment:
2925 #include <a href="#7.19"><stdio.h></a>
2928 printf("%s\n", __func__);
2931 Each time the function is called, it will print to the standard output stream:
2935 <p><b> Forward references</b>: function definitions (<a href="#6.9.1">6.9.1</a>).
2943 <p><small><a name="note61" href="#note61">61)</a> Since the name __func__ is reserved for any use by the implementation (<a href="#7.1.3">7.1.3</a>), if any other
2944 identifier is explicitly declared using the name __func__, the behavior is undefined.
2947 <h4><a name="6.4.3" href="#6.4.3">6.4.3 Universal character names</a></h4>
2951 universal-character-name:
2953 \U hex-quad hex-quad
2955 hexadecimal-digit hexadecimal-digit
2956 hexadecimal-digit hexadecimal-digit</pre>
2957 <h6>Constraints</h6>
2959 A universal character name shall not specify a character whose short identifier is less than
2960 00A0 other than 0024 ($), 0040 (@), or 0060 ('), nor one in the range D800 through
2961 DFFF inclusive.<sup><a href="#note62"><b>62)</b></a></sup>
2962 <h6>Description</h6>
2964 Universal character names may be used in identifiers, character constants, and string
2965 literals to designate characters that are not in the basic character set.
2968 The universal character name \Unnnnnnnn designates the character whose eight-digit
2969 short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.<sup><a href="#note63"><b>63)</b></a></sup> Similarly, the universal
2970 character name \unnnn designates the character whose four-digit short identifier is nnnn
2971 (and whose eight-digit short identifier is 0000nnnn).
2979 <p><small><a name="note62" href="#note62">62)</a> The disallowed characters are the characters in the basic character set and the code positions reserved
2980 by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by
2983 <p><small><a name="note63" href="#note63">63)</a> Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
2986 <h4><a name="6.4.4" href="#6.4.4">6.4.4 Constants</a></h4>
2993 enumeration-constant
2994 character-constant</pre>
2995 <h6>Constraints</h6>
2997 Each constant shall have a type and the value of a constant shall be in the range of
2998 representable values for its type.
3001 Each constant has a type, determined by its form and value, as detailed later.
3003 <h5><a name="6.4.4.1" href="#6.4.4.1">6.4.4.1 Integer constants</a></h5>
3009 decimal-constant integer-suffixopt
3010 octal-constant integer-suffixopt
3011 hexadecimal-constant integer-suffixopt
3014 decimal-constant digit
3017 octal-constant octal-digit
3018 hexadecimal-constant:
3019 hexadecimal-prefix hexadecimal-digit
3020 hexadecimal-constant hexadecimal-digit
3021 hexadecimal-prefix: one of
3023 nonzero-digit: one of
3027 hexadecimal-digit: one of
3032 unsigned-suffix long-suffixopt
3033 unsigned-suffix long-long-suffix
3034 long-suffix unsigned-suffixopt
3035 long-long-suffix unsigned-suffixopt
3036 unsigned-suffix: one of
3040 long-long-suffix: one of
3042 <h6>Description</h6>
3044 An integer constant begins with a digit, but has no period or exponent part. It may have a
3045 prefix that specifies its base and a suffix that specifies its type.
3047 A decimal constant begins with a nonzero digit and consists of a sequence of decimal
3048 digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
3049 digits 0 through 7 only. A hexadecimal constant consists of the prefix 0x or 0X followed
3050 by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
3051 10 through 15 respectively.
3054 The value of a decimal constant is computed base 10; that of an octal constant, base 8;
3055 that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
3057 The type of an integer constant is the first of the corresponding list in which its value can
3061 Octal or Hexadecimal</pre>
3062 Suffix Decimal Constant Constant
3066 long int unsigned int
3067 long long int long int
3070 unsigned long long int</pre>
3072 u or U unsigned int unsigned int
3074 unsigned long int unsigned long int
3075 unsigned long long int unsigned long long int</pre>
3077 l or L long int long int
3079 long long int unsigned long int
3081 unsigned long long int</pre>
3083 Both u or U unsigned long int unsigned long int
3084 and l or L unsigned long long int unsigned long long int
3086 ll or LL long long int long long int
3088 unsigned long long int</pre>
3090 Both u or U unsigned long long int unsigned long long int
3093 If an integer constant cannot be represented by any type in its list, it may have an
3094 extended integer type, if the extended integer type can represent its value. If all of the
3095 types in the list for the constant are signed, the extended integer type shall be signed. If
3096 all of the types in the list for the constant are unsigned, the extended integer type shall be
3097 unsigned. If the list contains both signed and unsigned types, the extended integer type
3098 may be signed or unsigned. If an integer constant cannot be represented by any type in
3099 its list and has no extended integer type, then the integer constant has no type.
3102 <h5><a name="6.4.4.2" href="#6.4.4.2">6.4.4.2 Floating constants</a></h5>
3108 decimal-floating-constant
3109 hexadecimal-floating-constant
3110 decimal-floating-constant:
3111 fractional-constant exponent-partopt floating-suffixopt
3112 digit-sequence exponent-part floating-suffixopt
3113 hexadecimal-floating-constant:
3114 hexadecimal-prefix hexadecimal-fractional-constant
3115 binary-exponent-part floating-suffixopt
3116 hexadecimal-prefix hexadecimal-digit-sequence
3117 binary-exponent-part floating-suffixopt
3118 fractional-constant:
3119 digit-sequenceopt . digit-sequence
3122 e signopt digit-sequence
3123 E signopt digit-sequence
3128 digit-sequence digit
3129 hexadecimal-fractional-constant:
3130 hexadecimal-digit-sequenceopt .
3131 hexadecimal-digit-sequence
3132 hexadecimal-digit-sequence .
3133 binary-exponent-part:
3134 p signopt digit-sequence
3135 P signopt digit-sequence
3136 hexadecimal-digit-sequence:
3138 hexadecimal-digit-sequence hexadecimal-digit
3139 floating-suffix: one of
3141 <h6>Description</h6>
3143 A floating constant has a significand part that may be followed by an exponent part and a
3144 suffix that specifies its type. The components of the significand part may include a digit
3145 sequence representing the whole-number part, followed by a period (.), followed by a
3146 digit sequence representing the fraction part. The components of the exponent part are an
3147 e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
3148 Either the whole-number part or the fraction part has to be present; for decimal floating
3149 constants, either the period or the exponent part has to be present.
3152 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
3153 digit sequence in the exponent part is interpreted as a decimal integer. For decimal
3154 floating constants, the exponent indicates the power of 10 by which the significand part is
3155 to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
3156 by which the significand part is to be scaled. For decimal floating constants, and also for
3157 hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
3158 the nearest representable value, or the larger or smaller representable value immediately
3159 adjacent to the nearest representable value, chosen in an implementation-defined manner.
3160 For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
3163 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
3164 type float. If suffixed by the letter l or L, it has type long double.
3166 Floating constants are converted to internal format as if at translation-time. The
3167 conversion of a floating constant shall not raise an exceptional condition or a floating-
3168 point exception at execution time.
3169 Recommended practice
3171 The implementation should produce a diagnostic message if a hexadecimal constant
3172 cannot be represented exactly in its evaluation format; the implementation should then
3173 proceed with the translation of the program.
3175 The translation-time conversion of floating constants should match the execution-time
3176 conversion of character strings by library functions, such as strtod, given matching
3177 inputs suitable for both conversions, the same result format, and default execution-time
3178 rounding.<sup><a href="#note64"><b>64)</b></a></sup>
3186 <p><small><a name="note64" href="#note64">64)</a> The specification for the library functions recommends more accurate conversion than required for
3187 floating constants (see <a href="#7.20.1.3">7.20.1.3</a>).
3190 <h5><a name="6.4.4.3" href="#6.4.4.3">6.4.4.3 Enumeration constants</a></h5>
3194 enumeration-constant:
3198 An identifier declared as an enumeration constant has type int.
3199 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>).
3201 <h5><a name="6.4.4.4" href="#6.4.4.4">6.4.4.4 Character constants</a></h5>
3208 L' c-char-sequence '
3211 c-char-sequence c-char
3213 any member of the source character set except
3214 the single-quote ', backslash \, or new-line character
3217 simple-escape-sequence
3218 octal-escape-sequence
3219 hexadecimal-escape-sequence
3220 universal-character-name
3221 simple-escape-sequence: one of
3223 \a \b \f \n \r \t \v
3224 octal-escape-sequence:
3226 \ octal-digit octal-digit
3227 \ octal-digit octal-digit octal-digit
3228 hexadecimal-escape-sequence:
3229 \x hexadecimal-digit
3230 hexadecimal-escape-sequence hexadecimal-digit</pre>
3231 <h6>Description</h6>
3233 An integer character constant is a sequence of one or more multibyte characters enclosed
3234 in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
3235 letter L. With a few exceptions detailed later, the elements of the sequence are any
3236 members of the source character set; they are mapped in an implementation-defined
3237 manner to members of the execution character set.
3239 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
3240 arbitrary integer values are representable according to the following table of escape
3248 octal character \octal digits
3249 hexadecimal character \x hexadecimal digits</pre>
3250 The double-quote " and question-mark ? are representable either by themselves or by the
3251 escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
3252 shall be represented, respectively, by the escape sequences \' and \\.
3254 The octal digits that follow the backslash in an octal escape sequence are taken to be part
3255 of the construction of a single character for an integer character constant or of a single
3256 wide character for a wide character constant. The numerical value of the octal integer so
3257 formed specifies the value of the desired character or wide character.
3259 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
3260 sequence are taken to be part of the construction of a single character for an integer
3261 character constant or of a single wide character for a wide character constant. The
3262 numerical value of the hexadecimal integer so formed specifies the value of the desired
3263 character or wide character.
3265 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
3266 constitute the escape sequence.
3268 In addition, characters not in the basic character set are representable by universal
3269 character names and certain nongraphic characters are representable by escape sequences
3270 consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
3271 and \v.<sup><a href="#note65"><b>65)</b></a></sup>
3277 <h6>Constraints</h6>
3279 The value of an octal or hexadecimal escape sequence shall be in the range of
3280 representable values for the type unsigned char for an integer character constant, or
3281 the unsigned type corresponding to wchar_t for a wide character constant.
3284 An integer character constant has type int. The value of an integer character constant
3285 containing a single character that maps to a single-byte execution character is the
3286 numerical value of the representation of the mapped character interpreted as an integer.
3287 The value of an integer character constant containing more than one character (e.g.,
3288 'ab'), or containing a character or escape sequence that does not map to a single-byte
3289 execution character, is implementation-defined. If an integer character constant contains
3290 a single character or escape sequence, its value is the one that results when an object with
3291 type char whose value is that of the single character or escape sequence is converted to
3294 A wide character constant has type wchar_t, an integer type defined in the
3295 <a href="#7.17"><stddef.h></a> header. The value of a wide character constant containing a single
3296 multibyte character that maps to a member of the extended execution character set is the
3297 wide character corresponding to that multibyte character, as defined by the mbtowc
3298 function, with an implementation-defined current locale. The value of a wide character
3299 constant containing more than one multibyte character, or containing a multibyte
3300 character or escape sequence not represented in the extended execution character set, is
3301 implementation-defined.
3303 EXAMPLE 1 The construction '\0' is commonly used to represent the null character.
3306 EXAMPLE 2 Consider implementations that use two's-complement representation for integers and eight
3307 bits for objects that have type char. In an implementation in which type char has the same range of
3308 values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
3309 same range of values as unsigned char, the character constant '\xFF' has the value +255.
3312 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
3313 specifies an integer character constant containing only one character, since a hexadecimal escape sequence
3314 is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
3315 two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
3316 escape sequence is terminated after three octal digits. (The value of this two-character integer character
3317 constant is implementation-defined.)
3320 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
3321 L'\1234' specifies the implementation-defined value that results from the combination of the values
3324 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), the mbtowc function
3325 (<a href="#7.20.7.2">7.20.7.2</a>).
3329 <p><small><a name="note65" href="#note65">65)</a> The semantics of these characters were discussed in <a href="#5.2.2">5.2.2</a>. If any other character follows a backslash,
3330 the result is not a token and a diagnostic is required. See ''future language directions'' (<a href="#6.11.4">6.11.4</a>).
3333 <h4><a name="6.4.5" href="#6.4.5">6.4.5 String literals</a></h4>
3338 " s-char-sequenceopt "
3339 L" s-char-sequenceopt "
3342 s-char-sequence s-char
3344 any member of the source character set except
3345 the double-quote ", backslash \, or new-line character
3346 escape-sequence</pre>
3347 <h6>Description</h6>
3349 A character string literal is a sequence of zero or more multibyte characters enclosed in
3350 double-quotes, as in "xyz". A wide string literal is the same, except prefixed by the
3353 The same considerations apply to each element of the sequence in a character string
3354 literal or a wide string literal as if it were in an integer character constant or a wide
3355 character constant, except that the single-quote ' is representable either by itself or by the
3356 escape sequence \', but the double-quote " shall be represented by the escape sequence
3360 In translation phase 6, the multibyte character sequences specified by any sequence of
3361 adjacent character and wide string literal tokens are concatenated into a single multibyte
3362 character sequence. If any of the tokens are wide string literal tokens, the resulting
3363 multibyte character sequence is treated as a wide string literal; otherwise, it is treated as a
3364 character string literal.
3366 In translation phase 7, a byte or code of value zero is appended to each multibyte
3367 character sequence that results from a string literal or literals.<sup><a href="#note66"><b>66)</b></a></sup> The multibyte character
3368 sequence is then used to initialize an array of static storage duration and length just
3369 sufficient to contain the sequence. For character string literals, the array elements have
3370 type char, and are initialized with the individual bytes of the multibyte character
3371 sequence; for wide string literals, the array elements have type wchar_t, and are
3372 initialized with the sequence of wide characters corresponding to the multibyte character
3375 sequence, as defined by the mbstowcs function with an implementation-defined current
3376 locale. The value of a string literal containing a multibyte character or escape sequence
3377 not represented in the execution character set is implementation-defined.
3379 It is unspecified whether these arrays are distinct provided their elements have the
3380 appropriate values. If the program attempts to modify such an array, the behavior is
3383 EXAMPLE This pair of adjacent character string literals
3386 produces a single character string literal containing the two characters whose values are '\x12' and '3',
3387 because escape sequences are converted into single members of the execution character set just prior to
3388 adjacent string literal concatenation.
3390 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), the mbstowcs
3391 function (<a href="#7.20.8.1">7.20.8.1</a>).
3394 <p><small><a name="note66" href="#note66">66)</a> A character 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
3395 it by a \0 escape sequence.
3398 <h4><a name="6.4.6" href="#6.4.6">6.4.6 Punctuators</a></h4>
3404 ++ -- & * + - ~ !
3405 / % << >> < > <= >= == != ^ | && ||
3407 = *= /= %= += -= <<= >>= &= ^= |=
3409 <: :> <% %> %: %:%:</pre>
3412 A punctuator is a symbol that has independent syntactic and semantic significance.
3413 Depending on context, it may specify an operation to be performed (which in turn may
3414 yield a value or a function designator, produce a side effect, or some combination thereof)
3415 in which case it is known as an operator (other forms of operator also exist in some
3416 contexts). An operand is an entity on which an operator acts.
3419 In all aspects of the language, the six tokens<sup><a href="#note67"><b>67)</b></a></sup>
3421 <: :> <% %> %: %:%:</pre>
3422 behave, respectively, the same as the six tokens
3425 except for their spelling.<sup><a href="#note68"><b>68)</b></a></sup>
3426 <p><b> Forward references</b>: expressions (<a href="#6.5">6.5</a>), declarations (<a href="#6.7">6.7</a>), preprocessing directives
3427 (<a href="#6.10">6.10</a>), statements (<a href="#6.8">6.8</a>).
3430 <p><small><a name="note67" href="#note67">67)</a> These tokens are sometimes called ''digraphs''.
3432 <p><small><a name="note68" href="#note68">68)</a> Thus [ and <: behave differently when ''stringized'' (see <a href="#6.10.3.2">6.10.3.2</a>), but can otherwise be freely
3436 <h4><a name="6.4.7" href="#6.4.7">6.4.7 Header names</a></h4>
3441 < h-char-sequence >
3445 h-char-sequence h-char
3447 any member of the source character set except
3448 the new-line character and >
3451 q-char-sequence q-char
3453 any member of the source character set except
3454 the new-line character and "</pre>
3457 The sequences in both forms of header names are mapped in an implementation-defined
3458 manner to headers or external source file names as specified in <a href="#6.10.2">6.10.2</a>.
3460 If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters,
3461 the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the
3467 sequence between the " delimiters, the behavior is undefined.<sup><a href="#note69"><b>69)</b></a></sup> Header name
3468 preprocessing tokens are recognized only within #include preprocessing directives and
3469 in implementation-defined locations within #pragma directives.<sup><a href="#note70"><b>70)</b></a></sup>
3471 EXAMPLE The following sequence of characters:
3474 #include <1/a.h>
3475 #define const.member@$</pre>
3476 forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
3477 by a { on the left and a } on the right).
3479 {0x3}{<}{1}{/}{a}{.}{h}{>}{1e2}
3480 {#}{include} {<1/a.h>}
3481 {#}{define} {const}{.}{member}{@}{$}</pre>
3483 <p><b> Forward references</b>: source file inclusion (<a href="#6.10.2">6.10.2</a>).
3486 <p><small><a name="note69" href="#note69">69)</a> Thus, sequences of characters that resemble escape sequences cause undefined behavior.
3488 <p><small><a name="note70" href="#note70">70)</a> For an example of a header name preprocessing token used in a #pragma directive, see <a href="#6.10.9">6.10.9</a>.
3491 <h4><a name="6.4.8" href="#6.4.8">6.4.8 Preprocessing numbers</a></h4>
3499 pp-number identifier-nondigit
3505 <h6>Description</h6>
3507 A preprocessing number begins with a digit optionally preceded by a period (.) and may
3508 be followed by valid identifier characters and the character sequences e+, e-, E+, E-,
3511 Preprocessing number tokens lexically include all floating and integer constant tokens.
3514 A preprocessing number does not have type or a value; it acquires both after a successful
3515 conversion (as part of translation phase 7) to a floating constant token or an integer
3521 <h4><a name="6.4.9" href="#6.4.9">6.4.9 Comments</a></h4>
3523 Except within a character constant, a string literal, or a comment, the characters /*
3524 introduce a comment. The contents of such a comment are examined only to identify
3525 multibyte characters and to find the characters */ that terminate it.<sup><a href="#note71"><b>71)</b></a></sup>
3527 Except within a character constant, a string literal, or a comment, the characters //
3528 introduce a comment that includes all multibyte characters up to, but not including, the
3529 next new-line character. The contents of such a comment are examined only to identify
3530 multibyte characters and to find the terminating new-line character.
3534 "a//b" // four-character string literal
3535 #include "//e" // undefined behavior
3536 // */ // comment, not syntax error
3537 f = g/**//h; // equivalent to f = g / h;
3539 i(); // part of a two-line comment
3541 / j(); // part of a two-line comment
3542 #define glue(x,y) x##y
3543 glue(/,/) k(); // syntax error, not comment
3544 /*//*/ l(); // equivalent to l();
3546 + p; // equivalent to m = n + p;</pre>
3554 <p><small><a name="note71" href="#note71">71)</a> Thus, /* ... */ comments do not nest.
3557 <h3><a name="6.5" href="#6.5">6.5 Expressions</a></h3>
3559 An expression is a sequence of operators and operands that specifies computation of a
3560 value, or that designates an object or a function, or that generates side effects, or that
3561 performs a combination thereof.
3563 Between the previous and next sequence point an object shall have its stored value
3564 modified at most once by the evaluation of an expression.<sup><a href="#note72"><b>72)</b></a></sup> Furthermore, the prior value
3565 shall be read only to determine the value to be stored.<sup><a href="#note73"><b>73)</b></a></sup>
3567 The grouping of operators and operands is indicated by the syntax.<sup><a href="#note74"><b>74)</b></a></sup> Except as specified
3568 later (for the function-call (), &&, ||, ?:, and comma operators), the order of evaluation
3569 of subexpressions and the order in which side effects take place are both unspecified.
3571 Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |,
3572 collectively described as bitwise operators) are required to have operands that have
3573 integer type. These operators yield values that depend on the internal representations of
3574 integers, and have implementation-defined and undefined aspects for signed types.
3576 If an exceptional condition occurs during the evaluation of an expression (that is, if the
3577 result is not mathematically defined or not in the range of representable values for its
3578 type), the behavior is undefined.
3580 The effective type of an object for an access to its stored value is the declared type of the
3581 object, if any.<sup><a href="#note75"><b>75)</b></a></sup> If a value is stored into an object having no declared type through an
3582 lvalue having a type that is not a character type, then the type of the lvalue becomes the
3586 effective type of the object for that access and for subsequent accesses that do not modify
3587 the stored value. If a value is copied into an object having no declared type using
3588 memcpy or memmove, or is copied as an array of character type, then the effective type
3589 of the modified object for that access and for subsequent accesses that do not modify the
3590 value is the effective type of the object from which the value is copied, if it has one. For
3591 all other accesses to an object having no declared type, the effective type of the object is
3592 simply the type of the lvalue used for the access.
3594 An object shall have its stored value accessed only by an lvalue expression that has one of
3595 the following types:<sup><a href="#note76"><b>76)</b></a></sup>
3597 <li> a type compatible with the effective type of the object,
3598 <li> a qualified version of a type compatible with the effective type of the object,
3599 <li> a type that is the signed or unsigned type corresponding to the effective type of the
3601 <li> a type that is the signed or unsigned type corresponding to a qualified version of the
3602 effective type of the object,
3603 <li> an aggregate or union type that includes one of the aforementioned types among its
3604 members (including, recursively, a member of a subaggregate or contained union), or
3605 <li> a character type.
3608 A floating expression may be contracted, that is, evaluated as though it were an atomic
3609 operation, thereby omitting rounding errors implied by the source code and the
3610 expression evaluation method.<sup><a href="#note77"><b>77)</b></a></sup> The FP_CONTRACT pragma in <a href="#7.12"><math.h></a> provides a
3611 way to disallow contracted expressions. Otherwise, whether and how expressions are
3612 contracted is implementation-defined.<sup><a href="#note78"><b>78)</b></a></sup>
3613 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), copying functions (<a href="#7.21.2">7.21.2</a>).
3621 <p><small><a name="note72" href="#note72">72)</a> A floating-point status flag is not an object and can be set more than once within an expression.
3623 <p><small><a name="note73" href="#note73">73)</a> This paragraph renders undefined statement expressions such as
3633 <p><small><a name="note74" href="#note74">74)</a> The syntax specifies the precedence of operators in the evaluation of an expression, which is the same
3634 as the order of the major subclauses of this subclause, highest precedence first. Thus, for example, the
3635 expressions allowed as the operands of the binary + operator (<a href="#6.5.6">6.5.6</a>) are those expressions defined in
3636 <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
3637 (<a href="#6.5.3">6.5.3</a>), and an operand contained between any of the following pairs of operators: grouping
3638 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
3639 the conditional operator ?: (<a href="#6.5.15">6.5.15</a>).
3642 Within each major subclause, the operators have the same precedence. Left- or right-associativity is
3643 indicated in each subclause by the syntax for the expressions discussed therein.</pre>
3645 <p><small><a name="note75" href="#note75">75)</a> Allocated objects have no declared type.
3647 <p><small><a name="note76" href="#note76">76)</a> The intent of this list is to specify those circumstances in which an object may or may not be aliased.
3649 <p><small><a name="note77" href="#note77">77)</a> A contracted expression might also omit the raising of floating-point exceptions.
3651 <p><small><a name="note78" href="#note78">78)</a> This license is specifically intended to allow implementations to exploit fast machine instructions that
3652 combine multiple C operators. As contractions potentially undermine predictability, and can even
3653 decrease accuracy for containing expressions, their use needs to be well-defined and clearly
3657 <h4><a name="6.5.1" href="#6.5.1">6.5.1 Primary expressions</a></h4>
3665 ( expression )</pre>
3668 An identifier is a primary expression, provided it has been declared as designating an
3669 object (in which case it is an lvalue) or a function (in which case it is a function
3670 designator).<sup><a href="#note79"><b>79)</b></a></sup>
3672 A constant is a primary expression. Its type depends on its form and value, as detailed in
3673 <a href="#6.4.4">6.4.4</a>.
3675 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>.
3677 A parenthesized expression is a primary expression. Its type and value are identical to
3678 those of the unparenthesized expression. It is an lvalue, a function designator, or a void
3679 expression if the unparenthesized expression is, respectively, an lvalue, a function
3680 designator, or a void expression.
3681 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>).
3684 <p><small><a name="note79" href="#note79">79)</a> Thus, an undeclared identifier is a violation of the syntax.
3687 <h4><a name="6.5.2" href="#6.5.2">6.5.2 Postfix operators</a></h4>
3693 postfix-expression [ expression ]
3694 postfix-expression ( argument-expression-listopt )
3695 postfix-expression . identifier
3696 postfix-expression -> identifier
3697 postfix-expression ++
3698 postfix-expression --
3699 ( type-name ) { initializer-list }
3700 ( type-name ) { initializer-list , }</pre>
3707 argument-expression-list:
3708 assignment-expression
3709 argument-expression-list , assignment-expression</pre>
3711 <h5><a name="6.5.2.1" href="#6.5.2.1">6.5.2.1 Array subscripting</a></h5>
3712 <h6>Constraints</h6>
3714 One of the expressions shall have type ''pointer to object type'', the other expression shall
3715 have integer type, and the result has type ''type''.
3718 A postfix expression followed by an expression in square brackets [] is a subscripted
3719 designation of an element of an array object. The definition of the subscript operator []
3720 is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that
3721 apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the
3722 initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th
3723 element of E1 (counting from zero).
3725 Successive subscript operators designate an element of a multidimensional array object.
3726 If E is an n-dimensional array (n >= 2) with dimensions i x j x . . . x k, then E (used as
3727 other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with
3728 dimensions j x . . . x k. If the unary * operator is applied to this pointer explicitly, or
3729 implicitly as a result of subscripting, the result is the pointed-to (n - 1)-dimensional array,
3730 which itself is converted into a pointer if used as other than an lvalue. It follows from this
3731 that arrays are stored in row-major order (last subscript varies fastest).
3733 EXAMPLE Consider the array object defined by the declaration
3736 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
3737 array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
3738 a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually
3739 entails multiplying i by the size of the object to which the pointer points, namely an array of five int
3740 objects. The results are added and indirection is applied to yield an array of five ints. When used in the
3741 expression x[i][j], that array is in turn converted to a pointer to the first of the ints, so x[i][j]
3744 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), address and indirection operators
3745 (<a href="#6.5.3.2">6.5.3.2</a>), array declarators (<a href="#6.7.5.2">6.7.5.2</a>).
3748 <h5><a name="6.5.2.2" href="#6.5.2.2">6.5.2.2 Function calls</a></h5>
3749 <h6>Constraints</h6>
3751 The expression that denotes the called function<sup><a href="#note80"><b>80)</b></a></sup> shall have type pointer to function
3752 returning void or returning an object type other than an array type.
3754 If the expression that denotes the called function has a type that includes a prototype, the
3755 number of arguments shall agree with the number of parameters. Each argument shall
3756 have a type such that its value may be assigned to an object with the unqualified version
3757 of the type of its corresponding parameter.
3760 A postfix expression followed by parentheses () containing a possibly empty, comma-
3761 separated list of expressions is a function call. The postfix expression denotes the called
3762 function. The list of expressions specifies the arguments to the function.
3764 An argument may be an expression of any object type. In preparing for the call to a
3765 function, the arguments are evaluated, and each parameter is assigned the value of the
3766 corresponding argument.<sup><a href="#note81"><b>81)</b></a></sup>
3768 If the expression that denotes the called function has type pointer to function returning an
3769 object type, the function call expression has the same type as that object type, and has the
3770 value determined as specified in <a href="#6.8.6.4">6.8.6.4</a>. Otherwise, the function call has type void. If
3771 an attempt is made to modify the result of a function call or to access it after the next
3772 sequence point, the behavior is undefined.
3774 If the expression that denotes the called function has a type that does not include a
3775 prototype, the integer promotions are performed on each argument, and arguments that
3776 have type float are promoted to double. These are called the default argument
3777 promotions. If the number of arguments does not equal the number of parameters, the
3778 behavior is undefined. If the function is defined with a type that includes a prototype, and
3779 either the prototype ends with an ellipsis (, ...) or the types of the arguments after
3780 promotion are not compatible with the types of the parameters, the behavior is undefined.
3781 If the function is defined with a type that does not include a prototype, and the types of
3782 the arguments after promotion are not compatible with those of the parameters after
3783 promotion, the behavior is undefined, except for the following cases:
3790 <li> one promoted type is a signed integer type, the other promoted type is the
3791 corresponding unsigned integer type, and the value is representable in both types;
3792 <li> both types are pointers to qualified or unqualified versions of a character type or
3796 If the expression that denotes the called function has a type that does include a prototype,
3797 the arguments are implicitly converted, as if by assignment, to the types of the
3798 corresponding parameters, taking the type of each parameter to be the unqualified version
3799 of its declared type. The ellipsis notation in a function prototype declarator causes
3800 argument type conversion to stop after the last declared parameter. The default argument
3801 promotions are performed on trailing arguments.
3803 No other conversions are performed implicitly; in particular, the number and types of
3804 arguments are not compared with those of the parameters in a function definition that
3805 does not include a function prototype declarator.
3807 If the function is defined with a type that is not compatible with the type (of the
3808 expression) pointed to by the expression that denotes the called function, the behavior is
3811 The order of evaluation of the function designator, the actual arguments, and
3812 subexpressions within the actual arguments is unspecified, but there is a sequence point
3813 before the actual call.
3815 Recursive function calls shall be permitted, both directly and indirectly through any chain
3818 EXAMPLE In the function call
3820 (*pf[f1()]) (f2(), f3() + f4())</pre>
3821 the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before
3822 the function pointed to by pf[f1()] is called.
3824 <p><b> Forward references</b>: function declarators (including prototypes) (<a href="#6.7.5.3">6.7.5.3</a>), function
3825 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>).
3828 <p><small><a name="note80" href="#note80">80)</a> Most often, this is the result of converting an identifier that is a function designator.
3830 <p><small><a name="note81" href="#note81">81)</a> A function may change the values of its parameters, but these changes cannot affect the values of the
3831 arguments. On the other hand, it is possible to pass a pointer to an object, and the function may
3832 change the value of the object pointed to. A parameter declared to have array or function type is
3833 adjusted to have a pointer type as described in <a href="#6.9.1">6.9.1</a>.
3836 <h5><a name="6.5.2.3" href="#6.5.2.3">6.5.2.3 Structure and union members</a></h5>
3837 <h6>Constraints</h6>
3839 The first operand of the . operator shall have a qualified or unqualified structure or union
3840 type, and the second operand shall name a member of that type.
3842 The first operand of the -> operator shall have type ''pointer to qualified or unqualified
3843 structure'' or ''pointer to qualified or unqualified union'', and the second operand shall
3844 name a member of the type pointed to.
3848 A postfix expression followed by the . operator and an identifier designates a member of
3849 a structure or union object. The value is that of the named member,<sup><a href="#note82"><b>82)</b></a></sup> and is an lvalue if
3850 the first expression is an lvalue. If the first expression has qualified type, the result has
3851 the so-qualified version of the type of the designated member.
3853 A postfix expression followed by the -> operator and an identifier designates a member
3854 of a structure or union object. The value is that of the named member of the object to
3855 which the first expression points, and is an lvalue.<sup><a href="#note83"><b>83)</b></a></sup> If the first expression is a pointer to
3856 a qualified type, the result has the so-qualified version of the type of the designated
3859 One special guarantee is made in order to simplify the use of unions: if a union contains
3860 several structures that share a common initial sequence (see below), and if the union
3861 object currently contains one of these structures, it is permitted to inspect the common
3862 initial part of any of them anywhere that a declaration of the complete type of the union is
3863 visible. Two structures share a common initial sequence if corresponding members have
3864 compatible types (and, for bit-fields, the same widths) for a sequence of one or more
3867 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or
3868 union, f().x is a valid postfix expression but is not an lvalue.
3873 struct s { int i; const int ci; };
3876 volatile struct s vs;</pre>
3877 the various members have the types:
3884 vs.ci volatile const int</pre>
3891 EXAMPLE 3 The following is a valid fragment:
3907 u.nf.doublenode = <a href="#3.14">3.14</a>;
3909 if (u.n.alltypes == 1)
3910 if (sin(u.nf.doublenode) == 0.0)
3912 The following is not a valid fragment (because the union type is not visible within function f):
3914 struct t1 { int m; };
3915 struct t2 { int m; };
3916 int f(struct t1 *p1, struct t2 *p2)
3918 if (p1->m < 0)
3919 p2->m = -p2->m;
3929 return f(&u.s1, &u.s2);
3932 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), structure and union
3933 specifiers (<a href="#6.7.2.1">6.7.2.1</a>).
3937 <p><small><a name="note82" href="#note82">82)</a> If the member used to access the contents of a union object is not the same as the member last used to
3938 store a value in the object, the appropriate part of the object representation of the value is reinterpreted
3939 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
3940 punning"). This might be a trap representation.
3942 <p><small><a name="note83" href="#note83">83)</a> If &E is a valid pointer expression (where & is the ''address-of '' operator, which generates a pointer to
3943 its operand), the expression (&E)->MOS is the same as E.MOS.
3946 <h5><a name="6.5.2.4" href="#6.5.2.4">6.5.2.4 Postfix increment and decrement operators</a></h5>
3947 <h6>Constraints</h6>
3949 The operand of the postfix increment or decrement operator shall have qualified or
3950 unqualified real or pointer type and shall be a modifiable lvalue.
3953 The result of the postfix ++ operator is the value of the operand. After the result is
3954 obtained, the value of the operand is incremented. (That is, the value 1 of the appropriate
3955 type is added to it.) See the discussions of additive operators and compound assignment
3956 for information on constraints, types, and conversions and the effects of operations on
3957 pointers. The side effect of updating the stored value of the operand shall occur between
3958 the previous and the next sequence point.
3960 The postfix -- operator is analogous to the postfix ++ operator, except that the value of
3961 the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
3963 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), compound assignment (<a href="#6.5.16.2">6.5.16.2</a>).
3965 <h5><a name="6.5.2.5" href="#6.5.2.5">6.5.2.5 Compound literals</a></h5>
3966 <h6>Constraints</h6>
3968 The type name shall specify an object type or an array of unknown size, but not a variable
3971 No initializer shall attempt to provide a value for an object not contained within the entire
3972 unnamed object specified by the compound literal.
3974 If the compound literal occurs outside the body of a function, the initializer list shall
3975 consist of constant expressions.
3978 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="#note84"><b>84)</b></a></sup>
3982 If the type name specifies an array of unknown size, the size is determined by the
3983 initializer list as specified in <a href="#6.7.8">6.7.8</a>, and the type of the compound literal is that of the
3984 completed array type. Otherwise (when the type name specifies an object type), the type
3985 of the compound literal is that specified by the type name. In either case, the result is an
3991 The value of the compound literal is that of an unnamed object initialized by the
3992 initializer list. If the compound literal occurs outside the body of a function, the object
3993 has static storage duration; otherwise, it has automatic storage duration associated with
3994 the enclosing block.
3996 All the semantic rules and constraints for initializer lists in <a href="#6.7.8">6.7.8</a> are applicable to
3997 compound literals.<sup><a href="#note85"><b>85)</b></a></sup>
3999 String literals, and compound literals with const-qualified types, need not designate
4000 distinct objects.<sup><a href="#note86"><b>86)</b></a></sup>
4002 EXAMPLE 1 The file scope definition
4004 int *p = (int []){2, 4};</pre>
4005 initializes p to point to the first element of an array of two ints, the first having the value two and the
4006 second, four. The expressions in this compound literal are required to be constant. The unnamed object
4007 has static storage duration.
4010 EXAMPLE 2 In contrast, in
4019 p is assigned the address of the first element of an array of two ints, the first having the value previously
4020 pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
4021 unnamed object has automatic storage duration.
4024 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:
4027 drawline((struct point){.x=1, .y=1},
4028 (struct point){.x=3, .y=4});</pre>
4029 Or, if drawline instead expected pointers to struct point:
4031 drawline(&(struct point){.x=1, .y=1},
4032 &(struct point){.x=3, .y=4});</pre>
4035 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
4037 (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}</pre>
4044 EXAMPLE 5 The following three expressions have different meanings:
4047 (char []){"/tmp/fileXXXXXX"}
4048 (const char []){"/tmp/fileXXXXXX"}</pre>
4049 The first always has static storage duration and has type array of char, but need not be modifiable; the last
4050 two have automatic storage duration when they occur within the body of a function, and the first of these
4054 EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory
4055 and can even be shared. For example,
4057 (const char []){"abc"} == "abc"</pre>
4058 might yield 1 if the literals' storage is shared.
4061 EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly
4062 linked object. For example, there is no way to write a self-referential compound literal that could be used
4063 as the function argument in place of the named object endless_zeros below:
4065 struct int_list { int car; struct int_list *cdr; };
4066 struct int_list endless_zeros = {0, &endless_zeros};
4067 eval(endless_zeros);</pre>
4070 EXAMPLE 8 Each compound literal creates only a single object in a given scope:
4072 struct s { int i; };
4075 struct s *p = 0, *q;
4078 q = p, p = &((struct s){ j++ });
4079 if (j < 2) goto again;
4080 return p == q && q->i == 1;
4082 The function f() always returns the value 1.
4084 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
4085 lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
4086 have an indeterminate value, which would result in undefined behavior.
4088 <p><b> Forward references</b>: type names (<a href="#6.7.6">6.7.6</a>), initialization (<a href="#6.7.8">6.7.8</a>).
4092 <p><small><a name="note84" href="#note84">84)</a> Note that this differs from a cast expression. For example, a cast specifies a conversion to scalar types
4093 or void only, and the result of a cast expression is not an lvalue.
4095 <p><small><a name="note85" href="#note85">85)</a> For example, subobjects without explicit initializers are initialized to zero.
4097 <p><small><a name="note86" href="#note86">86)</a> This allows implementations to share storage for string literals and constant compound literals with
4098 the same or overlapping representations.
4101 <h4><a name="6.5.3" href="#6.5.3">6.5.3 Unary operators</a></h4>
4109 unary-operator cast-expression
4110 sizeof unary-expression
4111 sizeof ( type-name )
4112 unary-operator: one of
4113 & * + - ~ !</pre>
4115 <h5><a name="6.5.3.1" href="#6.5.3.1">6.5.3.1 Prefix increment and decrement operators</a></h5>
4116 <h6>Constraints</h6>
4118 The operand of the prefix increment or decrement operator shall have qualified or
4119 unqualified real or pointer type and shall be a modifiable lvalue.
4122 The value of the operand of the prefix ++ operator is incremented. The result is the new
4123 value of the operand after incrementation. The expression ++E is equivalent to (E+=1).
4124 See the discussions of additive operators and compound assignment for information on
4125 constraints, types, side effects, and conversions and the effects of operations on pointers.
4127 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
4128 operand is decremented.
4129 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), compound assignment (<a href="#6.5.16.2">6.5.16.2</a>).
4131 <h5><a name="6.5.3.2" href="#6.5.3.2">6.5.3.2 Address and indirection operators</a></h5>
4132 <h6>Constraints</h6>
4134 The operand of the unary & operator shall be either a function designator, the result of a
4135 [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is
4136 not declared with the register storage-class specifier.
4138 The operand of the unary * operator shall have pointer type.
4141 The unary & operator yields the address of its operand. If the operand has type ''type'',
4142 the result has type ''pointer to type''. If the operand is the result of a unary * operator,
4143 neither that operator nor the & operator is evaluated and the result is as if both were
4144 omitted, except that the constraints on the operators still apply and the result is not an
4145 lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor
4147 the unary * that is implied by the [] is evaluated and the result is as if the & operator
4148 were removed and the [] operator were changed to a + operator. Otherwise, the result is
4149 a pointer to the object or function designated by its operand.
4151 The unary * operator denotes indirection. If the operand points to a function, the result is
4152 a function designator; if it points to an object, the result is an lvalue designating the
4153 object. If the operand has type ''pointer to type'', the result has type ''type''. If an
4154 invalid value has been assigned to the pointer, the behavior of the unary * operator is
4155 undefined.<sup><a href="#note87"><b>87)</b></a></sup>
4156 <p><b> Forward references</b>: storage-class specifiers (<a href="#6.7.1">6.7.1</a>), structure and union specifiers
4157 (<a href="#6.7.2.1">6.7.2.1</a>).
4160 <p><small><a name="note87" href="#note87">87)</a> Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). It is
4161 always true that if E is a function designator or an lvalue that is a valid operand of the unary &
4162 operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of
4163 an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points.
4164 Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an
4165 address inappropriately aligned for the type of object pointed to, and the address of an object after the
4166 end of its lifetime.
4169 <h5><a name="6.5.3.3" href="#6.5.3.3">6.5.3.3 Unary arithmetic operators</a></h5>
4170 <h6>Constraints</h6>
4172 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
4173 integer type; of the ! operator, scalar type.
4176 The result of the unary + operator is the value of its (promoted) operand. The integer
4177 promotions are performed on the operand, and the result has the promoted type.
4179 The result of the unary - operator is the negative of its (promoted) operand. The integer
4180 promotions are performed on the operand, and the result has the promoted type.
4182 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is,
4183 each bit in the result is set if and only if the corresponding bit in the converted operand is
4184 not set). The integer promotions are performed on the operand, and the result has the
4185 promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent
4186 to the maximum value representable in that type minus E.
4188 The result of the logical negation operator ! is 0 if the value of its operand compares
4189 unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int.
4190 The expression !E is equivalent to (0==E).
4197 <h5><a name="6.5.3.4" href="#6.5.3.4">6.5.3.4 The sizeof operator</a></h5>
4198 <h6>Constraints</h6>
4200 The sizeof operator shall not be applied to an expression that has function type or an
4201 incomplete type, to the parenthesized name of such a type, or to an expression that
4202 designates a bit-field member.
4205 The sizeof operator yields the size (in bytes) of its operand, which may be an
4206 expression or the parenthesized name of a type. The size is determined from the type of
4207 the operand. The result is an integer. If the type of the operand is a variable length array
4208 type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an
4211 When applied to an operand that has type char, unsigned char, or signed char,
4212 (or a qualified version thereof) the result is 1. When applied to an operand that has array
4213 type, the result is the total number of bytes in the array.<sup><a href="#note88"><b>88)</b></a></sup> When applied to an operand
4214 that has structure or union type, the result is the total number of bytes in such an object,
4215 including internal and trailing padding.
4217 The value of the result is implementation-defined, and its type (an unsigned integer type)
4218 is size_t, defined in <a href="#7.17"><stddef.h></a> (and other headers).
4220 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage
4221 allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to
4222 allocate and return a pointer to void. For example:
4224 extern void *alloc(size_t);
4225 double *dp = alloc(sizeof *dp);</pre>
4226 The implementation of the alloc function should ensure that its return value is aligned suitably for
4227 conversion to a pointer to double.
4230 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
4232 sizeof array / sizeof array[0]</pre>
4235 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a
4238 #include <a href="#7.17"><stddef.h></a>
4239 size_t fsize3(int n)
4241 char b[n+3]; // variable length array
4242 return sizeof b; // execution time sizeof
4252 size = fsize3(10); // fsize3 returns 13
4256 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), declarations (<a href="#6.7">6.7</a>),
4257 structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), type names (<a href="#6.7.6">6.7.6</a>), array declarators (<a href="#6.7.5.2">6.7.5.2</a>).
4260 <p><small><a name="note88" href="#note88">88)</a> When applied to a parameter declared to have array or function type, the sizeof operator yields the
4261 size of the adjusted (pointer) type (see <a href="#6.9.1">6.9.1</a>).
4264 <h4><a name="6.5.4" href="#6.5.4">6.5.4 Cast operators</a></h4>
4270 ( type-name ) cast-expression</pre>
4271 <h6>Constraints</h6>
4273 Unless the type name specifies a void type, the type name shall specify qualified or
4274 unqualified scalar type and the operand shall have scalar type.
4276 Conversions that involve pointers, other than where permitted by the constraints of
4277 <a href="#6.5.16.1">6.5.16.1</a>, shall be specified by means of an explicit cast.
4280 Preceding an expression by a parenthesized type name converts the value of the
4281 expression to the named type. This construction is called a cast.<sup><a href="#note89"><b>89)</b></a></sup> A cast that specifies
4282 no conversion has no effect on the type or value of an expression.
4284 If the value of the expression is represented with greater precision or range than required
4285 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
4286 type of the expression is the same as the named type.
4287 <p><b> Forward references</b>: equality operators (<a href="#6.5.9">6.5.9</a>), function declarators (including
4288 prototypes) (<a href="#6.7.5.3">6.7.5.3</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>), type names (<a href="#6.7.6">6.7.6</a>).
4296 <p><small><a name="note89" href="#note89">89)</a> A cast does not yield an lvalue. Thus, a cast to a qualified type has the same effect as a cast to the
4297 unqualified version of the type.
4300 <h4><a name="6.5.5" href="#6.5.5">6.5.5 Multiplicative operators</a></h4>
4304 multiplicative-expression:
4306 multiplicative-expression * cast-expression
4307 multiplicative-expression / cast-expression
4308 multiplicative-expression % cast-expression</pre>
4309 <h6>Constraints</h6>
4311 Each of the operands shall have arithmetic type. The operands of the % operator shall
4315 The usual arithmetic conversions are performed on the operands.
4317 The result of the binary * operator is the product of the operands.
4319 The result of the / operator is the quotient from the division of the first operand by the
4320 second; the result of the % operator is the remainder. In both operations, if the value of
4321 the second operand is zero, the behavior is undefined.
4323 When integers are divided, the result of the / operator is the algebraic quotient with any
4324 fractional part discarded.<sup><a href="#note90"><b>90)</b></a></sup> If the quotient a/b is representable, the expression
4325 (a/b)*b + a%b shall equal a.
4328 <p><small><a name="note90" href="#note90">90)</a> This is often called ''truncation toward zero''.
4331 <h4><a name="6.5.6" href="#6.5.6">6.5.6 Additive operators</a></h4>
4335 additive-expression:
4336 multiplicative-expression
4337 additive-expression + multiplicative-expression
4338 additive-expression - multiplicative-expression</pre>
4339 <h6>Constraints</h6>
4341 For addition, either both operands shall have arithmetic type, or one operand shall be a
4342 pointer to an object type and the other shall have integer type. (Incrementing is
4343 equivalent to adding 1.)
4345 For subtraction, one of the following shall hold:
4347 <li> both operands have arithmetic type;
4352 <li> both operands are pointers to qualified or unqualified versions of compatible object
4354 <li> the left operand is a pointer to an object type and the right operand has integer type.
4356 (Decrementing is equivalent to subtracting 1.)
4359 If both operands have arithmetic type, the usual arithmetic conversions are performed on
4362 The result of the binary + operator is the sum of the operands.
4364 The result of the binary - operator is the difference resulting from the subtraction of the
4365 second operand from the first.
4367 For the purposes of these operators, a pointer to an object that is not an element of an
4368 array behaves the same as a pointer to the first element of an array of length one with the
4369 type of the object as its element type.
4371 When an expression that has integer type is added to or subtracted from a pointer, the
4372 result has the type of the pointer operand. If the pointer operand points to an element of
4373 an array object, and the array is large enough, the result points to an element offset from
4374 the original element such that the difference of the subscripts of the resulting and original
4375 array elements equals the integer expression. In other words, if the expression P points to
4376 the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
4377 (P)-N (where N has the value n) point to, respectively, the i+n-th and i-n-th elements of
4378 the array object, provided they exist. Moreover, if the expression P points to the last
4379 element of an array object, the expression (P)+1 points one past the last element of the
4380 array object, and if the expression Q points one past the last element of an array object,
4381 the expression (Q)-1 points to the last element of the array object. If both the pointer
4382 operand and the result point to elements of the same array object, or one past the last
4383 element of the array object, the evaluation shall not produce an overflow; otherwise, the
4384 behavior is undefined. If the result points one past the last element of the array object, it
4385 shall not be used as the operand of a unary * operator that is evaluated.
4387 When two pointers are subtracted, both shall point to elements of the same array object,
4388 or one past the last element of the array object; the result is the difference of the
4389 subscripts of the two array elements. The size of the result is implementation-defined,
4390 and its type (a signed integer type) is ptrdiff_t defined in the <a href="#7.17"><stddef.h></a> header.
4391 If the result is not representable in an object of that type, the behavior is undefined. In
4392 other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of
4393 an array object, the expression (P)-(Q) has the value i-j provided the value fits in an
4394 object of type ptrdiff_t. Moreover, if the expression P points either to an element of
4395 an array object or one past the last element of an array object, and the expression Q points
4396 to the last element of the same array object, the expression ((Q)+1)-(P) has the same
4398 value as ((Q)-(P))+1 and as -((P)-((Q)+1)), and has the value zero if the
4399 expression P points one past the last element of the array object, even though the
4400 expression (Q)+1 does not point to an element of the array object.<sup><a href="#note91"><b>91)</b></a></sup>
4402 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
4408 int (*p)[m] = a; // p == &a[0]
4409 p += 1; // p == &a[1]
4410 (*p)[2] = 99; // a[1][2] == 99
4411 n = p - a; // n == 1
4413 If array a in the above example were declared to be an array of known constant size, and pointer p were
4414 declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
4417 <p><b> Forward references</b>: array declarators (<a href="#6.7.5.2">6.7.5.2</a>), common definitions <a href="#7.17"><stddef.h></a>
4418 (<a href="#7.17">7.17</a>).
4421 <p><small><a name="note91" href="#note91">91)</a> Another way to approach pointer arithmetic is first to convert the pointer(s) to character pointer(s): In
4422 this scheme the integer expression added to or subtracted from the converted pointer is first multiplied
4423 by the size of the object originally pointed to, and the resulting pointer is converted back to the
4424 original type. For pointer subtraction, the result of the difference between the character pointers is
4425 similarly divided by the size of the object originally pointed to.
4426 When viewed in this way, an implementation need only provide one extra byte (which may overlap
4427 another object in the program) just after the end of the object in order to satisfy the ''one past the last
4428 element'' requirements.
4431 <h4><a name="6.5.7" href="#6.5.7">6.5.7 Bitwise shift operators</a></h4>
4437 shift-expression << additive-expression
4438 shift-expression >> additive-expression</pre>
4439 <h6>Constraints</h6>
4441 Each of the operands shall have integer type.
4444 The integer promotions are performed on each of the operands. The type of the result is
4445 that of the promoted left operand. If the value of the right operand is negative or is
4446 greater than or equal to the width of the promoted left operand, the behavior is undefined.
4453 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with
4454 zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo
4455 one more than the maximum value representable in the result type. If E1 has a signed
4456 type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is
4457 the resulting value; otherwise, the behavior is undefined.
4459 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
4460 or if E1 has a signed type and a nonnegative value, the value of the result is the integral
4461 part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
4462 resulting value is implementation-defined.
4464 <h4><a name="6.5.8" href="#6.5.8">6.5.8 Relational operators</a></h4>
4468 relational-expression:
4470 relational-expression < shift-expression
4471 relational-expression > shift-expression
4472 relational-expression <= shift-expression
4473 relational-expression >= shift-expression</pre>
4474 <h6>Constraints</h6>
4476 One of the following shall hold:
4478 <li> both operands have real type;
4479 <li> both operands are pointers to qualified or unqualified versions of compatible object
4481 <li> both operands are pointers to qualified or unqualified versions of compatible
4486 If both of the operands have arithmetic type, the usual arithmetic conversions are
4489 For the purposes of these operators, a pointer to an object that is not an element of an
4490 array behaves the same as a pointer to the first element of an array of length one with the
4491 type of the object as its element type.
4493 When two pointers are compared, the result depends on the relative locations in the
4494 address space of the objects pointed to. If two pointers to object or incomplete types both
4495 point to the same object, or both point one past the last element of the same array object,
4496 they compare equal. If the objects pointed to are members of the same aggregate object,
4497 pointers to structure members declared later compare greater than pointers to members
4498 declared earlier in the structure, and pointers to array elements with larger subscript
4500 values compare greater than pointers to elements of the same array with lower subscript
4501 values. All pointers to members of the same union object compare equal. If the
4502 expression P points to an element of an array object and the expression Q points to the
4503 last element of the same array object, the pointer expression Q+1 compares greater than
4504 P. In all other cases, the behavior is undefined.
4506 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
4507 (greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is false.<sup><a href="#note92"><b>92)</b></a></sup>
4508 The result has type int.
4511 <p><small><a name="note92" href="#note92">92)</a> The expression a<b<c is not interpreted as in ordinary mathematics. As the syntax indicates, it
4512 means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
4515 <h4><a name="6.5.9" href="#6.5.9">6.5.9 Equality operators</a></h4>
4519 equality-expression:
4520 relational-expression
4521 equality-expression == relational-expression
4522 equality-expression != relational-expression</pre>
4523 <h6>Constraints</h6>
4525 One of the following shall hold:
4527 <li> both operands have arithmetic type;
4528 <li> both operands are pointers to qualified or unqualified versions of compatible types;
4529 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4530 qualified or unqualified version of void; or
4531 <li> one operand is a pointer and the other is a null pointer constant.
4535 The == (equal to) and != (not equal to) operators are analogous to the relational
4536 operators except for their lower precedence.<sup><a href="#note93"><b>93)</b></a></sup> Each of the operators yields 1 if the
4537 specified relation is true and 0 if it is false. The result has type int. For any pair of
4538 operands, exactly one of the relations is true.
4540 If both of the operands have arithmetic type, the usual arithmetic conversions are
4541 performed. Values of complex types are equal if and only if both their real parts are equal
4542 and also their imaginary parts are equal. Any two values of arithmetic types from
4543 different type domains are equal if and only if the results of their conversions to the
4544 (complex) result type determined by the usual arithmetic conversions are equal.
4549 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a
4550 null pointer constant, the null pointer constant is converted to the type of the pointer. If
4551 one operand is a pointer to an object or incomplete type and the other is a pointer to a
4552 qualified or unqualified version of void, the former is converted to the type of the latter.
4554 Two pointers compare equal if and only if both are null pointers, both are pointers to the
4555 same object (including a pointer to an object and a subobject at its beginning) or function,
4556 both are pointers to one past the last element of the same array object, or one is a pointer
4557 to one past the end of one array object and the other is a pointer to the start of a different
4558 array object that happens to immediately follow the first array object in the address
4559 space.<sup><a href="#note94"><b>94)</b></a></sup>
4561 For the purposes of these operators, a pointer to an object that is not an element of an
4562 array behaves the same as a pointer to the first element of an array of length one with the
4563 type of the object as its element type.
4566 <p><small><a name="note93" href="#note93">93)</a> Because of the precedences, a<b == c<d is 1 whenever a<b and c<d have the same truth-value.
4568 <p><small><a name="note94" href="#note94">94)</a> Two objects may be adjacent in memory because they are adjacent elements of a larger array or
4569 adjacent members of a structure with no padding between them, or because the implementation chose
4570 to place them so, even though they are unrelated. If prior invalid pointer operations (such as accesses
4571 outside array bounds) produced undefined behavior, subsequent comparisons also produce undefined
4575 <h4><a name="6.5.10" href="#6.5.10">6.5.10 Bitwise AND operator</a></h4>
4581 AND-expression & equality-expression</pre>
4582 <h6>Constraints</h6>
4584 Each of the operands shall have integer type.
4587 The usual arithmetic conversions are performed on the operands.
4589 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
4590 the result is set if and only if each of the corresponding bits in the converted operands is
4598 <h4><a name="6.5.11" href="#6.5.11">6.5.11 Bitwise exclusive OR operator</a></h4>
4602 exclusive-OR-expression:
4604 exclusive-OR-expression ^ AND-expression</pre>
4605 <h6>Constraints</h6>
4607 Each of the operands shall have integer type.
4610 The usual arithmetic conversions are performed on the operands.
4612 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
4613 in the result is set if and only if exactly one of the corresponding bits in the converted
4616 <h4><a name="6.5.12" href="#6.5.12">6.5.12 Bitwise inclusive OR operator</a></h4>
4620 inclusive-OR-expression:
4621 exclusive-OR-expression
4622 inclusive-OR-expression | exclusive-OR-expression</pre>
4623 <h6>Constraints</h6>
4625 Each of the operands shall have integer type.
4628 The usual arithmetic conversions are performed on the operands.
4630 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
4631 the result is set if and only if at least one of the corresponding bits in the converted
4635 <h4><a name="6.5.13" href="#6.5.13">6.5.13 Logical AND operator</a></h4>
4639 logical-AND-expression:
4640 inclusive-OR-expression
4641 logical-AND-expression && inclusive-OR-expression</pre>
4642 <h6>Constraints</h6>
4644 Each of the operands shall have scalar type.
4647 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
4648 yields 0. The result has type int.
4650 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
4651 there is a sequence point after the evaluation of the first operand. If the first operand
4652 compares equal to 0, the second operand is not evaluated.
4654 <h4><a name="6.5.14" href="#6.5.14">6.5.14 Logical OR operator</a></h4>
4658 logical-OR-expression:
4659 logical-AND-expression
4660 logical-OR-expression || logical-AND-expression</pre>
4661 <h6>Constraints</h6>
4663 Each of the operands shall have scalar type.
4666 The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it
4667 yields 0. The result has type int.
4669 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; there is
4670 a sequence point after the evaluation of the first operand. If the first operand compares
4671 unequal to 0, the second operand is not evaluated.
4674 <h4><a name="6.5.15" href="#6.5.15">6.5.15 Conditional operator</a></h4>
4678 conditional-expression:
4679 logical-OR-expression
4680 logical-OR-expression ? expression : conditional-expression</pre>
4681 <h6>Constraints</h6>
4683 The first operand shall have scalar type.
4685 One of the following shall hold for the second and third operands:
4687 <li> both operands have arithmetic type;
4688 <li> both operands have the same structure or union type;
4689 <li> both operands have void type;
4690 <li> both operands are pointers to qualified or unqualified versions of compatible types;
4691 <li> one operand is a pointer and the other is a null pointer constant; or
4692 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4693 qualified or unqualified version of void.
4697 The first operand is evaluated; there is a sequence point after its evaluation. The second
4698 operand is evaluated only if the first compares unequal to 0; the third operand is evaluated
4699 only if the first compares equal to 0; the result is the value of the second or third operand
4700 (whichever is evaluated), converted to the type described below.<sup><a href="#note95"><b>95)</b></a></sup> If an attempt is made
4701 to modify the result of a conditional operator or to access it after the next sequence point,
4702 the behavior is undefined.
4704 If both the second and third operands have arithmetic type, the result type that would be
4705 determined by the usual arithmetic conversions, were they applied to those two operands,
4706 is the type of the result. If both the operands have structure or union type, the result has
4707 that type. If both operands have void type, the result has void type.
4709 If both the second and third operands are pointers or one is a null pointer constant and the
4710 other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
4711 of the types pointed-to by both operands. Furthermore, if both operands are pointers to
4712 compatible types or to differently qualified versions of compatible types, the result type is
4713 a pointer to an appropriately qualified version of the composite type; if one operand is a
4714 null pointer constant, the result has the type of the other operand; otherwise, one operand
4715 is a pointer to void or a qualified version of void, in which case the result type is a
4718 pointer to an appropriately qualified version of void.
4720 EXAMPLE The common type that results when the second and third operands are pointers is determined
4721 in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two
4722 pointers have compatible types.
4724 Given the declarations
4731 const char *c_cp;</pre>
4732 the third column in the following table is the common type that is the result of a conditional expression in
4733 which the first two columns are the second and third operands (in either order):
4735 c_vp c_ip const void *
4736 v_ip 0 volatile int *
4737 c_ip v_ip const volatile int *
4738 vp c_cp const void *
4744 <p><small><a name="note95" href="#note95">95)</a> A conditional expression does not yield an lvalue.
4747 <h4><a name="6.5.16" href="#6.5.16">6.5.16 Assignment operators</a></h4>
4751 assignment-expression:
4752 conditional-expression
4753 unary-expression assignment-operator assignment-expression
4754 assignment-operator: one of
4755 = *= /= %= += -= <<= >>= &= ^= |=</pre>
4756 <h6>Constraints</h6>
4758 An assignment operator shall have a modifiable lvalue as its left operand.
4761 An assignment operator stores a value in the object designated by the left operand. An
4762 assignment expression has the value of the left operand after the assignment, but is not an
4763 lvalue. The type of an assignment expression is the type of the left operand unless the
4764 left operand has qualified type, in which case it is the unqualified version of the type of
4765 the left operand. The side effect of updating the stored value of the left operand shall
4766 occur between the previous and the next sequence point.
4768 The order of evaluation of the operands is unspecified. If an attempt is made to modify
4769 the result of an assignment operator or to access it after the next sequence point, the
4770 behavior is undefined.
4773 <h5><a name="6.5.16.1" href="#6.5.16.1">6.5.16.1 Simple assignment</a></h5>
4774 <h6>Constraints</h6>
4776 One of the following shall hold:<sup><a href="#note96"><b>96)</b></a></sup>
4778 <li> the left operand has qualified or unqualified arithmetic type and the right has
4780 <li> the left operand has a qualified or unqualified version of a structure or union type
4781 compatible with the type of the right;
4782 <li> both operands are pointers to qualified or unqualified versions of compatible types,
4783 and the type pointed to by the left has all the qualifiers of the type pointed to by the
4785 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4786 qualified or unqualified version of void, and the type pointed to by the left has all
4787 the qualifiers of the type pointed to by the right;
4788 <li> the left operand is a pointer and the right is a null pointer constant; or
4789 <li> the left operand has type _Bool and the right is a pointer.
4793 In simple assignment (=), the value of the right operand is converted to the type of the
4794 assignment expression and replaces the value stored in the object designated by the left
4797 If the value being stored in an object is read from another object that overlaps in any way
4798 the storage of the first object, then the overlap shall be exact and the two objects shall
4799 have qualified or unqualified versions of a compatible type; otherwise, the behavior is
4802 EXAMPLE 1 In the program fragment
4807 if ((c = f()) == -1)
4809 the int value returned by the function may be truncated when stored in the char, and then converted back
4810 to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
4811 values as unsigned char (and char is narrower than int), the result of the conversion cannot be
4816 negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
4817 variable c should be declared as int.
4820 EXAMPLE 2 In the fragment:
4826 the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
4827 of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
4828 that is, long int type.
4831 EXAMPLE 3 Consider the fragment:
4836 cpp = &p; // constraint violation
4837 *cpp = &c; // valid
4838 *p = 0; // valid</pre>
4839 The first assignment is unsafe because it would allow the following valid code to attempt to change the
4840 value of the const object c.
4844 <p><small><a name="note96" href="#note96">96)</a> The asymmetric appearance of these constraints with respect to type qualifiers is due to the conversion
4845 (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
4846 qualifiers that were applied to the type category of the expression (for example, it removes const but
4847 not volatile from the type int volatile * const).
4850 <h5><a name="6.5.16.2" href="#6.5.16.2">6.5.16.2 Compound assignment</a></h5>
4851 <h6>Constraints</h6>
4853 For the operators += and -= only, either the left operand shall be a pointer to an object
4854 type and the right shall have integer type, or the left operand shall have qualified or
4855 unqualified arithmetic type and the right shall have arithmetic type.
4857 For the other operators, each operand shall have arithmetic type consistent with those
4858 allowed by the corresponding binary operator.
4861 A compound assignment of the form E1 op = E2 differs from the simple assignment
4862 expression E1 = E1 op (E2) only in that the lvalue E1 is evaluated only once.
4865 <h4><a name="6.5.17" href="#6.5.17">6.5.17 Comma operator</a></h4>
4870 assignment-expression
4871 expression , assignment-expression</pre>
4874 The left operand of a comma operator is evaluated as a void expression; there is a
4875 sequence point after its evaluation. Then the right operand is evaluated; the result has its
4876 type and value.<sup><a href="#note97"><b>97)</b></a></sup> If an attempt is made to modify the result of a comma operator or to
4877 access it after the next sequence point, the behavior is undefined.
4879 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot
4880 appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists
4881 of initializers). On the other hand, it can be used within a parenthesized expression or within the second
4882 expression of a conditional operator in such contexts. In the function call
4884 f(a, (t=3, t+2), c)</pre>
4885 the function has three arguments, the second of which has the value 5.
4887 <p><b> Forward references</b>: initialization (<a href="#6.7.8">6.7.8</a>).
4895 <p><small><a name="note97" href="#note97">97)</a> A comma operator does not yield an lvalue.
4898 <h3><a name="6.6" href="#6.6">6.6 Constant expressions</a></h3>
4902 constant-expression:
4903 conditional-expression</pre>
4904 <h6>Description</h6>
4906 A constant expression can be evaluated during translation rather than runtime, and
4907 accordingly may be used in any place that a constant may be.
4908 <h6>Constraints</h6>
4910 Constant expressions shall not contain assignment, increment, decrement, function-call,
4911 or comma operators, except when they are contained within a subexpression that is not
4912 evaluated.<sup><a href="#note98"><b>98)</b></a></sup>
4914 Each constant expression shall evaluate to a constant that is in the range of representable
4915 values for its type.
4918 An expression that evaluates to a constant is required in several contexts. If a floating
4919 expression is evaluated in the translation environment, the arithmetic precision and range
4920 shall be at least as great as if the expression were being evaluated in the execution
4923 An integer constant expression<sup><a href="#note99"><b>99)</b></a></sup> shall have integer type and shall only have operands
4924 that are integer constants, enumeration constants, character constants, sizeof
4925 expressions whose results are integer constants, and floating constants that are the
4926 immediate operands of casts. Cast operators in an integer constant expression shall only
4927 convert arithmetic types to integer types, except as part of an operand to the sizeof
4930 More latitude is permitted for constant expressions in initializers. Such a constant
4931 expression shall be, or evaluate to, one of the following:
4933 <li> an arithmetic constant expression,
4934 <li> a null pointer constant,
4940 <li> an address constant, or
4941 <li> an address constant for an object type plus or minus an integer constant expression.
4944 An arithmetic constant expression shall have arithmetic type and shall only have
4945 operands that are integer constants, floating constants, enumeration constants, character
4946 constants, and sizeof expressions. Cast operators in an arithmetic constant expression
4947 shall only convert arithmetic types to arithmetic types, except as part of an operand to a
4948 sizeof operator whose result is an integer constant.
4950 An address constant is a null pointer, a pointer to an lvalue designating an object of static
4951 storage duration, or a pointer to a function designator; it shall be created explicitly using
4952 the unary & operator or an integer constant cast to pointer type, or implicitly by the use of
4953 an expression of array or function type. The array-subscript [] and member-access .
4954 and -> operators, the address & and indirection * unary operators, and pointer casts may
4955 be used in the creation of an address constant, but the value of an object shall not be
4956 accessed by use of these operators.
4958 An implementation may accept other forms of constant expressions.
4960 The semantic rules for the evaluation of a constant expression are the same as for
4961 nonconstant expressions.<sup><a href="#note100"><b>100)</b></a></sup>
4962 <p><b> Forward references</b>: array declarators (<a href="#6.7.5.2">6.7.5.2</a>), initialization (<a href="#6.7.8">6.7.8</a>).
4970 <p><small><a name="note98" href="#note98">98)</a> The operand of a sizeof operator is usually not evaluated (<a href="#6.5.3.4">6.5.3.4</a>).
4972 <p><small><a name="note99" href="#note99">99)</a> An integer constant expression is used to specify the size of a bit-field member of a structure, the
4973 value of an enumeration constant, the size of an array, or the value of a case constant. Further
4974 constraints that apply to the integer constant expressions used in conditional-inclusion preprocessing
4975 directives are discussed in <a href="#6.10.1">6.10.1</a>.
4977 <p><small><a name="note100" href="#note100">100)</a> Thus, in the following initialization,
4980 static int i = 2 || 1 / 0;</pre>
4981 the expression is a valid integer constant expression with value one.
4984 <h3><a name="6.7" href="#6.7">6.7 Declarations</a></h3>
4989 declaration-specifiers init-declarator-listopt ;
4990 declaration-specifiers:
4991 storage-class-specifier declaration-specifiersopt
4992 type-specifier declaration-specifiersopt
4993 type-qualifier declaration-specifiersopt
4994 function-specifier declaration-specifiersopt
4995 init-declarator-list:
4997 init-declarator-list , init-declarator
5000 declarator = initializer</pre>
5001 <h6>Constraints</h6>
5003 A declaration shall declare at least a declarator (other than the parameters of a function or
5004 the members of a structure or union), a tag, or the members of an enumeration.
5006 If an identifier has no linkage, there shall be no more than one declaration of the identifier
5007 (in a declarator or type specifier) with the same scope and in the same name space, except
5008 for tags as specified in <a href="#6.7.2.3">6.7.2.3</a>.
5010 All declarations in the same scope that refer to the same object or function shall specify
5014 A declaration specifies the interpretation and attributes of a set of identifiers. A definition
5015 of an identifier is a declaration for that identifier that:
5017 <li> for an object, causes storage to be reserved for that object;
5018 <li> for a function, includes the function body;<sup><a href="#note101"><b>101)</b></a></sup>
5019 <li> for an enumeration constant or typedef name, is the (only) declaration of the
5023 The declaration specifiers consist of a sequence of specifiers that indicate the linkage,
5024 storage duration, and part of the type of the entities that the declarators denote. The init-
5025 declarator-list is a comma-separated sequence of declarators, each of which may have
5028 additional type information, or an initializer, or both. The declarators contain the
5029 identifiers (if any) being declared.
5031 If an identifier for an object is declared with no linkage, the type for the object shall be
5032 complete by the end of its declarator, or by the end of its init-declarator if it has an
5033 initializer; in the case of function parameters (including in prototypes), it is the adjusted
5034 type (see <a href="#6.7.5.3">6.7.5.3</a>) that is required to be complete.
5035 <p><b> Forward references</b>: declarators (<a href="#6.7.5">6.7.5</a>), enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), initialization
5036 (<a href="#6.7.8">6.7.8</a>).
5039 <p><small><a name="note101" href="#note101">101)</a> Function definitions have a different syntax, described in <a href="#6.9.1">6.9.1</a>.
5042 <h4><a name="6.7.1" href="#6.7.1">6.7.1 Storage-class specifiers</a></h4>
5046 storage-class-specifier:
5052 <h6>Constraints</h6>
5054 At most, one storage-class specifier may be given in the declaration specifiers in a
5055 declaration.<sup><a href="#note102"><b>102)</b></a></sup>
5058 The typedef specifier is called a ''storage-class specifier'' for syntactic convenience
5059 only; it is discussed in <a href="#6.7.7">6.7.7</a>. The meanings of the various linkages and storage durations
5060 were discussed in <a href="#6.2.2">6.2.2</a> and <a href="#6.2.4">6.2.4</a>.
5062 A declaration of an identifier for an object with storage-class specifier register
5063 suggests that access to the object be as fast as possible. The extent to which such
5064 suggestions are effective is implementation-defined.<sup><a href="#note103"><b>103)</b></a></sup>
5066 The declaration of an identifier for a function that has block scope shall have no explicit
5067 storage-class specifier other than extern.
5073 If an aggregate or union object is declared with a storage-class specifier other than
5074 typedef, the properties resulting from the storage-class specifier, except with respect to
5075 linkage, also apply to the members of the object, and so on recursively for any aggregate
5076 or union member objects.
5077 <p><b> Forward references</b>: type definitions (<a href="#6.7.7">6.7.7</a>).
5080 <p><small><a name="note102" href="#note102">102)</a> See ''future language directions'' (<a href="#6.11.5">6.11.5</a>).
5082 <p><small><a name="note103" href="#note103">103)</a> The implementation may treat any register declaration simply as an auto declaration. However,
5083 whether or not addressable storage is actually used, the address of any part of an object declared with
5084 storage-class specifier register cannot be computed, either explicitly (by use of the unary &
5085 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
5086 <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
5090 <h4><a name="6.7.2" href="#6.7.2">6.7.2 Type specifiers</a></h4>
5106 struct-or-union-specifier *
5109 <h6>Constraints</h6>
5111 At least one type specifier shall be given in the declaration specifiers in each declaration,
5112 and in the specifier-qualifier list in each struct declaration and type name. Each list of
5113 type specifiers shall be one of the following sets (delimited by commas, when there is
5114 more than one set on a line); the type specifiers may occur in any order, possibly
5115 intermixed with the other declaration specifiers.
5121 <li> short, signed short, short int, or signed short int
5122 <li> unsigned short, or unsigned short int
5123 <li> int, signed, or signed int
5125 <li> unsigned, or unsigned int
5126 <li> long, signed long, long int, or signed long int
5127 <li> unsigned long, or unsigned long int
5128 <li> long long, signed long long, long long int, or
5129 signed long long int
5130 <li> unsigned long long, or unsigned long long int
5136 <li> double _Complex
5137 <li> long double _Complex
5138 <li> struct or union specifier *
5143 The type specifier _Complex shall not be used if the implementation does not provide
5144 complex types.<sup><a href="#note104"><b>104)</b></a></sup>
5147 Specifiers for structures, unions, and enumerations are discussed in <a href="#6.7.2.1">6.7.2.1</a> through
5148 <a href="#6.7.2.3">6.7.2.3</a>. Declarations of typedef names are discussed in <a href="#6.7.7">6.7.7</a>. The characteristics of the
5149 other types are discussed in <a href="#6.2.5">6.2.5</a>.
5151 Each of the comma-separated sets designates the same type, except that for bit-fields, it is
5152 implementation-defined whether the specifier int designates the same type as signed
5153 int or the same type as unsigned int.
5154 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
5155 (<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="#6.7.7">6.7.7</a>).
5163 <p><small><a name="note104" href="#note104">104)</a> Freestanding implementations are not required to provide complex types. *
5166 <h5><a name="6.7.2.1" href="#6.7.2.1">6.7.2.1 Structure and union specifiers</a></h5>
5170 struct-or-union-specifier:
5171 struct-or-union identifieropt { struct-declaration-list }
5172 struct-or-union identifier
5176 struct-declaration-list:
5178 struct-declaration-list struct-declaration
5180 specifier-qualifier-list struct-declarator-list ;
5181 specifier-qualifier-list:
5182 type-specifier specifier-qualifier-listopt
5183 type-qualifier specifier-qualifier-listopt
5184 struct-declarator-list:
5186 struct-declarator-list , struct-declarator
5189 declaratoropt : constant-expression</pre>
5190 <h6>Constraints</h6>
5192 A structure or union shall not contain a member with incomplete or function type (hence,
5193 a structure shall not contain an instance of itself, but may contain a pointer to an instance
5194 of itself), except that the last member of a structure with more than one named member
5195 may have incomplete array type; such a structure (and any union containing, possibly
5196 recursively, a member that is such a structure) shall not be a member of a structure or an
5197 element of an array.
5199 The expression that specifies the width of a bit-field shall be an integer constant
5200 expression with a nonnegative value that does not exceed the width of an object of the
5201 type that would be specified were the colon and expression omitted. If the value is zero,
5202 the declaration shall have no declarator.
5204 A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed
5205 int, unsigned int, or some other implementation-defined type.
5209 As discussed in <a href="#6.2.5">6.2.5</a>, a structure is a type consisting of a sequence of members, whose
5210 storage is allocated in an ordered sequence, and a union is a type consisting of a sequence
5211 of members whose storage overlap.
5213 Structure and union specifiers have the same form. The keywords struct and union
5214 indicate that the type being specified is, respectively, a structure type or a union type.
5216 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
5217 within a translation unit. The struct-declaration-list is a sequence of declarations for the
5218 members of the structure or union. If the struct-declaration-list contains no named
5219 members, the behavior is undefined. The type is incomplete until after the } that
5220 terminates the list.
5222 A member of a structure or union may have any object type other than a variably
5223 modified type.<sup><a href="#note105"><b>105)</b></a></sup> In addition, a member may be declared to consist of a specified
5224 number of bits (including a sign bit, if any). Such a member is called a bit-field;<sup><a href="#note106"><b>106)</b></a></sup> its
5225 width is preceded by a colon.
5227 A bit-field is interpreted as a signed or unsigned integer type consisting of the specified
5228 number of bits.<sup><a href="#note107"><b>107)</b></a></sup> If the value 0 or 1 is stored into a nonzero-width bit-field of type
5229 _Bool, the value of the bit-field shall compare equal to the value stored.
5231 An implementation may allocate any addressable storage unit large enough to hold a bit-
5232 field. If enough space remains, a bit-field that immediately follows another bit-field in a
5233 structure shall be packed into adjacent bits of the same unit. If insufficient space remains,
5234 whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is
5235 implementation-defined. The order of allocation of bit-fields within a unit (high-order to
5236 low-order or low-order to high-order) is implementation-defined. The alignment of the
5237 addressable storage unit is unspecified.
5239 A bit-field declaration with no declarator, but only a colon and a width, indicates an
5240 unnamed bit-field.<sup><a href="#note108"><b>108)</b></a></sup> As a special case, a bit-field structure member with a width of 0
5241 indicates that no further bit-field is to be packed into the unit in which the previous bit-
5242 field, if any, was placed.
5247 Each non-bit-field member of a structure or union object is aligned in an implementation-
5248 defined manner appropriate to its type.
5250 Within a structure object, the non-bit-field members and the units in which bit-fields
5251 reside have addresses that increase in the order in which they are declared. A pointer to a
5252 structure object, suitably converted, points to its initial member (or if that member is a
5253 bit-field, then to the unit in which it resides), and vice versa. There may be unnamed
5254 padding within a structure object, but not at its beginning.
5256 The size of a union is sufficient to contain the largest of its members. The value of at
5257 most one of the members can be stored in a union object at any time. A pointer to a
5258 union object, suitably converted, points to each of its members (or if a member is a bit-
5259 field, then to the unit in which it resides), and vice versa.
5261 There may be unnamed padding at the end of a structure or union.
5263 As a special case, the last element of a structure with more than one named member may
5264 have an incomplete array type; this is called a flexible array member. In most situations,
5265 the flexible array member is ignored. In particular, the size of the structure is as if the
5266 flexible array member were omitted except that it may have more trailing padding than
5267 the omission would imply. However, when a . (or ->) operator has a left operand that is
5268 (a pointer to) a structure with a flexible array member and the right operand names that
5269 member, it behaves as if that member were replaced with the longest array (with the same
5270 element type) that would not make the structure larger than the object being accessed; the
5271 offset of the array shall remain that of the flexible array member, even if this would differ
5272 from that of the replacement array. If this array would have no elements, it behaves as if
5273 it had one element but the behavior is undefined if any attempt is made to access that
5274 element or to generate a pointer one past it.
5276 EXAMPLE After the declaration:
5278 struct s { int n; double d[]; };</pre>
5279 the structure struct s has a flexible array member d. A typical way to use this is:
5281 int m = /* some value */;
5282 struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));</pre>
5283 and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
5284 p had been declared as:
5286 struct { int n; double d[m]; } *p;</pre>
5287 (there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
5290 Following the above declaration:
5293 struct s t1 = { 0 }; // valid
5294 struct s t2 = { 1, { <a href="#4.2">4.2</a> }}; // invalid
5296 t1.d[0] = <a href="#4.2">4.2</a>; // might be undefined behavior</pre>
5297 The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
5298 contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
5300 sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)</pre>
5301 in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming
5304 After the further declaration:
5306 struct ss { int n; };</pre>
5309 sizeof (struct s) >= sizeof (struct ss)
5310 sizeof (struct s) >= offsetof(struct s, d)</pre>
5311 are always equal to 1.
5313 If sizeof (double) is 8, then after the following code is executed:
5317 s1 = malloc(sizeof (struct s) + 64);
5318 s2 = malloc(sizeof (struct s) + 46);</pre>
5319 and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
5320 purposes, as if the identifiers had been declared as:
5323 struct { int n; double d[8]; } *s1;
5324 struct { int n; double d[5]; } *s2;</pre>
5325 Following the further successful assignments:
5327 s1 = malloc(sizeof (struct s) + 10);
5328 s2 = malloc(sizeof (struct s) + 6);</pre>
5329 they then behave as if the declarations were:
5331 struct { int n; double d[1]; } *s1, *s2;</pre>
5336 dp = &(s1->d[0]); // valid
5338 dp = &(s2->d[0]); // valid
5339 *dp = 42; // undefined behavior</pre>
5343 only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes
5344 of the structure, they might be copied or simply overwritten with indeterminate values.
5346 <p><b> Forward references</b>: tags (<a href="#6.7.2.3">6.7.2.3</a>).
5350 <p><small><a name="note105" href="#note105">105)</a> A structure or union can not contain a member with a variably modified type because member names
5351 are not ordinary identifiers as defined in <a href="#6.2.3">6.2.3</a>.
5353 <p><small><a name="note106" href="#note106">106)</a> The unary & (address-of) operator cannot be applied to a bit-field object; thus, there are no pointers to
5354 or arrays of bit-field objects.
5356 <p><small><a name="note107" href="#note107">107)</a> 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,
5357 then it is implementation-defined whether the bit-field is signed or unsigned.
5359 <p><small><a name="note108" href="#note108">108)</a> An unnamed bit-field structure member is useful for padding to conform to externally imposed
5363 <h5><a name="6.7.2.2" href="#6.7.2.2">6.7.2.2 Enumeration specifiers</a></h5>
5368 enum identifieropt { enumerator-list }
5369 enum identifieropt { enumerator-list , }
5373 enumerator-list , enumerator
5375 enumeration-constant
5376 enumeration-constant = constant-expression</pre>
5377 <h6>Constraints</h6>
5379 The expression that defines the value of an enumeration constant shall be an integer
5380 constant expression that has a value representable as an int.
5383 The identifiers in an enumerator list are declared as constants that have type int and
5384 may appear wherever such are permitted.<sup><a href="#note109"><b>109)</b></a></sup> An enumerator with = defines its
5385 enumeration constant as the value of the constant expression. If the first enumerator has
5386 no =, the value of its enumeration constant is 0. Each subsequent enumerator with no =
5387 defines its enumeration constant as the value of the constant expression obtained by
5388 adding 1 to the value of the previous enumeration constant. (The use of enumerators with
5389 = may produce enumeration constants with values that duplicate other values in the same
5390 enumeration.) The enumerators of an enumeration are also known as its members.
5392 Each enumerated type shall be compatible with char, a signed integer type, or an
5393 unsigned integer type. The choice of type is implementation-defined,<sup><a href="#note110"><b>110)</b></a></sup> but shall be
5394 capable of representing the values of all the members of the enumeration. The
5395 enumerated type is incomplete until after the } that terminates the list of enumerator
5403 EXAMPLE The following fragment:
5405 enum hue { chartreuse, burgundy, claret=20, winedark };
5409 if (*cp != burgundy)
5411 makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
5412 pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
5414 <p><b> Forward references</b>: tags (<a href="#6.7.2.3">6.7.2.3</a>).
5417 <p><small><a name="note109" href="#note109">109)</a> Thus, the identifiers of enumeration constants declared in the same scope shall all be distinct from
5418 each other and from other identifiers declared in ordinary declarators.
5420 <p><small><a name="note110" href="#note110">110)</a> An implementation may delay the choice of which integer type until all enumeration constants have
5424 <h5><a name="6.7.2.3" href="#6.7.2.3">6.7.2.3 Tags</a></h5>
5425 <h6>Constraints</h6>
5427 A specific type shall have its content defined at most once.
5429 Where two declarations that use the same tag declare the same type, they shall both use
5430 the same choice of struct, union, or enum.
5432 A type specifier of the form
5434 enum identifier</pre>
5435 without an enumerator list shall only appear after the type it specifies is complete.
5438 All declarations of structure, union, or enumerated types that have the same scope and
5439 use the same tag declare the same type. The type is incomplete<sup><a href="#note111"><b>111)</b></a></sup> until the closing brace
5440 of the list defining the content, and complete thereafter.
5442 Two declarations of structure, union, or enumerated types which are in different scopes or
5443 use different tags declare distinct types. Each declaration of a structure, union, or
5444 enumerated type which does not include a tag declares a distinct type.
5446 A type specifier of the form
5448 struct-or-union identifieropt { struct-declaration-list }</pre>
5451 enum identifier { enumerator-list }</pre>
5454 enum identifier { enumerator-list , }</pre>
5455 declares a structure, union, or enumerated type. The list defines the structure content,
5458 union content, or enumeration content. If an identifier is provided,<sup><a href="#note112"><b>112)</b></a></sup> the type specifier
5459 also declares the identifier to be the tag of that type.
5461 A declaration of the form
5463 struct-or-union identifier ;</pre>
5464 specifies a structure or union type and declares the identifier as a tag of that type.<sup><a href="#note113"><b>113)</b></a></sup>
5466 If a type specifier of the form
5468 struct-or-union identifier</pre>
5469 occurs other than as part of one of the above forms, and no other declaration of the
5470 identifier as a tag is visible, then it declares an incomplete structure or union type, and
5471 declares the identifier as the tag of that type.113)
5473 If a type specifier of the form
5475 struct-or-union identifier</pre>
5478 enum identifier</pre>
5479 occurs other than as part of one of the above forms, and a declaration of the identifier as a
5480 tag is visible, then it specifies the same type as that other declaration, and does not
5483 EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
5487 struct tnode *left, *right;
5489 specifies a structure that contains an integer and two pointers to objects of the same type. Once this
5490 declaration has been given, the declaration
5492 struct tnode s, *sp;</pre>
5493 declares s to be an object of the given type and sp to be a pointer to an object of the given type. With
5494 these declarations, the expression sp->left refers to the left struct tnode pointer of the object to
5495 which sp points; the expression s.right->count designates the count member of the right struct
5496 tnode pointed to from s.
5498 The following alternative formulation uses the typedef mechanism:
5505 typedef struct tnode TNODE;
5508 TNODE *left, *right;
5513 EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential
5514 structures, the declarations
5516 struct s1 { struct s2 *s2p; /* ... */ }; // D1
5517 struct s2 { struct s1 *s1p; /* ... */ }; // D2</pre>
5518 specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
5519 declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
5520 D2. To eliminate this context sensitivity, the declaration
5523 may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then
5524 completes the specification of the new type.
5526 <p><b> Forward references</b>: declarators (<a href="#6.7.5">6.7.5</a>), array declarators (<a href="#6.7.5.2">6.7.5.2</a>), type definitions
5527 (<a href="#6.7.7">6.7.7</a>).
5530 <p><small><a name="note111" href="#note111">111)</a> An incomplete type may only by used when the size of an object of that type is not needed. It is not
5531 needed, for example, when a typedef name is declared to be a specifier for a structure or union, or
5532 when a pointer to or a function returning a structure or union is being declared. (See incomplete types
5533 in <a href="#6.2.5">6.2.5</a>.) The specification has to be complete before such a function is called or defined.
5535 <p><small><a name="note112" href="#note112">112)</a> If there is no identifier, the type can, within the translation unit, only be referred to by the declaration
5536 of which it is a part. Of course, when the declaration is of a typedef name, subsequent declarations
5537 can make use of that typedef name to declare objects having the specified structure, union, or
5540 <p><small><a name="note113" href="#note113">113)</a> A similar construction with enum does not exist.
5543 <h4><a name="6.7.3" href="#6.7.3">6.7.3 Type qualifiers</a></h4>
5551 <h6>Constraints</h6>
5553 Types other than pointer types derived from object or incomplete types shall not be
5557 The properties associated with qualified types are meaningful only for expressions that
5558 are lvalues.<sup><a href="#note114"><b>114)</b></a></sup>
5560 If the same qualifier appears more than once in the same specifier-qualifier-list, either
5561 directly or via one or more typedefs, the behavior is the same as if it appeared only
5569 If an attempt is made to modify an object defined with a const-qualified type through use
5570 of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is
5571 made to refer to an object defined with a volatile-qualified type through use of an lvalue
5572 with non-volatile-qualified type, the behavior is undefined.<sup><a href="#note115"><b>115)</b></a></sup>
5574 An object that has volatile-qualified type may be modified in ways unknown to the
5575 implementation or have other unknown side effects. Therefore any expression referring
5576 to such an object shall be evaluated strictly according to the rules of the abstract machine,
5577 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
5578 object shall agree with that prescribed by the abstract machine, except as modified by the
5579 unknown factors mentioned previously.<sup><a href="#note116"><b>116)</b></a></sup> What constitutes an access to an object that
5580 has volatile-qualified type is implementation-defined.
5582 An object that is accessed through a restrict-qualified pointer has a special association
5583 with that pointer. This association, defined in <a href="#6.7.3.1">6.7.3.1</a> below, requires that all accesses to
5584 that object use, directly or indirectly, the value of that particular pointer.<sup><a href="#note117"><b>117)</b></a></sup> The intended
5585 use of the restrict qualifier (like the register storage class) is to promote
5586 optimization, and deleting all instances of the qualifier from all preprocessing translation
5587 units composing a conforming program does not change its meaning (i.e., observable
5590 If the specification of an array type includes any type qualifiers, the element type is so-
5591 qualified, not the array type. If the specification of a function type includes any type
5592 qualifiers, the behavior is undefined.<sup><a href="#note118"><b>118)</b></a></sup>
5594 For two qualified types to be compatible, both shall have the identically qualified version
5595 of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers
5596 does not affect the specified type.
5598 EXAMPLE 1 An object declared
5600 extern const volatile int real_time_clock;</pre>
5601 may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
5608 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers
5609 modify an aggregate type:
5611 const struct s { int mem; } cs = { 1 };
5612 struct s ncs; // the object ncs is modifiable
5613 typedef int A[2][3];
5614 const A a = {{4, 5, 6}, {7, 8, 9}}; // array of array of const int
5618 cs = ncs; // violates modifiable lvalue constraint for =
5619 pi = &ncs.mem; // valid
5620 pi = &cs.mem; // violates type constraints for =
5621 pci = &cs.mem; // valid
5622 pi = a[0]; // invalid: a[0] has type ''const int *''</pre>
5626 <p><small><a name="note114" href="#note114">114)</a> The implementation may place a const object that is not volatile in a read-only region of
5627 storage. Moreover, the implementation need not allocate storage for such an object if its address is
5630 <p><small><a name="note115" href="#note115">115)</a> This applies to those objects that behave as if they were defined with qualified types, even if they are
5631 never actually defined as objects in the program (such as an object at a memory-mapped input/output
5634 <p><small><a name="note116" href="#note116">116)</a> A volatile declaration may be used to describe an object corresponding to a memory-mapped
5635 input/output port or an object accessed by an asynchronously interrupting function. Actions on
5636 objects so declared shall not be ''optimized out'' by an implementation or reordered except as
5637 permitted by the rules for evaluating expressions.
5639 <p><small><a name="note117" href="#note117">117)</a> For example, a statement that assigns a value returned by malloc to a single pointer establishes this
5640 association between the allocated object and the pointer.
5642 <p><small><a name="note118" href="#note118">118)</a> Both of these can occur through the use of typedefs.
5645 <h5><a name="6.7.3.1" href="#6.7.3.1">6.7.3.1 Formal definition of restrict</a></h5>
5647 Let D be a declaration of an ordinary identifier that provides a means of designating an
5648 object P as a restrict-qualified pointer to type T.
5650 If D appears inside a block and does not have storage class extern, let B denote the
5651 block. If D appears in the list of parameter declarations of a function definition, let B
5652 denote the associated block. Otherwise, let B denote the block of main (or the block of
5653 whatever function is called at program startup in a freestanding environment).
5655 In what follows, a pointer expression E is said to be based on object P if (at some
5656 sequence point in the execution of B prior to the evaluation of E) modifying P to point to
5657 a copy of the array object into which it formerly pointed would change the value of E.<sup><a href="#note119"><b>119)</b></a></sup>
5658 Note that ''based'' is defined only for expressions with pointer types.
5660 During each execution of B, let L be any lvalue that has &L based on P. If L is used to
5661 access the value of the object X that it designates, and X is also modified (by any means),
5662 then the following requirements apply: T shall not be const-qualified. Every other lvalue
5663 used to access the value of X shall also have its address based on P. Every access that
5664 modifies X shall be considered also to modify P, for the purposes of this subclause. If P
5665 is assigned the value of a pointer expression E that is based on another restricted pointer
5666 object P2, associated with block B2, then either the execution of B2 shall begin before
5667 the execution of B, or the execution of B2 shall end prior to the assignment. If these
5668 requirements are not met, then the behavior is undefined.
5670 Here an execution of B means that portion of the execution of the program that would
5671 correspond to the lifetime of an object with scalar type and automatic storage duration
5676 A translator is free to ignore any or all aliasing implications of uses of restrict.
5678 EXAMPLE 1 The file scope declarations
5682 extern int c[];</pre>
5683 assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
5684 program, then it is never accessed using either of the other two.
5687 EXAMPLE 2 The function parameter declarations in the following example
5689 void f(int n, int * restrict p, int * restrict q)
5694 assert that, during each execution of the function, if an object is accessed through one of the pointer
5695 parameters, then it is not also accessed through the other.
5697 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence
5698 analysis of function f without examining any of the calls of f in the program. The cost is that the
5699 programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the
5700 second call of f in g has undefined behavior because each of d[1] through d[49] is accessed through
5706 f(50, d + 50, d); // valid
5707 f(50, d + 1, d); // undefined behavior
5711 EXAMPLE 3 The function parameter declarations
5713 void h(int n, int * restrict p, int * restrict q, int * restrict r)
5716 for (i = 0; i < n; i++)
5719 illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
5720 are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
5721 modified within function h.
5724 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a
5725 function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments
5726 between restricted pointers declared in nested blocks have defined behavior.
5733 p1 = q1; // undefined behavior
5735 int * restrict p2 = p1; // valid
5736 int * restrict q2 = q1; // valid
5737 p1 = q2; // undefined behavior
5738 p2 = q2; // undefined behavior
5741 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more
5742 precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For
5743 example, this permits new_vector to return a vector.
5745 typedef struct { int n; float * restrict v; } vector;
5746 vector new_vector(int n)
5750 t.v = malloc(n * sizeof (float));
5756 <p><small><a name="note119" href="#note119">119)</a> In other words, E depends on the value of P itself rather than on the value of an object referenced
5757 indirectly through P. For example, if identifier p has type (int **restrict), then the pointer
5758 expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer
5759 expressions *p and p[1] are not.
5762 <h4><a name="6.7.4" href="#6.7.4">6.7.4 Function specifiers</a></h4>
5768 <h6>Constraints</h6>
5770 Function specifiers shall be used only in the declaration of an identifier for a function.
5772 An inline definition of a function with external linkage shall not contain a definition of a
5773 modifiable object with static storage duration, and shall not contain a reference to an
5774 identifier with internal linkage.
5776 In a hosted environment, the inline function specifier shall not appear in a declaration
5780 A function declared with an inline function specifier is an inline function. The
5781 function specifier may appear more than once; the behavior is the same as if it appeared
5782 only once. Making a function an inline function suggests that calls to the function be as
5783 fast as possible.<sup><a href="#note120"><b>120)</b></a></sup> The extent to which such suggestions are effective is
5784 implementation-defined.<sup><a href="#note121"><b>121)</b></a></sup>
5786 Any function with internal linkage can be an inline function. For a function with external
5787 linkage, the following restrictions apply: If a function is declared with an inline
5789 function specifier, then it shall also be defined in the same translation unit. If all of the
5790 file scope declarations for a function in a translation unit include the inline function
5791 specifier without extern, then the definition in that translation unit is an inline
5792 definition. An inline definition does not provide an external definition for the function,
5793 and does not forbid an external definition in another translation unit. An inline definition
5794 provides an alternative to an external definition, which a translator may use to implement
5795 any call to the function in the same translation unit. It is unspecified whether a call to the
5796 function uses the inline definition or the external definition.<sup><a href="#note122"><b>122)</b></a></sup>
5798 EXAMPLE The declaration of an inline function with external linkage can result in either an external
5799 definition, or a definition available for use only within the translation unit. A file scope declaration with
5800 extern creates an external definition. The following example shows an entire translation unit.
5803 inline double fahr(double t)
5805 return (9.0 * t) / 5.0 + 32.0;
5807 inline double cels(double t)
5809 return (5.0 * (t - 32.0)) / 9.0;
5811 extern double fahr(double); // creates an external definition
5812 double convert(int is_fahr, double temp)
5814 /* A translator may perform inline substitutions */
5815 return is_fahr ? cels(temp) : fahr(temp);
5817 Note that the definition of fahr is an external definition because fahr is also declared with extern, but
5818 the definition of cels is an inline definition. Because cels has external linkage and is referenced, an
5819 external definition has to appear in another translation unit (see <a href="#6.9">6.9</a>); the inline definition and the external
5820 definition are distinct and either may be used for the call.
5822 <p><b> Forward references</b>: function definitions (<a href="#6.9.1">6.9.1</a>).
5828 <p><small><a name="note120" href="#note120">120)</a> By using, for example, an alternative to the usual function call mechanism, such as ''inline
5829 substitution''. Inline substitution is not textual substitution, nor does it create a new function.
5830 Therefore, for example, the expansion of a macro used within the body of the function uses the
5831 definition it had at the point the function body appears, and not where the function is called; and
5832 identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a
5833 single address, regardless of the number of inline definitions that occur in addition to the external
5836 <p><small><a name="note121" href="#note121">121)</a> For example, an implementation might never perform inline substitution, or might only perform inline
5837 substitutions to calls in the scope of an inline declaration.
5839 <p><small><a name="note122" href="#note122">122)</a> Since an inline definition is distinct from the corresponding external definition and from any other
5840 corresponding inline definitions in other translation units, all corresponding objects with static storage
5841 duration are also distinct in each of the definitions.
5844 <h4><a name="6.7.5" href="#6.7.5">6.7.5 Declarators</a></h4>
5849 pointeropt direct-declarator
5853 direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
5854 direct-declarator [ static type-qualifier-listopt assignment-expression ]
5855 direct-declarator [ type-qualifier-list static assignment-expression ]
5856 direct-declarator [ type-qualifier-listopt * ]
5857 direct-declarator ( parameter-type-list )
5858 direct-declarator ( identifier-listopt )
5860 * type-qualifier-listopt
5861 * type-qualifier-listopt pointer
5862 type-qualifier-list:
5864 type-qualifier-list type-qualifier
5865 parameter-type-list:
5867 parameter-list , ...
5869 parameter-declaration
5870 parameter-list , parameter-declaration
5871 parameter-declaration:
5872 declaration-specifiers declarator
5873 declaration-specifiers abstract-declaratoropt
5876 identifier-list , identifier</pre>
5879 Each declarator declares one identifier, and asserts that when an operand of the same
5880 form as the declarator appears in an expression, it designates a function or object with the
5881 scope, storage duration, and type indicated by the declaration specifiers.
5883 A full declarator is a declarator that is not part of another declarator. The end of a full
5884 declarator is a sequence point. If, in the nested sequence of declarators in a full
5886 declarator, there is a declarator specifying a variable length array type, the type specified
5887 by the full declarator is said to be variably modified. Furthermore, any type derived by
5888 declarator type derivation from a variably modified type is itself variably modified.
5890 In the following subclauses, consider a declaration
5893 where T contains the declaration specifiers that specify a type T (such as int) and D1 is
5894 a declarator that contains an identifier ident. The type specified for the identifier ident in
5895 the various forms of declarator is described inductively using this notation.
5897 If, in the declaration ''T D1'', D1 has the form
5900 then the type specified for ident is T .
5902 If, in the declaration ''T D1'', D1 has the form
5905 then ident has the type specified by the declaration ''T D''. Thus, a declarator in
5906 parentheses is identical to the unparenthesized declarator, but the binding of complicated
5907 declarators may be altered by parentheses.
5908 Implementation limits
5910 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of pointer, array, and
5911 function declarators that modify an arithmetic, structure, union, or incomplete type, either
5912 directly or via one or more typedefs.
5913 <p><b> Forward references</b>: array declarators (<a href="#6.7.5.2">6.7.5.2</a>), type definitions (<a href="#6.7.7">6.7.7</a>).
5915 <h5><a name="6.7.5.1" href="#6.7.5.1">6.7.5.1 Pointer declarators</a></h5>
5918 If, in the declaration ''T D1'', D1 has the form
5920 * type-qualifier-listopt D</pre>
5921 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5922 T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list
5923 pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer.
5925 For two pointer types to be compatible, both shall be identically qualified and both shall
5926 be pointers to compatible types.
5928 EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer
5929 to a constant value'' and a ''constant pointer to a variable value''.
5932 const int *ptr_to_constant;
5933 int *const constant_ptr;</pre>
5934 The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
5935 but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
5936 int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
5939 The declaration of the constant pointer constant_ptr may be clarified by including a definition for the
5940 type ''pointer to int''.
5942 typedef int *int_ptr;
5943 const int_ptr constant_ptr;</pre>
5944 declares constant_ptr as an object that has type ''const-qualified pointer to int''.
5947 <h5><a name="6.7.5.2" href="#6.7.5.2">6.7.5.2 Array declarators</a></h5>
5948 <h6>Constraints</h6>
5950 In addition to optional type qualifiers and the keyword static, the [ and ] may delimit
5951 an expression or *. If they delimit an expression (which specifies the size of an array), the
5952 expression shall have an integer type. If the expression is a constant expression, it shall
5953 have a value greater than zero. The element type shall not be an incomplete or function
5954 type. The optional type qualifiers and the keyword static shall appear only in a
5955 declaration of a function parameter with an array type, and then only in the outermost
5956 array type derivation.
5958 An ordinary identifier (as defined in <a href="#6.2.3">6.2.3</a>) that has a variably modified type shall have
5959 either block scope and no linkage or function prototype scope. If an identifier is declared
5960 to be an object with static storage duration, it shall not have a variable length array type.
5963 If, in the declaration ''T D1'', D1 has one of the forms:
5965 D[ type-qualifier-listopt assignment-expressionopt ]
5966 D[ static type-qualifier-listopt assignment-expression ]
5967 D[ type-qualifier-list static assignment-expression ]
5968 D[ type-qualifier-listopt * ]</pre>
5969 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5970 T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.<sup><a href="#note123"><b>123)</b></a></sup>
5971 (See <a href="#6.7.5.3">6.7.5.3</a> for the meaning of the optional type qualifiers and the keyword static.)
5973 If the size is not present, the array type is an incomplete type. If the size is * instead of
5974 being an expression, the array type is a variable length array type of unspecified size,
5975 which can only be used in declarations with function prototype scope;<sup><a href="#note124"><b>124)</b></a></sup> such arrays are
5976 nonetheless complete types. If the size is an integer constant expression and the element
5979 type has a known constant size, the array type is not a variable length array type;
5980 otherwise, the array type is a variable length array type.
5982 If the size is an expression that is not an integer constant expression: if it occurs in a
5983 declaration at function prototype scope, it is treated as if it were replaced by *; otherwise,
5984 each time it is evaluated it shall have a value greater than zero. The size of each instance
5985 of a variable length array type does not change during its lifetime. Where a size
5986 expression is part of the operand of a sizeof operator and changing the value of the
5987 size expression would not affect the result of the operator, it is unspecified whether or not
5988 the size expression is evaluated.
5990 For two array types to be compatible, both shall have compatible element types, and if
5991 both size specifiers are present, and are integer constant expressions, then both size
5992 specifiers shall have the same constant value. If the two array types are used in a context
5993 which requires them to be compatible, it is undefined behavior if the two size specifiers
5994 evaluate to unequal values.
5998 float fa[11], *afp[17];</pre>
5999 declares an array of float numbers and an array of pointers to float numbers.
6002 EXAMPLE 2 Note the distinction between the declarations
6005 extern int y[];</pre>
6006 The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
6007 (an incomplete type), the storage for which is defined elsewhere.
6010 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
6019 int (*r)[n][n][n+1];
6020 p = a; // invalid: not compatible because 4 != 6
6021 r = c; // compatible, but defined behavior only if
6022 // n == 6 and m == n+1
6030 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or
6031 function prototype scope. Array objects declared with the static or extern storage-class specifier
6032 cannot have a variable length array (VLA) type. However, an object declared with the static storage-
6033 class specifier can have a VM type (that is, a pointer to a VLA type). Finally, all identifiers declared with a
6034 VM type have to be ordinary identifiers and cannot, therefore, be members of structures or unions.
6037 int A[n]; // invalid: file scope VLA
6038 extern int (*p2)[n]; // invalid: file scope VM
6039 int B[100]; // valid: file scope but not VM
6040 void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
6041 void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
6043 typedef int VLA[m][m]; // valid: block scope typedef VLA
6045 int (*y)[n]; // invalid: y not ordinary identifier
6046 int z[n]; // invalid: z not ordinary identifier
6048 int D[m]; // valid: auto VLA
6049 static int E[m]; // invalid: static block scope VLA
6050 extern int F[m]; // invalid: F has linkage and is VLA
6051 int (*s)[m]; // valid: auto pointer to VLA
6052 extern int (*r)[m]; // invalid: r has linkage and points to VLA
6053 static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
6056 <p><b> Forward references</b>: function declarators (<a href="#6.7.5.3">6.7.5.3</a>), function definitions (<a href="#6.9.1">6.9.1</a>),
6057 initialization (<a href="#6.7.8">6.7.8</a>).
6060 <p><small><a name="note123" href="#note123">123)</a> When several ''array of'' specifications are adjacent, a multidimensional array is declared.
6062 <p><small><a name="note124" href="#note124">124)</a> Thus, * can be used only in function declarations that are not definitions (see <a href="#6.7.5.3">6.7.5.3</a>).
6065 <h5><a name="6.7.5.3" href="#6.7.5.3">6.7.5.3 Function declarators (including prototypes)</a></h5>
6066 <h6>Constraints</h6>
6068 A function declarator shall not specify a return type that is a function type or an array
6071 The only storage-class specifier that shall occur in a parameter declaration is register.
6073 An identifier list in a function declarator that is not part of a definition of that function
6076 After adjustment, the parameters in a parameter type list in a function declarator that is
6077 part of a definition of that function shall not have incomplete type.
6080 If, in the declaration ''T D1'', D1 has the form
6082 D( parameter-type-list )</pre>
6086 D( identifier-listopt )</pre>
6087 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
6088 T '', then the type specified for ident is ''derived-declarator-type-list function returning
6091 A parameter type list specifies the types of, and may declare identifiers for, the
6092 parameters of the function.
6094 A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to
6095 type'', where the type qualifiers (if any) are those specified within the [ and ] of the
6096 array type derivation. If the keyword static also appears within the [ and ] of the
6097 array type derivation, then for each call to the function, the value of the corresponding
6098 actual argument shall provide access to the first element of an array with at least as many
6099 elements as specified by the size expression.
6101 A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to
6102 function returning type'', as in <a href="#6.3.2.1">6.3.2.1</a>.
6104 If the list terminates with an ellipsis (, ...), no information about the number or types
6105 of the parameters after the comma is supplied.<sup><a href="#note125"><b>125)</b></a></sup>
6107 The special case of an unnamed parameter of type void as the only item in the list
6108 specifies that the function has no parameters.
6110 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a
6111 parameter name, it shall be taken as a typedef name.
6113 If the function declarator is not part of a definition of that function, parameters may have
6114 incomplete type and may use the [*] notation in their sequences of declarator specifiers
6115 to specify variable length array types.
6117 The storage-class specifier in the declaration specifiers for a parameter declaration, if
6118 present, is ignored unless the declared parameter is one of the members of the parameter
6119 type list for a function definition.
6121 An identifier list declares only the identifiers of the parameters of the function. An empty
6122 list in a function declarator that is part of a definition of that function specifies that the
6123 function has no parameters. The empty list in a function declarator that is not part of a
6124 definition of that function specifies that no information about the number or types of the
6125 parameters is supplied.<sup><a href="#note126"><b>126)</b></a></sup>
6127 For two function types to be compatible, both shall specify compatible return types.<sup><a href="#note127"><b>127)</b></a></sup>
6131 Moreover, the parameter type lists, if both are present, shall agree in the number of
6132 parameters and in use of the ellipsis terminator; corresponding parameters shall have
6133 compatible types. If one type has a parameter type list and the other type is specified by a
6134 function declarator that is not part of a function definition and that contains an empty
6135 identifier list, the parameter list shall not have an ellipsis terminator and the type of each
6136 parameter shall be compatible with the type that results from the application of the
6137 default argument promotions. If one type has a parameter type list and the other type is
6138 specified by a function definition that contains a (possibly empty) identifier list, both shall
6139 agree in the number of parameters, and the type of each prototype parameter shall be
6140 compatible with the type that results from the application of the default argument
6141 promotions to the type of the corresponding identifier. (In the determination of type
6142 compatibility and of a composite type, each parameter declared with function or array
6143 type is taken as having the adjusted type and each parameter declared with qualified type
6144 is taken as having the unqualified version of its declared type.)
6146 EXAMPLE 1 The declaration
6148 int f(void), *fip(), (*pfi)();</pre>
6149 declares a function f with no parameters returning an int, a function fip with no parameter specification
6150 returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an
6151 int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the
6152 declaration suggests, and the same construction in an expression requires, the calling of a function fip,
6153 and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the
6154 extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function
6155 designator, which is then used to call the function; it returns an int.
6157 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the
6158 declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either
6159 internal or external linkage (depending on what file scope declarations for these identifiers are visible), and
6160 the identifier of the pointer pfi has block scope and no linkage.
6163 EXAMPLE 2 The declaration
6165 int (*apfi[3])(int *x, int *y);</pre>
6166 declares an array apfi of three pointers to functions returning int. Each of these functions has two
6167 parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and
6168 go out of scope at the end of the declaration of apfi.
6171 EXAMPLE 3 The declaration
6173 int (*fpfi(int (*)(long), int))(int, ...);</pre>
6174 declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two
6175 parameters: a pointer to a function returning an int (with one parameter of type long int), and an int.
6176 The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more
6177 additional arguments of any type.
6180 EXAMPLE 4 The following prototype has a variably modified parameter.
6182 void addscalar(int n, int m,
6183 double a[n][n*m+300], double x);
6187 addscalar(4, 2, b, <a href="#2.17">2.17</a>);
6190 void addscalar(int n, int m,
6191 double a[n][n*m+300], double x)
6193 for (int i = 0; i < n; i++)
6194 for (int j = 0, k = n*m+300; j < k; j++)
6195 // a is a pointer to a VLA with n*m+300 elements
6200 EXAMPLE 5 The following are all compatible function prototype declarators.
6202 double maximum(int n, int m, double a[n][m]);
6203 double maximum(int n, int m, double a[*][*]);
6204 double maximum(int n, int m, double a[ ][*]);
6205 double maximum(int n, int m, double a[ ][m]);</pre>
6208 void f(double (* restrict a)[5]);
6209 void f(double a[restrict][5]);
6210 void f(double a[restrict 3][5]);
6211 void f(double a[restrict static 3][5]);</pre>
6212 (Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
6213 non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
6215 <p><b> Forward references</b>: function definitions (<a href="#6.9.1">6.9.1</a>), type names (<a href="#6.7.6">6.7.6</a>).
6219 <p><small><a name="note125" href="#note125">125)</a> The macros defined in the <a href="#7.15"><stdarg.h></a> header (<a href="#7.15">7.15</a>) may be used to access arguments that
6220 correspond to the ellipsis.
6222 <p><small><a name="note126" href="#note126">126)</a> See ''future language directions'' (<a href="#6.11.6">6.11.6</a>).
6224 <p><small><a name="note127" href="#note127">127)</a> If both function types are ''old style'', parameter types are not compared.
6227 <h4><a name="6.7.6" href="#6.7.6">6.7.6 Type names</a></h4>
6232 specifier-qualifier-list abstract-declaratoropt
6233 abstract-declarator:
6235 pointeropt direct-abstract-declarator
6236 direct-abstract-declarator:
6237 ( abstract-declarator )
6238 direct-abstract-declaratoropt [ type-qualifier-listopt
6239 assignment-expressionopt ]
6240 direct-abstract-declaratoropt [ static type-qualifier-listopt
6241 assignment-expression ]
6242 direct-abstract-declaratoropt [ type-qualifier-list static
6243 assignment-expression ]
6244 direct-abstract-declaratoropt [ * ]
6245 direct-abstract-declaratoropt ( parameter-type-listopt )</pre>
6248 In several contexts, it is necessary to specify a type. This is accomplished using a type
6249 name, which is syntactically a declaration for a function or an object of that type that
6250 omits the identifier.<sup><a href="#note128"><b>128)</b></a></sup>
6252 EXAMPLE The constructions
6261 (h) int (*const [])(unsigned int, ...)</pre>
6262 name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
6263 array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
6264 with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
6265 returning an int, and (h) array of an unspecified number of constant pointers to functions, each with one
6266 parameter that has type unsigned int and an unspecified number of other parameters, returning an
6275 <p><small><a name="note128" href="#note128">128)</a> As indicated by the syntax, empty parentheses in a type name are interpreted as ''function with no
6276 parameter specification'', rather than redundant parentheses around the omitted identifier.
6279 <h4><a name="6.7.7" href="#6.7.7">6.7.7 Type definitions</a></h4>
6285 <h6>Constraints</h6>
6287 If a typedef name specifies a variably modified type then it shall have block scope.
6290 In a declaration whose storage-class specifier is typedef, each declarator defines an
6291 identifier to be a typedef name that denotes the type specified for the identifier in the way
6292 described in <a href="#6.7.5">6.7.5</a>. Any array size expressions associated with variable length array
6293 declarators are evaluated each time the declaration of the typedef name is reached in the
6294 order of execution. A typedef declaration does not introduce a new type, only a
6295 synonym for the type so specified. That is, in the following declarations:
6297 typedef T type_ident;
6299 type_ident is defined as a typedef name with the type specified by the declaration
6300 specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
6301 type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
6302 typedef name shares the same name space as other identifiers declared in ordinary
6307 typedef int MILES, KLICKSP();
6308 typedef struct { double hi, lo; } range;</pre>
6312 extern KLICKSP *metricp;
6315 are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
6316 parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
6317 such a structure. The object distance has a type compatible with any other int object.
6320 EXAMPLE 2 After the declarations
6322 typedef struct s1 { int x; } t1, *tp1;
6323 typedef struct s2 { int x; } t2, *tp2;</pre>
6324 type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
6325 s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
6328 EXAMPLE 3 The following obscure constructions
6330 typedef signed int t;
6337 declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
6338 with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
6339 qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
6340 [-16, +15], and one named r that contains values in one of the ranges [0, 31], [-15, +15], or [-16, +15].
6341 (The choice of range is implementation-defined.) The first two bit-field declarations differ in that
6342 unsigned is a type specifier (which forces t to be the name of a structure member), while const is a
6343 type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed
6344 in an inner scope by
6348 then a function f is declared with type ''function returning signed int with one unnamed parameter
6349 with type pointer to function returning signed int with one unnamed parameter with type signed
6350 int'', and an identifier t with type long int.
6353 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the
6354 following declarations of the signal function specify exactly the same type, the first without making use
6355 of any typedef names.
6357 typedef void fv(int), (*pfv)(int);
6358 void (*signal(int, void (*)(int)))(int);
6359 fv *signal(int, fv *);
6360 pfv signal(int, pfv);</pre>
6363 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the
6364 time the typedef name is defined, not each time it is used:
6369 typedef int B[n]; // B is n ints, n evaluated now
6371 B a; // a is n ints, n without += 1
6372 int b[n]; // a and b are different sizes
6373 for (int i = 1; i < n; i++)
6377 <h4><a name="6.7.8" href="#6.7.8">6.7.8 Initialization</a></h4>
6382 assignment-expression
6383 { initializer-list }
6384 { initializer-list , }
6386 designationopt initializer
6387 initializer-list , designationopt initializer
6392 designator-list designator
6394 [ constant-expression ]
6396 <h6>Constraints</h6>
6398 No initializer shall attempt to provide a value for an object not contained within the entity
6401 The type of the entity to be initialized shall be an array of unknown size or an object type
6402 that is not a variable length array type.
6404 All the expressions in an initializer for an object that has static storage duration shall be
6405 constant expressions or string literals.
6407 If the declaration of an identifier has block scope, and the identifier has external or
6408 internal linkage, the declaration shall have no initializer for the identifier.
6410 If a designator has the form
6412 [ constant-expression ]</pre>
6413 then the current object (defined below) shall have array type and the expression shall be
6414 an integer constant expression. If the array is of unknown size, any nonnegative value is
6417 If a designator has the form
6420 then the current object (defined below) shall have structure or union type and the
6421 identifier shall be the name of a member of that type.
6425 An initializer specifies the initial value stored in an object.
6427 Except where explicitly stated otherwise, for the purposes of this subclause unnamed
6428 members of objects of structure and union type do not participate in initialization.
6429 Unnamed members of structure objects have indeterminate value even after initialization.
6431 If an object that has automatic storage duration is not initialized explicitly, its value is
6432 indeterminate. If an object that has static storage duration is not initialized explicitly,
6435 <li> if it has pointer type, it is initialized to a null pointer;
6436 <li> if it has arithmetic type, it is initialized to (positive or unsigned) zero;
6437 <li> if it is an aggregate, every member is initialized (recursively) according to these rules;
6438 <li> if it is a union, the first named member is initialized (recursively) according to these
6442 The initializer for a scalar shall be a single expression, optionally enclosed in braces. The
6443 initial value of the object is that of the expression (after conversion); the same type
6444 constraints and conversions as for simple assignment apply, taking the type of the scalar
6445 to be the unqualified version of its declared type.
6447 The rest of this subclause deals with initializers for objects that have aggregate or union
6450 The initializer for a structure or union object that has automatic storage duration shall be
6451 either an initializer list as described below, or a single expression that has compatible
6452 structure or union type. In the latter case, the initial value of the object, including
6453 unnamed members, is that of the expression.
6455 An array of character type may be initialized by a character string literal, optionally
6456 enclosed in braces. Successive characters of the character string literal (including the
6457 terminating null character if there is room or if the array is of unknown size) initialize the
6458 elements of the array.
6460 An array with element type compatible with wchar_t may be initialized by a wide
6461 string literal, optionally enclosed in braces. Successive wide characters of the wide string
6462 literal (including the terminating null wide character if there is room or if the array is of
6463 unknown size) initialize the elements of the array.
6465 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-
6466 enclosed list of initializers for the elements or named members.
6468 Each brace-enclosed initializer list has an associated current object. When no
6469 designations are present, subobjects of the current object are initialized in order according
6470 to the type of the current object: array elements in increasing subscript order, structure
6472 members in declaration order, and the first named member of a union.<sup><a href="#note129"><b>129)</b></a></sup> In contrast, a
6473 designation causes the following initializer to begin initialization of the subobject
6474 described by the designator. Initialization then continues forward in order, beginning
6475 with the next subobject after that described by the designator.<sup><a href="#note130"><b>130)</b></a></sup>
6477 Each designator list begins its description with the current object associated with the
6478 closest surrounding brace pair. Each item in the designator list (in order) specifies a
6479 particular member of its current object and changes the current object for the next
6480 designator (if any) to be that member.<sup><a href="#note131"><b>131)</b></a></sup> The current object that results at the end of the
6481 designator list is the subobject to be initialized by the following initializer.
6483 The initialization shall occur in initializer list order, each initializer provided for a
6484 particular subobject overriding any previously listed initializer for the same subobject;<sup><a href="#note132"><b>132)</b></a></sup>
6485 all subobjects that are not initialized explicitly shall be initialized implicitly the same as
6486 objects that have static storage duration.
6488 If the aggregate or union contains elements or members that are aggregates or unions,
6489 these rules apply recursively to the subaggregates or contained unions. If the initializer of
6490 a subaggregate or contained union begins with a left brace, the initializers enclosed by
6491 that brace and its matching right brace initialize the elements or members of the
6492 subaggregate or the contained union. Otherwise, only enough initializers from the list are
6493 taken to account for the elements or members of the subaggregate or the first member of
6494 the contained union; any remaining initializers are left to initialize the next element or
6495 member of the aggregate of which the current subaggregate or contained union is a part.
6497 If there are fewer initializers in a brace-enclosed list than there are elements or members
6498 of an aggregate, or fewer characters in a string literal used to initialize an array of known
6499 size than there are elements in the array, the remainder of the aggregate shall be
6500 initialized implicitly the same as objects that have static storage duration.
6502 If an array of unknown size is initialized, its size is determined by the largest indexed
6503 element with an explicit initializer. At the end of its initializer list, the array no longer
6504 has incomplete type.
6510 The order in which any side effects occur among the initialization list expressions is
6511 unspecified.<sup><a href="#note133"><b>133)</b></a></sup>
6513 EXAMPLE 1 Provided that <a href="#7.3"><complex.h></a> has been #included, the declarations
6515 int i = <a href="#3.5">3.5</a>;
6516 double complex c = 5 + 3 * I;</pre>
6517 define and initialize i with the value 3 and c with the value 5.0 + i3.0.
6520 EXAMPLE 2 The declaration
6522 int x[] = { 1, 3, 5 };</pre>
6523 defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
6524 and there are three initializers.
6527 EXAMPLE 3 The declaration
6534 is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
6535 y[0]), namely y[0][0], y[0][1], and y[0][2]. Likewise the next two lines initialize y[1] and
6536 y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
6540 1, 3, 5, 2, 4, 6, 3, 5, 7
6542 The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
6543 next three are taken successively for y[1] and y[2].
6546 EXAMPLE 4 The declaration
6549 { 1 }, { 2 }, { 3 }, { 4 }
6551 initializes the first column of z as specified and initializes the rest with zeros.
6554 EXAMPLE 5 The declaration
6556 struct { int a[3], b; } w[] = { { 1 }, 2 };</pre>
6557 is a definition with an inconsistently bracketed initialization. It defines an array with two element
6558 structures: w[0].a[0] is 1 and w[1].a[0] is 2; all the other elements are zero.
6565 EXAMPLE 6 The declaration
6567 short q[4][3][2] = {
6572 contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
6573 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
6574 q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
6575 q[0][0] does not begin with a left brace, so up to six items from the current list may be used. There is
6576 only one, so the values for the remaining five elements are initialized with zero. Likewise, the initializers
6577 for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their
6578 respective two-dimensional subaggregates. If there had been more than six items in any of the lists, a
6579 diagnostic message would have been issued. The same initialization result could have been achieved by:
6581 short q[4][3][2] = {
6588 short q[4][3][2] = {
6600 in a fully bracketed form.
6602 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
6606 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the
6609 typedef int A[]; // OK - declared with block scope</pre>
6612 A a = { 1, 2 }, b = { 3, 4, 5 };</pre>
6615 int a[] = { 1, 2 }, b[] = { 3, 4, 5 };</pre>
6616 due to the rules for incomplete types.
6619 EXAMPLE 8 The declaration
6621 char s[] = "abc", t[3] = "abc";</pre>
6622 defines ''plain'' char array objects s and t whose elements are initialized with character string literals.
6623 This declaration is identical to
6625 char s[] = { 'a', 'b', 'c', '\0' },
6626 t[] = { 'a', 'b', 'c' };</pre>
6627 The contents of the arrays are modifiable. On the other hand, the declaration
6629 char *p = "abc";</pre>
6630 defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char''
6631 with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to
6632 modify the contents of the array, the behavior is undefined.
6635 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using
6638 enum { member_one, member_two };
6639 const char *nm[] = {
6640 [member_two] = "member two",
6641 [member_one] = "member one",
6645 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
6647 div_t answer = { .quot = 2, .rem = -1 };</pre>
6650 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
6651 might be misunderstood:
6653 struct { int a[3], b; } w[] =
6654 { [0].a = {1}, [1].a[0] = 2 };</pre>
6657 EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator:
6661 1, 3, 5, 7, 9, [MAX-5] = 8, 6, 4, 2, 0
6663 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less
6664 than ten, some of the values provided by the first five initializers will be overridden by the second five.
6667 EXAMPLE 13 Any member of a union can be initialized:
6669 union { /* ... */ } u = { .any_member = 42 };</pre>
6671 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>).
6675 <p><small><a name="note129" href="#note129">129)</a> If the initializer list for a subaggregate or contained union does not begin with a left brace, its
6676 subobjects are initialized as usual, but the subaggregate or contained union does not become the
6677 current object: current objects are associated only with brace-enclosed initializer lists.
6679 <p><small><a name="note130" href="#note130">130)</a> After a union member is initialized, the next object is not the next member of the union; instead, it is
6680 the next subobject of an object containing the union.
6682 <p><small><a name="note131" href="#note131">131)</a> Thus, a designator can only specify a strict subobject of the aggregate or union that is associated with
6683 the surrounding brace pair. Note, too, that each separate designator list is independent.
6685 <p><small><a name="note132" href="#note132">132)</a> Any initializer for the subobject which is overridden and so not used to initialize that subobject might
6686 not be evaluated at all.
6688 <p><small><a name="note133" href="#note133">133)</a> In particular, the evaluation order need not be the same as the order of subobject initialization.
6691 <h3><a name="6.8" href="#6.8">6.8 Statements and blocks</a></h3>
6698 expression-statement
6701 jump-statement</pre>
6704 A statement specifies an action to be performed. Except as indicated, statements are
6705 executed in sequence.
6707 A block allows a set of declarations and statements to be grouped into one syntactic unit.
6708 The initializers of objects that have automatic storage duration, and the variable length
6709 array declarators of ordinary identifiers with block scope, are evaluated and the values are
6710 stored in the objects (including storing an indeterminate value in objects without an
6711 initializer) each time the declaration is reached in the order of execution, as if it were a
6712 statement, and within each declaration in the order that declarators appear.
6714 A full expression is an expression that is not part of another expression or of a declarator.
6715 Each of the following is a full expression: an initializer; the expression in an expression
6716 statement; the controlling expression of a selection statement (if or switch); the
6717 controlling expression of a while or do statement; each of the (optional) expressions of
6718 a for statement; the (optional) expression in a return statement. The end of a full
6719 expression is a sequence point.
6720 <p><b> Forward references</b>: expression and null statements (<a href="#6.8.3">6.8.3</a>), selection statements
6721 (<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>).
6723 <h4><a name="6.8.1" href="#6.8.1">6.8.1 Labeled statements</a></h4>
6728 identifier : statement
6729 case constant-expression : statement
6730 default : statement</pre>
6731 <h6>Constraints</h6>
6733 A case or default label shall appear only in a switch statement. Further
6734 constraints on such labels are discussed under the switch statement.
6737 Label names shall be unique within a function.
6740 Any statement may be preceded by a prefix that declares an identifier as a label name.
6741 Labels in themselves do not alter the flow of control, which continues unimpeded across
6743 <p><b> Forward references</b>: 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>).
6745 <h4><a name="6.8.2" href="#6.8.2">6.8.2 Compound statement</a></h4>
6750 { block-item-listopt }
6753 block-item-list block-item
6759 A compound statement is a block.
6761 <h4><a name="6.8.3" href="#6.8.3">6.8.3 Expression and null statements</a></h4>
6765 expression-statement:
6766 expressionopt ;</pre>
6769 The expression in an expression statement is evaluated as a void expression for its side
6770 effects.<sup><a href="#note134"><b>134)</b></a></sup>
6772 A null statement (consisting of just a semicolon) performs no operations.
6774 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the
6775 discarding of its value may be made explicit by converting the expression to a void expression by means of
6786 EXAMPLE 2 In the program fragment
6790 while (*s++ != '\0')
6792 a null statement is used to supply an empty loop body to the iteration statement.
6795 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
6810 <p><b> Forward references</b>: iteration statements (<a href="#6.8.5">6.8.5</a>).
6813 <p><small><a name="note134" href="#note134">134)</a> Such as assignments, and function calls which have side effects.
6816 <h4><a name="6.8.4" href="#6.8.4">6.8.4 Selection statements</a></h4>
6820 selection-statement:
6821 if ( expression ) statement
6822 if ( expression ) statement else statement
6823 switch ( expression ) statement</pre>
6826 A selection statement selects among a set of statements depending on the value of a
6827 controlling expression.
6829 A selection statement is a block whose scope is a strict subset of the scope of its
6830 enclosing block. Each associated substatement is also a block whose scope is a strict
6831 subset of the scope of the selection statement.
6833 <h5><a name="6.8.4.1" href="#6.8.4.1">6.8.4.1 The if statement</a></h5>
6834 <h6>Constraints</h6>
6836 The controlling expression of an if statement shall have scalar type.
6839 In both forms, the first substatement is executed if the expression compares unequal to 0.
6840 In the else form, the second substatement is executed if the expression compares equal
6842 to 0. If the first substatement is reached via a label, the second substatement is not
6845 An else is associated with the lexically nearest preceding if that is allowed by the
6848 <h5><a name="6.8.4.2" href="#6.8.4.2">6.8.4.2 The switch statement</a></h5>
6849 <h6>Constraints</h6>
6851 The controlling expression of a switch statement shall have integer type.
6853 If a switch statement has an associated case or default label within the scope of an
6854 identifier with a variably modified type, the entire switch statement shall be within the
6855 scope of that identifier.<sup><a href="#note135"><b>135)</b></a></sup>
6857 The expression of each case label shall be an integer constant expression and no two of
6858 the case constant expressions in the same switch statement shall have the same value
6859 after conversion. There may be at most one default label in a switch statement.
6860 (Any enclosed switch statement may have a default label or case constant
6861 expressions with values that duplicate case constant expressions in the enclosing
6865 A switch statement causes control to jump to, into, or past the statement that is the
6866 switch body, depending on the value of a controlling expression, and on the presence of a
6867 default label and the values of any case labels on or in the switch body. A case or
6868 default label is accessible only within the closest enclosing switch statement.
6870 The integer promotions are performed on the controlling expression. The constant
6871 expression in each case label is converted to the promoted type of the controlling
6872 expression. If a converted value matches that of the promoted controlling expression,
6873 control jumps to the statement following the matched case label. Otherwise, if there is
6874 a default label, control jumps to the labeled statement. If no converted case constant
6875 expression matches and there is no default label, no part of the switch body is
6877 Implementation limits
6879 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
6887 EXAMPLE In the artificial program fragment
6895 /* falls through into default code */
6899 the object whose identifier is i exists with automatic storage duration (within the block) but is never
6900 initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
6901 access an indeterminate value. Similarly, the call to the function f cannot be reached.
6905 <p><small><a name="note135" href="#note135">135)</a> That is, the declaration either precedes the switch statement, or it follows the last case or
6906 default label associated with the switch that is in the block containing the declaration.
6909 <h4><a name="6.8.5" href="#6.8.5">6.8.5 Iteration statements</a></h4>
6913 iteration-statement:
6914 while ( expression ) statement
6915 do statement while ( expression ) ;
6916 for ( expressionopt ; expressionopt ; expressionopt ) statement
6917 for ( declaration expressionopt ; expressionopt ) statement</pre>
6918 <h6>Constraints</h6>
6920 The controlling expression of an iteration statement shall have scalar type.
6922 The declaration part of a for statement shall only declare identifiers for objects having
6923 storage class auto or register.
6926 An iteration statement causes a statement called the loop body to be executed repeatedly
6927 until the controlling expression compares equal to 0. The repetition occurs regardless of
6928 whether the loop body is entered from the iteration statement or by a jump.<sup><a href="#note136"><b>136)</b></a></sup>
6930 An iteration statement is a block whose scope is a strict subset of the scope of its
6931 enclosing block. The loop body is also a block whose scope is a strict subset of the scope
6932 of the iteration statement.
6940 <p><small><a name="note136" href="#note136">136)</a> Code jumped over is not executed. In particular, the controlling expression of a for or while
6941 statement is not evaluated before entering the loop body, nor is clause-1 of a for statement.
6944 <h5><a name="6.8.5.1" href="#6.8.5.1">6.8.5.1 The while statement</a></h5>
6946 The evaluation of the controlling expression takes place before each execution of the loop
6949 <h5><a name="6.8.5.2" href="#6.8.5.2">6.8.5.2 The do statement</a></h5>
6951 The evaluation of the controlling expression takes place after each execution of the loop
6954 <h5><a name="6.8.5.3" href="#6.8.5.3">6.8.5.3 The for statement</a></h5>
6958 for ( clause-1 ; expression-2 ; expression-3 ) statement</pre>
6959 behaves as follows: The expression expression-2 is the controlling expression that is
6960 evaluated before each execution of the loop body. The expression expression-3 is
6961 evaluated as a void expression after each execution of the loop body. If clause-1 is a
6962 declaration, the scope of any identifiers it declares is the remainder of the declaration and
6963 the entire loop, including the other two expressions; it is reached in the order of execution
6964 before the first evaluation of the controlling expression. If clause-1 is an expression, it is
6965 evaluated as a void expression before the first evaluation of the controlling expression.<sup><a href="#note137"><b>137)</b></a></sup>
6967 Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a
6971 <p><small><a name="note137" href="#note137">137)</a> Thus, clause-1 specifies initialization for the loop, possibly declaring one or more variables for use in
6972 the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration,
6973 such that execution of the loop continues until the expression compares equal to 0; and expression-3
6974 specifies an operation (such as incrementing) that is performed after each iteration.
6977 <h4><a name="6.8.6" href="#6.8.6">6.8.6 Jump statements</a></h4>
6985 return expressionopt ;</pre>
6988 A jump statement causes an unconditional jump to another place.
6995 <h5><a name="6.8.6.1" href="#6.8.6.1">6.8.6.1 The goto statement</a></h5>
6996 <h6>Constraints</h6>
6998 The identifier in a goto statement shall name a label located somewhere in the enclosing
6999 function. A goto statement shall not jump from outside the scope of an identifier having
7000 a variably modified type to inside the scope of that identifier.
7003 A goto statement causes an unconditional jump to the statement prefixed by the named
7004 label in the enclosing function.
7006 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The
7007 following outline presents one possible approach to a problem based on these three assumptions:
7009 <li> The general initialization code accesses objects only visible to the current function.
7010 <li> The general initialization code is too large to warrant duplication.
7011 <li> The code to determine the next operation is at the head of the loop. (To allow it to be reached by
7012 continue statements, for example.)
7017 // determine next operation
7019 if (need to reinitialize) {
7020 // reinitialize-only code
7023 // general initialization code
7027 // handle other operations
7033 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably
7034 modified types. A jump within the scope, however, is permitted.
7036 goto lab3; // invalid: going INTO scope of VLA.
7039 a[j] = <a href="#4.4">4.4</a>;
7041 a[j] = <a href="#3.3">3.3</a>;
7042 goto lab4; // valid: going WITHIN scope of VLA.
7043 a[j] = <a href="#5.5">5.5</a>;
7045 a[j] = <a href="#6.6">6.6</a>;
7047 goto lab4; // invalid: going INTO scope of VLA.</pre>
7050 <h5><a name="6.8.6.2" href="#6.8.6.2">6.8.6.2 The continue statement</a></h5>
7051 <h6>Constraints</h6>
7053 A continue statement shall appear only in or as a loop body.
7056 A continue statement causes a jump to the loop-continuation portion of the smallest
7057 enclosing iteration statement; that is, to the end of the loop body. More precisely, in each
7059 while (/* ... */) { do { for (/* ... */) {
7061 /* ... */ /* ... */ /* ... */
7062 continue; continue; continue;
7063 /* ... */ /* ... */ /* ... */</pre>
7064 contin: ; contin: ; contin: ;
7065 } } while (/* ... */); }
7066 unless the continue statement shown is in an enclosed iteration statement (in which
7067 case it is interpreted within that statement), it is equivalent to goto contin;.<sup><a href="#note138"><b>138)</b></a></sup>
7070 <p><small><a name="note138" href="#note138">138)</a> Following the contin: label is a null statement.
7073 <h5><a name="6.8.6.3" href="#6.8.6.3">6.8.6.3 The break statement</a></h5>
7074 <h6>Constraints</h6>
7076 A break statement shall appear only in or as a switch body or loop body.
7079 A break statement terminates execution of the smallest enclosing switch or iteration
7086 <h5><a name="6.8.6.4" href="#6.8.6.4">6.8.6.4 The return statement</a></h5>
7087 <h6>Constraints</h6>
7089 A return statement with an expression shall not appear in a function whose return type
7090 is void. A return statement without an expression shall only appear in a function
7091 whose return type is void.
7094 A return statement terminates execution of the current function and returns control to
7095 its caller. A function may have any number of return statements.
7097 If a return statement with an expression is executed, the value of the expression is
7098 returned to the caller as the value of the function call expression. If the expression has a
7099 type different from the return type of the function in which it appears, the value is
7100 converted as if by assignment to an object having the return type of the function.<sup><a href="#note139"><b>139)</b></a></sup>
7104 struct s { double i; } f(void);
7120 g.u2.f3 = f();</pre>
7121 there is no undefined behavior, although there would be if the assignment were done directly (without using
7122 a function call to fetch the value).
7130 <p><small><a name="note139" href="#note139">139)</a> 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
7131 apply to the case of function return. The representation of floating-point values may have wider range
7132 or precision and is determined by FLT_EVAL_METHOD. A cast may be used to remove this extra
7133 range and precision.
7136 <h3><a name="6.9" href="#6.9">6.9 External definitions</a></h3>
7141 external-declaration
7142 translation-unit external-declaration
7143 external-declaration:
7146 <h6>Constraints</h6>
7148 The storage-class specifiers auto and register shall not appear in the declaration
7149 specifiers in an external declaration.
7151 There shall be no more than one external definition for each identifier declared with
7152 internal linkage in a translation unit. Moreover, if an identifier declared with internal
7153 linkage is used in an expression (other than as a part of the operand of a sizeof
7154 operator whose result is an integer constant), there shall be exactly one external definition
7155 for the identifier in the translation unit.
7158 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,
7159 which consists of a sequence of external declarations. These are described as ''external''
7160 because they appear outside any function (and hence have file scope). As discussed in
7161 <a href="#6.7">6.7</a>, a declaration that also causes storage to be reserved for an object or a function named
7162 by the identifier is a definition.
7164 An external definition is an external declaration that is also a definition of a function
7165 (other than an inline definition) or an object. If an identifier declared with external
7166 linkage is used in an expression (other than as part of the operand of a sizeof operator
7167 whose result is an integer constant), somewhere in the entire program there shall be
7168 exactly one external definition for the identifier; otherwise, there shall be no more than
7169 one.<sup><a href="#note140"><b>140)</b></a></sup>
7177 <p><small><a name="note140" href="#note140">140)</a> Thus, if an identifier declared with external linkage is not used in an expression, there need be no
7178 external definition for it.
7181 <h4><a name="6.9.1" href="#6.9.1">6.9.1 Function definitions</a></h4>
7185 function-definition:
7186 declaration-specifiers declarator declaration-listopt compound-statement
7189 declaration-list declaration</pre>
7190 <h6>Constraints</h6>
7192 The identifier declared in a function definition (which is the name of the function) shall
7193 have a function type, as specified by the declarator portion of the function definition.<sup><a href="#note141"><b>141)</b></a></sup>
7195 The return type of a function shall be void or an object type other than array type.
7197 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
7200 If the declarator includes a parameter type list, the declaration of each parameter shall
7201 include an identifier, except for the special case of a parameter list consisting of a single
7202 parameter of type void, in which case there shall not be an identifier. No declaration list
7205 If the declarator includes an identifier list, each declaration in the declaration list shall
7206 have at least one declarator, those declarators shall declare only identifiers from the
7207 identifier list, and every identifier in the identifier list shall be declared. An identifier
7208 declared as a typedef name shall not be redeclared as a parameter. The declarations in the
7209 declaration list shall contain no storage-class specifier other than register and no
7218 The declarator in a function definition specifies the name of the function being defined
7219 and the identifiers of its parameters. If the declarator includes a parameter type list, the
7220 list also specifies the types of all the parameters; such a declarator also serves as a
7221 function prototype for later calls to the same function in the same translation unit. If the
7222 declarator includes an identifier list,<sup><a href="#note142"><b>142)</b></a></sup> the types of the parameters shall be declared in a
7223 following declaration list. In either case, the type of each parameter is adjusted as
7224 described in <a href="#6.7.5.3">6.7.5.3</a> for a parameter type list; the resulting type shall be an object type.
7226 If a function that accepts a variable number of arguments is defined without a parameter
7227 type list that ends with the ellipsis notation, the behavior is undefined.
7229 Each parameter has automatic storage duration. Its identifier is an lvalue, which is in
7230 effect declared at the head of the compound statement that constitutes the function body
7231 (and therefore cannot be redeclared in the function body except in an enclosed block).
7232 The layout of the storage for parameters is unspecified.
7234 On entry to the function, the size expressions of each variably modified parameter are
7235 evaluated and the value of each argument expression is converted to the type of the
7236 corresponding parameter as if by assignment. (Array expressions and function
7237 designators as arguments were converted to pointers before the call.)
7239 After all parameters have been assigned, the compound statement that constitutes the
7240 body of the function definition is executed.
7242 If the } that terminates a function is reached, and the value of the function call is used by
7243 the caller, the behavior is undefined.
7245 EXAMPLE 1 In the following:
7247 extern int max(int a, int b)
7249 return a > b ? a : b;
7251 extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
7252 function declarator; and
7254 { return a > b ? a : b; }</pre>
7255 is the function body. The following similar definition uses the identifier-list form for the parameter
7263 extern int max(a, b)
7266 return a > b ? a : b;
7268 Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
7269 that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
7270 to the function, whereas the second form does not.
7273 EXAMPLE 2 To pass one function to another, one might say
7278 Then the definition of g might read
7280 void g(int (*funcp)(void))
7283 (*funcp)(); /* or funcp(); ... */
7287 void g(int func(void))
7290 func(); /* or (*func)(); ... */
7295 <p><small><a name="note141" href="#note141">141)</a> The intent is that the type category in a function definition cannot be inherited from a typedef:
7298 typedef int F(void); // type F is ''function with no parameters
7300 F f, g; // f and g both have type compatible with F
7301 F f { /* ... */ } // WRONG: syntax/constraint error
7302 F g() { /* ... */ } // WRONG: declares that g returns a function
7303 int f(void) { /* ... */ } // RIGHT: f has type compatible with F
7304 int g() { /* ... */ } // RIGHT: g has type compatible with F
7305 F *e(void) { /* ... */ } // e returns a pointer to a function
7306 F *((e))(void) { /* ... */ } // same: parentheses irrelevant
7307 int (*fp)(void); // fp points to a function that has type F
7308 F *Fp; // Fp points to a function that has type F</pre>
7310 <p><small><a name="note142" href="#note142">142)</a> See ''future language directions'' (<a href="#6.11.7">6.11.7</a>).
7313 <h4><a name="6.9.2" href="#6.9.2">6.9.2 External object definitions</a></h4>
7316 If the declaration of an identifier for an object has file scope and an initializer, the
7317 declaration is an external definition for the identifier.
7319 A declaration of an identifier for an object that has file scope without an initializer, and
7320 without a storage-class specifier or with the storage-class specifier static, constitutes a
7321 tentative definition. If a translation unit contains one or more tentative definitions for an
7322 identifier, and the translation unit contains no external definition for that identifier, then
7323 the behavior is exactly as if the translation unit contains a file scope declaration of that
7324 identifier, with the composite type as of the end of the translation unit, with an initializer
7327 If the declaration of an identifier for an object is a tentative definition and has internal
7328 linkage, the declared type shall not be an incomplete type.
7333 int i1 = 1; // definition, external linkage
7334 static int i2 = 2; // definition, internal linkage
7335 extern int i3 = 3; // definition, external linkage
7336 int i4; // tentative definition, external linkage
7337 static int i5; // tentative definition, internal linkage
7338 int i1; // valid tentative definition, refers to previous
7339 int i2; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
7340 int i3; // valid tentative definition, refers to previous
7341 int i4; // valid tentative definition, refers to previous
7342 int i5; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
7343 extern int i1; // refers to previous, whose linkage is external
7344 extern int i2; // refers to previous, whose linkage is internal
7345 extern int i3; // refers to previous, whose linkage is external
7346 extern int i4; // refers to previous, whose linkage is external
7347 extern int i5; // refers to previous, whose linkage is internal</pre>
7350 EXAMPLE 2 If at the end of the translation unit containing
7353 the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to
7354 zero on program startup.
7357 <h3><a name="6.10" href="#6.10">6.10 Preprocessing directives</a></h3>
7373 if-group elif-groupsopt else-groupopt endif-line
7375 # if constant-expression new-line groupopt
7376 # ifdef identifier new-line groupopt
7377 # ifndef identifier new-line groupopt
7380 elif-groups elif-group
7382 # elif constant-expression new-line groupopt
7384 # else new-line groupopt
7388 # include pp-tokens new-line
7389 # define identifier replacement-list new-line
7390 # define identifier lparen identifier-listopt )
7391 replacement-list new-line
7392 # define identifier lparen ... ) replacement-list new-line
7393 # define identifier lparen identifier-list , ... )
7394 replacement-list new-line
7395 # undef identifier new-line
7396 # line pp-tokens new-line
7397 # error pp-tokensopt new-line
7398 # pragma pp-tokensopt new-line
7401 pp-tokensopt new-line
7405 a ( character not immediately preceded by white-space
7410 pp-tokens preprocessing-token
7412 the new-line character</pre>
7413 <h6>Description</h6>
7415 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the
7416 following constraints: The first token in the sequence is a # preprocessing token that (at
7417 the start of translation phase 4) is either the first character in the source file (optionally
7418 after white space containing no new-line characters) or that follows white space
7419 containing at least one new-line character. The last token in the sequence is the first new-
7420 line character that follows the first token in the sequence.<sup><a href="#note143"><b>143)</b></a></sup> A new-line character ends
7421 the preprocessing directive even if it occurs within what would otherwise be an
7424 invocation of a function-like macro.
7426 A text line shall not begin with a # preprocessing token. A non-directive shall not begin
7427 with any of the directive names appearing in the syntax.
7429 When in a group that is skipped (<a href="#6.10.1">6.10.1</a>), the directive syntax is relaxed to allow any
7430 sequence of preprocessing tokens to occur between the directive name and the following
7432 <h6>Constraints</h6>
7434 The only white-space characters that shall appear between preprocessing tokens within a
7435 preprocessing directive (from just after the introducing # preprocessing token through
7436 just before the terminating new-line character) are space and horizontal-tab (including
7437 spaces that have replaced comments or possibly other white-space characters in
7438 translation phase 3).
7441 The implementation can process and skip sections of source files conditionally, include
7442 other source files, and replace macros. These capabilities are called preprocessing,
7443 because conceptually they occur before translation of the resulting translation unit.
7445 The preprocessing tokens within a preprocessing directive are not subject to macro
7446 expansion unless otherwise stated.
7451 EMPTY # include <file.h></pre>
7452 the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
7453 begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
7458 <p><small><a name="note143" href="#note143">143)</a> Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic
7459 significance, as all white space is equivalent except in certain situations during preprocessing (see the
7460 # character string literal creation operator in <a href="#6.10.3.2">6.10.3.2</a>, for example).
7463 <h4><a name="6.10.1" href="#6.10.1">6.10.1 Conditional inclusion</a></h4>
7464 <h6>Constraints</h6>
7466 The expression that controls conditional inclusion shall be an integer constant expression
7467 except that: it shall not contain a cast; identifiers (including those lexically identical to
7468 keywords) are interpreted as described below;<sup><a href="#note144"><b>144)</b></a></sup> and it may contain unary operator
7469 expressions of the form
7476 defined identifier</pre>
7479 defined ( identifier )</pre>
7480 which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is
7481 predefined or if it has been the subject of a #define preprocessing directive without an
7482 intervening #undef directive with the same subject identifier), 0 if it is not.
7484 Each preprocessing token that remains (in the list of preprocessing tokens that will
7485 become the controlling expression) after all macro replacements have occurred shall be in
7486 the lexical form of a token (<a href="#6.4">6.4</a>).
7489 Preprocessing directives of the forms
7491 # if constant-expression new-line groupopt
7492 # elif constant-expression new-line groupopt</pre>
7493 check whether the controlling constant expression evaluates to nonzero.
7495 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
7496 the controlling constant expression are replaced (except for those macro names modified
7497 by the defined unary operator), just as in normal text. If the token defined is
7498 generated as a result of this replacement process or use of the defined unary operator
7499 does not match one of the two specified forms prior to macro replacement, the behavior is
7500 undefined. After all replacements due to macro expansion and the defined unary
7501 operator have been performed, all remaining identifiers (including those lexically
7502 identical to keywords) are replaced with the pp-number 0, and then each preprocessing
7503 token is converted into a token. The resulting tokens compose the controlling constant
7504 expression which is evaluated according to the rules of <a href="#6.6">6.6</a>. For the purposes of this
7505 token conversion and evaluation, all signed integer types and all unsigned integer types
7506 act as if they have the same representation as, respectively, the types intmax_t and
7507 uintmax_t defined in the header <a href="#7.18"><stdint.h></a>.<sup><a href="#note145"><b>145)</b></a></sup> This includes interpreting
7508 character constants, which may involve converting escape sequences into execution
7509 character set members. Whether the numeric value for these character constants matches
7510 the value obtained when an identical character constant occurs in an expression (other
7511 than within a #if or #elif directive) is implementation-defined.<sup><a href="#note146"><b>146)</b></a></sup> Also, whether a
7512 single-character character constant may have a negative value is implementation-defined.
7514 Preprocessing directives of the forms
7520 # ifdef identifier new-line groupopt
7521 # ifndef identifier new-line groupopt</pre>
7522 check whether the identifier is or is not currently defined as a macro name. Their
7523 conditions are equivalent to #if defined identifier and #if !defined identifier
7526 Each directive's condition is checked in order. If it evaluates to false (zero), the group
7527 that it controls is skipped: directives are processed only through the name that determines
7528 the directive in order to keep track of the level of nested conditionals; the rest of the
7529 directives' preprocessing tokens are ignored, as are the other preprocessing tokens in the
7530 group. Only the first group whose control condition evaluates to true (nonzero) is
7531 processed. If none of the conditions evaluates to true, and there is a #else directive, the
7532 group controlled by the #else is processed; lacking a #else directive, all the groups
7533 until the #endif are skipped.<sup><a href="#note147"><b>147)</b></a></sup>
7534 <p><b> Forward references</b>: macro replacement (<a href="#6.10.3">6.10.3</a>), source file inclusion (<a href="#6.10.2">6.10.2</a>), largest
7535 integer types (<a href="#7.18.1.5">7.18.1.5</a>).
7538 <p><small><a name="note144" href="#note144">144)</a> Because the controlling constant expression is evaluated during translation phase 4, all identifiers
7539 either are or are not macro names -- there simply are no keywords, enumeration constants, etc.
7541 <p><small><a name="note145" href="#note145">145)</a> Thus, on an implementation where INT_MAX is 0x7FFF and UINT_MAX is 0xFFFF, the constant
7542 0x8000 is signed and positive within a #if expression even though it would be unsigned in
7543 translation phase 7.
7545 <p><small><a name="note146" href="#note146">146)</a> Thus, the constant expression in the following #if directive and if statement is not guaranteed to
7546 evaluate to the same value in these two contexts.
7548 if ('z' - 'a' == 25)
7551 <p><small><a name="note147" href="#note147">147)</a> As indicated by the syntax, a preprocessing token shall not follow a #else or #endif directive
7552 before the terminating new-line character. However, comments may appear anywhere in a source file,
7553 including within a preprocessing directive.
7556 <h4><a name="6.10.2" href="#6.10.2">6.10.2 Source file inclusion</a></h4>
7557 <h6>Constraints</h6>
7559 A #include directive shall identify a header or source file that can be processed by the
7563 A preprocessing directive of the form
7565 # include <h-char-sequence> new-line</pre>
7566 searches a sequence of implementation-defined places for a header identified uniquely by
7567 the specified sequence between the < and > delimiters, and causes the replacement of that
7568 directive by the entire contents of the header. How the places are specified or the header
7569 identified is implementation-defined.
7571 A preprocessing directive of the form
7577 # include "q-char-sequence" new-line</pre>
7578 causes the replacement of that directive by the entire contents of the source file identified
7579 by the specified sequence between the " delimiters. The named source file is searched
7580 for in an implementation-defined manner. If this search is not supported, or if the search
7581 fails, the directive is reprocessed as if it read
7583 # include <h-char-sequence> new-line</pre>
7584 with the identical contained sequence (including > characters, if any) from the original
7587 A preprocessing directive of the form
7589 # include pp-tokens new-line</pre>
7590 (that does not match one of the two previous forms) is permitted. The preprocessing
7591 tokens after include in the directive are processed just as in normal text. (Each
7592 identifier currently defined as a macro name is replaced by its replacement list of
7593 preprocessing tokens.) The directive resulting after all replacements shall match one of
7594 the two previous forms.<sup><a href="#note148"><b>148)</b></a></sup> The method by which a sequence of preprocessing tokens
7595 between a < and a > preprocessing token pair or a pair of " characters is combined into a
7596 single header name preprocessing token is implementation-defined.
7598 The implementation shall provide unique mappings for sequences consisting of one or
7599 more nondigits or digits (<a href="#6.4.2.1">6.4.2.1</a>) followed by a period (.) and a single nondigit. The
7600 first character shall not be a digit. The implementation may ignore distinctions of
7601 alphabetical case and restrict the mapping to eight significant characters before the
7604 A #include preprocessing directive may appear in a source file that has been read
7605 because of a #include directive in another file, up to an implementation-defined
7606 nesting limit (see <a href="#5.2.4.1">5.2.4.1</a>).
7608 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
7610 #include <a href="#7.19"><stdio.h></a>
7611 #include "myprog.h"</pre>
7614 EXAMPLE 2 This illustrates macro-replaced #include directives:
7622 #define INCFILE "vers1.h"
7624 #define INCFILE "vers2.h" // and so on
7626 #define INCFILE "versN.h"
7628 #include INCFILE</pre>
7630 <p><b> Forward references</b>: macro replacement (<a href="#6.10.3">6.10.3</a>).
7633 <p><small><a name="note148" href="#note148">148)</a> Note that adjacent string literals are not concatenated into a single string literal (see the translation
7634 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.
7637 <h4><a name="6.10.3" href="#6.10.3">6.10.3 Macro replacement</a></h4>
7638 <h6>Constraints</h6>
7640 Two replacement lists are identical if and only if the preprocessing tokens in both have
7641 the same number, ordering, spelling, and white-space separation, where all white-space
7642 separations are considered identical.
7644 An identifier currently defined as an object-like macro shall not be redefined by another
7645 #define preprocessing directive unless the second definition is an object-like macro
7646 definition and the two replacement lists are identical. Likewise, an identifier currently
7647 defined as a function-like macro shall not be redefined by another #define
7648 preprocessing directive unless the second definition is a function-like macro definition
7649 that has the same number and spelling of parameters, and the two replacement lists are
7652 There shall be white-space between the identifier and the replacement list in the definition
7653 of an object-like macro.
7655 If the identifier-list in the macro definition does not end with an ellipsis, the number of
7656 arguments (including those arguments consisting of no preprocessing tokens) in an
7657 invocation of a function-like macro shall equal the number of parameters in the macro
7658 definition. Otherwise, there shall be more arguments in the invocation than there are
7659 parameters in the macro definition (excluding the ...). There shall exist a )
7660 preprocessing token that terminates the invocation.
7662 The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like
7663 macro that uses the ellipsis notation in the parameters.
7665 A parameter identifier in a function-like macro shall be uniquely declared within its
7669 The identifier immediately following the define is called the macro name. There is one
7670 name space for macro names. Any white-space characters preceding or following the
7671 replacement list of preprocessing tokens are not considered part of the replacement list
7672 for either form of macro.
7675 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
7676 a preprocessing directive could begin, the identifier is not subject to macro replacement.
7678 A preprocessing directive of the form
7680 # define identifier replacement-list new-line</pre>
7681 defines an object-like macro that causes each subsequent instance of the macro name<sup><a href="#note149"><b>149)</b></a></sup>
7682 to be replaced by the replacement list of preprocessing tokens that constitute the
7683 remainder of the directive. The replacement list is then rescanned for more macro names
7686 A preprocessing directive of the form
7688 # define identifier lparen identifier-listopt ) replacement-list new-line
7689 # define identifier lparen ... ) replacement-list new-line
7690 # define identifier lparen identifier-list , ... ) replacement-list new-line</pre>
7691 defines a function-like macro with parameters, whose use is similar syntactically to a
7692 function call. The parameters are specified by the optional list of identifiers, whose scope
7693 extends from their declaration in the identifier list until the new-line character that
7694 terminates the #define preprocessing directive. Each subsequent instance of the
7695 function-like macro name followed by a ( as the next preprocessing token introduces the
7696 sequence of preprocessing tokens that is replaced by the replacement list in the definition
7697 (an invocation of the macro). The replaced sequence of preprocessing tokens is
7698 terminated by the matching ) preprocessing token, skipping intervening matched pairs of
7699 left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
7700 tokens making up an invocation of a function-like macro, new-line is considered a normal
7701 white-space character.
7703 The sequence of preprocessing tokens bounded by the outside-most matching parentheses
7704 forms the list of arguments for the function-like macro. The individual arguments within
7705 the list are separated by comma preprocessing tokens, but comma preprocessing tokens
7706 between matching inner parentheses do not separate arguments. If there are sequences of
7707 preprocessing tokens within the list of arguments that would otherwise act as
7708 preprocessing directives,<sup><a href="#note150"><b>150)</b></a></sup> the behavior is undefined.
7710 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
7711 including any separating comma preprocessing tokens, are merged to form a single item:
7712 the variable arguments. The number of arguments so combined is such that, following
7716 merger, the number of arguments is one more than the number of parameters in the macro
7717 definition (excluding the ...).
7720 <p><small><a name="note149" href="#note149">149)</a> Since, by macro-replacement time, all character constants and string literals are preprocessing tokens,
7721 not sequences possibly containing identifier-like subsequences (see <a href="#5.1.1.2">5.1.1.2</a>, translation phases), they
7722 are never scanned for macro names or parameters.
7724 <p><small><a name="note150" href="#note150">150)</a> Despite the name, a non-directive is a preprocessing directive.
7727 <h5><a name="6.10.3.1" href="#6.10.3.1">6.10.3.1 Argument substitution</a></h5>
7729 After the arguments for the invocation of a function-like macro have been identified,
7730 argument substitution takes place. A parameter in the replacement list, unless preceded
7731 by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
7732 replaced by the corresponding argument after all macros contained therein have been
7733 expanded. Before being substituted, each argument's preprocessing tokens are
7734 completely macro replaced as if they formed the rest of the preprocessing file; no other
7735 preprocessing tokens are available.
7737 An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
7738 were a parameter, and the variable arguments shall form the preprocessing tokens used to
7741 <h5><a name="6.10.3.2" href="#6.10.3.2">6.10.3.2 The # operator</a></h5>
7742 <h6>Constraints</h6>
7744 Each # preprocessing token in the replacement list for a function-like macro shall be
7745 followed by a parameter as the next preprocessing token in the replacement list.
7748 If, in the replacement list, a parameter is immediately preceded by a # preprocessing
7749 token, both are replaced by a single character string literal preprocessing token that
7750 contains the spelling of the preprocessing token sequence for the corresponding
7751 argument. Each occurrence of white space between the argument's preprocessing tokens
7752 becomes a single space character in the character string literal. White space before the
7753 first preprocessing token and after the last preprocessing token composing the argument
7754 is deleted. Otherwise, the original spelling of each preprocessing token in the argument
7755 is retained in the character string literal, except for special handling for producing the
7756 spelling of string literals and character constants: a \ character is inserted before each "
7757 and \ character of a character constant or string literal (including the delimiting "
7758 characters), except that it is implementation-defined whether a \ character is inserted
7759 before the \ character beginning a universal character name. If the replacement that
7760 results is not a valid character string literal, the behavior is undefined. The character
7761 string literal corresponding to an empty argument is "". The order of evaluation of # and
7762 ## operators is unspecified.
7765 <h5><a name="6.10.3.3" href="#6.10.3.3">6.10.3.3 The ## operator</a></h5>
7766 <h6>Constraints</h6>
7768 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
7769 list for either form of macro definition.
7772 If, in the replacement list of a function-like macro, a parameter is immediately preceded
7773 or followed by a ## preprocessing token, the parameter is replaced by the corresponding
7774 argument's preprocessing token sequence; however, if an argument consists of no
7775 preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
7776 instead.<sup><a href="#note151"><b>151)</b></a></sup>
7778 For both object-like and function-like macro invocations, before the replacement list is
7779 reexamined for more macro names to replace, each instance of a ## preprocessing token
7780 in the replacement list (not from an argument) is deleted and the preceding preprocessing
7781 token is concatenated with the following preprocessing token. Placemarker
7782 preprocessing tokens are handled specially: concatenation of two placemarkers results in
7783 a single placemarker preprocessing token, and concatenation of a placemarker with a
7784 non-placemarker preprocessing token results in the non-placemarker preprocessing token.
7785 If the result is not a valid preprocessing token, the behavior is undefined. The resulting
7786 token is available for further macro replacement. The order of evaluation of ## operators
7789 EXAMPLE In the following fragment:
7791 #define hash_hash # ## #
7792 #define mkstr(a) # a
7793 #define in_between(a) mkstr(a)
7794 #define join(c, d) in_between(c hash_hash d)
7795 char p[] = join(x, y); // equivalent to
7796 // char p[] = "x ## y";</pre>
7797 The expansion produces, at various stages:
7800 in_between(x hash_hash y)
7804 In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
7805 this new token is not the ## operator.
7811 <p><small><a name="note151" href="#note151">151)</a> Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
7812 exist only within translation phase 4.
7815 <h5><a name="6.10.3.4" href="#6.10.3.4">6.10.3.4 Rescanning and further replacement</a></h5>
7817 After all parameters in the replacement list have been substituted and # and ##
7818 processing has taken place, all placemarker preprocessing tokens are removed. Then, the
7819 resulting preprocessing token sequence is rescanned, along with all subsequent
7820 preprocessing tokens of the source file, for more macro names to replace.
7822 If the name of the macro being replaced is found during this scan of the replacement list
7823 (not including the rest of the source file's preprocessing tokens), it is not replaced.
7824 Furthermore, if any nested replacements encounter the name of the macro being replaced,
7825 it is not replaced. These nonreplaced macro name preprocessing tokens are no longer
7826 available for further replacement even if they are later (re)examined in contexts in which
7827 that macro name preprocessing token would otherwise have been replaced.
7829 The resulting completely macro-replaced preprocessing token sequence is not processed
7830 as a preprocessing directive even if it resembles one, but all pragma unary operator
7831 expressions within it are then processed as specified in <a href="#6.10.9">6.10.9</a> below.
7833 <h5><a name="6.10.3.5" href="#6.10.3.5">6.10.3.5 Scope of macro definitions</a></h5>
7835 A macro definition lasts (independent of block structure) until a corresponding #undef
7836 directive is encountered or (if none is encountered) until the end of the preprocessing
7837 translation unit. Macro definitions have no significance after translation phase 4.
7839 A preprocessing directive of the form
7841 # undef identifier new-line</pre>
7842 causes the specified identifier no longer to be defined as a macro name. It is ignored if
7843 the specified identifier is not currently defined as a macro name.
7845 EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
7848 int table[TABSIZE];</pre>
7851 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments.
7852 It has the advantages of working for any compatible types of the arguments and of generating in-line code
7853 without the overhead of function calling. It has the disadvantages of evaluating one or the other of its
7854 arguments a second time (including side effects) and generating more code than a function if invoked
7855 several times. It also cannot have its address taken, as it has none.
7857 #define max(a, b) ((a) > (b) ? (a) : (b))</pre>
7858 The parentheses ensure that the arguments and the resulting expression are bound properly.
7861 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
7864 #define f(a) f(x * (a))
7875 #define r(x,y) x ## y
7877 f(y+1) + f(f(z)) % t(t(g)(0) + t)(1);
7878 g(x+(3,4)-w) | h 5) & m
7880 p() i[q()] = { q(1), r(2,3), r(4,), r(,5), r(,) };
7881 char c[2][6] = { str(hello), str() };</pre>
7884 f(2 * (y+1)) + f(2 * (f(2 * (z[0])))) % f(2 * (0)) + t(1);
7885 f(2 * (2+(3,4)-0,1)) | f(2 * (~ 5)) & f(2 * (0,1))^m(0,1);
7886 int i[] = { 1, 23, 4, 5, };
7887 char c[2][6] = { "hello", "" };</pre>
7890 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the
7894 #define xstr(s) str(s)
7895 #define debug(s, t) printf("x" # s "= %d, x" # t "= %s", \
7897 #define INCFILE(n) vers ## n
7898 #define glue(a, b) a ## b
7899 #define xglue(a, b) glue(a, b)
7900 #define HIGHLOW "hello"
7901 #define LOW LOW ", world"
7903 fputs(str(strncmp("abc\0d", "abc", '\4') // this goes away
7904 == 0) str(: @\n), s);
7905 #include xstr(INCFILE(2).h)
7907 xglue(HIGH, LOW)</pre>
7911 printf("x" "1" "= %d, x" "2" "= %s", x1, x2);
7913 "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0" ": @\n",
7915 #include "vers2.h" (after macro replacement, before file access)
7917 "hello" ", world"</pre>
7918 or, after concatenation of the character string literals,
7920 printf("x1= %d, x2= %s", x1, x2);
7922 "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0: @\n",
7924 #include "vers2.h" (after macro replacement, before file access)
7926 "hello, world"</pre>
7927 Space around the # and ## tokens in the macro definition is optional.
7930 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
7932 #define t(x,y,z) x ## y ## z
7933 int j[] = { t(1,2,3), t(,4,5), t(6,,7), t(8,9,),
7934 t(10,,), t(,11,), t(,,12), t(,,) };</pre>
7937 int j[] = { 123, 45, 67, 89,
7938 10, 11, 12, };</pre>
7941 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
7943 #define OBJ_LIKE (1-1)
7944 #define OBJ_LIKE /* white space */ (1-1) /* other */
7945 #define FUNC_LIKE(a) ( a )
7946 #define FUNC_LIKE( a )( /* note the white space */ \
7947 a /* other stuff on this line
7949 But the following redefinitions are invalid:
7951 #define OBJ_LIKE (0) // different token sequence
7952 #define OBJ_LIKE (1 - 1) // different white space
7953 #define FUNC_LIKE(b) ( a ) // different parameter usage
7954 #define FUNC_LIKE(b) ( b ) // different parameter spelling</pre>
7957 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
7960 #define debug(...) fprintf(stderr, __VA_ARGS__)
7961 #define showlist(...) puts(#__VA_ARGS__)
7962 #define report(test, ...) ((test)?puts(#test):\
7963 printf(__VA_ARGS__))
7965 debug("X = %d\n", x);
7966 showlist(The first, second, and third items.);
7967 report(x>y, "x is %d but y is %d", x, y);</pre>
7970 fprintf(stderr, "Flag" );
7971 fprintf(stderr, "X = %d\n", x );
7972 puts( "The first, second, and third items." );
7973 ((x>y)?puts("x>y"):
7974 printf("x is %d but y is %d", x, y));</pre>
7977 <h4><a name="6.10.4" href="#6.10.4">6.10.4 Line control</a></h4>
7978 <h6>Constraints</h6>
7980 The string literal of a #line directive, if present, shall be a character string literal.
7983 The line number of the current source line is one greater than the number of new-line
7984 characters read or introduced in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>) while processing the source
7985 file to the current token.
7987 A preprocessing directive of the form
7989 # line digit-sequence new-line</pre>
7990 causes the implementation to behave as if the following sequence of source lines begins
7991 with a source line that has a line number as specified by the digit sequence (interpreted as
7992 a decimal integer). The digit sequence shall not specify zero, nor a number greater than
7995 A preprocessing directive of the form
7997 # line digit-sequence "s-char-sequenceopt" new-line</pre>
7998 sets the presumed line number similarly and changes the presumed name of the source
7999 file to be the contents of the character string literal.
8001 A preprocessing directive of the form
8003 # line pp-tokens new-line</pre>
8004 (that does not match one of the two previous forms) is permitted. The preprocessing
8005 tokens after line on the directive are processed just as in normal text (each identifier
8006 currently defined as a macro name is replaced by its replacement list of preprocessing
8007 tokens). The directive resulting after all replacements shall match one of the two
8008 previous forms and is then processed as appropriate.
8011 <h4><a name="6.10.5" href="#6.10.5">6.10.5 Error directive</a></h4>
8014 A preprocessing directive of the form
8016 # error pp-tokensopt new-line</pre>
8017 causes the implementation to produce a diagnostic message that includes the specified
8018 sequence of preprocessing tokens.
8020 <h4><a name="6.10.6" href="#6.10.6">6.10.6 Pragma directive</a></h4>
8023 A preprocessing directive of the form
8025 # pragma pp-tokensopt new-line</pre>
8026 where the preprocessing token STDC does not immediately follow pragma in the
8027 directive (prior to any macro replacement)<sup><a href="#note152"><b>152)</b></a></sup> causes the implementation to behave in an
8028 implementation-defined manner. The behavior might cause translation to fail or cause the
8029 translator or the resulting program to behave in a non-conforming manner. Any such
8030 pragma that is not recognized by the implementation is ignored.
8032 If the preprocessing token STDC does immediately follow pragma in the directive (prior
8033 to any macro replacement), then no macro replacement is performed on the directive, and
8034 the directive shall have one of the following forms<sup><a href="#note153"><b>153)</b></a></sup> whose meanings are described
8037 #pragma STDC FP_CONTRACT on-off-switch
8038 #pragma STDC FENV_ACCESS on-off-switch
8039 #pragma STDC CX_LIMITED_RANGE on-off-switch
8040 on-off-switch: one of
8041 ON OFF DEFAULT</pre>
8042 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), the FENV_ACCESS pragma
8043 (<a href="#7.6.1">7.6.1</a>), the CX_LIMITED_RANGE pragma (<a href="#7.3.4">7.3.4</a>).
8051 <p><small><a name="note152" href="#note152">152)</a> An implementation is not required to perform macro replacement in pragmas, but it is permitted
8052 except for in standard pragmas (where STDC immediately follows pragma). If the result of macro
8053 replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still
8054 implementation-defined; an implementation is permitted to behave as if it were the standard pragma,
8055 but is not required to.
8057 <p><small><a name="note153" href="#note153">153)</a> See ''future language directions'' (<a href="#6.11.8">6.11.8</a>).
8060 <h4><a name="6.10.7" href="#6.10.7">6.10.7 Null directive</a></h4>
8063 A preprocessing directive of the form
8068 <h4><a name="6.10.8" href="#6.10.8">6.10.8 Predefined macro names</a></h4>
8070 The following macro names<sup><a href="#note154"><b>154)</b></a></sup> shall be defined by the implementation:
8071 __DATE__ The date of translation of the preprocessing translation unit: a character
8073 string literal of the form "Mmm dd yyyy", where the names of the
8074 months are the same as those generated by the asctime function, and the
8075 first character of dd is a space character if the value is less than 10. If the
8076 date of translation is not available, an implementation-defined valid date
8077 shall be supplied.</pre>
8078 __FILE__ The presumed name of the current source file (a character string literal).<sup><a href="#note155"><b>155)</b></a></sup>
8079 __LINE__ The presumed line number (within the current source file) of the current
8081 source line (an integer constant).155)</pre>
8082 __STDC__ The integer constant 1, intended to indicate a conforming implementation.
8083 __STDC_HOSTED__ The integer constant 1 if the implementation is a hosted
8085 implementation or the integer constant 0 if it is not.</pre>
8086 __STDC_MB_MIGHT_NEQ_WC__ The integer constant 1, intended to indicate that, in
8088 the encoding for wchar_t, a member of the basic character set need not
8089 have a code value equal to its value when used as the lone character in an
8090 integer character constant.</pre>
8091 __STDC_VERSION__ The integer constant 199901L.<sup><a href="#note156"><b>156)</b></a></sup>
8092 __TIME__ The time of translation of the preprocessing translation unit: a character
8094 string literal of the form "hh:mm:ss" as in the time generated by the
8095 asctime function. If the time of translation is not available, an
8096 implementation-defined valid time shall be supplied.</pre>
8102 The following macro names are conditionally defined by the implementation:
8103 __STDC_IEC_559__ The integer constant 1, intended to indicate conformance to the
8105 specifications in <a href="#F">annex F</a> (IEC 60559 floating-point arithmetic).</pre>
8106 __STDC_IEC_559_COMPLEX__ The integer constant 1, intended to indicate
8108 adherence to the specifications in informative <a href="#G">annex G</a> (IEC 60559
8109 compatible complex arithmetic).</pre>
8110 __STDC_ISO_10646__ An integer constant of the form yyyymmL (for example,
8113 199712L). If this symbol is defined, then every character in the Unicode
8114 required set, when stored in an object of type wchar_t, has the same
8115 value as the short identifier of that character. The Unicode required set
8116 consists of all the characters that are defined by ISO/IEC 10646, along with
8117 all amendments and technical corrigenda, as of the specified year and
8119 The values of the predefined macros (except for __FILE__ and __LINE__) remain
8120 constant throughout the translation unit.
8122 None of these macro names, nor the identifier defined, shall be the subject of a
8123 #define or a #undef preprocessing directive. Any other predefined macro names
8124 shall begin with a leading underscore followed by an uppercase letter or a second
8127 The implementation shall not predefine the macro __cplusplus, nor shall it define it
8128 in any standard header.
8129 <p><b> Forward references</b>: the asctime function (<a href="#7.23.3.1">7.23.3.1</a>), standard headers (<a href="#7.1.2">7.1.2</a>).
8132 <p><small><a name="note154" href="#note154">154)</a> See ''future language directions'' (<a href="#6.11.9">6.11.9</a>).
8134 <p><small><a name="note155" href="#note155">155)</a> The presumed source file name and line number can be changed by the #line directive.
8136 <p><small><a name="note156" href="#note156">156)</a> This macro was not specified in ISO/IEC 9899:1990 and was specified as 199409L in
8137 ISO/IEC 9899/AMD1:1995. The intention is that this will remain an integer constant of type long
8138 int that is increased with each revision of this International Standard.
8141 <h4><a name="6.10.9" href="#6.10.9">6.10.9 Pragma operator</a></h4>
8144 A unary operator expression of the form:
8146 _Pragma ( string-literal )</pre>
8147 is processed as follows: The string literal is destringized by deleting the L prefix, if
8148 present, deleting the leading and trailing double-quotes, replacing each escape sequence
8149 \" by a double-quote, and replacing each escape sequence \\ by a single backslash. The
8150 resulting sequence of characters is processed through translation phase 3 to produce
8151 preprocessing tokens that are executed as if they were the pp-tokens in a pragma
8152 directive. The original four preprocessing tokens in the unary operator expression are
8155 EXAMPLE A directive of the form:
8157 #pragma listing on "..\listing.dir"</pre>
8158 can also be expressed as:
8161 _Pragma ( "listing on \"..\\listing.dir\"" )</pre>
8162 The latter form is processed in the same way whether it appears literally as shown, or results from macro
8166 #define LISTING(x) PRAGMA(listing on #x)
8167 #define PRAGMA(x) _Pragma(#x)
8168 LISTING ( ..\listing.dir )</pre>
8170 <h3><a name="6.11" href="#6.11">6.11 Future language directions</a></h3>
8172 <h4><a name="6.11.1" href="#6.11.1">6.11.1 Floating types</a></h4>
8174 Future standardization may include additional floating-point types, including those with
8175 greater range, precision, or both than long double.
8177 <h4><a name="6.11.2" href="#6.11.2">6.11.2 Linkages of identifiers</a></h4>
8179 Declaring an identifier with internal linkage at file scope without the static storage-
8180 class specifier is an obsolescent feature.
8182 <h4><a name="6.11.3" href="#6.11.3">6.11.3 External names</a></h4>
8184 Restriction of the significance of an external name to fewer than 255 characters
8185 (considering each universal character name or extended source character as a single
8186 character) is an obsolescent feature that is a concession to existing implementations.
8188 <h4><a name="6.11.4" href="#6.11.4">6.11.4 Character escape sequences</a></h4>
8190 Lowercase letters as escape sequences are reserved for future standardization. Other
8191 characters may be used in extensions.
8193 <h4><a name="6.11.5" href="#6.11.5">6.11.5 Storage-class specifiers</a></h4>
8195 The placement of a storage-class specifier other than at the beginning of the declaration
8196 specifiers in a declaration is an obsolescent feature.
8198 <h4><a name="6.11.6" href="#6.11.6">6.11.6 Function declarators</a></h4>
8200 The use of function declarators with empty parentheses (not prototype-format parameter
8201 type declarators) is an obsolescent feature.
8203 <h4><a name="6.11.7" href="#6.11.7">6.11.7 Function definitions</a></h4>
8205 The use of function definitions with separate parameter identifier and declaration lists
8206 (not prototype-format parameter type and identifier declarators) is an obsolescent feature.
8208 <h4><a name="6.11.8" href="#6.11.8">6.11.8 Pragma directives</a></h4>
8210 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
8212 <h4><a name="6.11.9" href="#6.11.9">6.11.9 Predefined macro names</a></h4>
8214 Macro names beginning with __STDC_ are reserved for future standardization.
8217 <h2><a name="7" href="#7">7. Library</a></h2>
8220 <h3><a name="7.1" href="#7.1">7.1 Introduction</a></h3>
8222 <h4><a name="7.1.1" href="#7.1.1">7.1.1 Definitions of terms</a></h4>
8224 A string is a contiguous sequence of characters terminated by and including the first null
8225 character. The term multibyte string is sometimes used instead to emphasize special
8226 processing given to multibyte characters contained in the string or to avoid confusion
8227 with a wide string. A pointer to a string is a pointer to its initial (lowest addressed)
8228 character. The length of a string is the number of bytes preceding the null character and
8229 the value of a string is the sequence of the values of the contained characters, in order.
8231 The decimal-point character is the character used by functions that convert floating-point
8232 numbers to or from character sequences to denote the beginning of the fractional part of
8233 such character sequences.<sup><a href="#note157"><b>157)</b></a></sup> It is represented in the text and examples by a period, but
8234 may be changed by the setlocale function.
8236 A null wide character is a wide character with code value zero.
8238 A wide string is a contiguous sequence of wide characters terminated by and including
8239 the first null wide character. A pointer to a wide string is a pointer to its initial (lowest
8240 addressed) wide character. The length of a wide string is the number of wide characters
8241 preceding the null wide character and the value of a wide string is the sequence of code
8242 values of the contained wide characters, in order.
8244 A shift sequence is a contiguous sequence of bytes within a multibyte string that
8245 (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
8246 corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
8247 character.<sup><a href="#note158"><b>158)</b></a></sup>
8248 <p><b> Forward references</b>: character handling (<a href="#7.4">7.4</a>), the setlocale function (<a href="#7.11.1.1">7.11.1.1</a>).
8256 <p><small><a name="note157" href="#note157">157)</a> The functions that make use of the decimal-point character are the numeric conversion functions
8257 (<a href="#7.20.1">7.20.1</a>, <a href="#7.24.4.1">7.24.4.1</a>) and the formatted input/output functions (<a href="#7.19.6">7.19.6</a>, <a href="#7.24.2">7.24.2</a>).
8259 <p><small><a name="note158" href="#note158">158)</a> For state-dependent encodings, the values for MB_CUR_MAX and MB_LEN_MAX shall thus be large
8260 enough to count all the bytes in any complete multibyte character plus at least one adjacent shift
8261 sequence of maximum length. Whether these counts provide for more than one shift sequence is the
8262 implementation's choice.
8265 <h4><a name="7.1.2" href="#7.1.2">7.1.2 Standard headers</a></h4>
8267 Each library function is declared, with a type that includes a prototype, in a header,<sup><a href="#note159"><b>159)</b></a></sup>
8268 whose contents are made available by the #include preprocessing directive. The
8269 header declares a set of related functions, plus any necessary types and additional macros
8270 needed to facilitate their use. Declarations of types described in this clause shall not
8271 include type qualifiers, unless explicitly stated otherwise.
8273 The standard headers are
8276 <a href="#7.2"><assert.h></a> <a href="#7.8"><inttypes.h></a> <a href="#7.14"><signal.h></a> <a href="#7.20"><stdlib.h></a>
8277 <a href="#7.3"><complex.h></a> <a href="#7.9"><iso646.h></a> <a href="#7.15"><stdarg.h></a> <a href="#7.21"><string.h></a>
8278 <a href="#7.4"><ctype.h></a> <a href="#7.10"><limits.h></a> <a href="#7.16"><stdbool.h></a> <a href="#7.22"><tgmath.h></a>
8279 <a href="#7.5"><errno.h></a> <a href="#7.11"><locale.h></a> <a href="#7.17"><stddef.h></a> <a href="#7.23"><time.h></a>
8280 <a href="#7.6"><fenv.h></a> <a href="#7.12"><math.h></a> <a href="#7.18"><stdint.h></a> <a href="#7.24"><wchar.h></a>
8281 <a href="#7.7"><float.h></a> <a href="#7.13"><setjmp.h></a> <a href="#7.19"><stdio.h></a> <a href="#7.25"><wctype.h></a></pre>
8282 If a file with the same name as one of the above < and > delimited sequences, not
8283 provided as part of the implementation, is placed in any of the standard places that are
8284 searched for included source files, the behavior is undefined.
8286 Standard headers may be included in any order; each may be included more than once in
8287 a given scope, with no effect different from being included only once, except that the
8288 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
8289 used, a header shall be included outside of any external declaration or definition, and it
8290 shall first be included before the first reference to any of the functions or objects it
8291 declares, or to any of the types or macros it defines. However, if an identifier is declared
8292 or defined in more than one header, the second and subsequent associated headers may be
8293 included after the initial reference to the identifier. The program shall not have any
8294 macros with names lexically identical to keywords currently defined prior to the
8297 Any definition of an object-like macro described in this clause shall expand to code that is
8298 fully protected by parentheses where necessary, so that it groups in an arbitrary
8299 expression as if it were a single identifier.
8301 Any declaration of a library function shall have external linkage.
8303 A summary of the contents of the standard headers is given in <a href="#B">annex B</a>.
8304 <p><b> Forward references</b>: diagnostics (<a href="#7.2">7.2</a>).
8312 <p><small><a name="note159" href="#note159">159)</a> A header is not necessarily a source file, nor are the < and > delimited sequences in header names
8313 necessarily valid source file names.
8316 <h4><a name="7.1.3" href="#7.1.3">7.1.3 Reserved identifiers</a></h4>
8318 Each header declares or defines all identifiers listed in its associated subclause, and
8319 optionally declares or defines identifiers listed in its associated future library directions
8320 subclause and identifiers which are always reserved either for any use or for use as file
8323 <li> All identifiers that begin with an underscore and either an uppercase letter or another
8324 underscore are always reserved for any use.
8325 <li> All identifiers that begin with an underscore are always reserved for use as identifiers
8326 with file scope in both the ordinary and tag name spaces.
8327 <li> Each macro name in any of the following subclauses (including the future library
8328 directions) is reserved for use as specified if any of its associated headers is included;
8329 unless explicitly stated otherwise (see <a href="#7.1.4">7.1.4</a>).
8330 <li> All identifiers with external linkage in any of the following subclauses (including the
8331 future library directions) are always reserved for use as identifiers with external
8332 linkage.<sup><a href="#note160"><b>160)</b></a></sup>
8333 <li> Each identifier with file scope listed in any of the following subclauses (including the
8334 future library directions) is reserved for use as a macro name and as an identifier with
8335 file scope in the same name space if any of its associated headers is included.
8338 No other identifiers are reserved. If the program declares or defines an identifier in a
8339 context in which it is reserved (other than as allowed by <a href="#7.1.4">7.1.4</a>), or defines a reserved
8340 identifier as a macro name, the behavior is undefined.
8342 If the program removes (with #undef) any macro definition of an identifier in the first
8343 group listed above, the behavior is undefined.
8346 <p><small><a name="note160" href="#note160">160)</a> The list of reserved identifiers with external linkage includes errno, math_errhandling,
8350 <h4><a name="7.1.4" href="#7.1.4">7.1.4 Use of library functions</a></h4>
8352 Each of the following statements applies unless explicitly stated otherwise in the detailed
8353 descriptions that follow: If an argument to a function has an invalid value (such as a value
8354 outside the domain of the function, or a pointer outside the address space of the program,
8355 or a null pointer, or a pointer to non-modifiable storage when the corresponding
8356 parameter is not const-qualified) or a type (after promotion) not expected by a function
8357 with variable number of arguments, the behavior is undefined. If a function argument is
8358 described as being an array, the pointer actually passed to the function shall have a value
8359 such that all address computations and accesses to objects (that would be valid if the
8360 pointer did point to the first element of such an array) are in fact valid. Any function
8361 declared in a header may be additionally implemented as a function-like macro defined in
8364 the header, so if a library function is declared explicitly when its header is included, one
8365 of the techniques shown below can be used to ensure the declaration is not affected by
8366 such a macro. Any macro definition of a function can be suppressed locally by enclosing
8367 the name of the function in parentheses, because the name is then not followed by the left
8368 parenthesis that indicates expansion of a macro function name. For the same syntactic
8369 reason, it is permitted to take the address of a library function even if it is also defined as
8370 a macro.<sup><a href="#note161"><b>161)</b></a></sup> The use of #undef to remove any macro definition will also ensure that an
8371 actual function is referred to. Any invocation of a library function that is implemented as
8372 a macro shall expand to code that evaluates each of its arguments exactly once, fully
8373 protected by parentheses where necessary, so it is generally safe to use arbitrary
8374 expressions as arguments.<sup><a href="#note162"><b>162)</b></a></sup> Likewise, those function-like macros described in the
8375 following subclauses may be invoked in an expression anywhere a function with a
8376 compatible return type could be called.<sup><a href="#note163"><b>163)</b></a></sup> All object-like macros listed as expanding to
8377 integer constant expressions shall additionally be suitable for use in #if preprocessing
8380 Provided that a library function can be declared without reference to any type defined in a
8381 header, it is also permissible to declare the function and use it without including its
8384 There is a sequence point immediately before a library function returns.
8386 The functions in the standard library are not guaranteed to be reentrant and may modify
8387 objects with static storage duration.<sup><a href="#note164"><b>164)</b></a></sup>
8393 EXAMPLE The function atoi may be used in any of several ways:
8395 <li> by use of its associated header (possibly generating a macro expansion)
8397 #include <a href="#7.20"><stdlib.h></a>
8400 i = atoi(str);</pre>
8401 <li> by use of its associated header (assuredly generating a true function reference)
8403 #include <a href="#7.20"><stdlib.h></a>
8407 i = atoi(str);</pre>
8410 #include <a href="#7.20"><stdlib.h></a>
8413 i = (atoi)(str);</pre>
8414 <li> by explicit declaration
8417 extern int atoi(const char *);
8420 i = atoi(str);</pre>
8424 <p><small><a name="note161" href="#note161">161)</a> This means that an implementation shall provide an actual function for each library function, even if it
8425 also provides a macro for that function.
8427 <p><small><a name="note162" href="#note162">162)</a> Such macros might not contain the sequence points that the corresponding function calls do.
8429 <p><small><a name="note163" href="#note163">163)</a> Because external identifiers and some macro names beginning with an underscore are reserved,
8430 implementations may provide special semantics for such names. For example, the identifier
8431 _BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
8432 appropriate header could specify
8435 #define abs(x) _BUILTIN_abs(x)</pre>
8436 for a compiler whose code generator will accept it.
8437 In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
8442 whether the implementation's header provides a macro implementation of abs or a built-in
8443 implementation. The prototype for the function, which precedes and is hidden by any macro
8444 definition, is thereby revealed also.
8446 <p><small><a name="note164" href="#note164">164)</a> Thus, a signal handler cannot, in general, call standard library functions.
8449 <h3><a name="7.2" href="#7.2">7.2 Diagnostics <assert.h></a></h3>
8451 The header <a href="#7.2"><assert.h></a> defines the assert macro and refers to another macro,
8454 which is not defined by <a href="#7.2"><assert.h></a>. If NDEBUG is defined as a macro name at the
8455 point in the source file where <a href="#7.2"><assert.h></a> is included, the assert macro is defined
8458 #define assert(ignore) ((void)0)</pre>
8459 The assert macro is redefined according to the current state of NDEBUG each time that
8460 <a href="#7.2"><assert.h></a> is included.
8462 The assert macro shall be implemented as a macro, not as an actual function. If the
8463 macro definition is suppressed in order to access an actual function, the behavior is
8466 <h4><a name="7.2.1" href="#7.2.1">7.2.1 Program diagnostics</a></h4>
8468 <h5><a name="7.2.1.1" href="#7.2.1.1">7.2.1.1 The assert macro</a></h5>
8472 #include <a href="#7.2"><assert.h></a>
8473 void assert(scalar expression);</pre>
8474 <h6>Description</h6>
8476 The assert macro puts diagnostic tests into programs; it expands to a void expression.
8477 When it is executed, if expression (which shall have a scalar type) is false (that is,
8478 compares equal to 0), the assert macro writes information about the particular call that
8479 failed (including the text of the argument, the name of the source file, the source line
8480 number, and the name of the enclosing function -- the latter are respectively the values of
8481 the preprocessing macros __FILE__ and __LINE__ and of the identifier
8482 __func__) on the standard error stream in an implementation-defined format.<sup><a href="#note165"><b>165)</b></a></sup> It
8483 then calls the abort function.
8486 The assert macro returns no value.
8487 <p><b> Forward references</b>: the abort function (<a href="#7.20.4.1">7.20.4.1</a>).
8495 <p><small><a name="note165" href="#note165">165)</a> The message written might be of the form:
8496 Assertion failed: expression, function abc, file xyz, line nnn.
8499 <h3><a name="7.3" href="#7.3">7.3 Complex arithmetic <complex.h></a></h3>
8501 <h4><a name="7.3.1" href="#7.3.1">7.3.1 Introduction</a></h4>
8503 The header <a href="#7.3"><complex.h></a> defines macros and declares functions that support complex
8504 arithmetic.<sup><a href="#note166"><b>166)</b></a></sup> Each synopsis specifies a family of functions consisting of a principal
8505 function with one or more double complex parameters and a double complex or
8506 double return value; and other functions with the same name but with f and l suffixes
8507 which are corresponding functions with float and long double parameters and
8513 expands to _Complex; the macro
8516 expands to a constant expression of type const float _Complex, with the value of
8517 the imaginary unit.<sup><a href="#note167"><b>167)</b></a></sup>
8525 are defined if and only if the implementation supports imaginary types;<sup><a href="#note168"><b>168)</b></a></sup> if defined,
8526 they expand to _Imaginary and a constant expression of type const float
8527 _Imaginary with the value of the imaginary unit.
8532 expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
8533 defined, I shall expand to _Complex_I.
8535 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
8536 redefine the macros complex, imaginary, and I.
8537 <p><b> Forward references</b>: IEC 60559-compatible complex arithmetic (<a href="#G">annex G</a>).
8544 <p><small><a name="note166" href="#note166">166)</a> See ''future library directions'' (<a href="#7.26.1">7.26.1</a>).
8546 <p><small><a name="note167" href="#note167">167)</a> The imaginary unit is a number i such that i 2 = -1.
8548 <p><small><a name="note168" href="#note168">168)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
8551 <h4><a name="7.3.2" href="#7.3.2">7.3.2 Conventions</a></h4>
8553 Values are interpreted as radians, not degrees. An implementation may set errno but is
8556 <h4><a name="7.3.3" href="#7.3.3">7.3.3 Branch cuts</a></h4>
8558 Some of the functions below have branch cuts, across which the function is
8559 discontinuous. For implementations with a signed zero (including all IEC 60559
8560 implementations) that follow the specifications of <a href="#G">annex G</a>, the sign of zero distinguishes
8561 one side of a cut from another so the function is continuous (except for format
8562 limitations) as the cut is approached from either side. For example, for the square root
8563 function, which has a branch cut along the negative real axis, the top of the cut, with
8564 imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with
8565 imaginary part -0, maps to the negative imaginary axis.
8567 Implementations that do not support a signed zero (see <a href="#F">annex F</a>) cannot distinguish the
8568 sides of branch cuts. These implementations shall map a cut so the function is continuous
8569 as the cut is approached coming around the finite endpoint of the cut in a counter
8570 clockwise direction. (Branch cuts for the functions specified here have just one finite
8571 endpoint.) For example, for the square root function, coming counter clockwise around
8572 the finite endpoint of the cut along the negative real axis approaches the cut from above,
8573 so the cut maps to the positive imaginary axis.
8575 <h4><a name="7.3.4" href="#7.3.4">7.3.4 The CX_LIMITED_RANGE pragma</a></h4>
8579 #include <a href="#7.3"><complex.h></a>
8580 #pragma STDC CX_LIMITED_RANGE on-off-switch</pre>
8581 <h6>Description</h6>
8583 The usual mathematical formulas for complex multiply, divide, and absolute value are
8584 problematic because of their treatment of infinities and because of undue overflow and
8585 underflow. The CX_LIMITED_RANGE pragma can be used to inform the
8586 implementation that (where the state is ''on'') the usual mathematical formulas are
8587 acceptable.<sup><a href="#note169"><b>169)</b></a></sup> The pragma can occur either outside external declarations or preceding all
8588 explicit declarations and statements inside a compound statement. When outside external
8591 declarations, the pragma takes effect from its occurrence until another
8592 CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit.
8593 When inside a compound statement, the pragma takes effect from its occurrence until
8594 another CX_LIMITED_RANGE pragma is encountered (including within a nested
8595 compound statement), or until the end of the compound statement; at the end of a
8596 compound statement the state for the pragma is restored to its condition just before the
8597 compound statement. If this pragma is used in any other context, the behavior is
8598 undefined. The default state for the pragma is ''off''.
8601 <p><small><a name="note169" href="#note169">169)</a> The purpose of the pragma is to allow the implementation to use the formulas:
8604 (x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
8605 (x + iy) / (u + iv) = [(xu + yv) + i(yu - xv)]/(u2 + v 2 )
8606 | x + iy | = (sqrt) x 2 + y 2
8607 ???????????????</pre>
8608 where the programmer can determine they are safe.
8611 <h4><a name="7.3.5" href="#7.3.5">7.3.5 Trigonometric functions</a></h4>
8613 <h5><a name="7.3.5.1" href="#7.3.5.1">7.3.5.1 The cacos functions</a></h5>
8617 #include <a href="#7.3"><complex.h></a>
8618 double complex cacos(double complex z);
8619 float complex cacosf(float complex z);
8620 long double complex cacosl(long double complex z);</pre>
8621 <h6>Description</h6>
8623 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
8624 interval [-1, +1] along the real axis.
8627 The cacos functions return the complex arc cosine value, in the range of a strip
8628 mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
8631 <h5><a name="7.3.5.2" href="#7.3.5.2">7.3.5.2 The casin functions</a></h5>
8635 #include <a href="#7.3"><complex.h></a>
8636 double complex casin(double complex z);
8637 float complex casinf(float complex z);
8638 long double complex casinl(long double complex z);</pre>
8639 <h6>Description</h6>
8641 The casin functions compute the complex arc sine of z, with branch cuts outside the
8642 interval [-1, +1] along the real axis.
8645 The casin functions return the complex arc sine value, in the range of a strip
8646 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
8647 along the real axis.
8650 <h5><a name="7.3.5.3" href="#7.3.5.3">7.3.5.3 The catan functions</a></h5>
8654 #include <a href="#7.3"><complex.h></a>
8655 double complex catan(double complex z);
8656 float complex catanf(float complex z);
8657 long double complex catanl(long double complex z);</pre>
8658 <h6>Description</h6>
8660 The catan functions compute the complex arc tangent of z, with branch cuts outside the
8661 interval [-i, +i] along the imaginary axis.
8664 The catan functions return the complex arc tangent value, in the range of a strip
8665 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
8666 along the real axis.
8668 <h5><a name="7.3.5.4" href="#7.3.5.4">7.3.5.4 The ccos functions</a></h5>
8672 #include <a href="#7.3"><complex.h></a>
8673 double complex ccos(double complex z);
8674 float complex ccosf(float complex z);
8675 long double complex ccosl(long double complex z);</pre>
8676 <h6>Description</h6>
8678 The ccos functions compute the complex cosine of z.
8681 The ccos functions return the complex cosine value.
8683 <h5><a name="7.3.5.5" href="#7.3.5.5">7.3.5.5 The csin functions</a></h5>
8687 #include <a href="#7.3"><complex.h></a>
8688 double complex csin(double complex z);
8689 float complex csinf(float complex z);
8690 long double complex csinl(long double complex z);</pre>
8691 <h6>Description</h6>
8693 The csin functions compute the complex sine of z.
8696 The csin functions return the complex sine value.
8699 <h5><a name="7.3.5.6" href="#7.3.5.6">7.3.5.6 The ctan functions</a></h5>
8703 #include <a href="#7.3"><complex.h></a>
8704 double complex ctan(double complex z);
8705 float complex ctanf(float complex z);
8706 long double complex ctanl(long double complex z);</pre>
8707 <h6>Description</h6>
8709 The ctan functions compute the complex tangent of z.
8712 The ctan functions return the complex tangent value.
8714 <h4><a name="7.3.6" href="#7.3.6">7.3.6 Hyperbolic functions</a></h4>
8716 <h5><a name="7.3.6.1" href="#7.3.6.1">7.3.6.1 The cacosh functions</a></h5>
8720 #include <a href="#7.3"><complex.h></a>
8721 double complex cacosh(double complex z);
8722 float complex cacoshf(float complex z);
8723 long double complex cacoshl(long double complex z);</pre>
8724 <h6>Description</h6>
8726 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch
8727 cut at values less than 1 along the real axis.
8730 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
8731 half-strip of non-negative values along the real axis and in the interval [-ipi , +ipi ] along
8734 <h5><a name="7.3.6.2" href="#7.3.6.2">7.3.6.2 The casinh functions</a></h5>
8738 #include <a href="#7.3"><complex.h></a>
8739 double complex casinh(double complex z);
8740 float complex casinhf(float complex z);
8741 long double complex casinhl(long double complex z);</pre>
8742 <h6>Description</h6>
8744 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts
8745 outside the interval [-i, +i] along the imaginary axis.
8749 The casinh functions return the complex arc hyperbolic sine value, in the range of a
8750 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
8751 along the imaginary axis.
8753 <h5><a name="7.3.6.3" href="#7.3.6.3">7.3.6.3 The catanh functions</a></h5>
8757 #include <a href="#7.3"><complex.h></a>
8758 double complex catanh(double complex z);
8759 float complex catanhf(float complex z);
8760 long double complex catanhl(long double complex z);</pre>
8761 <h6>Description</h6>
8763 The catanh functions compute the complex arc hyperbolic tangent of z, with branch
8764 cuts outside the interval [-1, +1] along the real axis.
8767 The catanh functions return the complex arc hyperbolic tangent value, in the range of a
8768 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
8769 along the imaginary axis.
8771 <h5><a name="7.3.6.4" href="#7.3.6.4">7.3.6.4 The ccosh functions</a></h5>
8775 #include <a href="#7.3"><complex.h></a>
8776 double complex ccosh(double complex z);
8777 float complex ccoshf(float complex z);
8778 long double complex ccoshl(long double complex z);</pre>
8779 <h6>Description</h6>
8781 The ccosh functions compute the complex hyperbolic cosine of z.
8784 The ccosh functions return the complex hyperbolic cosine value.
8786 <h5><a name="7.3.6.5" href="#7.3.6.5">7.3.6.5 The csinh functions</a></h5>
8791 #include <a href="#7.3"><complex.h></a>
8792 double complex csinh(double complex z);
8793 float complex csinhf(float complex z);
8794 long double complex csinhl(long double complex z);</pre>
8795 <h6>Description</h6>
8797 The csinh functions compute the complex hyperbolic sine of z.
8800 The csinh functions return the complex hyperbolic sine value.
8802 <h5><a name="7.3.6.6" href="#7.3.6.6">7.3.6.6 The ctanh functions</a></h5>
8806 #include <a href="#7.3"><complex.h></a>
8807 double complex ctanh(double complex z);
8808 float complex ctanhf(float complex z);
8809 long double complex ctanhl(long double complex z);</pre>
8810 <h6>Description</h6>
8812 The ctanh functions compute the complex hyperbolic tangent of z.
8815 The ctanh functions return the complex hyperbolic tangent value.
8817 <h4><a name="7.3.7" href="#7.3.7">7.3.7 Exponential and logarithmic functions</a></h4>
8819 <h5><a name="7.3.7.1" href="#7.3.7.1">7.3.7.1 The cexp functions</a></h5>
8823 #include <a href="#7.3"><complex.h></a>
8824 double complex cexp(double complex z);
8825 float complex cexpf(float complex z);
8826 long double complex cexpl(long double complex z);</pre>
8827 <h6>Description</h6>
8829 The cexp functions compute the complex base-e exponential of z.
8832 The cexp functions return the complex base-e exponential value.
8834 <h5><a name="7.3.7.2" href="#7.3.7.2">7.3.7.2 The clog functions</a></h5>
8839 #include <a href="#7.3"><complex.h></a>
8840 double complex clog(double complex z);
8841 float complex clogf(float complex z);
8842 long double complex clogl(long double complex z);</pre>
8843 <h6>Description</h6>
8845 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
8846 cut along the negative real axis.
8849 The clog functions return the complex natural logarithm value, in the range of a strip
8850 mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
8853 <h4><a name="7.3.8" href="#7.3.8">7.3.8 Power and absolute-value functions</a></h4>
8855 <h5><a name="7.3.8.1" href="#7.3.8.1">7.3.8.1 The cabs functions</a></h5>
8859 #include <a href="#7.3"><complex.h></a>
8860 double cabs(double complex z);
8861 float cabsf(float complex z);
8862 long double cabsl(long double complex z);</pre>
8863 <h6>Description</h6>
8865 The cabs functions compute the complex absolute value (also called norm, modulus, or
8869 The cabs functions return the complex absolute value.
8871 <h5><a name="7.3.8.2" href="#7.3.8.2">7.3.8.2 The cpow functions</a></h5>
8875 #include <a href="#7.3"><complex.h></a>
8876 double complex cpow(double complex x, double complex y);
8877 float complex cpowf(float complex x, float complex y);
8878 long double complex cpowl(long double complex x,
8879 long double complex y);</pre>
8880 <h6>Description</h6>
8882 The cpow functions compute the complex power function xy , with a branch cut for the
8883 first parameter along the negative real axis.
8886 The cpow functions return the complex power function value.
8889 <h5><a name="7.3.8.3" href="#7.3.8.3">7.3.8.3 The csqrt functions</a></h5>
8893 #include <a href="#7.3"><complex.h></a>
8894 double complex csqrt(double complex z);
8895 float complex csqrtf(float complex z);
8896 long double complex csqrtl(long double complex z);</pre>
8897 <h6>Description</h6>
8899 The csqrt functions compute the complex square root of z, with a branch cut along the
8903 The csqrt functions return the complex square root value, in the range of the right half-
8904 plane (including the imaginary axis).
8906 <h4><a name="7.3.9" href="#7.3.9">7.3.9 Manipulation functions</a></h4>
8908 <h5><a name="7.3.9.1" href="#7.3.9.1">7.3.9.1 The carg functions</a></h5>
8912 #include <a href="#7.3"><complex.h></a>
8913 double carg(double complex z);
8914 float cargf(float complex z);
8915 long double cargl(long double complex z);</pre>
8916 <h6>Description</h6>
8918 The carg functions compute the argument (also called phase angle) of z, with a branch
8919 cut along the negative real axis.
8922 The carg functions return the value of the argument in the interval [-pi , +pi ].
8924 <h5><a name="7.3.9.2" href="#7.3.9.2">7.3.9.2 The cimag functions</a></h5>
8929 #include <a href="#7.3"><complex.h></a>
8930 double cimag(double complex z);
8931 float cimagf(float complex z);
8932 long double cimagl(long double complex z);</pre>
8933 <h6>Description</h6>
8935 The cimag functions compute the imaginary part of z.<sup><a href="#note170"><b>170)</b></a></sup>
8938 The cimag functions return the imaginary part value (as a real).
8941 <p><small><a name="note170" href="#note170">170)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
8944 <h5><a name="7.3.9.3" href="#7.3.9.3">7.3.9.3 The conj functions</a></h5>
8948 #include <a href="#7.3"><complex.h></a>
8949 double complex conj(double complex z);
8950 float complex conjf(float complex z);
8951 long double complex conjl(long double complex z);</pre>
8952 <h6>Description</h6>
8954 The conj functions compute the complex conjugate of z, by reversing the sign of its
8958 The conj functions return the complex conjugate value.
8960 <h5><a name="7.3.9.4" href="#7.3.9.4">7.3.9.4 The cproj functions</a></h5>
8964 #include <a href="#7.3"><complex.h></a>
8965 double complex cproj(double complex z);
8966 float complex cprojf(float complex z);
8967 long double complex cprojl(long double complex z);</pre>
8968 <h6>Description</h6>
8970 The cproj functions compute a projection of z onto the Riemann sphere: z projects to
8971 z except that all complex infinities (even those with one infinite part and one NaN part)
8972 project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is
8975 INFINITY + I * copysign(0.0, cimag(z))</pre>
8978 The cproj functions return the value of the projection onto the Riemann sphere.
8985 <h5><a name="7.3.9.5" href="#7.3.9.5">7.3.9.5 The creal functions</a></h5>
8989 #include <a href="#7.3"><complex.h></a>
8990 double creal(double complex z);
8991 float crealf(float complex z);
8992 long double creall(long double complex z);</pre>
8993 <h6>Description</h6>
8995 The creal functions compute the real part of z.<sup><a href="#note171"><b>171)</b></a></sup>
8998 The creal functions return the real part value.
9006 <p><small><a name="note171" href="#note171">171)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
9009 <h3><a name="7.4" href="#7.4">7.4 Character handling <ctype.h></a></h3>
9011 The header <a href="#7.4"><ctype.h></a> declares several functions useful for classifying and mapping
9012 characters.<sup><a href="#note172"><b>172)</b></a></sup> In all cases the argument is an int, the value of which shall be
9013 representable as an unsigned char or shall equal the value of the macro EOF. If the
9014 argument has any other value, the behavior is undefined.
9016 The behavior of these functions is affected by the current locale. Those functions that
9017 have locale-specific aspects only when not in the "C" locale are noted below.
9019 The term printing character refers to a member of a locale-specific set of characters, each
9020 of which occupies one printing position on a display device; the term control character
9021 refers to a member of a locale-specific set of characters that are not printing
9022 characters.<sup><a href="#note173"><b>173)</b></a></sup> All letters and digits are printing characters.
9023 <p><b> Forward references</b>: EOF (<a href="#7.19.1">7.19.1</a>), localization (<a href="#7.11">7.11</a>).
9026 <p><small><a name="note172" href="#note172">172)</a> See ''future library directions'' (<a href="#7.26.2">7.26.2</a>).
9028 <p><small><a name="note173" href="#note173">173)</a> In an implementation that uses the seven-bit US ASCII character set, the printing characters are those
9029 whose values lie from 0x20 (space) through 0x7E (tilde); the control characters are those whose
9030 values lie from 0 (NUL) through 0x1F (US), and the character 0x7F (DEL).
9033 <h4><a name="7.4.1" href="#7.4.1">7.4.1 Character classification functions</a></h4>
9035 The functions in this subclause return nonzero (true) if and only if the value of the
9036 argument c conforms to that in the description of the function.
9038 <h5><a name="7.4.1.1" href="#7.4.1.1">7.4.1.1 The isalnum function</a></h5>
9042 #include <a href="#7.4"><ctype.h></a>
9043 int isalnum(int c);</pre>
9044 <h6>Description</h6>
9046 The isalnum function tests for any character for which isalpha or isdigit is true.
9048 <h5><a name="7.4.1.2" href="#7.4.1.2">7.4.1.2 The isalpha function</a></h5>
9052 #include <a href="#7.4"><ctype.h></a>
9053 int isalpha(int c);</pre>
9054 <h6>Description</h6>
9056 The isalpha function tests for any character for which isupper or islower is true,
9057 or any character that is one of a locale-specific set of alphabetic characters for which
9062 none of iscntrl, isdigit, ispunct, or isspace is true.<sup><a href="#note174"><b>174)</b></a></sup> In the "C" locale,
9063 isalpha returns true only for the characters for which isupper or islower is true.
9066 <p><small><a name="note174" href="#note174">174)</a> The functions islower and isupper test true or false separately for each of these additional
9067 characters; all four combinations are possible.
9070 <h5><a name="7.4.1.3" href="#7.4.1.3">7.4.1.3 The isblank function</a></h5>
9074 #include <a href="#7.4"><ctype.h></a>
9075 int isblank(int c);</pre>
9076 <h6>Description</h6>
9078 The isblank function tests for any character that is a standard blank character or is one
9079 of a locale-specific set of characters for which isspace is true and that is used to
9080 separate words within a line of text. The standard blank characters are the following:
9081 space (' '), and horizontal tab ('\t'). In the "C" locale, isblank returns true only
9082 for the standard blank characters.
9084 <h5><a name="7.4.1.4" href="#7.4.1.4">7.4.1.4 The iscntrl function</a></h5>
9088 #include <a href="#7.4"><ctype.h></a>
9089 int iscntrl(int c);</pre>
9090 <h6>Description</h6>
9092 The iscntrl function tests for any control character.
9094 <h5><a name="7.4.1.5" href="#7.4.1.5">7.4.1.5 The isdigit function</a></h5>
9098 #include <a href="#7.4"><ctype.h></a>
9099 int isdigit(int c);</pre>
9100 <h6>Description</h6>
9102 The isdigit function tests for any decimal-digit character (as defined in <a href="#5.2.1">5.2.1</a>).
9104 <h5><a name="7.4.1.6" href="#7.4.1.6">7.4.1.6 The isgraph function</a></h5>
9108 #include <a href="#7.4"><ctype.h></a>
9109 int isgraph(int c);</pre>
9115 <h6>Description</h6>
9117 The isgraph function tests for any printing character except space (' ').
9119 <h5><a name="7.4.1.7" href="#7.4.1.7">7.4.1.7 The islower function</a></h5>
9123 #include <a href="#7.4"><ctype.h></a>
9124 int islower(int c);</pre>
9125 <h6>Description</h6>
9127 The islower function tests for any character that is a lowercase letter or is one of a
9128 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
9129 isspace is true. In the "C" locale, islower returns true only for the lowercase
9130 letters (as defined in <a href="#5.2.1">5.2.1</a>).
9132 <h5><a name="7.4.1.8" href="#7.4.1.8">7.4.1.8 The isprint function</a></h5>
9136 #include <a href="#7.4"><ctype.h></a>
9137 int isprint(int c);</pre>
9138 <h6>Description</h6>
9140 The isprint function tests for any printing character including space (' ').
9142 <h5><a name="7.4.1.9" href="#7.4.1.9">7.4.1.9 The ispunct function</a></h5>
9146 #include <a href="#7.4"><ctype.h></a>
9147 int ispunct(int c);</pre>
9148 <h6>Description</h6>
9150 The ispunct function tests for any printing character that is one of a locale-specific set
9151 of punctuation characters for which neither isspace nor isalnum is true. In the "C"
9152 locale, ispunct returns true for every printing character for which neither isspace
9153 nor isalnum is true.
9155 <h5><a name="7.4.1.10" href="#7.4.1.10">7.4.1.10 The isspace function</a></h5>
9159 #include <a href="#7.4"><ctype.h></a>
9160 int isspace(int c);</pre>
9161 <h6>Description</h6>
9163 The isspace function tests for any character that is a standard white-space character or
9164 is one of a locale-specific set of characters for which isalnum is false. The standard
9166 white-space characters are the following: space (' '), form feed ('\f'), new-line
9167 ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
9168 "C" locale, isspace returns true only for the standard white-space characters.
9170 <h5><a name="7.4.1.11" href="#7.4.1.11">7.4.1.11 The isupper function</a></h5>
9174 #include <a href="#7.4"><ctype.h></a>
9175 int isupper(int c);</pre>
9176 <h6>Description</h6>
9178 The isupper function tests for any character that is an uppercase letter or is one of a
9179 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
9180 isspace is true. In the "C" locale, isupper returns true only for the uppercase
9181 letters (as defined in <a href="#5.2.1">5.2.1</a>).
9183 <h5><a name="7.4.1.12" href="#7.4.1.12">7.4.1.12 The isxdigit function</a></h5>
9187 #include <a href="#7.4"><ctype.h></a>
9188 int isxdigit(int c);</pre>
9189 <h6>Description</h6>
9191 The isxdigit function tests for any hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
9193 <h4><a name="7.4.2" href="#7.4.2">7.4.2 Character case mapping functions</a></h4>
9195 <h5><a name="7.4.2.1" href="#7.4.2.1">7.4.2.1 The tolower function</a></h5>
9199 #include <a href="#7.4"><ctype.h></a>
9200 int tolower(int c);</pre>
9201 <h6>Description</h6>
9203 The tolower function converts an uppercase letter to a corresponding lowercase letter.
9206 If the argument is a character for which isupper is true and there are one or more
9207 corresponding characters, as specified by the current locale, for which islower is true,
9208 the tolower function returns one of the corresponding characters (always the same one
9209 for any given locale); otherwise, the argument is returned unchanged.
9212 <h5><a name="7.4.2.2" href="#7.4.2.2">7.4.2.2 The toupper function</a></h5>
9216 #include <a href="#7.4"><ctype.h></a>
9217 int toupper(int c);</pre>
9218 <h6>Description</h6>
9220 The toupper function converts a lowercase letter to a corresponding uppercase letter.
9223 If the argument is a character for which islower is true and there are one or more
9224 corresponding characters, as specified by the current locale, for which isupper is true,
9225 the toupper function returns one of the corresponding characters (always the same one
9226 for any given locale); otherwise, the argument is returned unchanged.
9229 <h3><a name="7.5" href="#7.5">7.5 Errors <errno.h></a></h3>
9231 The header <a href="#7.5"><errno.h></a> defines several macros, all relating to the reporting of error
9239 which expand to integer constant expressions with type int, distinct positive values, and
9240 which are suitable for use in #if preprocessing directives; and
9243 which expands to a modifiable lvalue<sup><a href="#note175"><b>175)</b></a></sup> that has type int, the value of which is set to a
9244 positive error number by several library functions. It is unspecified whether errno is a
9245 macro or an identifier declared with external linkage. If a macro definition is suppressed
9246 in order to access an actual object, or a program defines an identifier with the name
9247 errno, the behavior is undefined.
9249 The value of errno is zero at program startup, but is never set to zero by any library
9250 function.<sup><a href="#note176"><b>176)</b></a></sup> The value of errno may be set to nonzero by a library function call
9251 whether or not there is an error, provided the use of errno is not documented in the
9252 description of the function in this International Standard.
9254 Additional macro definitions, beginning with E and a digit or E and an uppercase
9255 letter,<sup><a href="#note177"><b>177)</b></a></sup> may also be specified by the implementation.
9263 <p><small><a name="note175" href="#note175">175)</a> The macro errno need not be the identifier of an object. It might expand to a modifiable lvalue
9264 resulting from a function call (for example, *errno()).
9266 <p><small><a name="note176" href="#note176">176)</a> Thus, a program that uses errno for error checking should set it to zero before a library function call,
9267 then inspect it before a subsequent library function call. Of course, a library function can save the
9268 value of errno on entry and then set it to zero, as long as the original value is restored if errno's
9269 value is still zero just before the return.
9271 <p><small><a name="note177" href="#note177">177)</a> See ''future library directions'' (<a href="#7.26.3">7.26.3</a>).
9274 <h3><a name="7.6" href="#7.6">7.6 Floating-point environment <fenv.h></a></h3>
9276 The header <a href="#7.6"><fenv.h></a> declares two types and several macros and functions to provide
9277 access to the floating-point environment. The floating-point environment refers
9278 collectively to any floating-point status flags and control modes supported by the
9279 implementation.<sup><a href="#note178"><b>178)</b></a></sup> A floating-point status flag is a system variable whose value is set
9280 (but never cleared) when a floating-point exception is raised, which occurs as a side effect
9281 of exceptional floating-point arithmetic to provide auxiliary information.<sup><a href="#note179"><b>179)</b></a></sup> A floating-
9282 point control mode is a system variable whose value may be set by the user to affect the
9283 subsequent behavior of floating-point arithmetic.
9285 Certain programming conventions support the intended model of use for the floating-
9286 point environment:<sup><a href="#note180"><b>180)</b></a></sup>
9288 <li> a function call does not alter its caller's floating-point control modes, clear its caller's
9289 floating-point status flags, nor depend on the state of its caller's floating-point status
9290 flags unless the function is so documented;
9291 <li> a function call is assumed to require default floating-point control modes, unless its
9292 documentation promises otherwise;
9293 <li> a function call is assumed to have the potential for raising floating-point exceptions,
9294 unless its documentation promises otherwise.
9300 represents the entire floating-point environment.
9305 represents the floating-point status flags collectively, including any status the
9306 implementation associates with the flags.
9320 is defined if and only if the implementation supports the floating-point exception by
9321 means of the functions in 7.6.2.<sup><a href="#note181"><b>181)</b></a></sup> Additional implementation-defined floating-point
9322 exceptions, with macro definitions beginning with FE_ and an uppercase letter, may also
9323 be specified by the implementation. The defined macros expand to integer constant
9324 expressions with values such that bitwise ORs of all combinations of the macros result in
9325 distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
9326 zero.<sup><a href="#note182"><b>182)</b></a></sup>
9331 is simply the bitwise OR of all floating-point exception macros defined by the
9332 implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
9340 is defined if and only if the implementation supports getting and setting the represented
9341 rounding direction by means of the fegetround and fesetround functions.
9342 Additional implementation-defined rounding directions, with macro definitions beginning
9343 with FE_ and an uppercase letter, may also be specified by the implementation. The
9344 defined macros expand to integer constant expressions whose values are distinct
9345 nonnegative values.<sup><a href="#note183"><b>183)</b></a></sup>
9354 represents the default floating-point environment -- the one installed at program startup
9356 <li> and has type ''pointer to const-qualified fenv_t''. It can be used as an argument to
9358 <a href="#7.6"><fenv.h></a> functions that manage the floating-point environment.
9360 Additional implementation-defined environments, with macro definitions beginning with
9361 FE_ and an uppercase letter, and having type ''pointer to const-qualified fenv_t'', may
9362 also be specified by the implementation.
9365 <p><small><a name="note178" href="#note178">178)</a> This header is designed to support the floating-point exception status flags and directed-rounding
9366 control modes required by IEC 60559, and other similar floating-point state information. Also it is
9367 designed to facilitate code portability among all systems.
9369 <p><small><a name="note179" href="#note179">179)</a> A floating-point status flag is not an object and can be set more than once within an expression.
9371 <p><small><a name="note180" href="#note180">180)</a> With these conventions, a programmer can safely assume default floating-point control modes (or be
9372 unaware of them). The responsibilities associated with accessing the floating-point environment fall
9373 on the programmer or program that does so explicitly.
9375 <p><small><a name="note181" href="#note181">181)</a> The implementation supports an exception if there are circumstances where a call to at least one of the
9376 functions in <a href="#7.6.2">7.6.2</a>, using the macro as the appropriate argument, will succeed. It is not necessary for
9377 all the functions to succeed all the time.
9379 <p><small><a name="note182" href="#note182">182)</a> The macros should be distinct powers of two.
9381 <p><small><a name="note183" href="#note183">183)</a> Even though the rounding direction macros may expand to constants corresponding to the values of
9382 FLT_ROUNDS, they are not required to do so.
9385 <h4><a name="7.6.1" href="#7.6.1">7.6.1 The FENV_ACCESS pragma</a></h4>
9389 #include <a href="#7.6"><fenv.h></a>
9390 #pragma STDC FENV_ACCESS on-off-switch</pre>
9391 <h6>Description</h6>
9393 The FENV_ACCESS pragma provides a means to inform the implementation when a
9394 program might access the floating-point environment to test floating-point status flags or
9395 run under non-default floating-point control modes.<sup><a href="#note184"><b>184)</b></a></sup> The pragma shall occur either
9396 outside external declarations or preceding all explicit declarations and statements inside a
9397 compound statement. When outside external declarations, the pragma takes effect from
9398 its occurrence until another FENV_ACCESS pragma is encountered, or until the end of
9399 the translation unit. When inside a compound statement, the pragma takes effect from its
9400 occurrence until another FENV_ACCESS pragma is encountered (including within a
9401 nested compound statement), or until the end of the compound statement; at the end of a
9402 compound statement the state for the pragma is restored to its condition just before the
9403 compound statement. If this pragma is used in any other context, the behavior is
9404 undefined. If part of a program tests floating-point status flags, sets floating-point control
9405 modes, or runs under non-default mode settings, but was translated with the state for the
9406 FENV_ACCESS pragma ''off'', the behavior is undefined. The default state (''on'' or
9407 ''off'') for the pragma is implementation-defined. (When execution passes from a part of
9408 the program translated with FENV_ACCESS ''off'' to a part translated with
9409 FENV_ACCESS ''on'', the state of the floating-point status flags is unspecified and the
9410 floating-point control modes have their default settings.)
9420 #include <a href="#7.6"><fenv.h></a>
9423 #pragma STDC FENV_ACCESS ON
9431 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
9432 x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
9433 contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.<sup><a href="#note185"><b>185)</b></a></sup>
9437 <p><small><a name="note184" href="#note184">184)</a> The purpose of the FENV_ACCESS pragma is to allow certain optimizations that could subvert flag
9438 tests and mode changes (e.g., global common subexpression elimination, code motion, and constant
9439 folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default
9440 modes are in effect and the flags are not tested.
9442 <p><small><a name="note185" href="#note185">185)</a> The side effects impose a temporal ordering that requires two evaluations of x + 1. On the other
9443 hand, without the #pragma STDC FENV_ACCESS ON pragma, and assuming the default state is
9444 ''off'', just one evaluation of x + 1 would suffice.
9447 <h4><a name="7.6.2" href="#7.6.2">7.6.2 Floating-point exceptions</a></h4>
9449 The following functions provide access to the floating-point status flags.<sup><a href="#note186"><b>186)</b></a></sup> The int
9450 input argument for the functions represents a subset of floating-point exceptions, and can
9451 be zero or the bitwise OR of one or more floating-point exception macros, for example
9452 FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
9453 functions is undefined.
9456 <p><small><a name="note186" href="#note186">186)</a> The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
9457 abstraction of flags that are either set or clear. An implementation may endow floating-point status
9458 flags with more information -- for example, the address of the code which first raised the floating-
9459 point exception; the functions fegetexceptflag and fesetexceptflag deal with the full
9463 <h5><a name="7.6.2.1" href="#7.6.2.1">7.6.2.1 The feclearexcept function</a></h5>
9467 #include <a href="#7.6"><fenv.h></a>
9468 int feclearexcept(int excepts);</pre>
9469 <h6>Description</h6>
9471 The feclearexcept function attempts to clear the supported floating-point exceptions
9472 represented by its argument.
9475 The feclearexcept function returns zero if the excepts argument is zero or if all
9476 the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
9481 <h5><a name="7.6.2.2" href="#7.6.2.2">7.6.2.2 The fegetexceptflag function</a></h5>
9485 #include <a href="#7.6"><fenv.h></a>
9486 int fegetexceptflag(fexcept_t *flagp,
9488 <h6>Description</h6>
9490 The fegetexceptflag function attempts to store an implementation-defined
9491 representation of the states of the floating-point status flags indicated by the argument
9492 excepts in the object pointed to by the argument flagp.
9495 The fegetexceptflag function returns zero if the representation was successfully
9496 stored. Otherwise, it returns a nonzero value.
9498 <h5><a name="7.6.2.3" href="#7.6.2.3">7.6.2.3 The feraiseexcept function</a></h5>
9502 #include <a href="#7.6"><fenv.h></a>
9503 int feraiseexcept(int excepts);</pre>
9504 <h6>Description</h6>
9506 The feraiseexcept function attempts to raise the supported floating-point exceptions
9507 represented by its argument.<sup><a href="#note187"><b>187)</b></a></sup> The order in which these floating-point exceptions are
9508 raised is unspecified, except as stated in <a href="#F.7.6">F.7.6</a>. Whether the feraiseexcept function
9509 additionally raises the ''inexact'' floating-point exception whenever it raises the
9510 ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
9513 The feraiseexcept function returns zero if the excepts argument is zero or if all
9514 the specified exceptions were successfully raised. Otherwise, it returns a nonzero value.
9522 <p><small><a name="note187" href="#note187">187)</a> The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations.
9523 Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
9524 in <a href="#F.7.6">F.7.6</a> is in the same spirit.
9527 <h5><a name="7.6.2.4" href="#7.6.2.4">7.6.2.4 The fesetexceptflag function</a></h5>
9531 #include <a href="#7.6"><fenv.h></a>
9532 int fesetexceptflag(const fexcept_t *flagp,
9534 <h6>Description</h6>
9536 The fesetexceptflag function attempts to set the floating-point status flags
9537 indicated by the argument excepts to the states stored in the object pointed to by
9538 flagp. The value of *flagp shall have been set by a previous call to
9539 fegetexceptflag whose second argument represented at least those floating-point
9540 exceptions represented by the argument excepts. This function does not raise floating-
9541 point exceptions, but only sets the state of the flags.
9544 The fesetexceptflag function returns zero if the excepts argument is zero or if
9545 all the specified flags were successfully set to the appropriate state. Otherwise, it returns
9548 <h5><a name="7.6.2.5" href="#7.6.2.5">7.6.2.5 The fetestexcept function</a></h5>
9552 #include <a href="#7.6"><fenv.h></a>
9553 int fetestexcept(int excepts);</pre>
9554 <h6>Description</h6>
9556 The fetestexcept function determines which of a specified subset of the floating-
9557 point exception flags are currently set. The excepts argument specifies the floating-
9558 point status flags to be queried.<sup><a href="#note188"><b>188)</b></a></sup>
9561 The fetestexcept function returns the value of the bitwise OR of the floating-point
9562 exception macros corresponding to the currently set floating-point exceptions included in
9565 EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set:
9572 #include <a href="#7.6"><fenv.h></a>
9575 #pragma STDC FENV_ACCESS ON
9577 feclearexcept(FE_INVALID | FE_OVERFLOW);
9578 // maybe raise exceptions
9579 set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
9580 if (set_excepts & FE_INVALID) f();
9581 if (set_excepts & FE_OVERFLOW) g();
9587 <p><small><a name="note188" href="#note188">188)</a> This mechanism allows testing several floating-point exceptions with just one function call.
9590 <h4><a name="7.6.3" href="#7.6.3">7.6.3 Rounding</a></h4>
9592 The fegetround and fesetround functions provide control of rounding direction
9595 <h5><a name="7.6.3.1" href="#7.6.3.1">7.6.3.1 The fegetround function</a></h5>
9599 #include <a href="#7.6"><fenv.h></a>
9600 int fegetround(void);</pre>
9601 <h6>Description</h6>
9603 The fegetround function gets the current rounding direction.
9606 The fegetround function returns the value of the rounding direction macro
9607 representing the current rounding direction or a negative value if there is no such
9608 rounding direction macro or the current rounding direction is not determinable.
9610 <h5><a name="7.6.3.2" href="#7.6.3.2">7.6.3.2 The fesetround function</a></h5>
9614 #include <a href="#7.6"><fenv.h></a>
9615 int fesetround(int round);</pre>
9616 <h6>Description</h6>
9618 The fesetround function establishes the rounding direction represented by its
9619 argument round. If the argument is not equal to the value of a rounding direction macro,
9620 the rounding direction is not changed.
9623 The fesetround function returns zero if and only if the requested rounding direction
9627 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the
9628 rounding direction fails.
9630 #include <a href="#7.6"><fenv.h></a>
9631 #include <a href="#7.2"><assert.h></a>
9632 void f(int round_dir)
9634 #pragma STDC FENV_ACCESS ON
9637 save_round = fegetround();
9638 setround_ok = fesetround(round_dir);
9639 assert(setround_ok == 0);
9641 fesetround(save_round);
9646 <h4><a name="7.6.4" href="#7.6.4">7.6.4 Environment</a></h4>
9648 The functions in this section manage the floating-point environment -- status flags and
9649 control modes -- as one entity.
9651 <h5><a name="7.6.4.1" href="#7.6.4.1">7.6.4.1 The fegetenv function</a></h5>
9655 #include <a href="#7.6"><fenv.h></a>
9656 int fegetenv(fenv_t *envp);</pre>
9657 <h6>Description</h6>
9659 The fegetenv function attempts to store the current floating-point environment in the
9660 object pointed to by envp.
9663 The fegetenv function returns zero if the environment was successfully stored.
9664 Otherwise, it returns a nonzero value.
9666 <h5><a name="7.6.4.2" href="#7.6.4.2">7.6.4.2 The feholdexcept function</a></h5>
9670 #include <a href="#7.6"><fenv.h></a>
9671 int feholdexcept(fenv_t *envp);</pre>
9672 <h6>Description</h6>
9674 The feholdexcept function saves the current floating-point environment in the object
9675 pointed to by envp, clears the floating-point status flags, and then installs a non-stop
9676 (continue on floating-point exceptions) mode, if available, for all floating-point
9677 exceptions.<sup><a href="#note189"><b>189)</b></a></sup>
9681 The feholdexcept function returns zero if and only if non-stop floating-point
9682 exception handling was successfully installed.
9685 <p><small><a name="note189" href="#note189">189)</a> IEC 60559 systems have a default non-stop mode, and typically at least one other mode for trap
9686 handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For
9687 such systems, the feholdexcept function can be used in conjunction with the feupdateenv
9688 function to write routines that hide spurious floating-point exceptions from their callers.
9691 <h5><a name="7.6.4.3" href="#7.6.4.3">7.6.4.3 The fesetenv function</a></h5>
9695 #include <a href="#7.6"><fenv.h></a>
9696 int fesetenv(const fenv_t *envp);</pre>
9697 <h6>Description</h6>
9699 The fesetenv function attempts to establish the floating-point environment represented
9700 by the object pointed to by envp. The argument envp shall point to an object set by a
9701 call to fegetenv or feholdexcept, or equal a floating-point environment macro.
9702 Note that fesetenv merely installs the state of the floating-point status flags
9703 represented through its argument, and does not raise these floating-point exceptions.
9706 The fesetenv function returns zero if the environment was successfully established.
9707 Otherwise, it returns a nonzero value.
9709 <h5><a name="7.6.4.4" href="#7.6.4.4">7.6.4.4 The feupdateenv function</a></h5>
9713 #include <a href="#7.6"><fenv.h></a>
9714 int feupdateenv(const fenv_t *envp);</pre>
9715 <h6>Description</h6>
9717 The feupdateenv function attempts to save the currently raised floating-point
9718 exceptions in its automatic storage, install the floating-point environment represented by
9719 the object pointed to by envp, and then raise the saved floating-point exceptions. The
9720 argument envp shall point to an object set by a call to feholdexcept or fegetenv,
9721 or equal a floating-point environment macro.
9724 The feupdateenv function returns zero if all the actions were successfully carried out.
9725 Otherwise, it returns a nonzero value.
9732 EXAMPLE Hide spurious underflow floating-point exceptions:
9735 #include <a href="#7.6"><fenv.h></a>
9738 #pragma STDC FENV_ACCESS ON
9741 if (feholdexcept(&save_env))
9742 return /* indication of an environmental problem */;
9744 if (/* test spurious underflow */)
9745 if (feclearexcept(FE_UNDERFLOW))
9746 return /* indication of an environmental problem */;
9747 if (feupdateenv(&save_env))
9748 return /* indication of an environmental problem */;
9752 <h3><a name="7.7" href="#7.7">7.7 Characteristics of floating types <float.h></a></h3>
9754 The header <a href="#7.7"><float.h></a> defines several macros that expand to various limits and
9755 parameters of the standard floating-point types.
9757 The macros, their meanings, and the constraints (or restrictions) on their values are listed
9758 in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
9761 <h3><a name="7.8" href="#7.8">7.8 Format conversion of integer types <inttypes.h></a></h3>
9763 The header <a href="#7.8"><inttypes.h></a> includes the header <a href="#7.18"><stdint.h></a> and extends it with
9764 additional facilities provided by hosted implementations.
9766 It declares functions for manipulating greatest-width integers and converting numeric
9767 character strings to greatest-width integers, and it declares the type
9770 which is a structure type that is the type of the value returned by the imaxdiv function.
9771 For each type declared in <a href="#7.18"><stdint.h></a>, it defines corresponding macros for conversion
9772 specifiers for use with the formatted input/output functions.<sup><a href="#note190"><b>190)</b></a></sup>
9773 <p><b> Forward references</b>: integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>), formatted input/output
9774 functions (<a href="#7.19.6">7.19.6</a>), formatted wide character input/output functions (<a href="#7.24.2">7.24.2</a>).
9777 <p><small><a name="note190" href="#note190">190)</a> See ''future library directions'' (<a href="#7.26.4">7.26.4</a>).
9780 <h4><a name="7.8.1" href="#7.8.1">7.8.1 Macros for format specifiers</a></h4>
9782 Each of the following object-like macros<sup><a href="#note191"><b>191)</b></a></sup> expands to a character string literal
9783 containing a conversion specifier, possibly modified by a length modifier, suitable for use
9784 within the format argument of a formatted input/output function when converting the
9785 corresponding integer type. These macro names have the general form of PRI (character
9786 string literals for the fprintf and fwprintf family) or SCN (character string literals
9787 for the fscanf and fwscanf family),<sup><a href="#note192"><b>192)</b></a></sup> followed by the conversion specifier,
9788 followed by a name corresponding to a similar type name in <a href="#7.18.1">7.18.1</a>. In these names, N
9789 represents the width of the type as described in <a href="#7.18.1">7.18.1</a>. For example, PRIdFAST32 can
9790 be used in a format string to print the value of an integer of type int_fast32_t.
9792 The fprintf macros for signed integers are:
9794 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
9795 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR</pre>
9802 The fprintf macros for unsigned integers are:
9805 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
9806 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
9807 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
9808 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR</pre>
9809 The fscanf macros for signed integers are:
9812 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
9813 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR</pre>
9814 The fscanf macros for unsigned integers are:
9817 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
9818 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
9819 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR</pre>
9820 For each type that the implementation provides in <a href="#7.18"><stdint.h></a>, the corresponding
9821 fprintf macros shall be defined and the corresponding fscanf macros shall be
9822 defined unless the implementation does not have a suitable fscanf length modifier for
9827 #include <a href="#7.8"><inttypes.h></a>
9828 #include <a href="#7.24"><wchar.h></a>
9831 uintmax_t i = UINTMAX_MAX; // this type always exists
9832 wprintf(L"The largest integer value is %020"
9839 <p><small><a name="note191" href="#note191">191)</a> C++ implementations should define these macros only when __STDC_FORMAT_MACROS is defined
9840 before <a href="#7.8"><inttypes.h></a> is included.
9842 <p><small><a name="note192" href="#note192">192)</a> Separate macros are given for use with fprintf and fscanf functions because, in the general case,
9843 different format specifiers may be required for fprintf and fscanf, even when the type is the
9847 <h4><a name="7.8.2" href="#7.8.2">7.8.2 Functions for greatest-width integer types</a></h4>
9849 <h5><a name="7.8.2.1" href="#7.8.2.1">7.8.2.1 The imaxabs function</a></h5>
9853 #include <a href="#7.8"><inttypes.h></a>
9854 intmax_t imaxabs(intmax_t j);</pre>
9855 <h6>Description</h6>
9857 The imaxabs function computes the absolute value of an integer j. If the result cannot
9858 be represented, the behavior is undefined.<sup><a href="#note193"><b>193)</b></a></sup>
9865 The imaxabs function returns the absolute value.
9868 <p><small><a name="note193" href="#note193">193)</a> The absolute value of the most negative number cannot be represented in two's complement.
9871 <h5><a name="7.8.2.2" href="#7.8.2.2">7.8.2.2 The imaxdiv function</a></h5>
9875 #include <a href="#7.8"><inttypes.h></a>
9876 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);</pre>
9877 <h6>Description</h6>
9879 The imaxdiv function computes numer / denom and numer % denom in a single
9883 The imaxdiv function returns a structure of type imaxdiv_t comprising both the
9884 quotient and the remainder. The structure shall contain (in either order) the members
9885 quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
9886 either part of the result cannot be represented, the behavior is undefined.
9888 <h5><a name="7.8.2.3" href="#7.8.2.3">7.8.2.3 The strtoimax and strtoumax functions</a></h5>
9892 #include <a href="#7.8"><inttypes.h></a>
9893 intmax_t strtoimax(const char * restrict nptr,
9894 char ** restrict endptr, int base);
9895 uintmax_t strtoumax(const char * restrict nptr,
9896 char ** restrict endptr, int base);</pre>
9897 <h6>Description</h6>
9899 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll,
9900 strtoul, and strtoull functions, except that the initial portion of the string is
9901 converted to intmax_t and uintmax_t representation, respectively.
9904 The strtoimax and strtoumax functions return the converted value, if any. If no
9905 conversion could be performed, zero is returned. If the correct value is outside the range
9906 of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned
9907 (according to the return type and sign of the value, if any), and the value of the macro
9908 ERANGE is stored in errno.
9909 <p><b> Forward references</b>: the strtol, strtoll, strtoul, and strtoull functions
9910 (<a href="#7.20.1.4">7.20.1.4</a>).
9913 <h5><a name="7.8.2.4" href="#7.8.2.4">7.8.2.4 The wcstoimax and wcstoumax functions</a></h5>
9917 #include <a href="#7.17"><stddef.h></a> // for wchar_t
9918 #include <a href="#7.8"><inttypes.h></a>
9919 intmax_t wcstoimax(const wchar_t * restrict nptr,
9920 wchar_t ** restrict endptr, int base);
9921 uintmax_t wcstoumax(const wchar_t * restrict nptr,
9922 wchar_t ** restrict endptr, int base);</pre>
9923 <h6>Description</h6>
9925 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll,
9926 wcstoul, and wcstoull functions except that the initial portion of the wide string is
9927 converted to intmax_t and uintmax_t representation, respectively.
9930 The wcstoimax function returns the converted value, if any. If no conversion could be
9931 performed, zero is returned. If the correct value is outside the range of representable
9932 values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the
9933 return type and sign of the value, if any), and the value of the macro ERANGE is stored in
9935 <p><b> Forward references</b>: the wcstol, wcstoll, wcstoul, and wcstoull functions
9936 (<a href="#7.24.4.1.2">7.24.4.1.2</a>).
9939 <h3><a name="7.9" href="#7.9">7.9 Alternative spellings <iso646.h></a></h3>
9941 The header <a href="#7.9"><iso646.h></a> defines the following eleven macros (on the left) that expand
9942 to the corresponding tokens (on the right):
9957 <h3><a name="7.10" href="#7.10">7.10 Sizes of integer types <limits.h></a></h3>
9959 The header <a href="#7.10"><limits.h></a> defines several macros that expand to various limits and
9960 parameters of the standard integer types.
9962 The macros, their meanings, and the constraints (or restrictions) on their values are listed
9963 in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
9966 <h3><a name="7.11" href="#7.11">7.11 Localization <locale.h></a></h3>
9968 The header <a href="#7.11"><locale.h></a> declares two functions, one type, and defines several macros.
9973 which contains members related to the formatting of numeric values. The structure shall
9974 contain at least the following members, in any order. The semantics of the members and
9975 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
9976 the values specified in the comments.
9980 char *decimal_point; // "."
9981 char *thousands_sep; // ""
9982 char *grouping; // ""
9983 char *mon_decimal_point; // ""
9984 char *mon_thousands_sep; // ""
9985 char *mon_grouping; // ""
9986 char *positive_sign; // ""
9987 char *negative_sign; // ""
9988 char *currency_symbol; // ""
9989 char frac_digits; // CHAR_MAX
9990 char p_cs_precedes; // CHAR_MAX
9991 char n_cs_precedes; // CHAR_MAX
9992 char p_sep_by_space; // CHAR_MAX
9993 char n_sep_by_space; // CHAR_MAX
9994 char p_sign_posn; // CHAR_MAX
9995 char n_sign_posn; // CHAR_MAX
9996 char *int_curr_symbol; // ""
9997 char int_frac_digits; // CHAR_MAX
9998 char int_p_cs_precedes; // CHAR_MAX
9999 char int_n_cs_precedes; // CHAR_MAX
10000 char int_p_sep_by_space; // CHAR_MAX
10001 char int_n_sep_by_space; // CHAR_MAX
10002 char int_p_sign_posn; // CHAR_MAX
10003 char int_n_sign_posn; // CHAR_MAX</pre>
10004 The macros defined are NULL (described in <a href="#7.17">7.17</a>); and
10012 which expand to integer constant expressions with distinct values, suitable for use as the
10013 first argument to the setlocale function.<sup><a href="#note194"><b>194)</b></a></sup> Additional macro definitions, beginning
10014 with the characters LC_ and an uppercase letter,<sup><a href="#note195"><b>195)</b></a></sup> may also be specified by the
10018 <p><small><a name="note194" href="#note194">194)</a> ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.
10020 <p><small><a name="note195" href="#note195">195)</a> See ''future library directions'' (<a href="#7.26.5">7.26.5</a>).
10023 <h4><a name="7.11.1" href="#7.11.1">7.11.1 Locale control</a></h4>
10025 <h5><a name="7.11.1.1" href="#7.11.1.1">7.11.1.1 The setlocale function</a></h5>
10029 #include <a href="#7.11"><locale.h></a>
10030 char *setlocale(int category, const char *locale);</pre>
10031 <h6>Description</h6>
10033 The setlocale function selects the appropriate portion of the program's locale as
10034 specified by the category and locale arguments. The setlocale function may be
10035 used to change or query the program's entire current locale or portions thereof. The value
10036 LC_ALL for category names the program's entire locale; the other values for
10037 category name only a portion of the program's locale. LC_COLLATE affects the
10038 behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of
10039 the character handling functions<sup><a href="#note196"><b>196)</b></a></sup> and the multibyte and wide character functions.
10040 LC_MONETARY affects the monetary formatting information returned by the
10041 localeconv function. LC_NUMERIC affects the decimal-point character for the
10042 formatted input/output functions and the string conversion functions, as well as the
10043 nonmonetary formatting information returned by the localeconv function. LC_TIME
10044 affects the behavior of the strftime and wcsftime functions.
10046 A value of "C" for locale specifies the minimal environment for C translation; a value
10047 of "" for locale specifies the locale-specific native environment. Other
10048 implementation-defined strings may be passed as the second argument to setlocale.
10052 At program startup, the equivalent of
10054 setlocale(LC_ALL, "C");</pre>
10057 The implementation shall behave as if no library function calls the setlocale function.
10060 If a pointer to a string is given for locale and the selection can be honored, the
10061 setlocale function returns a pointer to the string associated with the specified
10062 category for the new locale. If the selection cannot be honored, the setlocale
10063 function returns a null pointer and the program's locale is not changed.
10065 A null pointer for locale causes the setlocale function to return a pointer to the
10066 string associated with the category for the program's current locale; the program's
10067 locale is not changed.<sup><a href="#note197"><b>197)</b></a></sup>
10069 The pointer to string returned by the setlocale function is such that a subsequent call
10070 with that string value and its associated category will restore that part of the program's
10071 locale. The string pointed to shall not be modified by the program, but may be
10072 overwritten by a subsequent call to the setlocale function.
10073 <p><b> Forward references</b>: formatted input/output functions (<a href="#7.19.6">7.19.6</a>), multibyte/wide
10074 character conversion functions (<a href="#7.20.7">7.20.7</a>), multibyte/wide string conversion functions
10075 (<a href="#7.20.8">7.20.8</a>), numeric conversion functions (<a href="#7.20.1">7.20.1</a>), the strcoll function (<a href="#7.21.4.3">7.21.4.3</a>), the
10076 strftime function (<a href="#7.23.3.5">7.23.3.5</a>), the strxfrm function (<a href="#7.21.4.5">7.21.4.5</a>).
10079 <p><small><a name="note196" href="#note196">196)</a> The only functions in <a href="#7.4">7.4</a> whose behavior is not affected by the current locale are isdigit and
10082 <p><small><a name="note197" href="#note197">197)</a> The implementation shall arrange to encode in a string the various categories due to a heterogeneous
10083 locale when category has the value LC_ALL.
10086 <h4><a name="7.11.2" href="#7.11.2">7.11.2 Numeric formatting convention inquiry</a></h4>
10088 <h5><a name="7.11.2.1" href="#7.11.2.1">7.11.2.1 The localeconv function</a></h5>
10092 #include <a href="#7.11"><locale.h></a>
10093 struct lconv *localeconv(void);</pre>
10094 <h6>Description</h6>
10096 The localeconv function sets the components of an object with type struct lconv
10097 with values appropriate for the formatting of numeric quantities (monetary and otherwise)
10098 according to the rules of the current locale.
10100 The members of the structure with type char * are pointers to strings, any of which
10101 (except decimal_point) can point to "", to indicate that the value is not available in
10102 the current locale or is of zero length. Apart from grouping and mon_grouping, the
10105 strings shall start and end in the initial shift state. The members with type char are
10106 nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not
10107 available in the current locale. The members include the following:
10108 char *decimal_point
10110 The decimal-point character used to format nonmonetary quantities.</pre>
10111 char *thousands_sep
10113 The character used to separate groups of digits before the decimal-point
10114 character in formatted nonmonetary quantities.</pre>
10117 A string whose elements indicate the size of each group of digits in
10118 formatted nonmonetary quantities.</pre>
10119 char *mon_decimal_point
10121 The decimal-point used to format monetary quantities.</pre>
10122 char *mon_thousands_sep
10124 The separator for groups of digits before the decimal-point in formatted
10125 monetary quantities.</pre>
10128 A string whose elements indicate the size of each group of digits in
10129 formatted monetary quantities.</pre>
10130 char *positive_sign
10132 The string used to indicate a nonnegative-valued formatted monetary
10134 char *negative_sign
10136 The string used to indicate a negative-valued formatted monetary quantity.</pre>
10137 char *currency_symbol
10139 The local currency symbol applicable to the current locale.</pre>
10142 The number of fractional digits (those after the decimal-point) to be
10143 displayed in a locally formatted monetary quantity.</pre>
10146 Set to 1 or 0 if the currency_symbol respectively precedes or
10147 succeeds the value for a nonnegative locally formatted monetary quantity.</pre>
10151 Set to 1 or 0 if the currency_symbol respectively precedes or
10152 succeeds the value for a negative locally formatted monetary quantity.</pre>
10153 char p_sep_by_space
10155 Set to a value indicating the separation of the currency_symbol, the
10156 sign string, and the value for a nonnegative locally formatted monetary
10158 char n_sep_by_space
10160 Set to a value indicating the separation of the currency_symbol, the
10161 sign string, and the value for a negative locally formatted monetary
10165 Set to a value indicating the positioning of the positive_sign for a
10166 nonnegative locally formatted monetary quantity.</pre>
10169 Set to a value indicating the positioning of the negative_sign for a
10170 negative locally formatted monetary quantity.</pre>
10171 char *int_curr_symbol
10173 The international currency symbol applicable to the current locale. The
10174 first three characters contain the alphabetic international currency symbol
10175 in accordance with those specified in ISO 4217. The fourth character
10176 (immediately preceding the null character) is the character used to separate
10177 the international currency symbol from the monetary quantity.</pre>
10178 char int_frac_digits
10180 The number of fractional digits (those after the decimal-point) to be
10181 displayed in an internationally formatted monetary quantity.</pre>
10182 char int_p_cs_precedes
10184 Set to 1 or 0 if the int_curr_symbol respectively precedes or
10185 succeeds the value for a nonnegative internationally formatted monetary
10187 char int_n_cs_precedes
10189 Set to 1 or 0 if the int_curr_symbol respectively precedes or
10190 succeeds the value for a negative internationally formatted monetary
10192 char int_p_sep_by_space
10195 Set to a value indicating the separation of the int_curr_symbol, the
10196 sign string, and the value for a nonnegative internationally formatted
10197 monetary quantity.</pre>
10198 char int_n_sep_by_space
10200 Set to a value indicating the separation of the int_curr_symbol, the
10201 sign string, and the value for a negative internationally formatted monetary
10203 char int_p_sign_posn
10205 Set to a value indicating the positioning of the positive_sign for a
10206 nonnegative internationally formatted monetary quantity.</pre>
10207 char int_n_sign_posn
10210 Set to a value indicating the positioning of the negative_sign for a
10211 negative internationally formatted monetary quantity.</pre>
10212 The elements of grouping and mon_grouping are interpreted according to the
10214 CHAR_MAX No further grouping is to be performed.
10215 0 The previous element is to be repeatedly used for the remainder of the
10218 other The integer value is the number of digits that compose the current group.
10221 The next element is examined to determine the size of the next group of
10222 digits before the current group.</pre>
10223 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space,
10224 and int_n_sep_by_space are interpreted according to the following:
10225 0 No space separates the currency symbol and value.
10226 1 If the currency symbol and sign string are adjacent, a space separates them from the
10228 value; otherwise, a space separates the currency symbol from the value.</pre>
10229 2 If the currency symbol and sign string are adjacent, a space separates them;
10231 otherwise, a space separates the sign string from the value.</pre>
10232 For int_p_sep_by_space and int_n_sep_by_space, the fourth character of
10233 int_curr_symbol is used instead of a space.
10235 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and
10236 int_n_sign_posn are interpreted according to the following:
10237 0 Parentheses surround the quantity and currency symbol.
10238 1 The sign string precedes the quantity and currency symbol.
10239 2 The sign string succeeds the quantity and currency symbol.
10240 3 The sign string immediately precedes the currency symbol.
10241 4 The sign string immediately succeeds the currency symbol.
10244 The implementation shall behave as if no library function calls the localeconv
10248 The localeconv function returns a pointer to the filled-in object. The structure
10249 pointed to by the return value shall not be modified by the program, but may be
10250 overwritten by a subsequent call to the localeconv function. In addition, calls to the
10251 setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may
10252 overwrite the contents of the structure.
10254 EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format
10255 monetary quantities.
10257 Local format International format</pre>
10259 Country Positive Negative Positive Negative
10261 Country1 1.234,56 mk -1.234,56 mk FIM 1.234,56 FIM -1.234,56
10262 Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234
10263 Country3 fl. 1.234,56 fl. -1.234,56 NLG 1.234,56 NLG -1.234,56
10264 Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C
10266 For these four countries, the respective values for the monetary members of the structure returned by
10267 localeconv could be:
10269 Country1 Country2 Country3 Country4</pre>
10271 mon_decimal_point "," "" "," "."
10272 mon_thousands_sep "." "." "." ","
10273 mon_grouping "\3" "\3" "\3" "\3"
10274 positive_sign "" "" "" ""
10275 negative_sign "-" "-" "-" "C"
10276 currency_symbol "mk" "L." "\u0192" "SFrs."
10277 frac_digits 2 0 2 2
10278 p_cs_precedes 0 1 1 1
10279 n_cs_precedes 0 1 1 1
10280 p_sep_by_space 1 0 1 0
10281 n_sep_by_space 1 0 2 0
10282 p_sign_posn 1 1 1 1
10283 n_sign_posn 1 1 4 2
10284 int_curr_symbol "FIM " "ITL " "NLG " "CHF "
10285 int_frac_digits 2 0 2 2
10286 int_p_cs_precedes 1 1 1 1
10287 int_n_cs_precedes 1 1 1 1
10288 int_p_sep_by_space 1 1 1 1
10289 int_n_sep_by_space 2 1 2 1
10290 int_p_sign_posn 1 1 1 1
10291 int_n_sign_posn 4 1 4 2
10294 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
10295 affect the formatted value.
10297 p_sep_by_space</pre>
10299 p_cs_precedes p_sign_posn 0 1 2
10302 0 0 (<a href="#1.25">1.25</a>$) (<a href="#1.25">1.25</a> $) (<a href="#1.25">1.25</a>$)
10303 1 +1.25$ +1.25 $ + <a href="#1.25">1.25</a>$
10304 2 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +
10305 3 <a href="#1.25">1.25</a>+$ <a href="#1.25">1.25</a> +$ <a href="#1.25">1.25</a>+ $
10306 4 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +</pre>
10310 1 0 ($1.25) ($ <a href="#1.25">1.25</a>) ($1.25)
10311 1 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
10312 2 $1.25+ $ <a href="#1.25">1.25</a>+ $1.25 +
10313 3 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
10314 4 $+1.25 $+ <a href="#1.25">1.25</a> $ +1.25</pre>
10316 <h3><a name="7.12" href="#7.12">7.12 Mathematics <math.h></a></h3>
10318 The header <a href="#7.12"><math.h></a> declares two types and many mathematical functions and defines
10319 several macros. Most synopses specify a family of functions consisting of a principal
10320 function with one or more double parameters, a double return value, or both; and
10321 other functions with the same name but with f and l suffixes, which are corresponding
10322 functions with float and long double parameters, return values, or both.<sup><a href="#note198"><b>198)</b></a></sup>
10323 Integer arithmetic functions and conversion functions are discussed later.
10329 are floating types at least as wide as float and double, respectively, and such that
10330 double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
10331 float_t and double_t are float and double, respectively; if
10332 FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
10333 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
10334 otherwise implementation-defined.<sup><a href="#note199"><b>199)</b></a></sup>
10339 expands to a positive double constant expression, not necessarily representable as a
10344 are respectively float and long double analogs of HUGE_VAL.<sup><a href="#note200"><b>200)</b></a></sup>
10349 expands to a constant expression of type float representing positive or unsigned
10350 infinity, if available; else to a positive constant of type float that overflows at
10355 translation time.<sup><a href="#note201"><b>201)</b></a></sup>
10360 is defined if and only if the implementation supports quiet NaNs for the float type. It
10361 expands to a constant expression of type float representing a quiet NaN.
10363 The number classification macros
10370 represent the mutually exclusive kinds of floating-point values. They expand to integer
10371 constant expressions with distinct values. Additional implementation-defined floating-
10372 point classifications, with macro definitions beginning with FP_ and an uppercase letter,
10373 may also be specified by the implementation.
10378 is optionally defined. If defined, it indicates that the fma function generally executes
10379 about as fast as, or faster than, a multiply and an add of double operands.<sup><a href="#note202"><b>202)</b></a></sup> The
10384 are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
10385 these macros expand to the integer constant 1.
10391 expand to integer constant expressions whose values are returned by ilogb(x) if x is
10392 zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
10393 -INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
10401 MATH_ERREXCEPT</pre>
10402 expand to the integer constants 1 and 2, respectively; the macro
10404 math_errhandling</pre>
10405 expands to an expression that has type int and the value MATH_ERRNO,
10406 MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is
10407 constant for the duration of the program. It is unspecified whether
10408 math_errhandling is a macro or an identifier with external linkage. If a macro
10409 definition is suppressed or a program defines an identifier with the name
10410 math_errhandling, the behavior is undefined. If the expression
10411 math_errhandling & MATH_ERREXCEPT can be nonzero, the implementation
10412 shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in
10413 <a href="#7.6"><fenv.h></a>.
10416 <p><small><a name="note198" href="#note198">198)</a> Particularly on systems with wide expression evaluation, a <a href="#7.12"><math.h></a> function might pass arguments
10417 and return values in wider format than the synopsis prototype indicates.
10419 <p><small><a name="note199" href="#note199">199)</a> The types float_t and double_t are intended to be the implementation's most efficient types at
10420 least as wide as float and double, respectively. For FLT_EVAL_METHOD equal 0, 1, or 2, the
10421 type float_t is the narrowest type used by the implementation to evaluate floating expressions.
10423 <p><small><a name="note200" href="#note200">200)</a> HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
10424 supports infinities.
10426 <p><small><a name="note201" href="#note201">201)</a> In this case, using INFINITY will violate the constraint in <a href="#6.4.4">6.4.4</a> and thus require a diagnostic.
10428 <p><small><a name="note202" href="#note202">202)</a> Typically, the FP_FAST_FMA macro is defined if and only if the fma function is implemented
10429 directly with a hardware multiply-add instruction. Software implementations are expected to be
10430 substantially slower.
10433 <h4><a name="7.12.1" href="#7.12.1">7.12.1 Treatment of error conditions</a></h4>
10435 The behavior of each of the functions in <a href="#7.12"><math.h></a> is specified for all representable
10436 values of its input arguments, except where stated otherwise. Each function shall execute
10437 as if it were a single operation without generating any externally visible exceptional
10440 For all functions, a domain error occurs if an input argument is outside the domain over
10441 which the mathematical function is defined. The description of each function lists any
10442 required domain errors; an implementation may define additional domain errors, provided
10443 that such errors are consistent with the mathematical definition of the function.<sup><a href="#note203"><b>203)</b></a></sup> On a
10444 domain error, the function returns an implementation-defined value; if the integer
10445 expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
10446 errno acquires the value EDOM; if the integer expression math_errhandling &
10447 MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised.
10449 Similarly, a range error occurs if the mathematical result of the function cannot be
10450 represented in an object of the specified type, due to extreme magnitude.
10452 A floating result overflows if the magnitude of the mathematical result is finite but so
10453 large that the mathematical result cannot be represented without extraordinary roundoff
10454 error in an object of the specified type. If a floating result overflows and default rounding
10455 is in effect, or if the mathematical result is an exact infinity from finite arguments (for
10456 example log(0.0)), then the function returns the value of the macro HUGE_VAL,
10460 HUGE_VALF, or HUGE_VALL according to the return type, with the same sign as the
10461 correct value of the function; if the integer expression math_errhandling &
10462 MATH_ERRNO is nonzero, the integer expression errno acquires the value ERANGE; if
10463 the integer expression math_errhandling & MATH_ERREXCEPT is nonzero, the
10464 ''divide-by-zero'' floating-point exception is raised if the mathematical result is an exact
10465 infinity and the ''overflow'' floating-point exception is raised otherwise.
10467 The result underflows if the magnitude of the mathematical result is so small that the
10468 mathematical result cannot be represented, without extraordinary roundoff error, in an
10469 object of the specified type.<sup><a href="#note204"><b>204)</b></a></sup> If the result underflows, the function returns an
10470 implementation-defined value whose magnitude is no greater than the smallest
10471 normalized positive number in the specified type; if the integer expression
10472 math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the
10473 value ERANGE is implementation-defined; if the integer expression
10474 math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow''
10475 floating-point exception is raised is implementation-defined.
10478 <p><small><a name="note203" href="#note203">203)</a> In an implementation that supports infinities, this allows an infinity as an argument to be a domain
10479 error if the mathematical domain of the function does not include the infinity.
10481 <p><small><a name="note204" href="#note204">204)</a> The term underflow here is intended to encompass both ''gradual underflow'' as in IEC 60559 and
10482 also ''flush-to-zero'' underflow.
10485 <h4><a name="7.12.2" href="#7.12.2">7.12.2 The FP_CONTRACT pragma</a></h4>
10489 #include <a href="#7.12"><math.h></a>
10490 #pragma STDC FP_CONTRACT on-off-switch</pre>
10491 <h6>Description</h6>
10493 The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
10494 state is ''off'') the implementation to contract expressions (<a href="#6.5">6.5</a>). Each pragma can occur
10495 either outside external declarations or preceding all explicit declarations and statements
10496 inside a compound statement. When outside external declarations, the pragma takes
10497 effect from its occurrence until another FP_CONTRACT pragma is encountered, or until
10498 the end of the translation unit. When inside a compound statement, the pragma takes
10499 effect from its occurrence until another FP_CONTRACT pragma is encountered
10500 (including within a nested compound statement), or until the end of the compound
10501 statement; at the end of a compound statement the state for the pragma is restored to its
10502 condition just before the compound statement. If this pragma is used in any other
10503 context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
10504 implementation-defined.
10511 <h4><a name="7.12.3" href="#7.12.3">7.12.3 Classification macros</a></h4>
10513 In the synopses in this subclause, real-floating indicates that the argument shall be an
10514 expression of real floating type.
10516 <h5><a name="7.12.3.1" href="#7.12.3.1">7.12.3.1 The fpclassify macro</a></h5>
10520 #include <a href="#7.12"><math.h></a>
10521 int fpclassify(real-floating x);</pre>
10522 <h6>Description</h6>
10524 The fpclassify macro classifies its argument value as NaN, infinite, normal,
10525 subnormal, zero, or into another implementation-defined category. First, an argument
10526 represented in a format wider than its semantic type is converted to its semantic type.
10527 Then classification is based on the type of the argument.<sup><a href="#note205"><b>205)</b></a></sup>
10530 The fpclassify macro returns the value of the number classification macro
10531 appropriate to the value of its argument.
10533 EXAMPLE The fpclassify macro might be implemented in terms of ordinary functions as
10535 #define fpclassify(x) \
10536 ((sizeof (x) == sizeof (float)) ? __fpclassifyf(x) : \
10537 (sizeof (x) == sizeof (double)) ? __fpclassifyd(x) : \
10538 __fpclassifyl(x))</pre>
10542 <p><small><a name="note205" href="#note205">205)</a> Since an expression can be evaluated with more range and precision than its type has, it is important to
10543 know the type that classification is based on. For example, a normal long double value might
10544 become subnormal when converted to double, and zero when converted to float.
10547 <h5><a name="7.12.3.2" href="#7.12.3.2">7.12.3.2 The isfinite macro</a></h5>
10551 #include <a href="#7.12"><math.h></a>
10552 int isfinite(real-floating x);</pre>
10553 <h6>Description</h6>
10555 The isfinite macro determines whether its argument has a finite value (zero,
10556 subnormal, or normal, and not infinite or NaN). First, an argument represented in a
10557 format wider than its semantic type is converted to its semantic type. Then determination
10558 is based on the type of the argument.
10566 The isfinite macro returns a nonzero value if and only if its argument has a finite
10569 <h5><a name="7.12.3.3" href="#7.12.3.3">7.12.3.3 The isinf macro</a></h5>
10573 #include <a href="#7.12"><math.h></a>
10574 int isinf(real-floating x);</pre>
10575 <h6>Description</h6>
10577 The isinf macro determines whether its argument value is an infinity (positive or
10578 negative). First, an argument represented in a format wider than its semantic type is
10579 converted to its semantic type. Then determination is based on the type of the argument.
10582 The isinf macro returns a nonzero value if and only if its argument has an infinite
10585 <h5><a name="7.12.3.4" href="#7.12.3.4">7.12.3.4 The isnan macro</a></h5>
10589 #include <a href="#7.12"><math.h></a>
10590 int isnan(real-floating x);</pre>
10591 <h6>Description</h6>
10593 The isnan macro determines whether its argument value is a NaN. First, an argument
10594 represented in a format wider than its semantic type is converted to its semantic type.
10595 Then determination is based on the type of the argument.<sup><a href="#note206"><b>206)</b></a></sup>
10598 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
10601 <p><small><a name="note206" href="#note206">206)</a> For the isnan macro, the type for determination does not matter unless the implementation supports
10602 NaNs in the evaluation type but not in the semantic type.
10605 <h5><a name="7.12.3.5" href="#7.12.3.5">7.12.3.5 The isnormal macro</a></h5>
10609 #include <a href="#7.12"><math.h></a>
10610 int isnormal(real-floating x);</pre>
10616 <h6>Description</h6>
10618 The isnormal macro determines whether its argument value is normal (neither zero,
10619 subnormal, infinite, nor NaN). First, an argument represented in a format wider than its
10620 semantic type is converted to its semantic type. Then determination is based on the type
10624 The isnormal macro returns a nonzero value if and only if its argument has a normal
10627 <h5><a name="7.12.3.6" href="#7.12.3.6">7.12.3.6 The signbit macro</a></h5>
10631 #include <a href="#7.12"><math.h></a>
10632 int signbit(real-floating x);</pre>
10633 <h6>Description</h6>
10635 The signbit macro determines whether the sign of its argument value is negative.<sup><a href="#note207"><b>207)</b></a></sup>
10638 The signbit macro returns a nonzero value if and only if the sign of its argument value
10642 <p><small><a name="note207" href="#note207">207)</a> The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is
10643 unsigned, it is treated as positive.
10646 <h4><a name="7.12.4" href="#7.12.4">7.12.4 Trigonometric functions</a></h4>
10648 <h5><a name="7.12.4.1" href="#7.12.4.1">7.12.4.1 The acos functions</a></h5>
10652 #include <a href="#7.12"><math.h></a>
10653 double acos(double x);
10654 float acosf(float x);
10655 long double acosl(long double x);</pre>
10656 <h6>Description</h6>
10658 The acos functions compute the principal value of the arc cosine of x. A domain error
10659 occurs for arguments not in the interval [-1, +1].
10662 The acos functions return arccos x in the interval [0, pi ] radians.
10669 <h5><a name="7.12.4.2" href="#7.12.4.2">7.12.4.2 The asin functions</a></h5>
10673 #include <a href="#7.12"><math.h></a>
10674 double asin(double x);
10675 float asinf(float x);
10676 long double asinl(long double x);</pre>
10677 <h6>Description</h6>
10679 The asin functions compute the principal value of the arc sine of x. A domain error
10680 occurs for arguments not in the interval [-1, +1].
10683 The asin functions return arcsin x in the interval [-pi /2, +pi /2] radians.
10685 <h5><a name="7.12.4.3" href="#7.12.4.3">7.12.4.3 The atan functions</a></h5>
10689 #include <a href="#7.12"><math.h></a>
10690 double atan(double x);
10691 float atanf(float x);
10692 long double atanl(long double x);</pre>
10693 <h6>Description</h6>
10695 The atan functions compute the principal value of the arc tangent of x.
10698 The atan functions return arctan x in the interval [-pi /2, +pi /2] radians.
10700 <h5><a name="7.12.4.4" href="#7.12.4.4">7.12.4.4 The atan2 functions</a></h5>
10704 #include <a href="#7.12"><math.h></a>
10705 double atan2(double y, double x);
10706 float atan2f(float y, float x);
10707 long double atan2l(long double y, long double x);</pre>
10708 <h6>Description</h6>
10710 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
10711 arguments to determine the quadrant of the return value. A domain error may occur if
10712 both arguments are zero.
10715 The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
10718 <h5><a name="7.12.4.5" href="#7.12.4.5">7.12.4.5 The cos functions</a></h5>
10722 #include <a href="#7.12"><math.h></a>
10723 double cos(double x);
10724 float cosf(float x);
10725 long double cosl(long double x);</pre>
10726 <h6>Description</h6>
10728 The cos functions compute the cosine of x (measured in radians).
10731 The cos functions return cos x.
10733 <h5><a name="7.12.4.6" href="#7.12.4.6">7.12.4.6 The sin functions</a></h5>
10737 #include <a href="#7.12"><math.h></a>
10738 double sin(double x);
10739 float sinf(float x);
10740 long double sinl(long double x);</pre>
10741 <h6>Description</h6>
10743 The sin functions compute the sine of x (measured in radians).
10746 The sin functions return sin x.
10748 <h5><a name="7.12.4.7" href="#7.12.4.7">7.12.4.7 The tan functions</a></h5>
10752 #include <a href="#7.12"><math.h></a>
10753 double tan(double x);
10754 float tanf(float x);
10755 long double tanl(long double x);</pre>
10756 <h6>Description</h6>
10758 The tan functions return the tangent of x (measured in radians).
10761 The tan functions return tan x.
10764 <h4><a name="7.12.5" href="#7.12.5">7.12.5 Hyperbolic functions</a></h4>
10766 <h5><a name="7.12.5.1" href="#7.12.5.1">7.12.5.1 The acosh functions</a></h5>
10770 #include <a href="#7.12"><math.h></a>
10771 double acosh(double x);
10772 float acoshf(float x);
10773 long double acoshl(long double x);</pre>
10774 <h6>Description</h6>
10776 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
10777 error occurs for arguments less than 1.
10780 The acosh functions return arcosh x in the interval [0, +(inf)].
10782 <h5><a name="7.12.5.2" href="#7.12.5.2">7.12.5.2 The asinh functions</a></h5>
10786 #include <a href="#7.12"><math.h></a>
10787 double asinh(double x);
10788 float asinhf(float x);
10789 long double asinhl(long double x);</pre>
10790 <h6>Description</h6>
10792 The asinh functions compute the arc hyperbolic sine of x.
10795 The asinh functions return arsinh x.
10797 <h5><a name="7.12.5.3" href="#7.12.5.3">7.12.5.3 The atanh functions</a></h5>
10801 #include <a href="#7.12"><math.h></a>
10802 double atanh(double x);
10803 float atanhf(float x);
10804 long double atanhl(long double x);</pre>
10805 <h6>Description</h6>
10807 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
10808 for arguments not in the interval [-1, +1]. A range error may occur if the argument
10813 The atanh functions return artanh x.
10815 <h5><a name="7.12.5.4" href="#7.12.5.4">7.12.5.4 The cosh functions</a></h5>
10819 #include <a href="#7.12"><math.h></a>
10820 double cosh(double x);
10821 float coshf(float x);
10822 long double coshl(long double x);</pre>
10823 <h6>Description</h6>
10825 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
10826 magnitude of x is too large.
10829 The cosh functions return cosh x.
10831 <h5><a name="7.12.5.5" href="#7.12.5.5">7.12.5.5 The sinh functions</a></h5>
10835 #include <a href="#7.12"><math.h></a>
10836 double sinh(double x);
10837 float sinhf(float x);
10838 long double sinhl(long double x);</pre>
10839 <h6>Description</h6>
10841 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
10842 magnitude of x is too large.
10845 The sinh functions return sinh x.
10847 <h5><a name="7.12.5.6" href="#7.12.5.6">7.12.5.6 The tanh functions</a></h5>
10851 #include <a href="#7.12"><math.h></a>
10852 double tanh(double x);
10853 float tanhf(float x);
10854 long double tanhl(long double x);</pre>
10855 <h6>Description</h6>
10857 The tanh functions compute the hyperbolic tangent of x.
10861 The tanh functions return tanh x.
10863 <h4><a name="7.12.6" href="#7.12.6">7.12.6 Exponential and logarithmic functions</a></h4>
10865 <h5><a name="7.12.6.1" href="#7.12.6.1">7.12.6.1 The exp functions</a></h5>
10869 #include <a href="#7.12"><math.h></a>
10870 double exp(double x);
10871 float expf(float x);
10872 long double expl(long double x);</pre>
10873 <h6>Description</h6>
10875 The exp functions compute the base-e exponential of x. A range error occurs if the
10876 magnitude of x is too large.
10879 The exp functions return ex .
10881 <h5><a name="7.12.6.2" href="#7.12.6.2">7.12.6.2 The exp2 functions</a></h5>
10885 #include <a href="#7.12"><math.h></a>
10886 double exp2(double x);
10887 float exp2f(float x);
10888 long double exp2l(long double x);</pre>
10889 <h6>Description</h6>
10891 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
10892 magnitude of x is too large.
10895 The exp2 functions return 2x .
10897 <h5><a name="7.12.6.3" href="#7.12.6.3">7.12.6.3 The expm1 functions</a></h5>
10902 #include <a href="#7.12"><math.h></a>
10903 double expm1(double x);
10904 float expm1f(float x);
10905 long double expm1l(long double x);</pre>
10906 <h6>Description</h6>
10908 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
10909 error occurs if x is too large.<sup><a href="#note208"><b>208)</b></a></sup>
10912 The expm1 functions return ex - 1.
10915 <p><small><a name="note208" href="#note208">208)</a> For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1.
10918 <h5><a name="7.12.6.4" href="#7.12.6.4">7.12.6.4 The frexp functions</a></h5>
10922 #include <a href="#7.12"><math.h></a>
10923 double frexp(double value, int *exp);
10924 float frexpf(float value, int *exp);
10925 long double frexpl(long double value, int *exp);</pre>
10926 <h6>Description</h6>
10928 The frexp functions break a floating-point number into a normalized fraction and an
10929 integral power of 2. They store the integer in the int object pointed to by exp.
10932 If value is not a floating-point number, the results are unspecified. Otherwise, the
10933 frexp functions return the value x, such that x has a magnitude in the interval [1/2, 1) or
10934 zero, and value equals x x 2*exp . If value is zero, both parts of the result are zero.
10936 <h5><a name="7.12.6.5" href="#7.12.6.5">7.12.6.5 The ilogb functions</a></h5>
10940 #include <a href="#7.12"><math.h></a>
10941 int ilogb(double x);
10942 int ilogbf(float x);
10943 int ilogbl(long double x);</pre>
10944 <h6>Description</h6>
10946 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
10947 compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
10948 a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
10949 the corresponding logb function and casting the returned value to type int. A domain
10950 error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
10951 the range of the return type, the numeric result is unspecified.
10959 The ilogb functions return the exponent of x as a signed int value.
10960 <p><b> Forward references</b>: the logb functions (<a href="#7.12.6.11">7.12.6.11</a>).
10962 <h5><a name="7.12.6.6" href="#7.12.6.6">7.12.6.6 The ldexp functions</a></h5>
10966 #include <a href="#7.12"><math.h></a>
10967 double ldexp(double x, int exp);
10968 float ldexpf(float x, int exp);
10969 long double ldexpl(long double x, int exp);</pre>
10970 <h6>Description</h6>
10972 The ldexp functions multiply a floating-point number by an integral power of 2. A
10973 range error may occur.
10976 The ldexp functions return x x 2exp .
10978 <h5><a name="7.12.6.7" href="#7.12.6.7">7.12.6.7 The log functions</a></h5>
10982 #include <a href="#7.12"><math.h></a>
10983 double log(double x);
10984 float logf(float x);
10985 long double logl(long double x);</pre>
10986 <h6>Description</h6>
10988 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
10989 the argument is negative. A range error may occur if the argument is zero.
10992 The log functions return loge x.
10994 <h5><a name="7.12.6.8" href="#7.12.6.8">7.12.6.8 The log10 functions</a></h5>
10999 #include <a href="#7.12"><math.h></a>
11000 double log10(double x);
11001 float log10f(float x);
11002 long double log10l(long double x);</pre>
11003 <h6>Description</h6>
11005 The log10 functions compute the base-10 (common) logarithm of x. A domain error
11006 occurs if the argument is negative. A range error may occur if the argument is zero.
11009 The log10 functions return log10 x.
11011 <h5><a name="7.12.6.9" href="#7.12.6.9">7.12.6.9 The log1p functions</a></h5>
11015 #include <a href="#7.12"><math.h></a>
11016 double log1p(double x);
11017 float log1pf(float x);
11018 long double log1pl(long double x);</pre>
11019 <h6>Description</h6>
11021 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.<sup><a href="#note209"><b>209)</b></a></sup>
11022 A domain error occurs if the argument is less than -1. A range error may occur if the
11023 argument equals -1.
11026 The log1p functions return loge (1 + x).
11029 <p><small><a name="note209" href="#note209">209)</a> For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x).
11032 <h5><a name="7.12.6.10" href="#7.12.6.10">7.12.6.10 The log2 functions</a></h5>
11036 #include <a href="#7.12"><math.h></a>
11037 double log2(double x);
11038 float log2f(float x);
11039 long double log2l(long double x);</pre>
11040 <h6>Description</h6>
11042 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
11043 argument is less than zero. A range error may occur if the argument is zero.
11046 The log2 functions return log2 x.
11053 <h5><a name="7.12.6.11" href="#7.12.6.11">7.12.6.11 The logb functions</a></h5>
11057 #include <a href="#7.12"><math.h></a>
11058 double logb(double x);
11059 float logbf(float x);
11060 long double logbl(long double x);</pre>
11061 <h6>Description</h6>
11063 The logb functions extract the exponent of x, as a signed integer value in floating-point
11064 format. If x is subnormal it is treated as though it were normalized; thus, for positive
11067 1 <= x x FLT_RADIX-logb(x) < FLT_RADIX</pre>
11068 A domain error or range error may occur if the argument is zero.
11071 The logb functions return the signed exponent of x.
11073 <h5><a name="7.12.6.12" href="#7.12.6.12">7.12.6.12 The modf functions</a></h5>
11077 #include <a href="#7.12"><math.h></a>
11078 double modf(double value, double *iptr);
11079 float modff(float value, float *iptr);
11080 long double modfl(long double value, long double *iptr);</pre>
11081 <h6>Description</h6>
11083 The modf functions break the argument value into integral and fractional parts, each of
11084 which has the same type and sign as the argument. They store the integral part (in
11085 floating-point format) in the object pointed to by iptr.
11088 The modf functions return the signed fractional part of value.
11091 <h5><a name="7.12.6.13" href="#7.12.6.13">7.12.6.13 The scalbn and scalbln functions</a></h5>
11095 #include <a href="#7.12"><math.h></a>
11096 double scalbn(double x, int n);
11097 float scalbnf(float x, int n);
11098 long double scalbnl(long double x, int n);
11099 double scalbln(double x, long int n);
11100 float scalblnf(float x, long int n);
11101 long double scalblnl(long double x, long int n);</pre>
11102 <h6>Description</h6>
11104 The scalbn and scalbln functions compute x x FLT_RADIXn efficiently, not
11105 normally by computing FLT_RADIXn explicitly. A range error may occur.
11108 The scalbn and scalbln functions return x x FLT_RADIXn .
11110 <h4><a name="7.12.7" href="#7.12.7">7.12.7 Power and absolute-value functions</a></h4>
11112 <h5><a name="7.12.7.1" href="#7.12.7.1">7.12.7.1 The cbrt functions</a></h5>
11116 #include <a href="#7.12"><math.h></a>
11117 double cbrt(double x);
11118 float cbrtf(float x);
11119 long double cbrtl(long double x);</pre>
11120 <h6>Description</h6>
11122 The cbrt functions compute the real cube root of x.
11125 The cbrt functions return x1/3 .
11127 <h5><a name="7.12.7.2" href="#7.12.7.2">7.12.7.2 The fabs functions</a></h5>
11131 #include <a href="#7.12"><math.h></a>
11132 double fabs(double x);
11133 float fabsf(float x);
11134 long double fabsl(long double x);</pre>
11135 <h6>Description</h6>
11137 The fabs functions compute the absolute value of a floating-point number x.
11141 The fabs functions return | x |.
11143 <h5><a name="7.12.7.3" href="#7.12.7.3">7.12.7.3 The hypot functions</a></h5>
11147 #include <a href="#7.12"><math.h></a>
11148 double hypot(double x, double y);
11149 float hypotf(float x, float y);
11150 long double hypotl(long double x, long double y);</pre>
11151 <h6>Description</h6>
11153 The hypot functions compute the square root of the sum of the squares of x and y,
11154 without undue overflow or underflow. A range error may occur.
11158 The hypot functions return (sqrt)x2 + y2 .
11161 ???????????????</pre>
11163 <h5><a name="7.12.7.4" href="#7.12.7.4">7.12.7.4 The pow functions</a></h5>
11167 #include <a href="#7.12"><math.h></a>
11168 double pow(double x, double y);
11169 float powf(float x, float y);
11170 long double powl(long double x, long double y);</pre>
11171 <h6>Description</h6>
11173 The pow functions compute x raised to the power y. A domain error occurs if x is finite
11174 and negative and y is finite and not an integer value. A range error may occur. A domain
11175 error may occur if x is zero and y is zero. A domain error or range error may occur if x
11176 is zero and y is less than zero.
11179 The pow functions return xy .
11181 <h5><a name="7.12.7.5" href="#7.12.7.5">7.12.7.5 The sqrt functions</a></h5>
11186 #include <a href="#7.12"><math.h></a>
11187 double sqrt(double x);
11188 float sqrtf(float x);
11189 long double sqrtl(long double x);</pre>
11190 <h6>Description</h6>
11192 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
11193 the argument is less than zero.
11196 The sqrt functions return (sqrt)x.
11201 <h4><a name="7.12.8" href="#7.12.8">7.12.8 Error and gamma functions</a></h4>
11203 <h5><a name="7.12.8.1" href="#7.12.8.1">7.12.8.1 The erf functions</a></h5>
11207 #include <a href="#7.12"><math.h></a>
11208 double erf(double x);
11209 float erff(float x);
11210 long double erfl(long double x);</pre>
11211 <h6>Description</h6>
11213 The erf functions compute the error function of x.
11219 The erf functions return erf x = e-t dt.
11230 <h5><a name="7.12.8.2" href="#7.12.8.2">7.12.8.2 The erfc functions</a></h5>
11234 #include <a href="#7.12"><math.h></a>
11235 double erfc(double x);
11236 float erfcf(float x);
11237 long double erfcl(long double x);</pre>
11238 <h6>Description</h6>
11240 The erfc functions compute the complementary error function of x. A range error
11241 occurs if x is too large.
11247 The erfc functions return erfc x = 1 - erf x = e-t dt.
11258 <h5><a name="7.12.8.3" href="#7.12.8.3">7.12.8.3 The lgamma functions</a></h5>
11262 #include <a href="#7.12"><math.h></a>
11263 double lgamma(double x);
11264 float lgammaf(float x);
11265 long double lgammal(long double x);</pre>
11266 <h6>Description</h6>
11268 The lgamma functions compute the natural logarithm of the absolute value of gamma of
11269 x. A range error occurs if x is too large. A range error may occur if x is a negative
11273 The lgamma functions return loge | (Gamma)(x) |.
11275 <h5><a name="7.12.8.4" href="#7.12.8.4">7.12.8.4 The tgamma functions</a></h5>
11279 #include <a href="#7.12"><math.h></a>
11280 double tgamma(double x);
11281 float tgammaf(float x);
11282 long double tgammal(long double x);</pre>
11283 <h6>Description</h6>
11285 The tgamma functions compute the gamma function of x. A domain error or range error
11286 may occur if x is a negative integer or zero. A range error may occur if the magnitude of
11287 x is too large or too small.
11290 The tgamma functions return (Gamma)(x).
11292 <h4><a name="7.12.9" href="#7.12.9">7.12.9 Nearest integer functions</a></h4>
11294 <h5><a name="7.12.9.1" href="#7.12.9.1">7.12.9.1 The ceil functions</a></h5>
11298 #include <a href="#7.12"><math.h></a>
11299 double ceil(double x);
11300 float ceilf(float x);
11301 long double ceill(long double x);</pre>
11302 <h6>Description</h6>
11304 The ceil functions compute the smallest integer value not less than x.
11308 The ceil functions return ???x???, expressed as a floating-point number.
11310 <h5><a name="7.12.9.2" href="#7.12.9.2">7.12.9.2 The floor functions</a></h5>
11314 #include <a href="#7.12"><math.h></a>
11315 double floor(double x);
11316 float floorf(float x);
11317 long double floorl(long double x);</pre>
11318 <h6>Description</h6>
11320 The floor functions compute the largest integer value not greater than x.
11323 The floor functions return ???x???, expressed as a floating-point number.
11325 <h5><a name="7.12.9.3" href="#7.12.9.3">7.12.9.3 The nearbyint functions</a></h5>
11329 #include <a href="#7.12"><math.h></a>
11330 double nearbyint(double x);
11331 float nearbyintf(float x);
11332 long double nearbyintl(long double x);</pre>
11333 <h6>Description</h6>
11335 The nearbyint functions round their argument to an integer value in floating-point
11336 format, using the current rounding direction and without raising the ''inexact'' floating-
11340 The nearbyint functions return the rounded integer value.
11342 <h5><a name="7.12.9.4" href="#7.12.9.4">7.12.9.4 The rint functions</a></h5>
11346 #include <a href="#7.12"><math.h></a>
11347 double rint(double x);
11348 float rintf(float x);
11349 long double rintl(long double x);</pre>
11350 <h6>Description</h6>
11352 The rint functions differ from the nearbyint functions (<a href="#7.12.9.3">7.12.9.3</a>) only in that the
11353 rint functions may raise the ''inexact'' floating-point exception if the result differs in
11354 value from the argument.
11358 The rint functions return the rounded integer value.
11360 <h5><a name="7.12.9.5" href="#7.12.9.5">7.12.9.5 The lrint and llrint functions</a></h5>
11364 #include <a href="#7.12"><math.h></a>
11365 long int lrint(double x);
11366 long int lrintf(float x);
11367 long int lrintl(long double x);
11368 long long int llrint(double x);
11369 long long int llrintf(float x);
11370 long long int llrintl(long double x);</pre>
11371 <h6>Description</h6>
11373 The lrint and llrint functions round their argument to the nearest integer value,
11374 rounding according to the current rounding direction. If the rounded value is outside the
11375 range of the return type, the numeric result is unspecified and a domain error or range
11379 The lrint and llrint functions return the rounded integer value.
11381 <h5><a name="7.12.9.6" href="#7.12.9.6">7.12.9.6 The round functions</a></h5>
11385 #include <a href="#7.12"><math.h></a>
11386 double round(double x);
11387 float roundf(float x);
11388 long double roundl(long double x);</pre>
11389 <h6>Description</h6>
11391 The round functions round their argument to the nearest integer value in floating-point
11392 format, rounding halfway cases away from zero, regardless of the current rounding
11396 The round functions return the rounded integer value.
11399 <h5><a name="7.12.9.7" href="#7.12.9.7">7.12.9.7 The lround and llround functions</a></h5>
11403 #include <a href="#7.12"><math.h></a>
11404 long int lround(double x);
11405 long int lroundf(float x);
11406 long int lroundl(long double x);
11407 long long int llround(double x);
11408 long long int llroundf(float x);
11409 long long int llroundl(long double x);</pre>
11410 <h6>Description</h6>
11412 The lround and llround functions round their argument to the nearest integer value,
11413 rounding halfway cases away from zero, regardless of the current rounding direction. If
11414 the rounded value is outside the range of the return type, the numeric result is unspecified
11415 and a domain error or range error may occur.
11418 The lround and llround functions return the rounded integer value.
11420 <h5><a name="7.12.9.8" href="#7.12.9.8">7.12.9.8 The trunc functions</a></h5>
11424 #include <a href="#7.12"><math.h></a>
11425 double trunc(double x);
11426 float truncf(float x);
11427 long double truncl(long double x);</pre>
11428 <h6>Description</h6>
11430 The trunc functions round their argument to the integer value, in floating format,
11431 nearest to but no larger in magnitude than the argument.
11434 The trunc functions return the truncated integer value.
11437 <h4><a name="7.12.10" href="#7.12.10">7.12.10 Remainder functions</a></h4>
11439 <h5><a name="7.12.10.1" href="#7.12.10.1">7.12.10.1 The fmod functions</a></h5>
11443 #include <a href="#7.12"><math.h></a>
11444 double fmod(double x, double y);
11445 float fmodf(float x, float y);
11446 long double fmodl(long double x, long double y);</pre>
11447 <h6>Description</h6>
11449 The fmod functions compute the floating-point remainder of x/y.
11452 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
11453 the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
11454 whether a domain error occurs or the fmod functions return zero is implementation-
11457 <h5><a name="7.12.10.2" href="#7.12.10.2">7.12.10.2 The remainder functions</a></h5>
11461 #include <a href="#7.12"><math.h></a>
11462 double remainder(double x, double y);
11463 float remainderf(float x, float y);
11464 long double remainderl(long double x, long double y);</pre>
11465 <h6>Description</h6>
11467 The remainder functions compute the remainder x REM y required by IEC 60559.<sup><a href="#note210"><b>210)</b></a></sup>
11470 The remainder functions return x REM y. If y is zero, whether a domain error occurs
11471 or the functions return zero is implementation defined.
11479 <p><small><a name="note210" href="#note210">210)</a> ''When y != 0, the remainder r = x REM y is defined regardless of the rounding mode by the
11480 mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever
11481 | n - x/y | = 1/2, then n is even. Thus, the remainder is always exact. If r = 0, its sign shall be that of
11482 x.'' This definition is applicable for all implementations.
11485 <h5><a name="7.12.10.3" href="#7.12.10.3">7.12.10.3 The remquo functions</a></h5>
11489 #include <a href="#7.12"><math.h></a>
11490 double remquo(double x, double y, int *quo);
11491 float remquof(float x, float y, int *quo);
11492 long double remquol(long double x, long double y,
11494 <h6>Description</h6>
11496 The remquo functions compute the same remainder as the remainder functions. In
11497 the object pointed to by quo they store a value whose sign is the sign of x/y and whose
11498 magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where
11499 n is an implementation-defined integer greater than or equal to 3.
11502 The remquo functions return x REM y. If y is zero, the value stored in the object
11503 pointed to by quo is unspecified and whether a domain error occurs or the functions
11504 return zero is implementation defined.
11506 <h4><a name="7.12.11" href="#7.12.11">7.12.11 Manipulation functions</a></h4>
11508 <h5><a name="7.12.11.1" href="#7.12.11.1">7.12.11.1 The copysign functions</a></h5>
11512 #include <a href="#7.12"><math.h></a>
11513 double copysign(double x, double y);
11514 float copysignf(float x, float y);
11515 long double copysignl(long double x, long double y);</pre>
11516 <h6>Description</h6>
11518 The copysign functions produce a value with the magnitude of x and the sign of y.
11519 They produce a NaN (with the sign of y) if x is a NaN. On implementations that
11520 represent a signed zero but do not treat negative zero consistently in arithmetic
11521 operations, the copysign functions regard the sign of zero as positive.
11524 The copysign functions return a value with the magnitude of x and the sign of y.
11527 <h5><a name="7.12.11.2" href="#7.12.11.2">7.12.11.2 The nan functions</a></h5>
11531 #include <a href="#7.12"><math.h></a>
11532 double nan(const char *tagp);
11533 float nanf(const char *tagp);
11534 long double nanl(const char *tagp);</pre>
11535 <h6>Description</h6>
11537 The call nan("n-char-sequence") is equivalent to strtod("NAN(n-char-
11538 sequence)", (char**) NULL); the call nan("") is equivalent to
11539 strtod("NAN()", (char**) NULL). If tagp does not point to an n-char
11540 sequence or an empty string, the call is equivalent to strtod("NAN", (char**)
11541 NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof
11545 The nan functions return a quiet NaN, if available, with content indicated through tagp.
11546 If the implementation does not support quiet NaNs, the functions return zero.
11547 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>).
11549 <h5><a name="7.12.11.3" href="#7.12.11.3">7.12.11.3 The nextafter functions</a></h5>
11553 #include <a href="#7.12"><math.h></a>
11554 double nextafter(double x, double y);
11555 float nextafterf(float x, float y);
11556 long double nextafterl(long double x, long double y);</pre>
11557 <h6>Description</h6>
11559 The nextafter functions determine the next representable value, in the type of the
11560 function, after x in the direction of y, where x and y are first converted to the type of the
11561 function.<sup><a href="#note211"><b>211)</b></a></sup> The nextafter functions return y if x equals y. A range error may occur
11562 if the magnitude of x is the largest finite value representable in the type and the result is
11563 infinite or not representable in the type.
11566 The nextafter functions return the next representable value in the specified format
11567 after x in the direction of y.
11573 <p><small><a name="note211" href="#note211">211)</a> The argument values are converted to the type of the function, even by a macro implementation of the
11577 <h5><a name="7.12.11.4" href="#7.12.11.4">7.12.11.4 The nexttoward functions</a></h5>
11581 #include <a href="#7.12"><math.h></a>
11582 double nexttoward(double x, long double y);
11583 float nexttowardf(float x, long double y);
11584 long double nexttowardl(long double x, long double y);</pre>
11585 <h6>Description</h6>
11587 The nexttoward functions are equivalent to the nextafter functions except that the
11588 second parameter has type long double and the functions return y converted to the
11589 type of the function if x equals y.<sup><a href="#note212"><b>212)</b></a></sup>
11592 <p><small><a name="note212" href="#note212">212)</a> The result of the nexttoward functions is determined in the type of the function, without loss of
11593 range or precision in a floating second argument.
11596 <h4><a name="7.12.12" href="#7.12.12">7.12.12 Maximum, minimum, and positive difference functions</a></h4>
11598 <h5><a name="7.12.12.1" href="#7.12.12.1">7.12.12.1 The fdim functions</a></h5>
11602 #include <a href="#7.12"><math.h></a>
11603 double fdim(double x, double y);
11604 float fdimf(float x, float y);
11605 long double fdiml(long double x, long double y);</pre>
11606 <h6>Description</h6>
11608 The fdim functions determine the positive difference between their arguments:
11610 ???x - y if x > y
11612 ???+0 if x <= y</pre>
11613 A range error may occur.
11616 The fdim functions return the positive difference value.
11618 <h5><a name="7.12.12.2" href="#7.12.12.2">7.12.12.2 The fmax functions</a></h5>
11622 #include <a href="#7.12"><math.h></a>
11623 double fmax(double x, double y);
11624 float fmaxf(float x, float y);
11625 long double fmaxl(long double x, long double y);</pre>
11630 <h6>Description</h6>
11632 The fmax functions determine the maximum numeric value of their arguments.<sup><a href="#note213"><b>213)</b></a></sup>
11635 The fmax functions return the maximum numeric value of their arguments.
11638 <p><small><a name="note213" href="#note213">213)</a> NaN arguments are treated as missing data: if one argument is a NaN and the other numeric, then the
11639 fmax functions choose the numeric value. See <a href="#F.9.9.2">F.9.9.2</a>.
11642 <h5><a name="7.12.12.3" href="#7.12.12.3">7.12.12.3 The fmin functions</a></h5>
11646 #include <a href="#7.12"><math.h></a>
11647 double fmin(double x, double y);
11648 float fminf(float x, float y);
11649 long double fminl(long double x, long double y);</pre>
11650 <h6>Description</h6>
11652 The fmin functions determine the minimum numeric value of their arguments.<sup><a href="#note214"><b>214)</b></a></sup>
11655 The fmin functions return the minimum numeric value of their arguments.
11658 <p><small><a name="note214" href="#note214">214)</a> The fmin functions are analogous to the fmax functions in their treatment of NaNs.
11661 <h4><a name="7.12.13" href="#7.12.13">7.12.13 Floating multiply-add</a></h4>
11663 <h5><a name="7.12.13.1" href="#7.12.13.1">7.12.13.1 The fma functions</a></h5>
11667 #include <a href="#7.12"><math.h></a>
11668 double fma(double x, double y, double z);
11669 float fmaf(float x, float y, float z);
11670 long double fmal(long double x, long double y,
11671 long double z);</pre>
11672 <h6>Description</h6>
11674 The fma functions compute (x x y) + z, rounded as one ternary operation: they compute
11675 the value (as if) to infinite precision and round once to the result format, according to the
11676 current rounding mode. A range error may occur.
11679 The fma functions return (x x y) + z, rounded as one ternary operation.
11686 <h4><a name="7.12.14" href="#7.12.14">7.12.14 Comparison macros</a></h4>
11688 The relational and equality operators support the usual mathematical relationships
11689 between numeric values. For any ordered pair of numeric values exactly one of the
11690 relationships -- less, greater, and equal -- is true. Relational operators may raise the
11691 ''invalid'' floating-point exception when argument values are NaNs. For a NaN and a
11692 numeric value, or for two NaNs, just the unordered relationship is true.<sup><a href="#note215"><b>215)</b></a></sup> The following
11693 subclauses provide macros that are quiet (non floating-point exception raising) versions
11694 of the relational operators, and other comparison macros that facilitate writing efficient
11695 code that accounts for NaNs without suffering the ''invalid'' floating-point exception. In
11696 the synopses in this subclause, real-floating indicates that the argument shall be an
11697 expression of real floating type.
11700 <p><small><a name="note215" href="#note215">215)</a> IEC 60559 requires that the built-in relational operators raise the ''invalid'' floating-point exception if
11701 the operands compare unordered, as an error indicator for programs written without consideration of
11702 NaNs; the result in these cases is false.
11705 <h5><a name="7.12.14.1" href="#7.12.14.1">7.12.14.1 The isgreater macro</a></h5>
11709 #include <a href="#7.12"><math.h></a>
11710 int isgreater(real-floating x, real-floating y);</pre>
11711 <h6>Description</h6>
11713 The isgreater macro determines whether its first argument is greater than its second
11714 argument. The value of isgreater(x, y) is always equal to (x) > (y); however,
11715 unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point
11716 exception when x and y are unordered.
11719 The isgreater macro returns the value of (x) > (y).
11721 <h5><a name="7.12.14.2" href="#7.12.14.2">7.12.14.2 The isgreaterequal macro</a></h5>
11725 #include <a href="#7.12"><math.h></a>
11726 int isgreaterequal(real-floating x, real-floating y);</pre>
11727 <h6>Description</h6>
11729 The isgreaterequal macro determines whether its first argument is greater than or
11730 equal to its second argument. The value of isgreaterequal(x, y) is always equal
11731 to (x) >= (y); however, unlike (x) >= (y), isgreaterequal(x, y) does
11732 not raise the ''invalid'' floating-point exception when x and y are unordered.
11739 The isgreaterequal macro returns the value of (x) >= (y).
11741 <h5><a name="7.12.14.3" href="#7.12.14.3">7.12.14.3 The isless macro</a></h5>
11745 #include <a href="#7.12"><math.h></a>
11746 int isless(real-floating x, real-floating y);</pre>
11747 <h6>Description</h6>
11749 The isless macro determines whether its first argument is less than its second
11750 argument. The value of isless(x, y) is always equal to (x) < (y); however,
11751 unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point
11752 exception when x and y are unordered.
11755 The isless macro returns the value of (x) < (y).
11757 <h5><a name="7.12.14.4" href="#7.12.14.4">7.12.14.4 The islessequal macro</a></h5>
11761 #include <a href="#7.12"><math.h></a>
11762 int islessequal(real-floating x, real-floating y);</pre>
11763 <h6>Description</h6>
11765 The islessequal macro determines whether its first argument is less than or equal to
11766 its second argument. The value of islessequal(x, y) is always equal to
11767 (x) <= (y); however, unlike (x) <= (y), islessequal(x, y) does not raise
11768 the ''invalid'' floating-point exception when x and y are unordered.
11771 The islessequal macro returns the value of (x) <= (y).
11773 <h5><a name="7.12.14.5" href="#7.12.14.5">7.12.14.5 The islessgreater macro</a></h5>
11777 #include <a href="#7.12"><math.h></a>
11778 int islessgreater(real-floating x, real-floating y);</pre>
11779 <h6>Description</h6>
11781 The islessgreater macro determines whether its first argument is less than or
11782 greater than its second argument. The islessgreater(x, y) macro is similar to
11783 (x) < (y) || (x) > (y); however, islessgreater(x, y) does not raise
11784 the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x
11789 The islessgreater macro returns the value of (x) < (y) || (x) > (y).
11791 <h5><a name="7.12.14.6" href="#7.12.14.6">7.12.14.6 The isunordered macro</a></h5>
11795 #include <a href="#7.12"><math.h></a>
11796 int isunordered(real-floating x, real-floating y);</pre>
11797 <h6>Description</h6>
11799 The isunordered macro determines whether its arguments are unordered.
11802 The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
11805 <h3><a name="7.13" href="#7.13">7.13 Nonlocal jumps <setjmp.h></a></h3>
11807 The header <a href="#7.13"><setjmp.h></a> defines the macro setjmp, and declares one function and
11808 one type, for bypassing the normal function call and return discipline.<sup><a href="#note216"><b>216)</b></a></sup>
11810 The type declared is
11813 which is an array type suitable for holding the information needed to restore a calling
11814 environment. The environment of a call to the setjmp macro consists of information
11815 sufficient for a call to the longjmp function to return execution to the correct block and
11816 invocation of that block, were it called recursively. It does not include the state of the
11817 floating-point status flags, of open files, or of any other component of the abstract
11820 It is unspecified whether setjmp is a macro or an identifier declared with external
11821 linkage. If a macro definition is suppressed in order to access an actual function, or a
11822 program defines an external identifier with the name setjmp, the behavior is undefined.
11825 <p><small><a name="note216" href="#note216">216)</a> These functions are useful for dealing with unusual conditions encountered in a low-level function of
11829 <h4><a name="7.13.1" href="#7.13.1">7.13.1 Save calling environment</a></h4>
11831 <h5><a name="7.13.1.1" href="#7.13.1.1">7.13.1.1 The setjmp macro</a></h5>
11835 #include <a href="#7.13"><setjmp.h></a>
11836 int setjmp(jmp_buf env);</pre>
11837 <h6>Description</h6>
11839 The setjmp macro saves its calling environment in its jmp_buf argument for later use
11840 by the longjmp function.
11843 If the return is from a direct invocation, the setjmp macro returns the value zero. If the
11844 return is from a call to the longjmp function, the setjmp macro returns a nonzero
11846 Environmental limits
11848 An invocation of the setjmp macro shall appear only in one of the following contexts:
11850 <li> the entire controlling expression of a selection or iteration statement;
11851 <li> one operand of a relational or equality operator with the other operand an integer
11852 constant expression, with the resulting expression being the entire controlling
11856 expression of a selection or iteration statement;
11857 <li> the operand of a unary ! operator with the resulting expression being the entire
11858 controlling expression of a selection or iteration statement; or
11859 <li> the entire expression of an expression statement (possibly cast to void).
11862 If the invocation appears in any other context, the behavior is undefined.
11864 <h4><a name="7.13.2" href="#7.13.2">7.13.2 Restore calling environment</a></h4>
11866 <h5><a name="7.13.2.1" href="#7.13.2.1">7.13.2.1 The longjmp function</a></h5>
11870 #include <a href="#7.13"><setjmp.h></a>
11871 void longjmp(jmp_buf env, int val);</pre>
11872 <h6>Description</h6>
11874 The longjmp function restores the environment saved by the most recent invocation of
11875 the setjmp macro in the same invocation of the program with the corresponding
11876 jmp_buf argument. If there has been no such invocation, or if the function containing
11877 the invocation of the setjmp macro has terminated execution<sup><a href="#note217"><b>217)</b></a></sup> in the interim, or if the
11878 invocation of the setjmp macro was within the scope of an identifier with variably
11879 modified type and execution has left that scope in the interim, the behavior is undefined.
11881 All accessible objects have values, and all other components of the abstract machine<sup><a href="#note218"><b>218)</b></a></sup>
11882 have state, as of the time the longjmp function was called, except that the values of
11883 objects of automatic storage duration that are local to the function containing the
11884 invocation of the corresponding setjmp macro that do not have volatile-qualified type
11885 and have been changed between the setjmp invocation and longjmp call are
11889 After longjmp is completed, program execution continues as if the corresponding
11890 invocation of the setjmp macro had just returned the value specified by val. The
11891 longjmp function cannot cause the setjmp macro to return the value 0; if val is 0,
11892 the setjmp macro returns the value 1.
11894 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation
11895 might cause memory associated with a variable length array object to be squandered.
11903 #include <a href="#7.13"><setjmp.h></a>
11910 int x[n]; // valid: f is not terminated
11916 int a[n]; // a may remain allocated
11921 int b[n]; // b may remain allocated
11922 longjmp(buf, 2); // might cause memory loss
11926 <p><small><a name="note217" href="#note217">217)</a> For example, by executing a return statement or because another longjmp call has caused a
11927 transfer to a setjmp invocation in a function earlier in the set of nested calls.
11929 <p><small><a name="note218" href="#note218">218)</a> This includes, but is not limited to, the floating-point status flags and the state of open files.
11932 <h3><a name="7.14" href="#7.14">7.14 Signal handling <signal.h></a></h3>
11934 The header <a href="#7.14"><signal.h></a> declares a type and two functions and defines several macros,
11935 for handling various signals (conditions that may be reported during program execution).
11937 The type defined is
11940 which is the (possibly volatile-qualified) integer type of an object that can be accessed as
11941 an atomic entity, even in the presence of asynchronous interrupts.
11943 The macros defined are
11948 which expand to constant expressions with distinct values that have type compatible with
11949 the second argument to, and the return value of, the signal function, and whose values
11950 compare unequal to the address of any declarable function; and the following, which
11951 expand to positive integer constant expressions with type int and distinct values that are
11952 the signal numbers, each corresponding to the specified condition:
11955 SIGABRT abnormal termination, such as is initiated by the abort function
11956 SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
11957 resulting in overflow
11958 SIGILL detection of an invalid function image, such as an invalid instruction
11959 SIGINT receipt of an interactive attention signal
11960 SIGSEGV an invalid access to storage
11961 SIGTERM a termination request sent to the program</pre>
11962 An implementation need not generate any of these signals, except as a result of explicit
11963 calls to the raise function. Additional signals and pointers to undeclarable functions,
11964 with macro definitions beginning, respectively, with the letters SIG and an uppercase
11965 letter or with SIG_ and an uppercase letter,<sup><a href="#note219"><b>219)</b></a></sup> may also be specified by the
11966 implementation. The complete set of signals, their semantics, and their default handling
11967 is implementation-defined; all signal numbers shall be positive.
11975 <p><small><a name="note219" href="#note219">219)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>). The names of the signal numbers reflect the following terms
11976 (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
11980 <h4><a name="7.14.1" href="#7.14.1">7.14.1 Specify signal handling</a></h4>
11982 <h5><a name="7.14.1.1" href="#7.14.1.1">7.14.1.1 The signal function</a></h5>
11986 #include <a href="#7.14"><signal.h></a>
11987 void (*signal(int sig, void (*func)(int)))(int);</pre>
11988 <h6>Description</h6>
11990 The signal function chooses one of three ways in which receipt of the signal number
11991 sig is to be subsequently handled. If the value of func is SIG_DFL, default handling
11992 for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored.
11993 Otherwise, func shall point to a function to be called when that signal occurs. An
11994 invocation of such a function because of a signal, or (recursively) of any further functions
11995 called by that invocation (other than functions in the standard library), is called a signal
11998 When a signal occurs and func points to a function, it is implementation-defined
11999 whether the equivalent of signal(sig, SIG_DFL); is executed or the
12000 implementation prevents some implementation-defined set of signals (at least including
12001 sig) from occurring until the current signal handling has completed; in the case of
12002 SIGILL, the implementation may alternatively define that no action is taken. Then the
12003 equivalent of (*func)(sig); is executed. If and when the function returns, if the
12004 value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined
12005 value corresponding to a computational exception, the behavior is undefined; otherwise
12006 the program will resume execution at the point it was interrupted.
12008 If the signal occurs as the result of calling the abort or raise function, the signal
12009 handler shall not call the raise function.
12011 If the signal occurs other than as the result of calling the abort or raise function, the
12012 behavior is undefined if the signal handler refers to any object with static storage duration
12013 other than by assigning a value to an object declared as volatile sig_atomic_t, or
12014 the signal handler calls any function in the standard library other than the abort
12015 function, the _Exit function, or the signal function with the first argument equal to
12016 the signal number corresponding to the signal that caused the invocation of the handler.
12017 Furthermore, if such a call to the signal function results in a SIG_ERR return, the
12018 value of errno is indeterminate.<sup><a href="#note220"><b>220)</b></a></sup>
12020 At program startup, the equivalent of
12022 signal(sig, SIG_IGN);</pre>
12026 may be executed for some signals selected in an implementation-defined manner; the
12029 signal(sig, SIG_DFL);</pre>
12030 is executed for all other signals defined by the implementation.
12032 The implementation shall behave as if no library function calls the signal function.
12035 If the request can be honored, the signal function returns the value of func for the
12036 most recent successful call to signal for the specified signal sig. Otherwise, a value of
12037 SIG_ERR is returned and a positive value is stored in errno.
12038 <p><b> Forward references</b>: the abort function (<a href="#7.20.4.1">7.20.4.1</a>), the exit function (<a href="#7.20.4.3">7.20.4.3</a>), the
12039 _Exit function (<a href="#7.20.4.4">7.20.4.4</a>).
12042 <p><small><a name="note220" href="#note220">220)</a> If any signal is generated by an asynchronous signal handler, the behavior is undefined.
12045 <h4><a name="7.14.2" href="#7.14.2">7.14.2 Send signal</a></h4>
12047 <h5><a name="7.14.2.1" href="#7.14.2.1">7.14.2.1 The raise function</a></h5>
12051 #include <a href="#7.14"><signal.h></a>
12052 int raise(int sig);</pre>
12053 <h6>Description</h6>
12055 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
12056 signal handler is called, the raise function shall not return until after the signal handler
12060 The raise function returns zero if successful, nonzero if unsuccessful.
12063 <h3><a name="7.15" href="#7.15">7.15 Variable arguments <stdarg.h></a></h3>
12065 The header <a href="#7.15"><stdarg.h></a> declares a type and defines four macros, for advancing
12066 through a list of arguments whose number and types are not known to the called function
12067 when it is translated.
12069 A function may be called with a variable number of arguments of varying types. As
12070 described in <a href="#6.9.1">6.9.1</a>, its parameter list contains one or more parameters. The rightmost
12071 parameter plays a special role in the access mechanism, and will be designated parmN in
12074 The type declared is
12077 which is an object type suitable for holding information needed by the macros
12078 va_start, va_arg, va_end, and va_copy. If access to the varying arguments is
12079 desired, the called function shall declare an object (generally referred to as ap in this
12080 subclause) having type va_list. The object ap may be passed as an argument to
12081 another function; if that function invokes the va_arg macro with parameter ap, the
12082 value of ap in the calling function is indeterminate and shall be passed to the va_end
12083 macro prior to any further reference to ap.<sup><a href="#note221"><b>221)</b></a></sup>
12086 <p><small><a name="note221" href="#note221">221)</a> It is permitted to create a pointer to a va_list and pass that pointer to another function, in which
12087 case the original function may make further use of the original list after the other function returns.
12090 <h4><a name="7.15.1" href="#7.15.1">7.15.1 Variable argument list access macros</a></h4>
12092 The va_start and va_arg macros described in this subclause shall be implemented
12093 as macros, not functions. It is unspecified whether va_copy and va_end are macros or
12094 identifiers declared with external linkage. If a macro definition is suppressed in order to
12095 access an actual function, or a program defines an external identifier with the same name,
12096 the behavior is undefined. Each invocation of the va_start and va_copy macros
12097 shall be matched by a corresponding invocation of the va_end macro in the same
12100 <h5><a name="7.15.1.1" href="#7.15.1.1">7.15.1.1 The va_arg macro</a></h5>
12104 #include <a href="#7.15"><stdarg.h></a>
12105 type va_arg(va_list ap, type);</pre>
12106 <h6>Description</h6>
12108 The va_arg macro expands to an expression that has the specified type and the value of
12109 the next argument in the call. The parameter ap shall have been initialized by the
12110 va_start or va_copy macro (without an intervening invocation of the va_end
12113 macro for the same ap). Each invocation of the va_arg macro modifies ap so that the
12114 values of successive arguments are returned in turn. The parameter type shall be a type
12115 name specified such that the type of a pointer to an object that has the specified type can
12116 be obtained simply by postfixing a * to type. If there is no actual next argument, or if
12117 type is not compatible with the type of the actual next argument (as promoted according
12118 to the default argument promotions), the behavior is undefined, except for the following
12121 <li> one type is a signed integer type, the other type is the corresponding unsigned integer
12122 type, and the value is representable in both types;
12123 <li> one type is pointer to void and the other is a pointer to a character type.
12127 The first invocation of the va_arg macro after that of the va_start macro returns the
12128 value of the argument after that specified by parmN . Successive invocations return the
12129 values of the remaining arguments in succession.
12131 <h5><a name="7.15.1.2" href="#7.15.1.2">7.15.1.2 The va_copy macro</a></h5>
12135 #include <a href="#7.15"><stdarg.h></a>
12136 void va_copy(va_list dest, va_list src);</pre>
12137 <h6>Description</h6>
12139 The va_copy macro initializes dest as a copy of src, as if the va_start macro had
12140 been applied to dest followed by the same sequence of uses of the va_arg macro as
12141 had previously been used to reach the present state of src. Neither the va_copy nor
12142 va_start macro shall be invoked to reinitialize dest without an intervening
12143 invocation of the va_end macro for the same dest.
12146 The va_copy macro returns no value.
12148 <h5><a name="7.15.1.3" href="#7.15.1.3">7.15.1.3 The va_end macro</a></h5>
12152 #include <a href="#7.15"><stdarg.h></a>
12153 void va_end(va_list ap);</pre>
12154 <h6>Description</h6>
12156 The va_end macro facilitates a normal return from the function whose variable
12157 argument list was referred to by the expansion of the va_start macro, or the function
12158 containing the expansion of the va_copy macro, that initialized the va_list ap. The
12159 va_end macro may modify ap so that it is no longer usable (without being reinitialized
12161 by the va_start or va_copy macro). If there is no corresponding invocation of the
12162 va_start or va_copy macro, or if the va_end macro is not invoked before the
12163 return, the behavior is undefined.
12166 The va_end macro returns no value.
12168 <h5><a name="7.15.1.4" href="#7.15.1.4">7.15.1.4 The va_start macro</a></h5>
12172 #include <a href="#7.15"><stdarg.h></a>
12173 void va_start(va_list ap, parmN);</pre>
12174 <h6>Description</h6>
12176 The va_start macro shall be invoked before any access to the unnamed arguments.
12178 The va_start macro initializes ap for subsequent use by the va_arg and va_end
12179 macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap
12180 without an intervening invocation of the va_end macro for the same ap.
12182 The parameter parmN is the identifier of the rightmost parameter in the variable
12183 parameter list in the function definition (the one just before the , ...). If the parameter
12184 parmN is declared with the register storage class, with a function or array type, or
12185 with a type that is not compatible with the type that results after application of the default
12186 argument promotions, the behavior is undefined.
12189 The va_start macro returns no value.
12191 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not
12192 more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of
12193 pointers is specified by the first argument to f1.
12196 #include <a href="#7.15"><stdarg.h></a>
12198 void f1(int n_ptrs, ...)
12201 char *array[MAXARGS];
12203 if (n_ptrs > MAXARGS)
12205 va_start(ap, n_ptrs);
12206 while (ptr_no < n_ptrs)
12207 array[ptr_no++] = va_arg(ap, char *);
12211 Each call to f1 is required to have visible the definition of the function or a declaration such as
12213 void f1(int, ...);</pre>
12216 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the
12217 indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list
12218 is gathered again and passed to function f4.
12221 #include <a href="#7.15"><stdarg.h></a>
12223 void f3(int n_ptrs, int f4_after, ...)
12225 va_list ap, ap_save;
12226 char *array[MAXARGS];
12228 if (n_ptrs > MAXARGS)
12230 va_start(ap, f4_after);
12231 while (ptr_no < n_ptrs) {
12232 array[ptr_no++] = va_arg(ap, char *);
12233 if (ptr_no == f4_after)
12234 va_copy(ap_save, ap);
12238 // Now process the saved copy.
12239 n_ptrs -= f4_after;
12241 while (ptr_no < n_ptrs)
12242 array[ptr_no++] = va_arg(ap_save, char *);
12247 <h3><a name="7.16" href="#7.16">7.16 Boolean type and values <stdbool.h></a></h3>
12249 The header <a href="#7.16"><stdbool.h></a> defines four macros.
12256 The remaining three macros are suitable for use in #if preprocessing directives. They
12260 which expands to the integer constant 1,
12263 which expands to the integer constant 0, and
12265 __bool_true_false_are_defined</pre>
12266 which expands to the integer constant 1.
12268 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
12269 redefine the macros bool, true, and false.<sup><a href="#note222"><b>222)</b></a></sup>
12277 <p><small><a name="note222" href="#note222">222)</a> See ''future library directions'' (<a href="#7.26.7">7.26.7</a>).
12280 <h3><a name="7.17" href="#7.17">7.17 Common definitions <stddef.h></a></h3>
12282 The following types and macros are defined in the standard header <a href="#7.17"><stddef.h></a>. Some
12283 are also defined in other headers, as noted in their respective subclauses.
12288 which is the signed integer type of the result of subtracting two pointers;
12291 which is the unsigned integer type of the result of the sizeof operator; and
12294 which is an integer type whose range of values can represent distinct codes for all
12295 members of the largest extended character set specified among the supported locales; the
12296 null character shall have the code value zero. Each member of the basic character set
12297 shall have a code value equal to its value when used as the lone character in an integer
12298 character constant if an implementation does not define
12299 __STDC_MB_MIGHT_NEQ_WC__.
12304 which expands to an implementation-defined null pointer constant; and
12306 offsetof(type, member-designator)</pre>
12307 which expands to an integer constant expression that has type size_t, the value of
12308 which is the offset in bytes, to the structure member (designated by member-designator),
12309 from the beginning of its structure (designated by type). The type and member designator
12310 shall be such that given
12312 static type t;</pre>
12313 then the expression &(t.member-designator) evaluates to an address constant. (If the
12314 specified member is a bit-field, the behavior is undefined.)
12315 Recommended practice
12317 The types used for size_t and ptrdiff_t should not have an integer conversion rank
12318 greater than that of signed long int unless the implementation supports objects
12319 large enough to make this necessary.
12320 <p><b> Forward references</b>: localization (<a href="#7.11">7.11</a>).
12323 <h3><a name="7.18" href="#7.18">7.18 Integer types <stdint.h></a></h3>
12325 The header <a href="#7.18"><stdint.h></a> declares sets of integer types having specified widths, and
12326 defines corresponding sets of macros.<sup><a href="#note223"><b>223)</b></a></sup> It also defines macros that specify limits of
12327 integer types corresponding to types defined in other standard headers.
12329 Types are defined in the following categories:
12331 <li> integer types having certain exact widths;
12332 <li> integer types having at least certain specified widths;
12333 <li> fastest integer types having at least certain specified widths;
12334 <li> integer types wide enough to hold pointers to objects;
12335 <li> integer types having greatest width.
12337 (Some of these types may denote the same type.)
12339 Corresponding macros specify limits of the declared types and construct suitable
12342 For each type described herein that the implementation provides,<sup><a href="#note224"><b>224)</b></a></sup> <a href="#7.18"><stdint.h></a> shall
12343 declare that typedef name and define the associated macros. Conversely, for each type
12344 described herein that the implementation does not provide, <a href="#7.18"><stdint.h></a> shall not
12345 declare that typedef name nor shall it define the associated macros. An implementation
12346 shall provide those types described as ''required'', but need not provide any of the others
12347 (described as ''optional'').
12350 <p><small><a name="note223" href="#note223">223)</a> See ''future library directions'' (<a href="#7.26.8">7.26.8</a>).
12352 <p><small><a name="note224" href="#note224">224)</a> Some of these types may denote implementation-defined extended integer types.
12355 <h4><a name="7.18.1" href="#7.18.1">7.18.1 Integer types</a></h4>
12357 When typedef names differing only in the absence or presence of the initial u are defined,
12358 they shall denote corresponding signed and unsigned types as described in <a href="#6.2.5">6.2.5</a>; an
12359 implementation providing one of these corresponding types shall also provide the other.
12361 In the following descriptions, the symbol N represents an unsigned decimal integer with
12362 no leading zeros (e.g., 8 or 24, but not 04 or 048).
12369 <h5><a name="7.18.1.1" href="#7.18.1.1">7.18.1.1 Exact-width integer types</a></h5>
12371 The typedef name intN_t designates a signed integer type with width N , no padding
12372 bits, and a two's complement representation. Thus, int8_t denotes a signed integer
12373 type with a width of exactly 8 bits.
12375 The typedef name uintN_t designates an unsigned integer type with width N . Thus,
12376 uint24_t denotes an unsigned integer type with a width of exactly 24 bits.
12378 These types are optional. However, if an implementation provides integer types with
12379 widths of 8, 16, 32, or 64 bits, no padding bits, and (for the signed types) that have a
12380 two's complement representation, it shall define the corresponding typedef names.
12382 <h5><a name="7.18.1.2" href="#7.18.1.2">7.18.1.2 Minimum-width integer types</a></h5>
12384 The typedef name int_leastN_t designates a signed integer type with a width of at
12385 least N , such that no signed integer type with lesser size has at least the specified width.
12386 Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits.
12388 The typedef name uint_leastN_t designates an unsigned integer type with a width
12389 of at least N , such that no unsigned integer type with lesser size has at least the specified
12390 width. Thus, uint_least16_t denotes an unsigned integer type with a width of at
12393 The following types are required:
12395 int_least8_t uint_least8_t
12396 int_least16_t uint_least16_t
12397 int_least32_t uint_least32_t
12398 int_least64_t uint_least64_t</pre>
12399 All other types of this form are optional.
12401 <h5><a name="7.18.1.3" href="#7.18.1.3">7.18.1.3 Fastest minimum-width integer types</a></h5>
12403 Each of the following types designates an integer type that is usually fastest<sup><a href="#note225"><b>225)</b></a></sup> to operate
12404 with among all integer types that have at least the specified width.
12406 The typedef name int_fastN_t designates the fastest signed integer type with a width
12407 of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer
12408 type with a width of at least N .
12415 The following types are required:
12417 int_fast8_t uint_fast8_t
12418 int_fast16_t uint_fast16_t
12419 int_fast32_t uint_fast32_t
12420 int_fast64_t uint_fast64_t</pre>
12421 All other types of this form are optional.
12424 <p><small><a name="note225" href="#note225">225)</a> The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear
12425 grounds for choosing one type over another, it will simply pick some integer type satisfying the
12426 signedness and width requirements.
12429 <h5><a name="7.18.1.4" href="#7.18.1.4">7.18.1.4 Integer types capable of holding object pointers</a></h5>
12431 The following type designates a signed integer type with the property that any valid
12432 pointer to void can be converted to this type, then converted back to pointer to void,
12433 and the result will compare equal to the original pointer:
12436 The following type designates an unsigned integer type with the property that any valid
12437 pointer to void can be converted to this type, then converted back to pointer to void,
12438 and the result will compare equal to the original pointer:
12441 These types are optional.
12443 <h5><a name="7.18.1.5" href="#7.18.1.5">7.18.1.5 Greatest-width integer types</a></h5>
12445 The following type designates a signed integer type capable of representing any value of
12446 any signed integer type:
12449 The following type designates an unsigned integer type capable of representing any value
12450 of any unsigned integer type:
12453 These types are required.
12455 <h4><a name="7.18.2" href="#7.18.2">7.18.2 Limits of specified-width integer types</a></h4>
12457 The following object-like macros<sup><a href="#note226"><b>226)</b></a></sup> specify the minimum and maximum limits of the
12458 types declared in <a href="#7.18"><stdint.h></a>. Each macro name corresponds to a similar type name in
12459 <a href="#7.18.1">7.18.1</a>.
12461 Each instance of any defined macro shall be replaced by a constant expression suitable
12462 for use in #if preprocessing directives, and this expression shall have the same type as
12463 would an expression that is an object of the corresponding type converted according to
12466 the integer promotions. Its implementation-defined value shall be equal to or greater in
12467 magnitude (absolute value) than the corresponding value given below, with the same sign,
12468 except where stated to be exactly the given value.
12471 <p><small><a name="note226" href="#note226">226)</a> C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined
12472 before <a href="#7.18"><stdint.h></a> is included.
12475 <h5><a name="7.18.2.1" href="#7.18.2.1">7.18.2.1 Limits of exact-width integer types</a></h5>
12478 <li> minimum values of exact-width signed integer types
12479 INTN_MIN exactly -(2 N -1 )
12480 <li> maximum values of exact-width signed integer types
12481 INTN_MAX exactly 2 N -1 - 1
12482 <li> maximum values of exact-width unsigned integer types
12483 UINTN_MAX exactly 2 N - 1
12486 <h5><a name="7.18.2.2" href="#7.18.2.2">7.18.2.2 Limits of minimum-width integer types</a></h5>
12489 <li> minimum values of minimum-width signed integer types
12490 INT_LEASTN_MIN -(2 N -1 - 1)
12491 <li> maximum values of minimum-width signed integer types
12492 INT_LEASTN_MAX 2 N -1 - 1
12493 <li> maximum values of minimum-width unsigned integer types
12494 UINT_LEASTN_MAX 2N - 1
12497 <h5><a name="7.18.2.3" href="#7.18.2.3">7.18.2.3 Limits of fastest minimum-width integer types</a></h5>
12500 <li> minimum values of fastest minimum-width signed integer types
12501 INT_FASTN_MIN -(2 N -1 - 1)
12502 <li> maximum values of fastest minimum-width signed integer types
12503 INT_FASTN_MAX 2 N -1 - 1
12504 <li> maximum values of fastest minimum-width unsigned integer types
12505 UINT_FASTN_MAX 2N - 1
12508 <h5><a name="7.18.2.4" href="#7.18.2.4">7.18.2.4 Limits of integer types capable of holding object pointers</a></h5>
12511 <li> minimum value of pointer-holding signed integer type
12513 INTPTR_MIN -(215 - 1)</pre>
12514 <li> maximum value of pointer-holding signed integer type
12517 INTPTR_MAX 215 - 1</pre>
12518 <li> maximum value of pointer-holding unsigned integer type
12519 UINTPTR_MAX 216 - 1
12522 <h5><a name="7.18.2.5" href="#7.18.2.5">7.18.2.5 Limits of greatest-width integer types</a></h5>
12525 <li> minimum value of greatest-width signed integer type
12526 INTMAX_MIN -(263 - 1)
12527 <li> maximum value of greatest-width signed integer type
12529 <li> maximum value of greatest-width unsigned integer type
12530 UINTMAX_MAX 264 - 1
12533 <h4><a name="7.18.3" href="#7.18.3">7.18.3 Limits of other integer types</a></h4>
12535 The following object-like macros<sup><a href="#note227"><b>227)</b></a></sup> specify the minimum and maximum limits of
12536 integer types corresponding to types defined in other standard headers.
12538 Each instance of these macros shall be replaced by a constant expression suitable for use
12539 in #if preprocessing directives, and this expression shall have the same type as would an
12540 expression that is an object of the corresponding type converted according to the integer
12541 promotions. Its implementation-defined value shall be equal to or greater in magnitude
12542 (absolute value) than the corresponding value given below, with the same sign. An
12543 implementation shall define only the macros corresponding to those typedef names it
12544 actually provides.<sup><a href="#note228"><b>228)</b></a></sup>
12546 <li> limits of ptrdiff_t
12549 <li> limits of sig_atomic_t
12550 SIG_ATOMIC_MIN see below
12551 SIG_ATOMIC_MAX see below
12552 <li> limit of size_t
12554 <li> limits of wchar_t
12559 WCHAR_MIN see below
12560 WCHAR_MAX see below
12561 <li> limits of wint_t
12566 If sig_atomic_t (see <a href="#7.14">7.14</a>) is defined as a signed integer type, the value of
12567 SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX
12568 shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
12569 type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
12570 SIG_ATOMIC_MAX shall be no less than 255.
12572 If wchar_t (see <a href="#7.17">7.17</a>) is defined as a signed integer type, the value of WCHAR_MIN
12573 shall be no greater than -127 and the value of WCHAR_MAX shall be no less than 127;
12574 otherwise, wchar_t is defined as an unsigned integer type, and the value of
12575 WCHAR_MIN shall be 0 and the value of WCHAR_MAX shall be no less than 255.<sup><a href="#note229"><b>229)</b></a></sup>
12577 If wint_t (see <a href="#7.24">7.24</a>) is defined as a signed integer type, the value of WINT_MIN shall
12578 be no greater than -32767 and the value of WINT_MAX shall be no less than 32767;
12579 otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
12580 shall be 0 and the value of WINT_MAX shall be no less than 65535.
12583 <p><small><a name="note227" href="#note227">227)</a> C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined
12584 before <a href="#7.18"><stdint.h></a> is included.
12586 <p><small><a name="note228" href="#note228">228)</a> A freestanding implementation need not provide all of these types.
12588 <p><small><a name="note229" href="#note229">229)</a> The values WCHAR_MIN and WCHAR_MAX do not necessarily correspond to members of the extended
12592 <h4><a name="7.18.4" href="#7.18.4">7.18.4 Macros for integer constants</a></h4>
12594 The following function-like macros<sup><a href="#note230"><b>230)</b></a></sup> expand to integer constants suitable for
12595 initializing objects that have integer types corresponding to types defined in
12596 <a href="#7.18"><stdint.h></a>. Each macro name corresponds to a similar type name in <a href="#7.18.1.2">7.18.1.2</a> or
12597 <a href="#7.18.1.5">7.18.1.5</a>.
12599 The argument in any instance of these macros shall be an unsuffixed integer constant (as
12600 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.
12602 Each invocation of one of these macros shall expand to an integer constant expression
12603 suitable for use in #if preprocessing directives. The type of the expression shall have
12604 the same type as would an expression of the corresponding type converted according to
12605 the integer promotions. The value of the expression shall be that of the argument.
12613 <p><small><a name="note230" href="#note230">230)</a> C++ implementations should define these macros only when __STDC_CONSTANT_MACROS is
12614 defined before <a href="#7.18"><stdint.h></a> is included.
12617 <h5><a name="7.18.4.1" href="#7.18.4.1">7.18.4.1 Macros for minimum-width integer constants</a></h5>
12619 The macro INTN_C(value) shall expand to an integer constant expression
12620 corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
12621 to an integer constant expression corresponding to the type uint_leastN_t. For
12622 example, if uint_least64_t is a name for the type unsigned long long int,
12623 then UINT64_C(0x123) might expand to the integer constant 0x123ULL.
12625 <h5><a name="7.18.4.2" href="#7.18.4.2">7.18.4.2 Macros for greatest-width integer constants</a></h5>
12627 The following macro expands to an integer constant expression having the value specified
12628 by its argument and the type intmax_t:
12630 INTMAX_C(value)</pre>
12631 The following macro expands to an integer constant expression having the value specified
12632 by its argument and the type uintmax_t:
12635 UINTMAX_C(value)</pre>
12637 <h3><a name="7.19" href="#7.19">7.19 Input/output <stdio.h></a></h3>
12639 <h4><a name="7.19.1" href="#7.19.1">7.19.1 Introduction</a></h4>
12641 The header <a href="#7.19"><stdio.h></a> declares three types, several macros, and many functions for
12642 performing input and output.
12644 The types declared are size_t (described in <a href="#7.17">7.17</a>);
12647 which is an object type capable of recording all the information needed to control a
12648 stream, including its file position indicator, a pointer to its associated buffer (if any), an
12649 error indicator that records whether a read/write error has occurred, and an end-of-file
12650 indicator that records whether the end of the file has been reached; and
12653 which is an object type other than an array type capable of recording all the information
12654 needed to specify uniquely every position within a file.
12656 The macros are NULL (described in <a href="#7.17">7.17</a>);
12661 which expand to integer constant expressions with distinct values, suitable for use as the
12662 third argument to the setvbuf function;
12665 which expands to an integer constant expression that is the size of the buffer used by the
12669 which expands to an integer constant expression, with type int and a negative value, that
12670 is returned by several functions to indicate end-of-file, that is, no more input from a
12674 which expands to an integer constant expression that is the minimum number of files that
12675 the implementation guarantees can be open simultaneously;
12678 which expands to an integer constant expression that is the size needed for an array of
12679 char large enough to hold the longest file name string that the implementation
12681 guarantees can be opened;<sup><a href="#note231"><b>231)</b></a></sup>
12684 which expands to an integer constant expression that is the size needed for an array of
12685 char large enough to hold a temporary file name string generated by the tmpnam
12691 which expand to integer constant expressions with distinct values, suitable for use as the
12692 third argument to the fseek function;
12695 which expands to an integer constant expression that is the maximum number of unique
12696 file names that can be generated by the tmpnam function;
12701 which are expressions of type ''pointer to FILE'' that point to the FILE objects
12702 associated, respectively, with the standard error, input, and output streams.
12704 The header <a href="#7.24"><wchar.h></a> declares a number of functions useful for wide character input
12705 and output. The wide character input/output functions described in that subclause
12706 provide operations analogous to most of those described here, except that the
12707 fundamental units internal to the program are wide characters. The external
12708 representation (in the file) is a sequence of ''generalized'' multibyte characters, as
12709 described further in <a href="#7.19.3">7.19.3</a>.
12711 The input/output functions are given the following collective terms:
12713 <li> The wide character input functions -- those functions described in <a href="#7.24">7.24</a> that perform
12714 input into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar,
12715 fwscanf, wscanf, vfwscanf, and vwscanf.
12716 <li> The wide character output functions -- those functions described in <a href="#7.24">7.24</a> that perform
12717 output from wide characters and wide strings: fputwc, fputws, putwc,
12718 putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
12722 <li> The wide character input/output functions -- the union of the ungetwc function, the
12723 wide character input functions, and the wide character output functions.
12724 <li> The byte input/output functions -- those functions described in this subclause that
12725 perform input/output: fgetc, fgets, fprintf, fputc, fputs, fread,
12726 fscanf, fwrite, getc, getchar, gets, printf, putc, putchar, puts,
12727 scanf, ungetc, vfprintf, vfscanf, vprintf, and vscanf.
12729 <p><b> Forward references</b>: files (<a href="#7.19.3">7.19.3</a>), the fseek function (<a href="#7.19.9.2">7.19.9.2</a>), streams (<a href="#7.19.2">7.19.2</a>), the
12730 tmpnam function (<a href="#7.19.4.4">7.19.4.4</a>), <a href="#7.24"><wchar.h></a> (<a href="#7.24">7.24</a>).
12733 <p><small><a name="note231" href="#note231">231)</a> If the implementation imposes no practical limit on the length of file name strings, the value of
12734 FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
12735 string. Of course, file name string contents are subject to other system-specific constraints; therefore
12736 all possible strings of length FILENAME_MAX cannot be expected to be opened successfully.
12739 <h4><a name="7.19.2" href="#7.19.2">7.19.2 Streams</a></h4>
12741 Input and output, whether to or from physical devices such as terminals and tape drives,
12742 or whether to or from files supported on structured storage devices, are mapped into
12743 logical data streams, whose properties are more uniform than their various inputs and
12744 outputs. Two forms of mapping are supported, for text streams and for binary
12745 streams.<sup><a href="#note232"><b>232)</b></a></sup>
12747 A text stream is an ordered sequence of characters composed into lines, each line
12748 consisting of zero or more characters plus a terminating new-line character. Whether the
12749 last line requires a terminating new-line character is implementation-defined. Characters
12750 may have to be added, altered, or deleted on input and output to conform to differing
12751 conventions for representing text in the host environment. Thus, there need not be a one-
12752 to-one correspondence between the characters in a stream and those in the external
12753 representation. Data read in from a text stream will necessarily compare equal to the data
12754 that were earlier written out to that stream only if: the data consist only of printing
12755 characters and the control characters horizontal tab and new-line; no new-line character is
12756 immediately preceded by space characters; and the last character is a new-line character.
12757 Whether space characters that are written out immediately before a new-line character
12758 appear when read in is implementation-defined.
12760 A binary stream is an ordered sequence of characters that can transparently record
12761 internal data. Data read in from a binary stream shall compare equal to the data that were
12762 earlier written out to that stream, under the same implementation. Such a stream may,
12763 however, have an implementation-defined number of null characters appended to the end
12766 Each stream has an orientation. After a stream is associated with an external file, but
12767 before any operations are performed on it, the stream is without orientation. Once a wide
12768 character input/output function has been applied to a stream without orientation, the
12772 stream becomes a wide-oriented stream. Similarly, once a byte input/output function has
12773 been applied to a stream without orientation, the stream becomes a byte-oriented stream.
12774 Only a call to the freopen function or the fwide function can otherwise alter the
12775 orientation of a stream. (A successful call to freopen removes any orientation.)<sup><a href="#note233"><b>233)</b></a></sup>
12777 Byte input/output functions shall not be applied to a wide-oriented stream and wide
12778 character input/output functions shall not be applied to a byte-oriented stream. The
12779 remaining stream operations do not affect, and are not affected by, a stream's orientation,
12780 except for the following additional restrictions:
12782 <li> Binary wide-oriented streams have the file-positioning restrictions ascribed to both
12783 text and binary streams.
12784 <li> For wide-oriented streams, after a successful call to a file-positioning function that
12785 leaves the file position indicator prior to the end-of-file, a wide character output
12786 function can overwrite a partial multibyte character; any file contents beyond the
12787 byte(s) written are henceforth indeterminate.
12790 Each wide-oriented stream has an associated mbstate_t object that stores the current
12791 parse state of the stream. A successful call to fgetpos stores a representation of the
12792 value of this mbstate_t object as part of the value of the fpos_t object. A later
12793 successful call to fsetpos using the same stored fpos_t value restores the value of
12794 the associated mbstate_t object as well as the position within the controlled stream.
12795 Environmental limits
12797 An implementation shall support text files with lines containing at least 254 characters,
12798 including the terminating new-line character. The value of the macro BUFSIZ shall be at
12800 <p><b> Forward references</b>: the freopen function (<a href="#7.19.5.4">7.19.5.4</a>), the fwide function (<a href="#7.24.3.5">7.24.3.5</a>),
12801 mbstate_t (<a href="#7.25.1">7.25.1</a>), the fgetpos function (<a href="#7.19.9.1">7.19.9.1</a>), the fsetpos function
12802 (<a href="#7.19.9.3">7.19.9.3</a>).
12810 <p><small><a name="note232" href="#note232">232)</a> An implementation need not distinguish between text streams and binary streams. In such an
12811 implementation, there need be no new-line characters in a text stream nor any limit to the length of a
12814 <p><small><a name="note233" href="#note233">233)</a> The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
12817 <h4><a name="7.19.3" href="#7.19.3">7.19.3 Files</a></h4>
12819 A stream is associated with an external file (which may be a physical device) by opening
12820 a file, which may involve creating a new file. Creating an existing file causes its former
12821 contents to be discarded, if necessary. If a file can support positioning requests (such as a
12822 disk file, as opposed to a terminal), then a file position indicator associated with the
12823 stream is positioned at the start (character number zero) of the file, unless the file is
12824 opened with append mode in which case it is implementation-defined whether the file
12825 position indicator is initially positioned at the beginning or the end of the file. The file
12826 position indicator is maintained by subsequent reads, writes, and positioning requests, to
12827 facilitate an orderly progression through the file.
12829 Binary files are not truncated, except as defined in <a href="#7.19.5.3">7.19.5.3</a>. Whether a write on a text
12830 stream causes the associated file to be truncated beyond that point is implementation-
12833 When a stream is unbuffered, characters are intended to appear from the source or at the
12834 destination as soon as possible. Otherwise characters may be accumulated and
12835 transmitted to or from the host environment as a block. When a stream is fully buffered,
12836 characters are intended to be transmitted to or from the host environment as a block when
12837 a buffer is filled. When a stream is line buffered, characters are intended to be
12838 transmitted to or from the host environment as a block when a new-line character is
12839 encountered. Furthermore, characters are intended to be transmitted as a block to the host
12840 environment when a buffer is filled, when input is requested on an unbuffered stream, or
12841 when input is requested on a line buffered stream that requires the transmission of
12842 characters from the host environment. Support for these characteristics is
12843 implementation-defined, and may be affected via the setbuf and setvbuf functions.
12845 A file may be disassociated from a controlling stream by closing the file. Output streams
12846 are flushed (any unwritten buffer contents are transmitted to the host environment) before
12847 the stream is disassociated from the file. The value of a pointer to a FILE object is
12848 indeterminate after the associated file is closed (including the standard text streams).
12849 Whether a file of zero length (on which no characters have been written by an output
12850 stream) actually exists is implementation-defined.
12852 The file may be subsequently reopened, by the same or another program execution, and
12853 its contents reclaimed or modified (if it can be repositioned at its start). If the main
12854 function returns to its original caller, or if the exit function is called, all open files are
12855 closed (hence all output streams are flushed) before program termination. Other paths to
12856 program termination, such as calling the abort function, need not close all files
12859 The address of the FILE object used to control a stream may be significant; a copy of a
12860 FILE object need not serve in place of the original.
12863 At program startup, three text streams are predefined and need not be opened explicitly
12865 <li> standard input (for reading conventional input), standard output (for writing
12867 conventional output), and standard error (for writing diagnostic output). As initially
12868 opened, the standard error stream is not fully buffered; the standard input and standard
12869 output streams are fully buffered if and only if the stream can be determined not to refer
12870 to an interactive device.
12872 Functions that open additional (nontemporary) files require a file name, which is a string.
12873 The rules for composing valid file names are implementation-defined. Whether the same
12874 file can be simultaneously open multiple times is also implementation-defined.
12876 Although both text and binary wide-oriented streams are conceptually sequences of wide
12877 characters, the external file associated with a wide-oriented stream is a sequence of
12878 multibyte characters, generalized as follows:
12880 <li> Multibyte encodings within files may contain embedded null bytes (unlike multibyte
12881 encodings valid for use internal to the program).
12882 <li> A file need not begin nor end in the initial shift state.<sup><a href="#note234"><b>234)</b></a></sup>
12885 Moreover, the encodings used for multibyte characters may differ among files. Both the
12886 nature and choice of such encodings are implementation-defined.
12888 The wide character input functions read multibyte characters from the stream and convert
12889 them to wide characters as if they were read by successive calls to the fgetwc function.
12890 Each conversion occurs as if by a call to the mbrtowc function, with the conversion state
12891 described by the stream's own mbstate_t object. The byte input functions read
12892 characters from the stream as if by successive calls to the fgetc function.
12894 The wide character output functions convert wide characters to multibyte characters and
12895 write them to the stream as if they were written by successive calls to the fputwc
12896 function. Each conversion occurs as if by a call to the wcrtomb function, with the
12897 conversion state described by the stream's own mbstate_t object. The byte output
12898 functions write characters to the stream as if by successive calls to the fputc function.
12900 In some cases, some of the byte input/output functions also perform conversions between
12901 multibyte characters and wide characters. These conversions also occur as if by calls to
12902 the mbrtowc and wcrtomb functions.
12904 An encoding error occurs if the character sequence presented to the underlying
12905 mbrtowc function does not form a valid (generalized) multibyte character, or if the code
12906 value passed to the underlying wcrtomb does not correspond to a valid (generalized)
12910 multibyte character. The wide character input/output functions and the byte input/output
12911 functions store the value of the macro EILSEQ in errno if and only if an encoding error
12913 Environmental limits
12915 The value of FOPEN_MAX shall be at least eight, including the three standard text
12917 <p><b> Forward references</b>: the exit function (<a href="#7.20.4.3">7.20.4.3</a>), the fgetc function (<a href="#7.19.7.1">7.19.7.1</a>), the
12918 fopen function (<a href="#7.19.5.3">7.19.5.3</a>), the fputc function (<a href="#7.19.7.3">7.19.7.3</a>), the setbuf function
12919 (<a href="#7.19.5.5">7.19.5.5</a>), the setvbuf function (<a href="#7.19.5.6">7.19.5.6</a>), the fgetwc function (<a href="#7.24.3.1">7.24.3.1</a>), the
12920 fputwc function (<a href="#7.24.3.3">7.24.3.3</a>), conversion state (<a href="#7.24.6">7.24.6</a>), the mbrtowc function
12921 (<a href="#7.24.6.3.2">7.24.6.3.2</a>), the wcrtomb function (<a href="#7.24.6.3.3">7.24.6.3.3</a>).
12924 <p><small><a name="note234" href="#note234">234)</a> Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END), has
12925 undefined behavior for a binary stream (because of possible trailing null characters) or for any stream
12926 with state-dependent encoding that does not assuredly end in the initial shift state.
12929 <h4><a name="7.19.4" href="#7.19.4">7.19.4 Operations on files</a></h4>
12931 <h5><a name="7.19.4.1" href="#7.19.4.1">7.19.4.1 The remove function</a></h5>
12935 #include <a href="#7.19"><stdio.h></a>
12936 int remove(const char *filename);</pre>
12937 <h6>Description</h6>
12939 The remove function causes the file whose name is the string pointed to by filename
12940 to be no longer accessible by that name. A subsequent attempt to open that file using that
12941 name will fail, unless it is created anew. If the file is open, the behavior of the remove
12942 function is implementation-defined.
12945 The remove function returns zero if the operation succeeds, nonzero if it fails.
12947 <h5><a name="7.19.4.2" href="#7.19.4.2">7.19.4.2 The rename function</a></h5>
12951 #include <a href="#7.19"><stdio.h></a>
12952 int rename(const char *old, const char *new);</pre>
12953 <h6>Description</h6>
12955 The rename function causes the file whose name is the string pointed to by old to be
12956 henceforth known by the name given by the string pointed to by new. The file named
12957 old is no longer accessible by that name. If a file named by the string pointed to by new
12958 exists prior to the call to the rename function, the behavior is implementation-defined.
12962 The rename function returns zero if the operation succeeds, nonzero if it fails,<sup><a href="#note235"><b>235)</b></a></sup> in
12963 which case if the file existed previously it is still known by its original name.
12966 <p><small><a name="note235" href="#note235">235)</a> Among the reasons the implementation may cause the rename function to fail are that the file is open
12967 or that it is necessary to copy its contents to effectuate its renaming.
12970 <h5><a name="7.19.4.3" href="#7.19.4.3">7.19.4.3 The tmpfile function</a></h5>
12974 #include <a href="#7.19"><stdio.h></a>
12975 FILE *tmpfile(void);</pre>
12976 <h6>Description</h6>
12978 The tmpfile function creates a temporary binary file that is different from any other
12979 existing file and that will automatically be removed when it is closed or at program
12980 termination. If the program terminates abnormally, whether an open temporary file is
12981 removed is implementation-defined. The file is opened for update with "wb+" mode.
12982 Recommended practice
12984 It should be possible to open at least TMP_MAX temporary files during the lifetime of the
12985 program (this limit may be shared with tmpnam) and there should be no limit on the
12986 number simultaneously open other than this limit and any limit on the number of open
12990 The tmpfile function returns a pointer to the stream of the file that it created. If the file
12991 cannot be created, the tmpfile function returns a null pointer.
12992 <p><b> Forward references</b>: the fopen function (<a href="#7.19.5.3">7.19.5.3</a>).
12994 <h5><a name="7.19.4.4" href="#7.19.4.4">7.19.4.4 The tmpnam function</a></h5>
12998 #include <a href="#7.19"><stdio.h></a>
12999 char *tmpnam(char *s);</pre>
13000 <h6>Description</h6>
13002 The tmpnam function generates a string that is a valid file name and that is not the same
13003 as the name of an existing file.<sup><a href="#note236"><b>236)</b></a></sup> The function is potentially capable of generating
13007 TMP_MAX different strings, but any or all of them may already be in use by existing files
13008 and thus not be suitable return values.
13010 The tmpnam function generates a different string each time it is called.
13012 The implementation shall behave as if no library function calls the tmpnam function.
13015 If no suitable string can be generated, the tmpnam function returns a null pointer.
13016 Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an
13017 internal static object and returns a pointer to that object (subsequent calls to the tmpnam
13018 function may modify the same object). If the argument is not a null pointer, it is assumed
13019 to point to an array of at least L_tmpnam chars; the tmpnam function writes its result
13020 in that array and returns the argument as its value.
13021 Environmental limits
13023 The value of the macro TMP_MAX shall be at least 25.
13026 <p><small><a name="note236" href="#note236">236)</a> Files created using strings generated by the tmpnam function are temporary only in the sense that
13027 their names should not collide with those generated by conventional naming rules for the
13028 implementation. It is still necessary to use the remove function to remove such files when their use
13029 is ended, and before program termination.
13032 <h4><a name="7.19.5" href="#7.19.5">7.19.5 File access functions</a></h4>
13034 <h5><a name="7.19.5.1" href="#7.19.5.1">7.19.5.1 The fclose function</a></h5>
13038 #include <a href="#7.19"><stdio.h></a>
13039 int fclose(FILE *stream);</pre>
13040 <h6>Description</h6>
13042 A successful call to the fclose function causes the stream pointed to by stream to be
13043 flushed and the associated file to be closed. Any unwritten buffered data for the stream
13044 are delivered to the host environment to be written to the file; any unread buffered data
13045 are discarded. Whether or not the call succeeds, the stream is disassociated from the file
13046 and any buffer set by the setbuf or setvbuf function is disassociated from the stream
13047 (and deallocated if it was automatically allocated).
13050 The fclose function returns zero if the stream was successfully closed, or EOF if any
13051 errors were detected.
13053 <h5><a name="7.19.5.2" href="#7.19.5.2">7.19.5.2 The fflush function</a></h5>
13058 #include <a href="#7.19"><stdio.h></a>
13059 int fflush(FILE *stream);</pre>
13060 <h6>Description</h6>
13062 If stream points to an output stream or an update stream in which the most recent
13063 operation was not input, the fflush function causes any unwritten data for that stream
13064 to be delivered to the host environment to be written to the file; otherwise, the behavior is
13067 If stream is a null pointer, the fflush function performs this flushing action on all
13068 streams for which the behavior is defined above.
13071 The fflush function sets the error indicator for the stream and returns EOF if a write
13072 error occurs, otherwise it returns zero.
13073 <p><b> Forward references</b>: the fopen function (<a href="#7.19.5.3">7.19.5.3</a>).
13075 <h5><a name="7.19.5.3" href="#7.19.5.3">7.19.5.3 The fopen function</a></h5>
13079 #include <a href="#7.19"><stdio.h></a>
13080 FILE *fopen(const char * restrict filename,
13081 const char * restrict mode);</pre>
13082 <h6>Description</h6>
13084 The fopen function opens the file whose name is the string pointed to by filename,
13085 and associates a stream with it.
13087 The argument mode points to a string. If the string is one of the following, the file is
13088 open in the indicated mode. Otherwise, the behavior is undefined.<sup><a href="#note237"><b>237)</b></a></sup>
13089 r open text file for reading
13090 w truncate to zero length or create text file for writing
13091 a append; open or create text file for writing at end-of-file
13092 rb open binary file for reading
13093 wb truncate to zero length or create binary file for writing
13094 ab append; open or create binary file for writing at end-of-file
13095 r+ open text file for update (reading and writing)
13096 w+ truncate to zero length or create text file for update
13097 a+ append; open or create text file for update, writing at end-of-file
13103 r+b or rb+ open binary file for update (reading and writing)
13104 w+b or wb+ truncate to zero length or create binary file for update
13105 a+b or ab+ append; open or create binary file for update, writing at end-of-file
13107 Opening a file with read mode ('r' as the first character in the mode argument) fails if
13108 the file does not exist or cannot be read.
13110 Opening a file with append mode ('a' as the first character in the mode argument)
13111 causes all subsequent writes to the file to be forced to the then current end-of-file,
13112 regardless of intervening calls to the fseek function. In some implementations, opening
13113 a binary file with append mode ('b' as the second or third character in the above list of
13114 mode argument values) may initially position the file position indicator for the stream
13115 beyond the last data written, because of null character padding.
13117 When a file is opened with update mode ('+' as the second or third character in the
13118 above list of mode argument values), both input and output may be performed on the
13119 associated stream. However, output shall not be directly followed by input without an
13120 intervening call to the fflush function or to a file positioning function (fseek,
13121 fsetpos, or rewind), and input shall not be directly followed by output without an
13122 intervening call to a file positioning function, unless the input operation encounters end-
13123 of-file. Opening (or creating) a text file with update mode may instead open (or create) a
13124 binary stream in some implementations.
13126 When opened, a stream is fully buffered if and only if it can be determined not to refer to
13127 an interactive device. The error and end-of-file indicators for the stream are cleared.
13130 The fopen function returns a pointer to the object controlling the stream. If the open
13131 operation fails, fopen returns a null pointer.
13132 <p><b> Forward references</b>: file positioning functions (<a href="#7.19.9">7.19.9</a>).
13135 <p><small><a name="note237" href="#note237">237)</a> If the string begins with one of the above sequences, the implementation might choose to ignore the
13136 remaining characters, or it might use them to select different kinds of a file (some of which might not
13137 conform to the properties in <a href="#7.19.2">7.19.2</a>).
13140 <h5><a name="7.19.5.4" href="#7.19.5.4">7.19.5.4 The freopen function</a></h5>
13144 #include <a href="#7.19"><stdio.h></a>
13145 FILE *freopen(const char * restrict filename,
13146 const char * restrict mode,
13147 FILE * restrict stream);</pre>
13148 <h6>Description</h6>
13150 The freopen function opens the file whose name is the string pointed to by filename
13151 and associates the stream pointed to by stream with it. The mode argument is used just
13153 as in the fopen function.<sup><a href="#note238"><b>238)</b></a></sup>
13155 If filename is a null pointer, the freopen function attempts to change the mode of
13156 the stream to that specified by mode, as if the name of the file currently associated with
13157 the stream had been used. It is implementation-defined which changes of mode are
13158 permitted (if any), and under what circumstances.
13160 The freopen function first attempts to close any file that is associated with the specified
13161 stream. Failure to close the file is ignored. The error and end-of-file indicators for the
13162 stream are cleared.
13165 The freopen function returns a null pointer if the open operation fails. Otherwise,
13166 freopen returns the value of stream.
13169 <p><small><a name="note238" href="#note238">238)</a> The primary use of the freopen function is to change the file associated with a standard text stream
13170 (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value
13171 returned by the fopen function may be assigned.
13174 <h5><a name="7.19.5.5" href="#7.19.5.5">7.19.5.5 The setbuf function</a></h5>
13178 #include <a href="#7.19"><stdio.h></a>
13179 void setbuf(FILE * restrict stream,
13180 char * restrict buf);</pre>
13181 <h6>Description</h6>
13183 Except that it returns no value, the setbuf function is equivalent to the setvbuf
13184 function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
13185 is a null pointer), with the value _IONBF for mode.
13188 The setbuf function returns no value.
13189 <p><b> Forward references</b>: the setvbuf function (<a href="#7.19.5.6">7.19.5.6</a>).
13191 <h5><a name="7.19.5.6" href="#7.19.5.6">7.19.5.6 The setvbuf function</a></h5>
13195 #include <a href="#7.19"><stdio.h></a>
13196 int setvbuf(FILE * restrict stream,
13197 char * restrict buf,
13198 int mode, size_t size);</pre>
13204 <h6>Description</h6>
13206 The setvbuf function may be used only after the stream pointed to by stream has
13207 been associated with an open file and before any other operation (other than an
13208 unsuccessful call to setvbuf) is performed on the stream. The argument mode
13209 determines how stream will be buffered, as follows: _IOFBF causes input/output to be
13210 fully buffered; _IOLBF causes input/output to be line buffered; _IONBF causes
13211 input/output to be unbuffered. If buf is not a null pointer, the array it points to may be
13212 used instead of a buffer allocated by the setvbuf function<sup><a href="#note239"><b>239)</b></a></sup> and the argument size
13213 specifies the size of the array; otherwise, size may determine the size of a buffer
13214 allocated by the setvbuf function. The contents of the array at any time are
13218 The setvbuf function returns zero on success, or nonzero if an invalid value is given
13219 for mode or if the request cannot be honored.
13222 <p><small><a name="note239" href="#note239">239)</a> The buffer has to have a lifetime at least as great as the open stream, so the stream should be closed
13223 before a buffer that has automatic storage duration is deallocated upon block exit.
13226 <h4><a name="7.19.6" href="#7.19.6">7.19.6 Formatted input/output functions</a></h4>
13228 The formatted input/output functions shall behave as if there is a sequence point after the
13229 actions associated with each specifier.<sup><a href="#note240"><b>240)</b></a></sup>
13232 <p><small><a name="note240" href="#note240">240)</a> The fprintf functions perform writes to memory for the %n specifier.
13235 <h5><a name="7.19.6.1" href="#7.19.6.1">7.19.6.1 The fprintf function</a></h5>
13239 #include <a href="#7.19"><stdio.h></a>
13240 int fprintf(FILE * restrict stream,
13241 const char * restrict format, ...);</pre>
13242 <h6>Description</h6>
13244 The fprintf function writes output to the stream pointed to by stream, under control
13245 of the string pointed to by format that specifies how subsequent arguments are
13246 converted for output. If there are insufficient arguments for the format, the behavior is
13247 undefined. If the format is exhausted while arguments remain, the excess arguments are
13248 evaluated (as always) but are otherwise ignored. The fprintf function returns when
13249 the end of the format string is encountered.
13251 The format shall be a multibyte character sequence, beginning and ending in its initial
13252 shift state. The format is composed of zero or more directives: ordinary multibyte
13253 characters (not %), which are copied unchanged to the output stream; and conversion
13257 specifications, each of which results in fetching zero or more subsequent arguments,
13258 converting them, if applicable, according to the corresponding conversion specifier, and
13259 then writing the result to the output stream.
13261 Each conversion specification is introduced by the character %. After the %, the following
13262 appear in sequence:
13264 <li> Zero or more flags (in any order) that modify the meaning of the conversion
13266 <li> An optional minimum field width. If the converted value has fewer characters than the
13267 field width, it is padded with spaces (by default) on the left (or right, if the left
13268 adjustment flag, described later, has been given) to the field width. The field width
13269 takes the form of an asterisk * (described later) or a nonnegative decimal integer.<sup><a href="#note241"><b>241)</b></a></sup>
13270 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
13271 o, u, x, and X conversions, the number of digits to appear after the decimal-point
13272 character for a, A, e, E, f, and F conversions, the maximum number of significant
13273 digits for the g and G conversions, or the maximum number of bytes to be written for
13274 s conversions. The precision takes the form of a period (.) followed either by an
13275 asterisk * (described later) or by an optional decimal integer; if only the period is
13276 specified, the precision is taken as zero. If a precision appears with any other
13277 conversion specifier, the behavior is undefined.
13278 <li> An optional length modifier that specifies the size of the argument.
13279 <li> A conversion specifier character that specifies the type of conversion to be applied.
13282 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
13283 this case, an int argument supplies the field width or precision. The arguments
13284 specifying field width, or precision, or both, shall appear (in that order) before the
13285 argument (if any) to be converted. A negative field width argument is taken as a - flag
13286 followed by a positive field width. A negative precision argument is taken as if the
13287 precision were omitted.
13289 The flag characters and their meanings are:
13290 - The result of the conversion is left-justified within the field. (It is right-justified if
13292 this flag is not specified.)</pre>
13293 + The result of a signed conversion always begins with a plus or minus sign. (It
13295 begins with a sign only when a negative value is converted if this flag is not</pre>
13302 specified.)<sup><a href="#note242"><b>242)</b></a></sup></pre>
13303 space If the first character of a signed conversion is not a sign, or if a signed conversion
13305 results in no characters, a space is prefixed to the result. If the space and + flags
13306 both appear, the space flag is ignored.</pre>
13307 # The result is converted to an ''alternative form''. For o conversion, it increases
13309 the precision, if and only if necessary, to force the first digit of the result to be a
13310 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
13311 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
13312 and G conversions, the result of converting a floating-point number always
13313 contains a decimal-point character, even if no digits follow it. (Normally, a
13314 decimal-point character appears in the result of these conversions only if a digit
13315 follows it.) For g and G conversions, trailing zeros are not removed from the
13316 result. For other conversions, the behavior is undefined.</pre>
13317 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
13320 (following any indication of sign or base) are used to pad to the field width rather
13321 than performing space padding, except when converting an infinity or NaN. If the
13322 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
13323 conversions, if a precision is specified, the 0 flag is ignored. For other
13324 conversions, the behavior is undefined.</pre>
13325 The length modifiers and their meanings are:
13326 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13328 signed char or unsigned char argument (the argument will have
13329 been promoted according to the integer promotions, but its value shall be
13330 converted to signed char or unsigned char before printing); or that
13331 a following n conversion specifier applies to a pointer to a signed char
13333 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13335 short int or unsigned short int argument (the argument will
13336 have been promoted according to the integer promotions, but its value shall
13337 be converted to short int or unsigned short int before printing);
13338 or that a following n conversion specifier applies to a pointer to a short
13339 int argument.</pre>
13340 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13342 long int or unsigned long int argument; that a following n
13343 conversion specifier applies to a pointer to a long int argument; that a</pre>
13347 following c conversion specifier applies to a wint_t argument; that a
13348 following s conversion specifier applies to a pointer to a wchar_t
13349 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
13351 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13353 long long int or unsigned long long int argument; or that a
13354 following n conversion specifier applies to a pointer to a long long int
13356 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
13358 an intmax_t or uintmax_t argument; or that a following n conversion
13359 specifier applies to a pointer to an intmax_t argument.</pre>
13360 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13362 size_t or the corresponding signed integer type argument; or that a
13363 following n conversion specifier applies to a pointer to a signed integer type
13364 corresponding to size_t argument.</pre>
13365 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13367 ptrdiff_t or the corresponding unsigned integer type argument; or that a
13368 following n conversion specifier applies to a pointer to a ptrdiff_t
13370 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
13372 applies to a long double argument.</pre>
13373 If a length modifier appears with any conversion specifier other than as specified above,
13374 the behavior is undefined.
13376 The conversion specifiers and their meanings are:
13377 d,i The int argument is converted to signed decimal in the style [-]dddd. The
13379 precision specifies the minimum number of digits to appear; if the value
13380 being converted can be represented in fewer digits, it is expanded with
13381 leading zeros. The default precision is 1. The result of converting a zero
13382 value with a precision of zero is no characters.</pre>
13383 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
13386 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
13387 letters abcdef are used for x conversion and the letters ABCDEF for X
13388 conversion. The precision specifies the minimum number of digits to appear;
13389 if the value being converted can be represented in fewer digits, it is expanded
13390 with leading zeros. The default precision is 1. The result of converting a
13391 zero value with a precision of zero is no characters.</pre>
13392 f,F A double argument representing a floating-point number is converted to
13394 decimal notation in the style [-]ddd.ddd, where the number of digits after
13395 the decimal-point character is equal to the precision specification. If the
13396 precision is missing, it is taken as 6; if the precision is zero and the # flag is
13397 not specified, no decimal-point character appears. If a decimal-point
13398 character appears, at least one digit appears before it. The value is rounded to
13399 the appropriate number of digits.
13400 A double argument representing an infinity is converted in one of the styles
13401 [-]inf or [-]infinity -- which style is implementation-defined. A
13402 double argument representing a NaN is converted in one of the styles
13403 [-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
13404 any n-char-sequence, is implementation-defined. The F conversion specifier
13405 produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
13406 respectively.<sup><a href="#note243"><b>243)</b></a></sup></pre>
13407 e,E A double argument representing a floating-point number is converted in the
13409 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
13410 argument is nonzero) before the decimal-point character and the number of
13411 digits after it is equal to the precision; if the precision is missing, it is taken as
13412 6; if the precision is zero and the # flag is not specified, no decimal-point
13413 character appears. The value is rounded to the appropriate number of digits.
13414 The E conversion specifier produces a number with E instead of e
13415 introducing the exponent. The exponent always contains at least two digits,
13416 and only as many more digits as necessary to represent the exponent. If the
13417 value is zero, the exponent is zero.
13418 A double argument representing an infinity or NaN is converted in the style
13419 of an f or F conversion specifier.</pre>
13420 g,G A double argument representing a floating-point number is converted in
13422 style f or e (or in style F or E in the case of a G conversion specifier),
13423 depending on the value converted and the precision. Let P equal the
13424 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
13425 Then, if a conversion with style E would have an exponent of X :
13426 -- if P > X >= -4, the conversion is with style f (or F) and precision
13428 -- otherwise, the conversion is with style e (or E) and precision P - 1.
13429 Finally, unless the # flag is used, any trailing zeros are removed from the</pre>
13433 fractional portion of the result and the decimal-point character is removed if
13434 there is no fractional portion remaining.
13435 A double argument representing an infinity or NaN is converted in the style
13436 of an f or F conversion specifier.</pre>
13437 a,A A double argument representing a floating-point number is converted in the
13439 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
13440 nonzero if the argument is a normalized floating-point number and is
13441 otherwise unspecified) before the decimal-point character<sup><a href="#note244"><b>244)</b></a></sup> and the number
13442 of hexadecimal digits after it is equal to the precision; if the precision is
13443 missing and FLT_RADIX is a power of 2, then the precision is sufficient for
13444 an exact representation of the value; if the precision is missing and
13445 FLT_RADIX is not a power of 2, then the precision is sufficient to
13446 distinguish<sup><a href="#note245"><b>245)</b></a></sup> values of type double, except that trailing zeros may be
13447 omitted; if the precision is zero and the # flag is not specified, no decimal-
13448 point character appears. The letters abcdef are used for a conversion and
13449 the letters ABCDEF for A conversion. The A conversion specifier produces a
13450 number with X and P instead of x and p. The exponent always contains at
13451 least one digit, and only as many more digits as necessary to represent the
13452 decimal exponent of 2. If the value is zero, the exponent is zero.
13453 A double argument representing an infinity or NaN is converted in the style
13454 of an f or F conversion specifier.</pre>
13455 c If no l length modifier is present, the int argument is converted to an
13457 unsigned char, and the resulting character is written.
13458 If an l length modifier is present, the wint_t argument is converted as if by
13459 an ls conversion specification with no precision and an argument that points
13460 to the initial element of a two-element array of wchar_t, the first element
13461 containing the wint_t argument to the lc conversion specification and the
13462 second a null wide character.</pre>
13463 s If no l length modifier is present, the argument shall be a pointer to the initial
13465 element of an array of character type.<sup><a href="#note246"><b>246)</b></a></sup> Characters from the array are</pre>
13470 written up to (but not including) the terminating null character. If the
13471 precision is specified, no more than that many bytes are written. If the
13472 precision is not specified or is greater than the size of the array, the array shall
13473 contain a null character.
13474 If an l length modifier is present, the argument shall be a pointer to the initial
13475 element of an array of wchar_t type. Wide characters from the array are
13476 converted to multibyte characters (each as if by a call to the wcrtomb
13477 function, with the conversion state described by an mbstate_t object
13478 initialized to zero before the first wide character is converted) up to and
13479 including a terminating null wide character. The resulting multibyte
13480 characters are written up to (but not including) the terminating null character
13481 (byte). If no precision is specified, the array shall contain a null wide
13482 character. If a precision is specified, no more than that many bytes are
13483 written (including shift sequences, if any), and the array shall contain a null
13484 wide character if, to equal the multibyte character sequence length given by
13485 the precision, the function would need to access a wide character one past the
13486 end of the array. In no case is a partial multibyte character written.<sup><a href="#note247"><b>247)</b></a></sup></pre>
13487 p The argument shall be a pointer to void. The value of the pointer is
13489 converted to a sequence of printing characters, in an implementation-defined
13491 n The argument shall be a pointer to signed integer into which is written the
13493 number of characters written to the output stream so far by this call to
13494 fprintf. No argument is converted, but one is consumed. If the conversion
13495 specification includes any flags, a field width, or a precision, the behavior is
13497 % A % character is written. No argument is converted. The complete
13500 conversion specification shall be %%.</pre>
13501 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note248"><b>248)</b></a></sup> If any argument is
13502 not the correct type for the corresponding conversion specification, the behavior is
13505 In no case does a nonexistent or small field width cause truncation of a field; if the result
13506 of a conversion is wider than the field width, the field is expanded to contain the
13514 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
13515 to a hexadecimal floating number with the given precision.
13516 Recommended practice
13518 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
13519 representable in the given precision, the result should be one of the two adjacent numbers
13520 in hexadecimal floating style with the given precision, with the extra stipulation that the
13521 error should have a correct sign for the current rounding direction.
13523 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
13524 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note249"><b>249)</b></a></sup> If the number of
13525 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
13526 representable with DECIMAL_DIG digits, then the result should be an exact
13527 representation with trailing zeros. Otherwise, the source value is bounded by two
13528 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
13529 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
13530 the error should have a correct sign for the current rounding direction.
13533 The fprintf function returns the number of characters transmitted, or a negative value
13534 if an output or encoding error occurred.
13535 Environmental limits
13537 The number of characters that can be produced by any single conversion shall be at least
13540 EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
13543 #include <a href="#7.12"><math.h></a>
13544 #include <a href="#7.19"><stdio.h></a>
13546 char *weekday, *month; // pointers to strings
13547 int day, hour, min;
13548 fprintf(stdout, "%s, %s %d, %.2d:%.2d\n",
13549 weekday, month, day, hour, min);
13550 fprintf(stdout, "pi = %.5f\n", 4 * atan(1.0));</pre>
13553 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the
13554 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
13555 the first of which is denoted here by a and the second by an uppercase letter.
13562 Given the following wide string with length seven,
13564 static wchar_t wstr[] = L" X Yabc Z W";</pre>
13567 fprintf(stdout, "|1234567890123|\n");
13568 fprintf(stdout, "|%13ls|\n", wstr);
13569 fprintf(stdout, "|%-13.9ls|\n", wstr);
13570 fprintf(stdout, "|%13.10ls|\n", wstr);
13571 fprintf(stdout, "|%13.11ls|\n", wstr);
13572 fprintf(stdout, "|%13.15ls|\n", &wstr[2]);
13573 fprintf(stdout, "|%13lc|\n", (wint_t) wstr[5]);</pre>
13574 will print the following seven lines:
13584 <p><b> Forward references</b>: conversion state (<a href="#7.24.6">7.24.6</a>), the wcrtomb function (<a href="#7.24.6.3.3">7.24.6.3.3</a>).
13587 <p><small><a name="note241" href="#note241">241)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
13589 <p><small><a name="note242" href="#note242">242)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
13590 include a minus sign.
13592 <p><small><a name="note243" href="#note243">243)</a> When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning;
13593 the # and 0 flag characters have no effect.
13595 <p><small><a name="note244" href="#note244">244)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so
13596 that subsequent digits align to nibble (4-bit) boundaries.
13598 <p><small><a name="note245" href="#note245">245)</a> The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
13599 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
13600 might suffice depending on the implementation's scheme for determining the digit to the left of the
13601 decimal-point character.
13603 <p><small><a name="note246" href="#note246">246)</a> No special provisions are made for multibyte characters.
13605 <p><small><a name="note247" href="#note247">247)</a> Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
13607 <p><small><a name="note248" href="#note248">248)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
13609 <p><small><a name="note249" href="#note249">249)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
13610 given format specifier. The number of significant digits is determined by the format specifier, and in
13611 the case of fixed-point conversion by the source value as well.
13614 <h5><a name="7.19.6.2" href="#7.19.6.2">7.19.6.2 The fscanf function</a></h5>
13618 #include <a href="#7.19"><stdio.h></a>
13619 int fscanf(FILE * restrict stream,
13620 const char * restrict format, ...);</pre>
13621 <h6>Description</h6>
13623 The fscanf function reads input from the stream pointed to by stream, under control
13624 of the string pointed to by format that specifies the admissible input sequences and how
13625 they are to be converted for assignment, using subsequent arguments as pointers to the
13626 objects to receive the converted input. If there are insufficient arguments for the format,
13627 the behavior is undefined. If the format is exhausted while arguments remain, the excess
13628 arguments are evaluated (as always) but are otherwise ignored.
13630 The format shall be a multibyte character sequence, beginning and ending in its initial
13631 shift state. The format is composed of zero or more directives: one or more white-space
13632 characters, an ordinary multibyte character (neither % nor a white-space character), or a
13633 conversion specification. Each conversion specification is introduced by the character %.
13634 After the %, the following appear in sequence:
13636 <li> An optional assignment-suppressing character *.
13637 <li> An optional decimal integer greater than zero that specifies the maximum field width
13640 <li> An optional length modifier that specifies the size of the receiving object.
13641 <li> A conversion specifier character that specifies the type of conversion to be applied.
13644 The fscanf function executes each directive of the format in turn. If a directive fails, as
13645 detailed below, the function returns. Failures are described as input failures (due to the
13646 occurrence of an encoding error or the unavailability of input characters), or matching
13647 failures (due to inappropriate input).
13649 A directive composed of white-space character(s) is executed by reading input up to the
13650 first non-white-space character (which remains unread), or until no more characters can
13653 A directive that is an ordinary multibyte character is executed by reading the next
13654 characters of the stream. If any of those characters differ from the ones composing the
13655 directive, the directive fails and the differing and subsequent characters remain unread.
13656 Similarly, if end-of-file, an encoding error, or a read error prevents a character from being
13657 read, the directive fails.
13659 A directive that is a conversion specification defines a set of matching input sequences, as
13660 described below for each specifier. A conversion specification is executed in the
13663 Input white-space characters (as specified by the isspace function) are skipped, unless
13664 the specification includes a [, c, or n specifier.<sup><a href="#note250"><b>250)</b></a></sup>
13666 An input item is read from the stream, unless the specification includes an n specifier. An
13667 input item is defined as the longest sequence of input characters which does not exceed
13668 any specified field width and which is, or is a prefix of, a matching input sequence.<sup><a href="#note251"><b>251)</b></a></sup>
13669 The first character, if any, after the input item remains unread. If the length of the input
13670 item is zero, the execution of the directive fails; this condition is a matching failure unless
13671 end-of-file, an encoding error, or a read error prevented input from the stream, in which
13672 case it is an input failure.
13674 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
13675 count of input characters) is converted to a type appropriate to the conversion specifier. If
13676 the input item is not a matching sequence, the execution of the directive fails: this
13677 condition is a matching failure. Unless assignment suppression was indicated by a *, the
13678 result of the conversion is placed in the object pointed to by the first argument following
13679 the format argument that has not already received a conversion result. If this object
13680 does not have an appropriate type, or if the result of the conversion cannot be represented
13684 in the object, the behavior is undefined.
13686 The length modifiers and their meanings are:
13687 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13689 to an argument with type pointer to signed char or unsigned char.</pre>
13690 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13692 to an argument with type pointer to short int or unsigned short
13694 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13696 to an argument with type pointer to long int or unsigned long
13697 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
13698 an argument with type pointer to double; or that a following c, s, or [
13699 conversion specifier applies to an argument with type pointer to wchar_t.</pre>
13700 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13702 to an argument with type pointer to long long int or unsigned
13703 long long int.</pre>
13704 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13706 to an argument with type pointer to intmax_t or uintmax_t.</pre>
13707 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13709 to an argument with type pointer to size_t or the corresponding signed
13710 integer type.</pre>
13711 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13713 to an argument with type pointer to ptrdiff_t or the corresponding
13714 unsigned integer type.</pre>
13715 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
13717 applies to an argument with type pointer to long double.</pre>
13718 If a length modifier appears with any conversion specifier other than as specified above,
13719 the behavior is undefined.
13721 The conversion specifiers and their meanings are:
13722 d Matches an optionally signed decimal integer, whose format is the same as
13724 expected for the subject sequence of the strtol function with the value 10
13725 for the base argument. The corresponding argument shall be a pointer to
13726 signed integer.</pre>
13727 i Matches an optionally signed integer, whose format is the same as expected
13730 for the subject sequence of the strtol function with the value 0 for the
13731 base argument. The corresponding argument shall be a pointer to signed
13733 o Matches an optionally signed octal integer, whose format is the same as
13735 expected for the subject sequence of the strtoul function with the value 8
13736 for the base argument. The corresponding argument shall be a pointer to
13737 unsigned integer.</pre>
13738 u Matches an optionally signed decimal integer, whose format is the same as
13740 expected for the subject sequence of the strtoul function with the value 10
13741 for the base argument. The corresponding argument shall be a pointer to
13742 unsigned integer.</pre>
13743 x Matches an optionally signed hexadecimal integer, whose format is the same
13745 as expected for the subject sequence of the strtoul function with the value
13746 16 for the base argument. The corresponding argument shall be a pointer to
13747 unsigned integer.</pre>
13748 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
13750 format is the same as expected for the subject sequence of the strtod
13751 function. The corresponding argument shall be a pointer to floating.</pre>
13752 c Matches a sequence of characters of exactly the number specified by the field
13754 width (1 if no field width is present in the directive).<sup><a href="#note252"><b>252)</b></a></sup>
13755 If no l length modifier is present, the corresponding argument shall be a
13756 pointer to the initial element of a character array large enough to accept the
13757 sequence. No null character is added.
13758 If an l length modifier is present, the input shall be a sequence of multibyte
13759 characters that begins in the initial shift state. Each multibyte character in the
13760 sequence is converted to a wide character as if by a call to the mbrtowc
13761 function, with the conversion state described by an mbstate_t object
13762 initialized to zero before the first multibyte character is converted. The
13763 corresponding argument shall be a pointer to the initial element of an array of
13764 wchar_t large enough to accept the resulting sequence of wide characters.
13765 No null wide character is added.</pre>
13766 s Matches a sequence of non-white-space characters.252)
13768 If no l length modifier is present, the corresponding argument shall be a
13769 pointer to the initial element of a character array large enough to accept the
13770 sequence and a terminating null character, which will be added automatically.
13771 If an l length modifier is present, the input shall be a sequence of multibyte</pre>
13776 characters that begins in the initial shift state. Each multibyte character is
13777 converted to a wide character as if by a call to the mbrtowc function, with
13778 the conversion state described by an mbstate_t object initialized to zero
13779 before the first multibyte character is converted. The corresponding argument
13780 shall be a pointer to the initial element of an array of wchar_t large enough
13781 to accept the sequence and the terminating null wide character, which will be
13782 added automatically.</pre>
13783 [ Matches a nonempty sequence of characters from a set of expected characters
13786 If no l length modifier is present, the corresponding argument shall be a
13787 pointer to the initial element of a character array large enough to accept the
13788 sequence and a terminating null character, which will be added automatically.
13789 If an l length modifier is present, the input shall be a sequence of multibyte
13790 characters that begins in the initial shift state. Each multibyte character is
13791 converted to a wide character as if by a call to the mbrtowc function, with
13792 the conversion state described by an mbstate_t object initialized to zero
13793 before the first multibyte character is converted. The corresponding argument
13794 shall be a pointer to the initial element of an array of wchar_t large enough
13795 to accept the sequence and the terminating null wide character, which will be
13796 added automatically.
13797 The conversion specifier includes all subsequent characters in the format
13798 string, up to and including the matching right bracket (]). The characters
13799 between the brackets (the scanlist) compose the scanset, unless the character
13800 after the left bracket is a circumflex (^), in which case the scanset contains all
13801 characters that do not appear in the scanlist between the circumflex and the
13802 right bracket. If the conversion specifier begins with [] or [^], the right
13803 bracket character is in the scanlist and the next following right bracket
13804 character is the matching right bracket that ends the specification; otherwise
13805 the first following right bracket character is the one that ends the
13806 specification. If a - character is in the scanlist and is not the first, nor the
13807 second where the first character is a ^, nor the last character, the behavior is
13808 implementation-defined.</pre>
13809 p Matches an implementation-defined set of sequences, which should be the
13812 same as the set of sequences that may be produced by the %p conversion of
13813 the fprintf function. The corresponding argument shall be a pointer to a
13814 pointer to void. The input item is converted to a pointer value in an
13815 implementation-defined manner. If the input item is a value converted earlier
13816 during the same program execution, the pointer that results shall compare
13817 equal to that value; otherwise the behavior of the %p conversion is undefined.</pre>
13818 n No input is consumed. The corresponding argument shall be a pointer to
13820 signed integer into which is to be written the number of characters read from
13821 the input stream so far by this call to the fscanf function. Execution of a
13822 %n directive does not increment the assignment count returned at the
13823 completion of execution of the fscanf function. No argument is converted,
13824 but one is consumed. If the conversion specification includes an assignment-
13825 suppressing character or a field width, the behavior is undefined.</pre>
13826 % Matches a single % character; no conversion or assignment occurs. The
13829 complete conversion specification shall be %%.</pre>
13830 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note253"><b>253)</b></a></sup>
13832 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
13833 respectively, a, e, f, g, and x.
13835 Trailing white space (including new-line characters) is left unread unless matched by a
13836 directive. The success of literal matches and suppressed assignments is not directly
13837 determinable other than via the %n directive.
13840 The fscanf function returns the value of the macro EOF if an input failure occurs
13841 before any conversion. Otherwise, the function returns the number of input items
13842 assigned, which can be fewer than provided for, or even zero, in the event of an early
13845 EXAMPLE 1 The call:
13847 #include <a href="#7.19"><stdio.h></a>
13849 int n, i; float x; char name[50];
13850 n = fscanf(stdin, "%d%f%s", &i, &x, name);</pre>
13851 with the input line:
13853 25 54.32E-1 thompson</pre>
13854 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
13858 EXAMPLE 2 The call:
13860 #include <a href="#7.19"><stdio.h></a>
13862 int i; float x; char name[50];
13863 fscanf(stdin, "%2d%f%*d %[0123456789]", &i, &x, name);</pre>
13870 56789 0123 56a72</pre>
13871 will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the
13872 sequence 56\0. The next character read from the input stream will be a.
13875 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
13878 #include <a href="#7.19"><stdio.h></a>
13880 int count; float quant; char units[21], item[21];
13882 count = fscanf(stdin, "%f%20s of %20s", &quant, units, item);
13883 fscanf(stdin,"%*[^\n]");
13884 } while (!feof(stdin) && !ferror(stdin));</pre>
13885 If the stdin stream contains the following lines:
13888 -12.8degrees Celsius
13892 100ergs of energy</pre>
13893 the execution of the above example will be analogous to the following assignments:
13895 quant = 2; strcpy(units, "quarts"); strcpy(item, "oil");
13897 quant = -12.8; strcpy(units, "degrees");
13898 count = 2; // "C" fails to match "o"
13899 count = 0; // "l" fails to match "%f"
13900 quant = 10.0; strcpy(units, "LBS"); strcpy(item, "dirt");
13902 count = 0; // "100e" fails to match "%f"
13908 #include <a href="#7.19"><stdio.h></a>
13910 int d1, d2, n1, n2, i;
13911 i = sscanf("123", "%d%n%n%d", &d1, &n1, &n2, &d2);</pre>
13912 the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure the value
13913 of 3 is also assigned to n2. The value of d2 is not affected. The value 1 is assigned to i.
13916 EXAMPLE 5 In these examples, multibyte characters do have a state-dependent encoding, and the
13917 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
13918 the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as
13919 such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes
13920 entry into the alternate shift state.
13925 #include <a href="#7.19"><stdio.h></a>
13928 fscanf(stdin, "a%s", str);</pre>
13929 with the input line:
13931 a(uparrow) X Y(downarrow) bc</pre>
13932 str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte
13933 characters, in the more general case) appears to be a single-byte white-space character.
13935 In contrast, after the call:
13937 #include <a href="#7.19"><stdio.h></a>
13938 #include <a href="#7.17"><stddef.h></a>
13941 fscanf(stdin, "a%ls", wstr);</pre>
13942 with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
13943 terminating null wide character.
13947 #include <a href="#7.19"><stdio.h></a>
13948 #include <a href="#7.17"><stddef.h></a>
13951 fscanf(stdin, "a(uparrow) X(downarrow)%ls", wstr);</pre>
13952 with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
13955 Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte
13956 character Y, after the call:
13958 #include <a href="#7.19"><stdio.h></a>
13959 #include <a href="#7.17"><stddef.h></a>
13962 fscanf(stdin, "a(uparrow) Y(downarrow)%ls", wstr);</pre>
13963 with the same input line, zero will again be returned, but stdin will be left with a partially consumed
13964 multibyte character.
13966 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>), the
13967 strtol, strtoll, strtoul, and strtoull functions (<a href="#7.20.1.4">7.20.1.4</a>), conversion state
13968 (<a href="#7.24.6">7.24.6</a>), the wcrtomb function (<a href="#7.24.6.3.3">7.24.6.3.3</a>).
13972 <p><small><a name="note250" href="#note250">250)</a> These white-space characters are not counted against a specified field width.
13974 <p><small><a name="note251" href="#note251">251)</a> fscanf pushes back at most one input character onto the input stream. Therefore, some sequences
13975 that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.
13977 <p><small><a name="note252" href="#note252">252)</a> No special provisions are made for multibyte characters in the matching rules used by the c, s, and [
13978 conversion specifiers -- the extent of the input field is determined on a byte-by-byte basis. The
13979 resulting field is nevertheless a sequence of multibyte characters that begins in the initial shift state.
13981 <p><small><a name="note253" href="#note253">253)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
13984 <h5><a name="7.19.6.3" href="#7.19.6.3">7.19.6.3 The printf function</a></h5>
13988 #include <a href="#7.19"><stdio.h></a>
13989 int printf(const char * restrict format, ...);</pre>
13990 <h6>Description</h6>
13992 The printf function is equivalent to fprintf with the argument stdout interposed
13993 before the arguments to printf.
13996 The printf function returns the number of characters transmitted, or a negative value if
13997 an output or encoding error occurred.
13999 <h5><a name="7.19.6.4" href="#7.19.6.4">7.19.6.4 The scanf function</a></h5>
14003 #include <a href="#7.19"><stdio.h></a>
14004 int scanf(const char * restrict format, ...);</pre>
14005 <h6>Description</h6>
14007 The scanf function is equivalent to fscanf with the argument stdin interposed
14008 before the arguments to scanf.
14011 The scanf function returns the value of the macro EOF if an input failure occurs before
14012 any conversion. Otherwise, the scanf function returns the number of input items
14013 assigned, which can be fewer than provided for, or even zero, in the event of an early
14016 <h5><a name="7.19.6.5" href="#7.19.6.5">7.19.6.5 The snprintf function</a></h5>
14020 #include <a href="#7.19"><stdio.h></a>
14021 int snprintf(char * restrict s, size_t n,
14022 const char * restrict format, ...);</pre>
14023 <h6>Description</h6>
14025 The snprintf function is equivalent to fprintf, except that the output is written into
14026 an array (specified by argument s) rather than to a stream. If n is zero, nothing is written,
14027 and s may be a null pointer. Otherwise, output characters beyond the n-1st are
14028 discarded rather than being written to the array, and a null character is written at the end
14029 of the characters actually written into the array. If copying takes place between objects
14030 that overlap, the behavior is undefined.
14034 The snprintf function returns the number of characters that would have been written
14035 had n been sufficiently large, not counting the terminating null character, or a negative
14036 value if an encoding error occurred. Thus, the null-terminated output has been
14037 completely written if and only if the returned value is nonnegative and less than n.
14039 <h5><a name="7.19.6.6" href="#7.19.6.6">7.19.6.6 The sprintf function</a></h5>
14043 #include <a href="#7.19"><stdio.h></a>
14044 int sprintf(char * restrict s,
14045 const char * restrict format, ...);</pre>
14046 <h6>Description</h6>
14048 The sprintf function is equivalent to fprintf, except that the output is written into
14049 an array (specified by the argument s) rather than to a stream. A null character is written
14050 at the end of the characters written; it is not counted as part of the returned value. If
14051 copying takes place between objects that overlap, the behavior is undefined.
14054 The sprintf function returns the number of characters written in the array, not
14055 counting the terminating null character, or a negative value if an encoding error occurred.
14057 <h5><a name="7.19.6.7" href="#7.19.6.7">7.19.6.7 The sscanf function</a></h5>
14061 #include <a href="#7.19"><stdio.h></a>
14062 int sscanf(const char * restrict s,
14063 const char * restrict format, ...);</pre>
14064 <h6>Description</h6>
14066 The sscanf function is equivalent to fscanf, except that input is obtained from a
14067 string (specified by the argument s) rather than from a stream. Reaching the end of the
14068 string is equivalent to encountering end-of-file for the fscanf function. If copying
14069 takes place between objects that overlap, the behavior is undefined.
14072 The sscanf function returns the value of the macro EOF if an input failure occurs
14073 before any conversion. Otherwise, the sscanf function returns the number of input
14074 items assigned, which can be fewer than provided for, or even zero, in the event of an
14075 early matching failure.
14078 <h5><a name="7.19.6.8" href="#7.19.6.8">7.19.6.8 The vfprintf function</a></h5>
14082 #include <a href="#7.15"><stdarg.h></a>
14083 #include <a href="#7.19"><stdio.h></a>
14084 int vfprintf(FILE * restrict stream,
14085 const char * restrict format,
14086 va_list arg);</pre>
14087 <h6>Description</h6>
14089 The vfprintf function is equivalent to fprintf, with the variable argument list
14090 replaced by arg, which shall have been initialized by the va_start macro (and
14091 possibly subsequent va_arg calls). The vfprintf function does not invoke the
14092 va_end macro.<sup><a href="#note254"><b>254)</b></a></sup>
14095 The vfprintf function returns the number of characters transmitted, or a negative
14096 value if an output or encoding error occurred.
14098 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
14100 #include <a href="#7.15"><stdarg.h></a>
14101 #include <a href="#7.19"><stdio.h></a>
14102 void error(char *function_name, char *format, ...)
14105 va_start(args, format);
14106 // print out name of function causing error
14107 fprintf(stderr, "ERROR in %s: ", function_name);
14108 // print out remainder of message
14109 vfprintf(stderr, format, args);
14119 <p><small><a name="note254" href="#note254">254)</a> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
14120 vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
14123 <h5><a name="7.19.6.9" href="#7.19.6.9">7.19.6.9 The vfscanf function</a></h5>
14127 #include <a href="#7.15"><stdarg.h></a>
14128 #include <a href="#7.19"><stdio.h></a>
14129 int vfscanf(FILE * restrict stream,
14130 const char * restrict format,
14131 va_list arg);</pre>
14132 <h6>Description</h6>
14134 The vfscanf function is equivalent to fscanf, with the variable argument list
14135 replaced by arg, which shall have been initialized by the va_start macro (and
14136 possibly subsequent va_arg calls). The vfscanf function does not invoke the
14140 The vfscanf function returns the value of the macro EOF if an input failure occurs
14141 before any conversion. Otherwise, the vfscanf function returns the number of input
14142 items assigned, which can be fewer than provided for, or even zero, in the event of an
14143 early matching failure.
14145 <h5><a name="7.19.6.10" href="#7.19.6.10">7.19.6.10 The vprintf function</a></h5>
14149 #include <a href="#7.15"><stdarg.h></a>
14150 #include <a href="#7.19"><stdio.h></a>
14151 int vprintf(const char * restrict format,
14152 va_list arg);</pre>
14153 <h6>Description</h6>
14155 The vprintf function is equivalent to printf, with the variable argument list
14156 replaced by arg, which shall have been initialized by the va_start macro (and
14157 possibly subsequent va_arg calls). The vprintf function does not invoke the
14161 The vprintf function returns the number of characters transmitted, or a negative value
14162 if an output or encoding error occurred.
14165 <h5><a name="7.19.6.11" href="#7.19.6.11">7.19.6.11 The vscanf function</a></h5>
14169 #include <a href="#7.15"><stdarg.h></a>
14170 #include <a href="#7.19"><stdio.h></a>
14171 int vscanf(const char * restrict format,
14172 va_list arg);</pre>
14173 <h6>Description</h6>
14175 The vscanf function is equivalent to scanf, with the variable argument list replaced
14176 by arg, which shall have been initialized by the va_start macro (and possibly
14177 subsequent va_arg calls). The vscanf function does not invoke the va_end
14181 The vscanf function returns the value of the macro EOF if an input failure occurs
14182 before any conversion. Otherwise, the vscanf function returns the number of input
14183 items assigned, which can be fewer than provided for, or even zero, in the event of an
14184 early matching failure.
14186 <h5><a name="7.19.6.12" href="#7.19.6.12">7.19.6.12 The vsnprintf function</a></h5>
14190 #include <a href="#7.15"><stdarg.h></a>
14191 #include <a href="#7.19"><stdio.h></a>
14192 int vsnprintf(char * restrict s, size_t n,
14193 const char * restrict format,
14194 va_list arg);</pre>
14195 <h6>Description</h6>
14197 The vsnprintf function is equivalent to snprintf, with the variable argument list
14198 replaced by arg, which shall have been initialized by the va_start macro (and
14199 possibly subsequent va_arg calls). The vsnprintf function does not invoke the
14200 va_end macro.254) If copying takes place between objects that overlap, the behavior is
14204 The vsnprintf function returns the number of characters that would have been written
14205 had n been sufficiently large, not counting the terminating null character, or a negative
14206 value if an encoding error occurred. Thus, the null-terminated output has been
14207 completely written if and only if the returned value is nonnegative and less than n.
14210 <h5><a name="7.19.6.13" href="#7.19.6.13">7.19.6.13 The vsprintf function</a></h5>
14214 #include <a href="#7.15"><stdarg.h></a>
14215 #include <a href="#7.19"><stdio.h></a>
14216 int vsprintf(char * restrict s,
14217 const char * restrict format,
14218 va_list arg);</pre>
14219 <h6>Description</h6>
14221 The vsprintf function is equivalent to sprintf, with the variable argument list
14222 replaced by arg, which shall have been initialized by the va_start macro (and
14223 possibly subsequent va_arg calls). The vsprintf function does not invoke the
14224 va_end macro.254) If copying takes place between objects that overlap, the behavior is
14228 The vsprintf function returns the number of characters written in the array, not
14229 counting the terminating null character, or a negative value if an encoding error occurred.
14231 <h5><a name="7.19.6.14" href="#7.19.6.14">7.19.6.14 The vsscanf function</a></h5>
14235 #include <a href="#7.15"><stdarg.h></a>
14236 #include <a href="#7.19"><stdio.h></a>
14237 int vsscanf(const char * restrict s,
14238 const char * restrict format,
14239 va_list arg);</pre>
14240 <h6>Description</h6>
14242 The vsscanf function is equivalent to sscanf, with the variable argument list
14243 replaced by arg, which shall have been initialized by the va_start macro (and
14244 possibly subsequent va_arg calls). The vsscanf function does not invoke the
14248 The vsscanf function returns the value of the macro EOF if an input failure occurs
14249 before any conversion. Otherwise, the vsscanf function returns the number of input
14250 items assigned, which can be fewer than provided for, or even zero, in the event of an
14251 early matching failure.
14254 <h4><a name="7.19.7" href="#7.19.7">7.19.7 Character input/output functions</a></h4>
14256 <h5><a name="7.19.7.1" href="#7.19.7.1">7.19.7.1 The fgetc function</a></h5>
14260 #include <a href="#7.19"><stdio.h></a>
14261 int fgetc(FILE *stream);</pre>
14262 <h6>Description</h6>
14264 If the end-of-file indicator for the input stream pointed to by stream is not set and a
14265 next character is present, the fgetc function obtains that character as an unsigned
14266 char converted to an int and advances the associated file position indicator for the
14267 stream (if defined).
14270 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
14271 of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the
14272 fgetc function returns the next character from the input stream pointed to by stream.
14273 If a read error occurs, the error indicator for the stream is set and the fgetc function
14274 returns EOF.<sup><a href="#note255"><b>255)</b></a></sup>
14277 <p><small><a name="note255" href="#note255">255)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
14280 <h5><a name="7.19.7.2" href="#7.19.7.2">7.19.7.2 The fgets function</a></h5>
14284 #include <a href="#7.19"><stdio.h></a>
14285 char *fgets(char * restrict s, int n,
14286 FILE * restrict stream);</pre>
14287 <h6>Description</h6>
14289 The fgets function reads at most one less than the number of characters specified by n
14290 from the stream pointed to by stream into the array pointed to by s. No additional
14291 characters are read after a new-line character (which is retained) or after end-of-file. A
14292 null character is written immediately after the last character read into the array.
14295 The fgets function returns s if successful. If end-of-file is encountered and no
14296 characters have been read into the array, the contents of the array remain unchanged and a
14297 null pointer is returned. If a read error occurs during the operation, the array contents are
14298 indeterminate and a null pointer is returned.
14305 <h5><a name="7.19.7.3" href="#7.19.7.3">7.19.7.3 The fputc function</a></h5>
14309 #include <a href="#7.19"><stdio.h></a>
14310 int fputc(int c, FILE *stream);</pre>
14311 <h6>Description</h6>
14313 The fputc function writes the character specified by c (converted to an unsigned
14314 char) to the output stream pointed to by stream, at the position indicated by the
14315 associated file position indicator for the stream (if defined), and advances the indicator
14316 appropriately. If the file cannot support positioning requests, or if the stream was opened
14317 with append mode, the character is appended to the output stream.
14320 The fputc function returns the character written. If a write error occurs, the error
14321 indicator for the stream is set and fputc returns EOF.
14323 <h5><a name="7.19.7.4" href="#7.19.7.4">7.19.7.4 The fputs function</a></h5>
14327 #include <a href="#7.19"><stdio.h></a>
14328 int fputs(const char * restrict s,
14329 FILE * restrict stream);</pre>
14330 <h6>Description</h6>
14332 The fputs function writes the string pointed to by s to the stream pointed to by
14333 stream. The terminating null character is not written.
14336 The fputs function returns EOF if a write error occurs; otherwise it returns a
14339 <h5><a name="7.19.7.5" href="#7.19.7.5">7.19.7.5 The getc function</a></h5>
14343 #include <a href="#7.19"><stdio.h></a>
14344 int getc(FILE *stream);</pre>
14345 <h6>Description</h6>
14347 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it
14348 may evaluate stream more than once, so the argument should never be an expression
14353 The getc function returns the next character from the input stream pointed to by
14354 stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
14355 getc returns EOF. If a read error occurs, the error indicator for the stream is set and
14358 <h5><a name="7.19.7.6" href="#7.19.7.6">7.19.7.6 The getchar function</a></h5>
14362 #include <a href="#7.19"><stdio.h></a>
14363 int getchar(void);</pre>
14364 <h6>Description</h6>
14366 The getchar function is equivalent to getc with the argument stdin.
14369 The getchar function returns the next character from the input stream pointed to by
14370 stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
14371 getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
14372 getchar returns EOF.
14374 <h5><a name="7.19.7.7" href="#7.19.7.7">7.19.7.7 The gets function</a></h5>
14378 #include <a href="#7.19"><stdio.h></a>
14379 char *gets(char *s);</pre>
14380 <h6>Description</h6>
14382 The gets function reads characters from the input stream pointed to by stdin, into the
14383 array pointed to by s, until end-of-file is encountered or a new-line character is read.
14384 Any new-line character is discarded, and a null character is written immediately after the
14385 last character read into the array.
14388 The gets function returns s if successful. If end-of-file is encountered and no
14389 characters have been read into the array, the contents of the array remain unchanged and a
14390 null pointer is returned. If a read error occurs during the operation, the array contents are
14391 indeterminate and a null pointer is returned.
14392 <p><b> Forward references</b>: future library directions (<a href="#7.26.9">7.26.9</a>).
14395 <h5><a name="7.19.7.8" href="#7.19.7.8">7.19.7.8 The putc function</a></h5>
14399 #include <a href="#7.19"><stdio.h></a>
14400 int putc(int c, FILE *stream);</pre>
14401 <h6>Description</h6>
14403 The putc function is equivalent to fputc, except that if it is implemented as a macro, it
14404 may evaluate stream more than once, so that argument should never be an expression
14408 The putc function returns the character written. If a write error occurs, the error
14409 indicator for the stream is set and putc returns EOF.
14411 <h5><a name="7.19.7.9" href="#7.19.7.9">7.19.7.9 The putchar function</a></h5>
14415 #include <a href="#7.19"><stdio.h></a>
14416 int putchar(int c);</pre>
14417 <h6>Description</h6>
14419 The putchar function is equivalent to putc with the second argument stdout.
14422 The putchar function returns the character written. If a write error occurs, the error
14423 indicator for the stream is set and putchar returns EOF.
14425 <h5><a name="7.19.7.10" href="#7.19.7.10">7.19.7.10 The puts function</a></h5>
14429 #include <a href="#7.19"><stdio.h></a>
14430 int puts(const char *s);</pre>
14431 <h6>Description</h6>
14433 The puts function writes the string pointed to by s to the stream pointed to by stdout,
14434 and appends a new-line character to the output. The terminating null character is not
14438 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
14442 <h5><a name="7.19.7.11" href="#7.19.7.11">7.19.7.11 The ungetc function</a></h5>
14446 #include <a href="#7.19"><stdio.h></a>
14447 int ungetc(int c, FILE *stream);</pre>
14448 <h6>Description</h6>
14450 The ungetc function pushes the character specified by c (converted to an unsigned
14451 char) back onto the input stream pointed to by stream. Pushed-back characters will be
14452 returned by subsequent reads on that stream in the reverse order of their pushing. A
14453 successful intervening call (with the stream pointed to by stream) to a file positioning
14454 function (fseek, fsetpos, or rewind) discards any pushed-back characters for the
14455 stream. The external storage corresponding to the stream is unchanged.
14457 One character of pushback is guaranteed. If the ungetc function is called too many
14458 times on the same stream without an intervening read or file positioning operation on that
14459 stream, the operation may fail.
14461 If the value of c equals that of the macro EOF, the operation fails and the input stream is
14464 A successful call to the ungetc function clears the end-of-file indicator for the stream.
14465 The value of the file position indicator for the stream after reading or discarding all
14466 pushed-back characters shall be the same as it was before the characters were pushed
14467 back. For a text stream, the value of its file position indicator after a successful call to the
14468 ungetc function is unspecified until all pushed-back characters are read or discarded.
14469 For a binary stream, its file position indicator is decremented by each successful call to
14470 the ungetc function; if its value was zero before a call, it is indeterminate after the
14471 call.<sup><a href="#note256"><b>256)</b></a></sup>
14474 The ungetc function returns the character pushed back after conversion, or EOF if the
14476 <p><b> Forward references</b>: file positioning functions (<a href="#7.19.9">7.19.9</a>).
14484 <p><small><a name="note256" href="#note256">256)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
14487 <h4><a name="7.19.8" href="#7.19.8">7.19.8 Direct input/output functions</a></h4>
14489 <h5><a name="7.19.8.1" href="#7.19.8.1">7.19.8.1 The fread function</a></h5>
14493 #include <a href="#7.19"><stdio.h></a>
14494 size_t fread(void * restrict ptr,
14495 size_t size, size_t nmemb,
14496 FILE * restrict stream);</pre>
14497 <h6>Description</h6>
14499 The fread function reads, into the array pointed to by ptr, up to nmemb elements
14500 whose size is specified by size, from the stream pointed to by stream. For each
14501 object, size calls are made to the fgetc function and the results stored, in the order
14502 read, in an array of unsigned char exactly overlaying the object. The file position
14503 indicator for the stream (if defined) is advanced by the number of characters successfully
14504 read. If an error occurs, the resulting value of the file position indicator for the stream is
14505 indeterminate. If a partial element is read, its value is indeterminate.
14508 The fread function returns the number of elements successfully read, which may be
14509 less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
14510 fread returns zero and the contents of the array and the state of the stream remain
14513 <h5><a name="7.19.8.2" href="#7.19.8.2">7.19.8.2 The fwrite function</a></h5>
14517 #include <a href="#7.19"><stdio.h></a>
14518 size_t fwrite(const void * restrict ptr,
14519 size_t size, size_t nmemb,
14520 FILE * restrict stream);</pre>
14521 <h6>Description</h6>
14523 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements
14524 whose size is specified by size, to the stream pointed to by stream. For each object,
14525 size calls are made to the fputc function, taking the values (in order) from an array of
14526 unsigned char exactly overlaying the object. The file position indicator for the
14527 stream (if defined) is advanced by the number of characters successfully written. If an
14528 error occurs, the resulting value of the file position indicator for the stream is
14533 The fwrite function returns the number of elements successfully written, which will be
14534 less than nmemb only if a write error is encountered. If size or nmemb is zero,
14535 fwrite returns zero and the state of the stream remains unchanged.
14537 <h4><a name="7.19.9" href="#7.19.9">7.19.9 File positioning functions</a></h4>
14539 <h5><a name="7.19.9.1" href="#7.19.9.1">7.19.9.1 The fgetpos function</a></h5>
14543 #include <a href="#7.19"><stdio.h></a>
14544 int fgetpos(FILE * restrict stream,
14545 fpos_t * restrict pos);</pre>
14546 <h6>Description</h6>
14548 The fgetpos function stores the current values of the parse state (if any) and file
14549 position indicator for the stream pointed to by stream in the object pointed to by pos.
14550 The values stored contain unspecified information usable by the fsetpos function for
14551 repositioning the stream to its position at the time of the call to the fgetpos function.
14554 If successful, the fgetpos function returns zero; on failure, the fgetpos function
14555 returns nonzero and stores an implementation-defined positive value in errno.
14556 <p><b> Forward references</b>: the fsetpos function (<a href="#7.19.9.3">7.19.9.3</a>).
14558 <h5><a name="7.19.9.2" href="#7.19.9.2">7.19.9.2 The fseek function</a></h5>
14562 #include <a href="#7.19"><stdio.h></a>
14563 int fseek(FILE *stream, long int offset, int whence);</pre>
14564 <h6>Description</h6>
14566 The fseek function sets the file position indicator for the stream pointed to by stream.
14567 If a read or write error occurs, the error indicator for the stream is set and fseek fails.
14569 For a binary stream, the new position, measured in characters from the beginning of the
14570 file, is obtained by adding offset to the position specified by whence. The specified
14571 position is the beginning of the file if whence is SEEK_SET, the current value of the file
14572 position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
14573 meaningfully support fseek calls with a whence value of SEEK_END.
14575 For a text stream, either offset shall be zero, or offset shall be a value returned by
14576 an earlier successful call to the ftell function on a stream associated with the same file
14577 and whence shall be SEEK_SET.
14580 After determining the new position, a successful call to the fseek function undoes any
14581 effects of the ungetc function on the stream, clears the end-of-file indicator for the
14582 stream, and then establishes the new position. After a successful fseek call, the next
14583 operation on an update stream may be either input or output.
14586 The fseek function returns nonzero only for a request that cannot be satisfied.
14587 <p><b> Forward references</b>: the ftell function (<a href="#7.19.9.4">7.19.9.4</a>).
14589 <h5><a name="7.19.9.3" href="#7.19.9.3">7.19.9.3 The fsetpos function</a></h5>
14593 #include <a href="#7.19"><stdio.h></a>
14594 int fsetpos(FILE *stream, const fpos_t *pos);</pre>
14595 <h6>Description</h6>
14597 The fsetpos function sets the mbstate_t object (if any) and file position indicator
14598 for the stream pointed to by stream according to the value of the object pointed to by
14599 pos, which shall be a value obtained from an earlier successful call to the fgetpos
14600 function on a stream associated with the same file. If a read or write error occurs, the
14601 error indicator for the stream is set and fsetpos fails.
14603 A successful call to the fsetpos function undoes any effects of the ungetc function
14604 on the stream, clears the end-of-file indicator for the stream, and then establishes the new
14605 parse state and position. After a successful fsetpos call, the next operation on an
14606 update stream may be either input or output.
14609 If successful, the fsetpos function returns zero; on failure, the fsetpos function
14610 returns nonzero and stores an implementation-defined positive value in errno.
14612 <h5><a name="7.19.9.4" href="#7.19.9.4">7.19.9.4 The ftell function</a></h5>
14616 #include <a href="#7.19"><stdio.h></a>
14617 long int ftell(FILE *stream);</pre>
14618 <h6>Description</h6>
14620 The ftell function obtains the current value of the file position indicator for the stream
14621 pointed to by stream. For a binary stream, the value is the number of characters from
14622 the beginning of the file. For a text stream, its file position indicator contains unspecified
14623 information, usable by the fseek function for returning the file position indicator for the
14624 stream to its position at the time of the ftell call; the difference between two such
14625 return values is not necessarily a meaningful measure of the number of characters written
14630 If successful, the ftell function returns the current value of the file position indicator
14631 for the stream. On failure, the ftell function returns -1L and stores an
14632 implementation-defined positive value in errno.
14634 <h5><a name="7.19.9.5" href="#7.19.9.5">7.19.9.5 The rewind function</a></h5>
14638 #include <a href="#7.19"><stdio.h></a>
14639 void rewind(FILE *stream);</pre>
14640 <h6>Description</h6>
14642 The rewind function sets the file position indicator for the stream pointed to by
14643 stream to the beginning of the file. It is equivalent to
14645 (void)fseek(stream, 0L, SEEK_SET)</pre>
14646 except that the error indicator for the stream is also cleared.
14649 The rewind function returns no value.
14651 <h4><a name="7.19.10" href="#7.19.10">7.19.10 Error-handling functions</a></h4>
14653 <h5><a name="7.19.10.1" href="#7.19.10.1">7.19.10.1 The clearerr function</a></h5>
14657 #include <a href="#7.19"><stdio.h></a>
14658 void clearerr(FILE *stream);</pre>
14659 <h6>Description</h6>
14661 The clearerr function clears the end-of-file and error indicators for the stream pointed
14665 The clearerr function returns no value.
14668 <h5><a name="7.19.10.2" href="#7.19.10.2">7.19.10.2 The feof function</a></h5>
14672 #include <a href="#7.19"><stdio.h></a>
14673 int feof(FILE *stream);</pre>
14674 <h6>Description</h6>
14676 The feof function tests the end-of-file indicator for the stream pointed to by stream.
14679 The feof function returns nonzero if and only if the end-of-file indicator is set for
14682 <h5><a name="7.19.10.3" href="#7.19.10.3">7.19.10.3 The ferror function</a></h5>
14686 #include <a href="#7.19"><stdio.h></a>
14687 int ferror(FILE *stream);</pre>
14688 <h6>Description</h6>
14690 The ferror function tests the error indicator for the stream pointed to by stream.
14693 The ferror function returns nonzero if and only if the error indicator is set for
14696 <h5><a name="7.19.10.4" href="#7.19.10.4">7.19.10.4 The perror function</a></h5>
14700 #include <a href="#7.19"><stdio.h></a>
14701 void perror(const char *s);</pre>
14702 <h6>Description</h6>
14704 The perror function maps the error number in the integer expression errno to an
14705 error message. It writes a sequence of characters to the standard error stream thus: first
14706 (if s is not a null pointer and the character pointed to by s is not the null character), the
14707 string pointed to by s followed by a colon (:) and a space; then an appropriate error
14708 message string followed by a new-line character. The contents of the error message
14709 strings are the same as those returned by the strerror function with argument errno.
14712 The perror function returns no value.
14713 <p><b> Forward references</b>: the strerror function (<a href="#7.21.6.2">7.21.6.2</a>).
14716 <h3><a name="7.20" href="#7.20">7.20 General utilities <stdlib.h></a></h3>
14718 The header <a href="#7.20"><stdlib.h></a> declares five types and several functions of general utility, and
14719 defines several macros.<sup><a href="#note257"><b>257)</b></a></sup>
14721 The types declared are size_t and wchar_t (both described in <a href="#7.17">7.17</a>),
14724 which is a structure type that is the type of the value returned by the div function,
14727 which is a structure type that is the type of the value returned by the ldiv function, and
14730 which is a structure type that is the type of the value returned by the lldiv function.
14732 The macros defined are NULL (described in <a href="#7.17">7.17</a>);
14738 which expand to integer constant expressions that can be used as the argument to the
14739 exit function to return unsuccessful or successful termination status, respectively, to the
14743 which expands to an integer constant expression that is the maximum value returned by
14744 the rand function; and
14747 which expands to a positive integer expression with type size_t that is the maximum
14748 number of bytes in a multibyte character for the extended character set specified by the
14749 current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX.
14757 <p><small><a name="note257" href="#note257">257)</a> See ''future library directions'' (<a href="#7.26.10">7.26.10</a>).
14760 <h4><a name="7.20.1" href="#7.20.1">7.20.1 Numeric conversion functions</a></h4>
14762 The functions atof, atoi, atol, and atoll need not affect the value of the integer
14763 expression errno on an error. If the value of the result cannot be represented, the
14764 behavior is undefined.
14766 <h5><a name="7.20.1.1" href="#7.20.1.1">7.20.1.1 The atof function</a></h5>
14770 #include <a href="#7.20"><stdlib.h></a>
14771 double atof(const char *nptr);</pre>
14772 <h6>Description</h6>
14774 The atof function converts the initial portion of the string pointed to by nptr to
14775 double representation. Except for the behavior on error, it is equivalent to
14777 strtod(nptr, (char **)NULL)</pre>
14780 The atof function returns the converted value.
14781 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>).
14783 <h5><a name="7.20.1.2" href="#7.20.1.2">7.20.1.2 The atoi, atol, and atoll functions</a></h5>
14787 #include <a href="#7.20"><stdlib.h></a>
14788 int atoi(const char *nptr);
14789 long int atol(const char *nptr);
14790 long long int atoll(const char *nptr);</pre>
14791 <h6>Description</h6>
14793 The atoi, atol, and atoll functions convert the initial portion of the string pointed
14794 to by nptr to int, long int, and long long int representation, respectively.
14795 Except for the behavior on error, they are equivalent to
14797 atoi: (int)strtol(nptr, (char **)NULL, 10)
14798 atol: strtol(nptr, (char **)NULL, 10)
14799 atoll: strtoll(nptr, (char **)NULL, 10)</pre>
14802 The atoi, atol, and atoll functions return the converted value.
14803 <p><b> Forward references</b>: the strtol, strtoll, strtoul, and strtoull functions
14804 (<a href="#7.20.1.4">7.20.1.4</a>).
14807 <h5><a name="7.20.1.3" href="#7.20.1.3">7.20.1.3 The strtod, strtof, and strtold functions</a></h5>
14811 #include <a href="#7.20"><stdlib.h></a>
14812 double strtod(const char * restrict nptr,
14813 char ** restrict endptr);
14814 float strtof(const char * restrict nptr,
14815 char ** restrict endptr);
14816 long double strtold(const char * restrict nptr,
14817 char ** restrict endptr);</pre>
14818 <h6>Description</h6>
14820 The strtod, strtof, and strtold functions convert the initial portion of the string
14821 pointed to by nptr to double, float, and long double representation,
14822 respectively. First, they decompose the input string into three parts: an initial, possibly
14823 empty, sequence of white-space characters (as specified by the isspace function), a
14824 subject sequence resembling a floating-point constant or representing an infinity or NaN;
14825 and a final string of one or more unrecognized characters, including the terminating null
14826 character of the input string. Then, they attempt to convert the subject sequence to a
14827 floating-point number, and return the result.
14829 The expected form of the subject sequence is an optional plus or minus sign, then one of
14832 <li> a nonempty sequence of decimal digits optionally containing a decimal-point
14833 character, then an optional exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
14834 <li> a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
14835 decimal-point character, then an optional binary exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
14836 <li> INF or INFINITY, ignoring case
14837 <li> NAN or NAN(n-char-sequenceopt), ignoring case in the NAN part, where:
14842 n-char-sequence digit
14843 n-char-sequence nondigit</pre>
14845 The subject sequence is defined as the longest initial subsequence of the input string,
14846 starting with the first non-white-space character, that is of the expected form. The subject
14847 sequence contains no characters if the input string is not of the expected form.
14849 If the subject sequence has the expected form for a floating-point number, the sequence of
14850 characters starting with the first digit or the decimal-point character (whichever occurs
14851 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
14853 decimal-point character is used in place of a period, and that if neither an exponent part
14854 nor a decimal-point character appears in a decimal floating point number, or if a binary
14855 exponent part does not appear in a hexadecimal floating point number, an exponent part
14856 of the appropriate type with value zero is assumed to follow the last digit in the string. If
14857 the subject sequence begins with a minus sign, the sequence is interpreted as negated.<sup><a href="#note258"><b>258)</b></a></sup>
14858 A character sequence INF or INFINITY is interpreted as an infinity, if representable in
14859 the return type, else like a floating constant that is too large for the range of the return
14860 type. A character sequence NAN or NAN(n-char-sequenceopt), is interpreted as a quiet
14861 NaN, if supported in the return type, else like a subject sequence part that does not have
14862 the expected form; the meaning of the n-char sequences is implementation-defined.<sup><a href="#note259"><b>259)</b></a></sup> A
14863 pointer to the final string is stored in the object pointed to by endptr, provided that
14864 endptr is not a null pointer.
14866 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
14867 value resulting from the conversion is correctly rounded.
14869 In other than the "C" locale, additional locale-specific subject sequence forms may be
14872 If the subject sequence is empty or does not have the expected form, no conversion is
14873 performed; the value of nptr is stored in the object pointed to by endptr, provided
14874 that endptr is not a null pointer.
14875 Recommended practice
14877 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
14878 the result is not exactly representable, the result should be one of the two numbers in the
14879 appropriate internal format that are adjacent to the hexadecimal floating source value,
14880 with the extra stipulation that the error should have a correct sign for the current rounding
14883 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
14884 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
14885 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
14886 consider the two bounding, adjacent decimal strings L and U, both having
14887 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
14888 The result should be one of the (equal or adjacent) values that would be obtained by
14889 correctly rounding L and U according to the current rounding direction, with the extra
14892 stipulation that the error with respect to D should have a correct sign for the current
14893 rounding direction.<sup><a href="#note260"><b>260)</b></a></sup>
14896 The functions return the converted value, if any. If no conversion could be performed,
14897 zero is returned. If the correct value is outside the range of representable values, plus or
14898 minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the return
14899 type and sign of the value), and the value of the macro ERANGE is stored in errno. If
14900 the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is no greater
14901 than the smallest normalized positive number in the return type; whether errno acquires
14902 the value ERANGE is implementation-defined.
14905 <p><small><a name="note258" href="#note258">258)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
14906 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
14907 methods may yield different results if rounding is toward positive or negative infinity. In either case,
14908 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
14910 <p><small><a name="note259" href="#note259">259)</a> An implementation may use the n-char sequence to determine extra information to be represented in
14911 the NaN's significand.
14913 <p><small><a name="note260" href="#note260">260)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
14914 to the same internal floating value, but if not will round to adjacent values.
14917 <h5><a name="7.20.1.4" href="#7.20.1.4">7.20.1.4 The strtol, strtoll, strtoul, and strtoull functions</a></h5>
14921 #include <a href="#7.20"><stdlib.h></a>
14923 const char * restrict nptr,
14924 char ** restrict endptr,
14926 long long int strtoll(
14927 const char * restrict nptr,
14928 char ** restrict endptr,
14930 unsigned long int strtoul(
14931 const char * restrict nptr,
14932 char ** restrict endptr,
14934 unsigned long long int strtoull(
14935 const char * restrict nptr,
14936 char ** restrict endptr,
14938 <h6>Description</h6>
14940 The strtol, strtoll, strtoul, and strtoull functions convert the initial
14941 portion of the string pointed to by nptr to long int, long long int, unsigned
14942 long int, and unsigned long long int representation, respectively. First,
14943 they decompose the input string into three parts: an initial, possibly empty, sequence of
14944 white-space characters (as specified by the isspace function), a subject sequence
14948 resembling an integer represented in some radix determined by the value of base, and a
14949 final string of one or more unrecognized characters, including the terminating null
14950 character of the input string. Then, they attempt to convert the subject sequence to an
14951 integer, and return the result.
14953 If the value of base is zero, the expected form of the subject sequence is that of an
14954 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
14955 not including an integer suffix. If the value of base is between 2 and 36 (inclusive), the
14956 expected form of the subject sequence is a sequence of letters and digits representing an
14957 integer with the radix specified by base, optionally preceded by a plus or minus sign,
14958 but not including an integer suffix. The letters from a (or A) through z (or Z) are
14959 ascribed the values 10 through 35; only letters and digits whose ascribed values are less
14960 than that of base are permitted. If the value of base is 16, the characters 0x or 0X may
14961 optionally precede the sequence of letters and digits, following the sign if present.
14963 The subject sequence is defined as the longest initial subsequence of the input string,
14964 starting with the first non-white-space character, that is of the expected form. The subject
14965 sequence contains no characters if the input string is empty or consists entirely of white
14966 space, or if the first non-white-space character is other than a sign or a permissible letter
14969 If the subject sequence has the expected form and the value of base is zero, the sequence
14970 of characters starting with the first digit is interpreted as an integer constant according to
14971 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
14972 is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
14973 as given above. If the subject sequence begins with a minus sign, the value resulting from
14974 the conversion is negated (in the return type). A pointer to the final string is stored in the
14975 object pointed to by endptr, provided that endptr is not a null pointer.
14977 In other than the "C" locale, additional locale-specific subject sequence forms may be
14980 If the subject sequence is empty or does not have the expected form, no conversion is
14981 performed; the value of nptr is stored in the object pointed to by endptr, provided
14982 that endptr is not a null pointer.
14985 The strtol, strtoll, strtoul, and strtoull functions return the converted
14986 value, if any. If no conversion could be performed, zero is returned. If the correct value
14987 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
14988 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
14989 and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
14992 <h4><a name="7.20.2" href="#7.20.2">7.20.2 Pseudo-random sequence generation functions</a></h4>
14994 <h5><a name="7.20.2.1" href="#7.20.2.1">7.20.2.1 The rand function</a></h5>
14998 #include <a href="#7.20"><stdlib.h></a>
14999 int rand(void);</pre>
15000 <h6>Description</h6>
15002 The rand function computes a sequence of pseudo-random integers in the range 0 to
15005 The implementation shall behave as if no library function calls the rand function.
15008 The rand function returns a pseudo-random integer.
15009 Environmental limits
15011 The value of the RAND_MAX macro shall be at least 32767.
15013 <h5><a name="7.20.2.2" href="#7.20.2.2">7.20.2.2 The srand function</a></h5>
15017 #include <a href="#7.20"><stdlib.h></a>
15018 void srand(unsigned int seed);</pre>
15019 <h6>Description</h6>
15021 The srand function uses the argument as a seed for a new sequence of pseudo-random
15022 numbers to be returned by subsequent calls to rand. If srand is then called with the
15023 same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
15024 called before any calls to srand have been made, the same sequence shall be generated
15025 as when srand is first called with a seed value of 1.
15027 The implementation shall behave as if no library function calls the srand function.
15030 The srand function returns no value.
15032 EXAMPLE The following functions define a portable implementation of rand and srand.
15035 static unsigned long int next = 1;
15036 int rand(void) // RAND_MAX assumed to be 32767
15038 next = next * 1103515245 + 12345;
15039 return (unsigned int)(next/65536) % 32768;
15041 void srand(unsigned int seed)
15047 <h4><a name="7.20.3" href="#7.20.3">7.20.3 Memory management functions</a></h4>
15049 The order and contiguity of storage allocated by successive calls to the calloc,
15050 malloc, and realloc functions is unspecified. The pointer returned if the allocation
15051 succeeds is suitably aligned so that it may be assigned to a pointer to any type of object
15052 and then used to access such an object or an array of such objects in the space allocated
15053 (until the space is explicitly deallocated). The lifetime of an allocated object extends
15054 from the allocation until the deallocation. Each such allocation shall yield a pointer to an
15055 object disjoint from any other object. The pointer returned points to the start (lowest byte
15056 address) of the allocated space. If the space cannot be allocated, a null pointer is
15057 returned. If the size of the space requested is zero, the behavior is implementation-
15058 defined: either a null pointer is returned, or the behavior is as if the size were some
15059 nonzero value, except that the returned pointer shall not be used to access an object.
15061 <h5><a name="7.20.3.1" href="#7.20.3.1">7.20.3.1 The calloc function</a></h5>
15065 #include <a href="#7.20"><stdlib.h></a>
15066 void *calloc(size_t nmemb, size_t size);</pre>
15067 <h6>Description</h6>
15069 The calloc function allocates space for an array of nmemb objects, each of whose size
15070 is size. The space is initialized to all bits zero.<sup><a href="#note261"><b>261)</b></a></sup>
15073 The calloc function returns either a null pointer or a pointer to the allocated space.
15076 <p><small><a name="note261" href="#note261">261)</a> Note that this need not be the same as the representation of floating-point zero or a null pointer
15080 <h5><a name="7.20.3.2" href="#7.20.3.2">7.20.3.2 The free function</a></h5>
15084 #include <a href="#7.20"><stdlib.h></a>
15085 void free(void *ptr);</pre>
15086 <h6>Description</h6>
15088 The free function causes the space pointed to by ptr to be deallocated, that is, made
15089 available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
15090 the argument does not match a pointer earlier returned by the calloc, malloc, or
15094 realloc function, or if the space has been deallocated by a call to free or realloc,
15095 the behavior is undefined.
15098 The free function returns no value.
15100 <h5><a name="7.20.3.3" href="#7.20.3.3">7.20.3.3 The malloc function</a></h5>
15104 #include <a href="#7.20"><stdlib.h></a>
15105 void *malloc(size_t size);</pre>
15106 <h6>Description</h6>
15108 The malloc function allocates space for an object whose size is specified by size and
15109 whose value is indeterminate.
15112 The malloc function returns either a null pointer or a pointer to the allocated space.
15114 <h5><a name="7.20.3.4" href="#7.20.3.4">7.20.3.4 The realloc function</a></h5>
15118 #include <a href="#7.20"><stdlib.h></a>
15119 void *realloc(void *ptr, size_t size);</pre>
15120 <h6>Description</h6>
15122 The realloc function deallocates the old object pointed to by ptr and returns a
15123 pointer to a new object that has the size specified by size. The contents of the new
15124 object shall be the same as that of the old object prior to deallocation, up to the lesser of
15125 the new and old sizes. Any bytes in the new object beyond the size of the old object have
15126 indeterminate values.
15128 If ptr is a null pointer, the realloc function behaves like the malloc function for the
15129 specified size. Otherwise, if ptr does not match a pointer earlier returned by the
15130 calloc, malloc, or realloc function, or if the space has been deallocated by a call
15131 to the free or realloc function, the behavior is undefined. If memory for the new
15132 object cannot be allocated, the old object is not deallocated and its value is unchanged.
15135 The realloc function returns a pointer to the new object (which may have the same
15136 value as a pointer to the old object), or a null pointer if the new object could not be
15140 <h4><a name="7.20.4" href="#7.20.4">7.20.4 Communication with the environment</a></h4>
15142 <h5><a name="7.20.4.1" href="#7.20.4.1">7.20.4.1 The abort function</a></h5>
15146 #include <a href="#7.20"><stdlib.h></a>
15147 void abort(void);</pre>
15148 <h6>Description</h6>
15150 The abort function causes abnormal program termination to occur, unless the signal
15151 SIGABRT is being caught and the signal handler does not return. Whether open streams
15152 with unwritten buffered data are flushed, open streams are closed, or temporary files are
15153 removed is implementation-defined. An implementation-defined form of the status
15154 unsuccessful termination is returned to the host environment by means of the function
15155 call raise(SIGABRT).
15158 The abort function does not return to its caller.
15160 <h5><a name="7.20.4.2" href="#7.20.4.2">7.20.4.2 The atexit function</a></h5>
15164 #include <a href="#7.20"><stdlib.h></a>
15165 int atexit(void (*func)(void));</pre>
15166 <h6>Description</h6>
15168 The atexit function registers the function pointed to by func, to be called without
15169 arguments at normal program termination.
15170 Environmental limits
15172 The implementation shall support the registration of at least 32 functions.
15175 The atexit function returns zero if the registration succeeds, nonzero if it fails.
15176 <p><b> Forward references</b>: the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
15178 <h5><a name="7.20.4.3" href="#7.20.4.3">7.20.4.3 The exit function</a></h5>
15182 #include <a href="#7.20"><stdlib.h></a>
15183 void exit(int status);</pre>
15184 <h6>Description</h6>
15186 The exit function causes normal program termination to occur. If more than one call to
15187 the exit function is executed by a program, the behavior is undefined.
15190 First, all functions registered by the atexit function are called, in the reverse order of
15191 their registration,<sup><a href="#note262"><b>262)</b></a></sup> except that a function is called after any previously registered
15192 functions that had already been called at the time it was registered. If, during the call to
15193 any such function, a call to the longjmp function is made that would terminate the call
15194 to the registered function, the behavior is undefined.
15196 Next, all open streams with unwritten buffered data are flushed, all open streams are
15197 closed, and all files created by the tmpfile function are removed.
15199 Finally, control is returned to the host environment. If the value of status is zero or
15200 EXIT_SUCCESS, an implementation-defined form of the status successful termination is
15201 returned. If the value of status is EXIT_FAILURE, an implementation-defined form
15202 of the status unsuccessful termination is returned. Otherwise the status returned is
15203 implementation-defined.
15206 The exit function cannot return to its caller.
15209 <p><small><a name="note262" href="#note262">262)</a> Each function is called as many times as it was registered, and in the correct order with respect to
15210 other registered functions.
15213 <h5><a name="7.20.4.4" href="#7.20.4.4">7.20.4.4 The _Exit function</a></h5>
15217 #include <a href="#7.20"><stdlib.h></a>
15218 void _Exit(int status);</pre>
15219 <h6>Description</h6>
15221 The _Exit function causes normal program termination to occur and control to be
15222 returned to the host environment. No functions registered by the atexit function or
15223 signal handlers registered by the signal function are called. The status returned to the
15224 host environment is determined in the same way as for the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
15225 Whether open streams with unwritten buffered data are flushed, open streams are closed,
15226 or temporary files are removed is implementation-defined.
15229 The _Exit function cannot return to its caller.
15236 <h5><a name="7.20.4.5" href="#7.20.4.5">7.20.4.5 The getenv function</a></h5>
15240 #include <a href="#7.20"><stdlib.h></a>
15241 char *getenv(const char *name);</pre>
15242 <h6>Description</h6>
15244 The getenv function searches an environment list, provided by the host environment,
15245 for a string that matches the string pointed to by name. The set of environment names
15246 and the method for altering the environment list are implementation-defined.
15248 The implementation shall behave as if no library function calls the getenv function.
15251 The getenv function returns a pointer to a string associated with the matched list
15252 member. The string pointed to shall not be modified by the program, but may be
15253 overwritten by a subsequent call to the getenv function. If the specified name cannot
15254 be found, a null pointer is returned.
15256 <h5><a name="7.20.4.6" href="#7.20.4.6">7.20.4.6 The system function</a></h5>
15260 #include <a href="#7.20"><stdlib.h></a>
15261 int system(const char *string);</pre>
15262 <h6>Description</h6>
15264 If string is a null pointer, the system function determines whether the host
15265 environment has a command processor. If string is not a null pointer, the system
15266 function passes the string pointed to by string to that command processor to be
15267 executed in a manner which the implementation shall document; this might then cause the
15268 program calling system to behave in a non-conforming manner or to terminate.
15271 If the argument is a null pointer, the system function returns nonzero only if a
15272 command processor is available. If the argument is not a null pointer, and the system
15273 function does return, it returns an implementation-defined value.
15276 <h4><a name="7.20.5" href="#7.20.5">7.20.5 Searching and sorting utilities</a></h4>
15278 These utilities make use of a comparison function to search or sort arrays of unspecified
15279 type. Where an argument declared as size_t nmemb specifies the length of the array
15280 for a function, nmemb can have the value zero on a call to that function; the comparison
15281 function is not called, a search finds no matching element, and sorting performs no
15282 rearrangement. Pointer arguments on such a call shall still have valid values, as described
15283 in <a href="#7.1.4">7.1.4</a>.
15285 The implementation shall ensure that the second argument of the comparison function
15286 (when called from bsearch), or both arguments (when called from qsort), are
15287 pointers to elements of the array.<sup><a href="#note263"><b>263)</b></a></sup> The first argument when called from bsearch
15290 The comparison function shall not alter the contents of the array. The implementation
15291 may reorder elements of the array between calls to the comparison function, but shall not
15292 alter the contents of any individual element.
15294 When the same objects (consisting of size bytes, irrespective of their current positions
15295 in the array) are passed more than once to the comparison function, the results shall be
15296 consistent with one another. That is, for qsort they shall define a total ordering on the
15297 array, and for bsearch the same object shall always compare the same way with the
15300 A sequence point occurs immediately before and immediately after each call to the
15301 comparison function, and also between any call to the comparison function and any
15302 movement of the objects passed as arguments to that call.
15305 <p><small><a name="note263" href="#note263">263)</a> That is, if the value passed is p, then the following expressions are always nonzero:
15308 ((char *)p - (char *)base) % size == 0
15309 (char *)p >= (char *)base
15310 (char *)p < (char *)base + nmemb * size</pre>
15313 <h5><a name="7.20.5.1" href="#7.20.5.1">7.20.5.1 The bsearch function</a></h5>
15317 #include <a href="#7.20"><stdlib.h></a>
15318 void *bsearch(const void *key, const void *base,
15319 size_t nmemb, size_t size,
15320 int (*compar)(const void *, const void *));</pre>
15321 <h6>Description</h6>
15323 The bsearch function searches an array of nmemb objects, the initial element of which
15324 is pointed to by base, for an element that matches the object pointed to by key. The
15328 size of each element of the array is specified by size.
15330 The comparison function pointed to by compar is called with two arguments that point
15331 to the key object and to an array element, in that order. The function shall return an
15332 integer less than, equal to, or greater than zero if the key object is considered,
15333 respectively, to be less than, to match, or to be greater than the array element. The array
15334 shall consist of: all the elements that compare less than, all the elements that compare
15335 equal to, and all the elements that compare greater than the key object, in that order.<sup><a href="#note264"><b>264)</b></a></sup>
15338 The bsearch function returns a pointer to a matching element of the array, or a null
15339 pointer if no match is found. If two elements compare as equal, which element is
15340 matched is unspecified.
15343 <p><small><a name="note264" href="#note264">264)</a> In practice, the entire array is sorted according to the comparison function.
15346 <h5><a name="7.20.5.2" href="#7.20.5.2">7.20.5.2 The qsort function</a></h5>
15350 #include <a href="#7.20"><stdlib.h></a>
15351 void qsort(void *base, size_t nmemb, size_t size,
15352 int (*compar)(const void *, const void *));</pre>
15353 <h6>Description</h6>
15355 The qsort function sorts an array of nmemb objects, the initial element of which is
15356 pointed to by base. The size of each object is specified by size.
15358 The contents of the array are sorted into ascending order according to a comparison
15359 function pointed to by compar, which is called with two arguments that point to the
15360 objects being compared. The function shall return an integer less than, equal to, or
15361 greater than zero if the first argument is considered to be respectively less than, equal to,
15362 or greater than the second.
15364 If two elements compare as equal, their order in the resulting sorted array is unspecified.
15367 The qsort function returns no value.
15374 <h4><a name="7.20.6" href="#7.20.6">7.20.6 Integer arithmetic functions</a></h4>
15376 <h5><a name="7.20.6.1" href="#7.20.6.1">7.20.6.1 The abs, labs and llabs functions</a></h5>
15380 #include <a href="#7.20"><stdlib.h></a>
15382 long int labs(long int j);
15383 long long int llabs(long long int j);</pre>
15384 <h6>Description</h6>
15386 The abs, labs, and llabs functions compute the absolute value of an integer j. If the
15387 result cannot be represented, the behavior is undefined.<sup><a href="#note265"><b>265)</b></a></sup>
15390 The abs, labs, and llabs, functions return the absolute value.
15393 <p><small><a name="note265" href="#note265">265)</a> The absolute value of the most negative number cannot be represented in two's complement.
15396 <h5><a name="7.20.6.2" href="#7.20.6.2">7.20.6.2 The div, ldiv, and lldiv functions</a></h5>
15400 #include <a href="#7.20"><stdlib.h></a>
15401 div_t div(int numer, int denom);
15402 ldiv_t ldiv(long int numer, long int denom);
15403 lldiv_t lldiv(long long int numer, long long int denom);</pre>
15404 <h6>Description</h6>
15406 The div, ldiv, and lldiv, functions compute numer / denom and numer %
15407 denom in a single operation.
15410 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
15411 lldiv_t, respectively, comprising both the quotient and the remainder. The structures
15412 shall contain (in either order) the members quot (the quotient) and rem (the remainder),
15413 each of which has the same type as the arguments numer and denom. If either part of
15414 the result cannot be represented, the behavior is undefined.
15421 <h4><a name="7.20.7" href="#7.20.7">7.20.7 Multibyte/wide character conversion functions</a></h4>
15423 The behavior of the multibyte character functions is affected by the LC_CTYPE category
15424 of the current locale. For a state-dependent encoding, each function is placed into its
15425 initial conversion state by a call for which its character pointer argument, s, is a null
15426 pointer. Subsequent calls with s as other than a null pointer cause the internal conversion
15427 state of the function to be altered as necessary. A call with s as a null pointer causes
15428 these functions to return a nonzero value if encodings have state dependency, and zero
15429 otherwise.<sup><a href="#note266"><b>266)</b></a></sup> Changing the LC_CTYPE category causes the conversion state of these
15430 functions to be indeterminate.
15433 <p><small><a name="note266" href="#note266">266)</a> If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
15434 character codes, but are grouped with an adjacent multibyte character.
15437 <h5><a name="7.20.7.1" href="#7.20.7.1">7.20.7.1 The mblen function</a></h5>
15441 #include <a href="#7.20"><stdlib.h></a>
15442 int mblen(const char *s, size_t n);</pre>
15443 <h6>Description</h6>
15445 If s is not a null pointer, the mblen function determines the number of bytes contained
15446 in the multibyte character pointed to by s. Except that the conversion state of the
15447 mbtowc function is not affected, it is equivalent to
15450 mbtowc((wchar_t *)0, s, n);</pre>
15451 The implementation shall behave as if no library function calls the mblen function.
15454 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte
15455 character encodings, respectively, do or do not have state-dependent encodings. If s is
15456 not a null pointer, the mblen function either returns 0 (if s points to the null character),
15457 or returns the number of bytes that are contained in the multibyte character (if the next n
15458 or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid
15459 multibyte character).
15460 <p><b> Forward references</b>: the mbtowc function (<a href="#7.20.7.2">7.20.7.2</a>).
15467 <h5><a name="7.20.7.2" href="#7.20.7.2">7.20.7.2 The mbtowc function</a></h5>
15471 #include <a href="#7.20"><stdlib.h></a>
15472 int mbtowc(wchar_t * restrict pwc,
15473 const char * restrict s,
15475 <h6>Description</h6>
15477 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with
15478 the byte pointed to by s to determine the number of bytes needed to complete the next
15479 multibyte character (including any shift sequences). If the function determines that the
15480 next multibyte character is complete and valid, it determines the value of the
15481 corresponding wide character and then, if pwc is not a null pointer, stores that value in
15482 the object pointed to by pwc. If the corresponding wide character is the null wide
15483 character, the function is left in the initial conversion state.
15485 The implementation shall behave as if no library function calls the mbtowc function.
15488 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte
15489 character encodings, respectively, do or do not have state-dependent encodings. If s is
15490 not a null pointer, the mbtowc function either returns 0 (if s points to the null character),
15491 or returns the number of bytes that are contained in the converted multibyte character (if
15492 the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not
15493 form a valid multibyte character).
15495 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
15498 <h5><a name="7.20.7.3" href="#7.20.7.3">7.20.7.3 The wctomb function</a></h5>
15502 #include <a href="#7.20"><stdlib.h></a>
15503 int wctomb(char *s, wchar_t wc);</pre>
15504 <h6>Description</h6>
15506 The wctomb function determines the number of bytes needed to represent the multibyte
15507 character corresponding to the wide character given by wc (including any shift
15508 sequences), and stores the multibyte character representation in the array whose first
15509 element is pointed to by s (if s is not a null pointer). At most MB_CUR_MAX characters
15510 are stored. If wc is a null wide character, a null byte is stored, preceded by any shift
15511 sequence needed to restore the initial shift state, and the function is left in the initial
15515 The implementation shall behave as if no library function calls the wctomb function.
15518 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte
15519 character encodings, respectively, do or do not have state-dependent encodings. If s is
15520 not a null pointer, the wctomb function returns -1 if the value of wc does not correspond
15521 to a valid multibyte character, or returns the number of bytes that are contained in the
15522 multibyte character corresponding to the value of wc.
15524 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
15526 <h4><a name="7.20.8" href="#7.20.8">7.20.8 Multibyte/wide string conversion functions</a></h4>
15528 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
15529 the current locale.
15531 <h5><a name="7.20.8.1" href="#7.20.8.1">7.20.8.1 The mbstowcs function</a></h5>
15535 #include <a href="#7.20"><stdlib.h></a>
15536 size_t mbstowcs(wchar_t * restrict pwcs,
15537 const char * restrict s,
15539 <h6>Description</h6>
15541 The mbstowcs function converts a sequence of multibyte characters that begins in the
15542 initial shift state from the array pointed to by s into a sequence of corresponding wide
15543 characters and stores not more than n wide characters into the array pointed to by pwcs.
15544 No multibyte characters that follow a null character (which is converted into a null wide
15545 character) will be examined or converted. Each multibyte character is converted as if by
15546 a call to the mbtowc function, except that the conversion state of the mbtowc function is
15549 No more than n elements will be modified in the array pointed to by pwcs. If copying
15550 takes place between objects that overlap, the behavior is undefined.
15553 If an invalid multibyte character is encountered, the mbstowcs function returns
15554 (size_t)(-1). Otherwise, the mbstowcs function returns the number of array
15555 elements modified, not including a terminating null wide character, if any.<sup><a href="#note267"><b>267)</b></a></sup>
15563 <p><small><a name="note267" href="#note267">267)</a> The array will not be null-terminated if the value returned is n.
15566 <h5><a name="7.20.8.2" href="#7.20.8.2">7.20.8.2 The wcstombs function</a></h5>
15570 #include <a href="#7.20"><stdlib.h></a>
15571 size_t wcstombs(char * restrict s,
15572 const wchar_t * restrict pwcs,
15574 <h6>Description</h6>
15576 The wcstombs function converts a sequence of wide characters from the array pointed
15577 to by pwcs into a sequence of corresponding multibyte characters that begins in the
15578 initial shift state, and stores these multibyte characters into the array pointed to by s,
15579 stopping if a multibyte character would exceed the limit of n total bytes or if a null
15580 character is stored. Each wide character is converted as if by a call to the wctomb
15581 function, except that the conversion state of the wctomb function is not affected.
15583 No more than n bytes will be modified in the array pointed to by s. If copying takes place
15584 between objects that overlap, the behavior is undefined.
15587 If a wide character is encountered that does not correspond to a valid multibyte character,
15588 the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
15589 returns the number of bytes modified, not including a terminating null character, if
15593 <h3><a name="7.21" href="#7.21">7.21 String handling <string.h></a></h3>
15595 <h4><a name="7.21.1" href="#7.21.1">7.21.1 String function conventions</a></h4>
15597 The header <a href="#7.21"><string.h></a> declares one type and several functions, and defines one
15598 macro useful for manipulating arrays of character type and other objects treated as arrays
15599 of character type.<sup><a href="#note268"><b>268)</b></a></sup> The type is size_t and the macro is NULL (both described in
15600 <a href="#7.17">7.17</a>). Various methods are used for determining the lengths of the arrays, but in all cases
15601 a char * or void * argument points to the initial (lowest addressed) character of the
15602 array. If an array is accessed beyond the end of an object, the behavior is undefined.
15604 Where an argument declared as size_t n specifies the length of the array for a
15605 function, n can have the value zero on a call to that function. Unless explicitly stated
15606 otherwise in the description of a particular function in this subclause, pointer arguments
15607 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
15608 function that locates a character finds no occurrence, a function that compares two
15609 character sequences returns zero, and a function that copies characters copies zero
15612 For all functions in this subclause, each character shall be interpreted as if it had the type
15613 unsigned char (and therefore every possible object representation is valid and has a
15617 <p><small><a name="note268" href="#note268">268)</a> See ''future library directions'' (<a href="#7.26.11">7.26.11</a>).
15620 <h4><a name="7.21.2" href="#7.21.2">7.21.2 Copying functions</a></h4>
15622 <h5><a name="7.21.2.1" href="#7.21.2.1">7.21.2.1 The memcpy function</a></h5>
15626 #include <a href="#7.21"><string.h></a>
15627 void *memcpy(void * restrict s1,
15628 const void * restrict s2,
15630 <h6>Description</h6>
15632 The memcpy function copies n characters from the object pointed to by s2 into the
15633 object pointed to by s1. If copying takes place between objects that overlap, the behavior
15637 The memcpy function returns the value of s1.
15644 <h5><a name="7.21.2.2" href="#7.21.2.2">7.21.2.2 The memmove function</a></h5>
15648 #include <a href="#7.21"><string.h></a>
15649 void *memmove(void *s1, const void *s2, size_t n);</pre>
15650 <h6>Description</h6>
15652 The memmove function copies n characters from the object pointed to by s2 into the
15653 object pointed to by s1. Copying takes place as if the n characters from the object
15654 pointed to by s2 are first copied into a temporary array of n characters that does not
15655 overlap the objects pointed to by s1 and s2, and then the n characters from the
15656 temporary array are copied into the object pointed to by s1.
15659 The memmove function returns the value of s1.
15661 <h5><a name="7.21.2.3" href="#7.21.2.3">7.21.2.3 The strcpy function</a></h5>
15665 #include <a href="#7.21"><string.h></a>
15666 char *strcpy(char * restrict s1,
15667 const char * restrict s2);</pre>
15668 <h6>Description</h6>
15670 The strcpy function copies the string pointed to by s2 (including the terminating null
15671 character) into the array pointed to by s1. If copying takes place between objects that
15672 overlap, the behavior is undefined.
15675 The strcpy function returns the value of s1.
15677 <h5><a name="7.21.2.4" href="#7.21.2.4">7.21.2.4 The strncpy function</a></h5>
15681 #include <a href="#7.21"><string.h></a>
15682 char *strncpy(char * restrict s1,
15683 const char * restrict s2,
15685 <h6>Description</h6>
15687 The strncpy function copies not more than n characters (characters that follow a null
15688 character are not copied) from the array pointed to by s2 to the array pointed to by
15690 s1.<sup><a href="#note269"><b>269)</b></a></sup> If copying takes place between objects that overlap, the behavior is undefined.
15692 If the array pointed to by s2 is a string that is shorter than n characters, null characters
15693 are appended to the copy in the array pointed to by s1, until n characters in all have been
15697 The strncpy function returns the value of s1.
15700 <p><small><a name="note269" href="#note269">269)</a> Thus, if there is no null character in the first n characters of the array pointed to by s2, the result will
15701 not be null-terminated.
15704 <h4><a name="7.21.3" href="#7.21.3">7.21.3 Concatenation functions</a></h4>
15706 <h5><a name="7.21.3.1" href="#7.21.3.1">7.21.3.1 The strcat function</a></h5>
15710 #include <a href="#7.21"><string.h></a>
15711 char *strcat(char * restrict s1,
15712 const char * restrict s2);</pre>
15713 <h6>Description</h6>
15715 The strcat function appends a copy of the string pointed to by s2 (including the
15716 terminating null character) to the end of the string pointed to by s1. The initial character
15717 of s2 overwrites the null character at the end of s1. If copying takes place between
15718 objects that overlap, the behavior is undefined.
15721 The strcat function returns the value of s1.
15723 <h5><a name="7.21.3.2" href="#7.21.3.2">7.21.3.2 The strncat function</a></h5>
15727 #include <a href="#7.21"><string.h></a>
15728 char *strncat(char * restrict s1,
15729 const char * restrict s2,
15731 <h6>Description</h6>
15733 The strncat function appends not more than n characters (a null character and
15734 characters that follow it are not appended) from the array pointed to by s2 to the end of
15735 the string pointed to by s1. The initial character of s2 overwrites the null character at the
15736 end of s1. A terminating null character is always appended to the result.<sup><a href="#note270"><b>270)</b></a></sup> If copying
15739 takes place between objects that overlap, the behavior is undefined.
15742 The strncat function returns the value of s1.
15743 <p><b> Forward references</b>: the strlen function (<a href="#7.21.6.3">7.21.6.3</a>).
15746 <p><small><a name="note270" href="#note270">270)</a> Thus, the maximum number of characters that can end up in the array pointed to by s1 is
15750 <h4><a name="7.21.4" href="#7.21.4">7.21.4 Comparison functions</a></h4>
15752 The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
15753 and strncmp is determined by the sign of the difference between the values of the first
15754 pair of characters (both interpreted as unsigned char) that differ in the objects being
15757 <h5><a name="7.21.4.1" href="#7.21.4.1">7.21.4.1 The memcmp function</a></h5>
15761 #include <a href="#7.21"><string.h></a>
15762 int memcmp(const void *s1, const void *s2, size_t n);</pre>
15763 <h6>Description</h6>
15765 The memcmp function compares the first n characters of the object pointed to by s1 to
15766 the first n characters of the object pointed to by s2.<sup><a href="#note271"><b>271)</b></a></sup>
15769 The memcmp function returns an integer greater than, equal to, or less than zero,
15770 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
15774 <p><small><a name="note271" href="#note271">271)</a> The contents of ''holes'' used as padding for purposes of alignment within structure objects are
15775 indeterminate. Strings shorter than their allocated space and unions may also cause problems in
15779 <h5><a name="7.21.4.2" href="#7.21.4.2">7.21.4.2 The strcmp function</a></h5>
15783 #include <a href="#7.21"><string.h></a>
15784 int strcmp(const char *s1, const char *s2);</pre>
15785 <h6>Description</h6>
15787 The strcmp function compares the string pointed to by s1 to the string pointed to by
15791 The strcmp function returns an integer greater than, equal to, or less than zero,
15792 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
15797 <h5><a name="7.21.4.3" href="#7.21.4.3">7.21.4.3 The strcoll function</a></h5>
15801 #include <a href="#7.21"><string.h></a>
15802 int strcoll(const char *s1, const char *s2);</pre>
15803 <h6>Description</h6>
15805 The strcoll function compares the string pointed to by s1 to the string pointed to by
15806 s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
15809 The strcoll function returns an integer greater than, equal to, or less than zero,
15810 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
15811 pointed to by s2 when both are interpreted as appropriate to the current locale.
15813 <h5><a name="7.21.4.4" href="#7.21.4.4">7.21.4.4 The strncmp function</a></h5>
15817 #include <a href="#7.21"><string.h></a>
15818 int strncmp(const char *s1, const char *s2, size_t n);</pre>
15819 <h6>Description</h6>
15821 The strncmp function compares not more than n characters (characters that follow a
15822 null character are not compared) from the array pointed to by s1 to the array pointed to
15826 The strncmp function returns an integer greater than, equal to, or less than zero,
15827 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
15828 to, or less than the possibly null-terminated array pointed to by s2.
15830 <h5><a name="7.21.4.5" href="#7.21.4.5">7.21.4.5 The strxfrm function</a></h5>
15834 #include <a href="#7.21"><string.h></a>
15835 size_t strxfrm(char * restrict s1,
15836 const char * restrict s2,
15838 <h6>Description</h6>
15840 The strxfrm function transforms the string pointed to by s2 and places the resulting
15841 string into the array pointed to by s1. The transformation is such that if the strcmp
15842 function is applied to two transformed strings, it returns a value greater than, equal to, or
15844 less than zero, corresponding to the result of the strcoll function applied to the same
15845 two original strings. No more than n characters are placed into the resulting array
15846 pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
15847 be a null pointer. If copying takes place between objects that overlap, the behavior is
15851 The strxfrm function returns the length of the transformed string (not including the
15852 terminating null character). If the value returned is n or more, the contents of the array
15853 pointed to by s1 are indeterminate.
15855 EXAMPLE The value of the following expression is the size of the array needed to hold the
15856 transformation of the string pointed to by s.
15858 1 + strxfrm(NULL, s, 0)</pre>
15861 <h4><a name="7.21.5" href="#7.21.5">7.21.5 Search functions</a></h4>
15863 <h5><a name="7.21.5.1" href="#7.21.5.1">7.21.5.1 The memchr function</a></h5>
15867 #include <a href="#7.21"><string.h></a>
15868 void *memchr(const void *s, int c, size_t n);</pre>
15869 <h6>Description</h6>
15871 The memchr function locates the first occurrence of c (converted to an unsigned
15872 char) in the initial n characters (each interpreted as unsigned char) of the object
15876 The memchr function returns a pointer to the located character, or a null pointer if the
15877 character does not occur in the object.
15879 <h5><a name="7.21.5.2" href="#7.21.5.2">7.21.5.2 The strchr function</a></h5>
15883 #include <a href="#7.21"><string.h></a>
15884 char *strchr(const char *s, int c);</pre>
15885 <h6>Description</h6>
15887 The strchr function locates the first occurrence of c (converted to a char) in the
15888 string pointed to by s. The terminating null character is considered to be part of the
15892 The strchr function returns a pointer to the located character, or a null pointer if the
15893 character does not occur in the string.
15896 <h5><a name="7.21.5.3" href="#7.21.5.3">7.21.5.3 The strcspn function</a></h5>
15900 #include <a href="#7.21"><string.h></a>
15901 size_t strcspn(const char *s1, const char *s2);</pre>
15902 <h6>Description</h6>
15904 The strcspn function computes the length of the maximum initial segment of the string
15905 pointed to by s1 which consists entirely of characters not from the string pointed to by
15909 The strcspn function returns the length of the segment.
15911 <h5><a name="7.21.5.4" href="#7.21.5.4">7.21.5.4 The strpbrk function</a></h5>
15915 #include <a href="#7.21"><string.h></a>
15916 char *strpbrk(const char *s1, const char *s2);</pre>
15917 <h6>Description</h6>
15919 The strpbrk function locates the first occurrence in the string pointed to by s1 of any
15920 character from the string pointed to by s2.
15923 The strpbrk function returns a pointer to the character, or a null pointer if no character
15924 from s2 occurs in s1.
15926 <h5><a name="7.21.5.5" href="#7.21.5.5">7.21.5.5 The strrchr function</a></h5>
15930 #include <a href="#7.21"><string.h></a>
15931 char *strrchr(const char *s, int c);</pre>
15932 <h6>Description</h6>
15934 The strrchr function locates the last occurrence of c (converted to a char) in the
15935 string pointed to by s. The terminating null character is considered to be part of the
15939 The strrchr function returns a pointer to the character, or a null pointer if c does not
15940 occur in the string.
15943 <h5><a name="7.21.5.6" href="#7.21.5.6">7.21.5.6 The strspn function</a></h5>
15947 #include <a href="#7.21"><string.h></a>
15948 size_t strspn(const char *s1, const char *s2);</pre>
15949 <h6>Description</h6>
15951 The strspn function computes the length of the maximum initial segment of the string
15952 pointed to by s1 which consists entirely of characters from the string pointed to by s2.
15955 The strspn function returns the length of the segment.
15957 <h5><a name="7.21.5.7" href="#7.21.5.7">7.21.5.7 The strstr function</a></h5>
15961 #include <a href="#7.21"><string.h></a>
15962 char *strstr(const char *s1, const char *s2);</pre>
15963 <h6>Description</h6>
15965 The strstr function locates the first occurrence in the string pointed to by s1 of the
15966 sequence of characters (excluding the terminating null character) in the string pointed to
15970 The strstr function returns a pointer to the located string, or a null pointer if the string
15971 is not found. If s2 points to a string with zero length, the function returns s1.
15973 <h5><a name="7.21.5.8" href="#7.21.5.8">7.21.5.8 The strtok function</a></h5>
15977 #include <a href="#7.21"><string.h></a>
15978 char *strtok(char * restrict s1,
15979 const char * restrict s2);</pre>
15980 <h6>Description</h6>
15982 A sequence of calls to the strtok function breaks the string pointed to by s1 into a
15983 sequence of tokens, each of which is delimited by a character from the string pointed to
15984 by s2. The first call in the sequence has a non-null first argument; subsequent calls in the
15985 sequence have a null first argument. The separator string pointed to by s2 may be
15986 different from call to call.
15988 The first call in the sequence searches the string pointed to by s1 for the first character
15989 that is not contained in the current separator string pointed to by s2. If no such character
15990 is found, then there are no tokens in the string pointed to by s1 and the strtok function
15992 returns a null pointer. If such a character is found, it is the start of the first token.
15994 The strtok function then searches from there for a character that is contained in the
15995 current separator string. If no such character is found, the current token extends to the
15996 end of the string pointed to by s1, and subsequent searches for a token will return a null
15997 pointer. If such a character is found, it is overwritten by a null character, which
15998 terminates the current token. The strtok function saves a pointer to the following
15999 character, from which the next search for a token will start.
16001 Each subsequent call, with a null pointer as the value of the first argument, starts
16002 searching from the saved pointer and behaves as described above.
16004 The implementation shall behave as if no library function calls the strtok function.
16007 The strtok function returns a pointer to the first character of a token, or a null pointer
16008 if there is no token.
16012 #include <a href="#7.21"><string.h></a>
16013 static char str[] = "?a???b,,,#c";
16015 t = strtok(str, "?"); // t points to the token "a"
16016 t = strtok(NULL, ","); // t points to the token "??b"
16017 t = strtok(NULL, "#,"); // t points to the token "c"
16018 t = strtok(NULL, "?"); // t is a null pointer</pre>
16021 <h4><a name="7.21.6" href="#7.21.6">7.21.6 Miscellaneous functions</a></h4>
16023 <h5><a name="7.21.6.1" href="#7.21.6.1">7.21.6.1 The memset function</a></h5>
16027 #include <a href="#7.21"><string.h></a>
16028 void *memset(void *s, int c, size_t n);</pre>
16029 <h6>Description</h6>
16031 The memset function copies the value of c (converted to an unsigned char) into
16032 each of the first n characters of the object pointed to by s.
16035 The memset function returns the value of s.
16038 <h5><a name="7.21.6.2" href="#7.21.6.2">7.21.6.2 The strerror function</a></h5>
16042 #include <a href="#7.21"><string.h></a>
16043 char *strerror(int errnum);</pre>
16044 <h6>Description</h6>
16046 The strerror function maps the number in errnum to a message string. Typically,
16047 the values for errnum come from errno, but strerror shall map any value of type
16050 The implementation shall behave as if no library function calls the strerror function.
16053 The strerror function returns a pointer to the string, the contents of which are locale-
16054 specific. The array pointed to shall not be modified by the program, but may be
16055 overwritten by a subsequent call to the strerror function.
16057 <h5><a name="7.21.6.3" href="#7.21.6.3">7.21.6.3 The strlen function</a></h5>
16061 #include <a href="#7.21"><string.h></a>
16062 size_t strlen(const char *s);</pre>
16063 <h6>Description</h6>
16065 The strlen function computes the length of the string pointed to by s.
16068 The strlen function returns the number of characters that precede the terminating null
16072 <h3><a name="7.22" href="#7.22">7.22 Type-generic math <tgmath.h></a></h3>
16074 The header <a href="#7.22"><tgmath.h></a> includes the headers <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> and
16075 defines several type-generic macros.
16077 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
16078 double) suffix, several have one or more parameters whose corresponding real type is
16079 double. For each such function, except modf, there is a corresponding type-generic
16080 macro.<sup><a href="#note272"><b>272)</b></a></sup> The parameters whose corresponding real type is double in the function
16081 synopsis are generic parameters. Use of the macro invokes a function whose
16082 corresponding real type and type domain are determined by the arguments for the generic
16083 parameters.<sup><a href="#note273"><b>273)</b></a></sup>
16085 Use of the macro invokes a function whose generic parameters have the corresponding
16086 real type determined as follows:
16088 <li> First, if any argument for generic parameters has type long double, the type
16089 determined is long double.
16090 <li> Otherwise, if any argument for generic parameters has type double or is of integer
16091 type, the type determined is double.
16092 <li> Otherwise, the type determined is float.
16095 For each unsuffixed function in <a href="#7.12"><math.h></a> for which there is a function in
16096 <a href="#7.3"><complex.h></a> with the same name except for a c prefix, the corresponding type-
16097 generic macro (for both functions) has the same name as the function in <a href="#7.12"><math.h></a>. The
16098 corresponding type-generic macro for fabs and cabs is fabs.
16105 <a href="#7.12"><math.h></a> <a href="#7.3"><complex.h></a> type-generic
16106 function function macro
16123 fabs cabs fabs</pre>
16124 If at least one argument for a generic parameter is complex, then use of the macro invokes
16125 a complex function; otherwise, use of the macro invokes a real function.
16127 For each unsuffixed function in <a href="#7.12"><math.h></a> without a c-prefixed counterpart in
16128 <a href="#7.3"><complex.h></a> (except modf), the corresponding type-generic macro has the same
16129 name as the function. These type-generic macros are:
16131 atan2 fma llround remainder
16132 cbrt fmax log10 remquo
16133 ceil fmin log1p rint
16134 copysign fmod log2 round
16135 erf frexp logb scalbn
16136 erfc hypot lrint scalbln
16137 exp2 ilogb lround tgamma
16138 expm1 ldexp nearbyint trunc
16139 fdim lgamma nextafter
16140 floor llrint nexttoward</pre>
16141 If all arguments for generic parameters are real, then use of the macro invokes a real
16142 function; otherwise, use of the macro results in undefined behavior.
16144 For each unsuffixed function in <a href="#7.3"><complex.h></a> that is not a c-prefixed counterpart to a
16145 function in <a href="#7.12"><math.h></a>, the corresponding type-generic macro has the same name as the
16146 function. These type-generic macros are:
16151 Use of the macro with any real or complex argument invokes a complex function.
16153 EXAMPLE With the declarations
16155 #include <a href="#7.22"><tgmath.h></a>
16162 long double complex ldc;</pre>
16163 functions invoked by use of type-generic macros are shown in the following table:
16167 exp(n) exp(n), the function
16169 sin(d) sin(d), the function
16173 pow(ldc, f) cpowl(ldc, f)
16174 remainder(n, n) remainder(n, n), the function
16175 nextafter(d, f) nextafter(d, f), the function
16176 nexttoward(f, ld) nexttowardf(f, ld)
16177 copysign(n, ld) copysignl(n, ld)
16178 ceil(fc) undefined behavior
16179 rint(dc) undefined behavior
16180 fmax(ldc, ld) undefined behavior
16181 carg(n) carg(n), the function
16183 creal(d) creal(d), the function
16184 cimag(ld) cimagl(ld)
16186 carg(dc) carg(dc), the function
16187 cproj(ldc) cprojl(ldc)</pre>
16190 <p><small><a name="note272" href="#note272">272)</a> Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to
16191 make available the corresponding ordinary function.
16193 <p><small><a name="note273" href="#note273">273)</a> If the type of the argument is not compatible with the type of the parameter for the selected function,
16194 the behavior is undefined.
16197 <h3><a name="7.23" href="#7.23">7.23 Date and time <time.h></a></h3>
16199 <h4><a name="7.23.1" href="#7.23.1">7.23.1 Components of time</a></h4>
16201 The header <a href="#7.23"><time.h></a> defines two macros, and declares several types and functions for
16202 manipulating time. Many functions deal with a calendar time that represents the current
16203 date (according to the Gregorian calendar) and time. Some functions deal with local
16204 time, which is the calendar time expressed for some specific time zone, and with Daylight
16205 Saving Time, which is a temporary change in the algorithm for determining local time.
16206 The local time zone and Daylight Saving Time are implementation-defined.
16208 The macros defined are NULL (described in <a href="#7.17">7.17</a>); and
16210 CLOCKS_PER_SEC</pre>
16211 which expands to an expression with type clock_t (described below) that is the
16212 number per second of the value returned by the clock function.
16214 The types declared are size_t (described in <a href="#7.17">7.17</a>);
16220 which are arithmetic types capable of representing times; and
16223 which holds the components of a calendar time, called the broken-down time.
16225 The range and precision of times representable in clock_t and time_t are
16226 implementation-defined. The tm structure shall contain at least the following members,
16227 in any order. The semantics of the members and their normal ranges are expressed in the
16228 comments.<sup><a href="#note274"><b>274)</b></a></sup>
16230 int tm_sec; // seconds after the minute -- [0, 60]
16231 int tm_min; // minutes after the hour -- [0, 59]
16232 int tm_hour; // hours since midnight -- [0, 23]
16233 int tm_mday; // day of the month -- [1, 31]
16234 int tm_mon; // months since January -- [0, 11]
16235 int tm_year; // years since 1900
16236 int tm_wday; // days since Sunday -- [0, 6]
16237 int tm_yday; // days since January 1 -- [0, 365]
16238 int tm_isdst; // Daylight Saving Time flag</pre>
16243 The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight
16244 Saving Time is not in effect, and negative if the information is not available.
16247 <p><small><a name="note274" href="#note274">274)</a> The range [0, 60] for tm_sec allows for a positive leap second.
16250 <h4><a name="7.23.2" href="#7.23.2">7.23.2 Time manipulation functions</a></h4>
16252 <h5><a name="7.23.2.1" href="#7.23.2.1">7.23.2.1 The clock function</a></h5>
16256 #include <a href="#7.23"><time.h></a>
16257 clock_t clock(void);</pre>
16258 <h6>Description</h6>
16260 The clock function determines the processor time used.
16263 The clock function returns the implementation's best approximation to the processor
16264 time used by the program since the beginning of an implementation-defined era related
16265 only to the program invocation. To determine the time in seconds, the value returned by
16266 the clock function should be divided by the value of the macro CLOCKS_PER_SEC. If
16267 the processor time used is not available or its value cannot be represented, the function
16268 returns the value (clock_t)(-1).<sup><a href="#note275"><b>275)</b></a></sup>
16271 <p><small><a name="note275" href="#note275">275)</a> In order to measure the time spent in a program, the clock function should be called at the start of
16272 the program and its return value subtracted from the value returned by subsequent calls.
16275 <h5><a name="7.23.2.2" href="#7.23.2.2">7.23.2.2 The difftime function</a></h5>
16279 #include <a href="#7.23"><time.h></a>
16280 double difftime(time_t time1, time_t time0);</pre>
16281 <h6>Description</h6>
16283 The difftime function computes the difference between two calendar times: time1 -
16287 The difftime function returns the difference expressed in seconds as a double.
16294 <h5><a name="7.23.2.3" href="#7.23.2.3">7.23.2.3 The mktime function</a></h5>
16298 #include <a href="#7.23"><time.h></a>
16299 time_t mktime(struct tm *timeptr);</pre>
16300 <h6>Description</h6>
16302 The mktime function converts the broken-down time, expressed as local time, in the
16303 structure pointed to by timeptr into a calendar time value with the same encoding as
16304 that of the values returned by the time function. The original values of the tm_wday
16305 and tm_yday components of the structure are ignored, and the original values of the
16306 other components are not restricted to the ranges indicated above.<sup><a href="#note276"><b>276)</b></a></sup> On successful
16307 completion, the values of the tm_wday and tm_yday components of the structure are
16308 set appropriately, and the other components are set to represent the specified calendar
16309 time, but with their values forced to the ranges indicated above; the final value of
16310 tm_mday is not set until tm_mon and tm_year are determined.
16313 The mktime function returns the specified calendar time encoded as a value of type
16314 time_t. If the calendar time cannot be represented, the function returns the value
16317 EXAMPLE What day of the week is July 4, 2001?
16319 #include <a href="#7.19"><stdio.h></a>
16320 #include <a href="#7.23"><time.h></a>
16321 static const char *const wday[] = {
16322 "Sunday", "Monday", "Tuesday", "Wednesday",
16323 "Thursday", "Friday", "Saturday", "-unknown-"
16325 struct tm time_str;
16333 time_str.tm_year = 2001 - 1900;
16334 time_str.tm_mon = 7 - 1;
16335 time_str.tm_mday = 4;
16336 time_str.tm_hour = 0;
16337 time_str.tm_min = 0;
16338 time_str.tm_sec = 1;
16339 time_str.tm_isdst = -1;
16340 if (mktime(&time_str) == (time_t)(-1))
16341 time_str.tm_wday = 7;
16342 printf("%s\n", wday[time_str.tm_wday]);</pre>
16346 <p><small><a name="note276" href="#note276">276)</a> Thus, a positive or zero value for tm_isdst causes the mktime function to presume initially that
16347 Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value
16348 causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time.
16351 <h5><a name="7.23.2.4" href="#7.23.2.4">7.23.2.4 The time function</a></h5>
16355 #include <a href="#7.23"><time.h></a>
16356 time_t time(time_t *timer);</pre>
16357 <h6>Description</h6>
16359 The time function determines the current calendar time. The encoding of the value is
16363 The time function returns the implementation's best approximation to the current
16364 calendar time. The value (time_t)(-1) is returned if the calendar time is not
16365 available. If timer is not a null pointer, the return value is also assigned to the object it
16368 <h4><a name="7.23.3" href="#7.23.3">7.23.3 Time conversion functions</a></h4>
16370 Except for the strftime function, these functions each return a pointer to one of two
16371 types of static objects: a broken-down time structure or an array of char. Execution of
16372 any of the functions that return a pointer to one of these object types may overwrite the
16373 information in any object of the same type pointed to by the value returned from any
16374 previous call to any of them. The implementation shall behave as if no other library
16375 functions call these functions.
16377 <h5><a name="7.23.3.1" href="#7.23.3.1">7.23.3.1 The asctime function</a></h5>
16381 #include <a href="#7.23"><time.h></a>
16382 char *asctime(const struct tm *timeptr);</pre>
16383 <h6>Description</h6>
16385 The asctime function converts the broken-down time in the structure pointed to by
16386 timeptr into a string in the form
16389 Sun Sep 16 01:03:52 1973\n\0</pre>
16390 using the equivalent of the following algorithm.
16391 char *asctime(const struct tm *timeptr)
16394 static const char wday_name[7][3] = {
16395 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
16397 static const char mon_name[12][3] = {
16398 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
16399 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
16401 static char result[26];
16402 sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
16403 wday_name[timeptr->tm_wday],
16404 mon_name[timeptr->tm_mon],
16405 timeptr->tm_mday, timeptr->tm_hour,
16406 timeptr->tm_min, timeptr->tm_sec,
16407 1900 + timeptr->tm_year);
16408 return result;</pre>
16412 The asctime function returns a pointer to the string.
16414 <h5><a name="7.23.3.2" href="#7.23.3.2">7.23.3.2 The ctime function</a></h5>
16418 #include <a href="#7.23"><time.h></a>
16419 char *ctime(const time_t *timer);</pre>
16420 <h6>Description</h6>
16422 The ctime function converts the calendar time pointed to by timer to local time in the
16423 form of a string. It is equivalent to
16425 asctime(localtime(timer))</pre>
16428 The ctime function returns the pointer returned by the asctime function with that
16429 broken-down time as argument.
16430 <p><b> Forward references</b>: the localtime function (<a href="#7.23.3.4">7.23.3.4</a>).
16433 <h5><a name="7.23.3.3" href="#7.23.3.3">7.23.3.3 The gmtime function</a></h5>
16437 #include <a href="#7.23"><time.h></a>
16438 struct tm *gmtime(const time_t *timer);</pre>
16439 <h6>Description</h6>
16441 The gmtime function converts the calendar time pointed to by timer into a broken-
16442 down time, expressed as UTC.
16445 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
16446 specified time cannot be converted to UTC.
16448 <h5><a name="7.23.3.4" href="#7.23.3.4">7.23.3.4 The localtime function</a></h5>
16452 #include <a href="#7.23"><time.h></a>
16453 struct tm *localtime(const time_t *timer);</pre>
16454 <h6>Description</h6>
16456 The localtime function converts the calendar time pointed to by timer into a
16457 broken-down time, expressed as local time.
16460 The localtime function returns a pointer to the broken-down time, or a null pointer if
16461 the specified time cannot be converted to local time.
16463 <h5><a name="7.23.3.5" href="#7.23.3.5">7.23.3.5 The strftime function</a></h5>
16467 #include <a href="#7.23"><time.h></a>
16468 size_t strftime(char * restrict s,
16470 const char * restrict format,
16471 const struct tm * restrict timeptr);</pre>
16472 <h6>Description</h6>
16474 The strftime function places characters into the array pointed to by s as controlled by
16475 the string pointed to by format. The format shall be a multibyte character sequence,
16476 beginning and ending in its initial shift state. The format string consists of zero or
16477 more conversion specifiers and ordinary multibyte characters. A conversion specifier
16478 consists of a % character, possibly followed by an E or O modifier character (described
16479 below), followed by a character that determines the behavior of the conversion specifier.
16480 All ordinary multibyte characters (including the terminating null character) are copied
16482 unchanged into the array. If copying takes place between objects that overlap, the
16483 behavior is undefined. No more than maxsize characters are placed into the array.
16485 Each conversion specifier is replaced by appropriate characters as described in the
16486 following list. The appropriate characters are determined using the LC_TIME category
16487 of the current locale and by the values of zero or more members of the broken-down time
16488 structure pointed to by timeptr, as specified in brackets in the description. If any of
16489 the specified values is outside the normal range, the characters stored are unspecified.
16490 %a is replaced by the locale's abbreviated weekday name. [tm_wday]
16491 %A is replaced by the locale's full weekday name. [tm_wday]
16492 %b is replaced by the locale's abbreviated month name. [tm_mon]
16493 %B is replaced by the locale's full month name. [tm_mon]
16494 %c is replaced by the locale's appropriate date and time representation. [all specified
16496 in <a href="#7.23.1">7.23.1</a>]</pre>
16497 %C is replaced by the year divided by 100 and truncated to an integer, as a decimal
16499 number (00-99). [tm_year]</pre>
16500 %d is replaced by the day of the month as a decimal number (01-31). [tm_mday]
16501 %D is equivalent to ''%m/%d/%y''. [tm_mon, tm_mday, tm_year]
16502 %e is replaced by the day of the month as a decimal number (1-31); a single digit is
16504 preceded by a space. [tm_mday]</pre>
16505 %F is equivalent to ''%Y-%m-%d'' (the ISO 8601 date format). [tm_year, tm_mon,
16508 %g is replaced by the last 2 digits of the week-based year (see below) as a decimal
16510 number (00-99). [tm_year, tm_wday, tm_yday]</pre>
16511 %G is replaced by the week-based year (see below) as a decimal number (e.g., 1997).
16513 [tm_year, tm_wday, tm_yday]</pre>
16514 %h is equivalent to ''%b''. [tm_mon]
16515 %H is replaced by the hour (24-hour clock) as a decimal number (00-23). [tm_hour]
16516 %I is replaced by the hour (12-hour clock) as a decimal number (01-12). [tm_hour]
16517 %j is replaced by the day of the year as a decimal number (001-366). [tm_yday]
16518 %m is replaced by the month as a decimal number (01-12). [tm_mon]
16519 %M is replaced by the minute as a decimal number (00-59). [tm_min]
16520 %n is replaced by a new-line character.
16521 %p is replaced by the locale's equivalent of the AM/PM designations associated with a
16523 12-hour clock. [tm_hour]</pre>
16524 %r is replaced by the locale's 12-hour clock time. [tm_hour, tm_min, tm_sec]
16525 %R is equivalent to ''%H:%M''. [tm_hour, tm_min]
16526 %S is replaced by the second as a decimal number (00-60). [tm_sec]
16527 %t is replaced by a horizontal-tab character.
16528 %T is equivalent to ''%H:%M:%S'' (the ISO 8601 time format). [tm_hour, tm_min,
16532 %u is replaced by the ISO 8601 weekday as a decimal number (1-7), where Monday
16534 is 1. [tm_wday]</pre>
16535 %U is replaced by the week number of the year (the first Sunday as the first day of week
16537 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]</pre>
16538 %V is replaced by the ISO 8601 week number (see below) as a decimal number
16540 (01-53). [tm_year, tm_wday, tm_yday]</pre>
16541 %w is replaced by the weekday as a decimal number (0-6), where Sunday is 0.
16544 %W is replaced by the week number of the year (the first Monday as the first day of
16546 week 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]</pre>
16547 %x is replaced by the locale's appropriate date representation. [all specified in <a href="#7.23.1">7.23.1</a>]
16548 %X is replaced by the locale's appropriate time representation. [all specified in <a href="#7.23.1">7.23.1</a>]
16549 %y is replaced by the last 2 digits of the year as a decimal number (00-99).
16552 %Y is replaced by the year as a decimal number (e.g., 1997). [tm_year]
16553 %z is replaced by the offset from UTC in the ISO 8601 format ''-0430'' (meaning 4
16555 hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
16556 zone is determinable. [tm_isdst]</pre>
16557 %Z is replaced by the locale's time zone name or abbreviation, or by no characters if no
16559 time zone is determinable. [tm_isdst]</pre>
16560 %% is replaced by %.
16562 Some conversion specifiers can be modified by the inclusion of an E or O modifier
16563 character to indicate an alternative format or specification. If the alternative format or
16564 specification does not exist for the current locale, the modifier is ignored.
16565 %Ec is replaced by the locale's alternative date and time representation.
16566 %EC is replaced by the name of the base year (period) in the locale's alternative
16568 representation.</pre>
16569 %Ex is replaced by the locale's alternative date representation.
16570 %EX is replaced by the locale's alternative time representation.
16571 %Ey is replaced by the offset from %EC (year only) in the locale's alternative
16573 representation.</pre>
16574 %EY is replaced by the locale's full alternative year representation.
16575 %Od is replaced by the day of the month, using the locale's alternative numeric symbols
16577 (filled as needed with leading zeros, or with leading spaces if there is no alternative
16578 symbol for zero).</pre>
16579 %Oe is replaced by the day of the month, using the locale's alternative numeric symbols
16581 (filled as needed with leading spaces).</pre>
16582 %OH is replaced by the hour (24-hour clock), using the locale's alternative numeric
16586 %OI is replaced by the hour (12-hour clock), using the locale's alternative numeric
16589 %Om is replaced by the month, using the locale's alternative numeric symbols.
16590 %OM is replaced by the minutes, using the locale's alternative numeric symbols.
16591 %OS is replaced by the seconds, using the locale's alternative numeric symbols.
16592 %Ou is replaced by the ISO 8601 weekday as a number in the locale's alternative
16594 representation, where Monday is 1.</pre>
16595 %OU is replaced by the week number, using the locale's alternative numeric symbols.
16596 %OV is replaced by the ISO 8601 week number, using the locale's alternative numeric
16599 %Ow is replaced by the weekday as a number, using the locale's alternative numeric
16602 %OW is replaced by the week number of the year, using the locale's alternative numeric
16605 %Oy is replaced by the last 2 digits of the year, using the locale's alternative numeric
16609 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system,
16610 weeks begin on a Monday and week 1 of the year is the week that includes January 4th,
16611 which is also the week that includes the first Thursday of the year, and is also the first
16612 week that contains at least four days in the year. If the first Monday of January is the
16613 2nd, 3rd, or 4th, the preceding days are part of the last week of the preceding year; thus,
16614 for Saturday 2nd January 1999, %G is replaced by 1998 and %V is replaced by 53. If
16615 December 29th, 30th, or 31st is a Monday, it and any following days are part of week 1 of
16616 the following year. Thus, for Tuesday 30th December 1997, %G is replaced by 1998 and
16617 %V is replaced by 01.
16619 If a conversion specifier is not one of the above, the behavior is undefined.
16621 In the "C" locale, the E and O modifiers are ignored and the replacement strings for the
16622 following specifiers are:
16623 %a the first three characters of %A.
16624 %A one of ''Sunday'', ''Monday'', ... , ''Saturday''.
16625 %b the first three characters of %B.
16626 %B one of ''January'', ''February'', ... , ''December''.
16627 %c equivalent to ''%a %b %e %T %Y''.
16628 %p one of ''AM'' or ''PM''.
16629 %r equivalent to ''%I:%M:%S %p''.
16630 %x equivalent to ''%m/%d/%y''.
16631 %X equivalent to %T.
16632 %Z implementation-defined.
16636 If the total number of resulting characters including the terminating null character is not
16637 more than maxsize, the strftime function returns the number of characters placed
16638 into the array pointed to by s not including the terminating null character. Otherwise,
16639 zero is returned and the contents of the array are indeterminate.
16642 <h3><a name="7.24" href="#7.24">7.24 Extended multibyte and wide character utilities <wchar.h></a></h3>
16644 <h4><a name="7.24.1" href="#7.24.1">7.24.1 Introduction</a></h4>
16646 The header <a href="#7.24"><wchar.h></a> declares four data types, one tag, four macros, and many
16647 functions.<sup><a href="#note277"><b>277)</b></a></sup>
16649 The types declared are wchar_t and size_t (both described in <a href="#7.17">7.17</a>);
16652 which is an object type other than an array type that can hold the conversion state
16653 information necessary to convert between sequences of multibyte characters and wide
16657 which is an integer type unchanged by default argument promotions that can hold any
16658 value corresponding to members of the extended character set, as well as at least one
16659 value that does not correspond to any member of the extended character set (see WEOF
16660 below);<sup><a href="#note278"><b>278)</b></a></sup> and
16663 which is declared as an incomplete structure type (the contents are described in <a href="#7.23.1">7.23.1</a>).
16665 The macros defined are NULL (described in <a href="#7.17">7.17</a>); WCHAR_MIN and WCHAR_MAX
16666 (described in <a href="#7.18.3">7.18.3</a>); and
16669 which expands to a constant expression of type wint_t whose value does not
16670 correspond to any member of the extended character set.<sup><a href="#note279"><b>279)</b></a></sup> It is accepted (and returned)
16671 by several functions in this subclause to indicate end-of-file, that is, no more input from a
16672 stream. It is also used as a wide character value that does not correspond to any member
16673 of the extended character set.
16675 The functions declared are grouped as follows:
16677 <li> Functions that perform input and output of wide characters, or multibyte characters,
16679 <li> Functions that provide wide string numeric conversion;
16680 <li> Functions that perform general wide string manipulation;
16684 <li> Functions for wide string date and time conversion; and
16685 <li> Functions that provide extended capabilities for conversion between multibyte and
16686 wide character sequences.
16689 Unless explicitly stated otherwise, if the execution of a function described in this
16690 subclause causes copying to take place between objects that overlap, the behavior is
16694 <p><small><a name="note277" href="#note277">277)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
16696 <p><small><a name="note278" href="#note278">278)</a> wchar_t and wint_t can be the same integer type.
16698 <p><small><a name="note279" href="#note279">279)</a> The value of the macro WEOF may differ from that of EOF and need not be negative.
16701 <h4><a name="7.24.2" href="#7.24.2">7.24.2 Formatted wide character input/output functions</a></h4>
16703 The formatted wide character input/output functions shall behave as if there is a sequence
16704 point after the actions associated with each specifier.<sup><a href="#note280"><b>280)</b></a></sup>
16707 <p><small><a name="note280" href="#note280">280)</a> The fwprintf functions perform writes to memory for the %n specifier.
16710 <h5><a name="7.24.2.1" href="#7.24.2.1">7.24.2.1 The fwprintf function</a></h5>
16714 #include <a href="#7.19"><stdio.h></a>
16715 #include <a href="#7.24"><wchar.h></a>
16716 int fwprintf(FILE * restrict stream,
16717 const wchar_t * restrict format, ...);</pre>
16718 <h6>Description</h6>
16720 The fwprintf function writes output to the stream pointed to by stream, under
16721 control of the wide string pointed to by format that specifies how subsequent arguments
16722 are converted for output. If there are insufficient arguments for the format, the behavior
16723 is undefined. If the format is exhausted while arguments remain, the excess arguments
16724 are evaluated (as always) but are otherwise ignored. The fwprintf function returns
16725 when the end of the format string is encountered.
16727 The format is composed of zero or more directives: ordinary wide characters (not %),
16728 which are copied unchanged to the output stream; and conversion specifications, each of
16729 which results in fetching zero or more subsequent arguments, converting them, if
16730 applicable, according to the corresponding conversion specifier, and then writing the
16731 result to the output stream.
16733 Each conversion specification is introduced by the wide character %. After the %, the
16734 following appear in sequence:
16736 <li> Zero or more flags (in any order) that modify the meaning of the conversion
16738 <li> An optional minimum field width. If the converted value has fewer wide characters
16739 than the field width, it is padded with spaces (by default) on the left (or right, if the
16743 left adjustment flag, described later, has been given) to the field width. The field
16744 width takes the form of an asterisk * (described later) or a nonnegative decimal
16745 integer.<sup><a href="#note281"><b>281)</b></a></sup>
16746 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
16747 o, u, x, and X conversions, the number of digits to appear after the decimal-point
16748 wide character for a, A, e, E, f, and F conversions, the maximum number of
16749 significant digits for the g and G conversions, or the maximum number of wide
16750 characters to be written for s conversions. The precision takes the form of a period
16751 (.) followed either by an asterisk * (described later) or by an optional decimal
16752 integer; if only the period is specified, the precision is taken as zero. If a precision
16753 appears with any other conversion specifier, the behavior is undefined.
16754 <li> An optional length modifier that specifies the size of the argument.
16755 <li> A conversion specifier wide character that specifies the type of conversion to be
16759 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
16760 this case, an int argument supplies the field width or precision. The arguments
16761 specifying field width, or precision, or both, shall appear (in that order) before the
16762 argument (if any) to be converted. A negative field width argument is taken as a - flag
16763 followed by a positive field width. A negative precision argument is taken as if the
16764 precision were omitted.
16766 The flag wide characters and their meanings are:
16767 - The result of the conversion is left-justified within the field. (It is right-justified if
16769 this flag is not specified.)</pre>
16770 + The result of a signed conversion always begins with a plus or minus sign. (It
16772 begins with a sign only when a negative value is converted if this flag is not
16773 specified.)<sup><a href="#note282"><b>282)</b></a></sup></pre>
16774 space If the first wide character of a signed conversion is not a sign, or if a signed
16776 conversion results in no wide characters, a space is prefixed to the result. If the
16777 space and + flags both appear, the space flag is ignored.</pre>
16778 # The result is converted to an ''alternative form''. For o conversion, it increases
16780 the precision, if and only if necessary, to force the first digit of the result to be a
16781 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
16782 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,</pre>
16786 and G conversions, the result of converting a floating-point number always
16787 contains a decimal-point wide character, even if no digits follow it. (Normally, a
16788 decimal-point wide character appears in the result of these conversions only if a
16789 digit follows it.) For g and G conversions, trailing zeros are not removed from the
16790 result. For other conversions, the behavior is undefined.</pre>
16791 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
16794 (following any indication of sign or base) are used to pad to the field width rather
16795 than performing space padding, except when converting an infinity or NaN. If the
16796 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
16797 conversions, if a precision is specified, the 0 flag is ignored. For other
16798 conversions, the behavior is undefined.</pre>
16799 The length modifiers and their meanings are:
16800 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16802 signed char or unsigned char argument (the argument will have
16803 been promoted according to the integer promotions, but its value shall be
16804 converted to signed char or unsigned char before printing); or that
16805 a following n conversion specifier applies to a pointer to a signed char
16807 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16809 short int or unsigned short int argument (the argument will
16810 have been promoted according to the integer promotions, but its value shall
16811 be converted to short int or unsigned short int before printing);
16812 or that a following n conversion specifier applies to a pointer to a short
16813 int argument.</pre>
16814 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16816 long int or unsigned long int argument; that a following n
16817 conversion specifier applies to a pointer to a long int argument; that a
16818 following c conversion specifier applies to a wint_t argument; that a
16819 following s conversion specifier applies to a pointer to a wchar_t
16820 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
16822 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16824 long long int or unsigned long long int argument; or that a
16825 following n conversion specifier applies to a pointer to a long long int
16827 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
16830 an intmax_t or uintmax_t argument; or that a following n conversion
16831 specifier applies to a pointer to an intmax_t argument.</pre>
16832 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16834 size_t or the corresponding signed integer type argument; or that a
16835 following n conversion specifier applies to a pointer to a signed integer type
16836 corresponding to size_t argument.</pre>
16837 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16839 ptrdiff_t or the corresponding unsigned integer type argument; or that a
16840 following n conversion specifier applies to a pointer to a ptrdiff_t
16842 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
16844 applies to a long double argument.</pre>
16845 If a length modifier appears with any conversion specifier other than as specified above,
16846 the behavior is undefined.
16848 The conversion specifiers and their meanings are:
16849 d,i The int argument is converted to signed decimal in the style [-]dddd. The
16851 precision specifies the minimum number of digits to appear; if the value
16852 being converted can be represented in fewer digits, it is expanded with
16853 leading zeros. The default precision is 1. The result of converting a zero
16854 value with a precision of zero is no wide characters.</pre>
16855 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
16857 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
16858 letters abcdef are used for x conversion and the letters ABCDEF for X
16859 conversion. The precision specifies the minimum number of digits to appear;
16860 if the value being converted can be represented in fewer digits, it is expanded
16861 with leading zeros. The default precision is 1. The result of converting a
16862 zero value with a precision of zero is no wide characters.</pre>
16863 f,F A double argument representing a floating-point number is converted to
16866 decimal notation in the style [-]ddd.ddd, where the number of digits after
16867 the decimal-point wide character is equal to the precision specification. If the
16868 precision is missing, it is taken as 6; if the precision is zero and the # flag is
16869 not specified, no decimal-point wide character appears. If a decimal-point
16870 wide character appears, at least one digit appears before it. The value is
16871 rounded to the appropriate number of digits.
16872 A double argument representing an infinity is converted in one of the styles
16873 [-]inf or [-]infinity -- which style is implementation-defined. A
16874 double argument representing a NaN is converted in one of the styles
16875 [-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
16876 any n-wchar-sequence, is implementation-defined. The F conversion
16877 specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
16878 nan, respectively.<sup><a href="#note283"><b>283)</b></a></sup></pre>
16879 e,E A double argument representing a floating-point number is converted in the
16881 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
16882 argument is nonzero) before the decimal-point wide character and the number
16883 of digits after it is equal to the precision; if the precision is missing, it is taken
16884 as 6; if the precision is zero and the # flag is not specified, no decimal-point
16885 wide character appears. The value is rounded to the appropriate number of
16886 digits. The E conversion specifier produces a number with E instead of e
16887 introducing the exponent. The exponent always contains at least two digits,
16888 and only as many more digits as necessary to represent the exponent. If the
16889 value is zero, the exponent is zero.
16890 A double argument representing an infinity or NaN is converted in the style
16891 of an f or F conversion specifier.</pre>
16892 g,G A double argument representing a floating-point number is converted in
16894 style f or e (or in style F or E in the case of a G conversion specifier),
16895 depending on the value converted and the precision. Let P equal the
16896 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
16897 Then, if a conversion with style E would have an exponent of X :
16898 -- if P > X >= -4, the conversion is with style f (or F) and precision
16900 -- otherwise, the conversion is with style e (or E) and precision P - 1.
16901 Finally, unless the # flag is used, any trailing zeros are removed from the
16902 fractional portion of the result and the decimal-point wide character is
16903 removed if there is no fractional portion remaining.
16904 A double argument representing an infinity or NaN is converted in the style
16905 of an f or F conversion specifier.</pre>
16906 a,A A double argument representing a floating-point number is converted in the
16908 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
16909 nonzero if the argument is a normalized floating-point number and is
16910 otherwise unspecified) before the decimal-point wide character<sup><a href="#note284"><b>284)</b></a></sup> and the
16911 number of hexadecimal digits after it is equal to the precision; if the precision
16912 is missing and FLT_RADIX is a power of 2, then the precision is sufficient</pre>
16917 for an exact representation of the value; if the precision is missing and
16918 FLT_RADIX is not a power of 2, then the precision is sufficient to
16919 distinguish<sup><a href="#note285"><b>285)</b></a></sup> values of type double, except that trailing zeros may be
16920 omitted; if the precision is zero and the # flag is not specified, no decimal-
16921 point wide character appears. The letters abcdef are used for a conversion
16922 and the letters ABCDEF for A conversion. The A conversion specifier
16923 produces a number with X and P instead of x and p. The exponent always
16924 contains at least one digit, and only as many more digits as necessary to
16925 represent the decimal exponent of 2. If the value is zero, the exponent is
16927 A double argument representing an infinity or NaN is converted in the style
16928 of an f or F conversion specifier.</pre>
16929 c If no l length modifier is present, the int argument is converted to a wide
16931 character as if by calling btowc and the resulting wide character is written.
16932 If an l length modifier is present, the wint_t argument is converted to
16933 wchar_t and written.</pre>
16934 s If no l length modifier is present, the argument shall be a pointer to the initial
16936 element of a character array containing a multibyte character sequence
16937 beginning in the initial shift state. Characters from the array are converted as
16938 if by repeated calls to the mbrtowc function, with the conversion state
16939 described by an mbstate_t object initialized to zero before the first
16940 multibyte character is converted, and written up to (but not including) the
16941 terminating null wide character. If the precision is specified, no more than
16942 that many wide characters are written. If the precision is not specified or is
16943 greater than the size of the converted array, the converted array shall contain a
16944 null wide character.
16945 If an l length modifier is present, the argument shall be a pointer to the initial
16946 element of an array of wchar_t type. Wide characters from the array are
16947 written up to (but not including) a terminating null wide character. If the
16948 precision is specified, no more than that many wide characters are written. If
16949 the precision is not specified or is greater than the size of the array, the array
16950 shall contain a null wide character.</pre>
16951 p The argument shall be a pointer to void. The value of the pointer is
16953 converted to a sequence of printing wide characters, in an implementation-</pre>
16957 defined manner.</pre>
16958 n The argument shall be a pointer to signed integer into which is written the
16960 number of wide characters written to the output stream so far by this call to
16961 fwprintf. No argument is converted, but one is consumed. If the
16962 conversion specification includes any flags, a field width, or a precision, the
16963 behavior is undefined.</pre>
16964 % A % wide character is written. No argument is converted. The complete
16967 conversion specification shall be %%.</pre>
16968 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note286"><b>286)</b></a></sup> If any argument is
16969 not the correct type for the corresponding conversion specification, the behavior is
16972 In no case does a nonexistent or small field width cause truncation of a field; if the result
16973 of a conversion is wider than the field width, the field is expanded to contain the
16976 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
16977 to a hexadecimal floating number with the given precision.
16978 Recommended practice
16980 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
16981 representable in the given precision, the result should be one of the two adjacent numbers
16982 in hexadecimal floating style with the given precision, with the extra stipulation that the
16983 error should have a correct sign for the current rounding direction.
16985 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
16986 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note287"><b>287)</b></a></sup> If the number of
16987 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
16988 representable with DECIMAL_DIG digits, then the result should be an exact
16989 representation with trailing zeros. Otherwise, the source value is bounded by two
16990 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
16991 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
16992 the error should have a correct sign for the current rounding direction.
16995 The fwprintf function returns the number of wide characters transmitted, or a negative
16996 value if an output or encoding error occurred.
16999 Environmental limits
17001 The number of wide characters that can be produced by any single conversion shall be at
17004 EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
17007 #include <a href="#7.12"><math.h></a>
17008 #include <a href="#7.19"><stdio.h></a>
17009 #include <a href="#7.24"><wchar.h></a>
17011 wchar_t *weekday, *month; // pointers to wide strings
17012 int day, hour, min;
17013 fwprintf(stdout, L"%ls, %ls %d, %.2d:%.2d\n",
17014 weekday, month, day, hour, min);
17015 fwprintf(stdout, L"pi = %.5f\n", 4 * atan(1.0));</pre>
17017 <p><b> Forward references</b>: the btowc function (<a href="#7.24.6.1.1">7.24.6.1.1</a>), the mbrtowc function
17018 (<a href="#7.24.6.3.2">7.24.6.3.2</a>).
17021 <p><small><a name="note281" href="#note281">281)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
17023 <p><small><a name="note282" href="#note282">282)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
17024 include a minus sign.
17026 <p><small><a name="note283" href="#note283">283)</a> When applied to infinite and NaN values, the -, +, and space flag wide characters have their usual
17027 meaning; the # and 0 flag wide characters have no effect.
17029 <p><small><a name="note284" href="#note284">284)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide
17030 character so that subsequent digits align to nibble (4-bit) boundaries.
17032 <p><small><a name="note285" href="#note285">285)</a> The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
17033 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
17034 might suffice depending on the implementation's scheme for determining the digit to the left of the
17035 decimal-point wide character.
17037 <p><small><a name="note286" href="#note286">286)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
17039 <p><small><a name="note287" href="#note287">287)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
17040 given format specifier. The number of significant digits is determined by the format specifier, and in
17041 the case of fixed-point conversion by the source value as well.
17044 <h5><a name="7.24.2.2" href="#7.24.2.2">7.24.2.2 The fwscanf function</a></h5>
17048 #include <a href="#7.19"><stdio.h></a>
17049 #include <a href="#7.24"><wchar.h></a>
17050 int fwscanf(FILE * restrict stream,
17051 const wchar_t * restrict format, ...);</pre>
17052 <h6>Description</h6>
17054 The fwscanf function reads input from the stream pointed to by stream, under
17055 control of the wide string pointed to by format that specifies the admissible input
17056 sequences and how they are to be converted for assignment, using subsequent arguments
17057 as pointers to the objects to receive the converted input. If there are insufficient
17058 arguments for the format, the behavior is undefined. If the format is exhausted while
17059 arguments remain, the excess arguments are evaluated (as always) but are otherwise
17062 The format is composed of zero or more directives: one or more white-space wide
17063 characters, an ordinary wide character (neither % nor a white-space wide character), or a
17064 conversion specification. Each conversion specification is introduced by the wide
17065 character %. After the %, the following appear in sequence:
17067 <li> An optional assignment-suppressing wide character *.
17068 <li> An optional decimal integer greater than zero that specifies the maximum field width
17069 (in wide characters).
17071 <li> An optional length modifier that specifies the size of the receiving object.
17072 <li> A conversion specifier wide character that specifies the type of conversion to be
17076 The fwscanf function executes each directive of the format in turn. If a directive fails,
17077 as detailed below, the function returns. Failures are described as input failures (due to the
17078 occurrence of an encoding error or the unavailability of input characters), or matching
17079 failures (due to inappropriate input).
17081 A directive composed of white-space wide character(s) is executed by reading input up to
17082 the first non-white-space wide character (which remains unread), or until no more wide
17083 characters can be read.
17085 A directive that is an ordinary wide character is executed by reading the next wide
17086 character of the stream. If that wide character differs from the directive, the directive
17087 fails and the differing and subsequent wide characters remain unread. Similarly, if end-
17088 of-file, an encoding error, or a read error prevents a wide character from being read, the
17091 A directive that is a conversion specification defines a set of matching input sequences, as
17092 described below for each specifier. A conversion specification is executed in the
17095 Input white-space wide characters (as specified by the iswspace function) are skipped,
17096 unless the specification includes a [, c, or n specifier.<sup><a href="#note288"><b>288)</b></a></sup>
17098 An input item is read from the stream, unless the specification includes an n specifier. An
17099 input item is defined as the longest sequence of input wide characters which does not
17100 exceed any specified field width and which is, or is a prefix of, a matching input
17101 sequence.<sup><a href="#note289"><b>289)</b></a></sup> The first wide character, if any, after the input item remains unread. If the
17102 length of the input item is zero, the execution of the directive fails; this condition is a
17103 matching failure unless end-of-file, an encoding error, or a read error prevented input
17104 from the stream, in which case it is an input failure.
17106 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
17107 count of input wide characters) is converted to a type appropriate to the conversion
17108 specifier. If the input item is not a matching sequence, the execution of the directive fails:
17109 this condition is a matching failure. Unless assignment suppression was indicated by a *,
17110 the result of the conversion is placed in the object pointed to by the first argument
17111 following the format argument that has not already received a conversion result. If this
17115 object does not have an appropriate type, or if the result of the conversion cannot be
17116 represented in the object, the behavior is undefined.
17118 The length modifiers and their meanings are:
17119 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17121 to an argument with type pointer to signed char or unsigned char.</pre>
17122 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17124 to an argument with type pointer to short int or unsigned short
17126 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17128 to an argument with type pointer to long int or unsigned long
17129 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
17130 an argument with type pointer to double; or that a following c, s, or [
17131 conversion specifier applies to an argument with type pointer to wchar_t.</pre>
17132 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17134 to an argument with type pointer to long long int or unsigned
17135 long long int.</pre>
17136 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17138 to an argument with type pointer to intmax_t or uintmax_t.</pre>
17139 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17141 to an argument with type pointer to size_t or the corresponding signed
17142 integer type.</pre>
17143 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17145 to an argument with type pointer to ptrdiff_t or the corresponding
17146 unsigned integer type.</pre>
17147 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
17149 applies to an argument with type pointer to long double.</pre>
17150 If a length modifier appears with any conversion specifier other than as specified above,
17151 the behavior is undefined.
17153 The conversion specifiers and their meanings are:
17154 d Matches an optionally signed decimal integer, whose format is the same as
17156 expected for the subject sequence of the wcstol function with the value 10
17157 for the base argument. The corresponding argument shall be a pointer to
17158 signed integer.</pre>
17159 i Matches an optionally signed integer, whose format is the same as expected
17162 for the subject sequence of the wcstol function with the value 0 for the
17163 base argument. The corresponding argument shall be a pointer to signed
17165 o Matches an optionally signed octal integer, whose format is the same as
17167 expected for the subject sequence of the wcstoul function with the value 8
17168 for the base argument. The corresponding argument shall be a pointer to
17169 unsigned integer.</pre>
17170 u Matches an optionally signed decimal integer, whose format is the same as
17172 expected for the subject sequence of the wcstoul function with the value 10
17173 for the base argument. The corresponding argument shall be a pointer to
17174 unsigned integer.</pre>
17175 x Matches an optionally signed hexadecimal integer, whose format is the same
17177 as expected for the subject sequence of the wcstoul function with the value
17178 16 for the base argument. The corresponding argument shall be a pointer to
17179 unsigned integer.</pre>
17180 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
17182 format is the same as expected for the subject sequence of the wcstod
17183 function. The corresponding argument shall be a pointer to floating.</pre>
17184 c Matches a sequence of wide characters of exactly the number specified by the
17186 field width (1 if no field width is present in the directive).
17187 If no l length modifier is present, characters from the input field are
17188 converted as if by repeated calls to the wcrtomb function, with the
17189 conversion state described by an mbstate_t object initialized to zero
17190 before the first wide character is converted. The corresponding argument
17191 shall be a pointer to the initial element of a character array large enough to
17192 accept the sequence. No null character is added.
17193 If an l length modifier is present, the corresponding argument shall be a
17194 pointer to the initial element of an array of wchar_t large enough to accept
17195 the sequence. No null wide character is added.</pre>
17196 s Matches a sequence of non-white-space wide characters.
17199 If no l length modifier is present, characters from the input field are
17200 converted as if by repeated calls to the wcrtomb function, with the
17201 conversion state described by an mbstate_t object initialized to zero
17202 before the first wide character is converted. The corresponding argument
17203 shall be a pointer to the initial element of a character array large enough to
17204 accept the sequence and a terminating null character, which will be added
17206 If an l length modifier is present, the corresponding argument shall be a
17207 pointer to the initial element of an array of wchar_t large enough to accept
17208 the sequence and the terminating null wide character, which will be added
17209 automatically.</pre>
17210 [ Matches a nonempty sequence of wide characters from a set of expected
17212 characters (the scanset).
17213 If no l length modifier is present, characters from the input field are
17214 converted as if by repeated calls to the wcrtomb function, with the
17215 conversion state described by an mbstate_t object initialized to zero
17216 before the first wide character is converted. The corresponding argument
17217 shall be a pointer to the initial element of a character array large enough to
17218 accept the sequence and a terminating null character, which will be added
17220 If an l length modifier is present, the corresponding argument shall be a
17221 pointer to the initial element of an array of wchar_t large enough to accept
17222 the sequence and the terminating null wide character, which will be added
17224 The conversion specifier includes all subsequent wide characters in the
17225 format string, up to and including the matching right bracket (]). The wide
17226 characters between the brackets (the scanlist) compose the scanset, unless the
17227 wide character after the left bracket is a circumflex (^), in which case the
17228 scanset contains all wide characters that do not appear in the scanlist between
17229 the circumflex and the right bracket. If the conversion specifier begins with
17230 [] or [^], the right bracket wide character is in the scanlist and the next
17231 following right bracket wide character is the matching right bracket that ends
17232 the specification; otherwise the first following right bracket wide character is
17233 the one that ends the specification. If a - wide character is in the scanlist and
17234 is not the first, nor the second where the first wide character is a ^, nor the
17235 last character, the behavior is implementation-defined.</pre>
17236 p Matches an implementation-defined set of sequences, which should be the
17238 same as the set of sequences that may be produced by the %p conversion of
17239 the fwprintf function. The corresponding argument shall be a pointer to a
17240 pointer to void. The input item is converted to a pointer value in an
17241 implementation-defined manner. If the input item is a value converted earlier
17242 during the same program execution, the pointer that results shall compare
17243 equal to that value; otherwise the behavior of the %p conversion is undefined.</pre>
17244 n No input is consumed. The corresponding argument shall be a pointer to
17247 signed integer into which is to be written the number of wide characters read
17248 from the input stream so far by this call to the fwscanf function. Execution
17249 of a %n directive does not increment the assignment count returned at the
17250 completion of execution of the fwscanf function. No argument is
17251 converted, but one is consumed. If the conversion specification includes an
17252 assignment-suppressing wide character or a field width, the behavior is
17254 % Matches a single % wide character; no conversion or assignment occurs. The
17257 complete conversion specification shall be %%.</pre>
17258 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note290"><b>290)</b></a></sup>
17260 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
17261 respectively, a, e, f, g, and x.
17263 Trailing white space (including new-line wide characters) is left unread unless matched
17264 by a directive. The success of literal matches and suppressed assignments is not directly
17265 determinable other than via the %n directive.
17268 The fwscanf function returns the value of the macro EOF if an input failure occurs
17269 before any conversion. Otherwise, the function returns the number of input items
17270 assigned, which can be fewer than provided for, or even zero, in the event of an early
17273 EXAMPLE 1 The call:
17275 #include <a href="#7.19"><stdio.h></a>
17276 #include <a href="#7.24"><wchar.h></a>
17278 int n, i; float x; wchar_t name[50];
17279 n = fwscanf(stdin, L"%d%f%ls", &i, &x, name);</pre>
17280 with the input line:
17282 25 54.32E-1 thompson</pre>
17283 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
17287 EXAMPLE 2 The call:
17289 #include <a href="#7.19"><stdio.h></a>
17290 #include <a href="#7.24"><wchar.h></a>
17292 int i; float x; double y;
17293 fwscanf(stdin, L"%2d%f%*d %lf", &i, &x, &y);</pre>
17296 56789 0123 56a72</pre>
17297 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
17298 56.0. The next wide character read from the input stream will be a.
17302 <p><b> Forward references</b>: the wcstod, wcstof, and wcstold functions (<a href="#7.24.4.1.1">7.24.4.1.1</a>), the
17303 wcstol, wcstoll, wcstoul, and wcstoull functions (<a href="#7.24.4.1.2">7.24.4.1.2</a>), the wcrtomb
17304 function (<a href="#7.24.6.3.3">7.24.6.3.3</a>).
17307 <p><small><a name="note288" href="#note288">288)</a> These white-space wide characters are not counted against a specified field width.
17309 <p><small><a name="note289" href="#note289">289)</a> fwscanf pushes back at most one input wide character onto the input stream. Therefore, some
17310 sequences that are acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
17312 <p><small><a name="note290" href="#note290">290)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
17315 <h5><a name="7.24.2.3" href="#7.24.2.3">7.24.2.3 The swprintf function</a></h5>
17319 #include <a href="#7.24"><wchar.h></a>
17320 int swprintf(wchar_t * restrict s,
17322 const wchar_t * restrict format, ...);</pre>
17323 <h6>Description</h6>
17325 The swprintf function is equivalent to fwprintf, except that the argument s
17326 specifies an array of wide characters into which the generated output is to be written,
17327 rather than written to a stream. No more than n wide characters are written, including a
17328 terminating null wide character, which is always added (unless n is zero).
17331 The swprintf function returns the number of wide characters written in the array, not
17332 counting the terminating null wide character, or a negative value if an encoding error
17333 occurred or if n or more wide characters were requested to be written.
17335 <h5><a name="7.24.2.4" href="#7.24.2.4">7.24.2.4 The swscanf function</a></h5>
17339 #include <a href="#7.24"><wchar.h></a>
17340 int swscanf(const wchar_t * restrict s,
17341 const wchar_t * restrict format, ...);</pre>
17342 <h6>Description</h6>
17344 The swscanf function is equivalent to fwscanf, except that the argument s specifies a
17345 wide string from which the input is to be obtained, rather than from a stream. Reaching
17346 the end of the wide string is equivalent to encountering end-of-file for the fwscanf
17350 The swscanf function returns the value of the macro EOF if an input failure occurs
17351 before any conversion. Otherwise, the swscanf function returns the number of input
17352 items assigned, which can be fewer than provided for, or even zero, in the event of an
17353 early matching failure.
17356 <h5><a name="7.24.2.5" href="#7.24.2.5">7.24.2.5 The vfwprintf function</a></h5>
17360 #include <a href="#7.15"><stdarg.h></a>
17361 #include <a href="#7.19"><stdio.h></a>
17362 #include <a href="#7.24"><wchar.h></a>
17363 int vfwprintf(FILE * restrict stream,
17364 const wchar_t * restrict format,
17365 va_list arg);</pre>
17366 <h6>Description</h6>
17368 The vfwprintf function is equivalent to fwprintf, with the variable argument list
17369 replaced by arg, which shall have been initialized by the va_start macro (and
17370 possibly subsequent va_arg calls). The vfwprintf function does not invoke the
17371 va_end macro.<sup><a href="#note291"><b>291)</b></a></sup>
17374 The vfwprintf function returns the number of wide characters transmitted, or a
17375 negative value if an output or encoding error occurred.
17377 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting
17380 #include <a href="#7.15"><stdarg.h></a>
17381 #include <a href="#7.19"><stdio.h></a>
17382 #include <a href="#7.24"><wchar.h></a>
17383 void error(char *function_name, wchar_t *format, ...)
17386 va_start(args, format);
17387 // print out name of function causing error
17388 fwprintf(stderr, L"ERROR in %s: ", function_name);
17389 // print out remainder of message
17390 vfwprintf(stderr, format, args);
17400 <p><small><a name="note291" href="#note291">291)</a> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
17401 invoke the va_arg macro, the value of arg after the return is indeterminate.
17404 <h5><a name="7.24.2.6" href="#7.24.2.6">7.24.2.6 The vfwscanf function</a></h5>
17408 #include <a href="#7.15"><stdarg.h></a>
17409 #include <a href="#7.19"><stdio.h></a>
17410 #include <a href="#7.24"><wchar.h></a>
17411 int vfwscanf(FILE * restrict stream,
17412 const wchar_t * restrict format,
17413 va_list arg);</pre>
17414 <h6>Description</h6>
17416 The vfwscanf function is equivalent to fwscanf, with the variable argument list
17417 replaced by arg, which shall have been initialized by the va_start macro (and
17418 possibly subsequent va_arg calls). The vfwscanf function does not invoke the
17422 The vfwscanf function returns the value of the macro EOF if an input failure occurs
17423 before any conversion. Otherwise, the vfwscanf function returns the number of input
17424 items assigned, which can be fewer than provided for, or even zero, in the event of an
17425 early matching failure.
17427 <h5><a name="7.24.2.7" href="#7.24.2.7">7.24.2.7 The vswprintf function</a></h5>
17431 #include <a href="#7.15"><stdarg.h></a>
17432 #include <a href="#7.24"><wchar.h></a>
17433 int vswprintf(wchar_t * restrict s,
17435 const wchar_t * restrict format,
17436 va_list arg);</pre>
17437 <h6>Description</h6>
17439 The vswprintf function is equivalent to swprintf, with the variable argument list
17440 replaced by arg, which shall have been initialized by the va_start macro (and
17441 possibly subsequent va_arg calls). The vswprintf function does not invoke the
17445 The vswprintf function returns the number of wide characters written in the array, not
17446 counting the terminating null wide character, or a negative value if an encoding error
17447 occurred or if n or more wide characters were requested to be generated.
17450 <h5><a name="7.24.2.8" href="#7.24.2.8">7.24.2.8 The vswscanf function</a></h5>
17454 #include <a href="#7.15"><stdarg.h></a>
17455 #include <a href="#7.24"><wchar.h></a>
17456 int vswscanf(const wchar_t * restrict s,
17457 const wchar_t * restrict format,
17458 va_list arg);</pre>
17459 <h6>Description</h6>
17461 The vswscanf function is equivalent to swscanf, with the variable argument list
17462 replaced by arg, which shall have been initialized by the va_start macro (and
17463 possibly subsequent va_arg calls). The vswscanf function does not invoke the
17467 The vswscanf function returns the value of the macro EOF if an input failure occurs
17468 before any conversion. Otherwise, the vswscanf function returns the number of input
17469 items assigned, which can be fewer than provided for, or even zero, in the event of an
17470 early matching failure.
17472 <h5><a name="7.24.2.9" href="#7.24.2.9">7.24.2.9 The vwprintf function</a></h5>
17476 #include <a href="#7.15"><stdarg.h></a>
17477 #include <a href="#7.24"><wchar.h></a>
17478 int vwprintf(const wchar_t * restrict format,
17479 va_list arg);</pre>
17480 <h6>Description</h6>
17482 The vwprintf function is equivalent to wprintf, with the variable argument list
17483 replaced by arg, which shall have been initialized by the va_start macro (and
17484 possibly subsequent va_arg calls). The vwprintf function does not invoke the
17488 The vwprintf function returns the number of wide characters transmitted, or a negative
17489 value if an output or encoding error occurred.
17492 <h5><a name="7.24.2.10" href="#7.24.2.10">7.24.2.10 The vwscanf function</a></h5>
17496 #include <a href="#7.15"><stdarg.h></a>
17497 #include <a href="#7.24"><wchar.h></a>
17498 int vwscanf(const wchar_t * restrict format,
17499 va_list arg);</pre>
17500 <h6>Description</h6>
17502 The vwscanf function is equivalent to wscanf, with the variable argument list
17503 replaced by arg, which shall have been initialized by the va_start macro (and
17504 possibly subsequent va_arg calls). The vwscanf function does not invoke the
17508 The vwscanf function returns the value of the macro EOF if an input failure occurs
17509 before any conversion. Otherwise, the vwscanf function returns the number of input
17510 items assigned, which can be fewer than provided for, or even zero, in the event of an
17511 early matching failure.
17513 <h5><a name="7.24.2.11" href="#7.24.2.11">7.24.2.11 The wprintf function</a></h5>
17517 #include <a href="#7.24"><wchar.h></a>
17518 int wprintf(const wchar_t * restrict format, ...);</pre>
17519 <h6>Description</h6>
17521 The wprintf function is equivalent to fwprintf with the argument stdout
17522 interposed before the arguments to wprintf.
17525 The wprintf function returns the number of wide characters transmitted, or a negative
17526 value if an output or encoding error occurred.
17528 <h5><a name="7.24.2.12" href="#7.24.2.12">7.24.2.12 The wscanf function</a></h5>
17532 #include <a href="#7.24"><wchar.h></a>
17533 int wscanf(const wchar_t * restrict format, ...);</pre>
17534 <h6>Description</h6>
17536 The wscanf function is equivalent to fwscanf with the argument stdin interposed
17537 before the arguments to wscanf.
17541 The wscanf function returns the value of the macro EOF if an input failure occurs
17542 before any conversion. Otherwise, the wscanf function returns the number of input
17543 items assigned, which can be fewer than provided for, or even zero, in the event of an
17544 early matching failure.
17546 <h4><a name="7.24.3" href="#7.24.3">7.24.3 Wide character input/output functions</a></h4>
17548 <h5><a name="7.24.3.1" href="#7.24.3.1">7.24.3.1 The fgetwc function</a></h5>
17552 #include <a href="#7.19"><stdio.h></a>
17553 #include <a href="#7.24"><wchar.h></a>
17554 wint_t fgetwc(FILE *stream);</pre>
17555 <h6>Description</h6>
17557 If the end-of-file indicator for the input stream pointed to by stream is not set and a
17558 next wide character is present, the fgetwc function obtains that wide character as a
17559 wchar_t converted to a wint_t and advances the associated file position indicator for
17560 the stream (if defined).
17563 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
17564 of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
17565 the fgetwc function returns the next wide character from the input stream pointed to by
17566 stream. If a read error occurs, the error indicator for the stream is set and the fgetwc
17567 function returns WEOF. If an encoding error occurs (including too few bytes), the value of
17568 the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.<sup><a href="#note292"><b>292)</b></a></sup>
17571 <p><small><a name="note292" href="#note292">292)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
17572 Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
17575 <h5><a name="7.24.3.2" href="#7.24.3.2">7.24.3.2 The fgetws function</a></h5>
17579 #include <a href="#7.19"><stdio.h></a>
17580 #include <a href="#7.24"><wchar.h></a>
17581 wchar_t *fgetws(wchar_t * restrict s,
17582 int n, FILE * restrict stream);</pre>
17583 <h6>Description</h6>
17585 The fgetws function reads at most one less than the number of wide characters
17586 specified by n from the stream pointed to by stream into the array pointed to by s. No
17590 additional wide characters are read after a new-line wide character (which is retained) or
17591 after end-of-file. A null wide character is written immediately after the last wide
17592 character read into the array.
17595 The fgetws function returns s if successful. If end-of-file is encountered and no
17596 characters have been read into the array, the contents of the array remain unchanged and a
17597 null pointer is returned. If a read or encoding error occurs during the operation, the array
17598 contents are indeterminate and a null pointer is returned.
17600 <h5><a name="7.24.3.3" href="#7.24.3.3">7.24.3.3 The fputwc function</a></h5>
17604 #include <a href="#7.19"><stdio.h></a>
17605 #include <a href="#7.24"><wchar.h></a>
17606 wint_t fputwc(wchar_t c, FILE *stream);</pre>
17607 <h6>Description</h6>
17609 The fputwc function writes the wide character specified by c to the output stream
17610 pointed to by stream, at the position indicated by the associated file position indicator
17611 for the stream (if defined), and advances the indicator appropriately. If the file cannot
17612 support positioning requests, or if the stream was opened with append mode, the
17613 character is appended to the output stream.
17616 The fputwc function returns the wide character written. If a write error occurs, the
17617 error indicator for the stream is set and fputwc returns WEOF. If an encoding error
17618 occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
17620 <h5><a name="7.24.3.4" href="#7.24.3.4">7.24.3.4 The fputws function</a></h5>
17624 #include <a href="#7.19"><stdio.h></a>
17625 #include <a href="#7.24"><wchar.h></a>
17626 int fputws(const wchar_t * restrict s,
17627 FILE * restrict stream);</pre>
17628 <h6>Description</h6>
17630 The fputws function writes the wide string pointed to by s to the stream pointed to by
17631 stream. The terminating null wide character is not written.
17634 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
17635 returns a nonnegative value.
17638 <h5><a name="7.24.3.5" href="#7.24.3.5">7.24.3.5 The fwide function</a></h5>
17642 #include <a href="#7.19"><stdio.h></a>
17643 #include <a href="#7.24"><wchar.h></a>
17644 int fwide(FILE *stream, int mode);</pre>
17645 <h6>Description</h6>
17647 The fwide function determines the orientation of the stream pointed to by stream. If
17648 mode is greater than zero, the function first attempts to make the stream wide oriented. If
17649 mode is less than zero, the function first attempts to make the stream byte oriented.<sup><a href="#note293"><b>293)</b></a></sup>
17650 Otherwise, mode is zero and the function does not alter the orientation of the stream.
17653 The fwide function returns a value greater than zero if, after the call, the stream has
17654 wide orientation, a value less than zero if the stream has byte orientation, or zero if the
17655 stream has no orientation.
17658 <p><small><a name="note293" href="#note293">293)</a> If the orientation of the stream has already been determined, fwide does not change it.
17661 <h5><a name="7.24.3.6" href="#7.24.3.6">7.24.3.6 The getwc function</a></h5>
17665 #include <a href="#7.19"><stdio.h></a>
17666 #include <a href="#7.24"><wchar.h></a>
17667 wint_t getwc(FILE *stream);</pre>
17668 <h6>Description</h6>
17670 The getwc function is equivalent to fgetwc, except that if it is implemented as a
17671 macro, it may evaluate stream more than once, so the argument should never be an
17672 expression with side effects.
17675 The getwc function returns the next wide character from the input stream pointed to by
17678 <h5><a name="7.24.3.7" href="#7.24.3.7">7.24.3.7 The getwchar function</a></h5>
17682 #include <a href="#7.24"><wchar.h></a>
17683 wint_t getwchar(void);</pre>
17689 <h6>Description</h6>
17691 The getwchar function is equivalent to getwc with the argument stdin.
17694 The getwchar function returns the next wide character from the input stream pointed to
17697 <h5><a name="7.24.3.8" href="#7.24.3.8">7.24.3.8 The putwc function</a></h5>
17701 #include <a href="#7.19"><stdio.h></a>
17702 #include <a href="#7.24"><wchar.h></a>
17703 wint_t putwc(wchar_t c, FILE *stream);</pre>
17704 <h6>Description</h6>
17706 The putwc function is equivalent to fputwc, except that if it is implemented as a
17707 macro, it may evaluate stream more than once, so that argument should never be an
17708 expression with side effects.
17711 The putwc function returns the wide character written, or WEOF.
17713 <h5><a name="7.24.3.9" href="#7.24.3.9">7.24.3.9 The putwchar function</a></h5>
17717 #include <a href="#7.24"><wchar.h></a>
17718 wint_t putwchar(wchar_t c);</pre>
17719 <h6>Description</h6>
17721 The putwchar function is equivalent to putwc with the second argument stdout.
17724 The putwchar function returns the character written, or WEOF.
17726 <h5><a name="7.24.3.10" href="#7.24.3.10">7.24.3.10 The ungetwc function</a></h5>
17730 #include <a href="#7.19"><stdio.h></a>
17731 #include <a href="#7.24"><wchar.h></a>
17732 wint_t ungetwc(wint_t c, FILE *stream);</pre>
17733 <h6>Description</h6>
17735 The ungetwc function pushes the wide character specified by c back onto the input
17736 stream pointed to by stream. Pushed-back wide characters will be returned by
17737 subsequent reads on that stream in the reverse order of their pushing. A successful
17739 intervening call (with the stream pointed to by stream) to a file positioning function
17740 (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the
17741 stream. The external storage corresponding to the stream is unchanged.
17743 One wide character of pushback is guaranteed, even if the call to the ungetwc function
17744 follows just after a call to a formatted wide character input function fwscanf,
17745 vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times
17746 on the same stream without an intervening read or file positioning operation on that
17747 stream, the operation may fail.
17749 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
17752 A successful call to the ungetwc function clears the end-of-file indicator for the stream.
17753 The value of the file position indicator for the stream after reading or discarding all
17754 pushed-back wide characters is the same as it was before the wide characters were pushed
17755 back. For a text or binary stream, the value of its file position indicator after a successful
17756 call to the ungetwc function is unspecified until all pushed-back wide characters are
17760 The ungetwc function returns the wide character pushed back, or WEOF if the operation
17763 <h4><a name="7.24.4" href="#7.24.4">7.24.4 General wide string utilities</a></h4>
17765 The header <a href="#7.24"><wchar.h></a> declares a number of functions useful for wide string
17766 manipulation. Various methods are used for determining the lengths of the arrays, but in
17767 all cases a wchar_t * argument points to the initial (lowest addressed) element of the
17768 array. If an array is accessed beyond the end of an object, the behavior is undefined.
17770 Where an argument declared as size_t n determines the length of the array for a
17771 function, n can have the value zero on a call to that function. Unless explicitly stated
17772 otherwise in the description of a particular function in this subclause, pointer arguments
17773 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
17774 function that locates a wide character finds no occurrence, a function that compares two
17775 wide character sequences returns zero, and a function that copies wide characters copies
17776 zero wide characters.
17779 <h5><a name="7.24.4.1" href="#7.24.4.1">7.24.4.1 Wide string numeric conversion functions</a></h5>
17781 <h5><a name="7.24.4.1.1" href="#7.24.4.1.1">7.24.4.1.1 The wcstod, wcstof, and wcstold functions</a></h5>
17785 #include <a href="#7.24"><wchar.h></a>
17786 double wcstod(const wchar_t * restrict nptr,
17787 wchar_t ** restrict endptr);
17788 float wcstof(const wchar_t * restrict nptr,
17789 wchar_t ** restrict endptr);
17790 long double wcstold(const wchar_t * restrict nptr,
17791 wchar_t ** restrict endptr);</pre>
17792 <h6>Description</h6>
17794 The wcstod, wcstof, and wcstold functions convert the initial portion of the wide
17795 string pointed to by nptr to double, float, and long double representation,
17796 respectively. First, they decompose the input string into three parts: an initial, possibly
17797 empty, sequence of white-space wide characters (as specified by the iswspace
17798 function), a subject sequence resembling a floating-point constant or representing an
17799 infinity or NaN; and a final wide string of one or more unrecognized wide characters,
17800 including the terminating null wide character of the input wide string. Then, they attempt
17801 to convert the subject sequence to a floating-point number, and return the result.
17803 The expected form of the subject sequence is an optional plus or minus sign, then one of
17806 <li> a nonempty sequence of decimal digits optionally containing a decimal-point wide
17807 character, then an optional exponent part as defined for the corresponding single-byte
17808 characters in <a href="#6.4.4.2">6.4.4.2</a>;
17809 <li> a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
17810 decimal-point wide character, then an optional binary exponent part as defined in
17811 <a href="#6.4.4.2">6.4.4.2</a>;
17812 <li> INF or INFINITY, or any other wide string equivalent except for case
17813 <li> NAN or NAN(n-wchar-sequenceopt), or any other wide string equivalent except for
17814 case in the NAN part, where:
17819 n-wchar-sequence digit
17820 n-wchar-sequence nondigit</pre>
17822 The subject sequence is defined as the longest initial subsequence of the input wide
17823 string, starting with the first non-white-space wide character, that is of the expected form.
17825 The subject sequence contains no wide characters if the input wide string is not of the
17828 If the subject sequence has the expected form for a floating-point number, the sequence of
17829 wide characters starting with the first digit or the decimal-point wide character
17830 (whichever occurs first) is interpreted as a floating constant according to the rules of
17831 <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
17832 if neither an exponent part nor a decimal-point wide character appears in a decimal
17833 floating point number, or if a binary exponent part does not appear in a hexadecimal
17834 floating point number, an exponent part of the appropriate type with value zero is
17835 assumed to follow the last digit in the string. If the subject sequence begins with a minus
17836 sign, the sequence is interpreted as negated.<sup><a href="#note294"><b>294)</b></a></sup> A wide character sequence INF or
17837 INFINITY is interpreted as an infinity, if representable in the return type, else like a
17838 floating constant that is too large for the range of the return type. A wide character
17839 sequence NAN or NAN(n-wchar-sequenceopt) is interpreted as a quiet NaN, if supported
17840 in the return type, else like a subject sequence part that does not have the expected form;
17841 the meaning of the n-wchar sequences is implementation-defined.<sup><a href="#note295"><b>295)</b></a></sup> A pointer to the
17842 final wide string is stored in the object pointed to by endptr, provided that endptr is
17843 not a null pointer.
17845 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
17846 value resulting from the conversion is correctly rounded.
17848 In other than the "C" locale, additional locale-specific subject sequence forms may be
17851 If the subject sequence is empty or does not have the expected form, no conversion is
17852 performed; the value of nptr is stored in the object pointed to by endptr, provided
17853 that endptr is not a null pointer.
17854 Recommended practice
17856 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
17857 the result is not exactly representable, the result should be one of the two numbers in the
17858 appropriate internal format that are adjacent to the hexadecimal floating source value,
17859 with the extra stipulation that the error should have a correct sign for the current rounding
17866 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
17867 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
17868 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
17869 consider the two bounding, adjacent decimal strings L and U, both having
17870 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
17871 The result should be one of the (equal or adjacent) values that would be obtained by
17872 correctly rounding L and U according to the current rounding direction, with the extra
17873 stipulation that the error with respect to D should have a correct sign for the current
17874 rounding direction.<sup><a href="#note296"><b>296)</b></a></sup>
17877 The functions return the converted value, if any. If no conversion could be performed,
17878 zero is returned. If the correct value is outside the range of representable values, plus or
17879 minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the return
17880 type and sign of the value), and the value of the macro ERANGE is stored in errno. If
17881 the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is no greater
17882 than the smallest normalized positive number in the return type; whether errno acquires
17883 the value ERANGE is implementation-defined.
17891 <p><small><a name="note294" href="#note294">294)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
17892 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
17893 methods may yield different results if rounding is toward positive or negative infinity. In either case,
17894 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
17896 <p><small><a name="note295" href="#note295">295)</a> An implementation may use the n-wchar sequence to determine extra information to be represented in
17897 the NaN's significand.
17899 <p><small><a name="note296" href="#note296">296)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
17900 to the same internal floating value, but if not will round to adjacent values.
17903 <h5><a name="7.24.4.1.2" href="#7.24.4.1.2">7.24.4.1.2 The wcstol, wcstoll, wcstoul, and wcstoull functions</a></h5>
17907 #include <a href="#7.24"><wchar.h></a>
17909 const wchar_t * restrict nptr,
17910 wchar_t ** restrict endptr,
17912 long long int wcstoll(
17913 const wchar_t * restrict nptr,
17914 wchar_t ** restrict endptr,
17916 unsigned long int wcstoul(
17917 const wchar_t * restrict nptr,
17918 wchar_t ** restrict endptr,
17920 unsigned long long int wcstoull(
17921 const wchar_t * restrict nptr,
17922 wchar_t ** restrict endptr,
17924 <h6>Description</h6>
17926 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial
17927 portion of the wide string pointed to by nptr to long int, long long int,
17928 unsigned long int, and unsigned long long int representation,
17929 respectively. First, they decompose the input string into three parts: an initial, possibly
17930 empty, sequence of white-space wide characters (as specified by the iswspace
17931 function), a subject sequence resembling an integer represented in some radix determined
17932 by the value of base, and a final wide string of one or more unrecognized wide
17933 characters, including the terminating null wide character of the input wide string. Then,
17934 they attempt to convert the subject sequence to an integer, and return the result.
17936 If the value of base is zero, the expected form of the subject sequence is that of an
17937 integer constant as described for the corresponding single-byte characters in <a href="#6.4.4.1">6.4.4.1</a>,
17938 optionally preceded by a plus or minus sign, but not including an integer suffix. If the
17939 value of base is between 2 and 36 (inclusive), the expected form of the subject sequence
17940 is a sequence of letters and digits representing an integer with the radix specified by
17941 base, optionally preceded by a plus or minus sign, but not including an integer suffix.
17942 The letters from a (or A) through z (or Z) are ascribed the values 10 through 35; only
17943 letters and digits whose ascribed values are less than that of base are permitted. If the
17944 value of base is 16, the wide characters 0x or 0X may optionally precede the sequence
17945 of letters and digits, following the sign if present.
17948 The subject sequence is defined as the longest initial subsequence of the input wide
17949 string, starting with the first non-white-space wide character, that is of the expected form.
17950 The subject sequence contains no wide characters if the input wide string is empty or
17951 consists entirely of white space, or if the first non-white-space wide character is other
17952 than a sign or a permissible letter or digit.
17954 If the subject sequence has the expected form and the value of base is zero, the sequence
17955 of wide characters starting with the first digit is interpreted as an integer constant
17956 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
17957 value of base is between 2 and 36, it is used as the base for conversion, ascribing to each
17958 letter its value as given above. If the subject sequence begins with a minus sign, the value
17959 resulting from the conversion is negated (in the return type). A pointer to the final wide
17960 string is stored in the object pointed to by endptr, provided that endptr is not a null
17963 In other than the "C" locale, additional locale-specific subject sequence forms may be
17966 If the subject sequence is empty or does not have the expected form, no conversion is
17967 performed; the value of nptr is stored in the object pointed to by endptr, provided
17968 that endptr is not a null pointer.
17971 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
17972 value, if any. If no conversion could be performed, zero is returned. If the correct value
17973 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
17974 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
17975 sign of the value, if any), and the value of the macro ERANGE is stored in errno.
17977 <h5><a name="7.24.4.2" href="#7.24.4.2">7.24.4.2 Wide string copying functions</a></h5>
17979 <h5><a name="7.24.4.2.1" href="#7.24.4.2.1">7.24.4.2.1 The wcscpy function</a></h5>
17983 #include <a href="#7.24"><wchar.h></a>
17984 wchar_t *wcscpy(wchar_t * restrict s1,
17985 const wchar_t * restrict s2);</pre>
17986 <h6>Description</h6>
17988 The wcscpy function copies the wide string pointed to by s2 (including the terminating
17989 null wide character) into the array pointed to by s1.
17992 The wcscpy function returns the value of s1.
17995 <h5><a name="7.24.4.2.2" href="#7.24.4.2.2">7.24.4.2.2 The wcsncpy function</a></h5>
17999 #include <a href="#7.24"><wchar.h></a>
18000 wchar_t *wcsncpy(wchar_t * restrict s1,
18001 const wchar_t * restrict s2,
18003 <h6>Description</h6>
18005 The wcsncpy function copies not more than n wide characters (those that follow a null
18006 wide character are not copied) from the array pointed to by s2 to the array pointed to by
18007 s1.<sup><a href="#note297"><b>297)</b></a></sup>
18009 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null
18010 wide characters are appended to the copy in the array pointed to by s1, until n wide
18011 characters in all have been written.
18014 The wcsncpy function returns the value of s1.
18017 <p><small><a name="note297" href="#note297">297)</a> Thus, if there is no null wide character in the first n wide characters of the array pointed to by s2, the
18018 result will not be null-terminated.
18021 <h5><a name="7.24.4.2.3" href="#7.24.4.2.3">7.24.4.2.3 The wmemcpy function</a></h5>
18025 #include <a href="#7.24"><wchar.h></a>
18026 wchar_t *wmemcpy(wchar_t * restrict s1,
18027 const wchar_t * restrict s2,
18029 <h6>Description</h6>
18031 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
18032 object pointed to by s1.
18035 The wmemcpy function returns the value of s1.
18042 <h5><a name="7.24.4.2.4" href="#7.24.4.2.4">7.24.4.2.4 The wmemmove function</a></h5>
18046 #include <a href="#7.24"><wchar.h></a>
18047 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
18049 <h6>Description</h6>
18051 The wmemmove function copies n wide characters from the object pointed to by s2 to
18052 the object pointed to by s1. Copying takes place as if the n wide characters from the
18053 object pointed to by s2 are first copied into a temporary array of n wide characters that
18054 does not overlap the objects pointed to by s1 or s2, and then the n wide characters from
18055 the temporary array are copied into the object pointed to by s1.
18058 The wmemmove function returns the value of s1.
18060 <h5><a name="7.24.4.3" href="#7.24.4.3">7.24.4.3 Wide string concatenation functions</a></h5>
18062 <h5><a name="7.24.4.3.1" href="#7.24.4.3.1">7.24.4.3.1 The wcscat function</a></h5>
18066 #include <a href="#7.24"><wchar.h></a>
18067 wchar_t *wcscat(wchar_t * restrict s1,
18068 const wchar_t * restrict s2);</pre>
18069 <h6>Description</h6>
18071 The wcscat function appends a copy of the wide string pointed to by s2 (including the
18072 terminating null wide character) to the end of the wide string pointed to by s1. The initial
18073 wide character of s2 overwrites the null wide character at the end of s1.
18076 The wcscat function returns the value of s1.
18078 <h5><a name="7.24.4.3.2" href="#7.24.4.3.2">7.24.4.3.2 The wcsncat function</a></h5>
18082 #include <a href="#7.24"><wchar.h></a>
18083 wchar_t *wcsncat(wchar_t * restrict s1,
18084 const wchar_t * restrict s2,
18086 <h6>Description</h6>
18088 The wcsncat function appends not more than n wide characters (a null wide character
18089 and those that follow it are not appended) from the array pointed to by s2 to the end of
18091 the wide string pointed to by s1. The initial wide character of s2 overwrites the null
18092 wide character at the end of s1. A terminating null wide character is always appended to
18093 the result.<sup><a href="#note298"><b>298)</b></a></sup>
18096 The wcsncat function returns the value of s1.
18099 <p><small><a name="note298" href="#note298">298)</a> Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is
18103 <h5><a name="7.24.4.4" href="#7.24.4.4">7.24.4.4 Wide string comparison functions</a></h5>
18105 Unless explicitly stated otherwise, the functions described in this subclause order two
18106 wide characters the same way as two integers of the underlying integer type designated
18109 <h5><a name="7.24.4.4.1" href="#7.24.4.4.1">7.24.4.4.1 The wcscmp function</a></h5>
18113 #include <a href="#7.24"><wchar.h></a>
18114 int wcscmp(const wchar_t *s1, const wchar_t *s2);</pre>
18115 <h6>Description</h6>
18117 The wcscmp function compares the wide string pointed to by s1 to the wide string
18121 The wcscmp function returns an integer greater than, equal to, or less than zero,
18122 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
18123 wide string pointed to by s2.
18125 <h5><a name="7.24.4.4.2" href="#7.24.4.4.2">7.24.4.4.2 The wcscoll function</a></h5>
18129 #include <a href="#7.24"><wchar.h></a>
18130 int wcscoll(const wchar_t *s1, const wchar_t *s2);</pre>
18131 <h6>Description</h6>
18133 The wcscoll function compares the wide string pointed to by s1 to the wide string
18134 pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the
18138 The wcscoll function returns an integer greater than, equal to, or less than zero,
18139 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
18143 wide string pointed to by s2 when both are interpreted as appropriate to the current
18146 <h5><a name="7.24.4.4.3" href="#7.24.4.4.3">7.24.4.4.3 The wcsncmp function</a></h5>
18150 #include <a href="#7.24"><wchar.h></a>
18151 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
18153 <h6>Description</h6>
18155 The wcsncmp function compares not more than n wide characters (those that follow a
18156 null wide character are not compared) from the array pointed to by s1 to the array
18160 The wcsncmp function returns an integer greater than, equal to, or less than zero,
18161 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
18162 to, or less than the possibly null-terminated array pointed to by s2.
18164 <h5><a name="7.24.4.4.4" href="#7.24.4.4.4">7.24.4.4.4 The wcsxfrm function</a></h5>
18168 #include <a href="#7.24"><wchar.h></a>
18169 size_t wcsxfrm(wchar_t * restrict s1,
18170 const wchar_t * restrict s2,
18172 <h6>Description</h6>
18174 The wcsxfrm function transforms the wide string pointed to by s2 and places the
18175 resulting wide string into the array pointed to by s1. The transformation is such that if
18176 the wcscmp function is applied to two transformed wide strings, it returns a value greater
18177 than, equal to, or less than zero, corresponding to the result of the wcscoll function
18178 applied to the same two original wide strings. No more than n wide characters are placed
18179 into the resulting array pointed to by s1, including the terminating null wide character. If
18180 n is zero, s1 is permitted to be a null pointer.
18183 The wcsxfrm function returns the length of the transformed wide string (not including
18184 the terminating null wide character). If the value returned is n or greater, the contents of
18185 the array pointed to by s1 are indeterminate.
18187 EXAMPLE The value of the following expression is the length of the array needed to hold the
18188 transformation of the wide string pointed to by s:
18191 1 + wcsxfrm(NULL, s, 0)</pre>
18194 <h5><a name="7.24.4.4.5" href="#7.24.4.4.5">7.24.4.4.5 The wmemcmp function</a></h5>
18198 #include <a href="#7.24"><wchar.h></a>
18199 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
18201 <h6>Description</h6>
18203 The wmemcmp function compares the first n wide characters of the object pointed to by
18204 s1 to the first n wide characters of the object pointed to by s2.
18207 The wmemcmp function returns an integer greater than, equal to, or less than zero,
18208 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
18211 <h5><a name="7.24.4.5" href="#7.24.4.5">7.24.4.5 Wide string search functions</a></h5>
18213 <h5><a name="7.24.4.5.1" href="#7.24.4.5.1">7.24.4.5.1 The wcschr function</a></h5>
18217 #include <a href="#7.24"><wchar.h></a>
18218 wchar_t *wcschr(const wchar_t *s, wchar_t c);</pre>
18219 <h6>Description</h6>
18221 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
18222 The terminating null wide character is considered to be part of the wide string.
18225 The wcschr function returns a pointer to the located wide character, or a null pointer if
18226 the wide character does not occur in the wide string.
18228 <h5><a name="7.24.4.5.2" href="#7.24.4.5.2">7.24.4.5.2 The wcscspn function</a></h5>
18232 #include <a href="#7.24"><wchar.h></a>
18233 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);</pre>
18234 <h6>Description</h6>
18236 The wcscspn function computes the length of the maximum initial segment of the wide
18237 string pointed to by s1 which consists entirely of wide characters not from the wide
18238 string pointed to by s2.
18242 The wcscspn function returns the length of the segment.
18244 <h5><a name="7.24.4.5.3" href="#7.24.4.5.3">7.24.4.5.3 The wcspbrk function</a></h5>
18248 #include <a href="#7.24"><wchar.h></a>
18249 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);</pre>
18250 <h6>Description</h6>
18252 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
18253 any wide character from the wide string pointed to by s2.
18256 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
18257 no wide character from s2 occurs in s1.
18259 <h5><a name="7.24.4.5.4" href="#7.24.4.5.4">7.24.4.5.4 The wcsrchr function</a></h5>
18263 #include <a href="#7.24"><wchar.h></a>
18264 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);</pre>
18265 <h6>Description</h6>
18267 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
18268 s. The terminating null wide character is considered to be part of the wide string.
18271 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
18272 not occur in the wide string.
18274 <h5><a name="7.24.4.5.5" href="#7.24.4.5.5">7.24.4.5.5 The wcsspn function</a></h5>
18278 #include <a href="#7.24"><wchar.h></a>
18279 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);</pre>
18280 <h6>Description</h6>
18282 The wcsspn function computes the length of the maximum initial segment of the wide
18283 string pointed to by s1 which consists entirely of wide characters from the wide string
18287 The wcsspn function returns the length of the segment.
18290 <h5><a name="7.24.4.5.6" href="#7.24.4.5.6">7.24.4.5.6 The wcsstr function</a></h5>
18294 #include <a href="#7.24"><wchar.h></a>
18295 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);</pre>
18296 <h6>Description</h6>
18298 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
18299 the sequence of wide characters (excluding the terminating null wide character) in the
18300 wide string pointed to by s2.
18303 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
18304 wide string is not found. If s2 points to a wide string with zero length, the function
18307 <h5><a name="7.24.4.5.7" href="#7.24.4.5.7">7.24.4.5.7 The wcstok function</a></h5>
18311 #include <a href="#7.24"><wchar.h></a>
18312 wchar_t *wcstok(wchar_t * restrict s1,
18313 const wchar_t * restrict s2,
18314 wchar_t ** restrict ptr);</pre>
18315 <h6>Description</h6>
18317 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
18318 a sequence of tokens, each of which is delimited by a wide character from the wide string
18319 pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
18320 which the wcstok function stores information necessary for it to continue scanning the
18323 The first call in a sequence has a non-null first argument and stores an initial value in the
18324 object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
18325 the object pointed to by ptr is required to have the value stored by the previous call in
18326 the sequence, which is then updated. The separator wide string pointed to by s2 may be
18327 different from call to call.
18329 The first call in the sequence searches the wide string pointed to by s1 for the first wide
18330 character that is not contained in the current separator wide string pointed to by s2. If no
18331 such wide character is found, then there are no tokens in the wide string pointed to by s1
18332 and the wcstok function returns a null pointer. If such a wide character is found, it is
18333 the start of the first token.
18335 The wcstok function then searches from there for a wide character that is contained in
18336 the current separator wide string. If no such wide character is found, the current token
18338 extends to the end of the wide string pointed to by s1, and subsequent searches in the
18339 same wide string for a token return a null pointer. If such a wide character is found, it is
18340 overwritten by a null wide character, which terminates the current token.
18342 In all cases, the wcstok function stores sufficient information in the pointer pointed to
18343 by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
18344 value for ptr, shall start searching just past the element overwritten by a null wide
18345 character (if any).
18348 The wcstok function returns a pointer to the first wide character of a token, or a null
18349 pointer if there is no token.
18353 #include <a href="#7.24"><wchar.h></a>
18354 static wchar_t str1[] = L"?a???b,,,#c";
18355 static wchar_t str2[] = L"\t \t";
18356 wchar_t *t, *ptr1, *ptr2;
18357 t = wcstok(str1, L"?", &ptr1); // t points to the token L"a"
18358 t = wcstok(NULL, L",", &ptr1); // t points to the token L"??b"
18359 t = wcstok(str2, L" \t", &ptr2); // t is a null pointer
18360 t = wcstok(NULL, L"#,", &ptr1); // t points to the token L"c"
18361 t = wcstok(NULL, L"?", &ptr1); // t is a null pointer</pre>
18364 <h5><a name="7.24.4.5.8" href="#7.24.4.5.8">7.24.4.5.8 The wmemchr function</a></h5>
18368 #include <a href="#7.24"><wchar.h></a>
18369 wchar_t *wmemchr(const wchar_t *s, wchar_t c,
18371 <h6>Description</h6>
18373 The wmemchr function locates the first occurrence of c in the initial n wide characters of
18374 the object pointed to by s.
18377 The wmemchr function returns a pointer to the located wide character, or a null pointer if
18378 the wide character does not occur in the object.
18381 <h5><a name="7.24.4.6" href="#7.24.4.6">7.24.4.6 Miscellaneous functions</a></h5>
18383 <h5><a name="7.24.4.6.1" href="#7.24.4.6.1">7.24.4.6.1 The wcslen function</a></h5>
18387 #include <a href="#7.24"><wchar.h></a>
18388 size_t wcslen(const wchar_t *s);</pre>
18389 <h6>Description</h6>
18391 The wcslen function computes the length of the wide string pointed to by s.
18394 The wcslen function returns the number of wide characters that precede the terminating
18395 null wide character.
18397 <h5><a name="7.24.4.6.2" href="#7.24.4.6.2">7.24.4.6.2 The wmemset function</a></h5>
18401 #include <a href="#7.24"><wchar.h></a>
18402 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);</pre>
18403 <h6>Description</h6>
18405 The wmemset function copies the value of c into each of the first n wide characters of
18406 the object pointed to by s.
18409 The wmemset function returns the value of s.
18411 <h4><a name="7.24.5" href="#7.24.5">7.24.5 Wide character time conversion functions</a></h4>
18413 <h5><a name="7.24.5.1" href="#7.24.5.1">7.24.5.1 The wcsftime function</a></h5>
18417 #include <a href="#7.23"><time.h></a>
18418 #include <a href="#7.24"><wchar.h></a>
18419 size_t wcsftime(wchar_t * restrict s,
18421 const wchar_t * restrict format,
18422 const struct tm * restrict timeptr);</pre>
18423 <h6>Description</h6>
18425 The wcsftime function is equivalent to the strftime function, except that:
18427 <li> The argument s points to the initial element of an array of wide characters into which
18428 the generated output is to be placed.
18430 <li> The argument maxsize indicates the limiting number of wide characters.
18431 <li> The argument format is a wide string and the conversion specifiers are replaced by
18432 corresponding sequences of wide characters.
18433 <li> The return value indicates the number of wide characters.
18437 If the total number of resulting wide characters including the terminating null wide
18438 character is not more than maxsize, the wcsftime function returns the number of
18439 wide characters placed into the array pointed to by s not including the terminating null
18440 wide character. Otherwise, zero is returned and the contents of the array are
18443 <h4><a name="7.24.6" href="#7.24.6">7.24.6 Extended multibyte/wide character conversion utilities</a></h4>
18445 The header <a href="#7.24"><wchar.h></a> declares an extended set of functions useful for conversion
18446 between multibyte characters and wide characters.
18448 Most of the following functions -- those that are listed as ''restartable'', <a href="#7.24.6.3">7.24.6.3</a> and
18449 <a href="#7.24.6.4">7.24.6.4</a> -- take as a last argument a pointer to an object of type mbstate_t that is used
18450 to describe the current conversion state from a particular multibyte character sequence to
18451 a wide character sequence (or the reverse) under the rules of a particular setting for the
18452 LC_CTYPE category of the current locale.
18454 The initial conversion state corresponds, for a conversion in either direction, to the
18455 beginning of a new multibyte character in the initial shift state. A zero-valued
18456 mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
18457 valued mbstate_t object can be used to initiate conversion involving any multibyte
18458 character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
18459 been altered by any of the functions described in this subclause, and is then used with a
18460 different multibyte character sequence, or in the other conversion direction, or with a
18461 different LC_CTYPE category setting than on earlier function calls, the behavior is
18462 undefined.<sup><a href="#note299"><b>299)</b></a></sup>
18464 On entry, each function takes the described conversion state (either internal or pointed to
18465 by an argument) as current. The conversion state described by the pointed-to object is
18466 altered as needed to track the shift state, and the position within a multibyte character, for
18467 the associated multibyte character sequence.
18475 <p><small><a name="note299" href="#note299">299)</a> Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and
18476 mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
18480 <h5><a name="7.24.6.1" href="#7.24.6.1">7.24.6.1 Single-byte/wide character conversion functions</a></h5>
18482 <h5><a name="7.24.6.1.1" href="#7.24.6.1.1">7.24.6.1.1 The btowc function</a></h5>
18486 #include <a href="#7.19"><stdio.h></a>
18487 #include <a href="#7.24"><wchar.h></a>
18488 wint_t btowc(int c);</pre>
18489 <h6>Description</h6>
18491 The btowc function determines whether c constitutes a valid single-byte character in the
18492 initial shift state.
18495 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
18496 does not constitute a valid single-byte character in the initial shift state. Otherwise, it
18497 returns the wide character representation of that character.
18499 <h5><a name="7.24.6.1.2" href="#7.24.6.1.2">7.24.6.1.2 The wctob function</a></h5>
18503 #include <a href="#7.19"><stdio.h></a>
18504 #include <a href="#7.24"><wchar.h></a>
18505 int wctob(wint_t c);</pre>
18506 <h6>Description</h6>
18508 The wctob function determines whether c corresponds to a member of the extended
18509 character set whose multibyte character representation is a single byte when in the initial
18513 The wctob function returns EOF if c does not correspond to a multibyte character with
18514 length one in the initial shift state. Otherwise, it returns the single-byte representation of
18515 that character as an unsigned char converted to an int.
18517 <h5><a name="7.24.6.2" href="#7.24.6.2">7.24.6.2 Conversion state functions</a></h5>
18519 <h5><a name="7.24.6.2.1" href="#7.24.6.2.1">7.24.6.2.1 The mbsinit function</a></h5>
18523 #include <a href="#7.24"><wchar.h></a>
18524 int mbsinit(const mbstate_t *ps);</pre>
18525 <h6>Description</h6>
18527 If ps is not a null pointer, the mbsinit function determines whether the pointed-to
18528 mbstate_t object describes an initial conversion state.
18532 The mbsinit function returns nonzero if ps is a null pointer or if the pointed-to object
18533 describes an initial conversion state; otherwise, it returns zero.
18535 <h5><a name="7.24.6.3" href="#7.24.6.3">7.24.6.3 Restartable multibyte/wide character conversion functions</a></h5>
18537 These functions differ from the corresponding multibyte character functions of <a href="#7.20.7">7.20.7</a>
18538 (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type
18539 pointer to mbstate_t that points to an object that can completely describe the current
18540 conversion state of the associated multibyte character sequence. If ps is a null pointer,
18541 each function uses its own internal mbstate_t object instead, which is initialized at
18542 program startup to the initial conversion state. The implementation behaves as if no
18543 library function calls these functions with a null pointer for ps.
18545 Also unlike their corresponding functions, the return value does not represent whether the
18546 encoding is state-dependent.
18548 <h5><a name="7.24.6.3.1" href="#7.24.6.3.1">7.24.6.3.1 The mbrlen function</a></h5>
18552 #include <a href="#7.24"><wchar.h></a>
18553 size_t mbrlen(const char * restrict s,
18555 mbstate_t * restrict ps);</pre>
18556 <h6>Description</h6>
18558 The mbrlen function is equivalent to the call:
18560 mbrtowc(NULL, s, n, ps != NULL ? ps : &internal)</pre>
18561 where internal is the mbstate_t object for the mbrlen function, except that the
18562 expression designated by ps is evaluated only once.
18565 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
18567 <p><b> Forward references</b>: the mbrtowc function (<a href="#7.24.6.3.2">7.24.6.3.2</a>).
18570 <h5><a name="7.24.6.3.2" href="#7.24.6.3.2">7.24.6.3.2 The mbrtowc function</a></h5>
18574 #include <a href="#7.24"><wchar.h></a>
18575 size_t mbrtowc(wchar_t * restrict pwc,
18576 const char * restrict s,
18578 mbstate_t * restrict ps);</pre>
18579 <h6>Description</h6>
18581 If s is a null pointer, the mbrtowc function is equivalent to the call:
18583 mbrtowc(NULL, "", 1, ps)</pre>
18584 In this case, the values of the parameters pwc and n are ignored.
18586 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with
18587 the byte pointed to by s to determine the number of bytes needed to complete the next
18588 multibyte character (including any shift sequences). If the function determines that the
18589 next multibyte character is complete and valid, it determines the value of the
18590 corresponding wide character and then, if pwc is not a null pointer, stores that value in
18591 the object pointed to by pwc. If the corresponding wide character is the null wide
18592 character, the resulting state described is the initial conversion state.
18595 The mbrtowc function returns the first of the following that applies (given the current
18597 0 if the next n or fewer bytes complete the multibyte character that
18599 corresponds to the null wide character (which is the value stored).</pre>
18600 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
18602 character (which is the value stored); the value returned is the number
18603 of bytes that complete the multibyte character.</pre>
18604 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
18606 multibyte character, and all n bytes have been processed (no value is
18607 stored).<sup><a href="#note300"><b>300)</b></a></sup></pre>
18608 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
18610 do not contribute to a complete and valid multibyte character (no
18611 value is stored); the value of the macro EILSEQ is stored in errno,
18612 and the conversion state is unspecified.</pre>
18617 <p><small><a name="note300" href="#note300">300)</a> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
18618 sequence of redundant shift sequences (for implementations with state-dependent encodings).
18621 <h5><a name="7.24.6.3.3" href="#7.24.6.3.3">7.24.6.3.3 The wcrtomb function</a></h5>
18625 #include <a href="#7.24"><wchar.h></a>
18626 size_t wcrtomb(char * restrict s,
18628 mbstate_t * restrict ps);</pre>
18629 <h6>Description</h6>
18631 If s is a null pointer, the wcrtomb function is equivalent to the call
18633 wcrtomb(buf, L'\0', ps)</pre>
18634 where buf is an internal buffer.
18636 If s is not a null pointer, the wcrtomb function determines the number of bytes needed
18637 to represent the multibyte character that corresponds to the wide character given by wc
18638 (including any shift sequences), and stores the multibyte character representation in the
18639 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
18640 wc is a null wide character, a null byte is stored, preceded by any shift sequence needed
18641 to restore the initial shift state; the resulting state described is the initial conversion state.
18644 The wcrtomb function returns the number of bytes stored in the array object (including
18645 any shift sequences). When wc is not a valid wide character, an encoding error occurs:
18646 the function stores the value of the macro EILSEQ in errno and returns
18647 (size_t)(-1); the conversion state is unspecified.
18649 <h5><a name="7.24.6.4" href="#7.24.6.4">7.24.6.4 Restartable multibyte/wide string conversion functions</a></h5>
18651 These functions differ from the corresponding multibyte string functions of <a href="#7.20.8">7.20.8</a>
18652 (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to
18653 mbstate_t that points to an object that can completely describe the current conversion
18654 state of the associated multibyte character sequence. If ps is a null pointer, each function
18655 uses its own internal mbstate_t object instead, which is initialized at program startup
18656 to the initial conversion state. The implementation behaves as if no library function calls
18657 these functions with a null pointer for ps.
18659 Also unlike their corresponding functions, the conversion source parameter, src, has a
18660 pointer-to-pointer type. When the function is storing the results of conversions (that is,
18661 when dst is not a null pointer), the pointer object pointed to by this parameter is updated
18662 to reflect the amount of the source processed by that invocation.
18665 <h5><a name="7.24.6.4.1" href="#7.24.6.4.1">7.24.6.4.1 The mbsrtowcs function</a></h5>
18669 #include <a href="#7.24"><wchar.h></a>
18670 size_t mbsrtowcs(wchar_t * restrict dst,
18671 const char ** restrict src,
18673 mbstate_t * restrict ps);</pre>
18674 <h6>Description</h6>
18676 The mbsrtowcs function converts a sequence of multibyte characters that begins in the
18677 conversion state described by the object pointed to by ps, from the array indirectly
18678 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
18679 pointer, the converted characters are stored into the array pointed to by dst. Conversion
18680 continues up to and including a terminating null character, which is also stored.
18681 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
18682 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
18683 characters have been stored into the array pointed to by dst.<sup><a href="#note301"><b>301)</b></a></sup> Each conversion takes
18684 place as if by a call to the mbrtowc function.
18686 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
18687 pointer (if conversion stopped due to reaching a terminating null character) or the address
18688 just past the last multibyte character converted (if any). If conversion stopped due to
18689 reaching a terminating null character and if dst is not a null pointer, the resulting state
18690 described is the initial conversion state.
18693 If the input conversion encounters a sequence of bytes that do not form a valid multibyte
18694 character, an encoding error occurs: the mbsrtowcs function stores the value of the
18695 macro EILSEQ in errno and returns (size_t)(-1); the conversion state is
18696 unspecified. Otherwise, it returns the number of multibyte characters successfully
18697 converted, not including the terminating null character (if any).
18705 <p><small><a name="note301" href="#note301">301)</a> Thus, the value of len is ignored if dst is a null pointer.
18708 <h5><a name="7.24.6.4.2" href="#7.24.6.4.2">7.24.6.4.2 The wcsrtombs function</a></h5>
18712 #include <a href="#7.24"><wchar.h></a>
18713 size_t wcsrtombs(char * restrict dst,
18714 const wchar_t ** restrict src,
18716 mbstate_t * restrict ps);</pre>
18717 <h6>Description</h6>
18719 The wcsrtombs function converts a sequence of wide characters from the array
18720 indirectly pointed to by src into a sequence of corresponding multibyte characters that
18721 begins in the conversion state described by the object pointed to by ps. If dst is not a
18722 null pointer, the converted characters are then stored into the array pointed to by dst.
18723 Conversion continues up to and including a terminating null wide character, which is also
18724 stored. Conversion stops earlier in two cases: when a wide character is reached that does
18725 not correspond to a valid multibyte character, or (if dst is not a null pointer) when the
18726 next multibyte character would exceed the limit of len total bytes to be stored into the
18727 array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb
18728 function.<sup><a href="#note302"><b>302)</b></a></sup>
18730 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
18731 pointer (if conversion stopped due to reaching a terminating null wide character) or the
18732 address just past the last wide character converted (if any). If conversion stopped due to
18733 reaching a terminating null wide character, the resulting state described is the initial
18737 If conversion stops because a wide character is reached that does not correspond to a
18738 valid multibyte character, an encoding error occurs: the wcsrtombs function stores the
18739 value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion
18740 state is unspecified. Otherwise, it returns the number of bytes in the resulting multibyte
18741 character sequence, not including the terminating null character (if any).
18749 <p><small><a name="note302" href="#note302">302)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
18750 include those necessary to reach the initial shift state immediately before the null byte.
18753 <h3><a name="7.25" href="#7.25">7.25 Wide character classification and mapping utilities <wctype.h></a></h3>
18755 <h4><a name="7.25.1" href="#7.25.1">7.25.1 Introduction</a></h4>
18757 The header <a href="#7.25"><wctype.h></a> declares three data types, one macro, and many functions.<sup><a href="#note303"><b>303)</b></a></sup>
18759 The types declared are
18762 described in <a href="#7.24.1">7.24.1</a>;
18765 which is a scalar type that can hold values which represent locale-specific character
18769 which is a scalar type that can hold values which represent locale-specific character
18772 The macro defined is WEOF (described in <a href="#7.24.1">7.24.1</a>).
18774 The functions declared are grouped as follows:
18776 <li> Functions that provide wide character classification;
18777 <li> Extensible functions that provide wide character classification;
18778 <li> Functions that provide wide character case mapping;
18779 <li> Extensible functions that provide wide character mapping.
18782 For all functions described in this subclause that accept an argument of type wint_t, the
18783 value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If
18784 this argument has any other value, the behavior is undefined.
18786 The behavior of these functions is affected by the LC_CTYPE category of the current
18795 <p><small><a name="note303" href="#note303">303)</a> See ''future library directions'' (<a href="#7.26.13">7.26.13</a>).
18798 <h4><a name="7.25.2" href="#7.25.2">7.25.2 Wide character classification utilities</a></h4>
18800 The header <a href="#7.25"><wctype.h></a> declares several functions useful for classifying wide
18803 The term printing wide character refers to a member of a locale-specific set of wide
18804 characters, each of which occupies at least one printing position on a display device. The
18805 term control wide character refers to a member of a locale-specific set of wide characters
18806 that are not printing wide characters.
18808 <h5><a name="7.25.2.1" href="#7.25.2.1">7.25.2.1 Wide character classification functions</a></h5>
18810 The functions in this subclause return nonzero (true) if and only if the value of the
18811 argument wc conforms to that in the description of the function.
18813 Each of the following functions returns true for each wide character that corresponds (as
18814 if by a call to the wctob function) to a single-byte character for which the corresponding
18815 character classification function from <a href="#7.4.1">7.4.1</a> returns true, except that the iswgraph and
18816 iswpunct functions may differ with respect to wide characters other than L' ' that are
18817 both printing and white-space wide characters.<sup><a href="#note304"><b>304)</b></a></sup>
18818 <p><b> Forward references</b>: the wctob function (<a href="#7.24.6.1.2">7.24.6.1.2</a>).
18821 <p><small><a name="note304" href="#note304">304)</a> For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call
18822 iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true
18823 (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc)
18824 && iswspace(wc) is true, but not both.
18827 <h5><a name="7.25.2.1.1" href="#7.25.2.1.1">7.25.2.1.1 The iswalnum function</a></h5>
18831 #include <a href="#7.25"><wctype.h></a>
18832 int iswalnum(wint_t wc);</pre>
18833 <h6>Description</h6>
18835 The iswalnum function tests for any wide character for which iswalpha or
18838 <h5><a name="7.25.2.1.2" href="#7.25.2.1.2">7.25.2.1.2 The iswalpha function</a></h5>
18842 #include <a href="#7.25"><wctype.h></a>
18843 int iswalpha(wint_t wc);</pre>
18844 <h6>Description</h6>
18846 The iswalpha function tests for any wide character for which iswupper or
18847 iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
18850 wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
18851 is true.<sup><a href="#note305"><b>305)</b></a></sup>
18854 <p><small><a name="note305" href="#note305">305)</a> The functions iswlower and iswupper test true or false separately for each of these additional
18855 wide characters; all four combinations are possible.
18858 <h5><a name="7.25.2.1.3" href="#7.25.2.1.3">7.25.2.1.3 The iswblank function</a></h5>
18862 #include <a href="#7.25"><wctype.h></a>
18863 int iswblank(wint_t wc);</pre>
18864 <h6>Description</h6>
18866 The iswblank function tests for any wide character that is a standard blank wide
18867 character or is one of a locale-specific set of wide characters for which iswspace is true
18868 and that is used to separate words within a line of text. The standard blank wide
18869 characters are the following: space (L' '), and horizontal tab (L'\t'). In the "C"
18870 locale, iswblank returns true only for the standard blank characters.
18872 <h5><a name="7.25.2.1.4" href="#7.25.2.1.4">7.25.2.1.4 The iswcntrl function</a></h5>
18876 #include <a href="#7.25"><wctype.h></a>
18877 int iswcntrl(wint_t wc);</pre>
18878 <h6>Description</h6>
18880 The iswcntrl function tests for any control wide character.
18882 <h5><a name="7.25.2.1.5" href="#7.25.2.1.5">7.25.2.1.5 The iswdigit function</a></h5>
18886 #include <a href="#7.25"><wctype.h></a>
18887 int iswdigit(wint_t wc);</pre>
18888 <h6>Description</h6>
18890 The iswdigit function tests for any wide character that corresponds to a decimal-digit
18891 character (as defined in <a href="#5.2.1">5.2.1</a>).
18893 <h5><a name="7.25.2.1.6" href="#7.25.2.1.6">7.25.2.1.6 The iswgraph function</a></h5>
18897 #include <a href="#7.25"><wctype.h></a>
18898 int iswgraph(wint_t wc);</pre>
18904 <h6>Description</h6>
18906 The iswgraph function tests for any wide character for which iswprint is true and
18907 iswspace is false.<sup><a href="#note306"><b>306)</b></a></sup>
18910 <p><small><a name="note306" href="#note306">306)</a> Note that the behavior of the iswgraph and iswpunct functions may differ from their
18911 corresponding functions in <a href="#7.4.1">7.4.1</a> with respect to printing, white-space, single-byte execution
18912 characters other than ' '.
18915 <h5><a name="7.25.2.1.7" href="#7.25.2.1.7">7.25.2.1.7 The iswlower function</a></h5>
18919 #include <a href="#7.25"><wctype.h></a>
18920 int iswlower(wint_t wc);</pre>
18921 <h6>Description</h6>
18923 The iswlower function tests for any wide character that corresponds to a lowercase
18924 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
18925 iswdigit, iswpunct, or iswspace is true.
18927 <h5><a name="7.25.2.1.8" href="#7.25.2.1.8">7.25.2.1.8 The iswprint function</a></h5>
18931 #include <a href="#7.25"><wctype.h></a>
18932 int iswprint(wint_t wc);</pre>
18933 <h6>Description</h6>
18935 The iswprint function tests for any printing wide character.
18937 <h5><a name="7.25.2.1.9" href="#7.25.2.1.9">7.25.2.1.9 The iswpunct function</a></h5>
18941 #include <a href="#7.25"><wctype.h></a>
18942 int iswpunct(wint_t wc);</pre>
18943 <h6>Description</h6>
18945 The iswpunct function tests for any printing wide character that is one of a locale-
18946 specific set of punctuation wide characters for which neither iswspace nor iswalnum
18949 <h5><a name="7.25.2.1.10" href="#7.25.2.1.10">7.25.2.1.10 The iswspace function</a></h5>
18953 #include <a href="#7.25"><wctype.h></a>
18954 int iswspace(wint_t wc);</pre>
18959 <h6>Description</h6>
18961 The iswspace function tests for any wide character that corresponds to a locale-specific
18962 set of white-space wide characters for which none of iswalnum, iswgraph, or
18965 <h5><a name="7.25.2.1.11" href="#7.25.2.1.11">7.25.2.1.11 The iswupper function</a></h5>
18969 #include <a href="#7.25"><wctype.h></a>
18970 int iswupper(wint_t wc);</pre>
18971 <h6>Description</h6>
18973 The iswupper function tests for any wide character that corresponds to an uppercase
18974 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
18975 iswdigit, iswpunct, or iswspace is true.
18977 <h5><a name="7.25.2.1.12" href="#7.25.2.1.12">7.25.2.1.12 The iswxdigit function</a></h5>
18981 #include <a href="#7.25"><wctype.h></a>
18982 int iswxdigit(wint_t wc);</pre>
18983 <h6>Description</h6>
18985 The iswxdigit function tests for any wide character that corresponds to a
18986 hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
18988 <h5><a name="7.25.2.2" href="#7.25.2.2">7.25.2.2 Extensible wide character classification functions</a></h5>
18990 The functions wctype and iswctype provide extensible wide character classification
18991 as well as testing equivalent to that performed by the functions described in the previous
18992 subclause (<a href="#7.25.2.1">7.25.2.1</a>).
18994 <h5><a name="7.25.2.2.1" href="#7.25.2.2.1">7.25.2.2.1 The iswctype function</a></h5>
18998 #include <a href="#7.25"><wctype.h></a>
18999 int iswctype(wint_t wc, wctype_t desc);</pre>
19000 <h6>Description</h6>
19002 The iswctype function determines whether the wide character wc has the property
19003 described by desc. The current setting of the LC_CTYPE category shall be the same as
19004 during the call to wctype that returned the value desc.
19006 Each of the following expressions has a truth-value equivalent to the call to the wide
19007 character classification function (<a href="#7.25.2.1">7.25.2.1</a>) in the comment that follows the expression:
19010 iswctype(wc, wctype("alnum")) // iswalnum(wc)
19011 iswctype(wc, wctype("alpha")) // iswalpha(wc)
19012 iswctype(wc, wctype("blank")) // iswblank(wc)
19013 iswctype(wc, wctype("cntrl")) // iswcntrl(wc)
19014 iswctype(wc, wctype("digit")) // iswdigit(wc)
19015 iswctype(wc, wctype("graph")) // iswgraph(wc)
19016 iswctype(wc, wctype("lower")) // iswlower(wc)
19017 iswctype(wc, wctype("print")) // iswprint(wc)
19018 iswctype(wc, wctype("punct")) // iswpunct(wc)
19019 iswctype(wc, wctype("space")) // iswspace(wc)
19020 iswctype(wc, wctype("upper")) // iswupper(wc)
19021 iswctype(wc, wctype("xdigit")) // iswxdigit(wc)</pre>
19024 The iswctype function returns nonzero (true) if and only if the value of the wide
19025 character wc has the property described by desc.
19026 <p><b> Forward references</b>: the wctype function (<a href="#7.25.2.2.2">7.25.2.2.2</a>).
19028 <h5><a name="7.25.2.2.2" href="#7.25.2.2.2">7.25.2.2.2 The wctype function</a></h5>
19032 #include <a href="#7.25"><wctype.h></a>
19033 wctype_t wctype(const char *property);</pre>
19034 <h6>Description</h6>
19036 The wctype function constructs a value with type wctype_t that describes a class of
19037 wide characters identified by the string argument property.
19039 The strings listed in the description of the iswctype function shall be valid in all
19040 locales as property arguments to the wctype function.
19043 If property identifies a valid class of wide characters according to the LC_CTYPE
19044 category of the current locale, the wctype function returns a nonzero value that is valid
19045 as the second argument to the iswctype function; otherwise, it returns zero. *
19048 <h4><a name="7.25.3" href="#7.25.3">7.25.3 Wide character case mapping utilities</a></h4>
19050 The header <a href="#7.25"><wctype.h></a> declares several functions useful for mapping wide characters.
19052 <h5><a name="7.25.3.1" href="#7.25.3.1">7.25.3.1 Wide character case mapping functions</a></h5>
19054 <h5><a name="7.25.3.1.1" href="#7.25.3.1.1">7.25.3.1.1 The towlower function</a></h5>
19058 #include <a href="#7.25"><wctype.h></a>
19059 wint_t towlower(wint_t wc);</pre>
19060 <h6>Description</h6>
19062 The towlower function converts an uppercase letter to a corresponding lowercase letter.
19065 If the argument is a wide character for which iswupper is true and there are one or
19066 more corresponding wide characters, as specified by the current locale, for which
19067 iswlower is true, the towlower function returns one of the corresponding wide
19068 characters (always the same one for any given locale); otherwise, the argument is
19069 returned unchanged.
19071 <h5><a name="7.25.3.1.2" href="#7.25.3.1.2">7.25.3.1.2 The towupper function</a></h5>
19075 #include <a href="#7.25"><wctype.h></a>
19076 wint_t towupper(wint_t wc);</pre>
19077 <h6>Description</h6>
19079 The towupper function converts a lowercase letter to a corresponding uppercase letter.
19082 If the argument is a wide character for which iswlower is true and there are one or
19083 more corresponding wide characters, as specified by the current locale, for which
19084 iswupper is true, the towupper function returns one of the corresponding wide
19085 characters (always the same one for any given locale); otherwise, the argument is
19086 returned unchanged.
19088 <h5><a name="7.25.3.2" href="#7.25.3.2">7.25.3.2 Extensible wide character case mapping functions</a></h5>
19090 The functions wctrans and towctrans provide extensible wide character mapping as
19091 well as case mapping equivalent to that performed by the functions described in the
19092 previous subclause (<a href="#7.25.3.1">7.25.3.1</a>).
19095 <h5><a name="7.25.3.2.1" href="#7.25.3.2.1">7.25.3.2.1 The towctrans function</a></h5>
19099 #include <a href="#7.25"><wctype.h></a>
19100 wint_t towctrans(wint_t wc, wctrans_t desc);</pre>
19101 <h6>Description</h6>
19103 The towctrans function maps the wide character wc using the mapping described by
19104 desc. The current setting of the LC_CTYPE category shall be the same as during the call
19105 to wctrans that returned the value desc.
19107 Each of the following expressions behaves the same as the call to the wide character case
19108 mapping function (<a href="#7.25.3.1">7.25.3.1</a>) in the comment that follows the expression:
19110 towctrans(wc, wctrans("tolower")) // towlower(wc)
19111 towctrans(wc, wctrans("toupper")) // towupper(wc)</pre>
19114 The towctrans function returns the mapped value of wc using the mapping described
19117 <h5><a name="7.25.3.2.2" href="#7.25.3.2.2">7.25.3.2.2 The wctrans function</a></h5>
19121 #include <a href="#7.25"><wctype.h></a>
19122 wctrans_t wctrans(const char *property);</pre>
19123 <h6>Description</h6>
19125 The wctrans function constructs a value with type wctrans_t that describes a
19126 mapping between wide characters identified by the string argument property.
19128 The strings listed in the description of the towctrans function shall be valid in all
19129 locales as property arguments to the wctrans function.
19132 If property identifies a valid mapping of wide characters according to the LC_CTYPE
19133 category of the current locale, the wctrans function returns a nonzero value that is valid
19134 as the second argument to the towctrans function; otherwise, it returns zero.
19137 <h3><a name="7.26" href="#7.26">7.26 Future library directions</a></h3>
19139 The following names are grouped under individual headers for convenience. All external
19140 names described below are reserved no matter what headers are included by the program.
19142 <h4><a name="7.26.1" href="#7.26.1">7.26.1 Complex arithmetic <complex.h></a></h4>
19147 cerfc clog10 clgamma
19148 cexp2 clog1p ctgamma</pre>
19149 and the same names suffixed with f or l may be added to the declarations in the
19150 <a href="#7.3"><complex.h></a> header.
19152 <h4><a name="7.26.2" href="#7.26.2">7.26.2 Character handling <ctype.h></a></h4>
19154 Function names that begin with either is or to, and a lowercase letter may be added to
19155 the declarations in the <a href="#7.4"><ctype.h></a> header.
19157 <h4><a name="7.26.3" href="#7.26.3">7.26.3 Errors <errno.h></a></h4>
19159 Macros that begin with E and a digit or E and an uppercase letter may be added to the
19160 declarations in the <a href="#7.5"><errno.h></a> header.
19162 <h4><a name="7.26.4" href="#7.26.4">7.26.4 Format conversion of integer types <inttypes.h></a></h4>
19164 Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
19165 added to the macros defined in the <a href="#7.8"><inttypes.h></a> header.
19167 <h4><a name="7.26.5" href="#7.26.5">7.26.5 Localization <locale.h></a></h4>
19169 Macros that begin with LC_ and an uppercase letter may be added to the definitions in
19170 the <a href="#7.11"><locale.h></a> header.
19172 <h4><a name="7.26.6" href="#7.26.6">7.26.6 Signal handling <signal.h></a></h4>
19174 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
19175 letter may be added to the definitions in the <a href="#7.14"><signal.h></a> header.
19177 <h4><a name="7.26.7" href="#7.26.7">7.26.7 Boolean type and values <stdbool.h></a></h4>
19179 The ability to undefine and perhaps then redefine the macros bool, true, and false is
19180 an obsolescent feature.
19182 <h4><a name="7.26.8" href="#7.26.8">7.26.8 Integer types <stdint.h></a></h4>
19184 Typedef names beginning with int or uint and ending with _t may be added to the
19185 types defined in the <a href="#7.18"><stdint.h></a> header. Macro names beginning with INT or UINT
19186 and ending with _MAX, _MIN, or _C may be added to the macros defined in the
19187 <a href="#7.18"><stdint.h></a> header.
19190 <h4><a name="7.26.9" href="#7.26.9">7.26.9 Input/output <stdio.h></a></h4>
19192 Lowercase letters may be added to the conversion specifiers and length modifiers in
19193 fprintf and fscanf. Other characters may be used in extensions.
19195 The gets function is obsolescent, and is deprecated.
19197 The use of ungetc on a binary stream where the file position indicator is zero prior to
19198 the call is an obsolescent feature.
19200 <h4><a name="7.26.10" href="#7.26.10">7.26.10 General utilities <stdlib.h></a></h4>
19202 Function names that begin with str and a lowercase letter may be added to the
19203 declarations in the <a href="#7.20"><stdlib.h></a> header.
19205 <h4><a name="7.26.11" href="#7.26.11">7.26.11 String handling <string.h></a></h4>
19207 Function names that begin with str, mem, or wcs and a lowercase letter may be added
19208 to the declarations in the <a href="#7.21"><string.h></a> header.
19210 <h4><a name="7.26.12" href="#7.26.12">7.26.12 Extended multibyte and wide character utilities <wchar.h></a></h4>
19212 Function names that begin with wcs and a lowercase letter may be added to the
19213 declarations in the <a href="#7.24"><wchar.h></a> header.
19215 Lowercase letters may be added to the conversion specifiers and length modifiers in
19216 fwprintf and fwscanf. Other characters may be used in extensions.
19218 <h4><a name="7.26.13" href="#7.26.13">7.26.13 Wide character classification and mapping utilities</a></h4>
19219 <a href="#7.25"><wctype.h></a>
19221 Function names that begin with is or to and a lowercase letter may be added to the
19222 declarations in the <a href="#7.25"><wctype.h></a> header.
19225 <h2><a name="A" href="#A">Annex A</a></h2>
19229 Language syntax summary</pre>
19230 NOTE The notation is described in <a href="#6.1">6.1</a>.
19233 <h3><a name="A.1" href="#A.1">A.1 Lexical grammar</a></h3>
19235 <h4><a name="A.1.1" href="#A.1.1">A.1.1 Lexical elements</a></h4>
19236 (<a href="#6.4">6.4</a>) token:
19243 (<a href="#6.4">6.4</a>) preprocessing-token:
19251 each non-white-space character that cannot be one of the above</pre>
19253 <h4><a name="A.1.2" href="#A.1.2">A.1.2 Keywords</a></h4>
19254 (<a href="#6.4.1">6.4.1</a>) keyword: one of
19257 auto enum restrict unsigned
19258 break extern return void
19259 case float short volatile
19260 char for signed while
19261 const goto sizeof _Bool
19262 continue if static _Complex
19263 default inline struct _Imaginary
19265 double long typedef
19266 else register union</pre>
19268 <h4><a name="A.1.3" href="#A.1.3">A.1.3 Identifiers</a></h4>
19269 (<a href="#6.4.2.1">6.4.2.1</a>) identifier:
19271 identifier-nondigit
19272 identifier identifier-nondigit
19273 identifier digit</pre>
19274 (<a href="#6.4.2.1">6.4.2.1</a>) identifier-nondigit:
19277 universal-character-name
19278 other implementation-defined characters</pre>
19279 (<a href="#6.4.2.1">6.4.2.1</a>) nondigit: one of
19281 _ a b c d e f g h i j k l m
19282 n o p q r s t u v w x y z
19283 A B C D E F G H I J K L M
19284 N O P Q R S T U V W X Y Z</pre>
19285 (<a href="#6.4.2.1">6.4.2.1</a>) digit: one of
19287 0 1 2 3 4 5 6 7 8 9</pre>
19289 <h4><a name="A.1.4" href="#A.1.4">A.1.4 Universal character names</a></h4>
19290 (<a href="#6.4.3">6.4.3</a>) universal-character-name:
19293 \U hex-quad hex-quad</pre>
19294 (<a href="#6.4.3">6.4.3</a>) hex-quad:
19296 hexadecimal-digit hexadecimal-digit
19297 hexadecimal-digit hexadecimal-digit</pre>
19299 <h4><a name="A.1.5" href="#A.1.5">A.1.5 Constants</a></h4>
19300 (<a href="#6.4.4">6.4.4</a>) constant:
19304 enumeration-constant
19305 character-constant</pre>
19306 (<a href="#6.4.4.1">6.4.4.1</a>) integer-constant:
19308 decimal-constant integer-suffixopt
19309 octal-constant integer-suffixopt
19310 hexadecimal-constant integer-suffixopt</pre>
19311 (<a href="#6.4.4.1">6.4.4.1</a>) decimal-constant:
19315 decimal-constant digit</pre>
19316 (<a href="#6.4.4.1">6.4.4.1</a>) octal-constant:
19319 octal-constant octal-digit</pre>
19320 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-constant:
19322 hexadecimal-prefix hexadecimal-digit
19323 hexadecimal-constant hexadecimal-digit</pre>
19324 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-prefix: one of
19327 (<a href="#6.4.4.1">6.4.4.1</a>) nonzero-digit: one of
19329 1 2 3 4 5 6 7 8 9</pre>
19330 (<a href="#6.4.4.1">6.4.4.1</a>) octal-digit: one of
19332 0 1 2 3 4 5 6 7</pre>
19333 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-digit: one of
19335 0 1 2 3 4 5 6 7 8 9
19338 (<a href="#6.4.4.1">6.4.4.1</a>) integer-suffix:
19340 unsigned-suffix long-suffixopt
19341 unsigned-suffix long-long-suffix
19342 long-suffix unsigned-suffixopt
19343 long-long-suffix unsigned-suffixopt</pre>
19344 (<a href="#6.4.4.1">6.4.4.1</a>) unsigned-suffix: one of
19347 (<a href="#6.4.4.1">6.4.4.1</a>) long-suffix: one of
19350 (<a href="#6.4.4.1">6.4.4.1</a>) long-long-suffix: one of
19353 (<a href="#6.4.4.2">6.4.4.2</a>) floating-constant:
19355 decimal-floating-constant
19356 hexadecimal-floating-constant</pre>
19357 (<a href="#6.4.4.2">6.4.4.2</a>) decimal-floating-constant:
19360 fractional-constant exponent-partopt floating-suffixopt
19361 digit-sequence exponent-part floating-suffixopt</pre>
19362 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-floating-constant:
19364 hexadecimal-prefix hexadecimal-fractional-constant
19365 binary-exponent-part floating-suffixopt
19366 hexadecimal-prefix hexadecimal-digit-sequence
19367 binary-exponent-part floating-suffixopt</pre>
19368 (<a href="#6.4.4.2">6.4.4.2</a>) fractional-constant:
19370 digit-sequenceopt . digit-sequence
19371 digit-sequence .</pre>
19372 (<a href="#6.4.4.2">6.4.4.2</a>) exponent-part:
19374 e signopt digit-sequence
19375 E signopt digit-sequence</pre>
19376 (<a href="#6.4.4.2">6.4.4.2</a>) sign: one of
19379 (<a href="#6.4.4.2">6.4.4.2</a>) digit-sequence:
19382 digit-sequence digit</pre>
19383 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-fractional-constant:
19385 hexadecimal-digit-sequenceopt .
19386 hexadecimal-digit-sequence
19387 hexadecimal-digit-sequence .</pre>
19388 (<a href="#6.4.4.2">6.4.4.2</a>) binary-exponent-part:
19390 p signopt digit-sequence
19391 P signopt digit-sequence</pre>
19392 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-digit-sequence:
19395 hexadecimal-digit-sequence hexadecimal-digit</pre>
19396 (<a href="#6.4.4.2">6.4.4.2</a>) floating-suffix: one of
19399 (<a href="#6.4.4.3">6.4.4.3</a>) enumeration-constant:
19402 (<a href="#6.4.4.4">6.4.4.4</a>) character-constant:
19405 ' c-char-sequence '
19406 L' c-char-sequence '</pre>
19407 (<a href="#6.4.4.4">6.4.4.4</a>) c-char-sequence:
19410 c-char-sequence c-char</pre>
19411 (<a href="#6.4.4.4">6.4.4.4</a>) c-char:
19413 any member of the source character set except
19414 the single-quote ', backslash \, or new-line character
19415 escape-sequence</pre>
19416 (<a href="#6.4.4.4">6.4.4.4</a>) escape-sequence:
19418 simple-escape-sequence
19419 octal-escape-sequence
19420 hexadecimal-escape-sequence
19421 universal-character-name</pre>
19422 (<a href="#6.4.4.4">6.4.4.4</a>) simple-escape-sequence: one of
19425 \a \b \f \n \r \t \v</pre>
19426 (<a href="#6.4.4.4">6.4.4.4</a>) octal-escape-sequence:
19429 \ octal-digit octal-digit
19430 \ octal-digit octal-digit octal-digit</pre>
19431 (<a href="#6.4.4.4">6.4.4.4</a>) hexadecimal-escape-sequence:
19433 \x hexadecimal-digit
19434 hexadecimal-escape-sequence hexadecimal-digit</pre>
19436 <h4><a name="A.1.6" href="#A.1.6">A.1.6 String literals</a></h4>
19437 (<a href="#6.4.5">6.4.5</a>) string-literal:
19439 " s-char-sequenceopt "
19440 L" s-char-sequenceopt "</pre>
19441 (<a href="#6.4.5">6.4.5</a>) s-char-sequence:
19444 s-char-sequence s-char</pre>
19445 (<a href="#6.4.5">6.4.5</a>) s-char:
19448 any member of the source character set except
19449 the double-quote ", backslash \, or new-line character
19450 escape-sequence</pre>
19452 <h4><a name="A.1.7" href="#A.1.7">A.1.7 Punctuators</a></h4>
19453 (<a href="#6.4.6">6.4.6</a>) punctuator: one of
19455 [ ] ( ) { } . ->
19456 ++ -- & * + - ~ !
19457 / % << >> < > <= >= == != ^ | && ||
19459 = *= /= %= += -= <<= >>= &= ^= |=
19461 <: :> <% %> %: %:%:</pre>
19463 <h4><a name="A.1.8" href="#A.1.8">A.1.8 Header names</a></h4>
19464 (<a href="#6.4.7">6.4.7</a>) header-name:
19466 < h-char-sequence >
19467 " q-char-sequence "</pre>
19468 (<a href="#6.4.7">6.4.7</a>) h-char-sequence:
19471 h-char-sequence h-char</pre>
19472 (<a href="#6.4.7">6.4.7</a>) h-char:
19474 any member of the source character set except
19475 the new-line character and ></pre>
19476 (<a href="#6.4.7">6.4.7</a>) q-char-sequence:
19479 q-char-sequence q-char</pre>
19480 (<a href="#6.4.7">6.4.7</a>) q-char:
19482 any member of the source character set except
19483 the new-line character and "</pre>
19485 <h4><a name="A.1.9" href="#A.1.9">A.1.9 Preprocessing numbers</a></h4>
19486 (<a href="#6.4.8">6.4.8</a>) pp-number:
19492 pp-number identifier-nondigit
19499 <h3><a name="A.2" href="#A.2">A.2 Phrase structure grammar</a></h3>
19501 <h4><a name="A.2.1" href="#A.2.1">A.2.1 Expressions</a></h4>
19502 (<a href="#6.5.1">6.5.1</a>) primary-expression:
19507 ( expression )</pre>
19508 (<a href="#6.5.2">6.5.2</a>) postfix-expression:
19511 postfix-expression [ expression ]
19512 postfix-expression ( argument-expression-listopt )
19513 postfix-expression . identifier
19514 postfix-expression -> identifier
19515 postfix-expression ++
19516 postfix-expression --
19517 ( type-name ) { initializer-list }
19518 ( type-name ) { initializer-list , }</pre>
19519 (<a href="#6.5.2">6.5.2</a>) argument-expression-list:
19521 assignment-expression
19522 argument-expression-list , assignment-expression</pre>
19523 (<a href="#6.5.3">6.5.3</a>) unary-expression:
19526 ++ unary-expression
19527 -- unary-expression
19528 unary-operator cast-expression
19529 sizeof unary-expression
19530 sizeof ( type-name )</pre>
19531 (<a href="#6.5.3">6.5.3</a>) unary-operator: one of
19533 & * + - ~ !</pre>
19534 (<a href="#6.5.4">6.5.4</a>) cast-expression:
19537 ( type-name ) cast-expression</pre>
19538 (<a href="#6.5.5">6.5.5</a>) multiplicative-expression:
19542 multiplicative-expression * cast-expression
19543 multiplicative-expression / cast-expression
19544 multiplicative-expression % cast-expression</pre>
19545 (<a href="#6.5.6">6.5.6</a>) additive-expression:
19547 multiplicative-expression
19548 additive-expression + multiplicative-expression
19549 additive-expression - multiplicative-expression</pre>
19550 (<a href="#6.5.7">6.5.7</a>) shift-expression:
19552 additive-expression
19553 shift-expression << additive-expression
19554 shift-expression >> additive-expression</pre>
19555 (<a href="#6.5.8">6.5.8</a>) relational-expression:
19558 relational-expression < shift-expression
19559 relational-expression > shift-expression
19560 relational-expression <= shift-expression
19561 relational-expression >= shift-expression</pre>
19562 (<a href="#6.5.9">6.5.9</a>) equality-expression:
19564 relational-expression
19565 equality-expression == relational-expression
19566 equality-expression != relational-expression</pre>
19567 (<a href="#6.5.10">6.5.10</a>) AND-expression:
19569 equality-expression
19570 AND-expression & equality-expression</pre>
19571 (<a href="#6.5.11">6.5.11</a>) exclusive-OR-expression:
19574 exclusive-OR-expression ^ AND-expression</pre>
19575 (<a href="#6.5.12">6.5.12</a>) inclusive-OR-expression:
19577 exclusive-OR-expression
19578 inclusive-OR-expression | exclusive-OR-expression</pre>
19579 (<a href="#6.5.13">6.5.13</a>) logical-AND-expression:
19581 inclusive-OR-expression
19582 logical-AND-expression && inclusive-OR-expression</pre>
19583 (<a href="#6.5.14">6.5.14</a>) logical-OR-expression:
19585 logical-AND-expression
19586 logical-OR-expression || logical-AND-expression</pre>
19587 (<a href="#6.5.15">6.5.15</a>) conditional-expression:
19590 logical-OR-expression
19591 logical-OR-expression ? expression : conditional-expression</pre>
19592 (<a href="#6.5.16">6.5.16</a>) assignment-expression:
19594 conditional-expression
19595 unary-expression assignment-operator assignment-expression</pre>
19596 (<a href="#6.5.16">6.5.16</a>) assignment-operator: one of
19598 = *= /= %= += -= <<= >>= &= ^= |=</pre>
19599 (<a href="#6.5.17">6.5.17</a>) expression:
19601 assignment-expression
19602 expression , assignment-expression</pre>
19603 (<a href="#6.6">6.6</a>) constant-expression:
19605 conditional-expression</pre>
19607 <h4><a name="A.2.2" href="#A.2.2">A.2.2 Declarations</a></h4>
19608 (<a href="#6.7">6.7</a>) declaration:
19610 declaration-specifiers init-declarator-listopt ;</pre>
19611 (<a href="#6.7">6.7</a>) declaration-specifiers:
19613 storage-class-specifier declaration-specifiersopt
19614 type-specifier declaration-specifiersopt
19615 type-qualifier declaration-specifiersopt
19616 function-specifier declaration-specifiersopt</pre>
19617 (<a href="#6.7">6.7</a>) init-declarator-list:
19620 init-declarator-list , init-declarator</pre>
19621 (<a href="#6.7">6.7</a>) init-declarator:
19624 declarator = initializer</pre>
19625 (<a href="#6.7.1">6.7.1</a>) storage-class-specifier:
19633 (<a href="#6.7.2">6.7.2</a>) type-specifier:
19646 struct-or-union-specifier *
19649 (<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union-specifier:
19651 struct-or-union identifieropt { struct-declaration-list }
19652 struct-or-union identifier</pre>
19653 (<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union:
19657 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration-list:
19660 struct-declaration-list struct-declaration</pre>
19661 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration:
19663 specifier-qualifier-list struct-declarator-list ;</pre>
19664 (<a href="#6.7.2.1">6.7.2.1</a>) specifier-qualifier-list:
19666 type-specifier specifier-qualifier-listopt
19667 type-qualifier specifier-qualifier-listopt</pre>
19668 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator-list:
19671 struct-declarator-list , struct-declarator</pre>
19672 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator:
19676 declaratoropt : constant-expression</pre>
19677 (<a href="#6.7.2.2">6.7.2.2</a>) enum-specifier:
19679 enum identifieropt { enumerator-list }
19680 enum identifieropt { enumerator-list , }
19681 enum identifier</pre>
19682 (<a href="#6.7.2.2">6.7.2.2</a>) enumerator-list:
19685 enumerator-list , enumerator</pre>
19686 (<a href="#6.7.2.2">6.7.2.2</a>) enumerator:
19688 enumeration-constant
19689 enumeration-constant = constant-expression</pre>
19690 (<a href="#6.7.3">6.7.3</a>) type-qualifier:
19695 (<a href="#6.7.4">6.7.4</a>) function-specifier:
19698 (<a href="#6.7.5">6.7.5</a>) declarator:
19700 pointeropt direct-declarator</pre>
19701 (<a href="#6.7.5">6.7.5</a>) direct-declarator:
19705 direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
19706 direct-declarator [ static type-qualifier-listopt assignment-expression ]
19707 direct-declarator [ type-qualifier-list static assignment-expression ]
19708 direct-declarator [ type-qualifier-listopt * ]
19709 direct-declarator ( parameter-type-list )
19710 direct-declarator ( identifier-listopt )</pre>
19711 (<a href="#6.7.5">6.7.5</a>) pointer:
19713 * type-qualifier-listopt
19714 * type-qualifier-listopt pointer</pre>
19715 (<a href="#6.7.5">6.7.5</a>) type-qualifier-list:
19718 type-qualifier-list type-qualifier</pre>
19719 (<a href="#6.7.5">6.7.5</a>) parameter-type-list:
19723 parameter-list , ...</pre>
19724 (<a href="#6.7.5">6.7.5</a>) parameter-list:
19726 parameter-declaration
19727 parameter-list , parameter-declaration</pre>
19728 (<a href="#6.7.5">6.7.5</a>) parameter-declaration:
19730 declaration-specifiers declarator
19731 declaration-specifiers abstract-declaratoropt</pre>
19732 (<a href="#6.7.5">6.7.5</a>) identifier-list:
19735 identifier-list , identifier</pre>
19736 (<a href="#6.7.6">6.7.6</a>) type-name:
19738 specifier-qualifier-list abstract-declaratoropt</pre>
19739 (<a href="#6.7.6">6.7.6</a>) abstract-declarator:
19742 pointeropt direct-abstract-declarator</pre>
19743 (<a href="#6.7.6">6.7.6</a>) direct-abstract-declarator:
19745 ( abstract-declarator )
19746 direct-abstract-declaratoropt [ type-qualifier-listopt
19747 assignment-expressionopt ]
19748 direct-abstract-declaratoropt [ static type-qualifier-listopt
19749 assignment-expression ]
19750 direct-abstract-declaratoropt [ type-qualifier-list static
19751 assignment-expression ]
19752 direct-abstract-declaratoropt [ * ]
19753 direct-abstract-declaratoropt ( parameter-type-listopt )</pre>
19754 (<a href="#6.7.7">6.7.7</a>) typedef-name:
19757 (<a href="#6.7.8">6.7.8</a>) initializer:
19759 assignment-expression
19760 { initializer-list }
19761 { initializer-list , }</pre>
19762 (<a href="#6.7.8">6.7.8</a>) initializer-list:
19764 designationopt initializer
19765 initializer-list , designationopt initializer</pre>
19766 (<a href="#6.7.8">6.7.8</a>) designation:
19769 designator-list =</pre>
19770 (<a href="#6.7.8">6.7.8</a>) designator-list:
19773 designator-list designator</pre>
19774 (<a href="#6.7.8">6.7.8</a>) designator:
19776 [ constant-expression ]
19779 <h4><a name="A.2.3" href="#A.2.3">A.2.3 Statements</a></h4>
19780 (<a href="#6.8">6.8</a>) statement:
19784 expression-statement
19785 selection-statement
19786 iteration-statement
19787 jump-statement</pre>
19788 (<a href="#6.8.1">6.8.1</a>) labeled-statement:
19790 identifier : statement
19791 case constant-expression : statement
19792 default : statement</pre>
19793 (<a href="#6.8.2">6.8.2</a>) compound-statement:
19795 { block-item-listopt }</pre>
19796 (<a href="#6.8.2">6.8.2</a>) block-item-list:
19799 block-item-list block-item</pre>
19800 (<a href="#6.8.2">6.8.2</a>) block-item:
19804 (<a href="#6.8.3">6.8.3</a>) expression-statement:
19806 expressionopt ;</pre>
19807 (<a href="#6.8.4">6.8.4</a>) selection-statement:
19810 if ( expression ) statement
19811 if ( expression ) statement else statement
19812 switch ( expression ) statement</pre>
19813 (<a href="#6.8.5">6.8.5</a>) iteration-statement:
19815 while ( expression ) statement
19816 do statement while ( expression ) ;
19817 for ( expressionopt ; expressionopt ; expressionopt ) statement
19818 for ( declaration expressionopt ; expressionopt ) statement</pre>
19819 (<a href="#6.8.6">6.8.6</a>) jump-statement:
19824 return expressionopt ;</pre>
19826 <h4><a name="A.2.4" href="#A.2.4">A.2.4 External definitions</a></h4>
19827 (<a href="#6.9">6.9</a>) translation-unit:
19829 external-declaration
19830 translation-unit external-declaration</pre>
19831 (<a href="#6.9">6.9</a>) external-declaration:
19833 function-definition
19835 (<a href="#6.9.1">6.9.1</a>) function-definition:
19837 declaration-specifiers declarator declaration-listopt compound-statement</pre>
19838 (<a href="#6.9.1">6.9.1</a>) declaration-list:
19841 declaration-list declaration</pre>
19843 <h3><a name="A.3" href="#A.3">A.3 Preprocessing directives</a></h3>
19844 (<a href="#6.10">6.10</a>) preprocessing-file:
19847 (<a href="#6.10">6.10</a>) group:
19850 group group-part</pre>
19851 (<a href="#6.10">6.10</a>) group-part:
19856 # non-directive</pre>
19857 (<a href="#6.10">6.10</a>) if-section:
19860 if-group elif-groupsopt else-groupopt endif-line</pre>
19861 (<a href="#6.10">6.10</a>) if-group:
19863 # if constant-expression new-line groupopt
19864 # ifdef identifier new-line groupopt
19865 # ifndef identifier new-line groupopt</pre>
19866 (<a href="#6.10">6.10</a>) elif-groups:
19869 elif-groups elif-group</pre>
19870 (<a href="#6.10">6.10</a>) elif-group:
19872 # elif constant-expression new-line groupopt</pre>
19873 (<a href="#6.10">6.10</a>) else-group:
19875 # else new-line groupopt</pre>
19876 (<a href="#6.10">6.10</a>) endif-line:
19878 # endif new-line</pre>
19879 (<a href="#6.10">6.10</a>) control-line:
19881 # include pp-tokens new-line
19882 # define identifier replacement-list new-line
19883 # define identifier lparen identifier-listopt )
19884 replacement-list new-line
19885 # define identifier lparen ... ) replacement-list new-line
19886 # define identifier lparen identifier-list , ... )
19887 replacement-list new-line
19888 # undef identifier new-line
19889 # line pp-tokens new-line
19890 # error pp-tokensopt new-line
19891 # pragma pp-tokensopt new-line
19893 (<a href="#6.10">6.10</a>) text-line:
19895 pp-tokensopt new-line</pre>
19896 (<a href="#6.10">6.10</a>) non-directive:
19898 pp-tokens new-line</pre>
19899 (<a href="#6.10">6.10</a>) lparen:
19901 a ( character not immediately preceded by white-space</pre>
19902 (<a href="#6.10">6.10</a>) replacement-list:
19906 (<a href="#6.10">6.10</a>) pp-tokens:
19908 preprocessing-token
19909 pp-tokens preprocessing-token</pre>
19910 (<a href="#6.10">6.10</a>) new-line:
19913 the new-line character</pre>
19915 <h2><a name="B" href="#B">Annex B</a></h2>
19918 Library summary</pre>
19920 <h3><a name="B.1" href="#B.1">B.1 Diagnostics <assert.h></a></h3>
19923 void assert(scalar expression);</pre>
19925 <h3><a name="B.2" href="#B.2">B.2 Complex <complex.h></a></h3>
19929 complex imaginary I
19930 _Complex_I _Imaginary_I
19931 #pragma STDC CX_LIMITED_RANGE on-off-switch
19932 double complex cacos(double complex z);
19933 float complex cacosf(float complex z);
19934 long double complex cacosl(long double complex z);
19935 double complex casin(double complex z);
19936 float complex casinf(float complex z);
19937 long double complex casinl(long double complex z);
19938 double complex catan(double complex z);
19939 float complex catanf(float complex z);
19940 long double complex catanl(long double complex z);
19941 double complex ccos(double complex z);
19942 float complex ccosf(float complex z);
19943 long double complex ccosl(long double complex z);
19944 double complex csin(double complex z);
19945 float complex csinf(float complex z);
19946 long double complex csinl(long double complex z);
19947 double complex ctan(double complex z);
19948 float complex ctanf(float complex z);
19949 long double complex ctanl(long double complex z);
19950 double complex cacosh(double complex z);
19951 float complex cacoshf(float complex z);
19952 long double complex cacoshl(long double complex z);
19953 double complex casinh(double complex z);
19954 float complex casinhf(float complex z);
19955 long double complex casinhl(long double complex z);
19956 double complex catanh(double complex z);
19957 float complex catanhf(float complex z);
19958 long double complex catanhl(long double complex z);
19959 double complex ccosh(double complex z);
19960 float complex ccoshf(float complex z);
19961 long double complex ccoshl(long double complex z);
19962 double complex csinh(double complex z);
19963 float complex csinhf(float complex z);
19964 long double complex csinhl(long double complex z);
19965 double complex ctanh(double complex z);
19966 float complex ctanhf(float complex z);
19967 long double complex ctanhl(long double complex z);
19968 double complex cexp(double complex z);
19969 float complex cexpf(float complex z);
19970 long double complex cexpl(long double complex z);
19971 double complex clog(double complex z);
19972 float complex clogf(float complex z);
19973 long double complex clogl(long double complex z);
19974 double cabs(double complex z);
19975 float cabsf(float complex z);
19976 long double cabsl(long double complex z);
19977 double complex cpow(double complex x, double complex y);
19978 float complex cpowf(float complex x, float complex y);
19979 long double complex cpowl(long double complex x,
19980 long double complex y);
19981 double complex csqrt(double complex z);
19982 float complex csqrtf(float complex z);
19983 long double complex csqrtl(long double complex z);
19984 double carg(double complex z);
19985 float cargf(float complex z);
19986 long double cargl(long double complex z);
19987 double cimag(double complex z);
19988 float cimagf(float complex z);
19989 long double cimagl(long double complex z);
19990 double complex conj(double complex z);
19991 float complex conjf(float complex z);
19992 long double complex conjl(long double complex z);
19993 double complex cproj(double complex z);
19994 float complex cprojf(float complex z);
19995 long double complex cprojl(long double complex z);
19996 double creal(double complex z);
19997 float crealf(float complex z);
19998 long double creall(long double complex z);</pre>
20000 <h3><a name="B.3" href="#B.3">B.3 Character handling <ctype.h></a></h3>
20002 int isalnum(int c);
20003 int isalpha(int c);
20004 int isblank(int c);
20005 int iscntrl(int c);
20006 int isdigit(int c);
20007 int isgraph(int c);
20008 int islower(int c);
20009 int isprint(int c);
20010 int ispunct(int c);
20011 int isspace(int c);
20012 int isupper(int c);
20013 int isxdigit(int c);
20014 int tolower(int c);
20015 int toupper(int c);</pre>
20017 <h3><a name="B.4" href="#B.4">B.4 Errors <errno.h></a></h3>
20019 EDOM EILSEQ ERANGE errno</pre>
20021 <h3><a name="B.5" href="#B.5">B.5 Floating-point environment <fenv.h></a></h3>
20024 fenv_t FE_OVERFLOW FE_TOWARDZERO
20025 fexcept_t FE_UNDERFLOW FE_UPWARD
20026 FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
20027 FE_INEXACT FE_DOWNWARD
20028 FE_INVALID FE_TONEAREST
20029 #pragma STDC FENV_ACCESS on-off-switch
20030 int feclearexcept(int excepts);
20031 int fegetexceptflag(fexcept_t *flagp, int excepts);
20032 int feraiseexcept(int excepts);
20033 int fesetexceptflag(const fexcept_t *flagp,
20035 int fetestexcept(int excepts);
20036 int fegetround(void);
20037 int fesetround(int round);
20038 int fegetenv(fenv_t *envp);
20039 int feholdexcept(fenv_t *envp);
20040 int fesetenv(const fenv_t *envp);
20041 int feupdateenv(const fenv_t *envp);</pre>
20043 <h3><a name="B.6" href="#B.6">B.6 Characteristics of floating types <float.h></a></h3>
20045 FLT_ROUNDS DBL_MIN_EXP FLT_MAX
20046 FLT_EVAL_METHOD LDBL_MIN_EXP DBL_MAX
20047 FLT_RADIX FLT_MIN_10_EXP LDBL_MAX
20048 FLT_MANT_DIG DBL_MIN_10_EXP FLT_EPSILON
20049 DBL_MANT_DIG LDBL_MIN_10_EXP DBL_EPSILON
20050 LDBL_MANT_DIG FLT_MAX_EXP LDBL_EPSILON
20051 DECIMAL_DIG DBL_MAX_EXP FLT_MIN
20052 FLT_DIG LDBL_MAX_EXP DBL_MIN
20053 DBL_DIG FLT_MAX_10_EXP LDBL_MIN
20054 LDBL_DIG DBL_MAX_10_EXP
20055 FLT_MIN_EXP LDBL_MAX_10_EXP</pre>
20057 <h3><a name="B.7" href="#B.7">B.7 Format conversion of integer types <inttypes.h></a></h3>
20061 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
20062 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
20063 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
20064 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
20065 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
20066 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
20067 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
20068 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
20069 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
20070 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
20071 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
20072 intmax_t imaxabs(intmax_t j);
20073 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
20074 intmax_t strtoimax(const char * restrict nptr,
20075 char ** restrict endptr, int base);
20076 uintmax_t strtoumax(const char * restrict nptr,
20077 char ** restrict endptr, int base);
20078 intmax_t wcstoimax(const wchar_t * restrict nptr,
20079 wchar_t ** restrict endptr, int base);
20080 uintmax_t wcstoumax(const wchar_t * restrict nptr,
20081 wchar_t ** restrict endptr, int base);</pre>
20083 <h3><a name="B.8" href="#B.8">B.8 Alternative spellings <iso646.h></a></h3>
20085 and bitor not_eq xor
20086 and_eq compl or xor_eq
20087 bitand not or_eq</pre>
20089 <h3><a name="B.9" href="#B.9">B.9 Sizes of integer types <limits.h></a></h3>
20091 CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
20092 SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
20093 SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
20094 UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
20095 CHAR_MIN USHRT_MAX LONG_MAX</pre>
20097 <h3><a name="B.10" href="#B.10">B.10 Localization <locale.h></a></h3>
20099 struct lconv LC_ALL LC_CTYPE LC_NUMERIC
20100 NULL LC_COLLATE LC_MONETARY LC_TIME
20101 char *setlocale(int category, const char *locale);
20102 struct lconv *localeconv(void);</pre>
20104 <h3><a name="B.11" href="#B.11">B.11 Mathematics <math.h></a></h3>
20111 float_t FP_INFINITE FP_FAST_FMAL
20112 double_t FP_NAN FP_ILOGB0
20113 HUGE_VAL FP_NORMAL FP_ILOGBNAN
20114 HUGE_VALF FP_SUBNORMAL MATH_ERRNO
20115 HUGE_VALL FP_ZERO MATH_ERREXCEPT
20116 INFINITY FP_FAST_FMA math_errhandling
20118 #pragma STDC FP_CONTRACT on-off-switch
20119 int fpclassify(real-floating x);
20120 int isfinite(real-floating x);
20121 int isinf(real-floating x);
20122 int isnan(real-floating x);
20123 int isnormal(real-floating x);
20124 int signbit(real-floating x);
20125 double acos(double x);
20126 float acosf(float x);
20127 long double acosl(long double x);
20128 double asin(double x);
20129 float asinf(float x);
20130 long double asinl(long double x);
20131 double atan(double x);
20132 float atanf(float x);
20133 long double atanl(long double x);
20134 double atan2(double y, double x);
20135 float atan2f(float y, float x);
20136 long double atan2l(long double y, long double x);
20137 double cos(double x);
20138 float cosf(float x);
20139 long double cosl(long double x);
20140 double sin(double x);
20141 float sinf(float x);
20142 long double sinl(long double x);
20143 double tan(double x);
20144 float tanf(float x);
20145 long double tanl(long double x);
20146 double acosh(double x);
20147 float acoshf(float x);
20148 long double acoshl(long double x);
20149 double asinh(double x);
20150 float asinhf(float x);
20151 long double asinhl(long double x);
20152 double atanh(double x);
20153 float atanhf(float x);
20154 long double atanhl(long double x);
20155 double cosh(double x);
20156 float coshf(float x);
20157 long double coshl(long double x);
20158 double sinh(double x);
20159 float sinhf(float x);
20160 long double sinhl(long double x);
20161 double tanh(double x);
20162 float tanhf(float x);
20163 long double tanhl(long double x);
20164 double exp(double x);
20165 float expf(float x);
20166 long double expl(long double x);
20167 double exp2(double x);
20168 float exp2f(float x);
20169 long double exp2l(long double x);
20170 double expm1(double x);
20171 float expm1f(float x);
20172 long double expm1l(long double x);
20173 double frexp(double value, int *exp);
20174 float frexpf(float value, int *exp);
20175 long double frexpl(long double value, int *exp);
20176 int ilogb(double x);
20177 int ilogbf(float x);
20178 int ilogbl(long double x);
20179 double ldexp(double x, int exp);
20180 float ldexpf(float x, int exp);
20181 long double ldexpl(long double x, int exp);
20182 double log(double x);
20183 float logf(float x);
20184 long double logl(long double x);
20185 double log10(double x);
20186 float log10f(float x);
20187 long double log10l(long double x);
20188 double log1p(double x);
20189 float log1pf(float x);
20190 long double log1pl(long double x);
20191 double log2(double x);
20192 float log2f(float x);
20193 long double log2l(long double x);
20194 double logb(double x);
20195 float logbf(float x);
20196 long double logbl(long double x);
20197 double modf(double value, double *iptr);
20198 float modff(float value, float *iptr);
20199 long double modfl(long double value, long double *iptr);
20200 double scalbn(double x, int n);
20201 float scalbnf(float x, int n);
20202 long double scalbnl(long double x, int n);
20203 double scalbln(double x, long int n);
20204 float scalblnf(float x, long int n);
20205 long double scalblnl(long double x, long int n);
20206 double cbrt(double x);
20207 float cbrtf(float x);
20208 long double cbrtl(long double x);
20209 double fabs(double x);
20210 float fabsf(float x);
20211 long double fabsl(long double x);
20212 double hypot(double x, double y);
20213 float hypotf(float x, float y);
20214 long double hypotl(long double x, long double y);
20215 double pow(double x, double y);
20216 float powf(float x, float y);
20217 long double powl(long double x, long double y);
20218 double sqrt(double x);
20219 float sqrtf(float x);
20220 long double sqrtl(long double x);
20221 double erf(double x);
20222 float erff(float x);
20223 long double erfl(long double x);
20224 double erfc(double x);
20225 float erfcf(float x);
20226 long double erfcl(long double x);
20227 double lgamma(double x);
20228 float lgammaf(float x);
20229 long double lgammal(long double x);
20230 double tgamma(double x);
20231 float tgammaf(float x);
20232 long double tgammal(long double x);
20233 double ceil(double x);
20234 float ceilf(float x);
20235 long double ceill(long double x);
20236 double floor(double x);
20237 float floorf(float x);
20238 long double floorl(long double x);
20239 double nearbyint(double x);
20240 float nearbyintf(float x);
20241 long double nearbyintl(long double x);
20242 double rint(double x);
20243 float rintf(float x);
20244 long double rintl(long double x);
20245 long int lrint(double x);
20246 long int lrintf(float x);
20247 long int lrintl(long double x);
20248 long long int llrint(double x);
20249 long long int llrintf(float x);
20250 long long int llrintl(long double x);
20251 double round(double x);
20252 float roundf(float x);
20253 long double roundl(long double x);
20254 long int lround(double x);
20255 long int lroundf(float x);
20256 long int lroundl(long double x);
20257 long long int llround(double x);
20258 long long int llroundf(float x);
20259 long long int llroundl(long double x);
20260 double trunc(double x);
20261 float truncf(float x);
20262 long double truncl(long double x);
20263 double fmod(double x, double y);
20264 float fmodf(float x, float y);
20265 long double fmodl(long double x, long double y);
20266 double remainder(double x, double y);
20267 float remainderf(float x, float y);
20268 long double remainderl(long double x, long double y);
20269 double remquo(double x, double y, int *quo);
20270 float remquof(float x, float y, int *quo);
20271 long double remquol(long double x, long double y,
20273 double copysign(double x, double y);
20274 float copysignf(float x, float y);
20275 long double copysignl(long double x, long double y);
20276 double nan(const char *tagp);
20277 float nanf(const char *tagp);
20278 long double nanl(const char *tagp);
20279 double nextafter(double x, double y);
20280 float nextafterf(float x, float y);
20281 long double nextafterl(long double x, long double y);
20282 double nexttoward(double x, long double y);
20283 float nexttowardf(float x, long double y);
20284 long double nexttowardl(long double x, long double y);
20285 double fdim(double x, double y);
20286 float fdimf(float x, float y);
20287 long double fdiml(long double x, long double y);
20288 double fmax(double x, double y);
20289 float fmaxf(float x, float y);
20290 long double fmaxl(long double x, long double y);
20291 double fmin(double x, double y);
20292 float fminf(float x, float y);
20293 long double fminl(long double x, long double y);
20294 double fma(double x, double y, double z);
20295 float fmaf(float x, float y, float z);
20296 long double fmal(long double x, long double y,
20298 int isgreater(real-floating x, real-floating y);
20299 int isgreaterequal(real-floating x, real-floating y);
20300 int isless(real-floating x, real-floating y);
20301 int islessequal(real-floating x, real-floating y);
20302 int islessgreater(real-floating x, real-floating y);
20303 int isunordered(real-floating x, real-floating y);</pre>
20305 <h3><a name="B.12" href="#B.12">B.12 Nonlocal jumps <setjmp.h></a></h3>
20308 int setjmp(jmp_buf env);
20309 void longjmp(jmp_buf env, int val);</pre>
20311 <h3><a name="B.13" href="#B.13">B.13 Signal handling <signal.h></a></h3>
20313 sig_atomic_t SIG_IGN SIGILL SIGTERM
20314 SIG_DFL SIGABRT SIGINT
20315 SIG_ERR SIGFPE SIGSEGV
20316 void (*signal(int sig, void (*func)(int)))(int);
20317 int raise(int sig);</pre>
20319 <h3><a name="B.14" href="#B.14">B.14 Variable arguments <stdarg.h></a></h3>
20322 type va_arg(va_list ap, type);
20323 void va_copy(va_list dest, va_list src);
20324 void va_end(va_list ap);
20325 void va_start(va_list ap, parmN);</pre>
20327 <h3><a name="B.15" href="#B.15">B.15 Boolean type and values <stdbool.h></a></h3>
20333 __bool_true_false_are_defined</pre>
20335 <h3><a name="B.16" href="#B.16">B.16 Common definitions <stddef.h></a></h3>
20337 ptrdiff_t size_t wchar_t NULL
20338 offsetof(type, member-designator)</pre>
20340 <h3><a name="B.17" href="#B.17">B.17 Integer types <stdint.h></a></h3>
20342 intN_t INT_LEASTN_MIN PTRDIFF_MAX
20343 uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
20344 int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
20345 uint_leastN_t INT_FASTN_MIN SIZE_MAX
20346 int_fastN_t INT_FASTN_MAX WCHAR_MIN
20347 uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
20348 intptr_t INTPTR_MIN WINT_MIN
20349 uintptr_t INTPTR_MAX WINT_MAX
20350 intmax_t UINTPTR_MAX INTN_C(value)
20351 uintmax_t INTMAX_MIN UINTN_C(value)
20352 INTN_MIN INTMAX_MAX INTMAX_C(value)
20353 INTN_MAX UINTMAX_MAX UINTMAX_C(value)
20354 UINTN_MAX PTRDIFF_MIN</pre>
20356 <h3><a name="B.18" href="#B.18">B.18 Input/output <stdio.h></a></h3>
20360 size_t _IOLBF FILENAME_MAX TMP_MAX
20361 FILE _IONBF L_tmpnam stderr
20362 fpos_t BUFSIZ SEEK_CUR stdin
20363 NULL EOF SEEK_END stdout
20364 _IOFBF FOPEN_MAX SEEK_SET
20365 int remove(const char *filename);
20366 int rename(const char *old, const char *new);
20367 FILE *tmpfile(void);
20368 char *tmpnam(char *s);
20369 int fclose(FILE *stream);
20370 int fflush(FILE *stream);
20371 FILE *fopen(const char * restrict filename,
20372 const char * restrict mode);
20373 FILE *freopen(const char * restrict filename,
20374 const char * restrict mode,
20375 FILE * restrict stream);
20376 void setbuf(FILE * restrict stream,
20377 char * restrict buf);
20378 int setvbuf(FILE * restrict stream,
20379 char * restrict buf,
20380 int mode, size_t size);
20381 int fprintf(FILE * restrict stream,
20382 const char * restrict format, ...);
20383 int fscanf(FILE * restrict stream,
20384 const char * restrict format, ...);
20385 int printf(const char * restrict format, ...);
20386 int scanf(const char * restrict format, ...);
20387 int snprintf(char * restrict s, size_t n,
20388 const char * restrict format, ...);
20389 int sprintf(char * restrict s,
20390 const char * restrict format, ...);
20391 int sscanf(const char * restrict s,
20392 const char * restrict format, ...);
20393 int vfprintf(FILE * restrict stream,
20394 const char * restrict format, va_list arg);
20395 int vfscanf(FILE * restrict stream,
20396 const char * restrict format, va_list arg);
20397 int vprintf(const char * restrict format, va_list arg);
20398 int vscanf(const char * restrict format, va_list arg);
20399 int vsnprintf(char * restrict s, size_t n,
20400 const char * restrict format, va_list arg);
20401 int vsprintf(char * restrict s,
20402 const char * restrict format, va_list arg);
20403 int vsscanf(const char * restrict s,
20404 const char * restrict format, va_list arg);
20405 int fgetc(FILE *stream);
20406 char *fgets(char * restrict s, int n,
20407 FILE * restrict stream);
20408 int fputc(int c, FILE *stream);
20409 int fputs(const char * restrict s,
20410 FILE * restrict stream);
20411 int getc(FILE *stream);
20413 char *gets(char *s);
20414 int putc(int c, FILE *stream);
20415 int putchar(int c);
20416 int puts(const char *s);
20417 int ungetc(int c, FILE *stream);
20418 size_t fread(void * restrict ptr,
20419 size_t size, size_t nmemb,
20420 FILE * restrict stream);
20421 size_t fwrite(const void * restrict ptr,
20422 size_t size, size_t nmemb,
20423 FILE * restrict stream);
20424 int fgetpos(FILE * restrict stream,
20425 fpos_t * restrict pos);
20426 int fseek(FILE *stream, long int offset, int whence);
20427 int fsetpos(FILE *stream, const fpos_t *pos);
20428 long int ftell(FILE *stream);
20429 void rewind(FILE *stream);
20430 void clearerr(FILE *stream);
20431 int feof(FILE *stream);
20432 int ferror(FILE *stream);
20433 void perror(const char *s);</pre>
20435 <h3><a name="B.19" href="#B.19">B.19 General utilities <stdlib.h></a></h3>
20439 size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
20440 wchar_t lldiv_t EXIT_SUCCESS
20441 div_t NULL RAND_MAX
20442 double atof(const char *nptr);
20443 int atoi(const char *nptr);
20444 long int atol(const char *nptr);
20445 long long int atoll(const char *nptr);
20446 double strtod(const char * restrict nptr,
20447 char ** restrict endptr);
20448 float strtof(const char * restrict nptr,
20449 char ** restrict endptr);
20450 long double strtold(const char * restrict nptr,
20451 char ** restrict endptr);
20452 long int strtol(const char * restrict nptr,
20453 char ** restrict endptr, int base);
20454 long long int strtoll(const char * restrict nptr,
20455 char ** restrict endptr, int base);
20456 unsigned long int strtoul(
20457 const char * restrict nptr,
20458 char ** restrict endptr, int base);
20459 unsigned long long int strtoull(
20460 const char * restrict nptr,
20461 char ** restrict endptr, int base);
20463 void srand(unsigned int seed);
20464 void *calloc(size_t nmemb, size_t size);
20465 void free(void *ptr);
20466 void *malloc(size_t size);
20467 void *realloc(void *ptr, size_t size);
20469 int atexit(void (*func)(void));
20470 void exit(int status);
20471 void _Exit(int status);
20472 char *getenv(const char *name);
20473 int system(const char *string);
20474 void *bsearch(const void *key, const void *base,
20475 size_t nmemb, size_t size,
20476 int (*compar)(const void *, const void *));
20477 void qsort(void *base, size_t nmemb, size_t size,
20478 int (*compar)(const void *, const void *));
20480 long int labs(long int j);
20481 long long int llabs(long long int j);
20482 div_t div(int numer, int denom);
20483 ldiv_t ldiv(long int numer, long int denom);
20484 lldiv_t lldiv(long long int numer,
20485 long long int denom);
20486 int mblen(const char *s, size_t n);
20487 int mbtowc(wchar_t * restrict pwc,
20488 const char * restrict s, size_t n);
20489 int wctomb(char *s, wchar_t wchar);
20490 size_t mbstowcs(wchar_t * restrict pwcs,
20491 const char * restrict s, size_t n);
20492 size_t wcstombs(char * restrict s,
20493 const wchar_t * restrict pwcs, size_t n);</pre>
20495 <h3><a name="B.20" href="#B.20">B.20 String handling <string.h></a></h3>
20500 void *memcpy(void * restrict s1,
20501 const void * restrict s2, size_t n);
20502 void *memmove(void *s1, const void *s2, size_t n);
20503 char *strcpy(char * restrict s1,
20504 const char * restrict s2);
20505 char *strncpy(char * restrict s1,
20506 const char * restrict s2, size_t n);
20507 char *strcat(char * restrict s1,
20508 const char * restrict s2);
20509 char *strncat(char * restrict s1,
20510 const char * restrict s2, size_t n);
20511 int memcmp(const void *s1, const void *s2, size_t n);
20512 int strcmp(const char *s1, const char *s2);
20513 int strcoll(const char *s1, const char *s2);
20514 int strncmp(const char *s1, const char *s2, size_t n);
20515 size_t strxfrm(char * restrict s1,
20516 const char * restrict s2, size_t n);
20517 void *memchr(const void *s, int c, size_t n);
20518 char *strchr(const char *s, int c);
20519 size_t strcspn(const char *s1, const char *s2);
20520 char *strpbrk(const char *s1, const char *s2);
20521 char *strrchr(const char *s, int c);
20522 size_t strspn(const char *s1, const char *s2);
20523 char *strstr(const char *s1, const char *s2);
20524 char *strtok(char * restrict s1,
20525 const char * restrict s2);
20526 void *memset(void *s, int c, size_t n);
20527 char *strerror(int errnum);
20528 size_t strlen(const char *s);</pre>
20530 <h3><a name="B.21" href="#B.21">B.21 Type-generic math <tgmath.h></a></h3>
20532 acos sqrt fmod nextafter
20533 asin fabs frexp nexttoward
20534 atan atan2 hypot remainder
20535 acosh cbrt ilogb remquo
20536 asinh ceil ldexp rint
20537 atanh copysign lgamma round
20538 cos erf llrint scalbn
20539 sin erfc llround scalbln
20540 tan exp2 log10 tgamma
20541 cosh expm1 log1p trunc
20542 sinh fdim log2 carg
20543 tanh floor logb cimag
20545 log fmax lround cproj
20546 pow fmin nearbyint creal</pre>
20548 <h3><a name="B.22" href="#B.22">B.22 Date and time <time.h></a></h3>
20552 CLOCKS_PER_SEC clock_t struct tm
20553 clock_t clock(void);
20554 double difftime(time_t time1, time_t time0);
20555 time_t mktime(struct tm *timeptr);
20556 time_t time(time_t *timer);
20557 char *asctime(const struct tm *timeptr);
20558 char *ctime(const time_t *timer);
20559 struct tm *gmtime(const time_t *timer);
20560 struct tm *localtime(const time_t *timer);
20561 size_t strftime(char * restrict s,
20563 const char * restrict format,
20564 const struct tm * restrict timeptr);</pre>
20566 <h3><a name="B.23" href="#B.23">B.23 Extended multibyte/wide character utilities <wchar.h></a></h3>
20570 wchar_t wint_t WCHAR_MAX
20571 size_t struct tm WCHAR_MIN
20572 mbstate_t NULL WEOF
20573 int fwprintf(FILE * restrict stream,
20574 const wchar_t * restrict format, ...);
20575 int fwscanf(FILE * restrict stream,
20576 const wchar_t * restrict format, ...);
20577 int swprintf(wchar_t * restrict s, size_t n,
20578 const wchar_t * restrict format, ...);
20579 int swscanf(const wchar_t * restrict s,
20580 const wchar_t * restrict format, ...);
20581 int vfwprintf(FILE * restrict stream,
20582 const wchar_t * restrict format, va_list arg);
20583 int vfwscanf(FILE * restrict stream,
20584 const wchar_t * restrict format, va_list arg);
20585 int vswprintf(wchar_t * restrict s, size_t n,
20586 const wchar_t * restrict format, va_list arg);
20587 int vswscanf(const wchar_t * restrict s,
20588 const wchar_t * restrict format, va_list arg);
20589 int vwprintf(const wchar_t * restrict format,
20591 int vwscanf(const wchar_t * restrict format,
20593 int wprintf(const wchar_t * restrict format, ...);
20594 int wscanf(const wchar_t * restrict format, ...);
20595 wint_t fgetwc(FILE *stream);
20596 wchar_t *fgetws(wchar_t * restrict s, int n,
20597 FILE * restrict stream);
20598 wint_t fputwc(wchar_t c, FILE *stream);
20599 int fputws(const wchar_t * restrict s,
20600 FILE * restrict stream);
20601 int fwide(FILE *stream, int mode);
20602 wint_t getwc(FILE *stream);
20603 wint_t getwchar(void);
20604 wint_t putwc(wchar_t c, FILE *stream);
20605 wint_t putwchar(wchar_t c);
20606 wint_t ungetwc(wint_t c, FILE *stream);
20607 double wcstod(const wchar_t * restrict nptr,
20608 wchar_t ** restrict endptr);
20609 float wcstof(const wchar_t * restrict nptr,
20610 wchar_t ** restrict endptr);
20611 long double wcstold(const wchar_t * restrict nptr,
20612 wchar_t ** restrict endptr);
20613 long int wcstol(const wchar_t * restrict nptr,
20614 wchar_t ** restrict endptr, int base);
20615 long long int wcstoll(const wchar_t * restrict nptr,
20616 wchar_t ** restrict endptr, int base);
20617 unsigned long int wcstoul(const wchar_t * restrict nptr,
20618 wchar_t ** restrict endptr, int base);
20619 unsigned long long int wcstoull(
20620 const wchar_t * restrict nptr,
20621 wchar_t ** restrict endptr, int base);
20622 wchar_t *wcscpy(wchar_t * restrict s1,
20623 const wchar_t * restrict s2);
20624 wchar_t *wcsncpy(wchar_t * restrict s1,
20625 const wchar_t * restrict s2, size_t n);
20626 wchar_t *wmemcpy(wchar_t * restrict s1,
20627 const wchar_t * restrict s2, size_t n);
20628 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
20630 wchar_t *wcscat(wchar_t * restrict s1,
20631 const wchar_t * restrict s2);
20632 wchar_t *wcsncat(wchar_t * restrict s1,
20633 const wchar_t * restrict s2, size_t n);
20634 int wcscmp(const wchar_t *s1, const wchar_t *s2);
20635 int wcscoll(const wchar_t *s1, const wchar_t *s2);
20636 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
20638 size_t wcsxfrm(wchar_t * restrict s1,
20639 const wchar_t * restrict s2, size_t n);
20640 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
20642 wchar_t *wcschr(const wchar_t *s, wchar_t c);
20643 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
20644 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2); *
20645 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
20646 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
20647 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
20648 wchar_t *wcstok(wchar_t * restrict s1,
20649 const wchar_t * restrict s2,
20650 wchar_t ** restrict ptr);
20651 wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
20652 size_t wcslen(const wchar_t *s);
20653 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
20654 size_t wcsftime(wchar_t * restrict s, size_t maxsize,
20655 const wchar_t * restrict format,
20656 const struct tm * restrict timeptr);
20657 wint_t btowc(int c);
20658 int wctob(wint_t c);
20659 int mbsinit(const mbstate_t *ps);
20660 size_t mbrlen(const char * restrict s, size_t n,
20661 mbstate_t * restrict ps);
20662 size_t mbrtowc(wchar_t * restrict pwc,
20663 const char * restrict s, size_t n,
20664 mbstate_t * restrict ps);
20665 size_t wcrtomb(char * restrict s, wchar_t wc,
20666 mbstate_t * restrict ps);
20667 size_t mbsrtowcs(wchar_t * restrict dst,
20668 const char ** restrict src, size_t len,
20669 mbstate_t * restrict ps);
20670 size_t wcsrtombs(char * restrict dst,
20671 const wchar_t ** restrict src, size_t len,
20672 mbstate_t * restrict ps);</pre>
20674 <h3><a name="B.24" href="#B.24">B.24 Wide character classification and mapping utilities <wctype.h></a></h3>
20678 wint_t wctrans_t wctype_t WEOF
20679 int iswalnum(wint_t wc);
20680 int iswalpha(wint_t wc);
20681 int iswblank(wint_t wc);
20682 int iswcntrl(wint_t wc);
20683 int iswdigit(wint_t wc);
20684 int iswgraph(wint_t wc);
20685 int iswlower(wint_t wc);
20686 int iswprint(wint_t wc);
20687 int iswpunct(wint_t wc);
20688 int iswspace(wint_t wc);
20689 int iswupper(wint_t wc);
20690 int iswxdigit(wint_t wc);
20691 int iswctype(wint_t wc, wctype_t desc);
20692 wctype_t wctype(const char *property);
20693 wint_t towlower(wint_t wc);
20694 wint_t towupper(wint_t wc);
20695 wint_t towctrans(wint_t wc, wctrans_t desc);
20696 wctrans_t wctrans(const char *property);</pre>
20698 <h2><a name="C" href="#C">Annex C</a></h2>
20702 Sequence points</pre>
20703 The following are the sequence points described in <a href="#5.1.2.3">5.1.2.3</a>:
20705 <li> The call to a function, after the arguments have been evaluated (<a href="#6.5.2.2">6.5.2.2</a>).
20706 <li> The end of the first operand of the following operators: logical AND && (<a href="#6.5.13">6.5.13</a>);
20707 logical OR || (<a href="#6.5.14">6.5.14</a>); conditional ? (<a href="#6.5.15">6.5.15</a>); comma , (<a href="#6.5.17">6.5.17</a>).
20708 <li> The end of a full declarator: declarators (<a href="#6.7.5">6.7.5</a>);
20709 <li> The end of a full expression: an initializer (<a href="#6.7.8">6.7.8</a>); the expression in an expression
20710 statement (<a href="#6.8.3">6.8.3</a>); the controlling expression of a selection statement (if or switch)
20711 (<a href="#6.8.4">6.8.4</a>); the controlling expression of a while or do statement (<a href="#6.8.5">6.8.5</a>); each of the
20712 expressions of a for statement (<a href="#6.8.5.3">6.8.5.3</a>); the expression in a return statement
20713 (<a href="#6.8.6.4">6.8.6.4</a>).
20714 <li> Immediately before a library function returns (<a href="#7.1.4">7.1.4</a>).
20715 <li> After the actions associated with each formatted input/output function conversion
20716 specifier (<a href="#7.19.6">7.19.6</a>, <a href="#7.24.2">7.24.2</a>).
20717 <li> Immediately before and immediately after each call to a comparison function, and
20718 also between any call to a comparison function and any movement of the objects
20719 passed as arguments to that call (<a href="#7.20.5">7.20.5</a>).
20723 <h2><a name="D" href="#D">Annex D</a></h2>
20727 Universal character names for identifiers</pre>
20728 This clause lists the hexadecimal code values that are valid in universal character names
20731 This table is reproduced unchanged from ISO/IEC TR 10176:1998, produced by ISO/IEC
20732 JTC 1/SC 22/WG 20, except for the omission of ranges that are part of the basic character
20734 Latin: 00AA, 00BA, 00C0-00D6, 00D8-00F6, 00F8-01F5, 01FA-0217,
20736 0250-02A8, 1E00-1E9B, 1EA0-1EF9, 207F</pre>
20737 Greek: 0386, 0388-038A, 038C, 038E-03A1, 03A3-03CE, 03D0-03D6,
20739 03DA, 03DC, 03DE, 03E0, 03E2-03F3, 1F00-1F15, 1F18-1F1D,
20740 1F20-1F45, 1F48-1F4D, 1F50-1F57, 1F59, 1F5B, 1F5D,
20741 1F5F-1F7D, 1F80-1FB4, 1FB6-1FBC, 1FC2-1FC4, 1FC6-1FCC,
20742 1FD0-1FD3, 1FD6-1FDB, 1FE0-1FEC, 1FF2-1FF4, 1FF6-1FFC</pre>
20743 Cyrillic: 0401-040C, 040E-044F, 0451-045C, 045E-0481, 0490-04C4,
20745 04C7-04C8, 04CB-04CC, 04D0-04EB, 04EE-04F5, 04F8-04F9</pre>
20746 Armenian: 0531-0556, 0561-0587
20747 Hebrew: 05B0-05B9, 05BB-05BD, 05BF, 05C1-05C2, 05D0-05EA,
20750 Arabic: 0621-063A, 0640-0652, 0670-06B7, 06BA-06BE, 06C0-06CE,
20752 06D0-06DC, 06E5-06E8, 06EA-06ED</pre>
20753 Devanagari: 0901-0903, 0905-0939, 093E-094D, 0950-0952, 0958-0963
20754 Bengali: 0981-0983, 0985-098C, 098F-0990, 0993-09A8, 09AA-09B0,
20756 09B2, 09B6-09B9, 09BE-09C4, 09C7-09C8, 09CB-09CD,
20757 09DC-09DD, 09DF-09E3, 09F0-09F1</pre>
20758 Gurmukhi: 0A02, 0A05-0A0A, 0A0F-0A10, 0A13-0A28, 0A2A-0A30,
20760 0A32-0A33, 0A35-0A36, 0A38-0A39, 0A3E-0A42, 0A47-0A48,
20761 0A4B-0A4D, 0A59-0A5C, 0A5E, 0A74</pre>
20762 Gujarati: 0A81-0A83, 0A85-0A8B, 0A8D, 0A8F-0A91, 0A93-0AA8,
20764 0AAA-0AB0, 0AB2-0AB3, 0AB5-0AB9, 0ABD-0AC5,
20765 0AC7-0AC9, 0ACB-0ACD, 0AD0, 0AE0</pre>
20766 Oriya: 0B01-0B03, 0B05-0B0C, 0B0F-0B10, 0B13-0B28, 0B2A-0B30,
20769 0B32-0B33, 0B36-0B39, 0B3E-0B43, 0B47-0B48, 0B4B-0B4D,
20770 0B5C-0B5D, 0B5F-0B61</pre>
20771 Tamil: 0B82-0B83, 0B85-0B8A, 0B8E-0B90, 0B92-0B95, 0B99-0B9A,
20773 0B9C, 0B9E-0B9F, 0BA3-0BA4, 0BA8-0BAA, 0BAE-0BB5,
20774 0BB7-0BB9, 0BBE-0BC2, 0BC6-0BC8, 0BCA-0BCD</pre>
20775 Telugu: 0C01-0C03, 0C05-0C0C, 0C0E-0C10, 0C12-0C28, 0C2A-0C33,
20777 0C35-0C39, 0C3E-0C44, 0C46-0C48, 0C4A-0C4D, 0C60-0C61</pre>
20778 Kannada: 0C82-0C83, 0C85-0C8C, 0C8E-0C90, 0C92-0CA8, 0CAA-0CB3,
20780 0CB5-0CB9, 0CBE-0CC4, 0CC6-0CC8, 0CCA-0CCD, 0CDE,
20782 Malayalam: 0D02-0D03, 0D05-0D0C, 0D0E-0D10, 0D12-0D28, 0D2A-0D39,
20784 0D3E-0D43, 0D46-0D48, 0D4A-0D4D, 0D60-0D61</pre>
20785 Thai: 0E01-0E3A, 0E40-0E5B
20786 Lao: 0E81-0E82, 0E84, 0E87-0E88, 0E8A, 0E8D, 0E94-0E97,
20788 0E99-0E9F, 0EA1-0EA3, 0EA5, 0EA7, 0EAA-0EAB,
20789 0EAD-0EAE, 0EB0-0EB9, 0EBB-0EBD, 0EC0-0EC4, 0EC6,
20790 0EC8-0ECD, 0EDC-0EDD</pre>
20791 Tibetan: 0F00, 0F18-0F19, 0F35, 0F37, 0F39, 0F3E-0F47, 0F49-0F69,
20793 0F71-0F84, 0F86-0F8B, 0F90-0F95, 0F97, 0F99-0FAD,
20794 0FB1-0FB7, 0FB9</pre>
20795 Georgian: 10A0-10C5, 10D0-10F6
20796 Hiragana: 3041-3093, 309B-309C
20797 Katakana: 30A1-30F6, 30FB-30FC
20798 Bopomofo: 3105-312C
20799 CJK Unified Ideographs: 4E00-9FA5
20801 Digits: 0660-0669, 06F0-06F9, 0966-096F, 09E6-09EF, 0A66-0A6F,
20803 0AE6-0AEF, 0B66-0B6F, 0BE7-0BEF, 0C66-0C6F, 0CE6-0CEF,
20804 0D66-0D6F, 0E50-0E59, 0ED0-0ED9, 0F20-0F33</pre>
20805 Special characters: 00B5, 00B7, 02B0-02B8, 02BB, 02BD-02C1, 02D0-02D1,
20808 02E0-02E4, 037A, 0559, 093D, 0B3D, 1FBE, 203F-2040, 2102,
20809 2107, 210A-2113, 2115, 2118-211D, 2124, 2126, 2128, 212A-2131,
20810 2133-2138, 2160-2182, 3005-3007, 3021-3029</pre>
20812 <h2><a name="E" href="#E">Annex E</a></h2>
20816 Implementation limits</pre>
20817 The contents of the header <a href="#7.10"><limits.h></a> are given below, in alphabetical order. The
20818 minimum magnitudes shown shall be replaced by implementation-defined magnitudes
20819 with the same sign. The values shall all be constant expressions suitable for use in #if
20820 preprocessing directives. The components are described further in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
20824 #define CHAR_MAX UCHAR_MAX or SCHAR_MAX
20825 #define CHAR_MIN 0 or SCHAR_MIN
20826 #define INT_MAX +32767
20827 #define INT_MIN -32767
20828 #define LONG_MAX +2147483647
20829 #define LONG_MIN -2147483647
20830 #define LLONG_MAX +9223372036854775807
20831 #define LLONG_MIN -9223372036854775807
20832 #define MB_LEN_MAX 1
20833 #define SCHAR_MAX +127
20834 #define SCHAR_MIN -127
20835 #define SHRT_MAX +32767
20836 #define SHRT_MIN -32767
20837 #define UCHAR_MAX 255
20838 #define USHRT_MAX 65535
20839 #define UINT_MAX 65535
20840 #define ULONG_MAX 4294967295
20841 #define ULLONG_MAX 18446744073709551615</pre>
20842 The contents of the header <a href="#7.7"><float.h></a> are given below. All integer values, except
20843 FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing
20844 directives; all floating values shall be constant expressions. The components are
20845 described further in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
20847 The values given in the following list shall be replaced by implementation-defined
20851 #define FLT_EVAL_METHOD
20852 #define FLT_ROUNDS</pre>
20853 The values given in the following list shall be replaced by implementation-defined
20854 constant expressions that are greater or equal in magnitude (absolute value) to those
20855 shown, with the same sign:
20860 #define DBL_MANT_DIG
20861 #define DBL_MAX_10_EXP +37
20862 #define DBL_MAX_EXP
20863 #define DBL_MIN_10_EXP -37
20864 #define DBL_MIN_EXP
20865 #define DECIMAL_DIG 10
20867 #define FLT_MANT_DIG
20868 #define FLT_MAX_10_EXP +37
20869 #define FLT_MAX_EXP
20870 #define FLT_MIN_10_EXP -37
20871 #define FLT_MIN_EXP
20872 #define FLT_RADIX 2
20873 #define LDBL_DIG 10
20874 #define LDBL_MANT_DIG
20875 #define LDBL_MAX_10_EXP +37
20876 #define LDBL_MAX_EXP
20877 #define LDBL_MIN_10_EXP -37
20878 #define LDBL_MIN_EXP</pre>
20879 The values given in the following list shall be replaced by implementation-defined
20880 constant expressions with values that are greater than or equal to those shown:
20883 #define DBL_MAX 1E+37
20884 #define FLT_MAX 1E+37
20885 #define LDBL_MAX 1E+37</pre>
20886 The values given in the following list shall be replaced by implementation-defined
20887 constant expressions with (positive) values that are less than or equal to those shown:
20890 #define DBL_EPSILON 1E-9
20891 #define DBL_MIN 1E-37
20892 #define FLT_EPSILON 1E-5
20893 #define FLT_MIN 1E-37
20894 #define LDBL_EPSILON 1E-9
20895 #define LDBL_MIN 1E-37</pre>
20897 <h2><a name="F" href="#F">Annex F</a></h2>
20900 IEC 60559 floating-point arithmetic</pre>
20902 <h3><a name="F.1" href="#F.1">F.1 Introduction</a></h3>
20904 This annex specifies C language support for the IEC 60559 floating-point standard. The
20905 IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
20906 microprocessor systems, second edition (IEC 60559:1989), previously designated
20907 IEC 559:1989 and as IEEE Standard for Binary Floating-Point Arithmetic
20908 (ANSI/IEEE 754-1985). IEEE Standard for Radix-Independent Floating-Point
20909 Arithmetic (ANSI/IEEE 854-1987) generalizes the binary standard to remove
20910 dependencies on radix and word length. IEC 60559 generally refers to the floating-point
20911 standard, as in IEC 60559 operation, IEC 60559 format, etc. An implementation that
20912 defines __STDC_IEC_559__ shall conform to the specifications in this annex. Where
20913 a binding between the C language and IEC 60559 is indicated, the IEC 60559-specified
20914 behavior is adopted by reference, unless stated otherwise.
20916 <h3><a name="F.2" href="#F.2">F.2 Types</a></h3>
20918 The C floating types match the IEC 60559 formats as follows:
20920 <li> The float type matches the IEC 60559 single format.
20921 <li> The double type matches the IEC 60559 double format.
20922 <li> The long double type matches an IEC 60559 extended format,<sup><a href="#note307"><b>307)</b></a></sup> else a
20923 non-IEC 60559 extended format, else the IEC 60559 double format.
20925 Any non-IEC 60559 extended format used for the long double type shall have more
20926 precision than IEC 60559 double and at least the range of IEC 60559 double.<sup><a href="#note308"><b>308)</b></a></sup>
20927 Recommended practice
20929 The long double type should match an IEC 60559 extended format.
20937 <p><small><a name="note307" href="#note307">307)</a> ''Extended'' is IEC 60559's double-extended data format. Extended refers to both the common 80-bit
20938 and quadruple 128-bit IEC 60559 formats.
20940 <p><small><a name="note308" href="#note308">308)</a> A non-IEC 60559 long double type is required to provide infinity and NaNs, as its values include
20944 <h4><a name="F.2.1" href="#F.2.1">F.2.1 Infinities, signed zeros, and NaNs</a></h4>
20946 This specification does not define the behavior of signaling NaNs.<sup><a href="#note309"><b>309)</b></a></sup> It generally uses
20947 the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
20948 functions in <a href="#7.12"><math.h></a> provide designations for IEC 60559 NaNs and infinities.
20951 <p><small><a name="note309" href="#note309">309)</a> Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are
20952 sufficient for closure of the arithmetic.
20955 <h3><a name="F.3" href="#F.3">F.3 Operators and functions</a></h3>
20957 C operators and functions provide IEC 60559 required and recommended facilities as
20960 <li> The +, -, *, and / operators provide the IEC 60559 add, subtract, multiply, and
20962 <li> The sqrt functions in <a href="#7.12"><math.h></a> provide the IEC 60559 square root operation.
20963 <li> The remainder functions in <a href="#7.12"><math.h></a> provide the IEC 60559 remainder
20964 operation. The remquo functions in <a href="#7.12"><math.h></a> provide the same operation but
20965 with additional information.
20966 <li> The rint functions in <a href="#7.12"><math.h></a> provide the IEC 60559 operation that rounds a
20967 floating-point number to an integer value (in the same precision). The nearbyint
20968 functions in <a href="#7.12"><math.h></a> provide the nearbyinteger function recommended in the
20969 Appendix to ANSI/IEEE 854.
20970 <li> The conversions for floating types provide the IEC 60559 conversions between
20971 floating-point precisions.
20972 <li> The conversions from integer to floating types provide the IEC 60559 conversions
20973 from integer to floating point.
20974 <li> The conversions from floating to integer types provide IEC 60559-like conversions
20975 but always round toward zero.
20976 <li> The lrint and llrint functions in <a href="#7.12"><math.h></a> provide the IEC 60559
20977 conversions, which honor the directed rounding mode, from floating point to the
20978 long int and long long int integer formats. The lrint and llrint
20979 functions can be used to implement IEC 60559 conversions from floating to other
20981 <li> The translation time conversion of floating constants and the strtod, strtof,
20982 strtold, fprintf, fscanf, and related library functions in <a href="#7.20"><stdlib.h></a>,
20983 <a href="#7.19"><stdio.h></a>, and <a href="#7.24"><wchar.h></a> provide IEC 60559 binary-decimal conversions. The
20984 strtold function in <a href="#7.20"><stdlib.h></a> provides the conv function recommended in the
20985 Appendix to ANSI/IEEE 854.
20988 <li> The relational and equality operators provide IEC 60559 comparisons. IEC 60559
20989 identifies a need for additional comparison predicates to facilitate writing code that
20990 accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
20991 isless, islessequal, islessgreater, and isunordered) in <a href="#7.12"><math.h></a>
20992 supplement the language operators to address this need. The islessgreater and
20993 isunordered macros provide respectively a quiet version of the <> predicate and
20994 the unordered predicate recommended in the Appendix to IEC 60559.
20995 <li> The feclearexcept, feraiseexcept, and fetestexcept functions in
20996 <a href="#7.6"><fenv.h></a> provide the facility to test and alter the IEC 60559 floating-point
20997 exception status flags. The fegetexceptflag and fesetexceptflag
20998 functions in <a href="#7.6"><fenv.h></a> provide the facility to save and restore all five status flags at
20999 one time. These functions are used in conjunction with the type fexcept_t and the
21000 floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
21001 FE_UNDERFLOW, FE_OVERFLOW, FE_INVALID) also in <a href="#7.6"><fenv.h></a>.
21002 <li> The fegetround and fesetround functions in <a href="#7.6"><fenv.h></a> provide the facility
21003 to select among the IEC 60559 directed rounding modes represented by the rounding
21004 direction macros in <a href="#7.6"><fenv.h></a> (FE_TONEAREST, FE_UPWARD, FE_DOWNWARD,
21005 FE_TOWARDZERO) and the values 0, 1, 2, and 3 of FLT_ROUNDS are the
21006 IEC 60559 directed rounding modes.
21007 <li> The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
21008 <a href="#7.6"><fenv.h></a> provide a facility to manage the floating-point environment, comprising
21009 the IEC 60559 status flags and control modes.
21010 <li> The copysign functions in <a href="#7.12"><math.h></a> provide the copysign function
21011 recommended in the Appendix to IEC 60559.
21012 <li> The unary minus (-) operator provides the minus (-) operation recommended in the
21013 Appendix to IEC 60559.
21014 <li> The scalbn and scalbln functions in <a href="#7.12"><math.h></a> provide the scalb function
21015 recommended in the Appendix to IEC 60559.
21016 <li> The logb functions in <a href="#7.12"><math.h></a> provide the logb function recommended in the
21017 Appendix to IEC 60559, but following the newer specifications in ANSI/IEEE 854.
21018 <li> The nextafter and nexttoward functions in <a href="#7.12"><math.h></a> provide the nextafter
21019 function recommended in the Appendix to IEC 60559 (but with a minor change to
21020 better handle signed zeros).
21021 <li> The isfinite macro in <a href="#7.12"><math.h></a> provides the finite function recommended in
21022 the Appendix to IEC 60559.
21023 <li> The isnan macro in <a href="#7.12"><math.h></a> provides the isnan function recommended in the
21024 Appendix to IEC 60559.
21026 <li> The signbit macro and the fpclassify macro in <a href="#7.12"><math.h></a>, used in
21027 conjunction with the number classification macros (FP_NAN, FP_INFINITE,
21028 FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
21029 function recommended in the Appendix to IEC 60559 (except that the classification
21030 macros defined in <a href="#7.12.3">7.12.3</a> do not distinguish signaling from quiet NaNs).
21033 <h3><a name="F.4" href="#F.4">F.4 Floating to integer conversion</a></h3>
21035 If the floating value is infinite or NaN or if the integral part of the floating value exceeds
21036 the range of the integer type, then the ''invalid'' floating-point exception is raised and the
21037 resulting value is unspecified. Whether conversion of non-integer floating values whose
21038 integral part is within the range of the integer type raises the ''inexact'' floating-point
21039 exception is unspecified.<sup><a href="#note310"><b>310)</b></a></sup>
21042 <p><small><a name="note310" href="#note310">310)</a> ANSI/IEEE 854, but not IEC 60559 (ANSI/IEEE 754), directly specifies that floating-to-integer
21043 conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those
21044 cases where it matters, library functions can be used to effect such conversions with or without raising
21045 the ''inexact'' floating-point exception. See rint, lrint, llrint, and nearbyint in
21046 <a href="#7.12"><math.h></a>.
21049 <h3><a name="F.5" href="#F.5">F.5 Binary-decimal conversion</a></h3>
21051 Conversion from the widest supported IEC 60559 format to decimal with
21052 DECIMAL_DIG digits and back is the identity function.<sup><a href="#note311"><b>311)</b></a></sup>
21054 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
21055 particular, conversion between any supported IEC 60559 format and decimal with
21056 DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
21057 rounding mode), which assures that conversion from the widest supported IEC 60559
21058 format to decimal with DECIMAL_DIG digits and back is the identity function.
21060 Functions such as strtod that convert character sequences to floating types honor the
21061 rounding direction. Hence, if the rounding direction might be upward or downward, the
21062 implementation cannot convert a minus-signed sequence by negating the converted
21071 <p><small><a name="note311" href="#note311">311)</a> If the minimum-width IEC 60559 extended format (64 bits of precision) is supported,
21072 DECIMAL_DIG shall be at least 21. If IEC 60559 double (53 bits of precision) is the widest
21073 IEC 60559 format supported, then DECIMAL_DIG shall be at least 17. (By contrast, LDBL_DIG and
21074 DBL_DIG are 18 and 15, respectively, for these formats.)
21077 <h3><a name="F.6" href="#F.6">F.6 Contracted expressions</a></h3>
21079 A contracted expression treats infinities, NaNs, signed zeros, subnormals, and the
21080 rounding directions in a manner consistent with the basic arithmetic operations covered
21082 Recommended practice
21084 A contracted expression should raise floating-point exceptions in a manner generally
21085 consistent with the basic arithmetic operations. A contracted expression should deliver
21086 the same value as its uncontracted counterpart, else should be correctly rounded (once).
21088 <h3><a name="F.7" href="#F.7">F.7 Floating-point environment</a></h3>
21090 The floating-point environment defined in <a href="#7.6"><fenv.h></a> includes the IEC 60559 floating-
21091 point exception status flags and directed-rounding control modes. It includes also
21092 IEC 60559 dynamic rounding precision and trap enablement modes, if the
21093 implementation supports them.<sup><a href="#note312"><b>312)</b></a></sup>
21096 <p><small><a name="note312" href="#note312">312)</a> This specification does not require dynamic rounding precision nor trap enablement modes.
21099 <h4><a name="F.7.1" href="#F.7.1">F.7.1 Environment management</a></h4>
21101 IEC 60559 requires that floating-point operations implicitly raise floating-point exception
21102 status flags, and that rounding control modes can be set explicitly to affect result values of
21103 floating-point operations. When the state for the FENV_ACCESS pragma (defined in
21104 <a href="#7.6"><fenv.h></a>) is ''on'', these changes to the floating-point state are treated as side effects
21105 which respect sequence points.<sup><a href="#note313"><b>313)</b></a></sup>
21108 <p><small><a name="note313" href="#note313">313)</a> If the state for the FENV_ACCESS pragma is ''off'', the implementation is free to assume the floating-
21109 point control modes will be the default ones and the floating-point status flags will not be tested,
21110 which allows certain optimizations (see <a href="#F.8">F.8</a>).
21113 <h4><a name="F.7.2" href="#F.7.2">F.7.2 Translation</a></h4>
21115 During translation the IEC 60559 default modes are in effect:
21117 <li> The rounding direction mode is rounding to nearest.
21118 <li> The rounding precision mode (if supported) is set so that results are not shortened.
21119 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
21121 Recommended practice
21123 The implementation should produce a diagnostic message for each translation-time
21129 floating-point exception, other than ''inexact'';<sup><a href="#note314"><b>314)</b></a></sup> the implementation should then
21130 proceed with the translation of the program.
21133 <p><small><a name="note314" href="#note314">314)</a> As floating constants are converted to appropriate internal representations at translation time, their
21134 conversion is subject to default rounding modes and raises no execution-time floating-point exceptions
21135 (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example
21136 strtod, provide execution-time conversion of numeric strings.
21139 <h4><a name="F.7.3" href="#F.7.3">F.7.3 Execution</a></h4>
21141 At program startup the floating-point environment is initialized as prescribed by
21144 <li> All floating-point exception status flags are cleared.
21145 <li> The rounding direction mode is rounding to nearest.
21146 <li> The dynamic rounding precision mode (if supported) is set so that results are not
21148 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
21151 <h4><a name="F.7.4" href="#F.7.4">F.7.4 Constant expressions</a></h4>
21153 An arithmetic constant expression of floating type, other than one in an initializer for an
21154 object that has static storage duration, is evaluated (as if) during execution; thus, it is
21155 affected by any operative floating-point control modes and raises floating-point
21156 exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma
21157 is ''on'').<sup><a href="#note315"><b>315)</b></a></sup>
21162 #include <a href="#7.6"><fenv.h></a>
21163 #pragma STDC FENV_ACCESS ON
21166 float w[] = { 0.0/0.0 }; // raises an exception
21167 static float x = 0.0/0.0; // does not raise an exception
21168 float y = 0.0/0.0; // raises an exception
21169 double z = 0.0/0.0; // raises an exception
21172 For the static initialization, the division is done at translation time, raising no (execution-time) floating-
21173 point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at
21181 <p><small><a name="note315" href="#note315">315)</a> Where the state for the FENV_ACCESS pragma is ''on'', results of inexact expressions like 1.0/3.0
21182 are affected by rounding modes set at execution time, and expressions such as 0.0/0.0 and
21183 1.0/0.0 generate execution-time floating-point exceptions. The programmer can achieve the
21184 efficiency of translation-time evaluation through static initialization, such as
21187 const static double one_third = 1.0/3.0;</pre>
21190 <h4><a name="F.7.5" href="#F.7.5">F.7.5 Initialization</a></h4>
21192 All computation for automatic initialization is done (as if) at execution time; thus, it is
21193 affected by any operative modes and raises floating-point exceptions as required by
21194 IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation
21195 for initialization of objects that have static storage duration is done (as if) at translation
21201 #include <a href="#7.6"><fenv.h></a>
21202 #pragma STDC FENV_ACCESS ON
21205 float u[] = { 1.1e75 }; // raises exceptions
21206 static float v = 1.1e75; // does not raise exceptions
21207 float w = 1.1e75; // raises exceptions
21208 double x = 1.1e75; // may raise exceptions
21209 float y = 1.1e75f; // may raise exceptions
21210 long double z = 1.1e75; // does not raise exceptions
21213 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is
21214 done at translation time. The automatic initialization of u and w require an execution-time conversion to
21215 float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations
21216 of x and y entail execution-time conversion; however, in some expression evaluation methods, the
21217 conversions is not to a narrower format, in which case no floating-point exception is raised.<sup><a href="#note316"><b>316)</b></a></sup> The
21218 automatic initialization of z entails execution-time conversion, but not to a narrower format, so no floating-
21219 point exception is raised. Note that the conversions of the floating constants 1.1e75 and 1.1e75f to
21220 their internal representations occur at translation time in all cases.
21228 <p><small><a name="note316" href="#note316">316)</a> Use of float_t and double_t variables increases the likelihood of translation-time computation.
21229 For example, the automatic initialization
21232 double_t x = 1.1e75;</pre>
21233 could be done at translation time, regardless of the expression evaluation method.
21236 <h4><a name="F.7.6" href="#F.7.6">F.7.6 Changing the environment</a></h4>
21238 Operations defined in <a href="#6.5">6.5</a> and functions and macros defined for the standard libraries
21239 change floating-point status flags and control modes just as indicated by their
21240 specifications (including conformance to IEC 60559). They do not change flags or modes
21241 (so as to be detectable by the user) in any other cases.
21243 If the argument to the feraiseexcept function in <a href="#7.6"><fenv.h></a> represents IEC 60559
21244 valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
21245 ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
21246 before ''inexact''.
21248 <h3><a name="F.8" href="#F.8">F.8 Optimization</a></h3>
21250 This section identifies code transformations that might subvert IEC 60559-specified
21251 behavior, and others that do not.
21253 <h4><a name="F.8.1" href="#F.8.1">F.8.1 Global transformations</a></h4>
21255 Floating-point arithmetic operations and external function calls may entail side effects
21256 which optimization shall honor, at least where the state of the FENV_ACCESS pragma is
21257 ''on''. The flags and modes in the floating-point environment may be regarded as global
21258 variables; floating-point operations (+, *, etc.) implicitly read the modes and write the
21261 Concern about side effects may inhibit code motion and removal of seemingly useless
21262 code. For example, in
21264 #include <a href="#7.6"><fenv.h></a>
21265 #pragma STDC FENV_ACCESS ON
21269 for (i = 0; i < n; i++) x + 1;
21272 x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
21273 body might not execute (maybe 0 >= n), x + 1 cannot be moved out of the loop. (Of
21274 course these optimizations are valid if the implementation can rule out the nettlesome
21277 This specification does not require support for trap handlers that maintain information
21278 about the order or count of floating-point exceptions. Therefore, between function calls,
21279 floating-point exceptions need not be precise: the actual order and number of occurrences
21280 of floating-point exceptions (> 1) may vary from what the source code expresses. Thus,
21281 the preceding loop could be treated as
21284 if (0 < n) x + 1;</pre>
21286 <h4><a name="F.8.2" href="#F.8.2">F.8.2 Expression transformations</a></h4>
21288 x / 2 <-> x * 0.5 Although similar transformations involving inexact
21290 constants generally do not yield numerically equivalent
21291 expressions, if the constants are exact then such
21292 transformations can be made on IEC 60559 machines
21293 and others that round perfectly.</pre>
21294 1 * x and x / 1 -> x The expressions 1 * x, x / 1, and x are equivalent
21296 (on IEC 60559 machines, among others).<sup><a href="#note317"><b>317)</b></a></sup></pre>
21297 x / x -> 1.0 The expressions x / x and 1.0 are not equivalent if x
21299 can be zero, infinite, or NaN.</pre>
21300 x - y <-> x + (-y) The expressions x - y, x + (-y), and (-y) + x
21302 are equivalent (on IEC 60559 machines, among others).</pre>
21303 x - y <-> -(y - x) The expressions x - y and -(y - x) are not
21305 equivalent because 1 - 1 is +0 but -(1 - 1) is -0 (in the
21306 default rounding direction).<sup><a href="#note318"><b>318)</b></a></sup></pre>
21307 x - x -> 0.0 The expressions x - x and 0.0 are not equivalent if
21309 x is a NaN or infinite.</pre>
21310 0 * x -> 0.0 The expressions 0 * x and 0.0 are not equivalent if
21312 x is a NaN, infinite, or -0.</pre>
21313 x + 0->x The expressions x + 0 and x are not equivalent if x is
21315 -0, because (-0) + (+0) yields +0 (in the default
21316 rounding direction), not -0.</pre>
21317 x - 0->x (+0) - (+0) yields -0 when rounding is downward
21319 (toward -(inf)), but +0 otherwise, and (-0) - (+0) always
21320 yields -0; so, if the state of the FENV_ACCESS pragma
21321 is ''off'', promising default rounding, then the
21322 implementation can replace x - 0 by x, even if x</pre>
21327 might be zero.</pre>
21328 -x <-> 0 - x The expressions -x and 0 - x are not equivalent if x
21330 is +0, because -(+0) yields -0, but 0 - (+0) yields +0
21331 (unless rounding is downward).</pre>
21334 <p><small><a name="note317" href="#note317">317)</a> Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
21335 other transformations that remove arithmetic operators.
21337 <p><small><a name="note318" href="#note318">318)</a> IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
21341 1/(1/ (+-) (inf)) is (+-) (inf)</pre>
21345 conj(csqrt(z)) is csqrt(conj(z)),</pre>
21349 <h4><a name="F.8.3" href="#F.8.3">F.8.3 Relational operators</a></h4>
21351 x != x -> false The statement x != x is true if x is a NaN.
21352 x == x -> true The statement x == x is false if x is a NaN.
21353 x < y -> isless(x,y) (and similarly for <=, >, >=) Though numerically
21355 equal, these expressions are not equivalent because of
21356 side effects when x or y is a NaN and the state of the
21357 FENV_ACCESS pragma is ''on''. This transformation,
21358 which would be desirable if extra code were required to
21359 cause the ''invalid'' floating-point exception for
21360 unordered cases, could be performed provided the state
21361 of the FENV_ACCESS pragma is ''off''.</pre>
21362 The sense of relational operators shall be maintained. This includes handling unordered
21363 cases as expressed by the source code.
21367 // calls g and raises ''invalid'' if a and b are unordered
21372 is not equivalent to
21374 // calls f and raises ''invalid'' if a and b are unordered
21381 // calls f without raising ''invalid'' if a and b are unordered
21382 if (isgreaterequal(a,b))
21386 nor, unless the state of the FENV_ACCESS pragma is ''off'', to
21389 // calls g without raising ''invalid'' if a and b are unordered
21394 but is equivalent to
21402 <h4><a name="F.8.4" href="#F.8.4">F.8.4 Constant arithmetic</a></h4>
21404 The implementation shall honor floating-point exceptions raised by execution-time
21405 constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See <a href="#F.7.4">F.7.4</a>
21406 and <a href="#F.7.5">F.7.5</a>.) An operation on constants that raises no floating-point exception can be
21407 folded during translation, except, if the state of the FENV_ACCESS pragma is ''on'', a
21408 further check is required to assure that changing the rounding direction to downward does
21409 not alter the sign of the result,<sup><a href="#note319"><b>319)</b></a></sup> and implementations that support dynamic rounding
21410 precision modes shall assure further that the result of the operation raises no floating-
21411 point exception when converted to the semantic type of the operation.
21414 <p><small><a name="note319" href="#note319">319)</a> 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
21417 <h3><a name="F.9" href="#F.9">F.9 Mathematics <math.h></a></h3>
21419 This subclause contains specifications of <a href="#7.12"><math.h></a> facilities that are particularly suited
21420 for IEC 60559 implementations.
21422 The Standard C macro HUGE_VAL and its float and long double analogs,
21423 HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive
21426 Special cases for functions in <a href="#7.12"><math.h></a> are covered directly or indirectly by
21427 IEC 60559. The functions that IEC 60559 specifies directly are identified in <a href="#F.3">F.3</a>. The
21428 other functions in <a href="#7.12"><math.h></a> treat infinities, NaNs, signed zeros, subnormals, and
21429 (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags
21430 in a manner consistent with the basic arithmetic operations covered by IEC 60559.
21432 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
21435 The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in
21436 subsequent subclauses of this annex.
21438 The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of
21439 rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value
21443 whose magnitude is too large.
21445 The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially
21446 subnormal or zero) and suffers loss of accuracy.<sup><a href="#note320"><b>320)</b></a></sup>
21448 Whether or when library functions raise the ''inexact'' floating-point exception is
21449 unspecified, unless explicitly specified otherwise.
21451 Whether or when library functions raise an undeserved ''underflow'' floating-point
21452 exception is unspecified.<sup><a href="#note321"><b>321)</b></a></sup> Otherwise, as implied by <a href="#F.7.6">F.7.6</a>, the <a href="#7.12"><math.h></a> functions do
21453 not raise spurious floating-point exceptions (detectable by the user), other than the
21454 ''inexact'' floating-point exception.
21456 Whether the functions honor the rounding direction mode is implementation-defined,
21457 unless explicitly specified otherwise.
21459 Functions with a NaN argument return a NaN result and raise no floating-point exception,
21460 except where stated otherwise.
21462 The specifications in the following subclauses append to the definitions in <a href="#7.12"><math.h></a>.
21463 For families of functions, the specifications apply to all of the functions even though only
21464 the principal function is shown. Unless otherwise specified, where the symbol ''(+-)''
21465 occurs in both an argument and the result, the result has the same sign as the argument.
21466 Recommended practice
21468 If a function with one or more NaN arguments returns a NaN result, the result should be
21469 the same as one of the NaN arguments (after possible type conversion), except perhaps
21473 <p><small><a name="note320" href="#note320">320)</a> IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on
21474 when the floating-point exception is raised.
21476 <p><small><a name="note321" href="#note321">321)</a> It is intended that undeserved ''underflow'' and ''inexact'' floating-point exceptions are raised only if
21477 avoiding them would be too costly.
21480 <h4><a name="F.9.1" href="#F.9.1">F.9.1 Trigonometric functions</a></h4>
21482 <h5><a name="F.9.1.1" href="#F.9.1.1">F.9.1.1 The acos functions</a></h5>
21485 <li> acos(1) returns +0.
21486 <li> acos(x) returns a NaN and raises the ''invalid'' floating-point exception for
21495 <h5><a name="F.9.1.2" href="#F.9.1.2">F.9.1.2 The asin functions</a></h5>
21498 <li> asin((+-)0) returns (+-)0.
21499 <li> asin(x) returns a NaN and raises the ''invalid'' floating-point exception for
21503 <h5><a name="F.9.1.3" href="#F.9.1.3">F.9.1.3 The atan functions</a></h5>
21506 <li> atan((+-)0) returns (+-)0.
21507 <li> atan((+-)(inf)) returns (+-)pi /2.
21510 <h5><a name="F.9.1.4" href="#F.9.1.4">F.9.1.4 The atan2 functions</a></h5>
21513 <li> atan2((+-)0, -0) returns (+-)pi .<sup><a href="#note322"><b>322)</b></a></sup>
21514 <li> atan2((+-)0, +0) returns (+-)0.
21515 <li> atan2((+-)0, x) returns (+-)pi for x < 0.
21516 <li> atan2((+-)0, x) returns (+-)0 for x > 0.
21517 <li> atan2(y, (+-)0) returns -pi /2 for y < 0.
21518 <li> atan2(y, (+-)0) returns pi /2 for y > 0.
21519 <li> atan2((+-)y, -(inf)) returns (+-)pi for finite y > 0.
21520 <li> atan2((+-)y, +(inf)) returns (+-)0 for finite y > 0.
21521 <li> atan2((+-)(inf), x) returns (+-)pi /2 for finite x.
21522 <li> atan2((+-)(inf), -(inf)) returns (+-)3pi /4.
21523 <li> atan2((+-)(inf), +(inf)) returns (+-)pi /4.
21527 <p><small><a name="note322" href="#note322">322)</a> atan2(0, 0) does not raise the ''invalid'' floating-point exception, nor does atan2( y , 0) raise
21528 the ''divide-by-zero'' floating-point exception.
21531 <h5><a name="F.9.1.5" href="#F.9.1.5">F.9.1.5 The cos functions</a></h5>
21534 <li> cos((+-)0) returns 1.
21535 <li> cos((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21538 <h5><a name="F.9.1.6" href="#F.9.1.6">F.9.1.6 The sin functions</a></h5>
21541 <li> sin((+-)0) returns (+-)0.
21542 <li> sin((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21550 <h5><a name="F.9.1.7" href="#F.9.1.7">F.9.1.7 The tan functions</a></h5>
21553 <li> tan((+-)0) returns (+-)0.
21554 <li> tan((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21557 <h4><a name="F.9.2" href="#F.9.2">F.9.2 Hyperbolic functions</a></h4>
21559 <h5><a name="F.9.2.1" href="#F.9.2.1">F.9.2.1 The acosh functions</a></h5>
21562 <li> acosh(1) returns +0.
21563 <li> acosh(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 1.
21564 <li> acosh(+(inf)) returns +(inf).
21567 <h5><a name="F.9.2.2" href="#F.9.2.2">F.9.2.2 The asinh functions</a></h5>
21570 <li> asinh((+-)0) returns (+-)0.
21571 <li> asinh((+-)(inf)) returns (+-)(inf).
21574 <h5><a name="F.9.2.3" href="#F.9.2.3">F.9.2.3 The atanh functions</a></h5>
21577 <li> atanh((+-)0) returns (+-)0.
21578 <li> atanh((+-)1) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
21579 <li> atanh(x) returns a NaN and raises the ''invalid'' floating-point exception for
21583 <h5><a name="F.9.2.4" href="#F.9.2.4">F.9.2.4 The cosh functions</a></h5>
21586 <li> cosh((+-)0) returns 1.
21587 <li> cosh((+-)(inf)) returns +(inf).
21590 <h5><a name="F.9.2.5" href="#F.9.2.5">F.9.2.5 The sinh functions</a></h5>
21593 <li> sinh((+-)0) returns (+-)0.
21594 <li> sinh((+-)(inf)) returns (+-)(inf).
21597 <h5><a name="F.9.2.6" href="#F.9.2.6">F.9.2.6 The tanh functions</a></h5>
21600 <li> tanh((+-)0) returns (+-)0.
21601 <li> tanh((+-)(inf)) returns (+-)1.
21605 <h4><a name="F.9.3" href="#F.9.3">F.9.3 Exponential and logarithmic functions</a></h4>
21607 <h5><a name="F.9.3.1" href="#F.9.3.1">F.9.3.1 The exp functions</a></h5>
21610 <li> exp((+-)0) returns 1.
21611 <li> exp(-(inf)) returns +0.
21612 <li> exp(+(inf)) returns +(inf).
21615 <h5><a name="F.9.3.2" href="#F.9.3.2">F.9.3.2 The exp2 functions</a></h5>
21618 <li> exp2((+-)0) returns 1.
21619 <li> exp2(-(inf)) returns +0.
21620 <li> exp2(+(inf)) returns +(inf).
21623 <h5><a name="F.9.3.3" href="#F.9.3.3">F.9.3.3 The expm1 functions</a></h5>
21626 <li> expm1((+-)0) returns (+-)0.
21627 <li> expm1(-(inf)) returns -1.
21628 <li> expm1(+(inf)) returns +(inf).
21631 <h5><a name="F.9.3.4" href="#F.9.3.4">F.9.3.4 The frexp functions</a></h5>
21634 <li> frexp((+-)0, exp) returns (+-)0, and stores 0 in the object pointed to by exp.
21635 <li> frexp((+-)(inf), exp) returns (+-)(inf), and stores an unspecified value in the object
21637 <li> frexp(NaN, exp) stores an unspecified value in the object pointed to by exp
21638 (and returns a NaN).
21641 frexp raises no floating-point exceptions.
21643 On a binary system, the body of the frexp function might be
21646 *exp = (value == 0) ? 0 : (int)(1 + logb(value));
21647 return scalbn(value, -(*exp));
21650 <h5><a name="F.9.3.5" href="#F.9.3.5">F.9.3.5 The ilogb functions</a></h5>
21652 If the correct result is outside the range of the return type, the numeric result is
21653 unspecified and the ''invalid'' floating-point exception is raised.
21656 <h5><a name="F.9.3.6" href="#F.9.3.6">F.9.3.6 The ldexp functions</a></h5>
21658 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
21660 <h5><a name="F.9.3.7" href="#F.9.3.7">F.9.3.7 The log functions</a></h5>
21663 <li> log((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21664 <li> log(1) returns +0.
21665 <li> log(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
21666 <li> log(+(inf)) returns +(inf).
21669 <h5><a name="F.9.3.8" href="#F.9.3.8">F.9.3.8 The log10 functions</a></h5>
21672 <li> log10((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21673 <li> log10(1) returns +0.
21674 <li> log10(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
21675 <li> log10(+(inf)) returns +(inf).
21678 <h5><a name="F.9.3.9" href="#F.9.3.9">F.9.3.9 The log1p functions</a></h5>
21681 <li> log1p((+-)0) returns (+-)0.
21682 <li> log1p(-1) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21683 <li> log1p(x) returns a NaN and raises the ''invalid'' floating-point exception for
21685 <li> log1p(+(inf)) returns +(inf).
21688 <h5><a name="F.9.3.10" href="#F.9.3.10">F.9.3.10 The log2 functions</a></h5>
21691 <li> log2((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21692 <li> log2(1) returns +0.
21693 <li> log2(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
21694 <li> log2(+(inf)) returns +(inf).
21697 <h5><a name="F.9.3.11" href="#F.9.3.11">F.9.3.11 The logb functions</a></h5>
21700 <li> logb((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21701 <li> logb((+-)(inf)) returns +(inf).
21705 <h5><a name="F.9.3.12" href="#F.9.3.12">F.9.3.12 The modf functions</a></h5>
21708 <li> modf((+-)x, iptr) returns a result with the same sign as x.
21709 <li> modf((+-)(inf), iptr) returns (+-)0 and stores (+-)(inf) in the object pointed to by iptr.
21710 <li> modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
21714 modf behaves as though implemented by
21716 #include <a href="#7.12"><math.h></a>
21717 #include <a href="#7.6"><fenv.h></a>
21718 #pragma STDC FENV_ACCESS ON
21719 double modf(double value, double *iptr)
21721 int save_round = fegetround();
21722 fesetround(FE_TOWARDZERO);
21723 *iptr = nearbyint(value);
21724 fesetround(save_round);
21726 isinf(value) ? 0.0 :
21727 value - (*iptr), value);
21730 <h5><a name="F.9.3.13" href="#F.9.3.13">F.9.3.13 The scalbn and scalbln functions</a></h5>
21733 <li> scalbn((+-)0, n) returns (+-)0.
21734 <li> scalbn(x, 0) returns x.
21735 <li> scalbn((+-)(inf), n) returns (+-)(inf).
21738 <h4><a name="F.9.4" href="#F.9.4">F.9.4 Power and absolute value functions</a></h4>
21740 <h5><a name="F.9.4.1" href="#F.9.4.1">F.9.4.1 The cbrt functions</a></h5>
21743 <li> cbrt((+-)0) returns (+-)0.
21744 <li> cbrt((+-)(inf)) returns (+-)(inf).
21747 <h5><a name="F.9.4.2" href="#F.9.4.2">F.9.4.2 The fabs functions</a></h5>
21750 <li> fabs((+-)0) returns +0.
21751 <li> fabs((+-)(inf)) returns +(inf).
21755 <h5><a name="F.9.4.3" href="#F.9.4.3">F.9.4.3 The hypot functions</a></h5>
21758 <li> hypot(x, y), hypot(y, x), and hypot(x, -y) are equivalent.
21759 <li> hypot(x, (+-)0) is equivalent to fabs(x).
21760 <li> hypot((+-)(inf), y) returns +(inf), even if y is a NaN.
21763 <h5><a name="F.9.4.4" href="#F.9.4.4">F.9.4.4 The pow functions</a></h5>
21766 <li> pow((+-)0, y) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception
21767 for y an odd integer < 0.
21768 <li> pow((+-)0, y) returns +(inf) and raises the ''divide-by-zero'' floating-point exception
21769 for y < 0 and not an odd integer.
21770 <li> pow((+-)0, y) returns (+-)0 for y an odd integer > 0.
21771 <li> pow((+-)0, y) returns +0 for y > 0 and not an odd integer.
21772 <li> pow(-1, (+-)(inf)) returns 1.
21773 <li> pow(+1, y) returns 1 for any y, even a NaN.
21774 <li> pow(x, (+-)0) returns 1 for any x, even a NaN.
21775 <li> pow(x, y) returns a NaN and raises the ''invalid'' floating-point exception for
21776 finite x < 0 and finite non-integer y.
21777 <li> pow(x, -(inf)) returns +(inf) for | x | < 1.
21778 <li> pow(x, -(inf)) returns +0 for | x | > 1.
21779 <li> pow(x, +(inf)) returns +0 for | x | < 1.
21780 <li> pow(x, +(inf)) returns +(inf) for | x | > 1.
21781 <li> pow(-(inf), y) returns -0 for y an odd integer < 0.
21782 <li> pow(-(inf), y) returns +0 for y < 0 and not an odd integer.
21783 <li> pow(-(inf), y) returns -(inf) for y an odd integer > 0.
21784 <li> pow(-(inf), y) returns +(inf) for y > 0 and not an odd integer.
21785 <li> pow(+(inf), y) returns +0 for y < 0.
21786 <li> pow(+(inf), y) returns +(inf) for y > 0.
21790 <h5><a name="F.9.4.5" href="#F.9.4.5">F.9.4.5 The sqrt functions</a></h5>
21792 sqrt is fully specified as a basic arithmetic operation in IEC 60559.
21794 <h4><a name="F.9.5" href="#F.9.5">F.9.5 Error and gamma functions</a></h4>
21796 <h5><a name="F.9.5.1" href="#F.9.5.1">F.9.5.1 The erf functions</a></h5>
21799 <li> erf((+-)0) returns (+-)0.
21800 <li> erf((+-)(inf)) returns (+-)1.
21803 <h5><a name="F.9.5.2" href="#F.9.5.2">F.9.5.2 The erfc functions</a></h5>
21806 <li> erfc(-(inf)) returns 2.
21807 <li> erfc(+(inf)) returns +0.
21810 <h5><a name="F.9.5.3" href="#F.9.5.3">F.9.5.3 The lgamma functions</a></h5>
21813 <li> lgamma(1) returns +0.
21814 <li> lgamma(2) returns +0.
21815 <li> lgamma(x) returns +(inf) and raises the ''divide-by-zero'' floating-point exception for
21816 x a negative integer or zero.
21817 <li> lgamma(-(inf)) returns +(inf).
21818 <li> lgamma(+(inf)) returns +(inf).
21821 <h5><a name="F.9.5.4" href="#F.9.5.4">F.9.5.4 The tgamma functions</a></h5>
21824 <li> tgamma((+-)0) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
21825 <li> tgamma(x) returns a NaN and raises the ''invalid'' floating-point exception for x a
21827 <li> tgamma(-(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21828 <li> tgamma(+(inf)) returns +(inf).
21831 <h4><a name="F.9.6" href="#F.9.6">F.9.6 Nearest integer functions</a></h4>
21833 <h5><a name="F.9.6.1" href="#F.9.6.1">F.9.6.1 The ceil functions</a></h5>
21836 <li> ceil((+-)0) returns (+-)0.
21837 <li> ceil((+-)(inf)) returns (+-)(inf).
21840 The double version of ceil behaves as though implemented by
21843 #include <a href="#7.12"><math.h></a>
21844 #include <a href="#7.6"><fenv.h></a>
21845 #pragma STDC FENV_ACCESS ON
21846 double ceil(double x)
21849 int save_round = fegetround();
21850 fesetround(FE_UPWARD);
21851 result = rint(x); // or nearbyint instead of rint
21852 fesetround(save_round);
21856 <h5><a name="F.9.6.2" href="#F.9.6.2">F.9.6.2 The floor functions</a></h5>
21859 <li> floor((+-)0) returns (+-)0.
21860 <li> floor((+-)(inf)) returns (+-)(inf).
21863 See the sample implementation for ceil in <a href="#F.9.6.1">F.9.6.1</a>.
21865 <h5><a name="F.9.6.3" href="#F.9.6.3">F.9.6.3 The nearbyint functions</a></h5>
21867 The nearbyint functions use IEC 60559 rounding according to the current rounding
21868 direction. They do not raise the ''inexact'' floating-point exception if the result differs in
21869 value from the argument.
21871 <li> nearbyint((+-)0) returns (+-)0 (for all rounding directions).
21872 <li> nearbyint((+-)(inf)) returns (+-)(inf) (for all rounding directions).
21875 <h5><a name="F.9.6.4" href="#F.9.6.4">F.9.6.4 The rint functions</a></h5>
21877 The rint functions differ from the nearbyint functions only in that they do raise the
21878 ''inexact'' floating-point exception if the result differs in value from the argument.
21880 <h5><a name="F.9.6.5" href="#F.9.6.5">F.9.6.5 The lrint and llrint functions</a></h5>
21882 The lrint and llrint functions provide floating-to-integer conversion as prescribed
21883 by IEC 60559. They round according to the current rounding direction. If the rounded
21884 value is outside the range of the return type, the numeric result is unspecified and the
21885 ''invalid'' floating-point exception is raised. When they raise no other floating-point
21886 exception and the result differs from the argument, they raise the ''inexact'' floating-point
21890 <h5><a name="F.9.6.6" href="#F.9.6.6">F.9.6.6 The round functions</a></h5>
21893 <li> round((+-)0) returns (+-)0.
21894 <li> round((+-)(inf)) returns (+-)(inf).
21897 The double version of round behaves as though implemented by
21899 #include <a href="#7.12"><math.h></a>
21900 #include <a href="#7.6"><fenv.h></a>
21901 #pragma STDC FENV_ACCESS ON
21902 double round(double x)
21906 feholdexcept(&save_env);
21908 if (fetestexcept(FE_INEXACT)) {
21909 fesetround(FE_TOWARDZERO);
21910 result = rint(copysign(0.5 + fabs(x), x));
21912 feupdateenv(&save_env);
21915 The round functions may, but are not required to, raise the ''inexact'' floating-point
21916 exception for non-integer numeric arguments, as this implementation does.
21918 <h5><a name="F.9.6.7" href="#F.9.6.7">F.9.6.7 The lround and llround functions</a></h5>
21920 The lround and llround functions differ from the lrint and llrint functions
21921 with the default rounding direction just in that the lround and llround functions
21922 round halfway cases away from zero and need not raise the ''inexact'' floating-point
21923 exception for non-integer arguments that round to within the range of the return type.
21925 <h5><a name="F.9.6.8" href="#F.9.6.8">F.9.6.8 The trunc functions</a></h5>
21927 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
21928 rounding direction).
21930 <li> trunc((+-)0) returns (+-)0.
21931 <li> trunc((+-)(inf)) returns (+-)(inf).
21935 <h4><a name="F.9.7" href="#F.9.7">F.9.7 Remainder functions</a></h4>
21937 <h5><a name="F.9.7.1" href="#F.9.7.1">F.9.7.1 The fmod functions</a></h5>
21940 <li> fmod((+-)0, y) returns (+-)0 for y not zero.
21941 <li> fmod(x, y) returns a NaN and raises the ''invalid'' floating-point exception for x
21942 infinite or y zero.
21943 <li> fmod(x, (+-)(inf)) returns x for x not infinite.
21946 The double version of fmod behaves as though implemented by
21948 #include <a href="#7.12"><math.h></a>
21949 #include <a href="#7.6"><fenv.h></a>
21950 #pragma STDC FENV_ACCESS ON
21951 double fmod(double x, double y)
21954 result = remainder(fabs(x), (y = fabs(y)));
21955 if (signbit(result)) result += y;
21956 return copysign(result, x);
21959 <h5><a name="F.9.7.2" href="#F.9.7.2">F.9.7.2 The remainder functions</a></h5>
21961 The remainder functions are fully specified as a basic arithmetic operation in
21964 <h5><a name="F.9.7.3" href="#F.9.7.3">F.9.7.3 The remquo functions</a></h5>
21966 The remquo functions follow the specifications for the remainder functions. They
21967 have no further specifications special to IEC 60559 implementations.
21969 <h4><a name="F.9.8" href="#F.9.8">F.9.8 Manipulation functions</a></h4>
21971 <h5><a name="F.9.8.1" href="#F.9.8.1">F.9.8.1 The copysign functions</a></h5>
21973 copysign is specified in the Appendix to IEC 60559.
21975 <h5><a name="F.9.8.2" href="#F.9.8.2">F.9.8.2 The nan functions</a></h5>
21977 All IEC 60559 implementations support quiet NaNs, in all floating formats.
21980 <h5><a name="F.9.8.3" href="#F.9.8.3">F.9.8.3 The nextafter functions</a></h5>
21983 <li> nextafter(x, y) raises the ''overflow'' and ''inexact'' floating-point exceptions
21984 for x finite and the function value infinite.
21985 <li> nextafter(x, y) raises the ''underflow'' and ''inexact'' floating-point
21986 exceptions for the function value subnormal or zero and x != y.
21989 <h5><a name="F.9.8.4" href="#F.9.8.4">F.9.8.4 The nexttoward functions</a></h5>
21991 No additional requirements beyond those on nextafter.
21993 <h4><a name="F.9.9" href="#F.9.9">F.9.9 Maximum, minimum, and positive difference functions</a></h4>
21995 <h5><a name="F.9.9.1" href="#F.9.9.1">F.9.9.1 The fdim functions</a></h5>
21997 No additional requirements.
21999 <h5><a name="F.9.9.2" href="#F.9.9.2">F.9.9.2 The fmax functions</a></h5>
22001 If just one argument is a NaN, the fmax functions return the other argument (if both
22002 arguments are NaNs, the functions return a NaN).
22004 The body of the fmax function might be<sup><a href="#note323"><b>323)</b></a></sup>
22006 { return (isgreaterequal(x, y) ||
22007 isnan(y)) ? x : y; }</pre>
22010 <p><small><a name="note323" href="#note323">323)</a> Ideally, fmax would be sensitive to the sign of zero, for example fmax(-0.0, +0.0) would
22011 return +0; however, implementation in software might be impractical.
22014 <h5><a name="F.9.9.3" href="#F.9.9.3">F.9.9.3 The fmin functions</a></h5>
22016 The fmin functions are analogous to the fmax functions (see <a href="#F.9.9.2">F.9.9.2</a>).
22018 <h4><a name="F.9.10" href="#F.9.10">F.9.10 Floating multiply-add</a></h4>
22020 <h5><a name="F.9.10.1" href="#F.9.10.1">F.9.10.1 The fma functions</a></h5>
22023 <li> fma(x, y, z) computes xy + z, correctly rounded once.
22024 <li> fma(x, y, z) returns a NaN and optionally raises the ''invalid'' floating-point
22025 exception if one of x and y is infinite, the other is zero, and z is a NaN.
22026 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if
22027 one of x and y is infinite, the other is zero, and z is not a NaN.
22028 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if x
22029 times y is an exact infinity and z is also an infinity but with the opposite sign.
22037 <h2><a name="G" href="#G">Annex G</a></h2>
22040 IEC 60559-compatible complex arithmetic</pre>
22042 <h3><a name="G.1" href="#G.1">G.1 Introduction</a></h3>
22044 This annex supplements <a href="#F">annex F</a> to specify complex arithmetic for compatibility with
22045 IEC 60559 real floating-point arithmetic. Although these specifications have been
22046 carefully designed, there is little existing practice to validate the design decisions.
22047 Therefore, these specifications are not normative, but should be viewed more as
22048 recommended practice. An implementation that defines
22049 __STDC_IEC_559_COMPLEX__ should conform to the specifications in this annex.
22051 <h3><a name="G.2" href="#G.2">G.2 Types</a></h3>
22053 There is a new keyword _Imaginary, which is used to specify imaginary types. It is
22054 used as a type specifier within declaration specifiers in the same way as _Complex is
22055 (thus, _Imaginary float is a valid type name).
22057 There are three imaginary types, designated as float _Imaginary, double
22058 _Imaginary, and long double _Imaginary. The imaginary types (along with
22059 the real floating and complex types) are floating types.
22061 For imaginary types, the corresponding real type is given by deleting the keyword
22062 _Imaginary from the type name.
22064 Each imaginary type has the same representation and alignment requirements as the
22065 corresponding real type. The value of an object of imaginary type is the value of the real
22066 representation times the imaginary unit.
22068 The imaginary type domain comprises the imaginary types.
22070 <h3><a name="G.3" href="#G.3">G.3 Conventions</a></h3>
22072 A complex or imaginary value with at least one infinite part is regarded as an infinity
22073 (even if its other part is a NaN). A complex or imaginary value is a finite number if each
22074 of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
22075 a zero if each of its parts is a zero.
22078 <h3><a name="G.4" href="#G.4">G.4 Conversions</a></h3>
22080 <h4><a name="G.4.1" href="#G.4.1">G.4.1 Imaginary types</a></h4>
22082 Conversions among imaginary types follow rules analogous to those for real floating
22085 <h4><a name="G.4.2" href="#G.4.2">G.4.2 Real and imaginary</a></h4>
22087 When a value of imaginary type is converted to a real type other than _Bool,<sup><a href="#note324"><b>324)</b></a></sup> the
22088 result is a positive zero.
22090 When a value of real type is converted to an imaginary type, the result is a positive
22094 <p><small><a name="note324" href="#note324">324)</a> See <a href="#6.3.1.2">6.3.1.2</a>.
22097 <h4><a name="G.4.3" href="#G.4.3">G.4.3 Imaginary and complex</a></h4>
22099 When a value of imaginary type is converted to a complex type, the real part of the
22100 complex result value is a positive zero and the imaginary part of the complex result value
22101 is determined by the conversion rules for the corresponding real types.
22103 When a value of complex type is converted to an imaginary type, the real part of the
22104 complex value is discarded and the value of the imaginary part is converted according to
22105 the conversion rules for the corresponding real types.
22107 <h3><a name="G.5" href="#G.5">G.5 Binary operators</a></h3>
22109 The following subclauses supplement <a href="#6.5">6.5</a> in order to specify the type of the result for an
22110 operation with an imaginary operand.
22112 For most operand types, the value of the result of a binary operator with an imaginary or
22113 complex operand is completely determined, with reference to real arithmetic, by the usual
22114 mathematical formula. For some operand types, the usual mathematical formula is
22115 problematic because of its treatment of infinities and because of undue overflow or
22116 underflow; in these cases the result satisfies certain properties (specified in <a href="#G.5.1">G.5.1</a>), but is
22117 not completely determined.
22124 <h4><a name="G.5.1" href="#G.5.1">G.5.1 Multiplicative operators</a></h4>
22127 If one operand has real type and the other operand has imaginary type, then the result has
22128 imaginary type. If both operands have imaginary type, then the result has real type. (If
22129 either operand has complex type, then the result has complex type.)
22131 If the operands are not both complex, then the result and floating-point exception
22132 behavior of the * operator is defined by the usual mathematical formula:
22134 * u iv u + iv</pre>
22137 x xu i(xv) (xu) + i(xv)</pre>
22140 iy i(yu) -yv (-yv) + i(yu)</pre>
22144 x + iy (xu) + i(yu) (-yv) + i(xv)</pre>
22145 If the second operand is not complex, then the result and floating-point exception
22146 behavior of the / operator is defined by the usual mathematical formula:
22151 x x/u i(-x/v)</pre>
22154 iy i(y/u) y/v</pre>
22158 x + iy (x/u) + i(y/u) (y/v) + i(-x/v)</pre>
22159 The * and / operators satisfy the following infinity properties for all real, imaginary, and
22160 complex operands:<sup><a href="#note325"><b>325)</b></a></sup>
22162 <li> if one operand is an infinity and the other operand is a nonzero finite number or an
22163 infinity, then the result of the * operator is an infinity;
22164 <li> if the first operand is an infinity and the second operand is a finite number, then the
22165 result of the / operator is an infinity;
22166 <li> if the first operand is a finite number and the second operand is an infinity, then the
22167 result of the / operator is a zero;
22173 <li> if the first operand is a nonzero finite number or an infinity and the second operand is
22174 a zero, then the result of the / operator is an infinity.
22177 If both operands of the * operator are complex or if the second operand of the / operator
22178 is complex, the operator raises floating-point exceptions if appropriate for the calculation
22179 of the parts of the result, and may raise spurious floating-point exceptions.
22181 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
22182 that the imaginary unit I has imaginary type (see <a href="#G.6">G.6</a>).
22186 #include <a href="#7.12"><math.h></a>
22187 #include <a href="#7.3"><complex.h></a>
22188 /* Multiply z * w ... */
22189 double complex _Cmultd(double complex z, double complex w)
22191 #pragma STDC FP_CONTRACT OFF
22192 double a, b, c, d, ac, bd, ad, bc, x, y;
22193 a = creal(z); b = cimag(z);
22194 c = creal(w); d = cimag(w);
22195 ac = a * c; bd = b * d;
22196 ad = a * d; bc = b * c;
22197 x = ac - bd; y = ad + bc;
22198 if (isnan(x) && isnan(y)) {
22199 /* Recover infinities that computed as NaN+iNaN ... */
22201 if ( isinf(a) || isinf(b) ) { // z is infinite
22202 /* "Box" the infinity and change NaNs in the other factor to 0 */
22203 a = copysign(isinf(a) ? 1.0 : 0.0, a);
22204 b = copysign(isinf(b) ? 1.0 : 0.0, b);
22205 if (isnan(c)) c = copysign(0.0, c);
22206 if (isnan(d)) d = copysign(0.0, d);
22209 if ( isinf(c) || isinf(d) ) { // w is infinite
22210 /* "Box" the infinity and change NaNs in the other factor to 0 */
22211 c = copysign(isinf(c) ? 1.0 : 0.0, c);
22212 d = copysign(isinf(d) ? 1.0 : 0.0, d);
22213 if (isnan(a)) a = copysign(0.0, a);
22214 if (isnan(b)) b = copysign(0.0, b);
22217 if (!recalc && (isinf(ac) || isinf(bd) ||
22218 isinf(ad) || isinf(bc))) {
22219 /* Recover infinities from overflow by changing NaNs to 0 ... */
22220 if (isnan(a)) a = copysign(0.0, a);
22221 if (isnan(b)) b = copysign(0.0, b);
22222 if (isnan(c)) c = copysign(0.0, c);
22223 if (isnan(d)) d = copysign(0.0, d);
22227 x = INFINITY * ( a * c - b * d );
22228 y = INFINITY * ( a * d + b * c );
22233 This implementation achieves the required treatment of infinities at the cost of only one isnan test in
22234 ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur.
22237 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
22241 #include <a href="#7.12"><math.h></a>
22242 #include <a href="#7.3"><complex.h></a>
22243 /* Divide z / w ... */
22244 double complex _Cdivd(double complex z, double complex w)
22246 #pragma STDC FP_CONTRACT OFF
22247 double a, b, c, d, logbw, denom, x, y;
22249 a = creal(z); b = cimag(z);
22250 c = creal(w); d = cimag(w);
22251 logbw = logb(fmax(fabs(c), fabs(d)));
22252 if (isfinite(logbw)) {
22253 ilogbw = (int)logbw;
22254 c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
22256 denom = c * c + d * d;
22257 x = scalbn((a * c + b * d) / denom, -ilogbw);
22258 y = scalbn((b * c - a * d) / denom, -ilogbw);
22259 /* Recover infinities and zeros that computed as NaN+iNaN; */
22260 /* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
22261 if (isnan(x) && isnan(y)) {
22262 if ((denom == 0.0) &&
22263 (!isnan(a) || !isnan(b))) {
22264 x = copysign(INFINITY, c) * a;
22265 y = copysign(INFINITY, c) * b;
22267 else if ((isinf(a) || isinf(b)) &&
22268 isfinite(c) && isfinite(d)) {
22269 a = copysign(isinf(a) ? 1.0 : 0.0, a);
22270 b = copysign(isinf(b) ? 1.0 : 0.0, b);
22271 x = INFINITY * ( a * c + b * d );
22272 y = INFINITY * ( b * c - a * d );
22274 else if (isinf(logbw) &&
22275 isfinite(a) && isfinite(b)) {
22276 c = copysign(isinf(c) ? 1.0 : 0.0, c);
22277 d = copysign(isinf(d) ? 1.0 : 0.0, d);
22278 x = 0.0 * ( a * c + b * d );
22279 y = 0.0 * ( b * c - a * d );
22284 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
22285 for multiplication. In the spirit of the multiplication example above, this code does not defend against
22286 overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
22287 with division, provides better roundoff characteristics.
22291 <p><small><a name="note325" href="#note325">325)</a> These properties are already implied for those cases covered in the tables, but are required for all cases
22292 (at least where the state for CX_LIMITED_RANGE is ''off'').
22295 <h4><a name="G.5.2" href="#G.5.2">G.5.2 Additive operators</a></h4>
22298 If both operands have imaginary type, then the result has imaginary type. (If one operand
22299 has real type and the other operand has imaginary type, or if either operand has complex
22300 type, then the result has complex type.)
22302 In all cases the result and floating-point exception behavior of a + or - operator is defined
22303 by the usual mathematical formula:
22305 + or - u iv u + iv</pre>
22308 x x(+-)u x (+-) iv (x (+-) u) (+-) iv</pre>
22311 iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)</pre>
22314 x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)</pre>
22316 <h3><a name="G.6" href="#G.6">G.6 Complex arithmetic <complex.h></a></h3>
22324 are defined, respectively, as _Imaginary and a constant expression of type const
22325 float _Imaginary with the value of the imaginary unit. The macro
22328 is defined to be _Imaginary_I (not _Complex_I as stated in <a href="#7.3">7.3</a>). Notwithstanding
22329 the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and then perhaps redefine the macro
22332 This subclause contains specifications for the <a href="#7.3"><complex.h></a> functions that are
22333 particularly suited to IEC 60559 implementations. For families of functions, the
22334 specifications apply to all of the functions even though only the principal function is
22336 shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument
22337 and the result, the result has the same sign as the argument.
22339 The functions are continuous onto both sides of their branch cuts, taking into account the
22340 sign of zero. For example, csqrt(-2 (+-) i0) = (+-)i(sqrt)2. ???
22342 Since complex and imaginary values are composed of real values, each function may be
22343 regarded as computing real values from real values. Except as noted, the functions treat
22344 real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
22345 manner consistent with the specifications for real functions in F.9.<sup><a href="#note326"><b>326)</b></a></sup>
22347 The functions cimag, conj, cproj, and creal are fully specified for all
22348 implementations, including IEC 60559 ones, in <a href="#7.3.9">7.3.9</a>. These functions raise no floating-
22351 Each of the functions cabs and carg is specified by a formula in terms of a real
22352 function (whose special cases are covered in <a href="#F">annex F</a>):
22355 cabs(x + iy) = hypot(x, y)
22356 carg(x + iy) = atan2(y, x)</pre>
22357 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
22358 a formula in terms of other complex functions (whose special cases are specified below):
22361 casin(z) = -i casinh(iz)
22362 catan(z) = -i catanh(iz)
22363 ccos(z) = ccosh(iz)
22364 csin(z) = -i csinh(iz)
22365 ctan(z) = -i ctanh(iz)</pre>
22366 For the other functions, the following subclauses specify behavior for special cases,
22367 including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For
22368 families of functions, the specifications apply to all of the functions even though only the
22369 principal function is shown. For a function f satisfying f (conj(z)) = conj( f (z)), the
22370 specifications for the upper half-plane imply the specifications for the lower half-plane; if
22371 the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the
22372 specifications for the first quadrant imply the specifications for the other three quadrants.
22374 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
22382 <p><small><a name="note326" href="#note326">326)</a> 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
22383 other part is a NaN.
22386 <h4><a name="G.6.1" href="#G.6.1">G.6.1 Trigonometric functions</a></h4>
22388 <h5><a name="G.6.1.1" href="#G.6.1.1">G.6.1.1 The cacos functions</a></h5>
22391 <li> cacos(conj(z)) = conj(cacos(z)).
22392 <li> cacos((+-)0 + i0) returns pi /2 - i0.
22393 <li> cacos((+-)0 + iNaN) returns pi /2 + iNaN.
22394 <li> cacos(x + i (inf)) returns pi /2 - i (inf), for finite x.
22395 <li> cacos(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22396 point exception, for nonzero finite x.
22397 <li> cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.
22398 <li> cacos(+(inf) + iy) returns +0 - i (inf), for positive-signed finite y.
22399 <li> cacos(-(inf) + i (inf)) returns 3pi /4 - i (inf).
22400 <li> cacos(+(inf) + i (inf)) returns pi /4 - i (inf).
22401 <li> cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
22402 result is unspecified).
22403 <li> cacos(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22404 point exception, for finite y.
22405 <li> cacos(NaN + i (inf)) returns NaN - i (inf).
22406 <li> cacos(NaN + iNaN) returns NaN + iNaN.
22409 <h4><a name="G.6.2" href="#G.6.2">G.6.2 Hyperbolic functions</a></h4>
22411 <h5><a name="G.6.2.1" href="#G.6.2.1">G.6.2.1 The cacosh functions</a></h5>
22414 <li> cacosh(conj(z)) = conj(cacosh(z)).
22415 <li> cacosh((+-)0 + i0) returns +0 + ipi /2.
22416 <li> cacosh(x + i (inf)) returns +(inf) + ipi /2, for finite x.
22417 <li> cacosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
22418 floating-point exception, for finite x.
22419 <li> cacosh(-(inf) + iy) returns +(inf) + ipi , for positive-signed finite y.
22420 <li> cacosh(+(inf) + iy) returns +(inf) + i0, for positive-signed finite y.
22421 <li> cacosh(-(inf) + i (inf)) returns +(inf) + i3pi /4.
22422 <li> cacosh(+(inf) + i (inf)) returns +(inf) + ipi /4.
22423 <li> cacosh((+-)(inf) + iNaN) returns +(inf) + iNaN.
22425 <li> cacosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
22426 floating-point exception, for finite y.
22427 <li> cacosh(NaN + i (inf)) returns +(inf) + iNaN.
22428 <li> cacosh(NaN + iNaN) returns NaN + iNaN.
22431 <h5><a name="G.6.2.2" href="#G.6.2.2">G.6.2.2 The casinh functions</a></h5>
22434 <li> casinh(conj(z)) = conj(casinh(z)) and casinh is odd.
22435 <li> casinh(+0 + i0) returns 0 + i0.
22436 <li> casinh(x + i (inf)) returns +(inf) + ipi /2 for positive-signed finite x.
22437 <li> casinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
22438 floating-point exception, for finite x.
22439 <li> casinh(+(inf) + iy) returns +(inf) + i0 for positive-signed finite y.
22440 <li> casinh(+(inf) + i (inf)) returns +(inf) + ipi /4.
22441 <li> casinh(+(inf) + iNaN) returns +(inf) + iNaN.
22442 <li> casinh(NaN + i0) returns NaN + i0.
22443 <li> casinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
22444 floating-point exception, for finite nonzero y.
22445 <li> casinh(NaN + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result
22447 <li> casinh(NaN + iNaN) returns NaN + iNaN.
22450 <h5><a name="G.6.2.3" href="#G.6.2.3">G.6.2.3 The catanh functions</a></h5>
22453 <li> catanh(conj(z)) = conj(catanh(z)) and catanh is odd.
22454 <li> catanh(+0 + i0) returns +0 + i0.
22455 <li> catanh(+0 + iNaN) returns +0 + iNaN.
22456 <li> catanh(+1 + i0) returns +(inf) + i0 and raises the ''divide-by-zero'' floating-point
22458 <li> catanh(x + i (inf)) returns +0 + ipi /2, for finite positive-signed x.
22459 <li> catanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
22460 floating-point exception, for nonzero finite x.
22461 <li> catanh(+(inf) + iy) returns +0 + ipi /2, for finite positive-signed y.
22462 <li> catanh(+(inf) + i (inf)) returns +0 + ipi /2.
22463 <li> catanh(+(inf) + iNaN) returns +0 + iNaN.
22465 <li> catanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
22466 floating-point exception, for finite y.
22467 <li> catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is
22469 <li> catanh(NaN + iNaN) returns NaN + iNaN.
22472 <h5><a name="G.6.2.4" href="#G.6.2.4">G.6.2.4 The ccosh functions</a></h5>
22475 <li> ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
22476 <li> ccosh(+0 + i0) returns 1 + i0.
22477 <li> ccosh(+0 + i (inf)) returns NaN (+-) i0 (where the sign of the imaginary part of the
22478 result is unspecified) and raises the ''invalid'' floating-point exception.
22479 <li> ccosh(+0 + iNaN) returns NaN (+-) i0 (where the sign of the imaginary part of the
22480 result is unspecified).
22481 <li> ccosh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22482 exception, for finite nonzero x.
22483 <li> ccosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22484 point exception, for finite nonzero x.
22485 <li> ccosh(+(inf) + i0) returns +(inf) + i0.
22486 <li> ccosh(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
22487 <li> ccosh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
22488 unspecified) and raises the ''invalid'' floating-point exception.
22489 <li> ccosh(+(inf) + iNaN) returns +(inf) + iNaN.
22490 <li> ccosh(NaN + i0) returns NaN (+-) i0 (where the sign of the imaginary part of the
22491 result is unspecified).
22492 <li> ccosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22493 point exception, for all nonzero numbers y.
22494 <li> ccosh(NaN + iNaN) returns NaN + iNaN.
22497 <h5><a name="G.6.2.5" href="#G.6.2.5">G.6.2.5 The csinh functions</a></h5>
22500 <li> csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
22501 <li> csinh(+0 + i0) returns +0 + i0.
22502 <li> csinh(+0 + i (inf)) returns (+-)0 + iNaN (where the sign of the real part of the result is
22503 unspecified) and raises the ''invalid'' floating-point exception.
22504 <li> csinh(+0 + iNaN) returns (+-)0 + iNaN (where the sign of the real part of the result is
22507 <li> csinh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22508 exception, for positive finite x.
22509 <li> csinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22510 point exception, for finite nonzero x.
22511 <li> csinh(+(inf) + i0) returns +(inf) + i0.
22512 <li> csinh(+(inf) + iy) returns +(inf) cis(y), for positive finite y.
22513 <li> csinh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
22514 unspecified) and raises the ''invalid'' floating-point exception.
22515 <li> csinh(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
22517 <li> csinh(NaN + i0) returns NaN + i0.
22518 <li> csinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22519 point exception, for all nonzero numbers y.
22520 <li> csinh(NaN + iNaN) returns NaN + iNaN.
22523 <h5><a name="G.6.2.6" href="#G.6.2.6">G.6.2.6 The ctanh functions</a></h5>
22526 <li> ctanh(conj(z)) = conj(ctanh(z))and ctanh is odd.
22527 <li> ctanh(+0 + i0) returns +0 + i0.
22528 <li> ctanh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22529 exception, for finite x.
22530 <li> ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22531 point exception, for finite x.
22532 <li> ctanh(+(inf) + iy) returns 1 + i0 sin(2y), for positive-signed finite y.
22533 <li> ctanh(+(inf) + i (inf)) returns 1 (+-) i0 (where the sign of the imaginary part of the result
22535 <li> ctanh(+(inf) + iNaN) returns 1 (+-) i0 (where the sign of the imaginary part of the
22536 result is unspecified).
22537 <li> ctanh(NaN + i0) returns NaN + i0.
22538 <li> ctanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22539 point exception, for all nonzero numbers y.
22540 <li> ctanh(NaN + iNaN) returns NaN + iNaN.
22544 <h4><a name="G.6.3" href="#G.6.3">G.6.3 Exponential and logarithmic functions</a></h4>
22546 <h5><a name="G.6.3.1" href="#G.6.3.1">G.6.3.1 The cexp functions</a></h5>
22549 <li> cexp(conj(z)) = conj(cexp(z)).
22550 <li> cexp((+-)0 + i0) returns 1 + i0.
22551 <li> cexp(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22552 exception, for finite x.
22553 <li> cexp(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22554 point exception, for finite x.
22555 <li> cexp(+(inf) + i0) returns +(inf) + i0.
22556 <li> cexp(-(inf) + iy) returns +0 cis(y), for finite y.
22557 <li> cexp(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
22558 <li> cexp(-(inf) + i (inf)) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts of
22559 the result are unspecified).
22560 <li> cexp(+(inf) + i (inf)) returns (+-)(inf) + iNaN and raises the ''invalid'' floating-point
22561 exception (where the sign of the real part of the result is unspecified).
22562 <li> cexp(-(inf) + iNaN) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts
22563 of the result are unspecified).
22564 <li> cexp(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
22566 <li> cexp(NaN + i0) returns NaN + i0.
22567 <li> cexp(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22568 point exception, for all nonzero numbers y.
22569 <li> cexp(NaN + iNaN) returns NaN + iNaN.
22572 <h5><a name="G.6.3.2" href="#G.6.3.2">G.6.3.2 The clog functions</a></h5>
22575 <li> clog(conj(z)) = conj(clog(z)).
22576 <li> clog(-0 + i0) returns -(inf) + ipi and raises the ''divide-by-zero'' floating-point
22578 <li> clog(+0 + i0) returns -(inf) + i0 and raises the ''divide-by-zero'' floating-point
22580 <li> clog(x + i (inf)) returns +(inf) + ipi /2, for finite x.
22581 <li> clog(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22582 point exception, for finite x.
22584 <li> clog(-(inf) + iy) returns +(inf) + ipi , for finite positive-signed y.
22585 <li> clog(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
22586 <li> clog(-(inf) + i (inf)) returns +(inf) + i3pi /4.
22587 <li> clog(+(inf) + i (inf)) returns +(inf) + ipi /4.
22588 <li> clog((+-)(inf) + iNaN) returns +(inf) + iNaN.
22589 <li> clog(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22590 point exception, for finite y.
22591 <li> clog(NaN + i (inf)) returns +(inf) + iNaN.
22592 <li> clog(NaN + iNaN) returns NaN + iNaN.
22595 <h4><a name="G.6.4" href="#G.6.4">G.6.4 Power and absolute-value functions</a></h4>
22597 <h5><a name="G.6.4.1" href="#G.6.4.1">G.6.4.1 The cpow functions</a></h5>
22599 The cpow functions raise floating-point exceptions if appropriate for the calculation of
22600 the parts of the result, and may raise spurious exceptions.<sup><a href="#note327"><b>327)</b></a></sup>
22603 <p><small><a name="note327" href="#note327">327)</a> This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding
22604 implementations that treat special cases more carefully.
22607 <h5><a name="G.6.4.2" href="#G.6.4.2">G.6.4.2 The csqrt functions</a></h5>
22610 <li> csqrt(conj(z)) = conj(csqrt(z)).
22611 <li> csqrt((+-)0 + i0) returns +0 + i0.
22612 <li> csqrt(x + i (inf)) returns +(inf) + i (inf), for all x (including NaN).
22613 <li> csqrt(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22614 point exception, for finite x.
22615 <li> csqrt(-(inf) + iy) returns +0 + i (inf), for finite positive-signed y.
22616 <li> csqrt(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
22617 <li> csqrt(-(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
22618 result is unspecified).
22619 <li> csqrt(+(inf) + iNaN) returns +(inf) + iNaN.
22620 <li> csqrt(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22621 point exception, for finite y.
22622 <li> csqrt(NaN + iNaN) returns NaN + iNaN.
22630 <h3><a name="G.7" href="#G.7">G.7 Type-generic math <tgmath.h></a></h3>
22632 Type-generic macros that accept complex arguments also accept imaginary arguments. If
22633 an argument is imaginary, the macro expands to an expression whose type is real,
22634 imaginary, or complex, as appropriate for the particular function: if the argument is
22635 imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the
22636 types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and
22637 the types of the others are complex.
22639 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh,
22640 sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real
22645 sin(iy) = i sinh(y)
22646 tan(iy) = i tanh(y)
22648 sinh(iy) = i sin(y)
22649 tanh(iy) = i tan(y)
22650 asin(iy) = i asinh(y)
22651 atan(iy) = i atanh(y)
22652 asinh(iy) = i asin(y)
22653 atanh(iy) = i atan(y)</pre>
22655 <h2><a name="H" href="#H">Annex H</a></h2>
22658 Language independent arithmetic</pre>
22660 <h3><a name="H.1" href="#H.1">H.1 Introduction</a></h3>
22662 This annex documents the extent to which the C language supports the ISO/IEC 10967-1
22663 standard for language-independent arithmetic (LIA-1). LIA-1 is more general than
22664 IEC 60559 (<a href="#F">annex F</a>) in that it covers integer and diverse floating-point arithmetics.
22666 <h3><a name="H.2" href="#H.2">H.2 Types</a></h3>
22668 The relevant C arithmetic types meet the requirements of LIA-1 types if an
22669 implementation adds notification of exceptional arithmetic operations and meets the 1
22670 unit in the last place (ULP) accuracy requirement (LIA-1 subclause <a href="#5.2.8">5.2.8</a>).
22672 <h4><a name="H.2.1" href="#H.2.1">H.2.1 Boolean type</a></h4>
22674 The LIA-1 data type Boolean is implemented by the C data type bool with values of
22675 true and false, all from <a href="#7.16"><stdbool.h></a>.
22677 <h4><a name="H.2.2" href="#H.2.2">H.2.2 Integer types</a></h4>
22679 The signed C integer types int, long int, long long int, and the corresponding
22680 unsigned types are compatible with LIA-1. If an implementation adds support for the
22681 LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are
22682 LIA-1 conformant types. C's unsigned integer types are ''modulo'' in the LIA-1 sense
22683 in that overflows or out-of-bounds results silently wrap. An implementation that defines
22684 signed integer types as also being modulo need not detect integer overflow, in which case,
22685 only integer divide-by-zero need be detected.
22687 The parameters for the integer data types can be accessed by the following:
22688 maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
22691 minint INT_MIN, LONG_MIN, LLONG_MIN
22693 The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
22694 is always 0 for the unsigned types, and is not provided for those types.
22697 <h5><a name="H.2.2.1" href="#H.2.2.1">H.2.2.1 Integer operations</a></h5>
22699 The integer operations on integer types are the following:
22706 absI abs(x), labs(x), llabs(x)
22713 where x and y are expressions of the same integer type.
22715 <h4><a name="H.2.3" href="#H.2.3">H.2.3 Floating-point types</a></h4>
22717 The C floating-point types float, double, and long double are compatible with
22718 LIA-1. If an implementation adds support for the LIA-1 exceptional values
22719 ''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
22720 with LIA-1. An implementation that uses IEC 60559 floating-point formats and
22721 operations (see <a href="#F">annex F</a>) along with IEC 60559 status flags and traps has LIA-1
22724 <h5><a name="H.2.3.1" href="#H.2.3.1">H.2.3.1 Floating-point parameters</a></h5>
22726 The parameters for a floating point data type can be accessed by the following:
22728 p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
22729 emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
22730 emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
22732 The derived constants for the floating point types are accessed by the following:
22734 fmax FLT_MAX, DBL_MAX, LDBL_MAX
22735 fminN FLT_MIN, DBL_MIN, LDBL_MIN
22736 epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
22737 rnd_style FLT_ROUNDS
22739 <h5><a name="H.2.3.2" href="#H.2.3.2">H.2.3.2 Floating-point operations</a></h5>
22741 The floating-point operations on floating-point types are the following:
22747 absF fabsf(x), fabs(x), fabsl(x)
22748 exponentF 1.f+logbf(x), 1.0+logb(x), 1.L+logbl(x)
22749 scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
22751 scalblnf(x, li), scalbln(x, li), scalblnl(x, li)</pre>
22752 intpartF modff(x, &y), modf(x, &y), modfl(x, &y)
22753 fractpartF modff(x, &y), modf(x, &y), modfl(x, &y)
22760 where x and y are expressions of the same floating point type, n is of type int, and li
22761 is of type long int.
22763 <h5><a name="H.2.3.3" href="#H.2.3.3">H.2.3.3 Rounding styles</a></h5>
22765 The C Standard requires all floating types to use the same radix and rounding style, so
22766 that only one identifier for each is provided to map to LIA-1.
22768 The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
22769 truncate FLT_ROUNDS == 0
22771 nearest FLT_ROUNDS == 1
22772 other FLT_ROUNDS != 0 && FLT_ROUNDS != 1
22773 provided that an implementation extends FLT_ROUNDS to cover the rounding style used
22774 in all relevant LIA-1 operations, not just addition as in C.
22776 <h4><a name="H.2.4" href="#H.2.4">H.2.4 Type conversions</a></h4>
22778 The LIA-1 type conversions are the following type casts:
22779 cvtI' -> I (int)i, (long int)i, (long long int)i,
22781 (unsigned int)i, (unsigned long int)i,
22782 (unsigned long long int)i</pre>
22783 cvtF -> I (int)x, (long int)x, (long long int)x,
22785 (unsigned int)x, (unsigned long int)x,
22786 (unsigned long long int)x</pre>
22787 cvtI -> F (float)i, (double)i, (long double)i
22788 cvtF' -> F (float)x, (double)x, (long double)x
22790 In the above conversions from floating to integer, the use of (cast)x can be replaced with
22791 (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
22792 (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer
22793 conversion functions, lrint(), llrint(), lround(), and llround(), can be
22794 used. They all meet LIA-1's requirements on floating to integer rounding for in-range
22795 values. For out-of-range values, the conversions shall silently wrap for the modulo types.
22797 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
22798 fmod( fabs(rint(x)), 65536.0 ) or (0.0 <= (y = fmod( rint(x),
22799 65536.0 )) ? y : 65536.0 + y) will compute an integer value in the range 0.0
22800 to 65535.0 which can then be cast to unsigned short int. But, the
22801 remainder() function is not useful for doing silent wrapping to signed integer types,
22802 e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
22803 range -32767.0 to +32768.0 which is not, in general, in the range of signed short
22806 C's conversions (casts) from floating-point to floating-point can meet LIA-1
22807 requirements if an implementation uses round-to-nearest (IEC 60559 default).
22809 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
22810 implementation uses round-to-nearest.
22813 <h3><a name="H.3" href="#H.3">H.3 Notification</a></h3>
22815 Notification is the process by which a user or program is informed that an exceptional
22816 arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
22817 allows an implementation to cause a notification to occur when any arithmetic operation
22818 returns an exceptional value as defined in LIA-1 clause 5.
22820 <h4><a name="H.3.1" href="#H.3.1">H.3.1 Notification alternatives</a></h4>
22822 LIA-1 requires at least the following two alternatives for handling of notifications:
22823 setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and-
22826 An implementation need only support a given notification alternative for the entire
22827 program. An implementation may support the ability to switch between notification
22828 alternatives during execution, but is not required to do so. An implementation can
22829 provide separate selection for each kind of notification, but this is not required.
22831 C allows an implementation to provide notification. C's SIGFPE (for traps) and
22832 FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
22833 can provide LIA-1 notification.
22835 C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
22836 provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
22837 math library function calls. User-provided signal handlers for SIGFPE allow for trap-
22838 and-resume behavior with the same constraint.
22840 <h5><a name="H.3.1.1" href="#H.3.1.1">H.3.1.1 Indicators</a></h5>
22842 C's <a href="#7.6"><fenv.h></a> status flags are compatible with the LIA-1 indicators.
22844 The following mapping is for floating-point types:
22845 undefined FE_INVALID, FE_DIVBYZERO
22846 floating_overflow FE_OVERFLOW
22847 underflow FE_UNDERFLOW
22849 The floating-point indicator interrogation and manipulation operations are:
22850 set_indicators feraiseexcept(i)
22851 clear_indicators feclearexcept(i)
22852 test_indicators fetestexcept(i)
22853 current_indicators fetestexcept(FE_ALL_EXCEPT)
22854 where i is an expression of type int representing a subset of the LIA-1 indicators.
22856 C allows an implementation to provide the following LIA-1 required behavior: at
22857 program termination if any indicator is set the implementation shall send an unambiguous
22859 and ''hard to ignore'' message (see LIA-1 subclause <a href="#6.1.2">6.1.2</a>)
22861 LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
22862 This documentation makes that distinction because <a href="#7.6"><fenv.h></a> covers only the floating-
22865 <h5><a name="H.3.1.2" href="#H.3.1.2">H.3.1.2 Traps</a></h5>
22867 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
22868 math library functions (which are not permitted to generate any externally visible
22869 exceptional conditions). An implementation can provide an alternative of notification
22870 through termination with a ''hard-to-ignore'' message (see LIA-1 subclause <a href="#6.1.3">6.1.3</a>).
22872 LIA-1 does not require that traps be precise.
22874 C does require that SIGFPE be the signal corresponding to arithmetic exceptions, if there
22875 is any signal raised for them.
22877 C supports signal handlers for SIGFPE and allows trapping of arithmetic exceptions.
22878 When arithmetic exceptions do trap, C's signal-handler mechanism allows trap-and-
22879 terminate (either default implementation behavior or user replacement for it) or trap-and-
22880 resume, at the programmer's option.
22883 <h2><a name="I" href="#I">Annex I</a></h2>
22887 Common warnings</pre>
22888 An implementation may generate warnings in many situations, none of which are
22889 specified as part of this International Standard. The following are a few of the more
22893 <li> 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>).
22894 <li> A block with initialization of an object that has automatic storage duration is jumped
22895 into (<a href="#6.2.4">6.2.4</a>).
22896 <li> An implicit narrowing conversion is encountered, such as the assignment of a long
22897 int or a double to an int, or a pointer to void to a pointer to any type other than
22898 a character type (<a href="#6.3">6.3</a>).
22899 <li> A hexadecimal floating constant cannot be represented exactly in its evaluation format
22900 (<a href="#6.4.4.2">6.4.4.2</a>).
22901 <li> An integer character constant includes more than one character or a wide character
22902 constant includes more than one multibyte character (<a href="#6.4.4.4">6.4.4.4</a>).
22903 <li> The characters /* are found in a comment (<a href="#6.4.7">6.4.7</a>).
22904 <li> An ''unordered'' binary operator (not comma, &&, or ||) contains a side effect to an
22905 lvalue in one operand, and a side effect to, or an access to the value of, the identical
22906 lvalue in the other operand (<a href="#6.5">6.5</a>).
22907 <li> A function is called but no prototype has been supplied (<a href="#6.5.2.2">6.5.2.2</a>).
22908 <li> The arguments in a function call do not agree in number and type with those of the
22909 parameters in a function definition that is not a prototype (<a href="#6.5.2.2">6.5.2.2</a>).
22910 <li> An object is defined but not used (<a href="#6.7">6.7</a>).
22911 <li> A value is given to an object of an enumerated type other than by assignment of an
22912 enumeration constant that is a member of that type, or an enumeration object that has
22913 the same type, or the value of a function that returns the same enumerated type
22914 (<a href="#6.7.2.2">6.7.2.2</a>).
22915 <li> An aggregate has a partly bracketed initialization (<a href="#6.7.7">6.7.7</a>).
22916 <li> A statement cannot be reached (<a href="#6.8">6.8</a>).
22917 <li> A statement with no apparent effect is encountered (<a href="#6.8">6.8</a>).
22918 <li> A constant expression is used as the controlling expression of a selection statement
22919 (<a href="#6.8.4">6.8.4</a>).
22921 <li> An incorrectly formed preprocessing group is encountered while skipping a
22922 preprocessing group (<a href="#6.10.1">6.10.1</a>).
22923 <li> An unrecognized #pragma directive is encountered (<a href="#6.10.6">6.10.6</a>).
22927 <h2><a name="J" href="#J">Annex J</a></h2>
22931 Portability issues</pre>
22932 This annex collects some information about portability that appears in this International
22935 <h3><a name="J.1" href="#J.1">J.1 Unspecified behavior</a></h3>
22937 The following are unspecified:
22939 <li> The manner and timing of static initialization (<a href="#5.1.2">5.1.2</a>).
22940 <li> The termination status returned to the hosted environment if the return type of main
22941 is not compatible with int (<a href="#5.1.2.2.3">5.1.2.2.3</a>).
22942 <li> The behavior of the display device if a printing character is written when the active
22943 position is at the final position of a line (<a href="#5.2.2">5.2.2</a>).
22944 <li> The behavior of the display device if a backspace character is written when the active
22945 position is at the initial position of a line (<a href="#5.2.2">5.2.2</a>).
22946 <li> The behavior of the display device if a horizontal tab character is written when the
22947 active position is at or past the last defined horizontal tabulation position (<a href="#5.2.2">5.2.2</a>).
22948 <li> The behavior of the display device if a vertical tab character is written when the active
22949 position is at or past the last defined vertical tabulation position (<a href="#5.2.2">5.2.2</a>).
22950 <li> How an extended source character that does not correspond to a universal character
22951 name counts toward the significant initial characters in an external identifier (<a href="#5.2.4.1">5.2.4.1</a>).
22952 <li> Many aspects of the representations of types (<a href="#6.2.6">6.2.6</a>).
22953 <li> The value of padding bytes when storing values in structures or unions (<a href="#6.2.6.1">6.2.6.1</a>).
22954 <li> The value of a union member other than the last one stored into (<a href="#6.2.6.1">6.2.6.1</a>).
22955 <li> The representation used when storing a value in an object that has more than one
22956 object representation for that value (<a href="#6.2.6.1">6.2.6.1</a>).
22957 <li> The values of any padding bits in integer representations (<a href="#6.2.6.2">6.2.6.2</a>).
22958 <li> Whether certain operators can generate negative zeros and whether a negative zero
22959 becomes a normal zero when stored in an object (<a href="#6.2.6.2">6.2.6.2</a>).
22960 <li> Whether two string literals result in distinct arrays (<a href="#6.4.5">6.4.5</a>).
22961 <li> The order in which subexpressions are evaluated and the order in which side effects
22962 take place, except as specified for the function-call (), &&, ||, ?:, and comma
22963 operators (<a href="#6.5">6.5</a>).
22965 <li> The order in which the function designator, arguments, and subexpressions within the
22966 arguments are evaluated in a function call (<a href="#6.5.2.2">6.5.2.2</a>).
22967 <li> The order of side effects among compound literal initialization list expressions
22968 (<a href="#6.5.2.5">6.5.2.5</a>).
22969 <li> The order in which the operands of an assignment operator are evaluated (<a href="#6.5.16">6.5.16</a>).
22970 <li> The alignment of the addressable storage unit allocated to hold a bit-field (<a href="#6.7.2.1">6.7.2.1</a>).
22971 <li> Whether a call to an inline function uses the inline definition or the external definition
22972 of the function (<a href="#6.7.4">6.7.4</a>).
22973 <li> Whether or not a size expression is evaluated when it is part of the operand of a
22974 sizeof operator and changing the value of the size expression would not affect the
22975 result of the operator (<a href="#6.7.5.2">6.7.5.2</a>).
22976 <li> The order in which any side effects occur among the initialization list expressions in
22977 an initializer (<a href="#6.7.8">6.7.8</a>).
22978 <li> The layout of storage for function parameters (<a href="#6.9.1">6.9.1</a>).
22979 <li> When a fully expanded macro replacement list contains a function-like macro name
22980 as its last preprocessing token and the next preprocessing token from the source file is
22981 a (, and the fully expanded replacement of that macro ends with the name of the first
22982 macro and the next preprocessing token from the source file is again a (, whether that
22983 is considered a nested replacement (<a href="#6.10.3">6.10.3</a>).
22984 <li> The order in which # and ## operations are evaluated during macro substitution
22985 (<a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>).
22986 <li> Whether errno is a macro or an identifier with external linkage (<a href="#7.5">7.5</a>).
22987 <li> The state of the floating-point status flags when execution passes from a part of the
22988 program translated with FENV_ACCESS ''off'' to a part translated with
22989 FENV_ACCESS ''on'' (<a href="#7.6.1">7.6.1</a>).
22990 <li> The order in which feraiseexcept raises floating-point exceptions, except as
22991 stated in <a href="#F.7.6">F.7.6</a> (<a href="#7.6.2.3">7.6.2.3</a>).
22992 <li> Whether math_errhandling is a macro or an identifier with external linkage
22993 (<a href="#7.12">7.12</a>).
22994 <li> The results of the frexp functions when the specified value is not a floating-point
22995 number (<a href="#7.12.6.4">7.12.6.4</a>).
22996 <li> The numeric result of the ilogb functions when the correct value is outside the
22997 range of the return type (<a href="#7.12.6.5">7.12.6.5</a>, <a href="#F.9.3.5">F.9.3.5</a>).
22998 <li> 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.9.6.5">F.9.6.5</a>).
23000 <li> The value stored by the remquo functions in the object pointed to by quo when y is
23001 zero (<a href="#7.12.10.3">7.12.10.3</a>).
23002 <li> Whether setjmp is a macro or an identifier with external linkage (<a href="#7.13">7.13</a>).
23003 <li> Whether va_copy and va_end are macros or identifiers with external linkage
23004 (<a href="#7.15.1">7.15.1</a>).
23005 <li> The hexadecimal digit before the decimal point when a non-normalized floating-point
23006 number is printed with an a or A conversion specifier (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23007 <li> The value of the file position indicator after a successful call to the ungetc function
23008 for a text stream, or the ungetwc function for any stream, until all pushed-back
23009 characters are read or discarded (<a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.24.3.10">7.24.3.10</a>).
23010 <li> The details of the value stored by the fgetpos function (<a href="#7.19.9.1">7.19.9.1</a>).
23011 <li> The details of the value returned by the ftell function for a text stream (<a href="#7.19.9.4">7.19.9.4</a>).
23012 <li> Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold
23013 functions convert a minus-signed sequence to a negative number directly or by
23014 negating the value resulting from converting the corresponding unsigned sequence
23015 (<a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>).
23016 <li> The order and contiguity of storage allocated by successive calls to the calloc,
23017 malloc, and realloc functions (<a href="#7.20.3">7.20.3</a>).
23018 <li> The amount of storage allocated by a successful call to the calloc, malloc, or
23019 realloc function when 0 bytes was requested (<a href="#7.20.3">7.20.3</a>).
23020 <li> Which of two elements that compare as equal is matched by the bsearch function
23021 (<a href="#7.20.5.1">7.20.5.1</a>).
23022 <li> The order of two elements that compare as equal in an array sorted by the qsort
23023 function (<a href="#7.20.5.2">7.20.5.2</a>).
23024 <li> The encoding of the calendar time returned by the time function (<a href="#7.23.2.4">7.23.2.4</a>).
23025 <li> The characters stored by the strftime or wcsftime function if any of the time
23026 values being converted is outside the normal range (<a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.5.1">7.24.5.1</a>).
23027 <li> The conversion state after an encoding error occurs (<a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>,
23028 <a href="#7.24.6.4.2">7.24.6.4.2</a>,
23029 <li> The resulting value when the ''invalid'' floating-point exception is raised during
23030 IEC 60559 floating to integer conversion (<a href="#F.4">F.4</a>).
23031 <li> Whether conversion of non-integer IEC 60559 floating values to integer raises the
23032 ''inexact'' floating-point exception (<a href="#F.4">F.4</a>).
23034 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise the ''inexact'' floating-point
23035 exception in an IEC 60559 conformant implementation (<a href="#F.9">F.9</a>).
23036 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise an undeserved ''underflow''
23037 floating-point exception in an IEC 60559 conformant implementation (<a href="#F.9">F.9</a>).
23038 <li> The exponent value stored by frexp for a NaN or infinity (<a href="#F.9.3.4">F.9.3.4</a>).
23039 <li> The numeric result returned by the lrint, llrint, lround, and llround
23040 functions if the rounded value is outside the range of the return type (<a href="#F.9.6.5">F.9.6.5</a>, <a href="#F.9.6.7">F.9.6.7</a>).
23041 <li> The sign of one part of the complex result of several math functions for certain
23042 exceptional values in IEC 60559 compatible implementations (<a href="#G.6.1.1">G.6.1.1</a>, <a href="#G.6.2.2">G.6.2.2</a>,
23043 <a href="#G.6.2.3">G.6.2.3</a>, <a href="#G.6.2.4">G.6.2.4</a>, <a href="#G.6.2.5">G.6.2.5</a>, <a href="#G.6.2.6">G.6.2.6</a>, <a href="#G.6.3.1">G.6.3.1</a>, <a href="#G.6.4.2">G.6.4.2</a>).
23046 <h3><a name="J.2" href="#J.2">J.2 Undefined behavior</a></h3>
23048 The behavior is undefined in the following circumstances:
23050 <li> A ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated
23052 <li> A nonempty source file does not end in a new-line character which is not immediately
23053 preceded by a backslash character or ends in a partial preprocessing token or
23054 comment (<a href="#5.1.1.2">5.1.1.2</a>).
23055 <li> Token concatenation produces a character sequence matching the syntax of a
23056 universal character name (<a href="#5.1.1.2">5.1.1.2</a>).
23057 <li> A program in a hosted environment does not define a function named main using one
23058 of the specified forms (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
23059 <li> A character not in the basic source character set is encountered in a source file, except
23060 in an identifier, a character constant, a string literal, a header name, a comment, or a
23061 preprocessing token that is never converted to a token (<a href="#5.2.1">5.2.1</a>).
23062 <li> An identifier, comment, string literal, character constant, or header name contains an
23063 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>).
23064 <li> The same identifier has both internal and external linkage in the same translation unit
23065 (<a href="#6.2.2">6.2.2</a>).
23066 <li> An object is referred to outside of its lifetime (<a href="#6.2.4">6.2.4</a>).
23067 <li> The value of a pointer to an object whose lifetime has ended is used (<a href="#6.2.4">6.2.4</a>).
23068 <li> The value of an object with automatic storage duration is used while it is
23069 indeterminate (<a href="#6.2.4">6.2.4</a>, <a href="#6.7.8">6.7.8</a>, <a href="#6.8">6.8</a>).
23070 <li> A trap representation is read by an lvalue expression that does not have character type
23071 (<a href="#6.2.6.1">6.2.6.1</a>).
23073 <li> A trap representation is produced by a side effect that modifies any part of the object
23074 using an lvalue expression that does not have character type (<a href="#6.2.6.1">6.2.6.1</a>).
23075 <li> The arguments to certain operators are such that could produce a negative zero result,
23076 but the implementation does not support negative zeros (<a href="#6.2.6.2">6.2.6.2</a>).
23077 <li> Two declarations of the same object or function specify types that are not compatible
23078 (<a href="#6.2.7">6.2.7</a>).
23079 <li> Conversion to or from an integer type produces a value outside the range that can be
23080 represented (<a href="#6.3.1.4">6.3.1.4</a>).
23081 <li> Demotion of one real floating type to another produces a value outside the range that
23082 can be represented (<a href="#6.3.1.5">6.3.1.5</a>).
23083 <li> An lvalue does not designate an object when evaluated (<a href="#6.3.2.1">6.3.2.1</a>).
23084 <li> A non-array lvalue with an incomplete type is used in a context that requires the value
23085 of the designated object (<a href="#6.3.2.1">6.3.2.1</a>).
23086 <li> An lvalue having array type is converted to a pointer to the initial element of the
23087 array, and the array object has register storage class (<a href="#6.3.2.1">6.3.2.1</a>).
23088 <li> An attempt is made to use the value of a void expression, or an implicit or explicit
23089 conversion (except to void) is applied to a void expression (<a href="#6.3.2.2">6.3.2.2</a>).
23090 <li> Conversion of a pointer to an integer type produces a value outside the range that can
23091 be represented (<a href="#6.3.2.3">6.3.2.3</a>).
23092 <li> Conversion between two pointer types produces a result that is incorrectly aligned
23093 (<a href="#6.3.2.3">6.3.2.3</a>).
23094 <li> A pointer is used to call a function whose type is not compatible with the pointed-to
23095 type (<a href="#6.3.2.3">6.3.2.3</a>).
23096 <li> An unmatched ' or " character is encountered on a logical source line during
23097 tokenization (<a href="#6.4">6.4</a>).
23098 <li> A reserved keyword token is used in translation phase 7 or 8 for some purpose other
23099 than as a keyword (<a href="#6.4.1">6.4.1</a>).
23100 <li> A universal character name in an identifier does not designate a character whose
23101 encoding falls into one of the specified ranges (<a href="#6.4.2.1">6.4.2.1</a>).
23102 <li> The initial character of an identifier is a universal character name designating a digit
23103 (<a href="#6.4.2.1">6.4.2.1</a>).
23104 <li> Two identifiers differ only in nonsignificant characters (<a href="#6.4.2.1">6.4.2.1</a>).
23105 <li> The identifier __func__ is explicitly declared (<a href="#6.4.2.2">6.4.2.2</a>).
23107 <li> The program attempts to modify a string literal (<a href="#6.4.5">6.4.5</a>).
23108 <li> The characters ', \, ", //, or /* occur in the sequence between the < and >
23109 delimiters, or the characters ', \, //, or /* occur in the sequence between the "
23110 delimiters, in a header name preprocessing token (<a href="#6.4.7">6.4.7</a>).
23111 <li> Between two sequence points, an object is modified more than once, or is modified
23112 and the prior value is read other than to determine the value to be stored (<a href="#6.5">6.5</a>).
23113 <li> An exceptional condition occurs during the evaluation of an expression (<a href="#6.5">6.5</a>).
23114 <li> An object has its stored value accessed other than by an lvalue of an allowable type
23115 (<a href="#6.5">6.5</a>).
23116 <li> An attempt is made to modify the result of a function call, a conditional operator, an
23117 assignment operator, or a comma operator, or to access it after the next sequence
23118 point (<a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.15">6.5.15</a>, <a href="#6.5.16">6.5.16</a>, <a href="#6.5.17">6.5.17</a>).
23119 <li> For a call to a function without a function prototype in scope, the number of
23120 arguments does not equal the number of parameters (<a href="#6.5.2.2">6.5.2.2</a>).
23121 <li> For call to a function without a function prototype in scope where the function is
23122 defined with a function prototype, either the prototype ends with an ellipsis or the
23123 types of the arguments after promotion are not compatible with the types of the
23124 parameters (<a href="#6.5.2.2">6.5.2.2</a>).
23125 <li> For a call to a function without a function prototype in scope where the function is not
23126 defined with a function prototype, the types of the arguments after promotion are not
23127 compatible with those of the parameters after promotion (with certain exceptions)
23128 (<a href="#6.5.2.2">6.5.2.2</a>).
23129 <li> A function is defined with a type that is not compatible with the type (of the
23130 expression) pointed to by the expression that denotes the called function (<a href="#6.5.2.2">6.5.2.2</a>).
23131 <li> The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
23132 <li> A pointer is converted to other than an integer or pointer type (<a href="#6.5.4">6.5.4</a>).
23133 <li> The value of the second operand of the / or % operator is zero (<a href="#6.5.5">6.5.5</a>).
23134 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
23135 integer type produces a result that does not point into, or just beyond, the same array
23136 object (<a href="#6.5.6">6.5.6</a>).
23137 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
23138 integer type produces a result that points just beyond the array object and is used as
23139 the operand of a unary * operator that is evaluated (<a href="#6.5.6">6.5.6</a>).
23140 <li> Pointers that do not point into, or just beyond, the same array object are subtracted
23141 (<a href="#6.5.6">6.5.6</a>).
23143 <li> An array subscript is out of range, even if an object is apparently accessible with the
23144 given subscript (as in the lvalue expression a[1][7] given the declaration int
23145 a[4][5]) (<a href="#6.5.6">6.5.6</a>).
23146 <li> The result of subtracting two pointers is not representable in an object of type
23147 ptrdiff_t (<a href="#6.5.6">6.5.6</a>).
23148 <li> An expression is shifted by a negative number or by an amount greater than or equal
23149 to the width of the promoted expression (<a href="#6.5.7">6.5.7</a>).
23150 <li> An expression having signed promoted type is left-shifted and either the value of the
23151 expression is negative or the result of shifting would be not be representable in the
23152 promoted type (<a href="#6.5.7">6.5.7</a>).
23153 <li> Pointers that do not point to the same aggregate or union (nor just beyond the same
23154 array object) are compared using relational operators (<a href="#6.5.8">6.5.8</a>).
23155 <li> An object is assigned to an inexactly overlapping object or to an exactly overlapping
23156 object with incompatible type (<a href="#6.5.16.1">6.5.16.1</a>).
23157 <li> An expression that is required to be an integer constant expression does not have an
23158 integer type; has operands that are not integer constants, enumeration constants,
23159 character constants, sizeof expressions whose results are integer constants, or
23160 immediately-cast floating constants; or contains casts (outside operands to sizeof
23161 operators) other than conversions of arithmetic types to integer types (<a href="#6.6">6.6</a>).
23162 <li> A constant expression in an initializer is not, or does not evaluate to, one of the
23163 following: an arithmetic constant expression, a null pointer constant, an address
23164 constant, or an address constant for an object type plus or minus an integer constant
23165 expression (<a href="#6.6">6.6</a>).
23166 <li> An arithmetic constant expression does not have arithmetic type; has operands that
23167 are not integer constants, floating constants, enumeration constants, character
23168 constants, or sizeof expressions; or contains casts (outside operands to sizeof
23169 operators) other than conversions of arithmetic types to arithmetic types (<a href="#6.6">6.6</a>).
23170 <li> The value of an object is accessed by an array-subscript [], member-access . or ->,
23171 address &, or indirection * operator or a pointer cast in creating an address constant
23172 (<a href="#6.6">6.6</a>).
23173 <li> An identifier for an object is declared with no linkage and the type of the object is
23174 incomplete after its declarator, or after its init-declarator if it has an initializer (<a href="#6.7">6.7</a>).
23175 <li> A function is declared at block scope with an explicit storage-class specifier other
23176 than extern (<a href="#6.7.1">6.7.1</a>).
23177 <li> A structure or union is defined as containing no named members (<a href="#6.7.2.1">6.7.2.1</a>).
23179 <li> An attempt is made to access, or generate a pointer to just past, a flexible array
23180 member of a structure when the referenced object provides no elements for that array
23181 (<a href="#6.7.2.1">6.7.2.1</a>).
23182 <li> When the complete type is needed, an incomplete structure or union type is not
23183 completed in the same scope by another declaration of the tag that defines the content
23184 (<a href="#6.7.2.3">6.7.2.3</a>).
23185 <li> An attempt is made to modify an object defined with a const-qualified type through
23186 use of an lvalue with non-const-qualified type (<a href="#6.7.3">6.7.3</a>).
23187 <li> An attempt is made to refer to an object defined with a volatile-qualified type through
23188 use of an lvalue with non-volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
23189 <li> The specification of a function type includes any type qualifiers (<a href="#6.7.3">6.7.3</a>).
23190 <li> Two qualified types that are required to be compatible do not have the identically
23191 qualified version of a compatible type (<a href="#6.7.3">6.7.3</a>).
23192 <li> An object which has been modified is accessed through a restrict-qualified pointer to
23193 a const-qualified type, or through a restrict-qualified pointer and another pointer that
23194 are not both based on the same object (<a href="#6.7.3.1">6.7.3.1</a>).
23195 <li> A restrict-qualified pointer is assigned a value based on another restricted pointer
23196 whose associated block neither began execution before the block associated with this
23197 pointer, nor ended before the assignment (<a href="#6.7.3.1">6.7.3.1</a>).
23198 <li> A function with external linkage is declared with an inline function specifier, but is
23199 not also defined in the same translation unit (<a href="#6.7.4">6.7.4</a>).
23200 <li> Two pointer types that are required to be compatible are not identically qualified, or
23201 are not pointers to compatible types (<a href="#6.7.5.1">6.7.5.1</a>).
23202 <li> The size expression in an array declaration is not a constant expression and evaluates
23203 at program execution time to a nonpositive value (<a href="#6.7.5.2">6.7.5.2</a>).
23204 <li> In a context requiring two array types to be compatible, they do not have compatible
23205 element types, or their size specifiers evaluate to unequal values (<a href="#6.7.5.2">6.7.5.2</a>).
23206 <li> A declaration of an array parameter includes the keyword static within the [ and
23207 ] and the corresponding argument does not provide access to the first element of an
23208 array with at least the specified number of elements (<a href="#6.7.5.3">6.7.5.3</a>).
23209 <li> A storage-class specifier or type qualifier modifies the keyword void as a function
23210 parameter type list (<a href="#6.7.5.3">6.7.5.3</a>).
23211 <li> In a context requiring two function types to be compatible, they do not have
23212 compatible return types, or their parameters disagree in use of the ellipsis terminator
23213 or the number and type of parameters (after default argument promotion, when there
23214 is no parameter type list or when one type is specified by a function definition with an
23216 identifier list) (<a href="#6.7.5.3">6.7.5.3</a>).
23217 <li> The value of an unnamed member of a structure or union is used (<a href="#6.7.8">6.7.8</a>).
23218 <li> The initializer for a scalar is neither a single expression nor a single expression
23219 enclosed in braces (<a href="#6.7.8">6.7.8</a>).
23220 <li> The initializer for a structure or union object that has automatic storage duration is
23221 neither an initializer list nor a single expression that has compatible structure or union
23222 type (<a href="#6.7.8">6.7.8</a>).
23223 <li> The initializer for an aggregate or union, other than an array initialized by a string
23224 literal, is not a brace-enclosed list of initializers for its elements or members (<a href="#6.7.8">6.7.8</a>).
23225 <li> An identifier with external linkage is used, but in the program there does not exist
23226 exactly one external definition for the identifier, or the identifier is not used and there
23227 exist multiple external definitions for the identifier (<a href="#6.9">6.9</a>).
23228 <li> A function definition includes an identifier list, but the types of the parameters are not
23229 declared in a following declaration list (<a href="#6.9.1">6.9.1</a>).
23230 <li> An adjusted parameter type in a function definition is not an object type (<a href="#6.9.1">6.9.1</a>).
23231 <li> A function that accepts a variable number of arguments is defined without a
23232 parameter type list that ends with the ellipsis notation (<a href="#6.9.1">6.9.1</a>).
23233 <li> The } that terminates a function is reached, and the value of the function call is used
23234 by the caller (<a href="#6.9.1">6.9.1</a>).
23235 <li> An identifier for an object with internal linkage and an incomplete type is declared
23236 with a tentative definition (<a href="#6.9.2">6.9.2</a>).
23237 <li> The token defined is generated during the expansion of a #if or #elif
23238 preprocessing directive, or the use of the defined unary operator does not match
23239 one of the two specified forms prior to macro replacement (<a href="#6.10.1">6.10.1</a>).
23240 <li> The #include preprocessing directive that results after expansion does not match
23241 one of the two header name forms (<a href="#6.10.2">6.10.2</a>).
23242 <li> The character sequence in an #include preprocessing directive does not start with a
23243 letter (<a href="#6.10.2">6.10.2</a>).
23244 <li> There are sequences of preprocessing tokens within the list of macro arguments that
23245 would otherwise act as preprocessing directives (<a href="#6.10.3">6.10.3</a>).
23246 <li> The result of the preprocessing operator # is not a valid character string literal
23247 (<a href="#6.10.3.2">6.10.3.2</a>).
23248 <li> The result of the preprocessing operator ## is not a valid preprocessing token
23249 (<a href="#6.10.3.3">6.10.3.3</a>).
23251 <li> The #line preprocessing directive that results after expansion does not match one of
23252 the two well-defined forms, or its digit sequence specifies zero or a number greater
23253 than 2147483647 (<a href="#6.10.4">6.10.4</a>).
23254 <li> A non-STDC #pragma preprocessing directive that is documented as causing
23255 translation failure or some other form of undefined behavior is encountered (<a href="#6.10.6">6.10.6</a>).
23256 <li> A #pragma STDC preprocessing directive does not match one of the well-defined
23257 forms (<a href="#6.10.6">6.10.6</a>).
23258 <li> The name of a predefined macro, or the identifier defined, is the subject of a
23259 #define or #undef preprocessing directive (<a href="#6.10.8">6.10.8</a>).
23260 <li> An attempt is made to copy an object to an overlapping object by use of a library
23261 function, other than as explicitly allowed (e.g., memmove) (clause 7).
23262 <li> A file with the same name as one of the standard headers, not provided as part of the
23263 implementation, is placed in any of the standard places that are searched for included
23264 source files (<a href="#7.1.2">7.1.2</a>).
23265 <li> A header is included within an external declaration or definition (<a href="#7.1.2">7.1.2</a>).
23266 <li> A function, object, type, or macro that is specified as being declared or defined by
23267 some standard header is used before any header that declares or defines it is included
23268 (<a href="#7.1.2">7.1.2</a>).
23269 <li> A standard header is included while a macro is defined with the same name as a
23270 keyword (<a href="#7.1.2">7.1.2</a>).
23271 <li> The program attempts to declare a library function itself, rather than via a standard
23272 header, but the declaration does not have external linkage (<a href="#7.1.2">7.1.2</a>).
23273 <li> The program declares or defines a reserved identifier, other than as allowed by <a href="#7.1.4">7.1.4</a>
23274 (<a href="#7.1.3">7.1.3</a>).
23275 <li> The program removes the definition of a macro whose name begins with an
23276 underscore and either an uppercase letter or another underscore (<a href="#7.1.3">7.1.3</a>).
23277 <li> An argument to a library function has an invalid value or a type not expected by a
23278 function with variable number of arguments (<a href="#7.1.4">7.1.4</a>).
23279 <li> The pointer passed to a library function array parameter does not have a value such
23280 that all address computations and object accesses are valid (<a href="#7.1.4">7.1.4</a>).
23281 <li> The macro definition of assert is suppressed in order to access an actual function
23282 (<a href="#7.2">7.2</a>).
23283 <li> The argument to the assert macro does not have a scalar type (<a href="#7.2">7.2</a>).
23284 <li> The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in
23285 any context other than outside all external declarations or preceding all explicit
23287 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>).
23288 <li> The value of an argument to a character handling function is neither equal to the value
23289 of EOF nor representable as an unsigned char (<a href="#7.4">7.4</a>).
23290 <li> A macro definition of errno is suppressed in order to access an actual object, or the
23291 program defines an identifier with the name errno (<a href="#7.5">7.5</a>).
23292 <li> Part of the program tests floating-point status flags, sets floating-point control modes,
23293 or runs under non-default mode settings, but was translated with the state for the
23294 FENV_ACCESS pragma ''off'' (<a href="#7.6.1">7.6.1</a>).
23295 <li> The exception-mask argument for one of the functions that provide access to the
23296 floating-point status flags has a nonzero value not obtained by bitwise OR of the
23297 floating-point exception macros (<a href="#7.6.2">7.6.2</a>).
23298 <li> The fesetexceptflag function is used to set floating-point status flags that were
23299 not specified in the call to the fegetexceptflag function that provided the value
23300 of the corresponding fexcept_t object (<a href="#7.6.2.4">7.6.2.4</a>).
23301 <li> The argument to fesetenv or feupdateenv is neither an object set by a call to
23302 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>).
23303 <li> The value of the result of an integer arithmetic or conversion function cannot be
23304 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="#7.20.6.1">7.20.6.1</a>, <a href="#7.20.6.2">7.20.6.2</a>, <a href="#7.20.1">7.20.1</a>).
23305 <li> The program modifies the string pointed to by the value returned by the setlocale
23306 function (<a href="#7.11.1.1">7.11.1.1</a>).
23307 <li> The program modifies the structure pointed to by the value returned by the
23308 localeconv function (<a href="#7.11.2.1">7.11.2.1</a>).
23309 <li> A macro definition of math_errhandling is suppressed or the program defines
23310 an identifier with the name math_errhandling (<a href="#7.12">7.12</a>).
23311 <li> An argument to a floating-point classification or comparison macro is not of real
23312 floating type (<a href="#7.12.3">7.12.3</a>, <a href="#7.12.14">7.12.14</a>).
23313 <li> A macro definition of setjmp is suppressed in order to access an actual function, or
23314 the program defines an external identifier with the name setjmp (<a href="#7.13">7.13</a>).
23315 <li> An invocation of the setjmp macro occurs other than in an allowed context
23316 (<a href="#7.13.2.1">7.13.2.1</a>).
23317 <li> The longjmp function is invoked to restore a nonexistent environment (<a href="#7.13.2.1">7.13.2.1</a>).
23318 <li> After a longjmp, there is an attempt to access the value of an object of automatic
23319 storage class with non-volatile-qualified type, local to the function containing the
23320 invocation of the corresponding setjmp macro, that was changed between the
23321 setjmp invocation and longjmp call (<a href="#7.13.2.1">7.13.2.1</a>).
23323 <li> The program specifies an invalid pointer to a signal handler function (<a href="#7.14.1.1">7.14.1.1</a>).
23324 <li> A signal handler returns when the signal corresponded to a computational exception
23325 (<a href="#7.14.1.1">7.14.1.1</a>).
23326 <li> A signal occurs as the result of calling the abort or raise function, and the signal
23327 handler calls the raise function (<a href="#7.14.1.1">7.14.1.1</a>).
23328 <li> A signal occurs other than as the result of calling the abort or raise function, and
23329 the signal handler refers to an object with static storage duration other than by
23330 assigning a value to an object declared as volatile sig_atomic_t, or calls any
23331 function in the standard library other than the abort function, the _Exit function,
23332 or the signal function (for the same signal number) (<a href="#7.14.1.1">7.14.1.1</a>).
23333 <li> The value of errno is referred to after a signal occurred other than as the result of
23334 calling the abort or raise function and the corresponding signal handler obtained
23335 a SIG_ERR return from a call to the signal function (<a href="#7.14.1.1">7.14.1.1</a>).
23336 <li> A signal is generated by an asynchronous signal handler (<a href="#7.14.1.1">7.14.1.1</a>).
23337 <li> A function with a variable number of arguments attempts to access its varying
23338 arguments other than through a properly declared and initialized va_list object, or
23339 before the va_start macro is invoked (<a href="#7.15">7.15</a>, <a href="#7.15.1.1">7.15.1.1</a>, <a href="#7.15.1.4">7.15.1.4</a>).
23340 <li> The macro va_arg is invoked using the parameter ap that was passed to a function
23341 that invoked the macro va_arg with the same parameter (<a href="#7.15">7.15</a>).
23342 <li> A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in
23343 order to access an actual function, or the program defines an external identifier with
23344 the name va_copy or va_end (<a href="#7.15.1">7.15.1</a>).
23345 <li> The va_start or va_copy macro is invoked without a corresponding invocation
23346 of the va_end macro in the same function, or vice versa (<a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.2">7.15.1.2</a>, <a href="#7.15.1.3">7.15.1.3</a>,
23347 <a href="#7.15.1.4">7.15.1.4</a>).
23348 <li> The type parameter to the va_arg macro is not such that a pointer to an object of
23349 that type can be obtained simply by postfixing a * (<a href="#7.15.1.1">7.15.1.1</a>).
23350 <li> The va_arg macro is invoked when there is no actual next argument, or with a
23351 specified type that is not compatible with the promoted type of the actual next
23352 argument, with certain exceptions (<a href="#7.15.1.1">7.15.1.1</a>).
23353 <li> The va_copy or va_start macro is called to initialize a va_list that was
23354 previously initialized by either macro without an intervening invocation of the
23355 va_end macro for the same va_list (<a href="#7.15.1.2">7.15.1.2</a>, <a href="#7.15.1.4">7.15.1.4</a>).
23356 <li> The parameter parmN of a va_start macro is declared with the register
23357 storage class, with a function or array type, or with a type that is not compatible with
23358 the type that results after application of the default argument promotions (<a href="#7.15.1.4">7.15.1.4</a>).
23360 <li> The member designator parameter of an offsetof macro is an invalid right
23361 operand of the . operator for the type parameter, or designates a bit-field (<a href="#7.17">7.17</a>).
23362 <li> The argument in an instance of one of the integer-constant macros is not a decimal,
23363 octal, or hexadecimal constant, or it has a value that exceeds the limits for the
23364 corresponding type (<a href="#7.18.4">7.18.4</a>).
23365 <li> A byte input/output function is applied to a wide-oriented stream, or a wide character
23366 input/output function is applied to a byte-oriented stream (<a href="#7.19.2">7.19.2</a>).
23367 <li> Use is made of any portion of a file beyond the most recent wide character written to
23368 a wide-oriented stream (<a href="#7.19.2">7.19.2</a>).
23369 <li> The value of a pointer to a FILE object is used after the associated file is closed
23370 (<a href="#7.19.3">7.19.3</a>).
23371 <li> The stream for the fflush function points to an input stream or to an update stream
23372 in which the most recent operation was input (<a href="#7.19.5.2">7.19.5.2</a>).
23373 <li> The string pointed to by the mode argument in a call to the fopen function does not
23374 exactly match one of the specified character sequences (<a href="#7.19.5.3">7.19.5.3</a>).
23375 <li> An output operation on an update stream is followed by an input operation without an
23376 intervening call to the fflush function or a file positioning function, or an input
23377 operation on an update stream is followed by an output operation with an intervening
23378 call to a file positioning function (<a href="#7.19.5.3">7.19.5.3</a>).
23379 <li> An attempt is made to use the contents of the array that was supplied in a call to the
23380 setvbuf function (<a href="#7.19.5.6">7.19.5.6</a>).
23381 <li> There are insufficient arguments for the format in a call to one of the formatted
23382 input/output functions, or an argument does not have an appropriate type (<a href="#7.19.6.1">7.19.6.1</a>,
23383 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23384 <li> The format in a call to one of the formatted input/output functions or to the
23385 strftime or wcsftime function is not a valid multibyte character sequence that
23386 begins and ends in its initial shift state (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>,
23387 <a href="#7.24.5.1">7.24.5.1</a>).
23388 <li> In a call to one of the formatted output functions, a precision appears with a
23389 conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23390 <li> A conversion specification for a formatted output function uses an asterisk to denote
23391 an argument-supplied field width or precision, but the corresponding argument is not
23392 provided (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23393 <li> A conversion specification for a formatted output function uses a # or 0 flag with a
23394 conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23396 <li> A conversion specification for one of the formatted input/output functions uses a
23397 length modifier with a conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>,
23398 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23399 <li> An s conversion specifier is encountered by one of the formatted output functions,
23400 and the argument is missing the null terminator (unless a precision is specified that
23401 does not require null termination) (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23402 <li> An n conversion specification for one of the formatted input/output functions includes
23403 any flags, an assignment-suppressing character, a field width, or a precision (<a href="#7.19.6.1">7.19.6.1</a>,
23404 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23405 <li> A % conversion specifier is encountered by one of the formatted input/output
23406 functions, but the complete conversion specification is not exactly %% (<a href="#7.19.6.1">7.19.6.1</a>,
23407 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23408 <li> An invalid conversion specification is found in the format for one of the formatted
23409 input/output functions, or the strftime or wcsftime function (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>,
23410 <a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.5.1">7.24.5.1</a>).
23411 <li> The number of characters transmitted by a formatted output function is greater than
23412 INT_MAX (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.3">7.19.6.3</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.10">7.19.6.10</a>).
23413 <li> The result of a conversion by one of the formatted input functions cannot be
23414 represented in the corresponding object, or the receiving object does not have an
23415 appropriate type (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23416 <li> A c, s, or [ conversion specifier is encountered by one of the formatted input
23417 functions, and the array pointed to by the corresponding argument is not large enough
23418 to accept the input sequence (and a null terminator if the conversion specifier is s or
23419 [) (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23420 <li> A c, s, or [ conversion specifier with an l qualifier is encountered by one of the
23421 formatted input functions, but the input is not a valid multibyte character sequence
23422 that begins in the initial shift state (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23423 <li> The input item for a %p conversion by one of the formatted input functions is not a
23424 value converted earlier during the same program execution (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23425 <li> The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf,
23426 vsscanf, vfwprintf, vfwscanf, vswprintf, vswscanf, vwprintf, or
23427 vwscanf function is called with an improperly initialized va_list argument, or
23428 the argument is used (other than in an invocation of va_end) after the function
23429 returns (<a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>, <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>,
23430 <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>).
23431 <li> The contents of the array supplied in a call to the fgets, gets, or fgetws function
23432 are used after a read error occurred (<a href="#7.19.7.2">7.19.7.2</a>, <a href="#7.19.7.7">7.19.7.7</a>, <a href="#7.24.3.2">7.24.3.2</a>).
23434 <li> The file position indicator for a binary stream is used after a call to the ungetc
23435 function where its value was zero before the call (<a href="#7.19.7.11">7.19.7.11</a>).
23436 <li> The file position indicator for a stream is used after an error occurred during a call to
23437 the fread or fwrite function (<a href="#7.19.8.1">7.19.8.1</a>, <a href="#7.19.8.2">7.19.8.2</a>).
23438 <li> A partial element read by a call to the fread function is used (<a href="#7.19.8.1">7.19.8.1</a>).
23439 <li> The fseek function is called for a text stream with a nonzero offset and either the
23440 offset was not returned by a previous successful call to the ftell function on a
23441 stream associated with the same file or whence is not SEEK_SET (<a href="#7.19.9.2">7.19.9.2</a>).
23442 <li> The fsetpos function is called to set a position that was not returned by a previous
23443 successful call to the fgetpos function on a stream associated with the same file
23444 (<a href="#7.19.9.3">7.19.9.3</a>).
23445 <li> A non-null pointer returned by a call to the calloc, malloc, or realloc function
23446 with a zero requested size is used to access an object (<a href="#7.20.3">7.20.3</a>).
23447 <li> The value of a pointer that refers to space deallocated by a call to the free or
23448 realloc function is used (<a href="#7.20.3">7.20.3</a>).
23449 <li> The pointer argument to the free or realloc function does not match a pointer
23450 earlier returned by calloc, malloc, or realloc, or the space has been
23451 deallocated by a call to free or realloc (<a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.4">7.20.3.4</a>).
23452 <li> The value of the object allocated by the malloc function is used (<a href="#7.20.3.3">7.20.3.3</a>).
23453 <li> The value of any bytes in a new object allocated by the realloc function beyond
23454 the size of the old object are used (<a href="#7.20.3.4">7.20.3.4</a>).
23455 <li> The program executes more than one call to the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
23456 <li> During the call to a function registered with the atexit function, a call is made to
23457 the longjmp function that would terminate the call to the registered function
23458 (<a href="#7.20.4.3">7.20.4.3</a>).
23459 <li> The string set up by the getenv or strerror function is modified by the program
23460 (<a href="#7.20.4.5">7.20.4.5</a>, <a href="#7.21.6.2">7.21.6.2</a>).
23461 <li> A command is executed through the system function in a way that is documented as
23462 causing termination or some other form of undefined behavior (<a href="#7.20.4.6">7.20.4.6</a>).
23463 <li> A searching or sorting utility function is called with an invalid pointer argument, even
23464 if the number of elements is zero (<a href="#7.20.5">7.20.5</a>).
23465 <li> The comparison function called by a searching or sorting utility function alters the
23466 contents of the array being searched or sorted, or returns ordering values
23467 inconsistently (<a href="#7.20.5">7.20.5</a>).
23469 <li> The array being searched by the bsearch function does not have its elements in
23470 proper order (<a href="#7.20.5.1">7.20.5.1</a>).
23471 <li> The current conversion state is used by a multibyte/wide character conversion
23472 function after changing the LC_CTYPE category (<a href="#7.20.7">7.20.7</a>).
23473 <li> A string or wide string utility function is instructed to access an array beyond the end
23474 of an object (<a href="#7.21.1">7.21.1</a>, <a href="#7.24.4">7.24.4</a>).
23475 <li> A string or wide string utility function is called with an invalid pointer argument, even
23476 if the length is zero (<a href="#7.21.1">7.21.1</a>, <a href="#7.24.4">7.24.4</a>).
23477 <li> The contents of the destination array are used after a call to the strxfrm,
23478 strftime, wcsxfrm, or wcsftime function in which the specified length was
23479 too small to hold the entire null-terminated result (<a href="#7.21.4.5">7.21.4.5</a>, <a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.4.4.4">7.24.4.4.4</a>,
23480 <a href="#7.24.5.1">7.24.5.1</a>).
23481 <li> The first argument in the very first call to the strtok or wcstok is a null pointer
23482 (<a href="#7.21.5.8">7.21.5.8</a>, <a href="#7.24.4.5.7">7.24.4.5.7</a>).
23483 <li> The type of an argument to a type-generic macro is not compatible with the type of
23484 the corresponding parameter of the selected function (<a href="#7.22">7.22</a>).
23485 <li> A complex argument is supplied for a generic parameter of a type-generic macro that
23486 has no corresponding complex function (<a href="#7.22">7.22</a>).
23487 <li> The argument corresponding to an s specifier without an l qualifier in a call to the
23488 fwprintf function does not point to a valid multibyte character sequence that
23489 begins in the initial shift state (<a href="#7.24.2.11">7.24.2.11</a>).
23490 <li> In a call to the wcstok function, the object pointed to by ptr does not have the
23491 value stored by the previous call for the same wide string (<a href="#7.24.4.5.7">7.24.4.5.7</a>).
23492 <li> An mbstate_t object is used inappropriately (<a href="#7.24.6">7.24.6</a>).
23493 <li> The value of an argument of type wint_t to a wide character classification or case
23494 mapping function is neither equal to the value of WEOF nor representable as a
23495 wchar_t (<a href="#7.25.1">7.25.1</a>).
23496 <li> The iswctype function is called using a different LC_CTYPE category from the
23497 one in effect for the call to the wctype function that returned the description
23498 (<a href="#7.25.2.2.1">7.25.2.2.1</a>).
23499 <li> The towctrans function is called using a different LC_CTYPE category from the
23500 one in effect for the call to the wctrans function that returned the description
23501 (<a href="#7.25.3.2.1">7.25.3.2.1</a>).
23505 <h3><a name="J.3" href="#J.3">J.3 Implementation-defined behavior</a></h3>
23507 A conforming implementation is required to document its choice of behavior in each of
23508 the areas listed in this subclause. The following are implementation-defined:
23510 <h4><a name="J.3.1" href="#J.3.1">J.3.1 Translation</a></h4>
23513 <li> How a diagnostic is identified (<a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a>).
23514 <li> Whether each nonempty sequence of white-space characters other than new-line is
23515 retained or replaced by one space character in translation phase 3 (<a href="#5.1.1.2">5.1.1.2</a>).
23518 <h4><a name="J.3.2" href="#J.3.2">J.3.2 Environment</a></h4>
23521 <li> The mapping between physical source file multibyte characters and the source
23522 character set in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>).
23523 <li> The name and type of the function called at program startup in a freestanding
23524 environment (<a href="#5.1.2.1">5.1.2.1</a>).
23525 <li> The effect of program termination in a freestanding environment (<a href="#5.1.2.1">5.1.2.1</a>).
23526 <li> An alternative manner in which the main function may be defined (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
23527 <li> 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>).
23528 <li> What constitutes an interactive device (<a href="#5.1.2.3">5.1.2.3</a>).
23529 <li> The set of signals, their semantics, and their default handling (<a href="#7.14">7.14</a>).
23530 <li> Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
23531 computational exception (<a href="#7.14.1.1">7.14.1.1</a>).
23532 <li> Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
23533 program startup (<a href="#7.14.1.1">7.14.1.1</a>).
23534 <li> The set of environment names and the method for altering the environment list used
23535 by the getenv function (<a href="#7.20.4.5">7.20.4.5</a>).
23536 <li> The manner of execution of the string by the system function (<a href="#7.20.4.6">7.20.4.6</a>).
23539 <h4><a name="J.3.3" href="#J.3.3">J.3.3 Identifiers</a></h4>
23542 <li> Which additional multibyte characters may appear in identifiers and their
23543 correspondence to universal character names (<a href="#6.4.2">6.4.2</a>).
23544 <li> 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>).
23548 <h4><a name="J.3.4" href="#J.3.4">J.3.4 Characters</a></h4>
23551 <li> The number of bits in a byte (<a href="#3.6">3.6</a>).
23552 <li> The values of the members of the execution character set (<a href="#5.2.1">5.2.1</a>).
23553 <li> The unique value of the member of the execution character set produced for each of
23554 the standard alphabetic escape sequences (<a href="#5.2.2">5.2.2</a>).
23555 <li> The value of a char object into which has been stored any character other than a
23556 member of the basic execution character set (<a href="#6.2.5">6.2.5</a>).
23557 <li> Which of signed char or unsigned char has the same range, representation,
23558 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>).
23559 <li> The mapping of members of the source character set (in character constants and string
23560 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>).
23561 <li> The value of an integer character constant containing more than one character or
23562 containing a character or escape sequence that does not map to a single-byte
23563 execution character (<a href="#6.4.4.4">6.4.4.4</a>).
23564 <li> The value of a wide character constant containing more than one multibyte character,
23565 or containing a multibyte character or escape sequence not represented in the
23566 extended execution character set (<a href="#6.4.4.4">6.4.4.4</a>).
23567 <li> The current locale used to convert a wide character constant consisting of a single
23568 multibyte character that maps to a member of the extended execution character set
23569 into a corresponding wide character code (<a href="#6.4.4.4">6.4.4.4</a>).
23570 <li> The current locale used to convert a wide string literal into corresponding wide
23571 character codes (<a href="#6.4.5">6.4.5</a>).
23572 <li> The value of a string literal containing a multibyte character or escape sequence not
23573 represented in the execution character set (<a href="#6.4.5">6.4.5</a>).
23576 <h4><a name="J.3.5" href="#J.3.5">J.3.5 Integers</a></h4>
23579 <li> Any extended integer types that exist in the implementation (<a href="#6.2.5">6.2.5</a>).
23580 <li> Whether signed integer types are represented using sign and magnitude, two's
23581 complement, or ones' complement, and whether the extraordinary value is a trap
23582 representation or an ordinary value (<a href="#6.2.6.2">6.2.6.2</a>).
23583 <li> The rank of any extended integer type relative to another extended integer type with
23584 the same precision (<a href="#6.3.1.1">6.3.1.1</a>).
23585 <li> The result of, or the signal raised by, converting an integer to a signed integer type
23586 when the value cannot be represented in an object of that type (<a href="#6.3.1.3">6.3.1.3</a>).
23588 <li> The results of some bitwise operations on signed integers (<a href="#6.5">6.5</a>).
23591 <h4><a name="J.3.6" href="#J.3.6">J.3.6 Floating point</a></h4>
23594 <li> The accuracy of the floating-point operations and of the library functions in
23595 <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>).
23596 <li> The accuracy of the conversions between floating-point internal representations and
23597 string representations performed by the library functions in <a href="#7.19"><stdio.h></a>,
23598 <a href="#7.20"><stdlib.h></a>, and <a href="#7.24"><wchar.h></a> (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
23599 <li> The rounding behaviors characterized by non-standard values of FLT_ROUNDS
23600 (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
23601 <li> The evaluation methods characterized by non-standard negative values of
23602 FLT_EVAL_METHOD (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
23603 <li> The direction of rounding when an integer is converted to a floating-point number that
23604 cannot exactly represent the original value (<a href="#6.3.1.4">6.3.1.4</a>).
23605 <li> The direction of rounding when a floating-point number is converted to a narrower
23606 floating-point number (<a href="#6.3.1.5">6.3.1.5</a>).
23607 <li> How the nearest representable value or the larger or smaller representable value
23608 immediately adjacent to the nearest representable value is chosen for certain floating
23609 constants (<a href="#6.4.4.2">6.4.4.2</a>).
23610 <li> Whether and how floating expressions are contracted when not disallowed by the
23611 FP_CONTRACT pragma (<a href="#6.5">6.5</a>).
23612 <li> The default state for the FENV_ACCESS pragma (<a href="#7.6.1">7.6.1</a>).
23613 <li> Additional floating-point exceptions, rounding modes, environments, and
23614 classifications, and their macro names (<a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>).
23615 <li> The default state for the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>). *
23618 <h4><a name="J.3.7" href="#J.3.7">J.3.7 Arrays and pointers</a></h4>
23621 <li> The result of converting a pointer to an integer or vice versa (<a href="#6.3.2.3">6.3.2.3</a>).
23622 <li> The size of the result of subtracting two pointers to elements of the same array
23623 (<a href="#6.5.6">6.5.6</a>).
23627 <h4><a name="J.3.8" href="#J.3.8">J.3.8 Hints</a></h4>
23630 <li> The extent to which suggestions made by using the register storage-class
23631 specifier are effective (<a href="#6.7.1">6.7.1</a>).
23632 <li> The extent to which suggestions made by using the inline function specifier are
23633 effective (<a href="#6.7.4">6.7.4</a>).
23636 <h4><a name="J.3.9" href="#J.3.9">J.3.9 Structures, unions, enumerations, and bit-fields</a></h4>
23639 <li> Whether a ''plain'' int bit-field is treated as a signed int bit-field or as an
23640 unsigned int bit-field (<a href="#6.7.2">6.7.2</a>, <a href="#6.7.2.1">6.7.2.1</a>).
23641 <li> Allowable bit-field types other than _Bool, signed int, and unsigned int
23642 (<a href="#6.7.2.1">6.7.2.1</a>).
23643 <li> Whether a bit-field can straddle a storage-unit boundary (<a href="#6.7.2.1">6.7.2.1</a>).
23644 <li> The order of allocation of bit-fields within a unit (<a href="#6.7.2.1">6.7.2.1</a>).
23645 <li> The alignment of non-bit-field members of structures (<a href="#6.7.2.1">6.7.2.1</a>). This should present
23646 no problem unless binary data written by one implementation is read by another.
23647 <li> The integer type compatible with each enumerated type (<a href="#6.7.2.2">6.7.2.2</a>).
23650 <h4><a name="J.3.10" href="#J.3.10">J.3.10 Qualifiers</a></h4>
23653 <li> What constitutes an access to an object that has volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
23656 <h4><a name="J.3.11" href="#J.3.11">J.3.11 Preprocessing directives</a></h4>
23659 <li> The locations within #pragma directives where header name preprocessing tokens
23660 are recognized (<a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>).
23661 <li> How sequences in both forms of header names are mapped to headers or external
23662 source file names (<a href="#6.4.7">6.4.7</a>).
23663 <li> Whether the value of a character constant in a constant expression that controls
23664 conditional inclusion matches the value of the same character constant in the
23665 execution character set (<a href="#6.10.1">6.10.1</a>).
23666 <li> Whether the value of a single-character character constant in a constant expression
23667 that controls conditional inclusion may have a negative value (<a href="#6.10.1">6.10.1</a>).
23668 <li> The places that are searched for an included < > delimited header, and how the places
23669 are specified or the header is identified (<a href="#6.10.2">6.10.2</a>).
23670 <li> How the named source file is searched for in an included " " delimited header
23671 (<a href="#6.10.2">6.10.2</a>).
23672 <li> The method by which preprocessing tokens (possibly resulting from macro
23673 expansion) in a #include directive are combined into a header name (<a href="#6.10.2">6.10.2</a>).
23675 <li> The nesting limit for #include processing (<a href="#6.10.2">6.10.2</a>).
23676 <li> Whether the # operator inserts a \ character before the \ character that begins a
23677 universal character name in a character constant or string literal (<a href="#6.10.3.2">6.10.3.2</a>).
23678 <li> The behavior on each recognized non-STDC #pragma directive (<a href="#6.10.6">6.10.6</a>).
23679 <li> The definitions for __DATE__ and __TIME__ when respectively, the date and
23680 time of translation are not available (<a href="#6.10.8">6.10.8</a>).
23683 <h4><a name="J.3.12" href="#J.3.12">J.3.12 Library functions</a></h4>
23686 <li> Any library facilities available to a freestanding program, other than the minimal set
23687 required by clause 4 (<a href="#5.1.2.1">5.1.2.1</a>).
23688 <li> The format of the diagnostic printed by the assert macro (<a href="#7.2.1.1">7.2.1.1</a>).
23689 <li> The representation of the floating-point status flags stored by the
23690 fegetexceptflag function (<a href="#7.6.2.2">7.6.2.2</a>).
23691 <li> Whether the feraiseexcept function raises the ''inexact'' floating-point
23692 exception in addition to the ''overflow'' or ''underflow'' floating-point exception
23693 (<a href="#7.6.2.3">7.6.2.3</a>).
23694 <li> Strings other than "C" and "" that may be passed as the second argument to the
23695 setlocale function (<a href="#7.11.1.1">7.11.1.1</a>).
23696 <li> The types defined for float_t and double_t when the value of the
23697 FLT_EVAL_METHOD macro is less than 0 (<a href="#7.12">7.12</a>).
23698 <li> Domain errors for the mathematics functions, other than those required by this
23699 International Standard (<a href="#7.12.1">7.12.1</a>).
23700 <li> The values returned by the mathematics functions on domain errors (<a href="#7.12.1">7.12.1</a>).
23701 <li> The values returned by the mathematics functions on underflow range errors, whether
23702 errno is set to the value of the macro ERANGE when the integer expression
23703 math_errhandling & MATH_ERRNO is nonzero, and whether the ''underflow''
23704 floating-point exception is raised when the integer expression math_errhandling
23705 & MATH_ERREXCEPT is nonzero. (<a href="#7.12.1">7.12.1</a>).
23706 <li> Whether a domain error occurs or zero is returned when an fmod function has a
23707 second argument of zero (<a href="#7.12.10.1">7.12.10.1</a>).
23708 <li> Whether a domain error occurs or zero is returned when a remainder function has
23709 a second argument of zero (<a href="#7.12.10.2">7.12.10.2</a>).
23710 <li> The base-2 logarithm of the modulus used by the remquo functions in reducing the
23711 quotient (<a href="#7.12.10.3">7.12.10.3</a>).
23713 <li> Whether a domain error occurs or zero is returned when a remquo function has a
23714 second argument of zero (<a href="#7.12.10.3">7.12.10.3</a>).
23715 <li> Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call
23716 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>).
23717 <li> The null pointer constant to which the macro NULL expands (<a href="#7.17">7.17</a>).
23718 <li> Whether the last line of a text stream requires a terminating new-line character
23719 (<a href="#7.19.2">7.19.2</a>).
23720 <li> Whether space characters that are written out to a text stream immediately before a
23721 new-line character appear when read in (<a href="#7.19.2">7.19.2</a>).
23722 <li> The number of null characters that may be appended to data written to a binary
23723 stream (<a href="#7.19.2">7.19.2</a>).
23724 <li> Whether the file position indicator of an append-mode stream is initially positioned at
23725 the beginning or end of the file (<a href="#7.19.3">7.19.3</a>).
23726 <li> Whether a write on a text stream causes the associated file to be truncated beyond that
23727 point (<a href="#7.19.3">7.19.3</a>).
23728 <li> The characteristics of file buffering (<a href="#7.19.3">7.19.3</a>).
23729 <li> Whether a zero-length file actually exists (<a href="#7.19.3">7.19.3</a>).
23730 <li> The rules for composing valid file names (<a href="#7.19.3">7.19.3</a>).
23731 <li> Whether the same file can be simultaneously open multiple times (<a href="#7.19.3">7.19.3</a>).
23732 <li> The nature and choice of encodings used for multibyte characters in files (<a href="#7.19.3">7.19.3</a>).
23733 <li> The effect of the remove function on an open file (<a href="#7.19.4.1">7.19.4.1</a>).
23734 <li> The effect if a file with the new name exists prior to a call to the rename function
23735 (<a href="#7.19.4.2">7.19.4.2</a>).
23736 <li> Whether an open temporary file is removed upon abnormal program termination
23737 (<a href="#7.19.4.3">7.19.4.3</a>).
23738 <li> Which changes of mode are permitted (if any), and under what circumstances
23739 (<a href="#7.19.5.4">7.19.5.4</a>).
23740 <li> The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
23741 sequence printed for a NaN (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23742 <li> The output for %p conversion in the fprintf or fwprintf function (<a href="#7.19.6.1">7.19.6.1</a>,
23743 <a href="#7.24.2.1">7.24.2.1</a>).
23744 <li> The interpretation of a - character that is neither the first nor the last character, nor
23745 the second where a ^ character is the first, in the scanlist for %[ conversion in the
23746 fscanf or fwscanf function (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23748 <li> The set of sequences matched by a %p conversion and the interpretation of the
23749 corresponding input item in the fscanf or fwscanf function (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23750 <li> The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
23751 functions on failure (<a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.9.4">7.19.9.4</a>).
23752 <li> The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
23753 converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold
23754 function (<a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>).
23755 <li> Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
23756 function sets errno to ERANGE when underflow occurs (<a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>).
23757 <li> Whether the calloc, malloc, and realloc functions return a null pointer or a
23758 pointer to an allocated object when the size requested is zero (<a href="#7.20.3">7.20.3</a>).
23759 <li> Whether open streams with unwritten buffered data are flushed, open streams are
23760 closed, or temporary files are removed when the abort or _Exit function is called
23761 (<a href="#7.20.4.1">7.20.4.1</a>, <a href="#7.20.4.4">7.20.4.4</a>).
23762 <li> The termination status returned to the host environment by the abort, exit, or
23763 _Exit function (<a href="#7.20.4.1">7.20.4.1</a>, <a href="#7.20.4.3">7.20.4.3</a>, <a href="#7.20.4.4">7.20.4.4</a>).
23764 <li> The value returned by the system function when its argument is not a null pointer
23765 (<a href="#7.20.4.6">7.20.4.6</a>).
23766 <li> The local time zone and Daylight Saving Time (<a href="#7.23.1">7.23.1</a>).
23767 <li> The range and precision of times representable in clock_t and time_t (<a href="#7.23">7.23</a>).
23768 <li> The era for the clock function (<a href="#7.23.2.1">7.23.2.1</a>).
23769 <li> The replacement string for the %Z specifier to the strftime, and wcsftime
23770 functions in the "C" locale (<a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.5.1">7.24.5.1</a>).
23771 <li> Whether the functions in <a href="#7.12"><math.h></a> honor the rounding direction mode in an
23772 IEC 60559 conformant implementation, unless explicitly specified otherwise (<a href="#F.9">F.9</a>).
23775 <h4><a name="J.3.13" href="#J.3.13">J.3.13 Architecture</a></h4>
23778 <li> The values or expressions assigned to the macros specified in the headers
23779 <a href="#7.7"><float.h></a>, <a href="#7.10"><limits.h></a>, and <a href="#7.18"><stdint.h></a> (<a href="#5.2.4.2">5.2.4.2</a>, <a href="#7.18.2">7.18.2</a>, <a href="#7.18.3">7.18.3</a>).
23780 <li> The number, order, and encoding of bytes in any object (when not explicitly specified
23781 in this International Standard) (<a href="#6.2.6.1">6.2.6.1</a>).
23782 <li> The value of the result of the sizeof operator (<a href="#6.5.3.4">6.5.3.4</a>).
23786 <h3><a name="J.4" href="#J.4">J.4 Locale-specific behavior</a></h3>
23788 The following characteristics of a hosted environment are locale-specific and are required
23789 to be documented by the implementation:
23791 <li> Additional members of the source and execution character sets beyond the basic
23792 character set (<a href="#5.2.1">5.2.1</a>).
23793 <li> The presence, meaning, and representation of additional multibyte characters in the
23794 execution character set beyond the basic character set (<a href="#5.2.1.2">5.2.1.2</a>).
23795 <li> The shift states used for the encoding of multibyte characters (<a href="#5.2.1.2">5.2.1.2</a>).
23796 <li> The direction of writing of successive printing characters (<a href="#5.2.2">5.2.2</a>).
23797 <li> The decimal-point character (<a href="#7.1.1">7.1.1</a>).
23798 <li> The set of printing characters (<a href="#7.4">7.4</a>, <a href="#7.25.2">7.25.2</a>).
23799 <li> The set of control characters (<a href="#7.4">7.4</a>, <a href="#7.25.2">7.25.2</a>).
23800 <li> The sets of characters tested for by the isalpha, isblank, islower, ispunct,
23801 isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
23802 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>,
23803 <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a>, <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, <a href="#7.25.2.1.10">7.25.2.1.10</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>).
23804 <li> The native environment (<a href="#7.11.1.1">7.11.1.1</a>).
23805 <li> Additional subject sequences accepted by the numeric conversion functions (<a href="#7.20.1">7.20.1</a>,
23806 <a href="#7.24.4.1">7.24.4.1</a>).
23807 <li> The collation sequence of the execution character set (<a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.24.4.4.2">7.24.4.4.2</a>).
23808 <li> The contents of the error message strings set up by the strerror function
23809 (<a href="#7.21.6.2">7.21.6.2</a>).
23810 <li> The formats for time and date (<a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.5.1">7.24.5.1</a>).
23811 <li> Character mappings that are supported by the towctrans function (<a href="#7.25.1">7.25.1</a>).
23812 <li> Character classifications that are supported by the iswctype function (<a href="#7.25.1">7.25.1</a>).
23816 <h3><a name="J.5" href="#J.5">J.5 Common extensions</a></h3>
23818 The following extensions are widely used in many systems, but are not portable to all
23819 implementations. The inclusion of any extension that may cause a strictly conforming
23820 program to become invalid renders an implementation nonconforming. Examples of such
23821 extensions are new keywords, extra library functions declared in standard headers, or
23822 predefined macros with names that do not begin with an underscore.
23824 <h4><a name="J.5.1" href="#J.5.1">J.5.1 Environment arguments</a></h4>
23826 In a hosted environment, the main function receives a third argument, char *envp[],
23827 that points to a null-terminated array of pointers to char, each of which points to a string
23828 that provides information about the environment for this execution of the program
23829 (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
23831 <h4><a name="J.5.2" href="#J.5.2">J.5.2 Specialized identifiers</a></h4>
23833 Characters other than the underscore _, letters, and digits, that are not part of the basic
23834 source character set (such as the dollar sign $, or characters in national character sets)
23835 may appear in an identifier (<a href="#6.4.2">6.4.2</a>).
23837 <h4><a name="J.5.3" href="#J.5.3">J.5.3 Lengths and cases of identifiers</a></h4>
23839 All characters in identifiers (with or without external linkage) are significant (<a href="#6.4.2">6.4.2</a>).
23841 <h4><a name="J.5.4" href="#J.5.4">J.5.4 Scopes of identifiers</a></h4>
23843 A function identifier, or the identifier of an object the declaration of which contains the
23844 keyword extern, has file scope (<a href="#6.2.1">6.2.1</a>).
23846 <h4><a name="J.5.5" href="#J.5.5">J.5.5 Writable string literals</a></h4>
23848 String literals are modifiable (in which case, identical string literals should denote distinct
23849 objects) (<a href="#6.4.5">6.4.5</a>).
23851 <h4><a name="J.5.6" href="#J.5.6">J.5.6 Other arithmetic types</a></h4>
23853 Additional arithmetic types, such as __int128 or double double, and their
23854 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
23855 more range or precision than long double, may be used for evaluating expressions of
23856 other floating types, and may be used to define float_t or double_t.
23859 <h4><a name="J.5.7" href="#J.5.7">J.5.7 Function pointer casts</a></h4>
23861 A pointer to an object or to void may be cast to a pointer to a function, allowing data to
23862 be invoked as a function (<a href="#6.5.4">6.5.4</a>).
23864 A pointer to a function may be cast to a pointer to an object or to void, allowing a
23865 function to be inspected or modified (for example, by a debugger) (<a href="#6.5.4">6.5.4</a>).
23867 <h4><a name="J.5.8" href="#J.5.8">J.5.8 Extended bit-field types</a></h4>
23869 A bit-field may be declared with a type other than _Bool, unsigned int, or
23870 signed int, with an appropriate maximum width (<a href="#6.7.2.1">6.7.2.1</a>).
23872 <h4><a name="J.5.9" href="#J.5.9">J.5.9 The fortran keyword</a></h4>
23874 The fortran function specifier may be used in a function declaration to indicate that
23875 calls suitable for FORTRAN should be generated, or that a different representation for the
23876 external name is to be generated (<a href="#6.7.4">6.7.4</a>).
23878 <h4><a name="J.5.10" href="#J.5.10">J.5.10 The asm keyword</a></h4>
23880 The asm keyword may be used to insert assembly language directly into the translator
23881 output (<a href="#6.8">6.8</a>). The most common implementation is via a statement of the form:
23883 asm ( character-string-literal );</pre>
23885 <h4><a name="J.5.11" href="#J.5.11">J.5.11 Multiple external definitions</a></h4>
23887 There may be more than one external definition for the identifier of an object, with or
23888 without the explicit use of the keyword extern; if the definitions disagree, or more than
23889 one is initialized, the behavior is undefined (<a href="#6.9.2">6.9.2</a>).
23891 <h4><a name="J.5.12" href="#J.5.12">J.5.12 Predefined macro names</a></h4>
23893 Macro names that do not begin with an underscore, describing the translation and
23894 execution environments, are defined by the implementation before translation begins
23895 (<a href="#6.10.8">6.10.8</a>).
23897 <h4><a name="J.5.13" href="#J.5.13">J.5.13 Floating-point status flags</a></h4>
23899 If any floating-point status flags are set on normal termination after all calls to functions
23900 registered by the atexit function have been made (see <a href="#7.20.4.3">7.20.4.3</a>), the implementation
23901 writes some diagnostics indicating the fact to the stderr stream, if it is still open,
23904 <h4><a name="J.5.14" href="#J.5.14">J.5.14 Extra arguments for signal handlers</a></h4>
23906 Handlers for specific signals are called with extra arguments in addition to the signal
23907 number (<a href="#7.14.1.1">7.14.1.1</a>).
23909 <h4><a name="J.5.15" href="#J.5.15">J.5.15 Additional stream types and file-opening modes</a></h4>
23911 Additional mappings from files to streams are supported (<a href="#7.19.2">7.19.2</a>).
23913 Additional file-opening modes may be specified by characters appended to the mode
23914 argument of the fopen function (<a href="#7.19.5.3">7.19.5.3</a>).
23916 <h4><a name="J.5.16" href="#J.5.16">J.5.16 Defined file position indicator</a></h4>
23918 The file position indicator is decremented by each successful call to the ungetc or
23919 ungetwc function for a text stream, except if its value was zero before a call (<a href="#7.19.7.11">7.19.7.11</a>,
23920 <a href="#7.24.3.10">7.24.3.10</a>).
23922 <h4><a name="J.5.17" href="#J.5.17">J.5.17 Math error reporting</a></h4>
23924 Functions declared in <a href="#7.3"><complex.h></a> and <a href="#7.12"><math.h></a> raise SIGFPE to report errors
23925 instead of, or in addition to, setting errno or raising floating-point exceptions (<a href="#7.3">7.3</a>,
23926 <a href="#7.12">7.12</a>).
23929 <h2><a name="Bibliography" href="#Bibliography">Bibliography</a></h2>
23931 <li> ''The C Reference Manual'' by Dennis M. Ritchie, a version of which was
23932 published in The C Programming Language by Brian W. Kernighan and Dennis
23933 M. Ritchie, Prentice-Hall, Inc., (1978). Copyright owned by AT&T.
23934 <li> 1984 /usr/group Standard by the /usr/group Standards Committee, Santa Clara,
23935 California, USA, November 1984.
23936 <li> ANSI X3/TR-1-82 (1982), American National Dictionary for Information
23937 Processing Systems, Information Processing Systems Technical Report.
23938 <li> ANSI/IEEE 754-1985, American National Standard for Binary Floating-Point
23940 <li> ANSI/IEEE 854-1988, American National Standard for Radix-Independent
23941 Floating-Point Arithmetic.
23942 <li> IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems,
23943 second edition (previously designated IEC 559:1989).
23944 <li> ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and
23945 symbols for use in the physical sciences and technology.
23946 <li> ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for
23947 information interchange.
23948 <li> ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1:
23950 <li> ISO 4217:1995, Codes for the representation of currencies and funds.
23951 <li> ISO 8601:1988, Data elements and interchange formats -- Information
23952 interchange -- Representation of dates and times.
23953 <li> ISO/IEC 9899:1990, Programming languages -- C.
23954 <li> ISO/IEC 9899/COR1:1994, Technical Corrigendum 1.
23955 <li> ISO/IEC 9899/COR2:1996, Technical Corrigendum 2.
23956 <li> ISO/IEC 9899/AMD1:1995, Amendment 1 to ISO/IEC 9899:1990 C Integrity.
23957 <li> ISO/IEC 9945-2:1993, Information technology -- Portable Operating System
23958 Interface (POSIX) -- Part 2: Shell and Utilities.
23959 <li> ISO/IEC TR 10176:1998, Information technology -- Guidelines for the
23960 preparation of programming language standards.
23961 <li> ISO/IEC 10646-1:1993, Information technology -- Universal Multiple-Octet
23962 Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
23964 <li> ISO/IEC 10646-1/COR1:1996, Technical Corrigendum 1 to
23965 ISO/IEC 10646-1:1993.
23966 <li> ISO/IEC 10646-1/COR2:1998, Technical Corrigendum 2 to
23967 ISO/IEC 10646-1:1993.
23968 <li> ISO/IEC 10646-1/AMD1:1996, Amendment 1 to ISO/IEC 10646-1:1993
23969 Transformation Format for 16 planes of group 00 (UTF-16).
23970 <li> ISO/IEC 10646-1/AMD2:1996, Amendment 2 to ISO/IEC 10646-1:1993 UCS
23971 Transformation Format 8 (UTF-8).
23972 <li> ISO/IEC 10646-1/AMD3:1996, Amendment 3 to ISO/IEC 10646-1:1993.
23973 <li> ISO/IEC 10646-1/AMD4:1996, Amendment 4 to ISO/IEC 10646-1:1993.
23974 <li> ISO/IEC 10646-1/AMD5:1998, Amendment 5 to ISO/IEC 10646-1:1993 Hangul
23976 <li> ISO/IEC 10646-1/AMD6:1997, Amendment 6 to ISO/IEC 10646-1:1993 Tibetan.
23977 <li> ISO/IEC 10646-1/AMD7:1997, Amendment 7 to ISO/IEC 10646-1:1993 33
23978 additional characters.
23979 <li> ISO/IEC 10646-1/AMD8:1997, Amendment 8 to ISO/IEC 10646-1:1993.
23980 <li> ISO/IEC 10646-1/AMD9:1997, Amendment 9 to ISO/IEC 10646-1:1993
23981 Identifiers for characters.
23982 <li> ISO/IEC 10646-1/AMD10:1998, Amendment 10 to ISO/IEC 10646-1:1993
23984 <li> ISO/IEC 10646-1/AMD11:1998, Amendment 11 to ISO/IEC 10646-1:1993
23985 Unified Canadian Aboriginal Syllabics.
23986 <li> ISO/IEC 10646-1/AMD12:1998, Amendment 12 to ISO/IEC 10646-1:1993
23988 <li> ISO/IEC 10967-1:1994, Information technology -- Language independent
23989 arithmetic -- Part 1: Integer and floating point arithmetic.
23994 <h2><a name="Index" href="#Index">Index</a></h2>
23996 ??? x ???, <a href="#3.18">3.18</a> , (comma punctuator), <a href="#6.5.2">6.5.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.7.2.2">6.7.2.2</a>,
23997 <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.8">6.7.8</a>
23998 ??? x ???, <a href="#3.19">3.19</a> - (subtraction operator), <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>
23999 ! (logical negation operator), <a href="#6.5.3.3">6.5.3.3</a> - (unary minus operator), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a>
24000 != (inequality operator), <a href="#6.5.9">6.5.9</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>
24001 # operator, <a href="#6.10.3.2">6.10.3.2</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>
24002 # preprocessing directive, <a href="#6.10.7">6.10.7</a> -= (subtraction assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
24003 # punctuator, <a href="#6.10">6.10</a> -> (structure/union pointer operator), <a href="#6.5.2.3">6.5.2.3</a>
24004 ## operator, <a href="#6.10.3.3">6.10.3.3</a> . (structure/union member operator), <a href="#6.3.2.1">6.3.2.1</a>,
24005 #define preprocessing directive, <a href="#6.10.3">6.10.3</a> <a href="#6.5.2.3">6.5.2.3</a>
24006 #elif preprocessing directive, <a href="#6.10.1">6.10.1</a> . punctuator, <a href="#6.7.8">6.7.8</a>
24007 #else 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="#6.7.5.3">6.7.5.3</a>, <a href="#6.10.3">6.10.3</a>
24008 #endif preprocessing directive, <a href="#6.10.1">6.10.1</a> / (division operator), <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>
24009 #error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> /* */ (comment delimiters), <a href="#6.4.9">6.4.9</a>
24010 #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 delimiter), <a href="#6.4.9">6.4.9</a>
24011 <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a> /= (division assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
24012 #ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a> : (colon punctuator), <a href="#6.7.2.1">6.7.2.1</a>
24013 #ifndef preprocessing directive, <a href="#6.10.1">6.10.1</a> :> (alternative spelling of ]), <a href="#6.4.6">6.4.6</a>
24014 #include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</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>,
24015 <a href="#6.10.2">6.10.2</a> <a href="#6.8.5">6.8.5</a>, <a href="#6.8.6">6.8.6</a>
24016 #line preprocessing directive, <a href="#6.10.4">6.10.4</a> < (less-than operator), <a href="#6.5.8">6.5.8</a>
24017 #pragma preprocessing directive, <a href="#6.10.6">6.10.6</a> <% (alternative spelling of {), <a href="#6.4.6">6.4.6</a>
24018 #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>
24019 <a href="#7.1.4">7.1.4</a> << (left-shift operator), <a href="#6.5.7">6.5.7</a>
24020 % (remainder operator), <a href="#6.5.5">6.5.5</a> <<= (left-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
24021 %: (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>
24022 %:%: (alternative spelling of ##), <a href="#6.4.6">6.4.6</a> <a href="#7.2"><assert.h></a> header, <a href="#7.2">7.2</a>, <a href="#B.1">B.1</a>
24023 %= (remainder assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.3"><complex.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.3">7.3</a>, <a href="#7.22">7.22</a>,
24024 %> (alternative spelling of }), <a href="#6.4.6">6.4.6</a> <a href="#7.26.1">7.26.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
24025 & (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="#7.4"><ctype.h></a> header, <a href="#7.4">7.4</a>, <a href="#7.26.2">7.26.2</a>
24026 & (bitwise AND operator), <a href="#6.5.10">6.5.10</a> <a href="#7.5"><errno.h></a> header, <a href="#7.5">7.5</a>, <a href="#7.26.3">7.26.3</a>
24027 && (logical AND operator), <a href="#6.5.13">6.5.13</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>,
24028 &= (bitwise AND assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#H">H</a>
24029 ' ' (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="#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="#7.20.1.3">7.20.1.3</a>,
24030 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>
24031 ( ) (cast operator), <a href="#6.5.4">6.5.4</a> <a href="#7.8"><inttypes.h></a> header, <a href="#7.8">7.8</a>, <a href="#7.26.4">7.26.4</a>
24032 ( ) (function-call operator), <a href="#6.5.2.2">6.5.2.2</a> <a href="#7.9"><iso646.h></a> header, <a href="#4">4</a>, <a href="#7.9">7.9</a>
24033 ( ) (parentheses punctuator), <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</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>
24034 ( ){ } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a> <a href="#7.11"><locale.h></a> header, <a href="#7.11">7.11</a>, <a href="#7.26.5">7.26.5</a>
24035 * (asterisk punctuator), <a href="#6.7.5.1">6.7.5.1</a>, <a href="#6.7.5.2">6.7.5.2</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="#7.22">7.22</a>, <a href="#F">F</a>,
24036 * (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="#F.9">F.9</a>, <a href="#J.5.17">J.5.17</a>
24037 * (multiplication operator), <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> <a href="#7.13"><setjmp.h></a> header, <a href="#7.13">7.13</a>
24038 *= (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="#7.26.6">7.26.6</a>
24039 + (addition 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="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#7.15"><stdarg.h></a> header, <a href="#4">4</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#7.15">7.15</a>
24040 <a href="#G.5.2">G.5.2</a> <a href="#7.16"><stdbool.h></a> header, <a href="#4">4</a>, <a href="#7.16">7.16</a>, <a href="#7.26.7">7.26.7</a>, <a href="#H">H</a>
24041 + (unary plus operator), <a href="#6.5.3.3">6.5.3.3</a> <a href="#7.17"><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>,
24042 ++ (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="#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="#7.17">7.17</a>
24043 ++ (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="#7.18"><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>,
24044 += (addition assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.18">7.18</a>, <a href="#7.26.8">7.26.8</a>
24045 , (comma operator), <a href="#6.5.17">6.5.17</a>
24047 <a href="#7.19"><stdio.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19">7.19</a>, <a href="#7.26.9">7.26.9</a>, <a href="#F">F</a> __cplusplus macro, <a href="#6.10.8">6.10.8</a>
24048 <a href="#7.20"><stdlib.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.20">7.20</a>, <a href="#7.26.10">7.26.10</a>, <a href="#F">F</a> __DATE__ macro, <a href="#6.10.8">6.10.8</a>
24049 <a href="#7.21"><string.h></a> header, <a href="#7.21">7.21</a>, <a href="#7.26.11">7.26.11</a> __FILE__ macro, <a href="#6.10.8">6.10.8</a>, <a href="#7.2.1.1">7.2.1.1</a>
24050 <a href="#7.22"><tgmath.h></a> header, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</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>
24051 <a href="#7.23"><time.h></a> header, <a href="#7.23">7.23</a> __LINE__ macro, <a href="#6.10.8">6.10.8</a>, <a href="#7.2.1.1">7.2.1.1</a>
24052 <a href="#7.24"><wchar.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24">7.24</a>, __STDC_, <a href="#6.11.9">6.11.9</a>
24053 <a href="#7.26.12">7.26.12</a>, <a href="#F">F</a> __STDC__ macro, <a href="#6.10.8">6.10.8</a>
24054 <a href="#7.25"><wctype.h></a> header, <a href="#7.25">7.25</a>, <a href="#7.26.13">7.26.13</a> __STDC_CONSTANT_MACROS macro, <a href="#7.18.4">7.18.4</a>
24055 = (equal-sign punctuator), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.8">6.7.8</a> __STDC_FORMAT_MACROS macro, <a href="#7.8.1">7.8.1</a>
24056 = (simple assignment operator), <a href="#6.5.16.1">6.5.16.1</a> __STDC_HOSTED__ macro, <a href="#6.10.8">6.10.8</a>
24057 == (equality operator), <a href="#6.5.9">6.5.9</a> __STDC_IEC_559__ macro, <a href="#6.10.8">6.10.8</a>, <a href="#F.1">F.1</a>
24058 > (greater-than operator), <a href="#6.5.8">6.5.8</a> __STDC_IEC_559_COMPLEX__ macro,
24059 >= (greater-than-or-equal-to operator), <a href="#6.5.8">6.5.8</a> <a href="#6.10.8">6.10.8</a>, <a href="#G.1">G.1</a>
24060 >> (right-shift operator), <a href="#6.5.7">6.5.7</a> __STDC_ISO_10646__ macro, <a href="#6.10.8">6.10.8</a>
24061 >>= (right-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a> __STDC_LIMIT_MACROS macro, <a href="#7.18.2">7.18.2</a>,
24062 ? : (conditional operator), <a href="#6.5.15">6.5.15</a> <a href="#7.18.3">7.18.3</a>
24063 ?? (trigraph sequences), <a href="#5.2.1.1">5.2.1.1</a> __STDC_MB_MIGHT_NEQ_WC__ macro,
24064 [ ] (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> <a href="#6.10.8">6.10.8</a>, <a href="#7.17">7.17</a>
24065 [ ] (brackets punctuator), <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.7.8">6.7.8</a> __STDC_VERSION__ macro, <a href="#6.10.8">6.10.8</a>
24066 \ (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> __TIME__ macro, <a href="#6.10.8">6.10.8</a>
24067 \ (escape character), <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>
24068 \" (double-quote escape sequence), <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>
24069 <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</a> _Bool type conversions, <a href="#6.3.1.2">6.3.1.2</a>
24070 \\ (backslash escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</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>
24071 \' (single-quote escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> _Complex_I macro, <a href="#7.3.1">7.3.1</a>
24072 \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> _Exit function, <a href="#7.20.4.4">7.20.4.4</a>
24073 padding of binary stream, <a href="#7.19.2">7.19.2</a> _Imaginary keyword, <a href="#G.2">G.2</a>
24074 \? (question-mark escape sequence), <a href="#6.4.4.4">6.4.4.4</a> _Imaginary types, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a>
24075 \a (alert escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> _Imaginary_I macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a>
24076 \b (backspace escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> _IOFBF macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.5">7.19.5.5</a>, <a href="#7.19.5.6">7.19.5.6</a>
24077 \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>, _IOLBF macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.6">7.19.5.6</a>
24078 <a href="#7.4.1.10">7.4.1.10</a> _IONBF macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.5">7.19.5.5</a>, <a href="#7.19.5.6">7.19.5.6</a>
24079 \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>, _Pragma operator, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a>
24080 <a href="#7.4.1.10">7.4.1.10</a> { } (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="#6.7.8">6.7.8</a>,
24081 \octal digits (octal-character escape sequence), <a href="#6.8.2">6.8.2</a>
24082 <a href="#6.4.4.4">6.4.4.4</a> { } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a>
24083 \r (carriage-return escape sequence), <a href="#5.2.2">5.2.2</a>, | (bitwise inclusive OR operator), <a href="#6.5.12">6.5.12</a>
24084 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a> |= (bitwise inclusive OR assignment operator),
24085 \t (horizontal-tab escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.5.16.2">6.5.16.2</a>
24086 <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="#7.25.2.1.3">7.25.2.1.3</a> || (logical OR operator), <a href="#6.5.14">6.5.14</a>
24087 \U (universal character names), <a href="#6.4.3">6.4.3</a> ~ (bitwise complement operator), <a href="#6.5.3.3">6.5.3.3</a>
24088 \u (universal character names), <a href="#6.4.3">6.4.3</a>
24089 \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>, 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="#7.19.3">7.19.3</a>,
24090 <a href="#7.4.1.10">7.4.1.10</a> <a href="#7.20.4.1">7.20.4.1</a>
24091 \x hexadecimal digits (hexadecimal-character abs function, <a href="#7.20.6.1">7.20.6.1</a>
24092 escape sequence), <a href="#6.4.4.4">6.4.4.4</a> absolute-value functions
24093 ^ (bitwise exclusive OR operator), <a href="#6.5.11">6.5.11</a> complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a>
24094 ^= (bitwise exclusive OR assignment operator), integer, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.20.6.1">7.20.6.1</a>
24095 <a href="#6.5.16.2">6.5.16.2</a> real, <a href="#7.12.7">7.12.7</a>, <a href="#F.9.4">F.9.4</a>
24096 __bool_true_false_are_defined abstract declarator, <a href="#6.7.6">6.7.6</a>
24097 macro, <a href="#7.16">7.16</a> abstract machine, <a href="#5.1.2.3">5.1.2.3</a>
24099 access, <a href="#3.1">3.1</a>, <a href="#6.7.3">6.7.3</a> array
24100 accuracy, see floating-point accuracy argument, <a href="#6.9.1">6.9.1</a>
24101 acos functions, <a href="#7.12.4.1">7.12.4.1</a>, <a href="#F.9.1.1">F.9.1.1</a> declarator, <a href="#6.7.5.2">6.7.5.2</a>
24102 acos type-generic macro, <a href="#7.22">7.22</a> initialization, <a href="#6.7.8">6.7.8</a>
24103 acosh functions, <a href="#7.12.5.1">7.12.5.1</a>, <a href="#F.9.2.1">F.9.2.1</a> multidimensional, <a href="#6.5.2.1">6.5.2.1</a>
24104 acosh type-generic macro, <a href="#7.22">7.22</a> parameter, <a href="#6.9.1">6.9.1</a>
24105 active position, <a href="#5.2.2">5.2.2</a> storage order, <a href="#6.5.2.1">6.5.2.1</a>
24106 actual argument, <a href="#3.3">3.3</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>
24107 actual parameter (deprecated), <a href="#3.3">3.3</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
24108 addition assignment operator (+=), <a href="#6.5.16.2">6.5.16.2</a> type, <a href="#6.2.5">6.2.5</a>
24109 addition 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="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, type conversion, <a href="#6.3.2.1">6.3.2.1</a>
24110 <a href="#G.5.2">G.5.2</a> variable length, <a href="#6.7.5">6.7.5</a>, <a href="#6.7.5.2">6.7.5.2</a>
24111 additive expressions, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
24112 address constant, <a href="#6.6">6.6</a> as-if rule, <a href="#5.1.2.3">5.1.2.3</a>
24113 address operator (&), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> ASCII code set, <a href="#5.2.1.1">5.2.1.1</a>
24114 aggregate initialization, <a href="#6.7.8">6.7.8</a> asctime function, <a href="#7.23.3.1">7.23.3.1</a>
24115 aggregate types, <a href="#6.2.5">6.2.5</a> asin functions, <a href="#7.12.4.2">7.12.4.2</a>, <a href="#F.9.1.2">F.9.1.2</a>
24116 alert escape sequence (\a), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> asin type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24117 aliasing, <a href="#6.5">6.5</a> asinh functions, <a href="#7.12.5.2">7.12.5.2</a>, <a href="#F.9.2.2">F.9.2.2</a>
24118 alignment, <a href="#3.2">3.2</a> asinh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24119 pointer, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.3">6.3.2.3</a> asm keyword, <a href="#J.5.10">J.5.10</a>
24120 structure/union member, <a href="#6.7.2.1">6.7.2.1</a> assert macro, <a href="#7.2.1.1">7.2.1.1</a>
24121 allocated storage, order and contiguity, <a href="#7.20.3">7.20.3</a> assert.h header, <a href="#7.2">7.2</a>, <a href="#B.1">B.1</a>
24122 and macro, <a href="#7.9">7.9</a> assignment
24123 AND operators compound, <a href="#6.5.16.2">6.5.16.2</a>
24124 bitwise (&), <a href="#6.5.10">6.5.10</a> conversion, <a href="#6.5.16.1">6.5.16.1</a>
24125 bitwise assignment (&=), <a href="#6.5.16.2">6.5.16.2</a> expression, <a href="#6.5.16">6.5.16</a>
24126 logical (&&), <a href="#6.5.13">6.5.13</a> operators, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.16">6.5.16</a>
24127 and_eq macro, <a href="#7.9">7.9</a> simple, <a href="#6.5.16.1">6.5.16.1</a>
24128 ANSI/IEEE 754, <a href="#F.1">F.1</a> associativity of operators, <a href="#6.5">6.5</a>
24129 ANSI/IEEE 854, <a href="#F.1">F.1</a> asterisk punctuator (*), <a href="#6.7.5.1">6.7.5.1</a>, <a href="#6.7.5.2">6.7.5.2</a>
24130 argc (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a> atan functions, <a href="#7.12.4.3">7.12.4.3</a>, <a href="#F.9.1.3">F.9.1.3</a>
24131 argument, <a href="#3.3">3.3</a> atan type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24132 array, <a href="#6.9.1">6.9.1</a> atan2 functions, <a href="#7.12.4.4">7.12.4.4</a>, <a href="#F.9.1.4">F.9.1.4</a>
24133 default promotions, <a href="#6.5.2.2">6.5.2.2</a> atan2 type-generic macro, <a href="#7.22">7.22</a>
24134 function, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a> atanh functions, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#F.9.2.3">F.9.2.3</a>
24135 macro, substitution, <a href="#6.10.3.1">6.10.3.1</a> atanh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24136 argument, complex, <a href="#7.3.9.1">7.3.9.1</a> atexit function, <a href="#7.20.4.2">7.20.4.2</a>, <a href="#7.20.4.3">7.20.4.3</a>, <a href="#7.20.4.4">7.20.4.4</a>,
24137 argv (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a> <a href="#J.5.13">J.5.13</a>
24138 arithmetic constant expression, <a href="#6.6">6.6</a> atof function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.1">7.20.1.1</a>
24139 arithmetic conversions, usual, see usual arithmetic atoi function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.2">7.20.1.2</a>
24140 conversions atol function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.2">7.20.1.2</a>
24141 arithmetic operators atoll function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.2">7.20.1.2</a>
24142 additive, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a> auto storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a>
24143 bitwise, <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> automatic storage duration, <a href="#5.2.3">5.2.3</a>, <a href="#6.2.4">6.2.4</a>
24144 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>
24145 multiplicative, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a> backslash character (\), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>
24146 shift, <a href="#6.5.7">6.5.7</a> backslash escape sequence (\\), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a>
24147 unary, <a href="#6.5.3.3">6.5.3.3</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>
24148 arithmetic types, <a href="#6.2.5">6.2.5</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>
24149 arithmetic, pointer, <a href="#6.5.6">6.5.6</a> basic types, <a href="#6.2.5">6.2.5</a>
24151 behavior, <a href="#3.4">3.4</a> call by value, <a href="#6.5.2.2">6.5.2.2</a>
24152 binary streams, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>, calloc function, <a href="#7.20.3">7.20.3</a>, <a href="#7.20.3.1">7.20.3.1</a>, <a href="#7.20.3.2">7.20.3.2</a>,
24153 <a href="#7.19.9.4">7.19.9.4</a> <a href="#7.20.3.4">7.20.3.4</a>
24154 bit, <a href="#3.5">3.5</a> carg functions, <a href="#7.3.9.1">7.3.9.1</a>, <a href="#G.6">G.6</a>
24155 high order, <a href="#3.6">3.6</a> carg type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24156 low order, <a href="#3.6">3.6</a> carriage-return escape sequence (\r), <a href="#5.2.2">5.2.2</a>,
24157 bit-field, <a href="#6.7.2.1">6.7.2.1</a> <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a>
24158 bitand macro, <a href="#7.9">7.9</a> case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
24159 bitor macro, <a href="#7.9">7.9</a> case mapping functions
24160 bitwise operators, <a href="#6.5">6.5</a> character, <a href="#7.4.2">7.4.2</a>
24161 AND, <a href="#6.5.10">6.5.10</a> wide character, <a href="#7.25.3.1">7.25.3.1</a>
24162 AND assignment (&=), <a href="#6.5.16.2">6.5.16.2</a> extensible, <a href="#7.25.3.2">7.25.3.2</a>
24163 complement (~), <a href="#6.5.3.3">6.5.3.3</a> casin functions, <a href="#7.3.5.2">7.3.5.2</a>, <a href="#G.6">G.6</a>
24164 exclusive OR, <a href="#6.5.11">6.5.11</a> type-generic macro for, <a href="#7.22">7.22</a>
24165 exclusive OR assignment (^=), <a href="#6.5.16.2">6.5.16.2</a> casinh functions, <a href="#7.3.6.2">7.3.6.2</a>, <a href="#G.6.2.2">G.6.2.2</a>
24166 inclusive OR, <a href="#6.5.12">6.5.12</a> type-generic macro for, <a href="#7.22">7.22</a>
24167 inclusive OR assignment (|=), <a href="#6.5.16.2">6.5.16.2</a> cast expression, <a href="#6.5.4">6.5.4</a>
24168 shift, <a href="#6.5.7">6.5.7</a> cast operator (( )), <a href="#6.5.4">6.5.4</a>
24169 blank character, <a href="#7.4.1.3">7.4.1.3</a> catan functions, <a href="#7.3.5.3">7.3.5.3</a>, <a href="#G.6">G.6</a>
24170 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> type-generic macro for, <a href="#7.22">7.22</a>
24171 block scope, <a href="#6.2.1">6.2.1</a> catanh functions, <a href="#7.3.6.3">7.3.6.3</a>, <a href="#G.6.2.3">G.6.2.3</a>
24172 block structure, <a href="#6.2.1">6.2.1</a> type-generic macro for, <a href="#7.22">7.22</a>
24173 bold type convention, <a href="#6.1">6.1</a> cbrt functions, <a href="#7.12.7.1">7.12.7.1</a>, <a href="#F.9.4.1">F.9.4.1</a>
24174 bool macro, <a href="#7.16">7.16</a> cbrt type-generic macro, <a href="#7.22">7.22</a>
24175 boolean type, <a href="#6.3.1.2">6.3.1.2</a> ccos functions, <a href="#7.3.5.4">7.3.5.4</a>, <a href="#G.6">G.6</a>
24176 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> type-generic macro for, <a href="#7.22">7.22</a>
24177 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="#6.7.8">6.7.8</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>
24178 <a href="#6.8.2">6.8.2</a> type-generic macro for, <a href="#7.22">7.22</a>
24179 brackets operator ([ ]), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> ceil functions, <a href="#7.12.9.1">7.12.9.1</a>, <a href="#F.9.6.1">F.9.6.1</a>
24180 brackets punctuator ([ ]), <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.7.8">6.7.8</a> ceil type-generic macro, <a href="#7.22">7.22</a>
24181 branch cuts, <a href="#7.3.3">7.3.3</a> cerf function, <a href="#7.26.1">7.26.1</a>
24182 break statement, <a href="#6.8.6.3">6.8.6.3</a> cerfc function, <a href="#7.26.1">7.26.1</a>
24183 broken-down time, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.3">7.23.3</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>
24184 <a href="#7.23.3.1">7.23.3.1</a>, <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a>, <a href="#7.23.3.5">7.23.3.5</a> type-generic macro for, <a href="#7.22">7.22</a>
24185 bsearch function, <a href="#7.20.5">7.20.5</a>, <a href="#7.20.5.1">7.20.5.1</a> cexp2 function, <a href="#7.26.1">7.26.1</a>
24186 btowc function, <a href="#7.24.6.1.1">7.24.6.1.1</a> cexpm1 function, <a href="#7.26.1">7.26.1</a>
24187 BUFSIZ macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.5.5">7.19.5.5</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>
24188 byte, <a href="#3.6">3.6</a>, <a href="#6.5.3.4">6.5.3.4</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>,
24189 byte input/output functions, <a href="#7.19.1">7.19.1</a> <a href="#6.3.1.8">6.3.1.8</a>
24190 byte-oriented stream, <a href="#7.19.2">7.19.2</a> CHAR_BIT macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24191 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>
24192 <a href="#C">C</a> program, <a href="#5.1.1.1">5.1.1.1</a> CHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24193 <a href="#C">C</a>++, <a href="#7.8.1">7.8.1</a>, <a href="#7.18.2">7.18.2</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.18.4">7.18.4</a> character, <a href="#3.7">3.7</a>, <a href="#3.7.1">3.7.1</a>
24194 cabs functions, <a href="#7.3.8.1">7.3.8.1</a>, <a href="#G.6">G.6</a> character array initialization, <a href="#6.7.8">6.7.8</a>
24195 type-generic macro for, <a href="#7.22">7.22</a> character case mapping functions, <a href="#7.4.2">7.4.2</a>
24196 cacos functions, <a href="#7.3.5.1">7.3.5.1</a>, <a href="#G.6.1.1">G.6.1.1</a> wide character, <a href="#7.25.3.1">7.25.3.1</a>
24197 type-generic macro for, <a href="#7.22">7.22</a> extensible, <a href="#7.25.3.2">7.25.3.2</a>
24198 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 classification functions, <a href="#7.4.1">7.4.1</a>
24199 type-generic macro for, <a href="#7.22">7.22</a> wide character, <a href="#7.25.2.1">7.25.2.1</a>
24200 calendar time, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.2">7.23.2.2</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.2.4">7.23.2.4</a>, extensible, <a href="#7.25.2.2">7.25.2.2</a>
24201 <a href="#7.23.3.2">7.23.3.2</a>, <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</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>
24203 character display semantics, <a href="#5.2.2">5.2.2</a> complex.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.3">7.3</a>, <a href="#7.22">7.22</a>, <a href="#7.26.1">7.26.1</a>,
24204 character handling header, <a href="#7.4">7.4</a>, <a href="#7.11.1.1">7.11.1.1</a> <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
24205 character input/output functions, <a href="#7.19.7">7.19.7</a> compliance, see conformance
24206 wide character, <a href="#7.24.3">7.24.3</a> components of time, <a href="#7.23.1">7.23.1</a>
24207 character sets, <a href="#5.2.1">5.2.1</a> composite type, <a href="#6.2.7">6.2.7</a>
24208 character string literal, see string literal compound assignment, <a href="#6.5.16.2">6.5.16.2</a>
24209 character type conversion, <a href="#6.3.1.1">6.3.1.1</a> compound literals, <a href="#6.5.2.5">6.5.2.5</a>
24210 character types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.8">6.7.8</a> compound statement, <a href="#6.8.2">6.8.2</a>
24211 cimag functions, <a href="#7.3.9.2">7.3.9.2</a>, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a> compound-literal operator (( ){ }), <a href="#6.5.2.5">6.5.2.5</a>
24212 cimag type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> concatenation functions
24213 cis function, <a href="#G.6">G.6</a> string, <a href="#7.21.3">7.21.3</a>
24214 classification functions wide string, <a href="#7.24.4.3">7.24.4.3</a>
24215 character, <a href="#7.4.1">7.4.1</a> concatenation, preprocessing, see preprocessing
24216 floating-point, <a href="#7.12.3">7.12.3</a> concatenation
24217 wide character, <a href="#7.25.2.1">7.25.2.1</a> conceptual models, <a href="#5.1">5.1</a>
24218 extensible, <a href="#7.25.2.2">7.25.2.2</a> conditional inclusion, <a href="#6.10.1">6.10.1</a>
24219 clearerr function, <a href="#7.19.10.1">7.19.10.1</a> conditional operator (? :), <a href="#6.5.15">6.5.15</a>
24220 clgamma function, <a href="#7.26.1">7.26.1</a> conformance, <a href="#4">4</a>
24221 clock function, <a href="#7.23.2.1">7.23.2.1</a> conj functions, <a href="#7.3.9.3">7.3.9.3</a>, <a href="#G.6">G.6</a>
24222 clock_t type, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.1">7.23.2.1</a> conj type-generic macro, <a href="#7.22">7.22</a>
24223 CLOCKS_PER_SEC macro, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.1">7.23.2.1</a> const type qualifier, <a href="#6.7.3">6.7.3</a>
24224 clog functions, <a href="#7.3.7.2">7.3.7.2</a>, <a href="#G.6.3.2">G.6.3.2</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>
24225 type-generic macro for, <a href="#7.22">7.22</a> constant expression, <a href="#6.6">6.6</a>, <a href="#F.7.4">F.7.4</a>
24226 clog10 function, <a href="#7.26.1">7.26.1</a> constants, <a href="#6.4.4">6.4.4</a>
24227 clog1p function, <a href="#7.26.1">7.26.1</a> as primary expression, <a href="#6.5.1">6.5.1</a>
24228 clog2 function, <a href="#7.26.1">7.26.1</a> character, <a href="#6.4.4.4">6.4.4.4</a>
24229 collating sequences, <a href="#5.2.1">5.2.1</a> enumeration, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
24230 colon punctuator (:), <a href="#6.7.2.1">6.7.2.1</a> floating, <a href="#6.4.4.2">6.4.4.2</a>
24231 comma operator (,), <a href="#6.5.17">6.5.17</a> hexadecimal, <a href="#6.4.4.1">6.4.4.1</a>
24232 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>, integer, <a href="#6.4.4.1">6.4.4.1</a>
24233 <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.8">6.7.8</a> octal, <a href="#6.4.4.1">6.4.4.1</a>
24234 command processor, <a href="#7.20.4.6">7.20.4.6</a> constraint, <a href="#3.8">3.8</a>, <a href="#4">4</a>
24235 comment delimiters (/* */ and //), <a href="#6.4.9">6.4.9</a> content of structure/union/enumeration, <a href="#6.7.2.3">6.7.2.3</a>
24236 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> contiguity of allocated storage, <a href="#7.20.3">7.20.3</a>
24237 common extensions, <a href="#J.5">J.5</a> continue statement, <a href="#6.8.6.2">6.8.6.2</a>
24238 common initial sequence, <a href="#6.5.2.3">6.5.2.3</a> contracted expression, <a href="#6.5">6.5</a>, <a href="#7.12.2">7.12.2</a>, <a href="#F.6">F.6</a>
24239 common real type, <a href="#6.3.1.8">6.3.1.8</a> control character, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a>
24240 common warnings, <a href="#I">I</a> control wide character, <a href="#7.25.2">7.25.2</a>
24241 comparison functions, <a href="#7.20.5">7.20.5</a>, <a href="#7.20.5.1">7.20.5.1</a>, <a href="#7.20.5.2">7.20.5.2</a> conversion, <a href="#6.3">6.3</a>
24242 string, <a href="#7.21.4">7.21.4</a> arithmetic operands, <a href="#6.3.1">6.3.1</a>
24243 wide string, <a href="#7.24.4.4">7.24.4.4</a> array argument, <a href="#6.9.1">6.9.1</a> *
24244 comparison macros, <a href="#7.12.14">7.12.14</a> array parameter, <a href="#6.9.1">6.9.1</a>
24245 comparison, pointer, <a href="#6.5.8">6.5.8</a> arrays, <a href="#6.3.2.1">6.3.2.1</a>
24246 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="#6.7.5">6.7.5</a> boolean, <a href="#6.3.1.2">6.3.1.2</a>
24247 compl macro, <a href="#7.9">7.9</a> boolean, characters, and integers, <a href="#6.3.1.1">6.3.1.1</a>
24248 complement operator (~), <a href="#6.5.3.3">6.5.3.3</a> by assignment, <a href="#6.5.16.1">6.5.16.1</a>
24249 complex macro, <a href="#7.3.1">7.3.1</a> by return statement, <a href="#6.8.6.4">6.8.6.4</a>
24250 complex numbers, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a> complex types, <a href="#6.3.1.6">6.3.1.6</a>
24251 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> explicit, <a href="#6.3">6.3</a>
24252 complex type domain, <a href="#6.2.5">6.2.5</a> function, <a href="#6.3.2.1">6.3.2.1</a>
24253 complex types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#G">G</a> function argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a>
24255 function designators, <a href="#6.3.2.1">6.3.2.1</a> type-generic macro for, <a href="#7.22">7.22</a>
24256 function parameter, <a href="#6.9.1">6.9.1</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>
24257 imaginary, <a href="#G.4.1">G.4.1</a> type-generic macro for, <a href="#7.22">7.22</a>
24258 imaginary and complex, <a href="#G.4.3">G.4.3</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>
24259 implicit, <a href="#6.3">6.3</a> type-generic macro for, <a href="#7.22">7.22</a>
24260 lvalues, <a href="#6.3.2.1">6.3.2.1</a> ctan functions, <a href="#7.3.5.6">7.3.5.6</a>, <a href="#G.6">G.6</a>
24261 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="#7.22">7.22</a>
24262 real and complex, <a href="#6.3.1.7">6.3.1.7</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>
24263 real and imaginary, <a href="#G.4.2">G.4.2</a> type-generic macro for, <a href="#7.22">7.22</a>
24264 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> ctgamma function, <a href="#7.26.1">7.26.1</a>
24265 real floating types, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#F.3">F.3</a> ctime function, <a href="#7.23.3.2">7.23.3.2</a>
24266 signed and unsigned integers, <a href="#6.3.1.3">6.3.1.3</a> ctype.h header, <a href="#7.4">7.4</a>, <a href="#7.26.2">7.26.2</a>
24267 usual arithmetic, see usual arithmetic current object, <a href="#6.7.8">6.7.8</a>
24268 conversions CX_LIMITED_RANGE pragma, <a href="#6.10.6">6.10.6</a>, <a href="#7.3.4">7.3.4</a>
24269 void type, <a href="#6.3.2.2">6.3.2.2</a>
24270 conversion functions data stream, see streams
24271 multibyte/wide character, <a href="#7.20.7">7.20.7</a> date and time header, <a href="#7.23">7.23</a>
24272 extended, <a href="#7.24.6">7.24.6</a> Daylight Saving Time, <a href="#7.23.1">7.23.1</a>
24273 restartable, <a href="#7.24.6.3">7.24.6.3</a> DBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24274 multibyte/wide string, <a href="#7.20.8">7.20.8</a> DBL_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24275 restartable, <a href="#7.24.6.4">7.24.6.4</a> DBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24276 numeric, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1">7.20.1</a> DBL_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24277 wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1">7.24.4.1</a> DBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24278 single byte/wide character, <a href="#7.24.6.1">7.24.6.1</a> DBL_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24279 time, <a href="#7.23.3">7.23.3</a> DBL_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24280 wide character, <a href="#7.24.5">7.24.5</a> DBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24281 conversion specifier, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, DBL_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24282 <a href="#7.24.2.2">7.24.2.2</a> decimal constant, <a href="#6.4.4.1">6.4.4.1</a>
24283 conversion state, <a href="#7.20.7">7.20.7</a>, <a href="#7.24.6">7.24.6</a>, <a href="#7.24.6.2.1">7.24.6.2.1</a>, decimal digit, <a href="#5.2.1">5.2.1</a>
24284 <a href="#7.24.6.3">7.24.6.3</a>, <a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4">7.24.6.4</a>, decimal-point character, <a href="#7.1.1">7.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24285 <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a> DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24286 conversion state functions, <a href="#7.24.6.2">7.24.6.2</a> <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.5">F.5</a>
24287 copying functions declaration specifiers, <a href="#6.7">6.7</a>
24288 string, <a href="#7.21.2">7.21.2</a> declarations, <a href="#6.7">6.7</a>
24289 wide string, <a href="#7.24.4.2">7.24.4.2</a> function, <a href="#6.7.5.3">6.7.5.3</a>
24290 copysign functions, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#7.12.11.1">7.12.11.1</a>, <a href="#F.3">F.3</a>, pointer, <a href="#6.7.5.1">6.7.5.1</a>
24291 <a href="#F.9.8.1">F.9.8.1</a> structure/union, <a href="#6.7.2.1">6.7.2.1</a>
24292 copysign type-generic macro, <a href="#7.22">7.22</a> typedef, <a href="#6.7.7">6.7.7</a>
24293 correctly rounded result, <a href="#3.9">3.9</a> declarator, <a href="#6.7.5">6.7.5</a>
24294 corresponding real type, <a href="#6.2.5">6.2.5</a> abstract, <a href="#6.7.6">6.7.6</a>
24295 cos functions, <a href="#7.12.4.5">7.12.4.5</a>, <a href="#F.9.1.5">F.9.1.5</a> declarator type derivation, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.5">6.7.5</a>
24296 cos type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> decrement operators, see arithmetic operators,
24297 cosh functions, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#F.9.2.4">F.9.2.4</a> increment and decrement
24298 cosh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> default argument promotions, <a href="#6.5.2.2">6.5.2.2</a>
24299 cpow functions, <a href="#7.3.8.2">7.3.8.2</a>, <a href="#G.6.4.1">G.6.4.1</a> default initialization, <a href="#6.7.8">6.7.8</a>
24300 type-generic macro for, <a href="#7.22">7.22</a> default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
24301 cproj functions, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a> define preprocessing directive, <a href="#6.10.3">6.10.3</a>
24302 cproj type-generic macro, <a href="#7.22">7.22</a> defined operator, <a href="#6.10.1">6.10.1</a>, <a href="#6.10.8">6.10.8</a>
24303 creal functions, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#G.6">G.6</a> definition, <a href="#6.7">6.7</a>
24304 creal type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> function, <a href="#6.9.1">6.9.1</a>
24305 csin functions, <a href="#7.3.5.5">7.3.5.5</a>, <a href="#G.6">G.6</a> derived declarator types, <a href="#6.2.5">6.2.5</a>
24307 derived types, <a href="#6.2.5">6.2.5</a> end-of-file indicator, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.1">7.19.7.1</a>,
24308 designated initializer, <a href="#6.7.8">6.7.8</a> <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>,
24309 destringizing, <a href="#6.10.9">6.10.9</a> <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.10.1">7.19.10.1</a>, <a href="#7.19.10.2">7.19.10.2</a>, <a href="#7.24.3.1">7.24.3.1</a>,
24310 device input/output, <a href="#5.1.2.3">5.1.2.3</a> <a href="#7.24.3.10">7.24.3.10</a>
24311 diagnostic message, <a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a> end-of-file macro, see EOF macro
24312 diagnostics, <a href="#5.1.1.3">5.1.1.3</a> end-of-line indicator, <a href="#5.2.1">5.2.1</a>
24313 diagnostics header, <a href="#7.2">7.2</a> endif preprocessing directive, <a href="#6.10.1">6.10.1</a>
24314 difftime function, <a href="#7.23.2.2">7.23.2.2</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>
24315 digit, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> enumerated type, <a href="#6.2.5">6.2.5</a>
24316 digraphs, <a href="#6.4.6">6.4.6</a> enumeration, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.2">6.7.2.2</a>
24317 direct input/output functions, <a href="#7.19.8">7.19.8</a> enumeration constant, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
24318 display device, <a href="#5.2.2">5.2.2</a> enumeration content, <a href="#6.7.2.3">6.7.2.3</a>
24319 div function, <a href="#7.20.6.2">7.20.6.2</a> enumeration members, <a href="#6.7.2.2">6.7.2.2</a>
24320 div_t type, <a href="#7.20">7.20</a> enumeration specifiers, <a href="#6.7.2.2">6.7.2.2</a>
24321 division assignment operator (/=), <a href="#6.5.16.2">6.5.16.2</a> enumeration tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
24322 division operator (/), <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> enumerator, <a href="#6.7.2.2">6.7.2.2</a>
24323 do statement, <a href="#6.8.5.2">6.8.5.2</a> environment, <a href="#5">5</a>
24324 documentation of implementation, <a href="#4">4</a> environment functions, <a href="#7.20.4">7.20.4</a>
24325 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>, environment list, <a href="#7.20.4.5">7.20.4.5</a>
24326 <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>, environmental considerations, <a href="#5.2">5.2</a>
24327 <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>, environmental limits, <a href="#5.2.4">5.2.4</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.19.2">7.19.2</a>,
24328 <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>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.4.4">7.19.4.4</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.20.2.1">7.20.2.1</a>, <a href="#7.20.4.2">7.20.4.2</a>,
24329 <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> <a href="#7.24.2.1">7.24.2.1</a>
24330 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> EOF macro, <a href="#7.4">7.4</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.1">7.19.5.1</a>, <a href="#7.19.5.2">7.19.5.2</a>,
24331 double _Complex type, <a href="#6.2.5">6.2.5</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.19.6.7">7.19.6.7</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.11">7.19.6.11</a>,
24332 double _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, <a href="#7.19.6.14">7.19.6.14</a>, <a href="#7.19.7.1">7.19.7.1</a>, <a href="#7.19.7.3">7.19.7.3</a>, <a href="#7.19.7.4">7.19.7.4</a>,
24333 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a> <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.9">7.19.7.9</a>, <a href="#7.19.7.10">7.19.7.10</a>,
24334 double _Imaginary type, <a href="#G.2">G.2</a> <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.2.4">7.24.2.4</a>,
24335 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="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.10">7.24.2.10</a>, <a href="#7.24.2.12">7.24.2.12</a>,
24336 <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.2">F.2</a> <a href="#7.24.3.4">7.24.3.4</a>, <a href="#7.24.6.1.1">7.24.6.1.1</a>, <a href="#7.24.6.1.2">7.24.6.1.2</a>
24337 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>, equal-sign punctuator (=), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.8">6.7.8</a>
24338 <a href="#6.3.1.8">6.3.1.8</a> equal-to operator, see equality operator
24339 double-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a> equality expressions, <a href="#6.5.9">6.5.9</a>
24340 double-quote escape sequence (\"), <a href="#6.4.4.4">6.4.4.4</a>, equality operator (==), <a href="#6.5.9">6.5.9</a>
24341 <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</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>,
24342 double_t type, <a href="#7.12">7.12</a>, <a href="#J.5.6">J.5.6</a> <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>, see
24344 EDOM macro, <a href="#7.5">7.5</a>, <a href="#7.12.1">7.12.1</a>, see also domain error erf functions, <a href="#7.12.8.1">7.12.8.1</a>, <a href="#F.9.5.1">F.9.5.1</a>
24345 effective type, <a href="#6.5">6.5</a> erf type-generic macro, <a href="#7.22">7.22</a>
24346 EILSEQ macro, <a href="#7.5">7.5</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a>, erfc functions, <a href="#7.12.8.2">7.12.8.2</a>, <a href="#F.9.5.2">F.9.5.2</a>
24347 <a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a>, erfc type-generic macro, <a href="#7.22">7.22</a>
24348 see also encoding error 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>,
24349 element type, <a href="#6.2.5">6.2.5</a> <a href="#7.12.1">7.12.1</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.10.4">7.19.10.4</a>,
24350 elif preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.24.3.1">7.24.3.1</a>,
24351 ellipsis punctuator (...), <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.10.3">6.10.3</a> <a href="#7.24.3.3">7.24.3.3</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>, <a href="#7.24.6.3.2">7.24.6.3.2</a>,
24352 else preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a>, <a href="#J.5.17">J.5.17</a>
24353 else statement, <a href="#6.8.4.1">6.8.4.1</a> errno.h header, <a href="#7.5">7.5</a>, <a href="#7.26.3">7.26.3</a>
24354 empty statement, <a href="#6.8.3">6.8.3</a> error
24355 encoding error, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a>, domain, see domain error
24356 <a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a> encoding, see encoding error
24357 end-of-file, <a href="#7.24.1">7.24.1</a> range, see range error
24359 error conditions, <a href="#7.12.1">7.12.1</a> extended characters, <a href="#5.2.1">5.2.1</a>
24360 error functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.9.5">F.9.5</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>,
24361 error indicator, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.1">7.19.7.1</a>, <a href="#7.18">7.18</a>
24362 <a href="#7.19.7.3">7.19.7.3</a>, <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.8">7.19.7.8</a>, extended multibyte/wide character conversion
24363 <a href="#7.19.7.9">7.19.7.9</a>, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.10.1">7.19.10.1</a>, <a href="#7.19.10.3">7.19.10.3</a>, utilities, <a href="#7.24.6">7.24.6</a>
24364 <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a> extensible wide character case mapping functions,
24365 error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> <a href="#7.25.3.2">7.25.3.2</a>
24366 error-handling functions, <a href="#7.19.10">7.19.10</a>, <a href="#7.21.6.2">7.21.6.2</a> extensible wide character classification functions,
24367 escape character (\), <a href="#6.4.4.4">6.4.4.4</a> <a href="#7.25.2.2">7.25.2.2</a>
24368 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> extern storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.7.1">6.7.1</a>
24369 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> external definition, <a href="#6.9">6.9</a>
24370 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.7.5">F.7.5</a> external identifiers, underscore, <a href="#7.1.3">7.1.3</a>
24371 evaluation order, <a href="#6.5">6.5</a> external linkage, <a href="#6.2.2">6.2.2</a>
24372 exceptional condition, <a href="#6.5">6.5</a>, <a href="#7.12.1">7.12.1</a> external name, <a href="#6.4.2.1">6.4.2.1</a>
24373 excess precision, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, external object definitions, <a href="#6.9.2">6.9.2</a>
24374 <a href="#6.8.6.4">6.8.6.4</a>
24375 excess range, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> fabs functions, <a href="#7.12.7.2">7.12.7.2</a>, <a href="#F.9.4.2">F.9.4.2</a>
24376 exclusive OR operators fabs type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24377 bitwise (^), <a href="#6.5.11">6.5.11</a> false macro, <a href="#7.16">7.16</a>
24378 bitwise assignment (^=), <a href="#6.5.16.2">6.5.16.2</a> fclose function, <a href="#7.19.5.1">7.19.5.1</a>
24379 executable program, <a href="#5.1.1.1">5.1.1.1</a> fdim functions, <a href="#7.12.12.1">7.12.12.1</a>, <a href="#F.9.9.1">F.9.9.1</a>
24380 execution character set, <a href="#5.2.1">5.2.1</a> fdim type-generic macro, <a href="#7.22">7.22</a>
24381 execution environment, <a href="#5">5</a>, <a href="#5.1.2">5.1.2</a>, see also FE_ALL_EXCEPT macro, <a href="#7.6">7.6</a>
24382 environmental limits FE_DFL_ENV macro, <a href="#7.6">7.6</a>
24383 execution sequence, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.8">6.8</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>
24384 exit function, <a href="#5.1.2.2.3">5.1.2.2.3</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.20">7.20</a>, <a href="#7.20.4.3">7.20.4.3</a>, FE_DOWNWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24385 <a href="#7.20.4.4">7.20.4.4</a> FE_INEXACT macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24386 EXIT_FAILURE macro, <a href="#7.20">7.20</a>, <a href="#7.20.4.3">7.20.4.3</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>
24387 EXIT_SUCCESS macro, <a href="#7.20">7.20</a>, <a href="#7.20.4.3">7.20.4.3</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>
24388 exp functions, <a href="#7.12.6.1">7.12.6.1</a>, <a href="#F.9.3.1">F.9.3.1</a> FE_TONEAREST macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24389 exp type-generic macro, <a href="#7.22">7.22</a> FE_TOWARDZERO macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24390 exp2 functions, <a href="#7.12.6.2">7.12.6.2</a>, <a href="#F.9.3.2">F.9.3.2</a> FE_UNDERFLOW macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24391 exp2 type-generic macro, <a href="#7.22">7.22</a> FE_UPWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24392 explicit conversion, <a href="#6.3">6.3</a> feclearexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.1">7.6.2.1</a>, <a href="#F.3">F.3</a>
24393 expm1 functions, <a href="#7.12.6.3">7.12.6.3</a>, <a href="#F.9.3.3">F.9.3.3</a> fegetenv function, <a href="#7.6.4.1">7.6.4.1</a>, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a>
24394 expm1 type-generic macro, <a href="#7.22">7.22</a> fegetexceptflag function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.2">7.6.2.2</a>, <a href="#F.3">F.3</a>
24395 exponent part, <a href="#6.4.4.2">6.4.4.2</a> fegetround function, <a href="#7.6">7.6</a>, <a href="#7.6.3.1">7.6.3.1</a>, <a href="#F.3">F.3</a>
24396 exponential functions feholdexcept function, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.6.4.3">7.6.4.3</a>,
24397 complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a> <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a>
24398 real, <a href="#7.12.6">7.12.6</a>, <a href="#F.9.3">F.9.3</a> fenv.h header, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F">F</a>, <a href="#H">H</a>
24399 expression, <a href="#6.5">6.5</a> FENV_ACCESS pragma, <a href="#6.10.6">6.10.6</a>, <a href="#7.6.1">7.6.1</a>, <a href="#F.7">F.7</a>, <a href="#F.8">F.8</a>,
24400 assignment, <a href="#6.5.16">6.5.16</a> <a href="#F.9">F.9</a>
24401 cast, <a href="#6.5.4">6.5.4</a> fenv_t type, <a href="#7.6">7.6</a>
24402 constant, <a href="#6.6">6.6</a> feof function, <a href="#7.19.10.2">7.19.10.2</a>
24403 full, <a href="#6.8">6.8</a> feraiseexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.3">7.6.2.3</a>, <a href="#F.3">F.3</a>
24404 order of evaluation, <a href="#6.5">6.5</a> ferror function, <a href="#7.19.10.3">7.19.10.3</a>
24405 parenthesized, <a href="#6.5.1">6.5.1</a> fesetenv function, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#F.3">F.3</a>
24406 primary, <a href="#6.5.1">6.5.1</a> fesetexceptflag function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.4">7.6.2.4</a>, <a href="#F.3">F.3</a>
24407 unary, <a href="#6.5.3">6.5.3</a> fesetround function, <a href="#7.6">7.6</a>, <a href="#7.6.3.2">7.6.3.2</a>, <a href="#F.3">F.3</a>
24408 expression statement, <a href="#6.8.3">6.8.3</a> fetestexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.5">7.6.2.5</a>, <a href="#F.3">F.3</a>
24409 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> 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>
24411 fexcept_t type, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> floating-point status flag, <a href="#7.6">7.6</a>, <a href="#F.7.6">F.7.6</a>
24412 fflush function, <a href="#7.19.5.2">7.19.5.2</a>, <a href="#7.19.5.3">7.19.5.3</a> floor functions, <a href="#7.12.9.2">7.12.9.2</a>, <a href="#F.9.6.2">F.9.6.2</a>
24413 fgetc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.7.1">7.19.7.1</a>, floor type-generic macro, <a href="#7.22">7.22</a>
24414 <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.8.1">7.19.8.1</a> FLT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24415 fgetpos function, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.3">7.19.9.3</a> FLT_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24416 fgets function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.2">7.19.7.2</a> FLT_EVAL_METHOD macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.8.6.4">6.8.6.4</a>,
24417 fgetwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.12">7.12</a>
24418 <a href="#7.24.3.6">7.24.3.6</a> FLT_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24419 fgetws function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.2">7.24.3.2</a> FLT_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24420 field width, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a> FLT_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24421 file, <a href="#7.19.3">7.19.3</a> FLT_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24422 access functions, <a href="#7.19.5">7.19.5</a> FLT_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24423 name, <a href="#7.19.3">7.19.3</a> FLT_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24424 operations, <a href="#7.19.4">7.19.4</a> FLT_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24425 position indicator, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, FLT_RADIX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24426 <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.1">7.19.7.1</a>, <a href="#7.19.7.3">7.19.7.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>
24427 <a href="#7.19.8.1">7.19.8.1</a>, <a href="#7.19.8.2">7.19.8.2</a>, <a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.2">7.19.9.2</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>
24428 <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.9.4">7.19.9.4</a>, <a href="#7.19.9.5">7.19.9.5</a>, <a href="#7.24.3.1">7.24.3.1</a>, fma functions, <a href="#7.12">7.12</a>, <a href="#7.12.13.1">7.12.13.1</a>, <a href="#F.9.10.1">F.9.10.1</a>
24429 <a href="#7.24.3.3">7.24.3.3</a>, <a href="#7.24.3.10">7.24.3.10</a> fma type-generic macro, <a href="#7.22">7.22</a>
24430 positioning functions, <a href="#7.19.9">7.19.9</a> fmax functions, <a href="#7.12.12.2">7.12.12.2</a>, <a href="#F.9.9.2">F.9.9.2</a>
24431 file scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.9">6.9</a> fmax type-generic macro, <a href="#7.22">7.22</a>
24432 FILE type, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> fmin functions, <a href="#7.12.12.3">7.12.12.3</a>, <a href="#F.9.9.3">F.9.9.3</a>
24433 FILENAME_MAX macro, <a href="#7.19.1">7.19.1</a> fmin type-generic macro, <a href="#7.22">7.22</a>
24434 flags, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a> fmod functions, <a href="#7.12.10.1">7.12.10.1</a>, <a href="#F.9.7.1">F.9.7.1</a>
24435 floating-point status, see floating-point status fmod type-generic macro, <a href="#7.22">7.22</a>
24436 flag fopen function, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.5.4">7.19.5.4</a>
24437 flexible array member, <a href="#6.7.2.1">6.7.2.1</a> FOPEN_MAX macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.4.3">7.19.4.3</a>
24438 float _Complex type, <a href="#6.2.5">6.2.5</a> for statement, <a href="#6.8.5">6.8.5</a>, <a href="#6.8.5.3">6.8.5.3</a>
24439 float _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, form-feed character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
24440 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a> form-feed escape sequence (\f), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>,
24441 float _Imaginary type, <a href="#G.2">G.2</a> <a href="#7.4.1.10">7.4.1.10</a>
24442 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> formal argument (deprecated), <a href="#3.15">3.15</a>
24443 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>, formal parameter, <a href="#3.15">3.15</a>
24444 <a href="#6.3.1.8">6.3.1.8</a> formatted input/output functions, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.19.6">7.19.6</a>
24445 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="#7.20.1.3">7.20.1.3</a>, wide character, <a href="#7.24.2">7.24.2</a>
24446 <a href="#7.24.4.1.1">7.24.4.1.1</a> fortran keyword, <a href="#J.5.9">J.5.9</a>
24447 float_t type, <a href="#7.12">7.12</a>, <a href="#J.5.6">J.5.6</a> forward reference, <a href="#3.11">3.11</a>
24448 floating constant, <a href="#6.4.4.2">6.4.4.2</a> FP_CONTRACT pragma, <a href="#6.5">6.5</a>, <a href="#6.10.6">6.10.6</a>, <a href="#7.12.2">7.12.2</a>, see
24449 floating suffix, f or <a href="#F">F</a>, <a href="#6.4.4.2">6.4.4.2</a> also contracted expression
24450 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>, FP_FAST_FMA macro, <a href="#7.12">7.12</a>
24451 <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> FP_FAST_FMAF macro, <a href="#7.12">7.12</a>
24452 floating types, <a href="#6.2.5">6.2.5</a>, <a href="#6.11.1">6.11.1</a> FP_FAST_FMAL macro, <a href="#7.12">7.12</a>
24453 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>, FP_ILOGB0 macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
24454 <a href="#7.20.1.3">7.20.1.3</a>, <a href="#F.5">F.5</a>, see also contracted expression FP_ILOGBNAN macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
24455 floating-point arithmetic functions, <a href="#7.12">7.12</a>, <a href="#F.9">F.9</a> FP_INFINITE macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24456 floating-point classification functions, <a href="#7.12.3">7.12.3</a> FP_NAN macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24457 floating-point control mode, <a href="#7.6">7.6</a>, <a href="#F.7.6">F.7.6</a> FP_NORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24458 floating-point environment, <a href="#7.6">7.6</a>, <a href="#F.7">F.7</a>, <a href="#F.7.6">F.7.6</a> FP_SUBNORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24459 floating-point exception, <a href="#7.6">7.6</a>, <a href="#7.6.2">7.6.2</a>, <a href="#F.9">F.9</a> FP_ZERO macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24460 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> fpclassify macro, <a href="#7.12.3.1">7.12.3.1</a>, <a href="#F.3">F.3</a>
24461 floating-point rounding mode, <a href="#5.2.4.2.2">5.2.4.2.2</a> fpos_t type, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>
24463 fprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.1">7.19.6.1</a>, language, <a href="#6.11">6.11</a>
24464 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.19.6.3">7.19.6.3</a>, <a href="#7.19.6.5">7.19.6.5</a>, <a href="#7.19.6.6">7.19.6.6</a>, library, <a href="#7.26">7.26</a>
24465 <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.3">F.3</a> fwide function, <a href="#7.19.2">7.19.2</a>, <a href="#7.24.3.5">7.24.3.5</a>
24466 fputc function, <a href="#5.2.2">5.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.7.3">7.19.7.3</a>, fwprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.2">7.19.6.2</a>,
24467 <a href="#7.19.7.8">7.19.7.8</a>, <a href="#7.19.8.2">7.19.8.2</a> <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.2.3">7.24.2.3</a>, <a href="#7.24.2.5">7.24.2.5</a>,
24468 fputs function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.4">7.19.7.4</a> <a href="#7.24.2.11">7.24.2.11</a>
24469 fputwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.3">7.24.3.3</a>, fwrite function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.8.2">7.19.8.2</a>
24470 <a href="#7.24.3.8">7.24.3.8</a> fwscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.2">7.24.2.2</a>,
24471 fputws function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.4">7.24.3.4</a> <a href="#7.24.2.4">7.24.2.4</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.12">7.24.2.12</a>, <a href="#7.24.3.10">7.24.3.10</a>
24472 fread function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.8.1">7.19.8.1</a>
24473 free function, <a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.4">7.20.3.4</a> gamma functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.9.5">F.9.5</a>
24474 freestanding execution environment, <a href="#4">4</a>, <a href="#5.1.2">5.1.2</a>, general utilities, <a href="#7.20">7.20</a>
24475 <a href="#5.1.2.1">5.1.2.1</a> wide string, <a href="#7.24.4">7.24.4</a>
24476 freopen function, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.5.4">7.19.5.4</a> general wide string utilities, <a href="#7.24.4">7.24.4</a>
24477 frexp functions, <a href="#7.12.6.4">7.12.6.4</a>, <a href="#F.9.3.4">F.9.3.4</a> generic parameters, <a href="#7.22">7.22</a>
24478 frexp type-generic macro, <a href="#7.22">7.22</a> getc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>
24479 fscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, getchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.6">7.19.7.6</a>
24480 <a href="#7.19.6.4">7.19.6.4</a>, <a href="#7.19.6.7">7.19.6.7</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#F.3">F.3</a> getenv function, <a href="#7.20.4.5">7.20.4.5</a>
24481 fseek function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, gets function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.7">7.19.7.7</a>, <a href="#7.26.9">7.26.9</a>
24482 <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.9.4">7.19.9.4</a>, <a href="#7.19.9.5">7.19.9.5</a>, <a href="#7.24.3.10">7.24.3.10</a> getwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.6">7.24.3.6</a>, <a href="#7.24.3.7">7.24.3.7</a>
24483 fsetpos function, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, getwchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.7">7.24.3.7</a>
24484 <a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.24.3.10">7.24.3.10</a> gmtime function, <a href="#7.23.3.3">7.23.3.3</a>
24485 ftell function, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.9.4">7.19.9.4</a> goto statement, <a href="#6.2.1">6.2.1</a>, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.6.1">6.8.6.1</a>
24486 full declarator, <a href="#6.7.5">6.7.5</a> graphic characters, <a href="#5.2.1">5.2.1</a>
24487 full expression, <a href="#6.8">6.8</a> greater-than operator (>), <a href="#6.5.8">6.5.8</a>
24488 fully buffered stream, <a href="#7.19.3">7.19.3</a> greater-than-or-equal-to operator (>=), <a href="#6.5.8">6.5.8</a>
24490 argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a> header, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.2">7.1.2</a>, see also standard headers
24491 body, <a href="#6.9.1">6.9.1</a> header names, <a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>, <a href="#6.10.2">6.10.2</a>
24492 call, <a href="#6.5.2.2">6.5.2.2</a> hexadecimal constant, <a href="#6.4.4.1">6.4.4.1</a>
24493 library, <a href="#7.1.4">7.1.4</a> hexadecimal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
24494 declarator, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.11.6">6.11.6</a> hexadecimal prefix, <a href="#6.4.4.1">6.4.4.1</a>
24495 definition, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.9.1">6.9.1</a>, <a href="#6.11.7">6.11.7</a> hexadecimal-character escape sequence
24496 designator, <a href="#6.3.2.1">6.3.2.1</a> (\x hexadecimal digits), <a href="#6.4.4.4">6.4.4.4</a>
24497 image, <a href="#5.2.3">5.2.3</a> high-order bit, <a href="#3.6">3.6</a>
24498 library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.4">7.1.4</a> horizontal-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
24499 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> horizontal-tab escape sequence (\r), <a href="#7.25.2.1.3">7.25.2.1.3</a>
24500 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> horizontal-tab escape sequence (\t), <a href="#5.2.2">5.2.2</a>,
24501 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>, <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>
24502 <a href="#6.7.5.3">6.7.5.3</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> 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>
24503 prototype scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.7.5.2">6.7.5.2</a> HUGE_VAL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24504 recursive call, <a href="#6.5.2.2">6.5.2.2</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.9">F.9</a>
24505 return, <a href="#6.8.6.4">6.8.6.4</a> HUGE_VALF macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24506 scope, <a href="#6.2.1">6.2.1</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.9">F.9</a>
24507 type, <a href="#6.2.5">6.2.5</a> HUGE_VALL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24508 type conversion, <a href="#6.3.2.1">6.3.2.1</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.9">F.9</a>
24509 function specifiers, <a href="#6.7.4">6.7.4</a> hyperbolic functions
24510 function type, <a href="#6.2.5">6.2.5</a> complex, <a href="#7.3.6">7.3.6</a>, <a href="#G.6.2">G.6.2</a>
24511 function-call operator (( )), <a href="#6.5.2.2">6.5.2.2</a> real, <a href="#7.12.5">7.12.5</a>, <a href="#F.9.2">F.9.2</a>
24512 function-like macro, <a href="#6.10.3">6.10.3</a> hypot functions, <a href="#7.12.7.3">7.12.7.3</a>, <a href="#F.9.4.3">F.9.4.3</a>
24513 future directions hypot type-generic macro, <a href="#7.22">7.22</a>
24515 <a href="#I">I</a> macro, <a href="#7.3.1">7.3.1</a>, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a> initial position, <a href="#5.2.2">5.2.2</a>
24516 identifier, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.5.1">6.5.1</a> initial shift state, <a href="#5.2.1.2">5.2.1.2</a>
24517 linkage, see linkage 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="#6.7.8">6.7.8</a>,
24518 maximum length, <a href="#6.4.2.1">6.4.2.1</a> <a href="#F.7.5">F.7.5</a>
24519 name spaces, <a href="#6.2.3">6.2.3</a> in blocks, <a href="#6.8">6.8</a>
24520 reserved, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a> initializer, <a href="#6.7.8">6.7.8</a>
24521 scope, <a href="#6.2.1">6.2.1</a> permitted form, <a href="#6.6">6.6</a>
24522 type, <a href="#6.2.5">6.2.5</a> string literal, <a href="#6.3.2.1">6.3.2.1</a>
24523 identifier list, <a href="#6.7.5">6.7.5</a> inline, <a href="#6.7.4">6.7.4</a>
24524 identifier nondigit, <a href="#6.4.2.1">6.4.2.1</a> inner scope, <a href="#6.2.1">6.2.1</a>
24525 IEC 559, <a href="#F.1">F.1</a> input failure, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.10">7.24.2.10</a>
24526 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">6.10.8</a>, <a href="#7.3.3">7.3.3</a>, <a href="#7.6">7.6</a>, input/output functions
24527 <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>, <a href="#H.1">H.1</a> character, <a href="#7.19.7">7.19.7</a>
24528 IEEE 754, <a href="#F.1">F.1</a> direct, <a href="#7.19.8">7.19.8</a>
24529 IEEE 854, <a href="#F.1">F.1</a> formatted, <a href="#7.19.6">7.19.6</a>
24530 IEEE floating-point arithmetic standard, see wide character, <a href="#7.24.2">7.24.2</a>
24531 IEC 60559, ANSI/IEEE 754, wide character, <a href="#7.24.3">7.24.3</a>
24532 ANSI/IEEE 854 formatted, <a href="#7.24.2">7.24.2</a>
24533 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>, input/output header, <a href="#7.19">7.19</a>
24534 <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a> input/output, device, <a href="#5.1.2.3">5.1.2.3</a>
24535 if statement, <a href="#6.8.4.1">6.8.4.1</a> int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.7.2">6.7.2</a>
24536 ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a> int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
24537 ifndef preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#6.3.1.8">6.3.1.8</a>
24538 ilogb functions, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#F.9.3.5">F.9.3.5</a> INT_FASTN_MAX macros, <a href="#7.18.2.3">7.18.2.3</a>
24539 ilogb type-generic macro, <a href="#7.22">7.22</a> INT_FASTN_MIN macros, <a href="#7.18.2.3">7.18.2.3</a>
24540 imaginary macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a> int_fastN_t types, <a href="#7.18.1.3">7.18.1.3</a>
24541 imaginary numbers, <a href="#G">G</a> INT_LEASTN_MAX macros, <a href="#7.18.2.2">7.18.2.2</a>
24542 imaginary type domain, <a href="#G.2">G.2</a> INT_LEASTN_MIN macros, <a href="#7.18.2.2">7.18.2.2</a>
24543 imaginary types, <a href="#G">G</a> int_leastN_t types, <a href="#7.18.1.2">7.18.1.2</a>
24544 imaxabs function, <a href="#7.8.2.1">7.8.2.1</a> INT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
24545 imaxdiv function, <a href="#7.8">7.8</a>, <a href="#7.8.2.2">7.8.2.2</a> INT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a>
24546 imaxdiv_t type, <a href="#7.8">7.8</a> integer arithmetic functions, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.8.2.2">7.8.2.2</a>,
24547 implementation, <a href="#3.12">3.12</a> <a href="#7.20.6">7.20.6</a>
24548 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>, integer character constant, <a href="#6.4.4.4">6.4.4.4</a>
24549 <a href="#6.7.5">6.7.5</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#E">E</a>, see also environmental integer constant, <a href="#6.4.4.1">6.4.4.1</a>
24550 limits integer constant expression, <a href="#6.6">6.6</a>
24551 implementation-defined behavior, <a href="#3.4.1">3.4.1</a>, <a href="#4">4</a>, <a href="#J.3">J.3</a> integer conversion rank, <a href="#6.3.1.1">6.3.1.1</a>
24552 implementation-defined value, <a href="#3.17.1">3.17.1</a> integer promotions, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.3.1.1">6.3.1.1</a>,
24553 implicit conversion, <a href="#6.3">6.3</a> <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.3.3">6.5.3.3</a>, <a href="#6.5.7">6.5.7</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#7.18.2">7.18.2</a>, <a href="#7.18.3">7.18.3</a>,
24554 implicit initialization, <a href="#6.7.8">6.7.8</a> <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>
24555 include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.2">6.10.2</a> integer suffix, <a href="#6.4.4.1">6.4.4.1</a>
24556 inclusive OR operators 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>,
24557 bitwise (|), <a href="#6.5.12">6.5.12</a> <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a>
24558 bitwise assignment (|=), <a href="#6.5.16.2">6.5.16.2</a> integer types, <a href="#6.2.5">6.2.5</a>, <a href="#7.18">7.18</a>
24559 incomplete type, <a href="#6.2.5">6.2.5</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="#7.18">7.18</a>
24560 increment operators, see arithmetic operators, interactive device, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.3">7.19.5.3</a>
24561 increment and decrement internal linkage, <a href="#6.2.2">6.2.2</a>
24562 indeterminate value, <a href="#3.17.2">3.17.2</a> internal name, <a href="#6.4.2.1">6.4.2.1</a>
24563 indirection operator (*), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> interrupt, <a href="#5.2.3">5.2.3</a>
24564 inequality operator (!=), <a href="#6.5.9">6.5.9</a> INTMAX_C macro, <a href="#7.18.4.2">7.18.4.2</a>
24565 INFINITY macro, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</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="#7.18.2.5">7.18.2.5</a>
24567 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="#7.18.2.5">7.18.2.5</a> iswalpha function, <a href="#7.25.2.1.1">7.25.2.1.1</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>,
24568 intmax_t type, <a href="#7.18.1.5">7.18.1.5</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24569 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> iswblank function, <a href="#7.25.2.1.3">7.25.2.1.3</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24570 INTN_C macros, <a href="#7.18.4.1">7.18.4.1</a> iswcntrl function, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.4">7.25.2.1.4</a>,
24571 INTN_MAX macros, <a href="#7.18.2.1">7.18.2.1</a> <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24572 INTN_MIN macros, <a href="#7.18.2.1">7.18.2.1</a> iswctype function, <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>
24573 intN_t types, <a href="#7.18.1.1">7.18.1.1</a> iswdigit function, <a href="#7.25.2.1.1">7.25.2.1.1</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>,
24574 INTPTR_MAX macro, <a href="#7.18.2.4">7.18.2.4</a> <a href="#7.25.2.1.5">7.25.2.1.5</a>, <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24575 INTPTR_MIN macro, <a href="#7.18.2.4">7.18.2.4</a> iswgraph function, <a href="#7.25.2.1">7.25.2.1</a>, <a href="#7.25.2.1.6">7.25.2.1.6</a>,
24576 intptr_t type, <a href="#7.18.1.4">7.18.1.4</a> <a href="#7.25.2.1.10">7.25.2.1.10</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24577 inttypes.h header, <a href="#7.8">7.8</a>, <a href="#7.26.4">7.26.4</a> iswlower function, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.7">7.25.2.1.7</a>,
24578 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> <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.3.1.1">7.25.3.1.1</a>, <a href="#7.25.3.1.2">7.25.3.1.2</a>
24579 isalpha function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.2">7.4.1.2</a> iswprint function, <a href="#7.25.2.1.6">7.25.2.1.6</a>, <a href="#7.25.2.1.8">7.25.2.1.8</a>,
24580 isblank function, <a href="#7.4.1.3">7.4.1.3</a> <a href="#7.25.2.2.1">7.25.2.2.1</a>
24581 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>, iswpunct function, <a href="#7.25.2.1">7.25.2.1</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>,
24582 <a href="#7.4.1.11">7.4.1.11</a> <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, <a href="#7.25.2.1.10">7.25.2.1.10</a>,
24583 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>, <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24584 <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> iswspace function, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>,
24585 isfinite macro, <a href="#7.12.3.2">7.12.3.2</a>, <a href="#F.3">F.3</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.6">7.25.2.1.6</a>,
24586 isgraph function, <a href="#7.4.1.6">7.4.1.6</a> <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, <a href="#7.25.2.1.10">7.25.2.1.10</a>,
24587 isgreater macro, <a href="#7.12.14.1">7.12.14.1</a>, <a href="#F.3">F.3</a> <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24588 isgreaterequal macro, <a href="#7.12.14.2">7.12.14.2</a>, <a href="#F.3">F.3</a> iswupper function, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>,
24589 isinf macro, <a href="#7.12.3.3">7.12.3.3</a> <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.3.1.1">7.25.3.1.1</a>, <a href="#7.25.3.1.2">7.25.3.1.2</a>
24590 isless macro, <a href="#7.12.14.3">7.12.14.3</a>, <a href="#F.3">F.3</a> iswxdigit function, <a href="#7.25.2.1.12">7.25.2.1.12</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24591 islessequal macro, <a href="#7.12.14.4">7.12.14.4</a>, <a href="#F.3">F.3</a> isxdigit function, <a href="#7.4.1.12">7.4.1.12</a>, <a href="#7.11.1.1">7.11.1.1</a>
24592 islessgreater macro, <a href="#7.12.14.5">7.12.14.5</a>, <a href="#F.3">F.3</a> italic type convention, <a href="#3">3</a>, <a href="#6.1">6.1</a>
24593 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>, iteration statements, <a href="#6.8.5">6.8.5</a>
24594 <a href="#7.4.2.2">7.4.2.2</a>
24595 isnan macro, <a href="#7.12.3.4">7.12.3.4</a>, <a href="#F.3">F.3</a> jmp_buf type, <a href="#7.13">7.13</a>
24596 isnormal macro, <a href="#7.12.3.5">7.12.3.5</a> jump statements, <a href="#6.8.6">6.8.6</a>
24597 ISO 31-11, <a href="#2">2</a>, <a href="#3">3</a>
24598 ISO 4217, <a href="#2">2</a>, <a href="#7.11.2.1">7.11.2.1</a> keywords, <a href="#6.4.1">6.4.1</a>, <a href="#G.2">G.2</a>, <a href="#J.5.9">J.5.9</a>, <a href="#J.5.10">J.5.10</a>
24599 ISO 8601, <a href="#2">2</a>, <a href="#7.23.3.5">7.23.3.5</a> known constant size, <a href="#6.2.5">6.2.5</a>
24600 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">6.10.8</a>
24601 ISO/IEC 10976-1, <a href="#H.1">H.1</a> L_tmpnam macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.4.4">7.19.4.4</a>
24602 ISO/IEC 2382-1, <a href="#2">2</a>, <a href="#3">3</a> label name, <a href="#6.2.1">6.2.1</a>, <a href="#6.2.3">6.2.3</a>
24603 ISO/IEC 646, <a href="#2">2</a>, <a href="#5.2.1.1">5.2.1.1</a> labeled statement, <a href="#6.8.1">6.8.1</a>
24604 ISO/IEC 9945-2, <a href="#7.11">7.11</a> labs function, <a href="#7.20.6.1">7.20.6.1</a>
24605 ISO/IEC TR 10176, <a href="#D">D</a> language, <a href="#6">6</a>
24606 iso646.h header, <a href="#4">4</a>, <a href="#7.9">7.9</a> future directions, <a href="#6.11">6.11</a>
24607 isprint function, <a href="#5.2.2">5.2.2</a>, <a href="#7.4.1.8">7.4.1.8</a> syntax summary, <a href="#A">A</a>
24608 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>, Latin alphabet, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
24609 <a href="#7.4.1.11">7.4.1.11</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>
24610 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>, LC_COLLATE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.4.3">7.21.4.3</a>,
24611 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.4.4.2">7.24.4.4.2</a>
24612 <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.2">7.24.2.2</a> LC_CTYPE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.20">7.20</a>, <a href="#7.20.7">7.20.7</a>,
24613 isunordered macro, <a href="#7.12.14.6">7.12.14.6</a>, <a href="#F.3">F.3</a> <a href="#7.20.8">7.20.8</a>, <a href="#7.24.6">7.24.6</a>, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>,
24614 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>, <a href="#7.25.3.2.1">7.25.3.2.1</a>, <a href="#7.25.3.2.2">7.25.3.2.2</a>
24615 <a href="#7.4.2.2">7.4.2.2</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>
24616 iswalnum function, <a href="#7.25.2.1.1">7.25.2.1.1</a>, <a href="#7.25.2.1.9">7.25.2.1.9</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>
24617 <a href="#7.25.2.1.10">7.25.2.1.10</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a> LC_TIME macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.3.5">7.23.3.5</a>
24619 lconv structure type, <a href="#7.11">7.11</a> llabs function, <a href="#7.20.6.1">7.20.6.1</a>
24620 LDBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> lldiv function, <a href="#7.20.6.2">7.20.6.2</a>
24621 LDBL_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> lldiv_t type, <a href="#7.20">7.20</a>
24622 LDBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> LLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>,
24623 LDBL_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#7.24.4.1.2">7.24.4.1.2</a>
24624 LDBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> LLONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>,
24625 LDBL_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#7.24.4.1.2">7.24.4.1.2</a>
24626 LDBL_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.9.6.5">F.9.6.5</a>
24627 LDBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llrint type-generic macro, <a href="#7.22">7.22</a>
24628 LDBL_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.9.6.7">F.9.6.7</a>
24629 ldexp functions, <a href="#7.12.6.6">7.12.6.6</a>, <a href="#F.9.3.6">F.9.3.6</a> llround type-generic macro, <a href="#7.22">7.22</a>
24630 ldexp type-generic macro, <a href="#7.22">7.22</a> local time, <a href="#7.23.1">7.23.1</a>
24631 ldiv function, <a href="#7.20.6.2">7.20.6.2</a> locale, <a href="#3.4.2">3.4.2</a>
24632 ldiv_t type, <a href="#7.20">7.20</a> locale-specific behavior, <a href="#3.4.2">3.4.2</a>, <a href="#J.4">J.4</a>
24633 leading underscore in identifiers, <a href="#7.1.3">7.1.3</a> locale.h header, <a href="#7.11">7.11</a>, <a href="#7.26.5">7.26.5</a>
24634 left-shift assignment operator (<<=), <a href="#6.5.16.2">6.5.16.2</a> localeconv function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24635 left-shift operator (<<), <a href="#6.5.7">6.5.7</a> localization, <a href="#7.11">7.11</a>
24636 length localtime function, <a href="#7.23.3.4">7.23.3.4</a>
24637 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> log functions, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#F.9.3.7">F.9.3.7</a>
24638 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> log type-generic macro, <a href="#7.22">7.22</a>
24639 identifier, <a href="#6.4.2.1">6.4.2.1</a> log10 functions, <a href="#7.12.6.8">7.12.6.8</a>, <a href="#F.9.3.8">F.9.3.8</a>
24640 internal name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a> log10 type-generic macro, <a href="#7.22">7.22</a>
24641 length function, <a href="#7.20.7.1">7.20.7.1</a>, <a href="#7.21.6.3">7.21.6.3</a>, <a href="#7.24.4.6.1">7.24.4.6.1</a>, log1p functions, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#F.9.3.9">F.9.3.9</a>
24642 <a href="#7.24.6.3.1">7.24.6.3.1</a> log1p type-generic macro, <a href="#7.22">7.22</a>
24643 length modifier, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, log2 functions, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#F.9.3.10">F.9.3.10</a>
24644 <a href="#7.24.2.2">7.24.2.2</a> log2 type-generic macro, <a href="#7.22">7.22</a>
24645 less-than operator (<), <a href="#6.5.8">6.5.8</a> logarithmic functions
24646 less-than-or-equal-to operator (<=), <a href="#6.5.8">6.5.8</a> complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a>
24647 letter, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> real, <a href="#7.12.6">7.12.6</a>, <a href="#F.9.3">F.9.3</a>
24648 lexical elements, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a> logb functions, <a href="#7.12.6.11">7.12.6.11</a>, <a href="#F.3">F.3</a>, <a href="#F.9.3.11">F.9.3.11</a>
24649 lgamma functions, <a href="#7.12.8.3">7.12.8.3</a>, <a href="#F.9.5.3">F.9.5.3</a> logb type-generic macro, <a href="#7.22">7.22</a>
24650 lgamma type-generic macro, <a href="#7.22">7.22</a> logical operators
24651 library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7">7</a> AND (&&), <a href="#6.5.13">6.5.13</a>
24652 future directions, <a href="#7.26">7.26</a> negation (!), <a href="#6.5.3.3">6.5.3.3</a>
24653 summary, <a href="#B">B</a> OR (||), <a href="#6.5.14">6.5.14</a>
24654 terms, <a href="#7.1.1">7.1.1</a> logical source lines, <a href="#5.1.1.2">5.1.1.2</a>
24655 use of functions, <a href="#7.1.4">7.1.4</a> long double _Complex type, <a href="#6.2.5">6.2.5</a>
24656 lifetime, <a href="#6.2.4">6.2.4</a> long double _Complex type conversion,
24657 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>
24658 environmental, see environmental limits long double _Imaginary type, <a href="#G.2">G.2</a>
24659 implementation, see implementation limits long double suffix, l or <a href="#L">L</a>, <a href="#6.4.4.2">6.4.4.2</a>
24660 numerical, see numerical 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>,
24661 translation, see translation limits <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.2">F.2</a>
24662 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> 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>,
24663 line buffered stream, <a href="#7.19.3">7.19.3</a> <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
24664 line number, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8">6.10.8</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="#7.19.6.1">7.19.6.1</a>,
24665 line preprocessing directive, <a href="#6.10.4">6.10.4</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>
24666 lines, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#7.19.2">7.19.2</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>,
24667 preprocessing directive, <a href="#6.10">6.10</a> <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
24668 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="#6.7.5.2">6.7.5.2</a>, <a href="#6.9">6.9</a>, <a href="#6.9.2">6.9.2</a>, long integer suffix, l or <a href="#L">L</a>, <a href="#6.4.4.1">6.4.4.1</a>
24669 <a href="#6.11.2">6.11.2</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>,
24671 <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> mbsinit function, <a href="#7.24.6.2.1">7.24.6.2.1</a>
24672 long long int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, mbsrtowcs function, <a href="#7.24.6.4.1">7.24.6.4.1</a>
24673 <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> mbstate_t type, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24674 long long integer suffix, ll or LL, <a href="#6.4.4.1">6.4.4.1</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.6">7.24.6</a>,
24675 LONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.24.6.2.1">7.24.6.2.1</a>, <a href="#7.24.6.3">7.24.6.3</a>, <a href="#7.24.6.3.1">7.24.6.3.1</a>, <a href="#7.24.6.4">7.24.6.4</a>
24676 LONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a> mbstowcs function, <a href="#6.4.5">6.4.5</a>, <a href="#7.20.8.1">7.20.8.1</a>, <a href="#7.24.6.4">7.24.6.4</a>
24677 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="#7.20.4.3">7.20.4.3</a> mbtowc function, <a href="#7.20.7.1">7.20.7.1</a>, <a href="#7.20.7.2">7.20.7.2</a>, <a href="#7.20.8.1">7.20.8.1</a>,
24678 loop body, <a href="#6.8.5">6.8.5</a> <a href="#7.24.6.3">7.24.6.3</a>
24679 low-order bit, <a href="#3.6">3.6</a> member access operators (. and ->), <a href="#6.5.2.3">6.5.2.3</a>
24680 lowercase letter, <a href="#5.2.1">5.2.1</a> member alignment, <a href="#6.7.2.1">6.7.2.1</a>
24681 lrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.9.6.5">F.9.6.5</a> memchr function, <a href="#7.21.5.1">7.21.5.1</a>
24682 lrint type-generic macro, <a href="#7.22">7.22</a> memcmp function, <a href="#7.21.4">7.21.4</a>, <a href="#7.21.4.1">7.21.4.1</a>
24683 lround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.9.6.7">F.9.6.7</a> memcpy function, <a href="#7.21.2.1">7.21.2.1</a>
24684 lround type-generic macro, <a href="#7.22">7.22</a> memmove function, <a href="#7.21.2.2">7.21.2.2</a>
24685 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> memory management functions, <a href="#7.20.3">7.20.3</a>
24686 memset function, <a href="#7.21.6.1">7.21.6.1</a>
24687 macro argument substitution, <a href="#6.10.3.1">6.10.3.1</a> minimum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.9.9">F.9.9</a>
24688 macro definition minus operator, unary, <a href="#6.5.3.3">6.5.3.3</a>
24689 library function, <a href="#7.1.4">7.1.4</a> miscellaneous functions
24690 macro invocation, <a href="#6.10.3">6.10.3</a> string, <a href="#7.21.6">7.21.6</a>
24691 macro name, <a href="#6.10.3">6.10.3</a> wide string, <a href="#7.24.4.6">7.24.4.6</a>
24692 length, <a href="#5.2.4.1">5.2.4.1</a> mktime function, <a href="#7.23.2.3">7.23.2.3</a>
24693 predefined, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a> modf functions, <a href="#7.12.6.12">7.12.6.12</a>, <a href="#F.9.3.12">F.9.3.12</a>
24694 redefinition, <a href="#6.10.3">6.10.3</a> modifiable lvalue, <a href="#6.3.2.1">6.3.2.1</a>
24695 scope, <a href="#6.10.3.5">6.10.3.5</a> modulus functions, <a href="#7.12.6.12">7.12.6.12</a>
24696 macro parameter, <a href="#6.10.3">6.10.3</a> modulus, complex, <a href="#7.3.8.1">7.3.8.1</a>
24697 macro preprocessor, <a href="#6.10">6.10</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>
24698 macro replacement, <a href="#6.10.3">6.10.3</a> multibyte conversion functions
24699 magnitude, complex, <a href="#7.3.8.1">7.3.8.1</a> wide character, <a href="#7.20.7">7.20.7</a>
24700 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>, extended, <a href="#7.24.6">7.24.6</a>
24701 <a href="#7.19.3">7.19.3</a> restartable, <a href="#7.24.6.3">7.24.6.3</a>
24702 malloc function, <a href="#7.20.3">7.20.3</a>, <a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.3">7.20.3.3</a>, wide string, <a href="#7.20.8">7.20.8</a>
24703 <a href="#7.20.3.4">7.20.3.4</a> restartable, <a href="#7.24.6.4">7.24.6.4</a>
24704 manipulation functions multibyte string, <a href="#7.1.1">7.1.1</a>
24705 complex, <a href="#7.3.9">7.3.9</a> multibyte/wide character conversion functions,
24706 real, <a href="#7.12.11">7.12.11</a>, <a href="#F.9.8">F.9.8</a> <a href="#7.20.7">7.20.7</a>
24707 matching failure, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.10">7.24.2.10</a> extended, <a href="#7.24.6">7.24.6</a>
24708 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="#7.22">7.22</a>, <a href="#F">F</a>, <a href="#F.9">F.9</a>, restartable, <a href="#7.24.6.3">7.24.6.3</a>
24709 <a href="#J.5.17">J.5.17</a> multibyte/wide string conversion functions, <a href="#7.20.8">7.20.8</a>
24710 MATH_ERREXCEPT macro, <a href="#7.12">7.12</a>, <a href="#F.9">F.9</a> restartable, <a href="#7.24.6.4">7.24.6.4</a>
24711 math_errhandling macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.12">7.12</a>, <a href="#F.9">F.9</a> multidimensional array, <a href="#6.5.2.1">6.5.2.1</a>
24712 MATH_ERRNO macro, <a href="#7.12">7.12</a> multiplication assignment operator (*=), <a href="#6.5.16.2">6.5.16.2</a>
24713 maximum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.9.9">F.9.9</a> multiplication operator (*), <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>
24714 MB_CUR_MAX macro, <a href="#7.1.1">7.1.1</a>, <a href="#7.20">7.20</a>, <a href="#7.20.7.2">7.20.7.2</a>, multiplicative expressions, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
24715 <a href="#7.20.7.3">7.20.7.3</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>
24716 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="#7.20">7.20</a> n-char sequence, <a href="#7.20.1.3">7.20.1.3</a>
24717 mblen function, <a href="#7.20.7.1">7.20.7.1</a>, <a href="#7.24.6.3">7.24.6.3</a> n-wchar sequence, <a href="#7.24.4.1.1">7.24.4.1.1</a>
24718 mbrlen function, <a href="#7.24.6.3.1">7.24.6.3.1</a> name
24719 mbrtowc function, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</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>
24720 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.6.3.1">7.24.6.3.1</a>, <a href="#7.24.6.3.2">7.24.6.3.2</a>, file, <a href="#7.19.3">7.19.3</a>
24721 <a href="#7.24.6.4.1">7.24.6.4.1</a> internal, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
24723 label, <a href="#6.2.3">6.2.3</a> octal-character escape sequence (\octal digits),
24724 structure/union member, <a href="#6.2.3">6.2.3</a> <a href="#6.4.4.4">6.4.4.4</a>
24725 name spaces, <a href="#6.2.3">6.2.3</a> offsetof macro, <a href="#7.17">7.17</a>
24726 named label, <a href="#6.8.1">6.8.1</a> on-off switch, <a href="#6.10.6">6.10.6</a>
24727 NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a> ones' complement, <a href="#6.2.6.2">6.2.6.2</a>
24728 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.9.8.2">F.9.8.2</a> operand, <a href="#6.4.6">6.4.6</a>, <a href="#6.5">6.5</a>
24729 NAN macro, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</a> operating system, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#7.20.4.6">7.20.4.6</a>
24730 NDEBUG macro, <a href="#7.2">7.2</a> operations on files, <a href="#7.19.4">7.19.4</a>
24731 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>, operator, <a href="#6.4.6">6.4.6</a>
24732 <a href="#F.9.6.3">F.9.6.3</a> operators, <a href="#6.5">6.5</a>
24733 nearbyint type-generic macro, <a href="#7.22">7.22</a> assignment, <a href="#6.5.16">6.5.16</a>
24734 nearest integer functions, <a href="#7.12.9">7.12.9</a>, <a href="#F.9.6">F.9.6</a> associativity, <a href="#6.5">6.5</a>
24735 negation operator (!), <a href="#6.5.3.3">6.5.3.3</a> equality, <a href="#6.5.9">6.5.9</a>
24736 negative zero, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.12.11.1">7.12.11.1</a> multiplicative, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
24737 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> postfix, <a href="#6.5.2">6.5.2</a>
24738 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>, precedence, <a href="#6.5">6.5</a>
24739 <a href="#7.4.1.10">7.4.1.10</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>
24740 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>, relational, <a href="#6.5.8">6.5.8</a>
24741 <a href="#F.9.8.3">F.9.8.3</a> shift, <a href="#6.5.7">6.5.7</a>
24742 nextafter type-generic macro, <a href="#7.22">7.22</a> unary, <a href="#6.5.3">6.5.3</a>
24743 nexttoward functions, <a href="#7.12.11.4">7.12.11.4</a>, <a href="#F.3">F.3</a>, <a href="#F.9.8.4">F.9.8.4</a> unary arithmetic, <a href="#6.5.3.3">6.5.3.3</a>
24744 nexttoward type-generic macro, <a href="#7.22">7.22</a> or macro, <a href="#7.9">7.9</a>
24745 no linkage, <a href="#6.2.2">6.2.2</a> OR operators
24746 non-stop floating-point control mode, <a href="#7.6.4.2">7.6.4.2</a> bitwise exclusive (^), <a href="#6.5.11">6.5.11</a>
24747 nongraphic characters, <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> bitwise exclusive assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
24748 nonlocal jumps header, <a href="#7.13">7.13</a> bitwise inclusive (|), <a href="#6.5.12">6.5.12</a>
24749 norm, complex, <a href="#7.3.8.1">7.3.8.1</a> bitwise inclusive assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
24750 not macro, <a href="#7.9">7.9</a> logical (||), <a href="#6.5.14">6.5.14</a>
24751 not-equal-to operator, see inequality operator or_eq macro, <a href="#7.9">7.9</a>
24752 not_eq macro, <a href="#7.9">7.9</a> order of allocated storage, <a href="#7.20.3">7.20.3</a>
24753 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> order of evaluation, <a href="#6.5">6.5</a>
24754 padding of binary stream, <a href="#7.19.2">7.19.2</a> ordinary identifier name space, <a href="#6.2.3">6.2.3</a>
24755 NULL macro, <a href="#7.11">7.11</a>, <a href="#7.17">7.17</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.20">7.20</a>, <a href="#7.21.1">7.21.1</a>, orientation of stream, <a href="#7.19.2">7.19.2</a>, <a href="#7.24.3.5">7.24.3.5</a>
24756 <a href="#7.23.1">7.23.1</a>, <a href="#7.24.1">7.24.1</a> outer scope, <a href="#6.2.1">6.2.1</a>
24757 null pointer, <a href="#6.3.2.3">6.3.2.3</a>
24758 null pointer constant, <a href="#6.3.2.3">6.3.2.3</a> padding
24759 null preprocessing directive, <a href="#6.10.7">6.10.7</a> binary stream, <a href="#7.19.2">7.19.2</a>
24760 null statement, <a href="#6.8.3">6.8.3</a> bits, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.18.1.1">7.18.1.1</a>
24761 null wide character, <a href="#7.1.1">7.1.1</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>
24762 number classification macros, <a href="#7.12">7.12</a>, <a href="#7.12.3.1">7.12.3.1</a> parameter, <a href="#3.15">3.15</a>
24763 numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1">7.20.1</a> array, <a href="#6.9.1">6.9.1</a>
24764 wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1">7.24.4.1</a> ellipsis, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.10.3">6.10.3</a>
24765 numerical limits, <a href="#5.2.4.2">5.2.4.2</a> 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>
24766 macro, <a href="#6.10.3">6.10.3</a>
24767 object, <a href="#3.14">3.14</a> main function, <a href="#5.1.2.2.1">5.1.2.2.1</a>
24768 object representation, <a href="#6.2.6.1">6.2.6.1</a> program, <a href="#5.1.2.2.1">5.1.2.2.1</a>
24769 object type, <a href="#6.2.5">6.2.5</a> parameter type list, <a href="#6.7.5.3">6.7.5.3</a>
24770 object-like macro, <a href="#6.10.3">6.10.3</a> parentheses punctuator (( )), <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a>
24771 obsolescence, <a href="#6.11">6.11</a>, <a href="#7.26">7.26</a> parenthesized expression, <a href="#6.5.1">6.5.1</a>
24772 octal constant, <a href="#6.4.4.1">6.4.4.1</a> parse state, <a href="#7.19.2">7.19.2</a>
24773 octal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.4">6.4.4.4</a> permitted form of initializer, <a href="#6.6">6.6</a>
24775 perror function, <a href="#7.19.10.4">7.19.10.4</a> PRIcPTR macros, <a href="#7.8.1">7.8.1</a>
24776 phase angle, complex, <a href="#7.3.9.1">7.3.9.1</a> primary expression, <a href="#6.5.1">6.5.1</a>
24777 physical source lines, <a href="#5.1.1.2">5.1.1.2</a> printf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.3">7.19.6.3</a>, <a href="#7.19.6.10">7.19.6.10</a>
24778 placemarker, <a href="#6.10.3.3">6.10.3.3</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>
24779 plus operator, unary, <a href="#6.5.3.3">6.5.3.3</a> printing wide character, <a href="#7.25.2">7.25.2</a>
24780 pointer arithmetic, <a href="#6.5.6">6.5.6</a> program diagnostics, <a href="#7.2.1">7.2.1</a>
24781 pointer comparison, <a href="#6.5.8">6.5.8</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>
24782 pointer declarator, <a href="#6.7.5.1">6.7.5.1</a> program file, <a href="#5.1.1.1">5.1.1.1</a>
24783 pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> program image, <a href="#5.1.1.2">5.1.1.2</a>
24784 pointer to function, <a href="#6.5.2.2">6.5.2.2</a> program name (argv[0]), <a href="#5.1.2.2.1">5.1.2.2.1</a>
24785 pointer type, <a href="#6.2.5">6.2.5</a> program parameters, <a href="#5.1.2.2.1">5.1.2.2.1</a>
24786 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 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>
24787 pointer, null, <a href="#6.3.2.3">6.3.2.3</a> program structure, <a href="#5.1.1.1">5.1.1.1</a>
24788 portability, <a href="#4">4</a>, <a href="#J">J</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>,
24789 position indicator, file, see file position indicator <a href="#5.1.2.3">5.1.2.3</a>
24790 positive difference, <a href="#7.12.12.1">7.12.12.1</a> program, conforming, <a href="#4">4</a>
24791 positive difference functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.9.9">F.9.9</a> program, strictly conforming, <a href="#4">4</a>
24792 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> promotions
24793 postfix expressions, <a href="#6.5.2">6.5.2</a> default argument, <a href="#6.5.2.2">6.5.2.2</a>
24794 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> integer, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.3.1.1">6.3.1.1</a>
24795 pow functions, <a href="#7.12.7.4">7.12.7.4</a>, <a href="#F.9.4.4">F.9.4.4</a> prototype, see function prototype
24796 pow type-generic macro, <a href="#7.22">7.22</a> pseudo-random sequence functions, <a href="#7.20.2">7.20.2</a>
24797 power functions PTRDIFF_MAX macro, <a href="#7.18.3">7.18.3</a>
24798 complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a> PTRDIFF_MIN macro, <a href="#7.18.3">7.18.3</a>
24799 real, <a href="#7.12.7">7.12.7</a>, <a href="#F.9.4">F.9.4</a> ptrdiff_t type, <a href="#7.17">7.17</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24800 pp-number, <a href="#6.4.8">6.4.8</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>
24801 pragma operator, <a href="#6.10.9">6.10.9</a> punctuators, <a href="#6.4.6">6.4.6</a>
24802 pragma preprocessing directive, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a> putc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.8">7.19.7.8</a>, <a href="#7.19.7.9">7.19.7.9</a>
24803 precedence of operators, <a href="#6.5">6.5</a> putchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.9">7.19.7.9</a>
24804 precedence of syntax rules, <a href="#5.1.1.2">5.1.1.2</a> puts function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.10">7.19.7.10</a>
24805 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="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a> putwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.8">7.24.3.8</a>, <a href="#7.24.3.9">7.24.3.9</a>
24806 excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> putwchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.9">7.24.3.9</a>
24807 predefined macro names, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a>
24808 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> qsort function, <a href="#7.20.5">7.20.5</a>, <a href="#7.20.5.2">7.20.5.2</a>
24809 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> qualified types, <a href="#6.2.5">6.2.5</a>
24810 preprocessing concatenation, <a href="#6.10.3.3">6.10.3.3</a> qualified version of type, <a href="#6.2.5">6.2.5</a>
24811 preprocessing directives, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10">6.10</a> question-mark escape sequence (\?), <a href="#6.4.4.4">6.4.4.4</a>
24812 preprocessing file, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.10">6.10</a> quiet NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24813 preprocessing numbers, <a href="#6.4">6.4</a>, <a href="#6.4.8">6.4.8</a>
24814 preprocessing operators 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="#7.20.4.1">7.20.4.1</a>
24815 #, <a href="#6.10.3.2">6.10.3.2</a> rand function, <a href="#7.20">7.20</a>, <a href="#7.20.2.1">7.20.2.1</a>, <a href="#7.20.2.2">7.20.2.2</a>
24816 ##, <a href="#6.10.3.3">6.10.3.3</a> RAND_MAX macro, <a href="#7.20">7.20</a>, <a href="#7.20.2.1">7.20.2.1</a>
24817 _Pragma, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a> range
24818 defined, <a href="#6.10.1">6.10.1</a> excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a>
24819 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> range error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#7.12.5.5">7.12.5.5</a>,
24820 preprocessing translation unit, <a href="#5.1.1.1">5.1.1.1</a> <a href="#7.12.6.1">7.12.6.1</a>, <a href="#7.12.6.2">7.12.6.2</a>, <a href="#7.12.6.3">7.12.6.3</a>, <a href="#7.12.6.5">7.12.6.5</a>,
24821 preprocessor, <a href="#6.10">6.10</a> <a href="#7.12.6.6">7.12.6.6</a>, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#7.12.6.8">7.12.6.8</a>, <a href="#7.12.6.9">7.12.6.9</a>,
24822 PRIcFASTN macros, <a href="#7.8.1">7.8.1</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="#7.12.6.13">7.12.6.13</a>, <a href="#7.12.7.3">7.12.7.3</a>,
24823 PRIcLEASTN macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.7.4">7.12.7.4</a>, <a href="#7.12.8.2">7.12.8.2</a>, <a href="#7.12.8.3">7.12.8.3</a>, <a href="#7.12.8.4">7.12.8.4</a>,
24824 PRIcMAX macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#7.12.11.3">7.12.11.3</a>, <a href="#7.12.12.1">7.12.12.1</a>,
24825 PRIcN macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.13.1">7.12.13.1</a>
24827 rank, see integer conversion rank same scope, <a href="#6.2.1">6.2.1</a>
24828 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>, save calling environment function, <a href="#7.13.1">7.13.1</a>
24829 <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> scalar types, <a href="#6.2.5">6.2.5</a>
24830 real floating types, <a href="#6.2.5">6.2.5</a> scalbln function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.9.3.13">F.9.3.13</a>
24831 real type domain, <a href="#6.2.5">6.2.5</a> scalbln type-generic macro, <a href="#7.22">7.22</a>
24832 real types, <a href="#6.2.5">6.2.5</a> scalbn function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.9.3.13">F.9.3.13</a>
24833 real-floating, <a href="#7.12.3">7.12.3</a> scalbn type-generic macro, <a href="#7.22">7.22</a>
24834 realloc function, <a href="#7.20.3">7.20.3</a>, <a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.4">7.20.3.4</a> scanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.4">7.19.6.4</a>, <a href="#7.19.6.11">7.19.6.11</a>
24835 recommended practice, <a href="#3.16">3.16</a> scanlist, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>
24836 recursion, <a href="#6.5.2.2">6.5.2.2</a> scanset, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>
24837 recursive function call, <a href="#6.5.2.2">6.5.2.2</a> SCHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24838 redefinition of macro, <a href="#6.10.3">6.10.3</a> SCHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24839 reentrancy, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a> SCNcFASTN macros, <a href="#7.8.1">7.8.1</a>
24840 library functions, <a href="#7.1.4">7.1.4</a> SCNcLEASTN macros, <a href="#7.8.1">7.8.1</a>
24841 referenced type, <a href="#6.2.5">6.2.5</a> SCNcMAX macros, <a href="#7.8.1">7.8.1</a>
24842 register storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a> SCNcN macros, <a href="#7.8.1">7.8.1</a>
24843 relational expressions, <a href="#6.5.8">6.5.8</a> SCNcPTR macros, <a href="#7.8.1">7.8.1</a>
24844 reliability of data, interrupted, <a href="#5.1.2.3">5.1.2.3</a> scope of identifier, <a href="#6.2.1">6.2.1</a>, <a href="#6.9.2">6.9.2</a>
24845 remainder assignment operator (%=), <a href="#6.5.16.2">6.5.16.2</a> search functions
24846 remainder functions, <a href="#7.12.10">7.12.10</a>, <a href="#F.9.7">F.9.7</a> string, <a href="#7.21.5">7.21.5</a>
24847 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>, utility, <a href="#7.20.5">7.20.5</a>
24848 <a href="#F.9.7.2">F.9.7.2</a> wide string, <a href="#7.24.4.5">7.24.4.5</a>
24849 remainder operator (%), <a href="#6.5.5">6.5.5</a> SEEK_CUR macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.9.2">7.19.9.2</a>
24850 remainder type-generic macro, <a href="#7.22">7.22</a> SEEK_END macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.9.2">7.19.9.2</a>
24851 remove function, <a href="#7.19.4.1">7.19.4.1</a>, <a href="#7.19.4.4">7.19.4.4</a> SEEK_SET macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.9.2">7.19.9.2</a>
24852 remquo functions, <a href="#7.12.10.3">7.12.10.3</a>, <a href="#F.3">F.3</a>, <a href="#F.9.7.3">F.9.7.3</a> selection statements, <a href="#6.8.4">6.8.4</a>
24853 remquo type-generic macro, <a href="#7.22">7.22</a> self-referential structure, <a href="#6.7.2.3">6.7.2.3</a>
24854 rename function, <a href="#7.19.4.2">7.19.4.2</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>,
24855 representations of types, <a href="#6.2.6">6.2.6</a> <a href="#6.8.5">6.8.5</a>, <a href="#6.8.6">6.8.6</a>
24856 pointer, <a href="#6.2.5">6.2.5</a> separate compilation, <a href="#5.1.1.1">5.1.1.1</a>
24857 rescanning and replacement, <a href="#6.10.3.4">6.10.3.4</a> separate translation, <a href="#5.1.1.1">5.1.1.1</a>
24858 reserved identifiers, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a> sequence points, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a>, <a href="#6.8">6.8</a>, <a href="#7.1.4">7.1.4</a>, <a href="#7.19.6">7.19.6</a>,
24859 restartable multibyte/wide character conversion <a href="#7.20.5">7.20.5</a>, <a href="#7.24.2">7.24.2</a>, <a href="#C">C</a>
24860 functions, <a href="#7.24.6.3">7.24.6.3</a> sequencing of statements, <a href="#6.8">6.8</a>
24861 restartable multibyte/wide string conversion setbuf function, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.1">7.19.5.1</a>, <a href="#7.19.5.5">7.19.5.5</a>
24862 functions, <a href="#7.24.6.4">7.24.6.4</a> setjmp macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.13.2.1">7.13.2.1</a>
24863 restore calling environment function, <a href="#7.13.2">7.13.2</a> setjmp.h header, <a href="#7.13">7.13</a>
24864 restrict type qualifier, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.3.1">6.7.3.1</a> setlocale function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24865 restrict-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a> setvbuf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.1">7.19.5.1</a>,
24866 return statement, <a href="#6.8.6.4">6.8.6.4</a> <a href="#7.19.5.5">7.19.5.5</a>, <a href="#7.19.5.6">7.19.5.6</a>
24867 rewind function, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.5">7.19.9.5</a>, shall, <a href="#4">4</a>
24868 <a href="#7.24.3.10">7.24.3.10</a> shift expressions, <a href="#6.5.7">6.5.7</a>
24869 right-shift assignment operator (>>=), <a href="#6.5.16.2">6.5.16.2</a> shift sequence, <a href="#7.1.1">7.1.1</a>
24870 right-shift operator (>>), <a href="#6.5.7">6.5.7</a> shift states, <a href="#5.2.1.2">5.2.1.2</a>
24871 rint functions, <a href="#7.12.9.4">7.12.9.4</a>, <a href="#F.3">F.3</a>, <a href="#F.9.6.4">F.9.6.4</a> short identifier, character, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.3">6.4.3</a>
24872 rint type-generic macro, <a href="#7.22">7.22</a> short int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24873 round functions, <a href="#7.12.9.6">7.12.9.6</a>, <a href="#F.9.6.6">F.9.6.6</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>
24874 round type-generic macro, <a href="#7.22">7.22</a> short int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>,
24875 rounding mode, floating point, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
24876 rvalue, <a href="#6.3.2.1">6.3.2.1</a> SHRT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24877 SHRT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24879 side effects, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a> source lines, <a href="#5.1.1.2">5.1.1.2</a>
24880 SIG_ATOMIC_MAX macro, <a href="#7.18.3">7.18.3</a> source text, <a href="#5.1.1.2">5.1.1.2</a>
24881 SIG_ATOMIC_MIN macro, <a href="#7.18.3">7.18.3</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>,
24882 sig_atomic_t type, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.18.3">7.18.3</a> <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a>
24883 SIG_DFL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sprintf function, <a href="#7.19.6.6">7.19.6.6</a>, <a href="#7.19.6.13">7.19.6.13</a>
24884 SIG_ERR macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sqrt functions, <a href="#7.12.7.5">7.12.7.5</a>, <a href="#F.3">F.3</a>, <a href="#F.9.4.5">F.9.4.5</a>
24885 SIG_IGN macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sqrt type-generic macro, <a href="#7.22">7.22</a>
24886 SIGABRT macro, <a href="#7.14">7.14</a>, <a href="#7.20.4.1">7.20.4.1</a> srand function, <a href="#7.20.2.2">7.20.2.2</a>
24887 SIGFPE macro, <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> sscanf function, <a href="#7.19.6.7">7.19.6.7</a>, <a href="#7.19.6.14">7.19.6.14</a>
24888 SIGILL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> standard error stream, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.10.4">7.19.10.4</a>
24889 SIGINT macro, <a href="#7.14">7.14</a> standard headers, <a href="#4">4</a>, <a href="#7.1.2">7.1.2</a>
24890 sign and magnitude, <a href="#6.2.6.2">6.2.6.2</a> <a href="#7.2"><assert.h></a>, <a href="#7.2">7.2</a>, <a href="#B.1">B.1</a>
24891 sign bit, <a href="#6.2.6.2">6.2.6.2</a> <a href="#7.3"><complex.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.3">7.3</a>, <a href="#7.22">7.22</a>, <a href="#7.26.1">7.26.1</a>,
24892 signal function, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.20.4.4">7.20.4.4</a> <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
24893 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> <a href="#7.4"><ctype.h></a>, <a href="#7.4">7.4</a>, <a href="#7.26.2">7.26.2</a>
24894 signal handling functions, <a href="#7.14.1">7.14.1</a> <a href="#7.5"><errno.h></a>, <a href="#7.5">7.5</a>, <a href="#7.26.3">7.26.3</a>
24895 signal.h header, <a href="#7.14">7.14</a>, <a href="#7.26.6">7.26.6</a> <a href="#7.6"><fenv.h></a>, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F">F</a>, <a href="#H">H</a>
24896 signaling NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#F.2.1">F.2.1</a> <a href="#7.7"><float.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24897 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> <a href="#7.24.4.1.1">7.24.4.1.1</a>
24898 signbit macro, <a href="#7.12.3.6">7.12.3.6</a>, <a href="#F.3">F.3</a> <a href="#7.8"><inttypes.h></a>, <a href="#7.8">7.8</a>, <a href="#7.26.4">7.26.4</a>
24899 signed char type, <a href="#6.2.5">6.2.5</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.9"><iso646.h></a>, <a href="#4">4</a>, <a href="#7.9">7.9</a>
24900 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> <a href="#7.10"><limits.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a>
24901 signed character, <a href="#6.3.1.1">6.3.1.1</a> <a href="#7.11"><locale.h></a>, <a href="#7.11">7.11</a>, <a href="#7.26.5">7.26.5</a>
24902 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> <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="#7.22">7.22</a>, <a href="#F">F</a>, <a href="#F.9">F.9</a>,
24903 signed type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#J.5.17">J.5.17</a>
24904 <a href="#6.3.1.8">6.3.1.8</a> <a href="#7.13"><setjmp.h></a>, <a href="#7.13">7.13</a>
24905 signed types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a> <a href="#7.14"><signal.h></a>, <a href="#7.14">7.14</a>, <a href="#7.26.6">7.26.6</a>
24906 significand part, <a href="#6.4.4.2">6.4.4.2</a> <a href="#7.15"><stdarg.h></a>, <a href="#4">4</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#7.15">7.15</a>
24907 SIGSEGV macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> <a href="#7.16"><stdbool.h></a>, <a href="#4">4</a>, <a href="#7.16">7.16</a>, <a href="#7.26.7">7.26.7</a>, <a href="#H">H</a>
24908 SIGTERM macro, <a href="#7.14">7.14</a> <a href="#7.17"><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>,
24909 simple assignment operator (=), <a href="#6.5.16.1">6.5.16.1</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="#7.17">7.17</a>
24910 sin functions, <a href="#7.12.4.6">7.12.4.6</a>, <a href="#F.9.1.6">F.9.1.6</a> <a href="#7.18"><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="#7.18">7.18</a>,
24911 sin type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> <a href="#7.26.8">7.26.8</a>
24912 single-byte character, <a href="#3.7.1">3.7.1</a>, <a href="#5.2.1.2">5.2.1.2</a> <a href="#7.19"><stdio.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19">7.19</a>, <a href="#7.26.9">7.26.9</a>, <a href="#F">F</a>
24913 single-byte/wide character conversion functions, <a href="#7.20"><stdlib.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.20">7.20</a>, <a href="#7.26.10">7.26.10</a>, <a href="#F">F</a>
24914 <a href="#7.24.6.1">7.24.6.1</a> <a href="#7.21"><string.h></a>, <a href="#7.21">7.21</a>, <a href="#7.26.11">7.26.11</a>
24915 single-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a> <a href="#7.22"><tgmath.h></a>, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24916 single-quote escape sequence (\'), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> <a href="#7.23"><time.h></a>, <a href="#7.23">7.23</a>
24917 sinh functions, <a href="#7.12.5.5">7.12.5.5</a>, <a href="#F.9.2.5">F.9.2.5</a> <a href="#7.24"><wchar.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24">7.24</a>, <a href="#7.26.12">7.26.12</a>,
24918 sinh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> <a href="#F">F</a>
24919 SIZE_MAX macro, <a href="#7.18.3">7.18.3</a> <a href="#7.25"><wctype.h></a>, <a href="#7.25">7.25</a>, <a href="#7.26.13">7.26.13</a>
24920 size_t type, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#7.17">7.17</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.1">7.19.1</a>, standard input stream, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>
24921 <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20">7.20</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.23.1">7.23.1</a>, standard integer types, <a href="#6.2.5">6.2.5</a>
24922 <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> standard output stream, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>
24923 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> standard signed integer types, <a href="#6.2.5">6.2.5</a>
24924 snprintf function, <a href="#7.19.6.5">7.19.6.5</a>, <a href="#7.19.6.12">7.19.6.12</a> state-dependent encoding, <a href="#5.2.1.2">5.2.1.2</a>, <a href="#7.20.7">7.20.7</a>
24925 sorting utility functions, <a href="#7.20.5">7.20.5</a> statements, <a href="#6.8">6.8</a>
24926 source character set, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a> break, <a href="#6.8.6.3">6.8.6.3</a>
24927 source file, <a href="#5.1.1.1">5.1.1.1</a> compound, <a href="#6.8.2">6.8.2</a>
24928 name, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8">6.10.8</a> continue, <a href="#6.8.6.2">6.8.6.2</a>
24929 source file inclusion, <a href="#6.10.2">6.10.2</a> do, <a href="#6.8.5.2">6.8.5.2</a>
24931 else, <a href="#6.8.4.1">6.8.4.1</a> strictly conforming program, <a href="#4">4</a>
24932 expression, <a href="#6.8.3">6.8.3</a> string, <a href="#7.1.1">7.1.1</a>
24933 for, <a href="#6.8.5.3">6.8.5.3</a> comparison functions, <a href="#7.21.4">7.21.4</a>
24934 goto, <a href="#6.8.6.1">6.8.6.1</a> concatenation functions, <a href="#7.21.3">7.21.3</a>
24935 if, <a href="#6.8.4.1">6.8.4.1</a> conversion functions, <a href="#7.11.1.1">7.11.1.1</a>
24936 iteration, <a href="#6.8.5">6.8.5</a> copying functions, <a href="#7.21.2">7.21.2</a>
24937 jump, <a href="#6.8.6">6.8.6</a> library function conventions, <a href="#7.21.1">7.21.1</a>
24938 labeled, <a href="#6.8.1">6.8.1</a> literal, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.5.1">6.5.1</a>, <a href="#6.7.8">6.7.8</a>
24939 null, <a href="#6.8.3">6.8.3</a> miscellaneous functions, <a href="#7.21.6">7.21.6</a>
24940 return, <a href="#6.8.6.4">6.8.6.4</a> numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1">7.20.1</a>
24941 selection, <a href="#6.8.4">6.8.4</a> search functions, <a href="#7.21.5">7.21.5</a>
24942 sequencing, <a href="#6.8">6.8</a> string handling header, <a href="#7.21">7.21</a>
24943 switch, <a href="#6.8.4.2">6.8.4.2</a> string.h header, <a href="#7.21">7.21</a>, <a href="#7.26.11">7.26.11</a>
24944 while, <a href="#6.8.5.1">6.8.5.1</a> stringizing, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.9">6.10.9</a>
24945 static storage duration, <a href="#6.2.4">6.2.4</a> strlen function, <a href="#7.21.6.3">7.21.6.3</a>
24946 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> strncat function, <a href="#7.21.3.2">7.21.3.2</a>
24947 static, in array declarators, <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.7.5.3">6.7.5.3</a> strncmp function, <a href="#7.21.4">7.21.4</a>, <a href="#7.21.4.4">7.21.4.4</a>
24948 stdarg.h header, <a href="#4">4</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#7.15">7.15</a> strncpy function, <a href="#7.21.2.4">7.21.2.4</a>
24949 stdbool.h header, <a href="#4">4</a>, <a href="#7.16">7.16</a>, <a href="#7.26.7">7.26.7</a>, <a href="#H">H</a> strpbrk function, <a href="#7.21.5.4">7.21.5.4</a>
24950 STDC, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a> strrchr function, <a href="#7.21.5.5">7.21.5.5</a>
24951 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>, strspn function, <a href="#7.21.5.6">7.21.5.6</a>
24952 <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="#7.17">7.17</a> strstr function, <a href="#7.21.5.7">7.21.5.7</a>
24953 stderr macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a> strtod function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24954 stdin macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.4">7.19.6.4</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.3">F.3</a>
24955 <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.7">7.19.7.7</a>, <a href="#7.24.2.12">7.24.2.12</a>, <a href="#7.24.3.7">7.24.3.7</a> strtof function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#F.3">F.3</a>
24956 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="#7.18">7.18</a>, strtoimax function, <a href="#7.8.2.3">7.8.2.3</a>
24957 <a href="#7.26.8">7.26.8</a> strtok function, <a href="#7.21.5.8">7.21.5.8</a>
24958 stdio.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19">7.19</a>, <a href="#7.26.9">7.26.9</a>, <a href="#F">F</a> strtol function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.2">7.20.1.2</a>,
24959 stdlib.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.20">7.20</a>, <a href="#7.26.10">7.26.10</a>, <a href="#F">F</a> <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.2">7.24.2.2</a>
24960 stdout macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.3">7.19.6.3</a>, strtold function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#F.3">F.3</a>
24961 <a href="#7.19.7.9">7.19.7.9</a>, <a href="#7.19.7.10">7.19.7.10</a>, <a href="#7.24.2.11">7.24.2.11</a>, <a href="#7.24.3.9">7.24.3.9</a> strtoll function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1.2">7.20.1.2</a>, <a href="#7.20.1.4">7.20.1.4</a>
24962 storage duration, <a href="#6.2.4">6.2.4</a> strtoul function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.2">7.20.1.2</a>,
24963 storage order of array, <a href="#6.5.2.1">6.5.2.1</a> <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.2">7.24.2.2</a>
24964 storage-class specifiers, <a href="#6.7.1">6.7.1</a>, <a href="#6.11.5">6.11.5</a> strtoull function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1.2">7.20.1.2</a>, <a href="#7.20.1.4">7.20.1.4</a>
24965 strcat function, <a href="#7.21.3.1">7.21.3.1</a> strtoumax function, <a href="#7.8.2.3">7.8.2.3</a>
24966 strchr function, <a href="#7.21.5.2">7.21.5.2</a> struct hack, see flexible array member
24967 strcmp function, <a href="#7.21.4">7.21.4</a>, <a href="#7.21.4.2">7.21.4.2</a> structure
24968 strcoll function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.21.4.5">7.21.4.5</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
24969 strcpy function, <a href="#7.21.2.3">7.21.2.3</a> content, <a href="#6.7.2.3">6.7.2.3</a>
24970 strcspn function, <a href="#7.21.5.3">7.21.5.3</a> dot operator (.), <a href="#6.5.2.3">6.5.2.3</a>
24971 streams, <a href="#7.19.2">7.19.2</a>, <a href="#7.20.4.3">7.20.4.3</a> initialization, <a href="#6.7.8">6.7.8</a>
24972 fully buffered, <a href="#7.19.3">7.19.3</a> member alignment, <a href="#6.7.2.1">6.7.2.1</a>
24973 line buffered, <a href="#7.19.3">7.19.3</a> member name space, <a href="#6.2.3">6.2.3</a>
24974 orientation, <a href="#7.19.2">7.19.2</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>
24975 standard error, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a>
24976 standard input, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> specifier, <a href="#6.7.2.1">6.7.2.1</a>
24977 standard output, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
24978 unbuffered, <a href="#7.19.3">7.19.3</a> type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a>
24979 strerror function, <a href="#7.19.10.4">7.19.10.4</a>, <a href="#7.21.6.2">7.21.6.2</a> strxfrm function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.4.5">7.21.4.5</a>
24980 strftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.3">7.23.3</a>, <a href="#7.23.3.5">7.23.3.5</a>, subscripting, <a href="#6.5.2.1">6.5.2.1</a>
24981 <a href="#7.24.5.1">7.24.5.1</a> subtraction assignment operator (-=), <a href="#6.5.16.2">6.5.16.2</a>
24983 subtraction operator (-), <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> tolower function, <a href="#7.4.2.1">7.4.2.1</a>
24984 suffix toupper function, <a href="#7.4.2.2">7.4.2.2</a>
24985 floating constant, <a href="#6.4.4.2">6.4.4.2</a> towctrans function, <a href="#7.25.3.2.1">7.25.3.2.1</a>, <a href="#7.25.3.2.2">7.25.3.2.2</a>
24986 integer constant, <a href="#6.4.4.1">6.4.4.1</a> towlower function, <a href="#7.25.3.1.1">7.25.3.1.1</a>, <a href="#7.25.3.2.1">7.25.3.2.1</a>
24987 switch body, <a href="#6.8.4.2">6.8.4.2</a> towupper function, <a href="#7.25.3.1.2">7.25.3.1.2</a>, <a href="#7.25.3.2.1">7.25.3.2.1</a>
24988 switch case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> translation environment, <a href="#5">5</a>, <a href="#5.1.1">5.1.1</a>
24989 switch default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> translation limits, <a href="#5.2.4.1">5.2.4.1</a>
24990 switch statement, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> translation phases, <a href="#5.1.1.2">5.1.1.2</a>
24991 swprintf function, <a href="#7.24.2.3">7.24.2.3</a>, <a href="#7.24.2.7">7.24.2.7</a> translation unit, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.9">6.9</a>
24992 swscanf function, <a href="#7.24.2.4">7.24.2.4</a>, <a href="#7.24.2.8">7.24.2.8</a> trap representation, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.3.2.3">6.3.2.3</a>,
24993 symbols, <a href="#3">3</a> <a href="#6.5.2.3">6.5.2.3</a>
24994 syntactic categories, <a href="#6.1">6.1</a> trigonometric functions
24995 syntax notation, <a href="#6.1">6.1</a> complex, <a href="#7.3.5">7.3.5</a>, <a href="#G.6.1">G.6.1</a>
24996 syntax rule precedence, <a href="#5.1.1.2">5.1.1.2</a> real, <a href="#7.12.4">7.12.4</a>, <a href="#F.9.1">F.9.1</a>
24997 syntax summary, language, <a href="#A">A</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>
24998 system function, <a href="#7.20.4.6">7.20.4.6</a> true macro, <a href="#7.16">7.16</a>
24999 trunc functions, <a href="#7.12.9.8">7.12.9.8</a>, <a href="#F.9.6.8">F.9.6.8</a>
25000 tab characters, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a> trunc type-generic macro, <a href="#7.22">7.22</a>
25001 tag compatibility, <a href="#6.2.7">6.2.7</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="#7.19.3">7.19.3</a>, <a href="#7.19.5.3">7.19.5.3</a>
25002 tag name space, <a href="#6.2.3">6.2.3</a> truncation toward zero, <a href="#6.5.5">6.5.5</a>
25003 tags, <a href="#6.7.2.3">6.7.2.3</a> two's complement, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.18.1.1">7.18.1.1</a>
25004 tan functions, <a href="#7.12.4.7">7.12.4.7</a>, <a href="#F.9.1.7">F.9.1.7</a> type category, <a href="#6.2.5">6.2.5</a>
25005 tan type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> type conversion, <a href="#6.3">6.3</a>
25006 tanh functions, <a href="#7.12.5.6">7.12.5.6</a>, <a href="#F.9.2.6">F.9.2.6</a> type definitions, <a href="#6.7.7">6.7.7</a>
25007 tanh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> type domain, <a href="#6.2.5">6.2.5</a>, <a href="#G.2">G.2</a>
25008 tentative definition, <a href="#6.9.2">6.9.2</a> type names, <a href="#6.7.6">6.7.6</a>
25009 terms, <a href="#3">3</a> type punning, <a href="#6.5.2.3">6.5.2.3</a>
25010 text streams, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.9.4">7.19.9.4</a> type qualifiers, <a href="#6.7.3">6.7.3</a>
25011 tgamma functions, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#F.9.5.4">F.9.5.4</a> type specifiers, <a href="#6.7.2">6.7.2</a>
25012 tgamma type-generic macro, <a href="#7.22">7.22</a> type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
25013 tgmath.h header, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> typedef declaration, <a href="#6.7.7">6.7.7</a>
25014 time typedef storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.7.7">6.7.7</a>
25015 broken down, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.3">7.23.3</a>, <a href="#7.23.3.1">7.23.3.1</a>, types, <a href="#6.2.5">6.2.5</a>
25016 <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a>, <a href="#7.23.3.5">7.23.3.5</a> character, <a href="#6.7.8">6.7.8</a>
25017 calendar, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.2">7.23.2.2</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.2.4">7.23.2.4</a>, compatible, <a href="#6.2.7">6.2.7</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.5">6.7.5</a>
25018 <a href="#7.23.3.2">7.23.3.2</a>, <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a> complex, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a>
25019 components, <a href="#7.23.1">7.23.1</a> composite, <a href="#6.2.7">6.2.7</a>
25020 conversion functions, <a href="#7.23.3">7.23.3</a> const qualified, <a href="#6.7.3">6.7.3</a>
25021 wide character, <a href="#7.24.5">7.24.5</a> conversions, <a href="#6.3">6.3</a>
25022 local, <a href="#7.23.1">7.23.1</a> imaginary, <a href="#G">G</a>
25023 manipulation functions, <a href="#7.23.2">7.23.2</a> restrict qualified, <a href="#6.7.3">6.7.3</a>
25024 time function, <a href="#7.23.2.4">7.23.2.4</a> volatile qualified, <a href="#6.7.3">6.7.3</a>
25025 time.h header, <a href="#7.23">7.23</a>
25026 time_t type, <a href="#7.23.1">7.23.1</a> UCHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
25027 tm structure type, <a href="#7.23.1">7.23.1</a>, <a href="#7.24.1">7.24.1</a> UINT_FASTN_MAX macros, <a href="#7.18.2.3">7.18.2.3</a>
25028 TMP_MAX macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.4.3">7.19.4.3</a>, <a href="#7.19.4.4">7.19.4.4</a> uint_fastN_t types, <a href="#7.18.1.3">7.18.1.3</a>
25029 tmpfile function, <a href="#7.19.4.3">7.19.4.3</a>, <a href="#7.20.4.3">7.20.4.3</a> UINT_LEASTN_MAX macros, <a href="#7.18.2.2">7.18.2.2</a>
25030 tmpnam function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.4.3">7.19.4.3</a>, <a href="#7.19.4.4">7.19.4.4</a> uint_leastN_t types, <a href="#7.18.1.2">7.18.1.2</a>
25031 token, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, see also preprocessing tokens UINT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
25032 token concatenation, <a href="#6.10.3.3">6.10.3.3</a> UINTMAX_C macro, <a href="#7.18.4.2">7.18.4.2</a>
25033 token pasting, <a href="#6.10.3.3">6.10.3.3</a> UINTMAX_MAX macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.18.2.5">7.18.2.5</a>
25035 uintmax_t type, <a href="#7.18.1.5">7.18.1.5</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, USHRT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
25036 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</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>,
25037 UINTN_C macros, <a href="#7.18.4.1">7.18.4.1</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>
25038 UINTN_MAX macros, <a href="#7.18.2.1">7.18.2.1</a> utilities, general, <a href="#7.20">7.20</a>
25039 uintN_t types, <a href="#7.18.1.1">7.18.1.1</a> wide string, <a href="#7.24.4">7.24.4</a>
25040 UINTPTR_MAX macro, <a href="#7.18.2.4">7.18.2.4</a>
25041 uintptr_t type, <a href="#7.18.1.4">7.18.1.4</a> va_arg macro, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.1">7.15.1.1</a>, <a href="#7.15.1.2">7.15.1.2</a>,
25042 ULLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.15.1.4">7.15.1.4</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>,
25043 <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>,
25044 ULONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>,
25045 <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>
25046 unary arithmetic operators, <a href="#6.5.3.3">6.5.3.3</a> va_copy macro, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.1">7.15.1.1</a>, <a href="#7.15.1.2">7.15.1.2</a>,
25047 unary expression, <a href="#6.5.3">6.5.3</a> <a href="#7.15.1.3">7.15.1.3</a>
25048 unary minus operator (-), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a> va_end macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.3">7.15.1.3</a>,
25049 unary operators, <a href="#6.5.3">6.5.3</a> <a href="#7.15.1.4">7.15.1.4</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>,
25050 unary plus operator (+), <a href="#6.5.3.3">6.5.3.3</a> <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>,
25051 unbuffered stream, <a href="#7.19.3">7.19.3</a> <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>,
25052 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="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>
25053 <a href="#7.1.4">7.1.4</a> va_list type, <a href="#7.15">7.15</a>, <a href="#7.15.1.3">7.15.1.3</a>
25054 undefined behavior, <a href="#3.4.3">3.4.3</a>, <a href="#4">4</a>, <a href="#J.2">J.2</a> va_start macro, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.1">7.15.1.1</a>,
25055 underscore character, <a href="#6.4.2.1">6.4.2.1</a> <a href="#7.15.1.2">7.15.1.2</a>, <a href="#7.15.1.3">7.15.1.3</a>, <a href="#7.15.1.4">7.15.1.4</a>, <a href="#7.19.6.8">7.19.6.8</a>,
25056 underscore, leading, in identifier, <a href="#7.1.3">7.1.3</a> <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>, <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>,
25057 ungetc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>, <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>,
25058 <a href="#7.19.9.3">7.19.9.3</a> <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>
25059 ungetwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.10">7.24.3.10</a> value, <a href="#3.17">3.17</a>
25060 Unicode required set, <a href="#6.10.8">6.10.8</a> value bits, <a href="#6.2.6.2">6.2.6.2</a>
25061 union variable arguments, <a href="#6.10.3">6.10.3</a>, <a href="#7.15">7.15</a>
25062 arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a> variable arguments header, <a href="#7.15">7.15</a>
25063 content, <a href="#6.7.2.3">6.7.2.3</a> variable length array, <a href="#6.7.5">6.7.5</a>, <a href="#6.7.5.2">6.7.5.2</a>
25064 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> variably modified type, <a href="#6.7.5">6.7.5</a>, <a href="#6.7.5.2">6.7.5.2</a>
25065 initialization, <a href="#6.7.8">6.7.8</a> vertical-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
25066 member alignment, <a href="#6.7.2.1">6.7.2.1</a> vertical-tab escape sequence (\v), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>,
25067 member name space, <a href="#6.2.3">6.2.3</a> <a href="#7.4.1.10">7.4.1.10</a>
25068 member operator (.), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a> vfprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>
25069 pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> vfscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>
25070 specifier, <a href="#6.7.2.1">6.7.2.1</a> vfwprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.5">7.24.2.5</a>
25071 tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a> vfwscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.3.10">7.24.3.10</a>
25072 type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a> visibility of identifier, <a href="#6.2.1">6.2.1</a>
25073 universal character name, <a href="#6.4.3">6.4.3</a> VLA, see variable length array
25074 unqualified type, <a href="#6.2.5">6.2.5</a> void expression, <a href="#6.3.2.2">6.3.2.2</a>
25075 unqualified version of type, <a href="#6.2.5">6.2.5</a> void function parameter, <a href="#6.7.5.3">6.7.5.3</a>
25076 unsigned integer suffix, u or <a href="#U">U</a>, <a href="#6.4.4.1">6.4.4.1</a> void type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.2">6.3.2.2</a>, <a href="#6.7.2">6.7.2</a>
25077 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> void type conversion, <a href="#6.3.2.2">6.3.2.2</a>
25078 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>, volatile storage, <a href="#5.1.2.3">5.1.2.3</a>
25079 <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a> volatile type qualifier, <a href="#6.7.3">6.7.3</a>
25080 unsigned types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, volatile-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a>
25081 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> vprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.10">7.19.6.10</a>
25082 unspecified behavior, <a href="#3.4.4">3.4.4</a>, <a href="#4">4</a>, <a href="#J.1">J.1</a> vscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.11">7.19.6.11</a>
25083 unspecified value, <a href="#3.17.3">3.17.3</a> vsnprintf function, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.12">7.19.6.12</a>
25084 uppercase letter, <a href="#5.2.1">5.2.1</a> vsprintf function, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.13">7.19.6.13</a>
25085 use of library functions, <a href="#7.1.4">7.1.4</a> vsscanf function, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.14">7.19.6.14</a>
25087 vswprintf function, <a href="#7.24.2.7">7.24.2.7</a> wctype.h header, <a href="#7.25">7.25</a>, <a href="#7.26.13">7.26.13</a>
25088 vswscanf function, <a href="#7.24.2.8">7.24.2.8</a> wctype_t type, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>
25089 vwprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.9">7.24.2.9</a> WEOF macro, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a>, <a href="#7.24.3.6">7.24.3.6</a>,
25090 vwscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.10">7.24.2.10</a>, <a href="#7.24.3.10">7.24.3.10</a> <a href="#7.24.3.7">7.24.3.7</a>, <a href="#7.24.3.8">7.24.3.8</a>, <a href="#7.24.3.9">7.24.3.9</a>, <a href="#7.24.3.10">7.24.3.10</a>,
25091 <a href="#7.24.6.1.1">7.24.6.1.1</a>, <a href="#7.25.1">7.25.1</a>
25092 warnings, <a href="#I">I</a> while statement, <a href="#6.8.5.1">6.8.5.1</a>
25093 wchar.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24">7.24</a>, <a href="#7.26.12">7.26.12</a>, white space, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>, <a href="#7.4.1.10">7.4.1.10</a>,
25094 <a href="#F">F</a> <a href="#7.25.2.1.10">7.25.2.1.10</a>
25095 WCHAR_MAX macro, <a href="#7.18.3">7.18.3</a>, <a href="#7.24.1">7.24.1</a> white-space characters, <a href="#6.4">6.4</a>
25096 WCHAR_MIN macro, <a href="#7.18.3">7.18.3</a>, <a href="#7.24.1">7.24.1</a> wide character, <a href="#3.7.3">3.7.3</a>
25097 wchar_t type, <a href="#3.7.3">3.7.3</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.7.8">6.7.8</a>, case mapping functions, <a href="#7.25.3.1">7.25.3.1</a>
25098 <a href="#6.10.8">6.10.8</a>, <a href="#7.17">7.17</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20">7.20</a>, extensible, <a href="#7.25.3.2">7.25.3.2</a>
25099 <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> classification functions, <a href="#7.25.2.1">7.25.2.1</a>
25100 wcrtomb function, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>, extensible, <a href="#7.25.2.2">7.25.2.2</a>
25101 <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a> constant, <a href="#6.4.4.4">6.4.4.4</a>
25102 wcscat function, <a href="#7.24.4.3.1">7.24.4.3.1</a> formatted input/output functions, <a href="#7.24.2">7.24.2</a>
25103 wcschr function, <a href="#7.24.4.5.1">7.24.4.5.1</a> input functions, <a href="#7.19.1">7.19.1</a>
25104 wcscmp function, <a href="#7.24.4.4.1">7.24.4.4.1</a>, <a href="#7.24.4.4.4">7.24.4.4.4</a> input/output functions, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3">7.24.3</a>
25105 wcscoll function, <a href="#7.24.4.4.2">7.24.4.4.2</a>, <a href="#7.24.4.4.4">7.24.4.4.4</a> output functions, <a href="#7.19.1">7.19.1</a>
25106 wcscpy function, <a href="#7.24.4.2.1">7.24.4.2.1</a> single-byte conversion functions, <a href="#7.24.6.1">7.24.6.1</a>
25107 wcscspn function, <a href="#7.24.4.5.2">7.24.4.5.2</a> wide string, <a href="#7.1.1">7.1.1</a>
25108 wcsftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.24.5.1">7.24.5.1</a> wide string comparison functions, <a href="#7.24.4.4">7.24.4.4</a>
25109 wcslen function, <a href="#7.24.4.6.1">7.24.4.6.1</a> wide string concatenation functions, <a href="#7.24.4.3">7.24.4.3</a>
25110 wcsncat function, <a href="#7.24.4.3.2">7.24.4.3.2</a> wide string copying functions, <a href="#7.24.4.2">7.24.4.2</a>
25111 wcsncmp function, <a href="#7.24.4.4.3">7.24.4.4.3</a> wide string literal, see string literal
25112 wcsncpy function, <a href="#7.24.4.2.2">7.24.4.2.2</a> wide string miscellaneous functions, <a href="#7.24.4.6">7.24.4.6</a>
25113 wcspbrk function, <a href="#7.24.4.5.3">7.24.4.5.3</a> wide string numeric conversion functions, <a href="#7.8.2.4">7.8.2.4</a>,
25114 wcsrchr function, <a href="#7.24.4.5.4">7.24.4.5.4</a> <a href="#7.24.4.1">7.24.4.1</a>
25115 wcsrtombs function, <a href="#7.24.6.4.2">7.24.6.4.2</a> wide string search functions, <a href="#7.24.4.5">7.24.4.5</a>
25116 wcsspn function, <a href="#7.24.4.5.5">7.24.4.5.5</a> wide-oriented stream, <a href="#7.19.2">7.19.2</a>
25117 wcsstr function, <a href="#7.24.4.5.6">7.24.4.5.6</a> width, <a href="#6.2.6.2">6.2.6.2</a>
25118 wcstod function, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a> WINT_MAX macro, <a href="#7.18.3">7.18.3</a>
25119 wcstod function, <a href="#7.24.4.1.1">7.24.4.1.1</a> WINT_MIN macro, <a href="#7.18.3">7.18.3</a>
25120 wcstof function, <a href="#7.24.4.1.1">7.24.4.1.1</a> wint_t type, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>,
25121 wcstoimax function, <a href="#7.8.2.4">7.8.2.4</a> <a href="#7.25.1">7.25.1</a>
25122 wcstok function, <a href="#7.24.4.5.7">7.24.4.5.7</a> wmemchr function, <a href="#7.24.4.5.8">7.24.4.5.8</a>
25123 wcstol function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>, wmemcmp function, <a href="#7.24.4.4.5">7.24.4.4.5</a>
25124 <a href="#7.24.4.1.2">7.24.4.1.2</a> wmemcpy function, <a href="#7.24.4.2.3">7.24.4.2.3</a>
25125 wcstold function, <a href="#7.24.4.1.1">7.24.4.1.1</a> wmemmove function, <a href="#7.24.4.2.4">7.24.4.2.4</a>
25126 wcstoll function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a> wmemset function, <a href="#7.24.4.6.2">7.24.4.6.2</a>
25127 wcstombs function, <a href="#7.20.8.2">7.20.8.2</a>, <a href="#7.24.6.4">7.24.6.4</a> wprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.11">7.24.2.11</a>
25128 wcstoul function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>, wscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.10">7.24.2.10</a>, <a href="#7.24.2.12">7.24.2.12</a>,
25129 <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.24.3.10">7.24.3.10</a>
25130 wcstoull function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>
25131 wcstoumax function, <a href="#7.8.2.4">7.8.2.4</a> xor macro, <a href="#7.9">7.9</a>
25132 wcsxfrm function, <a href="#7.24.4.4.4">7.24.4.4.4</a> xor_eq macro, <a href="#7.9">7.9</a>
25133 wctob function, <a href="#7.24.6.1.2">7.24.6.1.2</a>, <a href="#7.25.2.1">7.25.2.1</a>
25134 wctomb function, <a href="#7.20.7.3">7.20.7.3</a>, <a href="#7.20.8.2">7.20.8.2</a>, <a href="#7.24.6.3">7.24.6.3</a>
25135 wctrans function, <a href="#7.25.3.2.1">7.25.3.2.1</a>, <a href="#7.25.3.2.2">7.25.3.2.2</a>
25136 wctrans_t type, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.3.2.2">7.25.3.2.2</a>
25137 wctype function, <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>